HUMAN PHYSIOLOGY.








A TREATISE
ON
HUMAN PHYSIOLOGY;
DESIGNED FOR THE USE OF
STUDENTS AND PRACTITIONERS OF MEDICINE.
BY
JOHN C. DALTON, JR., M. D.,
PROFESSOR OF PHYSIOLOGY AND MICROSCOPIC ANATOMY IN THE COLLEGE OF PHYSICIANS AND SURGEONS,
NEW YORK; MEMBER OF THE NEW YORK ACADEMY OF MEDICINE; OF THE NEW YORK
PATHOLOGICAL SOCIETY; OF THE AMERICAN ACADEMY OF ARTS AND SCIENCES,
BOSTON, MASS.; AND OF THE BIOLOGICAL DEPARTMENT OF THE
ACADEMY OF NATURAL SCIENCES OF PHILADELPHIA.
Hrconsb dbiftlo, Arbiorb anb OnIarqgb.
WITH TWO HUNDRED AND SEVENTY-ONE ILLUSTRATIONS.
PHILADELPHIA:
BLANCHARD AND LEA.
1861.




Entered according to the Act of Congress, in the year 1859, by
BLANCHARD AND LEA,
in the Office of the Clerk of the District Court of the United States in and for the
Eastern District of the State of Pennsylvania.
PHILADELPHIA:
COLLINS, PRINTER, 705 JAYNE STREET.




TO MY FATHER,
JOHN C. DALTON, M.D.,
IN
HOMAGE OF HIS LONG AND SUCCESSFUL DEVOTION
TO THE
SCIENCE AND ART OF MEDICINE,
AND IN
GRATEFUL RECOLLECTION OF HIS PROFESSIONAL PRECEPTS AND EXAMPLE,
W91s fglumt
IS RESPECTFULLY AND AFFECTIONATELY
INSCRIBED.








PREFACE TO THE SECOND EDITION.
IN presenting a new edition of this work, the author desires to
express his sincere acknowledgments to his professional brethren
for the very favorable manner in which it was received at the
time of its first appearance, two years ago. In the present edition,
the author has endeavored to supply, as fully as possible, the
deficiencies which, he is well aware, existed in the former volume.
Some of these deficiencies were evident to his own mind, while
others were indicated by the suggestions of judicious criticism.
These suggestions, accordingly, have been adopted in all cases in
which they appeared to be well founded, and not inconsistent with
the general plan of the work. In those instances, on the other
hand, in which the views of the author on physiological questions
seemed to him to be positively sustained by the results of observation, he has retained these views unchanged in the present edition.
At the same time, he has abstained, as before, from the lengthened
discussion of theoretical points, and has purposely avoided even
the enumeration of new experiments and observations, wherever
they have not materially affected the position of physiological
doctrines; for in a work like the present, it is not the object of
the writer to give a detailed history of physiological science, but
only such prominent and essential points in its development as
will enable the reader fully to comprehend its actual condition at
the present time.
The principal additions and alterations which have thus been
found advisable are:First, the introduction of an entire chapter devoted to the consideration of the Special Senses, which were only incidentally treated
of in the former edition.




viii        PREFACE TO THE SECOND EDITION.
Second, the re-arrangement of the chapter on the Cranial Nerves,
and the introduction of some new views and facts in regard to their
physiology.
Third, an account of some new experiments, original with the
author, relating to the function of the Cerebellum, and the conclusions to which they lead.
Fourth, certain considerations respecting the general properties
of Sensation and Motion, as resident in the nervous system, which
are important as an introduction to the more detailed study of
these functions.
Fifth, the introduction of a chapter on Imbibition and Exhalation,
and the functions of the Lymphatic System; including the study of
endosmosis and exosmosis, and their mode of action in the animal
frame, the experiments of Dutrochet, Chevreuil, Gosselin, Matteucci,
and others, on this subject, the constitution and circulation of the
lymph and chyle, and, finally, a quantitative estimate of the entire
processes of exudation and reabsorption, as taking place in the
living body.
Additions have also been made, in various parts, to the chapters
on Secretion, Excretion, the Circulation, and the functions of the
Digestive Apparatus. In every instance, these alterations have
been incorporated with the text in such a manner as to avoid, so
far as possible, increasing unnecessarily the size of the book.
Twenty-two new and original illustrations have been introduced
into the present volume, of which number five replace others in
the former edition, which were regarded as imperfect, either in
design or execution. The remaining seventeen are additional.
It is hoped that the above alterations and additions will be found
to be improvements, and that they will enable the work, in its present form, to accomplish more fully the object for which it was
designed.
NEW YORK, February, 1861.




PREFACE TO THE FIRST EDITION.
TnIS volume is offered to the medical profession of the United
States, as a text-book for students, and also as a means of communicating, in a condensed form, such new facts and ideas in physiology, as have marked the progress of the science within a recent
period. Many of these topics are of great practical importance to
the medical man, as influencing, in various ways, his views on
pathology and therapeutics; and they are all of interest for the
physician who desires to keep pace with the annual advance of his
profession, as indicating the present position and extent of one of
the most progressive of the departments of medicine.
It has been the object of the author, more particularly, to present, at the same time with the conclusions which physiologists
have been led to adopt on any particular subject, the experimental
basis upon which those conclusions are founded; and he has endeavored, so far as possible, to establish or corroborate them by
original investigation, or by a repetition of the labors of others.
This is more especially the case in that part of the book (Section
1.) devoted to the function of Nutrition; and as a general thing,
throughout the work, any statement of experimental facts, not
expressly referred to the authority of some other writer, is given
by the author as the result of direct personal observation.
The illustrations for the work have been prepared with special
reference to the subject-matter; and it is hoped* that they will be
found of such a character as materially to assist the student in
comprehending the most important and intricate parts of the subject. It is more particularly in the departments of the Nervous
System and Embryonic Development that simple, clear, and faithful




X            PREFACE TO THE FIRST EDITION.
illustrations are indispensable for the proper understanding of the
printed descriptions; the latter being often necessarily somewhat
intricate, and requiring absolutely the assistance of properly
arranged figures and diagrams.  Of the two hundred and fiftyfour illustrations in the present volume, only eleven have been
borrowed from other writers, to whom they will be found duly
credited in the list of woodcuts.
Of the remaining illustrations, prepared expressly for the present work, the drawings of anatomical structures, crystals, and
microscopic views generally, were all taken from  nature. The
diagrams were arranged, for purposes of convenience, in such
a manner as to illustrate known anatomical or physiological appearances, in the most compact and intelligible form.
Physiological questions which are in an altogether unsettled
state, as well as purely hypothetical topics, have been purposely
avoided, as not coming within the plan of this work, nor as calculated to increase its usefulness.
NEW YORK, January 1, 1859.




CONTENTS.
I N T RO D U C T ION.
PAGE
Definition of Physiology-Its mode of study-Nature of Vital PhenomenaDivision of the subject..                               33-43
SECTION  I.
NUTRITION.
CHAPTER I.
PROXIMATE PRINCIPLES IN GENERAL.
Definition of Proximate Principles-Mode of their extraction-Manner in which
they are associated with each other-Natural variation in their relative
quantities-Three distinct classes of proximate principles..   45-52
CHAPTER II.
PROXIMATE PRINCIPLES OF THE FIRST CLASS.
Inorganic Substances-Water-Chloride of Sodium-Chloride of PotassiumPhosphate of Lime-Carbonate of Lime-Carbonate of Soda-Phosphates of
Magnesia, Soda, and Potassa-Inorganic proximate principles not altered in
the body-Their discharge-Nature of their function...   53-62
CHAPTER III.
PROXIMATE PRINCIPLES OF THE SECOND CLASS.
STARCH- Percentage of starch in different kinds of food-Varieties of this
substance-Properties and reactions of starch-Its conversion into sugarSUGAn-Varieties of sugar-Physical and chemical properties-Proportion
in different kinds of food-FATS-Varieties-Properties and reactions of fat
-Its crystallization-Proportion in different kinds of food-Its condition in
the body-Internal production of fat-Origin and destination of proximate
principles of this class... 63-78




xii                             CONTENTS.
CHAPTER IV.
PROXIMATE PRINCIPLES OF THE THIRD CLASS.
PAGE
General characters of organic substances-Their chemical constitution-Hygroscopic properties - Coagulation -Catalysis-Fermentation-PutrefactionFibrin-Albumen-Casein-Globuline-Pepsine-Pancreatine-MMucosine
Osteine - Cartilagine - Musculine- Haematine- Melanine -BiliverdineUrosacine-Origin and destruction of proximate principles of this class  79-88
CHAPTER V.
OF FOOD.
Importance of inorganic substances as ingredients of food-Of saccharine and
starchy substances-Of fatty matters-Insufficiency of these substances
when used alone-Effects of an exclusive non-nitrogenous diet-Organic
substances also insufficient by themselves-Experiments of Magendie on
exclusive diet of gelatine or fibrin-Food requires to contain all classes of
proximate principles-Composition of various kinds of food-Daily quantity
of food required by man-Digestibility of food-Effect of cooking.    89-98
CHAPTER VI.
DIGESTION.
Nature of digestion-Digestive apparatus of fowl-Of ox-Of man-MASTICATION-Varieties of teeth-Effect of mastication-SALIVA-Its compositionDaily quantity produced-Its action on starch-Effect of its suppressionFunction of the saliva-GASTRIC JUICE, AND STOMACH DIGESTION-Structure of
gastric mucous membrane-Dr. Beaumont's experiments on St. MartinArtificial gastric fistulae-Composition and properties of gastric juice-Its
action on albuminoid substances-Peristaltic action of stomach-Time required for digestion-Daily quantity of gastric juice-Influences modifying
its secretion-INTESTINAL JUICES, AND THE DIGESTION OF SUGAR AND STARCHFollicles of intestine-Properties of intestinal juice-PANCREATIC JUICE, AND
THE DIGESTION OF FAT-Composition and properties of pancreatic juice-Its
action on oily matters-Successive changes in intestinal digestion-The large
intestine and its contents......  99-144
CHAPTER VII.
ABSORPTION.
Closed follicles and villi of small intestine-Peristaltic motion-Absorption
by bloodvessels and lymphatics-Chyle-Lymph-Absorbent system-Lacteals and lymphatics-Absorption of fat-Its accumulation in the blood
during digestion-Its final decomposition and disappearance.. 145-157




CONTENTS.                               xiii
CHAPTER VIII.
THE BILE.
PAGE
Physical properties of the bile-Its composition-Biliverdine-CholesterinBiliary salts-Their mode of extraction-Crystallization-Glyko-cholate of
soda —Tauro-cholate of soda-Biliary salts in different species of animals
and in man-Tests for bile-Variations and functions of bile-Daily quantity-Time of its discharge into intestine-Its disappearance from the alimentary canal-Its reabsorption-Its ultimate decomposition.. 158-181
CHAPTER IX.
FORMATION OF SUGAR IN THE LIVER.
Existence of sugar in liver of all animals-Its percentage-Internal origin of
liver-sugar-Its production after death-Glycogenic matter of the liver-Its
properties and composition-Absorption of liver-sugar by hepatic veinsIts accumulation in the blood during digestion —Its final decomposition and
disappearance....... 182-189
CHAPTER X.
THE SPLEEN.
Capsule of Spleen-Variations in size of the organ-Its internal structureMalpighian bodies of the spleen-Action of spleen on the blood-Effect of
its extirpation....... 190-194
CHAPTER XI.
THE BLOOD.
RED GLOBULES of the blood-Their microscopic characters-Structure and composition-Variations in size in different animals-WHITE GLOBULES of the
blood-Independence of the two kinds of blood-globules-PLAsMA-Its composition-Fibrin-Albumen-Fatty matters-Saline ingredients-Extractive
matters-CoAGULATION OF THE BLOOD-Separation of clot and serum-Influences hastening or retarding coagulation-Coagulation not a commencement
of organization-Formation of buffy coat-Entire quantity of blood in body
195-213
CHAPTER XII.
RESPIRATION.
Respiratory apparatus of aquatic and air-breathing animals-Structure of
lungs in human subject-Respiratory movements of chest-Of glottisChanges in the air during respiration-Changes in the blood-Proportions
of oxygen and carbonic acid, in venous and arterial blood-Solution of gases
by the blood-globules-Origin of carbonic acid in the blood-Its mode of
production-Quantity of carbonic acid exhaled from the body-Variations
according to age, sex, temperature, &c.-Respiration by the skin. 214-234




xiv                            CONTENTS.
CHAPTER XIII.
ANIMAL HEAT.
PAGE
Standard temperature of animals-How maintained-Production of heat by
Vegetables-Mode of generation of animal heat-Theory of combustionObjections to this theory-No oxidation in vegetables during production of
heat-Quantities of oxygen and carbonic acid in animals do not correspond
with each other-Production of animal heat a local process-Depends on
the chemical phenomena of nutrition... 235-245
CHAPTER XIV.
THE CIRCULATION.
Circulatory apparatus of fish-Of reptiles-Of mammalians-Course of blood
through the heart-Action of valves-Sounds of heart-Movements-Impulse-Successive pulsations-Arterial system-Movement of blood through
the arteries-Arterial pulse-Arterial pressure-Rapidity of arterial circulation-The veins-Causes of movement of blood in the veins-Rapidity of
venous current —Capillary circulation —Phenomena and causes of capillary
circulation-Rapidity of entire circulation-Local variations in different
parts........ 246-288
CHAPTER XV.
IMBIBITION AND EXHALATION.-THE LYMPHATIC SYSTEM.
Endosmosis and exosmosis-Mode of exhibiting them-Conditions which regulate their activity-Nature of the membrane-Extent of contact-Constitution of the liquids-Temperature-Pressure-Nature of endosmosis-Its
conditions in the living body-Its rapidity-Phenomena of endosmosis in
the circulation-The lymphatics-Their origin-Constitution of the lymph
and chyle-Their quantity-Liquids secreted and reabsorbed in twenty-four
hours........ 289-305
CHAPTER XVI.
SECRETION.
Nature of secretion-Variations in activity-Mucus-Sebaceous matter-Its
varieties-Perspiration-Structure of perspiratory glands-Composition and
quantity of the perspiration-Its use in regulating the animal temperatureTears-Milk-Its acidification-Secretion of bile-Anatomical peculiarities.
306-322




CONTENTS.                               XV
CHAPTER XVII.
EXCRETION.
PAGE
Nature of excretion-Excrementitious substances-Effect of their retentionUrea-Its source-Conversion into carbonate of ammonia-Daily quantity
of urea-Creatine-Creatinine-Urate of soda-Urates of potassa and ammonia-General characters of the urine-Its composition-Variations-Accidental ingredients of the urine-Acid and alkaline fermentations-Final
decomposition of the urine...    323-346
SECTION II.
NERVOUS SYSTEM.
CHAPTER I.
GENERAL CHARACTER AND FUNCTIONS OF THE NERVOUS SYSTEM.
Nature of the function performed by nervous system-Two kinds of nervous
tissue-Fibres of white substance-Their minute structure-Division and
inosculation of nerves-Gray substance-Nervous system of radiata-Of
mollusca-Of articulata-Of mammalia and human subject-Structure of
encephalon-Connections of its different parts..    347-369
CHAPTER  II.
OF NERVOUS IRRITABILITY, AND ITS MODE OF ACTION.
Irritability of muscles-How exhibited-Influences which exhaust and destroy
it-Nervous irritability-How exhibited-Continues after death-Exhausted
by repeated excitement-Influence of direct and inverse electrical currents
-Nervous irritability distinct from muscular irritability-Nature of the
nervous force-Its resemblance to electricity-Differences between the two
370-381
CHAPTER III.
THE SPINAL CORD.
Power of sensation-Power of motion-Distinct seat of sensation and motion
in nervous system-Sensibility and excitability-Distinct seat of sensibility
and excitability in spinal cord-Crossed action of spinal cord-Independent
and associated action of motor and sensitive filaments-Reflex action of
spinal cord-How manifested during disease-Influence in health on
sphincters, voluntary muscles, urinary bladder, &c...        382-400




xvi                            CONTENTS.
CHAPTER IV.
THE BRAIN.
PAGE
Seat of sensibility and excitability in different parts of the encephalon-Olfactory ganglia-Optic thalami-Corpora striata-Hemispheres-Remarkable
cases of injury of hemispheres-Effect of their removal-Imperfect development in idiots-Aztec children-Theory of phrenology-Cerebellum-Effect
of its injury or removal-Comparative development in different classesTubercula quadrigemina-Tuber annulare-Medulla oblongata-Three kinds
of reflex action in nervous system..401-429
CHAPTER V.
THE CRANIAL NERVES.
Olfactory nerves-Optic nerves-Auditory nerves-Classification of cranial
nerves-Motor nerves-Sensitive nerves-Motor oculi communis-Patheticus-Motor externus-Fifth pair-Its sensibility-Effect of division-Influence on mastication-Influence on the organ of sight-Facial nerve-Effect
of its paralysis-Glosso-pharyngeal nerve-Pneumogastric-Its distribution
-Influence on pharynx and cesophagus-On larynx-On lungs-On stomach
and digestion-Spinal accessory nerve-Hypoglossal... 430-461
CHAPTER VI.
THE SPECIAL SENSES.
General and special sensibility-Sense of touch in the skin and mucous membranes-Nature of the special senses-TAsTE-Apparatus of this sense-Its
conditions-Its resemblance to ordinary sensation-Injury to the taste in
paralysis of the facial nerve-SMELL-Arrangement of nerves in nasal passages-Conditions of this sense-Distinction between odors and irritating
vapors-SIGHT-Structure of the eyeball-Special sensibility of the retinaAction of the lens-Of the iris-Combined action of two eyes-Vivid nature
of the visual impressions-HEARING-Auditory apparatus-Action of membrana tympani-Of chain of bones-Of their muscles-Appreciation of the
direction of sound-Analogies of hearing with ordinary sensation. 462-497
CHAPTER VII.
SYSTEM OF THE GREAT SYMPATHETIC.
Ganglia of the great sympathetic-Distribution of its nerves-Sensibility and
excitability of sympathetic-Sluggish action of this nerve-Influence over
organs of special sense-Elevation of temperature after division of sympathetic-Contraction of pupil following the same operation-Reflex actions
taking place through the great sympathetic..498-508




CONTENTS.                            XVii
SECTION   III.
REPRODUCTION.
CHAPTER I.
ON THE NATURE (F REPRODUCTION, AND THE ORIGIN OF PLANTS AND
ANIMALS.
PAGE
Nature and objects of the function of reproduction-Mode of its accomplishment-By generation from parents-Spontaneous generation-Mistaken instances of this mode of generation-Production of infusoria-Conditions of
their development-Schultze's experiment on generation of infusoria-Production of animal and vegetable parasites-Encysted entozoa-Trichina
spiralis-Taenia-Cysticercus-Production of tsenia from cysticercus-Of
cysticercus from eggs of tsenia-Planlts and animals always produced by
generation from parents...... 509-523
CHAPTER  II.
ON SEXUAL GENERATION AND THE MODE OF ITS ACCOMPLISHMENT.
Sexual apparatus of plants-Fecundation of the germ-Its development into
a new plant-Sexual apparatus of animals-Ovaries and testicles-Unisexual and' bisexual species-Distinctive characters of the two sexes  524-527
CHAPTER III.
ON THE EGG, AND THE FEMALE ORGANS OF GENERATION.
Size and appearance of the egg-Vitelline membrane-Vitellus-Germinative
vesicle-Germinative spot-Ovaries-Graafian follicles-Oviducts-Female
generative organs of frog-Ovary and oviduct of fowl-Changes in the egg,
while passing through the oviduct-Complete fowl's egg-Uterus and ovaries of the sow —Female generative apparatus of the human subject-Fallopian tubes-Body of the uterus-Cervix of the uterus.. 528-539
CHAPTER IV.
ON THE SPERMATIC FLUID, AND THE MALE ORGANS OF GENERATION.
The spermatozoa-Their varieties in different species-Their movement-Formation of spermatozoa in the testicles-Accessory male organs of generation
- Epididymis - Vas deferens -Vesiculae seminales - Prostate - Cowper's
glands-Function of spermatozoa-Physical conditions of fecundation 540-546
2




xv1ii                          CONTENTS.
CHAPTER V.
ON PERIODICAL OVULATION, AND THE FUNCTION OF MENSTRUATION.
PAGE
PERIODICAL OVULATION-Pre-existence of eggs in the ovaries of all animalsTheir increased development at the period of puberty-Their successive
ripening and periodical discharge-Discharge of eggs independently of sexual
intercourse-Rupture of Graafian follicle, and expulsion of the egg-Phenomena of cestruation-MENSTRUATION-Correspondence of menstrual periods
with periods of ovulation in the lower animals-Discharge of egg during
menstrual period-Conditions of its impregnation, after leaving the ovary
547-559
CHAPTER VI.
ON THE CORPUS LUTEUM OF MENSTRUATION AND PREGNANCY.
CoRPUS LUTEUM OF MENSTRUATION-Discharge of blood into the ruptured Graafian
follicle-Decolorization of the clot, and hypertrophy of the membrane of the
vesicle-Corpus luteum of menstruation, at the end of three weeks-Yellow
coloration of convoluted wall-Corpus luteum of menstruation at the end
of four weeks-Shrivelling and condensation of its tissues-Its condition at
the end of nine weeks-Its final atrophy and disappearance-CORPUS LUTEUAI
OF PREGNANCY-Its continued development after the third week-Appearance
at the end of second month-Of fourth month-At the termination of pregnancy-Its atrophy and disappearance after delivery-Distinctive characters
of corpora lutea of menstruation and pregnancy... 560-569
CHAPTER VII.
ON THE DEVELOPMENT OF THE IMPREGNATED EGG.
Segmentation of the vitellus-Formation of blastodermic membrane-Two
layers of blastodermic membrane-Thickening of external layer-Formation
of primitive trace-Dorsal plates-Abdominal plates-Closure of dorsal and
abdominal plates on the median line-Formation of intestine-Of mouth
and anus-Of organs of locomotion-Continued development of organs, after
leaving the egg........ 570-579
CHAPTER VIII.
THE UMBILICAL VESICLE.
Separation of vitelline sac into two cavities-Closure of abdominal walls, and
formation of umbilical vesicle in fish-Mode of its disappearance after hatching-Umbilical vesicle in human embryo-Formation and growth of pedicle
-Disappearance of umbilical vesicle during embryonic life.. 580-582




CONTENTS.                               xiX
CHAPTER IX.
AMNION AND ALLANTOIS-DEVELOPMENT OF THE CHICK.
PAGE
Necessity for accessory organs in thedevelopment of birds and quadrupedsFormation of amniotic folds-Their union and adhesion-Growth of allantois
from lower part of intestine-Its vascularity-Allantois in the egg of the
fowl-Respiration of the egg-Absorption of calcareous matter from the
shell-Ossification of skeleton-Fracture of egg-shell-Casting off of amnion
and allantois....... 583-591
CHAPTER X.
DEVELOPMENT OF THE EGG IN THE HUMAN SPECIES-FORMATION OF THE
CHORION.
Conversion of allantois into chorion-Subsequent changes of the chorionIts villosities-Formation of bloodvessels in villosities-Action of villi of
chorion in providing for nutrition of foetus —Proofs that the chorion is formed
from the allantois-Partial disappearance of villosities of chorion, and
changes in its external surface....                592-597
CHAPTER XI.
DEVELOPMENT OF UTERINE MUCOUS MEMBRANE-FORMATION OF THE
DECIDUA.
Structure of uterine mucous membrane-Uterine tubules-Thickening of uterine mucous membrane after impregnation-Decidua vera-Entrance of egg
into uterus-Decidua reflexa-Inclosure of egg by decidua reflexa-Union
of chorion with decidua-Changes in the relative development of different
portions of chorion and decidua..... 598-604
CHAPTER XII.
THE PLACENTA.
Nourishment of foetus by maternal and fcetal vessels-Arrangement of the
vascular membranes in different species of animals-Membranes of foetal
pig-Cotyledon of cow's uterus-Development of fcetal tufts in human placenta-Development of uterine sinuses-Relation of fcetal and maternal
bloodvessels in the placenta-Proofs that the maternal sinuses extend
through the whole thickness of the placenta-Absorption and exhalation
by the placental vessels.... 605-613




XX                            CONTENTS.
CHAPTER XIII.
DISCHARGE OF THE OVUM, AND INVOLUTION OF THE UTERUS.
PAGE
Enlargement of amniotic cavity-Contact of amnion and chorion-Amniotic
fluid-Movements of foetus-Union of decidua vera and reflexa-Expulsion
of the ovum and discharge of decidual membrane-Separation of the placenta-Formation of new mucous membrane underneath the old deciduaFatty degeneration and reconstruction of muscular walls of uterus    614-620
CHAPTER XIV.
DEVELOPMENT OF THE EMBRYO-NERVOUS SYSTEM, ORGANS OF SENSE,
SKELETON AND LIMBS.
Formation of spinal cord and cerebro-spinal axis-Three cerebral vesiclesHemispheres-Optic thalaini-Tubercula quadrigemina-Cerebellum-Medulla oblongata-Eye-Pupillary membrane-Skeleton-Chorda dorsalisBodies of the vertebre —Laminse and ribs-Spina bifida —Anterior and posterior extremities -Tail-Integument-Hair-Vernix caseosa-Exfoliation
of epidermis....... 621-627
CHAPTER XV.
DEVELOPMENT OF THE ALIMENTARY CANAL AND ITS APPENDAGES.
Formation of intestine  Stomach-Duodenum-Convolutions of intestineLarge and small intestine-Caput coli and appendix vermiformis-Umbilical hernia-Formation of urinary bladder-Urachus-Vesico-rectal septum
-Perineum -Liver-Secretion of bile —Gastric juice-Meconium-Glycogenic function of liver-Diabetes of foetus-Pharynx and cesophagus-Diaphragm-Diaphragmatio hernia-Heart and pericardium-Ectopia cordisDevelopment of the face....628-637
CHAPTER XVI.
DEVELOPMENT OF THE KIDNEYS, WOLFFIAN BODIES, AND INTERNAL ORGANS
OF GENERATION.
Wolffian bodies-Their structure-First appearance of kidneys -Growth of
kidneys, and atrophy of Wolffian bodies-Testicles and ovaries-Descent of
the testicles-Tunica vaginalis testis-Congenital inguinal hernia-Descent
of the ovaries-Development of the uterus.                   638-647




CONTENTS.                               xxi
CHAPTER XVII.
DEVELOPMENT OF THE CIRCULATORY APPARATUS.
PAGE
First, or vitelline circulation-Area vasculosa-Sinus terminalis-Vitelline
circulation of fish-Arrangement of arteries and veins in body of foetusSecond, or placental circulation-Omphalo-mesenteric arteries and veinCirculation of the umbilical vesicle-Of the allantois and placenta-Umbilical arteries and veins-Third, or adult circulation-Portal and pulmonary
systems-Development of the arterial system-Development of the venous
system-Changes in the hepatic circulation-Portal vein-Umbilical vein
-Ductus venosus-Changes in the cardiac circulation-Division of heart
into right and left cavities-Aorta and pulmonary artery-Ductus arteriosus
-Foramen ovale and Eustachian valve-Changes in circulation at the period of birth....... 648-669
CHAPTER XVIII.
DEVELOPMENT OF THE BODY AFTER BIRTH.
Condition of foetus at birth-Gradual establishment of respiration-Inactivity
of the animal functions-Preponderance of reflex actions in the nervous
system-Peculiarities in the action of drugs on infant-Difference in relative
size of organs, in infant and adult-Withering and separation of umbilical
cord-Exfoliation of epidermis-First and second sets of teeth-Subsequent
changes in osseous, muscular and tegumentary systems, and general development of the body....... 670-673
2*








LIST OF ILLUSTRATIONS,
ALL OF WHICH HAVE BEEN PREPARED FROM ORIGINAL DRAWINGS, WITH THE
EXCEPTION OF TEN, CREDITED TO THEIR AUTHORITIES.
FIG.                                                                          PAGE
1. Fibula tied in a knot, after maceration in a dilute acid...    59
2. Grains of potato starch.......    64
3. Starch grains of Bermuda arrowroot.....    64
4. Starch grains of wheat flour....            65
5. Starch grains of Indian corn......    65
6. Starch grains from wall of lateral ventricle....    66
7. Stearine........    71
8. Oleaginous principles of human fat.....    72
9. Human adipose tissue.......    74
10. Chyle........    74
11. Globules of cow's milk.......    75
12. Cells of costal cartilages.......    75
13. Hepatic cells........    76
14. Uriniferous tubules of dog......    76
15. Muscular fibres of human uterus.....    77
16. Alimentary canal of fowl...... 101
17. Compound stomach of ox...   From IRymer Jones   102
18. Human alimentary canal......   103
19. Skull of rattlesnake...        From Achille Richard   105
20. Skull of polar bear...... 106
21. Skull of the horse.......   106
22. Molar tooth of the horse....... 106
23. Human teeth-upper jaw...                                    107
24. Buccal and glandular epithelium deposited from saliva...   108
25. Gastric mucous membrane, viewed from above....   117
26. Gastric mucous membrane, in vertical section.... 117
27. Mucous membrane of pig's stomach.....   117
28. Gastric tubules from pig's stomach, pyloric portion...   118
29. Gastric tubules from pig's stomach, cardiac portion...   118
30. Confervoid vegetable, growing in gastric juice...124
31. Follicles of Lieberkiihn....... 135
32. Brunner's duodenal glands......   136
33. Contents of stomach, during digestion of meat...142
34. From duodenum of dog, during digestion of meat...   142
35. From middle of small intestine......   143




Xxiv                    LIST  OF  ILLUSTRATIONS.
FIG.                                                                           PAGE
36. From last quarter of small intestine.                          143
37. One of the closed follicles of Peyer's patches.... 145
38. Glandulae agminatae.......   145
39. Extremity of intestinal villus......   146
40. Panizza's experiment on absorption by bloodvessels...   148
41. Chyle, from commencement of thoracic duct....   150
42. Lacteals, thoracic duct, &....... 151
43. Lacteals and lymphatics.                                                   153
44. Intestinal epithelium, in intervals of digestion...   155
45. Intestinal epithelium, during digestion.....   155
46. Cholesterin........ 160
47. Ox-bile, crystallized....... 161
48. Glyko-cholate of soda from ox-bile.....   161
49. Glyko-cholate and tauro-cholate of soda, from ox-bile...   162
50. Dog's bile, crystallized....... 165
51. Human bile, showing resinous matters.....   166
52. Crystalline and resinous biliary substances, from dog's intestine.  172
53. Duodenal fistula........   173
54. Human blood-globules....... 196
55. The same, seen out of focus...... 196
56. The same, seen within the focus.                                           197
57. The same, adhering together in rows... 197
58. The same, swollen by addition of water...199
59. The same, shrivelled by evaporation.....   199
60. Blood-globules of fog.......   202
61. White globules of the blood......   203
62. Coagulated fibrin........   205
63. Coagulated blood....... 208
64. Coagulated blood, after separation of clot and serum...   209
65. Recent coagulum........   212
66. Coagulated blood, clot buffed and cupped..   212
67. Head and gills of menobranchus....215
68. Lung of frog........   216
69. Human larynx, trachea, bronchi, and lungs....   217
70. Single lobule of human lung... 217
71. Diagram illustrating the respiratory movements...   219
72. Small bronchial tube.......   221
73. Human larynx, with glottis closed...   222
74. The same, with glottis open... 222
75. Human larynx-posterior view......   223
76. Circulation of fish.......   247
77. Circulation of reptiles.......   248
78. Circulation of mammalians.....   249
79. Human heart, anterior view.....   250
80. Human heart, posterior view.....   250
81. Right auricle and ventricle, tricuspid valve open, arterial valves closed    250
82. Right auricle and ventricle, tricuspid valve closed, arterial valves open    251
83. Course of blood through the heart....   252
84. Illustrating production of valvular sounds.... 255
85. Heart of frog, in relaxation..... 258




LIST  OF  ILLUSTRATIONS.                             XXV
FIG.                                                                          PAGE
86. Heart of frog, in contraction......   258
87. Simple looped fibres.......258
88. Bullock's heart, showing superficial muscular fibres...   259
89. Left ventricle of bullock's heart, showing deep fibres...  259
90. Diagram of circular fibres of the heart.... 260
91. Converging fibres of the apex of the heart....   260
92. Artery in pulsation......265
93. Curves of the arterial pulsation...           267
94. Volkmann's apparatus.....   271
95. The same.                                                        271
96. Vein, with valves open......   275
97. Vein, with valves closed.....           275
98. Small artery, with capillary branches.                                  277
99. Capillary network.......278
100. Capillary circulation....... 279
101. Diagram of the circulation......   287
102. Follicles of a compound mucous glandule.         From Kolliker   309
103. Meibomian glands..                From Ludovic   311
104. Perspiratory gland...     From Todd and Bowman   312
105. Glandular structure of mamma.....   315
106. Colostrum corpuscles....... 316
107. Milk-globules....... 317
108. Division of portal vein in liver.....   320
109. Lobule of liver........ 321
110. Hepatic cells........ 322
111. Urea....    From Lehmann (Funke's Atlas)   326
112. Creatine....     From Lehmann (Funke's Atlas)   328
113. Creatinine...    From Lehmann (Funke's Atlas)   329
114. Urate of soda.......           330
115. Uric acid....... 336
116. Oxalate of lime........ 342
117. Phosphate of magnesia and ammonia.....   344
118. Nervous filaments, from brain.....   351
119. Nervous filaments, from sciatic nerve.....   352
120. Division of a nerve......           353
121. Inosculation of nerves.......                       354
122. Nerve cells.......           354
123. Nervous system of starfish......   355
124. Nervous system of aplysia......   357
125. Nervous system of centipede......358
126. Cerebro-spinal system of man....   361
127. Spinal cord.......362
128. Brain of alligator......   364
129. Brain of rabbit........ 365
130. Medulla oblongata of human brain.....   366
131. Diagram of human brain.....   368
132. Experiment showing irritability of muscles....   371
133. Experiment showing irritability of nerve....   373
134. Action of direct and inverse currents.....   376
135. Diagram of spinal cord and nerves.....   386




xxvi                     LIST OF ILLUSTRATIONS.
FIG.                                                                              PAGE
136. Spinal cord in vertical section......   393
137. Experiment, showing effect of poisons on nerves...   396
138. Pigeon, after removal of the hemispheres....   405
139. Aztec children..                                  410
140. Brain in situ.......   412
141. Transverse section of brain......   413
142. Pigeon, after removal of the cerebellum....   415
143. Brain of healthy pigeon in profile.....   417
144. Brain of operated pigeon in profile..... 417
145. Brain of healthy pigeon, posterior view....   417
146. Brain of operated pigeon, posterior view....   417
147. Inferior surface of brain of cod......   420
148. Inferior surface of brain of fowl.....   420
149. Course of optic nerves in man......   421
150. Distribution of fifth nerve upon the face....   436
151. Facial nerve........   441
152. Pneumogastric nerve.....   446
153. Diagram of tongue.......   467
154. Distribution of nerves in the nasal passages....   473
155. Vertical section of eyeball...... 477
156. Dispersion of rays of light......   479
157. Action of crystalline lens.....   479
158. Myopia......... 480
159. Presbyopia........ 480
160. Vision at short distance......   481
161. Vision at long distance.......   481
162. Refraction of lateral rays...... 484
163. Skull, as seen by left eye......   486
164. Skull, as seen by right eye...... 486
165. Human auditory apparatus......   491
166. Great sympathetic.......   499
167. Cat, after division of sympathetic in the neck....   506
168. Different kinds of infusoria......   514
169. Experiment on spontaneous generation..        From Schultze   516
170. Trichina spiralis....... 5i9
171. Taenia......... 520
172. Cysticercus, retracted.......   521
173. Cysticercus, unfolded.......   521
174. Blossom of Convolvulus purpureus....   524
175. Single articulation of Tenia crassicollis....   525
176. Human ovum........   528
177.  tuman ovum, ruptured by pressure.....   529
178. Female generative organs of frog.....   531
179. Mature frogs' eggs.......   532
180. Female generative organs of fowl.....   535
181. Fowl's egg........   536
182. Uterus and ovaries of the sow......   537
183. Generative organs of human female.....   538
184. Spermatozoa........   541
185. Graafian follicle....... 552




LIST  OF  ILLUSTRATIONS.                           XXvii
FIG.                                                                          PAGE
186. Ovary with Graafian follicle ruptured....          552
187. Graafian follicle, ruptured and filled with blood...   561
188. Corpus luteum, three weeks after menstruation...   562
189. Corpus luteum, four weeks after menstruation...   563
190. Corpus luteum, nine weeks after menstruation...   563
191. Corpus luteum of pregnancy, at end of second month...   566
192. Corpus luteum of pregnancy, at end of fourth month...   566
193. Corpus luteum of pregnancy, at term.....   567
194. Segmentation of the vitellus......   571
195. Impregnated egg, showing embryonic spot....   574
196. Impregnated egg, showing two layers of blastodermic membrane.   575
197. Impregnated egg, farther advanced.....   575
198. Frog's egg, at an early period.....   576
199. Egg of frog, in process of development.....   576
200. Egg of frog, farther advanced.....           576
201. Tadpole, fully developed...... 577
202. Tadpole, changing into frog......   578
203. Perfect frog........ 578
204. Egg of fish........ 580
205. Young fish, with umbilical vesicle.....   581
206. Human embryo, with umbilical vesicle.... 581
207. Fecundated egg, showing formation of amnion...584
208. Fecundated egg, showing commencement of allantois...   585
209. Fecundated egg, with allantois nearly complete...   585
210. Fecundated egg, with allantois fully formed....   586
211. Egg of fowl, showing area vasculosa....   587
212. Egg of fowl, showing allantois, amnion, &c.....   588
213. Human ovum, showing formation of chorion....   592
214. Human chorion.......   594
215. Villosity of chorion....... 595
216. Human ovum, at end of third month..... 596
217. Uterine mucous membrane...... 599
218. Uterine tubules........ 599
219. Impregnated uterus, showing formation of decidua...   601
220. Impregnated uterus, showing formation of decidua reflexa..   601
221. Impregnated uterus, with decidua refiexa complete...   601
222. Impregnated uterus, showing union of chorion and decidua..   603
223. Pregnant uterus, showing formation of placenta...   604
224. Foetal pig, with membranes.....   606
225. Cotyledon of cow's uterus......   606
226. Fcetal tuft of human placenta.                                          609
227. Vertical section of placenta.....   609
228. Human ovum, at end of first month..   614
229. Human ovum, at end of third month.....   615
230. Gravid human uterus and contents..   616
231. Muscular fibres of unimpregnated uterus.... 619
232. Muscular fibres of human uterus, ten days after parturition..   619
233. Muscular fibres of human uterus, three weeks after parturition.   620
234. Formation of cerebro-spinal axis....   621
235. Formation of cerebro-spinal axis.....   622




xxviii                  LIST  OF  ILLUSTRATIONS.
FIG.                                                                          PAGE
236. Fcetal pig, showing brain and spinal cord....   622
237. Fcetal pig, showing brain and spinal cord.... 623
238. Head of foetal pig.......   623
239. Brain of adult pig......623
240. Formation of alimentary canal.                                           6. 29
241. Head of human embryo, at twenty days.. From Longet   635
242. Head of human embryo, at end of sixth week....   636
243. Head of human embryo, at end of second month...   636
244. Feetal pig, showing Wolffian bodies..                  638
245. Foetal pig, showing first appearance of kidneys...   640
246. Internal organs of generation.....   640
247. Internal organs of generation.....   642
248. Formation of tunica vaginalis testis....   643
249. Congenital inguinal hernia.....   644
250. Egg of fowl, showing area vasculosa.....   649
251. Egg of fish, showing vitelline circulation....   649
252. Young embryo and its vessels......   650
253. Embryo and its vessels, farther advanced...   651
254. Arterial system, embryonic form...           653
255. Arterial system, adult form.....653
256. Early condition of venous system..   655
257. Venous system, farther advanced....   656
258. Continued development of venous system.... 656
259. Adult condition of venous system.....   657
260. Early form of hepatic circulation.....   658
261. Hepatic circulation farther advanced.....   659
262. Hepatic circulation, during latter part of foetal life...   659
263. Adult form of hepatic circulation..... 660
264. Fcetal heart........ 661
265. Foetal heart........   661
266. Foetal heart.......661
267. Foetal heart........ 662
268. Heart of infant.......   662
269. Heart of human foetus, showing Eustachian valve...   664
270. Circulation through the foetal heart....   665
271. Adult circulation through the heart...   668




HUMAN PHYSIOLOGY.
I N TRODU C T ION.
I. PHYSIOLOGY is the study of the phenomena presented by
organized bodies, animal and vegetable.
These phenomena are different from those presented by inorganic
substances. They require, for their production, the existence of
peculiarly formed animal and vegetable organisms, as well as the
presence of various external conditions, such as warmth, light, air,
moisture, &c.
They are accordingly more complicated than the phenomena of
the inorganic world, and require for their study, not only a previous acquaintance with the laws of chemistry and physics, but, in
addition, a careful examination of other characters which are peculiar to them.
These peculiar phenomena, by which we so readily distinguish
living organisms from inanimate substances, are called Vitalphenomena, or the phenomena of Life. Physiology consequently includes
the study of all these phenomena, in whatever order or species of
organized body they may originate.
We find, however, upon examination, that there are certain
general characters by which the vital phenomena of vegetables resemble each other, and by which they are distinguished from the
vital phenomena of animals.  Thus, vegetables absorb carbonic
acid, and exhale oxygen; animals absorb oxygen, and exhale carbonic acid. Vegetables nourish themselves by the absorption of
unorganized liquids and gases, as water, ammonia, saline solutions,
&c.; animals require for their support animal or vegetable substances as food, such as meat, fruits, milk, &c. Physiology, then,
3




34                      INTRODUCTION.
is naturally divided into two parts, viz., Vegetable Physiology, and
Animal Physiology.
Again, the different groups and species of animals, while they
resemble each other in their general characters, are distinguished
by certain minor differences, both of structure and function, which
require a special study. Thus, the physiology of fishes is not
exactly the same with that of reptiles, nor the physiology of birds
with that of quadrupeds.  Among the warm-blooded quadrupeds,
the carnivora absorb more oxygen, in proportion to the carbonic
acid exhaled, than the herbivora. Among the herbivorous quadrupeds, the process of digestion is comparatively simple in the
horse, while it is complicated in the ox, and other ruminating animals. There is, therefore, a special physiology for every distinct
species of animal.
HUMAN PHYSIOLOGY treats of the vital phenomena of the human
species. It is more practically important than the physiology of
the lower animals, owing to its connection with human pathology
and therapeutics.  But it cannot be made the exclusive subject of
our study; for the special physiology of the human body cannot
be properly understood without a previous acquaintance with the
vital phenomena common to all animals, and to all vegetables;
beside which, there are many physiological questions that require
for their solution experiments and observations, which can only be
made upon the lower animals.
While the following treatise, therefore, has for its principal subject the study of Human Physiology, this will be illustrated, whenever it may be required, by what we know in regard to the vital
phenomena of vegetables and of the lower animals.
II. Since Physiology is the study of the active phenomena of
living bodies, it requires a previous acquaintance with their structure, and with the substances of which they are composed; that is,
with their anatomy.
Anatomy, again, requires a previous acquaintance with inorganic
substances; since some of these inorganic substances enter into the
composition of the body. Chloride of sodium, for example, water,
and phosphate of lime, are component parts of the animal frame,
and therefore require to be studied as such by the anatomist.
Now these inorganic substances, when placed under the requisite
external conditions, present certain active phenomena, which are
characteristic of them, and by which they may be recognized.




INTRODUCTION.                         35
Thus lime, dissolved in water, if brought into contact with carbonic acid, alters its condition, and takes part in the formation of
an insoluble substance, carbonate of lime, which is thrown downi
as a deposit. A knowledge of such chemical reactions as these is
necessary to the anatonist, since it is by them that he is enabled to
recognize the inorganic substances, forming a part of the animal
body.
It is important to observe, however, that a knowledge of these
reactions is necessary to the anatomist only in order to enable him
to judge of the presence or absence of the inorganic substances to
which they belong. It is the object of the anatomist to make himself acquainted with every constituent part of the body. Those
parts, therefore, which cannot be recognized by their form  and
texture, he distinguishes by their chemical reactions. But afterward, he has no occasion to decompose them further, or to make
them enter into new combinations; for he only wishes to know
these substances as they exist in the body, and not as they may exist
under other conditions.
The unorganized substances which exist in the body as component parts of its structure, such as chloride of sodium, water, phosphate of lime, &c., are called the proximate principles of the body.
Mingled together in certain proportions, they make up the animal
fluids, and associated also in a solid form, they constitute the tissues
and organs, and in this way make up the entire frame.
Anatomy makes us acquainted with all these component parts of
the body, both solid and fluid. It teaches us the structure of the
body in a state of rest; that is, just as it would be after life had
suddenly ceased, and before putrefaction had begun.  On the other
hand, Physiology is a description of the body in a state of activity.
It shows us its movements, its growth, its reproduction, and the
chemical changes which go on in its interior; and in order to comprehend these, we must know, beforehand, its entire mechanical,
textural, and chemical structure.
It is evident, therefore, that the description of the proximate prin.
ciples, or the chemical substances entering into the constitution of
the body, is, strictly speaking, a part of Anatomy. But there are
many reasons why this study is more conveniently pursued in connection with Physiology; for some of the proximate principles are
derived directly, as we shall hereafter show, from the external world,
and some are formed from the elements of the food in the process
of digestion; while most of them undergo certain changes in the




36                     INTRODUCTION.
interior of the body, which result in the formation of new substances; all these active phenomena belonging necessarily to the
domain of Physiology.
The description of the proximate principles of animals and vegetables will therefore be introduced into the following pages.
The description of the minute structures of the body, or JMicroscopic Anatomy, is also so closely connected with some parts of Physiology as to make it convenient to speak of them  together; and
this will accordingly be done, whenever the nature of the subject
may make it desirable.
III. The study of Physiology, like that of all the other natural
sciences, is a study of phenomena, and of phenomena alone. The
essential nature of the vital processes, and their ultimate causes,
are questions which are beyond the reach of the physiologist, and
cannot be determined by the means of investigation which are at
his disposal.
Consequently, all efforts to solve them will only serve to mislead
the investigator, and to distract his attention from the real subject
of examination. Much time has been lost, for example, in discussing the probable reason why menstruation returns, in the human
female, at the end of every four weeks. But the observation of
nature, which is our only means of scientific investigation, cannot
throw any light on this point, but only shows us the fact that menstruation does really recur at the above periods, together with the
phenomena which accompany it, and the conditions under which it
is hastened or retarded, and increased or diminished, in intensity
duration, &c. If we employ ourselves, consequently, in the discussion of the reason above mentioned, we shall only become involved
in a network of hypothetical surmises, which can never lead to any
definite result. Our time, therefore, will be much more profitably
devoted to the study of the above phenomena, which can be learned
from nature, and which constitute, afterward, a permanent acquisition.
The physiologist, accordingly, confines himself strictly to the
study of the vital phenomena, their characters, their frequency,
their regularity or irregularity, and the conditions under which
they originate.
When he has discovered that a certain phenomenon always takes
place in the presence of certain conditions, he has established what
is called a general principle, or a LAW of Physiology.




INTRODUCTION.                        37
As, for example, when he has ascertained that sensation and
motion occupy distinct situations in every part of the nervous
system.
This "Law," however, it must be remembered, is not a discovery
by itself, nor does it give him any new information, but is simply
the expression, in convenient and comprehensive language, of the
facts with which he was already previously acquainted. It is very
dangerous, therefore, to make these laws or general principles the
subjects of our study instead of the vital phenomena, or to suppose
that they have any value, except as the expression of previously
ascertained facts. Such a misconception would lead to bad practical results. For if we were to observe a phenomenon in discordance with a "law" or "principle," we might be led to neglect or
misinterpret the phenomenon, in order to preserve the law. But
this-would be manifestly incorrect. For the law is not superior to
the phenomenon, but, on the contrary, depends upon it, and derives
its whole authority from it. Such mistakes, however, have been
repeatedly made in Physiology, and have frequently retarded its
advance.
IV. There is only one means by which Physiology can be
studied: that is, the observation of nature. Its phenomena cannot
be reasoned out by themselves, nor inferred, by logical sequence,
from any original principles, nor from any other set of phenomena
whatever.
In Mathematics and Philosophy, on the other hand, certain truths
are taken for granted, or perceived by intuition, and the remainder
afterward derived from them by a process of reasoning. But in
Physiology, as in all the other natural sciences, there is no such
starting point, and it is impossible to judge of the character of a
phenomenon until after it has been observed. Thus, the only way
to learn what action is exerted by nitric acid upon carbonate of
soda is to put the two substances together, and observe the changes
which take place; for there is nothing in the general characters of
these two substances which could guide us in anticipating the result.
Neither can we infer the truths of Physiology from those of
Anatomy, nor the truths of one part of Physiology from those of
another part; but all must be ascertained directly and separately
by observation.
For, although one department of natural science is almost always
a necessary preliminary to the study of another, yet the facts of




38                     INTRODUCTION.
the latter can never be in the least degree inferred from those of the
former, but must be studied by themselves.
Thus Chemistry is essential to Anatomy, because certain substances, as we have already shown, belonging to Chemistry, such
as chloride of sodium, occur as constituents of the animal body.
Chemistry teaches us the composition, reactions, mode of crystallization, solubility, &c., of chloride of sodium; and if we did not
know these, we could not extract it, or recognize it when extracted
from the body. But, however well we might know the chemistry
of this substance, we could never, on that account, infer its presence
in the body or otherwise, nor in what quantities nor in what situations it would present itself. These facts must be ascertained for
themselves, by direct investigation, as a part of anatomy proper.
So, again, the structure of the body in a state of rest, or its
anatomy, is to be first understood; but its active phenomena or its
physiology must then be ascertained by direct observation and
experiment. The most intimate knowledge of the minute structure of the muscular and nervous fibres could not teach us anything of their physiology.  It is only by experiment that we
ascertain one of them to be contractile, the other sensitive.
Many of the phenomena of life are chemical in their character,
and it is requisite, therefore, that the physiologist know the ordinary chemical properties of the substances composing the animal
frame.  But no amount of previous chemical knowledge will
enable him to foretell the reactions of any chemical substance in
the interior of the body; because the peculiar conditions under
which it is there placed modify these reactions, as an elevation or
depression of temperature, or other external circumstance, might
modify them outside the body.
We must not, therefore, attempt to deduce the chemical phenomena of physiology from  any previously established facts, since
these are no safe guide; but must study them by themselves, and
depend for our knowledge of them upon direct observation alone.
V. By the term  Vital phenomena, we mean those phenomena
which are manifested in the living body, and which are characteristic of its functions.
Some of these phenomena are physical or mechanical in their
character; as, for example, the play of the articulating surfaces
upon each other, the balancing of the spinal column with its appendages, the action of the elastic ligaments. Nevertheless, these




INTRODUCTION.                         39
phenomena, though strictly physical in character, are often entirely
peculiar and different from those seen elsewhere, because the mechanism of their production is peculiar in its details. Thus the
human voice and its modulations are produced in the larynx, in
accordance with the general physical laws of sound; but the
arrangement of the elastic and movable vocal chords, and their
relations with the columns of air above and below, the moist and
flexible mucous membrane, and the contractile muscles outside, are
of such a special character that the entire apparatus, as well as the
sounds produced by it, is peculiar; and its action cannot be properly
compared with that of any other known musical instrument.
In the same manner, the movements of the heart are so complicated and remarkable that they cannot be comprehended, even by
one who is acquainted with the anatomy of the organ, without a
direct examination. This is not because there is anything essentially obscure or mysterious in their nature, for they are purely
mechanical in character; but because their conditions are so peculiar, owing to the tortuous course of the muscular fibres, their
arrangement in interlacing layers, their attachments and relations,
that their combined action produces an effect altogether peculiar,
and one which is not similar to anything outside the living body.
A  very large and important class of the vital phenomena are
those of a chemical character. It is one of the characteristics of
living bodies that a succession of chemical actions, combinations
and decompositions, is constantly going on in their interior. It is
one of the necessary conditions of the existence of every animal
and every vegetable, that it should constantly absorb various substances from without, which undergo different chemical alterations
in its interior, and are finally discharged from it under other forms.
If these changes be prevented from taking place, life is immediately
extinguished.  Thus animals constantly absorb, on the one hand,
water, oxygen, salts, albumen, oil, sugar, &c., and give up, on the
other hand, to the surrounding media, carbonic acid, water, ammonia,
urea, and the like; while between these two extreme points, of absorption and exhalation, there take place a multitude of different
transformations which are essential to the continuance of life.
Some of these chemical actions are the same with those which
are seen outside the body; but most of them are entirely peculiar,
and do not take place, and cannot be made to take place, anywhere
else. This, again, is not because there is anything particularly
mysterious or extraordinary in their nature, but because the con



40                      INTRODUCTION.
ditions necessary for their accomplishment exist in the body, and
do not exist elsewhere. All chemical phenomena are liable to be
modified by surrounding conditions. Many reactions, for example,
which will take place at a high temperature, will not take place at
a low temperature, and vice versa. Some will take place in the light,
but not in the dark; others will take place in the dark, but not in
the light. If a hot concentrated solution of sulphate of soda be
allowed to cool in contact with the atmosphere, it crystallizes;
covered with a film of oil, it remains fluid. Because a chemical
reaction, therefore, takes place under one set of conditions, we cannot be at all sure that it will also take place under others, which
are different.
The chemical conditions of the living body are exceedingly complicated. In the animal solids and fluids there are many substances
mingled together in varying quantities, which modify or interfere
with each other's reactions. New substances are constantly entering
by absorption, and old ones leaving by exhalation; while the circulating fluids are constantly passing from one part of the body to
another, and coming in contact with different organs of different
texture and composition. All these conditions are peculiar, and so
modify the chemical actions taking place in the body, that they are
unlike those met with anywhere else.
If starch and iodine be mingled together in a watery solution,
they unite with each other, and strike a deep opaque blue color;
but if they be mingled in the blood, no such reaction takes place,
because it is prevented by the presence of certain organic substances
which interfere with it.
If dead animal matter be exposed to warmth, air, and moisture,
it putrefies; but if introduced into the living stomach, even after
putrefaction has commenced, this process is arrested, because the
fluids of the stomach cause the animal substance to undergo a
peculiar transformation (digestion), after which the bloodvessels
immediately remove it by absorption. There are also certain substances which make their appearance in the living body, both of
animals and vegetables, and which cannot be formed elsewhere;
such as fibrin, albumen, casein, pneumic acid, the biliary salts, morphine, &c. These substances cannot be manufactured artificially,
simply because the necessary conditions cannot be imitated. They
require for their production the presence of a living organism.
The chemical phenomena of the living body are, therefore, not
different in their nature from any other chemical phenomena; but




INTRODUCTION.                       41
they are different in their conditions and in their results, and are
consequently peculiar and characteristic.
Another set of vital phenomena are those which are manifested
in the processes of reproduction and development. They are again
entirely distinct from  any phenomena which are exhibited by
matter not endowed with life. An inorganic substance, even when
it has a definite form, as, for example, a crystal of fluorspar, has
no particular relation to any similar form which has preceded, or
any other which is to follow it. On the other hand, every animal
and every vegetable owes its origin to preceding animals or vegetables of the same kind; and the manner in which this production
takes place, and the different forms through which the new body
successively passes in the course of its development, constitute the
phenomena of reproduction. These phenomena are mostly dependent on the chemical processes of nutrition and growth, which take
place in a particular direction and in a particular manner; but their
results, viz., the production of a connected series of different forms,
constitute a separate class of phenomena, which cannot be explained
in any manner by the preceding, and require, therefore, to be studied
by themselves.
Another set of vital phenomena are those which belong to the
nervous system. These, like the processes of reproduction and
development, depend on the chemical changes of nutrition and
growth. That is to say, if the nutritive processes did not go on in
a healthy manner, and maintain the nervous system in a healthy
condition, the peculiar phenomena which are characteristic of it
could not take place. The nutritive processes are necessary conditions of the nervous phenomena. But there is no other connection
between them; and the nervous phenomena themselves are distinct
from all others, both in their nature and in the mode in which they
are to be studied.
A troublesome confusion might arise if we were to neglect the
distinction that really exists between these different sets of phenomena, and confound them  together under the expectation of
thereby simplifying our studies. Since this can only be done by
overlooking real points of difference, its effect will merely be to
introduce erroneous ideas and suggest unfounded similarities, and
will therefore inevitably retard our progress instead of advancing it.
It has been sometimes maintained, for example, that all the vital
phenomena, those of the nervous system included, are to be reduced
to the chemical changes of nutrition, and that these again are to be




42                      INTRODUCTI'ON.
regarded as not at all different in any respect from the ordinary
chemical changes taking place outside the body. This, however,
is not only erroneous in theory, but conduces also to a vicious
mode of study. For it draws away our attention from the phenomena themselves and their real characteristics, and leads us to
deduce one set of phenomena from what we know of another; a
method which we have already shown to be unsafe and pernicious.
It has also been asserted that the phenomena of the nervous
system are identical with those of electricity; for no other reason
than that there exist between them certain general resemblances.
But when we examine the phenomena in detail, we find that, beside
these general resemblances, there are many essential points of dissimilarity, which must be suppressed and kept out of sight in order
to sustain the idea of the assumed identity. This assumption is
consequently a forced and unnatural one, and the simplicity which
it was intended to introduce into our physiological theories is
imaginary and deceptive, and is attained only by sacrificing a part
of those scientific truths, which are alone the real object of our
study.  We should avoid, therefore, making any such unfounded
comparisons; for the theoretical simplicity which results from them
does not compensate for the loss of essential scientific details.
VI. The study of Physiology is naturally divided into three distinct Sections:
The first of these includes everything which relates to the NUTRITION of the body in its widest sense. It comprises the history of
the proximate principles, their source, the manner of their production, the proportions in which they exist in different kinds of food
and drink, the processes of digestion and absorption, and the constitution of the circulating fluids; then the physical phenomena of
the circulation and the forces by which it is accomplished; the
changes which the blood undergoes in different parts of the body;
all the phenomena, both physical and chemical, of respiration; those
of secretion and excretion, and the character and destination of the
secreted and excreted fluids. All these processes have reference to
a common object, viz., the preservation of the internal structure and
healthy organization of the individual. With certain modifications,
they take place in vegetables as well as in animals, and are consequently known by the name of the vegetative functions.
The Second Section, in the natural order of study, is devoted to
the phenomena of the NERVOUS SYSTEM. These phenomena are




INTRODUCTION.                        43
not exhibited by vegetables, but belong exclusively to animal organizations. They bring the animal body into relation with the
external world, and preserve it from external dangers, by means of
sensation, movement, consciousness, and volition. They are more
particularly distinguished by the name of the animalfunctions.
Lastly comes the study of the entire process of REPRODUCTION.
Its phenomena, again, with certain modifications, are met with in
both animals and vegetables; and might, therefore, with some pro.
priety, be included under the head of vegetative functions. But
their distinguishing peculiarity is, that they have for their object
the production of new organisms, which take the place of the old
and remain after they have disappeared.  These phenomena do
not, therefore, relate to the preservation of the individual, but to
that of the species; and any study which concerns the species
comes properly after we have finished everything relating to the
individual.








SECTION I.
NUTRITION.
CHAPTER I.
PROXIMATE PRINCIPLES IN GENERAL.
THE study of NUTRITION begins naturally with that of the proximate principles, or the substances entering into the composition of
the different parts of the body, and the different kinds of food. In
examining the body, the anatomist finds that it is composed, first,
of various parts, which are easily recognized by the eye, and which
occupy distinct situations. In the case of the human body, for
example, a division is easily made of the entire frame into the
head, neck, trunk, and extremities. Each of these regions, again,
is found, on examination, to contain several distinct parts, or
" organs," which require to be separated from each other by dissection, and which are distinguished by their form, color, texture, and
consistency. In a single limb, for example, every bone and every
muscle constitutes a distinct organ. In the trunk, we have the
heart, the lungs, the liver, spleen, kidneys, spinal cord, &c., each of
which is also a distinct organ. When a number of organs, differing
in size and form, but similar in texture, are found scattered throughout the entire frame, or a large portion of it, they form a connected
set or order of parts, which is called a "system."  Thus, all the
muscles taken together constitute the muscular system; all the
bones, the osseous system; all the arteries, the arterial system.
Several entirely different organs may also be connected with each
other, so that their associated actions tend to accomplish a single
object, and they then form an "apparatus."  Thus the heart, arteries, capillaries, and veins, together, form the circulatory apparatus;
the stomach, liver, pancreas, intestine, &c., the digestive apparatus.
Every organ, again, on microscopic examination, is seen to be made




46         PROXIMATE PRINCIPLES IN GENERAL.
up of minute bodies, of definite size and figure, which are so small
as to be invisible to the naked eye, and which, after separation
from  each other, cannot be further subdivided without destroying
their organization.  They are, therefore, called "anatomical elements." Thus, in the liver, there are hepatic cells, capillary bloodvessels, the fibres of Glisson's capsule, and the ultimate filaments
of the hepatic nerves. Lastly, two or more kinds of anatomical
elements, interwoven with each other in a particular manner, form
a "tissue."   Adipose vesicles, with capillaries and nerve tubes,
form adipose tissue. White fibres and elastic fibres, with capillaries
and nerve tubes, form areolar tissue. Thus the solid parts of the
entire body are made up of anatomical elements, tissues, organs,
systems, and apparatuses.  Every organized frame, and even every
apparatus, every organ, and every tissue, is made up of different
parts, variously interwoven and connected with each other, and it
is this character which constitutes its organization.
But beside the above solid forms, there are also certain fluids,
which are constantly present in various parts of the body, and which,
from their peculiar constitution, are termed "animal fluids." These
fluids are just as much an essential part of the body as the solids.
The blood and the lymph, for example, the pericardial and synovial
fluids, the saliva, which always exists more or less abundantly in
the ducts of the parotid gland, the bile in the biliary ducts and the
gall-bladder: all these go to make up the entire body, and are quite
as necessary to its structure as the muscles or the nerves. Now, if
these fluids be examined, they are found to be made up of many
different substances, which are mingled together in certain proportions; these proportions being constantly maintained at or about
the same standard by the natural processes of nutrition.  Such a
fluid is termed an organized fluid.  It is organized by virtue of the
numerous ingredients which enter into its composition, and the
regular proportions in which these ingredients are maintained.
Thus, in the plasma of the blood, we have albumen, fibrin, water,
chlorides, carbonates, phosphates, &c. In the urine, we find water,
urea, urate of soda, creatine, creatinine, coloring matter, salts, &c.
These substances, which are mingled together so as to make up, in
each instance, by their intimate union, a homogeneous liquid, are
called the PROXIMATE PRINCIPLES of the animal fluid.
In the solids, furthermore, even in those parts which are apparently homogeneous, there is the same mixture of different ingredients.  In the hard substance of bone, for example, there is, first,




PROXIMATE PRINCIPLES IN GENERAL.                  47
water, which may be expelled by evaporation; second, phosphate
and carbonate of lime, which may be extracted by the proper solvents; third, a peculiar animal matter, with which these calcareous
salts are in union; and fourth, various other saline substances, in
special proportions. In the muscular tissue, there is chloride of
potassium, lactic acid, water, salts, albumen, and an animal matter
termed musculine. The difference in consistency between the solids
and fluids does not, therefore, indicate any radical difference in their
constitution. Both are equally made up of proximate principles,
mingled together in various proportions.
It is important to understand, however, exactly what are proximate principles, and what are not such; for since these principles
are extracted from the animal solids and fluids, and separated from
each other by the help of certain chemical manipulations, such as
evaporation, solution, crystallization, and the like, it might be supposed that every substance which could be extracted from an organized solid or fluid, by chemical means, should be considered as a
proximate principle. That, however, is not the case. A proximate
principle is properly defined to be any substance, whether simple or
compound, chemicall spealcing, which exists, under its own form, in the
animal solid or fluid, and which can be extracted by means which do
not alter or destroy its chemical properties. Phosphate of lime, for
example, is a proximate principle of bone, but phosphoric acid is
not so, since it does not exist as such in the bony tissue, but is
produced only by the decomposition of the calcareous salt; still
less phosphorus, which is obtained only by the decomposition of
the phosphoric acid.
Proximate principles may, in fact, be said to exist in all solids or
fluids of mixed composition, and may be extracted from them by
the same means as in the case of the animal tissues or secretions.
Thus, in a watery solution of sugar, we have two proximate principles, viz: first, the water, and second, the sugar. The water may
be separated by evaporation and condensation, after which the
sugar remains behind, in a crystalline form. These two substances
have, therefore, been simply separated from each other by the process of evaporation.  They have not been decomposed, nor their
chemical properties altered.  On the other hand, the oxygen and
hydrogen of the water were not proximate principles of the original
solution, and did not exist in it under their own forms, but only in
a state of combination; forming, in this condition, a fluid substance
(water), endowed with sensible properties entirely different from




48         PROXIMATE PRINCIPLES IN GENERAL.
theirs. If we wish to ascertain, accordingly, the nature and properties of a saccharine solution, it will afford us but little satisfaction to
extract its ultimate chemical elements; for its nature and properties
depend not so much on the presence in it of the ultimate elements,
oxygen, hydrogen, and carbon, as on the particular forms of combination, viz., water and sugar, under which they are present.
It is very essential, therefore, that in extracting the proximate
principles from the animal body, only such means should be adopted
as will isolate the substances already existing in the tissues and
fluids, without decomposing them, or altering their nature.  A
neglect of this rule has been productive of much injury in the pursuit of organic chemistry; for chemists, in subjecting the animal
tissues to the action of acids and alkalies, of prolonged boiling, or
of too intense heat, have often obtained, at the end of the analysis,
many substances which were erroneously described as proximate
principles, while they were only the remains of an altered and disorganized material. Thus, the fibrous tissues, if boiled steadily for
thirty-six hours, dissolve, for the most part, at the end of that time,
in the boiling water; and on cooling the whole solution solidifies
into a homogeneous, jelly-like substance, which has received the
name of gelatine. But this gelatine does not really exist in the body
as a proximate principle, since the fibrous tissue which produces it
is not at first soluble, even in boiling water, and its ingredients
become altered and converted into a gelatinous matter only by prolonged ebullition. So, again, an animal substance containing acetates or lactates of soda or lime will, upon incineration in the open
air, yield carbonates of the same bases, the organic acid having been
destroyed, and replaced by carbonic acid; or sulphur and phosphorus, in the animal tissue, may be converted by the same means into
sulphuric and phosphoric acids, which, decomposing the alkaline
carbonates, become sulphates and phosphates. In either case, the
analysis of the tissues, so conducted, will be a deceptive one, and
useless for all anatomical and physiological purposes, because its
real ingredients have been decomposed, and replaced by others, in
the process of manipulation.
It is in this way that different chemists, operating upon the same
animal solid or fluid, by following different plans of analysis, have
obtained different results; enumerating as ingredients of the body
many artificially formed substances, which are not, in reality,
proximate principles, thereby introducing much confusion into
physiological chemistry.




PROXIMATE PRINCIPLES IN GENERAL.                  49
It is to be kept constantly in view, in the examination of an
animal tissue or fluid, that the object of the operation is simply the
separation of its ingredients from each other, and not their decolnposition or ultimate analysis. Only the simplest forms of chemical
manipulation should, therefore, be employed.  The substance to
be examined should first be subjected to evaporation, in order to
extract and estimate its water. This evaporation must be conducted
at a heat not above 212~ F., since a higher temperature would destroy or alter some of the animal ingredients.  Then, from the
dried residue, chloride of sodium, alkaline sulphates, carbonates,
and phosphates may be extracted with water. Coloring matters
may be separated by alcohol. Oils may be dissolved out by ether,
&c. &c. When a chemical decomposition is unavoidable, it must
be kept in sight and afterward corrected.  Thus the glyko-cholate
of soda of the bile is separated from certain other ingredients by
precipitating it with acetate of lead, forming glyko-cholate of lead;
but this is afterward decomposed, in its turn, by carbonate of soda,
reproducing the original glyko-cholate of soda. Sometimes it is
impossible to extract a proximate principle in an entirely unaltered
form. Thus the fibrin of the blood can be separated only by allowing it to coagulate; and once coagulated, it is permanently altered,
and can no longer present all its original characters of fluidity, &c.,
as it existed beforehand in the blood. In such instances as this,
we can only make allowance for an unavoidable difficulty, and be
careful that the substance sufelrs no further alteration. By bearing
in mind the above considerations, we may form a tolerably correct
estimate of the nature and quantity of all of the proximate principles existing in the substance under examination.
The manner in which the proximate principles are associated
together, so as to form the animal tissues, is deserving of notice.
In every animal solid and fluid, there is a considerable number of
proximate principles, which are present in certain proportions, and
which are so united with each other that the mixture presents a
homogeneous appearance. But this union is of a complicated character; and the presence of each ingredient depends, to a certain
extent, upon that of the others. Some of them, such as the alkaline
carbonates and phosphates, are in solution directly in the water.
Some, which are insoluble in water, are held in solution by the
presence of other soluble substances.  Thus, phosphate of lime is
held in solution in the urine by the bi-phosphate of soda. In the
blood, it is dissolved by the albumen, which is itself fluid by union
4




50         PROXIMATE PRINCIPLES IN GENERAL.
with the water. The same substance may be fluid in one part of
the body, and solid in another part. Thus in the blood and secretions the water is fluid, and holds in solution other substances, both
animal and mineral, while in the bones and cartilages it is solidnot crystallized, as in the case of ice or of saline substances which
contain water of crystallization, but amorphous and solid, by the
fact of its intimate union with the animal and saline ingredients,
which are abundant in quantity, and which are themselves present
in the solid form. Again, the phosphate of lime in the blood is
fluid by solution in the albumen; but in the bones it forms a solid
substance with the animal matter of the osseous tissue; and yet
the union of the two is as intimate and homogeneous in the bones
as in the blood. A  proximate principle, therefore, never exists
alone in any part of the body, but is always intimately associated
with a number of others, by a kind of homogeneous mixture or
solution.
Every animal tissue and fluid contains a number of proximate
principles which are present, as we have already mentioned, in
certain characteristic proportions. Thus, water is present in very
large quantity in the perspiration and the saliva, but in very small
quantity in the bones and teeth. Chloride of sodium is comparatively abundant in the blood and deficient in the muscles. On the
other hand, chloride of potassium is more abundant in the muscles,
less so in the blood. But these proportions, it is important to observe, are nowhere absolute or invariable. There is a great difference, in this respect, between the chemical composition of an inorganic substance and the anatomical constitution of an animal fluid.
The former is always constant and definite; the latter is always
subject to certain variations. Thus, water is always composed of
exactly the same relative'quantities of oxygen and hydrogen; and
if these proportions be altered in the least, it thereby ceases to be
water, and is converted into some other substance. But in the
urine, the proportions of water, urea, urate of soda, phosphates,
&c., vary within certain limits in different individuals, and even in
the same individual, from one hour to another. This variation,
which is almost constantly taking place, within the limits of health,
is characteristic of all the animal solids and fluids; for they are
composed of different ingredients which are supplied by absorption
or formed in the interior, and which are constantly given up again,
under the same or different forms, to the surrounding media by the
unceasing activity of the vital processes.  Every variation, then,




PROXIMATE PRINCIPLES IN GENERAL.                  51
in the general condition of the body, as a whole, is accompanied by
a corresponding variation, more or less pronounced, in the constitution of its different parts. This constitution is consequently of
a very different character from the chemical constitution of an
oxide or a salt.  Whenever, therefore, we meet with the quantitative analysis of an animal fluid, in which the relative quantity of
its different ingredients is represented in numbers, we must understand that such an analysis is always approximative, and not absolute.
The proximate principles are naturally divided into three different classes.
The first of these classes comprises all the proximate principles
which are purely INORGANIC in their nature. These principles are
derived mostly from the exterior. They are found everywhere, in
unorganized as well as in organized bodies; and they present themselves under the same forms and with the same properties in the
interior of the animal frame as elsewhere. They are crystallizable,
and have a definite chemical composition. They comprise such
substances as water, chloride of sodium, carbonate and phosphate
of lime, &c.
The second class of proximate principles is known as CRYSTALLIZABLE SUBSTANCES OF ORGANIC ORIGIN. This is the name given
to them by Robin and Verdeil,l whose classification of the proximate principles is the best which has yet been offered. They are
crystallizable, as their name indicates, and have a definite chemical
composition.  They are said to be of "organic origin," because they
first make their appearance in the interior of organized bodies, and
are not found in external nature as the ingredients of inorganic
substances. Such are the different kinds of sugar, oil, and starch.
The third class comprises a very extensive and important order
of proximate principles, which go by the name of the ORGANIC
SUBSTANCES proper.  They are sometimes known as "albuminoid"
substances or "protein compounds."  The name organic substances
is given to them in consequence of the striking difference which
exists between them and all the other ingredients of the body. The
substances of the second class differ from those of the first by their
I Chimie Anatomique et Physiologique. Paris, 1853.




52         PROXIMATE PRINCIPLES IN GENERAL.
exclusively organic origin, but they resemble the latter in their crystallizability and their definite chemical composition; in consequence
of which their chemical investigation may be pursued in nearly
the same manner, and their chemical changes expressed in nearly
the same terms. But the proximate principles of the third class
are in every respect peculiar. They have an exclusively organic
origin; not being found except as ingredients of living or recently
dead animals or vegetables. They have not a definite chemical
composition, and are consequently not crystallizable; and the forms
which they present, and the chemical changes which they undergo
in the body, are such as cannot be expressed by ordinary chemical
phraseology.  This class includes such substances as albumen,
fibrin, casein, &c.




PROXIMATE PRINCIPLES OF THE FIRST CLASS.   53
CHAPTER II.
PROXIMATE PRINCIPLES OF THE FIRST CLASS.
THE proximate principles of the first class, or those of an inorganic nature, are very numerous. Their most prominent characters
have already been stated. They are all crystallizable, and have a
definite chemical composition. They are met with extensively in
the inorganic world, and form a large part of the crust of the earth.
They occur abundantly in the different kinds of food and drink;
and are necessary ingredients of the food, since they are necessary
ingredients of the animal frame. Some of them are found universally
in all parts of the body, others are met with only in particular
regions; but there are hardly any which are not present at the
same time in more than one animal solid or fluid. The following
are the most prominent of them, arranged in the order of their
respective importance.
1. WATER.-Water is universally present in all the tissues and
fluids of the body. It is abundant in the blood and secretions,
where its presence is indispensable in order to give them the fluidity
which is necessary to the performance of their functions; for it
is by the blood and secretions that new substances are introduced
into the body, and old ingredients discharged. And it is a necessary condition both of the introduction and discharge of substances
naturally solid, that they assume, for the time being, a fluid form;
water is therefore an essential ingredient of the fluids, for it holds
their solid materials in solution, and enables them to pass and repass
through the animal frame.
But water is an ingredient also of the solids. For if we take a
muscle or a cartilage, and expose it to a gentle heat in dry air, it
loses water by evaporation, diminishes in size and weight, and becomes dense and stiff. Even the bones and teeth lose water by
evaporation in this way, though in smaller quantity. In all these
solid and semi-solid tissues, the water which they contain is useful




54    PROXIMATE PRINCIPLES OF THE FIRST CLASS.
by giving them the special consistency which is characteristic of
them, and which would be lost without it.  Thus a tendon, in its
natural condition, is white, glistening, and opaque; and though very
strong, perfectly flexible. If its water be expelled by evaporation
it becomes yellowish in color, shrivelled, semi-transparent, inflexible, and totally unfit for performing its mechanical functions. The
same thing is true of the skin, muscles, cartilages, &c.
The following is a list, compiled by Robin and Verdeil from
various observers, showing the proportion of water per thousand
parts, in different solids and fluids:QUANTITY OF WATER IN 1,000 PARTS IN
Epidermis...  37        Bile...880
Teeth... 100        Milk..887
Bones....130            Pancreatic juice. 900
Cartilage... 550          Urine.               936
Muscles... 750        Lymph.                960
Ligaments... 768        Gastric juice... 975
Brain.... 789         Perspiration..    986
Blood.... 795        Saliva...  995
Synovial fluid... 805
According  to the best calculations, water constitutes, in the
human subject, between two-thirds and three-quarters of the entire
weight of the body.
The water which thus forms a part of the animal frame is derived
from without. It is taken in the different kinds of drink, and also
forms an abundant ingredient in the various articles of food. For
no articles of food are taken in an absolutely dry state, but all
contain a larger or smaller quantity of water, which may readily
be expelled by evaporation.  The quantity of water, therefore,
which is daily taken into the system, cannot be ascertained in any
case by simply measuring the quantity of drink, but its proportion
in the solid food, taken at the same time, must also be determined
by experiment, and this ascertained quantity added to that which
is taken in with the fluids. By measuring the quantity of fluid
taken with the drink, and calculating in addition the proportion
existing in the solid food, we have found that, for a healthy adult
man, the ordinary quantity of water introduced per day, is a little
over 41 pounds.
After forming a part of the animal solids and fluids, and taking
part in the various physical and chemical processes of the body, the
water is again discharged; for its presence in the body, like that
of all the other proximate principles, is not permanent, but only




CHLORIDE OF SODIUM.                       55
temporary.  After being taken in with the food and drink, it is
associated with other principles in the fluids and solids, passing
from the intestine to the blood, and from the blood to the tissues
and secretions. It afterward makes its exit from the body, from
which it is discharged by four different passages, viz., in a liquid
form with the urine and the feces, and in a gaseous form with the
breath and the perspiration. Of all the water which is expelled in
this way, about 48 per cent. is discharged with the urine and feces,'
and about 52 per cent. by the lungs and skin. The researches of
Lavoisier and Seguin, Valentin, and others, show that from a pound
and a half to two pounds is discharged daily by the skin, a little
over one pound by exhalation from the lungs, and a little over two
pounds by the urine. Both the absolute and relative amount discharged, both in a liquid and gaseous form, varies according to
circumstances. There is particularly a compensating action in this
respect between the kidneys and the skin, so that when the cutaneous perspiration is very abundant the urine is less so, and vice versa.
The quantity of water exhaled from the lungs varies also with the
state of the pulmonary circulation, and with the temperature and
dryness of the atmosphere. The water is not discharged at any
time in a state of purity, but is mingled in the urine and feces with
saline substances which it holds in solution, and in the cutaneous
and pulmonary exhalations with animal vapors and odoriferous
substances of various kinds. In the perspiration it is also mingled
with saline substances, which it leaves behind on evaporation.
2. CHLORIDE OF SODIUM.-This substance is found, like water,
throughout the different tissues and fluids of the body. The only
exception to this is perhaps the enamel of the teeth, where it has
not yet been discovered. Its presence is important in the body, as
regulating the phenomena of endosmosis and exosmosis in different
parts of the frame. For we know that a solution of common salt
passes through animal membranes much less readily than pure
water; and tissues which have been desiccated will absorb pure
water more abundantly than a saline solution. It must not be supposed, however, that the presence or absence of chloride of sodium,
or its varying quantity in the animal fluids, is the only condition
which regulates their transudation through the animal membranes.
The manner in which endosmosis and exosmosis take place in the
1 Op. cit., vol. ii. pp. 143 and 145.




56    PROXIMATE PRINCIPLES OF THE FIRST CLASS.
animal frame depends upon the relative quantity of all the ingredients of the fluids, as well as on the constitution of the solids
themselves; and the chloride of sodium, as one ingredient among
many, influences these phenomena to a great extent, though it does
not regulate them exclusively.
It exerts also an important influence on the solution of various
other ingredients, with which it is associated.  Thus, in the blood
it increases the solubility of the albumen, and perhaps also of the
earthy phosphates.  The blood-globules, again, which become disintegrated and dissolved in a solution of pure albumen, are maintained in a state of integrity by the presence of a small quantity of
chloride of sodium.
It exists in the following proportions in several of the solids and
fluids:'QUANTITY OF CHLORIDE OF SODIUM IN 1,000 PARTS IN THE
Muscles..   2        Bile...   3.5
Bones...   2.5       Blood..            4.5
Milk...   1        Mucus...   6
Saliva...   1.5      Aqueous humor..  11
Urine.               3        Vitreous humor..  14
In the blood it is rather more abundant than all the other saline
ingredients taken together.
Since chloride of sodium is so universally present in all parts of
the body, it is an important ingredient also of the food. It occurs,
of course, in all animal food, in the quantities in which it naturally
exists in the corresponding tissues; and in vegetable food also,
though in smaller amount.  Its proportion in muscular flesh,
however, is much less than in the blood and other fluids. Consequently, it is not supplied in sufficient quantity as an ingredient of
animal and vegetable food, but is taken also by itself as a condiment. There is no other substance so universally used by all races
and conditions of men, as an addition to the food, as chloride of
sodium.  This custom does not simply depend on a fancy for gratifying the palate, but is based upon an instinctive desire for a substance which is necessary to the proper constitution of the tissues
and fluids. Even the herbivorous animals are greedy of it, and if
freely supplied with it, are kept in a much better condition than
when deprived of its use.
The importance of chloride of sodium in this respect has been
well demonstrated by Boussingault, in his experiments on the
1 Robin and Verdeil.




CHLORIDE OF SODIUM.                       57
fattening of animals.  These observations were made upon six
bullocks, selected, as nearly as possible, of the same age and vigor,
and subjected to comparative experiment. They were all supplied
with an abundance of nutritious food; but three of them (lot No.
1) received also a little over 500 grains of salt each per day. The
remaining three (lot No. 2) received no salt, but in other respects
were treated like the first. The result of these experiments is given
by Boussingault as follows:-'
"Though salt administered with the food has but little effect in
increasing the size of the animal, it appears to exert a favorable
influence upon his qualities and general aspect. Until the end of
March (the experiment began in October) the two lots experimented
on did not present any marked difference in their appearance; but
in the course of the following April, this difference became quite
manifest, even to an unpractised eye. The lot No. 2 had then been
without salt for six months. In the animals of both lots the skin
had a fine and substantial texture, easily stretched and separated
from the ribs; but the hair, which was tarnished and disordered in
the bullocks of the second lot, was smooth and glistening in those
of the first. As the experiment went on, these characters became
more marked; and at the beginning of October the animals of lot
No. 2, after going without salt for an entire year, presented a rough
and tangled hide, with patches here and there where the skin was
entirely uncovered.  The bullocks of lot No. 1 retained, on the
contrary, the ordinary aspect of stall-fed animals. Their vivacity
and their frequent attempts at mounting contrasted strongly with
the dull and unexcitable aspect presented by the others. No doubt,
the first lot would have commanded a higher price in the market
than the second."
Chloride of sodium acts also in a favorable manner by exciting
the digestive fluids, and assisting in this way the solution of the
food. For food which is tasteless, however nutritious it may be in
other respects, is taken with reluctance and digested with difficulty;
while the attractive flavor which is developed by cooking, and by
the addition of salt and other condiments in proper proportion,
excites the secretion of the saliva and gastric juice, and facilitates
consequently the whole process of digestion.  The chloride of
sodium is then taken up by absorption from the intestine, and is
deposited in various quantities in different parts of the body.
I Chimie Agricole, Paris, 1854, p. 271.




58     PROXIMATE PRINCIPLES OF THE FIRST CLASS.
It is discharged with the urine, mucus, cutaneous perspiration,
&c., in solution in the water of these fluids. According to the estimates of M. Barral,' a small quantity of chloride of sodium disappears in the body; since he finds by accurate comparison that all
the salt introduced with the food is not to be found in the excreted
fluids, but that about one-fifth of it remains unaccounted for. This
portion is supposed to undergo a double decomposition in the blood
with phosphate of potassa, forming chloride of potassium and phosphate of soda. By far the greater part of the chloride of sodium,
however, escapes under its own form with the secretions.
3. CHLORIDE OF POTASSIUM.-This substance is found in the
muscles, the blood, the milk, the urine, and various other fluids
and tissues of the body. It is not so universally present as chloride of sodium, and not so important as a proximate principle.
In some parts of the body it is more abundant than the latter salt,
in others less so. Thus, in the blood there is more chloride of
sodium than chloride of potassium, but in the muscles there is more
chloride of potassium than chloride of sodium. This substance is
always in a fluid form, by its ready solubility in water, and is easily
separated by lixiviation. It is introduced mostly with the food, but
is probably formed partly in the interior of the body from chloride
of sodium by double decomposition, as already mentioned. It is
discharged with the mucus, the saliva, and the urine.
4. PHOSPHATE OF LIME.-This is perhaps the most important
of the mineral ingredients of the body next to chloride of sodium.
It is met with universally, in every tissue and every fluid. Its
quantity, however, varies very much in different parts, as will be
seen by the following list:QUANTITY OF PHOSPHATE OF LIME IN 1,000 PARTS IN THE
Enamel of the teeth.. 885      Muscles... 2.5
Dentine...      643       Blood... 0.3
Bones... 550        Gastric juice... 0.4
Cartilages..     40
It occurs also under different physical conditions.  In the bones,
teeth, and cartilages it is solid, and gives to these tissues the resistance and solidity which are characteristic of them. The calcareous
salt is not, however, in these instances, simply deposited mechanically in the substance of the bone or cartilage as a granular powder,
I In Robin and Verdeil, op. cit., vol. ii. p. 193.




PHOSPHATE OF LIME.                        59
but is intimately united with the animal matter of the tissues, like
a coloring matter in colored glass, so as to present a more or less
homogeneous appearance.  It can, however, be readily dissolved
out by maceration in dilute muriatic acid, leaving behind the
animal substance, which still retains the original form of the bone
or cartilage. It is not, therefore, united with the animal matter so
as to lose its identity and form a new chemical substance, as where
an acid combines with an alkali to form  a salt, but in the same
manner as salt unites with water in a saline solution, both substances retaining their original character and composition, but so
intimately associated that they cannot be separated by mechanical
means.
In the blood, phosphate of lime is in a liquid form, notwithstanding its insolubility in water and in alkaline fluids, being held in
solution by the albuminous matters of the circulating fluid. In the
urine, it is retained in solution by the bi-phosphato of soda.
In all the solid tissues it is useful by giving to them their proper
consistence and solidity.  For example, in the enamel of the teeth, the hardest tissue of the body, it    Fig. 1
predominates very much over the animal matter, 
and is present in greater abundance there than in
any other part of the frame. In the dentine, a
softer tissue, it is in somewhat smaller quantity, 
and in the bones smaller still; though in the bones
it continues to form more than one-half the entire
mass of the osseous substance.  The importance of
phosphate of lime, in communicating to bones their
natural stiffness and consistency, may be readily
shown by the alteration which they suffer from its 
removal. If a long bone be macerated in dilute
muriatic acid, the earthy salt, as already mentioned, 
is entirely dissolved out, after which the bone loses
its rigidity, and may be bent or twisted in any direction without breaking. (Fig. 1.)
TT-n   I   ~-   n   I    l   l'  i-^  FIBULA  TIED IN
Whenever the nutrition of the bone during life  A KNOT, after mais interfered with from  any pathological cause, so      in a dilte
acid. (From a specithat its phosphate of lime becomes deficient in  men in the museum
amount, a softening of the osseous tissue is the  oftheColl.ofPhysiclans and Surgeons.)
consequence, by which the bones yield to external
pressure, and become more or less distorted. (Osteo-malakia.)
After forming, for a time, a part of the tissues and fluids, the




60    PROXIMATE PRINCIPLES OF THE FIRST CLASS.
phosphate of lime is discharged from  the body by the urine, the
perspiration, mucus, &c. Much the larger portion is discharged by
the urine. A small quantity also occurs in the feces, but this is probably only the superfluous residue of what is taken in with the food.
5. CARBONATE OF LImE.-Carbonate of lime is to be found in
the bones, and sometimes in the urine.  The concretions of the
internal ear are almost entirely formed of it. It very probably
occurs also in the blood, teeth, cartilages, and sebaceous matter;
but its presence here is not quite certain, since it may have been
produced from  the lactate, or other organic combination, by the
process of incineration. In the bones, it is in much smaller quantity than the phosphate.  Its solubility in the blood and the urine
is accounted for by the presence of free carbonic acid, and also of
chloride of potassium, both of which substances exert a solvent
action on carbonate of lime.
6. CARBONATE OF SODA.-This substance exists in the bones,
blood, saliva, lymph, and urine. As it is readily soluble in water,
it naturally assumes the liquid form in the animal fluids. It is
important principally as giving to the blood its alkalescent reaction,
by which the solution of the albumen is facilitated, and various
other chemico-physiological processes in the blood accomplished.
The alkalescence of the blood is, in fact, necessary to life; for it is
found that, in the living animal, if a mineral acid be gradually
injected into the blood, so dilute as not to coagulate the albumen,
death takes place before its alkaline reaction has been completely
neutralized.'
The carbonate of soda of the blood is partly introduced as such
with the food; but the greater part of it is formed within the body
by the decomposition of other salts, introduced with certain fruits
and vegetables. These fruits and vegetables, such as apples, cherries, grapes, potatoes, &c., contain malates, tartrates, and citrates
of soda and potassa. Now, it has been often noticed that, after
the use of acescent fruits and vegetables containing the above salts,
the urine becomes alkaline in reaction from the presence of the
alkaline carbonates.  Lehmann2 found, by experiments upon his
own person, that, within thirteen minutes after taking half an ounce
I. Bernard. Lectures on the Blood; reported by W. F. Atlee, M. D. Philadelphia, 1854, p. 31.
2 Physiological Chemistry. Philadelphia ed., vol. i. p. 97.




PHOSPHATES OF MAGNESIA, SODA, AND POTASSA.  61
of lactate of soda, the urine had an alkaline reaction. IHe also observed that, if a solution of lactate of soda were injected into the
jugular vein of a dog, the urine became alkaline at the end of five,
or, at the latest, of twelve minutes. The conversion of these salts
into carbonates takes place, therefore, not in the intestine but in the
blood. The same observer' found that, in many persons living on
a mixed diet, the urine became alkaline in two or three hours after
swallowing ten grains of acetate of soda. These salts, therefore,
on being introduced into the animal body, are decomposed. Their
organic acid is destroyed and replaced by carbonic acid; and they
are then discharged under the form of carbonatesof soda and potassa.
7. CARBONATE OF POTASSA.-This substance occurs in very
nearly the same situations as the last. In the blood, however, it is
in smaller quantity. It is mostly produced, as above stated, by
the decomposition of the malate, tartrate, and citrate, in the same
manner as the carbonate of soda. Its function is also the same as
that of the soda salt, and it is discharged in the same manner from
the body.
8. PHOSPHATES OF MAGNESIA, SODA, AND POTASS&A. —AI1 these
substances exist universally in all the solids and fluids of the body,
but in very small quantity. The phosphates of soda and potassa
are easily dissolved in the animal fluids, owing to their ready solubility in water. The phosphate of magnesia is held in solution in
the blood by the alkaline chlorides and phosphates; in the urine,
by the acid phosphate of soda.
A peculiar relation exists between the alkaline phosphates and
carbonates in different classes of animals. For while the fluids of
carnivorous animals contain a preponderance of the phosphates,
those of the herbivora contain a preponderance of the carbonates:
a peculiarity readily understood when we recollect that muscular
flesh and the animal tissues generally are comparatively abundant
in phosphates; while vegetable substances abound in salts of the
organic acids, which give rise, as already described, by their decomposition in the blood, to the alkaline carbonates.
The proximate principles included in the above list resemble
each other not only in their inorganic origin, their crystallizability,
I Physiological Chemistry, vol. ii. p. 130.




62    PROXIMATE PRINCIPLES OF THE FIRST CLASS.
and their definite chemical composition, but also in the part which
they take in the constitution of the animal frame. They are
distinguished in this respect, first, by being derived entirely from
without. There are a few exceptions to this'rule; as, for example,
in the case of the alkaline carbonates, which partly originate in
the body from the decomposition of malates, tartrates, &c. These,
however, are only exceptions; and in general, the proximate principles belonging to the first class are introduced with the food,
and taken up by the animal tissues in precisely the same form
under which they occur in external nature. The carbonate of lime
in the bones, the chloride of sodium  in the blood and tissues, are
the same substances which are met with in the calcareous rocks,
and in solution in sea water. They do not suffer any chemical
alteration in becoming constituent parts of the animal frame.
They are equally exempt, as a general rule, from any alteration
while they remain in the body, and during their passage through
it. The exceptions to this rule are very few; as, for example, where
a small part of the chloride of sodium suffers double decomposition
with phosphate of potassa, giving rise to chloride of potassium and
phosphate of soda; or where the phosphate of soda itself gives up
a part of its base to an organic acid (uric), and is converted in this
way into a bi-phosphate of soda.
Nearly the whole of these substances, finally, are taken up unchanged from the tissues, and discharged unchanged with the excretions. Thus we find the phosphate of lime and the chloride of sodium, which were taken in with the food, discharged again under
the same form in the urine. They do not, therefore, for the most
part, participate directly in the chemical changes going on in the
body; but only serve by their presence to enable those changes to
be accomplished in the other ingredients of the animal frame, which
are necessary to the process of nutrition.




PROXIMATE PRINCIPLES OF THE SECOND CLASS.  63
CHAPTER III.
PROXIMATE PRINCIPLES OF THE SECOND CLASS.
THE  proximate principles belonging to the second class are
divided into three principal groups, viz: starch, sugar, and oil.
They are distinguished, in the first place, by their organic origin.
Unlike the principles of the first class, they do not exist in
external nature, but are only found as ingredients of organized
bodies. They exist both in animals and in vegetables, though in
somewhat different proportions. All the substances belonging to
this class have a definite chemical composition; and are further
distinguished by the fact that they are composed of oxygen,
hydrogen, and carbon alone, without nitrogen, whence they are
sometimes called the "non-nitrogenous" substances.
1. STARCH (C,2H,,O,,).-The first of these substances seems to
form an exception to the general rule in a very important particular, viz., that it is not crystallizable. Still, since it so closely
resembles the rest in all its general properties, and since it is easily
convertible into sugar, which is itself crystallizable, it is naturally
included in the second class of proximate principles. Though not
crystallizable, furthermore, it still assumes a distinct form, by
which it differs from substances that are altogether amorphous.
Starch occurs in some part or other of almost all the flowering
plants.  It is very abundant in corn, wheat, rye, oats, and rice, in
the parenchyma of the potato, in peas and beans, and in most
vegetable substances used as food. It constitutes almost entirely
the different preparations known as sago, tapioca, arrowroot, &c.,
which are nothing more than varieties of starch, extracted from
different species of plants.
The following is a list showing the percentage of starch occurring
in different kinds of food:- 
Pereira on Food and Diet, New York, 1843, p. 39.




64   PROXIMATE PRINCIPLES OF THE SECOND  CLASS.
QUANTITY OF STARCH IN 100 PARTS IN
Rice.. 85.07      Wheat flour... 56.50
Maize... 80.92           Iceland moss.. 44.60
Barley meal... 67.18       Kidney bean... 35.94
Rye meal... 61.07         Peas....32.45
Oat meal... 59.00     Potato...      15.70
When purified from  foreign substances, starch is a white, light
powder, which gives rise to a peculiar crackling sensation when
rubbed between the fingers.
Fig. 2.                 It is not amorphous, as we
have already stated, but is
composed of solid granules,
O/  I  0  \      which, while they have a
general resemblance to each
o 0\   other, differ somewhat in various particulars. The starch
o ) Q   A11       A/l         grains of the potato (Fig. 2)
o            Cl  o <) \         vary  considerably  in  size.
0\  C ~ /    The smallest have a diameter
o\ p p  ~i    /      of f' O. the largest 40 of
an inch.  They are irregularly pear-shaped in form,
GRA=IN OF' POTATO STARCH.       and are marked by concenGRA.INS OF- POTATO' STARCTi,.
tric laminae, as if the matter
of which they are composed had been deposited in successive layers.
At one point on the surface of every starch grain,,there is a minute
pore or depression, called the
Fig. S.                 hilus, around which the circular markings are arranged
/ X (7 ^     in a concentric form.
The  starch  granules of
arrowroot (Fig. 3) are gene\ rally smaller and more unih\  (-/  (^    \form  in size, than those of
^<91K)      D %1)the potato. They vary from
\2U  to - 5, of an inch in
diameter. Theyareelongated
and cylindrical in form, and
the concentric markings are
less distinct than in the pre.
STARCH GRAINS OF BERMUDA ARROWROOT.   ceding variety.  The hilus




STARCH.:65
has here sometimes the form of a circular pore, and sometimes that
of a transverse fissure or slit.
The grains of wheat starch (Fig. 4) are still smaller than those
of arrowroot.   They  vary
from    00 to 7   of an inch                    Fig. 4.
in  diameter.   They  are
nearly circular in form, with
a round or transverse hilus,       / 
but without  any  distinct
appearance  of  lamination.   /   @ 
Many of them  are flattened 
or compressed laterally, so                 0    
that they present a broad   \                           Q   0
surface in one position, and    \ 
a narrow edge when viewed 
in the opposite direction.                        
The starch grains of Indian  corn  (Fig. 5) are of
STARCH GRAINS OF WHEAT Fl.OUR.
nearly the same size with
those of wheat flour.  They are somewhat more irregular and
angular in shape; and are often marked with crossed or radiating
lines, as if from partial fracture.
Starch is also an ingre-ig. 5.
dient of the animal body..
It was first observed  by/ 
Purkinje, and afterward by         /                            \
Kolliker,' that certain bodies   / 
are to be found in the interior  / 
of the brain, about the late-     \ 
ral ventricles, in the fornix,          O 
septum  lucidum  and other \             o  
parts, which present a cer-  
tain  resemblance to starch    \  
grains, and which have there- 
fore been - called  "corpora
amylacea."    Subsequently
Virchow2 corroborated  the          STARCH GRAINS OF INDIAN CORN.
above observations, and ascertained the corpora amylacea to be
I Handbuch der Gewebelehre, Leipzig, 1852, p. 311.
2 In American Journal Med. Sci., April, 1854, p. 466.
5




66   PROXIMATE PRINCIPLES OF THE SECOND CLASS.
really substances of a starchy nature; since they exhibit the usual
chemical reactions of vegetable starch.
The starch granules of the human brain (Fig. 6) are transparent
and colorless, like those from
-Fig. 6.              plants. They refract the light
strongly, and vary in size
from     %  to JTT   of an
inch. Their average is T'o, @  \   of an inch. They are sometimes rounded or oval, and
I ^^  /^^ @sometimes angular in shape.
01) iw  They resemble considerably
in  appearance  the  starch
granules of Indian corn. The
0\  A        /           largest of them  present a
very faint concentric lamination, but the greater number
STARCH GRAINS FROM WALL OF LATERAL are destitute  of any such
VENTRTCLES; from a woman aged 35.     appearance.    They  have
nearly always a distinct hilus, which is sometimes circular and
sometimes slit-shaped. They are also often marked with delicate
radiating lines and shadows. On the addition of iodine, they become
colored, first purple, afterward of a deep blue. They are less firm
in consistency than vegetable starch grains, and can be more readily
disintegrated by pressing or rubbing them upon the glass.
Starch, derived from all these different sources, has, so far as
known, the same chemical composition, and may be recognized by
the same tests.  It is insoluble in cold water, but in boiling water
its granules first swell, become gelatinous and opaline, then fuse
with each other, and finally liquefy altogether, provided a sufficient
quantity of water be present. After that, they cannot be made to
resume their original form, but on cooling and drying merely solidify
into a homogeneous mass or paste, more or less consistent, according to the quantity of water which remains in union with it. The
starch is then said to be amorphous or "hydrated." By this process
it is not essentially altered in its chemical properties, but only in
its physical condition. Whether in granules, or in solution, or in
an amorphous and hydrated state, it strikes a deep blue color on
the addition of free iodine.
Starch may be converted into sugar by three different methods.
First, by boiling with a dilute acid. If starch be boiled with dilute




SUGAR.                            67
nitric, sulphuric, or muriatic acid during thirty-six hours, it first
changes its opalescent appearance, and becomes colorless and transparent; losing at the same time its power of striking a blue color
with iodine. After a time, it begins to acquire a sweet taste, and
is finally altogether converted into a peculiar species of sugar.
Secondly, by contact with certain animal and vegetable substances.  Thus, boiled starch mixed with human saliva and kept
at the temperature of 100~ F., is converted in a few minutes into
sugar.
Thirdly, by the processes of nutrition and digestion in animals
and vegetables. A large part of the starch stored up in seeds and
other vegetable tissues is, at some period or other of the growth of
the plant, converted into sugar by the molecular changes going on
in the vegetable fabric. It is in this way, so far as we know, that
all the sugar derived from vegetable sources has its origin.
Starch, as a proximate principle, is more especially important as
entering largely into the composition of many kinds of vegetable
food. With these it is introduced into the alimentary canal, and
there, during the process of digestion, is converted into sugar.
Consequently, it does not appear in the blood, nor in any of the
secreted fluids.
2. SUGAR.-This group of proximate principles includes a considerable number of substances, which differ in certain minor
details, while they resemble each other in the following particulars:
They are readily soluble in water, and crystallize more or less
perfectly on evaporation; they have a distinct sweet taste; and
finally, by the process of fermentation, they are converted into
alcohol and carbonic acid.
These substances are derived from  both animal and vegetable
sources. Those varieties of sugar which are most familiar to us
are the following six, three of which are of vegetable and three of
animal origin.
Veg e  Cane sugar,                  An       Milk sugar,
Vegetable                              Animal
Grape sugar,                         Liver sugar,
sugars.   Sugar of starch.             gars.  Sugar of honey.
The cane and grape sugars are held in solution in the juices of
the plants from which they derive their name. Sugar ofstarch, or
glucose, is produced by boiling starch for a long time with a dilute
acid. Liver sugar and the sugar of milk are produced in the
tissues of the liver and the mammary gland, and the sugar of




68   PROXIMATE PRINCIPLES OF THE SECOND CLASS.
honey is prepared in some way by the bee from materials of vegetable origin.
These varieties differ but little in their ultimate chemical composition. The following formulae have been established for three of
them.
Cane sugar                        =       C24H2202
Milk sugar                        = C24H124024
Glucose....= C24H2Os2
Cane sugar is sweeter than most of the other varieties, and more
soluble in water. Some sugars, such as liver sugar and sugar of
honey, crystallize only with great difficulty; but this is probably
owing to their being mingled with other substances, from which it
is difficult to separate them completely. If they could be obtained
in a state of purity, they would doubtless crystallize as perfectly as
cane sugar. The different sugars vary also in the readiness with
which they undergo fermentation. Some of them, as grape sugar
and liver sugar, enter into fermentation very promptly; others,
such as milk and cane sugar, with considerable difficulty.
The above are not to be regarded as the only varieties of sugar
existing in nature. On the contrary, it is probable that nearly
every different species of animal and vegetable produces a distinct
kind of sugar, differing slightly from the rest in its degree of sweetness, its solubility, its crystallization, its aptitude for fermentation,
and perhaps in its elementary composition. Nevertheless, there is
so close a resemblance between them that they are all properly
regarded as belonging to a single group.
The test most commonly employed for detecting the presence of
sugar is that known as Trommer's test. It depends upon the fact
that the saccharine substances have the power of reducing the
persalts of copper when heated with them-in an alkaline solution.
The test is applied in the following manner: A very small quantity
of sulphate of copper in solution should be added to the suspected
liquid, and the mixture then rendered distinctly alkaline by the
addition of caustic potassa. The whole solution then takes a deep
blue color. On boiling the mixture, if sugar be present, the insoluble suboxide of copper is thrown down as an opaque red,
yellow, or orange-colored deposit; otherwise no change of color
takes place.
This test requires some precautions in its application. In the
first place, it is not applicable to all varieties of sugar. Cane
sugar, for example, when pure, has no power of reducing the salts




SUGAR.                           69
of copper, even when present in large quantity. Maple sugar, also,
which resembles cane sugar in some other respects, reduces the
copper, in Trommer's test, but slowly and imperfectly. Beet-root
sugar, according to Bernard, presents the same peculiarity. If
these sugars, however, be boiled for two or three minutes with a
trace of sulphuric acid, they become converted into glucose, and
acquire the power of reducing the salts of copper. Milk sugar,
liver sugar, and sugar of honey, as well as grape sugar and glucose,
all act promptly and perfectly with Trommer's test in their natural
condition.
Secondly, care must be taken to add to the suspected liquid only
a small quantity of sulphate of copper, just sufficient to give to the
whole a distinct blue tinge, after the addition of the alkali. If a
larger quantity of the copper salt be used, the sugar in solution
may not be sufficient to reduce the whole of it; and that which
remains as a blue sulphate will mask the yellow color of the suboxide thrown down as a deposit.  By a little care, however, in
managing the test, this source of error may be readily avoided.
Thirdly, there are some albuminous substances which have the
power of interfering with Trommer's test, and prevent the reduction of the copper, even when sugar is present. Certain animal
matters, to be more particularly described hereafter, which are
liable to be held in solution in the gastric juice, have this effect.
This source of error may be avoided, and the substances in question eliminated when present, by treating the suspected fluid with
animal charcoal, or by evaporating and extracting it with alcohol
before the application of the test.
A  less convenient but somewhat more certain test for sugar is
that of fermentation. The saccharine fluid is mixed with a little
yeast, and kept at a temperature of 700 to 1000 F. until the fermenting process is completed. By this process, as already mentioned, the sugar is converted into alcohol and carbonic acid. The
gas, which is given off in minute bubbles during fermentation,
should be collected and examined. The remaining fluid is purified
by distillation and also subjected to examination. If the gas be
found to be carbonic acid, and the remaining fluid contain alcohol,
there can be no doubt that sugar was present at the commencement
of the operation.
The following list shows the percentage of sugar in various
articles of food.''Pereira, op. cit., p. 55.




70   PROXIMATE PRINCIPLES OF THE SECOND CLASS.
QUANTITY OF SUGAR IN 100 PARTS IN
Figs... 62.50      Wheat flour.  4.20 to 8.48
Cherries... 18.12  Rye meal..  3.28
Peaches.           16.48      Indian meal.  1.45
Tamarinds... 12.50  Peas...  2.00
Pears.        11.52       Cow's milk.4.77
Beets.               9.00       Ass's milk.  6.08
Sweet almonds.      6.00       Human milk.  6.50
Barley meal...  5.21
Beside the sugar, therefore, which is taken into the alimentary
canal in a pure form, a large quantity is also introduced as an ingredient of the sweet-flavored fruits and vegetables.  All the
starchy substances of the food are also converted into sugar in the
process of digestion.  Two of the varieties of sugar, at least,
originate in the interior of the body, viz., sugar of milk and liver
sugar.  The former exists in a solid form  in the substance of the
mammary gland, from  which it passes in solution into the milk.
The liver sugar is found in the substance of the liver, and almost
always also in the blood of the hepatic veins. The sugar which is
introduced with the food, as well as that which is formed in the
liver, disappears by decomposition in the animal fluids, and does
not appear in any of the excretions.
3. FATs. —These substances, like the sugars, are derived from
both animal and vegetable sources.  There are three principal
varieties of them, which may be considered as representing the
class, viz:Oleine..... = C94 H87 
Margarine.....= C7 H7 0,
Stearine..... = C42H4,,7
The principal difference between the oleaginous and saccharine
substances, so far as regards their ultimate chemical composition,
is that in the sugars the oxygen and hydrogen always exist together
in the proportion to form water; while in the fats the proportions of
carbon and hydrogen are nearly the same, but that of oxygen is
considerably less.  The fats are all fluid at a high temperature, but
assume the solid form on cooling. Stearine, which is the most
solid of the three, liquefies only at 1430 F.; margarine at 118~ F.;
while oleine remains fluid considerably below 1000 F., and even
very near the freezing point of water. The fats are all insoluble
in water, but readily soluble in ether.  When treated with a solution of a caustic alkali, they are decomposed, and as the result of




FATS.                            71
the decomposition there are formed two new bodies; first, glycerine,
which is a neutral fluid substance, and secondly, a fatty acid, viz:
oleic, megaric, or stearic acid, corresponding to the kind of fat
which has been used in the experiment. The glycerine remains in
a free state, while the fatty acid unites with the alkali employed,
forming an oleate, margarate, or stearate.  This combination is
termed a soap, and the process by which it is formed is called
saponification.  This process, however, is not a simple decomposition
of the fatty body, since it can only take place in the presence of
water; several equivalents of which unite with the elements of the
fatty body, and enter into the composition of the glycerine, &c., so
that the fatty acid and the glycerine together weigh more than the
original fatty substance which was decomposed. It is not proper,
therefore, to regard an oleaginous body as formed by the union of a
fatty acid with glycerine. It is formed, on the contrary, in all probability, by the direct combination of its ultimate chemical elements.
The different kinds of oil, fat, lard, suet, &c., contain the three
oleaginous matters mentioned above, mingled together in different
proportions.  The more solid fats contain a larger quantity of
stearine and margarine; the less consistent varieties, a larger proportion of oleine.  Neither of the oleaginous matters, stearine,
margarine, or oleine, ever occur separately; but in every fatty substance they are mingled together, so that the more fluid of them hold
in solution the more solid.
Generally speaking, in the                   Fig. 7.
living body, these mixtures
are fluid or nearly so; for
though both  stearine and
margarine are solid, when                      r             i
pure, at the ordinary temperature of the body, they
are held in solution, during
life, by the oleine with which
they are associated.  After
death, however, as the body
cools, the stearine and margarine sometimes separate
from the mixture in a crystalline form, since the oleine   STEARtINE crystallized from a Warm Solution in
can no longer hold in solution so large a quantity of them  as it had dissolved at a higher
temperature.




72    PROXIMATE  PRINCIPLES OF THE  SECOND  CLASS.
These substances crystallize in very slender needles, which are
sometimes straight, but more often somewhat curved or wavy in
their outline. (Fig. 7.)
They are always deposited in a more or less radiated form; and
have sometimes a very elegant, branched, or arborescent arrangement.
When in a fluid state, the fatty substances present themselves
under the form of drops or
Fig. 8.                 globules, which vary indefinitely  in  size, but which
may be readily recognized
/'          \        Vby their optical properties.
They are circular in shape,
_ A s   Q111 O    \ 0and have a faint amber color,
distinct in the larger globules,
less so in the smaller. They
0\        wl   ~O  />,have a sharp, well defined
outline (Fig. 8); and as they
Q~\ t^  l    /      refract the  light strongly,
and act therefore as double
\`-^~ ~,    ~convex lenses, they present
~-~~ ~~  ~a brilliant centre, surrounded
OLEAGINOUS PRINCIPLES OF HUMAN FAT. 
Stearine and Margarine crystallized; Oleine fluid.    by a dark  border.  These
marks  will  generally  be
sufficient to distinguish them under the microscope.
The following list shows the percentage of oily matter present in
various kinds of animal and vegetable food.
QUANTITY OF FAT IN 100 PARTS IN
Filberts...     60.00        Ordinary meat..14.30
Walnuts... 50.00        Liver of the ox..  3.89
Cocoa-nuts... 47.00        Cow's milk...  3.13
Olives... 32.00        Human milk..  3.55
Linseed...       22.00        Asses' milk...  0.11
Indian corn...  9.00        Goats' milk...  3.32
Yolk of eggs... 28.00
The oleaginous matters present a striking peculiarity as to the
form  under which they exist in the animal body; a peculiarity
which distinguishes them from all the other proximate principles.
The rest of the proximate principles are all intimately associated
together by molecular union, so as to form either clear solutions or
I Pereira, op. cit., p. 81.




FATS.                           73
homogeneous solids. Thus, the sugars of the blood are in solution
in water, in company with the albumen, the phosphate of lime,
chloride of sodium, and the like; all of them equally distributed
throughout the entire mass of the fluid. In the bones and cartilages, the animal matters and the calcareous salts are in similarly
intimate union with each other; and in every other part of the
body the animal and inorganic ingredients are united in.the same
way. But it is different with the fats. For, while the three principal varieties of oleaginous matter are always united with each
other, they are not united with any of the other kinds of proximate
principles; that is, with water, saline substances, sugars, or albuminous matters. Almost the only exception to this is in the nervous tissue; in which, according to Robin and Verdeil, the oily
matters seem to be united with an albuminoid substance. Another
exception is, perhaps, in the bile; since some of the biliary salts
have the power of dissolving a certain quantity of fat. Everywhere else, instead of forming a homogeneous solid or fluid with
the other proximate principles, the oleaginous matters are found
in distinct masses or globules, which are suspended in serous fluids,
interposed in the interstices between the anatomical elements, included in the interior of cells, or deposited in the substance of
fibres or membranes. Even in the vegetable tissues, the oil is
always deposited in this manner in distinct drops or granules.
Owing to this fact, the oils can be easily extracted from the
organized tissues by the employment of simply mechanical processes. The tissues, animal or vegetable, are merely cut into small
pieces and subjected to pressure, by which the oil is forced out
from the parts in which it was entangled, and separated, without
any further manipulation, in a state of purity.  A  moderately
elevated temperature facilitates the operation by increasing the
fluidity of the oleaginous matter; but no other chemical agency is
required for its separation. Under the microscope, also, the oildrops and granules can be readily perceived and distinguished
from  the remaining parts of the tissue, and can, moreover, be
easily recognized by the dissolving action of ether, which acts
upon them, as a general rule, without attacking the other proximate principles.
Oils are found, in the animal body, most abundantly in the
adipose tissue.  Here they are contained in the interior of the
adipose vesicles, the cavities of which they entirely fill, in a state




74   PROXIMATE PRINCIPLES OF THE SECOND CLASS.
of health.  These vesicles are transparent, and have a somewhat
angular form, owing to their mutual compression. (Fig, 9.)  They
vary in diameter, in the huFig. 9.                man subject, from -g   to   
of an inch, and are composed
I/J d^ d  t3of a thin, structureless animal membrane, forming  a
wclosed sac, in the interior of
which the oily matter is contained. There is here, accord-? ingly, no union whatever of
the oil with the other proximate principles, but only a
mechanical inclusion of it in
the interior of the vesicles.
Sometimes, when emaciation
HU -~ ADIPOSE. TSUis going on, the oil partially
HUMAN ADIPOSE TISSUE.              o'
disappears from the cavity of
the adipose vesicle, and its place is taken by a watery serum; but
the serous and oily fluids always remain distinct, and occupy different parts of the cavity of the vesicle.
In the chyle, the oleaginous matter is in a state of emulsion or
suspension in the form of minute particles in a serous fluid. Its
subdivision is here more comFig. 10.               plete, and its molecules more
minute, than anywhere else in:.C. -.  the body. It presents the appearance of a fine granular;/  =. c\ ~   dust, which has been known:/      x6.~  <'5.U O  \  by the name of the "molecular base of the chyle."  A
few of these granules are to
\I3~:c~a"3~q               be seen which measure T oBo 
/ of an inch in diameter; but
\^   >;D   / -    they are generally much less
\r J~^ ^Ai  /  than this, and the greater part
are so small that they cannot
c-YLE, Thorn         be accurately measured. (Fig.
CHYLE, from commencement of Thoracic Duct, be accurately measured. (Fig.
from the Dog.                          10.)  For the same reason
they do not present the brilliant centre and dark border of the larger oil-globules; but appear




FATS.                            75
by transmitted light only as minute dark granules.  The white
color and opacity of the chyle, as of all other fatty emulsions,
depend upon this molecular condition of the oily ingredients. The
albumen, salts, &c., which are in intimate union with each other,
and in solution in the water, would alone make a colorless and
transparent fluid; but the oily matters, suspended in distinct particles, which have a different refractive power from the serous fluid,
interfere with its transparency
and give it the white color and              Fig. 11.
opaque appearance which are 
characteristic  of emulsions.                o   0 
The oleaginous nature of these    /      0      0o  \0
particles is readily shown by       0   0      \ 
their solubility in ether.       o           8   0  \
In the milk, the oily matter         O              ~  
occurs in larger masses than               0    0 
in the chyle.  In cow's milk       0               o            /
(Fig. 11), these oil-drops, or           o0 0                  /0
"milk-globules," are not quite    \        O                 /
fluid, but have a pasty consistency, owing to the large
quantity of margarine which           GLOBULES OF Cow' MILK.
they contain, in proportion to
the oleine.  When forcibly amalgamated with each other and
collected into a mass by prolonged beating or churning, they constitute butter. In cow's milk,
the globules vary somewhat                  Fig. 12.
in  size, but their average
diameter is  1o6 of an inch.
They are simply suspended
in the  serous fluid of the
milk, and are not covered
with any albuminous mem-                 
brane.
In the cells of the laryn- 
geal, tracheal, and costal cartilages (Fig. 12), there  is
always more or less fat deposited in the form of rounded globules, somewhat similar
ed globules, somewhat similar  CELLS OF COSTAL CARTILAGES, containing Oilto those of the milk.         Globules. Human.




76   PROXIMATE PRINCIPLES OF THE SECOND CLASS.
In the glandular cells of the liver, oil occurs constantly, in a
state of health. It is here deposited in the substance of the cell
(Fig. 13), generally in smaller
Fig. 13.               globules than the preceding.
In some cases of disease, it
accumulates  in  excessive
quantity, and produces the
c/ Hli          _d_ A_,s  \   sstate known as fatty degene-'*/....5:i^       \  -ration of the liver.  This is
I  co\       I \consequently  only  an  ex-,:^      boq:ig)           ] |aggerated condition of that
\:~;-',,       % Ao t      which  normally  exists in
--'.'':':.1 51    /    health.
\  /ao         /        In the carnivorous animals,
x-  -'       / 0     oil exists  in  considerable
quantity in the convoluted
CEL^~ S.omain..  I      portion  of the  uriniferous
ErPATIC CELLS. Human.
tubules. (Fig. 14.) It is here
in the form of granules and rounded drops, which sometimes appear
to fill nearly the whole calibre of the tubules.
It is found also in the secreting cells of the sebaceous and other
glandules, deposited in the
Fig. 14.              same manner as in those of
-f ~~ ~ ^      ~ the  liver, but in  smaller
quantity.  It exists, beside,
in  large  proportion, in a
/f  /.":g/      \    granular form, in the secreO/ Oo.o    / /                 tion of the sebaceous glando0,,, 0 0             It occurs abundantly in
o\   a                         the narrow  of the bones,
o.0.\,,,.\/0                  /both under the form of free
~\  ^  / ~   oil-globules and inclosed in
the vesicles of adipose tissue.
It is found inconsiderable
quantity in the substance of
URINIFEROUS TUBULES OF Dook, from Cortical quantity in the substance of
Portion of Kidney.                   the yellow wall of the corpus
luteum, and is the immediate
cause of the peculiar color of this body.
It occurs also in the form  of granules and oil-drops in the
muscular fibres of the uterus (Fig. 15), in which it begins to be




FATS.                            77
deposited soon after delivery, and where it continues to be present
during the whole period of the resorption or involution of this organ.
In all these instances, the oleaginous matters remain distinct in
form and situation from the
other ingredients of the ani-                Fig. 15.
mal frame, and are only me-  =
chanically entangled among         /
its fibres and cells, or im-     /  
bedded separately in their
interior.                      /
A  large part of the fat 
which is found in the body                     
may be accounted for by that'   
which is taken in with the   \,:?          1           /
food, since oily matter occurs  O   
in both animal and vegetable 
substances. Fat is, however, 
formed in the body, independ-    UrrMUSCULA R FIBRES OF HUMAN UTERUS, three
ently of what is introduced weeks after parturition.
with  the food.  This important fact has been definitely ascertained by the experiments of
MM. Dumas and Milne-Edwards on bees,' M. Persoz on geese,2 and
finally by those of M. Boussingault on geese, ducks, and pigs.3 The
observers first ascertained the quantity of fat existing in the whole
body at the commencement of the experiment.  The animals were
then subjected to a definite nutritious regimen, in which the
quantity of fatty matter was duly ascertained by analysis. The
experiments lasted for a period varying, in different instances, from
thirty-one days to eight months; after which the animals were
killed and all their tissues examined.  The result of these investigations showed that considerably more fat had been accumulated
by the animal during the course of the experiment than could be
accounted for by that which existed in the food; and placed it
beyond a doubt that oleaginous substances may be, and actually
are, formed in the interior of the animal body by the decomposition
or metamorphosis of other proximate principles.
It is not known from what proximate principles the fat is produced, when it originates in this way in the interior of the body.
Particular kinds of food certainly favor its production and accuAnnales de Chim. et de Phys., 3d series, vol. xiv. p. 400.   2 Ibid., p. 408.
a Chimie Agricole, Paris, 1854.




78   PROXIMATE PRINCIPLES OF THE SECOND CLASS.
mulation to a considerable degree. It is well known, for instance,
that in sugar-growing countries, as in Louisiana and the West
Indies, during the few weeks occupied in gathering the cane and
extracting the sugar, all the negroes employed on the plantations,
and even the horses and cattle, that are allowed to feed freely on
the saccharine juices, grow remarkably fat; and that they again lose
their superabundant flesh when the season is past. Even in these
instances, however, it is not certain whether the saccharine substances
are directly converted into fat, or whether they are first assimilated
and only afterward supply the materials for its production. The
abundant accumulation of fat in certain regions of the body, and its
absence in others; and more particularly its constant occurrence in
certain situations to which it could not be transported by the blood,
as for example the interior of the cells of the costal cartilages, the
substance of the muscular fibres of the uterus after parturition, &c.,
make it probable that under ordinary conditions the oily matter is
formed by decomposition of the tissues upon the very spot where it
subsequently makes its appearance.
In the female during lactation a large part of the oily matter
introduced with the food, or formed in the body, is discharged with
the milk, and goes to the support of the infant. But in the female
in the intervals of lactation, and in the male at all times, the oily
matters almost entirely disappear by decomposition in the interior
of the body; since the small quantity which is discharged with the
sebaceous matter by the skin bears only an insignificant proportion
to that which is introduced daily with the food.
The most important characteristic, in a physiological point of
view, of the proximate principles of the second class, relates to their
origin and their final destination. Not only are they all of a purely
organic origin, making their appearance first in the interior of vegetables; but the sugars and the oils are formed also, to a certain extent, in the bodies of animals; continuing to make their appearance
when no similar substances, or only an insufficient quantity of them,
have been taken with the food. Furthermore, when introduced
with the food, or formed in the body and deposited in the tissues,
these substances do not reappear in the secretions. They, therefore,
for the most part disappear by decomposition in the interior of the
body. They pass through a series of changes by which their essential characters are destroyed; and they are finally replaced in
the circulation by other substances, which are discharged with the
ex-creted fluids.




PROXIMATE PRINCIPLES OF THE THIRD GLASS.   79
CHAPTER IV.
PROXIMATE PRINCIPLES OF THE THIRD CLASS.
THE substances belonging to this class are very important, and'
form by far the greater part of the entire mass of the body. They
are derived both from animal and vegetable sources. They have
been known by the name of the "protein compounds" and the
"albuminoid substances."  The name organic substances was given
to them by Robin and Verdeil, by whom their distinguishing properties were first accurately described. They have not only an
organic origin, in common with the proximate principles of the
second class, but their chemical constitution, their physical structure and characters, and the changes which they undergo, are all so
different from those met with in any other class, that the term "organic substances" proper appears particularly appropriate to them.
Their first peculiarity is that they are not crystallizable. They
always, when pure, assume an amorphous condition, which is sometimes solid (organic substance of the bones), sometimes fluid (albumen of the blood), and sometimes semi-solid in consistency, midway
between the solid and fluid condition (organic substance of the
muscular fibre).
Their chemical constitution differs from that of bodies of the
second class, first in the fact that they all contain the four chemical
elements, oxygen, hydrogen, carbon, and nitrogen; while the
starches, sugars, and oils are destitute of the last named ingredient.
The organic matters have therefore been sometimes known by the
name of the "nitrogenous substances," while the sugars, starch, and
oils have been called "non-nitrogenous." Some of the organic matters, viz., albumen, fibrin, and casein, contain sulphur also, as an ingredient; and others, viz., the coloring matters, contain iron. The
remainder consist of oxygen, hydrogen, carbon, and nitrogen alone.
The most important peculiarity, however, of the organic substances, relating to their. chemical composition, is that it is not
definite. That is to say, they do not always contain precisely the




80    PROXIMATE PRINCIPLES OF THE THIRD CLASS.
same proportions of oxygen, hydrogen, carbon, and nitrogen; but
the relative quantities of these elements vary within certain limits,
in different individuals and at different times, without modifying, in
any essential degree, the peculiar properties of the animal matters
which they constitute. This fact is altogether a special one, and
characteristic of organic substances. No substance having a definite
chemical composition, like phosphate of lime, starch, or olein, can
suffer the slightest change in its ultimate constitution without being,
by that fact alone, totally altered in its essential properties.  If
phosphate of lime, for example, were to lose one or two equivalents
of oxygen, an entire destruction of the salt would necessarily result,
and it would cease to be phosphate of lime. For its properties as a
salt depend entirely upon its ultimate chemical constitution; and if
the latter be changed in any way, the former are necessarily lost.
But the properties which distinguish the organic substances, and
which make them  important as ingredients of the body, do not
depend immediately upon their ultimate chemical constitution, and
are of a peculiar character; being such as are only manifested in
the interior of the living organism.  Albumen, therefore, though
it may contain a few equivalents more or less of oxygen or nitrogen,
does not on that account cease to be albumen, so long as it retains
its fluidity and its. aptitude for undergoing the processes of absorption and transformation, which characterize it as an ingredient of
the living body.
It is for this reason that considerable discrepancy has existed at
various times among chemists as to the real ultimate composition
of these substances, different experimenters often obtaining different analytical results.  This is not owing to any inaccuracy in the
analyses, but to the fact that the organic substance itself really has
a different ultimate constitution at different times.  The most approved formulhe are those which have been established by Liebig
for the following substances: —
Fibrin...... -0298H22sN40092S2
Albumen.... = C2]6H169N2708S,2
Casein..                 = C28sH228N3609oS2
Owing to the above mentioned variations, however, the same
degree of importance does not attach to the quantitative ultimate
analysis of an organic matter, as to that of other substances.
This absence of a definite chemical constitution in the organic substances is undoubtedly connected with their incapacity for crystallization. It is also connected with another almost equally peculiar




ORGANIC SUBSTANCES.                      81
fact, viz., that although the organic substances unite with acids and
with alkalies, they do not play the part of an acid towards the base,
or of a base toward the acid; for the acid or alkaline reaction of
the substance employed is not neutralized, but remains as strong
after the combination as before. Furthermore, the union does not
take place, so far as can be ascertained, in any definite proportions.
The organic substances have, in fact, no combining equivalent; and
their molecular reactions and the changes which they undergo in
the body cannot therefore be expressed by the ordinary chemical
phrases which are adapted to inorganic substances.  Their true
characters, as proximate principles, are accordingly to be sought
for in other properties than those which depend upon their exact
ultimate composition.
One of these characters is that they are hygroscopie. As met with
in different parts of the body, they present different degrees of consistency; some being nearly solid, others more or less fluid. But on
being subjected to evaporation they all lose water, and are reduced
to a perfectly solid form. If after this desiccation they be exposed
to the contact of moisture, they again absorb water, swell, and
regain their original mass and consistency.  This phenomenon is
quite different from that of capillary attraction, by which some inorganic substances become moistened when exposed to: the contact
of water; for in the latter case the water is simply entangled mechanically in the meshes and pores of the inorganic body, while that
which is absorbed by the organic matter is actually united with its
substance, and diffused equally throughout its entire mass. Every
organic matter is naturally united in this way with a certain quantity
of water, some more and some less. Thus the albumen of the blood
is in union with so much water that it has the fluid form, while the
organic substance of cartilage contains less and is of a firmer consistency. The quantity of water contained in each organic substance may be diminished by artificial desiccation, or by a deficient
supply; but neither of them can be made to take up more than a
certain amount. Thus if the albumen of the blood and the organic
substance of cartilage be both reduced by evaporation to a similar
degree of dryness and then placed in water, the albumen will absorb
so much as again to become fluid, but the cartilaginous substance
only so much as to regain its usual nearly solid consistency. Even
where the organic substance, therefore, as in the case of albumen,
becomes fluid under these circumstances, it is not exactly a solution
6




82    PROXIMATE PRINCIPLES OF THE THIRD CLASS.
of it in water, but only a reabsorption by it of that quantity of fluid
with which it is naturally, associated.
Another peculiar phenomenon characteristic of organic substances
is their coagulation. Those which are naturally fluid suddenly assume, under certain conditions, a solid or semi-solid consistency.
They are then said to be coagulated; and after coagulation they
cannot be made to resume their original condition.  Thus fibrin
coagulates on being withdrawn from the bloodvessels, albumen on
being subjected to the temperature of boiling water, casein on being
placed in contact with an acid.  When an organic substance thus
coagulates, the change which takes place is a peculiar one, and has
no resemblance to the precipitation of a solid substance from a
watery solution. On the contrary, the organic substance merely
assumes a special condition; and in passing into the solid form it
retains all the water with which it was previously united. Albumen,
for example, after coagulation, retains the same quantity of water in
union with it, which it held before. After coagulation, accordingly,
this water may be driven off by evaporation, in the same manner
as previously; and on being again exposed to moisture, the organic
matter will again absorb the same quantity, though it will not resume the fluid form.
By coagulation, an organic substance is permanently altered; and
though it may be afterwards dissolved by certain chemical re-agents,
as, for example, the caustic alkalies, it is not thereby restored to its
original condition, but only suffers a still further alteration.
In many instances we are obliged to resort to coagulation in
order to separate an organic substance from the other proximate
principles with which it is associated. This is the case, for example,
with the fibrin of the blood, which is obtained in the form of floeculi, by beating freshly drawn blood with a bundle of rods.  But
when separated in this way, it is already in an unnatural condition,
and no longer represents exactly the original fluid fibrin, as it existed in the circulating blood. Nevertheless, this is the only mode
in which it can be examined, as there are no means of bringing it
back to its previous condition.
Another important property of the organic substances is that
they readily excite, in other proximate principles and in each other,
those peculiar indirect chemical changes which are termed catalyses
or catalytic transformnations. That is to say, they produce the changes
referred to, not directly, by combining with the substance which
suffers alteration, or with any of its ingredients; but simply by their




ORGANIC SUBSTANCES.                      83
presence, which induces the chemical change in an indirect manner.
Thus, the organic substances of the intestinal fluids induce a catalytic action by which starch is converted into sugar. The albumen
of the blood, by contact with the organic substance of the muscular
fibre, is transformed into a substance similar to it. The entire
process of nutrition, so far as the organic matters are concerned,
consists of such catalytic transformations.  Many crystallizable
substances, which when pure remain unaltered in the air, become
changed if mingled with organic substances, even in small quantity.
Thus the casein of milk, after being exposed for a short time to a
warm atmosphere, becomes a catalytic body, and converts the sugar
of the milk into lactic acid. In this change there is no loss nor
addition of any chemical element, since lactic acid has precisely the
same ultimate composition with sugar of milk.  It is simply a
transformation induced by the presence of the casein. Oily matters,
which are entirely unalterable when pure, readily become rancid at
warm temperatures, if mingled with an organic impurity.
Fourthly, The organic substances, when beginning to undergo
decay, induce in certain other substances the phenomenon of fermentation. Thus, the mucus of the urinary bladder, after a short
exposure to the atmosphere, causes the urea of the urine to be converted into carbonate of ammonia, with the development of gaseous
bubbles. The organic matters of grape juice, under similar circumstances, give rise to fermentation of the sugar, by which it is converted into alcohol and carbonic acid.
Fifthly, The organic substances are the only ones capable of
undergoing the process of putrefaction.  This process is a complicated one, and is characterized by a gradual liquefaction of the animal substance, by many mutual decompositions of the saline matters
which are associated with it, and by the development of peculiarly
fetid and unwholesome gases, among which are carbonic acid,
nitrogen, sulphuretted, phosphoretted, and carburetted hydrogen,
and ammoniacal vapors. Putrefaction takes place constantly after
death, if the organic tissue be exposed to a moist atmosphere at a
moderately warm temperature. It is much hastened by the presence
of other organic substances, in which decomposition has already
commenced.
The organic substances are readily distinguished, by the above
general characters, from all other kinds of proximate principles.
They are quite numerous; nearly every animal fluid and tissue
containing at least one which is peculiar to itself. They have not
as yet been all accurately described.  The following list, however,




84    PROXIMATE PRINCIPLES OF THE THIRD CLASS.
comprises the most important of them, and those with which we are
at present most thoroughly acquainted. The first seven are fluid,
or nearly so, and either colorless or of a faint yellowish tinge.
1. FIBRIN.-Fibrin is found in the blood; where it exists, in the
human subject, in the proportion of two to three parts per thousand.
It is fluid, and mingled intimately with the other ingredients of the
blood. It occurs also, but in much smaller quantity, in the lymph.
It is distinguished by what is called its "spontaneous" coagulation;
that is, it coagulates on being withdrawn from the vessels, or on the
occurrence of any stoppage to the circulation. It is rather more
abundant in the blood of some of the lower animals than in that of
the human subject. In general, it is found in larger quantity in
the blood of the herbivora than in that of the carnivora.
2. ALBUMEN.-Albumen occurs in the blood, the lymph, the
fluid of the pericardium, and in that of the serous cavities generally. It is also present in the fluid which may be extracted by
pressure from the muscular tissue. In the blood it occurs in the
proportion of about seventy-five parts per thousand. The white of
egg, which usually goes by the same name, is not identical with the
albumen of the blood, though it resembles it in some respects; it is
properly a secretion from the mucous membrane of the fowl's oviduct, and should be considered as a distinct organic substance.
Albumen coagulates on being raised to the temperature of 160~ F.;
and the coagulum, like that of all the other proximate principles, is
soluble in caustic potassa. It coagulates also by contact with alcohol, the mineral acids, ferrocyanide of potassium  in an acidulated
solution, tannin, and the metallic salts. The alcoholic coagulum, if
separated from the alcohol by washing, does not redissolve in water.
A very small quantity of albumen has been sometimes found in the
saliva.
3. CASEIN.-This substance exists in milk, in the proportion of
about forty parts per thousand. It coagulates by contact with all
the acids, mineral and organic; but is not affected by a boiling
temperature. It is coagulated also by the juices of the stomach.
It is important as an article of food, being the principal organic
ingredient in all the preparations of milk. In a coagulated form, it
constitutes the different varieties of cheese, which are more or less
highly flavored with various oily matters remaining entangled in
the coagulated casein.




GLOBULINE.-MUCOSINE.                        85
What is called vegetable casein or "legumine," is different from
the casein of milk, and constitutes the organic substance present in
various kinds of peas and beans.
4. GLOBULINE.-This is the organic substance forming the principal mass of the red globules of the blood. It is nearly fluid in
its natural condition, and readily dissolves in water. It does not
dissolve, however, in the serum  of the blood; and the globules,
therefore, retain their natural form and consistency, unless the
serum  be diluted with an excess of water.  Globuline resembles
albumen in coagulating at the temperature of boiling water. It is
said to differ from it, however, in not being coagulated by contact
with alcohol.
5. PEPSINE. —This substance occurs as an ingredient in the gastric juice. It is not the same substance which Schwann extracted
by maceration from  the mucous membrane of the stomach, and
which is regarded by Robin, Bernard, &c., as only an artificial product of the alteration of the gastric tissues. There seems no good
reason, furthermore, why we should not designate by this name the
organic substance which really exists in the gastric juice. It occurs
in this fluid in very small quantity, not over fifteen parts per
thousand. It is coagulable by heat, and also by contact with alcohol. But if the alcoholic coagulum  be well washed, it is again
soluble in a watery acidulated fluid.
6. PANCREATINE.-This is the organic substance of the pancreatic
juice, where it occurs in great abundance. It coagulates by heat,
and by contact with sulphate of magnesia in excess. In its natural
condition it is fluid, but has a considerable degree of viscidity.
7. MUCOSINE is the organic substance which is found in the different varieties of mucus, and which imparts to them their viscidity
and other physical characters. Some of these mucous secretions
are so mixed with other fluids, that their consistency is more or less
diminished; others which remain pure, like that secreted by the
mucous follicles of the cervix uteri, have nearly a semi-solid consistency. But little is known with regard to their other specific
characters.
The next three organic substances are solid or semi-solid in consistency.




86   PROXIMATE PRINCIPLES OF THE THIRD CLASS.
8. OSTEINE is the organic substance of the bones, in which it is
associated with a large proportion of phosphate of lime. It exists,
in those bones which have been examined, in the proportion of
about two hundred parts per thousand. It is this substance which
by long boiling of the bones is transformed into gelatine or glue.
In its natural condition, however, it is insoluble in water, even at
the boiling temperature, and becomes soluble only after it has been
permanently altered by ebullition.
9. CARTILAGINE. —This forms the organic ingredient of cartilage.
Like that of the bones, it is altered by long boiling, and is converted
into a peculiar kind of gelatine termed "chondrine." Chondrine
differs from the gelatine of bones principally in being precipitated
by acids and certain metallic salts which have no effect on the latter.
Cartilagine, in its natural condition, is very solid, and is closely
united with the calcareous salts.
10. MUSCULINE.-This substance forms the principal mass of the
muscular fibre. It is semi-solid, and insoluble in water, but soluble
in dilute muriatic acid, from which it may be again precipitated by
neutralizing with an alkali. It closely resembles albumen in its
chemical composition, and like it, contains, according to Scherer,
two equivalents of sulphur.
The four remaining organic substances form a somewhat peculiar
group.  They are the coloring matters of the body. They exist
always in small quantity, compared with the other ingredients, but
communicate to the tissues and fluids a very distinct coloration.
They all contain iron as one of their ultimate elements.
11. HImIMATINE is the coloring matter of the red globules of the
blood. It is nearly fluid like the globuline, and is united with it
in a kind of mutual solution. It is much less abundant than the
globuline, and exists in the proportion of about one part of hbematine to seventeen parts of globuline. The following is the formula
for its composition which is adopted by Lehmann:Hematine.                    C44H22N3O0Fe.
When the blood-globules from any cause become disintegrated, the
haematine is readily imbibed after death by the walls of the bloodvessels and the neighboring parts, staining them of a deep red
color. This coloration has sometimes been mistaken for an evidence




MELANINE. U ROSAGINE.                       87
of arteritis; but is really a simple effect of post-mortem imbibition,
as above stated.
12. MELANINE.-This is the blackish-brown coloring matter
which is found in the choroid coat of the eye, the iris, the hair, and
more or less abundantly in the epidermis. So far as can be ascertained, the coloring matter is the same in all these situations. It is
very abundant in the black and brown races, less so in the yellow
and white, but is present to a certain extent in all. Even where
the tinges produced are entirely different, as, for example, in brown
and blue eyes, the coloring matter appears to be the same in character, and to vary only in its quantity and the mode of its arrangement; for the tinge of an animal tissue does not depend. on its
local pigment only, but also on the muscular fibres, fibres of areolar
tissue, capillary bloodvessels, &c.  All these ingredients of the
tissue are partially transparent, and by their mutual interlacement
and superposition modify more or less the effect of the pigment
which is deposited below or among them.
Melanine is insoluble in water and the dilute acids, but dissolves
slowly in caustic potassa. Its ultimate composition resembles that
of haematine, but the proportion of iron is smaller.
13. BILIVERDINE is the coloring matter of the bile.  It is yellow
by transmitted light, greenish by reflected light. On exposure to
the air in its natural fluid condition, it absorbs oxygen and assumes
a bright grass green color. The same effect is produced by treating
it with nitric acid or other oxidizing substances. It occurs in very
small quantity in the bile, from which it may be extracted by precipitating it with milk of lime (Robin), from which it is afterward
separated by dissolving out the lime with muriatic acid. Obtained
in this form, however, it is insoluble in water, having been coagulated by contact with the calcareous matter; and is not, therefore,
precisely in its original condition.
14. UROSACINE is the yellowish red coloring matter of the urine.
It consists of the same ultimate elements as the other coloring matters, but occurs in the urine in such minute quantity, that the
relative proportion of its elements has never been determined. It
readily adheres to insoluble matters when they are precipitated from
the urine, and is consequently found almost always, to a greater or
less extent, as an ingredient in urinary calculi formed of the urates




88    PROXIMATE PRINCIPLES OF THE THIRD CLASS.
or of uric acid. When the urates are thrown down also in the form
of a powder, as a urinary deposit, they are usually colored more or
less deeply, according to the quantity of urosacine which is precipitated with them.
The organic substances which exist in the body require for their
production an abundant supply of similar substances in the food.
All highly nutritious articles of diet, therefore, contain more or less
of these substances.  Still, though nitrogenous matters must be
abundantly supplied, under some form, from without, yet the particular kinds of organic substances, characteristic of the tissues, are
formed in the body by a transformation of those which are. introduced with the food. The organic matters derived from vegetables,
though similar in their general characters to those existing in the
animal body, are yet specifically different. The gluten of wheat,
the legumine of peas and beans, are not the same with animal albumen and fibrin. The only organic substances taken with animal
food, as a general rule, are the albumen of eggs, the casein of milk,
and the musculine of flesh; and even these, in the food of the
human species, are so altered and coagulated by the process of
cooking, as to lose their specific characters before being introduced
into the alimentary canal. They are still further changed by the
process of digestion, and are absorbed under another form into the
blood. But from their.subsequent metamorphoses there are formed,
in the different parts of the body, osteine, cartilagine, hematine,
globuline, and all the other varieties of organic matter that characterize the different tissues. These varieties, therefore, originate
as such in the animal economy by the catalytic changes which the
ingredients of the blood undergo in nutrition.
Only a very small quantity of organic matter is discharged
with the excretions. The coloring matters of the bile and urine,
and the mucus of the urinary bladder, are almost the only ones
that find an exit from the body in this way. There is a minute
quantity of organic matter exhaled in a volatile form with the
breath, and a little also, in all probability, from the cutaneous surface. But the entire quantity so discharged bears but a very small
proportion to that which is daily introduced with the food. The
organic substances, therefore, are decomposed in the interior of the
body. They are transformed by the process of destructive assimilation, and their elements are finally eliminated and discharged
under other forms of combination.




OF FOOD.                          89
CHAPTER V.
OF FOOD.
UNDER the term  "food" are included all those substances, solid
and liquid, which are necessary to sustain the process of nutrition.
The first act of this process is the absorption from without of all
those materials which enter into the composition of the living frame,
or of others which may be converted into them in the interior of
the body.
The proximate principles of the first class, or the "inorganic
substances," require to be supplied in sufficient quantity to keep up
the natural proportion in which they exist in the various solids and
fluids. As we have found it to be characteristic of these substances,
except in a few instances, that they suffer no alteration in the interior of the body, but, on the contrary, are absorbed, deposited in
its tissue, and pass out of it afterward unchanged, nearly every one
of them requires to be present under its own proper form, and in
sufficient quantity in the food. The alkaline carbonates, which
are formed, as we have seen, by a decomposition of the malates,
citrates and tartrates, constitute almost the only exception to this
rule.
Since water enters so largely into the composition of nearly every
part of the body, it is equally important as an ingredient of the
food. In the case of the human subject, it is probably the most
important substance to be supplied with constancy and regularity,
and the system suffers more rapidly when entirely deprived of
fluids, than when the supply of solid food only is withdrawn. A
man may pass eight or ten hours, for example, without solid food,
and suffer little or no inconvenience; but if deprived of water for
the same length of time, he becomes rapidly exhausted, and feels
the deficiency in a very marked degree. Magendie found, in his
experiments on dogs subjected to inanition,' that if the animals
I Comptes Rendus, vol. xiii. p. 256.




90                          OF FOOD.
were supplied with water alone they lived six, eight, and even ten
days longer than if they were deprived at the same time of both
solid and liquid food. Chloride of sodium, also, is usually added
to the food in considerable quantity, and requires to be supplied
with tolerable regularity; but the remaining inorganic materials,
such as calcareous salts, the alkaline phosphates, &c., occur naturally in sufficient quantity in most of the articles which are used as
food.
The proximate principles of the second class, so far as they constitute ingredients of the food, are naturally divided into two
groups: 1st, the sugar, and 2d, the oily matters.  Since starch is
always converted into sugar in the process of digestion, it may be
included, as an alimentary substance, in the same group with the
sugars.  There is a natural desire in the human species for both
saccharine and oleaginous food. In the purely carnivorous animals,
however, though no starch or sugar be taken, yet the body is maintained in a healthy condition. It has been supposed, therefore, that
saccharine matters could not be absolutely necessary as food; the
more so since it has been found, by the experiments of C1. Bernard,
that, in carnivorous animals kept exclusively on a diet of flesh,
sugar is still formed in the liver, as well as in the mammary gland.
The above conclusion, however, which has been drawn from these
facts, does not apply practically to the human species. The carnivorous animals have no desire for vegetable food, while in the
human species there is a natural craving for it, which is almost
universal. It may be dispensed with for a few days, but not with
impunity for any great length of time.  The experiment has often
enough been tried, in the treatment of diabetes, of confining the
patient to a strictly animal diet. It has been invariably found that,
if this regimen be continued for some weeks, the desire for vegetable
food on the part of the patient becomes so imperative that the plan
of treatment is unavoidably abandoned.
A similar question has also arisen with regard to the oleaginous
matters.  Are these substances indispensable as ingredients of the
food, or may they be replaced by other proximate principles, such
as starch or sugar? It has already been seen, from the experiments
of Boussingault and others, that a certain amount of fat is produced
in the body over and above that which is taken with the food; and
it appears also that a regimen abounding in saccharine substances
is favorable to the production of fat. It is altogether probable,
therefore, that the materials for the production of fat may be




OF FOOD.                           91
derived, under these circumstances, either directly or indirectly
from saccharine matters. But saccharine matters alone are not
entirely sufficient. M. Huber' thought he had demonstrated that
bees fed on pure sugar would produce enough wax to show that
the sugar could supply all that was necessary to the formation of
the fatty matter of the wax. Dumas and Milne-Edwards, however,
in repeating Huber's experiments,2 found that this was not the case.
Bees, fed on pure sugar, soon cease to work, and sometimes perish
in considerable numbers; but if fed with honey, which contains
some waxy and other matters beside the sugar, they thrive upon
it; and produce, in a given time, a much larger quantity of fat than
was contained in the whole supply of food.
The same thing was established by Boussingault with regard to
starchy matters.  He found that in'fattening pigs, though the
quantity of fat accumulated by the animal considerably exceeded
that contained in the food, yet fat must enter to some extent into
the composition of the food in order to maintain the animals in a
good condition; for pigs, fed on boiled potatoes alone (an article
abounding in starch but nearly destitute of oily matter), fattened
slowly and with great difficulty; while those fed on potatoes mixed
with a greasy fluid fattened readily, and accumulated, as mentioned
above, much more fat than was contained in the food.
The apparent discrepancy between these facts may be easily explained, when we recollect that, in order that the animal may become
fattened, it is necessary that he be supplied not only with the
materials of the fat itself, but also with everything else which is
necessary to maintain the body in a healthy condition. Oleaginous
matter is one of these necessary substances. The fats which are
taken in with the food are not destined to be simply transported
into the body and deposited there unchanged.  On the contrary,
they are altered and used up in the processes of digestion and
nutrition; while the fats which appear in the body as constituents
of the tissues are, in great part, of new formation, and are produced
from materials derived, perhaps, from a variety of different sources.
It is certain, then, that either one or the other of these two
groups of substances, saccharine or oleaginous, must enter into the
composition of the food; and furthermore, that, though the oily
matters may sometimes be produced in the body from the sugars,
I Natural History of Bees, Edinboro', 1821, p. 330.
2 Annales de Chim. et de Phys., 3d series, vol. xiv. p. 400.




92                         OF FOOD.
it is also necessary for the perfect nutrition of the body that fat be
supplied, under its own form, with the food.  For the human
species, also, it is natural to have them both associated, in the
alimentary materials. They occur together in most vegetable substances, and there is a natural desire for them both, as elements of
the food.
They are not, however, when alone, or even associated with each
other, sufficient for the nutrition of the animal body. Magendie
found that dogs, fed exclusively on starch or sugar, perished after a
short time with symptoms of profound disturbance of the nutritive
functions. An exclusive diet of butter or lard had a similar effect.
The animal became exceedingly debilitated, though without much
emaciation; and after death, all the internal organs and tissues
were found infiltrated with oil. Boussingault' performed a similar
experiment, with a like result, upon a duck, which was kept upon
an exclusive regimen of butter.  "The duck received 1350 to 1500
grains of butter every day. At the end of three weeks it died of
inanition. The butter oozed from every part of its body. The
feathers looked as though they had been steeped in melted butter,
and the body exhaled an unwholesome odor like that of butyric
acid."
Lehmann was also led to the same result by some experiments
which he performed upon himself for the purpose of ascertaining
the effect produced on the urine by different kinds of food.2
This observer confined himself first to a purely animal diet for
three weeks, and afterwards to a purely vegetable one for sixteen
days, without suffering any marked inconvenience. He then put
himself upon a regimen consisting entirely of non-nitrogenous substances, starch, sugar, gum, and oil, but was only able to continue
this diet for two, or at most for three days, owing to the marked
disturbance of the general health which rapidly supervened. The
unpleasant symptoms, however, immediately disappeared on his
return to an ordinary mixed diet.  The same fact has been established more recently by Prof. Wm. A. Hammond,3 in a series of
experiments which he performed upon himself. He was enabled
to live for ten days on a diet composed exclusively of boiled starch
and water. After the third day, however, the general health began
1 Chimie Agricole, p. 166.
2 Journal fir praktische Chemie, vol. xxvii. p. 257.
3 Experimental Researches, &c., being the Prize Essay of the American Medical
Association for 1857.




OF FOOD.                           93
to deteriorate, and became very much disturbed before the termination of the experiment. The prominent symptoms were debility,
headache, pyrosis, and palpitation of the heart. After the starchy
diet was abandoned, it required some days to restore the health to
its usual condition.
The proximate principles of the third class, or the organic substances proper, enter so largely into the constitution of the animal
tissues and fluids, that their importance, as elements of the food, is
easily understood.  No food can be long nutritious, unless a certain
proportion of these substances be present in it. Since they are so
abundant as ingredients of the body, their loss or absence from the
food is felt more speedily and promptly than that of any other substance except water. They have, therefore, sometimes received the
name of "nutritious substances," in contradistinction to those of
the second class, which contain no nitrogen, and which have been
found by the experiments of Magendie and others to be insufficient
for the support of life. The organic substances, however, when
taken alone, are no more capable of supporting life indefinitely than
the others. It was found in the experiments of the French "Gelatine Commission"' that animals fed on pure fibrin and albumen, as
well as those fed on gelatine, become after a short time much enfeebled, refuse the food which is offered to them, or take it with
reluctance, and finally die of inanition.  This result has been
explained by supposing that these substances, when taken alone,
excite after a time such disgust in the animal that they are either
no longer taken, or if taken are not digested. But this disgust
itself is simply an indication that the substances used are insufficient
and finally useless as articles of food, and that the system demands
instinctively other materials for its nourishment.
The instinctive desire of animals for certain substances is the
surest indication that they are in reality required for the nutritive
process; and on the other hand, the indifference or repugnance
manifested for injurious or useless substances, is an equal evidence
of their unfitness as articles of food. This repugnance is well described by Magendie, in the report of the commission above alluded
to, while detailing the result of his investigations on the nutritive
qualities of gelatine.  "The result," he says, "of these first trials
was that pure gelatine was not to the taste of the dogs experimented
on.  Some of them suffered the pangs of hunger with the gelatine' Comptes Rendus, 1841, vol. xiii. p. 267.




94                         OF FOOD.
within their reach, and would not touch it; others tasted of it, but
would not eat; others still devoured a certain quantity of it once
or twice, and then obstinately refused to make any further use of it."
In one instance, however, Magendie succeeded in inducing a dog
to take a considerable quantity of pure fibrin daily throughout the
whole course of the experiment; but notwithstanding this, the
animal became emaciated like the others, and died at last with the
same symptoms of inanition.
The alimentary substances of the second class, however, viz., the
sugars and the oils, have been sometimes thought less important
than the albuminous matters, because they do not enter so largely
or so permanently into the composition of the solid tissues. The
saccharine matters, when taken as food, cannot be traced farther
than the blood. They undergo already, in the circulating fluid,
some change by which their essential character is lost, and they
cannot be any longer recognized. The appearance of sugar in the
mammary gland and the milk is only exceptional, and does not
occur at all in the male subject. The fats are, it is true, very generally distributed throughout the body, but it is only in the brain
and nervous matter that they exist intimately united with the remaining ingredients of the tissues. Elsewhere, as already mentioned,
they are deposited in distinct drops and granules, and so long as
they remain in this condition must of course be inactive, so far as
regards any chemical nutritive process. In this condition they
seem to be held in reserve, ready to be absorbed by the blood,
whenever they may be required for the purposes of nutrition.  On
being reabsorbed, however, as soon as they again enter the blood
or unite intimately with the substance of the tissues, they at once
change their condition and lose their former chemical constitution
and properties.
It is for these reasons that the albuminoid matters have been
sometimes considered as the only "nutritious" substances, because
they alone constitute under their own form a great part of the
ingredients of the tissues, while the sugars and the oils rapidly disappear by decomposition. It has even been assumed that the process by which the sugar and the oils disappear is one of direct
combustion or oxidation, and. that they are destined solely to be
consumed in this way, not to enter at all into the composition of
the tissues, but only to maintain the heat of the body by an incessant process of combustion in the blood. They have been therefore
termed the "combustible" or "heat-producing" elements, while the




OF FOOD.                          95
albuminoid substances were known as the nutritious or "plastic"
elements.
This distinction, however, has no real foundation. In the first
place, it is not at all certain that the sugars and the oils which disappear in the body are destroyed by combustion. This is merely
an inference which has been made without any direct proof. All
we know positively in regard to the matter is that these substances
soon become so altered in the blood that they can no longer be
recognized by their ordinary chemical properties; but we are still
ignorant of the exact nature of the transformations which they
undergo. Furthermore, the difference between the sugars and the
oils on the one hand, and the albuminoid substances on the other,
so far as regards their decomposition and disappearance in the
body, is only a difference in time. The albuminoid substances
become transformed more slowly, the sugars and the oils more
rapidly.  Even if it should be ascertained hereafter that the sugars
and the oils really do not unite at all with the solid tissues, but are
entirely decomposed in the blood, this would not make them any
less important as alimentary substances, since the blood is as
essential a part of the body as the solid tissues, and its nutrition
must be provided for equally with theirs.
It is evident, therefore, that no single proximate principle, nor
even any one class of them alone, can be sufficient for the nutrition
of the body; but that the food, to be nourishing, must contain
substances belonging to all the different groups of proximate principles. The albuminoid substances are first in importance because
they constitute the largest part of the entire mass of the body; and
exhaustion therefore follows more rapidly when they are withheld
than when the animal is deprived of other kinds of alimentary
matter.  But starchy and oleaginous substances are also requisite;
and the body feels the want of them sooner or later, though it may
be plentifully supplied with albumen and fibrin. Finally, the inorganic saline matters, though in smaller quantity, are also necessary to the continuous maintenance of life.  In order that the
animal tissues and fluids remain in a healthy condition and take
their proper part in the functions of life, they must be supplied
with all the ingredients necessary to their constitution; and a man
may be starved to death at last by depriving him of chloride of
sodium or phosphate of lime just as surely, though not so rapidly,
as if he were deprived of albumen or oil.
In the different kinds of food, accordingly, which have been




96                            OF FOOD.
adopted by the universal and instinctive choice of man, the three
different classes of proximate principles are all more or less abundantly represented. In all of them there exists naturally a certain
proportion of saline substances; and water and chloride of sodium
are generally taken with them in addition. In milk, the first food
supplied to the infant, we have casein which is an albuminoid
substance, butter which represents the oily matters, and sugar of
milk belonging to the saccharine group, together with water and
saline matters, in the following proportions:-'
COMPOSITION OF COW'S MILK.
Water.......87.02
Casein......  4.48
Butter..                                                     3.13
Sugar of milk......  4.77
Soda.....
Chlorides of potassium and sodium...
Phosphates of soda and potassa....
Phosphate of lime...0.60
"  magnesia.. 
Alkaline carbonates.....
Iron, &c......
100.00
In wheat flour, gluten is the albuminoid matter, sugar and starch
the non-nitrogenous principles.
COMPOSITION OF WHEAT FLOUR.
Gluten... 10.2         Gum...  2.8
Starch.. 72.8       Water....10.0
Sugar....  4.2
100.0
Tihe other cereal grains mostly contain oil in addition to the
above.
COMPOSITION OF DRIED OATMEAL.
Starch.                                                    59.00
Bitter matter and sugar....8.25
Gray albuminous matter.   4.30
Fatty oil.....  2.00
Gum......  2.50
Husk, mixture, and loss....23.95
100.00
Eggs contain albumen and salts in the white, with the addition
of oily matter in the yolk.
1 The accompanying analyses of various kinds of food are taken from Pereira
on Food and Diet, New York, 1843.




OF FOOD.                             97
COMPOSITION OF EGGS.
White of Egg.                      Yolk of Egg.
Water..  80.00                              53.78
Albumen and mucus.  15.28...  12.75
Yellow oil..........  28.75
Salts.            4.72......   4.72
100.00                            100.00
In ordinary flesh or butcher's meat, we have the albuminoid
matter of the muscular fibre and the fat of the adipose tissue.
COMPOSITION OF ORDINARY BUTCHER'S MEAT.
Meat devoid of fat. 85.7     S Water                 63.418
Solid matter..      22.282
Fat, cellular tissue, &c.                               14.300
100.000
From what has been said above, it will easily be seen that the
nutritious character of any substance, or its value as an article of
food, does not depend simply upon its containing either one of the
alimentary substances mentioned above in large quantity; but upon
its containing them  mingled  together in such proportion as is
requisite for the healthy nutrition of the body. What these proportions are cannot be determined from simple chemical analysis,
nor from any other data than those derived from direct observation
and experiment.
The total quantity of food required by man has been variously
estimated. It will necessarily vary, indeed, not only with the constitution and habits of the individual, but also with the quality of
the food employed; since some articles, such as corn and meat, contain very much more alimentary material in the same bulk than
fresh fruits or vegetables. Any estimate, therefore, of the total
quantity should state also the kind of food used; otherwise, it will
be altogether without value.  From  experiments performed while
living on an exclusive diet of bread, fresh meat, and butter, with
coffee and water for drink, we have found that the entire quantity
of food required during twenty-four hours by a man infull health,
and taking free exercise in the open air, is as follows:Meat..16 ounces or 1.00 lb. Avoirdupois.
Bread.    19  " " 1.19 "                         "
Butter or fat... 3    "      0.22"      "
Water.... 52fluidoz." 3.38 " 
That is to say, rather less than two and a half pounds of solid food,
and rather over three pints of liquid food.
7




98                          OF FOOD.
Another necessary consideration, in estimating the value of any
substance as an article of food, is its digestibility. A vegetable or
animal tissue may contain an abundance of albuminoid or starchy
matter, but may be at the same time of such an unyielding consistency as to be insoluble in the digestive fluids, and therefore useless
as an article of food. Bones and cartilages, and the fibres of yellow
elastic tissue, are indigestible, and therefore not nutritious. The
same remark may be made with regard to the substances contained
in woody fibre, and the hard coverings and kernels of various fruits.
Everything, accordingly, which softens or disintegrates a hard alimentary substance renders it more digestible, and so far increases
its value as an article of food.
The preparation of food by cooking has a twofold object: first,
to soften or disintegrate it, and second, to give it an attractive
flavor.  Many vegetable substances are so hard as to be entirely
indigestible in a raw state. Ripe peas and beans, the different kinds
of grain, and many roots and fruits, require to be softened by boiling, or some other culinary process, before they are ready for use.
With them, the principal change produced by cooking is an alteration in consistency.  With most kinds of animal food, however, the
effect is somewhat different.  In the case of muscular flesh, for example, the muscular fibres themselves are almost always more or
less hardened by boiling or roasting; but, at the same time, the
fibrous tissue by which they are held together is gelatinized and
softened, so that the muscular fibres are more easily separated from
each other, and more readily attacked by the digestive fluids. But
beside this, the organic substances contained in meat, which are all
of them very insipid in the raw state, acquire, by the action of heat
in cooking, a peculiar and agreeable flavor. This flavor excites
the appetite and stimulates the flow of the digestive fluids, and
renders, in this way, the entire process of digestion more easy and
expeditious.
The changes which the food undergoes in the interior of the body
may be included under three different heads: first, digestion, or the
preparation of the food in the alimentary canal; second, assimilation,
by which the elements of the food are converted into the animal
tissues; and third, excretion, by which they are again decomposed,
and finally discharged from the body.




DIGESTION.                         99
CHAPTER VI.
DIGESTION.
DIGESTION is that process by which the food is reduced to a form
in which it can be absorbed from the intestinal canal, and taken np
by the bloodvessels. This process does not occur in vegetables.
For vegetables are dependent for their nutrition, mostly, if not
entirely, upon a supply of inorganic substances, as water, saline
matters, carbonic acid and ammonia. These materials constitute
the food upon which plants subsist, and are converted in their interior into other substances, by the nutritive process. These materials, furthermore, are constantly supplied to the vegetable under
such a form as to be readily absorbed. Carbonic acid and ammonia
exist in a gaseous form in the atmosphere, and are also to be found
in solution, together with the requisite saline matters, in the water
with which the soil is penetrated. All these substances, therefore,
are at once ready for absorption, and do not require any preliminary
modification.  But with animals and man the case is different.
They cannot subsist upon these inorganic substances alone, but
require for their support materials which have already been organized, and which have previously constituted a part of animal or
vegetable bodies. Their food is almost invariably solid or semi-solid
at the time when it is taken, and insoluble in water. Meat, bread,
fruits, vegetables, &c., are all taken into the stomach in a solid and
insoluble condition; and even those substances which are naturally
fluid, such as milk, albumen, white of egg, are almost always, in
the human species, coagulated and solidified by the process of cooking, before being taken into the stomach.
In animals, accordingly, the food requires to undergo a process
of digestion, or liquefaction, before it can be absorbed. In all cases,
the general characters of this process are the same. It consists
essentially in the food being received into a canal, running through
the body from  mouth to anus, called the "alimentary canal," in
which it comes in contact with certain digestive fluids, which act




100                       DIGESTION.
upon it in such a way as to liquefy and dissolve it. These fluids
are secreted by the mucous membrane of the alimentary canal, and
by certain glandular organs situated in its neighborhood. Since the
food always consists, as we have already seen, of a mixture of various substances, having different physical and chemical properties,
the several digestive fluids are also different from each other; each
one of them exerting a peculiar action, which is more or less con.
fined to particular species of food. As the food passes through the
intestine from above downward, those parts of it which become
liquefied are successively removed by absorption, and taken up by
the vessels; while the remaining portions, consisting of the indigestible matter, together with the refuse of the intestinal secretions,
gradually acquire a firmer consistency owing to the absorption of
the fluids, and are finally discharged from the intestine under the
form of feces.
In different species of animals, however, the difference in their
habits, in the constitution of their tissues, and in the character of
their food, is accompanied with a corresponding variation in the
anatomy of the digestive apparatus, and the character of the secreted
fluids. As a general rule, the digestive apparatus of herbivorous
animals is more complex than that of the carnivora; since, in vegetable substances, the nutritious matters are often present in a very
solid and unmanageable form, as, for example, in raw starch and
the cereal grains, and are nearly always entangled among vegetable
cells and fibres of an indigestible character. In those instances
where the food consists mostly of herbage, as grass, leaves, &c., the
digestible matters bear only a small proportion to the entire quantity; and a large mass of food must therefore be taken, in order
that the requisite amount of nutritious material may be extracted
from it. In such cases, accordingly, the alimentary canal is large
and long; and is divided into many compartments, in which
different processes of disintegration, transformation, and solution
are carried on.
In the common fowl, for instance (Fig. 16), the food, which consists mostly of grains, and frequently of insects with hard, coriaceous integument, first passes down the  esophagus (a) into a
diverticulum or pouch (b) termed the crop. Here it remains for
a time, mingled with a watery secretion in which the grains are
macerated and softened.  The food is then carried farther down
until it reaches a second dilatation (c), the proventriculus, or
secreting stomach.  The mucous membrane here is thick  and




DIGESTION.                           101
glandular, and is provided with numerous se-            Fig. 16.
creting follicles or crypts.  From  them  an
acid fluid is poured out, by which the food is
subjected to further changes.  It next passes
into the gizzard (d), or triturating stomach, a
cavity inclosed by thick, muscular walls, and
lined with a remarkably tough  and  horny 
epithelium.  Here it is subjected to the crushing and grinding action of the muscular pa-            i l'
rietes, assisted by grains of sand and gravel,
which the animal instinctively swallows with
the food, by which it is so triturated and disintegrated, that it is reduced to a uniform pulp,
upon which the digestive fluids can effectually 
operate.  The mass then passes into the intes- 
tine (e), where it meets with the intestinal
juices, which complete the process of solution;.f
and from  the intestinal cavity it is finally absorbed in a liquid form, by the vessels of the
mucous membrane.
In'the ox, again, the sheep, the camel, the
deer, and all ruminating animals, there are 
four distinct stomachs  through  which the
food passes in succession; each lined with
mucous membrane of a different structure,            j [
and adapted to perform  a different part in   "
the digestive process. (Fig. 17.)  When first   ALIMENTARY CANAL
swallowed, the food is received into the ru- O FOWL.-a. (Esophagus.
b. Crop.  c. Proventriculus,
men, or paunch (b), a large sac, itself par- or secretingstomach. d. Giz*11 i a -.,'~ w   1 *   l   * *zard   or triturating stomach.
tially divided by incomplete partitions, and zer.  Inttine. f.r longtoach.
e. Intestine. f. Two long ealined by a mucous membrane  thickly  set cal tubes which open into the
intestine a short distance
with long prominences or villi.  Here it ac- aboveits termination.
cumulates while the animal is feeding, and is
retained and macerated in its own fluids.  When the animal has
finished browsing, and the process of rumination commences, the
food is regurgitated into the mouth by an inverted action of the
muscular walls of the paunch and oesophagus, and slowly masticated.
It then descends again along the cesophagus; but instead of entering the first stomach, as before, it is turned off by a muscular valve
into the second stomach, or reticulum (c), which is distinguished
by the intersecting folds of its mucous membrane, which give it




102                        DIGESTION.
a honey-combed or reticulated appearance.  Here the food, already
triturated  in  the  mouth, and
Fig. 17.       mixed with the saliva, is further
macerated in the fluids swallowed
___I  c\     by the animal, which always accumulate in considerable quantity in the reticulum. The next
cavity is the omasus, or "psalterium" (d), in which the mucous
l b           f /lH   ^ l  membrane is arranged in longitudinal folds, alternately broad
and narrow, lying parallel with
each other, like the leaves of a
book, so that the extent of mucous
surface, brought in contact with
COMPOUND STOMACH OF OX.-a. (Eso- the food, is very much increased.
phagus. b. Rumen, or first stomach. c. Reticulum, orsecond. d. Omasus, orthird. e. Abo- The exit from  this cavity leads
masus,orfourth. f. Duodenum. (From Rymer directly  into the  abomasus   or
Jones.)                                 -'
"rennet" (e), which is the true
digestive stomach, in which the mucous membrane is softer, thicker,
and more glandular than elsewhere, and in which an acid and
highly solvent fluid is secreted. Then follows the intestinal canal
with its various divisions and variations.
In the carnivora, on the other hand, the alimentary canal is
shorter and narrower than in the preceding, and presents fewer
complexities.  The food, upon which these animals subsist, is softer
than that of the herbivora, and less encumbered with indigestible
matter; so that the process of its solution requires a less extensive
apparatus.
In the human species, the food is naturally of a mixed character, containing both animal and vegetable substances. But the
digestive apparatus in man resembles almost exactly that of the
carnivora. For the vegetable matters which we take as food are,
in the first place, artificially separated, to a great extent, from indigestible impurities; and secondly, they are so softened by the
process of cooking as to become nearly or quite as easily digestible
as animal substances.
In the human species, however, the process of digestion, though
simpler than in the herbivora, is still complicated. The alimentary
canal is here, also, divided into different compartments or cavities,
which communicate with each other by narrow  orifices.  At its




DIGESTION.                          103
commencement (Fig. 18), we find the cavity of the mouth, which is
guarded at its posterior extremity by the muscular valve of the
isthmus  of  the  fauces.
Through the pharynx and                      Fig. 18
cesophagus (a), it communicates  with  the  second
compartment, or the  stomach  (b), a  flask-shaped
dilatation, which is guarded
at the cardiac and pyloric;;
orifices by circular bands
of muscular fibres.  Then.
comes the small intestine (e),                  1
different parts of which,
owing to the varying struc- 
ture of their mucous membranes, have received the 
different names of duode-. 
num, jejunum, and ileum.
In the duodenum, we have
the orifices of the bilicfry
and pancreatic ducts (f, g).
Finally, we have the large
intestine (h, i, j, k), separated
from  the smaller by the           -.
ileo-caecal valve, and  ter- 
minating, at its lower extremity, by the anus, at
which is situated. a double
sphincter, for the purpose  
of  guarding  its  orifice.
Everywhere the alimentary 
canal is composed  of  a
mucous membrane and a
muscular coat, with a layer   HUMAN ALIMENTARY CANAL.-a. Esophagus.
Of sUbmucous areolar tissue  b. Stomach. c. Cardiac orifice. d. Pylorus. e. Small
of submucous areolar ie  intestine. f. Biliary duct. g. Pancreatic duct. h. Asbetween the two. The mus- cending colon. i. Transverse colon. j. Descending colon. k. Rectum.
cular coat is everywhere
composed of a double layer of longitudinal and transverse fibres,
by the alternate contraction and relaxation of which the food is
carried through the canal from  above downward.  The mucous




104                       DIGESTION.
membrane presents, also, a different structure, and has different
properties in different parts. In the mouth and oesophagus, it is
smooth, with a hard, whitish, and tessellated epithelium. This kind
of epithelium terminates abruptly at the cardiac orifice of the
stomach.  The mucous membrane of the gastric cavity is soft and
glandular, covered with a transparent, columnar epithelium, and
thrown into minute folds or projections on its free surface, which
are sometimes reticulated with each other. In the small intestine,
we find large transverse folds of mucous membrane, the valvulce
conniventes, the minute villosities which cover its surface, and the
peculiar glandular structures which it contains.  Finally, in the
large intestine, the mucous membrane is again different. It is here
smooth and shining, free from villosities, and provided with a different glandular apparatus.
Furthermore, the digestive secretions, also, vary in these different
regions.  In its passage from  above downward, the food meets
with no less than five different digestive fluids. First it meets with
the saliva in the cavity of the mouth; second, with the gastric juice,
in the stomach; third, with the bile; fourth, with the pancreatic
fluid; and fifth, with the intestinal juice. It is the most important
characteristic of the process of digestion, as established by modern
researches, that different elements of the food are digested in different
parts of the alimentary canal by the agency of different digestive fluids.
By their action, the various ingredients of the alimentary mass are
successively reduced to a fluid condition, and are taken up by the
vessels of the intestinal mucous membrane.
The action which is exerted upon the food by the digestive
fluids is not that of a simple chemical solution. It is a transformation, by which the ingredients of the food are altered in character
at the same time that they undergo the process of liquefaction.
The active agent in producing this change is in every instance an
organic matter, which enters as an ingredient into the digestive
fluid; and which, by coming in contact with the food, exerts upon
it a catalytic action, and transforms its ingredients into other substances.  It is these newly formed substances which are finally
absorbed by the vessels, and mingled with the general current of
the circulation.
In our study of the process of digestion, the different digestive
fluids will be examined separately, and their action on the alimentary substances in the different regions of the digestive apparatus
successively investigated.




MASTICATION.                        105
MASTICATION.-In the first division of the alimentary canal, viz.,
the mouth, the food undergoes simultaneously two different operations, viz., mastication and insalivation. Mastication consists in
the cutting and trituration of the food by the teeth, by the action
of which it is reduced to a state of minute subdivision. This process is entirely a mechanical one. It is necessary, in order to prepare the food for the subsequent action of the digestive fluids. As
this action is chemical in its nature, it will be exerted more promptly
and efficiently if the food be finely divided than if it be brought in
contact with the digestive fluids in a solid mass. This is always
the case when a solid body is subjected to the chemical action of a
solvent fluid; since, by being broken up into minute particles, it
offers a larger surface to the contact of the fluid, and is more readily
attacked and dissolved or decomposed by it.
In the structure of the teeth, and their physiological action, there
are certain marked differences, corresponding with the habits of the
animal, and the kind of food upon which it subsists.  In fish and
serpents, in which the food is swallowed entire, and in which the
process of digestion, accordingly, is comparatively slow, the teeth
are simply organs of prehension.  They have generally the form
of sharp, curved spines, with their points set backward (Fig. 19),
and arranged in a double or triple row
about the edges of the jaws, and sometimes         Fig. 19.
covering the mucous surfaces of the mouth,
tongue, and palate.  They serve merely to
retain the prey, and prevent its escape,
after it has been seized by the animal. In
the carnivorous quadrupeds, as those of   s, ORAT TLE SNAKF.
X-~~ ~(After Achille-Richard)
the dog and cat kind, and other similar
families, there are three different kinds of teeth adapted to different
mechanical purposes. (Fig. 20.) First, the incisors, twelve in number, situated at the anterior part of the jaw, six in the superior,
and six in the inferior maxilla, of flattened form, and placed with
their thin edges running from side to side. The incisors, as their
name indicates, are adapted for dividing the food by a cutting
motion, like that of a pair of shears. Behind them come the canine
teeth, or tusks, one on each side of the upper and under jaw.
These are long, curved, conical, and pointed; and are used as
weapons of offence, and for laying hold of and retaining the prey.
Lastly, the molars, eight or more in number on each side, are
larger.and broader than the incisors, and provided with serrated




106                         DIGESTION.
edges, each presenting several sharp points, arranged generally in
a direction parallel with the line of the jaw. In these animals,
mastication is very imperfect, since
Fig. 20.            the food is not ground up, but only
11  j!~      pierced and mangled by the action
A  ii  I. of the teeth before being swallowed
into the stomach.  In the herbivora, on the other hand, the incisors are present only in the lower
jaw in the ruminating animals,
though in the horse they are found
in both the upper and lower maxSKULL OF POLAR BEAR. Anterior  illa. (Fig.21.) Theyareusedmerely
view; showing incisors and canines. 
for cutting off the bundles of grass
or herbage, on which the animal feeds.  The canines are either
absent or slightly developed, and the real process of mastication is
Fig. 21.
SKULL OF TH HORSE.
SKULL OF THE HORSE.
performed altogether by the molars. These are large and thick
(Fig. 22), and present a broad, flat surface, diversified by variously
folded and projecting ridges of enamel, with shalFig. 22.    low grooves, intervening between them.  By the.
lateral rubbing motion of the roughened surfaces
against each other, the food is effectually comminuted and reduced to a pulpy mass.
In the human subject, the teeth combine the
SS i   ~characters of those of the carnivora and the herbiMOLAR TOOTH OF vora. (Fig. 23.)  The incisors (a), four in number
THE HORSE. Grind- 
ing surface.     in each jaw, have, as in other instances, a cutting




SALIVA.                          107
edge running from side to side.  The canines (b), which are situated
immediately behind the former, are much less prominent and
pointed than in the carnivora, and differ less in                   Fig. 23.
form from the incisors on 
the one hand, and the first        b  
molars on the other. The
molars, again (c, d), are     C..e
thick and strong, and have
comparatively  flat  surfaces, like those of the her- 
bivora; but instead of pre-               ".. 
senting curvilinear ridges,       " 
are covered with more or
less conical  eminences,
like those of the carnivora.
HUMAN TEETH-UPPER JAW.-a. Incisors. b. CaIn  the  human  subject, nines. c. Anteriormolars.. Posteriormolars.
therefore, the teeth are
evidently adapted for a mixed diet, consisting of both animal and
vegetable food. Mastication is here as perfect as it is in the herbivora, though less prolonged and laborious; for the vegetable substances used by man, as already remarked, are previously separated
to a great extent from their impurities, and softened by cooking;
so that they do not require, for their mastication, so extensive and
powerful a triturating apparatus. Finally, animal substances are
more completely masticated in the human subject than they are in
the carnivora, and their digestion is accordingly completed with
greater rapidity.
We can easily estimate, from  the facts above stated, the great
importance, to the digestive process, of a thorough preliminary
mastication. If the food be hastily swallowed in undivided masses,
it must remain a long time undissolved in the stomach, where it
will become a source of irritation and disturbance; but if reduced
beforehand, by mastication, to a state of minute subdivision, it is
readily attacked by the digestive fluids, and becomes speedily and
completely liquefied.
SALIVA.-At the same time that the food is masticated, it is mixed
in the cavity of the mouth with the first of the digestive fluids, viz.,
the saliva.  Human saliva, as it is obtained directly from  the buccal cavity, is a colorless, slightly viscid and alkaline fluid, with a




108                          DIGESTION.
specific gravity of 1005.  When first discharged, it is frothy and
opaline, holding in suspension minute, whitish flocculi.  On being
allowed to stand for some hours in a cylindrical glass vessel, an
opaque, whitish deposit collects at the bottom, while the supernatant
fluid becomes clear.  The deposit, when examined by the microscope (Fig. 24), is seen to
Fig. 24.                 consist of abundant epithelium scales from the internal
n~i:/ ^ll^^lwllllS'lll    \       tached by mechanical irrita/'.:I:.tion, minute, roundish, gra/o.                                   nular, nucleated cells, appa0/^'/llllll,rently epithelium  from  the
mucous follicles, a  certain.\.Sl^"    /llpZ   /   amount of granular matter,
\  a...t    /    and a few oil-globules.  The
~~~\  H ~II      / ~supernatant fluid has a faint
0   /          bluish  tinge, and becomes
\,_   / ^slightly opalescent by boilBUCCAL AND GLANDULAR EPITHELIUM, with  ing, and by the addition of
Granular Matter and Oil-globules; deposited as sedi- nitric acid   Alcohol in exment from human saliva.
cess, causes the precipitation
of abundant whitish flocculi.  According to Bidder and Schmidt,'
the composition of saliva is as follows:COMPOSITION OF SALIVA.
Water.......  995.16
Organic matter.......    1.34
Sulpho-eyanide of potassium...                        0.06
Phosphates of soda, lime, and magnesia...98
Chlorides of sodium and potassium......84
Mixture of epithelium.......                 1.62
1000.00
The organic substance present in the saliva has been occasionally
known by the name of ptyaline.  It is coagulable by alcohol, but
not by a boiling temperature. A very little albumen is also present, mingled with the  ptyaline, and produces the opalescence
which appears in the saliva when raised to a boiling temperature.
The sulpho-cyanogen may be detected by a solution of chloride of
iron, which produces the characteristic red color of sulpho-cyanide
Verdauungsssefte und Stoffwechsel. Leipzig, 1852.




SALIVA.                           109
of iron. The alkaline reaction of the saliva varies in intensity
during the day, but is nearly always sufficiently distinct.
The saliva is not a simple secretion, but a mixture of four distinct fluids, which differ from each other in the source from which
they are derived, and in their physical and chemical properties.
These secretions are, in the human subject, first, that of the parotid
gland; second, that of the submaxillary; third, that of the sub.
lingual; and fourth, that of the mucous follicles of the mouth.
These different fluids have been comparatively studied, in the
lower animals, by Bernard, Frerichs, and Bidder and Schmidt.
The parotid saliva is obtained in a state of purity from the dog by
exposing the duct of Steno where it crosses the masseter muscle,
and introducing into it, through an artificial opening, a fine silver
canula. The parotid saliva then runs directly from its external
orifice, without being mixed with that of the other salivary glands.
It is clear, limpid, and watery, without the slightest viscidity, and
has a faintly alkaline reaction. The submaxillary saliva is obtained in a similar manner, by inserting a canula into Wharton's
duct.  It differs from the parotid secretion, so far as its physical
properties are concerned, chiefly in possessing a well-marked viscidity. It is alkaline in reaction. The sublingual saliva is also
alkaline, colorless, and transparent, and possesses a greater degree
of viscidity than that from the submaxillary. The mucous secretion of the follicles of the mouth, which forms properly a part of
the saliva, is obtained by placing a ligature simultaneously on
Wharton's and Steno's ducts, and on that of the sublingual gland,
so as to shut out from the mouth all the glandular salivary secretions, and then collecting the fluid secreted by the buccal mucous
membrane.  This fluid is very scanty, and much more viscid than
either of the other secretions; so much so, that it cannot be poured
out in drops when received in a glass vessel, but adheres strongly
to the surface of the glass
According to Bernard,' the principal distinction between these
different salivary fluids resides in the character of the organic
matter peculiar to each one. The organic ingredient of the parotid
saliva is small in quantity, perfectly fluid, and analogous in some
respects to albumen, since it coagulates by a boiling temperature.
That of the submaxillary is moderately viscid, and has a tendency
to solidify or. gelatinize on cooling; while that of the sublingual
Leqons de Physiologie Experimentale, Paris, 1856, p. 93.




110                       DIGESTION.
and mucous secretions is excessively viscid, but does not gelatinize
at a low temperature.
The saliva proper consists, therefore, of a nearly homogeneous
mixture of all these different secretions; of which that from the
parotid is the most abundant, that of the sublingual and of the
mucous follicles of the mouth the least so. Bidder and Schmidt
obtained, from one of the parotid glands of the dog, one hundred
and thirty-six grains of fluid in an hour; from the submaxillary,
eighty-seven grains; and from the mucous follicles of the mouth,
after ligature of both Wharton's and Steno's ducts, thirty-one
grains.  The saliva, as a whole, is not secreted with uniform
rapidity at all times.  While fasting, and while the tongue and
jaws are at rest, it is supplied in but small quantity, just sufficient
to keep the mucous membrane of the mouth moist and pliable.
Any movement of the jaws, however, increases the rapidity of its
flow. It is still more powerfully stimulated by the introduction of
food, particularly that which has a decided taste, or which requires
an active movement of the jaws for its mastication. The saliva is
then poured out in abundance, and continues to be rapidly secreted
until the food is masticated and swallowed.
A very curious fact has been observed by M. Colin, Professor of
Anatomy and Physiology at the Veterinary School of Alfort,l viz.,
that in the horse and ass, as well as in the cow and other ruminating animals, the parotid glands of the two opposite sides, during
mastication, are never in active secretion at the same time; but
that they alternate with each other, one remaining quiescent while
the other is active, and vice versa. In these animals, mastication is
said to be unilateral, that is, when the animal commences feeding
or ruminating, the food is triturated, for fifteen minutes or more, by
the molars of one side only.  It is then changed to the opposite
side; and for the next fifteen minutes mastication is performed by
the molars of that side only. It is then changed back again, and
so on alternately, so that the direction of the lateral movements of
the jaw may be reversed many times during the course of a meal.
By establishing a salivary fistula simultaneously on each side, it is
found that the flow of saliva corresponds with the direction of the
masticatory movement.  When the animal masticates on the right
side, it is the right parotid which secretes actively, while but little
saliva is supplied by the left; when mastication is on the left side,
Trait6 de Physiologie Compar6e, Paris, 1854, p. 468.




SALIVA.                         11I
the left parotid pours out an abundance of fluid, while the right is
nearly inactive. It is probable, however, that this alternation of
function does not exist, to the same extent at least, in man and the
carnivora, in whom mastication is performed very nearly on both
sides at once.
Owing to the variations in the rapidity of its secretion, and also
to the fact that it is not so readily excited by artificial means as
by the presence of food, it becomes somewhat difficult to estimate
the total quantity of saliva secreted daily. The first attempt to do so
was made by Mitscherlich,l who collected from two to three ounces
in twenty-four hours from an accidental salivary fistula of Steno's
duct in the human subject; from which it was supposed that the
total amount secreted by all the glands was from ten to twelve
ounces daily. As this man was a hospital patient, however, and
suffering from constitutional debility, the above calculation cannot
be regarded as an accurate one, and accordingly Bidder and Schmidt2
make a higher estimate. One of these observers, in experimenting
upon himself, collected from the mouth in one hour, without using
any artificial stimulus to the secretion, 1500 grains of saliva; and
calculates, therefore, the amount secreted daily, making an allowance of seven hours for sleep, as not far from 25,000 grains, or
about three and a half pounds avoirdupois.
On repeating this experiment, however, we have not been able to
collect from the mouth, without artificial stimulus, more than 556
grains of saliva per hour. This quantity, however, may be greatly
increased by the introduction into the mouth of any smooth unirritating substance, as glass beads or the like; and during the
mastication of food, the saliva is poured out in very much greater
abundance. The very sight and odor of nutritious food, when the
appetite is excited, will stimulate to a remarkable degree the flow
of saliva; and, as it is often expressed, "bring the water into the
mouth."  Any estimate, therefore, of the total quantity of saliva,
based on the amount secreted in the intervals of mastication, would
be a very imperfect one.  We may make a tolerably accurate
calculation, however, by ascertaining how much is really secreted
during a meal, over and above that which is produced at other times.
We have found, for example, by experiments performed for this
purpose, that wheaten bread gains during complete mastication 55
per cent. of its weight of saliva; and that fresh cooked meat gains,
I Simon's Chemistry of Man. Phila. ed., 1846, p. 295.   2 Op. cit., p. 14.




112                       DIGESTION.
under the same circumstances, 48 per cent. of its weight. We have
already seen that the daily allowance of these two substances, for a
man in full health, is 19 ounces of bread, and 16 ounces of meat.
The quantity of saliva, then, required for the mastication of these
two substances, is, for the bread 4,572 grains, and for the meat 3,360
grains. If we now calculate the quantity secreted between meals
as continuing for 22 hours at 556 grains per hour, we have:Saliva required for mastication of bread =  4572 grains.
"     "    "     "     "meat =  3360   "
"  secreted in intervals of meals = 12232  "
Total quantity in twenty-four hours = 20164 grains;
or rather less than 3 pounds avoirdupois.
The most important question, connected with this subject, relates
to the function of the saliva in the digestive process.  A very remarkable property of this fluid is that which was discovered by Leuchs
in Germany, viz., that it possesses the power of converting boiled
starch into sugar, if mixed with it in equal proportions, and kept
for a short time at the temperature of 100~ F. This phenomenon
is one of catalysis, in which the starch is transformed into sugar by
simple contact with the organic substance contained in the saliva.
This organic substance, according to the experiments of Mialhe,
may even be precipitated by alcohol, and kept in a dry state for an
indefinite length of time without losing the power of converting
starch into sugar, when again brought in contact with it in a state
of solution.
This action of ordinary human saliva on boiled starch takes place
sometimes with great rapidity. Traces of glucose may occasionally
be detected in the mixture in one minute after the two substances
have been brought in contact; and we have even found that starch
paste, introduced into the cavity of the mouth, if already at the
temperature of 100~ F., will yield traces of sugar at the end of half
a minute.  The rapidity, however, with which this action is manifested, varies very much, as was formerly noticed by Lehmann, at
different times; owing, in all probability, to the varying constitution
of the saliva itself. It is often impossible, for example, to find any
evidences of sugar, in the mixture of starch and saliva, under five,
ten, or fifteen minutes; and it is frequently a longer time than this
before the whole of the starch is completely transformed. Even
when the conversion of the starch commences very promptly, it is
i Chimie appliquee a la Physiologie et a la Therapeutique, Paris, 1856, p. 43.




SALIVA.                          113
often a long time before it is finished. If a thin starch paste, for
example, which contains no traces of sugar, be taken into the mouth
and thoroughly mixed with the buccal secretions, it will often, as
already mentioned, begin to show the reaction of sugar in the course
of half a minute; but some of the starchy matter still remains, and
will continue to manifest its characteristic reaction with iodine, for
fifteen or twenty minutes, or even half an hour.
The above action of the saliva on starch, according to the experiments of Magendie, Bernard, Bidder and Schmidt, &c., does not
reside in either the parotid, submaxillary or mucous secretions
taken separately; but only in the mixed saliva, as it comes from
the cavity of the mouth. The submaxillary and mucous secretions,
however, taken together, produce the change; though neither of them
has any effect alone, nor even when mixed artificially with the saliva
of the parotid.
It was supposed, when this property of converting starch into
sugar was first discovered in the saliva, that it constituted the true
physiological action of this secretion, and that the function of the
saliva was, in reality, the digestion and liquefaction of starchy
substances.  It was very soon noticed, however, by the French
observers, that this property of the saliva was rather an accidental
than an essential one; and that, although starchy substances are
really converted into sugar, if mixed with saliva in a test-tube,
yet they are not affected by it to the same degree in the natural
process of digestion.  We have already mentioned the extremely
variable activity of the saliva, in this respect, at different times;
and it must be recollected, also, that in digestion the food is not
retained in the cavity of the mouth, but passes at once, after mastication, into the stomach. Several German observers, as Frerichs,
Jacubowitsch, Bidder and Schmidt, maintained at first that the
saccharine conversion of starch, after being commenced in the
mouth, might be, and actually was, completed in the stomach. We
have convinced ourselves, however, by frequent experiments, that
this is not the case. If a dog, with a gastric fistula, be fed with a
mixture of meat and boiled starch, and portions of the fluid contents of the stomach withdrawn afterward through the fistula,
the starch is easily recognizable by its reaction with iodine for ten,
fifteen, and twenty minutes afterward. In forty-five minutes, it is
diminished in quantity, and in one hour has usually altogether disappeared; but no sugar is to be detected at any time. Sometimes
8




114                        DIGESTION.
the starch disappears more rapidly than this; but at no time, according to our observations, is there any indication of the presence of
sugar in the gastric fluids. Bidder and Schmidt have also concluded,
from subsequent investigations,' that the first experiments performed
under their direction by Jacubowitsch were erroneous; and it is
now acknowledged by them, as well as by the French observers,
that sugar cannot be detected in the stomach, after the introduction
of starch, in any form or by any method.  In the ordinary process
of digestion, in fact, starchy matters do not remain long enough in
the mouth to be altered by the saliva, but pass at once into the stomach.  Here they meet with the gastric fluids, which become mingled with them, and prevent the change which would otherwise be
effected by the saliva. We have found that the gastric juice will
interfere, in this manner, with the action of the saliva in the testtube, as well as in the stomach. If two mixtures be made, one of
starch and saliva, the other of starch, saliva, and gastric juice, and
both kept for fifteen minutes at the temperature of 1000 F., in the
first mixture the starch will be promptly converted into sugar, while
in the second no such change will take place. The above action,
therefore, of saliva on starch, though a curious and interesting property, has no significance as to its physiological function, since it
does not take place in the natural digestive process. We shall see
hereafter that there are other means provided for the digestion of
starchy matters, altogether independent of the action of the saliva.
The true function of the saliva is altogether a physical one. Its
action is simply to moisten the food and facilitate its mastication,
as well as to lubricate the triturated mass, and assist its passage
down the oesophagus.  Food which is hard and dry, like crusts,
crackers, &c., cannot be masticated and swallowed with readiness,
unless moistened by some fluid. If the saliva, therefore, be prevented
from entering the cavity of the mouth, its loss does not interfere
directly with the chemical changes of the food in digestion, but only
with its mechanical preparation. This is the result of direct experiments performed by various observers. Bidder and Schmidt,2 after
tying Steno's duct, together with the common duct of, the submaxillary and sublingual glands on both sides in the dog, found
that the immediate effect of such an operation was "a remarkable
diminution of the fluids which exude upon the surfaces of the mouth;
so that these surfaces retained their natural moisture only so long' Op cit., p. N6.               2 Op. cit., p. 3.




SATLIVA.                        115
as the mouth was closed, and readily became dry on exposure to
contact with the air. Accordingly, deglutition became evidently
difficult and laborious, not only for dry food, like bread, but even
for that of a tolerably moist consistency, like fresh meat. The
animals also became very thirsty, and were constantly ready to
drink."
Bernard' also found that the only marked effect of cutting off
the flow of saliva from the mouth was a difficulty in the mechanical processes of mastication and deglutition. He first administered
to a horse one pound of oats, in order to ascertain the rapidity with
which mastication would naturally be accomplished. The above
quantity of grain was thoroughly masticated and swallowed at the
end of nine minutes. An opening had been previously made in
the cesophagus at the lower part of the neck, so that none of the
food reached the stomach; but each mouthful, as it passed down the
cesophagus, was received at the oesophageal opening and examined
by the experimenter.  The parotid duct on each side of the face
was then divided, and another pound of oats given to the animal.
Mastication and deglutition were both found to be immediately
retarded. The alimentary masses passed down the cesophagus at
longer intervals, and their interior was no longer moist and pasty,
as before, but dry and brittle. Finally, at the end of twenty-five
minutes, the animal had succeeded in masticating and swallowing
only about three-quarters of the quantity which he had previously
disposed of in nine minutes.
It appears also, from the experiments of Magendie, Bernard, and
Lassaigne, on horses and cows, that the quantity of saliva absorbed
by the food during mastication is in direct proportion to its hardness and dryness, but has no particular relation to its chemical
qualities. These experiments were performed as follows: The oesophagus was opened at the lower part of the neck, and a ligature
placed upon it, between the wound and the stomach. The animal
was then supplied with a previously weighed quantity of food, and
this, as it passed out by the oesophageal opening, was received into
appropriate vessels and again weighed. The difference in weight,
before and after swallowing, indicated the quantity of saliva absorbed
by the food. The following table gives the results of some of Lassaigne's experiments,2 performed upon a horse:1 Leqons de Physiologie Experimentale, Paris, 1856, p. 146.
2 Comptes Rendus, vol. xxi. p. 362.




116                        DIGESTION.
KIND OF FOOD EMPLOYED.           QUANTITY OF SALIVA ABSORBED.
For 100 parts of hay     there were absorbed 400 parts saliva.
"       barley meal         "        186     "
"       oats                "        113     "
"       green stalks and leaves "     49     "
It is evident, from the above facts, that the quantity of saliva
produced has not so much to do with the chemical character of the
food as with its physical condition.  When the food is dry and
hard, and requires much mastication, the saliva is secreted in
abundance; when it is soft and moist, a smaller quantity of the
secretion is poured out; and finally, when the food is taken in a
fluid form, as soup or milk, or reduced to powder and moistened
artificially with a very large quantity of water, it is not mixed at
all with the saliva, but passes at once into the cavity of the stomach.
The abundant and watery fluid of the parotid gland is most useful
in assisting mastication; while the glairy and mucous secretion of
the submaxillary gland and the muciparous follicles serve to lubricate the exterior of the triturated mass, and facilitate its passage
through the oesophagus.
By the combined operation of the two processes which the food
undergoes in the cavity of the mouth, its preliminary preparation
is accomplished.  It is triturated and disintegrated by the teeth,
and, at the same time, by the movements of the jaws, tongue, and
cheeks, it is intimately mixed with the salivary fluids, until the
whole is reduced to a soft, pasty mass, of the same consistency
throughout. It is then carried backward by the semi-involuntary
movements of the tongue into the pharynx, and conducted by the
muscular contractions of the oesophagus into the stomach.
GASTRIC JUICE, AND STOMACH DIGESTION.-The mucous membrane of the stomach is distinguished by its great vascularity
and the abundant glandular apparatus with which it is provided.
Its entire thickness is occupied by certain glandular organs, the
gastric tubules or follicles, which are so closely set as to leave
almost no space between them  except what is required for the
capillary bloodvessels.  The free surface of the gastric mucous
membrane is not smooth, but is raised in minute ridges and projecting eminences. In the cardiac portion (Fig. 25), these ridges
are reticulated with each other, so as to include between them
polygonal interspaces, each of which is encircled by a capillary
network. In the pyloric portion (Fig. 26), the eminences are more




GASTRIC JUICE, AND STOMACH DIGESTION.   117
or less pointed  and  conical in  form, and  generally flattened  from
side to side. They contain each a capillary bloodvessel, which reFig. 25.                                      Fig. 26.
/. "   \   /  \~:11::::.::::: I............
Fig. 25. Free surface of G ASTRIC MUCOUS  MEMBRAN E, viewed from above; from Pig's Stomach, Cardiac portion. Magnified 70 diameters.
Fig. 26. Free surface of G A S T R I C M u c o Is   E M  B R A N E, viewed in vertical section; from
Pig's Stomach, Pyloric portion. Magnified 420 diameters.
turns upon itself in a loop at the  extremity of the  projection, and
communicates freely with adjacent vessels. The gastric follicles are
very different in different
parts of the stomach.   In the                              Fig. 27.
pyloric portion (Fig. 27), they
are   nearly  straight,  simple
tubules            of an  inch  in
diameter,   easily    separated                                            (
from   each  other, lined  with
mucous membrane. They are                                                      i
sometimes slightly branched,
or provided with one or two
rounded  diverticula, a  short
distance above their terminaMUCOUS MI EMBRANE OF PIG'S STOMACH, from
tion.   They open on the free   Pyloric portion; vertical section; showing gatric
Pig'surface  of the   iucos  me -  tubules, and, at a, a closed follicle. Magnified  70
surface of the mucous   em-  diametersle                                            ae
diameters.
brane, in the  interspaces between the projecting folds or villi.  Among these tubular glandules




118                          DIGESTION.
there is also found, in the gastric mucous membrane, another kind
of glandular organ, consisting of closed follicles, similar to the solitary glands of the small intestine. These follicles, which are not very
numerous, are seated in the lower part of the mucous membrane,
and enveloped by the caecal extremities of the tubules. (Fig. 27, a.)
Fig. 28.                             Fig. 29.
Fig. 28. G A STRIC TU B U L E S FROM P I G'S STOMAC, Pyloric portion, showing their Ceocal
Extremities. At a, the torn extremity of a tubule, showing its cavity
Fig. 29. GASTRIC TUBULES FROM PIG'S STOMACH; Cardiac portion. At a, a large tubule
dividing into two small ones. b. Portion of a tubule, seen endwise. c. Its central cavity.
In the cardiac portion of the stomach, the tubules are very wide
in the superficial part of the mucous membrane, and lined with
large, distinctly marked cylinder epithelium cells. (Fig. 29.) In the
deeper parts of the membrane they become branched and considerably reduced in size. From the point where the branching takes
place to their termination below, they are lined with small glandular
epithelium cells, and closely bound together by intervening areolar
tissue, so as to present somewhat the appearance of compound
glandules.
The bloodvessels which come up from  the submucous layer of
areolar tissue form a close plexus around all these glandules, and
provide the mucous membrane with an abundant supply of blood,
for the purposes both of secretion and absorption.
That part of digestion which takes place in the stomach has
always been regarded as nearly, if not quite, the most important
part of the whole process.  The first observers who made any
approximation to a correct idea of gastric digestion were Reaumur
and Spallanzani, who showed by various methods that the reduction




GASTRIC JUICE, AND STOMACH DIGESTION.    119
and liquefaction of the food in the stomach could not be owing to
mere contact with the gastric mucous membrane, or to compression
by the muscular walls of the organ; but that it must be attributed
to a digestive fluid secreted by the mucous membrane, which penetrates the food and reduces it to a fluid form. They regarded this
process as a simple chemical solution, and considered the gastric
juice as a universal solvent for all alimentary substances. They
succeeded even in obtaining some of this gastric juice, mingled
probably with many impurities, by causing the animals upon which
they experimented to swallow sponges attached to the ends of
cords, by which they were afterward withdrawn, the fluids which
they had absorbed being then expressed and examined.
The first decisive experiments on this point, however, were those
performed by Dr. Beaumont, of the U. S. Army, on the person of
Alexis St. Martin, a Canadian boatman, who had a permanent gastric fistula, the result of an accidental gunshot wound. The musket,
which was loaded with buckshot at the time of the accident, was
discharged, at the distance of a few feet from St. Martin's body, in
such a manner as to tear away the integument at the lower part of
the left chest, open the pleural cavity, and penetrate, through the
lateral portion of the diaphragm, into the great pouch of the stomach.
After the integument and the pleural and peritoneal surfaces had
united and cicatrized, there remained a permanent opening, of about
four-fifths of an inch in diameter, leading into the left extremity of
the stomach, which was usually closed by a circular valve of protruding mucous membrane. This valve could be readily depressed
at any time, so as to open the fistula and allow the contents of the
stomach to be extracted for examination.
Dr. Beaumont experimented upon this person at various intervals
from the year 1825 to 1832.1  He established during the course of
his examinations the following important facts: First, that the active agent in digestion is an acid fluid, secreted by the walls of the
stomach; secondly, that this fluid is poured out by the glandular
walls of the organ only during digestion, and under the stimulus of
the food; and finally, that it will exert its solvent action upon the
food outside the body as well as in the stomach, if kept in glass
phials upon a sand bath, at the temperature of 100~ F. He made
also a variety of other interesting investigations as to the effect
of various kinds of stimulus on the secretion of the stomach, the
Experiments and Observations upon the Gastric Juice. Boston, 1834.




120                       DIGESTION.
rapidity with which the process of digestion takes place, the comparative digestibility of various kinds of food, &c. &c.
Since Dr. Beaumont's time it has been ascertained that similar
gastric fistule may be produced at will on some of the lower animals
by a simple operation; and the gastric juice has in this way been
obtained, usually from the dog, by Blondlot, Schwann, Bernard,
Lehmann and others. The simplest and most expeditious mode
of doing the operation is the best. An incision should be made
through the abdominal parietes in the median line, over the great
curvature of the stomach. The anterior wall of the organ is then
to be seized with a pair of hooked forceps, drawn out at the external
wound, and opened with the point of a bistoury. A short silver
canula, one-half to three-quarters of an inch in diameter, armed at
each extremity with a narrow projecting rim or flange, is then inserted into the wound in the stomach, the edges of which are fastened round the tube with a ligature in order to prevent the escape
of the gastric fluids into the peritoneal cavity. The stomach is then
returned to its place in the abdomen, and the canula allowed to remain with its external flange resting upon the edges of the wound
in the abdominal integuments, which are to be drawn together by
sutures. The animal may be kept perfectly quiet, during the operation, by the administration of ether or chloroform.  In a few
days the ligatures come away, the wounded peritoneal surfaces are
united with each other, and the canula is retained in a permanent
gastric fistula; being prevented by its flaring extremities both from
falling out of the abdomen and from being accidentally pushed into
the stomach. It is closed externally by a cork, which may be withdrawn at pleasure, and the contents of the stomach withdrawn for
examination.
Experiments conducted in this manner confirm, in the main, the
results obtained by Dr. Beaumont.  Observations of this kind are
in some respects, indeed, more satisfactory when made upon the
lower animals, than upon the human subject; since animals are
entirely under the control of the experimenter, and all sources of
deception or mistake are avoided, while the investigation is, at the
same time, greatly facilitated by the simple character of their food.
The gastric juice, like the saliva, is secreted in considerable
quantity only under the stimulus of recently ingested food. Dr.
Beaumont states that it is entirely absent during the intervals of
digestion; and that the stomach at that time contains no acid fluid,
but only a little neutral or alkaline mucus. He was able to obtain




GASTRIC JUICE, AND STOMACH DIGESTION.    121
a sufficient quantity of gastric juice for examination, by gently irritating the mucous membrane with a gum-elastic catheter, or the end
of a glass rod, and by collecting the secretion as it ran in drops
from  the fistula.  On the introduction of food, he found that the
mucous membrane became turgid and reddened, a clear acid fluid
collected everywhere in drops underneath the layer of mucus lining the walls of the stomach, and was soon poured out abundantly
into its cavity.  We have found, however, that the rule laid down
by Dr. Beaumont in this respect, though correct in the main, is not
invariable. The truth is, the irritability of the gastric mucous
membrane, and the readiness with which the flow of gastric juice
may be excited, varies considerably in different animals; even in
those belonging to the same species. In experimenting with gastric
fistulae on different dogs, for example, we have found in one instance,
like Dr. Beaumont, that the gastric juice was always entirely absent
in the intervals of digestion; the mucous membrane then presenting invariably either a neutral or slightly alkaline reaction. In
this animal, which was a perfectly healthy one, the secretion could
not be excited by any artificial means, such as glass rods, metallic
catheters, and the like; but only by the natural stimulus of ingested
food.  We have even seen tough and indigestible pieces of tendon,
introduced through the fistula, expelled again in a few minutes, one
after the other, without exciting the flow of a single drop of acid
fluid; while pieces of fresh meat, introduced in the same way, produced at once an abundant supply. In other instances, on the contrary, the introduction of metallic catheters, &c., into the empty
stomach has produced a scanty flow of gastric juice; and in experimenting upon dogs that have been kept without food during various
periods of time and then killed by section of the medulla oblongata,
we have usually, though not always, found the gastric mucous membrane to present a distinctly acid reaction, even after an abstinence
of six, seven, or eight days. There is at no time, however, under
these circumstances, any considerable amount of fluid present in
the stomach; but only just sufficient to moisten the gastric mucous
membrane, and give it an acid reaction.
The gastric juice, which is obtained by irritating the stomach
with a metallic catheter, is clear, perfectly colorless, and acid in
reaction. A sufficient quantity of it cannot be obtained by this
method for any extended experiments; and for that purpose, the
animal should be fed, after a fast of twenty-four hours, with fresh
lean meat, a little hardened by short boiling, in order to coagulate




122                        DIGESTION.
the fluids of the muscular tissue, and prevent their mixing with the
gastric secretion. No effect is usually apparent within the first five
minutes after the introduction of the food.  At the end of that time
the gastric juice begins to flow; at first slowly, and in drops. It is
then perfectly colorless, but very soon acquires a slight amber
tinge. It then begins to flow more freely, usually in drops, but
often running for a few seconds in a continuous stream. In this
way from  3ij to ~iiss may be collected in the course of fifteen
minutes.  Afterward it becomes somewhat turbid with the debris
of the food, which has begun to be disintegrated; but from this it
may be readily separated by filtration. After three hours, it continues to run freely, but has become very much thickened, and
even grumous in consistency, from  the abundant admixture of
alimentary debris. In six hours after the commencement of digestion it runs less freely, and in eight hours has become very scanty,
though it continues to preserve the same physical appearances as
before. It ceases to flow altogether in from nine to twelve hours,
according to the quantity of food taken.
For purposes of examination, the fluid drawn during the first
fifteen minutes after feeding should be collected, and separated by
filtration from accidental impurities. Obtained in this way, the
gastric juice is a clear, watery fluid, without any appreciable viscidity, very distinctly acid to test paper, of a faint amber color,
and with a specific gravity of 1010.  It becomes opalescent on
boiling, owing to the coagulation of its organic ingredients.  The
following is the composition of the gastric juice of the dog, based
on a comparison of various analyses by Lehmann, and Bidder and
Schmidt:COMPOSITION OF GASTRIC JUICE.
Water........                               975.00
Organic matter....    15.00
Lactic acid.....                               4.78
Chloride of sodium.......     1.70
" "potassium...                               1.08
"    " calcium.......                   0.20
"    " ammonium....                           0.65
Phosphate of lime....                              1.48
"    "magnesia......     0.06
"  " iron....  0.05
1000.00
In place of lactic acid, Bidder and Schmidt found, in most of their
analyses, hydrochloric acid. Lehmann admits that a small quantity
of hydrochloric acid is sometimes present, but regards lactic acid




GASTRIC JUICE, AND STOMACH DIGESTION.    123
as much the most abundant and important of the two. Robin and
Verdeil also regard the acid reaction of the gastric juice as due to
lactic acid; and, finally, Bernard has shown,' by a series of well
contrived experiments, that the free acid of the dog's gastric juice
is undoubtedly the lactic; and that the hydrochloric acid obtained
by distillation, is really produced by a decomposition of the chlorides, which enter into the composition of the fresh juice.
The free acid is an extremely important ingredient of the gastric
secretion, and is, in fact, essential to its physiological properties;
for the gastric juice will not exert its solvent action upon the food,
after it has been neutralized by the addition of an alkali or an
alkaline carbonate.
The most important ingredient of the gastric juice, beside the
free acid, is its organic matter or "ferment," which is sometimes
known under the name of pepsine.  This name, "pepsine," was
originally given by'Schwann to a substance which he obtained
from the mucous membrane of the pig's stomach, by macerating it
in distilled water until a putrid odor began to be developed.  The
substance in question was precipitated from the watery infusion by
the addition of alcohol, and dried; and if dissolved afterward in
acidulated water, it was found to exert a solvent action on boiled
white of egg. This substance, however, did not represent precisely
the natural ingredient of the gastric secretion, and was probably a
mixture of various matters, some of them the products of commencing decomposition of the mucous membrane itself. The name
pepsine, if it be used at all, should be applied to the organic matter
which naturally occurs in solution in the gastric juice. It is altogether unessential, in this respect, from what source it may be
originally derived. It has been regarded by Bernard and others,
on somewhat insufficient grounds, as a product of the alteration of
the mucus of the stomach. But whatever be its source, since it is
always present in the secretion of the stomach, and takes an active
part in the performance of its function, it can be regarded in no
other light than as a real anatomical ingredient of the gastric juice,
and as essential to its constitution.
Pepsine is precipitated from its solution in the gastric juice by
absolute alcohol, and by various metallic salts, but is not affected
by ferrocyanide of potassium. It is precipitated also, and coagulated, by a boiling temperature; and the gastric juice, accordingly,
X Lemons de Physiologie Exp6rimentale, Paris, 1856, p. 396.




124                        DIGESTION.
after being boiled, becomes turbid, and loses altogether its power
of dissolving alimentary substances.  Gastric juice is also affected
in a remarkable manner by being mingled with bile.  We have
found that four to six drops of dog's bile precipitate completely
with 3j of gastric juice from the same animal; so that the whole of
the biliary coloring matter is thrown down as a deposit, and the
filtered fluid is found to have lost entirely its digestive power,
though it retains an acid reaction.
A very singular property of the gastric juice is its inaptitudefor
putrefaction.  It may be kept for an indefinite length of time in a
common glass-stoppered bottle without developing any putrescent
odor. A light deposit generally collects at the bottom, and a confervoid vegetable growth or
Fig. 30.                "mould" often shows itself
in the fluid after it has been
J/^~ \^~ ~kept for one or two weeks.
d b0 ^\       This growth has the form of
/  I\r  \    white, globular masses, each
of which is composed of delicate radiating branched filaments (Fig. 30); each filament
consisting of a row of elongated cells, like other vege/  table growths of a similar
tri\o ceof te  g          nature. These growths, however, are not accompanied by
any putrefactive changes, and
CONFERVOID VEGETABLE, growing in the Gas- the gastric juice retains its
tric Juice of the Dog. The fibres have an. average 
diameter of 1-7000 of an inch.        acidreaction  nd itsdigestive
properties for many months.
By experimenting artificially with gastric juice on various alimentary substances, such as meat, boiled white of egg, &c., it is
found, as Dr. Beaumont formerly observed, to exert a solvent action
on these substances outside the body, as well as in the cavity of the
stomach.  This action is most energetic at the temperature of 1000
F. It gradually diminishes in intensity below that point, and ceases
altogether near 320. If the temperature be elevated above 1000
the action also becomes enfeebled, and is entirely suspended about
160~, or the temperature of coagulating albumen.  Contrary to
what was supposed, however, by Dr. Beaumont and his predecessors, the gastric juice is not a universal solvent for all alimentary




GASTRIC JUICE, AND STOMACH DIGESTION.    125
substances, but, on the contrary, affects only a single class of the
proximate principles, viz., the albuminoid or organic substances.
Neither starch nor oil, when digested in it at the temperature of
the body, suffers the slightest chemical alteration. Fatty matters
are simply melted by the heat, and starchy substances are only
hydrated and gelatinized to a certain extent by the combined influence of the warmth and moisture. Solid and semi-solid albuminoid
matters, however, are at once attacked and liquefied by the digestive fluid. Pieces of coagulated white of egg suspended in it, in a
test-tube, are gradually softened on their exterior, and their edges
become pale and rounded.  They grow  thin and transparent;
and their substance finally melts away, leaving a light scanty deposit, which collects at the bottom of the test-tube. While the
disintegrating process is going on, it may almost always be noticed
that minute, opaque spots show themselves in the substance of the
liquefying albumen, indicating that certain parts of it are less easily
attacked than the rest; and the deposit which remains at the bottom is probably also composed of some ingredient, not soluble in
the gastric juice. If pieces of fresh meat be treated in the same
manner, the areolar tissue entering into its composition is first
dissolved, so that the muscular bundles become more distinct, and
separate from each other. They gradually fall apart, and a little
brownish deposit is at last all that remains at the bottom of the
tube. If the hard, adipose tissue of beef or mutton be subjected
to the same process, the walls of the fat vesicles and the intervening areolar tissue, together with the capillary bloodvessels, &c.,
are dissolved; while the oily matters are set free from their envelops, and collect in a white, opaque layer on the surface. In
cheese, the casein is dissolved, and the oil which it contains set
free. In bread, the gluten is digested, and the starch left unchanged. In milk, the casein is first coagulated by contact with
the acid gastric fluids, and afterward slowly liquefied, like other
albuminoid substances.
The time required for the complete liquefaction of these substances varies with the quantity of matter present, and with its state
of cohesion. The process is hastened by occasionally shaking up
the mixture, so as to separate the parts already disintegrated, and
bring the gastric fluid into contact with fresh portions of the digestible substance.
The liquefying process which the food undergoes in the gastric
juice is not a simple solution. It is a catalytic transformation,




126                       DIGESTION.
produced in the albuminoid substances by contact with the organic
matter of the digestive fluid. This organic matter acts in a similar
manner to that of the catalytic bodies, or "ferments," generally.
Its peculiarity is that, for its active operation, it requires to be dissolved in an acidulated fluid. In common with other ferments, it
requires also a moderate degree of warmth; its action being checked,
both by a very low, and a very high temperature.  By its operation the albuminoid matters of the food, whatever may have been
their original character, are all, without distinction, converted into
a new substance, viz., albuminose.  This substance has the general
characters belonging to the class of organic matters. It is uncrystallizable, and contains nitrogen as an ultimate element. It is precipitated, like albumen, by an excess of alcohol, and by the metallic
salts; but unlike albumen, is not affected by nitric acid or a boiling temperature. It is freely soluble in water, and after it is once
produced by the digestive process, remains in a fluid condition,
and is ready to be absorbed by the vessels. In this way, casein,
fibrin, musculine, gluten, &c., are all reduced to the condition of
albuminose.  By experimenting as above, with a mixture of food
and gastric juice in test-tubes, we have found that the casein of
cheese is entirely converted into albuminose, and dissolved under
that form. A very considerable portion of raw white of egg, however, dissolves in the gastric juice directly as albumen, and retains
its property of coagulating by heat. Soft-boiled white of egg and
raw meat are principally converted into albuminose; but at the
same time, a small portion of albumen is also taken up unchanged.
The above process is a true liquefaction of the albuminoid substances, and not a simple disintegration. If fresh meat be cut into
small pieces, and artificially digested in gastric juice in test-tubes,
at 1000 F., and the process assisted by occasional gentle agitation,
the fluid continues to take up more and more of the digestible
material for from eight to ten hours. At the end of that time if it
be separated and filtered, the filtered fluid has a distinct, brownish
color, and is saturated with dissolved animal matter. Its specific
gravity is found to have increased from 1010 to 1020; and on the
addition of alcohol it becomes turbid, with a very abundant whitish
precipitate (albuminose). There is also a peculiar odor developed
during this process, which resembles that produced in the malting
of barley.
Albuminose, in solution in gastric juice, has several peculiar
properties.  One of the most remarkable of these is that it inter



GASTRIC JUICE, AND STOMACH DIGESTION.    127
feres with the operation of Trommer's test for grape sugar (see
page 68). We first observed and described this peculiarity in
1864,' but could not determine, at that time, upon what particular
ingredient of the gastric juice it depended. A short time subsequently it was also noticed by M. Longet, in Paris, who published
his observations in the Gazette Hebdomadaire for February 9th,
1855.2  He attributed the reaction not to the gastric juice itself,
but to the albuminose held in solution by it.  We have since found
this explanation to be correct. Gastric juice obtained from the
empty stomach of the fasting animal, by irritation with a metallic
catheter, which is clear and perfectly colorless, does not interfere
in any way with Trommer's test; but if it be macerated for some
hours in a test-tube with finely chopped meat, at a temperature of
100~, it will then be found to have acquired the property in a
marked degree.  The reaction therefore depends undoubtedly upon
the presence of albuminose in solution. As the gastric juice, drawn
from the dog's stomach half an hour or more after the introduction
of food, already contains some albuminose in solution, it presents
the same. reaction. If such gastric juice be mixed with a small
quantity of glucose, and Trommer's test applied, no peculiarity is
observed on first dropping in the sulphate of copper; but on adding
afterward the solution of potassa, the mixture takes a rich purple hue,
instead of the clear blue tinge which is presented under ordinary
circumstances. On boiling, the color changes to claret, cherry red,
and finally to a light yellow; but no oxide of copper is deposited, and
the fluid remains clear. If the albuminose be present only in small
quantity, an incomplete reduction of the copper takes place, so that
the mixture becomes opaline and cloudy, but still without any well
marked deposit.  This interference will take place when sugar is
present in very large proportion. We have found that in a mixture of honey and gastric juice in equal volumes, no reduction of
copper takes place on the application of Trommer's test. It is
remarkable, however, that if such a mixture be previously diluted
with an equal quantity of water, the interference does not take
place, and the copper is deposited as usual.
Usually this peculiar reaction, now that we are acquainted with
its existence, will not practically prevent the detection of sugar,' American Journ. Med. Sci., Oct. 1854, p. 319.
2 Nouvelles recherches relatives a'action du sue gastrique sur les substances
albuminoides.- Gaz. Hebd. 9 Fevrier, 1855, p. 103.




128                       DIGESTION.
when present; since the presence of the sugar is distinctly indicated by the change of color, as above mentioned, from purple to
yellow, though the copper may not be thrown down as a precipitate.  All possibility of error, furthermore, may be avoided by
adopting the following precautions. The purple color, already mentioned, will, in the first place, serve to indicate the presence of the
alburninoid ingredient in the suspected fluid.' The mixture should
then be evaporated to dryness, and extracted with alcohol, in order
to eliminate the animal matters. After that, a watery solution of
the sugar contained in the alcoholic extract will react as usual with
Trommer's test, and reduce the oxide of copper without difficulty.
Another remarkable property of gastric juice containing albuminose, which is not, however, peculiar to it, but common to many
other animal fluids, is that of interfering with the mutual reaction
of starch and iodine. If 3j of such gastric juice be mixed with 3j
of iodine water, and boiled starch be subsequently added, no blue
color is produced; though if a larger quantity of iodine water be
added, or if the tincture be used instead of the aqueous solution,
the superabundant iodine then combines with the starch, and produces the ordinary blue color. This property, like that described
above, is not possessed by pure, colorless; gastric juice, taken from
the empty stomach, but is acquired by it on being digested with
albuminoid substances.
Another important action which takes place in the stomach,
beside the secretion of the gastric juice, is the pleristaltic movement
of the organ. This movement is accomplished by the alternate
contraction and relaxation of the longitudinal and circular fibres
of its muscular coat. The motion is minutely described by Dr.
Beaumont, who examined it both by watching the movements of
the food through the gastric fistula, and also by introducing into
the stomach the bulb and stem of a thermometer. According to
his observations, when the food first passes into the stomach, and
the secretion of the gastric juice commences, the muscular coat,
which was before quiescent, is excited and begins to contract actively. The contraction takes place in such a manner that the food,
after entering the cardiac orifice of the stomach, is first carried to
the left, into the great pouch of the organ, thence downward and
along the great curvature to the pyloric portion. At a short distance
from the pylorus, Dr. B. often found a circular constriction of the
gastric parietes, by which the bulb of the thermometer was gently
grasped and drawn toward the pylorus, at the same time giving a




GASTRIC JUICE, AND STOMACH DIGESTION.    129
twisting motion to the stem of the instrument, by which it was
rotated in his fingers. In a moment or two, however, this constriction was relaxed, and the bulb of the thermometer again released,
and carried together with the food along the small curvature of
the organ to its cardiac extremity. This circuit was repeated so
long as any food remained in the stomach; but, as the liquefied
portions were successively removed toward the end of digestion, it
became less active, and at last ceased altogether when the stomach
had become completely empty, and the organ returned to its ordinary quiescent condition.
It is easy to observe the muscular action of the stomach during
digestion in the dog, by the assistance of a gastric fistula, artificially
established. If a metallic catheter be introduced through the fistula
when the stomach is empty, it must usually be held carefully in
place, or it will fall out by its own weight. But immediately upon
the introduction of food, it can be felt that the catheter is grasped
and retained with some force, by the contraction of the muscular
coat. A twisting or rotatory motion of its extremity may also be
frequently observed, similar to that described by Dr. Beaumont.
This peristaltic action of the stomach, however, is a gentle one,
and not at all active or violent in character. We have never seen,
in opening the abdomen, any such energetic or extensive contractions of the stomach, even when full of food, as may be easily
excited in the small intestine by the mere contact of the atmosphere,
or by pinching them with the blades of a forceps. This action of
the stomach, nevertheless, though quite gentle, is sufficient to produce a constant churning movement of the masticated food, by
which it is carried back and forward to every part of the stomach,
and rapidly incorporated with the gastric juice which is at the
same time poured out by the mucous membrane; so that the
digestive fluid is made to penetrate equally every part of the alimentary mass, and the digestion of all its albuminous ingredients
goes on simultaneously. This gentle and continuous movement of
the stomach is one which cannot be successfully imitated in experiments on artificial digestion with gastric juice in test-tubes; and
consequently the process, under these circumstances, is never so
rapid or so complete as when it takes place in the interior of the
stomach.
The length of time which is required for digestion varies in
different species of animals. In the carnivora, a moderate meal of
fresh uncooked meat requires from  nine to twelve hours for its
9




130                         D1GESTION.
complete solution and disappearance from the stomach. According
to Dr. Beaumont, the average time required for digestion in the
human subject is considerably less; varying from one hour to five
hours and a half, according to the kind of food employed. This
is probably owing to the more complete mastication of the food
which takes place in man, than in the carnivorous animals.  By
examining the contents of the stomach at various intervals after
feeding, Dr. Beaumont made out a list, showing the comparative
digestibility of different articles of food, of which the following are
the most important:Time required for digestion, according to Dr. Beaumont:KIND OF FOOD.                               HOURS. MINUTES.
Pig's feet.....                1      00
Tripe....1                                      00
Trout (broiled)...1                                30
Venison steak....1                                 35
Milk..........   2      00
Roasted turkey....... 2                       30
"   beef....3                                  00
mutton....... 3                      15
Veal (broiled).....4                              00
Salt beef (boiled)...4                            15
Roasted pork....5                                 15
The comparative digestibility of different substances varies more
or less in different individuals according to temperament; but the
above list undoubtedly gives a correct average estimate of the time
required for stomach digestion under ordinary conditions.
A  very interesting question is that which relates to the total
quantity of gastric juice secreted daily.  Whenever direct experiments have been performed with a view of ascertaining this point,
their results have given a considerably larger quantity than was
anticipated.  Bidder and Schmidt found that, in a dog weighing
34 pounds, they were able to obtain by separate experiments, consuming in all 12 hours, one pound and three-quarters of gastric
juice. The total quantity, therefore, for 24 hours, in the same animal, would be 31 pounds; and, by applying the same calculation to
a man of medium size, the authors estimate the total daily quantity
in the human subject as but little less than 14 pounds (av.).  This
estimate is probably not an exaggerated one. In order to determine the question, however, if possible, in a different way, we
adopted the following plan of experiment with the gastric juice of
the dog. It was first ascertained, by direct experiment, that the




GASTRIC JUICE, AND STOMACH DIGESTION.    131
fresh lean meat of the bullock's heart loses, by complete desiccation,
78 per cent. of its weight.  300 grains of such meat, cut into small
pieces, were then digested for ten hours, in ~iss of gastric juice at
1000 F.; the mixture being thoroughly agitated as often as every
hour, in order to insure the digestion of as large a quantity of meat
as possible.  The meat remaining undissolved was then collected
on a previously weighed filter, and evaporated to dryness.  The
dry residue weighed 55 grains.  This represented, allowing for the
loss by evaporation, 250 grains of the meat, in its natural  moist
condition; 50 grains of meat were then dissolved by aiss of gastric
juice, or 33- grains per ounce.
From these data we can form some idea of the large quantity of
gastric juice secreted in the dog during the process of digestion.
One pound of meat is only a moderate meal for a medium-sized
animal; and yet, to dissolve this quantity, no less than thirteen pints
of gastric juice will be necessary. This quantity, or any. approximation to it, would be altogether incredible if we did not recollect
that the gastric juice, as soon as it has dissolved its quota of food,
is immediately reabsorbed, and again enters the circulation, together
with the alimentary substances which it holds in solution.  The
secretion and reabsorption of the gastric juice then go on simultaneously; and the fluids which the blood loses by one process are
incessantly restored to it by the other.  A  very large quantity,
therefore, of the secretion may be poured out during the digestion
of a meal, at an expense to the blood, at any one time, of only two
or three ounces of fluid. The simplest investigation shows that
the gastric juice does not accumulate in the stomach in any considerable quantity during digestion; but that it is gradually
secreted so long as any food remains undissolved, each portion, as
it is digested, being disposed of by reabsorption, together with its
solvent fluid. There is accordingly, during digestion, a constant
circulation of the digestive fluids from the bloodvessels to the alimentary canal, and from  the alimentary canal back again to the
bloodvessels.
That this circulation really takes place is proved by the following facts: First, if a dog be killed some hours after feeding,
there is never more than a very small quantity of fluid found in
the stomach, just sufficient to smear over and penetrate the half
digested pieces of meat; and, secondly, in the living animal, gastric
juice, drawn from the fistula five or six hours after digestion has
been going on, contains little or no more organic matter in solution




132                        DIGESTION.
than that extracted fifteen to thirty minutes after the introduction
of food. It has evidently been freshly secreted; and, in order to
obtain gastric juice saturated with alimentary matter, it must be
artificially digested with food in test-tubes, where this constant absorption and renovation cannot take place.
An unnecessary difficulty has sometimes been felt in understanding how it is that the gastric juice, which digests so readily all albuminous substances, should not destroy the walls of the stomach
itself, which are composed of similar materials. This, in fact, was
brought forward at an early day, as an insuperable objection to the
doctrine of Reaumur and Spallanzani, that digestion was a process
of chemical solution performed by a digestive fluid. It was said
to be impossible that a fluid capable of dissolving animal matters
should be secreted by the walls of the stomach without attacking
them  also, and thus destroying the organ by which it was itself
produced.  Since that time, various complicated hypotheses have
been framed, in order to reconcile these apparently contradictory
facts. The true explanation, however, as we believe, lies in thisthat the process of digestion is not a simple solution, but a catalytic
transformation of the alimentary substances, produced by contact
with the pepsine of the gastric juice.  We know that all the organic substances in the living tissues are constantly undergoing, in
the process of nutrition, a series of catalytic changes, which are
characteristic of the vital operations, and which are determined by
the organized materials with which they are in contact, and by all
the other conditions present in the living organism. These changes,
therefore, of nutrition, secretion, &c., necessarily exclude for the
time all other catalyses, and take precedence of them. In the same
way, any dead organic matter, exposed to warmth, air, and moisture, putrefies; but if immersed in gastric juice, at the same
temperature, the putrefactive changes are stopped or altogether
prevented, because the catalytic actions, excited by the gastric
juice, take precedence of those which constitute putrefaction.  For
a similar reason, the organic ingredient of the gastric juice, which
acts readily on dead animal matter, has no effect on the living
tissues of the stomach, because they are already subject to other
catalytic influences, which exclude those of digestion, as well as
those of putrefaction.  As soon as life departs, however, and the
peculiar actions taking place in the living tissues come to an end
with the stoppage of the circulation, the walls of the stomach are
really attacked by the gastric juice remaining in its cavity, and




INTESTINAL JUICES, DIGESTION OF SUGAR, ETC. 133
are more or less completely digested and liquefied. In the human
subject, it is rare to make an examination of the body twenty-four
or thirty-six hours after death, without finding the mucous membrane of the great pouch of the stomach more or less softened and
disintegrated from this cause. Sometimes the mucous membrane
is altogether destroyed, and the submucous cellular layer exposed;
and occasionally, when death has taken place suddenly during
active digestion, while the stomach contained an abundance of
gastric juice, all the coats of the organ have been found destroyed,
and a perforation produced leading into the peritoneal cavity.
These post-mortem changes show that, after death, the gastric juice
really dissolves the coats of the stomach without difficulty. But
during life, the chemical changes of nutrition, which are going on
in their tissues, protect them from its influence, and effectually
preserve their integrity.
The secretion of the gastric juice is much influenced by nervous
conditions. It was noticed by Dr. Beaumont, in his experiments
upon St. Martin, that irritation of the temper, and other moral
causes, would frequently diminish or altogether suspend the supply
of the gastric fluids. Any febrile action in the system, or any
unusual fatigue, was liable to exert a similar effect. Every one is
aware how readily any mental disturbance, such as anxiety, anger,
or vexation, will take away the appetite and interfere with digestion. Any nervous impression of this kind, occurring at the commencement of digestion, seems moreover to produce some change
which has a lasting effect upon the process; for it is very often
noticed that when any annoyance, hurry, or anxiety occurs soon
after the food has been taken, though it may last only for a few
moments, the digestive process is not only liable to be suspended
for the time, but to be permanently disturbed during the entire
day. In order that digestion, therefore, may go on properly in the
stomach, food must be taken only when the appetite demands it;
it should also be thoroughly masticated at the outset; and, finally,
both mind and body, particularly during the commencement of the
process, should be free from any unusual or disagreeable excitement.
INTESTINAL JUICES, AND THE DIGESTION OF SUGAR AND STARCH.
-From  the stomach, those portions of the food which have not
already suffered digestion pass into the third division of the alimentary canal, viz., the small intestine. As already mentioned, it




134                        DIGESTION.
is only the albuminous matters which are digested in the stomach.
Cane sugar, it is true, is slowly converted by the gastric juice, outside the body, into glucose.  We have found that ten grains of
cane sugar, dissolved in 9ss of gastric juice, give traces of glucose
at the end of two hours; and in three hours, the quantity of this
substance is considerable.  It cannot be shown, however, that the
gastric juice exerts this effect on sugar during ordinary digestion.
If pure cane sugar be given to a dog with a gastric fistula, while
digestion of meat is going on, it disappears in from two to three
hours, without any glucose being detected in the fluids withdrawn
from the stomach. It is, therefore, either directly absorbed under
the form of cane sugar, or passes, little by little, into the duodenum,
where the intestinal fluids at once convert it into glucose.
It is equally certain that starchy matters are not digested in the
stomach, but pass unchanged into the small intestine. Here they
meet with the mixed intestinal fluids, which act at once upon the
starch, and convert it rapidly into sugar.  The intestinal fluids,
taken from  the duodenum  of a recently killed dog, exert this
transforming action upon starch with the greatest promptitude, if
mixed with it in a test-tube and kept at the temperature of 1000 F.
Starch is converted into sugar by this means much more rapidly
and certainly than by the saliva; and experiment shows that the
intestinal fluids are the active agents in its digestion during life.
If a dog be fed with a mixture of meat and boiled starch, and killed
a short time after the meal, the stomach is found to contain starch
but no sugar; while in the small intestine there is an abundance of
sugar, and but little or no starch. If some observers have failed
to detect sugar in the intestine after feeding the animal with
starch, it is because they have delayed the examination until too
late. For it is remarkable how rapidly starchy substances, if previously disintegrated by boiling, are disposed of in the digestive
process. If a dog, for example, be fed as above with boiled starch
and meat, while some of the meat remains in the stomach for
eight, nine, or ten hours, the starch begins immediately to pass into
the intestine, where it is at once converted into sugar, and then as
rapidly absorbed.  The whole of the starch may be converted into
sugar, and completely absorbed, in an hour's time. We have even
found, at the end of three-quarters of an hour, after a tolerably
full meal of boiled starch and meat, that all trace of both starch
and sugar had disappeared from both stomach and intestine. The
rapidity with which this passage of the starch into the duodenum




INTESTINAL JUICES, DIGESTION  OF SUGAR, ETC. 135
takes place varies, to some extent, in different animals, according
to the general activity of the digestive apparatus; but it is always
a comparatively rapid process, when the starch is already liquefied
and is administered in a pure form. There can be no doubt that
the natural place for the digestion of starchy matters is the small
intestine, and that it is accomplished by the action of the intestinal
juices.
Our knowledge is not very complete with regard to the exact
nature of the fluids by which this digestion of the starch is accomplished.  The juices taken from the duodenum  are generally a
mixture of three different secretions, viz., the bile, the pancreatic
fluid, and the intestinal juice proper.  Of these, the bile may be
left out of the question; since it does not, when in a pure state,
exert any digestive action on starch. The pancreatic juice, on the
other hand, has the property
of converting starch into su-                Fig. 31.
gar; but it is not known
whether this fluid be always
present in  the duodenum.
The true intestinal juice is the    /:                   \
product of two sets of glandular organs, seated in the 
substance of or beneath the
mucous membrane, viz., the  II:             /
follicles of Lieberkihn and             i 
the glands of Brunner.  The
first of these, or Lieberkihn's
follicles (Fig. 31), are the most
numerous. They aresimple
numerous. The  are simpe,   FOLLICLES OF LIEBERKUHN, from Small Innearly straight tubules, lined testine of Dog.
with a continuation of the
intestinal epithelium, and somewhat similar in their appearance to
the follicles of the pyloric portion of the stomach. They occupy
the whole thickness of the mucous membrane, and are found in
great numbers throughout the entire length of the small and large
intestine.
The glands of Brunner (Fig. 32), or the duodenal glandulae, as
they are sometimes called, are confined to the upper part of the duodenum, where they exist as a closely set layer, in the deeper portion
of the mucous membrane, extending downward a short distance from
the pylorus. They are composed of a great number of rounded fol



136                        DIGESTION.
licles, clustered round a central excretory duct.  Each follicle
consists of a delicate membranous wall, lined with glandular
epithelium, and covered  on
Fig. 32.               its surface with small, distinctly marked nuclei.  The
follicles  collected   around
each duct are bound together'/.: X'~  \    by a thin layer of areolar tis/  l.:!;         \ i   sue, and covered with a plext/..!..- us of capillary bloodvessels.
I:>  The intestinal juice, which.\               9..;-... -.is the secreted product of the
\            t         Oabove glandular organs, has
\'. ""/  /            been less successfully studied
6\^ l  P-;/.than  the  other  digestive
\./~^ ^^fluids, owing to the difficulty
of obtaining  it in a pure
Portion of one of BRUNNER'S DUODENAL f obtaining  it in a pure
GLANDS, from Human Intestine.         state. The method usually
adopted has been to make an
opening in the abdomen of the living animal, take out a loop of intestine, empty it by gentle pressure, and then to shut off a portion of
it from  the rest of the intestinal cavity by a couple of ligatures,
situated six or eight inches apart; after which the loop is returned
into  the abdomen, and the external wound closed by sutures.
After six or eight hours the animal is killed, and the fluid, which
has collected in the isolated portion of intestine, taken out and
examined. The above was the method adopted by Frerichs. Bidder and Schmidt, in order to obtain pure intestinal juice, first tied
the biliary and pancreatic ducts, so that both the bile and the pancreatic juice should be shut out from the intestine, and then established an intestinal fistula below, from which they extracted the
fluids which accumulated in the cavity of the gut. From the great
abundance of the follicles of Lieberkihn, we should expect to find
the intestinal juice secreted in large quantity. It appears, however,
in point of fact, to be quite scanty, as the quantity collected in the
above manner by experimenters has rarely been sufficient for a
thorough examination of its properties.: It seems to resemble very
closely, in its physical characters, the secretion of the mucous follicles of the mouth. It is colorless and glassy in appearance, viscid
and mucous in consistency, and has a distinct alkaline reaction.




PANCREATIC JUICE, AND THE DIGESTION OF FAT. 137
It has the property when pure, as well as when mixed with other
secretions, of rapidly converting starch into sugar, at the temperature of the living body.
PANCREATIC JUICE, AND THE DIGESTION OF FAT.-The only remaining ingredients of the food that require digestion are the oily
matters. These are not affected, as we have already stated, by contact with the gastric juice; and examination shows, furthermore,
that they are not digested in the stomach. So long as they remain
in the cavity of this organ they are unchanged in their essential
properties. They are merely melted by the warmth of the stomach,
and set free by the solution of the vesicles, fibres, or capillary tubes
in which they are contained, or among which they are entangled;
and are still readily discernible by the eye, floating in larger or
smaller drops on the surface of the semi-fluid alimentary mass.
Very soon, however, after its entrance into the intestine, the oily
portion of the food loses its characteristic appearance, and is converted into a white, opaque emulsion, which is gradually absorbed.
This emulsion is termed the chyle, and is always found in the small
intestine during the digestion of fat, entangled among the valvulae
conniventes, and adhering to the surface of the villi. The digestion
of the oil, however, and its conversion into chyle, does not take
place at once upon its entrance into the duodenum, but only after
it has passed the orifices of the pancreatic and biliary ducts. Since
these ducts almost invariably open into the intestine at or near the
same point, it was for a long time difficult to decide by which of
the two secretions the digestion of the oil was accomplished. M.
Bernard, however, first threw some light on this question by experimenting on some of the lower animals, in which the two ducts
open separately. In the rabbit, for example, the biliary duct opens
as usual just below the pylorus, while the pancreatic duct communicates with the intestine some eight or ten inches lower down.
Bernard fed these animals with substances containing oil, or injected melted butter into the stomach; and, on killing them afterward, found that there was no chyle in the intestine between the
opening of the biliary and pancreatic ducts, but that it was abundant immediately below the orifice of the latter. Above this point,
also, he found the lacteals empty or transparent, while below it
they were full of white and opaque chyle. The result of these experirents, which have since been confirmed by Prof. Samuel Jack



138                       DIGESTION.
son, of Philadelphia,1 led to the conclusion that the pancreatic fluid
is the active agent in the digestion of oily substances; and an examination of the properties of this secretion, when obtained in a
pure state from the living animal, fully confirms the above opinion.
In order to obtain pancreatic juice from the dog, the animal
must be etherized soon after digestion has commenced, an incision
made in the upper part of the abdomen, a little to the right of the
median line, and a loop of the duodenum, together with the lower
extremity of the pancreas which lies adjacent to it, drawn out at
the external wound. The pancreatic duct is then to be exposed
and opened, and a small silver canula inserted into it and secured
by a ligature. The whole is then returned into the abdomen and
the wound closed by sutures, leaving only the end of the canula
projecting from it. In the dog there are two pancreatic ducts,
situated from  half an inch to an inch apart. The lower one of
these, which is usually the larger of the two, is the one best adapted
for the insertion of the canula. After the effects of etherization
have passed off; and the digestive process has recommenced, the
pancreatic juice begins to run from the orifice of the canula, at first
very slowly and in drops. Sometimes the drops follow each other
with rapidity for a few moments, and then an interval occurs during
which the secretion seems entirely suspended. After a time it recommences, and continues to exhibit similar fluctuations during
the whole course of the experiment. Its flow, however, is at all
times scanty, compared with that of the gastric juice; and we have
never been able to collect more than a little over two fluidounces
and a half during a period of three hours, in a dog weighing not
more than forty-five pounds.  This is equivalent to about 364
grains per hour; but as the pancreatic juice in the dog is secreted
with freedom only during digestion, and as this process is in operation not more than twelve hours out of the twenty-four,'the entire
amount of the secretion for the whole day, in the dog, may be estimated at 4,368 grains. This result, applied to a man weighing 140
pounds, would give, as the total daily quantity of the pancreatic
juice, about 13,104 grains, or 1.872 pounds avoirdupois.
Pancreatic juice obtained by the above process is a clear, colorless, somewhat viscid fluid, with a distinct alkaline reaction. Its
composition according to the analysis of Bidder and Schmidt, is as
follows:
1 American Journ. Med. Sci., Oct. 1854.




PANCREATIC  JUICE, AND THE DIGESTION  OF FAT.  139
COMPOSITION OF PANCREATIC JUICE.
Water......   900.76
Organic matter (pancreatine)....    90.38
Chloride of sodium....                           7.36
Free soda.......      0.32
Phosphate of soda.                                       0.45
Sulphate of soda...  0.10
Sulphate of potassa.....                         0.02
(Lime.......     0.54
Combinations of    Magnesia....                       0.05
Oxide of iron..                        0.02
1000.00
The most important ingredient of the pancreatic juice is its
organic matter, or pancreatine.  It will be seen that this is much
more abundant in proportion to the other ingredients of the secretion than the organic matter of any other digestive fluid. It is
coagulable by heat; and the pancreatic juice often solidifies completely on boiling, like white of egg, so that not a drop of fluid remains after its coagulation.  It is precipitated, furthermore, by
nitric acid and by alcohol, and also by sulphate of magnesia in
excess.  By this last property, it may be distinguished from  albumen, which is not affected by contact with sulphate of magnesia.
Fresh pancreatic juice, brought into contact with oily matters at
the temperature of the body, exerts upon them, as was first noticed
by Bernard, a very peculiar effect. It disintegrates them, and reduces them to a state of complete emulsion, so that the mixture is
at once converted into a white, opaque, creamy-looking fluid. This
effect is instantaneous and permanent, and only requires that the
two substances be well mixed by gentle agitation. It is singular
that some of the German observers should deny that the pancreatic
juice possesses the property of emulsioning fat, to a greater extent
than the bile and some other digestive fluids; and should state that
although, when shaken up with oil, outside the body, it reduces
the oily particles to a state of extreme minuteness, the emulsion
is not permanent, and the oily particles "soon separate again on
the surface."' We have frequently repeated this experiment with
different specimens of pancreatic juice obtained from the dog, and
have never failed to see that the emulsion produced by it is by
far more prompt and complete than that which takes place with
saliva, gastric juice, or bile. The effect produced by these fluids is
i Lehmann's Physiological Chemistry. Philada. ed., vol. i. p. 507.




140                        DIGESTION.
in fact altogether insignificant, in comparison with the prompt and
energetic action exerted by the pancreatic juice. The emulsion
produced with the latter secretion may be kept, furthermore, for at
least twenty-four hours, according to our observations, without any
appreciable separation of the oily particles, or a return to their
original condition.
The pancreatic juice, therefore, is peculiar in its action on oily
substances, and reduces them at once to the condition of an emulsion. The oil, in this process, does not suffer any chemical alteration. It is not decomposed or saponified, to any appreciable extent.
It is simply emulsioned; that is, it is broken up into a state of minute
subdivision, and retained in suspension, by contact with the organic
matter of the pancreatic juice. That its chemical condition is not
altered is shown by the fact that it is still soluble in ether, which
will withdraw the greater part of the fat from a mixture of oil and
pancreatic juice, as well as from the chyle in the interior of the
intestine. In a state of emulsion, the fat, furthermore, is capable
of being absorbed, and its digestion may be then said to be accomplished.
We find, then, that the digestion of the food is not a simple
operation, but is made up of several different processes, which
commence successively in different portions of the alimentary
canal. In the first place, the food is subjected in the mouth to the
physical operations of mastication and insalivation. Reduced to a
soft pulp and mixed abundantly with the saliva, it passes, secondly,
into the stomach.  Here it excites the secretion of the gastric juice,
by the influence of which its chemical transformation and solution
are commenced.  If the meal consist wholly or partially of muscular flesh; the first effect of the gastric juice is to dissolve the
intervening cellular substance, by which the tissue is disintegrated
and the muscular fibres separated from  each other.  Afterward
the muscular fibres themselves become swollen and softened by
the imbibition of the gastric fluid, and are finally disintegrated
and liquefied. In the small intestine, the pancreatic and intestinal
juices convert the starchy ingredients of the food into sugar, and
break up the fatty matters into a fine emulsion, by which they are
converted into chyle.
Although the separate actions of these digestive fluids, however,
commence at different points of the alimentary canal, they afterward go on simultaneously in the small intestine; and the changes
which take place here, and which constitute the process of intestinal




PHENOMENA OF INTESTINAL DIGESTION.                141
digestion, form at the same time one of the most complicated, and
one of the most important parts of the whole digestive function.
The phenomena of intestinal digestion may be studied, in the
dog, by killing the animal at various periods after feeding, and
examining the contents of the intestine. We have also succeeded,
by establishing in the same animal an artificial intestinal fistula,
in gaining still more satisfactory information on this point. The
fistula may be established, for this purpose, by an operation precisely
similar to that already described as employed for the production of
a permanent fistula in the stomach. The silver tube having been
introduced into the lower part of the duodenum, the wound is
allowed to heal, and the intestinal secretions may then be withdrawn at will, and subjected to examination at different periods
during digestion.
By examining in this way, from  time to time, the intestinal
fluids, it at once becomes manifest that the action of the gastric
juice, in the digestion of albuminoid substances, is not confined to
the stomach, but continues after the food has passed into the intestine. About half an hour after the ingestion of a meal, the gastric
juice begins to pass into the duodenum, where it may be recognized
by its strongly-marked acidity, and by its peculiar action, already
described, in interfering with Trommer's test for grape sugar. It
has accordingly already dissolved some of the ingredients of the
food while still in the stomach, and contains a certain quantity of
albuminose in solution. It soon afterward, as it continues to pass
into the duodenum, becomes mingled with the debris of muscular
fibres, fat vesicles, and oil drops; substances which are easily
recognizable under the microscope, and which produce a grayish
turbidity in the fluid drawn from the fistula. This turbid admixture grows constantly thicker from  the second to the tenth or
twelfth hour; after which the intestinal fluids become less abundant, and finally disappear almost entirely, as the process of digestion comes to an end.
The passage of disintegrated muscular tissue into the intestine
may also be shown, as already mentioned, by killing the animal
and examining the contents of the alimentary canal. During the
digestion of muscular flesh and adipose tissue, the stomach contains masses of softened meat, smeared over with gastric juice, and
also a moderate quantity of grayish, grumous fluid, with an acid
reaction. This fluid contains muscular fibres, isolated from each
other, and more or less disintegrated, by the action of the gastric




142                           DIGESTION.
juice. (Fig. 33.)  The fat vesicles are but little or not at all altered
in the stomach, and there are only a few free oil globules to be
seen floating in the mixed
Fig. 33.                fluids, contained in the cavity
of the organ.  In the duodenum  the muscular fibres are
/       0    C\ —-.   further disintegrated.  (Fig.,/;;       A  \ o34.) They become very much
broken up, pale and transparent, but can still be recognized by the granular markings and striations which are
characteristic of them.  The. ~h —'11,..           / /,    fat  vesicles  also  begin  to
-^                       become altered in the duodenum.  The solid granular fat
-o~,~ o ~ s~o~,~o~  ~,~ D~o~IO~  of beef, and similar kinds of
CONTENTS OF STOMACH DURING DIGESTION  of beef and similar kindsof
OF MEAT, from the Dog.-a. Fat Vesicle, filled with  meat, becomes liquefied and
opaque, solid, granular fat. b, b. Bits of partially dis    ulsio
integrated muscular fibre. c. Oil globules.  emuls ed; andappears under the form of free oil drops
Fig. 34.                 and  fatty molecules; while
~   ^^~/  \^ ^ ~the fat vesicle itself is par/  ---  - -    \       tially emptied, and becomes
more or less collapsed and
-/.c \    shrivelled.  In  the  middle
/  c  b1             \ 0and lower parts of the intesI ~ o                               tine (Figs. 35 and 36) these
7',   -       changes continue.  Themus\  v~ ~   / e  cular fibres become constant7'\  "^      /~   ly  more and  more disinte\    i- I-    g   a/    grated, and a large quantity
of granular debris  is produced, which is at last also
FROM DUODENUM OF DOG, DURING DIGES-  dissolved.  The fat also proTION OF MEAT 1-a Fat Vesicle, with its contents
diminishing. The vesicle is beginning to shrivel and  gressively disappears, and the
the fat breaking up. b, b Disintegrated muscular  vesicles may be seen in the
fibre.  c, c. Oil globules.
lower part of the intestine,
entirely collapsed and empty.
In this way the digestion of the different ingredients of the food
goes on in a continuous manner, from  the stomach throughout the
entire length of the small intestine.  At the same time, it results




THE LARGE INTESTINE AND ITS CONTENTS.    143
in the production of three different substances, viz: 1st. Albuminose, produced by the action of the gastric juice on the albuminoid
matters; 2d. An oily emulsion, produced by the action                   Fig 35.
of the pancreatic juice on fat; 
and, 3d. Sugar, produced from
the transformation of starch- 
by the mixed intestinal fluids.   /   
These substances  are  then  S,;                                \
ready to be taken up into the  X/   O 
circulation; and as the min-. ^, -,_.j
gled ingredients of the intes-  o  
tinal contents pass successively downward, through the
duodenum, jejunum, and ileum, the products of digestion,                 _ 
together with  the digestive   PROM MIDDLE OF SMALL INTESTIE.-a, a
secretions themselves, are gra- Fat vesicles, nearly emptied of their contents.
dually absorbed, one  after. 36
another, by the vessels of the 
mucous membrane, and car-             /
ried away by the current of         /  N
the circulation.                     /::              "     \
The Large Intestine and its                                    \
Contents.-Throughout  the' ~o,          \
small intestine, as we have  l t          1,'"L,      ~ o~ I
just seen, the secretions are    l,  6's.' ~\ ~\   t,'< I','se'. 0 "''" ~~":~   /
intended exclusively or main-            i -'' i,$', ( o  0  /
ly to act upon the food, to   \  
liquefy or disintegrate it, and    0\ 0:. "  v"
to prepare it for absorption.  
But below the situation of the 
ileo-coecal valve, and through-   FROM LAST QATER, OF SMALL TNTESTINE.
o t7tlr i       -cta, a. Fat vesicles, quite empty and shrivelled.
out the large intestine, the
contents of the alimentary canal exhibit a different appearance, and
are distinct in their color, odor, and consistency.  This portion of
the intestinal contents, or thefeces, are not composed, for the most
part, of the undigested remains of the food, but consist principally
of animal substances excreted by the mucous membrane of the
large intestine. These substances have not been very fully investigated; for although they are undoubtedly of great importance in




144                        DIGESTION.
regard to the preservation of health, yet the peculiar manner in
which they are discharged by the mucous membrane and united
with each other in the feces has interfered, to a great extent, with
a thorough investigation of their physiological characters.
They have been examined, however, by various observers, but
more particularly by Dr. W. Marcet.' In the contents of the large
intestine, Dr. Marcet found that the most characteristic ingredient
was a peculiar neutral crystallizable substance, termed excretine. It
crystallizes in radiated groups of four-sided prismatic needles. It
is insoluble in water, but soluble in ether and slightly so in alcohol.
It fuses and burns at a high temperature. This substance is nonnitrogenous, and consists of carbon, hydrogen, oxygen, and sulphur,
in the following proportions:C78 H78 02 S.
It is thought to be present mostly in a free state, but partly in union
with certain organic acids, as a saline compound.
Beside this substance, the feces contain a certain amount of fat,
fatty acids, cholesterine, and the remnants of undigested food.
Vegetable cells and fibres may be detected and some debris of the
disintegrated muscular fibres may almost always be found after a
meal composed of animal and vegetable substances.  But little
absorption, accordingly, takes place in the large intestine. Its office
is mainly confined to the separation and discharge of certain excrementitious substances.
In American Journal of the Medical Sciences, January, 1858.




ABSORPTION.                          145
CHAPTER VII.
ABSORPTION.
BESIDE the glands of Brunner and the follicles of Lieberktihn,
already described, there are, in the inner part of the walls of the
intestine, certain glandular-                  Fig. 37.
looking  bodies  which  are
termed "glandulme solitariae,"
and  "glandulse agminatse."   
The glandulae solitariae are             /  (
globular  or ovoid  bodies,        i          /,
about one-thirtieth of an inch   _ 
in diameter, situated partly 
in and partly beneath the in-      \   _
testinal mucous membrane.
Each glandule (Fig. 37) is               K       \        \
formed of an investing cap-                 —.
sule, closed on all sides, and                  _ L'(
containing in its interior a.ONE OF THE CLOSED FOLLICLES OF PEYER'S
soft pulpy mass, which con-  PATCHES, from Small Intestine of Pig. Magnified
sists of minute cellular bodies, 50 diameters.
Fig. 38.
imbedded in a homogeneous                     -
substance. The inclosed mass          / 
is penetrated  by  capillary 
blood vessels, which pass in
through  the investing cap- 
sule, inosculate freely with
each other, and return upon
themselves in loops near the 
centre of the glandular body.
There is no external opening             
or duct; in fact, the contents
of the vesicle, being pulpy
and vascular, as already de- 
G L AN  D  L LE  Ar cD L  Ir  A T, from Small Intestine
scribed, are not to be regarded  of Pig. Magnified 20 diameters.
10




146                       ABSORPTION.
as a secretion, but as constituting a kind of solid glandular tissue.
The glandulre agminatoe (Fig. 38), or "Peyer's patches," as they are
sometimes called, consist of aggregations of similar globular or
ovoid bodies, found most abundantly toward the lower extremity of
the small intestine. Both the solitary and agminated glandules are
evidently connected with the lacteals and the system of the mesenteric glands, which latter organs they resemble very much in their
minute structure. They are probably to be regarded as the first
row of mesenteric glands, situated in the walls of the intestinal
canal.
Another set of organs, intimately connected with the process of
absorption, are the villi of the small intestine. These are conical
vascular eminences of the mucous membrane, thickly set over the
whole internal surface of the small intestine. In the upper portion of
the intestine, they are flattened and triangular in form, resembling
somewhat the conical projections of the pyloric portion of the stomach. In the lower part, they are long and filiform, and often
slightly enlarged, or club-shaped at their free extremity (Fig. 39),
and frequently attaining the length of
Fig. 39.         one thirty-fifth of an inch. They are
covered externally with  a layer of
columnar epithelium, similar to that
trans   wwhich lines the rest of the intestinal
mucous membrane, and contain in their
interior two sets of vessels. The most
superficial of these are the capillary
bloodvessels, which are supplied in each
villus by a twig of the mesenteric
recise m      artery, and which form, by their free  v sis t k  quent inosculation, an exceedingly close
and abundant network, almost immediately beneath the  epithelial layer.
They unite at the base of the villus,
and form a minute vein, which is one
of the commencing rootlets of the porEXTREMITY  OF INTESTINAL  tal vein. In the central part of the vilVIL L us, fron the Dog.-a. Layer of
epithelium. b. Bloodvessel. c. Lacteal lUS, and lying nearly in its axis, there
vessel.                    is another vessel, with thinner and more
transparent walls, which is the commencement of a lacteal.  The
precise manner in which the lacteal originates in the extremity of
the villus is not known. It commences near the apex, either by a




ABSORPTION.                        147
blind extremity or,by an irregular plexus, passes, in a straight or
somewhat wavy line, toward the base of the villus, and then becomes continuous with a small twig of the mesenteric lacteals.
The villi are the active agents in the process of absorption. By
their projecting form, and their great abundance, they increase enormously the extent of surface over which the digested fluids come
in contact with the intestinal mucous membrane, and increase, also,
to a corresponding degree, the energy with which absorption takes
place. They hang out into the nutritious, semi-fluid mass contained
in the intestinal cavity, as the roots of a tree penetrate the soil; and
they imbibe the liquefied portions of the food, with a rapidity which
is in direct proportion to their extent of surface, and the activity of
their circulation.
The process of absorption is also hastened by the peristaltic
movements of the intestine. The muscular layer here, as in other
parts of the alimentary canal, is double, consisting of both circular
and longitudinal fibres. The action of these fibres may be readily
seen by pinching the exposed intestine with the blades of a forceps.
A contraction then takes place at the spot irritated, by which the
intestine is reduced in diameter, its cavity obliterated, and its contents forced onward into the succeeding portion of the alimentary
canal. The local contraction then propagates itself to the neighboring parts, while the portion originally contracted becomes relaxed;
so that a slow, continuous, creeping motion of the intestine is produced, by successive waves of contraction and relaxation, which
follow each other from above downward. At the same time, the
longitudinal fibres have a similar alternating action, drawing the
narrowed portions of intestine up and down, as they successively
enter into contraction, or become relaxed in the intervals. The effect
of the whole is to produce a peculiar, writhing, worm-like, or
"vermicular" motion, among the different coils of intestine. During
life, the vermicular or peristaltic motion of the intestine is excited
by the presence of food undergoing digestion. By its action, the
substances which pass from  the stomach into the intestine are
steadily carried from above downward, so as to traverse the entire
length of the small intestine, and to come in contact successively
with the whole extent of its mucous membrane. During this passage, the absorption of the digested food is constantly going on.
Its liquefied portions are taken up by the villi of the mucous membrane, and successively disappear; so that, at the termination of the
small intestine, there remains only the undigestible portion of the




148                        ABSORPTION.
food, together, with the refuse of the intestinal secretions. These
pass through the ileo-caecal orifice into the large intestine, and there
become reduced to the condition of feces.
The absorption of the digested fluids is accomplished both by
the bloodvessels and the lacteals.  It was formerly supposed that
the lacteals were the only agents in this process; but it has now
been long known that this opinion was erroneous, and that the
bloodvessels take at least an equal part in absorption, and are in
some respects the most active and important agents of the two.
Abundant experiments have demonstrated not only that soluble
substances introduced  into the intestine may be soon afterward
detected in the blood of the portal vein, but that absorption takes
place more rapidly and abundantly by the bloodvessels than by
the lacteals. The most decisive of these experiments were those
performed by Panizza on the abdominal circulation.l  This observer opened the abdomen of a horse, and drew out a fold of the
small intestine, eight or nine inches in length (Fig. 40, a, a), which
Fig. 40.
C
PANIZZA'S EXPERIMENT.-aa. Intestine. b. Point of ligature of mesenteric vein. c. Opening
in intestine for introduction of poison. d. Opening in mesenteric vein behind the ligature.
he included between two ligatures. A ligature was then placed (at
b) upon the mesenteric vein receiving the blood from this portion
of intestine; and, in order that the circulation might not be interrupted, an opening was made (at d) in the vein behind the ligature,
In Matteucci's Lectures on the Physical Phenomena of Living Beings, Pereira's
edition, p. 83.




ABSORPTION.                       149
so that the blood brought by the mesenteric artery, after circulating
in the intestinal capillaries, passed out at the opening, and was
collected in a vessel for examination. Hydrocyanic acid was then
introduced into the intestine by an opening at c, and almost immediately afterward its presence was detected in the venous blood
flowing from the orifice at d. The animal, however, was not poisoned, since the acid was prevented from gaining an entrance into
the general circulation by the ligature at b.
Panizza afterward varied this experiment in the following manner: Instead of tying the mesenteric vein, he simply compressed it.
Then, hydrocyanic acid being introduced into the intestine, as above,
no effect was produced on the animal, so long as compression was
maintained upon the vein. But as soon as the blood was allowed
to pass again through the vessels, symptoms of general poisoning
at once became manifest. Lastly, in a third experiment, the same
observer removed all the nerves and lacteal vessels supplying the
intestinal fold, leaving the bloodvessels alone untouched. Hydrocyanic acid now being introduced into the intestine, found an
entrance at once into the general circulation, and the animal was
immediately poisoned. The bloodvessels, therefore, are not only
capable of absorbing fluids from the intestine, but may even take
them up more rapidly and abundantly than the lacteals.
These two sets of vessels, however, do not absorb all the alimentary matters indiscriminately. It is one of the most important of
the facts which have been established by modern researches on
digestion that the different substances, produced by the operation of
the digestive fluids on the food, pass into the circulation by different
routes. The fatty matters are taken up by the lacteals under the form
of chyle, while the saccharine and albuminous matters pass by absorption into the portal vein. Accordingly, after the digestion of a
meal containing starchy and animal matters mixed, albuminose and
sugar are both found in the blood of the portal vein, while they cannot be detected, in any large quantity, in the contents of the lacteals.
These substances, however, do not mingle at once with the general
mass of the circulation, but owing to the anatomical distribution of
the portal vein, pass first through the capillary circulation of the
liver. Soon after being introduced into the blood and coming in
contact with its organic ingredients, they become altered and converted, by catalytic transformation, into other substances.  The
albuminose passes into the condition of ordinary albumen, and
probably also partly into that of fibrin; while the sugar rapidly




150                      ABSORPTION.
becomes decomposed, and loses its characteristic properties; so
that, on arriving at the entrance of the general circulation, both
these newly absorbed ingredients have become already assimilated
to those which previously existed in the blood.
The chyle in the intestine consists, as we have already mentioned,
of oily matters which have not been chemically altered, but simply
reduced to a state of emulsion. In chyle drawn from the lacteals
or the thoracic duct (Fig. 41), it still presents itself in the same
condition and retains all the
Fig. 41.               chemical properties of oil.
Am — ^~^ ^ ~Examined by the microscope,
/? J (i; i:-~ t:o;t \...;  it is seen to exist under the./...o.o,;    \       form  of fine granules and
~/    X..ei';':.  \ x molecules, which present the
I/0.:;......;.:.:    \  ordinary appearances of oil
\   cdgpy r,:.'?oA,:;;{-'z.;:  in a state of minute subdivi-'.. x  ~;~,o.;.L:o.   ^..  sion.  The chyle, therefore,
O oO\.);,s;~  te:;,:;:~,:;.    /  does not represent the entire,\ IStobb24,;-.       /    product of the digestive pro-.\ "0:;:'-,?:.'^      /      cess, but contains only the
_\' ^'"''  /      ffatty substances, suspended
"-_  /^  ~ by emulsion in a serous fluid.
CHYLE FROM COMMENCEMENT OF THORACIC    During the time that intesDUCT, from the Dog.-The molecules vary in size tinal absorption is going on,
from 1-10,000th of an inch downward.
after a meal containing fatty
ingredients, the lacteals may be seen as white, opaque vessels, distended with milky chyle, passing through the mesentery, and converging from its intestinal border toward the receptaculum chyli,
near the spinal column.  During their course, they pass through
several successive rows of mesenteric glands, which also become
turgid with chyle, while the process of digestion is going on.  The
lacteals then conduct the chyle to the receptaculum chyli, whence
it passes upward through the thoracic duct, and is finally discharged, at the termination of this canal, into the left subclavian
vein. (Fig. 42.)  It is then mingled with the returning current of
venous blood, and passes into the right cavities of the heart.
The lacteals, however, are not a special system of vessels by themselves, but are simply a part of the great system of " absorbent" or
"lymphatic" vessels, which are to be found everywhere in the integuments of the head, the parietes of the trunk, the upper and lower
extremities, and in the muscular tissues and mucous membranes




ABSORPTION.                          151
throughout the body.  The walls of these vessels are thinner and
more transparent than those of the arteries and veins, and they are
consequently less easily detected by ordinary dissection.                 Fig. 42.
They originate in the tissues 
of the above-mentioned parts
by an irregular plexus. They                          -  
pass from  the extremities toward the trunk, convergingand
uniting with each other like the b 
veins, their principal branches
taking usually the same direction with the nerves and blood- 
vessels, and passing, at various   1 
points in their course, through 
certain glandular bodies, the
"lymphatic" or "absorbent"
glands. The lymphatic glands,
among which are included the
mesenteric glands, consist of an
external layer of fibrous tissue
and a contained pulp or parenchyma, The investing layer
of fibrous tissue sends off thin
septa or laminre from its inter-.
nal surface which penetrate
nal su, w h          LACTEALS, TTORACIC DUCT, &c. —a. Intesthe substance of the gland in  tine. b. Vena cava inferior. e, c. Right and left
every direction and unite with  subclavian veins. d. Point of opening of thoracic
duct into left subclavian.
each other at various points.
In this way they form an interlacing laminated framework, which
divides the substance of the gland into numerous rounded spaces
or alveoli. These alveoli are not completely isolated, but communicate with each other by narrow openings, where the intervening
septa are incomplete.  These cavities are filled with a soft, reddish
pulp, which is penetrated, according to K1lliker, like the solitary
and agminated glands of the intestine, by a fine network of capillary bloodvessels. The solitary and agminated glands of the intestine are, therefore, closely analogous in their structure to the lymphatics.  The former are to be regarded as simple, the latter as
compound vascular glands.
The arrangement of the lymphatic vessels in the interior of the




152                      ABSORPTION.
glands is not precisely understood. Each lymphatic vessel, as it
enters the gland, breaks up into a number of minute ramifications,
the vasa afferentia; and other similar twigs, forming the vasa efferentia, pass off in the opposite direction, from the farther side of the
gland; but the exact mode of communication between the two has
not been definitely ascertained. The fluids, however, arriving by
the vasa afferentia, must pass in some way through the tissue of
the gland, before they are carried away again by the vasa efferentia.
From the lower extremities the lymphatic vessels enter the abdomen
at the groin and converge toward the receptaculum chyli, into
which their fluid is discharged, and afterward conveyed, by the
thoracic duct, to the left subclavian vein.
The fluid which these vessels contain is called the lymph. It is
a colorless or slightly yellowish transparent fluid, which is absorbed
by the lymphatic vessels from the tissues in which they originate.
So far as regards its composition, it is known to contain, beside
water and saline matters, a small quantity of fibrin and albumen.
Its ingredients are evidently derived from the metamorphosis of
the tissues, and are returned to the centre of the circulation in
order to be eliminated by excretion, or in order to undergo some
new transforming or renovating process.  We are ignorant, however, with regard to the precise nature of their character and
destination.
The lacteals are simply that portion of the absorbents which
originate in the mucous membrane of the small intestine. During
the intervals of digestion, these vessels contain a colorless and
transparent lymph, entirely similar to that which is found in other
parts of the absorbent system.  After a meal containing only
starchy or albuminoid substances, there is no apparent change in
the character of their contents. But after a meal containing fatty
matters, these substances are taken up by the absorbents of the
intestine, which then become filled with the white chylous emulsion, and assume the appearance of lacteals. (Fig. 43.) It is for
this reason that lacteal vessels do not show themselves upon the
stomach nor upon the first few inches of the duodenum; because
oleaginous matters, as we have seen, are not digested in the stomach,
but only after they have entered the intestine and passed the orifice
of the pancreatic duct.
The presence of chyle in the lacteals is, therefore, not a constant, but only a periodical phenomenon.  The fatty substances
constituting the chyle begin to be absorbed during the process of




ABSORPTION.                        153
digestion, as soon as they have been disintegrated and emulsioned
by the action of the intestinal fluids. As digestion proceeds, they
accumulate in larger quantity, and gradually fill the whole lacteal
Fig. 43.
LACTEALS AND LYMPHATICS.
system  and the thoracic duct. As they are discharged into the
subclavian vein, and mingled with the blood, they can still be distinguished in the circulating fluid, as a mixture of oily molecules
and granules, between the orifice of the thoracic duct and the right
side of the heart. While passing through the pulmonary circulation, however, they disappear. Precisely what becomes of them,
or what particular chemical changes they undergo, is not certainly




154                      ABSORPTION.
known. They are, at all events, so altered in the blood, while
passing through the lungs, that they lose the form of a fatty emulsion, and are no longer to be recognized by the usual tests for
oleaginous substances.
The absorption of fat from  the intestine is not, however, exclusively performed by the lacteals. Some of it is also taken up,
under the same form, by the bloodvessels. It has been ascertained
by the experiments of Bernard' that the blood of the mesenteric
veins, in the carnivorous animals, contains, during intestinal digestion, a considerable amount of fatty matter in a state of minute
subdivision. Other observers, also (Lehmann, Schultz, Simon), have
found the blood of the portal vein to be considerably richer in fat
than that of other veins, particularly while intestinal digestion is
going on with activity. In birds, reptiles, and fish, furthermore,
according to Bernard, the intestinal lymphatics are never filled
with opaque chyle, but only with a transparent lymph; so that these
animals may be said to be destitute of lacteals, and in them the fatty
substances, like other alimentary materials, are taken up altogether
by the bloodvessels. In quadrupeds, on the other hand, and in
the human subject, the absorption of fat is accomplished both by
the bloodvessels and the lacteals. A certain portion is taken up
by the former, while the superabundance of the fatty emulsion is
absorbed by the latter.
A difficulty has long been experienced in accounting for the absorption of fat from the intestine, owing to its being considered as a
non-endosmotic substance; that is, as incapable, in its free or undissolved condition, of penetrating and passing through an animal
membrane by endosmosis. It is stated, indeed, that if a fine oily
emulsion be placed on one side of an animal membrane in an endosmometer, and pure water on the other, the water will readily penetrate the substance of the membrane, while the oily particles cannot
be made to pass, even under a high pressure. Though this be true,
however, for pure water, it is not true for slightly alkaline fluids,
like the serum of the blood and the lymph.  This has been demonstrated by the experiments of Matteucci, in which he made
an emulsion with an alkaline fluid containing 43 parts per thousand of caustic potassa. Such a solution has no perceptible alkaline
taste, and its action on reddened litmus paper is about equal to
I Legons de Physiologie Experimentale. Paris, 1856, p. 325.




ABSORPTION.                         155
that of the lymph and chyle. If this emulsion were placed in an
endosmometer, together with a watery alkaline solution of similar
strength, it was found that the oily particles penetrated through the
animal membrane without much difficulty, and mingled with the fluid
on the opposite side. Although, therefore, we cannot explain the
exact mechanism  of absorption in the case of fat, still we know
that it is not in opposition to
the ordinary phenomena of                    Fig 44.
endosmosis; for endosmosis
will take place with a fatty
emulsion, provided the fluids
used in the experiment be
slightly alkaline in reaction.
It is, accordingly, by a process of endosmosis, or imbi- 
bition, that the villi take up 
the digested fatty substances.
There are no open orifices
or canals, into which the oil
penetrates; but it passes directly into and through the   INTESTINAL EPITHLIUM; fromtheDog,while
substance of the villi.  The  fsting.
epithelial cells covering the external surface of the villus are the first
active agents in this absorption. In the intervals of digestion (Fig.
44) these cells are but slightly
granular and  nearly trans-                  Fig. 45.
parent in appearance. But if
examined during the digestion and absorption of fat
(Fig. 45), their substance is
seen to be crowded with oily
particles, which they have 
taken up from the intestinal 
cavity by absorption. The
oily matter then passes onward, penetrating deeper and  
deeper into the substance of
the villus, until it is at last
received by the capillary vesr ce.ived by.   INTESTINAL EPITHELIUM; from the Dog, dursels and lacteals in its centre. ig the digestion of fat.




156                      ABSORPTION.
The fatty substances taken up by the portal vein, like those absorbed by the lacteals, do not at once enter the general circulation,
but pass first through the capillary system of the liver. Thence
they are carried, with the blood of the hepatic vein, to the right
side of the heart, and subsequently through the capillary system of
the lungs. During this passage they become altered in character,
as above described, and lose for the most part the distinguishing
characteristics of oily matter, before they have passed beyond the
pulmonary circulation.
But as digestion proceeds, an increasing quantity of fatty matter
finds its way, by these two passages, into the blood; and a time at
last arrives when the whole of the fat so introduced is not destroyed
during its passage through the lungs. Its absorption taking place
at this time more rapidly than its decomposition, it begins to appear, in moderate quantity, in the blood of the general circulation;
and, lastly, when the intestinal absorption is at its point of greatest
activity, it is found in considerable abundance throughout the
entire vascular system. At this period, some hours after the ingestion of food rich in oleaginous matters, the blood of the general
circulation everywhere contains a superabundance of fat, derived
from the digestive process. If blood be then drawn from the veins
or arteries in any part of the body, it will present the peculiar
appearance known as that of "chylous" or "milky" blood. After
the separation of the clot, the serum presents a turbid appearance;
and the fatty substances, which it contains, rise to the top after a
few hours, and cover its surface with a partially opaque and creamylooking pellicle. This appearance has been occasionally observed
in the human subject, particularly in bleeding for apoplectic attacks
occurring after a full meal, and has been mistaken, in some instances,
for a morbid phenomenon. It is, however, a perfectly natural one,
and depends simply on the rapid absorption, at certain periods of
digestion, of oleaginous substances from the intestine. It can be
produced at will, at any time, in the dog, by feeding him with fat
meat, and drawing blood, seven or eight hours afterward, from the
carotid artery or the jugular vein.
This state of things continues for a varying length of time, according to the amount of oleaginous matters contained in the food.
When digestion is terminated, and the fat ceases to be introduced
in unusual quantity into the circulation, its transformation and
decomposition continuing to take place in the blood, it disappears
gradually from the veins, arteries, and capillaries of the general




ABSORPTION.                        157
system; and, finally, when the whole of the fat has been disposed
of by the nutritive processes, the serum again becomes transparent,
and the blood returns to its ordinary condition.
In this manner the nutritive elements of the food, prepared for
absorption by the digestive process, are taken up into the circulation
under the different forms of albuminose, sugar, and chyle, and accumulate as such, at certain times, in the blood. But these conditions
are only temporary, or transitional. The nutritive materials soon
pass, by catalytic transformation, into other forms, and become
assimilated to the preexisting elements of the circulating fluid.
Thus they accomplish finally the whole object of digestion; which
is to replenish the blood by a supply of new materials from without.
There are, however, two other intermediate processes, taking place
partly in the liver and partly in the intestine, at about the same
time, and having for their object the final preparation and perfection of the circulating fluid. These two processes require to be
studied, before we can pass on to the particular description of the
blood itself. They are: 1st, the secretion and reabsorption of the
bile; and 2d, the production of sugar in the liver, and its subsequent decomposition in the blood.




158                      THE BILE.
CHAPTER VIII.
THE BILE.
THE bile is more easily obtained in a state of purity than any
other of the secretions which find their way into the intestinal
canal, owing to the existence of a gall-bladder in which it accumulates, and from which it may be readily obtained without any
other admixture than the mucus of the gall-bladder itself. Notwithstanding this, its study has proved an unusually difficult one.
This difficulty has resulted from the peculiar nature of the biliary
ingredients, and the readiness with which they become altered by
chemical manipulation; and it is, accordingly, only quite recently
that we have arrived at a correct idea of its real constitution.
The bile, as it comes from the gall-bladder, is a somewhat viscid
and glutinous fluid, varying in color and specific gravity according
to the species of animal from which it is obtained. Human bile is
of a dark golden brown color, ox bile of a greenish yellow, pig's
bile of a nearly clear yellow, and dog's bile of a deep brown. We
have found the specific gravity of human bile to be 1018, that of
ox bile 1024, that of pig's bile 1030 to 1036. The reaction of the
bile with test-paper cannot easily be determined; since it has only
a bleaching or decolorizing effect on litmus, and does not turn it
either blue or red. It is probably either neutral or very slightly
alkaline. A very characteristic physical property of the bile is
that of frothing up into a soap-like foam when shaken in a testtube, or when air is forcibly blown into it through a small glass
tube or blowpipe. The bubbles of foam, thus produced, remain
for a long time without breaking, and adhere closely to each other
and to the sides of the glass vessel.
The following is an analysis of the bile of the ox, based on the
calculations of Berzelius, Frerichs, and Lehmann:




THE BILE.                            159
COMPOSITION OF OX BILE.
Water.. 888.00
Glyko-cholate of soda........
Tauro-cholate" ".......               9000
Biliverdine......
Fats.....
Oleates, margarates, and stearates of soda and potassa.  13.42
Cholesterin..........
Chloride of sodium....
Phosphate of soda...
"    " lime...                                  15.24
"    " magnesia....
Carbonates of soda and potassa.. 
Mucus of the gall-bladder....  1.34
1000.00
BILIVERDINE. —Of the above mentioned ingredients, biliverdine
is peculiar to the bile, and therefore important, though not present in large quantity. This is the coloring matter of the bile.
It is, like the other coloring matters, an uncrystallizable organic
substance, containing nitrogen, and yielding to ultimate analysis a
small quantity of iron. It exists in such small quantity in the bile
that its exact proportion has never been determined. It is formed,
so far as can be ascertained, in the substance of the liver, and does
not pre-exist in the blood.  It may, however, be reabsorbed in
cases of biliary obstruction, when it circulates with the blood and
stains nearly all the tissues and fluids of the body, of a peculiar
lemon yellow color.  This is the symptom which is characteristic
of jaundice.
CHOLESTERIN (CIH,,O).-This is a crystallizable substance which
resembles the fats in many respects; since it is destitute of nitrogen,
readily inflammable, soluble in alcohol and ether, and entirely insoluble in water. It is not saponifiable, however, by contact with
the alkalies, and is distinguished on this account from the ordinary
fatty substances. It occurs, in a crystalline form, mixed with coloring matter, as an abundant ingredient in most biliary calculi; and
is found also in different regions of the body, forming a part of
various morbid deposits.  We have met with it in the fluid of
hydrocele, and in the interior of many encysted tumors.  The
crystals of cholesterin (Fig. 46) have the form of very thin, colorless, transparent, rhomboidal plates, portions of which are often
cut out by lines of cleavage parallel to the sides of the crystal.
They frequently occur deposited in layers, in which the outlines of




160                        THE BILE.
the subjacent crystals show very distinctly through the substance
of those which are placed above. Cholesterin is not formed in the
liver, but originates in the
Fig. 46.               substance of the brain and
~^    - ~-~ ^     ~nervous tissue, from  which
it may be extracted in large
/~/ A~      \      quantity by the  action  of
i   /                \   alcohol.  From these tissues
/-.-/ / I"~''-   7      \  it is absorbed by the blood,
\ / _./7   /,-!~     \then conveyed to the liver,
/~-   /, 7  |  and discharged with the bile.
/ f'i/ /                     The fatty substances and
\  / /g7-  X/      inorganic saline ingredients.^ -i-~-    y        of the bile require no special
"   A"/ ^description.
CHOLE S TE RTN, from an Encysted Tumor.
BILIARY SALTS.-By far
the most important and characteristic ingredients of this secretion
are the two saline substances mentioned above as the glyko-cholate
and tauro-cholate of soda. These substances were first discovered
by Strecker, in 1848, in the bile of the ox. They are both freely
soluble in water and in alcohol, but insoluble in ether.  One of
them, the tauro-cholate, has the property, when itself in solution
in water, of dissolving a certain quantity of fat; and it is probably
owing to this circumstance that some free fat is present in the bile.
The two biliary substances are obtained from ox bile in the following manner:The bile is first evaporated to dryness by the water-bath. The
dry residue is then pulverized and treated with absolute alcohol, in
the proportion of at least 3j of alcohol to every five grains of dry
residue. The filtered alcoholic solution has a clear yellowish color.
It contains, beside the glyko-cholate and tauro-cholate of soda, the
coloring matter and more or less of the fats originally present in
the bile. On the addition of a small quantity of ether, a dense,
whitish precipitate is formed, which disappears again on agitating
and thoroughly mixing the fluids.  On the repeated addition of
ether, the precipitate again falls down, and when the ether has been
added in considerable excess, six to twelve times the volume of the
alcoholic solution, the precipitate remains permanent, and the whole
mixture is filled with a dense, whitish, opaque deposit, consisting




THE  BILE.                            161
of the glyko-cholate and tauro-cholate of soda, thrown down under
the form of heavy flakes and granules, part of which subside to
the bottom of the test-tube, while part remain for a time in suspension. Gradually these flakes and granules unite with each other
and fuse together into clear, brownish-yellow, oily, or resinouslooking drops. At the bottom of the test-tube, after two or three
hours, there is usually collected a nearly homogeneous layer of
this deposit, while the remainder continues to adhere to the sides
of the glass, in small, circular, transparent drops.  The deposit is
semi-fluid in consistency, and sticky, like Canada balsam or halfmelted resin; and it is on this account that the ingredients composing it have been called the "resinous matters" of the bile. They
have, however, no real chemical relation with true resinous bodies,
since they both contain nitrogen, and differ from resins also in
other important particulars.
At the end of twelve to twenty-four hours, the glyko-cholate of
soda begins to crystallize. The crystals radiate from various points
in the resinous deposit, and shoot upward into the supernatant
fluid, in white, silky bundles. (Fig. 47.) If some of these crystals
Fig. 47.                              Fig. 48.
OLYKO-CHOLATE OF SODA FROM OX-BILE,
after two days' crystallization. At the lower part of
the figure the crystals are melting into drops, from the
OX-B I L E, extracted with absolute 
evaporation of the ether and absorption of moisture.
alcohol and precipitated with ether.
be removed and examined by the microscope, they are found to be
of a very delicate acicular form, running to a finely pointed
extremity, and radiating, as already mentioned, from a central
11




162                         THE BILE.
point. (Fig. 48.)  As the ether evaporates, the crystals absorb
moisture from the air, and melt up rapidly into clear resinous
drops; so that it is difficult to keep them under the microscope
long enough for a correct drawing and measurement. The crystallization in the test-tube goes on after the first day, and the crystals
increase in quantity for three or four, or even five or six days, until
the whole of the glyko-cholate of soda present has assumed the
solid form.  The tauro-cholate, however, is uncrystallizable, and
remains in an amorphous condition. If a portion of the deposit be
now removed and examined by the microscope, it is seen that the
crystals of glyko-cholate of
Fig. 49.               soda have increased considerably in thickness (Fig. 49),
j/J^ ~ (^.     \ ~so that their transverse dia-,/  O    meter may be readily estio/  Q/0  / i/       f Q    \    mated. The uncrystallizable
I  D  /    g/ 0// /'~   \  tauro-cholate appears under
0 X I   D /I//////D/            \the form  of circular drops,
/  f//varying considerably in size,
clear, transparent, strongly
refractive, and bounded by
a dark, well-defined outline.
\^    ^_____J_  ~    ^/ -These drops are not to be distinguished, by any of their optical
properties, from oil-globules, as
GLYKO-CHOLATE AND TAURO-CHOLATE OF
SODA, FROM Ox-BIL, after six days' crystalliza- they usually appear under
tion. The glyko-cholate is crystallized; the tauro- the microscope. They have
cholate is in fluid drops.
the same refractive power,
the same dark outline and bright centre, and the same degree of
consistency.  lThey would consequently be liable at all times to be
mistaken for oil-globules, were it not for the complete dissimilarity
of their chemical properties.
Both the glyko-cholate and tauro-cholate of soda are very freely
soluble in water. If the mixture of alcohol and ether be poured
off and distilled water added, the deposit dissolves rapidly and
completely, with a more or less distinct yellowish color, according
to the proportion of coloring matter originally present in the bile.
The two biliary substances present in the watery solution may be
separated from each other by the following means.  On the addition of acetate of lead, the glyko-cholate of soda is decomposed,
and precipitates as a glyko-cholate of lead.  The precipitate, sepa



THE BILE.                         163
rated by filtration from the remaining fluid, is then decomposed in
turn by carbonate of soda, and the original glyko-cholate of soda
reproduced. The filtered fluid which remains, and which contains
the tauro-cholate of soda, is then treated with subacetate of lead,
which precipitates a tauro-cholate of lead. This is separated by
filtration, washed, and decomposed again by carbonate of soda, as
in the former case.
The two biliary substances in ox bile may, therefore, be distinguished by their reactions with the salts of lead.  Both are
precipitable by the subacetate; but the glyko-cholate of soda is
precipitable also by the acetate, while the tauro-cholate is not so.
If subacetate of lead, therefore, be added to the mixed watery solution of the two substances, and the whole filtered, the subsequent
addition of acetate of lead to the filtered fluid will produce no precipitate, because both the biliary matters have been entirely thrown
down with the deposit; but if the acetate of lead be first added, it
will precipitate the glyko-cholate alone, and the tauro-cholate may
afterward be thrown down separately by the subacetate.
These two substances, examined separately, have been found to
possess the following properties:Glyko-cholate of soda (NaO,CH42NO,) crystallizes, when precipitated by ether from its alcoholic solution, in radiating bundles of
fine white silky needles, as above described. It is composed of
soda, united with a peculiar acid of organic origin, viz., glyko-cholic
acid (C52E42NO1,HO). This acid is crystallizable and contains nitrogen, as shown by the above formula, which is that given by Lehmann.  If boiled for a long time with a dilute solution of potassa,
glyko-cholic acid is decomposed with the production of two new
substances; the first a non-nitrogenous acid body, cholic acid
(C48H3gOg,7H); the second a nitrogenous neutral body, glycine
(C415NO4).  Hence the name, glyko-cholic acid, given to the
original substance, as if it were a combination of cholic acid with
giycine. In reality, however, these two substances do not exist
originally in the glyko-cholic acid, but are rather new combinations
of its elements, produced by long boiling, in contact with potassa
and water. They are not, therefore, to be regarded as, in any way,
natural ingredients of the bile, and do not throw any light on the
real constitution of glyko-cholic acid.
ITuro-cholate of soda (NaO,C,,H45NS20,) is also a very abundant
ingredient of the bile. It is said by Robin and Verdeil' that it is
i Chimie Anatomique et Physiologique, vol. ii. p. 473.




164                        THE BILE.
not crystallizable, owing probably to its not having been separated
as yet in a perfectly pure condition. Lehmann states, on the contrary, that it may crystallize,' when kept for a long time in contact
with ether.  We have not been able to obtain this substance, however, in a crystalline form. Its acid constituent, taurocholic acid,
is a nitrogenous body, like glyko-cholic acid, but differs from the
latter by containing in addition two equivalents of sulphur. By
long boiling in a dilute solution of potassa. it is decomposed with
the production of two other substances; the first of them the same
acid body mentioned above as derived from the glyko-cholic, viz.,
cholic acid; and the second a new nitrogenous neutral body, viz.,
taurine (C,4HlNSO). The same remark holds good with regard to
these two bodies, that we have already made in respect to the supposed constituents of glyko-cholic acid. Neither cholic acid nor
taurine can be properly regarded as really ingredients of taurocholic acid, but only as artificial products resulting from its alteration and decomposition.
The glyko-cholates and tauro-cholates are formed, so far as we
know, exclusively in the liver; since they have not been found in
the blood, nor in any other part of the body, in healthy animals;
nor even, in the experiments of Kunde, Moleschott, and Lehmann
on frogs,2 after the entire extirpation of the liver, and consequent
suppression of the bile. These substances are, therefore, produced
in the glandular cells of the liver, by transformation of some other
of their ingredients. They are then exuded in a soluble form, as
part of the bile, and finally discharged by the excretory hepatic
ducts.
The two substances described above as the tauro-cholate and
glyko-cholate of soda exist, properly speaking, only in the bile of
the ox, where they were first discovered by Strecker. In examining the biliary secretions of different species of animals, Strecker
found so great a resemblance between them, that he was disposed
to regard their ingredients as essentially the same. Having established the existence in ox-bile of two peculiar substances, one
crystallizable and non-sulphurous (glyko-cholate), the other uncrystallizable and sulphurous (tauro-cholate), he was led to consider
the bile in all species of animals as containing the same substances,
and as differing only in the relative quantity in which the two
Physiological Chemistry, Phil. ed., vol. i. p. 209.
2 Lehmann's Physiological Chemistry, Phil. ed., vol. i. p. 476.




THE BILE.                          165
were present. The only exception to this was supposed to be pig's
bile, in which Strecker found a peculiar organic acid, the "hyocholic" or " hyo-cholinic" acid, in combination with soda as a base.
The above conclusion of his, however, was not entirely correct.
It is true that the bile of all animals, so far as examined, contains
peculiar substances, which resemble each other in being freely
soluble in water, soluble in absolute alcohol, and insoluble in ether;
and in giving also a peculiar reaction with Pettenkofer's test, to be
described presently. But, at the same time, these substances present certain minor differences in different animals, which show them
not to be identical.
In dog's bile, for example, there are, as in ox-bile, two substances
precipitable by ether from their alcoholic solution; one crystallizable, the other not so. But the former of these substances crystallizes
much more readily than the glyko-cholate of soda from ox-bile. Dog's
bile will not unfrequently begin to crystallize freely in five to six
hours after precipitation by ether (Fig. 50); while
in ox-bile it is usually twelve, and often twenty-     Fig. 50.
four or even forty-eight hours before crystallization is fully established.  But it is more particularly in their reaction with the salts of lead that
the difference between these substances becomes
manifest.  For while the crystallizable substance
of ox-bile is precipitated by acetate of lead, that 
of dog's bile is not affected by it.  If dog's bile
be evaporated to dryness, extracted with absolute
alcohol, the alcoholic solution precipitated by 
ether, and the ether precipitate then dissolved
in water, the addition of acetate of lead to the
watery solution produces not the slightest tur- 
bidity.  If subacetate of lead be then added in
excess, a copious precipitate falls, composed of
both the crystallizable and uncrystallizable substances.  If the lead precipitate be then separated   Dos' sBILE. extractby filtration, washed, and decomposed, as above  edwithabsolutealcohol
and precipitated with
described, by carbonate of soda, the watery solu-  ether.
tion will contain the re-formed soda salts of the
bile. The watery solution may then be evaporated to dryness,
extracted with absolute alcohol, and the alcoholic solution precipitated by ether; when the ether precipitate crystallizes partially




166                        THE BILE.
after a time, as in fresh bile. Both the biliary matters of dog's bile
are therefore precipitable by subacetate of lead, but neither of them
by the acetate. Instead of calling them, consequently, glyko-cholate
and tauro-cholate of soda, we shall speak of them simply as the
"crystalline" and "resinous" biliary substances.
In cat's bile, the biliary substances act very much as in dog's
bile. The ether-precipitate of the alcoholic solution contains here
also a crystalline and a resinous substance; both of which are
precipitable from their watery solution by subacetate of lead, but
neither of them by the acetate.
In pig's bile, on the other hand, there is no crystallizable substance, but the ether-precipitate is altogether resinous in appearance. Notwithstanding this, its watery solution precipitates abundantly by both the acetate and subacetate of lead.
In human bile, again, there is no crystallizable substance. We
have found that the dried bile, extracted with absolute alcohol,
makes a clear, brandy-red solution, which precipitates abundantly
with ether in excess; but the ether-precipitate, if allowed to stand,
shows no sign of crystallization, even at the end
Fig. 51.    of three weeks. (Fig. 51.)  If the resinous preci- _^ ^ ~  pitate be separated by decantation and dissolved
in water, it precipitates, as in the case of pig's
bile, by both the acetate and subacetate of lead.
This might, perhaps, be attributed to the preJig^    ~sence of two different substances, as in ox-bile,
one precipitated, by the acetate, the other by the
-ll-    ~ subacetate of lead.  Such, however, is not the
case. For if the watery solution be precipitated
by the acetate of lead and then filtered, the filtered
fluid gives no precipitate afterward by the subacetate; and if first precipitated by the subacetate,
it gives no precipitate after filtration by the acetate.  The entire biliary ingredients, therefore, of
Hi-  [human bile are precipitated by both or either of
the salts of lead.
HUMAN BILE, ex-    Different kinds of bile vary also in other retracted with absolute spects; as, for example, their specific gravity, the
alcohol and precipitated by ether.     depth and tinge of their color, the quantity of fat
which they contain, &c. &c. We have already
mentioned the variations in color and specific gravity. The alcoholic solution of dried ox-bile, furthermore, does not precipitate at




TESTS FOR BILE.                      167
all on the addition of water; while that of human bile, of pig's
bile, and of dog's bile precipitate abundantly with distilled water,
owing to the quantity of fat which they hold in solution.  These
variations, however, are of secondary importance compared with
those which we have already mentioned, and which show that the
crystalline and resinous substances in different kinds of bile, though
resembling each other in very many respects, are yet in reality far
from being identical.
TESTS FOR BILE.-In investigating the physiology of any animal
fluid it is, of course, of the first importance to have a convenient
and reliable test by which its presence may be detected. For a
long time the only test employed in the case of bile, was that which
depended on a change of color produced by oxidizing substances. If
the bile, for example, or a mixture containing bile, be exposed in
an open glass vessel for a few hours, the upper layers of the fluid,
which are in contact with the atmosphere, gradually assume a
greenish tinge, which becomes deeper with the length of time which
elapses, and thequantity of bile existing in the fluid. Nitric acid,
added to a mixture of bile and shaken up, produces a dense precipitate which takes a bright grass-green hue. Tincture of iodine
produces the same change of color, when added in small quantity;
and probably there are various other substances which would have
the same effect. It is by this test that the bile has so often been
recognized in the urine, serous effusions, the solid tissues, &c., in
cases of jaundice.  But it is very insufficient for anything like
accurate investigation, since the appearances are produced simply
by the action of an oxidizing agent on the coloring matter of the
bile. A green color produced by nitric acid does not, therefore,
indicate the presence of the biliary substances proper, but only of
the biliverdine. On the other hand, if the coloring matter be absent, the biliary substances themselves cannot be detected by it.
For if the biliary substances of dog's bile be precipitated by ether
from an alcoholic solution, dissolved in water and decolorized by
animal charcoal, the colorless watery solution will then give no
green color on the addition of nitric acid or tincture of iodine,
though it may precipitate abundantly by subacetate of lead, and
give the other reactions of the crystalline and resinous biliary
matters in a perfectly distinct manner.
Pettenkofer's Test.-This is undoubtedly the best test yet proposed for the detection of the biliary substances. It consists in




168                       THE BILE.
mixing with a watery solution of the bile, or of the biliary substances, a little cane sugar, and then adding sulphuric acid to the
mixture until a red, lake, or purple color is produced. A solution
may be made of cane sugar, in the proportion of one part of sugar to
four parts of water, and kept for use. One drop of this solution is
mixed with the suspected fluid, and the sulphuric acid then immediately added. On first dropping in the sulphuric acid, a whitish
precipitate falls, which is abundant in the case of ox-bile, less so in
that of the dog. This precipitate redissolves in a slight excess of
sulphuric acid, which should then continue to be added until the
mixture assumes a somewhat syrupy consistency and an opalescent
look, owing to the development of minute bubbles of air. A red
color then begins to show itself at the bottom of the test-tube, and
afterward spreads through the mixture, until the whole fluid is of
a clear, bright, cherry red. This color gradually changes to a lake,
and finally to a deep, rich, opaque purple. If three or four volumes of water be then added to the mixture, a copious precipitate
falls down, and the color is destroyed.
Various circumstances modify, to some extent, the rapidity and
distinctness with which the above changes are produced. If the
biliary substances be present in large quantity, and nearly pure,
the red color shows itself at once after adding an equal volume of
sulphuric acid, and almost immediately passed into a strong purple.
If they be scanty, on the other hand, the red color may not show
itself for seven or eight minutes, nor the purple under twenty
or twenty-five minutes. If foreign matters, again, not of a biliary
nature, be also present, they are apt to be acted on by the sulphuric
acid, and, by becoming discolored, interfere with the clearness and
brilliancy of the tinges produced. On this account it is indispensable, in delicate examinations, to evaporate the suspected fluid to
dryness, extract.the dry residue with absolute alcohol, precipitate
the alcoholic solution with ether, and dissolve the ether-precipitate
in water before applying the test. In this manner, all foreign substances which might do harm will be eliminated, and the test will
succeed without difficulty.
It must not be forgotten, furthermore, that the sugar itself is
liable to be acted on and discolored by sulphuric acid when added
in excess, and may therefore by itself give rise to confusion. A little
care and practice, however, will enable the experimenter to avoid
all chance of deception from this source.  When sulphuric acid is
mixed with a watery solution containing cane sugar, after it has




TESTS FOR BILE.                      169
been added in considerable excess, a yellowish color begins to show
itself, owing to the commencing decomposition of the sugar. This
color gradually deepens until it has become a dark, dingy, muddy
brown; but there is never at any time any clear red or purple
color, unless biliary matters be present. If the bile be present in
but small quantity, the colors produced by it may be modified and
obscured by the dingy yellow and brown of the sugar; but even
this difficulty may be avoided by paying attention to the following
precautions. In the first place, only very little sugar should be
added to the suspected fluid. In the second place, the sulphuric
acid should be added very gradually, and the mixture closely
watched to detect the first changes of color. If bile be present, the
red color peculiar to it is always produced before the yellowish
tinge which indicates the decomposition of the sugar.  When the
biliary matters, therefore, are present in small quantity, the addition of sulphuric acid should be stopped at that point, and the
colors, though faint, will then remain clear, and give unmistakable
evidence of the presence of bile.
The red color alone is not sufficient as an indication of bile. It
is in fact only the commencement of the change which indicates the
biliary matters. If these matters be present, the color passes, as
we have already mentioned, first into a lake, then into a purple;
and it is this lake and purple color alone which can be regarded as
really characteristic of the biliary reaction.
It is important to observe that Pettenkofer's reaction is produced
by the presence of either or both of the biliary substances proper;
and is not at all dependent on the coloring matter of the bile. For
if the two biliary substances, crystalline and resinous, be extracted
by the process above described, and, after being dissolved in water,
decolorized with animal charcoal, the watery solution will still give
Pettenkofer's reaction perfectly, though no coloring matter be present, and though no green tinge can be produced by the addition
of nitric acid or tincture of iodine. If the two biliary substances
be then separated from each other, and tested in distinct solutions,
each solution will give the same reaction promptly and completely.
Various objections have been urged against this test. It has
been stated to be uncertain and variable in its action. Robin and
Verdeil1 say that its reactions "do not belong exclusively to the
bile, and may therefore give rise to mistakes."  Some fatty sub-' Op cit., vol. ii. p. 468.




170                       THE BILE.
stances and volatile oils (olein, oleic acid, oil of turpentine, oil of
caraway) have been stated to produce similar red and violet colors,
when treated with sugar and sulphuric acid. These objections,
however, have not much, if any, practical weight. The test no
doubt requires some care and practice in its application, as we have
already pointed out; but this is the case also, to a greater or less
extent, with nearly all chemical tests, and particularly with those
for substances of organic origin. No other substance is, in point
of fact, liable to be met with in the intestinal fluids or the blood,
which would simulate the reactions of the biliary matters. We
have found that the fatty matters of the chyle, taken from the thoracic duct, do not give any coloration which would be mistaken for
that of the bile. When the volatile oils (caraway and turpentine)
are acted on by sulphuric acid, a red color is produced which afterward becomes brown and blackish, and a peculiar, tarry, empyreumatic odor is developed at the same time; but we do not get the
lake and purple colors spoken of above. Finally, if the precaution
be observed-first of extracting the suspected matters with absolute
alcohol, then precipitating with ether and dissolving the precipitate
in water, no ambiguity could result from the presence of any of the
above substances.
Pettenkofer's test, then, if used with care, is extremely useful,
and may lead to many valuable results. Indeed, no other test than
this can be at all relied on to determine the presence or absence of
the biliary substances proper.
VARIATIONS AND FUNCTIONS OF BILE.-With regard to the
entire quantity of bile secreted daily, we have had no very positive
knowledge, until the experiments of Bidder and Schmidt, published
in 1852.1 These experiments were performed on cats, dogs, sheep,
and rabbits, in the following manner. The abdomen was opened,
and a ligature placed upon the ductus cormunis choledochus, so
as to prevent the bile finding its way into the intestine. An opening was then made in the fundus of the gall-bladder, by which
the bile was discharged externally. The bile, so discharged, was
received into previously weighed vessels, and its quantity accurately
determined. Each observation usually occupied about two hours,
during which period the temporary fluctuations occasionally observable in the quantity of bile discharged were mutually corrected, so
Verdaungssaefte und Stoffwechsel. Leipzig, 1852.




VARIATIONS AND FUNCTIONS OF BILE.                  171
far as the entire result was concerned. The animal was then killed,
weighed, and carefully examined, in order to make sure that the
biliary duct had been securely tied, and that no inflammatory alteration had taken place in the abdominal organs. The observations
were made at very different periods after the last meal, so as to
determine the influence exerted by the digestive process upon the
rapidity of the secretion. The average quantity of bile for twentyfour hours was then calculated from  a comparison of the above
results; and the quantity of its solid ingredients was also ascertained in each instance by evaporating a portion of the bile in the
water bath, and weighing the dry residue.
Bidder and Schmidt found in this way that the daily quantity
of bile varied considerably in different species of animals. It was
very much greater in the herbivorous animals used for experiment
than in the carnivora.  The results obtained by these observers
are as follows:For every pound weight of the entire body there is secreted
during 24 hours
FRESH BILE.    DRY RESIDUE.
In the cat.... 102 grains.    5.712 grains.
"  dog.. 140  "        6.916  "
"  sheep..                  178  "        9.408  "
"  rabbit..     958"         17.290  "
Since, in the human subject, the digestive processes and the
nutritive actions generally resemble those of the carnivora, rather
than those of the herbivora, it is probable that the daily quantity
of bile in man is very similar to that in the carnivorous animals.
If we apply to the human subject the average results obtained by
Bidder and Schmidt from the cat and dog, we find that, in an adult
man, weighing 140 pounds, the daily quantity of the bile will be
certainly not less than 16,940 grains, or very nearly 21 pounds
avoirdupois.
It is a matter of great importance, in regard to the bile, as well
as the other intestinal fluids, to ascertain whether it be a constant
secretion, like the urine and perspiration, or whether it be intermittent, like the gastric juice, and discharged only during the digestive
process. In order to determine this point, we have performed the
following series of experiments on dogs. The animals were kept
confined, and killed at various periods after feeding, sometimes by
the inoculation of woorara, sometimes by hydrocyanic acid, but
most frequently by section of the medulla oblongata.  The con



172                        THE BILE.
tents of the intestine were then collected and examined. In all
instances, the bile was also taken from the gall-bladder, and treated
in the same way, for purposes of comparison. The intestinal contents always presented some peculiarities of appearance when treated
with alcohol and ether, owing probably to the presence of other
substances than the bile; but they always gave evidence of the
presence of biliary matters as well. The biliary substances could
almost always be recognized by the microscope in the ether-precipitate of the alcoholic solution; the resinous substance, under the
form of rounded, oily-looking drops (Fig. 52), and the other, under
the form of crystalline groups, generally presenting the appearance
of double bundles of slender,
Fig. 52..
^^^Fig. 52.radiating, slightly curved or
/^// )i Q, ^\,  0wavy, needle-shaped crys/      7'miy'^ IA. "'i~ d,.      tals. These substances, dis~ l^    ^) i ^1  \ ~solved in water, gave a pur-,   //   \v.11..ple color with sugar and
sulphuric acid. These exI  /       li'          periments were tried after
\\f:(72 U   T                     te the animals had been kept
\             \111~,  ^^^~w   /t for one, two, three, five, six,
0I             seven, eight, and  twelve
days without food.  The
00 80 ~^ l  EAresult showed that, in all.co'O./ Q                    these instances, bile was preCRASTALLINE AND nRaSio.Ir BIIARY StuB- sent in the small intestine.
STANCES; from Small Intestine of Dog, after two days' It is, therefore, plainly not
fasting.                              an  intermittent secretion,
nor one which is concerned exclusively in the digestive process;
but its secretion is constant, and it continues to be discharged into
the intestine for many days after the animal has been deprived of
food.
The next point of importance to be examined relates to the time
afterfeeding at which the bile passes into the intestine in the greatest
abundance.  Bidder and Schmidt have already investigated this
point in the following manner. They operated, as above described,
by tying the common bile-duct, and then opening the fundus of the
gall-bladder, so as to produce a biliary fistula, by which the whole
of the bile was drawn off: By doing this operation, and collecting
and weighing the fluid discharged at different periods, they came




VARIATIONS AND  FUNCTIONS OF BILE.                   173
to the conclusion that the flow of bile begins to increase within two
and a half hours after the introduction of food into the stomach,
but that it does not reach its maximum of activity till the end of
twelve or fifteen hours. Other observers, however, have obtained
different results. Arnold,' for example, found the quantity to be
largest soon after meals, decreasing again after the fourth hour.
Kolliker and MUller,2 again, found it largest between the sixth and
eighth hours. Bidder and Schmidt's experiments, indeed, strictly
speaking, show only the time at which the bile is most actively
secreted by the liver, but not when it is actually discharged into
the intestine.
Our own experiments, bearing on this point, were performed on
dogs, by making a permanent
duodenal fistula, on  the same                   Fig. 53.
plan that gastric fistulse have so 
often been  established for the
examination of the gastric juice.
(Fig. 53.) An incision was made
through the abdominal walls, a
short distance to the right of
the  median  line, the floating          d
portion of the duodenum drawn
up toward the external wound,
opened by a longitudinal incision, and a silver tube, armed 
at each  end with  a  narrow
projecting collar or flange, inserted into it by one extremity,
five and a half inches below the
pylorus, and  two and  a half
inches below the orifice of the   DUODENAL FIsTULA.-a. Stomach. b. Duolower pancreatic  duct.   The  denum  c, c,. Pancreas; its two ducts are seen
opening into the duodenum, one near the orifice
other extremity of the tube was of the biliary duct, d, the other a short distance
left projecting from the external lower down. e. Silver tube pasing through the
abdominal walls and opening into the duodenum.
opening in the abdominal parietes, the parts secured by sutures, and the wound allowed to heal.
After cicatrization was complete, and  the animal had entirely
recovered his healthy condition and appetite, the intestinal fluids
were drawn off at various intervals after feeding, and their contents
In Am. Journ. Med. Sci., April, 1856.       2 Ibid., April, 1857.




174                          THE BILE.
examined.  This operation, which is rather more difficult than that
of making a permanent gastric fistula, is nevertheless exceedingly
useful when it succeeds, since it enables us to study, not only the
time and rate of the biliary discharge, but also, as mentioned in a
previous chapter (Chap. VI.), many other extremely interesting
matters connected with intestinal digestion.
In order to ascertain the absolute quantity of bile discharged
into the intestine, and its variations during digestion, the duodenal
fluids were drawn off, for fifteen minutes at a time, at various
periods after feeding, collected, weighed, and examined separately,
as follows: each separate quantity was evaporated to dryness, its
dry residue extracted with absolute alcohol, the alcoholic solution
precipitated with ether, and the ether-precipitate, regarded as representing the amount of biliary matters present, dried, weighed, and
then treated with Pettenkofer's test, in order to determine, as nearly
as possible, their degree of purity or admixture. The result of
these experiments is given in the following table.  At the eighteenth hour so small a quantity of fluid was obtained, that the
amount of its biliary ingredients was not ascertained. It reacted
perfectly, however, with Pettenkofer's test, showing that bile was
really present.
Time after    Quantity of fluid   Dry residue  Quantity of    Proportion of
feeding.   in 15 minutes.   of same.    biliary matters.  biliary matters
to dry residue.
Immediately     640 grains     33 grains     10 grains.30
1 hour        1,990  "       105"            4   ".03
3 hours        780 "          60             4   ".07
6  "           750   -        73  "          3".05
9  "           860  "         78  "          41 ".06
12  "           325   "        23  "          3; ".16
15  "           347  "         18  "          4  ".22
18".                      - 
21  "           384   "        11  "          1  ".09
24  "           163  "          9H   "        31 ".34
25  "           151  "          5"            3  ".60
From  this it appears that the bile passes into the intestine in by
far the largest quantity immediately after feeding, and within the
first hour. After that time its discharge remains pretty constant;
not varying much from four grains of solid biliary matters every
fifteen minutes, or sixteen grains per hour. The animal used for
the above observations weighed thirty-six and a half pounds.
The next point to be ascertained with regard to this question is
the following, viz: What becomes of the bile in its passage through
the intestire? Our experiments, performed with a view of settling




VARIATIONS AND FUNCTIONS OF BILE.                175
this point, were tried on dogs. The animals were fed with fresh
meat, and then killed at various intervals after the meals, the abdomen opened, ligatures placed upon the intestine at various points,
and the contents of its upper, middle, and lower portions collected
and examined separately. The results thus obtained show that,
under ordinary circumstances, the bile, which is quite abundant in
the duodenum and upper part of the small intestine, diminishes in
quantity from above downward, and is not to be found in the large
intestine. The entire quantity of the intestinal contents also diminishes, and their consistency increases, as we approach the ileocaecal valve; and at the same time their color changes from a light
yellow to a dark bronze or blackish-green, which is always strongly
pronounced in the last quarter of the small intestine.
The contents of the small and large intestine were furthermore
evaporated to dryness, extracted with absolute alcohol, and the
alcoholic solutions precipitated with ether; the quantity of etherprecipitate being regarded as representing approximatively that of
the biliary substances proper. The result showed that the quantity
of this ether-precipitate is, both positively and relatively, very much
less in the large intestine than in the small. Its proportion to the
entire solid contents is only one-fifth or one-sixth as great in the
large intestine as it is in the small. But even this inconsiderable
quantity, found in contents of the large intestine, does not consist of biliary matters; for the watery solutions being treated with
sugar and sulphuric acid, those from both the upper and lower
portions of the small intestine always gave Pettenkofer's reaction
promptly and perfectly in less than a minute and a half; while in
that from the large intestine no red or purple color was produced,
even at the end of three hours.
The small intestine consequently contains, at all times, substances
giving all the reactions of the biliary ingredients; while in the
contents of the large intestine no such substances can berecognized
by Pettenkofer's test.
The biliary matters, therefore, disappear in their passage through
the intestine.
In endeavoring to ascertain what is the precisefunction of the bile
in the intestine, our first object must be to determine what part, if
any, it takes in the digestive process. As the liver is situated, like
the salivary glands and the pancreas, in the immediate vicinity of
the alimentary canal, and like them, discharges its secretion into




176                       THE BILE.
the cavity of the intestine, it seems at first natural to regard the
bile as one of the digestive fluids. We have previously shown,
however, that the digestion of all the different elements of the food
is provided for by other secretions; and furthermore, if we examine
experimentally the digestive power of bile on alimentary substances,
we obtain only a negative result. Bile exerts no special action upon
either albuminoid, starchy, or oleaginous matters, when mixed with
them in test-tubes and kept at the temperature of 1000 F. It has
therefore, apparently, no direct influence in the digestion of these
substances.
It is a very remarkable fact, in this connection, that the bile precipitates by contact with the gastricjuice. If four drops of dog's bile
be added to 3j of gastric juice from the same animal, a copious
yellowish white precipitate falls down, which contains the whole of
the coloring matter of the bile which has been added; and if the
mixture be then filtered, the filtered fluid passes through quite
colorless. The gastric juice, however, still retains its acid reaction.
This precipitation depends upon the presence of the biliary substances proper, viz., the glyko-cholate and tauro-cholate of soda, and
not upon that of the incidental ingredients of the bile. For if the
bile be evaporated to dryness and the biliary substances extracted
by alcohol and precipitated by ether, as above described, their
watery solution will precipitate with gastric juice, in the same
manner as fresh bile would do.
Although the biliary matters, however, precipitate by contact
with fresh gastric juice, they do not do so with gastric juice which holds
albuminose in solution. We have invariably found that if the gastric juice be digested for several hours at the temperature of 100~
F., with boiled white of egg, the filtered fluid, which contains an
abundance of albuminose, will no longer give the slightest precipitate on the addition of bile, or of a watery solution of the biliarv
substances, even in very large amount. The gastric juice and the
bile, therefore, are not finally antagonistic to each other in the
digestive process, though at first they produce a precipitate on
being mingled together.
It appears, however, from the experiments detailed above, that
the secretion of the bile and its discharge into the intestine are not
confined to the periods of digestion, but take place constantly, and
continue even after the animal has been kept for many days without food. These facts would lead us to regard the bile as simply
an excrementitious fluid; containing only ingredients resulting from




VARIATIONS AND FUNCTIONS OF BILE.                177
the waste and disintegration of the animal tissues, and not intended
to perform  any particular function, digestive or otherwise, but
merely to be eliminated from the blood, and discharged from the
system. The same view is more or less supported, also, by the
following facts, viz:1st. The bile is produced, unlike all the other animal secretions,
from venous blood; that is, the blood of the portal vein, which has
already become contaminated by circulation through the abdominal
organs, and may be supposed to contain disorganized and effete
ingredients; and
2d. Its complete suppression produces, in the human subject,
symptoms of poisoning of the nervous system, analogous to those
which follow the suppression of the urine, or the stoppage of respiration, and the patient dies, usually in a comatose condition, at the
end of ten or twelve days.
The above circumstances, taken  together, would combine to
make it appear that the bile is simply an excrementitious fluid, not
necessary or useful as a secretion, but only destined like the urine,
to be eliminated and discharged. Nevertheless, experiment has
shown that such is not the case; and that, in point of fact, it is
necessary for the life of the animal, not only that the bile be secreted
and discharged, but furthermore that it be discharged into the
intestine, and pass through the tract of the alimentary canal. The
most satisfactory experiments of this kind are those of Bidder and
Schmidt, in which they tied the common biliary duct in dogs, and
then established a permanent fistula in the fundus of the gall-bladder,
through which the bile was allowed to flow by a free external orifice.
In this manner the bile was effectually excluded from the intestine,
but at the same time was freely and wholly discharged from the
body, by the artificial fistula. If the bile therefore were simply an
excrementitious fluid, its deleterious ingredients being all eliminated
as usual, the animals would not suffer any serious injury from this
operation. If, on the contrary, they were found to suffer or die in
consequence of it, it would show that the bile has really some important function to perform in the intestinal canal, and is not simply
excrementitious in its nature.
The result showed that the effects of such an experiment were
fatal to the animal. Four dogs only survived the immediate effects
of the operation, and were afterward frequently used for purposes
Op. cit., p. 103.
12




178                       THE BILE.
of experiment. One of them was an animal from which the spleen
had been previously removed, and whose appetite, as usual after
this operation, was morbidly ravenous; his system, accordingly,
being placed under such unnatural conditions as to make him an
unfit subject for further experiment. In the second animal that
survived, the communication of the biliary duct with the intestine
became re-established after eighteen days, and the experiment consequently had no result. In the remaining two animals, however,
everything was successful. The fistula in the gall-bladder became
permanently established; and the bile-duct, as was proved subsequently by post-mortem examination, remained completely closed,
so that no bile found its way into the intestine. Both these animals died; one of them at the end of twenty-seven days, the other
at the end of thirty-six days. In both, the symptoms were nearly
the same, viz., constant and progressive emaciation, which proceeded
to such a degree that nearly every trace of fat disappeared from the
body. The loss of flesh amounted, in one case to more than twofifths, and in the other to nearly one-half the entire weight of the
animal. There was also a falling off of the hair, and an unusually
disagreeable, putrescent odor in the feces and in the breath. Notwithstanding this, the appetite remained good. Digestion was not
essentially interfered with, and none of the food was discharged
with the feces; but there was much rumbling and gurgling in the
intestines, and abundant discharge of flatus, more strongly marked
in one instance than in the other. There was no pain; and death
took place, at last, without any violent symptoms, but by a simple
and gradual failure of the vital powers.
How is it, then, that although the bile be not an active agent in
digestion, its presence in the alimentary canal is still essential to
life? What office does it perform there, and how is it finally disposed of?
We have already shown that the bile disappears in its passage
through the intestine. This disappearance may be explained in
two different ways. First, the biliary matters may be actually reabsorbed from the intestine, and taken up by the bloodvessels; or
secondly, they may be so altered and decomposed by the intestinal
fluids as to lose the power of giving Pettenkofer's reaction with
sugar and sulphuric acid, and so pass off with the feces in an
insoluble form. Bidder and Schmidt' have finally determined this' Op. cit., p. 217.




VARIATIONS AND FUNCTIONS OF BILE.                    179
point in a satisfactory manner; and have demonstrated that the
biliary substances are actually reabsorbed, by showing that the
quantity of sulphur present in the feces is far inferior to that
contained in the biliary ingredients as they are discharged into the
intestine.
These observers collected and analyzed all the feces passed, during five days, by a healthy dog, weighing 17.7 pounds.  The entire
fecal mass during this period weighed 1508.15 grains,
Containing  Water.                          874.20 grains.
Solid residue.....   633.95  "
1508.15
The solid residue was composed as follows:Neutral fat, soluble in ether.. 43.710 grains.
Fat, with traces of biliary matter. 77.035 
Alcohol extract with biliary matter 58.900 containing 1.085 grs. of sulphur.
Substances not of a biliary nature
extracted by muriatic acid and
hot alcohol.  148.800 containing 1.302 grs. of sulphur.
2.387
Fatty acids with oxide of iron. 98.425
Residue consisting of hair, sand, &c., 207.080
633.950
Now, as it has already been shown that the dog secretes, during
24 hours, 6.916 grains of solid biliary matter for every pound weight
of the whole body, the entire quantity of biliary matter secreted
in five days by the above animal, weighing 17.7 pounds, must have
been 612.5 grains, or nearly as much as the whole weight of the
dried feces. But furthermore, the natural proportion of sulphur
in dog's bile (derived from the uncrystallizable biliary matter), is six
per cent. of the dry residue. The 612.5 grains of dry bile, secreted
during five days, contained therefore 36.75 grains of sulphur.
But the entire quantity of sulphur, existing in any form in the
feces, was 5.952 grains; and of this only 2.387 grains were derived
from  substances which could have been the products of biliary
matters-the remainder being derived from  the hairs which are
always contained in abundance in the feces of the dog. That is,
not more than one-fifteenth part of the sulphur, originally present
in the bile, could be detected in the feces. As this is a simple
chemical element, not decomposable by any known means, it must,
accordingly, have been reabsorbed from the intestine.
We have endeavored to complete the evidence thus furnished by




180                       THE BILE.
Bidder and Schmidt, and to demonstrate directly the reabsorption
of the biliary matters, by searching for them in the ingredients of
the portal blood. We have examined, for this purpose, the portal
blood of dogs, killed at various periods after feeding. The animals
were killed by section of the medulla oblongata, a ligature immediately placed on the portal vein, while the circulation was still
active, and the requisite quantity of blood collected by opening
the vein. The blood was sometimes immediately evaporated to
dryness by the water bath. Sometimes it was coagulated by boiling in a porcelain capsule, over a spirit lamp, with water and an
excess of sulphate of soda, and the filtered watery solution afterward examined. But most frequently the blood, after being collected from the vein, was coagulated by the gradual addition of
three times its volume of alcohol at ninety-five per cent., stirring
the mixture constantly, so as to make the coagulation gradual and
uniform. It was then filtered, the moist mass remaining on the filter
subjected to strong pressure in a linen bag, by a porcelain press,
and the fluid thus obtained added to that previously filtered. The
entire spirituous solution was then evaporated to dryness, the dry
residue extracted with absolute alcohol, and the alcoholic solution
treated as usual, with ether, &c., to discover the presence of biliary
matters. In every instance, blood was taken at the same time from
the jugular vein, or the abdominal vena cava, and treated in the
same way for purposes of comparison.
We have examined the blood, in this way, one, four, six, nine,
eleven and a half, twelve, and twenty hours after feeding. As the
result of these examinations, we have found that in the venous
blood, both of the portal vein and of the general circulation, there
exists a substance soluble in water and absolute alcohol, and precipitable by ether from its alcoholic solution. This substance is
often considerably more abundant in the portal blood than in that
taken from the general venous system. It adheres closely to the
sides of the glass after precipitation, so that it is always difficult,
and often impossible, to obtain enough of it, mixed with ether, for
microscopic examination. It dissolves, also, like the biliary substances, with great readiness in water; but in no instance have we
ever been able to obtain from it such a satisfactory reaction with
Pettenkofer's test, as would indicate the presence of bile. This is
not because the reaction is masked, as might be suspected, by some
of the other ingredients of the blood; for if at the same time, two
drops of bile be added to half an ounce of blood taken from the




VARIATIONS AND FUNCTIONS OF BILE.                 181
abdominal vena cava, and the two specimens treated alike, the etherprecipitate may be considerably more abundant in the case of the
portal blood; and yet that from the blood of the vena cava, dissolved in water, will give Pettenkofer's reaction for bile perfectly,
while that of the portal blood will give no such reaction.
Notwithstanding, then, the irresistible evidence afforded by the
experiments of Bidder and Schmidt, that the biliary matters are
really taken up by the portal blood, we have failed to recognize
them there by Pettenkofer's test. They must accordingly undergo
certain alterations in the intestine, previously to their absorption,
so that they no longer give the ordinary reaction of the biliary substances. We cannot say, at present, precisely what these alterations
are; but they are evidently transformations of a catalytic nature,
produced by the contact of the bile with the intestinal juices.
The bile, therefore, is a secretion which has not yet accomplished
its function when it is discharged from the liver and poured into the
intestine. On the contrary, during its passage through the intestine
it is still in the interior of the body, in contact with glandular surfaces, and mingled with various organic substances, the ingredients
of the intestinal fluids, which act upon it as catalytic bodies, and
produce in it new transformations. This may account for the fact
stated above, that the bile, though a constant and uninterrupted
secretion, is nevertheless poured into the intestine in the greatest
abundance immediately after a hearty meal. This is not because it
is to take any direct part in the digestion of the food; but because
the intestinal fluids, being themselves present at that time in the
greatest abundance, can then act upon and decompose the greatest
quantity of bile. At all events, the biliary ingredients, after being
altered and transformed in the intestine, as they might be in the
interior of a glandular organ, re-enter the blood under some new
form, and are carried away by the circulation, to complete their
function in some other part of the body.




182       FORMATION OF SUGAR IN THE LIVER.
CHAPTER IX.
FORMATION OF SUGAR IN THE LIVER.
BESIDE the secretion of bile, the liver performs also another
exceedingly important function, viz., the production of sugar by a
metamorphosis of some of its organic ingredients.
Under ordinary circumstances a considerable quantity of saccharine matter is introduced with the food, or produced from
starchy substances, by the digestive process, in the intestinal canal.
In man and the herbivorous animals, accordingly, an abundant
supply of sugar is derived from these sources; and, as we have
already shown, the sugar thus introduced is necessary for the proper
support of the vital functions. For though the saccharine matter
absorbed from the intestine is destroyed by decomposition soon
after entering the circulation, yet the chemical changes by which
its decomposition is effected are themselves necessary for the proper
constitution of the blood, and the healthy nutrition of the tissues.
Experiment shows, however, that the system does not depend, for
its supply of sugar, entirely upon external sources; but that saccharine matter is also produced independently, in the tissue of the
liver, whatever may be the nature of the food upon which the
animal subsists.
This important function was first discovered by M. Claude Bernard' in 1848, and described by him under the name of the glycogenic function of the liver.
It has long been known that sugar may be abundantly secreted,
under some circumstances, when no vegetable matters have been
taken with the food. The milk, for example, of all animals, carnivorous as well as herbivorous, contains a notable proportion of
sugar; and the quantity thus secreted, during lactation, is in some
instances very great. In the human subject, also, when suffering
from diabetes, the amount of saccharine matter discharged with the
Nouvelle Fonction du Foie. Paris, 1853.




FORMATION OF SUGAR IN THE LIVER.                 183
urine has often appeared to be altogether out of proportion to that
which could be accounted for by the vegetable substances taken as
food. The experiments of Bernard, the most important of which
we have repeatedly confirmed, in common with other investigators,
show that in these instances most of the sugar has an internal
origin, and that it first makes its appearance in the tissue of the
liver.
If a carnivorous animal, as, for example, a dog or a cat, be fed
for several days exclusively upon meat, and then killed, the liver
alone of all the internal organs is found to contain sugar among its
other ingredients. For this purpose, a portion of the organ should
be cut into small pieces, reduced to a pulp by grinding in a mortar
with a little water, and the mixture coagulated by boiling with an
excess of sulphate of soda, in order to precipitate the albuminous
and coloring matters. The filtered fluid will then reduce the oxide
of copper, with great readiness, on the application of Trommer's
test. A decoction of the same tissue, mixed with a little yeast, will
also give rise to fermentation, producing alcohol and carbonic acid,
as is usual with saccharine solutions. On the contrary, the tissues
of the spleen, the kidneys, the lungs, the muscles, &c., treated in
the same way, give no indication of sugar, and do not reduce the
salts of copper. Every other organ in the body may be entirely
destitute of sugar, but the liver always contains it in considerable
quantity, provided the animal be healthy. Even the blood of the
portal vein, examined by a similar process, contains no saccharine
element, and yet the tissue of the organ supplied by it shows an
abundance of saccharine ingredients.
It is remarkable for how long a time the liver will continue to
exhibit the presence of sugar, after all external supplies of this
substance have been cut off. Bernard kept two dogs under his own
observation, one for a period of three, the other of eight months,
during which period they were confined strictly to a diet of animal
food (boiled calves' heads and tripe), and then killed. Upon examination, the liver was found, in each instance, to contain a proportion of sugar fully equal to that present in the organ under ordinary
circumstances.
The sugar, therefore, which is found in the liver after death, is a
normal ingredient of the hepatic tissue. It is not formed in other
parts of the body, nor absorbed from the intestinal canal, but takes
I Nouvelle Fonction du Foie, p. 50.




184         FORMATION OF SUGAR IN  THE LIVER.
its origin in the liver itself; it is produced, as a new formation,
by a secreting process in the tissue of the organ.
The presence of sugar in the liver is common to all species of
animals, so far as is yet known.  Bernard found it invariably in
monkeys, dogs, cats, rabbits, the horse, the ox, the goat, the sheep,
in birds, in reptiles, and in most kinds of fish. It was only in two
species of fish, viz., the eel and the ray (Murena anguilla and Raia
batis), that he sometimes failed to discover it; but the failure in
these instances was apparently owing to the commencing putrescence of the tissue, by which the sugar had probably been destroyed.
In the fresh liver of the human subject, examined after death from
accidental violence, sugar was found to be present in the proportion
of 1.10 to 2.14 per cent. of the entire weight of the organ.
The following list shows the average percentage of sugar present
in the healthy liver of man and different species of animals, according to the examinations of Bernard:PERCENTAGE OF SUGAR IN THE LIVER.
In man.. 1.68      In ox....2.30
monke... 2.15  " horse.. 4.08
dog.... 1.69               goat... 3.89
" cat....1.94            "birds..           1.49
" rabbit... 1.94        "reptiles... 1.04
sheep... 2.00         " fish.... 1.45
With regard to the nature and properties of the liver sugar, it
resembles very closely glucose, or the sugar of starch, the sugar of
honey, and the sugar of milk, though it is not absolutely identical
with either one of them. Its solution reduces, as we have seen, the
salts of copper in Trommer's test, and becomes colored brown when
boiled with caustic potassa. It ferments very readily, also, when
mixed with yeast and kept at the temperature of 70~ to 100~ F.
It is distinguished from all the other sugars, according to Bernard,'
by the readiness with which it becomes decomposed in the bloodsince cane sugar and beet root sugar, if injected into the circulation
of a living animal, pass through the system without sensible decomposition, and are discharged unchanged with the urine; sugar of
milk and glucose, if injected in moderate quantity, are decomposed
in the blood, but if introduced in greater abundance make their
appearance also in the urine; while a solution of liver sugar, though
injected in much larger quantity than either of the others, may disI Leqons de Physiologie Exp6rimentale. Paris, 1855, p. 213.




FORMATION  OF SUGAR IN THE LIVER.                 185
appear altogether in the circulation, without passing off by the
kidneys.
This substance is therefore a sugar of animal origin, similar in
its properties to other varieties of saccharine matter, derived from
different sources.
The sugar of the liver is not produced in the blood by a direct
decomposition of the elements of the circulating fluid in the vessels
of the organ, but takes its origin in the solid substance of the hepatic
tissue, as a natural ingredient of its organic texture. The blood
which may be pressed out from a liver recently extracted from the
body, it is true, contains sugar; but this sugar it has absorbed from
the tissue of the organ in which it circulates. This is demonstrated
by the singular fact that the fresh liver of a recently killed animal,
though it may be entirely drained of blood and of the sugar which
it contained at the moment of death, will still continue for a certain
time to produce a saccharine substance. If such a liver be injected
with water by the portal vein, and all the blood contained in its
vessels washed out by the stream, the water which escapes by the
hepatic vein will still be found to contain sugar.  M. Bernard has
found' that if all the sugar contained in a fresh liver be extracted in
this manner by a prolonged watery injection, so that neither the
water which escapes by the hepatic vein, nor the substance of the
liver itself, contain any further traces of sugar, and if the organ be
then laid aside for twenty-four hours, both the tissue of the liver and
the fluid which exudes from it will be found at the end of that time
to have again become highly saccharine. The sugar, therefore, is
evidently not produced in the blood circulating through the liver,
but in the substance of the organ itself.  Once having originated
in the hepatic tissue, it is absorbed thence by the blood, and transported by the circulation, as we shall hereafter show, to other parts
of the body.
The sugar which thus originates in the tissue of the liver, is produced by a mutual decomposition and transformation of various
other ingredients of the hepatic substance; these chemical changes
being a part of the nutritive process by which the tissue of the
organ is constantly sustained and nourished. There is probably a
series of several different transformations which take place in this
manner, the details of which are not yet known to us. It has been
discovered, however, that one change at least precedes the final
Gazette Hebdomadaire, Paris, Oct. 5, 1855.




186        FORMATION OF SUGAR IN THE LIVER.
production of saccharine matter; and that the sugar itself is produced by the transformation of another peculiar substance, of anterior formation. This substance, which precedes the formation of
sugar, and which is itself produced in the tissue of the liver, is
known by the name of glycogenic matter, or glycogene.
This glycogenic matter may be extracted from the liver in the
following manner. The organ is taken immediately from the body
of the recently killed animal, cut into small pieces, and coagulated by
being placed for a few minutes in boiling water. This is in order
to prevent the albuminous liquids of the organ from acting upon
the glycogenic matter and decomposing it at a medium temperature.
The coagulated tissue is then drained, placed in a mortar, reduced
to a pulp by bruising and grinding, and afterward boiled in distilled water for a quarter of an hour, by which the glycogenic
matter is extracted and held in solution by the boiling water.
The liquid of decoction, which should be as concentrated as possible, must then be expressed, strained, and filtered, after which it
appears as a strongly opalescent fluid, of a slightly yellowish tinge.
The glycogenic matter which is held in solution may be precipitated by the addition to the filtered fluid of five times its volume
of alcohol. The precipitate, after being repeatedly washed with
alcohol in order to remove sugar and biliary matters, may then be
redissolved in distilled water. It may be precipitated from its
watery solution either by alcohol in excess or by crystallizable
acetid acid, in both of which it is entirely insoluble, and may be
afterward kept in the dry state for an indefinite time without losing
its properties.
The glycogenic matter, obtained in this way, is regarded as
intermediate in its nature and properties between hydrated starch
and dextrine. Its ultimate composition, according to M. Pelouze,'
is as follows:
0C12H12012.
When brought into contact with iodine, it produces a coloration
varying from violet to a deep, clear, maroon red. It does not
reduce the salts of copper in Trommer's test, nor does it ferment
when placed in contact with yeast at the proper temperature. It
does not, therefore, of itself contain sugar. It may easily be converted into sugar, however, by contact with any of the animal
ferments, as, for example, those contained in the saliva or in the
l Journal de Physiologie, Paris, 1858, p. 552.




FORMATION OF SUGAR IN THE LIVER.                187
blood. If a solution of glycogenic matter be mixed with fresh
human saliva, and kept for a few minutes at the temperature of
1000 F., the mixture will then be found to have acquired the power
of reducing the salts of copper and of entering into fermentation by
contact with yeast. The glycogenic matter has therefore been
converted into sugar by a process of catalysis, in the same manner
as vegetable starch would be transformed under similar conditions.
The glycogenic matter which is thus destined to be converted
into sugar, is formed in the liver by the processes of nutrition. It
may be extracted, as we have seen above, from the hepatic tissue
of carnivorous animals, and is equally present when they have been
exclusively confined for many days to a meat diet. It is not introduced with the food; for the fleshy meat of the herbivora does
not contain it in appreciable quantity, though these animals so
constantly take starchy substances with their food. In them, the
starchy matters are transformed into sugar by digestion, and the
sugar so produced is rapidly destroyed after entering the circulation; so that usually neither saccharine nor starchy substances are
to be discovered in the muscular tissue. M. Poggiale' found that
in very many experiments, performed by a commission of the
French Academy for the purpose of examining this subject, glycogenic matter was detected in ordinary butcher's meat only once.
We have also found it to be absent from the fresh meat of the
bullock's heart, when examined in the manner described above.
Nevertheless, in dogs fed exclusively upon this food for eight days,
glycogenic matter may be found in abundance in the liver, while
it does not exist in other parts of the body, as the spleen, kidney,
lungs, &c.
Furthermore, in a dog fed exclusively for eight days upon the
fresh meat of the bullock's heart, and then killed four hours after
a meal of the same food, at which time intestinal absorption is
going on in full vigor, the liver contains, as above mentioned, both
glycogenic matter and sugar; but neither sugar nor glycogenic matter can be found in the blood of the portal vein, when subjected to
a similar examination.
The glycogenic matter, accordingly, does not originate from any
external source, but is formed in the tissue of the liver; where it
is soon afterward transformed into sugar, while still forming a part
of the substance of the organ.
I Journal de Physiologie, Paris, 1858, p. 558.




188        FORMATION OF SUGAR IN THE LIVER.
The formation of sugar in the liver is therefore a function composed of two distinct and successive processes, viz: first, the formation, in the hepatic tissue, of a glycogenic matter, having some
resemblance to dextrine; and secondly, the conversion of this
glycogenic matter into sugar, by a process of catalysis and transformation.
The sugar thus produced in the substance of the liver is absorbed
from it by the blood circulating in its vessels. The mechanism of
this absorption is probably the same with that which goes on in
other parts of the circulation.  It is a process of transudation and
endosmosis, by which the blood in the vessels takes up the saccharine fluids of the liver, during its passage through the organ.
While the blood of the portal vein, therefore, in an animal fed
exclusively upon meat, contains no sugar, the blood of the hepatic
vein, as it passes upward to the heart, is always rich in saccharine
ingredients. This difference can easily be demonstrated by examining comparatively the two kinds of blood, portal and hepatic,
from the recently killed animal. The blood in its passage through
the liver is found to have acquired a new ingredient, and shows,
upon examination, all the properties of a saccharine liquid.
The sugar produced in the liver is accordingly to be regarded as
a true secretion, formed by the glandular tissue of the organ, by a
similar process to that of other glandular secretions.  It differs
from the latter, not in the manner of its production, but only in
the mode of its discharge. For while the biliary matters produced
in the liver are absorbed by the hepatic ducts and conducted downward to the gall-bladder and the intestine, the sugar is absorbed by
the bloodvessels of the organ and carried upward, by the hepatic
veins, toward the heart and the general circulation.
The production of sugar in the liver during health is a constant
process, continuing, in many cases, for several days after the animal
has been altogether deprived of food. Its activity, however, like
that of most other secretions, is subject to periodical augmentation
and diminution.  Under ordinary circumstances, the sugar, which
is absorbed by the blood from the tissue of the liver, disappears
very soon after entering the circulation. As the bile is transformed
in the intestine, so the sugar is decomposed in the blood. We are
not yet acquainted, however, with the precise nature of the changes
which it undergoes after entering the vascular system. It is very
probable, according to the views of Lehmann and Robin, that it is
at first converted into lactic acid (C,H606), which decomposes in




FORMATION OF SUGAR IN THE LIVER.                 189
turn the alkaline carbonates, setting free carbonic acid, and forming
lactates of soda and potassa. But whatever be the exact mode of
its transformation, it is certain that the sugar disappears rapidly;
and while it exists in considerable quantity in the liver and in the
blood of the hepatic veins and the right side of the heart, it is not
usually to be found in the pulmonary veins nor in the blood of the
general circulation.
About two and a half or three hours, however, after the ingestion
of food, according to the investigations of Bernard, the circulation
of blood through the portal system and the liver becomes considerably accelerated. A larger quantity of sugar is then produced in
the liver and carried away from the organ by the hepatic veins;
so that a portion of it then escapes decomposition while passing
through the lungs, and begins to appear in the blood of the arterial
system. Soon afterward it appears also in the blood of the capillaries; and from four to six hours after the commencement of
digestion it is produced in the liver so much more rapidly than it
is destroyed in the blood, that the surplus quantity circulates
throughout the body, and the blood everywhere has a slightly saccharine character. It does not, however, in the healthy condition,
make its appearance in any of the secretions.
After the sixth hour, this unusual activity of the sugar-producing
function begins again to diminish; and, the transformation of the
sugar in the circulation going on as before, it gradually disappears
as an ingredient of the blood. Finally, the ordinary equilibrium
between its production and its decomposition is re-established, and
it can no longer be found except in the liver and in that part of
the circulatory system which is between the liver and the lungs.
There is, therefore, a periodical increase in the amount of undecomposed sugar in the blood, as we have already shown to be the
case with the fatty matter absorbed during digestion; but this
increase is soon followed by a corresponding diminution, and during
the greater portion of the time its decomposition keeps pace with
its production, and it is consequently prevented from appearing in
the blood of the general circulation.
There are produced, accordingly, in the liver, two different secretions, viz., bile and sugar. Both of them originate by transformation of the ingredients of the hepatic tissue, from which they are
absorbed by two different sets of vessels. The bile is taken up by
the biliary ducts, and by them discharged into the intestine; while
the sugar is carried off by the hepatic veins, to be decomposed in the
circulation, and become subservient to the nutrition of the blood.




190                      THE SPLEEN.
CHAPTER X.
THE SPLEEN.
THE spleen is an exceedingly vascular organ, situated in the
vicinity of the great pouch of the stomach and supplied abundantly by branches of the coeliac axis. Its veins, like those of the
digestive abdominal organs, form a part of the great portal system,
and conduct the blood which has passed through it to the liver,
before it mingles again with the general current of the circulation.
The spleen is covered on its exterior by an investing membrane
or capsule, which forms a protective sac, containing the soft pulp
of which the greater part of the organ is composed. This capsule,
in the spleen of the ox, is thick, whitish, and opaque, and is cornposed to a great extent of yellow elastic tissue. It accordingly
possesses, in a high degree, the physical property of elasticity, and
may be widely stretched without laceration; returning readily to
its original size as soon as the extending force is relaxed.
In the carnivorous animals, on the other hand, the capsule of
the spleen is thinner, and more colorless and transparent. It contains here but very little elastic tissue, being composed mostly of
smooth, involuntary muscular fibres, connected in layers by a little
intervening areolar tissue. In the herbivorous animals, accordingly,
the capsule of the spleen is simply elastic, while in the carnivora it
is contractile.
In both instances, however, the elastic and contractile properties
of the capsule subserve a nearly similar purpose. There is every
reason to believe that the spleen is subject to occasional and perhaps regular variations in size, owing to the varying condition of
the abdominal circulation.  Dr. William Dobson' found that the
size of the organ increased, from the third hour after feeding up to
the fifth; when it arrived at its maximum, gradually decreasing
after that period.  When these periodical congestions take place,
In Gray, on the Structure and Uses of the Spleen. London, 1854, p. 40.




THE SPLEEN.                         191
the organ becoming turgid with blood, the capsule is distended;
and limits, by its resisting power, the degree of tumefaction to
which the spleen is liable. When the disturbing cause has again
passed away, and the circulation is about to return to its ordinary
condition, the elasticity of the capsule in the herbivora, and its contractility in the carnivora, compress the soft vascular tissue within,
and reduce the organ to its original dimensions. This contractile
action of the investing capsule can be readily seen in the dog or
the cat, by opening the abdomen while digestion is going on, exposing the spleen and removing it, after ligature of its vessels.
When first exposed, the organ is plump and rounded, and presents
externally a smooth and shining surface. But as soon as it has
been removed from the abdomen and its vessels divided, it begins
to contract sensibly, becomes reduced in size, stiff; and resisting to
the touch; while its surface, at the same time, becomes uniformly
wrinkled, by the contraction of its muscular fibres.
In its interior, the substance of the spleen is traversed everywhere
by slender and ribbon-like cords of fibrous tissue, which radiate
from the sheath of its principal arterial trunks, and are finally
attached to the internal surface of its investing capsule. These
fibrous cords, or trabecuIe, as they are called, by their frequent
branching and mutual interlacement, form  a kind of skeleton or
framework by which the soft splenic pulp is embraced, and the
shape and integrity of the organ maintained. They are composed
of similar elements to those of the investing capsule, viz., elastic
tissue and involuntary muscular fibres, united with each other by
a varying quantity of the fibres of areolar tissue.
The interstices between the trabecuhe of the spleen are occupied
by the splenic pulp; a soft, reddish substance, which contains,
beside a few nerves and lymphatics, capillary bloodvessels in great
profusion, and certain whitish globular bodies, which may be regarded as the distinguishing anatomical elements of the organ, and
which are termed the flalpighian bodies of the spleen.
The Malpighian bodies are very abundant, and are scattered
throughout the splenic pulp, being most frequently attached to the
sides, or at the point of bifurcation of some small artery. They
are readily visible to the naked eye in the spleen of the ox, upon a
fresh section of the organ, as minute, whitish, rounded bodies, which
may be separated, by careful manipulation, from the surrounding
parts. In the carnivorous animals, on the other hand, and in the
human subject, it is more difficult to distinguish them  by the un



192                      THE SPLEEN.
aided eye, though they always exist in the spleen in a healthy
condition.  Their average diameter, according to K6lliker, is v, of
an inch. They consist of a closed sac, or capsule, containing in
its interior a viscid, semi-solid mass of cells, cell-nuclei, and homogeneous substance. Each Malpighian body is covered, on its exterior, by a network of fine capillary bloodvessels; and it is now
perfectly well settled, by the observations of various anatomists
(K1lliker, Busk, Huxley, &c.), that bloodvessels also penetrate into
the substance of the Malpighian body, and there form an internal
capillary plexus.
The spleen is accordingly a glandular organ, analogous in its
minute structure to the solitary and agminated glands of the small
intestine, and to the lymphatic glands throughout the body. Like
them, it is a gland without an excretory duct; and resembles, also,
in this respect, the thyroid and thymus glands and the supra-renal
capsules. All these organs have a structure which is evidently
glandular in its nature, and yet the name of glands has been sometimes refused to them because they have, as above mentioned, no
duct, and produce apparently no distinct secretion.  We have
already seen, however, that a secretion may be produced in the
interior of a glandular organ, like the sugar in the substance of the
liver, and yet not be discharged by its excretory duct. The veins
of the gland, in this instance, perform the part of excretory ducts.
They absorb the new materials, and convey them, through the
medium of the blood, to other parts of the body, where they suffer
subsequent alterations, and are finally decomposed in the circulation.
The action of such organs is consequently to modify the constitution of the blood. As the blood passes through their tissue, it
absorbs from the glandular substance certain materials which it did
not previously contain, and which are necessary to the perfect constitution of the circulating fluid. The blood, as it passes out from
the organ, has therefore a different composition from that which it
possessed before its entrance; and on this account the name of vascular glands has been applied to all the glandular organs above
mentioned, which are destitute of excretory ducts, and is eminently
applicable to the spleen.
The precise alteration, however, which is effected in the blood
during its passage through the splenic tissue, has not yet been
discovered. Various hypotheses have been advanced from time to
time, as to the processes which go on in this organ; many of them




THE SPLEEN.                        193
vague and indefinite in character, and some of them directly contradictory of each other. None, however, have yet been offered
which are entirely satisfactory in themselves, or which rest on sufficiently reliable evidence.
A very remarkable fact with regard to the spleen is that it may
be entirely removed in many of the lower animals, without its loss
producing any serious permanent injury. This experiment has
been frequently performed by various observers, and we have ourselves repeated it several times with similar results. The organ
may be easily removed, in the dog or the cat, by drawing it out of
the abdomen, through an opening in the median line, placing a few
ligatures upon the vessels of the gastro-splenic omentum, and then
dividing the vessels between the ligatures and the spleen. The
wound usually heals without difficulty; and if the animal be killed
some weeks afterward, the only remaining trace of the operation
is an adhesion of the omentum to the inner surface of the abdominal parietes, at the situation of the original wound.
The most constant and permanent effect of a removal of the
spleen is an unusual increase of the appetite. This symptom we
have observed in some instances to be excessively developed; so
that the animal would at all times throw himself, with an unnatural
avidity, upon any kind of food offered him.  We have seen a dog,
subjected to this operation, afterward feed without hesitation upon
the flesh of other dogs; and even devour greedily the entrails, taken
warm from the abdomen of the recently killed animal. The food
taken in this unusual quantity is, however, perfectly well digested;
and the animal will often gain very perceptibly in weight. In one
instance, a cat, in whom the unnatural appetite was marked though
not excessive, increased in weight from five to six pounds, in the
course of a little less than two months; and at the same time the
fur became sleek and glossy, and there was a considerable improvement in the general appearance of the animal.
Another symptom, which usually follows removal of the spleen,
is an unnatural ferocity of disposition. The animal will frequently
attack others, of its own or a different species, without any apparent cause, and without any regard to the difference of size, strength,
&c. This symptom is sometimes equally excessive with that of an
unnatural appetite; while in other instances it shows itself only in
occasional outbursts of irritability and violence.
Neither of the symptoms, however, which we have just described, appears to exert any permanently injurious effect upon the
13




194                      THE SPLEEN.
animal which has been subjected to the operation; and life may be
prolonged for an indefinite period, without any serious disturbance
of the nutritive process, after the spleen has been completely
extirpated.
We must accordingly regard the spleen, not as a single organ,
but as associated with others, which may completely, or to a great
extent, perform  its functions after its entire removal.  We have
already noticed the similarity in structure between the spleen and
the mesenteric and lymphatic glands; a similarity which has led
some writers to regard them as more or less closely associated with
each other in function, and to consider the spleen as an unusually
developed lymphatic or mesenteric gland.  It is true that this
organ is provided with a comparatively scanty supply of lymphatic
vessels; and the chyle, which is absorbed from the intestine, does
not pass through the spleen, as it passes through the remaining
mesenteric glands. Still, the physiological action of the spleen
may correspond with that of the other lymphatic glands, so far as
regards its influence on the blood; and tlere can be little doubt
that its function is shared, either by them or by some other glandular organs, which become unnaturally active, and more or less
perfectly supply its place after its complete removal.




BLOOD-GLOBULES.                       195
CHAPTER XI.
THE BLOOD.
THE blood, as it exists in its natural condition, while circulating
in the vessels, is a thick opaque fluid, varying in color in different
parts of the body from a brilliant scarlet to a dark purple. It has
a slightly alkaline reaction, and a specific gravity of 1055. It
is not, however, an entirely homogeneous fluid, but is found on
microscopic examination to consist, first, of a nearly colorless,
transparent, alkaline fluid, termed the plasma, containing water,
fibrin, albumen, salts, &c., in a state of mutual solution; and,
secondly, of a large number of distinct cells, or corpuscles, the
blood-globules, swimming freely in the liquid plasma. These globules, which are so small as not to be distinguished by the naked
eye, by being mixed thus abundantly with the fluid plasma, give
to the entire mass of the blood an opaque appearance and a uniform
red color.
BLOOD-GLOBULES.-On microscopic examination it is found that
the globules of the blood are of two kinds, viz., red and white; of
these the red are by far the most abundant.
The red globules of the blood present, under the microscope, a
perfectly circular outline and a smooth exterior. (Fig. 54.)  Their
size varies somewhat, in human blood, even in the same specimen.
The greater number of them have a transverse diameter of 3-  of
an inch; but there are many smaller ones to be seen, which are
not more than'a  or even 4o  of an inch in diameter. Their
form  is that of a spheroid, very much flattened on its opposite
surfaces, somewhat like a round biscuit, or a thick piece of money
with rounded edges. The blood-globule accordingly, when seen
flatwise, presents a comparatively broad surface and a circular outline(a); but if it be made to roll over, it will present itself edgewise during its rotation and assume the flattened form indicated at
b. The thickness of the globule, seen in this position, is about




196                        THE BLOOD.
Tr1     of an inch, or a little less than one-fifth of its transverse
diameter.
When the globules are examined lying upon their broad surfaces, it can be seen that these surfaces are not exactly flat, but that
there is on each side a slight
Fig. 54.               central depression, so that
the rounded  edges of the
blood-globule are evidently
thicker than its middle por/  -        \   tion.  This inequality pro/  1-g)             \   ^^duces a remarkable optical.1 Q     effect.  The  substance  of
I a m. "   l~ I ~which the blood-globule is
composed refracts light more
strongly than the fluid plas0\ l-n c&I          ma.  Therefore, when examined with the microscope,
by  transmitted  light, the
HUMAN BLOOD-GLOBULES.-a Red globules, thick edges of the globules
seen flatwise. b. Red globules, seen edgewise. c. act as double convex lenses,
White globule.          t
and  concentrate  the  light
above the level of the fluid.  Consequently, if the object-glass be
carried upward by the adjusting screw of the microscope, and lifted
away from the stage, so that
Fig. 55.               the blood-globules fall be^^^~^^^^^^  ~         yond its focus, their edges
~/^~ ^~\ ~will appear brighter.  But
the central portion of each
globule, being excavated on./  X.          \   both sides, acts as a double
\ -.,J.%x\  concave lens, and disperses
the light from a point below
the level of the fluid. It,
\IBM" ~        / (therefore, grows brighter as
the  object-glass is carried
\.^            /^~ ~downward, and  the object
falls within its focus.  An
^ ~-"^"^    ~ ~     ~alternating appearance of the
RED GLOBULES OF THE BLOOD, seen a littlein                      
beyond the focus of the microscope.    blood-globules may, therefore, be produced by viewing them first beyond and then within the focus of the instrument.




BLOOD-GLOBULES.                       197
When beyond the focus, the globules will be seen with a bright
rim and a dark centre. (Fig. 55.)  When within it they will appear
with a dark rim and a bright
centre. (Fig. 56.)                           Fig. 56.
The blood-globules accordingly have the form  of a
thickened disk with rounded                                  \
edges and a double central
excavation. They have, con-  / 
sequently, been  sometimes                          
called "blood-disks," instead                     o  i
of blood-globules. The term  
"disk," however, does not indicate their exact shape, any    \
more than  the other; and
the term  "blood-corpuscle,"
which is also sometimes used,
THE SAME, seen a little within the focus.
does not indicate it at all.
And although the term  "blood-globule" may not be precisely a
correct one, still it is the most convenient; and need not give rise
to any confusion, if we remember the real shape of the bodies designated by it. This term will, consequently, be employed whenever we have occasion to
speak of the blood-globules                  Fig. 57.
in the following pages.
Within a minute after being
placed under the microscope,
the blood-globules, after a
fluctuating   movement  of 
short duration, very  often
arrange themselves in slightly curved rows or chains, in
which they adhere to each
other by their flat surfaces, 
presenting  an  appearance
which has been aptly compared with that of rolls of
rcoin. This is probably ow-   BLOOD-GLOBUL E adhering together, like rolls
coin.  This is probably ow- of coin.
ing merely to the coagulation
of the blood, which takes place very rapidly when it is spread out
in thin layers and in contact with glass surfaces; and which, by




198                       THE BLOOD.
compressing the globules, forces them into such a position that they
may occupy the least possible space. This position is evidently
that in which they are applied to each other by their flat surfaces,
as above described.
The color of the blood-globules, when viewed by transmitted
light and spread out in a thin layer, is a light amber or pale yellow.
It is, on the contrary, deep red when they are seen by reflected
light, or piled together in comparatively thick layers. When viewed
singly, they are so transparent that the outlines of those lying underneath can be easily seen, showing through the substance of the
superjacent globules. Their consistency is peculiar. They are not
solid bodies, as they have been sometimes inadvertently described;
but on the contrary have a consistency which is very nearly fluid.
They are in consequence exceedingly flexible, and easily elongated,
bent, or otherwise distorted by accidental pressure, or in passing
through the narrow currents of fluid which often establish themselves accidentally in a drop of blood under microscopic examination. This distortion, however, is only temporary, and the globules
regain their original shape, as soon as the accidental pressure is
taken off. The peculiar flexibility and elasticity thus noticed are
characteristic of the red globules of the blood, and may always
serve to distinguish them from any other free cells which may be
found in the animal tissues or fluids.
In structure the blood-globules are homogeneous.  They have
been sometimes erroneously described as consisting of a closed
vesicle or cell-wall, containing in its cavity some fluid or semi-fluid
substance of a different character from that composing the wall of
the vesicle itself. No such structure, however, is really to be seen
in them. Each blood-globule consists of a mass of organized animal substance, perfectly or nearly homogeneous in appearance, and
of the same color, consistency and composition throughout.  In
some of the lower animals (birds, reptiles, fish) it contains also a
granular nucleus, imbedded in the substance of the globule; but
in no instance is there any distinction to be made out between an
external cell-wall and an internal cavity.
The appearance of the blood-globules is altered by the addition
of various foreign substances. If water be added, so as to dilute
the plasma, the globules absorb it by imbibition, swell, lose their
double central concavity and become paler. If a larger quantity
of water be added, they finally dissolve and disappear altogether.
When a moderate quantity of water is mixed with the blood, the




BLOOD-GLOBULES.                         199
edges of the globules, being thicker than the central portions, and
absorbing water more abundantly, become turgid, and encroach
gradually upon the central
part. (Fig. 58.)  It is very                   Fig. 58.
common to see the central
depression, under these circumstances, disappear on one
side before it is lost on the
other, so that the globule, as  
it swells up, curls over to-                      (                \
wards one side, and assumes                                
a peculiar cup-shaped form   \'             (
(a). This form may often be
seen in blood-globules that    \
have been soaking for some
time in the urine, or in any
other animal fluid of a less
BL OOD-O LOBULES, swollen by the imbibition of
density than the plasma of,ater.
the blood. Dilute acetic acid
dissolves the blood-globules more promptly than water, and solutions of the caustic alkalies more promptly still.
If a drop of blood be allowed partially to evaporate while under
the microscope, the globules
near the edges of the prepa-                  Fig. 59.
ration often diminish in size,
and at the same time present
a shrunken and crenated ap-  
pearance, as if minute granules were  projecting  from   /           
their surfaces (Fig. 59); an
effect apparently  produced
by the evaporation of part  
of their watery ingredients. 
For some unexplained reason, however, a similar distortion is often produced in
some of the globules by the.   BLOOD-GLOBULES, shrunken, with their margins
addition of certain other ani- crenated.
mal fluids, as for example the
saliva; and a few can even be seen in this condition after the
addition of pure water.




200                        THE BLOOD.
The entire mass of the blood-globules, in proportion to the rest
of the circulating fluid, can only be approximately measured by
the eye in a microscopic examination.  In ordinary analyses the
globules are usually estimated as amounting to about fifteen per
cent., by weight, of the entire blood. This estimate, however, refers,
properly speaking, not to the globules themselves, but only to their
dry residue, after the water which they contain has been lost by
evaporation. It is easily seen, by examination with the microscope,
that the globules, in their natural semi-fluid condition, are really
much more abundant than this, and constitute fully one-half the
entire mass of the blood; that is, the intercellular fluid, or plasma, is
not more abundant than the globules themselves which are suspended in it.  When separated from the other ingredients of the
blood and examined by themselves, the globules are found, according to Lehmann, to present the following composition:COMPOSITION OF THE BLOOD-GLOBULES IN 1000 PARTS.
Water...........688.00
Globulie..........   282.22
HEeniatine....    16.75
Fatty substances......... 2.31
Undetermined (extractive) matters...   2.60
Chloride of sodium....
"    potassium....
Phosphates of soda and potassa
Sulphate    "      ".                               12
Phosphate of lime........
magnesia...
1000.00
The most important of these ingredients is the globulire.  This
is an organic substance, nearly fluid in its natural condition by
union with water, and constituting the greater part of the mass of
the blood-globules.  It is soluble in water, but insoluble in the
plasma of the blood, owing to the presence in that fluid of albumen
and saline matters.  If the blood be largely diluted, however, the
globuline is dissolved, as already mentioned, and the blood-globules
are destroyed.  Globuline coagulates by heat; but, according to
Robin and Verdeil, only becomes opalescent at 160~, and requires
for its complete coagulation a temperature of 200~ F.
The hcematine is the coloring matter of the globules.  It is, like
globuline, an organic substance, but is present in much smaller quantity than the latter. It is not contained in the form of a powder,




BLOOD-GLOBULES.                         201
mechanically deposited in the globuline, but the two substances are
intimately mingled throughout the mass of the blood-globule, just
as the fibrin and albumen are mingled in the plasma. Haematine
contains, like the other coloring matters, a small proportion of iron.
This iron has been supposed to exist under the form of an oxide;
and to contribute directly in this way to the red color of the substance in question.  But it is now ascertained that although the
iron is found in an oxidized form in the ashes of the blood-gobules
after they have been destroyed by heat, its oxidation probably takes
place during the process of incineration. So far as we know, therefore, the iron exists originally in the haematine as an ultimate
element, directly combined with the other ingredients of this substance, in the same manner as the carbon, the hydrogen, or the
nitrogen.
The blood-globules of all the warm blooded quadrupeds, with
the exception of the family of the camelidse, resemble those of the
human species in shape and structure. They differ, however, somewhat in size, being usually rather smaller than in man. There are
but two species in which they are known to be larger than in man,
viz., the Indian elephant, in which they are ~-v   of anl inch, and
the two-toed sloth (Bradypus didactylus), in which they are'1 o of
an inch in diameter. In the musk deer of Java they are smaller
than in any other known species, measuring rather less than  2  o o
of an inch.  The following is a list showing the size of the red
globules of the blood in the principal mammalian species, taken
from the measurement of Mr. Gulliver.l
DIAMETER OF RED GLOBULES IN THE
Ape...'sof an inch.   Cat...       of an inch.
Horse...  4To "              Fox...   ToO 
Ox  -..a.            "        Wolf..        "
Sheep...          "       Elephant..   o       "
Goat...           "        Red deer..
Dog...'6    "         Musk deer..           "
In all these instances the form  and general appearance of the
globules are the same. The only exception to this rule among the
mammalians is in the family of the carnelidae (camel, dromedary,
lama), in which the globules present an oval outline instead of a
circular one. In other respects they resemble the foregoing.
In the three remaining classes of vertebrate animals, viz., birds,
In Works of William Hewson, Sydenham edition, London, 1846, p. 327.




202                       THE BLOOD.
reptiles and fish, the blood-globules differ so much from the above
that they can be readily distinguished by microscopic examination.
They are oval in form, and contain a colorless granular nucleus
imbedded in their substance.  They are also considerably larger
than the blood-globules of the mammalians, particularly in the
class of reptiles. In the frog
Fig. 60.               (Fig. 60) they measure T20
of an  inch  in  their long
/^    C~ ^\       diameter; and in Mienobranchus, the great water lizard
/  Id l ^\    of the northern lakes, 4 0 of
an inch.  In Proteus anguif )  \     s nus they attain the size, according to Dr. Carpenter,' of
(            4'~ of an inch.
\  l t   /  Beside the corpuscles described above, there are globules of another kind found
in the blood, viz., the white
BLOOD^ USaB   b globules.  These gldbules are
BLOOD-GLOBULES OF FRO. —a. BIoodglobulTe
seen edgewise. b. White-globule.     very  much  less numerous
than the red; the proportion
between the two, in human blood, being one white to two or three
hundred red globules.  In reptiles, the relative quantity of the
white globules is greater, but they are always considerably less
abundant than the red.  They differ also from the latter in shape,
size, color, and consistency.  They are globular in form, white or
colorless, and instead of being homogeneous like the others, their
substance is filled everywhere with minute dark molecules, which
give them  a finely granular appearance. (Fig. 54, c.)  In size they
are considerably larger than the red globules, being about 5   of
an inch in diameter. They are also more consistent than the others,
and do not so easily glide along in the minute currents of a drop of
blood under examination, but adhere readily to the surfaces of the
glass. If treated with dilute acetic acid, they swell up and become
smooth and circular in outline; and at the same time a separation
or partial coagulation seems to take place in the substance of which
they are composed, so that an irregular collection of granular
matter shows itself in their interior, becoming more divided and
l The Microscope and its Revelations, Philadelphia edition, p. 600.




BLOOD-GLOBULES.                       203
broken up as the action of the acetic acid upon the globule is
longer continued. (Fig. 61.)  This collection of granular matter
often assumes a curved or crescentic form, as at a, and sometimes
various other irregular shapes. It does not indicate the existence
of a nucleus in the white globule, but it is merely an appearance
produced by the coagulating
and disintegrating action of                 Fig. 61.
aceticacid upon the substance
of which it is composed.            /
The chemical constitution 
of the white  globules, as
distinguished from  the red,   /                    (
has never been determined;  
owing to the small quantity                   0
in which they occur, and the           ) 
difficulty of separating them  
from the others for purposes                    ( 
of analysis.\ 
The two kinds of bloodglobules, white and red, are
WIIT E GLOBULES OF THEB BLOOD; altered by
to be regarded as distinct dilute acetic acid.
and independent anatomical
forms.  It has been sometimes supposed that the white globules
were converted, by a gradual transformation, into the red. There
is, however, no direct evidence of this; as the transformation has
never been seen to take place, either in the human subject or in
the mammalia, nor even its intermediate stages satisfactorily observed. When, therefore, in default of any such direct evidence,
we are reduced to the surmise which has been adopted by some
authors, viz., that the change " takes place too rapidly to be detected by our means of observation,"' it must be acknowledged
that the above opinion has no solid foundation. It has been stated
by some authors (Kolliker, Gerlach) that in the blood of the
batrachian reptiles there are to be seen certain bodies intermediate
in appearance between the white and the red globules, and which
represent different stages of transition from one form to the other;
but this is not a fact which is generally acknowledged. We have
repeatedly examined, with reference to this point, the fresh blood
of the frog, as well as that of the menobranchus, in which the large
1 Kolliker, Handbuch der Gewebelehre, Leipzig, 1852, p. 582.




204                      THE BLOOD.
size of the globules would give every opportunity for detecting any
such changes, did they really exist; and it is our unavoidable conclusion from these observations, that there is no good evidence, even
in the blood of reptiles, of any such transformation taking place.
There is simply, as in human blood, a certain variation in size and
opacity among the red globules; but no such connection with, or
resemblance to, the white globules as to indicate a passage from one
form to the other. The red and white globules are therefore to be
regarded as distinct and independent anatomical elements. They
are mingled together in the blood, just as capillary bloodvessels and
nerves are mingled in areolar tissue; but there is no other connection
between them, so far as their formation is concerned, than that of
juxtaposition.
Neither is it at all probable that the red globules are produced or
destroyed in any particular part of the body. One ground for the
belief that these bodies were produced by a metamorphosis of the
white globules was a supposition that they were continually and
rapidly destroyed somewhere in the circulation; and as this loss
must be as rapidly counterbalanced by the formation of new globules, and as no other probable source of their reproduction appeared, they were supposed to be produced by transformation of
the white globules. But there is no reason for believing that the
red globules of the blood are any less permanent, as anatomical
forms, than the muscular fibres or the nervous filaments. They
undergo, it is true, like all the constituent parts of the body, a
constant interstitial metamorphosis. They absorb incessantly nutritious materials from the blood, and give up to the circulating
fluid, at the same time, other substances which result from their
internal waste and disintegration. But they do not, so far as we
know, perish bodily in any part of the circulation. It is not the
anatomical forms, anywhere, which undergo destruction and renovation in the nutritive process; but only the proximate principles of
which they are composed. The effect of this interstitial nutrition,
therefore, in the blood-globules as in the various solid tissues, is
merely to maintain them  in a natural and healthy condition of
integrity. Their ingredients are incessantly altered, by transformation and decomposition, as they pass through various parts of the
vascular system; but the globules themselves retain their form
and texture, and still remain as constituent parts of the circulating
fluid.




PLASMA.                             205
PLASMA.-The plasma of the blood, according to Lehmann, has
the following constitution:
COMPOSITION OF THE PLASMA IN 1,000 PARTS.
Water.....902.90
Fibrin..........           4 05
Albumen...........  78.84
Fatty matters....   ].72
Undetermined (extractive) matters..   3.94
Chloride of sodium....
" potassium...
Phosphates of soda and potassa.....
Sulphates    "  8.55
Phosphate of lime...
9"      magnesia.......J                       ~
1000.00
The above ingredients are all intimately mingled in the bloodplasma, in a fluid form, by mutual solution; but they may be separated from each other for examination by appropriate means. The
two ingredients belonging to the class of organic substances are the
fibrin and the albumen.
The fibrin, though present in small quantity, is evidently an important element in the constitution of the blood. It may be obtained in a tolerably pure form by gently stirring freshly drawn
blood with a glass rod or a bundle of twigs; upon which the fibrin
coagulates, and adheres to the twigs in the form of slender threads
and flakes. The fibrin, thus coagulated, is at first colored red by
the haematine of the blood-globules entangled in it; but it may be
washed colorless by a few hours' soaking in running water. The
fibrin then presents itself
under the form  of nearly                       Fig. 62.
"fibThe coagulation of fibrin    n.
takes place in a peculiar
manner. It does not solidify
in a perfectly homogeneous
mass; but if examined by the
microscope in thin layers it
is seen to have a fibroid or
filamentous texture. In this
condition  it is said  to be                                      d"fibrillated." (Fig. 62.) The dition.
take  plae ina i?!/~//~ if!




206                       THE BLOOD.
filaments of which it is composed are colorless and elastic, and when
isolated are seen to be exceedingly minute, being not more than
4    or even      of an inch in diameter.  They are in part
arranged so as to lie parallel with each other; but are more generally interlaced in a kind of'irregular network, crossing each other
in every direction. On the addition of dilute acetic acid, they swell
up and fuse together into a homogeneous mass, but do not dissolve.
They are often interspersed everywhere with minute granular molecules, which render their outlines more or less obscure.
Once coagulated, fibrin is insoluble in water and can only be
again liquefied by the action of an alkaline or strongly saline solution, or by prolonged boiling at a very high temperature.  These
agents, however, produce a complete alteration in the properties of
the fibrin, and after being subjected to them it is no longer the
same substance as before.
The quantity of fibrin in the blood varies in different parts of the
body. According to the observations of various writers,' there is
more fibrin generally in arterial than in venous blood. The blood
of the veins near the heart, again, contains a smaller proportion of
fibrin than those at a distance.  The blood of the portal vein contains less than that of the jugular; and that of the hepatic vein less
than that of the portal.
The albumen is undoubtedly the most important ingredient of the
plasma, judging both from its nature and the abundance in which
it occurs.  It coagulates at once on being heated to 160~ F., or by
contact with alcohol, the mineral acids, the metallic salts, or with
ferrocyanide of potassium in an acidulated solution. It exists naturally in the plasma in a fluid form  by reason of its union with
water.  The greater part of the water of the plasma, in fact, is in
union with the albumen; and when the albumen coagulates, the
water remains united with it, and assumes at the same time the
solid form. If the plasma of the blood, therefore, after the removal
of the fibrin, be exposed to the temperature of 160~ F., it solidifies
almost completely; so that only a few drops of water remain that
can be drained away from the coagulated mass.  The phosphates
of lime and magnesia are also held in solution principally by the
albumen, and are retained by it in coagulation.
The fatty matters exist in the blood mostly in a saponified form,
excepting soon after the digestion of food rich in fat.  At that
period, as we have already mentioned, the emulsioned fat finds its
Robin and Verdeil, op. cit., vol. ii. p. 202.




COAGULATION OF THE BLOOD.                  207
way into the blood, and circulates for a time unchanged. Afterward it disappears as free fat, and: remains partly in the saponified
condition.
The saline ingredients of the plasma are of the same nature with
those existing in the globules. The chlorides of sodium and potassium, and the phosphates of soda and potassa are the most abundant
in both, while the sulphates are present only in minute quantity.
The proportions in which the various salts are present are very different, according to Lehmann,' in the blood-globules and in the
plasma. Chloride of potassium is most abundant in the globules,
chloride of sodium in the plasma. The phosphates of soda and
potassa are more abundant in the globules than in the plasma. On
the other hand, the phosphates of lime and magnesia are more
abundant in the plasma than in the globules.
The substances known under the name of extractive matters consist
of a mixture of different ingredients, belonging mostly to the class
of organic substances, which have not yet been separated in a state
of sufficient purity to admit of their being thoroughly examined
and distinguished from each other. They do not exist in great
abundance, but are undoubtedly of considerable importance in the
constitution of the blood. Beside the substances enumerated in the
above list, there are still others which occur in small quantity as
ingredients of the blood. Among the most important are the alkaline carbonates, which are held in solution in the serum. It has
already been mentioned that while the phosphates are most abundant in the blood of the carnivora, the carbonates are most abundant in that of the herbivora  Thus Lehmann2 found carbonate of
soda in the blood of the ox in the proportion of 1.628 per thousand
parts. There are also to be found, in solution in the blood, urea,
urate of soda, creatine, creatinine, sugar, &c.; all of them crystallizable substances derived from the transformation of other ingredients
of the blood, or of the tissues through which it circulates. The
relative quantity, however, of these substances is very minute, and
has not yet been determined with precision.
COAGULATION OF THE BLOOD.-A few moments after the blood
has been withdrawn from the vessels, a remarkable phenomenon
presents itself, viz., its coagulation or clotting. This process commences at nearly the same time throughout the whole mass of the
blood. The blood becomes first somewhat diminished in fluidity,
I Op. cit., vol. i. p. 546.         2 Op. cit., vol. i. p. 393.




208                       THE BLOOD.
so that it will not run over the edge of the vessel, when slightly
inclined; and its surface may be gently depressed with the end of
the finger or a glass rod. It then becomes rapidly thicker, and at
last solidifies into a uniformly red, opaque, consistent, gelatinous
mass, which takes the form of the vessel in which the blood was
received. Its coagulation is then complete. The process usually
commences, in the case of the human subject, in about fifteen minutes after the blood has been drawn, and is completed in about
twenty minutes.
The coagulation of the blood is dependent entirely upon the
presence of the fibrin. This fact has been demonstrated in various
ways. In the first place, if frog's blood be filtered, so as to separate
the globules and leave them upon the filter, while the plasma is
allowed to run through, the colorless filtered fluid which contains
the fibrin soon coagulates; while no coagulation takes place in the
moist globules remaining on the filter. Again, if the freshly drawn
blood be stirred with a bundle of rods, as we have already described above, the fibrin coagulates upon them by itself, while the
rest of the plasma, mixed with the globules, remains perfectly fluid.
It is the fibrin, therefore, which, by its own coagulation, induces
the solidification of the entire blood. As the fibrin is uniformly
distributed throughout the blood, when its coagulation takes place
the minute filaments which make their appearance in it entangle
in their meshes the globules and the albuminous fluids of the
plasma.  A very small quantity of fibrin, therefore, is sufficient to
entangle by its coagulation all the fluid and semi-fluid parts of the
blood, and convert the whole into a volurniFig. 63.       nous, trembling, jelly-like mass, which is
known by the name of the "crassamentum,"
or "clot." (Fig. 63.)
As soon as the clot has fairly formed, it
begins to contract and diminish in size. Exactly how this contraction of the clot is produced, we are unable to say; but it is probably a continuation of the same process by
Bowl of recently COA( I- which its solidification isat first accomplished,
LATED BLOOD, showingthe or at least one very similar to it. As the
whole mass uniformly solidified                  contraction proceeds, the albuminous fluids
begin to be pressed out from the meshes in
which they were entangled.  A few isolated drops first appear on
the surface of the clot. These drops soon increase in size and be



COAGULATION  OF THE BLOOD.                     209
come more numerous.  They run together and coalesce with each
other, as more and more fluid exudes from the coagulated mass,
until the whole surface of the clot is covered with a thin layer of
fluid. The clot at first adheres pretty strongly to the sides of the
vessel into which the blood was drawn; but as its contraction goes
on, its edges are separated, and the fluid continues to exude between
it and the sides of the vessel. This exudation
continues for ten or twelve hours; the clot           Fig. 64.
growing constantly smaller and firmer, and
the expressed fluid more and more abundant.
The globules, owing to their greater consistency, do not escape with the albuminous
fluids, but remain entangled in the fibrinous
coagulum.  Finally, at the end of ten or
twelve hours the whole of the blood has
usually separated into two parts, viz., the clot,   Bowl of COAGULATED
which is a red, opaque, dense and resisting,  BLOOD, after twelve hours;
X7^~~~~  7           X^~  ^showing  the  clot contracted
semi-solid mass, consisting of the fibrin and  andfloating in the fluid serum.
the blood-globules; and the serum, which is a
transparent, nearly colorless fluid, containing the water, albumen,
and saline matters of the plasma. (Fig. 64.)
The change of the blood in coagulation may therefore be expressed as follows:Before coagulation the blood consists of
f Fibrin,
Albumen,
1st. GLOBULEs; and 2d. PLASMA-containing              Alben,
l Salts.
After coagulation it is separated into
Firin and an                       Albumen,
1st. CLOT, containing,^ l Gloul s and 2d. SERUM, containing { Water,''.Tst~~vU~~~  ~Salts.
The coagulation of the blood is hastened or retarded by various
physical conditions, which have been studied with care by various
observers, but more particularly by Robin and Verdeil. The conditions which influence the rapidity of coagulation are as follows:
First, the rapidity with which the blood is drawn from  the vein,
and the size of the orifice from which it flows. If blood be drawn
rapidly, in a full stream, from a large orifice, it remains fluid for a
comparatively long time; if it be drawn slowly, from a narrow
orifice, it coagulates quickly. Thus it usually happens that in the
14




210                      THE BLOOD.
operation of venesection, the blood drawn immediately after the
opening of the vein runs freely and coagulates slowly; while that
which is drawn toward the end of the operation, when the tension
of the veins has been relieved and the blood trickles slowly from
the wound, coagulates quickly. Secondly, the shape of the vessel
into which the blood is received and the condition of its internal
surface. The greater the extent of surface over which the blood
comes in contact with the vessel, the more is its coagulation
hastened. Thus, if the blood be allowed to flow into a tall, narrow,
cylindrical vessel, or into a shallow plate, it coagulates more rapidly
than if it be received into a hemispherical bowl, in which the extent of surface is less, in proportion to the entire quantity of blood
which it contains. For the same reason, coagulation takes place
more rapidly in a vessel with a roughened internal surface, than in
one which is smooth and polished. The blood coagulates most
rapidly when spread out in thin layers, and entangled among the
fibres of cloth or sponges. For the same reason, also, hemorrhage
continues longer from an incised wound than from a lacerated one;
because the blood, in flowing over the ragged edges of the lace.
rated bloodvessels and tissues, solidifies upon them readily, and thus
blocks up the wound.
In all these cases, there is an inverse relation between the rapidity
of coagulation and the firmness of the clot. When coagulation
takes place slowly, the clot afterward becomes small and dense, and
the serum  is abundant.  When coagulation is rapid, there is but
little contraction of the coagulum, an imperfect separation of the
serum, and the clot remains large, soft, and gelatinous.
It is well known to practical physicians that a similar relation
exists when the coagulation of the blood is hastened or retarded by
disease. In cases of lingering and exhausting illness, or in diseases
of a typhoid or exanthematous character, with much depression of
the vital powers, the blood coagulates rapidly and the clot remains
soft. In cases of active inflammatory disease, as pleurisy or pneumonia, occurring in previously healthy subjects, the blood coagulates
slowly, and the clot becomes very firm. In every instance, the
blood which has coagulated liquefies again at the commencement of
putrefaction.
The coagulation of the fibrin is not a commencement of organization.
The filaments already described, which show themselves in the clot
(Fig. 62), are not, properly speaking, organized fibres, and are entirely different in their character from the fibres of areolar tissue, or




COAGULATION OF THE BLOOD.                   211
any other normal anatomical elements. They are simply the ultimate form which fibrin assumes in coagulating, just as albumen
takes the form  of granules under the same circumstances.  The
coagulation of fibrin does not differ in character from that of any
other organic substance; it merely differs in the physical conditions
which give rise to it. All the coagulable organic substances are
naturally fluid, and coagulate only when they are placed under
certain unusual conditions. But the particular conditions necessary for coagulation vary with the different organic substances.
Thus albumen coagulates by the application of heat. Casein, which
is not affected by heat, coagulates by contact with an acid body.
Pancreatine, again, is coagulated by contact with sulphate of magnesia, which has no effect on albumen. So fibrin, which is naturally
fluid, and which remains fluid so long as it is circulating in the
vessels, coagulates when it is withdrawn from them and brought in
contact with unnatural surfaces. Its coagulation, therefore, is no
more "spontaneous," properly speaking, than that of any other
organic substance. Still less does it indicate anything like organization, or even a commencement of it. On the contrary, in the
natural processes of nutrition, fibrin is assimilated by the tissues
and takes part in their organization, only when it is absorbed by
them from the bloodvessels in a fluid form. As soon as it is once
coagulated by any means, it passes into an unnatural condition, and
must be again liquefied and absorbed into the blood before it can
be assimilated.
As the fibrin, therefore, is maintained in its natural condition of
fluidity by the movement of the circulating blood in the interior of
the vessels, anything which interferes with this circulation will induce its coagulation. If a ligature be placed upon an artery in the
living subject, the blood which stagnates above the ligature coagulates, just as it would do if entirely removed from the circulation.
If the vessel be ruptured or lacerated, the blood which escapes from
it into the areolar tissue coagulates, because here also it is withdrawn from the circulation. It coagulates also in the interior of
the vessels after death owing to the same cause, viz: stoppage of
the circulation. During the last moments of life, when the flow of
blood through the cavities of the heart is impeded, the fibrin often
coagulates, in greater or less abundance, upon the moving chordse
tendineae and the edges of the valves, just as it would do if withdrawn from the body and stirred with a bundle of twigs. In every
instance, the coagulation of the fibrin is a morbid phenomenon, dependent on the cessation or disturbance of the circulation.




212                       THE BLOOD.
If the blood be allowed to coagulate in a bowl, and the clot be
then divided by a vertical section, it will be seen that its lower
portion is softer and of a deeper red than the upper. (Fig. 65.)
This is because the globules, which are of
Fig. 65.       greater specific gravity than the plasma, sink
toward the bottom of the vessel before coagulation takes place, and accumulate in the
lower portion of the blood. This deposit of
the globules, however, is only partial; be_od _          ~~cause they are soon fixed and entangled by
the solid mass of the coagulum, and are thus
Vertical section of a RE- retained in the position in which they hapCENT COAGULUM, showing pen to be at the moment that coagulation
the greater accumulation of
blood-globules at the bottom, takes place.
If the coagulation, however, be delayed
longer than usual, or if the globules sink more rapidly than is customary, they will have time to subside entirely from the upper portion of the blood, leaving a layer at the surface which is composed
of plasma alone.  When coagulation then takes place, this upper
portion solidifies at the same time with the rest, and the clot then
presents two different portions, viz., a lower portion of a dark red
color, in which the globules are accumulated, and an upper portion
from which the globules have subsided, and which is of a grayish
white color and partially transparent. This whitish layer on the
surface of the clot is termed the " buffy coat;" and the blood presenting it is said to be "buffed." It is an appearance which often
presents itself in cases of acute inflammatory disease, in which the
coagulation of the blood is unusually retarded.
When a clot with a buffy coat begins to contract, the contraction takes place perfectly well in its upper
Fig. 66.
Fg. 6.     portion, but in the lower part it is impeded
by the presence of the globules which have
accumulated in large quantity at the bottom
of the clot.  While the lower part of the
coagulum, therefore, remains voluminous,
and hardly separates from the sides of the,,== 3 ~   vessel, its upper colorless portion diminishes
Bowl of COA t, LATIED very much in size; and as its edges separate
BLOOD, showing the clot from the sides of the vessel, they curl over
buffed and cupped.
toward each other, so that the upper surface
of the clot becomes more or less excavated or cup-shaped. (Fig. 66.)




COAGULATION  OF THE BLOOD.                  213
The blood is then said to be "buffed and cupped." These appearances do not present themselves underordinary conditions, but only
when the blood has become altered by disease.
The entire quantity of blood existing in the body has never been
very accurately ascertained. It is not possible to extract the whole
of it by opening the large vessels,since a certain portion will always
remain in the cavities of the heart, in the veins, and in the capillaries of the head and abdominal organs. The other methods
which have been practised or proposed from time to time are all
liable to some practical objection.  We have accordingly only
been able thus far to ascertain the minimum  quantity of blood
existing in the body.  Weber and Lehmannl ascertained as nearly
as possible the quantity of blood in two criminals who suffered
death by decapitation; in both of which cases they obtained essentially similar results. The body weighed before decapitation 133
pounds avoirdupois. The blood which escaped from the vessels at
the time of decapitation amounted to 12.27 pounds. In order to
estimate the quantity of blood which remained in the vessels, the
experimenters then injected the arteries of the head and trunk with
water, collected the watery fluid as it escaped from the veins, and
ascertained how  much solid matter it held in solution.  This
amounted to 477.22 grains, which corresponded to 4.38 pounds of
blood. The result of the experiment is therefore as follows:
Blood which escaped from the vessels.... 12.27 pounds.
("   remained in the body...4.38  "
Whole quantity of blood in the living body, 16.65
The weight of the blood, then, in proportion to the entire weight
of the body, was as 1: 8; and the body of a healthy man, weighing
140 pounds, will therefore contain on the average at least 171pounds of blood.'Physiological Chemistry, vol. i. p. 638.




214                     RESPIRATION.
CHAPTER XII.
RESPIRATION.
THE blood as it circulates in the arterial system has a bright
scarlet color; but as it passes through the capillaries it gradually
becomes darker, and on its arrival in the veins its color is a deep
purple, and in some parts of the body nearly black. There are,
therefore, two kinds of blood in the body; arterial blood, which is
of a bright color, and venous blood, which is dark. Now it is found
that the dark-colored venous blood, which has been contaminated
by passing through the capillaries, is unfit for further circulation.
It is incapable, in this state, of supplying the organs with their
healthy stimulus and nutrition, and has become, on the contrary,
deleterious and poisonous. It is accordingly carried back to the
heart by the veins, and thence sent to the lungs, where it is reconverted into arterial blood. The process by which the venous blood
is thus arterialized and renovated, is known as the process of
respiration.
This process takes place very actively in the higher animals, and
probably does so to a greater or less extent in all animals without
exception. Its essential conditions are that the circulating fluid
should be exposed to the influence of atmospheric air, or of an
aerated fluid; that is, of a fluid holding atmospheric air or oxygen
in solution. The respiratory apparatus consists essentially of a
moist and permeable animal membrane, the respiratory membrane,
with the bloodvessels on one side of it, and the air or aerated fluid
on the other. The blood and the air, consequently, do not come in
direct contact with each other, but absorption and exhalation take
place from one to the other through the thin membrane which lies
between.
The special anatomical arrangement of the respiratory apparatus
differs in different species of animals. In most of those inhabiting
the water, the respiratory organs have the form of gills or branchice;
that is, delicate filamentous prolongations of some part of the




RESPIRATION.                        215
integument or mucous membranes, which contain  an abundant
supply of bloodvessels, and which hang out freely into the surrounding water. In many kinds of aquatic lizards, as, for example, in menobranchus (Fig. 67),
there are upon each side of the              Fig. 67.
neck three delicate feathery
tufts of thread-like prolonga- 
tions from  the mucous mem- 
brane of the pharynx, which 
pass out through fissures in 
the side of the neck.  Each 
tuft is composed -of a principal stem, upon which the
X                II^ E^ AHEAD AND GILLS OF MENOBRANCH US.
filaments are arranged in a
pinnated form, like the plume upon the shaft of a feather.  Each
filament, when examined by itself, is seen to consist of a thin, ribbon-shaped fold of mucous membrane, in the interior of which
there is a plentiful network of minute bloodvessels. The dark
blood, as it comes into the filament from the branchial artery, is
exposed to the influence of the water in which the filament is
bathed, and as it circulates through the capillary network of the
gills is reconverted into arterial blood. It is then carried away by
the branchial vein, and passes into the general current of the circulation. The apparatus is further supplied with a cartilaginous
framework, and a set of muscles by which the gills are gently waved
about in the surrounding water, and constantly brought into contact with fresh portions of the aerated fluid.
Most of the aquatic animals breathe by gills similar in all their
essential characters to those described above. In terrestrial and
air-breathing animals, however, the respiratory apparatus is situated
internally.  In them, the air is made to penetrate into the interior
of the body, into certain cavities or sacs called the lungs, which
are lined with a vascular mucous membrane.  In the salamanders,
for example, which, though aquatic in their habits, are air-breathing
animals, the lungs are two long cylindrical sacs, running nearly the
entire length of the body, commencing anteriorly by a communication with the pharynx, and terminating by rounded extremities
at the posterior part of the abdomen.  These lungs, or air-sacs,
have a smooth internal surface; and the blood which circulates
through their vessels is arterialized by exposure to the air contained
in their cavities.  The air is forced into the lungs by a kind of




216                     RESPIRATION.
swallowing movement, and is after a time regurgitated and discharged, in order to make room for a fresh supply.
In frogs, turtles, serpents, &c., the structure of the lung is a
little more complicated, since respiration is more active in these
animals, and a more perfect organ is requisite to accomplish the
arterialization of the blood. In these animals, the cavity of the
lung, instead of being simple, is divided by incomplete partitions
into a number of smaller cavities or "cells."  The cells all communicate with the central pulmonary cavity; and the partitions, which
join each other at various angles, are all composed of thin, projecting folds of the lining membrane, with bloodvessels ramifying
between them. (Fig. 68.) By this arrangement,
Fig. 68.     the extent of surface presented to the air by the
)J',  pulmonarv membrane is much increased, and the
Xz^^^^  arterialization of the blood takes place with a
corresponding degree of rapidity.
In the human subject, and in all the warmblooded quadrupeds, the lungs are constructed
on a plan which is essentially similar to the
above, and which differs from it only in the
greater extent to which the pulmonary cavity is
LUNG OF FROG, subdivided, and the surface of the respiratory
showing its internal sur- membrane increased. The respiratory apparatus
face.
(Fig. 69) commences with the larynx, which
communicates with the pharynx at the upper part of the neck.
Then follows the trachea, a membranous tube with cartilaginous
rings; which, upon its entrance into the chest, divides into the right
and left bronchus. These again divide successively into secondary
and tertiary bronchi; the subdivision continuing, while the bronchial tubes grow smaller and more numerous, and separate constantly from each other. As they diminish in size, the tubes grow
more delicate in structure, and the cartilaginous rings and plates
disappear from their walls. They are finally reduced, according to
Kolliker, to the size of 2s of an inch in diameter; and are cornposed only of a thin mucous membrane, lined with pavement epithelium, which rests upon an elastic fibrous layer. They are then
known as the "ultimate bronchial tubes."
Each ultimate bronchial tube terminates in a division or islet of
the pulmonary tissue, about 1  of an inch in diameter, which is
termed a "pulmonary lobule."  Each pulmonary lobule resembles
in its structure the entire frog's lung in miniature. It consists of a




RESPIRATION.                            217
Fig. 69.
HUMAN LARYNX, TRACHEA, BRONCHI, AND LUNGS; showing the ramification of the
bronchi, and the division of the lungs into lobules.
vascular membrane  inclosing a cavity; which cavity is divided
into a large number of secondary compartments by thin septa or
partitions, which project from its internal surface. (Fig. 70.) These
secondary  cavities  are  the  "pulmonary
cells," or "vesicles."  Each vesicle is about            Fig. 70.. of an inch in diameter; and is covered
on its exterior with a close network of ca-  
pillary bloodvessels, which dip down into
the spaces between the adjacent vesicles, and    Cp 
expose in this way a double surface to the  
air which is contained  in  their cavities.                           
Between the vesicles, and in the interstices
between the lobules, there is a large quan- 
tity of yellow  elastic tissue, which gives
firmness and resiliency to the pulmonary                      I
structure.  The pulmonary vesicles, accordSINGLE LOBULE OF HUing  to the observations of K6lliker, are  MNLuN.-a. Utimatebronlined everywhere with a layer of pavement  chial tube. b. Cavity of lobule.,c, c,. Pulmonary cells, or vesiepithelium, continuous with  that in  the  cles.




218                      RESPIRATION.
ultimate bronchial tubes. The whole extent of respiratory surface in both lungs has been calculated by Lieberkiihn' at fourteen
hundred square feet. It is plainly impossible to make a precisely
accurate calculation of this extent; but there is every reason to
believe that the estimate adopted by Lieberkiihn, regarded as
approximative, is not by any means an exaggerated one. The
great multiplication of the minute pulmonary vesicles, and of the
partitions between them, must evidently increase to an extraordinary degree the extent of surface over which the blood, spread
out in a thin layer, is exposed to the action of the air. These
anatomical conditions are, therefore, the most favorable for its rapid
and complete arterialization.
RESPIRATORY MOVEMENTS OF THE CHEST.-The air which is contained in the pulmonary lobules and vesicles becomes rapidly vitiated
in the process of respiration, and. requires therefore to be expelled
and replaced by a fresh supply. This exchange or renovation of
the air is effected by alternate movements of the chest, of expansion
and collapse, which are termed the " respiratory movements of the
chest." The expansion of the chest is effected by two sets of muscles, viz., first, the diaphragm, and, second, the intercostals. While
the diaphragm is in a state of relaxation, it has the form of a vaulted
partition between the thorax and abdomen, the edges of which are
attached to the inferior extremity of the sternum, the inferior
costal cartilages, the borders of the lower ribs and the bodies of
the lumbar vertebrae, while its convexity rises high into the cavity
of the chest, as far as the level of the fifth rib. When the fibres
of the diaphragm  contract, their curvature is necessarily diminished; and they approximate a straight line, exactly in proportion
to the extent of their contraction.  Consequently, the entire convexity of the diaphragm  is diminished in the same proportion,
and it descends toward the abdomen, enlarging the cavity of the
chest from above downward. (Fig. 71.) At the same time the intercostal muscles enlarge it in a lateral direction. For the ribs, articulated behind with the bodies of the vertebrae, and joined in front
to the sternum by the flexible and elastic costal cartilages, are so
arranged that, in a position of rest, their convexities look obliquely
outward and downward.  When the movement of inspiration is
about to commence, the first rib is fixed by the contraction of the
In Simon's Chemistry of Man, Philada. ed., 1846, p. 109.




RESPIRATORY  MOVEMENTS OF THE CHEST.    219
scaleni muscles, and the intercostal muscles then contracting simultaneously, the ribs are drawn upward.  In this movement, as each
rib rotates upon its articulation with the
spinal column at one extremity, and with             Fig. 71.
the sternum  at the other, its convexity is
necessarily carried outward at the same
time that it is drawn upward, and the pa-           -        /
rietes of the chest are, therefore, expanded 
laterally. The sternum itself rises slightly
with the same movement, and enlarges to
some extent the antero-posterior diameter 
of the thorax. By the simultaneous action,./ 
therefore, of the diaphragm which descends,                 T
and of the intercostal muscles which lift-  /
the ribs and the sternum, the cavity of the    /
chest is expanded in every direction, and
the air passes inward, through the trachea
and bronchial tubes, by the simple force of
aspiration.
After the movement of inspiration is ac-. 
complished, and the lungs are filled with         \
air, the diaphragm and intercostal muscles
relax, and a movement of expiration takes
place, by which the chest is partially collapsed, and a portion of the air contained   DIAGRAM ILLUSTRA
in the pulmonary cavity expelled.  The THE RESPIRATORY MovE-,-   M  1. XE N T s.-a. Cavity of the chest.
movement of expiration is entirely a passive b. Diaphragm.  The dark outone, and is accomplished by the action of lines show the figure of the chest
when collapsed; the dotted lines
three different forces. First, the abdominal show the same when expanded.
organs, which have been pushed out of their
usual position by the descent of the diaphragm, fall backward by
their own weight and carry upward the relaxed diaphragm before
them.  Secondly, the costal cartilages, which are slightly twisted
out of shape when the ribs are drawn upward, resume their natural
position as soon as the muscles are relaxed, and, drawing the ribs
down again, compress the sides of the chest. Thirdly, the pulmonary tissue, as we have already remarked, is abundantly supplied with yellow  elastic fibres, which retract by virtue of their
own elasticity, in every part of the lungs, after they have been
forcibly distended, and, compressing the pulmonary vesicles, drive
out a portion of the air which they contained. By the constant




220                     RESPIRATION.
recurrence of these alternating movements of inspiration and expiration, fresh portions of air are constantly introduced into and
expelled from the chest.
The average quantity of atmospheric air, taken into and discharged from the lungs with each respiratory movement, is, according to the results of various observers, twenty cubic inches. At
eighteen respirations per minute, this amounts to 360 cubic inches
of air inspired per minute, 21,600 cubic inchesper hour, and 518,400
cubic inches per day. But as the movements of respiration are
increased both in extent and rapidity by every muscular exertion,
the entire quantity of air daily used in respiration is not less than
600,000 cubic inches, or 350 cubic feet.
The whole of the air in the chest, however, is not changed at each
movement of respiration.  On the contrary, a very considerable
quantity remains in the pulmonary cavity after the most complete
expiration; and even after the lungs have been removed from the
chest, they still contain a large quantity of air which cannot be
entirely displaced by any violence short of disintegrating and disorganizing the pulmonary tissue. It is evident, therefore, that only
a comparatively small portion of the air in the lungs passes in and
out with each respiratory movement; and it will require several
successive respirations before all the air in the chest can be entirely
changed. It has not been possible to ascertain with certainty the
exact proportion in volume which exists between the air which is
alternately inspired and expired, or "tidal" air, and that which
remains constantly in the chest, or "residual" air, as it is called.
It has been estimated, however, by Dr. Carpenter,' from the reports
of various observers, that the volume of inspired and expired air
varies from 10 to 13 per cent. of the entire quantity contained in
the chest. If this estimate be correct, it will require from eight to
ten respirations to change the whole quantity of air in the cavity of
the chest.
It is evident, however, from the foregoing, that the inspiratory
and expiratory movements of the chest cannot be sufficient to
change the air at all in the pulmonary lobules and vesicles. The
air which is drawn in with each inspiration penetrates only into
the trachea and bronchial tubes, until it occupies the place of that
which was driven out by the last expiration. By the ordinary
respiratory movements, therefore, only that small portion of the' Human Physiology, Philada. ed., 1855, p. 300.




RESPIRATORY MOVEMENTS OF THE GLOTTIS.   221
air lying nearest the exterior, in the trachea and large bronchi,
would fluctuate backward and forward, without ever penetrating
into the deeper parts of the lung, were there no other means provided for its renovation. There are, however, two other forces in
play for this purpose. The first of these is the diffusive power of
the gases themselves. The air remaining in the deeper parts of
the chest is richer in carbonic acid and poorer in oxygen than that
which has been recently inspired; and by the laws of gaseous diffusion there must be a constant interchange of these gases between
the pulmonary vesicles and the trachea, tending to mix them
equally in all parts of the lung. This mutual diffusion and intermixture of the gases will therefore tend to renovate, partially at
least, the air in the pulmonary lobules and vesicles. Secondly, the
trachea and bronchial tubes, down to those even of the smallest
size, are lined with a mucous membrane which is covered with
ciliated epithelium. The movement of these cilia is found to be
directed  always from  below  upward; and, like ciliary motion
wherever it occurs, it has the effect of producing a current in the
same direction, in the fluids covering the mucous membrane.  The
air in the tubes must participate, to a certain  extent, in                Fig. 72.
this current, and  a double
stream of air therefore is established in each bronchial tube;
one current passing from within outward along the walls of
the tube, and a return current
passing from  without inward,
assing from  without inward,   SMALL BRONCHIAL TUBE, showing outward
along the central part of its. and inward current, produced by ciliary motion.
cavity. (Fig. 72.)   By  this
means a kind of aerial circulation is constantly maintained in the
interior of the bronchial tubes; which, combined with the mutual
diffusion of the gases and the alternate expansion and collapse of
the chest, effectually accomplish the renovation of the air contained
in all parts of the pulmonary cavity.
RESPIRATORY MOVEMENTS OF THE GLOTTIS.-Beside the movements of expansion and collapse already described, belonging to
the chest, there are similar respiratory movements which take place
in the larynx. If the respiratory passages be examined after death,
in the state of collapse in which they are usually found, it will be




222                        RESPIRATION.
noticed that the opening of the glottis is very much smaller than
the cavity of the trachea below. The glottis itself presents the
appearance of a narrow chink, while the passage for the inspired
air widens in the lower part of the larynx, and in the trachea
constitutes a spacious tube, nearly cylindrical in shape, and over
half an inch in diameter.  We have found, for instance, that in
the human subject the. space included between the vocal chords
has an area of only 0.15 to 0.17 square inch; while the calibre
of the trachea in the middle of its length is 0.45 square inch.
This disproportion, however, which is so evident after death, does
not exist during life.  While respiration is going on, there is a
constant and regular movement of the vocal chords, synchronous
with the inspiratory and expiratory movements of the chest, by
Fig. 73.                             Fig. 74.
He s, wh te gs o d 
i  its A o  L dA r p N, viewed from above  The same, with the glottis opened by
in its ordinary post-mortem condition-a.  separation of the vocal chords.-a. Vocal
Vocal chords. b. Thyroid cartilage. cc. Ary-    chords. b. Thyroid cartilage. cc. Arytetenoid cartilages. o. Opening of the glottis.  noid cartilages. o. Opening of the glottis.
which the size of the glottis is alternately enlarged and diminished.
At every inspiration, the glottis opens and allows the air to pass
freely into the trachea; at every expiration it collapses, and the
air is driven out through it from  below.  These movements are
called the " respiratory movements of the glottis."  They correspond
in every respect with those of the chest, and are excited or retarded
by similar causes.  Whenever the general movements of respiration
are hurried and labored, those of the glottis become accelerated and
increased in intensity at the same time; and when the movements
of the chest are slower or fainter than usual, owing to debility,
coma, or the like, those of the glottis are diminished in the same
proportion.




CHANGES IN THE AIR DURING RESPIRATION.   223
In the respiratory motions of the glottis, as in those of the chest,
the movement of inspiration is an active one, and that of expiration passive. In inspiration, the glottis
is opened by contraction of the posterior          Fig. 75.
crico-arytenoid  muscles.   (Fig. 75.)
These muscles originate from  the posterior surface of the cricoid cartilage,
near the median line; and their fibres,
running upward and outward, are inserted into the external angle of the    \       1
arytenoid cartilages. By the contraction of these muscles, during the movement of inspiration, the arytenoid cartilages are rotated upon their articulations with the cricoid, so that their
anterior extremities are carried outward,
and the vocal chords stretched and sepa~*_ f  -\ - \ T    *\' HITMAN LARYNX,POSTERIOR
rate from each other. (Fig. 74.) In this  vE.   Thyroid cartilage. b. Epi
way, the size of the glottis may be in- glottis cc Arytenoid cartilages d.
Cricoid cartilage,   ee. Posterior cricocreased from  0.15 to 0.27 square inch. arytenoid muscles. f. Trachea.
In expiration, the posterior cricoarytenoid muscles are relaxed, and the elasticity of the vocal chords
brings them back to their former position.
The motions of respiration consist, therefore, of two sets of movements: viz., those of the chest, and those of the glottis. These movements, in the natural condition, correspond with each other both in
time and intensity. It is at the same time and by the same nervous
influence, that the chest expands to enhale the air, while the glottis
opens to admit it; and in expiration, the muscles of both chest and
glottis are relaxed, while the elasticity of the tissues, by a kind of
passive contraction, restores the parts to their original condition.
CHANGES IN THE AIR DURING RESPIRATION. —The atmospheric
air, as it is drawn into the cavity of the lungs, is a mixture of oxygen and nitrogen, in the proportion of about 21 per cent., by volume,
of oxygen, to 79 per cent. of nitrogen. It also contains about onetwentieth per cent. of carbonic acid, a varying quantity of watery
vapor, and some traces of ammonia.  The last named ingredients,
however, are quite insignificant in comparison with the oxygen and
nitrogen, which form the principal part of its mass.
If collected and examined, after passing through the lungs, the




224                     RESPIRATION.
air is found to have become altered in the following essential particulars, viz:1st. It has lost oxygen.
2d. It has gained carbonic acid. And
3d. It has absorbed the vapor of water.
Beside the two latter substances, there are also exhaled with the
expired air a very small quantity of nitrogen, over and above what
was taken in with inspiration, and a little animal matter in a
gaseous form, which communicates a slight but peculiar odor to
the breath. The air is also somewhat elevated in temperature, by
contact with the pulmonary mucous membrane.
The watery vapor, which is exhaled with the breath, is given off
by the pulmonary mucous membrane, by which it is absorbed from
the blood. At ordinary temperatures it is transparent and invisible; but in cold weather it becomes partly condensed, on leaving
the lungs, and appears under the form of a cloudy vapor discharged
with the breath.  According to the researches of Valentin, the
average quantity of water, exhaled daily from the lungs, is 8100
grains, or about 1 pounds avoirdupois.
By far the most important part, however, of the changes suffered
by the air in respiration, consists in its loss of oxygen, and its
absorption of carbonic acid.
According to the researches of Valentin, Vierordt, Regnault and
Reiset, &c.; the air loses during respiration, on an average, five per
cent. of its volume of oxygen. At each inspiration, therefore,
about one cubic inch of oxygen is removed from the air and absorbed by the blood; and as we have seen that the entire daily
quantity of air used in respiration is about 350 cubic feet, the entire
quantity of oxygen thus consumed in twenty-four hours is not less
than seventeen and a half cubic feet. This is, by weight, 7,134
grains, or a little over one pound avoirdupois.
The oxygen which thus disappears from the inspired air is not
entirely replaced in the carbonic acid exhaled; that is, there is less
oxygen in the carbonic acid which is returned to the air by expiration than has been lost during inspiration.
There is even more oxygen absorbed than is given off again in
both the carbonic acid and aqueous vapor together, which are
exhaled from the lungs.l There is, then, a constant disappearance
of oxygen from the air used in respiration, and a constant accumulation of carbonic acid.
Lehmann's Physiological Chemistry, Philada. ed., vol. ii. p. 432.




CHANGES IN TITE BLOO'D DURING RESPIRATION. 225
The proportion of oxygen which disappears in the interior of the
body, over and above that which is returned in the breath under
the form of carbonic acid, varies in different kinds of animals.  In
the herbivora, it is about 10 per cent. of the whole amount of oxygen inspired; in the carnivora, 20 or 25 per cent., and even more.
It is a very remarkable fact, also, and an important one, as regards
the theory of respiration, that, in the same animal, the proportion of
oxygen absorbed, to that of carbonic acid exhaled, varies according
to the quality of the food. In dogs, for instance, while fed on animal food, according to the experiments of Regnault and Reiset, 25
per cent. of the inspired oxygen disappeared in the body of the
animal; but when fed on starchy substances, all but 8 per cent.
reappeared in the expired carbonic acid. It is already evident,
therefore, from these facts, that the oxygen of the inspired air is
not altogether employed in the formation of carbonic acid.
CHANGES IN THE BLOOD DURING RESPIRATION.-If we pass from
the consideration of the changes produced in the air by respiration
to those which take place in the blood during the same process, we
find, as might have been expected, that the latter correspond
inversely with the former.  The blood, in passing through the
lungs, suffers the following alterations:1st. Its color is changed from venous to arterial.
2d. It absorbs oxygen. And
3d. It exhales carbonic acid and the vapor of water.
The interchange of gases, which takes place during respiration
between the air and the blood, is a simple phenomenon of absorption and exhalation. The inspired oxygen does not, as Lavoisier
once supposed, immediately combine with carbon in the lungs, and
return to the atmosphere under the form of carbonic acid. On the
contrary, almost the first fact of importance which has been established by the examination of the blood in this respect is the following, viz: that carbonic acid exists ready formed in the venous blood
before its entrance into the lungs; and, on the other hand, that the
oxygen which is absorbed during respiration passes off in a free state
with the arterial blood. The real process, as it takes place in the
lung, is, therefore, for the most part, as follows: The blood comes to
the lungs already charged with carbonic acid. In passing through
the pulmonary capillaries, it is exposed to the influence of the air
in the cavity of the pulmonary cells, and a transudation of gases
15




226                     RESPIRATION.
takes place through the moist animal membranes of the lung.
Since the blood in the capillaries contains a larger proportion of
carbonic acid than the air in the air-vesicles, a portion of this gas
leaves the blood and passes out through the pulmonary membrane;
while the oxygen, being more abundant in the air of the vesicles
than in the circulating fluid, passes inward at the same time, and is
condensed by the blood.
In this double phenomenon of exhalation and absorption, which
takes place in the lungs, both parts of the process are equally
necessary to life. It is essential for the constant activity and nutrition of the tissues that they be steadily supplied with oxygen by the
blood; and if this supply be cut off; their functional activity ceases.
On the other hand, the carbonic acid which is produced in the body
by the processes of nutrition becomes a poisonous substance, if it
be allowed to collect in large quantity. Under ordinary circumstances, the carbonic acid is removed by exhalation through the
lungs as fast as it is produced in the interior of the body; but if
respiration be suspended, or seriously impeded, since the production
of carbonic acid continues, while its elimination is prevented, it
accumulates in the blood and in the tissues, and terminates life in a
few moments, by a rapid deterioration of the circulating fluid, and
more particularly by its poisonous effect on the nervous system.
The deleterious effects of breathing in a confined space will
therefore very soon become apparent. As respiration goes on, the
oxygen of the air constantly diminishes, and the carbonic acid,
mingled with it by exhalation, increases in quantity. After a time
the air becomes accordingly so poor in oxygen that, by that fact
alone, it is incapable of supporting life. At the same time, the
carbonic acid becomes so abundant in the air vesicles that it prevents the escape of that which already exists in the blood; and the
deleterious effect of its accumulation in the circulating fluid is
added to that produced by a diminished supply of oxygen. An
increased proportion of carbonic acid in the atmosphere is therefore
injurious in a similar manner, although there may be no diminution
of oxygen; since by its presence it impedes the elimination of the
carbonic acid already formed in the blood, and induces the poisonous effects which result from its accumulation.
Examination of the blood shows furthermore that the interchange
of gases in the lungs is not complete but only partial in its extent.
It results from the experiments of Magendie, Magnus, and others,
that both oxygen and carbonic acid are contained in both venous




CHANGES IN THE BLOOD DURING RESPIRATION. 227
and arterial blood. Magnus' found that the proportion of oxygen
to carbonic acid, by volume, in arterial blood was as 10 to 25; in
venous blood as 10 to 40. The venous blood, then, as it arrives at
the lungs, still retains a remnant of the oxygen which it had previously absorbed; and in passing through the pulmonary capillaries it gives off only a part of the carbonic acid with which it has
become charged in the general circulation.
The oxygen and carbonic acid of the blood exist in a state of
solution in the circulating fluid, and not in a state of intimate chemical combination. This is shown by the fact that both of these
substances may be withdrawn from the blood by simple exhaustion
with an air-pump, or by a stream of any other indifferent gas, such
as hydrogen, which possesses sufficient physical displacing power.
Magnus found2 that freshly drawn arterial blood yielded by simple
agitation with carbonic acid more than 10 per cent. of its volume
of oxygen.  The carbonic acid may also be expelled from venous
blood by a current of pure oxygen, or of hydrogen, or, in great
measure, by simple agitation with atmospheric air. There is some
difficulty in determining, however, whether the carbonic acid of
the blood be altogether in a free state, or whether it be partly in a
state of loose chemical combination with a base, under the form of
an alkaline bicarbonate. A solution of bicarbonate of soda itself
will lose a portion of its carbonic acid, and become reduced to the
condition of a carbonate by simple exhaustion under the air-pump,
or by agitation with pure hydrogen at the temperature of the body.
Lehmann has found3 that after the expulsion of all the carbonic
acid removable by the air-pump and a current of hydrogen, there
still remains, in ox's blood, 0.1628 per cent. of carbonate of soda;
and he estimates that this quantity is sufficient to have retained all
the carbonic acid, previously given off, in the form of a bicarbonate.
It makes little or no difference, however, so far as regards the process of respiration, whether the carbonic acid of the blood exist in
an entirely free state, or under the form of an alkaline bicarbonate;
since it may be readily removed from this combination, at the temperature of the body, by contact with an indifferent gas.
The oxygen and carbonic acid of the blood are in solution principally in the blood-globules, and not in the plasma. The researches
of Magnus have shown4 that the blood holds in solution 2- times' In Lehmann, op. cit., vol. i. p. 570.
2 In Robin and Verdeil, op. cit., vol. ii. p. 34.
3 Op. cit., vol. i. p. 393.
In Robin and Verdeil, op. cit., vol. ii. pp. 28-32.




228                      RESPIRATION.
as much oxygen as pure water could dissolve at the same temperature; and that while the serum of the blood, separated from the
globules, exerts no more solvent power on oxygen than pure water,
defibrinated blood, that is, the serum and globules mixed, dissolves
quite as much oxygen as the fresh blood itself. The same thing is
true with regard to the carbonic acid. It is therefore the semifluid blood-globules which retain these two gases in solution-; and
since the color of the blood depends entirely upon that of the globules, it is easy to understand why the blood should alter its hue
from purple to scarlet in passing through the lungs, where the
globules give up carbonic acid, and absorb a fresh quantity of
oxygen.  The above change may readily be produced outside the
body. If freshly drawn venous blood be shaken in a bottle with
pure oxygen, its color changes at once from purple to red; and the
same change will take place, though more slowly, if the blood be
simply agitated with atmospheric air. It is for this reason that the
surface of defibrinated venous blood, and the external parts of a
dark-colored clot, exposed to the atmosphere, become rapidly reddened, while the internal portions retain their original color.
The process of respiration, so far as we have considered it, consists in an alternate interchange of carbonic acid and oxygen in the
blood of the general and pulmonary circulations. In the pulmonary
circulation, carbonic acid is given off and oxygen absorbed; while
in the general circulation the oxygen gradually disappears, and is
replaced, in the venous blood, by carbonic acid. The oxygen which
thus disappears from the blood in the general circulation does not,
for the most part, enter into direct combination in the blood itself.
On the contrary, it exists there, as we have already stated, in the
form of a simple solution. It is absorbed, however, from the blood
of the capillary vessels, and becomes fixed in the substance of the
vascular tissues. The blood may be regarded, therefore, in this
respect, as a circulating fluid, destined to transport oxygen from the
lungs to the tissues; for it is the tissues themselves which finally
appropriate the oxygen, and fix it in their substance.
The next important question which presents itself in the study
of the respiratory process relates to the origin of the carbonic acid in
the venous blood. It was formerly supposed, when Lavoisier first
discovered the changes produced in the air by respiration, that the
production of the carbonic acid could be accounted for in a very
simple manner. It was thought to be produced in the lungs by a




CHANGES IN THE BLOOD DURING RESPIRATION. 229
direct union of the inspired oxygen with the carbon of the blood
in the pulmonary vessels. It was found afterward, however, that
this could not be the case; since carbonic acid exists already formed
in the blood, previously to its entrance into the lungs. It was then
imagined that the oxidation of carbon, and the consequent production of carbonic acid, took place in the capillaries of the general
circulation, since it could not be shown to take place in the lungs,
nor between the lungs and the capillaries.  The truth is, however,
that no direct evidence exists of such a direct oxidation taking
place anywhere. The formation of carbonic acid, as it is now
understood, takes place in three different modes: 1st, in the lungs;
2d, in the blood; and 3d, in the tissues.
First, in the lungs. There exists in the pulmonary tissue a peculiar acid substance, first described by Verdeil' under the name of
"pneumic" or "pulmonic" acid. It is a crystallizable body, soluble
in water, which is produced in the substance of the pulmonary
tissue by transformation of some of its other ingredients, in the
same manner as sugar is produced in the tissue of the liver. It is
on account of the presence of this substance that the fresh tissue of
the lung has usually an acid reaction to test-paper, and that it has
also the property, which has been noticed by several observers, of
decomposing the metallic cyanides, with the production of hydrocyanic acid; a property not possessed by sections of areolar tissue,
the internal surface of the skin, &c. &c. When the blood, therefore, comes in  contact with  the  pulmonary tissue, which is
permeated everywhere by pneumic acid in a soluble form, its
alkaline carbonates and bicarbonates, if any be present, are decomposed with the production on the one hand of the pneumates of
soda and potassa, and on the other of free carbonic acid, which is
exhaled. M. Bernard has found2 that if a solution of bicarbonate
of soda be rapidly injected into the jugular vein of a rabbit, it
becomes decomposed in the lungs with so rapid a development of
carbonic acid, that the gas accumulates in the pulmonary tissue,
and even in the pulmonary vessels and the cavities of the heart, to
such an extent as to cause immediate death by stoppage of the
circulation. In the normal condition, however, the carbonates and
bicarbonates of the blood arrive so slowly at the lungs that as fast
as they are decomposed there, the carbonic acid is readily exhaled
by expiration, and produces no deleterious effect on the circulation.
Robin and Verdeil, op. cit., vol. ii. p. 4G0.
2 Archives G6n. de Med., xvi. 222.




230                     RESPIRATION.
Secondly, in the blood. There is little doubt, although the fact has
not been directly proved, that some of the oxygen definitely disappears, and some of the carbonic acid is also formed, in the substance of the blood-globules during their circulation. Since these
globules are anatomical elements, and since they undoubtedly go
through with nutritive processes analogous to those which take
place in the elements of the solid tissues, there is every reason for
believing that they also require oxygen for their support, and that
they produce ca bonic acid as one of the results of their interstitial
decomposition.  While the oxygen and carbonic acid, therefore,
contained in the globules, are for the most part transported by
these bodies from the lungs to the tissues, and from the tissues back
again to the lungs, they probably take part, also, to a certain extent,
in the nutrition of the blood-globules themselves.
Thirdly, in the tissues. This is by far the most important source
of the carbonic acid in the blood. From the experiments of Spallanzani, W. Edwards, Marchand and others, the following very
important fact has been established, viz., that every organized tissue
and even every organic substance, when in a recent condition, has the
power of absorbing oxygen and of exhaling carbonic acid. G. Liebig,
for example,' found that frog's muscles, recently prepared and completely freed from blood, continued to absorb oxygen and discharge
carbonic acid. Similar experiments with other tissues have led
to a similar result. The interchange of gases, therefore, in the
process of respiration, takes place mostly in the tissues themselves.
It is in their substance that the oxygen becomes fixed and assimilated, and that the carbonic acid takes its origin. As the blood in
the lungs gives up its carbonic acid to the air, and absorbs oxygen
from it, so in the general circulation it gives up its oxygen to the
tissues, and absorbs from them carbonic acid.
We come lastly to examine the exact mode by which the carbonic acid originates in the animal tissues. Investigation shows
that even here it is not produced by a process of oxidation, or direct
union of oxygen with the carbon of the tissues, but in some other and more
indirect mode. This is proved by the fact that animals and fresh
animal tissues will continue to exhale carbonic acid in an atmosphere of hydrogen or of nitrogen, or even when placed in a vacuum.
Marchand found2 that frogs would live for from half an hour to an
hour in pure hydrogen gas; and that during this time they exhaled
even more carbonic acid than in atmospheric air, owing probably
I In Lehmann, op. cit., vol. ii. p. 474.  2 Ibid., p. 442.




CHANGES IN THE BLOOD DURING RESPIRATION. 231
to the superior displacing power of hydrogen for carbonic acid.
For while 15,500 grains' weight of frogs exhaled about 1.13 grain
of carbonic acid per hour in atmospheric air, they exhaled during
the same time in pure hydrogen as much as 4.07 grains. The same
observer found that frogs would recover on the admission of air
after remaining for nearly half an hour in a nearly complete
vacuum; and that if they were killed by total abstraction of the
air, 15,500 grains' weight of the animals were found to have
eliminated 9.3 grains of carbonic acid. The exhalation of carbonic
acid by the tissues does not, therefore, depend directly upon the
access of free oxygen. It cannot go on, it is true, for an indefinite
time, any more than the other vital processes, without the presence
of oxygen. But it may continue long enough to show that the
carbonic acid exhaled is not a direct product of oxidation, but that
it originates, on the contrary, in all probability, by a decomposition of the organic ingredients of the tissues, resulting in the production of carbonic acid on the one hand, and of various other
substances on the other, with which we are not yet fully acquainted;
in very much the same manner as the decomposition of sugar
during fermentation gives rise to alcohol on the one hand and to
carbonic acid on the other. The fermentation of sugar, when it has
once commenced, does not require the continued access of air. It
will go on in an atmosphere of hydrogen, or even when confined in
a close vessel over mercury; since its carbonic acid is not produced
by direct oxidation, but by a decomposition of the sugar already
present. For the same reason, carbonic acid will continue to be
exhaled by living or recently dead animal tissues, even in an atmosphere of hydrogen, or in a vacuum.
Carbonic acid makes its appearance, accordingly, in the tissues,
as one product of their decomposition in the nutritive process.
From them it is taken up by the blood, either in simple solution or
in loose combination as a bicarbonate, transported by the circulation
to the lungs, and finally exhaled from the pulmonary mucous membrane in a gaseous form.
The carbonic acid exhaled from the lungs should accordingly be
studied by itself as one of the products of the animal organism, and
its quantity ascertained in the different physiological conditions of
the body.  The expired air usually contains about four per cent. of
its volume of carbonic acid. According to the researches of Vierordt,' which are regarded as the most accurate on this subject, an
i In Lehmann, op. cit., vol. ii. p. 439.




232                      RESPIRATION.
adult man gives off 1.62 cubic inch of carbonic acid with each normal expiration. This amounts to very nearly 1,150 cubic inches
per hour, or fifteen and a half cubic feet per day. This quantity
is, by weight, 10,740 grains, or a little over one pound and a half.
The amount of carbonic acid exhaled, however, varies from time to
time, according to many different circumstances; so that no such
estimate can represent correctly its quantity at all times. These
variations have been very fully investigated by Andral and Gavarret,' who found that the principal conditions modifying the amount
of this gas produced were age, sex, constitution and development.
The variations were very marked in different individuals, notwithstanding that the experiments were made at the same period of the
day, and with the subject as nearly as possible in the same condition.  Thus they found that the quantity of carbonic acid exhaled
per hour in five different individuals was as follows:QUANTITY OF CARBONIC ACID PER HOUR.
In subject No. 1....  1207 cubic inches.
"   "   " 2..... 970"    "
" " " 3.1250 "  "
"        "4.....  1250  "    "
"   " " 5...  1591  "    "
With regard to the difference produced by age, it was found that
from the period of eight years up to puberty the quantity of carbonic acid increases constantly with the age. Thus a boy of eight
years exhales, on the average, 564 cubic inches per hour; while a
boy of fifteen years exhales 981 cubic inches in the same time.
Boys exhale during this period more carbonic acid than girls of the:same age. In males this augmentation of the quantity of carbonic
acid continues till the twenty-fifth or thirtieth year, when it reaches,
on the average, 1398 cubic inches per hour. Its quantity then
remains stationary for ten or fifteen years; then diminishes slightly
from the fortieth to the sixtieth year; and after sixty years diminishes in a marked degree, so that it may fall so low as 1038 cubic
inches. In one superannuated person, 102 years of age, Andral
and Gavarret found the hourly quantity of carbonic acid to be
only 665 cubic inches.
In women, the increase of carbonic acid ceases at the period of
puberty; and its production then remains constant until the cessation of menstruation, about the fortieth or forty-fifth year. At that
time it increases again until after fifty years, when it subsequently
i Annales de Chimie et de Pharmacie, 1843, vol. viii. p. 129.




CHANGES IN TIIE BLOOD DURING RESPIRATION. 233
diminishes with the approach of old age, as in men. Pregnancy,
occurring at any time in the above period, immediately produces a
temporary increase in the quantity of carbonic acid.
The strength of the constitution, and more particularly the development of the muscular system, was found to have a very great influence in this respect; increasing the quantity of carbonic acid
very much, in proportion to the weight of the individual. The
largest production of carbonic acid observed was in a young man,
26 years of age, whose frame presented a remarkably vigorous and
athletic development, and who exhaled 1591 cubic inches per hour.
This large quantity of carbonic acid, moreover, in well developed
persons, is not owing simply to the size of the entire body, but
particularly to the development of the muscular system, since an
unusually large skeleton, or an abundant deposit of adipose tissue;
is not accompanied by any such increase of the carbonic acid.
Andral and Gavarret finally sum up the results of their investigations as follows:1. The quantity of carbonic acid exhaled from the lungs in a
given time varies with the age, the sex, and the constitution of the
subject.
2. In the male, as well as in the female, the quantity of carbonic
acid varies according to the age; and that independently of the
weight of the individual subjected to experiment.
3. During all the periods of life, from that of eight years up to
the most advanced age, the male and female may be distinguished
by the different quantities of carbonic acid which they exhale in a
given time. Other things being equal, the male exhales always a
larger quantity than the female. This difference is particularly
marked between the ages of 16 and 40 years, during which period
the male usually exhales twice as much carbonic acid as the female.
4. In the male, the quantity of carbonic acid increases constantly
from eight to thirty years; and the rate of this increase undergoes
a rapid augmentation at the period of puberty.  Beyond thirty
years the exhalation of carbonic acid begins to decrease, and its
diminution is more marked as the individual approaches extreme
old age; so that near the termination of life, the quantity of carbonic
acid produced may be no greater than at the age of ten years.
5. In the female, the exhalation of carbonic acid increases according to the same law as in the male, from  the age of eight years
until puberty.  But at the period of puberty, at the same time with
the appearance of menstruation, the exhalation of carbonic acid,




234                       RESPIRATION.
contrary to what happens in the male, ceases to increase; and it
afterward remains stationary so long as the menstrual periods recur
with regularity.. At the cessation of the menses, the quantity of
carbonic acid exhaled increases in a notable manner; then it decreases again, as in the male, as the woman advances toward old age.
6. During the whole period of pregnancy, the exhalation of carbonic acid rises, for the time, to the same standard as in women
whose menses have ceased.
7. In both sexes, and at all ages, the quantity of carbonic acid is
greater as the constitution is stronger, and the muscular system
more fully developed.
Prof. Scharling, in a similar series of investigations' found that
the quantity of carbonic acid exhaled was greater during the digestion of food than in the fasting condition. It is greater, also, in the
waking state than during sleep; and in a state of activity than in
one of quietude.  It is diminished, also, by fatigue, and by most
conditions which interfere with perfect health.
The process of respiration is not altogether confined to the lungs,
but the interchange of gases takes place, also, to some extent through
the skin.  It has been found, by inclosing one of the limbs in an
air-tight case, that the air in which it is confined loses oxygen and
gains in carbonic acid. By an experiment of this sort, performed by
Prof. Scharling,2 it was ascertained that the carbonic acid given off
from the whole cutaneous surface, in the human subject, is from
one-sixtieth to one-thirtieth of that discharged during the same
period from  the lungs.  In the true amphibious animals, that is,
those which breathe by lungs, and can yet remain under water for
an indefinite period without injury (as frogs and salamanders), the
respiratory function of the skin is very active. In these animals,
the integument is very vascular, moist, and flexible; and is covered,
not with dry cuticle, but with a very thin and delicate layer of
epithelium. It, therefore, presents all the conditions necessary for
the accomplishment of respiration; and while the animal remains
beneath the surface, and the lungs are in a state of inactivity, the
exhalation and absorption of gases continue to take place through
the skin, and the process of respiration goes on in a nearly uninterrupted manner.
I Annales de Chimie et de Pharmacie, vol. viii. p. 490.
2 In Carpenter's Human Physiology, Philada. ed, 1855, p. 308.




ANIMAL HEAT.                       235
CHAPTER XIII.
ANIMAL HEAT.
ONE of the most important phenomena presented by animals and
vegetables is the property which they possess of maintaining, more
or less constantly, a standard temperature, notwithstanding the
external vicissitudes of heat and cold to which they may be subjected. If a bar of iron, or a jar of water, be heated up to 1000 or
2000 F., and then exposed to the air at 50~ or 600, it will immediately begin to lose heat by radiation and conduction; and this
loss of heat will steadily continue, until, after a certain time, the
temperature of the heated body has become reduced to that of the
surrounding atmosphere. It then remains stationary at this point,
unless the temperature of the atmosphere should happen to rise or
fall: in which case, a similar change takes place in the inorganic
body, its temperature remaining constant, or varying with that of
the surrounding medium.
With living animals, the case is different. If a thermometer be
introduced into the stomach of a dog, or placed under the tongue
of the human subject, it will indicate a temperature of 100~ F., very
nearly, whatever may be the condition of the surrounding atmosphere at the time. This internal temperature is the same in summer and in winter. If the individual upon whom the experiment
has been tried be afterward exposed to a cold of zero, or even of 20~
or 30~ below zero, the thermometer introduced into the interior of
the body will still stand at 100~ F. As the body, during the whole
period of its exposure, must have been losing heat by radiation and
conduction, like any inorganic mass, and has, notwithstanding, maintained a constant temperature, it is plain that a certain amount of
heat has been generated in the interior of the body by means of the
vital processes, sufficient to compensate for the external loss. The
internal heat, so produced, is known by the name of vital or animal
heat.
There are two classes of animals in which the production of vital




236                     ANIMAL HEAT.
heat takes place with such activity that their blood and internal
organs are nearly always very much above the external temperature; and which are therefore called "warm-blooded animals."
These are mammalia and birds.  Among the birds, some species,
as the gull, have a temperature as low as 1000 F.; but in most of
them, it is higher, sometimes reaching as high as 110~ or 111~. In
the mammalians, to which class man belongs, the animal temperature is never far from 1000. In the seal and the Greenland whale,
it has been found to be 104~; and in the porpoise, which is an airbreathing animal, 990.5. In the human subject it is 98~ to 100~.
When the temperature of the air is below this, the external parts
of the body, being most exposed to the cooling influences of radiation and conduction, fall a little below the standard, and may indicate a temperature of 97~, or even several degrees below this point.
Thus, on a very cold day, the thinner and more exposed parts, such
as the nose, the ears, and the ends of the fingers, may become
cooled down considerably below the standard temperature, and may
even be congealed, if the cold be severe; but the temperature of
the internal organs and of the blood still remains the same under
all ordinary exposures.
If the cold be so intense and long continued as to affect the
general temperature of the blood, it at once becomes fatal. It has
been found that although a warm-blooded animal usually preserves
its natural temperature when exposed to external cold, yet if the
actual temperature of the blood become reduced by any means
more than 50 or 6~ below its natural standard, death inevitably
results. The animal, under these circumstances, gradually becomes
torpid and insensible, and all the vital operations finally cease.
Birds, accordingly, whose natural temperature is about 110~, die if
the blood be cooled down to 100~, which is the natural temperature
of the mammalia; and the mammalians die if their blood be cooled
down below 94~ or 95~. Each of these different classes has therefore a natural temperature, at which the blood must be maintained
in order to sustain life; and even the different species of animals,
belonging to the same class, have each a specific temperature which
is characteristic of them, and which cannot be raised or lowered, to
any considerable extent, without producing death.
While in the birds and mammalians, however, the internal production of heat is so active, that their temperature is nearly always
considerably above that of the surrounding media, and suffers but
little variation; in reptiles and fish, on the other hand, its produc



ANIMAL HEAT.                            237
tion is much less rapid, and the temperature of their bodies differs
but little from that of the air or water which they inhabit. Birds
and mammalians are therefore called "warm-blooded," and reptiles
and fish "cold-blooded" animals.  There is, however, no other distinction between them, in this respect, than one of degree. In
reptiles and fish there is also an internal source of heat; only this
is not so active as in the other classes.  Even in these animals a
difference is usually found to exist between the temperature of their
bodies and that of the surrounding media.  John Hunter, Sir
Humphrey Davy, Czermak, and others,' have found the temperature
of Proteus anguinus to be 63~.5, when that of the air was 55~.4;
that of a frog 480, in water at 440.4; that of a serpent 88~.46, in
air at 81~.5; that of a tortoise 84~, in air at 79~.5; and that of fish
to be from 10.7 to 2~.5 above that of the surrounding water.
The following list2 shows the mean temperature belonging to
animals of different classes and species.
ANIMAL.                             MEAN TEMPERATURE.
F Swallow...                         1110.25
Heron....   1110.2
BIRDS.       Raven...                    1080.5
BIRDS. eon..
Pigeon.......         1070.6
Fowl...                            1060.7
L Gull......           1000.0
F Squirrel...   1050
Goat.....        1020.5
Cat...                            1010.3
Hare......      1000.4
MAMMALIA.    X...  990.5
Dog......    990.4
Man......                      980.6
L Ape......          950.9
REPTILE.     Toad.      510.6
Carp.......    510.25
F         Tench.......    520.10
In the invertebrate animals, as a general rule, the internal heat
is produced in too small quantity to be readily estimated. In some
of the more active kinds, however, such as insects and arachnida,
it is occasionally generated with such activity that it may be
appreciated by the thermometer.  Thus, the temperature of the
butterfly, when in a state of excitement, is from  50 to 90 above
I Simon's Chemistry of Man, Philadelphia edition, p. 124.
2 Ibid., pp. 123-126.




238                     ANIMAL HEAT.
that of the air; and that of the humble-bee from 30 to 100 higher
than the exterior. According to the experiments of Mr. Newport,'
the interior of a hive of bees may have a temperature of 48~.5,
when the external atmosphere is at 34~.5, even while the insects
are quiet; but if they be excited, by tapping on the outside of the
hive, it may rise to 102~. In all cases, while the insect is at rest,
the temperature is very moderate; but if kept in rapid motion in
a confined space, it may generate heat enough to affect the thermometer sensibly, in the course of a few minutes.
Even in vegetables a certin n degree of heat-producing power is
occasionally manifest. Usually, the exposed surface of a plant is
so extensive in proportion to its mass, that whatever caloric may
be generated is too rapidly lost by radiation and evaporation, to be
appreciated by ordinary means. Under some circumstances, however, it may accumulate to such an extent as to become readily
perceptible. In the process of malting, for example, when a large
quantity of germinating grain is piled together in a mass, its elevated temperature may be readily distinguished, both by the hand
and the thermometer. During the flowering process, also, an unusual evolution of heat takes place in plants. The flowers of the
geranium  have been found to have a temperature of 870, while
that of the air was 81~; and the thermometer, placed in the centre
of a clump of blossoms of arum cordifolium, has been seen to rise
to 1110, and even 121~, while the temperature of theexternal air
was only 660.2
Dutrochet has moreover found, by a series of very ingenious and
delicate experiments,3 that nearly all parts of a living plant generate a certain amount of heat. The proper heat of the plant is
usually so rapidly dissipated by the continuous evaporation of its
fluids, that it is mostly imperceptible by ordinary means; but if
this evaporation be prevented, by keeping the air charged with
watery vapor, the heat becomes sensible and can be appreciated by
a delicate thermometer. Dutrochet used for this purpose a thermoelectric apparatus, so constructed that an elevation of temperature
of 10 F., in the substances examined, would produce a deviation in
the needle of nearly nine degrees. By this means he found that he
could appreciate, without difficulty, the proper temperature of the
plant. A certain amount of heat was constantly generated, during
Carpenter's General and Comparative Physiology, Philadelphia, 1851, p. 852.
2 Carpenter's Gen. and Comp. Physiology, p. 846.
3 Annales des Sciences Naturelles, 2d series, xii. p. 277.




ANIMAL HEAT.                        239
the day, in the green stems, the leaves, the buds, and even the
roots and fruit. The maximum temperature of these parts, above
that of the surrounding atmosphere, was sometimes a little over
one-half a degree, Fahrenheit; though it was often considerably
less than this.
The different parts of the vegetable fabric, therefore, generate
different quantities of caloric. In the same manner, the heatproducing power is not equally active in different species of animals; but its existence is nevertheless common to both animals
and vegetables.
With regard to the mode of generation of this internal or vital
heat, we may start with the assertion that its production depends
upon changes of a chemical nature, and is so far to be regarded as
a chemical phenomenon. The sources of heat which we meet with
in external nature are of various kinds. Sometimes the heat is of
a physical origin; as, for example, that derived from the rays of
the sun, the friction of solid substances, or the passage of electric
currents. In other instances it is produced by chemical changes;
and the most abundant and useful source of artificial heat is the
oxidation, or combustion, of carbon and carbonaceous compounds.
Wood and coal, substances rich in carbon, are mostly used for this
purpose; and charcoal, which is nearly pure carbon, is frequently
employed by itself. These substances, when burnt, or oxidized,
evolve a large amount of heat; and produce, as the result of their
oxidation, carbonic acid. In order that the process may go on, it
is of course necessary that oxygen, or atmospheric air, should have
free access to the burning body; otherwise the combustion and
evolution of heat cease, for want of a necessary agent in the chemical combination. In all these instances, the quantity of heat generated is in direct proportion to the amount of oxidation; and may
be measured, either by the quantity of carbon consumed, or by that
of carbonic acid produced. It may be made to go on, also, either
rapidly or slowly, according to the abundance and purity in which
oxygen is supplied to the carbonaceous substance.  Thus, if charcoal be ignited in an atmosphere of pure oxygen, it burns rapidly
and violently, raises the temperature to a high point, and is soon
entirely consumed. On the other hand, if it be shut up in a close
stove, to which the air is admitted but slowly, it produces only a
slight elevation of temperature, and may require a much longer
time for its complete disappearance. Nevertheless, for the same
quantity of carbon consumed, the amount of heat generated, and




240                    ANIMAL HEAT.
that of carbonic acid produced, will be equal in the two cases. Tn
one instance we have a rapid combustion, in the other a slow cornbustion; the total effect being the same in both.
Such is the mode in which heat is commonly produced by artificial means. Its evolution is here dependent upon two principal
conditions, which are essential to it, and by which it is always
accompanied, viz., the consumption of oxygen, and the production
of carbonic acid.
Now, since the two phenomena just mentioned are presented
also by the living body, and since they are accompanied here, too,
by the production of animal heat, it was very natural to suppose
that in the animal organization, as well as elsewhere, the internal
heat must be owing to an oxidation or combustion of carbon. According to Lavoisier, the oxygen taken into the lungs was supposed to combine immediately with the carbon of the pulmonary
tissues and fluids, producing carbonic acid, and to be at once returned under that form to the atmosphere; the same quantity of
heat resulting from the above process as would have been produced
by the oxidation of a similar quantity of carbon in wood or coal.
Accordingly, he regarded the lungs as a sort of stove or furnace,
by which the rest of the body was warmed, through the medium of
the circulating blood.
It was soon found, however, that this view was altogether erroneous; for the slightest examination shows that the lungs are not
perceptibly warmer than the rest of the body; and that the heatproducing power, whatever it may be, does not reside exclusively
in the pulmonary tissue. Furthermore, subsequent investigations
showed the following very important facts, which we have already
mentioned, viz., that the carbonic acid is not formed in the lungs,
but exists in the blood before its arrival in the pulmonary capiliaries; and that the oxygen of the inspired air, so far from combining
with carbon in the lungs, is taken up in solution by the bloodglobules, and carried away by the current of the general circulation.
It is evident, therefore, that this oxidation or combustion of the
blood must take place, if at all, not in the lungs, but in the capillaries of the various organs and tissues of the body.
Liebig accordingly adopted Lavoisier's theory of the production
of animal heat, with the above modification. He believed the heat
of the animal body to be produced by the oxidation or combustion
of certain elements of the food while still circulating in the blood;
these substances being converted into carbonic acid and water by




ANIMAL HEAT.                        241
the oxidation of their carbon and hydrogen, and immediately expelled from the body without ever having formed a part of the solid
tissues. He therefore divided the food into two different classes of
alimentary substances; viz., 1st, the nitrogenous or plastic elements,
which are introduced in comparatively small quantity, and which
are to be actually converted into the substance of the tissues, such as
albumen, muscular flesh, &c.; and 2d, the hydro-carbons or respiratory
elements, such as sugar, starch, and fat; which, according to his view,
are taken into the blood solely to be burned, never being assimilated
or converted into the tissues, but only oxidized in the circulation,
and immediately expelled, as above, under the form of carbonic
acid and water. He- therefore regarded these elements of the food
only as so much fuel; destined simply to maintain the heat of the
body, but taking no part in the proper function of nutrition.
The above theory of animal heat has been very generally adopted
and acknowledged by the medical profession until within a recent
period. A few years ago, however, some of its deficiencies and
inconsistencies were pointed out, by Lehmann in Germany, and by
Robin and Verdeil in France; and since that time it has begun to
lose ground and give place to a different mode of explanation, more
in accordance with the present state of physiological science. We
believe it, in fact, to be altogether erroneous; and incapable of
explaining, in a satisfactory manner, the phenomena of animal heat,
as exhibited by the living body. We shall now proceed to pass in
review the principal objections to the theory of combustion, considered as a physiological doctrine.
1. It is not at all necessary to regard the evolution of heat as
dependent solely on direct oxidation. This is only one of its
sources, as we see constantly in external nature. The sun's rays,
mechanical friction, electric currents, and more particularly a great
variety of chemical actions, such as various saline combinations and
decompositions, are all capable of producing heat; and even simple
solutions, such as the solution of caustic potassa in water, the mixture
of sulphuric acid and water, or of alcohol and water, will often proluce a very sensible elevation of temperature. Now we know that
in the interior of the body a thousand different actions of this
nature are constantly going on; solutions, combinations and decompositions in endless variety, all of which, taken together, are amply
sufficient to account for the production of animal heat, provided the
theory of combustion should be found insufficient or improbable.
16




242                     ANIMAL HEAT.
II. In vegetables there is an internal production of heat, as well
as in animals; a fact which has been fully demonstrated by the
experiments of Dutrochet and others, already described. In vegetables, however, the absorption of oxygen and exhalation of carbonic acid do not take place; excepting, to some extent, during the
night. On the contrary, the diurnal process in vegetables, it is well
known, is exactly the reverse of this. Under the influence of the
solar light they absorb carbonic acid and exhale oxygen. And it
is exceedingly remarkable that, in Dutrochet's experiments, he
found that the evolution of heat by plants was always accompanied
by the disappearance of carbonic acid and the exhalation of oxygen.
Plants which, in the daylight, exhale oxygen and evolve heat, if
placed in the dark, immediately begin to absorb oxygen and exhale
carbonic acid; and, at the same time, the evolution of heat is suspended. Dutrochet even found that the evolution of heat by plants
presented a regular diurnal variation; and that its maximum of
intensity was about the middle of the day, just at the time when the
absorption of carbonic acid and the exhalation of oxygen are going on
with the greatest activity. The proper heat of plants, therefore, cannot be the result of oxidation or combustion, but must be dependent
on an entirely different process.
III. In animals. the quantities of oxygen absorbed and of carbonic
acid exhaled do not correspond with each other. Most fiequently
a certain amount of oxygen disappears in the body, over and above
that which is returned in the breath under the form of carbonic
acid. This overplus of oxygen has been said to unite with the
hydrogen of the food, so as to form water which also passes out
by the lungs; but this is a pure assumption, resting on no direct
evidence whatever, for we have no experimental proof that any
more watery vapor is exhaled from the lungs than is supplied by
the fluids taken into the stomach. It is superfluous, therefore, to
assume that any of it is produced by the oxidation of hydrogen.
Furthermore, the proportion of overplus oxygen which disappears in the body, beside that which is exhaled in the carbonic acid
of the breath, varies greatly in the same animal according to the
quality of the food. Regnault and Reiset' found that in dogs, fed
on meat, the oxygen which reappeared under the form of carbonic
acid was only 75 per cent. of the whole quantity absorbed; while
Annales de Chinie et de Physique, 3d series, xxvi. p. 428.




ANIMAL HEAT.                        243
in dogs fed on vegetable substances it amounted to over 90 per
cent. In some instances,' where the animals (rabbits and fowls)
were fed on bread and grain exclusively, the proportion of expired
oxygen amounted to 101 or even 102 per cent.; that is, more oxygen
was actually contained in the carbonic acid exhaled, than had been absorbed in afree statefrom the atmosphere.  A portion, at least, of the
carbonic acid must therefore have been produced by other means
than direct oxidation.
IV. It has already been shown, in a previous chapter, that the
carbonic acid which is exhaled from the lungs is not primarily
formed in the blood, but makes its appearance in the substance of
the tissues themselves; and furthermore, that even here it does not
originate by a direct oxidation, but rather by a process of decomposition, similar to that by which sugar, in fermentation, is resolved
into alcohol and carbonic acid. We understand from this how to
explain the singular fact alluded to in the last paragraph, viz., the
abundant production of carbonic acid, under some circumstances,
with a comparatively small supply of free oxygen. The statement
made by Liebig, therefore, that starchy and oily matters taken with
the food are immediately oxidized in the circulation without ever
being assimilated by the tissues, is without foundation. It never,
in fact, rested on any other ground than a supposed probability;
and as we see that carbonic acid is abundantly produced in the
body by other means, we have no longer any reason for assuming,
without direct evidence, the existence of a combustive process in
the blood.
V. The evolution of heat in the animal body is not general, as it
would be if it resulted from a combustion of the blood; but local,
since it takes place primarily in the substance of the tissues themselves. Various causes will therefore produce a local elevation or
depression of temperature, by modifying the nutritive changes
which take place in the tissues. Thus, in the celebrated experiment
of Bernard, which we have often verified, division of the sympathetic nerve in the middle of the neck produces very soon a marked
elevation of temperature in the corresponding side of the head and
face. Local inflammations, also, increase very sensibly the temperature of the part in which they are seated, while that of the general
I Annales de Chimie et de Physique, 3d series, xxvi. pp. 409-451.




244                     ANIMAL HEAT.
mass of the blood is not altered. Finally it has been demonstrated
by Bernard that in the natural state of the system there is a marked
difference in the temperature of the different organs and of the blood
returning from them.' The method adopted by this experimenter
was to introduce, in the living animal, the bulb of a fine thermometer successively into the bloodvessels entering and those leaving
the various internal organs. The difference of temperature in these
two situations showed whether the blood had lost or gained in heat
while traversing the capillaries of the organ. Bernard found, in
the first place, that the blood in passing through the lungs, so far
from increasing, was absolutely diminished in temperature; the
blood on the left side of the heart being sometimes a little more
and sometimes a little less than one-third of a degree Fahr. lower
than on the right side.  This slight cooling of the blood in the
lungs is owing simply to its exposure to the air through the pulmonary membrane, and to the vaporization of water which takes
place in these organs. In the abdominal viscera, on the contrary,
the blood is increased in temperature. It is sensibly warmer in the
portal vein than in the aorta; and very considerably warmer in the
hepatic vein than in either the portal or the vena cava. The blood
of the hepatic vein is in fact warmer than that of any other part
of the body. The production of heat, therefore, according to Bernard's observations, is more active in the liver than in any other
portion of the system. As the chemical processes of nutrition are
necessarily different in the different tissues and organs, it is easy to
understand why a specific amount of heat should be produced in
each of them.  A similar fact, it will be recollected, was noticed by
Dutrochet, in regard to the different parts of the vegetable organization.
VI. Animal heat has been supposed to stand in a special relation
to the production of carbonic acid, because in warm-blooded animals
the respiratory process is more active than in those of a lower
temperature; and because, in the same animal, an increase or
diminution in the evolution of heat is accompanied by a corresponding increase or diminution in the products of respiration. But
this is also true of all the other excretory products of the body. An
elevation of temperature is accompanied by an increased activity
of all the nutritive processes.  Not only carbonic acid, but the
i Gazette Hebdomadaire, Aug. 29 and Sept. 20, 1856.




ANIMAL HEAT.                        245
ingredients of the urine and the perspiration are discharged in larger
quantity than usual. An increased supply of food also is required,
as well as a larger quantity of oxygen; and the digestive and
secretory processes both go on, at the same time, with unusual
activity.
Animal heat, then, is a phenomenon which results from  the
simultaneous activity of many different processes, taking place in
many different organs, and dependent, undoubtedly, on different
chemical changes in each one. The introduction of oxygen and
the exhalation of carbonic acid have no direct connection with each
other, but are only the beginning and the end of a long series of
continuous changes, in which all the tissues of the body successively
take a part. Their relation is precisely that which exists between
the food introduced through the stomach, and the urinary ingredients eliminated by the kidneys. The tissues require for their
nutrition a constant supply of solid and liquid food which is introduced through the stomach, and of oxygen which is introduced
through the lungs. The disintegration and decomposition of the
tissues give rise, on the one hand, to urea, uric acid, &c., which are
discharged with the urine, and on the other hand to carbonic acid,
which is exhaled from the lungs. But the oxygen is not directly
converted into carbonic acid, any more than the food is directly
converted into urea and the urates.
Animal heat is not to be regarded, therefore, as the result of a
combustive process. There is no reason for believing that the
greater part of the food is "burned" in the circulation. It is, on
the contrary, assimilated by the substance of the tissues; and these,
in their subsequent disintegration, give rise to several excretory
products, one of which is carbonic acid.
The numerous cornbination's and decompositions which follow
each other incessantly during the nutritive process, result in the
production of an internal or vital heat, which is present in both
animals and vegetables, and which varies in amount in different
species, in the same individual at different times, and even in
different parts and organs of the same body.




246                   THE CIRCULATION.
CHAPTER XIV.
THE CIRCULATION.
THE blood may be regarded as a nutritious fluid, holding in
solution all the ingredients necessary for the formation of the
tissues. In some animals and vegetables, of the lowest organization,
such as infusoria, polypes, algae, and the like, neither blood nor
circulation is required; since all parts of the body, having a similar
structure, absorb nourishment equally from the surrounding media,
and carry on nearly or quite the same chemical processes of growth
and assimilation. In the higher animals and vegetables, however,
as well as in the human subject, the case is different. In them, the
structure of the body is compound. Different organs, with widely
different functions, are situated in different parts of the frame; and
each of these functions is more or less essential to the continued
existence of the whole.  In the intestine, for example, the process
of digestion takes place; and the prepared ingredients of the food
are thence absorbed into the bloodvessels, by which they are
transported to distant tissues and organs. In the lungs, again,
the blood absorbs oxygen which is afterward to be appropriated by
the tissues; and carbonic acid, which was produced in the tissues,
is exhaled from the lungs.  In the liver, the kidneys, and the skin,
other substances again are produced or eliminated, and these local
processes are all of them necessary to the preservation of the general
organization. The circulating fluid is therefore, in the higher
animals, a means of transportation, by which the substances produced in particular organs are dispersed throughout the body, or
by which substances produced generally in the tissues are conveyed
to particular organs, in order to be eliminated and expelled.
The circulatory apparatus consists of four different parts, viz:
1st. The heart; a hollow, muscular organ, which receives the blood
at one orifice and drives it out, in successive impulses, at another.
2d. The arteries; a series of branching tubes, which convey the
blood fiom the heart to the different tissues and organs of the body.




TIHE HEART.                         247
3d. The capillaries; a network of minute inosculating tubules,
which are interwoven with the substance of the tissues, and which
bring the blood into intimate contact with the cells and fibres of
which they are composed; and 4th. The veins; a set of converging vessels, destined to collect the blood from the capillaries, and
return it to the heart. In each of these four different parts of the
circulatory apparatus, the movement of the blood is peculiar and
dependent on special conditions. It will therefore require to be
studied in each one of themn separately.
THE HEART.
The structure of the heart, and of the large vessels connected
with it, varies considerably in different classes of animals, owing to
the different arrangement of the respiratory organs.  For the respiratory apparatus being one of the most important in the bodly, and
the one most closely connected
by anatomical relations with                  Fig. 76.
the organs of circulation, the
latter are necessarily modified
in structure to correspond with 
the former.  In fish, for exam- 
ple (Fig. 76), the heart is an
organ consisting of two principal cavities: an auricle (a) into
which the blood is received from
the central extremity of the
vena cava, and a ventricle (b)
into which the blood is driven
by the contraction of the auricle.
The ventricle is considerably
larger and more powerful than
the auricle, and by its contraction drives the blood into the
main artery supplying the gills.
In the gills (cc) the blood is
CIRCULATION OF Fisrr.-a. Auricle. b.
arterialized; after which it is  Ventricle. cc. Gills. d. Aorta. ee. Venmcavs.
collected by the branchial veins.
These veins unite upon the median line to form  the aorta (d) by
which the blood is finally distributed throughout the frame.  In




24S                   THE CIRCULATION.
these animals the respiratory process is not a very active one; but
the gills, which are of small size, being the only respiratory organs,
all the blood requires to pass through them for purposes of aeration.
The heart here is a single organ, destined only to drive the blood
from the termination of the venous system to the capillaries of the
gills.
In reptiles, the heart is composed of two auricles, placed side by
side, and one ventricle. (Fig. 77.) The vente cavse discharge their
blood into  the right auricle (a),
Fig. 77.           whence it passes into the ventricle
(c).  From the ventricle, a part of it
is carried into the aorta and distributed throughout the body, while a
part is sent to the lungs through the
pulmonary artery.  The arterialized
blood, returning from  the lungs by
the pulmonary vein, is discharged
into the left auricle (b), and thence
a  muh    into  the  ventricle  (c), where  it
mingles  with  the  venous  blood
which has just arrived by the venme
cavme.  In the reptile, therefore, the
ventricle is a common organ of propulsion, both for the lungs and for
the general circulation.  In these
CIRCUATtON OF REPTILES.-a.  animals the aeration of the blood in
Right auricle. b. Left auricle. c. Ventricle. the lungs is only partial; a certain
d. Lung~  e. Aorta.. f. Vena cava.
portion of the blood which leaves
the heart being carried to these organs, just as in the human subject,
it is only a portion of the blood which is carried to the kidney by
the renal artery. This arrangement is sufficient for the reptiles,
because in many of them, such as serpents and turtles, the lungs
are much more extensive and efficient, as respiratory organs, than
the gills of fish; while in others, such as frogs and water-lizards,
the integument itself, which is moist, smooth, and naked, takes an
important share in the aeration of the blood.
In  quadrupeds and the human species, however, the respiratory  process is not only exceedingly active, but the lungs
are, at the same time, the only organs in which the aeration of
the blood can be fully accomplished. In them, accordingly, we
find the two circulations, general and pulmonary, entirely dis



TIHE HEART.                        249
tinct from  each other. (Fig. 78.)  All the blood returning from
the body by the veins must pass through the lungs before it is
again distributed through the
arterial system.  We have                   Fig. 78.
therefore a double circulation, and also a double heart;
the  two  sides  of  which,
though  united  externally,
are separate internally. The
mammalian heart consists of          
a right auricle and ventricle
(a, b), receiving the blood
from  the vena cava (i), and                 t
driving it to the lungs; and
a left auricle and ventricle
(f, g) receiving the blood
from the lungs and driving
it outward through the arterial system.
In the complete or double   CIRCULATION IN MAtMAo IANS.-a. Right
mammalian heart, the differ-  auricle. b. Right ventricle. c. Pulmonary artery,.
Thetwvntred a Lungs. e. Pulmonary vein. f. Left auricle. g.
ent parts of the organ present  Left ventricle. h. Aorta i. Venaava.
certain peculiarities and bear
certain relations to each other, which it is necessary to understand
before we can properly appreciate its action and movements.  The
entire organ has a more or less conical form, its base being situated
on the median line, directed upward and backward; the whole being
suspended in the chest, and loosely' fixed to the spinal column, by
the great vessels which enter and leave it at this point. The apex,
on the contrary, is directed downward, forward, and to the left, surrounded by the pericardium and the pericardial fluid, but capable
of a very free lateral and rotatory motion. The auricles, which
have a smaller capacity and thinner walls than the ventricles, are
situated at the upper and posterior part of the organ (Figs. 79 and
80); while the ventricles occupy its anterior and lower portions.
The two ventricles, moreover, are not situated on the same plane,
but the right ventricle occupies a position somewhat in front and
above that of the left; so that in an anterior view of the heart the
greater portion of the left ventricle is concealed by the right (Fig.
79), and in a posterior view the greater portion of the right ventricle is concealed by the left (Fig. 80); while in both positions the




250                           THE CIRCULATION.
apex of the heart is constituted altogether by the point of the left
ventricle.
Fig. 79.                                      Fig. 80.
eQd
HUMAN H EA RT, anterior viewv-              H UM AN HEART, posterior view.a. Right ventricle. b. Left ventricle.      a. Right ventricle.  b Left ventricle.
c. Right auricle.  d. Left auricle. e.      c. Right auricle. d. Left auricle.
Pulmonary artery. f. Aorta.
The  different cavities  of the  heart and  of the  adjacent bloodvessels, though continuous with each other, are partially separated
by certain constrictions. These constricted orifices, by which the
different cavities  communicate, are  known  by  the  names of the
Fig. 81.
R I   T A u R IC L E A ND VENT R I C L E; Auriculo-ventricular Valves open, Arterial Valves closed.
auricular, auriculo-ventricular, and  aortic  and  pulmonary orifices;
the auricular orifices being  the passages from   the venae cavae and




THE HEART.                            251
pulmonary veins into the right and left auricles; the auriculoventricular orifices leading from the auricles into the ventricles;
and the aortic and pulmonary orifices leading from the ventricles
into the aortic and pulmonary arteries respectively.
The auriculo-ventricular, aortic and pulmonary orifices are furnished with valves, which allow the blood to pass readily from the
auricles to the ventricles, and from the ventricles to the arteries,
but shut back, with the contractions of the organ, so as to prevent
its return in an opposite direction.  The course of the blood
through the heart is, therefore, as follows. From the vena cava it
passes into the right auricle; and from  the right auricle into the
right ventricle. (Fig. 81.)  On the contraction of the right ventricle,
the tricuspid valves shut back, preventing its return into the auricle
(Fig. 82); and it is thus driven through the pulmonary artery to the
Fig. 82.
R   Jr T AU R  C L E A N D VENTRICLE; Auriculo-ventricular Valves closed, Arterial Valves open.
lungs.  Returning from the lungs, it enters the left auricle, thence
passes into the left ventricle, from which it is finally delivered into
the aorta, and distributed throughout the body. (Fig. 83.) This
movement of the blood, however, through the cardiac cavities, is
not a continuous and steady flow, but is accomplished by alternate
contractions and relaxations of the muscular parietes of the heart;
so that with every impulse, successive portions of blood are received
by the auricles, delivered into the ventricles, and by them  dis



252                    THE CIRCULATION.
charged into the arteries. Each one of these successive actions is
called a beat, or pulsation of the heart.
Fig. 83.
CO'RSE OF BLOOD THROUGH THE HEART.-a, a. Vena cava, superior and inferior.
b. Right ventricle c. Pulmonary artery d. Pulmonary vein. e. Left ventricle. f. Aorta.
Each pulsation of the heart is accompanied by certain important
phenomena, which require to be studied in detail.  These are the
sounds, the movements, and the impulse.
The sounds of the heart are two in number. They can readily be
heard by applying the ear over the cardiac region, when they are
found to be quite different from each other in position, in tone, and
in duration.  They are distinguished as the first and second sounds
of the heart.  The first sound is heard with the greatest intensity
over the anterior surface of the heart, and more particularly over
the fifth rib and the fifth intercostal space. It is long, dull, and
smothered in tone, and occupies one-half the entire duration of a
single beat.  It corresponds in time with the impulse of the heart
in the precordial region, and the stroke of the large arteries in the
immediate vicinity of the chest.  The second sound follows immediately upon the first. It is heard most distinctly at the situation
of the aortic and pulmonary valves, viz., over the sternum  at the
level of the third costal cartilage. It is short, sharp, and distinct
in tone, and occupies only about one-quarter of the whole time of




THE HEART.                          253
a pulsation.  It is followed by an equal interval of silence; after
which the first sound again recurs. The whole time of a cardiac
pulsation may then be divided into four quarters, of which the first
two are occupied by the first sound, the third by the second sound,
and the fourth by an interval of silence, as follows:i 1st quarter t 
I 2d   A   JFirst sound.
Time of pulsation. 3
3d   "    Second sound.
14th  "    Interval of silence.
The cause of the second sound is universally acknowledged to be
the sudden closure and tension of the aortic and pulmonary valves.
This fact is established by the following proofs: 1st, this sound is
heard with perfect distinctness, as we have already mentioned,
directly over the situation of the above-mentioned valves; 2d, the
farther we recede in any direction from this point, the fainter becomes the sound; and 3d, in experiments upon the living animal,
often repeated by different observers, it has been found that if a
curved needle be introduced into the base of the large vessels, so
as to hook back the semilunar valves, the second sound at once disappears, and remains absent until the valve is again liberated. These
valves consist of fibrous sheets, covered with a layer of endocardial
epithelium.  They have the form  of semilunar festoons, the free
edge of which is directed away from  the cavity of the ventricle,
while the attached edge is fastened to the inner surface of the base
of the artery. While the blood is passing from the ventricle to the
artery, these valves are thrown forward and relaxed; but when the
artery reacts upon its contents they shut back, and their fibres, becoming suddenly tense, yield a clear, characteristic, snapping sound.
The production of the first sound has been attributed by some
writers to a combination of various causes; such as the rush of
blood through the cardiac orifices, the muscular contraction of the
parietes of the heart, the tension of the auriculo-ventricular valves,
the collision of the particles of blood with each other and with the
surface of the ventricle, &c. &c. We believe, however, with Andry'
and some others, that the first sound of the heart has a similar
origin with the second; and that it is dependent altogether on the
closure of the auriculo-ventricular valves.  The reasons for this conclusion are the following:1st. The second sound is undoubtedly caused by the closure of
Diseases of the Heart, Knieeland's translation, Boston, 1846.




254                   THE CIRCULATION.
the semilunar valves, and in the action of the heart the shutting
back of the two sets of valves alternate with each other precisely
as do the first and second sounds; and there is every probability,
to say the least, that the sudden tension of the valvular fibres produces a similar effect in each instance.
2d. The first sound is heard most distinctly over the anterior
surface of the ventricles, where the tendinous cords supporting the
auriculo-ventricular valves are inserted, and where the sound produced by the tension of these valves would be most readily conducted to the ear.
3d. There is no reason to believe that the current of blood
through the cardiac orifices could give rise to an appreciable sound,
so long as these orifices, and the cavities to which they lead, have
their normal dimensions. An unnatural souffle may indeed originate from this cause when the orifices of the heart are diminished
in size, as by calcareous or fibrinous deposits; and it may also
occur in cases of aneurism.  A souffle may even be produced at
will in any one of the large arteries by pressing firmly upon it
with the end of a stethoscope, so as to diminish its calibre. But in
all these instances, the abnormal sound occurs only in consequence
of a disturbance in the natural relation existing between the volume
of the blood and the size of the orifice through which it passes.
In the healthy heart, the different orifices of the organ are in exact
proportion to the quantity of the circulating blood; and there is no
more reason for believing that its passage should give rise to a
sound in the cardiac cavities than in the larger arteries or veins.
4th. The difference in character between the two sounds of the
heart depends, in all probability, on the different arrangement of
the two sets of valves. The second sound is short, sharp, and distinct, because the semilunar valves are short and narrow, superficial
in their situation, and supported by the highly elastic, dense and
fibrous bases of the aortic and pulmonary arteries. The first sound
is dull and prolonged, because the auriculo-ventricular valves are
broad and deep-seated, and are attached, by their long chordae
tendineme to the comparatively soft and yielding fleshy columns of
the heart. The difference between the first and second sounds can,
in fact, be easily imitated, by simply snapping between the fingers
two pieces of tape or ribbon, of the same texture but of different
lengths. (Fig. 84.) The short one will give out a distinct and sharp
sound; the long one a comparatively dull and prolonged sound.
Together with the first sound of the heart there is also to be




THE HEART.                         255
heard a slight friction sovnd, produced by the collision of the point
of the heart against the parietes of the chest. This sound, which is
heard in the fifth intercostal space, is very faint, and is more or less
Fig. 84.
masked by the strong valvular sound which occurs at the same
time.  It is different, however, in character from  the latter, and
may usually be distinguished from it by careful examination.
The movements of the heart during the time of a pulsation are
of a peculiar character, and have been very often erroneously
described.  In fact altogether the best description of the move
ments of the heart which has yet appeared, is that given by William Harvey, in his celebrated work on the Motion of the Heart and
Blood, published in 1628. He examined the motion of the heart
by opening the chest of the living animal; and though the same or
similar experiments have been frequently performed since his time,
the descriptions given by subsequent observers have been for the
most part singularly inferior to his, both in clearness and fidelity.
The method which we have adopted for examining the motions of
the heart in the dog is as follows: The animal is first rendered
insensible by ether, or by the inoculation of woorara.  The latter
mode is preferable, since a long-continued etherization seems to
exert a sensibly depressing effect on the heart's action, which is
not the case with woorara.  The trachea is then exposed and
opened just4below the larynx, and the nozzle of a bellows inserted
and secured by ligature. Finally, the chest is opened on the median line, its two sides widely separated, so as to expose the heart
and lungs, the pericardium slit up and carefully cut away from its
attachments, and the lungs inflated by insufflation through the
trachea.  By keeping up a steady artificial respiration, the move



256                   THE CIRCULATION.
ments of the heart may be made to continue, in favorable cases, for
more than an hour; and its actions may be studied by direct observation, like those of any external organ.
The examination, however, requires to be conducted with certain
precautions, which are indispensable to success. When the heart
is first exposed, its movements are so complicated, and recur with
such rapidity, that it is difficult to distinguish them perfectly from
each other, and to avoid a certain degree of confusion. Singular
as it may seem, it is even difficult at first to determine what period
in the heart's pulsation corresponds to contraction, and what to
relaxation of the organ. Wie have even seen several medical men,
watching together the pulsations of the same heart, unable to agree
upon this point. It is very evident, indeed, that several English
and continental observers have mistaken, in their examinations, the
contraction for the relaxation, and the relaxation for the contraction. The first point, therefore, which it is necessary to decide, in
examining the successive movements of a cardiac pulsation, is the
following, viz: Which is the contraction and which the relaxation of
the ventricles?  The method which we have adopted is to pass a
small silver canula directly through the parietes of the left ventricle into its cavity. The blood is then driven from the external
orifice of the canula in interrupted jets; each jet indicating the
time at which the ventricle contracts upon  its contents. The
canula is then withdrawn, and the different muscular layers of the
ventricular walls, crossing each other obliquely, close the opening,
so that there is little or no subsequent hemorrhage.
When the successive actions of contraction and relaxation have
by this means been fairly recognized and distinguished from each
other, the cardiac pulsations are seen to be characterized by-the
following phenomena.  The changes in form  and position of the
entire heart are mainly dependent on those of the ventricles, which
contract simultaneously with each other, and which constitute much
the largest portion of the entire mass of the organ.
1. At the time of its contraction the heart hardens. This phenomenon is exceedingly well marked, and is easily appreciated by
placing the finger upon the ventricles, or by grasping them between
the finger and thumb. The muscular fibres become swollen and
indurated, and, if grasped by the hand, communicate the sensation
of a somewhat sudden and powerful shock. It is this forcible induration of the heart, at the time of contraction, which has been mistaken by some writers for an active dilatation, and described as




THE HEART.                         257
such. It is, however, a phenomenon precisely similar to that which
takes place in the contraction of a voluntary muscle, which becomes
swollen and indurated at the same moment and in the same proportion that it diminishes in length.
2. At the time of contraction, the ventricles elongate and the
point of the heart protrudes. This phenomenon was very well
described by Dr. Harvey.'':The heart," he says, "is erected, and
rises upward to a point, so that at this time it strikes against the
breast and the pulse is felt externally." The elongation of the
ventricles during contraction has, however, been frequently denied
by subsequent writers.  The only modern observers, so far as we
are aware, who have recognized its existence, are Drs. C. W. Pennock and Edward M. Moore, who performed a series of very careful
and interesting experiments on the action of the heart, in Philadelphia, in the year 189.2 These experimenters operated upon calves,
sheep, and horses, by stunning the animal with a blow upon the
head, opening the chest, and keeping up artificial respiration.  They
observed an elongation of the ventricle at the time of contraction,
and were even able to measure its extent by applying a shoemaker's
rule to the heart while in active motion. We are able to corroborate
entirely the statement of these observers by the result of our own
experiments on dogs, rabbits, frogs, &c. The ventricular contraction is an active movement, the relaxation entirely a passive one.
When contraction occurs and a stream of blood is thrown out of
the ventricle, its sides approximate each other and its point elongates; so that the transverse diameter of the heart is diminished,
and its longitudinal diameter increased. This can be readily felt
by grasping the base of the heart and the origin of the large vessels
gently between the first and middle fingers, and allowing the end
of the thumb of the same hand to rest lightly upon its apex.
With every contraction the thumb is sensibly lifted and separated
from the fingers, by a somewhat forcible elevation of the point of
the heart.
The same thing can be seen, and even measured by the eye,
in the following manner: If the heart of the frog or even of any
small warm-blooded animal, as the rabbit, be rapidly removed from
the chest, it will continue to beat for some minutes afterward; and
when the rhythmical pulsations have finally ceased, contractions
Works of William Harvey, M. D. Sydenham ed., London, 1847, p. 21.
2 Philadelphia Medical Examiner, No. 44.
17




258                   THE CIRCULATION.
can still be readily excited by touching the heart with the point of
a steel needle.  If the heart be now held by its base between the
thumb and finger, with its point directed upward, it will be seen
to have a pyramidal or conical form, representing very nearly in
its outline an equilateral triangle (Fig. 85); its base, while in a
condition of rest, bulging out laterally, while the apex is comparatively obtuse.
Fig. 85.                          Fig. 86.
HEART OF FRO                / 
in a state of relaxation.                           H E A RT' O FR O G in contraction.
When the heart, held in this position, is touched with the point
of a needle (Fig. 86), it starts up, becomes instantly narrower and
longer, its sides approximating and its point rising to an acute
angle.  This contraction is immediately followed by a relaxation;
the point of the heart sinks down, and its sides again bulge outward.
Let us now see in what manner this change in the figure of the
ventricles during contraction is produced. If the muscular fibres
of the heart were arranged in the form of
Fig. 87.         simple loops, running parallel with the
axis of the organ, the contraction of these
fibres would merely have the effect of diminishing the size of the heart in every
direction.  This effect can be seen in the
accompanying hypothetical diagram (Fig.
87), where the white outline represents
such simple looped fibres in a state of relaxation, and the dotted internal line indiDiagram of SIMPLE LOOPED  cates the form which they would take in
FIBRES, in relaxation aid con- contraction.  In point of fact, however,
none of the muscular fibres of the heart
run parallel to its longitudinal axis. They are disposed, on the
contrary, in a direction partly spiral and partly circular. The most
superficial fibres start from the base of the ventricles, and pass




THE HEART.                           259
toward the apex, curling round the heart in such a manner as to
pass over its anterior surface in an obliquely spiral direction, from
above downward, and from right to left. (Fig. 88.)  They converge
toward the point of the heart, curlFig. 88.           ing round the centre of its apex, and
then, changing their direction, become deep-seated, run upward along
Fig. 89.
LEFT:VENTRICLE  OF
BULLOCK'S HEART, anteriorview,      BULLOCK'S HEART, shIowsh.wing the superficial muscular fibres.  ing the deep fibres.
the septum and internal surface of the ventricles, and terminate
in the columnae carnere, and in the inner border of the auriculoventricular ring.  The deepest layers of fibres, on the contrary, are
wrapped round the ventricles in a nearly circular direction (Fig.
89); their points of origin and attachment being still the auriculoventricular ring, and the points of the fleshy columns.  The entire
arrangement of the muscular bundles may be readily seen in a
heart which has been boiled for six or eight hours, so as to soften
the connecting areolar tissue, and enable the fibrous layers to be
easily separated from each other.
By far the greater part of the mass of the fibres have therefore
a circular instead of a longitudinal direction. When they contract,
their action tends to draw the lateral walls of the ventricles together,
and thus to diminish the transverse diameter of the heart; but as
each muscular fibre becomes thickened in direct proportion to its
contraction, their combined lateral swelling necessarily pushes out
the apex of the ventricle, and the heart elongates at the same time
that its sides are drawn together. This effect is illustrated in the
accompanying diagram  (Fig. 90), where the white lines show the
figure of the heart during relaxation, with the course of its circular




260                   THE CIRCULATION.
fibres, while the dotted line shows the narrowed and elongated
figure necessarily produced by their contraction. This phenomenon,
therefore, of the protrusion of the apex
Fig. 90.        of the heart at the time of contraction, is
not only fully established by observation,
_             fiebut is readily explained by the anatomical
structure of the organ.
~_____________         3. Simultaneously with the hardening
and elongation of the heart, its apex moves
uIpward i s  h     etslightly from left to right, and rotates also
upon its own axis in the same direction.
Both these movements result from  the
peculiar spiral arrangement of the cardiac
fibres.  If we refer again to the preceding
Diagram of C rcuAR FIBRa  diagrams, we shall see that, provided the
OF TrHE HEART, and their cont        -
traction.     a   e        fibres were arranged in simple longituditraltione. Its curvature is diminishedinexactproportiontotheextent
nal loops (Fig. 87), their contraction would
merely have the effect of drawing the point of the heart directly
upward in a straight line toward its base. On the other hand, if
they were arranged together in a circular direction (Fig. 90), the
apex would be simply protruded forward, also in a direct line,
without deviating or twisting either to the
Fig. 91.       right or to the left. But in point of fact,
the superficial fibres, as we have already
described, run spirally, and curling round
the point of the heart, turn inward toward
its base; so that if the apex of the organ be
viewed externally, it will be seen that the
superficial fibres converge toward its central point in curved lines, as in Fig. 91. It
is well known that every curved muscular
CONVEII.-N'G FIBRES OF
THE APEX OF TiHE HEART.  fibre, at the time of its shortening, necessarily approximates more or less to a straight
line. Its curvature is diminished in exact proportion to the extent
of its contraction; and if arranged in a spiral form, its contraction
tends in the same degree to untwist the spiral. During the contraction of the heart, therefore, its apex rotates on its own axis in
the direction indicated by the arrows in Fig. 91, viz., from left to
right anteriorly, and from right to left posteriorly. This produces
a twisting movement of the apex in the above direction, which is




TIHE HEART.                        261
very perceptible to the eye at every pulsation of the heart, when
exposed in the living animal.
4. The protrusion of the point of the heart at the time of contraction, together with its rotation upon its axis from left to right,
brings the apex of the organ in contact with the parietes of the
chest, and produces the shock or impulse of the heart, which is
readily perceptible externally, both to the eye and to the touch.
In the human subject, when in an erect position, the heart strikes
the chest in the fifth intercostal space, midway between the edge of
the sternum and a line drawn perpendicularly downward from the
left nipple. In a supine position of the body, the heart falls away
from the anterior parietes of the chest so much that the impulse may
disappear for the time altogether.  This alternate recession and
advance of the point of the heart, in relaxation and contraction,
is provided for by the anatomical arrangement of the pericardium,
and the existence of the pericardial fluid. As the heart plays backward and forward, the pericardial fluid constantly follows its
movements, receding as the heart advances, and advancing as the
heart recedes. It fulfils, in this respect, the same purpose as the
synovial fluid, and the folds of adipose tissue in the cavity of the
large articulations; and allows the cardiac movements to take place
to their full extent without disturbing or injuring in any way the
adjacent organs.
5. The rhythm of the heart's pulsations is peculiar and somewhat
complicated. Each pulsation is made up of a double series of contractions and relaxations. The two auricles contract together, and
afterward the two ventricles; and in each case the contraction is
immediately followed by a relaxation. The auricular contraction
is short and feeble, and occupies the first part of the time of a
pulsation. The ventricular contraction is longer and more powerful,
and occupies the latter part of the same period. Following the
ventricular contraction there comes a short interval of repose, after
which the auricular contraction again recurs. The auricular and
ventricular contractions, however, do not alternate so distinctly
with h  each other (like the strokes of the two pistons of a fire engine)
as we should be led to believe from the accounts which have been
given by some observers. On the contrary, they are connected and
continuous.  The contraction, which commences at the auricle, is
immediately propagated to the ventricle, and runs rapidly from the
base of the heart to its apex, very much in the manner of a peristaltic motion, except that it is more sudden and vigorous.




262                  THE CIRCULATION.
William Harvey, again, gives a better account of this part of the
heart's action than has been published by any subsequent writer.
The following exceedingly graphic and appropriate description,
taken from  his book, shows that he derived his knowledge, not
from any secondary or hypothetical sources, but from direct and
careful study of the phenomena in the living animal.
"First of all," he says,' "the auricle contracts, and in the course
of its contraction throws the blood (which it contains in ample
quantity as the head of the veins, the storehouse and cistern of the
blood) into the ventricle, which being filled, the heart raises itself
straightway, makes all its fibres tense, contracts the ventricles, and
performs a beat, by which beat it immediately sends the blood
supplied to it by the auricle, into the arteries; the right ventricle
sending its charge into the lungs by the vessel which is called vena
arteriosa, but which, in structure and function, and all things else,
is an artery; the left ventricle sending its charge into the aorta,
and through this by the arteries to the body at large.
"These two motions, one of the ventricles, another of the auricles,
take place consecutively, but in such a manner that there is a kind
of harmony or rhythm preserved between them, the two concurring
in such wise that but one motion is apparent, especially in the
warmer blooded animals, in which the movements in question are
rapid. Nor is this for any other reason than it is in a piece of
machinery, in which, though one wheel gives motion to another,
yet all the wheels seem  to move simultaneously; or in that
mechanical contrivance which is adapted to fire-arms, where the
trigger being touched, down comes the flint, strikes against the
steel, elicits a spark, which falling among the powder, it is ignited,
upon which the flame extends, enters the barrel, causes the explosion, propels the ball, and the mark is attained; all of which incidents, by reason of the celerity with which they happen, seem to
take place in the twinkling of an eye."
The above description indicates precisely the manner in which
the contraction of the ventricle follows successively and yet continuously upon that of the auricle. The entire action of the auricles
and ventricles during a pulsation is accordingly as follows: The
contraction begins, as we have already stated, at the auricle.
Thence it runs immediately forward to the apex of the heart. The
entire ventricle contracts vigorously, its walls harden, its apex'Op. cit., p. 31.




THE ARTERIES AND THE ARTERIAL CIRCULATION.  263
protrudes, strikes against the walls of the chest, and twists from
left to right, the auriculo-ventricular valves shut back, the first
sound is produced, and the blood is driven into the aorta and
pulmonary artery.  These phenomena occupy about one-half the
time of an entire pulsation.  Then the ventricle is immediately
relaxed, and a short period of repose ensues.  During this period
the blood flows in a steady stream  from  the large veins into the
auricle, and through the auriculo-ventricular orifice into the ventricle; filling the ventricle, by a kind of passive dilatation, about
two-thirds or three-quarters full. Then the auricle contracts with a
quick sharp motion, forces the last drop of blood into the ventricle,
distending it to its full capacity, and then the ventricular contraction
follows, as above described, driving the blood into the large arteries.
These movements of contraction and relaxation continue to alternate with each other, and form, by their recurrence, the successive
cardiac pulsations.
THE ARTERIES AND THE ARTERIAL CIRCULATION.
The arteries are a series of branching tubes which commence
with the aorta and ramify throughout the body, distributing the
blood to all the vascular organs.  They are composed of three
coats, viz: an internal homogeneous tunic, continuous with the
endocardium; a middle coat, composed of elastic and muscular
fibres; and an external or "cellular" coat, composed of condensed
layers of areolar tissue. The essential anatomical difference between the larger and the smaller arteries consists in the structure
of their middle coat. In the smaller arteries this coat is composed
exclusively of smooth muscular fibres, arranged in a circular manner around the vessel, like the circular fibres of the muscular coat
of the intestine.  In arteries of medium size the middle coat contains both muscular and elastic fibres; while in those of the largest
calibre it consists of elastic tissue alone. The large arteries, accordingly, possess a remarkable degree of elasticity and little or no
contractility; while the smaller are contractile, and but little or not
at all elastic.
It is found, by measuring the diameters of the successive arterial ramifications, that the combined area of all the branches given
off from  a trunk is somewhat greater than that of the original
vessel; and therefore that the combined area of all the small arteries must be considerably larger than that of the aorta, from which




264                   THE CIRCULATION.
the arterial system originates. As the blood, consequently, in its
passage from the heart outward, flows successively through larger
and larger spaces, the rapidity of its circulation must necessarily
be diminished, in the same proportion as it recedes from the heart.
It is driven rapidly through the larger trunks, more slowly through
those of medium size, and more slowly still as it approaches the
termination of the arterial system  and the commencement of the
capillaries.
The movement of the blood through the arteries is primarily caused
by the contractions of the heart; but is, at the same time, regulated
and modified by the elasticity of the vessels. The mode in which
the arterial circulation takes place is as follows. The arterial system is, as we have seen, a vast and connected ramification of tubular
canals, which may be regarded as a great vascular cavity, divided
and subdivided from within outward by the successive branching
of its vessels, but communicating freely with the heart and aorta
at one extremity, and with the capillary plexus at the other;
and this vascular system is filled everywhere with the circulating
fluid. At the time of the heart's contraction, the muscular walls of
the ventricle act powerfully upon its fluid contents. The auriculoventricular valves at the same time shutting back and preventing
the blood from regurgitating into the ventricle, it is forced out
through the aortic orifice. A charge of blood is therefore driven
into the arterial ramifications, distending their walls by the additional quantity of fluid forced into their cavities. When the ventricle immediately afterward relaxes, the active distending force is
removed; and the elastic arterial walls, reacting upon their contents,
would force the blood back again into the heart, were it not for the
semilunar valves, which shut together and close the aortic orifice.
The blood is therefore urged onward, under the pressure of the
arterial elasticity, into the capillary system. When the arteries
have thus again partially emptied themselves, and returned to their
original dimensions, they are again distended by another contraction
of the heart. In this manner a succession of impulses or distensions
are produced, which alternate with the reaction or subsidence of the
vessels, and which can be felt throughout the body, wherever the
arterial ramifications penetrate.  This phenomenon is known by
the name of the arterial pulse.
When the blood is thus driven by the cardiac pulsations into the
arteries, the vessels are not only distended laterally, but are elongated
as well as widened, and enlarged in every direction. Particularly




THE ARTERIES AND THE ARTERIAL CIRCULATION.  265
when the vessel takes a curved or serpentine course, its elongation
and the increase of its curvatures may be observed at every pulsation.  This may be seen, for example, in the temporal, or even
in the radial arteries, in emaciated persons. It is also very well
seen in the mesenteric arteries, when the abdomen is opened in the
living animal.  At every contraction of the heart the curves of
the artery on each side become more strongly pronounced. (Fig.
92.) The vessel even rises up partially out of its
bed, particularly where it runs over a bony sur-      Fig  2
face, as in the case of the radial artery.  In old
persons the curves of the vessels become permanently enlarged from frequent distension; and all
the arteries tend to assume, with the advance of
age, a more serpentine and even spiral course.
But the arterial pulse has certain other peculiarities which deserve a special notice. In the
first place, if we place one finger upon the chest
at the situation of the apex of the heart, and another upon the carotid artery at the middle of 
the neck, we can distinguish little or no difference
in time between the two impulses.  The disten-  Elongation and curvasion of the carotid seems to take place at the ture of an ARTERY IN
same instant with the contraction of the heart.
But if the second finger be placed upon the temporal artery, instead
of the carotid, there is a perceptible interval between the two beats.
The impulse of the temporal artery is felt a little later than that of
the heart. In the same way the pulse of the radial artery at the
wrist seems a little later than that of the carotid, and that of the
posterior tibial at the ankle joint a little later than that of the radial.
So that, the greater the distance from the heart at which the artery
is examined, the later is the pulsation perceived by the finger laid
upon the vessel.
But it has been conclusively shown, particularly by the investigations of M. Marey,l that this difference in time of the arterial
pulsations, in different parts of the body, is rather relative than
absolute.  By the contraction of the heart, the impulse is communicated at the same instant to all parts of the arterial system; but
the apparent difference between them, in this respect, depends upon
the fact, that, although all the arteries begin to be distended at the
I Dr. Brown-S6quard's Journal de Physiologie, April, 1859.




266                   THE CIRCULATION.
same moment, yet those nearest the heart are distended suddenly
and rapidly, while for those at a distance, the distension takes place
more slowly and gradually.  Thus the impulse given to the finger,
which marks the condition of maximum  distension of the vessel,
occurs a little later at a distance from the heart, than in immediate
proximity.
This modification of the arterial pulse is produced in the following way:The contraction of the left ventricle is a brusque, vigorous and
sudden motion. The charge of blood, thus driven into the arterial
system, meeting with a certain amount of resistance from the fluid
already filling the vessels, does not instantly displace and force
onward a quantity of blood equal to its own mass, but a large
proportion of its force is used in expanding the distensible walls
of'the vessels.  In the immediate neighborhood, therefore, the
expansion of the arteries is sudden and momentary, like the contraction of the heart itself. But this expansion requires for its
completion a certain expenditure, both of force and time; so that
at a little distance farther on, the vessel will neither be distended
to the same degree nor with the same rapidity. At the more distant point, accordingly, the arterial impulse will be less powerful
and will arrive at its maximum more slowly.
On the other hand, when the heart becomes relaxed, the artery
in its immediate neighborhood contracts upon the blood by its own
elasticity; and as its contraction at this time meets with no other
resistance than that of the blood in the smaller vessels beyond, it
drives a portion of its own blood into them, and thus supplies these
vessels with a certain degree of distending force even in the intervals of the heart's action. Thus the difference in size of the carotid
artery, at the two periods of the heart's contraction and its relaxation, is very marked; for the degree of its distension is great when
the heart contracts, and its own reaction afterward empties it of
blood to a very considerable extent. But in the small branches of
the radial or ulnar artery, there is less distension at the time of the
cardiac contraction, because this force has been partly expended in
overcoming the elasticity of the larger vessels; and there is less
emptying of the vessel afterward, because it is still kept partially
filled by the reaction of the aorta and its larger branches. In other
words, there is progressively less variation in size, at the periods of
distension and collapse, for the smaller and distant arteries than for
those which are larger and nearer the heart.




THE ARTERIES AND THE ARTERIAL CIRCULATION. 267
Mr. Marey has illustrated these facts by an exceedingly ingenious
and effectual contrivance. He attached to the pipe of a small forcing
pump, to be worked by alternate strokes of the piston, a long elastic
tube open at the farther extremity. At different points upon this
tube there rested little movable levers, which were raised by the
distension of the tube whenever water was driven into it by the
forcing pump. Each lever carried upon its extremity a small pencil, which marked upon a strip of paper, revolving with uniform
rapidity, the lines produced by its alternate elevation and depression.
By these curves, therefore, both the extent and rapidity of distension
of different parts of the elastic tube were accurately registered.
The curves thus produced were as follows:Fig. 93.
CURVES OF THE ARTERIAL PULSATION, as illustrated by M. Marey's experiment.-1. Near
the distending force.  2 At a distance from it.  3. Still farther removed.
It will be seen that the whole time of pulsation is everywhere of
equlal length, and that the distension everywhere begins at the same
moment.  But at the beginning of the tube the expansion is wide
and sudden, and occupies only a sixth part of the entire pulsation,
while all the rest is taken up by a slow reaction. At the more
remote points, however, the period of expansion becomes longer
and that of collapse shorter; until at 3 the two periods are completely equalized, and the amount of expansion is at the same time
reduced one-half. Thus, the farther the blood passes from the heart
outward, the more uniform is its flow, and the more moderate the
distension of the arteries.
Owing to the alternating contractions and relaxations of the heart,
accordingly, the blood passes through the arteries, not in a steady
stream, but in a series of welling impulses; and the hemorrhage
from  a wounded artery is readily distinguished from  venous or
capillary hemorrhage by the fact that the blood flows in successive
jets, as well as more rapidly and abundantly. If a puncture be
made in the walls of the ventricle, and a slender canula introduced,




268                   THE CIRCULATION.
the flow of the blood through it is seen to be entirely intermittent.
A strong jet takes place at each ventricular contraction, and at each
relaxation the flow is completely interrupted. If the puncture be
made, however, in any of the large arteries near the heart, the flow
of blood through the orifice is no longer intermittent, but is continuous; only it is very much stronger at the time of ventricular
contraction, and diminishes, though it does not entirely cease, at
the time of relaxation. If the blood were driven through a series
of perfectly rigid and unyielding tubes, its flow would be everywhere intermittent; and it would be delivered from an orifice situated at any point, in perfectly interrupted jets. But the arteries
are yielding and elastic; and this elasticity, as we have already
explained, moderates the force of the separate arterial pulsations,
and gradually fuses them  with each other.  The interrupted or
pulsating character of the arterial current, therefore, which is
strongly pronounced in the immediate vicinity of the heart, becomes
gradually lost and equalized, during its passage through the vessels,
until in the smallest arteries it is nearly imperceptible.
The same effect of an elastic medium in equalizing the force of
an interrupted current may be shown by fitting to the end of a
common syringe a long glass or metallic tube.  Whatever be the
length of the inelastic tubing, the water which is thrown into one
extremity of it by the syringe will be delivered from the other end
in distinct jets, corresponding with the strokes of the piston; but if
the metallic tube be replaced by one of India rubber, of sufficient
length, the elasticity of this substance merges the force of the separate impulses into each other, and the water is driven out from the
farther extremity in a continuous stream.
The elasticity of the arteries, however, never entirely equalizes
the force of the separate cardiac pulsations, since a pulsating character can be seen in the flow of the blood through even the smallest
arteries, under the microscope; but this pulsating character diminishes very considerably from the heart outward, and the current
becomes much more continuous in the smaller vessels than in the
larger.
The primary cause, therefore, of the motion of the blood in the
arteries is the contraction of the ventricles, which, by driving out
the blood in interrupted impulses, distends at every stroke the
whole arterial system.  But the arterial pulse is not exactly synchronous everywhere with the beat of the heart; since a certain
amount of time is required to propagate the blood-wave from the




THE ARTERIES AND THE ARTERIAL CIRCULATION.  269
centre of the circulation outward. The pulse of the radial artery
at the wrist is perceptibly later than that of the heart; and the
pulse of the posterior tibial at the ankle, again, perceptibly later
than that at the wrist.  The arterial circulation, accordingly, is not
an entirely simple phenomenon; but is made up of the combined
effects of two different physical forces. In the first place, there is
the elasticity of the entire arterial system, by which the blood is
subjected to a constant and uniform pressure, quite independent of
the action of the heart.  Secondly, there is the alternating contraction and relaxation of the heart, by which the blood is driven in
rapid and successive impulses from the centre of the circulation, to
be thence distributed throughout the body.
The passage of the blood through the arterial system takes place
under a certain degree of constant pressure. For these vessels being
everywhere elastic, and filled with blood, they constantly tend to
react, more or less vigorously, and to compress the circulating fluid
which they contain.  If any one of the arteries, accordingly, be
opened in the living animal, and a glass tube inserted, the blood
will immediately be seen to rise in the tube to a height of about
five and a half or six feet, and will remain at that level; thus indicating the pressure to which it was subjected in the interior of the
vessels. This constant pressure, which is thus due to the reaction
of the entire arterial system, is known as the arterial pressure.
The degree of arterial pressure may be easily measured by connecting the open artery, by a flexible tube, with a small reservoir
of mercury, which is provided with a narrow upright glass tube,
open at its upper extremity.  When the blood, therefore, urged by
the reaction of the arterial walls, presses upon the surface of the
mercury in the receiver, the mercury rises in the upright tube, to
a corresponding height. By the use of this instrument it is seen,
in the first place, that the arterial pressure is nearly the same all
over the body.  Since the cavity of the arterial system  is everywhere continuous, the pressure must necessarily be communicated,
by the blood in its interior, equally in all directions. Accordingly,
the constant pressure is the same, or nearly so, in the larger and the
smaller arteries, in those nearest the heart, and those at a distance.
This constant pressure averages, in the higher quadrupeds, six
inches of mercury, which is equivalent to from five and a half to
six feet of blood.
It is also seen, however, in employing such an instrument, that
the level of the mercury, in the upright tube, is not perfectly steady,




270                   THE CIRCULATION.
but rises and falls with the pulsations of the heart. Thus, at every
contraction of the ventricle, the mercury rises for about half an
inch, and at every relaxation it falls to its previous level. Thus the
instrument becomes a measure, not only for the constant pressure of
the arteries, but also for the intermitting pressure of the heart; and
on that account it has received the name of the cardiometer. It is
seen, accordingly, that each contraction of the heart is superior in
force to the reaction of the arteries by about one-twelfth; and these
vessels are kept filled by a succession of cardiac pulsations, and
discharge their contents in turn into the capillaries, by their own
elastic reaction.
The rapidity with which the blood circulates through the arterial
system is very great. Its velocity is greatest in the immediate
neighborhood of the heart, and diminishes somewhat as the blood
recedes farther and farther from the centre of the circulation. This
diminution in the rapidity of the arterial current is due to the successive division of the aorta and its primary branches into smaller
and smaller ramifications, by which the total calibre of the arterial
system, as we have already mentioned, is somewhat increased. The
blood, therefore, flowing through a larger space as it passes outward,
necessarily goes more slowly.  At the same time the increased
extent of the arterial parietes with which the blood comes in contact, as well as the mechanical obstacle arising from the division of
the vessels and the separation of the streams, undoubtedly contribute more or less to retard the currents. The mechanical obstacle,
however, arising from the friction of the blood against the walls of
the vessels, which would be very serious in the case of water or any
similar fluid flowing through glass or metallic tubes, has comparatively little effect on the rapidity of the arterial circulation. This
can readily be seen by microscopic examination of any transparent
and vascular tissue. The internal surface of the arteries is so smooth
and yielding, and the consistency of the circulating fluid so accurately adapted to that of the vessels which contain it, that the
retarding effects of friction are reduced to a minimum, and the
blood in flowing through the vessels meets with the least possible
resistance.
It is owing to this fact that the arterial circulation, though somewhat slower toward the periphery than near the heart, yet retains
a very remarkable velocity throughout; and even in arteries of the
minutest size it is so rapid that the shape of the blood-globules cannot be distinguished in it on microscopic examination, but only a




THE ARTERIES AND THE ARTERIAL CIRCULATION.  271
mingled current shooting forward with increased velocity at every
cardiac pulsation. Volkmann, in Germany, has determined, by a
very ingenious contrivance, the velocity of the current of blood in
some of the large sized arteries in dogs, horses, and calves. The
instrument which he employed (Fig. 94) consisted of a metallic
cylinder (a), with a perforation running from end to end, and corresponding in size with the artery to be examined. The artery was
then divided transversely, and its cardiac extremity fastened to the
upper end (b) of the instrument, while its peripheral extremity was
Fig. 94.                       Fig. 95.
VOL KMANN' S APPARAT US for measuring tle rapidity of the arterial circulation.
fastened in the same manner to the lower end (c). The blood
accordingly still kept on its usual course; only passing for a short
distance through the artificial tube (a), between the divided extremities of the artery. The instrument, however, was provided, as shown
in the accompanying figures, with two transverse cylindrical plugs,
also perforated; and arranged in such a manner, that when, at a




272                   THE CIRCULATION.
given signal, the two plugs were suddenly turned in opposite
directions, the stream of blood would be turned out of its course
(Fig. 95), and made to traverse a long bent tube of glass (d, d, d),
before again finding its way back to the lower portion of the artery.
In this way the distance passed over by the blood in a given time
could be readily measured upon a scale attached to the side of the
glass tube. Volkmann found, as the average result of his observations, that the blood moves in the carotid arteries of warm-blooded
quadrupeds with a velocity of 12 inches per second.
VENOUS CIRCULATION.
The veins, which collect the blood from the tissues and return it
to the heart, are composed, like the arteries, of three coats; an inner,
middle, and exterior.  In structure, they differ from the arteries in
containing a much smaller quantity of muscular and elastic fibres,
and a larger proportion of simple condensed areolar tissue. They
are consequently more flaccid and compressible than the arteries,
and less elastic and contractile.  They are furthermore distinguished, throughout the limbs, neck, and external portions of the
head and trunk, by being provided with valves, consisting of fibrous
sheets arranged in the form of festoons, and so placed in the cavity
of the vein as to allow the blood to pass readily from the periphery
toward the heart, while they prevent altogether its reflux in an
opposite direction.
Although the veins are provided with walls which are very much
thinner and less elastic than those of the arteries, yet, contrary to
what we might expect, their capacity for resistance to pressure is
equal, or even superior, to that of the arterial tubes.  Milne Ed
wards' has collected the results of various experiments, which show
that the veins will sometimes resist a pressure which is sufficient to
rupture the walls of the arteries. In one instance the jugular vein
supported, without breaking, a pressure equal to a column of water
148 feet in height; and in another, the iliac vein of a sheep resisted
a pressure of more than four atmospheres.  The portal vein was
found capable of resisting a pressure of six atmospheres; and in
one case, in which the aorta of a sheep was ruptured by a pressure
of 158 pounds, the vena cava of the same animal supported a pressure equal to 176 pounds.
Legons sur la Physiologie, &(.. vol. iv. p. 301.




VENOUS CIRCULATION.                      273
This resistance of the veins is to be attributed to the large proportion of white fibrous tissue which enters into their composition;
the same tissue which forms nearly the whole of the tendons and
fasciae, and which is distinguished by its density and unyielding
nature.
The elasticity of the veins, however, is much less than that of the
arteries. When they are filled with blood, they enlarge to a certain
size, and collapse again when the pressure is taken off; but they do
not react by virtue of an elastic resilience, or, at least, only to a
slight extent, as compared with the arteries. Accordingly, when
the arteries are cut across, as we know, and emptied of blood, they
still remain open and pervious, retaining the tubular form, on account of the elasticity of their walls; while, if the veins be.treated
in the same way, their sides simply fall together and remain in contact with each other.
Another peculiarity of the venous system  is the abundance of
the separate chiannels, which it affords, for the flow of blood from
the periphery towards the centre.  The arteries pass directly from
the heart outward, each separate branch, as a general rule, going
to a separate region, and supplying that part of the body with
all the blood which it requires; so that the arterial system is kept
constantly filled to its entire capacity with the blood which passes
through it.  But that is not the case with the veins. Ininjected
preparations of the vascular system, we have often two, three,
four, or even five veins, coming together from  the same region of
the body. There are also abundant inosculations between the different veins. The deep veins which accompany the brachial artery
inosculate freely with each other, and also with the superficial veins
of the arm. In the veins coming from the head, we have the external jugular communicating with the thyroid veins, the anterior
jugular, and the brachial veins. The external and internal jugulars
communicate with each other, and the two thyroid veins also form
an abundant plexus in front of the trachea.
Thus the blood, coming from the extremities toward the heart,
flows, not in a single channel, but in many channels; and as these
channels communicate freely with each other, the blood passes sometimes through one of them, and sometimes through another.
The flow of blood through the veins is less powerful and regular
than that through the arteries.  It depends on the combined action
of three different forces.
IS




274                   THE CIRCULATION.
1. Theforce of aspiration of the thorax.-When the chest expands,
by the lifting of the ribs and the descent of the diaphragm, its
movement, of course, tends to diminish the pressure exerted upon
its contents, and so has the effect of drawing into the thoracic cavity
all the fluids which can gain access to it. The expanded cavity is
principally filled by the air, which passes in through the trachea
and fills the bronchial tubes and pulmonary vesicles. But the
blood in the veins is also drawn, into the chest at the same time and
by the same force. This force of aspiration, exerted by the expansion of the chest, is gentle and uniform in character, like the movements of respiration themselves. Accordingly its influence is extended, without doubt, to. the farthest extremities of the venous
system, the blood being gently solicited toward the heart, at each
expansion of. the chest, without any visible alteration in the size of
the veins, which are filled up from behind as fast as they are emptied
in front.
But if the movement:of inspiration be sudden and violent, instead
of gentle and easy, a different effect is produced. For then the walls
of the veins, which are thin and flaccid, cannot retain their position,
but collapse under the external pressure too rapidly to allow the
blood to flow in from behind. In this case, therefore, the vein is;
simply emptied in the immediate neighborhood of the chest, but
the entire venous circulation is not assisted by the movement.
The same difference in the effect of an easy and a violent suction
movement, may be readily shown by attaching to the nozzle of an
air-tight syringe a flexible elastic tube with thin walls, and placing
the other extremity of the tube under water. If the piston of the
syringe be now withdrawn with a gentle and gradual motion, the
water will be readily drawn up into the tube, while the tube itself
suffers no visible change; but if the suction movement be made
rapid and violent, the tube will collapse instantly under the pressure of the air, and will fail to draw the water into, its cavity.
A similar effect shows itself in the living body. If the jugular
or subclavian vein be exposed in a dog or cat, it will be seen that
while the movements of respiration are natural and easy no fluctuation in the vein can be perceived'. But as soon as the respiration becomes disturbed and laborious, then at each inspiration the
vein is collapsed and emptied; while during expiration, the chest
being strongly compressed and the inward flow of the blood arrested,
the vein becomes turgid with blood which accumulates in it from
behind. In young children, also, the spasmodic movements of res



VENOUS CIRCULATION.                      275
piration in crying produce a similar turgescence and engorgement
of the large veins during expiration, while they are momentarily
emptied during the hurried and forcible inspiration.
In natural and quiet respiration, therefore, the movements of the
chest hasten and assist the venous circulation; but in forced or.
laborious respiration, they do not assist and may even retard its flow.
2. The contraction of the voluntary muscles.-The veins which
convey the blood through the limbs, and the parietes of the head
and trunk, lie among voluntary muscles, which are more or less
constantly in a state of alternate contraction and relaxation. At
every contraction these muscles become swollen laterally, and, of
course, compress the veins which are situated between them.  The
blood, driven out from the vein by this pressure, cannot regurgitate
toward the capillaries, owing to the valves, already described, which
shut back and prevent its reflux. It is accordingly forced onward
toward the heart; and when the muscle relaxes and the vein is
liberated from pressure, it again fills up from behind, and the circulation goes on as before.  This force is a very efficient one in
producing the venous circulation; since the voluntary muscles are
more or less active in every position of the body, and the veins
constantly liable to be compressed by them. It is on this account
Fig. 96.                         Fig. 97.
VEIN with valves open.       V E IN with valves closed; stream of
blood passing off by a lateral channel.
that the veins, in the external parts of the body, communicate so
freely with each other by transverse branches; in order that the
current of blood, which is momentarily excluded from one vein by




276                   THE CIRCULATION.
the pressure of the muscles, may readily find a passage through
others, which colnmunicate by cross branches with the first. (Figs.
96 and 97.)
3. The force of the capillary circulation.-This last cause of the
motion of the blood through the veins is the most important of all,
as it is the only one which is constantly and universally active. In
fish, for example, respiration is performed altogether by gills; and
in reptiles the air is forced down into the lungs by a kind of deglutition, instead of being drawn in by the expansion of the chest. In
neither of these classes, therefore, can the movements of respiration
assist mechanically in the circulation of the blood. In the splanchnic cavities, again, of all the vertebrate animals, the veins coming
from the internal organs, as, for example, the cerebral, pulmonary,
portal, hepatic, and renal veins, are unprovided with valves; and
the passage of the blood through them cannot therefore be effected
by any lateral pressure. The circulation, however, constantly going
on in the capillaries, everywhere tends to crowd the radicles of the
veins with blood; and this vis a tergo, or pressure from behind, fills
the whole venous system  by a constant and steady accumulation.
So long, therefore, as the veins are relieved of blood at their cardiac
extremity by the regular pulsations of the heart, there is no backward pressure to oppose the impulse derived from the capillary circulation; and the movement of the blood through the veins continues
in a steady and u-niform course.
With regard to the rapidity of the venous circulation, no direct
results have been obtained by experiment. Owing to the flaccidity
of the venous parietes, and the readiness with which the flow of
blood through them is disturbed, it is not possible to determine this
point for the veins, in the same manner as it has been determined
for the arteries. The only calculation which has been made in this
respect is based upon a comparison of the total capacity of the
arterial and venous systems. As the same blood which passes outward through the arteries, passes inward again through the veins,
the rapidity of its flow in each must be in inverse proportion to the
capacity of the two sets of vessels. That is to say, a quantity of
blood which would pass in a given time, with a velocity of x,
through an opening equal to one square inch, would pass during
the same time through an opening equal to two square inches, with
a velocity of 2-; and would require, on the other hand, a velocity
of 2 x, to pass in the same time through an opening equal to onehalfa square inch. Now the capacity of the entire venous system,




THE CAPILLARY CIRCULATION.                    277
when distended by injection, is about twice as great as that of the
entire arterial system.  During life, however, the venous system is
at no time so completely filled with blood as is the case with the
arteries; and, making allowance for this difference, we find that the
entire quantity of venous blood is to the entire quantity of arterial
blood nearly as three to two.  The velocity of the venous blood,
as compared with that of the arterial, is therefore as two to three;
or about 8 inches per second. It will be understood, however, that
this calculation is altogether approximative, and not exact; since
the venous current varies, according to many different circumstances,
in different parts of the body; being slower near the capillaries,
and more rapid near the heart. It expresses, however, with sufficient accuracy, the relative velocity of the arterial and venous currents, at corresponding parts of their course.
THE CAPILLARY CIRCULATION.
The capillary bloodvessels are minute inosculating tubes, which
permeate the vascular organs in every direction, and bring the
blood into intimate contact with the substance of the tissues. They
are continuous with the terminal ramifications of the arteries on
the one hand, and with the commencing rootlets of the veins on               Fig. 98.
the other.  They vary somewhat
in size in different organs, and in
different species of animals; their
average diameter in the human
subject being a little over 3     mt of
an inch. They are composed of
a single, transparent, homogeneous, somewhat elastic, tubular
membrane, which is provided at
various intervals with flattened,
oval nuclei. As the smaller arteries approach the capillaries, they
diminish constantly in size by
successive subdivision, and lose   SM AL, T. A RTER Y, With its muscular tunic
(a) breaking up into capillaries. From the pia
first their external or fibrous  matter.
tunic. They are then composed
only of the internal or homogeneous coat, and the middle or muscular. (Fig. 98, a.)  The middle coat then diminishes in thickness,




278                   THE CIRCULATION.
until it is reduced to a single layer of circular, fusiform, unstriped,
muscular fibres, which in their turn disappear altogether, as the
artery merges at last in the capillaries; leaving only, as we have
already mentioned, a simple, homogeneous, nucleated, tubular membrane, which is continuous with the internal arterial tunic.
The capillaries are further distinguished from both arteries and
veins by their frequent inosculation.  The arteries constantly
divide and subdivide, as they pass from  within outward; while
the veins as constantly unite with each other to form  larger and
less numerous branches and trunks, as they pass from the circumference toward the centre.  But the capillaries simply inosculate
with each other in every direction, in such a manner as to form an
interlacing network or plexus, the capillary plexus (Fig. 99), which
is exceedingly rich and abundant in some organs, less so in others.
The spaces included between the meshes of the capillary network
vary also, in shape as well as in size, in different parts of the body.
In the muscular tissue they
Fig. 99.               form long parallelograms; in
the areolar tissue, irregular
shapeless figures, correspondand in t o   t e i ide   ing with the direction of the
fibrous bundles of which the
*R  "      tissue is composed.  In the
mucous membrane of the
large intestine, the capillaries
include hexagonal or nearly
11sufficie  dee  f         circular spaces, inclosing the
for. ts p e     orifices of the follicles. In
the papillie of the tongue and
of the skin, and in the tufts
CA P I L LA RY NETWORK from web of frog's foot.  of the  placenta, they are
arranged in long spiral loops,
and in the adipose tissue in wide meshes, among which the fat
vesicles are entangled.
The motion of the blood in the capillaries may be studied by
examining under the microscope any transparent tissue, of a
sufficient degree of vascularity.  One of the most convenient parts
for this purpose is the web of the frog's foot.  When properly
prepared and kept moistened by the occasional addition of water
to the integument, the circulation will go on in its vessels for an
indefinite length of time.  The blood can be seen entering the




THE CAPILLARY CIRCULATION.                   279
field by the smaller arteries, shooting along through them with
great rapidity and in successive impulses, and flowing offagain by
the veins at a somewhat slower rate. In the capillaries themselves
the circulation is considerably less rapid than in either the arteries
or the veins. It is also perfectly steady and uninterrupted in its
flow. The blood passes along in a uniform and continuous current,
without any apparent contraction or dilatation of the vessels, very
much as if it were flowing
Fig. 100.
through glass tubes.  An-                      
other very remarkable peculiarity  of the  capillary
circulation is that it has no
definite direction. The nuinerous streams of which it
is composed (Fig. 100) do
not tend to the right or to.r 
the left, nor toward any one
particular point.  On the
contrary, they pass above
and  below  each other, at
right angles to each other's
course, or even in opposite  CAPILLARY CIRCULATION in web of frog's foot.
directions; so that the blood,
while in the capillaries, merely circulates promiscuously among
the tissues, in such a manner as to come intimately in contact with
every part of their substance.
The motion of the white and red globules in the circulating blood
is also peculiar, and shows very distinctly the difference in their
consistency and other physical properties. In the larger vessels
the red globules are carried along in a dense column, in the central
part of the stream; while near the edges of the vessel there is a
transparent space occupied only by the clear plasma of the blood,
in which no red globules are to be seen. In the smaller vessels,
the globules pass along in a narrower column, two by two, or
following each other in single file. The flexibility and semi-fluid
consistency of these globules are here very apparent, from the
readiness with which they become folded up, bent or twisted in
turning corners, and the ease with which they glide through minute
branches of communication, smaller in diameter than themselves.
The white globules, on the other band, flow more slowly and with
greater difficulty through the vessels.  They drag along the exter



280                   THE CIRCULATION.
nal portions of the current, and are sometimes momentarily arrested;
apparently adhering for a few seconds to the internal surface of the
vessel. Whenever the current is obstructed or retarded in any
manner, the white globules accumulate in the affected portion, and
become more numerous there in proportion to the red.
It is during the capillary circulation that the blood serves for
the nutrition of the vascular organs.  Its fluid  portions slowly
transude through the walls of the vessels, and are absorbed by the
tissues in such proportion as is requisite for their nourishment.
The saline substances enter at once into the composition of the
surrounding parts, generally without undergoing any change. The
phosphate of lime, for example, is taken up in large quantity by
the bones and cartilages, and in smaller quantity by the softer parts;
while the chlorides of sodium and potassium, the carbonates, sulphates, &c., are appropriated in special proportions by the different
tissues, according to the quantity necessary for their organization.
The albuminous ingredients of the blood, on the other hand, are
not only absorbed in a similar manner by the animal tissues, but at
the same time are transformed by catalysis, and converted into new
materials, characteristic of the different tissues. In this way are
produced the musculine of the muscles, the osteine of the bones, the
cartilagine of the cartilages, &c. &c. It is probable that this transformation does not take place in the interior of the vessels themselves; but that the organic ingredients of the blood are absorbed
by the tissues, and at the same moment converted into new materials, by contact with their substance. The blood in this way furnishes, directly or indirectly, all the materials necessary for the
nutrition of the body.
The physical conditions which influence the movement of the
blood in the capillaries, are somewhat different from those which
regulate the arterial and venous circulations. We must remember
that as the arteries pass from the heart outward they subdivide and
ramify to such an extent that the surface of the arterial walls is
very much increased, in proportion to the quantity of blood which
they contain. It is on this account that the arterial pulsation is so
much equalized at a distance from the heart, since the influence of
the elasticity of the arterial coats is thus constantly increased fiom
within outward. But as these vessels finally reach the confines of
the arterial system, having already been very much increased in
number and diminished in size, they then suddenly break up into




THE CAPILLARY  CIRCULATION.                   281
a terminal ramification of still smaller and more numerous vessels,
and so lose themselves at last in the capillary network.
By this final increase of the vascular surface, the equalization of
the heart's:action is completed. There is no longer any intermitting
or pulsatile character in the force which acts upon the circulating
fluid; and the blood, accordingly, is delivered from  the arteries
into the capillaries under a perfectly continuous and uniform pressure.
This pressure is sufficient to cause the blood to pass with considerable rapidity, through the capillary plexus, into the commencement of the veins.  This fact was first demonstrated by Prof.
Sharpey,' of London, who employed an injecting syringe with a
double nozzle, one extremity of which was connected with a mercurial gauge, while the other was inserted into the artery of a recently
killed animal.  When the syringe, filled with defibrinated blood,
was fixed in this position and the vessels of the animal injected, the
defibrinated blood would press with equal force upon the mercury
in the gauge and upon the fluid in the bloodvessels; and thus it
was easy to ascertain the exact amount of pressure required to force
the defibrinated blood through the capillaries of the animal, and to
make it return by the corresponding vein.  In this way Prof.
Sharpey found that when the free end of the injecting tube was
attached to the mesenteric artery of the dog, a pressure of 90 millimetres of mercury caused the blood to pass through the capillaries
of the intestine and of the liver; and that under a pressure of 130
millimetres, it flowed in a full stream from  the divided extremity
of the vena cava.
We have also performed a similar experiment on the vessels of
the lower extremity.  A  full grown healthy dog was killed, and
the lower extremity immediately injected with defibrinated blood,
by the femoral artery, in order to prevent coagulation in the smaller
vessels. A syringe with a double flexible nozzle was then filled
with defibrinated blood, and one extremity of its injecting tube
attached to the femoral artery, the other to the mouthpiece of a
cardiometer.  By making the injections, it was then found that the
defibrinated blood ran from the femoral vein in a continuous stream
under a pressure of 120 millimetres, and that it was discharged very
freely under a pressure of 130 millimetres.
Since, as we have already seen, the arterial pressure upon the
Todd and Bowman, Physiological Anatomy and Physiology of Man, vol. ii. p.
350.




282                   THE CIRCULATION.
blood is equal to six inches, or 150 millimetres, of mercury, it is
evident that this pressure is sufficient to propel the blood through
the capillary circulation.
Beside, the blood is not altogether relieved from the influence of
elasticity, after it has left the arteries.  For the capillaries themselves are elastic, notwithstanding the delicate texture of their
walls; and even the tissues of the organs which they traverse
possess, in many instances, a considerable share of elasticity, owing
to the minute elastic fibres which are scattered through their substance.  These elastic fibres are found in considerable quantity in
the lungs, the spleen, the skin, the lobulated glands, and more or
less in the mucous membranes.  They are abundant, of course, in
the fibrous tissues of the extremities, in the fascia, the tendons, and
the intermuscular substance.
In the experiment of injecting the vessels of the lower extremity
with defibrinated blood, if the injection be stopped, the blood does
not instantly cease flowing from the extremity of the femoral vein,
but continues for a short time, until the elasticity of the intervening
parts is exhausted.
The same thing may be observed even in the liver.  If the end
of a water-pipe be inserted into the portal vein, and the liver injected with water under the pressure of a hydrant, the liquid will
distend the vessels of the organ, and pass out by the hepatic veins.
But if the portal vein be suddenly tied or compressed, so as to shut
off the pressure from behind, the stream will continue to run, for
several seconds afterward, from  the hepatic vein, owing to the reaction of the organ itself upon the fluid contained in its vessels.
As a general rule, also, the capillaries do not suffer any backward
pressure from the venous system.  On the contrary, as soon as the
blood has been delivered into the veins, it is hurried onward toward
the heart by the compression of the muscles and the action of the
venous valves. The right side of the heart itself continues the same
process, by its regular contractions, and by the action of its own
valvular apparatus; so that the blood is constantly lifted away from
the capillaries, by the muscular action of the surrounding parts.
These are the most important of the mechanical influences under
which the blood moves through the continuous round of the circulation. The heart, by its alternating contractions and relaxations,
and by the backward play of its valves, continually urges the blood
forward into the arterial system. The arteries, by their dilatable
and elastic walls, convert the cardiac pulsations into a uniform and




THE CAPILLARY CIRCULATION.                    283
steady pressure. Under this pressure, the blood passes through the
capillary vessels; and it is then carried backward to the heart
through the veins, assisted by the action of the muscles and the
respiratory movements of the chest.
At the same time there are certain phenomena which are very
important in this respect, and which show that various local influences will either excite or retard the capillary circulation in particular parts, independently of the heart's action.  The pallor or
suffusion of the face under mental emotion, the congestion of the
mucous membranes during the digestive process, the local and defined redness produced in the skin by an irritating application, are
all instances of this sort. These phenomena are usually explained
by the contraction or dilatation of the smaller arteries immediately
supplying the part with blood, under the influence of nervous
action. As we know that the smaller arteries are in fact provided
with organic muscular fibres, this may undoubtedly have something
to do with the local variations of the capillary circulation; but the
precise manner in which these effects are produced is at present
unknown.
The rapidity of the circulation in the capillary vessels is much
less than in the arteries or the veins.  It may be measured, with a
tolerable approach to accuracy, during the microscopic examination
of transparent and vascular tissues, as, for example, the web of the
frog's foot, or the mesentery of the rat. The results obtained in
this way by different observers (Valentine, Weber, Volkmann,.&c.)
show that the rate of movement of the blood through the capillaries is rather less than one-thirtieth of an inch per second; or not
quite two inches per minute. Since the rapidity of the current, as
we have mentioned above, must be in inverse ratio to the entire
calibre of the vessels through which it moves, it follows that the
united calibre of all the capillaries of the body must be from 350 to
400 times greater than that of the arteries. It must not be supposed from this, however, that the whole quantity of blood contained
in the capillaries at any one time is so much greater than that in
the arteries; since, although the united calibre of the capillaries is
very large, their length is very small. The effect of the anatomical
structure of the capillary system is, therefore, merely to disseminate
a comparatively small quantity of blood over a very large space, so
that the chemico-physiological reactions, necessary to nutrition, may
take place with promptitude and energy. For the same reason,
although the rate of movement of the blood in these vessels is very




284                    THE CIRCULATION.
slow, yet as the distance to be passed over between the arteries and
veins is very small, the blood really requires but a short time to
traverse the capillary system, and to commence its returning passage
by the veins.
GENERAL CONSIDERATIONS.
The rapidity with which the blood passes through the entire round
of the circulation is a point of great interest, and one which has
received a considerable share of attention.  The results of such
experiments, as have been tried, show that this rapidity is much
greater than would have been anticipated. Hering, Poisseuille, and
Matteucci,' have all experimented on this subject in the following
manner.  A  solution of ferrocyanide of potassium  was injected
into the right jugular vein of a horse, at the same time that a ligature was placed upon the corresponding vein on the left side, and
an opening made in it above the ligature.  The blood flowing from
the left jugular vein was then received in separate vessels, which
were changed every five seconds, and the contents afterward examined. It was thus found, that the blood drawn from  the first to
the twentieth second contained no traces of the ferrocyanide; but
that which escaped from  the vein at the end of from  twenty to
twenty-five seconds, showed unmistakable evidence of the presence
of the foreign salt.  The ferrocyanide of potassium must, therefore,
during this time, have passed from  the point of injection to the
right side of the heart, thence to the lungs and through the pulmonary circulation, returned to the heart, passed out again through
the arteries to the capillary system of the head and neck, and
thence have commenced its returning passage to the right side of
the heart, through the jugular vein.
By extending these investigations to different animals, it was
found that the duration of the circulatory movement varied, to
some extent, with the size and species. In the larger quadrupeds,
as a general rule, it was longer; in the smaller, the time required
was less.
In the Horse,2-the mean duration was 28 seconds.
"  Dog    "          "     "15
"  Goat   "   "    "         13  "
"  Fox    "   "    "       "' 12.  "
"  Rabbit "   "    "    "  7  "
1 Physical Phenomena of Living Beings, Pereira's translation, Philada. ed., 1848,
p. 317.
In Milne Edwards, Leqons sur la Physiologie, &c., vol. iv. p. 364.




LOCAL VARIATIONS.                      285
When these results were first published, it was thought to be
doubtful whether the circulation were really as rapid as they would
make it appear. It was thought that the saline matter which was
injected, "travelled faster than the blood;" that it became "diffused"
through the circulating fluid; that it transuded through dividing
membranes; or passed round to the point at which it was detected,
by some short and irregular route.
But none of these explanations have ever been found to be correct. They are all really more improbable than the fact which
they are intended to explain. The physical diffusion of liquids
does not take place with such rapidity as that manifestated by the
circulation; and there is no other route so likely to give passage to
the injected fluid, as the bloodvessels and the movement of the blood
itself. Beside, the first experiments of Poisseuille and others have
not been since invalidated, in any essential particular. It was found,
it is true, that certain other substances, injected at the same time
with the saline matter, might hasten or retard the circulation to a
certain degree. But these variations were not very marked, and
never exceeded the limits of from eighteen to forty-five seconds.
There is no doubt that the blood itself makes the same circuit in
very nearly the same interval of time.
The truth is, however, that we cannot fix upon any absolutely
uniform rate which shall express the time required by the entire
blood to pass the round of the whole vascular system, and return
to a given point. The circulation of the blood, far from being a
simple phenomenon, like a current of water through a circular tube,
is, on the contrary, extremely complicated in all its anatomical and
physiological conditions; and it differs in rapidity, as well as in its
physical and chemical phenomena, in different parts of the circulatory apparatus.  We have already seen how much the form  of
the capillary plexus varies in different organs. In some the vascular network is close, in others comparatively open. In some its
meshes are circular in shape, in others polygonal, in others rectangular. In some the vessels are arranged in twisted loops, in others
they communicate by irregular but abundant inosculations.  The
mere distance at which an organ is situated from the heart must
modify to some extent the time required for its blood to return
again to the centre of the circulation. The blood which passes
through the coronary arteries, for example, and the capillaries of
the heart itself, must be returned to the right auricle in a comparatively short time; while that which is carried by the carotids into




286                   THIE CIRCULATION.
the capillary system of the head and neck, to return by the jugulars,
will require a longer interval. That, again, which descends by the
abdominal aorta and its divisions to the lower extremities, andl
which, after circulating through the tissues of the leg and foot,
mounts upward through the whole course of the saphena, femoral,
iliac And abdominal veins, must be still longer on its way; while
that which circulates through the abdominal digestive organs and
is then collected by the portal system, to be again dispersed through
the glandular tissue of the liver, requires undoubtedly a longer
period still to perform its double capillary circulation. The blood,
therefore, arrives at the right side of the heart, from different parts
of the body, at successive intervals; and may pass several times
through one organ while performing a single circulation through
another..
Furthermore, the chemical phenomena taking place inthe blood
and, the tissues vary to a similar extent in different organs.  The
actions of transformation and decomposition, of nutrition and secretion, of endosmosis and exosmosis, which go on simultaneously
throughout the body, are yet extremely varied in their character,
and produce a similar variation in the phenomena of the circulation. In one organ the blood loses more fluid than it absorbs; in
another it absorbs more than it loses., The venous blood, consequently, has a different, composition as it returns from different
organs. In the brain and spinal cord it gives upthose ingredients
necessary for the nutrition of the nervous matter, and absorbs cholesterine and other materials resulting from its waste; in the muscles
it loses those substances necessary for the supply of the muscular
tissue, and in the bones those which are requisite for the osseous
system. In the parotid gland it yields the ingredients of the saliva;
in the kidneys, those of the urine.  In the intestine it absorbs in
large quantity the nutritious elements of the digested food; and in
the liver, gives up substances destined finally to produce the bile,
at the same time that it absorbs sugar, which has been produced
in the hepatic tissue. In the lungs, again, it is the elimination of
carbonic acid and the absorption of oxygen that constitute its principal changes. It has been already remarked that the temperature
of the blood varies in different veins, according to the peculiar
chemical and nutritive changes going on in the organs from which
they originate. Its color, even, which is also dependent on the
chemical and nutritive actions taking place in the capillaries, varies
in a similar manner. In the lungs, it changes from blue to red;




LOCAL VARIATIONS.                        287
in the capillaries of the general system, from red to blue. But its
tinge also varies very considerably in different parts of the general
circulation. The blood of the hepatic
veins is darker than that of the femoral          Fig. 101.
or brachial vein. In the renal veins
it is very much brighter than in the
vena cava; and when the circulation
through the kidneys is free, the blood
returning from them is nearly as red
as arterial blood.
We must regard the circulation of
the blood, therefore, not as a simple
process, but as made up of many different circulations, going on simultaneously in different organs. It has been
customary to illustrate it, in diagram,
by a double circle, or figure of 8, of
which the upper arc is used to represent the pulmonary, the lower the gen- 
eral circulation. This, however, gives 
but a very imperfect idea of the entire
circulation, as it really takes place. It
would be much more accurately represented by such a diagram  as that
in Fig. 101, in which its variations   1
in different parts of the body are                            
indicated in such a manner as to show,   i
in some degree, the complicated character of its phenomena. The circula- 
tion is modified in these different parts,
not only in its mechanism, but also in
its rapidity and quantity, and in the 
nutritive functions performed by the
blood. In one part, it stimulates the
nervous centres and the organs of
special sense; in others it supplies the
fluid secretions, or the ingredients of   Diagram of the CIRCTLATION.-1.
the solid tissues.  One portion, in  Heart. 2. Lungs. 3. Head and upper
extremities. 4. Spleen. 5. Intestine. 6.
passing through the digestive appara-  Kidney. 7. Lower extremities. 8. Liver.
tus, absorbs the materials requisite
for the nourishment of the body; another, in circulating through




288                   THE CIRCULATION.
the lungs, exhales the carbonic acid which it has accumulated elsewhere, and absorbs the oxygen which is afterward transported to
distant tissues by the current of arterial blood. The phenomena of
the circulation are even liable, as we have already seen, to periodical
variations in the same organ; -increasing or diminishing inintensity
with the condition of rest or activity of the whole body, or of the
particular organ which is the subject of observation.




IMBIBITION AND EXHALATION.                  289
CHAPTER XV.
IMBIBITION AND EXHALATION.-THE LYMPHATIC
SYSTEM.
DURING the passage of the blood through the capillaries of the
circulatory system, a very important series of changes takes place
by which its ingredients are partly transferred to the tissues by
exhalation, and at the same time replaced by others which the blood
derives by absorption from the adjacent parts. These phenomena
depend upon the property, belonging to animal membranes, of
imbibing or absorbing certain fluid substances in a peculiar way.
They are known more particularly as the phenomena of endosmosis
and exosmosis.
These phenomena may be demonstrated in the following way. If
we take two different liquids, for example a solution of salt and an
equal quantity of distilled water, and inclose them in a glass vessel
with a fresh animal membrane stretched between, so that there is
no direct communication from one to the other, the two liquids
being in contact with opposite sides of the membrane, it will be
found after a time that the liquids have become mixed, to a certain extent, with each other. A part of the salt will have passed
into the distilled water, giving it a saline taste; and a part of the
water will have passed into the saline solution, making it more
dilute than before. If the quantities of the two liquids, which
have become so transferred, be measured, it will be found that a
comparatively large quantity of the water has passed into the
saline solution, and a comparatively small quantity of the saline
solution has passed out into the water. That is, the water passes
inward to the salt more rapidly than the salt passes outward to the
water.  The consequence is, that an accumulation soon begins to
show itself on the side of the salt. The saline solution is increased
in volume and diluted, while the water is diminished in volume,
and acquires a saline ingredient. This abundant passage of the
water, through the membrane, to the salt, is called endosmosis; and
19




290            IMBIBITION AND EXHALATION.
the more scanty passage of the salt outward to the water is called
exosmosis.
The mode usually adopted for measuring the rapidity of endosmosis is to take a glass vessel, shaped somewhat like an inverted
funnel, wide at the bottom and narrow at the top. The bottom of
the vessel is closed by a thin animal membrane, like the mucous
membrane of an ox-bladder, which is stretched tightly over its edge
and secured by a ligature. From the top of the vessel there rises
a very narrow glass tube, open at its upper extremity. When the
instrument is thus prepared, it is filled with a solution of sugar
and placed in a vessel of distilled water, so that the animal membrane, stretched across its mouth, shall be in contact with pure
water on one side and with the saccharine solution on the other.
The water then passes in through the membrane, by endosmosis,
faster than the saccharine solution passes out. An accumulation
therefore takes place inside the vessel, and the level of the fluid
rises in the upright tube. The height to which the fluid thus rises
in a given time is a measure of the intensity of the endosmosis, and
of its excess over exosmosis. By varying the constitution of the
two liquids, the arrangement of the membrane, &c., the variation
in endosmotic action under different conditions may be easily
ascertained. Such an instrument is called an endosmometer.
If the extremity of the upright tube be bent over, so as to point
downward, as endosmosis continues to go on after the tube has
become entirely filled by the rising of the fluid, the saccharine solution will be discharged in drops from the end of the tube, and fall
back into the vase of water. A steady circulation will thus be
kept up for a time by the force of endosmosis. The water still
passes through the membrane, and accumulates in the endosmometer; but, as this is already full of fluid, the surplus immediately
falls back into the outside vase, and thus a current is established,
which will go on until the two liquids have become intimately
mingled.
The conditions which influence the rapidity and extent of endosmosis have been most thoroughly investigated by Dutrochet, who
was the first to make a systematic examination of the subject.
The first of these conditions is the freshness of the membrane itself.
This is an indispensable requisite for the success of the experiment.
A membrane that has been dried and moistened again, or one that
has begun to putrefy, will not produce the desired effect. It has
been also found that if the membrane of the endosmometer be




THE LYMPHATIC SYSTEM.                      291
allowed to remain and soak in the fluids, after the column has risen
to a certain height in the upright tube, it begins to descend again
as soon as putrefaction commences, and the two liquids finally sink
to the same level.
The next condition is the extent of contact between the membrane
and the two liquids. The greater the extent of this contact, the
more rapid and forcible is the current of endosmosis. An endosmometer with a wide mouth will produce more effect than with a
narrow one, though the volume of the liquid contained in it may be
the same in both instances. The action takes place at the surface
of the membrane, and is proportionate to its extent.
Another very important circumstance is the constitution of the two
liquids, and their relation to each other. As a general thing, if we
use water and a saline solution in our experiments, endosmosis is
more active, the more concentrated is the solution in the endosmometer. A larger quantity of water will pass inward toward a dense
solution than toward one which is already dilute. But the force of
endosmosis varies with different liquids, even when they are of the
same density.  Dutrochet measured the force with which water
passed through the mucous membrane of an ox-bladder into different solutions of the same density. He found that the force varies
with different substances, as follows:'Endosmosis of water, with a solution of albumen..   12
"        "           "       sugar...   11
"        "           "      gum...    5
g'      "9           "      gelatine..    3
The position of the membrane also makes a difference. With some
fluids, endosmosis is more rapid when the membrane has its mucous
surface in contact with the dense solution, and its dissected surface
in contact with the water.  With other substances the most favorable position is the reverse. Matteucci found that, in using the
mucous membrane of the ox-bladder with water and a solution of
sugar, if the mucous surface of the membrane were in contact with
the saccharine solution, the liquid rose in the endosmometer between
four and five inches.  But if the same surface were turned outward
toward the water, the column of fluid was less than three inches in
height. Different membranes also act with different degrees of force.
The effect produced is not the same with the integument of different
animals, nor with mucous membranes taken from different parts of
the body.
In Matteucci's Lectures on the Physical Phenomena of Living Beings. Philada.,
1848, p. 48.




292            IMBIBITION  AND EXHALATION.
Generally speaking, endosmosis is more active when the temperature is moderately elevated. Dutrochet noticed that an endosmometer, containing a solution of gum, absorbed only one volume of
water at a temperature of 32~ Fahr., but absorbed three volumes
at a temperature a little above 900. Variations of temperature will
sometimes even change the direction of the endosmosis altogether,
particularly with dilute solutions of hydrochloric acid. Dutrochet
found, for example,' that when the endosmometer was filled with
dilute hydrochloric acid and placed in distilled water, at the temperature of 50~ F., endosmosis took place from the acid to the water,
if the density of the acid solution were less than 1.020; but that it
took place from the water to the acid, if its density were greater
than this. On the other hand, at the temperature of 72~ F., the
current was from within outward when the density of the acid solution was below 1.003, and from without inward when it was above
that point.
Finally, the pressure which is exerted upon the fluids and the
membrane favors their endosmosis. Fluids that pass slowly under
a low pressure will pass more rapidly with a higher one. Different
liquids, too, require different degrees of pressure to make them
pass the same membrane.  Liebig2 has measured the pressure required for several different liquids, in order to make them pass
through the same membrane. He found that this pressure was
INCHES OF MERCURY.
For alcohol........ 52
For oil.........    37
For solution of salt...20
For water.....13
There are some cases in which endosmosis takes place without
being accompanied by exosmosis.  This occurs, for example, when
we use water and albumen as the two liquids. For while water
readily passes in through the animal membrane, the albumen does
not pass out. If an opening be made, for example, in the large
end of an egg, so as to expose the shell-membrane, and the whole
be then placed in a goblet of water, endosmosis will take place very
freely from the water to the albumen, so as to distend the shellmembrane and make it protrude, like a hernia, from the opening in
the shell. But the albumen does not pass outward through the
membrane, and the water in the goblet remains pure. After a time,' In Milne Edwards, Leqons sur la Physiologie, &c., vol. v. p. 164.
2 In Longet's Traite de Physiologic, vol. i. p. 384.




THE LYMPHATIC SYSTEM.                     293
however, the accumulation of fluid in the interior becomes so excessive as to burst the shell-membrane, and then the two liquids
become mixed indiscriminately together.
These are the principal conditions by which endosmosis is influenced and regulated. Let us now see what is the nature of the
process, and upon what its phenomena depend.
Endosmosis is not dependent upon the simple force of diffusion
or admixture of two different liquids. For sometimes, as in the
case of albumen and water, all the fluid passes in one direction and
none in the other. It is true that the activity of the process depends very much, as we have already seen, upon the difference in
constitution of the two liquids.  With water and a saline solution,
for instance, the stronger the solution of salt, the more rapid is the
endosmosis of the water.  And if two solutions of salt be used,
with a membranous septum  between them, endosmosis takes place
from  the weaker solution to the stronger, and is proportionate in
activity to the difference in their densities. From this fact, Dutrochet was at first led to believe that the direction of endosmosis was
determined by the difference in density of the two liquids, and that
the current of accumulation was always directed from the lighter
liquid to the denser. But we now know that this is not the case.
For though, with solutions of salt, sugar, and the like, the current
of endosmosis is from the lighter to the denser liquid; in other
instances, it is the reverse.  With water and alcohol, for example,
endosmosis takes place, not from the alcohol to the water, but from
the water to the alcohol; that is, from the denser liquid to the lighter.
The difference in density of the liquids, therefore, is not the only
condition which regulates the direction of the endosmotic current.
In point of fact, the process of endosmosis does not depend principally upon the attraction of the two liquids for each other, but
upon the attraction of the animal membrane for the two liquids.  The
membrane is not a passive filter through which the liquids mingle,
but it is the active agent which determines their passage. The
membrane has the power of absorbing liquids, and of taking them
up into its own substance. This power of absorption, belonging to
the membrane, depends upon the organic or albuminous ingredients
of which it is composed; and, with different animal substances, the
power of absorption is different. The tissue of cartilage, for example, will absorb more water, weight for weight, than that of the
tendons; and the tissue of the cornea will absorb nearly twice as
much as that of cartilage.




294             IMBIBITION  AND EXHALATION.
Beside, the power of absorption of an animal membrane is different for different liquids. Nearly all animal membranes absorb
pure water more freely than a solution of salt. If a membrane,
partly dried, be placed in a saturated saline solution, it will absorb
the water in larger proportion than the salt, and a part of the salt
will, therefore, be deposited in the form of crystals on the surface
of the membrane.
Oily matters, on the other hand, are usually absorbed less readily
than either water or saline solutions.
Chevreuil has investigated the absorbent power of different
animal substances for different liquids, by taking definite quantities of the animal substance and immersing it for twenty-four
hours in different liquids. At the end of that time, the substance
was removed and weighed.  Its increase in weight showed the
quantity of liquid which it had absorbed. The results which were
obtained are given in the following table: —
100 PARTS OF                         WATER. SALINE SOLUTION.   OIL.
Cartilage,          1' 231 parts.   125 parts.
Tendon,                          178 "      114 "       8.6 parts.
Elastic ligament,     absorb in  148 "       30 "       7.2  "
Cornea,               24 hours,  461 "      370 "       9.1  "
Cartilaginous ligament,  319 "                          3.2  "
Dried fibrin,                   301 "       154 "
The same substance, therefore, will take up different quantities
of water, saline solutions, and oil.
Accordingly, when an animal membrane is placed in contact
with two different liquids, it absorbs one of them more abundantly
than the other; and that which is absorbed in the greatest quantity
is also diffused most abundantly into the liquid on the opposite side
of the membrane.  A rapid endosmosis takes place in one direction, and a slow exosmosis in the other. Consequently, the least
absorbable fluid increases in volume by the constant admixture of
that which is taken up more rapidly.
The process of endosmosis, therefore, is essentially one of imbibition or absorption of the liquid by an animal membrane, composed of organic ingredients.  We have already shown, in describing the organic proximate principles in a previous chapter,
that these substances have the power of absorbing watery and
serous fluids in a peculiar way. In endosmosis, accordingly, the
In Longet's Trait6 de Physiologie, vol. i. p. 383.




THE LYMPHATIC SYSTEM.                    295
imbibed fluid penetrates the membrane by a kind of chemical
combination, and unites intimately with the substance of which its
tissues are composed.
It is in this way that all imbibition and transudation take place
in the living body. Under the most ordinary conditions, the transudation of certain fluids is accomplished with great rapidity. It has
been shown by M. Gosselin,' that if a watery solution of iodide of
potassium  be dropped upon the cornea of a living rabbit, the
iodine penetrates into the cornea, aqueous humor, iris, lens, sclerotic
and vitreous body, in the course of eleven minutes; and that it
will penetrate through the cornea into the aqueous humor in three
minutes, and into the substance of the cornea in a minute and a
half. In these experiments it was evident that the iodine actually
passed into the deeper portions of the eye by simple endosmosis,
and was not transported by the vessels of the general circulation;
since no trace of it could be found in the tissues of the opposite
eye, examined at the same time.
The same observer showed that the active principle of belladonna
penetrates the tissues of the eyeball in a similar manner. M. Gosselin applied a solution of sulphate of atropine to both eyes of two
rabbits. Half an hour afterward, the pupils were dilated. Three
quarters of an hour later, the aqueous humor was collected by
puncturing the cornea with a trocar; and this aqueous humor,
dropped upon the eye of a cat, produced dilatation and immobility
of the pupil in half an hour. These facts show that the aqueous
humor of the affected eye actually contains atropine, which it
absorbs from without through the cornea, and this atropine then
acts directly and locally upon the muscular fibres of the iris.
But in all the vascular organs, the processes of endosmosis and
exosmosis are very much accelerated by two important conditions,
viz., first, the movement of the blood in circulating through the
vessels, and secondly the minute dissemination and distribution of
these vessels through the tissue of the organs.
The movement of a fluid in a continuous current always favors
endosmosis through the membrane with which it is in contact. For
if the two liquids be stationary, on the opposite sides of an animal
membrane, as soon as endosmosis commences they begin to approximate in constitution to each other by mutual admixture; and,
as this admixture goes on, endosmosis of course becomes less active,
I Gazette Hebdomadaire, Sept. 7, 1855.




296            IMBIBITION  AND EXHALATION.
and ceases entirely when the two liquids have become perfectly
similar in composition.  But if one of the liquids be constantly
renewed by a continuous current, those portions of it which have
become contaminated are immediately carried away by the stream
and replaced by fresh portions in a state of purity.  Thus the
difference in constitution of the two liquids is preserved, and
transudation will continue to take place between them with unabated rapidity.
Matteucci demonstrated the effect of a current in facilitating
endosmosis by attaching to the stopcock of a glass reservoir filled
with water, a portion of a vein also filled with water. The vein
was then immersed in a very dilute solution of hydrochloric acid.
So long as the water remained stationary in the vein it did not give
any indications of the presence of the acid, or did so only very
slowly; but if a current were allowed to pass through the vein by
opening the stopcock of the reservoir, then the fluid running from
its extremity almost immediately showed an acid reaction.
The same thing may be shown even more distinctly upon the
living animal.  If a solution of the extract of nux vomica be injected into the subcutaneous areolar tissue of the hind leg of two
rabbits, in one of which the bloodvessels of the extremity have
been left free, while in the other they have been previously tied,
so as to stop the circulation in that part-in the first rabbit, the
poison will be absorbed and will produce convulsions and death in
the course of a few minutes; but in the second animal, owing to the
stoppage of the local circulation, absorption will be much retarded,
and the poison will find its way into the general circulation so
slowly, and in such small quantities, that its specific effects will show
tlemselves only at a late period, or even may not be produced at all.
The anatomical arrangement of the bloodvessels and adjacent
tissues is the second important condition' regulating endosmosis
and exosmosis.  We have already seen that the network of capillary bloodvessels results from the excessive division and ramification of the smaller arteries. The blood, therefore, as it leaves the
arteries and enters the capillaries, is constantly divided into smaller
and more numerous currents, which are finally disseminated in the
most intricate manner throughout the substance of the organs and
tissues.. Thus, the blood is brought into intimate contact with the
surrounding tissues, over a comparatively very large extent of surface. It has already been stated, as the result of Dutrochet's investigations, that the activity of endosmosis is in direct proportion to




THE LYMPHATIC SYSTEM.                     297
the extent of surface over which the two liquids come in contact
with the intervening membrane. It is very evident, therefore, that
it will be very much facilitated by the anatomical distribution of
the capillary bloodvessels.
It is in some of the glandular organs, however, that the transudation of fluids can be shown to take place with the greatest rapidity.  For in these organs the exhaling and absorbing surfaces are
arranged in the form of minute ramifying tubes and follicles, which
penetrate everywhere through the glandular substance; while the
capillary bloodvessels form an equally complicated and abundant
network, situated between the adjacent follicles and ducts. In this
way, the union and interlacement of the glandular membrane, on
the one hand, and the bloodvessels on the other, become exceedingly intricate and extensive; and the ingredients of the blood are
almost instantaneously subjected, over a very large surface, to the
influence of the glandular membrane.
The rapidity of transudation through the glandular membranes
has been shown in a very striking manner by Bernard.' This observer injected a solution of iodide of potassium  into the duct of
the parotid gland on the right side, in a living dog, and immediately
afterward found iodine to be present in the saliva of the corresponding gland on the opposite side. In the few instants, therefore, required to perform the experiment, the salt of iodine must have
been taken up by the glandular tissue on one side, carried by the
blood of the general circulation to the opposite gland, and there
transuded through the secreting membrane.
We have also found the transudation of iodine through the
glandular tissue to be exceedingly rapid, by the following experiment. The parotid duct was exposed and opened, upon one side,
in a living dog, and a canula inserted into it, and secured by ligature. The secretion of the parotid saliva was then excited, by introducing a little vinegar into the mouth of the animal, and the
saliva, thus obtained, found to be entirely destitute of iodine. A
solution of iodide of potassium  being then injected into the jugular vein, and the parotid secretion again immediately excited by
the introduction of vinegar, as before, the saliva first discharged
from the canula showed evident traces of iodine, by striking a blue
color on the addition of starch and nitric acid.
The processes ofexosmosis and endosmnosis, therefore, in the living
Legons de Physiologie Experimentale, Paris, 1856, p. 107.




298            IMBIBITION AND EXHALATION.
body, are regulated by the same conditions as in artificial experiments, but they take place with infinitely greater rapidity, owing to
the movement of the circulating blood, and the extent of contact
existing between the bloodvessels and adjacent tissues.  We have
already seen that the absorption of the same fluid is accomplished
with different degrees of rapidity by different animal substances.
Accordingly, though the arterial blood is everywhere the same in
composition, yet its different ingredients are imbibed in varying
quantities by the different tissues. Thus, the cartilages absorb
from the circulating fluid a larger proportion of phosphate of lime
than the softer tissues, and the bones a larger proportion than the
cartilages; and the watery and saline ingredients generally are
found in different quantities in different parts of the body. The
same animal membrane, also, as it has been shown by experiment,
will imbibe different substances with different degrees of facility.
Thus, the blood, for example, contains more chloride of sodium
than chloride of potassium; but the muscles, which it supplies with
nourishment, contain more chloride of potassium than chloride of
sodium. In this way, the proportion of each ingredient derived
from the blood is determined, in each separate tissue, by its special
absorbing or endosmotic power.
Furthermore, we have seen that albumen, under ordinary conditions, is not endosmotic; that is, it will not pass by transudation
through an animal membrane. For the same reason, the albumen
of the blood, in the natural state of the circulation, is not exhaled
from the secreting surfaces, but is retained within the circulatory
system, while the watery and saline ingredients transude in varying
quantities. But the degree of pressure to which a fluid is subjected,
has great influence in determining its endosmotic action. A substance which passes but slowly under a low pressure, may pass
much more rapidly if the force be increased. Accordingly, we find
that if the pressure upon the blood in the vessels be increased, by
obstruction to the venous current and backward congestion of the
capillaries, then not only the saline and watery parts of the blood
pass out in larger quantities, but the albumen itself transudes, and
infiltrates the neighboring parts. It is in this way that albumen
makes its appearance in the urine, in consequence of obstruction to
the renal circulation, and that local cedema or general anasarca
may follow upon venous congestion in particular regions, or upon
general disturbance of the circulation.'I'he processes of imbibition and exudation, which thus take




THE LYMPHATIC SYSTEM.                     299
place incessantly throughout the body, are intimately connected
with the action of the great absorbent or lymphatic system of vessels, which is to be considered as secondary or complementary to
that of the sanguiferous circulation.
The lymphatics may be regarded as a system of vessels, commencing in the substance of the various tissues and organs, and
endowed with the property of absorbing certain of their ingredients.  Theircommencement has been demonstrated by injections,
more particularly in the membranous parts of the body; viz., in
the skin, the mucous membranes, the serous and synovial surfaces,
and the inner tunic of the arteries and veins. They originate in
these situations by vascular networks, not very unlike those of the
capillary. bloodvessels. Notwithstanding this resemblance in form
between the capillary plexuses of the lymphatics and the bloodvessels, it is most probable that they are anatomically distinct from
each other. It has been supposed, at various times, that there
might be communications between them, and even that the lymphatic plexus might be a direct continuation of that originating from
the smaller arteries; but this has never been demonstrated, and it
is now almost universally conceded that the anatomical evidence is
in favor of a complete separation between the two vascular systems.
Commencing in this way in the substance of the tissues, by a
vascular network, the minute lymphatics unite gradually with each
other to form larger vessels; and, after continuing their course for
a certain distance from without inward, they enter and are distributed to the substance of the lymphatic glands. According to M.
Colin,' beside the more minute and convoluted vessels in each gland,
there are always some larger branches which pass directly through
its substance, from the afferent to the efferent vessels; so that only
a portion of the lymph is distributed to its ultimate glandular
plexus. This portion, however, in passing through the organ, is
evidently subjected to some glandular influence, which may serve
to modify its composition.
After passing through these glandular organs, the lymphatic
vessels unite into two great trunks (Fig. 43): the thoracic duct, which
collects the fluid from the absorbents of the lower extremities, the
intestines and other abdominal organs, the chest, the left upper
extremity, and the left side of the head and neck, and terminates
in the left subclavian vein, at the junction of the internal jugular;
and the right lymphatic duct, which collects the fluid from the right
1 Physiologie comipar6e des Animaux domestiques, Paris, 1856, vol. ii. p. 68.




300            IMBIBITION AND EXHALATION.
upper extremity and right side of the head and neck, and joins' the
right subclavian vein at its junction with the corresponding jugular.
Thus nearly all the lymph from the external parts, and the whole
of that from the abdominal organs, passes, by the thoracic duct,
into theeleft subclavian vein.
We already know that the lymphatic vessels are not to be regarded as the exclusive agents of absorption. On the contrary,
absorption takes place by the bloodvessels even more rapidly and
abundantly than by the lymphatics. Even the products of digestion, including the chyle, are taken up from  the intestine in large
proportion by the bloodvessels, and are only in part absorbed by
the lymphatics. But the main peculiarity of the lymphatic system
is that its vessels all pass in one direction, viz., from without inward,
and none from within outward. Consequently, there is no circulation of the lymph, strictly speaking, like that of the blood, but it
is all supplied by exudation and absorption from the tissues.
The lymph has been obtained, in a state of purity, by various
experimenters, by introducing a canula into the thoracic duct, at
the root of the neck, or into large lymphatic trunks in other parts
of the body. It has been obtained by Rees from the lacteal vessels
and the lymphatics of the leg in the ass, by Colin from the lacteals
and thoracic duct of the ox, and from the lymphatics of the neck
in the horse. We have also obtained it, on several different occasions, from the thoracic duct of the dog and of the goat.
The analysis of these fluids shows a remarkable similarity in
constitution between them  and the plasma of the blood.  They
contain water, fibrin, albumen, fatty matters, and the usual saline
substances of the animal fluids.  At the same time, the lymph is
very much poorer in albuminous ingredients than the blood. The
following is an analysis, by Lassaigne,' of the fluid obtained from
the thoracic duct of the cow:PARTS PER THOUSAND.
Water......964.0
Fibrin........               0.9
Albumen........                     28.0
Fat..........   0.4
Chloride of sodium.....   5.0
Carbonate, 
Phosphate and of Soda......   1.2
Sulphate 
Phosphate of lime....    0.5
1000.0' Colin, Physiologie compar6e des Animaux domestiqjues, vol. ii. p. 111.




THE LYMPHATIC SYSTEM.                     301
It thus appears that both the fibrin and the albumen of the blood
actually transude to a certain extent from the bloodvessels, even in
the ordinary condition of the circulatory system. But this transudation takes place in so small a quantity that the albuminous matters
are all taken up again by the lymphatic vessels, and do not appear
in the excreted fluids.
The first important peculiarity which is noticed in regard to the
fluid of the lymphatic system, especially in the carnivorous animals,
is that it varies very much, both in appearance and constitution, at
different times.  In the ruminating and graminivorous animals,
such as the sheep, ox, goat, horse, &c., it is either opalescent in
appearance, with a slight amber tinge, or nearly transparent and
colorless. In the carnivorous animals, such as the dog and cat, it
is also opaline and amber colored, in the intervals of digestion, but
soon after feeding becomes of dense, opaque, milky white, and continues to present that appearance until the processes of digestion
and intestinal absorption are completed. It then regains its original
aspect, and remains opaline or semi-transparent until digestion is
again in progress.
The cause of this variable constitution of the fluid discharged
by the thoracic duct is the absorption of fatty substances from the
intestine during digestion. Whenever fatty substances exist in considerable quantity in the food, they are reduced, by the process of
digestion, to a white, creamy mixture of molecular fat, suspended
in an albuminous menstruum. The mixture is then absorbed by
the lymphatics of the mesentery, and transported by them through
the thoracic duct to the subclavian vein. While this absorption is
going on, therefore, the fluid of the thoracic duct alters its appearance, becomes white and opaque, and is then called chyle; so that
there are two different conditions in which the contents of the great
lymphatic trunks present different appearances.  In the fasting
condition, these vessels contain a semi-transparent, or opaline and
nearly colorless lymph; and during digestion, an opaque, milky
chyle. It is on this account that the lymphatics of the mesentery
are called "lacteals."
The chyle, accordingly, is nothing more than the lymph which
is constantly absorbed by the lymphatic system everywhere, with
the addition of more or less fatty ingredients taken up from the
intestine during the digestion of food.
The results of analysis show positively that the varying appearance of the lymphatic fluids is really due to this cause; for though




302             IMBIBITION  AND EXHALATION.
the chyle is also richer than the lymph in albuminous matters, the
principal difference between them consists in the proportion of fat.
This is shown by the following comparative analysis of the lymph
and chyle of the ass, by Dr. Rees:1
LYMPH.      CHYLE.
Water......                  965.36       902.37
Albumen.....  12.00          35.16
Fibrin......   1.20         3.70
Spirit extract.....            240         3.32
Water extract.....  13.19         12.33
Fat.....        traces.       36.01
Saline matter..   5.85          7.11
1,000.00    1,000.00
When a canula, accordingly, is introduced into the thoracic duct
at various periods after feeding, the fluid which is discharged varies
considerably, both in appearance and quantity.  We have found
that, in the dog, the fluid of the thoracic duct never becomes quite
transparent, but retains a very marked opaline tinge even so late
as eighteen hours after feeding, and at least three days and a half
after the introduction of fat food. Soon after feeding, however, as
we have already seen, it becomes whitish and opaque, and remains
so while digestion and absorption are in progress. It also becomes
more abundant soon after the commencement of digestion, but
diminishes again in quantity during its latter stages. We have
found the lymph and chyle to be discharged from the thoracic duct,
in the dog, in the following quantities per hour, at different periods
of digestion. The quantities are calculated in proportion to the
entire weight of the animal.
PER THOUSAND PARTS.
31 hours after feeding. 2.45
7   "    "    "...... 2.20
13        " "... 0.99
18   "   "    "...                1.15
18l   "   "    "...... 1.99
It would thus appear that the hourly quantity of lymph, after
diminishing during the latter stages of digestion, increases again
somewhat, about the eighteenth hour, though it is still considerably less abundant than while digestion was in active progress.
The lymph obtained from the thoracic duct at all periods coagulates soon after its withdrawal, owing to the fibrin which it contains
I In Colin, op. cit., vol. ii. p. 18.




THE LYMPHATIC SYSTEM.                     303
in small quantity. After coagulation, a separation takes place between the clot and serum, precisely as in the case of blood.
The movement of the lymph in the lymphatic vessels, from the
extremities toward the heart, is accomplished by various forces.
The first and most important of these forces is that by which the
fluids are originally absorbed by the lymphatic capillaries. Throughout the entire extent of the lymphatic system, an extensive process
of endosmosis is incessantly going on, by which the ingredients of
the lymph are imbibed from.the surrounding tissues, and compelled to pass into the lymphatic vessels. The lymphatics are thus
filled at their origin; and, by mere force of accumulation, the fluids
are then compelled, as their absorption continues, to discharge
themselves into the large veins in which the lymphatic trunks
terminate.
The movement of the fluids through the lymphatic system is
also favored by the contraction of the voluntary muscles and the
respiratory motions of the chest. For as the lymphatic vessels are
provided with valves, arranged like those of the veins, opening
toward the heart and shutting backward toward the extremities,
the alternate compression and relaxation of the adjacent muscles,
and the expansion and collapse of the thoracic parietes, must have
the same effect upon the movement of the lymph as upon that of
the venous blood. By these different influences the chyle and
lymph are incessantly carried from without inward, and discharged,
in a slow but continuous stream, into the returning current of the
venous blood.
The entire quantity of the lymph and chyle has been found, by
direct experiment, to be very much larger than was previously
anticipated. M. Colinl measured the chyle discharged from the
thoracic duct of an ox during twenty-four hours, and found it to
exceed eighty pounds. In other experiments of the same kind, he
obtained still larger quantities.2  From  two experiments on the
horse, extending over a period of twelve hours each, he calculates
the quantity of chyle and lymph in this animal as from twelve to
fifteen thousand grains per hour, or between forty and fifty pounds
per day. But in the ruminating animals, according to his observations, the quantity is considerably greater. In an ordinary-sized
cow, the smallest quantity obtained in an experiment extending over'Gazette Hebdornadaire, April, 24, 1857, p. 285.
2 Colin, op. cit., vol. ii. p. 100.




304            IMBIBITION AND EXHALATION.
a period of twelve hours, was a little over 9,000 grains in fifteen
minutes; that is, five pounds an hour, or 120 pounds per day. In
another experiment, with a young bull, he actually obtained a little
over 100 pounds from a fistula of the thoracic duct, in twenty-four
hours.
We have also obtained similar results by experiments upon the
dog and goat. In a young kid, weighing fourteen pounds, we have
obtained from  the thoracic duct 1890 grains of lymph in three
hours and a half. This quantity would represent 540 grains in an
hour, and 12,690 grains, or 1.85 pounds, in twenty-four hours; and
in a ruminating animal weighing 1000 pounds, this would correspond to 132 pounds of lymph and chyle discharged by the thoracic
duct in the course of twenty-four hours.
The average of all the results obtained by us, in the dog, at different periods after feeding, gives very nearly four and a half per
cent. of the entire weight of the animal, as the total daily quantity
of lymph and chyle. This is substantially the same result as that
obtained by Colin, in the horse; and for a man weighing 140
pounds, it would be equivalent to between six and six and a half
pounds of lymph and chyle per day.
But of this quantity a considerable portion consists of the chyle
which is absorbed from the intestines during the digestion of fatty
substances. If we wish, therefore, to ascertain the total amount of
the lymph, separate from that of the chyle, the calculation should
be based upon the quantity of fluid obtained from  the thoracic
duct in the intervals of digestion, when no chyle is in process of
absorption.  We have seen that in the dog, eighteen hours after
feeding, the lymph, which is at that time opaline and semi-transparent, is discharged from the thoracic duct, in the course of an hour,
in a quantity equal to 1.15 parts per thousand of the entire weight
of the animal. In twenty-four hours this would amount to 27.6
parts per thousand; and for a man weighing 140 pounds this would
give 3.864 pounds as the total daily quantity of the lymph alone.
It will be seen, therefore, that the processes of exudation and
absorption, which go on in the interior of the body, produce a very
active interchange or internal circulation of the animal fluids, which
may be considered as secondary to the circulation of the blood.
For all the digestive fluids, as we have found, together with the bile
discharged into the intestine, are reabsorbed in the natural process
of digestion and again enter the current of the circulation. These
fluids, therefore, pass and repass through the mucous membrane of




THE LYMPHATIC SYSTEM.                       305
the alimentary canal and adjacent glands, becoming somewhat
altered in constitution at each passage, but still serving to renovate
alternately the constitution of the blood and the ingredients of the
digestive secretions. Furthermore the elements of the blood itself
also transude in part from the capillary vessels, and are again taken
up, by absorption, by the lymphatic vessels, to be finally restored
to the returning current of the venous blood, in the immediate
neighborhood of the heart.
The daily quantity of all the fluids, thus secreted and reabsorbed
during twenty-four hours, will enable us to estimate the activity
with which endosmosis and exosmosis go on in the living body.
In the following table, the quantities are all calculated for a man
weighing 140 pounds.
SECRETED AND REABSORBED DURING 24 HouRs.
Saliva        20,164 grains, or 2.880 pounds.
Gastric juice   98,000  "   " 14.000   "
Bile          16,940  "   "  2.420   "
Pancreatic juice 13,104  "   "  1.872   "
Lymph         27,048   "   "  3.864 
25.036
A little over twenty-five pounds, therefore, of the animal fluids
transude through the internal membranes and are restored to the
blood by reabsorption in the course of a single day.  It is by this
process that the natural constitution of the parts, though constantly
changing, is still maintained in its normal condition by the movement of the circulating fluids, and the incessant renovation of their
nutritious materials.
20




306                       SECRETION.
CHAPTER XVI.
SECRETION.
WE have already seen, in a previous chapter, how the elements of
the blood are absorbed by the tissues during the capillary circulation, and assimilated by them or converted into their own substance.
In this process, the inorganic or saline matters are mostly taken up
unchanged, and are merely appropriated by the surrounding parts in
particular quantities; while the organic substances are transformed
into new compounds, characteristic of the different tissues by which
they are assimilated. In this way the various tissues of the body,
though they have a different chemical composition from the blood,
are nevertheless supplied by it with appropriate ingredients, and
their nutrition constantly maintained.
Beside this process, which is known by the name of "assimilation," there is another somewhat similar to it, which takes place in
the different glandular organs, known as the process of secretion. It
is the object of this function to supply certain fluids, differing in
chemical constitution from the blood, which are required to assist
in various physical and chemical actions going on in the body.
These secreted fluids, or "secretions," as they are called, vary in
consistency, density, color, quantity, and reaction. Some of them
are thin and watery, like the tears and the perspiration; others are
viscid and glutinous, like mucus and the pancreatic fluid. They
are alkaline like the saliva, acid like the gastric juice, or neutral
like the bile. Each secretion contains water and the inorganic salts
of the blood, in varying proportions; and is furthermore distinguished by the presence of some peculiar animal substance which
does not exist in the blood, but which is produced by the secreting
action of the glandular organ. As the blood circulates through the
capillaries of the gland, its watery and saline constituents transude
in certain quantities, and are discharged into the excretory duct.
At the same time, the glandular cells, which have themselves been
nourished by the blood, produce a new substance by the catalytic




SECRETION.                        307
transformation of their organic constituents; and this new substance
is discharged also into the excretory duct and mingled with the
other ingredients of the secreted fluid. A true secretion, therefore,
is produced only in its own particular gland, and cannot be formed
elsewhere, since the glandular cells of that organ are the only
ones capable of producing its most characteristic ingredient. Thus
pepsine is formed only in the tubules of the gastric mucous membrane, pancreatine only in the pancreas, tauro-cholate of soda only
in the liver.
One secreting gland, consequently, can never perform vicariously
the office of another. Those instances which have been from time
to time reported of such an unnatural action are not, properly
speaking, instances of "vicarious secretion;" but only cases in
which certain substances, already existing in the blood, have made
their appearance in secretions to which they do not naturally belong.
Thus cholesterine, which is produced in the brain and is taken up
from it by the blood, usually passes out with the bile; but it may
also appear in the fluid of hydrocele, or in inflammatory exudations. The sugar, again, which is produced in the liver and taken
up by the blood, when it accumulates in large quantity in the circulating fluid, may pass out with the urine. The coloring matter
of the bile, in cases of biliary obstruction, may be reabsorbed, and
so make its appearance in the serous fluids, or even in the perspiration. In theseinstances, however, the unnatural ingredient is not
actually produced by the kidneys, or the perspiratory glands, but
is merely supplied to them, already formed, by the blood. Cases
of " vicarious menstruation" are simply capillary hemorrhages
which take place from various mucous membranes, owing to the
general disturbance of the circulation in amenorrhcea.  A true
secretion, however, is always confined to the gland in which it
naturally originates.
The force by which the different secreted fluids are prepared in
the glandular organs, and discharged into their ducts, is a peculiar
one, and resident only in the glands themselves. It is not simply
a process of filtration, in which the ingredients of the secretion
exude from the bloodvessels by exosmosis under the influence of
pressure; since the most characteristic of these ingredients, as we
have already mentioned, do not pre-exist in the blood, but arc
formed in the substance of the gland itself.  Substances, even,
which already exist in the blood in a soluble form, may not have
the power of passing out through the glandular tissue.  Bernard




308                       SECRETION.
has ound' that ferrocyanide of potassium, when injected into the
jugular vein, though it appears with great facility in the urine,
does not pass out with the saliva; and even that a solution of
the same salt, injected into the duct of the parotid gland, is absorbed, taken up by the blood, and discharged with the urine; but
does not appear in the saliva, even of the gland into which it has
been injected. The force with which the secreted fluids accumulate
in the salivary ducts has also been shown by Ludwig's experiments' to be sometimes greater than the pressure in the bloodvessels. This author found, by applying mercurial gauges at the same
time to the duct of Steno and to the artery of the parotid gland, that
the pressure in the duct from the secreted saliva was considerably
greater than that in the artery from  the circulating blood; so that
the passage of the secreted fluids had really taken place in a direction contrary to that which would have been caused by the simple
influence of pressure.
The process of secretion, therefore, is one which depends upon
the peculiar anatomical and chemical constitution of the glandular
tissue and its secreting cells. These cells have the property of
absorbing and transmitting from the blood certain inorganic and
saline substances, and of producing, by chemical metamorphosis,
certain peculiar animal matters from their own tissue. These substances are then mingled together, dissolved in the watery fluids
of the secretion, and discharged simultaneously by the excretory
duct.
All the secreting organs vary in activity at different periods.
Sometimes they are nearly at rest; while at certain periods they
become excited, under the influence of an occasional or periodical
stimulus, and then pour out their secretion with great rapidity and in
large quantity. The perspiration, for example, is usually so slowly
secreted that it evaporates as rapidly as it is poured out, and the
surface of the skin remains dry; but under the influence of unusual
bodily exercise or mental excitement it is secreted much faster
than it can evaporate, and the whole integument becomes covered
with moisture. The gastric juice, again, in the intervals of digestion,
is either not secreted at all, or is produced in a nearly inappreciable
quantity; but on the introduction of food into the stomach, it is
immediately poured out in such abundance, that between two and
three ounces may be collected in a quarter of an hour.
I Leqons de Physiologie Experimentale. Paris, 1856, tome ii. p. 96 et seq.
2 Ibid., p. 106.




Mucus.                           309
The principal secretions met with in the animal body are as
follows:1. Mucus.                       6. Saliva.
2. Sebaceous matter.            7. Gastric juice.
3. Perspiration.                8. Pancreatic juice.
4. The tears.                   9. Intestinal juice.
5. The milk.                   10. Bile.
The last five of these fluids have already been described in the
preceding chapters.  We shall therefore only require to examine
at present the five following, viz., mucus, sebaceous matter, perspiration, the tears, and the milk, together with some peculiarities
in the secretion of the bile.
1. Mucus.-Nearly all the mucous membranes are provided with
follicles or glandule, in which the mucus is prepared. These follicles are most abundant in the lining membrane of the mouth, nares,
pharynx, oesophagus, trachea and bronchi, vagina, and male urethra.
They are generally of a compound form, consisting of a number of
secreting sacs or cavities, terminating at one end in- a blind extremity, and opening by the other into a common duct by which
the secreted fluid is discharged. Each ultimate secreting sac or
follicle is lined with glandular epithelium (Fig. 102), and surrounded on its external surface by a network of capillary bloodvessels.
These vessels, penetrating deeply into the
interstices between the follicles, bring the
blood nearly into contact with the epithelial
cells lining its cavity.  It is these cells  
which prepare the secretion, and discharge                        1
it afterward into the commencement of the
excretory duct.                                FOLLICLES OF A COMThe mucus, produced  in the manner  POUND Mucous GLANDULE.
From the human subject. (After
above described, is a clear, colorless fluid, Kiilliker.)-a. Membrane of the
which is poured out in larger or smaller follicle. b,. Epithelium of the
same.
quantity on the surface of the mucous
membranes:  It is distinguished from  other secretions by its viscidity, which is its most marked physical property, and which
depends on the presence of a peculiar animal matter, known under
the name of mucosine.  When unmixed with other animal fluids,
this viscidity is so great that the mucus has nearly a semi-solid or
gelatinous consistency. Thus, the mucus of the mouth, when obtained unmixed with the secretions of the salivary glands, is so




310                       SECRETION.
tough and adhesive that the vessel containing it may be turned
upside down without its running out.  The mucus of the cervix
uteri has a similar firm consistency, so as to block up the cavity
of this part of the organ with a semi-solid gelatinous mass. Mucus
is at the same time exceedingly smooth and slippery to the touch,
so that it lubricates readily the surfaces upon which it is exuded,
and facilitates the passage of foreign substances, while it defends
the mucous membrane itself from injury.
The composition of mucus, according to the analyses of Nasse,'
is as follows:
COMPOSITION OF PULMONARY MUCUS.
Water..                                             955.52
Animal matter.....    33.57
Fat...........     2.89
Chloride of sodium......                          5.83
Phosphates of soda and potassa...           1.05
Sulphates    ".....    0.65
Carbonates    ".......                         0.49
1000.00
The animal matter of mucus is insoluble in water; and consequently mucus, when dropped into water, does not mix with it, but
is merely broken up by agitation into gelatinous threads and flakes,
which subside after a time to the bottom. It is miscible, however,
to some extent, with other animal fluids, and may be incorporated
with them, so as to become thinner and more dilute. It readily
takes on putrefactive changes, and communicates them to other
organic substances with which it may be in contact.
The varieties of mucus found in different parts of the body are
probably not identical in composition, but differ a little in the character of their principal organic ingredient, as well as in the proportions of their saline constituents. The function of mucus is for
the most part a physical one, viz., to lubricate the mucous surfaces,
to defend them from injury, and to facilitate the passage of foreign
substances through their cavities.
2. SEBACEOUS MATTER.-The sebaceous matter is distinguished
by containing a very large proportion of fatty or oily ingredients.
There are three varieties of this secretion met with in the body,
viz., one produced by the sebaceous glands of the skin, another
by the ceruminous glands of the external auditory meatus, and
a third by the Meibonian glands of the eyelid.  The sebaceous
Simon's Chemistry of Man, Philada., 1846, p. 352.




SEBACEOUS MATTER.                      311
glands of the skin are found most abundantly in those parts which
are thickly covered with hairs, as well as on the face, the labia
minora of the female generative organs, the glans penis, and the
prepuce. They consist sometimes of a simple follicle, or flaskshaped cavity, opening by a single orifice; but more frequently of
a number of such follicles grouped round a common excretory duct.
The duct nearly always opens just at the root of one of the hairs,
which is smeared more or less abundantly
with its secretion. Each follicle, as in the    Fig. 103.
case of the mucous glandules, is lined
with epithelium, and its cavity is filled
with the secreted sebaceous matter.
In the Meibomian glands of the eyelid (Fig. 103), the follicles are ranged
along the sides of an excretory duct,
situated just beneath the conjunctiva, on
the posterior surface of the tarsus, and 
opening upon its free edge, a little behind the roots of the eyelashes. The
ceruminous glands of the external auditory meatus, again, have the form of long
tubes, which terminate, at the lower part    IBOIN  G, af
niIEIBOMIAN GLANDS,  after
of the integument lining the meatus, in  Ldovic.
a globular coil, or convolution, covered
externally by a network of capillary bloodvessels.
The sebaceous matter of the skin has the following composition,
according to Esenbeck. C
COMPOSITION OF SEBACEOUS MATTER.
Animal substances....  358
Fatty matters..                                  368
Phosphate of lime..                            200
Carbonate of lime....  21
Carbonate of magnesia..                           16
Chloride of sodium
Acetate of soda, &c...37
1000
Owing to the large proportion of stearine in the fatty ingredients
of the sebaceous matters, they have a considerable degree of consistency. Their office is to lubricate the integument and the hairs,
to keep them soft and pliable, and to prevent their drying up by
Simon's Chemistry of Man, p. 379.




312                       SECRETION.
too rapid evaporation. When the sebaceous glands of the scalp
are inactive or atrophied, the hairs become dry and brittle, are
easily split or broken off, and finally cease growing altogether.
The cerurinous matter of the ear is intended without doubt partly
to obstruct the cavity of: the meatus, and by its glutinous consistency and strong odor to prevent small insects from  accidentally
introducing themselves into the meatus.  The secretion of the
Meibomian glands, by being smeared on the edges of the eyelids,
prevents the tears from running over upon the cheeks, and confines
them within the cavity of the lachrymal canals.
3. PERSPIRATION.-The perspiratory glands of the skin are scattered everywhere throughout the integument, being most abundant
on the anterior portions of the body. They consist each of a slender
tube, about a-  of an inch in diameter, lined with glandular epithelium, which penetrates nearly through the entire thickness of
the skin, and terminates below in a globular coil, very similar in
appearance to that of the cerumiFig. 104.            nous glands of the ear. (Fig. 104.)
A  network of capillary vessels
envelops the tubular coil and supplies the gland with the materials
Kll ~      necessary to its secretion.
These glands are very abundant,~\^~~ IIin some parts.  On the posterior,/L'.  ysI <..~/portion of the trunk, the cheeks,
and the skin of the thigh and leg
there are according to Krause,
"<^ l/^p,,~"'-'    about 500 to the square inch; on'2/< < )Pthe anterior part of the trunk, the
-^^^~ ~        forehead, the neck, the forearm,
A PERSPIRATORY GLAND, with its ves- and the back of the hand and foot
sels; magnified35 times. (After Todd and Bowman.)-a.Glandular coil. b.Plexus ofvessels. 1000 to the square inch; and on
the sole of the foot and the palm
of the hand about 2700 in the same space. According to the same
observer, the whole number of perspiratory glands is not less than
2,300,000, and the length of each tubular coil, when unravelled,
about T5 of an inch. The entire length of the glandular tubing
must therefore be not less than 153,000 inches, or about two miles
and a half.' Kolliker, Handbuch der Gewebelehre, Leipzig, 1S52, p. 147.




PERSPIRATION.                         313
It is easy to understand, therefore, that a very large quantity of
fluid may be supplied from so extensive a glandular apparatus. It
results from  the researches of Lavoisier and Seguin' that the average quantity of fluid lost by cutaneous perspiration during 24
hours is 13,500 grains, or nearly two pounds avoirdupois.  A still
larger quantity than this may be discharged during a shorter time,
when the external temperature is high and the circulation active.
Dr. Southwood Smith2 found that the laborers employed in gas
works lost sometimes as much as 31 pounds' weight, by both cutaneous and pulmonary exhalation, in less than an hour. In these
cases, as Seguin has shown, the amount of cutaneous transpiration
is about twice as great as that which takes place through the lungs.
The perspiration is a colorless watery fluid, generally with a
distinctly acid reaction, and having a peculiar odor, which varies
somewhat according to the part of the body from which the specimen is obtained. Its chemical constitution, according to Anselmino,3 is as follows:COMPOSITION OF THE PERSPIRATION.
Water......995.00
Animal matters, with lime.....10
Sulphates, and substances soluble in water...   1.05
Chlorides of sodium and potassium, and spirit-extract..   2.40
Acetic acid, acetates, lactates, and alcohol-extract...   1.45
1000.00
The office of the cutaneous perspiration is principally to regulate
the temperature of the body. We have already seen, in a preceding chapter, that the living body will maintain the temperature of
1000 F., though subjected to a much lower temperature by the
surrounding atmosphere, in consequence of the continued generation of heat which takes place in its interior; and that if, by long
continued or severe exposure, the blood become cooled down much
below its natural standard, death inevitably results. But the body
has also the power of resisting an unnaturally high temperature,
as well as an unnaturally low one. If exposed to the influence of
an atmosphere warmer than 100~ F., the body does not become
heated up to the temperature of the air, but remains at its natural
standard.  This is provided for by the action of the cutaneous
glands, which are excited to unusual activity, and pour out a large
quantity of watery fluid upon the skin. This fluid immediately
I Milne Edwards, Leqons sur la Physiologie, &c., vol. ii. p. 623.
Philosophy of Health, London, 1838, chap. xiii.
Simon. Op. cit., p. 374.




314                      SECRETION.
evaporates, and in assuming the gaseous form causes so much heat
to become latent that the cutaneous surfaces are cooled down to
their natural temperature.
So long as the air is dry, so that evaporation from the surface
can go on rapidly, a very elevated temperature can be borne with
impunity. The workmen of the sculptor Chantrey were in the
habit, according to Dr. Carpenter, of entering a furnace in which
the air was heated up to 3500; and other instances have been known
in which a temperature of 4000 to 600~ has been borne for a time
without much inconvenience. But if the air be saturated with
moisture, and evaporation from the skin in this way retarded, the
body soon becomes unnaturally warm; and if the exposure be long
continued, death is the result. It is easily seen that horses, when
fast driven, suffer much more from a warm and moist atmosphere
than from a warm and dry one. The experiments of Magendie and
others have shown' that quadrupeds confined in a dry atmosphere
suffer at first but little inconvenience, even when the temperature
is much above that of their own bodies; but as soon as the atmosphere is loaded with moisture, or the supply of perspiration is exhausted, the blood becomes heated, and the animal dies. Death
follows in these cases as soon as the blood has become heated up to
80 or 9~ F., above, its natural standard. The temperature of 110~,
therefore, which is the natural temperature of birds, is fatal to quadrupeds; and we have found that frogs, whose natural temperature
is 50~ or 60~, die very soon if they are kept in water at 100~ F.
The amount of perspiration is liable to variation, as we have
already intimated, from the variations in temperature of the surrounding atmosphere. It is excited also by unusual muscular
exertion, and increased or diminished by various nervous conditions, such as anxiety, irritation, lassitude, or excitement.
4. THE TEARS.-The tears are produced by lobulated glands
situated at the upper and outer part of the orbit of the eye, and
opening, by from six to twelve ducts, upon the surface of the conjunctiva, in the fold between the eyeball and the outer portion of
the upper lid. The secretion is extremely watery in its composition,
and contains only about one part per thousand of solid matters,
consisting mostly of chloride of sodium and animal extractive
matter. The office of the lachrymal secretion is simply to keep the
I Bernard, Lectures on the Blood. Atlee's translation, p. 25.




THE MILK.                         315
surfaces of the cornea and conjunctiva moist and polished, and to
preserve in this way the transparency of the parts. The tears,
which are constantly secreted, are spread out uniformly over the
anterior part of the eyeball by the movement of the lids in winking, and are gradually conducted to the inner angle of the eye.
Here they are taken up by the puncta lachrymalia, pass through
the lachrymal canals, and are finally discharged into the nasal passages beneath the inferior turbinated bones. A constant supply of
fresh fluid is thus kept passing over the transparent parts of the
eyeball, and the bad results avoided-which would follow from  its
accumulation and putrefactive alteration.
5. THE MILK.-The mammary glands are conglomerate glands,
resembling closely in their structure the pancreas, the salivary, and
the lachrymal glands.  They consist of numerous secreting sacs or
follicles, grouped together in lobules, each lobule being supplied
with a common excretory duct, which joins those coming from
adjacent parts of the gland.
(Fig. 105.)  In this way, by                Fig. 105.
their successive union, they
form  larger branches and
trunks, until they are reduced
in numbers to some 15 or 20
cylindrical ducts, the laciferous ducts, which open finally
by as many minute orifices
upon the extremity of the
nipple.
The secretion of the milk
becomes fairly established at
the end of two or three days
after delivery, though  the      GLANDULAR STRUCTURE OF MAMMA.I.
breasts often contain a milky
fluid during the latter part of pregnancy.  At first the fluid discharged from the nipple is a yellowish turbid mixture, which is
called the colostrum. It has the appearance of being thinner than
the milk, but chemical examinations have shown' that it really contains a larger amount of solid ingredients than the perfect secretion.  When examined under the microscope it is seen to contain,
beside the milk-globules proper, a large amount of irregularly gloi Lehniann, op. cit., vol. ii p. 63.




316                         SECRETION.
bular or oval bodies, from  T-s  to so of an inch in diameter,
which are termed the "colostrum  corpuscles." (Fig. 106.)  These
bodies are more yellow and
Fig. 106.                opaque than the true milkglobules, as well as being very
/  \     much larger.  They have a
/  0  <           \-  well defined outline, and con/   \                       sist apparently of a group of
_/ A    \   minute oily granules or globules, imbedded  in  a mass
of organic substance.  The
0\ o~  II       /   milk-globules at this time
D\ o0  o                    / o   are less abundant than after\  II:" Q -'          / 0ward, and  of larger  size,
measuring mostly from aoW,/^^  ^to Ti o  of an inch  in diameter.
COLOSTRUM CORPUSCLES, with milk-globules;    A         
from a woman, one day after delivery.      At the end of a day or
two after its first appearance,
the colostrum  ceases to be discharged and is replaced by the true
milky secretion.
The milk, as it is discharged from the nipple, is a white, opaque
fluid, with a slightly alkaline reaction, and a specific gravity of
about 1030.  Its proximate chemical constitution, according to
Pereira and Lehmann, is as follows:
COMPOSITION OF COW'S MILK.
Water......   870.2
Casein.....    44.8
Butter..                                  31.3
Sugar.....47.7
Soda.....
Chlorides of sodium and potassium.....
Phosphates of soda and potassa.  
Phosphate of lime....                  6.0
"   magnesia..
"    "'  iron....
Alkaline carbonates...... 
1000.0
Human milk is distinguished from the above by containing less
casein, and a larger proportion of oily and saccharine ingredients.
The entire amount of solid ingredients is also somewhat less than
in cow's milk.




THE MILK.                          317
The casein is one of the most important ingredients of the milk.
It is an extremely nutritious organic substance, which is held in a
fluid form by union with the water of the secretion. Casein is not
coagulable by heat, and consequently, milk may be boiled without
changing its consistency to any considerable extent. It becomes
a little thinner and more fluid during ebullition, owing to the melting of its oleaginous ingredients; and a thin, membranous film
forms upon its surface, consisting probably of a very little albumen,
which the milk contains, mingled with the casein. The addition of
any of the acids, however, mineral, animal, or vegetable, at once
coagulates the casein, and the milk becomes curdled.  Milk is
coagulated, furthermore, by the gastric juice in the natural process
of digestion, immediately after being taken into the stomach; and
if vomiting occur soon after a meal containing milk, it is thrown
off in the form of semi-solid, curd-like flakes.
The mucous membrane of the calves' stomach, or rennet, also
has the power of coagulating casein; and when milk has been
curdled in this way, and its watery, saccharine, and inorganic ingredients separated by mechanical pressure, it is converted into
cheese.  The peculiar flavor of the different varieties of cheese
depends on the quantity and quality of the oleaginous ingredients
which have been entangled with the coagulated casein, and on the
alterations which these substances have undergone by                   Fig. 107.
the lapse of time and ex-o 0O
posure to the atmosphere.          /   oo o  o       o oo 
u 0    0o 0ou
The sugar and saline sub-    /          0o     o  0 o 0o \0
stances of the milk are in  o/0o  Oo0 o o oO oo0           0  \
0    l o     OCo       000o
solution, together with the  /  0o0  o  0OoOooo 00              \
0 V           po0   000
casein and water, forming a      O   0         o  
o        O    oO    ooXoOo 00     O-'
clear, colorless, homogene-     o        o  o        o   o 
ous, serous fluid. The but-  \        oo  oooo  o o   0o0 ooo oo o 0
ter, or oleaginous ingredient,  0\  o   o o o    o o o         /
however, is suspended  in    \ o          ~  o o         0ooo    /
-  \'   o o o  Y 00 (00)O 0 o o" /
this serous fluid in the form          o        oo  o o   o
of  minute  granules  and             oCoo 00 o
globules, the true  "milkglobules." (Fig 107.) These    MILK-GLOBULES; from same woman as above,
globules." (Fi. 17.  These  four days after delivery. Secretion fully established.
globules are nearly fluid at
the temperature of the body, and have a perfectly circular outline. In the perfect milk, they are very much more abundant and




318                       SECRETION.
smaller in size than in the colostrum; as the largest of them  are
not over 2'- of an inch in diameter, and the greater number
about T —   of an inch.
The following is the composition of the butter of cow's milk,
according to Robin and Verdeil:Margarine.....68
Oleine.......30
Butyrine.....                          2
100
It is the last of these ingredients, the butyrine, which gives the
peculiar flavor to the butter of milk.
The milk-globules have sometimes been described as if each one
were separately covered with a thin layer of coagulated casein or
albumen. No such investing membrane, however, is to be seen.
The milk-globules are simply small masses of semi-fluid fat, suspended by admixture in the watery and serous portions of the
secretion, so as to make an opaque, whitish emulsion. They do
not fuse together when they come in contact under the microscope,
simply because they are not quite fluid, but contain a large proportion of margarine, which is solid at ordinary temperatures of the
body, and is only retained in a partially fluid form by the oleine
with which it is associated. The globules may be made to fuse with
each other, however, by simply heating the milk and subjecting it
to gentle pressure between two slips of glass.
When fresh milk is allowed to remain at rest for twelve to twentyfour hours, a large portion of its fatty matters rise to the surface,
and form there a dense and rich-looking yellowish-white layer, the
cream, which may be removed, leaving the remainder still opaline,
but less opaque than before. At the end of thirty-six to forty-eight
hours, if the weather be warm, the casein begins to take on a
putrefactive change. In this condition it exerts a catalytic action
upon the other ingredients of the milk, and particularly upon the
sugar.  A pure watery solution of milk-sugar (C24,IO24) may be
kept for an indefinite length of time, at ordinary temperatures,
without undergoing any change.  But if kept in contact with the
partially altered casein, it suffers a catalytic transformation, and is
converted into lactic acid (C61606). This unites with the free soda,
and decomposes the alkaline carbonates, forming lactates of soda
and potassa. After the neutralization of these substances has been
accomplished, the milk loses its alkaline reaction and begins to turn
sour. The free lactic acid then coagulates the casein, and the milk




SECRETION OF THE BILE.                    319
is curdled. The altered organic matter also acts upon the oleaginous ingredients, which are partly decomposed; and the milk
begins to give off a rancid odor, owing to the development of
various volatile fatty acids, among which are butyric acid, and the
like.  These changes are very much hastened by a moderately
elevated temperature, and also by a highly electric state of the
atmosphere.
The production of the milk, like that of other secretions, is liable
to be much influenced by nervous impressions. It may be increased
or diminished in quantity, or vitiated in quality by sudden emotions; and it is even said to have been sometimes so much altered
in this way as to produce indigestion, diarrhoea, and convulsions in
the infant.
Simon found' that the constitution of the milk varies from day to
day, owing to temporary causes; and that it undergoes also more
permanent modifications, corresponding with the age of the infant.
He analyzed the milk of a nursing woman during a period of nearly
six months, commencing with the second day after delivery, and
repeating his examinations at intervals of eight or ten days. It
appears, from these observations, that the casein is at first in small
quantity; but that it increases during the first two months, and
then attains a nearly uniform standard. The saline matters also
increase in a nearly similar manner. The sugar, on the contrary,
diminishes during the same period; so that it is less abundant in
the third, fourth, fifth and sixth months, than it is in the first and
second. These changes are undoubtedly connected with the increasing development of the infant, which requires a corresponding
alteration in the character of the food. supplied to it. Finally, the
quantity of butter in the milk varies so much from  day to day,
owing to incidental causes, that it cannot be said to follow any
regular course of increase or diminution.
6. SECRETION OF THE BILE.-The anatomical peculiarities in the
structure of the liver are such as to distinguish it in a marked
degree from the other glandular organs. Its first peculiarity is
that it is furnished principally with venous blood. For, although
it receives its blood from the hepatic artery as well as from the
portal vein, the quantity of arterial blood with which it is supplied
is extremely small in comparison with that which it receives from
I Op. cit., p. 337.




320                       SECRETION.
the portal system. The blood which has circulated through the
capillaries of the stomach, spleen, pancreas, and intestine is collected by the roots of the corresponding veins, and discharged into
the portal vein, which enters the liver at the great transverse
fissure of the organ. Immediately upon its entrance, the portal
vein divides into two branches, right and left, which supply the
corresponding portions of the liver; and these branches successively subdivide into smaller twigs and ramifications, until they are
reduced to the size, according to K6lliker, of i2J0 of an inch in
diameter. These veins, with their terminal branches, are arranged
in such a manner as to include between them  pentagonal or
hexagonal spaces, or portions of the hepatic substance, -g  to T1
of an inch in diameter in the human subject, which can readily be
distinguished by the naked eye, both on the exterior of the organ
and by the inspection of cut surfaces. The portions of hepatic
substance included in this way between the terminal branches
of the portal vein (Fig. 108)
Fig. 108              are termed the "acini" or
"lobules" of the liver; and
x/^ \. y^   J ^\ ~the terminal venous branches,
occupying the spaces between
//,     the adjacent lobules, are the
\   "interlobular" veins. In the
spaces between the lobules
l:< 1;.           we also  find  the  minute
\k D i' S  branches of the hepatic: arb                                tery, and  the commencing
X\*~~~' ^^  A/ ~rootlets of the hepatic ducts.
As the portal vein, the he\^'a1  /^~'patic artery, and the hepatic
duct enter the liver at the
Ramification of PORTAL VEIN 7T LIVER — a.
Twig of portal vein. b, b. Interlobular veins. c Acini. transverse fissure, they are
closely invested by a fibrous
sheath, termed Glisson's capsule, which accompanies them in their
divisions and ramifications. In some of the lower animals, as in the
pig, this sheath extends even to the interlobular spaces, inclosing
each lobule in a thin fibrous investment, by which it is distinctly
separated from the neighboring parts. In the human subject, however, Glisson's capsule becomes gradually thinner as it penetrates
the liver, and disappears altogether before reaching the interlobular
spaces; so that here the lobules are nearly in contact with each




SECRETION  OF THE BILE.                     321
other by their adjacent surfaces, being separated only by the interlobular veins and the minute branches of the hepatic artery and
duct previously mentioned.
From  the sides of the interlobular veins, and also from  their
terminal extremities, there are given off capillary vessels, which
penetrate the substance of each lobule and converge from  its circumference toward its centre, inosculating at the same time freely
with each other, so as to form a minute vascular plexus, the "lobular" capillary plexus. (Fig. 109.) At the centre of each lobule, the
Fig. 109.
LOBULE OF LTVER, showing distribution of bloodvessels; magnified 22 diameters.-a, a. Interlobular veins. b. Intralobular vein. c, c, c. Lobular capillary plexus. d, d. Twigs of interlobular vein passing to adjacent lobules.
converging capillaries unite into a small vein (b), the "intralobular" vein, which is one of the commencing rootlets of the hepatic
vein. These rootlets, uniting, successively with each other, so as
to form larger and larger branches, finally leave the liver at its
posterior edge, to empty into the ascending vena cava.
Beside the capillary bloodvessels of the lobular plexus, each
acinus is made up of an abundance of minute cellular bodies, about
JoU of an inch in diameter, the "hepatic cells." (Fig. 110.)  These
cells have an irregularly pentagonal figure, and a soft consistency.
They are composed of a homogeneous organic substance, in the
midst of which are imbedded a large number of minute granules,
and generally several well defined oil-globules. There is also a
round or oval nucleus, with a nucleolus, imbedded in the substance
21




322                       SECRETION.
of the cell, sometimes more or less obscured by the granules and
oil drops with which it is surrounded.
The exact mode in which these cells are connected with the
hepatic duct was for a long time the most obscure point in the
minute anatomy of the liver.
Fig. 110.              It has now been ascertained,
however, by the researches of
Dr. Leidy, of Philadelphia.l
/41          \       and Dr. Beale, of London,2
/  ( > H,  \    that they are really contained
/r~ k ~     0 o   ~    \  in the interior of secreting
( o\                \tubules, which pass off from
the smaller hepatic ducts, and
\ a(~ /^':" -^penetrate  everywhere  the
o\   D~ ^1        / ~substance  of the  lobules.
The cells fill nearly or com\-^ ~.^/ ~pletely the whole cavity of
the tubules, and the tubules
HEPATIC CELLS. From the human subject.   themselves lie in close proximity with each other, so as
to leave no space between them except that which is occupied by
the capillary bloodvessels of the lobular plexus.
These cells are the active agents in accomplishing the function of
the liver. It is by their influence that the blood which is brought
in contact with them suffers certain changes which give rise to the
secreted products of the organ. The ingredients of the bile first
make their appearance in the substance of the cells. They are
then transuded from  one to the other, until they are at last discharged into the small biliary ducts seated in the interlobular
spaces. Each lobule of the liver must accordingly be regarded as
a mass of secreting tubules, lined with glandular cells, and invested
with a close network of capillary bloodvessels. It follows, therefore, from the abundant inosculation of the lobular capillaries, and
the manner in which they are entangled with the hepatic tissue,
that the blood, in passing through the circulation of the liver,
comes into the most intimate relation with the glandular cells of
the organ, and gives up to them the nutritious materials which are
afterward converted into the ingredients of the bile.: American Journal Med. Sci., January, 1848.
2 On Some Points in the Minute Anatomy of the Liver. London, 1856.




EXCRETION.                       323
CHAPTER XVII.
EXCRETION.
WE have now come to the last division of the great nutritive
function, viz., the process of excretion. In order to understand fairly
the nature of this process we must remember that all the component
parts of a living organism are necessarily in a state of constant
change. It is one of the essential conditions of their existence and
activity that they should go through with this incessant transformation and renovation of their component substances. Every living
animal and vegetable, therefore, constantly absorbs certain materials
from the exterior, which are modified and assimilated by the process of nutrition, and converted into the natural ingredients of the
organized tissues. But at the same time with this incessant growth
and supply, there goes on in the same tissues an equally incessant
process of waste and decomposition. For though the elements of
the food are absorbed by the tissues, and converted into musculine,
osteine, haematine and the like, they do not remain permanently in
this condition, but almost immediately begin to pass over, by a continuance of the alterative process, into new forms and combinations,
which are destined to be expelled from the body, as others continue
to be absorbed. Thus Spallanzani and Edwards found that every
organized tissue not only absorbs oxygen from the atmosphere
and fixes it in its own substance; but at the same time exhales
carbonic acid, which has been produced by internal metamorphosis.
This process, by which the ingredients of the organic tissues, already formed, are decomposed and converted into new substances,
is called the process of Destructive Assimilation.
Accordingly we find that certain substances are constantly making their appearance in the tissues and fluids of the body, which
did not exist there originally, and which have not been introduced
with the food, but which have been produced by the process of internal metamorphosis. These substances represent the waste, or
physiological detritus of the animal organism. They are the forms




324                      EXCRETION.
under which those materials present themselves, which have once
formed a part of the living tissues, but which have become altered
by the incessant changes characteristic of organized bodies, and
which are consequently no longer capable of exhibiting vital properties, or of performing the vital functions. They are, therefore,
destined to be removed and discharged from the animal frame, and
are known accordingly by the name of Excrementitious Substances.
These excrementitious substances have peculiar characters by
which they may be distinguished from the other ingredients of the
living body; and they might, therefore, be made to constitute a
fourth class of proximate principles, in addition to the three which
we have enumerated in the preceding chapters. They are all substances of definite chemical composition, and all susceptible of
crystallization. Some of the most important of them contain nitrogen, while a few are non-nitrogenous in their composition., They
originate in the interior of living bodies, and are not found elsewhere, except occasionally as the result of decomposition. They
are nearly all soluble in water, and are soluble without exception in
the animal fluids. They are formed in the substance of the tissues,
from which they are absorbed by the blood, to be afterward conveyed
by the circulating fluid to certain excretory organs, particularly the
kidneys, from which they are finally discharged and expelled from
the body. This entire process, made up of the production of the
excrementitious substances, their absorption by the blood, and their
final elimination, is known as the process of excretion.
The importance of this process to the maintenance of life is readily
shown by the injurious effects which follow upon its disturbance.
If the discharge of the excrementitious substances be in any way
impeded or suspended, these substances accumulate, either in the
blood or in the tissues, or in both. In consequence of this retention
and accumulation, they become poisonous, and rapidly produce a
derangement of the vital functions. Their influence is principally
exerted upon the nervous system, through which they produce
most frequently irritability, disturbance of the special senses, delirium, insensibility, coma, and finally death. The readiness with
which these effects are produced depends on the character of the
excrementitious substance, and the rapidity with which it is produced in the body. Thus, if the elimination of carbonic acid be
stopped, by overloading the atmosphere with an abundance of the
same gas, death takes place at the end of a few minutes; but if the
elimination of urea by the kidneys be checked, it requires three or




UREA.                            325
four days to produce a fatal result.  A fatal result, however, is certain to follow, at the end of a longer or shorter time, if any one of
these substances be compelled to remain in the body, and accumulate in the animal tissues and fluids.
The principal exerementitious substances known to exist in the
human body are as follows:1. Carbonic acid...                  CO0
2. Cholesterine  C 2H220
3. Urea......                CHN202
4. Creatine...                       CHN30
5. Creatinine....  CsH7N0
6. Urate of soda....   NaO,CHN,02+HO
7. Urate of potassa..          KO,CHN202
8. Urate of ammonia     N...        NH4O,2C5HN202+HO
Of these substances the first two have already been studied at
sufficient length in the preceding chapters. We will merely repeat
here that carbonic acid is produced in large quantity in nearly all
the tissues of the body, from which it is absorbed by the blood,
conveyed to the lungs, and there exhaled at the same time that
oxygen is absorbed.  Cholesterine is a non-saponifiable fatty substance, originating in the brain and spinal cord, in the tissue of
which organs it exists in the proportion of 58 parts per thousand.
It is thence taken up by the blood, conveyed to the liver and discharged with the bile.  Cholesterine is extremely insoluble in
water, but is held in solution in the blood and the bile, by some of
the other ingredients present in these animal fluids.
The remaining excrementitious substances may be examined
together with the more propriety, since they are all ingredients of
a single excretory fluid, viz., the urine.
UREA.-This is a neutral, crystallizable, nitrogenous substance,
very readily soluble in water, and easily decomposed by various
external influences. It occurs in the urine in the proportion of 30
parts per thousand; in the blood, according to Picard,' in the proportion of 0.016 per thousand.  The blood, however, is the source
from which this substance is supplied to the urine; and it exists,
accordingly, in but small quantity in the circulating fluid, for the
reason that it is constantly drained off by the kidneys. But if the
kidneys be extirpated, or the renal arteries tied, or the excretion
of urine suspended by inflammation or otherwise, the urea then' In Milne Edwards, Lemons sur la Physiologie, &c, vol. i. p. 297.




326                        EXCRETION.
accumulates in the blood, and presents itself there in considerable
quantity.  It has been found in the blood, under these circumstances, in the proportion of 1.4 per thousand.l It is not yet known
from what source the urea is
Fig. 111.              originally derived; whether it
be produced in the blood itself,
/  \  \      or whether it be formed in some
of the solid tissues, and thence
taken up by the blood.  It has
S  11i~ nnot yet been found, however,
in any of the solid tissues, in a
state of health.
Urea isobtained most readily
\  I I~ II/       from the urine. For thispurf 1/1t A^/       pose the fresh urine is evaporated in the water bath until it
has a syrupy consistency.  It
UREA, prepared from urine, and crystallized by  i then mixed with an equal
slow evaporation. (After Lehmann.)
volume of nitric acid, which
forms nitrate of urea. This salt, being less soluble than pure urea,
rapidly crystallizes, after which it is separated by filtration from
the other ingredients.  It is then dissolved in water and decomposed by carbonate of lead, forming nitrate of lead which remains
in solution, and carbonic acid which escapes. The solution is then
evaporated, the urea dissolved out by alcohol, and finally crystallized in a pure state.
Urea has no tendency to spontaneous decomposition, and may
be kept, when perfectly pure, in a.dry state or dissolved in water,
for an indefinite length of time.  If the watery solution be boiled,
however, the urea is converted, during the process of ebullition,
into carbonate of ammonia.  One equivalent of urea unites with
two equivalents of water, and becomes transformed into two equivalents of carbonate of ammonia, as follows:C2H4N202=Urea.           NH3,CO2=Carbonate of ammonia.
H.2 02=Water.               2
C2H,6N04                N2H6C204
Various impurities, also, by acting as catalytic bodies, will induce the same change, if water be present. Animal substances in
a state of commencing decomposition are particularly liable to act'Robin and Verdeil, vol. ii. p. 502.




UREA.                           327
in this way. In order that the conversion of the urea be thus produced, it is necessary that the temperature of the mixture be not
far from 700 to 1000 F.
The quantity of urea produced and discharged daily by a healthy
adult is, according to the experiments of Lehmann, about 500
grains. It varies to some extent, like all the other secreted and
excreted products, with the size and development of the body.
Lehmann, in experiments on his own person, found the average
daily quantity to be 487 grains. Prof. William A. Hammond,1
who is a very large man, by similar experiments found it to be
670 grains. Dr. John C. Draper2 found it 408 grains. No urea is
to be detected in the urine of very young children;3 but it soon
makes its appearance, and afterward increases in quantity with the
development of the body.
The daily quantity of urea varies also with the degree of mental
and bodily activity.  Lehmann and Hammond both found it very
sensibly increased by muscular exertion and diminished by repose.
It has been thought, from these facts, that this substance must be
directly produced from disintegration of the muscular tissue. This,
however, is by no means certain; since in a state of general bodily
activity it is not only the urea, but the excretions generally, carbonic
acid, perspiration, &c., which are increased in quantity simultaneously. Hammond has also shown that continued mental application will raise the quantity of urea above its normal standard,
though the muscular system remain comparatively inactive.
The quantity of urea varies also with the nature of the food.
Lehmann, by experiments on his own person, found that the quantity was larger while living exclusively on animal food than with
a mixed or vegetable diet; and that its quantity was smallest when
confined to a diet of purely non-nitrogenous substances, as starch,
sugar, and oil.  The following table' gives the result of these experiments.
KIND OF FOOD.                      DAILY QUANTITY OF UREA.
Animal....   798 grains.
Mixed.......   487  "
Vegetable.....                       337
Non-nitrogenous..                       231 "
1 American Journal Med. Sci., Jan., 1855, and April, 1856.
2 New York Journal of Medicine, March, 1856.
3 Robin and Verdeil, vol. ii. p. 500.
4 Lehmann, op. cit., vol. ii. p. 163.




328                       EXCRETION.
Finally, it has been shown by Dr. John C. Draper' that there is
also a diurnal variation in the normal quantity of urea. A smaller
quantity is produced during the night than during the day; and
this difference exists even in patients who are confined to the bed
during the whole twenty-four hours, as in the case of a man under
treatment for fracture of the leg. This is probably owing to the
greater activity, during the waking hours, of both the mental and
digestive functions.  More urea is produced in the latter half than
in the earlier half of the day; and the greatest quantity is discharged during the four hours from 6- to 10~ P. M.
Urea exists in the urine of the carnivorous and many of the
herbivorous quadrupeds; but there is little or none to be found in
that of birds and reptiles.
CREATINE.-This is a neutral crystallizable substance, found in
the muscles, the blood, and the urine. It is soluble in water, very
slightly soluble in alcohol, and
Fig. 112.             not at all so in ether. By boiling with an alkali, it is either
~/^  ^ G   converted into carbonic  acid
At/'''\;,' %     x, \and ammonia, or is decomposed
/                                w D.,    \ z  Pwith the production of urea and
//G;    A Tan artificial nitrogenous cryscosine. By being heated with
strong acids, it loses two equiva\  r / /  lents of water, and is converted
into the substance next to be
As  _'  <  described, viz., creatinine.
Creatine exists in the urine,
CR(EATINE, crystallized from hot water. (After i, 
Lehmann.)                          n the human subject, in the
proportion of about 1.25 parts,
and in the muscles in the proportion of 0.67 parts per thousand.
Its quantity in the blood has not been determined. In the muscular tissue it is simply in solution in the interstitial fluid of the parts,
so that it may be extracted by simply cutting the muscle into
small pieces, treating it with distilled water, and subjecting it to
pressure.  Creatine evidently originates in the muscular tissue, is
absorbed thence by the blood, and is finally discharged with the
urine.
I Loc. cit.




CREATININE-URATE OF SODA.                      329
CREATININE.-This is also a crystallizable substance. It differs
in composition from creatine by containing two equivalents less of
the elements of water. It is more soluble in water and in spirit
than creatine, and dissolves slightly also in ether. It has a distinctly alkaline reaction. It occurs, like creatine, in the muscles,
the blood, and the urine; and
is undoubtedly first produced                  Fig. 113.
in the muscular tissue, to be
discharged finally by the kid-  A
neys.  It is very possible that
it originates, not directly from 
the muscles, but indirectly, by
transformation of a part of the
creatine; since it may be artificially produced, as we have
already  mentioned, by transformation of the latter substance
under the influence of strong
acids, and since, furthermore,,,  n   sc   ft h,    CREATININE, crystallized from hot water
while creatine is more abundant  (After Lehmann.)
in the muscles than creatinine,
in the urine, on the contrary, there is a larger quantity of creatinine
than of creatine. Both these substances have been found in the
muscles and in the urine of the lower animals.
URATE OF SODA.-As its name implies, this substance is a neutral salt, formed by the union of soda, as a base, with a nitrogenous
animal acid, viz., uric acid (C,5IN20,HO).  Uric acid is sometimes
spoken of as though it were itself a proximate principle, and a
constituent of the urine; but it cannot properly be regarded as
such, since it never occurs in a free state, in a natural condition of
the fluids.  When present, it has always been produced by decomposition of the urate of soda.
Urate of soda is readily soluble in hot water, from which a large
portion again deposits on cooling. It is slightly soluble in alcohol,
and insoluble in ether. It crystallizes in small globular masses,
with projecting, curved, conical, wart-like excrescences. (Fig. 114.)
It dissolves readily in the alkalies; and by most acid solutions it
is decomposed, with the production of free uric acid.
Urate of soda exists in the urine and in the blood. It is either
produced originally in the blood, or is formed in some of the solid




330                      EXCRETION.
tissues, and absorbed from them by the circulating fluid. It is constantly eliminated by the kidneys, in company with the other ingredients of the urine.  The
Fig. 114.             average  daily quantity  of
-/^"  ^urate of soda discharged by
the healthy human subject is,
according to Lehmann, about
/```- r25 grains.  This substance
exists in the urine of the carnivorous  and  Qmnivorous
~'^   J animals, but not in that of
the herbivora. In the latter,
it is replaced by another substance, differing  somewhat,~ y/  ~ from it in composition and
\  _ ^ /   properties, viz., hippurate of
URATE OF SODA; from a urinary deposit.    sda. The urine of herbivora, however, while still
very young, and living upon the milk of the mother, has been found
to contain urates. But when the young animal is weaned, and becomes herbivorous, the urate of soda disappears, and is replaced by
the hippurate.
URATES OF POTASSA AND AMMONIA.-The urates of potassa and
ammonia resemble the preceding salt very closely in their physiological relations. They are formed in very much smaller quantity
than the urate of soda, and appear like it as ingredients of the urine.
The substances above enumerated closely resemble each other in
their most striking and important characters. They all contain
nitrogen, are all crystallizable, and all readily soluble in water.
They all originate in the interior of the body by the decomposition
or catalytic transformation of its organic ingredients, and are all
conveyed by the blood to the kidneys, to be finally expelled with
the urine. These are the substances which represent, to a great
extent, the final transformation of the organic or albuminoid ingredients of the tissues.. It has already been mentioned, in a previous chapter, that these organic or albuminoid substances are not
discharged from the body, under their own form, in quantity at all
proportionate to the abundance with which they are introduced.
By far the greater part of the mass of the frame is made up of
organic  substances: albumen, musculine, osteine, &c.  Similar




GENERAL CHARACTERS OF THE URINE.                 331
materials are taken daily in large quantity with the food, in order
to supply the nutrition and waste of those already composing the
tissues; and yet only a very insignificant quantity of similar
material is expelled with the excretions.  A minute proportion of
volatile animal matter is exhaled with the breath, and a minute
proportion also with the perspiration.  A very small quantity is
discharged under the form of mucus and coloring matter, with the,
urine and feces; but all these taken together are entirely insufficient to account for the constant and rapid disappearance of organic
matters in the interior of the body. These matters, in fact, before
being discharged, are converted by catalysis and decomposition into
new substances. Carbonic acid, under which form 3500 grains of
carbon are daily expelled from the body, is one of these substances;
the others are urea, creatine, creatinine, and the urates.
We see, then, in what way the organic matters, in ceasing to form
a part of the living body, lose their characteristic properties, and
are converted into crystallizable substances, of definite chemical
composition. It is a kind of retrograde metamorphosis, by which
they return more or less to the condition of ordinary inorganic
materials. These excrementitious matters are themselves decomposed, after being expelled from the body, under the influence of
the atmospheric air and moisture; so that the decomposition and
destruction of the organic substance are at last complete.
It will be seen, consequently, that the urine has a character
altogether peculiar, and one which distinguishes it completely
from every other animal fluid. All the others are either nutritive
fluids, like the blood and milk, or are destined, like the secretions
generally, to take some direct and essential part in the vital operations. Many of them, like the gastric and pancreatic juices, are
reabsorbed after they have done their work, and again enter the
current of the circulation. But the urine is merely a solution of
excrementitious substances. Its materials exist beforehand in the
circulation, and are simply drained away by the kidneys from
the blood. There is a wide difference, accordingly, between the
action of the kidneys and that of the true glandular organs, in
which certain new and peculiar substances are produced by the
action of the glandular tissue. The kidneys, on the contrary, do
not secrete anything, properly speaking, and are not, therefore,
glands. In their mode of action, so far as regards the excretory
function, they have more resemblance to the lungs than to any
other of the internal organs. But this resemblance is not complete;




332                      EXCRETION.
since the lungs perform a double function, absorbing oxygen at the
same time that they exhale carbonic acid. The kidneys alone are
purely excretory in their office. The urine is not intended to
fulfil any function, mechanical, chemical, or otherwise; but is destined only to be eliminated and expelled. Since it possesses so
peculiar and important a character, it will require to be carefully
studied in detail.
The urine is a clear, watery, amber-colored fluid, with a distinct
acid reaction. It has, while still warm, a peculiar odor, which disappears more or less completely on cooling, and returns when the
urine is gently heated. The ordinary quantity of urine discharged
daily by a healthy adult is about ~xxxv, and its mean specific
gravity, 1024. Both its total quantity, however, and its mean
specific gravity are liable to vary somewhat from day to day, owing
to the different proportions of water and solid ingredients entering
into its constitution. Ordinarily the water of the urine is more
than sufficient to hold all its solid matter in solution; and its proportion, may therefore be diminished by accidental causes without
the urine becoming turbid by the formation of a deposit. Under
such circumstances, it merely becomes deeper in color, and of a
higher specific gravity. Thus, if a smaller quantity of water than
usual be taken into the system with the drink, or if the fluid exhalations from the lungs and skin, or the intestinal discharges, be
increased, a smaller quantity of water will necessarily pass off by
the kidneys; and the urine will be diminished in quantity, while its
specific gravity is increased. We have observed the urine to be
reduced in this way to eighteen or twenty ounces per day, its specific
gravity rising at the same time to 1030. On the other hand, if the
fluid ingesta be unusually abundant, or if the perspiration be diminished, the surplus quantity of water will pass off by the kidneys; so
that the amount of urine in twenty-four hours may be increased to
forty-five or forty-six ounces, and its specific gravity reduced at
the same time to 1020 or even 1017. Under these conditions the
total amount of solid matter discharged daily remains about the
same. The changes above mentioned depend simply upon the
fluctuating quantity of water, which may pass off by the kidneys
in larger or smaller quantity, according to accidental circumstances.
In these purely normal or physiological variations, therefore, the
entire quantity of the urine and its mean specific gravity vary
always in an inverse direction with regard to each other; the former
increasing while the latter diminishes, and vice vers. If, however, it




DIURNAL VARIATIONS OF THE URINE.                  333
should be found that both the quantity and specific gravity of the
urine were increased or diminished at the same time, or if either
one were increased or diminished while the other remained stationary, such an alteration would show an actual change in the total
amount of solid ingredients, and would indicate an unnatural and
pathological condition. This actually takes place in certain forms
of disease.
The amount of variation in the quantity of water, even, may be
so great as to constitute by itself a pathological condition.  Thus,
in hysterical attacks there is sometimes a very abundant flow of
limpid, nearly colorless urine, with a specific gravity not over 1005
or 1006.  On the other hand, in the onset of febrile attacks, the
quantity of water is often so much diminished that it is no longer
sufficient to retain in solution all the solid ingredients of the urine,
and the urate of soda is thrown down, after cooling, as a fine red
or yellowish sediment.  So long, however, as the variation is confined within strictly physiological limits, all the solid ingredients
are held in solution, and the urine remains clear.
There is also, in a state of health, a diurnal variation of the urine,
both in regard to its specific gravity and its degree of acidity.
The urine is generally discharged from the bladder five or six
times during the twenty-four hours, and at each of these periods
shows more or less variation in its physical characters.  We have
found that the urine which collects in the bladder during the
night, and is first discharged in the morning, is usually dense,
highly colored, of a strongly acid reaction, and a high specific
gravity.  That passed during the forenoon is pale, and of a low
specific gravity, sometimes not more than 1018 or even 1015. It
is at the same time neutral or slightly alkaline in reaction. Toward
the middle of the day, its density and depth of color increase, and
its acidity returns.  All these properties become more strongly
marked during the afternoon and evening, and toward night the
urine is again deeply colored and strongly acid, and has a specific
gravity of 1028 or 1030.
The following instances will serve to show the general characters
of this variation:OBSERVATION FIRST. March 20th.
Urine of 1st discharge, acid,  sp. gr. 1025.
" 2d    "    alkaline, "  1015.
" 3d    "    neutral,  "  1018..
" 4th   "    acid,     "  1018.
" 5th   "    acid,     "  1027.




334                          EXCRETION.
OBSERVATION SECOND. March 21st.
Urine of 1st discharge, acid,   sp. gr. 1029.
2d    "    neutral,   "   1022.
" 3d    "    neutral,   "   1025.
" 4th   "    acid,       "   1027.
" 5th   "    acid,       "   1030.
These variations do  not always follow  the perfectly regular
course manifested in the above instances, since they are somewhat
liable, as we have already mentioned, to temporary modification
from accidental causes during the day; but their general tendency
nearly always corresponds with that given above.
It is evident, therefore, that whenever we wish to test the specific
gravity and acidity of the urine in cases of disease, it will not be
sufficient to examine any single specimen taken at random; but all
the different portions discharged during the day should be collected
and examined together.  Otherwise, we should incur the risk of
regarding  as a permanently  morbid  symptom  what might be
nothing more than a purely accidental and temporary variation.
The chemical constitution of the urine as it is discharged from the
bladder, according to the analyses of Berzelius, Lehmann, Becquerel,
and others, is as follows:
COMIPOSITION OF THE URINE.
Water..........  938.00
Urea...30.00
Creatine.......    1.25
Creatinine......                            1.50
Urate of soda 
"  potassa.                                    1.80
"  ammonia
Coloring matter and                                           30
Mucus       o s 
Biphosphate of soda
Phosphate of soda [
"       potassa.....        12.45
"      mmagnesia I
"       lime    J
Chlorides of sodium and potassium....  7.80
Sulphates of soda and potassa....    6.90
1000.00
We need not repeat that the proportionate quantity  of these
different ingredients, as given above, is not absolute, but only
approximative; and that they vary, from time to time, within certain
physiological limits, like the ingredients of all other animal fluids.
The urea, creatine, creatinine and urates have all been suffi



REACTIONS OF THE URINE.                    335
ciently described above. The mucus and coloring matter, unlike
the other ingredients of the urine, belong to the class of organic
substances proper. They are both present, as may be seen by the
analysis quoted above, in very small quantity.  The coloring
matter, or urosacine, is in solution in a natural condition of the
urine, but is apt to be entangled by any accidental deposits which
may be thrown down, and more particularly by those consisting of
the urates. These deposits, from being often strongly colored red
or pink by the urosacine thus thrown down with them, are known
under the name of "brick-dust" sediments.
The mucus of the urine comes from the lining membrane of the
urinary bladder.  When first discharged it is not visible, owing to
its being uniformly disseminated through the urine by mechanical
agitation; but if the fluid be allowed to remain at rest for some
hours in a cylindrical glass vessel, the mucus collects at the bottom,
and may then be seen as a light cottony cloud, interspersed often
with minute semi-opaque points. It plays, as we shall hereafter
see, a very important part in the subsequent fermentation and
decomposition of the urine.
Biphosphate of soda exists in the urine by direct solution, since it is
readily soluble in water. It is this salt which gives to the urine its
acid reaction, as there is no free acid present in the recent condition.
It is probably derived from the neutral phosphate of soda in the
blood, which is decomposed by the uric acid at the time of its formation; producing, on the one hand, a urate of soda, and converting
a part of the neutral phosphate of soda into the acid biphosphate.
The phosphates of lime and magnesia, or the "earthy phosphates,"
as they are called, exist in the urine by indirect solution. Though
insoluble, or very nearly so, in pure water, they are held in solution in the urine by the acid phosphate of soda, above described.
They are derived from the blood, in which they exist in considerable quantity. When the urine is alkaline, these phosphates are
deposited as a light-colored precipitate, and thus communicate a
turbid appearance to the fluid. When the urine is neutral, they
may still be held in solution, to some extent, by the chloride of
sodium, which has the property of dissolving a small quantity of
phosphate of lime.
The remaining ingredients, phosphates of soda and potassa, sulphates and chlorides, are all derived from the blood, and are held
directly in solution by the water of the urine.
The urine, constituted by the above ingredients, forms, as we




336                      EXCRETION.
have already described, a clear amber-colored fluid, with a'reaction
for the most part distinctly acid, sometimes neutral, and occasionally slightly alkaline. In its healthy condition it is affected by
chemical and physical reagents in the'following manner.
Boiling the urine does not produce any visible change, provided
its reaction be acid. If it be neutral or alkaline, and if, at the same
time, it contain a larger quantity than usual of the earthy phosphates, it will become turbid on boiling; since these salts are less
soluble at a high than at a low temperature.
The addition of nitric or other mineral acid produces at first only
a slight darkening of the color, owing to the action of the acid upon
the organic coloring matter of the urine. If the mixture, however,
be allowed to stand for some time, the urates of soda, potassa, &c.,
will be decomposed, and pure uric acid, which is very insoluble,
will be deposited in a crystalline form upon the sides and bottom
of the glass vessel. The crystals of uric acid have most frequently
the form of transparent rhomboidal plates, or oval laminae with
pointed extremities. They are usually tinged of a yellowish hue
by the coloring matter of the urine which is united with them
at the time of their deposit.  They are frequently arranged in
radiated clusters, or small spheroidal masses, so as to present the
appearance of minute calcuFig. 115.             lous concretions. (Fig. 115.)
f/^^~^^~ ~           The crystals vary very much
/  (\    Ad\    ^in size and regularity, ac/~  \).  I u/   - \   in their formation.
If a free alkali, such as
fh (^    l\\potassa or soda, be added to
^  the urine, so as to neutralize
its acid reaction, it becomes
immediately turbid  from  a
\  h    A  /    deposit of the earthy phos-.
phates, which are insoluble
in alkaline fluids.
The addition of nitrate of
UR I C A ID; deposited from urine.
baryta, chloride of barium,
or subacetate of lead to healthy urine, produces a dense precipitate, owing to the presence of the alkaline sulphates.
Nitrate of silver produces a precipitate with the chlorides of
sodium and potassium.




REACTIONS OF THE URINE.                     337
Subacetate of lead and nitrate of silver precipitate also the organic substances, mucus and coloring matter, present in the urine.
All the above reactions, it will be seen, are owing to the presence
of the natural ingredients of the urine, and do not, therefore, indicate any abnormal condition of the excretion.
Beside the properties mentioned above, the urine has several
others which are of some importance, and which have not been
usually noticed in previous descriptions. It contains, among other
ingredients, certain organic substances which have the power of
interfering with the mutual reaction of starch and iodine, and even
of decomposing the iodide of starch, after it has once been formed.
This peculiar action of the urine was first noticed and described
by us in 1856.1 If 3j of iodine water be mixed with a solution
of starch, it strikes an opaque blue color; but if 3j of fresh urine
be afterward added to the mixture, the color is entirely destroyed
at the end of four or five seconds. If fresh urine be mixed with
four or five times its volume of iodine water, and starch be
subsequently added, no union takes place between the starch and
iodine, and no blue color is produced. In these instances, the iodine
unites with the animal matters of the urine in preference to combining with the starch, and is consequently prevented from striking
its ordinary blue color with the latter. This interference occurs
whether the urine be acid or alkaline in reaction. In all cases in
which iodine exists in the urine, as for example where it has been
administered as a medicine, it is under the form of an organic combination; and in order to detect its presence by means of starch, a
few drops of nitric acid must be added at the same time, so as to
destroy the organic matters, after which the blue color immediately
appears, if iodine be present. This reaction with starch and iodine
belongs also, to some extent, to most of the other animal fluids, as
the saliva, gastric and pancreatic juices, serum of the blood, &c.;
but it is most strongly marked in the urine.
Another remarkable property of the urine, also dependent on its
organic ingredients, is that of interfering with Trommer's test for
grape sugar. If clarified honey be mixed with fresh urine, and sulphate of copper with an excess of potassa be afterward added, the
mixture takes a dingy, grayish blue color. On boiling, the color
turns yellowish or yellowish-brown, but the suboxide of copper is
not deposited. In order to remove the organic matter and detect
American Journal Med. Sci., April, 1856.
22




338                      EXCRETION.
the sugar, the urine must be first treated with an excess of animal
charcoal and filtered. By this means the organic substances are
retained upon the filter, while the sugar passes through in solution,
and may then be detected as usual by Trormer's test.
ACCIDENTAL INGREDIENTS OF THE URINE.-Since the urine, in
its natural state, consists of materials which are already prepared in
the blood, and which merely pass out through the kidneys by a
kind of filtration, it is not surprising that most medicinal and
poisonous substances, introduced into the circulation, should be
expelled -frm  the body by the same channel. Those substances
which teenid to unite strongly with the animal matters, and to form
with them insoluble compounds, such as the preparations of iron,
lead, silver, arsenic, mercury, &c., are least liable to appear in the
urine. They may occasionally be detected in this fluid when they
have been given in large doses, but when administered in moderate
quantity are not usually to be found there. Most other substances,
however, accidentally present in the circulation, pass off readily by
the kidneys, either in their original form, or after undergoing certain chemical modifications.
The salts of the organic acids, such as lactates, acetates, malates,
&G., of soda and potassa, when introduced into the circulation, are
replaced by the carbonates of the same bases, and appear under
that form in the urine. The urine accordingly becomes alkaline
from the presence of the carbonates, whenever the above salts have
been taken in large quantity, or after the ingestion of fruits and
vegetables which contain them. We have already spoken (Chap. II.)
of the experiments of Lehmann, in which he found the urine exhibiting an alkaline reaction, a very few minutes after the administration of lactates and acetates. In one instance, by experimenting
upon a person with congenital extroversion of the bladder, in whom
the orifices of the ureters were exposed,' he found that the urine
became alkaline in the course of seven minutes after the ingestion
of half an ounce of acetate of potassa.
The pure alkalies and their carbonates, according to the same observer, produce a similar effect. Bicarbonate of potassa, for example,
administered in doses of two or three drachms, causes the urine
to become neutral in from thirty to forty-five minutes, and alkaline
in the course of an hour. It is in this way that certain "anti-calPhysiological Chemistry, vol. ii. p. 133.




ACCIDENTAL INGREDIENTS OF THE URINE.    339
culous" or " anti-lithic" nostrums operate, when given with a view
of dissolving concretions in the bladder. These remedies, which
are usually strongly alkaline, pass into the urine, and by giving it
an alkaline reaction, produce a precipitation of the earthy phosphates.  Such a precipitate, however, so far from  indicating the
successful disintegration and discharge of the calculus, can only
tend to increase its size by additional deposits.
Ferrocyanide of potassium, when introduced into the circulation,
appears readily in the urine. Bernard' observed that a solution of
this salt, after being injected into the duct of the submaxillary
gland, could be detected in the urine at the end of twenty minutes.
Iodine, in all its combinations, passes out by the same channel.
We have found that after the administration of half a drachm of
the syrup of iodine of iron, iodine appears in the urine at the end
of thirty minutes, and continues to be present for nearly twentyfour hours. In the case of two patients who had been taking iodide
of potassium freely, one of them for two months, the other for six
weeks, the urine still contained iodine at the end of three days
after the suspension of the medicine. In three days and a half,
however, it was no longer to be detected.  Iodine appears also,
after being introduced into the circulation, both in the saliva and
the perspiration.
Quinine, when taken as a remedy, has also been detected in the
urine. Ether passes out of the circulation in the same way.  We
have observed the odor of this substance very perceptibly in the
urine, after it had been inhaled for the purpose of producing ansesthesia. The bile-pigment passes into the urine in great abundance
in some cases of jaundice, so that the urine may have a deep yellow
or yellowish brown tinge, and may even stain linen clothes, with
which it comes in contact, of a similar color.  The saline biliary
substances, viz., glyko-cholate and tauro-cholate of soda, have occasionally, according to Lehmann, been also found in the urine.  In
these instances the biliary matters are reabsorbed from the hepatic
ducts, and afterward conveyed by the blood to the kidneys.
Sugar.-When sugar exists in unnatural quantity in the blood,
it passes out with the urine.  We have repeatedly found that if
sugar be artificially introduced into the circulation in rabbits, or
injected into the subcutaneous areolar tissue so as to be absorbed by
the blood, it is soon discharged by the kidneys. It has been shown
Leqons de Physiologie Experimentale, 1856, p. 111.




340                      EXCRETION.
by Bernard' that the rapidity with which this substance appears in
the urine under these circumstances varies with the quantity injected and the kind of sugar used for the experiment. If a solution
of 15 grains of glucose be injected into the areolar tissue of a rabbit
weighing a little over two pounds, it is entirely destroyed in the
circulation, and does not pass out with the urine. A dose of 23
grains, however, injected in the same way, appears in the urine at
the end of two hours, 30 grains in an hour and a half, 38 grains in
an hour, and 188 grains in fifteen minutes. Again, the kind of
sugar used makes a difference in this respect. For while 15 grains
of glucose may be injected without passing out by the kidneys,
71 grains of cane sugar, introduced in the same way, fail to be completely destroyed in the circulation, and may be detected in the
urine. In certain forms of disease (diabetes), where sugar accumulates in the blood, it is eliminated by the same channel; and a
saccharine condition of the urine, accompanied by an increase in
its quantity and specific gravity, constitutes the most characteristic
feature of the disease.
Finally, albumen sometimes shows itself in the urine in consequence of various morbid conditions.  Most acute inflammations
of the internal organs, as pneumonia, pleurisy, &c., are liable to be
accompanied, at their outset, by a congestion of the kidneys, which
produces a temporary exudation of the albumrninous elements of the
blood. Albumen has been found in the urine, according to Simon,
Becquerel, and others, in pericarditis, pneumonia, pleurisy, bronchitis, hepatitis, inflammation of the brain, peritonitis, metritis, &c.
We have observed it, as a temporary condition, in pneumonia and
after amputation of the thigh. Albuminous urine also occurs frequently in pregnant women, and in those affected with abdominal
tumors, where the pressure upon the renal veins is sufficient to
produce passive congestion of the kidneys. When the renal congestion is spontaneous in its origin, and goes on to produce actual
degeneration of the tissue of the kidneys, as in Bright's disease, the
same symptom occurs, and remains as a permanent condition. In
all such instances, however, as the above, where foreign ingredients
exist in the urine, these substances do not originate in the kidneys
themselves, but are derived from the blood, in the same manner as
the natural ingredients of the excretion.' Leqons de Phys. Exp., 1855, p. 214 et seq.




ACID FERMENTATION OF THE URINE.                 341
CHANGES IN THE URINE DURING DECOMPOSITION.-When the
urine is allowed to remain exposed, after its discharge, at ordinary
temperatures, it becomes decomposed, after a time, like any other
animal fluid; and this decomposition is characterized by certain
changes which take place in a regular order of succession, as follows:After a few hours of repose, the mucus of the urine, as we have
mentioned above, collects near the bottom of the vessel as a light,
nearly transparent, cloudy layer. This mucus, being an organic
substance, is liable to putrefaction; and if the temperature to which
it is exposed be between 60~ and 100~ F., it soon becomes altered, and
communicates these alterations more or less rapidly to the supernatant fluid. The first of these changes is called the acidfermentation
of the urine. It consists in the production of a free acid, usually
lactic acid, from some of the undetermined animal matters contained in the excretion. This fermentation takes place very early;
within the first twelve, twenty-four, or forty-eight hours, according
to the elevation of the surrounding temperature. Perfectly fresh
urine, as we have already stated, contains no free acid, its acid
reaction with test paper being dependent entirely on the presence
of biphosphate of soda. Lactic acid nevertheless has been so frequently found in nearly fresh urine as to lead some eminent
chemists (Berzelius, Lehmann) to regard it as a natural constituent
of the excretion. It has been subsequently found, however, that
urine, though entirely free from lactic acid when first passed, may
frequently present traces of this substance after some hours' exposure to the air. The lactic acid is undoubtedly formed, in these
cases, by the decomposition of some animal substance contained in
the urine. Its production in this way, though not constant, seems
to be sufficiently frequent to be regarded as a normal process.
In consequence of the presence of this acid, the urates are partially decomposed; and a crystalline deposit of free uric acid slowly
takes place, in the same manner as if a little nitric or muriatic acid
had been artificially mixed with the urine. It is for this reason
that urine which is abundant in the urates frequently shows a deposit of crystallized uric acid some hours after it has been passed,
though it may have been perfectly free from deposit at the time
of its emission.
During the period of the "acid fermentation," there is reason to
believe that oxalic acid is also sometimes produced, in a similar
manner with the lactic. It is very certain that the deposit of oxa



342                       EXCRETION.
late of lime, far from being a dangerous or even morbid symptom,
as it was at one time regarded, is frequently present in perfectly
normal urine after a day or two of exposure to the atmosphere.
We have often observed it, under these circumstances, when no
morbid symptom could be detected in connection either with the
kidneys or with any other bodily organ. Now, whenever oxalic
acid is formed in the urine, it must necessarily be deposited under
the form ofoxalate of lime; since this salt is entirely insoluble
both in water and in the urine, even when heated to the boiling
point. It is difficult to understand, therefore, when oxalate of lime
is found as a deposit in the urine, how it can previously have been
held in solution. Its oxalic acid is in all probability gradually
formed, as we have said, in the urine itself; uniting, as fast as it is
produced, with the lime previously in solution, and thus appearing
as a crystalline deposit of oxalate of lime. It is much more probable
that this is the true explanation, since, in the cases to which we
allude, the crystals of oxalate of lime grow, as it were, in the cloud
of mucus which collects at the bottom  of the vessel, while the
supernatant fluid remains clear. These crystals are of minute size,
transparent, and  colorless,
Fig. 116.              and have the form of regular
octohedra, or double quad~/^~ ^~\ ~rangular pyramids, united
base to base. (Fig.116.) They
make their appearance usu/          @      \  ally about the commence|  id^     \  ^ment of the second day, the
v\  X O <^)e        urine at the same time continuing clear and retaining
~~\  Q  o^        / ~its acid reaction. Thisdepo\   "     /O~ ~sit is of frequent occurrence
when no substance containing oxalic acid or oxalates
has been taken with the food.
OXALATE OF L IME; depositedfromhealthy urine,   A      s
during the acid fermentation.          At the end ofsome days
the changes above described
come to an end, and are succeeded by a different process known as
the alkcalinefermentation. This consists essentially in the decomposition or metamorphosis of the urea into carbonate of ammonia.
As the alteration of the mucus advances, it loses the power of producing lactic and oxalic acids, and becomes a ferment capable of




ALKALINE FERMEN.TATION OF THE URINE.    343
acting by catalysis upon the urea, and of exciting its decomposition
as above. We have already mentioned that urea may be converted
into carbonate of ammonia by prolonged boiling or by contact
with decomposing animal substances. In this conversion, the urea
unites with the elements of two equivalents of water; and consequently it is not susceptible of the transformation when in a dry
state, but only when in solution or supplied with a sufficient quantity of moisture. The presence of mucus, in a state of incipient
decomposition, is also necessary, to act the part of a catalytic
body. Consequently if the urine, when first discharged, be passed
through a succession of close filters, so as to separate its mucus, it
may be afterward kept, for an indefinite time, without alteration.
But under ordinary circumstances, the mucus, as soon as its putrefaction has commenced, excites the decomposition of the urea, and
carbonate of ammonia begins to be developed.
The first portions of the ammoniacal salt thus produced begin to
neutralize the biphosphate of soda, so that the acid reaction of the
urine diminishes in intensity. This reaction gradually becomes
weaker, as the fermentation proceeds, until it at last disappears
altogether, and the urine becomes neutral. The production of
carbonate of ammonia still continuing, the reaction of the fluid
then becomes alkaline, and its alkalescence grows more strongly
pronounced with the constant accumulation of the ammoniacal salt.
The rapidity with which this alteration proceeds depends on the
character of the urine, the quantity and quality of the mucus which
it contains, and the elevation of the surrounding temperature. The
urine passed early in the forenoon, which is often neutral at the
time of its discharge, will of course become alkaline more readily
than that which has at first a strongly acid reaction. In the summer,
urine will become alkaline, if freely exposed, on the third, fourth,
or fifth day; while in the winter, a specimen kept in a cool place
may still be neutral at the end of fifteen days. In cases of paralysis
of the bladder, on the other hand, accompanied with cystitis, where
the mucus is increased in quantity and altered in quality, and the
urine is retained in the bladder for ten or twelve hours at the temperature of the body, the change may go on much more rapidly, so
that the urine may be distinctly alkaline and ammoniacal at the
time of its discharge. In these cases, however, it is really acid
when first secreted by the kidneys, and becomes alkaline while
retained in the interior of the bladder.
The first effect of the alkaline condition of the urine, thus pro



344                      EXCRETION.
duced, is the precipitation of the earthy phosphates. These salts,
being insoluble in neutral and alkaline fluids, begin to precipitate as
soon as the natural acid reaction of the urine has fairly disappeared,
and thus produce in the fluid a whitish turbidity.  This precipitate
slowly settles upon the sides and bottom of the vessel, or is partly
entangled with certain animal matters which rise to the surface and
form a thin, opaline scum upon the urine. There are no crystals
to be seen at this time, but the deposit is entirely amorphous and
granular in character.
The next change consists in the production of two new double
salts by the action of carbonate of ammonia on the phosphates of
soda and magnesia. One of these is the " triple phosphate," phosphate of magnesia and ammonia (2MgO,NH40,PO5 + 2HO). The
other is the phosphate of soda and ammonia (NaO,NHO4,HO,POs+
8HO). The phosphate of magnesia and ammonia is formed from
the phosphate of magnesia in the urine (3MgO,PO^+7HO) by
the replacement of one equivalent of magnesia by one of ammonia. The crystals of this salt are very elegant and characteristic. They show themselves throughout all parts of the mixture; growing gradually in the mucus at the bottom, adhering to
the sides of the glass, and
Fig. 117.              scattered  abundantly  over
= ^^ ^^^^~          ~ the film which collects upon
~/^~ ~ /~  ^\ ~the surface. By their refractive power, they give to this
film  a peculiar glistening
and iridescent appearance,
which is nearly always visible at the end of six or seven
days. The crystals are perfectly colorless and transparent, and have the form  of
triangular prisms, generally
with  bevelled  extremities.
PHOSPHATE OF MAGNESIA AND AMMONIA; (Fig. 117.) Frequently, also,
deposited from healthy urine, during alkaline fermen- their edges and angles are
tation.
replaced by secondary facets.
They are insoluble in alkalies, but are easily dissolved by acids,
even in a very dilute form. At first they are of minute size, but
gradually increase, so that after seven or eight days they may
become visible to the naked eye.




RENOVATION BY NUTRITIVE PROCESS.                  345
The phosphate of soda and ammonia is formed, in a similar
manner to the above, by the union of ammonia with the phosphate
of soda previously existing in the urine.  Its crystals resemble
very much those just described, except that their prisms are of a
quadrangular form, or some figure derived from  it.  They are
intermingled with the preceding in the putrefying urine, and are
affected in the same way by chemical reagents.
As the putrefaction of the urine continues, the carbonate of ammonia which is produced, after saturating all the other ingredients
with which it is capable of entering into combination, begins to
be given off in a free form. The urine then acquires a strong
ammoniacal odor; and a piece of moistened test paper, held a little
above its surface, will have its color immediately turned by the
alkaline gas escaping from the fluid. This is the source of the
ammoniacal vapor which is so freely given off from stables and from
dung heaps, or wherever urine is allowed to remain and decompose.
This process continues until all the urea has been destroyed, and
until the products of its decomposition have either united with
other substances, or have finally escaped in a gaseous form.
RENOVATION OF THE BODY BY THE NUTRITIVE PROCESS.-We
can now estimate, from the foregoing details, the quantity of the
different materials which are daily assimilated and decomposed by
the living body. For we have already seen how much food is
taken into the alimentary canal and absorbed by the blood after
digestion, and how much oxygen is appropriated from the atmosphere in the process of respiration.  We have also learned the
amount of carbonic acid evolved with the breath, and that of the
various excretory substances discharged from the body.  The following table shows the absolute quantity of these different ingredients of the ingesta and egesta, compiled from the results of direct
experiment which have already been given in the foregoing pages.
ABSORBED DURING 24 HOURS.     DISCHARGED DURING 24 HOURS.
Oxygen...1.019 lbs.    Carbonic acid. 1.535 lbs.
Water... 4.735 "     Aqueous vapor. 1.155 "
Albuminous matter..396 "     Perspiration.. 1.930 "
Starch..660 "          Water of the urine  2.020 "
Fat...          220 "      Urea and salts..110 "
Salts..040 "            Feces....320 "
7.070                         7.070
Rather more than seven pounds, therefore, are absorbed and dis



346                     EXCRETION.
charged daily by the healthy adult human subject; and, for a man
having the average weight of 140 pounds, a quantity of material,
equal to the weight of the entire body, thus passes through the
system in the course of twenty days.
It is evident, also, that this is not a simple phenomenon of the
passage, or filtration, of foreign substances through the animal
frame. The materials which are absorbed actually combine with
the tissues, and form a part of their substance; and it is only after
undergoing subsequent decomposition, that they finally make their
appearance in the excretions. None of the solid ingredients of the
food are discharged under their own form in the urine, viz., as
starch, fat, or albumen; but they are replaced by urea and other
crystallizable substances, of a different nature. Even the carbonic
acid exhaled by the breath, as experience has taught us, is not produced by a direct oxidation of carbon; but originates by a steady
process of decomposition, throughout the tissues of the body, somewhat similar to that by which it is generated in the decomposition
of sugar by fermentation. These phenomena, therefore, indicate an
actual change in the substance of which the body is composed, and
show that its entire ingredients are incessantly renewed under the
influence of the vital operations.




SECTION II.
NERYO A S SYSTEM.
CHAPTER I.
GENERAL STRUCTURE  AND FUNCTIONS OF THE
NERVOUS SYSTEM.
IN entering upon the study of the nervous system, we commence
the examination of an entirely different order of phenomena from
those which have thus far engaged our attention. Hitherto we
have studied the physical and chemical actions taking place in the
body and constituting together the process of nutrition. We have
seen how the lungs absorb and exhale different gases; how the
stomach dissolves the food introduced into it, and how the tissues
produce and destroy different substances by virtue of the varied
transformations which take place in their interior. In all these
instances, we have found each organ and each tissue possessing
certain properties and performing certain functions, of a physical
or chemical nature, which belong exclusively to it, and are characteristic of its action.
The functions of the nervous system, however, are neither physical nor chemical in their nature. They do not correspond, in
their mode of operation, with any known phenomena belonging to
these two orders. The nervous system, on the contrary, acts only
upon other organs, in some unexplained manner, so as to excite or
modify the functions peculiar to them. It is not therefore an apparatus which acts for itself, but is intended entirely for the purpose
of influencing, in an indirect manner, the action of other organs.
Its object is to connect and associate the functions of different parts
of the body, and to cause them to act in harmony with each other.




348        GENERAL STRUCTURE AND FUNCTIONS
This object may be more fully exemplified as follows:Each organ and tissue in the body has certain properties peculiar
to it, which may be called into activity by the operation of a stimulus or exciting cause. This capacity, which all the organs possess,
of reacting under the influence of a stimulus, is called their excitability, or irritability. We have often had occasion to notice this property of irritability, in experiments related in the foregoing pages.
We have seen, for example, that if the heart of a frog, after being
removed from  the body, be touched with the point of a needle, it
immediately contracts, and repeats the movement of an ordinary
pulsation. If the leg of a frog be separated from the thigh, its
integument removed, and the poles of a galvanic battery brought
in contact with the exposed surface of the muscles, a violent contraction takes place every time the electric circuit is completed.
In this instance, the stimulus to the muscles is supplied by the
electric discharge, as, in the case of the heart above mentioned, it is
supplied by the contact of the steel needle; and in both, a muscular contraction is the immediate consequence. If we introduce a
metallic catheter into the empty stomach of a dog through a gastric
fistula, and gently irritate with it the mucous membrane, a secretion
of gastric juice at once begins to take place; and if food be introduced the fluid is poured out in still greater abundance. We know
also that if the integument be exposed to contact with a heated
body, or to friction with an irritating liquid, an excitement of the
circulation is at once produced, which again passes away after the
removal of the irritating cause.
In all these instances we find that the organ which is called into
activity is excited by the direct application of some stimulus to its
own tissues. But this is not usually the manner in which the different functions are excited during life. The stimulus which calls
into action the organs of the living body is usually not direct, but
indirect in its operation. Generally speaking, the organs which are
situated in distant parts of the body are connected with each other
by such a sympathy, that the activity of one is influenced by the
condition of the others. The muscles, for example, are almost never
called into action by an external stimulus operating directly upon
their own fibres, but by one which is applied to some other organ,
either adjacent or remote. Thus the peristaltic action of the muscular coat of the intestine commences when the food is brought in
contact with its mucous membrane. The lachrymal gland is excited
to increased activity by anything which causes irritation of the




OF THE NERVOUS SYSTEM.                    349
conjunctiva. In all such instances, the physiological connection
between two different organs is established through the medium of
the nervous system.
The function of the nervous system may therefore be defined, in
the simplest terms, as follows: It is intended to associate the different
parts of the body in such a manner, that an action may be excited in one
organ by means of a stimulus applied to another.
The instances of this mode of action are exceedingly numerous.
Thus, the light which falls upon the retina produces a contraction
of the pupil. The presence of food in the stomach causes the gallbladder to discharge its contents into the duodenum. The expulsive efforts of coughing are excited by a foreign body entangled in
the glottis.
It is easy to understand the great importance of this function,
particularly in the higher animals and in man, whose organization
is an exceedingly complicated one.- For the different organs of
the body, in order to preserve the integrity of the whole frame,
must not only act and perform their functions, but they must act in
harmony with each other, and at the right time, and in the right
direction.  The functions of circulation, of respiration, and of
digestion, are so mutually dependent, that if their actions do not
take place harmoniously, and in proper order, a serious disturbance must inevitably follow. When the muscular system  is excited by unusual exertion, the circulation is also-quickened. The
blood arrives more rapidly at the heart, and is sent in greater
quantity to the lungs. If the movements of respiration were not
accelerated at the same time, through the connections of the nervous system, there would immediately follow deficiency of aeration,
vascular congestion, and derangement of the circulation. If the
iris were not stimulated to contract by the influence of the light
falling on the retina, the delicate expansion of the optic nerve
would be dazzled by any unusual brilliancy, and vision would be
obscured or confused. In all the higher animals, therefore, where
the different functions of the body are performed by distinct organs,
situated in different parts of the frame, it is necessary that their
action should be thus regulated and harmonized by the operation
of the nervous system.
The manner in which this is accomplished is as follows:The nervous system, however simple or however complicated it
may be, consists always of two different kinds of tissue, which are




350        GENERAL STRUCTURE AND FUNCTIONS
distinguished from each other by their color, their structure, and
their mode of action. One of these is known as the white substance,
or the fibrous tissue. It constitutes the whole of the substance of the
nervous trunks and branches, and is found in large quantity on the
exterior of the spinal cord, and in the central parts of the brain
and cerebellum. In the latter situations, it is of a soft consistency,
like curdled cream, and of a uniform, opaque white color. In
the trunks and branches of the nerves it has the same opaque
white color, but is at the same time of a firmer consistency, owing
to its being mingled with condensed areolar tissue. Examined by
the microscope, the white substance is seen to be composed everywhere of minute fibres or filaments, the "ultimate nervous filaments," running in a direction very nearly parallel with each other.
These filaments are cylindrical in shape, and vary considerably in
size. Those which are met with in the spinal cord and the brain
are the smallest, and have an average diameter of T-oo- of an
inch. In the trunks and branches of the nerves they average ~I o
of an inch.
The structure of the ultimate nervous filament is as follows:
The exterior of each filament consists of a colorless, transparent
tubular membrane, which is seen with some difficulty in the natural
condition of the fibre, owing to the extreme delicacy of its texture,
and to its cavity being completely filled with a substance very
similar to it in refractive power. In the interior of this tubular
membrane there is contained a thick, semi-fluid nervous matter,
which is white and glistening by reflected light, and is called the
"white substance of Schwann."  Finally, running longitudinally
through the central part of each filament, is a narrow ribbonshaped cord, of rather firm consistency, and of a semi-transparent
grayish color. This central portion is called the " axis cylinder,"
or the "flattened band."  It is enveloped everywhere by the semifluid white substance, and the whole invested by the external tubular membrane.
When nervous matter is prepared for the microscope and examined by transmitted light, two remarkable appearances are observed in its filaments, produced by the contact of foreign substances. In the first place the unequal pressure, to which the filaments are accidentally subjected in the process of dissection and
preparation, produces an irregularly bulging or varicose appearance
in them at various points, owing to the readiness with which the
semi-fluid white substance in their interior is displaced in different




OF THE NERVOUS SYSTEM.                       351
directions. (Fig. 118.)  Sometimes spots may be seen here and
there, where the nervous matter has been entirely pressed apart in
the centre of a filament, so
that there appears to be an                  Fig. 118.
entirebreak in its continuity, 
while the investing mem-            /a    
brane maybe still seen, pass-                             (
ing across from one portion
to the other. When a nervous filament is torn across
under the microscope and 
subjected to pressure, a cer-                      (
tain quantity of the semi- 
fluid  white  substance  is 
pressed out from  its torn
extremity, and may be entirely separated from it, so
as to present itself under t   NERvoUS FILAMENTS from white substance of
a to present tel  ner  e  brain.-a, a, a. Soft substance of the filaments pressed
form of irregularly rounded  out, and floating in irregularly rounded drops.
drops of various sizes (a, a,
a), scattered over the field of the microscope. The varicose appearance above alluded to is more frequently seen in the smaller nervous filaments from the brain and spinal cord, owing to their soft
consistency and the readiness with which they yield to pressure.
The second effect produced by the artificial preparation of the
nervous matter is a partial coagulation of the white substance of
Schwann.  In its natural condition this substance has the same
consistency throughout, and appears perfectly  transparent and
homogeneous by transmitted light. As soon, however, as the nervous filament is removed from its natural situation, and brought in
contact with air, water, or other unnatural fluids, the soft substance
immediately under the investing membrane begins to coagulate.
It increases in consistency, and at the same time becomes more
highly refractive; so that it presents on each side, immediately
underneath the investing membrane,: a thin layer of a peculiar
glistening aspect. (Fig. 119.)  At first, this change takes place
only in the outer portions of the white substance of Schwann.
The coagulating  process, however, subsequently  goes on, and
gradually advances from  the edges of the filament toward its
centre, until its entire thickness after a time presents the same
appearance.  The effect of this process can also be seen in those




352         GENERAL STRUCTURE AND FUNCTIONS
portions of the white substance which have been pressed out from
the interior of the filaments, and which float about in the form of
drops. (Fig. 118, a.) These
Fig. 119.                 drops  are  always covered
with a layer of coagulated
(/  \  ) / \       material which  is  thicker
and more opaque in propor.
/    i  ///  i  \        tion to  the length of time
which has elapsed since the
commencement of the altere       ation.
\    /      The  nervous  filaments
have  essentially  the  same
structure in  the brain and
spinal cord as in the nervous
1< )trunks and branches; only
they  are of much  smaller
NERVOUS F ILA MENTSfromsciaticnerve, showing  size in the forer than in
their coagulation.-At a, the torn extremity of a
nervous filament with the axis cylinder (b) protruding  the latter situation.  In the
from it. At c, the white substance of Schwann is nearly        
separated by accidental compression, but the axis-  ner trn
cylinder passes across the ruptured portion. The out-  however, outside the cranial
line of the tubular membrane is also seen at c on the
outside of the nervous filament.          and  spinal cavities, there
exists, superadded  to  the
nervous filaments and interwoven with them, a large amount of
condensed areolar or fibrous tissue, which protects them from
injury, and gives to this portion of the nervous system a peculiar
density and resistance. This difference in consistency between the
white substance of the nerves and that of the brain and spinal cord
is owing, therefore, exclusively to the presence of ordinary fibrous
tissue in the nerves, while it is wanting in the brain and spinal
cord. The consistency of the nervous filaments themselves is the
same in each situation.
The nervous filaments are arranged, in the nervous trunks and
branches, in a direction nearly parallel with each other.  A certain
number of them  are collected in the form  of a bundle, which is
invested with a layer of fibrous tissue, in which run the small
bloodvessels, destined for the nutrition of the nerve.  These pri.
mary bundles are again united into secondary, the secondary into
tertiary, &c.  A  nerve, therefore, consists of a large bundle of ultimate filaments, associated with each other in larger or smaller
packets, and bound together by the investing fibrous layers. When




OF THE NERVOUS SYSTEM.                      353
a nerve is said to become branched or "divided" in any part of its
course, this division merely implies that some of its filaments leave
the bundles with which they were
previously associated, and pursue             Fig. 120.
a different direction. (Fig. 120.)
A nerve which originates, for example, from the spinal cord in the
region of the neck, and runs down
the upper extremity, dividing and 
subdividing, to be finally distributed to the integument andmuscles of the hand, contains at its
point of origin all the filaments
into which it is afterward divided,
and which are merely separated
at successive points from  the
main bundle.  The ultimate filaments, accordingly, are continuous throughout, and do not themselves divide at any point between
their origin and their final distribution.
When a nerve, furthermore, is
said to "inosculate" with another
nerve, as when the infra-orbital   Division of a NERVE, showing portion of
nervous trunk (a), and the separation of its
inosculates with the facial, or the  filaments (b, c, d, e).
cervical nerves inosculate with
each other, this means simply that some of the filaments composing
the first nervous bundle separate from it, and cross over to form  a
part of the second, while some of those belonging to the second
cross over and join the first (Fig. 121); but the individual filaments
in each instance remain continuous and preserve their identity
throughout. This fact is of great physiological importance; since
the white or fibrous nerve-substance is everywhere simply an
organ of transmission. It serves to convey the nervous impulse in
various directions, from without inward, or from within outward;
and as each nervous filament acts independently of the others, it
will convey an impression or a stimulus continuously from its
origin to its termination, and will always have the same character
and function in every part of its course.
T'he other variety of nervous matter is known as the gray sub



354         GENERAL STRUCTURE AND FUNCTIONS
stance.  It is sometimes called "cineritious matter," and sometimes
"vesicular neurine."  It is found in the central parts of the spinal
Fig. 121.
Inosculation of N E R VES.
cord, at the base of the brain in isolated masses, and is also spread
out as a continuous layer on the external portions of the cerebrum
and cerebellum. It also constitutes the substance of all the ganglia of the great sympathetic.  Examined by the microscope, it
consists of vesicles or cells, of
Fig. 122.                various forms and sizes, imbedded in a grayish, granular,
intercellular substance, and
containing, also, very  frequently, granules of grayish
pigmentary matter.  It is to
the presence of this granular
o                           0pigment that this kind  of
nervous matter owes the ashy
or "cineritious" color from
which  it derives its name.
\(  f /^     The cells composing it vary
in size, according to Kolliker,
from -i0v  to -g  of an inch.
NERVE CELLS, intermingled with fibres; from  40      300
semilunar ganglion of cat.              The largest of them  have a




OF THE NERVOUS SYSTEM.                      355
very distinct nucleus and nucleolus. (Fig. 122.)  Many of them are
provided with long processes or projections, which are sometimes
divided into two or three smaller branches. These cells are intermingled, in all the collections of gray matter, with nervous filaments,
and are entangled with their extremities in such a manner that it
is exceedingly difficult to ascertain the exact nature of the anatomical relations existing between them. It is certain that in some
instances the slender processes running out from the nervous vesicles become at last continuous with the filaments; but it is not
known whether this be the case in all or even in a majority of
instances.  The extremities of the filaments, however, are at all
events brought into very close relation with the vesicles or cells of
the gray matter.
Every collection of gray matter, whatever be its situation or
relative size in the nervous system, is called a ganglion or nervous
centre.  Its function is to receive impressions conveyed to it by the
nervous filaments, and to send out by them impulses which are to
be transmitted to distant organs.  The ganglia, therefore, originate
nervous power, so to speak; while the filaments and the nerves
only transmit it.  Now we shall find that, in the structure of every
nervous system, the ganglia are connected, first with the different
organs, by bundles of filaments which are called nerves; and
secondly with each other, by other bundles which are termed commissures.  The entire system  is accordingly made up of ganglia,
nerves, and commissures.
The simplest form of nervous system  is probably that found in
the five-rayed starfish.  This animal belongs to the type known
as radiata; that is, animals whose
organs radiate from a central point,            Fig. 123.
so as to form  a circular series of
similar parts, each organ being repeated at different points- of the
circumference.  The starfish (Fig.
123) consists of a  central mass, 
with five arms or limbs radiating
from it. In the centre is the mouth,      -
and immediately beneath it the stomach  or digestive  cavity, which
sends prolongations into every one 
of the projecting limbs.  There is
also contained in each limb a portion    NERVOUS SYSTEM OF STARFI3H.




356        GENERAL STRUCTURE AND FUNCTIONS
of the glandular and muscular systems, and the whole is covered
by a sensitive integument. The nervous system consists of five
similar ganglia, situated in the central portion, at the base of the
arms. These ganglia are connected with each other by commissures, so as to form a nervous collar or chain, surrounding the
orifice of the digestive cavity. Each ganglion also sends off nerves,
the filaments of which are distributed to the organs contained in
the corresponding limb.
We have already stated that the proper function of the nervous
system is to enable a stimulus, acting upon one organ, to produce
motion or excitement in another. This is accomplished, in the
starfish, in the following manner:When any stimulus or irritation is applied to the integument of
one of the arms, it is transmitted by the nerves of the integument
to the ganglion situated near the mouth. Arrived here, it is
received by the gray matter of the ganglion, and immediately converted into an impulse which is sent out by other filaments to the
muscles of the corresponding limb; and a muscular contraction and
movement consequently take place. The muscles therefore contract
in consequence of an irritation which has been applied to the skin.
This is called the "reflex action" of the nervous system; because the
stimulus is first sent inward by the nerves of the integument, and
then returned or reflected back from the ganglion upon the muscles.
It must be recollected that this action does not necessarily indicate
any sensation or volition, nor even any consciousness on the part of
the animal. The function of the gray matter is simply to receive
the impulse conveyed to it, and to reflect or send back another; and
this may be accomplished altogether involuntarily, and without the
existence of any conscious perception.
Where the irritation applied to the integument is of an ordinary
character and not very intense, it is simply reflected, as above
described, from the corresponding ganglion back to the same limb.
But if it be of a peculiar character, or of greater intensity than usual,
it may be also transmitted by the commissures to the neighboring
ganglia; and so two, three, four, or even all five of the limbs may
be set in motion by a stimulus applied to the integument of one of
them. Now, as all the limbs of the animal have the same structure
and contain the same organs, their action will also be the same;
and the effects of this communication of the stimulus from one to
the other by means of commissures will be a repetition, or rather
a sirnultaneous production of similar movements in different parts




OF THE NERVOUS SYSTEM.                       357
of the body. According to the character and intensity, therefore,
of the original stimulus, it will be followed by a response from
one, several, or all of the different parts of the animal frame.
It will be seen also that there are two kinds of nervous filaments,
differing essentially in their functions. One set of these fibres run
from the sensitive surfaces to the ganglion, and convey the nervous
impression inward.  These are called sensitive fibres. The other
set run from the ganglion to the muscles, and carry the nervous
impression outward. These are called motor fibres.
In the starfish, where the body is composed of a repetition of similar parts arranged round a common centre, and where all the limbs
are precisely alike in structure, the several ganglia composing the
nervous system are also similar to each other, and act in the same
way. But in animals which are constructed upon a different plan,
and whose bodies are composed of distinct organs, situated in different regions, we find that the nervous ganglia, presiding over
the function of these organs, present a corresponding degree of
dissimilarity.
In Aplysia, for example, which belongs to the type of mollusca,
or soft-bodied animals, the digestive apparatus consists of a mouth,
an oesophagus, a triple stomach, and a somewhat convoluted intestine. The liver is large, and placed on one side of the body, while
the gills, in the form of vascular laminae, occupy the opposite side.
There are both testicles and ovaries in the
same animal, the male and female functions           Fig. 124.
co-existing, as in many other invertebrate
species. All the organs, furthermore, are
here arranged without any reference to a          )
regular or symmetrical plan.  The body is
covered with a muscular mantle, which expands at the ventral surface into a tolerably
well developed "foot," or organ of locomotion, by which the animal is enabled to
change its position  and  move. from  one 
locality to another.
The nervous system of this animal is constructed  upon a plan corresponding with
that of the entire body. (Fig. 124.)  There   NERVOUS  SYSTEM  OF
is a small ganglion (i) situated anteriorly, APLYSIA-1  Digestive or
oesophageal ganglion.  2. Cerewhich sends nerves to the commencement bral ganglion. 3,3. Pedal or
locomotory ganglia. 4. Respiof the digestive apparatus, and is regarded  ratory ganglion.




358        GENERAL STRUCTURE AND FUNCTIONS
as the oesophageal or digestive ganglion. Immediately behind it is
a larger one (2) called the cephalic or cerebral ganglion, which
sends nerves to the organs of special sense, and which is regarded
as the seat of volition and general sensation for the entire body.
Following this is a pair of ganglia (3, 3), the pedal or locomotory
ganglia, which supply the muscular mantle and its foot-like expansion, and which regulate the movement of these organs.  Finally,
another ganglion (4), situated at the posterior part of the body,
sends nerves to the branchiae or gills, and is termed the branchial
or respiratory ganglion. All these nervous centres are connected
by commissures with the central or cerebral ganglion, and may
therefore act either independently or in association with each other,
by means of these connecting fibres.
In the third type of animals, again, viz., the articulata, the general plan of structure of the body is different from the foregoing,
and the nervous system is accordingly modified to correspond with
it. In these animals, the body is composed of a
Fig. 125.   number of rings or sections, which are articulated
y-, % _   with each other in linear series.  A very good
example of this type may be found in the common centipede, or scolopendra.  Here the body is
composed of twenty-two successive and nearly
similar articulations, each of which has a pair of
legs attached, and contains a portion of the glan—.8 I    dular, respiratory, digestive and reproductive
apparatuses.  The animal, therefore, consists of a
repetition of similar compound parts, arranged in
a longitudinal chain or series.  The only excep-.  -;.   tions to this similarity are in the first and last
~ l1 II " articulations. The first is large, and contains
the mouth; the last is small, and contains the
anus.  The first articulation, which is called the,     "head," is also furnished with eyes, with antennme,
and with a pair of jaws, or mandibles.
The nervous system of the centipede (Fig. 125),
corresponding in structure with the above plan,
NERvou, SYSTEM  consists of a linear series of nearly equal and
OF CENTI'PED,.    similar ganglia arranged in pairs, situated upon
the median line, along the ventral surface of the
alimentary canal. Each pair of ganglia is connected with the integurnent and muscles of its own articulation  by sensitive and




OF THE NERVOUS SYSTEM.                    359
motor filaments; and with those which precede and follow by a
double cord of longitudinal comrissural fibres. In the first articulation, moreover, or the head, the ganglia are larger than elsewhere,
and send nerves to the antennae and to the organs of special sense.
This pair is termed the cerebral ganglion, or the "brain."
A reflex action may take place, in these animals, through either
one or all of the ganglia composing the nervous chain. An impression received by the integument of any part of the body may
be transmitted inward to its own ganglion and thence reflected
immediately outward, so as to produce a movement of the limbs
belonging to that articulation alone; or it may be propagated,
through the longitudinal commissures, forward or back, and produce simultaneous movements in several neighboring articulations;
or, finally, it may be propagated quite up to the anterior pair of
ganglia, or "brain," where its reception will be accompanied with
consciousness, and a voluntary movement reflected back upon any
or all of the limbs at once. The organs of special sense, also, communicate directly with the cerebral ganglia; and impressions conveyed through them  may accordingly give rise to movements in
any distant part of the body. In these animals the ventral ganglia,
or those which simply stand as a medium  of communication between the integument and the muscles, are nearly similar throughout; while the first pair, or those which receive the nerves of special
sense, and which exercise a general controlling.power over the rest
of the nervous system, are distinguished from the remainder by a
well-marked preponderance in size.
In the centipede it will be noticed that nearly all the organs and
functions are distributed in an equal degree throughout the whole
length of the body. The organs of special sense alone, with those
of mastication and the functions of perception and volition, are
confined to the head. The ganglia occupying this part are therefore the only ones which are distinguished by any external peculiarities; the remainder being nearly uniform both in size and
activity. In some kinds of articulated animals, however, particular
functions are concentrated, to a greater or less extent, in particular
parts of the body; and the nervous ganglia which preside over
them  are modified in a corresponding manner. In the insects,
for example, the body is divided into three distinct sections, viz:
the head, containing the organs of prehension, mastication, tact
and special sense; the chest, upon which are concentrated the organs of locomotion, the legs and wings; and the abdomen, containing the greater part of the alimentary canal, together with the




360        GENERAL STRUCTURE AND FUNCTIONS
glandular and generative organs. As the insects have a greater
amount of intelligence and activity than the centipedes and other
worm-like articulata, and as the organs of special sense are more
perfect in them, the cerebral ganglia are also unusually developed,
and are evidently composed of several pairs, connected by commissures so as to. form a compound mass. As the organs of locomotion, furthermore, instead of being distributed, as in the centipede,
throughout the entire length of the animal, are concentrated upon
the chest, the locomotory ganglia also preponderate in size in this
region of the body; while the ganglia which preside over the secretory and generative functions are situated together, in the cavity of
the abdomen.
All the above parts, however, are connected, in the same manner
as previously described, with the anterior or cerebral pair of ganglia.  In all articulate animals, moreover, the general arrangement
of the body is symmetrical. The right side is, for the most part,
precisely like the left, as well in the internal organs as in the external covering and the locomotory appendages. The only marked
variation between different parts of the body is in an antero-posterior direction; owing to different organs being concentrated, in
some cases, in the head, chest, and abdomen.
Finally, in the vertebrate type of animals, comprising man, the
quadrupeds, birds, reptiles, and fish, the external parts of the body,
together with the locomotory apparatus and the organs of special
sense, are symmetrical, as in the articulata; but the internal organs,
especially those concerned in the digestive and secretory functions,
are unsymmetrical and irregular, as in the molluscs. The organs
of respiration, however, are nearly symmetrical in the vertebrata,
for the reason that the respiratory movements, upon which the
function of these organs is immediately dependent, are performed
by muscles belonging to the general locomotory apparatus. The
nervous system of the vertebrata partakes, accordingly, of the structural arrangement of the organs under its control. That portion
which presides over the locomotory, respiratory, sensitive, and intellectual functions forms a system by itself, called the cerebro spinal
system. This system is arranged in a manner very similar to that
of the articulata. It is composed of two equal and symmetrical
halves, running along the median line of the body, the different
parts of which are connected by transverse and longitudinal commissures.  Its ganglia occupy the cavities of the cranium and the
spinal canal, and send out their nerves through openings in the
bony walls of these cavities.




OF THE NERVOUS SYSTEM.                      361
The other portion of the nervous system of vertebrata is that
which presides over the functions of vegetative life. It is called
the ganglionic, or great sympathetic system. Its ganglia are situated
anteriorly to the spinal column, in the visceral cavities of the body,
and are connected, like the others, by transverse and longitudinal
commissures. This part of the nervous system  is symmetrical in
the neck and thorax, but is unsymmetrical in the abdomen, where
it attains its largest size and its most complete development.
The vertebrate animals, as a general rule, are very much superior
to the other classes, in intelligence and activity, as well as in the
variety and complicated character of their motions; while their
nutritive or vegetative functions, on the other hand, are not particularly well developed. Accordingly we find that in these animals
the cerebro-spinal system of nerves preponderates very much, in
importance and extent, over that of the great sympathetic. The
quantity of nervous matter contained in the brain and spinal cord
is, even in the lowest vertebrate animal, very much greater than
that contained in the system of the
great sympathetic; and this prepon-             Fig. 126.
derance  increases, in  the higher
classes, just in proportion to their superiority in intelligence, sensation,
power of motion, and other fune.
tions of a purely animal character.
The spinal cord is very nearly
alike in the different classes of vertebrate animals.  It is a nearly
cylindrical cord, running from one
end of the spinal canal to the other,
and connected at its anterior extremity  with the ganglia of the
brain. (Fig. 126.)  It is divided, by
an anterior and posterior' median
fissure, into two lateral halves, which
still remain connected with each
other by a central mass or commissure. Its inner portions are occupied
by gray matter, which forms a continuous ganglionic chain, running   CEREBRO-SPINAL SYSTEM OF MAN.
from  one extremity of the cord to  -l.Cerebrum. 2.Cerebellum. 3,3,3. Spinal
cord and nerves. 4, 4. Brachial nerves.
the other.  Its outer portions are  5,5. Sacralnerves.




362        GENERAL STRUCTURE AND FUNCTIONS
composed of white substance, the filaments of which run for the
most part in a longitudinal direction, connecting the different parts
of the cord with each other, and the cord itself with the ganglia
of the brain.
The spinal nerves are given off from the spinal cord at regular
intervals, and in symmetrical pairs; one pair to each successive
portion of the body. Their filaments are distributed to the integument and muscles of the corresponding regions. In serpents, where
locomotion is performed by simple, alternate, lateral movements
of the spinal column, the spinal cord and its nerves are of the
same size throughout. But in the other vertebrate classes, where
there exist special organs of locomotion, such as fore and hind
legs, wings, and the like, the spinal cord is increased in size at
the points where the nerves of these organs are given off; and the
nerves themselves, which supply the limbs, are larger than those
originating from other parts of the spinal cord.  Thus, in the human subject (Fig. 126), the cervical nerves, which go to the arms,
and the sacral nerves, which are distributed to the legs, are larger
than the dorsal and lumbar nerves.  They form, also, by frequent
inosculation, two remarkable plexuses, before entering their corresponding limbs, viz., the brachial plexus above, and the sacral
plexus below. The cord itself, moreover, presents two enlargements
at the point of origin of these nerves, viz., the cervical enlargement
from which the brachial nerves (4, 4) are given off, and the lumbar
enlargement from which the sacral nerves (5, 5) originate.
If the spinal cord be examined in transverse section (Fig. 127),
it will be seen that the gray
Fig. 127.               matter in its central portion
forms a double crescenticshaped mass, with the concavity of the crescents turned outward. Thesecrescentic
masses of gray matter, occupying the two lateral halves
of the cord, are united with
each other by a transverse
band of the same substance,
Transverse Section of S P I NA L C O R D.-a, b. Spinal band of the same substance,
nerves of right and left side, showing their two roots. which  is called  the gray
d. Origin of anterior root. e. Origin of posterior root.    o  he    -
c. Ganglion of posterior root.           mm      e of the  rd
rectly in front of this is a
transverse band of white substance, connecting in a similar manner




OF THE NERVOUS SYSTEM.                      363
the white portions of the two lateral halves.  It is called the white
commissure of the cord.
The spinal nerves originate from  the cord on each side by two
distinct roots; one anterior, and one posterior.  The anterior root
(Fig. 127, d) arises from the surface of the cord near the extremity
of the anterior peak of gray matter.  The posterior root (e) originates at the point corresponding with the posterior peak of gray
matter.  Both roots are composed of a considerable number of
ultimate nervous filaments, united with each other in parallel
bundles.  The posterior root is distinguished by the presence of a
small ganglion (c), which appears to be incorporated with it, and
through which its fibres pass. There is no such ganglion on the
anterior root. The two roots unite with each other shortly after
leaving the cavity of the spinal canal, and mingle their filaments
in a single trunk.
It will be seen, on referring to the diagram (Fig. 127), that each
lateral half of the spinal cord is divided into two portions, an
anterior and a posterior portion. The posterior peak of gray mat.
ter comes quite up to the surface of the cord, and it is just at this
point (e) that the posterior roots of the nerves have their origin
The whole of the white substance included between this point and
the posterior median fissure is called the posterior column of the
cord. That which is included between the same point and the
anterior median fissure is the anterior column of the cord.  The
white substance of the cord may then be regarded as consisting
for the most part of four longitudinal bundles of nervous filaments,
viz., the right and left anterior, and the right and left posterior
columns.  The posterior median fissure penetrates deeply into the
substance of the cord, quite down to the gray matter, so that the
posterior columns appear entirely separated from each other in a
transverse section; while the anterior median fissure is more shallow and stops short of the gray matter, so that the anterior columns
are connected with each other by the white commissure above mentioned.
By the encephalon we mean the whole of that portion of the
cerebro-spinal system which is contained in the cranial cavity. It
is divided into three principal parts, viz., the cerebrum, cerebellum,
and medulla oblongata.  The anatomy of these parts, though somewhat complicated, can be readily understood if it be recollected
that they are simply a double series of nervous ganglia, connected with
each other and with the spiatal cord by transverse and longitudinal




364        GENERAL STRUCTURE AND FUNCTIONS
commissures. The number and relative size of these ganglia, in
different kinds of animals, depend upon the perfection of the bodily
organization in general, and more especially on that of the intelligence and the special senses. They are most readily described by
commencing with the simpler forms and terminating with the more
complex.
The brain of the Alligator (Fig. 128) consists of five pair of
ganglia, ranged one behind the other in the interior of the cranium.
The first of these are two rounded masses (i), lying just above and
behind the nasal cavities, which distriFig. 128.        bute their nerves upon the Schneiderian
mucous membrane.  These are the ofactory ganglia.    They are connected with
the rest of the brain by two long and
slender commissures, the "olfactory commissures."  The next pair (2) are somem we v  a igwhat larger and of a triangular shape,
mat 4,    when viewed  from  above downward.
tio        They are termed the  cerebral ganglia,"
beA_~  eor the hemispheres. Immediately followms ()t     ing them are two quadrangular masses (3)
which give origin to the optic nerves, and
are therefore called the optic ganrglia.
They are termed also the "optic tuberBRAIN OF ALGATOR.-1. 01- cles;" and in some of the higher animals,
factoryganglia. 2 Hemnisperes. 3. where they present an imperfect division
Optic tubercles. 4. Cerebellum. 5.
Medulla oblongata.       into four nearly equal parts, they are
known as the "tubercula quadrigemina."
Behind them, we have a single triangular collection of nervous
matter (4), which is called the cerebellum. Finally, the upper portion of the cord, just behind and beneath the cerebellum, is seen to
be enlarged and spread out laterally, so as to form a broad oblong
mass (5), the medulla oblongata. It is from this latter portion of the
brain that the pneumogastric or respiratory nerves originate, and
its ganglia are therefore sometimes termed the "pneumogastric" or
"respiratory" ganglia.
It will be seen that the posterior columns of the cord, as they
diverge laterally, in order to form the medulla oblongata, leave between them an open space, which is continuous with the posterior
median fissure of the cord. This space is known as the "fourth
ventricle." It is partially covered in by the backward projection




OF THE NERVOUS SYSTEM.                      365
of the cerebellum, but in the alligator is still somewhat open posteriorly, presenting a kind of chasm or gap between the two lateral
halves of the medulla oblongata.
The successive ganglia which compose the brain, being arranged
in pairs as above described, are separated from each other on the
two sides by a longitudinal median fissure, which is continuous
with the posterior median fissure of the cord. In the brain of the
alligator this fissure appears to be interrupted at the cerebellum;
but in the higher classes, where the lateral portions of the cerebellum are more highly developed, as in the human subject (Fig. 126),
they are also separated from each other posteriorly on the median
line, and the longitudinal median fissure is complete throughout.
In birds, the hemispheres are of much larger size than in reptiles, and partially conceal the optic ganglia.  The cerebellum,
also, is very well developed in this class, and presents on its surface a number of transverse foldings or convolutions, by which
the quantity of gray matter which it contains is considerably increased. The cerebellum here extends so far backward as almost
completely to conceal the medulla oblongata and the fourth ventricle.
In the quadrupeds, the hemispheres and cerebellum attain a still
greater size in proportion to the remaining parts of the brain.
There are also two other pairs
of ganglia, situated beneath the               Fig. 129.
hemispheres, and between them
and the tubercula quadrigemina.
These are the corpora striata in
front and the optic thalami behind.
In Fig. 129 is shown the brain of
the rabbit, with the hemispheres
laid open and turned aside, so as 
to show the internal parts in their
natural situation.  The olfactory
ganglia are seen in front (l) connected with the remaining parts
by  the  olfactory  commissures.
The separation of the hemispheres
(2, 2) shows the corpora striata (3)
a1n.he optic thalami). \ l    BRAIN O F R A B B I T viewsed from aboveand the optic thalami (4). Then  1. Olfactory ganglia. 2. Hemispheres, turned
come the tubercula quadrigemina  aside. 3. Corpora striata. 4. Optic thalami.
), which are here composed, as  5. Tubercula quadrigemina. 6. Cerebellum.
()above which  are here composeds, nearly as
above mentioned, of four rounded masses, nearly equal in size.




366         GENERAL STRUCTURE AND  FUNCTIONS
The cerebellum (6) is considerably enlarged by the development of
its lateral portions, and shows an abundance of transverse convolutions. It conceals from view the fourth ventricle and most of the
medulla oblongata.
In other species of quadrupeds the hemispheres increase in size
so as to project entirely over the olfactory ganglia in front, and to
cover in the tubercula quadrigemina and the cerebellum behind.
The surface of the hemispheres also becomes covered with nurnerous convolutions, which are curvilinear and somewhat irregular
in form and direction, instead of being transverse, like those of the
cerebellum. In man, the development of the hemispheres reaches
its highest point; so that they preponderate altogether in size over
the rest of the ganglia constituting the brain.  In the human brain,
accordingly, when viewed from above downward, there is nothing
to be seen but the convex surfaces of the hemispheres; and even
in a posterior view, as seen in Fig. 126, they conceal everything
but a portion of the cerebellum. All the remaining parts, however, exist even here, and have the same connections and relative
situation as in other instances. They may be best studied in the
following order.
As the spinal cord, in the human subject, passes upward into the
cranial cavity, it enlarges into the medulla oblongata as already
described. The medulla oblongata presents on each side three projections, two anterior and one posterior. The middle projections
on its anterior surface (Fig. 130, i, I), which
Fig. 130.       are called the anterior pyramids, are the con~ —- ~-~ —-_  tinuation  of the anterior columns of the
cord.  They pass onward, underneath the
o-   _ l  9    transverse fibres of the pons Varolii, run up12 ( 1  2 m 2   ward to the corpora striata, pass through
these bodies, and radiate upward and outward
from  their external surface, to terminate in
--— 4     the gray  matter of the hemispheres.  The
projections immediately  on the outside of
MEDULLA OBLONoATA the anterior pyramids, in the medulla obOF HUMAN BRAIN', ante- longata, are the olivary bodies (2, 2). They
rior view.-1, 1. Anterior py-.. 
rainids 2,2. Olivarybodies. contain  in their interior a thin  layer of
3.3. Restiform bodies. 4. De- gray matter folded upon itself, the functions
cussation of the anterior columns. The medulla oblong- and connections of which are but little una-a is seen terminated above  derstood  and are  ot, apparently, of very
by the transverse fibres of the                                 ve
puns Varolii.         great importance.




OF THE NERVOUS SYSTEM.                    367
The anterior columns of the cord present, at the lower part of the
medulla oblongata, a remarkable interchange or crossing of their
fibres (4). The fibres of the left anterior column pass across the
median line at this spot, and becoming continuous with the right
anterior pyramid, are finally distributed to the right side of the
cerebrum; while the fibres of the right anterior column, passing
over to the left anterior pyramid, are distributed to the left side of
the cerebrum. This interchange or crossing of the nervous fibres
is known as the decussation of the anterior columns of the cord.
The posterior columns of the cord, as they diverge on each side
of the fourth ventricle, form the posterior and lateral projections of
the medulla oblongata (3, 3). They are sometimes called the "restiform  bodies," and are extremely important parts of the brain.
They consist in great measure of the longitudinal filaments of
the posterior columns, which pass upward and outward, and are
distributed partly to the gray matter of the cerebellum.  The
remainder then pass forward, underneath the tubercula quadrigemina, into and through the optic thalami; and radiating thence
upward and outward, are distributed, like the continuation of the
anterior columns, to the gray matter of the cerebrum. The restiform bodies, however, in passing upward to the cerebellum, are
supplied with some fibres from the anterior columns of the cord,
which, leaving the lower portion of the anterior pyramids, join the
restiform bodies, and are distributed with them to the cerebellum.
From this description it will be seen that both the cerebrum and
the cerebellum are supplied with filaments from both the anterior
and posterior columns of the cord.
In the substance of each restiform body, moreover, there is imbedded a ganglion which gives origin to the pneumogastric nerve,
and presides over the functions of respiration. This ganglion is
surrounded and covered by the longitudinal fibres passing upward
from the cord to the cerebellum, but may be discovered by cutting
into the substance of the restiform body, in which it is buried. It
is the first important ganglion met with, in dissecting the brain
from below upward.
While the anterior columns are passing beneath the pons Varolii,
they form, together with the continuation of the posterior columns
and the transverse fibres of the pons itself, a rounded prominence
or tuberosity, which is known by the name of the tuber annulare.
In the deeper portions of this protuberance there is situated, among
the longitudinal fibres, another collection of gray matter, which




368         GENERAL STRUCTURE AND FUNCTIONS
though not of large size, has very important functions and connections.  This is known as the ganglion of the tuber annulare.
Situated almost immediately above these parts we have the corpora striata in front, and the optic thalarni behind, nearly equal in
size, and giving passage, as above described, to the fibres of the
anterior and posterior columns. Behind them still, and on a little
lower level, are the tubercula quadrigemina, giving origin to the
optic nerves.; The olfactory ganglia rest upon the cribriform plate
of the ethmoid bone, and send the olfactory filaments through the
perforations in this plate, to be distributed upon the mucous membrane of the upper and middle turbinated bones.  The cerebellum
covers in  the fourth ventricle and the posterior surface of the
medulla oblongata; and finally the cerebrum, which has attained
the size of the largest ganglion in the cranial cavity, extends so far
in all directions, forward, backward, and laterally, as to form a convoluted arch or vault, completely covering all the remaining parts
of the encephalon.
The entire brain may therefore be regarded as a connected series
of ganglia, the arrangement of which is shown in the accompanying diagram. (Fig. 131.) These
Fig. 131.             ganglia- occur in the following
order, counting from before backward: 1st. The olfactory ganglia. 2d. The cerebrum or hemispheres. 3d. The corpora striata.
4th. The optic thalami. 5th. The
tubercula  quadrigemina.   6th.
-\W      The cerebellum.  7th. The ganglion of the tuber annulare. And
8th. The ganglion of the medulla
oblongata.   Of these  ganglia,
only the hemispheres and cereDiagram of H1  M A N B R A I N, in vertical sec- 
tion; showing the situation of the different gan- bellum are convoluted, while the
glia, and the course of the fibres. 1. Olfactory remainder are smooth and roundganglion. 2. Hemisphere. 3 Corpus striatum.
4. Optic thalamus. 5. Tuberculaquadrigemina. ed  or somewhat irregular  in
6. Cerebellum. 7. Ganglion of tuber annulare. shape.  The course of the fibres
8. Ganglion of medulla oblongata.
coming from  the anterior and
posterior columns of the cord is also to be seen in the accompanying figure. A portion of the anterior fibres, we have already observed, pass upward and backward, with the restiform bodies, to the
cerebellum; while the remainder run forward through the tuber




OF THE NERVOUS SYSTEM.                     369
annulare and the corpus striatum, and then radiate to the gray
matter of the cerebrum. The posterior fibres, constituting the restiform body, are distributed partly to the cerebellum, and then pass
forward, as previously described, underneath the tubercula quadrigemina to the optic thalami, whence they are also finally distributed
to the gray matter of the cerebrum.
The cerebrum and cerebellum, each of which is divided into two
lateral halves or "lobes," by the great longitudinal fissure, are both
provided with transverse commissures, by which a connection is
established between their right and left sides. The great transverse commissure of the cerebrum is that layer of white substance
which is situated at the bottom  of the longitudinal fissure, and
which is generally known by the name of the "corpus callosum."
It consists of nervous filaments, which originate from  the gray
matter of one hemisphere, converge to the centre, where they become parallel, cross the median line, and are finally distributed to
the corresponding parts of the hemisphere upon the opposite side.
The transverse commissure of the cerebellum  is the pons Varolii.
Its fibres converge from the gray matter of the cerebellum on one
side, and pass across to the opposite; encircling the tuber annulare
with a band of parallel curved fibres, to which the name of "pons
Varolii" has been given from their resemblance to an arched bridge.
The cerebro-spinal system, therefore, consists of a series of ganglia situated in the cranio-spinal cavities, connected with each other
by transverse and longitudinal commissures, and sending out nerves
to the corresponding parts of the body. The spinal cord supplies
the integument and muscles of the neck, trunk, and extremities;
while the ganglia of the brain, beside supplying the corresponding
parts of the head, preside also over the organs of special sense, and
perform various other functions of a purely nervous character.
24




370             OF NERVOUS IRRITABILITY
C HAPTER II.
OF NERVOUS IRRITABILITY AND ITS MODE OF
ACTION.
WE have already mentioned, in a previous chapter, that every
organ in the body is endowed with the property of irritability; that
is, the property of reacting in some peculiar manner when subjected
to the action of a direct stimulus. Thus the irritability of a gland
shows itself by increased secretion, that of the capillary vessels by
congestion, that of the muscles by contraction. Now the irritability
of the muscles, indicated as above by their contraction, is extremely
serviceable as a means of studying and exhibiting nervous phenomena. We shall therefore commence this chapter by a study of
some of the more important facts relating to muscular irritability.
The irritability of the muscles is a property inherent in the muscular
fibre itself. The existence of muscular irritability cannot be explained by any known physical or chemical laws, so far as they
relate to inorganic substances. It must be regarded simply as a
peculiar property, directly dependent on the structure and constitution of the muscular fibre; just as the property of emitting light
belongs to phosphorus, or that of combining with metals to oxygen.
This property may be called into action by various kinds of stimulus; as by pinching the muscular fibre, or pricking it with the point
of a needle, the application of an acid or alkaline solution, or the
discharge of a galvanic battery. All these irritating applications
are immediately followed by contraction of the muscular fibre.
This contraction will even take place under the microscope, when
the fibre is entirely isolated, and removed from contact with any
other tissue; showing that the properties of contraction and irritability reside in the fibre itself, and are not communicated to it by
other parts.
Muscular irritability continues for a certain time after death. The
stoppage of respiration and circulation does not at once destroy
the vital properties of the tissues, but nearly all of them retain
these properties to a certain extent for some time afterward. It is
only when the constitution of the tissues has become altered by




AND ITS MODE OF ACTION.                     371
being deprived of blood, and by the consequent derangement of
the nutritive process, that their characteristic properties are finally
lost. Thus, in the muscles, irritability and contractility may be
easily shown to exist for a short time after death by applying to the
exposed muscular fibre the same kind of stimulus that we have
already found to affect it during life.  It is easy to see, in the
muscles of the ox, after the animal has been killed, flayed, and
eviscerated, different bundles of muscular fibres contracting irregularly for a long time, where they are exposed to the contact of the
air. Even in the human subject the same phenomenon may be
seen in cases of amputation; the exposed muscles of the amputated
limb frequently twitching and quivering for many minutes after
their separation from the body.
The duration of muscular irritability, after death, varies considerably in different classes of animals. It disappears most rapidly
in those whose circulation and respiration are naturally the most
active; while it continues for a longer time in those whose circulation and respiration are sluggish.  Thus in birds the muscular
irritability continues only a few minutes after the death of the
animal. In quadrupeds it lasts somewhat longer; while in reptiles
it remains, under favorable circumstances, for many hours. The
cause of this difference is probably that in birds and quadrupeds,
the tissues being very vascular, and the molecular changes of nutrition, going on with rapidity, the constitution of the muscular
fibre becomes so rapidly altered after the circulation has ceased, that its irritability soon disappears.  Fig. 132.
In reptiles, on the other hand, the tissues are less
vascular than in birds and quadrupeds, and all the
nutritive changes go on more slowly. Respiration  
and circulation can therefore be dispensed with for    \
a longer period, before the constitution of the tis-    a _6
sues becomes so much altered as to destroy altogether their vital properties.
Owing to this peculiarity of the cold-blooded
animals, their tissues may be used with great advantage for purposes of experiment.  If a frog's 
leg, for example, be separated from  the body of
the animal.(Fig. 132), the skin removed, and the
poles of a galvanic apparatus applied to the sur-   F  o' S L EG
face of the muscle (a, b), a contraction takes place  with poles of galevery.'me.'e.'rcuit  I.L3 c.T o.  vLanic battery applied
every time the circuit is completed and a discharge  tothemuci.s att, ab.




372              OF NERVOUS IRRITABILITY
passed through the tissues of the limb. The leg of the frog, prepared in this way, may be employed for a long time for the purpose of exhibiting the effect of various kinds of stimulus upon the
muscles.  All the mechanical and chemical irritants which we
have mentioned, pricking, pinching, cauterization, galvanism, &.,
act with more or less energy and promptitude, though the most
efficient of all is the electric discharge.
Continued irritation exhausts the irritability of the muscles. It is
found that the irritability of the muscles wears out after death more
rapidly if they be artificially excited, than if they be allowed to
remain at rest.  During life, the only habitual excitant of muscular contraction is the peculiar stimulus conveyed by the nerves.
After death this stimulus may be replaced or imitated, to a certain
extent, by other irritants; but their application gradually exhausts
the contractility of the muscle and hastens its final disappearance.
Under ordinary circumstances, the post-mortem  irritability of the
muscle remains until the commencement of cadaveric rigidity.
When this has become fairly established, the muscles will no longer
contract under the application of an artificial stimulus.
Certain poisonous substances have the power of destroying the
irritability of the muscles by a direct action upon their tissue.
Sulphoeyanide of potassium, for example, introduced into the circulation in sufficient quantity to cause death, destroys entirely the
muscular irritability, so that no contraction can afterward be produced by the application of an external stimulant.
Nervous Irritability.-The irritability of the nerves is the property by which they may be excited by an external stimulus, so as
to be called into activity and excite in their turn other organs to
which their filaments are distributed. When a nerve is irritated,
therefore, its power of reaction, or its irritability, can only be estimated by the degree of excitement produced in the organ to which the
nerve is distributed. A nerve running from the integument to the
brain produces, when irritated, a painful sensation; one distributed
to a glandular organ produces increased secretion; one distributed
to a muscle produces contraction. Of all these effects, muscular
contraction is found to be the best test and measure of nervous
irritability, for purposes of experiment. Sensation cannot of course
be relied on for this purpose, since both consciousness and volition
are abolished at the time of death.  The activity of the glandular
organs, owing to the stoppage of the circulation, disappears also
very rapidly, or at least cannot readily be demonstrated.  The




AND ITS MODE OF ACTION.                       373
contractility of the muscles, however, lasts, as we have seen, for a
considerable time after death, and may accordingly be employed
with great readiness as a test of hervous irritability.  The manner
of its employment is as follows:The leg of a frog is separated from  the body and stripped of its
integument; the sciatic nerve having been previously dissected
out and cut off at its point of emergence from the
spinal canal, so that a considerable portion of it        Fig. 133.
remains in connection with the separated  limb.              N
(Fig. 133.)  If the two poles of a galvanic appa- 
ratus be now  placed in contact with different             el   /
points (a b) of the exposed nerve, and a discharge           X
allowed to pass between them, at the moment
of discharge a sudden contraction takes place in            i
the muscles below. It will be seen that this ex- 
periment is altogether different from the one re- 
presented in Fig. 132.  In that experiment the
galvanic discharge is passed through the muscles
themselves, and acts upon them  by direct stimulus.  Here, however, the discharge passes only
from a to b through the tissues of the nerve, and           i
acts directly  upon the nerve alone; while the
nerve, acting upon the muscles by its own peculiar agency, causes in this way a muscular contraction.  It is evident that in order to produce          nerve (N) atthis effect, two conditions are equally essential: 1st. tached. —ab. Poles of
The irritability of the muscles; and 2d. The irri-  galvani atter,' 
tability of the nerve.  So long, therefore, as the
muscles are in a healthy condition, their contraction, under the
influence of a stimulus applied to the nerve, demonstrates the irritability of the latter, and'may be used as a convenient measure of
its intensity.
The irritability of the nerve continues after death.  The knowledge
of this fact follows from what has just been said with regard to experimenting upon the frog's leg, prepared as above.  The irritability of the nerve, like that of the muscle, depends directly upon
its anatomical structure and constitution; and so long as these remain unimpaired, the nerve will retain its vital properties, though
respiration and circulation may have ceased.  For the same reason,
also, as that given above with regard to the muscles, nervous irritability lasts much longer after death in the cold-blooded than in




374              OF NERVOUS IRRITABILITY
the warm-blooded animals. Various artificial irritants may be employed to call it into activity. Pinching or pricking the exposed
nerve with steel instruments, the application of caustic liquids, and
the passage of galvanic discharges, all have this effect. The electric
current, however, is much the best means to employ for this purpose, since it is more delicate in its operation than the others, and
will continue to succeed for a longer time.
The nerve is, indeed, so exceedingly sensitive to the electric current, that it will respond to it when insensible to all other kinds of
stimulus.  A  frog's leg freshly prepared with the nerve attached,
as in Fig. 133, will react so readily whenever a discharge is passed
through the nerve, that it forms an extremely delicate instrument
for detecting the presence of electric currents of low intensity, and
has even been used for this purpose by Matteucci, under the name
of the "galvanoscopic frog."  It is only necessary to introduce the
nerve as part of the electric circuit; and if even a very feeble current be present, it is at once betrayed by a muscular contraction.
The superiority of electricity over other means of exciting nervous action, such as mechanical violence or chemical agents, probably depends upon the fact that the latter necessarily alter and
disintegrate more or less the substance of the nerve, so that its irritability soon disappears. The electric current, on the other hand,
excites the nervous irritability without any marked injury to the
substance of the nervous fibre. Its action may, therefore, be continued for a longer period.
Nervous irritability, like that of the muscles,'is exhausted by repeated
excitement. If a frog's leg be prepared as above, with the sciatic
nerve attached, and allowed to remain at rest in a damp and cool
place, where its tissue will not become altered by desiccation, the
nerve will remain irritable for many hours; but if it be excited,
soon after its separation from the body, by repeated galvanic shocks,
it soon begins to react with diminished energy, and becomes gradually less and less irritable, until it at last ceases to exhibit any
further excitability. If it be now allowed to remain for a time at
rest, its irritability will be partially restored; and muscular contraction will again ensue on the application of a stimulus to the nerve.
Exhausted a second time, and a second time allowed to repose, it
will again recover itself; and this may even be repeated several
times in succession. At each repetition, however, the recovery of
nervous irritability is less complete, until it finally disappears altogether, and can no longer be recalled.




AND ITS MODE OF ACTION.                    375
Various accidental circumstances tend to diminish or destroy
nervous irritability. The action of the woorara poison, for example,
destroys at once the irritability of the nerves; so that in animals
killed by this substance, no muscular contraction takes place on
irritating the nervous trunk. Severe and sudden mechanical injuries often have the same effect; as where death is produced by
violent and extensive crushing or laceration of the body or limbs.
Such an injury produces a general disturbance, or shock as it is
called, which affects the entire nervous system, and destroys or
suspends its irritability. The effects of such a nervous shock may
frequently be seen in the human subject after railroad accidents,
where the patient, though very extensively injured, may remain
for some hours without feeling the pain of his wounds. It is only
after reaction has taken place, and the activity of the nerves has
been restored, that the patient begins to be sensible of pain.
It will often be found, on preparing the frog's leg for experiment
as above, that immediately after the limb has been separated from
the body and the integument removed, the nerve is destitute of
irritability. Its vitality has been suspended by the violence inflicted in the preparatory operation. In a few moments, however,
if kept under favorable conditions, it recovers from the shock, and
regains its natural irritability.
The action of the galvanic current upon the nerve, as first shown
by the experiments of Matteucci, is in many respects peculiar. If
the current be made to traverse the nerve in the natural direction
of its fibres, viz., from its origin toward its distribution, as from a
to b in Fig. 133, it is called the direct current. If it be made to
pass in the contrary direction, as from b to a, it is called the inverse
current.  When the nerve is fresh and exceedingly irritable, a
muscular contraction takes place at both the commencement and
termination of the current, whether it be direct or inverse. But
very soon afterward, when the activity of the nerve has become
somewhat diminished, it will be found that contraction takes place
only at the commencement of the direct and at the termination of the
inverse current. This may readily be shown by preparing the two
legs of the same frog in such a manner that they remain connected
with each other by the sciatic nerves and that portion of the spinal
column from which these nerves take their origin. The two legs,
so prepared, should be placed each in a vessel of water, with the
nervous connection hanging between. (Fig. 134.) If the positive
pole, a, of the battery be now placed in the vessel which holds leg




376               OF NERVOUS IRRITABILITY
No. 1, and the negative pole, b, in that containing leg No. 2, it will
be seen that the galvanic current will traverse the two legs in opposite directions.  In No. 1 it will pass in a direction contrary to
the course of its nervous fibres, that is, it will be for this leg an
Fig. 134.....................................................................................a                                         /
inverse current; while in No. 2 it will pass in the same direction
with that of the nervous fibres, that is, it will be for this leg a direct
current.  It will now be found thatat the moment when the circuit is completed, a contraction takes place in No. 2 by the direct
current, while No. I remains at rest; but at the time the circuit is
broken, a contraction is produced in No. I by the inverse current,
but no movement takes place in No. 2.  A succession of alternate
contractions may thus be produced in the two legs by repeatedly
closing and opening the circuit.  If the position of the poles, a, b,
be reversed, the effects of the current will be changed in a corresponding manner.
After a nerve has become exhausted by the direct current, it is
still sensitive to the inverse; and after exhaustion by the inverse,
it is still sensitive to the direct.  It has even been found by Matteucci that after a nerve has been exhausted for the time by the direct
current, the return of its irritability is hastened by the subsequent
passage of the inverse current; so that it will become again sensitive to the direct current sooner than if allowed to remain at rest.
Nothing, accordingly, is so exciting to a nerve as the passage of
direct and inverse currents, alternating with each other in rapid
succession.  Such a mode of applying the electric stimulus is that
usually adopted in the galvanic machines used in medical practice,
for the treatment of certain paralytic affections. In these machines,




AND ITS MODE OF ACTION.                     377
the electric circuit is alternately formed and broken with great
rapidity, thus producing the greatest effect upon the nerves with
the smallest expenditure of electricity. Such alternating currents,
however, if very powerful, exhaust the nervous irritability more
rapidly and completely than any other kind of irritation; and in
an animal killed by the action of a battery used in this manner, the
nerves may be found to be entirely destitute of irritability from the
moment of death.
The irritability of the nerves is distinct from that of the muscles; and
the two may be destroyed or suspended independently of each other.
When the frog's leg has been prepared and separated from  the
body, with the sciatic nerve attached, the muscles contract, as we
have seen, whenever the nerve is irritated. The irritability of the
nerve, therefore, is manifested in this instance only through that of
the muscle, and that of the muscle is called into action only through
that of the nerve. The two properties may be separated from each
other, however, by the action of woorara, which has the power, as
first pointed out by Bernard, of destroying the irritability of the
nerve without affecting that of the muscles. If a frog be poisoned
by this substance, and'the leg prepared as above, the poles of a
galvanic battery applied to the, nerve will produce no effect; showing that the nervous irritability has ceased to exist. But if the
galvanic discharge be passed directly through the muscles, contraction at once takes place. The muscular irritability has survived
that of the nerves, and must therefore be regarded as essentially
distinct from it.
It will be recollected, on the other hand, that in cases of death
from the action of sulphocyanide of potassium, the muscular irritability is itself destroyed; so that no contractions occur, even when
the galvanic discharge is made to traverse the muscular tissue.
There are, therefore, two kinds of paralysis: first, a muscular
paralysis, in which the muscular fibres themselves are directly
affected; and second, a nervous paralysis, in which the affection is
confined to the nervous filaments, the muscles retaining their natural
properties, and being still capable of contracting under the influence
of a direct stimulus.
Nature of the Nervous Force.-It will readily be seen that the
nervous force, or the agency by which the nerve acts upon a muscle
and causes its contraction, is entirely a peculiar one, and cannot be
regarded as either chemical or mechanical in its nature.  The force
which is exerted by a nerve in a state of activity is not directly




378              OF NERVOUS IRRITABILITY
appreciable in any way by the senses, and can be judged of only
by its effect in causing muscular contraction. This peculiar vitality
of the nerve, or, as it is sometimes called, the "nervous force," does
not precisely resemble in its operation any of the known physical
forces. It has, however, a partial resemblance in some respects to
electricity; and this has been sufficient to lead some writers into the
error of regarding the two as identical, and of supposing electricity
to be really the force acting in the nerves, and operating through
them  upon the muscles.  The principal points of resemblance
existing between the two forces, and which have been used in
support of the above opinion, are the following:
1st. The identity of their effects upon the muscular fibre.
2d. The rapidity and peculiarity of their action, by which the
force is transmitted almost instantaneously to a distant point, without producing any visible effect on the intervening parts.
3d. The extreme sensibility of nerves to the electric current; and
4th. The phenomena of electrical fishes.
As these considerations are of some importance in settling the
question which now occupies us, we shall examine them in succession.
1st. The Identity of their Effects upon the Muscular Fibre.-It is
very true that the muscular fibre contracts under the influence of
electricity, as it does under that of the nervous force. This fact,
however, does not show the identity of the two forces, but only
that they are both capable of producing one particular phenomenon;
or that electricity may replace or imitate the nervous force in its
action on the muscles. But there are various other agents, as we
have already seen, both mechanical and chemical, which will produce the same effect, when applied to the muscular tissue. Electricity, therefore, is only one among several physical forces which
resemble each other in this respect, but which are not on that
account to be regarded as identical.
2d. The Rapidity and Peculiarity of their Action, by which the
force is transmitted almost instantaneously to a distant point, without
producing any visible effect on the intervening parts.-This is a very
remarkable and important character, both of the nervous force and
of electricity. In neither case is there any visible effect produced
on the nervous or metallic fibre which acts as a conducting medium;
but the final action is exerted upon the substance or organ with
which it is in connection. No definite conclusion, however, can
be properly derived from the rapidity of their transmission, since




AND ITS MODE OF ACTION.                    379
this rapidity has never been accurately measured in either instance.
We know that light and sound both travel with much greater
rapidity than most other physical forces, and that electricity is more
rapid in its transmission than either; but there is no evidence that
the velocity of the latter and that of the nervous force are the same.
We can only say that in both instances the velocity is very great,
without being able to compare them  together with any degree of
accuracy.  The mode of transmission, moreover, alluded to above,
is not peculiar to the two forces which are supposed to be identical.
Light, for example, is transmitted like them through conducting
media, without producing in its passage any sensible effect until it
meets with a body capable of reflecting it. In the interval, therefore, between the luminous body and the reflecting one, there is
the same apparent want of action as in the nerve, between the point
at which the irritation is applied and its termination in the muscular tissue.
3d. The extreme Sensibility of Nerves to the Electric Current.-It
has already been mentioned that the electric current is the most
delicate of all the means of irritation that may be applied to the
nerve after death; and that it may be used with less deleterious
effect than any other. The evident reason for this, however, has
already been given.  Electricity is one among several physical
agents by which the nerve may be artificially excited after death.
It is less destructive to the nervous texture than any other, and
consequently exhausts its vitality less rapidly. All these agents
vary in the delicacy of their operation; and though the electric
current happens to be the most efficient of all, it is still simply an
artificial irritant, like the rest, capable of imitating, in its own way,
the natural stimulus of the nerve.
4th. The Phenomena of Electrical Fishes.-It has been fully demonstrated that certain fish (gymnotus and torpedo) have the power of
generating electricity, and of producing electric discharges, which
are often sufficiently powerful to kill small animals that may come
within their reach. That the force generated by these animals is
in reality electricity, is beyond a doubt. It is conducted by the
same bodies which serve as conductors for electricity, and is stopped
by those which are non-conductors of the same. All the ordinary
phenomena produced by the electric current, viz: the heating and
melting of a fine conducting wire, the induction of secondary
currents and of magnetism, the decomposition of saline solutions,
and even the electric spark, have all been produced by the force




380              OF NERVOUS IRRITABILITY
generated by these animals. There is, accordingly, no room for
doubt as to its nature.
This fact, however, is very far from demonstrating the electric
character of the nervous force in general. It is, on the contrary,
directly opposed to such a supposition; since the gymnotus and
torpedo are capable of generating electricity simply because they
have a special organ destined for this purpose.  This organ, which is
termed the "electrical organ," is peculiar to these fish, and where
it is absent, the power of generating electricity is absent also. The
electrical organs of the gymnotus and torpedo occupy a considerable
portion of the body, and are largely supplied with nerves which
regulate their function. If these nerves be divided, tied, or injured
in any way, the electrical organ is weakened or paralyzed, just as
the muscles would be if the nerves distributed to them were subjected to a similar violence.  The electricity produced by these
animals is not supplied by the nerves, but by a special generating
organ, the action of which is regulated by nervous influence.
The reasons quoted above, therefore, are quite insufficient for
establishing any relation of identity between the nervous force and
electricity. There are, moreover, certain well authenticated facts
directly opposed to such a supposition, the most important of which
are the following:
The first is, that no electrical current has been actually found to exist
in an irritated nerve. The most conclusive experiments on this point
are those which were made by Longet and Matteucci, in company
with each other, at the veterinary school of Alfort.' The galvanometer employed in these investigations was constructed under the
personal direction of the experimenters, and was of extreme delicacy.
The oscillating needle was surrounded by 2500 turns of conducting
wire, and the poles were each armed with a platinum plate, having
an exposed surface of one-sixth of a square inch. When the poles
of the apparatus had been repeatedly immersed in spring water, so
that no further variation was produced from this source, the instrument was considered as ready for use. The sciatic nerve of a living horse was then exposed, and the poles of the galvanometer
placed in contact with it, in various positions, both diagonally and
longitudinally, and at various depths in its interior. The examination was continued for a quarter of an hour, during which time the
painful sensations of the animal were testified by constant struggling movements of the limbs; showing that both the motor and
i Longet, Trait de Physiologie. Paris, 1850, vol. ii. p. 130.




AND ITS MODE OF ACTION.                     381
sensitive filaments of the nerve were in a high state of activity.
The conclusion, however, to which the experimenters were conducted was the following, viz: that "there was no constant and reliable evidence of the existence of an electric current in the nerve."
Secondly. The mode of conduction of the nervous force is different
from that of electricity. The latter force, in order to exert its characteristic effects, must be transmitted through isolated conductors, so
arranged as to form a complete circuit. No such circuit has ever
been shown to exist in the nervous system; and the nerves themselves, the only tissues capable of conducting the nervous force, are
not particularly good conductors of electricity; no better, for example, than the muscles or the areolar tissue. We know of nothing,
therefore, which should prevent an electric current, passing through
a nerve, from being dispersed and lost among the adjacent tissues.
This is not the case, however, with the natural stimulus conveyed
by the nervous filament.
Moreover the nerve, in order to conduct its own peculiar force,
must be in a state of complete integrity. If a ligature be applied
to it, or if it be pinched or lacerated, the muscles to which it is distributed are paralyzed for all voluntary motion, and yet it transmits
the electric current as readily as before. If the nerve be divided,
and its divided extremities replaced in apposition with each other,
it will still act perfectly well as a conductor of electricity, though
it is needless to say that its natural function is at once destroyed.
The difference in the mode of conduction between the two forces
may be shown in a still more striking manner, as follows.  Let the
nerve connected with a frog's leg be divided, and its two extremities joined to each other by a piece of moist cotton thread. If the
galvanic current be now passed through the detached portion of the
nerve, no contraction will take place; because the nervous force,
excited in the detached portion, cannot be transmitted through the
cotton thread to the remainder. But if one of the galvanic poles
be applied above, and the other below the point of division, a contraction is immediately produced; since the electric current is
readily transmitted by the cotton thread, and excites the lower
portion of the nerve, which is still in connection with the muscles.
The nervous force, therefore, while it has some points of resemblance with electricity, presents also certain features of dissimilarity
which are equally important. It must be regarded accordingly as
distinct in its nature from  other known physical forces, and as
altogether peculiar to the nervous tissue in which it originates.




382                  THE SPINAL CORD.
CHAPTER III.
THE SPINAL  CORD.
WE have already seen that the spinal cord is a long ganglion,
covered with longitudinal bundles of nervous filaments, and occupying the cavity of the spinal canal. It sends out nerves which
supply the muscles and integument of at least nine-tenths of the
whole body, viz., those of the neck, trunk, and extremities. All
these parts of the body are endowed with two very remarkable
properties, the exercise of which depends, directly or indirectly,
upon the integrity and activity of the spinal cord, viz., the power
of sensation and the power of motion. Both these properties are
said to reside in the nervous system, because they are so readily
influenced by its condition, and are so closely connected with its
physiological action. We shall therefore commence the study of
the spinal cord with an examination of these two functions, and of
the situation which they occupy in the nervous system.
SENSATION.-The power of sensation, or sensibility, is the power
by which we are enabled to receive impressions from  external
objects. These impressions are usually of such a nature that we
can derive from them some information in regard to the qualities
of external objects and the effect which they may produce upon
our own systems. Thus, by bringing a foreign body into contact
with the skin, we feel that it is hard or soft, rough or smooth, cold
or warm. We can distinguish the separate impressions produced
by several bodies of a similar character, and we can perceive whether either one of them, while in contact with the skin, be at rest
or in motion. This power, which is generally distributed over the
external integument, is dependent on the nervous filaments ramifying in its tissue. For if the nerves distributed to any part of the
body be divided, the power of sensation in the corresponding region
is immediately lost.
The sensibility, thus distributed over the integument, varies in




SENSATION.                         383
its acuteness in different parts of the body. Thus, the extremities
of the fingers are more sensitive to external impressions than the
general surface of the limbs and trunk. The surfaces of the fingers
which lie in contact with each other are more sensitive than their
dorsal or palmar surfaces. The point of the tongue, the lips, and
the orifices of most of the mucous passages are endowed with a
sensibility which is more acute than that:of the general integument.
If the impression to which these parts are subjected be harsh or
violent in its character, or of such a nature as to injure the texture
of the integument or its nerves, it then produces a sensation of pain.
It is essential to notice, however, that the sensation of pain is not
a mere exaggeration of ordinary sensitive impressions, but is one
of quite a different character, which is superadded to the others, or
takes their place altogether. Just in proportion as the contact of a
foreign body becomes painful, our ordinary perceptions of its physical properties are blunted, and the sense of suffering predominates
over ordinary sensibility. Thus if the integument be gently touched
with the blade of a knife we easily feel that it is hard, cold, and
smooth; but if an incision be made with it in the skin, we lose all
distinct perception of these qualities, and feel only the suffering
produced by the incision.  We perceive, also, the difference in
temperature between cold and warm substances brought in contact
with the skin, so long as this difference is moderate in degree; but
if the foreign body be excessively cold or excessively hot, we can
no longer appreciate its temperature by the touch, but only its
injurious and destructive effect.  Thus the sensation caused by
touching frozen carbonic acid is the same with that produced by a
red-hot metal. Both substances blister the surface, but their actual
temperatures cannot be distinguished.
It is, therefore, a very important fact, in this connection, that the
sensibility to pain is distinct from the power of ordinary sensation. This
distinction was first fully established by M. Beau, of Paris, who has
shown conclusively that the sensibility to pain may be diminished
or suspended, while ordinary sensation remains. This is often seen
in patients who are partially under the influence of ether or chloroform. The etherization may be carried to such an extent that
the patient may be quite insensible to the pain of a surgical operation, and yet remain perfectly conscious, and even capable of feeling
the incisions, ligatures, &c., though he does not suffer from them.
It not unfrequently happens, also, when opium has been administered for the relief of neuralgia, that the pain is completely abolished




384                   THE SPINAL CORD.
by the influence of the drug, while the patient retains completely
his consciousness and his ordinary sensibility.
In all cases, however, if the influence of the narcotic be pushed
to its extreme, both kinds of sensibility are suspended together, and
the patient becomes entirely unconscious of external impressions.
MoTIoN.-Wherever muscular tissue exists, in any part of the
body, we find, the power of motion, owing to the contractility of
the muscular fibres. But this power of motion, as we have already
seen, is dependent on the nervous system. The excitement which
causes the contraction of the muscles is transmitted to them by the
nervous filaments; and if the nerves supplyingoa muscle or a limb
be divided or seriously injured, these parts are at once paralyzed
and become incapable of voluntary movement. A nerve which,
when irritated, acts directly upon a muscle, producing contraction,
is said to be excitable; and its excitability, acting through the muscle, produces motion in the part to which it is distributed.
The excitability of various nerves, however, often acts during
life upon other organs, beside the muscles; and the ultimate effect
varies, of course, with the properties of the organ which is acted
upon. Thus, the nervous excitement transmitted to a muscle produces contraction, while that transmitted to a gland produces an
increased secretion, and that conveyed to a vascular surface causes
congestion. In all such instances, the effect is produced by an
influence transmitted by a nerve directly to the organ which is
called into activity.
But in all the external parts of the body muscular contraction
is the most marked and palpable effect produced by the direct
influence of nervous excitement.  We find, therefore, that, so far
as we have yet examined it, the nervous action shows itself principally in two distinct and definite forms; first, as sensibility, or the
power of sensation, and second, as excitability, or the power of producing motion.
DISTINCT SEAT OF SENSATION AND MOTION IN THE NERVOUS
SYSTEM.-Sensation and motion are usually the first functions
which suffer by any injury inflicted on the nervous system. As a
general rule, they are both suspended or impaired at the same time,
and in a nearly equal degree. In a fainting fit, an attack of apoplexy, concussion or compression of the brain or spinal cord, or a
wound of any kind involving the nerves or nervous centres, insen



DISTINCT SEAT OF SENSATION AND MOTION.   385
sibility and loss of motion usually appear simultaneously. It is
difficult, therefore, under ordinary conditions, to trace out the
separate action of these two functions, or to ascertain the precise
situation occupied by each.
This difficulty, however, may be removed by examining separately different parts of the nervous system.  In the instances
mentioned above, the injury which is inflicted is comparatively an
extensive one, and involves at the same time many adjacent parts.
But instances sometimes occur in which the two functions, sensation and motion, are affected independently of each other, owing to
the peculiar character and situation of the injury inflicted. Sensation may be impaired without loss of motion, and loss of motion
may occur without injury to sensation. In tic douloureux, for
example, we have an exceedingly painful affection of the sensitive
parts of the face, without any impairment of its power of motion;
and in facial paralysis we often see a complete loss of motion affecting one side of the face, while the sensibility of the part remains
altogether unimpaired.
The above facts first gave rise to the belief that sensation and
motion might occupy distinct parts of the nervous system; since it
would otherwise be difficult to understand how the two could be
affected independently of each other by anatomical lesions. It has
accordingly been fully established, by the labors of Sir Charles Bell,
Miller, Panizza, and Longet, that the two functions do in reality
occupy distinct parts of the nervous system.
If any one of the spinal nerves, in the living animal, after being
exposed at any part of its course outside the spinal canal, be divided,
ligatured, bruised, or otherwise seriously injured, paralysis of motion
and loss of sensation are immediately produced in that part of the
body to which the nerve is distributed. If, on the other hand, the
same nerve be pricked, galvanized, or otherwise gently irritated, a
painful sensation and convulsive movements are produced in the
same parts. The nerve is therefore said to be both sensitive and
excitable; sensitive, because irritation of its fibres produces a painful sensation, and excitable, because the same irritation causes muscular contraction in the parts below.
The result of the experiment, however, will be different if it be
tried upon the parts situated inside the spinal canal, and particularly
upon the anterior and posterior roots of the spinal nerves. If an
irritation be applied, for example, to the anterior root of a spinal
nerve, in the living animal, convulsive movements are produced in
25




386                    THE SPINAL CORD.
the parts below, but there is no painful sensation.  The anterior
root accordingly is said to be excitable, but not sensitive. If the
posterior root, on the other hand, be irritated, acute pain is produced, but no convulsive movements.  The posterior root is therefore sensitive, but not excitable. A similar result is obtained by a
complete division of the two roots. Division of the anterior root
produces paralysis of motion, but no insensibility; division of the
posterior root produces complete loss of sensibility, but no muscular
paralysis.
We have here, then, a separate localization of sensation and
motion in the nervous system; and it is accordingly easy to understand how one may be impaired:without injury to the other, or
how both may be simultaneously.affected, according to the situation
and ektent of the anatomical lesion.
The two roots of a spinal nerve differ from  each other, furthermore, in their mode of transmitting the nervous impulse. If the
posterior root be divided (Fig. 135) at a, b, and an irritation applied
Fig. 135.
Diagram of SPINAL CORD AND NERVES. The posterior root is seen divided at a, b, the
anterior at c, d.
to the separated extremity (a), no effect will be produced; but if
the irritation be applied to the attached extremity (b), a painful
sensation is immediately the result. The nervous force, therefore,
travels in the posterior root from without inward, but cannot pass
from within outward. If the anterior root, on the other hand, be
divided at c, d, and its attached extremity (d) irritated, no effect
follows; but if the separated extremity (c) be irritated, convulsive
movements instantly take place.  The nervous force, consequently,




SENSIBILITY AND EXCITABILITY IN SPINAL CORD. 387
travels in the anterior root from within outward, but cannot pass
from without'inward.
The same thing is true with regard to the transmission of sensation and motion in the spinal nerves outside the spinal canal. If
one of these nerves be divided in the living animal, and its attached
extremity irritated, pain is produced, but no convulsive motion; if
the irritation be applied to its separated extremity, muscular contractions follow, but no painful sensation.
There are. therefore, two kinds of filaments in the spinal nerves,
not distinguishable by the eye, but entirely distinct in their character and function, viz., the "sensitive" filaments, or those which
convey sensation, and the "motor" filaments, or those which excite
movement. These filaments are never confounded with each other
in their action, nor can they perform  each other's functions. The
sensitive filaments convey the nervous force only in a centripetal,
the motor only in a centrifugal direction. The former preside over
sensation, and have nothing to do with motion; the latter preside
over motion, and have nothing to do with sensation.  Within the
spinal canal the two kinds of filaments are separated from each
other, constituting the anterior and posterior roots of each spinal
nerve; but externally they are mingled together in a common
trunk. While the anterior and posterior roots, therefore, are exclusively sensitive or exclusively motor, the spinal nerves beyond
the junction of the roots are called mixed nerves, because they contain at the same time motor and sensitive filaments. The mixed
nerves accordingly preside at the same time over the functions of
movement and sensation.
DISTINCT SEAT OF SENSIBILITY AND EXCITABILITY IN THE
SPINAL CORD.-Various experimenters have demonstrated the fact
that different parts of the spinal cord, like the two roots of the
spinal nerves, are separately endowed with sensibility and excitability. The anterior columns of the cord, like the anterior roots of
the spinal nerves, are excitable but not sensitive; the posterior
columns, like the posterior roots of the spinal nerves, are sensitive
but not excitable. Accordingly, when the spinal canal is opened
in the living animal, an irritation applied to the anterior columns
of the cord produces immediately convulsions in the limbs below;
but there is no indication of pain. On the other hand, signs of
acute pain become manifest whenever the irritation is applied to
the posterior column; but no muscular contractions follow, other




388                  THE SPINAL CORD.
than those of a voluntary character. Longet has found' that if the
spinal cord be exposed in the lumbar region and completely divided
at that part by transverse section, the application of any irritant to
the anterior surface of the separated portion produces at once convulsions below; while if applied to the posterior columns behind
the point of division, it has no sensible effect whatever. The anterior and posterior columns of the cord are accordingly, so far,
analogous in their properties to the anterior and posterior roots of
the spinal nerves, and are plainly composed, to a greater or less extent, of a continuation of their filaments.
These filaments, derived from the anterior and posterior roots of
the spinal nerves, pass upward through the spinal cord toward the
brain. An irritation applied to any part of the integument is then
conveyed, along the sensitive filaments of the nerve and its posterior root, to the spinal cord; then upward, along the longitudinal
fibres of the cord to the brain, where it produces a sensation corresponding in character with the original irritation. A motor impulse, on the other hand, originating in the brain, is transmitted
downward, along the longitudinal fibres of the cord, passes outward
by the anterior root of the spinal nerve, and, following the motor
filaments of the nerve through its trunk and branches, produces at
last a muscular contraction at the point of its final distribution.
CROSSED ACTION OF THE SPINAL CORD.-As the anterior columns
of the cord pass upward to join the medulla oblongata, a decussation takes place between them, as we have already mentioned in
Chapter I. The fibres of the right anterior column pass over to
the left side of the medulla oblongata, and so upward to the left side
of the brain; while the fibres of the left anterior column pass over
to the right side of the medulla oblongata, and so upward to the right
side of the brain. This decussation may be readily shown (as in
Fig. 130) by gently separating the anterior columns from each other,
at the lower extremity of the medulla oblongata, where the decussating bundles may be seen crossing obliquely from side to side, at
the bottom of the anterior median fissure. Below this point, the
anterior columns remain distinct from each other on each side, and
do not communicate by any further decussation.
If the anterior columns of the spinal cord, therefore, be wounded
at any point in the cervical, dorsal, or lumbar region, a paralysis
Traite de Physiologie, vol. ii. part 2, p. 8.




CROSSED ACTION  OF THE SPINAL CORD.                389
of voluntary motion is produced in the limbs below, on the same
side with the injury. But if a similar lesion occur in the brain, the
paralysis which results is on the opposite side of the body. Thus
it has long been known that an abscess or an apoplectic hemorrhage
on the right side of the brain will produce paralysis of the left side
of the body; and injury of the left side of the brain will be followed by paralysis of the right side of the body.
The spinal cord has also a crossed action in transmitting sensitive as well as motor impulses. It has been recently demonstrated
by Dr. Brown-Sequard,' that the crossing of the sensitive fibres in
the spinal cord does not take place, like that of the motor fibres,
at its upper portion only, but throughout its entire length; so that
the sensitive fibres of the right spinal nerves, very soon after their
entrance into the cord, pass over to the left side, and those of the
left spinal nerves pass over to the right side. For if one lateral
half of the spinal cord of a dog be divided in the dorsal region,
the power of sensation remains upon the corresponding side of the
body, but is lost upon the opposite side. It has been shown, furthermore, by the same observer,2 that the sensitive fibres of the
spinal nerves when they first enter the cord join the posterior
columns, which are everywhere extremely sensitive; but that they
very soon leave the posterior columns, and, passing through the
central parts of the cord, run upward to the opposite side of the
brain.  If the posterior columns, accordingly, be alone divided at
any part of the spinal cord, sensibility is not destroyed in all the
nerves behind the seat of injury, but only in those which enter the
cord at the point of section; since the posterior columns consist
of different nervous filaments, joining them constantly on one side
from below, and leaving them on the other to pass upward toward
the brain.
The spinal cord has therefore a crossed action, both for sensation
and motion; but the crossing of the motor filaments occurs only at
the medulla oblongata, while that of the sensitive filaments takes
place throughout the entire length of the cord itself.
There are certain important facts which still remain to be noticed,
regarding the mode of action of the spinal cord and its nerves.
They are as follows:i Experimental Researches applied to Physiology and Pathology. New York,
1853.
2 M6moirs sur la Physiologie de la Moelle 6piniere; Gazette Medicale de Paris,
1855.




390                   THE SPINAL CORD.
1. An irritation applied to a spinal nerve at the middle of its course
produces the same effect as if it traversed its entire length. Thus, if the
sciatic or median nerve be irritated at any part of its course, contraction is produced in the muscles to which these nerves are distributed, just as if the impulse had originated as usual from the
brain.  This fact depends upon the character of the nervous filaments, as simple conductors. Wherever the impulse may originate,
the final effect is manifested only at the termination of the nerve.
As the impulse in the motor nerves travels always in an outward
direction, the effect is always produced at the muscular termination
of the filaments, no matter how small or how large a portion of
their length may have been engaged in transmitting the stimulus.
If the irritation, again, be applied to a sensitive nerve in the
middle of its course, the painful sensation is felt, not at the point
of the nerve directly irritated, but in that portion of the integument
to which its filaments are distributed.  Thus, if the ulnar nerve be
accidentally struck at the point where it lies behind the inner condyle of the humerus, a sensation of tingling and numbness is produced in the last two fingers of the corresponding hand.  It is
common to hear patients who have suffered amputation complain of
painful sensations in the amputated limb, for weeks or months, and
sometimes even for years after the operation.  They assert that
they can feel the separated parts as distinctly'as if they were still
attached to the body. This sensation, which is a real one and not
fictitious, is owing to some irritation operating upon the divided
extremities of the nerves in the cicatrized wound. Such an irritation, conveyed to the brain by the sensitive fibres, will produce
precisely the same sensation as if the amputated parts were still
present, and the irritation actually applied to them.
It is on this account also that division of the trifacial nerve is
not always effectual in the cure of tic douloureux. If the cause of
the difficulty be seated upon the trunk of the nerve, between its
point of emergence from the bones and its origin in the brain, it is
evident that division of the nerve upon the face will be of no
avail; since the cause of irritation will still exist behind the point
of section, and the same painful sensations will still be produced in
the brain.
2. The irritability of the motor filaments disappears from within outward, that of the sensitive filaments from  without inward. Immediately after the separation of the fiog's leg from the body, irritation
of the nerve at any point produces muscular contraction in the




INDEPENDENCE OF NERVOUS FILAMENTS.                  391
limb below.  As time elapses, however, and the irritability of the
nerve diminishes, the galvanic current, in order to produce contraction, must be applied at a point nearer its termination. Subsequently, the irritability of the nerve is entirely lost in its upper
portions, but is retained in:the parts situated lower down, from
which it also, in turn, afterward disappears; receding in this manner farther and farther toward the terminal distribution of the
nerve, where it finally disappears altogether.
On the other hand, sensibility disappears, at the time of death,
first in the extremities. From them the numbness gradually creeps
upward, invading successively the middle and upper portions of the
limbs, and the more distant portions of the trunk.  The central
parts are the last to become insensible.
S. Each nervous filament acts independently of the rest throughout its
entire length, and does not communicate its irritation to those which are
in proximity with it. It is evident that this is true with regard to
the nerves of sensation, from the fact that if the integument be
touched with the point of a needle, the sensation is referred to that
spot alone.  Since the nervous-filaments coming from  it and the
adjacent parts are all bound together in parallel bundles, to form
the trunk of the nerve, if any irritation were communicated from
one sensitive filament to another, the sensation produced would be
indefinite and diffused, whereas it is really confined to the spot irritated. If a frog's leg, furthermore, be prepared, with the sciatic
nerve attached, a few of the fibres separated laterally from  the
nervous trunk for a portion of its length, and the poles of a galvanic
battery applied to the separated portion, the contractions which
follow in the leg will not be general, but will be confined to those
muscles in which the galvanized nervous fibres especially have
their distribution.  There are also various instances, in the body,
of antagonistic muscles, which must act independently of each
other, but which are supplied with nerves from  a common trunk.
The superior and inferior straight muscles of the eyeball, for
example, are both supplied by the motor oculi communis nerve.
Extensor and flexor, muscles, as, for example, those of the fingers,
are often supplied by the same nerve, and yet act alternately without mutual interference.  It is easy to see that if this were not the
case, confusion would constantly arise, both in the perception of
sensations, and in the execution of movements.
4. There are certain sensations which are excited simultaneously
by the same causes, and which are termed associated sensations; and




392                  THE SPINAL CORD.
there are also certain movements which take place simultaneously,
and are called associated movements. In the former instance, one of
the associated sensations is called up immediately upon the perception of the other, without requiring any direct impulse of its own.
Thus, tickling the soles of the feet produces a peculiar sensation
at the epigastrium. Nausea is occasioned by certain disagreeable
odors, or by rapid rotation of the body, so that the landscape seems
to turn round. A striking example of associated movements, on
the other hand, may be found in the action of the muscles of the
eyeball. The eyeballs always accompany each other in their lateral
motions, turning to the right or the left side simultaneously. It is
evident, however, that in producing this correspondence of motion,
the left internal rectus muscle must contract and relax together
with the right external; while a similar harmony of action must
exist between the right internal and the left external. The explanation of such singular correspondences cannot be found in the anatomical arrangement of the muscles themselves, nor in that of the
nervous filaments by which they are directly supplied, but must be
looked for in some special endowment of the nervous centres from
which they originate.
REFLEX ACTION OF THE SPINAL CORD.-The spinal cord, as we
have thus far examined it, may be regarded simply as a great nerve;
that is, as a bundle of motor and sensitive filaments, connecting
the muscles and integument below with the brain above, and
assisting, in this capacity, in the production of conscious sensation
and voluntary motion. Beside its nervous filaments, however, it
contains also a large quantity of gray matter, and is, therefore,
itself a ganglionic centre, and capable of independent action as
such. We shall now proceed to study it in its second capacity, as
a distinct nervous centre.
If a frog be decapitated, and the body allowed to remain at rest
for a few moments, so as to recover from the depressing effects of
shock upon the nervous system, it will be found that, although sensation and consciousness are destroyed, the power of motion still
remains. If the skin of one of the feet be irritated by pinching it
with a pair of forceps, the leg is immediately drawn up toward the
body, as if to escape the cause of irritation. If the irritation applied
to the foot be of slight intensity, the corresponding leg only will
move; but if it be more severe in character, motions will often be
produced in the posterior extremity of the opposite side, and even




REFLEX ACTION  OF THE SPINAL CORD.                 393
in the two fore legs, at the same time. These motions, it is important to observe, are never spontaneous. The decapitated frog remains
perfectly quiescent if left to himself. It is only when some cause
of irritation is applied externally, that movements occur as above
described.
It will be seen that the character of these phenomena indicates
the active operation of some part of the nervous system, and particularly of some ganglionic centre. The irritation is applied to
the skin of the foot, and the muscles of the leg contract in consequence; showing evidently the intermediate action of a nervous
connection between the two.
The effect in question is due to the activity of the spinal cord,
operating as a nervous centre. In order that the movements may
take place as above, it is essential that both the integument and the
muscles should be in communication with the spinal cord by nervous filaments, and that the cord itself be in a state of integrity. If
the sciatic nerve be divided in the upper part of the thigh, irritation
of the skin below is no longer followed by any muscular contraction. If either the anterior or posterior roots of the nerve be
divided, the same want of action results; and finally, if, the nerve
and its roots remaining entire, the spinal cord itself be broken up
by a needle introduced into the spinal
canal, the integument may then be                Fig. 136.
irritated or mutilated to any extent,
without exciting the least muscular
contraction. It is evident, therefore,
that the spinal cord acts, in this case,
as a nervous centre, through which
the irritation applied to the skin is
cothmunicated to the muscles.  The
irritation first passes upward, as shown
in the accompanying diagram  (Fig.
136), along the sensitive fibres of the
posterior root (a) to the gray matter   Diagram of SPINAL CORD IN VERof the cord, and is then reflected back, TICAL SECTION, showing reflex action.
-a. Posterior root of spinal nerve. b. Analong the motor fibres of the anterior terior root of spinal nerve.
root (b), until it finally reaches the
muscles, and produces a contraction. This action is known, accordingly, as the reflex action of the spinal cord.
It will be remembered that this reflex action of the cord is not
accompanied by volition, nor even by any conscious sensation.




394                   THE SPINAL CORD.
The function of the spinal cord as a nervous centre is simply to
convert an impression, received from the skin, into a motor impulse
which is sent out again to the muscles. There is absolutely no
farther action than this; no exercise of will, consciousness, or judgment. This action will therefore take place perfectly well after
the brain has been removed, and after the entire sympathetic system has also been taken away, provided only that the spinal cord
and its nerves remain in a state of integrity.
The existence of this reflex action after death is accordingly an
evidence of the continued activity of the spinal cord, just as contractility is an evidence of the activity of the muscles, and irritability of that of the nerves. Like the two last-mentioned properties,
also, it continues for a longer time after death in cold-blooded than
in warm-blooded animals. It is for this reason that frogs and other
reptiles are the most useful subjects for the study of these phenomena, as for that of most others belonging to the nervous system.
The irritability of the spinal cord, as manifested by its reflex
action, may be very much exaggerated by certain diseases, and by
the operation of poisonous substances. Tetanus and poisoning by
strychnine both act in this way, by heightening the irritability of
the spinal cord, and causing it to produce convulsive movements
on the application of external stimulus. It has been observed that
the convulsions in tetanus are rarely, if ever, spontaneous, but that
they always require to be excited by some external cause, such as
the accidental movement of the bedclothes, the shutting of a door,
or the sudden passage of a current of air. Such slight causes of
irritation, which would be entirely inadequate to excite involuntary
movements in the healthy condition, act upon the spinal cord, when
its irritability is heightened by disease, in such a manner as to produce violent convulsions.
Similar appearances are to be seen in animals poisoned by strychnine. This substance acts upon the spinal cord and increases its
irritability, without materially affecting the functions of the brain.
Its effects will show themselves, consequently, without essential
modification, after the head has been removed. If a decapitated
frog be poisoned with a moderate dose of strychnine, the body and
limbs will remain quiescent so long as there is no external source
of excitement; but the linbs are at once thrown into convulsions
by the slightest irritation applied to the skin, as, for example, the
contact of a hair or a feather, or even the jarring of the table on
which the animal is placed.  That the convulsions in cases of




REFLEX ACTION OF THE SPINAL CORD.                  395
poisoning by strychnine are always of a reflex character, and never
spontaneous, is shown by the following fact first noticed by Bernard,1 viz., that if a frog be poisoned after division of the posterior
roots of all the spinal nerves, while the anterior roots are left untouched, death takes place as usual, but is not preceded by any convulsions.  In this instance the convulsions are absent simply
because, owing to the division of the posterior roots, external irritations cannot be communicated to the cord.
The reflex action, above described, may be seen very distinctly
in the human subject, in certain cases of disease of the spinal cord.
If the upper portion of the cord be disintegrated by inflammatory
softening, so that its middle and lower portions lose their natural
connection with the brain, paralysis of voluntary motion and loss of
sensation ensue in all parts of the body below the seat of the anatomical lesion. Under these conditions, the patient is incapable of
making any muscular exertion in the paralyzed parts, and is unconscious of any injury done to the integument in the same region.
Notwithstanding this, if the soles of the feet be gently irritated
with a feather, or with the point of a needle, a convulsive twitching of the toes will often take place, and even retractile movements
of the leg and thigh, altogether without the patient's knowledge.
Such movements may frequently be excited by simply allowing
the cool air to come suddenly in contact with the lower extremities.
We have repeatedly witnessed these phenomena, in a case of disease of the spinal cord where the paralysis and insensibility of the
lower extremities were complete.  Many other similar instances
are reported by various authors.
The existence of this reflex action of the cord has enabled the
physiologist to ascertain several other important facts concerning
the mode of operation of the nervous system.  M. Bernard has
demonstrated,' by a series of extremely ingenious experiments on
the action of poisonous substances, 1st, that the irritability of the
muscles may be destroyed, while that of the nerves remains unaltered; and 2d, that the motor and sensitive nervous filaments may
be paralyzed independently of each other.  The above facts are
shown by the three following experiments:1. In a living frog (Fig. 137), the sciatic nerve (N) is exposed in
I Leqons sur les effets des Substances toxiques et medicamenteuses, Paris, 1857,
p. 357.
L Ibid., Chaps. 23 and 24.




396                   THE SPINAL CORD.
the back part of the thigh, after which a ligature is passed underneath it and drawn tight around the bone and the remaining soft
parts. In this way the circulation is entirely cut off from the limb
(d), which remains in connection with the trunk only by means of
the sciatic nerve. A solution of sulphocyanide of potassium is then
introduced beneath the skin
Fig. 137.             of the back, at i, in sufficient
quantity to produce its speci/    O' A  fic effect. The poison is then
absorbed, and is carried by
^a. (,I/  -/)/&            the circulation throughout the.^   (. I.t.' l~        trunk and the three extremi/::! j~J           ties a, b, c; while it is prer.-.. \   i:!  vented from entering the limb
I I^''! 0d, by the ligature which has
been placed about the thigh.
2  ~\   i ^ \Sulphocyanide of potassium
produces paralysis, as we have!  -" ^  ) ~ previously mentioned, by act/; 1 -,    ing directly upon the muscu-—...-.- - (                 lar tissue. Accordingly, a galvanic discharge passed through
\,i:        x, ^^^^^ the limbs a, b, and c, produces
Jii:; I"~ ~no contraction in them, while
d  ithe same stimulus, applied to
d, is followed by a strong and
healthy reaction. But at the
moment when the irritation
is applied to the poisoned
i~/lll g 2limbs a, b, and c, though no
visible effect is produced in
them, an  active movement
takes place  in the healthy
limb, d. This can only be
owing to a reflex action of the spinal cord, originating in the integument of a, b, and c, and transmitted, by sensitive and motor filaments, through the cord, to d.  While the muscles of the poisoned
limbs, therefore, have been directly paralyzed, the nerves of the same
parts have retained their irritability.
2. If a frog be poisoned with woorara by simply placing the
poison under the skin, no reflex action of the spinal cord can be




REFLEX ACTION OF THE SPINAL CORD.                 397
demonstrated after death.  We have already shown, from experiments detailed in Chapter II., that this substance destroys the irritability of the motor nerves, without affecting that of the muscles. In
the above instance, therefore, where the reflex action is abolished, its
loss may be owing to a paralysis of both motor and sensitive filaments, or to that of the motor filaments alone. The following experiment, however, shows that the motor filaments are the only ones
affected. If a frog be prepared as in Fig. 137, and poisoned by the
introduction of woorara at 1, when the limb d is irritated its own
muscles react, while no movement takes place in a, b, or c; but if
the irritation be applied to a, b, or c, reflex movements are immediately produced in d. In the poisoned limbs, therefore, while the
~motor nerves have been paralyzed, the sensitive filaments have retained
their irritability.
3. If a frog be poisoned with strychnine, introduced underneath
the skin in sufficient quantity, death takes place after general convulsions, which are due, as we have seen above, to an unnatural
excitability of the reflex action. This is followed, however, by a
paralysis of sensibility, so that after death no reflex movements
can be produced by irritating the skin or even the posterior roots
of the spinal nerves. But if the anterior roots, or the motor nerves
themselves be galvanized, contractions immediately take place in
the corresponding muscles. In this case, therefore, the sensitive filaments have been paralyzed, while the motor filaments and the muscles
have retained their irritability.
We now come to investigate the reflex action of the spinal cord,
as it takes place in a healthy condition during life. This action
readily escapes notice, unless our attention be particularly directed
to it, because the sensations which we are constantly receiving, and
the many voluntary movements which are continually executed,
serve naturally to mask those nervous phenomena which take place
without our immediate knowledge, and over which we exert no
voluntary control. Such phenomena, however, do constantly take
place, and are of extreme physiological importance. If the surface
of the skin, for example, be at any time unexpectedly brought in
contact with a heated body, the injured part is often withdrawn by
a rapid and convulsive movement, long before we feel the pain, or
even fairly understand the cause of the involuntary act. If the
body by any accident suddenly and unexpectedly loses its balance,
the limbs are thrown into a position calculated to protect the exposed parts, and to break the fall, by a similar involuntary and in



398                   THE SPINAL CORD.
stantaneous movement. The brain does not act in these cases, for
there is no intentional character in the movement, nor even any
complete consciousness of its object. Everything indicates that it
is the immediate result of a simple reflex action of the spinal cord.
The cord exerts also an important and constant influence upon
the sphincter muscles. The sphincter ani is habitually in a state of
contraction, so that the contents of the intestine are not allowed to
escape.  When any external irritation is applied to the anus, or
whenever the feces present themselves internally, the sphincter
contracts involuntarily, and the discharge of the feces is prevented.
This habitual closure of the sphincter depends on the reflex action
of the spinal cord. It is entirely an involuntary act, and will continue, in the healthy condition, during profound sleep, as complete
and efficient as in the waking state.
When the rectum, however, has become filled by the accumulation of feces from above, the nervous action changes. Then the
impression produced on the mucous membrane of the distended
rectum, conveyed to the spinal cord, causes at the same time relaxation of the sphincter and contraction of the rectum  itself; so
that a discharge of the feces consequently takes place.
Now all these actions are to some extent under the control of
sensation and volition. The distended state of the rectum is usually
accompanied by a distinct sensation, and the resistance of the
sphincter may be voluntarily prolonged for a certain period, just as
the respiratory movements, which are usually involuntary, may be
intentionally hastened or retarded, or even temporarily suspended.
But this voluntary power over the sphincter and the rectum is
limited.  After a time the involuntary impulse, growing more
urgent with the increased distension of the rectum, becomes irresistible; and the discharge finally takes place by the simple reflex
action of the spinal cord.
If the spinal cord be injured in its middle or upper portions, the
sensibility and voluntary action of the sphincter are lost, because its
connection with the brain has been destroyed. The evacuation
then takes place at once, by the ordinary mechanism, as soon as
the rectum is filled, but withoutany knowledge on the part of the
patient. The discharges are then said to be "involuntary and unconscious."
If the irritability of the cord, on the other hand, be exaggerated
by disease, while its connection with the brain remains entire, the
distension of the rectum is announced by the usual sensation, but




REFLEX ACTION OF THE SPINAL CORD.                  399
the reflex impulse to evacuation is so urgent that it cannot be
controlled by the will, and the patient is compelled to allow it to
take place at once. The discharges are then said to be simply
"involuntary."
Finally, if the substance of the spinal cord be extensively destroyed by accident or disease, the sphincter is permanently relaxed.
The feces are then evacuated almost continuously, without any
knowledge or control on the part of the patient, as fast as they
descend into the rectum from the upper portions of the intestine.
Injury of the spinal cord produces a somewhat different effect on
the urinary bladder. Its muscular fibres are directly paralyzed;
and the organ, being partially protected by elastic fibres, both at
its own orifice and along the urethra, becomes gradually distended
by urine from  the kidneys. The urine then overcomes the elasticity of the protecting fibres, by simple force of accumulation, and
afterward dribbles away as fast as it is excreted by the kidneys.
Paralysis of the bladder, therefore, first causes a permanent distension of the organ, which is afterward followed by a continuous,
passive, and incomplete discharge of its contents.
Injury of the spinal cord produces also an important, though
probably an indirect effect on nutrition, secretion, animal heat, &c.,
in the paralyzed parts. Diseases of the cord which result in its
softening or disintegration, are notoriously accompanied by constipation, often of an extremely obstinate character. In complete
paraplegia, also, the lower extremities become emaciated. The
texture and consistency of the muscles are altered, and the animal
temperature is considerably reduced.  All such disturbances of
nutrition, however, which almost invariably follow upon local paralysis, are no doubt immediately owing to the inactive condition of
the muscles; a condition which naturally induces debility of the
circulation, and consequently of all those functions which are dependent upon it.
It is less easy to explain the connection between injury of the
spinal cord and inflammation of the urinary passages. It is, however, a matter of common observation among pathologists, that
injury or disease of the cord, particularly in the dorsal and upper
lumbar regions, is soon followed by catarrhal inflammation of the
urinary passages. This gives rise to an abundant production of
altered mucus, which in its turn, by causing an alkaline fermentation of the urine contained in the bladder, converts it into an irri



400                  THE SPINAL CORD.
tating and ammoniacal liquid, which reacts upon the mucous membrane and aggravates the previous inflammation.
We find, therefore, that the spinal cord, in its character of a
nervous centre, exerts a general protective action over the whole
body. It presides over the involuntary movements of the limbs
and trunk; it regulates the action of the sphincters, the rectum,
and the bladder; while at the same time it exerts an indirect influence on the nutritive changes in those parts which it supplies with
nerves.




THE BRAIN.                        401
CHAPTER IV.
THE BRAIN.
BY the brain, or encepha7on, as it is sometimes called, we mean all
that portion of the nervous system which is situated within the
cavity of the cranium. It consists, as we have already shown, of
a series of different ganglia, connected with each other by transverse
and longitudinal commissures.
Since we have found the functions of sensation and motion, or
sensibility and excitability, so distinctly separated in the spinal
cord, we should expect to find the same distinction in the interior
of the brain. These two properties have indeed been found to be
distinct from each other, so far as they exist at all, in the encephalic
mass; but it is a very remarkable fact that they are both confined
to very small portions of the brain, in comparison with its entire
bulk. According to the investigations of Longet, neither the
olfactory ganglia, the corpora striata, the optic thalami, the tubercula quadrigemina, nor the white or gray substance of the cerebrum
or the cerebellum, are in the least degree excitable. Mechanical
irritation of these parts does not produce the slightest convulsive
movement in the muscles below. The application of caustic liquids
and the passage of galvanic currents are equally without effect.
The only portions of the brain in which irritation is followed by
convulsive movements are the anterior surface of the medulla oblongata, the tuber annulare, and the lower part of the crura cerebri;
that is, the lower and central parts of the brain, containing continuations of the anterior columns of the cord. On the other hand,
neither the olfactory ganglia, the corpora striata, the tubercula
quadrigemina nor the white or gray substance of the cerebrum or
cerebellum, give rise, on being irritated, to any painful sensation.
The only sensitive parts are the posterior surface of the medulla
oblongata, the restiform bodies, the processus e cerebello ad testes,
and the upper part of the crura cerebri; that is, those portions of
the base of the brain which contain prolongations of the posterior
columns of the cord.
26




402                      THE BRAIN.
The most central portions of the nervous system, therefore, and
particularly the gray matter, are destitute of both excitability and
sensibility. It is only those portions which serve to conduct sensations and nervous impulses that can be excited by mechanical
irritation; not the ganglionic centres themselves, which receive and
originate the nervous impressions.
We shall now study in succession the different ganglia of which
the brain is composed.
OLFACTORY GANGLTA. —These ganglia, which in some of the
lower animals are Very large, corresponding in size with the extent of the olfactory membrane and the acuteness of the sense of
smell, are very small in the human subject. They are situated on
the cribriform plate of the ethmoid bone, on each side of the crista
galli, just beneath the anterior lobes of the cerebrum. They send
their nerves through the numerous perforations which exist in the
ethmoid bone at this part, and are connected with the base of the
brain by two longitudinal commissures.  The olfactory ganglia
with their commissures are sometimes spoken of as the "olfactory
nerves."  They are not nerves, however, but ganglia, since they are
mostly composed of gray matter; and the term "olfactory nerves"
can be properly applied only to the filaments which originate from
them, and which are afterward spread out in the substance of the
olfactory membrane.
It has been found difficult to determine the function of these
ganglia by direct experiment on the lower animals. They may be
destroyed by means of a strong needle introduced through the bones
of the cranium; but the signs of the presence or absence of the
sense of smell, after such an operation, are too indefinite to allow us
to draw from them a decided conclusion. The anatomical distribution of their nerves, however, and the evident correspondence which
exists, in different species of animals, between their degree of development and that of the external olfactory organs, leaves no doubt
as to their true function. They are the ganglia of the special sense
of smell, and are not connected, in any appreciable degree, with
ordinary sensibility, nor with the production of voluntary movements.
OPTIC THALAMI.-These bodies are not, as their name would
imply, the ganglia of vision. Longet has found that the power of
sight and the sensibility of the pupil both remain, in birds, after




CORPORA STRIATA.-  EMISPHERES.                 403
the optic thalami have been thoroughly disorganized; and that artificial irritation of the same ganglia has no effect in producing
either contraction or dilatation of the pupil. The optic thalami,
however, according to the same observer, have a peculiar crossed
action upon the voluntary movements. If both hemispheres and
both optic thalami be removed in the rabbit, the animal is still
capable of standing and of using his limbs in progression. But if
the right optic thalamus alone be removed, the animal falls at once
upon his left side; and if the left thalamus be destroyed, a similar
debility is manifest on. the right side of the body. In these instances there is no absolute paralysis of the side upon which the
animal falls, but rather a simple want of balance between the two
opposite sides. The exact mechanism of this peculiar functional
disturbance is not well understood; and but little light has yet
been thrown, either by direct experiment or by the facts of comparative anatomy, on the real function of the optic thalami.
CORPORA- STRIATA.-The function of these ganglia is equally
uncertain with that of the preceding. They are traversed, as we
have already seen, by fibres coming from the anterior columns of
the cord; and they are connected, by the continuation of these
fibres, with the gray substance of the hemispheres. They have,
therefore, in all probability, like the optic thalami, some connection
with sensation and volition; but the precise nature of this connection is at present altogether unknown.
HEMISPHERES.-The hemispheres, or the cerebral ganglia, constitute in the human subject about nine-tenths of the whole mass
of the brain. Throughout their whole extent they are entirely
destitute, as we have already mentioned, of both sensibility and excitability. Both the white and gray substance may be wounded,
burned, lacerated, crushed, or galvanized in the living animal, without exciting any convulsive movement or any apparent sensation.
In the human subject a similar insensibility has been observed
when the substance of the hemispheres has been exposed by accidental violence, or in the operation of trephining.
Very severe mechanical injuries may also be inflicted upon the
hemispheres, even in the human subject, without producing any
directly fatal result. One of the most remarkable instances of this
fact is a case reported by Dr. William Detmold, of New York,' in
An. Journ. of Med. Sci., January, 1850.




404                      THE BRAIN.
which an abscess in the anterior lobe of the brain was opened by an
incision passing through the cerebral substance, not only without
any immediate bad effect, but with great temporary relief to the
patient. This was the case of a laborer who was struck on the left
side of the forehead by a piece of falling timber, which produced a
compound fracture of the skull at this part. One or two pieces of
bone afterward became separated and were removed, and the wound
subsequently healed. Nine weeks after the accident, however,
headache and drowsiness came on; and the latter symptom, becoming rapidly aggravated, soon terminated in complete stupor. At
this time, the existence of an abscess being suspected, the cicatrix,
together with the adherent portion of the dura mater, was dissected
away, several pieces of fractured bone removed, and the surface of
the brain exposed. A knife was then passed into the cerebral substance, making a wound one inch in length and half an inch in
depth, when the abscess was reached and over two ounces of pus
discharged. The patient immediately aroused from his comatose
condition, so that he was able to speak; and in a fewdays recovered, to a very considerable extent, his cheerfulness, intelligence,
and appetite. Subsequently, however, the collection of pus returned, accompanied by a renewal of the previous symptoms; and
the patient finally died at the end of seven weeks from the time of
opening the abscess.
Another and still more striking instance of recovery from severe
injury of the brain is reported by Prof. H. J. Bigelow in the
American Journal of Medical Sciences for July, 1850. In this case, a
pointed iron bar, three feet and a half in length, and one inch and a
quarter in diameter, was driven through the patient's head by the
premature blasting of a rock. The bar entered the left side of the
face, just in front of the angle of the jaw, and passed obliquely
upward, inside the zygomatic arch and through the anterior part
of the cranial cavity, emerging from the top of the frontal bone on
the median line, just in front of the point of union of the coronal
and sagittal sutures. The patient was at first stunned, but soon
recovered himself so far as to be able to converse intelligently, rode
home in a common cart, and with a little assistance walked up stairs
to his room. He became delirious within two days after the accident, and subsequently remained partly delirious and partly comatose for about three weeks. He then began to improve, and at the
end of rather more than two months from the date of the injury,
was able to walk about. At the end of sixteen months he was in




HEMISPHERES.                        405
perfect health, with the wounds healed, and with the mental and
bodily functions entirely unimpaired, except that sight was permanently lost in the eye of the injured side.
The hemispheres, furthermore, are not the seat of sensation or of
volition, nor are they immediately essential to the continuance of
life. In quadrupeds, the complete removal of the hemispheres is
attended with so much hemorrhage that the operation is generally
fatal from this cause within a few minutes. In birds, however, it
may be performed without any immediate danger to life. Longet
has removed the hemispheres in pigeons and fowls, and has kept
these animals afterward for several days, with most of the organic
functions unimpaired.  We have frequently performed the same
experiment upon pigeons, with a similarly favorable result.
The effect of this mutilation is simply to plunge the animal into
a state of profound stupor, in which he is almost entirely inattentive to surrounding objects. The bird remains sitting motionless
upon his perch, or standing upon the ground, with the eyes closed,
and the head sunk between the shoulders. (Fig. 138.)  The pluFig. 138.
PIGEON, AFTER REMOVAL OF THE HEMISPHERES.
mage is smooth and glossy, but is uniformly expanded, by a kind
of erection of the feathers, so that the body appears somewhat
puffed out, and larger than natural. Occasionally the bird opens
his eyes with a vacant stare, stretches his neck, perhaps shakes his
bill once or twice, or smooths down the feathers upon his shoulders,
and then relapses into his former apathetic condition. This state
of immobility, however, is not accompanied by the loss of sight, of
hearing, or of ordinary sensibility. All these functions remain, as




406                      THE BRAIN.
well as that of voluntary motion. If a pistol be discharged behind
the back of the animal, he at once opens his eyes, moves his head
half round, and gives evident signs of having heard the report; but
he immediately becomes quiet again, and pays no farther attention
to it. Sight is also retained, since the bird will sometimes fix its
eye on a particular object, and watch it for several seconds together.
Longethas even found that by moving a lighted candle before the
animal's eyes in a dark place, the head of the bird will often follow
the movements of the candle from side to side or in a circle, showing
that the impression of light is actually perceived by the sensorium.
Ordinary sensation also remains, after removal of the hemispheres,
together with voluntary motion. If the foot be pinched with a
pair of forceps, the bird becomes partially aroused, moves uneasily
once or twice from side to side, and is evidently annoyed at the
irritation.
The animal is still capable, therefore, after removal of the hemispheres, of receiving sensations from external objects. But these
sensations appear to make upon him no lasting impression. He is
incapable of connecting with his perceptions any distinct succession
of ideas. He hears, for example, the report of a pistol, but he is not
alarmed by it; for the sound, though distinctly enough perceived,
does not suggest any idea of danger or injury. There is accordingly no power of forming mental associations, nor of perceiving
the relation between external objects. The memory, more particularly, is altogether destroyed, and the recollection of sensations is
not retained from one moment to another. The limbs and muscles
are still under the control of the will; but the will itself is inactive,
because apparently it lacks its usual mental stimulus and direction.
The powers which have been lost, therefore, by destruction of the
cerebral hemispheres, are altogether of a mental or intellectual
character; that is, the power of comparing with each other different
ideas, and of perceiving the proper relation between them.
The same result is well known to follow, in the human subject,
from injury or disease of these parts. A disturbance of the mental
powers has long been recognized as the ordinary consequence of
lesions of the brain. In cases of impending apoplexy, for example,
or of softening of the cerebral substance, among the earliest and
most constant phenomena is a loss or impairment of the memory.
The patient forgets the names of particular objects or of particular
persons; or he is unable to calculate numbers with his usual facility.
His mental derangement is often shown in the undue estimate which




HEMISPHERES.                        407
he forms of passing events. He is no longer able to appreciate the
true relation between different objects and different phenomena.
Thus, he will show an exaggerated degree of solicitude about a
trivial occurrence, and will pay no attention to other matters of
real importance. As the difficulty increases, he becomes careless
of the directions and advice of his attendants, and must be watched
and managed like a child or an imbecile. After a certain period,
he no longer appreciates the lapse of time, and even loses the distinction between day and night. Finally, when the injury to the
hemispheres is complete, the senses may still remain active and
impressible, while the patient is completely deprived of intelligence,
memory, and judgment.
If we examine the comparative development of the hemispheres
in different species of animals, and in different races of men, we
shall find that the size of these ganglia corresponds very closely
with the degree of intelligence possessed by the individual. We
have already traced, in a preceding chapter, the gradual increase
in size of the hemispheres in fish, reptiles, birds and quadrupeds:
four classes of animals which may be arranged, with regard to the
amount of intelligence possessed by each, in precisely the same
order of succession.  Among quadrupeds, the elephant has much
the largest and most perfectly formed cerebrum, in proportion to
the size of the entire body; and of all quadrupeds he is proverbially
the most intelligent and the most teachable. It is important to
observe, in this connection, that the kind of intelligence which
characterizes the elephant and some other of the lower animals,
and which most nearly resembles that of man, is a teachable intelligence; a very different thing from the intelligence which depends
upon instinct, such as that of insects, for example, or birds of passage. Instinct is unvarying, and always does the same thing in the
same manner, with endless repetition; but intelligence is a power
which adapts itself to new circumstances, and enables its possessor,
by comprehending and retaining new ideas, to profit byexperience.
It is this quality which distinguishes the higher classes of animals
from  the lower; and which, in a very much greater degree, constitutes the intellectual superiority of man himself. The size of
the cerebrum in man is accordingly very much greater, in proportion to that of the entire body, than in any of the lower animals;
while other parts of the brain, on the contrary, such as the olfactory
ganglia or the optic tubercles, are frequently smaller in him than
in them. For while man is superior in general intelligence to all




408                       THE BRAIN.
the lower animals, he is inferior to many of them in the acuteness
of the special senses.
As a general rule, also, the size of the cerebrum  in different
races and in different individuals corresponds with the grade of
their intelligence. The size of the cranium, as compared with that
of the face, is smallest in the savage negro and Indian tribes; larger
in the civilized or semi-civilized Chinese, Malay, Arab, and Japanese; while it is largest of all in the enlightened European races.
This difference in the development of the brain is not probably an
effect of long-continued civilization or otherwise; but it is, on the
contrary, the superiority in cerebral development which makes
some races readily susceptible of civilization, while others are
either altogether incapable of it, or can only advance in it to a
certain limit. Although all races therefore may, perhaps, be said
to start from  the same level of absolute ignorance, yet after the
lapse of a certain time one race will have advanced farther in
civilization than another, owing to a superior capacity for improvement, dependent on original organization.
The same thing is true with regard to different individuals.  At
birth, all men are equally ignorant; and yet at the end of a certain
period one will have acquired a very much greater intellectual
power than another, even under similar conditions of training,
education, &c. He has been able to accumulate more information
from the same sources, and to use the same experience to better
advantage than his associates; and the result of this is a certain
intellectual superiority, which becomes still greater by its own
exercise. This superiority, it will be observed, lies not so much
in the power of perceiving external objects and events, and of recognizing the connection between them, as in that of drawing conclusions from one fact to another, and of adapting to new combinations the knowledge which has already been acquired.
It is this particular kind of intellectual difference, existing in a
marked degree, between animals, races, and individuals, which corresponds with the difference in development of the cerebral hernispheres. We have, therefore, evidence from three different sources
that the cerebral hemispheres are the seat of the reasoning powers,
or of the intellectual faculties proper. First, when these ganglia
are removed, in the lower animals, the intellectual faculties are the
only ones which are lost. Secondly, injury to these ganglia, in the
human subject, is followed by a corresponding impairment of the
same faculties.  Thirdly, in different species of animals, as well as




HEMISPHERES.                        409
in different races of men and in different individuals, the development of these faculties is in proportion to that of the cerebral
hemispheres.
When we say, however, that the hemispheres are the seat of the
intellectual faculties, of memory, reason, judgment, and the like,
we do not mean that these faculties are, strictly speaking, located
in the substance of the hemispheres, or that they belong directly to
the matter of which the hemispheres are composed. The hemispherical ganglia are simply the instruments through which the
intellectual powers manifest themselves, and which are accordingly
necessary to their operation. If these instruments be imperfect in
structure, or be damaged in any manner by violence or disease, the
manifestations of intelligence are affected in a corresponding degree.
So far, therefore, as the mental faculties are the subject of physiological research and experiment, they are necessarily connected
with the hemispherical ganglia; and the result of investigation
shows this connection to be extremely intimate and important in
its character.
There are, however, various circumstances which modify, in
particular cases, the general rule given above, viz., that the larger
the cerebrum the greater the intellectual superiority. The functional activity of the brain is modified, no doubt, by its texture as
well as by its size; and an increased excitability may compensate,
partially or wholly, for a deficiency in bulk. This fact is sometimes illustrated in the case of idiots. There are instances where
idiotic children with small brains are less imbecile and helpless
than others with a larger development, owing to a certain vivacity
and impressibility of organization which take the place, to a certain
extent, of the purely intellectual faculties.
This was the case, in a marked degree, with a pair of dwarfed
and idiotic Central American children, who were exhibited some
years ago in various parts of the United States, under the name of
the " Aztec children." They were a boy and a girl, aged respectively
about seven and five years. The boy was 2 feet 9A inches high, and
weighed a little over 20 pounds. The girl was 2 feet 51 inches
high, and weighed 17 pounds. Their bodies were tolerably well
proportioned, but the cranial cavities, as shown by the accompanying portraits, were extremely small.
The antero-posterior diameter of the boy's head was only 4inches, the transverse diameter less than 4 inches. The anteroposterior diameter of the girl's head. was 44 inches, the transverse




410                      THE BRAIN.
diameter only 3- inches. The habits of these children, so far as
regards feeding and taking care of themselves, were those of chilFig. 139.
A  T EC C HI L D R EN.-Taken from life, at five and seven years of age.
dren two or three years of age. They were incapable of learning
to talk, and could only repeat a few isolated words. Notwithstanding, however, the extremely limited range of their intellectual
powers, these children were remarkably vivacious and excitable.
While awake they were in almost constant motion, and any new
object or toy presented to them immediately attracted their attention, and evidently awakened a lively curiosity. They were accordingly easily influenced by proper management, and understood
readily the meaning of those who addressed them, so far as this
meaning could be conveyed by gesticulation and the tones of the
voice. Their expression and general appearance, though decidedly
idiotic, were not at all disagreeable or repulsive; and they were
much less troublesome to the persons who had them in charge than
is often the case with idiots possessing a larger cerebral development.
It may also be observed that the purely intellectual or reasoning
powers are not the only element in the mental superiority of certain
races or of particular individuals over their associates. There is
also a certain rapidity of perception and strength of will which may
sometimes overbalance greater intellectual acquirements and more
cultivated reasoning powers. These, however, are different faculties from the latter; and occupy, as we shall hereafter see, different
parts of the encephalon.
A very remarkable physiological doctrine, dependent partly on
the foregoing facts, was brought forward some years ago by Gall
and Spurzheim, under the name of Phrenology. These observers
recognized the fact that the intellectual powers are undoubtedly




HEMISPHERES.                       411
seated in the brain, and that the development of the brain is, as a
general rule, in correspondence with the activity of these powers.
They noticed also that in other parts of the nervous system, different
functions occupy different situations; and regarding the mind as
made up of many distinct mental faculties, they conceived the idea
that these different faculties might be seated in different parts of
the cerebral mass. If so, each separate portion of the brain would
undoubtedly be more or less developed in proportion to the activity
of the mental trait or faculty residing in it. The shape of the head
would then vary in different individuals, in accordance with their
mental peculiarities; and the character and endowments of the individual might therefore be estimated from an examination of the
elevations and depressions on the surface of the cranium.
Accordingly, the authors of this doctrine endeavored, by examining the heads of various individuals whose character was already
known, to ascertain the location of the different mental faculties.
In this manner they finally succeeded, as they supposed, in accomplishing their object; after which they prepared a chart, in which
the surface of the cranium was mapped out into some thirty or forty
different regions, corresponding with as many different mental traits
or faculties.  With the assistance of this chart it was thought that
phrenology might be practised as an art; and that, by one skilled
in its application, the character of a stranger might be discovered
by simply examining the external conformation of his head.
We shall not expend much time in discussing the claims of phrenology to rank as a science or an art, since we believe that it has
of late years been almost wholly discarded by scientific men, owing
to the very evident deficiencies of the basis upon which it was
founded.  Passing over, therefore, many minor details, we will
merely point out, as matters of physiological interest, the principal
defects which must always prevent the establishment of phrenology
as a science, and its application as an art.
First, though we have no reason for denying that different parts
of the brain may be occupied by different intellectual faculties,
there is no direct evidence which would show this to be the case.
Phrenologists include, in those parts of the brain which they employ for examination, both the cerebrum and cerebellum; and they
justly regard the external parts of these bodies, viz., the layer of
gray matter which occupies their surface, as the ganglionic portion
in which must reside more especially the nervous functions which
they possess. But this layer of gray matter, in each principal por



412                       THE BRAIN.
tion of the brain, is continuous throughout. There is no anatomical
division or limit between its different parts, like those between
the different ganglia in other portions of the nervous system; and
consequently such divisions of the cerebrum and cerebellum must
be altogether arbitrary in character, and not dependent on any
anatomical basis.
Secondly, the only means of ascertaining the location of the
different mental traits, supposing them to occupy different parts of
the brain, would be that adopted by Gall and Spurzheim, viz., to
make an accurate comparison, in a sufficient number of cases, of the
form of the head in individuals of known character. But the practical difficulty of accomplishing this is very great. It requires a
long acquaintance and close observation to learn accurately the
character of a single person; and it is in this kind of observation,
more than in any other, that we are proverbially liable to mistakes.
It is extremely improbable, therefore, that either Gall or Spurzheim
could, in a single lifetime, have accomplished this comparison in so
many instances as to furnish a reliable basis for the construction of
a phrenological chart.
A still more serious practical difficulty, however, is the following.
The different intellectual faculties being supposed to reside in the
layer of gray substance constituting the surfaces of the cerebrum
and cerebellum, they must of course be distributed throughout this
layer, wherever it exists. Gall and Spurzheim located all the mental
faculties in those parts of the brain which are accessible to external
exploration. An examination of different sections of the brain
will show, however, that the greater portion of the gray substance
is so placed, that its quantity cannot be
Fig. 140.        estimated by an external examination
through the skull. The only portions
~/,   - \   \ 4which are exposed to such an examina</6)' (l OV    ^tion are the upper and lateral portions.-~'c' <?  Wof the convexities of the hemispheres,
/    2A~^/           together with the posterior edge and
9^^   Ad/         Ppart of the under surface of the cerebellum. (Fig. 140.)  A  very extensive
portion of the cerebral surface, however,
~i' ^         remains concealed in such a manner that
it cannot possibly be subjected to exDiagram of the BRAiN ri sT,'c, amination, viz., the entire base of the
showing those portions which are exposed to examination.     brain, with the under surface of the an



HEMISPHERES.                        413
terior and middle lobes (1, 2); the upper surface of the cerebellum
(3) and the inferior surface of the posterior lobe of the cerebrum
which covers it (4); that portion of the cerebellum situated above the
medulla oblongata(5); and the two opposite convoluted surfaces in
the fissure of Sylvius (6, 7), where the anterior and middle lobes of
the cerebrum  lie in contact with each other.  The whole extent,
also, of the cerebral surfaces which are opposed to each other in the
great longitudinal fissure (Fig. 141), throughout its entire length,
are equally protected by their position, and
concealed from externalexamination.  The           Fig. 141.
whole of the convoluted surface of the brain
must, however, be regarded as of equal importance in the distribution of the mental
qualities; and yet it is evident that not
more than one-third or one-quarter of this
surface is so placed that it can be examined
by external manipulation. It must furthermore be recollected that the gray matter of
the cerebrum and cerebellum is everywhere   Transverse section of B R AI N,
convoluted, and that the convolutions penes- howing depth of great longiconvoluted, and that the convolutions pene-  tn fs  a a
tudinal fissure, at a.
trate to various depths in the substance of
the brain. Even if we were able to feel, therefore, the external
surface of the brain itself, it would not be the entire convolutions,
but only their superficial edges, that we should really be able to
examine.  And yet the amount of gray matter contained in a given
space depends quite as much upon the depth to which the convolutions penetrate, as upon the prominence of their edges.
While phrenology, therefore, is partially founded upon acknowledged physiological facts, there are yet essentially deficiencies in
its scientific basis, as well as insurmountable difficulties in the way
of its practical application.
CEREBELLUM.-The cerebellum  is the second ganglion of the
encephalon, in respect to size.  If it be examined, moreover, in
regard to the form  and disposition of its  convolutions, it will be
seen that these are much more complicated and more numerous
than in the cerebrum, and penetrate much deeper into its substance.
Though the cerebellum therefore is smaller, as a whole, than the
cerebrum, it contains, in proportion to its size, a much larger quantity of gray matter.
In examining the comparative development of the brain, also, in




414                      THE BRAIN.
different classes and species of animals, we find that the cerebellum
nearly always keeps pace, in this respect, with the cerebrum. These
facts would lead us to regard- it as a ganglion hardly secondary in
importance to the cerebrum itself.
Physiologists, however, have thus far failed to demonstrate the
nature of its function with the same degree of precision as that of
many other parts of the brain. The opinion of Gall, which located
in the cerebellum the sexual impulse and instincts, is at the present
day generally abandoned; for the reason that it has not been found
to be sufficiently supported by anatomical and experimental facts,
many of which are indeed directly opposed to it.  The opinion
which has of late years been received with the most favor is that
first advocated by Flourens, which attributes to the cerebellum the
power of associating or "co-ordinating" the different voluntary
movements.
It is evident, indeed, that such a power does actually reside in
some part of the nervous system. No movements are effected by
the independent contraction of single muscles; but always by
several muscles acting in harmony with each other. The number
and complication of these associated movements vary in different
classes of animals. In fish, for example, progression is accomplished in the simplest possible manner, viz., by the lateral flexion
and extension of the vertebral column. In serpents it is much the
same. In frogs, lizards, and turtles, on the other hand, the four
jointed extremities come into play, and the movements are somewhat complicated. They are still more so in birds and quadrupeds;
and finally, in the human subject they become both varied and
complicated in the highest degree. Even in maintaining the ordinary postures of standing and sitting, there are many different muscles acting together, in each of which the degree of contraction, in
order to preserve the balance of the body, must be accurately proportioned to that of the others. In the motions of walking and
running, or in the still more delicate movements of the hands and
fingers, this harmony of muscular action becomes still more evident,
and is seen also to be absolutely indispensable to the efficiency of
the muscular apparatus.
The opinion which locates the above harmonizing or associating
power in the cerebellum was first suggested by the effects observed
after experimentally injuring or destroying this part of the brain.
If the cerebellum be exposed in a living pigeon, and a portion of
its substance removed, the animal exhibits at once a peculiar un



CEREBELLUM.                        415
certainty in his gait, and in the movement of his wings. If the
injury be more extensive, he loses altogether the power of flight,
and can walk, or even stand, only with great difficulty. This is not
owing to any actual paralysis, for the movements of the limbs are
exceedingly rapid and energetic; but is due to a peculiar want of
control over the muscular contractions, precisely similar to that
which is seen in a man in a state of intoxication. The movements
of the legs and wings, though forcible and rapid, are confused and
blundering; so that the animal cannot direct his steps to any particular spot, nor support himself in the air by flight.  He reels and
tumbles, but can neither walk nor fly.
Fig. 142.
PIGEON, AFTER REMOVAL OF THE CEREBELLUM.
The senses and intelligence at the same time are unimpaired. It
is extremely curious, as first remarked by Longet, to compare the
different phenomena produced by removal of the cerebrum and
that of the cerebellum. If we do these operations upon two different pigeons, and place the animals side by side, it will be seen
that the first pigeon, from whom the cerebrum only has been removed, remains standing firmly upon his feet, in a condition of
complete repose; and that when aroused and compelled to stir, he
moves sluggishly and unwillingly, but otherwise acts in a perfectly
natural manner.  The second pigeon, on the other hand, from
whom the cerebellum only has been taken away, is in a constant
state of agitation. He is easily terrified, and endeavors, frequently
with violent struggles, to, escape the notice of those who are




416                      THE BRAIN.
watching him; but his movements are sprawling and unnatural,
and are evidently no longer under the effectual control of the will.
(Fig. 142.) If the entire cerebellum be destroyed, the animal is
no longer capable of assuming or retaining any natural posture.
His legs and wings are almost constantly agitated with ineffectual
struggles, which are evidently voluntary in character, but are at
the same time altogether irregular and confused. Death generally
takes place after this operation within twenty-four hours.
We have often performed the above operation, and always with
the same effect. Indeed there are few experiments that have been
tried upon the nervous system, which give results so uniform and
so constant as this. Taken by themselves, these results would
invariably sustain the theory of Flourens, which, indeed, is founded
entirely upon them.
But we have met with another very important fact, in this respect,
which has hitherto escaped notice. That is, that birds, which have
lost their power of muscular co-ordination from injury of the cerebellum, may recover this power in process of time, notwithstanding that
a large portion of the cerebellum has been permanently removed.
Usually such an operation upon the cerebellum, as we have mentioned above, is fatal within twenty-four hours, probably on account
of the close proximity of the medulla oblongata. But in some
instances, the pigeons upon which we have operated have survived,
and in these cases a re-establishment of the co-ordinating power
took place.
In the first of theoe ingtance whioh was observed, about twothirds of the cerebellum was taken away, by an opening in the
posterior part of the cranium. Immediately after the operation,
the animal showed all the usual effects of the operation, being
incapable of flying, walking, or even standing still, but reeled and
sprawled about in a perfectly helpless manner. In the course of five
or six days, however, he had regained a very considerable control
over his voluntary movements, and at the end of sixteen days his
power of muscular co-ordination was so nearly perfect, that its deficiency, if any existed, was imperceptible. He was then killed; and
on examination, it was found that his cerebellum remained in nearly
the same condition as immediately after the operation; about twothirds of its substance being deficient, and no attempt having been
made at its regeneration.  The accompanying figures show the
appearance of parts, in this case, as compared with the brain of a
healthy pigeon.




CEREBELLUM.                           417
We have also met with three other cases, similar to the above, in
which about one-half of the cerebellum was removed by operation.
Fig. 143.                          Fig. 144.
BRAIN OF HEALTHY PIGEo —Profile        BRAIN OF OPERATED PI(tEONview.-I. Hemisphere. 2. Optic tubercle. 3.  Profile view-showing the mutilation
Cerebellum. 4. Optic nerve. 5. Medulla ob-  of cerebellum.
longata.
Fig. 145.                          Fig. 146.
BR^TIN OF HiEAL'T:i'fY'PIERON-Poste-   BRAINOF OPERATED PIGEONrior view.                             Posterior view-showing the mutila-'
tion of cerebellum.
The loss of co-ordinating power, immediately after the operation,
though less complete than in the instance above mentioned, was
perfectly well marked in character; and in little more than a fortnight the animals had nearly or quite recovered the natural control
of their motions.
These instances show, accordingly, that a large portion of the
cerebellum  may be wanting without a corresponding deficiency of
the co-ordinating power.  If the theory of Flourens be correct,
therefore, these cases can only be explained by supposing that
those parts of the cerebellum which remain gradually become enabled to supply the place of those which are removed. It is more
probable, however, that the loss of co-ordinating power, which is
immediately produced by taking away a considerable portion of
this nervous centre, is to be regarded rather as the effect of the
sudden injury to the cerebellum as a whole, than as due to the mere
removal of a portion of its mass.
Morbid alterations of the cerebellum, furthermore, particularly
of a chronic nature, such as slow inflammations, abscesses, tumors,
&c., have often been observed in the human subject, without giving
rise to any marked disturbance of the voluntary movements.
27




418                      THE BRAIN.
On the other hand, many facts derived from comparative anatomy
seem to favor the opinion of Flourens. If we compare different
classes of animals with each other, as fish with reptiles, or birds
with quadrupeds, in which the development and activity of the
entire nervous system vary extremely, the results of the comparison
will be often contradictory. But if the comparison be made between different species in which the general structure and plan of
organization are similar, we often find the development of the cerebellum to correspond very closely with the perfection and variety
of the voluntary movements. The frog, for example, is an aquatic
reptile, provided with anterior and posterior extremities; but its
movements, though rapid and vigorous, are exceedingly simple in
character, consisting of little else than flexion and extension of the
posterior limbs.  The cerebellum  in this animal is exceedingly
small, as compared with the rest of the brain; being nothing more
than a thin, narrow ribbon of nervous matter, stretched across the
upper part of the fourth ventricle. In the common turtle we have
another aquatic reptile, where the movements of swimming, diving,
progression, &c., are accomplished by the consentaneous action of
anterior and posterior extremities, and where the motions of the
head and neck are also much more varied than in the frog. In
this instance the cerebellum is very much more highly developed
than in the former. In the alligator, again, a reptile whose motions,
both of the head, limbs, and tail, approach very closely to those of
the quadrupeds, the cerebellum is still larger in proportion to the
remaining ganglia of the encephalon.
The complete function of the cerebellum, accordingly, as a nervous centre, cannot be regarded as positively ascertained; but so far
as we may rely on the results of direct experiment, this organ has
evidently such an intimate and peculiar connection with the voluntary movements, that a sudden and extensive injury inflicted upon
its substance is always followed by an immediate, though temporary, disturbance of the co-ordinating power.
TUBERCULA QUADRIGEMINA. - These bodies, notwithstanding
their small size, are very important in regard to their function.
They give origin to the optic nerves, and preside, as ganglia, over
the sense of sight; on Which account they are also known by the
name of the "optic ganglia."  Their development corresponds very
closely with that of the external organs.of vision. Thus, they are
large in fish, reptiles, and birds, in which the eyeball is for the




TUBERCULA QUADRIGEMINA.                    419
most part very large in proportion to the entire head; and are small
in quadrupeds and in man, where the eyeball is, comparatively
speaking, of insignificant size. Direct experiment also shows the
close connection between the tubercula quadrigemina and the sense
of sight. Section of the optic nerve at any point between the
retina and the tubercles, produces complete blindness; and destruction of the tubercles themselves has the same effect. But if the
division be made between the tubercles and the cerebrum, or if the
cerebrum  itself be taken away while the tubercles are left untouched, vision, as we have already seen, still remains. It is the
tubercles, therefore, in which the impression of light is perceived.
So long as these ganglia are uninjured and retain their connection
with the eye, vision remains. As soon as this connection is cut
off, or the ganglia themselves are injured, the power of vision is
destroyed.
The tubercula quadrigemina not only serve as nervous centres
for the perception of light, but a reflex action also takes place
through them, by which the quantity of light admitted to the eye
is regulated to suit the sensibility of the pupil. In darkness and
in twilight, or wherever the light is obscure and feeble, the pupil
is enlarged by a relaxation of its circular fibres, so as to admit as
large a quantity of light as possible. On first coming into a dark
room, accordingly, everything is nearly invisible; but gradually,
as the pupil dilates and as more light is admitted, objects begin to
show themselves with greater distinctness, and at last we can see
tolerably well in a place where we were at first unable to perceive
a single object. On the other hand, when the eye is exposed to an
unusually brilliant light, the pupil contracts and shuts out so much
of it as would be injurious to the retina.
The above is a reflex action, in which the impression received by
the retina is transmitted along the optic nerve to the tubercula
quadrigemina. From  the tubercles, a motor impulse is then sent
out through the motor nerves of the eye and the filaments distributed to the iris, and a contraction of the pupil takes place in
consequence. The optic nerves act here as sensitive fibres, which
convey the impression from the retina to the ganglion; and if
they be irritated in any part of their course with the point of a
needle, the result is a contraction of the pupil. This influence is
not communicated directly from  the nerve to the iris, but is first
sent inward to the tubercles, to be afterward reflected outward by
the motor nerves. So long as the eyeball remains in connection




420                            THE  BRAIS.
with the brain, mechanical irritation of the optic nerve, as we have
shown above, causes contraction of the pupil; but if the nerve be
divided, and the extremity which remains in connection with the
eyeball be subjected to irritation, no effect upon the pupil is produced.
The anatomical arrangement of the optic nerves, and the connections of the optic tubercles, are modified in a remarkable degree in
different animals, to correspond with the position of the two eyes.
In fish, for example, the eyes are so placed, on opposite sides of the
head, that their axes cannot be brought into parallelism with each
other, and the two eyes can never be directed together to the same
object. In these animals, the optic nerves cross each other at the
base of the brain without any intermixture of their fibres; that
from the right optic tubercle passing to the left eye, and that from
the left optic tubercle passing to the right eye. (Fig. 147.) The two
Fig. 147.                                     Fig. 148.
INFERIOR SURFACE OF BRAT N            I, x  E  R   SURFACE OF BRAI  OF
o F Co  -1 Right optic nerve. 2 Left  F WL.-1. Right optic nerve. 2. Left optic
optic nerve. 3. Right optic tubercle. 4.  nerve. 3. Right optic tubercle.  4-. Left
Left (ptie tubercle. 5, 6. IHemispheres  optic tubercle. 5, 6 Heii.spheres. 7. Me7. Medulla oblongata.                 dullLa oblongata.
nervous cords are here totally distinct from each other throughout
their entire length; and are only connected, at the point of crossing, by intervening areolar tissue.  Impressions made on the right
eye must therefore be perceived on the left side of the brain; while
those which enter the left eye are conveyed to the right side of the
braino




TUBERCULA  QUAIDRIGEMITNA.                   421
In birds, also, the axes of the two eyes are so widely divergent
that an object cannot be distinctly in focus for both of them at the
same time.  The optic nerves are here united, and apparently soldered together, at their point of crossing; but the decussation of
their fibres is nevertheless complete. (Fig. 148.)  The nervous filaments coming from the left side pass altogether over to the right;
and those coming from the right side pass over to the left. The
result of direct experiment on the crossed action of the tubercles in
these animals corresponds with the anatomical arrangement of the
nervous fibres. If one of the optic tubercles be destroyed in the
pigeon, complete blindness is at once produced in the eye of the
opposite side; but vision remains unimpaired in the eye of the side
on which the injury was inflicted.
In the human subject, on the other hand, where the visual axes
are parallel, and where both eyes are simultaneously directed to the
same object, the optic nerves decussate with each other in such a
manner as to form a connection between the two opposite sides, as
Fig. 149.
CO UR PSE OF OPTIC NERVES IN M AN.-1, 2. Right and left eyeballs. 3. Docussation of optic
nerves. 4, 4. Tubercula quadrigemina.
well as between each tubercle and retina of the same side. (Fig.
149.) This decussation, which is somewhat complicated, takes place




422                      THE BRATN.
in the following manner. From each optic tubercle three different
bundles or "tracts" of nervous fibres are given off: One set passes
across transversely at the point of decussation, and, turning backward, terminates in the tubercle of the opposite side; another, crossing diagonally, continues onward to the opposite eyeball; while a
third passes directly forward to the eyeball of the same side. A
fourth set of fibres, still, passes across, in front of the decussation,
from the retina of one eye to that of the opposite side. We have,
therefore, by this arrangement, the two retinae, as well as the two
optic tubercles, connected with each other by commissural fibres;
while each tubercle is, at the same time, connected both with its
own retina and with that of the opposite side. It is undoubtedly
owing to these connections that when, in the human subject, the
eyes are directed in their proper axes, the two retina, as well as
the two optic tubercles, act as a single organ. Vision is single,
therefore, though there are two images upon the retine. Double
vision occurs only when the eyeballs are turned out of their proper
direction, so that the parallelism of their axes is lost, and the image
no longer falls upon corresponding parts of the two retinae.
TUBER ANNULARE.-The collection of gray matter imbedded in
the deeper portions of the tuber annulare occupies a situation near
the central part of the brain, and lies directly in the course of the
ascending fibres of the anterior and posterior columns of the cord.
This ganglion is immediately connected with the functions of sensation and voluntary motion. We have already seen-that these functions are not destroyed by taking away the cerebrum, and that they
also remain after removal of the cerebellum. According to the experiments of Longet, even after complete removal of the olfactory
ganglia, the cerebrum, cerebellum, optic tubercles, corpora striata
and optic thalami, and when nothing remains in the cavity of the
cranium but the tuber annulare and the medulla oblongata, the
animal is still sensitive to external impressions, and will still endeavor by voluntary movements to escape from a painful irritation.
The same observer has found, however, that as soon as the ganglion
of the tuber annulare is broken up, all manifestations of sensation
and volition cease, and even consciousness no longer appears to
exist. The only movements which then follow external irritation
are the occasional convulsive motions which are due to reflex action
of the spinal cord, and which may be readily distinguished from
those of a voluntary character.  The animal, under these circum



MEDULLA OBLONGATA.                      423
stances, is to all appearance reduced to the condition of a dead
body, except for the movements of respiration and circulation,
which still go on for a certain time. The tuber annulare must
therefore be regarded as the ganglion by which impressions, conveyed inward through the nerves, are first converted into conscious
sensations; and in which the voluntary impulses originate, which
stimulate the muscles to contractioin.
We must carefully distinguish, however, in this respect, a simple
sensation from the ideas to which it gives origin in the mind, and
the mere act of volition from the train of thought which leads to
it. Both these purely mental operations take place, as we have
seen, in the cerebrum; for mere sensation and volition may exist
independently of any intellectual action, as they may exist after
the cerebrum has been destroyed. A  sensation may be felt, for
example, without our having the power of thoroughly appreciating
it, or of referring it to its proper source.  This condition is often
experienced in a state of deep sleep, when, the body being exposed
to cold, or accidentally placed in a constrained position, we feel a
sense of suffering, without being able to understand its cause. We
may even, under such circumstances, execute voluntary movements
to escape the cause of annoyance; but these movements, not being
directed by any active intelligence, fail of accomplishing their object. We therefore remain in a state of discomfort until, on awakening, the activity of the reason and judgment is restored, when the
offending cause is at once removed.
We distinguish, then, between the simple power of sensation,
and the power of fully appreciating a sensitive impression and of
drawing a conclusion from it. We distinguish also between the
intellectual process which leads us to decide upon a voluntary
movement, and the act of volition itself. The former must precede,
the latter must follow. The former takes place, so far as experiment can show, in the cerebral hemispheres; the latter, in the ganglion of the tuber annulare.
MEDULLA OBLONGATA.-The last remaining ganglion of the encephalon is that of the medulla oblongata. This ganglion, it will
be remembered, is imbedded in the substance of the restiform body,
occupying the lateral and posterior portions of the medulla, at the
point of origin of the pneumogastric nerves. This portion of the
brain has long been known to be particularly essential to the preservation of life; so that it has received the name of the "vital




424                       THE BRAIN.
point," or the " vital knot."  All the other parts of the brain may
be injured or removed, as we have already seen, without the immediate and necessary destruction of life; but so soon as the medulla
oblongata is broken up, and its ganglion destroyed, respiration
ceases instantaneously, and the circulation also soon comes to an
end. Removal of the medulla oblongata produces, therefore, as its
immediate and direct result, a stoppage of respiration; and death
takes place principally as a consequence of this fact.
Flourens and Longet have determined, with considerable accuracy, the precise limits of this vital spot in the medulla oblongata.
Flourens ascertained that in rabbits it extended from just above
the origin of the pneumogastric nerve, to a level situated three lines
and a half below this origin. In larger animals, its extent is proportionately increased. Longet ascertained, furthermore, that the
properties of the medulla were not the same throughout its entire
thickness; but that its posterior and anterior parts might be de
stroyed with comparative impunity, the peculiarly vital spot being
confined to the intermediate portions. This vital point accordingly
is situated in the layer of gray matter, imbedded in the thickness
of the restiform bodies, which has been previously spoken of as
giving origin to the pneumogastric nerves.
The precise nature of the connection between this ganglion and
the function of respiration may be described as follows.  The
movements of respiration, which follow each other with incessant
regularity through the whole period of life, are not voluntary
movements.  We may, to a certain extent, hasten or retard them
at will, but our power over them, even in this respect, is extremely
limited; and in point of fact they are performed, during the greater
part of the time, in a perfectly quiet and regular manner, without
our volition and even without our consciousness. They continue
uninterruptedly through the deepest slumber, and even in a condition of insensibility from accident or disease.
These movements are the result of a reflex action taking place
through the medulla oblongata. The impression which gives rise
to them originates principally in the lungs, from the accumulation
of carbonic acid in the pulmonary vessels and air-cells, is transmitted by the pneumogastric nerves to the medulla, and is thence
reflected back along the motor nerves to the respiratory muscles.
These muscles are then called into action, producing an expansion
of the chest. The impression so conveyed to the medulla is usually
unperceived by the consciousness. It is generally converted directly




MEDULLA OBLONGATA.                      425
into a motor impulse, without attracting our attention or giving
rise to any conscious sensation. Respiration, accordingly, goes on
perfectly well without our interference and without our knowledge.
The nervous impression, however, conveyed to the medulla, though
usually imperceptible, may be made evident at any time by voluntarily suspending the respiration. As the carbonic acid begins to
accumulate in the blood and in the lungs, a peculiar sensation makes
itself felt, which grows stronger and stronger with every moment,
and impels us to recommence the movements of inspiration. This
peculiar sensation, entirely different in character from any other, is
designated by the French under the name of "besoin de respirer."
It becomes more urgent and distressing, the longer respiration is
suspended, until finally the impulse to expand the chest can no
longer be resisted by any effort of the will.
During ordinary respiration, therefore, each inspiratory movement is excited by the partial vitiation of the air contained in the
lungs. As soon as a new supply has been inhaled, the impulse to
respire is satisfied, the muscles relax, and the chest collapses. In
a few seconds the previous condition recurs and the same movements are repeated, producing in this way a regular alternation of
inspirations and expirations.
Since the movements of respiration are performed partly by the
diaphragm  and partly by the intercostal muscles, they will be
differently modified by injuries of the nervous system, according to
the spot at which the injury is inflicted. If the spinal cord, for
example, be divided or compressed in the lower part of the neck,
all the intercostal muscles will be necessarily paralyzed, and respiration will then be performed entirely by the diaphragm.  The
chest in these cases remaining motionless, and the abdomen alone
rising and falling with the movements of the diaphragm, such
respiration is called "abdominal" or "diaphragmatic" respiration.
It is a common symptom  of fracture of the spine in the lower
cervical region. If the phrenic nerve, on the other hand, be
divided, the diaphragm will be paralyzed, and respiration will then
be performed altogether by the rising and falling of the ribs. It
is then called "thoracic" or "costal" respiration.  If the injury
inflicted upon the spinal cord be above the origin of the second
and third cervical nerves, both the phrenic and intercostal nerves
are at once paralyzed, and death necessarily takes place from suffocation. The attempt at respiration, however, still continues in
these cases, showing itself by ineffectual inspiratory movements of




426                      THE BRAIN.
the mouth and nostrils. Finally, if the medulla itself be broken up
by a steel instrument introduced through the foramen magnum, so
as to destroy the nervous centre in which the above reflex action
takes place, both the power and the desire to breathe are at once
taken away. No attempt is made at inspiration, there is no struggle, and no appearance of suffering. The animal dies simply by
a want of aeration of the blood, which leads in a few moments to
an arrest of the circulation.
It is owing to the above action of the medulla oblongata that injuries of this part are so promptly and constantly fatal. When the
" neck is broken," as in hanging or by sudden falls upon the head, a
rupture takes place of the transverse ligament of the atlas; the
head, together with the first cervical vertebra, is allowed to slide
forward, and the medulla is compressed between the odontoid process of the axis in front and the posterior part of the arch of the
atlas behind. In cases of apoplexy, where any part of the hemispheres, corpora striata, or optic thalami, is the seat of the hemorrhage, the patient generally lives at least twelve hours; but if the
hemorrhage take place into the medulla itself, or at the base of the
brain in its immediate neighborhood, so as to compress its substance, death follows instantaneously, and by the same mechanism
as where the medulla is intentionally destroyed.
An irregularity or want of correspondence in the movements of
respiration is accordingly found to be one of the most threatening
of all symptoms in affections of the brain. A disturbance or suspension of the intellectual powers does not indicate necessarily any
immediate danger to life. Even sensation and volition may be impaired without serious and direct injury to the organic functions.
These symptoms only indicate the threatening progress of the disease, and show that it is gradually approaching the vital centre. It
is common to see, however, as the medulla itself begins to be implicated, a paralysis first showing itself in the respiratory movements
of the nostrils and lips, while those of the chest and abdomen still
go on as usual. The cheeks are then drawn in with every inspiration and puffed out sluggishly with every expiration, the nostrils
themselves sometimes participating in these unnatural movements.
A still more threatening symptom, and one which frequently precedes death, is an irregular, hesitating respiration, which sometimes
attracts the attention of the physician, even before the remaining.
cerebral functions are seriously impaired. These'phenomena de



MEDULLA OBLONGATA.                      427
pend on the connection between the respiratory movements and the
reflex action of the medulla oblongata.
We have now, in studying the functions of various parts of the
cerebro-spinal system, become familiar with three different kinds of
reflex action.
The first is that of the spinal cord. Iere, there is no proper
sensation and no direct consciousness of the act which is performed.
It is simply a nervous impression, coming from the integument,
and transformed by the gray matter of the spinal cord into a motor
impulse destined for the muscles. This action will take place after
the removal of the hemispheres and the abolition of consciousness,
as well as in the ordinary condition. The respiratory action of the
medulla oblongata is of the same general character; that is, it is
not necessarily connected with either volition or consciousness.
The only peculiarity in this instance is that the original nervous
impression is of a special character, and its influence is finally
exerted upon a special muscular apparatus. Actions of this nature
are termed, par excellence, reflex actions.
The second kind of reflex action takes place in the tuber annulare. Here the nervous impression, which is conveyed inward
from the integument, instead of stopping at the spinal cord, passes
onward to the tuber annulare, where it first gives rise to a conscious sensation; and this sensation is immediately followed by a
voluntary act. Thus, if a crumb of bread fall into the larynx, the
sensation produced by it excites the movement of coughing. The
sensations of hunger and thirst excite a desire for food and drink.
The sexual impulse acts in precisely the same manner; the perception of particular objects giving rise immediately to special desires
of a sexual character.
It will be observed, in these instances, that in the first place,
the nervous sensation must be actually perceived, in order to produce its effect; and in the second place that the action which
follows is wholly voluntary in character. But the most important
peculiarity, in this respect, is that the voluntary impulse follows
directly upon the receipt of the sensation. There is no intermediate
reasoning or intellectual process. We do not cough because we
know that this is the most effectual way to clear the larynx; but
simply because we are impelled to do so by the sensation which is
felt at the time. We do not take food or drink because we know
that they are necessary to support life, much less because we understand the mode in which they accomplish this object; but merely




428                      THE BRAIN.
because we desire them whenever we feel the sensations of hunger
and thirst.
All actions of this nature are termed instinctive. They are voluntary in character, but are performed blindly; that is, without any
idea of the ultimate object to be accomplished by them, and simply
in consequence of the receipt of a particular sensation. Accordingly experience, judgment, and adaptation have nothing to do with
these actions. Thus the bee builds his cell on the plan of a mathematical figure, without performing any mathematical calculation.
The silkworm  wraps himself in a cocoon of his own spinning,
certainly without knowing that it is to afford him shelter during
the period of his metamorphosis. The fowl incubates her eggs
and keeps them at the proper temperature for development, simply
because the sight of them creates in her a desire to do so. The
habits of these animals, it is true, are so arranged by nature, that
such instinctive actions are always calculated to accomplish an
ultimate object. But this calculation is not made by the animal
himself, and does not form  any part of his mental operations.
There is consequently no improvement in the mode of performing
such actions, and but little deviation under a variety of circumstances.
The third kind of reflex action requires the co-operation of the
hemispheres. Here, the nervous impression is not only conveyed
to the tuber annulare and converted into a sensation, but, still
following upward the course of the fibres to the cerebrum, it there
gives rise to a special train of ideas. We understand then the
external source of the sensation, the manner in which it is calculated to affect us, and how by our actions we may turn it to our
advantage or otherwise. The action which follows, therefore, in
these cases, is not simply voluntary, but reasonable. It does not
depend directly upon the external sensation, but upon an intellectual process which intervenes between the sensation and the volition. These actions are distinguished, accordingly, by a character
of definite contrivance, and a conscious adaptation of means to
ends; characteristics which do not belong to any other operations
of the nervous system.
The possession of this kind of intelligence and reasoning power
is not confined to the human species. We have already seen that
there are many purely instinctive actions in man, as well as in
animals. It is no less true that in the higher animals there is often
the same exercise of reasoning power as in man. The degree of




MEDULLA OBLONGATA.                      429
this power is much less in them than in him, but its nature is the
same. Whenever, in an animal, we see any action performed with
the evident intention of accomplishing a particular object, to which
it is properly adapted, such an act is plainly the result of reasoning powers, not essentially different from our own. The establishment of sentinels by gregarious animals, to warn the herd of the
approach of danger, the recollection of punishment inflicted for a
particular action, and the subsequent avoidance or concealment of
that action, the teachability of many animals, and their capacity of
forming new habits or of improving the old ones, are all instances
of the same kind of intellectual power, and are quite different from
instinct, strictly speaking. It is this faculty which especially predominates over the others in the higher classes of animals, and
which finally attains its maximum of development in the human
species.




430                THE CRANIAL NERVES.
CHAPTER V.
THE  CRANIAL NERVES.
IN examining the cranial nerves, we shall find that although they
at first seem quite different in their distribution and properties
from the spinal nerves, yet they are in reality arranged for the
most part on the same plan, and may be studied in a similar
manner.
At the outset, however, we find that there are three of the cranial nerves, commonly so called, which must be arranged in a class
by themselves; since they have no character in common with the
other nerves originating either from the brain or the spinal cord.
These are the three nerves of special sense; viz., the Olfactory,
Optic, and Auditory. They are, properly speaking, not so much
nerves as commissures, connecting different parts of the encephalic
mass with each other. They are neither sensitive nor motor, in
the ordinary meaning of these terms; but are capable of conveying
only the special sensation characteristic of the organ with which
they are connected.
OLFACTORY NERYES.-We have already described the socalled
olfactory nerves as being in reality commissures, connecting the
olfactory ganglia with the central parts of the brain. The masses
situated upon the cribriform plate of the ethmoid bone are composed of gray matter; and even the filaments which they send
outward to be distributed in the Schneiderian mucous membrane,
are gray and gelatinous in their texture, and quite different from
the fibres of ordinary nerves. The olfactory nerves are not very
well adapted for direct experiment. It is, however, at least certain
with regard to them that they serve to convey the special sensation
of smell; that their mechanical irritation does not give rise to
either pain or convulsions; and finally that their destruction,
together with that of the olfactory ganglia, does not occasion any
paralysis nor loss of ordinary sensibility.




THE CRANIAL NERVES.                     431
OPTIC NERVES. —We have already given some account of these
nerves and their decussations, in connection with the history of the
tubercula quadrigemina. They consist of rounded bundles of white
fibres, running between the tubercles and the retinae. As the retinas themselves are membranous expansions consisting mostly of
vesicular or cellular nervous matter, the optic nerves, or "tracts,"
must be regarded as commissures connecting the retinae with the
tubercles. We have also seen that they serve, by some of their
fibres, to connect the two retinae with each other, as well as the two
tubercles with each other.
The optic nerves convey only the special impression of light from
without inward, and give origin to the reflex action of the optic
tubercles, by which the pupil is made to contract. According to
Longet, the optic nerves are absolutely insensible to pain throughout their entire length. When a galvanic current is passed through
the eyeball, or when the retina is touched in operations upon the
eye, the irritation has been found to produce the impression of luminous sparks and flashes, instead of an ordinary painful sensation.
The impression of colored rings or spots may be easily produced
by compressing the eye in particular directions; and a sudden
stroke upon the eyeball will often give rise to an apparent discharge
of brilliant sparks. Division of the optic nerves produces complete
blindness, but does -not destroy ordinary sensibility in any part of
the eye, nor occasion any muscular paralysis.
AUDITORY NERVES. —The nervous expansion in the cavity of
the internal ear contains, like the retina, vesicles or cells as well as
fibres; and the auditory nerves are therefore to be regarded, like
the optic and olfactory, as commissural in their character. They
are also, like the preceding, destitute of ordinary sensibility. According to Longet, they may be injured or destroyed without giving
rise to any sensation of pain. They serve to convey to the brain
the special sensation of sound, and seem incapable of transmitting
any other. Longet' relates an experiment performed by Volta, in
which, by passing a galvanic current through the ears, the observer
experienced the sensation of an interrupted hissing noise, so long
as the connection of the wires was maintained.  Inflammations
within the ear, or in its neighborhood, are often accompanied by
the perception of various noises, like the ringing of bells, the
Trait6 de Physiologie, vol. ii. p. 2S6.




432                  THE CRANIAL NERVES.
washing of the waves, the humming of insects; sounds which have
no external existence, but which are simulated by the morbid irritation of the auditory nerve.
It is evident, from the facts detailed above, that the nerves of
special sense are neither motor or sensitive, properly speaking;
and that they are distinct in their nature from the ordinary spinal
nerves.
The remainder of the cranial nerves, however, present the
ordinary qualities belonging to the spinal nerves.  Some of them
are exclusively motor in character, others exclusively sensitive;
while most of them exhibit the two properties, to a certain extent,
as mixed nerves.  They may be conveniently arranged in three
pairs, according to the regions in which they are distributed, corresponding very closely with the motor and sensitive roots of the
spinal nerves. According to such a plan, the arrangement of the
cranial nerves would be as follows:CRANIAL NERVES.
Nerves of Special Senwe.
1. Olfactory. 2. Optic. 3. Auditory.
Motor Nerves.        Sensitive Nerves.   Distributed to
r Motor oculi com.
1st PAIR.  Motor oc. externus   Large root of 5th pair.   Face.
Small root of 5th pair
L Facial            J
2d PAIR.   Hypoglossal          Glosso-pharyngeal.     Tongue.
3d PAIR.   Spinal accessory      Pneumogastric.        Neck, &c.
The above arrangement of the cranial nerves is not absolutely
perfect in all its details.  Thus, while the hypoglossal supplies the
muscles of the tongue alone, the glosso-pharyngeal sends part of
its sensitive fibres to the tongue and part to the pharynx; and
while the large root of the 5th pair is mostly distributed in the
face, one of its branches, viz., the gustatory, is distributed to the
tongue.  Notwithstanding these irregularities, however, the above
division of the cranial nerves is in the main correct, and will be
found extremely useful as an assistant in the study of their func.
tions.
There is no impropriety, moreover, in regarding all the motor
branches distributed upon the face as one nerve; since even the
anterior roots of the spinal nerves originate from the spinal cord,
each by several distinct filaments, which are associated into a single




THE CRANIAL NERVES.                       433
bundle only at a certain distance from their point of origin.  The
mere fact that two nerves leave the cavity of the cranium  by the
same foramen does not indicate that they have the same or even a
similar function.  Thus the facial and auditory both escape from
the cavity of the cranium by the foramen auditorium internum, and
yet we do not hesitate to regard them  as entirely distinct in their
nature and functions.  It is the ultimate distribution of a nerve,
and not its course through the bones of the skull, that indicates
its physiological character and position.  For while the ultimate
distribution of any particular nerve is always the same, its arrangement as to trunk and branches may vary, in different species
of animals, with the anatomical arrangement of the bones of the
skull. This is well illustrated by a fact first pointed out by Prof.
Jeffries Wyman' in the anatomy of the nervous system  of the
bullfrog.  In this animal, both the facial nerve and motor oculi
externus, instead of arising as distinct nerves, are actually given
off as branches of the 5th pair; while their ultimate distribution is
the same as in other animals.  All the motor and sensitive nerves
distributed to the face are accordingly to be regarded as so many
different branches of the same trunk; varying sometimes in their
course, but always the same in their ultimate distribution.
The motor nerves of the head are in all respects identical in their
properties with the anterior roots iof the spinal nerves. For, in the
first place, they are distributed to muscles, and not to the integument or to mucous membranes; secondly, their division causes
muscular paralysis; and thirdly, mechanical irritation applied at
their origin produces muscular contraction in the parts to which
they are distributed, but does not give rise to a painful sensation. In several instances, nevertheless, the motor nerves, though
insensible at their origin, show a certain degree of sensibility when
irritated after their exit from the skull, owing to fibres of communication which they receive from  the purely sensitive nerves.
In this respect they resemble the spinal nerves, the motor and
sensitive filaments of which are at first distinct in the anterior
and posterior roots, but afterward  mingle with each other, on
leaving the cavity of the spinal canal.
The three sensitive nerves originating from  the brain are the
large root of the fifth pair, the glosso-pharyngeal, and the pneumoI Nervous System of Rana pipiens; published by the Smithsonian Institution.
Washington, 1853.
28




434                THE CRANIAL NERVES.
gastric. It will be observed that, in all their essential properties,
they correspond with the posterior roots of the spinal nerves. Like
them  they are inexcitable, but extremely sensitive. Irritated at
their point of origin, they give rise to acutely painful sensations,
but to no convulsive movements. Secondly, if divided at the same
situation, the operation is followed by loss of sensibility in the
parts to which they are distributed, without any disturbance of the
motive power. Each of these nerves, furthermore, like the posterior root of a spinal nerve, is provided with a ganglion through
which its fibres pass: the fifth pair, with the Casserian ganglion,
situated near the inner extremity of the petrous portion of the temporal bone; the glosso-pharyngeal, with the ganglion of Andersch,
situated in the jugular fossa; while the pneumogastric presents,
just before its passage through the jugular foramen, a ganglion
known as the ganglion of the pneumogastric nerve. Finally, the
sensitive fibres of all these nerves, beyond the situation of their ganglia, are intermingled with others of a motor origin. The large root
of the fifth pair, which is exclusively sensitive, is accompanied by
the fibres of the small root, which are exclusively motor. The
glosso-pharyngeal receives motor filaments from the facial and spinal accessory, becoming consequently a mixed nerve outside the
cranial cavity; while the pneumogastric is joined by fibres from the
spinal accessory and various other nerves of a motor character.
These nerves, accordingly, are exclusively sensitive only at their
point of origin. Though they afterward retain the predominating
character of sensitive nerves, they are yet found, if irritated in the
middle of their course, to be intermingled with motor fibres, and
to have consequently acquired, to a certain extent, the character of
mixed nerves.
The resemblance, therefore, between the cranial and spinal nerves
is complete.
MOTOR OCULI COMMUNIS.-This nerve, which is sometimes known
by the more convenient name of the oculo-motorius, originates from
the inner edge of the crus cerebri, passes into the cavity of the
orbit by the sphenoidal fissure, and is distributed to the levator
palpebrae superioris, and to all the muscles moving the eyeball,
except the external rectus and the superior oblique. Its irritation
accordingly produces convulsive movements in these parts, and
its division has the effect of paralyzing the muscles to which it is




FIFTH PAIR.                        435
distributed. The superior eyelid falls down over the pupil, and
cannot be raised, owing to the inaction of its levator muscle, so
that the eye appears constantly half shut. This condition is known
by the name of "ptosis."  The movements of the eyeball are also
nearly suspended, and permanent external strabismus takes place,
owing to the paralysis of the internal rectus muscle, while the external rectus, animated by a different nerve, preserves its activity.
PATHETICUS.-This nerve, which supplies the superior oblique
muscle of the eyeball, is similar in its general properties to the preceding. Its section causes paralysis of the above muscle, without
any loss of sensibility.
MOTOR EXTERNUS.-This nerve, the sixth pair, according to the
usual anatomical arrangement, is distributed to the external rectus
muscle of the eyeball. Its division or injury by disease is followed
by internal strabismus, owing to the unopposed action of the internal
rectus muscle.
FIFTH PAIR.-This is one of the most important and remarkable
in its properties of all the cranial nerves. It is the great sensitive
nerve of the face, and of the adjoining mucous membranes. Its
large root, after emerging from the outer and under surface of the
pons Varolii, passes forward over the inner extremity of the petrous
portion of the temporal bone. It there expands into a crescenticshaped swelling, containing a quantity of gray matter with which
its fibres are intermingled, and which is known as the Casserian
ganglion. The fibres of the smaller root, passing forward in company with the others, do not take any part in the formation of this
ganglion, but may be seen passing beneath it as a distinct bundle,
and continuing their course forward to the foramen ovale, through
which they emerge from the skull. In front of the anterior and
external border of the Casserian ganglion, the fifth nerve separates
into three principal divisions, viz., the ophthalmic, the superior
maxillary, and the inferior maxillary. The first of these divisions,
viz., the ophthalmic, is so called because it passes through the orbit
of the eye. It enters the sphenoidal fissure, and runs along the
upper portion of the orbit, sending branches to the ophthalmic ganglion of the sympathetic, to the lachrymal gland, the conjunctiva,
and the mucous membrane of the lachrymal sac. It also sends off




436                 THE CRANIAL NERVES.
a small branch (nasal branch) which penetrates into the nasal passages and supplies the Schneiderian mucous membrane. It then
emerges upon the face by the supra-orbital foramen, and is distributed to the integument of the forehead and side of the head as far
back as the vertex.
The second division of this nerve, or the superior maxillary,
passes out by the foramen rotundum, and runs along the longitudinal canal in the floor of the orbit, giving off branches during its
passage to the teeth of the upper jaw and to the mucous membrane
of the antrum maxillare.  It finally emerges upon the middle of the
face by the infra-orbital foramen, and is distributed to the integument of the lower eyelid, nose, cheek, and upper lip.
The third, or inferior maxillary division of the fifth pair, which
is the largest of the three, leaves the cavity of the cranium by the
foramen ovale. It comprises a conFig. 150.           siderable portion of the large root
of the nerve, and all the fibres of
the small root.  This division is
therefore a mixed nerve, containing
both motor and  sensitive fibres,
while the two former are exclusively sensitive.  It is distributed,
accordingly, both to muscles and
to the sensitive surfaces. Soon after
emerging from the foramen ovale
it sends branches to the temporal
muscle, to the masseter, the buccinator, and to the internal and external pterygoids; that is, to the
muscles which are particularly conUPON THE FACE.-a. Casserian ganglion. cerned in the movements of the
1. Ophthalmic division. 2. Superior maxil- lower jaw It also sends sensitive
lary division  3. Inferior maxillary division.
filaments to the integument of the
temple, to that of a portion of the external ear and external auditory meatus. The third division of:the fifth pair, then passing
downward and forward, gives off a branch of considerable size, the
lingual branch, which is distributed to the mucous membrane of the
anterior two-thirds of the tongue, and which also sends filaments to
the arches of the palate and to the mucous membrane of the cheek.
The remaining portion of the third division, after giving a few




FIFTH  PAIR.                       437
branches to the mylo-hyoid muscle and to the anterior belly of the
digastric, then enters the inferior dental canal, sends filaments to
the teeth of the lower jaw, emerges at the mental foramen, and is
finally distributed to the integument of the chin, lower lip, and
inferior part of the face.
This nerve is accordingly distributed to the sensitive surfaces,
that is, the integument and mucous membranes about the face, and
to the muscles of mastication.  A few of its fibres are sent also to
the superficial muscles of the face, such as the buccinator and the
orbicularis oris; but these fibres are sensitive in their character,
and serve merely to impart to the muscles a certain degree of
sensibility. It has been ascertained by Longet that if the various
branches of this nerve be irritated by a galvanic current, no convulsive movements whatever are produced in those superficial
muscles of the face, which it supplies with filaments; but if its
smaller or non-ganglionic root be irritated in the same way, contractions instantly follow in the muscles of mastication.
The fifth pair is the most acutely sensitive nerve in the whole
body.  Its irritation by mechanical means always causes intense
pain, and even though the animal be nearly unconscious from the
influence of ether, any severe injury to its large root is almost
invariably followed by cries which indicate the extreme sensibility
of its fibres.
If this nerve be completely divided, in the living animal, within
the cranium, at the situation of the Casserian ganglion, the operation
is followed by total loss of sensibility in the skin of the face and in
the adjacent mucous membranes. The conjunctiva, upon the affected
side, is then completely insensible, and may be touched with the
point of a needle or the blade of a knife, without exciting any uneasiness, and even without the consciousness of the animal. Probes
and needles may be passed into the nostril, and the lips or the
cheek may be pinched, pierced or cut, without exciting the least
sign of sensibility. The animal is entirely indifferent to all mechanical injuries upon the affected side, though upon the opposite
side the parts retain their natural sensibility.
Owing to the paralysis of the lingual nerve, also, after this operation, the tongue, in its anterior two-thirds, becomes insensible to
ordinary irritations, and loses beside the power of taste.
Another peculiar effect of the division of the fifth pair depends
upon the paralysis of its motor fibres, which are distributed, as we




438                THE CRANIAL NERVES.
have seen, to the muscles of mastication. In many of the lower
animals, consequently, the movements of mastication become exceedingly enfeebled upon the-affected side. In the cat, for example,
an animal in which mastication is usually very thoroughly performed, this process becomes excessively laborious, so that the
animal after this operation cannot masticate solid meat, but requires
to be fed with that which has already been cut in pieces.
The fifth pair, beside supplying the sensibility of the integument
of the face, has a peculiar and important influence on the organs of
special sense. This influence appears to consist in some connection
between the action of the fifth pair and the processes of nutrition;
so that when the former is injured, the latter very soon become
deranged.  For the perfect action of any one of the organs of
special sense, two conditions are necessary: first, the sensibility of
the special nerve belonging to it, and, secondly, the integrity of the
component parts of the organ itself. Now as the nutrition of the
organ is, to a certain extent, under the control of the fifth pair, any
serious injury to this nerve produces a derangement in the tissues
of the organ, and consequently interferes with the due performance
of its function.
The mucous membrane of the nasal passages, for example, is
supplied by two different nerves; first, the olfactory, distributed
throughout its upper portion, by which it is endowed with the
special sense of smell; and, secondly, the nasal branch of the fifth
pair, distributed throughout its middle and lower portions, by
which it is supplied with ordinary sensibility.
Since the fifth pair, accordingly, supplies general sensibility to
the nasal passages, this property will remain after the special sense
of smell has been destroyed. If, however, the fifth pair itself be
divided, not only is general sensibility destroyed in the Schneiderian
mucous membrane, but a disturbance begins to take place in the
nutrition of its tissue, by which it is gradually rendered unfit for
the performance of its special function, and the power of smell is
finally lost. The mucous membrane, under these circumstances,
becomes injected and swollen, and the nasal passage is obstructed
by an accumulation of puriform mucus. According to Longet, the
mucous membrane also assumes a fungous consistency, and is liable
to bleed at the slightest touch. The effect of this alteration is to
blunt or altogether destroy the sense of smell. It is owing to a
similar unnatural condition of the mucous membrane that the power




FIFTH PAIR.                       439
of smell is always more or less impaired in cases of coryza and
influenza. The olfactory nerves become inactive in consequence
of the morbid alteration in their mucous membrane, and in the
secretions which cover it.
The influence of this nerve over the organ of vision is still more
remarkable. It has been known for many years that division of
the fifth pair within the cranium, or of its ophthalmic branch, is followed by an inflammation of the corresponding eye which usually
goes on to complete and permanent destruction of the organ.
Immediately after the operation, the pupil becomes contracted and
the conjunctiva loses its sensibility. At the end of twenty-four
hours, the cornea begins to become opaline, and by the second
day the conjunctiva is already inflamed and begins to discharge a
purulent secretion. The inflammation, after commencing in the
conjunctiva, increases in intensity and soon spreads to the iris,
which becomes covered with a layer of inflammatory exudation.
The cornea grows constantly more opaque, until it is at last
altogether impermeable to light, and vision is consequently suspended. Blindness, therefore, does not result in these instances
from any direct affection of the optic nerve or of the retina, but is
owing simply to opacity of the cornea. Sometimes the diseased
action goes on until it results in ulceration of:the cornea and discharge of the humors of the eye; sometimes, after the lapse of
several days, the inflammatory appearances subside, and the eye is
finally restored to its natural condition.
It has been observed, however, that, although the above consequences always follow division of the fifth pair, when performed at
the level of the Casserian ganglion, or between it and the eyeball,
they are either much diminished in intensity or altogether wanting
when the division is made at a point posterior to the ganglion.
This circumstance has led to the belief that the influence of the fifth
pair on the nutrition of the eyeball does not reside in its own proper
fibres, but in some filaments of the sympathetic nerve which join
the fifth pair at the level of the Casserian ganglion. If the section
accordingly be made at this point, or in front of it, the fibres of the
sympathetic will be divided with the others, and inflammation of
the eye will result; but if the section be made behind the ganglion,
the fibres of the sympathetic will escape division, and the injurious
effects upon the eye will be wanting. Such is the explanation
usually given of the above-mentioned facts; but the question has
not as yet been determined in a positive manner.




440                 THE CRANIAL NERVES.
Division of the fifth pair destroys also the general sensibility of
the external auditoryn meatus, the lining membrane of.which is
supplied by its filaments.  Inflammation of this membrane and its
consequent alterations, it is well known, interfere seriously with
the sense of hearing. It is no uncommon occurrence for an accumulation of cerumen to take place after inflammation of this part,
so as to block up the auditory canal and produce partial or complete deafness.  It has not been ascertained, however, whether
division of the fifth pair is usually followed by similar changes in
this part.
The lingual branch of the fifth pair supplies the anterior extremity and middle portion of the tongue both with general sensibility and with the power of taste.  The sensibility of the tongue
is accordingly provided for by two different nerves; in its anterior
two-thirds, by the lingual branch of the fifth pair; in its posterior
third, by the fibres of the glosso-pharyngeal.
The facial branches of the fifth pair are the ordinary seat of tic
douloureux.  This affection is not unfrequently confined to either
the supra-orbital, the infra-orbital, or the mental branch; and the
pain may be accurately traced in the direction of their diverging
fibres.  It has already been mentioned that the painful sensations
sometimes also follow the course of the facial, owing to some sensitive filaments which that nerve receives from the fifth pair.
FACIAL.-This nerve was known to the older anatomists as the
"portio dura of the seventh pair."  It leaves the cavity of the
cranium by the internal auditory foramen, in company with the
auditory nerve; and, as the latter is of a softer consistency than the
former, they have received the names respectively of the " portio
mollis" and "portio dura" of the seventh pair. There is, however,
no physiological connection between these two nerves; for while
the auditory is spread out in the cavity of the internal ear, the facial
passes onward through the petrous portion of the temporal bone,
emerges at the stylo-mastoid foramen, bends round beneath the
external ear, and passes forward through the substance of the
parotid gland, forming a plexus, called the "pes anserinus," by the
abundant inosculation of its different branches.  It then sends its
filaments forward in a diverging course, and is finally distributed
to the muscles of the external ear, to the frontalis and superciliaris
muscles, to the orbicularis oculi, the compressors and dilators of
the nares, the orbicularis oris, and to the elevators and depressors




FACIAL NERVE.                       441
of the lips; that is, to the superficial muscles of the face, which are
concerned in the production of expression. (Fig. 151.)
The facial, consequently, is the            F. 151.
motor nerve of the face. It has
nothing to do with transmitting
sensitive impressions, since it has
been frequently shown that after
section of the fifth pair, the facial
remaining entire, the sensibility of
the face is completely lost; so that
the integument may be cut, pricked,
pierced, or lacerated, without any
sign of pain being exhibited by the
animal. The facial, therefore, does
not transmit sensation from these
parts; and its division, which was  
formerly resorted to in cases of
tic douloureux, is accordingly alto-       FACIAL NERVE.
gether incapable of relieving neuralgic pains.
This nerve, however, is directly connected with muscular action,
since mechanical or galvanic irritation of its fibres produces convulsive twitching in the ears, nostrils, lips and cheeks.
If the facial nerve be divided in one of the lower animals, as, for
example, in the cat, immediately after its emergence from  the
stylo-mastoid foramen, it will be found that complete muscular
paralysis has occurred in all those parts to which the nerve is distributed, while the power of sensation remains unimpaired. The
animal is incapable of moving the ear, which remains constantly in
the same position. There is also incapacity of closing the eyelids,
owing to paralysis of the orbicularis oculi, and the eye accordingly
remains constantly open, even when the opposite eye is closed;
as during sleep, or in the act of winking. If the conjunctiva be
touched, the animal feels the irritation, and endeavors to escape
from it; but the eyeball is only drawn partially backward into the
socket by the action of the recti muscles, and the third eyelid
pushed partly across the cornea. The complete closure of the eye
is impossible. It will be observed, accordingly, that precisely opposite effects are produced upon the eyelids by paralysis of the oculomotorius nerve, and by that of the facial. In the former instance,
owing to the paralysis of the levator palpebrme superioris, the eve
is always partially closed; in the latter, owing to paralysis of the




442                 THE CRANIAL NERVES.
orbicularis, it is always partially open. The movements of the
nares are also suspended on the side of the injury, and if the angle
of the mouth be examined on that side, it will be found to hang
down lower than on the opposite side, and to be constantly partly
open, owing to the paralysis of the orbicularis oris and the elevators of the angle of the mouth.
These are the only inconveniences which follow the division of
the facial nerve in the cat, but in some other of the lower animals,
where various muscular organs in this region are particularly developed, the consequences are more troublesome. Thus, in the rabbit,
the ear, upon the affected side, falls down, and cannot be raised or
pointed in different directions; and as the movements of the ear
are important in these animals, as aids to the hearing, the perfection of this sense must be considerably impaired by paralysis of
the facial nerve.  In the horse, it has been noticed by Bernard,'
that division of the facial on both sides is fatal by suffocation. For
this animal breathes exclusively through the nostrils, which open
widely at the time of inspiration, to allow the admission of air. If
these movements be suspended, by paralysis of the facial nerve, the
nostrils immediately collapse, and the animal dies by suffocation.
In the human subject, the facial nerve is occasionally paralyzed
upon one side, sometimes from  sympathetic irritation, sometimes
from organic disease in the petrous portion of the temporal bone,
or within the cranial cavity near the origin of the nerve. In either
case, an extremely well-marked affection is the result, known as
"facial paralysis."  This condition is chiefly characterized by an
entire absence of expression on the affected side of the face. The
lower eyelid sinks downward, from  paralysis of the orbicularis
muscle, and cannot be closed.
The corner of the mouth also falls downward, and the whole
lower part of the face is drawn over to the opposite side by the
force of the antagonistic muscles. The lips are unable to retain
the fluids of the mouth; and the saliva dribbles away from between
them, giving to the face a remarkably vacant and helpless appearance.
The principal inconvenience, however, suffered by the human
subject in facial paralysis, depends upon the want of action of the
muscles about the lips and cheek. In drinking, the fluids escape
I Leqons sur la Physiologie et la Pathologie du Systeme Nerveux, Paris, 1858,
vol. ii. p. 38.




GLOSSO-PHARYNGEAL NERVE.                     443
by the corner of the mouth, and in mastication the food has partly
a tendency to escape by the same opening, and partly accumulates,
on the affected side, between the gums and the cheek, owing to the
paralysis of the buccinator muscle, which receives its motor filaments from the facial nerve. Thus, the action of all the superficial
facial muscles is suspended, the expression of the face is destroyed,
and the movements of the lips and the prehension of the food
seriously interfered with.
Though the facial, however, be essentially a motor nerve, yet its
principal branches distributed to the face have a certain degree of
sensibility; that is, when these branches are irritated in the middle
of their course, the animal immediately gives evidence of a painful
sensation. Longet has shown, by an extremely ingenious mode
of experiment,' that this sensibility of the branches of the facial
does not depend on any sensitive fibres of their own, but upon
those which they derive frome inosculation with the fifth pair.  He
exposes, for example, the facial nerve in the dog, and, irritating its
principal branches one after the other, at each application of the
irritant there are evident signs of pain. He then divides the facial
nerve at its point of exit from the stylo-mastoid foramen, and
finds that, after this operation, the sensibility of its branches still
remains.  The fibres, accordingly, upon which this sensibility
depends, do not pass out with the trunk of the nerve, but are
derived from  some other source. The experimenter, then, upon
another animal, divides the fifth pair within the skull, leaving the
facial untouched; and afterward, on irritating as before the exposed branches of the latter nerve, he finds that its sensibility has
entirely disappeared. It is by filaments, accordingly, derived from
the fifth pair, that a certain degree of sensibility is communicated
to the branches of the facial.
These facts account for the peculiar circumstance that, in cases
of tic douloureux, the spasmodic pain sometimes follows exactly
the course of the facial nerve, viz: from behind the ear forward
upon the side of the face; and yet the section of this nerve does not
put an end to the neuralgia, but only causes paralysis of the facial
muscles.
GLOSSO-PHARYNGEAL.-This nerve originates from  the lateral
portion of the medulla oblongata, passes outward, and enters the' Traite de Physiologie, vol. ii. pp. 354-357.




444                 THE CRANIAL NERVES.
posterior foramen lacerum in company with the pneumogastric and
spinal accessory. While in the jugular fossa it presents a gangliform
enlargement, called the ganglion of Andersch, below the level of
which it receives branches of communication from  the facial and
the spinal accessory. It then runs downward and forward, and is
distributed to the mucous membrane of the base of the tongue,
pillars of the fauces, soft palate, middle ear, and upper part of the
pharynx.  It also sends some branches to the constrictors of the
pharynx and the neighboring muscles.  Longet has found this
nerve at its origin to be exclusively sensitive; but below the level
of its ganglion it has been found by him, as well as by various
other observers, to be both sensitive and motor, owing to the fibres
of communication received from the motor nerves mentioned above.
Its final distribution is, however, as we have seen, principally to
sensitive surfaces. The principal office of this nerve is to impart
the sense of taste to the posterior third of the tongue, to which it is
distributed.  It also presides over the general sensibility of this
part of the tongue, as well as that of the fauces and pharynx.
Dr. John Reid,' who has performed a great variety of experiments
upon this nerve, comes to the following conclusions in regard to it.
First, that it is essentially a sensitive nerve, since there are unequivocal signs of pain when it is pricked, pinched, or cut. Second,
that irritation of this nerve produces convulsive movements of the
throat and lower part of the face; but that these movements are, in
great measure, not direct, but reflex in their character, since they
will take place equally well after the glosso-pharyngeal has been
divided, if the irritation be applied to its cranial extremity. Third,
that this nerve supplies the special sensibility of taste to a portion
of the tongue; but that it is not the exclusive nerve of this sense,
since the power of taste remains, after it has been divided on both
sides.
There are certain reflex actions, furthermore, which take place
through the medium  of the glosso-pharyngeal nerve. After the
food has been thoroughly masticated, it is carried, by the movements of the tongue and sides of the mouth, through the fauces,
and brought in contact with the mucous membrane of the pharynx.
This produces an impression which, conveyed to the medulla
oblongata by the filaments of the glosso-pharyngeal, excites the
In Todd's Cyclopaedia of Anatomy and Physiology, article Glosso-pharyngeal
NVerve.




PNEUMOGASTRTC NERVE.                     445
muscles of the fauces and pharynx by:reflex action. The food is
consequently grasped by these muscles, without the concurrence of
the will, and the process of deglutition is commenced. This action
is not only involuntary, but it will frequently take place even in
opposition to the will. The food, once past the isthmus of the fauces,
is beyond the control of volition, and cannot be returned except by
convulsive action, equally involuntary in its character.
Natural stimulants, therefore, applied to the mucous membrane
of the pharynx, excite deglutition; unnatural stimulants, applied
to the same part, excite vomiting. If the finger be introduced into
the fauces and pharynx, or if the mucous membrane of these parts
be irritated by prolonged tickling with the end of a feather, the
sensation of nausea, conveyed through the glosso-pharyngeal nerve,
is sometimes so great as to produce immediate and copious vomiting. This method may often be successfully employed in cases of
poisoning, when it is desirable to excite vomiting rapidly, and when
emetic medicines are not at hand.
PNEUMOGASTRIC.-Owing to the numerous connections of the
pneumogastric with other nerves, its varied and extensive distribution, and the important character of its functions, this is properly
regarded as one of the most remarkable nerves in the whole body.
Owing to the wandering course of its fibres, which are distributed
to no less than four different vital organs, viz., the heart, lungs,
stomach and liver, as well as to several other parts of secondary
importance, it has been often known by the name of the par vagum.
The pneumogastric arises, by a number of separate filaments, from
the lateral portion of the medulla oblongata, in the groove between
the olivary and restiform bodies. These filaments unite into a
single trunk, which emerges from the cranium by the jugular foramen, where it is provided with a longitudinal ganglionic swelling,
the "ganglion of the pneumogastric nerve." Immediately below
the level of this ganglion the nerve receives an important branch
of communication from the spinal accessory, and afterward from
the facial, the hypoglossal, and the anterior branches of the first
and second cervicals.
At its origin, the pneumogastric is exclusively a sensitive nerve.
Irritated above the situation of its ganglion, it has been found to
convey painful sensations alone; but if the irritation be applied at
a lower level, it causes at the same time muscular contractions,
owing to the filaments which it has received from the above-men



446                 THE CRANIAL NERVES.
tioned motor nerves. It becomes, consequently, after emerging
from the cranial cavity, a mixed nerve; and has accordingly, in
nearly all its branches, a double distribuFig. 152.        tion, viz., to the mucous membranes and
the muscular coat of the organs to which
-ii~ ~it belongs.
The ordinary sensibility of the pneumogastric nerve, however. as all experimenters have observed, is exceedingly
dull, in comparison with that of the other
sensitive cranial nerves.  We have often
divided this nerve in the middle of the
neck, without any distinct manifestation
of pain being given bythe animal; and
though Bernard has found that at some
fa ll 3' 1       ~times its sensibility is well marked, while
at others it is very indistinct, he is not
able to say upon what special physiological conditions this difference depends.
While the pneumogastric, however, is
decidedly deficient, as a general rule, in
ordinary sensibility, it possesses, as we
shall see hereafter, a sensibility of a peculiar kind, which is exceedingly important
for the maintenance of the vital functions.
In passing down the neck, this nerve
sends branches to the mucous membrane
and muscular coat of the pharynx, cesoDiagram of PNEUMOoASTRIC  phagus, and respiratory passages. Among
NERVE, withits principal branches. the most important of these branches are
-1. Pharyngeal branch. 2. Supe-., 
rior laryngeal. 3 Inferior laryn-  he two laryngeal nerves, v., the supegeal. 4. Pulmonary branches.. rior and inferior. The superior laryngeal
Stomach. 6. Liver.
nerve, which is given off from the trunk
of the pneumogastric just after it has emerged from the cavity of the
skull, passes downward and forward, penetrates the larynx by an
opening in the side of the thyro-hyoid membrane, and is distributed
to the mucous membrane of the larynx and glottis, and also to a
single laryngeal muscle, viz., the crico-thyroid.  This branch is
therefore partly muscular, but mostly sensitive in its distribution.
The inferior laryngeal branch is given off just after the pneumo



PNEUMOGASTRIC NERVE.                     447
gastric has entered the cavity of the chest. It curves round the
subclavian artery on the right side and the arch of the aorta on
the left, and ascends in the groove between the trachea and oesophagus, to the larynx. It then enters the larynx between the
cricoid cartilage and the posterior edge of the thyroid, and is distributed to all the muscles of the larynx, with the exception of the
crico-thyroid. This branch is, therefore, exclusively muscular in
its distribution.
The trunk of the pneumogastric, after supplying the above
branches, as well as sending numerous filaments to the trachea
and oesophagus in the neck, gives off in the chest its pulmonary
branches, which follow the bronchial tubes in the lungs to their
minutest ramifications. It then passes into the abdomen and supplies the muscular and mucous layers of the stomach, ramifying
over both the anterior and posterior surfaces of the organ; after
which its fibres spread out and are distributed to the liver, spleen,
pancreas, and gall-bladder.
The functions of the pneumogastric will now be successively
studied in the various organs to which it is distributed.
Pharynx and (Esophagus.-The reflex action of deglutition, which
has already been described as commencing in the upper part of the
pharynx, by means of the glosso-pharyngeal, is continued in the
lower portion of the pharynx and throughout the esophagus by
the aid of the pneumogastric. As the food is compressed by the
superior constrictor muscle of the pharynx and forced:downward, it
excites the mucous membrane with which it is brought in contact
and gives rise to another contraction of the middle constrictor. The
lower constrictor is then brought into action in its turn in a similar
manner; and a wave-like or peristaltic contraction is thence propagated throughout the entire length of the cesophagus, by which
the food is carried rapidly from above downward, and conducted at
last to the stomach. Each successive portion of the mucous membrane, in this instance, receives in turn the stimulus of the food,
and' excites instantly its own muscles to contraction; so that the
food passes rapidly from one end of the oesophagus to the other, by
an action which is wholly reflex in character and entirely withdrawn
from the control of the will. Section of the pneumogastric, or of
its pharyngeal and oesophageal branches, destroys therefore at the
same time the sensibility and the motive power of these parts. The
food is no longer conveyed readily to the stomach, but accumulates
in the paralyzed cesophagus, into which it is forced by the voluntary




448                 THE CRANIAL NERVES.
movements of the mouth and fauces, and by the continued action
of the upper part of the pharynx.
It must be remembered that the general sensibility of the oesophagus is very slight, as compared with that of the integument, or
even of the mucous membranes near the exterior. It is a general
rule, in fact, that the sensibility of the mucous membranes is most
acute at the external orifices of their canals; as, for example, at the
lips, anterior nares, anus, orifice of the urethra, &c. It diminishes
constantly from  without inward, and disappears altogether at a
certain distance from the surface. The sensibility of the pharynx
is less acute than that of the mouth, but is still sufficient to enable
us to perceive the contact of ordinary substances; while in the
oesophagus we are not usually sensible of the impression of the food
as it passes from  above downward.  The reflex action takes place
here without any assistance from the consciousness; and it is only
when substances of an unusually pungent or irritating nature are
mingled with the food, that its passage through the cesophagus produces a distinct sensation.
Larynx.-We have already described the course and distribution
of the two laryngeal branches of the pneumogastric. The superior
laryngeal nerve is principally the sensitive nerve of the larynx.
Its division destroys sensibility in the mucous membrane of this
organ, but paralyzes only one of its muscles, viz: the crico-thyroid.
Galvanization of this nerve has also been found to induce contractions in the crico-thyroid, but in none of the other muscles
belonging to the larynx.  The inferior laryngeal, on the other
hand, is a motor nerve. Its division paralyzes all the muscles of
the larynx except the crico-thyroid; and irritation of its divided
extremity produces contraction in the same muscles. The muscles
and mucous membrane of the larynx are therefore supplied by two
different branches of the same trunk, viz., the superior laryngeal
nerve for the mucous membrane, and the inferior laryngeal nerve
for the muscles.
The larynx, in man and in all the higher animals, performs a
double function; one part of which is connected with the voice, the
other with respiration.
The formation of the voice in the larynx takes place as follows.
If the glottis be exposed in the living animal, by opening the
pharynx and oesophagus on one side, and turning the larynx forward, it will be seen that so long as the vocal chords preserve
their usual relaxed condition during expiration, no sound is heard,




PNEUMOGASTRIC NERVE.                     449
except the ordinary faint whisper of the air passing gently through
the cavity of the larynx. When a vocal sound, however, is to be
produced, the chords are suddenly made tense and applied closely
to each other, so as to diminish very considerably the size of the
orifice; and the air, driven by an unusually forcible expiration
through the narrow opening of the glottis, in passing between the
vibrating vocal chords, is itself thrown into vibrations which produce the sound required. The tone, pitch, and intensity of this
sound, vary with the conformation of the larynx, the degree of tension and approximation of the vocal chords, and the force of the
expiratory effort. The narrower the opening of the glottis, and the
greater the tension of the chords, under ordinary circumstances, the
more acute the sound; while a wider opening and a less degree of
tension produce a graver note. The quality of the sound is also
modified by the length of the column of air included between the
glottis and the mouth, the tense or relaxed condition of the walls
of the pharynx and fauces, and the state of dryness or moisture of
the mucous membrane lining the aerial passages.
Articulation, on the other hand, or the division of the vocal sound
into vowels and consonants, is accomplished entirely by the lips,
tongue, teeth, and fauces. These organs, however, are under the
control of other nerves, and the mechanism of their action need not
occupy us here.
Since the production of a vocal sound, therefore, depends upon
the tension and position of the vocal chords, as determined by the
action of the laryngeal muscles, it is not surprising that division of
the inferior laryngeal nerves, by paralyzing these muscles, should
produce a loss of voice. It has been sometimes found that in very
young animals the crico-thyroid muscles, which are the only ones
not affected by division of the inferior laryngeal nerves, are still
sufficient to give some degree of tension to the vocal chords, and
to produce in this way an imperfect sound; but usually the voice
is entirely lost after such an operation.
It is a very remarkable fact, however, in this connection, that all
the motor filaments of the pneumogastric, which are concerned in
the formation of the voice, are derived from a single source. It
will be remembered that the pneumogastric, itself originally a
sensitive nerve, receives motor filaments, on leaving the cranial
cavity, from no less than five different nerves. Of these filaments,
however, those coming from the spinal accessory are the only ones
necessary to the production of vocal sounds. For it has been found
29




450                 THE CRANIAL NERVES.
by Bischoff and by Bernard' that if all the roots of the spinal accessory be divided at their origin, or if the nerve itself be torn away
at its exit from  the skull, all the other cranial nerves remaining
untouched, the voice is lost as completely as if the inferior laryngeal itself had been destroyed. All the motor fibres of the pneumogastric, therefore, which act in the formation of the voice are
derived, by inosculation, from the spinal accessory nerve.
In respiration, again, the larynx performs another and still more
important function. In the first place, it stands as a sort of guard,
or sentinel, at the entrance of the respiratory passages, to prevent
the intrusion of foreign substances. If a crum of bread accidentally
fall within the aryteno-epiglottidean folds, or upon the edges of the
vocal chords, or upon the posterior surface of the epiglottis, the
sensibility of these parts immediately excites a violent expulsive
cough, by which the foreign body is dislodged. The impression,
received and conveyed inward by the sensitive fibres of the superior
laryngeal nerve, is reflected back upon the expiratory muscles
of the chest and abdomen, by which the instinctive movements of
coughing are accomplished.  Touching the above parts with the
point of a needle, or pinching them with the blades of a forceps,
will produce the same effect. This reaction is essentially dependent
on the sensibility of the laryngeal mucous membrane; and it can
no longer be produced after section of the pneumogastric nerve, or
of its superior laryngeal branch.
In the second place, the respiratory movements of the glottis, already
described in a previous chapter, are of the greatest importance to
the preservation of life. We have seen that at the moment of
inspiration the vocal chords are separated from each other, and the
glottis opened, by the action of the posterior crico-arytenoid muscles;
and that in expiration the muscles and the vocal chords are both
relaxed, and the air allowed to pass out readily through the glottis.
The opening of the glottis in inspiration, therefore, is an active
movement, while its partial closure or collapse in expiration is a
passive one. Furthermore, the opening of the glottis in inspiration
is necessary in order to afford a sufficiently wide passage for the
air, in its way to the trachea, bronchi, and pulmonary vesicles.
Now we have found, as Budge and Longet had previously noticed, that if the inferior laryngeal nerve on the right side be
divided while the glottis is exposed as above, the respiratory moveRecherches Exp6rimentales sur les fonctions du nerf spinal. Paris, 1851.




PNEUMOGASTRIC NERVE.                      451
ments of the right vocal chord instantly cease, owing to the paralysis of the posterior crico-arytenoid muscle on that side. If the
inferior laryngeal nerve on the left side be also divided, the paralysis of the glottis is then complete, and its respiratory movements
cease altogether. A serious difficulty in respiration is the immediate consequence of this operation.  For the vocal chords, being
no longer stretched and separated from each other at the moment of
inspiration, but remaining lax and flexible, act as a double valve,
and are pressed inward by the column of inspired air; thus partially blocking up the passage and impeding the access of air to
the lungs. If the pneumogastrics be divided in the middle of the
neck, the larynx is of course paralyzed precisely as after section
of the inferior laryngeal nerves, since these nerves are given off
only after the main trunks have entered the cavity of the chest.
The immediate effect of either of these operations is to produce
a difficulty of inspiration, accompanied by a peculiar wheezing or
sucking noise, evidently produced in the larynx and dependent on
the falling together of the vocal chords. In very young animals,
as, for example, in pups a few days old, in whom the glottis is
smaller and the larynx less rigid than in adult dogs, this difficulty
is much more strongly marked. Legallois' has even seen a pup
two days old almost instantly suffocated after section of the two
inferior laryngeal nerves. We have found that, in pups two
weeks old, division of the inferior laryngeals is followed by death
at the end of from thirty to forty hours, evidently from impeded
respiration.
The importance, therefore, of these movements of the glottis in
respiration becomes very evident.  They are, in fact, part and
parcel of the general respiratory movements, and are necessary to
a due performance of the function. It has been found, moreover,
that the motor filaments concerned in this action are not derived,
likb those of the voice, from  a single source.  While the vocal
movements of the larynx are arrested, as mentioned above, by.
division of the spinal accessory alone, those of respiration still go
on; and in order to put a stop to the latter, either the pneumogastrics themselves must be divided, or all five of the motor nerves
from which their accessory filaments are derived. This fact has
been noticed by Longet as showing that nature multiplies the safeguards of a function in proportion to its importance; for while the
I In Longet's Traite de Physiologie, vol. ii. p. 324.




452                THE CRANIAL NERVES.
spinal accessory, or any other one of the above-mentioned nerves,
might be affected by local accident or disease, it would be very
improbable that any single injury should paralyze simultaneously
the spinal accessory, the facial, the hypoglossal, and the first and
second cervicals. The respiratory movements of the larynx are
consequently much more thoroughly protected than those which
are merely concerned in the formation of the voice.
Lungs.-The influence of the pneumogastric upon the function
of the lungs is exceedingly important. The nerve acts here, as in
most other organs to which it is distributed, in a double or mixed
capacity; but it is principally as the sensitive nerve of the lungs
that it has thus far received attention.  It is this nerve which
conveys from the lungs to the medulla oblongata that peculiar
impression, termed besoin de respirer, which excites by reflex action
the diaphragm and intercostal muscles, and keeps up the play of
the respiratory movements. As we have already shown, this action
is an involuntary one, and will even take place when consciousness
is-entirely suspended. It may indeed be arrested for a time by an
effort of the will; but the impression conveyed to the medulla soon
becomes so strong, and the stimulus to inspiration so urgent, that
they can no longer be resisted, and the muscles contract in spite of
our attempts to restrain them.
A very remarkable effect is accordingly produced on respiration
by simultaneous division of both pneumogastric nerves.  This
experiment is best performed on adult dogs, which may be etherized, and the nerves exposed while the animal is in a condition of
insensibility, avoiding, in this way, the disturbance of respiration,
which would follow if the dissection were performed while the animal was conscious and sensible to pain. After the effects of the
etherization have entirely passed off; and respiration and circulation
have both returned to a quiescent condition, the two nerves, which
have been previously exposed and secured by a loose ligature, may
be instantaneously divided, and the effects of the operation readily
appreciated.
Immediately after the division of the nerves, when performed in
the above manner, the respiration is hurried and difficult, owing to
the sudden paralysis of the larynx and partial closure of the glottis
by the vocal chords, as already described. This condition, however, is of short continuance. In a few moments, the difficulty of
breathing and the general agitation subside, the animal becomes
perfectly quiet, and the only remaining visible effect of the opera



PNEUMOGASTRIC NERVE.                     453
tion is a diminished frequency in the movements of respiration. This
diminution is frequently strongly marked from the first, the number
of respirations falling at once to ten or fifteen per minute, and becoming, in an hour or two, still farther reduced. The respirations
are performed easily and quietly; and the animal, if left undisturbed,
remains usually crouched in a corner, without giving any special
signs of discomfort.  If he be aroused and compelled to move
about, the frequency of the respiration is temporarily augmented;
but as soon as he is again quiet, it returns to its former standard.
By the second or third day, the number of respirations is often
reduced to five, four, or even three per minute; when this is the
case, the animal usually appears very sluggish, and is roused with
difficulty from his inactive condition. At this time, the respiration
is not only diminished in frequency, but is also performed in a
peculiar manner. The movement of inspiration is slow, easy, and
silent, occupying several seconds in its accomplishment; expiration,
on the contrary, is sudden and audible, and is accompanied by a well
marked expulsive effort, which has the appearance of being, to a
certain extent, voluntary in character. The intercostal spaces also
sink inward during the lifting of the ribs; and the whole movement
of respiration has an appearance of insufficiency, as if the lungs
were not thoroughly filled with air. This insufficiency of respiration is undoubtedly owing to a peculiar alteration in the pulmonary
texture, which has by this time already commenced.
Death takes place at a period varying from one to six days after
the operation, according to the age and strength of the animal.
The only symptoms accompanying it are a steady failure of the
respiration, with increased sluggishness and indisposition to be
aroused.  There are no convulsions, nor any evidences of pain.
After death, the lungs are found in a peculiar state of solidification,
which is almost exclusively a consequence of this operation, and
which is entirely different from ordinary inflammatory hepatization.
They are not swollen, but rather smaller than natural. They are
of a dark purple color, leathery and resisting to the feel, destitute
of crepitation, and infiltrated with blood. Pieces of the lung cut
out sink in water. The pleural surfaces, at the same time, are bright
and polished, and their cavity contains no effusion or exudation.
The lungs, in a word, are simply engorged with blood and empty
of air; their tissue having undergone no other alteration.
These changes are not generally uniform over both lungs. The
organs are usually mottled on their exterior; the variations in color




454                THE CRANIAL NERVES.
corresponding with the different degrees of alteration exhibited by
different parts.
The explanation usually adopted of the above consequences following division of the pneumogastrics is as follows: The nerves
being divided, the impression which originates in the lungs from
the accumulation of carbonic acid, and which is destined to excite
the respiratory movements by reflex action, can no longer be transmitted to the medulla oblongata. The natural stimulus to respiration being wanting, it is, accordingly, less perfectly performed. The
respiratory movements diminish in frequency, and, growing continually slower and slower, finally cease altogether, and death is
the result.
The above explanation, however, is not altogether sufficient. It
accounts very well for the diminished frequency of respiration, but
not for its partial continuance. For if the pneumogastric nerves
be really the channel through which the stimulus to respiration is
conveyed to the medulla, the difficulty is not to understand why
respiration should be retarded after division of these nerves, but
why it should continue at all. In point of fact, the respiratory
movements, though diminished in frequency, continue often for
some days after this operation. This cannot be owing to force of
habit, or to any remains of nervous influence, as has been sometimes suggested, since, when the medulla itself is destroyed, respiration, as we know, stops instantaneously, and no attempt at movement is made after the action of the nervous centre is suspended.
It is evident, therefore, that the pneumogastric nerve, though the
chief agent by which the respiratory stimulus is conveyed to the
medulla, is not the only one.  The lungs are undoubtedly the
organs which are most sensitive to an accumulation of carbonic
acid, and an imperfect arterialization of the blood; and the sensation which results from such an accumulation is accordingly first
felt in them. There is reason to believe, however, that all the vascular organs are more or less capable of originating this impression,
and that all the sensitive nerves are capable, to some extent, of transmitting it. Although the first disagreeable sensation, on holding
the breath, makes itself felt in the lungs, yet, if we persist in suspending the respiration, we soon become conscious that the feeling
of discomfort spreads to other parts; and at last, when the accumulation of carbonic acid and the impurity of the blood have
become excessive, all parts of the body suffer alike, and are pervaded by a general feeling of derangement and distress. It is easy,




PNEUMOGASTRIC NERVE.                     455
therefore, to understand why respiration should be retarded, after
section of the pneumogastrics, since the chief source of the stimulus
to respiration is cut off; but the movements still go on, though more
slowly than before, because the other sensitive nerves, which continue to act, are also capable, in an imperfect manner, of conveying
the same impression.
The immediate cause of death, after this operation, is no doubt
the altered condition of the lungs. These organs are evidently
very imperfectly filled with air, for some time previous to death;
and their condition, as shown in post-mortem examination, is evidently incompatible with a due performance of the respiratory
function. It is not at all certain, however, that these alterations
in the pulmonary tissue are directly dependent on division of the
pneumogastric nerves. It must be recollected that when the section of the pneumogastrics is performed in the middle of the neck,
the filaments of the inferior laryngeal nerves are also divided, and
the narrowing of the glottis, produced by their paralysis, must
necessarily interfere with the free admission of air into the chest.
This difficulty, either alone or combined with the diminished frequency of respiration, must have a very considerable effect in impeding the pulmonary circulation, and bringing the lungs into such
a condition as unfits them for maintaining life.
In order to ascertain the comparative influence upon the lungs
of division of the inferior laryngeals and that of the other filaments
of the pneumogastrics, we have resorted to the following experiment.
Two pups were taken, belonging to the same litter and of the
same size and vigor, about two weeks old. In one of them (No. 1)
the pneumogastrics were divided in the middle of the neck; and
in the other (No. 2) a section was made at the same time of the
inferior laryngeals, the trunk of the pneumogastrics being left untouched. For the first few seconds after the operation, there was
but little difference in the condition of the two animals. There was
the same obstruction of the breath (owing to closure of the glottis),
the same gasping and sucking inspiration, and the same frothing at
the mouth. Very soon, however, in pup No. 1, the respiratory
movements became quiescent, and at the same time much reduced
in frequency, falling to ten, eight, and five respirations per minute,
as usual after section of the pneumogastrics; while in No. 2 the respiration continued frequent as well as laborious, and the general
signs of agitation and discomfort were kept up for one or two hours.




456                THE CRANIAL NERVES.
The animal, however, after that time became exhausted, cool, and
partially insensbile, like the other. They both died, between thirty
and forty hours after the operation. On post-mortem inspection it
was found that the peculiar congestion and solidification of the
lungs, considered as characteristic of division of the pneumogastrics,
existed to a similar extent in each instance; and the only appreciable difference between the two bodies was that in No. 1 the blood
was coagulated, and the abdominal organs natural, while in No. 2
the blood was fluid and the abdominal organs congested. We are
led, accordingly, to the following conclusions with regard to the
effect produced by division of this nerve.
1. After section of the pneumogastrics, death takes place by a peculiar congestion of the lungs.
2. This congestion is not directly produced by division of the
nerves, but is caused by the imperfect admission of air into the
chest.
In adult dogs, the closure of the glottis from paralysis of the
laryngeal muscles' is less complete than in pups; but it is still
sufficient to exert avery decided influence on respiration, and to
take an active part in the production of the subsequent morbid
phenomena.
We therefore regard the death which takes place after division
of both pneumogastric nerves, as produced in the following manner:The glottis is first narrowed by paralysis of the laryngeal muscles, and an imperfect supply of air is consequently admitted, by
each inspiration, into the trachea. Next, the stimulus to respiration
being very much diminished, the respiratory movements take place
less frequently than usual. From these two causes combined, the
blood is imperfectly arterialized, and the usual consequence of such
a condition then follows, viz., a partial stagnation of the pulmonary
circulation. This stagnation still further impedes the action of the
lungs; while it does not excite the respiratory muscles to increased
activity as it would do in health, owing to the division of the pneumogastrics. At the same time, the accumulation of carbonic acid
in the blood and in the tissues begins to exert a narcotic effect,
diminishing the sensibility of the nervous centres, and tending to
retard still more the movements of respiration. Thus all these
causes react upon and aggravate each other; because the connection, naturally existing between imperfectly arterialized blood and
the stimulus to respiration, is now destroyed. The narcotism and




PNEUMOGASTRIC NERVE.                     457
pulmonary engorgement, therefore, continue to increase, until the
lungs are so seriously altered and engorged that they are no longer
capable of transmitting the blood, and circulation and respiration
come to an end at the same time.
It must be remembered, also, that the pneumogastric nerve has
other important distributions, beside those to the larynx and the
lungs; and the effect produced by its division upon these other
organs has no doubt a certain share in producing the results which
follow. Bearing in mind the very extensive distribution of the
pneumogastric nerve and the complicated character of its functions, we may conclude that after section of this nerve death takes
place from a combination of various causes; the most active of
which is a peculiar engorgement of the lungs and imperfect performance of the respiratory function.
Stomach, and Digestive Function.-After division of the pneumogastric nerves, the sensations of hunger and thirst remain, and the
secretion of gastric juice continues. Nevertheless the digestive
function is disturbed in various ways, though not altogether abolished. The appetite is more or less diminished, as it would be
after any serious operation, but it remains sufficiently active to
show that its existence is not directly dependent on the integrity of
the pneumogastric nerve. Digestion, however, very seldom takes
place, to any considerable extent, owing to the following circumstances: The animal is frequently seen to take food and drink with
considerable avidity; but in a few moments afterward the food and
drink are suddenly rejected by a peculiar kind of regurgitation.
This regurgitation does not resemble the act of vomiting, but the
substances swallowed are again discharged so easily and instantaneously as to lead to the belief that they had never passed into
the stomach. Such, indeed, is actually the case, as any one may
convince himself by watching the process, which is often repeated
by the animal at short intervals. The food and drink, taken voluntarily, pass down into the oesophagus, but owing to the paralysis of
the muscular fibres of this canal, are not conveyed into the stomach.
They accumulate consequently in the lower and middle part of the
oesophagus; and in a few moments are rejected by a sudden antistaltic action of the parts, excited, apparently, through the influence
of the great sympathetic.
The muscular coat of the stomach is also paralyzed to a considerable extent by section of this nerve. Longet has shown, by
introducing food artificially into the stomach, that gastric juice




458                THE CRANIAL NERVES.
may be secreted and the food be actually digested and disappear,
when introduced in small quantity. But when introduced in large
quantity, it remains undigested, and is found after death, with the
exterior of the mass softened and permeated by gastric juice, while
the central portions are unaltered, and do not even seem to have
come in contact with the digestive fluid. This is undoubtedly
owing both to the diminished sensibility of the mucous membrane
of the stomach, and to the paralysis of its muscular fibres. The
peristaltic action of the organ is very important in digestion, in
order to bring successive portions of the food in contact with the
mucous membrane, and to carry away such as are already softened
or as are not capable of being digested in the stomach.  This
constant movement and agitation of the food is probably also one
great stimulus to the continued secretion of the gastric juice. The
digestive fluid will therefore be deficient in quantity after division
of the pneumogastric nerve, at the same time that the peristaltic
movements of the stomach are suspended. Under these circumstances, the secretion of gastric juice may be sufficient to permeate
and digest small quantities of food, while a larger mass may resist
its action, and remain undigested. The effect produced by division
of these nerves on the digestive, as on the respiratory organs, is
therefore of a complicated character, and results from the combined
action of several different causes, which influence and modify each
other.
The effect produced upon the liver by section of the pneumogastrics, as well as the influence usually exerted by these nerves
upon the hepatic functions, has been so little studied that nothing
definite has been ascertained in regard to it. We shall therefore
pass over this portion of the subject in silence.
SPINAL ACCESSORY.-This nerve originates, by many filaments,
from the side of the medulla oblongata, below the level of the
pneumogastric, and also from the lateral portions of the spinal cord,
between the anterior and posterior roots of the: upper five or six
cervical nerves. These fibres of spinal origin pass upward, uniting
into a slender rounded filament, which enters the cavity of the
cranium by the foramen magnum, and is then joined by the fibres
which originate from the medulla oblongata. The spinal accessory
nerve, thus constituted, passes out from the cavity of the skull by
the posterior foramen lacerum, in company with the glosso-pharyngeal and pneumogastric nerves. Immediately afterward it divides




SPINAL ACCESSORY.                       459
into two principal branches: First, the internal or anastomotic
branch, which joins the pneumogastric nerve, and becomes mingled
with its fibres; and, secondly, the external or muscular branch,
which passes downward and outward, and is distributed to the
sterno-mastoid and trapezius muscles.
The spinal accessory is essentially a motor nerve.  It has been
found, both by Bernard and Longet, to be insensible at its origin,
like the anterior roots of the spinal nerves; but if irritated after
its exit from the skull, it gives signs of sensibility. This sensibility it acquires from the filaments of inosculation which it receives
from the anterior branches of the first and second cervical nerves.
Though its external branch, accordingly, is exclusively distributed
to muscles, as we have already seen, this branch contains some sensitive fibres, which have the same destination. The reason for this
anatomical fact, viz., that motor nerves are supplied during their
course with sensitive fibres, becomes evident when we reflect that the
muscles themselves possess a certain degree of sensibility, though
less acute than that which belongs to the skin. The sensibility of
the muscles is undoubtedly essential to the perfect performance of
their function; and as the motor nerves are incapable, by themselves, of transmitting sensitive impressions, they are joined, soon
after their origin, by other filaments which communicate to them
this necessary power.
The most important result which has been obtained by experiment upon the spinal accessory nerve is that its internal or anastomotic branch is directly connected with the vocal movements of the
glottis. It has been found by Bischoff, by Longet, and by Bernard,
that if the spinal accessory nerves on both sides, or their branches
of inosculation with the pneumogastric, be divided or lacerated,
the pneumogastric nerves themselves being left entire, the voice is
instantly lost, and the animal becomes incapable of making a vocal
sound. We have also found this result to follow, in the cat, after
the spinal accessory nerves have been torn out by their roots,
through the jugular foramen.  The animal, after this operation, can
no longer make an audible sound. At the same time the respiratory movements of the glottis go on undisturbed, and most of the
other animal functions remain unaffected.
The fibres of communication, therefore, derived from  the spinal
accessory, pass to the pneumogastric nerve and become entangled
with its other filaments, so that they can no longer be traced by
anatomical dissection. They pass downward, however, and become




460                 THE CRANIAL NERVES.
a part of the motor fibres of the inferior laryngeal or recurrent
branches of the pneumogastric; being finally distributed to the
muscles of the larynx, which they supply with those nervous influences which are required for the formation of the voice.
The special function of the external or muscular branch of the
spinal accessory is not so fully understood. This branch, as we
have seen, is distributed to the sterno-mastoid and trapezius muscles. But these muscles also receive filaments from  the cervical
spinal nerves; and, accordingly, they still retain the power of motion, to a certain degree, after the external branches of the spinal
accessory have been divided on both sides.
The spinal accessory is, accordingly, a nerve of very peculiar
distribution. For it partly supplies motor fibres to the pneumogastric nerve, and is partly distributed to two muscles, both of
which also receive motor nerves from another source. Sir Charles
Bell, noticing the close connection between this nerve and the
pneumogastric, regarded the two as associated also in their function, as nerves of respiration.  He considered, therefore, the external branch of the spinal accessory as destined to assist in the
movements of respiration, when these movements become unusually laborious, by bringing into play the sterno-mastoid and trapezius muscles, in aid of the action of the intercostals.  He therefore
called this nerve the "superior respiratory nerve."
But the most satisfactory explanation of this peculiarity is that
proposed by M. Bernard. According to this explanation, whenever
a muscle, or set of muscles, derive their nervous influence from two
lifferent sources, this is not for the purpose of assisting them in the
performance of the same function, but of enabling them to perform
two different functions.  We have seen this already exemplified in
the muscles of the larynx.  For these muscles perform  certain
movements of respiration for which they receive indirectly filaments
from the facial, hypoglossal, and cervical nerves. But they also
perform the movements necessary to the formation of the voice, the
nervous stimulus for which is derived altogether from the spinal
accessory.
The internal branch of the spinal accessory, accordingly, excites,
in the parts to which it is distributed, a function which is incompatible with respiration.  For the movements of respiration cannot
go on while the voice is sounded; and a necessary preliminary
to the production of a vocal sound, is the temporary stoppage of
respiration.  The movements of respiration, therefore, and the




HYPOGLOSSAL.                        461
movements of the voice alternate with each other, but are never
simultaneous; so that the internal branch of the spinal accessory is
antagonistic to the motor fibres of the larynx derived from other
nerves.
It is thought by M. Bernard, that the fibres of the external
branch of the spinal accessory have also a function which is antagonistic to respiration. For respiration is naturally suspended in
all steady and prolonged muscular efforts. In these efforts, such as
those of straining, lifting, and the like, the movements of respiration cease, the spinal column is made rigid by the contraction of
its muscles, and the head and neck are placed in a fixed position,
principally by the contraction of the sterno-mastoid and trapezius
muscles. The function of the spinal accessory, in both its branches,
is therefore regarded as destined to excite movements which are
incompatible with those of respiration; and which accordingly come
into play only when the ordinary movements of respiration have
been temporarily suspended.
HYPOGLOSSAL. The hypoglossal nerve originates from the anterior and lateral portions of the medulla oblongata, and passing out
by the anterior condyloid foramen, is distributed exclusively to the
muscles of the tongue. Irritation of its fibres in any part of their
course produces convulsive twitching in this organ. Its section
paralyzes completely the movements of the tongue, without affecting directly the sensibility of its mucous membrane. This nerve,
accordingly, is the motor nerve of the tongue. If irritated at its
origin, the hypoglossal nerve, according to the experiments of
Longet, is entirely insensible; but if the irritation be applied in the
middle of its course, signs of pain are immediately manifested. Its
sensibility, like that of the facial, is consequently derived from its
inosculation with other sensitive nerves, after its emergence from
the skull.




462                THE SPECIAL SENSES.
CHAPTER VI.
THE SPECIAL SENSES
GENERAL AND SPECIAL SENSIBILITY.-We have already seen
that there exists, in the general integument, a power of sensation, by
which we are made acquainted with surrounding objects and some
of their most important physical qualities. By this power we feel
the sensations of heat and cold, and are enabled to distinguish
between hard and soft substances, rough bodies and smooth, solids
and liquids.  This kind of power is termed General Sensibility,
because it resides in the general integument, and because by its
aid we obtain information with regard to the simplest and most
material properties of external objects.
The general sensibility, thus existing in the integument, is an
endowment of the sensitive nerves derived from the cerebro-spinal
system. These nerves ramify in the substance of the skin, and by
subsequent inosculation form a minute plexus in the superficial
portions of the tissue of the corium. From this plexus, the ultimate filaments, reduced to an exceedingly minute size, pass upward into the conical papillae with which the free surface of the
corium is covered. In the papillae the nervous filaments terminate,
sometimes by loops returning upon themselves, and sometimes apparently by free extremities. The papillae are also supplied with
looped capillary bloodvessels, and are capable of receiving an
abundant vascular injection.
These papillae appear to be the most essential organs of general
sensation, since the sensibility of the skin is most acute where they
are most abundant and most highly developed, as, for example, on
the palm of the hand and the tips of the fingers.
The best method of measuring accurately the sensibility of different regions is that adopted by Professors Weber and Valentin.
They applied the rounded points of a pair of compasses to the
integument of different parts, and found that if they were held
very near together they could no longer be distinguished as sepa



GENERAL AND SPECIAL SENSIBILITY.                     463
rate points, but the two sensations were confounded into one. The
distance, however, at which the two points failed to be distinguished
from  each other, was much shorter for some parts of the body
than for others.  Prof. Valentin's measurements,' which are the
most varied and complete, give the following as the limits of distinct perception in various parts:PARIS LINE.
At the tip of tongue....483
"  palmar surface of tips of fingers...723
"'    "    "   of second phalanges..   1.558
"     "    "   of first phalanges..   1.650
"  dorsum of tongue....   2.500
"  dorsal surface of fingers.....   3.900
"   cheek......4.541
"   back of hand....                            6.966
"   skin of throat....   8.292
"   dorsum of foot.......12.525
"   skin over sternum..                15.875
"  middle of back....  24.208
This method cannot, of course, give the absolute measure of the
acuteness of sensibility in the different regions, since the two points
might be less easily distinguished from each other in any one region, and yet the absolute amount of sensation produced might be
as great as in the surrounding parts; still it is undoubtedly a very
accurate measure of the delicacy of tactile sensation, by which we
are enabled to distinguish slight inequalities in the surface of solid
bodies.  We find, furthermore, that certain parts of the body are
particularly well adapted to exercise the function of general sensation, not only on account of the acute sensibility of their integument, but also owing to their peculiar formation. Thus, in man,
the hands are especially well formed in this respect, owing to the
articulation and mobility of the fingers, by which they may be
adapted to the surface of solid bodies, and brought successively
in contact with all their irregularities and depressions. The hands
are therefore more especially used as organs of touch, and we are
thus enabled to obtain by their aid the most delicate and precise
information as to the texture, consistency, configuration, &c., of
foreign bodies.
But the hands are not the exclusive organs of touch, even in the
human subject, and in some of the lower animals, the same func1 In Todd's Cyclopwdia of Anatomy and Physiology, vol. iv., article on Touch,
by Dr. Carpenter.




464                 THE SPECIAL SENSES.
tion is fully performed by various other parts of the body. Thus
in the cat and in the seal, the long bristles seated upon the lips are
used for this purpose, each bristle being connected at its base with
a highly developed nervous papilla: in some of the monkeys the
extremity of the prehensile tail, and in the elephant the end of the
nose, which is developed into a flexible and sensitive proboscis, is
employed as an organ of touch. This function, therefore, may be
performed by either one part of the body or another, provided the
accessory organs be developed in a favorable manner.
About the head and face, the sensibility of the skin is dependent
mainly upon branches of the fifth pair. In the neck, trunk, and
extremities it is due to the sensitive fibres of the cervical, dorsal,
and lumbar spinal nerves. It exists also, to a considerable extent,
in the mucous membranes of the mouth and nose, and of the passages leading from  them  to the interior of the body. In these
situations, it depends upon the sensitive filaments of certain of the
cranial nerves, viz., the fifth pair, the glosso-pharyngeal, and the
pneumogastric.  The sensibility of the mucous membranes is most
acute in those parts supplied by branches of the fifth pair, viz., the
conjunctiva, anterior part of the nares, inside of the lips and cheeks,
and the anterior two-thirds of the tongue.  At the base of the
tongue and in the fauces, where the mucous membrane is supplied
by filaments of the glosso-pharyngeal nerve, the general sensibility
is less perfect; and finally it diminishes rapidly from the upper
part of the oesophagus and the glottis toward the stomach and the
lungs. Thus, we can appreciate the temperature and consistency
of a foreign substance very readily in the mouth and fauces, but
these qualities are less distinctly perceived in the cesophagus, and
not at all in the stomach, unless the foreign body happen to be
excessively hot or cold, or unusually hard and angular in shape.
The general sensibility, which is resident in the skin and in a certain
portion of the mucous membranes, diminishes in degree from without inward, and disappears altogether in those organs which are
not supplied with nerves from the cerebro-spinal system.
It is particularly to be observed, however, that while the general
sensibility of the skin, and of the mucous membranes above mentioned, varies in acuteness in different parts of the body, it is everywhere the same in kind. The tactile sensations, produced by the
contact of a foreign body, are of precisely the same nature whether
they be felt by the tips of the fingers, the dorsal or palmar surfaces
of the hands, the lips, cheeks, or any other part of the integument.




TASTE.                          465
The only difference in the sensibility of these parts lies in the degree of its development.
But there are certain other sensations which are different in kind
from those perceived by the general integument, and which, owing
to their peculiar and special character, are termed special sensations.
Such are, for example, the sensation of light, the sensation of sound,
the sensation of savor, and the sensation of odors. The special
sensibility which enables us to feel the impressions derived from
these sources is not distributed over the body, like ordinary sensibility, but is localized in distinct organs, each of which is so constituted as to receive the special sensation peculiar to it, and no
other.
Thus we have, beside the general sensibility of the skin and
mucous membranes, certain peculiar faculties or special senses, as
they are called, which enable us to derive information from external objects, which we could not possibly obtain by any other
means. Thus light, however intense, produces no perceptible sensation when allowed to fall upon the skin, but only when admitted
to the eye. The sensation of sound is perceptible only by the
ear, and that of odors only by the olfactory membrane.  These
different sensations, therefore, are not merely exaggerations of
ordinary sensibility, but are each distinct and peculiar in their
nature, and are in relation with distinct properties of external
objects.
In examining the organs of special sense, we shall find that they
each consist-First, of a nerve, endowed with the special sensibility
required for the exercise of its peculiar function; and, Secondly, of
certain accessory parts, forming an apparatus more or less complicated, which is intended to assist in its performance and render it
more delicate and complete.  We shall take up the consideration
of the special senses in the following order.  First, the sense of
Taste; second, that of Smell; third, that of Sight; and fourth, that
of Hearing.
TASTE.-We begin the study of the special senses with that of
Taste, because this sense is less peculiar than any of the others, and
differs less, both in its nature and its conditions, from the ordinary
sensibility of the skin. In the first place, the organ of taste is no
other than a portion of the mucous membrane, beset with vascular
and nervous papillae, similar to those of the general integument.
Secondly, it gives us impressions of such substances only as are
30




466                 THE SPECIAL SENSES.
actually in contact with sensitive surfaces, and can establish no
communication with objects at a distance. Thirdly, the surfaces
which exercise the sense of taste are also endowed with general sensibility; and Fourthly, there is no one special and distinct nerve
of taste, but this property resides in portions of two different
nerves, viz., the fifth pair and the glosso-pharyngeal; nerves which
also supply general sensibility to the mouth and surrounding parts.
The sense of taste is localized in the mucous membrane of the
tongue, the soft palate, and the fauces. The tongue, which is more
particularly the seat of this sense, is a flattened, leaf-like, muscular
organ, attached to the inner surface of the symphysis of the lower
jaw in front, and to the os hyoides behind. It has a vertical sheet
or lamina of fibrous tissue, in the median line, which serves as a
framework; and is provided with an abundance of longitudinal
transverse and radiating muscular fibres, by which it can be elongated, retracted, and moved about in every direction.
The mucous membrane of the fauces and posterior third of the
tongue, like that lining the cavity of the mouth, is covered with
minute vascular papillae, similar to those of the skin, which are,
however, imbedded and concealed in the smooth layer of epithelium forming the surface of the organ. But about the junction of
its posterior and middle thirds, there is, upon the dorsum of the
tongue, a double row of rounded eminences, arranged in a V-shaped
figure, running forward and outward, on each side, from the situation of the foramen caecum; and, from this point forward, the upper
surface of the organ is everywhere covered with an abundance of
thickly-set, highly developed papillae, projecting from its surface,
and readily visible to the naked eye.
These lingual papillae are naturally divided into threu different
sets or kinds. First, the filiform papillce, which are the most numerous, and which cover most uniformly the upper surface of the
organ. They are long and slender, and are covered with a somewhat horny epithelium, usually prolonged at their free extremity
into a filamentous tuft. At the edges of the tongue these papillae
are often united into parallel ranges or ridges of the mucous membrane. Secondly, the fungiform papillce. These are thicker and
larger than the others, of a rounded club-shaped figure, and covered
with soft, permeable epithelium. They are most abundant at the
tip of the tongue, but may be seen elsewhere on the surface of the
organ, scattered among the filiform papillae. Thirdly, the circumvallatepapilloe. These are the rounded eminences which form the




TASTE.                          467
V-shaped figure near the situation of the foramen caecum. They
are eight or ten in number. Each one of them is surrounded by
a circular wall, or circumvallation, of mucous membrane, which
gives to them  their distinguishing appellation. The circumvallation, as well as the central eminence, has a structure similar to that
of the fungiform papillae.
The sensitive nerves of the tongue, as we have already seen, are
two in number, viz., the lingual branch of the fifth pair, and the
lingual portion of the glosso-pharyngeal. The lingual branch of
the fifth pair enters the tongue at the anterior border of the hyoglossus muscle, and its fibres then run through the muscular tissue
of the organ, from below upward and from behind forward, without any ultimate distribution, until they reach the mucous membrane.  The nervous filaments then penetrate into the lingual
papillae, where they finally terminate. The exact mode of their
termination is not positively known. According to Kolliker, they
sometimes seem to end in loops, and sometimes by free extremities.
The lingual portion of the glosso-pharyngeal nerve passes into
the tongue below the posterior border of the hyo-glossus muscle.
It then divides into various branches, which pass through the muscular tissue, and are finally distributed to the mucous membrane of
the base and sides of the organ.
Fig. 153.
D TAG R A   OF T o N    r E, with its sensitive nerves and papilla.-1. Lingual branch of fifth pair,
2. Glosso-pharyngeal neive.
The mucous membrane of the base of the tongue, of its edges,
and its under surface near the tip, as well as the mucous membrane
of the mouth and fauces generally, is also supplied with mucous
follicles, which furnish a viscid secretion by which the free surface
of the parts is lubricated.
Finally, the muscles of the tongue, it will be remembered, are
animated exclusively by the filaments of the hypoglossal nerve.




468                 THE SPECIAL SENSES.
The exact seat of the sense of taste has been determined by
placing in contact with different parts of the mucous membrane a
small sponge, moistened with a solution of some sweet or bitter
substance. The experiments of VerniBre, Longet and others have
shown that the sense of taste resides in the whole superior surface,
the point and edges of the tongue, the soft palate, fauces, and part
of the pharynx.  The base, tip, and edges of the tongue seem to
possess the most acute sensibility to savors, the middle portion of
its dorsum less of this sensibility, and its inferior surfaces little or
none. Now as the whole anterior part of the organ is supplied by
the lingual branch of the fifth pair alone, and the whole of its
posterior portion by the glosso-pharyngeal, it follows that the sense
of taste, in these different parts, is derived from these two different
nerves.
Furthermore, the tongue is supplied, at the same time and by the
same nerves, with general sensibility and with the special sensibility of
taste. The general sensibility of the anterior portion of the tongue,
and that of the branch of the fifth pair with which it is supplied,
are sufficiently well known. Section of the fifth pair destroys the
sensibility of this part of the tongue as well as that of the rest of
the face. Longet has found that after the lingual branch of this
nerve has been divided, the mucous membrane of the anterior twothirds of the tongue may be cauterized with a hot iron or with
caustic potassa, in the living animal, without producing any sign of
pain. Dr. John Reid, on the other hand, together with other experimenters, has determined that ordinary sensibility exists in a marked
degree in the glosso-pharyngeal, and is supplied by it to the parts
to which this nerve is distributed.
Accordingly we must distinguish, in the impressions produced
by foreign substances taken into the mouth, between the special
impressions derived from  their sapid qualities, and the general sensations produced by their ordinary physical properties. As the tongue is
exceedingly sensitive to ordinary impressions, and as the same body
is often capable of exciting both the tactile and gustatory functions,
these two properties are sometimes liable to be confounded with
each other. by careless observation. The truly sapid qualities,
however, the only ones, properly speaking, which we perceive by
the sense of taste, are such savors as we designate by the term
sweet, bitter, salt, sour, alkaline, and the like. But there are many
other properties, belonging to various articles of food, which belong
really to the class of ordinary physical qualities and are appre



TASTE.                          469
ciated by the ordinary sensibility of the tongue, though we usually
speak of them  as being perceived by the taste. Thus a starchy,
viscid, watery, or oleaginous taste is merely a certain variety of consistency in the substance tasted, which may exist either alone or in
connection with real savors, but which is exclusively perceived by
means of the general sensibility.  So also with a pungent or burning
taste, such as that of red pepper or any other irritating powder.
The quality of piquancy in the preparation of artificial kinds of
food is always communicated to them by the addition of some such
irritating substance. The styptic taste seems to be a combination of
an ordinary irritant or astringent effect with a peculiar taste, which
we always associate with the former quality in astringent substances.
There is also sometimes a liability to confound the real taste of
certain substances with their odorous properties, or flavors.  Thus
in most aromatic articles of food, such as tea and coffee, and in
various kinds of wine, a great part of what we call the taste is in
reality due to the aroma, or smell, which reaches the nares during
the act of swallowing.  Even in many solid kinds of food, such as
freshly cooked meats, the odor produces a very important part of
their effect on the senses. We can easily convince ourselves of this
by holding the nose while swallowing such substances, or by recollecting how much a common catarrh interferes with our perception
of their taste.
The most important conditions of the sense of taste are the following:In the first place, the sapid substance, in order that its taste may
be perceived, must be brought in contact with the mucous membrane of the mouth in a state of solution. So long as it remains
solid, however marked a savor it may possess, it gives no other
impression than that of any foreign body in contact with the sensitive surfaces. But if it be applied in a liquid form, it is then spread
over the surface of-the mucous membrane, and its taste is immediately perceived. Thus it is only the liquid and soluble portions
of our food which are tasted, such as the animal and vegetable
juices and the soluble salts. Saline substances which are insoluble,
such as calomel or carbonate of lead, when applied to the tongue,
produce no gustatory sensation whatever.
The mechanism of the sense of taste is, therefore, in all probability, a direct and simple one. The sapid substances in solution
penetrate the lingual papillae by endosmosis, and, coming in actual




470                 THE SPECIAL SENSES.'contact with the terminal nervous filaments, excite their sensibility
by uniting with their substance. We have already seen that the
rapidity with which endosmosis will take place under certain conditions is sufficiently great to account for the almost instantaneous
perception of the taste of sapid substances when introduced into the
mouth.
It is on this account that a free secretion of the salivary fluids is
so essential to the full performance of the gustatory function. If
the mouth be dry and parched, our food seems to have lost its taste;
but when the saliva is freely secreted, it is readily mixed with the
food in mastication, and assists in the solution of its sapid ingredients; and the fluids of the mouth, thus impregnated with the savory
substances, are absorbed by the mucous membrane, and excite the
gustatory nerves. An important part, also, is taken in this process
by the movements of the tongue; for by these movements the food
is carried from one part of the mouth to another, pressed against
the hard palate, the gums, and the cheeks, its solution assisted, and
the penetration of the fluids into the substance of the papilla more
rapidly accomplished. If a little powdered sugar, or some vegetable extract be simply placed upon the dorsum of the tongue, but
little effect is produced; but as soon as it is pressed by the tongue
against the roof of the mouth, as naturally happens in eating or
drinking, its taste is immediately perceived. This effect is easily
explained; since we know how readily movement over a free surface, combined with slight friction, will facilitate the imbibition of
liquid substances. The nervous papillae of the tongue may therefore be regarded as the essential organs of the sense of taste, and
the lingual muscles as its accessory organs.
The full effect of sapid substances is not obtained until they are actually swallowed. During the preliminary process of mastication a
sufficient degree of impression is produced to enable us to perceive
the presence of any disagreeable or injurious ingredient in the food,
and to get rid of it, if we desire. But it is only when the food is
carried backward into the fauces and pharynx, and is compressed
by the constrictor muscles of these parts, that we obtain a complete
perception of its sapid qualities. For at that time the food is spread
out by the compression of the muscles, and brought at once in
contact with the entire extent of the mucous membrane possessing
gustative sensibility. Then, it is no longer under the control of the
will, and is carried by the reflex actions of the pharynx and oesophagus downward to the stomach.




TASTE.                         471
The impressions of taste made upon the tongue remainfor a certain time afterward.  When a very sweet or very bitter substance
is taken into the mouth, we retain the taste of its sapid qualities
for several seconds after it has been ejected or swallowed. Consequently, if several different savors be presented to the tongue in
rapid succession, we soon become unable to distinguish them, and
they produce only a confused impression, made up of the union of
various different sensations; for the taste of the first, remaining in
the mouth, is mingled with that of the second, the taste of these
two with that of the third, and so on, until so many savors become
confounded together that we are no longer able to recognize either
of them. Thus it is notoriously impossible to recognize two or
three different kinds of wine with the eyes closed, if they be repeatedly tasted in quick succession.
If the substance first tasted have a particularly marked savor,
its taste will preponderate over that of the others, and perhaps prevent our recognizing them at all. This effect is still more readily
produced by substances which excite the general sensibility of the
tongue, such as acrid or stimulating powders.  In the same manner
as a painful sensation, excited in the skin, prevents the nerves, for
the time, from perceiving delicate tactile impressions, so any pungent
or irritating substance, which excites unduly the general sensibility
of the tongue, blunts for a time its special sensibility of taste. This
effect is produced, however, in the greatest degree, by substances
which are at the same time sapid, pungent and aromatic, like sweetmeats flavored with peppermint. Advantage is sometimes taken
of this in the administration of disagreeable medicines. By first
taking into the mouth some highly flavored and pungent substance,
nauseous drugs may be swallowed immediately afterward with but
little perception of their disagreeable qualities.
A very singular fact, in connection with the sense of taste, is that
it is sometimes affected in a marked degree by paralysis of the facial
nerve. No less than six cases of this kind, occurring in the human
subject, have been collected by M. Bernard; and the same observer
has seen a similar effect upon the taste produced in animals by
division of the facial nerve within the cranium. The result of these
experiments and observations is as follows: When the facial nerve
is divided or seriously injured by organic disease, before its emergence from the stylo-mastoid foramen, not only is there a paralysis
of the superficial muscles of the face, but the sense of taste is
diminished on the corresponding side of the tongue. If the tongue




472                 THE SPECIAL SENSES.
be protruded, and powdered citric acid or sulphate of quinine be
placed upon its surface on the two sides of the median line, the taste
of these substances is perceived on the affected side more slowly
and obscurely than on the other. It is not, therefore, a destruction,
but only a diminution of the sense of taste, which follows paralysis
of the facial in these instances. At the same time the general tactile
sensibility of the tongue is unaltered, retaining its natural acuteness
on both sides of the tongue.
The exact mechanism of this peculiar influence of the facial nerve
upon the sense of taste is not perfectly understood. It may be
considered as certain, however, that it is derived through the
medium of that branch of the facial nerve known as the chorda
tympani.  This. filament leaves the facial at the intumescentia
gangliformis, in the interior of the aqueduct of Fallopius, enters the
cavity of the tympanum, passes across the membrane of the tympanum, and then, emerging from the cranium, runs downward and
forward and joins the lingual branch of the fifth pair. It then accompanies this nerve as far as the posterior extremity of the submaxillary gland. Here it divides into two portions; one of which
passes to the submaxillary ganglion, and, through it, to the substance of the submaxillary gland, while the other continues onward,
still in connection with the lingual branch of the fifth pair, and, in
company with the filaments of this nerve, is distributed to the tongue.
The chorda tympani thus forms the only anatomical connection
between the facial nerve and the anterior part of the tongue. When
the facial, accordingly, is divided or injured after its emergence
from  the stylo-mastoid foramen, no effect is produced upon the
sense of taste; but when it is injured during its course through the
aqueduct of Fallopius, and before it has given off the chorda tympani, this nerve suffers at the same time, and the sense of taste is
diminished in activity, as above described. It is probable that this
effect is produced in an indirect way, by a diminution in the activity
of secretion in the lingual follicles, or by some alteration in the
vascularity of the parts.
SMELL.-The main peculiarity of the sense of smell consists in
the fact that it gives us intelligence of the physical character of
bodies in a gaseous or vaporous condition. Thus we are enabled to
perceive the existence of an odorous substance at a distance, and
when it is altogether concealed from sight. The minute quantity
of volatile material emanating from it, and thus pervading the




SMELL.                           473
atmosphere, comes in contact with the mucous membrane of the
nose, and thus produces a peculiar and special sensation.
The apparatus of this sense consists, first, of the olfactory membrane, supplied by the filaments of the olfactory nerve, as its
special organ; and secondly, of the turbinated nasal passages, with
the turbinated bones and the muscles of the anterior and posterior
nares, as its accessory organs. At the upper part of the nasal fossae,
the mucous membrane is very thick, soft, spongy and vascular, and
is supplied with mucous follicles which exude a secretion, by which
its surface is protected and kept in a moist and sensitive condition.
It is only this portion of the mucous membrane of the nares
which is supplied by filaments of the olfactory nerve, and which is
capable of receiving the impressions of smell; it is therefore called
the Olfactory membrane. Elsewhere, the nasal passages are lined
with a mucous membrane which is less vascular and spongy in
structure, and which is called the Schneiderian membrane.
The filaments derived from the olfactory ganglia, and which
penetrate through the cribriform plate of the ethmoid bone, are
distributed to the mucous membrane of the superior and middle
turbinated bones, and to that of the upper part of the septum nasi.
The exact mode in which these filaments terminate in the olfactory
membrane has not been definitely ascertained. They are of a soft
consistency and gray color, and, after dividing and ramifying freely
in the membrane, appear to become lost in its substance. It is
these nerves which exercise
the special function of smell.               Fig. 154.
They are, to all appearance,
incapable of receiving ordi-            (
nary impressions, and must  
be regarded as entirely peculiar in their nature and endow-            I.:
ments. The nasal passages,
however, are  supplied with
other nerves beside the olfactory.  The nasal branch of
the ophthalmic division of the
fifth pair, after entering the
anterior part of the cavity of
the nares, just in advance of  DISTRIBUTION OF NERVES I THE NASAL
the cribriform  plate of the  PASSAG ES. —1 Ofactoryganglion,withits nerves.
2. Nasal branch of fifth pail.  3. Spheno-palatine
ethmoid bone, is distributed  gangl;u.




474                 TIHE SPECIAL SENSES.
to the mucous membrane of the inferior turbinated bone and the
inferior meatus. Thus the organ of smell is provided with sensitive nerves from two different sources, viz., at its upper part, with
the olfactory nerves proper, derived from the olfactory ganglion
(Fig. 154, i), which are nerves of special sensation; and secondly,
at its lower part, with the nasal branch of the fifth pair (2) a nerve
of general sensation. Beside which, the spheno-palatine ganglion
of the great sympathetic (3) sends filaments to the mucous membrane of the whole posterior part of the nasal passages, and to the
levator palati and azygos uvulae muscles. Finally, the muscles of
the anterior nares are supplied by filaments of the facial nerve.
The conditions of the sense of smell are much more special in
their nature than those of taste. For, in the first place, this sense is
excited, riot by actual contact with the foreign body, but only with
its vaporous emanations; and the quantity of these emanations,
sufficient to excite the smell, is often so minute as to be altogether
inappreciable.  We cannot measure the loss of weight in an
odorous body, though it may affect the atmosphere of an entire
house, and the senses of all its inhabitants, for days and weeks
together.  Secondly, in the olfactory organ, the special sensibility
of smell and the general sensibility of the mucous membrane are
separated from  each other and provided for by different nerves,
not mingled together and exercised by the same nerves, as is the
case in the tongue.
In order to produce an olfactory impression, the emanations of
the odorous body must be drawn freely through the nasal passages.
As the sense of smell, also, is situated only in the upper part of these
passages, whenever an unusually faint or delicate odor is to be perceived, the air is forcibly directed upward, toward the superior
turbinated bones, by a peculiar inspiratory movement of the nostrils. This movement is very marked in many of the lower animals.
As the odoriferous vapors arrive in the upper part of the nasal
passages, they are undoubtedly dissolved in the secretions of the
olfactory membrane, and thus brought into relation with its nerves.
Inflammatory disorders, therefore, interfere with the sense of smell,
both by checking or altering the secretions of the parts, and by
producing an unnatural tumefaction of the mucous membrane,
which prevents the free passage of the air through the nasal fossae.
As in the case of the tongue, also, we must distinguish here
between the perception of true odors, and the excitement of the
general sensibility of the Schneiderian mucous membrane by irri



SMELL.                         475
tating substances. Some of the true odors are similar in their nature
to impressions perceived by the sense of taste. Thus we have
sweet and sour smells, though none corresponding to the alkaline
or the bitter tastes. Most of the odors, however, are of a very
peculiar nature and are difficult to describe; but they are always
distinct from the simply irritating properties, which may belong to
vapors as well as to liquids. Thus, pure alcohol has little or no
odor, and is only irritating to the mucous membrane; while the
odor of wines, of cologne water, &c., is communicated to them by
the presence of other ingredients of a vegetable origin. In the
same way, pure acetic acid is simply irritating; while vinegar has
a peculiar odor in addition, derived from its vegetable impurities.
Ammonia, also, is an irritating vapor, but contains in itself no
odoriferous principle.
The sensations of smell, like those of taste, remain for a certain time
after they have been produced, and modify in this way other less
strongly marked odors which are presented afterward.  As a
general thing, the longer we are exposed to a particular odor, the
longer its effect upon our senses continues; and in some cases it
may be perceived many hours after the odoriferous substance has
been removed.  Odors, however, are particularly apt to remain
after the removal or destruction of the source from which they
were derived, owing to their vaporous character, and the facility
with which they are entangled and retained by porous substances,
such as plastered walls, woollen carpets and hangings, and woollen
clothes. It is supposed to be in this way that the odor of a postmortem examination will sometimes remain so as to be perceptible
for several hours, or even an entire day afterward. But this alone
does not fully explain the fact. For if it depended simply on the
retention of the odor by porous substances, it would afterward be
perceived constantly, until it gradually and continuously wore off;
while, in point of fact, the physician who has made an autopsy of
this kind does not afterward perceive its odor constantly, but only
occasionally, and by sudden and temporary fits.
The explanation is probably this. As the odor remains constantly by us, we soon become insensible to its presence, as in the
case of all other continuous and unvarying impressions. Our attention is only called to it when we meet suddenly with another
and familiar odor. This second odor, we find, does not produce its
usual impression, because it is mingled with and modified by the
other, which is more persistent and powerful. Thus we are again




476                 THE SPECIAL SENSES.
made aware of the former one, to which we had become insensible
by reason of its constant presence.
The sense of smell is comparatively feeble in the human species,
but is excessively acute in some of the lower animals. Thus, the
dog will not only distinguish different kinds of game in the forest,
by this sense, and follow them by their tracks, but will readily distinguish particular individuals by their odor, and will recognize
articles of dress belonging to them by the minute quantity of odoriferous vapors adhering to their substance.
SIGHT.-The sight undoubtedly occupies the first rank in the
list of special nervous endowments. It is the most peculiar in its
operation, and the most immaterial in its nature, of all the senses,
and it is through it that we receive the most varied and valuable
impressions. The physical agent, also, to which the organ of sight
is adapted, and by which its sensibility is excited, is more subtle
and peculiar than any of those which act upon our other senses.
For the senses of touch, taste, and smell require, for their exercise,
the actual contact of a foreign body, either in a solid, liquid, or
aeriform  condition; and even the hearing depends upon the mechanical vibrations of the atmosphere, or some other sonorous
medium. But the eye does not need to be in contact with the
luminous body.  It will receive the impressions of light with perfect distinctness, even when they are transmitted from an immeasurable distance, as in the case of the fixed stars; and the light
itself is not only immaterial in its nature, so far as we can ascertain,
but is also capable of being transmitted through space without the
intervention of any material conducting medium, yet discoverable.
Finally, the apparatus of vision is more complicated in its structure than that of any other of the special senses. This apparatus
consists, first, of the retina, as a special sensitive nervous membrane;
and secondly, of the vitreous body, crystalline lens, choroid, sclerotic, iris and cornea, together with the muscles moving the eyeball and eyelids, lachrymal gland, &c., as accessory organs. The
arrangement of the parts, constituting the globe of the eye, is shown
in the following figure. (Fig. 155.)
The filaments of the optic nerve, after running forward and penetrating the posterior part of the eyeball, spread out into the substance of the retina (3), thus forming a delicate and vascular nervous expansion, in the form of a spheroidal bag or sac, with a wide
opening in front, where the retina terminates at the posterior mar



SIGHT.                           477
gin of the ciliary body. This expansion of the retina is the essen
tial nervous apparatus of the eye. It is endowed with the special
Fig. 155,
-    2. R.  4. L   5 
Vertical Section of the EYEBALL. —1. Sclerotic. 2. Choroid. 3. Retina. 4. Lens. 5. HTyaloid
membrane. 6. Cornea. 7. Iris. 8. Ciliary muscle and processes.
sensibility which renders it capable of receiving luminous impressions; and, so far as we have been able to ascertain, it is incapable of
perceiving any other. On the outside, the retina is covered by the
choroid coat (2), a vascular membrane, which is rendered opaque by
the presence of an abundant layer of blackish-brown pigment-cells,
and which thus absorbs the light which has once passed through
the retina, and prevents its being reflected in such a way as to
confuse and dazzle the sight.  Inside the retina is the vitreous body,
a transparent spheroidal mass of a gelatinous consistency, which is
surrounded and retained in position by a thin, structureless membrane, called the hyaloid membrane (5), lying immediately in
contact with the internal surface of the retina. The lens (4) is
placed in front of the vitreous body, in the central axis of the eyeball, enveloped in its capsule, which is continuous with the hyaloid
membrane. Just at the edge of the lens, the hyaloid membrane
divides into two laminae, which separate from  each other, leaving
between them a triangular canal, the canal of Petit, which can be
seen in the above figure. In front of the lens is the iris (7), a nearly
vertical muscular curtain, formed of radiating and concentric fibres,
pierced at its centre with a circular opening, the pupil, through
which the light is admitted, and covered on its posterior surface
with a continuation of the choroidal pigment, which excludes the
passage of any other rays than those which pass through the pupil.




478                 THE SPECIAL SENSES.
At the same time, the whole globe is inclosed and protected by a
thick, fibrous, laminated tunic, which in its posterior and middle
portions is opaque, forming the sclerotic (1), and in its anterior portion is transparent, forming the cornea (s). The muscles of the eyeball are attached to the external surface of the sclerotic in such a
way that the cornea may be readily turned in various directions;
while the eyelids, which may be opened and closed at will, protect
the eye from injury, and, with the aid of the lachrymal secretion,
keep its anterior surfaces moist, and preserve the transparency of
the cornea.
The organ of vision is supplied with nerves of ordinary sensibility by the ophthalmic branch of the fifth pair. The filaments
of this nerve which terminate about the eye are distributed mostly
to the conjunctiva, lachrymal gland, and skin of the eyelids; while
a very few of them run forward in company with the ciliary nerves
proper, and are distributed to the ciliary circle and iris. All these
parts, therefore, but more particularly the conjunctiva and skin of
the eyelids, possess ordinary sensibility, which appears to be totally
wanting in the deeper parts of the eye. The ophthalmic ganglion
gives off the ciliary nerves, which are distributed to the iris and
ciliary muscle. Finally, the muscles moving the eyeball and eyelids are supplied with motor nerves from the third, fourth, sixth
and seventh pairs.
Of all the properties and functions belonging to the different
structures of the eyeball, the most peculiar and characteristic is the
special sensibility of the retina. This sensibility is such that the
retina appreciates both the intensity and the quality of the lightthat is to say, its color and the different shades which this color
may present. On account of the form, also, in which the retina is
constructed, viz., that of a spheroidal membranous bag, with an
opening in front, it becomes capable of appreciating the direction
from which the rays of light have come, and, of course, the situation
of the luminous body and of its different parts. For the rays which
enter through the pupil from below can reach the retina only at its
upper part, while those which come in from  above, can reach it
only at its lower part; so that in both instances the rays strike the
sensitive surface perpendicularly, and thus convey the impression
of their direction from above or below.
But beside the sensibility of the retina, the perfection and value
of the sense of sight depend very much on the arrangement of the
accessory organs, the most important of which is the crystalline
lens.




SIGHT.                          479
The function of the crystalline lens is to produce distinct perception
of form and outline. For if the eye consisted merely of a sensitive
retina, covered with transparent integument, though the impressions
of light would be received by such a retina they could not give
any idea of the form of particular objects, but could only produce
the sensation of a confused luminosity. This condition is illustrated in Fig. 156, where the arrow, a, b, represents the luminous
object, and the vertical dotted line, at the right of the diagram,
represents the retina. Rays, of course, will diverge from every
point in the object in every direction, and will thus reach every
part of the retina.  The different parts of the retina, consequently,
1, 2, 3, 4, will each receive rays coming both from the point of the
arrow, a, and from its butt, b. There will therefore be no distinction, upon the retina, between the different parts of the object, and no
Fig. 156.                         Fig. 157.
definite perception of its outline. But if, between the object and the
retina, there be inserted a double convex refracting lens, with the
proper curvatures and density, as in Fig. 157, the effect will be different. For then all the rays emanating from a will be concentrated
at x, and all those emanating from b will be concentrated at y.
Thus the retina will receive the impression of the point of the
arrow separate from  that of the butt; and all parts of the object,
in like manner, will be distinctly and accurately perceived.
This convergence of the rays of light is accomplished to a certain
extent by the other transparent and refracting parts of the eyeball;
but the lens is the most important of all in this respect, owing to
its superior density and the double convexity of its figure. The
distinctness of vision, therefore, depends upon the action of the
lens in converging all the rays of light, emanating from a given
point, to an accurate focus, at the surface of the retina. To accomplish
this, the density of the lens, the curvature of its surfaces, and its
distance from  the retina, must all be accurately adapted to each
other.  For if the lens be too convex, and its refractive power con



480                 THE SPECIAL SENSES.
sequently too great, the rays will-be converged to a focus too soon,
and will not reach the retina until after they have crossed each
other and become partially dispersed; as in Fig. 158. The visual
impression, therefore, coming from any particular point in the
object is not concentrated and distinct, but diffused and dim, from
being dispersed more or less over the retina, and interfering with
the impressions coming from other parts.. This is the condition
which is present in myopia, or near-sightedness. On the other hand,
Fig. 158.                         Fig. 159.
MYOPIA.                         PRESBYOPIA.
if the lens be too flat, and its convergent power too feeble, as in
Fig. 159, the rays will fail to come together at all, and will strike
the retina separately, producing a confused image, as before. This
is the defect which exists in presbyopia, or long-sightedness. In
both cases, the immediate cause of the confusion of sight is the
same, viz., the rays coming from  the same point of the object
striking the retina at different points; but in the first instance, this
is because the rays have actually converged to a point, and then
crossed; in the second, it is because they have only approached
each other, but have never converged to a focus.
Another important particular in regard to the action of the lens
is the accommodation of the eye to distinct vision at different distances.
It is evident that the same arrangement of the refractive parts, in
the eye, will not produce distinct vision when the distance of the
object from the eye is changed.  If this arrangement be such that
the object is seen distinctly at a certain distance, as in Fig. 160,
and the object be then removed to a remoter point, as in Fig. 161,
the image will become confused; for the rays will then be converged to a focus at a point in front of the retina; because, being
less divergent, when they strike the lens, the same amount of refraction will bring them together sooner than before. On the other
hand, if the object be moved to a point nearer the eye, the rays,
becoming more divergent as they strike the lens, will be converged
less rapidly to a focus, and vision will again become indistinct.




SIGHT.                          481
This may easily be seen by the aid of a very simple experiment.
If two needles be placed upright, at different distances from the eye,
one for example at eight and
Fig. 160.
the other at eighteen inches, but
nearly in the same linear range,
and if then, closing one eye, we
look at them alternately, we shall
find that we cannot see both distinctly at the same time. For as
soon as we look at the one nearFig. 161.
est the eye, so as to perceive its form distinctly, the image of the
more remote one becomes confused; and when we see the more remote object in perfection, that which is nearer loses its sharpness of
outline. This shows, in the first place, that the same condition of
the eye will not allow us to see two objects at different distances
with distinctness at the same time; and secondly that, on looking
from one to the other, there is a change of some kind in the focus of
the eye, by which it is adapted to different distances. Indeed we
are conscious of a certain effort at the time when the point of vision
is transferred from one object to the other, by which it is adapted
to the new distance; and this alteration is not quite instantaneous,
but requires a certain interval of time for its completion.
This accommodation of the eye to different distances is undoubtedly effected by an antero-posterior movement of the lens
within the eyeball. It will at once be perceived, on referring to
Fig. 161, that if the lens were moved a little backward toward the
retina, at the same time that the object is removed to a greater distance from the eye, the focus of the convergent rays would still fall
upon the retina, and the image would still be distinct. In the opposite case, where the object is brought nearer the eye, a similar
movement of the lens forward would again secure perfect vision.
Thus, when we look at near objects, the lens moves forward
31




482                 THE SPECIAL SENSES.
toward the pupil; when we look at remote objects, it moves backward toward the retina.
This movement of the lens is apparently accomplished by the
action of the ciliary muscle. This muscle (Fig. 155, 8) arises, in
front, from the conjunction of the sclerotic and the cornea, and running backward and outward, is inserted into the anterior part of
the choroid, about the situation at which the hyaloid membrane
passes off, to become the suspensory ligament of the lens. As
already mentioned, this muscle is supplied with nervous filaments
from the ophthalmic ganglion. Its action is to draw the lens forward, by means of its attachment to the hyaloid membrane and
choroid coat; and, in the human subject, its retreat or retrogression toward the retina, after the ciliary muscle is relaxed, seems to
be due to the elastic resiliency of the remaining tissues of the eyeball.
But in order to allow of such a backward and forward movement
of the lens, since the liquids of the eyeball are incompressible, there
must be a corresponding displacement of other parts, both before
and behind. This is undoubtedly provided for by the vascularity
of the choroid coat. This membrane is supplied with an exceedingly
abundant vascular plexus over its whole posterior portion; and in
front it is thrown into a circle! of prominent converging folds, or
processes, the ciliary processes, which are nothing more than erectile
congeries of bloodvessels, covered with the pigment of the choroid.
A portion of the ciliary processes projects in front of the lens, and
their vascular network is continued over a great part of the posterior surface of the iris. Thus there is, both behind and in front
of the lens, an erectile system of bloodvessels; and as these bloodvessels become alternately empty or turgid, they will allow of the
displacement of the lens in an anterior or posterior direction.
Accordingly there is a certain accommodation of the eye necessary to the distinct sight of objects at different distances. But the
range of this accommodation is limited, and the same eye cannot be
made to see distinctly at all distances. For all ordinary eyes, the
accommodation fails, and vision becomes imperfect, when the object
is placed at less than six inches distance from the eye. But from
that point outward, the eye can adapt itself to any distance at which
light is perceptible, even to the immeasurable distances of the fixed
stars.  A  much greater accommodating power, however, is required for near distances than for remote, since the difference in
divergence between rays, entering the pupil from a distance of one




SIGHT.                          483
inch and from that of six inches, is greater than the difference between six inches and a yard, or even distances which are immeasurably remote.  Accordingly,'near-sighted persons can see objects
distinctly when placed very near the eye; since, as their lens converges the rays of light more powerfully than usual, they can be
brought to a focus upon the retina, even when excessively divergent at the time they enter the eye. But distant objects become
indistinct, since, however far backward the lens is moved, the rays
are still brought to a focus and cross each other, before reaching
the retina, as in Fig. 161. Near-sighted persons, therefore, have a
limited range of accommodation, like all others, only it is confined
within short distances, owing to the excessive refracting power of
the lens.
On the other hand, long-sighted persons can see remote objects
without trouble, since a very little movement of the lens will be
sufficient to adapt it for long distances; but within short distances,
the divergence of the rays becomes too great, and they cannot be
brought to a focus.
Circle of Vision.-Since the opening of the pupil will admit rays
of light coming from various directions, there is in front of the eye
a circle, or space, within which luminous objects are perceived, and
beyond which nothing can be seen, because the rays, coming from
the side or from behind, cannot enter the pupil. This space, within
which external objects can be perceived, is called the "circle of
vision." But, for short distances, there is only a single point, in the
centre of the circle of vision, at which objects can be seen distinctly.
Thus, if we place ourselves in front of a row of vertical stakes or
palisades, we can see those directly in front of the eye with perfect
distinctness, but those at a little distance on each side are only perceived in a confused and uncertain manner. On looking at the
middle of a printed page, in the direct range of vision, we see the
distinct outlines of the letters; while at successive distances from
this point, the eye remaining fixed, we can distinguish first only
the separate letters with confused outlines, then only the words, and
lastly only the lines and spaces.
This is because rays of light coming into the eye very obliquely,
in a lateral direction, are not brought to their proper focus. Thus,
in Fig. 162, the rays diverging from the point a, directly in front of
the eye, fall upon the lens in such a way that they are all brought
together at x, at the surface of the retina; but those coming from b
fall upon the lens so obliquely that, for rays having an equal diver



484                 THE SPECIAL SENSES.
gence with those coming from a, there is more difference in their
angles of incidence, and of course more difference in the amount
of their refraction. They are consequently brought together more
rapidly, and on reaching the retina are dispersed over the space y, z.
Fig. 162.
The perfection of the eye, as a visual apparatus, is very much
increased by the action of the iris. This organ, as we have already
mentioned, is a nearly vertical muscular curtain, placed in front of
the lens, attached by its external margin to the junction of the
cornea and sclerotic, and pierced about its centre by the circular
opening of the pupil. It consists, according to most anatomists, of
two sets of muscular fibres-viz., the circular and the radiating.
The circular fibres, which are much the most abundant, are arranged
in concentric lines about the inner edge of the iris, near the pupil:
the others are said to radiate in a scattered manner, from its central
parts to its outer margin. The action of these two sets of fibres is
to contract and enlarge the orifice of the pupil. The circular fibres,
in contracting, draw together the edges of the pupil, and so diminish
its opening; and when these are relaxed, the radiating fibres come
into play, and, by drawing apart the edges of the orifice, enlarge
the pupillary opening.  The action of the circular fibres, at the
same time, is much the most marked and important of the two.
For when the whole muscular apparatus of the eye is paralyzed
by the action of belladonna, or by the division of the third pair of
nerves, or in the general relaxation of the muscular system at the
moment of death, the pupil is invariably dilated, probably by the
passive elasticity of its tissues.




SIGHT.                          485
During life, however, these different conditions of the pupil correspond with the different degrees of light to which the eye is exposed. In a strong light, the pupil contracts and shuts out the
superfluous rays; in a feeble light, it dilates, in order to collect
into the eye all the light which can be received from the object.
This contractile and expansive movement of the pupil is a reflex
action. It is not produced by the direct impression of the light
upon the iris itself, but upon the retina; since, if the retina be
affected with complete amaurosis, or if the light be entirely shut out
from it by an opacity of the lens, no such effect is produced, though
the iris itself be exposed to the direct glare of day. From  the
retina the impression is transmitted, through the optic nerve, to the
optic tubercles and the brain, thence reflected outward by the oculomotorius nerve to the ophthalmic ganglion, and so through the
ciliary nerves to the iris.
The pupil is subject, however, to various other nervous influences
beside the impressions of light received by the retina. Thus in
poisoning by opium, it is contracted; in coma from compression of
the brain, it is dilated; in natural sleep it is contracted, and the eyeball rolled upward and inward. In various mental conditions, the
pupil is also enlarged or diminished, and thus modifies the expression of the eye; and in viewing remote objects, it is generally
enlarged, while, in looking at near objects, it is comparatively contracted. But still, the most constant and important function be.
longing to the iris is the admission or exclusion of the rays, according to the intensity of the light.
Our impressions of distance and solidity, in viewing external
objects, are produced mainly by the combined action of the two eyes.
For, as the eyes are seated a certain distance apart from each other
in the head, when they are both directed toward the same object,
their axes meet at the point of sight, and form a certain angle with
each other; and this angle varies with the distance of the object.
Thus, when the object is within a short distance, the axes of the
two eyes will necessarily be very convergent, and the angle which
they form with each other a large one; but for remote objects, the
visual axes will become more nearly parallel, and their angle consequently smaller. It is on this account that we can always distinguish whether any person at a short distance is looking at us,
or at some other object in our direction; since we instinctively
appreciate, from the appearance of the eyes, whether their visual
axes meet at the level of our own face.




486                 THE SPECIAL SENSES.
In looking at a landscape, accordingly, we do not see the whole
of it distinctly at the same moment, but only those parts to which
our attention is immediately directed. This is because, in the first
place, the focus of distinct vision varies, in each eye, for different
distances, as we have seen in a former paragraph, and secondly,
because both eyes can only be directed together, at one time, to
objects at a certain distance. Thus, when we see the foreground
or the middle ground distinctly, the distance is vague and uncertain, and when we direct our eyes more particularly to the horizon,
objects in the foreground become indistinct. In this way we appreciate the difference in distance between the various portions of
the landscape, as a whole. In the case of particular objects, we are
assisted also by the alteration in their individual characters; for
distance produces a diminution, both in apparent size and in intensity of color.
The combined action of the two eyes is also very valuable, for
near objects, in giving us an idea of solidity or projection. For
within a certain distance, the visual axes, when directed together
at a solid object, are so convergent that the two eyes do not receive
the same image.  As in Figs. 163 and 164, which represent a skull
Fig. 163.                        Fig. 164.
As SEEN BY THE LEFT EYE.           As SEEN BY THE RIGHTEYE.
as seen by the two eyes, when placed exactly in front of the observer at the distance of eighteen inches or two feet, the right eye
will see the object partly on one side, and the left eye partly on the
other. And by the union or combination of these two images by
the visual organs, the impression of solidity is produced.
By the employment of double pictures, so drawn as to represent




SIGHT.                         487
the appearances presented to the two eyes by the same object, and
so arranged that each shall be seen only by the corresponding eye,
a deceptive resemblance may be produced to the actual appearance
of solid objects. This is accomplished in the contrivance known
as the Stereoscope. Thus, if two pictures similar to those in Figs.
163 and 164 be so placed that one shall be seen only with the right
eye and the other with the left, the combination of the two figures
will take place as if they came from the real object, and all the
natural projections will come out in relief.
But this effect is produced only in the case of objects situated
within a moderately short distance. For very remote objects, we
lose the impression of solidity, since the difference in the images on
the two eyes becomes so, slight as to be inappreciable, and we see
only a plane expanse of surface, with sharp outlines and various
shades of color, but no actual projections or depressions.
The sensibility of the retina is such that it cannot distinguish
luminous points which are received upon its surface at a very
minute distance from  each other. In this - particular, the sensibility
of the retina resembles that of the skin, since we have already
found that the integument cannot distinguish the impressions
made by the points of two needles placed a very short distance
apart. The delicacy of this discriminating power, in the retina, is
immeasurably superior to that of the skin; and yet it has its
limits, even in the nervous expansion of the eye. For if we look
at an object which is excessively minute, or which is so remote
that its apparent size is very much diminished, we lose the power
of distinguishing its different parts, and can no longer perceive
its real outline. This is a very different condition from that in
which the confusion of vision arises from defect of focusing in the
eye, as, for example, in long or short-sightedness, or where the
object is placed too near the eye or too much on one side. For
when the difficulty depends simply on its minute size or its remoteness, the rays coming from the top of the object and those coming
from the bottom, are all brought to their proper focus at distinct
points on the retina-only these points are too near. each other for the
retina to distinguish them apart. Consequently we can no longer
appreciate the form of the object.
For the same reason, when we mix together minute grains of a
different hue, we produce an intermediate color. If yellow and
blue be mingled in this way, we no longer perceive the separate
blue and yellow grains, but only a uniform tinge of green; and




488                 THE SPECIAL SENSES.
white and black granules, mixed together, produce, at a short distance, the appearance of a continuous shade of gray.
Impressions, once produced upon the retina, remain for a short time
afterward. Usually these impressions are so evanescent after the
removal of their immediate cause, and are so soon followed by
others which are more vivid, that we do not notice their existence.
They may very readily be demonstrated, however, by swinging
rapidly in a circle before the eyes, in a dark room, a stick lighted
at one end. As soon as the motion has attained a certain degree of
velocity, the impression produced on the retina, when the lighted
end of the stick arrives at any particular spot, remains until it has
completed its revolution and has again reached the same point;
so that the effect thus produced upon the eye is that of a continuous circle of light.  The same fact has been illustrated by the
optical contrivance, known as the Thaumatrope, in which successive
pictures of similar figures in different positions are made to revolve
rapidly before the eye, and thus to produce the apparent effect of a
single figure in rapid motion;-since the eye fails to perceive the
intervals between the different pictures.
The sense of vision, therefore, through the impressions of light,
gives us ideas of form, size, color, position, distance, and movement.
But these ideas may also be excited by impressions derived from
an internal source, as well as those produced by rays coming from
without. And it is one of the most striking peculiarities of the
sense of sight that these ideal or internal impressions, which are
excited in it by various causes, are much more vivid and powerful
than those of any other of the senses. Thus, in a dream, we often see
external objects, with all their visible peculiarities of light, color,
form, &c., nearly or quite as distinctly as when we are awake; but
the imaginary impressions of sound, in this condition, are always
comparatively faint, and those of taste, smell, and touch, almost
entirely imperceptible. Even in a reverie, in the waking condition, when the absorption of the mind in its own thoughts is complete, and we are withdrawn altogether from outward influences,
we see objects which have no present existence as if they were
actually before us. It is this sense also which becomes most easily
and thoroughly excited in certain nervous disorders; as, for example, in delirium tremens, where the patient often sees passing before
his eyes extensive and magnificent landscapes, crowds of human
faces and figures, and series of towns and cities, which seem to be
depicted upon the imagination with a force and distinctness, much




HEARING.                         489
superior to that of other delirious impressions. Since the sense of
sight, therefore, depends less directly than the other senses upon
the actual contact of material objects, it is also more easily thrown
into activity when withdrawn from their influence.
HEARING.-The sense of hearing depends upon the vibrations
excited in the atmosphere by sonorous bodies, which are themselves
first thrown into vibration by various causes, and which then communicate similar undulations to the surrounding air. These sonorous vibrations are of such a character that they cannot be directly
appreciated by ordinary sensibility, but the result of numerous and
well-directed physical experiments on this subject leaves no doubt
whatever of their existence; and when such vibrations are communicated to the auditory apparatus, they produce in it the sensation
of sound.
In the case of the aquatic animals, which pass their entire existence beneath the surface of the water, the water itself, which is
capable of vibrating in the same way, communicates the sonorous
impressions to the organ of hearing; but in the terrestrial animals,
and particularly in man, it is the atmosphere which always serves
as the medium of transmission.
The auditory apparatus, in man and in the quadrupeds, consists,
first, of a somewhat expanded and trumpet-shaped mouth, or external ear, destined to receive and collect the sonorous impulses
coming from various quarters. This external ear is constructed
of a cartilaginous framework, covered with integument, loosely
attached to the bones of the head, and more or less movable by
means of various muscles, which by their contraction turn its
expanded orifice in different directions. In man, the movements
of the external ear are almost always inappreciable, though the
muscles are easily demonstrated; but in many of the lower animals
these movements are exceedingly varied and extensive, and play a
very important part in the working of the auditory apparatus.
At the bottom of the external ear, its orifice is prolonged into a
tube or canal, the external auditory meatus, partly cartilaginous and
partly bony, which penetrates the lateral part of the temporal bone
in a nearly horizontal and transverse direction. In the human
subject, this canal is a little over one inch in length, and is lined
by a continuation of the external integument. The integument
toward its outer portion is beset with small hairs, and provided
with ceruminous glands which supply a secretion of a waxy or




490                THE SPECIAL SENSES.
resinous consistency. By these means the passage is protected
from the accidental ingress of various foreign bodies.
Secondly, at the bottom of the external meatus the auditory passage is closed by a thin fibrous membrane, stretched across its cavity,
called the membrana tympani. Upon this membrane are received the
sonorous vibrations which have been collected by the external ear
and conducted inward by the external auditory meatus. Behind
the membrana tympani is the cavity of the middle ear, or the cavity
of the tympanum. This cavity communicates posteriorly with the
mastoid cells, and anteriorly with the pharynx, by a narrow passage,
lined with ciliated epithelium, and running downward, forward and
inward, called the Eustachian tube. A chain of small bones, the
malleus, incus, and stapes, is stretched across the cavity of the
tympanum, and forms a communication between the membrana
tympani on the outside, and the membrane closing the foramen
ovale in the petrous portion of the temporal bone. All the vibrations, accordingly, which are received by the membrana tympani,
are transmitted by the chain of bones to. the membrane of the
foramen ovale. The tension of the membranes is regulated by two
small muscles, the tensor tympani and stapedius muscles, which arise
from the bony parts in the neighborhood, and are inserted respectively into the neck of the malleus and the head of the stapes, and
which draw these bones forward and backward upon their articulations.
Thirdly, behind the membrane of the foramen ovale lies the
labyrinth, or internal ear. This consists of a complicated cavity,
excavated in the petrous portion of the temporal bone, and comprising an ovoid central portion, the vestibule, a double spiral canal,
the cochlea, and three semicircular canals, all communicating by
means of the common vestibule. All parts of this cavity contain
a watery fluid, termed the perilymph. The vestibule and semicircular canals also contain closed membranous sacs, suspended in
the fluid of the perilymph, which reproduce exactly the form of
the bony cavities themselves, and communicate with each other in
a similar way. These sacs are filled with another watery fluid,
the endolymph; and the terminal filaments of the auditory nerve
are distributed upon the membranous sac of the vestibule and upon
the ampullke, or membranous dilatations, at the commencement of
the three semicircular canals. The remaining portion of the auditory nerve is distributed upon the septum between the two spiral
canals of the cochlea.




HEARING.                         491
Thus, the essential or fundamental portion of the auditory apparatus is evidently the internal ear, a cavity, partly membranous and
partly bony, in which is distributed a nerve of special sense, the
auditory nerve, capable of appreciating sonorous impressions. The
accessory parts, on the other hand, are the chain of bones and the
membrane of the tympanum, which communicate the sonorous
vibrations directly to the internal ear; and the meatus and external
ear, which collect them from the atmosphere. The reception of
Fig. 165.
H IIMAN AuDITORY APPARATUS, showing external auditory meatus, tympanum, and labyrinth.
sonorous impulses is therefore accomplished in a very indirect way.
For the sonorous body first communicates its vibrations to the
atmosphere. By the atmosphere these vibrations are communicated
to the membrana tympani. From the membrana tympani, they are
transmitted, through the chain of bones, to the membrane of the
foramen ovale; thence to the perilymph, or fluid of the labyrinthic
cavity, and from the perilymph to the membranous parts of the
labyrinth and the nerves which are distributed upon them.
The arrangement of the different parts composing the tynmpanum
is of the greatest importance for the perfect enjoyment of the sense
of hearing. For the air on the two sides of the membrane of the
tympanur should be in the same condition of elasticity in order to
allow of the proper vibration of the membrane; and this equilibrium
would be liable to disturbance if the air within the tympanum were
completely confined, while that outside is subjected to variations
of barometric pressure. By means of the Eustachian tube, how.



492                 THE SPECIAL SENSES.
ever, a communication is established between the cavity of the
tympanum and the exterior, and the free vibration of the membrane
is thus secured.
The exact tension of the membrana tympani itself is also provided
for, as we have already observed, by the action of the two muscles
inserted into the malleus and the stapes. By the contraction of
the internal muscle. of the malleus, or tensor tympani, the membrane
of the tympanum  is drawn inward and rendered more tense than
usual. The action of the stapedius muscle is by some thought to
relax the membrana tympani, by others to assist in the tension
both of this membrane and that of the foramen ovale, to which
the stapes is attached. But there is no doubt that both these muscles, by their combined or alternate action, can regulate the tension
of the tympanic membrane, to an extraordinary degree of nicety,
and thus increase the ease and delicacy with which various sounds
are distinguished. For if the membrane be so put upon the stretch
that its fundamental note shall be the same with that of the sound
which is to be heard, it will vibrate more readily in consonance
with the undulations of the atmosphere, and the sound will be
more distinctly heard. On the contrary, if the membrane be too
highly stretched, very grave sounds may not be heard at all, until
its tension is diminished to the requisite degree.
Contrary to what is sometimes asserted, the communication of
sonorous impulses to the internal ear is accomplished altogether by
means of the tympanum and chain of bones. It has been thought that
sounds were transmitted, in many instances, directly to the internal
ear by the medium of the cranial bones. This was inferred from
such facts as the following. If a tuning-fork, in vibration, be taken
between the teeth, its sound will appear very much louder than
if it were simply held near the external ear; and if, while it is so
held, one of the ears be closed, the sound will appear very much
louder on that side than on the other. The sound will also be heard
if the tuning-fork be applied to the upper part of the cranium  or
the mastoid process, with a similar increase of resonance on closing
the ears. Finally our own voices are heard, though the ears be
both closed, and the sound is much louder with the ears closed
than open.
These are the facts which have led to the belief that, in such
instances, the sound was communicated directly through the bones
of the head, vibrating in consonance with the sounding body. But
a little examination will show that such is not the case. When we




HEARING.                         493
hold the end of a vibrating tuning-fork between the teeth, we no
longer hear the sound in the vibrating extremity of the instrument
or its neighborhood, but in the mouth and the nasal fossce. It is the
vibration of the air in these passages which produces the sound;
and this vibration is communicated to the cavity of the tympanum
through the Eustachian tube. The apparent increase of sound, also,
on closing the ears, which could not be explained on the supposition
that it was conducted directly through the bones of the cranium,
is due to the same cause. For it can easily be seen, on trying the
experiment, either with a tuning-fork held between the teeth or
simply with our own voices, that this apparent increase of sound
takes place only when the ears are closed by gentle pressure. If the
pressure be excessive, so that the integument is forced inward into
the -neatus and the air in the meatus subjected to undue compression, the sound no longer appears louder in the corresponding ear,
and may even be lost altogether.
The apparent increase of sound, therefore, in such cases, when
the ear is gently closed, is due to the fact that the meatus is thus
converted into a reverberatory cavity, by which the vibrations of
the tympanum  are increased in intensity. But if the air in the
meatus be too much compressed by forcible closure, the vibrations
of the tympanum  are then interfered with and the sound is diminished or destroyed.
In all cases, then, it is the sonorous vibrations of the air which
produce the sound, and these vibrations are received invariably by
the membrane of the tympanum, and thence transmitted to the
internal ear by the chain of bones. The cranial bones are incapable
of communicating these vibrations to the labyrinth and its contents,
except very faintly and imperfectly. For common experience shows
that even the loudest and sharpest sounds, coming from without,
are almost entirely lost on closing the external ears; and our own
respiratory and cardiac sounds, which are so easily heard as soon
as the chest is connected with the ear by a flexible stethoscope, are
entirely inaudible to us in the usual condition.
The exact function of the different parts of the internal ear is
not well understood. It has been thought to be the office of the
semicircular canals to determine the direction from which the sono
rous impulses are propagated. This opinion was based upon the
curious fact that these canals, always three in number, are placed
in such positions as to correspond with the three different directions
of vertical height, lateral extension, and longitudinal extension;




494                THE SPECIAL SENSES.
for one of them is nearly vertical and transverse, another vertical
and longitudinal, and the third horizontal in position. The sonorous impulses, therefore, coming in either of these directions, would
be received by only one of the semicircular canals (by direct conduction through the bones of the head) perpendicularly to its own
plane; and an intermediate direction, it was thought, might be
appreciated by the combined effect of the impulse upon two adjacent canals.
Enough has already been said, however, in regard to the communication of sound directly through the bones of the head to the
internal ear, to show that this cannot be the way in which the direction of sound is ascertained. Indeed, when we hear any loud and
well-marked sound coming from  a particular region, such as the
music of a military band or the whistle of a locomotive, we have only
to close the external ears to lose our perception both of the sound
and its direction. The direction of sonorous impressions is appreciated in a different way. In the first place, we feel that the sound
comes from one side or the other, by its making a more distinct
impression on one ear than the opposite; and by inclining the
head slightly in various directions, we easily ascertain whether the
sound becomes more or less acute, and so judge of its actual source.
Many of the lower animals, whose ears are very large and movable,
use this method to great extent. A horse, for example, when upon
the road, often keeps his ears in constant motion, feeling, as it were,
in the distance, for the origin of the various sounds which excite
his attention.
Beside the above, we are further assisted in our judgment of the
direction of sounds by our previous knowledge of the localities,
the direction of the wind, and the manner in which the sound is
reflected by surrounding objects. When these sources of information fail us, we are often at a loss. It is notoriously difficult, for
example, to judge of the place of the chirping of a cricket in a
perfectly closed room, or of the direction of a bell heard on the
water in a thick fog.
The sense of hearing has a much closer analogy with ordinary
sensibility than that of sight. Thus, in the first place, hearing is
accomplished by the direct intervention and contact of a material
body-the atmosphere; for sonorous impulses cannot be produced
in a vacuum, and we hear no sound from  a bell rung under an
exhausted receiver. Secondly, the nature of the impressions produced by sound is such that we can often describe them by the




ON THE SENSES IN GENERAL.                   495
same terms which are applied to ordinary sensations. Thus, we
speak of sounds as sharp and dull, piercing, smooth, or rough; and
we feel the impulse of a sudden and violent explosive sound, like
that of a blow upon the tympanum.
By this sense, therefore, we distinguish the quality, intensity,
pitch, duration, and direction of sonorous impulses. The delicacy
with which these distinctions are appreciated varies considerably
in different individuals; and in different kinds of animals there is
reason to believe that the diversity is much greater, some of them
being almost insensible to sounds which are readily perceived by
others. In man, the number and variety of tones which can usually be discriminated is very great; and this sense, accordingly, in
the complication and finish of its apparatus, and the perfection and
delicacy of its action, must be regarded as second only to that of
vision.
ON THE SENSES IN GENERAL. —There are several facts connected
with the operation of the senses, both general and special, which
are common to all of them, and which still remain to be considered.
In the first place, an impression of any kind, made upon a sensitive organ, remains for a time after the removal of its exciting cause.
We have already noticed this in regard to the senses of taste, smell,
and sight, but it is equally true of the hearing and the touch.
Thus, if the skin be touched with a piece of ice, the acute sensation remains for a few seconds, whether the ice be removed or not.
For the higher order of the special senses, the time during which
this secondary impression remains is a shorter one. In the case of
hearing, however, it has been measured with a tolerable approach
to accuracy; for it has been found that, if the sonorous undulations
follow each other with a greater rapidity than sixteen times per
second, they become fused together into a continuous sound, producing upon the ear the impression of a musical note. The varying
pitch of the note depends upon the rapidity with which the vibrations succeed each other.  When the succession of vibrations is
very rapid, a high note is the result, and when comparatively slow,
a low note is produced; but when the number of impulses falls
below sixteen per second, we then begin to perceive the distinct
vibrations, and so lose the impression of a continuous note.
All the senses, in the second place, become accustomed to a continued impression, so that they no longer perceive its existence.
Thus, if a perfectly uniform pressure be exerted upon any part of




496                 THE SPECIAL SENSES.
the body, the compressing substance after a time fails to excite any
sensation in the skin, and we remain unconscious of its existence.
In order to attract our notice, it is then necessary to increase or
diminish the pressure; while, so long as this remains uniform, no
effect is perceived. But if, after the skin has thus become accustomed to its presence, the foreign body be suddenly removed, our
attention is then immediately excited, and we notice the absence of
an impression, in the same way as if it were a positive sensation.
We all know how rapidly we become habituated to odors, whether
agreeable or disagreeable in their nature, in the confined air of a
close apartment; although, on first entering from  without our
attention may have been attracted by them  in a very decided
manner. A continuous and uniform  sound, also, like the steady
rumbling of carriages, or the monotonous hissing of boiling water,
becomes after a time inaudible to us; but as soon as the sound
ceases, we notice the alteration, and our attention is at once excited.
The senses, accordingly, receive their stimulus more from the variations and contrasts of external impressions, than from these impressions themselves.
Another important particular, in regard to the senses, is their
capacityfor education. The proofs of this are too common and too
apparent to need more than a simple allusion. The touch may be
so trained that the blind may read words and sentences by its aid,
in raised letters, where an ordinary observer would hardly detect
anything more than a barely distinguishable inequality of surface.
The educated eye of the artist, or the naturalist, will distinguish
variations of color, size, and outline, altogether inappreciable to
ordinary vision; and the senses of taste and smell, in those who are
in the habit of examining wines and perfumes, acquire a similar
superiority of discriminating power.
In these instances, however, it is not probable that the organ of
sense itself becomes any more perfect in organization, or more
susceptible to  sensitive impressions.  The increased functional
power, developed by cultivation, depends rather upon the greater
delicacy of the perceptive and discriminative faculties. It is a mental
and hot a physical superiority which gives the painter or the
naturalist a greater power of distinguishing colors and outlines,
and which enables the physician to detect nice variations of quality
in the sounds of the heart or the respiratory murmur of the lungs.
The impressions of external objects, therefore, in order to produce
their complete effect, must first be received by a sensitive appa



ON THE SENSES IN GENERAL.                 497
ratus, which is perfect in organization and functional activity;
and, secondly, these impressions must be subjected to the action of
an intelligent perception, by which their nature, source and relations may be fully appreciated.
That part of the nervous system  which we have hitherto
studied, viz., the cerebro-spinal system, consists of an apparatus of
nerves and ganglia, destined to bring the individual into relation
with the external world. By means of the special senses, he is
made cognizant of sights, sounds, tastes, and odors, by which he
is attracted or repelled, and which guide him in the pursuit and
choice of food. By the general sensations of touch and the voluntary movements, he is enabled to alter at will his position and
location, and to adapt them to the varying conditions under which
he may be placed. The great passages of entrance into the body,
and of exit from it, are guarded by the same portion of the nervous system. The introduction of food into the mouth, and its
passage through the cesophagus to the stomach, are regulated by
the same nervous apparatus; and even the passage of air through
the larynx, and its penetration into the lungs, are equally under
the guidance of sensitive and motor nerves belonging to the
cerebro-spinal system.
It will be observed that the above functions relate altogether
either to external phenomena or to the simple introduction into the
body of food and air, which are destined to undergo nutritive
changes in the interior of the frame.
If we examine, however, the deeper regions of the body, we find
located in them a series of internal phenomena, relating only to
the substances and materials which have already penetrated into
the frame, and which form or are forming a part of its structure.
These are the purely vegetative functions, as they are called; or
those of growth, nutrition, secretion, excretion, and reproduction.
These functions, and the organs to which they belong, are not
under the direct influence of the cerebro-spinal nerves, but are
regulated by another portion of the nervous system, viz., the
"ganglionic system;" or, as it is more commonly called, the "system of the great sympathetic."
32




498       SYSTEM OF THE GREAT SYMPATHETIC.
CHAPTER VII.
SYSTEM OF THE GREAT SYMPATHETIC.
THE sympathetic system consists of a double chain of nervous
ganglia, running from the anterior to the posterior extremity of the
body, along the front and sides of the spinal column, and connected
with each other by slender longitudinal filaments. Each ganglion
is reinforced by a motor and sensitive filament derived from the
cerebro-spinal system, and thus the organs under its influence are
brought indirectly into communication with external objects and
phenomena. The nerves of the great sympathetic are distributed
to organs over which the consciousness and the will have no imnediate control, as the intestine, kidneys, heart, liver, &c.
The first sympathetic ganglion in the head is the ophthalmic ganglion. This ganglion is situated within the orbit of the eye, on the
outer aspect of the optic nerve. It communicates by slender filaments with the carotid plexus, which forms the continuation of the
sympathetic system from below; and receives a motor root from
the oculo-motorius nerve, and a sensitive root from the ophthalmic
branch of the fifth pair. Its filaments of distribution, known as the
"ciliary nerves," pass forward upon the eyeball, pierce the sclerotic,
and finally terminate in the iris.
The next division of the great sympathetic in the head is the
spheno-palatine ganglion, situated in the spheno-maxillary fossa. It
communicates, like the preceding, with the carotid plexus, and
receives a motor root from the facial nerve, and a sensitive root
from the superior maxillary branch of the fifth pair. Its filaments
are distributed to the levator palati and azygos uvula muscles, and
to the mucous membrane about the posterior nares.
The third sympathetic ganglion in the head is the submaxillary,
situated upon the submaxillary gland. It communicates with the
superior cervical ganglion of the sympathetic by filaments which
accompany the facial and external carotid arteries. It derives its
sensitive filaments from the lingual branch of the fifth pair, and its




SYSTEM  OF THE GREAT SYMPATHETIC.               499
motor filaments from the facial nerve, by means of the chorda
tympani. Its branches of distribution pass to the sides of the tongue
and to the submaxillary and sublingual glands.
The last sympathetic ganglion in the head is the otic ganglion.
It is situated just beneath the
base of the skull, on the inner            Fig. 166.
side of the third division of
the fifth pair. It sends filaments of communication to 
the carotid plexus; and receives a motor root from the
facial nerve, and a sensitive
root from the inferior maxillary division of the fifth pair.
Its branches are sent to the
internal muscle of the malleus in the middle ear (tensor
tympani), and to the mucous  
membrane of the tympanum 
and Eustachian tube.
The continuation of the
sympathetic nerve in the neck
consists of two and sometimes three ganglia, the superior, middle, and inferior.
These ganglia communicate          s
with  each  other, and  also
with the anterior branches
of the cervical spinal nerves.
Their filaments follow  the
course of the carotid artery,
and  its' branches, covering           E'~
them with a network of interlacing fibres, and are finally
distributed to the substance of
Course and distribution of the GREAT SYMPrAthe thyroid gland, and to the THETIC.
walls of the larynx, trachea,
pharynx, and cesophagus. By the superior, middle, and inferior
cardiac nerves, they also supply sympathetic fibres to the cardiac
plexuses and to the substance of the heart.
In the chest, the ganglia of the sympathetic nerve are situated on




500        SYSTEM  OF THE GREAT SYMPATHETIC.
each side the spinal column, just over the heads of the ribs, with
which they accordingly correspond in number. Their communications with the intercostal nerves are double; each sympathetic
ganglion receiving two filaments from the intercostal nerve next
above it. The filaments originating from the thoracic ganglia are
distributed upon the thoracic aorta, and to the lungs and cesophagus.
In the abdomen, the continuation of the sympathetic system consists principally of the aggregation of ganglionic enlargements
situated upon the cceliac artery, known as the semilunar or coeliac
ganglion. From this ganglion a multitude of radiating and inosculating branches are sent out, which, from their diverging course and
their common origin from a central mass, are termed the "solar
plexus."  From  this, other diverging plexuses originate, which
accompany the abdominal aorta and its branches, and are distributed to the stomach, small and large intestine, spleen, pancreas,
liver, kidneys, supra-renal capsules, and internal organs of generation.
Beside the above ganglia there are in the abdomen four other
pairs, situated in front of the lumbar vertebrae, and having similar
connections with those occupying the cavity of the chest. Their
filaments join the plexuses radiating from the semilunar ganglion.
In the pelvis, the sympathetic system is continued by four or five
pairs of ganglia, situated on the anterior aspect of the sacrum, and
terminating, at the lower extremity of the spinal column, in a single
ganglion, the "ganglion impar," which is probably to be regarded
as a fusion of two separate ganglia.
The entire sympathetic series is in this way composed of numerous small ganglia which are connected throughout, first, with each
other; secondly, with the cerebro-spinal system; and thirdly, with
the internal viscera of the body.
The properties and functions of the great sympathetic have been
less successfully studied than those of the cerebro-spinal system,
owing to the anatomical difficulties in the way of reaching and
operating upon this nerve for purposes of experiment. The cerebrospinal axis and its nerves are easily exposed and subjected to examination. It is also easy to isolate particular portions of this system,
and to appreciate the disturbances of sensation and motion consequent upon local lesions or irritations.  The phenomena, furthermore, which result from experiments upon this part of the nervous
apparatus, are promptly produced, are well-marked in character,
and are, as a general rule, readily understood by the experimenter.




SYSTEM  OF THE GREAT SYMPATHETIC.               501
On the other hand, the principal part of the sympathetic system is
situated in the interior of the chest and abdomen; and the mere
operation of opening these cavities, so as to reach the ganglionic
centres, causes such a disturbance in the functions of vital organs,
and such a shock to the system at large, that the results of these
experiments have been always more or less confused and unsatisfactory. Furthermore, the connections of the sympathetic ganglia
with each other and with the cerebro-spinal axis are so numerous
and so scattered, that these ganglia cannot be completely isolated
without resorting to an operation still more mutilating and injurious in its character. And finally, the sensible phenomena which
are obtained by experimenting on the great sympathetic are, in
the majority of cases, slow in making their appearance, and not
particularly striking or characteristic in their nature.
Notwithstanding these difficulties, however, some facts have been
ascertained with regard to this part of the nervous system, which
give us a certain degree of insight into its character and functions.
The great sympathetic is endowed both with sensibility and the
power of exciting motion; but these properties are less active
here than in the cerebro-spinal system, and are exercised in a different manner. If we irritate, for example, a sensitive nerve in
one of the extremities, or apply the galvanic current to the posterior root of a spinal nerve, the evidences of pain or of reflex
action are acute and instantaneous. There is no appreciable interval between the application of the stimulus and the sensations
which result from it. On the other hand, experimenters who have
operated upon the sympathetic ganglia and nerves of the chest and
abdomen find that evidences of sensibility are distinctly manifested
here also, but much less acutely and only after somewhat prolonged
application of the irritating cause. These results correspond very
closely with what we know of the vital properties of the organs
which are supplied either principally or exclusively by the sympathetic; as the liver, intestine, kidneys, &c. These organs are
insensible, or nearly so, to ordinary impressions. We are not conscious of the changes and operations going on in them, so long as
these changes and operations retain their normal character. But
they are still capable of perceiving unusual or excessive irritations,
and may even become exceedingly painful, when in a state of inflammation.
There is the same peculiar character in the action of the motor
nerves belonging to the sympathetic system. If the facial or hypo



502       SYSTEM OF THE GREAT SYMPATHETIC.
glossal, or the anterior root of a spinal nerve be irritated, the convulsive movement which follows is instantaneous, violent, and only
momentary in its duration. But if the semilunar ganglion or its
nerves be subjected to a similar experiment, no immediate effect is
produced. It is only after a few seconds that a slow, vermicular,
progressive contraction takes place in the corresponding part of the
intestine, which continues for some time after the exciting cause
has been removed.
Morbid changes taking place in organs supplied by the sympathetic present a similar peculiarity in the mode of their production. If the body be exposed to cold and dampness, for example,
congestion of the kidneys shows itself perhaps on the following
day. Inflammation of any of the internal organs is very rarely
established within twelve or twenty-four hours after the application
of the exciting cause. The internal processes of nutrition, together
with their derangements, which are regarded as especially under
the control of the great sympathetic, always require a longer time
to be influenced by incidental causes, than those which are regulated
by the nerves and ganglia of the cerebro-spinal system.
In the head, the sympathetic has a close and important connection with the exercise of the special senses. This is illustrated
more particularly, in the case of the eye, by its influence over the
alternate expansion and contraction of the pupil. The ophthalmic
ganglion sends off a number of ciliary nerves, which are distributed
to the iris. It is connected, as we have seen, with the remaining
sympathetic ganglia in the head, and receives, beside, a sensitive
root from the ophthalmic branch of the fifth pair, and a motor root
from the oculo-motorius. The reflex action by which the pupil
contracts under a strong light falling upon the retina, and expands
under a diminution of light, takes place, accordingly, through this
ganglion. The impression conveyed by the optic nerve to the
tubercula quadrigemina, and reflected outward by the fibres of
the oculo-motorius, is not transmitted directly by the last named
nerve to the iris; but passes first to the ophthalmic ganglion, and
is thence conveyed to its destination by the ciliary nerves.
The reflex movements of the iris exhibit consequently a somewhat sluggish character, which indicates the intervention of a part
of the sympathetic system. The changes in the size of the pupil
do not take place instantaneously, with the variation in the amount
of light, but always require an appreciable interval of time. If
we pass suddenly from a brilliantly lighted apartment into a dark




SYSTEM  OF THE GREAT SYMPATHETIC.               503
room, we are unable to distinguish surrounding objects until a
certain time has elapsed, and the expansion of the pupil has taken
place; and vision even continues to grow more and more distinct
for a considerable period afterward, as the expansion of the pupil
becomes more complete. Again, if we cover the eyes of another
person with the hand or a folded cloth, and then suddenly expose
them to the light, we shall find that the pupil, which is at first
dilated, contracts somewhat rapidly to a certain extent, and afterward continues to diminish in size during several seconds, until the
proper equilibrium  is fairly established. Furthermore, if we pass
suddenly from a dark room into the bright sunshine, we are immediately conscious of a painful sensation in the eye, which lasts for
a considerable time; and which results from the inability of the
pupil to contract with sufficient rapidity to shut out the excessive
amount of light. All such exposures should be made gradually,
so that the movements of the iris may keep pace with the varying
quantity of stimulus, and so protect the eye from injurious impressions.
The reflex movements of the iris, however, though accomplished
through the medium  of the ophthalmic ganglion, derive their
original stimulus, through the motor root of this ganglion, from
the oculo-motorius nerve. For it has been found that if the oculomotorius nerve be divided between the brain and the eyeball, the
pupil becomes immediately dilated, and will no longer contract
under the influence of light. The motive power originally derived
from the brain is, therefore, in the case of the iris, modified by
passing through one of the sympathetic ganglia before it reaches
its final destination.
An extremely interesting fact in this connection is the following.
Of the three organs of special sense in the head, viz., the eye, the
nose, and the ear, each one is provided with two sets of muscles,
superficial and deep, which together regulate the quantity of stimulus admitted to the organ, and the mode in which it is received.
The superficial set of these muscles is animated by branches of the
facial nerve; the deep-seated or internal set, by filaments from a
sympathetic ganglion.
Thus, the front of the eyeball is protected by the orbicularis and
levator palpebrae superioris muscles, which open or close the eyelids at will, and allow a larger or smaller quantity of light to reach
the cornea. These muscles are supplied by the oculo-motorius and
facial nerves, and are for the most part voluntary in their action.




504        SYSTEM  OF THE GREAT SYMPATHETIC.
The iris, on the other hand, is a more deeply-seated muscular
curtain, which regulates the quantity of light admitted through the
pupil. There is also the ciliary muscle, which regulates the position
of the crystalline lens, and secures a correct focusing of the light,
at different distances. Both these muscles are supplied, as we have
seen, by filaments from the ophthalmic ganglion, and their movements are involuntary in character.
In the olfactory apparatus, the anterior or superficial set of
muscles are the compressors and elevators of the ale nasi, which
are animated by filaments of the facial nerve. By their action,
odoriferous vapors, when faint and delicate in their character, are
snuffed up and directed into the upper part of the nasal passages,
where they come in contact with the most sensitive portions of the
olfactory membrane; or, if too pungent or disagreeable in flavor,
are excluded from  entrance.  These muscles are not very important or active in the human subject; but in many of the lower
animals with a more active and powerful sense of smell, as, for
example, the carnivora, they may be seen to play a very important
part in the mechanism of olfaction. Furthermore, the levators and
depressors of the velum palati, which are more deeply situated,
serve to open or close the orifice of the posterior nares, and accomplish a similar office with the muscles already named in front. The
levator palati and azygos uvulae muscles, which, by their action,
tend to close the posterior nares, are supplied by filaments from the
spheno-palatine ganglion, and are involuntary in their character.
The ear has two similar sets of muscles, similarly supplied. The
first, or superficial set, are those moving the external ear, viz., the
anterior, superior, and posterior auriculares. Like the muscles of
the anterior nares, they are comparatively inactive in man, but in
many of the lower animals are well developed and important. In
the horse, the deer, the sheep, &c., they turn the ear in various
directions so as to catch more distinctly faint and distant sounds, or
to exclude those which are harsh and disagreeable. These muscles
are supplied by filaments of the facial nerve, and are voluntary in
their action.
The deep-seated set are the muscles of the middle ear. In order
to understand their action, we must recollect that sounds are transmitted from the external to the middle ear through the membrane
of the tympanum, which vibrates, like the head of a drum, on
receiving sonorous impulses from without.
The membrane of the tympanum, accordingly, which is an elastic




SYSTEM  OF THE GREAT SYMPATHETIC.                505
sheet, stretched across the passage to the internal ear, may be made
more or less sensitive to sonorous impressions by varying its condition of tension or relaxation. This condition is regulated, as we
have already seen, by the combined action of the two muscles of
the middle ear, viz., the tensor tympani and the stapedius. The
first named muscle, the action of which is perfectly well understood,
is supplied with nervous filaments from the otic ganglion of the
sympathetic. By its contraction, the handle of the malleus is drawn
inward, bringing the membrana tympani with it, and putting this
membrane upon the stretch. On the relaxation of the muscle, the
chain of bones returns to its ordinary position, by the elasticity of
the neighboring parts, and the previous condition of the tympanic
membrane is restored. This action, so far as we can judge, is purely
involuntary. But the stapedius muscle is separately supplied by a
minute branch of the facial nerve. It is probable that this arrangement enables us to make also a certain degree of voluntary exertion, in listening intently for faint or distant sounds.
In all these instances, the reflex action taking place in the
deeper seated muscles, originates from  a sensation which is conveyed inward to the cerebro-spinal centres, and is then transmitted
outward to its final destination through the medium of one of the
sympathetic ganglia.
Another very striking fact concerning the sympathetic relates to
the changes produced by its division, in the nutritive processes of
the parts supplied by it. One of the most important and remarkable of these changes is an elevation of temperature in the affected
parts. If the sympathetic nerve be divided on one side of the neck,
in the rabbit, cat, or dog, an elevation of temperature begins to be
perceptible on the corresponding side of the head in a very short
time. In the cat, we have found a very sensible difference in temperature between the two sides at the end of five or ten minutes;
and in the rabbit, at the end of half an hour. A vascular congestion of the parts also takes place, which may be seen to great
advantage in the ear of the rabbit, when held up between the eye
and the light. The elevation of temperature, in these cases, is very
perceptible to the touch, and may be also measured by the thermometer. Bernard' has found it to reach 80 or 90 F. The elevation
of temperature and congested state of the parts are sometimes found
to be diminished by the next day, and afterward disappear rapidly.
Occasionally, however, they last for a long time. Bernard (op. cit.)
I Recherches exp6rimentales sur le Grand Sympathique. Paris, 1854.




506        SYSTEM  OF THE GREAT SYMPATHETIC.
has seen the unnatural temperature of the affected parts remain, in
the rabbit, from fifteen to eighteen days, and in the dog for two
months. Where the superior cervical ganglion has been extirpated,
he has even found the above appearances to continue, in the dog, for
a year and a half. They may also, according to the same authority,
be reproduced several times in the same animal, by repeated divisions of the sympathetic nerve.
The above effect is due to a peculiar modification in the nutrition of the affected parts, which has some analogy with inflammation. The unnatural heat, the congestion, and the increased sensibility which are present, all serve to indicate a certain resemblance
between the two conditions. None of the more serious consequences
of inflammation, however, such as cedema, exudation, sloughing or
ulceration, have ever been known to follow from this operation;
and the term inflammation, accordingly, cannot properly be applied
to its results.
Division of the sympathetic nerve in the middle of the neck
has also a very singular and instantaneous effect on the muscular
apparatus of the eye. Within a very few seconds after the above
operation has been performed upon the cat, the pupil of the corresponding eye becomes strongly contracted, and remains in that
condition. At the same time the third eyelid, or "nictitating membrane," with which these animals are provided, is drawn partially
over the cornea, and the upper and lower eyelids also approximate very considerably to each other; so that all the apertures
guarding the eyeball are very
Fig. 167.           perceptibly narrowed, and the ex-i      pression of the face on that side is
altered in a corresponding degree.
This effect upon the pupil has
]:  m'~! been explained by supposing the
circular fibres of the iris, or the'/ ~!     /!constrictors of the pupil, to be
animated exclusively by nervous
X)    | filaments derived from the oculo/  f\:,,;..J.\\    motorius; and the radiating fibres,
jk, J           or the dilators, to be supplied by
CAT, after section of the right sympathetic.  the sympathetic.  Accordingly,
while division of the oculo-motorious would produce dilatation of the pupil, by paralysis of the
circular fibres only, division of the sympathetic would be fol



SYSTEM  OF THE GREAT SYMPATHETIC.                507
lowed by exclusive paralysis of the dilators, and a permanent
contraction of the pupil would consequently take place. The
above explanation, however, is not a satisfactory one; since, in
the first place, division of the oculo-motorius, as the experiments of
Bernard have shown,' does not by itself produce complete dilatation of the pupil; and, secondly, afterdivision of the sympathetic
nerve in the cat, as we have already shown, not only is the pupil
contracted, but both the upper and lower eyelids and the nictitating
membrane are also partially drawn over the cornea, and assist in
excluding the light. The last-named effect cannot be owing to any
direct paralysis, from division of the fibres of the sympathetic. It
is more probable that the section of this nerve operates simply by
exaggerating for a time the sensibility of the retina, as it does that
of the integument;- and that the partial closure of the eyelids and
pupil is a secondary consequence of that condition.
It will be remembered that in describing the inflammation of the
eyeball, consequent upon section of the fifth pair of nerves, we
found that there were reasons for believing this effect to be due
to injury of certain sympathetic fibres which accompany the fifth
pair. If the fifth pair in fact be divided at the level of the Casserian ganglion, where it is joined by sympathetic fibres from the
carotid plexus, or between this ganglion and the eyeball, a destructive inflammation of the organ follows. But if the section be made
behind the ganglion, so as to avoid the filaments of communication
with the sympathetic, no inflammatory change takes place. If this
fact be really owing to the presence of sympathetic fibres which
accompany the fifth pair, it indicates a remarkable difference in the
effects of dividing the sympathetic near the eyeball and at a distance from it; since no real inflammation of the eyeball or its
appendages is ever produced by division of this nerve in the middle
of the neck, but only the elevation of temperature and increase of
sensibility which have been already described.
The influence of the sympathetic nerve and the consequences
of its division upon the thoracic and abdominal viscera have been
only very imperfectly investigated by experimental methods. It
undoubtedly serves as a medium of reflex action between the sensitive and motor portions of the digestive, excretory, and generative
apparatuses; and it is certain that it also takes part in reflex actions
I Leqons sur la Physiologie et la Pathologie du Systeme nerveux, Paris, 1858,
vol. ii. p. 203.




508        SYSTEM  OF THE GREAT SYMPATHETIC.
in which the cerebro-spinal system is at the same time interested.
There are accordingly three different kinds of reflex action, taking
place wholly or partially through the sympathetic system, which
may be observed to occur in the living body.
1st. Reflex actions taking place from the internal organs, through the
sympathetic and cerebro-spinal systems, to the voluntary muscles and
sensitive surfaces.-The convulsions of young children are often
owing to the irritation of undigested food in the intestinal canal.
Attacks of indigestion are also known to produce temporary amaurosis, double vision, strabismus, and even hemiplegia. Nausea, and
a diminished or capricious appetite, are often prominent symptoms
of early pregnancy, induced by the peculiar condition of the uterine
mucous membrane.
2d. Reflex actions taking place from the sensitive surfaces, through
the cerebro-spinal and sympathetic systems, to the involuntary muscles
and secreting organs.-Imprudent exposure of the integument to
cold and wet, will often bring on a diarrhcea. Mental and moral
impressions, conveyed through the special senses, will affect the
motions of the heart, and disturb the processes of digestion and
secretion. Terror, or an absorbing interest of any kind, will produce a dilatation of the pupil, and communicate in this way a peculiarly wild and unusual expression to the eye. Disagreeable sights
or odors, or even unpleasant occurrences, are capable of hastening
or arresting the menstrual discharge, or of inducing premature
delivery.
3d. Reflex actions taking place through the sympathetic system from
one part of the internal organs to another.-The contact of food with
the mucous membrane of the small intestine excites a peristaltic
movement in the muscular coat. The mutual action of the digestive, urinary and internal generative organs upon each other takes
place through the medium  of the sympathetic ganglia and their
nerves. The variations of the capillary circulation in different
abdominal viscera, corresponding with the state of activity or repose of their associated organs, are to be referred to a similar nervous influence. These phenomena are not accompanied by any
consciousness on the part of the individual, nor by any apparent
intervention of the cerebro-spinal system.




SECTION III.
REPRODUCTION.
CHAPTER I.
ON THE NATURE OF REPRODUCTION, AND THE
ORIGIN OF PLANTS AND ANIMALS.
THE process of reproduction is the most characteristic, and in
many respects the most interesting, of all the phenomena presented
by organized bodies. It included the whole history of the changes
taking place in the organs and functions of the individual at successive periods of life, as well as the production, growth, and development of the new germs which make their appearance by
generation.
For all organized bodies pass through certain well defined epochs
or phases of development, by which their structure and functions
undergo successive alterations. We have already seen that the
living animal or plant is distinguished from inanimate substances
by the incessant changes of nutrition and growth which take place
in its tissues. The muscles and the mucous membranes, the osseous and cartilaginous tissues, the secreting and circulatory organs,
all incessantly absorb oxygen and nutritious material from without, and assimilate their molecules; while new substances, produced
by a retrogressive alteration and decomposition, are at the same
time excreted and discharged. These nutritive changes correspond
in rapidity with the activity of the other vital phenomena; since
the production of these phenomena, and the very existence of the
vital functions, depend upon the regular and normal continuance
of the nutritive process. Thus the organs and tissues, which are
always the seat of this double change of renovation and decay,
retain nevertheless their original constitution, and continue to be
capable of exhibiting the vital phenomena.




510              NATURE OF REPRODUCTION.
The above changes, however, are not in reality the only ones
which take place. For although the structure of the body and the
composition of its constituent parts appear to be maintained in an
unaltered condition, by the nutritive process, from one moment to
another, or from day to day, yet a comparative examination of
them at greater intervals of time will show that this is not precisely the case; but that the changes of nutrition are, in point of
fact, progressive as well as momentary. The composition and properties of the skeleton, for example, are not the same at the age of
twenty-five that they were at fifteen. At the latter period it contains more calcareous and less organic matter than before; and its
solidity is accordingly increased, while its elasticity is diminished.
Even the anatomy of the bones alters in an equally gradual manner;
the medullary cavities enlarging with the progress of growth, and
the cancellated tissue becoming more open and spongy in texture.
We have already noticed the difference in the quantity of oxygen
and carbonic acid inspired and exhaled at different ages. The
muscles, also, if examined after the lapse of some years, are found
to be less irritable than formerly; owing to a slow, but steady and
permanent deviation in their intimate constitution.
The vital properties of the organs, therefore, change with their
varying structure; and a time comes at last when they are perceptibly less capable of performing their original functions than
before. This alteration, being dependent on the varying activity of
the nutritive process, continues necessarily to increase. The very
exercise of the vital powers is inseparably connected with the subsequent alteration of the organs employed in them; and the functions of life, therefore, instead of remaining indefinitely the same,
pass through a series of successive changes, which finally terminate
in their complete cessation.
The history of a living animal or plant is, therefore, a history of
successive epochs or phases of existence, in each of which the structure and functions of the body differ more or less from those in
every other. Every living being has a definite term of life, through
which it passes by the operation of an invariable law, and which,
at some regularly appointed time, comes to an end. The plant
germinates, grows, blossoms, bears fruit, withers, and decays. The
animal is born, nourished, and brought to maturity, after which he
retrogrades and dies. The very commencement of existence, by
leading through its successive intermediate stages, conducts at last
necessarily to its own termination.




NATURE OF REPRODUCTION.                    511
But while individual organisms are thus constantly perishing and
disappearing from the stage, the particular kind, or species, remains
in existence, apparently without any important change in the character or appearance of the organized forms belonging to it. The
horse and the ox, the oak and the pine, the different kinds of wild
and domesticated animals, even the different races of man himself,
have remained without any essential alteration ever since the earliest
historical epochs. Yet during this period innumerable individuals,
belonging to each species or race, must have lived through their
natural term and successively passed out of existence. A species
may therefore be regarded as a type or class of organized beings, in
which the particular forms or structures composing it die off constantly and disappear, but which nevertheless repeats itself from
year to year, and maintains its ranks constantly full by the regular
accession of new individuals. This process, by which new organisms make their appearance, to take the place of those which are
destroyed, is known as the process of reproduction or generation. Let
us now see in what manner it is accomplished.
It has always been known that, as a general rule in the process
of generation, the young animals or plants are produced directly
from the bodies of the elder. The relation between the two is that
of parents and progeny; and the new organisms, thus generated,
become in turn the parents of others who succeed them. For this
reason wherever such plants or animals exist, they indicate the
previous existence of others belonging to the same species; and if
by any accident the whole species should be destroyed in any particular locality, no new individuals could be produced there, unless
by the previous importation of others of the same kind.
The commonest observation shows this to be true in regard to
those animals and plants with whose history we are more familiarly
acquainted. An opinion, however, has sometimes been maintained
that there are exceptions to this rule; and that living beings may,
under certain circumstances, be produced from inanimate substances,
without any similar plants or animals having preceded them; presenting, accordingly, the singular phenomenon of a progeny without
parents. Such a production of organized bodies is known by the
name of spontaneous generation. It is believed by the large majority
of physiologists at the present day that no such spontaneous generation ever takes place; but that plants and animals are always
derived, by direct reproduction, from previously existing parents
of the same species. As this, however, is a question of some in



512             NATURE OF REPRODUCTION.
portance, and one which has been frequently discussed in works on
physiology, we shall proceed to pass in review the facts which have
been adduced in favor of the occurrence of spontaneous generation,
as well as those which would lead to its disproval and rejection.
It is evident, in the first place, that many apparent instances of
spontaneous generation are found to be of a very different character
as soon as they are subjected to a critical examination. Thus grasshoppers and beetles, earthworms and crayfish, the swarms of minute
insects that fill the air over the surface of stagnant pools, and even
frogs, moles, and lizards, have been supposed in former times to be
generated directly from the earth or the atmosphere; and it was
only by investigating carefully the natural history of these animals
that they were ascertained to be produced in the ordinary manner
by generation from parents, and were found to continue the reproduction of their species in the same way. A still more striking
instance is furnished by the production of maggots in putrefying
meat, vegetables, flour paste, fermenting dung, &c. If a piece of
meat be exposed, for example, and allowed to undergo the process
of putrefaction, at the end of a few days it will be found to contain
a multitude of living maggots, which feed upon the decomposing
flesh. Now these maggots are always produced under the same
conditions of warmth, moisture and exposure, and at the same stage
of the putrefactive process. They are never to be found in fresh
meat, nor, in fact, in any other situation than the one just mentioned.
They appear, consequently, without any similar individuals having
existed in the same locality; and considering the regularity of their
appearance under the given conditions, and their absence elsewhere,
it has been believed that they were spontaneously generated, under
the influence of warmth, moisture, and the atmosphere, from the
decaying organic substances.
A little examination, however, discovers a very simple solution
of the foregoing difficulty. On watching the exposed animal or
vegetable substances during' the earlier periods of their decomposition, it is found that certain species of flies, attracted by the odor
of the decaying material, hover round it and deposit their eggs
upon its surface or in its interior. These eggs, hatched by the
warmth to which they are exposed, produce the maggots; which
are simply the young of the winged insects, and which after a time
become transformed, by the natural progress of development, into
perfect insects similar to their parents. The difficulty of accounting for the presence of the maggots by generation, therefore, de



INFUSORIAL ANIMALCULES.                    513
pends simply on the fact that they are different in appearance from
the parents that produce them. This difference, however, is merely
a temporary one, corresponding with the difference in age, and disappears when the development of the animal is complete; just as
the young chicken, when recently hatched, has a different form and
plumage from those which it presents in its adult condition.
Nearly all the causes of error, in fact, which have suggested at
various times the doctrine of spontaneous generation, have been
derived from these two sources. First, the ready transportation of
eggs or germs, and their rapid hatching under favorable circumstances; and secondly, the different appearances presented by the
same animal at different ages, in consequence of which the youthful
animal may be mistaken, by an ignorant observer, for an entirely
different species. These sources of error are, however, so readily
detected, as a general rule, by scientific investigation, that it is
hardly necessary to point out the particular instances in which they
exist. In fact, whenever a rare or comparatively unknown animal
or plant has been at any time supposed to be produced by spontaneous generation, it has only been necessary, for the most part, to
investigate thoroughly its habits and functions, to discover its secret
methods of propagation, and to show that they correspond, in all-:
essential particulars, with the ordinary laws of reproduction.  The
limits, therefore, within which the doctrine of spontaneous generation can be applied, have been narrowed in precisely the same
degree that the study of natural history and comparative physiology
has advanced.  At present, indeed, there remain but two classes
of phenomena which are ever supposed to lend any support to the
above doctrine; viz., the existence and production, 1st, of infusorial animalcules, and 2d, of animal and vegetable parasites.  We
shall now proceed to examine these two parts of the subject in
succession.
INFUSORIAL ANIMALCULES.-If water, holding in solution organic substances, be exposed to the contact of the atmosphere at
ordinary temperatures, it is found after a short time to be filled
with swarms of minute living organisms, which are visible only by
the microscope. The forms of these microscopic animalcules are
exceedingly varied; owing either to the great number of species
in existence, or to their rapid alteration during the successive periods of their growth. Ehrenberg has described more than 300
38




514             NATURE OF REPRODUCTION.
different varieties of them. They are generally provided with cilia
attached to the exterior of their bodies, and are, for the most part,
in constant and rapid motion in the fluid which they inhabit.
Owing to their presence in
Fig. 168.             animal and vegetable watery
infusions, they have received
/  {"~'.\ the name of "infusoria," or
/..  1 \  "infusorial animalcules.",/ // N^l"                       " "   " I \ Now  these infusoria are
/   ~ d 1  ^.  \always produced under the
conditions which we have de-:'o@:~  -  " ( a       scribed above. The animal
\\   1  \  o) \\'    or   vegetable substance used;.\ v: \~ 0  \ L      /   for the infusion may be pre\  B.: ]:I  / ~   viously baked or boiled, so
as to destroy all living germs
\-~,~;.~   ^which it might accidentally
Different kinds of INF SORIA.  contain; the water in which
Different kinds of I N FU S OR I A.
it is infused may be carefully
distilled, and thus freed from all similar contamination; and yet the
infusorial animalcules will make their appearance at the usual time
and in the usual abundance. It is only requisite that the infusion
be exposed to a moderately elevated temperature, and to the access
of atmospheric air; conditions which are equally necessary for
maintaining the life of all animal and vegetable organisms, whatever be the source from which they are derived. Under the above
circumstances, therefore, either the animalcules must have been
produced by spontaneous generation in the watery infusion, or their
germs must have been introduced into it through the medium of
the atmosphere. No such introduction has ever been directly demonstrated, nor have even any eggs or germs belonging to the
infusoria ever been detected.
Nevertheless, there is every probability that the infusoria are
produced from germs, and not by spontaneous generation. Since
the infusoria themselves are microscopic in size, it is not surprising
that their eggs, which must be smaller still, should have escaped
observation.  We know, too, that in many instances the minute
germs of animals or plants may be wafted about in a dry state by
the atmosphere, until, by accidentally coming in contact with warmth
and moisture, they become developed and bring forth living organisms. The eggs of the infusoria, accordingly, may be easily raised




INFUSORIAL ANIMALCULES.                    515
and held suspended in the atmosphere, under the form of minute
dust-like particles, ready to germinate and become developed whenever they are caught by the surface of a stagnant pool, or of any
artificially prepared infusion. In point of fact, the atmosphere
does really contain an abundance of such dust-like particles, even
when it appears to be most transparent and free from impurities.
This may be readily demonstrated by admitting a single beam of
sunshine into a darkened apartment, when the shining particles suspended in the atmosphere become immediately visible in the track
of the sunbeam. Again, if a perfectly clean and polished mirror
be placed with its face upward in a securely closed room, and left
undisturbed for several days, its surface at the end of that time will
be found to be dimmed by the settling upon it of minute dust,
deposited from the atmosphere. There is no reason, therefore, for
disbelieving that the air may always contain a sufficient number of
organic germs for the production of infusorial animalcules.
There is some difficulty, however, in obtaining direct proof that it
is through the medium of the atmosphere that organic germs penetrate into the watery infusions. It is true that if such an infusion
be prepared from baked meat or vegetables and distilled water, and
afterward hermetically sealed, no infusoria are developed in it; but
this only shows, as we have already intimated, that the free access
of air is necessary to the development of all organic life, just as it is
to the support of animals and plants under ordinary conditions of
growth and reproduction. Such a result, therefore, proves nothing
with regard to the external origin of the infusoria. In order to be
conclusive, such an experiment should be so contrived that the
watery infusion, previously freed from all foreign contamination,
should be supplied with a free access of atmospheric air, while the
introduction of living germs by this channel should at the same time
be rendered impossible. An experiment of this kind has in reality
been contrived and successfully carried out by Schultze, of Berlin.'
This observer prepared an infusion containing organic substances
in solution, and inclosed it in a glass flask (Fig. 169, a) of such a
size, that the infusion filled about one-half the entire capacity of the
vessel. The mouth of the flask was fitted with an air-tight stopper
provided with two holes, through which were passed narrow glass
tubes bent at right angles. To each of these tubes was attached a
potass-apparatus (b, c), similar to those used for condensing carbonic
Edinburgh New Philosophical Journal, Oct., 1837.




516              NATURE OF REPRODUCTION.
acid in organic analyses. One of these (b) was filled with concentrated sulphuric acid, the other (c) with a solution of caustic potassa.
The flask with the organic infusion
Fig. 169.          having been subjected to a boiling
C __temperature, in order to destroy any
living  germs which it might contain, the stopper was inserted, and
the whole apparatus exposed to the
light, at the ordinary summer temperature. The connections of the apparatus;i"XlT,r~being perfectly tight, no air could penetrate into the flask, except bypassing
ICE   ~    through either the sulphuric acid or
Schultze's experiment on SPONTA  the potassa; either of which would
NEOUS GENERATION. —a. Flask containing watery infusion. b. Potassa ap- retain and destroy any organic germs
paratus containing sulphuric acid. c. whichmightbe pendedinit Every
Potass-apparatus containing caustic po- 
tassa.                       day a fresh supply of air was introduced
into the flask by drawing it through
the tubes b, c; and in this way the atmospheric air above the infusion was constantly renewed, while at the same time the introduction
of living germs from without was effectually prevented.
Schultze kept this apparatus under his observation, as above, from
the last of May till the first of August; frequently examining the
edges of the fluid with a lens, through the sides of the glass jar,
but without ever detecting in it any traces of living organisms. At
the end of that period the flask was opened, and the fluid which it
contained subjected to direct examination, equally without result.
It was then exposed, in the same vessel and in the same situation
as before, to the free access of the atmosphere, and at the end of
two or three days it was found to be swarming with infusoria.
It is plain, therefore, that the infusoria cannot be regarded as
produced by spontaneous generation, but must be considered as
originating in the usual manner from germs; since they do not
make their appearance in the watery infusion, when the accidental
introduction of germs from without has been effectually prevented.
ANIMAL AND VEGETABLE  PARASITES.-This very remarkable
group of organized bodies is distinguished by the fact that they
live either upon the surface or in the interior of other animal or
vegetable organisms.  Thus, the mistletoe fixes itself on the branches
of aged trees; the Oidium albicans vegetates upon the mucous sur



ANIMAL AND VEGETABLE PARASITES.                517
faces of the mouth and pharynx; the Botrytis Bassiana attacks the
body of the silkworm, and plants itself in its tissues; while many
species of trematoid worms live attached to the gills of fish and of
water-lizards.
These parasites are usually nourished by the fluids of the animal
whose body they inhabit. Each particular species of parasite is
found to inhabit the body of a particular species of animal, and is
not found elsewhere. They are met with, moreover, as a general
rule, only in particular organs, or even in particular parts of a
single organ. Thus the Tricocephalus dispar is found only in the
caecum; the Strongylus gigas in the kidney; the Distoma hepaticum in the biliary passages. The Distoma variegatum  is found
only in the lungs of the green frog, the Distoma cylindraceum in
those of the brown. The Toenia solium is found in the intestine of
the human subject in certain parts of Europe, while the Taenia lata
occurs exclusively in others. It appears, therefore, as though some
local combination of conditions were necessary to the production
of these parasites; and they have been supposed, accordingly, to
originate by spontaneous generation in the localities where they
are exclusively known to exist.
A little consideration will show, however, that the above conditions are not, properly speaking, necessary or sufficient for the
production, but only for the development of these parasites. All the
parasites mentioned above reproduce their species by generation.
They have male and female organs, and produce fertile eggs, often
in great abundance. The eggs contained in a single female Ascaris
are to be counted by thousands; and in a tapeworm, it is said, even
by millions. Now these eggs, in order that they may be hatched
and produce new individuals, require certain special conditions
which are favorable for their development; in the same manner
as the seeds of plants require, for their germination and growth, a
certain kind of soil and a certain supply of warmth and moisture.
It is accordingly no more surprising that the Ascaris vermicularis
should inhabit the rectum, and the Ascaris lumbricoides the ileum,
than that the Lobelia inflata should grow only in dry pastures, and
the Lobelia cardinalis by the side of running brooks. The lichens
flourish on the exposed surfaces of rocks and stone walls; while
the fungi vegetate in darkness and moisture, on the decaying trunks
of dead trees. Yet no one imagines these vegetables to be spontaneously generated from the soil which they inhabit. The truth
is simply this, that if the animal or vegetable germ be deposited in




518             NATURE OF REPRODUCTION.
a locality which affords the requisite conditions for its development,
it becomes developed; otherwise not. Each female Ascaris produces, as we have stated above, many thousands of ova. Now,
though the chances are very great against any particular one of
these ova being accidentally transported into the intestinal canal of
another individual, it is easy to see that there are many causes in
operation by which some of them might be so transported. By far
the greater number undoubtedly perish, from not meeting with the
conditions necessary for their development. One in a thousand, or
perhaps one in a million, is accidentally introduced into the body
of another individual, and consequently becomes developed there
into a perfect Ascaris.
The circumstance, therefore, that particular parasites are confined
to particular localities, presents no greater difficulty as to their
mode of reproduction, than the same fact regarding other animal
and vegetable organisms.
Neither is there any difficulty in accounting for the introduction
of parasitic germs into the interior of the body. The air and the
food offer a ready means of entrance into the respiratory and
digestive passages; and, a parasite once introduced into the intestine, there is no difficulty in accounting for its presence in any of
the ducts leading from or opening into the alimentary canal. Some
parasites are known to insinuate themselves directly underneath
the surface of the skin; as the Pulex penetrans or "chiggo" of
South America, and the Ixodes Americanus or "tick."  Others,
like the (Estrus bovis, penetrate the integument for the purpose of
depositing their eggs in the subcutaneous areolar tissue. Some
may even gain an entrance into the bloodvessels, and circulate in
this way all over the body. Thus the Filaria rubella is found alive
in the bloodvessels of the frog, the Distoma hematobium in those
of the human subject, and a species of Spiroptera in those of the
dog. It is easy to see, therefore, how, by such means, parasitic
germs may be conveyed to any part of the body; and may even be
deposited, by accidental arrest of the circulation, in the substance
of the solid organs.
The most serious difficulty, however, in the way of accounting
for the production of parasitic organisms, was that presented by the
existence of a class known as the encysted or sexless entozoa. These
parasites for the most part occupy the interior of the solid organs
and tissues, into which they could not have gained access by the
mucous canals. Thus the Coenurus cerebralis is found imbedded




ANIMAL AND VEGETABLE PARASITES.                   519
in the substance of the brain, the Trichina spiralis between the
fibres of the voluntary muscles, and the Cysticercus cellulosae in the
areolar tissue of various parts of the body. They are also distinguished from all other parasites by two peculiar characters. First,
they are inclosed in a distinct cyst, with which they have no organic
connection and from which they may be readily separated; and secondly, they have no generative organs, nor is there any                Fig. 170.
apparent difference between
the sexes. The Trichina spiralis, for example (Fig. 170),
is inclosed in an ovoid or
spindle-shaped cyst, swollen
in the middle and tapering at
each extremity, with a roundTRICHINA SPIRALIS; from rectus femoris mused cavity in its central por-  le of human subject. Magnified 57 diameters.
tion, in which the worm lies
coiled up in a spiral form. The worm itself has neither testicles
nor ovaries, nor does it present any trace of a sexual organization.
Now we have seen that it is easy to account for theconveyance
of these or any other parasites into the interior of vascular organs
and tissues; the eggs from which they are produced being transported by the bloodvessels to any part of the body, and there
retained by a local arrest of the capillary circulation. In the case
of the encysted entozoa, however, we have a much greater difficulty; since these parasites are entirely without sexual organs or
generative apparatus of any sort, nor have they ever been discovered in the act of producing eggs, or of developing in any
manner a progeny similar to themselves. It appears, accordingly,
difficult to understand how animals, which are without a sexual
apparatus, should have been produced by sexual generation. As
it is certain that they can have no progeny, it would seem equally
evident that they must have been produced without a parentage.
This difficulty, however, serious as it at first appears, is susceptible
of a very simple explanation. The case is in many respects analogous
to that of the maggots, hatched from the eggs of flies in putrefying
meat.  These maggots are also without sexual organs; for they
are still imperfectly developed, and in a kind of embryonic condition. It is only after their metamorphosis into perfect insects, that
generative organs are developed and a distinction between the
sexes manifests itself. This is, indeed, more or less the case with




520              NATURE OF REPRODUCTION.
all animals and with all vegetables. The blossom, which is the
sexual apparatus of the plant, does not appear, as a general rule,
until the growth of the vegetable has continued for a certain time,
and it has acquired a certain age and strength.  Even in the human
subject the sexual organs, though present at birth, are still very
imperfectly developed as to size, and altogether inactive in function. It is only later that these organs acquire their full growth,
and the sexual characters become complete. In very many of the
lower animals the sexual organs are entirely absent at birth, and
appear only at a later period of development.
Now the encysted or sexless entozoa are simply the undeveloped
young of other parasites which propagate by sexual generation;
the membrane in which  they are inclosed
Fig. 171.     being either an embryonic envelope, or else
an adventitious cyst formed round the parasitic embryo. These embryos have come, in
the natural course of their migrations, into
a situation which is not suitable for their complete development.  Their development is
accordingly arrested before it arrives at maturity; and the parasite never reaches the adult
condition, until removed from the situation in
more favorable locality.
The above explanation has been demonstrated to be the true one, more particularly
with regard to the Taenia, or tapeworm, and
several varieties of Cysticercus. The Tcenia
(Fig. 171) is a parasite of which different species
are found in the intestine of the human subject,
the dog, cat, fox, and other of the lower animals.
Its upper extremity, termed te d  he "head," consists of a nearly globular mass, presenting upon
its lateral surfaces a set of four muscular disks
or "suckers," and terminating anteriorly in a
conical projection which is provided with a
crown of curved processes or hooks, by which'rNlA.       the parasite attaches itself to the intestinal
mucous membrane. To this "head" succeeds
a slender ribbon-shaped neck, which is at first smooth, but which
soon becomes transversely wrinkled, and afterward divided into




ANIMAL AND VEGETABLE PARASITES.                     521
distinct rectangular pieces or "articulations." These articulations
multiply by a process of successive growth or budding, from the
wrinkled portion of the neck; and are constantly removed farther
and farther from their point of origin by new ones formed behind
them.  As they gradually descend, by the process of growth,
farther down the body of the tapeworm, they become larger and
begin to exhibit:a sexual apparatus, developed in their interior.
In each fully formed articulation there are contained both male
and female organs of generation; and the mature eggs, which are
produced in great numbers, are thrown off together with the articulation itself from the lower extremity of the tapeworm.  Since the
articulations are successively produced, as we have mentioned above,
by budding from the neck and the back part of the head, the parasite cannot be effectually dislodged by taking away any portion of
the body, however large; since it is subsequently reproduced from
the head, and continues its growth as before.  But if the head itself
be removed from the intestine, no further reproduction of the articulations can take place.
The Cysticercus is an encysted parasite, different varieties of which
are found in the liver, the peritoneum, and the meshes of the areolar
tissue in various parts of the body.  It consists (Fig. 172), first, of
a globular sac, or cyst (a), which is not adherent to the tissues of
the organ in which the parasite is found, but may be easily separated from  them.  In its interior is found another sac (b), lying
Fig. 172.                         Fig. 173.
CYSTICERCUS.-a. External cyst. b. Internal sac, containing fluid. c. Narrow canal,
formed by involution of walls of sac, at the
bottom of which is the head of the tsenia.  CYSTICER CUS, unfolded.
loose in the cavity of the former, and filled with a serous fluid.
This second sac presents, at one point upon its surface, a puckered
depression, leading into a long, narrow canal (c). This canal, which
is formed by an involution of the walls of the second sac, presents




522              NATURE OF REPRODUCTION.
at its bottom a small globular mass, like the head of the Taenia,
provided with suckers and hooks, and supported upon a short
slender neck. If the outer investing sac be removed, the narrow
canal just described may be everted by careful manipulation, and
the parasite will then appear as in Fig. 173, with the head and neck
resembling those of a Taenia, but terminating behind in a dropsical
sac-like swelling, instead of the chain of articulations which are
characteristic of the fully formed tapeworm.
Now it has been shown, by the experiments of KI(chenmeister,
Siebold, and others, that the Cysticercus is only the imperfectly
developed embryo, or young, of the Taenia. When the mature
articulation of the tapeworm is thrown off, as already mentioned,
from its posterior extremity, the eggs which it incloses have already
passed through a certain period of development, so that each one
contains an imperfectly formed embryo. The articulation, containing the eggs and embryos, is then taken, with the food, into the
stomach of another animal; the substance of the articulation, together with the external covering of the eggs, is destroyed by digestion, and the embryos are thus set free. They then penetrate,
through the walls of the stomach, into the neighboring organs or
the areolar tissue, and, becoming encysted in these situations, are
there developed into cysticerci, as represented in Fig. 172. Afterward, the tissues in which they are contained being devoured by
another animal, the cysticercus passes into the intestine, fixes itself
to the mucous membrane, and, by a process of budding, produces
the long tape-like series of articulations, by which it is finally converted into the full-grown Taenia.
Prof. Siebold found the head of the Cysticercus fasciolaris, met
with in the liver of rats and mice, presenting so close a resenmblance to the Taenia crassicollis, inhabiting the intestine of the cat.
that he was led to believe the two parasites to be identical. This
identitywas, in fact, proved by the experiments of Kiichenmeister;
and Siebold afterward demonstrated1 the same relation to exist
between the Cysticercus pisiformis, found in the peritoneum of rabbits, and the Taenia serrata, from the intestine of the dog. This
experimenter succeeded in administering to dogs a quantity of the
cysticerci, fresh from the body of the rabbit, mixed with milk; and
on killing the dogs, at various periods after the meal, from  three
I In Buffalo Medical Journal, Feb. 1853; also in Siebold on Tape and Cystic
Worms, Sydenham translation: London, 1857, p. 59.




ANIMAL AND VEGETABLE PARASITES.                   523
hours to eight weeks, he found the cysticerci in various stages of
development in the intestine, and finally converted into the full
grown Tsenia, with complete articulations and mature eggs.
Dr. Ktichenmeister' has also performed the same experiment, with
success, on the human subject.  A number of cysticerci were administered to a criminal, at different periods before his execution,
varying from 12 to 72 hours; and upon post-mortem examination
of the body, no less than ten young teeniae were found in the
intestine, four of which could be distinctly recognized as specimens
of Tsenia solium.
Finally, both Leuckart and Ktichenmeister2 have shown, on the
other hand, that the eggs of Tsenia soliurt, introduced into the body
of the pig, will give rise to the development of Cysticercus cellulosae:
thus demonstrating that the two kinds of parasites are identical in
their nature, and differ only in the manner and degree of their
development.
There remains, accordingly, no good reason for believing that
even the encysted parasites are produced by spontaneous generation. Whatever obscurity may hang round the origin or reproduction of any class or species of animals, the direct investigations of
the physiologist always tend to show that they do not, in reality,
form any exception to the general law in this respect; and the only
opinion which is admissible, from the facts at present within our
knowledge, is that organized beings, animal and vegetable, wherever they
may be found, are always the progeny of previously existing parents.
On Animal and Vegetable Parasites, Sydenham translation: London, 1857,
p. 115.
2 Op. cit., p. 120.




524                 SEXUAL GENERATION.
CHAPTER II.
ON SEXUAL GENERATION, AND THE MODE OF ITS
ACCOM PLISHMENT.
THE function of generation is performed by means of two sets of
organs, each of which gives origin to a peculiar product, capable
of uniting with the other so as to produce a new individual. These
two sets of organs, belonging to the
Fig. 174.        two different sexes, are called the male
-  - and female organs of generation. The
-^ ~  l^ ^ ~female organs produce a globular body
called the germ, or egg, which is capable
of being developed into the body of
the young animal or plant; the male
organs produce a substance which is
necessary to fecundate the germ, and
enable it to go through with its natural
E_ ^l""~     growth and development.,2   (  — a  Such are the only essential and universal characters of the organs of generation. These organs, however, exhibit
Aid(  ~    various additions and modifications in
</K  ~ different classes of organized beings,
while they show throughout the same
fundamental and essential characters.
B L OSSO M OF  CONVOL 0VULUS
PURPUREUS. (Morning glory.)-a.   In the flowering plants, for example,
Germ. b. Pistil. c.e. Stamens, with th  blossom  which is the generative
anthers.  d. Corolla   e. Calyx.   
apparatus (Fig. 174), consists first of a
female organ containing the germ (a), situated usually upon the
highest part of the leaf-bearing stalk. This is surmounted by a
nearly straight column, termed the pistil (b), dilated at its summit
into a globular expansion, and occupying the centre of the flower.
Around it are arranged several slender filaments, or stamens, bearing upon their extremities the male organs, or anthers (c, c). The




SEXUAL GENERATION.                         525
whole is surrounded by a circle or crown of delicate and brilliantly
colored leaves, termed the corolla (d), which is frequently provided
with a smaller sheath of green leaves outside, called the calyx (e).
The anthers, when arrived at maturity, discharge a fine organic
dust, called the pollen, the granules of which are caught upon the
extremity of the pistil, and then penetrate downward through its
tissues, until they reach its lower extremity and come in contact
with the germ.  The germ thus fecundated, the process of generation is accomplished. The pistil, anthers, and corolla wither and
fall off, while the germ increases rapidly in size, and changes in
form and texture, until it ripens into the mature fruit or seed. It
is then ready to be separated from the parent stem; and, if placed
in the proper soil, will germinate and at last produce a new plant
similar to the old.
In the above instance, the male and female organs are both
situated upon the same flower; as in the lily, the violet, the convolvulus, &c. In other cases, there are separate male and female
flowers upon the same plant, of which the male flowers produce
only the pollen, the female, the
germ and fruit.  In others still,               Fi 175
the male and female flowers are
situated  upon  different plants,.
which. otherwise resemble each
other, as in the willow, poplar,.... 
and hemp.                                                    \
In animals, the female organs         \_
of generation are called ovaries,.""'
since it is in them that the egg,  r
or "ovum," is produced.  The
male  organs  are  the  testicles,
which give origin to the fecun- 
dating  product,  or "seminal  i 
fluid," by which the egg is fertilized.  We have already men-         / 
tioned above that in the articula-   SINGLE ARTICULATION OF TNITA
tions of the tapeworm the ovaries  C R A S SI C O L, I, from small intestine of cat.a, a, a Ovary filled with eggs. b. Testicle. c.
and testicles are developed to-  Genital orifice.
gether. (Fig. 175.) The ovary
(a, a, ) is a series of branching follicles terminating in rounded
extrenities, and communicating with each other by a central canal.
The testicle (b) is a narrow, convoluted tube, very much folded




526                 SEXUAL GENERATION.
upon itself, which opens by an external orifice (c) upon the lateral
border of the articulation, about midway between its two extremities. The spermatic fluid produced in the testicle is introduced into the female generative passage, which opens at the same
spot, and, penetrating deeply into the interior, comes in contact
with the eggs, which are thereby fecundated and rendered fertile.
The fertile eggs are afterward set free by the rupture or decay of
the articulation, and a vast number of young produced by their
development.
In snails, also, and in some other of the lower animals, the ovaries
and testicles are both present in the same individual; so that these
animals are sometimes said to be "hermaphrodite," or of double
sex. In reality, however, it appears that the male and female
organs do not come to maturity at the same time; but the ovaries
are first developed and perform their function, after which the testicles come into activity in their turn. The same individual, therefore, is not both male and female at any one time; but is first
female and afterward male, exercising the two generative functions
at different ages.
In all the higher animals, however, the two sets of generative
organs are located in separate individuals; and the species is
consequently divided into two sexes, lnale and female. All that
is absolutely requisite to constitute the two sexes is the existence
of testicles in the one, and of ovaries in the other. Beside these,
however, there are, in most instances, certain secondary or accessory organs of generation, which assist more or less in the accomplishment of the process, and which occasion a greater difference
in the anatomy of the two sexes. Such are the uterus and mammary glands of the female, the vesicula seminales and prostate
of the male. The female naturally having the immediate care of
the young after birth, and the male being occupied in providing
food and protection for both, there are also corresponding differences in the general structure of the body, which affect the whole
external appearance of the two sexes, and which even show themselves in their mental and moral, as well as in their physical
characteristics. In some cases this difference is so excessive that
the male and female would never be recognized as belonging to the
same species, unless they were seen in company with each other.
Not to mention some extreme instances of this among insects and
other invertebrate animals, it will be sufficient to refer to the well
known examples of the cock and the hen, the lion and lioness, the




SEXUAL GENERATION.                     527
buck and the doe.  In the human species, also, the distinction
between the sexes shows itself in the mental constitution, the disposition, habits, and pursuits, as well as in the general conformation of the body, and the peculiarities of external appearance.
We shall now study more fully the character of the male and
female organs of generation, together with their products, and the
manner in which these are discharged from the body, and brought
into relation with each other.




528    EGG AND FEMALE ORGANS OF GENERATION.
CHAPTER III.
ON THE EGG, AND THE FEMALE ORGANS OF
GENERATION.
THE egg is a globular body which varies considerably in size in
different classes of animals, according to the peculiar conditions
under which its development is to take place. In the frog it measures    of an inch in diameter, in the lamprey 2, in quadrupeds
and in the human species    o. It consists, first, of a membranous
external sac or envelope, the vitelline membrane; and secondly, of a
spherical mass inclosed in its interior, called the vitellus.
The vitelline membrane in birds and reptiles is very thin, measuring often not more than Tsoo of an inch in thickness, and is at the
same time of a somewhat fibrous texture.
Fig. 176.      TIn man and the higher animals, on the
contrary, it is perfectly smooth, structureless and transparent, and is about sop  of
an inch in thickness.  Notwithstanding
its delicate and transparent appearance, it
has a considerable degree of resistance
and elasticity.  The egg of the human
subject, for example, may be perceptibly
HUMAN OvUM, magnified 5 flattened out under the microscope by
diameters. a Vitelline membrane. pressing with the point of a needle upon
b. Vitellus. c. Germinative vesicle.
d. Germinative spot.    the slip of glass which covers it; but it
still remains unbroken, and when the
pressure is removed, readily resumes its globular form. When the
egg is somewhat flattened under the microscope in this way, by
pressure of the glass slip, the apparent thickness of the vitelline
membrane is increased, and it then appears (Fig. 176) as a rather
wide, colorless, and pellucid border or zone, surrounding the granular and opaque vitellus. Owing to this appearance, it has sometimes received the name of the "zona pellucida."  The name of
vitelline membrane, however, is the one more generally adopted
and is also the more appropriate of the two.




EGG AND FEMALE ORGANS OF GENERATION.   529
The vitellus (b) is a globular, semi-solid mass, contained within
the vitelline membrane. It consists of a colorless albuminoid substance, with an abundance of minute molecules and oleaginous
granules scattered through it. These minute oleaginous masses
give to the vitellus a partially opaque and granular aspect under
the microscope. Imbedded in the vitellus, usually near its surface
and almost immediately beneath the vitelline membrane, there is a
clear, colorless, transparent vesicle (c) of a rounded form, known
as the germinative vesicle. In the egg of the human subject and of
the quadrupeds, this vesicle measures -g  to -o   of an inch in
diameter. It presents upon its surface a
dark spot, like a nucleus (d), which is known      Fig. 177.
by the name of the germinative spot. The..
germinative vesicle, with its nucleus-like             lo'V~o\
spot, is often partially concealed by the                 ~',
granules of the vitellus by which it is sur-: 
rounded, but it may always be discovered
by careful examination. 
If the egg be ruptured by excessive pres-   H U,,MAN OVM, ruptnred by
sure under the microscope, the vitellus is pressure; showing the vitellus
partially expelled, the germinaseen to have a gelatinous consistency.  It  ive vesicle at a, and the smooth
is gradually expelled from  the vitelline  fracture of the vitelline  e
cavity, but still retains the granules and oil
globules entangled in its substance. (Fig. 177.) The edges of the
fractured vitelline membrane, under these circumstances, present a
smooth and nearly straight outline, without any appearance of
laceration or of a fibrous structure.  The membrane is, to all appearance, perfectly homogeneous.
The most essential constituent of the egg is the vitellus. It is
from the vitellus that the body of the embryo will afterward be
formed, and the organs of the new individual developed.  The
vitelline membrane is merely a protective inclosure, intended to
protect the vitellus from injury, and enable it to retain its figure
during the early periods of development.
The egg, as above described, consists therefore of a simple
vitellus of minute size, and a vitelline membrane inclosing it. It
is such an egg which is found in the human subject, the quadrupeds, most aquatic reptiles, very many fish, and some invertebrate
animals. In nearly all those species, in fact, where the fecundated
eggs are deposited and hatched in the water, as well as those in
which they are retained in the body of the female until the develop34




530    EGG AND FEMALE ORGANS OF GENERATION.
ment of the young is completed, such an egg as above described is
sufficient for the formation of the embryo; since during its development it can absorb freely, either from the water in which it floats,
or from the mucous membrane of the female generative organs, the
requisite supply of nutritious fluids. But in birds and in the
terrestrial reptiles, such as lizards, tortoises, &c., where the eggs
are expelled from the body of the female at an early period, and
incubated on land, there is no external source of nutrition, to provide for the support of the young animal during its development.
In these instances accordingly the vitellus, or "yolk," as it is called,
is of very large size; and the bulk of the egg is still further increased by the addition, within the female generative passages, of
layers of albumen and various external fibrous and calcareous
envelopes. The essential constituents of the egg, however, still
remain the same in character, and the process of embryonic development follows the same general laws as in other cases.
The eggs are produced in the interior of certain organs, situated
in the abdominal cavity, called the ovaries. These organs consist
of a number of globular sacs, or follicles, known as the "Graafian
follicles," each one of which contains a single egg. The follicles
are connected with each other by a quantity of vascular areolar
tissue, which binds them together into a well-defined and consistent
mass, covered upon its exterior by a layer of peritoneum. The
egg has sometimes been spoken of as a "product," or even as a
"secretion" of the ovary. Nothing can be more inappropriate,
however, than to compare the egg with a secretion, or to regard the
ovary as in any respect resembling a glandular organ. The egg is
simply an organized body, growing in the ovary like a tooth in its
follicle, and forming a constituent part of the body of the female.
It is destined to be finally separated from its attachments and
thrown off; but until that time, it is, properly speaking, a part of
the ovarian texture, and is nourished like any other portion of the
female organism.
The ovaries, accordingly, since they are directly concerned in
the production of the eggs, are to be regarded as the essential
parts of the female generative apparatus. Beside them, however,
there are usually present certain other organs, which play a secondary or accessory part in the process of generation. The most
important of these accessory organs are two symmetrical tubes, or
oviducts, which are destined to receive the eggs at their internal
extremity and convey them to the external generative orifice. The




EGG AND FEMALE ORGANS OF GENERATION.   531
mucous membrane lining the oviducts is also intended to supply
certain secretions during the passage of the egg, which are requisite either to complete its structure, or to provide for the nutrition
of the embryo.
In the frog, for example, the oviduct commences at the upper
part of the abdomen, by a rather wide orifice, which communicates
directly with the peritoneal cavity. It
soon after contracts to a narrow  tube,           Fig. 178.
and pursues a zigzag course down the                c  j
side of the abdomen (Fig. 178), folded
upon  itself in  convolutions, like  the              J
small intestine, until it opens, near its                   i
fellow  of the  opposite side, into the
"cloaca," or lower part of the intestinal   /
canal. The oviducts.present the same   (\^   1a(^>,
general characters with those described
above, in nearly all species of reptiles
and birds; though there are some modifications, in particular instances, which
do not require any special notice. 
The ovaries, as well as the eggs which
they contain, undergo at particular seasons a periodical development or increase    ^S OF FR^-a, a. Ovaries.
in growth.  If we examine the female  b,b. Oviducts. c,c. Their internal
orifices.  d. Cloaca, showing exterfrog in the latter part of summer or the   al orifices of oviducts.
fall, we shall find the ovaries presenting
the appearance of small clusters of minute and nearly colorless
eggs, the smaller of which are perfectly transparent and not over
T4i  of an inch in diameter.  But in the early spring, when the
season of reproduction approaches, the ovaries will be found increased to four or five times their former size, and forming large
lobulated masses, crowded with dark-colored opaque eggs, measuring 1  of an inch in diameter.  At the approach of the generative
season, in all the lower animals, a certain number of the eggs, which
were previously in an imperfect and inactive condition, begin to
increase in size and become somewhat altered in structure. The
vitellus more especially, which was before colorless and transparent,
becomes granular in texture as well as increased in volume; and
assumes at the same time, in many species of animals, a black,
brown, yellow, or orange color. In the human subject, however,




532    EGG AND FEMALE ORGANS OF GENERATION.
the change consists only in an increase of size and granulation,
without any remarkable alteration of color.
The eggs, as they ripen in this way, becoming enlarged and
changed in texture, gradually distend the Graafian follicles and
project from the surface of the ovary. At last, when fully ripe,
they are discharged by a rupture of the walls of the follicles, and,
passing into the oviducts, are conveyed by them  to the external
generative orifice, and there expelled. In this way, as successive
seasons come round, successive crops of eggs enlarge, ripen, leave
the ovaries, and are discharged.  Those which are to be expelled
at the next generative epoch may always be recognized by their
greater degree of development; and in this way, in many animals,
the eggs of no less than three different crops may be recognized in
the ovary at once, viz., 1st, those which are perfectly mature and
ready to be discharged; 2d, those which are to ripen in the following season; and 3d, those which are as yet altogether inactive and
undeveloped.  In most fish and reptiles, as well as in birds, this
regular process of maturation and discharge of eggs takes place
but once a year. In different species of quadrupeds it may take
place annually, semi-annually, bi-monthly, or even monthly; but
in every instance it recurs at regular intervals, and exhibits accordingly, in a marked degree, the periodic character which we have
seen to belong to most of the other vital phenomena.
Action of the Oviducts and Female Generative Passages.-In frogs
and lizards, the ripening and discharge of the eggs take place, as
above mentioned, in the early spring.  At the time of leaving the
ovary, the eggs consist simply of the dark-colored and granular
vitellus, inclosed in the vitelline membrane. They are then received
by the inner extremity of the oviducts, and carried downward by
the peristaltic movement of these canals, aided by the more powerful contraction of the abdominal musFig. 179.          cles. During the passage of the eggs,
moreover, the mucous membrane of
the oviduct secretes a colorless, viscid,
6Q0~6                       albuminoid substance, which is depoa1.;  ~sited in successive layers round each
-b      egg, forming a thick and tenacious
IATURE FROo' EGs. —a. While coating or envelope. (Fig. 179.) When
still in  the  ovary.  b. After passing 
through the oviduct.        the eggs are finally discharged, this
albuminoid matter absorbs the water
in which the spawn is deposited, and swells up into a transparent




EGG AND FEMALE ORGANS OF GENERATION.   533
gelatinous mass, in which the eggs are separately imbedded. This
substance supplies, by its subsequent liquefaction and absorption,
a certain amount of nutritious material, during the development
and early growth of the embryo.
In the terrestrial reptiles and in birds, the oviducts perform a
still more important secretory function. In the common fowl, the
ovary consists, as in the frog, of a large number of follicles, loosely
connected by areolar tissue, in which the eggs can be seen in different
stages of development. (Fig. 180, a.) As the egg which is approaching maturity enlarges, it distends the cavity of its follicle and projects farther from the general surface of the ovary; so that it hangs
at last into the peritoneal cavity, retained only by the attenuated
wall of the follicle, and a slender pedicle through which run the
bloodvessels by which its circulation is supplied.. Arupture of the
follicle then occurs, at its most prominent part, and the egg is discharged from the lacerated opening.
At the time of its leaving the ovary, the egg of the fowl consists
of a large, globular, orange-colored vitellus, or "yolk," inclosed in
a thin and transparent vitelline membrane. Immediately underneath the vitelline membrane, at one point upon the surface of the
vitellus, is a round white spot, consisting of a layer of minute
granules, termed the "cicatricula." It is in the central part of the
cicatricula that the germinative vesicle is found imbedded, at an
early stage of the development of the egg. At the time of its
discharge from the ovary, the germinative vesicle has usually disappeared; but the cicatricula is still a very striking and important
part of the vitellus, as it is from this spot that the body of the chick
begins afterward to be developed.
At the same time that the egg protrudes from the surface of the
ovary, it projects into the inner orifice of the oviduct; so that, when
discharged from its follicle, it is immediately embraced by the upper
or fringed extremity of this tube, and commences its passage downward. In the fowl, the muscular coat of the oviduct is highly developed, and its peristaltic contractions gently urge the egg fron above
downward, precisely as the oesophagus or the intestines transport
the food in a similar direction.  While passing through the first
two or three inches of the oviduct (c, d), where the mucous membrane is smooth and transparent, the yolk merely absorbs a certain
quantity of fluid, so as to become more flexible and yielding in consistency. It then passes into a second division of the generative
canal, in which the mucous membrane is thick and glandular in




534    EGG AND FEMALE ORGANS OF GENERATION.
texture, and is also thrown into numerous longitudinal folds, which
project into the cavity of the oviduct. This portion of the oviduct
(d, e) extends over about nine inches of its entire length. In its
upper part, the mucous membrane secretes a viscid material, by
which the yolk is encased, and which soon consolidates into a gelatinous, membranous deposit; thus forming a second homogeneous
layer, outside the vitelline membrane.
Now the peristaltic movements of this part of the oviduct are
such as to give a rotatory, as well as a progressive motion to the
egg; and the two extremities of the membranous layer described
above become, accordingly, twisted, in opposite directions, into two
fine cords, which run backward and forward from the opposite poles
of the egg. These cords are termed the "chalazze," and the membrane with which they are connected, the "chalaziferous membrane."
Throughout the remainder of the second division of the oviduct,
the mucous membrane exudes an abundant, gelatinous, albuminoid
substance, which is deposited in successive layers round the yolk,
inclosing at the same time the chalaziferous membrane and the
chalazze. This substance, which forms the so-called albumen, or
" white of egg," is semi-solid in consistency, nearly transparent, and
of a faint amber color. It is deposited in greater abundance in front
of the advancing egg than behind it, and forms accordingly a
pointed or conical projection in front, while behind, its outline is
rounded off, parallel with the spherical surface of the yolk. In this
way, the egg acquires, when covered with its albumen, an ovoid
form, of which one end is round, the other pointed; the pointed
extremity being always directed downward, as the egg descends
along the oviduct.
In the third division of the oviduct (/), which is about three and
a half inches in length, the mucous membrane is arranged in longitudinal folds, which are narrower and more closely packed than in
the preceding portion. The material secreted in this part, and deposited upon the egg, condenses into a firm fibrous covering, composed of three different layers which closely embrace the surface
of the albuminous mass, forming a tough, flexible, semi-opaque
envelope for the whole. These layers are known as the external,
middle, and internal fibrous membranes of the egg.
Finally the egg passes into the fourth division of the oviduct (g),
which is wider than the rest of the canal, but only a little over two
inches in length. Here the mucous membrane, which is arranged
in abundant, projecting, leaf-like villosities, exudes a fluid very rich




EGG AND FEMALE ORGANS OF GENERATION.  535
in calcareous salts. The most external of the three membranes
just described is permeated by this fluid, and very soon the calcareous matter begins to crystallize in the interstices of its fibres. This
deposit of calcareous matter goes on, growing constantly thicker
and more condensed, until the entire
external membrane is converted into                    Fig. 180.
a white, opaque, brittle, calcareous
shell, which  incloses the remaining
portions and protects them  from  external injury. The egg is then driven   
outward  by the contraction of the 
muscular coat through a narrow por-                                c
tion of the oviduct (h), and, gradually 
dilating the passages by its conical                 b
extremity, is finally discharged from
the external orifice.                             cZ
The egg of the fowl, after it has
been discharged from the body, consists, accordingly, of various parts;
solne of which, as the yolk and the
vitelline membrane, entered into its
original formation, while the remainder have been deposited round it dur-.           1 
ing its passage through the oviduct.
On examining such an egg (Fig. 181)
we  find  externally  the  calcareous 
shell (h), while immediately beneath
it are situated the middle and internal
fibrous shell-membranes (e, f).               l
Soon after the expulsion of the egg 
there is a partial evaporation of its
watery ingredients, which are replaced
by air penetrating through the pores                           k
of the shell at its rounded extremity.
The air thus introduced accumulates
between  the  middle  and  internal
fibrous membranes at this spot, sepaFEMALE GENERATIVE ORGANS OF FOWL.-a. Ovary. b. Graafian vesicle, from which the
egg has just been discharged. c. Yolk, entering upper extremity of oviduct. d, e. Second division
of oviduct, in which chalaziferous membrane, chalazae, and albumen are formed. f. Third portion,
in which the fibrous shell membranes are produced. g. Fourth portion laid open, showing egg completely formed, with calcareous shell. h. Narrow canal through which the egg is discharged.




536    EGG AND FEMALE  ORGANS OF GENERATION.
rating them from each other, and forming a cavity or air-chamber
(g), which is always found between the two fibrous membranes at
the rounded end of the egg.  Next we come to the albumen or
white" of the egg (d); next to the chalaziferous membrane and
chalaza (c); and finally to the vitelline membrane (b) inclosing the
Fig. 181.
Diagram of FOWL'S E(. —a. Yolk. b. Vitelline membrane. c. Chalaziferous' membrane d.
Albumen. e,f. Middle and internal shell membranes. g. Air-chamber. h.Calcareous shell.
yolk (a).  After the expulsion of the egg, the external layers of the
albumen liquefy; and the vitellus, being specifically lighter than
the albumen, owing to the large proportion of oleaginous matter
which it contains, rises toward the surface of the egg, with the cicatricula uppermost.  This part, therefore, presents itself almost immediately on breaking open the egg upon its lateral surface, and is
placed in the most favorable position for the action of warmth and
atmospheric air in the development of the chick.
The vitellus, therefore, is still the essential and constituent portion
of the egg; while all the other parts consist either of nutritious material, like the albumen, provided for the support of the embryo, or
of protective envelopes, like the shell and the fibrous membranes.
In the quadrupeds, another and still more important modification
of the oviducts takes place.  In these animals, the egg, which is
originally very minute in size, is destined to be retained within the
generative passages of the female curing the development of the
embryo.  While the upper part of the oviduct, therefore, is quite
narrow, and intended merely to transmit the egg from the ovary,
and to supply it with a little albuminous secretion, its lower portions are very much increased in size, and are lined, moreover, with




EGG AND FEMALE ORGANS OF GENERATION.   537
a mucous membrane, so constructed as to provide for the protection
and nourishment of the embryo, during the entire period of gestation. The upper and narrower portions of the oviduct are known
as the "Fallopian tubes" (Fig. 182); while the lower and more
Fig. 182.
UTERUS AND OVARIES OF THE Sow.-a, a. Ovaries. b, b. Fallopian tubes. c, c Horns of
uterus. d. Body of uterus. e. Vagina.
highly developed portions constitute the uterus. These lower portions unite with each other upon the median line near their inferior termination, so as to form a central organ, termed the "body"
of the uterus; while the remaining ununited parts are known as
its "cornua," or "horns."
In the human subject, the female generative apparatus presents
the following peculiarities. The ovaries consist of Graafian follicles,
which are imbedded in a somewhat dense areolar tissue, supplied
with an abundance of bloodvessels. The entire mass is covered
with a thick, opaque, yellowish white layer of fibrous tissue called
the "albugineous tunic."  Over the whole is a layer of peritoneum,
which is reflected upon the vessels which supply the ovary, and is
continuous with the broad ligaments of the uterus.
The oviducts commence by a wide expansion, provided with
fringed edges, called the "fimbriated extremity of the Fallopian
tube."  The Fallopian tubes themselves are very narrow and convoluted, and terminate on each side in'the upper part of the body
of the uterus. In the human subject, the body of the uterus is so
much developed at the expense of the cornua, that the latter hardly
appear to have an existence; and in fact no trace of them is visible
externally. But on opening the body of the uterus its cavity is
seen to be nearly triangular in shape, its two superior angles running out on each side to join the lower extremities of the Fallopian
tubes. This portion evidently consists of the cornua, which have




538    EGG AND  FEMALE ORGANS OF GENERATION.
been consolidated with the body of the uterus, and enveloped' in
its thickened layer of muscular fibres.
Fig. 183.
GENERATIVE OROANS OF IIHMAN FEMALE. —a, a. Ovaries. b, b. Fallopian tubes.
c. Body of uterus. d. Cervix. e. Vagina.
The cavity of the body of the uterus terminates below by a constricted portion termed the os internum, by which it is separated
from the cavity of the cervix. These two cavities are not only
different from each other in shape, but differ also in the structure
of their mucous membrane and the functions which it is destined
to perform.
The mucous membrane of the body of the uterus in its usual
condition is smooth and rosy in color, and closely adherent to the
subjacent muscular tissue. It consists of minute tubular follicles
somewhat similar to those of the gastric mucous membrane, ranged
side by side, and opening by distinct orifices upon its free surfaceThe secretion of these follicles is destined for the nutrition of the
embryo during the earlier periods of its formation.
The internal surface of the neck of the uterus, on the other hand,
is raised in prominent ridges, which are arranged usually in two
lateral sets, diverging from a central longitudinal ridge; presenting
the appearance known as the "arbor vitae uterina."  The follicles
of this part of the uterine mucous membrane are different in structure from those of the foregoing. They are of a globular or saclike form, and secrete a very firm, adhesive, transparent mucus,
which is destined to block up the cavity of the cervix during ges



EGG AND FEMALE ORGANS OF GENERATION.   539
tation, and guard against the accidental displacement of the egg.
Some of these follicles are frequently distended with their secretion,
and project, as small, hard, rounded eminences, from the surface
of the mucous membrane. In this condition they are sometimes
designated by the name of "ovula Nabothi," owing to their having
been formerly mistaken for eggs, or ovules.
The cavity of the cervix uteri is terminated below by a second
constriction, the "os externum."  Below this comes the vagina,
which constitutes the last division of the female generative passages.
The accessory female organs of generation consist therefore of
ducts or tubes, by means of which the egg is conveyed from within
outward.  These ducts vary in the degree and complication of
their development, according to the importance of the task assigned
to them. In the lower orders, they serve merely to convey the egg
rapidly to the exterior, and to supply it more or less abundantly
with an albuminous secretion. In the higher classes and in the
human subject, they are adapted to the more important function of
retaining the egg during the period of gestation, and of providing
during the same time for the nourishment of the young embryo.




540           MALE ORGANS OF GENERATION.
CHAPTER IV.
ON THE SPERMATIC FLUID, AND THE MALE ORGANS
OF GENERATION.
THE mature egg is not by itself capable of being developed into
the embryo. If simply discharged from the ovary and carried
through the oviducts toward the exterior, it soon dies and is decomposed, like any other portion of the body separated from its
natural connections. It is only when fecundated by the spermatic
fluid of the male, that it is stimulated to continued development,
and becomes capable of a more complete organization.
The product of the male generative organs consists of a colorless,
somewhat viscid, and albuminous fluid, containing an innumerable
quantity of minute filamentous bodies, termed spermatozoa. The
name spermatozoa has been given to these bodies, on account of
their exhibiting under the microscope a very active and continuous movement, bearing some resemblance to that of certain animalcules.
The spermatozoa of the human subject (Fig. 184, a) are about
G-< of an inch in length, according to the measurements of Kolliker.  Their anterior extremity presents a somewhat flattened,
triangular-shaped enlargement, termed the "head." The head constitutes about one-tenth part the entire length of the spermatozoon. The remaining portion is a very slender filamentous prolongation, termed the "tail," which tapers gradually backward,
becoming so exceedingly delicate toward its extremity, that it is
difficult to be seen except when in motion. There is no further
organization or internal structure to be detected in any part of the
spermatozoon; and the whole appears to consist, so far as can be
seen by the microscope, of a completely homogeneous, tolerably
firm, albuminoid substance. The terms head and tail, therefore,
as justly remarked by Bergmann and Leuckart,' are not used,
when describing the different parts of the spermatozoon, in the
same sense as that in which they would be applied to the correVergleichende Physiologie. Stuttgart, 1852.




MALE ORGANS OF GENERATION.                     541
sponding parts of an animal, but simply for the sake of convenience; just as one might speak of the head of an arrow, or the tail
of a comet.
In the lower animals, the spermatozoa have usually the same
general form as in the human subject; that is, they are slender
filamentous bodies, with the anterior extremity more or less enlarged. In the rabbit they have a head which is roundish and
flattened in shape, somewhat resembling the globules of the blood.
In the rat (Fig. 184, b) they are much larger than in man, measuring nearly yT  of an inch in length.  The head is conical in shape,
Fig. 184.
SP R  A TOZOA.-a. Human. b. Of Rat. c. Of Menobranchus. Magnified 480times.
about one-twentieth the whole length of the filament, and often
slightly curved at its anterior extremity.  In the frog and in reptiles generally, the spermatozoa are longer than in quadrupeds.
In the Menobranchus, or great American water-lizard, they are of
very unusual size (Fig. 184, c), measuring not less than 4-  of an
inch in length, about one-third of which is occupied by the head,
or enlarged portion of the filament.




542           MALE ORGANS OF GENERATION.
The most remarkable peculiarity of the spermatozoa is their
very singular and active movement, to which we have already
alluded.  If a drop of fresh seminal fluid be placed under the
microscope, the numberless minute filaments with which it is
crowded are seen to be in a state of incessant and agitated motion.
This movement of the spermatozoa, in many species of animals,
strongly resembles that of the tadpole; particularly when, as in the
human subject, the rabbit, &c., the spermatozoa consist of a short
and well defined head, followed by a long and slender tail. Here
the tail-like filament keeps up a constant lateral or vibratory movement, by which the spermatozoon is driven from place to place in
the spermatic fluid, just as the fish or the tadpole is propelled
through the water. In other instances, as for example in the waterlizard, and in some parasitic animals, the spermatozoa have a continuous writhing or spiral-like movement, which presents a very
peculiar and elegant appearance when large numbers of them are
viewed together.
It is the existence of this movement which first suggested the
name of spermatozoa to designate the animated filaments of the
spermatic fluid; and which has led, some writers to attribute to
them  an independent animal nature. This is, however, a very
erroneous mode of regarding them; since they cannot properly be
considered as animals, notwithstanding the active character of their
movement, and the striking resemblance which it sometimes presents to a voluntary act.  The spermatozoa are organic forms,
which are produced in the testicles, and constitute a part of their
tissue; just as the eggs, which are produced in the ovaries, naturally form a part of the texture of these organs. Like the egg,
also, the spermatozoon is destined to be discharged from the organ
where it grew, and to retain, for a certain length of time afterward,
its vital properties. One of the most peculiar of these properties
is its power of keeping in constant motion; which does not, however, mark it as a distinct animal, but only distinguishes it as a
peculiar structure belonging to the parent organism. The motion
of a spermatozoon is precisely analogous to that of a ciliated epithelium cell. The movement of the latter will continue for some
hours after it has been separated from its mucous membrane, provided its texture be not injured, nor the process of decomposition
allowed to commence. In the same manner, the movement of the
spermatozoa is a characteristic property belonging to them, which
continues for a certain time, even after they have been separated
from all connection with the rest of the body.




MALE ORGANS OF GENERATION.                   543
In order to preserve their vitality, the spermatozoa must be
kept at the ordinary temperature of the body, and preserved
from the contact of the air or other unnatural fluids. In this way,
they may be kept without difficulty many hours for purposes of
examination. But if the fluid in which they are kept be allowed
to dry, or if it be diluted by the addition of water, in the case of
birds and quadrupeds, or if it be subjected to extremes of heat or
cold, the motion ceases, and the spermatozoa themselves soon begin
to disintegrate.
The spermatozoa are produced in certain glandular-looking
organs, the testicles, which are characteristic of the male, as the ovaries are characteristic of the female. In man and all the higher
animals, the testicles are solid, ovoid-shaped bodies, composed
principally of numerous long, narrow, and convoluted tubes, the
"seminiferous tubes," somewhat similar in their general anatomical
characters to the tubuli uriniferi of the kidneys. These tubes lie
for the most part closely in contact with each other, so that nothing
intervenes between them except capillary bloodvessels and a little
areolar tissue. They commence, by blind, rounded extremities, near
the external surface of the testicle, and pursue an intricately convoluted course toward its central and posterior part. They are not
strongly adherent to each other, but may be readily unravelled by
manipulation, and separated from each other.
The formation of the spermatozoa, as it takes place in the
substance of the testicle, has been fully investigated by K6lliker.
According to his observations, as the age of puberty approaches,
beside the ordinary pavement epithelium lining the seminiferous
tubes, other cells or vesicles of larger size make their appearance
in these tubes, each containing from one to fifteen or twenty nuclei,
with nucleoli. It is in the interior of these vesicles that the spermatozoa are formed; their number corresponding usually with that
of the nuclei just mentioned. They are at first developed in bundles
of ten to twenty, held together by the thin membranous substance
which surrounds them, but are afterward set free by the liquefaction of the vesicle, and then fill nearly the entire cavity of the
seminiferous ducts, mingled only with a very minute quantity of
transparent fluid.
In the seminiferous tubes themselves, the spermatozoa are always inclosed in the interior of their parent vesicles; they are liberated, and mingled promiscuously together, only after entering the
rete testis and the head of the epididymis.




544            MALE ORGANS OF GENERATION.
Beside the testicles, which are, as above stated, the primary and
essential parts of the male generative apparatus; there are certain
secondary or accessory organs, by means of which the spermatic
fluid is conveyed to the exterior, and mingled with various secretions which assist in the accomplishment of its functions.
As the sperm leaves the testicle, it consists, as above mentioned,
almost entirely of the spermatozoa, crowded together in an opaque,
white, semi-fluid mass, which fills up the vasa efferentia, and completely distends their cavities. It then enters the single duct which
forms the body and lower extremity of the epididymis, following
the long and tortuous course of this tube, until it becomes continuous with the vas deferens; through which it is still conveyed
onward to the point where this canal opens into the urethra.
Throughout this course, it is mingled with a glairy, mucus like
fluid, secreted by the walls of the epididymis and vas deferens, in
which the spermatozoa are enveloped.  The mixture is then deposited in the vesiculhe seminales, where it accumulates as fresh quantities are produced in the testicle and conveyed downward by the
spermatic duct. It is probable that a second secretion is supplied
also by the internal surface of the vesiculae seminales, and that the
sperm, while retained in their cavities, is not only stored up for
subsequent use, but is at the same time modified in its properties
by the admixture of another fluid.
At the time when the evacuation of the sperm takes place, it is
driven out from the seminal vesicles by the muscular contraction
of the surrounding parts, and meets in the urethra with the secretions of the prostate gland, the glands of Cowper, and the mucous
follicles opening into the urethral passage. All these organs are at
that time excited to an unusual activity of secretion, and pour out
their different fluids in great abundance.
The sperm, therefore, as it is discharged from the urethra, is an
exceedingly mixed fluid, consisting of the spermatozoa derived
from the testicles, together with the secretions of the epididymis
and vas deferens, the prostate, Cowper's glands, and the mucous follicles of the urethra. Of all these ingredients, it is the spermatozoa
which constitute the essential part of the seminal fluid. They are
the true fecundating element of the sperm, while all the others are
secondary in importance, and perform only accessory functions.
Spallanzani found that if frog's semen be passed through a succession of filters, so as to separate the spermatozoa from the liquid
portions, the filtered fluid is destitute of any fecundating properties;




MALE ORGANS OF GENERATION.                   545
while the spermatozoa remaining entangled in the filter, if mixed
with a sufficient quantity of fluid of the requisite density for dilution, may still be successfully used for the impregnation of eggs.
It is well known, also, that animals or men from whom both testicles have been removed, are incapable of impregnating the female
or her eggs; while a removal or imperfection of any of the other
generative organs does not necessarily prevent the accomplishment
of the function.
In most of the lower orders of animals there is a periodical
development of the testicles in the male, corresponding in time with
that of the ovaries in the female. As the ovaries enlarge and the
eggs ripen in the one sex, so in the other the testicles increase in
size, as the season of reproduction approaches, and become turgid
with spermatozoa.  The accessory organs of generation, at the
same time, share the unusual activity of the testicles, and become
increased in vascularity and ready to perform their part in the
reproductive function.
In the fish, for example, where the testicles occupy the same
position in the abdomen as the ovaries in the opposite sex, these
bodies enlarge, become distended with their contents, and project
into the peritoneal cavity. Each of the two sexes is then at the
same time under the influence of a corresponding excitement. The
unusual development of the generative organs reacts upon the entire
system, and produces a state of peculiar activity and excitability,
known as the condition of "erethism."  The female, distended with
eggs, feels the impulse which leads to their expulsion; while the
male, bearing the weight of the enlarged testicles and the accumulation of newly-developed spermatozoa, is impelled by a similar
sensation to the discharge of the sperrnatic fluid. The two sexes,
accordingly, are led by instinct at this season to frequent the same
situations. The female deposits her eggs in some spot favorable
to the protection and development of the young; after which the
male, apparently attracted and stimulated by the sight of the newlaid eggs, discharges the spermatic fluid upon them, and their
impregnation is accomplished.
In such instances as the above, where the male and female generative products are discharged separately by the two sexes, the
subsequentnt contact of the eggs with the spermatic fluid would seem
to be altogether dependent on the occurrence of fortuitous circumstances, and their impregnation, therefore, often liable to fail. In
point of fact, however, the simultaneous functional excitement of
35




546           MALE ORGANS OF GENERATION.
the two sexes and the operation of corresponding instincts, leading
them to ascend the same rivers and to frequent the same spots,
provide with sufficient certainty for the impregnation of the eggs.
In these animals, also, the number of eggs produced by the female
is very large, the ovaries being often so distended as to fill nearly
the whole of the abdominal cavity; so that, although many of the
eggs may be accidentally lost, a sufficient number will still be impregnated and developed, to provide for the continuation of the
species.
In other instances, an actual contact takes place between the
sexes at the time of reproduction. In the frog, for example, the
male fastens himself upon the back of the female by the anterior
extremities, which seem to retain their hold by a kind of spasmodic
contraction. This continues for one or two days, during which
time the mature eggs, which have been discharged from the ovary,
are passing downward through the oviducts. At last they are expelled from the anus, while at the same time the seminal fluid of
the male is discharged upon them, and impregnation takes place.
In the higher classes of animals, however, and in man, where the
egg is to be retained in the body of the female parent during its
development, the sperratic fluid is introduced into the female
generative passages by sexual congress, and meets the egg at or
soon after its discharge from the ovary. The same correspondence,
however, between the periods of sexual excitement in the male and
female, is visible in many of these animals, as well as in fish and
reptiles. This is the case in most species which produce young but
once a year, and at a fixed period, as the deer and the wild hog. In
other species, on the contrary, such as the dog, as well as the rabbit,
the guinea pig, &c., where several broods of young are produced
during the year, or where, as in the human subject, the generative
epochs of the female recur at short intervals, so that the particular
period of impregnation is comparatively indefinite, the generative
apparatus of the male is almost constantly in a state of full development; and is excited to action at particular periods, apparently
by some influence derived from the condition of the female.
In the quadrupeds, accordingly, and in the human species, the
contact of the sperm with the egg and the fecundation of the latter
take place in the generative passages of the female; either in the
uterus, the Fallopian tubes, or even upon the surface of the ovary;
in each of which situations the spermatozoa have been found, after
the accomplishment of sexual intercourse.




PERIODICAL OVULATION.                   547
CHAPTER V.
ON PERIODICAL OVULATION, AND THE FUNCTION
OF MENSTRUATION.
I. PERIODICAL OVULATION.
WE have already spoken in general terms of the periodical ripening of the eggs and their discharge from the generative organs of
the female. This function is known by the name of " ovulation,"
and may be considered as the primary and most important act in
the process of reproduction. We shall therefore enter more fully
into the consideration of certain particulars in regard to it, by
which its nature and conditions may be more clearly understood.
1st. Eggs exist originally in the ovaries of all animals, as part of
their natural structure. In describing the ovaries of fish and reptiles
we have said that they consist of nothing more than Graafian vesicles, each vesicle containing an egg, and united with the others by
loose areolar tissue and a peritoneal investment. In the higher
animals and in the human subject, the essential constitution of the
ovary is the same; only its fibrous tissue is more abundant, so that
the texture of the entire organ is more dense, and its figure more
compact. In all classes, however, without exception, the interior
of each Graafian vesicle is occupied by an egg; and it is from this
egg that the young offspring is afterward produced.
The process of reproduction was formerly regarded as essentially
different in the oviparous and the viviparous animals. In the oviparous classes, such as most fish, and all reptiles and birds, the young
animal was well known to be formed from an egg produced by the
female; while in the viviparous animals, or those which bring
forth their young alive, such as the quadrupeds and the human
species, the embryo was supposed to originate in the body of the
female, by some altogether peculiar and mysterious process, in
consequence of sexual intercourse.  As soon, however, as the
microscope began to be used in the examination of the tissues,




548  OVULATION AND FUNCTION OF MENSTRUATION.
the ovaries of quadrupeds were also found to contain eggs. These
eggs had previously escaped observation on account of their simple
structure and minute size; but they were nevertheless found to
possess all the most essential characters belonging to the larger
eggs of the oviparous animals.
The true difference in the process of reproduction, between the
two classes, is therefore merely an apparent, not a fundamental one.
In fish, reptiles, and birds, the egg is discharged by the female
before or immediately after impregnation, and the embryo is subsequently developed and hatched externally. In the quadrupeds and
the human species, on the other hand, the egg is retained within
the body of the female until the embryo is developed; when the
membranes are ruptured and the young expelled at the same time.
In all classes, however, viviparous as well as oviparous, the young
is produced equally from an egg; and in all classes the egg, sometimes larger and sometimes smaller, but always consisting essentially
of a vitellus and a vitelline membrane, is contained originally in
the interior of an ovarian follicle.
The egg is accordingly, as we have already intimated, an integral
part of the ovarian tissue. It may be found there long before the
generative function is established, and during the earliest periods
of life. It may be found without difficulty in the newly born
female infant, and may even be detected in the foetus before birth.
Its growth and nutrition, also, are provided for in the same manner with that of other portions of the bodily structure.
2d. These eggs become more fully developed at a certain age, when
the generative function is about to be established. During the early
periods of life, the ovaries and their contents, like many other
organs, are imperfectly developed. They exist, but they are as
yet inactive, and incapable of performing any function. In the
young chick, for example, the ovary is of small size; and the eggs,
instead of presenting the voluminous, yellow, opaque vitellus which
they afterward exhibit, are minute, transparent, and colorless. In
the young quadrupeds, and in the human female during infancy
and childhood, the ovaries are equally inactive. They are small,
friable, and of a nearly homogeneous appearance to the naked eye;
presenting none of the enlarged follicles, filled with transparent
fluid, which are afterward so readily distinguished.  At this time,
accordingly, the female is incapable of bearing young, because the
ovaries are inactive, and the eggs which they contain immature.
At a certain period, however, which varies in the time of its




PERIODICAL OVULATION.                    549
occurrence for different species of animals, the sexual apparatus
begins to enter upon a state of activity. The ovaries increase in
size, and their circulation becomes more active. The eggs, also,
instead of remaining quiescent, take on a rapid growth, and the
structure of the vitellus is completed by the abundant deposit of
oleaginous granules in its interior. Arrived at this state, the eggs
are ready for impregnation, and the female becomes capable of
bearing young. She is then said to have arrived at the state of
"puberty," or that condition in which the generative organs are
fully developed.  This condition is accompanied by a visible
alteration in the system at large, which indicates the complete
development of the entire organism. In many birds, for example,
the plumage assumes at this period more varied and brilliant
colors; and in the common fowl the comb, or "crest," enlarges
and becomes red and vascular. In the American deer (Cervus
virginianus), the coat, which during the first year is mottled with
white, becomes in the second year of a uniform tawny or reddish
tinge. In nearly all species, the limbs become more compact and
the body more rounded; and the whole external appearance is so
altered, as to indicate that the animal has arrived at the period of
puberty, and is capable of reproduction.
3d. Successive crops of eggs, in the adult female, ripen and are
discharged independently of sexual intercourse. It was formerly supposed, as we have mentioned above, that in the viviparous animals
the germ was formed in the body of the female only as a consequence of sexual intercourse.  Even after the important fact
became known that eggs exist originally in the ovaries of these
animals, and are only fecundated by the influence of the spermatic fluid, the opinion still prevailed that the occurrence of sexual
intercourse was the cause of their being discharged from the ovary,
and that the rupture of a Graafian vesicle in this organ was a
certain indication that coitus had taken place.
This opinion, however, was altogether unfounded. We already
know that in fish and reptiles the mature eggs not only leave the
ovary, but are actually discharged from the body of the female
while still unimpregnated, and only subsequently come in contact
with the spermatic fluid. In fowls, also, it is a matter of common
observation that the hen will continue to lay fully-formed eggs, if
well supplied with nourishment, without the presence of the cock;
only these eggs, being unimpregnated, are incapable of producing




550  OVULATION AND FUNCTION  OF MENSTRUATION.
chicks. In oviparous animals, therefore, the discharge of the egg,
as well as its formation, is independent of sexual intercourse.
Continued observation shows this to be the case, also, in the
viviparous quadrupeds. The researches of Bischoff, Pouchet, and
Coste have demonstrated that in the sheep, the pig, the bitch, the
rabbit, &c., if the female be carefully kept from the male until after
the period of puberty is established, and then killed, examination
of the ovaries will show that Graafian vesicles have matured, ruptured, and discharged their eggs, in the same manner as though
sexual intercourse had taken place. Sometimes the vesicles are
found distended and prominent upon the surface of the ovary;
sometimes recently ruptured and collapsed; and sometimes in various stages of cicatrization and atrophy. Bischoff,' in several instances of this kind, actually found the unimpregnated eggs in the
oviduct, on their way to the cavity of the uterus. In those animals
in which the ripening of the eggs takes place at short intervals, as,
for example, the sheep, the pig, and the cow, it is very rare to examine the ovaries in any instance where traces of a more or less
recent rupture of the Graafian follicles are not distinctly visible.
One of the most important facts, derived from the examination
of such cases as the above, is that the ovarian eggs become developed and are discharged in successive crops, which follow each
other regularly at periodical intervals. If we examine the ovary
of the fowl, for example (Fig. 180), we see at a glance how the eggs
grow and ripen, one after the other, like fruit upon a vine. In this
instance, the process of evolution is very rapid; and it is easy to
distinguish, at the same time, eggs which are almost microscopic in
size, colorless, and transparent; those which are larger, firmer,
somewhat opaline, and yellowish in hue; and finally those which
are fully developed, opaque, of a deep orange color, and just ready
to leave the ovary.
It will be observed that in this instance the difference between
the undeveloped and the mature eggs consists principally in the
size of the vitellus, which is furthermore, for reasons previously
given (Chap. III.), very much larger than in the quadrupeds. It
is also seen that it is the increased size of the vitellus alone, by
which the ovarian follicle is distended and ruptured, and the egg
finally discharged.
In the human species and the quadrupeds, on the other hand,
Memoire sur la chute periodique de'ceuf, &c., Annales des Sciences Naturelles,
Aout-Septembre, 1844.




PERIODICAL OVULATION.                    551
the microscopic egg never becomes large enough to distend the
follicle by its own size. The rupture of the follicle and the libera.
tion of the egg are accordingly provided for, in these instances, by
a totally different mechanism.
In the earlier periods of life, in man and the higher animals, the
egg is contained in a Graafian follicle which closely embraces its
exterior, and is consequently hardly larger than the egg itself. As
puberty approaches, those follicles which are situated near the free
surface of the ovary become enlarged by the accumulation of a
colorless serous fluid in their cavity. We then find that the ovary,
when cut open, shows a considerable number of globular, transparent vesicles, readily perceptible by the eye, the smaller of which
are deep seated, but which increase in size as they approach the
free surface of the organ. These vesicles are the Graafian follicles,
which, in consequence of the advancing maturity of the eggs contained in them, gradually enlarge as the period of generation approaches.
The Graafian follicle at this time consists of a closed globular
sac or vesicle, the external wall of which, though quite translucent,
has a fibrous texture under the microscope and is well supplied
with bloodvessels. This fibrous and vascular wall is distinguished
by the name of the "membrane of the vesicle."  It is not very
firm in texture, and if roughly handled is easily ruptured.
The membrane of the vesicle is lined throughout by a thin layer
of minute granular cells, which form for it a kind of epithelium,
similar to the epithelium of the pleura, pericardium, and other
serous membranes. This layer is termed the membrana granulosa.
It adheres but slightly to the membrane of the vesicle, and may
easily be detached by careless manipulation before the vesicle is
opened, being then mingled, in the form of light flakes and shreds,
with the serous fluid contained in the vesicle.
At the most superficial part of the Graafian follicle, or that
which is nearest the surface of the ovary, the membrana granulosa
is thicker than elsewhere. Its cells are here accumulated, in a
kind of mound or "heap," which has received the name of the
cumulus proligerus.  It is sometimes called the discus proligerus,
because the thickened mass, when viewed from above, has a somewhat circular or disk-like form. In the centre of this thickened
portion of the membrana granulosa the egg is imbedded. It is
accordingly always situated at the most superficial portion of the
follicle, and advances in this way toward the surface of the ovary.




552   OVULATION  AND FUNCTION  OF MENSTRUATION.
As the period approaches at which the egg is destined to be discharged, the Graafian follicle becomes more vascular, and enlarges
by an increased exudation of serum into its cavity. It then begins
Fig. 185.
GR AAFI A  FOLLICLE, near the period of rupture.-a. Membrane of the vesicle. b. Membrana
granulosa. c. Cavity of follicle. d. Egg e. Peritoneum. f. Tunica albuginea. g, g. Tissue of
the ovary.
to project from the surface of the ovary, still covered by the albugineous tunic and the peritoneum. (Fig. 185.) The constant accumulation of fluid, however, in the follicle, exerts such a steady and
increasing pressure from within outward, that the albugineous tunic
and the peritoneum successively yield before it; until the Graafian
follicle protrudes from  the ovary as a tense, rounded, translucent
vesicle, in which the sense of fluctuation can be readily perceived
on applying the fingers to its surface.  Finally, the process of effusion and distension still going on, the wall of the vesicle yields at
its most prominent portion, the contained fluid is driven out with a
gush, by the reaction and elasticity of the neighboring ovarian
tissues, carrying with it the egg,
Fig. 186.              still entangled in the cells of the
/.    proligerous disk.
The rupture of the Graafian
vesicle is accompanied, in some
instances, by an abundant hemorrhage, which takes place from the
internal surface of the congested
follicle, and by which its cavity
is filled with blood. This occurs
in the human subject and in thepig, and to a certain extent, also,
OVARY WITH GRAAFIAN FOLLIC.LE  in other of the lower animals.
RUPTURED; at a, egg just discharged with a                 
portion of menbriana gra nulosa.      ometimes, as in the cow, where




PERIODICAL OVULATION.                     553
no hemorrhage takes place, the Graafian vesicle when ruptured
simply collapses; after which, a slight exudation, more or less tinged
with blood, is poured out during the course of a few hours.
Notwithstanding, however, these slight variations, the expulsion
of the egg takes place, in the higher animals, always in the manner
above described, viz., by the accumulation of serous fluid in the
cavity of the Graafian follicle, by which its walls are gradually distended and finally ruptured.
This process takes place in one or more Graafian follicles at a
time, according to the number of young which the animal produces
at a birth.  In the bitch and the sow, where each litter consists of
from six to twenty young ones, a similar number of eggs ripen and
are discharged at each period. In the mare, in the cow, and in the
human female, where there is usually but one foetus at a birth, the
eggs are matured singly, and the Graafian vesicles ruptured, one
after another, at successive periods of ovulation.
4th. The ripening and discharge of the egg are accompanied by a peculiar condition of the entire system, known as the " rutting" condition, or
"cestruation." The peculiar congestion and functional activity of
the ovaries at each period of ovulation, act by sympathy upon the
other generative organs, and produce in them a greater or less degree of excitement, according to the particular species of animal.
Almost always there is a certain amount of congestion of the entire
generative apparatus; Fallopian tubes, uterus, vagina, and external
organs. The secretions of the vagina and neighboring parts are
more particularly affected, being usually increased in quantity and
at the same time altered in quality.  In the bitch, the vaginal mucous membrane becomes red and tumefied, and pours out an abundant secretion which is often more or less tinged with blood. The
secretions acquire also at this time a peculiar odor, which appears to attract the male, and to excite in him the sexual impulse.
An unusual tumefaction and redness of the vagina and vulva are
also very perceptible in the rabbit; and in some species of apes it
has been observed that these periods are accompanied not only by
a bloody discharge from the vulva, but also by an engorgement and
infiltration of the neighboring parts, extending even to the skin of
the buttocks, the thighs, and the under part of the tail.'
The system at large is also visibly affected by the process going
on in the ovary.  In the cow, for example, the approach of ani
Pouchet, Th6orie positive de l'ovulatiou, &c. Paris, 1847, p. 230.




554  OVULATION AND FUNCTION OF MENSTRUATION.
cestrual period is marked by an unusual restlessness and agitation,
easily recognized by an ordinary observer. The animal partially
loses her appetite. She frequently stops browsing, looks about uneasily, perhaps runs from one side of the field to the other, and then
recommences feeding, to be disturbed again in a similar manner
after a short interval. Her motions are rapid and nervous, and her
hide often rough and disordered; and the whole aspect of the animal indicates the presence of some unusual excitement. After this
condition is fully established, the vaginal secretions show themselves in unusual abundance, and so continue for one or two days;
after which the symptoms, both local and general, subside spontaneously, and the animal returns to her usual condition.
It is a remarkable fact, in this connection, that the female of
these animals will allow the approaches of the male only during and
immediately after the cestrual period; that is, just when the egg is
recently discharged, and ready for impregnation. At other times,
when sexual intercourse would be necessarily fruitless, the instinct
of the animal leads her to avoid it; and the concourse of the sexes
is accordingly made to correspond in time with the maturity of the
egg and its aptitude for fecundation.
II. MENSTRUATION.
In the human female, the return of the periods of ovulation is
marked by a peculiar group of phenomena which are known as
menstruation, and which are of sufficient importance to be described
by themselves.
During infancy and childhood the sexual system, as we have
mentioned above, is inactive. No discharge of eggs takes place
from the ovaries, and no external phenomena show themselves,
connected with the reproductive function.
At the age of fourteen or fifteen years, however, a change begins
to manifest itself. The limbs become rounder, the breasts increase
in size, and the entire aspect undergoes a peculiar alteration, which
indicates the approaching condition of maturity. At the same
time a discharge of blood takes place from the generative passages,
accompanied by some disturbance of the general system, and the
female is then known to have arrived at the period of puberty.
Afterward, the bloody discharge just spoken of returns at regular
intervals of four weeks; and, on account of this recurrence corresponding with the passage of successive lunar months, its phenomena




MENSTRUATION.                       555
are designated by the name of the "menses" or the "menstrual
periods." The menses return with regularity, from the time of
their first appearance, until the age of about forty-five years.
During this period, the female is capable of bearing children, and
sexual intercourse is liable to be followed by pregnancy. After
the forty-fifth year, the periods first become irregular, and then
cease altogether; and their final disappearance is an indication that
the woman is no longer fertile, and that pregnancy cannot again
take place.
Even during the period above referred to, from the age of fifteen
to forty-five, the regularity and completeness of the menstrual
periods indicate to a great extent the aptitude of individual females
for impregnation. It is well known that all those causes of ill
health which derange menstruation are apt at the same time to
interfere with pregnancy; so that women whose menses are habitually regular and natural are much more likely to become pregnant, after sexual intercourse, than those in whom the periods are
absent or irregular.
If pregnancy happen to take place, however, at any time during
the child-bearing period, the menses are suspended during the continuance of gestation, and usually remain absent, after delivery, as
long as the woman continues to nurse her child. They then recommence, and subsequently continue to appear as before.
The menstrual discharge consists of an abundant secretion of
mucus mingled with blood. When the expected period is about
to come on, the female is affected with a certain degree of discomfort
and lassitude, a sense of weight in the pelvis, and more or less disinclination to society.  These symptoms are in some instances
slightly pronounced, in others more troublesome.  An unusual
discharge of vaginal mucus then begins to take place, which soon
becomes yellowish or rusty brown in color, from the admixture of
a certain proportion of blood; and by the second or third day the
discharge has the appearance of nearly pure blood. The unpleasant
sensations which were at first manifest then usually subside; and
the discharge, after continuing for a certain period, begins to grow
more scanty. Its color changes from a pure red to a brownish or
rusty tinge, until it finally disappears altogether, and the female
returns to her ordinary condition.
The menstrual epochs of the human female correspond with the
periods of cestruation in the lower animals. Their general resemblance to these periods is too evident to require demonstration.




556  OVULATION  AND FUNCTION  OF MENSTRUATION.
Like them, they are absent in the immature female; and begin
to take place only at the period of puberty, when the aptitude for
impregnation commences. Like them, they recur during the childbearing period at regular intervals; and are liable to the same
interruption by pregnancy and lactation. Finally, their disappearance corresponds with the cessation of fertility.
The periods of oestruation, furthermore, in many of the lower
animals, are accompanied, as we have already seen, with an unusual
discharge from the generative passages; and this discharge is frequently more or less tinged with blood. In the human female the
bloody discharge is more abundant than in other instances, but it is
evidently a phenomenon differing only in degree from that which
shows itself in many species of animals.
The most complete evidence, however, that the period of menstruation is in reality that of ovulation, is derived from the results
of direct observation. A sufficient number of instances have now
been observed to show that at the menstrual epoch a Graafian
vesicle becomes enlarged, ruptures, and discharges its egg. Cruikshank' noticed such a case so long ago as 1797. Negrier2 relates
two instances, communicated to him  by Dr. Ollivier d'Angers, in
which, after sudden death during menstruation, a bloody and ruptured Graafian vesicle was found in the ovary. Bischoff3 speaks of
four similar cases in his own observation, in three of which, the
vesicle was just ruptured, and in the fourth distended, prominent,
and ready to burst.  Coste4 has met with several of the same kind.
Dr. Michel5 found a vesicle ruptured and filled with blood in a
woman who was executed for murder while the menses were present.  We have also6 met with the same appearances in a case of
death from acute disease, on the second day of menstruation.
The process of ovulation, accordingly, in the human female,
accompanies and forms a part of that of menstruation.  As the
menstrual period comes on, a congestion takes place in nearly the
whole of the generative apparatus; in the Fallopian tubes and the
uterus, as well as in the ovaries and their contents. One of the
London Philosophical Transactions, 1797, p. 135.
2 Recherches sur les Ovaires, Paris, 1840, p. 78.
3 Annales des Sciences Naturelles, August, 1844.
4 Histoire du Developpement des Corps Organis6s, Paris, 1847, vol. i. p. 221.
5 Am. Journ. Med. Sci., July, 1848.
6 Corpus Luteum of Menstruation and Pregnancy, in Transactions of American
Medical Association, Philadelphia, 1851.




MENSTRUATION.                        557
Graafian follicles is more especially the seat of an unusual vascular
excitement. It becomes distended by the fluid which accumulates
in its cavity, projects from the surface of the ovary, and is finally
ruptured, in the same manner as we have already described this
process taking place in the lower animals.
It is not quite certain at what particular period of the menstrual
flow the rupture of the vesicle and discharge of the egg take place.
It is the opinion of Bischoff, Pouchet, and Raciborski, that the
regular time for this rupture and discharge is not at the commencement, but toward the termination of the period. Coste' has ascertained, from his observations, that the vesicle ruptures sometimes
in the early part of the menstrual epoch, and sometimes later. So
far as we can learn, therefore, the precise period of the discharge
of the egg is not invariable. Like the menses themselves, it may
apparently take place a little earlier or a little later, according to
various accidental circumstances; but it always occurs at some
time in connection with the menstrual flow, and constitutes the
most essential and important part of the catamenial process.
The egg, when discharged from the ovary, enters the fimbriated
extremity of the Fallopian tube, and commences its passage toward
the uterus. The mechanism by which it finds its way into and
through the Fallopian tube is different, in the quadrupeds and the
human species, and in birds and reptiles. In the latter, the bulk
of the egg or mass of eggs discharged is so great as to fill entirely
the wide extremity of the oviduct, and they are afterward conveyed
downward by the peristaltic action of the muscular coat of this
canal. In the higher classes, on the contrary, the egg is microscopic in size, and would be liable to be lost, were there not some
further provision for its safety. The wide extremity of the Fallopian tube, accordingly, which is here directed toward the ovary, is
lined with ciliated epithelium; and the movement of the cilia,
which is directed from the ovary toward the uterus, produces a
kind of converging stream, or vortex, by which the egg is necessarily drawn toward the narrow portion of the tube, and subsequently conducted to the cavity of the uterus.
Accidental causes, however, sometimes disturb this regular course
or passage of the egg. The egg may be arrested, for example,
at the surface of the ovary, and so fail to enter the tube at all.
If fecundated in this situation, it will then give rise to "ovarian
1 Loc. cit.




558  OVULATION AND FUNCTION OF MENSTRUATION.
pregnancy."  It may escape from the fimbriated extremity into the
peritoneal cavity, and form attachments to some one of the neighboring organs, causing "abdominal pregnancy;" or finally, it may
stop at any part of the Fallopian tube, and so give origin to " tubal
pregnancy."
The egg, immediately upon its discharge from the ovary, is ready
for impregnation. If sexual intercourse happen to take place about
that time, the egg and the spermatic fluid meet in some part of the
female generative passages, and fecundation is accomplished. It
appears, from various observations of Bischoff, Coste, and others,
that this contact may take place between the egg and the sperm,
either in the uterus or any part of the Fallopian tubes, or even
upon the surface of the ovary. If, on the other hand, coitus do not
take place, the egg passes down to the uterus unimpregnated, loses
its vitality after a short time, and is finally carried away with the
uterine secretions.
It is easily understood, therefore, why sexual intercourse should
be more liable to be followed by pregnancy when it occurs about
the menstrual epoch than at other times. This fact, which was long
since established as a matter of observation by practical obstetricians, depends simply upon the coincidence in time between menstruation and the discharge of the egg. Before its discharge, the
egg is immature, and unprepared for impregnation; and after the
menstrual period has passed, it gradually loses its freshness and
vitality. The exact length of time, however, preceding and following the menses, during which impregnation is still possible, has not
been ascertained. The spermatic fluid, on the one hand, retains its
vitality for an unknown period after coition, and the egg for an
unknown period after its discharge. Both these occurrences may,
therefore, either precede or follow each other within certain limits,
and impregnation be still possible; but the precise extent of these
limits is still uncertain, and is probably more or less variable in
different individuals.
The above facts indicate also the true explanation of certain
exceptional cases, which have sometimes been observed, in which
fertility exists without menstruation. Various authors (Churchill,
Reid, Velpeau, &c.) have related instances of fruitful women in whom
the menses were very scanty and irregular, or even entirely absent.
The menstrual flow is, in fact, only the external sign and accompaniment of a more important process taking place within.  It is
habitually scanty in some individuals, and abundant in others.




MENSTRUATION.                      559
Such variations depend upon the condition of vascular activity of
the system at large, or of the uterine organs in particular; and
though the bloody discharge is usually an index of the general
aptitude of these organs for successful impregnation, it is not an
absolute or necessary requisite. Provided a mature egg be discharged from the ovary at the appointed period, menstruation properly speaking exists, and pregnancy is possible.
The blood which escapes during the menstrual flow is supplied
by the uterine mucous membrane. If the cavity of the uterus be
examined after death during menstruation, its internal surface is
seen to be smeared with a thickish bloody fluid, which may be
traced through the uterine cervix and into the vagina. The Fallopian tubes themselves are sometimes found excessively congested,
and filled with a similar bloody discharge. The menstrual blood
has also been seen to exude from the uterine orifice in cases of procidentia uteri, as well as in the natural condition by examination
with the vaginal speculum. It is discharged by a kind of capillary
hemorrhage, similar to that which takes place from the lungs in
cases of haemoptysis, only less sudden and violent. The blood does
not form any visible coagulum, owing to its being gradually exuded
from many minute points, and mingled with a large quantity of
mucus.  When poured out, however, more rapidly or in larger
quantity than usual, as in cases of menorrhagia, the menstrual blood
coagulates in the same manner as if derived from any other source.
The hemorrhage which supplies it comes from the whole extent of
the mucous membrane of the body of the uterus, and is, at the same
time, the consequence and. the natural termination of the periodical
congestion of the parts.




560          MENSTRUATION  AND PREGNANCY.
CHAPTER VI.
ON THE CORPUS LUTEUM OF MENSTRUATION AND
P REGNANCY.
AFTER the rupture of the Graafian vesicle at the menstrual
period, a bloody cavity is left in the ovary which is subsequently
obliterated by a kind of granulating process, somewhat similar in
character to the healing of an abscess. For the Graafian vesicle
is intended simply for the formation and growth of the egg.
After the egg therefore has arrived at maturity and has been discharged, the Graafian follicle has no longer any function to perform. It then only remains for it to pass through a process of
obliteration and atrophy, as an organ which has become useless
and obsolete.  While undergoing this process, the Graafian vesicle
is at one time converted into a peculiar, solid, globular body, which
is called the corpus luteum; a name given to it on account of the
yellow color which it acquires at a certain period of its formation.
We shall proceed to describe the corpus luteum  in the human
species; first, as it follows the ordinary course of development
after menstruation; and secondly, as it is modified in its growth
and appearance during the existence of pregnancy.
I. CORPUS LUTEUM OF MENSTRUATION.
We have already described, in the preceding chapter, the manner in which a Graafian vesicle, at each menstrual epoch, swells,
protrudes from the surface of the ovary, and at last ruptures and
discharges its egg. At the moment of rupture, or immediately
after it, an abundant hemorrhage takes place in the human subject from  the vessels of the follicle, by which its cavity is filled
with blood.  This blood coagulates soon after its exudation, as
it would do if extravasated in any other part of the body, and
the coagulum  is retained in the interior of the Graafian follicle.
The opening by which the egg makes its escape is usually not an




CORPUS LUTEUM OF MENSTRUATION.                   561
extensive laceration, but a minute rounded perforation, often not
more than half a line in diameter. A  small probe, introduced
through this opening, passes directly into the
Fig. 187.
cavity of the follicle. If the Graafian follicle
be opened at this time by a longitudinal incision (Fig. 187), it will be seen to form a globular cavity, one-half to three-quarters of an
inch in diameter, containing a soft, recent,
dark-colored coagulum.  This coagulum  has
no organic connection with the walls of the
follicle, but lies loose in its cavity and may be
easily turned out with the handle of a knife.
There is sometimes a slight mechanical adhesion of the clot to the edges of the lacerated   GRAAFIA rFOLLICLE
recently ruptured during
opening, just as the coagulum  in a recently  menstruation, and filled
ligatured artery is entangled by the divided  with abloody coaglum;
shown in longitudinal secedges of the internal and middle coats; but tion.-a. Tissue of the
there is no continuity of substance between  ovary. b. embrale oftlle
vesicle. c. Point of rupture.
them, and the clot may be everywhere readily
separated by careful manipulation. The membrane of the vesicle
presents at this time a smooth, transparent, and vascular internal
surface, without any alteration of colori consistency, or texture.
An important change, however, soon begins to take place, both
in the central coagulum and in the membrane of the vesicle.
The clot, which is at first large, soft, and gelatinous, like any
other mass of coagulated blood, begins to contract; and the serum
separates from  the coagulum  proper.  The serum, as fast as it
separates from the coagulum, is absorbed by the neighboring parts;
and the clot, accordingly, grows every day smaller and denser than
before. At the same time the coloring matter of the blood undergoes the changes which usually take place in it after extravasation,
and is partially reabsorbed together with the serum. This second
change is somewhat less rapid than the former, but still a diminution of color is very perceptible in the clot, at the expiration of
two weeks.
The membrane of the vesicle during this time is beginning to
undergo a process of hypertrophy or development, by which it
becomes thickened and convoluted, and tends partially to fill up
the cavity of the follicle. This hypertrophy and convolution of
the membrane just named commences and proceeds most rapidly
36




562           MENSTRUATION AND PREGNANCY.
at the deeper part of the follicle, directly opposite the situation of
the superficial rupture. From this point the membrane gradually
becomes thinner and less convoluted as it approaches the surface
of the ovary and the edges of the ruptured orifice.
At the end of three weeks, this hypertrophy of the membrane of
the vesicle has reached its maximum. The ruptured Graafian follicle has now become so completely solidified by the new growth
above described, and by the condensation of its clot, that it receives
the name of the corpus luteum.  It forms a perceptible prominence
on the surface of the ovary, and may be felt between the fingers
as a well-defined rounded tumor, which is nearly always somewhat
flattened from side to side. It measures about three-quarters of an
inch in length and half an inch in
Fig. 188.          depth.  On its surface may be seen a
minute cicatrix  of the peritoneum,
occupying the spot of the original
rupture.
X-c 1.'~5       On cutting it open at this time (Fig.
188), the corpus luteum is seen to consi st     above described, of a central
e oi      coagulum  and  a  convoluted  wall.
aind c lt:     The coagulum  is semi-transparent, of
any::,i\     a gray or light greenish color, more
or less mottled with red.  The convoluted wall is about one-eighth of
OVARY cut open, showing corpus 
luteum divided longitudinally; three an inch thick at its deepest part, and
weeks after menstruation. From a girl of an indefinite yellowish or rosy
dead of hsemoptysis.
dead of hmopys        hue, not very different in tinge from
the rest of the ovarian tissue. The convoluted wall and the contained clot lie simply in contact with each other, as at first, without
any intervening membrane or other organic connection; and they
may still be readily separated from each other by the handle of a
knife or the flattened end of a probe. The corpus luteum at this
time may also be stripped out, or enucleated entire, from the ovarian
tissue, just as might have been done with the Graafian follicle previously to its rupture. When enucleated in this way, the corpus
luteum presents itself under the form of a solid globular or flattened tumor, with convolutions upon it somewhat similar in appearance to those of the brain, and covered with the remains of
the areolar tissue, by which it was previously connected with the
substance of the ovary.




CORPUS LUTEUM OF MENSTRUATION.                   563
After the third week from the close of menstruation, the corpus
luteum passes into a retrograde condition. It diminishes perceptibly in size, and the central coagulum continues to be absorbed
and loses still farther its coloring matter. The whole body undergoes a process of partial atrophy; and at
the end of the fourth week it is not more           Fig. 189.
than three-eighths of an inch in its longest
diameter. (Fig. 189.)  The external cicatrix
may still usually be seen, as well as the
point where the central coagulum  comes
in contact with the peritoneum. There is
still no organic connection  between  the
central coagulum  and the convoluted wall;            I
but the partial condensation of the clot and
the continued folding of the wall prevent the
separation of the two being so easily accomplished as before, though it may still be   OVAR, slowing corpus
luteurn four weeks after ineneffected by careful management. The entire  struation; fror a woman dead
corpus luteum  may also still be extracted  of apoplexy.
from its bed in the ovarian tissue.
The color of the convoluted wall, during the early part of this
retrograde stage, instead of fading, like that of the fibrinous coagulum, becomes more strongly marked. From having a dull yellowish
or rosy hue, as at first, it gradually assumes a brighter and more
decided yellow. This change of color in the convoluted wall is
produced in consequence of a kind of fatty degeneration which
takes place in its texture; a large quantity of oil-globules being
deposited in it at this time, as may be readily recognized under
the microscope. At the end of the fourth
Fig. 190.
week, this alteration in hue is complete;
and the outer wall of the corpus luteum
is then of a clear chrome-yellow color, by
which it is readily distinguished from all
the neighboring tissues.
After this period, the process of atrophy 
and degeneration goes on rapidly.  The
clot becomes constantly more dense and
shrivelled, and is soon converted into a
minute, stellate, white, or reddish white   OARY, showing corpus ]ucicatrix. The yellow wall becomes softer teum, nine weeks after menstru
and   ore.fiae,  ai.s e witall. tion; from a girl dead of tuberand more friable, as is the case with all cauv, meligitig.




564          MENSTRUATION AND PREGNANCY.
tissues undergoing fatty degeneration, and shows less distinctly
the marking of its convolutions. At the same time, its surfaces
become confounded with the central coagulum  on the one hand,
and the neighboring tissues on the other, so that it is no longer
possible to separate them fairly from each other. At the end of
eight or nine weeks the whole body is reduced to the condition of
an insignificant, yellowish, cicatrix-like spot, measuring less than a
quarter of an inch in its longest diameter, in which the original
texture of the corpus luteum can be recognized only by the peculiar folding and coloring of its constituent parts. Subsequently its
atrophy goes on in a less active manner, and a period of seven or
eight months sometimes elapses before its final and complete disappearance.
The corpus luteum, accordingly, is a formation which results
from the filling up and obliteration of a ruptured Graafian follicle.
Under ordinary conditions, a corpus luteum is produced at every
menstrual period; and notwithstanding the rapidity with which it
retrogrades and becomes atrophied, a new one is always formed
before its predecessor has completely disappeared.
When, therefore, we examine the ovaries of a healthy female, in
whom  the menses have recurred with regularity for some time
previous to death, several corpora lutea will be met with in different
stages of formation and atrophy. Thus we have found, under such
circumstances, four, five, six, and even eight corpora lutea in the
ovaries at the same time, perfectly distinguishable by their texture,
but very small, and most of them evidently, in a state of advanced
retrogression. They finally disappear altogether, and the number
of those present in the ovary, therefore, no longer corresponds with
that of the Graafian follicles which have been ruptured.
II. CORPUS LUTEUM OF PREGNANCY.
Since the process above described takes place at every menstrual
period, it is independent of impregnation and even of sexual intercourse. The mere presence of a corpus luteum, therefore, is no
indication that pregnancy has existed, but only that a Graafian
follicle has been ruptured, and its contents discharged. We find,
nevertheless, that when pregnancy takes place, the appearance of
the corpus luteum  becomes so much altered as to be readily distinguished from that which simply follows the ordinary menstrual




CORPUS LUTEUM OF PREGNANCY.                   565
process. It is proper, therefore, to speak of two kinds of corpora
lutea; one belonging to menstruation, the other to pregnancy.
The difference between these two kinds of corpora lutea is not
an essential or fundamental difference; since they both originate in
the same way, and are composed of the same structures. It is,
properly speaking, only a difference in the degree and rapidity of
their development. For while the corpus luteum of menstruation
passes rapidly through its different stages, and is very soon reduced
to a condition of atrophy, that of pregnancy continues its development for a long time, attains a larger size and firmer organization,
and disappears finally only at a much later period.
This variation in the development and history of the corpus
luteum depends upon the unusually active condition of the pregnant
uterus. This organ exerts a powerful sympathetic action, during
pregnancy, upon many other parts of the system. The stomach
becomes irritable, the appetite is capricious, and even the mental
faculties and the moral disposition are frequently more or less
affected. The ovaries, however, feel the disturbing influence of
gestation more certainly and decidedly than the other organs, since
they are more closely connected with the uterus in the ordinary
performance of their function. The moment that pregnancy takes
place, the process of menstruation is arrested. No more eggs come
to maturity, and no more Graafian follicles are ruptured, during the
whole period of gestation.  It is not at all singular, therefore, that
the growth of the corpus luteur should also be modified, by an
influence which affects so profoundly the system at large, as well
as the ovaries in particular.
During the first three weeks of its formation, the growth of the
corpus luteum is the same, in the impregnated, as in the unimpregnated condition. After that time, however, a difference becomes
manifest. Instead of commencing a retrograde course during the
fourth week, the corpus luteum of pregnancy continues its development. The external wall grows thicker, and its convolutions
more abundant. Its color alters in the same way as previously
described, and becomes a bright yellow by the deposit of fatty
matter in microscopic globules and granules.
By the end of the second month, the whole corpus luteum  has
increased in size to such an extent as to measure seven-eighths of
an inch in length by half an inch in depth. (Fig. 191.) The central
coagulum has by this time become almost entirely decolorized, so as




566           MENSTRUATION AND PREGNANCY.
to present the appearance of a purely fibrinous deposit. Sometimes
we find that a part of the serum, during its separation from the clot,
has accumulated in the centre of the mass, as in Fig. 191, forming a
little cavity containing a few drops of clear fluid and inclosed by a
whitish, fibrinous layer, the remains of the solid portion of the clot.
It is this fibrinous layer
Fig. 191.                which has sometimes been
mistaken for a distinct organized membrane, lining
-:,_....  the internal surface of the
convoluted wall, and which
has thus led to the belief
that the yellow matter of the
corpus luteum is normally
deposited outside the memCORPUS L u T EU M of pregnancy, at end of second
month; from a woman dead from induced abortion.    brane of the Graafian follicle. Such, however, is not
its real structure. The convoluted wall of the corpus luteum is the
membrane of the follicle itself, partially altered by hypertrophy,
as may be readily seen by examination in the earlier stages of its
growth; and the fibrinous layer, situated internally, is the original
bloody coagulum, decolorized and condensed by continued absorption.  The existence of a central cavity, containing serous fluid, is
merely an occasional, not a constant phenomenon. More frequently,
the fibrinous clot is solid throughout, the serum being gradually
absorbed, as it separates spontaneously from the coagulum.
During the third and fourth
Fig. 192.              months, the enlargement of the
I~T'; \corpus luteum  continues; so
that at the end of that time it
may measure seven-eighths of
an inch  in length by threequarters of an inch in depth.
(Fig. 192.)   The  convoluted
wall is still thicker and more
highly developed than before,
having a thickness, at its deepest part, of three-sixteenths of
CoRs LUTEM ofpregnancy, tendof fourth  an inch. Its color however, has
month; from a woman dead by poison.  already begun to fade, and is




CORPUS LUTEUM OF PREGNANCY.                    567
now of a dull yellow, instead of the bright, clear tinge which it
previously exhibited.  The central coagulum, perfectly colorless
and fibrinous in appearance, is often so much flattened out, by the
lateral compression of its mass, that it has hardly a line in thickness.  The other relations of the different parts of the corpus luteum
remain the same.
The corpus luteum  has now attained its maximum of development, and remains without any very perceptible alteration during
the fifth and sixth months. It then begins to retrograde, diminishing constantly in size during the seventh and eighth months. Its
external wall fades still more perceptibly in color, becoming of a
faint yellowish white, not unlike that which it presented at the end
of the third week.  Its texture is thick, soft, and elastic, and it is
still strongly convoluted. An abundance of fine red vessels can be
seen penetrating from the exterior into the interstices of its convolutions. The central coagulum is reduced by this time to the condition of a whitish, radiated cicatrix.
The atrophy of the organ continues during the ninth month.
At the termination of pregnancy, it is re.
duced to the size of half an inch in length         Fig. 193.
and  three-eighths of an inch  in depth.
(Fig. 193.)  It is then of a faint indefinite
hue, but little contrasted with the remain- 
ing tissues of the ovary. The central cicatrix has become very small, and appears
only as a thin whitish lamina, with radiating
processes which run in between the inter- 
stices of the convolutions.  The whole mass,
however, is still quite firm and resisting to
the touch, and  is readily distinguishable,
both from  its size and texture, as a prominent feature in the ovarian tissue, and a   cORPUrs LUTEUM of preg.
reliable indication of preg.        T   con  nancy. Then- ny,at term; from a woman
dead in delivery from rupture
voluted structure of its external wall is  of the uterus.
very perceptible, and the point of rupture,
with its external peritoneal cicatrix, distinctly visible.
After delivery, the corpus luteum  retrogrades rapidly.  At the
end of eight or nine weeks, it has become so much altered that its
color is. no longer distinguishable, and only faint traces of its convoluted structure are to be discovered by close examination. These




568          MENSTRUATION  AND PREGNANCY.
traces may remain, however, for a long time afterward, more or less
concealed in the ovarian tissue. We have distinguished them so
late as nine and a half months after delivery. They finally disappear entirely, together with the external cicatrix which previously
marked their situation.
During the existence of gestation, the process of menstruation
being suspended, no new follicles are ruptured, and no new corpora
lutea produced; and as the old ones, formed before the period of
conception, gradually fade and disappear, the corpus luteum which
marks the occurrence of pregnancy after a short time exists alone
in the ovary, and is not accompanied by any others of older date.
In twin pregnancies, we of course find two corpora lutea in the
ovaries; but these are precisely similar to each other, and, being
evidently of the same date, will not give rise to any confusion.
Where there is but a single foetus in the uterus, and the ovaries
contain two corpora lutea of similar appearance, one of them
belongs to an embryo which has been blighted by some accident
in the early part of pregnancy. The remains of the blighted embryo may often be discovered, in such cases, in some part of the
Fallopian tubes, where it has been arrested in its descent toward
the uterus.
After the process of lactation comes to an end, the ovaries again
resume their ordinary function. The Graafian follicles mature and
rupture in succession, as before, and new corpora lutea follow each
other in alternate development and disappearance.
We find, then, that the corpus luteum of menstruation differs from
that of pregnancy in the extent of its development and the duration of its existence. While the former passes through all the important phases of its growth and decline in the period of two
months, the latter lasts from  nine to ten months, and presents,
during a great portion of the time, a larger size and a more solid
organization.  It will be observed that, even with the corpus
luteum of pregnancy, the bright yellow color, which is so important a characteristic, is only temporary in its duration; not making
its appearance till about the end of the fourth week, and again
disappearing after the sixth month.
The following table contains, in a brief form, the characters of
the corpus luteum, as belonging to the two different conditions of
menstruation and pregnancy, corresponding with different periods
of its development.




CORPUS LUTEUM OF PREGNANCY.                              569
CORPUS LUTEUM OF MENSTRUATION.  CORPUS LUTEUM OF PREGNANCY.
At the end of Three-quarters of an inch in diameter; central clot reddish; conthree weeks   voluted wall pale.
One month   Smaller; convoluted wall bright Larger; convoluted wall bright
yellow; clot still reddish.      yellow; clot still reddish.
Two months  Reduced to the condition of an Seven-eighths of an inch in diainsignificant cicatrix.          meter; convoluted wall bright
yellow; clot perfectly decolorized.
Six months   Absent.                           Still as large as at end of second
month; clot fibrinous; convoluted wall paler.
Nine months Absent.                            One-half an inch in diameter;
central clot converted into a
radiating cicatrix; the external
wall tolerably thick and convoluted, but without any bright
yellow color.




570    DEVELOPMENT OF THE IMPREGNATED EGG.
CHAPTER VII.
ON THE DEVELOPMENT OFTHE IMPREGNATED EGGSEGMENTATION OF THE VITELLUS-BLASTODERMIC
MEMBRANE-FORMA.TION OF ORGANS IN THE FROG.
WE have seen, in the foregoing chapters, how the egg, produced
in the ovarian follicle, becomes gradually developed and ripened,
until it is ready to be discharged. The egg, accordingly, passes
through several successive stages of formation, even while still contained within the ovary; and its vitellus becomes gradually completed, by the formation of albuminous material and the deposit of
molecular granulations. The last change which the egg undergoes,
in this situation, and which marks its complete maturity, is the disappearance of the germinative vesicle. This vesicle, which is, in
general, a prominent feature of the ovarian egg, disappears but a
short time previous to its discharge, or even just at the period of
its leaving the Graafian follicle.
The egg, therefore, consisting simply of the mature vitellus and
the vitelline membrane, comes in contact, after leaving the ovary,
and while passing through the Fallopian tube, with the spermatic
fluid, and thereby becomes fecundated. By the influence of fecundation, a new stimulus is imparted to its growth; and while the
vitality of the unimpregnated germ, arrived at this point, would
have reached its termination, the fecundated egg, on the contrary,
starts upon a new and more extensive course of development, by
which it is finally converted into the body of the young animal.
The egg, in the first place, as it passes down the Fallopian tube,
becomes covered with an albuminous secretion. In the birds, as we
have seen, this secretion is very abundant, and is deposited in successive layers around the vitellus. In the reptiles, it is also poured
out in considerable quantity, and serves for the nourishment of the
egg during its early growth. In quadrupeds, the albuminous matter
is supplied in the same way, though in smaller quantity, by the




SEGMENTATION OF THE VITELLUS.                571
mucous membrane of the Fallopian tubes, and envelopes the egg
in a layer of nutritious material.
Avery remarkable change now takes place in the impregnated egg,
which is known as the spontaneous division, or segmentation, of the
vitellus. A furrow first shows itself,
running round the globularmass of the        Fig. 194.
vitellus in a vertical direction, which
gradually deepens until it has divided
the vitellus into two separate halves or
hemispheres. (Fig. 194, a.) Almost at
the same time another furrow, running
at right angles with the first, penetrates
also the substance of the vitellus and
cuts it in a transverse direction. The
vitellus is thus divided into four equal
portions (Fig. 194, b), the edges and
angles of which are rounded off, and
which are still contained in the cavity
of the vitelline membrane. The spaces
between them and the internal surface
of the vitelline membrane are occupied by a transparent fluid.
The process thus commenced goes
on by a successive formation of furrows and sections, in various directions.  The four vitelline segments
already produced are thus subdivided
into sixteen, the sixteen into sixtyfour, and so on; until the whole vitellus is converted into a mulberry
shaped mass, composed of minute,
nearly spherical bodies, which are
called the "vitelline spheres." (Fig.
194, c.) These vitelline spheres have
a somewhat firmer consistency than
the original substance of the vitellus;
and this consistency appears to in- SEGMNTATION OF THE VIELLS
crease, as they successively multiply
in numbers and diminish in size. At last they have become so
abundant as to be closely crowded together, compressed into polygonal forms, and flattened against the internal surface of the vitel



572    DEVELOPMENT OF THE IMPREGNATED EGG.
line membrane. (Fig. 194, d.) They have by this time been converted into true animal cells; and these cells, adhering to each other
by their adjacent edges, form a continuous organized membrane,
which is termed the Blastodermic membrane.
During the formation of this membrane, moreover, the egg, while
passing through the Fallopian tubes into the uterus, has increased
in size. The albuminous matter with which it was enveloped has
liquefied; and, being absorbed by endosmosis through the vitelline
membrane, has furnished the materials for the more solid and extensive growth of the newly-formed structures. It may also be
seen that a large quantity of this fluid has accumulated in the
central cavity of the egg, inclosed accordingly by the blastodermic
membrane, with the original vitelline membrane still forming an
external envelope round the whole.
The next change which takes place consists in the division or
splitting of the blastodermic membrane into two layers, which are
known as the external and internal layers of the blastodermic membrane.
They are both still composed exclusively of cells; but those of the
external layer are usually smaller and more compact, while those
of the internal are rather larger and looser in texture. The egg
then presents the appearance of a globular sac, the walls of which
consist of three concentric layers, lying in contact with and inclosing each other, viz., 1st, the structureless vitelline membrane on the
outside; 2d, the external layer of the blastodermic membrane, composed of cells; and 3d, the internal layer of the blastodermic membrane, also composed of cells. The cavity of the egg is occupied
by a transparent fluid, as above mentioned.
This entire process of the segmentation of the vitellus and the
formation of the blastodermic membrane is one of the most remarkable and important of all the changes which take place during
the development of the egg. It is by this process that the simple
globular mass of the vitellus, composed of an albuminous matter
and oily granules, is converted into an organized structure. For
the blastodermic membrane, though consisting only of cells nearly
uniform in size and shape, is nevertheless a truly organized membrane, made up of fully formed anatomical elements. It is, moreover, the first sign of distinct organization which makes its appearance in the egg; and as soon as it is completed, the body of the
new foetus is formed. The blastodermic membrane is, in fact, the
body of the foetus. It is at this time, it is true, exceedingly simple
in texture; but we shall see hereafter that all the future organs




BLASTODERMIC MEMBRANE.                      573
of the body, however varied and complicated in structure, arise out
of it, by modification and development of its different parts.
The segmentation of the vitellus, moreover, and the formation
of the blastodermic membrane, take place in essentially the same
manner in all classes of animals.  It is always in this way that
the egg commences its development, whether it be destined to
form afterward a fish or a reptile, a bird, a quadruped or a man.
The peculiarities belonging to different species show themselves
afterward, by variations in the manner and extent of the development of different parts. In the higher animals and in the human
subject the development of the egg becomes an exceedingly complicated process, owing to the formation of various accessory
organs, which are made requisite by the peculiar conditions under
which the development of the embryo takes place. It is, in fact,
impossible to describe or understand properly the complex embryology of the quadrupeds, and more particularly that of the human
subject, without first tracing the development of those species in
which the process is more simple. We shall commence our description, therefore, with the development of the egg of the frog, which
is for many reasons particularly appropriate for our purpose.
The egg of the frog, when discharged from the body of the female
and fecundated by the spermatic fluid of the male, is deposited in
the water, enveloped in a soft elastic cushion of albuminous substance. It is therefore in a situation where it is freely exposed to
the light, the air, and the moderate warmth of the sun's rays, and
where it can absorb directly an abundance of moisture and appropriate nutritious material.  We find accordingly that under these
circumstances the development of the egg is distinguished by a
character of great simplicity; since the whole of the vitellus is
directly converted into the body of the embryo. There are no accessory organs required, and consequently no complication of the
formative process.
The two layers of the blastodermic membrane, above described,
represent together the commencement of all the organs of the fcetus.
They are intended, however, for the production of two different
systems; and the entire process of their development may be expressed as follows: The external layer of the blastodermic membrane
produces the spinal column and all the organs of animal life; while the
internal layer produces the intestinal canal, and all the organs of vegetative life.
The first sign of advancing organization in the external layer of




574    DEVELOPMENT OF THE IMPREGNATED EGG.
the blastodermic membrane shows itself in a thickening and condensation of its structure. This thickened portion has the form of an
elongated oval.shaped spot, termed the "embryonic spot" (Fig. 195),
the wide edges of which are somewhat
Fig. 195.        more opaque than the rest of the blastodermic  membrane.  Inclosed within
these opaque edges is a narrower colorless and transparent space, the "area
a  E  |i  t   pellucida," and in its centre is a delicate
line, or furrow, running longitudinally
from front to rear, which is called the
"primitive trace."
On each side of the primitive trace,
IMPREGNATED EGG, with com- in the area pellucida, the substance of
Mnencement of formation of embryo: the blastodermic membrane rises up in
showing embryonic spot, area pellucida, and primitive trace.  such a manner as to form two nearly
parallel vertical plates or ridges, which
approach each other over the dorsal aspect of the foetus and are
therefore called the "dorsal plates."  They at last meet on the
median line, so as to inclose the furrow above described and convert it into a canal. This afterward becomes the spinal canal, and
in its cavity is formed the spinal cord, by a deposit of nervous
matter upon its internal surface. At the anterior extremity of this
canal, its cavity is large and rounded, to accommodate the brain
and medulla oblongata; at its posterior extremity it is narrow and
pointed, and contains the extremity of the spinal cord.
In a transverse section of the egg at this stage (Fig. 196), the
dorsal plates may be seen approaching each other above, on each
side of the primitive furrow or "trace."  At a more advanced
period (Fig. 197) they may be seen fairly united with each other,
so as to inclose the cavity of the spinal canal. At the same time,
the edges of the thickened portion of the blastodermic membrane
grow outward and downward, so as to spread out more and more
over the lateral portions of the vitelline mass. These are called
the "abdominal plates;" and as they increase in extent they tend
to unite with each other below and inclose the abdominal cavity,
just as the dorsal plates unite above, and inclose the spinal canal.
At last the abdominal plates actually do unite with each other on
the median line (at i, Fig. 197), embracing of course the whole
internal layer of the blastodermic membrane (5), which incloses in




FORMATION  OF ORGANS.                           575
its turn the remains of the original vitellus and the albuminous
fluid which has accumulated in its cavity.
Fig. 196.                             Fig. 197.
IMPREGNATED EGG, at a somewhat
more advanced period.-1. Umbilicus, or
Transverse section of Eo a in an early  point of union between abdominal plates.
stage of development.-1. External layer  2, 2. Dorsal plates united with each other
of blastodermic membrane. 2, 2. Dorsal  on the median line and inclosing the spinal
plates. 3. Internal layer of blastodermic  canal. 3, 3. Abdominal plates. 4. Secmembrane.                           tion of spinal column, with laminae and
ribs. 5. Internal layer of blastodermic
membrane.
During this time, there is formed, in the thickness of the external
blastodermic layer, immediately beneath the spinal canal, a longitudinal cartilaginous cord, called the'chorda dorsalis." Around the
chorda dorsalis are afterward developed the bodies of the vertebrae
(Fig. 197, 4), forming the chain of the vertebral column; and the
oblique processes of the vertebrae run upward from this point into
the dorsal plates; while the transverse processes, and ribs, run outward and downward in the abdominal plates, to encircle more or
less completely the corresponding portion of the body.
If we now examine the egg in longitudinal section, while this
process is going on, the thickened portion of the external blastodermic layer may be seen in profile, as at i, Fig. 198. The anterior
portion (M), which will form the head, is thicker than the posterior
(3), which will form the tail of the young animal. As the whole
mass grows rapidly, both in the anterior and the posterior direction, the head becomes very thick and voluminous, while the tail also
begins to project backward, and the whole egg assumes a distinctly
elongated form. (Fig. 199.)  The abdominal plates at the same time
meet upon its under surface, and the point at which they finally




576   DEVELOPMENT OF THE IMPREGNATED EGG.
unite forms the abdominal cicatrix or urzbilicus. The internal blastodermic layer is seen, of course, in the longitudinal section of the
Fig. 198.                             Fig. 199.
Diagram of FROG'S EGG, in an early   E, ( OF FR oG, in process of developstage of development; longitudinal sec-  ment.
tion.-1. Thickened portion of external
blastodermic layer, forming body of fetus.
2. Anterior extremity of foetus. 3. Posterior extremity. 4. Internal layer of blastodermic membrane. 5. Cavity of vitellus.
egg, as well as in the transverse, embraced by the abdominal plates,
and inclosing, as before, the remains of the vitellus.
As the development of the above parts goes on (Fig. 200), the
head becomes still larger, and soon shows traces of the formation
Fig. 200.
E G  O  FR  G, farther advanced.
of organs of special sense. The tail also increases in size, and projects farther from the posterior extremity of the embryo. The
spinal cord runs in a longitudinal direction from front to rear, and
its anterior extremity enlarges, so as to form  the brain and medulla
oblongata. In the mean time, the internal blastodermic layer, which
is subsequently to be converted into the intestinal canal, has been
shut in by the abdominal walls, and still forms a perfectly closed
sac, of a slightly elongated figure, without either inlet or outlet.
Afterward, the mouth is formed by a process of atrophy and perforation, which takes place through both external and internal layers,
at the anterior extremity, while a similar perforation, at the posterior extremity, results in the formation of the anus.




FORMATION  OF ORGANS.                     577
All these parts, however, are as yet imperfect; and, being merely
in the course of formation, are incapable of performing any active
function.
By a continuation of the same process, the different portions of
the external blastodermic layer are further developed, so as to result in the complete formation of the various parts of the skeleton,
the integument, the organs of special sense, and the voluntary
nerves and muscles. The tail at the same time acquires sufficient
size and strength to be capable of acting as an organ of locomotion. (Fig. 201.)  The intestinal canal, which has been formed from
Fig. 201.
TADPOLE fully developed.
the internal blastodermic layer, is at first a short, wide, and nearly
straight tube, running directly from the mouth to the anus. It
soon, however, begins to grow faster than the abdominal cavity
which incloses it, becoming longer and narrower, and is at the
same time thrown into numerous convolutions. It thus presents a
larger internal surface for the performance of the digestive process.
Arrived at this period, the young tadpole ruptures the vitelline
membrane, by which he has heretofore been inclosed, and leaves the
cavity of the egg. He at first fastens himself upon the remains of
the albuminous matter deposited round the egg, and feeds upon it for
a short period. He soon, however, acquires sufficient strength and
activity to swim about freely in search of other food, propelling
himself by means of his large, membranous, and muscular tail.
The alimentary canal increases very rapidly in length and becomes
spirally coiled up in the abdominal cavity, so as to attain a length
from seven to eight times greater than that of the entire body.
After a time, a change takes place in the external form of the
young animal. The posterior extremities or limbs begin to show
themselves, by budding or sprouting from the sides of the body,
just at the base of the tail. (Fig. 202.) The anterior extremities also
grow at this time, but are at first concealed underneath the integument.  They afterward, however, become liberated, and show thern87




578    DEVELOPMENT OF THE IMPREGNATED EGG.
selves externally. At first both the fore and hind legs are very
small, imperfect in structure, and altogether useless for purposes of
locomotion. They soon, however, increase in size and strength;
and while they keep pace with the increasing development of the
whole body, the tail on the contrary ceases to grow, and becomes
shrivelled and atrophied. The limbs, in fact, are destined finally
to replace the tail as organs of locomotion; and a time at last
arrives (Fig. 203) when the tail has altogether disappeared, while
Fig. 202.                      Fig. 203.
TADPOLE, with limbs beginning to be formed.  Perfect FRO G.
the legs have become fully developed, muscular and powerful.
Then the animal, which was before confined to an aquatic mode
of life, becomes capable of living also upon land, and a transformation is thus effected from the tadpole into the perfect frog.
During the same time, other changes of an equally important
character have taken place in the internal organs. The tadpole at
first breathes by gills; but these organs subsequently become
atrophied and disappear, being finally replaced by well developed
lungs. The structure of the mouth, also, of the integument, and
of the circulatory system, is altered to correspond with the varying
conditions and wants of the growing animal; and all these changes,
taking place in part successively and in part simultaneously,
bring the animal at last to a state of complete formation.
The process of development may then be briefly recapitulated as
follows:1. The blastodermic membrane, produced by the segmentation
of the vitellus, consists of two cellular layers, viz., an external and
an internal blastodermic layer.




FORMATION OF ORGANS IN THE FROG.                679
2. The external layer of the blastodermic membrane incloses by
its dorsal plates the cerebro-spinal canal, and by its abdominal
plates the abdominal or visceral cavity.
3. The internal layer of the blastodermic membrane forms the
intestinal canal, which becomes lengthened and convoluted, and
communicates with the exterior by a mouth and anus of secondary
formation.
4. Finally the cerebro-spinal axis and its nerves, the skeleton,
the organs of special sense, the integument, and the muscles, are
developed from. the external blastodermic layer; while the anterior
and posterior extremities are formed from the same layer by a process of sprouting, or continuous growth.




580              THE UMBILICAL VESICLE.
CHAPTER VIII
THE UMBILICAL VESICLE.
TN the frog, as we have seen, the abdominal plates, closing
together in front and underneath the body of the animal, shut in
directly the whole of the vitellus, and join each other upon the
median line, at the umbilicus. The whole remains of the vitellus
are then inclosed in the abdomen of the animal, and in the intestinal
sac formed by the internal blastodermic layer.
In many instances, however, as, for example, in several kinds of
fish, and in all the birds and quadrupeds, the abdominal plates do
not immediately embrace the whole of
Fig. 204.       the vitelline mass, but tend to close
together about its middle; so that the
vitellus is constricted, in this way, and
the satne     divided into two portions: one internal,
and one external. (Fig. 204.)  As the
process of development proceeds, the body
of the foetus increases in size, out of proo F  isnp sho   form ortion to the vitelline sac, and the conEoc, o F F I s   showing formation of bilical vesicle  striction just mentioned becomes at the
same time more strongly marked; so that
the separation between the internal and external portions of the
vitelline sac is nearly complete. (Fig. 205.) The internal layer of
the blastodermic membrane is by the same means divided into
two portions, one of which forms the intestinal canal, while the
other, remaining outside, forms a sac-like appendage to the abdomen, which is known by the name of the umbilical vesicle.
The umbilical vesicle is accordingly lined by a portion of the
internal blastodermic layer, continuous with the mucous membrane
of the intestinal canal; while it is covered on the outside by a portion of the external blastodermic layer, continuous with the integumnent of the abdomen.




THE UMBILICAL VESICLE.                    581
After the young animal leaves the egg, the umbilical vesicle
in some species becomes withered and atrophied by the absorption
of its contents; while in others, the abdominal walls gradually
Fig. 205.
Young FIs H with umbilical vesicle.
extend over it, and crowd it back into the abdomen; the nutritious
matter which it contained passing from the cavity of the vesicle
into that of the intestine by the narrow passage or canal which
remains open between them.
In the human subject, however, as well as in the quadrupeds, the
umbilical vesicle becomes more completely separated from the abdomen than in the cases just mentioned. There is at first a wide communication between the cavity of the umbilical vesicle and that of
the intestine; and this communication, as in other instances, becomes
gradually narrowed by the increasing constriction of the abdominal
walls.  Here, however, the constriction proceeds so far that the
opposite surfaces of the canal come in contact with each other, and
adhere; so that the narrow passage previously
existing, between the cavity of the intestine       Fig. 206.
and that of the umbilical vesicle, is obliterated,
and the vesicle is then connected with the
abdomen only by an impervious cord. This
cord afterward elongates, and becomes converted into a slender, threadlike pedicle (Fig.
206), passing out from  the abdomen of the
foetus, and connected by its farther extremity
with the umbilical vesicle, which is filled with
a transparent, colorless fluid. The umbilical   HUMAN EMBRYO, with
umbilical vesicle; about the
vesicle is very distinctly visible in the human  fifth week.
foetus so late as the end of the third month.
After that period it diminishes in size, and is gradually lost in the
advancing development of the neighboring parts.
In the formation of the umbilical vesicle, we have the first varia



582               THE UMBILICAL VESICLE.
tion from the simple plan of development described in the preceding
chapter.  Here, the whole of the vitellus is not directly converted
into the body of the embryo; but while a part of it is taken, as
usual, into the abdominal cavity, and used immediately for the
purposes of nutrition, a part is left outside the abdomen, in the
umbilical vesicle, a kind of secondary organ or appendage of the
foetus. The contents of the umbilical vesicle, however, are afterward absorbed, and so appropriated, finally, to the nourishment of
the newly-formed tissues.




AMNION AND ALLANTOIS.                    583
CHAPTER IX.
AMNION  AND ALLANTOIS.-DEVELOPMENT  OF
THE CHICK.
WE shall now proceed to the description of two other accessory
organs, which are formed, during the development of the fecundated
egg, in all the higher classes of animals. These are the amnion and
the allantois; two organs which are always found in company with
each other, since the object of the first is to provide for the formation of the second. The amnion is formed from the external layer
of the blastodermic membrane, the allantois from the internal layer.
In the frog and in fish, as we have seen, the egg is abundantly
supplied with moisture, air, and nourishment, by the water with
which it is surrounded. It can absorb directly all the gaseous and
liquid substances, which it requires for the purposes of nutrition
and growth. The absorption of oxygen, the exhalation of carbonic
acid, and the imbibition of albuminous and other liquids, can all
take place without difficulty through the simple membranes of the
egg; particularly as the time required for the formation of the
embryo is very short, and as a great part of the process of development remains to be accomplished after the young animal leaves
the egg.
But in birds and quadrupeds, the time required for the development of the foetus is longer. The young animal also acquires a
much more perfect organization during the time that it remains
inclosed within the egg; and the processes of absorption and exhalation necessary for its growth, being increased in activity to a
corresponding degree, require a special organ for their accomplishment. This special organ, destined to bring the blood of the foetus
into relation with the atmosphere and external sources of nutrition,
is the allantois.
In the frog and the fish, the internal blastodermic layer, forming
the intestinal mucous membrane, is inclosed'everywhere, as above
described, by the external layer, forming the integument; and




584               AMNION  AND ALLANTOIS.
consequently it can nowhere come in contact with the investing
membrane of the egg. But in the higher animals, the internal
blastodermic layer, which is the seat of the greatest vascularity,
and which is destined to produce the allantois, is made to come in
contact with the external membrane of the egg for purposes of
exhalation and absorption; and this can only be accomplished by
opening a passage for it through the external germinative layer.
This is done in the following manner, by the formation of the
amnzon.
Soon after the body of the foetus has begun to be formed by the
thickening of the external layer of the blastodermic membrane,
a double fold of this external layer rises up on all sides about
the edges of the newly-formed embryo; so that the body of the
foetus appears as if sunk in a kind of depression, and surrounded
with a membranous ridge or embankment, as in
Fig. 207.    Fig. 207. The embryo (c) is here seen in profile,
i      with the double membranous folds, above men_  L\ i      tioned, rising up just in advance of the head,
and behind the posterior extremity. It must be...    understood, of course, that the same thing takes
place on the two sides of'the foetus, by the formaDiagram of FECux- tion of lateral folds simultaneously with the
DArE:D EGO; showing
ormation of; samnion.  appearance of those in front and behind. As it
forination of amnion.~,
a. Vitellus. b. External is these folds which are destined to form the
layer of blastodermic
membrane. e. Body of arnnion, they are called the "amniotic folds."
embryo. d,d. Amniotic    The amniotic folds continue to grow, and exfolds e. Vitelline membrane.           tend themselves, forward, backward and laterally,
until they approach each other at a point over
the back of the foetus (Fig. 208), which is termed the "amniotic
umbilicus." Their opposite edges afterward actually come in contact with each other at this point, and adhere together, so as to
shut in a space or cavity (Fig. 208, b) between their inner surface
and the body of the foetus. This space, which is filled with a clear
fluid, is called the amniotic cavity. At the same time, the intestinal
canal has begun to be formed, and the umbilical vesicle has been
partially separated from it, by the constriction of the abdominal
walls on the under surface of the body.
There now appears a prolongation or diverticulum (Fig. 208, c)
growing out from the posterior portion of the intestinal canal, and
following the course of the amniotic fold which has preceded it;
occupying, as it gradually enlarges and protrudes, the space left




AMNION AND ALLANTOIS.                       585
vacant by the rising up of the amniotic fold. This diverticulum
is the commencement of the allantois. It is an elongated membranous sac, continuous with the posterior portion of the intestine,
and containing bloodvessels derived from those
of the intestinal circulation.  The cavity of the       Fig. 208.
allantois is also continuous with the cavity of,
the intestine. 
After the amniotic folds have approached and 
touched each other, as already described, over   /_ 
the back of the foetus, at the amniotic umbilicus,  
the adjacent surfaces, thus brought in contact,
fuse together, so that the cavities of the two
folds, coming respectively from  front and rear, fl,  advaned.-a.'-'-~I     7"""b                      fatrther advanced. —a.
are separated only by a single membranous par- Ubilical vesicle. b.
Amniotic cavity.  c. Altition (Fig. 209, c) running from the inner to the  in.tois.
outer lamina of the amniotic folds. This partition itself soon after atrophies and disappears; and the inner and
outer laminae become consequently separated from each other. The
inner lamina (Fig. 209, a) which remains continuous with the integument of the fcetus, in-        Fig. 209
closing the body of the embryo in a distinct.~
cavity, is called the amnion (Fig. 210, b), and 
its cavity is known as the amniotic cavity.
The outer lamina of the amniotic fold, on the 
other hand (Fig. 209, b), recedes farther and
farther from the inner, until it comes in contact with the original vitelline membrane, still
covering the exterior of the egg; and by con-   FECUNDATEI   EGG,
with allantois nearly corntinned growth and expansion it at last fuses p]ete.-a. Inner lamina of
with the vitelline membrane and unites with  amniotic fold. b. Outer lamina of ditto e. Point
its substance, so that the two membranes form   where the amniotic folds
but one. This membrane, formed by the fusion  come in c      The
tois is seen penetrating beand consolidation of two others, constitutes then  tween the inner and outer
*  * i} ~,.   i   r~ J.1laminae  of   the   amniotic
the external investing membrane of the egg.  folds.
The allantois, during all this time, is increasing in size and vascularity.  Following the course of the amniotic
folds as before, it insinuates itself between them, and of course soon
comes in contact with the external investing membrane just described. It then begins to expand laterally in every direction,
enveloping more and more the body of the foetus, and bringing its
vessels into contact with the external membrane of the egg.




586               AMNION AND ALLANTOIS.
By a continuation of the above process, the allantois at last
grows to such an extent as to envelope completely the body of the
embryo, together with the amnion; its two
Fig. 210.       extremities coming in contact with each
E n"*  ~ other and fusing together over the back of
/c  the foetus, just as the amniotic folds had
previously done. (Fig. 210.) It lines, therefore, the whole internal surface of the investing membrane with a flattened, vascular sac, the vessels of which come from the
interior of the body of the foetus, and which
FECUNDATED Euo, with  still communicates with the cavity of the
allantois fully formed.-a. Unm- intestinal canal.
bilical vesicle.  b. Amnion.  c.
Allantois.                It is evident, from the above description,
that there is a close connection between the
formation of the amnion and that of the allantois. For it is only
in this manner that the allantois, which is an extension of the internal layer of the blastodermic membrane, can come to be situated
outside the foetus and the amnion, and be brought into relation
with external surrounding media. The two laminae of the amniotic folds, in fact, by separating from each other as above described,
open a passage for the allantois, and allow it to come in contact
with the external membrane of the egg.
In order to explain more fully the physiological action of the
allantois, we shall now proceed to describe the process of development, as it takes place in the egg of the fowl.
In order that the embryo may be properly developed in any
case, it is essential that it be freely supplied with air, warmth,
moisture, and nourishment. The egg of the fowl contains already,
when discharged from the generative passages, a sufficient quantity
of moisture and albuminous material.  The necessary warmth is
supplied by the body of the parent during incubation; while the
atmospheric gases can pass and repass through the porous eggshell, and by endosmosis through the fibrous membranes which
line its cavity.
When the egg is first laid, the vitellus, or yolk, is enveloped in
a thick layer of semi-solid albumen.  On the commencement of
incubation, a liquefaction takes place in the albumen immediately
above that part of the vitellus which is occupied by the cicatricula; so that the vitellus rises or floats upward toward the surface
by virtue of its specific gravity, and the cicatricula comes to be




DEVELOPMENT OF THE CHICK.                     587
placed almost immediately underneath the lining membrane of the
egg-shell. As the cicatricula is the spot from which the process of
embryonic development commences, the body of the young foetus
is by this arrangement placed in the most favorable position for
the reception of warmth and other necessary external influences
through the egg-shell. The liquefied albumen is also absorbed by
the vitelline membrane, and the vitellus thus becomes larger, softer,
and more diffluent than before the commencement of incubation.
As soon as the circulatory apparatus of the embryo has been
fairly formed, two minute arteries are seen to run out from its
lateral edges and spread out into the neighboring parts of the
blastodermic membrane, breaking up into inosculating branches,
and covering the adjacent portions of the vitellus with a plexus of
capillary bloodvessels. The space occupied in the blastodermic
membrane, on the surface of the vitellus, by these vessels, is called
the area vasculosa. (Fig. 211.)  It is of a nearly circular shape,
Fig. 211.
Eoo OF FOWL during early periods of incubation; showing the body of the embryo, and the
area vasculosa partially covering the surface of the vitellus.
and is limited, on its outer edge, by a terminal vein or sinus, called
the "sinus terminalis." The blood is returned to the body of the
fcetus by two veins which penetrate beneath its edges, one near the
head and one near the tail.
The area vasculosa tends to increase in extent, as the development of the foetus proceeds and its circulation becomes more active.
It soon covers the upper half, or hemisphere, of the vitellus, and
the terminal sinus then runs like an equator round the middle of
the vitelline sphere. As the growth of the vascular plexus con



588                 AMNION AND ALLANTOIS.
tinues, it passes this point, and embraces more and more of the inferior, as well as of the superior hemisphere, the vessels converging
toward its under surface, until at last nearly the whole of the
vitellus is covered with a network of inosculating capillaries.
The function of the vessels of the area vasculosa is to absorb
nourishment from the cavity of the vitelline sac. As the albumen
liquefies during the process of incubation, it passes by endosmosis,
more and more abundantly, into the vitelline cavity; the whole
vitellus growing constantly larger and more fluid in consistency.
The blood of the foetus, then circulating in the vessels of the area
vasculosa, absorbs freely the oleagino-albuminous matters of the
vitellus, and, carrying them back to the foetus by the returning
veins, supplies the newly-formed tissues and organs with abundance of appropriate nourishment.
During this period the amnion and the allantois have been also
in process of formation. At first the body of the foetus lies upon
its abdomen, as in the cases previously described; but, as it increases
in size, it alters its position so as to lie more upon its side.  The
allantois then, emerging from the posterior portion of the abdominal
cavity, turns directly upward over the body of the foetus, and comes
immediately in contact with the shell membrane.  (Fig. 212.)  It
Fig. 212.
Eo  OF Fow l at a more advanced period of development. The body of the fetus i. enveloped
by the atnuion, and has the umbilical vesicle hanging from its under surface; while the vascular
allantois is seen turning upward and spreading out over the internal surface of the shell-lmenbrane.
then spreads out rapidly, extending toward the extremities and
down the sides of the egg, enveloping more and more completely




DEVELOPMENT OF THE CHICK.                   589
the fcetus and the vitelline saGc and taking the place of the albumen
which has been liquefied and absorbed.
It will also be seen, by reference to the figure, that the umbilical
vesicle is at the same time formed by the separation of part of the
vitellus from the abdomen of the chick; and the vessels of the area
vasculosa, which were at first distributed over the vitellus, now
ramify, of course, upon the surface of the umbilical vesicle.
At last the allantois, by its continued growth, envelopes nearly
the whole of the remaining contents of the egg; so that toward the
later periods of incubation, at whatever point we break open the
egg, we find the internal surface of the shell-membrane lined with
a vascular membranous expansion, supplied by arteries which
emerge from the abdomen of the foetus.
It is easy to see, accordingly, with what readiness the absorption
and exhalation of gases may take place by means of the allantois.
The air penetrates from the exterior through the minute pores of
the calcareous shell, and then acts upon the blood in the vessels of
the allantois very much in the same manner that the air in the minute
bronchial tubes and air-vesicles of the lungs acts upon the blood in
the pulmonary capillaries. Examination of the egg, furthermore,
at various periods of incubation, shows that changes take place in
it which are entirely analogous to those of respiration.
The egg, in the first place, during its development, loses water by
exhalation. This exhalation is not a simple effect of evaporation,
but is the result of the nutritive changes going on in the interior
of the egg; since it does not take place, except in a comparatively
slight degree, in unimpregnated eggs, or in those which are not
incubated, though they may be freely exposed to the air. The
exhalation of fluid is also essential to the processes of development,
for it has often been found, in hatching eggs by artificial warmth,
that if the air of the chamber in which they are inclosed become
unduly charged with moisture, so as to retard or prevent further
exhalation, the eggs readily become spoiled, and the development
of the embryo is arrested  The loss of weight during natural incubation, principally due to the exhalation of water, has been found
by Baudrimont and St. Ange' to be over 15 per cent. of the entire
weight of the egg.
Secondly, the egg absorbs oxygen and exhales carbonic acid.
The two observers mentioned above, ascertained that during eighDu D6veloppement du Fetus. Paris, 1850, p. 143.




590               AMNION AND ALLANTOIS.
teen days' incubation, the egg absorbs nearly 2 per cent. of its
weight of oxygen, while the quantity of carbonic acid exhaled from
the sixteenth to the nineteenth day of incubation amounts to no less
than 3 grains in the twenty-four hours.' It is curious to observe,
also, that in the egg during incubation, as well as in the adult
animal, more oxygen is absorbed than is returned by exhalation
under the form of carbonic acid.
It is evident, therefore, that a true respiration takes place, by
means of the allantois, through the membranes of the shell.
The allantois, however, is not simply an organ of respiration; it
takes part also in the absorption of nutritious matter. As the process of development advances, the skeleton of the young chick, at
first entirely cartilaginous, begins to ossify. The calcareous matter, necessary for this ossification, is, in all probability, derived from
the shell.  The shell is certainly lighter and more fragile toward
the end of incubation than at first; and, at the same time, the calcareous ingredients of the bones increase in quantity. The limesalts, requisite for the process of ossification, are apparently absorbed from the shell by the vessels of the allantois, and by them
transferred to the skeleton of the growing chick; so that, in the
same proportion that the former becomes weaker, the latter grows
stronger. This diminution in density of the shell is connected not
only with the development of the skeleton, but also with the final
escape of the chick from the egg. This deliverance is accomplished
mostly by the movements of the chick itself, which become, at a
certain period, sufficiently vigorous to break out an opening in the
attenuated and weakened egg-shell. The first fracture is generally
accomplished by a stroke from the end of the bill; and it is precisely at this point that the solidification of the skeleton is most
advanced.  The egg-shell itself, therefore, which at first only serves
for the protection of the imperfectly-formed embryo, afterward
furnishes the materials which are used to accomplish its own demolition, and at the same time to effect the escape of the fully developed foetus.
Toward the latter periods of incubation, the allantois becomes
more and more adherent to the internal surface of the shell-membrane. At last, when the chick, arrived at the full period of development, escapes from its confinement, the allantoic vessels are
torn off at the umbilicus; and the allantois itself, cast off as a useOp. cit., pp. 138 and 149.




DEVELOPMENT OF THE CHICK.                    591
less and effete organ, is left behind in the cavity of the abandoned
egg-shell. The allantois is, therefore, strictly speaking, a foetal
organ. Developed as an accessory structure from a portion of the
intestinal canal, it is- exceedingly active and important during the
middle and latter periods of incubation; but when the chick is
completely formed, and has become capable of carrying on an independent existence, both the amnion and the allantois are detached
and thrown off as obsolete structures, their place being afterward
supplied by other organs belonging to the adult condition.




592  DEVELOPMENT OF THE EGG IN HUMAN SPECIES.
CHAPTER X.
DEVELOPMENT OF THE EGG IN THE HUMAN
SPECIES.-FORMATION OF THE CHORION.
WVE have already described, in a preceding chapter, the manner
in which the outer lamina of the amniotic fold becomes adherent
to the adjacent surface of the vitelline membrane, so as to form
with it but a single layer; and in which these two membranes, thus
fused and united with each other, form at that time the single external investing membrane of the egg. The allantois, in its turn,
afterward comes in contact with the investing membrane, and lies
immediately beneath it, as a double vascular membranous sac. In
the egg of the human subject the development of the membranes,
though carried on essentially upon the same plan with that which
we have already described, undergoes, in addition, some further
modifications, which we shall now proceed to explain.
The first of these peculiarities is that the allantois, after spread.
ing out upon the inner surface of
Fig. 213.           the external investing membrane,
adheres to, and fuses with it, just
as the outer lamina of the amniotic fold  has previously fused
with the vitelline membrane. At
the same time, the two layers belonging to the allantois itself also
come in contact and fuse togem o  be g, ather; so that the cavity of the
allantois is obliterated, and instead
of forming a membranous sac conH UA AN OvUM, about the end of the first taining fluid, this organ is convertmonth; showing fornation of chorion. —. ed into a simple vascular membrane.
Umbilical vesicle.  2. Amniion.  3. Chorion.
(Fig. 213.)   This  membrane,
moreover, being, after a time, thoroughly fused and united with the
two which have preceded it, takes the place which was previously




FORMATION OF THE CHORION.                     593
occupied by them. It is then termed the chorion, and thus becomes
the sole external investing membrane of the egg.
We find, therefore, that the chorion, that is, the external coat or
investment of the egg, is formed successively by three distinct
membranes, as follows: first, the original vitelline membrane;
secondly, the outer lamina of the amniotic fold; and, thirdly, the
allantois; the last predominating over the two former by the rapidity
of its growth, and absorbing them into its substance, so that they
become finally completely incorporated with its texture.
It is easy to see, also, how, in consequence of the above process,
the body of the foetus, in the human egg, becomes inclosed in two
distinct membranes, viz., the amnion, which is internal and continuous with the foetal integument, and the chorion, which is external
and supplied with vessels from the cavity of the abdomen.  The
umbilical vesicle is, of course, situated between the two; and the
rest of the space between the chorion and the amnion is occupied
by a semi-fluid gelatinous material, somewhat similar in appearance
to that of the vitreous body of the eye.
The obliteration of the cavity of the allantois takes place very
early in the human subject, and, in fact, keeps pace almost entirely
with the progress of its growth; so that this organ never presents,
in the human egg, the appearance of a hollow sac, filled with
fluid, but rather that of a flattened vascular membrane, enveloping
the body of the foetus, and forming the external membrane of the
egg.  Notwithstanding this difference, however, the chorion of the
human subject, in respect to its mode of formation, is the same
thing with the allantois of the lower animals; its chief peculiarity
consisting in the fact that its opposite surfaces are adherent to each
other, instead of remaining separate and inclosing a cavity filled
with fluid.
The next peculiarity of the human chorion is, that it becomes
shaggy. Even while the egg is still very small, and has but recently
found its way into the uterine cavity, its exterior is already seen
to be covered with little transparent prominences, like so many
villi (Fig. 213), which increase the extent of its surface, and assist
in the absorption of fluids from without. The villi are at this time
quite simple in form, and altogether homogeneous in structure.
As the egg increases in size, the villi rapidly elongate, and become divided and ramified by the repeated budding and sprouting of
lateral offshoots from every part. After this process of growth has
gone on for some time, the external surface of the chorion presents
88




594  DEVELOPMENT OF THE EGG IN HUMAN SPECIES.
a uniformly velvety or shaggy appearance, owing to its being covered everywhere with these tufted and compound villosities.
The villosities themselves, when examined by the microscope,
have an exceedingly well-marked and characteristic appearance.
(Fig. 214.) They originate from the surface of the chorion by a
somewhat narrow. stem, and divide
Fig. 214.         into a multitude of secondary and
tertiary branches, of varying size
1~ ^    and figure; some of them  slender
and filamentous, others club-shaped,
many of them irregularly swollen at
various points. All of them terminate by rounded extremities, giving
1^   S:y   a    to the whole tuft a certain resemli'^ ~''     blance to some varieties of sea-weed.
The larger trunks and branches of
the villosity are seen to contain numerous minute nuclei, imbedded in
a nearly homogeneous, or finely gra-.. "C     nular substratum.  The smaller ones
appear, under a low  magnifying
Compound villosity of Hi MAN Cue- power, simply granular in texture.
RION, ramified extremity. From a three    These villi are altogether peculiar
months' foetus. Magnified 30 diameters.
in appearance, and quite unlike any
other structure which may be met with in the body. Whenever we
find, in the uterus, any portion of a membrane having villosities
like these, we may be sure that pregnancy has existed; for such
villosities can only belong to the chorion, and the chorion itself is
a part of the fcetus. It is developed, as we have seen, as an outgrowth from the intestinal canal, and can only exist, accordingly,
as a portion of the fecundated egg. The presence of portions of a
shaggy chorion is therefore as satisfactory proof of the existence
of pregnancy, as if we had found the body of the foetus itself.
While the villosities which we have just described are in process of formation, the allantois itself has completed its growth, and
has become converted into a permanent chorion. The bloodvessels
coming from  the allantoic arteries accordingly ramify over the
chorion, and supply it with a tolerably abundant vascular network.
The growth of the foetus, moreover, at this time, has reached such
a state of activity, that it requires to be supplied with nourishment
by vascular absorption, instead of the slow process of imbibition,




FORMATION  OF THE CHORION.                    595
which has heretofore taken place through the comparatively incomplete and structureless villi of the chorion.  The capillary vessels, accordingly,         Fig. 215.
with which the chorion is supplied, begin
to penetrate into the substance of its vil- ~
losities.  They enter the base or stem of
each villosity, and, following every division of its compound ramifications, finally 
reach its rounded extremities. Here they 
turn upon themselves in loops (Fig. 215),
like the vessels in the papillae of the skin, 
and retrace their course, to unite finally
with the venous trunks of the chorion.
The villi of the chorion are therefore   Extremity of vILTOSITY OF
very analogous in structure to those of CHORTON, more highly magnified' showing the arrangement of
the intestine; and their power of absorp- bloodvessels i its interior.
tion, as in other similar instances, corresponds with the abundance of their ramifications, and the extent
of their vascularity.
It must be remembered, also, that these vessels all come from the
abdomen of the fcetus; and that whatever substances are taken up
by them are transported directly to the interior of the embryo, and
used for the nourishment of its tissues. The chorion, therefore, as
soon as its villi and bloodvessels are completely developed, becomes
an exceedingly active organ in the nutrition of the foetus; and constitutes, in fact, the only means by which new material can be introduced from without.
The existence of this general vascularity of the chorion affords
also, as Coste was the first to point out, a striking indication that
this membrane is in reality identical with the allantois of the
lower animals. If the reader will turn back to the illustrations of
the formation of the amnion and allantois (Chap. IX.), he will see
that the first chorion or investing membrane is formed exclusively
by the vitelline membrane, which is never vascular and cannot become so by itself, since it has no direct connection with the foetus.
The second chorion is formed by the union of the vitelline membrane with the outer lamina of the amniotic fold. Both laminae
of the amniotic fold are at first vascular, since they are portions of
the external blastodermic layer, and derive their vessels from the
integument of the foetus. But after the outer lamina has become
completely separated from the inner, by the disappearance of the




596  DEVELOPMENT OF THE EGG IN HUMAN SPECIES.
partition which for a time connected the two with each other (Fig.
209, c), this source of vascular supply is cut off; and the second
chorion cannot, therefore, remain vascular after that period. But
the third or permanent chorion, that is, the allantois, derives its vessels directly from those of the foetus, and retains its connection with
them during the whole period of gestation. A chorion, therefore,
which is universally and permanently vascular, can be no other
than the allantois, converted into an external investing membrane
of the egg.
Thirdly, the chorion, which is at one time, as we have seen, everywhere villous and shaggy, becomes afterward partially bald. This
change begins to take place about the end of the second month.
It commences at a point opposite the situation of the foetus and the
insertion of the foetal vessels. The villosities of this region cease
growing; and as the entire egg continues to enlarge, the villosities
at the point indicated fail to keep pace with its growth, and with
the progressive expansion of the chorion.  They accordingly become at this part thinner and more scattered, leaving the surface
of the chorion comparatively smooth and bald. This baldness increases in extent and becomes more and more complete, spreading
and advancing over the adjacent portions of the chorion, until at
least two-thirds of its surface have become nearly or quite destitute
of villosities.
At the opposite point of the surface of the egg, however, that
portion, namely, which corre
Fig. 216.             spends with the insertion of
the foetal vessels, the villosities,
instead of becoming atrophied,
continue to grow; and this
portion of the chorion becomes
even more shaggy and thickly
set than before.  The consequence is that the chorion
afterward presents a very different appearance at different
portions of its surface. (Fig.
216.) The greater part of it is
Hu MAN OVUM at end of third month; slowing sm oth; but a certain portion,
placental portion of the chorion fully lormed.
constituting about one-third of
the whole, is covered with a soft and spongy mass of long, thicklyset, compound villosities.  It is this thickened and shaggy portion,




FORMATION OF THE CHORION.                    597
which is afterward concerned in the formation of the placenta;
while the remaining smooth portion continues to be known under
the name of the chorion. The placental portion of the chorion
becomes distinctly limited and separated from the remainder by
about the end of the third month.
The vascularity of the chorion keeps pace, in its different parts
respectively, with the atrophy and development of its villosities.
As the villosities shrivel and disappear over a part of its extent,
the looped capillary vessels, which they at first contained, disappear
also; so that the smooth portion of the chorion shows afterward
only a few straggling vessels running over its surface, and does not
contain any abundant capillary plexus. In the thickened portion,
on the other hand, the vessels lengthen and ramify to an extent
corresponding with that of the villosities in which they are situated.
The allantoic arteries, coming from the abdomen of the foetus, enter
the villi, and penetrate through their whole extent; forming, at the
placental portion of the chorion, a mass of tufted and ramified vascular loops, while over the rest of the membrane they are merely
distributed as a few single and scattered vessels.
The chorion, accordingly, is the external investing membrane of
the egg, produced by the consolidation and transformation of the
allantois. The placenta, furthermore, so far as it has now been
described, is evidently a part of the chorion; that part, namely,
which is thickened, shaggy, and vascular, while the remainder is
comparatively thin, smooth, and membranous.




598  DEVELOPMENT OF UTERINE MUCOUS AMEMBRANE.
CHAPTER XI.
DEVELOPMENT OF UTERINE MUCOUS MEMBRANE.FORMATION  OF THE DECIDUA.
IN fish, reptiles, and birds, the egg is either provided with a supply of nutritious material contained within its membranes, or it is
so placed, after its discharge from the body of the parent, that it
can absorb these materials from without. Thus, in the egg of the
bird, the young embryo is supported upon the albuminous matter
deposited around the vitellus; while in the frog and fish, moisture,
oxygen, saline substances, &c., are freely imbibed from the water
in which the egg is placed.
But in the quadrupeds, as well as in the human species, the egg
is of minute size, and the quantity of nutritious matter which it
contains is sufficient to last only for a very short time. Moreover,
the development of the foetus takes place altogether within the body
of the female, and no supply, therefore, can be obtained directly
from the external media. In these instances, accordingly, the mucous membrane of the uterus, which is found to be unusually
developed and increased in functional activity during the period of
gestation, becomes a source of nutrition for the fecundated egg.
The uterine mucous membrane, thus developed and hypertrophied,
is known by the name of the Decidua.
It has received this name because, as we shall hereafter see, it
becomes exfoliated and thrown off, at the same time that the egg
itself is finally discharged.
The mucous membrane of the body of the uterus, in the unimpregnated condition, is quite thin and delicate, and presents a smooth
and slightly vascular internal surface. There is, moreover, no layer
of submucous cellular tissue between it and the muscular substance
of the uterus; so that the mucous membrane cannot here, as in
most other organs, be easily dissected up and separated from the
subjacent parts.  The structure of the mucous membrane itself,
however, is sufficiently well marked and readily distinguishable




FORMATION OF THE DECIDUA.                     599
from  that of other parts.  It consists, throughout, of minute
tubular follicles, ranged side by side, and running perpendicularly
to the free surface of the mucous membrane. (Fig. 217.) Near
this free surface, they are nearly
straight; but toward the deeper sur-            Fig. 217.
face of the mucous membrane, where
they terminate in blind extremities,
they become more or less wavy or
spiral in their course.  The tubules
are about T-O of an inch in diameter,
and are lined throughout with columnar epithelium. (Fig. 218.)  They
-.    *   I' -I.   ft  1  i    U I' F tt I N E M IT,  C 0oUs MEMBRANE, AS
occupy the entire thickness of the ute- UTENE M      S MEBRE, as,occupy the entire thickness of the ute- seen in vertical section. —a. Free surface.
rine mucous membrane, their closed  b. Attached surface.
extremities resting upon the subjacent
muscular tissue, while their mouths open into the cavity of the uterus. A few fine bloodvessels penetrate the mucous membrane from
below, and, running upward
between the tubules, encircle               Fig. 218.
their superficial extremities
with  a capillary network.
There is no areolar tissue in 
the uterine  mucous membrane, but only a small quan- 
tity of spindle-shaped fibroplastic fibres, scattered between the tubules. 
As the fecundated egg is
about to descend into the
cavity of the uterus, the mu- 
cous membrane, above described, takes on an increased
UTERINE TUB'ULES, from mucous membrane of
activity of growth and an  unimpregnated human uterus.
unusual development. It becomes tumefied and vascular; and, as it increases in thickness, it
projects, in rounded eminences or convolutions, into the uterine
cavity. (Fig. 219.)  In this process, the tubules of the uterus increase in length, and also become wider; so that their open mouths
may be readily seen by the naked eye upon the uterine surface, as
numerous minute perforations.  The bloodvessels of the mucous
membrane also enlarge and multiply, and inosculate freely with




600  DEVELOPMENT OF UTERINE MUCOUS MEMBRANE.
each other; so that the vascular network encircling the tubules becomes more extensive and abundant.
The internal surface of the uterus, accordingly, after this process
has been for some time going on, presents a thick, rich, soft, vascular, and velvety lining, quite different from that which is to be
found in the unimpregnated condition. In consequence of this
difference, the lining membrane of the uterus, in the impregnated
condition, was formerly supposed to be an entirely new product,
thrown out by exudation from the uterine surface, and analogous,
in this respect, to the inflammatory exudations of croup and pleurisy. It is now known, however, to be no other than the mucous
membrane of the uterus itself, thickened and hypertrophied to an
extraordinary degree, but still retaining all its natural connections
and its original anatomical structure.
The hypertrophied mucous membrane, above described, constitutes the Decidua vera. Its formation is confined altogether to the
body of the uterus, the mucous membrane of the cervix taking no
part in the process, but retaining its original appearance. The
decidua vera, therefore, commences above, at the orifices of the
Fallopian tubes, and ceases below, at the situation of the os internum. The cavity of the cervix, meanwhile, begins to be filled
with an abundant secretion of its peculiarly viscid mucus, which
blocks up, more or less completely, its passage, and protects the
internal cavity. But there is no membranous partition at this time
covering the os internum, and the mucous membranes of the cervix
and of the body of the uterus, though very different in appearance,
are still perfectly continuous with each other. When we cut open
the cavity of the uterus, therefore, in this condition, we find its
internal surface lined with the decidua vera, with the opening of
the os internum below and the orifices of the Fallopian tubes above,
perfectly distinct, and in their natural positions. (Fig. 219.)
As the fecundated egg, in its journey from above downward,
passes the lower orifice of the Fallopian tube, it insinuates itself
between the opposite surfaces of the uterine mucous membrane,
and becomes soon afterward lodged in one of the furrows or depressions between the projecting convolutions of the decidua.
(Fig. 219.) It is at this situation that an adhesion subsequently
takes place between the external membranes of the egg, on the
one hand, and the uterine decidua on the other. Now, at the point
where the egg becomes fixed and entangled, as above stated, a still
more rapid development than before takes place in the uterine




FORMATION  OF TIE  DECIDUA.                           601
mucous membrane.  Its projecting folds begin to grow up around
the egg in such a manner as to partially inclose it in a kind of
circumvallation of the decidua, and to shut it off, more or less comFig. 219.                             Fig 220.
IMPREGNATED UTERUS; showing             IMPREGNATED UTERUS, with proformation of decidua. The decidua is   jecting folds of decidua growing up
represented in black; and the egg is    around the egg. The narrow opening,
seen, at the fundus of the uterus, en-  where the edges of the folds approach
gaged between two of its projecting     each other, is seen over the most promiconvolutions.                           nent portion of the egg.
pletely, from  the general cavity of the uterus. (Fig. 220.)  The egg
is thus soon contained in a special cavity of its own, which still
communicates for a time with the general cavity of the uterus by
a small opening, situated over its most prominent portion, which
is known  as the "decidual umbilicus."  As the above process of
growth goes on, this opening becomes narrower and narrower, while
the projecting folds of decidua approach each other over the surface of the egg.  At last these folds actually touch each other and
unite, forming a kind of cicatrix which
remains for a certain time, to mark the                     Fig. 221.
situation of the original opening.
When the development of the uterus and
its contents has reached this point (Fig.   /                 S
221), it will be seen that the egg is completely inclosed in a distinct cavity of its 
own; being  everywhere  covered with  a
decidual layer of new  formation, which  
has thus gradually enveloped it, and by 
which it is concealed from  view when the
uterine cavity is laid open.  This newlyformed  layer of decidua, enveloping, as    I M P R EGNATED UrTER,;showing egg completely inclosed
above described, the projecting portion of  by decidua reflexa.




602  DEVELOPMENT OF UTERINE MUCOUS MEMBRANE.
the egg, is called the Decidua refexa; because it is reflected over
the egg, by a continuous growth from the general surface of the
uterine mucous membrane. The orifices of the uterine tubules,
accordingly, in consequence of the manner in which the decidua
reflexa is formed, will be seen not only on its external surface, or
that which looks toward the cavity of the uterus, but also on its
internal surface, or that which looks toward the egg.
The decidua vera, therefore, is the original mucous membrane
lining the surface of the uterus; while the decidua reflexa is a new
formation, which has grown up round the egg and inclosed it in a
distinct cavity.
If abortion occur at this time, the mucous membrane of the
uterus, that is, the decidua vera, is thrown off; and of course brings
away with it the egg and decidua reflexa. On examining the mass
discharged in such an abortion, the egg will accordingly be found
imbedded in the substance of the decidual membrane. One side
of this membrane, where it has been torn away from its attachment
to the uterine walls, is ragged and shaggy; the other side, corresponding to the cavity of the uterus, is smooth or gently convoluted,
and presents very distinctly the orifices of the uterine tubules;
while the egg itself can only be extracted by cutting through the
decidual membrane, either from one side or the other, and opening
in this way the special cavity in which it has been inclosed.
During the formation of the decidua reflexa, the entire egg, as
well as the body of the uterus which contains it, has considerably
enlarged. That portion of the uterine mucous membrane situated
immediately underneath the egg, and to which the egg first became
attached, has also continued to increase in thickness and vascularity.
The remainder of the decidua vera, however, ceases to grow as
rapidly as before, and no longer keeps pace with the increasing
size of the egg and of the uterus. It is still very thick and vascular at the end of the third month; but after that period it becomes
comparatively thinner and less glandular in appearance, while the
unusual activity of growth and development is concentrated in the
egg, and in that portion of the uterine mucous membrane which is
in immediate contact with it.
Let us now see in what manner the egg becomes attached to the
decidual membrane, so as to derive from it the requisite supply of
nutritious material. It must be recollected that, while the above
changes have been taking place in the walls of the uterus, the
formation of the embryo in the egg, and the development of the




FORMATION OF THE DECIDUA.                     603
amnion and chorion have been going on simultaneously.  Soon
after the entrance of the egg into the uterine cavity, its external
investing membrane becomes covered with projecting filaments, or
villosities, as previously described. (Chap. X.) These villosities,
which are at first, as we have seen, solid and non-vascular, insinuate
themselves, as they grow, into the uterine tubules, or between the
folds of the decidual surface with which the egg is in contact, penetrating in this way into little cavities or follicles of the uterine
mucous membrane, formed either from  the cavities of the tubules
themselves, or by the adjacent surfaces of minute projecting folds.
When the formation of the decidua reflexa is accomplished, the
chorion has already become uniformly
shaggy; and its villosities, spreading in all      Fig. 222.
directions from its external surface, penetrate everywhere into the follicles above de- 
scribed, both of the decidua vera underneath   / 
it, and the contiguous surface of the decidua
reflexa with which it is covered. (Fig. 222.)
In this way the egg becomes entangled 
with the decidua, and cannot then be readily separated from  it, without rupturing
some of the filaments which have grown
from  its surface, and have been received
IMPRE(TNATET  UTERUS;
into the cavity of the follicles. The nu- showing connection between viltritious fluids, exuded from  the soft and  lositie of chorion and decidual'                             membranes.
glandular textures of the decidua, are now
readily imbibed by the villosities of the chorion; and a more rapid
supply of nourishment is thus provided, corresponding in abundance with the increased and increasing size of the egg.
Very soon, however, a still greater activity of absorption becomes necessary; and, as we have seen in a preceding chapter, the
external membrane of the egg becomes vascular by the formation
of the allantoic bloodvessels, which emerge from the body of the
foetus, to ramify in the chorion, and penetrate everywhere into the
villosities with which it is covered. Each villosity, then, as it lies
imbedded in its uterine follicle, contains a vascular loop through
which the fcetal blood circulates, increasing the rapidity with which
absorption and exhalation take place.
Subsequently, furthermore, these vascular tufts, which are at first
uniformly abundant throughout the whole extent of the chorion,
disappear over a portion of its surface, while they at the same time




604  DEVELOPMENT OF UTERINE MUCOUS MEMBRANE.
become concentrated and still further developed at a particular
spot, the situation of the future placenta. (Fig. 223.) This is the
spot at which the egg is in contact with
Fig. 223.         the decidua vera. Here, therefore, both
the decidual membrane and the tufts
of the chorion continue to increase in
thickness and vascularity; while elsewhere, over the prominent portion of
_____   H     the egg, the chorion not only becomes
bare of villosities, and comparatively
destitute of vessels, but the decidua reflexa, which is in contact with it, also
)  1^  {    loses its activity of growth, and becomes expanded into athin layer, nearly
PRER    s g  destitute of vessels, and without any
PREGNANT UTERUS; showing
formation of placenta, by the united  remaining trace of tubules or follicles.
development or a portion of the de-    rin 
cidua and  the villosities of the chorion.                       therefore developed, during the process
of gestation, in such a way as to provide
for the nourishment of the foetus in the different stages of its growth.
At first, the whole of it is uniformly increased in thickness (decidua
vera). Next, a portion of it grows upward around the egg, and
covers its projecting surface (decidua reflexa). Afterward, both the
decidua reflexa and the greater part of the decidua vera diminish
in the activity of their growth, and lose their importance as a means
of nourishment for the egg; while that part which is in contact with
the vascular tufts of the chorion continues to grow, becoming exceedingly developed, and taking an active part in the formation of
the placenta.
In the following chapter, we shall examine more particularly the
structure and development of the placenta itself, and of those parts
which are immediately connected with it.




THE PLACENTA.                       605
CHAPTER XII.
THE PLACENTA.
WE have shown in the preceding chapters that the foetus, during
its development, depends for its supply of nutriment upon the lining
membrane of the maternal uterus; and that the nutriment, so supplied, is absorbed by the bloodvessels of the chorion, and transported
in this way into the circulation of the foetus. In all instances. accordingly, in which the development of the foetus takes place within
the body of the parent, it is provided for by the relation thus established between two sets of membranes; namely, the maternal
membranes which supply nourishment, and the foetal membranes
which absorb it.
In some species of animals, the connection between the maternal
and foetal membranes is exceedingly simple. In the pig, for example, the uterine mucous membrane is everywhere uniformly
vascular; its only peculiarity consisting in the presence of numerous transverse folds, which project from its surface, analogous to
the valvulae conniventes of the small intestine. The external investing membrane of the egg, which is the allantois, is also smooth
and uniformly vascular like the other. No special development of
tissue or of vessels occurs at any part of these membranes, and
no direct adhesion takes place between them; but the vascular
allantois or chorion of the fcetus is everywhere closely applied to
the vascular mucous membrane of the maternal uterus, each of the
two contiguous surfaces following the undulations presented by the
other. (Fig. 224.) By this arrangement, transudation and absorption take place from the bloodvessels of the mother to those of the
foetus, in sufficient quantity to provide for the nutrition of the latter.
When parturition takes place, accordingly, in these animals, a very
moderate contraction of the uterus is sufficient to expel its contents.
The egg, displaced from its original position, slides easily forward
over the surface of the uterine mucous membrane, and is at last
discharged without any hemorrhage or laceration of connecting
parts.  In other instances, however, the development of the fcetus




606                       THE  PLACENTA.
requires a more elaborate arrangement of the vascular membranes.
In the cow, for example, the external membrane of the egg, beside
Fig. 224.
FETAL PIG, with its membranes, contained in cavity of uterus.-a, a, b, b. Walls of uterus.
c, c. Cavity of uterus. d. Amnion. e, e. Allantois.
being everywhere supplied with branching vessels, presents upon
various points of its surface no less than from seventy to eighty oval
spots, at each of which the vessels of the chorion are developed into
abundant tufted prominences, hanging from its exterior as a thick,
velvety, vascular mass. At each point of the uterine mucous membrane, corresponding with one of these tufted masses, the maternal
bloodvessels are developed in a similar manner, projecting into the
uterine cavity as a flattened rounded mass or cake; which, with that
part of the foetal chorion which is adherent to it, is known by the
Fig. 225.
COTYLEDON OF Cow's UTER S.-a, a. Surface of fetal chorion. b, b. Bloodvessels of fetal
chorion. d, d. Bloodvessels of uterine mucous membrane. c, c. Surface of uterine mucous membrane.
name of the Cotyledon.  Each cotyledon forms, therefore, a little
placenta. (Fig. 225.)  In its substance the tufted vascular loops




THE PLACENTA.                       607
coming from the uterine mucous membrane (d, d) are entangled
with those coming from the membranes of the foetus (b, b). There
is no absolute adhesion between the two sets of vessels, but only
an interlacement of their ramified extremities; and, with a little
care in manipulation, the foetal portion of the cotyledon may be
extricated from the maternal portion, without lacerating either. In
consequence, however, of this intricate interlacement of the vessels,
transudation of fluids will evidently take place with great readiness,
from one system to the other.
The form of placenta, therefore, met with in these animals, is one
in which the bloodvessels of the foetal chorion are simply entangled
with those of the uterine mucous membrane. In the human subject, the structure of the placenta is a little more complicated,
though the main principles of its formation are the same as in the
above instances.
From what has been said in the foregoing chapters, it appears
that in the human subject, as well as in the lower animals, the
placenta is formed partly by the vascular tufts of the chorion,
and partly by the thickened mucous Membrane of the uterus in
which they are entangled. During the third month, those portions
of the chorion and, decidua which are destined to undergo this
transformation become more or less distinctly limited in their form
and dimensions; and a thickened vascular mass, partly maternal
and partly foetal in its origin, shows itself at the spot where the
placenta is afterward to be developed. This mass is constituted in
the following manner.
It will be recollected that the villi of the chorion, when first
formed, penetrate into follicles situated in the substance of the
uterine mucous membrane; and that after they have become vascular, they rapidly elongate and are developed into tufted ramifications of bloodvessels, each one of which turns upon itself in a
loop at the end of the villus. At the same time the uterine follicle,
into which the villus has penetrated, enlarges to a similar extent;
sending out branching diverticula, corresponding with the multi.
plied ramifications of the villus. In fact, the growth of the follicle
and that of the villus go on simultaneously and keep pace with
each other; the latter constantly advancing as the cavity of the
former enlarges.
But it is not only the uterine follicles which increase in size and
in complication of structure at this period. The capillary bloodvessels, which lie between them and ramify over their exterior,




608                    THE PLACENTA.
also become unusually developed. They enlarge and inosculate
freely with each other; so that every uterine follicle is soon covered
with an abundant network of dilated capillaries, derived from the
bloodvessels of the original decidua. At this time, therefore, each
vascular loop of the fetal chorion is covered, first, with a layer
forming the wall of the villus. This is in contact with the lining
membrane of a uterine follicle, and outside of this again are the
capillary vessels of the uterine mucous membrane; so that two
distinct membranes intervene between the walls of the fcetal capillaries on the one hand and those of the maternal capillaries on the
other, and all transudation must take place through the substance
of these two membranes.
As the formation of the placenta goes on, the anatomical arrangement of the fcetal vessels remains the same. They continue to
form vascular loops, penetrating deeply into the decidual membrane; only they become constantly more elongated, and their
ramifications more abundant and tortuous. The, maternal capillaries, however, situated on the outside of the uterine follicles, become
considerably altered in their anatomical relations. They enlarge
excessively; and, by encroaching constantly upon the little islets
or spaces between them, fuse successively with each other; and,
losing gradually in this way the characters of a capillary network,
become dilated into wide sinuses, which communicate freely with
the enlarged vessels in the muscular walls of the uterus. As the
original capillary plexus occupied the entire thickness of the
hypertrophied decidua, the vascular sinuses, into which it is thus
converted, are equally extensive. They commence at the inferior
surface of the placenta, where it is in contact with the muscular
walls of the uterus, and extend through its whole thickness, quite
up to the surface of the fcetal chorion.
As the maternal sinuses grow upward, the vascular tufts of the
chorion grow downward, and extend also through the entire thickness of the placenta. At this period, the development of the bloodvessels, both in the foetal and maternal portions of the placenta, is
so excessive that all the other tissues, which originally co-existed
with them, become retrograde and disappear almost altogether. If
a villus from the fcetal portion of the placenta be examined at this
time by transparency, in the fresh condition, it will be seen that its
bloodvessels are covered only with a layer of homogeneous, or finely
granular material,,,o of an inch in thickness, in which are imbedded small oval-shaped nuclei, similar to those seen at an earlier




THE PLACENTA.                           609
period in the villosities of the chorion. The villosities of the chorion are now, therefore, hardly anything more than ramified and tortuous vascular loops; the remaining substance of the villi having been atrophied              Fig. 226.
and absorbed in the excessive growth of
the bloodvessels. (Fig. 226.)  The uterine
follicles have at the same time lost all trace
of their original structure, and have become mere vascular sinuses, into which
the tufted fcetal bloodvessels are received,
as the villosities of the chorion were at
first received into the uterine follicles.
Finally, the walls of the fcetal bloodvessels having come into  close contact
with the walls of the maternal sinuses, the   Extremity of FETAL TUFT of
two become adherent and fuse together; so  huma placenta; from an injected 
specimen. Magnified 40 diameters.
that a time at last arrives, when we can
no longer separate the foetal vessels, in the substance of the placenta, from the maternal sinuses without lacerating either the one
or the other, owing to the secondary adhesion which has taken place
between them.
The placenta, therefore, when perfectly formed, has the structure
which is shown in the accompanying diagram  (Fig. 227), repreFig. 227.
c r 3
Vertical section of P L AC E N T A, showing arrangement of maternal and fcetal vessels. a, a. Chorion. b, b. Decidua. c, c,c, c. Orifices of uterine sinuses.
89




610                     THE PLACENTA.
senting a vertical section of the organ through its entire thickness.
At a, a, is seen the chorion, receiving the umbilical vessels from the
body of the foetus through the umbilical cord, and sending out its
compound and ramified vascular tufts into the substance of the
placenta. At b h, is the attached surface of the decidua, or uterine
mucous membrane; and at c, c, c, c, are the orifices of uterine vessels which penetrate it from below. These vessels enter the placenta
in an extremely oblique direction, though they are represented in
the diagram, for the sake of distinctness, as nearly perpendicular.
When they have once penetrated, however, the lower portion of
the decidua, they immediately dilate into the placental sinuses
(represented, in the diagram, in black), which extend through the
whole thickness of the organ, closely embracing all the ramifications of the foetal tufts. It will be seen, therefore, that the placenta,
arrived at this stage of completion, is composed essentially of nothing but bloodvessels. No other tissues enter into its structure;
for all those which it originally contained have disappeared, excepting the bloodvessels of the foetus, entangled with and adherent to
the bloodvessels of the mother.
There is, however, no direct communication between the foetal
and maternal vessels. The blood of the foetus is always separated
from  the blood of the mother by a membrane which has resulted
from the successive union and fusion of four different membranes,
viz., first, the membrane of the foetal villus; secondly, that of the
uterine follicle; thirdly, the wall of the foetal bloodvessel; and,
fourthly, the wall of the uterine sinus. The single membrane, however, into which these four finally coalesce, is extremely thin, as
we have seen, and of enormous extent, owing to the extremely
abundant branching and subdivision of the fetal tufts. These tufts,
accordingly, in which the blood of the foetus circulates, are bathed
everywhere, in the placental sinuses, with the blood of the mother;
and the processes of endosmosis and exosmosis, of exhalation and
absorption, go on between the two with the greatest possible
activity.
It is very easy to demonstrate the arrangement of the foetal
tufts in the human placenta.  They can be readily seen by the
naked eye, and may be easily traced from their attachment at the
under surface of the chorion to their termination near the uterine
surface of the placenta.  The anatomical disposition of the placental sinuses, however, is much more difficult of examination.
During life, and while the placenta is still attached to the uterus,




THE PLACENTA.                       611
they are filled, of course, with the blood of the mother and occupy
fully one-half the entire mass of the placenta. But when the placenta is detached, the maternal vessels belonging to it are torn off
at their necks (Fig. 227, c, c, c, c), and the sinuses, being then
emptied of blood by the compression to which the placenta is subjected, are apparently obliterated; and the fcetal tufts, falling together and lying in contact with each other, appear to constitute
the whole of the placental mass. The existence of the placental
sinuses, however, and their true extent, may be satisfactorily demonstrated in the following manner.
If we take the uterus of a woman who has died undelivered at
the full term or thereabout, and open it in such a way as to avoid
wounding the placenta, this organ will be seen remaining attached
to the uterine surface, with all its vascular connections complete.
Let the foetus now be removed by dividing the umbilical cord, and
the uterus, with the placenta attached, placed under water, with its
internal surface uppermost.  If the end of a blowpipe be now
introduced into one of the divided vessels of the uterine walls, and
air forced in by gentle insufflation, we can easily inflate, first, the
venous sinuses of the uterus itself, and next, the deeper portions
of the placenta; and lastly, the bubbles of air insinuate themselves
everywhere between the foetal tufts, and appear in the most superficial portions of the placenta, immediately underneath the transparent chorion (a, a, Fig. 227); thus showing that the placental
sinuses, which freely communicate with the uterine vessels, really
occupy the entire thickness of the placenta, and are equally extensive with the tufts of the chorion. We have verified this fact in
the above manner, on four different occasions, and in the presence
of Prof. C. R. Gilman, Dr. Geo. T. Elliot, Dr. Henry B. Sands,
Dr. T. G. Thomas, Dr. T. C. Finnell, and various other medical
gentlemen of New York.
If the placenta be now detached and examined separately, it will
be found to present upon its uterine surface a number of openings
which are extremely oblique in their position, and which are
accordingly bounded on one side by a very thin, projecting, crescentic edge. These are the orifices of the uterine vessels, passing
into the placenta and torn off at their necks, as above described;
and by carefully following them with the probe and scissors, they
are found to lead at once into extensive empty cavities (the placental sinuses), situated between the foetal tufts.  We have already
shown that these cavities are filled during life with the maternal




612                    THE PLACENTA.
blood; and there is every reason to believe that before delivery,
and while the circulation is going on, the placenta is at least twice
as large as after it has been detached and expelled from the uterus.
The placenta, accordingly, is a double organ, formed partly by
the chorion and partly by the decidua; and consisting of maternal
and fcetal bloodvessels, inextricably entangled and united with each
other.
The part which this organ takes in the development of the foetus
is an exceedingly important one. From the date of its formation,
at about the beginning of the fourth month, it constitutes the only
channel through which nourishment is conveyed from the mother
to the foetus. The nutritious materials, which circulate in abundance in the blood of the maternal sinuses, pass through the intervening membrane by endosmosis, and enter the blood of the fcetus.
The healthy or injurious regimen, to which the mother is subjected,
will accordingly exert an almost immediate influence upon the
child. Even medicinal substances, taken by the mother and absorbed into her circulation, may readily transude through the placental vessels; and they have been known in this way to exert a
specific effect upon the foetal organization.
The placenta is, furthermore, an organ of exhalation as well as
of absorption. The excrementitious substances, produced in the
circulation of the foetus, are undoubtedly in great measure disposed
of by transudation through the walls of the placental vessels, to be
afterward discharged by the excretory organs of the mother. The
system of the mother may therefore be affected in this manner by
influences derived from the foetus. It has been remarked more
than once, in the lower animals, that when the female has two successive litters of young by different males, the young of the second
litter will sometimes bear marks resembling those of the first male.
In these instances, the peculiar influence which produces the external mark must have been transmitted by the first male directly
to the foetus, from the foetus to the mother, and from the mother to
the foetus of the second litter.
It is also through the placental circulation that those disturbing
effects are produced upon the nutrition of the foetus, which result
from sudden shocks or injuries inflicted upon the mother. There is
now little room for doubt that various deformities and deficiencies of
the foetus, conformably to the popular belief, do really originate, in
certain cases, from nervous impressions, such as disgust, fear or anger,
experienced by the mother. The mode in which these effects may




THE PLACENTA.                         613
be produced is readily understood from what has been said above
of the anatomy and functions of the placenta. We know very well
how easily nervous impressions will disturb the circulation in the
brain, the face, the lungs, &c.; and the uterine circulation is quite
as readily influenced by similar causes, as physicians see every day
in cases of amenorrhcea, menorrhagia, &c. If a nervous shock may
excite premature contraction in the muscular fibres of the pregnant
uterus and produce abortion, as not unfrequently happens, it is certainly capable of disturbing the course of the circulation through
the same organ. But the fcetal circulation is dependent, to a great
extent, on the maternal. Since the two sets of vessels are so closely
entwined in the placenta, and since the fcetal blood has here much
the same relation to the maternal, that the blood in the pulmonary
capillaries has to the air in the air-vesicles, it will be liable to derangement from similar causes. If the circulation of air through
the pulmonary tubes and vesicles be suspended, that of the blood
through the capillaries is disturbed also. In the same way, whatever arrests or disturbs the circulation through the vessels of the
maternal uterus must necessarily be liable to interfere with that
in the fcetal capillaries forming part of the placenta. And lastly,
as the nutrition of the foetus is provided for wholly by the placenta,
it will of course suffer immediately from  any such disturbance of
the placental circulation. These effects may be manifested either
in the general atrophy and death of the foetus; or, if the disturbing
cause be slight, in the atrophy or imperfect development of particular parts; just as, in the adult, a morbid cause operating through
the entire system, may be first or even exclusively manifested in
some particular organ, which is more sensitive to its influence than
other parts.
The placenta must accordingly be regarded as an organ which
performs, during intra-uterine life, offices similar to those of the
lungs and the intestine after birth.  It absorbs nourishment, renovates the blood, and discharges by exhalation various excrementitious matters, which originate in the processes of foetal nutrition.




614.             DISCHARGE OF THE OVUM.
CHAPTER XIII.
DISCHARGE OF THE OVUM, AND RETROGRADE.
DEVELOPMENT (INVOLUTION) OF THE UTERUS.
DURING the growth of the ovum  and the formation of the placental structures, the muscular substance of the uterus also increases
in thickness, while the whole organ enlarges, in order to accommodate the growing foetus and its appendages. The relative positions
of the amnion and chorion, furthermore, undergo a change during
the latter periods of gestation, and the umbilical cord becomes
developed, at the same time, in the following manner.
In the earlier periods of foetal life the umbilical cord consists
simply of that portion of the allantois lying next the abdomen. It
is then very short, and contains the umbilical vessels running in a
nearly straight course, and parallel with each other, from the abdomen of the foetus to the external portions of the chorion. At this
time the amnion closely invests the body of the foetus, so that the
size of its cavity is but little larger
Fig. 228. thn t   of      f                    228.)
The space between the amnion
and the chorion is then occupied
by an amorphous gelatinous material, in which lies imbedded the
umbilical vesicle.
Afterward, however, the amnion enlarges faster than the cho.
rion, and encroaches upon the
layer of gelatinous matter situated
between the two (Fig. 229), at
HUMA N 0 v u t about the end of the first the same time that an albuminous
month.-1. Umbilicalvesicle. 2. Amnion. 3  fluid, the "amniotic fluid," is exChorion.
uded into its cavity, in constantly
increasing quantity. Subsequently, the gelatinous layer, above described, altogether disappears, and the amnion, at about the begin



ENLARGEMENT OF THE AMNION.                    615
ning of the fifth month, comes in contact with the internal surface
of the chorion. Finally, toward the end of gestation, the contact
becomes so close between these
two membranes that they are                  Fig. 229.
partially  adherent to  each
other, and it requires a little
care to separate them without
laceration.
The quantity of the amniotic
fluid continues to increase during the latter period of gestation in order to accommodate
the movements of the foetus.
These movements begin to be
peiceptible  about the  fifth
month. ast which  time  the    U UM AN 0 V ut at end of third month; showing
monThe uilical cord elongates, at the samewhich time, in proportion to
the increasing siet of the a mniotic cavity n.
muscular system  has already 
attained a considerable degree of development, but become afterward mor       e frequent and more strongly pronounced.  The space
and freedom requisite for these movements are provided for by the
fluid accumulated in the cavity of the amnion.
The umbilical cord elongates, at the same time, in proportion to
the increasing size of the amniotic cavity. During its growth, it
becomes spirally twisted from right to left, the two umbilical arteries winding round the vein in the same direction. The gelatinous
matter, already described as existing between the amnion and
chorion, while it disappears elsewhere, accumulates in the cord in
considerable quantity, covering the vessels with a thick, elastic envelope, which protects them from injury and prevents their being
accidentally compressed or obliterated. The whole is covered by a
portion of the amnion, which is connected at one extremity with the
integument of the abdomen, and invests the whole of the cord with
a continuous sheath, like the finger of a glove. (Fig. 230.)
The cord also contains, for a certain period, the pedicle or stem
of the umbilical vesicle. The situation of this vesicle, it will be
recollected, is always between the chorion and the amnion. Its
pedicle gradually elongates with the growth of the umbilical cord;
and the vesicle itself, which generally disappears soon after the
third month, sometimes remains as late as the fifth, sixth, or seventh.
According to Prof. Mayer, of Bonn, it may even be found, by careful search, at the termination of pregnancy.  When discovered in




616               DISCHARGE OF THE OVUM.
the middle and latter periods of gestation, it presents itself as a
small, flattened, and shrivelled vesicle, situated underneath the
amnion, at a variable distance from the insertion of the umbilical
cord.  A minute bloodvessel is often seen running to it from  the
cord, and ramifying upon its surface.
Fig. 230.
GRAVID HUMAN UTERUS AND CONTE NTS, showing the relations of the cord, placenta, membranes, &c., about the end of the seventh month.-. Decidua vera. 2 Decidua reflexa. 3. Chorion.
4. Amnion.
The decidua reflexa, during the latter months of pregnancy, is
constantly distended and pushed back by the increasing size of the
egg; so that it is finally pressed closely against the opposite surface
of the decidua vera, which still lines the greater part of the uterine
cavity. By the end of the seventh month, the opposite surfaces
of the decidua vera and reflexa are in complete contact with each
other, though still distinct and capable of being separated without
difficulty. After that time, they fuse together and become confounded with each other; the two at last forming only a single,
thin, friable, semi-opaque layer, in which no trace of their original
glandular structure can be discovered.
This is the condition of things at the termination of pregnancy.
Then, the time having arrived for parturition to take place, the
hypertrophied muscular walls of the uterus contract forcibly upon
its contents, and the egg is discharged, together with the whole of
the decidual uterine mucous membrane.
In the human subject, as well as in most quadrupeds, the mein



SEPARATION OF THE PLACENTA.                  617
branes of the egg are usually ruptured during the process of parturition; and the fcetus escapes first, the placenta and the rest of
the appendages following a few moments afterward. Occasionally,
however, even in the human subject, the egg is discharged entire,
and the foetus liberated afterward by the laceration of the membranes. In each case, however, the mode of separation and expulsion is, in all important particulars, the same.
The process of parturition, therefore, consists essentially in a
separation of the decidual membrane, which, on being discharged,
brings away the ovum with it. The greater part of the decidua
vera, having fallen into a state of atrophy during the latter months
of pregnancy, is by this time nearly destitute of vessels, and separates, accordingly, without any perceptible hemorrhage. That portion, however, which enters into the formation of the placenta, is,
on the contrary, excessively vascular; and when the placenta is
separated, and its maternal vessels torn off at their necks, as before
mentioned, a gush of blood takes place, which accompanies or
immediately follows the birth of the fcetus. This hemorrhage,
which occurs as a natural phenomenon at the time of parturition,
does not come from the uterine vessels proper. It consists of the
blood which was contained in the placental sinuses, and which is
expelled from them owing to the compression of the placenta by
the walls of the uterus. Since the whole amount of blood thus
lost was previously employed in the placental circulation, and since
the placenta itself is thrown off at the same time, no unpleasant
effect is produced upon the mother by such a hemorrhage, because
the natural proportion of blood in the rest of the maternal system
remains the same. Uterine hemorrhage at the time of parturition,
therefore, becomes injurious only when it continues aftercomplete
separation of the placenta; in which case it is supplied by the
mouths of the uterine vessels themselves, left open by failure of the
uterine contractions. These vessels are usually instantly closed,
after separation of the placenta, by the contraction of the muscular
fibres of the uterus. They pass, as we have already mentioned, in
an exceedingly oblique direction, from the uterine surface to the
placenta; and the muscular fibres, which cross them transversely
above and below, necessarily constrict them, and effectually close
their orifices, immediately on being thrown into a state of contraction.
Another very remarkable phenomenon, connected with pregnancy and parturition, is the appearance in the uterus of a new
mucous membrane, growing underneath the old, and ready to
take the place of the latter after its discharge.




618              DISCHARGE OF THE OVUM.
If the internal surface of the body of the uterus be examined
immediately after parturition, it will be seen that at the spot where
the placenta was attached every trace of mucous membrane has
disappeared. The muscular fibres of the uterus are here perfectly
exposed and bare; while the mouths of the ruptured uterine sinuses
are also visible, with their thin, ragged edges hanging into the
cavity of the uterus, and their orifices plugged with more. or less
abundant bloody coagula.
Over the rest of the uterine surface, the decidua vera has also
disappeared. Here, however, notwithstanding the loss of the original mucous membrane, the muscular fibres are not perfectly bare,
but are covered with a thin, semi-transparent film, of a whitish color
and soft consistency. This film is an imperfect mucous membrane
of new formation, which begins to be produced, underneath the
old decidua vera, as early as the beginning of the eighth month.
We have seen this new mucous membrane very distinctly in the
uterus of a woman who died undelivered at the above period.
The old mucous membrane, or decidua vera, is at this time somewhat opaque, and of a slightly yellowish color, owing to a partial
fatty degeneration which it undergoes in the latter months of pregnancy. It is easily raised and separated from the subjacent parts,
owing to the atrophy of its vascular connections; and the new
mucous membrane, situated beneath it, is readily distinguished by
its fresh color, and healthy, transparent aspect.
The mucous membrane of the cervix uteri, which takes no part
in the formation of the decidua, is not thrown off in parturition,
but remains in its natural position; and after delivery it may be
seen to terminate at the os internum by an uneven, lacerated edge,
where it was formerly continuous with the decidua vera.
Subsequently, a regeneration of the mucous membrane takes place
over the whole extent of the body of the uterus. The mucous
membrane of new formation, which is already in existence at the
time of delivery, becomes thickened and vascular; and glandular
tubules are gradually developed in its substance.  At the end of
two months after delivery, according to Heschl' and Longet,2 it has
entirely regained the natural structure of the uterine mucous membrane. It unites at the os internum, by a linear cicatrix, with the
mucous membrane of the cervix, and the traces of its laceration at
this spot afterward cease to be visible. At the point, however,
1 Zeitschrift der K. K. Gesellschaft der Aerzte, in Wien, 1852.
2 Trait6 de Physiologie. De la G6n6ration, p. 173.




RETROGRADE  DEVELOPMENT  OF THE UTERUS.   619
where the placenta was attached, the regeneration of the mucous
membrane is less rapid; and a cicatrix-like spot is often visible at
this situation for several months after delivery.
The only further change, which remains to be described in this
connection, is the fatty degeneration and reconstruction of the
muscular substance of the uterus.  This process, which is sometimes known as the "involution" of the uterus, takes                   Fig. 231.
place in the following manner.  The muscular fibres 
of the unimpregnated uterus
are pale, flattened, spindle-...  
shaped bodies (Fig. 231) near-. 
ly homogeneous in structure              \           A 
or very faintly granular, and   /
measuring from   A-  to                     X; 
of an inch  in  length, by
UO  to   1   of an inch
T l        6 50 a -0 6NI 
in width.  During gestation
these  fibres  increase very 
considerably in size.  Their 
texture becomes much more    MuSCULAR FIBRES OF UNIMPRENA TED
UTERUS; from.a woman aged 40, dead of phthiisi
distinctly granular, and their  pulnonalis.
outlines more strongly marked.  An oval nucleus also
shows itself in the central                    Fig. 232.
part of each fibre.  The entire walls of the uterus, at the    /
time of delivery, are corn-       /
posed of such muscular fibres  
as these, arranged in circular, oblique, and longitudinal 
bundles.                                   1     1
About the end of the first
week  after delivery, these 
fibres begin  to undergo a                                       /
fatty  degeneration.   (Fig. 
232.)   Their granules become larger and more proMUSCULAR FIBRFESOF HUMIAN UTERUS, ten
Tminent, and very soon  as-   M.cuLA    FREso   HUMAN UTR s, ten
net   a  verysoonasdays after parturition; from a woman dead of puersume the appearance of mole- peral fever.




620               DISCHARGE OF THE OVUM.
cules of fat, deposited in the substance of the fibre. The fatty
deposit, thus commenced, increases in abundance, and the molecules continue to enlarge until they become converted into fully
formed oil-globules, which fill the interior of the fibre more or less
completely, and mask, to a
Fig. 233.              certain extent, its anatomical
characters. (Fig. 233.)  The
universal fatty degeneration,'/,,~ -^. \ ~ thus induced, gives to the
e           Id ^.,.- \    uterus a softer consistency,
g/ 1^:jj        \ ~ and a pale yellowish color
\  I:.:I W ^\  which is characteristic of it
~:.1  X~i;at this period.  The muscu\ tl    11- ^it    ]lar fibres which have become
~\'/oO! X i    I X     /   altered by the fatty deposit
%\ -o'?  /  are afterward gradually absorbed and disappear; their
place  being  subsequently
taken by other fibres of new
MUSCULAR, FIBRES OF HUMAN UTERUS, three formation, which already beweeks after parturition from a woman dead of peri- n t     
tonitis.                              gin to make their appearance
before the old ones have been
completely destroyed. As this process goes on, it results finally
in a complete renovation of the muscular substance of the uterus.
The organ becomes again reduced in size, compact in tissue, and
of a pale ruddy hue, as in the ordinary unimpregnated condition.
This entire renewal or reconstruction of the uterus is completed,
according to Heschl,. about the end of the second month after
delivery.
Op. cit.




DEVELOPMENT OF THE EMBRYO.                     621
CHAPTER XIV.
DEVELOPMENT OF THE EMBRYO-NERVOUS SYSTEM,
ORGANS OF SENSE, SKELETON, AND LIMBS.
THE first trace of a spinal cord in the embryo consists of the
double longitudinal fold or ridge of the blastodermic membrane,
which shows itself at an early period, as above described, on each
side the median furrow.  The two laminse of which this is cornposed, on the right and left sides (Fig. 234, a, b), unite with each
other in front, forming a rounded dilatation (c),
the cephalic extremity, and behind at (, forming      Fig. 234.
a pointed or caudal extremity.  Near the posterior extremity, there is a smaller dilatation,
which marks the future situation of the lumbar
enlargement of the spinal cord.
As the laminae above described grow upward
and backward, they unite with each other upon
the median line, so that the whole is converted
into a hollow cylindrical cord, terminating anteriorly by a bulbous enlargement, and posteriorly
by a pointed enlargement; the central cavity
which it contains running continuously through
it, from front to rear.                            Folmation of CiReBRO-SPINAL AXIS.The next change which shows itself is a divi-  a, b. Spinal cord. c: Cesion of the anterior bulbous enlargement into  phalic extremity.  d.
Caudal extremity.
three secondary compartments or vesicles (Fig.
235), which are partially separated from each other by transverse
constrictions. These vesicles are known as the three cerebral vesicles, from which all the different parts of the encephalon are afterward to be developed. The first, or most anterior cerebral vesicle
is destined to form the hemispheres; the second, or middle, the
tubercula quadrigemina; and the third, or posterior, the medulla
oblongata.  All three vesicles are at this time hollow, and their




622            DEVELOPMENT OF THE EMBRYO.
cavities communicate freely with each other, through the intervening constrictions.
Very soon the anterior and the posterior cerebral vesicles suffer
a further division; the middle one remainFig. 235.        ing undivided.  The anterior vesicle thus
separates into two portions, of which the
first, or larger,. constitutes the hemispheres,
while the second, or smaller, becomes the
optic thalami. The third vesicle also separates into two portions, of which the anterior becomes the cerebellum, and the posterior the medulla oblongata.
There are, therefore, at this time five
cerebral vesicles, all of whose cavities communicate with each other and with the
central cavity' of the spinal cord. The
entire cerebro-spinal axis, at the same time,
becomes very strongly curved in an anterior direction, corresponding with the anteFormation of the CEREBO-    cuvtrebd
Formtif of the CEEo-  rior curvature of the body of the embryo
SPINAL Axis.-1. Vesicle of
the hemispheres. 2. Vesicle of (Fig. 236); so that the middle vesicle, or
the tubercula quadrigemina. 3.1    
Vesicle ofthe nedulla oblongata. that of the tubercula quadrigemina, occupies a prominent angle at the upper part of
the encephalon, while the hemispheres and the medulla oblongata
are situated below it, anteriorly and posteriorly.
At first, it will be observed, the relative size of the various parts
of the encephalon is very different from that which
Fig. 236.    they afterward attain in the adult condition.  The
2        ~ hemispheres, for example, are hardly larger than'jD       the tubercula quadrigemina; and the cerebellum'.... is very much inferior in size to the medulla oblongata. Soon afterward, the relative position and size
of the parts begin to alter.  The hemispheres and
FMrTAL PI(, five- tubercula quadrigemina grow faster than the posteeighths of an inch
long, showing brain  rior portions of the encephalon; and the cerebellum
and spinal cord.-.  becomes doubled backward over the medulla oblonHemispheres. 2; Tubercula  quadrigemi-  gata. (Fig. 237.)  Subsequently, the hemispheres
4a e.  LCerebellum    rapidly enlarge, growing upward and backward,
4. Medulla oblongata.
so as to cover in and conceal both the optic thalami and the tubercula quadrigemina (Fig. 238); the cerebellum
tending in the same way to grow backward, and projecting farther




NERVOUS SYSTEM.                            623
and farther over the medulla oblongata.  The subsequent history
of the development of the encephalon is little more than a conFig. 237.                         Fig. 238.
FETAL PIG, one and a quarter inch   HEAD'OF FCETAL PIo, three and a
long.-I. Hemispheres. 2. Tubercula  half inches long.-1. Hemispheres. 3.
quadrigemina. 3. Cerebellum. 4. Me-  Cerebellum. 4. Medulla oblongata.
dulla oblongata.
tinuation of the same process; the relative dimensions of the parts
constantly changing, so that the hemispheres become, in the adult
condition (Fig. 239), the largest of all the divisions of the enceFig. 239.
BRAIN OF ADULT Pi(.-1. Hemispheres. 3. Cerebellum. 4. Medulla oblong.lta.
phalon. while the cerebellum is next in size, and covers entirely
the upper portion of the medulla oblongata. The surfaces, also, of
the hemispheres and cerebellum, which were at first smooth, become
afterward convoluted; increasing, in this way, still farther the
extent of their nervous matter.  In the human foetus, these convolutions begin to appear about the beginning of the fifth month
(Longet), and grow constantly deeper and more abundant during
the remainder of foetal life.
The lateral portions of the brain growing at the same time more
rapidly than that.which is situated on the median line, they soon
project on each side outward and upward; and, by folding over
against each other in the median line, form the right and left hemispheres, separated  from  each  other by  the  longitudinal fissure.




624           DEVELOPMENT OF THE EMBRYO.
A similar process of growth taking place in the spinal cord results
in the formation of the two lateral columns and the anterior and posterior median fissures of the cord. Elsewhere the median fissure is
less complete, as, for example, between the two. lateral halves of the
cerebellum, the two optic thalami and corpora striata, and the two
tubercula quadrigemina; but it exists everywhere, and marks more
or less distinctly the division between the two sides of the nervous
centres, produced by the excessive growth of their lateral portions.
In this way the whole cerebro-spinal axis is converted into a double
organ, equally developed upon the right and left sides, and partially
divided by a longitudinal median fissure.
Organs of Special Sense.-The eyes are formed by a diverticulum
which grows out on each side from the first cerebral vesicle. This
diverticulum is at first hollow, its cavity communicating with that
of the hemisphere. Afterward, the passage between the two is filled
up with a deposit of nervous matter, and becomes the optic nerve.
The globular portion of the diverticulum, which is converted into
the globe of the eye, has a very thin layer of nervous matter deposited upon its internal surface, which becomes the retina; the rest
of its cavity being occupied by a gelatinous semi-fluid substance,
the vitreous body. The crystalline lens is formed in a distinct follicle, which is an offshoot of the integument, and becomes partially
imbedded in the anterior portion of the globe of the eye.  The
cornea also is originally a part of the integument, and remains
partially opaque until a very late period of development. Its tissue
clears up, however, and becomes perfectly transparent, shortly before birth.
The iris is a muscular septum which is formed in'front of the
crystalline lens, separating the anterior and posterior chambers of
the aqueous humor.  Its central opening, which afterward becomes
the pupil, is at first closed by a vascular membrane, the pupillary
membrane, passing directly across the axis of the eye.  The vessels
of this membrane, which are derived from those of the iris, subsequently become atrophied.  They disappear first from  its centre,
and afterward recede gradually toward its circumference; returning
always upon themselves in loops, the convexities of which are directed
toward the centre of the membrane. The pupillary membrane itself
finally becomes atrophied and destroyed, following in this retrograde process the direction of its receding bloodvessels, viz., from
the centre toward the circumference. It has completely disappeared
by the end of the seventh month. (Cruveilhier.)




SKELETON AND LIMBS.                     625
The eyelids are formed by folds of the integument, which
gradually project from above and below the situation of the eyeball. They grow so rapidly during the second and third months
that their free margins come in contact and adhere together, so that
they cannot be separated at that time without some degree of violence. They remain adherent from this period until the seventh
month (Guy), when their margins separate and they become perfectly free and movable. In the carnivorous animals, however
(dogs and cats), the eyelids do not separate from each other until
eight or ten days after birth.
The internal ear is formed in a somewhat similar manner with
the eyeball, by an offshoot from the third cerebral vesicle; the
passage between them filling up by a deposit of white substance,
which becomes the auditory nerve. The tympanum and auditory
meatus are both offshoots from the external integument.
Skeleton.-At a very early period of development there appears,
as we have already described (Chap. VII.), immediately beneath the
cerebro-spinal axis, a cylindrical cord, of a soft, cartilaginous consistency, termed the chorda dorsalis. It consists of a fibrous sheath
containing a mass of simple cells, closely packed together and
united by adhesive material. This cord is not intended to be a
permanent part of the skeleton, but is merely a temporary organ
destined to disappear as development proceeds.
Immediately around the chorda dorsalis there are deposited soon
afterward a number of cartilaginous plates, which encircle it in a
series of rings, corresponding in number with the bodies of the future
vertebrae. These rings increase in thickness from without inward,
encroaching upon the substance of the chorda dorsalis, and finally
taking its place altogether. The thickened rings, which have been
filled up in this way and solidified by cartilaginous deposit, become
the bodies of the vertebrae; while their transverse and articulating
processes, with the laminae and spinous processes, are formed by
subsequent outgrowths from the bodies in various directions.
When the union of the dorsal plates upon the median line fails
to take place, the spinal canal remains open at that situation, and
presents the malformation known as spina bifida. This malforma
tion may consist simply in a fissure of the spinal canal, more or
less extensive, in which case it may often be cured, or even close
spontaneously; or it may be complicated with an imperfect development or complete absence of the spinal cord at the same spot,
40




626           DEVELOPMENT OF THE EMBRYO.
when it is accompanied of course by paralysis of the lower extremities, and almost necessarily results in early death.
The entire skeleton is at first cartilaginous. The first points of
ossification show themselves about the beginning of the second
month, almost simultaneously in the clavicle and the upper and
lower jaw. Then come, in the following order, the long bones of
the extremities, the bodies and processes of the vertebrae, the bones
of the head, the ribs, pelvis, scapula, metacarpus and metatarsus,
and the phalanges of the fingers and toes. The bones of the carpus,
however, are all cartilaginous at birth, and do not begin to ossify
until a year afterward. The calcaneum and astragalus begin to
ossify, according to Cruveilhier, during the latter periods of foetal
life, but the remainder of the tarsus is cartilaginous at birth. The
lower extremity of the femur begins to ossify, according to the
same author, during the.last half of the ninth month. The pisiform
bone of the carpus is said to commence its ossification later than
any other bone in the skeleton, viz., at from twelve to fifteen years
after birth. Nearly all the bones ossify from several distinct points;
the ossification spreading as the cartilage itself increases in size,
and the various bony pieces, thus produced, uniting with each other
at a later period, usually some time after birth.
The limbs appear, by a kind of budding process, as offshoots of
the external layer of the blastodermic membrane. They are at
first mere rounded elevations, without any separation between the
fingers and toes, or any distinction between the different articulations. Subsequently the free extremity of each limb becomes divided into the phalanges of the fingers or toes; and afterward the
articulations of the wrist and ankle, knee and elbow, shoulder and
hip, appear successively from below upward.
The posterior extremities, in the human subject, are less rapid in
their development than the anterior.  Throughout the term  of
foetal life, indeed, the anterior parts of the body are generally more
voluminous than the posterior. The younger the embryo, the larger
are the head and upper extremities in proportion to the rest of the
body. The lower limbs and the pelvis, more particularly, are very
slightly developed in the early periods of growth, as compared with
the spinal column, to which they are attached. The inferior extremity of the spinal column, formed by the sacrum and coccyx,
projects at this time considerably beyond the pelvis, forming a tail,
like that of the lower animals, which is curled forward toward the
abdomen, and terminates in a pointed extremity. Subsequently the




SKELETON AND LIMBS.                     627
pelvis and the muscular parts seated upon it grow so much faster
than the sacrum  and coccyx, that the latter become concealed
under the adjoining soft parts, and the rudimentary tail accordingly disappears.
The integument of the embryo is at first thin, vascular, and exceedingly transparent. It afterward becomes thicker, more opaque,
and whitish in color; though even at birth it is more vascular than
in the adult condition, and the ruddy color of its abundant capillary vessels is then very strongly marked. The hairs begin to
appear about the middle of intra-uterine life; showing themselves
first upon the eyebrows, and afterward upon the scalp, trunk and
extremities. The nails are in process of formation from the third
to the fifth month; and, according to Kolliker, are still covered
with a layer of epidermis until after the latter period. The sebaceous matter of the cutaneous glandules accumulates upon the skin
after the sixth month, and forms a whitish, semisolid, oleaginous
layer, termed the vernix caseosa, which is most abundant in the
flexures of the joints, between the folds of the integument, behind
the ears and upon the scalp.
The cells of the epidermis are repeatedly exfoliated after the first
five months of foetal life (Kolliker), and replaced by others, of new
formation and of larger size. These exfoliated epidermic cells are
found mingled with the sebaceous matter of the vernix caseosa in
great abundance. This semi-oleaginous layer, with which the integument is covered, becomes exceedingly useful in the process of
parturition, by lubricating the surface of the body, and allowing it
to pass easily through the generative passages.




628   DEVELOPMENT OF THE ALIMENTARY CANAL
CHAPTER XV.
DEVELOPMENT OF THE ALIMENTARY CANAL
AND ITS APPENDAGES.
WE have already seen, in a preceding chapter, that the intestinal
canal is formed by the internal layer of the blastodermic membrane,
which curves forward on each side, and is thus converted into a
nearly straight cylindrical tube, terminating at each extremity in
a rounded cul-desac, and inclosed by the external layer of the
blastodermic membrane. The abdominal walls, however, do not
unite with each other upon the median line until long after the
formation of the intestinal canal; so that, during a certain period,
the abdomen of the embryo is widely open in front, presenting a
long oval excavation, in which the nearly straight intestinal tube
is to be seen, running from its anterior to its posterior extremity.
The formation of the stomach takes place in the following manner: The alimentary canal, originally straight, soon presents two
lateral curvatures at the upper part of the abdomen; the first to
the left, the second to the right. The first of these curvatures
becomes expanded into a wide sac, projecting laterally from the
median line into the left hypochondrium, forming the great pouch
of the stomach. The second curvature, directed to the right, marks
the boundary between the stomach and the duodenurn; and the
tube at that point becoming constricted and furnished with a circular
layer of muscular fibres, is converted into the pylorus. Immediately below the pylorus, the duodenum again turns to the left; and
these curvatures, increasing in number and complexity, form the
convolutions of the small intestine. The large intestine forms a
spiral curvature; ascending on the right side, then crossing over
to the left as the transverse colon, and again descending on the left
side, to terminate by the sigmoid flexure in the rectum.
The curvatures of the intestinal canal take place, however, in an
antero-posterior, as well as in a lateral direction, and may be beat
studied in a profile view, as in Fig. 240. The abdominal walls are




AND ITS APPENDAGES.                       629
here still imperfectly closed, leaving a wide opening at a b, where
the integument of the feetus becomes continuous with the commencement of the amniotic membrane.  The intestine makes at
Fig. 240.
Formation of A IM ENTARY CANAL.-a, b. Commencement of amnion. c, c. Intestine. d.
Pharynx. e. Urinary bladder. f. Allantois. g. Umbilical vesicle. a. Dotted line, showing the
place of formation of the oesophagus.
first a single angular turn forward, and opposite the most prominlent portion of this angle is to be seen the obliterated duct, which
forms the stem of the umbilical vesicle. A short distance below
this point the intestine subsequently enlarges in its calibre, and the
situation of this enlargement marks the commencement of the
colon. The two portions of the intestine, after this period, become
widely different from each other. The upper portion, which is the
small intestine, grows mostly in the direction of its length, and
becomes a very long, narrow, and convoluted tube; while the lower
portion, which is the large intestine, increases rapidly in diameter,
but elongates less than the former.
At the point of junction of the small and large intestines, a lateral bulging or diverticulum of the latter shows itself, and increases
in extent, until the ileum seems at last to be inserted obliquely into
the side of the colon.  This diverticulum of the colon is at first
uniformly tapering or conical in shape; but afterward that portion
which forms its free extremity, becomes narrow and elongated, and
is slightly twisted upon itself in a spiral direction, forming the
appendix vermiformis; while the remaining portion, which is continuous with the intestine, becomes exceedingly enlarged, and forms
the caput coli.
The caput coli and the appendix are at first situated near the




630    DEVELOPMENT OF THE ALIMENTARY CANAL
umbilicus; but between the fourth and fifth months (Cruveilhier)
their position is altered, and they then become fixed in the right
iliac region. During the first six months, the internal surface of
the small intestine is smooth. At the seventh month, according to
Cruveilhier, the valvule conniventes begin to appear, after which
they increase in size till birth.  The division of the colon into
sacculi by longitudinal and transverse bands, is also an appearance
which presents itself only during the last half of foetal life. Previous to that time, the colon is smooth and cylindrical in figure,
like the small intestine.
After the small intestine is once formed, it increases very rapidly
in length. It grows, indeed, at this time, faster than the walls of
the abdomen; so that it can no longer be contained in the abdominal cavity, but protrudes, under the form of an intestinal loop, or
hernia, from the umbilical opening. In the human embryo, this
protrusion of the intestine can be readily seen during the latter part
of the second month. At a subsequent period, however, the walls
of the abdomen grow more rapidly than the intestine. They accordingly gradually envelop the hernial protrusion, and at last
inclose it again in the cavity of the abdomen.
Owing to an imperfect development of the abdominal walls, and
an imperfect closure of the umbilicus, this intestinal protrusion,
which is normal during the early stages of fcetal life, sometimes
remains at birth, and we then have a congenital umbilical hernia.
As the parts at that time, however, have a natural tendency to
cicatrize and unite with each other, simple pressure is generally
effectual, in such cases, in retaining the hernia within the abdomen,
and in producing at last a complete cure.
Urinary Bladder, Urethra, &c.-It will be recollected that very
soon after the formation of the intestine, a vascular outgrowth takes
place from its posterior portion, which gradually protrudes from the
open walls of the abdomen in front, until it comes in contact with
the external investing membrane of the egg, and forms, by its continued growth and expansion, the allantois. (Fig. 240,f.) It is at
first, as we have shown above, a hollow sac; but, as it spreads out
over the surface of the investing membrane of the egg, its two
opposite walls adhere to each other, so that its cavity is obliterated
at this situation, and it is thus converted into a single vascular
membrane, the chorion.  This obliteration of the cavity of the
allantois commences at its external portion, and gradually extends
inward toward the point of its emergence from the abdomen. The




AND ITS APPENDAGES.                     631
hollow tube, or duct, which connects the cavity of the allantois with
the posterior part of the intestine, is accordingly converted, as the
process of obliteration proceeds, into a solid, rounded cord. This
cord is termed the urachus.
After the walls of the abdomen have come in contact, and united
with each other at the umbilicus, that portion of the above duct
which is left outside the abdominal cavity, forms a part of the umbilical cord, and remains connected with the umbilical arteries and
vein. That portion, on the contrary, which is included in the abdomen, does not close completely, but remains as a pointed fusiform
sac, terminating near the umbilicus in the solid cord of the urachus,
and still communicating at its base with the lower extremity of the
intestinal canal. This fusiform  sac (Fig. 240, e), becomes the urinary bladder; and in the foetus at term, the bladder is still conical
in form, its pointed extremity being attached, by means of the urachus, to the internal surface of the abdominal walls at the situation
of the umbilicus. Afterward, the bladder loses this conical form,
and its fundus in the adult becomes rounded and bulging.
The urinary bladder, as it appears from the above description, at
first communicates freely with the intestinal cavity. The intestine,
in fact, terminates, at this time, in a wide passage, or cloaca, at its
lower extremity, which serves as a common outlet for the urinary
and intestinal passages. Subsequently, however, a horizontal partition makes its appearance just above the point of junction between
the bladder and rectum, and grows downward and forward in such
a manner as to divide the above-mentioned cloaca into two parallel
and unequal passages. The anterior or smaller of these passages
becomes the urethra, the posterior or larger becomes the rectum;
and the lower edge of the septum  between them  becomes finally
united with the skin, forming, at its most superficial part, a tolerably wide band of integument, the perineum, which intervenes
between the anus and the external portion of the urethra.
The contents of the intestine, which accumulate during foetal life,
vary in different parts of the alimentary canal. In the small intestine they are semifluid or gelatinous in consistency, of a light
yellowish or grayish-white color in the duodenum, becoming yellow,
reddish-brown and greenish-brown below. In the large intestine
they are of a dark greenish hue, and pasty in consistency; and the
contents of this portion of the alimentary canal have received the
name of meconium, from  their resemblance to inspissated poppyjuice.  The mneconium contains a large quantity of fat, as well as




632    DEVELOPMENT OF THE ALIMENTARY CANAL
various insoluble substances, probably the residue of epithelial and
mucous accumulations. It does not contain, however, any trace of
the biliary substances (tauro-cholates and glyko-cholates) when carefully examined by Pettenkofer's test; and cannot therefore properly
be regarded, as is sometimes incorrectly asserted, as resulting from
the accumulation of bile. In the contents of the small intestine, on
the- contrary, traces of bile may be found, according to Lehmann,1
so early as between the fifth and sixth months.  We have also
found distinct traces of bile in the small intestine at birth, but it is
even then in extremely small quantity, and is sometimes altogether
absent.
The meconium, therefore, and the intestinal contents generally,
are not composed principally, or even to any appreciable extent, of
the secretions of the liver. They appear rather to be produced by
the mucous membrane of the intestine itself. Even their yellowish
and greenish color does not depend on the presence of bile, since
the yellow color first shows itself, in very young foetuses, about
the middle of the small intestine, and not at its upper extremity.
The material which accumulates afterward appears to extend from
this point upward and downward, gradually filling the intestine,
and becoming, in the ileum and large intestine, darker and more
pasty as gestation advances.
It is a singular fact, perhaps of some importance in this connection, that the amniotic fluid, during the latter half of foetal life,
finds its way, in greater or less abundance, into the stomach, and
through that into the intestinal canal. Small cheesy-looking masses
may sometimes be found at birth in the fluid contained in the
stomach, which are seen on microscopic examination to be no other
than portions of the vernix caseosa exfoliated from the skin into
the amniotic cavity, and afterward swallowed. According to Kolliker,2 the soft downy hairs of the foetus, exfoliated from the skin,
are often swallowed in the same way, and may be found in the
meconium.
The gastric juice is not secreted before birth; the contents of the
stomach being generally in small quantity, clear, nearly colorless,
and neutral or alkaline in reaction.
The liver is developed at a very early period. Its size in proportion to that of the entire body is, in fact, very much greater in
the early months than at birth or in the adult condition. In the
I Physiological Chemistry, Philadelphia edition, vol. i. p. 532.
2 Gewebelehre. Leipzig, 1852, p. 139.




AND ITS APPENDAGES.                      633
fcetal pig we have found the relative size of the liver greatest
within the first month, when it amounts to very nearly 12 per cent.'of the entire weight of the body. Afterward, as it grows less rapidly
than other parts, its relative weight diminishes successively to 10
per cent. and 6 per cent.; and is reduced before birth to 3 or 4 per
cent.  In the human subject, also, the weight of the liver at birth
is between 3 and 4 per cent. of that of the entire body.
The secretion of bile takes place, as we have intimated above,
during foetal life, in a very scanty manner. We have found it, in
minute quantity, in the gall-bladder as well as in the small intestine at birth; but it does not probably take any active part in the
nutritive or other functions of the foetus before that period.
The glycogenic function of the liver commences during foetal life,
and at birth the tissue of the organ is abundantly saccharine.  It is
remarkable, however, that in the early periods of gestation sugar is
produced in the fcetus from other sources than the liver.  In very
young foetuses of the pig, for example, both the allantoic and
amniotic fluids are saccharine, a considerable time before any sugar
makes its appearance in the tissue of the liver. Even the urine, in
half-grown foetal pigs, contains an appreciable quantity of sugar,
and the young animal is therefore, at this period, in a diabetic condition. This sugar, however, disappears from the urine before birth,
and also from the amniotic fluid, as has been ascertained by M. Bernard;' while the liver begins to produce a saccharine substance, and
to exercise the glycogenic function, which it continues after birth.
Development of the Pharynx, G(sophagus, &c.-We have already
seen that the intestinal canal consists at first of a cylindrical tube,
terminated, at each extremity of the abdominal cavity, by a rounded
cul-de-sac (Fig. 240, c, c); and that the openings of the mouth and
anus are subsequently formed by perforations which take place
through the integument and the intervening tissues, and so establish a communication with the intestinal tube. The formation of
the anterior perforation, and its appendages, takes place in the following manner:
After the early development of the intestinal tube in the mode
above described, the head increases in size out of all proportion to
the remainder of the foetus, projecting as a large rounded mass from
the anterior extremity of the body, and containing the brain and the
organs of special sense. This portion soon bends over toward the
Leqons de Physiologie Experimentale, Paris, 1855, p. 398.




634    DEVELOPMENT OF THE ALIMENTARY CANAL
abdomen, in consequence of the increasing curvature of the whole
body which takes place at this time. In the interior of this
cephalic mass there is now formed a large cavity (Fig. 240, d), by
the melting down and liquefaction of a portion of its substance.
This cavity is the pharynx. It corresponds by its anterior extremity to the future situation of the mouth; and by its posterior
portion to the upper end of the intestinal canal, the future situation
of the stomach. It is still, however, closed on all sides, and does
not as yet communicate either with the exterior or with the cavity
of the stomach. There is, accordingly, at this time, no thorax
whatever; but the stomach lies at the upper extremity of the abdomen, immediately beneath the lower extremity of the pharynx, from
which it is separated by a wall of intervening tissue.
Subsequently, a perforation takes place between the adjacent
extremities of the pharynx and stomach, by a short narrow tube,
the situation of which is marked by the dotted lines x, in Fig. 240.
This tube afterward lengthens by the rapid growth of that portion
of the body in which it is contained, and. becomes the oesophagus.
Neither the pharynx nor cesophagus, therefore, are, properly speaking, parts of the intestinal canal, formed from the internal layer of
the blastodermic membrane; but are, on the contrary, formations
of the external layer, from which the entire cephalic mass is produced. The lining membrane of the pharynx and oesophagus is to
be regarded, also, for the same reason, as rather a continuation of
the integument than of the intestinal mucous membrane; and even
in the adult, the thick, whitish, and opaque pavement epithelium
of the oesophagus may be seen to terminate abruptly, by a welldefined line of demarcation, at the cardiac orifice of the stomach;
beyond which, throughout the remainder of the alimentary canal,
the epithelium is of the columnar variety, and easily distinguishable by its soft, ruddy, and transparent appearance.
As the oesophagus lengthens, the lungs are developed on each
side of it by a protrusion from the pharynx which extends and
becomes repeatedly subdivided, forming the bronchial tubes and
their ramifications. At first, the lungs project into the upper
part of the abdominal cavity; for there is still no distinction between the chest and abdomen. Afterward, a horizontal partition
begins to form on each side, at the level of the base of the lungs,
which gradually closes together at a central point, so as to form
the diaphragm, and finally to shut off altogether the cavity of
the chest from that of the abdomen. Before the closure of the




AND ITS APPENDAGES.                      635
diaphragm, thus formed, is complete, a circular opening exists on
each side the median line, by which the peritoneal and pleural
cavities communicate with each other. In some instances the development of the diaphragm is arrested at this point, either on one
side or the other, and the opening accordingly remains permanent.
The abdominal organs then partially protrude into the cavity of
the chest on that side, forming congenital diaphragmatic hernia.
The lung on the affected side also usually remains in a state of
imperfect development.  Diaphragmatic hernia of this character is
more frequently found upon the left side than upon the right. It
may sometimes continue until adult life without causing any serious inconvenience.
The heart is formed, at a very early period, directly in front of
the situation of the cesophagus. Its size soon becomes very large
in proportion to the rest of the body; so that it protrudes beyond
the level of the thoracic parietes, covered only by the pericardium.
Subsequently, the walls of the thorax, becoming more rapidly
developed, grow over it and inclose it. In certain instances, however, they fail to do so, and the heart then remains partially or
completely uncovered, in front of the chest, presenting the condition
known as ectopia cordis. This malformation is necessarily fatal.
Development of the Face.-While the lower extremity of the
pharynx communicates with the cavity of the stomach, as above
described, its upper extremity also becomes perforated in a similar
manner, and establishes a communication with the exterior. This
perforation is at first wide and gaping.  It afterward becomes
divided into the mouth and nasal passages; and the different parts
of the face are formed round it in the folFig. 241.
lowing manner:From the sides of the cephalic mass five
buds or processes shoot out, and grow
toward each other, so as to approach the
centre of the oral orifice above mentioned.
(Fig. 241.) One of them grows directly
downward from the frontal region (1), and
is called the frontal or intermaxillary process, because it afterward contains in its
EA ) OF H U  A  E MBY IO,
lower extremity the intermaxillary bones,  at about the twentieth day. After
in which the incisor teeth of the upper  Longet; from a specimen in the
in which. the incisor teeth of the upper  collection of M. Coste.-. Frontal
jaw are inserted.  The next process (2)  orinterin-xillayv prices.s. 2. Process of superior  maxilla.  3. Prooriginates from the side of the opening,  cess of inferior maxilla.




636   DEVELOPMENT OF THE ALIMENTARY CANAL
and, advancing toward the median line, forms, with its fellow of the
opposite side, the superior maxilla. The processes of the remaining
pair (3) also grow from the side, and form, by their subsequent
union upon the median line, the inferior maxilla. The inferior
maxillary bone is finally consolidated, in man, into a single piece,
but remains permanently divided, in the lower animals, by a suture
upon the median line.
As the frontal process grows from above downward, it becomes
double at its lower extremity, and at
Fig. 242.         the same time two offshoots show
themselves upon its sides, which curl
round and inclose two circular orifices, the opening of the anterior
au inares; the offshoots themselves becoming the alge nasi. (Fig. 242.) The
mouth at this period is very widely
open, owing to the imperfect development of the upper and lower jaw, and
the incomplete formation of the lips
H E A D O F H Ut A N E B R Y O atabout and cheeks.
the sixth week. From a specimen in the    The processes of the superior maxilla continue their growth, but less
rapidly than those of the inferior; so that the two sides of the
lower jaw are already consolidated with each other, while those of
the upper jaw are still separate.
As the processes of the superior maxilla continue to enlarge, they
also tend to unite with each other on the median line, but are prevented from doing so by the intermaxillary processes which grow
down between them.  They then unite with the intermaxillary
processes, which have at the same time'Fig. 24_3.       united with each other, and the upper
jaw and lip are thus completed. (Fig.
243.)  The external edge of the ala
nasi also adheres to the superior maxillary process and unites with it, leaving
only a curved crease or furrow, as a
sort of cicatrix, to mark the line of
union between them.
Sometimes the superior maxillary
and the intermaxillary processes fail
HEAD OF HUMAN EhBiRYO, about to unite with each other; and we then
the end of the second month.-Fromr a
specimen in the authlor's possession.    have the malformation known as heare



AND ITS APPENDAGES.                      637
lip. The fissure of hare-lip, consequently, is never exactly in the
median line, but a little to one side of it, on the external edge of
the intermaxillary process. Occasionally, the same deficiency exists
on both sides, producing "double hare-lip;" in which case, if the
fissures extend through the bony structures, the central piece of the
superior maxilla, which is detached from the remainder, contains
the four upper incisor teeth, and corresponds with the intermaxillary bone of the lower animals.
The eyes at an early period are situated upon the sides of the
head, so that they cannot be seen in an anterior view. (Fig. 241.)
As development proceeds, they come to be situated farther forward
(Fig. 242), their axes being divergent and directed obliquely forward and outward.  At a later period still they are placed on the
anterior plane of the face (Fig. 243), and have their axes nearly
parallel and looking directly forward. This change in the situation of the eyes is effected by the more rapid growth of the posterior and lateral parts of the head, which enlarge in such a manner
as to alter the relative position of the parts seated in front of them.
The palate is formed by a septum between the mouth and nares,
which arises on each side as a horizontal plate or offshoot from the
superior maxilla.  These two plates afterward unite with each
other upon the median line, forming a complete partition between
the oral and nasal cavities. The right and left nasal passages are
also separated from each other by a vertical plate (vomer), which
grows from  above downward and fuses with the palatal plates below. Fissure of the palate is caused by a deficiency, more or less
complete, of one of the horizontal maxillary plates.  It is accordingly situated a little to one side of the median line, and is fre.
quently associated with hare-lip and fissure of the upper jaw. The
fissures of the palate and of the lip are very often continuous with
each other.
The anterior and posterior pillars of the fauces are incomplete
vertical partitions, which grow from  the sides of the oral cavity,
and tend to separate, by a slight constriction, the cavity of the
mouth from that of the pharynx.
When all the above changes are accomplished, the pharynx,
oesophagus, mouth, nares, and fauces, with their various protections
and divisions, have been successively formed; and the development
of the upper part of the alimentary canal is then complete.




638           DEVELOPMENT OF THE KIDNEYS.
CHAPTER XVI.
DEVELOPMENT OF THE KIDNEYS, WOLFFIAN
BODIES, AND INTERNAL ORGANS OF GENERATION.
THE first trace of a urinary apparatus in. the embryo, consists of
two long, fusiform bodies, which make their appearance in the abdomen at a very early period, situated on each side the spinal
column. These are known by the name of the Wolfan bodies.
They are fully formed, in the human subject, toward the end of the
first month (Coste), at which time they are the largest organs in the
cavity of the abdomen, extending from just below the heart, nearly
to the posterior extremity of the body. In the feetal pig, when a
little over half an inch in length (Fig. 244), the Wolffian bodies are
rounded and kidney-shaped, and occupy a very large part of the
abdominal cavity. Their importance may be estimated from the
fact that their weight at this time is equal to
Fig. 244.      a little over g' of that of the entire body-a
proportion which is seven or eight times as
large as that of the kidneys, in the adult
condition. There are, indeed, at this period,
only three organs perceptible in the abdomen, viz., the liver, which has begun to be
formed at the upper part of the abdominal
cavity; the intestine, which is already someF(ETAL PL,  of aninch what convoluted, and occupies its central
long; from a specimen in the portion; and the Wolffian bodies, which proauthor's possession. 1. Heart.     
2. Anterior extremity. 3. Pos- ject on each side the spinal column.
terior extremity. 4. Wolffian    The   f  di
body. The abdominal walls   The Wolffian bodies, in their intimate
have been cut away, in order structure, closely resemble the adult kidney.
to sh w the position of the
Wolffian bodies.     They consist of secreting tubules, lined with
epithelium, which run from the outer toward
the inner edge of the organ, terminating at their free extremities
in small rounded dilatations. Into each of these dilated extremities




WOLFFIAN BODIES.                     639
is received a globular coil of capillary bloodvessels, or glomerulus,
similar to that of the adult kidney. The tubules of the Wolffian
body all empty into a common excretory duct, which leaves the
organ at its lower extremity, and communicates afterward with
the lower part of the intestinal canal, just at the point where the
diverticulum of the allantois is given off, and where the urinary
bladder is afterward to be situated.  The principal, if not the
only distinction, between the minute structure of the Wolffian
bodies and that of the true kidneys, consists in the size of the
tubules and of their glomeruli, these elements being considerably
larger in the Wolffian.body than in the kidney.  In the fcetal
pig, for example, when about an inch and a half in length, the
diameter of the tubules of the Wolffian body is,-L of an inch,
while in the kidney of the same foetus, the diameter of the tubules
is only qg of an inch. The glomeruli in the Wolffian bodies
measure - of an inch in diameter, while those of the kidney measure only T8o of an inch. The Wolffian bodies are therefore urinary
organs, so far as regards their anatomical structure, and are sometimes known, accordingly, by the name of the "false kidneys."
There is little doubt that they perform, at this early period, a function analogous to that of the kidneys, and separate from the blood
of the embryo an excrementitious fluid which is discharged by the
ducts of the organ into the cavity of the allantois.
Subsequently, the Wolffian bodies increase for a time in size,
though not so rapidly as the rest of the body; and consequently
their relative magnitude diminishes. Still later, they begin to
suffer an absolute diminution or atrophy, and become gradually
less and less perceptible. In the human subject, they are hardly
to be detected after the end of the second month (Longet), and in
the quadrupeds also they completely disappear long before birth.
They are consequently foetal organs, destined to play an important
part during a certain stage of development, but to become afterward atrophied and absorbed, as the physiological condition of the
fcetus alters. During the period, however, of their retrogression
and atrophy, other organs appear in their neighborhood, which
become afterward permanently developed. These are, first, the
kidneys, and secondly, the internal organs of generation.
The kidneys are formed just behind the Wolffian bodies, and are
at first entirely concealed by them in a front view, the kidneys
being at this time not more than a fourth or a fifth part the size of




640           DEVELOPMENT OF THE KIDNEYS.
the Wolffian bodies. (Fig. 245.) As the kidneys, however, subsequently enlarge, while the Wolffian bodies diminish, the proportions existing between the two organs are
Fig. 245.        reversed; and the Wolffian bodies at last
come to be mere small rounded or ovoid
masses, situated on the anterior surface
of the kidneys. (Figs. 246 and 247.)  The
kidneys, during this period, grow  more
rapidly in an upward than in a downward
direction, so that the Wolffian bodies
come to be situated near their inferior... d i      extremity, and seem  to have performed
a sliding movement from above downF(ETA  PIo, one and a half ward, over their anterior surface.  This
inhes long From a specimen iapparent sliding movement, or descent
the author's possession.-1. Wolffian 
body. 2. Kidney.          of the Wolffian bodies, is owing entirely
to the rapid growth of the kidneys in an
upward direction, as we have already explained.
The kidneys, during the succeeding periods of fcetal life, become
in their turn very largely developed in proportion to the rest of the
organs; attaining a size, in the fxetal pig, equal to i  (in weight)
of that of the entire body. This proportion, however, diminishes
again very considerably before birth, owing to the increased development of other parts. In the human foetus at birth, the weight
of the two kidneys taken together is T-    that of the entire body.
Internal Organs of Generation.-About the same time that the kidneys are formed behind the Wolffian bo.
Fig. 246.
dies, two oval-shaped organs make their
appearance in front, on the inner side of
the Wolffian bodies and between them
and the Spinal column. These bodies are
the internal organs of generation; viz.,
the testicles in the male, and the ovaries
in the female.  At first they occupy
precisely the same situation and present
precisely the same appearance, whether
INTERN AL ORGANS OF GENE- the fcetus is afterward to belong to the
RATION, &C.; in a fcetal pig three
inches long. From a specimen in the male or the female sex. (Fig. 246.)
author's possession — 1, 1. Kidneys.  
2, 2. Wolffian bodies. 3,3. Internal    A  short distance above the internal
organs of generation; testicles or ova- organs of generation there commences,
ries. 4. Urinary bladder, turned over
in front. 5. Intestine,    on each side, a narrow  tube or duct,




MIALE ORGANS OF GENERATION.                   641
which runs from above downward along the anterior border of the
Wolffian body, immediately in front of and parallel with the excretory duct of this organ. The two tubes, right and left, then approach
each other below; and, joining upon the median line, empty, together
with the ducts of the Wolffian bodies, into the base of the allantois,
or what will afterward be the base of the urinary bladder.  These
tubes serve as the excretory ducts of the internal organs of generation; and will afterward become the vasa deferentia in the male, and
the Fallopian tubes in the female. According to Coste, the vasa deferentia at an early period are disconnected with the testicles; and
originate, like the Fallopian tubes, by free extremities, presenting
each an open orifice. It is only afterward, according to the same
author, that the vasa deferentia become adherent to the testicles, and
a communication is established between them and the tubuli seminiferi. In the female, the Fallopian tubes remain permanently
disconnected with the ovaries, except by the edge of the fimbriated
extremity; which in many of the lower animals becomes closely
adherent to the ovary, and envelopes it more or less completely.
Male Organs of Generation; Descent of the Testicles. —In the male
foetus there now commences a movement of translation, or change
of place, in the internal organs of generation, which is known as
the "descent of the testicles."  In consequence of this movement,
the above organs, which are at first placed near the middle of the
abdomen, and directly in front of the kidneys, come at last to be
situated in the scrotum, altogether outside and below the abdominal
cavity. They also become inclosed in a distinct serous sac of their
own, the tunica vaginalis testis. This apparent movement of the
testicles is accomplished in the same manner as that of the Wolf
fian bodies, above mentioned, viz., by a disproportionate growth of
the middle and upper portions of the abdomen and of the organs
situated above the testicles, so that the relative position of these
organs becomes altered. The descent of the testicles is accompanied
by certain other alterations in the organs themselves and their
appendages, which take place in the following manner.
By the upward enlargement of the kidneys, both the Wolffian
bodies and the testicles are soon found to be situated near the
lower extremity of these organs. (Fig. 247.)  At the same time, a
slender rounded cord (not represented in the figure) passes from
the lower extremity of each testicle in an outward and downward
direction, crossing the corresponding vas deferens a short distance
above its union with its fellow of the opposite side. Below this
41




642           DEVELOPMENT OF THE KIDNEYS.
point, the cord spoken of continues to run obliquely outward and
downward; and, passing through the abdominal walls at the situation of the inguinal canal, is inserted into the subcutaneous tissues
near the symphysis pubis. The
Fig. 247.
lower part of this cord becomes
the gubernaculum testis; and muscular fibres are soon developed in
its substance which may be easily
_Ic.,        detected, even in the human foetus,
during the latter half of gestation.
At the period of birth, however,
or soon afterward, these muscular
covete i tfibres disappear and can no longer
be recognized.
All that portion of the excreINAERNAL ORGANS OF GENERATION, tory tube of the testicle which is
&c., in a fcetal pig nearly four inches long.
From a specimen in the author's possession.- situated outside the crossing of the
1,1. Kidneys. 2, 2 Wolfflan bodies. 3, 3  gubernaculum, is destined to beTesticles. 4. Urinary bladder. 5. Intestine.
come afterward  convoluted, and
converted into the epididymis.  That portion which is situated inside the same point remains comparatively straight, but becomes
considerably elongated, and is finally known as the vas deferens.
As the testicles descend still farther in the abdomen, they continue to grow, while the Wolffian bodies, on the contrary, diminish
rapidly in size, until the latter become much smaller than the testicles; and at last, when the testicles have arrived at the internal
inguinal ring, the Wolffian bodies have altogether disappeared, or
at least have become so much altered that their characters are no
longer recognizable.  In the human foetus, the testicles arrive at
the internal inguinal ring, about the termination of the sixth month
(Wilson).
During the succeeding month, a protrusion of the peritoneum
takes place through the inguinal canal, in advance of the testicle;
while the last named organ still continues its descent. As it then
passes downward into the scrotum, certain muscular fibres are given
off from  the lower border of the internal oblique muscle of the
abdomen, growing downward with the testicle, in such a manner as
to form a series of loops upon it, and upon the elongating spermatic
cord. These loops constitute afterward the cremaster muscle.
At last, the testicle descends fairly to the bottom of the scrotum,
the gubernaculum constantly shortening, and the vas deferens




MALE ORGANS OF GENERATION. -                   643
elongating as it proceeds. The convoluted portion of the efferent
duct, viz., the epididymis, then remains closely attached to the body
of the testicle; while the vas deferens passes upward, in a reverse
direction, enters the abdomen through the inguinal canal, again
bends downward, and joins its fellow of the opposite side; after
which they both open into the prostatic portion of the urethra by
distinct orifices, situated on each side the median line. At the
same time, two diverticula arise from the median portion of the
vasa deferentia, and, elongating in a backward direction, underneath
the base of the bladder, become developed into two compound
sacculated reservoirs-the vesiculce seminales.
The left testicle is a little later in its descent than the right, but
it afterward passes farther into the scrotum, and, in the adult condition, usually hangs a little lower than its fellow of the opposite side.
After the testicle has fairly passed into the scrotum, the serous
pouch, which preceded its descent, remains for a time in communication with the peritoneal cavity. In many of the lower animals,
as, for example, the rabbit, this condition is permanent; and the
testicle, even in the adult animal, may be alternately drawn downward into the scrotum, or retracted into the abdomen, by the action
of the gubernaculum and the cremaster muscle. But in the human
foetus, the two opposite surfaces of the peritoneal pouch, covering
the testicle, approach each other at the inguinal canal, forming at
that point a constriction or neck, which partly shuts off the testicle
from  the cavity of the abdomen. By a
continuation of this process, the serous          Fig. 248.
surfaces come actually in contact with
each other, and, adhering together at
this situation (Fig. 248, 4), form  a kind
of cicatrix, or umbilicus, by the complete 
closure and consolidation of which the
cavity of the tunica vaginalis (2) is finally
shut off altogether from the general cavity
of the peritoneum (3). The tunica vaginalis testis is, therefore, originally a part
of the peritoneum, from which it is sub-   Formation of TUNICA VAnt   a eG be. B    GINALIS TESTIS -1. Testicle,
sequently  separated by the process just nearly at the bottom of the srodescribed.                 -tumrn. 2. Cavity oftunica vaginalis.
3. Cavity of peritoneum. 4. ObliterThe separation of the tunica vaginalis  ated neck of peritoneal sac.
from the peritoneum is usually completed
in the human subject before birth. But sometimes it fails to take




644       DEVELOPMENT OF THE KIDNEYS, ETC.
place at the proper time, and the intestine is then apt to protrude
into the scrotum, in front of the spermatic cord, giving rise, in this
way, to a congenital inguinal hernia. (Fig. 249.) The parts implicated, however, in this malformation, have
Fig. 249.       still, as in the case of congenital umbilical hernia, a tendency to unite with each
other and obliterate the unnatural openings; and if the intestine be retained by
pressure in the cavity of the abdomen,
cicatrization usually takes place at the
inguinal canal, and a cure is effected.
The descent of the testicle, above described, is not accomplished by the forcible traction of the muscular fibres of the
CONGENITAL INGOINALHER-  gubernaculum, as has been described by
NIA.-.  Testicle.  2, 2, 2.  Intestine.                   certain writers, but by a simple process
of growth taking place in different parts,
in diffTrent directions, at successive periods of fretal life. The
gubernaculum, accordingly, has no proper function as a muscular
organ, in the human subject, but is merely the anatomical vestige,
or analogue, of a corresponding muscle in certain of the lower
animals, where it has really an important function to perform. For
in them, as we have already mentioned, both the gubernaculum
and the cremaster remain fully developed in the adult condition,
and are then employed to elevate and depress the testicle, by the
alternate contraction of their muscular fibres.
Female Organs of Generation.-At an early period, as we have
mentioned above, the ovaries have the same external appearance,
and occupy the same position in the abdomen, as the testicles in the
opposite sex. The descent of the ovaries also takes place, to a great
extent, in the same manner with the descent of the testicles. When,
in the early part of this descent, they have reached the level of the
lower edge of the kidneys, a cord, analogous to the gubernaculum,
may be seen proceeding from their lower extremity, crossing the
efferent duct on each side, and passing downward, to be attached
to the subcutaneous tissues at the situation of the inguinal ring.
That part of the duct situated outside the crossing of this cord,
becomes afterward convoluted, and is converted into the Fallopian
tube; while that part which is inside the same point, becomes converted into the uterus. The upper portion of the cord itself becomes




FEMALE ORGANS OF GENERATION.                 645
the ligament of the ovary; its lower portion, the round ligament of
the uterus.
As the ovaries continue their descent, they pass below and behind the Fallopian tubes, which necessarily perform at the same
time a movement of rotation, from  before backward and from
above downward; the whole, together with the ligaments of the
ovaries and the round ligaments, being enveloped in double folds
of peritoneum, which enlarge with the growth of the parts themselves, and constitute finally the broad ligaments of the uterus.
It will be seen from what has been said above, that the situation
occupied by the Wolffian bodies in the female is always the space
between the ovaries and the Fallopian tubes; for the Wolffian
bodies accompany the ovaries in their descent, just as, in the male,
they accompany the testicles. As these bodies now become gradually atrophied, their glandular structure disappears altogether;
but their bloodvessels, in many instances, remain as a convoluted
vascular plexus, occupying the situation above mentioned. The
Wolffian bodies may therefore be said, in these instances, to undergo a kind of vascular degeneration. This peculiar degeneration
is quite evident in the Wolffian bodies of the foetal pig, some time
before the organs have entirely lost their original form. In the
cow, a collection of convoluted bloodvessels may be seen, even in
the adult condition, near the edge of the ovary and between the
two folds of peritoneum forming the broad ligament. These are
undoubtedly vestiges of the Wolffian bodies, which have undergone the vascular degeneration above described.
While the above changes are taking place in the adjacent organs,
the two lateral halves of the uterus fuse with each other more and
more upon the median line, and become covered with an excessively developed layer of muscular fibres. In the lower animals,
the uterus remains divided at its upper portion, running out into
two long conical tubes or cornua (Fig. 182), presenting the form
known as the uterus bicornis. In the human subject, however, the
fusion of the two lateral halves of the organ is nearly complete;
so that the uterus presents externally a rounded, but somewhat
flattened and triangular figure (Fig. 183), with the ligaments of the
ovary and the round ligaments passing off from its superior angles.
But, internally, the cavity of the organ still presents a strongly
marked triangular form, the vestige of its original division.
Occasionally the human uterus, even in the adult condition, re



646        DEVELOPMENT OF THE KIDNEYS, ETC.
mains divided into two lateral portions by a vertical septum, which
runs from the middle of its fundus downward toward the os internum. This septum  may even be accompanied by a partial
external division of the organ, corresponding with it in direction,
and producing the malformation known as "uterus bicornis," or
" double uterus."
The os internum and os externum are produced by partial constrictions of the original generative passage; and the anatomical
distinctions between the body of the uterus, the cervix and the
vagina, are produced by the different development of the mucous
membrane and muscular tunic in its corresponding  portions.
During fcetal life, however, the neck of the uterus grows much
faster than its body; so that, at the period of birth, the entire
organ is very far from presenting the form which it exhibits in the
adult condition. In the human foetus at term, the cervix uteri
constitutes nearly two-thirds of the entire length of the organ;
while the body forms but little over one third. The cervix, at
this time, is also much larger in diameter than the body; so that
the whole organ presents a tapering form from  below upward.
The arbor vitas uterina of the cervix is at birth very fully developed, and the mucous membrane of the body is also thrown
into three or four folds which radiate upward from the os internum.
The cavity of the cervix is filled with a transparent semi-solid
mucus.
The position of the uterus at birth is also different from that
which it assumes in adult life; nearly the entire length of the organ
being above the level of the symphysis pubis, and its inferior
extremity passing below that point only by about a quarter of an
inch. It is also slightly anteflexed at the junction of the body and
cervix. After birth, the uterus, together;with its appendages, continues to descend; until, at the period of puberty, its fundus is
situated just below the level of the symphysis pubis.
The ovaries at birth are narrow and elongated in form. They
contain at this time an abundance of eggs; each inclosed in a
Graafian follicle, and averaging     of an inch in diameter. The
vitellus, however, is imperfectly formed in most of them, and in
some is hardly to be distinguished. The Graafian follicle at this
period envelopes each egg closely, there being nothing between its
internal surface and the exterior of the egg, excepting the thin
layer of cells forming the "membrana granulosa."  Inside this




FEMALE ORGANS OF GENERATION.                    647
layer is to be seen the germinative vesicle, with the germinative
spot, surrounded  by a faintly granular vitellus, more or less
abundant in different parts.  Some of the Graafian follicles containing eggs are as large as a-, of an inch; others as small as TW^.
In the very smallest, the cells of the membrana granulosa appear
to fill entirely the cavity of the follicle, and no vitellus or germinative vesicle is to be seen.




648  DEVELOPMENT OF THE CIRCULATORY APPARATUS.
CHAPTER XVII.
DEVELOPMENT OF THE CIRCULATORY APPARATUS.
THERE are three distinct forms or phases of development assumed
by the circulatory system during different periods of life. These
different forms of the circulation are intimately connected with the
manner in which nutrition and respiration, or the renovation of the
blood, are accomplished at different epochs; and they follow each
other in the progress of development, as different organs are employed in turn to accomplish the above functions. The first form
is that of the vitelline circulation, which exists at a period when the
vitellus, or the umbilical vesicle, is the sole source of nutrition for
the foetus.  The second is the placental circulation, which lasts
through the greater part of foetal life, and is characterized by the
existence of the placenta; and the third is the complete or adult
circulation, in which the renovation and nutrition of the blood are
provided for by the lungs and the intestinal canal.
First, or Vitelline Circulation.-It has already been shown, in a
previous chapter, that when the body of the embryo has begun to
be formed in the centre of the blastodermic membrane, a number
of bloodvessels shoot out from  its sides, and ramify over the
remainder of the vitelline sac, forming, by their inosculation, an
abundant vascular plexus. The area occupied by this plexus in the
blastodermic membrane around the foetus is, as we have seen, the
"area vasculosa."  In the egg of the fowl (Fig. 250), the plexus is
limited, on its external border, by a terminal vein or sinus-the
"sinus terminalis"; and the blood of the embryo, after circulating
through the capillaries of the plexus, returns by several venous
branches, the two largest of which enter the body near its anterior
and posterior extremities. The area vasculosa is, accordingly, a
vascular appendage to the circulatory apparatus of the embryo,
spread out over the surface of the vitellus for the purpose of absorbing from it the nutritious material requisite for the growth of the
newly-formed tissues. In the egg of the fish (Fig. 251), the princi



VITELLINE  CIRCULATION.                       649
pal vein is seen passing up in front underneath the head; while the
arteries emerge all along the lateral edges of the body.  The entire
vitellus, in this way, becomes covered with an abundant vascular
Fig. 250.
Eoo O F FOWL il process of development, showing area vasculosa, with vitelline circulation,
terminal sinus, &c.
network, connected with the internal circulation of the foetus by
arteries and veins.
Very soon, as the embryo and the entire egg increase in size,
there are two arteries and two veins which become
larger than the others, and which subsequently            Fig. 251.
(lo the whole work of conveying the blood of
the foetus to and from the area vasculosa.  These 
two arteries emerge from  the lateral edges of
the foetus, on the right and left sides; while the
two veins re-enter at about the same point, and
nearly parallel with them. These four vessels are
uEo OF FIsH (TJarthen termed  the omphalo-mesenteic arteries and  rabacca),showing vitelveins.                                               line circulation.
The arrangement of the circulatory apparatus
in the interior of the body of the foetus, at this time, is as follows:
The heart is situated on the median line, just beneath the head and
in front of the oesophagus. It receives at its lower extremity the
trunks of the two omphalo-mesenteric veins, and at its upper
extremity divides into two vessels, which, arching over backward,
attain the anterior surface of the vertebral column, and then run
from  above downward along the spine, quite to the posterior
extremity of the foetus.  These arteries are called the vertebral
arteries, on account of their course and situation, running parallel




650  DEVELOPMENT OF THE CIRCULATORY APPARATUS.
with the vertebral column. They give off, throughout their course,
many small lateral branches, which supply the body of the foetus,
and also two larger branches-the omphalo-mesenteric arterieswhich pass out, as above described, into the area vasculosa. The
two vertebral arteries remain separate in the upper part of the body,
but soon fuse with each other a little below the level of the heart;
so that, below this point, there remains afterward but one large
artery, the abdominal aorta, running from  above downward along
the median line, giving off the omphalo-mesenteric arteries to the
area vasculosa, and supplying smaller branches to the body, the
walls of the intestine, and the other organs of the foetus.
The above description shows the origin and formation of the first
or vitelline circulation. A change, however, now begins to take
place, by which the vitellus is superseded, as an organ of nutrition,
by the placenta, which takes its place; and the second or placental
circulation becomes established in the following manner:Second Circulation.-After the umbilical vesicle has been formed
by the process already described, a part of the vitellus remains
included in it, while the rest is retained in the abdomen and inclosed
in the intestinal canal. As these
Fig. 252.            two organs (umbilical vesicle and
intestine) are originally parts of
the same vitelline sac, they remain
supplied by the same vascular
system, viz: the omphalo-mesenteric vessels. Those which remain
within the abdomen of the faetus
supply the mesentery and intes*   ( it; & Dtine; but the larger trunks pass
outward, and ramify upon the
walls of the umbilical vesicle.
(Fig. 252.)  At first, there are,
as we have mentioned above,
DIiagrall of YOUNG EMBRYO AND ITS
VESSELS, showing circulation of umbilical two omphalo-mesenteric arteries
vesicle, and also that of allantois, beginning to emerging from the body, and two
be formed.
omphalo-mesenteric veins returning to it; but soon afterward, the two arteries are replaced by a
common trunk, while a similar change takes place in the two veins.
Subsequently, therefore, there remains but a single artery and a
single vein, connecting the internal and external portions of the
vitelline circulation.




PLACENTAL  CIRCULATION.                          651
The vessels belonging to this system are therefore called the
omphalo-mesenteric vessels, because a part of them (omphalic vessels) pass outward, by the umbilicus, or "omphalos," to the umbilical vesicle, while the remainder (mesenteric vessels) ramify upon
the mesentery and the intestine.
At first, the circulation of the umbilical vesicle is more important than that of the intestine; and the omphalic artery and vein
appear accordingly as large trunks, of which the mesenteric vessels are simply small branches. (Fig. 252.) Afterward, however,
the intestine rapidly enlarges, while the umbilical vesicle diminishes, and the proportions existing between the two sets of vessels
are therefore reversed. (Fig. 258.) The mesenteric vessels then
Fig. 253.
Diagram of EMBRYO AND ITS VESSELS; showing the second circulation. The pharynx,
oesophagus, and intestinal canal, have become further developed, and the mesenteric arteries have
enlarged, while the umbilical vesicle and its vascular branches are very much reduced in size. The
large umbilical arteries are seen passing out to the placenta.
come to be the principal trunks, while the omphalic vessels are
simply minute branches, running out along the slender cord of the
umbilical vesicle, and ramifying in a few scanty twigs upon its
surface.
In the mean time, the allantois is formed by a protrusion from
the lower extremity of the intestine, which, carrying with it two




652  DEVELOPMENT OF THE CIRCULATORY APPARATUS.
arteries and two veins, passes out by the anterior opening of the
body, and comes in contact with the external membrane of the
egg. The arteries of the allantois, which are termed the umbilical
arteries, are supplied by branches of the abdominal aorta; the umbilical veins, on the other hand, join the mesenteric veins, and
empty with them into the venous extremity of the heart. As the
umbilical vesicle diminishes, the allantois enlarges; and the latter
soon becomes converted, in the human subject, into a vascular
chorion, a part of which is devoted to the formation of the placenta.
(Fig. 253.) As the placenta soon becomes the only source of nutrition for the foetus, its vessels are at the same time very much
increased in size, and preponderate over all the other parts of the
circulatory system. During the early periods of the formation of
the placenta, there are, as we have stated above, two umbilical
arteries and two umbilical veins. But subsequently one of the
veins disappears, and the whole of the blood is returned to the body
of the foetus by the other, which becomes enlarged in proportion.
For a long time previous to birth, therefore, there are in the umbilical cord two umbilical arteries, and but a single umbilical vein.
Such is the second, or placental circulation. It is exchanged, at
the period of birth, for the third or adult circulation, in which the
blood which had previously circulated through the placenta, is
diverted to the lungs and the intestine. These are the organs
upon which the whole system  afterward depends for the nourishment and renovation of the blood.
During the occurrence of the above changes, certain other alterations take place in the arterial and venous systems, which will now
require to be described by themselves.
Development of the Arterial System.-At anearly period of development, as we have shown above, the principal arteries pass off
from the anterior extremity of the heart in two arches, which curve
backward on each side, from  the front of the body toward the
vertebral column, after which they again become longitudinal in
direction, and receive the name of "vertebral arteries." Very soon
these arches divide successively into two, three, four, and five
secondary arches, placed one above the other, along the sides of
the neck. (Fig. 254.)  These are termed the cervical arches. In the
fish, these cervical arches remain permanent, and give off from their
convex borders the branchial arteries, in the form of vascular tufts,
to the gills on each side of the neck; but in the human subject and
the quadrupeds. the branchial tufts are never developed, and the




DEVELOPMENT OF THE ARTERIAL SYSTEM.   653
cervical arches, as well as the trunks with  which  they  are connected, become modified  by  the progress of development in the
following manner:Fig. 254.                                   Fig. 255.
2                     — 2 
Early condition of ARTERIAL SYSTEM:       Adult condition of ARTERIAL S'showing the heart (1), with its two ascend-  TEM.-1, 1. Carotids. 2, 2. Vertebrals.
ing arterial trunks, giving off on each side  3, 3. Right and left sunbclavians. 4, 4.
five cervical arches, which terminate in the  Right and left superior intercostals. 5.
vertebral arteries (2, 2). The vertebral arte-  Left aortic arch, which remains permaries unite below the heart to form  the   nent. 6. Right aortic arch, which disaorta (3).                                appears.
The two ascending  arterial trunks on  the anterior part of the
neck, from which the cervical arches are given off' become converted  into the carotids. (Fig. 255, i, i.)  The fifth, or uppermost
cervical arch, remains at the base of the brain as the inosculation,
through the circle of Willis, between the internal carotids and the
basilar artery, which  is produced  by the union of the two vertebrals.  The next, or fourth cervical arch, may be recognized in an
inosculation which is said to be very constant between the superior
thyroid arteries, branches of the carotids, and the inferior thyroids,
which come from  the subclavians at nearly the  same point from
which the vertebrals are given off. The next, or third cervical arch
remains on each side, as the subclavian  artery (3, s).  This vessel,
though at first a mere branch of communication between the carotid and the vertebral, has now increased in size to such an extent,
that it has become the principal trunk, from  which the vertebral




654  DEVELOPMENT OF THE CIRCULATORY APPARATUS.
itself is given off as a small branch. Immediately below this point
of intersection, also, the vertebral artery diminishes very much in
its relative size, loses its connection with the abdominal aorta, and
supplies only the first two intercostal spaces, under the name of the
superior intercostal artery (4, 4). The second cervical arch becomes
altered in a very different manner on the two opposite sides. On
the left side, it becomes enormously enlarged, so as to give off, as
secondary branches, all the other arterial trunks which have been
described, and is converted in this manner into the arch of the
aorta (5). On the right side, however, the corresponding arch (6),
becomes smaller and smaller, and at last altogether disappears; so
that, finally, we have only a single aortic, arch, projecting to the
left of the median line, and continuous with the thoracic and abdominal aorta.
The first cervical arch remains during foetal life upon the right
side, as the "ductus arteriosus," presently to be described. In the
adult condition, however, it has disappeared equally upon the right
and left sides. In this way the permanent condition of the arterial
circulation is gradually established in the upper part of the body.
Corresponding changes take place, however, during the same
time, in the lower part of the body. Here the abdominal aorta
runs undivided, upon the median line, quite to the end of the
spinal column; giving off on each side successive lateral branches,
which supply the intestine and the parietes of the body. When
the allantois begins to be developed, two of these lateral branches
accompany it, and become consequently the umbilical arteries.
These two vessels increase so rapidly in size, that they soon appear
as divisions of the aortic trunk; while the original continuation of
this trunk, running to the end of the spinal column, appears only
as a small branch given off at the point of bifurcation. When the
lower limbs begin to be developed, they are supplied by two small
branches, given off from the umbilical arteries near their origin.
Up to this time the pelvis and posterior extremities are but
slightly developed.  Subsequently, however, they grow  more
rapidly, in proportion to the rest of the body, and the arteries
which supply them  increase in a corresponding manner. That
portion of the umbilical arteries, lying between the bifurcation of
the aorta and the origin of the branches going to the lower extremities, becomes the common iliacs, which in their turn afterward
divide into the umbilical arteries proper, and the femorals. Subsequently, by the continued growth of the pelvis and lower




DEVELOPMENT OF THE NERVOUS SYSTEM.                  655
extremities, the relative size of their vessels is still further increased; and at last the arterial system in this part of the body
assumes the arrangement which belongs to the latter periods of
gestation. The aorta divides, as before, into the two common iliacs.
These also divide into the external iliacs, supplying the lower extremities, and the internal iliacs, supplying the pelvis; and this
division is so placed that the umbilical or hypogastric arteries arise
from the internal iliacs, of which they now appear to be secondary
branches.
After the birth of the fcetus and the separation of the placenta,
the hypogastric arteries become partially atrophied, and are converted, in the adult condition, into solid, rounded cords, running
upward toward the umbilicus.  Their lower portion, however,
remains pervious, and gives off arteries supplying the urinary
bladder.  The obliterated hypogastric arteries, therefore, the remnants of the original umbilical or allantoic arteries, run upward
from the internal iliacs along the sides of the urinary bladder, which
is the remnant of the original allantois itself. The terminal continuation of the original abdominal aorta, is the arteria sacra media,
which, in the adult, runs downward on the anterior surface of the
sacrum, supplying branches to the rectum and the anterior sacral
nerves.
Development of the Venous System.-According         Fig. 256.
to the observations of M. Coste, the venous system
at first presents the same simplicity and symmetry
with the arterial.  The principal veins of the
body consist of two long venous trunks, the vertebral veins (Fig. 256), which run along the sides
of the spinal column, parallel with the vertebral
arteries. They receive in succession all the intercostal veins, and empty into the heart by two  
lateral trunks of equal size, the canals of Cuvier. 
When the inferior extremities become developed,  
their two veins, returning from  below, join the    - 
vertebral veins near the posterior portion of the 
body; and, crossing them, afterward unite with
each other, thus constituting another vein of new
formation (Fig. 257, a), which runs upward a little  Early condition of VEto the right of the median line, and empties by  iogUS sYSverte;  hns
itself into the lower extremity of the heart.  The emptying into the heart
by two lateral trunks
two branches, by means of which the veins of the "canalsof cvier."




0o0  I'PEYTLOrIENIT  OF TiHB CI( UIJLATOYN  ArFrAATUB.
Fig. 257.       the lower extremities thus unite, become afteri-\  ^       ward, by enlargement, the common iliac veins;
while the single trunk (a) resulting from  their.j  ~   _       union becomes the vena cava inferior.  Subse-.          q quently, the vena cava inferior becomes very
a t  -    ~much larger than the vertebral veins; and its
two branches of bifurcation  are afterward re~1-.i        presented by the two iliacs.
Above the level of the heart, the vertebral
and intercostal veins retain their relative size
until the development of the superior extremi/~l  ^     ties has commenced.  Then two of the intercostal veins increase in diameter (Fig. 257), and
/~\ ~      become converted into the right and left subVENOuS SYSTEM ar-  clavians; while those portions of the vertebral
ther advanced, showing 
formation of iliac and ub-  veins situated above the subclavians become
clavinveins.-a. Vinof the right and  left jugulars.  Just below  the
new formation, which be- 
comne the inferior vena  junction of the jugulars with the subolavians,
cava,. b. Transversebranch  ^ r     1              ~ i.'
cav. n. Transiorebranch  a small branch of communication now appears
of new formation, which
afterward becomes the left  between the two vertebrals (Fig. 257, b), passvena innominata.
ing over from left to right, and emptying into
Fig. 258.       the right vertebral vein a little above the level
of the heart; so that a part of the blood coming
from the left side of the head, and the left upper
extremity, still passes down the left vertebral
vein to the heart upon its own side, while a part
-   crosses over by the communicating branch (b),
and is finally conveyed to the heart by the
right descending vertebral. Soon afterward, this
branch of communication enlarges so rapidly
El ~ \    that it preponderates altogether over the left
- j >  \    superior vertebral vein, from  which  it originated (Fig. 258), and, serving then to convey
all the blood coming from  the left side of the
head and left upper extremity over to the right
Further development of
the r dEN loS SYTEMn   side above the heart, it becomes the left vena
The vertebral veins are  innominata.
much diminished in size,
and the canal of Cuvier, on  On the left side, that portion of the superior
the left side, is gradually  vertebral vein, which is below the subclavian,
disappearing. c. Trans-               
verse branchof new forma-  remains as a small branch of the vena innomition, which is to become  nata receivino the six or seven upper intercostal
the vena azygos minor.




DEVELOPMENT OF THE NERVOUS SYSTEM.                    657
veins; while on the right side it becomes excessively enlarged,
receiving the blood of both jugulars and both subclavians, and is
converted into the vena cava superior.
The left canal of Cuvier, by which the left vertebral vein at first
communicates with the heart, subsequently becomes atrophied and
disappears; while on the right side it becomes excessively enlarged,
and forms the lower extremity of the vena cava superior.
The superior and inferior venae cavae, accordingly, do not correspond with each other so far as regards their
mode of origin, and are not to be regarded as         Fig. 259.
analogous veins.  For the superior vena cava                 3i
is one of the original vertebral veins; while
the inferior vena cava is a totally distinct vein,                4
of new formation, resulting from the union of
the two lateral trunks coming from  the infe-    A'
rior extremities.
The remainder of the vertebral veins finally
assume the condition shown in Fig. 259, which             8
is the complete or adult form of the venous            a 
circulation. At the lower part of the abdomen,
the vertebral veins send inward small trans- 
verse branches, which communicate with the
vena cava inferior, between the points at which 
they receive the intercostal veins.  These
branches of communication, by increasing in
size, become the lumbar veins (7), which, in the 
adult condition, communicate with each other   Adult condition of VEby arched branches, a short distance to the side  NIOU  SYSTEM.-. Right
auricle of heart.  2. Vena
of the vena cava.  Above the level of the  cava superior. 3,3. Jugular
lumbar arches, the vertebral veins retain their  veins, 4,4.Subclavianveins.
5. Vena cava inferior.  6, 6.
original direction.  That upon the right side  Iiacveins. 7.Lumbar veins
still receives all the right intercostal veins, and. Ven azygos major. 9.
Vena azygos minor. 10. Subecomes the vena azygos major (8).  It also  periorintercostal vein.
receives a small branch of communication from
its fellow of the left side (Fig. 258, c), and this branch soon enlarges
to such an extent as to bring over to the vena azygos major all the
blood of the five or six lower intercostal veins of the left side,
becoming, in this way, the vena azygos minor (9). The six or seven
upper intercostal veins on the left side still empty, as before, into
their own vertebral vein (io), which, joining the left vena innominata above, is known as the superior intercostal vein. The left canal
42




658  DEVELOPMENT OF THE CIRCULATORY APPARATUS.
of Cuvier has by this time entirely disappeared; so that all the
venous blood now enters the heart by the superior or the inferior
vena cava. But the original vertebral veins are still continuous
throughout, though very much diminished in size at certain points;
since both the greater and lesser azygous veins inosculate below
with the superior lumbar veins, and the superior intercostal vein
also inosculates below with the lesser azygous, just before it passes
over to the right side.
There are still two parts of the circulatory apparatus, the development of which presents peculiarities sufficiently important to
be described separately. These are, first, the liver and the ductus
venosus, and secondly, the heart, with the ductus arteriosus.
Development of the Hepatic Circulation and the Ductus Venosus.The liver appears at a very early period in the upper part of the
abdomen, as a mass of glandular and vascular tissue, which is developed around the upper portion of the omFig. 260.      phalo-mesenteric vein, just below its termiI  nation in the heart. (Fig. 260.)  As soon as
the organ has attained a considerable size,
the omphalo-mesenteric vein (i) breaks up in
v4/,- -~. I    its interior into a capillary plexus, the vessels
of which unite again into venous trunks, and
so convey the blood finally to the heart.
"  The omphalo-mesenteric vein below the liver
Early form of HEPATIC  then becomes the portal vein; while above the
CIRC~ULATIO. 1. Ompha-  liver, and between that organ and the heart,
to-mesenteric vein. 2. Hepa-                     n
ticvein. 3. Heart. The dotted  it receives the name of the hepatic vein (2).
line shows the situation of
the future umbilical vein.   The liver, accordingly, is at this time supplied
with blood entirely by the portal vein, coming from the umbilical vesicle and the intestine; and all the blood
derived from this source must pass through the hepatic circulation
before reaching the venous extremity of the heart.
But soon afterward the allantois makes its appearance, and becomes rapidly developed into the placenta; and the umbilical vein
coming from it joins the omphalo-mesenteric vein in the substance
of the liver, and takes part in the formation of the hepatic capillary
plexus. As the umbilical vesicle, however, becomes atrophied, and
the intestine also remains inactive, while the placenta increases in
size and in functional importance, a time soon arrives when the
liver receives more blood by the umbilical vein than by the portal
vein. (Fig. 261.)  The umbilical vein then passes into the liver at




DEVELOPMENT  OF THE  HEPATIC.'CIRCULA'TION.  659
the longitudinal fissure, and supplies the left lobe entirely with its
own branches.  To the right it sends off a large branch of communication, which opens into the portal vein, and partially supplies
the right lobe with umbilical blood.  The liver is thus supplied
with blood from two different sources, the
most abundant of which is the umbilical                Fig. 261.
vein; and all the blood entering the liver 
circulates, as before, through its capillary
vessels.
But we have already seen that the liver
is much larger, in proportion to the entire,
body, at an early period of fcetal life than
in the later months.  In  the foetal pig,
when very young, it amounts to nearly            HEPATIC  CIRCU.ATION
twelve per cent. of the weight of the whole  furtheradvanced. —. Portalveiu.
2. Umbilical vein. 3. Iepatic
body; but before birth it diminishes to.vein
seven, six, and even three or four per cent.
For some time, therefore, previous to birth, there is much more
blood returned from the placenta than is required for the capillary
circulation of the liver.  Accordingly, a vascular duct or canal is
formed in its interior, by which a portion:of. the placental blood is
carried directly through the organ,
and conveyed to the heart without                   Fig. 262.
having passed through the; hepatic
capillaries.  This duct is called. the
Ductus'venosus.
The ductus venosus is formed by a 
gradual dilatation of one of the hepatic capillaries at (5) (Fig. 262),
which, enlarging  excessively, becomes at last converted into a wide                                l
canal, or branch of communication,            3 
passing directly from  the umbilical
vein below to the hepatic vein above. 
The circulation  through the liver,   HEPATIC CIRCULATION duing latter p A rt of foetal life.-1. Portal vein. 2.
thus established, is as follows:  A   Umbilic vein. 3 Left brnch of unmbilicertain quantity of venous blood still cal vein. 4. Right br;ach of umbilical
vein. 5. Ductus venosus. 6. Hepatic
enters through the portal vein (i), vein
and circulates in a part of the capillary system of the right lobe.  The umbilical vein (2), bringing a
much larger quantity of blood, enters the liver also, a little to the




660  DEVELOPMENT OF THE CIRCULATORY APPARATUS.
left, and the blood which it contains divides into three principal
streams.  One of them  passes through the left branch (3) into the
capillaries of the left lobe; another turns off through the right
branch (4), and, joining the blood of the portal vein, circulates
through the capillaries of the right lobe; while the third passes
directly onward through the venous duct (5), and reaches the hepatic vein without having passed through any part of the capillary
plexus.
This condition of the hepatic circulation continues until birth.
At that time, two important changes take place.  First, the placental circulation is altogether cut off; and secondly, a much larger
quantity of blood than before begins to circulate through the lungs
and the intestine. The superabundance of blood, previously coming
from the placenta, is now diverted into the lungs; while the intestinal canal, entering upon the active performance of its functions,
becomes the sole source of supply for the hepatic venous blood.
The following changes, therefore, take place at birth in the vessels
of the liver. (Fig. 263.) First, the umbilical vein shrivels and
becomes converted into a solid rounded cord (2).  This cord may
be seen, in the adult condition, running from the internal surface of
the abdominal walls, at the umbilicus, to the longitudinal fissure of
the liver. It is then known under the
Fig. 263.           name of the round ligament. Secondly,
the ductus venosus also becomes obliterated, and converted into a fibrous
cord. Thirdly, the blood entering the
3zn ~,..liver by the portal vein (1), passes off
by its right branch, as before, to the
right lobe. But inethe branch (4), the
course of the:blood is reversed. This
was formerly the right branch of the
umbilical vein, its blood passing in a
2.:'..           direction from  left to right.  It now
becomes the left branch of the portal
Adult form of HEPATIC CrRrLA-   vein; and its blood passes from right
TION.-1. Portal vein. 2. Obliterated 
umbilical vein, forming the round liga- to left, to be distributed to the capilment; the continuation of the dotted  lries of the left lobe.
lines through the liver shows the situation of the obliterated ductus venosus.    According to Dr. Guy, the umbili3. Hepatic vein. 4. Left branch of portal Cal vein is completely closed at the
vein.
end of the fifth day after birth.
Development of the Heart, and the Ductus Arteriosus.-When the




DEVELOPMENT OF TIHE HEART.                         661
embryonic circulation is first established, the heart is a simple tubular sac (Fig. 264),.receiving the veins at its lower extremity, and
giving off thearterial trunks at its upper extremity.  By the progress of its growth, it soon becomes twisted upon itself; so that the
entrance of the veins, and the exit of the arteries, come to be placed
more nearly upon the same horizontal level (Fig. 265); but the
entrance of the veins (i) is behind and a little below, while the exit
of the arteries (2) is in front and a little above.  The heart is, at
this time, a simple twisted tube; and the blood passes through it
in a single continuous stream, turning upon itself at the point of
curvature, and passing directly out by the arterial orifice.
Fig. 264.              Fig. 265.               Fig. 266.
~2..?~2
M                                        I  /      3
FTETAL HE ART, divided
Earliest form of F; T A L     FCETAL HEART, twisted  into right and left cavities.HEART.-1 Venous ex-  upon itself.-1. Venous ex-  1. Venous extremity. 2.
tremity. 2. Arterial ex-  tremity. 2. Arterial extre-   Arterial extremity. 3, 3.
tremity.              nity.                   Pulmonary branches.
Soon afterward, this single cardiac tube isdivided into two parallel tubes, right and left, by a longitudinal partition, which grows
from the inner surface of its walls and follows the twisted course
of the organ itself. (Fig. 266.) This partition, which is indicated
in the figure by a dotted line, extends a short distance into the
commencement of the primitive arterial trunk, dividing it into two
lateral halves, one of which is in communication with the right side
of the heart, the other with the left.
About the same time, the pulmonary branches (3, 3) are given
off from each side of the arterial trunk near its origin; and the
longitud'inal partition, above spoken of, is so placed that both these
branches fall upon one side of it, and are both, consequently, given
off from that division of the artery which is connected with the right
side of the heart.
Very soon a superficial line of demarcation, or furrow, shows
itself upon the external surface of the heart, corresponding in situation with the internal septum; while at the root of the arterial
trunk this furrow becomes much deeper, and finally the two lateral
portions of the vessel are separated from each other altogether, in




662   DEVELOPMENT OF TIHE CIRC:ULATORY  APPARATUS.
Fig. 2:57.     the  immediate -neighborhood  of the  heart,
joining again, however, a short distance beyond
4B ff    -   the origin of the pulmonary branches. (Fig.
2\ y \ +  267.)  It then becomes evident that the left
/ /  \\>      lateral division of the arterial trunk  is the
commencement of the aorta (i); while its right
lateral division is the trunk of the pulmonary
E TAHEA Tstillfa.r- artery (2), giving off the right and left pulmother developed.-1. Aorta,
2. Pulmonary artery. 3, 3  nary branches (3, 3), at a short distance from
Pulmonary bianclhes. 4. its origin.  That portion  of the pulmonary
Ducus arteriosus.
trunk (4) which is beyond the origin of the
pulmonary branches, and  which  communicates freely with  the
aorta, is the Ductus arteriosus.
The ductus arteriosus is at first as large as the pulmonary trunk
itself; and nearly the whole of the blood, coming from the right
ventricle, passes directly onward  through the arterial duct, and
enters the aorta without going to the lungs.  But as the lungs
gradually become developed, they require a larger quantity of
blood for their nutrition, and the pulmonary branches increase in
proportion to the pulmonary trunk and the ductus arteriosus. At
the termination of foetal life, in the human  subject, the ductus
arteriosus is about as large as either one of the pulmonary
branches; and a very considerable portion of the blood, therefore,
coming from the right ventricle still passes onward to the aorta
without being distributed to the lungs.
But at the period of birth, the lungs enter upon the active performance of the function of respiration,
Fig. 268.
Fig. 268.         and immediately require a much larger
5-~-,.\:              supply of blood.   The right and left
12-,   /.-      pulmonary  branches then  enlarge, so
-—'   a    <   as to  become the two  principal divis((  F    ions of the pulmonary trunk. (Fig. 268.)
The ductus arteriosus at the same time
/     -                    becomes contracted and shrivelled to such
an extent that its cavity is obliterated;
and  is finally converted  into. an imHEAT OF INFA.NT, showing  pervious, rounded cord, which remains
disappearance of arterial duct after  until ault  runningfr th  point
birth.-1. Aorta. 2. Pulmonary ar-                      o     
tery: 3,3. Pulmonary branclles. 4. of bifurcation of the pulmonary iartery
Ductus arteriosus becoming oblite-        
rated.                      to the under side of the arch of the
rated.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~




DEVELOPMENT OF THE HEART.                     663
aorta. The obliteration of the arterial duct is complete, at latest,
by the tenth week after birth. (Guy.)
The two auricles are separated from  the two ventricles by horih
zontal septa which grow from the internal surface of the cardiac
walls; but these septa remaining incomplete, the auriculo-ventricular orifices continue pervious, and allow the free passage of the
blood from the auricles to the ventricles.
The interventricular septum, or that which separates the two
ventricles from each other, is completed at a very early date; but
the interauricular septum, or that which is situated between the
two auricles, remains incomplete for a long time, being perforated
by an oval-shaped opening, the foramen ovale, allowing, at this
situation, a free passage from the right to the left side of the heart.
The existence of the foramen ovale and of the ductus arteriosus
gives rise to a peculiar crossing of the streams of blood in passing
through the heart, which is characteristic of fcetal life, and which
may be described as follows:It will be found upon examination that the two venae cave,
superior and inferior, do not open into the auricular sac on the
same plane or in the same direction; for while the superior vena
cava is situated anteriorly, and is directed downward and forward,
the inferior is situated quite posteriorly, and passes into the auricle
in a direction from right to left, and transversely to the axis of
the heart.  A  nearly vertical curtain or valve at the same time
hangs downward behind the orifice of the superior vena cava and
in front of the orifice of the inferior. This curtain is formed by
the lower edge of the septum  of the auricles, which, as we have
before stated, is incomplete at this age, and which terminates
inferiorly and toward the right in a crescentic border, leaving at
that part an oval opening, the foramen ovale. The stream of blood,
coming from the superior vena cava, falls accordingly in front of
this curtain, and passes directly downward, through the auriculoventricular orifice, into the right ventricle. But the inferior vena
cava, being situated farther back and directed transversely, opens,
properly speaking, not into the right auricle, but into the left: for
its stream of blood, falling behind the curtain above mentioned,
passes across through the foramen ovale directly into the cavity of
the left auricle. This direction of the current of blood, coming
from the inferior vena cava, is further secured by a peculiar membranous valve, which: exists at this period, termed the Eustachian




664  DEVELOPMENT OF TIE CIRCULATORY APPARATUS.
valve.  This valve, which is very thin and transparent (Fig. 269, ),
is attached to the anterior border of the orifice of the inferior vena
cava, and terminates by a crescentic edge, directed toward the left;
the valve, in this way, standing
Fig. 269.                 as an incomplete membranous
partition between the cavity of
the inferior vena cava and that
ofthe right auricle. A  bougie,
accordingly, placed in  the inferior vena cava, as shown in
Fig. 269, lies naturally quite
behind the Eustachian valve,
and passes directly through
the foramen ovale into the left
auricle.
The two streams of blood,
therefore, coming from  the superior and inferior venae cavae,
HEART OF HMAN F(ETUS, at the end of the  cross each other upon entering
sixth month; from a specimen in the author's pos-  the heart. This crossino  of the
session.-a. Inferior vena cava. b. Superior vena'
cava. c. Cavity of right auricle, laid open from   streams does  not take  place,
the front. d. Appendix auricularis. e. Cavity of  hoeer  as it is  sometimes
right ventricle, also laid open. f. Eustachian valve.    i t    
The bougie, which is placed in the inferior vena  described, in the cavity of the
cava, can be seen passing behind the Eustachian   aic         b     oi     
valve, just below the point indicated by f, then  riht auricle  but, owing to the
crossing behind the cavity of the right auricle, and  peculiar position and direction
passing through the foramen ovale, to the left side        in     
of the heart.                             of the two veins at this period,
with regard to the septum of
the auricles, the stream  coming from  the superior vena cava enters
the righttauricle exclusively, while that from  the inferior passes
almost directly into the left auricle.
It will also be seen, by examining the positions of the aorta, pulmonary artery, and ductus arteriosus, at this time, that the arteria
innominata, together with the left carotid and left subclavian, are
given off from  the arch of the aorta, before its junction with the
ductus arteriosus, and this arrangement causes the blood of the two
vense cavce, not only to enter the heart in different directions, but
also to be distributed, after leaving the ventricles, to different parts
of the body. (Fig. 270.)  For the blood of the superior vena cava
passes through the right auricle downward into the right ventricle,
thence through  the pulmonary artery and ductus arteriosus, into
the thoracic aorta, while the blood of the inferior vena cava, enter



DEVELOPMENT OF THE HEART.                     660
ing the left auricle, passes into the left ventricle, thence into the arch
of the aorta, and is distributed to the head and upper extremities,
before reaching the situation of the arterial duct. The two streams,
therefore, in passing through the heart, cross each other both behind
and in front.  The venous blood, returning from  the head and
upper extremities by the superior
vena cava, passes through the abdo-             Fig. 270.
minal aorta and the umbilical arteries, to the lower part of the body,
and to the placenta; while that returning from  the placenta, by the
inferior vena cava, is distributed to
the head  and  upper extremities,
through the vessels given off from
the arch of the aorta.
This division of the streams of
blood, during a certain period of
foetal life, is so complete that Dr.
John Reid,' on injecting the infe-   Diagram of CIRCUIATION THROUGH
THE FCETAL HEART.-a. Superior vena
rior vena cava with red, and the  cava. b. lneriorvenacava. c,c,,c Arch
superior with yellow, in a seven  of aorta and its branches. d. Pulmonary
superior with yellow, in a seven artery.
months' human fcetus, found that
the red had passed through the foramen ovale into the left auricle
and ventricle and arch of the aorta, and had filled the vessels of
the head and upper extremities; while the yellow had passed into
the right ventricle, pulmonary artery, ductus arteriosus, and thoracic aorta, with only a slight admixture of red at the posterior
part of the right auricle.  All the branches of the thoracic and
abdominal aorta were filled with yellow, while the whole of the red
had passed to the upper part of the body.
We have repeated the above experiment several times on the
foetal pig, when about one-half and three-quarters grown, first taking
the precaution to wash out the heart and large vessels with a watery injection, immediately after the removal of the fcetus from the
body of the parent, and before the blood had been allowed to coagulate. The injections used were blue for the superior vena cava,
and yellow for the inferior.  The two syringes were managed, at
the same time, by the right and left hands; their nozzles being
firmly held in place by the fingers of an assistant.  When the
Edinburgh Medical and Surgical Journal, vol. xliii. 1835.




666  DEVELOPMENT OF THE CIRCULATORY APPARATUS.
points of the syringes were introduced into the veins, at equal distances from the heart, and the two injections made with equal force
and rapidity, it was found that the admixture of the colors which
took place was so slight, that at least nineteen-twentieths of the
yellowinjection had passed into the left auricle, and nineteen-twentieths of the blue into the right. The pulmonary artery and ductus
arteriosus contained a similar proportion of blue, and the arch of
the aorta of yellow. In the thoracic and abdominal aorta, however,
contrary to what was found by Dr. Reid, there was always an admixture of the two colors, generally in about equal proportions.
This discrepancy may be owing to the smaller size of the head and
upper extremities, in the pig, as compared with those of the human
subject, which would prevent their receiving all the blood coming
from the left ventricle; or to some differences in the manipulation
of these experiments, in which it is not always easy to imitate exactly the force and rapidity of the different currents of blood in
the living foetus. The above results, however, are such as to leave
no doubt of the principal fact, viz., that up to an advanced stage of
fcetal life, by far the greater portion of the blood coming from the
inferior vena cava passes through the foramen ovale, into the left
side of the heart; while by far the greater portion of that coming
from the head and upper extremities passes into the right side of
the heart, and thence outward by the pulmonary trunk and ductus
arteriosus. Toward the latter periods of gestation, this division
of the venous currents becomes less complete, owing to the three
following causes:First, the lungs increasing in size, the two pulmonary arteries, as
well as the pulmonary veins, enlarge in proportion; and a greater
quantity of the blood, therefore, coming from  the right ventricle,
instead of going onward through the ductus arteriosus, passes to
the lungs, and returning thence by the pulmonary veins to the left
auricle and ventricle, joins the stream passing out by the arch of
the aorta.
Secondly, the Eustachian valve diminishes in size. This valve,
which is very large and distinct at the end of the sixth month
(Fig. 269), subsequently becomes atrophied to such an extent that,
at the end of gestation, it has altogether disappeared, or is at least
reduced to the condition of a very narrow, almost imperceptible
membranous ridge, which can exert no influence. on the direction
of the current of blood passing by it. Thus, the cavity of the inferior vena cava, at its upper extremity, ceases to be separated from




DEVELOPMENT OF THE IHEART.                   667
that of the right auricle; and a passage of blood from one;to the
other may, therefore, more readily take place.
Thirdly, the foramen ovale becomes partially closed by a valve
which passes across its orifice from behind forward. This valve,
which begins to be formed at a very early period, is called the
valve of theforamen ovale. It consists of a thin, fibrous sheet, which
grows from the posterior surface of the auricular cavity, just to the
left of the foramen ovale, and projects into the left auricle, its free
edge presenting a thin crescentic border, and being attached, by its
two extremities, to the auricular septum  upon the left side. This
valve does not at first interfere at all with the flow of blood from
right to left, since its edge hangs freely and loosely into the cavity
of the left auricle. It only opposes, therefore, during the early
periods, any accidental regurgitation from left to right.
But as gestation advances, while the walls of the heart continue to enlarge, and its cavities to expand in every direction, the
fibrous bundles, forming the valve, do not elongate in proportion.
The valve, accordingly, becomes drawn downward more and more
toward the foramen ovale. It thus comes in contact with the edges
of the interauricular septum, and unites with its substance; the
adhesion taking place first at the lower and posterior portion, and
proceeding gradually upward and forward, so as to make the passage, from the right auricle to the left, more and more oblique in
direction.
At the same time, an alteration takes place in the position of the
inferior vena cava. This vessel, which at first looked transversely
toward the foramen ovale, becomes directed more obliquely forward; so that, the Eustachian valve having imostly disappeared, a
part of the blood of the inferior vena cava enters the right auricle,
while the remainder still passes through the equally oblique opening of the foramen ovale.
At the period of birth a change takes place, by which the
foramen ovale is completely occluded, and all the blood coming
through the inferior vena cava is turned into the right auricle.
This change depends upon the commencement of respiration.
A much larger quantity of blood than before is then sent to the
lungs, and of course returns from  them to the left auricle.  The
left auricle, being then completely filled with the pulmonary blood,
no longer admits a free access from the right auricle through the
foramen ovale; and the valve of the foramen, pressed backward
more closely against the edges of the septum, becomes after a time




668  DEVELOPMENT OF THE CIRCULATORY  APPARATUS.
adherent throughout, and obliterates the opening altogether. The
cutting off of the placental circulation diminishes at the same time
the quantity of blood arriving at the heart by the inferior vena
cava. It is evident, indeed, that the same quantity of blood which
previously returned from the placenta by the inferior cava, on the
right side of the auricular septum, now returns from the lungs, by
the pulmonary veins upon the left side of the same septum; and it
is owing to all these circumstances combined, that while before birth
a portion of the blood always passed from  the right auricle to the
left through the foramen ovale, no such passage takes place after
birth, since the pressure is then equal on both sides of the auricular
septum.
The fcetal circulation, represented in Fig. 270, is then replaced
by the adult circulation, represented in Fig. 271.
Fig. 271.
Diagram of AD ULT C ICULATION THROU GH THE H EART — a, a. Sllperior and infroriorl ven
c:tiv. b. Right ventricle.  c. Pulmonary artery, dividing into riglt and left branches.  d. Pulmonary vein.  e. Left ventricle.  f. Aorta.
That portion of the septuni of the auricles, originally occupied
by the foramen ovale, is accordingly constituted, in the adult condition, by the valve of' the foramen ovale, which has become adherent to the edges of the septurn. The auricular septum in the adult
heart is, therefore, thinner at this spot than elsewhere; and presents,
on the side of the right auricle, an oval depression, termed the fossa




DEVELOPMENT OF THE HEART.                    669
ovalis, which indicates the site of the original foramen ovale. The
fossa ovalis is surrounded by a slightly raised ring, the annulus
oval&s, representing the curvilinear edge of the original auricular
septum.
The foramen ovale is sometimes completely obliterated within a
few days after birth. It often, however, remains partially pervious
for several weeks or months.  We have a specimen, taken from a
child of one year and nine months, in which the opening is still
very distinct; and it is not unfrequent to find a small aperture
existing even in adult life. In these instances, however, although
the adhesion and solidification of the auricular septum may not be
complete, yet no disturbance of the circulation results, and no admixture of blood takes place between the right and left sides of the
heart; since the passage through the auricular septum  is always
very oblique in its direction, and its valvular arrangement prevents
any regurgitation from  left to right, while the complete filling of
the left auricle with pulmonary blood, as above mentioned, equally
opposes any passage from right to left.




670    DEVELOPMENT OF THE BODY AFTER BIRTH.
CHAPTER XVIII.
DEVELOPMENT OF THE BODY AFTER BIRTH.
THE newly-born infant is still very far from having arrived at a
state of complete development.  The changes through which it has
passed during intra-uterine life are not more marked than those
which are to follow during the periods of infancy, childhood, and
adolescence. The anatomy of the organs, both internal and external, their physiological functions, and even the morbid derangements to which they are subject, continue to undergo gradual and
progressive alterations, throughout the entire course of subsequent
life. The history of development extends, properly speaking, from
the earliest organization of the embryonic tissues to the complete
formation of the adult body. The period of birth, accordingly,
marks only a single epoch in a constant series of changes, some of
which have preceded, while many others are to follow.
The weight of the newly-born infant is a little over six pounds.
The middle point of the body is nearly at the umbilicus, the head
and upper extremities being still very large, in proportion to the
lower extremities and pelvis. The abdomen is larger and the
chest smaller, in proportion, than in the adult. The lower extremities are curved inward, as in the fcetal condition, so that the soles of
the feet look obliquely toward each other, instead of being directed
horizontally downward, as at a subsequent period. Both upper
and lower extremities are habitually curled upward and forward
over the chest and abdomen, and all the joints are constantly in a
semi-flexed position.
The process of respiration is very imperfectly performed for
some time after birth. The expansion of the pulmonary vesicles,
and the changes in the circulatory apparatus described in the preceding chapter, far from  being sudden and instantaneous, are
always more or less gradual in their character, and require an
interval of several days for their completion. Respiration, indeed,
seems to be accomplished, during this period, to a considerable




DEVELOPMENT OF THE BODY AFTER BIRTH.   671
extent through the skin, which is remarkably soft, vascular, and
ruddy in color. The animal heat is also less actively generated
than in the adult, and requires to be sustained by careful protection, and by contact with the body of the mother. The young
infant sleeps during the greater part of the time; and even when
awake there are but few manifestations of intelligence or perception. The special senses of sight and hearing are dull and inexcitable, though  their organs are perfectly formed; and even
consciousness seems present only to a very limited extent. Voluntary motion and sensation are nearly absent; and the almost constant irregular movements of the limbs, observable at this time,
are evidently of a reflex or automatic character. Nearly all the
nervous phenomena,. indeed, presented by the newly-born infant,
are of a similar nature. The motions of its hands and feet, the act
of suckling, and even its cries and the contortions of its face, are
reflex in their origin, and do not indicate the existence of any
active volition, or any distinct perception of external objects.
There is at first but little nervous connection established with the
external world, and the system is as yet almost exclusively occupied with the functions of nutrition and respiration.
This preponderance of the simple reflex actions in the nervous
system of the infant, is observable even in the diseases to which it
is peculiarly subject for some: years after birth.  It is at this age
that convulsions from indigestion are of most frequent occurrence,
and even temporary strabismus and paralysis, resulting from the
same cause. It is well known to physicians, moreover, that the
effect of various drugs upon the infant is very different from that
which they exert upon the adult. Opium, for example, is very
much more active, in proportion to the dose, in, the infant than in
the adult. Mercury, on the other hand, produces salivation with
greater difficulty in the former than in the latter Blisters excite
more constitutional irritation in the young than in the old subject;
and antimony, when given to children, is proverbially uncertain
and dangerous in its operation.
The difference in the anatomy of the newly-born infant, and that
of the adult, may be represented, to a certain extent, by the following list, which gives the relative weight of the most important
internal organs at the period of birth and that of adult age; the
weight of the entire body being reckoned, in each case, as 1000.
The relative weight of the adult organs has been calculated from




672    DEVELOPMENT OF THE BOIY AFTER BIRTH.
the estimates of Cruveilhier, Solly, Wilson, &c.; that of the organs
in the foetus at term from our own observations.
F(ETUS AT TERM.    ADULT.
Weight of the entire body... 1000.00    1000.00
"   "   encephalon...  148.00          23.00
"   "   liver...   37.00                  29.00
" " heart....    7.77              4.17
" "   kidneys..6.00                         4.00
"   "   renal capsules...    1.63         0.13
"   "   thyroid gland    0.60                     0.51
"'   "   thymus gland...   3.00         0.00
It will be observed that most of the internal organs diminish in
relative size after birth, owing principally to the increased development of the osseous and muscular systems, both of which are in a
very imperfect condition throughout intra-uterine life, but which
come into activity during childhood and youth.
Within the first day after birth the remains of the umbilical
cord begin to wither, and become completely desiccated by about
the third day. A superficial ulceration then takes place about the
point of its attachment, and it is separated and thrown off within
the first week. After the separation of the cord, the umbilicus
becomes completely cicatrized by the tenth or twelfth day after
birth. (Guy.)
An exfoliation and renovation of the cuticle also take place
over the whole body soon after the birth.  According to K6lliker,
the eyelashes, and probably all the hairs of the body and head, are
thrown off and replaced by new ones, within the first year.
The teeth in the newly-born infant are but partially developed,
and are still inclosed in their follicles, and concealed beneath the
gums.  They are twenty in number; viz., two incisors, one canine,
and two molars, on each side of each jaw. At birth there is a thin
layer of dentine and enamel covering their upper surfaces, but
the body of the tooth and its fangs are formed subsequently by
progressive elongation  and ossification of the tooth-pulp.  The
fully-formed teeth emerge from the gums in the following order.
The central incisors in the seventh month after birth; the lateral
incisors in the eighth month; the anterior molars at the end of the
first year; the canines at a year and a half; and the second molars
at two years (K6lliker). The eruption of the teeth in the lower
jaw generally precedes by a short time that of the corresponding
teeth in the upper.
During the seventh year a change begins to take place by which




DEVELOPMENT OF THE BODY AFTER BIRTH.   673
the first set of teeth are thrown off and replaced by a second or
permanent set, differing in number, size, and shape from those
which preceded. The anterior permanent molar first shows itself
just behind the posterior temporary molar, on each side. This
happens at about six and a half years after birth. At the end of
the seventh year the middle incisors are thrown off and replaced
by corresponding permanent teeth, of larger size. At the eighth
year a similar exchange takes place in the lateral incisors. In the
ninth and tenth years, the anterior and second molars are replaced
by the anterior and second permanent bicuspids. In the twelfth
year, the canine teeth are changed. In the thirteenth year, the
second permanent molars show themselves; and from the seventeenth to the twenty-first year, the third molars, or "wisdom teeth,"
emerge from the gums, at the posterior extremities of the dental
arch. (Wilson.) Thejaw, therefore, in the adult condition, contains
three teeth on each side more than in childhood, making in all
thirty-two permanent teeth; viz., on each side, above and below,
two incisors, one canine, two bicuspids, and three permanent
molars.
The entire generative apparatus, which is still altogether inactive
at birth, begins to enter upon a condition of functional activity
from the fifteenth to the twentieth year. The entire configuration
of the body alters in a striking manner at this period, and the distinction  between the sexes becomes more complete and well
marked. The beard is developed in the male; and in the female
the breasts assume the size and form characteristic of the condition
of puberty. The voice, which is shrill and sharp in infancy and
childhood, becomes deeper in tone, and the countenance assumes a
more sedate and serious expression. After this period, the muscular system increases still further in size and strength, and the
consolidation of the skeleton also continues; the bony union of its
various parts not being entirely accomplished until the twenty-fifth
or thirtieth year. Finally, all the different organs of the body arrive
at the adult condition, and the entire process of development is
then complete.
43








INDE  X.
Absorption, 145                            Alimentary canal, in different animals,
by bloodvessels, 148                          100-104
by lacteals, 150-153                       development of, 628
of fat, 154                            Alkalies, effect of, on urine, 336
of different liquids by animal sub- Alkaline chlorides, 55-58
stances, 294                             phosphates, 61
of oxygen in respiration, 225              carbonates, 60-61
by egg during incubation, 590          Alkaline fermentation of urine, 342
of calcareous matter by allantois, Alkalescence of blood, due to carbonates,
590                                    60
Absorbent glands, 151, 299                 Allantois, 583
vessels, 150, 299                          formation of, 585
Acid, carbonic, 224-234                         in fowl's egg, 588
lactic, in gastric juice, 122, 123         function of, 589
in souring milk, 318                       in foetal pig, 606
glyko-cholic, 163                      Alligator, brain of, 364
tauro. cholic, 164                     Amnion, 583
pneumic, 229                               formation of, 584
uric, 329, 336                             enlargement of, during latter part
oxalic, in urine, 341                         of pregnancy, 614
Acid fermentation of urine, 341                 contact with chorion, 615
Acidity, of gastric juice, cause of, 123    Amniotic folds, 584
of urine, 335                          Amniotic fluid, 614
Acini, of liver, 320, 321                       its use, 615
Adipose vesicles, 74                            contains sugar at a certain period,
digestion of, 142, 143                        633
Adult circulation, 652                     Amniotic umbilicus, 584
establishment of, 667                  Analysis, of animal fluids, 48, 49
Aerial respiration, 215-217                     of milk, 96, 316
Age, influence of, on exhalation of car-        of wheat flour, 96
bonic acid, 232                          of oatmeal, 96
on comparative weight of organs,           of eggs, 97
672                                      of meat, 97
Air, quantity of, used in respiration, 220      of saliva, 108
alterations of, in respiration, 223        of gastric juice, 122
circulation of, in lungs, 221              of pancreatic juice, 139
Air-cells of lungs, 217                         of bile, 159
Air-chamber, in fowl's egg, 536                 of blood-globules, 200
Albumen, 84                                     of blood-plasma, 205
of the blood, 206                          of mucus, 310
in saliva, 108                             of sebaceous matter, 311
in milk, 317                               of perspiration, 313
of the egg, how produced, 535              of butter, 318
its liquefaction and absorption dur-       of urine, 334
ing development of foetus, 586-          of fluid of thoracic duct, 300
588                                      of chyle and lymph, 302
Albuminoid substances, 79                  ANDRAL AND GAVARRET, production of
digestion of, 125                        carbonic acid in respiration, 232
Albuminose, 126                            Animal functions, 43
interference with  Trommer's  test, Animal heat, 235-245
127                                      in different species, 237
with action of iodine and starch, 128      mode of generation, 239




676                                 INDEX.
Animal heat influenced by local causes, BIDDER AND SCHMIDT, on daily quantity
243                                       of bile, 171
in different organs, 244                  on effect of excluding bile from inincrease of, after section of sympa-        testine, 177
thetic nerve, 505                       on reabsorption of bile, 179
Animal and vegetable parasites, 516       Bile, 158
Animalcules, infusorial, 513                  composition of, 159
mode of production, 514                  tests for, 167
Annulus ovalis, 668                           daily quantity of, 171
Anterior columns of spinal cord, 363          functions of, 175
their excitability, 387                   reaction with gastric juice, 176
Aorta, development of, 653                    reabsorption, 179
Aplysia, nervous system of, 357               mode of secretion, 319
Appetite, disturbed by anxiety, &c., 133 Biliary salts, 160
necessary to digestion of food, 133       of human bile, 166
Aquatic respiration, 215                  Biliverdine, 87, 159
Area pellucida, 574                           tests for, 167
vasculosa, 587, 649                       passage into the urine, 339
Arch of aorta, formation of, 653          Blastodermic membrane, 572
Arches, cervical, 652                     Blood, 195
transformation of, 653                    red globules of, 196
Arteries, 263                                 white globules, 202
motion of blood in, 264                   plasma, 205
pulsation of, 265-268                     coagulation of, 208
elasticity of, 263-266                    buffy coat, 212
rapidity of circulation in, 271           entire quantity of, 213
omphalo-mesenteric, 649                   alterations of, in respiration, 225
vertebral, 652                            temperature of, 236
umbilical, 652                                in different organs, 244
Arterial pressure, 269                        circulation of, 246
Arterial system, development of, 652-661           through the heart, 251
Articulata, nervous system of, 358                through the arteries, 263
reflex action in, 359                         through the veins, 272
Articulation of tapeworm, 525                     through the capillaries, 277
Arytenoid cartilages, 222                 BOUSSINGAULT, on chloride of sodium  in
movements of, 223                           food, 57
Assimilation, 306                             on internal production of fat, 77
destructive, 323                     Brain, 401
Auricle, single, of fish, 247                 of alligator, 364
double, of reptiles, birds, and mam-      of rabbit, 365
malians, 248, 249                      human, 368
contraction of, 261                       remarkable cases of injury to, 403,
Auriculo-ventricular valves, action of,         404
251                                       size of, in different races, 407
Auditory apparatus, 491                           in idiots, 409
nerves, 431, 490                          development of, 622, 623
Axis-cylinder, of nervous filaments, 350, Branchiae, 214
352                                         of meno-branchus, 215
Aztec children, 410                       Broad ligaments, formation of, 645
Azygous veins, formation of, 657          Bronchi, division of, 216-217
ciliary motion in, 221
BEAUMONT, Dr., experiments on Alexis St. Brunner's glands, 136
Martin, 119, 130                       Buffy coat of the blood, 212
BERNARD, on the different kinds of saliva, Butter, 317
109                                    composition of, 318
on effect of dividing Steno's duct, 115   condition in milk, 75, 317
on digestion of fat in intestine, 137   Butyrine, 318
on formation of liver-sugar, 182, 183,
184                                Canals of Cuvier, 655
on decomposition of bicarbonates in  Capillaries, 277
lung, 229                              their inosculation, 278
on temperature of blood in different      motion of blood in, 279
organs, 244                        Capillary circulation, 278




INDEX.                                   677
Capillary circulation, causes of, 281     Chloride of sodium, importance of, in the
rapidity of, 283                            food, 57
peculiarities of, in different parts,     mode of discharge from the body, 58
285                                    partial decomposition of, in the body,
Caput coli, formation of, 629                    58
Carbonic acid, in the breath, 224         Chloride of potassium, 58
proportion of, to oxygen absorbed, Cholesterine, 159
225                                Chorda dorsalis, 575
in the blood, 227                    Chorda tympani, 472
origin of, in lungs, 229             Chordse vocales, movement of, in respiin the blood, 230                      ration, 222
in the tissues, 230                  action of, in the production of vocal
mode of production, 230                     sounds, 449
daily quantity of, 232                    obstruction of glottis by, after divivariations of, 233                          sion of pneumogastric, 451
exhaled by skin, 234                 Chorion, formation of, 592
by egg, during incubation, 590       villosities of, 594
absorbed by vegetables, 242               source of vascularity of, 595
Carbonate of lime, 60                         union with decidua, 603
of soda, 60                          Chyle, 150, 156, 301
of potassa, 61                            in lacteals, 153
of ammonia, in putrefying urine,          absorption of, 154
343                                         by intestinal epithelium, 155
Cardiac circulation, in foetus, 665           in blood, 156
in adult, 668                        Ciliary motion, in bronchi, 221
Carnivorous animals, respiration of, 34,      in Fallopian tubes, 557
225                                Ciliary nerves, 498
urine of, 328, 330                   Circulation, 246
Cartilagine, 86                               in the heart, 247-252
Caseine, 84                                   in the arteries, 263
Cat, secretion of bile in, 171                in the veins, 272
closure of eyelids, after division of     in the capillaries, 277
sympathetic, 506                       rapidity of, 284
Catalytic action, 82                          peculiarities of, in different parts,
of pepsin, 125                              285
Centipede, nervous system of, 358             in liver, 321
Centre, nervous, definition of, 355           in placenta, 609-663
Cerebrum, 368.  See Hemispheres.          Circulatory apparatus, development of,
Cerebral ganglia, 364-369.  See Hemi-   648-669
spheres.                               Civilization, aptitude for, of different
Cerebellum, 413                             races, 408
effects of injury to, 415            Classification of cranial nerves, 432
removal of, 415-417                  Clot, formation of, 208
function of, 414                          separation from serum, 209
development of, 622, 623                  buffed and cupped, 212
Cerebro-spinal system, 360, 361           Coagulation, 82
development of, 621                       of fibrin, 205
Cervix uteri, 538                             of blood, 208
in foetus, 646                            of white substance of Schwann, in
Cervical arches, 652                            nerve-fibres, 351
transformation of, 653               COLIN, on unilateral mastication, 110
Changes, in egg, while passing through  Cold, resistance to, by animals, 235
oviduct, 532, 535, 570                 effect of, when long continued, 236
in hepatic circulation at birth, 660   Colostrum, 316
in comparative size of organs, after Coloring matters, 86, 87
birth, 672                             of blood, 86, 200
CHEVREUIL, experiments on imbibition,         of the skin, 87
294                                         of bile, 87, 159
Chick, development of, 586-591                of urine, 87
Children, Aztec, 410                      Commissure, of spinal cord, gray, 362
Chloride of sodium, 55                        white, 363
its proportion in the animal tissues      transverse, of cerebrum, 369
and fluids, 56                         of cerebellum, 369




678                                  INDEX.
Commissures, nervous, 355                  Crystals, of creatinine, 329
olfactory, 364, 402                        of urate of soda, 330
Congestion, of ear, &c., after division of      of uric acid, 336
sympathetic, 505                             of oxalate of lime, 342
Convolvulus, sexual apparatus of, 524           of triple phosphate, 344
Contact, of chorion and amnion, 615        Crystallizable substances of organic oriof decidua vera and reflexa, 616         gin, 51
Consentaneous action of muscles, 414    Crossing of fibres in medulla oblongata,
Contraction, of stomach  during diges-            366
tion, 128                                of sensitive fibres in spinal cord,
of spleen, 190                                389
of blood-clot, 209                         of streams of blood in fcetal heart,
of diaphragm  and intercostal mus-            664, 665
cles, 219                           CRUIKSHANK, rupture of Graafian follicle
of posterior crico-arytenoid muscles,   in menstruation, 556
223                                 Cumulus proligerus, 551
of ventricles, 256                     Cutaneous respiration, 234
of muscles after death, 370                perspiration, 312
of sphincter ani, 398                 Cuticle, exfoliation of, during fetal life,
of rectum, 398                                627
of urinary bladder, 399                    after birth, 672
of pupil, under influence of light, Cysticercus, 521
419, 484, 502                       transformation of into tsenia, 522
after division of sympathetic,        production of, from  eggs of tsenia,
506                                   523
Cooking, effect of, on food, 98
Cord, spinal, 382-400                      Death, a necessary consequence of life,
umbilical, 615                           510
withering and separation of, 672 Decidua, 593
Corpus callosum, 369                            vera, 600
Corpus luteum, 560                              reflexa, 601
of menstruation, 560-564                   union with chorion, 603
of pregnancy, 564-569                      its discharge in cases of abortion,
three weeks after menstruation, 562               602
four weeks after menstruation, 563              at the time of delivery, 617
nine weeks after menstruation, 563 Decussation of anterior columns of spinal
at end of second month  of preg-             cord, 366
nancy, 566                               of optic nerves, 420, 421
at end of fourth month, 566            Degeneration, fatty, of muscular fibres
at term, 567                             of uterus, after delivery, 619
disappearance of, after delivery, 568 Deglutition, 116
Corpora Malpighiana, of spleen, 191             retarded by division of Steno's duct,
Corpora striata, 365, 368, 403                         115
Corpora olivaria, 366                               by division of pneumogastric,
Corpora Wolffiana, 638                                 447
COSTE, on rupture of Graafian follicle in  Dentition, first, 672
menstruation, 556, 557                        second, 673
Cranial nerves, 430                        Descent of the testicles, 641
classification of, 432                     of the ovaries, 644
motor, 433                             Destructive assimilation, 323
sensitive, 434                        Development of the impregnated egg, 570
Creatine, 328                                   of allantois, 585
Creatinine, 329                                 of chorion, 592
Cremaster muscle, formation of, 642             of villosities of chorion, 593, 594
function of, in lower animals, 643         of decidua, 598
Crystals, of stearine, 71                       of placenta, 607-613
and margarine, 72                     of nervous system, 621
of cholesterin, 160                        of eye, 624
of glyko-cholate of soda, 161,162          of ear, 625
of biliary matters of dog's bile, 165,     of skeleton, 625
172                                      of limbs, 626
of urea, 326                               of integument, 627
of creatine, 328                           of alimentary canal, 628, 630




INDEX.                                   679
Development of urinary passages, 630   DUTROCHET, on endosmosis of water with
of liver, 632                               different liquids, 291
of pharynx and oesophagus, 633
of face, 635                         Ear, 491
of Wolffian bodies, 638                   muscular apparatus of, 492, 504
of kidneys, 639                           development of, 612
of internal generative organs, 640   Earthy phosphates, 58, 61
of circulatory apparatus, 648             in urine, 335
of arterial system, 652                   precipitated by addition of an alkali,
of venous system, 655                       336
of hepatic circulation, 658          Ectopia cordis, 635
of heart, 660                        Egg, 524-528
of the body after birth, 670              its contents, 529
Diabetes, 339                                 where formed, 530
in foetus, 633                            of frog, 532
Diaphragm, action of in breathing, 218,       of fowl, 535-536
219                                    changes in, while passing through
formation of, 634                           the oviduct, 532-535
Diaphragmatic hernia, 635                     pre-existence of, in ovary, 547
Diet, influence of on nutrition, 90-92        development of, at period of puberty,
on products of respiration, 225             548
on formation of urea, 327                 periodical ripening and discharge,
of urate of soda, 330                   549
Diffusion of gases inlungs, 221               discharge of, from  Graafian follicle,
Digestion, 99                                    552
of starch, 134                            impregnation of, how accomplished,
of fats, 137, 139                           545, 546
of sugar, 134                             development of, after impregnation,
of organic substances, 124-126              570
time required for, 130                    of fowl, showing area vasculosa, 587
Digestive apparatus of fowl, 101              ditto, showing formation of allantois,
of ox, 102                                  588
of man, 103                               of fish, showing vitelline circulation,
Discharge of eggs from ovary, 532                589
independent of sexual intercourse,        attachment of, to uterine mucous
549                                       membrane, 603
mechanism of, 552                         discharge of from uterus, at the time
during menstruation, 556                    of delivery, 617
Discus proligerus, 551                        condition of in newly born infant, 646
Distance and solidity, appreciation of, by Elasticity, of spleen, 191
the eye, 485-487                            of red globules of blood, 198
Distinction  between  corpora lutea of        of lungs, 217
menstruation and pregnancy, 568-569         of costal cartilages, 219
Diurnal variations, in exhalation of car-     of vocal chords, 223
bonic acid, 234                         of arteries, 263
in production of urea, 328           Electrical current, effect of, on muscles,
in density and acidity of urine, 333        371
Division of nerves, 353                       on nerve, 373
of heart, into right and left cavities,   different effects of direct and inverse,
661                                       376
DOBSON, on variation in size of spleen, 190 Electrical fishes, phenomena of, 379
DRAPER, John C., on production of urea, Electricity, no manifestations of in irri327, 328                                  tated nerve, 380
Drugs, effect of, on newly born infant, Elevation of temperature, after division
671                                       of sympathetic, 243, 505
Ductus arteriosus, 662                    Elongation of heart in pulsation, 257, 258
closure of, 662-663                       anatomical causes of, 259
venosus, 659                         Embryo, formation of, 570
obliteration of, 660                 Embryonic spot, 574
Duodenal glands, 136                      Encephalon, 363, 368, 401
fistula, 173                              ganglia of, 368
DUTROCHET, on temperature of plants, 238, Endosmosis, 289
242                                    of fatty substances, 155




680                                 INDEX.
Endosmosis in capillary circulation, 280 Farinaceous substances, 63
conditions of, 290-292                    in food, 64
cause of, 293                             digestion of, 134
of iodide of potassium, 295, 297     Fat, decomposition of, in the blood, 153
of atropine, 295                     Fats, 70
of nux vomica, 296                        proportion of, in different kinds of
Endosmometer, 290                               food, 72
Enlargement of amnion, during preg-           condition, in the various tissues and
nancy, 614, 615                               fluids, 73
Entozoa, encysted, 518                        internal source of, 77
mode of production, 520                   decomposed in the body, 78
Epithelium, in saliva, 108                    indispensable as ingredients of the
of gastric follicles, 118                   food, 91, 95
of intestine, during digestion, 155    Fatty matters of the blood, 206
Epidermis, exfoliation of, in fcetal life, 627 Fatty degeneration of decidua, 618
after birth, 672                          of muscular fibres of uterus, after
Epididymis, 642                                  delivery, 619
Excretine, 144                            Feces, 144
Excretion, 323                            Female generative organs, 528
nature of, 324                            of frog, 531
importance to life, 324, 325              of fowl, 535
products of, 325                          of sow, 537
by placenta, 612                          of human species, 538
Excrementitious substances, 323                    development of, 644
mode of formation of, 324            Fermentation, 83
effect of retention of, 324               of sugar, 69
Exfoliation of cuticle, during fcetal life,   acid, of urine, 341
627                                    alkaline, of ditto, 342
after birth, 672                     Fibrin, 84
Exhalation, 289                               of the blood, 205
of watery vapor, 55                       coagulation of, 205
from the lungs, 224                       varying quantity of, in blood of diffrom the skin, 312                          ferent veins, 206
from the egg, during incubation, 589 Fifth pair of cranial nerves, 435
of carbonic acid, 225                     its distribution, 436
of nitrogen, 224                          division of, paralyzes sensibility of
of animal vapor, 224                             face, 437
Exhaustion, of muscles, by repeated irri-          and of nasal passages, 438
tation, 372                                 produces inflammation of eyeof nerves, by ditto, 374                         ball, 439
Exosmosis, 289                                lingual branch of, 440
Expiration, movements of, 219                 small root of, 438
after section of pneumogastric, 453   Fish, circulation of, 247
Extractive matters of the blood, 207          formation of umbilical vesicle in,
Eye, protection of, by movements of pu-          580
pil, 419, 484, 503                      vitelline circulation, in embryo of,649
by two sets of muscles, 504          Fish, electrical, phenomena of, 379
Eyeball, inflammation of, after division  Fissure, longitudinal, of brain and spinal
of 5th pair, 439                              cord, 361
Eyelids, formation of, 625                    formation of, 623
Fissure of palate, 637
Face, sensitive nerves of, 434            Fistula, gastric, Dr. Beaumont's case of,
motor nerve, 440                            119
development of, 635                       mode of operating for, 120
Facial nerve, 440                             duodenal, 173
sensibility of, 443                  Feetal circulation, first form of, 648
influence of, on muscular apparatus       second form of, 650
of eye, 441                        Follicles, of stomach, 117, 118
of nose, 442                              of Lieberkiihn, 135
of ear, 442                               of Brunner's glands, 136
paralysis of, 442, 443                    Graafian, 530, 552
Fallopian tubes, 537                          of uterus, 599
formation of, 641, 644               Food, 89




INDEX.                                   681
Food, composition of, 96, 97              Gastric juice, daily quantity of, 130
daily quantity required, 97               solvent action of, on stomach, after
effect of cooking on, 98                    death, 132
Foramen ovale, 663                        Gelatine, how produced, 48
valve of, 667                             effect of feeding animals on, 93
closure of, 667                      Generation, 511
Force, nervous, nature of, 381                spontaneous, 511
Formation of sugar in liver, 182              of infusoria, 514
in foetus, 633                            of parasites, 516
Fossa ovalis, 668                             of encysted entozoa, 518
Functions, animal, 43                         of tsenia, 520
vegetative, 42                            sexual, by germs, 524
of teeth, 105                        Germ, nature of, 524
of saliva, 112                       Germination, heat produced in, 238
of gastric juice, 124                Germinative vesicle, 529
of pancreatic juice, 140                  disappearance of, in mature egg, 570
of intestinal juices, 137            Germinative spot, 529
of bile, 175                         Gills, of fish, 214
of spleen, 194                            of menobranchus, 215
of mucus, 310                        Glands, of Brunner, 136
of sebaceous matter, 311                  mesenteric, 151, 299
of perspiration, 313                      vascular, 192
of the tears, 315                         Meibomian, 311
perspiratory, 312
Galvanism, action of, on muscles, 371         action of, in secretion, 306
on nerves, 373                       Glandulae, solitarise and agmninate, 145
Ganglion, of spinal cord, 393             Globules, of blood, 195
of tuber annulare, 422                    red, 196
of medulla oblongata, 423                     different appearances of, under
Casserian, 435                                   microscope, 196, 197
of Andersch, 444                              mutual adhesion of, 197
pneumogastric, 445                            color, consistency, and structure
ophthalmic, 498                                  of, 198
spheno-palatine, 473, 498                     action of water on, 199
submaxillary, 498                             composition of, 200
otic, 499                                     size, &c., in different animals,
semilunar, 500                                   201, 202
impar, 500                                white, 202
Ganglionic system of nerves, 498                   action of acetic acid on, 203
Ganglia, nervous, 354, 355                         red and white, movement of, in
of radiata, 355                                  circulation, 279
of mollusca, 357                     Globuline, 85, 200
of articulata, 358                   Glomeruli, of Wolffian bodies, 639
of posterior roots of spinal nerves, Glosso-pharyngeal nerve, 443, 467
362, 363                               action of, in swallowing, 444
of alligator's brain, 364            Glottis, movements of, in respiration, 222
of rabbit's brain, 365                   in formation of voice, 448
of medulla oblongata, 366                 closure of, after section of pneumoof human brain, 368                         gastrics, 451
of great sympathetic, 499            Glycine, 163
olfactory, 402, 473                  Glyco-cholic acid, 163
optic, 364, 418                      Glyco-cholate of soda, 163
Gases, diffusion of, in lungs, 221            its crystallization, 161, 162
absorption and exhalation of, by  Glycogenic function of liver, 182
lungs, 224                         in foetus, 633
by the tissues, 230              Glycogenic matter, 186
Gastric follicles, 117, 118                   its conversion into sugar, 187
Gastric juice, mode of obtaining, 120     GOSSELIN, experiments on imbibition by
composition of, 122                    cornea, 295
action on food, 124                  Graafian follicles, 530
interference with Trommer's test, 127     structure of, 551
interference with action of starch        rupture of, and discharge of egg, 552
and iodine, 128                         ruptured during menstruation, 556




682                                 INDEX.
Graafian follicles, condition in fcetus at Hunger and thirst, continue after diviterm, 646                            sion of pneumogastric, 457
Gray substance, of nervous system, 354 Hydrogen, displacement of gases in blood
of spinal cord, 362                         by, 227
of brain, 368                             exhalation of carbonic acid in an
its want oI irritability, 401               atmosphere of, 230
Great sympathetic, 498                    Hygroscopic property of organic subanatomy of, 499                         stances, 81
sensibility and excitability of, 501   Hypoglossal nerve, 461
connection of, with special senses,
502, 505                           Imbibition, 289
division of, influence on animal heat,    of liquids, by different tissues, 294
505                                    by cornea, experiments on, 295
on pupil and eyelids, 506            Impulse, of heart, 261
reflex actions of, 508               Infant, newly-born, characteristics of, 670
Gubernaculum testis, 642                  Inflammation of eyeball, after division
function of, in lower animals, 643      of 5th pair, 439
Gustatory nerve, 440, 467                 Infusoria, 513
different kinds of, 514
HAMMOND, Prof. Wm. A., on effects of non-     conditions of their production, 514
nitrogenous diet, 92                    Schultze's experiment on generation
on production of urea, 327                  of, 516
Heematine, 86, 200                        Inguinal hernia, congenital, 644
Hairs, formation of, in embryo, 627       Injection of placental sinuses from vesHare-lip, 636                               sels of uterus, 611
HARVEY, on motions of heart, 257          Inorganic substances, as proximate prinHearing, sense of, 489                          ciples, 53
apparatus of, 491                         their source and destination, 62
analogy of with touch, 494           Inosculation, of veins, 273
Heart, 247                                    of capillaries, 278
of fish, 247                              of nerves, 354
of reptiles, 248                     Insalivation, 107
of mammalians, 249                       importance of, 115
of man, 250                               function of, 116
circulation of blood through, 252    Inspiration, how accomplished, 218
sounds of, 252                            movements of glottis in, 221
movements of, 255                    Instinct, nature of, 428
impulse, 261                         Integument, respiration by, 234
development of, 660                       development of, 627
Heat, vital, of animals, 235              Intellectual powers, 409
of plants, 238                            in animals, 428
how produced, 239                    Intestine, of fowl, 101
increased by division of sympathetic      of man, 103
nerve, 243, 505                        juices of, 133
Hemispheres, cerebral, 403                    digestion in, 133-143
remarkable cases of injury to, 404        epithelium of, 155
effect of removal, on pigeons, 405        disappearance of bile in, 175
effect of disease, in man, 406            development of, 576, 629
comparative size of, in different races, Intestinal digestion, 141
408                                Intestinal juices, 133
functions of, 409                         action of, on starch, 134
development of, 622                  Involution of uterus after delivery, 619
Hemorrhage, from placenta, in parturi- Iris, movements of, 419, 484, 503
tion, 617                                   after division of sympathetic, 506
Hepatic circulation, 320, 321             Irritability, of gastric mucous membrane,
development of, 658                         121
Herbivorous animals, respiration of, 34,      of the heart, 258
225                                     of muscles, 371
urine of, 328, 330                        of nerves, 373
Hernia, congenital, diaphragmatic, 635
umbilical, 630                       JACKSON, Prof. Samuel, on digestion of fat
inguinal, 644                          in intestine, 137
Hippurate of soda, 330                    Jaundice, 167




INDEX.                                  683
Jaundice, yellow color of urine in, 339   LONGET, on irritability of anterior spinal
roots, 385
Kidneys, peculiarity of circulation in, Long and short-sightedness, 480
287                               LONGET AND MATTEUCCI, experiment on
elimination of medicinal substances    signs of electricity in  an irritated
by, 338                              nerve, 380
formation of, 639                    Lungs, structure of, in reptiles, 216
KUCHENMEISTER, experiments on produc-             in man, 217
tion of teenia from cysticercus,  alteration of, after division of pneu522                                  mogastrics, 453
of cysticercus from eggs of tee- Lymph, 152, 300, 302
nia, 523                          quantity of, 305
Lymphatic system, 151, 299
Lachrymal secretion, 314
its function, 315                    MAGNUS, on proportions of oxygen and
Lactation, 315                             carbonic acid in blood, 227
variations in composition of milk  Male organs of generation, 540
during, 319                            development of, 640
Lacteals, 146, 151, 301                  Malpighian bodies of spleen, 191
and lymphatics, 153, 301             Mammalians, circulation in, 249
Larynx, action of, in respiration, 222   Mammary gland, structure of, 315
in formation of voice, 448           secretion of, 316
nerves of, 446                       MARCET, on excretine, 144
protective action of, 450            MAREY, M., experiments on arterial pulmovements in respiration, 222          sation, 267
LASSAIGNE, experiments on saliva, 115    Mastication, 105
analysis of lymph, 300                   unilateral, in ruminating animals,
Layers, external and internal, of blasto-       110
dermic membrane, 572                       retarded by suppressing saliva, 115
Lead, salts of, action in distinguishing  Meconium, 631
the biliary matters, 162, 163          Medulla oblongata, 366, 423
LEHMANN, on formation of carbonates in       ganglia of, 367, 368
blood, 60                              reflex action of, 424
on total quantity of blood, 213          effect of destroying, 426
on effects of non-nitrogenous diet, 92   development of, 622
Lens, crystalline, action of, 479        Meibomian glands, 311
LEUCKART, on production of cysticercus, Melanine, 87
523                                    Membrane, blastodermic, 572
LIEBIG, on absorption of different liquids Membrana granulosa, 551
under pressure, 292                    Membrana tympani, action of, 492
Ligament of the ovary, formation of, 645 Memory, connection of, with  cerebral
Limbs, formation of, in frog, 578          hemispheres, 406
in human embryo, 626            Menobranchus, size of blood-globules in,
Liver, vascularity of, 320                      202
lobules of, 320, 321                     gills of, 215
secreting cells, 322                     spermatozoa of, 541
formation of sugar in, 182           Menstruation, 554
congestion of, after feeding, 189        commencement and duration of, 555
development of, 642, 658                 phenomena of, 555
Liver cells, 322                             rupture of Graafian follicles in, 556
their action in secretion, 322           suspended during  pregnancy, 555
Liver-sugar, formation of, 182                  568
after death, 185                Mesenteric glands, 151, 299
in foetus, 633                  MICHEL, Dr. Myddleton, rupture of GraafLobules, of lung, 217                      ian follicle in menstruation, 556
of liver, 320                       Milk, 315
Local production of carbonic acid, 230       composition and properties of, 96,
of animal heat, 243                        316
Local variations of circulation, 286         microscopic characters, 317
LONGET, on interference of albuminose        souring and coagulation of, 318
with Trommer's test, 127               variations in, during lactation, 319
on sensibility of glosso-pharyngeal Milk-sugar, 67, 68
nerve, 444                             converted into lactic acid, 318




684                                 INDEX.
Mollusca, nervous system of, 357         Nervous filaments, of brain, 351
MOORE AND  PENNOCK, experiments on            of sciatic nerve, 352
movements of heart, 257                    motor and sensitive, 357
motion, 384                          Nervous force, how excited, 373
Motor cranial nerves, 433                     nature of, 381
Motor nervous fibres, 357                     mode of transmission, 381
Motor oculi communis, 434                Nervous tissue, two kinds of, 349
externus, 435                        Nervous irritability, 372
Movements, of stomach, 128                    how shown, 373
of intestine, 147                        duration of, after death, 373
of heart, 255                            exhausted by excitement, 374
of chest in respiration, 218             destroyed by woorara, 375
of glottis, 222                          distinct from muscular, 396
associated, 392                          nature of, 381
of foetus, 615                       Nervous system, 347
Mucosine, 85                                  general structure and functions of,
Mucous follicles, 309                           347-369
Mucous membrane, of stomach, 117              of radiata, 355
of intestine, 135                        of mollusca, 357
of tongue, 467                           of articulata, 358
of uterus, 598                           of vertebrata, 361
Mucus, 309                                    reflex action of, 356
composition and properties of, 310   Network, capillary, in Peyer's glands,
of mouth, 109                              145
of cervix uteri, 538                     in web of frog's foot, 278
Muscles, irritability of, 371                 in lobule of liver, 321
directly paralyzed by sulpho-cya- Newly-born infant, weight of, 640
nide of potassium, 372                 respiration in, 640
consentaneous action of, 414             nervous phenomena of, 671
of respiration, 218, 219                 comparative size of organs in, 672
Muscular fibres, of spleen, 191          NEWPORT, on temperature of insects, 238
of heart, spiral and circular, 259   Nitric acid, action of, on bile-pigment,
Muscular irritability, 371                      167
duration after death, 372                precipitation of uric acid by, 336
exhausted by repeated  irritation, Nitrogen, exhalation of, in respiration,
373                                  224
Musculine, 86                            Nutrition, 45-346
Nails, formation of, in embryo, 627      Obliteration, of ductus venosus, 660
NEGRIER, on rupture of Graafian follicle,     of ductus arteriosus, 662
in menstruation, 556                   Oculo-motorius nerve, 434
Nerve-cells, 354                         (Esophagus, paralysis of, after division
Nerves, division of, 353                        of pneumogastric, 447
inosculation of, 354                     development of, 634
irritability of, 373                 (Estruation, phenomena of, 553
spinal, 386                          Oleaginous substances, 70
cranial, 430                             in different kinds of food, 72
olfactory, 430                           condition  of, in the tissues and
optic, 431                                 fluids, 73, 76
auditory, 431                            partly produced in the body, 77
oculo-motorius, 434                      decomposed in the body, 78
patheticus, 435                               in the blood, 156
motor externus, 435                      indispensable as ingredients of the
masticator, 436                            food, 91
facial, 440                              insufficient for nutrition, 92
hypoglossal, 461                     Olfactory apparatus, 473
spinal accessory, 458                    protected by two sets of muscles, 504
trifacial (5th pair), 435                commissures, 364, 430
glosso-pharyngeal, 443               Olfactory ganglia, 402, 473
pneumogastric, 445                       their function, 402
superior and inferior laryngeal, 446  Olfactory nerves, 430, 473
great sympathetic, 498               Olivary bodies, 366
Nervous filaments, 350                   Omphalo-mesenteric vessels, 649-651




INDEX.                                   685
Ophthalmic ganglion, 498                  Paralysis, of sensitive nerves, by strychOptic ganglia, 364, 418                          nine, 397
Optic nerves, 431                             of voluntary motion and sensation,
decussation of, 420                         after destroying tuber annulare,
Optic thalami, 402                              422
development of, 622                       of pharynx and oesophagus, after secOrgans of special sense, 465, 467, 473,         tion of pneumogastrics, 447
477, 491                                of larynx, 449, 451
development of, 624                       of muscular coat of stomach, 457
Organic substances, 79                    Paraplegia, reflex action of spinal cord
indefinite chemical composition of,   in, 395
80                                 Parasites, 516
hygroscopic properties, 81                conditions of development of, 517
coagulation of, 82                        mode of introduction into body, 518
catalytic action, 82                      sexless, reproduction of, 518
putrefaction, 83                     Parotid saliva, 109
source and destination, 88           Parturition, 616, 617
digestion of, 125                    Par vagum, 445.  See Pneumogastric
Origin, of plants and animals, 511        Patheticus nerve, 435
of infusoria, 513                    PELOUZE, composition of glycogenic matof animal and vegetable parasites,   ter, 186
516                                Pelvis, development of, 636
of encysted entozoa, 518             PENNOCK  AND  MOORE, experiments on
Ossification of skeleton, 626               movements of heart, 257
Osteine, 86                               Pepsine, 85
Otic ganglion, 499                            in gastric juice, 123
Ovary,.525                               Perception of sensations, after removal of
of tsenia, 525                              hemispheres, 406
of frog, 531                              destroyed, after removal of tuber
of fowl, 535                                annulare, 422
of human female, 537, 538            Periodical ovulation, 547
Ovaries, descent of, in foetus, 644       Peristaltic motion, of stomach, 128
condition at birth, 646                   of intestine, 147
Oviparous and viviparous animals, dis-        of oviduct, 532, 535
tinction between, 647                       of Fallopian tubes, 557
Oxalic acid, produced in urine, 341       Perspiration, 312
Oxygen, absorbed in respiration, 225          daily quantity of, 313
daily quantity consumed, 224              composition and properties of, 313
state of solution in blood, 227           function, in regulating temperature,
dissolved by blood-globules, 227            313
absorbed by the tissues, 230         Pettenkofer's test for bile, 167
exhaled by plants, 242               Peyer's glands, 145
Pharynx, action of, in swallowing, 447
Palate, formation of, 637                     formation of, 633
Pancreatic juice, 137                     Phosphate of lime, its proportion in the
mode of obtaining, 138                      animal tissues and fluids, 58
composition of, 139                       in the urine, 335
action on fat, 139                        precipitated by alkalies, 336
daily quantity of, 138               Phosphate, triple, in putrefying urine,
Pancreatine, 85                             344
in pancreatic juice, 139             Phosphates, alkaline, 61
PANIZZA, experiment on absorption by               in urine, 335
bloodvessels, 148                           earthy, 58, 61
Paralysis, after division of anterior root         in urine, 335
of spinal nerve, 386                   of magnesia, soda, and potassa, 61
direct, after lateral injury of spinal Phosphorus, not a proximate principle, 47
cord, 388                          Physiology, definition of, 33
crossed, after lateral injury of brain, Phrenology, 410
389                                    objections to, 411
facial, 442                               practical difficulties of, 412, 413
of muscles, by sulpho-cyanide of Pigeon, after removal of cerebrum, 405
potassium, 372                              of cerebellum, 416
of motor nerves, by woorara, 396    Placenta, 605




686                                 INDEX.
Placenta, comparative anatomy of, 606   Putrefaction, 83
formation of, in human species, 607       of the urine, 341
foetal tufts of, 609                  Pyramids, anterior, of medulla oblonmaternal sinuses of, 609                gata, 366
injection of, from uterine vessels, 611
function of, 612                     Quantity, daily, of water exhaled, 55
separation of, in delivery, 617           of food, 97
Placental circulation, 650, 652               of saliva, 112
Plants, vital heat of, 238                    of gastric juice, 130
generative apparatus of, 524              of pancreatic juice, 138
Plasma of the blood, 205                      of bile, 170
Pneumic acid, 229                             of air used in respiration, 220
Pneumogastric nerve, 445                      of oxygen used in respiration, 224
its distribution, 446                     of carbonic acid exhaled, 232
action of, on pharynx and cesopha-        of lymph and chyle, 302-305
gus, 447                           of fluids secreted and reabsorbed, 305
on larynx, 448                       of material absorbed and discharged,
in formation of voice, 449              345
in respiration, 450                  of perspiration, 313
effect of its division, on respiratory    of urine, 332
movements, 451                          of urea, 327
cause of death after division of, 455     of urate of soda, 330
influence of, on oesophagus and sto- Quantity, entire, of blood in body, 213
mach, 457
Pneumogastric ganglion, 445               Rabbit, brain of, 365
POGGIALE, on glycogenic matter in but- Races of men, different capacity of, for
cher's meat, 187                          civilization, 408
Pons Varolii, 369                         Radiata, nervous system of, 355
Portal blood, quantity of fibrin in, 206   Rapidity of circulation, 284
temperature of, 244                       of transmission of nervous force,
Portal vein, in liver, 320, 321                 378, 379
development of, 658                  Reactions, of starch, 66
Posterior columns of spinal cord, 387         of sugar, 68
Primitive trace, 574                          of fat, 71
Production, of sugar in liver, 182            of saliva, 108, 109
of carbonic acid, 228                     of gastric juice, 123
of animal heat, 239                       of intestinal juice, 136
of urea in blood, 326                     of pancreatic juice, 139
of infusorial animalcules, 513            of bile, 158
of animal and vegetable parasites,        of mucus, 309
516                                     of milk, 317
Proximate principles, 45                      of urine, 336
definition of, 47                    Reasoning powers, 407
mode of extraction, 48                    in animals, 428
manner of their association, 49      Red globules of blood, 195
varying proportions of, 50           Reflex action, 356
three distinct classes of, 51             in centipede, 359
Proximate principles of the first class       of spinal cord, 392
(inorganic), 53                        of medulla oblongata, 424
of the second class (crystallizable       of tuber annulare, 427
substances of organic origin), 63      of brain, 428
of the third  class (organic sub-         of optic tubercles, 419
stances), 79                           in newly born infant, 671
Ptyaline, 108                             Regeneration, of uterine mucous memPuberty, period of, 549                         brane after pregnancy, 618
signs of, in female, 554                  of walls of uterus, 619-620
Pulsation, of heart, 252                  REGNAULT AND REISET, on absorption of
in living animal, 256                  oxygen, 225
of arteries, 264-268                 REID, Dr. John, experiment on crossing
Pupil, action of, 419, 484, 502             of streams in fcetal heart, 665
contraction of, after division of sym- Reproduction, 509
pathetic, 506                           nature and object of, 509, 511
Pupillary membrane, 624                       of parasites, 516




INDEX.                                   687
Reproduction, of tsenia, 520              Secretion, of sebaceous matter, 310
by germs, 521                             of perspiration, 312
Reptiles, circulation of, 248                 of the tears, 314
Respiration, 214                              of bile in foetus, 633
by gills, 215                        Segmentation of the vitellus, 571
by lungs, 216                        Seminal fluid, 540
by skin, 234                              mixed constitution of, 544
changes in air during, 224           Sensation, 382
changes in blood, 225                     remains after destruction of hemiof newly born infant, 670                   spheres, 406
Respiratory movements of chest, 218           lost after removal of tuber annulare,
of glottis, 222                             422
after section of pneumogastrics, 451,     special, conveyed by pneumogastric
453                                       nerve, 424, 448
after injury of spinal cord, 425     Sensation and motion, distinct seat of, in
Restiform bodies, 367                           nervous system, 384
Rhythm of heart's movements, 261              in spinal cord, 387
Rotation of heart during contraction, 260 Sensibility, of nerves to electric current,
Round ligament of the uterus, formation         373
of, 645                                 and excitability, definition of, 384
of liver, 660                             seat of, in spinal cord, 387
Rumination, movements of, 101, 110            in brain, 401
Rupture of Graafian follicle, 552             of facial nerve, 443
in menstruation, 556                      of hypoglossal nerve, 461
Rutting condition, in lower animals, 553      of spinal accessory, 459
of great sympathetic, 501
Saccharine substances, 67                 Sensibility, general and special, 462-465
in stomach and intestine, 134             special, of olfactory nerves, 430
in liver, 182                             of optic nerves, 431
in blood, 189                             of auditory nerves, 431
in urine, 339                             of lingual branch of 5th pair, 440
Saliva, 107                                   of glosso-pharyngeal, 445
different kinds of, 109                   of pneumnogastric, 446
daily quantity of, 111               Sensitive nervous filaments, 357
action on boiled starch, 112         Sensitive fibres, crossing of, in spinal cord,
variable, 112                               389
does not take place in stomach, 113       of facial nerve, source of, 443
physical function of saliva, 114     Sensitive cranial nerves, 434
quantity absorbed by different kinds Septa, inter-auricular and inter-ventriof food, 116                         cular, formation of, 663
Salivary glands, 109                      SEQUARD, on crossing of sensitive fibres
Salts, biliary, 160                         in spinal cord, 389
of the blood, 207                    Serum, of the blood, 209
of urine, 335                        Sexes, distinctive characters of, 526
Saponification, of fats, 71               Sexless entozoa, 518
SCHARLING, on diurnal variations in exha- Sexual generation, 524
lation of carbonic acid, 234           Shock, effect of, in destroying nervous
SCHULTZE, experiment on generation of   irritability, 372
infusoria, 516                         SIEBOLD, on production of tsenia from
Scolopendra, nervous system of, 358         cysticercus, 522
Sebaceous matter, 310                    Sight, 476
composition and properties of, 311        apparatus of, 477.  See Vision.
function of, 312                     Sinus terminalis, of area vasculosa, 587
in foetus, 627                       Sinuses, placental, 609
Secretion, 306                            Skeleton, development of, 625
varying activity of, 308             Skin, respiration by, 234
of saliva, 109                            sebaceous glands of, 311
of gastric juice, 120                     perspiratory glands of, 312
of intestinal juice, 136                  development of, 627
of pancreatic juice, 138             Smell, 473
of bile, 170, 319                         ganglia of, 402, 473
of sugar in liver, 182                    nerves of, 430, 473
of mucus, 309                            injured by division of 5th pair, 438




688                                 INDEX.
SMITH, Dr. Southwood, on cutaneous and  Sugar, composition of, 68
pulmonary exhalation, 313                   tests for, 68
Solar plexus of sympathetic nerve, 500        fermentation of, 69
Solid bodies, vision of with two eyes, 486    proportion in different kinds of food,
Sounds, of heart, 252                            70
how produced, 253                         source and destination, 70
vocal, how produced, 448                  produced in liver, 182
destroyed by section of inferior la-      discharged by urine in disease, 339
ryngeal nerves, 449            Sugar in liver, formation of, 182
of spinal accessory, 459             percentage of, 184
Sounds, acute and grave, transmitted by       produced in hepatic tissue, 185
membrana tympani, 492                       from glycogenic matter, 186
Special senses, 462, 465                      absorbed by hepatic blood, 188
Species, mode of continuation, 511            decomposed in circulation, 188
Spermatic fluid, 540                      Sulphates, alkaline, in urine, 335
mixed constitution of, 544           Sulphur of the bile, 164
Spermatozoa, 540                              not discharged with the feces, 179
movements of, 542                    Swallowing, 116
formation of, 543                         retarded by suppression of saliva,
Spina bifida, 625                                115
Spinal accessory, 458                         by division of pneumogastric, 457
sensibility of, 459                  Sympathetic nerve, 498
communication of, with pneumogas-        its distribution, 499
tric, 459                               sensibility and excitability of, 501
influence of, on larynx, 459, 460         influence of, on special senses, 502
Spinal column, formation of, 575, 625              on pupil, 502'Spinal cord, 382-400                               on nutrition of eyeball, 439
commissures of, 362, 363                      on nasal passages, 504
anterior and posterior columns, 363           on ear, 504, 505
origin of nerves from, 362, 363               on temperature  of particular
sensibility and excitability of, 387            parts, 505
crossed action of, 388                    reflex actions of, 508
reflex action of, 392
protective action of, 397            Tadpole, development of, 576
influence on sphincters, 398              transformation into frog, 578
effect of injury to, 398, 399        Tenia, 520
on respiration, 425                       produced by metamorphosis of cysformation of, in embryo, 575, 625           ticercus, 522
Spinal nerves, origin of, 362, 363            single articulation of, 525
Spleen, 190                               Tapeworm, 520
Malpighian bodies of, 191                 mode of generation, 521
extirpation of, 193                  Taste, 465
Spontaneous generation, 511                   nerves of, 440, 444, 467
Starch, 63                                    conditions of, 469
proportion of, in different kinds of      injury of, by paralysis of facial nerve,
food, 64                                  471
varieties of, 64                     Taurine, 164
reactions of, 66                     Tauro-cholate of soda, 163
action of saliva on, 112                  microscopic characters of, 162
digestion of, 134                    Tauro-cholic acid, 164
Starfish, nervous system of, 355          Tears, 314
Stereoscope, 487                              their function, 315
St. Martin, case of gastric fistula in, 119  Teeth, of serpent, 105
Strabismus, after division of motor oculi     of polar bear, 106
communis, 435                          of horse, 106
of motor externus, 435                    of man, 107
Striated bodies, 403                          first and second sets of, 672
Sublingual gland, secretion of, 109-110   Temperature of the blood, 236
Submaxillary ganglion, 498                    of different species of animals, 237
gland, secretion of, 109                  of the blood in different organs, 244
Sudoriparous glands, 312                      elevation of, after section of sympaSugar, 67                                       thetic nerve, 244, 505
varieties of, 67                     Tensor tympani, action of, 492, 505




INDEX.                                  689
Tests, for starch, 66                    Uric acid, 329, 336
for sugar, 68                       Urine, 331
for bile, 167                            general character and properties of,
Pettenkofer's, 167                         332
Testicles, 543                               quantity and specific gravity, 332
periodical activity of, in fish, 545     diurnal variations of, 333
development of, 640                      composition of, 334
descent of, 641                          reactions, 336
Tetanus, pathology of, 394                   interference with Trommer's test, 337
Thalami, optic, in rabbit, 365               accidental ingredients of, 338
in man, 402                              acid fermentation of, 341
function of, 403                         alkaline fermentation of, 342
Thoracic duct, 153                           final decomposition of, 345
Thoracic respiration, 425                Urinary bladder, paralysis and inflamTongue, motor nerve of, 461, 467               mation of, after injury to spinal
sensitive, 440, 444, 467                   cord, 399
Trichina spiralis, 518                       formation of, in embryo, 630
Tricuspid valve, 251. See Auriculo-ven- Urosacine, 87
tricular.                              Uterus, of lower animals, 537
Triple phosphate, in putrefying urine, 344   of human female, 538
Trommer's test for sugar, 68                 mucous membrane of, 599
interfered with by gastric juice, 127    changes in, after impregnation, 600
Tuber annulare, 422                          involution of, after delivery, 619
effect of destroying, 422                development of, in foetus, 644
action of, 423                           position of, at birth, 646
Tubercula quadrigemina, 364, 368, 418   Uterine mucous membrane, 598
reflex action of, 419                   tubules of, 599
crossed action of, 420                   conversion into decidua, 601
development of, 622                      exfoliation of, at the time of delivery,
Tubules of uterine mucous membrane,             617
599                                        its renovation, 618
Tufts, placental, 609
Tunica vaginalis testis, formation of, 643 Valve, Eustachian, 663, 664
Tympanum, function of, in hearing, 491       of foramen ovale, 667
Valves, cardiac, action of, 250
Umbilical cord, formation of, 615            cause of heart's sounds, 253
withering and separation of, 672    Vasa deferentia, formation of, 641
Umbilical hernia, 630                    Vapor, watery, exhalation of, 55
Umbilical vesicle, 580                       from lungs, 224
in human embryo, 581                     from the skin, 313
in chick, 588                       Variation, in quantity of bile in different
disappearance of, 615                      animals, 171, 174
Umbilical vein, formation of, 652            in production of liver-sugar, 184
obliteration of, 660                    in size of spleen, 190
Umbilicus, abdominal, 576                    in rapidity of coagulation of blood,
amniotic, 584                              209
decidual, 601                            in size of glottis in respiration, 222
Unilateral mastication, in  ruminating       in exhalation of carbonic acid, 232
animals, 110                               in temperature of blood in different
Urate of soda, 329                             parts, 243
its properties, source, daily quantity,  in composition of milk during lac&c., 330                                 tation, 319
Urates of potassa and ammonia, 330           in quantity of urea, 327
Urachus, 631                                 in density and acidity of urine, 332
Urea, 325                                Varieties of starch, 64
source of, 326                           of sugar, 67
mode of obtaining, 326                   of fat, 70
conversion into carbonate of am-         of biliary salts in different animals,
monia, 326                               164
daily quantity of, 327              Vegetable food, necessary to man, 90
diurnal variations in, 328          Vegetables, production of heat in, 238
decomposed in putrefaction of urine,     absorption of carbonic acid and ex343                                      halation of oxygen by, 33, 242
44




690                                INDEX.
Vegetable parasites, 516                 Vital phenomena, their nature and pecuVegetative functions, 42                   liarities, 38
Veins, 272                               Vitellus, 529
their resistance to pressure, 272        segmentation of, 571
absorption by, 148                       formation of, in ovary of fcetus, 646,
action of valves in, 275                   647
motion of blood through, 273-275    Vitelline circulation, 648, 649
rapidity of circulation in, 276          membrane, 528
omphalo-mesenteric, 649                  spheres, 571
umbilical, 652                       Vocal sounds, how produced, 448
vertebral, 655                       Voice, formation of, in larynx, 448
Venae cava, formation of, 656                lost, after division of spinal accesposition of, in foetus, 663                sory nerve, 449
Vena azygos, superior and. inferior, for- Volition, seat of, in tuber annulare, 422
mation of, 657                         Vomiting, peculiar, after division  of
Venous system, development of, 655         pneumogastrics, 457
Ventricles of heart, single in fish and
reptiles, 247, 248                Water, as a proximate principle, 53
double in birds and mammalians,          its proportion in the animal tissues
249                                      and fluids, 54
situation of, 250                        its source, 54
contraction and relaxation of, 256       mode of discharge from the body, 55
elongation during contraction, 257   Weight of organs, comparative, in newly
muscular fibres of, 259                born infant and in adult, 672
Vernix caseosa, 627                      White globules of the blood, 202
Vertebrata, nervous system of, 360           action of acetic acid on, 203
Vertebrm, formation of, 575, 625             sluggish movement of, in circulaVesicles, adipose, 74                          tion, 279
pulmonary, 217                       White substance, of nervous system, 350
seminal, 544, 643                        of Schwann, 350
Vesiculae seminales, 544                      of spinal cord, 362
formation of, 643                        of brain, insensible and inexcitable,
Vicarious secretion, non-existence of, 307      401
Vicarious menstruation, nature of, 307   Withering and separation of umbilical
Villi, of intestine, 146                   cord, after birth, 672
absorption by, 147                   Wolffian bodies, 638
of chorion, 594                          structure of, 639
Vision, 476                                   atrophy and disappearance of, 642
ganglia of, 364, 418                     vestiges of, in adult female, 645
nerves of, 431, 477                  WYMAN, Prof. Jeffries, on cranial nerves
apparatus of, 477                      of Rana pipiens, 433
distinct, at different distances, 479481                               Yellow color, of urine in jaundice, 339
circle of, 483                           of corpus luteum, 563
of solid bodies with both eyes, 485487                                Zona pellucida, 528
THE END.












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4                       BLANCHARD & LEA'S MEDICAL
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enlarged London edition. In one very handsome octavo volume, extra cloth, with four beautifully colored plates, and numerous wood-cuts. pp. 500. $3 00.
Has fairly established for itself a place among the is not perceptibly changed, the history of liver disclassical medical literature of England.-British  eases is made more complete, and is kept upon a level
and Foreign Medico-Chir. Review, July, 1857.    with the progress of modern science. It is the best
Dr. Budd's Treatise on Diseases of the Liver is work on Diseases of the Liver in any language.
now a standard work in Medical literature, and dur- London Med. Times and Gazette, June 27, 1857.
ing the intervals which have elapsed between the   This work, now the standard book of reference on
successive editions, the author has incorporated into  the diseases of which it treats, has been carefully
the text the most striking novelties which have cha- revised, and many new illustrations of the views of
racterized the recent progress of hepatic physiology  the learned author added in the present edition.and pathology; so that although the size of the book  Dublin Quarterly.Tournal, Aug. 1857.
BY THE SAME AUTHOR.
ON THE. ORGANIC DISEASES AND FUNCTIONAL DISORDERS O0
THE STOMACH. In one neat octavo volume, extra cloth. $1 50.
BUCKNILL (J. C.), M. D.,
Medical Superintendent of the Devon County Lunatic Asylum; and
DANIEL  H. TUKE, M. D.,
Visiting Medical Officer to the York Retreat.
A M/ANUAL OF PSYCHOLOGICAL MEDICINE; containing the Hlistory,
Nosology, Description, Statistics, Diagnosis, Pathology, and Treatment of INSANITY. With
a Plate. In one handsome octavo volume, of 536 pages. $3 00.
The increase of mental disease in its various forms, and the difficult questions to which it is
constantly giving rise, render the subject one of daily enhanced interest, requiring on the part of
the physician a constantly greater familiarity with this, the most perplexing branch of his profes-.
sion. At the same time there has been for some years no work accessible in this country, presenting the results of recent investigations in the Diagnosis and Prognosis of Insanity, and the greatly
improved methods of treatment which have done so much in alleviating the condition or restoring
the health of the insane. To fill this vacancy the publishers present this volume, assured that
the distinguished reputation and experience of the authors will entitle it at once to the confidence
of both student and practitioner. Its scope may be gathered from the declaration of the authors
that "their aim has been to supply a text- book which may serve as a guide in the acquisition oi
such knowledge, sufficiently elementary to be adapted to the wants of the student, and sufficiently
modern in its views and explicit in its teaching to suffice for the demands of the practitioner."
BENNETT  (J. HUGHES), Ml. D., F. R. S. E.,
Professor of Clinical Medicine in the University of Edinburgh, &c.
THE PATHOLOGY AND TREATMENT OF PULMONARY TUBEIRCULOSIS, and on the Local Medication of Pharyngeal and Laryngeal Diseases frequently mistakes
for or associated with, Phthisis. One vol. 8vo.,extra cloth, with wood-cuts. pp. 130. $1 25.
BENNETT  (HENRY), M. D.
A PRACTICAL TREATISE ON INFLAMMATION OF THE UTERUS,
ITS CERVIX AND APPENDAGES, and on its connection with Uterine Disease. To which
is added, a Review of the present state of Uterine Pathology.  Fifth American, from the third
English edition. In one octavo volume, of about 500 pages, extra cloth. $2 00. (Nowm  Ready.)
The ill health of the author having prevented the promised revision of this work, the present
edition is a reprint of the last, without alteration. As the volume has been for some time out of
print, gentlemen desiring copies can now procure them.
BOWMAN    (JOHN  E.)J  M.D.
PRACTICAL HANDBOOK OF MaEDICAL CHEMISTRY. Second American, from the third and revised English Edition. In one neat volume, royal 12mo., extra cloth,
with numerous illustrations. pp. 288. $1 25.
BY THE SAME AUTHOR.
INTRODUCTI)ON TO PRACTICAL CHEMISTRY, INCLUDING ANALYSIS. Second American, from the second and revised London edition. With nunerous illustrations. In one neat vol., royal 12mo., extra cloth. pp. 350. $1 25.
BEALE ON THE LAWS OF HEALTH IN RE- BUCKLER ON THE ETIOLOGY,PATHOLOGY,
LATION TO MIND AND BODY. A Series of   AND TREATMENT OF FIBRO-BRONCHILetters from an old Practitioner to a Patient. In   TIS AND RHEUMATIC PNEUMONIA.  In
one volume, royal 12mo., extra cloth. pp. 296.   one 8vo. volume, extra cloth. pp. 150. 61 25.
80 cents.                                      BLOOD  AND  URINE (MANUALS ON). BY
BUSHNAN'S PHYSIOLOGY OF ANIMAL AND    JOHN  WILLIAM   GRIFFITH, G. OWEN
VEGETABLE LIFE; a Popular Treatise on the   REESE, AND ALFRED  MARKWICK.  One
Functions and Phenomena of Organic Life. In   thick volume, royal 12mo., extra cloth, with
one handsome royal 12mo. volume, extra cloth,   plates. pp. 460. $1 25.
with over 100 illustrations. pp. 234. 80 cents.   BRODIE'S CLINICAL LECTURES ON  SURGERY.   vol.8vo. cloth. 350pp.  1 25.




AND SCIENTIFIC PUBLICATIONS.                                               5
BARCLAY (A. W.) M. D.,
Assistant Physician to St. George's Hospital, &c.
A MANUAL OF MEDICAL DIAGNOSIS; being an Analysis of the Signs
and Symptoms of Disease. In one neat octavo volume, extra cloth, of424 pages. $2 00. (Lately
issued.)
Of works exclusively devoted to this important The task of composing such a work is neither an
branch, our profession has at command, compara- easy nor a light one; but Dr. Barclay has performed
tively, but few, and, therefore, in the publication of it in a manner which meets our most unqualified
the present work, Messrs. Blanchard & Lea have approbation. He is no mere theorist; he knows his
conferred a great favor upon us. Dr. Barclay, from  work thoroughly, and in attempting to perform it,
having occupied, for a long period, the position of hasnotexceededhispowers.-.British Med. Journal,
Medical Registrar at St. George's Hospital, pos- Dec. 5, 1857.
sessed advantages for correct observation and reli-   We venture to predict that the work will be deable conclusions, as to the significance of symptoms, servedly popular, and soon become, like Watson's
which have fallen to the lot of but few, either in  Practice, an indispensable necessity to the practihis own or any other country. He has carefully  tioner.-N. A. Med. Journal Apil, 1858.
systematized the results of his observation of over                  
twelve thousand patients, and by his diligence and   An inestimable work of reference for the young
judicious classification, the profession has been practitioner and student.ashville Med. Journal,
presented with the most convenient and reliable May, 1858.
work on the subject of Diagnosis that it has been    We hope the volume will have an extensive cirour good fortune ever to examine; we can, there- culation, not among students of medicine only, but
fore, say of Dr. Barclay's work, that, from his sys- practitioners also. They will never regret a faithtematic manner of arrangement, his work is one of ful study of its pages.-CincinnatiLancet, Mar.'58.
the best works " for reference" in the daily emer-   An important acquisition to medical literature.
gencies of the practitioner, with which we are ac- It s a work of high merit, both from the vast imquainted; but, at the same time, we would recom- portance of the subject upon which it treats, and
mend our readers, especially the younger ones, to also from the real ability displayed in its elaboraread thoroughly and study diligently thewole work, tion. In conclusion, let us bespeak for this volume
and the "emergencies" will not occur so often.-  that attention of every student of our art which it
Southern Med. and Surg. Journ., March, 1858.       so richly deserves - that place in every medical
To give this information, to supply this admitted  library which it can so well adorn.-Peninsular
deficiency, is the object of Dr. Barclay's Manual. Medical Journal, Sept. 1858.
BARLOW  (GEORGE H.), M. D.
Physician to Guy's Hospital, London, &c.
A MANUAL OF THE PRACTICE OF MEDICINE. With Additions by D.
F. CONDIE, M.D., author of" A Practical Treatise on Diseases of Children," &c. In one handsome octavo volume, leather, of over 600 pages. $2 75.
We recommendDr. Barlow'sManual in the warm- will be found hardly less useful to the experienced
est manner as a most valuable vade-mecum. We physician. The American editor has added to the
have had frequent occasion to consult it, and have work three chapters-on Cholera Infantum, Yellow
found it clear, concise, practical, and sound. It is Fever, and Cerebro-spinal Meningitis. These addieminently a practical work, containing all that is tions, the two first of which are indispensable to a
essential, and avoiding useless theoretical discus- work on practice destined for the profession in this
sion. The work supplies what has been for some country, are executed with great judgment and fitime wanting, a manual of practice based upon mo- delity, by Dr. Condie, who has also succeeded hapdern discoveries in pathology and rational views of pily in imitating the conciseness and clearness of
treatment of disease. It is especially intended for style which are such agreeable characteristics of
the use of students and junior practitioners, but it the original book.-Boston Mled. and Surg. Journal.
BARTLETT  (ELISHA), VM. D.
THE H-ISTORY, DIAGNOSIS, AND TREATMENT OF THE FEVERS
OF THE UNITED STATES.  A new and revised edition.  By ALONZO CLARK, M. D., Prof.
of Pathology and Practical Medicine in the N. Y. College of Physicians and Surgeons, &c. In
one octavo volume, of six hundred pages, extra cloth. Price $3 00.
It is the best work on fevers which has emanated  logy. His annotations add much to the interest of
from the American press, and the present editor has the work, and have brought it well up to the condicarefully availed himself of all information exist- tion of the science as it exists at the present day
ing upon the subject in the Old and New World, so in regard to this class of diseases.-Southern Meid.
that the doctrines advanced are brought down to the and Surg. Journal, Mar. 1857.
latest date in the progress of this department of   It is a work of great practical value and interest
Medical Science.-London Med. Times and Gazette, containing much that is new relative to the several
May 2, 1857.                                      diseases of which it treats, and, with the additions
This excellent monograph on febrile disease, has of the editor, is fully up to the times. The distinctstood deservedly high since its first publication. It ive features of the different forms of fever are plainly
will be seen that it has now reached its fourth edi- and forcibly portrayed, and the lines of demarcation
tion under the supervision of Prof. A. Clark, a gen- carefully and accurately drawn, and to the Ameritleman who, from the nature of his studies and pur- can practitioner is a more valuable and safe guide
suits, is well calculated to appreciate and discuss than any work on fever extant —Ohio Med. and
the many intricate and difficult questions in patho- Surg. Journal, May, 1857.
BROWN (ISAAC BAKER),
Surgeon-Accoucheur to St. Mary's Hospital, &c.
ON SOME DISEASES OF WOMEN ADMITTING OF SURGICAL TREATMENT. With handsome illustrations.  One vol. 8vo., extra cloth, pp. 276. $1 60.
Mr. Brown has earned for himself a high reputa- and merit the careful attention of every surgeontion in the operative treatment of sundry diseases accoucheur.-Association Journal.
and injuries to which females are peculiarly subject.
We can truly say of his work that it is an important   We have no hesitation in recommending this book
addition to obstetrical literature. The operative to tte careful attention of all surgeons who make
suggestions and contrivances which Mr. Brown de- fenale compiaints a part of their study and practien.
scribes, exhibit much practical sagacity and skill, -Dublin Quarterly Journal.




6                       BLANGHARD & LEA'S MEDICAL
CARPENTER  (WILLIAM   B.), M. D., F. R. S., &c.,
Examiner in Physiology and Comparative Anatomy in the University of London.
PRINCIPLES OF HUMAN PHYSIOLOGY; with their chief applications to
Psychology, Pathology, Therapeutics, Hygiene, and Forensic Medicine. A new American, from
the last and revised London edition. With nearly three hundred illustrations. Edited, with additions, by FRANCIS GURNEY SMITH, M.D., Professor of the Institutes of Medicine in the Pennsylvania Medical College, &c. In one very large and beautiful octavo volume, of about nine hundred
large pages, handsomely printed and strongly bound in leather, with raised bands. $4 25.
In the preparation of this new edition, the author has spared no labor to render it, as heretofore,
a complete and lucid exposition of the most advanced condition of its important subject. The
amount of the additions required to eftect this object thoroughly, joined to the former large size of
the volume, presenting objections arising from the unwieldy bulk of the work, he has omitted all
those portions not bearing directly upon HUMAN PHYSIOLOGY, designing to incorporate them in
his forthcoming Treatise on GENERAL PHYSIOLOGY. As a full and accurate text-book on the Physiology of lMan, the work in its present condition therefore presents even greater claims upon
the student and physician than those which have heretofore won for it the very wide and distinguished favor which it has so long enjoyed. The additions of Prof. Smith will be found to supply
whatever may have been wanting to the American student, while the introduction of many new
illustrations, and the most careful mechanical execution, render the volume one of the most attractive as yet issued.
For upwards of thirteen years Dr. Carpenter's   To eulogize this great work would be superfluous.
work has been considered by the profession gene- We should observe, however, that in this edition
rally, both in this country and England, as the most the author has remodelled a large portion of the
valuable compendium on the subject of physiology former, and the editor has added much matter of inin our language. This distinction it owes to the high terest, especially in the form of illustrations. We
attainments and unwearied industry of its accom- may confidently recommend it as the most complete
plished author. The present edition (which, like the work on Human Physiology in our language.last American one,was prepared by the author him- Southern Med. and Surg. Journal.
self), is the result of such extensive revision, that it   The most complete work on the science in our
may almost be considered a new work. We need language.m. Med Journal
hardly say, in concluding this brief notice, that while.     
the work is indispensable to every student of medi-   The most complete work now extant in our 1an9
cine in this country, it will amply repay the practi- guage.-N. 0. Med. Register.
tioner for its perusal by the interest and value of its   The best text-book in the language on this excontents.-Boston Med. and Surg. Journal.         tensive subject.-London Med. Times.
This is a standard work-the text-book used by all   A complete cyclopadia of this branch of science,
medical students who read the English language.   N. Y. Med. Times.
It has passed through several editions in order to   The profession of this country, and perhaps also
keep pace with the rapidly growing science of Phy- of Europe, have anxiously and for some time awaited
siology. Nothing need be said in its praise, for its the announcement of this new edition of Carpenter's
merits are universally known; we have nothing to Human Physiology. His former editions have for
say of its defects, for they only appear where the many years been almost the only text-book on Physcience of which it treats is incomplete.-Western siology in all our medical schools, and its circulaLancet.                                          tion among the profession has been unsurpassed by
The most complete exposition of physiology which any work in any department of medical science.
any language can at present give.-Brit. and For.  It is quite unnecessary for us to speak of this
Med.-Ca rurg. Review.                            work as its merits would justify. The mere announcement of its appearance will afford the highest
The greatest, the most reliable, and the best book pleasure to every student of Physiology, while its
on the subject which we know of in the English perusal will be of infinite service in advancing
language.-Stethoscope.                           physiological science.-Ohio Med. and Surg. Journ.
BY THE SAME AUTHOR.
PRINCIPLES OF COMPARATIVE PHYSIOLOGY. New American, from
the Fourth and Revised London edition. In one large and handsome octavo volume, with over
three hundred beautiful illustrations. pp. 752. Extra cloth, $4 80; leather, raised bands, $5 25.
The delay which has existed in the appearance of this work has been caused by the very thorough
revision and remodelling which it has undergone at the hands of the author, and the large number
of new illustrations which have been prepared for it. It will, therefore, be found almost a new
work, and fully up to the day in every department of the subject, rendering it a reliable text-book
for all students engaged in this branch of science. Every effort has been made to render its typographical finish and mechanical execution worthy of its exalted reputation, and creditable to the
mechanical arts of this country.
This book should not only be read but thoroughly no man, we believe, could have brought to so sucstudied by every member of the profession. None cessful an issue as Dr. Carpenter. It required for
are too wise or old, to be benefited thereby. But its production a physiologist at once deeply read in
especially to the younger class would we cordially the labors of others, capable of taking a general,
commend it as best fitted of any work in the English critical, and unprejudiced view of those labors, and
tanguage to qualify them for the reception and coin- of combining the varied, heterogeneous materials at
prehension of those truths which are dailybeing de- his disposal, so as to form an harmonious whole.
veloped in physiology.-Medical Counsellor.       We feel that this abstract can give the reader a very
Without pretending to it, it is an encyclopedia of imperfect idea of the fulness of this work, and no
the subject, accurate and complete in all respects-  idea of its unity, of the admirable manner in which
a truthful reflection of the advanced state at which material has been brought, from  the  most various
the science has now arrived.-Dublin Quarterly  sources, to conduce to its completeness, of the lucidJournal of Medical Science.                      ity of the reasoning it contains, or of the clearness
of language in which the whole is clothed. Not the
A truly magnificentwork-in itself a perfect phy- profession only, but the scientific world at large,
siological study-.Rantking's iAlbstract,        mmust feel deeply indebted to Dr. Carpenter for this
This work stands without its fellow. It is one great work. It must, indeed, add largely even to
few men in Earopecould have undertaken; it is one his high reputation.-Medical Times.




AND  SCIENTIFIC  PUBLICATIONS.                                       7
CARPENTER  (WILLIAM  B.), M. D., F. R. S.,
Examiner in Physiology and Comparative Anatomy in the University of London.
THE MICROSCOPE AND ITS REVELATIONS. With an Appendix containing the Applications of the Microscope to Clinical Medicine, &c. By F. G. SMITH, M. D.
Illustrated by four hundred and thirty-four beautiful engravings on wood. In one large and very
handsome octavo volume, of 724 pages, extra cloth, $4 00; leather, $4 50.
Dr. Carpenter's position as a microscopist and physiologist, and his great experience as a teacher,
eminently qualify him to produce what has long been wanted-a good text-book on the practical
use of the microscope. In the present volume his object has been, as stated in his Prefice, " to
combine, within a moderate compass, that information with regard to the use of his'tools,' which
is most essential to the working microscopist, with such an account of the objects best fitted for
his study, as might qualify him to comprehend what he observes, and might thus prepare him to
benefit science, whilst expanding and refreshing his own mind."  That he has succeeded in accomplishing this, no one acquainted with his previous labors can doubt.
The great importance of the microscope as a means of diagnosis, and the number of microscopists who are also physicians, have induced the American publishers, with the author's approval, to
add an Appendix, carefully prepared by Professor Smith, on the applications of the instrument to
clinical medicine, together with an account of American Microscopes, their modifications and
accessories. This portion of the work is illustrated with nearly one hundred wood-cuts, and, it is
hoped, will adapt the volume more particularly to the use of the American student.
Every care has been taken in the mechanical execution of the work, which is confidently presented as in no respect inferior to the choicest productions of the London press.
The mode in which the author has executed his intentions may be gathered from the following
condensed synopsis of the
CONTENTS.
tNTRODuCTiON-History of the Microscope.  CHAP. I. Optical Principles of the Microscope.
CHAP. II. Construction of the Microscope.  CHAP. III. Accessory Apparatus. CHAP. IV.
Management of the Microscope  CHAP. V. Preparation, Mounting, and Collection of Objects.
CHAP. VI. Microscopic Forms of Vegetable Life-Protophytes. CHAP. VII. Higher Cryptoga.
mia. CHAP. VIII. Phanerogamic Plants. CHAP. IX. Microscopic Forms of Animal Life-Pro.
tozoa-Animalcules. CHAP. X. Foraminifera, Polycystina, and Sponges. CHAP. XI. Zoophytes.
CHAP. XII. Echinodermata. CHAP. XIII. Polyzoa and Compound Tunicata. CHAP. XIV.
Molluscous Animals Generally. CHAP. XV. Annulosa. CHAP. XVI. Crustacea. CHAP. XVII.
Insects and Arachnida. CHAP. XVIII. Vertebrated Animals. CHAP. XIX. Applications of the
Microscope to Geology. CHAP. XX. Inorganic or Mineral Kingdom-Polarization. APPENDIX,
Microscope as a means of Diagnosis-Injections-Microscopes of American Manufacture.
Those who are acquainted with Dr. Carpenter's medical work, the additions by Prof. Smith give it
previous writings on Animal and Vegetable Physio- a positive claim upon the profession, for which we
logy, will fully understand how vast a store of know- doubt not he will receive their sincere thanks. Inledge he is able to bring to bear upon so comprehen- deed, we know not where the student of medicine
sive a subject as the revelations of the microscope; will find such a complete and satisfactory collection
and even those who have no previous acquaintance of microscopic facts bearing upon physiology and
with the construction or uses of this instrument, practical medicine as is contained in Prof. Smith's
will find abundance of information conveyed in clear appendix; and this of itself, it seems to us, is fully
and simple language. —Med. Times and Gazette. worth the cost of the volume.-Louisville feidical
Although originally not intended as a strictly  Review, Nov. 1856.
BY THE SAME AUTHOR.
ELEMENTS (OR MANUAL) OF PHYSIOLOGY, INCLUDING PHYSIOLOGICAL ANATOMY. Second American, from a new and revised London edition. With
one hundred and ninety illustrations. In one very handsome octavo volume, leather. pp. 586.
$3 00.
In publishing the first edition of this work, its title was altered from that of the London volume,
by the substitution of the word " Elements" for that of " Manual," and with the author's sanction
the title of " Elements" is still retained as being more expressive of the scope of the treatise.
To say that it is the best manual of Physiology   Those who have occasion for an elementary treanow before the public, would not do sufficient justice tise on Physiology, cannot do better than to possess
to the author.-Buffalo lMedical Journal.      themselves of the manual of Dr. Carpenter.-Medical
In his former works it would seem that he had Examiner.
exhausted the subject of Physiology. In the present,  The best and most complete expos6 of modern
he gives the essence, as it were, of the whole.-N. Y. Physiology, in one volume, extant in the English
Journal of Medicies.                          language.-St. Louis Medical Journal.
BY THE SAME AUTHOR. (Preparing.)
PRINCIPLES OF GENERAL PHYSIOLOGY, INCLUDING ORGANIC
CHEMISTRY AND HISTOLOGY. With a General Sketch of the Vegetable and Animal
Kingdom. In one large and very handsome octavo volume, with several hundred illustrations.
The subject of general physiology having been omitted in the last editions ot the author's " Comparative Physiology" and "Human Physiology," he has undertaken to prepare a volume which
shall present it more thoroughly and fully than has yet been attempted, and which may be regarded
as an introduction to his other works.
BY THE SAME AUTHOR.
A PRIZE ESSAY ON TH   E USE OF ALCOHOLIC LIQUORS IN HEALTH
AND DISEASE. New edition, with a Preface by D. F. CONDIE, M. D., and explanations f
scientific words. In one neat 12mo. volume, extra cloth. pp. 178. 50 cents.




8                      BLANCHARD & LEA'S MEDICAL
CONDIE (D. F.), M. D., &c.
A PRACTICAL TREATISE ON THE DISEASES OF CHILDREN. Fifth
edition, revised and augmented. In one large volume, 8vo., leather, of over 750 pages. $3 25.
(Just Issued, 1859.)
In presenting a new and revised edition of this favorite work, the publishers have only to state
that the author has endeavored to render it in every respect " a complete and faithful exposition of
the pathology and therapeutics of the maladies incident to the earlier stages of existence-a full
and exact account of the diseases of infancy and childhood."  To accomplish this he has subjected
the whole work to a careful and thorough revision, rewriting a considerable portion, and adding
several new chapters. In this manner it is hoped that any deficiencies which may have previously
existed have been supplied, that the recent labors of practitioners and observers have been thoroughly incorporated, and that in every point the work will be found to maintain the high reputation
it has enjoyed as a complete and thoroughly practical book of reference in infantile affections.
A few notices of previous editions are subjoined.
Dr. Condie's scholarship, acumen, industry, and   We pronounced the first edition to be the best
practical sense are manifested in this, as in all his work on the diseases of children in the English
numerous contributions to science.-Dr. Holmes's language, and, notwithstanding all that has been
Report to the American Medical Association.    published, we still regard it in that light. —Medical
Taken as a whole, in our judgment, Dr. Condie's Examiner.
Treatise is the one from the perusal of which the   The value of works by native authors on the dispractitioner in this country will rise with the great- eases which the physician is called upon to combat,
est satisfaction.-Western Journal of Medicine and will be appreciated by all; and the work of Dr. ConSurgery.                                        die has gained for itself the character of a safe guide
One of the best works upon the Diseases of Chil- for students, and a useful work for consultation by
dren in the English language.-Western Lancet.    those engaged in practice.-N. Y. Med. Times.
le feel assured from actual experience that no   This is the fourth edition of this deservedly popuphysician's library can be complete without a copylar treatise. During the interval since the last di
of this work.-N. Y. Journal of Medicine.   OPYtion, it has been subjected to a thorough revision
by the author; and all new observations in the
A veritable pasdiatric encyclopedia, and an honor pathology and therapeutics of children have been
to American medical literature.-Ohio Medical and included in the present volume. As we said before,
Surgical Journal.                               we do not know of a better book on diseases of ehilWe feel persuaded that the American medical pro- dren, and to a large part of its recommendations we
fession will soon regard it not only as a very good, yield an unhesitating concurrence. —Buffalo Med.
but as the VERY BEST " Practical Treatise on the Journal.
Diseases of Children." —American Medical Journal,  Perhaps the most full and complete work now beIn the department of infantile therapeutics, the fore the profession of the United States; indeed, we
work of Dr. Condie is considered one of the best may say in the English language. It is vastly supewhich has been published in the English language. rior to most of its predecessors.-Transylvatia Mied.
-The Stethoscope.                              Journal.
CHRISTISON  (ROBERT), M. D., V. P. R. S. E., &c.
A  DISPENSATORY; or, Commentary on the Pharmacopoeias of Great Britain
and the United States; comprising the Natural History, Description, Chemistry, Pharmacy, Actions, Uses, and Doses of the Articles of the Materia Medica. Second edition, revised and improved, with a Supplement containing the most important New Remedies. With copious Additions, and two hundred and thirteen large wood-engravings. By R. EGLESFELD GRIFFITH, M. D.
In one very large and handsome octavo volume, leather, raised bands, of over 1000 pages. $3 50.
COOPER  (BRANSBY  B.), F. R. S.
LECTURES ON THE PRINCIPLES AND PRACTICE OF SURGERYIn one very large octavo volume, extra cloth, of 750 pages. $3 00.
COOPER  ON  DISLOCATIONS AND  FRAC- COPLAND ON THE CAUSES, NATURE, AND
TURES OF THE JOINTS.-Edited by BRANSBY   TREATMENT OF PALSY AND APOPLEXY,
B. COOPER, F. R. S., &c. With additional Ob-   In one volume, royal 12mo., extra cloth. pp. 326.
servations by Prof. J. C. WARREN. A new Ame-   80 cents.
rican edition. In one handsome octavo volume, CLME   O   F               T I   I       OI,
extra cloth, of about 500 pages, with numerous    MER ON         FEVANRS; TRE ATMENT  In one
illustrations on wood. $3 25.                   octavo
illustrations on wood. $3 25.                   PATHOLOGY,  AND  TREATMENT    In one
COOPER ON THE ANATOMY AND DISEASES                      volume,leather 600. 
OF THE BREAST, with twenty-five Miscellane- COLOMBAT DE L'ISERE ON THE DISEASES
ous and Surgical Papers. One large volume, im-   OF FEMALES, and on the special Hygiene of
perial 8vo., extra cloth, with 252 figures, on 36   their Sex. Translated, with many Notes and Adplates. $2 50.                                  ditions, by C. D. MEIGS, M. D. Second edition,
COOPER  ON  THE STRUCTURE AND DIS-   revised and improved. In one large volume, ocEASES OF THE  TESTIS, AND  ON  THE    tavo, leather, with numerous wood-cuts. pp. 720.
THYMUS GLAND. One vol. imperial 8vo., ex-   $3 50.
tya cloth, with 177 figures on 29 plates. $2 00.
CARSON  (JOSEPH), M. D.,
Professor of Materia Medica and Pharmacy in the University of Pennsylvania.
SYNOPSIS OF THE COURSE OF LECTURES ON MATERIA MEDICA
AND PHARMACY, delivered in the University of Pennsylvania. Second and revised edition. In one very neat octavo volume, extra cloth, of 208 pages. $1 50.
CURLING  (T. B.), F.R.S.,
Surgeon to the London Hospital, President of the Hunterian Society, &e.
A PRACTICAL TREATISE ON DISEASES OF THE TESTIS, SPERMATIC CORD, AND SCROTUM. Second American, from the second and enlarged English edition. In one handsome octavo volume, extra cloth, with numerous illustrations. pp. 420. $2 0W.




AND SCIENTIFIC PUBLICATIONS.                                             9
CHURCHILL  (FLEETWOOD), M. D., M. R. 1. A.
ON THE TTHEORY AND PRACTICE OF MIDWIFERY. A new American
froil the fourth revised and enlarged London edition. With Notes and Additions, by D. FRANCIS
CONDIE, M. D., author of a "Practical Treatise on the Diseases of Children," &c. With 194
illustrations. In one very handsome octavo volume, leather, of nearly 700 large pages.  $3 50.
(Now Ready, October, 1860.)
This work has been so long an established favorite, both as a text-book for the learner and as a
reliable aid in consultation for the practitioner, that in presenting a new edition it is only necessary
to call attention to the very extended improvements which it has received. Having had the benefit
of two revisions by the author since the last American reprint, it has been materially enlarged, and
Dr. Churchill's well-known conscientious industry is a guarantee that every portion has been thoroughly brought up with the latest results of European investigation in all departments of the science and art of obstetrics. The recent date of the last Dublin edition has not left much of novelty
for the American editor to introduce, btt he has endeavored to insert whatever has since appeared,
together with such matters as his experience has shown him would be desirable for the American
student, including a large number of illustrations.  With the sanction of the author he has added
in the form of an appendix, some chapters from a little "Manual for Midwives and Nurses," recently issued by Dr. Churchill, believing that the details there presented can hardly fail to prove of
advantage to the junior practitioner.  The result of all these additions is that the work now contains fully one-half more matter than the last American edition, with nearly one-half more illustrations, so that notwithstanding the use of a smaller type, the volume contains almost two hundred
pages more than before.
No effirt has been spared to;.secure an improvement in the mechanical execution of the work
equal to that which the text has received, and the volume is confidently presented as one of the
handsomest that has thus far been laid before the American profession; while the very low price
at which it is offered should secure for it a place in every lecture-room and on every office table.
A better book in which to learn these important   The most popular work on midwifery ever issued
points we have not met than Dr. Churchill's. Every  from the American press.-Charleston Med. Journal.
page of it is full of instruction; the opinion of all   Were we reduced to the necessity of having but
writers of authority is given on questions of diffi-  tne work on midwifery, and permitted to choose,
culty, as well as the directions and advice of the  we would unhesitatingly take Churchill. —Western
learned autnor himself, to which he adds the result  elsed. and Surg. Journal.
of statistical inquiry, putting statistics in their pro     
per place and giving them their due weight, and no  is impossible to conceive a more  seful and
more. We have never read a book more free from    egant manual than Dr. Churchill's Practice of
professional jealousy than Dr. Churchill's. It ap-  lidwifery.-Provincial Medical Journal.
pears to be written with the true design of a book on   Certainly, in our opinion, the very best work on
medicine, viz: to give all that is known on the sub- he subject which exists.-N. Y. Annalist.
ject of which he treats, both theoretically and prac-   No work holds a higher position, or is more detically, and to advance such opinions of his own as serving of being placed in the hands of the tyro,
he believes will benefit medical science, and insure the advanced student, or the practitioner.-Medical
the safety of the patient. We have said enough to  Examiner.
convey to the profession that this book of Dr. Chur-.
chill's is admirably suited for a book of reference   Previous editions, under the editorial supervision
for the practitioner, as well as a text-book for the of Prof. R. M. Huston, have been received with
student, and we hope it may be extensively pur- marked favor, and they deserved it; but this, rechased amongst our readers. To them we most printed from a very late Dublin edition, carefully
strongly recommend it. —Dublin M         Pedical Press,
strongly recommend it.- Dbublin  Medical Press, revised and brought up by the author to the present
June 20, 180.                                   time, does present an unusually accurate and able
Junev' 20', 1860,              exposition of every important particular embraced
To bestow praise on a book that has received such in the department of midwifery. * * The clearnhssA
marked approbationwould be superfluous. We need directness, and precision of its teachings, togetnier
only say, therefore, that if the first edition was with the great amount of statistical research which
thought worthy of a favorable reception by the its text exhibits, have served to place it already in
medical public, we can confidently affirm that this the foremost rank of works in this department of rewill be found much more so. The lecturer, the medial science.-N. 0. Med. and Surg. Journal.
practitioner, and the student, may all have recourse   In our opinion, it forms one of the best if not the
to its pages, and derive from their perusal much in- very best text-book and epitome of obstetric science
terest and instruction in everything relating to theo- which we at present possess in the English lanretical and practical midwifery.-Dublin Quarterly guage.-Monthly Journal of Medical Science.,journal of Medical Science.
oursnal of Medical Science.           The clearness and precision of style in which it is
A work of very great merit, and such as we can  written, and the great amount of statistical research
confidently recommend to the study of every obste- which it contains, have served to place it in the first
tric practitioner.-London Medical Gazette,       rank of works in this departmentof medical science.
— N. Y. Journal of Medicine.
This is certainly the most perfect system extant.
It is the best adapted for the purposes of a text-   Few treatises will be found better adapted as a
book, and that which he whose necessities confine text-book for the student, or as a manual for the
him to one book, should select in preference to all frequent consultation of the young practitioner. —
others.~-Southern Miedical and Surgical Journal.   American Medical Journal.
BY THE SAME AUTHOR. (Lately Published.)
ON THE DISEASES OF INFANTS AND CHILDREN. Second American
Edition, revised and enlarged by the author. Edited, with Notes, by W. V. KEATING, M. D. In
one large and handsome volume, extra cloth, of over 700 pages. $3 00, or in leather, $3 25.
In preparing this work a second time for the American profession, the author has spared no
labor in giving it a very thorough revision, introducing several new chapters, and rewriting others,
while every portion of the volume has been subjected to a severe scrutiny. The efforts of the
American editor have been directed to supplying such information relative to matters peculiar
to this country as might have escaped the attention of the author, and the whole may, therefore, be safely pronounced one of the most complete works on the subject accessible to the American Profession. By an alteration in the size of the page, these very extensive additions have
been accommodated without unduly increasing the size of the work.
BY THE SAME AUTHOR.
ESSAYS ON THE PUERPERAL FEVER, AND OTHER DISEASES PECULIAR TO WOMEN. Selected from the writings of British Authors previous to the close of
the Eighteenth Century. In one neat octavo volume, extra cloth, of about 450 pages. $2 50.




10                      BLANCHARD & LEA'S MEDICAL
CHURCHILL  (FLEETWOOD), M. D., M. R.. IA., &c.
ON THE DISEASES OF WOMEN; including those of Pregnancy and Childbed. A new American edition, revised by the Author. With Notes and Additions, by D. FRANCIS CONDIE, M. D., author of "A Practical Treatise on the Diseases of Children."  With numerous illustrations. In one large and handsome octavo volume, leather, of 768 pages. $3 00.
This edition of Dr. Churchill's very popular treatise may almost be termed a new work, so
thoroughly has he revised it in every portion. It will be found greatly enlarged, and completely
brought up to the most recent condition of the subject, while the very handsome series of illustrations introduced, representing such pathological conditions as can be accurately portrayed, present
a novel feature, and afford valuable assistance to the young practitioner.  Such additions as appeared desirable for the American student have been made by the editor, Dr. Condie, while a
marked improvement in the mechanical execution keeps pace with the advance in all other respects
which the volume has undergone, while the price has been kept at the former very moderate rate.
It comprises, unquestionably, one of the most ex- extent that Dr. Churchill does. His, indeed, is the
act and comprehensive expositions of the present only thorough treatise we know of on the subject;
state of medical knowledge in respect to the diseases and it may be commended to practitioners and stuof women that has yet been published.-Am. Journ. dents as a masterpiece in its particular department.
IMed. Sciences, July, 1857.                      -The Western Journal of Medicine and Surgery.
This work is the most reliable which we possess   As a comprehensive manual for students, or a
on this subject; and is deservedly popular with the work of reference for practitioners, it surpasses any
profession.-Charleston aed. Journal, July, 1857.   other that has ever issued on the same subject from
We know of no author who deserves that appro- the British press. —.Dublin Quart. Journal.
bation, on " the diseases of females," to the same
DICKSON  (S.  H.), M. D.,
Professor of Practice of Medicine in the Jefferson Medical College, Philadelphia.
ELEMENTS OF MEDICINE; a Compendious View of Pathology and Thompeutics, or the History and Treatment of Diseases. Second edition, revised. In one large and
handsome octavo volume, of 750 pages, leather. $3 75. (Just Issued.)
The steady demand which has so soon exhausted the first edition of this work, sufficiently shows
that the author was not mistaken in supposing that a volume of this character was needed-an
elementary manual of practice, which should present the leading principles of medicine with the
practical results, in a condensed and perspicuous manner. Disencumbered of unnecessary detail
and fruitless speculations, it embodies what is most requisite for the student to learn, and at the
same time what the active practitioner wants when obliged, in the daily calls of his profession, to
refresh his memory on special points. The clear and attractive style of the author renders the
whole easy of comprehension, while his long experience gives to his teachings an authority everywhere acknowledged. Few physicians, indeed, have had wider opportunities for observation and
experience, and few, perhaps, have used them to better purpose. As the result of a long life devoted to study and practice, the present edition, revised and brought up to the date of publication,
will doubtless maintain the reputation already acquired as a condensed and convenient American
text-book on the Practice of Medicine.
DRUITT  (ROBERT), M. t. C. S., &c.
TH1E PRINCIPLES AND PRACTICE OF MODERN SURGERY. A new
and revised American from the eighth enlarged and improved London edition. Illustrated with
four hundred and thirty-two wood-engravings. In one very handsomely printed octavo volume,
leather, of nearly 700 large pages. $3 50. (Now Ready, October, 1860.)
A work which like DRUITT'S SURGERY has for so many years maintained the position of a leading favorite with all classes of the profession, needs no special recommendation to attract attention
to a revised edition.  It is only necessary to state that the author has spared no pails to keep the
work up to its well earned reputation of presenting in a small and convenient compass the latest
condition of every department of surgery, considered both as a science and as an art; and that the
services of a competent American editor have been employed to introduce whatever novelties may
have escaped the author's attention, or may prove of service to the American practitioner.  As
several editions have appeared in London since the issue of the last American reprint, the volume
has had the benefit of repeated revisions by the author, resulting in a very tiorough alteration and
improvement.  The extent of these additions may be estimated from the fact that it now contains
about one-third more matter than the previous American edition, and that notwithstanding the
adoption of a smaller type, the pages have been increased by about one hundred, while nearly two
hundred and fifty wood-cuts have been added to the former list of illustrations.
A marked improvement will also be perceived in the mechanical and artistical execution of the
work, which, printed in the best style, on new type, and fine paper, leaves little to be desired as
regards external finish; while at the very low price affixed it will be found one of the cheapest
volumes accessible to the profession.
This popular volume, now a most comprehensive nothing of real practical importance has been omitwork on surgery, has undergone many corrections, ted; it presents a faithful epitome of everything reimprovements, and additions, and theprinciples and lating t) surgery up to the present hour. It is dethe practice of the art have been brought down to servedly a popular manual, both with the student
the latest record and observation. Of the operations and practitioner.-London Lancet, Nov. 19, 1859.
in surgery it is impossible to speak too highly. The
descriptions are so clear and concise, and the illus-   In closing this brief notice, we recommend as cortrations so accurate and numerous, that the student dially as ever this most useful and comprehensive
can have no difficulty, with instrument inhand, and  hand-book. It must prove a vast assistance, nor
book by his side, over the dead body, in obtainin     to the student of surgery, but also to the busy
a proper knowledge and sufficient tact in this much practitioner who may not have the leisure to devote
nelecteddceparIment ofredical education.-Brtis   himself to the study of more lengthy volumes.and Foreign Medico-Chirurg. Review, Jan. 1S60.   London Med. Times and Gazette, Oct. 22, 1859.
In the present edition the author has entirely re-   In a word, this eighth edition of Dr. Druitt's
written many of the chapters, and has incorporated  Manual of Surgery is all that the surgical student
the various improvements and additions in modern  or practitioner could desire.-Dublin Quarterly
surgery. On carefully going over it, we find that Journal of Med. Sciences, Nov. 1859.




AND SCIENTIFIC PUBLICATIONS.                                              11
DALTON, JR.. (J. C.), M. D.
Professor of Physiology in the College of Physicians, New York.
A TREATISE ON HUMAN PHYSIOLOGY, designed for the use of Students
and Practitioners of Medicine. WTith two hundred and fifty-four illustrations on wood.  In one
very beautiful octavo volume, of over 600 pages, extra cloth, $4 00; leather, raised bands, $4 25.
(Ju-st Issued.)
This system  of Physiology, both from the ex- its author; to his talents, his industry, his training
cellence of the arrangement studiously observed  to the institution with which he is connected, and
throughout every page. and the clear, lurid, and in- to American science.-Boston Med. and Surgical
structive manner in which each subject is treated, Journal, Feb. 24, 1859.
promises to form one of the most generally received    
class-books in the English language,. It is, in fact,
class-boolks in the En-lish lan-rua e. It is, in fact,   A NEW book and a first rate one; an original book,
a most admirable epitome of all the really important d  ne which cannot be too highly appreciated,
discoveries that have always been received as incon-nd which  e are prod to see eranating fro  our
testable truths, as well as of those which have been  country's press. It is by an author who, though
recently added to our stock of knowiedg e  on this sub- young, is considerably famous for physiological ret.  ill owever, proceed to gve a few ex- search, and who in this work has erected for himtracts from the book itself, as a specimen of its style slf an enduring monument, a token at once of his
and composition, and this, we conceive, will be quite laborandhsu.Nasille Medcao             l
sufficient to awaken a general interest in a work  Iarch, I859.
which isimmeasurabll superior in its details to the   Throughout the entire work, the definitions are
majority of those of the same class to which it be- clear and precise, the arrangement admirable, the
longs. In its purity of style and elegance of corn- argument briefly and well stated, and the style
position it may safely take its place with the very  nervous, simple, and concise. Section third, treatbest of our English classics; while in accuracy of ing of Reproduction, is a monograph of unapdescription it is impossible that it could be surpass- proached excellence, upon this subject, in the Enged. In every line is beautifully shadowed forth the lish tongue. For precision, elegance and force of
enanations of the polished scholar, whose reflec- style, exhaustive method and extent of treatment,
tions are clothed in a garb as interesting as they are fulness of illustration and weight of personal reimpressive; -with the one predominant feeling ap- search, we know of no American contribution to
pearing to pervade the whole-an anxious desire to  medical science which surpasses it, and the day is
please and at the same time to instruct.-Dublin  far distant when its claims to the respectful attenQuarterly Journ. of Med. Sciences, Nov. 1859.     tion of even the best informed scholars will not be
cheerfully conceded by all acquainted with its range
The work before us, however, in ourhumblejudg- ana depth.-Charleston Med. Journal, May, 1859.
ment, is precisely what it purports to be, and will   A new elementary work on 
A new elementary work on tHuman Physiology
answer admirably the purpose for which it is in- lifting up its voice in the presen   of late and sturdy
tended. It is par excellence, a text-book; and the eitions  of  ies  Cpencer's, Tod  and stBow
best text-book in this department that we have ever editions  of Kirke's, Carpentgrs, Tod  and Bowseen. We have carefully read the book, and speak  man's, to say nothing of Durglison's and Draper's
ofeen.  We  h ave carefully more  than cursook, and sy perusal. should have something superior in the matter or the
of its merits from a more than cursory perusal. manner of its utterance in order to win for itself
Looking back upon the work we have just finished, deserved attention anc e in order to win for itself
deserved attention and a name. That matter and
-e must say a word concerning the excellence of its
Ee must say sword ccrntheexcellnceofi that manner, atter a candid perusal, we think disillustrations. No department is so dependent upon
itlusrrtions  No department i so dependent upon  tinguish this work, and we are proud to welcome it
good illustrations, and those which keep pace with              or
ou  nwledge of the suject, as  at of pysioloy. not merely for its nativity's sake, but for its own
our knowledge of the subject, as that of physiology, intrinsic excellence.  Its language we find to he
The wood-cuts in the work before us are the best
plain, direct, unambitious, and falling with a just
we have ever seen, and, heing   original serve to
willurae preveselen, hat, i s ing   igial wservto  conciseness on hypothetical or unsettled questions,
Jillustrate precisy what is desired.-Buffel Med. and yet with sufficient fulness on those living topics
Journal, March, 1859.                              already understood, or the path to whose solution
A book of genuine merit like this deserves hearty  is definitely marked out. It does not speak exhaustpraise before subjecting it to any minute criticism. i rely upon every subject that it notices, but it does
We are not prepared to find any fault with its design  speak suggestively, experimentally, and to their
until we have had more time to appreciate its merits main utilities.  Into the subject of Reproduction
as a manual for daily consultation, and to weigh  our author plunges with a kind of loving spirit.
its statements and conclusions more deliberately. Throughout this interesting and obscure department
Its excellences we are sure of; its defects we have  he is a clear and admirable teacher, sometimes a
yet to discover. It is a work highly honorable to  brilliant leader.-Am. Med. MIonthly, May, 1859.
DUNGLISON, FORBES, TWEEDIE, AND CONOLLY.
THE CYCLOPFEDIA OF PRACTICAL MEDICINE: comprising Treatises on
the Nature and Treatment of Diseases, Materia Medica, and Therapeutics, Diseases of Women
and Children, Medical Jurisprudence, &c. &c.  In four large super-royal octavo volumes, of
3254 double-columned pages, strongly and handsomely bound, with raised bands. $12 00.
*g  This work contains no less than four hundred and eighteen distinct treatises, contributed by
sixty-eight distinguished physicians, rendering it a complete library of reference for the country
practitioner.
The most complete work on Practical Medicine titioner. This estimate of it has not been formed
extant; or, at least, in our language.-Buffalo from a hasty examination, but after an intimate acMedical and Surgical Journal.                      quaintance derived from frequent consultation of it
For reference, it isrice to eivery prac- during the past nine or ten years. The editors are
titioner.- rester n Lancet.                        practitioners of established reputation, and the list
of contributors embraces many of the most eminent
One of the most valuable medical publications of professors and teachers of London, Edinburgh, Dubthe day-as a work of reference it is invaluable.-  in, and Glasgow. It is, indeed, the great merit of
W.estern Journal of Medicine and Surgery.         this work that the principal articles have been furIt has been to us, both as learner and teacher, a nished by practitioners who have not only devoted
work for ready and frequent reference, one in which  especial attention to the diseases about which they
modern English medicine is exhibited in the most have written, but have also enjoyed opportunities
advantageous light. —efedical Examiner.           for an extensive practical acquaintance with them,
and whose reputation carries the assurance of their
We rejoice that this work is to be placed within  competency justly to appreciate the opinions of
the reach of the profession in this country, it being others, while it stamps their own doctrines with
unquestionably one of very great value to the prac- high and just authority.-American Medical,Tourn.
DEWEES'S COMPREHENSIVE. SYSTEM OF  AND MEDICAL TREATMENT OF CHILDMIDWIFERY. Illustrated by occasional cases   REN. The last edition. In one volume, octavo,
and many engravings. Twelfth edition, with the   extra cloth, 548 pages. $2 80
stuthor's last improvements and corrections  In  DEWEES'S TREATISE  ON  THE DISEASES
one octavo volume, extra cloth, of 600pages. $320.   OF FEMALES. T h e. In oe vl
OF TREATISE  ON   THE PHYSICAL    otavo edition. In one volume.DbWEES:S TREATIBE  ON  THE PHYSICAL    octavo extra cloth, 532 pages, with plates. $3 O0




12                       BLANCHARD & LEA'S MEDICAL
DUNGLISON  (ROBLEY), M. D.,
Professor of Institutes of Medicine in the Jefferson Medical College, Philadelphia.
NEW AND ENLARGED EDITION.
MEDICAL  LEXICON; a Dictionary of Medical Science, contaiing a concise
Explanation of the various Subjects and Terms of Anatomy, Physiology, Pathology, Hygiene,
Therapeutics; Pharmacology, Pharmacy, Surgery, Obstetrics, Medical Jurisprudence, Dentistry,
&c. Notices of Climate and of Mineral Waters; Formulae for Officinal, Empirical, and Dietetic
Preparations, &c. With French and other Synonymes. Revised and very greatly enlarged.
In one very large and handsome octavo volume, of 992 double-columned pages, in small type;
strongly bound in leather, with raised bands. Price $4 00.
Especial care has been devoted in the preparation of this edition to render it in every respect
worthy a continuance of the very remarkable favor which it has hitherto enjoyed.  The rapid
sale of FIFTEEN large editions, and the constantly increasing demand, show that it is regarded by
the profession as the standard authority. Stimulated by this fact, the author has endeavored in the
present revision to introduce whatever might be necessary "to make it a satisfactory and desirable-if not indispensable-lexicon, in which the student may search without disappointment for
every term that has been legitimated in the nomenclature of the science." To accomplish this,
large additions have been found requisite, and the extent of the author's labors may be estimated
from the fact that about Six THOUSAND subjects and terms have been introduced throughout, rendering the whole number of definitions about SIXTY THOUSAND, to accommodate which, the number of pages has been increased by nearly a hundred, notwithstanding an enlargement in the size
of the page. The medical press, both in this country and in England, has pronounced the work indispensable to all medical students and practitioners, and the present improved edition will not lose
that enviable reputation.
The publishers have endeavored to render the mechanical execution worthy of a volume of such
universal use in daily reference. The greatest care has been exercised to obtain the typographical
accuracy so necessary in a work of the kind. By the small but exceedingly clear type employed,
an immense amount of matter is condensed in its thousand ample pages, while the binding will be
found strong and durable. With all these improvements and enlargements, the price has been kept
at the former very moderate rate, placing it within the reach of all.
This work, the appearance of the fifteenth edition  tells us in his preface that he has added about six
of which, it has become our duty and pleasure to  thousand terms and subjects to this edition, which,
announce, is perhaps the most stupendous monument before, was considered universally as the best work
of labor and erudition in medical literature. One of the kind in any language.-Silliman's Journal,
would hardly suppose after constant use of the pre- March, 1858.
ceding editions, where we have never failed to find   He has razed his gigantic structure to the foundaa sufficiently full explanation of ever) medical term, tions, and remodelled and reconstructed the entire
that in this edition " about six thousand subjects pile. No less than six thousand additional subjects
and terms have been added," with a careful revision  and terms are illustrated and analyzed in this new
and correction of the entire work. It is only neces- edition, swelling the grand aggregate to beyond
sary to announce the advent of this edition to make sixty thousand    Thus is placed before the profesit occupy the place of the preceding one on the table  sion a complete and thorough exponent of medical
of every medical man, as it is without doubt the best terminology, without rival or possibility of rivalry
and most comprehensive work of the kind which has -Nashville Journ. of Med. and Surg. Jan. 1858.
ever appeared. —Buffalo Mved.Joourn. Jan. 1858.   
ever appeared-Bfflo Med. our, J.     It is universally acknowledged, we believe, that
The work is a monument of patient research, this work is incomparably the best and most conskilful judgment, and vast physical labor, that will plete Medical Lexicon in the English language.
perpetuate the name of the author more effectually  The amount of labor which the distinguished author
than any possible device of stone or metal. Dr. has bestowed upon it is truly wonderful, and the
Dunglison deserves the thanks not only of the Ame- learning and research displayed in its preparation
rican profession, but of the whole medical world.- are equally remarkable. Comment and commendaNorth Am. Medico-Chir. Review, Jan. 1858.        tion are unnecessary, as no one at the present day
A Medical Dictionary better adapted for the wantsthinks of purchasing any other Medical Dictionary
of the profession than any other with which we are than this.-St. Lous  ed. and Surg. Jour., Jan.
acquainted, and of a character which places it far  88.
above comparison and competition.-Am. Journ.   It is the foundation stone of a good medical librai.Med. Sciences, Jan. 1858.                     ry, and should always be included in the first list of
We need only say, that the addition of 6,000 new  books purchased by the medical student.-m. Med.
terms, with their accompanying definitions, may be Mothly, Jan. 185.
said to constitute a new work, by itself. We have   A very perfect work of the kind, undoubtedly the
examined the Dictionary attentively, and are most most perfect in the English language. —tMed. and
happy to pronounce it unrivalled of its kind. The Surg. Reporter, Jan. 1858.
erudition displayed, and the extraordinary industry   It is now emphatically the Medical Dictionary of
which must have been demanded, in its preparation  the English language, and for it there is no substiand perfection, redound to the lasting credit of its tute.-N. H. Med. Journ., Jan. 1858.
author, and have furnished us with a volume indis-        r           r    r
pensable at the present day, to all who would find   It l   arcy necessary to reark tat any medi
themselves au niveau with the highest standards ofa liba  wanting a copy of Dunlison's Lexico
medical information.-Bostonz Medical and Surgical      be imperfect.-Ci. Lancet, San. 1858.
Joournal, Dec. 31, 1857.                           We have ever considered it the best anthority pubGood lexicons and encyclopedic works generally, lished, and the present edition we may safely say lia
are the most labor-saving contrivances which lite- n) equal in the world.-Petinsular Med. Journal,
rary men enjoy; and the labor which is required to  Jan. 1858.
produce them in the perfect manner of this example.The most complete authority on the subject to be
is something appalling to contemplate. The author found in any language.- Va. Mled. Journal, Feb.'5.
BY THE SAME AUTHOR.
TIE PRACTICE OF MEDICINE. A Treatise on Special Pathology and The.
rapeutics.  Third Edition. In two large octavo volumes, leather, of 1,500 pages. $6 25.




AND SCIENTIFIC PUBLICATIONS.                                            13
DUNGLISON  (ROBLEY), M.D.,
Professor of Institutes of Medicine in the Jefferson Medical College, Philadelphia.
HUMAN   PHYSIOLOGY.   Eighth  edition.   Thoroughly revised  and extensively modified and enlarged, with five hundred and thirty-two illustrations. In two large and
handsomely printed octavo volumes, leather, of about 1500 pages. $7 00.
In revising this work for its eighth appearance, the author has spared no labor to render it worthy
a continuance of the very great favor which has been extended to it by the profession. The whole
contents have been rearranged, and to a great extent remodelled; the investigations which of late
years have been so numerous and so important, have been carefully examined and incorporated,
and the work in every respect has been brought up to a level with the present state of the subject.
The object of the author has been to render it a concise but comprehensive treatise, containing the
whole body of physiological science, to which the student and man of science can at all times refer
with the certainty of finding whatever they are in search of, fully presented in all its aspects; and
on no former edition has the author bestowed more labor to secure this result.
We believe that it can truly be said, no more com-   The best work of the kind in the English 1lnplete repertory of facts upon the subject treated, guage.-Silliman's Journal.
can anywhere be found. The author has, moreover,   The present edition the author has made a pc-cct
that enviable tact at description and that facility mirror of the science as it is at the present hour.
and ease of expression which render him peculiarly  As a work upon physiology proper, the science of
acceptable to the casual, or the studious reader. the functions performed by the body, the student will
This faculty, so requisite in setting forth many find it all e wishes.-Nashville Journ of Ied
graver and less attractive subjects, lends additional
hams to one always fascinating.-Boston  bed    That he has succeeded, most admirably succeeded
oid Sirag.i Journal.                           in his purpose, is apparent from the appearance of
an eighth edition. It is now the great encyclopaedia
The most complete and satisfactory system of on the subject, and worthy of a place in every phyPhysiology in the English language.-Amer. Med. sician's library.-Western Lancet.
Journal.
BY THE SAME AUTHOR. (A new edition.)
GENERAL THERAPEUTICS AND MATERIA MEDICA; adapted for a
Medical Text-book. With Indexes of Remedies and of Diseases and their Remedies. SIXTH
EDITION, revised and improved. With one hundred and ninety-three illustrations. In two large
and handsomely printed octavo vols., leather, of about 1100 pages. $6 00.
In announcing a new edition of Dr. Dunglison's   The work will) we have little doubt, be bought
General Therapeutics and Materia Medica, we have and read by the majority of medical students; its
no words of commendation to bestow upon a work  size, arrangement, and reliability recommend it to
whose merits have been heretofore so often and so  all; no one, we venture to predict, will study it
justly extolled. It must not be supposed, however, without profit, and there are few to whom it will
that the present is a mere reprint of the previous not be in some measure useful as a work of referedition; the character of the author for laborious ence. The young practitioner, more especially,will
research, judicious analysis, and clearness of ex- find the copious indexes appended to this edition of
pression, is fully sustained by the numerous addi- great assistance in the selection and preparation of
tions he has made to the work, and the careful re- suitable formula.-Charleston lMed. Journ. and Revision to which he has subjected the whole.-N. A. view, Jan. 1858.
Medico-Chir. Review, Jan. 1858.
BY THE SAME AUTHOR. (A new Edition.)
NEW REMEDIES, WITH FORMULA FOR THEIR PREPARATION AND
ADMINISTRATION. Seventh edition, with extensive Additions. In one very large octavo
volume, leather, of 770 pages. $3 75.
Another edition of the " New Remedies" having been called for, the author has endeavored to
add everything of moment that has appeared since the publication of the last edition.
The articles treated of in the former editions will be found to have undergone considerable expansion in this, in order that the author might be enabled to introduce, as far as practicable, the
results of the subsequent experience of others, as well as of his own observation and reflection;
and to make the work still more deserving of the extended circulation with which the preceding
editions have been favored by the profession. By an enlargement of the page, the numerous additions have been incorporated without greatly increasing the bulk of the volume.-Preface.
One of the most useful of the author's works.-    The great learning of the author, and his remarkSouthern Medical and Surgical Journal.          able industry in pushing his researches into every
This elaborate and useful volume should be source whence information is derivable,have enabled
found in every medical library, for as a book of re-im to throw together an extensive mass of facts
ference, for physicians, it is unsurpassed by any and statements, accompanied by full reference to
other work in existence, and the double index for authorities; which last feature renders the work
diseases and for remedies, will be founid greatly to practically valuable to investigators who desire to
enhance its value. —New York JMed. Gazette.     examine the original papers.-The American Journ.aI
of Pharmacy.
ELLIS (BENJAMIN), M.D. 
THE  MEDICAL  FORMULARY: being a Collection of Prescriptions, derived
from the writings and practice of many of the most eminent physicians of America and Europe.
Together with the usual Dietetic Preparations and Antidotes for Poisons. To which is added
an Appendix, on the Endermic use of Medicines, and on the use of Ether and Chloroform.  The
whole accompanied with a few brief Pharmaceutic and Medical Observations. Tenth edition,
revised and much extended by ROBERT P. THOMAS, M. D., Professor of Materia Medica in the
Philadelphia College of Pharmacy. In one neat octavo volume, extra cloth, of 296 pages. $1 75.




14                        BLANCHARD & LEA'S MEDICAL
ERICHSEN   (JOHN),
Professor of Surgery in University College, London, &c.
THE SCITENCE AND ART OF SURGERY; BEING A TREATISE ON SUIJOCAL
INJURIES, DISEASES, AND OPERATIONS. New and improved American, from the second enlarged
and carefilly revised London edition.  Illustrated with over four hundred engravings on wood.
In one large and handsome octavo volume, of one thousand closely printed pages, leather,
raised bands. $4 50. (Just Issued.)
The very distinguished favor with which this work has been received on both sides of the Atlantic has stimulated the author to render it even more worthy of the position which it has so rapidly
attained as a standard authority. Every portion has been carefully revised, numerous additions
have been made, and the most watchful care has been exercised to render it a complete exponent
of the most advanced condition of surgical science. In this manner the work has been enlarged by
about a hundred pages, while the series of engravings has been increased by more than a hundred,
rendering it one of the most thoroughly illustrated volumes before the profession. The additions of
the author having rendered unnecessary most of the notes of the former American editor, but little
has been added in this country; some few notes and occasional illustrations have, however, been
introduced to elucidate American modes of practice.
It is, in our humble judgment, decidedly the best step of the operation, and not deserting him until the
book of the kind in the English language. Strange  final issue of the case is decided.-Sethoscope.
that just such books are notoftener produced by pub-   Erbracing, as will be perceived, the whole surgilii teachers of surgery in thlis country and Great cal domain, and each division of itself almost comBritain. Ideed, it is a matter of great astonishment, plete and perfect, each chapter full and explicit, each
but no less true than astonishing, that of the many  subject faithfully exhibited, we can only express om
works on surgery republished in this country within  estimate of it in the aggregate. We consider it an
the last fifteen or twenty years as text-books for excellent contribution to surgery, as probably the
medical students, this is the only one that even ap- best single volume now extant on the subject, and
proximates to the fulfilment of the peculiar wants of with 0reatpleasure we add it to our text-boos.youngmen jus enteringupon the study ofthis branch   ashcille Journl of Medicine nd Surgery.
of the profession. —WesternJour. of Med. and Surgery.
Prof. Erichsen's work, for its size, has not been
Its value is greatly enhanced by a very copious surpassed; his nine hundred and eight pages, prowell-arranged index. We regard this as one of the fusely illustrated, are rich in physiological, patholomost valuable contributions to modern surgery. To  gical, and operative suggestions, doctrines, details,
one entering his novitiate of practice, we regard it and processes; and will prove a reliable resource
the most serviceable guide which he can consult. He  for information, both to physician and surgeon, in thi
will find a fulness ofdetail leading him through every  hour ofperil. —X  0. Med. and Surg. Jousrnal.
FLINT  (AUSi TIN), M. D.)
Professor of the Theory and Practice of Medicine in the University of Louisville, &e.
PHYSICAL EXPLORATION AND DIAGNOSIS OF DISEASES AFFECT.
ING  THE RESPIRATORY ORGANS.  In one large and handsome octavo volume, extra
cloth, 636 pages.  $3 00.
We regard it, in point both of arrangement and of   A work oforiginal observation of the highest merit.
the marked ability of its treatment of the subjects, We recommend the treatise to every one who wishes
as destined to take the first rank in works of this to become a correct auscultator.  Based to a very
class. So far as our information extends, it has at large extent upon cases numerically examined, it.
present no equal. To the practitioner, as well as carries the evidence of careful study and diserimina.
the student, it will be invaluable in clearing up the  tion upon every page. It does credit to the authoy,
diaonosis of doubtful cases, and in shedding light and, through him, to the profession in this country.
upon difficult phenomena.-BuGfalo Ned. Journal.  It is, what we cannot call every book upon auscultation, a readable book.-Am. Jour. Med. Sciences,
BY THE SAME AUTHOR.  (NTOw Ready.)
A PRACTICAL TREATISE ON THE DIAGNOSIS, PATHOLOGY, AND
TREATMENT  OF DISEASES OF THE HEART.  In one neat octavo volume, of about
500 pages, extra cloth. $2 75.
We do no' know that Dr. Flint has written any- diseases of the chest. We have adopted his work
thing which is not first rate; but this, his latest con- upon the heart as a text-book, believing it to be
tribution to medical literature, in our opinion, sur- more valuable for that purpose than any work of the
passes all the others. The work is most comprehen- kind lhat has yet appeared.-Nashville Mled. Journ.,
sive in its scope, and most sound in the views it enun- Dec. 1859.
ciatss. The descriptions are clear and methodical;   With more than pleasure do we hail the advent of
the statements are substantiated by facts, and are  this work, for it fills a wide gap on the list of textmade with such simplicity and sincerity, that with- books for our schools, and is, for the practitioner,
out them they would carry conviction. The style  the most valuable practical work of its kind. —N. 0.
is admirably clear, direct, and free from dryness  Med. News Nov. 1859.
With Dr. Walsle's excellent treatise before us, we
have no hesitation in saying that Dr. Flint's book is   In regard to the merits of the work, we have no
the best work on the heart in the English language. hesitation in pronouncing it full, accurate, and ju-Boston Med. and Surg. Journal, Dec. 15, 1859.   dicious. Considering the present state of science,
We have thus endeavored to present our readers  UCs a work was much needed. It shouldl be in the
with a fair analysis of this remarkable work. Pre- hands of every practitioner.-Chica o Hied. Journal
ferring to employ the very words of thedistinguished  April, 1860.
author, wherever it was possible, we have essayed    But these are very trivial spots, and in no wise
to condense into the briefest spacea general view of prevent us from declaring our most hearty approval
his observations and suggestions, and to direct the of the author's ability, industry, and conscientiousattention of our brethren to the abounding stores of ness.-Dublin Quarterly Journal of Med. Sciences,
valuable matter here collected and arranged for their Feb. 1860.
use and instruction. No medical library will here-   He haslabored on with the same industry and care,
after be considered complete without this volume; and his place among thefirst authors of our country
and we trust it will promptly find its way into the  is becoming fully establibhed. To this end, the work
hands of every A me ican student and physician.- whose title is given above, con ributes in no small
N. Am. Med. Chir. Revsiew, Jan 1860.                degree. Our spate will not admit of en extended
This last work of Prof. Flint will add much to  analysis, and we will elose this brief notice by
his previous well-earned celebrity, as a writer of commending it without reserve to every class of
great force and beauty; and, with his previous work, readers in the profession.-Peninsular Miled. Journ.,
places him at the head of American writers upoa  Feb. 1860.




AND SCIENTIFIC PUBLICATIONS.                                               15
FOWNES (GEORGE), PH.D., D                  &c.
A MANUAL OF ELEMENTARY CHEMISTRY; Theoretical and Practical,'From the seventh revised and corrected London edition. With one hundred and ninety-seven
illustrations. Edited by ROBERT BRIDGES, M. D. In one large royal 12mo. volume, of 600
pages. In leather, $1 65; extra cloth, $1 50.  (Just Issued.)
The death of the author having placed the editorial care of this work in the practised hands of
Drs. Bence Jones and A. WV. Hoffman, everything has been done in its revision which experience
could suggest to keep it on a level with the rapid advance of chemical science.  The additions
requisite to this purpose have secessitated an enlargement of the page, notwithstanding which the
work has been increased by about fifty pages.  At the same time every care has been used to
maintain its distinctive character as a condensed manual for the student, divested of all unnecessary
detail or mere theoretical speculation.  The additions have, of course, been mainly in the department of Organic Chemistry, which has made such rapid progress within the last few years, but
yet equal attention has been bestowed on the other branches of the subject-Chemical Physics and
Inorganic Chemistry-to present all investigations and discoveries of importance, and to keep up
the reputation of the volume as a complete manual of the whole science, admirably adapted for the
learner.  By the use of a small but exceedingly clear type the matter of a large octa7o is compressed
within the convenient and portable limits of a moderate sized duodecimo, and at the very low price
affixed, it is offered as one of the cheapest volumes before the profession.
Dr. Fownes' excellent work has been universally    The work of Dr. Fownes has long been before
recognized everywhere in his own ant this country, the public, and its merits have been fully apprecias the best elementary treatise on chemistry in the ated as the best text-book on chemistry now  in
English tongue, and is very generally adopted, we existence. We do not, of course, place it in a rank
believe, as the standard text book in all  ur colleges, superior to the works of Brande, Grahani, Turner,
both literary and scientific.-/Charleston Med. Journ. Gregory, or Gmelin, but we say that, as a work
and Review, Sept. 1859.                          for students, it is preferable to any of them.-LonA standard manual, which has long enjoyed the  don Journal of Mledicine.
reputation of embodying much knowledge in a small   A work well adapted to the wants of the student
space. The author hasachieved tle difficult task of It is an excellent exposition of the chief doctrines
condensation with masterly tact. His book is con- and facts of modern chemistry. The size of the work,
else without being dry, and brief without being too  and still more the condensed yet perspicuous style
diogmatical or general.-Virginia Med. and Surgical in which it is written, absolve it from the charges
Jo'urnal.                                          very properly urged against most manuals termed
popular.-Edinburghk Journal of Medical Science.
FISKE  FUND  PRTZE  ESSAYS.-THE  EF-   EDWARD WARREN, M.D.,ofEdenton,N.C. ToFECTS OF CLIMATE ON  TUBERCULOUS    getler in one neat 8vo. volume, extra cloth. $1 00.
DISEASE. By ETWTN LEE,M.R. C.S,London, FRICK ON RENAL AFFECTIONS; theirDiagand TH-Ie  INFLUENCE  )F PREGNANCY ON    nosis and Pathology.  With illustrations.  One
7-THE DEVELOPM' ENT OF TUBERCLES  By  volume, royal 12mo., extra cloth. 75 cents.
FERGUSSON  (WILLIAM), F. R. S.,
Professor of Surgery in King's College, London, &e.
A SYSTEM   1 OF PRACTICAL SURGERY. Fourth American, from tle tbird
and enlarged London edition. In one large and beautifully printed octavo volume, of about 700
pages, with 393 handsome illustrations, leather.  $3 00.
GRAHAM (THOMAS), F. R. S.
THTE ELEMENTS OF TNORGANIC CHEMISTRY, including the Applications of the Science in the Arts. New and much enlarged edition, by HENRY WATTS and ROBERT
BRIDGES, M. D. Complete in one large and handsome octavo volume, of over 800 very large
pages, vith two hundred and thirty-two wood-cuts, extra cloth.  $4 00.,-, Part II., completing the work from p. 431 to end, with Index, Title Matter, &c., may be
thad separate, cloth backs and paper sides. Price $2 50.
From Prof. E. N. Horsford, Harvard College.   afford to be without this edition of Prof. Graham's
It has, in its earlier and less perfect editions, been  Elements.-Silliman's Journal, March, 1858.
familiar to me, and the excellence of its plan and   Fron Prnf. Wolcott G7bbs, N. Y. Free Academy.
the clearness and completeness of its discussions,
heave long been mny admiration.                      The work is an admirable one in all respects, and
its republication here cannot fail to exert a positive
No reader of English works on this science can influence upon the progress of sciene in this country.
GRiFFITH  (ROBERT  E.), M. D., &c.
A UNIVERSAL FORMULARY, containing the methods of Preparing and Administering Officinal and other Medicines.  The whole adapted to Physicians and Pharmaceu.
lists. SECOND EDITION, thoroughly revised, with numerous additions, by ROBERT P. THOMAS,
M. D., Professor of Materia Medica in the Philadelphia College of Pharmacy.  In one large and
handsome octavo volume, extra cloth, of 650 pages, double columns.  $3 00; or in sheep, $3 25.
It was a work requiring much perseverance, and   This is a work of six hundred and fifty one pages,
trhen published was looked upon as by far the best embracing all on the subject of Dreparing   and admiwork of its kind that had issued from the American nistering medicines that canl be desired by the physipress. Prof. Tholnma   s as certainly " improved," as cian and pharmaceutist.- Western Lanecet.
well as added to this Formulary, and has rendered it   Te amountofuseful, every-day matter.for a pracadditionally deserving of the confidence of pharma- tiing physician, is really immense.-Boston Med.
ceutists and physicians. —An. Journal of Pharmacy.  and Surg. Joaurnal.
We are happy to announce a new and improved   This edition has been greatly improved by the reedition of this, one of the most valuable and useful vision and ample additions of Dr. Thornas, and is
works that have emanated from an American pen. now, we believe,  e of the mos complete works
It would do credit to any country, and will be foun f it kind in any language. The additions a    nt
of daily usefulness to practitioners of medicine; it is to about seventy pages, and no effort has been spared
better adapted to their purposes than the dispensato- to include in them all the recent improvementsp.  
ries.-Southern Med. a.nd Surg. Journal.            to i        i t       al t  r     iprovemento  A
nries.-Sosrt.7ken n lIied. a-nezdi Snrg. Jourln-~ala.  work of this kind appears to us indispensable to the
It is one of the most useful books a country practi. physician, and there is none we can more cordially
tioner can possibly have.-Medical Chronicle.       recolmmend.-N. Y. Journal of Medicine.




16                       BLANCHARD & LEA'S MEDICAL
GROSS (SAMUEL D.), M. D.,
Professor of Surgery in the Jefferson Medical College of Philadelphia, &e.
Just Issued.
A  SYSTEM   OF  SURGERY: Pathological, Diagnostic, Therapeutic, and Operative.  Illustrated by NINE HUNDRED AND THIRTY-SIX ENGRAVINGS. In two large and beautifully
printed octavo volumes, of nearly twenty-four hundred pages; strongly bound in leather, with
raised bands. Price $12.
FROM THE AUTHOR'S PREFACE.
" The object of this work is to furnish a systematic and comprehensive treatise on the science and
practice of surgery, considered in the broadest sense; one that shall serve the practitioner as a
faithful and available guide in his daily routine of duty. It has been too much the custom  of modern writers on this department of the healing art to omit certain topics altogether, and to speak of
others at undue length, evidently assuming that their readers could readily supply the deficiencies
from other sources, or that what has been thus slighted is of no particular practical value.  My aim
has been to embrace the whole domain of surgery, and to allot to every subject itS legitimate claim
to notice in the great family of external diseases and accidents.  How far this object has been accomplished, it is not for me to determine. It may safely be affirmed, however, that there is no topic,
properly appertaininl to surgery, that will not be found to be discussed, to a greater or less extent,
in these volumes.  If a larger space than is customary has been devoted to the consideration of
inflammation and its results, or the great principles of surgery, it is because of the conviction,
grounded upon long and close observation, that there are no subjects so little understood by the
general practitioner. Special attention has also been bestowed upon the discrimination of diseases'
and an elaborate chapter has been introduced on general diagnosis."
That these intentions have been carried out in the fullest and most elaborate manner is sufficiently
shown by the great extent of the work, and the length of time during which the author has been
concentrating on the task his studies and his experience, guided by the knowledge which twenty
years of lecturing on surgical topics have given him of the wants of the profession.
Of Dr. Gross's treatise on Surgery we can say   At present, however, our object is not to review
no more than that it is the most elaborate and corn- the work (this we purpose doing hereafter), but
plete work on this branch of the healing art which  simply to announce its appearance, that in the
has ever been published in any country. A svs- meantime our readers may procure and examine it
tematic work, it admits of no analytical review; for themselves. But even this much we cannot do
but, did our space permit, we should gladly give without expressing the opinion that, in putting fortl
some extracts from it, to enable our readers to judge these two volumes, Dr. Gross has reared for himof the classical style of the author, and the exhaust- self a lasting monument to his skill as a surgeon,
ing way in which each subject is treated.-Dublin  and to his industry and learning as an author.-Si,
Quarterly Journal of Med. Science, Nov. 1859.     Louis Mled. and Surg. Journal, Nov. 1859.
The work is so superior to its predecessors in   With pleasure we record the competion of this
matter and extent, as well as in illustrations and  long-anticipsted work. The reputation which the
style of publication, that we can honestly reco- author has fr many years sustained, both as a surmend it as the best work of the kind to be taken geon and as a writer, had prepared us to expect a
home by the young practitioner.-Am. Med. Journ., treatise of great excellence and originality; but we
Jan. 1S60.                                         confess we were by no means prepared for the work
The treatise of Prof. Gross is not, therefore, a which is before us-the most complete treatise upon.
mere text-book for undergraduates, but a systema- surgery ever published, either in this or any other
tic record of more than thirty years' experience, country, and we might, perhaps, safely say, the
reading, and reflection by a man of observation, most original. There is no subject belonging prosound judgment, and iare practical tact,and as such perly to surgery which has not received from the
deserves to take rank with the renowned produc- authoi a due share of attention. Dr. GroEs has suptions of a similar character, by Vidal and Boyer, of plied a want in surgical literature which has long
France, or those of Chelius, Blasius, and Langen- been felt by practitioners; he has furnishedt us with
beck, of Germany. Hence, we do not hesitate to a complete practical treatise upon surgery in all its
express the opinion that it will speedily take the departments. As Americans, we are proud of the
same elevated position in regard to surgery that has achievement; as surgeons, we are most sincerely
been given by common consent to the masterly work thankful to him for his extraord nary labors in our
of Pereira in IMateria Medica, or to Todd and Bow- behalf.-N. Y. Monthly Review and.B.ffalo lmed.
man in Physiology.-N. 0. IM.ed. and Surg. Journal, Journa?, Oct. 1850.
Jan. 1860.
BY THE SAME AUTHOR.
ELEMENTS OF PATHOLOGICAL ANATOMY. Third edition, thoroughly
revised and greatly improved.  In one large and very handsome octavo volume, with about three
hundred and fifty beautiful illustrations, of which a large number are from  original drawings.
Price in extra cloth, $4 75; leather, raised bands, $5 25. (Lately Published.)
The very rapid advances in the Science of Pathological Anatomy during the last few years have
rendered essential a thorough modification of this work, with a view of making it a correct exponent of the present state of the subject. The very careful manner in which this task has been
executed, and the amount of alteration which it has undergone, have enabled the author to say that
" with the many changes and improvements now introduced, the work may be regarded almost as
a new treatise," while the efforts of the author have been seconded as regards the mechanical
execution of the volume, rendering it one of the handsomest productions of the American press.
We most sincerely congratulate the author on the   We have been favorably impressed with the genesuccessful manner in which he has accomplished his ral manner in which Dr. Gross has executed his task
proposed object. His book is most admirably cal- of affording a comprehensive digest of the present
culated to fill up a blank which has long been felt to  state of the literature of Pathological Anatomy, and
exist in this department of medical literature, and  have much pleasure in recommending his work to
as such must become verywidely circulated amongst our readers, as we believe one well deserving of
all classes of the profession.-Dublin Quarterly  diligent perusal and careful study.-MIontreal Med.
Journ. of Med. Science, Nov. 1857.                 Chron., Sept. 1857.
BY THE SAME AUTHOR.
A PRACTICAL TREATISE ON FOREIGN BODIES IN THE AIR-PASSAGES. In one handsome octavo volume, extra cloth, with illustrations. pp. 468. $2 75,




AND SCIENTIFIC PUBLICATIONS.                                               17
GROSS (SAMUEL D.), M. D.,
Professor of Surgery in the Jefferson Medical College of Philadelphia, &c.
A PRACTICAL TREATISE ON THE DIESASES, INJURIES, AND
MALFORMATIONS OF THE URINARY BLADDER, THE PROSTATE GLAND, AND
THE  URETHRA.  Second Edition, revised and much enlarged, with one hundred and eightyfour illustrations. In one large and very handsome octavo volume, of over nine hundred pages.
In leather, raised bands, $5 25; extra cloth, $4 75.
Philosophical in its design, methodical in its ar- agree with us, that there is no work in the English
rangement, ample and sound in its practical details, language which can make any just pretensions to
it may in truth be said to leave scarcely anything to be its equal.-N. Y. Journal of Medicine.
be desired on so important a subject. —Boston Med.   Avolume replete with truths and principles of the
and Surg. Journal.                                 utmost value in the investigation of these diseases. -
Whoever will peruse the vast amount of valuable American Medical Jozurnal.
practical information it contains, will, we think,
GRAY  (HENRY), F,. R,.,
Lecturer on Anatomy at St. George's Hospital, London, &e.
ANATOMY, DESCRIPTIVE AND SURGICAL.  The Drawings by H. V.
CARTER, M. D., late Demonstrator on Anatomy at St. George's Hospital; the Dissections jointly
by the AUTHOR and Dr. CARTER. In one magnificent imperial octavo volume, of nearly 800
pages, with 363 large and elaborate engravings on wood: Price in extra cloth, $6 25; leather
raised bands, $7 00. (.Just Issued.)
The author has endeavored in this work to cover a more extended range of subjects than is
customary in the ordinary text-books, by giving not only the details necessary for the student, but
also the application of those details in the practice of medicine and surgery, thus rendering it both
a guide for the learner, and an admirable work of reference for the active practitioner.  The
engravings form a special feature in the work, many of them  being the size of nature, nearly all
original, and having the names of the various parts printed on the body of the cut, in place of figures
of reference with descriptions at the foot.  They thus form a complete and splendid series, which
will greatly assist the student in obtaining a clear idea of Anatomy, and will also serve to refresh
the memory of those who may find in the exigencies of practice the necessity of recalling the details
of the dissecting room; while combining, as it does, a complete Atlas of Anatomy, with a thorough
treatise on systematic, descriptive, and applied Anatomy, the work will be found of essential use
to all physicians who receive students in their offices, relieving both preceptor and pupil of much
labor in laying the groundwork of a thorough medical education.
The work before us is one entitled to the highest to exist in this country. Mr. Gray writes throughpraise, end we accordingly welcome it as a valu- out with both branches of his subject in view. His
able addition to medical literature. Intermediate  description of each particular part is followed by a
in fulness of detail between the treatises of Slar  notice of its relations to the parts with which it is
pey and of Wilson, its characteristic merit lies in  connected, and this, too, sufficiently ample for all
the number and excellence of the engravings it the purposes of the operative surgeon.  After decontains.  Most of these are original, of much  scribing the bones and muscles, he gives a concise
larger than ordinary size, and admirably executed. statement of the fractures to which the bones of
The various parts are also lettered after the plan  the extremities are most liable, together with the
adopted in Holden's Osteology. It would be diffi- amount and direction of the displacement to which
cult to over-estimate the advantages offered by this the fragments are subjected by muscular action.
mode of pictorial illustration.  Bones, ligaments, The section on arteries is remarkably full and acmuscles, bloodvessels, and nerves are each in turn  curate. Not only is the surgical anatomy given to
figured, and marked with their appropriate names; every important vessel, with directions for its ligathiusenabling the studentto compreliend,ataglance, tion, but at the end of the description of each artewhat would otherwise often be ignored, or at any  rial trunk we have a useful summary of the irregurate, acquired only by prolonged and irksome ap- larities which may occur in its origin, course, and
plication. In conclusion, we heartily commend the termination.-N. A. Med. Chir. Review, Mar. 1859.
work of Mr. Gray to the attention of the medical
profession, feeling certain that it should be regarded    Mr. Gray's book, in excellency of arrangement
as one of the most valuable contributions ever made and comleteness of execution, exceeds any work
to educational literature.-N. Y. Monthly Review.on anatomy hitherto published in the English lanDec. 185.                                         guage, affording a complete view of the structure of
the human body, with especial reference to practical
In this view, we regard the work of Mr. Gray as surgery. Thus the volume constitutes a perfect book
far better adapted to the wants of the profession,      reference for the practitioner, demanding  a place
and especially of the student, than any treatise on  in even the most limited library of the physician or
anatomyyetlpublishedinthiscountry. itIsdestined, surgeon, and a work of necessity for the student to
we believe, to supersede all others, both as a manual fix in is mind what he has learned by the dissecting
of dissections, and a standard of reference to the knife from the book of nature.-The Dublin Quarstudent of general or relative anatomy.-N. Y. terly Journal of Med. Sciences, Nov. 1858.
Journal of  edicine, Nov. 1859...,.           I,      i    In our judgment, the mode of illustration adopted
This is by all comparison the most excellent work      t  preset volume cannot but present many adin the present volume cannot but present many adon Anatomy extant. It is just the thing that has vantages to the student of anatomy. To the zealous
been long desired by the profession.  Wiith such a discile of Vesalius, earnestly desirous of real imguide as this, the student of anatomy, the practi- provement, the book will certainly be of immense
tioner of medicine, and the surgical devotee have vue       t,  the same time, we must also confess
all a newer, clearer, and more radiant light thrown  that to those simply  desirous of mut also con  it
upon the intricacies and mysteries of this wondterupon the intricacies and mysteries of this wonder- will be an undoubted godsend. The peculiar value
ful science, and are thus enabled to accomplish re-of Mr. Gray's mode of illustration is nowhere more
suits which hitherto seemed possible only to the  markedly evident than in the chapter on osteology,
specialist. The plates, which are copied Irom re-and especially in those portions which treat of the
cent dissections, are so well executed, that the most bones of the head and of their development. The
superficial observer cannot fail to perceive the posi- study of these parts is thus made one of comparative
tions, retations, and distinctive features of the vari- ease, if not of positive pleasure; and those bugbears
ous parts, and to take in more of anatomy at a glance, of the student, the temporal and sphenoid bones, are
than by many long hours of diligent study over the  shorn of half their terrors. It is, in our estimation,
most erudite treatise, or, perhaps, at the dissecting  an admirable and complete text-book for the student,
table itself.-Med. Journ. of N. Carolina, Oct. 1859. and a useful work of reference for the practitioner;
For this truly admirable work the profession is its pictorial character forming a novel element, to
indebted to the distinguished author of " Gray on  which we have already sufficiently alluded.-Am.
the Spleen."  The vacancy it fills has been long felt Journ. Med. Sci., July, 1859.




18                       BLANCHARD) & LEA'S MEDICAL
GIBSON'S INSTITUTES AND PRACTICE OF    tions, by JOSEPH LEIDY, MI. D. In one volume,
SURGERY. Eighth edition, improved and al-   very large imperial quarto, extra cloth, wit;  320
tered. With thirty-fourplates. In two handsome   copper- plate figures, plain and colored, $5 00.
octavo volumes, containing about 1,000 pages,' NTON                                  TE  P
leather, raised bandi. 86 50.                    f IHGHES' INTRODUCTION TO  THE PRAClTICE  OF  AUSCULTA'ION  AND  OTHER
GARDNER'S MEDICAL CHEMISTRY, for the   MODES OF PHYSICAL DIAGNOSS. IN DISuse of Students and the Profession. In one royal   EASES OF    E  UNGS AND HEART. Se
12mo. vol., cloth, pp. 396, with wood cuts. $1.   cond edition   1 vol. royal limo., ex. cloth, pp.
GLUGE'S ATLAS OF PATHOLOGICAL HIS-   304. $1 00.
TOLOGY.  Translated, with Notes and AddiHAMILTON  (FRANK  H.), M. D.,
Professor of Surgery in the University of Buffalo, &c.
A PRACTICAL TREATISE ON FRACTURES AND DISLOCATIONS. In
one large and handsome octavo volume, of over 750 pages, with 289 illustrations. 84 25. (NTow
Ready, January, 1860.)
This is a valuable contribution to the surgery of illustrated, which will be a desideratum for those
most important atfeetions, and is the more welcome, practitioners who cannot conveniently see the moinasmuch as at the present time we do not possess dels applied.-New York ~Med. Press, Feb. 4, 1860.
a single complete treatise on Fractures and Dislo-    We reward this work as an honor not only to its
cations in the Ennglish language. It has remained for author, bt tothe professionofourcountry. Were
our American brother to produce a complete treatise  we to review it thoroughly, we could not convey to
upon the subject, and brin  together in aconvenient the mind of the reader more forcibly our honest
form those alterations and improvements that have opinion expressed in the few words-we think it the
been made from time to time in the treatment ofthese  best book of its kind extant. Every man interested
affections. One great and valuable feature in the  in surgery will soon have this work on his desk.
work before us is the fact that it comprises all the  Ie who does not, will be the lose.-New  Orleans
improvements introduced into the practice of both  Medical News, March, 1800.
English and American surgery, and though far from
omitting mention of our continental neighbors the   Now that it is before us, we feel bound to say that
author by no means encourages the notion-but too  much as was expected from it, and onerous as was
prevalent in some quarters-that nothing is good the undertaking, it has surpassed expectation, and
unless imported from France or Germany.  The achieved more thln was pledged in its behalf; for
latter half of the work is devoted to the considera- its title does not express in full the richress of its
tion of the various dislocations and their appropri- contents.  On the whole, we are prouder of this
ate treatment, and its merit is fully equal to  at of  k than o f any which las for years emanated
the preceding portion.-The Losndon Lancet, lay 5  from the American medical press; its sale will cerg1860                                             tainly be very large in this country, and we antici.
pate its eliciting much attention in Europe. —ashIt is emphatically the book upon the subjects of ville Medical Record, Mar. 1860.
which it treats, and we cannot doubt that it will
continue so to be for an indefinite period of time.   Every surgeon, young and old, should possess
When we say, however, that we believe it will at himself of it, and give it a careful perusal, in doing
once take its place as the best book for consultation  which he will be richly repaid.-St.  Louis Med,
by the practitioner; and that it will form the most   d bu8rg Journal Marcl, 1860.
complete, available, and reliable guide in emergen-   Dr. Hamilton is fortunate in having succeeded in
cies of every nature connected wvith its subjects; and filling the void, so long felt, with what cannot fail
also that the student of surgery may make it his text- to be at once accepted as a model monograph in some
book with entire confidence, and with pleasure also, respects, and a work of classical authority. We
from its agreeable and easy style-we think our own  sincerely congratulate the profession of the United
opinion may be gathered as to its value.-Boston  States on the appearance of such apublication from
M.:edical and Surgical Journal, March 1, 1860.     one of their number. We have reason to be proud
The work is concise, judicious, and accurate, and  of it as an original work, both in a literary and saiadapted to the wants of the student, practiticner  entific point of view, and to esteem it as a valuabl
and investigator, honorable to the author and to the guide in a most difficult and important branch of
profession.-Chicago Med. Journal, March, 1860.   study and practice. On every account, therefore,
we hope that it may soon be widely known abroad
We venture to say that this is not alone the only  as an evidence of genuine progress on this side of
complete treatise on the subject in the language, the Atlantic, and further, that it may be still more
but the best and most practical we have ever read. widely known at home as an authoritative teacher
The arrangement is simple and systematic, the die- from which every one may profitably learn, and as
tion clear and graphic, and the illustrations nume- affording an example of honest, well-directed, and
rous and remarkable for accuracy of delineation. untiring industry in authorship which every surgeon
The various mechanical appliances are faithfully may emulate.- Am. Mfed. Journal, April, 1880.
HOBLYN  (RFICHARD D.), M. D.
A DICTIONARY O  THE TERMS USED IN MiEDICINE AND THE
COLLATERAL SCIENCES.  A new American edition.  Revised, with numerous Additions,
by ISAAC HAYS, M. D., editor of the " American Journal of the Medical Sciences."  In one large
royal 12mo. volume, leather, of over 500 double columned pages.  $1 50.
To both practitioner and student, we recommend use; embracing every department of medical science
this dictionary as being convenient in size, accurate down to the very latest date.-Western Lancet.
in definition, and sufficiently full and complete for   Hoblyn's Dictionary has long been afavoritewith
ordinary censultation-Clearleston Med. Jou.rn     us. It is the best book of definitions we have, and
We know of no dictionary better arranged and  ought always to be upon the student's table. —
adapted. Itis not encumbered with the obsoleteterms Southern Med. and Surg. Journal.
of a bygone age, but it contains all that are now in
HOLLAND'S  MEDICAL  NOTES  AND  RE-   TOLOGY. Eighth edition. Extensively revised
FLECTIONS. From the third London edition.   and modified. In two large octavo volumes, exIn one handsome octavo volume, extra cloth. $3.   tra cloth, of more than 1000 pages, with over 300
HORNER'S SPECIAL ANATOMY AND HIS-   illustrations. $600.
HABERSHON  (S. 0.), M. D.,
Assistant Physician to and Lecturer on Materia MIedica and Therapeutics at Guy's Hospital, &c.
PATHOLOGICA L AND  RACGTICAL  OBSERlVATONS ON DISE SES
OF THE ALIMENTARY CANAL, CESOPHAGUS, STOMACH, CAECUM, AND INTESTINES. With illustrations on wood.  In one handsome octavo volume of 312 pages, extra
cloth   $1 75.  (Now Ready.)




AND SCIENTIFIC PUBLICATIONS.                                              19
HODGE (HUGH   L.), M. D.,
Professor of Midwifery andthe Diseases of Women and Children in the University of Pennsylvania, &c.
ON  DISEASES PECULIAR  TO WOMIEN, including Displacements of the
Uterus.  With original illustrations.  In one beautifully printed octavo volume, of nearly 500
pages.  (1Not Ready.)
The profession will look with much interest on a volume embodying the long and extensive experience of Professor Hodge on an important branch of practice in which his opportunities for
investigation have been so extensive. A short summary of the contents will show the scope of
the work, and the manner in which the subject is presented. It will be seen that, with the exception of Displacements of the Uterus, he divides the Diseases peculiar to Women into two great
constitutional classes-those arising from irritation, and those arising from sedation.
CONTENTS.
PART I. DISEASES OF IRRITATION.-CHAPTER I. Ndrvous Irritation, and its Consequences —.
Irritable Uterus.-IlI. Local Symptoms of Irritable Uterus: Menorrhagia and Haemorrhagia;
Leucorrhcea; Dysmenorrhea -IV. Local Symptoms of Irritable Uterus; Complications. —V.
General Symptoms of Irritable Uterus: Cerebro-spinal Irritations.-VI. General Symptoms of
Irritable Uterus.-VII. Progress and Results of Irritable Uterus.-VIII. Causes and Pathology
of Irrilable Diseases -IX. Treatment of Irritable Uterus; Removal or Palliation of the Cause.
-X. Treatment of Irritable Uterus: To Diminish or Destroy the Morbid Irritability-X[.
Treatment of the Complications of Irritable Uterus.-XII, Treatment of the Complications of
Irritable Uterus.
PART II. DISPLACEMENTTS OF THE UTERTTS.-CHAPTER I. Natural Position and Supports of the
Uterus. —I. Varieties of Displacements of the Uterus, and their Causes.-III. Symptoms of
Displacements of the Uterus.-IV. Treatment of Displacements of the Uterus.-V. Treatment
of Displacements; Internal Supports.-VI. Treatment of Displacements; Lever Pessaries.VII. Treatment of the Varieties of Displacements.-VIII. Treatment of' Complications of Displacements of the Uterus.-IX. Treatment of Enlargements and Displacements of the Ovaries, &c.
PART III. DISEASES OF SEDATION —CHAPTER I. Sedation and its Consequences: Organic and
Nervous Sedation; Passive Congestion; Reaction; Treatment —II. Sedation of the Uterus;
Amenorrhe.a: Sedation of the Uterus from Moral Causes; Sedation of the Uterus from Physical
Causes.-III. Diagnosis and Treatment of Sedation of the Uterus.
The illustrations, which are all original, are drawn to a uniform scale of one-half the natural size.
JONES (T. WHARTON), F. R. S.,
Professor of Ophthalmic Medicine and Surgery in University College, London, &c.
THE PRINCIPLES AND PRACTICE OF OPHTHALMIC 5IEDICINE
AND SURGERY. With one hundred and ten illustrations. Second American from the second
and revised London edition, with additions by EDWARD HARTSHOtRNE, M. D., Surgeon to Wills'
Hospital, &c. In one large, handsome royal 12mo. volume, extra cloth, of 50) pages. $1 50.
JON ES (C. HANDFIELD), F. R. S., &  EDWARD  H. S  EV   KIN   M DD.,
Assistant Physicians and Lecturers in St. Mary's Hospital, London.
A. IANUAL OF PATHOLOG(ICAL ANATOMY. First American Edition,
Revised. With three hundred and ninety-seven handsome wood engravings. In one large and
beautiful octavo volume of nearly 750 pages, leather.  $3 75.
As a concise text-book, containing, in a condensed obliged to glean from a great number of monographs,
form, a complete outline of what is known in the and the field was so extensive that but few cultivated
domain of Pathological Anatomy, it is perhaps the  it with any degree of success. As a simple work
best work in the English language. Its great merit of reference, therefore, it is of great value to the
consists in its completeness and brevity, and in this student of pathological anatomy, and should be in
respect it supplies a great desideratum in our lite- every physician's library. —Western Lancet.
rature. Heretofore the student of pathology was
KIRKES (WILLIAM  SENHOU$E), M. O.,
Demonstrator of Morbid Anatomy at St. Bartholomew's Hospital, &c.
A  1MANUAL OF PHYSIOLOG-Y.  A new American, from the third and
improved London edition. WVith two hundred illustrations. In one large and handsome royal
12nmo. volume, leather.  pp. 586. $2 00. (Lately Published.)
This is a new and very much improved edition of   One of the very best handbooks of Physiology we
Dr. Kirkes' well-known Handbook of Physiology. possess-presenting just such an outline of the sciIt combines conciseness with completeness, and is, ence as the student requires during his attendance
therefore, admirably adapted for consultation by the upon a course of lectures, or for reference whilst
busy practitioner.-Dublin Quarterly Journal.      preparing for examination.-Am. Medical Journal,
Its excellence is in its compactness, its clearness,   For the student beginning this study, and the
and its carefully cited authorities. It is the most practitioner who has but leisure to refresh his
convenientoftext-books. Thesegentlemen, Messrs. memory, this book is invaluable, as it contains all
Kirkes and Paget, have really an immense talent for that it is important to know, without special details,
silence, which is not so common or so cheap as prat- which are read with interest only by those who
ing people fancy. They have the gift of telling us would make a specialty, or desire to possess a critiwhat we want to know, without thinking it neces- cal knowledge of the subject.-Charleston Med.
sary to tell us all they know. —Bostosn Med. and Josural.
Surg. Joaurnal.




20                     BLANCHARD & LEA'S MEDICAL
KNAPP'S TECHNOLOGY; or,Chemistry applied LAYCOCK'S LECTURES ON THE PRINCIto the Arts and to Manufactures. Edited by Dr.   PLES AND METHODS OF MEDICAL OBRONALDS, Dr. RICHARDSON, and Prof. W. R.   SERVATION AND RESEARCH. For the Use
JOHNSON. In two handsome 8vo.vols.,witlhabout   of Advanced Students and Junior Practitioners.
500 wood engravings. $6 00.                   In one royal 12mo. volume, extra cloth. Price $1.
LALLEMAND AND WILSON.
A PRACTICAL TREATISE ON THE CAUSES, SYMPTOMS, AND
TREATMENT OF SPERMATORRHCEA. By M. LALLEMAND. Translated and edited by
HENRY J MCDOUGALL. Third American edition. To which is added   ~  ON DISEASES
OF THE VESICULJE SEMINALES; AND THEIR ASSOCIATED ORGANS. With special reference to the Morbid Secretions of the Prostatic and Urethral Mucous Membrane. By MARRIS
WILSON, M. D. In one neat octavo volume, of about 400 pp., extra cloth. $2 00. (Just Issued.)
LA  ROCHE (R.), M. D, &c,.
YELLOW   FEVER, considered in'its Historical, Pathological, Etiological, and
Therapeutical Relations. Including a Sketch of the Disease as it has occurred in Philadelphia
from 1699 to 1854, with an examination of the connections between it and the fevers known under
the same name in other parts of temperate as well as in tropical regions. In two large and
handsome octavo volumes of nearly 1500 pages, extra cloth. $7 00.
From Professor S. H. Dickson, Charleston, S. C., nant and unmanageable disease of modern times,
September 18, 1855.             has for several years been prevailing in our country
A monument of intelligent and well applied re- to a greater extent than ever before; that it is no
search, almost without example. It is, indeed, in longer confined to either large or small cities, but
itself. a large library, and is destined to constitute penetrates country villages, plantations, and farmthe special resort as a book of reference, in the houses; that it is treated with scarcely better sucsubject of which it treats, to all future time.  cess now than thirty or forty years ago; that there
We have not time at present, en-aged as we are, is vast mischief done by ignorant pretenders to known a   o i     pen eae         aeledge in regard to the disease, and in view of the proby day and by night, in the work of combating this          t    dise    and invie  of thepr
very disease, now prevailing in our city, to do more bability that a majority of southern physicians will
than give this cursory notice of what we consider be called upon to treat the disease, we trust that this
as undoubtedly the most able and erudite medical ableand comprehensive treatise wille vey genepublication our country has yet produced. But in rally read in the south.-Memphis Iled. Recorder,
view of the startling fact, that this, the most maligBY THE SAME AUTHOR.
PNEUMONIA; its Supposed Connection, Pathological and Etiological, with Anu
tumnal Fevers, including an Inquiry into the Existence and Morbid Agency of Malaria. In one
handsome octavo volume, extra cloth, of 500 pages. $3 00.
LUDLOW (J. L.), M. D.
A YMANUAL OF EXAMINATIONS upon Anatomy, Physiology, Surgery,
Practice of Medicine, Obstetrics, Materia Medica, Chemistry, Pharmacy, and Therapeutics. To
which is added a Medical Formulary.  Third edition, thoroughly revised and greatly extended
and enlarged. With 370 illustrations. In one handsome royal 12mo. volume, leather, of 816
large pages. $2 50.
The great popularity of this volume, and the numerous demands for it during the two years in which
it has been out of print, have induced the author in its revision to spare no pains to render it a
correct and accurate digest of the most recent condition of all the branches of medical science. In
many respects it may, therefore, be regarded rather as a new book than a new edition, an entire
section on Physiology having been added, as also one on Organic Chemistry, and many portions
having been rewritten. A very complete series of illustrations has been introduced, and every
care has been taken in the mechanical execution to render it a convenient and satisfactory book for
study or reference. The arrangement of the volume in the form of question and answer renders it
especially suited for the office examination of students and for those preparing for graduation.
We know of no better companion for the student crammed into his head by the various professors to
during the hours spent in the lecture room, or to re- whom he is compelled to listen.-Western Lancet,
fresh, at a glance, his memory of the various topics May, 1857.
LEHMANN  (C. G.)
PHYSIOLOGICAL   CHEMISTRY.   Translated from  the second  edition  by
GEORGE E. DAY, M. D., F. R. S., &c., edited by R. E. ROGERS, M. D., Professor of Chemistry
in the Medical Department of the University of Pennsylvania, with illustrations selected from
Funke's Atlas of Physiological Chemistry, and an Appendix of plates. Complete in two large
and handsome octavo volumes, extra cloth, containing 1200 pages, with nearly two hundred illustrations. $6 00.
The work of Lehmann stands unrivalled as the   The most important contribution as yet made to
most comprehensive book of reference and informa- Physiological Chemistry.-Am. Journal lZied. Scition extant on every branch of the subject on which  nces, Jan. 1856.
it treats.-~Edinburgh Journal of Medical Science.
BY THE SAME AUTHOR. (Lately Published.)
MANUAL OF CHEMICAL PHYSIOLOGY.  Translated from the German,
with Notes and Additions, by J. CHESTON MORRIS, M. D., with an Introductory Essay on Vital
Force, by Professor SAMUEL JACKSON, M. D., of the University of Pennsylvania. With illustrations on wood. In one very handsome octavo volume, extra cloth, of 336 pages. $2 25.
Fror, Prof. Jackson's Introductory Essay.
In adopting the handbook of Dr. Lehmann as a manual of Organic Chemistry for the use of the
students of the University, and in recommending his original work of PHYSIOLOGICAL CHEMISTRY
for their more mature studies, the high value of his researches, and the great weight of his authority in that important department of medical science are fully recognized.




AND SCIENTIFIC PUBLICATIONS.                                           21
LAWRENCE (W.), F. R. S., &c.
A TREATISE ON DISEASES OF THE EYE. A  new edition, edited,
with numerous additions, and 243 illustrations, by ISAAC HAYS, M. D., Surgeon to Will's Hospital, &c. In one very large and handsome octavo volume, of 950 pages, strongly bound in leather
with raised bands. $5 00.
M EIGS (CHARLES D.), M. D.,
Professor of Obstetrics, &c. in the Jefferson Medical College, Philadelphia.
OBSTETRICS: THE SCIENCE AND THE ART. Third edition, revised
and improved. With one hundred and twenty-nine illustrations. In one beautifully printed octavo
volume, leather, of seven hundred and fifty-two large pages. $3 75.
The rapid demand for another edition of this work is a sufficient expression of the favorable
verdict of the profession. In thus preparing it a third time for the press, the author has endeavored
to render it in every respect worthy of the favor which it has received. To accomplish this he
has thoroughly revised it in every part. Some portions have been rewritten, others added, new
illustrations have been in many instances substituted for such as were not deemed satisfactory,
while, by an alteration in the typographical arrangement, the size of the work has not been increased,
and the price remains unaltered. In its present improved form, it is, therefore, hoped that the work
will continue to meet the wants of the American profession as a sound, practical, and extended
SYSTEM OF MIDWIFERY.
Though the work has received only five pages of   The best American work on Midwifery that is
enlargement, its chapters throughout wear the im- accessible to the student and practitioner —N. W.
press of careful revision. Expunging and rewriting, Med. and Surg. Journal, Jan. 1857.
remodelling its sentences, with occasional new ma-   This is a standard work by a great American Ob
terial, all evince a lively desire that it shall deserve setrician. It is the third and last edition, and, ii
to be regarded as improved in manner as well as the language of the nreface, the author has "brouh
matter. In the matter, every stroke of the pen has the subject up to the latest dates of real improve
increased the value of the book, both in expungings   ntin our art and Science.-Nas^eil l Jozur. if
and additions -Western Lancet, Jan. 1857.       Med. and  S      nrg., May, 1857.
BY THE SAME AUTHOR. (Julst Issued.)
WOMAN: HER DISEASES AND THEIR REMEDIES. A Series of Lotures to his Class. Fourth and Improved edition. In one large and beautifully printed octevo
volume, leather, of over 700 pages. $3 60.
In other respects, in our estimation, too much can-   Full of important matter, conveyed in a ready nd
not be said in praise of this work. It abounds with  agreeable manner.-St.Louis Med. and Surg. J~ur.
beautiful passages, and for conciseness, for originality, and for all that is commendable in a work on   There is an off-hand fervor, a glow, and a wirmthe diseases of females, it is not excelled, and pro- heartedness infecting the effort of Dr. Meigs, vhich
bably not equalled in the English language. On the  is entirely captivating, and which absolutely hurwhole, we know of no work on the diseases of wo-  is the reader through from beginning to end. Bemen which we can so cordially commend to the  sides, the book teems with solid instruction, and
student and practitioner as the one before us.-Ohio it shows the very highest evidence of ability, viz.,
Med. and Surg. Journal.                         the clearness with which the information is presented. We know of no better test of one's underThe body of the book is worthy of attentive con- standing a subject than the evidence of the power
sideration, and is evidently the production of a  of lucidly explaining it. The most elementary, as
clever, thoughtful, and sagacious physician. Dr. well as the obscurest subjects, under the pencil of
Meigs's letters on the diseases of the external or-  Prof. Meigs, are isolated and made to stand out in
gans, contain many interesting and rare cases, and  such bold relief, as to produce distinct impressions
many instructive observations. We take our leave upon the mind and memory of the reader.-Th
of Dr. Meigs, with a high opinion of his talents and  Charleston Med. Journal.
originality.-The British and Foreign Medico-Chirurgical Review.                                  Professor Meigs has enlarged and amended this
great work, for such it unquestionably is, having
Every chapter is replete with practical instruc-   ate ordl of criticism at home and abroad
tioipress of hn the composition  passed the ordeal of criticism at home and abroad,
tion, a e and     eperie  in    he  is    s      ut been itproved thereby; for in this new edition
ofe an acut e and experienced mind.  T   is   - hereisterse-   author has introduced real mprovemets, and
ness, and at the same time an accuracy in his de- increased the value and utility of the book iscription of symptoms, and in the rules for diagnosis, ineasurabl. It pesents o mani y nof el, bright,
which cannot fail to recommend the volame to the an sparking thoughts such an exuberance of ew
and sparkling thoughts; such an exuberance of new
attention of the reader.-  Abstact  ideas on almost every page, that we confess ourIt contains a vast amount of practical knowledge, selves to have become enamored with the book
by one who has accurately observed and retained  and its author; and cannot withhold our congratuthe experience of many years. —Dublin Quarterly lations from our Philadelphia confreres, that such a.ournal.                                        teacher is in their service. —. Y. Med. Gazette.
BY THE SAME AUTHOR.
ON THE NATURE, SIGNS, AND TREATMENT OF CHILDBED
FEVER. In a Series of Letters addressed to the Students of his Class. In one handsone
octavo volume, extra cloth, of 365 pages. $2 50.
The instructive and interesting author of this lectable book. *  *  * This treatise upon o(ildwork, whose previous labors have placed his coun- bed fevers will have an extensive sale, beinV destrymen under deep and abiding obligations, again  tined, as it deserves, to find a place in the library
challenges their admiration in the fresh and vigor- of every practitioner who scorns to lag in thetear.ous, attractive and racy pages before us. It is a de- Nashville Journal of Mfedicine and Surgery.
BY THE SAME AUTHOR; WITH COLORED PLATES.
A TEATIS ON ACTE               TE AND CHRONIC DISEASES OF THE NECK
OF THE UTERUS. With numerous plates, drawn and colored from nature in thie highest
style of art. In one handsome octavo volume, extra cloth. $4 50.
MAYNE'S DISPENSATORY  AND  THERA- MALGAIGNE'S OPERATIVE SURGERY, based
PEUTICAL REMEMBRANCER. With every   on Normal and Pathological Anatomy. TransPractical Formula contained in the three British   lated from the French by FREDERICK BRITTAN,
Pharmacopoeias. Edited, with the addition of the   A.B.,M.D. Withnumerous illustrations onwood.
Formulm of the U. S. Pharmacopoeia, by R. E.   In one handsome octavo volume, extra cloth, of
GRIFFITH, 5I. D. 1 12mo. vol. ex. cl., 300 pp. 75 c.   nearly six hundred pages. $2 25.




22                       BLANCHARD & LEA'S MEDICAL
MACLISE (JOSEPH), SURGEON.
SUJRGICAL ANATOMY. Forming one volume, very large imperial quarto.
With sixty-eight large and splendid Plates, drawn in the best style and beautifully colored. Containing one hundred and ninety Figures, many of them the size of life. Together with copious
and explanatory letter-press.  Strongly and handsomely bound in extra cloth, being one of the
cheapest and best executed Surgical works as yet issued in this country. $11 00.
*** The size of this work prevents its transmission through the post-office as a whole, but those
who desire to have copies forwarded by mail, can receive them  in five parts, done up in stout
wrappers.  Price $9 00.
One of the greatest artistic triumphs of the age   A work which has no parallel in point of acenu
in Surgical Anatomy.-British American Medical racy and cheapness in the English language.-N. Y.
Journal.                                           Journal of Medicine.
No practitioner whose means will admit should
fail to possess it.-Ranking's Abstract.              We are extremely gratified to announce to the
Too mueth cannot be said in its praise; indeed, profession the completion of this truly magnificent
Too much cannot be said in its praise; indeed, wk, which,' as a whole, certsinly stands unriwork, which,'as a whole certainly stands anti.we have not language to do it justice.-Ohio Xedicwe  have not language to do itjustic..O     eo ed —  valled, both for accuracy of drawing, beauty of
cal and Surgical Journal.             coloring, and all the requisite explanations of the
The most accurately engraved and beautifully  subject in hand —The New  Orleans Medica and
colored plates we have ever seen in an American  Surgical Journal.
book-one of the best and cheapest surgical works
ever published.~-Bualo Medical Journal.              This is by far the ablest work on Surgical Anaever* publihed.-ufl Mtomy that has come under our observation. We
It is very rare that so elegantly printed, so well know of no other work that would justify a stuillustrated, and so useful a work, is offered at so  dent, in any degree, for neglect of actual dissecmoderate a price.-Charleston M.edical Journal.    tion. In those sudden emergencies that so often
arise, and which require theinstantaneous command
ts plates can boast a speriority which places of minute anatomical knowledge, a work of this kind
hem almost beyond the reachof competition.-~Medi- keeps the details of the dissecting-room perpetually
l. Examiner.                                      fresh in the memory.-The Western Journal of MediCountry practitioners will find these plates of im- cine and Surgery.
lense value. —. Y. Medical Gazette.
MILLER  (HENRY), M. D.,
Professor of Obstetrics and Diseases of Women and Children in the University of Louisville.
PMINCIPLES AND PRACTICE OF OBSTETRICS, &c.; including the Treatnent of Chronic Inflammation of the Cervix and Body of the Uterus considered as a frequent
ciuse of Abortion.  With about one hundred illustrations on wood. In one very handsome octawo volume, of over 600 pages. (Lately Published.) $3 75.
Tie reputation of Dr. Miller as an obstetrician is too widely spread to require the attention of
the Irofession to be specially called to a volume containing the experience of his long and extensive
practice.  The very favorable reception accorded to his " Treatise on Human Parturition," issued
some years since, is an earnest that the present work will fulfil the author's intention of providing
withirt a moderate compass a complete and trustworthy text-book for the student, and book of reference for the practitioner.
We congratulate the author that the task is done. tion to which its merits justly entitle it. The style
We congratulate him that he has given to the medi- is such that the descriptions are clear, and each subcal public a work which will secure for him a high  ject is discussed and elucidated with due regard to
and permanent position among the standard autho- its practical bearings, which cannot fail to make it
rities on the principles and practice of obstetrics, acceptable and valuable to both students and pracCongratulations are not less due to the medical pro- titioners.  We cannot, however, close this brief
fession of this country, on the acquisition of a trea- notice without congratulating the author and the
tise embodying the results of the studies, reflections, profession on the production of such. an excellent
and experience of Prof. Miller. Few men, if any, treatise. The author is a western man of whomwe
in this country, are more competent than he to write feel proud, and we cannot but think that his book
on thisdepartment of medicine. Engaged for thirty-  will find many readers and warm admirers wherever
five years in an extended practice of obstetrics, for obstetrics is taught and studied as a science and an
many years a teacher of this branch of instruction  art.-The Cincinnati Lancetand Observer, Feb. 1858.
in one of the largest of our institutions, a diligent   A most respectable and valuable addition to our
student as well as a careful observer, an original and  home medical literature, and one reflecting credit
independent thinker, wedded to no hobbies, ever alike on the author and the institution to which he
ready to consider without prejudice new views, and  is attached. The student will find in this work a
to adopt innovations if they are really improvements, most useful guide to his studies; the country pracand withal a clear, agreeable writer, a practical titioner, rusty in his reading, can obtain from its,reatise from his pen could not fail to possess great pages a fair resume of the modern literature of the
alue. —Bufalo Med Journal, Mar. 1858.             science; and we hope to see this American producIn fact, this volume must tale its place among the  tion generally consulted by the profession.-Va.
standard systematic treatises on obstetrics; a posi- Med. Journal, Feb. 1858.
MACKENZIE (W.), M. D.,
Surgeon Oculist in Scotland in ordinary to Her Majesty, &c. &c.
A PRACTICAL TREATISE ON DISEASES AND INJURIES OF THE
EYe. To which is prefixed an Anatomical Introduction explanatory of a Horizontal Section of
the Human Eyeball, by THOMAS WHARTON JONES, F. R. S. From  the Fourth Revised and Enlarget London Edition. With Notes and Additions by ADDINELL HEWSON, M. D., Surgeon to
Wills Hiospital, &c. &c. In one very large and handsome octavovolume, leather, raised bands, with
plates and numerous wood-cuts. $5 25.
The treatise of Dr. Mackenzie indisputably holds able manner in which the author's stores of learning
the first place and forms, in respect of learning and and experience were rendered available for general
research, an lIncyclopaedia unequalled in extent by use, at once procured for the first edition, as well on
any other work of the kind, either English or foreign. the continent as in this country, that high position
-Dixon on Diseases of the Eye.                     as a standard work which each successive edition
Few modern books on any department of medicine has more firmly established.  We consider it the
or surgery have met with such extended circulation, duty of every ne who has the love of his profession
or have procured for their authors a like amount of and the welfare of his patient at heart, to make himEuropean celebrity. The immense research which  self familiar with this the most complete work in
it displayed, the thorough acquaintance with the the English language upon the diseases of the eye,
subject, practically as well as   --- -fiefly, and the — ed. Times and Gazette.




AND SCIENTIFIC PUBLICATIONS.                                               23
MiLLER  (JAMES), F. R. S. E.,
Professor of Surgery in the University of Edinburgh, &c.
RP[t-qIN-IPLES OF SURGERY. Fourth American, from the third and revised
Edinburgh edition. In one large and very beautiful volume, leather, of 700 pages, with two
hundred and forty illustrations on wood. $3 75.
The work of Mr. Miller is too well and too favor-   The work takes rank with Watson's Practice of
ably known among us, as one of our best text-books, Physic; it certainly does not fall behind that great
to render any further notice of it necessary than the  work in soundness of principle or depth of reasonannouncement of a new edition, the fourth in our ing and research. No physician who values his recountry, a proof of its extensive circulation among putation, or seeks the interests of his clients, can
us. As a concise and reliable exposition of the sci- acquit himself before his God and the world without
ence of modern surgery, it stands deservedly high-  making himself familiar with the sound and philowe know not its superior.-Boston Med. and Surg. sophical views developed in the foregoing book.Journal.                                           New Orleans 3Med. and Surg. Journal.
BY TH'IE SAME AUTHOR. (Just Issued.)
THE PRACTICE OF SURGERY.  Fourth American fron  the last Edinburgh edition. Revised by the American editor. Illustrated by three hundred and sixty-four
engravings on wood. In one large octavo volume, leather, of nearly 700 pages. $3 75.
No encomium of ours could add to the popularity  his works, both on the principles and practice of
of Miller's Surgery. Its reputation in this country  surgery have been assigned thehighest rank. If we
is unsurpassed by that of any other work, and, when  were limited to but one work on surgery, that one
taken in connection with the author's Principles of should be Mliller's, as we regard it as superior to all
Surgery, constitutes a whole, without reference to  others.-St. Louis Med. and Surg. Journal.
to which no conscientious surgeon would be willing
practice his art. —Southern Med. aed Surg. Journal.   The author has in this and his " Principles," pre-. seated to the profession one of the most completeand
It is seldom that two volumes have ever made so reliable systems of Surgery extant. His style of
profound an impression in so short a time as the writing is original, impessive, and en-aging, ener~
Prineiples" and the " Practice" of Surgery by  getic, concise, and lucid. Few have the faculty of
Mr. Miller-or so richly merited the reputation they  condensing so much in small space, and at the same
have acquired. The author is an eminently sensi- time  so persistently holding tattent      hether
ble, practical, and well-informed man, who knows as a text-book for students or a book of reference
exactly what he is talking about and exactly how to  for practitioners, it cannot be too strongly recomtalk it.-Kentucky M:edical Recorder.               mended.-Southern Journal of Med. and Physical
By the almost unanimous voice of the profession, Sciences.
MORLAND  (W. W.), M. D.,
Fellow of the Massachusetts Medical Society, &c.
DISEASES OF THE URINARY ORGANS; a Compendium of their Diagnosil,
Pathology, and Treatment.  With illustrations.  In one large and handsome octavo volume, of
about 600 pages, extra cloth.  (Just Issued.)  $3 50.
Taken as a whole, we can recommend Dr. Mor- yet in a succinct, narrational style, such as to renler
land's compendium as a very desirable addition to  the work one of great interest, and one which will
the library of every medical or surgical practi- prove in the highest degree useful to the general
tioner.-B rit. and For. Med.-Chir. Rev., April, 1859. practitioner. To the members of the professionin the
Every medical practitioner whose attention has country it will be peculiarly valuable, on account
been to any extent attracted towards the class of of the characteristics which we have mentioned,
diseases to which this treatise relates, must have  and the ione broad aim of practical utility which is
often and sorely experienced the want of some full, kept in view, and which shines out upon every page,
yet concise r-cent compendium to which he could together with the skill which is evinced in the conrefer. This desideratumn has been supplied by Dr. bination of this grand requisite with the utmost
Morland, and it has been ably done. He has placed  brevity which a just treatment of the subjects would
before us a full, judicious, and reliable digest. adimit. —N. Y. Journ. of Medicine, Nov. 1858.
Each subject is treated with sufficientminulteness,'MONTGOMr ERY  (W                ),. F.)  M. D.  M. R   1. A., &c.
Professor of Midwifery in the King and Queen's College of Physicians in Ireland, &c.
AN EXPOSITION OF THE SIGNS AND SYMLPTOMS OF PREGNANCY.
With some other Papers on Subjects connected with Midwifery.  From the second and enlarged
English edition.  With two exquisite colored plates, and numerous wood-cuts.  In one very
handsome octavo volume, extra cloth, of nearly 600 pages.  (Lately Published.)  $3 75.
A book unusually rich in practical suggestions.-  has been weighed and reweighed through years f
Am. Journal Med. Sciences, Jan. 1857.             preparation; that this is of all others the bookof
These several subjects so interesting in them- Obstetric Law, on each of its several topics; onall
selves, and so important, every one of them, to the points connected with pregnancy, to be everywlere
most delicte and precious of social relations, con- received as a manual of special jurisprudence at
trolling often the honor and domestic peace of a once announcing fact, affordingargument, esta)lislfamily, the legitimacy of offspring, or the life of its 1ig precedent, and governing alike the jurymmn, adparent, are all treated with an elegance of diction  vocate, and judge. It is not merely in its lgal refulness of illustrations, acuteness and justice of rea  lations that we fnd tis work so interesting. Hardly
soning, unparalleled inobstetrics, and unsurpassed in a page but that lias its hints or facts imp:,rtant to
medicine. The reader's interest can never flag, so the general practitioner; and not a chapter without
fresh, and vigorous, and classical is our author's especial matter for the anatomist, phys-ologist, or
style; and one forgets, in the renewed charm of pathologist.-N. A. Jled.-Chir. Reiew) March,
every page, that it, and every line, and every word 1857.
MOHR (FRANC IS), PH. D., AND REDWOOD (THEOPHILUS).
PRACTICAL PHARMACY. Comprising the Arrangements, Apparatus, and
Manipulations of the Pharmaceutical Shop and Laboratory.  Edited, with extensive Additions,
by Prof: WILLIAM  PROCTER, of the Philadelphia College of Pharmacy. In one handsomely
printed octav  volume, extra cloth, of 570 pages, with over 500 engravings on wood.  $2 75,




24                     BLANCHARD & LEA'S MEDICAL
NEILL (JOHN), M. D.,
Surgeon to the Pennsylvania Hospital, &c.; and
FRANCIS GURNEY SMITH, M. D.,
Professor of Institutes of Medicine in the Pennsylvania Medical College.
AN ANALYTICAL COMPENDIUM OF THE VARIOUS BBRANCHES
OF IVEDICAL SCIENCE; for the Use and Examination of Students. A new edition, revised
and improved. In one very large and handsomely printed royal. 12mo. volume, of about one
thousand pages, with 374 wood-cuts. Strongly bound in leather, with raised bands. $3 00.
The very flattering reception which has been accorded to this work, and the high estimate placed
upon it by the profession, as evinced by the constant and increasing demand which has rapidly exhausted two large editions, have stimulated the authors to render the volume in its present revision
more worthy of the success which has attended it. It has accordingly been thoroughly examined,
and such errors as had on former occasions escaped observation have been corrected, and whatever
additions were necessary to maintain it on a level with the advance of science have been introduced.
The extended series of illustrations has been still further increased and much improved, while, by
a slight enlargement of the page, these various additions have been incorporated without increasing
the bulk of the volume.
The work is, therefore, again presented as eminently worthy of the favor with which it has hitherto
been received. As a book for daily reference by the student requiring a guide to his more elaborate
text-books, as a manual for preceptors desiring to stimulate their students by frequent and accurate
examination, or as a source from which the practitioners of older date may easily and cheaply acquire
a knowledge of the changes and improvement in professional science, its reputation is permanently
established.
The best work of the kind with which we are the students is heavy, and review necessary for an
acquainted.-Mfed. Examiner.                     examination, a compend is not only valuable, but
Having made free use of this volume in our ex-it is almost a sine qua non. The one before us is,
aminations of pupils, we can speak from experi- in most of the divisions, the most unexceptionable
ence in recommending it as an admirable compend     all books of the kind that we know of.  The
newest and soundest doctrines and the latest imfor students, and as especially useful to preceptors nwet an  soundest doctries and the latest imo
who examine their pupils. It will save the teacher provements and discoveries are explicitly, though
much labor by enabling him readily to recall all of concisely, laid before the student  There is a class
the points upon which his pupils should be ex- to whom we very sincerely commend this cheap book
amined. A work of this sort should be in the hands as worth its weight in silver-that class is thegraduof every one who takes pupils into his office with a ates in medicine of more than ten years' standing
viewof examining them; and this is unquestionably  who have not studied medicine since. They will
he best of its class.-Transylenia Med. Journal,   perhaps find out from it that the science is not exactly
now what it was when they left it off. —The StethoIn the rapid course of lectures, where work for scope.
NELIGAN  (J. MOORE), M. D., M. R. I.A., &c,
(A splendid work. Just Issued.)
ATLAS OF  CUTANEOUS DISEASES.  In one beautiful quarto volume, extra
cloth, with splendid colored plates, presenting nearly one hundred elaborate representations of
disease. $4 50.
This beautiful volume is intended as a complete and accurate representation of all the varieties
of Diseases of the Skin. While it can be consulted in conjunction with any work on Practice, it has
especial reference to the author's " Treatise on Diseases of the Skin," so favorably received by the
profession some years since. The publishers feel justified in saying that few more beautifully executed plates have ever been presented to the profession of this country.
Neligan's Atlas of Cutaneous Diseases supplies a give, at a coup d'cil, the remarkable peculiarities
long existent desideratum much felt by the largest of each individual variety. And while thus the disclass of our profession. It presents, in quarto size, ease is rendered more definable, there is yet no loss
16 plates, each containing from 3 to 6 figures, and of proportion incurred by the necessary concentraforming in all a total of 90 distinct representations tion. Each figure is highly colored, and so truthful
of the different species of skin affections, grouped has the artist been that the mostfastid ous observer
together in genera or families. The illustrations could not justly take exception to the correctness of
have been taken from nature, and have been copied the execution of the pictures under his scrutiny.with such fidelity that they present a striking picture Montreal Med. Chronicle.
of life; in which the reduced scale aptly serves to
BY THE SAME AUTHOR.
A PRACTICAL TREATISE ON DISEASES OF THE SKIN. Third
2.merican edition. In one neat royal 12mo. volume, extra cloth, of 334 pages. $1 00.
The two volumes will be sent by mail on receipt of Five Dollars.
OWEi  ON  THE DIFFERENT FORMS OF I One vol. royal 12mo., extra cloth vith numerous
THE,KE.E OTON, AND OF THE TEETH.   illustrations. $1 25.
PI RRIlE (WILLIAM), F. R. S. E.,
Professor of Surgery in the University of Aberdeen.
THE PREINCIPLES AND PRACTICE OF SURGERY. Edited by JOIN
NEILL, M. D., Professor of Surgery in the Penna. Medical College, Surgeon to the Pennsylvania
Hospital, &c. In one very handsome octavo volume, leather, of 780 pages, with 316 illustrations.
$3 75.
We know of no other surgical work of a reason- rately discussed the principles of surgery, and a
able size, wherein there is so much theory and prac- safe and effectual practice predicated upon them.
tice, or where subjects are more soundly or clearly  Perhaps no work upon this subject heretofore issued
taught.-The Stethoscope.                        is so full upon the science of the art of surgery. —
Prof. Pirrie, in the work before us, has elabo- Nashville Journal of Medicine and Surgery.




AND SCIENTIFIC PUBLICATIONS.                                          25
PARRISH  (EDWARD),
Lecturer on Practical Pharmacy and Materia Medica in the Pennsylvania Academy of Medicine, &c.
AN INTRODUCTION TO PRACTICAL PHARMACY. Designed as a TextBook for the Student, and as a Guide for the Physician and Pharmaceutist. With many Formule  and Prescriptions.  Second edition, greatly enlarged and improved.  In one handsome
octavo volume of 720 pages, with several hundred Illustrations, extra cloth. $3 50. (NVow
Ready.)
During the short time in which this work has been before the profession, it has been received
with very great favor, and in assuming the position of a standard authority, it has filled a vacancy
which had been severely felt. Stimulated by this encouragement, the author, in availing himself
of the opportunity of revision, has spared no pains to render it more worthy of the confidence bestowed upon it, and his assiduous labors have made it rather a new book than a new edition, many
portions having been rewritten, and much new and important matter added. These alterations and
improvements have been rendered necessary by the rapid progress made by pharmaceutical science
during the last few years, and by the additional experience obtained in the practical use of the
volume as a text-book and work of reference.  To accommodate these improvements, the size of
the page has been materially enlarged, and the number of pages considerably increased, presenting
in all nearly one.halfrmore matter than the last edition. The worlc is therefore now presented as a
complete exponent of the subject in its most advanced condition. From the most ordinary matters
ill the dispensing office, to the most complicated details of the vegetable alkaloids, it is hoped that
everything requisite to the practising physician, and to the apothecary, will be found fully and
clearly set forth, and that the new matter alone will be worth more than the very moderate cost of
the work to those who have been consulting the previous edition.
That Edward Parrish, in writing a book upon there is no production of the kind in the English
practical Pharmacy some few years ago —one emi- lanuage so well adapted to the wants of the pharnently original and unique-did the medical and maceutist and druggist. To physicians, also, it canpharmaceutical professions a great and valuable ser- not fail to be highly valuable, especially to those
vice, no one, we think, who has had access to its who are obliged to prepare and compound many of
pages will deny; doubly welcome, then, is this new  their own medicines.-N. Am. Med. Chir. Review,
edition, containing the added results of his recent Jan. 1860.
and rich experience as an observer, teacher, and
practic tl operator in the pharmaceutical laboratory.   Of course, all apothecaries who have not already
The excellent plan of the first is more thoroughly, a copy of the first edition will procure one of this;
and in detail, carried out in this edition. —Peninsular it is, therefore, to physicians residing in the country
Rled. Journal, Jan. 1860.                       and in small towns, who cannot avail themselves of
We know of no work on the subject which would the skill of an educated pharmaceutist, that we
be more indispensable to the physician or student woul especially commend this work. In it they
desiring information on the subjectof which it treats. will find all that they desire to know, and should
With Griffith's " Medical Formulary" and this, the know, but very little of which they do really rnow
practising physician would be supplied with nearly in reference to this important collateral branch of
or quite all the most useful information on the sub- their profession; for it is a well established fact,
jct.- ChaIrleston Med. sJournal and Reiew, Jan.  that, in the education of physicians, while the sci-18t.                                           ence of medicine is generally well taught, very
little attention is paid to the art of preparing them
This edition, now much enlarged, is one of the  i,  and we know not how this defect can be so
mssfwokothpa  year-Nfor use, ad we know not how this defect can be so
most useful works of the past year.- N. 0. Med. well remedied as by procuring and consulting Dr.
anxd Surg. Journal, Jan. 1860.                  Parrish's excellent work. —St. Louis MIed. Journal.
The whole treatise is eminently practical; and Jan. 1860.
PEASLEE  (E. R.), M. D.,
Professor of Physiology and General Pathology in the New York Medical College.
HUMAN   IHISTOLOGY, in its relations to Anatomy, Physiology, and Pathology;
for the use of Medical Students. With four hundred and thirty-four illustrations. In one handsome octavo volume, of over 600 pages. (Lately Published.)  $3 75.
It embraces a library upon the topics discussed   We would recommend it to the medical student
within itself, and is just what the teacher and learner and practitioner, as containing a summary of all that
need. Another advantage, by no means to be over- is known of the important subjects which it treats;
looked, everything of real value in the wide range of all that is contained in the great works of Simon
which it embraces, is with great skill compressed and Lehmann, and the organic chemists in general.
into an octavo volume of but little more than six Master this one volume, we would say to the medical
hundred pages. We have not only the whole sub- student and practitioner-master this book and you
ject of Histology, interesting in itself, ably and fully know all that is known of the great fundamental
discussed, but what is of infinitely greater interest principles of medicine, and we have no hesitation
to the student, because of greater practical value, in saying that it is an honor to the American mediare its relations to Anatomy, Physiology, and Pa- cal profession that one of its members should have
thology, which are here fully and satisfactorily set produced it.-St. Louis Med. and Surg. Journal,
forth.-Nashville Journ. of Med. and Surgery, Dec. March, 1858.
1857.
PEREIRA (JONATHAN), M. D., F. R. S., AND  L. S.
THE ELEMIENTS OF MATERIA MEDICA AND THERAPEUTICS.
Third American edition, enlarged and improved by the author; including Notices of most of the
Medicinal Substances in use in the civilized world, and forming an Encyclopedia of Materia
Medica. Edited, with Additions, by JOSEPH CARSON, M. D., Professor of Materia Medica and
Pharmacy in the University of Pennsylvania. In two very large octavo volumes of 2100 pages,
on small type, with about 500 illustrations on stone and wood, strongly bound in leather, with
raised bands. $9 00.
~*   Vol. II. will no longer be sold separate.
PARKER (LANGSTON),
Surgeon to the Queen's Hospital, Birmingham.
THE MODERN TREATMENT OF SYPHILITIC DISEASES, BOTH PRI.
MARY AND SECONDARY; comprising the Treatment of Constitutional and Confirmed Syphilis, by a safe and successful method. With numerous Cases, Formula, and Clinical Observations. From the Third and entirely rewritten London edition. In one.eat octavo volume,
extra cloth, of 316 pages. $1 75.




26                      BLANCHARD  E LEA'S MEDICAL
R.AMSBOTHAM  (FRANCIS H.), M.D.
THE PRINCIPLES AND PRACTICE OF OBSTETRIC MEDICINE AND
SURGERY, in reference to the Process of Parturition. A new and enlarged edition, thoroughly
revised by the Author. With Additions by W. V. KEATING, M. D. In one large and handsome
imperial octavo volume, of 650 pages, strongly bound in leather, with raised bands; with sixtyfour beautiful Plates, and numerous Wood-cuts in the text, containing in all nearly two hundred
large and beautiful figures. $5 00.
From Prof. Hodge, of the University of Pa.
To the American public, it is most valuable, from its intrinsic undoubted excellence, and as being
the best authorized exponent of British Midwifery. Its circulation will, I trust, be extensive throughout
our country.
It is unnecessary to say anything in regard to the truly elegant style in which they have brought it
utility of this work. It is already appreciated in our out, excelling themselves in its production, especountry for the value of the matter, the clearness of cially in its plates. It is dedicated to Prof. Meigs,
its style, and the fulness of its illustrations. To the and has the emphatic endorsement of Prof. Hodge,
physician's library it is indispensable, while to the as the best exponent of British Midwifery. We
student as a text-book, from which to extract the kn(,w of no text-book which deserves in all respects
material for laying the foundation of an education on  to be more highly recommended to students, and we
obstetrical science, it has no superior.-Ohio Med. could wish to see it in the hands of every practitioner,
and Surg. Journal.                              for they will find it invaluable for reference.-iMVed.
The publishers have secured its success by the Gazette.
RICORD  (P.), M. D.
A TREATISE ON THE VENEREAL DISEASE. By JOHN HUNTER, F. R. S.
With copious Additions, by PH. RICORD, M.D. Translated and Edited, with Notes, by FREEMAN
J. BUJMSTEAD, M. D., Lecturer on Venereal at the College of Physicians and Surgeons, New York.
Second edition, revised, containing a rdsumz  of RICORD'S RECENr LECTURES ON CHANCRE. In
one handsome octavo volume, extra cloth, of 550 pages, with eight plates. $3 25. (Just Issued.)
In revising this work, the editor has endeavored to introduce whatever matter of interest the recent investigations of syphilographers have added to our knowledge of the subject. The principal
source from which this has been derived is the volume of "Lectures on Chancre," published a few
months since by M. Ricord, which affords a large amount of new and instructive material on many
controverted points. In the previous edition, M. Ricord's additions amounted to nearly one-third
of the whole, and with the matter now introduced, the work may be considered to present his views
and experience more thoroughly and completely than any other.
Every one will recognize the attractiveness and secretaries, sometimes accredited and sometimes no,.
alnue which this work derives from thies presenting   In the notes to iHunter, the master substitutes himthe opinions of these twro mr'asters side by side. But, self for his interpreters, and gives his original thouglts
it must be admitted, what has made the fortune of to tle worll in a lucid and perfectly intelligible manthe book, is the fact that it contains the "most corn- ner. In conclusion we can say that this is inconplete embodiment of the veritable doctrines of the testably the best treatise on syphilis with which vwe
HO6pital du Midi," which has ever been made public. are acquainted, and, as we do not often employ the
The doctrinal ideas of M. Ricord, ideas which, if not phrase, we may be excused for expressing the hlop
universally adopted, are incontestably dominant, have that it may find a place in the library of every ph~heretofore onlybeeninterpretedby moreor Lessskilful sician. —Virginia tled. and Surg. Journal.
BY THE SAME AUTHOR.
RICOlRD'S LETTERS ON SYPHILIS. Translated by W. P. LATTiMOur M. D,
In one neat octavo volume, of 270 pages, extra cloth. $2 00.
RBOYLE'S MATERIA MEDICA AND THERAPEUTTCS  including the
Preparations of the Pharmacopoeias of London, Edinburgh, Dublin, and of the United States,
With many new medicines. Edited by JOSEPH CARSON, M. D. With ninety-eight illustrationts,
In one large octavo volume, extra cloth, of about 700 pages. $3 00.
ROKITANSKY  (CARL), M.D.,
Curator of the Imperial Pathological Museum, and Professor at the University of Vienna, &e.
A MANUAL OF PATHOLOGICAL ANATOMY. Four volumes, octavo,
bound in two, extra cloth, of about 1200 pages. Translated by W. E. SWAINE, EDWARD SIEVBKING, C. H. MOORE, and G. E. DAY. $5 50
The profession is too well acquainted with the re- so charged his text with valuable truths, that any
putation of Rokitansky's work to need our assur- attempt of a reviewer to epitomize is at once paraance that this is one of the mostprofound, thorough, lyzed, and must end in a failure.-Western Lancet,
and valuable books ever issued from the medical   As this is the highest source of knowledge upon
press. It is si generis, andhasno standardofcom- the important subject of which it treats, no real
parison. It is only necessary to announce that it is student can afford to be without it. The American
issued in a form as cheap as is compatible with its publishers have entitled themselves to the thanks of
size and preservation, and its sale follows as a the profession of their country, for this timeous and
matter of course. No library can be called cor- beautiful edition.-Nashille Journal of  edicine.
plete without it.-Buffalo Med. Journal.
As a book of reference, therefore, this work must
Ans attempt to give our readers any adequate idea prove of inestimablevalue, and we cannot toohighly
of the vast amount of instruction accumulated in recommend it to the profession.-Charleston Med.
these volumes, would be feeble and hopeless. The Journal and Revuiew.
effort of the distinguished author to concentrate   This book is a necessity to every practitioner.in a small space his great fund of knowledge, has Am. Med. iMornthly.
RIGBY  (EDWARD), M. D.,
Senior Physician to the General Lying-in Hospital, &c.
A   SYSTEM   OF   MIDN1WIFERK.   With Notes and  Additional Illustrations.
Second American Edition. One volume octavo, extra cloth, 422 pages. $2 50.
BY THE SAME AUTHOR. (Lately Published.)
ON THE CONSTITUTIONAL TREATMENT OF FEMALE DISEASES.
In one neat royal 12mo. volume, extra cloth, of about 250 pages. $1 00,




AND SCIENTIFIC PUBLICATIONS.                                            27
STILLE  (ALFRED), M.D.
THERAPEUTICS AND MATERIA MEDICA; a Systematic Treatise on the
Action, and Uses of Medicinal Agents, including their Description and History. In two large and
handsome octavo volumes, of 1789 pages. (Novw Ready, 1860.) $8 00.
This work is designed especially for the student and practitioner of medicine, and treats the various
articles of the Materia Medica from the point of view of the bedside, and not of the shop or of the
lecture-room. While thus endeavoring to give all practical information likely to be useful with.
respect to the employment of special remedies in special aflections, and the results to be anticipated
from their administration, a copious Index of Diseases and their Remedies renders the work eminertlv fitted for reference by showing at a glance the different means which have been employed,
and enabling the practitioner to extend his resources in difficult cases with all that the experience
of the profession has suggested. At the same time particular care has beet given to the subject
of General Therapeutics, and at the commencement of each class of medicines there is a chapter
devoted to the consideration of their common influence upon morbid conditions. The action of
remedial agents upon the healthy economy and on animals has likewise received particular notice,
from the conviction that their physiological effects will afford frequent explanations of their pathological influence, and in many cases lead to new and important suggestions as to their practical use
in disease. Within the scope thus designed by the author, no labor has been spared to accumulate
all the facts which have accrued from the experience of the profession in all ages and all countries;
and the vast amount of recent researches recorded in the periodical literature of both hemispheres
has been zealously laid under contribution. resulting in a mass of practical information scarcely
attempted hitherto in any similar work in the language.
Our expectations of the value of this work were  the practical utility of his book by passing briefly
based on the vwell-known reputation and character over the physical, botani al, ai: d commercial history
(t4 the author as a man of scholarly attainments, an  of medicines, and directirg attention chiefly to their
elegant writer, a candid inquirer after truth, and a physiological action, and their application for the
philosophical thinker; we knew that the task would  amelioration or cure of disease. He ignores hypothe.
be conscientiously performed, and that few, if any, sie and theory which are so alluring to many medical
among the distinguished medical teachers in this writers, and so liable to lead them astray, and concountry are better qualified than he to prepare a fines himself to such facts as have been tried in the
systematic treatise on therapeutics in accordance crucible of experience.-Chicago Medical Journal,
with the present requirements of medical science. March, 1860.
Our preliminary examination of the work has satis-   The plan pursued by the author in these very elafied us that we were not mistaken in our anticipa- borate volumes is not strictly one of scientific unity
tions. In congratulating the author on the comple- and precision; he has rather subordinated these to
tion of the great labor which such a work involves, practical utility. Dr. Stille has produced a work
we are hapi)y in expressing the conviction that its which will be valuable equally to the student of
merits will receive that reward which is above all medicine and the busy practitioner. -London Lanprice- the grateful appreciation of his medical bre- cet March 10 1860.
thren. —~ew Orleans Medical News, Marchl, 1860.  
thrs M l N, M, 10.   WVith Pereira, Dunglison, Mitchell, and Wood beWe think this work will do much to obviate the fore us, we may well ask if there was a necessity
reluctance to a thorough investigation of this branch  for a new book on the subject. After examining this
of scientific study, for in the wide range of medical work with some care, we can answer affirmatively.
literature treasured in the English tongue, we shall Dr. Wood's book is well adapted for students, while
hardly find a work written in a style more clear and Dr. Stille's will be more satisfactory to the practisimple, conveying forcibly the facts taught, and yet tioner, who desires to study the action of medicines.
free from turgirity and redundancy. Thereisafas- The author needs no encomiums from us, for he is
cination in its pages that will insure to it a wide well known as a ripe scholar and a man of the most
popularity and attentive perusal, and a degree of extensive readingin his profession. This work bears
usefulness not often attained through the influence  evidence of this fact on every page. —Cincinnati
of a single work. The author has much enhanced  Lancet, April, 1I60.
SMITH   (HENRY   H.), M.D.
MINOR  SURGERY; or, Hints on the Every-day Duties of the Surgeon.  With
247 illustrations. Third edition. 1 vol. royal 12mo., pp. 456. In leather, $2 25; cloth, $2 00.
BY THE SAME AUTHOR, AND
HORNER (WILLIAM  E.), M. 0D,
Late Professor of Anatomy in the University of Pennsylvania.
AN  ANATOMICAL  ATLAS, illustrative of the Structure of the 11Human Body.
In one volume, large imperial octavo, extra cloth, with about six hundred and fifty beautiful
figures. $3 00.
These figures are well selected, and present a late the student upon the completion of this Atlas,
complete and accurate representation of that won- as it is the most convenient work of the kind that
derful fabric, the human body. The plan of this has yet appeared; and we must add, the very beauAtlas, which renders it so peculiarly convenient tiful manner in which it is "got up" is so creditable
for the student, and its superb artistical execution, to the country as to be flattering to our national
have been already pointed out. We must congratu- pride.-American Medical JournaIl.
SHARPEY  (WILLIAM), M. D., JONES  QUAIN   M. D.,  AND
RICHARD  QUAIN, F. R. S., &c.
HUMAN ANATOMY. Revised, with Notes and Additions, by JosuPEPH LrDE)f
M. D., Professor of Anatomy in the University of Pennsylvania.  Complete ini two large octavo
volumes, leather, of about thirteen hundred pages. Beautifully illustrated with over five hundred
engravings on wood. $6 00.
SIMPSON  (J. Y.   M. D.,
Professor of Midwifery, &c., in the University of Edinburgh, &e.
CLINICAL LECTURES ON THE DISEASES OF FEMALES. With numerous illustrations.
This valuable series of practical Lectures is now  appearing in the c"MEDICAL NEWS AND
LIBRARY" for 1860, and can thus be had without cost by subscribers to the "AMERICAN JOURNAL
OF THE MEDICAL SCIENCES."  See p. 2.




28                     BLANCHARD & LEA'S MEDICAL
SARGENT  (F. W.), M. D.
ON BANDAGING AND OTHER OPERATIONS OF MINOR SURGERY.
Second edition, enlarged. One handsome royal 12mo. vol., of nearly 400 pages, with 182 woodcuts. Extra cloth, $1 40; leather, $1 50.
Sargent' s Minor Surgery has always been popular,   A work that has been so long and favorably known
and deservedly so. Itfurnishesthatknowledgeofthe to the profession as Dr. Sargent's Minor Surgery,
most frequently requisite performances of surgical needs no commendation from us. We would remark,
art which cannot be entirely understood by attend- however, in this connection, that minor surgery seling clinical lectures. The art of bandaging, which dom gets that attention in our schools that its imis regularly taught in Europe, is very frequently  portance deserves. Our larger works are also very
overlooked by teachers in this country; the student defective in their teaching on these small practical
and junior practitioner, therefore, may often require points. This little book will supply the void which
that knowledge which this little volume so tersely all must feel who have not studied its pages. —Westand happily supplies.-Charleston Med. Journ. and ern Lancet, March, 1856.
Review, March, 1856.
SMITH  (W. TYLER), M. D.,
Physician Accoucheur to St. Mary's Hospital, &c.
ON PARTURITION, AND THE PRINCIPLES AND PRACTICE OB
OBSTETRICS. In one royal 12mo. volume, extra cloth, of 400 pages. $1 25.
BY THE SAME AUTHOR.
A PRACTICAL TREATISE ON THE PATHOLOGY AND TREATMENT
OF LEUCORRHCEA. With numerous illustrations. In one very handsome octavo volume,
extra cloth, of about 250 pages. $1 50.
SOLLY ON THE HUMAN BRAIN; its Structure,  handsome octavo volume, extra cloth, of over 650
Physiology, and Diseases. From the Second and   pages, with about one hundred wood-cuts. $3 25.
much enlarged London edition. In one octave SIMON' GENERAL PATHOLOGY, as conducvolume, extra cloth, of 500 pages, with 120 wood-   ive to the Establishment of Rational Principles
cuts. $2 00.                                    for the prevention and Cure of Disease. In one
SKEY'S OPERATIVE SURGERY. In one very   octavo volume, extra cloth, of 212 pages. $1 25.
TODD  (R. B.), M. D,, F. R. S., &c.
CLINICAL LECTURES ON CERTAIN DISEASES OF THE URINARY
ORGANS AND ON DROPSIES. In one octavo volume, 284 pages. $1 50.
BY THE SAME AUTHOR. (NouW Ready.)
CLINICAL LECTURES ON CERTAIN ACUTE DISEASES. In one neat
octavo volume, of 320 pages, extra cloth. $1 75.
The subjects treated in this volume are-RHEUMATIC FEVER, CONTINUED FEVER, ERYSIPELAS,
ACUTE INTERNAL INFLAMMATION, PYEvMIA, PNEUMONIA, and the THERAPEUTICAL ACTION OF ALCOHOL. The importance of these matters in the daily practice of every physician, and the sound
practical nature of Dr. Todd's writings, can hardly fail to attract to this work the general attention
that it merits.
TANNER  (T. H.), M. D.,
Physician to the Hospital for Women, &c.
A MANUAL OF CLINICAL MEDICINE AND PHYSICAL DIAGNOSIS.
To which is added The Code of Ethics of the American Medical Association. Second
American Edition. In one neat volume, small 12mo., extra cloth, 87{ cents.
TAYLOR  (ALFRED  S.), M. D., F. R. S.,
Lecturer on Medical Jurisprudence and Chemistry in Guy's Hospital.
MEDICAL JURISPRUDENCE. Fourth American Edition. With Notes and
References to American Decisions, by EDWARD HARTSHORNE, M. D. In one large octavo volume,
leather, of over seven hundred pages. $3 00.
No work upon the subject can be put into the   It is not excess of praise to say that the volume
hands of students either of law or medicine which  before us is the very best treatise extant on Medical
will engage them more closely or profitably; and Jurisprudence. In saying this, we do not wish to
none could be offered to the busy practitioner of be understood as detracting from the merits of the
either calling, for the purpose of casual or hasty excellent works of Beck, Ryan, Traill, Guy, and
reference, that would be more likely to afford the aid others; but in interest and value we think it must
desired. We thereforerecommend it as the best and be conceded that Taylor is superior to anything that
safest manual for daily use.-American Journal of has preceded it.-N. W. Medical and Surg. Journal.
Medical Sciences.
BY THE SAME AUTHOR. (New Edition, just issued.)
ON POISONS, IN RELATION TO MEDICAL JURISPRUDENCE AND
MEDICINE. Second American, from a second and revised London edition.  In one large
octavo volume, of 755 pages, leather. $3 50.
Since the first appearance of this work, the rapid advance of Chemistry has introduced into
use many new substances which may become fatal through accident or design-while at the
same time it has likewise designated new and more exact modes of counteracting or detecting those
previously treated of. Mr. Taylor's position as the leading medical jurist of England, has during
this period conferred on him extraordinary advantages in acquiring experience on these subjects,
nearly all cases of moment being referred to him for examination, as an expert whose testimony
is generally accepted as final. The results of his labors, therefore, as gathered together in this
volume, carefully weighed and sifted, and presented in the clear and intelligible style for which
he is noted, may be received as an acknowledged authority, and as a guide to be followed with
implicit confidence.




AND SCIENTIFIC PUBLICATIONS.                                        29
TODD (ROBERT  BENTLEY), M. D., F. R. S.,
Professor of Physiology in King's College, London; and
WILLIAM  BOWMAN, F. R. S.,
Demonstrator of Anatomy in King's College, London.
THE PHYSIOLOGICAL ANATOMY AND PHYSIOLOGY OF MIAN. With
about three hundred large and beautiful illustrations on wood. Complete in one large octavo
volume, of 950 pages, leather. Price $4 50.
PP  Gentlemen who have received portions of this work, as published in the " MEDICAL NEWS
AND LIBRARY," can now complete their copies, if immediate application be made. It will be furnished as follows, free by mail, in paper covers, with cloth backs.
PARTS I., II., III. (pp. 25 to 552), $2 50.
PART IV. (pp. 553 to end, with Title, Preface, Contents, &c.), $2 00.
Or, PART IV., SECTION II. (pp. 725 to end, with Title, Preface, Contents, &c.), $1 25.
A magnificent contribution to British medicine, so well adapted to the wants of the medical student.
and the American physician who shall fail to peruse Its completion has been thus long delayed, that the
it, will have failed to read one of the most instruc- authors might secure accuracy by personal observative books of the nineteenth century.-N. 0. PMed, tion.-St. Louis Med. and Surg. Journal, Sept.'57.
and Surg. Journal, Sept. 1857.
and Surg. Joural, Sept. 1857..        Our notice, though it conveys but a very feeble
It is more concise than Carpenter'sPrinciples, and and imperfect idea of the magnitude and importance
more modern than the accessible edition of Muller's of the work now under consideration, already tranElements; its details are brief, but sufficient; its scends our limits; and, with the indulgence of our
descriptions vivid; its illustrations exact and copi- readers, and the hope that they will peruse the book
ous; and its language terse and perspicuous. —  for themselves, as we feel we can with confidence
Charleston Med. Journal, July, 1857.           recommend it, we leave it in their hands. - The
We know of no work on the subject of physiology Northwestern Med. and Surg. Journal.
TOYNBEE (JOSEPH), F. R. S.,
Aural Surgeon to, and Lecturer on Surgery at, St. Mary's Hospital.
A PRACTICAL TREATISE ON DISEASES OF THE EAR; their Diagnosis, Pathology, and Treatment. Illustrated with one hundred engravings on wood. In one
very handsome octavo volume, extra cloth, $3 00. (Now Ready.)
Mr. Toynbee's name is too widely known as the highest authority on all matters connected with
Aural Surgery and Medicine, to require special attention to be called to anything which he may
communicate to the profession on the subject. Twenty years' labor devoted to the present work
has embodied in it the results of an amount of experience and observation which perhaps no other
living practitioner has enjoyed. It therefore cannot fail to prove a complete and trustworthy guide
on all matters connected with this obscure and little known class of diseases, which so frequently
embarrass the general practitioner.
The volume will be found thoroughly illustrated with a large number of original wood-engravings, elucidating the pathology of the organs of hearing, instruments, operations, &c., and in every
respect it is one of the handsomest specimens of mechanical execution issued from the American
press.
The following condensed synopsis of the contents will show the plan adopted by the author, and
the completeness with which all departments of the subject are brought under consideration.
CHAPTER I. Introduction-Mode cf Investigation-Dissection.  I[. The External Ear-Anatomy-Pathology-Malformations - Diseases.  III. The External Meatus-Its Exploration.
IV. The External Meatus-Foreign Bodies and Accumulations of Cerumen. V. The External
Meatus-The Dermis and its Diseases. VI. The External Meatus —Polypi. VII. The External
Meatus-Tumors. VIII. The Membrana Tyinpani-Structure and Functions. IX. The Membrana Tympani-Diseases.  X. The Membrana Tympani-Diseases.  XI. The Eustachian
Tube-Obstructions.  XII. The Cavity of the Tympanum-Anlatomy-Pathology-Diseases.
XIII. The Cavity of the Tympanum-Diseases. XIV. The Mastoid Cells-Diseases. XV.
The Diseases of the Nervous Apparatus of the Ear, producing what is commonly called " Nervous Deafiess."  XVI. The Diseases of the Nervous Apparatus, continued. XVII. Malignant
Disease of the Ear.  XVIII. On the Deaf and Dumb.  XIX. Ear-Trumpets and their uses.
APPENDIX.
WILLIAMS (C. J. B.), M. D., F. R. S.,
Professor of Clinical Medicine in University College, London, &c.
PRINCIPLES  OF MEDICINE.  An Elementaiy View  of the Causes, Nature,
Treatment, Diagnosis, and Prognosis of Disease; with brief remarks on Hygienics, or the preservation of health. A new American, from the third and revised Bondon edition. In one octavo
volume, leather, of about 500 pages. $2 50. (Juzst Issued.)
We find that the deeply-interesting matter and expressed. It is a judgment of almost unqualified
style of this book have so far fascinated us, that we praise.-London Lancet.
have unconsciously hung upon its pages, not too   A text-book to which no other in our language is
long, indeed, for our own profit, but longer than re- comparable.-Charleston Medical Journal.
viewers can be permitted to indulge. We leave the
further analysis to the student and practitioner. Our   No work has ever achieved or maintained a more
judgment of the work has already been sufficiently deserved reputation.-Va. Med. and Surg. Journal.
WHAT TO OBSERVE
AT THE BEDSIDE AND AFTER DEATH, IN MEDICAL CASES.
Publishedunder the authority of the London Society for Medical Observation. A new American,
from the second and revised Londoi edition. In one very handsome volume, royal 12mo., extra
cloth. $1 00.
To the observer who prefers accuracy to blunders i One of the finest aids to a young practitioner we
and precision to carelessness, this little book is ins- have ever seen.-Pesninsular Journal of Medicins.
valuable. —fN. I. Journal of Medicine.




30                      BLANCHARD & LEA'S MEDICAL
laew  and much enlarged edition-(Just Issued.)
WATSON (THOMAS), M. D, &c.,
Late Physician to the Middlesex Hospital, &c.
LECTURES ON THE PRINCIPLES AND PRACTICE OF PHYSIC.
Delivered at King's College, London.  A new American, froma the last revised and enlarged
English edition, with Additions, by D. FRANCIS CONDIE, M. D., author of" A Practical Treatise
on the Diseases of Children," &c.  With one hundred and eighty.five illustrations on wood.  In
one very large and handsome volume, imperial octavo, of over 1200 closely printed pages in
small type; the whole strongly bound in leather, with raised bands.  Price $4 25.
That the high reputation of this work might be fully maintained, the author has subjected it to a
thorough revision; every portion has been examined with the aid of the most recent researches
in pathology, and the results of modern investigations in both theoretical and practical subjects
have been carefully weighed and embodied throughout its pages.  The watchful scrutiny of the
editor has likewise introduced whatever possesses immediate importance to the American physician
in relation to diseases incident to our climate which are little known in England, as well as those
points in which experience here has led to different modes of practice; and he has also added largely
to the series of illustrations, believing that in this manner valuable assistance may be conveyed to
the student in elucidating the text.  The work will, therefore, be found thoroughly on a level with
the most advanced state of medical science on both sides of the Atlantic.
The additions which the work has received are shown by the fact that notwithstanding an enlargement in the size of the page, more than two hundred additional pages have been necessary
to accommodate the two large volumes of the London edition (which sells at ten dollars), within
the compass of a single volume, and in its present form it contains the matter of at least three
ordinary octavos.  Believing it to be a work which should lie on the table of every physician, and
be in the hands of every student, the publishers have put it at a price within the reach of all, making
it one of the cheapest books as yet presented to the American profession, while at the sanme time
the beauty of its mechanical execution renders it an exceedingly attractive volume.
The fourth edition now appears, so carefully re-   The lecturer's skill, his wisdom, his learning, are
vised, as to add considerably to the value of a book  equalled by the ease of his graceful diction, his eloalready acknowledged, wherever the English lan- quence, and the far higher qualities of candor, of
guage is read, to bebeyond all comparison the best courtesy, of modesty, and of generous appreciation
systematic work on the Principles and Practice of of merit in others. May he long remain to instruct
Physic in the whole range of medical literature. us, and to enjoy, in the glorious sunset of his deEvery lecture contains proof of the extreme anxiety  dining years, the honors, the confidence and love
of the author to keep pace wvi h he advancing know- gained during his useful life.-. A. A. ied.-Chir,
ledge of the day, and to bring the results of the Review, July, 1858.
labors, not only of physicians, but of chemists and
histologists, before his readers, wherever they can    Watson's unrivalled, perhaps  unapproachable
be turned to useful account. And this is done with  wok on Practice-the copious additions nmade to
such a cordial appreciation of the merit due to the which (the fourth edition) have iven it all the noindustrious observer, such a generous desire to en- velty and much of the interest of a new book.courage younger and rising  men, and such a candid  Charleston Med. Journal, July, 1858.
acknowledgment of his own obligations to them,   Lecturers, practitioners, and students of medicine
that one scarcely knows whether to admire most the will equally hail the rea.ppearance of the work of
pure, simple, forcible English-the vast amount of Dr. Watson in the form of a new-a fourth-edition.
useful practical information condensed into the We merely do justice to our own feelings, and, we
Lectures —or the manly, kind-hearted, unassuming  are sure, of the whole profession, if we thank himn
character of the lecturer shining through his work. for having, in the trouble and turmoil of a large
-London lMed. Times and Gazette, Oct. 31, 1S57.   practice, made leisure to supply the hiatus caused
Thus these admirable volumes come before the  by the exhaustion of the publisher's stock of the
profession in theirfourth edition, abounding in those  third edition, which has been severely felt for the
distinguished attributes of moderation, judgment, last three years. For Dr. Watson has not merely
erudite cultivation, clearness, and eloquence, with  caused the lectures to be reprinted, but scattered
which they were from the first invested, but yet through the whole work we find additions or alteraricher than before in the results of more prolonged  tions which prove that the author has in every way
observation, and in the able appreciation of the sought to bring up his teaching to the level of the
latest advances in pathology and medicine by one most recent acquisitions in science.-Brit. and Fozr,
of the most profound medical thinkers of the day. —  Iedico-Chir. Review, Jan. 1858.
London Lancet, Nov. 14, 1857.
WALSHE (W. H.), M. D.,
Professor of the Principles and Practice of Medicine in University College, London, &c.
A PRACT1TCAL TREATISE ON DIBEASES OF THE LUNGS; including
the Principles of Physical Diagnosis.  A new American, from the third revised and much enlarged London edition.  In one vol. octavo, of 468 pages.  (Jeust Issged, June, 1860.)  $2 25.
The present edition has beeh carefully revised and much enlarged, and may be said in the main
to be rewritten. Descriptions of several diseases, previously omitted, are now  introduced; the
causes and mode of production of the more important affections, so far as they possess direct practical significance, are succinctly inquired into; an effort has been made to bring the description of
anatomical characters to the level of the wants of the practical physician; and the diagnosis and
prognosis of each complaint are more completely considered.  The sections on TREATMENT and
the Appendix (concerning the influence of climate on pulmonary disorders), have, especially, been
largely extended.-Author's Preface.
U:S'  To be followed by a similar volume on Diseases of the Heart and Aorta.
WILSON  (ERASMVUS), F. R. S.,
Lecturer on Anatomy, London.
ITHE   DISS ECTOR'S  MIA.NUAL; or, Prcetical and Surgicta  Anatonmy.  Third
American, from  the last revised and enlarged English edition. Modified and rearranged, by
W.ILLIAM HuNT, M. 1D., Demonstrator of Anatomy in the University of Pennsylvania.  In one
large and handsome royal 12smo. volume, leather, of 582 pages, with 154 illustrations.  $2 00.




AND SCIENTIFIC PUBLICATIONS                                            31
New  and much enlarged edition-(Just Issued.)"
WILSON  (ERASMUS), F. R,. S.
A SYSTEM OF HIUMAN ANATOMY, General and Special. A new and revised American, from the last and enlarged English Edition. Edited by W. H. GOBRECHT, M. i.,
Professor of Anatomy in the Pennsylvania Medical College, &c. Illustrated with three hundred
and ninety-seven engravings on wood. In one large and exquisitely printed octavo volume, of
over 600 large pages; leather.  $3 25.
The publishers trust that the well earned reputation so long enjoyed by this work will be more
than maintained by the present edition. Besides a very thorough revision by the author, it has been
most carefully examined by the editor, and the efforts of both have been directed to introducing
everything which increased experience in its use has suggested as desirable to render it a complete
text-book for those seeking to obtain or to renew an acquaintance with Human Anatomy. The
amount of additions which it has thus received may be estimated from the fact that the present
edition contains over one-fourth more matter than the last, rendering a smaller type and an enlarged
page requisite to keep the volume within a convenient size. The author has not only thus added
largely to the work, but he has also made alterations throughout, wherever there appeared the
opportunity of improving the arrangement or style, so as to present every fact in its most appropriate manner, and to render the whole as clear and intelligible as possible. The editor has
exercised the utmost caution to obtain entire accuracy in the text, and has largely increased the
number of illustrations, of which there are about one hundred and fifty more in this edition than
in the last, thus bringing distinctly before the eye of the student everything of interest or importance.
It may be recommended to the student as no less beauty of its mechanical execution, and the cleardistinguished by its accuracy and clearness of de- ness of the descriptions which it contains is equally
scription than by its typographical elegance. The evident. Let students, by all means examine tie
wood-cuts are exquisite.-Brit. and For. Medical claims of this work on their notice, before they purReview.                                          chase a text-book of the vitally important science..  which this volume so fully and easily unfolds.An elegant edition of one of the most useful and Lancet.
accurate systems of anatomical science which has
been issued from the press  The illustrations are    Ve regard it as the best system now extant for
really beautiful. In its style the work is extremely students.-Vestern Lancet.
concise and intelligible. No one can possibly take   It therefore receives our highest commendation._
up this volume without being struck with the great Southern tMed. and Surg. Journal.
BY THE SAME AUTHOR. (Just Issued.)
ON  DISEASES  OF THE SKIN.  Fourth and enlarged American, from Pn    he last.
and improved London edition. In one large octavo volume, of 650 pages, extra cloth, $2 75.
Thewritingsof Vilson, upondiseases of the skin, at some of the more salient points with which it
are by far the most scientific and practical that abounds,andwhichmakeitincomparaosysuperiorin
have ever been presented to the medical world on  excellence to all other treatises on the subject of derthis subject. The presenteditionisagreat improve- matology. No mere speculative views are allowed
ment on all its predecessors. To dwell upon all the a place in this volume, which, without a doubt. will,
great merits and high claims of the work before us, for a very long period, be acknowledged as the chief
seriatimn, would indeed be an agreeable service; it standard work on dermatology. The principles of
would be a mental homage which we could freely  an enlightened and rational therapeia are introduced
offer, but we should thus occupy an undue amount on every appropriate occasion.-Amn. Jour. hMed.
ot space in this Journal. W3e will, however, look  Science, Oct. 1857.
ALSO, NOW READY,
A SE3 IES OF PLATES ILLUSTRATING WILSON ON DIS[EASES OF
THE SKIN; consisting of nineteen beautifully executed plates, of which twelve are exquisitely
colored, presenting the Normal Anatomy and Pathology of the Skin, and containing accurate representations of about one hundred vareties of disease, most of them the size of nature. Price
in cloth $4 25.
In beauty of drawing and accuracy and finish of coloring these plates will be found equal to
anything of the kind as yet issued in this country.
The plates by which this edition is accompanied   lWe have already expressed our high appreciation
ieave nothing to be desired, so far as excellence of of Mr. Wilson's treatise on Diseases of the Skin.
delineation and perfect accuracy of illustration are The plates are comprised in a separate volume,
concerned.-.Medico-Chirurgical Review.           which we counsel all those who possess the text to
Of these plates it is impossible to speak too highly  purchase. It is a beautiful specimen of color printThe representations of thevarious forms of cutane- ine, and the representations of the various  forms of
ous disease are singularly accurate, and the color- skin disease are as faithful as is possible in plates
ing exceeds almost anything we have met with in of the size.-Busto-  lfe.d. and jsurg. Journal, April
point of delicacy and finish. —British and Foreign  8, 1858.
iledicc. Review.
BY THE SAME AUTHOR.
ON CONSTI]TUTIONAL AND HEREDITARYA SYPHILILS, AND) ON
SYPHILITIC ERUPTIONS.  In one small octavo volume, extra cloth, beautifully printed, with
four exquisite colored plates, presenting more than thirty varieties of syphilitic eruptions. $2 25,
BY THE SAME AUTHOR.
HEALTHY  SKIN; & Popular Treatise on the Skin and Hair, their Preservation and Management. Second American, from the fourth London edition. One neat volume,
royal 12mo.) extra cloth, of about 300 pages, with numerous illustrations. $1 00; paper cover,
75 cents.
WHITEHEAD ON THE CAUSES AND TREAT- I Second American Edition. In one volume, octsM.xNT OF ABORTION  AND STERILITY.   vo extra cloth, pp. 308. $I 7,.




32         BLANCHARD & LEA'S MEDICAL PUBLICATIONS.
~WINSLOW   (FORBES), M.., D.C. L., &c.
ON OBSCURE DISEASES OF THE BRAIN AND DISORDERS OF THE
MIND; their incipient Symptoms, Pathology, Diagnosis, Treatment, and Prophylaxis. In one
handsome octavo volume, of nearly 600 pages. (Just Issued, June, 1860.)  $3 00.
The momentous questions discussed in this volume have perhaps not hitherto been so ably and
elaborately treated. Dr. Winslow's distinguished reputation and long experience in everything relating to insanity invest his teachings with the highest authority, and in this carefilly considered
volume he has drawn upon the accumulated resources of a life of observation. His deductions
are founded on a vast number of cases, the peculiarities of which are related in detail, rendering
the work not only one of sound instruction, but of lively interest; the author's main object being
to point out the connection between organic disease and insanity, tracing the ]atter through all its
stages from mere eccentricity to mania, and urging the necessity of early measures of prophylaxis
and appropriate treatment. A subject of greater importance to society at large could scarcely be
named; while to the physician who may at any moment be called upon for interference in the most
delicate relations of life, or for an opinion in a court of justice, a work like the present may be considered indispensable.
The treatment of the subject may be gathered from the following summary of the contents:CHAPTER I. Introduction.-II. Morbid Phenomena of Intelligence. III. Premonitory Symptoms
of Insanity.-IV. Confessions of Patients after Recovery.-V. State of the Mind during Recovevy.-VI. Anomalous and Masked Affections of the Mind. —VII. The Stage of Consciousness.
-VIII. Stage of Exaltation.-IX. Stage of Mental Depression.-X. Siage of Aberration.-XI.
Impairment of Mind.-XIl. Morbid Phenomena of Attention.-XIII. Morbid Phenomena of
Meniory.-XIV. Acute Disorders of Memory.-XV. Chronic Affections of' Memory.-XVJ.
Perversion and Exaltation of Memory.-XVII. Psychology and Pathology of Memory.-XVIII.
Morbid Phenomena of Motion.-XIX. Morbid Phenomena of Speech.-XX. Morbid Phenomena
of Sensation.-XXI. Morbid Phenomena of the Special Senses.-XXII. Morbid Phenomena of
Vision, Hearing, Taste, Touch, and Smell.-XXIII. Morbid Phenomena of Sleep and Dreaming.
-XXIV. Morbid Phenomena of Organic and Nutritive Life.-XXV. General Principles of' Pathology, Diagnosis, Treatment, and Prophylaxis.
WEST  (CHARLES), M. D.,
Accoucheur to and Lecturer on Midwifery at St. Bartholomew's Hospital, Physician to the Hospital for
Sick Children, &e.
LECTURES ON THE DISEASES OF WOMEN. Now complete in one handsome octavo volume, extra cloth, of about 500 pages; price $2 50.
Also, for sale separate, PART II, being pp. 309 to end, with Index, Title matter,
&c., 8vo., cloth, price $1.
We mustnow conclude this hastily written sketch  and children is not to be found in any country.with the confident assurance to our readers that the Southern Med. and Surg. Journal, January 1853.
work will well repay perusal. The conscientious,   We gladly recommend his Lectures as in the highpainstaking, practical physician is apparent on every  est degree instructive to all who are interested in
page. —N. Y. Journal of Medicine, March, 1858.  obstetric practie.       aondol Lancet.
We know of no treatise of the kind so complete   We have to say of it, briefly and decidedly, that
and yet so compact.-Chicago Med. Journal, Janu- it is the best work on the subject in any language;
ary, 1858.                                      and that it stamps Dr. West as the facile princeps
A fairer, more honest, more earnest, and more re- of British obstetric authors. —Edinb. Med. Journ,
liable investigator of the many diseases of women
BY THE SAME AUTHOR. (NosW Ready.)
LECTURES ON THE DISEASES OF INFANCY AND CHILDHOOD.
Third American, fiom  the fourth enlarged and improved London edition. In one handsome
octavo volume, extra cloth, of about six hundred and fifty pages. $2 75.
The continued favor with which this work has been received has stimulated the author to render it in every respect more complete and more worthy the confidence of the profession.  Containing nearly two hundred pages more than the last American edition, with several additional
Lectures and a careful revision and enlargement of those formerly comprised in it, it car hardly
fail to maintain its reputation as a clear and judicious text-book for the student, and a safe and
reliable g'uide for the practitioner. The fact stated by the author that these Lectures'" now embody
the results of 900 observations and 288 post-mortem  examinations made among nearly 30,000
children, who, during the past twenty-years, have come under my care," is sufficient to show their
high practical value as the result of an amount of experience which few physicians enjey.
The three former editions of the work now before diseases it omits to notice altogether. But those
us have placed the author in tne foremost rank of who know anything of the present condition of
those physicians who have devoted special attention pediatrics will readily admit that it would be next
to the diseases of early life  We attempt no ana- to impossible to effect more, or effect it better, than
lysis of this edition, but may refer the reader to some the accoucheur of St. Bartholomew's has done in a
of the chapters to which the largest additions have single volume. The lecture (XVI.) upon Disorders
been made-those on Dipltheria, Disorders of the of the Mind in children is an admirable specimen of
Mind, and Idiocy, for instance-as a proof that the the value of the later information conve ed in the
work is really a new edition; not a mere reprint. Lectures of Dr. Charles West.-London Lancet,
In its pref ent shape it will be iound of the greatest Oct. 22, 1859.
possible service in the every-day practice of nine-   Since the appearance of the first edition, about
tenths of the profession.-Med. Times and Gazette, eleven years ago, the experience of the author has
London, Dec. 10, 1859.                          doubled; so that, whereas the lectures at first were
All things consid red, this book of Dr. West is founded on six hundred observations, and one hunby far the best treatise in our language upon such dred and eighty dissections made among nearly fourmodifications of morbid action and disease as are teen thousand children, they now embody the results
witntssed when we have to deal with infancy and of nine hundred observations, and two hundred and
childhood. It is true that it confines itself to such eighty-eight post-mortem examinations made among
disorders as come wichin the province of the phy- nearly thirty thousand children, who, during the
sician, and even with respect to these it is unequal past twenty years, have been under his care.as regards minuteness of consideration, and some British Med. Journal, Oct. 1, 1859.
BY THE SAME AUTHOR.
AN ENlQUIRY INTO THE PATHOLOGICAL IMPORTANCE OF ULCERATION OF THE OS UTERI. In one neat octavo volume, extra cloth. $1 00.