f^^ C-' THE COMPARATIVE ANATOMY OF THE DOMESTICATED ANIMALS. THE COMPARATIVE ANATOMY OF THE DOMESTICATED ANIMALS. By a. CHAUVEAU, PROFESSOR AT THE LTONS VETERINARY SCHOOL. ntrnts ©Mtion, ^ebiscb anb 6nlargfb, foitlj the Co-operation of S. ARLOING, LATE PEINCIPAL OF AXATOMT AT THE LTONS VETERINARY SCHOOL ; PROFESSOR AT THE TOULOUSE VETEBI:NARY SCHOOL. TRANSLATED AND EDITED GEOEGE FLEMING, F. R. G. S., M A. I., vetbrlnart surgeon, royal engineers, author of '-travels on h0e8eback in mantchtj taktart," "hor8b-8hoe3 and horse-shoeing,' "animal plagues," "practical HORSE-SHOEING," "RABIES AND HYDROPHOBIA," ETC. 'WITH 4SO ILLUSTRATIONS. NEW YORK: D. APPLE TON AND COMPANY, 549 & 551 BROADWAY. 1873. Digitized by the Internet Archive in 2009 with funding from NCSU Libraries http://www.archive.org/details/comparativeanaOOchau BftJtcatctJ TO THE MEMORY OF JOHX LA^ysoN, m. rc.v.s., OF MANCHESTER, WHO FIRST URGED THE DESIRABILITY OF UNDERTAKING THIS TASK, AND AVHOSE SINCERE AND INESTIMABLE FRIENDSHIP AND ENCOURAGEMENT FOR MANY YEARS THE EDITOR, AND TRANSLATOR HEREBY ACKNOWLEDGES WITH SORROWFUL AFFECTION AND GRATITUDE. PREFACE BY THE TRANSLATOR AND EDITOR. In undertaking the arduous task of translating and editing the ' Traite d* Anatomie Gomparee des Animaux Domestiques ' of M. Chauveau, I have been moved by a desire to fill a void in medical literature which has always existed, so far as the English language is concerned. There has been no complete treatise on the anatomy of the domesticated animals, and the absence of such a work has exerted a serious influence on the progress of veterinary science, and doubtless proved more or less of a loss to the community at large. The only text book to which the student or practitioner of animal medicine could until recently refer, has been that on the anatomy of the Horse, written by the late distinguished army veterinary surgeon, William Percivall, more than forty years ago : a book which, though in every way creditable to its author, was notoriously incomplete, even as regards the anatomy of the only animal it treated of, and was without illustrations. No serious attempt has been made to teach the structure of the other useful creatures domesticated by man, valuable though many of them are ; and the student who was anxious to acquire this knowledge had no guide to lead or instruct him. At college, this loss may not have been so severely felt as when, having graduated, he entered on the jiractice of his profession ; and if the experience of veterinary surgeons in general has been like my owTi, they will be ready to testify to the almost daily regret they felt at the very meagre notions of anatomy they possessed, and the benefit a complete and trustworthy manual would confer. My professional avocations in the army would not permit me to make the necessary dissections for the production of such a work • and indeed so many classical and standard treatises on the subject have appeared, during this century, on the Continent, and notably in France and Germany, that it would seem a mere waste of time and labour to attempt a task which viii PREFACE BY THE TRANSLATOR AND EDITOR. has been already so thoroughly accomplished by very zealous and pro- ficient anatomists. In selecting for translation the present treatise in preference to other works which are justly held in high estimation, I was influenced not only by the knowledge that it was written by one of the most talented com- parative anatomists and physiologists of the day, but by the ability and ori""inality which are so conspicuous in every page, I was also aware that, for more than a century, the French veterinary schools have been celebrated for the careful and thorough manner in which anatomy has been taught by most efficient teachers, who are all selected by open com- petition ; and that Professor Chauveau's book was the approved dissection manual of these and other Continental schools. Escellent as was the first edition of the work, the second is still more complete ; indeed it may be said to be almost a new book, owing to the assistance afforded by M. Arloiug, an anatomist who promises to assume a high rank in his profession. The French treatise is illustrated by three himdred and sixty-eight wood- cuts, but for several reasons it was deemed advisable to select only one hundred and seventy-three from this number : those rejected being chiefly human figures, and either far larger than was necessary or compatible with the space at disposal, or not so well suited for such a work as 1 was intent on producing. Nearly sixty original figures have been added to those selected; and through the courtesy and liberality of Messrs. J. and A. Churchill, the total number has been increased to four hundred and fifty. The profuseness and general excellence of these drawings, and their great accuracy, will, it is hoped, materially lessen the fatigue and time demanded for the study of this most important subject, and prove valuable for reference to the operator or busy practitioner. No labour or pains have been spared to make the work the most complete and useful of any that has been produced. The best treatises in German, French, and Italian have been consulted in editing it, and when necessary, I have added to the descriptions. These additions are contained within brackets, thus ( ). As my task has been accomplished without any aid, I assume the entire responsibility for any errors of omission or commission that may exist ; my aim being to furnish what has been an urgent desideratum for very many years — a complete dissection manual for the student of veterinary science, a book of reference for the veterinary surgeon, and a work that might be available for the zoologist, comparative anatomist, ethnologist, and medical practitioner. I have for a long time believed that the two branches of medicine — human and animal — should be more closely allied than they are at present, and that this alliance can only be effected by a mutual study and recognition of the facts which prove that the two are really one — wide apart though they have hitherto been kept in this country — and that each is capable of conferring on the other great and lasting benefits. Hence my retaining what constitutes a new feature PREFACE BY THE TRANSLATOR AND EDITOR. ix in the second edition of Chauveau's treatise — the comparison of the organs of Man with those of Animals. I have omitted from the translation the references made to the Dro- medary and Eabbit ; these animals seldom, if ever, coming under the notice of the comparative pathologist in this country. My grateful acknowledgments are due to my friend and colleague, Professor Chauveau, for the great courtesy with which he not only sanc- tioned the translation now before the i^ublic, but offered to supply me with the proof sheets of the new edition as it passed through the press. To the numerous professional friends who pressed upon me the necessity of making such an extensive sacrifice of my few leisure hours, by under^ taking a work of this magnitude, I have to express my deep regret at the delay which has occured in its appearance. The fault was not mine : but for the disturbance and abeyance of all business, save that of slaughter, in and around Paris while the book was in course of publication, my task must have been achieved nearly two years ago. I may assure them, how^ever,, that the delay has been rather beneficial than otherwise ; as it has allowed me to give more time to perfect what might, under other circumstances, have been less complete and satisfactory. GEOKGE FLEMING. Brompton Baebacks, Chatham. February, 1873. PEEFACE TO THE FIRST EDITION, To present iu a concise and complete form an exact description of tlie anatomical machinery of which, the bodies of our domesticated animals are composetl, has been onr aim in writing the book now offered for public appreciation. We have sought for concision, not only in language, but also in the choice of facts and ideas, with a kind of stubbornness.' In imposing on ourselves this condition, we believe we have rendered a service to those who may have recourse to the book, in economising their time. In an age of progress like the present, when the sciences are becoming multiplied and developed, and when the hiunan mind, seized by the fever of production, gives forth every day books consecrated to the study of these sciences, there is scarcely leisure to read and to learn. It is, therefore, the duty of a writer to be brief. If he loads his book with puerile details ; if he says that which may easily be divined by his reader ; and if he describes facts and ideas too redundantly ; will he have attained the wished-for perfection —in a word, will he be complete ? No, he will be tedious : a serious inconvenience, which neither elegance, warmth, nor brilliancy of style will always excuse when met with in a didactic work, and especially in an elementary treatise. No effort has been spared to achieve exactitude — the primary desideratum in such a work as this ; neither have evenings spent in bibliographic re- searches, nor fatigue in the dissecting-room been considered. All iniblished writings on animal organisation, general treatises, special manuals, mono- graphs, and articles in periodicals have been read and interrogated. But we have more particularly sought for information from Nature — that certain and infallible guide, always wise, even in her diversities ; we have consulted her, scaljiel in hand, with a perseverance that nothing could repel. Animals of every kind were had recourse to, and we have largely profited by the immense resources which our position as principal of anatomical teaching in the Imperial Veterinary School has placed at our disposal. xii FEE FACE TO THE FIRST EDITION. It was not enougli that we should be correct, that we should faithfully describe the organs of the animal economy. It was desirable tliat the truth might be presented from a high philosophical point of view — one that should rise above details. It is necessary in a book, and especially in one on anatomy, that there should be a salient idea which might indicate its purpose and originality, and distinguish it as something more than a mere arid catalogue, by unifying the thousand different objects of which it treats. In support of this, we would ask permission to explain, in a few words, the idea that presided in the construction of our work. Among the beings or objects composing the natural world, animals are distinguished by diversity in size and external conformation. Is this diversity repeated in their internal structure ? When order and simi^licity prevail everywhere else in nature, should we expect to find disorder and complication there, or look for as many different organisations as there are particular sj)ecies ? To state these questions, and to resolve them in the affirmative, would be to insult the wisdom of the Creator. The early naturalists, guided by instinct rather than knowledge, admired a certain uniformity in the composition of animals. It was a good inspiration, which threatened to become effaced at the period when anatomical science, diffused and cultivated everywhere with the most laudable eagerness, daily discovered the secrets of the organisation of new species. Without a guide in the search for analogies, struck with the apparent differences their scalpel exposed every moment, the anatomists of that epoch neglected to compare the diverse animals. In presence of a new form of organs, they believed in the existence of a new instrument, and created a new name to designate it. Then was human anatomy, and that of the Horse, Ox, etc., established ; monographs became multiplied ; as the different opinions increased, so there was the greater need for a bond to unite these incongruous materials ; confusion commenced, and chaos was about to appear ; and the principle of analogies was on the point of being buried beneath the ruins of science. Hapj)ily, two men appeared, men of genins, who were the glory of France — G. Cuvier and Etienne Geoffrey Saint- Hilaire ; two names which will be for ever illustrious, and which we love to unite as the expression of one and the same symbol. The first, after immense researches, ventured to compare the innu- merable species in the animal kingdom with each other; he seized their general characters — the analogies which allied them to one another ; he weighed these analogies, contrasted them with the dissimilarities, and established among them different kinds and different degrees ; and in this way was he able to form natural groups, themselves subdivided into several categories in which individuals were gathered togetlier according to their analogies and affinities. Then the chaos was swept away, light appeared, and the field of science was no longer obscured ; comparative anatomy was created in all its branches, and the structure of the animal kingdom was PREFACE TO THE FIRST EDITION. xiii brought within those laws of uniformity which shine throughout the other parts of creation. Geoffiroy Saint-Hilaire followed Cuvier over the same ground. More exclusive than Cuvier, he entirely neglected the differential characters, and allowed himself to be governed by the consideration of resemblances. He especially pursued the discovery of a fixed rule for guidance in the search after these resemblances — a difficult task, and a dangerous reef, upon which the sagacity of his illustrious rival was stranded. To be more certain than Cuvier, and the better to grasp his subject, he restricted the scope of his observations, confining himseK more particularly to the class of vertebrata in order to solve the enigma whose answer he sought. At last he found it, and made it known to us in those memorable, though abstruse pages, in which the meaning is often obscui-e and hidden, but which contain, nevertheless, magnificent hymns chanted to the honour of the Creator. The shape and functions of organs, he says, do not offer any stability, only their relations are invariable ; these alone cannot give deceptive indications in the comparison of the vital instruments. He thus founded his great principle of connections, firmly established its value, fortified it by accessory principles, and held it up to the generations to come as a compass, a succourable beacon-light, under whose protection they might proceed to the conquest of analogies with confidence and security. Then was the philosophical sentiment decidedly introduced into the researches in organisation, and anatomy became a veritable science. Enthusiastically admiring these two great masters, we glory in be- longing to their school ; it is, therefore, enough to say that the prevailing idea in our work has been inspired by their labours. Thus, in describing the organs in the somewhat numerous species of animals treated of, and noting their differential characters, we have always endeavoured to demonstrate their analogies. The hojies that Geoffroy Saint-Hilaire entertained for the future of philosophical anatomy have not been entirely realised. Natm-alists, it is true, have always cultivated this admirable science ; Lecoq has preserved its traditions at the Lyons Veterinary School, in his simple, lucid, and elevated teaching ; and at Toulouse, an able and learned professor, Lavocat, has courageously hoisted his flag. But everywhere else, and particularly in the Medical Schools, has not anatomy remained essentially monographic and purely surgical ? And many medical men and veterinary surgeons, only looking at the practical side of this science, and full of defiance with respect to speculative theories, will perhaps give us no credit for our efforts in bringing the anatomy of animals into philosophical courses. To these we have nothing to say ; if they do not see how much science is developed and becomes comprehensible with such elements: if they cannot under- stand all that is noble and useful in these generalising views ; and if they do not feel elevated sentiments .revolve in their mind in jjresence of the simplicity of Nature's laws, it is because their thoughts are not in unison xlv PREFACE TO THE FIRST EDITION. with onrs, and we carefully abstain from engaging in a sterile discussion with them. Such is our plan : have we executed it in a satisfactory manner ? We have not deluded ourselves with regard to our strength, and willingly acknowledge that many resources and many qualities have failed us in carrying the enterprise to a favourable termination ; therefore we hope to be indulgently judged. If we have succeeded in facilitating the study of so important a subject as anatomy for the pupils of the veterinary schools ; if our book becomes, in the hands of practitioners, a useful surgical guide ; if, lastly, medical men and naturalists find that it will assist them in their researches in com- parative anatomy, our object will have been attained, and we shall have received the best recompense which the honest writer can hope to obtain. Before terminating, a sentiment of justice and recognition again brings the honourable name of M. Lecoq to our pen ; the idea of this book was conceived at his lectures, and it is from these lectures that we have derived the major part of our materials ; it was to satisfy the most imperious desire of our heart and conscience that we offered to dedicate this first attempt to him. Could it be better placed than under his patronage ? We have also willingly joined to his name that of M. H. Bouley, that eminent and devoted master, to whose advice we owe so much, and who has evinced the liveliest solicitude for us in circumstances which we can never forget. May he deign to accept this homage as the expression of our sincere recognition. We have found in the obligingness and intelligence of M. Eodet a very efficacious aid ; he will permit us to tender all our gratitude. We have frequently put the complaisance of the students around us to a severe test ; bi;t they have never failed, and we are gratified in being able to thank them most cordially. We especially mention the name of M. Violet, whose intelligent zeal has spared us much toil in the difficult task imposed upon us. A. Chauveau. Lyons, September 30, 1854. PEEFACE TO THE SECOND EDITION. CiECUMSTANCES independent of my "wiU Iniv^ prevented me from publishing the Second Edition of my ' Treatise on Anatomy ' earlier. Those to whom the work is addressed will have lost nothing by the delay, as it has allowed me to procm-e the co-operation of one of my most distinguished and best- esteemed pupils. The researches in pathological physiology and experimental medicine, to which I have consecrated my efforts and resources for some years, would have left me no leisure to do more than give a simple reprint of my first edition ; consequently, I must have allowed important omissions to remain, and have renounced the idea of re-casting it according to a new plan I had conceived, even before that edition was terminated. Thanks to the assistance of M. Arloing, who had long before been initiated into my projects, and the details as to their execution which had been present to my mind, this re-casting has been aceomj)lished, and the ' Treatise on the Comparative Anatomy of the Domesticated Animals ' has thus become an almost entirely new work. I need not attempt to indicate the importance of the modifications and considerable additions that this remodelling has entailed ; nor the ame- liorations which the publishers have introduced in the execution of the material portion of the work. It is sufficient to open the book to be convinced of these advantages. A. Chauveau. Lyons, March 15th, 1872, v^ TABLE OF CONTENTS. Translator and Editor's Preface Preface to the First Edition .. Preface to the Second Edition Table of Contents Table of Illustrations PAGE vii si sv xvii xxxvi GENERAL CONSIDEKATIONS. Definition and Division of Anatomy ...... Enumeration and Classification of the Domesticated Animals . General Idea of the Organisation of Animals, and the order followed in studying their apparatus ......... BOOK I. LOCOMOTOEY APPARATUS. First Sectiox. — The Bones ..... Chapter I. — The Bones in G eneral .... Article i. — The Skeleton ..... Article n. — General Principles applicable to the Study of all the Bones Name, Situation, Direction, and Configuration of the Bones Internal Conformation of the Bones. Structure of the Bones Development of the Bones .... Chapter II. — The Bones of Mammalia in Particular Article i. — Vertebral Column .... Characters Common to all tlie Vertebrae Characters Proper to the Vei tubras in each region 1. Cervical VertebrsB ..... 2. Dorsal Vertebrae ..... 3. Lumbar Vertebraa ..... 4. Sacrum ..... ^ 5. Coccygeal Vertebrae ..... Of the Spine in General .... DitTerential Cliaracters in the Vertebral Column of other than Animals ...... Comparison of the Vertebral Column of Man with that of Animals Article n. — Tne Head ..... The Bones of the Cranium 1. Occipital . . .... 2. Parietal ....... 3. Frontal' ...... 2 . 6 6 7 les 10 10 13 16 18 , 18 19 21 21 , 24 25 . 26 27 28 Solipec I 29 32 33 ^ 33 33 , 35 36 TABLE OF CONTENTS. 4. Ethmoid ..... 5. Sphenoid .... 6. Temporal .... The Boues of the Face 1. Superior Maxillary or Great Supermaxillary 2. Intermaxilla, Incisive Bone, Small Supermaxilla, or Premaxilla 3. Palate .... 4. Pterygoid .... 5. Zygomatic . 6. Lachrymal .... 7. Bones proper to the Nose, or Supcrnasal 8. Turbinated Bones 9. Vomer .... 10. Inferior Maxillary 11. Hyoid .... Of the Head in General ...... Differential Characters in the Head of other tiian Soliped Animals Comparison of the Head of Man with that of Animals Article in. — The Thorax ...... The Bones of the Thorax in Particular .... 1. Sternum of the Horse ..... 2. Eibs ........ Of the Thorax in General ..... Differential Characters in the Thorax of other than Soliped Animals 1. Sternum ....... 2. Eibs . Comparison of the Thorax of Man with that of Animals 1. Sternum 2." Ribs Article rv. — Anterior Limbs Shoulder Scajjula Arm Humerus . Fore-Hrm 1. Eadius 2. Ulna Anterior Foot 1. Bones of the Carpus 2. Bones of the Metacarpus 3. Bones of the Digit, or Phalangeal Region Differential Characters in tiie Anterior Limb nf other than Soliped Animal Comparison of the Thoracic Limb of Man with that of the Domesticated Animals Article v. — Posterior Limbs Pelvis A. Coxse B. The Pelvis in General Tiiigii . Femur Leg . 1. Tibia . 2. Fibula 3. Patella TABLE OF CONTENTS. Posterior Foot ........ 1. Bones of the Tarsus ....... 2. Bones of the Metatarsus ....... 3. Bones of the Digital Begion ...... Differential Characters in the Posterior Limb of other than Soliped Animals ........ Comparison of the Abdominal Limb of Man with that of the Domesticated Animals ...... Article vr. — The Limbs in General, and their Parallelism Chapter III. — The Bones in Birds .... Chapter IV. — Theory of the Vertebr.d Constitution of the Skeleton Second Section. — The Articulations .... Chapter I. — The Articulations in Geneial .... General Characters of Diarthroses .... General Characters of Synarthroses .... General Characters of Amjohiartli roses or Symphyses Chapter II. — The Articulations of Mammalia in Particular Article i. — Articulations of the Spine Articulations between the Vertebra;, or Intervertebral Articulations Article ii. — Articulations of the Head 1. Atlo-axoid Articulation 2. Occipito-atloid Articulation 3. Articulations between the Bones of the Head 4. Temporo-maxillary Articulation 5. Hyoideal Articulations Article III. — Articulations of the Thorax 1. Costo-vertebral, or Articulations of the Kibs with the Vertebral Cohm 2. Costo-sternal Articulations 3. Chondro-costal Articulations, or Articulations between the Eibs 4. Articvdations between the Costal Carti'ages . 5. Sternal Articulation peculiar to the Ox and Pig . 6. The Articulations of the Thorax considered in a general manner, witl respect to their IMovements . Article iv. — Articidations of the Anterior Limbs . 1. Scapulo-hunit-ral Articulation. 2. Humero-radial Articulation 3. Radio-ulnnr Articulation 4. Articulations of the Carpus 5. Intermetacarpal Articulations. 6. Metacarpo-phalangeal Articulations .... 7. Articulation of the First Plialanx with tlie Second, or first Inter phalangeal Articulation ..... 8. Articulation of the Second Phalanx with the Third, Second Inter phalangeal Articulation, or Artienlation of the Foot Article v. — Articulations of the Posterior Limbs 1. Articulations of the Pelvis 2. Coxo-femoral Articulation 3. Femoro-tibial Articulation 4. Tibio-fibular Articulation 5. Articulations of the Tarsus, or Hock Chapter III. — The Articulations in Birds Third Section. — The Muscles. Chapteu I. — General Considerations o;i the Striped Muscles The Striped Muscles in General XIX. PAGE 102 102 105 105 105 107 109 112 118 121 121 123 128 129 129 130 130 135 135 137 137 138 139 140 I 140 141 142 142 142 142 143 143 144 147 148 152 153 156 157 159 159 161 163 167 168 172 173 174 174 s TABLE OF CONTENTS. Structure of the Striped Muscles Physico-chemical Properties of the Striped Muscles Physiological Properties of the Striped Muscles Annexes of the Muscles Manner of Studying the Muscles . Chapter II. — The Muscles of Mammalia in Particular Article i. — The Muscles of the Trunk Subcutaneous Eegion .... Fleshy Pauniculus Cervical Kegion .... A. Superior Cervical or Spinal Region of the Neck 1. Ehomboideus ..... 2. Angularis Muscle of the Scapula 3. Splenius ...... 4. Great Complexus ..... 5. Small Complexus (Trachelo-mastoideus) . 6. Transverse Spinous Muscle of the Neck (Spinalis Colli) 7. Intertransversal Muscle of the Neck 8. Great Oblique Musfle of the Head (Obliquus Capitis Inferior) 9. Small Oblique Muscle of the Head Obliquus Capitis Superior) 10. Great Posterior Straight Muscle of the Head . 11. Small Posterior Straight Muscle (Rectus Capitis Posticus Minor B. Inferior Cervical or Trachelian Region .... 1. Subcutaneous Muscle of the Neck (Panniculus Carnosus) . 2. Mastoido-humeralis (Levator Humeri). 3. Sterno-maxillaris ...... 4. Sterno-hyoideus ...... 5. Sterno-thyroideus. ..... 6. Omo-hyoideus, or Subscapulo-hyoideus 7. Great Anterior Straiglit Muscle of the Head (Pectus Capitis Anticus Major) ...... 8. Small Anterior Straight Muscle of the Head (Eeetus Capitis Anticus Minor) ...... 9. Small Lateral Straight Muscle (Obliquus Capitis Anticus) 10. Scalenus ...... 11. Long Muscle of the Neck (Longus Colli) . Differential Characters in the Muscles of the Cervical Region of other Soliped Animals ...... A. Superior Cervical Region .... B. Inferior Cervical or Trachelian Region Spinal Region of the Back and Loins 1. Trapezius ...... 2. Great Dorsal (Latissimus Dorsi) 3. Small Anterior Serrated Jluscle (Superficialis Costarum) 4. Small Posterior Serrated Muscle (Superficialis Costarum) 5. Ilio-spinalis Muscle (Longissimus Dorsi) 6. Common Intercostal Muscle (Transversalis Costarum) 7. Transverse Spinous Muscle of the Back and Loins (Spinalis and Semispinalis Dorsi ...... Differential Ciiaracters in the Muscles of the Spinal Region of the Back and Loins of other than Soliped Animals ..... Comparison of the Muscles of the Back, Neck, and Cervix in Man with the analogous Muscles in the Domesticated Animals A. Muscles of the Back and Cervix ..... PAGE 178 180 181 183 183 186 186 186 186 187 187 188 189 189 191 191 193 193 193 194 195 195 195 196 196 198 198 198 198 199 199 199 200 200 201 201 201 203 203 203 205 205 206 208 209 209 209 210 TABLE OF CONTENTS. xxi PAGE B. Muscles of the Neck . . . . , . . .211 Sublumbar or Inferior Lumbar Ecgion . . . . 211 1. Iliac Fascia or Lumbo-iliac Aponeurosis .... 212 2. Great Psoas Muscle ...... 212 3. Iliac Psoas Muscle (Iliacus) ...... 212 4. Small Psoas Muscle ...... 214 5. Square Muscle of the Loins (Sacrn-lumbalis) . . . 214 6. Intertransverse Muscles of the Loins (Intertransversales Lumborum) 215 Differential Characters in the Muscles of the Sublumbar Region of other than Soliped Animals ....... 215 Comparison of the Sublumbar Muscles of Man with those of Animals . 215 Coccygeal Region . ....... 215 1. Sacro-coccygeal Muscles . . . . • 215 2. Ischio-coccygeus (Compressor Coccygeus) .... 217 Region of the Head .....•■ 217 A. Facial Region ....... 217 1. Labialis (Orbicularis Oris) ..... 217 2. Alveolo-labialis (Buccinator) ..... 218 3. Zygomatico-labialis (Zygomaticus) .... 219 4. Lachrymo-labial, or Lachrymal Muscle .... 220 5. Supernaso-labialis (Levator Labii Superioris) . . 220 6. Supermaxillo-labialis (Nasalis Longus Labii Superioris) . . 220 7. Great SupermaxiUo Nasalis (Dilatator Naris Lateralis) . 221 8. Small Supermaxillo-nasalis (Nasalis Brevis Labii Superioris) . 221 9. Transversalis Nasi (Dilatator Naris Anterior ) . . . 221 10. jMiddle Anterior Muscle (Depressor Labii Superior!) . . 222 11. Maxillo-labialis (Depressor Labii Iiiferiorisj . . , 222 12. Mento-labialis, or Muscle of the Chin . . . .222 13. Middle Posterior Muscle (Levator Menti) ... 222 B. Masseterine or Temporo-maxillary Region .... 223 1. Masseter ....... 223 2. Temporal or Crotaphitic Muscle ..... 223 3. Internal Pterygoid (Pterygoidtus Internus) . . . 224 4. External Pterygoid ...... 224 5. Digastricus ....... 225 c. Hyoideal Region ....... 225 1. Mylo-hyoideus ...... 225 2. Genio-hyoideus ....... 226 3. Stylo-hyoideus (Hyoideus Magnus) .... 227 4. Kerato-hyoideus (Hyoideus Parvus) .... 227 5. Occipito-styloideus ...... 227 6. Tranversalis Hyoidei ■ . • . • • • 228 Differential Characters in the Muscles of the Head of other than Soliped Animals ....•••• 228 A. Facial Region ....••• 228 u. Masseterine or Temporo-maxillary Region .... -29 c. Hyoid Region .....•• ^30 Comparison of the Muscles of the Human Head with those of the Domes ticated Animals ....••• A. Epicranial Muscles . . . • • • » ' B. Muscles of the Fiice ...••• c. IMuscles of the Lower Jaw . . • • • D. Hvoid Muscles ....••• -^'■ 9Q1 Axillary Region ....••• • " 230 230 230 231 TABLE OF CONTENTS. 1. Superficial Pectoral (Pi ctoralis Transversus) 2. Deep Pectoral ..... Difi'ereatial Characters in the Muscles of the Axillary Ivegiou of other than Soliped Animals ..... Costal Kegion ..... 1. Great Serralus ..... 2. Transverse Muscle of the Ribs (Lateralis Sterni) 3. External lutercostals .... 4. Internal Intercostala .... 5. Supercostals (Levatores Costarum) . 6. Triangularis of the Sternum (Stenio-co.^tales) . Differential Characters in the Muscles of the Costal Eegion of other than Soliped Animals ..... Comparison of the Thoracic Muscles of Man with those of the D( mesticated Animals ...... Inferior Abdominal Kegion .... 1. Abdominal Tunic .... 2. White Line. .... 3. Great or External Oblique of the Abdomen 4. Small or Internal Oblique of the Abdomen . 5. Great Rectus Muscle of the Abdomen . 6. Transverse Muscle of the Abdomen ..... Ditferential Characters in the Muscles of the Abdominal Region of other than Soliped Animals ...... Comparison of the Abdominal Muscles of Man with those of Animals Diaphragmatic Region ...... Diaphragm ........ Differential Characters in the Diaphiagm of other than S, and Goat. With regard to poultry, they range themselves :— 1. In the gallinaceous order, the genera to which the common fowl, guinea fowl, turhey, and pigeon belong ; 2. In the order of palmipeds, the geese and ducJcs. Girard has proposed a special classification for the domesticated mammals, based upon the number of digits terminating each of their limbs, and has defined four categories : the first comprises the horse, ass, mule, and hinny, which take the name of monodactyles, because their digital region is composed of a single digit ; in the second, under the denomination of didactyles or bisulcate animals, those with two digits, such as the ox, sheep, and goat ; in the third, or regular tetradactyles, is found rauged the pig, each of whose limbs shows four digits ; lastly, the dog and cat, which most frequently have four digits on the posterior members and five on the anterior ones, and form the class of irregular tetradactyles. This nomenclature will not be followed here, as it is opposed to the general laws of organisation ; philosophical anatomy has, in fact, demonstrated that there are really no veritable monodactyles, didactyles, etc., all are materially or virtually pentadactyles. It is therefore considered better to keep to the classification established by zoologists, because it prevents confusion in scientific language, which should always be the same for everyone engaged in the study of anatomy. The regimen and habits of the domesticated animals bring about differ- ences in their organisation which appear very great at first sight, though in reality they are not so profound as they seem. In order to study the descriptive anatomy of all these animals, we will not pass them in review, one after another, giving for each the description of every organ ; but shall take a type, which will most frequently be the Horse, and briefly compare all the others with it. In the majority of cases, we will describe, without leaving the Horse, all the organs of an apparatus ; afterwards the same organs in the other species will be studied in the same order. In this comparison, the animals will be generally classed according to their domestic value ; though exceptions will be made to the rule which has been instituted by our predecessors, whenever any advantage in point of concision or perspicuity is likely to be obtained. GENERAL CONSIDERATIONS. 3 GENERAL IDEA OF THE OEGANISATION OF ANIMALS. Order followed in studying the Various Apparatus. The bodies of animals, formed of organised matter, contain fluids and solids. The fluids are very abimdant in the animal economy ; not only do they fill certain vessels constructed for them, but they also impregnate all the solid parts of the body. Their importance is very great, for witlioiit them the organic solids would perish ; an element deprived of humidity is an element deprived of life. Fluids vary in their nature and composition. Apart from those that the solids imbibe, there is not one whicb is completely amorphous. In the midst of a liquid holding organised matter in solution there are always elements which will be referred to hereafter. Examples : the blood and lymph. In studying the organic solids, we will proceed from the simple to the complicated. Elements. — Solid organised matter presents itself in the form of more or less voluminous particles, in every instance invisible to the naked eye, and named the anatomical elements. They may be reduced to three principal : the granule, cell, and fibre. Granules. — These are the smallest known elements. They may be held in suspension in animal fluids, remain free among the other elements, or be enclosed in the interior of cells. Their nature is not always the same : they are proteic or fatty. They are called pigmentary when they exhibit a brown colour. Cells. — The cell is pre-eminently the anatomical element. It may be represented to the mind as a microscopic collection of a nitrogenous substance, viscid or slightly granular, and endowed with extreme vitality. Frequently in the midst of this protoplasm (for so it has been called), there is perceived a nucleus provided with a nucleolus, and at its periphery an enveloping membrane is discovered. It must not be forgotten that this membrane, and even the nucleus, is necessarily a constituent portion of the cell. The cell lives like an entire organism : it feeds, grows, nniltiplies, absorbs, secretes, moves, etc. It behaves like a complete animal, though it be a microscopic one. The form of the cell varies greatly, as does its volume and its nature. It has therefore received various names. There are round, polyhedral, fusiform, stellate, and other shaped cells. Some have a diameter of l-12000th part of an inch, while others are l-2000th part. Cells multiply in various ways : 1st, by the division of the nucleus and segmentation of the protoplasm in the interior of the enveloping membrane (endogenous multiplication); 2nd, by constriction, the division of the nucleus, protoplasm, and enveloping membrane [fissiparous midtipli- cation) ; 3rd, by a kind of bulging or swelling of the enveloping membrane, and strangulation and separation of the enlargement thus formed {gemmation). A large number of cells only temporarily remain in this condition. In consequence of modifications that cannot be referred to here, they are con- verted into fibrillse or other elements, in which it is difficult to recognise them. Others maintain the cellular form : then they are developed, live, and die in several ways. Sometimes they are worn by the contact of foreign i GENERAL CONSIDEBATIOXS. bodies, as on the surface of tlie skin ; at other times they become dissolved, as in some glands : finally, at other periods they submit to fatty degeneration, which gradually brings about their complete destruction. The permanent cells have been arranged according to the following denominations : — 1. Ucematies or red globules, which are found in a state of suspension in the blood ; they are round or elliptical. 2. Leucocytes, or ichite globules, which float in the blood, lymph, and chyle. 3. Connective cells, comprising the connective cell properly so-called, the plasmatic cell, and the adipose cell. 4. Medullary cells, forming the principal elements of the marrow of bones (myeloplaxes and medullo-cells). 5. Coniractile cells, which constitute the basis of muscular tissue. 6. Nerve cells, met with in the cerebro-spinal centres and the ganglia of the cerebro-spinal and sympathetic systems. 7. Epithelial cells, comprising the epithelial cells properly called, situated on the surface of the skin and mucous membranes, and the glandular cells. Fibres. — A fibre is an elongated anatomical element, of variable dimensions and composition. It may be very fine and represented by a single line, or thicker and marked by two lines more or less apart from one another. It is homogeneous throughout, or the contents are distinct from the envelope. The vitality of fibres is not to be compared with that of cells ; after they are formed, they can only be nourished, and cannot multiply of themselves. In the animal economy four kinds of fibres are distinguished : — the connective fibre, elastic fibre, muscidar fibre, and nervous (or nerve) fibre. Tissues. — Tlie elements that have now been rapidly described, in becoming united and grouped in diflerent fashions, form the tissues. Some tissues are composed of one kind of element ; these are the simple tissues. Example : — The epithelium. The majority, however, are formed by the union of several different elements : these are the composite tissues. Example : — Nervous tissue. It is also remarked that there are tissues in which exists a fundamental intercellular substance, and others in which this is absent. The latter are few in number, for the vessels and nerves may, in certain tissues, be considered as intercellular substance. The anatomical, physico-chemical, and physiological characters of the tissues repeat, as might easily be inferred, the anatomical, physico-chemical, and physiological properties of the elements entering into their formation. Only four fundamental tissues are recognised, basing them on the morphological, chemical, and physiological characters of the elements. In the first place, the tissue of the conjunctivcd substance should be noticed ; this, in consequence of some differential characters, may be divided into : — gelatinous tissue, conjunctival (or connective) tissue, cartilaginous tissue, and boni/ tissue. Then comes the cellular tissue, formed entirely of persistent cells. It comprises the epithelial tissue and the glandular tissue. The cells of the epithelial tissue may aftcct different arrangements. If they are disposed in a single row, there results a simple epithelium ; if they are superposed it is a stratified epithelium. According to the form of the cells of the superficial layer, the epithelium is polyhedral, pavement, cylindrical, or sphericcd. In certain points, these superficial cells are furnished with vibratile filaments ; they are then designated vibratik (or ciliated) e^pithelium. GENERAL CONSIDERATIONS. 5 In tlie third place, is tlae muscular tissiie, which may be divided into striated and non-striated (or striped, and non-striped or smooth) fibres. Lastly comes the nervous tissue, whicli offers two aspects : the white and grey substance. The tii-st is entirely formed by nerve fibres, and the second by fibres and nerve cells. Organs. — The term organ is given to an agglomeration of tissues possessing a determinate form, and having a function to fulfil. Organs are therefore composed of tissues, as the tissues themselves are constituted by anatomical elements. All animal organs are enclosed between two membranes named limitary or tegumentary membranes, which are continuous with one another at the margin of the natural openings. These are the skin and the mucous membranes, in whose composition is included a layer of connective tissue covered by an epithelium. Organs are distinguished into those which are solid, and those which are hollow. Among the first, a certain number act as supports : such are the organs formed by the connective tissue, and particularly the cartilages and bones. Others are destined to produce movements : these are the two kinds of muscles. The action of the muscles is communicated directly to the organs that are to be moved, or it is transmitted through the medium of other organs, such as the tendons and ai)oneui'oses. The central nervous organs, nerves properly so called, and the vascular glands, belong to this group of solid organs. With regard to the hollow organs, they are everywhere covered by the internal, tegumentary, or mucous membrane. Examples : — the lungs and stomach. There must also be included the vessels formed by elastic and contractile membranes arranged as canals, in which the blood and lymj^h circulate ; and, lastly, the serous membranes, which line the interior of the splauclmic cavities, and cover the sm-face of the organs contained in them. Apparatus. — Organs are very numerous in the animal economy, and in order to study them profitably it is necessary to classify them in a methodi- cal manner, according to their physiological afiinities. Consequently, there have been collected into a single category all those organs which are destined to achieve the same physiological finality, and to such a group has been given the name of fljjpara^HS. An apparatus is, then, an assemblage of all those organs of an animal which concur to the same end, and which serve for the accomplishment of the same function. We will successively describe, in the following order, the different appa- ratus of which the organism is composed : — 1. Locomotm'y Apparatus ; 2. Digestive Apparatus ; 3. Respiratory Apparatus ; 4. Urinary Depurative Apparatus ; 5. Circulatory Apparatus; 6. Innervatory Aj^paratus ; 7. Sensory Apparatus ; 8. Generative Apparatus ; This description will be terminated by a brief exposition of the evolution of the foetus and its appendages. 4 BOOK I. LocoMOTORY Apparatus. The locomotory apparatus is composed of all those organs which minister to the movements an animal may execute. It is certainly one of the most im- portant in the economy, from the number and volume of the pieces which enter into its formation, and by the necessary co-operation that it affords the other apparatus in the performance of the physiological acts which are allotted to them. It is constituted of two kinds of organs ; the bones and muscles. The hones, hard and resisting, stony in appearance, are real inert levers, joined to each other by firm and movable articulations, which permit their playing upon each other with the greatest facility, at the same time maintaining them in tlieir relative positions. The muscles, grouped around the bones and attached to them, are soft organs which possess the pro^jerty of contrac- tion, under certain determinate conditions and of involving in that move- ment the bones to which they are fixed by their extremities. The first are altogether passive in their motion, while the second are really the active .organs of locomotion — the powers intended to move the bony levers. We will treat successively of: — 1. The study of the bones, a particular branch of descriptive anatomy whicli has received the name of osteology ; 2. The study of the articulations, or arthrologtf , 3. The study of the muscles, or myology. FIKST SECTION. The Bones. CHAPTEE L THE BONES IN GENERAL. Bones, properly speaking, are only to be found in vertebrate animals, and constitute their principal zoological character. In the animal body they form an internal framework which consolidates the entire edifice, and gives it its general form and dimensions. It is advantageous, before commencing a particular description of each bone, to survey them in a general manner. This study comprises : 1, The description of the skeleton ; 2, The summary indication of the general principles which should be known in order to com- prehend the details of the special descriptions. TEE SKELETON. 7 Article I. — The Skeleton. The whole of the bones, considered in their natural relations to each other, constitute the skeleton. In order to prepare the skeleton of any animal, it is sufficient to free it from the soft parts surrounding it. The skeleton should be designated natural, if in this operation the ligaments SKELETON OF THE DOG. Tig-. 2. SKELETON OF THE PIG. 8 THE BONES. that naturally join the various pieces together are allowed to remain ; and artificial if, after these ligaments have been destroyed, it is necessary to replace them by materials foreign to organisation, such as iron or brass wii'e. The skeleton is divided into trunk and limbs. The trunk offers for consideration, in the median line, the sjnne or vertebral column, a flexible stalk measuring the entire length of the animal, and composed of a series of distinct pieces articulated one behind the other. Anteriorly, this stalk supports the head, a pyramidal protuberance which itself results from the assemblage of a large number of bones. On each side of the middle portion of the spine, there are detached bony SKELETON OF THE HORSE. arches which have received the name of ribs, and which rest, directly or indu'ectly, by their inferior extremities, on a single bone called the sternum. These bony arches in this way circumscribe the tliorax, a spacious cavity destined for the reception of the principal organs of re- spiration and circulation. The limbs, four in number, two anterior and two posterior, are the appendages which support the trunk. Each represents a column divided into several rays resting upon one another, and generally forming more or less acute angles. The anterior limbs are each divisible into four principal regions : the shoulder, applied against the front jiart of the thorax ; the arm, which succeeds the shoulder ; and the fore-cmn and foot. The posterior limbs also comprise four regions : the haunch or pelds, which articulates with the posterior part of the spine : and the thigh, leg, and posterior foot. THE SKELETON. 9 In birds, the posterior limbs alone assume the function of columns of support. The anterior limbs, formed for flight, constitute the wings. Fig. 4. SKELETON OF THE COW, Fis. 5. SKELETON OF THE SHEEP. The number of bones entering into the composition of the skeleton of the domesticated animals, arrived at the adult period of life varies according 10 GENERAL PRINCIPLES APPLICABLE TO to the species. They are apportioned to the regions of the trunk and limbs just mentioned, in the manner indicated in the following table : DESIGNATION. Vertebral Column ' Head* .... Thorax .... Shoulder . 1 Arm . . I Fore-arm. | Fore-foot . Pelvis Thigh . Leg . . Hind-foot Double regions Solipeds.i Ruminants. Pig. Dog.2 44 43 42 43 28 28 29 28 37 27 29 27 1-2 1-2 1-2 1-2 1-2 1-2 1-2 1-2 2-4 2-4 2-4 2-4 16-32 20-40 36-72 36-72 1-2 1-2 1-2 1-2 1-2 1-2 1-2 1-2 3-6 3-6 3-6 3-6 15-30 19-38 30-72 32-64 Article II. — General Principles Applicable to the Study of all THE Bones. The description of any bone comprises its name, situation, direction, conformation, structure, and mode of development. Name. The nomenclature of osteology does not rest on any basis capable of conferring upon it a methodic form. Consequently, we find bones which derive their name from their shape, (example : the fibula) ; others from their resemblance to known objects (the tibia and vomer). Some owe it to their position (cotes, sides or ribs), or their uses (the axis and parietal bones). Several attempts have been made to submit the nomenclature of the bones to more precise and uniform rules, but the new designations proposed have not been sanctioned by custom. Situation. The situation of a bone should be viewed in two ways : 1st, Relative to tlie median plane of the body ; 2ud, Belative to the other portions of the skeleton. A. Situation relative to the median plane of the body. The designation of median plane, or improperly median line, is given to an imaginary vertical plane, passing through the middle of the skeleton which it divides, from before to behind, into two equal portions. The bones may be situated on the median plane, in which case there is only one of each kind, and they are called single; they are also named symmetrical bones, because the median plane divides them into two equal lateral halves exactly alike. The bones disposed in a double and regular manner on the sides of the median plane bear, for this reason, the name of pairs ; they are also called asymmetrical bones, because their form does not admit of their being separated in any sense into two similar portions. On the contrary, a bone of this kind always offers the most perfect symmetry with its fellow on the opposite side. ' One lumbar vertebra less is found in the ass, and sometimes also in the mule. ' The OS penis has not been included. ' The sacrum is reckoned as a single bone, and the number of coccygeal vertebrae at an average of 12 for the Horse, 16 for the Ox, 14 for the Pig, and 15 for the Dog. * The OS hyoides comprises, and is reckoned as, a single bone. TEE STUDY OF THE BONES. 11 B. Belative situation to the other parts of the skeleton. — To indicate the situation of a bone, considered from this point of view, is to make known the place it occupies in the region to which it bek^ngs, and the connections it may have with adjoining regions. Thus the radius is situated in front of the ulna between the arm-bone and the carpus. Direction. This is absolute or relative. The direction of a bone may be vertical, horizontal, or oblique. Example : the scapula is placed in an oblique direc- tion from above to below, and from behind to before. Configuration of the Bones. Form. — This is also absolute or relative. A. Absolute Form. — The absolute form of a bone is that which it owes to the relations existing between its three dimensions — length, width, and thickness, a. A bone in which one of its dimensions much exceeds those of the other two is a long bone. Example : — the femur. All the long bones are hollowed out internally by an elongated space — the medullarij cavity. Long bones belong exclusively to the limbs. In the animal economy, there are found bones which resemble them in their dimensions, but they have no medullary canal. Example :^the ribs. These differ essentially from the true long bones, and are sometimes distinguished from them by the appellation of elongated bones, b. A bone that offers two dimensions much more developed than the third, is a flat or ivide bone. Example : — the parietal bone. The bones of this category, destitute of a medullary cavity, are met with in the head and the upper regions of the limbs, c. A bone which offers nearly the same development in all its dimensions, is called a short-bone. Example : — the astragalus. Destitute, like the preceding, of a medullary cavity, the short bones are found in the spine and some regions of the limbs. B. Belative Form. — To make known the relative form of a bone is to indicate the greater or less exact resemblance it may bear to geometrical figures, or to familiar objects. Thus the scapula is a bone of a triangular form. External Peculiarities of Bones. — These markedly attract the atten- tion, because they modify the general shape of bones, and singularly assist us in distinguishing one bone from another. These peculiarities, which are real distinctive features that permit their description to be precisely esta- blished, are always either eminences {processes) or depressions. Eminences. — The eminences that stand out in relief from the surfaces of bones are divided into two different categories. One class concurs in the formation of the articulations which join the bones to each other ; they are named articular eminences, in which, again, are distinguished dinrthrodial and synarthrodial eminences, according as they belong to movable or immovable articulations. The others, usually destined for the insertion of ligaments and muscles, are called non-articular, or eminences of hisertion. (The term imprint is also used in anatomy, and signifies a collection of small rugged eminences which make the surface of the bone uneven and rough. There are muscular, tendinous, ligamentous, and aponeurotic im- prints, according as they give attachment to muscles, tendons, ligaments, or aponeuroses.) The synarthrodia! eminences are always indentations more or less deep and finely cut. 12 GENERAL PRINCIPLES APPLICABLE TO The diarthrodial eminences are voluminous and smooth, and in a fresh state are covered with cartilage. They are named heads and condyles : heads, when they describe the segment of a sphere (head of the femur, head of the humerus) ; condyles, when they represent the segment of an oval figure, cut parallel to its large axis (condyles of the femur.) The non-articular eminences receive various names. If they are volumi- nous and much detached from the bone, they are called processes or apophyses. Apophyses receive qualificatives derived from the analogies jierceived between them and knowTi objects. (Examples : — the styloid, clinoid, corouoid and coracoid processes.) The appellations of protaherances and tuberosities are given to non-articular eminences when they are large and round, and but slightly prominent. Lastly, they are named lines, crests, and ridges, when they are narrow and very long. Cavities. — The cavities of bones have also been divided into articular and non-articular cavities. The first correspond to the eminences of the same name in the bony joints. They take the designation of cotyloid cadties when they are deeply excavated, like a basin or the cup of an acorn (the glenoid cavity of the scapula, and the cotyloid cavity of the coxa). The non-articular cavities serve either for ligamentous or muscular implantation, or for the passage of vessels, nerves, tendons, etc. They are termed channels or fiirroics, when they are wide, deep, and smooth ; grooves, when they are long, narrow, and even at the bottom ; fissures, when they are narrow and rough. Digital impressions is the name given to those excavations in bones which look as if produced by the pressure of the finger. The fossce, sinuses, cells, and notches are also non- articular cavities of bones. The sinuses and cells are formed by open spaces in the interior of bones; notches, by cavities excavated on their margins. When a cavity passes quite through a bone it is termed a foramen. If this foramen offers a certain length, it is then designated a conduit or canal. Fissures are long, narrow foramina; hiatus is the term aj)plied to wide openings with irregular outlines. Regions of the Bones. — When it is desired to describe the eminences and external cavities of a bone, it is essential not to notice them, as it were, by chance — passing indifferently from one to another. In order to avoid the difficulties which would result from the application of such an irrational system, it is convenient to divide the bone to be described into several regions, in which are examined, one after another, all the external peculiari- ties that may offer. The following is the course to pursue in order to establish the regions of a long, a flat, and a short bone. (rt) A long bone is always divided into three parts : a body and two extremities. The body, middle part, or dlaphysis, is the narrowest portion of the bone. It represents a geometrical solid, approaching more or less the figure of a very elongated prism. In a long bone, therefore, it is necessary to study as many faces, angles, or borders, as the prism it represents may offer. With regard to the extremities, or epiphyses, these are more or less con- siderable enlargements, showing articular surfaces, as well as surfaces intended for muscular or ligamentous insertion. (h) A flat bone must necessarily have two faces, as well as borders and angles. THE STUDY OF THE BONES. 13 (c) A short bone offers for description a variable number of faces, and plane or salient angles, which are often neglected because of theii- trifling importance. Internal Conformation of Bones. Sections made in various directions through the substance of bones show that theii* internal conformation varies, according as they belong to the category of long, flat, or short bones. The diaphysis of long bones is hollowed out into a large fusiform cavity ; this is the medullary canal. This canal is absent in the flat and short bones. Its walls are formed by a very dense bony tissue, whose pores are scarcely visible to the naked eye, and which is called the compact substance. The extremities of long bones are surroimded by a thin layer of compact substance, while the remainder of their mass is constituted by the sjMngy substance — bony tissue channeled into cells, or very large areolae, which freely communicate with each other. (Reticulated bony tissue is but another form of spongy substance, the only diflerence between the two consisting in the cells or meshes of the first being formed of intercrossed osseous fibres, while those of the second are formed of lamellce.) The medullary canal, and areolfe of the spongy tissue, are filled by a cellulo-fatty substance, the marroio (or medulla). The flat bones are constituted by a layer of spongy tissue placed between two laminfe of compact substance. In the flat bones of the cranium, the two layers of compact tissue are termed the vitreous tables, while the cells of the spongy tissue are designated diploe. In certain points of their extent, the spongy substance disappears, and then the bone is found to be composed of a single lamina of comj^act tissue. The short bones have a nucleus of spongy substance, enveloped in a layer, more or less thick, of compact tissue. The compact substance of the bones being very resisting, is found in all those situations which have to sustain violent efforts. The spongy substance is very light and bulky, and is met with in the widened portions of the bones, to which it affords increased size without adding sensibly to their weight. Structure of Bones. Bones are formed of a proper tissue, covered externally by a particular membrane, the periosteum, and occupied internally by the medulla, vessels, and nerves. Proper tissue. — The texture of the proper tissue of bones varies slightly in the compact and spongy substance. The compact tissue is composed of a funda- mental substance, which is amorphous, or slightly granular, white, and more or less opaque, accord- ing to the thickness it offers. This fundamental substance is penetrated by an infinite number of vascular canaliculi, known as the Haversiayi canals. These canals, which measure from l-2500th to l-200th of an inch in diameter, are parallel to each other and to the larger axis of the bone ; they frequently com- municate by transverse branches. The most „ , ^„ „^„„ r. ■ ^ '' ^1 J, J. XT 1 1 VERTICAL SECTION OF BONE, superficial open on the surfixce oi the bone, be- showin" the network of neath the periosteum, and the deepest into the Haveisfan canals. u GENERAL FRINCIFLES AP FLIC ABLE TO medullary canal; while a certain number tei-minate in the areolaa of the spongy substance. The walls of these canals are constituted by several concentric lamellaa of fundamental substance, and in "■ ■ the body of these are lodged the essential elements of the bony tissue, or osteoplasts {corpuscles or lacunce). These are minute cavi- ties lined by a cellular membrane, and furnished, at their circum- ference, with a great number of canaliculated prolongations, which communicate with the adjacent osteoplasts, or with the Haversian canals. In a thin dried section of bone, the osteoplasts appear black by transmitted light, and white and brilliant by direct light ; MINUTE STRCCTURE OF BONE, as shown in a tliin tjjjg appeai-ance has led some ob- spction cut transversely to the direction of the , ii j. j.\ setiiou cuL Lictusveiscij Ku servers to suppose that they were Haversian canals. „ ^ /> ^^ n ^ 1, A Haversian canal surrounded by its concentric formed of small masses of calca- lamellce; the lacunre are seen between the la- reous matter, it IS noW well mella;, but the radiating tubuli are omitted; knowu that they are minute 2, Ibid, with its concentric lamina, lacunae, and ramifying cavities, lodging a cell radiating tubuli; 3, The area of o^e of the i^preanated with liquid, canals; 4, 4, Intervening lamellai, and between them, at the upper part, several very long lacunse with their tubuli. Fi9c. 8. LACUN.E, OR OSTEOPLASTS OF OSSEOUS SUBSTANCE, magnified 500 diameters. imjwegnatea witn liqui In the spongy texture no Haversian canals can be seen , the osteoplasts are irregularly disposed in the thickness of the fundamental substance, which con- stitutes the septa of the areolae of this tissue. As a rule, the proper tissue of the bones is composed of a frame- work of organic matter which has gelatine for its base, and in which are deposited the calcareous phos- phates and carbonates, which give to this tissue its characteristic a, Central cavity ; b, Its ramifications. i^^^rdness. This is easily rendered evident by immersing any bone in dilute nitric or hydrochloric acid ; acids dissolve the calcareous salts, but do not act upon the organic framework. So it is that, after some days' maceration, the bone becomes flexible, like cartilage, and loses part of its weight, although it preserves its volume. The counterpart of this experiment may be made by submitting it to the action of fire. It is then rendered quite friable, because its organic skeleton has been destroyed without the earthy salts it contained being affected. Periosteum. — This is a very vascular and nervous fibrous membrane that covers the entire bone, with the exception of the articular surfaces. Its thickness and adliercnce are not the same everywhere. By its inner face it corresponds to the surface of the bone ; by its external face, it is confounded with the insertion of the tendons and ligaments, or with the surrounding connective tissue. THE STUDY OF THE BONES. 15 The periosteum may be resolved into two layers, though these are not very distinct. The superficial layer is essentially fibrous, and is formed by a mixture of connective and elastic fibres and plasmatic cells. The deep layer also contains a loose connective tissue, but more especially elastic fibres, and more or less voluminous sj)herical or fusiform cells. This is called the osteofjenotis layer. Medulla. — The medulla, or marrow, is a pulpy, fatty substance, which fills the medullary canal and the areolaB of the spongy tissue of the bones. Somewhat consistent, and of a rose tint in the bones of the young animal, the marrow becomes difiiueut and yellow in the bones of those advanced in age. In the first instance, it only contains traces of fat; while in the second it has 96 per cent, of this substance. The medulla of bones is composed of: 1st, Some trabeculfe of delicate connective tissue, which serves to support the vessels and nerves ; 2nd, Fat either free or inclosed in vesicles ; 3rd, Particular cells, named by M. Kobin meduUo-cells and myeloplaxes. The medulla cells, abundant in the red or foetal marrow, are small cells with a spherical nucleus; while tlie myeloplaxes are large, flattened, or polyhedral elements of an irregular outline, containing a great number of nuclei. Rare in the yellow marrowy they are more particularly found adhering to the walls of the medullary canal, or the alveoli of the spongy tissue. Blood-vessels. — The arteries of bones belong to three orders ; a distinction founded on their volume and the extent of their distribution. The arteries of the fii'st order penetrate to the interior of the medullary canal of long bones by a particular orifice, the nutritious foramen. They soon divide into two branches, which break uj) into a network that lines the walls of the canal and enters the tissue of the medulla. Tliis network communicates with the arteries of the second order, which are destined to the spongy tissue of the extremities of the long bones, penetrating them by the numerous nutritious foramina that surround the epiphyses. Lastly, the arteries of the third order are branches of the i:)eriostic network which enter the superficial Haversian canals. These canals which open in this manner on the surface of the bones may be considered, strictly speaking, as a third category of nutritious conduits. In the flat and short bones there are no arteries of the first order. Veins accomi^any the arteries, and are always more voluminous than these ; they frequently make their exit by special and very large openings at those points where the sjiongy tissue is abundant. The veins of bones sometimes exhibit saccular dilatations on their course. Certain veins in the cranial bones have their parietes entirely composed of osseous tissue. Lymphatic vessels. — The existence of these in the interior of bones cannot be affirmed. iVeri'cs.— These belong to the cerebro-spinal and ganglionic system of nerves ; the latter are always vaso-motory nerves. Almost constantly a somewhat voluminous nerve enters the medullary canal by passing through the nutritious foramen, and is distributed to the medulla. The compact tissue receives few nervous filaments ; while, on the contrary, the spongy tissue at the extremities of the long bones, as well as the short bones, obtains an abundant supply. Certain short bones, such as the vertebrae, are especially remarkable for the numerous nerves they receive. 16 GENERAL PRINCIPLES APPLICABLE TO DEVELOPMENT OP BONES. Bones, before arriving at the state in which they present themselves in the adult animal, pass through several successive phases, whose study consti- tutes what is termed osteogeny. In the embryo, at a very early period, the bones are composed of a mucous material analogous to that which enters into the composition of all the other organs ; this matter is constituted by a mass of what are called embryonic culls. At a later period they are impregnated with gelatine, and nearly all become harder, white, and elastic, passing into the cartilaginous state. Exception must be made, however, to the lateral and anterior parietes of the cranium and the face, the bones of which are at first fibrous but never cartilaginous. The cartilaginous bones show a fundamental amorphous substance, in which are disseminated spherical cells containing one or more nuclei. This condition is transitory ; the cartilaginous tissue soon submits to modifications which result in conferring on the pieces that it composes the hardness and structure of perfect osseous tissue. These modifications constitute the process of ossification. There are several portions of the skeleton which do not undergo this osseous transformation, and which most frequently remain in the cartilaginous condition during the entire life of the animal. These permanent cartilages are met with at those points where the bony skeleton must preserve a certain degree of flexibility, and on the articular surfaces. During the process of ossification, the cartilages become vascular, are impregnated with calcareous salts, and excavated with Haversian canaliculi and medullary cavities. The saline molecules are deposited in the amorphous substance, which grows more hard and opaque ; at the same time the cartilaginous cells become the point of departure of a new embryonic proliferation, from which results the neoplasts. Ossification begins at the same time in several parts of the skeleton, and in each of the bones in particular ; though it does not appear over the whole extent of the latter at once ; on the contrary, in certain determinate points of the cartilaginous mass, bony tissue can be perceived developing itself and extending gradually until it finishes by completely invading it. These points are called centres of ossification. These centres are primary or complementary ; the latter are in some way added to the bone, and form, wholly or in part, certain processes. Although these centres of ossification enlarge from day to day, yet for a somewhat long period they remain completely independent of one another, and are only connected by cartilaginous tissue. The term epnphyses is given to the osseous centres which are placed at the extremities of the principal centre. When the skeleton is completely developed, the various centres of ossification are fused into each other, and then there are no longer epiphyses ; this fusion always takes place at an almost determinate epoch. It has been remarked that, of two epiphyses, it is con- stantly the one near which the nutritious foramen is directed that is first united to the body of the bone. Growth. — Bones grow in width and thickness by the apposition of new elements. In the long bones, the growth in length takes place by the ossification of the cartilage uniting the epiphyses to the body of the bone. Consequently, elongation should cease as soon as the epiphyses are incor- porated with the diaj)hysis. With regard to the long bones of the limbs, Duhamel, Floureus, and particularly MM. Oilier and Humi^hry, have remarked that, in the thoracic limb, the extremity furthest removed from THE STUDY OF TEE BONES. 17 the hiimero-radial articulation grows fastest ; while in the abdominal limb, the extremity most distant from the femoro-tibial articulation grows the least. Concerning the growth of the bones in thickness, this occurs by the ossifi- cation of the devY> layer of the periosteum called the osteogenetic layer. The experiments of the above-named authors have irrefutably demonstrated this fact. The formation of bony tissue in the deep layer of the periosteum is very active during the youth of animals ; but it soon slackens, and in advanced age ceases completely. In the first period of life, in proportion as the new layers are added to the surface of the bone, the old layers, those nearest the medullary canal, disappear by resorption. Later, the process of resorption exceeds that of formation, which is, in old age, completely annihilated. It has also been observed that the formation of a certain quantity of the osseous elements takes place on the inner face of the medullary canal, at the expense of the medullary tissue. In the flat bones, the primitive centre of ossification is developed nearly in the middle, and the calcareous salts are afterwards deposited in radiating lines from this sjjot towards the perijihery. These bones are augmented in thickness by the formation of subperiostic layers, and by the development of the spongy tissue between their two compact laminas ; they increase in width by the ossification of what are termed the marginal epiphyses. The short bones grow from the periosteum and the epiphysery cartilages, when they possess complementary centres. Nutrition. — The exj^eriments which consisted in feeding young animals with madder, and afterwards examining their osseous system, have for a long period demonstrated the nutrition of bones. When bones cease to grow, their nutri- tion becomes less active ; but it is evident that it does go on, in order to maintain the organic matter of the osseous tissue in a proper con- dition. (Professor Owen has explicitly and concisely stated the development of bone to occur as fol- lows : — " The primitive basis, or ' blastema ' of bone is a transparent glairy matter containing numerous minute corpuscles. It progressively acquires increased firmness ; sometimes assuming a membranous or ligamentous state, usually a gristly consistence, before its conversion into bone. The change into cartilage is noted by the appearance of minute nucleated cells, which increase in number and size, and are aggregated in rows, with intercellular tracts, where the ossification is about to begin, as in fig. 9, These rows, in the cartilaginous basis of long bones, are vertical to its ends ; in that of flat bones they are vertical to the margin. The cells furthest from the seat of ossification are flattened and in close contact ; nearest that seat they become enlarged and separated. The first appearance of bone is that of minute granules in the inter- columnar and intercellular tissue. Canals are next formed in tlie bone by CARTILAGE AT THE SEAT OF OSSIFICATION, showing at its lower portions the clusters of cells arranged in columns, each of which is inclosed in a sheath of calcified intercellular substance. 18 THE BONES absorption, which ultimately receive bloodvessels, and become the * vascular canals.' The immediate nutrition of bone is i)rovided for by the production of minute ' plasmatic canals ' from the vascular ones. When these canals become dilated, so as to oifer definite forms, they are termed ' lacuna} ' or ' bone-cells,' and to some extent characterise, by their shape and size, the osseous tissue of the respective vertebrate classes. lu the concentric laminae sm-rounding the vascular canal, the bone-cells or osteoplasts are arranged concentrically, between the laminae, with the long axis in the direction of the circular line of the plate. Most of the plasmatic tubes con- tinued from the bone-cells pierce the plates at right angles in their course to the vascular canal, with which they connnuuicate ; and they form the essential vehicle of the material for future growth. Extension of parts, however, is not the sole process which takes place in the growth of bone ; to adapt it to its destined offices, changes are wrought in it by the removal of parts previously formed. In marine creatures, the bones usually remain solid ; but in the active land quadrupeds, the shaft of the long bones is hollow, the first-formed osseous substance being absorbed, as new bone is being deposited without. The strength and lightness of the limb-bones are thus increased after the well-known principle of the hollow column. The bones of birds i^resent this quality in the highest degree, particularly those of powerful flight. In these the medullary cavity of beasts is transformed into a capacious cavity containing rarified air instead of marrow. In the mam- malian class, the air-cells of bone are confined to the head, and are filled from the cavities of the nose or ear, not from the lungs, as in birds. Such cells are called ' frontal sinuses,' ' antrum,' ' sphenoidal,' and ' ethmoidal.' The frontal sinuses extend backward over the top of the skull in the rumi- nant and some other quadrupeds, and penetrate the cores of the horns in oxen, sheep, and cei'tain antelopes. The most remarkable development of cranial air-cells is presented by the elephant, the intellectual jihysiognomy of this large quadruped being caused, as in the owl, not by the actual capacity of the brain-case, but by the vast extent of the pneumatic cellular structure between the outer and inner plates of the skull-wall. All these varied changes in the osseous tissue, from mere cancelli to large medullary or pneumatic cavities, are the residt of secondary changes by absorption, and not of the primitive constitution of bones, which were at first solid.") CHAPTEE II. THE BONES OF MAMMALIA IN PARTICULAR. Article I. — ^Vertebral Column. The vertebral column, or spine, is a solid and flexible stalk situated in the middle and upper part of the trunk, of which it forms the essential portion. It protects the S2)iual cord and sustains the thorax, as well as the principal organs of the circulation, respiration, and digestion. Articulated anteriorly with the head, and terminating in a point at its posterior extremity, this piece is formed by a somewhat considerable assemblage of short, single, tuberous bones, to which has been given the name of vertehree. These TUE VERTEBRAL COLUMN. 19 bones, though all constructed on an uniform type, yet do not offer the same configuration throughout the whole rachidean stalk. The differences they present into this respect, have allowed of their being formed into five prin- cipal groups ; whence the division of the vertebral column in five regions, which are, enumerating them from before to behind: 1, Cervical region; 2, Dorsal region ; 3, Lumbar region ; 4, Sacral region ; 5, Coccygeal region. The first comprises seven vertebrae, which serve as a base for the animal's neck : the second has eighteen, against which the ribs are placed ; the third has only six, which correspond to the loins ; in the fourth there arc five, constantly solidified into one mass in the adult, to constitute a single bone — the sacrum ; while the fifth possesses a variable number of small degenerate vertebrae, gradually decreasing in size to form the tail. The pieces consti- tuting the first three regions are called true vertebras ; those of the last two are designated false vertehrse. The characters belonging to all these verteorae will be first studied ; then a particular description of the vertebne of each region will be given ; and, finally, an examination will be made of the spine as a whole. , CHARACTERS COMMON TO ALL THE VERTEBRA. Each of these small bones is pierced from before to behind by a wide Figr. 10. ELEMENTS OF A VERTEBRA: AFTER OWEN. A, Ideal typical vertebra ; B, Actual thoracic vertebra of a bird ; c, Centrum (or 6oc?.v), giving off, d, d, the diapophyses, and p, 2^, the parapophyses (transverse and articular processes); the neural arch, inclosing the spinal cord, is tbrmed by n, n, the neurapophyses {lamiiuv), and n, s, the neural spine Cspinous j^roccss); the hamal arch, inclosing the great centres of the circulation, is formed by h, h, the hsemapophyses (costal cartilages), and h, s, the ha;mal spine (sternum). From both the neurapophyses and htemapophyses maybe given off the zygapophyses, z, z. The lateral arches, which may inclose the vertebral arteries, o, o, are completed by the pleurapophyses (ribs), pi. ; these in B are bent downwards, so as to form part of the hasmal arch, and give off the diverging appendages, a, a. opening, the spinal foramen ; whence results, for the entire spine, a long canal traversing its whole length, and which lodges a very important 20 THE BONES. portion of the nervous centres — the spinal marrow. This canal, which traverses the vertebra from one end to the other, transforms it into a veritable ring in which we recognise, for facility of description, two parts — the one inferior, the other superior. The first, or body, is very thick, and forms the base of the vertebra ; the second, which is thin, has been de- signated spinous or spinal, from one of the peculiarities it jiresents, or annular, because it circumscribes the major portion of the spinal foramen. This division is not altogether an arbitrary (me, for the body and the annular por- tion constitute, in the foetus, two distinct i)ieces, which do not become united for a long time after birth. Body, — The shape of the body of a vertebra is that of a prism with four faces, of which two only — the superior and inferior — are free, and can be studied in the adult ; the two lateral faces being united and confounded with the annular portion. This prism also presents two extremities — an anterior and posterior. Faces. — The superior face, limited in extent, forms part of the spinal foramen, constituting its flour. It exhibits : 1, On the median line, two roughened, prominent surfaces, rejsresenting two triangles, whose summits are opposed ; 2, On the sides, two depressed smooth surfaces, perforated by one or more openings that lead to the interior of the bone. The inferior face is divided into two lateral portions by a median crest. Extremities. — The anterior has a prominent convex head, more or less detached. The posterior offers a cavity for the reception of the head of the next vertebra. These two planes, the one convex, the other concave, do not come into immediate contact ; an elastic, flexible fibro-cartilage, firmly attached to each, being interposed between them. Annular Portion. — This is formed by an osseous plate that curves sud- denly downwards, in the shape of an arch, the two extremities of which approach each other, inclose the body, and become united to it. It offers for study : 1, An internal and an external surface ; 2, An anterior and a posterior border. Surfaces. — The internal surface, concave and smooth, forms, with the superior face of the body, the spinal foramen. The external, convex and irregular, presents; 1, A single prominence, raised in the middle of the superior portion, and named the spinous p>'>'ocess ; 2, The transverse processes are a double pair of eminences, one on each side, and projected transversely outwards. Borders. — The anterior harder has two articular facets looking upwards : these are the anterior articular processes, right and left. In each is a notch which, when placed in opposition to a similar excavation in the preceding vertebra, forms the intervertebral foramen. The posterior border presents the same peculiarities, with this difference, that the articular faces of the pos- terior articular processes are inclined downwards, to correspond with the anterior facets of the succeeding vertebra. Structure of the vertehrce. — The compact substance, which is abundant in the spinous portion, forms, in the body, an extremely thin layer, inclosing a voluminous nucleus of spongy tissue. The latter is traversed by numerous venous canals, which open on the surface of the bone. Development. — It has been already shown that the body and spinous portion of a vertebra constitute, in young animals, two distinct pieces. Each was primarily formed from two lateral centres, which met on the median line. In the body, the fusion of these centres is so prompt, that it is generally believed, perhaps justly, that the develojiment of this part of the vertebra THE VERTEBRAL COLUMN. 21 proceeds from a single centre of ossification. The union of the tv\-o centres iu the anuuhu" portion, usually designated the vertebral lamince, is slower. It commences iu the most anterior vertebrje, and is latest in the sacral and coccygeal regions. To the two principal pieces of the vertebra in process of ossification, is added, at a subsequent period, complementary points of ossifi- cation, five or six iu number : one or two for the sjunous process, one for the summit of each transverse process, another for the head, and the last for the posterior cavity of the body. CHAEACTERS TKOPEU TO THE VERTEBRA OF EACH EEGIOX. A casual inspection of a vertebra might suffice, strictly speaking, to dis- tinguish the region of the spine to which it belonged. For instance, a cervical vertebra is recognised by its volume, the absence of a spinous process, and the foramen which traverses the base of its transverse processes. The dorsal vertebra is conspicuous by its tubercular transverse processes, and by being furnished, outwardly, with an articular surface, as well as by the defu-ession on its body destined to receive the heads of the ribs. The lumbar vertebra has its long flattened transverse processes ; while the coccygeal vertebra oflFers rudimentary laminte and processes. There is no necessity for noticing the sacrum, whose five pieces form one bone : a feature which markedly distinguishes it from the other regions of the vertebral column. But these few distinctive characteristics do not satisfy the require- ments of descriptive anatomy ; so that it is necessary to undertake a more extensive study of each of these regions. 1. Cerdcal Vertehrce. General Characters. — These vertebrse, the longest and thickest in the spine, present generally a cubic form. They are usually distinguished from the vertebrfe of the other regions by the following characters : — The inferior spine of the body is strongly marked, especially behind, where it terminates in a small tubercle. The head is well detached from the re- mainder of the bone, and describes a very short curve. The posterior cavity, wide and deep, represents a veritable cotyloid depression, which is too large to fit the head exactly : the intermediate fibro-cartilage on these two suiiaees is also of a groat thickness. The spinous process forms a simple roughened, and but slightly prominent, ridge. The transverse p-ocesses, very developed, are elongated in an antero-posterior direction, and inclined down- wards. In this region they are designated the trachelian processes, because of their relations with the trachea ; a foramen that traverses them from before to behind at their base has been, for the same reason, named the iraclielian foramen (vertebral foramen). The articular processes, large and prominent, are inclined downwards and inwards. The notches are wide and deep. Specific Characters. — The seven cervical vertebraB are reckoned from before to behind, and receive numerical names indicating their place in the region. First. — The first vertebra of the neck, which has been named the atlas,''- deserves a very careful description. At first sight there is recognised the ' So named from the mythological personage who was supposed to support the earth, as the first vertebra (human) supports the head. (For this bone in the domesticated animals the name is not appropriate.) 5 29 THE BONES. Yiz. 11. great development of its transversal diameter, the considerable dimensions of the spinal foramen, and the thinness of its body. The intra-rachidian face of the latter is divided into two portions by a transverse ridge ; one anterior, furnished with ligamentous imprints, exhibits, laterally, two deep excavations, which lodge the venous sinuses ; the other, posterior, is smooth and concave from side to side, and forms an articular surface into which is received the odontoid j)rocess of the axis ; this surface resembles the cotyloid cavity. The inferior spine of the body appears as a large tubercle. The head is absent, and is replaced by two concave facets. The anterior articular processes have their gliding surfaces looking downwards ; they are joined to the two preceding facets to constitute two large diarthrodial cavities, which correspond to the occii)ital condyles. There is no spinous process, but a rough- ened surface instead. The transverse jiro- cesses are large, flattened above and below, incline forwards and downwards, and are provided with a thick rugged lip. Pos- teriorly, quite at their base, and on each side of the spinal foramen, they show two large vertical facets wliich rej^resent the posterior 4, Posterior, or cervical fora- a^-ticular processes : these facets are uneven, are confounded with the articular cavity oi the upper face of the body, and correspond to the two analogous facets of the axis. Each transverse i)rocess is pierced at its base by two foramina, which traverse it from below upwards. The posterior rejn-e- sents the vertebral foramen of the other ver- tebra ; while the anterior is continued to the external surface of the process by a wide, deep, but very short channel, running from without to within, and joins a third fora- men, which enters the spinal canal. These last two ojienings, with the demi-canal which unites them, rejilace the anterior notch ; the posterior is altogether absent. Lastly, an inflected venous canal, whose position varies, and whose presence is not constant, crosses the lamina) of the atlas, and opens, on one side, into the spinal canal, and on the other, beneath the trans- verse process. The atlas contains much compact tissue, and is generally developed two for the body, which at an early period becomes a solid piece, and two for the annular part ; the other two are complemientary centres, each of which forms one of the two posterior undulated facets, and the lip of the corresponding transverse process. Second. — This is named the axis (or dentafa). It is the longest of all the cervical vertebrfe ; those which succeed it gradually diminish in length and augment in thickness. The body of the axis has not any head anteriorly, ATLAS; INFERIOR SURFACE. 1, Articular processes for condyles of the occipital bone ; 2, ibidem ; 3, Vertebral or antero-internal fora- men men ; 5, Transverse process ; 6 Tubercle representing the inferior spinous process ; 7, Superior arch, forming the roof of the spinal fora- men. Fig. 12. A CERVICAL VERTEBRA. 1, Superior spinous process; 2, An- terior articular processes ; 3, Pos- terior articular processes ; 5, An- terior convex fiice of body , 6, 7, Transverse processes, with their tubercles or rudimentary ribs ; 8, Inferior crest, or spine ; 9, Concave posterior face. from six centres of ossification THE VERTEBRAL COLUMN. 23 Fig. 13. but a conical process termed the odontoid, wliicli is flattened above and below, concave and rough from one side to the other on its superior face ; convex in the same direction, and perfectly smooth on its inferior face. The latter represents an articular half-hinge, around \vhich glides the concave arti- cular surface on the sujierior face of the body of the atlas. The anterior articular processes are carried to the base and to each side of the odon- toidian pivot, in the shape of two un- dulated facets, which are confounded with the gliding surface of the latter, whose destination has been already noted. The spinous process, very powerful and elongated antero-pos- teriorly, is divided behind into two roughened lijjs THE AXIS, OR dentata; lateral view. i ne transverse pro- j^ Superior spinous process ; 2, Odontoid pro- cesses are slightly developed, and ter minate posteriorly in a single tubercle, directed backwards. The anterior notches are very deep, and are most frequently converted into foramina, cess; 3, Intervertebral foramen, or hole of conjugation ; 4, Body ; 5, Inferior spinous process ; 6, 7, Inferior and superior articu- lating processes. This vertebra, although voluminous, IS light, in consequence of its containing much spongy substance. In the young animal, the odontoid process and the articular surfaces on each side, constitute two centres, distinct from each other and from the body of the vertebra. After the axis, the cervical vertebrae diminish in length and increase in thickness ; while the obliquity of their articular processes becomes the more pronounced the more distant they are from that vertebra. Third, fourth, and fifth. — Each of these has, at its transverse processes, two prolongations, one anterior, the other posterior. The inferior face of their bodies exhibits a median spine terminated posteriorly by a tubercle, which gradually increases in volume from the third to the fifth vertebra. The third presents, between its anterior and j^osterior articular j^rocesses an almost comjilete gap ; if its anterior extremity be jilaced on a horizontal plane, it will touch that plane by its articular and transverse processes and its head. In the fourth, the articular processes are united by a thin, shar]) osseous plate, notched only in front. Laid on a horizontal plane, the head remains some distance from it. The fifth is known by the continuous, thick, and rugged lamina which unites the articular processes, and by the tubercle of the inferior sj)ine on the body, which is in shape like the heart on a playing-card. Si.ith. — This is distinguished by the slight prominence of the spinous process, but particularly by the almost total disappearance of the inferior spine, and the presence of a third prolongation, very strong and inclining downwards at its transverse jjrocess, a circumstance to which this vertebra owes its designation of tricuspid. Seventh. — This has received the name of prominens, because its spinous process, terminating in a point, is more distinct than in the preceding vertebrae, the axis excepted. It exhibits, besides . deep imprints, which replace the inferior spine, a concave demi-facet on each side of the posterior cavity for the articulation of the head of the first rib ; a particular disposition of its transverse processes, which are unituberculous ; the complete absence of the vertebral foramen; and, lastly, the depth and width of its notches. 24 THE BONES. The spinal foramen, whicli lias already assumed a somewhat considerable diameter in the sixth cervical vertebra, is still larger in the seventh.^ Fisj. 14. 2. — Dorsal VertehrcB. General Characters. — In the dorsal vertebrae the body is very short, and in front has a large slightly i)rojecting head ; behind, it has a shallow cavity. Laterally, these vertebrae present, at the base of the transverse processes, fonr concave articular facets, the two anterior of which are situated near the head, while the posterior two are hollow^ed out of the border of the articular cavity of the body. Each of these facets is joined to an analogous facet on the neighbouring ver- tebra to form a small excavation, into which is received the head of the corresponding rib. The spinous process is very high, is compressed on both sides, inclines backwards, and its summit is terminated by a tubercle. The transverse pi-ocesses are unitubcrcular, and directed obliquely outwards and up- wards ; on their external aspect they have a diarthrodial plane facet which corresponds to the tuberosity of the rib. The articular jrrocesses are narrow, and constitute simple unrelieved facets cut on the base of the spinous pi'ocess. The posterior notches are deep, and sometimes converted into foramina. Specific Characters. — None of the eighteen dorsal vertebra) diifer mucli from the type just described ; and it is diiScult to establish special characters for each. It is, nevertheless, possible to assign to a dorsal vertebra, approximately, the rank it should occujiy, in accepting the following facts as a guide : — 1. The vertical diameter of the vertebral hodies augments progi-es- sively from before to behind. Their lateral diameter, which determines that of the sjiinal canal, becomes, on the contrary, less from tlie TYPE OF A DORSAL VEBiXEBKA ; THE FOURTH. 1, Body ; 2, 2, Articular facets for the head of rib ; 3, Articular facet for tuberosity of the rib ; 4, Articular processes ; 5, Spiual foramen ; 6, Tuberous base of spinous process ; 7, Posterior articular face of body ; 8, 8, Transverse processes ; 9, Superior spinous process; 10, An- terior articulation of body. first to the tenth vertebra ; after which it assumes increasing proportions to the last one. The articular surfaces, which serve for the mutual contact of head and cavity, become larger and shallower in proportion as the vertebrae are more posterior. The inferior spine on the body is very salient and tuberculous in the two first vertebrae, very acute in the third and fourth ; it disappears in the sixth and ninth, to re-appcar and become more marked from the tenth to the last. 2. The intci-vertebnd cavities, intended for the reception of the heads of the ribs, diminish in depth and extent from the first to the last. 3. The longest S2)! nous process belongs to the third, fourth, and fifth vertebrae : those whicli follow gi-adually decrease to the eighteenth. Their width diminishes from the second to the eighth ; it afterwards increases in a progi-cssive manner in the succeeding vertebrae ; • M. Goubaux lias somotimcs met -with asymmetrical cervical vertebrae j certaiu vertebrse, tricuspid on one side, are only bicuspid or unicuspid on the opposite side. TEE VERTEBRAL COLUMN. 25 from the second to the tenth vertebra, the summit of the si^inous process is hxrge and tuberculous ; in the last seven it is flattened laterally. Their obliquity is less marked as they proceed backwards ; in the sixteenth and seventeenth vertebrse, the spinous process is nearly vertical ; it inclines slightly forward in the eighteenth. Those of the tenth, eleventh, and twelfth vertebrae are slightly curved like an S. 4. The articular p-ocesses, from the first to the tenth vertebra, gradually contract and approach the median line ; in the succeeding vertebrte they, on the contrary, increase, and become concave and wider apart from those of the opposite side. 5. The volume of the transverse processes and the size of their diarthrodial facets diminish from before to behind. In the three first vertebrfe this facet is concave ; in the first nine the articular facet looks outwards and backwards, while the facet on the body looks forwards ; in the last the two facets are directed forwards. These two facets are generally confounded in the seventeenth and eigliteenth vertebree. The first dorsal vertebra much resembles the prominens ; it is distinguished from it, however, by the presence of four diarthrodial facets on its extremities. It also differs from the other vertebrae by the shortness of its spinous process, which terminates in a point ; by the size and 2:)rominence of its articular processes ; and by the depth of its notches. The last vertebra never has facets on the contour of its posterior cavity.^ 3. Lumhar Vertebrce. General Characters. — A little longer and wider than the dorsal vertebrte, which they resemble in the arrangement of their bodies, these vertebri^ are characterised : 1, By their short, thin, and wide spinous processes, which are slightly inclined forwards, and are provided at their summits with a scabrous tubercle ; 2, By their largely developed transverse processes, flattened above and below, and directed horizontally outwards;- 3, By the salient anterior articular processes, hollowed out on each side, and provided externally with a tubercle for insertion ; 4, By theii" equally prominent posterior articular processes, rounded in the form of a half-hinge. Specific Characters. — The characteristics which may serve to distinguish these vertebrfe from one another are derived from the body, and the spinous and tranverse processes. 1. From the first to the last there is a progressive diminution in tLe vertical diameter of the bodies, and an increase in their transverse diameter. The inferior spine on the body becomes shorter and wider from the fii-st to the last vertebra ; in the six vertebrae it resembles an elongated triangle whose summit is directed forwards. 2. The spinous processes decrease in width from before to behind, and their anterior border becomes more and more concave ; their summits are thickened and tuberculous in the three first, and thin and slo2:)ing forward in the three last. 3. The transverse processes are longer in the middle vertebrae than in those placed before and behind. The processes in the first and ' In well-formed horses, it is not unconimon to find nineteen dorsal vertebra?, with an equal number of ribs; though in these in>tances there are most frequently only five lumbar vertebrse. Husson and Goubaux have sometimes met with nineteen, and the normal number in the other regions. Sometimes there are only seventeen dorsal vertebrce. ^ It has been correctly stated that these processes are the representatives of rudi- mentary ribs which have become united to the vertebrae. Therefore it is that they are frequently designated costi/orm processes. 26 THE BONES. second vertebrje iucline slightly backward; in the third they are more up- right ; and in the succeeding ones are directed a little forward. In the last tw'O they are remarkable for their thickness ; in the tifth an oval-shaped articular facet is observed on their posterior border ; in the sixth, two are present — one in front, corresjjond- ing to the preceding, and one behind, slightly concave, meeting a similar facet on the sacrum. The fourth and tifth vertebrae very often correspond, at their transverse processes, by means of analogous facets.^ In the Ass, and sometimes in the Mule, only five lumbar vertebras are found. According to M. Sanson, this is the natural number in the Arab Horse. ^ 4. Sacrum. The sacrum results, as already stated, from the consolidation of five vertebra3. This single bone articulates, in front, with the last lumbar vertebra ; behind, with the first coccygeal bone, and on the sides with the ossa innominata. It is triangular, flattened above and below, and from before to behind describes a slight curve up- wards. It offers for study a superior and an infei'ior face, two borders, a base, a summit, and a central canal, the exten sion of the spinal canal. Faces. — The superior face presents, on its middle, the spi- nous jirocesscs of the sacral vertebra3, which together con- stitute what is called the sacral or supersacral spine. These LUMBAR VERTEBRA ;froxt VIEW. proccsscs are xmited at their ^\^.l^' \^?'''^'7^''*"''^^^^T''''f°r l^ase only, and remain is.dated process , 4, Spiual foramen ; 5, Anterior articular „ ^ '' ' . ^ i! ^ • processes; 6, 6, Transverse, or costiform pro- ^^^' *'!« remainder ot their ex- cesses, 7, Posterior articular process. tent ; they all incline backwards ' We possess the skeleton of a horse which has seven lumbiir vertebra;, with the normal compleniont in the other regions. The seventli is no doubt the first sacral, as it has all its characters. The fifth sacral vertebra is evidently derived from the coccygeal region. - (This statement is scarcely correct. M. Sanson has established tlie fact that there is in reality no Arab horse; and asserts that the specific type with five lumbar vertebra-, is very probably of African origin, and that these vertebinj, independently of their numb( r, offer individual characteristics different from those observed in the vertubrte of the type which has six.) UPPER SURFACE OF LUMBAR VERTEBRA. 1, Summit of spinous process j 2, 2, Anterior articular processes; 3, 3, Posterior articu- lar processes ; 4, 4, Transverse processes. Ficr. 16. THE VERTEBRAL COLUMN. 27 and terminate, witli the exception of the first, by a tuberous summit, which is often bifid ; their length diminishes from the second to the fifth bone. On each side of the sacral spine exists a groove, at the bottom t'ig. 17. of which are foiu" openings — the supersacrcd foramina. These orifices open into the spinal canal, and communicate with four analogous, but wider aper- tures, pierced at the inferior face of the bone, and for this reason named the subsacral fo- ramina. The inferior face is smooth, and shows traces of the primitive separation of the ver- tebral bodies ; the subsacral fo- ramina, which represent, with the corresponding supersacral openings, the intervertebral fo- ramina of ihe other regions of the spine, are observed on this surface. Borders. — The two borders, thick and concave, form, posteriorly, a rugged lip ; in front, they present an irregular sui-face inclining obliquely from above to below, from within outwards, and from before to behind. This surface, which is intended for the articulation of the sacrum with the ossa innominata, is divided into two parts : one, the inferior, named in man the auricular facet, is slightly imdulated and diarthrodial ; the other, the superior, serves for ligamentous insertions. Base. — This offers : 1, On the median line, the anterior orifice of the sacral canal, and the anterior articular snrface of the body of the first sacral vertebra, which is oval and slightly convex ; 2, On the borders, the articular processes and anterior notches of this vertebra, as well as the elliptical and somewhat convex facets which bring it into contact with the transverse processes of the last lumbar vertebra. Summit. — The summit, thrown back, presents : 1, The posterior orifice of the sacral canal ; 2, The posterior articular surface of the body of the last sacral vertebra ; 3, The vestiges of the articular processes and posterior notches of that vertebra. Sacral canal. — This is the portion of the spinal canal which is channeled out of the sacrum ; it is triangular, and diminishes in width from before to behind. LATERAL VIEW OF SACRUM. 1, Articular surface of body : 2, 3, Articular surfaces corresponding to those on the transverse processes of last lumbar vertebra; 4, Spinal foramen; 5, Auricular facet ; 6, Anterior articular processes ; 7, Inferior or subsacral foramina ; 8, Superior spinous processes ; 9, Summit or coccygeal ex- tremity. 5. Coccygeal Vertehrce. The coccygeal region, or coccyx, comprises from fifteen to eighteen de- generate vertebrae, which gradually diminish from the first to the last. In the first three or foui", nearly all the characteristics of true vertebrae are found ; they show a spinal foramen, a body, a spinous process, and transverse processes, looking backwards ; the articular processes only are altogether absent. In the succeeding vertebrte, these characters become effaced ; the vertebral laminfe do not join completely, and the spinal canal is only a simjile groove, which, gradually decreasing in depth, at last 28 TEE BONES. entirely disappears. The insertion eminences also become less salient, and the coccygeal vertebrfe are soon reduced to small bony cylinders, narrow in the middle and wider at both extremities, with a convex articular surface at each end (except the last, which has only one ai'ticular surface^. These small cylinders, the last traces of the vertebral bodies, are each developed from three centres of ossification ; they are very spongy and light. The fii'st coccygeal vertebra is frequently consolidated with the sacrum in aged animals. THE SPINE IN GENERAL. The vertebral column has now to be considered in its entirety, and examined successively in its superior face, its inferior face, its lat.ral faces, and its spinal canal. Afterwards its direction and mobility will be noticed. Superior face. — This presents, on its median line, the series of spinous processes. But little salient in the cervical region, these eminences are much developed in the dorsal and lumbar, where they constitute a long crest, the dorso-lumhar spine, as well as in the sacrum, where they form the sacral spine. They soon disappear in the coccyg^l vertebrte. Outwards, and on each side of these processes, is seen a succession of tubercles of insertion, represented in the cervical and lumbar vertebrae by articular processes, and in the dorsal vertebrfe by the superior or rugose portion of the transverse processes. These tubercles are disposed in line, and sejxarated from the spinous processes by a channel designated the vertebral groove, which is more or less deep and wide. It is on these, and on the spinous processes, that the extensor muscular fasciculi of the spine receive the greater portion of their fixed or moveable insertions. Inferior surface. — -Wide at the neck, this face becomes narrow in the dorsal region, to be again widened at the lumbo-sacral region, and once more contracted at the coccyx. Crests more or less developed, which divide the vertebral bodies into two lateral portions, right and left, are remarked. Lateral surfaces. — These offer for study the thirty-six intervertebral foramina, through which the spinal nerves pass. They exhibit besides, on the neck, the transverse processes ; in the back, the external facets of these processes, and the intervertebral facets, all destined to sustain the heads of the ribs ; on the loins, the transverse or costiform processes. It may be remarked that the ribs and the transverse processes of the neck and loins furnish points of insertion to the powerful muscles which produce the lateral movements of the spine. In the sacrum, the lateral faces are formed for the articulation of the spine with the ossa innominata. Spinal canal. — This canal communicates, in front, with the cranial cavity. Very wide in the atlas, for the reception of the odontoid process and to permit the rotatory movements of the head without iujm-y to the spinal cord, this canal suddenly diminishes in the axis. It again dilates at the termination of the cervical region and the commencement of the dorsal ; there the sjnnal cord presents a greater volume, and the movements of the spine are very extensive. Towards the middle of the back, the spinal canal offers its smallest diameter ; it Avidens from this part to the lumbo-sacral articula- tion ; after which it contracts rapidly, and disappears altogether near the fourth or fifth coccygeal vertebra. The lumbo-sacral dilatation coincides with the enlargement of the cord in this region, and with the enormous quantity of nerves lying beside it. TEE VERTEBRAL COLUMN. 29 Direction of the vertebral column. — The spine docs not extend in a straifjbt line from the head to the posterior extremity of the body. If it is foUowed from the caudal termination, which is free and looks downwards, to the anterior extremity, it will be seen that it rises upwards and forwards, forming a convex intlexion corresponding to the roof of the pelvis. lu the lumbar and the posterior half of the doi-sal region it is nearly horizontal and rectilinear ; from thence it descends to the cervical region, when it again rises and forms two curves, the one posterior, bending upwards, the other anterior, turned down. This disposition of the cervical spine gives it the shape of a console. Mobility of the vertebral column. — In the cervical region, the almost total absence of spinous processes, the great development of the articular processes, and the very short curve described by the surfaces of contact of the vertebral bodies, allows the spine very extensive and very diverse movements. In the dorsal region, however, these movements are very limited, the spinous processes and the costal arches preventing the play of the vertebrte on each other. In the lumbar region, the spine can be flexed or extended more than in the dorsal ; but its lateral movements are quite as restricted, owing to the jiresence of the transverse processes and the reciprocal joining or dovetailing of the articular processes. Lateral motion is even rendered impossible in the posterior half of this region, from the manner in which the transverse processes are adapteil to each other. It may be remarked, however, that this disposition singularly favours the integral transmission of the propulsive efforts thrown ujJon the trxmk by the posterior extremities. The sacral vertebrae, having to afford the ossa innominata a solid fixed point, could not j^reserve their independence and mobility, and are conse- quently consolidated into a single piece which fulfils all its requirements in this respect. In the coccyx the rachidean stalk again recovers its mobility, and to a degree more marked than elsewhere ; the coccygeal bones, articulated with, each other by means of convex siirfaces, and deprived of long processes at their extremities, are placed in the best possible conditions for variety and extent of movement. DrETEKENTIAL CHARACTERS IN THE VERTEBRAL COLUMN OF OTHER THAN SOLIPED ANIMALS. The Number of Pieces composing the Spine slightly varies in the Domesticated Animals, as will be seen in the following Table. ANIMALS. Ox . Sheep Goat Pig . Do- Cat . ^TERTEBR.E. Cervical. DorsaL Lumbar. SacraL Coccygeal. 13 6 5 13 6 or 7 4 13 6 4 14 6 or 7 4 13 7 3 13 7 3 l^to20 16 to 24 11 to 12 21 to 23 16 to 21 21 A. VERTEBR.E OP THE Ox, Sheep, AND GoAT. — 1. Cewical VeHehrx. — The cervical vertebrpe of the Ox diflfer from those of solipeds by their shortness and the greater deve- lopment of their insertion eminences. In the Sheep and Goat they are relatively longer. than in the Ox. The transverse processes of the atlas are less inclined than in the Horse, 30 TEE BONES. and Lave no vertebral foramiua ; the posterior facets for articulation with the axis are nearly flat and join each other. The axis has a semicylindrical, not a conical, odontoid process, which is so concave on its upper surface that it looks like a groove. Its spinous process is not so thick as in the Horse, and is not bifid posteriorly. In the five succeeding vertebrx, a rugged continuous lamina unites the anterior articular processes to the posterior. Tiie spinous process inclines forward and is flattened trans- versely at its summit, which is sometimes bifid ; it augments progressively in height from the third to the filth vertebra. In the sixlli, the transverse processes have only two prolongations — a superior and inferior ; the latter, large and flattened on botli sides, is bent abruptly downwards. The spinous process has already attained the height of IJ to 2 inches in this vertebra, and is flattened laterally. The seventh well deserves the name of prominens • its sjainous process being no less than from i to -i^ inchi-s. 2. Dorsal vertebra;. — In the Ox these bones are longer and thicker than in the Horse. Their spinous processes are larger and incline more backward ; their transverse processes are very voluminous, and are provided with a convex facet from above to below; while their posterior notches are nearly always converted into foramiua. Cousidered individually, they are more slender in the middle than at the extremities. Their spinous processes diminish in width, especially at their summits, from the first to the eleventh vertebra, and widen again in the two last ; they progressively increase in slope to the teuth, after which they become more and more upright ; the first four are the longest, and are nearly the same in height ; the others gradually decrease. In the lirst four or five vertebraj, the articular facet of the transverse processes, while retaining its vertical convexity, is concave in an antero-posterior direction. This facet is always absent in the last vertebra, and sometimes even in the preceding one. The two bones terminating the dorsal region show, in addition, the articular processes disposed like those of the lumbar vertebrae. The dorsal vertebrae of the Sheep and Goat are relatively less strong than those of the Ox ; their spinous processes are not so wide, and their posterior notches are never con- verted into tViramina. 3. Luiahar vcrtehrse. — The lumbar vertebrae of the Ox are longer and thicker than in the Horse. The transverse processes are also generally more developed, are concave on the anterior border, convex ou tiie posterior, and incline slightly downward, with the exception of tlie two fiist, which remain nearly horizontal. They increase in length from the first to the fourth vertebra; in the latter and the fifth, they are nearly of tlie tame dimensions ; in the last they suddenly become shorter. Their width gradually decreases from before to behind. In the fifth and sixth vertebra, these processes have no articular fecets between them and the sacrum, these being only met with in solipeds. The artic- ular processes are prominent, and further removed from the median line as they belong to posterior vertebrae. In the G >at the transverse processes are more inclined downwards. In the Sheep, on the contrary, the processes rise up towards their extremities. 4. Sacrum. — Tiie tacrum of the Ox is more voluminous and curved than that of the Horse. The spinous processes are entirely consolidated, and are surmounted by a thick rugged lip ; tkey are leugtheued at their base and on each side by a ridge that represents the rudiments of the articular processes. Tlie lateral borders are sharp and bent down- wards. The surfaces that serve to unite the sacrum to the ossa innorainata have a some- what vertical direction. There are no lateral facets on the base of the bone for the union of tlie sacrum with the transverse processes of the last lumbar vertebra. In the Slieej) and Goat, the sacrum is shorter ; sometimes the consolidation of the spinous processes is late, or never occurs. 5. Coeeyrieal verfebrx. — In proportion, the coccygeal vertebrae of ruminants are stronger and more kiberous than those of the Horse. The anterior articular processes exist in a rudimentary condition. B. Veutebu.ts of the Pig. — 1. Cervical vertehree. — Of all the domesticated animals, this has the shortest, the widest, the most tuberous, and consequently the strongest cervi- cal vertebrae. The body of these bones is deprived of its crest ou the inferior face ; its held, but little detached, is scarcely round, and looks as if driven back on itself; con- sequently, its posterior cavity is not deep. The vertebral laminoo are very narrow, and scarcely extend from one part of the vertebra to the other in the superior portion ; so that the spinal canal appears at this point to be incomplete. In the atlas, the transverse processes are yet less inclined than in ruminants ; the vertebral foramen is not constant, and when it exists, opens on one side, under the THE VERTEBRAL COLUMN. SI transverse proces3, and on the other, oa its posterior margin, after pursuing a certain truck in the substance of the bone. The odontoid process of the axis is constricted at its base. This vertebra is distin- guished by its high and thin spinous process inclining slightly back, by its transverse processes being but slightly piouiiueut and perforated by an enormous vertebral loramen. in the four succeeding vtriehnv, the spinous process terminates in a blunt point, and uiclincs forward; slightly salient in the tirst, it gradually rises in the others. The trans- verse processes form two prolongations : one, tlie superior, is tulj>erculous, and is joined to the anterior articular process by a plate of bone, which is pierced by a foramen; the other, the inferior, flattened on both sides, bent downwards, and large, as it belongs to the posterior vertebra;, transforms the inferior face of these vertebral bodies into- a large groove. The seventh is provided with a spinous process as long as those of the dorsa.! region. A perforated bony plate, as in the preceding vertebraj, unites the anterior articular process to the single tubercle composing the transverse process ; the latter is continued back nearly to the posterior notch by a second plate, also perforated with a foramen (see Fig. 2j. 2 Dorsal vertebra;. — The Pig has fourteen dorsal vertebrfe, which, in their general disposition, are not unlike those of the Ox. As with that animal, the intervertebral fora;- mina are double, each vertebral lamina being perforated laterally by an opening situated in front of the posterior notch. In addition, the vertebrse of the Fig present this pecu- liarity, that their transverse processes are generally traversed at the base by a single or multiple foramen which communicates with the jjieeeding. With regard to the special characters proper to some of the vertebrse, these are, as witk the other animals, very few, and may be described as follows; 1. The transverse pro- cesses of the four vertebra preceding the last project but slightly; 2. In the fourteenth this process resembles those of the lumbar vertebrse ; 3. The articular facet of the trans- verse process in the four last vertebra; is confounded with the anterior lateral facet corresponding to the head of the rib, 4. The articular processes of the last five vertebrse are arranged like those of the lumbar vertebrre ; and the prominence formed by the tubercle on the outside of the anterior articular process replaces, to a certain degree, the transverse process of these vertebrse. 3. Lumbar vertehrx. — These bones in the Pig greatly resemble those of ruminant animals. It commonly happens that seven are met w ith ; but in this case the supple- mentary vertebra is generally a sacral one. It is not denied, however, that seven lumbar vertebrse may exist in the Pig, along witli the normal num1:>er of sacial vertebrae. 4. Sacrum. — This is formed by four vertebrse, which are a long time in becoming fused together , and it is often dilticult to discover where the sacrum ends and the coccyx begins.' The spinous processes are entirely absent. The vertebral laminse are not consolidated , so that the spinal canal is half cut through in its upper portion, as in the cervical region ; this canal is also much compressed above and below. 5. Coccygeal vertehrx. — These vertebrse in the Fig are more particularly distin- guished by the presence of articular processes, by means of which the foremost bones correspond with each other. C. Vektebr.?; of the Dog anp Cat. — 1. Cervical Vertehrx. — In these animals, tlie cervical vertebrse are long and thick, and much resemble those of solipeds. Nevertheless, besides their smaller volume, they are distinguished : 1, By the disposition of their corresponding articular surfaces; the anterior, or'head, is nearly flat, and is even slightly excavated in its centre ; tlie posterior, or cavity, is but little hollowed to receive the head of the next vertebra ; 2, By the width of the vertebral laminse, which exactly cover one another ; 3, By the height of their spinous processes, which increases as the vertebriB extend back ; 4, By the great extent of the anterior and posterior articular processes, whic'.i are united by means of a continuous and very salient bony plate, that considerably augments the transversal diameter of each vertebra. In the atlas, the articular surface for the odontoid pivot is confounded in front with the cavities which correspond to the occipital condyles. The two facets which are annexed l)osteriorly to this articular surface, instead of being plane or gently undulated, as in the ' This can always be made out. however, by con.sulting the disposition of the articular processes. Thus, in the sacral vertebrse these eminences— if we except the anterior ones of the first and the. posterior of the last— never exist except in a rudi- mentary state; while in the other five coccygeal vertebrae they ro-appear with all their characters. S2 THE BONES. other domesticated animals, are transformed into real glenoid cavities.' The transverse processes are carried directly outwards and a little backwaid; the lip which borders each is slii^htly raised ; of the two foramina which replace the anterior notch, one only exists, and this penetrates to the interior of the spinal canal ; the other is merely a simple notch. In the axis, the odontoid process is cylindrical, narrow at its base, and bent a little upwards; the lateral facets of this eminence represent true condyles.- The spinous process is veiy thin and undivided, and is curved forward above the laminiB of the atlas. The anterior notches are never converted into foramina. The tliird cervical vertebra is the largest, and the succeeding ones gradually diminish in thickness to the last, contrary to what occm-s in the other species. The seventh does not show the spinous process so developed as in ruminants and pachyderms (see Fig. 1). 2. Dorsal vertehrx. — In the Dog the dorsal vertebrse are formed on the .same model as those of the Horse ; but their spinous processes are in general narrower and tliicker. The tenth always has its spinous process vertical, triangular, and terminated in a sharp point. The last three have no posterior facets for the articulation of the heads of the ribs, and exhibit, in the conformation of their articular processes, the same disposition as the lumbar vertebrse. In the Cat, the transverse processes of the three last dorsal vertebrae are thin, sharp, and turned backwards , they never possess facets for the tuberosity of the ribs. 3. Lumbar verfebrx. — In the Dog and Cat, the lumbar vertebrse are remarkable for their strengtli, due to their length, thickness, and the development of the eminences of insertion. The spinous process is low, and becomes acute in the last vertebra. The transverse processes incline very much forward and downward , they become longer from the first to the second-last bone, in the latter they become contracted, and in the seventh vertebra they are still more diminished, and terminate in an obtuse point. The tubercle of the anterior articular process is extremely promment, and the posterior notches are surmounted by a small, very acute prolongation, directed backwards, which becomes more developed towards the anterior vertebrae. Tiiis small prolongation exactly i-epresents the transverse process of the dorsal vertebrse. 4. Sacrnm. — -The three vertebrse which form tiie sacrum of carnivora are early con- solidated. The supersacral spine constitutes a thin siiarp ridge, while the lateral surfaces for articulation with the ossa innominata are turned quite outwards and are nearly vertical. 5. Coccygeal vertebrse. — The vertebrse ot the coccyx are very strong and tuberous. The first five or six are as perfect as the true vertebrae, and comport themselves in every respect like them. The last are small V-shaped bones, which M. Goubaux has described by the name of hypsiloid bones. COMPARISON OF THE VERTEBRAL COLUMN OF MAN WITH THAT OF THE DOMESTICATED ANIMALS. The vertebral column of Man is composed of twenty-nine bones . twenty-four vertebrse. the sacrum, and four pieces constituting the coccyx. The twenty-four vertebrae arc thus distributed : Cervical vertebrae " Dorsal „ 12 Lumbar „ 5 In all these vertebrae, the bodies are slightly excavated at the two extremities, while in the domesticated animals, the superior or anterior is convex, and the inferior or posterior concave. 1. Cervical verfebr.v.— These are wide and short. The spinous processes are mode- rately developed and bifid at their summits , the transverse processes are also divided into two branches — a posterior and an anterior. 2. Dorsal vertebrx. — In these vertebrse, the bodies increase in thickness from the first to the last. In the first as well as in the last dorsal vertebrse, the spinous process is almost immediately directed backwards; in the middle portion of this region these processes are very obliquely directed downwards and backwards. ' (A glenoid cavity is a shallow, oval, articular depression.) 2 (A condyle is an articular eminence representing an ovoid segment. Condyles always corresj^nd to the glenoid cavities in the articulations.) TEE HEAD. 33 3. Lumhar vertehrx. — The lumbar vertebrae are the strongest bones in the spine, and their bodies are marly as ihick as those of the larger domestic.ited animals. This enormous development of the lumbar vertebrae in Man is related to his position as a bipe^l. In the fifth, the lower face of the body is cut very oi'liijuely backwards and upwards, and ti.e transverse processes are more voluminous than those of the otlier lumbar vertebrae. 4. Sacrum. — The sacrum is lormed by the union of five pieces. It is very concave from above to Fig. is. below and before to behind. In becoming united to the lumbar region, it forms a salient angle in front, to which has been given the name of promon- tory or sacro-vertebra] angle. The sacral spine is continuous or interrujited, according to the subject ; it is alway bifid inferiorly. 5. Coccygeal vertehrx. — These are little bones or flattened tubercles, four in number, rarely five, and usually consoliilated. The coccyx is conical in shape. Its base shows two processes directed up- warJs, which are called the cornua of the coccyx. Its summit is often deviated to the right or left. Article II. — The Head. The head is a large bony pyramid, elon- gated from above to below, and quadran- gular, suspended to the anterior extremity of the spine ; it is in a direction varying with the attitudes of the animal, but which we will suppose, for convenience of description, to be nearly vertical. It is formed of a great number of particular bones, which are only distinct from one another in very young animals ; for well before the adult period is reached the majority of the bones are united and cannot be separated. The head is divided into two parts : the cranium and the face. BOXES OF THE CRANimi. The cranium, or upper part of the head, is composed of seven flat bones, five of which are single : the occipital, parietal, frontal, sphenoid, and ethmoid ; one only, the temporal, is double. These bones circum- scribe a central cavity, the cranial, which communicates behind with the spinal canal, and lodges the principal portion of the nervous centres — the encei^halon. 1. Occipital Bone. The occipital bone occupies the superior extremity of the head, which it supports from the anterior extremity of the spine. This bone is very irregular in its form, and is bent at a right angle in front and behind. It has an external and an internal face, and a circumference which brings it into contact with the adjoining cranial bones ; the latter HORSE S HEAD ; FRONT VIEW. 1, Occipital protuberance; 2, Origin of the mastoid crest ; 3, Parietal bone ; 4, Saggital suture ; 5, Junc- tion of the parietal and temporal bones ; 6, Zygomatic arch ; 7, Frontal bone ; 8, Frontal suture ; 9, Temporal fossa ; 10, Supraorbi- tal foramen; 11, 12, Lachrymal bone; 13, Malar bone; 14, Xasal border of frontal bone ; 1 5, Nasal bone; 16, Suture of nasal bones ; 17, Superior maxillary bone; 18, Infraorbital foramen; 19, Ante- rior, or pre-maxillary bone ; 20, Foramen incisivum ; 21, Incisor teeth — young mouth. is subdivided into two anterior 34 THE BONES. lateral borders, two posterior lateral horders, an anterior and posterior salient angle, and two lateral re-entering angles. Faces. — The external face is divided into three portions by the double flexure of the bone : one looks forward, another upward, and the third backward. It exhibits : — 1. On the median line, and from before to behind : a, an antero-posterior ridge which constitutes the origin of the jjarietal ridges, to be mentioned hereafter ; h, a transverse, voluminous, and very prominent eminence, marked posteriorly by deep imjprints, with a medimn projection named the cervical tuberosity ; this is the external occipital pro- tuberance which, in the Horse, corresponds at the same time to the superior curved lines of the occipital bone of Man. This protuberance forms the culminating point of the head, and divides the anterior aud superior parts of the external face of the bone ; c, the occipital foramen (foramen magnum), a large orifice that passes through the bone at the posterior flexure, aud esta- blishes a communication between the cranial cavity and spinal canal ; d, the external surface of the basilar process, a narrow and thick prolongation formed by the bone as it passes to meet the sphenoid : this surface is convex laterally. 2. On the sides : a, A sharp crest which prolongs, laterally, the superior curved lines, and descends on the middle of the lateral anterior border to be continued with the superior root of the zygomatic process and the mastoid crest of the temporal bone ; b, Linear imprints, parallel to the latter, and prolonged on the base of the styloid process : they are destined for the insertion of the small oblique muscle of the head, and rejiresent the inferior curved lines of the occipital bone of Man ; c, Within these imprints is a slightly- roughened cavity for the insertion of the posterior recti muscles ; d. The two condyles, articular eminences with a double convexity, one superior, the other inferior : these eminences are situated on each side of the occij^ital foramen (foi-amen magnum), and corresjDond to the anterior cavities of the atlas ; e. More outwards are the two styloid processes, or jugular eminences, long projections flattened on each side, terminated in blunt points, directed back- wards, and separated from the condyles by a deep space, the stylo-condyloid notch ; f. Under the condyles is the condyloid fossa, a smooth depression, pierced at the bottom by the condyloid foramen, which penetrates the cranium. The internal face of the occipital bone is concave, and shows: beliind, the foramen magnum ; above, an uneven surface, which forms the roof of the cerebral cavity ; below, the superior face of the basilar process, slightly hollowed into a groove ; on the sides, the internal orifice of the condyloid foramen. Circumference. — The anterior lateral borders are thick, and are united by suture with the parietal bone, and vnXh. the tuberous jiortion of the temporal bone by the harmonia^ suture. The posterior lateral borders are sharp, and constitute the sides of the basilar process ; each coucurs in the formation of the occipito-splieno-temporal hiatus, also termed the lacerated foramen, a vast irregular opening, extending from above downwards, jienetrating the cranium, and divided by a ligament, in the fresli state, into two jiortions, one inferior, the anterior lacerated foramen, the other superior,'- the posterior lacerated foramen. The anterior angle, which is dcntated, is dovetailed into the parietal bone. The posterior angle is very thick, aud forms the summit of the basilar process ; it is united by suture with the body of the sphenoid. The lateral re-entering angles, or jugular notches, correspond to the ' (The harmonia suture (&pe7v, to adapt) is the simple apposition of contiguous borders, whicli nre roufihened to facilitate retention.) ' (The anterior and posterior lacerated foramen of Man.) THE HEAD. 35 point where tlie bono is bent posteriorly ; they separate the anterior lateral from the corresponding posterior lateral border, and ai'e occupied by the tuberous portion of the temporal bone. Structure. — The occipital bone contains much spongy substance. Development. — It is developed from four centres of ossification : one, the anterior, is single, and forms the occij)ital protuberance; another, the posterior, also single, forms the basilar process ; the other two are pairs, and comprise each a condyle, with the styloid process and the corresponding condyloid foramen. 2. The Parietal Bone. The parietal is a wide and thin bone, very much arched to form the roof of the cranial cavity. It is bounded above by the occipital bone, below by the frontal, and laterally by the two temporal bones. It otters for study an external and internal face, and a circumference divided into four regions or borders. Faces. — The external face is convex. It exhibits two curved ridges whose concavity is directed outwards ; these two crests, which are termed the parietal ridges, approach each other and unite superiorly, to be continued with the antero-posterior ridge of the occipital bone ; below they diverge and proceed, one on each side, to join the supraorbital process. They divide the surface of the bone into three portions : two lateral, which are rough and traversed by vascular channels, forming part of the temporal fossae ; the third, or middle, is plane, smooth, and of a triangular form, and covered by the skin. The internal face is concave, covered by digital impressions, and grooved by small vascular canals ; it offers, on the median line, and altogether above, the parietal eminence.^ This trifacial and very salient pro- jection presents at its base, on each side, an excavation elongated trans- versely, into which opens the parieto-temporal canal, and which is destined to lodge a venous sinus. It is continued, in front, by a median crest, which is often replaced by a slight groove, the saggitcd furrow, bordered by linear imprints. Two other ridges, resulting from the abutment of the lateral border of the bone against the anterior face of the petrous bone, rise from the sides of this eminence and descend to the sphenoid bone ; they separate the cerebral from the cerebellar cavity. Borders. — The superior border is notched, thick, and slightly dentated ; it articulates with the occipital bone. The inferior border, slightly concave, and deeply dentated, offers an external bevel in its middle portion, and an internal bevel on its sides ; it corresponds with the frontal bone. The latercd borders are very thin, and are cut at the expense of the external plate into a wide, sloping edge, which shows a groove destined to form the parieto-temporal canal. A very prominent angle separates each into two portions, an inferior, that articulates by suture with the squamous portion of the temporal bone ; and a superior, curved inwards towards the centre of the cranial cavity ; the latter portion of the lateral border is in contact with the anterior face of the petrous portion of the temporal bone, with which it concurs to form the lateral crest that descends to the parietal eminence. Structure. — This bone contains much compact tissue, the spongy sub- stance existing only in its middle. Development. — It is developed from two large centres of ossification, to ' The internal occipital eminence of Man. 36 TSE BONES. which is added a single ceutre to form the parietal eminence.^ In early- life the parietal ridges are absent. 3. Frontal Bone. The frontal is a flat quadrilateral bone, whose sides are bent in the middle at an acute angle, and are carried back, and a little inwards, to meet the wings of the sphenoid bone. It assists in forming the cranial roof and part of the face. It is bordered : above, by the parietal bone ; below, by the nasal and lachrymal bones ; and on each side, by the temporal bones. It otfers for study an external and an internal face, and /o?fr herders. Faces. — The external face is divided, by the double flexui-e of the bone, into thi'ee regions : a middle and two lateral. The first, nearly plane, is lozenge-shaped, is covered by the skin, and constitutes the base of the fore- head. It gives rise on each side, at the point where it is inflected, to a long 2)rocess, flattened above and below, which curves backward, forming the orbital arch. The superior or external face of this pi'ocess is convex and slightly roughened ; the intei'nal face is smooth and concave, and forms part of the orbital fossa. Its posterior border, thick and concave, is continued, in- wardly, with the corresponding parietal ridge, and outwardly with the superior border of the zygomatic process. It limits, in front, the temporal fossa. The anterior border, also concave, but thin, concurs in the forma- tion of the orbital margin ; the summit, thickened and denticulated, rests upon, and is united to, the zygomatic j^rocess of the temjioral bone ; the base is wide, and is traversed by an opening termed the sup-aorhital, or super- ciliary foramen. The two lateral regions of the external face of the frontal bone are slightly excavated, and assist, for the greater portion of their extent, to form tlie orbits. They often show, near the base of the orbital arch, a small depression corresponding to the flexure described by the great oblique muscle of the eye in 2)assing through its pulley. The internal face of the frontal bone is concave, and divided into two unequal jjarts by a transverse ridge, corresponding to the anterior border of the cribriform plate of the ethmoid bone. The superior, the most extensive, is covered with digital impressions, and belongs to the cranial cavity. It exhibits : 1, On the median line, a slight furrow, or a crest which is con- tinuous, above, with the median ridge of the parietal bone, and below, with the crista- gain process ; 2, On the sides, and in the re-entering angle formed by the flexure of the bone, there is a narrow slit, or mortice, which receives the wing of the sphenoid bone. The inferior part is united, on the median line, to the perpendicular plate of the ethmoid. It assists in forming the bottom of the nasal cavities, and presents laterally two large openings which lead to the frontal sinuses — vast anfractuous spaces excavated between the two plates of the bone. Borders. — Tlie superior border is denticulated, and cut obliquely, in its middle portion, at the expense of the internal plate, and on the lateral parts at the expense of the external table ; it is in contact with the parietal and ' Tliis centre is described as the interparietal hone by those anatomists who consider the two lateral centres as two distinct parietals. (Leyh is one of the veterinary anatomists who describe thi.s nucleus as a separate bone, designating it the /aZe//'o?-m or mfe»7jar/etoZ Ijone. He also describes the parietal as a •pair or double bone ; whereas the majority of French anatomists include the interparietal bone as tlie mediiin protuberance of the parietal, which they look upon as a single or impair bone. Percivall names it a pair bone, but follows the example of the French hippotomists with regard to the interparietal.) THE HEAD. 37 squamous portion of the temporal bone. Tlie inferior, prolonged to a point in tlie middle, is in apposition witli the nasal bones through the medium of a wide external bevel ; laterally, it is very thin, faintly serrated, and artieulates with the lachrymal bone. The lateral borders, thin and irregular, present two notches : one, the superior, is wide and deep, and occupied by the wing of the sj)henoid bone ; the other, inferior, is very narrow, and uniting with a similar notch in the sphenoid bone, forms the orbital foramen, which opens into the cranium, very near, but external to, the ethmoid fossa. Each of these borders, also, is adapted, for a limited extent, to the- corresponding palate bone* Structure. — The two compact plates of the frontal bone are separated by spongy texture towards the middle and in the upper part ; they separate below to form the frontal sinuses. Laterally, they are very thin and consolidated with each other. Dcrelopment. — The frontal bone is developed from two lateral centres of ossification, which only coalesce at a late period. In youth the cranial portion of the bone forms, in front of the head, a large rounded protuberance standing beyond the facial portion. This prominence disappears when the frontal sinuses begin to be developed. These cavities do not exist at an early period of foetal life ; but commence to form about the fourth month of conception, by a process of resorjition, which removes the spongy substance interposed between the two compact tables of bone, and may even cause the destruction of the internal table. The sinuses enlarge with age, and remain during life separated from one another by a vertical septum. 4. Ethmoid Bone. The ethmoid hone, deeply situated in the limit between the cranium and the face, is inclosed between the frontal, the sphenoid, the vomer, the palate, and the supermaxillary bones. It is composed of three portions : a jperpendlcular plate, and tivo lateral masses. The Perpendicular Lamina of the Ethmoid Bone. — Situated in the median j^lane, and flattened on both sides, this bone presents two faces, a left and right, and four borders. Faces. — The faces, covered by the pituitary membrane, present, pos- teriorly, small sinuous crests ; elsewhere they are smooth. A very narrow interval, constituting the bottom of the nasal cavities, separates them from the lateral masses. Borders. — The superior border looks towards the centre of the cranial cavity, and constitutes what is called the ethmoidal ridge, or crista-galli process. It is free, concave, and sharp, prolonged in front and above by the median crest of the frontal bone, and confounded behind with the middle portion of the inferior sphenoid. The inferior border is continuous with the cartilaginous plate which separates the nasal cavities. When this plate becomes ossified, which is not unfrequent, it is impossible to discover the point where it begins or the ethmoid bone terminates. The middle septum of the nose has been considered, and justly, as a prolongation of the perpen- dicular plate (or lamina) of this bone. The anterior border is consolidated with the vertical septum which separates the frontal sinuses. The posterior border is joined, above, to the median plate which divides the si:)henoidal sinuses into two compartments. Below, it is fixed in the groove of the vomer, and soon becomes confounded with that bone, which is itself conso- lidated with the inferior sphenoid. Lateral Masses of the Ethmoid Bone. — These are two large pyrifonn 6 38 THE BONES. tuberosities placed on each side of the perpendicular lamina, and offering for study a middle portion, a base, and a summit. Each of these is formed by an assemblage of numerous, extremely thin, osseous plates, curved into small and very fragile convolutions. These, elongated from above to below, become lonf^er as they are more anterior ; they are attached by their superior extremities to the transverse plate which separates the cranium from the nasal cavities, and by one of their borders to a thin leaf of bone which envelops the lateral masses out- wardly. They have received the name of the ethmoidal volutes (or cells). Middle portion. — This should be studied externally and inter- nally. The external surface of each ethmoidal mass is divided into two sections : an internal, making part of the nasal cavities ; the other, external, concurs in form- ing the walls of the f 'ontal and maxillary sinuses. The first, the least extensive, is almost plane ; jmrallel to the perpeudicitlar la- mina, it is isolated from it by the narrow space which forms the bottom of the nasal cavities ; it jiresents several openings which separate the most superficial cells, and join the internal canals to be hereafter noticed. The second, A, Occipital bone. — 1, Condyle ; 2, Con- dyloid foramen; 3, Styloid process; 4, Summit of basilar process. — n, Parie- tal bone. — 8, Parietal protuberance; 9, Channel which concurs to form the parieto-temporal canal. — C, Frontal bone. — 10, Transverse crests separating the cranial from the facial portion of the bone; 11, Frontal sinuses; 12, Notch on the lateral border occupied by the wing of the sphenoid bone ; 13, Notch for the formation of the oi-bital foramen ; 1-1, Summit of the orbital process : 15, Sujiraorbital foramen. — D, Perpendicular lamma of the ethmoid bone. — E, E, Lateral masses of the eth- moid bone. — 16, The great ethmoid cell. — F, Squamous portion of the temporal bone. — 17, Supercondyloid process ; 18, Channel for tlie formation of the parieto-temporal canal. — G, Tuberous portion of the temporal bone. — 5, Mas- toid process; G, Internal auditory hiatus ; 7, Opening for the eustachian ANTERIOR BONES OF THE HEAD OF A FCETUS tube into the tympanum. — H, Lach- (horse) at birth ; DISARTICULATED, AND rymal bone. — I, Nasal bone. — J, Su- VIEWED FROM BEHIND. perior turbinated bone. THE HEAD. 39 very extensive and convex, looks outwards in front and behind, and is covered by an osseous i)late traced with shallow furrows, which correspond internally -with the small crests to which the cells are attached. This lamella is prolonged, inferiorly, a little beneath the inferior extremity of these latter, and turns outwards to articulate with the palate and superior maxillary bones ; superiorly, it coalesces with the sphenoid and the orbital portion of the frontal bone. Internalhj, the lateral masses are hollowed from above to below by extremely diverging canals, which open inferiorly into the nasal cavities, and separate the cells from one another. The latter are so incurvated that the internal cells communicate with each other. There are some, however, which are com2)letely closed ; the anterior, or great cell, is frequently so.^ Base. — The base of each lateral mass looks upwards, and is formed by the transverse septum between the cranium and the nasal cavities. This septum is perforated by openings which give passage to the ethmoidal nerves ; it is named the cribriform plate of the ethmoid bone. It is concave on the superior surface, which constitutes the ethmoidal fossa, and convex on the opposite face, where attachment is given to the superior extremities of the cells. It is consolidated internally -with the perpendicular j^late ; the other points of its circumference are attached to the sphenoid bone, and to the transverse ridge on the internal face of the frontal bone. Summit. — The summit of each lateral mass is formed by the inferior extremity of the ethmoidal cells, which is directed downwards towards the nasal cavities. One, more voluminous than the others, is carried much lower, and terminates by a rounded protuberance. It corresponds to the middle cornu (concha media) of Man. Structure of the ethmoid bone. — Very little spongy tissue enters into the composition of this bone, and this is only found near the anterior border of the jjerpendicular plate. Development. — The ethmoid bone is late in attaining its development, and the adjoining bones are nearly completely ossified when it is yet entirely cartilaginous. The bony transfoimation commences in it at the inferior extremity of the cells, and advances progressively from below upwards. The peri^endicular plate is only ossified in part when the cells have passed through the first half of the process : at the same time it coalesces with the inferior sphenoid. The cribriform plate is the last to become ossified ; this transformation having scarcely been achieved when the animal is six or eight months old. 5. Sphenoid Bone. The sphenoid bone is situated behind the cranium, between the occipital, ethmoidal, palate, vomer, pterygoid, frontal, and temporal bones. It is flattened from before to behind, curved from one side to the other, thick in its middle part, named the body, and thin on the sides, which, in their inferior half, are prolonged in the form of alee or wings. It has two surfaces and four borders. Surfaces. — The external surface is convex, and presents : 1, On the median line, the external surface of the body, rounded from one side to the other, is continued with that of the basilar process, and has marked mus- cular imprints superiorly; 2, On the sides and from within outwards : a, the vidian (or pterygoid) fisnire, directed from above downwards, and con- tinued by the vidian canal, a very small foramen which opens into the ' It is not rare to find it opening into the frontal sinus. 40 THE BONES. orbital hiatus ; h, the snhspJienoidal, or ptenjgoid process, a long eminence, flattened on both sides, inclining downwards, articulating with the palate and pterygoid boues, and traversed at its base by the vidian canal ; c, a little behind and above this eminence, the superior orifice of the siih- sphenoidal foramen, a large canal which bifurcates inferiorly ; d, more in front, the orbital hiatus, a kind of vestibule into which open in common the principal branch of the subsi^henoidal canal, the three supersj^hcnoidal canals, the vidian and optic canals, and the orbital opening : this hiatus is surmounted by a thin and sharp bony plate, above which opens the smallest branch of the subspheuoidal foramen ; e, altogether without the hiatus is remarked a smooth surface belonging to the wing of the sphenoid, and which concurs to form the orbital cavity. The internal face is concave from side to side. It shows : 1, On the median line, and from before to behind, a small projection united to the crista-galli ; the optic fossa, elongated transversely in the form of a shuttle, and presenting at the bottom, and on each side, the superior orifice of the optic foramen, a cylindrical canal directed obliquely downwards, forwards, and outwards, to reach the orbital hiatus ; the supersp>lienoidal or pituitary fossa, also named the sella turcica, a slight depression, limited behind by a scarcely noticeable transverse projection separating it from the superior channel of the basilar process; 2, On the sides, and in front, the internal surface of the wings, depressed by very superficial digital impressions ; more behind and outwards, a fossa, elongated from before to behind, which lodges the mastoid lobule of the brain ; between this fossa and the sella turcica, two vertical fissures : an internal, named the cavernous sinus, and an external, wider and deeper, for the passage of a large nervous branch. These two fissures open below, near the junction of the three super- sphenoidal canals. Two of these, which are very wide, are placed one before the other, and separated only by a slight partition. The superior of these constitutes tlie great sphenoidal fissure ; the other, the lower, is i\\Q foramen rotundum, and opens into the orbital hiatus. The third, very small, is situated outside the great anterior canal, opens above the optic foramen, witliin the bony mass surmounting the hiatus, and sometimes on the free margin of this lamina. Borders. — The superior is a little concave, and shows, in its middle, the superior extremity of the body, mammillated and articulated with the summit of the basilar process ; on each side, two notches which circumscribe below the occipito-si^heno-temporal hiatus (foramina lacera basis cranii). The internal notch is the narrowest, and from its afibrding a passage for the internal carotid artery, is called the carotid notch ; it is continued on the external face of the bone by a smooth excavation to which Eigot has given the name of carotid fossa. The external is also j)rolonged on the exterior surface cf the sj)henoid by a short and wide fissure ; it lodges the inferior maxillary nerve. Outside this is another very narrow notch, intended for the passage of the middle meningeal artery. The fibro-cartilaginous sub- stance that partly fills the occii>ito-spheno-temporal hiatus, transforms these notches into foramina, the first of which is named the carotid canal, the second, i\iG foramen ovale, and the third, the foramen spinosum. The inferior border, also concave, is likewise divided into three portions, a middle and two lateral. The first is thick, and formed by the inferior extremity of the body ; it is excavated by two large cavities belonging to the sphenoidal sinus. These cavities are separated from one another by a vertical osseous plate, often perforated, which, at an early period, is fused with the perpendicular THE HEAD. 41 lamina of the etlimoicl bone. The very thin lateral portions form part of the notched near their union with the circuraff;rcuce of the wings ; they are niidclle piece to assist in the formation of the orbital foramen. The ta-o htcral borders are thin aiul convex in their an- terior half, as is also the contour of the wings, which are mortised in the frontal bone. For the remainder of tlieir extent they are thick, denticulated, and bevelled at the expense of the external plate, to articulate with the sq[uamous portion of the temporal bone. Structure. — This bone is compact on its sides, and spongy in its middle part ; inferiorly, it is excavated by the splie- noidal sinuses. Development. — It is developed from two principal nuclei of ossification ; a superior forms the subsphenoidal pro- cess and the canal of the same name, the vidian fissure, pituitary fossa, fissures of the internal face, and the most pos- terior of the great supersphenoidal canals ; the other, the inferior, forms that portion of the body hollowed by the sinuses, the lateral ala3,^ and the optic fossa and canals. In meeting each other, these centres form the vidian canal and the two anterior supersphenoidal canals. They are not consolidated with each other until a very late pei'iod ; for which reason they are sometimes de- scribed as two distinct bones. M. Tabourin has even proposed to attach the description of the inferior sjjhenoid to that of the ethmoid, because it is a, Sphenoid bone, united with this bone a long time before it is joined to the superior portion. I'iir. 20. 6. Temporal Bone, temporal hones inclose POSTERIOR BONES OF THE HEAD OF A FCETUS (horse) AT BIRTH; DISARTICU- LATED AND VIEWED IN FRONT, 1, Maxillary notch ; 2, Carotid notch ; 3, Groove for the passage of the maxillary nerve; 4, Cavernous sinus; 5, Optic fossa; 6, Great wing; 6', Unossified portion of the great wing ; 7, Kotch for the formation of the orbital foramen. — B, Vomer. — C, Palate bone. — D, Zygoma. — E, Superior maxilla. — 8, In- ferior orifice of the maxillo-dental canal. — F, Premaxillai-y bone. The temporal hones inclose the cranial cavity laterally, and articulate with the occipital, parietal, frontal, sphenoidal, and the zygomatic bones ; also with the inferior maxilla and the hyoid bone. Each is divided into two pieces, whicli are never consolidated in the horse ; one forms the squamous portion of the temporal hone ; the other, the tuberous portion. They will be described separately. Squamous Portion. — This is flattened on both sides, oval, and slightly incurvated like a shell, a shape to which it owes its name. It offers for study an external and an infernal face, and a circumference. > These wings arc not analogous to those portions of the sphenoid bone in Man bear- ing the same name. They are the processes of Ingrassias enormously developed. 42 TEE BONES. Faces. — The external face is convex, and marked by some muscular imprints, vascular fissures, and openings which penetrate the parieto- temporal canal. It forms part of the temporal fossa, and gives origin near its middle to the zygomatic process, a long eminence which at first runs outwards, and soon curves forwards and downwards to terminate in a thin summit. The base of this eminence forms, in front, a concave surface belonging to the temporal fossa; behind, it offers the articular surface which corresponds with the maxillary bone. The latter is composed of: 1, A condyle transversely elongated, convex above and below, and slightly concave from side to side ; 2, A glenoid cavity, limited below by the condyle, above by a mammiform eminence, the super condyloid, '^ against which rests the maxillary condyle when tliis bone is drawn backwards; it is immediately above this eminence that the inferior orifice of the parieto-temporal canal opens. The ea-fernaZ /ace of the zygomatic process is smooth and convex; the internal, concave, is also smooth, and bordered outwards by the temporal fossa. Its anterior border is sharp and convex ; the posterior, very short, is thick and roughened. Its summit is flattened from before to behind, and marked by notches on its two faces; it somewhat resembles a wedge, fixed as it is between tlie orbital process of the frontal bone and the zygoma ; it comes in contact with the maxillary bone, and by a small portion of its anterior face, which is deprived of notches, it concurs in circumscribing the orbital cavity. In the domesticated animals, as in Man, the zygomatic process appears to arise from the surface of the bone by two roots : one, the inferior or transverse, is represented by the condyle ; the other, the superior, forms a sharp crest which is continuous with the anterior border of the process, and above, joins the lateral crest of the occipital protuberance. The internal or cerebral face of the squamous portion is divided into two parts by an almost vertical channel which terminates above the super- condyloid eminence, and which, meeting a similar furrow on the parietal bone, forms the parieto-temporal canal. The superior portion is but of small extent, and of a triangular form ; it articulates by a simple harmonia suture with the external face of the petrous portion. The inferior part, the widest, presents in its middle some cerebral impressions. For the re- mainder of its extent or circumference, it is cut into a wide, dentated, and lamellar bevel, which brings it in contact with the surrounding bones. Circumference. — This may be divided into two borders : one, anterior, is convex and united with the parietal and frontal bones ; the other, posterior, articulates with the sphenoid in its inferior moiety, and is provided, above the level of the supra-condyloid eminence, with a deep notch which receives the external auditory canal. Superiorly, the two borders unite at the summit in a thin point which rests on the occipital bone. Structure.— The squamous portion of the temporal bone is formed of two very thin compact plates which have but little spongy tissue between them ; the latter, however, is very abundant in the body of the zygomatic process. Development. — It is developed from a single nucleus of ossification. Tuberous Pouiion. — This is one of the most interesting parts of the skeleton for study, in consequence of its containing two systems of cavities which inclose the essential organs of hearing. One of these systems is named the cavity of the tympanum or middle ear ; the other forms the internal ear. These cavities mil be studied when we come to speak of the auditory ' In Man Ihis is rei:)resentecl by the inferior or vertical ramus of the upper root of tho zygomatic process. THE HEAD. 43 apparatus. In the meantime, only the exterior surface and the structure and development of this portion of the temporal hone will be noticed. It is wedged between the antero-lateral border of the occipital bone, the lateral border of the ])arietal, and the superior part of the internal face of the temporal shell. It represents a quadrangular pyramid whose base is turned downwards and a little backwards. It will be studied successively in its four faces, a summit, and base. Faces. — The anterior face is united by harmonia suture to the parietal bone. The posteriir face articulates in the same manner A^'ith the occipital bone. The external face lies against the squamous portion of the bone. The internal face, slightly concave and marked by very superficial digital impressions, furms a part of the lateral wall of the cerebellar cavity. It presents the canal or internal auditory hiatus (meatus auditorius internus), a small fossa, the bottom of which is pierced by several foramina for the transmission of nerves ; the largest of these is the internal orifice of the aquceductts Fallopii, a flexuous canal which passes through the bone and opens at the external surface of its base ; the other foramina penetrate tlie cavities of the internal ear. These faces are separated from each other by so many borders or plane angles, two of which more particularly merit attention ; one of these isolates the external from the posterior face, and the other separates the anterior from the internal face. The frst is thick and rugged, and constitutes the mastoid crest ; it is continuous above with the lateral ridge of the occipital bone, after being united to the superior root of the zygomatic jirocess, and terminates, near the base of the bone, by a tuberosity for muscular insertion, to which has been given the name of mastoid process. This border is traversed by a slit, the mastoid fissure,^ which passes under the squamous portion and enters the jiarieto-temporal canal. The second is thin, and, with the superior part of the lateral border of the parietal bone, forms the crest which establishes the line of demarcation between the cerebral and cerebellar cavities of the cranium ; it gives attachment to the tentorium cerebelli. Summit. — This is slightly denticulated, and articulates with the occipital bone. Base. — This is very irregular, and offers : outwardly, the external auditory canal which penetrates the middle ear, and the external orifice of which has been named in veterinary anatomy the external auditory hiatus ; inwardly, a sharp crest which circumscribes the external contour of the lacerated foramen ; above, and under the mastoid process, the stylo-mastoid ov pre-mastoid foramen, the external orifice of the aqueduct of Fallopius ; below, the subuliform (or styloid) process for the attachment of the stylo-staphyleus (tensor palati) muscle and the Eustachian tube : this is a long, thin, and pointed process presenting, at its base and within, a canal which enters the cavity of the tympanum, and which is incompletely partitioned by a small bony plate into two parallel portions : in the centre, the liyoid prolongation or vaginal process^^ a little cylindrical eminence surrounded by a bony sheath, and the nKistoid protuberance or process, a slightly salient, smooth, and round eminence hollowed internally by numerous cells, which form part of the middle ear. The several small and very remarkable canals which pass through the tuberous portion of the temporal bone, will be noticed when the nervous and arterial branches they ledge are described. * This is the analogue of the mastoid canal in Man. - This process is prokmged by a cartilage that unites it to the sfijloid hone. 44 THE BONES. Development. — The tuberous portion of the temporal bone is fleveloped from two principal centres of ossification which are consolidated at birth, and which are often described as two distinct portions : the one as the petrous or stony portion, the other as the mastoid p>oriion. The faces, borders, summit and inner side of the base of the bone are formed by the ^;ure — a trace TORE- ARM AND FOOT OF of the primitive separation "of the bone in two pieces. This THE DOG ; ANTERIOR fissuro presents, interiorly, the anterior orifice of a canal that '^^G^- completily traverses the bone. The posterior face is also 1, First digit; 2, Second marked by a very slight longituflinal groove. Tlie superior digit ; 3, Third digit ; extremity exhibits, externally and posteriorly, a single diar- 4, Fourth digit ; 5, throdial facet for the articulation of the rudimentary meta- Thumb; G, 7, 8, 9, First carpal. The inferior extremity is diviiled by a dei-p notch second, third, and fourth into two articular surfaces, which together resemble the single bones of the lower row surface in the Horse ; each corresponds to one of the digits ; of carpal bones ; 10,11, the external is always smaller than the internal. In the First and second bones foetus, the two long bones that form the great metacarpal of the upper row; 12, are simply laid together, and their medullary canals are sepa- Supercarpal bone •, 13, rated from each other by the double partition which results Body of the ulna; 14, from this apposition ; after their coalescence, however, the par- Apex of the olecranon ; titions are completely destroyed by resorption, and in a short 15, Beak of the olecra- time there is oidy a single medullary canal for the entire bone, non; 16, Body of the The rudimentary metacarpal is only a small osseous stylet, radius. articulating, by a diarthrodial facet, behind and to the outside of the superior extremity of the principal metacarpal ; it is sometimes absent in the Sheep and Goat, THJi: ANTERIOR LULBS. 89 8. Digital Region. — In the domesticated animals the number of complete digits is as follows : — Carnivora 5 Pig 4 Euminants 2 The five digits of the Dog and Cat are exactly analogous to those of Man. Thus, the external corresponds to the auricularis, the second to the annularis, the third to the ruedius. the fourth to the index, and the internal to the thumb. — The latter, very small, has only two plialanges and does not cotne into contact witli the ground. Eath of the first fuur is composeJ: 1, Of a first phulanx, to wliich are annexed two sesamoids; 2, A second fhalanx, which yet represents a veritable long bone; 3. A conical phalan- gette, pointed, bent downwards, and hollowed at its base by a circular groove, in which is lodged the matrix of the claw. The small sesamoid (,or navicular bone) is absent, but is replaced by a prominence of the ungual phahmx. The auricularis and index are alike, and not so long as the annularis and mediiis, which are the same in length. The Pig has four complete digits articulating from the metacarpals; the thumb is absent. The index and auricularis, or fourth and fifth digits, are short, and do not usually rest on the gruund. Huminaiits certainly possess four digits, but only two are perfect— the medius and annularis — and these articulate with the inferior e.ttremity of the principal metacarpal. The two others— the index and auricularis - are in a rudimentary condition, and are represented by two small bones situated above and J^hind the naetacarpo-phalangeal articulation. In the Ox, Sheep, and Goat, each of the perfect digits comprises three phalanges and three sesamoids. The ^r*i^/(«?ana; fairly represents the moiety p. r, of the phalanx in the Horse. It has no posterior °' imprints, but shows them on its inner surface for the attachment of several ligaments. This internal face is plane, and the external convex ; these characters are repeated in the other two W^^^^>^ ^-K H^ ■.„...-...,„.„„ HiB phalanges. It is also remarked in all the pha- ^^^^^^»tP^ >-~-^ '^'i -"■/jip langeal bones, that the external articular facet ^peaa^k^-ist-. .. of the extremities is always larger than the ^* internal. Of the two sesamoids, the external is larger and less elongated than the internal. ^Ifiiit^llS- first particulate witii each other, and with the '^wE^#' ■ They halanx by small diarthrodial facets. The second phalayix is hollowed internally by a small raedullary cavity. y^t'-W/'- ^ ' The ungual phalanx, as a whole, resembles ^V : 'ft, '''.//•, '■■ ^-'•* one of the lateral moitties of the os pedis of Vv '•' ■ ' ■ '■. ')/■/ solipeds. This phalanx has no complementary ■■* '' ' ' '" '/' fibro-cartilage, basilar process, or retrossal emi- neme, nor yet a cavity of insertion on the sides of the pyramidal eminence. The semilunar ^rl* crest is replaced by an obtuse, thick, and rugged relief, which occupies quite the posterior limit %^ of the inferior face of the bone. Three large 7 canals penetrate the third phalanx, two to the htiman scapula ; external aspect. base of the pyramidal eminence, and one towards ^ Supraspinous fossa; 2, Infraspinous the origm of the preplantar fissure. They form, ' ^^ J ^ ^ .^^. ^^^.^ ^ ^ m the interior of the bone, a vast sinus, gmng .eapular notch ; 5, Anterior or axillary rise to several vascular canals which open on the ^J^^^ g ^^^^ ^^ the scapular and snrface. There is only one foramen at the base of j^^^;^' ^^^.^^. ^ ^^^^^-^^ ^^ 1, g the pyramidal eminence in the«man€ri?M»Hnanital, parietal, frontal, ethmoid, sj)henoiii, and two temporals. The.se bones are net isolated from each other, excepting during early life in the shell, and the ossifying process which unites them is so rapid, that the cranium, shortly after hatching, is alrea iy a single piece. No detailed description of the separate bones will be given here, but only a few brief observations which may be of some utility. Thus, the occipital b(me shows for articulation with the spine only a single condyle, situated under the occipital foramen, and excavateil by a slight groove. In palmipedes, this bone is pierced, behind the crests which give attachment to the extensor muscles, by two foramina which pt-mtrate the cranium, and represent permanent fontanella. The parietal bone is feebly developed, and formed from only two primary nuclei. The frontal is the largest bone of the cranium ; its orbital process is supported by a particular piece which is generally considered as belonging to tlie large wing of the sphenoid. The perjiendicular lamina of the ethmoid is considerable, and forms between the two orbits a thin vertical septum ( fig. 73, 8). Its posterior border is notehtd opposite to the optic foramen, and thus constitutes an opening which com- municates between the two orbital cavities (fig. 73, 9). It is also channeled, near its upper border, by a fissure which terminates by two openings at its extremities, one entering the cranium, the other the nasal cavities. This fissure and these foramina permit the passage of the ethmoidal nerve, which in this wiiy traverses tlie orbit before arriving at its destination. The ethmoidal cells are more membranous than bony ; their base is attached to a very delicate transverse pLite, which is often mendoranous and not cribbled, a:id forms part of the anterior orbital wall. These cells rejilae, at the same time, the lateral masses of the ethmoid and turbinated bones of mammalia. The sphenoid appears to be formed of a single piece, and shows on its sides two diarlhrodial facets corresponding to the pterygoids. It is pierced by one foramen for the passage of the optic nerves ; but this foramen opens on the outer and opposite side of the posterior notch of the interorbital septum, and thus allows each of the nerves passing through it to reach the eye for which it was intended. It is worthy of remark, thut an analogous disposition is also noticed in the rabbit.' The temporal bones present at their base an articular surface corresponding to the square bone. In the fowl species, the zj'gomatic process forms a small flattened tongue, directed forwards, sometimes free, and at other times united by its superior border to the summit of the orbital process. These two eminences are exceedingly short in pigeons. In j;«i»itpef7es they are consolidated and conlbunded so intimately, that it becomes impossible to distingui.-h them from one another. From this union results a long and strong process, which inclines forward and meets a particular prolongation of the OS unguis, forming with it areal bony arch. This arch limits, below and outwardly, the orbital cavity. Bones of the face. — The supermaxilla c mprises ; a premaxilla, two nasal, two lachrymal, two palate, two pterygoid, two zygomatic bones, and a vomer. The inferior jaw has for its base a maxillary bone, which articulates with the cranium by means of two supplementary pieces named the square bones. The premaxiUary hone is found, before hatching is completed, of two lateral pieces, which represent the two small premaxillaries of mammals. This bone is very considerable, and of itself forms the base of the upper beak, whose form it determines , it is pointed and conical in the gallinacea, and wide and flattened above and below in palmipedes. In front it circumscribes the external openings of the nose, and is prolonged superiorly into two lengthy processes which dovetail between the nasal bones. Two inferior processes belonging idso to this bone concur in the formation of the palatine roof. The supermaxillaries, analogues of the supermaxillaries of mammals, are two rudimenlary bones situated on the sides and at the base of the beak. They form a part of the palatine roof and the walls of the nasal cavities. The nasal hones circumscribe above, inwardly, and even outwardly, the external orifices of these civities. The palate hones encircle, as in mammals, the guttural openings of the nose, and constitute in great part the roof of the palate ; their p(>sterior extremity lies against the pterygoids ; the anterior joins the supermaxillaries and the inferior process of the premaxillary bone. The pterygoids extend obliquely from the sphenoid to the square bones, and are united to the sphenoid by diarthrodial articulation, ' This analogy is really striking, and might, in our opinion, serve as a basis for a new determination of the interorbital septum. We are tempted, indeed, to consider this bony lamina as the inferior sphenoid and the middle portion of the ethmoid of birds. This manner of viewing it tends to confirm the ideas of M. Tabourin on the inferior sphenoid and the ethmoid of mammals. 116 THE BONES. The zygomatic hones have the form of two very thin stylets, and are united to the square bone by their posterior, and consolidated with the snpermaxillary by their anterior extremity. The vomer separates the guttural openings of the nose from one another. Tlie bones of the upper jaw are not fused with eacii other so rapidly as the b(jne3 of the cranium. The ascending processes of the premaxillary and nasal bones even remain for a long time united to the frontal bone by a simple synarthrodia! articulation. This arrangement allows the upper beak to execute a certain elevating movement, of which we will speak when describing the articulations. The inferior maxillary hone is originally formed of a great number of distinct seg- ments which are soon united into a solid piece. The square, petrous, or hone of the tympanum ought to be considered as detached from tlie temporal. It is prismatic in shape, and provided on its upper surface with a diarthrodial facet which unites it to the temporal, and on its lower face with another facet articulating with the branch of the maxilla. Outwards it joins the zygomatic bone, and inwards with the pterygoid. Behind, it gives attachment to the membrane of the tympanum; and in front it presents a small eminence of insertion which Meckel considered a second zygomatic process. Thorax. — Sternum (fig. 73, h). — The sternum of birds, serving as a basis of support to the muscles moving the wings, should offer, and does in fact show, a remarkable degree of strength, because of the extraordinary volume of these muscles. And these being more powerfid and energetic as the bird exhibits a greater degree of aptitude for flight, it results that the structure of the sternum is solid in proportion as the bird is strong on the wing. For this reason we may infallibly pronounce as to the extent and power of a bird's flight by an inspection of the sternum of individuals of its species. In this respect, however, we only announce what is well known to be a particular application of the rules established by the great law of concordance between the anatomical disposition of organs and their physiological finality. Studied in Palmipedes, which will serve as a type for description, the sternum presents itself in the form of a large rectangular cuirass, elongate! from before to behind, of itself constituting the inferior wall of the thoracic cavity, and also largely protecting the abdominal cavity. Its superior face is concave, wliile the inferior is convex, and entirely occupied by tlie insertion of the pectoral muscles. It presents, on the median line, a tliin and very salient ridge, named the hrisket (or keel), which in a remarkable manner multiplies the points of attachment of these muscles. The anterior border offers in its middle a small eminence of insertion, the episternal. Laterally, two articular grooves are seen which correspond to the coracoids. The posterior border is cut by two notches which are often converted into foramina. On the lateral borders are observed small double articular facets answering to the inferior riba. The angles which separate these two borders from the anterior are both prolonged into a little eminence, named by some authors the costal process. In the Fowl, the sternum is not so strong as in the Goose or Duck. On each side of the biisket it shows two wide notches, which greatly reduce its substance. These notches, closed in the fresh state by membranes, are distinguished as external and internal. The latter, of greater size than tlie former, extends nearly to the extremity of the bone. From this division of the lateral plates of the sternum result two long and slender processes directed backwards. The external terminates by becoming widened, and forming a kind of bony plate, whicli covers the last inferior ribs. The sternum of Pigeons is distinguished by the enormous development of the brisket. The two notches of the fowl are also" met with in these birds, but the internal is nearly always converted into a narrow foramen. This comparative study of the sternum in the chief domesticated birds leads us to appreciate the correctness of the principles just enunciated, with regard to the form and extent this bone may exhibit. The Gallinaceous Birds, properly so called, which fly little and badly, have the sternum singularly weakened by the deep notches cut in its lateral parts. With Palmipedes, the sternum is wide and but slightly notched, so that the goose and duck, which waddle along so awkwardly in our poultry yards, are capable of sustaining long and rapid flight, like that of the wild individuals of the same species. With regard to Pigeons, which are well known to be swift and powerful flyers, may this advantage not be due to the extraordinary development of the keel which constitutes th€ brisket ? Bibs. — In the Fowl and Pigeon there are seven pairs of ribs ; and in the Buck nine pairs. Articulated superiorly with the dorsal vertebrpe, as in mammals, these bones are provided near their middle with a flat eminence which commences at the posterior border, and is directed backwards and upwards to rest liy its free extremity on the external face of the next rib. These eminences (Fig. 73, 20) form an epiphysis at an THE BONES IN BIBDS. 117 early period, and are usually absent in the first and last ribs. They concur in an efficacious manner to increase the solidity of the thorax. The costal cartilages in mammalia are in birds often transformed into veritable inferior ribs, joined to the superior ribs by a diartbrodial articulation (Fig. 73, i). These pieces are long and strong, and all ti^rminate at their lower extremity by a double facet -which articulates with the lateral border of the sternum; they are nearly always absent in the two first ribs. It is not rare to see the last united to the one before it, instead of passing directly to the sternum; in which case it comports itself like the asternal ribs of the mammalia. Anterior Members. — Shoulder-hone. — The shoulder comprises ; a scapula , a par- ticular bone named the coracoid by Cuvier ; and a clavicle, which forms, in coalescing with that of the opposite side, a single bone called the fork (fnrculum), or os furculare. The scapula is narrow, elongated, and falciform, and shows no trace of a spine. Its anterior extremity only forms a portion of the glenoid cavity, and is united by means of a fibro-cartilage with the fork of the coracoid bone. The latter is so named because it represents the coracoid process of mammals, and is a long prismatic bone, directed obliquely from above downwards, and before to behind. Its superior extremity is often fused with the scapula, and united at an acute angle with that bone to form a portion of the articular cavity which receives the head of the humerus. Its inferior extremity is flattened from before to behind, and responds by a diarthrodial articulation to the anterior border of the sternum. The coracoid is long in birds which fly slowly ; it is, on the contrary, short, thick, and therefore very solid in quick flyers. The fork is a single bone, shaped like a V or U, situated at the base of the two wings, in front of the trunk, and in an. oblique direction downwards and backwards. The two branches which form it represent the clavicles; Ihey meet and are united at their inferior extremities, where they describe a curvilinear angle more or less open, attached to the brisket by means of a membranous ligament. Their superior extremity rests within, and opposite to the glenoid cavity, against the scapula and coracoid, forming with these bones a remarkable foramen, through which passes the tendon of the elevator muscle of the wing (Fig. 73, A, 4, B, 6). The fork plays the part of an elastic spring, whose office it is to prevent the wings coming towards each other during contraction of the depressor muscles. The conformation of this bone is, therefore, like the sternum, related to the extent and power of flight ; and for this reason it is that, in swift flyers, the two blanches of the fuiculum are thick, solid, widely separated, and curved like a U ; while in those which fly heavily and with difficulty, these branches are thin and weak, and joined at an acute angle. The latter formation greatly diminishes its strength, and lessens, in a singular manner, the reactionary power of the bony arch it represents. Bone of the arm. — The humerus offers an articular oval-shaped head, and an air- opening placed beneath this eminence. It is long in Palmipedes, ordinarily so in the GaUinacx proper, and very short in Pigeons. Bones of the fore-arm. — The radius is much less volximinous than the ulna. The latter has an extremely short olecranon ; and the two bones are separated from one another in their middle part to meet again at tlieir extremities, where they are united by ligamentous bands in such a way as to render the movements of pronation and supination impossible. This mode of fastening, which nevertheless does not prevent the two bones from gliding slightly on each other in the direction of their length, has been wisely adopted by nature in order that the wing might strike the air, like an oar, by its inferior face ; otherwise, the resistance of the aerial medium would make these two bones pivot, and cause the wing to present itself to the air in a wrong direction. Bones of the carpus. — These are only two, and are distinguished by the names of radius and ulna, in consequence of their corresponding more particularly to these bones in other animals. Bones of the metacarpus. — These also number only two, and are separated at their middle portion, to be consolidated at their extremities. Bones of the digital region. — The wing of a bird is composed of three digits. One of them, which resembles the thumb and forms the basis of the false wing, is composed of a single styloid-shaped phalanx, articulated at the base of a small particular process belonging to the superior extremity of tlie largest metacarpal bone. The largest digit comprises two phalanges which succeed the last bone. The third digit is represented by a small rudimentary phalanx, which corresponds to the inferior extremity of the small metacarpal bone, and lies beside the first phalanx of the large digit in the closest manner. It is well to remark that the hand and the fore-arm are longer in proportion to the quality of flight ; those two regions of the wing, for example, are very short in Gallinaceous Birds. PosTERiOB Members. — Coxa or os iliac. — This is a voluminous and very solid piece, 11 118 THE BONES. particularly in vralking birds, and composed, as in the mammalia, of an ilium, iscliium, and pubis. The ilium is consolidated with the last dorsal, the lumbar, and thu sacral vertebrae; it is excavated on its internal face. The ischium partly incloses the side of the pelvic cavity ; between its internal border and the external border of the ilium is an orifice which replaces the great i&chiatic notch. Its Inferior border is united to the pubis. The latter is thin and elongated, and follows tlie direction of the inferior border of the ischium, with it circumscribing an ocal openinq more or less spacious. Its inferior extremity extends beyond tiie ischium to curve inwards towards that of the opposite .side, but without uniting witii it. We do not, therefore, find the pelvic symphysis in birds, and the pelvis is widely open below, a circumstance which iavours the passage of the egg through the cavity and out of tlie cloaca. The cotyloid cavity is perforated by an opening at the bottom which traverses tlie bone. Thigh hone. — The femur is articulated inferiorly with the patella, tibia, and fibula. In all walking birds, like the galiinacae, it is long and strong, as well as the rays "below it. Leg hones. — The patella is wide auii thin. The tibia terminates, below, by two con- dyles separated by a groove which becomes articular behind. The fibula articulates by its head with the external condyle of the femur, and is consolidated with the tibia ; it never descends to the inferior extremity of that bone. Tarsal hones. — The tarsus appears to be altogether absent in birds. Nevertheless we may venture to consider, as a vestige of the bones of this region, a small bony nucleus buried in a fibrocartilaginous mass which glides on the posterior pulley of the tibia. This nucleus represents the calcaneus of mammals. Metatarsal bone.— A. single metatarsal bone is found in birds, articulating superiorly with the inferior extremity of the tibia, and terminating inferiorly by three pulleys which support the three principal digits. This bone shows in the Fowl, near its inferior third, a conical process turned backwards, which serves as a base for the spur. Behind its superior extremity, it exhibits another which may be considered as a consolidated metatarsal bone. Bones of the digital region. — All the domesticated birds have four digits on the inferior members : three principal, directed forwards, and one rudimentary, carried backwards. The first, designated as internal, median, and external, articulate with the inferior pulleys of the metatarsal bones. The internal is formed by three phalanges, the second has four, and the tlurd five. These phalan2;es are formed something like those of the cariiivora : the last is pointed, conical, and enveloped in a horny slieath. The fourth digit, or thumb, is composed of three pieces : one of these, the fir:^t, is generally con- sidered as a rudimentary metatarsal bone. It is attached by fibro-cartilaginous tissue to the inner and posterior aspect of the inferior extremity of the principal metatarsal bone. CHAPTER IV. THEORY OF THE VERTEBRAL CONSTITUTION OF THE SKELETON. In the series of vertebrated animals tlie bony pieces of the trunk bearing the name of vertebras are those which offer the highest degree of fixity, and io which the existence or the arrangement of the others appears to be subor- -dinate. This feature in organisation, recognised by E. Geoffroy Saint- Hilaire and Professor Owen, has caused these men of science to assert that the type of construction of vertebrated animals is the vertebra. After E. Geoffroy Saint-Hilaire and Professor Owen, several German, English, and French anatomists have studied the vertebral composition of the skeleton ; and among the works published in France on this subject must be specially noticed those of M. Lavocat.^ In principle, all the writers have arrived at the same conclusions, and only difter in some few details. It is certain that the base of the vertebral column is formed by a series of bony segments. Each of these segments is called an osteodesm, and each osteodesm represents the body or centrum of a vertebra. (' The distinguished anatomist and Director of the Imperial Veterinary School of ToulousB.J THE VERTEBRAL CONSTITUTION OF THE SKELETON. 119 In examining the dorsal region, it is evident that to the body or centrum of a vertebra are added two complete osseous arches, a superior and an inferior. The superior arch is formed by the vertebral lamina ; the inferior by the ribs, the cartilages, and a portion of the sternum. The tu'st is desig- nated the neural arch, because it furnishes a protecting sheath for the nervous centres ; and the second, which more particularly protects the vascular system, is called the hcemal arch (see Fig. 10). The haemal arch may have prolongations or appendices more or less developed, and comparable to the apophysary jirolongations of the ribs in birds and some fishes. Such is the general composition of a typical vertebra ; but there are also to be distinguished in the neural and htemal arches the following parts : — NEVRAL ARCH. ' H^MAL ARCH. 1. Xeiiral parapophysis = the posterior 1. Hremal parapoplnsis = the tuberosity costal cupola. of the rib. 2. Neural metapophysis = the anterior 2. Ha?mal metapophysis = the head of the costal cupola. rib. 3. Neural diapophysis = the summit of the [ 3. Hsemal diapopliysis = the rib proper. transver.-e process. 4. Heumapophysis = the costal cartilage. 4. Neurapophysis = the vertebral lamina. ' 5. Hsemal spine = the corresponding 5. Neural spine = the summit of tiiC sternal portion. spinous process. ; The vertebras sometimes depart more or less from the model just described. They may vary not only from one species to another, but also in the same animal, and even in the same region. Thus the neural arch may be absent, as has been observed in certain coccygeal vertebrae ; or the haemal arch is incomplete or null, as in the cervical or lumbar vertebrte ; or, lastly, the arches are often unequal ; though this inequality is of no import- ance, since their size is in relation to the volume of the pai'ts they should protect. Notwitstanding these differences and variations, or the transformations experienced by certain parts, there is not a bone in the skeleton which can- not be included in the vertebral type The vertebra being admitted as the type of construction of the skeleton, it is easy to find it in all the regions of the bony framework. In the thoraco-abdominal region, the centrum, neural arch, and hfemal arch are readily perceived ; in the lumbar vertebrae, the enormously developed trans- verse process indicates the existence of an infravertebral arch. In the sacral region, the bony girdle of the pelvis represents the hfemal arch. The posterior limbs, articulating with the bones of the pelvis, belong to the haemal arch, and should be considered as appendices of this arch, analogous to the costal ajipendices of birds. The cervical region may be compared to the sacral region , as in it the inferior haemal arch is represented by the osseous ring supporting the anterior limbs — the scapnlo-clavicular cincture. The limbs themselves are appendices of the cervical hsemal arch. Difliculties begin to appear when the extremities of the trunk — the head and coccyx — come to be examined. Nevertheless, the composition of the coccyx is revealed when the caudal vertebrae of certain fishes, especially those of the pleuronectidae, in which the neural and haemal arches are com plete, are examined. But the vertebral constitution of the head remained for a long time an insoluble question, or was solved in a contradictory 120 TEE BONES. manner by the naturalists who attempted it. Some admitted a single cei^lialic vertebra; others admitted three or four; while others again arrived at six or seven. These difficulties and contradictory results may be understood, when it is . a P o PL, tH < -° borne in mind what profound modifications the vertebrge must have ex- perienced to constitute the bones of the head ♦ At present the problem appears solved. The head is composed of four vertebras, in which are found the various parts enumerated in the description^ of the typical vertebra. TEE VERTEBRAL CONSTITUTION OF THE SKELETON. 121 In the four classes of vertebrata, the head is constantly formed of four vertebrae, which ai'e determined as follows :" * VERTEBRJi. CENTRUM. i NEURAL ARCH. H.EMAL ARCH. Oecipito-hyoide;il. Basilar process ; Occipital (3 pieces). ! Hyoideal appa- 1 of the Uccipi- Mastoid walls of the | ratus (5 pieces). I tal. Tympanum. i Parieto-maxillary. Body of the pos- i Wing and pterygoid teiior Sphe- i process of the pos noid. i terior Sphfenoid. Squamous portion and zygomatic process of 1 the Temporal. Parietal. Inferior IM axilla 5 pieces). Fronto-mandibular. Body of the Wing and pterygoid Jugal. Anterior Sphe- process of the anterior Lachrymal, noid. Sphenoid. Palatine. ] Posterior Frontal and , Supenuaxillary. its orbital process. i Premaxillarv. : Frontal. { 1 Naso-turbiuaL Vomer, Ethmoid. 1 Turbinated Nasal. 1 SubetLimoidal. The number of cephalic vertebrte is invariable, as each is destined to lodge the organs of one of the four senses. The occipito-hyoideal lodges the principal organs of hearing ; the parieto-maxillary osteodesm protects the sense of taste ; finally, the organs of vision are sustained by the fronto-man- dibular vertebra, while the naso-turbinal contains the sense of smell. It was therefore with reason that GeofFroy Saiut-Hilaire and Professor Owen proclaimed that the type of construction of the vertebrated animals is the vertebra- SECOND SECTIOK The Articulations. CHAPTER I. THE ARTICULATIONS IN GENERAL. The different pieces constituting the solid framework of the animal body are, as has been said, united in such a manner that they can move one upon the other From this union results the articulations or articular joints, whose construction will now be referred to in a general manner, before commencing a particular description of each To form articulations, the bones correspond to each other by certain points of their periphery, which are named articular surfaces. Every articu- ' Lavocat^ ' Nouvelles e'tudes sur le systeme verte'bral,' 1S60. 122 THE ABTICULATIONS. lation IS, therefore, essentially constituted by two opposite osseous surfaces, which are moulded to each other. These are either contiguous, independent, and very movable — continuous with each other by means of a cartilaginous substance which condemns them, if not to total immobility, at least to very Yis- PLANS OP THE DIFFERENT GLASSES OF ARTICULATIONS. A, Suture. — 1, Periosteum; 2, Sutural ligament. — B, Amphiarthrosis ; a. First degree. — 1, Periosteum ; 2, Articular cartilage ; 3, Interarticular ligament. — 6, Second degree ; 4, Single cavity in the interarticular ligament. — c, Tliird degree ; 5, Double cavity in the interarticular ligament. — C, Diarthrosis ; 6, Simple diartlirosis. — 1, Periosteum; 2, Articular cartilage; 3, Epithelial layer of the synovial membrane — dotted line; 4. P^ibrous capsule; 5, Cul-de-sac of the syno- vial membrane ; 6, Fibrous layer of the synovial membrane. — c, Double diarthrosis ; 7, Interarticular meniscus ; 8, 9, Cavities of the two synovial membranes. limited movements : or united by a fibro-cartilage whose elasticity permits a certain degree of displacement between the bnnes wliich are in contact. In the first case, the articulations are classed as diarihroses, or movable articulations. In the second, they are designated synarthroses, sutures, or immovable articulations. THE ARTICULATIONS IN GENERAL. 123 In the third, they are amphiarthroses, or mixed articulations ; so termed because they participate in the movements of the other two classes ; synar- throses, by the continuity established between the articular surfaces , and diarthroses, by the extensive motion they j^ermit. The general characters that distinguish each of these three great classes of articulations will be successively studied. (The study of the articulations, or rather of the ligaments, is termed syndesmology — from avv, together, and Secr/Aos, bond ; or arthrology — from apdpov, a joint, and Xdyos, a description.) GENERAL CHARACTERS OF DIARTHROSES. We ought to consider in the diarthrodial articulations : 1, The con tiguous bony surfaces which form them ; 2, The cartilaginous layer {cartilages of incrustation) which cover these ; 3, The fibro-cartilaginous tissue (articular Jibro-cariilages) which complete them, when they are not shaped so as to be reciprocally adapted to each other ; 4, The ligaments which maintain tbem in contact ; 5, The serous membranes (synovial capsules) that cover the internal face of the latter, and which secrete the synovia, a kind of animal oil that facilitates the gliding of the articular surfaces; 6, The movements of which these articulations may be the seat ; 7, Their methodical classifica- tion ; 8, Their nomenclature. Articular Surfaces. — These surfaces have the common character of being destitute of asperities, so that they can glide with the greatest facility on each other. They are designated, according to their form, by the names of facets, heads, condyles, cotyles, glenes, p>^dleys, etc. There is no need to revert to their general description, as they have already been sufficiently studied in the osteology; so we will confine ourselves to repeating that they are found at the extremities of long bones, on the faces of short bones, and on the angles of ^vide bones. We may mention also that they are often excavated by one or several hollows named synovial fossce, a sort of natural reservoirs which receive the unctuous fluid secreted by the interarticular serous membranes Cartilages of Incrustation. — This designation is given to the layers of cartilaginous matter which, as it were, varnish the articular surfaces they adhere to by their inner face; their free surface is distinguished by a remarkable polish and brilliancy Thicker towards the centre than at the circumference when they cover bony eminences, these cartilages show an inverse disposition when they line cavities They are elastic, of a pearly whiteness, and resisting, though they are soft enough to be cut by a sharp instrimient ; in a word, they possess all the physical characteristics of the primary cartilage of bones They appear to be formed of parallel fibres placed perpendicular to the bony surfaces, and implanted ii^ these by one of their extremities : the opposite extremity corresponding to the free surface of the cartilage. Viewed by the microscope, they are found to consist of a fundamental substance excavated by small cavities The cartilage of incrustation therefore belongs to the group of true or hyaline cartilages. The fundamental matter is amorphous and homogeneous, and more or less transparent, according to its thicloiess. It is transformed into chondrine by boiling in water. The cavities are irregular, and more or less wide. They contain from one to five cells whose walls are very thin, and their contents slightly gran^ ular; in the centre of each cell is a nucleus with a nucleolus. These 124 TEE ARTICULATIONS. Fi2. 76. cavities are elongated and directed almost perpendicularly towards tlie articular surface in the deep layer , in the middle layer they are oblique, and are parallel to the surface of friction in the superficial layer. (Under a high magnifying power the fundamental substance, or matrix, loses its homogeneous and amorphous character, and appears to be granular or faintly striated. In the midst of this granular matrix, the lacun89 or cavities are observed to contain from one to six different-sized cells. It has been stated that a membrane lines these spaces. In addition to the granular matter observed in the cells, it is not rare to find fat globules. The nuclei of the cells vary from to ^^QQ of an inch in diameter. SECTION OF BRANCHIAL CARTILAGE OF TADPOLE. a, Group of four cells separating from each other ; 6, Pair of cells in apposition ; c, c, Nuclei of cartilage-cells ; d. Cavity con- taining three cells. These cells are im- bedded in the finely-granular matrix, or fundamental substance. 4000 The cells multiply endogenously.) Tlie cartilage cells are insoluble in boiling water ; consequently, so far as their chemical composition is con- cerned, they are distinct from the fundamental substance. The diarthrodial cartilages receive neither vessels nor nerves. The presence of cartilages of incrustation in the articulations is of the greatest importance. When they are worn, absorbed, or transformed into bone in consequence of certain articular maladies, the movements become painful and very difficult. With regard to the part they play in the economy, it may be said that" 1, They favour, by their smoothness, the gliding and displace- ment of the bones , 2, They attenuate, by their suppleness and elasticity, the violent shocks to which the articulations are exposed ; 3, They resist the wear and deformation of the articular surfaces. Complementary Fibro-cartilages. — There are several kinds of com- plementary fibro -cartilages : — Some (interosseous) represent circular cushions which bolster the margins of certain cavities, filling up the notches which might render them imperfect. They increase the depth of these cavities Fig. 77. FIBRO-CARTILAGE ; MAGNIFIED 155 TIMES. Showing interlacement of fibrous fasciculi, with scattered groups of cartilage-cells. and protect their borders from injury. Others (inter articular) are inter- posed between articulaz' surfaces when these do not exactly fit each other, as TEE ARTICULATIONS IN GENERAL 125 when two opposing extremities are convex. It may be remembered that the lateral tuberosities of each tibial surface present, for articulation with the condyles of the femur, two convex diarthrodial faces whose coaptation is rendered perfect by the interposition between each condyle and correspond- ing tibial surface of a crescent-shaped fibro-cartilage, which for this reason has been named a meniscus. In other joints these interarticular fibro- cartilages are shaped like discs or biconcave lenses. There then result double diarthroses : — example, the temporo-maxillary articulation. (Fibro- cartilage also covers bony surfaces over which tendons play, as on the trochlear surface of the humerus, postero-inferior face of the navicular bone, and elsewhere. In these situations it is named stratiform fibro-cartilage.^ These organs are formed, as their name indicates, by fibrous and car- tilaginous tissue ; their mode of association need not be referred to here, though it may be observed that the cartilage is more particularly found in all those points where there is most articular friction. They receive vessels, and sometimes nerves. Ligaments. — These are bands which unite contiguous diarthrodial surfaces. They are sometimes formed of white fibrous tissue, and some- times of yellow ; from whence their division into two great classes of white and yellow ligaments. a. The white ligaments are distinguished by the pearly whiteness of their tissue and want of elasticity. Those which are found on the outer Fiff 78 Fig 79. I^^ '' ., ^ . ^ '1 1^ t«. WHITE OR NON-ELASTIC FIBROUS TISSUE, YELLOW OR ELASTIC FIBROUS TISSUE, FROM THE LIGAMENTUM NUCH^. aspect of the articulations are termed peripheral, and those in their interior are designated interosseous or interarticular ligaments. The peripheral ligaments are generally composed of parallel fibres collected in fasciculi, or spread out as membranes. In the first they are called funicular, or ribbon-shaped ; in the second, they are termed mem- hraniform, or capsular. The funicular ligaments constitute short, round, or flattened bands, attached by their extremities to the two bones they unite ; they are lined on their inner aspect by the synovial capsule, and covered externally by tendons, aponeuroses, muscles, vessels, or nerves. The capsular ligaments are often complete — that is to say, they envelope the whole articulation like a sack. At other times they are incomplete, and 126 TEE ARTICULATIONS. then they are simple membranes, binding together the different funicular bands of a joint. The interosseous ligaments, less numerous than the preceding, are often formed of interlacing fibres ; they are always funicular, and fixed by their extremities into excavations in the centre of articular surfaces. h. The yellow ligaments arc all peripheral, funicular, or membranous, and enjoy a marked degree of elasticity, which permits them mechanically to bring back to their usual position the bony levers which have been momen- tarily displaced. These ligaments, which are powerful auxiliaries to the muscular forces, are destined to give equilibrium in a permanent manner to the weight of certain parts of the body which incessantly tend to fall to the ground. Synovial. Capsules. — These are very thin membranes of a serous nature, intended to secrete the synovia. They are composed of two layers : a deep, formed by fasciculi of the connective tissue ; the other, superficial, is of an epithelial character. The first sometimes adheres intimately to the inner face of the funicular or membranous ligaments of the articulation ; at other times it is loosely attached to them by an abundance of connective tissue. The second layer is constituted by a single row of flattened polygonal cells. It is generally admitted that the synovial membranes comport themselves like the other serous membranes, by forming sacs which are everywhere closed. According to this admission, a synovial membrane, after covering the internal face of the peripheral ligaments of a diarthrodial articulation, ought to be prolonged on the free surface of the cartilages of incrustation, and should give them their brilliancy and polish. But it is necessary to state that this is a pure hypothesis, against which rises a multitude of care- fully-observed facts. The discussion of these belongs to general anatomy, but they will be referred to here as briefly as possible. 1. If direct observation be consulted, it gives on this debated subject the most precise information ; the cartilages are uncovered, and there is no synovial membrane on their face. The anatomists who have mistaken for this membrane the thin pellicle which it is possible to render evident on the cartilages in obliquely cutting their substance and separating morsels by tearing it off, were evidently deceived. This pellicle has nothing of a serous nature in its texture ; it is not vascular, for it has never been possible to inject vessels on the surface of cartilages, nor yet in their thickness ; it is not covered by epithelium ; and submitted to microscopical examination, it exhibits -all the characters of the amorjihous matter of cartilage. It ought, then, to be considered as a cartilaginous pellicle, detached from the super- ficial layers of the articular surface — a pellicle which it has always been impossible to find on cartilages which are quite fresh ; and it has never been possible to observe it without giving, by a preliminary desiccation, a certain degree of tenacity to the cartilaginous substance about to be examined. 2. Pathological facts prove nothing in favour of the existence of a synovial membrane on the cartilages. Hypertrophy of this pretended membrane has never been witnessed ; the fungosities looked upon as a result of this hypertrophy are derived from another source. It has been demonstrated that they extend, in certain cases, from the articular margins of the cartila- ginous surface, whence their successive invasions may often be followed. In other cases, the vegetating membrane which constitutes them appears in the centre of the articular surfaces, at points deprived of cartilage ; they after- wards extend to a certain distance on the remaining cartilage. THE ARTICULATIONS IN GENERAL. 127 3. It may be asked of the partisans of the opinion now combated, how they can believe in the existence of a serous membrane between two articular surfaces, without its being exposed to bruises and destruction a thousand times in the day? Do they take into account tbe amount of pressure sustained by certain articulations, and the intense friction to which their surfaces are submitted ? Have they compared the intensity of these destructive influences, with the delicate texture of the serous membranes, and their great inflammatory susceptibility ? It is sufficient to lightly touch in this way the weak side of our adversaries' argument, and to conclude the third portion of this discussion : There is friction between the cartilages of the two opposed articular surfaces, therefore there must be wear , this is a physical law which no body escapes, let it be as hard as the diamond, or as soft as caoutchouc. And if there is wear between these rubbing surfaces, there cannot be an irritable and sensitive membrane lying on the inert and insensible strata which constitute them. In fine, a synovial membrane, after being fixed to the margin of the articular cartilage of a diarthrodial joint, is reflected in every direction to cover the inner aspect of the liga- ments, and becomes attached to the periphery of the diarthrodial surface corresponding to the first. There are generally found within articulations little masses of fat which push the synovial membrane enveloping them inwards. Erroneously con- sidered by Clopton Havers as glands for the secretion of synovia, tliese accumulations of fat have been named synovial fringes. They are more par- ticularly numerous in the neighbourhood of the articular margins : that is, on the edges of diarthrodial surfaces. The synovia is a viscid, colourless, or slightly yellow fluid, in its physical characters somewhat resembling oil ; it does not possess them, however, so far as its composition is concerned, for chemical analysis has not demonstrated the presence of fatty principles. It is the albumen it contains which gives it its viscidity, and which fits it for lubricating the articular surfaces over which it is spread. Its use in the animal economy is absolutely identical with that of the greasy substances employed to lubricate the axles of carriages. MovEiMENTS. — The movements peculiar to diarthrodial articulations are divided into seven principal classes : 1. Simple gliding, the only movement possible between two plane or undulating facets. 2. Flexion, which brings two bony pieces nearer each other by closing more or less their angle of union. 3. Extension, the inverse movement, during which the bones are straightened on each other. 4. Adduction, which brings the inferior extremity of the movable bone towards the median line. 5 Abduction, the contrary movement to the preceding 6 Circumduction, or the sling movement, during which the bone passes successively through the last four positions 7, Rotation, in which one bone pivots on another Classification of the Diarthroses. — The basis of this classification is founded on the configuration of the articular surfaces and tlie nature of the movements they permit. This double base serves to establish five kinds of diarthrodial articulation 1. Enartlirosis, characterised by the reception of an articular head within 128 TEE ARTICULATIONS. a cavity of appropriate form. This articulation may be the seat of the most extensive and varied movements : flexion, extension, abduction, adduction, circumduction, and rotation. Example : the coxo-femoral articulation. 2. The trochlean, angular ginglymoid, or perfect hinge articulation, when the articular surfaces are formed into trochlea, recii)rocally fitting into each other, and whose movements — flexion and . extension only — are executed with the precision of a hinge. Example : the tibio-tarsal ar- ticulation. 3. The condyloid, or imperfect hinge articulation, which permits, like the preceding, the two principal movements of extension and flexion, and. the accessory movements of rotation or lateral inclination. The articular surfaces, fhough very diversely shaped, nevertheless exhibit in all the articulations one or more condyles opposed to an equal number of oval excavations. Example : the femoro-tibial articulation. 4. The pivot, trochoid, or lateral ginglymoid articulation, is a diarthrosis formed by a pivot which turns in a semi-cylindrical cavity. Rotation is the only movement. Example ; the atlo-axoid articulation. 5. Arthrodia, or planiform diarthrosis, is constituted by plane, or nearly plane facets. Gliding is the only possible movement. Example : the carpo- metacarpal articulation. Nomenclature. — The names of the articulations are usually those of the bones which form them. For instance, the scapido-humcral articulation is the joint between the scapula and humerus ; the intervertebral articulations join to each other the various pieces constituting the spine. When the qualifying name of an articulation is composed of two elements, as in the first instance, it is well to place first the word which indicates the bone usually most fixed. GENERAL CHARACTERS OF THE SYNARTHROSES. Sutures are the temporary articulations which exist only at an early period of life. They nearly all disappear in the adult animal, in con- sequence of the bones forming them becoming consolidated. They belong almost exclusively to the bones of the head. Articdlar Surfaces. — The bones forming these come in contact by their borders or angles, which, for this purpose, generally present very anfractuous surfaces. Sometimes they are cut perpendicularly and simply roughened ; at other times they are bevelled and joined by means of fine laminas or trifling inequalities ; again, they are notched into deep and sinuous dentations ; and lastly, one bone is fixed into a groove cut in the other. It will be understood that such conformations of the articular surfaces ought to limit their movements and assure the solidity of their union. Modes of Union. — Cartilage interposed between these synarthrodial surfaces directly unites them to each other. It absolutely possesses the same texture as the primary cartilage of the bones, and like it, has the property of becoming ossified after having been vascularised. This ossi- fication, which causes the disappearance of the sutures, occurs earlier inwards than outwards. The periosteum, in passing from one bone to another, adheres intimately to the sutural cartilage, and also aids in bringing about a more complete synarthroses. It should, therefore, be included in their means of union. Movements. — These are very obscure, and only noticeable in young ABTICULATIONS OF MAMMALIA IX FARTICULAB. 129 animals by the elasticity they communicate to the bony walls of the cranium or face. In the adult, they may be said to be null. Classification. — There arc four principal descriptions of sutures : 1, When two viide bones corresj)ond by means of deuticulatious fitting into each other, the suture is named true or dentated. Example : the articulations uniting the three portions of the parietal bone. 2. If the opposed borders of two bones in contact are widely bevelled, one inwards, the other outwards, it forms a scaly or squamous suture. Example : the parieto-temporal articulations. 3. When the union of bones takes place by plane or roughened surfaces, cut perpendicularly on their borders or angles, this constitutes the harmonia suture, ov suture by juxtaposition (or appo- sition). Example : the occipito-temporal articulations. 4. The schindylesis, or mortised suture, results from the reception of a bony plate into a groove more or less deep in another bone. Example : the spheno-frontal and supermaxillo-nasal articulations. GENERAL CHARACTERS OF THE AMPHIARTHROSES OR STSIPHTSES. Articular Surfaces. — They are frequently smooth, and formed almost on the same model as the diarthrodial surfaces. They are covered by a thin layer of cartilage, but instead of being smooth and polished, they are more or less rugged, without, however, presenting the anfractuous disposition of the majority of synarthrodial surfaces. Modes of Union. — The organs which perform this office are : 1, The fibro-cartilage which establishes continuity between the articular surfaces ; 2, Eibbon-shaped or j)eripheral ligaments. These latter do not differ from the analogous bands attaching the diarthrodial articulations. With regai'd to the fibro-cartilage, it is distinguished from the complementary discs of these same articulations by a less intimate mixture of the cartilaginous and fibrous elements entering into its composition. The last may be sometimes absent, as well as the peripheral bands ; and then the articulation only differs from the synarthroses by the extent of motion it permits Occasionally the interarticular fibro-cartilages are excavated by one or two little narrow cavities : but these are never lined by a synovial membrane like the diarthrodial cavities. Movements. — The amphiarthroses only permit of a see-saw or swinging movement, the extent of which depends on the thickness of the intermediate fibro-cartilage. Classification. — Only one kind of amphiarthrosis is recognised, the most remarkable example of which is found in the articulations between the bodies of the vertebree. CHAPTER II. AETICULATIONS OF MAMMALIA IN PAETICULAR. In the special study of the articulations, the same order will be followed as for the bones ; the articulations of the spine will be fii'st noticed, then those of the head, thorax, and anterior and posterior limbs. Preparation. — The preparation of the bones which have been described has not been made the subject of any particular recommendation, because it suffices, in order to study them, to remove the soft parts by which they 130 TEE ARTICULATIONS. are surrounded either by boiling, maceration, or scraping. But when we come to examine the soft textures, in order to do so profitably it is necessary to learn beforehand the rules which should be fullowed in their preijaratiou. The following are laid down with regard to the study of the articulations : 1. To prepare the articulations, young subjects are chosen in preference to those ad- vanced in years, because the density of the cellular tissue in them is uot so great, and this tissue is easily removed from around the ligaments. As these are prepared with difficulty when the external surface is in a dry state, care should be taken before dissecting them to have them excluded from the air by covering them with damp cloths, or with the skin of the animal. 2. It is convenient to separate the articulation we wish to dissect by sawing through the bones at a certain distance from the articular surfaces. The manipulation of the part is then rendered easier, and its dissection can be made under the most favourable conditions. 3. It is necessary to preserve as carefully as possible the muscles surrounding the articulations, in order to be able to study their relations with the ligaments whicli bind these. If it be absolutely necessary to remove them, their insertions corresponding to the articulation should always be retained. 4. The capsular ligaments should be the first studied, as these have soon to be removed the better to show the funicular ligaments. These, in their turn, must be sacrificed in order to display, by different sections, the interosseous cords, when these exist. Lastly, the two articular surfaces should be completely separated, so as to examine their conformation. 5. The synovial membranes, with their different culs-de-sac, being a very important study, with reference to the diagnosis and treatment of articular tumours, it is convenient to devote a special piece to the examination of these serous membranes. It is very useful to inject their interior with plaster or tallow coloured black, in order to distend their cavities, and thus aid the study of their relations Avith ligaments, tendons, or muscles. For the preparation of each articulation it is not necessary to give any directions; a glance at the figures accompanying the description will suffice to dispel any embarass- ment the student may experience, while he always requires particul ir indications. (Notwithstanding the above remarks with regard to the preparation of the ligaments, I have thought it advisable to follow the example given in the last edition of ' Leyh'a Anatomy' by Zundel, and briefly indicate the readiest method of demonstrating these organs, for the special benefit of the student.) Article I. — Articulations of the Spine. (Preparation. — Remove all the soft parts surrounding the vertebral column, taking care not to injure the inferior longitudinal ligament in cutting away the pillars of the diaphragm and the psoas muscles ; nor the ligaments uniting the articular processes to each other and the transverse processes of the dorsal vertebra; to the ribs, in removing the supercostal and transverse spinal muscles. To expose the common superior longitudinal ligament, separate the bodies of the vertebrfe from their annular portions by the saw or chisel, and remove the spinal cord and dura mater ; in doing this the inferior face of the interannular ligaments will be also removed. Examine an intervertebral fibro-cartilage by two sections — a transverse at an equal distance from the two vertebrae, and a longi- tudinal through the middle line of the bodies.) These articulations are intrinsic and extrinsic. The first comprises all the articulations of the vertebrse with each other ; the second those of the spine with the head, the ribs, and the coxse. Intervertebral Articulations. The vertebrae correspond : 1, By their bodies ; 2, By their spinal or annular portion. There results from this union two kinds of articulation, which must be studied separately, as they do not belong to the same class. It is well to mention, however, that the general details into which this study leads us apply only to the articulations uniting the last six AUTICULATIONS OF THE SFWE. 131 cervical vertebras, all the dorsal and lumbar vertebrae, and tbe first sacral vertebra. Union of the Vertebra by their Bobies. — The articulations forniing this union are so many ami^biarthroses. Articular surfaces. — Tbe vertebral bodies come into contact by the surfaces which terminate them before and behind. In the cervical region these surfaces represent, anteriorly, a veritable head, posteriorly, a cotyloid cavity which receives the head of the next vertebra. Beginning from the first dorsal vertebra and passiug on to the sacrum, these tend to become effaced and more and more plane, though they still preserve their convexity and concavity. Modes of union. — 1, By fibro-cartilages interposed between the articular surfaces ; 2, By a common superior vertebral ligament ; 3, By a common inferior vertebral ligament. a. Intervertebral fihro-cartilages (Fig. 80, 1, 1). — These are circular or elliptical discs, convex in front, concave behind, and solidly fixed by their faces to the articular planes which they separate. The fibro-cartilaginous substance composing them consists of concentric layers, which become denser and closer to each other as they near the circumference ; they even disappear towards the centre of the disc, where this substance becomes pulpy and assumes the histological characters of pure cartilage. It may be remarked, that each of these layers is made up of a collection of thick parallel filaments, which cross with those of other layers like an X, and are attached by their extremities to the articular surfaces. From this arrangement results so inti- mate an adherence between the vertebral bodies and their intermediate fibro- cartilages, that an attempt to disunite them is more likely to determine a fracture of the former. The fibro-cartilages, thicker in the cervical and lumbar regions than in the dorsal, respond by their circumference to the two common ligaments. Those which sejjarate the vertebriB of the back concur to form the intervertebral cavities, \\ hich are destined for the reception of the heads of the ribs, and give attachment to the interosseous costo- vertebral ligaments. (Leyh designates the superficial fibres of the excentric layer of these fibro-cartilages as intervertebral ligaments. Luschka has shown that the cartilages are in reality articular capsules.) h. Common superior vertebral ligament (Fig 83, 1). — This ligament extends from the axis to the sacrum, and is lodged in the spinal canal ; it represents a long fibrous band cut on its borders into wide festoons. (The wide portions correspond to the discs.) By its inferior face, it is attached to the intervertebral discs and the triangular imprints on the upper faces of the bodies of the vertebrae. Its superior face is in contact with the dura mater thi'ough the medium of an abundant cellulo-adipose tissue. Its borders are margined by the intra- vertebral venous sinuses (vence hasium vertebrariuni). c. Common inferior vertebral ligament (Fig. 84, 5). — Situated under the spine, this ligament is absent in the cervical and the anterior third of thedorsal region. It only really begins about the sixth or eighth vertebra of the latter region, and is prolonged in the form of a cord, at first narrow, then gradually widening until it reaches the sacrum, on the inferior surface of which it terminates by a decreasing expansion. From its commencement, it is attached to the inferior crest of the bodies of the vertebras and the interver- tebral discs. By its inferior face, it responds to the posterior aorta. (Leyh commences this ligament at the seventh cervical vertebra, and says 132 THE ARTICULATIONS. that it adheres to the crests on the bodies of the dorsal and lumbar vertebrae, as well as to the lower face of the sacrum and coccyx. At the fifth dorsal vertebra it widens and thickens, and in the lumbar region is bound ui> with the pillars of the diaphragm and confounded on each side ^ith the large ligaments of the pelvis.) Union of the Vertebra by their Spinal Portions — Each vertebra, in uniting by its annular portion with that which follows or precedes it, forms a double arthrodial joint. Articular surfaces. — These are the facets cut on the anterior or posterior articular processes, and which have been described when speaking of the vertebrae themselves. They are covered by a thin layer of cartilage. Modes of union. — 1, A common superspinous ligament; 2, Interspinous ligaments ; 3, Interlamellar ligaments ; 4, Ligamentous capsvdes, proper to the articular processes. a. Commoa superspinous ligament. — This ligament, whose name suf- ficiently indicates its situation, extends from the sacrum to the occipital bone and is divided into two portions : one posterior, or superspinous dorso-lumbar ligament; the other anterior, or superspinous cervical ligament. These two ligaments, although continuous with one another, yet differ so strikingly in form and structure that they are best described separately. 1. Superdorso-lumhar ligament (Fig. 80, 2).— This is a cord of white fibrous tissue, which cormnences behind on the sacral spine and ceases in fi-ont about the inferior third of the dorsal region by insensibly assuming the texture and elasticity of the cervical ligament, with which it is continuous. It is attached in its course to the summits of all the lumbar spinous processes and to the ten or twelve last dorsal. On the sacral spine, it is confounded with the superior ilio-sacral ligaments. In the lumbar region, it is united on each side to the aponeuroses of the common mass of muscles. 2. Superspinous cervical, or simply cervical ligament (Fig. 104, 1, 2). — This ligiimenfc is entirely formed of yellow fibrous tissue, and constitutes, in the median plane of the body, a very remarkable elastic apparatus which separates the superior cervical muscles of the right side from those of the left, and plays the part not entirely of an articular band, but rather of a permanent stay charged to balance the weight of the head. In the cervical ligament there is distinguished a funicular and a lamellar portion. The first, usually called the cord of the cervical ligament, is a wide funiculus which extends directly from the first dorsal spinous processes to the summit of the head. Divided into two lateral lips by a median groove, this cord is continued posteriorly with the dorso-lumbar ligament, and is inserted forwards into the cervical tuberosity of the occipital bone. It is covered above by a mass of fibro -adipose tissue which, in certain common- bred horses, is very abundant. Below, it gives rise, in its posterior two- thirds, to the majority of the fibres belonging to the lamellar portion. On the sides, it receives the insertions of several cervical muscles. The lamellar portion, comprised between the funicular portion, the spinous processes of the second dorsal vertebra, and the cervical stalk, constitutes a vast triangular and vertical septum, which itself results from the apposition of the two laminae which lie back to back, and are imited by cellular tissue ; they are bordered above by the two lateral lips of the cord. The elastic fibres which enter into their composition are given off either from the latter, or from the spinous processes of the second and third dorsal vertebrae ; they are directed downwards or forwards, and reach the spinous processes of the last six cervical vertebraB, into which they are inserted by so many digitatious, ARTICULATIONS OF THE SPINE. 133 Ficr. 80. becoming confounded with the interspinous ligaments of the neck. The fibres of the two hist digitations are lew in number, widely separated from one another, and united by many anastomosing brandies, which make them appear as a kind of wide network. The lamiuas of the cervical ligament are in relation, outwardly, with the superior branch of the ilio-spinal ligament, the transverse sjiiuous muscle of the neck, and the great complcxus. (This important structure, which is in reality the mechanical stay and support of the heavy head and neck of quadrupeds, and is usually termed the ligamentum nuchce, is all but abseut in Man, being represented in him by a thin narrow band, or rather two thin planes of fibres, the ligamenta suhflava. It is described by Leyh as if there were not two portions, and that excellent anatomist does not appear to insist sufficiently on the difierence between the dorso-nuchal and the dorso-lumbar divisions. Percivall, who almost entirely neglects the ligaments, also makes no distinction. The dilference in structure, elasticity, and situation, warrants the distinction made by Chauveau. As already indicated, the function of this ligament, and more particularly of its nuchal division, is to maintain the head and neck in their natural position dm-ing repose, and to allow the most extensive movements at other times.) b. Interspinous ligaments (Fig. 80, 3). — Fibrous laminfe fill the inter- spinous spaces, and are attached, before and behind, to the opposite borders of the spinous processes which they unite ; they are continued below by the interlamellar liga- ments, forming two lateral planes which are applied against each other, like the laminae of the cervical ligament, and covered outwardly by the transverse spinous (dorsalis colli) mixscle. In the region of the neck, the interspinous ligaments are yellow and elastic. In the dorso- lumbar region, they are formed by fasciculi of white fibrous tissue, loosely united to each other at their extremities, and directed very obliquely backwards and downwards. In consequence of this disposition, and notwithstanding their in- extensibility, they permit the separation of the spinous processes. Their lateral surfaces are divided by a layer of grey elastic fibres, which cross like an X the direction of the preceding fasciculi. Very abundant in the anterior moiety of the dorsal region, these fibres operate, by their proper elasticity, in bringing the spinous pro- cesses towards each other. c. Interlamellar, or interannular ligaments. — Situated, as their name indicates, between the vertebral laminae, and divided into two lateral moieties, these ligaments appear to be produced by the two fibrous planes of the preceding ligaments, which, on arriving at the base of the spinous processes, separate from one another to be carried outwards. Their anterior border is inserted into the posterior margin of the vertebral lamina in front. Their posterior border is fixed to the anterior border and inferior face of the lamina behind. Their superior face is in relation with some spinal muscles, and their inferior face is in contact with the dura mater. Outwardly, they are confounded with the capsules proper 12 INTEKVERTEBRAL ARTICULA- TIONS. A, B, c, Bodies of three dorsal vertebras divided longitudi- nally and vertically to show (1, 1) a section of the in- tervertebral discs; 2, Super- spinous dorso-lumbar liga- ment ; 3, Interspinous liga- ment ; 4, Fibrous fascia, con- stituting the proper capsule to the articular processes in the dorsal region. 134 THE ARTICULATIONS. to the articular processes. Yellow and elastic in the cervical region, these ligaments are white and inelastic in the dorso-lumbar region. d. Capsules p-oper to the articular processes (Fig. 81, 5). — Each anterior articular process is maintained against the corresponding posterior process by a dii'ect band : this is a perii^heric capsule attached around the diarthrodial facets, doubled internally by a synovial membrane -which facilitates their gliding, and covered, outwardly, by the insertions of some spinal muscles. These capsules, yellow and elastic in the cervical, are composed of white fibrous tissue in the dorso-lumbar region. Very developed at the neck, in consequence of the thickness of the articular tubercles they envelope, they become reduced, near the middle of the back, to some fibres which cover, outwardly, the diarthrodial facets in contact. Characters proper to some Intervertebral Articulations. — 1. Inter- coccygeal and sacro-coccygeal articulations. — These are constructed after the same type as the other spinal articulations, except that they are appropriate to the rudimentary state of the vertebrae they unite. The coccygeal bones only come in contact by their bodies, their spinal laminae being reduced to the merest traces, or are altogether absent. The anterior and posterior articular surfaces of each vertebra are convex, and the interarticular fibro-cartilages, hollow on both faces, resemble a biconcave lense. With regard to the peripheral bands, they are represented by a bundle of longitudinal fibres spread over the surface of the bones, which they envelope in a common sheath. 2. Intersacral articulations. — The sacral vertebrae being fused into one piece — the os sacrum — there is no occasion to study the true articulations in this region. It may be remarked, however, that the superspinous dorso- lumbar ligament is continued on the sacral spine, and tljat there exist be- tween the processes formed by this spine veritable interspinous ligaments. 3. Sacro-Iumhar articidatiun. — In this articulation, the great thickness of the fibro-cartilage is to be remarked ; and, in addition, that the last lumbar vertebra corresponds with the sacrum not only by its body and articular processeSy^ but also by the oval and slightly concave facets shown on the posterior border of its transverse processes, which are adapted to analogous slightly-convex facets on the sides of the base of the sacrum. The bundles of fibres thrown from one bone to another from around these sacra- transversals (real planiforra diarthroses) maintain the articular surfaces in contact, and cover, outwardly, the synovial membrane which facilitates their gliding. 4. Articidation of the two last lumbar vertebrse. — This is distinguished by the presence, between the transverse processes, of a planiform diurthrosis like that of the sacro-transversal just noticed. These two articulations are only found in Solipcds. 5. Atlo-axoid articulation. — This is so far removed by its conformation and special uses from the other intervertebral articulations, that it will be described as an extrinsic articulation of the head and spine. (See the Articidations of the Head. ) The Movements of the Spine in general. — Each intervertebral articula- tion is the seat of very obscure movements, whose separate study oficrs little interest. But these movements, when conjoined with those of the other articulations, result in bending the whole sjunal stalk in a somewhat marked manner, and producing either the flexion, extension, or lateral inclination of this flexuons column. When flexion takes place, the spine is arched upwards, the common inferior ligament is relaxed, tlie spinous processes separate from one ARTICULATIONS OF THE HEAD. 135 another, and the superspinous ligament, becoming very tense, soon imposes limits to this movement. Extension is etiected by an inverse mechanism, and is checked by the tension of the common inferior ligament and the meeting of the spinous processes. Lateral inclination takes place when the spine bends to one side. This movement is very easily executed in the cervical and coccygeal regions, but is arrested by the ribs and the costiform processes in the dorso-lumbar region, A circumflex movement is possible at the two extremities of the vertebral column — neck and tail ; for they pass easily from extension to lateral inclination, and from this to flexion, etc. Owing to the elasticity of the intervertebral fibro-cartilages. the spine is endowed with a very limited amount of rotation, or rather of torsion. For the special study of the movements of each spinal region, reference must be made to what has been already said (page 29) regarding the mobility of this column. In the Ox the intervertebral discs are much thicter than in the Horse. The common inferior vertebral ligament is very strong in the lumbar region. The superspinous dorso-lumbar ligament is composed of yellow elastic tissue. Tlie cervical ligament 13 much more developed than in Solipeds, in consequence of the greater weight of the head ; and it presents a conformation altogether special, which M. Lecoq has made known in the following terms : " On leaving the withers, the superspinous ligament ceases to cover the head of the spinous processes, and extends from each side ia a wide and strong band, taking points of attachment on the sides of the processes, and becoming separated, on leaving that of the first dorsal vertebra, into two parts — a superior and inferior. The first reaches the cervical tuberosity in the form of a thick cord united to the cord of the opposite ; the other thins oft" into a baud which is attached to the posterior half of the spinous process of the axis and to that of the third and fourth vertebra. A production of tlie same nature, an auxiliary to the principal portion, leaves the anterior border of the spinous process of the first dorsal vertebra, and is attached to that of the fourth, fifth, sixth, and seventh vertebra. The superior border of this auxiliary liga- mentous prodiiction is concealed between the two lamina of the principal ligament." ' The Pig. remarkable for the shortness of its neck and the limited movements of this region, does not show any cervical ligament, properly so called. It is replaced by a superficial fibrous raphe' extending from the occipital bone to the spinous process of the first dorsal vertebra. The Cat has no cervical ligament, and shows, instead, a raphe like the Pig. In the Bog the ligament is reduced to a simple cord, continued from the dorso-lumbar ligament, and which goes no further than behind the spinous process of the axis. In the Cat the interspinous ligaments are replaced by small muscular fasciculi ; with the Dog this substitution only takes place in the cervical region. The laminse of the first coccygeal vertebrae possess the principal characters which distinguish perfect vertebr». and are imited by vestiges of the articular bands which exist in the other regions of the spiue. Article II. — ABTiCTJiiATioxs of the Head. We will first study the two extrinsic ai'ticulations which, are the centre of the movements of the head on the spine — the atlo-axoid and occipito-atloid articulations. Afterwards, we will pass to the examination of the joints which unite the different bones of the head. 1. Atlo-axoid Articulation. {Preparaiion. — It suffices to remove the soft parts from around the articulation to expose the interannular, the interspinous, and the inferior odontoid ligament. To examine ' Joiurnal de Me'decine Ve'te'rinaire ' (Lyons, 1848;, p. 122. 136 THE ARTICULATIONS. the superior odontoid ligament and the synovial membrane, one half the atlas and axis must be separated by sawing longitudinally through them from one side to the other.) This may be considered as tlie type of the troclioides. Articular surfaces. — To form this articulation, the axis offers its odontoid pivot and the undulated diarthrodial facets at its base. The atlas opposes to the pivot the concave semicylindi-ical surface hollowed on the superior face of its body ; and for the lateral undulated facets it has analogous facets which are cut on the transverse processes, on each side of the vertebral canal. 3Iode of union. — 1. An odontoid, or odonto-atloid ligament ; 2. An inferior atlo-axoid ligament ; 3. A superior ditto ; 4. A fibrous capsule. a. Odontoid ligament (Fig. 81, 3). — Continued to the common superior vertebral ligament, very short and strong, flattened from above to below, and triangular in shape, the odontoid ligament is composed of glistening white fibres, fixed behind in the superior channel of the odontoid process, and inserted in front on the transverse ridge which separates the superior face from the inferior arch of the atlas, as well as on the imprints situated in front of this ridge. This ligament is covered, on its lower face, by the synovial membrane of the articulation ; and by its upper surface is in contact with the spinal dura mater. It sends some bands within the condyles of the occipital bone. b. Inferior atlo-axoid ligament. — This is a wide, thin, and nacrous- looking band, extending from the inferior face of the axis to the inferior tubercle of the atlas, and covered by the long muscle of the neck ; it is united to the synovial membrane by its deep face, and confounded on its borders with the fibrous capsule to be immediately described. c. Superior atlo-axoid ligament.— This exactly represents the inter- spinous ligaments of the other cervical articulations. Yellow, elastic, and formed like the two lateral bands, it is continuous, laterally, with the capsular ligament. d. Capsular ligament. — This, it may be said, is only the interlamellar ligament proper to the atlo-axoid articulation. It commences from the sides of the preceding ligament, and becomes united to the inferior atlo- axoid one, after contracting adhesions with the borders of the odontoid ligament. In this way it encloses the articulation and the spinal canal. Before and behind, it is attached to the anterior or posterior margin of the bones it unites. Its external face is in contact with the great oblique muscle of the head ; its internal responds, in its inferior half, to the articular synovial membrane, and its superior moiety to the spinal dura mater. (Leyli describes this ligament as the interannular.) Synovicd membrane. — This lines the odontoid ligament, the atlo-axoid ligament, and the articular portion of the perijiheral capsule. Movements. — Botation, the only movement possible in the atlo-axoid articulation, is effected in the following manner : the axis remains fixed, and the first vertebra, drawn to one side chiefly by the great oblique muscle, rotates on the odontoid pivot, carrying the head with it. In the Dog and Cat the odontoid ligament is replaced by Ihree particular ligaments : 1, Two lateral cords, rising in common from tlie summit of the odontoid process, and inserted, each on its own side, within the condyles of the oceijiital bone ; 2, A transverse ligament, passing over the odontoid process, which it maintains in its place against the inferior arch of the atlas, and is attached by its extremities to the superior face of the latter. A small synovial capsule facilitates the gliding of the odontoid process beneath this ligament. The articular synovial membrane always communicates with that of the occipito-atloid articulation. In the Pig the disposition is nearly the same as in the Caruivora ARTICULATIONS OF THE HEAD. 137 2. OccipHo-atloid Articulation. (Preparation. — Dissect away all the soft parts that pass from the neck to the head and cover the articulation, and more particularly the flexor, the recti, and the small oblique muscles of the head. To pig_ g^^ expose the synovial membranes, open the sides of the capsular ligament.) This is a condyloid articulation. Articular surfaces. — In the atlas, the two cavities which replace the anterior articular processes and the heads of the other vertebrfe ; in the occipital bone, the two condyles flanking the sides of the occi- pital foramen. Mode of union. — A single capsular ligament en- velopes the entu-e articulation ; it is attached by its anterior border to the margin of the occipital con- dyles, and by its posterior to the anterior contour of the atlas. Thin and slightly elastic in its inferior half, this ligament presents, superiorly, foui* reinforcing fasciculi : two middle, which intercross in X — from whence the name " cruciform," sometimes given to this ligament (Fig. 81, 1, 1) ; and two lateral, which pass from the sides of the atlas to the base of the styloid processes (Fig. 81, 2, 2). It is lined within by the synovial membranes,, and is enveloped externally by a large number of muscles, which protect the articu- lation and greatly strengthen it everywhere. Among these may be particularly noticed the straight muscles of the head, the small oblique, and the great com- plexus. There is also the cord of the cervical liga- ment. Synovial membranes. — These membranes are two in number, one for each condyle and corresponding rtloid cavity. Sustained above, below, and outwardly by the capsular ligament, they are related inwardly to the dm-a mater and to the fibrous tractus which, from the odontoid ligament, is carried to the in- ternal face of the occipital condyles. Movements.^-Extension, flexion, lateral inclination, and circumduction, ai'e the possible movements of the occipito-atloid articulation. In the Pig, Dog, and Cat this articulation, strengthened as it is by the capsular and odontoido-occipital ligaments already mentioned, has only one synovial capsule. 3. Articulations of the Bones of the Head. If we except the articulation which unites the inferior jaw to the cranium — the temporo-maxillary — and the hyoideal articulations, it will be found that all the bones of the cranium and face are united to each other by synarthrosis, forming the diiferent kinds of sutures already generally described (page 128). Nothing is to be gained by entering into more detail ATLO-OXOID AND OCCIPI- TO-ATLOID ARTICULA- TIONS. The upper arch of the atlas has been removed to show the odontoid ligament. 1, 1, Middle accessory fas- ciculi ; 2. 2, Lateral fasciculi of the capsular ligament of the occipito- atloid articulation •, 3, Odontoid ligament ; 4, Interspinous ligament uniting the second and third vertebraj of the neck ; 5, Fibrous capsule uniting the articular processes of these verte- bra;. — A, Anterior in- ternal foramen of the atlas converted into a groove by the section of the bone ; B, B, Verte- bral foramina of the atlas • C, C, Foramina replacing the anterior notches of the axis. Fi^. 82. 138 THE ARTICULATIONS. with regard to these articulations, as it will be found sufficient to call to mind the topographical description of each piece entering into their formation. 4. Temporo-maxillary Articulation. {Preparation. — Eemove the masseter muscle and the parotid gland. Saw through the head about the middle line. Open the articulation externally to exhibit tlie inter- arlicular meniscus.) The lower jaw, in its imion with the cranium, constitutes a double condyloid articulation. Articular surfaces. — With the temporal bone, these are the condyle, the glenoid cavity, and the supracondyloid process which exists at the base of the zygomatic process. The glenoid cavity is not lined by cartilage, and appears to be merely covered by synovial membrane. With the maxillary bone there is the oblong condyle situated in front of the coronoid process. Interarticular fibro-cartilage. — The articular surfaces just named are far from fitting each other accurately ; this is only accomplished by the interposition of a fibro-cartilaginous disc between the temporal and maxillary bones. This disc is a kind of irregular plate, flattened above and below, thicker before than behind, and moulded on each of the diarthrodial surfaces it separates. Its superior face, therefore, presents : in front, a cavity to receive the condyle of the temporal bone; behind, a boss which is lodged in the glenoid cavity. The inferior face is hollowed by an oblong fossa in which the maxillary con- dyle is lodged. Mode of union. — A fibrous envelope — a true capsular ligament — surrounds the articulation, and is attached by its borders to the margin of 1, InterarticulLi^fibro-cartilage ; the articular surfaces it unites. Formed, out- 2, External fasciculus of the wardly, by a thick fasciculus of white vertical capsular ligament. — A, Base of fibres (Fig. 82, 2), this ligament becomes grey- the coronoid process ; J.^Neck igj^.^oloured and elastic for the remainder of MasLid 'JJoceiT DrExteraal its extent, and greatly diminishes in thickness, auditory hiatus. especially in front. Its inner lace is Imed by the synovial capsules, and adheres to the cir- cumference of the interarticular fibro-cartilage. Its external face responds, in fi*ont, to the temporal and masseter muscles; behind, to the parotid gland; inwardly, to the external pterygoid muscle; and outwardly, to a fibrous expansion which separates it from the skin. (Leyh mentions a lateral external and a posterior ligament for this articulation, but Chauveau and Eigot evidently look upon these as portions of the capsular.) Synovial membranes. --This articulation has two synovial sacs, one above the other, which are separated by the fibro-cartilaginous disc. Movements. — The temporo-maxillary articulation is the centre of all the movements performed by the lower jaw. These are : depression, elevation, lateral motion, and horizontal gliding. The lower jaw is depressed when it separates from the superior one, and is elevated when it approaches this. These two opposite movements are executed by a mechanism of such great simplicity that it need not be TEMPORO-MAXILLARY ARTICU- LATION. ARTICULATIONS OF THE HEAD. 139 described here. Lateral movements take place when the inferior extremity of the jaw is carried alternately to the right and left. It then happens that one of the maxiUary condyles, taking with it the hbro-eartilage, is brougbt into contact with the temporal condyle, while the other is imbedded in the glenoid cavity of the opposite side. The horizontal tjliding is effected from behind to before, or vice versa. In the first case, the two maxillary condyles are carried at the same time under the temporal condyles, bear in cr with them the fibro-cartilages. In the second case, they are drawn into the glenoid cavities, and rest against the supracondyloid eminence, which prevents their going further. It will be understood, after tliis brief description, that the presence of the fibro-cartilages singularly favours the lateral movements and horizontal gliding of the lower jaw. In the Pig the temporo-masillary articulation is formed after the same type as that of rodents, and allows very extensive movements from before to behind ; a circmnstance due to the complete absence of the supracondyloid eminence. In the Dog and Cat the maxillary condyle is exactly fitted into the temporal cavity. This disposition, in giving gi-eat precision to the movements of depression and elevation, restrains in a singular manner the lateral and horizontal gliding motions. The inter- articular tibro-cartilage is extremely thin in these animals. 5. Hyoideal Articulations. (Preparation. — Disarticulate the lower jaw, and dissect away from the right of each articulation the muscles that may conceal the view.) These are of two kinds : extriiisic and intrinsic. The first comprise the two temporohyoideal articulations ; to the second belong the joints which unite the different pieces of the hyoid bone — the interhijoideal articulations. TEMroKo-HYOiDEAL AuTicuLATioxs.— These are two amphiarthrodial joints, in the formation of which each great branch of the* hyoid bone opposes its upper extremity to the hyoideal prolongation lodf^ed in the vaginal sheath of the temporal bone. An elastic cartilage, from i-lOths to 6-lOths of an inch in length, unites the two bones in a solid manner ; and it is owing to the flexibility of this cartilage that the hyoid bone can move entirely on the temporal bones. Interhtoideal ARTICUL.A.TIONS. — A. The great branch articulates with the small one by an amphi arthrosis analogous to the preceding. To form this articulation, these two pieces of bone are joined at an acute ano-le through the medium of a more or less thick cartilaginous band, in the centre of which there is often a little bony nucleus. This cartilage is elastic and flexible, and permits the opening and closing of the articular ancfle at the summit of which it is jilaced. B. Each small branch is united to the body of the hyoid bone by an arthrodial articulation. The articular surfaces are : for the hyoideal branch, the small cavity terminating its inferior extremity ; for the body, the rounded lateral facet situated at the origin of the comu. These surfaces are covered by cartilage, and enveloped by a small synovial sac and a peripheral fibrous capsule. They can glide on each other in nearly every direction. (Median and superior hyoideal capsular ligaments are described by Leyh as sometimes present. The latter imites the upper and middle branches, and the former the middle with the inferior branches. They are absent when these branches are confounded with the superior ones. j HO THE ARTICULATIONS. Article III. — Articulations of the Thorax. These are also divided into extrinsic and intrinsic. The jSrst, named costo-vertebral, unite the ribs to the spine. The second join the different pieces of the thorax together ; they comprise : 1, The chondro-sternal articulations ; 2, Chondro-costai articulations ; 3, The articulations of the costal cartilages with each other ; 4, The sternal articulation peculiar to the larger Euminants and the Pig. All these joints will be first studied in a particular manner, then examined in a general way as to their movements. 1. Articulations of the Bihs with the Vertebral Column, or Costo-vertebral Articulations. Each rib responds to the vertebral column by two points— its head and its tuberosity. The first is received into one of the intervertebral cavities hollowed out on the sides of the spine, and is therefore in contact with two dorsal vertebrae ; the second rests against the transverse process of the posterior vertebra. From this arrangement arises two particular articulations belonging to the arthrodial class, which are named costo-vertebral and costo- transverse. CosTO- VERTEBRAL ARTICULATIONS. — Articular surfaces. — Pertaining to the rib, we have the two convex facets of the head, separated from each other by a gi'oove of insertion and covered by a thin layer of cartilage. On the vertebrae, the concave facets which by their union form the inter- vertebral cavity ; these facets are also covered with cartilage, and separated, at the bottom of the cavity by the corresponding intervertebral disc. Mode of union. — 1. An interarticular ligament (Figs. 83, 2 ; 84, 1), im- planted in the groove of insertion of the head of the rib, and attached to Fig. 83. Fifr. 84-. ARTICULATIONS OF THE RIBS WITH THE VER- TEBR.«, AND OP THESE WITH EACH OTHER (UPPER plane). 1, Spinal canal, upper face, showing the common superior ligament ; 2, Interar- ticular costo-vertebi-al ligament; 3, Inter- osseous costo-ti'ansverse ligament ; t. Pos- terior costo-transverse ligament. ARTICULATIONS OF THE RIBS WITH THE VER- TEBR.E, AND OF THESE WITH EACH OTHER (INFERIOR PLANE). 1, Interarticular costo-vertebral ligament; 2, 3, 4, Fasciculi of the stellate, or in- ferior costo-vertebral ligament ; 5, Common inferior vertebral ligament. the superior border of the intervertebral disc, which it encircles upwards and inwards, to unite on the median line with the ligament of the opposite side. 2. An inferior periphera i ligament (Fig. 84, 2, 3, 4), flat above and below, thin and radiating (whence it is often named the stellate ligament), formed of three fasciculi which are fixed in common on the inferior face of ARTICULATIONS OF THE THOBAX. 141 the head of the rib, and in diverging are carried over the bodies of the two vertebrfB and the intervertebral disc. Lined above by the synovial mem- branes, this ligament is covered below by the pleura. (Loyh inchides a capsular ligament for the head of the rib and another for the costal tuberosity. He probably viewed the synovial membrane of these articula- tions as such.) Synovial membranes. — Two in number, these are distinguished into anterior and posterior, lying against each other, and separated in part by the interarticiilar ligament they cover. Supported below by the stellate ligament, above they are directly in contact with the small supercostal muscles, and with vessels and nerves. CosTO-TRANSVERSE ARTICULATIONS. — Articular surfaces. — In the rib, the diarthrodial facet cut on the tuberosity. In the vertebra, the analogous facet on the outside of the transverse process. Mode of union. — Two ligaments bind this articulation : 1, The posterior costo-transverse ligament (Fig. 83, 4), a white fibrous band attached by its extremities behind the tranverse process and the costal tuberosity, lined by synovial membrane, and covered by the transverse insertions of several spinal muscles ; 2, The anterior costo-transverse, or interosseous ligament (Fig. 83, 3), a fasciculus of short, thick, white fibres, fixed on the anterior siu'face of the transverse process near its base, and in the rugged excavation on the neck of the rib. This ligament is invested, posteriorly, by the synovial membrane, and covered in front by pads of adipose tissue which separate it from the costo-vertebral articulation. Synovial membrane. — This is a small particular capsule kept apart from the posterior synovial membrane of the costo-vertebral articulation by the costo-transverse interosseous ligament. Characters peculiar to some Costo-vertebral Articulations.— 1. The first, and sometimes the second, costo-vertebral articulation has no interosseous ligament, and only exhibits one synovial membrane. The intervertebral cavity which concurs in forming the first is often excavated between the last cervical and first dorsal vertebrae. 2. The two or three last costo-transverse articulations are confounded with the corresi)ondiug costo-vertebral joints. They have no proper serous membrane, but the posterior synovial membrane of the latter is prolonged around their articular surfaces. 2. The Chondro-sternal or Costo-sternal Articulations. {Preparation. — To show the articulation of the ribs with the cartilages, these with the sternum, and the cartilages with each other, carefully remove the pleura, the triangular muscle of the sternum, the diaphragm, the transverse muscle of the abdomen, then the pectorals, the great oblique, the transversalis of the ribs, and the intercostal muscles.) The first eight ribs, in resting upon the sternum by the inferior extremity of their cartilages, form eight similar arthrodial articulations. Articular surfaces. — Each sternal cartilage opposes to one of the lateral cavities of the sternum the convex and oblong facet at its lower extremity. Mode of union.— The diarthrosis resulting from the union of these two surfaces is enveloped everywhere by bundles of white, radiating, fibrous tissue, which constitute a veritable ligamentous capsule. The superior part of this capsule, known as the stellate or superior costo-sternal ligament, is covered by the triangular (sterno-costalis internus) muscle ; it is joined .to a fibrous cord lying on the superior face of the sternum, and which 112 THE ARTICULATIONS. is confounded in front with that of the opposite side. The inferior portion, the inferior stellate or costo-sternal ligament, is in relation with. the pectoral muscles. Si/novial capsule. — There is one for each articulation. Characters proper to the first costo-sternal articulation. — The first costo- sternal articulation is not separated from its fellow of the opposite side ; so that these two joints are, in reality, only one, and the two cartilages lying close to each other cori-espond by a small diarthrodial facet, continuous with that for the sternum. The two sternal facets are inclined upwards, and confounded with one another. Only one synovial cavity exists for this complex articulation, which unites the two first ribs to each other and to the sternum. 3. Chrondo-costal Articulations uniting the Bibs to their Cartilages. These are synarthrodia! articulations whose movements are very obscure. They are formed by the imi^lantation of the cartilages in the rugged cavities the ribs present at their inferior extremities. The solidity of these articu- lations is assured by the adherence of the fibro-cartilage to the proi)er substance of the ribs, and by the periosteum which, in passing from the bone to the cartilage, plays the part of a powerful peripheral band. In the Ox, the sternal ribs, in uniting with their cartilages, form a veritable ginglymoid diarthrosis, whose movement is facilitated by a small synovial cai^sule. 4. Articulations of the Costal Cartilages with each other. The ribs, attached to each other by means of the intercostal muscles, are not united by real articulations ; neither are their cartilages of prolougment. But the asternal cartilages are bound together by a small yellow elastic ligament, which is carried from the free extremity of each to the posterior border of the preceding cartilage ; the anterior border of the first asternal cartilage is directly united to the posterior border of the last sternal cartilage, through the medium of the perichondrium and very short ligamentous bands. Tliis same asternal cartilage is also bound to the inferior face of the xiphoid appendage by a small white ligament (the chondro-xiphoid), under which passes the anterior abdominal artery. 5. Sternal Articulation peculiar to the Ox and Pig. It has been already shown that in tliese animals the anterior piece of the sternum is not consolidated with the second portion. The two are united by a diarthrodial articulation ; and for this purpose the anterior presents a concave surface, the posterior a convex one. Bundles of peripheral fibres firmly bind them to each other, and a special small synovial capsule facilitates their movements, which are very limited. 6. The Articulations of the TJiorax considered in a general manner in regard to Movements. The thorax can increase or diminish in diameter in an antero-posterior and a transverse direction ; whence arises the dilatation and contraction of this cavity : the inspiratory movements accompanying the entrance of the external air into the kings, and the expiratory movements expelling the air contained in these organs. The variations in the antero-posterior diameter of the chest being due to changes in the figure of the diaphragm, need not be noticed here. But the transverse variations being the result of the play of the costal arches on the ABTICULATIOXS OF THE ASTERIOR LUIBS. 143 spine and sternum, it is advantageous to study the mechaiiism whicli presides in the execution of their movements. The costal arches being inclined backwards on the middle plane, the space they inclose in their concavity is not nearly so extensive as if they had been perpendicular to this plane. Owing to their double arthrodial joints, the ribs are movable on the spine, and their inferior extremity, also movable, rests either directly or indirectly on the sternum. Therefore it is that, when they are drawn forward by their middle portions, they pivot on their extremities, and tend to assume a perpendicuhir direction, which is the most favoui-able for the largest increase of the space they limit ; then there is enlargement of the lateral diameter of the thorax, which signifies dilatation of its cavity. The inverse movement, by an opposite mechanism, causes the contraction of the chest. The ribs are said to be elevated during the forward movement, and depressed when they fall backwai'ds. These expressions, though perfectly applicable to Man, who stands in a vertical position, are not correct when employed in veterinary anatomy. AbTICLE IY. — APvTICrLATIOXS OF THE AXTERIOR LlMBS. 1. Scapula-humeral Articulation. {Preparation. — ^Detach the limb from the trunk. Eemove from the upper extremity those muscles whicli are inserted in the vicinity of the glenoid cavity of the scapula ; turn down from its lower extremity those which are inserted into the' superior end of the humerus or a little below, preserving the attachments of their tendons with the capsular hgament. The thin scapulo-humeralis muscle may be allowed to remain in order to show its relations.) To constitute this enarthrodial articulation, the scapula is united to the humerus, and forms an obtuse angle which is open behind. Articular surfaces. — In the scapula there is the glenoid cavity, the shallow, oval fossa, elongated in an antero-posterior direction, notched in- wardly, and excavated at its centre or near the internal notch by a small synovial fossette. A ligamentous band, attached to the brim of the cavity, tills up this notch, and is the vestige of the glenoid ligament of man. In the humerus, the articular head, fixed between the large and small tuberosities, is often excavated by a shallow synovial fossette. Mode of union. — One capsular ligament (Fig. 85, 1), a kind of sac having two openings : one inferior, embracing the head of the humerus ; the superior, inserted into the mai'gia of the glenoid cavity. This capsule pre- sents in front two supporting fasciculi, which diverge as they descend from the coracoid process to the great and small tuberosities. The aponeurotic expansion thus formed is very thin and loose, so as to allow the two bones to separate to the extent of from yt- to y% of an inch ; but it is far from being sufficiently strong to bind them fii-mly together. The articulation is, therefore, consolidated by the powerful muscles which surround it, among which may be noticed: 1, In front, the coraco-radial (flexor brachii i, separated from the fibrous capsule by an adipose cushion ; 2, Behind, the large extensor of the fore-arm and thin scapulo-humeral (teres minor) muscles, whose office appears to be to pull up this capsule during the move- ments of flexion, so as to prevent its being pinched between the articular surfaces ; 3, Outwards, the short abductor of the arm and the subspinous (postea spinatus j tendon ; ■!, Inwards, the wide and strong tendon of the subscapular muscle. In addition to these powerful retaining appai-atus, 144 THE ABTICULATIONS. there is the atmospheric pressure, whose influence is of a certain impor- tance. This may be proved by removing all the surrounding muscles, when it will be found that the capsule is not relaxed, nor are the articular surfaces separated ; to etfect this, it is necessary to make an opening in the capsule, so as to allow the air to enter its cavity, when the surfaces immediately separate. Synovial capsule. — This is very loose, and entirely enveloped by the peripheral capsule, whose internal surface it lines. Movements. — Like all the enarthrodial articulations, the scapulo-humeral permits extension, flexion, abduction, adduction, circumduction, and rotation. These various movements, however, are far from being so extensive as in Man, the arm in the domesticated animals not being detached from the trunk, but being, on the contrary, fixed with the shoulder against the lateral parietes of the thorax. Flexion and extension are the least limited and the most frequently repeated movements; their execution always demands a displacement of the two bones, which are almost equally movable. Inflexion, the scapulo-humeral angle is closed, not only because the inferior extremity of the humerus is carried backwards and upwards, but also because the scapula pivots on its superior attachments in such a manner as to throw its glenoid angle forward and upward. Extension is produced by an inverse mechanism. During the execution of the other movements, the scapula remains fixed, and the humerus alone is displaced, bringing with it the inferior rays of the limbs. If it is carried outwards, we have abduction^ or inwai'ds, addaction ; if the member passes successively from flexion to abduction, anil from that to extension, etc., in describing a circle by its lower extremity, then there is circumduction ; if it pivots from left to right, or right to left, we have rotation. In the Plfi, Doj, and Cat, the synovial membrane is not exactly inclosed by the fibrous capsule, but forms in front a cul-de-sac, which descends in the bicipital groove to favour the gliding of the coraco- radial tendon. In Man, the scapulo-humeral articulation is disposed as in animals, but it is also protected above by the coraco -acromion roof. For the reasons noted above, this articulat'on allows of more extensive motion tlian in animals. As remarked by Cruveilhier, of all the joints in the human body, the scapulo-humeral is that which has the most extensive motion; in movements forward and outward, the humerus can become horizontal; in those of circumduction it describes a comj^lete cone, which is more extensive in front and laterally than behind and inwardly. 2. Kumero-radial, or Elboiv Articulation. (Preparation. — Turn down the inferior extremity of the flexors of the fore-arm, remove the olecranian, epicondyloid, and epitrochlean muscles, taking care not to damage the ligaments to which they somewhat closely adhere.) Three bones concur to form this articulation, which presents a remark- able example of an angular ginglymus : the hinnerus, by its inferior ex- tremity, and the two bones of the arm by their upper extremities. Articular surfaces. — The humeral surface, already described at page 74, is transversely elongated, and convex from before to behind. It jiresents : 1, A median groove excavated by a synovial fossette ; 2, An external groove (humeral trochlea) not so deep as the preceding ; 3, A kind of voluminous condyle which borders, inwardly, the internal pulley, and whose antero- posterior diameter is much greater than that of the external lip of the trochlea of the opposite side. The antibracJiicd surface, divided into two portions, is moulded to the humeral surface ; it is, therefore, concave before and behind, and is composed : 1, Of a double external groove ; 2, Of an ARTICULATIONS OF TEE ANTERIOR LIMBS. 145 Fi2. 85. internal glenoid cavity, both excavated, on the superior extremity of the radius ; 3, A middle ridge re- sponding to the middle groove of the humerus, separating the two preceding sm-faces, and prolonged on the ulnar beak, where it forms the sygmoid notch. This ridge shows a small synovial fossette hol- lowed out on the radius and ulna. Mode of union. — Three ligaments : two lateral and an anterior. a. The external lateral liga- ment (Fig. 85, 8) is a thick, short, and strong funicle, at- tached above to the crest limit- ing outwardly and posteriorly the furrow of torsion, and in the small cavity placed at the external side of the humeral articular surface. Below, it is inserted into the supero-ex- ternal tuberosity of the radius. Its anterior border is con- founded with the capsular liga- ment, and is margined by the principal extensor of the pha- langes, which derives from it numerous points of attach- ment. By its posterior border it is in contact with the ex- ternal flexor of the metacarpus. Its internal face is lined by synovial membrane, and its external face is only separated from the skin by the anti- brachial aponeurosis and some of the fasciculi from the origin of the lateral extensor muscle of the phalanges. Its super- ficial fibres are vertical, and are continuous, behind, with the arciform ligamentous bands which stretch from the ulna to the radius. Its deep fibres are slightly oblique downwards and forwards. h. The lateral internal liga- ment, also funicular, is longer, scapitlo-hujieral and hu5ier0-radial aeticxt- latioxs, with the muscles surrounding them (external face). 1, Scapulo-humeral capsular ligament ; 2, Short ab- ductor muscle of the arm ; 3, Its insertion in the humerus; 4, Insertion of the subspinous muscle on the crest of the great tuberosity ; 5, Coraco- radial muscle; 6, Its tendon of origin attached to the coracoid process; 7, Its radial insertion con- founded with the anterior ligament of the ulnar articulation ; 8, 8, External lateral ligament of that articulation; 9, Anterior ligament ; 10, Aconeus, or small extensor of the fore-arm; 11, Origin of the external flexor muscle of the metacarpus ; 12, Short flexor muscle of the fore-arm. — A, Tuberosity or the scapular spine. — B, Superspmous fossa. — C, Sub- spinous fossa. — D, Convexity of the small trochan- ter. — E, Summit of the trochanter. but not SO strong as the pre- ceding. It arises from the small tuberosity on the inner side of the 146 THE ARTICULATIONS. superior articular face of the humerus and, widening as it descends, reaches the radius. Its median fibres, which are the longest, are directed vertically downwards to reach the imprints situated below the bicipital tuberosity ; its anterior fibres, curved forwards, are united to the tendon of the coraco- radial muscle, or are confounded with the anterior ligament ; the posterior are turned backwards, near their inferior extremities, to join the arcifurm fibrous fasciculi which inwardly unite the ulna to the radius. The middle fibres of this ligament cover the inferior insertion of the short flexor of the fore-arm and, in part only, that of the long flexor. It is covered by the ulna-plantar nerve and the posterior radial artery and vein. c. The anterior or capsular ligament (Fig. 85, 9) is a membraniform band, attached by its superior border above the humeral articular surface, and by its inferior to the anterior margin of the radial surface. By its lateral borders, it is confoimded with the funicular ligaments. Its internal half is formed of vertical fibres which descend from the humerus and expand over the radius, where they become united with the inferior tendon of the coraco-radial muscle. In its external moiety it is extremely thin, and composed of fibres crossed in various directions. Lined internally by synovial membrane, this ligament is in contact, by its external surface, with the anterior radial vessels and nerves, the two flexor muscles of the fore-arm, the anterior extensor of the metacarpus, and anterior extensor of the phalanges. The two latter muscles are even attached to it in a very evident manner. The elbow articulation, closed in front and on the sides by the three ligaments just described, has no particular ligaments posteriorly ; but it is powerfully consolidated there by the olecranian insertion of the extensor muscles of the fore-arm, and by the tendons of origin of the five flexor muscles of the metacarpus or phalanges. Synovial membrane.— Thin membrane is very extensive and, stretched out on the internal face of the before-mentioned ligaments, forms behind three great culs-de-sac of prolongment : a superior, occupying the olecranian fossa, and covered by a fatty cushion, as well as by the small extensor muscle of the fore-arm ;^ two lateral, which descend from each side of the ulnar beak, and are distinguished as internal and external ; the first lines the tendon of the external flexor of the metacarpus ; the second facilitates the play on the upper radial extremity of the four flexor muscles of the foot or dibits, and which are attached in common to the epitrochlea. This synovial sac also' furnishes the radio-ulnar articulation with a diverticulum which descends between the bones of the fore-arm to below the adjacent diar- throdial facets. Movements. — Flexion and extension. In flexion, the two bones do not approach each other directly, the inferior extremity of the radius deviating a little outwards. This is due more to the slight obliquity of the articular grooves than to the difference in thickness existing between the external and internal extremities of the humeral surface. Extension is limited by the reception of the beak of the olecranon in its fossa, and by the tension of the lateral ligaments ; so that the two rays cannot be straightened on one another in a complete manner, or placed on the same line. In the Dog and Cat, the external lateral ligament is very thick, and forms in its > Some grey elastic fibres wliich cover this cul-de-sac externally, have been wrongly described as a posterior membraniform ligament. ARTICULATIONS OF THE ANTERIOR LIMBS. 147 inferior moiety a fibro-cartilaginous cap which is fixed on the ulna and radius, and united in trout to tlie annular ligament of the superior radio-ulnar joint. This cap, with the last- named ligament, complcti s the osteo-fibrous ring iu which the superior extremity of the radius turns. The internal lateral ligament is inserted by two very short fasciculi into the ulna and inner side of the head of the radius. A third fasciculus, deeper and median, much more developed than tlie first, and covered by the inferior insertion of the flexors of the fore-arm, descends between the radius and ulna to tlie posterior face of the former, and is there inserted near the inferior attachment of the external ligament, whicii it appears as if about to join. In Man. tiie elbow articulation is formed nearly on the same plan as that of the Dog and Cat. The radius and ulua move together when the fore-arm is flexed and extended on the humerus. 3. Badio-iilnar Articulation. Articular surfaces. — The two bones of the fore-arm correspond by diartliroclial and synarthrodia! surfaces. a. The diarthrudial surfaces consist of* four undulated, transversely elongated facets, two of which are radial and two ulnar. The first border, posteriorly, the great articulai* surface forming the elbow joint ; the second are situated beneath the sigmoid notch. h. The synartkrodial surfaces are plane and roughened, and are also two on each bone : one, superior, extends below the diarthrudial facets to the radio-ulnar arch ; the other, inferior, more extensive, occupies all the anterior face of the ulna frnm this arch ; on the radius it forms a very elongated triangular imprint which descends to the lower fourth of the bone. See pages 75, 76. Mode of union. — Two interosseous and two peripheral ligaments. a. The interosseous ligaments, interposed between the syuarthrodial surfaces, are composed of extremely short white fibres passing from one to the other surface, and which are endowed with a very remarkable power of resistance. The inferior always ossifies a long time before the animal is full grown : a circumstance which caused the older veterinary anatomists to describe, and with some show of reason, the radius and ulna as a single bone. Ossification of the superior ligament is very rare. 6. The peripheral bands are bundles of arciform fibres which, from the beak of the olecranon to the radio-ulnar arch, leave the lateral faces of the ulna to pass, some inwards, others outwards, to the posterior face of the radius. The fibres of the external ligament are confounded with the external humero-radial ligament. The internal fibres are united to the internal hiunero-radial ligament, and to the small ulnar tendon belonging to the short flexor of the tore-ann. Analogous fibres are found beneath the radio-ulnar arch ; but they are much shorter and less apparent (This is the externcd transverse radio-ulnar ligament of Leyh.) Movements. — Very obscure in youth ; nearly null when consolidation of the two bones takes place. In the Ox, ossification of the superior interosseous ligament is constant at adult age. In the Dog and Cat, we have already seen fp. 87) that the radius and ulna are not fused to each other, but remain independent during life. They are united in their middle portion by an interosseous ligament, and join by diarthrosis at their two extremities. These animals therefore exhibit: 1, An interosseous ligament, 2, A superior radio-ulnar articulation ; 3, An inferior radio-ulnar articulation. Interosseous ligament. — It is composed of very resisting white fibres, attached by their extremities to the bodies of the bones. Notwithstanding their shortness, they are loose enough to allow movements talking place between tlie radio-ulnar articulations. Superior radio-ulnar artindalion. — This is a trochoid articulation, which only allows movements of rotation or pivoting. 148 THE ARTICULATIONS. The articular surfaces which form this articulation are: in the ulna, the small sigmoid cavity, a surface excavated in the lateral sense, and semicircular ; in the radius, a cylindi'ical half-hinge received into the preceding cavity. To unite these there is an annular ligament, a kind of fibrous web thrown around the superior extremity of the radius, lixed inwardly on the ulna near the inner extremity of the small sigmoid cavity, attached outwardly to the external lateral ligament of the elbow articulation, and confounded superiorly with the anterior ligament of the same articulation. Tliis fibrous web, in uniting with tlie fibro- cartilaginous cap of the external humero-radial ligament, and joining the small sigmoid cavity by its internal extremity, transforms this last into a complete ring, covered with cartilage in its bony portion, and lined by synovial memijraue — that of the elbow articulation — in its ligamentous portion. The liead or superior extremity of the radius is also incrusted over its entire contour with a layer of cartilage : a disposition which permits it to glide not only in the concave face of the small sigmoid cavity, but also on the internal face of the two ligaments which complete this cavity. Inferior radio-ulnar articulation. — This is also a trochoid articulation analogous to the preceding, but inversely disposed. Thus, the concave articular surface is hollowed on the radius, outside the inferior extremity ; the convex surface lies within the ulna. These two facets are very small, and are maintained in contact by a diminutive peiiplieral fibrous capsule. A strong interosseous ligament, situated imder the articular facets, also consolidates this diarthrosis, and concurs by its inferior border to form the antibrachial surface of the radio-cari:)al articulation. A small synovial capsule is specially devoted to this articulation. Mechanism of the radio-ulnar joints. — The play of these two articulations is simultaneous, and tends to the ?ame end; that is, to the execution of the double rotatory movement which constitutes supination and pronation. Sujrination is when the ulna remains fixed, and the radius pivots on it in such a manner as to carry its anterior face outwards. Its superior extremity then turns from within forwards, and even from before outwards if the movement is exaggerated, in the articular girdle formed by the small sigmoid cavity of the ulna and the ligaments which complete it. The inferior extremity also rolls on the ulnar facet in describing a similar movement, and the internal tuberosity of this extremity is carried forwards. In the movement of pronation, this tuberosity is brought inwards, and the anterior face of the radius comes forward by an opposite mechanism. The inferior ray of the anterior member being articulated in a hinge-like manner with the radius, it follows that bone in its rotatory movements, the anterior face of the metacarpus looking outwards during supination and forwards in pronation. The radio-ulnar articulation in Man resembles that of the Dog and Cat, the articular surfaces only being larger and the movements more extensive. In supination, tlie palmar face is turned forward, and the radius, situated on the outer side of the ulna, is in the same direction as the latter. In pronation, on the contrary, the palmar face of the hand looks backwards, and the radius, remaining outwards in its upper part, crosses the ulna in front in such a manner that its lower extremity is placed within the ulna. 4. Articulations of the Carpus. (Preparation. — Kemove the tendons from around the articulation, detaching their sheaths, but taking care of the ligaments.) These comprise : 1, The articulations uniting the carpal bones of the first row to each other ; 2, The analoszous articulations of the second row ; 3, The radio-carpal articulation ; 4, The articulation of the two rows with each other ; 5, The carpo-metacarpal articulation. Akticulations which unite the Bones of the First Eow to each OTHEU. — These bones, four in number, are joined by the diarthi'odial facets on their lateral faces and form small arthrodial articulations.'^ They are maintained in contact by sis ligaments, three anterior, and three interosseous. The anterior ligaments are small flattened bands carried from the fourth bone to the first, from the first to the second, and from that to the third. The first, placed outside rather than in front of the carpus, is covered by the ' The facet uniting the supercarpal to the first bone is not situated on one of its faces, but rather on the anterior part of its circumference. ARTICULATIONS OF THE ANTERIOR LIMBS. 149 external lateral ligament and the inferior tendon of the external flexor of the metacurpui? ; the others adhere to the eapsidur ligament. The inter- osseous lujaments are implanted in the grooves of insertion which separate the diarthrodial facets. One of them, derived from the common superior ligament, unites the first to the second bone. The two others, situated between the three last carpal bones, are confounded with the corresponding anterior ligaments. Articulations uniting the Carpal Bones of the Second Eow. — These are arthrodial articulations, like the preceding, but numbering only two. Tliey are fixed by tivo ankrior and two interosseous ligaments. One of the anterior ligaments joins the first bone to the second, and strongly adheres to the capsular ligament ; the other is entirely covered by the lateral internal ligament, and attaches the two last bones to each other. Of the two inter- osseous ligaments, the second alone is confounded with the corresponding anterior ligament. That which is situated between the two first bones is separated from the anterior ligament by one of the diarthrodial facets between these bones. Eadio-carpal Articulation. — The inferior extremity of the radius, in becoming united to the upper row of carpal bones, constitutes a diarthrosis which, from the nature of the movements it permits, may be considered as an imperfect hinge joint. Articular surfaces. — The radial surface, elongated transversely and very irregular, presents : 1, Outwardly, a wide groove, limited in front by a small glenoid cavity, and bounded, posteriorly, by a non-articular excavation which receives a prolongation of the second bone in the movement of flexion , 2, Inwardly, a condyle, with a more extensive curvature than that of the preceding groove and, like it, completed by a small anterior glenoid cavity. The carj)al surface, moulded exactly on tLe radial, oifers depressions corre- sponding to the projections on it, and vice versci. 3Iode of union. — The radio-carpal articulation is bound by three liga- ments which entirely belong to it, and by four strong ligaments that are common to it and articulations which will be studied hereafter. Of the three ligaments proper belonging to the radio-carpal articulation, one forms a thick, rounded funicle, extending from the radius to the fourth bone in an oblique direction downwards and inwards, and concealed by the common posterior ligament. The second (Fig. 87. 5), much smaller, is carried from the supercarpal bone to the external side of the inferior extremity of the radius, and is partly covered by the common external ligament. When tbe synovial capsule is distended by dropsy, it may form a hernia at the outer side of the carpus, by passing between this small ligament and the common posterior ligament. The third, very delicate, but always present, is deeply situated beneath the last ; it is inserted, for one part, into the radius near the first proper ligament, and for the other, into the second bone and the interosseous ligament which unites the supercarpal to the second bone. Synovial membrane. — After lining these three ligaments and the four great ligaments yet to be described, this membrane is prolonged between the three first carpal bones to cover the superior face of the interosseous ligaments which unite them. It even more frequently descends into the articulation which joins the supercarpal to the fiirst bone ; though it also sometimes happens that this has a particular synovial capsule of its own. Articulation of the Two Rows between Each Other. — Like the preceding, this is an imperfect hinge articulation. 13 150 THE ARTICULATIONS. Ficr. 86. Articular surfaces. — These are two, and are both transversely elongated, very irregular in tlieir configuration, and divided into three portions. The inferior shows : behind, three small condyles placed side by side ; in front, two slightly concave facets. The superior corresponds to the first by three glenoid cavities aud two convex facets. Mode of union. — For this articulation, besides the common great liga- ments, there are three particular ligaments. Two of these are very short, and are situated behind the carpus, underneath the great common posterior ligament. They are readily perceived by removing the capsular ligament, and strongly flexing the carpus. " The strongest extends vertically from the internal bone of the superior row to the second and third bones of the metacarpal row ; the other descends obliquely from the first bone of the antibrachial row to the second of the inferior row," — Bigot. The third licrament proper, much stronger than the other two, reaches from the supercarpal to the first bone of the inferior row and the head of the external metacarpal bone. It is confounded, outwardly, with the great external lateral ligament ; inwardly, with the common posterior ligament. Its posterior border gives attachment to the fibrous arch which completes the carpal sheath. This ligament has also a branch which is fixed on the second bone of the upper row (Fig. 87, 4). Synovial membrane. — This lines all the ligaments, and is prolonged above and below, between the carpal bones, to facilitate the gliding of their articular facets. Two upper pro- longations ascend between the three first bones of the antibrachial row to cover the inferior face of the inter- osseous ligaments uniting them. Two other prolong- ations descend between the carpal bones of the second row ; the external, after covering the first interosseous ligament, passes between it and the corresponding an- terior ligament, and communicates with the synovial capsule of the carpo-metacarpal articulation. The in- ternal forms a cul-de-sac which rests on the inter- osseous ligament Caepo-Metacarpal Articulation. — The carpal bones of the second row articulate with the superior extremity of the metacarpal bones, constituting a plani- form diarthrosis. Articular surfaces. — These are, on each side, plane facets more or less inclined one on the another, and continued between each other The largest is in the carpal bones of each mifidie, and is generally hollowed by a small, shallow, row; 2, 2, Anterior • i i> xi. ligaments proper to Sjnovial fossette. the carpo-metacar- Jilode of union. — There are the four great common pal articulation; 3, ligaments, and also six special ligaments : two anterior, Common external two posterior, and two interosseous. moTinternai hZ'. . P^ *^?^' ^'''^ anterior ligaments (Fig. 86, 2, 2), one is ment. divided into two distinct bands, and unites the second bone to the princij)al metacarpal ; the other, concealed by the external lateral ligament, attaches the first bone to the head of the external metacarpal bone. The two posterior ligaments described by Rigot do not appear to us to be sufiiciently distinct from the great ligament to merit a sjiecial description. The two interosseous ligaments, completely overlooked by that able CARPAL ARTICULA TIONS; FRONT VIEW. 1, 1, Anterior liga^ ments uniting the ABTICULATIONS OF THE ANTERIOR LLUBS. 151 Ficr. 87. anatomist, start from tlie interstices which separate the median metacarpal bone from the lateral metacarpals, and join the interosseous ligaments of the second row ; they are thick and short. ^\ e have sometimes noted one or other of them to be absent. Synovial membrane. — This communicates, as indicated above, with the synovial capsule of the preceding ai-ticulation. It furnishes a superior cul- de-sac which rests on the interosseous ligament interposed between the two last carpal bones of the second row. Two inferior culs-de-sac descend into the intermetacarpal arthrodial articulations. Ligaments common to the three preceding Articulations. — As before mentioned, these are fom* in number two lateral, one anterior, and one posterior. a. The external lateral ligament (Figs. 86 and 87, 3) is a thick funicular cord composed of two orders of fibres — a deep- seated and a superficial order, slightly crossed. It leaves the external and inferior tuberosity of the radius, descends vertically to the side of the carpus, transmits a fasciculus to the first bone of the upper row, gives off another fasci- culus which stops at the external bone of the second row, and terminates on the head of the corresponding metacar- pal bone. Traversed obliquely by the lateral extensor of the phalanges, this ligament covers the external carpal bones. In front, it is united to the capsiilar ligament; near its inferior extremity, it is confounded with the strong ligament which joins the supercarpal bone to the first bone of the inferior row and to the head of the external meta- carpal bone. h. The internal lateral ligament (Fig. 86, 4 ), analogous l, 1, Anterior liga. to the preceding and situated on the opposite side, is wider ments uniting and thicker than it. It commences on the internal tube- rosity of the radius, and terminates on the upper extremity of the middle and internal metacarpal bones, after being attached, by two distinct fasciculi, to the third carpal bone of the upper row, and the two last of the metacarpal row In contact by its external face with the tendon of the oblique extensor muscle of the metacarpus, this ligament responds, by its deep face, to the synovial membranes of the carpus and to the bones to which it is attached. By its anterior border it is united to the capsular ligament , the opposite border is intimately confounded with the pos- terior ligament, from which it is impossible to distinguish it. c. The anterior, or capsular ligament, is a membranous band covering the anterior face of the carpal articulations. Its superior border is attached to the radius , the inferior is inserted into the superior extremity of the principal metacarpal bone. The two right and left borders are united with the lateral ligaments. Its external face is in contact with the tendons of the anterior extensor muscles of the metacarpus and phalanges. The internal fiice is lined at certain points by synovial membrane, and adheres in others to the carpal bones and the anterior ligaments binding these to one another. This ligament is composed of ti-ansverse LATERAL VIEW OF THE CARPAL AR- TICULATIONS. the two rows ot carpal bones ; 2, 2, Anterior liga- ments proper to the carpo-meta- carpal articula- tion; 3, Common external liga- ment ; 4, One ot the ligaments proper to the articulation of the two rows (metacarpo - su- pracarpal) ; 5, One of the liga- ments proper to the radio-carpal articulation (ra- dio - supracar- pal). — A, Groove on the external surface of the su- pra carpi 1 bone for the passage of the external flexor of the me- tacarpus. 152 THE ARTICULATIONS. fibres more or less oblique, and arranged crosswise; by its amplitude it can adapt itself to tbe movements of flexion of the knee. d. The posterior ligament, one of the strongest in the animal economy, covers the posterior face of the carpus, filling up the asperities which roughen it. It is inserted : above, on the transverse crest surmounting the articular surface of the radius ; by its middle portion into all the carpal bones ; below, into the head of the principal metacarpal bone. Confounded inwardly with the internal lateral ligament, united outwardly to the band which attaches the supercarpal to the external metacarpal and the second carpal bone of the upper row, this ligament is continued, by its inferior extremity, with the carpal stay (or check ligament) which sustains the perforans tendon. Its posterior face is perfectly smooth, and is covered by the synovial membrane of the carpal sheath. Movements of the Carpal Articulations. — The carpus is the seat of two very extensive and opposite movements — flexion and extension ; to which are added three very limited accessory movements — adduction, abduction, and cii'cumduction. All the carpal articulations do not take an equal part in the execu- tion of these movements , for it is easy to discover that they are chiefly jierformed in the radio-carpal diarthrosis, and in the imperfect hinge articulation uniting the two rows of carpal bones. Each of these articula- tions participates in the movements of the carpus in nearly the same pro- portions, and both act in an identical manner. Their mechanism is most simple. In flexion, the first tier of bones rolls backwards on the radius, the inferior row moves in the same sense on the upper, the metacarpus is carried back- wards and uj)wards, the common posterior ligament is relaxed, the capsular ligament becomes tense, and the articular surfaces, particularly those of the second joint, separate from each other in front. In extension, the metacarpus is carried downwards and forwards by an inverse mechanism. This move- ment stops when the ray of the fore-arm and that of the metacarpus are in the same vertical line. In flexion, these rays never directly approach each other ; the inferior extremity of the metacarpus lacing always carried outwards. It may also be remarked, that the slight movements of abduction, adduction, and circumduction of the carpus are only possible at the moment when the foot is flexed on the fore-arm. With regard to the planiform diarthrosis articulating the carpal bones of the same row, they only allow a simple gliding between the surfaces in contact ; and with the carpo-metacarpal arthrodia it is absolutely the same. The restricted mobility of these various articulations has but a very secondary influence on the general movements of the carpus ; but it nevertheless favoiu'S them by permitting the carpal bones to change their reciprocal relaticms, and adapt themselves, during the play of the radio-carpal and intercarpal lunges, to a more exact coaptation of the articular planes which they form. In the other animals, the carpal articulations have the s-ame essential characteristics we have noticed in Solipeds. I'he four principal peripheral bands differ but Httle in them ; though in the Bog and Cat they are lax enough to allow somewhat extensive lateral movements. 5. Intermetacarpal Articulations. I Each lateral metacarpal bone articulates with the middle one by means of diarthrodial and synarthrodial surfaces, for the description of which refer to page 82. An interosseous ligament, composed of very short and strong ASTICULATIONS OF THE ANTERIOR LIMBS. 153 fasciculi, is interposed between the synarthrodia! surfaces, and binds them firmly together. Its ossification is not rare. The diarthrodial facets are maintained in contact by the preceding ligament, and by the carpal ligaments inserted into the head of the lateral metacarpal bones. The intermetacarpal ai'ticulations only allow a very obscure, vertical, gliding movement. In the Ox, there is only one intermetacarpal articulation, which is much simpler than tliose in the Horse. In the Pig, the four metacarpal bones correspond, at their upper extremity, by means of small diarthrodial facets on their sides. Fibrous fasciculi, derived from tlie great anterior and posterior ligaments of the carpus, protect tliese intermetacarpal articula- tions before and behind. Other fibres, situated between the adjacent faces of the metacarpal bones, are real interosseous ligaments. In the DcH] and Cat, the four great metacarpal bones articulate \n.th each other in almost the same manner as iu the Pig, but their mobility is greater. 6, Metacarpo-phalangeal Articulation. {Preparation. — Turndown the anterior and lateral extensor tendons of the phalanges, after carefully cutting tlirough their attachment with the capsular ligament. Lay open the metacarpo-phalangeal sheath from above to below, and txura down the flexor tendons. J This is a perfect hinge-joint, formed by the inferior extremity of the median metacarpal bone on the one part, and the superior extremity of the upper ]>halanx and sesamoids on the other. Articular surfaces. — For the metacarpal bone, there are two lateral condyles and a median antero-posterior eminence ; for the first phalanx, two glenoid cavities and an intermediate groove prolonged posteriorly on the anterior face of the two sesamoids. Divided in this manner into three por- tions, the digital surface is well constituted for solidity, because the pressure transmitted to this region is diminished and diffused by the natural elasticity of the bands which tmite these three pieces to each other. Mode of union. The means of union may be divided into two categories: 1, Those which join together the several bones of the inferior surface; 2, Those which maintain in contact the two opposed articular surfaces. A. The first have received the generic name of sesamoid li(jaments, and are six in number; an intersesamoid ligament, which keeps together the two complementary bones of the digital surface ; three inferior and tico lateral sesamoid ligaments, which unite these bones to the fu-st phalanx. a. The intersesamoid ligament is composed of fibro-cartilaginous substance which appears to be the matrix in which the two sesamoids were developed, as it is spread around these bones, after being solidly fixed on their internal face. Behind, this ligament, in common with the posterior face of the sesa- moids, forms the channel (Fig. 89, 5) in which the flexor tendons glide. In front, it occupies the bottom of the intersesamoid articular groove. 6. The inferior sesamoid ligaments, situated at the iwsterior face of the first phalanx, are distinguished as superficial, middle, and deep. The superficial ligament (Fig. 89, 8), the longest of the three, is a narrow band flattened before and behind. It arises from the middle of the fibro- cartilaginous mass which completes, posteriorly, the superior articular surface of the second phalanx, and slightly \v4dening, ascends to the base of the sesamoids, into which it is inserted by becoming confounded with the intersesamoid ligament. Its posterior face, lined by the synovial membrane of the so-called sesamoid sheath, is covered by the flexor tendons ; it partly covers the middle ligament. The middle ligament, triangular and radiating, is composed of three 154 THE ABHCVLAT10N8. particular fasciculi : two lateral (seen on each side of the superficial liga- ment in Fig. 89, 8), and a median which has been generally confounded with the superficial ligament, although it is clearly distinguished from it by its inferior insertion. Fixed in common to the posterior imprints of the first phalanx, these three fasciculi diverge in ascending to the base of the sesamoids, where they have their upper insertion. The deep lujament is constituted by two small bands concealed beneath the middle ligament. Thin, short, flattened before and behind, and inter- crossed, these bands are fixed to the base of tho sesamoids in one direction, and in the other to the superior extremity of the first phalanx, near the margin of its articular surface. This ligament is lined on its anterior face by the synovial membrane of the articulation.' c. The lateral sesamoid ligaments are two thin layers extending from the external face of each sesamoid to the tubercle of insertion on the side of the superior extremity of the first phalanx. They are covered by the digital vessels and nerves, by the fibrous stay detached from the suspensory liga- ment to the anterior extensor tendon of the phalanges, and by the superficial fasciculus of the lateral metacarpo-phalangeal ligament ; they are covered by synovial membrane on their internal face. B. The ligaments destined to unite the two articular surfiices of the meta- carpo-phalangeal joint are four : two lateral, one anterior, and one posterior. a. Each lateral ligament comprises two fasciculi, a superficial and a deep, firmly united by their adjacent faces. The superficial fasciculus commences on the button of the lateral metacarpal bone, attaches itself to the median metacarpal, and descends vertically to terminate at the superior extremity of the first phalaux. It covers the phalangeal insertion of the lateral sesamoid ligament and the deep fasciculus. The latter, attached suiDcriorly in the lateral excavation of the inferior extremity of the jirincipal metacarpal, radiates as it reaches the sesamoid and the superior extremity of the first phalanx, where it is fixed by mixing its fibres with those of the lateral sesamoid ligament. The inner face of this fasciculus is lined by the articular synovial membrane. h. The anterior ligament belongs to the class of capsular ligaments. It is a very resisting membraniform expansion which envelops the anterior face of the articulation. Attached by its upper border to the anterior margin of the metacarpal surface, and by its inferior border to the first phalanx, this expansion is confounded at its sides with the lateral ligaments. It is covered by the extensor tendons of tlie phalanges, which glide on its sui-face by means of small serous sacs. Its internal face adheres throughout its whole extent to the synovial capsule. c. The posterior ligament,'^ very appropiately nan>ed the suspensory ligament of the fetlock (Figs. 88 , 89, 4), is a long and powerful bi-ace, composed of white fibrous tissue, and often containing fasciculi of fleshy fibres in its texture. Lodged behind the median metacarpal, and between the two lateral meta- carpal bones, this brace is quite thin at its origin, but it soon becomes enlarged, and preserves its great thickness to the extent of its upper fourth. Examined in section, it appears to be formed of two superposed portions which are closely adherent to each other. The superficial portion, the thinnest, commences by three small branches, which are fixed to the first and second * The two bands described by Kigot as forming part of this ligament, belong to the lateral fasciculi of the middle ligament. * It corresponds to the two muscles which, iu Man, lie alongside the interosseous metacarpal muscles. See the Mvscles of the foot. ABTICULATIOXS OF THE ANTERIOR LIMBS. 155 Fisj. 88. bones of the lower carpal row ; the deep portion, much thicker, is attached to the posterior face of the principal metacarpal foi- about 8-lOths of an inch. Jt has been wrongly asserted that the suspensory ligament of the fetlock is continuous with the common posterior ligament of the carpus ; it is, on the contrary, quite distinct from it. The carpal stay or deep palmar aponeu- rosis of Man, is alone in direct continuity with the common posterior liga- ment of the carpus. The suspensory ligament of the fetlock is bifid at its inferior extremity ; its two branches, after being fixed into the summits of the sesamoid bones, give origin to two fibrous bands which pass downwards and forwards to become united on each side to the anterior ex- tensor tendon of the phalanges. It is in relation, by its posterior face, with the perforans tendon and its carpal stay ; by its anterior face, with the median metacarpal bone, and arteries and veins ; by its borders, with two small interosseous muscles, the lateral metacarpal bones, and the digital vessels and nerves. Synovial membrane. — This membrane is pro- longed as a cul-de-sac between the terminal branches of the preceding ligament. It is the distention of this sac which causes the articular swellings vulgarly designated "windgalls." Movements. — The metacarpo-phalangeal articu- lation permits the extension and flexion of the digit, and some slight lateral motion wlien the movable osseous ray is carried to the limits of flexion. SECTION OF THK INFERIOR ROW OF CARPAL BONES, THE METACARPAL, AND THE SUSPENSORY LIGAMENT OF THE FETLOCK. 1, Os magnum ; 2, Common posterior ligament of the carpus; 3, Stay, or band for the perforans tendon ; 4, Suspensory ligament of the fetlock ; 5, Its super- ficial layer; 6, Its deep fasciculus , 7, Principal metacarpal bone. In the Ox, Slieep, and Goat, this articulation consti. tutes a double hinge which resembles the simple gin- glymus of monodactyles. They have tliree intersesamoid ligaments two lateral to unite the large sesamoids of each digit, and a median ■which unites the internal sesamoids. The inferior sesa- moidean ligamentous apparatus is far from showing the same degree of development as in the Horse ; it is reduced for each diiiit to four small bands, which remind one very much of the deep ligament of the latter animal, as it has been described by Kigot : two lateral bands pass directly from the sesamoids lo the upper extremity of the first phalanx ; the other two, situnted between the first, inter- cross and are confounded with the latter by their ex- tremities. — A lateral sesamoid ligament unites the first phalanx to the external sesamoid. For each digit there are two lateral metacarpo-phalangeal ligaments an external, analogous to that of the Hor^e, but less complicated, is attaciied by its inferior extremity to the first plialanx only ; the other, internal, fixed superiorly in the bottom of the inter- articular notch of the metacarpal bone, is inserted into the inner face of the first phalanx in mixing its fibres with those of the superior interdigital ligament. This latter is situated between the two first phalanges, and is composed of short, intercrossed fibres, attached to the imprints which in part cover the internal face of the two first phalangeal bones. In the Sheep there are only traces of this interdigital ligament, and each internal metacarpo-phalangeal ligament gives rise, near its phalangeal insertion, to a fibrous branch which is directed backwards from the interdigital space, and ia terminated in the bone of the ergot (or posterior rudimentary digit), which it sustains. The anterior or capsular ligament, single as in Solipeds, unites the two external lateral ligaments. The suspensory ligament, single superiorly, is divided inferiorly into eight branches, two of which are joined to the perforatus tendon to form with it the double ling through which the two branches of the perforans pass. Four other branches, in 156 TEE ABTICULATIONS. Fig. pairs, extend to the summits of the sesamoids. That which is sent to each external sesamoid gives off, on the side of the first phalanx, a reinforcing band to the proper extensor of the digit. The two last, profound and median, dcsooiid into the interarticular notch of the metacarpal bone, after becoming a single fasciculus , afterwards, they pass between the two internal metacarpo-phalangeal ligaments, and separate from each other in passing downwards and forwards on the inner side of the first phalanx, to join the proper extensor tendon of each digit. In the Pig, Dog, and Cat, for each metacarpo-phalangeal there is : a proper synovial membrane ; an intersesamoid ligament ; au inferior sesamoid ligament composed of two cross-bands ; two small lateral sesamoid ligaments; two lateral metacarpo-phalangeal liga- ments, attached inferiorly to the first phalanx and the sesamoids ; an anterior capsular ligament, in the centre of which is found a small bony nucleus, a kind of anterior sesamoid, over which glides one of the branches of the common extensor of the digits. The suspensory ligament is replaced by real palmar interosseous muscles (see the iluscles of the fore-foot). Some fibres situated between the first phalanges of the great digits in the Pig, remind one of the superior interdigital ligament of the Ox. In Man, the cavity in the upper extremity of the first phalanx is completed by a glenoid ligament. The glenoid ligaments of tlie four first digits are united to each other by a transverse ligament of the metacarpus. The articulaticms are consolidated by two lateral ligaments. The metacarpo-phalangeal articulations allow flexion and extension movements, as well as those of abduction and adduction ; but the latter are limited by the lateral ligaments. /'\' J 7. Articulation of the First loith the Second Phalanx, or First Ivterphalangenl Articulation. {Preparation. — Remove the extensor tendon; throw open the metacarjJO-phalangeal sheath, and turn down the flexor tendons.) This is an imperfect hiuge-joint. Articular surfaces. — On the inferior extremity of the fii'st phahxnx, there are two lateral condyles separated by a groove. On the superior surface of the second phalanx, tliere are two glenoid cavities and an an tero- posterior ridge. The latter surface is completed behind by a glenoidal Ji.hr o-cartilage, very dense and thick, which also acts as a ligament. It is attached, in one direction, to the second phalanx, between the superior articular surface and the kind of fixed sesamoid which margins it behind ; in the other, it is inserted into the first phalanx by means of six fibrous bands : two superior, which embrace the GEAL AETicuLA- inferior, middle, and superficial sesamoid ligaments ; two TioNs ; RIGHT ^j-^j^jjq ^j^^j ^wo inferior, which extend to the sides of the 1 3 Outer and inner inferior extremity of the first phalanx. This fibro-car- ' rudimentary me- tilage is moulded, in front, to the articular surface of the tatarsal bones ; 2, latter bone, aud forms, by its posterior face, a gliding Perforans tendon and its check ligament ; 4, Suspensory ligament ; 5, Gliding surface, or sheath for the flexor tendons, formed by the posterior face of the sesamoid bones, and intersesamoid, transverse, and annular ligaments ; 6, Section of lateral sesamoid ligament ; 7, Lateral fasciculus of the middle inferior sesamoid ligament ; 8, Inferior superficial sesamoid ligament- 9, Lateral ligament of the first interphalangeal articulation; 10, Section of the terminal branch of the perforatus tendon; 11, Section of the lateral cartilage of the foot- 12, Postero-inferior surface of navicular bone; 13, Section of latei-al car- tilage, plantar cushion, and wing of pedal bone ; 14, Perforatus tendon ; 15, Perforans tendon. POSTKRIOR VIEW OF THE METACARPO- PHALANGEAL AND INTER - PHALAN- ARTICULATIONS OF THE ANTERIOR LIMBS. 157 surface for the perforans tendon (Fig. 89, 5). It is confounded, laterally, •with the two branches of the perfuratus, aud receives in the middle of its superior border the insertion of the inferior superlicial sesamoid ligament. Mode of union. — Tico lateral ligaments, to which are added, behind, the fibro-cartilage just described, aud in front the tendon of the anterior extensor of the phalanges These ligaments are large and thick, and passing obliquely downwards and backwards, are inserted, superiorly, into the lateral tubercles on the inferior extremity of the first phalanx. They are attached, beneath, to the sides of the second phalanx. Their most inferior fibres are even prolonged below that point to reach the extremities of the navicular bone, and constitute the posterior lateral ligaments of the pedal articulation. Synovial rnemhrane. — This covers the tendon of the anterior extensor of the phalanges, the lateral ligaments, and the glenoid fibro-cartilage. Behind, it forms a cul-de-sac which extends between the latter and the posterior face of the fii'st phalanx. Movements. This imperfect hinge is the seat of two principal movements: extension and flexion. It also allows the second jihalanx to pivot on the first, aud permits some lateral movements. la the Ox, Sheep, and Goat, the glenoid f3bro-cartilage is confounded with the per- foratus tendon, and is only attached to the first phalanx by two lateral bands. The internal lateral Ugament comprises two fasciculi : one, very short, which terminates in the second phalanx ; and another, very long, descending to the internal face of the third phalanx. The external is very thin, and is also prolonged to the terminal phalanx; so that the two last iuterphalungeal articulations of each digit are fixed by two common lateral ligaments which correspond exactly, by their position and inferior attachments, to the anterior lateral ligaments of the pedal joint of Solipeds. In the Dog and Cat, the glenoid cartilage, also confounded by its posterior face with the perforatus tendon, only adlieres to the first phalanx by some cellular bands. The two lateral ligaments pass from the inferior extremity of the first phalanx to the superior extremity of the second. In the Pig, there is somewhat the same arrangement as in Carnivora. The external lateral ligament is, nevertheless, more like that of the Horse, in its most anterior fasciculi being prolonged to the external extremity of the navicular bone. 8. Articulation of the Second Phalanx icith the Third, Second Interphalangeal Articulation, or Articulation of the Foot. To form this imperfect hinge-joint, the second phalanx is opposed to the third, and to the navicular bone. Articular surfaces. — On the inferior face of the second phalanx there are two lateral condyles and a median groove. On the superior face of the third phalanx and the navicular bone, are two glenoid cavities separated by an antero-posterior ridge. The two bones which form this last sm-face arti- culate with each other by an arthrodia ; the navicular bone presents for this purpose an elongated facet on its anterior border ; the os pedis also ofiers an analogous facet on the posterior contour of the principal articular surface. Mode of union. — Five ligaments : a single interosseous one which joins the navicular to the pedal bone; and four lateral pairs, distinguished as anterior and posterior. a. Interosseous ligament. — This is formed of very short fibres which are inserted, behind, into the anterior groove of the navicular bone; and in front, into the posterior border and inferior face of the third phalanx. This ligament is lined, on its superior surface, by the synovial membrane, and on its iuferior face is covered by the navicular sheath, h. Anterior lateral ligaments. — These are two thick, short, and wide 158 THE ARTICULATIONS. fasciculi, attached by their superior extremities to the lateral imprints of the second phalanx, and by their inferior extremities into the two cavities at the base of the pyramidal eminence of the os pedis. Each ligament is partly covered by the complementary fibro-cartilage of that bone, and appears to form a portion of it. Its anterior border is continuous with the common extensor tendon of the phalanges ; its internal face is covered by the synovial membrane, which adheres closely to it. c. Posterior lateral ligaments. — These have been already noticed. Each is composed of the lowermost fibres of the lateral ligament of the first interjihalangeal articulation ; these fibres, after being attached to the second phalanx, unite into a sensibly elastic fibrous cord, which is chiefly fixed into the extremity and superior border of the navicular bone, where the ligaments join each other, and in this way form a kind of complementary cushion which increases the navicular articular surface. It also sends off a short fasciculus to the retrossal process, and a small band to the internal face of the lateral fibro-cartilage. Partly concealed by the latter and the plantar cushion, this ligament is covered inwardly by the articular synovial membrane. (For full details as to the manner in which the navicular is attached to the pedal bone, the student is referred to the series of papers on the Horse's Foot, published by me in the ' Veterinarian ' for 1870. It is only necessary to refer here to the intimate connection there exists between the lateral and interosseous ligaments, and the stratiform fibro-cartilage covering the pos- terior face of this sesamoid : a connection, or rather unification, which has been strangely overlooked by hippotomists and hippo-pathologists, but which has undoubtedly a most important bearing on the genesis of that very prevalent and formidable malady of the anterior foot of the Horse — navicularthritis.) Synovial membrane. — This descends below the facets which unite the navicular to the pedal bone. It offers, posteriorly, a vast cul-de-mc which reaches the posterior face of the second phalanx, and lies against the two navicular sheaths. It also forms another much smaller, by being prolonged between the two lateral ligaments of the same side. This is very often dis- tended, and it is liable to be opened in the operation for diseased cartilages. Movements. — The same as those of the fii'st interphalangeal articulation. In the Sheep are found : 1, An interosseniis ligament to unite the navicular bone to the third phalanx; 2, Two anterior lateral ligaments commencing, as already stated, at the first phalanx ; 3, Two lateral posterior ligaments, passing to the posterior face of the second phalanx and the navicular bone (the internal is yellow and elastic); 4, A single, .anterior, elastic ligament, attached above to the superior extremity of the second phalanx, and fixed below into the third, between the insertion of tlie common extensor of the digits and tliat of the internal anterior lateral ligament; an interior interdigital ligament, situated between the uugueal phalanges, whose scjjaration from each otiier it limits. This ligament is comfiosed of parallel fibres, wliinh extend transversely from tiie one navicular bone to the otlier, and is covered on its inferior face by the skin of the interdigital space. Its upper face is in contact with an adipose cushion. In the Ox, the external anterior lateral ligament, wide and expanding, is almost entirely covered by the long branch of the proper extensor of the digit, to which it is intimately adherent. The interdigital ligament has a much more complicated character than that of the Sheep. It is formed of fibres intercrossed on the median line, and divided at its extremities into two fasciculi: a superior passes over the perforans ti-ndon, to which it serves as a restraining band, and is fixed to the outside of the inferior extremity of the first phalanx, after contracting very close adhesions with a strong fibrous ■web which descends from tlie posterior metacarpal region, and which will be more fully noticed when descriliing the muscles; an inferior, shorter than the preceding, attached to the internal extremity of the navicular bone and the internal face of the third phalanx, ARTICULATIONS OF THE POSTERIOR LIMBS. 159 becoming confounded with the perforans tendon, the plantar cushion, and the kera- togenous membrane. In tlie Fig, for the maintenance of the second interphalangeal articulation, there are : 1, Two lateral ligaments, carried from the lateral fiices of the second phalanx to the external and internal faces of the third; 2, A third ligament, exactly resembling one of tlie posterior lateral ligaments of the pedal articulation of the Horse; this ligament descends from the inferior extremity of the first phalanx to the internal extremity of the navicular bone. Its analogue of the inner side appears to be altogether absent; but in tlie large digits there is an anterior yellow elastic ligament like that of Ruminants. In the"Do<7, the two last phalanges are united by two lateral ligaments, very simply arranged. A third ligament, formed of elastic tissue, divided into two lateral portions, ami situated in front of the articulation, plays the part of a spring, which mechanically produces the retraction of the claw when the flexor muscles cease to contract. In the Cat, this yellow ligament is very strong; and this animal also exhibits a very striking obliquity of the articular pulleys by which the two phalanges correspond : an arrange- ment which permits the claw to be lodged between two digits when they are raised, and thus favour its retraction. The second interphalangeal articulation of the Dog and Cat is also distinguished by another essential arrangement. The articular surface of the third phalanx is com- pleted by a glenoid fibro-cartilage analogous to that of the first articulation, but much thicker." This fibro-cartilage (see iVIiscLES of the h.and) is fixed into thu posterior projeetion of the third phalanx, and serves, by its inferior face, as a pulley for the per- forans tendon and, with, the projection just named, plays the part of the navicular bona in other animals. The interphalangeal articulations of Man are formed on the same plan as the metacarpo-phalangeal articulations. They are eonsolidated by a glenoid and lateral ligaments, and possess only the two movements o( flexion and extension. Article V. — Articulations of the Posterior Limbs. 1. Articulations of the Pelvis. {Preparation. — These ligaments are all exposed to view by carefully removing the soft parts connected with the sacrum and coxae.) A. Sacro-iliac Articulation (Fig. 90). — This is a pair articulation whicli establishes the union of the posterior limb with the spine, and is formed by the sacrum and coxa. It belongs to the arthrodial class. Articular surfaces. — On the sacrum, the irregular diarthrodial facet named the " auricular," cut on the sides and near the base of the bone. For the coxa, the analogous facet on the internal face of the ilium. 3Iode of union. — By four ligaments, which, after the example of Eigot, we will name sacro-iliac, superior ilio-sacral, inferior ilio-sacral, and the sacro-ischiatic. a. Sacro-iliac ligament. — This is composed of thick fibrous fasciculi, which envelope the whole articulation in being firmly attached by their extremities to the imijrints around the diarthrodial facets. The inferior moiety of this ligament is covered by the psoas-iliacus (iliacus) muscle. Its posterior half ^ is much stronger, is hidden by the ilium, and gives attach- ment to the ilio-spinalis (longissimus dorsi) muscle. b. Superior ilio-sacral ligament. — A thick and short funicle which, rising from the internal angle of the ilium, is carried backwards to be fixed to the sacral spine, where its fibres are confounded with those of the sujser- spinous dorso-lumbar ligament. c. Inferior ilio-sacral ligament. — This is a very resisting, triangular, membranous band, formed of parallel fibres passing obliquely downwards and backwards. It is attached, by its anterior margin, to the upper half of ' It represents the interosseous sacro-iliac ligament of Man. The inferior half corre- sponds to the anterior sacro-iliac ligament. 160 THE AETICCLATIONS. the ischiatic border and the internal angle of the ilium, in becoming confounded with the pi'eccding ligament. Its inferior margin is inserted into tlie rugged lip which borders the sacrum laterally. Its posterior border is united to the aponeurosis covering the coccygeal muscles, and its external face is in contact with the principal gluteal and the long vastus muscles ; while the internal corresponds to the lateral sacro-coccygeal muscle. d. Sacro-sciatic or ischiatic ligament (Fig. 90, 2). — This is a vast mem- branous expansion situated on the side of the pelvis, between the sacrum and the coxa, and serves more as a means for inclosing this portion of the pelvic cavity than to assure the solidity of the sacro-iliac articulation. Its form is irregularly quadrilateral, and permits its circumference to be divided into four borders : a superior, attached to the rugged lateral ridge of the sacrum ; an inferior, fi.\;ed to the supercotyloid ridge, as well as the ischial tuberosity, and forming by the portion comprised between these two in- sertions, with the small ischiatic notch, the opening by which the internal obturator and pyramidal muscles leave the pelvis ; an anterior, imperfectly limited, along with the great ischiatic notch, circumscribes the ojiening through which the gluteal vessels and nerves, and the sciatic nerves pass ; a posterior, doubled in the form of two laminte which embrace the semi- membranosus muscle, and is confounded superiorly with the aponeurosis enveloi)ing the coccygeal muscles. The external face of this ligament is traversed by the sciatic nerves, and is covered by the long vastus and the semitendinosus muscles, which derive numerous insertions from it. Its internal face is covered, in front, by the peritoneum, and posteriorly is in contact with the ischio-coccygeal and ischio-anal muscles, to which it gives attachment. Synovial membrane. — This lines tlie sacro-iliac ligament, but only furnishes a small quantity of synovia. Movements. — The two sacro-iliac articulations being the centres towards which all the impulsive efforts communicated to the trunk by the posterior limbs converge, they do not offer much mobility, as that would oppose the integral transmission of the quantity of movement. So that they permit only a very restricted gliding of the articular surfaces ; and the union of the sacrum and coxa by diarthrosis appears to be exclusively designed to prevent the fractures to which these bones would be incessantly exposed if they were fixed together in a more intimate manner. B. Articulation of the Two Cox^, or Ischio-pubic Symphysis. — The two coxae are united to each other throughout the whole extent of the inner border of the pubis and the ischial bones. In youth, this is a veritable amphiarthrosis, fixed by an interosseous cartilage and bundles of peripheral fibres. The cartilage is solidly fixed to the small rugged eminences which cover the adjacent articular surfaces, and becomes ossified, like the sutural cartilages, as the animal advances in age. In adult Solipeds the coxre are always fused with each other. The peripheral fibrous fasciculi extend tranverscly from one bone to the other, above and below the symphysis ; those on the inferior face are incomparably stronger and more abundant than the others. The movements of this articulation are most restricted, and depend solely upon the elasticity of the interosseous cartilage. They cease after its ossification. The fusion of the two coxse proceeds very slowly in the female of the Cat, Dog, Pig, Ox, Sheep, and Goat species. ARTICULATIONS OF THE POSTERIOB LIMBS. 161 2. Coxo-femoral Articulation. (Preparation. — Remove the muscles surroiiiniiug the articulation. To view the interior, divide the capsular ligament by a circular incision.) This is an enarthrosis, formed by the reception of the head of the femur into the cotyloid cavity of the coxa. Articular surfaces. — As already shown, the cotyloid cavity represents the segment of a hollow sphere, deeply notched on the inner side, and Flo;. 90. SACRO-ILIAC AND COXO-FEMORAL ARTICULATIONS, WITH THE SMALL DEEP MUSCLES SURROUNDING THE LATTER. 1, Saci'o-lliac ligament ; 2, Sacro-ischiatic ligament ; 3, Great ischiatic notch ; 4, Anterior portion of the capsular ligament of the coxo-femoral articulation ; 5, Internal band of cotyloid ligament ; 6, Coxo-femoral ligament ; 7, Pubio-femoral ligament; 8, Its insertion into the femur; 9, Small gluteal muscle; 10, Origin of the straight anterior muscle of the thigh (rectus); 11, Anterior thin muscle (rectus parvus); 12, Pyramidal muscle of the pelvis; 13, External obturator muscle; 14, Square crural muscle (quadratus femoris); 15, Inferior sacro- coccygeal muscle. provided at the bottom with a wide depression, the internal moiety of which is destined for the insertion of one of the interosseous ligaments, while the external half plays the part of a synovial fossa. This depression is not covered by cartilage, and communicates by the internal notch with the inferior furrow on the pubis. The lip of the cotyloid cavity is covered by a complementary fibro-cartilage — the cotyloid ligament. This fibro-cartilage is not interrupted at the notch just mentioned, but passes over it, forming a remarkable band (Fig. 90, 5) that converts it into a foramen, through which pass the pubio- or ilio-femoral ligament and the vessels of the articulation. 162 THE AR TICULA TIOXS. Fixed by its adhercut border to the margiu of the cotyloid cavity, this ligament is lined by synovial membrane on its faces and free border. It is thickest in front and within. Witli regard to tlie head of the femur, it will be remembered that it is exactly moulded to the cavity, and, like it, is excavated by a rugged fossa which is entirely occupied by the insertion of the interarticular ligaments. 3Ijde of union. — This joint is maintained by a peripheral ca^jsule, and by two interarticular bands constituting the coxo-femoral and pubio-femoral ligaments. a. Capsular ligament (Fig 90, 4). — This is a membranous sac, like that of the scapulo-humei-al articulation, embracing the head of the femur by its inferior oj^ening, and attached by its opjjosite aperture to the margin of the cotyloid cavity and its protecting fibro-cartilage. This ligament is com- posed of intercrossed fibres, and is strengthened in front by an oblique fasciculus which descends to the body of the femur, along with the anterior thin muscle, near wliich it is fixed. Its internal face is covered by the articular synovial membrane, and its external face is in contact, through the medium of adipose cushions, with : in front, the anterior thin muscle (crureus) and the straight muscle (rectus) of the thigh ; behind, to the gemini, the intex'nal oblrurator, and the pyramidal muscles ; outwards and upwards, to the small gluteal muscle ; within and below, to the external obturator. h. Coxo-femoral ligament (ligamentum teres. Fig. 90, 6).^ — ^A thick and short funicle of a triangular shape, deeply situated between the two bony surfaces, which it cannot, notwithstanding its shortness, maintain exactly in contact without the other muscular or ligamentous structures enveloping the articulation. Its upper insertion occupies the internal moiety of the bottom of the cotyloid cavity ; and its inferior extremity is confounded with the pubio-femoral ligament, being fixed with it into the rough fossa in the head of the femur. It is enveloped by the synovial membrane. c. Pablo femoral ligament (Fig. 90, 7, 8). — This ligament, longer and stronger than the last, originates from the pubic tendon of the abdominal muscles and the anterior border of the pubis. Lodged in the inferior channel of that bone, it passes outwards, enters the internal notch of the cotyloid cavity, is inflected downwards on the fibrous band which converts that notch into a foramen, and goes witli the preceding ligament to be inserted into the fossa in the head of the femur. Its pubic portion lies between the two branches of the pectineus, while its interarticular surface is covered by synovial membrane. Synovial membrane. — This membrane is very extensive; it lines the internal face of the capsular and cotyloid ligaments, and is reflected on the interarticular ligaments to form around them a serous vaginal covering. It is even prolonged into the synovial fossa occupying the centre of the cotyloid cavity. Movements. — The coxo-femoral articulation is one of the joints wdiich is endowed with the most varied and extensive movements. It permits the flexion, extension, abduction, adduction, circumduction, and rotation of the thigh on the pelvis. The mechanism of these movements is so simple, that they need no particular consideration. The domesticated animals other than Snlipcds, are distinguished by the complete absence of the pubio-femoral lijj;amf'nt; so that in tliem the movements of abduction, which are limited in Solipeds by tlie tension of this liizament. are much more extensive; anil it is the absence of the liijament in question, which explains the facility with which the larger Rumiuanis arc enabled to strike sideways, a movement known as a " cow's kick." ARTICULATIONS OF THE POSTERIOR LUIBS. 163 In Man, the head of the femur is more detached than in the domesticated animal:?, and the Cotyloid cavity, encircled by the cotyloid lii.'aii)ent, is deeper. The femur is united to the coxa : 1, By a capsular ligament ; '2, By a triangular ligament, tixed above, to the cotyloid ligament at the notch, and IjcIow, iuto the depression in tiie head of the femur. Al^o, as the brothers Weber have shown, the atmospheric pressure is a powerful adjunct to these means of union. The cuxu-femoral articulation of Man permits more extensive movements than that of animals, and especially abduction and adductiun, which can be carried to 90 degrees. 3. Femoro-tibial Articulation} (Preparation. — Remove the soft parts surrounding the articulation, taking care not to wound the synovial membrane. To expose the ciuci;d ligaments, make an antero- posterior vertical section vi the femur in such a way as to separate the condyles.) This is the most complicated joint in the body, and is formed by the union of the femiu' with two of the thigh bones — the tibia and iiateUa. It represents an imj^erfect hinge-joint. Articular surfaces. — To form this articulation, the femur opposes its two condyles to the wide, convex, and undulated facets on the superior face of the lateral tuberosities of the tibia, and its articular pulley to the posterior face of the patella. The femoral faces have ah-eady been described in detail at page 98 ; but it may be repeated that the two condyles, placed side by side, are elongated in an antero-posterior direction, and are separated by a non-articular notch called the intercondyloid ; also, that the femoral trochlea situated in front of these two condyles appears to continue the preceding notch, and that its internal border is much more elevated than the external ; an arrangement which explains why it is so difficult, if not impossible, for the patella to be dislocated inwards. The tibial facets ascend on each side to the lateral faces of the tibial spine. They are seimrated from one another by the antero-posterior groove cut on the summit of that bone, and by the fossas of insertion sitiiated at its base before and behind. The external facet, wider than the internal, is devoted in part to the gliding of the originating tendon of the popliteal muscle. (See page 100. j The 2)atellar surface, moulded on the femoral pulley, fits it in an imper- fect manner. It is bordered, outwardly, by a small fibro-cartilaginous ring, which is united to the fibrous capsule of the femoro-patellar articulation (Fig. 92, 1). Inwardly, it is completed by the insertion of the internal patellar ligament, to be noticed immediately. Interarticnlar meniscii (semilunar jihro-cartilages) — (Figs. 91, No. 1, 2, 3. 4; and 1'2, 5, 6. 7, 8). — By this designation is known the two fibro- cartilages interposed between tlie condyles of the femur and the tibial facets, to assure their coaptation. They are crescent shaped bodies, and present : an internal, concave, thin and sharp border, embracing the tibial spine ; an external, thick, and convex border ; a superior face, excavated and moulded to one of the condyles ; an inferior face, nearly plane, gliding on the tibia ; and two extremities terminated by ligaments, and fixed to the bones in apposition. The articular surfaces are not entirely separated throughout their extent by * By this name is understood the joint uniting the femur to the tibia, and that which articulates it with tlie patella. Followinp:itellar articulation distinct from the femom-tihiul, properly so called. This innovation appears to le just tied by the com- munity of the principal articular bands which bind these two joints, and by the reciprocal dependence of their movements. 164 THE AMTICULATI0N8. these complementary meniscii, for the tibial spine rubs directly against the inner sides of the femoral condyles. The internal semilunar fihro-cartilage, the widest and thickest, is inserted by its anterior extremity into one of the excavations situated in front of the spine ; its posterior extremity is attached in the fossa behind that eminence. The external semilunar fihro-cartilage is fixed, in front, near the anterior insertion of the opposite fibro-cartilage ; its posterior extremity gives origin to two slips or cords, one superior, the other inferior. The first, the strongest and longest, terminates in the fossa near the posterior extremity of the intercondyloid notch. The second, thin and flat, is inserter) on the posterior outline of the external tibial facet. Fis;. 91. No. 1 No. 2. FEMORO-TIBIAL ARTICULATION. No. 1. Posterioi- face : the posterior ligament has been removed. — 1, External menis- cus; 2, Fibrous fasciculi fixing it to the femur; 3, Fibrous fascia which attaches it to the posterior contour of the tibial surface ; 4, Internal meniscus ; 5, Tibial insertion of the posterior crucial ligament j 6, External lateral ligament ; 7, Internal lateral ligament. No. 2. External face : the external condyle of the femur and the meniscus have been removed to show the crucial ligaments. — 1, Anterior crucial ligament ; 2, Posterior ditto 5 3, Fibular insertion of the external lateral ligament ; 4, Anterior patellar ligaments. — A, Internal meniscus ; b, Anterior insertion of the external meniscus •, C, Passage for the tendinous cord common to the flexor of the metatarsus and the anterior extensor of the phalanges ; D, Anterior and superior tuberosity of the tibia 5 E, Tibial crest. The external border of this meniscus is separated from the external lateral ligament by the tendon of the popliteus muscle, and acts, with regard to this tendon, as a pulley. Mode of union. — The bands which bind this complicated articulation are very numerous. They will be successively described as : 1, Those which attach the patella to the tibia ; 2, Those which unite the femur with the tibia. A. Ligaments attaching the jJatella to the tibia. — The patella is bound to the tibia by three funicular ligaments, designated by the generic epithet of " patellar." They are situated in front of the articulation, and are charged ARTICULATIONS OF THE POSTERIOR LIMBS. 1G5 witli the duty of transmitting to the leg the action of the muscles which are attached to the patella. They are distinguished according to their position, as external, internal, and middle. (Fig. 92, 2, 3, 4.) a. The external imteUar ligament, the largest and most powerful, is a flattened band, attached, by its lower extremity, to the cuhuinating point of the anterior tuberosity of the tibia. Its upper extremity is lixed to the anterior face of the patella, and is confounded with the patellar insertion of the long vastus muscle. It is joined to the internal ligament by a very resisting aponeurotic expansion, a dependency of the fascia lata. b. The internal patellar ligament also forms a flattened band, longer, but not so wide or thick as tlie preceding. Its inferior extremity is attached to the inner side of the anterior tuberosity of the tibia. Its superior extremity becomes much thickened and fibro-cartilaginous, and is inserted into a prominence inside the patella. This fibro-cartilaginous portion (Fig. 92, 3') of the ligament glides on the internal border of the femoral trochlea, and may justly be considered as a comi)lementary apparatus of the patellar surface. The ligament, joined to the preceding by the fibrous fascia already mentioned, is mixed up, inwardly, with the aponeurosis of the adductor muscles of the leg. c. The middle patellar ligatnent is a round cord, situated, as its name indicates, between the other two, concealed beneath the aponeurosis which unites these, and in the middle of the adipose tissue protecting the synovial capsules in front. It leaves the anterior face of the patella, and descends vertically to the tibia, to be lodged in the fossa in the middle of the anterior tuberosity, where a small synovial bursa facilitates its movements. Its inferior extremity is inserted into the most declivitous part of this excavation. !b. Ligaments ichich attach the thigh and leg hones. — These are six in number : 1 , A femoro-patellar capsule maintaining the patella against the femoral trochlea ; 2, Five femoro-tibial ligaments, as follows : two lateral, two external and internal ; a posterior ; and two interarticular, distinguished with reference to their inferior insertion into anterior and posterior. a. The femoro-patellar capsule is a membranous expansion which covers, above and laterally, the superior synovial membrane. This capsule is attached by its borders around the femoral trochlea and the periphery of the patellar surface. It is extremely thin in its superior part ; but laterally it is thicker, and constitutes two wide fibrous fasciculi which bind the patella to the eccentric sides of the two condyles, and is described in several works as two special ligaments. Its external face is covered by the insertion of the long vastus and the crural triceps. 6. The lateral ligaments are two ribbon -shaped cords situated at the extremities of the transversal axis of the articulation, more behind than before ; they are relaxed during flexion, and very tense in extension. The external, the shortest and strongest, proceeds from one of the hollow facets on the external condyle of the femur, and is inserted into the head of the fibula by its inferior extremity, after gliding over the external tuberosity of the tibia by means of a special synovial bursa. It is covered by the crural or tibial aponeurosis, and covers the tendon of the popliteus, from whicli it is sometimes separated by a vesicular synovial membrane. The internal is attached, superiorly, to the eminence of insertion that surmounts the eccentric face of the internal condyle, and descends vertically to the tibia, gliding over the margin of its articular surface by means of a email facet covered with cartilage, and a cul-de-sac prolongation of the 14 166 THE ARTICULATIONS.] internal synovial membrane. It is fixed by its inferior extremity to the imprints which cover the internal tibial tuberosity. Its fibres are disposed in two layers, which slightly intercross in X fashion ; those jiassing downwards and forwards adhere to the border of the internal meniscus. Covered by the aponeurosis of the adductor muscles of the leg, this ligament adheres by its deep face to the internal meniscus. c. The posterior ligament belongs to the class of membranous or capsular ligaments. It is formed of two aponeurotic laminaa separated superiorly, but confounded infcriorly. The superficial lamina is composed of strong, fibrous, intercrossed fasciculi, perftu-ated with vascular openings. It is fixed, above, to the posterior face of the femur, below the external gastrocnemius muscle. The deep lamina envelopes, like a cap, the femoral condyles. After becoming united, these two laminfe are attached to the posterior face of the tibia, closa to the superior articular face of that bone. Its external face is in contact with the popliteal vessels, and the external gastrocnemius muscle. Its internal face is covered throughout nearly the whole of its extent by the lateral synovial membranes, embraces the condyles of the femur, and adheres to the posterior crucial ligament, as well as to the interarticular meniscii. d. The interosseous ligaments are two funicular bands lodged in the inter- condyloid notch. They are more commonly designated crucial ligaments, becanse they cross each other at their middle j)art, like the letter X. (Fig. 91.) The anterior, oblique downwards and forwards, is attached by its superior extremity to the bottom of the intercondyloid notch, and inwardly to the external condyle. Its inferior extremity is fixed in the groove on the summit of the tibial spine. The fibres entering into its formation are not parallel, but slightly twisted in a spiral manner. The posterior, longer than the preceding, and oblique in the opposite direction, is inserted, inferiorly, into the little eminence behind the internal tibial facet ; whence it goes to the bottom of the intercondyloid notch, to bo attached by its superior extremity within the internal condyle. Synovial memhranes. — For this articulation there are three synovial membranes : a superior and two lateral. The first, very large and sustained by the femoro-patellar capsule, facilitates the gliding of the patella on the femoral pulley ; it is prolonged in a cul-de-sac below the insertion of the crural triceps. The other two, which lubricate the articular surfaces of the projier femoro-tibial joint, include the crucial ligaments between them, and cover the posterior ligament, the lateral ligaments, and the fibrous fasciculi for the attachment of the meniscii. The external covers, in addition, the tendon of the popliteus muscle, and furnishes a vast cwZ-f/e-sac which descends in the anterior groove of the tibia to envelop the tendon common to the anterior extensor of the phalanges and the flexor of the metatarsus. These two femoro-tibial synovial membranes lie against that of the femoro-patellar articulation, in front of the condyles and the notch which separates them, and if not always, at least not unfrequently, they communicate with it. The three are separated from the ligaments of the patella by a considerable mass of adipose tissue which is prolonged into the intercondyloid notch, at the bottom of which it appears to be fixed. Movements. — This imperfect hinge joint can execute the two principal and opposite movements of ^/Zex/on and extension, sinCi a somewhat limited acces- sory movement of rotation. The mechanism of these movements being simple enough to be readily understood without any preliminary explanation, AETICULATIOXS OF TEE POSTERIOR LUIBS. 167 they will not be detailed here ; but some remarks will be made with regard to the displacement the tibro-cartilages undergo when the articulation is in motion. During flexion and extension, tliese bodies, fixed on the tibial facets, which they transform into glenoid cavities, move with them on the condyles of the Fig. 92. femur, from before to behinil,or behind ^*'- 1- ^o. 2. to before, according to the movement executed. But at the same time they also gliy reciprocal ball and socket. Oecipito-atloid articulation.~lt has been sbown that there is only one more or less spheroidal condyle of the occipital bone, and a single cavity on the interior margin of tlie spinal canal of the atlas. The oecipito-atloid articulation is Iherelore a true enar- throsis, with varied and very extensive movements; a disposition which accounts for the facility with which birds can pivot their heads on the superior extremity of the vertebral stalk. Temporo-maxillary articulation. — The play of this articulation offers one peculiarity in that it causes, during the separation of the mandibles, not only the depression of the inferior, but also the elevation of the superior mandible. The arrangement which permits this movement has been aheady made known ; but yet it is dithcult to understand, be- cause there is no active agent, no proper muscle to directly eflect it. Nevertheless, the meclmnism which executes it is most simjile, and may be given in a few words: Thus, We know that the square bone, interposed betwii-u the temporal nnd maxillary bones, like the interarticular n.eniscus of mammals, is united outwardly with the jugiil bone, and inwardly with the pterygoid. We know also that the latter rests, by means of a diarthrodial facet, on the body of the sphenoid, and that it abuts against the posterior extremity of the palate bones ; while the first, the zygomaticus, is joined directly to the supermaxillary bone. The superior jaw, it is also known, is movable on the cranium, because of the flexibility of the cartilages or bony plates uniting these two portions of the head. It may then be added, that the square bone receives on its anterior process one or two small muscles which are attached to the base of the cranium, and that these bones may be pushed, or rather drawn forward, by ti.e contraction of the.airs and single muscles. The last, very few in number, are far from exhibiting the symmetry which exists in the bones of this division, as may be seen in the diaphragm. 2. In relation to the other organs, such as the bones and surrounding muscles. C. Form. — With regard to their absolute form, the muscles, again, like the bones, are classed as long, wide, and short. Long muscles. — These muscles are more particularly met with in the limbs. Provided with a principal axis, to which we may ascribe the eficct of their contraction, they present a middle portion — usually protuberant, and GENERAL CONSIDERATIONS ON THE STRIPED MUSCLES. 175 two extremities of unequal thickness ; the most voluminous, always turned upwards, is metaphorically designated the head, the other the tail. They are most frequently fusiform, sometimes conical, but rarely cylindrical, prismatic or flattened into thin bands. " There is a particular kind of long muscles which have no analogy with those of the extremities, except in their external appearance. They are those which lie below, but more particularly above, the spine. Although at the first glance they appear simple, yet they present as many distinct fasciculi as there are vertebrte. The transverse spinous [spinalis dorsi), etc., is no doubt an elongated fasciculus like the sartorious. etc., but the structure of this fasciculus has nothing in common with that of the latter muscle : it is a series of small fasciculi which have each their distinct origin and termination, and only appear as a single muscle because they are in juxta- position." — Bichat, ' Anatomie Generale.' Wide muscles. — Wide muscles are those which have two princii^al axes, and are stretched beneath the skin, or around the great cavities of the trunk, which they concur in inclosing and separating from one another. They are elliptical, quadrilateral, triangular, trapezoid, etc. Short muscles. — These are found chiefly around the short bones, or at the periphery of the articulations which are deeply buried under enormous muscular masses. Although their name indicates that their three axes offer nearly the same dimensions, yet there is most frequently one, and even two, which predominate. They may therefore be assimilated, in this respect, to the long or wide muscles. D. Direction. — Cruveilhier has justly remarked, that the direction of a muscle is one of the most important features in its history ; for it allows the determination of the angle of incidence of the muscle on its arm of the lever, the power of its action, and the nature of its uses. With regard to the direction of the muscles, we may observe : 1, The form of their principal axis; 2, The relation of this axis to the plumb- line ; 3, Its comparison with the axis of the bony levers which the muscles surround or move. a. A muscle is termed rectilinear when its principal axis is straight ; it is curvilinear, or circular, if this axis describes a cui-ve more or less marked ; it becomes inflected when it proceeds in a certain direction, and afterwards turns on a bony or cartilaginous pulley in another direction : that is to say, when its principal axis is broken into several lines. If the muscle offers two axes, it will be flat or concave, these being one or the other, or straight or curvilinear. h. With regard to the direction of the muscles to that of the plumb-line, it is either vertical, horizontal, or oblique, expressions which carry their own definition and require no explanation. c. If the direction of the muscles be compared with that of the bony levers they surround and move, it will be found that they are either parallel to these levers, or form with them angles more or less acute. The proper direction of the bones being known, it is sufficient to indicate that of the muscles to clearly establish this comparison. For instance, in saying that the majority of the muscles of the shoulder are oblique from above to below, and from before to behind, it is understood that these muscles are parallel to the scapula, and that their incidence on the humerus takes place at a right angle. E. Attachments or Insertions. — This is undoubtedly the most essential part of the study of the muscles ; for with the knowledge of their insertions 176 TEE MUSCLES. we may determine their extent and direction, and even their relations and uses. By the term attachment, fixed insertion, or origin, is meant the point of the muscle which most usually remains lixed while that organ contracts ; the attachment, movable insertion, or termination is the name given to that portion which corresponds to the lever displaced hy the muscular contraction. Muscles are frequently met with whose two insertions are alternately fixed or movable ; and in such cases care is taken not to give these insertions one or other of the designations. The fixed insertion is often confounded with that of other muscles ; the movable insertion is generally free and independent. The muscles are sometimes directly attached to the bones by the ex- tremities of their fleshy fibres ; but most frequently they are fixed to these inert levers through the medium of a tendon or an aponeurosis, whose volume is less considerable than that of the fibres. Without this latter disposition, the surface of the skeleton would not have been suflicieutly extensive to give insertion to all the external muscles. The attachment of the muscles to the bony levers is effected by a kind of fusion between the fleshy or tendinous fibres, and the periosteum. F. Relations. — The indication of the relations of the muscles completes the idea of their situation, and is of great importance in a surgical point of view. They should, therefore, be studied with all the precision possible. The muscles entertain relations either with the skin, the bones, other muscles, or with vessels and nerves. a. It is only, properly speaking, the subcutaneous muscles, such as the panniculus caruosus and the muscles of the face, which are really in im- mediate contact with the skin. The others are separated from it by the aponeurotic fascia which will be described as the appendices of the muscular system. h. The superficial muscles are only related to the bones by their ex- tremities. Those which are deeply situated are immediately applied by their bodies against the bones of the skeleton. c. The muscles are related to each other in a more or less intimate manner. Sometimes they adhere closely to one another ; and at other times they are separated by interstices filled with fat or cellular tissue, and generally traversed by vessels and nerves. d. The connections of the muscles with the latter organs sometimes assume a remarkable character ; this is when one of them accompanies, like a satellite, the vascular and nervous trunks concealed beneath its deep face. There is in this circumstance an important fact with regard to surgical anatomy. G. Nomenclature.— Before the time of Sylvius, the muscles had not received particidar names. Since the days of Galen they had been dis- tinguished by the numerical epithets oi first, second, third, aid., to iM^iciLiQ their place and their order of superposition in the regions to which tliey belonged. It is in this fashion that they are designated in the Italian work on the Anatomy of the Horse by Ruini. Sylvius was the first to give the muscles real names ; and his example being followed by succeeding anthropotomists, the nomenclature of these organs was soon completed. But no general view, no methodic spirit guided Sylvius and his successors ; it was sometimes their form, and sometimes their direction, position, uses, etc. to which the muscles owed their names. GENERAL CONSIDERATIONS ON THE STRIFE D MUSCLES. ]77 Bourgelat applied this nomenclature to the horse, but modified it in many points. Chaussier, struck by the imperfections of the nomenclature introduced into scien(^e by Sylvius, sought to substitute for it another much more philo- sophical. This anatomist gave to each muscle a name formed by two words indicating the insertions of the organ. Girard imported this ingenious idea into veterinary anatomy. Nevertheless, notwithstanding its advantages, tbis new nomenclature did not supersede the old one ; because it ceased to be correct when applied to comparative anatomy, the same muscles not having the same insertions in all the species.^ ' It is not, however, that the ancient nomenclature has more advantages in this respect thnn the new. Wliat can be more improper, for example, than the names of deltoid, splenius, solens, digastricus, etc. ? Do tiie muscles which receive these desig- nations, considered in mammals only, offer in all species the foim or the structure which justifies the employment of these names in the human species? Are the distinctive epithets of great, medium, little, etc., given to many of them, reasonably applicable in every case ? May not the same objection be urged against the majority of the names derived from their uses, comiilications. etc. ? No system of m\ological nomenclature is really philosophical, and we are of those ■who believe it to be indispensably necessary to create one ; indeed, we are inclined to think that it would be simple and easy to attain this resnlt in starting from a basis whose fixity and invariability should be well defined. And this basis is, in our opinion, already discovered ; it is the principle of coinections founded by E. Geoffroy b'aint-Hilaire in his immortal ' Philosophie Anatomique,' a principle to which modern science certainly owes its finest conquests. This is a subject which it is our intention to treat in a special work ; but we may, nevertht'less, indicate here the manner in which it presents itself to us. We are desirous that the viyolo(jicctl nomenclature should rest entirely, in the first place, on the relations of the muscles icitli the pieces of the skeleton, or loith other organs equally fixed and very important ; in the second place, on the reciprocal connections of the muscles. Such is our plan ; and it is not precisely new. for the old anatomists were often inspired with it, though unwittingly, as the jirinciple on which it is founded was to them entirely unknown; this circumstance, however, immi diately leads us to an appre- ciation of its value. For instance, what could be hajipier tl an the name of intercostals given to the muscles situated between the ribs, and their distinction into external and internal V Here we have names wliich indicate the relations of the muscles they desig- nate ivith the portions of the skeleton and the reciprocal connections of these muscles. It can also be applied in an equally rigorous manner to every species. We may also cite the snpiacostals, the intertransverse, the transverse spinous, the subscapularis, the supraspinous, the subspinous, etc., as they are found in a greater or less marked degree in identical conditions. Other muscles have received names derived in part from their situation, and in part from their volume. These names are far from being as convenient as the iirst ; as may be judged from the following examples : In the majority of vertebrate animals, there are three important muscles sitnated above and behind the pelvis, and forming the basis of the buttock ; they have beeu designated gluteals, and this name is convenient, because it designates their situation. But to distinguish them from each other, regard has been had to their volume ; so that there is a great, a medium, and a small gluteus. This is an error, however, for the volume of the muscles is subject to the greatest variations, and a voluiuinous muscle in one species may be a very small one in another, and vice versa. The muscle analogous to the gluteus maximus in Man has been described by Bourgelat as the minimus, and by Lafosse and Rigot as the medius. With regard to the gluteus medius of Man, its representative in the lower animals has been designated as the maximus by the majority of veterinary anatomists. What confusion ! And how easy it was to evade it by distinguishing these muscles, not by their volume, but by their reciprocal connections, which are the same in every species ! Is it not, indeed, more natural to substitute the names of superficia], middle, and deep gluteals, for tho? e of great, etc ? The same remark is applicable to the muscles which, in Man, cover the anterior aspect of the chest. Designated in common, and justly so, as pectorals, these muscles are wrongly distinguished into great and little; for the last, which is already an 178 THE MUSCLES. In this work we will follow the nomenclature of Bourgelat, which will however, be submitted to some change. But as the names given by Girard are, in our opinion, of some assistance to students, care will be taken to include them in the synonymy. (It only remains for me to add that Chauveau's nomenclature will be follo\ved as closely as possible. It possesses advantages which are greatly superior to that adopted by Percivall ; and as, in my opinion, the names and terms imjjorted into science should be as nearly alike in all languages as may be compatible with circumstances, in order to facilitate study, comparison, and reference, I the more readily venture to take this step. Percivall's nomenclature will, however, be added in brackets to the synonyms, as well as that of Leyh and Gurlt when occasion appears to demand it.) STEUCTURE OF THE STRIPED MUSCLES. There enter into the structure of muscles : 1, Muscular tissue, properly so-called ; 2, Conjunctival tissue in the form of delicate lamellfe, aponeuroses, or tendons ; 3, Vessels and nerves. A. Muscular Tissue. — This tissue is composed of prismatic fasciculi, which it is jiossible to divide and subdivide into several smaller and smaller fasciculi, until the muscular fibre ov primitive fasciculus is reached. The muscular fibre is a kind of irregular polyhedron, with rounded angles, and extremities terminating in a blunt point. It is sometimes straight, sometimes wrinkled, but always striped either in a longitudinal or transversal direction, or both at once. This fibre is formed by an envelope and contents. The envelope is a very delicate, structureless mem- brane of an elastic nature, named the sarcolemma or hio-hlymao-nified, its myolemma. Nuclei in greater or less number can be myolemma being so seen on its inner face. The contents are resolved into contractile fihrillce and an interstitial substance. The contractile fibrilla constitutes the primary ele- ment of striped muscle. It is a minute column whose surface, according to Eouget, exhibits the alternate prominences and depressions of the turns of a more or less fine screw ; and which, according to Bowman, is formed by a mass of small discs, named by him the sarcous elements. The interstitial substance, granular and nucleated, unites the fibrillaj in the interior of the sarcolemma and, in addition, according to Bowman's MUSCULAR FIBRE BROKEN ACROSS SHOWING J^ t^^^gj thc disCS CUteriug iutO THE UNTORN SARCOLEMMA CONNECTING •"Jl'"'' 5 O THE FRAGMENTS. "iG compositiou 01 cach nbrilJa. The aggregation of the fibrillas produces the longitudinal striation : the transverse striation is the result B, ULTIMATE FIIJRIL OF MUSCLE, accord- ing to Bowman. Muscular fibre more c, thin and transparent as to allow the ulti- mate fibrilL-c to be seen. 96. enormous muscle in the smaller Ruminants, is represented in Solipeds by two consider- able mu.SL-les, mucb more voluminous than the muscle analogous to the great pectoral. It is only necessary, in this case, to change their names into superficial and deep pectorals. GENERAL CONSIDERATIONS ON THE STRIPED MUSCLES. 179 Fi?. 97. either of the helicoid disposition of the fibrillse, or of the fusion of the sarcous elements which compose the hitter, according to the admitted opinion as to the structure of the contractile element. The muscular fibres are united parallel to each other to form secondary- fasciculi, which are surrounded by a con- junctival sheath — the perimysium. The secondary fasciculi are lai(i together to constitute more voluminous fasciculi which, in their turn, form the entire muscle. The conjunctival sheath enve- loping the muscle is named the external perimysium. B. Tendons and Aponeuroses.— The tendons are white, nacreous, round, or flattened cords fixed to the extremities of the long muscles. They are composed of fasciculi of condensed conjunctival tissue, afiectiug a parallel direction, and united to one another by connective sheaths. The aponeuroses belong almost ex- clusively to the wide muscles ; they are formed of several planes of parallel fibres which are not intercrossed in their middle part ; at their superficies, how- ever, the fibrous fasciculi are matted toge- ther in a more or less inextricable manner. It is very interesting to study the mode of union of the muscular fibres with the tissue of the aponeuroses and tendons, as well as the reciprocal rela- tions of these two parts. The muscular fibre may be found passing in the same direction as the tendon, or it may fall upon the latter obliquely. In both cases there is no insensible transition between the muscular fibre and the fasciculus of the fibrous tissue ; on the contrary, the contractile fibre terminates by a rounded extremity, which is buried in a corresponding depression in the tendon or aponeurosis. The union of the muscular with the fibrous tissue is very intimate ; when the muscles are submitted to a degree of traction sufficient to cause a rupture, this never happens at the point of union. The tendons commence sometimes by a hollow cone, which receives on its internal face the insertions of its muscular fibres ; and sometimes by a thin point, often divided, wdiich is plunged into the substance of the muscle. It is worthy of remark that a muscle provided with two tendons shows the first-named arrangement at one of its extremities, and the other at its oppo- site extremity ; so that all the fibres which comjiose the muscle offer nearly the same length, those which leave the summit of the internal tendon being fixed to the bottom of the hollow cone formed by the second tendon, and so on reciprocally. The muscular fibres which are continued by the fibrous fasciculi may be divergent or parallel. In the first case — the diaphragm, for example — the connective fibres run in the same direction as the muscular fil>res. In the second case, several arrangements may be observed : TRANSVERSE SECTION OF FROZEN MUSCLE, MAGNIFIED 400 DIAMETERS. N, Nerve ; M, Muscular fibre, surrounded by portions of six others. — a, Nucleus of the nerve sheath ; b, Nucleus of the sarcolemma ; c, Section of nucleus of terminal plate of nerve ; d, Transverse section of terminal plate; surrounded by granular material ; e, Transverse section of muscle nuclei ; /, Fine fat drops. The angular dark particles are sections of sarcous elements : the clear intervening spaces represent the fluid isotropal part of the muscle substance. 180 THE MUSCLES. Fi?. 98. 1. Tendons may pass in the same direction as the muscular fibres. This is the most simple manner. But the muscle may be divided into two bodies or bellies by a middle tendon ; it is then called a digastric muscle. 2. Muscular fasciculi, passing altogether from the same side to become anited into a tendinous cord, constitute a semi-penniform muscle. 3. Muscular fasciculi may be implanted to right and left of the tendon, and form a pennated or penniform muscle. " This arrangement of fibres demonstrates that the length of the muscle, the length of its belly, and the length of its muscular fibres, should be care- fully distinguished. The first term is applicable to the whole of the muscle, the tendon included ; the second, to the fleshy body of the muscle, with the exception of the tendon ; the third, to the muscidar fasciculi constituting this fleshy body : the latter idea is the most important, for it alone indicates the amount of conti-action a muscle is sus- ceptible of, and consequently the possible ex- tent of movement it is capable of effecting." — Beaunis and Bouchard. C. Vessels and Nerves. — -The muscular tissue receives much blood ; the fibrous tissue very little. The arteries are large, numerous, and each is acccompanied by two veins. The capillary vessels anastomose in such a manner as to form rectangular meshes, whose greatest diameter is directed towards the length of the muscle. The lymphatic vessels of the muscles are few ; they sometimes j^enetrate their interior in following the capillaries ; at other times they remain on the surface, in the external perimysium. The exist- ence of lymjihatics has not yet been demonstrated in tendons, aponeu- roses, or synovial membranes. The nerves emanate from the cerebro-spinal centre. At their terminal extremity they offer a small enlargement, called by Rouget the terminal motor plate, and by Doyere and Kiihne the ner- vous colline (hillock). It is ad- mitted that the motor tube traverses the sarcolemma, losing its enve- lope ; and tliat the substance of the cylinder is spread over the surface of the muscular fibrillfe to form the distribution op capillaries In muscle. Fi?. 99. PORTION OF AN ELEMENTARY MUSCULAR FIBRE, WITH FOUR DARK-BORDERED FIBRES (a) CROSS- ING ITS SURFACE ; after Beale. b, Capillary blood-vessel, with fine nerve-fibres ; motor plate or nervous colline, a few only of the transverse markings of the muscle are represented ; c, Two of the dark- bordered nerve-fibres passing over the ele- mentary fibre to be distributed to adjacent fibres. This arrangement, in which a dark- bordered nerve-fibre, distributed to muscle, divides into branches, one of which passes to a vessel, while the other ramifies upon a muscle, is frequent. Magnified 700 diameters. PHTSICO-CHEMICAL PROPERTIES OP STRIPED MUSCLES. Muscles arc soft organs, re- markable for their more or loss deep-red colour, which varies with the species, and even in these with the age and health of the animals. GENERAL CONSIDERATIONS ON TEE STRIFED MUSCLES. 181 By desiccation, muscles become hard and bro'wn ; by repeated wasliing tliey assume a straw-yellow tint. Muscles are extensible and elastic ; they are also tenacious, and their tenacity is more marked during life than after death. It has been remarked that the juice impregnating the muscular tissue is distinguished from the serum of the blood by an acid reaction. (The iluid or " muscle plasma " obtained by pressing flesh, is either neutral or slightly alkaline. It soon coagulates and separates into two portions — a semi-solid portion, " myosin," and the fluid serum that at ordinary temi^eratures quickly acquires an acid reaction.) It holds in solution a variable quantity of albumen, casein, fat, a little creatine, creatinine, and a somewhat large proportion of lactic acid. The solid substance of the muscle may be partly transformed into gelatine by boiling in water ; but its largest portion is a nitrogenous substance, soluble in dilute hydrochloric acid, called "' syntonine," or muscular fibrine ; it differs but little from the fibrine of the blood. PHYSIOLOGICAL PROPEETIES OF THE STRIPED MUSCLES. In this paragraph will only be discussed the development of the muscles, muscular contractility, and the part the muscles assume in locomotion. A, Development of the Muscles. — A muscle is derived from a mass of embryonic cells. Each cell becomes considerably elongated, and its nucleus becomes multiple, to constitute a muscular fibre. The membrane of the cell, enormously developed, forms the sarcolemma, while the contents of the cell, becoming more dense, divide longitudinally and give rise to the contractile fibrillte. Lastly, when the muscles are formed, they grow by the augmenta- tion in length and thickness of the primary fasciculi or muscular fibres. B. Muscular Contractibility. — Muscles possess the property of con- tracting under the influence of a natural or artificial stimulus. Muscular contraction is the phenomenon resulting from the operation of this property. Muscles in a state of contraction are the seat of physical and chemical phenomena ; they change their form and consistency, and become the theatre of a relatively abundant production of carbonic acid, creatinine, and inosinic acid. During contraction, it has been remarked that the muscular fibres contract by increasing in volume, like an india-rubber tube left to itself after being extended : the zig-zag doubling mentioned by Prevost and Dxmias has not been observed. But these physical and chemical modifications, important as they are in Fig. 100. MUSCCXAR FIBRE IN A STATE OF CONTRACTION IN THE CENTRE; THE STRI.IT APPROXIMATED ; THE BREADTH OF THE FIBRE INCREASED ; AND THE MYO- LEiniA RAISED IN VESICLES ON ITS SURFACE. a physiological point of view, cannot longer be dwelt upon here. It is parti- cularly important to speak of muscular contraction. A muscle that contracts becomes shortened ; its two extremities approach each other if they are free ; or one draws near the other if the latter is fixed 15 182 THE MUSCLES. to an immovable point. If tlie extremities of a muscle are attached to two movable levers, its contraction will bring about the displacement of one or other of these ; from this a movement is produced. The degree of shortening of a muscle varies, according to its being entirely free, or having a resistance to overcome. The mean limit of this shortening is about one-fourth the length of the muscular fibres ; from tliis it will be understood that the movement produced by the contraction will be in proportion to the length of the fibres ; though in this appreciation it will be necessary to keep in mind the density and energy of the fibre, as well as the intensity of the contractile stimulant. As each fibre represents a force independent in its action, it results that we may judge of the power of a muscle by the number of its fibres, or its volume. Muscles are often aided in their action by mechanical conditions : such as the disposition of the levers on which they act, the direction of the muscular fibres in connection with these levers, and, lastly, by the presence of lamellae or elastic cords. C. Uses of Muscles. — There are flexor, extensor, abductor, adductor, rotator, and other muscles, for all the movements of which the articulations are the centre. To determine the functions or uses of the muscle, it is sufficient to know their insertions, and the mode in which the bones furnishing these insertions articulate with each other. The result of muscular contraction, being influenced by the form of their principal axis, and the length and direction of their levers, it is necessary to briefly examine these two points ; 1. The immediate effect of the contraction of rectilinear muscles is the ap- proximation of the bones to which they are attached. This approximation is usually brought about by the displacement of a single ray : that which receives the movable insertion of the muscle. Sometimes, however, the two rays move simultaneously, or they are alternately fixed and movable. The first result produced by a curvilinear muscle is the straightening of its component fibres ; after which it may act on the bony levers as do the rectilinear muscles, if its contractile power be not entirely expended. When a muscle is quite circular, its only action is to contract the opening it circum- scribes. With regard to the inflected muscles, their action can only be estimated from their point of inflexion ; they operate as if this point represented their origin or fixed insertion. 2. The muscular powers are submitted to the statical and dynamical laws which govern the theory of levers , for the bony rays are only levers moved by the muscles. In the locomotory apparatus we find the three kinds of lever recognised by physicists. Thus the head, extended by the great complexus muscle, represents an interflxed, or lever of the first class ; the foot, extended by the gastrocnemii muscles, offers an example of the interresisting, or second kind, when this member remains fixed on the ground ; lastly, the lower jaw raised towards the upper by the masseter muscle, forms an interpuissant or third kind. It is worthy of remark that the arm of resistance in the bony levers is always extremely long ; a circumstance which favours speed and the extent of movement at the expense of power. On the other hand, muscles are rarely perpendicular to the arm of their GEXEBAL COXSIDEBATIOXS ON TEE STEEPED MUSCLES. 183 levers, at least at the commencement of their action ; another ciroumstance which again diminishes their energy. APPENDAGES OF THE MTSCLES. These are : 1, The enveloping or contentive aponeuroses ; 2, The serous or mucous bursje ; 3, The tendinous and synovial sheaths. A. CoxTE>-TivE Aponeuroses. — These are layers of white fibrous tissue, which envelop, in common, all the muscles 6f one or several adjoining regions, principally those of the inferior rays of the limbs, where they con- stitute a kind of hollow cylinder. These aponeuroses are formed by very resisting interwoven fibres, which are attached to the bones at nvmierous points. At their periphery they receive the insertion of one or several muscles, which keep them more or less tense. Their external face responds to a thin fibro-cellular layer that separates them from the skin. The internal face sends lamellar prolong- ations between the muscles, which are destined to isolate these organs in special sheaths. The aponeuroses maintain the muscles in their position, and sustain them during their contraction. B. Seeocs Buks^. — The serous or mucous bursas are small cavities, filled with a serous fluid, which are met with at those points where the muscles glide over resisting surfaces. They are generally orbicular or rounded, and their interior is often divided by fibrous bands. Their walls are formed by slightly condensed conjunctival tissue, and may be lined by a pavement epithelium ; in which case it is believed that the serous bursa is produced by the simple dilatation of one of the con- junctival meshes. C. TENDixors Sheaths axd Synovial Membbaxes. — Tendinous sheaths is the name given to the half-bony, half-fibrous, sometimes exclusively fibrous, gliding grooves into which the tendons pass when they are inflected to change their direction. The tendinous synodal membranes are serous membranes lining the ten- dinous sheaths and covering the tendons at the points where these tn^o parts correspond. They secrete a synovial fluid quite like that of the articulations. When they almost completely envelop the tendon, and are afterwards carried to the walls of the sheath, they are termed vaginal. Their walls are composed of: 1, A very fine conjunctival membrane, con- founded by its external face with the tendinous sheath, by the other face with the tendon ; 2, A simple layer composed of pavement epithelium, extended over the whole or a part of the internal face of the conjunctival membrane. manner op studying the muscles. A. Classification. — To facilitate the study of the muscles, two methods may be employed in grouping them. The first consists in classifying them according to their uses ; describing, for example, all the flexors, extensors, etc., of the same region. In the second method, the uses of the muscles are not taken into account, their relations only being considered; and they are divided into groups or regions, which comprise all the muscles situated around a bony ray. The latter is the method now adopted, because it is the most convenient, useful, and rational. (Leyh describes the muscles by layers, or according to their situation, 184 THE MUSCLES. which, he asserts, facilitates the study of anatomy in a surgical point of view}. B. Peepaeation. — We will limit ourselves to some general remarks on the following points : Choice of a subject. — If there is for disposal a certain number of subjects from among which it is possible to make a selection, the preference should be given to those thiit have the muscular system best developed ; not that large, soft, l}'mphatic liorses witli enormous masses of muscle should be chosen, for tliese animals are always less convenient than small or middle-sized, well-bred horses. Asses and mules, when very emaciated, answer well for tlie preparation of the muscles. Position of the suhject. — It is necessary to place the subject, immediately after death, in a convenient jDosition, in order that the cadaveric rigidity may set in while it is in tliat attitude. Without this precaution, the various parts of the body may assume an incon- venient shape or direction, and all attempts to amend them will prove almost unavailing, particularly in the larger animals. Three principal positions may be given to subjects : 1. The animal is in the first position when it is placed on its back, the four ex- tremities in the air, and maintained in that posture by means of long cords passed round the pasterns and fixed to the movable rings which terminate the extremity of the fom- bars of the wheeled-table on which the subject is laid. The head should be beyond the end of the table and rest upon a stool. The animal should always be placed in such a manner that the head be opjiosite the forepart of the table, so tliat the movements of the pole or shaft be not impeded during the displacement of the apparatus. In order that the neck be not twisted to the right or left, in attaching the fore-limbs the siiliject should be raised so that the withers rest lightly on the table. According to the bulk of the animal and the length uf the bars, the ropes should be passed around either the pasterns, above the fetlocks, or even above the knees. 2. To place the animal iu the second 'position, it is turned on the belly, the two thighs flexed, the extremities carried beyond the table, and the head fixed between two bars by means of a rope passed under the zygomatic arches. 3. The subject is in the third position wlien it rests on its side. Rules to be observed during the preparation.— \. By no means, if possible, remove the skin from the regions to be dissected until quite ready to begin the dissection. I f this is impossible, then take the precauti »n of enveloping these regions in damp cloths, or in the animal's skin, to prevent desiccation of tlie aponeuroses and tlie superficial muscles. 2. To dissect a muscle, it is necessary to remove the aponeuroses or the other muscles which cover it, the cellular tissue enveloping it, and the fat, glands, vessels, and nerves lodged in the neighbouring interstices. The aponeuroses should be removed in shreds by making tliem very tense with the forceps, but without raising them, and causing the blade of tlie scalpel to glide between the fibrous and muscular surfaces, keeping it always parallel to these two planes. The covering muscles slinuld not be entirely excised, but ought to be cut through the middle, across their fibres, and the ends thrown back ; in this way it is always possible to replace a muscle by bringing the two portions together ; the study of its relations is then much more easy. The cellular tissue is got rid of by removing it with the forceps, and carrying the edge of the scalpel in the re-entering angle formed by the cellular layer and the surface of the muscle. This method also suffices for removing aponeiuoses when they are slightly adherent to the muscular fibres. But when they give attachment to these by their under face, as may be noticed in the external scapular aponeurosis, it is necessary to have recourse to the method indicated above. To remove fat, glands, etc., scissors will be found very advantageous. Order to follow in preparing all the muscles of the same subject, and to derive most advantage therefrom. — 1. Place the subject in the first position, and commence by study- ing the muscles of the inferior abdominal region. Then excise them, leaving the posti'rior extremity of the great pectoral muscle, the prepubic tendon, and the crural arch intact. The abdominal cavity having been emptied of the viscera it contnins, dissect and study successively the diai)hragm, the internal crural region, except the deep muscles, the Bublumbar region, the femoral and posterior crural regions, the superficial muscles of the inferior cervical region, and the pectoral region. 2. After detaching for future use one of the anterior limbs, the animal is plnced in the second positinn, and one after another may be dissected the muscles of the ear. those of the superior cervical region, the croup and costal regions, except the triangular muscle, and the spinal region of the back and loina. GENERAL CONSIDERATIONS ON THE STRIPED MUSCLES. 185 3. The regions of the anterior limb may be prepared at the same time, or immediately afterwards. 4. Separate the two posterior limbs by sawing the femurs through their middle, and proceed to the dissection of the muscles of the posterior leg and foot. 5. By means of another application of the saw across the middle of the loins, the pelvis is completely isolated for the preparatum of the coccygeal muscles, and the deep muscles of the internal crural region, nearly as they are represented in figures 9U and 131. 6. The animal being placed on its side, the pectoral cavity is opened by sawing through the ribs near their extremities ; on the two particular portions thus obtained may be studied, in one part, the triangularis of the sternum, and in the other the deep muscles of the inftrior cervical region, including the long muscle of the neck and the anterior and lateral straight muscles of the head. 7. Lastly, the head is disarticulated and the muscles of this region are prepared The subject may afterwards serve for the study of nearly all tlie articulations. Freser rat ion of the muscles. — The muscles maybe preserved by immersing them in appropriate fluids, and the muscular preparations by drying them. A large number of liquids preserve muscles from putrefaction. We may mention alcohol ; a mixture of alcohol and spirits of turpentine ; alcohol, water, and chloroform ; a solution of siUphate of iron, bichloride of mercury, or arsenious acid. The best preservative fluid, however, is nitric acid diluted with water, in the proportion of one of the former to three of the latter. The acid hardens the muscles and softens the conjunctival tissue ; this allows all the interstices to be completely cleared out, and even permits the primitive muscular fasciculi which have been concealed by the white tissues to be exposed. Desiccation, after immersion in a bath of arsenious acid or sulphate of iron, causes the muscles to become hardened and deformed. It is therefore a bad procedure. (A careful dissection of the muscles, with regard to their origin, insertion, action, and relations, is of infinite importance to the student of human anatomy ; to the Veterinary Student it is no less important, and more particularly with reference to the muscles of the limbs. A correct knowledge of their situation, attachments, and functions is often the only guide the Veterinary Surgeon can rely upon in the diagnosis of those api^arently obscure cases of lameness which are of such comparatively frequent occurence. In the words of Mr. Henry Gray, we may repeat that " an accurate knowledge of the points of attachment of the muscles is of great importance in the determination of their action. By a knowledge of the action of the muscles, the surgeon is able at once to explain the causes of displacement in the various forms of fracture, or the causes which produce distortion in the various forms of deformities, and, consequently, to adopt appropriate treatment in each case. The relations also of some of the muscles, especially those in immediate apposition with the larger bloodvessels, and the surface markings* they pro- duce, should be especially remembered, as they form most useful guides to the surgeon in the application of a ligatm-e to these vessels." — ' Anatomy, Descriptive and Surgical.' An accurate knowledge of the muscular system is also of great service to the Veterinary Surgeon in estimating the value to be placed upon the external conformation presented by animals intended for different kinds of labour. " In dissecting," says Mr. Holden, " there are four principal objects to be constantly borne in mind by the student : 1st, The impression on the memory of those facts of general anatomy taught in the lectures. 2nd, The study of those parts of the body more especially concerned in surgical atfections and operations. 3rd, The education of the sense of touch, and of the hand in the use of instruments ; and 4th, The education of the eye in the knowledge of the several tissues of the body, in various positions, and varying circumstances. . . . The education of the eye is a gradual and tedious process, but one which is pretty certain to be satisfactorily accomplished if the student do but use his hands properly, and therefore a few words on the manual part of dissection may not be out of place. " First, as to the instruments requisite for dissection. A case, containing six or eight scalpels, two pairs of scissors, a pair of dissecting forceps, a set of chain-hooks, a blow- pipe, and a probe, will enable the student to make all requisite dissections, supposing that he is allowed the use of a saw and chisel in the dissecting-room. Great variety exists in dissecting-cases, both as to form and expense, but so long as the instruments themselves are strong and good, the simpler the case the better. Scalpels for dissection are made of two principal shapes ; in one, the edge is bevelled to the point, the back being straight; in the other, both back and edge are bevelled to a point midway between the two. The latter form is preferable for most purposes. The blade should not be more than an inch and a half long, and never double edged ; but the material of which the handle is constructed is a matter of indifferencer 186 THE MUSCLES. " For all ordinary dissection, it will be found most convenient to hold the scalpel like a pen; but for cleaning the fascia off muscles, and following out small nerves, it is better to hold it reversed, so that the hack of the knife may be against the tissue which is to be preserved. In making the first incision through the skin of a limb, or in any other position where a long incision is required, the knife may, with advantage, be held under the hand, by which the wrist has more play, and the student has the opportunity of practising a mode of holding the knife, which he will find very useful when operating on the living body. "The forceps should be broad at the extremities and coarsely serrated, so that it may retain a firm hold on small portions of tissue. It is very important that the forceps should not be too strong in the spring, for in that case it becomes so fatiguing to the hand that it is impossible to continue its use for any length of time. The forceps should be held lightly between the thumb and the first and second fingers of the left hand, which may be steadied by resting the little finger on a neighbouring part. " The chain-hooks should be strong, and bent in the direction of the thickness and not of the breadth of the steel, as is sometimes done. These latter are very inferior, being liable to be unbent imder any considerable strain. Care should be taken that the chains are firmly linked, and that the central ring is sufficiently stout to bear any force that may be applied. The scissors should be large and strong, and it will be found advantageous to have one curved pair, which is very useful in preparing the ligaments. " The student will do well to bear in mind that he will probably be called upon in ftfter life to operate on the living body, the only true preparation for which is careful dissection; he should therefore, as "far as possible, conduct all his dissections as methodically, and with as much care, as if operating on tiie living body. " The student should bear in mind that his manual lalx)ur is only a part of his duty, and will be thrown away, unless he at the same time study the description of the part upon which he is engaged ; he should not, therefore, carry the dissection further than he can learn the description on the same day, and at the subject, and should, if possible, re-peruse the description in the evening, and always on the next morning, before carrying the dissection any further.") CHAPTER II. . THE MUSCLES OF MAMMALIA. Aktiole I. — Muscles of the Trunk. SUBCUTANEOUS EEGION. This only comprises a single muscle, the fleshy panniculus (pannicidus carnosus), destined to move the skin covering the trunk. Strictly si^eaking, however, we may describe as dermal muscles all those which are attached to the inner surface of the superficial integument — the muscles of the face, for example; Fleshy Panniculus. Preparation. — Place the animal on its side, and carefully remove the skin, allowing the cuticular muscle to remain on the subjacent muscles. Situation — Form — Extent. — Situated on the inner surface of the skin cover- ing the sides of the thorax and abdomen, the fleshy panniculus is an immense broad muscle, irregularly triangular in shape, thin at its borders, and thicker in the middle than elsewhere. The upper border corresponds to a curved line, convex superiorly, and extending obliquely from the flank to the withers. The inferior border is carried horizontally from the flank to the j)osterior border of the olecranian mass of muscles, passing along the upper margin of the great pectoral muscle, which it covers, and to which it adheres somewhat closely. The MUSCLES OF THE TRUNK. 187 anterior border descends from tlie superior extremity of the shoulder on to the muscles of the fore-ai-m. Structure — Attachments. — The fleshy fibres entering into the composition of this muscle are dii'ected forward for its posterior two-thirds ; but on arriving on the shoulder they gradually straighten and become vertical. They are continued, on the margins of the muscle, by aponem-oses which attach it either to the internal surface of the skin or to the fibrous fasciaj of the superficial muscles. This muscle has, besides, a very remarkable insertion into the hiunerus, which was noticed by G. Cuvier, in his 'Lecons d' Anatomic Comparee,' and which appears to have been omitted, at least so far as Solipeds are concerned, in every treatise on Veterinary Anatomy. The following is what we have often observed in this respect : — On reaching the posterior border of the ulnar mass of muscles, the panniculus divides into two superposed layers : one, superficial, is carried to the muscles of the anterior member ; the other, deep, soon terminates by an aponeurosis which is united to the great pectoral muscle, and is bordered at its upper margin by a nacrous aponeurotic band, which penetrates between the thorax and the muscles of the arm to be fixed to the small trochanter. JRelations. — By its superficial face, , with the skin, to which it closely adheres ; by its deep face, with the great dorsal, the dorsal portion of the trapezius, the abdominal tunic, the great oblique muscle of the abdomen, the great serratus, some external intercostals, the spur vein, and the superficial muscles of the shoulder and arm. Action. — The animal, in contracting this muscle, shakes the whole of the cutaneous integument which covers it : thus preventing insects from alighting on the surface of the body, or tormenting by their bites or stings. In the Bog, the panniculus camosus is prolonged over the croup, and is united along the dorso-lumbar spine to that of the opposite side. It is very developed in the Cat. CERVICAL REGION. This region comprises all the muscles grouped around the cervical vertebrse — muscles which are conspicuous by their volume and the important part they play in the animal economy. There are described a superior and an inferior cervical. A. Superior Cervical, or Spinal Begton of the Neck. This includes seventeen pairs of muscles, which are : the cervical portion of the trapezius^ rhomhoideus, amjularis of the scapula, splenius, great complexus, small complexus, transverse spinous of the neck, the six intertransverse muscles of the neck, great oblique muscle of the head, great posterior rectus, and small pos- terior rectus. These form fom- superposed layers on each side of the cervical ligament, and occupy the triangular space circumscribed by the upper border of that ligament, the transverse processes of the vertebrae of the neck, and the spinous process of the second dorsal vertebra. Freparation.—'Place the subject in the second position and dissect in succession the four layers of the region. To study the first layer, which is formed by the cervical portion of the trapezius, remove the skin, cellular tissue, and the fibrous fascia covering that muscle (See fig. 102). The prej aration and study of the second layer, composed of the rhomboideus. angtxlaiis. and splenius. is Ciirried out in two stages. In the first, the trapeziiun and the mastoido-hutueralis is removed, leaving only the cer\ical insertions For the description of this muscle, see the Spinal Kegion of the back and loins. 188 THE MUSCLES. of the latter muscle ; then the limb is removed by sawing through the scapula beneath the insertions of tlie angularis and great serrated muscles, as in figure 105. But as neither the cervical or dorsal insertions of the sjilenius are exposed, it is necessary to proceed to the second part of the operation by removing the rhomboideus, angularis, and the superior extremity of the shoulder. To prepare the third layer, which com- prises the great and small complexus, it is sufficient to excise the splenius, in following the direction of the neck, and to turn upwards and downwards the two portions of the muscle (^See fig. 100). Lastly, the deep layer — the transverse spinous, intertransverse, oblique, and jDosterior straight muscles, as well as the cervical ligament — is exposed by removing the two complexus and the ilio-spiualis muscles (See fig. 104). 1. Bhomhoideus. (Figs. 101, 6; 104, 1, 2.) Synonyms. — Described by Bourgelat as two muscles, the proper elevator of the shoulder and the rhomboideus, these were termed by Girard the cervico-subscapularis and dorso-subscapularia. (This is the rhomboideus longus and brevis of Percivall, and the dorso-scapularis and cervico-subscapularis of Leyh.) Form — Situation — Direction. — This muscle has the form of a very elongated triangle, and is situated at the inner as2:)ect of the cervical trapezius and the scapular cartilage, beneath the cervical ligament, whose direction it follows. Fig. 101. LATERAL VIEW OF THE NECK; SUPERFICIAL MUSCLES. 1, 1, Parotid gland; 2, Sterno-maxillaris and, 14, Its junction with its fellow of the opposite side; 3, 4, ]\Iastoido-humeralis, or levator humeri; 5, Splenius; 6, Ehoniboideus ; 7, Funicular portion of the cervical ligament, or ligamentum colli; 8, Angularis of the scapula; 9, Supra-, or antea-spinatus ; 10, Trapezius; 11, Infra-, or postea-spinatus ; 12, Jugular vein; 13, Subscapulo-hyoideus ; 15, Trachea. Structure — Attachments. — It is composed of thick, fleshy fasciculi, the anterior of which are oblique downwards and backwards, the posterior passing directly downwards. These fasciculi are fixed by tlieir superior extremity to the funicular portion of the cervical ligament and the summits of the spinous processes of the four or five dorsal vertebra3 succeeding the MUSCLES OF THE TBUXK. 189 first — fixed insertion ; by their inferior extremity, to the inner aspect of the scapular cartilage, where the anterior fasciculi are confounded with those of the angularis. Relations. — Covered by the cervical portion of the trapezius, the scapular cartilage, and the aponeurosis of the great dorsal miiscle, the rhomboideus covers the sphenius, which is excavated near its superior border for its reception, as well as the aponeurosis of the anterior small serrated muscle thi'ough the medium of a yellow elastic lamina. Action. — It draws the shoulder upwards and forwards. 2. Anguhns Muscle of the Scajmla. (Figs. 102, 4; 105, 3.) Synonyms. — Trachelo-subscapularis — Girard. Portion of the serratus magnua — Bourgelat. Elevator of tlie scapula — Cuvier. (Anterior portion of the serratus magnus of PercivaU. The levator anguli scapulis of Man.) Situation — Form — Structure. — This is a very strong muscle, situated in front of the shoulder, triangular, flattened on both sides, thin at its superior border, thick behind and below, and almost entirely fleshy. Attachments. — It takes its origin from the transverse processes of the five last cervical vertebrte by five distinct portions, which are directed towards the scapula in converging towards each other, and soon join to form a single muscular body, which is inserted into the internal face of the scapula, on its anterior triangular surface. Eekitions. — This mtiscle is confounded at its inferior border with the serratus magnus. It is covered by the cervical trapezius, the mastoido- humeralis, and the small pectoral muscle. It covers the splenius, the in- ferior branch of the ilio-spinalis, and the common intercostal muscle. Near its junction with the serratus magnus, its internal face adheres very closely to the transverse processes of the three first dorsal vertebrte. Action. — It draws forward the superior extremity of the scapula, while the humeral angle is carried backwards. If the shoulder becomes the fi-sed point, it can act in the extension or lateral inclination of the neck. 3. S})lenius. (Figs. 105, 4, 5 ; 106, 5.) Synonyms. — Cervico-trachelian — Girard. Form — Situation. — A considerable muscle, flattened on both sides, triangular, and comprised between the cord of the cervical ligament, the inferior branch of the ilio-spinalis muscle, and the transverse processes of the four first cervical ribs. Structure. — The splenius, aponeurotic only at its periphery, is composed of thick fleshy fasciculi which are all directed forwards and upwards, to reach the head and the first cervical vertebrje. Attachments. — It is fixed, by its posterior border, to the lip of the cervical ligament and the summits of the spinous processes of the first dorsal vertebrae, by means of an aponeurosis which is continuous behind with that of the small anterior serratus, and confounded, by its inner surface, with that of the great complexus. Its anterior border is cut into four or five digitations which constitute the movable insertions of the muscle : a. The superior digitation is the widest and thinnest, and terminates in an aponeurosis (Fig. 105, 5), which unites it to the mastoid tendon of the small complexus, and passes to the mastoid crest, b. The second joins a very strong tendon common to the splenius, the small complexus, and the mastoido-hmneralis, which tendon is attached to the transverse process of 190 THE MUSCLES. the atlas (Fig. 105, 9). c, d. The two or three others are dii-ectly inserted into the transverse processes of the third, foui'th, and fifth cervical vertebrsB. Belations. — The splenius is related, outwardly, to the rhoniboideus, the angularis, cervical trapezius, and mastoido-humeralis ; inwardly, to the two complexus and two oblique muscles of the head ; by its inferior border, to the superior margin of the inferior branch of the ilio-spinalis (longissimus dorsi). Action.— li extends the head and neck in inclining them to one side. If the two act in concert, the extension is direct. Fig. 102. SUPERFICIAL MUSCLES OF THE NECK AND SPINAL REGION OF THE RACK AND LOINS. 1, Dorsal trapezius; 2, Great dorsal; 3, Cervical trapezius; 4, Levator anguli scapulae; 5, Spleaius; 6, Anterior, or superficial portion of the mastoido-hume- ralis ; 7, Its humeral insertion; 7' Its mastoid insertion ; 8, The thin aponeurosis uniting this insertion to the sterno-maxillary muscle; 8', Posterior portion of the mastoido-humeralis ; 9, Its inferior aponeurosis inserted into the interstice of the long abductor of the arm ; 10, Sterno-maxillaris ; 11, Subscapulo-hyoideus; 12, Porlion of the dermal muscle of the neck; 13, Portion of the great extensor of the fore-arm; 14, Posterior belly of the long abductor of the arm; 15, Great pectoi'al muscle. MUSCLES OF THE TRUNK. 191 4. The Ch-eat Complexus. (Fig. 106, 6, 7.) Synonyms. — Dorso-occipitalis — Girard. (Complexus major — Percivall.') Situation — Direction — Form. — A powerful muscle, included between the internal surface of the splenius and the cervical ligament, whose oblique direction forwards and upwards it follows ; it is triangular, flattened on both sides, elongated from before to behind, and divided longitudinally into two unequal portions — a posterior and anterior. Structure. — The posterior portion (Fig. 106, 6), the most considerable, is aponeurotic at its origin, intersected by linear fibrous bands which obliquely cross its direction, and is formed of fleshy fibres directed forwards. Those which compose the anterior portion (Fig. 106, 7), intermixed with some tendinous fasciculi, are directed upwards, and appear to be inserted into the preceding. It is this difference in the direction of the fibres of the two portions of the great complexus which allows them to be distinguished from one another ; the two being only really separated by an interstice near their inferior extremity. Superiorly, the muscle is constricted to form the summit of the elongated triangle it represents, and terminates by a strong tendon. Fixed insertions. — The posterior portion derives its origin : 1, From the summit of the spinous processes of the first dorsal vertebrae, by a strong aponeurosis which is confounded with that of the splenius and the anterior small serratus ; 2, From the transverse processes of the four or five dorsal vertebrae which follow the second, by as many aponeurotic digitations united by their margins. The anterior portion is fixed : 1, To the transverse processes of the two first dorsal vertebra, by two tendinous digitations analogous to those of the posterior portion ; 2, To the articular tubercles of the cervical vertebrae, by the inferior extremity of its fleshy fasciculi. Movable insertion. — The movable insertion of the great complexus is effected through its superior tendon, which is fixed to the posterior face of the occipital protuberance, beside the cervical tuberosity. Relations. — It is covered by the splenius and the small complexus. It covers the cervical ligament, the upper branch of the ilio-spinalis, the trans- verse spinous of the neck, and the oblique and posterior straight muscles of the head. The aponeurotic digitations which attach it to the dorsal trans- verse processes are comprised between the two branches of the ilio-spinalis. The interstice which separates, inferiorly, the two portions of the muscle affords a passage to the superior cervical artery. Action. — It is a powerful extensor of the head. 5. Small Complexus. (Figs. 105, 6, 7 ; 106, 8, 9.) Synonyms. — Dorso-mastoideus— (remrd. (JTrachelo-mastoideus — Percivall.') Situation — Direction. — Situated at the internal face of the splenius, in an oblique direction upwards and forwards, this muscle lies along the anterior border of the great complexus, and follows the inferior branch of the ilio- si)inalis, which it appears to continue to the head. Form — Structure. — The small complexus is a long muscle, divided into two fleshy, fusiform, and parallel portions — anterior and posterior — which we might strictly consider as two distinct muscles. Both are composed of successive fasciculi, which become longer as they are superficial, and terminate by a tendon at their superior extremity. The tendon of the posterior muscle is flattened, and joins the mastoid aponeurosis of the 192 TEE MUSCLES. splenius. That of the anterior muscle is funicular, and receives, before its insertion, a digitation from the sj)lenius (fig. 106, 10), and another from the mastoido-humeralis (fig. 106). Fixed attachments. — The two fleshy portions of the small complexus have their fixed insertion in common with the anterior portion of the great com- plexus : 1, On the transverse processes of the two first dorsal vertebrte, through the medium of aponeurotic digitations which serve as an origin to the last-named muscle ; 2, On the articular tubercles of the cervical vertebrae, by the inferior extremity of their component fasciculi. Movable attachments. — The terminal tendon of the posterior muscle passes to the mastoid process of the temporal bone. The anterior passes to the transverse process of the atlas. Fis. 103. LATERAL VIEW OF THE NECK; MIDDLE LAYER OF MUSCLES. 1, Funicular portion of the cei-vical ligament ; 2, Complexus major ; 3, Complexus minor; 4, Rectus capitis posticus major; 5, Rectus capitis posticus minor; 6, Stylo-maxillaris ; 7, Carotid artery ; 8, Pneumogastric nerve and branch of sympathetic; 9, Longus colli; 10, Recurrent nerve; 11, Inferior scalenus; 12, Spinalis, or trausversalis colli ; 13, Incision through rhomboideus and trapezius ; 14, Trachea. Belations. — Outwardly, with the splenius; inwardly, with the great eomplexus and the oblique muscles of the head. The tendon of the posterior fleshy portion is covered by the mastoid aponeurosis of the mastoido- humeralis. Action. — The small complexus inclines to its side the head and upper part of the neck. It also acts as an extensor of the head.* ' Bourgelat has described, by the name of long transversal, the anterior portion of this miiscle, and attached it to the posterior portion of the splenius. We do not know where to find one or other of these in Ihe crude description of Lafosse and Vitet. Girard considered them, like ourselves, as a single muscle, which he designates tlie dorso- mastoideus. Rigot has united them with the anterior portion of the great complexus and the foremost fasciculi of the short transverse muscle (inferior branch of the ilio-spinalis), to make his long transversal; in doing so he has only complicated their description. These two muscular fasciculi, being, to oiu- view, exactly represented, the posterior, at MUSCLES OF THE TBUSK. 193 6. Tramverse Sjnnoiis Muscle of the Nech (Fig. 104, 4.) Synonyms. — Short spinous — Boimjelat. Dorso-spinalis — Girard. (^Spinalis coUi — Percicall. Transversal is colli of Man.) Situat{o7i. — Between the great complexiis and the cervical ligament, on the laniinte of the last five vertebrae of the neck. Form — Structure — Attachments. — This muscle, a continuation in the cervical region of that of the back and loins, is generally formed of five thick and short fasciculi, strongly aponeurotic, directed forwards, upwards, and inwards. These fasciculi, attached by their posterior extremities — fixed insertion — to the five last articular tubercles of the cervical region, are fixed by their anterior or superior extremities — movable insertion — into the sixth, fifth, foui"th, third, and second spinous processes of that region. Relations. — Outwards, with the great complexus ; inwards, with the superior branch of the ilio-spinalis and the cervical ligament. By its anterior face, with the laminae of the cervical vertebrae and the interlamellar ligaments. Action. — An extensor and flexor of the cervical spine. 7. Intertransversal Muscles of the Nech. (Fig. 104, 9.) Synonyms. — Intercervicals — Girard. (The intertraiisversales oi Man. Not mentioned by Percivall.) These are six small, short, and very tendinous fasciculi, each of which is doubled into two secondary fasciculi, a suj^erior and inferior. They are lodged in the lateral excavations comprised '«ithin the transverse and artic- idar processes of the cervical vertebrae, and are carried from one vertebra to another, except from the first to the second. Covered by the cervical attachments of the majority of the muscles of the neck, they cover the vertebrae to which they are attached, as well as the vertebral arteries and veins, and the intervertebral foramen. They incline the neck to the side. 8. Great Oblique Muscle of the Head. (Fig. 104, 7.) Synonyms. — Axoido-atloideus — Girard. {Obliquus capitis inferior — Percivall.) Form — Direction — Situation. — A short, thick, and broad muscle, oblique forwards and outwardly, and applied to the superior face of the two fii-st vertebrte of the neck. Structure and Attachments. — Its fibres are nearly all fleshy, parallel to each other, and longer as they become superficial ; they are attached by their posterior extremity — fixed insertion — to the external face of the spinous process of the axis, and by their anterior extremity — movable insertion — to the superior surface of the transverse process of the atlas. Relations. — Outwards, with the splenius, the great and little complexus ; inwards, with the atlas, the axis, and the atlo-axoid articulation ; above. least, by the smxiU complexus of anthropfitomists, we have thought it proper to give it that name. With regard to the muscle generally termed the small complexus by veterinary anatomists, following the example of Meckel we will describe it as a portion of the great posterior straight muscle of the head. (Percivall names Girard's axoido-occipitalis longus the " complexus minor," and his dorsoinastoideus the " trachelo-maatoideus." Leyh, following Girard, designates the latter muscle the dorso-mastoideus.) 194 TEE MUSCLES. with the posterior straight muscles of the head ; below, with the anterior great straight muscle. Action. — It pivots the atlas on the odontoid process of the axis ; it is therefore, the special rotator of the head. Fiff. 104. CERVICAL LIGAMENT AND DEEP MUSCLES OF THE NECK. 1, Lamellar portion of the cervical ligameat ; 2, Funicular portion ; 3, 3. The transversales muscle of the back and loins ; 4, 4, Transversales of the neck ; 5, Posterior great straight muscle of the head ; 6, Small ditto ; 7, Great oblique muscle of the head ; 8, Small ditto ; 9, 9, Intertransversales of the neck ; 10, Anterior great straight muscle of the head; 11, Inferior scalenus muscle; 12, Superior ditto. 9. Small Oblique. (Fig. 104, 8.) Synonyms. — Atloido-mastoideiis — Girard. (Ohliquus capitis superior — Percivall. Lateral atloido-occipitaUs of Loyh. Olliquus superior of Man.) A short, thick, quadrilateral, and strongly aponeurotic miiscle. Its fibres are fixed posteriorly — origin — to the lip bordering the transverse process MUSCLES OF THE TRUNK 195 of the atlas ; they are carried from thence forward, upward, and inward, to to be attached — termination — 1, To the styloid process of the occipital bones ; 2, To the external sm-face of that bone, on the imprints which border the mastoid crest posteriorly ; 3, To the mastoid crest itself. This muscle is covered by the mastoid tendon of the small complexus, by the superior aponeurosis of the splenius, and that of the mastoido-humeralis. It cuvers the occipito-atloid articulation, the occipital insertion of the posterior straight muscles of the head, and the origin of the occipito-styloid and digastric muscles. It inclines the head on the atlas, and slightly extends it. 10. Posterior Great Straight Muscle of the Head. (Fig. 104, 5.) Synonym^.— SxaaW complexus and great posterior straight muscle — Bourgelat. Long and short axoido-occipitalis— (r/Vard. {Complexus minor and rectus capitis posticus major. — Perciiall. Leyh gives this muscle the same designations as Girard. It is the rectus capitis posticus major and medius of Man.) Form — Structure — Situation. — Elongated, prismatic, easily divisible into two fasciculi — one superficial, the comj)le.rus miiwr of Bourgelat (and Per- civall) ; the other deep, the great posterior straight muscle of Bourgelat (and the rectus capitis posticus major of Percivall) — entirely fleshy, and formed of parallel fibres, this muscle is lodged, with the small posterior straight muscle, in a triangular space circumscribed by the cord of the cervical liga- ment and the internal border of the oblique muscles. Attachments. — It is attached, by its superior extremity, to the whole extent of the uneven lip which terminates the spinous process of the axis — fixed insertion. Its anterior extremity is insinuated beneath the small oblique muscle, and is fixed to the occipital bone, behind the superior insertion of the great complexus, whose tendon receives some of the fibres of the superficial fasciculus — movable insertion. Helations. — Above, with the great complexus ; below, with the small straight muscle ; inwards, with the cord of the cervical ligament and the analogous muscle of the opposite side ; outwards, with the oblique muscles. Action. — This muscle, a congener of the great complexus, aids in extending the head. 11. Small Posterior Straight Muscle. (Fig. 104, 6.) Synonyms. — Atloido-occipitalis— G/rarrf. (Rectus capitis posticus minor— PercivalL The Atioido-occipitalis superior of Leyh. The rectus capitis posticus minor of Man.) A very small, wide, and triangular muscle, flat above and below, and lying immediately upon the fibrous capsule of the occipito-atloid articulation. It is attached, posteriorly, to the superior face of the atlas — origin ; in front, to the external surface of the occipital bone, below the preceding muscle, whose action it shares. B. Inferior Cervical or Trachelian Begion. The muscles composing this region are situated in front of the cervical vertebrae, and are, for the most part, grouped aruund the trachea, which they envelop as in a kind of sheath. They are eleven in number : the cuticular muscle of the neck, the mastoido-humeralis, sterno-maxillaris, sterno-hyoideus, sterno-thyroideus, omo- or suhscajndu-hyoideus, the great and small anterior straight muscles of the head, the small straight lateral muscle, the scalenus, and the long muscle of the neck. 196 THE MUSCLES. Preparation. — 1. Place the animal in the first position. 2. Remove the skin of this region, in order to expose and study the cuticular muscle. 3. Remove that muscle and the parotid gland to prepare the mastoido-humeralis/ the stylo-maxillaris, sterno- hyoideus, and sterno-thyroideus. 4. Transversely cut through tiie mastoido-humeralis near the angle of the shoulder, and isolate it from the subscapulo-hyoidens to exjjose this muscle ; taking care to preserve the jugular vein and parotid gland, in order to study their relations witii it. 5. Kemove the fore limbs ; open the thoracic cavity by sawing through the eight first ribs near their suiDerior extremity ; take out the viscera contained in this cavity, as well as the trachea, cesoi^hagus, jiharynx, and larynx, to expose the long muscle of the neck, the scalenus, and the straight muscles of the head. 1. Subcutaneous Muscle of the Neck. (Figs. 102, 12 ; 114, 1.) Si/noHymx. — It has been described by Bourgelat, and the majority of veterinary anatomists wlio have followed him, as two muscles : the cuticularis of the neck and the face. (Percivall includes this muscle in his description of the paniiiculus carnosus.) This is a membraniform expansion, partly fleshy, partly aponeurotic, which covers the muscles of the neck, the intermaxillary space, and the face. The fleshy fibres form, in front of the neck, a thin band, which is united, through the medium of a fibrous raphe, to that of the opjwsite side. This baud is in contact with the sterno-maxillary, steruo-hyoid, subscapulo-hyoid, and sterno-thyroid muscles, as well as the jugular vein : enveloping them all as in a sort of gutter. It gradually thins from below uj)wards, in such a manner that around the upper part of the throat it is only composed of some scattered fibres. In the intermaxillary sjiace, and on the expanding borders of the maxillary branches, the fleshy fibres appear agam of a certain thickness, but only to become attenuated on the external sm'face of the cheeks. These fleshy fibres leave the anterior prolongment of the sternum^ and intermediate middle raj^h^ of the two muscles, and directing their course outwards and upwards, soon become confounded with the aponeurosis. The latter, extremely thin, is spread over the mastoido-humeralis, the sujierior cervical muscles, parotid region, and the cheeks, and is finally attached to the zygomatic crest. On arriving near the commissure of the lips, the cuticular muscle is united to the alveolo-labialis (or buccinator muscle) by a fleshy fasciculus named, in Man, the risorius santorini (Fig. 110, 24). The cuticularis colli braces the muscles it covers during their contraction and pulls backwards the commissures of the lips. We doubt very much whether it has, in the cervical region at least, any action on the skin, for it adheres but very slightly to its inner surface. 2. Mastoido-humeralis. (Figs. 102, 105, 106, 114.) Synonyms. — The muscle common to the arm, neck, and head — Bourgelat. Eepre- Benting the cleido-mastoid, and the clavicular portions of the trapezius and deltoid of ' The mastoido-humeralis may be dissected at the same time as the trapezius, the subject being placed in the second position. This conveniently permits the superior insertions of the muscle to be studied. (See fig. 102). - It wdl be seen, on referring to figure 114 and its legend, that we restore to the cuticular muscle of the neck the sternal band attributed until now to the mastoido- humeralis. These arc the considerations wliich induce us to make this modification : I, This band is not distinct from the cuticularis of the neck ; a separation between the two muscles can only be artificially obtained. 2, In dissecting this band with care, we can see that its fibres, like those of the cuticularis, are not mixed with those of the mastoido-humeralis (superficial portion) ; they pass along the external surface of that muscle, to which they intimately adhere, it is true, but they can easily be separated, and are continuous with the aponeurosis of the first. MUSCLES OF THE TBUNK. 197 Man, and the trachelo-acromialis peculiar to quadruped mammals' — G. Cuvier, ' Lemons d'Anatuiiiie Compare'e,' 2nd edition. (This is the muscle which Percivall names the levator humeri. The above is the designation given to it by Girard and Chauveau. Leyh gives it the same designation as Bourgelat.) Extent — Situation — Direction — Composition. — This muscle extends from tlie summit of the head to tlie inferior part of the arm, and is applied to the scapulo-humeral angle at the side of the neck, in an oblique direction down- wards and backwards. it is composed of two portions lying longitudi- nally and somewhat intimately united, and distinguished into anterior and posterior. Form — Structure — Attachments. — A. The anterior or superficial portion (Fig. 106, 6) constitutes a long fleshy band, which appears to bo united, by its anterior border, to the cuticular muscle of the neck. Its sui)erior extremity, thin and wide, is attached to the mastoid process and crest by an ajjoneurosis (Fig. 102, 7), which is united, in front, to the tendon of the sterno-maxillaris by a very thin cellulo-aponeurotic fascia. Its inferior ex- tremity, thicker than the superior, is inserted by means of a very short aponeurosis into the humerus, on the salient border descending from the deltoid imprint, and which limits, in front, the fm-row of torsion on the body of that bone (Fig. 102, 7). B. The posterior or deep ptort ion (Fig. 102, 9) is a second muscular band, shorter and stronger than the preceding. It is attached, above, to the transverse processes of the first four cervical vertebrte by as many fleshy bands (Fig. 102, 8'), which cover the superficial portion. The upper digitation, given ofl:' to tnu atlas, is united to the tendon common to the small complexus and splenius (Figs. 105, 9 ; 106, 9', 10, 11). The inferior extremity of this portion of the muscle widens on the scapulo-liumeral angle, which it envelops in becoming closely united to the anterior portion, terminating with it on the humerus. An aponeurosis, which is confounded with that of the trapezius, and sends oif a septum into the interstice between the two portions of the long abductor of the arm, concurs to fix this extremity by spreading over the muscles of the arm. Relations. — It is covered, near its mastoid insertion, by the parotid gland and the cervico-auricularis muscles ; for the remainder of its extent, by the aponeurosis of the cuticularis colli, from which it is separated by a thin fascia continuous with that which extends over the trapezius. It covers the splenius, the small comjdexus, the oblique muscles of the head, subscapulo- hyoideus (to which it adheres intimately), the digastricus, long flexor of the head, the angularis, scalenus, small pectoral, supra- and infraspinatus, the long abductor of the arm, and the coraco-radialis. 1 At first sight we might hesitate to admit that this muscle is formed of such varied and complicated elements as are enumerated above. Nevertheless, it is a scientific fact; and we will give a demonstration, as simple as it is clear, that such is the case — the idea we owe to J. F. Meckel. If we take the Dog, for example, and suppose it to be possessed of a clavicle extcndinir from the anterior extremity of the sternum to the acromion ; this clavicle would cnt, transversely, the inferior portion of the mastoido- humeralis, which would thus be divided into two portions, a superior ami an inferior. The fii st, extending from the clavicle to the mastoid process, on this side, and on the other to the mastoid crest, as well as to the cervical ligament, where it is confounded with the trapezius, would exactly represent the clavicular portion of the latter muscle, and the cleidn-masfoideits. With resi ect to the interior portion, it perfectly resembles, by its attachments, the clavicular portion of the deltoid. But, on the contrary, if we suppose Man deprived of a clavicle, the three muscular fasciculi indicated, in becoming con- founded with each other, would form the mastoido-humeralis of the Dog, minus the posterior portion, or the trachelo-acromialis, which is not reijresented in Man. 16 198 THE JIUSCLES. Action. — When the superior is the fixed point, it carries the entire anterior limb forward. This muscle, therefore, plays a very important part in locomotion ; as it is called into action when the animal raises the fore-limb in getting over the groxmd. If the fixed point of the muscle is the limb, it inclines the head and neck to one side. 3. Sterno-maxillaris. (Figs. 102, 10; 114, 4.) Synonym. — The sterno-mastoiJeiis of IVIan and a large number of the lower animals. Form — Structure — Situation — Direction — Attachments. — A long narrow- muscle, almost entirely fleshy, and terminated at its upper extremity by a flat- tened tendon ; situated in front of the neck, beneath the cuticularis, and parallel to the anterior border of the superficial portion of the mastoido- humeralis, from which it is separated by a space that lodges the jugular vein ; attached, inferiorly, to the cariniform cartilage of the sternum — fixed insertion ; and sui^eriorly — movable insertion — to the curved portion of the posterior border of the maxillary bone by its terminal tendon. Belations. — The muscle is covered by the cuticularis colli, and the parotid gland. It covers the trachea, the subscapulo-hyoideus, sterno- hyoideus, sterno-thyroideus, and the maxillary gland. Its external border, parallel to the anterior border of the mastoido-humeralis, forms with it a longitudinal depression termed the jugular furroio, because it lodges the vein of that name. Its inner border is intimately united, in its lower third, to that of the opposite muscle. Action. — It directly flexes the head, when acting in concert with its congener ; but alone it turns it to one side. Lafosse and Rigot have wrongly considered this muscle as a depressor of the lower jaw. Bourgelat has correctly stated that it cannot move this jaw independently. (Percivall says that the pair will assist in opening the mouth ; and Leyh asserts that when the mouth is closed, each muscle will act as a flexor to the head.) 4. Sterno-hyoideus. — 5. Sterno-thyroideus. (Fig. 114, 6, 7.) (^Synonym. — The sterno-thyro-hyoideus of Percivall.) Form — Structure — Situation — Attachments. — Small, ribbon-shaped, long, and slender muscles ; digastric ; situated in front of the trachea ; confounded at their inferior extremity and united to those of the opposite side, so as to form a single fasciculus which is attached to the cariniform cartilage of the sternum — fixed insertion ; isolated from each other above the tendon which makes them digastric, and terminating by their superior extremity — movable insertion : the first, on the inferior surface of the body of the hyoid bone in common with the subscapulo-hyoideus ; the second, on the posterior border of the thyroid cartilage. Belations. — Covered by the sterno-maxillaris and the cuticularis muscle, they cover the anterior face of the trachea. Action. — Depressors of the hyoid bone and larynx. 6. Omo-hjoideus or Suhscapulo-hjoideus. (Figs. 102, 11; 114, 5.) Synonyms, — Hyoideus — Boiirrjelat. {Subscapulo-hyoideus — Percivall.) Form — Structure— Situation — Direction. — This muscle forms a thin and wide band, almost entirely fleshy, oblique forwards and upwards, extending from the scapulo- humeral angle to the intermaxillary space, and applied to the side of the trachea, whose direction it slightly crosses. MUSCLES OF TEE TEFXK. 199 Attachments. — It derives its fixed insertion from the inner surface of the subscixpularis, by an aponeurosis which is detached from that covering the latter muscle. Its movable insertion is into the body of the hyoid bone, in becoming confounded vdth. the sterno-hyoideus, and in being intimately united to the muscles of the opposite side. Belations. — Outwsirdly, with the subscapularis, supraspinatus, small pectoral, mastoido-humeralis^ which closely adheres to it, the jugular vein, the sterno-maxillaris, and the cuticularis. Inwardly, with the scalenus, the large anterior straight muscle of the head, the main trunk of the carotid artery and the nerves accompanying it, the trachea, thyroid gland, and the inferior face of the larynx. The jugular vein is entirely separated fi-om the carotid artery by this muscle in the upper haK of the neck. Action. — It is a depressor of the hyoid bone and its appendages. 7. Great Anterior Straight Muscle of the Head. (Figs. 104 and 105, 10; 106, 13.) Synonyms. — Long flexor of the hend—Bourgelat. Trachelo-suboccipitalis — Girard. {Bectus capitis anticis major — Percicall. TracheJo-occlpitalis — Leyh.) Form — Structure — Situation — Direction. — A long, flat muscle, fescicu- lated in its posterior half, terminated in a tendinous cone at its anterioi' extremity, and passing along the first cervical vertebrae in front. Attachments. — Behind, to the transverse processes of the third, fourth, and fifth cervical vertebrje by as many fleshy digitations, the most inferior of which are the longest — jixed insertion. In front, into the imprints on the body of the sphenoid bone and the basilar process, by its terminal tendon — moiohle insertion. Belations. — Outwardly, with the mastoido-hnmeralis, the subscapulo- hyoideus, and the small anterior straight muscle. Inwardly, with the long muscle of the neck and the muscle of the opposite side. In front, with the common carotid, the nerves accompanying this artery, and the guttural pouch, which lines it near its movable insertion. Behind, with the great oblique muscle of the head and the occipito-atloid articulation. Action. — It either directly flexes the head or carries it to one side, according as it acts alone or with its fellow of the opposite side. 8. Small Anterior Straight Muscle of the Head. Synonyms. — Flexor capitis brevis — Bourgelat. AtL dilo-suboccipitalis — Girard. (^Rectus capitis anticus minor — Percivall. Atloido-occipitalis inferior — Ltyh.) A small, entirely fleshy, prismatic fasciculus, lying to the external side of the preceding muscle ; attached, posteriorly, to the inferior face of the body of the atlas : in front, to the body of the sphenoid heme and the basilar process, beside the great anterior straight muscle. It is covered by the guttural pouch, and covers the occipito-atloid articulation. It concurs in flexing the head. 9. Small Lateral Straight Muscle. Synonyms. — Flexor capitis parvus — Bourgelat. Atloido-styloideus — Girard. 'Ohli' quus capitis anticus — PercivaJt. The rectus capitis tateralis of Man.) Yet smaller than the preceding, and prismatic and entirely fleshy, like it this muscle lies on the side of the occipito-atloid articulation : it is attached to the atlas, outside the small anterior straight muscle — fxed insertion ; and to the inner face of the styloid process of the occipital bone — movable insertion. It is the congener of the two anterior straight muscles of the head. 200 THE MUSCLES. 10. Scalenus. (Figs. 104, 105, 106.) Synomjms. — Costo-tracheleus — Girard. (Scalenus anticus and posticus of Man.) Situation — Direction — Composition. — Deeply situated at the inferior part of tlae neck, in an oblique direction downwards and backwards, this muscle comprises two portions of unequal dimensions, placed one above another. Form — Structure — Attachments. — A. The superior portion (scalenus posti- cus of Man), the smallest, is composed of three or four fleshy fasciculi, attached by their extremities to the transverse processes of the last three or four cervical vertebrte. The last terminates at the superior extremity of the first rib. B. The inferior (scalenus anticus of Man), the most considerable, is flattened on both sides, thick and wide posteriorly, thin and narrow anteriorly, and is comj)osed almost entirely of fleshy fibres which are longest as they are inferior. It is attached : 1 , To the transverse processes of the last four cervical vertebrae by short fasciculi scarcely distinct from one another, the first of which is crossed by the last digitation of the great anterior straight muscle ; 2, To the anterior border and external face of the first rib, where all its fibres end. Belations. — The scalenus responds : by its external face, to the sub- scapulo-hyoideus, raastoido-humeralis, and the sterno-i>rescapularis ; by its internal face, to the longus colli, trachea, common carotid artery and its accompanying nerves, and — on the left side only — to the oesophagus ; by its inferior border, to the jugular vein. The two portions of the scalenus are separated from one another, in front of the first rib, by an interspace traversed by the nerves of the brachial plexus. Action. — When the first rib is the fixed point, this muscle either directly flexes the neck or inclines it to one side. When the neck is the fixed point, it draws forward the first rib and fixes it in this position during the dilatation of the chest, in order to aid the inspiratory action of the external intercostal muscles. 11. Long Muscle of the NecJc. Symnyms.— Flexor longus colli — Bourgelat. Subdorso-atloideus — Girard. {Longus colli — Percivall. Dorso-atloideus — Leyh.) Situation — Composition. — A single and considerable muscle, immediately covering the inferior aspect of all the cervical and the first six dorsal vertebra3, and composed of two lateral portions which are united on the median line, and constitute, in certain animals, two distinct muscles. Structure — Attachments.— 'Each, lateral portion of the longus colli is composed of a succession of very tendinous fasciculi. The most posterior of these is attached to the inferior face of the bodies of the first six dorsal vertebrte, and proceeds directly forward to reach the inferior tubercle of the sixth cervical vertebra, into* which it is inserted by a strong tendon. The other fasciculi, less considerable, and confounded outwardly with the inter- transversales of the neck, are carried from one cervical vertebra to another, and are directed forwards, upwards, and inwards, in convei'ging towards those of the ojjposite side. They are attached successively : outwardly, to the transverse processes of the last six cervical vertebrae; inwardly, to the inferior ridge on the bodies of the first six. The most anterior fasciculus passes to the inferior tubercle of the atlas, into which it is inserted by a MUSCLES OF THE TRUNK. 201 tendon common to it and the fasciculus of the opposite side, and which receives the most supcrliciul libres of the three or four preceding fasciculi. Relations. — Above and behind, with the vertebras which it covers, ag well as their intervertebral discs ; below and iu front, with the trachea and cesoi)hagus, and the vessels and nerves accompauying those two tubes ; on the sides, with the great anterior straight and the scalenus muscles in its cervical portion, and in its intrathoracic portion, with the pleurfe, and important vessels and nerves. Action. — It flexes the whole neck, and the cervical vertebrae on one another. DIFFERENTIAL CHABACTEBS OF THE MUSCLES OF THE CERVICAL REGION IN OTHER THAN SOLIPED ANIMALS. A. Superior Cervical Region. 1. RuJiiNANTS. — In the Ox, the angularis arises by six digitations from all the cervical vertebrffi except the first ; the splenius is little developed, and is not attached to either the third or fourth cervical vertebra. 2. Pig. — The muscles of the superior cervical region in tliis animal are generally very developed. The rltomboideus is divided into two fleshy bodies, one of which proceeds to the occipital protuberance, and the other to the rudimentary cervical ligament and the first dorsal vertebrae. The angularis is attached, as in Ruminants, to tlie six cervical vertebrae ; sometimes it even shows a digitation that descends to the atlas. The s2Aenius only terminates anteriorly by three fleshy bodies; but they are voluminous, and are inserted, one into the atla.s, another into tlie mastoid crest, and the third into the occipital protuberance. In the great complexus, tlie two jDortions are completely separated from each other, except at their upper extremity, by the interspace lodging the superior cervical artery. The aponeurosis attaching the muscle to the spinous processes of the first dorsal vertebrae is not confoumled with that of the splenius or the small anterior serrated respiratory muscle. The atloidean fleshy body of the small complexus is scarcely distinct from the superior branch of the ilio-spinalis and the intertransver.-ales. Lastly, it is diflicult to distinguish the small poderior straight muscle from the deep fasciculus of the great straight muscle. 3. Carnivora. — In these animals the muscles of the superior cervical region are nearly all voluminous, as in the Pig. The rhomhoideus is bifid at its origin, and its anterior branch arises from the mastoid crest. The angularis is also attached to the la^t six cervical vertebrae. Very thick and bnad, the splenius only passes to the atlas and mastoid crest. The oblique and straight posterior muscles of the head are also remarkably thick. B. Inferior Cervical or Trachelian Region. 1. EuMiNANTS — In the Ox and Sheep, the disposition of the cuticularis colli offers a very considerable difterenco from that observed in Solipeds. The fleshy portion is absent, or appears to be absent, in the cervical region ; the anterior muscles of the neck are only covered by a thin fascia developed on the sides of the neck. "When this fascia reaches the face, it becomes continuous with the fleshy fibres; a fasciculus of these fibres comports itself as in the Horse, and goes to join the alveo-labialis; an ither is intercrossed in the maxillary space by the analogous fasciculus of the opposite side. The cervical cuticularis muscle of the Ox is also distinguished by an extremely remarliable peculiarity which it is necessary to allude to here : — The fleshy cervical ban(l, altogether absent in the Sheep, is not so in the Ox ; we have found it forming, beneath the above-mentioned aponeurotic fascia, the long, thick strip which has been described by veterinary anatomists ao the analogue of the sterno-maxillaris in the Horse. 1 his strip is attached, like the muscular band Avhich represents it in Solipeds, to the anterior point of the sternum. But its fibres, instead of being spread outwards over the mastoido- humeralis, ascend, perfectly isolated from that muscle, to the posterior border of the maxillaris. There it terminates (Fig. 112, 18 ) by a flattened tendon which, after reaching the anterior lionler of tlie massetsr, is confounded with the aponeurosis of that muscle, and sends some fibrous bands over the muscles of the face. The two portions of the ma4nid(i-humeralis of Ruminants are better defined, and more oblique on one another, than iu the Horse. The superficial portion receives on its iuuer 202 TEE 3IUSCLES. fa«e a small, bright-red, fimicniar fasciculus, which proceeds from tlie cartilage of the first rib, and which Meckel is inclined to consider as tiie vestige of the subclavius. It is divided, superiorly, into two branches : one, the clavicular portion of the traptzius, very wide, passes to the mastoid process, the curved line of the occipital bone, and to the cervical ligament, in becoming confounded with the trapezium (Fig. 112, 22); the otiier, the cleido-mastoideus, terminates in a tendon that joins the sterno-suboccipitalis, and la inserted into the basilar process, after receiving the fibres of tlie long flexor of the head (Fif. 112,21). The upper extremity of tlie deep portion of the mastoido-humeralis is insCTted into the atlas by a flattened tendon alone, which is quite distinct from the atloid insertions of the splenius and the small complexus. In the Sheep aiid Goat, tiie costal band that joins the superficial portion is absent. The latter is divided at its inferior extremity into two branches, between which pass the biceps. The upper branch passes to the epitrochlea. The sterno-maxillury muscle, instead of heing inserted into the inferior maxilla, is united to the suboccipital branch of the mastoido-humeralis, to be attached to the l>asilar process. At another time we will discuss the determination of this muscle, and that of the fleshy bund here considered as belonging to the first (see Spinal Nerve). The sterno-hyoid and sterna-thyroid muscles are thicker than in the Horse, and not digastric. The sid)scapulo-hyoideus of Ruminants is but slightly developed, and might be termed the trachelu-hyoideiis ; as it proceeds to the transverse process of the third or fourth cervical vertebra. In its passage beneath the basilar branch of the mastoido-humeralis and sterno-suboccipitalis (sterno-maxillaris), it contracts adhesions with the fibres of these two muscles. Tiie great anterior straight muscle of the head descends to the sixth cervical vertebra. Its cervical insertions are covered by a very strong muscular fasciculus, which is annexed to it. Like it, this fasciculus leaves the sixth cervical vertebra, and is attached to tlie transverse processes of the four vertebrse preceding the last, by becoming confounded with the intertransversales, and finally terminating at the tracheal process of the atlas by fleshy and aponeurotic fibres. This muscular fasciculus singularly strengthens tlie neck when it is inclined to one side. In consequence of its attachments, it might be named the trachelo-atloideus (Fig. 112, 24). Lastly, in Ruminants the superior scalenus is very developed, being a flattened band which, gradually expanding, is prolonge 1 to the surface of the serratus magnus. 2. Pig. — In this animal, the cuticularis colli is in two portions : an inferior, which comes from the point of the sternum ; and a superior, from the external scapular region. They unite in front, and are prolonged in common on the muscles of the face, con- tracting adhesions with the external aspect of the body and the branches of the maxillary bone. The other muscles of the inferior cervical region are not unlike those of Ruminants. Of the two portions of the uiastoido-humeralis, the superficial is bifid at its superior extremity. The posterior branch, the clavicular portion of the trapezius, is attacheil to the side of the occipital protuberance ; the anterior branch, the cleido-mastoideus, goes beneath the external auditory hiatus, to the crest that replaces the mastoid process ; the deep portion is attached above to the atlas only. In the Pig, the sterno-maxillaris exactly represents the sterno-mastoideus, as its tendon passes directly to the mastoid process. 'i'he sterno-thyroideus is double ; the supjjlementary branch going to the inferior face of the thyroideus. The siihscapulo-hyoideus and great anterior straight muscle of the head, resemble those of the Ox. The small straight lateral muscle is scarcely distinct from the small oblique. The superior scalenus extends to the third rib. The two lateral portions of the long muscU of the neck are separate, and form two distinct muscles. 3. Cabmvora. — In the Dog, each cuticularis is doubled into two portions, as in the Pig. The fibres from the breast are directed in a diverging manner over the face, the sub- maxillary space, and the parotid gland, where they form the parotido-auricularis muscle. The portion coming from the external scapular region is thicker and wider; it covers the lateral parts of the neck, the parotid gland, the parotido-auricularis, passes above the preceding, and terminates on the face and in the submaxillary space, where its fibres join those of the opposite side. The mastoido-humeralis comports itself somewhat as in Ruminants and the Pig. The superficial portion is bifid superiorly ; one of its branches is fixed into the mastoid process — the cleido-mastoideus ; the other into the mastoid crest and cervical ligament, in uniting by aponeurosis with the trapezius — the clavicular portion of the trapezius. The deep portion passes from the atlas to the scapular spine. MUSCLES OF THE TRUNK. 203 The tendon of the sterno-maxillaris goes to the mastoid process. The sterno-hi/oideus and thyroideiis are thick and not digastric, and commence from the cartilage of the first rib. The Carnivora have no subscapulo-hi/oideus ; but they possess a very long scalenus, which passes to the cightli rib, and a long muscle of the neck, which tends to become divided into two lateral portions. SPINAL REGION OP THE BACK AND LOINS. This offers for study eight pairs of muscles, nearly all of which have their insertions extended over the dorso-lurabar spine, and are disposed in Beveral layers on each side of this long multitidious crest. These muscles are, enumerating them according to their order of superposition : 1, The trapezius ; 2, Great dorsal ; 3, Small anterior respiratory serratus ; 4, Small posterior serratus; 5, Ilio-spinalis (longissimus dorsi) ; 6, Common intercostal; 7, Transver sales of the hack and loins {semispinalis doisi and lumhorum). Preparation. — 1. Place the animal in the second position. 2. Remove the skin with the panniculus and tlie mass of olecranian muscles, to show, in a first operation, the trapezius and great dorsal muscles (Fig. 102). 3. In a second operation, remove tlie entire fore-limb, with the great dorsal muscle, whose mode of termination may then be studied ; then prepare the two small serrated muscles. 4. Remove these two muscles, as well as the angularis of the sfapula and the splenius, to expose the common intercostal and ilio-spinalis (Fig. 1 06). The superior branch of tlie latter remaining covered by the great complexus, excise tliis muscle, leaving only its insertions into the transverse processes of the dorsal vertebra}, to show liow tliey are fixed between the two branches of the ilio-spinalis (longissimus dorsi). 5. Dissect the transversales (semispinalis) by removing the ilio-spinalis and the internal angle of the ilium. 1. Trapezius. (Fig. 102, 1, 3.) Synonym. — Dorso- and cervico-acromialis — Girard. Situation — Form — Structure. — This is a superficial membranous muscle, situated on the sides of the neck and withers. Its shape is that of a triangle whose base is ujjwards. It is aponeurotic at its upper border and in its centre, which allows it to be distinguished, especially in emaciated subjects, into a cervical and a dorsal portion. The fleshy fibres of the first are du-ected downwards and backwards; those of the second are oblique forwards. Attachments. — By its superior aponeurosis, it is fixed to the cervical cord and to the siunmits of the transverse ijrocesses of the first dorsal vertebrfe, where it adheres to the external face of the great dorsal muscle. By its central aponeurosis and that of its summit, it is attached to the tuberosity of the olecranian spine and the external scapular aponeurosis. Melalions. — This muscle is covered by two aponeurotic planes, whose fibres cross its own at a right angle. Inwardly, it responds to the rhom- boideus, splenius, angularis, steruo-prescapularis, the supra- and infra- S2)inatus, and the great dorsal. Action. — It raises the shoulder, and carries it forward or backward, according as one or other of its muscular portions contract. 2. Ch-eat Dorsal. (Fig. 102, 2.) Synonyms. — Dorso-himieralis — Girard. (Latissimue dorsi — Percivall.) Form — Situation — Structure — Attachments. — A very broad triangular muscle, extended over the loins, back, and side of the thorax, and formed of an aponeurotic and a muscular portion. The aponeurosis is attached, by its superior border, to the summits 204 THE MUSCLES. of the spinous processes of all the lumbar and the last fourteen or fifteen dorsal vertebrse — fixed insertion of the muscle. The fibres of the fleshy portion are detached from the inferior border of the aponeurosis, at the twelth or thirteenth ribs, to the cartilage of the scapula. They are directed forwards and downwards, and all converge into a flat tendon which is inserted into the internal tuberosity on the body of the humerus — movable insertion. This tendon is remarkable, at its termination, for being placed at the external face of the teres magnus or adductor of the arm, from which it receives fibres, and between it and the long extensor of the fore-arm ; it then turns inwards, on the inferior extremity of the first, in such a manner that this extremity is comprised Fig. 105. MUSCLES OF THE SPINAL REGION OF THE NECK, EACK, AND LOINS, MIDDLE LAYER; AND OF THE COSTAL AND ABDOMINAL REGION, SUPERFICIAL LAYER. 1, 2, Rhomboideus ; 3, Angular muscle of the scapula ; 4, Splenitis ; 5, Its mastoid aponeurosis; 6, Mastoid portion of the small complexus; 7, Its tendon; 8, Cer- vical insertions of the mastoido-humeralis ; 9, Atloidean tendon common to the mastoido-humeralis, splenius, and small complexus; 10, Great anterior straight muscle of the head; 11, Inferior scalenus; 12, Superior scalenus; 13, Small anterior serratus ; 14, Posterior ditto; 15, Great serratus; 16, Transverse muscle of the ribs; 17, One of the external intercostals ; 18, Great oblique muscle of the abdomen; 20, Straight muscle of the abdomen; 21, Stylo-maxil- lary portion of the digastric muscle. within a duplicature of the membranous tendon of the latissimus dorsi (Fig. 121). Belations. — This muscle is covered by the skin, panniculus carnosus, dorsal portion of the trapezius, and the mass of olecranian muscles. It covers the infraspinatus ; the cartilage of the scapula ; the rhomboideus ; the small anterior and posterior serrated muscles, whose aponeurosis is directly joined to its own ; the ilio-spinalis ; the principal gluteal ; a portion of the' external surface of the last ribs, to which its aponeurosis strongly adheres ; as well as the corresponding external intercostals, and the great serrated muscle. Between the last rib and the external angle of the ilium, MUSCLES OF TEE TRUNK. 205 the ajioneurosis unites with the small obliiiue, but more particularly with the great oblique, muscle of the abdomen ; it is prolonged, posteriorly, on the muscles of the croup to constitute the gluteal aponeurosis. Action. — It carries the arm backwards and ujiwards ; and it may, r.ccordiug to a great number of authors, serve as an auxiliary in insj^iration when its uxcd point is the liumcrus. According to others, but in whose opinion we do not share, it is an expiratory muscle. 3, Small Anterior Serrated Muscle. (Fig. 105, 13.) Synonyms. — Dorso-costalis — Girard. Anterior portion of the long serrated muscle — Bvunjelat.. (^Supcrjjcialis costarum — Percivall. Anterior serrated muscle of Leyh. Serratus posticus superior of Man.) Form — Situation. — This is a flat, thin, and quadrilateral muscle, situated beneath the rhomboideus and the great dorsal muscle. Structure. — It is composed of an aponeurotic and a fleshy portion. The first is confounded, in front, with the aponeurosis of the sjjlenius, and is insinuated, behind, underneatb that of the posterior small serratus, with which it soon becomes imited. Its inferior border gives origin to the muscular portion, a little above the interval which separates the common intercostal and the ilio-sjDinalis. Narrow and elongated antero-posteriorly, the muscular portion is composed of bright-red fibres directed obliquely backwards and downwards, and which form at the inferior border irregular, and sometimes but faintly marked, festoons. Attachments. — It takes its fixed insertion, by the superior border of its aponeurosis, from the summits of the anterior dorsal spines, with the exception of the first, to the thirteenth inclusive. The movable insertion takes place on the external surface and anterior border of the nine ribs succeeding the fourth, by means of the digitations of the fleshy portion. This muscle is also attached to the external surface of these ribs by a short fibrous band, which, is detached from the internal face of the aponeurosis, near its inferior border, and penetrates the space between the ilio-spinalis and the common intercostal muscle. Relations. — Outwards, with the rhomboideus, great serratus, gi"eat dorsal, and the posterior small serratus, which covers its three last festoons ; inwards, with the ilio-spinalis, the common intercostal, and the external intercostals. Action. — This is an inspiratory muscle, and it also serves as a check to the deep spinal muscles. 4. Small Posterior Serrated 3Iuscle. (Fig 105, 14.) Synonyms. — Lumbo-costalis — Girard. Posterior portion of the long serrated muscle — Bourgelat. {Superficial is costarum — Fercivall. The posterior serrated muscle of Leyh. The serratus posticus inferior of Man.) Situation. — Situated behind the preceding, which it follows, and jiresent- ing the same form and arrangement, this muscle also offers the following particular features for study : 1. Structure.— Its muscular portion, which is thicker and of a deep-red colour, is cut into nine well-defined digitations.^ The fibres which compose it run in an almost vertical direction. 2. Attachments. — Its aponeurosis, closely united to that of the gi-eat dorsal muscle, which covers it, is attached to the spinous processes of the dorsal * It frequently happens that only eight digitations are found. 206 THE MUSCLES. vertebrfe after tlie tenth, and to some lumbar vertebrae. Its digitations are fixed to the posterior border and external face of the nine last ribs. 3. Relations. — Outwards, with the great dorsal ; inwards, with the small anterior serratus, the ilio-si)iualis, common intercostal, and the external intercostals. Some of its posterior digitations are partly con- cealed by those of the great oblique muscle of the abdomen; the last, indeed, is entirely covered by that muscle. 4. Action. — This is an expiratory muscle, in consequence of its drawing the ribs backwards and upwards, 5. The Uio-spinalis Muscle. (Fig. 106.) Synonyms. — It represents the long dorsal, short transversal, and long spinous of Bourgelat. Cuvier and others have described it as consisting generally, in mammalia, of live particular muscles, designated as longissimus dorsi, transversalis cervicis, semi- spiiialis dorsi, and semispinalis colli. It corresponds to the longissimus dorsi, and trans- versalis cervicis of Man. (Percivall designates this important muscle the longissimus-dorsi — the name given to its analogue in Man. By Girard, Leyh, and Chauveau, it is styled the ilio-spinalis.) Extent — Situation. — This, the most powerful and complex of all the muscles in the body, extends along the dorso-lumbar spine, above the costal arches, from the anterior border of the ilium to the middle of the cervical stalk. Form. — It is elongated from before to behind, and flattened above and below in its posterior half, which rei)resents the common mass in Man ; this mass is prismatic in form, thick inwards, and thin outwards. Anteriorly, it is flat on both sides, and bifurcates into two voluminous branches, a superior and inferior, between which pass the insertions of the complexus to be fixed into the transverse processes of the first dorsal vertebras. Attachments. — 1, Uj)on the lumbar border, the external angle and internal surface of the ilium, the sacro-iliac ligament, and the sacrum ; 2, To the spinous processes of all the lumbar and dorsal, and last four cervical vertebrje ; 3, To the articular tubercles of the lumbar vertebrae and the transverse processes of all the dorsal, and the last fom- cervical vertebrte ; 4, To the costiform processes of the lumbar vertebrae, and the external surface of the fifteen or sixteen last ribs. Structure. — If this muscle is examined posteriorly, in the part which forms the common mass, it will be found to be composed of very compact fleshy fibres, covered in common by a thick ajjoneurosis. Tliese fibres commence at the jjosterior extremity of the muscle, and all proceed forward, stopping to take successive insertions on the various bony eminences in its track, and forming three different orders of fasciculi, which are more or less tendinous at their anterior or terminal extremity. These fasciculi are internal and .supei-ficial, internal and dcei), and external. The internal and superficial, or spinal fasciculi, pass to the summits of the spinous jirocesses already noticed when speaking of the attachments. These fasciculi are little, if at all distinct posteriorly ; but they become more so anteriorly. About the sixth dorsal vertebra, they separate from the other fasciculi to form the superior branch of the muscle (Fig. 106, 3). The internal and profound, or transverse fasciculi, are those which attach the muscle to the articular tubercles of the lumbar vertebrfe and transverse processes of the back and neck. They are well detached from each other, even posteriorly, and are very tendinous. Anteriorly, they pass into the inferior branch of the ilio-spinalis, which they, in common with MUSCLES OF THE TRUNK. 207 Fis. 106, 1, 2, 3, 4, Ilio-spinalis ; 5, Com- mon intercostal ; 6, Principal portion of the great complexus ; 7, Anterior portion of the same ; 8, Mastoid tascicnlus of the small complexus; 8', Its ten- don ; 9, Atloid fasciculus of that muscle; 9', Its tendon; 10. At- loid insertion of the splenius turned forward; 11, Ditto of the mastoido-humeralis ; 12, Intertransversales of the neck ; 13. Long tlexorofthe head; 14, Inferior scalenus; 15, Superior scalenus ; 16, Internal inter- costals; 1", Dependent fasci- culus of the small oblique, form- ing the retractor of the last rib, according to German anatom- ists; 17'. Small oblique muscle of the abdomen ; 18, Transverse muscle of the abdomen. DEEP MUSCLES OF THE SPIXAL REGION OF THE XECK, BACK, A>"D LOIXS, AXD THE COSTAL A>"D I>"FEF.IOB ABD03IIXAL EEGI0X3. 20S TEE MUSCLES. tlie external fasciculi, go to form. From profound, they now become superficial ; and they are seen springing up between the others, which appear to separate to allow them to pass (Fig. 106, 4, 4). The external, or costal fasciculi, turn a little outwards to reach the ribs and costiform processes of the lumbar region ; they are not very apparent in this direction (Fig 106, 2, 2). It will be easily understood that all these fasciculi do not come from the common mass, which would be expended long before its termination at the neck, in consequence of the successive emissions of the fasciculi composing it. To prevent this expenditure, there are continually added to it numerous reinforcing bundles of fibres, which arise either from its aponeurotic envelope, or from the bones on which the primary fasciculi terminate, and comport themselves absolutely like these, which they are charged to continue to the neck. Belations. — The ilio-spinalis is covered by the pyramidal point of the principal gluteal muscle, which it receives in a particular excavation, and by the aponeurosis of the great dorsal and the small serrated muscles. It covers the intertransversales of the himbar region, the transversales of the back and loins, the supercostals (levatores costarum) and the external intercostals. Outwards, it is bordered by the common intercostal. The superior branch is covered by the great complexus and the trans- versales colli. Inwardly, it responds to the cervical ligament and the analo- gous branch of the opposite muscle. The inferior branch responds, outwardly, to the angularis of the scapula ; it covers some intertransversales colli, and the aponeurotic digitations which attach the great complexus to the transverse processes of the first dorsal vertehrae. From these digitations it even detaches a number of muscular fasciculi, which go to strengthen this branch of the ilio-spinalis. Action. — It is a powerful extensor of the vertebral column, which, when it acts singly, it inclines to one side. It may also take part in expiration. 6. Common Intercostal Muscle. (Fig. 106, 5.) Synonyms. — Trachelo-costalis — Girard, The sacro-luvibalis of Man. {Transrersalis costarum — Percivall.) Form — Situation. — A long, narrow, and thin muscle — particularly at its extremities — situated along the external border of the preceding muscle, with which it is confounded behind the last rib. Structure — Attachments. — This muscle, whose structure has been com- plicated at will by so many anatomists, is yet extremely simple. It is formed of a series of fasciculi, directed obliquely forwards, downwards, and out- wards, tendinous at their extremities, and originating and ternruating successively on tlie external surface of the ribs. The most posterior leave the external border and inferior face of the common mass. The tendinous digitation of the anterior fasciculus is inserted into the transverse process of the last cervical vertebra, in common with the inferior branch of the ilio- spinalis. Belations. — Outwards, with the great and small scrratus ; inwards, with the external intercostals. Action. — It depresses the ribs, and may extend the dorsal portion of the spine. MUSCLES OF TEE TRUNK. 209 7. Transverse Spinous Muscle of the Bach and Loins. (Fig. 106, 3.) Sytionymx. — Transverso-spinous— Girarrf. Dorso-lumbar portion of the semispinalis of Miiu. (The spinalis and semispinalis dorsi — Percivall.) Situation — Extent. — This is a very long muscle, directly applied to the supersacral and dorso lumbar spine, and cuntiuuous, in front, with the trausversales colli ; these two muscles, therefore, meat^ure nearly the whole length of the spine. Structure. — It is formed of an assemblage of short fasciculi, whicli are flattened on both sides, tendinous at their extremities, directed obliquely forwards and downwards, and a little inwards, thus crossing at a right angle the spinous processes they cover. Attachments. — These fasciculi are attached, below, to the lateral lip of the sacrum, the articular tubercles of the lumbar vertebrte, and the trans- verse processes of the dorsal vertebras — origin. They are fixed, above, to the spinous processes of the sacral, lumbar, and dorsal vertebra?, and into that of the last cervical vertebra — termination. It is to be remarked that they do not attain the summits of these spinous processes in the first half of the dorsal region. Belations. — Outwards, with the lateral sacro-coccygeal and ilio-spinalis muscles, which are confounded with it near its posterior extremity ; inwards. with the sacral spine and the spines of the lumbar and dorsal vertebras, and with the interspinous ligaments of these three regions. Action. — It is an extensor of the spine. DIFFEBEXTIAL CHARACTERS OP THE MUSCLES IN THE SPINAL REGION OF THE BACK AND LOrS'S IN OTHER THAN SOLIPED ANIMALS. 1. KuMiNANTS. — In the Ox, Sheep, and Goat, the trapezim is thick and very broad. The anterior small serrated musde is inserted, by its last digitution, into the ninth rib. The posterior serrated is fixed into the four last ribs. 2. Pig. — Its trapezius is well developed. The great dorsal is voluminous, and ia attached to the surface of the ribs, which it covers by digitations from its fleshy portion. It is fixed near the small trochanter to the lip of the bicipital groove. The inferior branch of the ilio-spinalis of this animal is easily divided into two portions, traces of which are found in the Horse: one is formed by the costal fascicidi, the other by the transversal fasciculi. The latter constitutes the muscle to which Bourgelat has given the name of short transversal. 3. Caenivora. — Several of the spinal muscles in the Doq resemble those of the Pig ; sitcli are the trapezium, the great dorsal, and the ■ilio-spi7ialis. In animals of this group, it is remarked that the anterior serrated is very thick and very developcil, atul that it is attached to the eight ribs succeeding the second by as many well-marked festoons. The posterior has only three digitations, which are attached to the three last ribs. The common intercostal exactly resembles the sacro-lumbalis of Man ; behind the last rib, it constitutes a tliick fleshy bod)', separated by a fissure from the ilio-spinalis, witli which it is attached to the coxa. Lastly, the transverse spinal muscle of the hack and loins is very strong in the lumbar region, and is prolonged on the coccygeal vertebrse. (According to Leyh, tlie interspinales muscles are absent in the Horse and Euminants ; they are found in the Pig between the spinous processes of the dorsal and lumbar vertebrae, and in Camivora between the spinous processes of the cervical vertebrae.) comparison OF THE MUSCLES OF THE BACK AND NECK IN MAN WITH THE ANALOGOUS MUSCLES IN THE DOMESTICATED ANIMALS. It is usual, in human anatomy, to describe by the name of muscles of the back and neck those which correspond to the superior cervical region, and those of the spinal region of the back and loins of the domesticated animals. The muscles of the inferior cervical region are described in Man as muscles of the neck, with the hyoid muscles and the scalemis. 210 THE MUSCLES. A, Muscles of the Back and Cervix. In the trapezius of Man, a cervical and a dorsal portion can no longer be distinguished. Above, it is attached to the superior occipital curved line ; below, it is fixed to tlio external tlurd of the upper border of the clavicle, and to the acromion and scapular spine. Fig. 107. FIRST, SECOND, AND PART OF THIRD LAYER OF MUSCLES OF THE BACK OF MAN; THE FIRST LAYER OCCUPIES THE RIGHT, THE SECOND THE LEFT SIDE. 1, Trapezius ; 2, Tendinous portion, forming, with a corresponding part of the opposite muscle, the tendinous ellipse on the back of the neck ; 3, Acromion process and spine of scapula; 4, Latissimus dorsi ; 5, Deltoid; 6, IMuscles of dorsum of the scapula: infraspinatus, teres minor, and teres major; 7, Obliquus esternus ; 8, Gluteus medius ; 9, Glutei maximi ; 10, Levator anguli scapulae ; 11, Rhomboideus minor; 12, Rhomboideus major; 13, S^denius capitis, overlying the splenius, above; 14, Splenius colli, partially seen: the common origin of the splenius is attached to the spinous processes below the origin of the rhomboideus major; 15, Vertebral aponeurosis; 16, Serratus posticus inferior; 17, Supra- spinatus; 18, Infraspinatus; 19, Teres minor; 20, Teres major; 21, Long head of triceps, passing between teres minor and maior to the arm ; 22, Serratus magnus, proceeding forwards from its origin at the base of the scapula; 23, Obliquus internus abdominis. The fibres of the trapezius which are fixed into the clavicle, represent a portion of the mastoido-humcralis of quadrupeds. The fireat dorsal resembles that of the Dog and Pig, its fleshy portion being very developed ; it is attached to the exteriiid face of the four last ribs by muscular digitations, and terminates ou the border of the bicipital groove. MUSCLES OF THE TRUNK. 211 The rliomhoideus is bifid, as in tlie smaller quadrupeds. Less developed than in these animals, tiie angulark is only fixal in front to the four first cervical vertebrse. In Man, the splenius is larjie, but bj' its insertions it resembles that of Solipeds. The great complexus, thick iind broad alwve, is incompletely divided into two fleshy bodies, which are attached, suprriorly, to the sides of the external occipital crest. The small complexus is not fixed into the axis and atlas, its superior extremity passing directly to tlie mastoid process. There is nothing particular to note regarding the straight posterior and oblique muscles of the head; the differences ihey ofler in their form are allied to the conformation of the bones in this region. Of the two small serrated muscles, that which corresponds to the anterior serrated of animals rises very high ; for it is attached by an aponeurosis to the spinous processes of the three first dorsal vertebrae, the seventh cervical, and the cervical ligament. There are found in ]Man, lying along the vertebral furrows, several muscles which represent the ilio-spinalis and the common intercostal of Solipeds. Thus the common vias< covering the lumbar vertebrae behind, is prolonged by two series of flesh)^ and ten- dinous fasciculi : one forms the sacro-lumbalis, which resembles the common intercostal of animals ; the other, the long dorsal, represents the infericjr branch of the ilio-spinalis. The superior branch of the latter is found in the transrerscdis colli. Lastly, there are also seen in Man a transverse spinal and intertransverse muscles, which correspond: the first, to the transverse s2)inous of the back and loins and transverse spinous of the neck ; the second, to the intertrunsversales of the loins of the domesticated species. B. Muscles of the Neck. The mastoido-humeralis is not present in Man, bt-ing peculiar to quadrupeds; but we should see a portion of its fasciculi in the cleido-mastoideus niuscle, and in the clavicular portions of the trapezius and deltoid. The sterno-mastoideus corresponds to the sterno-maxillaris of animals ; as in the Dog, it is inserted into the external face of the mastoid process and the external two-thirds of the superior occipital curved line. Below, it commences by two fasciculi— one from tlie sternum, the other from the clavicle. We have already alluded to this clavicular fasciculus. The sterno-hyoideus and sterno-thyroideus are large and well developed, resembling in their disposition those of the smaller animals. It is to be noted that the sterno-hyoideus leaves the sternum, the first costal cartilage, and the internal extremity of the clavicle. The scapulo-hyoideus is digastric. The anterior great straight muscle of the head is attached to tour cervical vertebra;, as in Ruminants and the Pig. The anterior small straight, the lateral small straight, and the long muscle of the neck, comport themselves as in the smaller animals. The anterior scalenus is very developed, for it is attached to the six last cervical vertebrae. SUBLUMBAR, OR INFERIOR LUMBAR REGION. The muscles of this region are deeply situated at the inferior face of the lumbar vertebrae and the ilium, concurring to form the roof of the abdominal cavity, and are in more or less direct contact with the viscera contained in that cavity. They are nine pairs. Three have received the generic name of psoas, and are of large volume ; they are maintained by a strong aponeurosis, the iliac fascia, and are distinguished as the great psoas, iliac psoas, and stuall psoas. A fourth is named the square muscle of the loins (quadratus lumhorum), The other five, placed between the transverse processes of the lumbar vertebrae, represent, in consequence of their connection with these kind of fixed ribs, veritable intercostal muscles ; these are the intertransverse muscles of tlie loins. Preparation. — 1. Place the subject in the first position ; open the abdominal cavity by completely removing its inferior walls ; empty the cavity of the viscera it contains, and excise the diaphragm, as that muscle prevents the anterior extremity of the great and small psoas muscles being seen. 2. First study the iliac fascia, its form, relations with the long abiluctor of the leg. its attachments, its continuity with tlie tendon of the small psoas, and the expansion reflected from the aponeurosis of the great abdominal oblique muscle. 3. Expose the three psoas muscles by removing the iliac fascia, the two adduc- tors of the leg, and the three adductors of the thigh. 4. Remove the psoas muscles for the dissection of the quadratus and intertransversales. 212 TEE MUSCLES 1. Hiac Fascia or Liimho-iliac Aponeurosis. (Fig. 108, a.) This is a very resisting fibrous expansion, covering the great and iliac psoas muscles. Attached, inwardly, to the tendon of the small psoas, out- wardly to the angle and external border of the ilium, this aponeurosis, as it extends forwards over the great psoas, degenerates into cellular tissue. Behind, it also becomes attenuated in accompanying the two muscles it covers until near their insertion into the internal trochanter of the femur. Its external or inferior face receives, posteriorly, the insertion of the crural arch, and gives attachment to the long adductor of the leg ; for the re- mainder of its extent, it is covered by the peritoneum. 2. Great Psoas Muscle. (Fig. 108, 1.) Synonyms. — Subliitnbo-trochantineus — Glrard. Psoas — Bour(jelat. (Lumho-femoral- Leyh. Psoas magnus — PercivalL] Form — Situation. — This is a long muscle, flattened above and below at its anterior extremity, prismatic in its middle, and terminated in a cone at its posterior extremity. It lies beneath the transverse processes of the lumbar vertebrae. Structure. — Almost entirely fleshy, this muscle is formed of fasciculi, very delicate in texture, directed backwards, and long in proportion to their superficial and deep situation. They all converge to a tendon which is enveloped by the iliac muscle, and is confounded with it. Attachments. — The great psoas is attached: 1, By the anterior extremity of its fleshy fasciculi to the bodies of the last two dorsal and the lumbar vertebrae, except the hindermost, and to the inferior face of the two last ribs and the transverse processes of the lumbar vertebrte ; 2, By its posterior tendon to the internal trochanter, in common with the j^soas iliacus. Belations. — Below, with the pleura, the superior border of the diaphragm, the lumbo-iliac aponeurosis, which separates it from the peritoneum and the abdominal viscera situated in the sublumbar region ; above, with the two last internal intercostals, the quadratus, and the intertransversales muscles ; inwardly, with the small psoas and the internal branch of the iliac psoas ; outwardly, for its posterior third, with the principal branch of the latter muscle. Action. — A flexor and rotator of the thigh outwards when its fixed point is the loins, this muscle also flexes the lumbar region when the thigh is a fixed point. It is, therefore, one of the agents which determine the arching of the loins, and which operate, during exaggerated rearing or pr.incing, in bringing the animal into a quadrupedal position again. 3. Hiac Psoas Muscle. (Fig. 108, 3, 4.) Synonyms. — Ilio-trochantineus — Girard. (Leyh divides this muscle into two j)or- tions. wliich Ik; describes as the qreat and middle ilio-femoralis. Iliacus — PercivalL) Form — Situation — Direction. — This is a very strong, thick, and prismatic muscle, incompletely divided into two unequal portions by the groove for the reception of the tendon of the great psoas : an external portion, somewhat considerable in size ; and an internal, small. These two muscular portions lie at the entrance to the pelvis, on the inner face of the ilium, in an oblique direction downwards, backwards, and inwards. Structure. — It is almost entirely fleshy. The fasciculi forming it are MUSCLES OF THE TRUNK. 213 spread ont in front, and collected behind, where they become slightly fibrous, and unite with the tendon of the great psoas. Attachments. — It has its fixed insertion on the whole of the iliac surface, on the external angle of the ilium, the sacro-iliac ligament, and the ilio- MUSCLES OF THE SUBLUilBAE, PATELLAE, AND INTERNAL CRTJEAL REGIONS 1, Psoas magnus; 1', Its terminal tendon; 2, Psoas parvus; 3, Iliac psoas; 4, Its small internal portion ; 5, Muscle of the fascia lata ; 6, Anterior straight muscle of the thigh; 7, Vastus internus ; 8, Long adductor of the leg; 9, Short adductor of the leg ; 11, Pectineus; 12, Great adductor of the thigh; 12', Small adductor of the thigh-, 13, Semimembranosis ; 14, Semitendinosis. — a. Portion of the fascia iliaca ; B, Portion of the membrane reflected from the aponeurosis of the abdominal great oblique muscle, forming the crural arch (Poupart's ligament); C, Pubic tendon of the abdominal muscles; D, Origin of the pubio-femoral ligament. pectineal crest. Its movable insertion is into the small internal trochanter, in common with the great psoas. Eelations. — Above, with the ilium ; below, with the iliac fascia and the long adductor of the leg ; outwardly, with the muscle of the fascia lata and 17 214 THE MUSCLES. the origin of the anterior straight muscle of the thigh, from which it is separated by a space filled with fat ; inwardly, with the crural vessels. It passes between the vastus internus and the pectineus, to reach the trochanter. Actions. — It is a flexor and rotator outwards of the thigh. 4. Small Psoas Muscle. (Fig. 108, 2.) Synonyms. — Psoas of the loins — Bourgelat. Sublumto-pubialis, or sublumbo-iliacus, according to Girard. {Psoas parvus — Percivall, The ktmbo-iliacus of Leyh.) Situation — Form — Structure. — Placed at the inner side of the great psoas, very much elongated, and semipenniform in shape, this muscle is terminated behind by a flattened tendon, and is composed of fleshy fibres, the longest of which ai"e anterior. These fasciculi are all directed backwards and outwards to gain the tendon. Attachments. — 1, To the bodies of the three or four last dorsal, and to all the lumbar vertebras, by the anterior extremity of its fleshy fibres ; 2, To the ilio-pectineal eminence and the lumbo-iliac aponeurosis, by the posterior extremity of its tendon. Belations. — By its inferior face with the pleura, the superior border of the diaphragm, the aorta or posterior vena cava, and the great sympathetic nerve ; by its upper face, with the psoas magnus. It is traversed, near its vertebral insertions, by numerous vascular and nervous branches. Actions. — It flexes the pelvis on the sj^ine, when the loins are the fixed point ; but should the pelvis be fixed, it arches or laterally inclines the lumbar region. It is also the tensor muscle of the lumbo-iliac aponeurosis. 5. Square Muscle of the Loins. (Fig. 109, "l.) Synonyms. — Sacro-costalis — Girard. {Sacro-lmnbalis — Ferclvall. Quadratus lumborum of Man.) Situation — Form — Structure — Attachments. — This muscle is comprised between the trans- verse processes of the lumbar region and the great psoas, and is elongated from before to be- hind, flattened above and below, and divided into several very tendinous fasciculi. The prin- cipal fiisciculus, situated out- wardly, takes its origin from the sacro-iliac ligament, near the angle of the sacrum, and ex- tends directly forward to gain the posterior border of the last rib, after being attached by its upper face to the summits of the transverse processes of the lum- bar vertebrae. The other fasci- culi are longer as they are an- terior; they leave the internal border of the first, and are directed oblic^uely forward and inward, to be DEEP MUSCLES OF THE SUnLUMBAR REGION. Quadratus lumborum ; 2, 2, Intertransversales ; 3, Small retractor muscle of the last rib — a de- pendent of the small oblique of the abdomen. MUSCLES OF THE TRUNK 215 fixed into the transverse processes of tlie majority of the lumbar vertebrte and the inner face of the two or three last ribs. Belations. — By its upper face, with the intertransversales, the small retractor of the last rib, and the fibrous fascia which unites that muscle to the small oblique of the abdomen. By its inferior face, to the great psoas. Actions. — It draws the last ribs backwards, and inclines the lumbar spine to one side. 6. Intertransverse Muscles of the Loins. (Fig. 109, 2, 2.) (Synonym — Intertransversales lumborum — Percitall.) These are very small flat muscles which fill the intervals between the transverse processes of the lumbar vertebrte. The muscular fibres entering into their composition are mixed with tendinous fibres, and are carried from the anterior border of one transverse process to the posterior border of the other. They respond, by theii- superior face, to the ilio-spinalis (longissimus dorsi), and by their inferior face to the quadratus, as well as the psoas magnus. They act by inclining the lumbar region to one side. DIFFEREKTI.\L CHARACTERS OF THE MUSCLES OF THE SUELOIBAK REGIOX IN OTHER THAN SOLIPED AXDIALS. In Hiiminants and the Pig, the muscles of this region so closely resemble those of Solipeds, that a special description is unnecessary. In the Bog, the great psoas is little developed, and only commences at the third, or even the fourth Imubar vertebra; the iliac psoas is very slender, particularly in its external portion : otherwise it is scarcely distinct from the great psoas, with which it may be said to form one muscle ; the small psoas is relatively larger than the great; it is not prolonged into the pectoral cavity, and its anterior extremity is confounded with the quadratus lumborum, which is longer and stronger than in all the other animals. COMPARISON OF THE SCBLOIBAR MUSCLES OP MAN WITH THOSE OF ANMALS. In human anatomy, by the names of psoas and iliacus are described the great psoas and iliac psoas of animals. The psoas magnus of Man is distinguished from that of Solipeds by its superior insertions, which do not go beyond the last dorsal vertebrse. The small psod-s is often absent ; when present, it is attached, above, to the bodies of the twelve dorsal vertebrae, below, to the ilio-pectineal crest. The intertransversales have been studied with the muscles of the back. The quadratus of the loins, classed by anthropotomists with the abdominal muscles, is distinctly divided into three series of fasciculi : ilio-costal fasciculi, which pass from the upper border of the ilium to the twelfth rib ; lumho-costal fasiculi. passing from the transverse processtr-s of the three or four last lumbar vertebrae to the twelfth rib, and ilio- lumhar fasciculi, going from the iliac crest to the posterior face of the transverse processes of all the lumbar vertebrai. COCCTGEAL EEGION. This region is composed of four pairs of muscles destined for the movements of the tail : three, named the sacro-coccygeal, are disposed longitudinally around the coccygeal vertebrte, which they completely envelop ; the fourth is designated the iscliio-coccygeus. 1. Sacro-coccygeal Muscles. (Fig. 131, 1, 2, 3.) These three muscles are inclosed, with those of the opposite side, in a common aponeurotic sheath which is continuous with the inferior ilio-sacral and sacro-ischiatic ligaments. They commence on the sacrum, are directed backwards and parallel AA-ith the coccyx, gradually diminishing in thickness, and are decomposed into several successive fasciculi terminated by small 216 THE MUSCLES. tendons, which are inserted into each of the coccygeal bones. With regard to their situation, these muscles are distinguished as sacro-coccygeus superior, sacro-coccygeus inferior, and sacro-coccygeus lateralis. a. Sacro-coccygeus Superior. (^Synonym. — Erector coccygis — Percivall. ) The fasciculi which form this muscle lake their fixed insertion either from the summits and sides of the three or four last processes of the super- sacral spine, or from the coccygeal vertebrae themselves. 'J'he tendons through which they effect their movable insertion into these vertebrge are always very short. This muscle, covered by the coccygeal aponeurosis, in turn covers the vertebrae it is designed to move. It responds ; inwardly, to the analogous muscle of the opposite side ; outwardly, to the lateral sacra-coccygeus, and, near its anterior extremity, to a very strong aponeurotic expansion which separates it from the transverse spinous muscle. It directly elevates the tail, or pulls it to one side, according as it acts in concert with its fellow or singly. h. Sacro-coccygeus Inferior. (Synonym. — Depressor coccygis — Percivall.) This muscle is thicker than the preceding; its constituent fasciculi take their origin from the inferior surface of the sacrum, towards the third vertebra, and from the internal face of the sacro-ischiatic ligament and the coccygeal bones. It readily divides into two parallel portions, which Bourgelat has described as two separate muscles. The fasciculi of the internal portion are inserted, by their posterior extremity, into the inferior face of the first coccygeal vertebrae. Those of the external portion are all furnished with strong superficial tendons, nearly all of which are for the bones of the tail. This muscle responds : outwardly, to the ischiatic ligament, the ischio- coccygeus and coccygeal aponeurosis ; inwardly, to the muscle of the opposite side, and to the coccygeal attachment of the rectum ; above, to the sacrum, the bones of the tail, and the lateral muscle ; below, to the rectum and the coccygeal aponeurosis. It either directly depresses the tail or inclines it to one side. c. Sacro-coccygeus Lateralis. {Synonym. — Curvator coccygis — Percivall.') This muscle may be considered as the transverse spinous of the coccygeal region ; indeed, it is confounded with that muscle of the back and loins by its anterior extremity, and appears to continue it to the inferior extremity of the tail. The fasciculi composing it have their origin from the spinous processes of the last lumbar vertebrae, through the medium of the transverse spinous, and from the coccygeal bones. The tendons terminating these fasciculi are deep and not very distinct. It responds ; outwardly, at the posterior extremity of the ilio-spinalis, to the inferior ilio-sacral ligament and the coccygeal aponeurosis; inwardly, to the transverse spinous and the coccygeal vertebrae ; above, to the superior muscle ; below to the inferior muscle, from which it is nevertheless MISCLES OF THE HEAD. 217 separated by several small independent muscular fasciculi, which are carried from one coccygeal vertebra to another. (Leyh designates these the inter transversales of the tail.) It inclines the tail to one side. 2. Ischio-coccygeus. (Fig 131, 41.) \^Synonym. — Compressor coccygis — I'trcicall.) A small, thin, wide, and triangular muscle, situated against the lateral wall of the pelvis, at the internal face of the sacro-ischiatic ligament. It is attached, by an aponeurosis, to that ligament and to the ischiatic crest ; it is then directed upwards to be fixed, by its muscular fibres, to the side of the last sacral vertebra and the first two coccygeal bones. It is related, outwardly, vnih the sacro-ischiatic ligament, and inwardly to the lateral sacro-coccygeus and the rectum. It depresses the entire caudal appendage. REGION OF THE HKAS. The head comprises a large number of muscles, of which only those covering the bones of the face, and those which move the lower jaw and os hyoides, will be described. The others will be studied with the apparatus to which they belong. A.. Facial Region. This region includes those muscles of the head which form a part of the framework of the lips, cheeks, and nostrils : that is, all those which are grouped around the face, properly called. Authors are far from being unanimous with regard to the nomenclature and description of these muscles. Girard recognised eleven, to which he gave the following names : labialis. alveolo-labialis, zygomatico-labialis, lachrymo-lahialis, supernaso-lahialis, super- maxillo-labialis, siqyerma.iillo-nasalis magnus. sii]3erma.Tillo-nasalis parvus, transversalis 7msi, ma.viUo-labialis, mento labialis. To these eleven muscles, three of which are single, two others are added ; these were described by Bourgelat as the middle (intermediate) anterior and middle (intermediate) pos- terior muscles, which Girard wrongly considered as belonging to the labial. 1. Labialis, or Orbicularis of the lAps. (Fig. 110, 27.) (Synonym. — Orbicularis oris — PercivaU.) rreparntiiin.—Fievaoxe with scissors the skin covering the two portions of this muscle : afterwards the buccal mucous membrane and subjacent glands within the lips, to expose its internal face. The labialis. disposed as a sphincter around the anterior opening of the mouth, is regarded as the intrinsic muscle of the lips, and is composed of two portions or fasciculi, one for the upper, the other for the lower lip. United to each other at the commissures of the mouth, and confounded with the superficial layer of the alveolo-labialis, which they appear to continue, these two muscular portions also receive a large portion of the fibres belonging to the majority of the extrinsic muscles, such as the supermaxillo- nasalis magnus and supcrnaso-labialis. The orbicularis is not attached to the neighbouring bone ; its component fibres afiecting a circular form, have, consequently, neither beginning nor ending, except in being continuous with other fibres. The internal face of the superior fasciculus responds to a layer of salivary 218 THE MUSCLES. glands, which in part separate it from the buccal mucous memhrane. The external, covered by the skin, adheres to it in the most intimate manner, and is found isolated from it only on the median line, at first by the aponeui'otic expansion of the suiiermaxillo-labialis, then by a musculo-fibrous layer analogous to that which forms the mento-labialis. By its internal face, the inferior fasciculus likewise responds to the buccal mucous membrane, and to some salivary glands. By its external face, it Fi?. 110. SUPERFICIAL MUSCLES OF THE FACE AND HEAD. 1, Temporo-auricularis e.xternus, or attollens maximus ; 2, Levator palpebrre, or corrugator supercilii ; 3, Temporo-auricularis internus, or attollens posterior; 4, 5, Zygomatico-auricularis, or attollens anterior ; 6, Orbicularis palpebrarum ; 7, Parotido-aurieularis, or deprimens aurem ; 8, Parotid gland ; 9, Temporal, or subzygomatlc vein; 10, Ditto, artery; 11, 12, Superior and inferior maxillary nerves; 13, Fascia of the masseter muscle; 14, Nasal bones; 15, Supernaso- labialis, or levator labii superioris alaique nasi ; 16, Supermaxillo-labialis, or nasalis longus labii superioris ; 17, External maxillary or facial artery ; 18, Facial vein ; 19, Supermaxillo-nasalis magnus, or dilatator naris lateralis ; 20, Superior maxillary nerve ; 21, Zygomatico-labialis, or zygomaticus ; 22, Parotid, or Stenon's duct ; 23, Masseter ; 24, Alveolo-labialis, or buccinator ; 25, Super- maxillo-nasalis parvus, or nasalis brevis labii superioris; 27, Labialis, or orbicu- laris oris ; 28, Maxillo-labialis, or depi-essor labii inferioris ; 29, Mento-labialis, or levator menti. forms an intimate union with the cutaneous integument, like the superior fasciculus. This muscle plays the part of a constrictor of the anterior opening of the mouth, and has complex functions to perform in suction, the prehension of food, and in mastication. 2. Aheolo-laUalis. (Fig. 110, 24.) Synonyms.— M.o\&r\ii externiis et internus — Bourgehd. {Buccinator — Percivall. Leyh divides this muscle into two portions ; its superlicial plane he designates the buccinator, and the deep plane the molaris.) Preparation.— Proceed to the ablation of the masseter ; dissect the external surface of the muscle, takinp; care of the risoiius Santorini and zygomaticus, which are confounded with it. Then divide it in the middle, as far as the commissure of the lips; turn down each strip on the jaw.s, and remove the mucous membrane, in order to study the inner face of the muscle and the attachments of the superficial plane to the maxillary bones. MUSCLES OF THE HEAD. 219 Situation — Form. — Situated on the sides of the face, partly concealed by the masseter muscle, and applied to the mucous membrane of the cheeks, the alveolo-labialis is a flat, thin muscle, elongated in the direction of the head, and formed of two superposed jilanes. Extent — Structure — Attachments. — The deep plane, the longest and least wide, is narrower at its extremities than its middle, and is formed of strongly aponeurotic muscular fasciculi, which are attached, posteriorly : 1, To the alveolar tuberosity ; 2, To the external surface of the superior maxillary bone, above the last three molar teeth; 3, To the anterior border of the inferior maxillary bone, behind the sixth molar, in common with the maxillo- labialis. On reaching the commissm-e of the lips, this muscular layer appears to be continued by small tendons with the fibres of the orbicularis. The superficial plane only begins about the middle of the deep one, whose anterior half it entirely covers. Its fibres, less tendinous than those of the latter, extend from a median raphe which also divides the deep layer in its length, and are directed, some forwards, some backwards, to terminate in the following manner : the first are inserted into the external face of the super- maxillary bone, above the first molar tooth and the superior interdental space ; the second are attached to the inferior interdental space alone. Relations. — Externally, with the masseter, zygomatico-labialis, cuticularis, great supermaxillo-nasalis, supernaso-labialis, the parotid duct, which crosses it to enter the mouth, and the facial artery and veins ; internally, with the buccal mucous membrane. The deep plane is accompanied and covered at its anterior border by the upper molar glands ; its posterior border is margined by the inferior molar teeth, which it partially covers. The superficial layer is distinctly separated from the deep one in its anterior part, which is attached to the superior maxillary bone. Behind, these two planes adhere more intimately to one another, though they are found completely isolated by an interstice in which one or two large veins pass. Actions. — The function of the alveolo-labialis is particularly related to mastication : this muscle, in fact, pushes between the molar teeth the portions of food which fall outside the alveolar arches ; but it cannot aid in bringing the two jaws together, as M. Lecoq has correctly observed. 3. Zygomatico-labialis. (Fig. 110, 21.) Synonyms. — Portion of the cuticularis of Bourgelat. The zygomaticus major of Man. (^Zygomaticus — Percivall.) A very small, pale, and thin ribbon-like muscle, arising from the surface of the masseter, near the maxillary spine, by an aponeurosis which is con- founded with the cuticularis ; it terminates on the surface of the alveolo- labialis, at a short distance from the commissure of the lijjs. Covered by the skin, it covers the alveolo-labialis muscle, and some of the superior molar glands, vessels, and nerves. This muscle pulls backwards the commissure of the lips when it is in a state of contraction. In Solipeds there is also sometimes found a muscle resembling the zygomaticus minor of Man. It is a very small fasciculus situated under the preceding muscle, near its superior extremity. It appears that this fasciculus is continued, above, by the fibres of the lachrymo-labialis, and is lost, below, on the alveolo -labial surface, a little beneath the carotid canal. 220 THE MUSCLES. 4. Laclirymo-ldbial, or Lachrymal Muscle. (^Synonym, — ^Not mentioned by Percivall. It is the inferior palpebral muscle of Leyh.) A wide and very thin muscle, situated superficially below the eye : it is continuous, in front, with tlie supernaso-labialis ; behind, with the cu- ticularis; above, with the orbicularis of the eyelids. Its fibres, partly muscular and partly aponeurotic, leave the external surface of the lachrymal and zygomatic bones, are directed downwards, and become lost in a cellular fascia which covers the alveolo-labialis ; some pass beneath the zygomatico- labialis and form the zygomaticus minor, when this is present. This muscle is supposed to corrugate and twitch the skin below the eye. 5. Supernaso-labialis. (Fig. 110, 15.) Synonyms. — ^The maxillaris of Bourgelat. The levator lahii superioris alasque nasi of Man. (Levator lahii superioris alxque nasi — Percivall. Fronto-labialis — Leyh.) Situation — Direction — Form — Structure. — Situated on the side of the face, in an oblique direction downwards and backwards,^ the supernaso- labialis is a wide muscle, flattened on both sides, elongated from below to above, aponeurotic at its superior extremity, and divided inferiorly into two unequal branches, between which passes the great supermaxillo-nasalis. Attachments. — It has its origin, by its superior aponeurosis, from the frontal and nasal bones, and unites on the median line with the muscle of the opposite side. Its anterior branch, the widest and thickest, goes to the external ala of the nose and to the upper lip, where its fibres are confounded with those of the orbicularis. The posterior branch terminates at the commissure of the lips. Belations.—Oiitwiirds, with the skin; inwards, with the . supermaxillo- labialis, the posterior portion of the small supermaxillo-nasalis, and vessels and nerves. Its posterior branch covers the great supermaxillo-nasalis, and the anterior is covered by that muscle. Actions. — It elevates the external ala of the nose, the upper lip, and the commissure of the lips. 6. Supermaxillo-lahialis. (Fig. 110, 16.) Synonyms. — Levator lahii superioris of Bourgelat. The levator lahii superioris proprii of Man. (Nasalis longtcs lahii superioris — Percivall.) Situation — Direction — Form — Structure. — Lying vertically on the side of the face, below the supernaso-labialis, this muscle is a thick and conical fleshy mass, terminated inferiorly by a tendon. Attachments. — It is attached, by the upper extremity of its fleshy body, to the external surface of the supermaxillary and zygomatic bones — origin. Its terminal tendon passes over the transverse muscle of the nose, to unite with that of the opposite side, and with it to form a single aponeurotic expansion, which dips by small fibres into the subcutaneous musculo-fibrous tissue of the upper lip. Belations. — Covered by the lachrymal and supernaso-labialis muscles, this muscle in turn covers the supermaxillary bone, the bottom of the false nostril, the small supermaxillo-nasalis, and the transversalis nasi. Actions. — It raises the upper lip, either directly or to one side, as it acts singly or in concert with its congener. ' It is to be remembered that we suppose the head maintained in a vertical position. MUSCLES OF THE HEAD. 221 7. Great Supermaxillo-nasalis. (Fig. 110, 19,) Synonyms. — The pyramidalis-nasi of Bourgelat. The canfnusof Man. f Dilatator naris lateralis — Percivall.') Situation — Direction — Form — Structure. — This muscle, situated on the side of the face, between tht two branches of the supernaso-labialis, in an almost vertical direction, is of a triangular form, and slightly tendinous at its summit. Attachme7its. — It has its origin, by the aponeurotic fibres of its summit, from the external face of the supermaxillary bone, below its ridge. — It terminates, by its base, on the skin covering the external wing of the nostril, its most posterior fibres being confounded with those of the orbicularis of the lips. Belations. — Outwardly, with the skin and the inferior branch of the supernaso-labialis ; inwardly, vrith the anterior branch of that muscle, and with vessels and nerves. Actions. — It dilates the external orifice of the nasal cavity, by pulling outwards the external wrng of the nostril. 8. Small Su]3erma.xiUo-nasalis. (Fig. 110, 25.) Synonyms. — The nasalis brevis, and portion of the subcutaneous muscle of Bourgelat. (Nasalis brevis labii superioris — Percivall.) Girard has described, by the above name, a small, thick, and short musciilar fasciculus which covers the external process of the premaxillary bone, and whose fibres, either originating from that, the supermaxillary bone, or the internal face of the supernaso-labialis muscle, terminate in the skin of the false nostril, and the appendix of the inferior turbinated bone. Eigot has attached to this muscle that described by Boui'gelat as the short muscle. The latter is composed of short, transverse fibres, applied to the expansion of the cartilaginous septum of the nose which projects laterally beyond the nasal spine. These fibres abut, by their most eccentric extremities, against the skin of the false nostril and the appendix of the superior turbinated bone. In adopting Eigot's description, it is found that the small supermaxillo- nasalis is composed of two portions, which border the re-enteriug angle formed by the large process of the premaxillary bone and the nasal spine. These two portions, posterior and anterior, unite at their upper extremities. The first appears to be confounded, below, -with the middle anterior (depressor alfe nasi), the second is continuous with the transversalis nasi. When they contract, they concur in the dilatation of the false nostril and the proper nasal cavity. 9. T)-ansversalis Nasi. Synonym. — [Dilatator naris anterior — Percivall) A single, short, and quadrilateral muscle, flattened before and behind, applied to the widened portion of the nasal cartilages, and composed of transverse fibres proceeding from one cartilage to the other. Covered by the skin and the aponeurotic expansion of the two elevator muscles of the upper lip, the transverse muscle of the nose covers the cartilages to which it is attached, and is confounded below with the orbicularis of the lips. Designed to bring together the internal alfe of the nose, this muscle ought to be considered more particulai-ly as the dilator of the nostrils. 222 THE MUSCLES. 10. The Middle (Intermediate) Anterior Muscle. Synonyms. — Medius aniarior—Bourgelat. Myrtiformis of Man. (Depreesor labii superior i—1'ercivall. Incisive muscle of the upper lip — Leyh. A portion of the orbicularis, according to Rigot.) Bourgelat thus names a deeply-situated muscle which is fixed to the inner face of the premaxillary bone, above the incisor teeth, and whose fibres ascend to meet those of the posterior portion of the small super- maxillo-nasalis muscle, to terminate with them on the anterior appendix of the inferior turbinated bone ; some fibres become lost in the lip. It is regarded as a dilator of the entrance to the nasal fossa. To study this muscle, it is necessary to raise the upper lip and remove the mucous membrane covering it. It may be dissected at the same time as the bony attachments of the superficial plane of the alveolo-labialis muscle. 11. Maxillo-lahialis. (Fig. 110, 28.) Synonyms. — Depressor labii inferioris — Rigot. A dependency of the buccinator of Man. (Depressor lahii inferioris — Percivall. Inferior maxillo-lahialis — Leyh. Depressor anguli oris of Man.) Situation — Direction — Form — Structure. — Situated along the inferior border of the alveolo-labialis, whose direction it follows, this muscle forms a long narrow fasciculus, terminating inferiorly by an expanded tendon. Attachments. — 1, By its superiol* extremity, to the anterior border of the lower jaw, in common with the deep plane of the alveolo labialis — fixed origin ; 2, By its terminal tendon, to the skin of the lower lip — movable insertion. Relations. — Outwardly, with the masseter and the facial portion of cuticularis of the neck ; inwardly, with the maxillary bone ; in front, with the alveolo-labialis muscle, with which it is directly united in its upper two- thirds. Actions. — It separates the lower from the upper lip, and pulls it to the side if one alone acts. 12. Mento-lahialis or Muscle of the Chin. (Fig. 110, 29.) (jSj/Honj/ms.— Percivall appears to describe this and the next muscle as one. It is the quadratus menti of Man.) This name is given to a musculo-fibrous nucleus, forming the base of the rounded protuberance beneath the lower lip in front of the beard. This single nucleus is confounded, in front, with the orbicularis of the lijjs, and receives into its upper face the insertion of the two posterior middle muscles (levatores menti). 13. Middle (Intermediate) Posterior Muscle. Synonyms.- -Medina posterior — Bourgelat. {Levator menti — Percivall. Incisive musde of the lower lip — Leyh.) Bourgelat describes, by this name, a small muscular fasciculus, analogous in every respect to the medius anterior. This little muscle takes its origia from the external surface of the body of the lower jaw, beneath the inter- mediate and corner incisors ; from thence it descends into the texture of the lip, to unite with that of the opposite side on the upper face of the mento- labialis. Several authors have described it as a dependent of the last muscle. MUSCLES OF THE HEAD. 223 It is an energetic elevator of the lower lip. To dissect this muscle, tlie directions given for the preparation of the anterior medius will suffice. B. Masseteric or Temporo-maxillary Region. This pair region comprises five muscles lor the movement of the lower Jaw. These are : the masseter, temporal, internal pterygoid, external pterygoid, and digastricus. Preparation. — 1. First study the digastricus and its stylo maxillary portion, with the internal pterygoid, in preparing the hyoid muscles as they are represented in fig. 111. 2. Expose the pterygoideus externus, by removing in this preparation the hyoid bone and its dependencies, as well as the two preceding muscles. 3. To dissect the temporalis, excise the external pterygoideus from its inferior border, an operation which exposes the orbital fasciculus of the temporalis ; then turn over the piece, saw oif the orbital process at each end, and remove the eye and auricular muscles. 4. Dissect the masseter in clearing away from its external surface the cuticularis and the vessels and nerves which cover it. 1. Masseter. (Fig. 110, 23.) Synonijms. — Zygomatico-maxillaris — Girard. (^The zygomatico maxillaris of Leyh.) Situation — Form —Structure. — Aj)plied against the external face of the lower jaw, the masseter is a short, wide, and very thick muscle, flattened on both sides, irregularly quadrilateral, and formed of several super2)osed planes, two of which are perfectly distinct towards the temporo-maxillary articula- tion, by the somewhat different direction of their fibres. These are divided by a considerable number of intersections, and are covered by a strong aponeui'otic layer, which becomes gradually thinner backwards and down- wards. Attachments. — The fasciculi of the masseter have their fixed insertion on the zygomatic crest. — Their movable insertion is on the imjjrints which cover the upj)er half of the inferior maxillary branch. Melations. — It responds, by its superficial face, to the facial portion of cuticularis colli, to the nerves of the zygomatic plexus, and several venous and arterial vessels ; by its deep face, to the inferior maxillary bone, the alveolo-labialis and maxillo-labialis muscles, the superior molar glands, and two large venous branches ; by its inferior border, with the parotid canal, and the glosso-facial artery and vein ; by its superior and posterior border, to the parotid gland. Its deep plane responds, anteriorly, with the temporo- maxillary articulation, and is so intimately confounded with the temporalis, that it is impossible to define the respective limits of the two muscles. Action. — This muscle, the special elevator of the lower jaw, plays an imj)ortant part in mastication. It always acts as a lever of the third class, the middle line, which represents the resultant of all its constituent fibres, passing behind the last molar. 2. Temporal or Crotaphitic Muscle. 5j/no?!?/ms.— Temporomaxillaris— G/rard. (The temporo-maxillaris of Leyh.) Situcdion — Form — Structure. — Situated in the temporal fossa, to which it is moulded, and which it fills, this muscle is flattened from above to below, divided by strong tendinous intersections, and covered by a nacrous aponeurotic layer. Attachaents. — It takes its origin: 1, In the temporal fossa and on the 221 THE MUSCLES. bony crests wtich margin it ; 2, By a wide fasciculus, paler than the other portion of the muscle, but not unconnected with it, from the imprints situated behind the crest sui-mounting the orbital hiatus. It terminates on the coronoid process and the anterior border of the branch of the lower jaw. Eclations. — This muscle covers the temporal fossa, and is covered by the temporo-auricularis muscles, scutiform cartilage, internal scuto-auricularis, the fatty cushion at the base of the ear, and by another adijiose mass which separates it from the ocular sheath. Its deep fasciculus responds, by its internal face, to the two pterygoid muscles. Action. — It brings the lower jaw in contact with the upper, by acting as a lever of the first kind ; but the orbital portion of the muscle elevates tho inferior maxilla and moves it laterally by a lever of the third class. 3. Internal Pterygoid. Synonyms. — Portion of the spheno-maxilliris of Bourgelat. (The pterygoideus intermts of Percivall. Leyh designates the pterygoideus internus and externus as one muscle, the spheno-maxillaris or internal masseter.) Situation — Form — Structure. — Situated in the intermaxillary space, opposite the masseter, the pterygoideus internus, although not so strong as that muscle, yet so closely resembles it in form and structure as to be named by Winslow the internal masseter. Attachments. — 1. To the palatine crest and subsphenoidal process — fixed insertion : 2. In the hollow excavated on the inner face of the branch of the lower jaw — movable insertion. Melations. — Outwardly, with the pterygoideus-externus. the orbital fasciculus of the temporal, the maxillo- dental nerves, mylo-hyoideal, and lingual muscles, arteries and veins, and the inner surface of the bone which receives its movable insertion. Inwardly, with the tensors palati — external and internal, the guttural pouch, the hyoideus magnus, hyoid bone, digastricus, the hypoglossal and glosso-pharyngeal nerves, glosso-facial artery and vein, the hyoglossus longus and brevis muscles, the laryngo-pharyngeal aj)paratus, the Stenonian duct, and the submaxillary glands. Action. — It is an elevator of the lower jaw, and also gives it a very marked lateral or deductive motion. If the left muscle acts, this movement carries the inferior extremity of the lower jaw to the right ; and if it be the right muscle, then in the contrary direction. 4. External Pterygoid. Synonym. — ^Portion of the spheno-maxillaris of Bourgelat. Form — Situation — Structure — Attachments. — A small, short, and very thick muscle, situated within and in front of the temporo-maxillary articulation, formed of slightly tendinous fasciculi which leave the inferior face of the si)henoid hone and the subsphenoidal process, and are directed backwards and upwards to be fixed to the neck of the inferior maxill iry condyle. Belations. — Outwardly, with the orbital fasciculus of the temporal muscle, and the temporo-maxillary articulation. Inwardly, with the numerous nerves emanating from the inferior maxillary branch, and with the internal pterygoid and tensors palati. Action. — When the two external pterygoids act in concert, the inferior maxilla is pulled forward; but if only one contract, the propulsion is MUSCLES OF THE HEAD. 225 accompanied by a lateral m< )vement, dui-ing wliich the extremity of the jaw is carried to the opposite side. 5. Digastncus. Synonyms. — Boursrelat has made two distinct muscles of this — the digastncus and stylo-maxillaris. Girard has described it as the stylo-maxillaris. (Percivall has evidently followed Bourirtlat's example, and divided tlie muscle into digadricm and stylo-maxUlaris. Leyh adopts the same course.) Form — Structure — Situation — Direction. — Composed of two fleshy bodies more or less divided by intersections, and united at their extremities by a median tendon, this muscle is situated in the intermaxillary space, and extends from the occiput to near the symphysis of the chin, describing a cui've upwards. Attachments. — It takes its origin from the styloid process of the occipital bone, by its superior fleshy body. It terminates : 1, On the curved portion of the posterior border of the lower jaw by a considerable fasciculus, which is detached from the superior fleshy body ;i 2, On the internal face of the same bone and the straight portion of its posterior border, by aponeurotic digitations which succeed the muscular fibres of the inferior fleshy body. Belations. — The superior belly of the muscle responds, superficially, to the parotid gland and the tendon of insertion of the sterno-maxillaris ; deeply, to the guttural pouch, the submaxillary gland, and the larynx and pharynx. The median tendon passes through the ring of the hyoideus magnus. The lower belly is in contact, outwards, with the ramus of the inferior maxilla ; inwards, with the mylo-hyoideus muscle. Action. — When this muscle contracts, it acts at the same time on the hyoid bone, which it raises in becoming straight, and on the lower jaw, which it pulls backwards and depresses at the same time. C. Hyoideal Region. This region includes six muscles grouped around the os hyoides, which they move. Five of these are pairs : the mylo-hyoideus. genio-hyoideus, sfylo- hyoideus, herato hyoideus, and the occipito-styloideus. The single one is the transversalis hyoiclei. Preparation. — Separate the head from the trunk, and remove the muscles of the cheeks on one side, with the parotid gland. 2. The branch of the inferior maxilla being thus exposed, it is sawn through in two places ; at first behind the last molar, then in front of the first. 3. After having separated the pterygoids and the stylo-maxillaris from the upper fragment or condyle, and the coronoid process, it is torn ofl" by pulling it backwards ; then the pterygoiiis and the digastricus are excised. 4. The inferior fragment of the jaw bearing the molar teeth is turned down V)y isolating the mylo-hyoideus from the mucous membrane. 5. Carefully remove the tongue by separating its extrinsic muscles from the genio-hyoideus, the anterior appendix of the hyoid bone, the transverse muscle, and the small hyoideus. The dissection having been performed in this manner, the large hyoideal branch may be separated from the small, by sawing thronuh the head longitudinally, leaving the symphysis menti intact, and turning down the corresponding half to the side already dissected, as well as the great hyoid branch, the pharynx, larynx, and soft palate. 1. Mylo-hyoideus. Form — Situation — Structure. — A membranous muscle situated in the intermaxillary space, flattened from side to side, elongated in the dii-ection > This is the fasciculus which Bourgelat has described as a distinct muscle, and named the stylo-maxiUaris, 226 THE MUSCLES. of the head, thinner and narrower below than above, and formed entirely of fleshy fibres which extend transversely from its anterior to its posterior border. Inferiorly, it is composed of a small fasciculus, which is distinguished from the princiijal portion by the slightly different direction of its fibres, and which covers in part the external surface of the muscle. Fig. 11] HYOIDEAL AND PHARYNGEAL REGIONS. 1, Neck of inferior maxilla ; 2, Hard palate ; 3, Molar teeth ; 4, Buccal membrane ; 5, Submaxillary glands; 6, Soft palate; 7, Tendon of hyoideus magnus through which the tendon, 8, of ;he digastricus passes; 9, Lower portion of digastncus; 10, Stylo-hyoideus ; 11, Buccal nerve; 12, Zygomatic arch , 13, Orbital branch of fifth pair of nerves ; 14, Articular process of temporal bone ; 15, Right cornu of hyoid bone ; 16, Hyo-glossus longus, or Kerato-glossus ; 17, Lingual nerve ; 18, 18, Tongue ; 19, Angle of left branch of mferior maxilla ; 20, Submaxillai-y gland, left side; 21, Subscapulo-hyoideus ; 22, Great hypoglossal nerve; 23, Hyo- thyroideus ; 24, Sterno-hyoideus ; 25, Stei'no-thyroideus ; 26, Subscapulo hyoi- deus ; 27, Thyroid gland ; 28, External carotid artery ; 29, Pneumogastric nerve ; 30, Stylo-hyoideus ; 31, Genio-hyoideus. Attachments. — It originates from the mylo-hyoid line by the anterior extremities of its fibres. Its movable insertion takes place on the inferior face of the hyoid body, on its anterior appendix, and on a fibrous raphe which extends from the free extremity of this appen-dix to near the genial surface, and which unites, on the median line, the two mylo-hyoideau muscles. JRelations. — By its external face, with the inferior maxilla, the digastric muscle, and the submaxillary lymphatic glands, B}' its internal face, with the sublingual gland, the Whartonian duct, the hypoglossal and lingual nerves, the genio-glossus, hyo-glossus longus and brevis, and genio-hyoideus. Its superior border responds to the internal pterygoid. Action. — In uniting on the median line with that of the opposite side, this muscle forms a kind of wide band or brace on which the tongue rests. When it contracts, it elevates this organ, or rather applies it against the palate. 2. Genio-hyoideus. Form — Structure — Situation. — A fleshy, elongated, and fusiform body, tendinous at its extremities, but especially at the inferior one, and applied, with its fellow of the opposite side, to the mylo-hyoidean brace. MUSCLES OF THE HEAD. 227 Attachments. — By its inferior extremity it is fixed to the genial surface — origin ; by its superior, it reaches the free extremity of the anterior appendix of the hyoid body — tenninadon. Belations. — Outn-ards and downwards, with the mylo-hyoideus ; inwards, with its fellow, which is parallel to it ; above, with the genio-glossus. Action. — It draws the hyoid bone towards the anterior and inferior part of the intermaxillary space. 3. Sfylo-hyoideus. (^Synonyms. — The hyoideus magnus o/Percivall. The kerato-hyoideus magnus of Leyh.) Form — Structure — Situation — Direction — Thin and fusiform, this muscle, smaller than the preceding, and, like it, tendinous at both its extremities, is situated on the side of the laryngo-pharyngeal ai:)paratus and the guttural pouch, behind the large branch of the hyoid bone, whose direction it follows. Attachments. — Above, to the superior and posterior angle of the styloid hone^Ji.ved insertion; below, to the base of the cornu of the os hyoides — movahJe insertion. Belations. — Outwards, with the pterygoideus internus; inwards, with the guttural pouch, the pharynx, and hypoglossal nerve. Its anterior border is separated from the posterior border of the styloid bone by the glosso-facial artery and glosso-pharyngeal nerve ; along the posterior border lies the upper belly of the digastricus. Its inferior tendon is perforated by a ring for the passage of the cord intermediate to the two portions of the latter muscle. Action. — It is antagonistic to the preceding muscle, drawing the body of the hyoid bone backwards and upwards. 4. Kerato-hyoideus. {Synonyms.— This is the hyoideus parvus of Percivall, and the smdl kerato-hyoideus of Leyh) A very small fasciculus, triangular in shape, and flattened on both sides. Inserted, on one side, into the posterior border of the styloid cornu and the inferior extremity of the styloid bone ; and on the other, to the superior border of the thyroid cornu. It responds, outwardly, to the basio-glossus and the lingual artery ; inwardly, to the buccal mucous membrane. It approximates the cornua of the os hyoides to each other. 5. Occipito-styloideus. Synonyms. — Tliis is the muscle which, up to the present time, has been described by veterinary anatomists as the siyh-hyoidem. This name has been given to the muscle nam£d by Girard the kerato-hyoideus magnus. A small, flat, and triangular muscle like the preceding, yet thicker and more spread, filling the space comprised between the styloid process of the occipital and the horizontal portion of the posterior border of the styloid bone. Its fasciculi become longer as they are situated posteriorly, are rather tendinous, and are carried from one of these bones to the other. Outwardly, it responds to the parotid gland ; inwardly, to the guttural pouch, which it covers for its whole extent ; its posterior border is largely confounded with the superior insertion of the digastricus. "When this muscle acts, it causes the os hyoides to swing, carrying its inferior extremity backwards and downwards. 228 THE MUSCLE 6. Transversalis Hyoidei. By this name Bourgelat has described a short riband of parallel muscular fibres, which unites the superior extremities of the styloid coruua, and approximates them to each other. DIFFERENTIAL CHARACTERS OF THE MUSCLES OF THE HEAD IN OTHER THAN SOLIPED ANIMALS. A. Facial Region. EuMiNANTS. — There are found in the Ox . 1. An orbicular muscle of the lips, analogous to that in the Horse. 2. An alveolo-labialis of the same kind (fig. 112, 5). 3. A zyqomaticus or zygomatico-lahiahs, stronger and redder than in Solipeds. Its aponeurosis of origin, covered by the cuticularis muscle of the face, extends upon, the surface of the masseter muscle as far back as the zygomatic arch, to which it is attached (fig. 112, 7). Fi2. 112. SUPERFICIAL MUSCLES OF THE OX's HEAD. 1, Supermaxillo-labialis ; 1, 1', Accessory fasciculi of the superma.xillo-labialis ; 2, Supermaxillo-nasalis inas;nus ; 3, Supernaso-labialis ; 4 Lachrymalis ; 5, Alveolo-labialis; (3. Maxillo-labialis confounded with the preceding; 7, Zygo- matico-labialis ; 8, Frontal, or cuticularis muscle of the forehead ; 9, Orbicular muscle of the eyelids; 10, Zygomatico-auricularis ; 11, External temporo-auricu- laris; 12, Scutiform cartilage; 1,5, External scuto-auricularis ; 14, Mastoid process; 15, Masseter; 16, Stylo-hyoideus ; 17, Digastricus ; 18, Sterno-maxil- lary fasciculus belonging to the cuticularis muscle of the neck ; 19, Trachelo- hyoideus (subscapulo-hyoideus) ; 20, Sterno-suboccipitalis (sterno-maxillaris, or mastoideus); 21, Anterior branch of the superficial portion of the mastoido- humeralis (levator humeri); 22, Superior branch of ditto; 23, Deep portion of same muscle; 24, Trachelo-atloideus, peculiar to Ruminants and Pachyderms; 25, Great anterior straight muscle of the head. MUSCLES OF TEE HEAD. 229 4. A laclirymalis, thicker and more developed than in the Horse. Its most anterior fibres glide beneath the zygomaticus. and are lost on the alveolo-labialis surface : tlie most posterior pass over the aponeurotic tendon of the zygomatico-labialis, and are confounded M'ith those of the cuticuhiris. Above, it joins the orbicularis of the eyelids in a still more intimate manner than in the Horse ; so that it is ahnost impossible to distinguish the limits of the two muscles (iig. 112, 4). 5. A swpernaso-lahialis continued, above, with tlie inferior border of the frontal or fronto-cuticularis muscle; and divided, inferiorly, into two branches, which comprise between them the supermaxillo-labialis and the pyramidalis-na^alis. These two branches, however, are not disposed as in Solipeds, the anterior covering the preceding muscles, and the posterior, of but little importance, passing beneath them to lose itself in the substance of the upijcr lip (fig. 112, 3). 6. A sirpermaxiUo-Iabiah's, Avliicli gains the middle of the muzzle by jjassing along the inner side of the nostrils (tig. 112. 1). 7. Two additional t the tendon of the coraco-ljumeralis. The stemo-prescapulaiis of the Dog is very feeble, and terminates with the principal muscle on the humerus. COSTAL EEGIOK. In each costal region we find fifty-four muscles, which concur, more or less directly, in the resjiiratory movements. These muscles are : 1, The great serratus ; 2, The costo-transversalis ; 3, Seventeen external intercostah ; 4, Seventeen internal intercostah; 5, Seventeen supercosfals ; 6, The triangularis sterni. Preparation. — 1. Place the subject in the second position. 2. Eeraove the fore- limb and all the muscles attaching it to the trunk, by sawing through the scapula as shown in figure 10.?, in order to expose the great serratus and costo-traii&versalis muschs ; finish the dissection of the former by taking away aU the yellow fibrous tissue which covers its posterior dentations. 3. Study the external intercostals and the supercostals, after removing the great oblique muscle of the abdomen, the serrati mnscles, the common intercostal (ilio-costalis), and the ilio-spinalis. 4. Excise some external inter- costals in order to show the corresponding internal ones. 5. The triangularis is dis- sected oil another portion, which is obtained in separatiug the sternum from the thorax by sawing through tlie sternal ribs a little above their inferior extremity. 23G THE MUSCLES. 1. Great Serratus. (Fig. 105, 15.) Synonyms. — Costo-subscapularis— G/rarrZ. Posterior portion of the serratus magnus of Bourgelat. (A portion of Percivall's serratus magnus.) Form — Situation. — A veiy wide muscle, disposed like a fon, split up into digitations at its inferior border, applied against the thoracic walls, and partly concealed by the shoulder. Structure. — It is composed of divergent fleshy fibres, all of which con- verge towards the superior extremity of the scapula, and are covered by a very strong aponeurosis that gradually diminishes from above to below, and only adheres to the muscle in its inferior part. Attachments. — 1, To the external face of the eight sternal ribs ; 2, To the anterior triangular surface of the internal face of the scapula, behind the angularis, with which it is confounded; 3, To the whole extent of the posterior triangular surface of that bone. On reaching the scapula, the aponeurosis separates from the fleshy fibres, and is inserted alone into the fibrous plane which covers the muscular fasciculi of the subscapularis. Relations. — The great serratus responds : outwardly, and through the medium of an abundant supply of cellular tissue, which facilitates the play of the limb against the lateral wall of the thorax, to the subscapularis, supraspinatus, the adductor of the arm, great dorsal (latissimus dorsi), and the mass of olecranian muscles ; inwardly, to the first seven external inter- costals, to the sides of the sternum, and the anterior small serratus. Its four posterior digitations cross the first five of the great oblique muscle of the abdomen, and are covered by a prolongation of the abdominal tunic. Action. — With that of the opposite side, this muscle constitutes a vast brace or girth on wliich the thorax rests when the animal is supported on its limbs; it therefore acts, in relation to the trunk, like a suspensory ligament. When it contracts, its fixed point being the thoracic walls, it pulls the superior extremity of the scapula do\vnward and backward, and causes this portion of the limb to perform a swinging movement which carries the inferior angle upwards and forwards. If the limb is the fixed point, then it raises the thorax between the two anterior members, and assists in the respiratory movements by elevating the ribs. 2. Transverse Muscle of the Bibs. (Fig. 105, 16.) Synonyms. — Costo-stcrnalis — Girarcl. {Lateralis sterni — Percivall.') Form — Structure — Direction — Situation. — This is a flattened band, aponeurotic at its extremities, oblique from upwards and forwards, and situated under the preceding muscle, at the inner aspect of the deep pectoral. Attachments. — Its posterior extremity is fixed to the sternum and the fouith sternal cartilage ; the anterior to the external face of the first rib. Relations. — Inwardly, with the second and third ribs, into which are often inserted some of its fasciculi, and with the three first intercostal muscles. Outwardly, with the two portions of the deep pectoral muscle. Action. — This is an auxiliary to the expiratory muscles. (Leyh says its action is to raise the ribs and their cartilages, and thus to enlarge the anterior portion of the thorax during inspiration.) TEE MUSCLES. 237 3. External Intercosfals. (Fig. 104, 68.) Situation — Form. — These muscles fill tlie spaces between the ribs, but do not descend beyond their inferior extremities ; they, therefore, do not occupy the intervals between the cartilages. They are flattened, fleshy bands, gradually diminishing in thickness from above to below. Structure — Attachments. — Each intercostal muscle is composed of a series of muscular fasciculi, intermixed with numerous aponeurotic fibres, both of which jiass obliquely backwards aud downwards, from the posterior border of the preceding to the external face of the succeeding rib. Belations. — They respoud, outwardly, to the different muscles applied against the thoracic walls ; inwardly, to the internal intercostals. 4. Internal Intercostals. (Fig. 106, 16.) These are placed at the internal face of the preceding, which they exactly repeat with regai-d to their general form, but from which they difier in the following jDoints : 1. Very thick between the costal cartilages, these muscles are reduced at the upper part of the intercostal spaces to a thin aponeurotic layer, supported only by some fleshy fibres. They therefore gradually diminish in thickness from below upwards. 2. Their fasciculi are less tendinous than those of the external inter- costals, and are carried obliquely forward and downward, from the anterior border of the posterior rib to the posterior border and internal face of the rib in front ; so that the fibres of the external and internal intercostals'- cross each other like the letter X. 3. Outwardly, they respond to the external intercostals ; inwardly, to the costal pleura. Action of the intercostal muscles. — The function of these muscles has been for a long time, and is even now, much discussed ; and it may be said that there were never, perhaps, more diverse or contrary oiunions given on any subject than on this. M. Berard, who has summed up the elements of the discussion with the greatest judgment, considers the external intercostals as inspiratory muscles, and the internal ones also as inspiratory by those fasciculi which occupy the siDaees between the costal cartilages ; the remainder, the majority, are expiratory. 5. Supercostals. Synonyms. — Transverso-costales — Girard. (Levatores costarum — Percivall.) Small, flat, triangular, muscular and tendinous fasciculi, constituting, it might be said, the heads of the external intercostals, from which they are scarcely distinguishable in the first and last costal intervals. They arise from the transverse processes of the dorsal vertebrfe, and are directed backwards and outwards, gradually expanding, to terminate on the external face of the one or two ribs which succeed their fixed insertion. Outwardly, they respond to the ilio-spinalis ; inwardly, to the external intercostals. The supercostals draw the ribs forward, and are consequently inspiratory muscles. 6. Triangularis of the Sternum. Stjnonyms. — Stemalis — BourgeJat. Stemo-costalis — Girard. 'The sterno-costales of Percivall, and sterno-cosfalis of Leyh.) 238 THE MUSCLES. Form — Situation. — This muscle, flattened above and below, elongated from before to behind, and dentated at its external or superior border, is situated in the thoracic cavity, above the sternum and the cartilages of the true ribs. Attachments. — It is fixed, by its internal border, on the superior face of the sternum, to the ligamentous cord which circumscribes it outwardly. It has its movable insertion on the cartilages of the sternal ribs, the first excepted, by means of digitations from its external border. Structure. — It is formed of strongly aponeurotic muscular fasciculi, which are directed from the internal to the external border. Belations. — Inwardly, with the pleura ; outwardly, with the cartilages to which it is attached, the internal intercostals, and the internal thoracic vein and artery. Action. — The triangularis of the sternum concui'S in expiration by depressing the costal cartilages. (Leyh asserts that if the fixed point be the sternum, this muscle pulls the I'ibs forwards, and so widens the thoracic cage ; but if the fixed point is the ribs, the sternum will be raised and the thoracic space diminished.) DIFFEEENTIAL CHARACTERS IN THE MUSCLES OF THE COSTAL REGION IN OTHER THAN SOLIPED ANIMALS. The muscles of the costal region cannot "be the same in number in all the domes- ticated animals; the intercostals and supercostals, for instance, must vary in number with that of the ribs. Beyond this, the differences are slight. In the Ox, the great serratus is very extensive, and the portion which passes to the posterior triangular surface of the scapula is readily distinguished from the anterior by its diminished thickness, the larger proportion of aponeurotic fibres it contains, and the flattened tendon by means of which it is inserted. In the Pi'd, it is remarked that the internal intercostals are prolonged, maintaining a certain thickness, to near the vertebral column, COMPARISON OF THE THORACIC MUSCLES OF MAN WITH THOSE OF THE DOMESTICATED ANIMALS. The muscles of the axillary region, the costal region, and the diaphragm are desig- nated in ]\Ian as the thoracic muscles. The pectoral muscles are distinguished into great and small. The great pectoral corresponds to the superficial pectoral of the Horse. It is attached, on one side, to the inner two-thirds of the clavicle, the anterior face of the sternum, and the cartilages of the first six ribs; on tlie other, to the anterior border of the bicipital groove and, by a fibrous expansion, to the aponeurosis of the arm. The costal fasciculi are distinctly separated from the clavicular and sternal fasciculi. The small pectoral, which corresponds to the deep pectoral of animals, is inserted, on the one part, into the external face of the third, fourth, and fifth ribs ; on the other part by a tendon to the anterior Ixirdcr of the coracoid process. In Man, tliere is found a muscle which does not exi.st in animals; this is the sub- clavhis, a very .slender fasciculus situated beneath the clavicle, and attached to the cartilage of the first rib and the external portion of the lower face of the clavicle (see Fig. 117, 5). The great serratus does not show any distinct aponeurosis on its surface ; it arises from the eight first ribs, and its digitations are grouped into three principal fasciculi. Lastly, in Man Ihe internal intercostals are prolonged to the vertebral column by small muscles, named the suhcostals (or intracostals). INFERIOR ABDOMINAL REGION. The lateral and inferior walls of the abdominal cavity are formed by a wide musculo-aponeurotic envelope, which rests, by its periphery, on the sternum, ribs, lumbar vertebra, ilium, lumbo-iliac aponeurosis, and the pubis. This envelope is concave on its superior surface, and results from the assemblage of four pairs of large membranous muscles arranged in MUSCLES OF TEE TEVNK. 239 superposed layers. Eeckoning tlaera from without inwards, these are designated the great, or external oblique, the small, or infernal oblique, the great straight, and the transverse muscle. Covered outwardly by an expan- sion of yellow fibrous tissue, the tunica abdominalis, and separated from those of the opposite side by the ichite line (linea alba), a medium raphe ex- tending from the sternum to the pubis, these muscles support the intestinal mass, and by their relaxation or contraction adapt themselves to the varia- tions in volume these viscera may experience. Preparation. — After placing the animal in the first position, a wide opening is to be made in the pectoral cavity by the ablation of a certain number of ribs, which should be divided inferiorly, above the costal attachments of the great oblique muscle. The heart and lungs are removed; then an incision is made in tlie diapliragm, to allow the digestive viscera contained in the abdominal cavity to be taken away. It is not abso- lutely necessary, however, to empty that cavity, and if its contents be" allowed to remain, several punctures should be made in the large intestine to prevent the accumulation of gas. and the too great distention of the abdominal parictes. These preliminary precautions having been adopted, then proceed in the following manner : 1. Eemove the skin from this region, and with it the panniculus camosus, in order to study the external surf;\ce of the abdominal tunic. 2. The dissection of the great oblique muscle is accomplished by removing the yellow fibrous envelope from the fleshy portion of the muscle, together with the stemo-trochineus. Tlie inguinal ring should be exposed by the ablation of the dartos muscle, the sheath and penis, or the mammae. 3. On the opposite side, tlie small oblique is uncovered by excising the great oblique, leaving, however, that portion of the aponeurosis which is mixed up with that of the first muscle. 4. The latter having been studied, dissect the great straight muscle of the abdomen on the same side, in separating from the white line, by a longitiidinal incision, the aponeurosis common to the two oblique muscles, dividiua: this aponeurosis and the fleshy portion of the internal oblique by another incision extending transversely from the umbilicus to the middle of the lumbar region, and laying back one of the musculo- aponeiu'otic sections on the thigh, the other on the ribs. 5. The transverse muscle is dissected on the same side as the external oblique has been. To expose it, nothing more is necessary than to make two incisions similar to the foregoing, but iucluding the two oblique and the straight muscle, throwing back the two portions as above. 6. Lastly, open the entire abdominal cavity hx cutting through the transverse muscle in the same way ; then study the muscular digitations of that muscle, the internal orifice of the inguinal canal, and the leaf reflected from the aponeurosis of the great oblique muscle. 1. Abdominal Tunic. The vast expansion of yellow elastic fibrous tissue spread over the two external oblique muscles of the abdomen is so named. Very thick towards the prepubic tendon of the abdominal muscles and in the vicinity of the linea alba, this expansion gradually thins as it ap- proaches the sternum, and disappears near the abdominal insertion of tlie sterno-trochineus muscles. It also diminishes in thickness as it extends from the linea alba ; and when it reaches the fleshy portion of the great oblique muscle it becomes reduced to an extremely thin leaf, whose fasciculi separate more and more from one another, until they completely disappear. Anteriorly, however, it is seen to be prolonged on each side to the posterior digitations of the serratus magnus. Posteriorly, it furnishes some bundles of fibres, which are detached from the surface of the common tendon, and • are carried between the thighs to be lost on the internal crural muscles. The abdominal tunic is covered by the skin and the panniculus carnosus, from which it is separated by an abundance of cellular tissue. In the male, its external surface gives attachment to the suspensory ligaments of the sheath, and to the dartos : and in the female, to the elastic capsule which envelops each mammary gland. By its internal face, it closely adheres to the aponeurosis of the great oblique muscle ; though it is easily 240 THE MUSCLES. separated from the fleshy portion. It is traversed by several openings which afford passage to the subcutaneous vessels and nerves of the abdominal region. The abdominal tunic acts as an immense elastic girth or bandage, which aids the muscles in sustaining the weight of the intestines. As the digestive organs increase in vohmie this tunic increases in thickness. In the Pig, Dog, and Cat, it is reduced to a simple cellulo-aponeurotic lamina, owing to the stomacli and intestines in these animals exercising but a small amount of pressure on the abdominal parietes. 2. WJiite Line. The white line (linea alba) is a fibrous cord comprised between the internal border of the two great straight muscles, and is considered as being formed by the intercrossing, on the median-line, of the aponeuroses belonging to the oblique and transverse muscles. Attached, in fi'ont, to the inferior surface of the xiphoid appendage, this cord is confounded, behind, with a large tendon, the prepubic or common tendon of the abdominal muscles, which is fixed to the anterior border of the pvibes (Figs. 90, A; 108, c; 116, i). This tendon, covered by the abdominal tunic, contributes to form the internal commissure of the inguinal ring, and gives origin to the pubio-femoral ligament. Towards the union of its posterior third with its two anterior thirds, the white line wideus, so as to form a lozenge-shaped space, in the centre of which is found the remains of the umbilicus and the umbilical cord (Fig. 116, 14). 3. Great Oblique, or External Oblique of the Abdomen. (Figs. 105, 18 ; 116, 5.) Synonyms. — Costo-abdominalis — Girard. {Ohliquus externus ahdomims — PercivaU.) Situation — Composition. — This muscle, the largest and the most super- ficial of the four, is composed of a flesliy and an aponeurotic portion. Form, Structure and Attachments of tlie fleshy portion. — This is composed of fibres directed obliquely downwards and backwards, and presents itself as a wide muscular band, narrower before than behind, applied to the inferior surface of the last thirteen or fourteen ribs. Its superior border is concave, and attached : 1, To the external surface of the ribs just mentioned by as many slightly aponeurotic digitations, the first four of which cross the denta- tions of the great serratus ; 2, To the aponeurosis of the great dorsal muscle, from the last rib to the external angle of the ilium (Fig. 105, 18). Its inferior border, convex and sinuous, is continuous witli the aponeurosis ; it descends, in front, to the cartilaginous circle of the false ribs, which it projects beyond posteriorly, increasing in this as it nears the lumbar region. Form, Structure, and Attachments of the aponeurosis. — This is narrow and thin in front, wide and thick behind, of a triangular form, and composed of white, nacrous-looking fibres passing in the same dii'cction as the fibres of the fleshy portion, with whose inferior border it is continuous by its external border. Its internal border is inserted into the white line and the preijubic tendon ; and its posterior border, extending from the external angle of the ilium to the anterior border of the pubis, responds to the jjlicature of the flank, embraces the corresptmding crural muscles, and establishes the line of demarcation between the trunk and the abdominal limb (Fig. 116, 10). The ajjoneurosis of the great oblique gives rise, at its posterior bordcsr, to two very remarkable fibrous leaves which appear to be produced by tlie MUSCLES OF THE TRUNK. 241 doubling of this aponeurosis into two layers. One of these leaves descends on the internal muscles of the thigh to constitute the crural aponeurosis (Fig. 116, 11); while the other is reflected ui)wards and forwards, to enter the abdominal cavity ; this reflected leaf of the great oblique aponeurosis is named the crural arch (lijament of Poupart or Fallopius). (Fig. 108, b.) Near the prepubic tendon of the abdominal musclesj and immediately before its division into two leaves, the aponeurosis of tbe external oblique is pierced by a large oval apertm-e (Fig. 116, 5), the inferior orifice of the canal through which passes the cord of the testicle in the male, and the mammary vessels in the female. This channel has been named the inguinal canal. The description of the femoral aponeurosis, the crural arch, and tbe inguinal ring — a necessary complement of the great oblique muscle — will be given hereafter. Itelations of tJie Great Oblique Muscle. — By its superficial face, the external oblique responds to tbe sterno-trochineus and tbe abdominal tunic, which latter separates it from the skin and tbe panniculus. By its deep face, it is related to the ribs, into which it is insertCLl, as well as with their carti- lages, tbe corresponding intercostal muscles, the small oblique, and the great straight muscle. The latter even appears to be attached, through the anterior moiety of its external border, to the fleshy portion of the great oblique, by means of a slight lamina of yellow elastic tissue, which covers, to a small extent, the deep face of the two muscles. Action. — The external oblique, in contracting, compresses the abdominal viscera, flexes the vertebral column, and acts as an exj^iratory muscle. (By its compression on the abdominal viscera it concm-s in the acts of defecation, mictui'ation, and parturition.) IxTERNAii Crural Aponeurosis. — This fibrous lamina descends from the plicature of tbe flank on the patella and the inner surface of the leg. Outwardly, it is confounded with the aj)oneurosis of the fascia lata; in- wardly, it degenerates into cellular tissue. It covers tbe long adductor of the leg, part of the short adductor, the vastus internus, and the crural vessels at theii- exit from the abdominal cavity. Crural Arch. — As already mentioned, this is the reflected leaf of the great oblique aponeurosis, and is also named the ligament of Fallopius anA Poupari's ligament. It is a ■nide, flat band, attached by its extremities to the external angle of the ilium and the anterior border of the pubis. Its anterior face (Fig. 108, b) forms, inwardly, tbe posterior wall of the inguinal canal ; it gives attachment, outwardly, to the posterior fibres of the small oblique miiscle. Its posterior face, applied against the superior extremity of the patellar muscles, the long adductor of tbe leg, the pectineus, and the crural vessels on their leaving the abdomfen, embraces all these parts as in a vast arch, and from this peculiarity it derives its name. Its superior border is inserted, for its external half, into the lumbo-iliac aponeurosis. In its middle part it is much thinner, and is prolonged to the external surface of the long adductor muscle of the leg and tbe iliac fascia, to be at last mixed up with the latter. Within the pectineal insertion of the small psoas muscle, it forms the anterior margin of the crural ring : a triangular orifice circumscribed on the other side by the anterior border of the pubis, the iliacus, and the long adductor of the leg, and tbrough which pass the crural vessels as they leave the abdomen by the crural arch.^ The inferior border * This orifice is covered by a very thin aponeurotic layer, wliich is prolonged, above, on the crural vessels, behind, into the pelvic cavity, and which appears to be continuous, 242 TEE MUSCLES. is continuous with the femoral aponeurosis and that of the great ohlique muscle. Inguinal Canal. — This is an infundibuliform canal compressed on each side, through which the spermatic cord and scrotal artery pass from the abdomen in the male, and the external mammary vessels in the female. Situated on the side of the prepubic region, in an oblique direction downwards, backwards, and inwards, and measuring from two to two-and- a-half inches in length, this canal lies between the crm-al arch, which con- stitutes its posterior wall, and the fleshy portion of the small oblique muscle, which forms the anterior wall. Its inferior (external ) or cutaneous orifice, also named the inguinal ring, is much larger than the suj)erior (internal). Pierced in the aponeurosis of the great oblique, in the angle formed by the union of the internal border with the posterior border of the aponeurosis, this openiDg is of an oval form, directed obliquely backwards and inwards, which permits it to be described as having two lips or pillars, and two extremities or commissures. The pillars, distinguished into anterior and posterior, are composed of the arciform fibres from the aponeurosis of the great oblique muscle. The commissures, internal and external, result from the union of the two pillars at their extremities. The internal is limited by the prepubic tendon of the abdominal muscles. The superior (internal) or peritoneal orifice of the inguinal canal is situated in front of, and directly opj)osite to, the crural ring. It is a simide dilatable slit, comprised, like the canal itself, between the crural arch and the small oblique muscle. Not well defined at its extremities, this ojieuing includes the neck of the vaginal sheath. 4. Small or Internal Oblique Muscle of tJie Abdomen. (Figs. 106, 17'; 116, 2.) Synonyms. — Ilio-abdominalis — Girard. (OUiquus internus abdominis — Percivall.) Situation — Composition. — Situated beneath the preceding, which exactly covers it, this muscle is, like it, composed of a fleshy and aponeurotic portion. Form, Structure, Position, and Attachments of the muscular portion. — The muscular portion is very thick, triangular, and flabelliform, and occui^ies the region of the flank. Its superior border is united, by a thick, yellow, elastic production, to the aponeurosis of the great dorsal (latissimus dorsi), and a peculiar small muscle, named hy the Germans the retractor costce (retractor of the last rib), which we consider as a dependency of the small oblique muscle. Its posterior border is slightly raised and lies against the crural arch, from which it separates, inwardly, to form the inguinal canal. Its anterior and inferior border is convex, irregular, and thinner than the other portions of the muscle, and is continuous with the aponeurosis. All the fibres entering into the composition of this muscular portion ai-e spread like a fan, and leave the external angle of the ilium and the external fourth of the crural arch to be directed, the posterior fibres backwards and inwards, the middle fibres downwards, and the anterior fibres forwards to reach the antero- inferior border of the muscle. inferiorly, with the upper hordcr of Poupnrt's ligament. Tliis lamina is perhnps only a dependency of the sub})eritnneal aponenrosis; and if so, it represents the only vestige of the fascia tram^versalis it has been p ssible to discover in Solipeds. MUSCLES OF TEE TRUNK. 24:^ Fig. IIG, Form, Structure, and Attachments of the aponeurosis. — The aponeurosis is irregularly triangular, and formed of nacrous-looking fibres, which are directed like the muscular fibres, and cross in X fashion the aponeurotic fibres of the external oblique. It succeeds the an- tero-inferior border of the muscular por- tion, and is separated, superiorly, into several digitations which reach the in- ternal face of the last asternal cartilages. Throughout the whole extent of its in- ternal border it is fixed to the white line. Melations. — This muscle is covered by the external oblique. The aponeuroses of the two muscles, which are merely superposed outwardly, are blended in- wardly in so intimate a manner that it might be thought their respective fasci- culi were woven into each other. The small oblique covers the great straight and the transverse muscles. Action. — This muscle, a congener of the preceding, compresses the abdominal viscera, depresses the last ribs, and causes the flexion, either dii-ect or lateral, of the vertebral column. The retractor muscle of the last rib. — This small muscle, flattened on each side, and triangular in form, originates by aponeurotic fibres from the summits of the first two or three transverse processes of the lumbar region. It terminates on the posterior border of the last rib. Covered by the last digitation of the pos- terior serratus and by the great oblique, it covers in turn the transverse muscle of the abdomen. In contracting, it draws the last rib backwards, and fixes it in that position, in order to permit the ex- piratory action of the internal intercostal muscles. It therefore plays the same part, in regard to these muscles, that the scalenus does to the external intercostal muscles (Fig. 106, 17). MUSCLES OF THE INFERIOR ABDOMINAL REGION. 1, Aponeurosis of the great oblique ; 2, Muscular portion of the small oblique ; 3, Rectus abdominis ; 3', Transverse muscle ; 4, Flat tendon by which the four abdominal muscles are inserted into the pubis ; 5, Inguinal ring ; 6, Its anterior pillar ; 7, Its posterior pillar; 8, Its external commissure; 9, Internal commissure; 10, Posterior border of the great oblique aponeu- rosis, 11, Internal crural aponeurosis; 12, Strip of the great oblique aponeu- rosis turned downwards to show the origin of Poupart's ligament , 14, Traces of the umbilicus. 5. Great Rectus Muscle of the Ahdomen. (Figs. 105,20; 116,3.) Synonyms. — Sterno-piibialis — Girard. {Rec- tus abdoniiius — Perciiall.) Situation — Extent — Form — Structure. — This is a wide and powerful muscular band, extending from the sternum to the pubis, included between the aponeurosis of the internal oblique and that of the transverse muscle, narrower at its extremities than in its middle portion, and divided by numerous transverse and zig-zag fibrous inter- 244 TEE MUSCLES. sections. These strongly adhere to the aponeurosis of the small oblique muscle, are nearer to each other, and more distinct, in front than behind, and are produced by small tendons which are placed at certain distances on the track of the muscular fasciculi, making it somewhat of a polygastric muscle. Attachments. — In front : 1, To the prolonging cartilages of the last four sternal, and the first asternal ribs ; 2, To the inferior face of the sternum. Outwardly, by the anterior moiety of its external border, to the internal face of the great oblique. Behind, to the anterior border of the pubis through the medium of the common tendon, which is a direct continuation of the great straight muscle. Belations. — By its inferior face, and in front, with the sterno-trochineus and great oblique ; for the remainder of its extent, with the aponeurosis of the small oblique. By its superior face, with the transverse muscle and the cartilages of several ribs. By its internal border, with the white line, which separates it from the opposite muscle. Action. — It draws the thorax backwards, and compresses the abdominal viscera. It is also the principal flexor of the spine. (Leyh, remarking that it shares in the functions of the preceding muscles, adds that it di-aws the pelvis forwards during copulation.) 6. Transverse Muscle of the Abdomen. (Figs. 106, 18; 116, 3'.) Synonyms. — Lumbo-abdominalis — Girard. ( Transversalis abdominis — Percivall. The costo-abdominalis internus of Leyh.) Situation — Composition. — This muscle is situated immediately without the peritoneum, and forms the deep layer of the abdominal parietes. It is muscular outwardly, and aponeurotic for the remainder of its extent. Form, Structure, and Attachments of the muscular portion. — It presents a band elongated from before to behind, extending from the sternum to the transverse processes of the last lumbar vertebrae, following in its course the direction of the cartilages of the ribs, and formed of parallel fibres passing from one border to the other. Its superior border, concave, is attached : 1, To the internal surface of the asternal ribs by digitations placed opposite those of the diaphi'agm, but the majority of which do not mix with theui ; 2, To the extremity of the transverse processes of the lumbar region by a thin fibrous lamina. Its inferior border is convex and continuous with the aponeurosis. Form, Structure, and Attachments of the aponeurosis. — This is triangular- shaped, with the base behind, and with its fibres running in a transverse direction to the median line. Closely laid one against another in front, these fibres separate behind, and form only a very thin and incomplete lamina. By its external border, the aponeurosis is joined to the inferior margin of the muscular portion. Its internal border is fixed to the xiphoid cartilage and the white line. Its posterior border, badly defined, appears to join the crural arch only on its outer aspect. Belations. — Outwards, with the inferior extremity of the asternal ribs and their cartilages, with the rectus abdominalis, the small oblique, and the depressor muscle of the last rib ; inwardly, with the peritoneum, from which it is separated by the subperitoneal aponeurosis : an extremely fibrous layer which, in Man and some animals, becomes much thickened towards the criu'al MUSCLES OF THE TRUSK. 245 arch, where it forms adhesions. It has been described, in human anatomy, as the fascia transversal Is. Action. — It compresses the abdominal viscera when it contracts, and presses them against the vertebral column. Fig. 117. DIFFEREXTIAL CHARACTEKS =" OF THE ^a•SCLES OF THE ABDOMINAL REGION IN OTHER THAN SOLIPED ANIMALS. As has been already said, the development of the abdomi)ial tunic is in pro- portion to the volume of the digestive viscera. This membrane is, therefore, very wide and thick in Buminants, while it is re- duced to an insignificant leaf in the Pig and Car- nivora. In these animals the internal crural aponeu- rosis does not exist, and is replaced by a cellular layer. The aponeurosis of the great oblique, instead of being doubled into two lamiuffi at its posterior border, is entirely reflected to form the crural arch. In the latter animals, the great oblique is also dis- tinguished by the extensive development of its mus- cular part, and the narrow- ness of its aponeurosis. The muscular portion of the small oblique of Eu- minants occupies the entire space comprised between the posterior border of the last rib, the extremity of mtscles of the anterior aspect of the body of man; the transverse processes of on the left side the superficial layer is seen, on the lumbar vertebrae, and the right the deeper layer. the external angle of the l, Pectoralis major; 2, Deltoid; 3, Anterior boraer of the ilium. The small retractor latissimus dorsi ; 4, Serratus magnus ; 5, Subclavius, right side ; 6, Pectoralis minor ; 7, Coraco-brachialis ; 8, Biceps, with its two heads; 9, Coracoid process of the scapula; 10, Serratus magnus, right side ; 11, External intercostal muscle of the fifth mtercostal space ; 12, External oblique ; 13, Its aponeurosis with the linea alba ; 14, Poupart's ligament ; 15, External abdominal ring; 16, Rectus muscle of right side; 17, Pyramidalis muscle; 18, Internal obhque ; 19, Conjoined tendon of internal oblique muscle and Poupart's lisament. of the last rib is not distinct from the principal muscle. This arrangement is like- wise present in the smaller domesticated animals. It is also to be remarked that, iuRurninants, the tendinous intersections of the great rectus muscle of the abdomen are more marked at its superior than its inferior face : and that the aponeurosis of the transverse is much thicker and more resisting than in Solipeds. comparison op the abdominal snrscLES OF MAN with those of animals. With the exception of some slight differences, the abdominal muscles of Man present the same disposition as those of the smaller animals. The abdominal tunic is not present, but is replaced by a cellular layer which 19 ■246 THE MUSCLES. separates the skiu from the aponeurosis of the great oblique. The muscular portion of this muscle has no attachment to tlie aponeurosis of the great dorsal. The aponeurosis of the small oblique is divided into two lamellse at the external border of the great straight muscle, the anterior is consolidated with the great oblique, and passes in front of the great straight ; the posterior is united to the transverse, and passes behind that muscle. The aponeurosis of the transverse is divided into two leave?, only one of which remains behind the great straight muscle; this is named the semilunar Aihl of Douglas. The great rectus muscle of the abdomen offers three transverse librous intersections in its length (linex transversa;). At its upper extremity, it divides into three branches : the internal is attached to the xiphoid appenda^'e and the cartilage of the seventh rib ; the middle, to that of tiie sixth rib ; the external, to the cartilage of the fifth rilj. "To the great rectus is annexed a small triangular muscle, the pyramplal, which is not found in animals. This muscle is about 2J inches long ; is sometimes absent ; most developed in children ; is attached by its base to the pubis, between the spine and tho symphysis ; and by its summit is continuous with a tendon which is lost in the white line, and constitutes, with that of the opposite side, a fibrous cord which may be followed to tiie umbilicus." — Beaunis and Bouchard. Lastly, at the inner aspect of all the abdominal muscles, beneath the peritoneum, is a fibrous lamella — the fascia transversalis. 'I'his fascia is not distinctly limiteel ujnvards or outwards; below, it is fixed to the crural arch, iu the viciuity of the inguinal canal, and sends a layer to the surface of the oord spermatic. DIAPHRAGMATIC REGION. This is composed of a single muscle, the diaphragm. Diaphragm. Preparation. — Place the subject in the first position ; open the abdomen and remove the viscera it contains, as well as the large vascular trunks lying upon the sublumbar region ; detach the peritoneum from the fleshy portion of the muscle, in order to show the digit ations of the latter more distinctly, taking care not to allow the air to enter the thoracic cavity, as it would destroy the tense and concave form of the diaphragm. Situation — Direction. — Tlie diaphragm is a vast musculo-aponeurotic partition separating the thoracic from the abdominal cavity, between which it is placed in an oblique direction downwards and forwards. Form. — It is flattened before and behind, elliptical, wider above than below, concave posteriorly, and convex anteriorly. Structure. — This muscle comprises: 1, A central aponeurotic portion designated the phrenic centre, which is incompletely divided into two folioles (leaflets) by the pillars— Qeshy columns which descend from the sublumbar region; 2, A peripheral (or circumferential) portion forming a wide muscular band around the phrenic centre. The phrenic centre (also named the speculum Helmontii or mirroi* of Helmont) is composed of white, glistening, radiating fibres which, originating from the pillars, extend in every direction to join the muscular fibres of the peripheral portion. It is pierced, in its right leaflet, by a large opening for the posterior vena cava. The pillars arc two in number, a right and left. The right pillar, the most considerable, is a very thick, fleshy fasciculus which commences under the loins by a strong tendon, united to the inferior common vertebral liga- ment. It descends to tho phrenic centre, to which it gives a heart-shaped appearance. Near its inferior extremity, it presents an opening for the pas- sage of the oesophagus into the abdominal cavity. — The left pillar is a small triangular fasciculus, partly separated from the preceding by an orifice for the transmission of the posterior aorta and the thoracic duct. It also arises MUSCLES OF THE TRUNK. 247 from the subliimbar region by a tendon, which is confounded with that of its congener. The peripheral muscular portion is continuous, by its concentric border, Fiff. 118. DIAPHRAGM OF THE HORSE; POSTERIOR FACE. 1, 1', The two portions of the right pillar ; 2, Left pillar ; 3, Tendons of the pillars ; 4, 4', Peripheral muscular portion ; 5, Left leaflet of the aponeurotic portion ; 5, 5', Right leaflet of the same ; 6, Posterior vena cava ; 7, (Esophagus pasijng through the opening in the right pillar; 8, Posterior aorta between the two pillars; 9. Cartilaginous circle of the ribs; 10, 11, Section of the psoas muscle; 12, Section of a lumbar vertebra ; 13, Section of the common mass ; 14, Retractor muscle of the last rib; 15, Xiphoid appendage of the sternum. with the central aponeurosis. Its excentric border is divided into dentations. Above, and on the left side, it nearly always joins the left pillar ; but ou the right side it stops at a certain distance from the corresponding pillar, 248 THE MUSCLES. so that towards this point the phrenic centre is not enveloped by the peripheral portion, and is in contact with the sublmnbar region. Attachments. — 1, To the bodies of the lumbar vertebrae by the tendons of its two pillars, which tendons are confounded with the inferior common vertebral ligament ; 2, By the external contour of its muscular portion, to the superior face of the xiphoid appendage and the inner face of the last twelve ribs, near their inferior extremities or cartilages. The digitations forming the last insertions do not intercross, in Solipeds, with those of the transverse muscle of the abdomen, being separated by an interval which is wider behind than before. Belations. — The anterior face of the diaphragm is covered by the pleura, and responds, mediately, to the base of the lung. The posterior aspect, covered by the peritoneum, is in contact with the greater part of the viscera contained in the abdominal cavity — the stomach, colon, spleen, and liver ; the latter is even attached to this surface for a portion of its extent. On each side of the pillars, the circumference of the muscle forms an arch which passes over the great and small psoas muscles. Action. — The diaphragm, in contracting, tends to become an inclined plane ; its central portion is carried backwards, and the antero-posterior diameter of the chest is increased. It is, therefore, essentially an inspiratory muscle. It may also raise the ribs by making the mass of abdominal viscera its fixed point ; it then acts as a reflected muscle, to which these viscera serve as a pulley. (The diaphragm also aids the other abdominal muscles in expulsive efforts and, when affected with irregular spasmodic contractions, produces the peculiar phenomenon in Man and some of the lower animals, known as hiccough.) DIFFEREXTIAL CHARACTERS OP THE DIAPHRAGM IN OTHFR THAN SOLIPED ANIMALS. In the Ox, the pillars of the diaphragm are very long and voluminous. "The attachments of the muscular portion are much farther distant from the cartilaginous circle than in the Horse, particularly at the superior part; this disposition explains the innocuousness of puncture of the paunch in the middle of the last intercostal space; for with the Horse, when the instrument is passed through this part, it penetrates the thorax. — Communicated to M. Lecoq by M. Tabourin. In the Sheep we have not remarked that the costal attachments were more forward than in the Horse. Kigot erroneously states that, in the Pig and Dori, the oesophagus passes between the two pillars of the diaphragm ; on several occasions we have convinced ourselves that this conduit traverses the right pillar, as in the otber animals. COMPARISON OF THE DIAPHRAGM OP MAN WITH THAT OF ANIMALS. In the human diaphragm, the aponeurotic portion is divided into three leaflets, which has caused it to be termed the aponeurotic trefoil. Between the middle and right leaflet is the orifice through which the inferior vena cava passes. The openings for the passage of the cesopliagus and the aorta are situated between the two pillars. There are frequently met with in Man one or two small accessory pillars, separated from the large pillars by an aperture that affords a passage, on the right side, to the vena azygos and the sympathetic nerve, and on the left side, to one of the lumbar veins and the other sympathetic nerve. The peripheric muscular portion always joins, posteriorly, the central muscular portion. Article II. — Muscles op the Anterior Limbs. These are divided into four principal groups : the muscles of the shoulder, arm, fore-arm, and foot. MUSCLES OF THE ASTEBIOR LIMBS. 249 MUSCLES OF THE SHOULDER. These muscles are grouped around the scapula, and all act upon the arm, which they extend, flex, abduct, adduct, etc. They form two regions : an external or suprascapular, and an internal or subscapular. A. External Scapular Begion. This comprises four muscles : the long abductor of the arm, the short abductor, the super- for supra-} spinatus. and sub- (or infra-) spinatus. These muscles are applied to the external surface of the scapula, and are covered by an aponeurotic lamella. Preparation of the external scapular region. — Separate the limb from the tnmk; remove the trapezius and mastoido-humeralis, to expose the external sm-face of the aponeurosis; take away, also, the small pectoral muscle, after studying its mode of insertion into this fascia. This bein? accomplished, next remove the latter muscle to show the supraspinatus, the subspinatus, and long abductor muscle of the arm ; leaving only the strip which attaches the anterior [.ortion of the latter to the tuberosity of the scapular spine. To study the short abductor muscle, it is only necessary to cut the long abductor and superspinatus across, and to throw back the sections : an operation requiring some care, because of the intimate adherence of the short abductor to the infraspinatus." 1. External Scapular Aponeurosis. This aponeurosis, to which the sterno-prescapularis and long adductor of the arm act as tensors, gives origin, by its internal face, to several septa which peneti-ate between the scapular muscles, and form around them more or less complete contentive sheaths. Its external face is separated from the skin by the panniculus caruosus, trapezius, mastoido-hmneralis, and the aponeurotic fascia which unites the last two muscles. It is continuous, in front, with the thin fibrous expansion extended over the internal scapular muscles ; behind and downwards, it is prolonged over the muscles of the arm and insensibly degenerates into conjunctival tissue ; above, it is attached to the fibro-cai-tilaginous prolongation of the scapula. 2. Long Abductor of the Arm, or Scapular Portion of the Deltoid. (Fig. 119, 1, 1.) Synonyms. — Seapulo-hmneralis voagaas—Girard. (Teres major— Percivall. Great scapulo-trochiterius — Leyh.) Situation — Composition — Form — Direction. — This muscle is situated beneath the scapular aponeurosis, behind the subspinatus, and is composed of two portions placed one above the other, separated by a superficial inter- space. The posterior portion, the most considerable, is elongated from above to below, bulging in its middle, narrow at its extremities, plane on its external, and convex on its internal surface. It accompanies the posterior border of the subspinatus, and is lodged in a depression in the thick extensor muscle of the fore-arm. The anterior portion, much shorter than the preceding, extends over the subspinatus and short abductor, by slightly crossing the direction of these two muscles. Thick inferiorly, this portion diminishes considerably towards its superior extremity. 250 TEE MUSCLES. Fis. 119. Structure and Attachments. — The first portion is generally paler than the second, and is composed of longitudinal fleshy fibres deeply fbtersected by tendinous strips. It takes its origin, by its superior extremity, from the dorsal angle of the scapula. The anterior portion is deeper-coloured and more tendinous than the other. Its superior ex- tremity, included within two fibrous folds resulting from the duijlicature of the scapular aponeurosis, is fixed, through the medium of these, to the tuberosity of the scapular spine. These two muscular bodies unite in- feriorly, and terminate together on the del- toid imprint or subtrochiterian crest by tendinous and muscular fasciculi. Relations. — This muscle responds : out- wardly, to the scapular a2)oneurosis, with which it may be said to form one body; inwardly, to the subspiuatus, the short ab- ductor of the arm, and the large and short extensors of the fore-arm. Action. — It gives a very marked abduc- tion movement to the humerus, and also makes it pivot outwards. It acts, besides, as a flexor of that bone, when its action is combined with that of the adductor of the arm. It should also be considered as a powerful tensor of the scapular aponeurosis. 3. Short Abductor of tlie Arm, or Teres Minor. (Fig. 85, 2, 3.) Synomjnis. — Scapiilo-humeralis minor — Girard. ( Teres minor — PercivaU. Scapulo-trochiterius, medium and parvum — Leyh.) Volume — Situation — Direction. — A small elongated muscle, situated below the pre- ceding and the subspinatus, along the pos- terior border of the scapula, whose dii'ection it follows. Form — Structure. — In its inferior half it 1, 1, Long abductor of the arm; 1', Its humeral insertion ; 2, Superspinatus ; 3, Subspinatus ; 3', Its tendon of insertion ; 4, Short abductor EXTERNAL MUSCLES OF THE of the arm ; 5, Biceps ; 6, Anterior brachialis ; RIGHT ANTERIOR LIMB. 7^ Large extensor of the fore-arm ; 8, Short extensor of the fore-arm ; 9, Anconeus; 11, Anterior extensor of the metacarpus ; 11', Its tendon; 12, Aponeurosis separating that muscle from the anterior brachialis ; 13, Oblique extensor of the metacarpus ; 14, Anterior extensor of the phalanges ; 14', Its principal tendon; 15, The small tendinous branch it furnishes to the lateral extensor; 16, Lateral extensor of the phalanges; 16', Its tendon; 17, The fibrous band it receives from the carpus; 18, External flexor of the metacarpus ; 19, Its metacarpal tendon ; 20, Its supracaipal tendon ; 21, Ulnar portion of the perforans ; 22, Tendon of the perforans ; 23, Its carpa lligament ; 24, Its reinforcing phalangeal sheath ; 25, Tendon of the perforatus. MUSCLES OF THE ANTEBIOR LIMBS. 251 is prismatic, muscular, divided by fibrous intersections, and easily separated into several irregular fasciculi. In its superior half it is flattened, entirely tendinous, and split into several digitations, the longest of wkich are behind. Attachments. — It originates 1, Through the medium of its tendinous digitations, from the posterior border of the scapula and the linear imprints in the posterior spinous fossa ; 2, From the smill tubercle situated on the external side of the margin of the glenoid cavity, by a short tendon. It terminates on the humerus, between the crest of the external tubercle and the deltoid imprint. Belations.- — Outwardly, with the subspinatus and the long abductor ; inwardly, with the large extensor of tlic fore-arm, the short extensor, and the capsule of the scapulo- humeral articulation. Action. — Like the preceding, this muscle is an abductor and outward rotator of the humerus. 4. Superspinatus. (Figs. 119, 2 ; 121, 5.) iSj/nonj/jMs.— Siipeiacrouiio-trochiterius— Girard. (^Antea spinatus — Percivall. An- terior spmatus — Leyh.) Form — Situation. — This muscle is thick and prismatic, stronger below than above, representing a very elongated pyramid, and completely filling, and even projecting beyond, the super- scapular fossa. Structure — Attachments. — It is almost entirely formed of fleshy fibres, which are attached, by their superior extremities, to the cartilage of prolong- ment of the scapula, the inner face of the scapular aponeurosis, the super- scapular fossa, and the anterior border and cervical angle of the scapula — fixed insertion. These fibres, on reaching the inferior extremity of the muscle, form two very thick, short, and slightly tendinous branches, united to each other by the enveloping coraco-radial or bicejis aponeurosis. The external branch reaches the summit of the external tubercle : the internal is inserted into the corresponding part of the internal tuberosity — movable insertion. Belations. — Outwards, with the scapular ajioneurosis, to which its fibres adhere in the most intimate manner , inwards, with the scapula and the sub- scapularis muscle ; forwards, with the small pectoral ; and behind, with the acromion spine and the subspinatus. The two terminal branches cover and embrace the coraco radialis tendon, and the cai)sule of the scapulo-humeral articulation. Action. — This muscle is an extensor of the humerus, and a tensor of the enveloping coraco-radial aponeurosis. With regard to the articulation of the shoulder, it plays the part of a powerful ligament : a function it shares with the majority of the other scapular muscles. 5. Subspinatus. (Fig. 119, 3, 3'.) %non?/ni.s.— Sub-acromio-trochiterius — Girard. {Postea spinatus — Percivall. Pos- terior spinatus — Leyh.) Situation — Form. — Situated, as its name indicates, in the subspinatus fossa, this muscle is wide, thin, and flattened on both sides at its superior extremity, thick and prismatic in its middle, and conoid at its inferior extremity, which is terminated by two short branches — an external and internal. 252 TEE MUSCLES. Structure. — The muscular fibres entering into its composition are directed, like the muscle itself, forward and downward ; they are deeply mixed with strong aponeurotic lamellae. Of the two branches which terminate it inferiorly the external is the strongest, and is entirely constituted by a powerful tendon ; the internal is both muscular and aponeurotic. Attachments.— All the fleshy fasciculi of this muscle are fixed, either directly, or through tlie medium of the internal aponeurotic lamellas : 1, To the whole extent of the subsjiinatus fossa ; 2, To the acromion spine and its tuberosity ; 8, To the cartilage of prolongment of the scapula ; 4, To the internal face of the scapular aponeurosis— ^xec? insertion. The movable insertion of the muscle takes place, on the external tuberosity, by its two terminal branches, the internal passing within the convexity : and the strong tendon constituting the external branch (Fig. 119, 3'j gliding, by moans of a synovial bursa, over the surface of this convexity, and attaching itself to the roughened facet which forms the crest of the external tubercle. Relations. — This muscle is covered by the anterior portion of the long abductor of the arm, and by the scapular aponeurosis. It covers the scapula, its cartilage, the fixed insertion of the large extensor of the fore-arm, and the short abductor, which adheres to it in the most intimate manner at its superior or aponeurotic portion. Its anterior border responds to the acromion spine and superspinatus ; the posterior is bordered by the long abductor of the arm. Its inferior extremity protects, outwardly, the capsule of the scapulo-humeral articulation, and is concealed beneath the mastoido- humei-alis. Action. — The subspinatus acts on the humerus as an abductor and out- ward rotator. B. Internal Scapular Begion. This is composed of four muscles : three principal, the suhsccqmlaris, adductor of the arm or teres major, and the coraco-brachialis, are situated at the internal face of the scapula, and are covered by a very small fibrous fascia which is formed of some scattered parallel fibres that run in a trans- verse direction. The last, named the small scapulo-humeralis, is a very slender fasciculus deeply lodged behind the articulation of the shoulder. Preparation.— Turn over the limb which has served for the dissection of the preceding region, and take away the slight internal scapular fascia. Be careful to preserve the ter- mination of the great dorsal muscle, in order that its relations nnd ndhesions with the adductor of the arm may be studied ; leave also th ' Immeral insertion of the sterno- trochineus, so that its union with the tendon of the coraco humeralis may be noted ; in a word, prepare the region as it is represented in figure 121. With regard to the small scapulo-humeral muscle, wliich is not shown in this preparation, it ought to be dissected at the same time as the short liexor of the fore-arm. Suhsca-pularis. (Fig. 121, 3). Synonym — Subscapulo-trochineus — Girard. Situation — Direction — Form. — This muscle, lodged in the subscapular fossa whose name it bears, affects the same oblique direction as the scapula. It is wider above than below, and divides superiorly into three portions ; so that its form exactly repeats that of the excavated surface it covers. Structure. — The muscular fibres of the subscapularis slightly converge towards its inferior extremity, and all end in a very strong, wide, and short tendon. They are intermixed with deep and superficial tendinous fibres, MUSCLES OF THE ANTERIOR LIMBS. 253 which singularly augment the tenacity of the muscle ; the superficial fibres are spread over the internal surface in glistening, nacrous layers. Attachments. — The subscapularis takes its origin from the whole extent of the fossa whose name it bears. Its movable insertion takes place on the internal tubercle, by means of a voluminous tendon it offers at its inferior extremity. A particular small synovial bursa facilitates the gliding of this tendon over the eminence into which it is inserted. Eelations. — The external face of the muscle is in contact with the scapula. Its internal face is applied against the great sen'atus, from which it is sepai-ated by a thick layer of cellular tissue, as well as by the rudimentary fascia covering the three muscles of the internal scapular region in common. Its anterior border, margined by the superspinatus, adheres closely to that muscle in its upper two-thirds, and forms with it, by its inferior third, the intermuscular space that lodges the subscapular vessels and nerves. Its posterior border responds to the adductor of the arm, with which it also unites for the greater part of its extent ; it is isolated from this muscle, in its inferior third, by the interspace lodging the subscapular vessels and nei-ves. Its terminal tendon covers the capsule of the scapulo-humeral ai'ticulation, which it powerfully binds ; it is in part covered by the tendon of origin of the coraco-himieralis muscle, which glides over its surface as on a pulley, by means of a synovial bursa. Action. — This muscle is principally, and perhaps exclusively, an adductor of the arm. It may be admitted, however, that it rotates the humerus inwards. Adductor of the Ann, or Teres Major. (Fig. 121, 4.) Synonyms. — Subscapulo-bumeralis — Girard. {Teres major — FercivaU. Great scapulo-humeralis — Leyh.) Form — Situation — Direction. — A long muscle, flattened on both sides, bulging in its middle, contracted at its extremities, thick at its anterior, and thin at its posterior border. It is situated behind the preceding, in the same oblique direction, and is parallel with the posterior portion of the long abductor, which it appears to repeat in the internal scapular region. Structure. — It is almost entirely muscular, showing only some tendinous fibres at its external surface and upper extremity. Its inferior extremity is terminated by a flat tendon, which also belongs to the great dorsal, and which has been already described (see page 203). Attachments. — It arises from the dorsal angle of the scapula, and the posterior border of the subscapular muscle — origin ; it passes to the circular imprint on the body of the humeras, to be attached by its inferior tendon — termination. Eelations. — Outwards, with the aponeurosis of the great dorsal and that of the long extensor of the fore-arm, which isolates it from the large extensor muscle ; inwards, with the great serratus, from which it is separated by the fibrous and cellular layers mentioned in the description of the sub- scapularis. Its inferior extremity covers the short flexor and middle extensor of the fore-arm ; it is covered by the long branch of the coraco-humeralis, and by the vascular and nervous trunks which send their ramifications to the arm, fore-arm, and foot. Action. — This muscle adducts the arm, and causes it to rotate inwards. If it contracts at the same time as the long abductor, it directly flexes the humerus. 25i THE MUSCLES. 3. Coraco-himeralis, Coraco-hrachialis, or Omo-brachialis. (Fig. 121, 10.) {Synonyms. — Coraco-humeralis — Percivall. Middle scajmlo-humeralis — Leyh., Volume — Situation — Direction. — A small elongated muscle, which ap- pears to belong to the arm rather than the shoukler, as it is situated at the internal face of the humerus, whose direction it slightly crosses. If it is described as in the subscapular region, it is because of its attachments and action, which are, in every respect, analogous to those of the other muscles of the shoulder. Attachments — Form, — Structure. — ^It commences on the beak of the coracoid process by a small flat tendon, which is at first included between the supraspinatus and subscapularis, but afterwards leaves the interstice formed by these two muscles, to glide and be inflected over the terminal tendon of the latter. This small tendon is succeeded by two muscular branches, one deep, the other superficial. The first is a wide, thin, and short band, almost entirely muscular, attached to the body of the humerus above the internal tuberosity. The second forms a fleshy body of a certain thickness, flattened on both sides, and strongly aponeurotic; the fasciculi composing it are longer as they are more posterior, and are inserted, by their inferior extre- mities, into the imprints on the anterior face of the humerus. Relations. — This muscle is covered by the coraco-radialis, and by the sterno-trochineus, which is partly attached to its tendon. It covers the internal insertion of the subscapularis, the humerus, the common tendon of the great dorsal, and the adductor of the arm, and a small j)ortiou of the short flexor and middle extensor of the fore-arm. Its posterior border is margined by the vascular and nervous trunks on the inner aspect of the arm. The anterior humeral nerve passes between its two branches, along with an arterial and venous ramification. Action. — -It is an adductor of the arm, and makes it also pivot inwards. Its direction and the disposition of its attachments do not permit it to produce rotation outwards, though it has been stated to do so by several authors. 4. Small Scapulo-Jiumeralis. (Synonyms. — Not mentioned by Percivall. Leyh, in addition to the above designation, names it the tensor of the capsular ligament.) The scapulo-humeralis gracilis is a very small cylindrical fasciculus, comprised between the large extensor of the fore-arm and the capsule of the scapulo-humeral articulation ; deriving its origin above the margin of the glenoid cavity of the scapula, and terminating below the head of the humerus by a thin tendon, which insinuates itself between the fibres of the short flexor of the fore-arm. This muscle apjiears to be peculiar to Solipeds, and has been regarded by Rigot as intended to raise the capsule of the scapulo- humeral articulation during flexion, so as to prevent its being pinched between the articular sui'faces. DIFFERENTIAL CHAKACTEES OF THE MUSCLES OF TEE SHOULDER IN OTHER THAN SOLIPED ANIMALS. The Carnivora are the only animals which offer somewhat notable differences in the muscles of the shoulder. 'J'hiis, the lont] abductor of the arm, very developed, has an anterior portion arising directly from the acromion, and a posterior portion which springs from the whole extent MUSCLES OF THE ANTERIOR LIMBS. 255 of the scapular spine, by a short aponeurosis. The mperspinatus is considerable, and terminates in a single branch that goes to the grealt trochanter. The i-uhiipinatus is not so large as the preceding, and is also undivided at its inferior extremity : it is the inferior branch which is absent. The coracoirrachialis is very short, and comix)sed of a single fasciculus, ■which terminates above the hiuueral insertion of the adductor of the arm. In the Pig, the disposition of this muscle is the same ; it is, besides, very tendinous. COMPAniSON OF THE MrSCLES OF THE SHOULDER OF MAX WITH THOSE OF ANIMALS. As muscles of the shoulder, there are only described the deltoid, suhspinatiis. teres minor and major, and the snhscapidaris ; the roraco-brachialis being included in the region of the arm, and the small scapido-humeralis is absent {see Fig. 120). The deltoid, represented in part by the long abductor of the arm of Solipeds, is a large, triangular, flat muscle, Fig. 120. that covers the articulation of the shoulder. Its fibres are . inserted into the external third of the anterior border of the clavicle, the external border of the acromion, and the inferior border of the scapular spine for the whole of its width ; below, it is attached, through the medium of a tendon, to the deltoid imprint. By their disposition, the superspinatus, suhspinatus, and subscapularis resemble the muscles of Carnivora The teres major, after establishing relations with the great dorsal, as in Solipeds, is fixed into the inner lip of the bicipital groove. MrSCLES OF THE ABM. These muscles, grouped around the humerus, are attached to the fore-arm bv their inferior ex- tremities. Those situated in front flex this por- tion of the limb, while those behind extend it. The fii'st form the anterior brachial region, the second the posterior brachial region. A. Anterior Brachial Begion. This region is composed of only two muscles, the long and short flexcns of the fore-arm. 1. Lonq Flexor of the Fore-arm or BracMal Biceps. (Figs. 85, 119, 121.) Synonyms. — Coraco-cubitalis, or coraco-radialis, accord- ing to Girard. (Flexor brachii — Percivall. Scapulo- or coraco-radialis — Leyh.) Preparation. — Place the limb on its internal face, throw back the brachial insertion of the mastoido-hxuueralis, stemo-humeralis, and sterno-aponeuroticus, over the ex- ternal muscles of the fnre-arm; excise, lengthways, the inferior extremity of the superspinatiis. ito show the originating lendon of the muscle. The inferior insertion may be studied with that of the short flexor muscle. Form — Situation — Direction — Structure. — A long, cylindrical muscle, thick in its middle portion, bifid inferiorly, situated in front of the humerus, in an oblique direction downwards and backwards, tendinous at its two extremities, divided by a great number of strong fibrous intersections, one of which, nearly central and much more considerable than the others, is a very resisting cord that traverses the muscle throughout its length, and becomes continuous with the tendons at its extremities. Attachments. — This muscle has its origin at the base of the coracoid MUSCLES OF ANTERIOR ASPECT OF man's upper arm. 1, Coracoid process of scapula ; 2, Coraco-clavicular liga- ment (trapezoid) passing up- ward to clavicle ; 3, Coraco acromial ligament, passing to acromion ; 4, Subscapu- laris ; 5, Teres major ; 6, Coraco-brachialis ; 7, Bi- ceps ; 8, Upper end of ra- dius ; 9, Brachialis anticus ; 10, Internal head of triceps. 256 TEE MUSCLES. process by a superior, round, and thick tendon (Fig. 85, 6) that reaches the bicipital groove, on which it is moulded in becoming fibro-cartilaginous, and over which it glides by means of a synovial sac, to be inflected backwards and confounded with the body of the muscle. Its inferior tendon, extremely short and strong, terminates on the superior and internal tuberosity of the radius — the bicipital tuberosity — in uniting itself to the capsular ligament of the elbow joint, and insinuating itself beneath the internal ligament of this articulation. At its origin, this tendon gives off a somewhat resisting fibrous band, which is spread over the surface of the anterior extensor of the metacarpus, and is confounded with the antibrachial aponeurosis. Relations. — The coraco-radialis covers an adipose cushion which sepa- rates it from the capsule of the scapulo-humeral articulation, the anterior face of the humerus, the coraco-humeralis, and the articulation of the elbow. It is covered : 1, By the superspinatus, between the two branches of which it passes ; 2, By a sj^ecial aponeurotic sheath, whose tensor is the above- named muscle, with the sterno-trochineus [see Fig. 114, 12, in which this aponeiu'osis has been partly preserved). This sheath separates the coraco- radialis from the mastoido-humeralis, the sterno-aponeuroticus, and from its congener, the short flexor. Action. — This muscle is a flexor of the fore-arm, and a tensor of the antibrachial aponeurosis. It acts, besides, through the cord which traverses its entire length, as an inextensible band that mechanically opposes the flexion of the scapulo-humeral angle while the animal is standing, and when the fore-arm is maintained fixed by the contraction of the humero-olecranian muscles. 2. Sliort Flexor of the Fore-arm. (Fig. 85, 12.j Synonyms. — Humero-cubitalis obliquus, or Iiumero-radialis — Girard. {Uumeralls externus — Fercivall. Iiumero-radialis — Leyh.) Preparation. — Lay the limb on its internal face, and remove the abductors of the arm, the subspiuatus, and the large and short extensors of the fore-arm, in order to expose the middle and upper extremity of this muscle. Then turn the limb on its external fuce to dissect the inferior extremity. To study it in all its details, it is a good plan to cut through the internal ligament of the ulnar articulation, and those muscles of the fore-arm which are attached to the epicondyle. Form — Structure — Situation — Direction. — This is a very thick muscle, almost entirely fleshy, voluminous in its superior part, and constricted infcriorly. It is lodged in the twisted furrow of the humerus, the direction of which it exactly follows as it turns round the bone to cover, successively, its posterior face, external face, anterior face, and the capsule belonging to the elbow articulation, until it finally reaches the inner side of the radius. Attachments. — The muscular fibres entering into its composition have their fixed insertion on the posterior face of the humerus, below the articular head. They terminate, inferiorly, on a flat tendon, which they almost entirely cover. This tendon glides in a transverse groove situated on the inner face of the radius, below the bicipital tuberosity, and afterwards passing under the internal ligament of the elbow joint, it divides into two very short fasciculi ; one of these goes to the radius, and the other to the ulna, where it is mixed up with the bundles of arciform fibres, which unite, on the inner side, the two bones of the fore-arm. Relations. — We already know the parts this muscle covers. It is covered, inwardly, by the adductor of the arm and the middle extensor of the fore- arm ; posteriorly and externally, by the large and short extensors of that ray. Its inferior extremity, comprised between the anterior extensor of the MUSCLES OF TEE ANTERIOR LIMBS. 257 metacarpus and the coraco-radialis, passes below the antibrachial band of the latter, as under a fibrous bridge. Action. — It is simply a flexor of the fore-arm. Fis. 121. INTERNAL ASPECT OF LEFT ANTERIOR LIMB. 1, Prolonging cartilage of scapula ; 2, Inner surface of scapula ; 3, Subscapularis ; 4, Adductor of the arm, or teres major ; 5, Supra- or antea-spinatus ; 6, Long extensor of the fore-arm, or portion of the caput magnum ; 7, Large extensor of the fore-arm, the other portion of the caput magnum ; 8, Middle extensor, or caput medium ; 9, Humeralis externus, or short flexor of the fore-arm ; 10, Coraco-humeralis ; 11, Upper extremity of humerus; 12, Coraco-radialis, or flexor brachii ; 13, Lower extremity of humerus ; 14, Brachial fascia ; 15, Anterior extensor of the metacarpus, or extensor metacarpi magnus ; 16, Belly and aponeurotic termination of the flexor brachii; 17, Ulna; 18, Ulnaris acces- sorius, or oblique flexor of the metacarpeus ; 19, Internal flexor of the meta- carpus, or epicondylo-metacarpeus ; 20, Radius; 21, Tendon of the oblique extensor ; 22, Large metacarpal bone ; 23, Flexor tendons of the foot ; 24, Sus- pensory ligament ; 25, Internal rudimentary metacarpal bone ; 26, Extensor tendon of the foot ; 27, Metacarpo-phalangeal sheath ; 28, Lateral cartilages of the foot ; 29, Podophyllse. 258 THE MUSCLES. B. Posterior Brachial Region. This is composed of five muscles, which have their movable insertion in common on the summit of the olecranon, and are consequently designated olecranian muscles. With reference to their action, they are also designated extensors of the fore-arm, and are distinguished into long, short, middle, and small. Preparation. — The muscles of this region ought to be studied before those of the preceding region. To dissect the large and short extensors, it is necessary to lay the limb on its inner face, remove the slight fibrous layer which covers these two muscles, and raise the abductors of the arm, which in great part conceal their origin. Tlie limb is kept in the same position for the dissection of the small extensor, which is not easily accomplished, as it is almost entirely concealed by the short extensors which, besides, closely adhere to it. To dissect the long and middle extensors, it suffices to turn the limb on its external surface and cut away the vessels, nerves, and lymphatics which partly cover the latter. The first, lying cl >sely to the internal face of the large extensor, requires some care in order to free it from its aponeurosis. 1. Long Extensor of the Fore-arm. (Fig. 121, 6.) Synonyms. — Scapulo-olecranius — Girard. (A portion of the cajmt magnum of the triceps extensor brachii—Percivall. Long scapulo-olecranius — Leyh.) Form — Situation. — This is a wide muscle, flattened within and without, and applied against the inner face of the large extensor, to which it closely adheres. Structure and Attachments. — It is composed of an aponeurosis, attached to the posterior border of the scapula — -fxed insertion : and a muscular portion, easily divisible into two fasciculi, one anterior, the other posterior. These two fiisciculi are formed of vertical fibres, the longest of which are posterior, and terminate at the posterior border of the ulna, as well as on the antibrachial aponeurosis — movable insertion, Relations. — Outwards, with the large and middle extensors; inwards, with the sterno-trochineus, the adductor of the arm, and the great dorsal. Its aponeurosis adheres closely to the tendinous portion which terminates the last-named muscle, and its anterior border is united to the aponeurotic sheath of the coraco-radialis by a particular fibrous fascia, which covers the vessels and nerves on the inner aspect of the arm. Action. — It extends the fore-arm, and renders the antibrachial aponeurosis tense. 2. Large Extensor of the Fore-arm. (Figs. 119, 7; 121, 7.) Synonyms. — Scapulo-olecranius major — Girard. The long portion of the triceps brachialis of Man. (Portion of the caput magnum of the triceps extensor brachii — Feruivall.) Volume— Form — Situation. — An enormous, short, and triangular muscle, occupying, with the short extensor, the space comprised between the posterior border of the scapula and the humerus. Structure and Attachments.— The fleshy mass constituting this muscle is formed of very thick fasciculi, among which are found some aj^oneurotic bands. These fasciculi have their origin on the dorsal angle and the axillary border of the scapula, either directly, or through the medium of two strong fibrous layers, between which they are at first included. They are afterwards directed backwards and downwards, and converge towards a thick tendon which occupies the posterior and inferior angle of the triangle represented by this muscle. The tendon terminates by attaching itself to the summit of MUSCLES OF THE ANTERIOR LIMBS. 259 the olecranon, after receiving a great munber of fibres from the short extensor, and after gliding, by moaus of a synovial capsule, over the eminence which serves for its insertion. Relations. — The external surface is covered by a thin, fibrous, white-and- yellow elastic layer, which separates it from the panniculus ; it is hollowed, near the upper border of the muscle, by an excavation into which is received the posterior portion of the long abductor. Its internal face responds to the great dorsal, the adductor of the arm, and to the long extensor. Its posterior border is margined by the latter muscle ; the superi(u- follows the axillary border of the scapula, and is attached to it to constitute the fixed insertion of the muscle ; the inferior responds to the short and middle extensors. Action. — It is an extensor of the fore- arm. 3. Short Extensor of tU Fore-arm. (Fig. 119, 8.) Synonyms. — Humero-olecranius exteinns — Girard. The vastus externus of the triceps brachialis of Man. {Caj)ut medium — Percirall.) Situation — Direction — Form — Structure. — This muscle is situated between the humerus and the inferior border of tbe preceding, and is directed oV)liquely downwards and backwards. It is thick and short, flattened and aponetirotic at its upper extremity, prismatic, and entirely formed of thick parallel muscular fasciculi for the remainder of its extent. Attachments. — One of its attachments is on the humerus, to the curved line extending from the deltoid imprint to the base of the articular head (see for this line Fig. 41, above 4), by the short aponeurosis of its superior extremity — fxcd insertion ; the other is to the olecranon, either directly, or through the tendon of the large extensor — movable insertion. Belations. — The prismatic shape of this muscle oflers three faces, which respond : externally, to the two abductors of the arm and to a slight fibrous layer continuous, above, with that which covers the large extensor, and below, with the antibrachial aponeurosis ; internally, to the small extensor, from which it is difficult to separate it, to the short flexor of the fore-arm, and to the anterior extensor of the metacarpus ; suj^eriorly, to the large extensor, which closely adheres to it. Action. — An extensor of the fore-arm. 4. Middle Extensor of the Fore-arm. (Figs. 119, 17 ; 121, 8.) Synonyms. — Humero-olecranius intemus—Girard. The vastus internus of the triceps brachialis of Man. (Caput parvum — Percivall.) Situation — Direction — Form — Structure. — This muscle is situated at the internal face of the humerus, along the inferior border of the large extensor. It is oblique downwards and backwards, pyriform, bulging at its superior extremity, contracted infericrly, vrhere it terminates by two small flat tendons. Attachments.— It originates, by its superior extremity, from the inner aspect of the humerus, behind and above the tuberosity on its body. One of its terminal tendons is attached to the summit of the olecranon : the other glides over a small convexity on the inner side of that eminence, and goes to be inserted a little lower than the first. Belations. — Above, with the inferior border of the large extensor ; out- wards, with the humerus, the short flexor, and short extensor of the fore- arm; inwards, with the humeral insertion of the great dorsal and the adductor of the arm, the long branch of the coraco-brachialis, the vessels 260 THE MUSCLES. Fis. 122. and nerves on the inner side of the arm, and the long extensor of the fore-arm. Action. — An extensor of the fore-arm. 5. Small Extensor of the Fore-arm or Anconeus. (Fig. 85, 10.) Synonym. — Humero-olecranius minor — Girard. Form — Structure — Sitnation — Relations. — This is a small, thick, and prismatic muscle, almost entirely fleshy, situated behind the elbow articulation. It is apjilied against the synovial cul-de-sac which ascends into the olecranian fossa, and to which it is strongly attached ; it is hidden by the short extensor, from which it is not easily distinguished. Attachments. — It originates from the margin of the olecranian fossa, chiefly above and out- wards. It terminates by being inserted into the anterior and external part of the olecranon. Action. — This little muscle, a congener of the preceding, raises the articular capsule it covers, and prevents its being pinched between the bony surfaces. DIFFERENTIAL CHARACTERS OF THE MUSCLES OF THE AKM IN OTHEU THAN SOLIPED ANIMALS. In all animals, the loixj flexor of the fore-arm,, or coraco-radialis, is less thick and tendinous than in iSoli- peds. In the Pig, Dog, and Cat, it comiDorts itself in a special manner at its inferior extremity , it is attached at first to the bicipital tuberosity, and also furnishes a small tendinous branch which glides over the inner side of the radius by means of a synovial burta, and is fixed within the ulna, towards the base of the olecranon. The short flexor of the fore-arm, or anterior brachial, is terminated, in the Pig, Dog, .^nd Cat, by a small tendon which is fixed in the ulna, below the ulnar branch of the coraco-radialis. The long extensor of the fore-arm, which is found in all the domesticated animals, arises from the external face of the great dorsal in the Pig and Dog. The middle extensor of the fore-arm and anconeus of these animals are remarkable for their volume. COMPAUISON OF THE MUSCLES OF THE ARM OF MAN WITH THOSK OF ANIMALS. In Man, three muscles are situated in front of the DEEP MUSCLES ON EXTERNAL ASPECT OF RIGHT ANTERIOR LIMB. T, Scapula ; 2, Coracoid process of scapula ; 3, Flexor brachii ; 4, Superior extremity of humerus ; 5, External tuberosity of humerus ; 6, Humeralis esternus ; 7, Body of humerus ; 8, Biceps ; 9, Aiiterior, or great extensor of the meta- carpus ; 10, Ulna , 11, Extensor pedis, or anterior extensor of the phalanges ; 12, Uluaris accessorius, or ulnar portion of the perforans ; 13, Lateral extensor of the metacar- pus, or extensor suffraginis ; 14, Oblique extensor of the metacarpus ; 15, Flexors of the foot; 16, Trapezium ; 17, Annular ligament; 18, Carpal ligament of perforans tendon, 20; 19, Perforatus; 21, Tendon of anterior extensor of metacarpus ; 22, Small metacarpal bone ; 23, Suspensory ligament ; 24, Lateral band of metacarpo-phalangeal sheath , 25, Perforans teadou ; 26, Branch of the suspensory ligament joining the extensor pedis, 27, MUSCLES OF THE ANTERIOR LIMBS. 261 hiunerus : the biceps, coraco-hrachialis, and the anterior brachialis ; behind are found the triceps brachialis and tlie anconeus. The biceps, which corresponds to the coraco-radialis of animals, commences on the capula' by two heads, which unite towards the upper part of the humerus. The lono- or tiou is detached fiom the upper part of the rim of the glenoid cavity ; the shortest commences from the summit of the coracoid process. The infer. or tendon of the biceps givt s otf, before fixing itself on the bicipital tuberosity, a fibrous lamella which is con- founded with the antibiadiial aponeurosis. Tlie coraro-brachialis has only one fleshy borly. As in the Carnivora and Pig, the anterior brachialis terminates on the ulna, below the coronoid process. The triceps brachialis exactly represents, by its three heads, the large, middle, and short exten.sors of the fore-arm of animals (See Fig. 120 ) There is nothing particular with regard to the anconeus. The long extensor of the fore-arm of the Horse has no representative in Man. MUSCLES OF THE FORE-ARM. These muscles, nine in number, distributed in two regions — anterior and posterior — envelop the bones of the fore-arm on every side except the internal, where the radius is in mediate contact with the skin. They all terminate on the different sections of the foot, which they flex or extend, and are contained in a common fibrous sheath, which constitutes the anti- brachial aponeurosis, Antibrachial Aponeurosis. This retaining fascia forms a very strong and resisting envelope, which is firmly fixed around the antibrachial muscles by the insertions it has on the bones of the fore-arm, being attached to the olecranon, the internal aspect of the radius, and to the inferior extremity of that bone, both inwards and outwards. Its external face is covered by superficial vessels and nerves, that are separated from the skin by a very thin fibrous layer, which is more particularly observable on the inner side, where it covers the antibrachial aponeurosis in a very evident manner ; it is rendered tense by the sterno- aponeuroticus. Up to the present time, this fibrous layer has not been distinguished from the aponeurosis it covers. The inner face of the latter gives rise to several septa, which penetrate the interstices of the muscles to form around some of them special retentive sheaths ; it adheres to several of them very intimately. At its upper border, this aponeurosis receives, inwardly, the insertion of the long extensor of the fore-arm ; in front, the accessory band of the coraco-radialis ; outwardly, it is continuous with the fibrous fascia covering the external face of the olecranian muscles. Inferiorly, it is prolonged around the knee to form the tendinous sheaths in that region. The antibrachial aponeurosis is made tense by the contraction of the long extensor of the fore-arm and the coraco-radialis. With reference to the sterno-aponeuroticus, which has hitherto been regarded as intended to play the same part, it can only act on the fibrous fascia which covers, externally, the antibrachial aponeurosis. Preparation of the muscles of the fore-arm. — The preparation of these muscles is extremely simple, as it suffices to remove tlie antibrachial aponeurosis' and the interstitial cellulo-adipose tissue, to expose and to isolate them from each other. No special recommendations need, therefore, be given, as a glance at figures 89. 119, 121, and 122 will guide the student in his dissection, and supplement the njanual details which would be superfluous here. Nevertheless, as the terminal insertions of some of these muscles are inclosed within the hoof, and as it is indispensable, in order to expose them, to remove this horny case, Bome explanation will be given as to the manner in which this should be eflected, 20 262 TEE MUSCLES. particulnrly as the apparent difficulty and labour too frequently cause this part to be omitttd in the dissecting rooms. 1. The instruments necessary to remove the hoof are . a scalpel, toe-knife, hammer, and a pair of pincers. 2. Tlie limb should be in a vertical position, held by one or two assistants, and the foot placed on a table, stool, or very solid block of wood. 3. Pass the scalpel as deeply as possible around the coronet, to separate the wall of the hoof trom the organised tissues. 4. With tlie knife and hammer, split the wall into four or five pieces by vertical incisions. 5. When the wall is thus divided, it is sufficient to insert the knife under the frag- ments, and making it serve as a lever, tear them olf ; pincers may also be used fur tliia purpose, each of the pieces being twisted from the sole. 6. To remove the sole, the blade of the scalpel sliould be passed between its upper face and the plantar surface of the third phalanx; afterwards the toe-knife may be inserted in tlie interval at the bulbs of the frog, so as to slightly raise the external border of the sole. This is thin seized by the pmcers and pulled oft', along with the frog, in a single piece, by a powerful twisting movement, aided by the as.-iistauts, who press on the limb in a contrary direetiou. A. Anterior Antihrachial Begion. In SoUpeds, this region includes four extensor muscles. Two act on the entire foot ; these are the anterior extensor and tlie oblique extensor of the metacarpus. Two others, the anterior and lateral extensor of the phalanges, terminate in the digital region. 1. Anterior Extensor of the Metacarpus. ('Figs. 119, 11 ; 121, 15; 122, 9.) Synonyms. — Epicondylo-premetacarpeus — Girard. It represents the two external radials of Man. (Extensor metacarpi magnus — PerciviU. Hamero-metacarpeus — Leyh.) Situation — Direction — Form — Structure. — The anterior extensor of the metacarpus, situated in front of the radius, in an almost vertical direction, is composed of a muscular body and a tendon. The first has the form of an inverted cone, is intersected by some aponeurotic lamellte, and is composed of muscular fibres slightly arciform at their superior extremities. The second, at first rounded, then flattened, commences below the middle third of the radius, and succeeds the inferior extremity of the muscular portion. Attachments.- This muscle has its fixed insertion : 1, By the upper ex- tremity of its fleshy fibres, on the crest that limits, behind and below, the furrow of torsion of the humerus ; 2, Above and in front of the inferior articular surface of the humerus, by means of a strong fibrous band common to it and the anterior extensor of the phalanges, and which expands on the deep face of these two muscles in becoming intimately united with the capsular ligament of the elbow articulation. Its movable insertion takes place on the anterior and superior tuberosity of the large metacarpal bone, by the inferior extremity of its tendon. Belations.— The muscular portion is covered by the antihrachial aponeurosis and the short extensor of the fore-arm. It covers the anterior face of the radius, as well as the elbow articulation ; outwards and behind, it is in contact with the inferior extremity of the short flexor of the fore- arm or brachialis anticus, whose aponeurosis adheres intimately to the arciform portion of the fibres of the anterior extensor of the metacarpus, and appears to attach this muscle to the deltoid imprint. Its tendon covers a small portion of the anterior aspect of the radius, and enters the internal vertical groove channeled in front of the inferior extremity of that bone ; afterwards it passes over the capsular ligament of the carpus, and is MUSCLES OF THE ANTERIOR LIMBS. 263 maintained against that membranous expansion by a wide fibrous sheath, through which it glides by the aid of two synovial membranes. This tendon is crossed above the knee by that of the oblique extensor, which passes to its surface. Action. — The name of this muscle indicates its function ; it extends the metacarpus on the fore-arm. 2. Obliqtie Extensor of the Metacarpus. (Figs. 119, 13; 121, 21 ; 122, 14.) Synonyms. — Cubitoprenietacarpeus, or radio-premetacarpeus — Girard. It is the representative of the long abductor and short extensor of the" thumb in Man. {Extensor metacarpi oLliquus vd parvus — Fercivall. Radio-metacarpeus — Leyh.) Situation — Form — Structure — Direction. — A small muscle situated at the internal side of the radius, beneath the anterior extensor of the phalanges, penniform in shape, strongly aponeurotic, and terminated by a tendon which turns obliquely round the anterior aspect of the radius in passing downwards and inwards, to reach the oblique channel on the inferior extremity of that bone, and to pass from thence to the inside of the knee. Attachments. — It has its origin on the external side of the radius ; its terminal tendon is fixed into the head of the internal metacarpal bone, by its fibres becoming confounded with those of the internal ligament of the carpus. Relations. — This muscle is covered by the anterior extensor of the phalanges and the antibrachial aponeurosis. It successively covers the anterior face of the radius, the tendon of the anterior extensor of the metacarpus, the radial groove lodging its tendon, and in which it glides by means of a small synovial bm'sa, as well as the internal ligament of the carpus. Action. — It extends the metacarpus, and may make it pivot from within forwards. 3. Anterior Extensor of the Phalanges. (Figs. 119, 14; 121, 15 : 122, 9.) Synonyms. — Epicondylo-prephalangeus — Girard. The extensor communis digitorum of Man. {Extensor pedis — Perciiall. Humero-prephalangeus — Leyh.) Situation — Direction — Extent — Farm — Structure. — This is a long vertical muscle, situated external to, and behind the anterior extensor of the metacarpus, which it resembles in being composed of a fleshy and a tendinous portion. The musculai- portion extends from the inferior extremity of the humerus to above the lower third of the radius ; it is fusiform in shape, intersected by aponeurotic lamellse, and bifid at its superior extremity.^ The tendinous portion forms two unequal cords, which succeed the two terminal branches of the muscular part, and lie close to each other. These two cords enter the most external of the three grooves in front of the inferior extremity of the radius, and reach the anterior face of the carpal capsular ligament, against which they are maintained by an annular ligamentous apparatus. After passing from beneath this ring, the smallest, which is the most external, joins the tendon of the lateral extensor (Fig. 119, 15). The principal branch (Fig. 119, 14' ) continues its course on the anterior aspect of the midd.e metacai-pal bone and articulation of the fetlock, until it arrives in front cf the digit ; here it terminates on the os pedis, after widening in a remarkable manner, and after receiving, laterally, at the middle of the first phalanx, a ' This division, which has been noticed by several writers, has not been shown in figure 119. This is a mistake, as it is constantly prtseut. i2G4 THE MUSCLES. reinforcing band wliicli appears to be given off from the inferior extremity of the suspensory ligament of the fetlock. Attachments. — The anterior extensor of the phalanges has its fixed attach- ment by the superior extremity of its muscular body : 1, Below the crest tliat limits, posteriorly, the furrow of torsion of the humerus ; 2, In front of the inferior extremity of the humerus ; 3, To the anterior border of the external ligament of the elbow joint ; 4, To the external and superior tuberosity of the radius ; 5, To the external border of that bone. Its princijial tendon is inserted into the pyramidal eminence of the third phalanx, after being successively attached to the capsular ligament of the fetlock joint and the anterior surfaces of the first two phalanges. Belations. — The muscular portion, covered by the antibrachial aponeu- rosis, covers the articulation of the elbow, the anterior face of the radius, and the oblique extensor of the metacarpus ; it responds, in front, to the anterior extensor of the same ray, to which it is intimately attached by its ujjper half ; behind, to the lateral extensor of the i)halanges. The tendinous cords cover the difl'erent parts already enumerated in describing the course of the muscle — that is, the anterior face of the radius, the carj^al joints, the principal metacarpal bone, the articulation of the fetlock, and the first two phalanges. A vaginal synovial membrane envelops them at the knee, to facilitate their gliding in the radial groove and on the anterior asjject of the capsular ligament of the carpus ; while the inner surface of the prin- cipal tendon is covered, in front of the fetlock, by a small vesicular capsule, and still lower by the synovial membranes of the two inter- phalangeal articulations. Action. — This muscle extends the third phalanx on the second, that on the first, and this again on the metacarpal bone. It may also concur in the extension of the entire foot on the fore-arm. (Two small muscles, which should be only considered as heads of this anterior extensor, have been particularly described by Thiernesse and Phillips, and named after these authors. The muscle of Phillips, according to Leyh, is long and thin ; it commences on the lateral external ligament of the ulnar articulation and the external superior tuberosity of the radius ; it is directed obliquely downwards and forwards, lying beside the muscular poi'tion of the common extensor. Towards the middle and outer aspect of the radius, it gives off a small tendon, which passes in the same sheath as the preceding, in front of the carpus, and continues its course between the two tendons of the extensors of the phalanges to near the fetlock, where it becomes confounded with that of the lateral extensor, a little above the first phalanx. , The muscle of Thiernesse is smaller than that of Phillips, and situated at its inner side. It arises in front of the transverse ligament of the ulna by a muscular portion, becomes thinner as it descends, and terminates by a fine tendon which is confounded with that of the common extensor, towards ths lower third of the fore-arm.) 4. Lateral Extensor of the Phalanges. (Figs. 119, 16 ; 122, 13.) Synonyms. — Cubito or radialis-prephalangeus, according to Girard. The extensor miuimi digiti of Man. (^Extensor suffraginu — Fercivall.) Direction — Situation — Extent— Form— Structure. — A small vertical muscle, situated at the external side of the fore-arm, between the jjreceding and the external flexor of the metacarpus, and formed of a fleshy body and a MUSCLES OF THE ANTERIOR LIMBS. 265 tendon. The fleshy body, not very considerable, and flattened from before backwards, extends from the upper extremit}- of the radius tu the lower fourth of the same bone. The tendon (Fig. 119, 16'), at first rounded, then flattened, reaches the gliding groove which divides the external inferior tuberosity of the radius into two portions, passes to the external side of the carpus, crossing the lateral ligament common to the articu- lations of this region, and arrives at the anterior surface of the princijial meta- carpal bone, where it receives the small tendinous branch detached from the anterior extensor, as well as a strong fibrous band coming from the external side of the carjms fFig. 119, 17). Afterwards, descending alongside the external border of tbe prmcipal tendon of its congener, and imited to it by a fibrous fascia, it gains the articulation of the fetlock, and expanding, ter- minates at the upper extremity of the first phalanx. Attachments. — 1, By its muscular body, to the external tuberosity of the radius, the external ligament of the elbow articulation, and to the bodies of the two bones of the fore-arm — origin ; 2, By the inferior extremity of its tendon, to the capsule of the metacarpo-phalangeal articulation, and in front of the superior extri-mity of the first phalanx — termination. Relations. — Its muscular portion, enveloped in a special aponeurotic sheath, responds : in front, to the anterior extensor of the phalanges ; behind, to the external flexor of the metacarpus and the perforatus and perforans muscles ; outwards, to the antibrachial aponeurosis. The tendon, surrounded by a vaginal synovial sheath, in passing over the cari)us, covers, beyond the knee, the anterior aspect of the metacarpus, and the anterior ligament of the metacarpo-phalangeal articulation, over which it glides by means of a small vesicular synovial bursa. It is covered by a slight fibrous fascia, which separates it from the skin, and which is also spread over the tendon of the anterior extensor. Action. — This muscle is an extensor of the digit, and also concurs in the extension of the entire foot on the fore-arm. B. Posterior Antibrachial Region. This is composed of five flexor muscles grouped vertically behind the bones of the fore-arm. Three are situated superficially, and act on the whole foot ; these are the external flexor, oblique flexor, and the internal flexor of the metacarpus. The other two, fixed to the digit by their inferior extremity, and covered by the preceding, are designated the superficial and deep flexors of the phalanges. 1, External Flexor of the Metacarpus, or Posterior Ulnaris.^ (Fig. 119, 18.) Si/nouyms. — Epicoudylo-supeicarpeus — Girard. {Flexor metacarpi externus — Percivall. Humero-supercarpeus exttrnus — Leyh.) Situation. — The external flexor of the metacarpus is situated at the ex- ternal side of the fore-aim, between the lateral extensor of the phalanges and the oblique flexor. Form — Structure — Attachments. — This muscle is elongated from above to below, flattened from one side to the other, thick in its middle part, and intersected by very strong aponeurotic bands. It commences on the summit • It is known that the bony eminences, hitherto termed in veterinary anatomy " epitrochlea " and '■ epicondyle," correspond . the first, to the epicondyle of IMan, the second, to the epitrochlea. It ne^d excite no surprise, therefore, to see the denominations given by Girard to the muscles of the posterior antibrachial region changed as above. 266 THE MUSCLES. of the epicondyle by a very powerful, but extremely short teudon. In- feriorly, it terminates by a second tendon longer than the preceding, and divides into two branches, an anterior and a posterior. The latter (Fig. 119, 20), short and wide, is inserted into the supercarpal bone in becoming mixed up with the oblique flexor. The former (Fig. 1 19, 19), rounded and funicular in shape, glides by means of a synovial bursa in the channel excavated on the external aspect of the supercarpal bone, and which is converted into a canal by a little fibrous apparatus ; this branch is afterwards fixed on the head of the external metacarpal bone by being confounded with the external ligament of the carpus. Eelations. — Covered by the antibrachial aponeurosis, this muscle covers the two flexors of the digit. Its anterior border responds to the lateral extensor of the phalanges ; the posterior to the oblique flexor. Its superior tendon lies behind the external ligament of the elbow joint, and is covered deeply by the external cul-de-sac of the synovial capsule belonging to that articulation. Action. — It flexes the foot on the fore-arm. (Leyh observes that it is more particularly concerned in what is known as "high action.") 2. Oblique Flexor of the Metacarpus, or Anterior Ulnar is. (Fig. 121, 19.) Synonyms. — Epitrochlea supercarpeus — Girard. (^Flexor metacarpi medius—PercivaU. Humero-met.acarpeus internus — Leyh.) Situation — Form — Structure. — This muscle, situated behind and within the fore-arm, is an exact counterpart of the preceding in form and structure. Direction. — Bourgelat has improperly named it an oblique flexor, for its direction is vertical like that of the other muscles of this region. Attachments. — It has its origin : 1, On the base of the epitrochlea by the tendinous fibres of its superior extremity ; 2, On the olecranon, by a small, very thin, and very pale fleshy band, which is annexed to the princijial muscular body, and soon unites with its posterior border. Its inferior tendon is undivided, and terminates on the supercarpal bone, along with the ex- ternal flexor, to which it is intimately attached. Belations. — By its superficial face, with the antibrachial aponeurosis, which strongly adheres to its tendon ; by its deep face, with the flexors of the phalanges. Its anterior border is covered by the internal flexor ; the posterior responds to the external flexor. Action. — It is a congener of the preceding. 3. Internal Flexor of the Metacarpus, or Palmaris Magnus. (Fig. 121, 19.) Synonyms.— 'Epitrochlea. metacarpeus— G/mrd. (Flexor metacarpi internus — Perci- vail. Humero-metacarpeus internus — Leyh.) Situation — Form— Structure — Attachment.^ — This muscle is situated within the fore-arm, against the posterior face of the radius, and in its general features resembles its congeners, the two preceding muscles. It is, however, not so wide, is thinner, and less aponeurotic. Its upper extremity is fixed, by tendinous fibres, to the base of the epitrochlea at the same point as the oblique flexor, with which it is confounded — origin. Its inferior extremity terminates in a long, thin, funicular tendon which passes through a fibrous sheath at the inner side of the knee, and is inserted into the head of the internal metacarpal bone — movable insertion. Belations. — It is covered by the antibrachial aponeurosis, and covers the oblique flexor, the pei-foratus and perforans, as well as important blood- MUSCLES OF THE ASTERIOR LIMBS. 267 vessels and nerves. Its anterior border responds to the radius. A synovial sheath envelops its terminal tendon, and facilitates its movenaents in the fibrous canal through which it passes. Action. — It is a congener of the preceding. 4. Superficial Flexor, Suhlimis of the Phalanges, or Perforatus. (Figs. 89, 119, 121, 122.) Synonyms. — Epitroclilo-plialanseus— G/rard. i^Flexor pedis perforatus — PercivaU Humeru-coronaris or humero-phalangeus — Leyh.) Situation. — The superficial flexor of the phalanges is situated, with its fellow, the perforans, beneath the flexors of the metacarpus, which form around them a kind of muscular envelope. Form — Structure — Extent. — It is composed of a muscular and tendinous portion. The first, long, thin, prismatic, and divided by a great number of aponeurotic intersections, extends from the inferior extremity of the arm nearly to the carpus. The tendon, continuous with the inferior extremity of the muscular portion, receives at its origin an enormous fibrous production that arises from the eminence of insertion situated at the posterior face of the end of the radius, and which contracts somewhat intimate adhesions with the antibrachial aponeurosis, as well as with the perforans. After being thus reinforced, this tendon passes through the carpal sheath and arrives behind the fetlock, where it forms a ring (Fig. 89, 14) for the jiassage of the tendon of the deep flexor. To this peculiarity is o\\'ing the designations of perforatus and perforans, given to the two flexors of the phalanges. Afterwards it is inflected forwards over the sesamoid groove, and terminates by two branches towards the middle of the digital region. Attachments. — It takes its origin, in common with the perfiirans, at the summit of the epitrochlea, and is inserted, by the bifurcations of its tendon, into the extremities of the pulley formed behind the superior extremity of the second phalanx. Relations. — The muscular portion, covered by the external and the oblique flexors of the metacarpus, may be said to be incrusted in the perforans, to which it adheres in the most intimate manner. The tendon covers that of the latter muscle, and is in turn covered by the fibrous expansions of the two metacarpal and metacarpo-phalangeal sheaths which are now to be described. The Carpal sheath is the name given to a very remarkable annular apparatus, formed by the superficial face of the common posterior ligament of the carpus, and by a thick expansion of inelastic white fibrous tissue, together constituting a perfect arch thrown across like a bridge, from the supercarpal bone to the inner side of the carpus. This arch is continuous, above, with the antibrachial aponeurosis, and is prolonged, below, over the metacarpal portion of the flexor tendons. An extensive synovial membrane covers the internal aspect of the carpal sheath, envelops the perforatus and perforans in their passage through this canal, ascends above the carpus, and descends as for as the lower third of the metacarpal region. The Metacarpo-phalangeal sheath is formed by the sesamoid groove, the posterior face of the principal navicular ligaments, that of the glenoid fibro- cartilage of the finst interphalangeal articulation, and by the posterior pulley of the second phalanx. It is completed by a very wide membranous expansion applied against the flexor tendons, closely adherent to the perforatus on the median line of the digit, and fixed, laterally, to the phalangeal bones by the 268 THE MUSCLES. aid of three special fibrous bands. A very extensive vaginal synovial mem- brane covers the internal walls of this jiassage, and is reflected on the flexor tendons ; it ascends along these tendons to the inferior extremities of the lateral metacarpals, and forms, inferiorly, a somewhat large cul-de sac which, behind the second phalanx, lies against the j)osterior cul-de-sac of the articular synovial membrane of the foot, and also against the superior cul-de- sac of the navicular sheath. The metacarpo-phalangeal sheath is also named the great sesamoid sheath ; but this designation is more frequently applied to the synovial membrane lining its walls. Action. — This muscle flexes the second phalanx on the first, that on the metacarpus, and the entire foot on the fore-arm. Its tendon, through the influence of the fibrous band which attaches it to the posterior face of the radius, acts mechanically as a stay while the animal is standing, by maintain- ing the metacarpo-phalangeal angle. 5. Beep Flexor of the Phalanges or Perforans. (Figs. 119, 121, 122.) Synonyms. — Ciibito-phalangeus, or radio-phalangeus — Girard. (Flexor pedis perforans — Percivall. Humero-radio-phalangeus — Leyh.) Situation — Composition — Extent. — This muscle is situated immediately behind the radius, and is composed of three portions which unite at the carpus, to be continued to the inferior extremity of the digit by a long powerful tendon. Form, Structure, and Attachments of the muscular portion of the perforans. — The three muscular portions may be distinguished, in regard to their origin, into epitrochlean, idnar, and radial. The epitrochlean portion is the most considerable, and lies beside the perforatus ; being three or four times the volume of that muscle, it is easily divided into several very tendinous fasciculi, which leave the summit of the epitrochlea along with the superficial flexor. The tdnar portion, situated between the external flexor and the oblique flexor of the metacarj^us, is very short and conoid, thick at its superior extremity, contracted at its inferior, to which succeeds a long flat tendon, united below to the principal tendon; it has its origin on the summit and the posterior border of the olecranon. The radial portion, representing the flexor longus pollicis of Man, is the smallest, and is deeply concealed beneath the epitrochlean muscular jiortion. The fibres composing it are fixed to the posterior surface of the radius, where they are slightly divergent, and collect upon a small particular tendon, which is confounded with the common tendon after contracting adhesions with the radial band of the perforatus. Course and Attachments of the tendon. — The tendon which succeeds these three portions enters the carjjal sheath with that of the superficial flexor. Towards the middle of the metacarpal region, it receives a strong fibrous band from the great posterior ligament of the carpus (Figs. 119, 23 ; 122, 18), traverses the sesamoid annular apparatus of the perforatus tendon, j^asses between the two terminal branches of that tendon, over the pulley on the posterior face of the second phalanx, and afterwards widens to form a large expansion designated the plantar aponeurosis. This aponeurosis glides, by its anterior face, over the inferior sui-face of the navicular bone, by means of a j)articular synovial membrane, the small navicular sheath, and is covered, posteriorly, by a fibrous layer, noticed for the first time by M H. Boulcy, who considers it as a reinforcing sheath for the perforans tendon. It is finally inserted into the semilunar MUSCLES OF THE ANTERIOR LIMBS. 269 crest of the os pedis, and the median imprints situated behind this crest, in becoming confounded at its sides with the tissue of the lateral fibro- cartilages. The jiavicular sheath is vesicular in form ; it covers the navicular bone and the single ligament of the pedal articulation, becomes reflected on the plantar aponeurosis in front of this ligament, and ascends to the inferior cul-de-sac of the sesamoid sheath, where it is again reflected and continued bv itself. It therefore forms two culs-de-sac, one superior, the other inferior, which are readily perceived in a longitudinal and vertical section of the digital region. The first is in contact with the posterior cid-de-sac of the synovial membrane of the pedal articulation, and is separated from the inferior sac of the sesamoid sheath by a transverse layer of yellow fibrous tissue which attaches the perforans tendon to the posterior face of the second phalanx. The second is situated beneath the interosseous ligament which unites the navicular bone to the third phalanx. The reinforcing sheath of the perforans tendon is formed by a fibrous membrane applied against the posterior face of the plantar aponeurosis. This membrane adheres intimately below, to the expansion it covers, and ends in becoming entirely confounded with it. It is fixed, at its borders, to the inferior extremity of the first phalanx, by means of two lateral bands. Eelations. — The epitrochleau muscular portion is covered, at its origin, by the external cul-de-sac of the elbow joint, wliich sac also covers the other muscles attached to the epitrochlea— the external and oblique flexors of the metacarpus. It responds, anteriorly, witb the radius and radial portion of the muscle ; posteriorly, with the perforatus ; externally, with the external flexor of the metacarpus; inwardly, with the internal and oblique flexors of the same ray. The ulnar portion, covered by the antibrachial aponeurosis, covers the epitrochlean portion. The radial division is comprised between the latter and the posterior face of the radius. The tendon is in contact, posteriorly, with that of the perforatus ; anteriorly, with the posterior ligament of the carpus, the suspensory ligament of the fetlock, and the sesamoid groove ; by its sides, with the vessels and nerves of the digit. Its tei-minal expansion is covered by the plantar cushion, which adheres to it, in front, in the most intimate manner ; it covers the navicular bone. Action. — This muscle flexes the phalanges on one another and on the metacarpus. It also concurs in the flexion of the entire foot on the fore-arm. The band which attaches its tendon behind the carpus, as well as its phalan- geal reinforcing sheath, gives it the mechanical power necessary to supjjort • the angle of the metacarpo-phalangeal articulation and the digital region, while the animal is in a standing posture. (In the "Deep Flexor," of 5l. Chauveau's description, we find included two portions which are separately named and described by Mr. Percivall and Professor Gurlt. These are the ulnaris accessorius and radialis accessorius of the former, and the cuhito-ulnar and radial branches of the latter. These, in reality, are portions of the perforans. and have been so designated in this treatise. Though arising independently, they terminate in the perforans tendon before it leaves the carpal sheath, and join with it in flexing the metacarpus and phalanges.) 270 THE MUSCLES. Fig. 12.",. DIFFEKENTIAL CHARACTERS OF THE MISCLES OF THE FORE- ARM IN OTHER THAN SOUPED ANIMALS, KiMiNANTS. — Tn the Ox and Sheep, the anterior ex- tensor of the metucarptis comports itself as in Solipeiis. The oblique extensor of the metacarpus of the same region terminates inside tlie upper extremity of the prin- cipal metacarpus. The anterior extensor of the phalanges ofters a remark- able disposition. This muscle is divided throughout its length into two parallel portions : an external, which forms the common extensor of the digits; and an internal, the propter extensor of the internal digit. a. The fleshy body of the common extensor (fig. 123, 3) is a little more voluminous than that of the second muscle. Its tendon (3') commences near the inferior third of the radius, passes over the knee, the metacarpal bone, and the metacarpo-phalangcal articulation. On arriving at the origin of the digits it bifurcates, and each of its branches goes to be inserted into the pyramidal eminence of the tiiird phalanx (3"). This muscle, in extending the digits, brings them together, as M. Lecoq has judiciously re- marked. b. The proper extensor of the internal digit (fig. 123, 4) much resembles the common extensor in volume, form,- and direction. Its tendon (4') passes, with that termi- nating the latter muscle, into one of the inferior grooves of the radius and over the ca[)sular ligament of the carpus, where the two cords are enveloped by a common synovial sheath.' Arrived at the metacarpo-phalangeal articulation, this tendon is placed at the excentric side of the internal digit, and descends, gradually expanding, until it reaches the inferior extremity of this bone ; towards the middle of the first phalanx, it receives from the suspensory ligament of the fetlock two constraining bands similar to those ■which, in Solipeds. bind the anterior extensor of the pha- langes on the same bone. ' This tendon bifurcates infe- riorly ; one of its branches is attached to the anterior face of the second phalanx ; the other, much wider than the THE FORE-ARM first, covers the common external lateral ligament of the OF THE ox ; EXTERNAL FACE, two inter-phalangeal articulations, and terminates on the 1, Anterior extensor of the whole external side of the third plialanx. In the Sheep, metacarpus; 1', In.sertion of this second branch is feeble, and is directed towards the its tendon ; 2, Oblique ex- heel, which it envelopes by uniting its fibres witli the per- tensor; 3, Common extensor forans tendon and the plantar cushion, of the digits; 3', Its tendon; The lateral extensor of the phalanges of Ruminants is 3", Terminal bifurcation of thicker than in the Horse, and constitutes the proper ex- that tendon; 4, Proper ex- tensor of the external digit (fig. 123, 5). Its terminal tensor of the internal digit ; tendon (4', 6, 7) comports itself exactly the same as that 4', Its tendon ; 5, Proper of the proper extensor of the internal digit, and conse- extensor of the external quently does not merit a special descripticni. We may , digit ; 5', Its tendon ; 6, Its remark, with M. Lecoq, that thei^e two muscles separate branch of insertion into the tlie digits from each other in extending them ; they are, second phalanx ; 7, Branch therefore, to a certain point, antagonists of the common to the third phalanx ; 8, extensor. External flexor of the meta- The perforatus of the Ox and Sheep is composed of carpus ; 9, Olecranian por- two portions, whose tendons unite towards the middle of tion of the perforans ; 10, the metacarpal region. The single tendon (fig. 124, 1, 2, 3) Tendon of the perforans ; which results from this union afterwards divides into two 11, Tendon of the perfo- branches, each of which comports itself, in regard to tho ratus ; 12, Suspensory liga- ment of the fetlock ; 13, The band it furnishes to the perforatus to form the ring through which the perforans « passes ; 14, The external band it gives off to the proper extensor of the external digit; 15, Coraco-radialis ; 16, Anterior brachial; 17, Anconeus. MUSCLES OF THE ANTERIOR LIMBS. 271 digits, as the sinixle perforatus tendon does in the Horse, except that they receive from the suspensory liijament a tibrous band analogous to that wliich, in Solipeds, goes to the pcrtbrans tendon. Tliis baud (tig. 123, 13) concurs in the Ibrmation of the annular ligament tlirough wliich the latter tendon passes. In the Ox, the terminal tendon of the perforans does not receive any carpal band ; this goes to the perforatus. Above the fetlock, it divides into two branches, one for each digit, which, after traversing tlio perforatus, terminates behind the inferior face of the third phalanx. There it is blended with the plantar cushion, the inferior interdigital ligament, and a fibrous fascia already noticed in the description of that ligament. This la3'er arises from the aponeurosis covering the Hexor tendons in the meta- carpal region ; it descends on the heels, behind and outside the digits, remains united to tiiat of the other digit by an inter- mediate fibrous fascia, and is attaclied to the enveloping sheaths of the flexor tendons, as well as to the superior interdigital liga- ment. Eacii terminates inferiorly, in becoming united to the proper extensor of the digit, the plantar cusliion, the inferior digital ligament, and the deep flexor of the phalanges. There is not, properly speaking, a phalangeal reinforcing sheath ; though we may consider as such the superior fasciculi of tlie inferior interdigital ligament (fig. 124. 6). Pig. — In this animal, the anterior extensor tendon of the phalanges passes to the superior extremity of the inner large metacarpal bone, and that of the oblique extensor to the small internal metacarpal. Instead of the anterior extensor of the phalanges, two muscles are found analogous to those described as existing in Ruminants. The external, or common extensor of the digits, is easily divided into several fasciculi, and is terminated by four tendinous branches which reach the -pyramidal eminence of the third phalanx of the four digits. The tendon of the small external digit often gives otf a thin bifid ramification, destined to supplement the tendons of the two large digits. The internal muscle, or proper extensor of the two internal digits, possesses a bifurcated tendon ; each branch texdixous and liga- goes to the excentric side of the third phalanx of the digit it is mextous apparA' charged to move. With regard to the muscles of the posterior antibrachial region, it is remarked : 1, That the anterior branch of the ter- minal tendon of the external fiexor of the metacarpus passes to the head of the outer metacarpal bone ; 2, That the internal flexor terminates on the metacarpal of tije great external digit ; 3, That the perforatus is formed by two muscular bodies, each terminated by a tendon inserted, inferiorly, into the second pha- lanx of one of the great digits. 4, That the perforans is divided into four terminal branches which arrive at the large phalanx of the digits. Carxivora. — In the Dog and Cat, the anterior extensor of the metacarpus divides, at its' lower extremity, into two branches, which resemble those of the two external mdial muscles of Man : one is inserted into the metacarpus of the index, the other into the metacarpus of the medius (fig. 125, A, 5, 6, 7). The oblique extensor passes to the metacarpus of the thumb; it furnishes, besides, a small particular branch that glides, by means of a sesamoid, over the third bone of the inferior row of the carpus, and is blended with the posterior ligament of the carpus (fig. 125, a, 8; b, 4; d. 8) ; it separates the thumb from the other digits, but we think it scarcely adapted for the function of extensor. The anterior extensor of the phalanges of solipeds is replaced by a single muscle, the common extensor of the digits, terminated by a quadrifurcated tendon, whose branches are distributed to the four great digits ,fig. 125, a, 9, 9'). The tendon of the lateral extensor is divided into three branches, which are inserted on tlie anterior face of the three outer digits, and are blended with the tendons of the common extensor, or with the fibrous bands furnished to these tendons by the inter- osseous metacarpal muscles. The external flexor of the metacarpus comports itself as in the Pig. But the oblique TUS OF THE POSTE- RIOR FACE OF THE DIGITAL REGION IX THE OX ; POSTERIOR LIMB. 1, Perforatus tendon ; 2, 2, Its terminal branches; 3, 3, Tiieir bifurcation ; 4, 4, Perforans ; 6, 6, Su- perior bands of the inferior digital liga- ment attached to the first phalanx ; 7, In- ferior interdigital hgament ; 8, 8, Sus- pensory ligament of the fetlock. 272 THE MUSCLES. flexor is covered by the perforatus, and its olecranian portion, thicker than in the other animals, is only united to the principal fleshy body altogether inferioily. Tlie internal flexor is feeble and conoid ; its tendon, thin and long, reaches the metacarpus of the index. The perforatus of the Dog and Cat offers a long, wide, and superficial body, separated from the perforans by the oblique flexor of the metacarpus. Its tendon passes outside the carpal slieath. and is divided into four branches, attached by their inferior extremity to the second phalanx of the four principal digits. For the perforans, it is noted : 1. That the radial portion of the muscle (the long flexor of the thumb in Man) com- mences towards the superior extremity of the radius (fig. 125, c, 4). 2. That the ulnar division is a semi-penniform muscle, attached by the superior extremities of its fibres to nearly the whole extent of the posterior face of tlie ulnar (fig. 125, c, 3). 3. That the epitrochlean portion sends off, above the knee, a small particular fasciculus terminating in a very thin tendon, which becomes lost in Ihe fibrous arch of the carpal sheath (fig. 125, c, 6). This small muscle represents the pal maris brevis of Man. The terminal tendon divides into five branches, one for each digit (fig. 125, d, 4, &c.). There have been already described in these animals : 1. Two external radial muscles, only distinct at their terminal extremity, and con- founded for the remainder of their extent. This is the anterior extensor of the meta- carpus in Solipeds ffig. 125, a, 5, G, 7). 2. A long abductor of the thumb, which appears to be the representative of the analogous muscle, and the short extensor of the same digit in Man. It is the oblique extensor of the metacarpus in the Horse (fig. 125, a, 8). 3. A common extensor of the digits; the anterior extensor of the phalanges in the Horse (fig. 125, a, 10). 4. A proper extensor of the three external digits, the proper extensor of the little finger in Man, or lateral extensor of the phalanges in tlie Horse (fig. 125, a, 10). 5. A posterior ulnar, or external flexor of the metacarpus in the Horse (fig. 125, A, 14). 6. An anterior ulnar, or oblique flexor of the metacarpus in the Horse (fig. 125, D, 6). 7. A great palmar, corresponding to the internal flexor of the metacarpus in the Horse (fig. 125, b, 8). 8. A small palmar, a dependency of the deep flexor of the phalanges (fig. 125, c, 6). 9. A flexor s'lblimis of the phalanges (fig. 125, D, 1). 10. A deep flexor of the phalanges (fig. 125, c, 5, D, 3). 11. A long flexor of the thumb, united to tiie preceding muscle, the radial portion of the perforans (fii,'. 125. c, 4). But in Carnirora there are five additional muscles, which are not generally found in the other animals. These are : the proper extensor of the thumb and index, long supinator, short supinator, round pronator, and the square pronator. A special descrip- tion will be given of these. MUSCLES PROPER TO THE FORE-ARM OF CARNIVORA. 1. Proper Extensor of the Thumb and Index. (Fig. 125, a, 11 ; b, 3.) Synonyms. — The e.xtensor secundi internodii pollicis and extensor indicis of Man. Ttus is a very small muscle, composed of a fleshy borly and a tendon. The first is thin and fusiform, and is situated under the lateral extensor; it has its origin with the oblique extensor of the metacarpus at tlie external side of the radius. The tendon crosses the anterior aspect of the knee, enveloped by the synovial slieath of the common extensor of the digits, under which it passes. It divides into two branches, one of which goes to the thumb, the other to the index.' 2. Long Supinator. (Fig. 125, A, 12; c, 8.) This muscle only exi-sts in the rudimentary state in Carnivora. Its existence in the Dog has even been denied, but this is an error ; our researches have demonstrated that it is present, in a more or less evident manner, in all breeds. * In very powerful Horses, and more frequently in the Ox, we have met with traces of this muscle in the form of a deep fasciculus situated in front of the lateral extensor. MUSCLES OF THE ANTERIOR LIMBS. Fig. 125. B. C. D. 273 MUSCLES OF THE FORE-ARM AXD PAW OF THE DOG. A. Aiiterior superficial region. — 1, Short flexor of tlie fore-arm (anterior brachial); 2, Long flexor of the fore-arm (brachial biceps) ; 3, Anconeus ; 4, Round pronator ; 5, Anterior extensor of the metacarpus (external radial); 6, Its tendon of inser- tion, destined for the fourth metacarpal bone ; 7, That which goes to the third ; 8, External oblique of the metacarpus (long abductor and short extensor of the thumb) ; 9, Common extensor of the digits ; 9', Its terminal tendon at the point" where it divides into four branches ; 10, Proper extensor of the three external digits, or lateral extensor of the phalanges in the Horse ; 10', Its terminal tendon at the commencement of its trifurcation; 11, Proper extensor of the thumb and index; 11', Its terminal tendon; 12, 12, Long supinator; 13, External flexor of the metacarpus (posterior ulnar). B. Veep anterior region.— \, Pvound pronator ; 2, Short supinator ; 3, Proper extensor of the thumb and index ; 4, Oblique extensor of the metacarpus ; 3, Superior insertion of the anterior extensor of the metacarpus ; 6, Ditto of the anterior extensor of the phalanges; 7, Proper extensor of the three external digits; 8, Internal flexor of the metacarpus (great palmar); 9, Levator humeri ; 10, 11, Long and short flexors of the fore-arm. C. Deep posterior region. — 1, Round pronator; 2, Square pronator; 3, Ulnar portion of the perforans; 4, Radial portion of the same (long flexor of the thumb); 5, Terminal tendon of the same ; 6, Tendon of the small palmar (division of the perforans); 7, Anterior extensor of the metacarpus; 8, Long su]iinator ; 9, Epicondyloid insertion of the perforatus, perforans, and oblique and internal flexors of the metacarpus; 10, Oleeranian in^^ertion of the oblique flexor; 11, Supercarpal insertion of the same; 12, Terminal tendon of the internal flexor; 13, Proper extensor of the external digits; 14, Coraco-radialis ; 15, Tendon of the extensors of the fore-arm. D. Superficial posterior region, and the special muscles of the foot or hand. — 1, Perfo- 27 1 TEE MUSCLES. It is a very delicate band, situated in front, and on the inner side of the anterior extensor of the metacarpus, taking its origin, alung with tliat muscle, from the crest limiting the furrow of torsion of the humerus, behind tbe ridge; and terminating within the inferior extremity of the radius by flesliy and aponeurotic fibres. This small muscle can have but a very limited influence on the movements of the bones of the fore-arm, because of its trifling volume. As its name indicates, it acts in supiiiatiou. 3. Short Sxipinator (Fig. 125, B, 2.) A triangular and slightly divergent muscle, covered by the anterior extensor of the mctucarpus and the comuiou extensor of the digits. It has its origin in the small fossa situated outside the humeral trocldea. by a flat tendon which is c mfounded with the external lateral ligament of the ell)ow joint. It terminates above the anterior face and the inner side of the radius, by the inferior extremities of its fleshy fibres. Covered by the two preceding muscles, it covers the elbow articulation and the bone receiving its insertion. It ought to be cousideied, in Carnivora, as the principal supinator; it pivots the radius ou the ulna, so as to turn the anterior face of the fii'st bone outwards. 4. Round Pronator. (Fig. 125, b, 1 ; c, 1.) Situated on the inner and upper part of the fore arm, between the great palmar or internal flexor of the metacarpus and the interior extensor of the same ray, the roimd pronator is a thick and thort; muscle, which originates on the small epicondyloid tuberosity of the humerus, and terminates at the internal side of the radius by aponeu- rotic fibres. 5, Square Pronator. (Fig. 125, c, 2.) This muscle is situated immediately behind the bones of the fore-arm, beneath the muscular masses of the posterior antibrachial region. It extends from the insertion of the flexors of tlie fore-arm to near the carpus, and is formed of transverse fibres which pass directly from the lUua to the radius. It is, then, no longer, as in ]\Ian, a square muscle attached only to the lower fourth of these two bones. The two pronators are antasfonists of the short supinator, turning forwards the anterior face of the radius anil metacarpus. COMPARISON OF THE MUSCLES OF THE FORE-ARM OP MAN WITH THOSE OF ANIMALS. All the muscles of the fore-arm of Man are more or less perfectly represented in the fore-arm of Carnivora. In Man, these muscles are described in placing the fore-arm in a state of supination, and are divided into three regions : anterior, external, and posterior. A. Anterior Region. This comprises eight muscles • — 1. The round pronator, absent in animals except the Carnivora. This muscle forms the internal oblique prominence in the bend of the elbow. It leaves the epitrochlea and the coronoid process of the ulna, terminating on the midJle third of the external face of the radius. 2. The great palmaris, which corresponds to the internal flexor of the metacai-pus of the Horse. Situated within the preceding, it is attached, above, to the epitrochlea ; below, to the base of the second metacarpal. It is more especially a flexor of the hand, , , . , . , . 3. The small palmaris, whose presence is not constant, and which is represented m the Dog by a portion of the deep flexor of the phalanges. ratus ; 1', Its tendon divided at its passage behind the carpal sheath ; 2, Do., Its terminal branches; 3, Perforans; .3'. Its tendon divided after its exit from the carpal sheath ; 4, Do., Its terminal branches ; 5. Tendon of the internal flexor of the metacarpus; 6, Oblique flexor (anterior ulnar); 7, Inferior extremity of the long supinator; 8, Terminal tendon of the oblique extensor of the metacarpus; 9, Short abductor of the thumb; 10. Opponent of the thumb; 11, Short flexor of the thumb; 12, Adductor of the thumb, transformed, in the Dog, into the adduc- tor of the index ; 13, Short flexor of the small digit ; 14, Adductor of the small digit; 15, Opponent of the small digit ; 16, 16, Metacarpal interosseous muscles; fl, a, a. Bands which maintain the flexor tendons on the metacarpo-])halangean articulations, and limit the sejiaration of the digits; collectively, tliey represent, in a rudimentary state, the palmar aponeurosis of Man. MUSCLES OF THE ANTERIOR LIMBS. 275 4. The superficial flexor or per/oratus has two planes of muscular fibres. The super- ficial plane is dt-stiued to the tindons of the mrdius and annularis ; the duep plane to tiie tendons of the index and little finger. These tendons are fixed into tiie secondary- phalanges of the above-named digits. 5. i'iie anterior ulnar resembles the oblique flexor of the metacarpus of the Horse. It is inserted, above, into the epitrochlea and the olecranon ; bel i\v, in the pisiform bone. Its action is transmittid, by a fibrous band, from this bone to the fifth metacarpal. It flexes the hand by inclining it inwards. Fi?. 126. Fig. 127. SUPERFICIAL MUSCLES OF HUSIAN FORE-ARM. 1, Biceps, with its tendon ; 2, Brachialis an- ticus; 3, Triceps; 4, Pronator radii teres; 5, Flexor carpi radialis ; 6, Palmaris lon- gus ; 7, A fiisciculus of flexor sublimis digitorum ; 8, Flexor carpi ulnaris ; 9, Palmar fascia; 10, Palmaris brevis ; 11, Abductor pollicis; 12, Flexor brevis pol- licis ; lo, Supinator longus ; 14, Extensor ossis metacarpi, and extensor primi inter- nodii pollicis. DEEP LAYER OF SUPERFICIAL MUSCLES OF HUMAN FORE-ARM. 1, Internal lateral ligament of elbow joint ; 2, Anterior ligament; 3, Orbicular ligament of radius ; 4, Flexor profundus digitorum ; 5, Flexor longus pollicis; 6, Pronator quad- ratus ; 7, Adductor pollicis ; 8, Dorsal in- terosseous of middle, and palmar inter- osseous of ring finger; 9, Dorsal inter- osseous muscle of rmg-finger, and palmar interosseous of little tincrer. 6. The deep flexor or perforamt is resolved into two fasciculi : one, the internal, for the little finger.'the annularis, and the niedius the other, the external, for the index. The three first tendons are ;it first united to each other by fibrous bands, and together pass through a sheath formf d by the perforatus. 7. The proper flexor of the thumb, represt-nted in the Dog by the radial portion of the perforans. It is attached, for one part, to the upper three-fourths of the anterior face of 276 THE MUSCLES. the radius, the interosseous aponeurosis, and the coronoiJ process of the ulna; on the other part, to the second phalanx of the thumb. 8. The square pronator, a thick, quacle, which it is essential to recognise in a surgical point of view, is the union of the anterior border of the long vastus of the Ox with the fascia lata, whose two lamelhe comprise th'it muscle between them, and closely adhere to each of its iaces. It very frequently happens that in emaciated beasts, this fascia is ruptured at the trochanter, and the latter, instead of gliding on the inner face of the long vastus, slips before its anterior boriler to pass through the solution of continuity, where it is fixed so firmly that it is some- 1, Middle gluteal; 2, 2, Long vastus; anterior times necessary to cut across the fibres of portion; 3, Ditto, posterior portion; 4, Semi- tlie long vastus in older to give the limb tendinosus i 5, Muscle of the fascia lata. liberty of movement. SUPERFICIAL MUSCLES OF THE CROUP AND THIGH IN THE COW. MUSCLES OF THE POSTERIOR LIMES. 295 The scmUendinosus has no sacral prolongation ; it arises only from the ischium. Tlie semimembrandsns is divided, inferiorly, into two branches : one, very thick, pnsses to the femur; the other, much smaller, terminates by a tendon which is in- sinuated beneath the internal lateral ligament of the ftmoro-tibial articulation, to gain the superior extrenuty of the tibia. CL'iRNivoEA. — lu th( si- animals it is somewhat difficult to isolate the two portions of the long vasltis from each other. The anterior only proceeds from the ischium. Infe- riorly, they terminate in common by an aponeurosis which passes to the tibial crest and the 1 sternal patellar ligament. The seniiteiuiiuusus and semimembranosus comport themselves as in the smaller Rumiuants. C. Internal Crural Region. RrMiNANTS. — The long adductor of the leg in the Ox and Sheep is traversed, near its origin, by the femoral artery. The pectineus of the Ox, single at its upper extremity, is divided into two branches at its inferior extremity. One of these brunches, tliin and pale, is prolonged to near the internal condyle of the femur, while the principal stops, as in the Horse, on tlie posterior face of the bone. The siiiull adductor of the thigh is scarcely distinct from the great adductor. The latttr is undivided at its inferior extremity, which stops at the posterior face of the femur without going to the inner condyle of that bone. Tlie internal obturator has no upper portion ; it is united to the external obturator in passing through the oval foiamen. Pig. — In this animal, the internal crural muscles offer somewhat the same disposition as in the Ox. Cahnivora. — In the Dog and Cat, the long adductor of the leg arises from the external an^le of the ilium, and by its muscular portion is prolonged to the inner face of the tibia. The short adductor is much thinner and narrower than in the other animals. The small adductor of the thigh is a little, dist nctly-isolated, muscle, which begins on the inferior face of the pubis, and terminates at the posterior face of the femur, below the square crural. The great adductor is, on the contrary, a wide, tliick, undivided muscle, attached to nearly the whole extent of the linea aspera of the femur. There is nothing particular to note wilh regard to the square crural and the obturators ; the gemelli of the pelvis are always composed of two small, distinctly-isolated, fasciculi, which comport themselves as in Man. COMrAKISON OF THE MUSCLES OF MAN's THIGH WITH THOSE OF THE THIGH OF ANIMALS. A. Anterior Muscles. The anterior gracilis is not found in Man ; nevertheless, there are reckoned three anterior muscles of the thigh, as the sartoiius, which corresponds to the long adductor of the It g of animals, is includeil in this region. The sartorius is a very long muscle, whose width at most is about two fingers' breadth. It is attached above, not to the lumbo-iliao aponeurosis, but to the anteriur and superior iliac spine : it is afterwards directed downwanls and inwards, to pa-s round the internal condyle of the femur, and terminate by an expanding tendon at the crest of the tibia. The trusor of the fascia labi {tensor vagina! femoris) shows the same general dis- position observed in animals. It is the same with the femoral tricejis. The anterior rectus arises by two tendinous l^ranches : one is detached from the auterior and iuferior iliac spine ; the other from the brim of the cotyloid cavity. B. Muscles of the Posterior Region. These are three in number : the femoral or crural biceps, semitendinosus, and semimembranosus. The femoral biceps is represented in Solipeds by the posterior portion of the long vastus. It is an elongated muscle arising by two heads: the long bead comes from the iscbiatic tuberosity ; the shortest from the middle of the linea aspera. After their union, these two heads give rise to a tendon which is fixed into the head of the fibula, and sends an expansion over the tibi.d aponeurosis. The semitendinosus arises in common with the long head of the biceps ; its inferior tendon is reflected beneath the internal tuberosity of the tibia, to be fixed into the crest 296 THE MUSCLES. of that bone. This tendon, with that of the sartorius, forms the aponeurotic expansion called the goose's foot. The semimembranosus is voluminous in its lower portion, and arises, like the otlier two, from tlie tuberosity of the ischium; its fibres pass to a tendon which, on reaching tlie inner side of the knee, teruiiuates in the tluee pieces composing that articulation (see fig. 134). Fis. 133. Fig. 134, MUSCLES OF THE ANTERIOR FEMORAL REGION IN MAN. 1, Crest of the ilium ; 2, Its antero-superior spinous process ; 3, Gluteus medius ; 4, Tensor vaginee femoris ; 5, Sartorius; 6, Rectus ; 7, Vastus externus ; 8, Vastus internus; 9, Patella; 10, lliacus internus; 11, Psoas magnus ; 12, Pectineus; 13, Adductor longus; 14, Portion of adductor magnus ; 1 5, Gracilis. MUSCLES OF THE POSTERIOR FEMORAL AND GLUTEAL REGION IN MAN. 1, Gluteus medius ; 2, Gluteus maximus ; 3, Vastus externus, covered by fascia lata ; 4, Long head of biceps ; 5, Short head ; 6, Semitendinosus ; 7, 7, Semimembrano- sus ; 8, Gracilis ; 9, Portion of inner border of adductor magnus ; 10, Edge of sartorius ; 11, Popliteal space ; 12, Gastroc- nemius, with its two heads. C. Muscles of the Internal Region. In books on liuman anatomy, these muscles are sometimes designated, from their action, by the generic name of adductors. They comprise : the internal rectus, pectineus, first or middle adductor, second or small adductor, and third or great adductor. Tiie square crural, the obturators, and the gemelli are described among the posterior muscles of the pelvis. They will, however, be briefly alluded to liere. The internal rectus corresponds to the short adductor of the leg of animals. It is a thin muscle, bordering the inner side of the thigh. It is attached, above, to the symphysis pubis ; below, to the crest of the tibia, in common with tlie sartorius tendon. MUSCLES OF TEE POSTERIOB LIMBS. 297 The pectineus repeats the anterior branch of the pectineus of the Horse. It is inserted, below, into the iiitenuil bifurcation of the linea aspera of the femur. The jirst adductor corresponds to the posterior branch of the pectineus of Solipeds. It is lepresenteil by a voluminous muscular mass, which arises from the spine of the I)ubis and terminates on the middle third of thf linea aspera. The second or small adductor corresponds to the muscle of the same name in animals. It is insert d into the same points as the preceding. The third or great ndductur is attahid. above, to the ischiatic tuberosity and to the whole of the lower branch of the iscliium by aponeurotic fibres. It afterwards divides into two branches: the external bra'ich. entirely muscular, is fixed into the entire interspace of the linea aspera ; the internal branch gives rise to a tendon which goes to the inner condyle of the femur. Between these two branches is found, as in the Horse, the ring of the adductors, in which pass the large vessels of the thigh. Tiie square crural of Man is nearly horizontal, as it is attached, inwardly, to the external border of the ischium, and outwardly, between the great and small trochanters. The internal obturator and gemelli resemble those of the Dog. MUSCLES OF THE LEG. These muscles, nine in number, are grouped around the two principal boues of the leg. so as almost to completely envelop them, leaving only the internal face of the tibia uncovered. Like those of the fore-arm, they form two jmrticular regions: an anterior q.\i^ a posterior ; and they are sheathed in common by the tibial aponeurosis, a very solid fibrous covering which in every respect corresponds to the autibrachial aponeurosis. TIBIAL APONEUROSIS. This aponeurosis is formed of several superposed layers which are intimately united, and receives, superiorly, the insertion of the long vastus, the semitendiuosus, and the short adductor of the leg, which may be con- sidered as its tensor muscles. It is continued, inferiorly, over the tarsus and the metatarsal region, in becoming singularly attenuated, and in covering the fibrous bauds which bind and retain the anterior tibial muscles in the bend of the hock. Its external surface is separated from the skin by a very thin cellulo-fibrous expansion ; its internal face furnishes special and very firm sheaths around the majority of the tibial muscles. The tibial aponeurosis is attached to the internal surface and crest of the tibia, as well as to the summit of the calcis. The latter attachment takes place by a thick fibrous band, whose singular and complicated disposition has not yet been exactly described. It is situated in front of the tendon of the hock, or between that tendon and the deep layer of the posterior tibial muscles. By its borders, it is continuous with the tibial aponeurosis or fascia. Superiorly, it adheres most intimately to the perforatus tendon, near the point where the latter originates ; there it sends off a thick fasciculus which descends to the gastrocnemius tendon. Below this, it appears to divide into two branches, an external and internal, which are united to the calcanean cap of the perforatus tendon, and are attached to the sides of the calcis in such a manner, that near its insertion the gastrocnemius tendon is found to be enveloped by a complete fibrous sheath, formed partly by the perforatus tendon and partly by the band just described. This latter, therefore, con- stitutes a strengthening apjiarattis for the tendon of the hock : a structure noticed by Girard, who made it a branch of insertion of the semitendiuosus ; and not without reason, perhaps, because it arises fi'om the tibial aponeurosis, which, in part at least, is itself derived from the semitendinosus muscle. Preparation of the Muscles of the Leg. — Separate the limb fi-om the trunk by sawing 298 TEE MUSCLES. through the femur at its middle. Dissect the insertions of the long vastus, the short adductor of ihe leg, and the seniitendinosus, to observe the continuity of tliese muscles with the tibial aponeurosis ; study the int-ertions of this aponeurosis, particularly that wliich it has on the summit of the calcis. To expose the muscles, remove their aponeurotic envelope, leaving, however, the band it forms in front of the tendon of the hock, as well as the bands which retain the tendons. Remove the hoof in the manner already indicated for the anterior extremity, and, finally, separate the muscles from one another — an operation so very simple as not to reqiure any special directions. A. Anterior Tibial JRegion. This is composed of three muscles : the flexor of the metatarsus, the anterior extensor, and the lateral extensor of the phalanges. The first is deep-seated, the other two are superficial. 1. Anterior Extensor of the Phalanges. (Fig. 135, 20.) Synonyms. — Femoro-preph:ilan'j:eus — Girard. The extensor longus digitorum pedis of Man. {Extensor pedis — Fercivall. ) Situation — Direction^Extent. — This muscle, situated in front of the leg and foot, follows the direction of these two rays for their whole extent. Form — Structure. — It is formed of a muscular body and a tendon. The first is fusiform, depressed from before to behind, aponeurotic at its superficies in its superior moiety, and tendinous internally in its inferior moiety. The tendon, at first round, then flat, commences a little above the inferior fourth of the tibia, and reaches the anterior face of the princiiial metatarsus, where it receives the pedal (extensor brevis digitorum) muscle, the tendon of the lateral extensor, and a funicular jirolongation of the tibial aponeurosis. It afterwards descends on the fetlock, where it comports itself exactly as the corresjjonding tendon in the anterior extremity. {See the anterior extensor of the phalanges in the fore-limb, page 2G2.) Attachments. — Above, in the digital fossa placed between the trochlea and external condyle of the femui", through the medium of the tendinous portion of the flexor of the metatarsus— ^j;erf insertion. Below, on the cajjsular liga- ment of the metatarso-j)halangeal articulation, the anterior face of the two first phalanges, and the pyramidal eminence of the os pedis. Relations. — The muscular portion responds : outwardly, with the tibial aponeurosis ; inwardly, to the flexor of the metatarsus ; posteriorly, to the lateral extensor of the phalanges. The tendon successively covers : the anterior aspect of the tibia, the anterior capsular ligament of the tarsus, the pedal muscle, the anterior face of the principal metatarsal, the articulation of the fetlock, and the two first phalanges. It is covered by the tibial aponeu- rosis, and by three annular fibrous bands destined to maintain the tendon in the bend of the hock. One of these bands, the superior, is fixed by its ex- tremities to the tibia, a little above the tibio-tarsal articulation ; it is common to the muscle we are describing, and to the flexor of the metatarsus. The middle band, attached to the cuboid branch of the latter muscle and the inferior extremity of the calcis, is exclusively intended for the anterior ex- tensor of the phalanges. The inferior maintains the two extensors against the superior extremity of the principal metatarsal. Action. — This muscle extends the digit and flexes the entire foot. 2. Lateral Extensor of the Phalanges. (Fig. 135, 28.) Synonyms.— Peroneo-prephalangeus — Girard. The peroneus brevis of Man. (Peroneus Fercivall. Tihio-prephulan(jeus~Leyh.) Situation — Form — Structure — Extent — Direction. — This muscle, situated MUSCLES OF THE POSTERIOR LIMBS. 299 on the external side of the leg, between the preceding and the deep flexor of the phalanges, is composed of a muscular portion and a tendon. The first, Fi2. 135. EXTERNAL DEEP MUSCLES OF EIGHT I'dSTKRIOR LIMB. 1, Crest of the ilium ; 2, Inferior saoro-sciatic ligament ; 3, Sacro-ischiatic ligament ; 4, Obturator ligament ; 5, Tuberosity of the ischium ; 6, Anterior tuberosity of the ilium ; 7, Small gluteus, or gluteus internus ; 8, Its insertion into the great trochanter, 9; 10, Iliacus. or iliac psoas; 11, Vastus externus ; 12, Rectus; 13, Great sciatic nerve; 14, Gracilis ; 15, Sartorius ; 16, Patella; 17, Lateral liga- ment; 18, Oblique flexor of the phalanges, or flexor pedis accessorius ; 19, Pero- neus; 20, Extensor pedis ; 21, Solearis, or plantaris ; 22, Gastrocnemius externus ; 23, Flexor pedis ; 24, Tendon of oblique flexor of the phalanges ; 25, Perforatus tendon ; 2G, Lateral ligament of gastrocnemius ; 27, 28, Annular ligament ; 29, Tendon of lateral extensor of the phalanges, or peroneus ; 30, External rudi- mentary metatarsal bone. elongated, prismatic, and slightly penniform, extends in the direction of the leg, from the superior extremity of that region to beyond its inferior extre- mity. The tendon succeeds the lower end of the muscular portion, and traverses the groove on the middle of the infero-external tuberosity of the 300 THE MUSCLES. tibia, passing to the external side of the tarsus, where it is enclosed in a very firm sheath, and is inflected forwards to become united to the tendon of the anterior extensor, near the middle of the metatarsal region. Attachments. — The lateral extensor is attached, by the superior extremity of its muscular fibres, to the external femoro-tibial ligament, to the whole extent of the fibula, and to the fibrous partition which separates this muscle from the perforans — origin. It terminates in the tendon of the anterior extensor. Belations. — Its muscular body is enveloped in a special containing aponeurosis, which separates it, in front, from the anterior extensor, and behind from the perforans. The tendon covers the tibia, and margins the external and suj)erficial ligament of the tibio-tarsal articulation ; which liga- ment supplies a fibrous ring destined for the formation of its reflected sheath. A vaginal synovial membrane facilitates its motion in the interior of this sheath. Action. — It acts like the preceding. 3. Flexor of the Metatarsus. (Fig. 136.) Synonyms. — Tibid-prcmetutarsus — Girard. Its muscular portion represents the tibialis anticus of anthropotoiiiiots. {Flexor Metatarsi — Fercivall.) This muscle is situated beneath the anterior extensor of the phalanges, on the external surface of the tibia, and is composed of two distinct portions : one muscular, the other aponeurotic, not united from end to end, but placed parallel one before the other. A. Tendinous Portion (Fig. 136, 1). — Course — Attach- ments. — This is a strong, pearly-white cord, comprised between the muscular port io7i and the anterior extensor of the phalanges. It commences at the inferior extremity of the femur, in the fossa excavated between the trochlea and the external condyle ; it afterwards passes through the superior groove of the tibia, where it is enveloped by a prolongation from one of the synovial membranes of the femoro-tibial articulation, giving origin, below this groove, to the muscular fibres of the anterior extensor of the phalanges. Lower, it receives some of the fasciculi from the muscular portion, to which it sends in exchange several aponeurotic layers; it passes under the superior annular band in front of the hock, in company with the anterior extensor, and reaches the level of the trochlea of the astragalus, where it is perforated to form a ring for the passage of the inferior extremity of the muscular portion. It finally terminates in two branches : a large one, inserted in front of the superior extremity of the principal metatarsus (Fig. 136, 4) ; the other, narrower, deviates outwards to reach the anterior surface of the cuboid bone (Fig. 136, 3). 1, Tendinous portion; 2, Its attachment to the femur; 3, Its cuboid branch; 4, Its metatarsal branch; 5, Muscular portion; 6, Its succeeding tendon passing through the ring of the tendi- FLEXOR MUSCLE OF jj^yg portion; 7, Cuneiform portion of this tendon; 8, Its meta- THE METATARSUS. tarsal branch ; 9, Anterior extensor of the phalanges drawn outwards by a hook. — A, Lateral extensor ; B, Tibial insertion of the middle patellar ligament ; C, Femoral trochlea. MUSCLES OF TEE POSTERIOR LIMBS. 301 "Relations. — In front, with tlie anterior extensor of tlie pTialangcs; behind, with the muscular portion, and the anterior caj)sular ligament of the tarsus. Action. — Tliis tendon enjoys the curious property of bending the hock by an action altogether mechanical, whenever flexion of the superior bones of the limb takes place. It is, therefore, a conducting cord, whose office it is to regulate the movements of flexion in the hock, and conform them to those taking place in the other joints, without requiring the intervention of an active agency for the execution of these movements. Another function has also been attributed to it : that of passively opposing the flexion of the femur on the tibia while the animal is standing, and. in this way serving as an adjunct to the muscular powers which support the weight of the body. But, in our opinion, this is incorrect ; as in order that it may perform this task, it would be necessary for the foot to be maintained in a fixed position by the contraction of its extensor muscles. But these muscles are really the gastrocnemii, which have their origin behind the femur, and which undoubtedly tend to flex that bone on the tibia — that is, to determine the movement it is supposed to prevent. And exjieriment clearly shows that we are justified in this opinion ; for division of this tendinous cord in the living animal does not interfere in the slightest degree with its natural attitude, either when standing at liberty or when forced to stand. ^ B. Muscular Portion. — Situation — Form — Structure. — Situated between the tendinous cord and the tibia, this portion is elongated from above to below, very wide at its superior part and narrow inferiorly, where it termi- nates in a bifid tendon. Attachments. — It originates, by the upper extremity of its muscular fibres, from the tibia, below and on the sides of the groove through wliich the tendinous cord passes ; its most superficial fibres are even attached to the aponeurotic sheath which envelops the lateral extensor. Its terminal tendon (Fig. 136, 6) traverses the annular ligament which the tendinous portion forms at its inferior extremity, and becomes inserted, by one of its branches, ' J. F Meckel rightly considers this tendinous cord, not as a portion of tlie anterior tibial, but as a dependency of the extensor longus digitoruiu. It would be wrong, however, to describe it apart from the anterior tibial, properly so-called — that is, the muscular portion of our flexor of the metatarsus, the tsvo being, in their action, essentially one. . Is there anything in the human species analogous to this fibrous cord ? After mucli liesitation, we answer in the affirmative, and give it as our opinion that this tendon repre- sents the anterior peroneus {ixroneus tertiits) in Man. These are our reasons for making this assertion, hazardous as it certainly is at first sight : In Man. Ihe peroneus tertius cannot always be easily distinguished from the extensor longus digitorum ; so that these two muscles may be regarded as a single one until reaching the instep, where it ex- tends to the plialanges of tlie toes on the one part, and the metatarsus on the other. Precisely tlie same arrangement is found in Solipeds ; the single muscle divides into two fasciculi, one for the digital region [anterior extensor of tlie phalanges), the other to the metatarsal region (tendinous cord of our flexor metatarsi). This tendinous cord, then, exactly represents the fasciculus of the long common extensor ot the toes (in Man), which goes to the metatarsus, and is designated the peroneus tertius. But to this it may be said : your peroneus tertius in the Horse has no relation whatever to the peroneus, and does not this prove that you are in error? No ; for if thi.-j muscle is attached to the fibula in Man, it is because the principal muscle on which it depends is inserted there itself. But as the anterior extensor of the phalanges of the Horse — that is, the common extensor of the toes — is not inserted into the fibula, and has no connection with it in any way, its metatarsal fasciculus, or rather its tendinous cord or peroneu-* tertius, ought to be absolutely in the same condition. We repeat, however, that this opinion may be, perhaps, a little hazardous ; aud we give it with reserve, though we have some rcasone for considering it to be correct. 302 THE MUSCLES. in front of the superior extremity of tlie princip.al metatarsal bone, along with the analogous branch of the tendinous division (Fig. 136, 8). The other ramification is directed to the inside of the tarsus, to be attached to the second cuneiform bone (Fig. 136, 7). Belatmis. — In front, with the tendinous portion of the muscle and the anterior extensor of the phalanges ; behind, with the external face of the tibia. The tendon, after traversing the annular ligament of the cord, covers the metatarsal branch of the latter, and is in turn covered by the anterior extensor. Action. — It is an active agent in flexing the foot on the leg. B. Posterior Tibial Region. This region comprises six muscles, which are arranged in two super- posed layers behind the tibia. The superficial layer is formed by the gastrocnemii, salens, and the superficial flexor of the phalanges. The deep layer is composed of the popliteus, the deep flexor, and the oblique flexor of tlte phalanges. ^ 1. Gastrocnemii, or Gemelli of the Tibia. (Figs. 135, 22 ; 137, 20.) Synonyms.— Bifemoro-calcaneus — Girard. ( Gastrocnemius externus — Percivall.') Situation — Compofiition — Extent. — The gemelli of the leg, situated behind the femoro-tibial articulation, below the ischio-tibial muscles, constitute two thick fleshy fasciculi distinct from one another only at their superior extremity, being confounded for the remainder of their extent, and continued inferiorly by a single tendon which extends to the point of the calcis. Porm — Structure. — Both of these muscular masses are flattened on both sides, thick, in the middle, narrow at the extremities, and intersected by strong tendinous bands. By their union they form a wide channel, open in front, which embraces the femoro-tibial articulation and the muscles of the deep layer. The tendon, at first fasciculated, then single and funicular, receives that of the soleus, and is reinforced by a fasciculus from the fibrous band annexed in front to the tendon of the perforatus {see the description of the tibial aponeu- rosis, p. 297). An aponeurotic lamina which covers the external gemellus, is continued downwards, partly with this fibrous band, and partly with the tendon of the muscle itself. Attachments. — The external gemellus arises on the femur, from thef rugged lip which margins in front the supracondyloid fossa ; the internal, from the collection of tubercles which constitutes the crest of the same name. The terminal tendon of the two bellies is fixed on the summit of the calcis, not at its anterior part, but posteriorly, this being lubricated by a vesicular synovial membrane forming a gliding surface on which the tendon rests during extreme flexion of the foot (Fig. 67, 1). Belations. — The gemelli respond : by their superficial face, to the three ischio-tibial muscles, and the tibial aponeurosis ; by their deep face, to the perforatus, which contracts intimate adhesions with the vastus externus, to the posterior ligament of the femoro-tibial articulation, the popliteal muscle and vessels, the great sciatic nerve, and the oblique and deep flexor muscles of the phalanges. The tendon lies beside that of the per- foratus, which is twisted around and completely envelopes it at its inferior extremity, in common with the fibrous band from the tibial aponeurosis. The two tendons form what is usually termed the tendon of the hock, or tendon of Achilles. MUSCLES OF THE POSTERIOR LIMBS. 303 Action. — The gastrocnemii extend the foot upon the tibia. They act as a lover of the first order when the limb is raised from the ground, and as Fig. 137. MUSCLES ON INNER ASPECT OF LEFT POSTERIOR LIMB. 1, Crest of the ilium ; 2, Section through it ; 3, Sacro-ischiatic ligament; 4, Pyri- formis ; 5, Posterior portion of sacro-ischiatic ligament ; 6, Tuberosity of ischium ; 7, Anterior portion of ischium, sawn through ; 8, Pubis ; 9, Obturator foramen; 10, External iliac artery and vein, 11 ; 12, Obturator artery and vein; the figures are placed on the internal obturator muscle; 13, Long adductor of the leg, or sartorius; 14, Small adductor of the thigh, or adductor brevis; 15, Short adductor of the leg, or gracilis ; 16, Ptcctus of the thigh ; 17, Vastus internus ; 18, Patella, with ^insertion of rectus; 19, Upper extremity of tibia; 20, Gas- trocnemius; 21, Popliteus; 22, Oblique flexor of the phalanges, or flexor pedis accessorius, with its tendon, 34 ; 23, Perforans muscle, with its tendon, 35 ; 24, Flexor metatarsi ; 25, Anterior extensor of the phalanges, or extensor pedis ; 26, Annular ligament ; 27, Tendon of flexor metatarsi, and its cunean branch,^ 28 ; 29, Tendon of superficial flexor or internal gastrocuemius ; 30, Tendon of gemelli or external gastrocnemius ; 31, Os calcis ; 32, Astragalus ; 33, Perloratus tendon ; 34, Tendon of oblique flexor joining the perforans tendon, 35 ; 36, Large -metatarsal bone; 37, Extensor pedis tendon; 38, Terminal knob of small meta- tarsal bone. 304 TEE MUSCLES. one of the second order when the hoof is placed on the ground. They maintain the tibio-tarsal angle while the animal is standing, and in pro- gression give to the hock that spring which carries the body forward. 2. Soleus (or Solearis). (Fig. 135, 21.) Sjpionyim. — Bourgelat and his successors have erroneously assimilated it to the plantaris of Man. In regarding this little muscle as the soleus, we conform to the well-founded opinion of Cuvier. It is the peroneo-calcaneus of Girard. {Plantaris — Percivall.) Form — Situation. — This is a thin, long, and riband-shaped rudimentary muscle, situated at the external side of the leg, between the tibial aponeu- rosis and the muscular portion of the perforans. Attachments. — It is fixed, by its superior extremity, behind the supero- external tuberosity of the tibia ; and terminates, inferiorly, by a small tendon, which joins that of the gastrocnemii. Action. — It is a feeble auxiliary of the last-named muscles. 3. Superficial Flexor of the Phalanges, or Perforatiis. (Figs. 135, 25 ; 137, 30.) Synonyms. — Femoro-phalangeus — GtVard. It is represented in Man by the jdantaris and ilexor brevis digitorum, or perforatus. These two, in the majority of ni;immalia, are united from end to end to form a single muscle. (The gastrocnemius infernus of Percivall.j Form — Structure. — The perforatus of the posterior limb is only repre- sented, in reality, by a long tendinous cord, that is somewhat muscular, slightly thickened, and fusiform in its upper fifth, which forms the body of the muscle. Origin — Direction and Relations — Termination. — It originates, by its upper extremity, in the supercondyloid fossa, descends between the two portions of the gastrocnemii, to the external of which it is intimately i*elated, on the posterior face of the femoro-tibial articulation and the three posterior deep tibial muscles. On reaching the inferior extremities of the muscular bellies of the gastrocnemii, it becomes exclusively tendinous, and is directly united to the fibrous band which reinforces the tendon of the hock. It afterwards disengages itself below the gastrocnemius, and is placed at the internal side of its tendon, then on its posterior surface, and in this position gains the summit of the os calcis. There it becomes widened to form a fibrous cap, which is covered by a large vesicular synovial membrane ; it is moulded to the posterior region of this bony eminence, which it com- pletely envelops in order to be fixed on its lateral portions, and is united to the calcanean band from the tibial aponeurosis. From this point the tendon of the perforatus is prolonged behind that of the perforans to the posterior face of the second phalanx, where it terminates in exactly the same manner as the analogous muscle of the anterior limb. Action. — It flexes the second phalanx on the first, and this on the meta- carpus. It also concurs in the extension of the foot. Its principal office, however, is that of a mechanical stay, destined to sustain the equilibrium of the body while the animal is in a standing posture, by preventing the diminution of the angle of the hock and that of the fetlcck, the femur being fixed by the contraction of the crural triceps and the gluteal muscles. 4. Poplifeus. (Fig. 137, 21.) S7jnonyms. — The abductor tibialis of Bourgelat, and femoro-tibialis obliquus of Girard. MUSCLES OF THE POSTERIOR LIMBS. 305 Situation — Direction — Form — Structure. — Situated beliincT the tibia, below the femoro-tibial articuhition, this muscle is oblique downwards aud inwards, short and triangular, tendinous at its supero-external angle, and formed, for the remainder of its extent, of divergent fleshy fibres, the longest of which are the most inferior. Attachments. — 1. In the lowest of the two fossaB excavated on the outside of the external condyle of the femur, by its tendon — origin. 2. On the supero-posterior triangular surface of the body of the tibia, by the inferior extremity of its muscular fibres — termination. Eelations. — Posteriorly, with the gastrocnemii and the perforatus. In front, with the posterior ligament of the femoro-tibial articulation, and the popliteal vessels. Outwards, with the oblique and deep flexors of the phalanges. Inwards, with the semitendinosus and tibial aponeurosis. The tendon, concealed at its origin beneath the external femoro-tibial ligament, glides, by its deej) face, over the contour of the external semilunar cartilage and the posterior portion of the external facet on the tibia. Action. — It flexes the tibia, and gives it a slight rotatory movement out- ■wai-ds. 5. Deejp Flexor of the Phalanges or Perforans. (Figs. 135, 23 ; 137, 23.) Synonyms. — Tibio-phalangeus — Girard. The flexor perfornns and flexor longus poUicis pedis of Man. (^Flexor pedis — Percimll. Great tihlo-phulangeus — Ltyh.') Extent — Situation — Direction — Composition, — Extending from the supe- rior extremity of the leg to the third phalanx, and situated behind the tibia and foot, whose direction it follows, this muscle is composed of a muscular body and a tendon. Form, Structure, and Attachments of the mvscular portion. — This is thick and prismatic, and incompletely divided into two portions — an internal,^ and an external,^ which is the most voluminous. It is attached : 1, To the posterior face of the tibia, on the linear imprints which occupy the inferior triangular surface ; 2, To the supero-external tuberosity of the same bone ; 3, To the peroneus ; 4, To the interosseous ligament uniting that bone to the tibia. Direction and Attachments of the tendon. — The tendon commences above the inferior extremity of the tibia, where it is most usually double, each muscular portion being succeeded by a tendinous cord whose volume is in harmony with the size of the muscle from which it proceeds. The single tendon resulting from the union of these two primary ones enters the groove formed by the inner face of the os calcis, where it is retained by a fibrous arch which transforms this channel into a perfect sheath, designated the tarsal sheath; it glides in the interior of this canal by nieuns of a very extensive vaginal synovial membrane, which extends upwards on the posterior ligament of the tibio-tarsal articulation, and is prolonged inferiorly to the middle third of the metatarsal region. The tendon of the perforans afterwards descends vertically behind the suspensory ligament, receiving from it a strong fibrous band analogous to that of the fore-limb, but less voluminous ; it then passes through the annular portion of the perforatus, is inflected mth that muscle over the great sesamoid groove, glides on the posterior articulating surface of the second phalanx and that on the small sesamoid bone, thinning out into a plantar aponeurosis which is provided with ' The tibialis posticus of Man. * The flexor longus pollicis of IMan. 306 THE MUSCLES. a phalangeal reinforcing sheath, and finally terminates on the semilunar crest of the os pedis. This tendon, therefore, on leaving the tarsus, com- ports itself exactly like that of the anterior limb. Relations. — Outwards, with the lateral extensor of the phalanges, the soleus, and the tibial aponeurosis. Inwards, with this aponeurosis and the oblique flexor Behind, with the gastrocnemii, the j)erforatus, and the fibrous band of tlie tendon of the hock. In front, with the tibia. Action. — This muscle flexes the phalanges on one another and on the metatarsus. It may also extend the foot in pressing, during its contraction, behind the tibio-tarsal articulation. In addition to this, its tendon acts, while the animal is standing, as a mechanical support to the phalanges and the articular angle of the fetlock. 6. Ohlique Flexor of ilie Phalanges. (Fig. 137, 22.) Synonyms. — Peroneo-phalangeus — Girard. The tibialis posticus of Man. (^Flexor pedis accessorius — Percivall. Small tibio-phalangeus — Leyh.) Situation — Direction. — A muscle situated behind the tibia, between the popliteus and the perfurans, in a direction slightly oblique downwards and inwards. Form — Structure. — It is composed of a fleshy fusiform body, intersected by numerous fibrous bands, and provided with a funicular tendon inferiorly. Attachments. — The superior extremity is fixed behind the external tuberosity of the tibia — origin. The tendon is united, by its inferior extremity, to that of the perforans towards the upper third of the meta- tarsal region — termination. Relations. — The muscular portion responds : in front, to the perforans, the popliteus, and the posterior tibial artery; behind, to the gastrocnemii and the perforatus. The tendon, at first lodged in a muscular channel in the perforans and covered by the tibial aponeurosis, afterwards enters a tortuous sheath at the inner side of the tarsus, and which is formed by the groove that bends behind the infero-internal tuberosity of the tibia. Action. — It is a congener of the deep flexor. DIFFERENTIAL CHARACTERS OF THE MUSCLES OF THE LEG IN OTHER THAN SOLIPED ANIMALS. A. Anterior Tibial Region. RrMiNANTS. — Among these animals, the Ox presents : 1. A complex muscle, wliifh is represented in the Horse by the anterior extensor of the phalanges, and the tendinous cord of the flexor metatarsi. Single at its superior extremity, which begins by a tendcm arising from the digital fossa situated between the trochlea and the external condyle of the femur (Fig. 138, 1), this muscle comprises in its middle part three fleshy divisions which are terminated inferiorly by tendons. One (if these divisions, situated in front of, and within the other two, has its tendon prolonged to the superior extremity of the principal metatarsal bone, and is also inserted into the cuneiform bones. It is a flexor of the metatarsal region, and replaces the tendinous cord which performs this function in Solij^eds ( Fig. 138, 2). The second, placed without the preceding, constitutes a common extensor of the digits, whose tendon comports itself exactly like that of the anterior limb (Fig. 138, 5, 5', (J) (.see p. 270). The third, concealed by the other two, forms the proper extensor of the internal digit, and resembles its fellow in the fore extremity see p. 270). 2. An anterior tibial muscle (muscular portion of the flexor of the metatarsal of the Horse). It is a triangular, muscular body, lodged in the antero-external fossa of the tibia into th.e upper part of which it is inserted, aad ia succeeded by a tendon that MUSCLES OF THE POSTERIOR LIMBS. 307 138. commences towards the middle of the tibia. This tendon passes through a ring pierced in the tendon of the muscle that represents the tendinous ])ortion of the tiexor of the metatarsus ; it then deviates inwards, and is fixed into the cuneiforms and the superior extremity of the principal metatarsal bone (Fig. 138, 4). 3. A ■proper extensor of the external difrC"SI. I. Occipital. The occipital gives insertion to nine pairs of muscles :— 1. Great complexus muscles. 2. Small oblique muscles of the head. 3. Great posterior recti muscles of the head. 4. Small posterior recti muscles of the head. 5. Great anterior recti muscles of the head. 6. Small anterior recti muscles of the heud. 7. Small lateral recti muscles. 8. Digastric muscles. 9. Occipito-styloid muscles. II. Parietal. The parietal gives attachment to one muscle ; — The temporal. III. Frontal. The frontal gives insertion to the — Supernaso-labial is. rV Sphenoid. The sphenoid gives attachment to four muscles : — 1. Great anterior recti muscles of the head. 2. Small anterior recti muscles of the head. 3. Internal pterygoid muscles. 4. External pterygoid muscles. V. Temporal. The temporal gives insertion to five muscles : — 1. Splenius. 2. Small complexus. 3. Small oblique muscle of the head. 4. Mastoido-humeraUs. 5. Temporal. B. BOXES OF THE FACE. I. Superior Maxillary. The supermaxillary gives insertion to the following muscles ; 1. Cuticularis of the neck. 2. Alveoli-labialis. 318 THE MUSCLES. 3. Supermaxillo-nasalis. 4. Great supermaxillo-nasalia. 5. Masseter. II. Premaxillary Bone. The premaxillary bone gives insertion to the — 1. Small supermaxillo-nasalis. 2. Anterior middle or intermediate muscle. III. Palatine Bone. The palatine bone gives insertion to the — Internal pterygoid muscle. IV. Zygomatic. The zygomatic bone gives insertion to one muscle, the — Supermaxillo-labialis. V. Lachrymal. The lachrymal bone gives insertion to one muscle, the — Lachrymo-labialis. VI. Nasal Bone. The nasal bone gives insertion to one muscle, the — Supernaso-labialis. VII. Inferior Maxilla. The inferior maxilla gives insertion to the following muscles : 1. Sterno-maxillaria. 2. Alveolo-labialis. 3. Maxillo-labialia. 4. Posterior middle or intermediate muscles. 5. Masseter muscles. 6. Temporal muscles. 7. Internal pterygoid muscles. 8. External pterygoid muscles. 9. Digastric muscles. 10. Mylo-liyoid muscle. 11. Genio-hyoid muscles. C. HYOID BONE. The hyoid bone gives insertion to the following muscles : — a. By its hody and its thyroid cornua — 1. Sterno hyoid muscles. 2. Sea pulo- hyoid muscles. 3. Mylo-hyoid muscles. 4. Genio-hyoid muscles. 5. Stylo-hyoid muscles. 6. Kerato-hyoid muscles. 7. Transverse muscle of the hyoid bone. b. By its branches (styloid cornua and styloid bones) — 1. Stylo-hyoid muscles. 2. Kerato-hyoid muscles. 3. Occipito-styloid muscles. GENERAL TABLE OF MUSCULAR INSERTIONS. 819 3. Bones of the Thorax. A. THE BIBS AXD THEIK CARTILAGES. The ribs and costal cartilages give insertion to the — 1. Scalenus (1st). 2. Small anterior serrated muscle (5th to 9th). 3. Small posterior serrated musfle (9th to 18th). 4. Dio-spinalis muscle (3rd to 18th). 5. Common intercostal muscle. 6. Great psoas (17th to 18th). 7. Square muscle of the loins (IGth to 18th). 8. Great serrated muscle 1 1st to 8th). 9. TransTcrse muscle of the ribs (1st). 10. External intercostal muscles. 11. Internal intercostal muscles. 12. Supercostal muscles. 13. Triangular muscle of the sternum (2nd to 8th) 14. Great oblique muscle of the abdomen (5th to ISth). 15. Small oblique muscle of the ahdomen (asternal caitilages). 16. Great rectus muscle of the abdomen (asternal cartilagesj. 17. Transverse muscle of the abdomen. 18. Diaphragm (7th to 18th). The sternum gives insertion to the — 1. Cuticularis of the neck. 2. Sterno-masillary muscles. 3. Sterno-thyroid muscles. 4. Sterno-hyoid muscles. 5. Superficial pectoral muscles. 6. Deep pectoral muscles. 7. Transverse muscles of the ribs. S. Triangular muscle of the sternum. 9. Great recti muscles of the abdomen. 10. Transverse muscles of the abdomen. 11. Diaphragm. 4. Thoracic Limb. A. BONNES OF THE SHOULDER. Scapula. The scapula gives insertion to seventeen muscles : — a. By its externnl face to the — 1. Supraspinatus. 2. Subspiuatus. 3. Short abductor of the arm, or teres minor. 4. Long abductor of the arm. 5. Trapezius 6. Mastoido-humeralis. h. By Us internal face, to the — 1. Ehomboid muscle. 2. Angular muscle of the scapula. 3. Great serrated muscle. 4. Subscapularis. 5. Small scapulo-humeral muscle. c. By its anterior border, comprised beiiceen the cervical angle and the coracoid process, to the — i. Sterno-prescapularis, or small pectoral muscle. 320 TEE MUSCLES. 2. Long flexor of the fore-arm, or brachial biceps. 3. Coraco-brachial muscle. 4. Supraspinatus muscle. d. By its posterior border, comprised betiveen the dorsal angle and the corrc sponding portion of the humeral angle, to the — 1. Long extensor of the fore-arm. 2. Large extensor of the fore-arm. 3. Adductor of the arm, or teres major. 4. Long alidii'tor of the arm. 5. Short abductor of the arm. B. BONES OF THE ARM. Humerus. The humerus gives insertion to twenty-four muscles : — a. By its superior extremity, to the — 1. Supraspinatus. 2. Subspinatus. 3. Subscapularis. 4. Small scapulo-humeralis. 5. Sterno-trochineus, or deep pectoral. 6. Panniculus carnosus. b. By its body, to the — 1. Long abductor of the arm. 2. Short abductor of the arm. 3. Coraco-brachial muscle by two points. 4. Adductor of the arm, or teres mnjor. 5. Short flexor of the fore-arm, or anterior brachial muscle. 6. Short extensor of tlie fore-arm. 7. Middle extensor of the fore-arm. 8. Small extensor of the fore-arm, or anconeus muscle. 9. Anterior extensor of the metacarpus. 10. Anterior extensor of the phalanges. 11. Great dorsal muscle. 12. Mastoido-humeralis muscle. 13. Sterno-humeralis, or superficial pectoral muscle. c. By its inferior extremity, to the — 1. Anterior extensor of the phalanges. 2. External flexor of the metacarpus. 3. Oblique flexor of the metacarpus. 4. Internal flexor of Ihe metacarpus. 5. Superficial flexor of the phalanges, or perforatus. 6. Deep flexor of the phalanges, or perforans. C. BOXES OF THE FORE-ARM. I. Radius. The radius gives insertion : — a. By its upper extremitij, to the — 1. Long flexor of the fore-arm, or brachial biceps. 2. Anterior extensor of the phalanges. 3. Lateral extensor of the phalanges. b. By its body, to the — 1. Short flexor of the fore-arm. or anterior brachial muscle. 2. Oblique extensor of the metacarpus 3. Anterior extensor of the phalanges. 4. Lateral extensor of tlie phalanges. 5. Deep flexor of the phalanges, or perforans. GEXERAL TABLE OF MUSCULAR INSEETJOXS. 321 II. Ulna. The ulna gives insertion : — o. By its upper extremity (olecranon) to the — 1. Long extensor of the fore-arm. 2. Large extensor of the fore-arm. 3. Short extensor of the fore-arm. 4. Middle extensor of the fore-arm. 5. Small extensor of the fore-arm, or anconeus muscle. 6. Oblique flexor of the metacarpus. 7. Deep flexor of the phalange;?, or perforans. b. By its body, to the — 1. Short flexor of the fore-arm, or anterior brachial muscle. 2. Lateral extensor of the phalanges. D. BOXES OF THE CARPUS. Supercarpcd Bone. The supercarpal bone, the only bone of the carpus whicli Las muscular attachments, gives insertion to two muscles : — 1. External flexor of the metacarpus, or posterior ulnar, 2. Oblique flexor of the metacarpus. E, BOXES OF THE METACARPUS. I. Princijml Metacarpal. The principal metacarpal gives insertion to a single muscle : — By its superior extremity, to the — Anterior extensor of the metacarpus. II. External Eudimentary Metacarpal. This gives insertion to a single muscle : — External flexor of the metacarpus, or posterior ulnar. III. I)iternal Eudimentary Metacarpal. This gives insertion to two muscles : — 1. Oblique extensor of the metacarpus. 2. Internal flexor of the metacarpus, or groat palmar muscle. F. BOXES OF THE DIGITAL REGION. I. First Phalanx. This gives insertion to two muscles : — 1. Anterior extensor of tlie phalanges. 2. Lateral extensor of the phalanges. II. Second Phalanx. This gives insertion to two muscles : — 1. Anterior extensor of the phalanges. 2. Superficial flexor of the phalanges. III. Tliird Phalanx. The third phalanx, or os pedis, gives insertion to two muscles : — 1. Anterior extensor of the phalanges. 2. Deep flexor of the phalanges. 322 THE MUSCLES. 5. Abdominal Limb. a. bones of the haunch. Coxa, The coxa gives insertion : — a. By the ilium, to the — 1. Ilio-spinalis muscle. 2. Iliac (psoas) muscle. 3. Small psoas muscle. 4. Square muscle of the loins. 5. Ischio-coccygeal muscle. 6. Great oblique muscle of the abdomen. 7. Small oblique muscle of the abdomen. 8. Transverse muscle of the abdomen ( through the medium of the crural arch). 9. Middle gluteal muscle. 1 0. Deep gluteal muscle. 11. Muscle of the fascia lata. 12. Anterior rectus muscle of the thigh. 13. Anterior gracilis muscle. 14. Internal obturator. b. By tlie jnibis, to the — 1. Great oblique muscle of the abdomen. 2. Small oblique muscle of the abdomen. 3. Great rectus muscle of the abdomen. 4. Transverse muscle of the abdomen (through the medium of the crural arch). 5. Short adductor of the leg. 6. Pectineus muscle. 7. Small adductor of the thigh. 8. External obturator muscle. 9. Internal obturator nmscle. c. By the ischium, to the — 1. Superficial gluteus muscle. 2. Long vastus muscle, 3. Semitendinous muscle. 4. Semimembranous muscle. 5. Short adductor of the leg. <;. Great adductor of the thigh. 7. Square crural muscle. 8. External obturator muscle. 9. Internal obturator muscle. 10. Gemelli muscles of the pelvis. B. BONES OF THE THIGH, Femur. The femur gives insertion : — a. By its upper extremity, to the — 1. Great psoas muscle. 2. Iliac psoas muscle. 3. Middle gluteus muscle. 4. Deep gluteus muscle. 5. External obturator muscle. 6. Internal obturator muscle. 7. Gemelli muscles of the pelvis. b. By its body, to the — 1. Superficial gluteus muscle. 2. Fascia lata. GENERAL TABLE OF MTSCULAE INSERTIONS. 323 3. External vastus muscle (crural triceps). 4. Internal vastus muscle (crmal triceps). 5. Anterior gracilis muscle. 6. Long vastus muscle. 7. Peetineus muscle. 8. Small adductor of the thigh. 9. Great adductor of the thigh. 10. Square crural muscle. 11. Gastrocnemii muscles. 12. Superficial flexor of the phalanges, or perforatus. c. By its inferior extremity, to the — 1. Semimembranous muscle. 2. Great adductor of the thigh. 3. Anterior extensor of the phalanges. 4. Flexor of the metatarsus. 5. Popliteus muscle. C. BONES OF THE LEG. I. Tibia. The tibia gives insertion : — a. By its upper extremity, to the — 1. Flexor of the metatarsus. 2. Soleus muscle. 3. Deep flexor of the phalanges, or perforans. 4. Oblique flexor of the phalanges. 5. Long adductor of the leg '^through the medium of the internal patellar ligament). b. By its hochj, to the — 1. Long vastus muscle. 2. Semitendinous mutcle. 3. Sl)ort adductor of the leg (in common with the long adductor) 4. Flexor of the metatarsus. 5. Popliteus muscle. 6. Deep flexor of the phalanges or perforans. II. Fibula. The fibula gives insertion to two muscles : — 1. Lateral extensor of the phalanges. 2. Deep flexor of the phalanges or perforans. III. Patdla. The patella gives insertion to five muscles : — 1. Fascia lata muscle (or tensor vaginae). 2. Anterior rectus of the thigh. 3. External vastus (crural triceps). 4. Internal vastus (crural triceps). 5. Long vastus muscle. D. BON'ES OF THE TAHSUS. Calcis, The calcis gives insertion to the :— Gastrocnemii muscles. Cuboides, The cuboides gives insertion to the — Flexor of the metatarsus. 324 THE MUSCLES. Second Cuneiform. This gives attachment to the — Flexor of the metatarsus. E. BONES OF THE METATARSUS. The principal metatarsal gives insertion to the — Flexor of the metatarsus. F. BONES OF THE FOOT. I. First Fhalanx. The first phalanx gives insertion to one muscle, the — Anterior extensor of the phalanges. II. Second Phalanx. The second phalanx gives insertion to two muscles : — 1. Anterior extensor of the phalanges. 2. Superficial flexor of the phalanges, or perforatus. III. Tliird Phalanx. The third phalanx gives insertion to two muscles : — 1. Anterior extensor of the phalanges. 2. Deep flexor of the phalanges, or perforans. BOOK IT. The Digestive Apparatus. CHAPTER I. GENEUAL CONSIDERATIONS ON THE DIGESTIVE APPARATUS. We have considered the animal as a machine composed of various levers and susceptible of various movements ; but it will be easily under- stood that the working of this machine will cause the wear or decomposition of the molecules which enter into the construction of its organs, and that these springs or animated wheels demand for their maintenance an incessant supply of new materials, destined to repair their continual losses. Animals, therefore, are under the necessity of taking aliment, from which they extract those reparative principles which, distributed to all the organs, are assimilated into their proper substance. The organs in wliich this work of preparation and absorption of the organisable material is carried on are collectively named the digestive apparatus : one of the most important of those which, as we will see, suc- cessively complicate and perfect the animal machine. This apparatus does not, properly speaking, constitute an essentially distinctive characteristic of animality, as there are animals without a digestive cavity ; but it is yet one of the most salient attributes, for the exceptions just mentioned are ex- tremely rare. Considered in the vertebra ta, this apparatus appears as a long tube, most frequently doubled on itself many times, bulging at intervals, and provided along its course with several supplementary organs, the majority of which are of a glandular nature. This tube extends the whole length of the animal's body, and opens externally by two orifices, one of these serving for the introduction of aliment, the other for the expulsion of the residue of digestion. These openings are at the extremities of the alimentary canal. The conformation of this apparatus is not identically the same in all the individuals composing the sub-kingdom of vertebrata ; on the contrary, it presents very numerous varieties, according to the habits and mode of life of these individuals, and this makes its study interesting from^ two points of view : in relation to the science of zoology, and to that of veterinary hygiene, which derives from this study valuaTale indications concerning the regime of the domesticated animals. But this diversity of characters does not suffice to establish sharply- defined limits between the conformations that are distinguished by it. There is, in reality, but one typical form for the digestive apparatus, and the same principle prevails in its construction throughout the entire series. Thus, whichever of the vertebrata we may be studying, its alimentary tube will be found composed of a collection of bulging or tubuliform cavities, which succeed each other from before to behind in the following order : the mouth, pharynx, oesophagus, stomach, and intestine, 24 326 GENERAL CONSIDERATIONS ON THE DIGESTIVE APrARATlfS. This system of cavities is divided, physiologically, into two principal sec- tions : the first comprises the mouth, pharynx, and oesophagus, or the compart- ments in which are carried on those digestive operations termed " preparatory," because they prepare the aliment for the subsequent modifications which constitute the essential phenomena of digestion ; the second section is formed by the stomach and intestine, where these phenomena take place. Each of these two sections is furnished in its course with annexed organs, which are present in the majority of vertebrata ; these are the salivary glands for the cavities of the first category, and the liver, pancreas, and spleen for those of the second. In considering the general position of these various parts, principally in mammals and birds, it is found that the first section of the digestive canal and its appended organs is lodged beneath the upper jaw and the base of the cranium, and under the cervico-thoracic portion of the vertebral column. The second section, with its annexes, occupies the great abdominal cavity. In Man, these two sections are divided into supra-diapliragmatic and infra-diaphragmatic, because of their relations to the diaphragm. The constituent parts of the first category might be termed, by reason of their functions, the preparatory organs of the digestive apparatus ; and those of the second, or abdominal portion, the essential organs of digestion. These various organs, with those composing the respiratory and genito- urinary apparatus, have received the name of viscera, and the term splanch- nology is often given to that branch of anatomy devoted to their study.^ These new organs differ so notably from those already described, that it is necessary to enter into some generalities as to their nomenclature, dis- position, form, structure, and physical or chemical characteristics. Nomenclaiure in splanchnology does not rest on any scientific basis ; the name of organs being sometimes derived from their form — as tlie amygdalce ; sometimes from their direction — rectum ; sometimes also from their uses — the oesophagus, salivary glands ; their length — duodenum ; the names of the anato- mists who have described them — the duct of Stenon, Fallopian tube; and at times these names are purely conventional, as the spleen. They are distinguished as hollotv and solid organs. 1. The hollow organs have a more or less considerable cavity, capable of being increased or diminished, but they are not of a definite shape or volume. Their consistency varies with their state of plenitude or vacuity, and they are single or double, symmetrical or asymmetrical. In all cases, the walls of the hollow organs are comj)osed of two or more membranes which we will now describe in a general manner. a. The innermost is called the mucous membkane, because of the mucus with which its free surface is always covered. It is made continuous with the skin at the natural openings ; and from its similarity of organisation it has been named the internal or re-entering skin, or internal tegumentary membrane. • The name fif viscera (from vescor, I nourish ) lias been given to the organs wliich aid in nutrition, and the term Splanchnology (from (riryaLxvov, a visciis or intestine) lias been bestowed on that division of anatomy whicli treats of these organs Splanclmology, thus understood, comprises the study of the digestive, respiratory, urinary, and circulatory apparatus. But the description of the latter forms a separate category, designated in the language of the schools by the name of Angioloriy. On tlie other hand, however, several authorities include in Splanchnology the organs of generation, and others even add the organs of sense. There is, therefore, no accord in the limits given to the detinition of Splanchnology ; and this being the case, we have thought it best to omit this expression and the distinction it seeks to establish. GENERAL CONSIDERATIONS ON THE DIGESTIVE APPARATUS. 327 Ficr. 143. A mucous membrane comprises a superficial or epitJielial layer and a deep portion which constitutes the derm or chorion [corium). The epitheluim is a very thin, inert pellicle, entirely comiiosed of epithelial cells united by an almost insignificant quantity of amorphous matter [blastema). The cells are flat or polygonal, round or cylindi'ical, polyhedral, or very irregular in shape. In consequence of these diverse forms, there is pavement (or squamous), spherical (or spheroidal), and cylindrical or conical (or columnar) epithelium. If the cells are furnished with small filiform appendages, named vibratile cilia, the epithelium is then designated ciliated. AVhen the cells are arranged in a single layer on the surface squamous epitheliuji fkom of the corium, the epithelium is said to be simple ; the mouth. it is stratified when the cells are arranged in strata The large scale is mao;nified upon each other. In stratified epithelium, the 310 diameters, and exhibits shape of the cells is not the same on the sm-face ^ nucleus with nucleolus in and beneath it, and it is named after the form of ^he centre, and seconlary ^. ,> • 1 1 nucleated cells forming the the superficial layer. _ body of the scale. The mucous derm or corium corresponds to that of the skin, as the epithelium corresponds to the epidermis. It is composed of connective ( or areolar) tissue, whose thickness, elasticity, vascularity, and sensibility varies with the situation and the func- tion of organs. The corium is thin and almost destitute of elastic fibres when applied to the bony walls of a cavity ; on the contrary, it is thick, elastic, and slightly adherent when it lines organs which, like the stomach, oesophagus, and intestines, are capable of increasing or diminishing in capacity. The fasciculi of the connective tissue in the deeper layers of the corium are loosely united, but nearer the surface they lie closer ; some- times they form, under the epithelium, an amorphous surface-layer, the basement (or limitary) membrane. The sub-epithelial face of the corium is scarcely ever smooth, but otfers minute prolongations named villositiesor Dapillce, which are very varied in their form columnar ciliated epithelium : and volume, and is more or less marked by magnified 310 diametep.s. depressions designated follicles. The villi a, Nucleated cells resting on their 1 _ J _ ii 1 ' i T smaller extremities ; 6, Cilia, are observed on the deep-seated mucous mem- ' ' braues ; they are mure particularly the vascular and absorbent organs. The papillae are found towards the natural apertures, and are rich in nerves ; they are more especially the organs of sensibility. The follicles, lined by one or other form of cell, are exclusively organs of secretion. h. Tlie second membrane met with in the walls of the hollow organs is of a muscular, and sometimes of a cartilaginous nature. The muscular mem- brane is formed of unstriped fibres whose slow contraction is involuntary. In certain organs — those adjoining the natural apertures — the unstriped fibres are replaced by strijied, which are under the influence of the will, or have the same physiological properties as the smooth fibres, as in the oesophagus. COLUMNAR epithelium. 1, Nucleus of the cell ; 2, Jlembrane of the cell raised from its contents by the absorption of water. Fig. 145. 328 GENERAL CONSIDERATIONS ON THE DIGESTIVE APPARATUS. (JJnstriped ov smooth bands of muscles are composed of long fusiform cells with staff-shaped, elongated nuclei, the cells varying from l-1125th to l-50th of an inch in length, and from l-5025th to l-1125th of an inch in breadth.) c. When the organs are lodged in one of the great splanchnic cavities, such as the chest or abdomen, they have a third mem- brane — a serous layer, which lines the cavity, and is reflected around the viscera contained in it, so as to envelop them more or less completely. This layer has, therefore, an adherent face, ai)plied either against the walls of the cavity or the external surface of the splanchnic organs ; and a free face always in contact with itself. A serous membrane is composed of two layers : a deep, connective portion, analogous to the mucous corium : and a superficial, which is only pavement epithelium. The free surface of this epithelium is perfectly smooth, and lubricated by a limpid serosity to facilitate the gliding of the parts the membrane covers. (The epithelium is a simple tesselated layer of flattened and polygonal nucleated cells, about 1— 1200th of an inch in diameter). 2. The solid organs are either contained in the splanchnic cavities or situated outside them, in the midst of connective tissue, which, in condensing around them, often forms a fibrous covering. Like the hollow organs, they are single — spleen, liver; or in pairs — Mdneys ; and symmetrical or asymmetrical. They are retained in their situation by their vessels and nerves, by adherence to the neighbouring organs, or by particular serous attachments. With the exception of the lungs of animals that have respired, all the solid organs have a density greater than water. Their iceiglit and volume oifer numerous difierences, which are individual or relating to the species to which they belong. Nevertheless, each organ pos- sesses a certain volume and weight which might be termed physiologic ; when the organ is above or below this average, we are authorized in saying that it is in a patho- logical condition. Organs are more or less round inform, and their surface is traversed by a variable number of furrows which indicate their division into lobes or lobules. COXICAL VILLI ON MUCOUS MEM- BRANE OF SMALL INTESTINE; MAGNIFIED 19 DIAMETERS. a, Zone of follicles surrouudiug a soli- tary gland ; b, Apertures of simple follicles. Fig. 147. FUSIFORM CELLS OF SMOOTH MUSCULAR FIBRE. a, Two cells in their natural state, one showing the staff-shaped nucleus ; with its nucleus, c, brought distinctly into view by acetic acid. 6, A cell GENERAL COXSIDEEATIOXS ON TEE DIGESTIVE ATFABATVS. 329 Their colour is diverse ; they may be very ^^\q— parotid gland ; or very dark — liver, spleen ; or uniform, or of different shades : varieties which are most frequently due to the mode of distribution of the vessels, or to the jiresence of certain anatomical elements. The colour of organs is not always the same in the deeper parts and at the surface, especially Avhcn they are enveloped by a thick, opaque membrane ; for instance, the testicle. Lastly, the coloration is less intense after death than during life, and particu- larly if the animal to which the organs belonged has been killed by effusion of blood. The consistence of organs depends on their internal fomiation and the nature of their constituent elements ; there are soft organs, such as the lungs, and resisting organs, as the testicles. As a general rule, the consistence of organs diminishes after jnitrefaction has set in. Cohesion is the resistance that organs offer to the forces which tend to tear them ; it depends upon the texture of the organs, and the more or less abundance in their interior of fibrous and elastic tissue. Cohesion is very different from consistency ; thus, such an organ as the lung may be easily compressed, but may be very difficult to tear. If organs are examined with regard to their structure, it will be observed that all have a thin or thick fibrous casing which throws septa into their interior, and which support their proper tissue ; this "tissue varies with the nature of the organs. It wall also be found that they are traversed by a more or less considerable number of blood-vessels — arteries and veins. These vessels expand into a capillary network, whose meshes have a shape closely allied to that of the elements of the proper tissue. The number and volume of the vessels of an organ give an exact idea of its importance, and of the activity of the physiological phenomena taking place in it. Finally, into the composition of organs enter supei-ficial and deep lymphatic vessels and nerves, which generally follow the arteries. The nerves show in their course small ganglionic enlargements ; their mode of termination is most frequently unknown. Glands are organs of a particular construction, whose function it is to eliminate certain fluid or solid products of the economy. The very simple (or tubular) glands consist of a straight or convoluted tube, or of a small vesicular cavity opening on a tegumentary membrane, and are lined on their inner face by one or more layers of cells. As examples, there may be cited the tubular glands of the intestines and stomach, the racemose (or lobulated) glands of Briinner, and the solitary follicles of the intestine. But there are also conglomerate glands, organs more complex, though belonging to the same groups as the simple glands. These are glands composed of tubes, like the kidneys and testicles ; racemose glands, such as the salivary glands and pancreas; a network of glands, like the liver; or glands witlti closed follicles, such as the thyroid. In these the essential anatomical element^ — the polygonal, cylindrical, or spherical gland-cell — is situated on the inner face of a tube, as in the Mdney, or a demi-vesicle, as is seen in the pancreas, or deposited without any order in the meshes of a plexus of canaliculi, as occurs in the liver. The conglomerate glands arc provided with a common excretory canal, that commences in their mass by a great number of arborescent ramifications. The walls of this canal are composed of an elastic, and sometimes con- tractile, conjunctival membrane, covered on its inner face by an epithelium, which may or may not be of the same character as that of the gland. 330 THE DIGESTIVE APPARATUS IN 3IA3IMALIA. For a long time there have been classed as glands certain organs — such as the si^leen and thymus body— without excretory ducts, and having only remote analogies to glands. The function of these organs is but little known ; though as they are always abundantly supplied with blood-vessels, and as they are therefore believed to have connections with the vascular system, they have been named vascular blood-glands. This is the limit to which the generalities relating to the viscera that form the object of splanchnology must be confined. We will now pass to the description of the digestive apparatus in mammals, and which consists, as mentioned above, of a series of enlarged or tubuliform cavities, to which are annexed the glandular organs designated the liver pancreas, and spleen. CHAPTER II. THE DIGESTIVE APPAEATUS IN MAMMALIA. We will study, successively : 1, The preparatory organs, which include the mouth, the salivary glands annexed to that cavity, the pharynx, and the oesophagus ; 2, Tlie essential organs, comprising the stomach and intestine, and their annexes— ihe liver, pancreas, and spleen; witliihQ abdominal cavity, which contains and protects these organs. Article I. — Preparatouy Organs op the Digestive Apparatus. THE BIOUTH. The mouth, the first vestibule of the alimentary canal, is a cavity situated between the two jaws, elongated in the direction of the larger r.xis of the head, and pierced by two openings : an anterior, for the introduction of food, and a posterior, by which the aliment passes into the pharynx. The mouth should be studied in six principal regions: 1, The lips, which circumscribe its anterior opening; 2, The c7«eeA-s, forming its lateral walls ; 3, The palate, which constitutes its roof or superior wall ; 4, The tongue, a muscular appendage, occupying its inferior wall ; 5, The soft palate (velum pendulum palati), a membranous partition situated at the posterior extremity of the buccal cavity, which it separates from the pharynx, and concurs in the formation, by its inferior border, of the isthmus of the fauces, or posterior opening of the mouth ; 6, The dental arches fixed on each jaw. We will study each of these regions in particular, before passing to the examination of the mouth in general. Preparation. — The whole of the mouth oupjht to be examined iu an antero-posterior and vertical section of the head, as in figure 152. 1. The Lips. (Fig. 110.) These are two membranous movable folds, placed one above, the other below, the anterior opening of the mouth, which they circumscribe. There is, consequently, a superior and an inferior lip, united at each side by a commissure. Each lip offers for study an external and internal face, and a free and an adherent border. m\Q external face is convex, and presents, on the median line: in tlie upper lip, a slight projection which divides it into two lateral lobes ; iu the THE MOUTH. 331 inferior lip, and altogether posteriorly, the single prominence named the tuft of the chin. This tace, formed by tlie skin, is garnished with fine, short hairs, amongst which may be remarked long, coarse bristles, whose bulbs are implanted perpeudicularly in the integument, and pass beyond its deep surface, to be lodged in the subjacent muscular tissue. These pilous tentacles ought to be considered as veritable tactile organs, as several sensitive nervous twigs penetrate to the bottom of their follicles. The internal face, constituted by the buccal mucous membrane, and moulded on the incisor teetli, is concave, smooth, rose-coloured, and often stained with black spots. In the superior lip, particularly, may be remarked numerous orifices opening on the summits of three small papillae ; these are the openings of the excretory canals by which the labial glands discharge their fluid into the interior of the mouth. • The free border, thin and sharp, bears the line of demarcation, which separates the two teguments. The adherent border is limited, in the buccal cavity, by a groove formed by the mucous membrane in its passage from the dental arches to the inner side of the lips. Beyond the mouth it is not indicated by any peculiarity of structure or arrangement, the skin being continued directly from the neighbouring parts on the lips. The commissures mark, on each side, the point of reunion between the free border of the two lips. They are rounded in Solipeds, and otfer nothing remarkable otherwise. Structtjke. — Each lip is composed of two tegumentary layers : one cutaneous, the other mucous, between which is found muscidar tissue and glands, and the general elements of every organisation — vessels and nerves. 1. Teijumentary layers. — Thesl-in adheres closely to the subjacent tissues, and apart from the chaiacters ali-eady indicated, there is nothing more to be said at present, with regard to its disposition, as it will be studied more completely with the organs of sense. With regard to the mucous membrane, it may be remarked that its derm is thick and dense, and lies on a layer of salivary glands ; that it is provided with simple conical jiai^illse, and is covered by stratified pavement epithelium. (It is sometimes streaked with pigment.) 2. Muscles. — These are: the labial or orbicularis, the sphincter of the buccal apertui-e, and common to the two lips ; in the ujjper lip, the aponeu- i-otic expansion of the supermaxillo-labialis, the musculo-fibrous tissue which separates this expansion from the cutaneous integument, and the terminal insertion of the sujiernasalis-labialis and the great supermaxillo- nasalis ; in the inferior lip, the tuft of the chin and its" suspensory muscles — the posterior intermediates (levatores menti). All these muscles having been studied in detail in the Myology (page 217), there is no necessity for their being again described. 3. Lcibial glandules. — These form an almost continuous laver between the mucous membrane and the labial muscle. They are little secretory organs, similar in their structure and uses to the salivary glands, and will be described when these come under notice. 4. Vessels and nerves. — The blood is carried to the lips by tlie palato- Idbial, and the superior and inferior coronary arteries. It is returned to tlie heart by the satellite veins of the two last vessels. The lymphatics are very numerous, and pass to the glands between the branches of the lower jaw. The nerves are of two kinds : the motor, which are given oft" from the facir,! nerve, and are distributed in the muscular tissue of the lips to cause itj 332 THE DIGESTIVE AFFABATVS IN MAMMALIA. contraction; the sensitive nerves, which are furnished by the maxillary branches of the fifth cncejihalic pair, are distinguished by their number and considerable volume, and are nearly all buried in the cutaneous integument, to which they communicate an exquisite sensibility. Functions. — The lips serve for the prehension of solid and liquid food ; they retain it in the mouth after its introduction thereto, and likewise pre- vent the escape of the saliva. They ought also to be regarded, especially the upper lip, as very delicate organs of touch. 2. The Cheeks. (Fig. 110.) These are two membranous walls, which inclose the mouth laterally. In the interior of the buccal cavity they are limited : behind, by the posterior pillars of the tongue ; in front, by the lips, with which they are confounded around the commissures; above and below, by the groove formed by the gingival mucous membrane, where it is reflected from the molar arches on to the cheeks. The greatest diameter of the cheeks is antero-posterior, like that of the cavity it incloses. Their vertical diameter is very narrow, esi^ecially behind ; in the anterior region, however, it can assume a certain amplitude by the separation of the jaws. Structure. — The cheeks are formed by the buccal mucous membrane, external to which we find muscular tissue and glands. Vessels and nerves pass through these parts for the conveyance of nutritive fluids, sensibility, or the stimulus to contractility. 1. Mucous membrane. — The external face of this membrane is united in an intimate manner to the buccinator muscle, and to the inferior molar glands. Its free face presents, at the level of the third superior molar tooth, the buccal opening of the parotid duct, pierced at the summit of a variable- sized tubercle. On the face of each dental arcade there is also remarked a linear series of little salient points, analogous in their constitution to the large parotideal tubercle ; these are the excretory orifices of the molar glands. Its structure is the same as the mucous meaibrane of the lips. (It is of a pale colour, and sometimes stained in patches with pigment.) 2. Muscular tissue. — This is the buccinator or alveolo-labialis muscle already described. It may be remembered that the external face of this muscle is covered by the masseter, the superior molar glands, and the skin ; while the internal responds to the mucous membrane and the inferior molar glands. 3. Glands. — These are two masses of glandular lobules, known as the molar glands. They will be described with the salivary glands. Vessels and nerves. — The external ma.xillary, coronary, and buccal arteries carry blood to the cheeks. The veins empty themselves into the satellite branches of these arteries. The lymphatics proceed to the submaxillary glands. The nerves are of the same kind, and proceed from the same source, as those supplying the lips : being the seventh pair of encephalic or facial nerves for the muscular layer, and tlie fifth pair for the integuments (with filaments of the sympathetic for the circulation and the labial glandules). Functions. — The cheeks are very active agents in mastication, by con- stantly pushing the aliment, through the action of the buccinator, between the dental grinding surfaces. 3. The Palate. (Fig. 148.) Freparatlon. — Separate the head from the trunk ; saw through the branches of the TEE MOUTH. 333 maxilla above the angle of the jaw, and from the crown of the last molar tooth, so as to pass between the curtain of the'soft palate on the one part, ami the base of the tongue on the other, leaving the latter organ adlierent to the lower jaw. TliLs last should be removed from tl- borders. The inferior or anterior face, tnrned towards the mouth, shows lono m yi . • a =* c >-> JH . . . o CO C3 a "2, *-* s c E s « C3 o? ■ * ■ a) o fc (S -J ^ t>-. »( d fk a _o CI- a o E <0 U ...... " „ ^ . . >= (MM p ^ 1 CO '-^ td td 2 S>t^ s s^ S3 o S pq s s lo rt ,-( CO td H c • • ^ o D3 i 11) M g a; w [2 " ' ' ■ ■ O "e- o >-. >-.>-.•••• 32 fcd < K rH (M CO -* s r-i (M CO C5 a) 1- . . a -.J r^ ^ >-H S-2 M '"' 1— 1 ;z; a o '^ ,i! O =« *J « ^ " 0) a) • w cj • • a . rl ^. ° S • o j3 . . £ -2 f^ =2-52 si o ^° a) rs rs H«^ p3 2 fe'"^ - «" CO o M '^ ^ (M fq S S CO >o s ^ g .—X >i t>% • >^ o (^ §>,•••• &c ^ ^l« — :« -IN 'P3 -,i« a P3 -> a) 3 « >.■£ to • as a * t^t^ , (M lO . w o O £ to pq S ""^ i-H CO ■* • i J^ C^ fc- c« Q o ti< VD E-i ck &-:/;• en Sti. 364 THE DIGESTIVE APPARATUS IN MAMMALIA. 1. Lips. — The lips have a thick, free, everted border. They are lined by a rosy mucous membrane, which is insensibly continued inwards by the buccal membrane. The upper lip is limited by the uo.se and the naso-labial furrow ; the lower is limited by the men to-labial groove. The first has in its middle the subnasal fuirow. Their structure is analogous to those of animals. 2. Cheelcs. — The cheeks are limited by the inferior border of the maxilla, the root of the ear, the prominence of the chin, and the naso-labial furrow. Between the skin and the mucous membrane, there is fouud, as in brutes, a glandular layer and muscles, chiefly the buccinator. An adipose ball is always fouud near the anterior border of the masseter. 3. Palate.— It does not possess a vascular membrane, as in the Horse, and its mucous membrane shows a longitudinal and transverse furrows in its anterior two-thirds. It is pale and resisting. 4. Tongue. — This is thick, short, and broad; its base is almost vertical, and in the middle is a perpendicular, fibrous, and semilunar lamina, the Ungual septum which gives insertion to muscular fibres. Anthropotomists distinguish intrinsic and extrinsic muscles. The first are : the lingualis superior and inferior, transversus, and longitudinalis. The second are, as in Solipeds, the stylo-glossus, genio-glossus, hyo-glossus, and phuryngo-glossus. There is also described a palato-glossus, which partly belongs to the solt palate. The mucous membrane shows the different characters recognised in that of animals. That of the dorsal face is divided into two portions by two A-shaped rows of papillas, -whose summit abuts on the deep mucous foUicle named the foramen cxcum. The posterior portion presents depressions which correspond to the closed follicles, and the fungiform and calyciform papillae ; the anterior portion has a villous aspect, due to the great inmaber of filiform papillae covering it. 5. Soft Palate. — In Mao, the soft palate is short and divided into two portions : an anterior, horizontal, attached to the base of the tongue by the anterior pillars of the curtain; a posterior, movable and oblique, having a free porti.m. the uvula, and fixed to the lateral walls of the pharynx by the posterior pillars. The amygdala', or mass of closed follicles, are lodged in the triangular space between the anterior and posterior pillars. The fibrous structure is not present, unless the small expansion of the external tensor of the palate represents it. The muscles are the same as in animals, and, in addition, there are described two palato-glossal muscles, included between the mucous folds that form the anterior pillars. The palato-pharyngeus extends to the posterior nasal spine. The isthmtis of the fauces is wider than in the Carnivora. 6. Teeth. — -The teeth are thirty-two in number, sixteen in each jaw. They are distributed in the following manner : four incisors, two canines, two small molars (hicuspidati), and three large molars (inuUi-cusp>iaati). Tlie incisors, when viewed in profile or longitudinal section, have a ■wedge-shape, and their free border is more or less sharp. The canines are irregularly conical ; the molars have a multiple fang, and the crown is studded with a variable number of tubercles: two on each small molar and four on the large. In youth, there are only twenty teeth, ten in each jaw. THE SALIVARY GLANDS. The salivary glands are secretory organs annexed to the buccal cavity, into which they pour saliva : a recrementitious fluid that softens the food, favours its mastication and deglutition, and has a chemical action upon it after its arrival in the abdominal portion of the digestive canal. Though very diversified in form, yet they j^resent in their structure such common characters, that, to obviate a recurrence to their organisation when speaking of each gland, we will describe it here. The salivary glands are constituted by a red or yellow spongy tissue, which is divided into small, rounded, or polyhedral masses, called salivary lobides. These extend in a layer beneath the adlierent fece of the mucous membrane, and remain isolated from each other, or are agglomerated in a body to form a single gland. In the latter case they are united by condensed connective tissue, which is disposed over the surface of the organ as a very thin enveloping membrane, and into the lobular interstices in lamellar prolongations. THE SALIVARY GLANDS. 365 In studying the organisation of one of these lobules, it will be observed that it is made up of many very small secondary lobules or acini, wliich are themselves due to the agglomeration of minute elementary vesicles or follicles, whose average diameter is from 1 -500th to 1-1 200th of an inch ; these open into the little canal belonging to each of the secondary lobules, and which again joins those of the other acini of the primary lobule, to form a single duct. The minute elementary vesicles or follicles, the glandular culs-de-sac (or ultimate follicles) consist of a thin amorphous membrane (memhrana propria), lined by a layer of j)olygonal epithelium cells. (They are closely sur- rounded by a plexus of capillary blood-vessels). When the salivary lobules remain isolated, this canal, which is designated as excretory, because it carries from the lobnle the saliva secreted within the elementary follicles, opens directly into the mouth. But when, on the contrary, they all unite and form a single gland, their excretory canals finally converge into one or more principal ducts, whose termination in every case takes place in the same manner — by oi:)euing into the mouth from the summit of a more or less salient tubercle, an arrangement which FiV. 169. Fiff. 170. LOBtTLE or PAROTID GLAND, INJECTED WITH CAPILLARY NETWORK AROUND THE FOLLI- MERCURY, AND MAGNIFIED 50 DIAMETERS. CLES OF THE PAROTID GLAND. renders the introduction of particles of food into these excretory orifices somewhat difiicult. The fibrous and elastic walls of these ducts are lined internally by columnar epithelium. If to the fundamental tissue just described, be added arteries, veins, and lymphatics, which convey the materials of secretion and nutrition, as well as the nerves which regulate the secretory and nutritive acts, all the elements entering into the organisation of the salivary glands are made known. The most voluminous of these glands — or those which comprise a very great number of agglomerated lobules, will be first noticed. They are the parotid, maxillary, sublingual, and molar glands, which are all pairs, and are placed in proximity to the mouth when they do not lie immediately beneath the adherent face of its mucous membrane. Secondly, the less im- portant glands — those which are spread in layers under that membrane, and including the labial, lingual, and palatine glands, will be examined. 1. Parotid Gland. (Figs. 110 ; 172, 8). Preparation. — This gland, with its excretory canal, is seen after the removal of the cervico-facial subcutaneous a,n(l parotido-auricularis nauscles. The parotid gland is situated in the space included between the posterior 366 THE DIGESTIVE APPARATCS IN MAMMALIA. border of the inferior maxilla and the transverse process of the atlas. It is elongated from above to below, flattened on both sides, and divided into two faces, two borders, and two extremities. The exfernnl face, nearly plane, is hollowed in its inferior part into a longitudinal channel, which is sometimes transformed into a complete canal, and lodges the jugular vein after it has traversed the gland from below to its superficies This external face responds to the jiarotido-auricularis muscle, the subcutaneous muscle, the atloideau loop, a cervical ramification of the facial nerve, and the posterior auricular vein. The internal face is very uneven and moulded on the subjacent parts. It covers the guttural pouch, the mastoid insertion of the small oblique muscle of the head, levator humeri, stylo-hyoideus, the tuberosity on the posterior border of the OS hyoides, the digastricus, the tendon of the sterno-maxillaris, and the submaxillary gland, which is sej)arated from it by the thin cellulo- aponeurotic layer uniting the latter muscle to the levator humeri ; also to Fig. 171 MODES OF TERMINATION OF THE NERVES IN THE SALIVARY GLANDS. 1, 2, Branching of tlie nerves between the salivary cells; 3, Termination of the nerve in the nucleus; 4, Union of a ganglion cell with a salivary cell; 5, Varicose nerve-fibres entering the cylindrical cells of the excretory ducts. the external carotid artery and its two terminal branches, the posterior auricularis, the muscles of the jaw, and, lastly, the facial nerve, which often passes through the substance of the gland. The anterior border of the gland is intimately imited to the posterior border of the maxilla; it is related to the tempoi-o- maxillary articulation, the subzygomatic vessels and nerves, and the maxillo-muscular vessels. The posterior border is thicker than the preceding, and is separated from the transverse process of the atlas by the terminal aponeurosis of the levator humeri, to which it is only feebly adherent : it can also be easily separated from it, in order to raise the parotid and pass through the stylo-hyoideus muscle, in the operation of hyo-vertebrotomy. The superior extremity is bifurcated, and embraces the base of the concha of the ear. The inferior extremity is comprised in the angle formed by the imion of the jugular and glosso-facial veins. THE SALIVARY GLANDS. 367 Vessels and nerves of the parotid gland. — This gland receives its blood by a multitude of arterial branches from the large vessels it covers. Its nerves are very numerous, and are derived from the facial and inferior maxillary nerves, and the carotid plexus. Excretory canal. — The parotid gland is provided with a single excretory canal, the duct of Stenon, so named from the anatomist who gave the first good description of it. It is detached from the anterior border of the gland, near its inferior extremity, where the eye may readily follow it be- tween the lobules to the three or four principal branches from which it originates (Fig. 172). At first in contact with the terminal tendon of the sterno-maxillaris, it after- wards turns round the pos- terior border of the digastric muscle (stylo-maxillaris por- tion), advances into the sub- maxillary space, creeps over the internal masseter muscle (pterygoid), beneath the glosso-facial vein, and arrives at the maxillary fissure, into which it enters with the aforesaid vein and corre- sponding artery, but behind both. It then ascends ex- ternally along the anterior border of the masseter muscle to the level of the inferior molars, when it passes beneath its two satel- lite vessels, obliquely crosses their direction, and pierces the cheek towards the third ujjper molar tooth, opening into the mouth by a large tubercle. The parotid duct is com- posed of two membranes : the internal, mucous, with columnar epithelium ; and the external, made up of con- nective tissue, and circular and longitudinal elastic fibres INFERIOR ASPECT OF HEAD AND NECK. 1, Inferior border of lower jaw ; 2, Genio-hyoideus ; 3, Mylo-hyoideus ; 4, Submaxillary artery ; 5, Ditto vein ; 6, Parotid duct ; 7, Sterno-maxillaris tendon ; 8, Parotid gland ; 9, Sterno-maxillaris muscle ; 10, 11, 12, Submaxillary glands; 13, Sterno-thyro- hyoideus and subscapulo-hyoideus muscles ; 14, Thy- roid gland ; 15, Pterygoideus interuus. 2. Maxillary or Submaxillary Gland. (Figs. 172, 173.) Preparatiim. — To expose this <:land, as well as the sublingual, divide the maxilla, as in preparing the muscles of the tongue lor dissection (see p. 334). This gland, smaller than the preceding, is situated in the intermaxillary space, on the lateral plane of the larynx, and within the j^arotid gland. 368 THE DIGESTIVE APPARATUS IN MAMMALIA. It is long and narrow, flattened on both sides, and describes a sligbt curve with the concavity turned upwards : a form which allows it to be studied, with regard to relations, on two faces, two borders, and two extremities. By its external face, it responds to the internal pterygoid muscle, the digastricus, the sterno-maxillaris tendon, and the cellulo-aponeurotic layer separating it from the parotid. Its internal face, applied to the side of the larynx, responds, sujieriorly, to the guttiu-al pouch, to the carotid artery, and to the nerves which accompany that vessel in the upper part of the neck. The superior border, thin and concave, is margined by the middle part of the digastricus. The inferior, thick and concave, is in contact with the glosso-facial vein. The posterior extremity is maintained beneath the transverse process of Fis. 173. MAXILLARY AND SUBLINGUAL GLANDS. R, Maxillary gland ; s, Wharton's duct ; T, Sublingual gland. the atlas, by an extremely loose and abundant cellular tissue ; the anterior is insinuated between the internal pterygoid and the thyro-hyoideus muscle. Vessels and nerves. — The blood is distributed to the maxillary gland by various small innominate arteries, like those of the parotid gland, and which are most frequently derived from the external carotid and the glosso-facial. The nerves are principally furnished by the carotid plexus. THE SALIVARY GLANDS. 369 Excretory Canal. — Wliartons duct, as it is termed, is long and narrow; has very attenuated walls, and exists for nearly tlie whole length of the sajjerior border of the gland : sometimes on its internal face, where it receives the raniilications from various lobules. At the anterior extremity of the organ it becomes free, and passes forward between the mylo-hyoidous and basio- (hyo-) glossus muscles. After crossing, outwardly, the glosso-facial artery and great hypoglossal nerve, and, inwardly, the tendon of the digas- tricus and the lingual nerve, it passes between the hyo-glossus lonffus and the sublingual gland, lying closely to the inner side of the latter ; thus it extends parallel to the lateral groove (or channel) of the lingual canal (on the floor of the mouth). Jt finally arrives near the fraenum of the tongue, but underneath the buccal membrane, and opens into the mouth by a small, but very salient, floating tubercle, situated a little in advance of the.frsnumj and vulgarly named the barb (barbillon). The structure of Wharton's duct is identical with that of Stenon, but its external tunic is extremely thin, and has not any circular elastic fibres. 3. Sublingual Gland. (Fig. 173.) This is less in volume than the preceding, and is situated under the tongue, in the intermaxillaiy space. Elongated from before to behind, and very flat laterally, it has, like the submaxillary gland, two faces, two borders, and two extremities, whose relations we will briefly indicate. The external face is covered by the mylo-hyoideus muscle; the internal responds to Wharton's duct and the genio-glossus and hyo-glossus langus muscles. The nj>2^er border projects beneath the mucous membrane on the floor of the mouth, where it forms the sublingual ridge ; the inferior, thin and sharp, is comprised between the mylo-hyoideus and the genio-glossus muscles. The two extremities are thin and tapering; the posterior contains a branch of the lingual nerve ; the anterior extends to the bottom of the angle formed by the union of the two branches of the inferior maxilla. Vessels and nerves. — This gland possesses a special, but small artery— the sublingucd Its nerves come from the lingual nerve, and even from the carotid plexus. Excretory canals. — These number fifteen or twenty, and are named the ductus Riciniani. Flexuous and very slender, they are detached from the superior border or internal face of the gland, ascend perpendicularly, and open into the mouth on the sublingual crest or ridge by a linear series of small orifices pierced, as usual, in the centre of a tubercle. 4. Molar Glands. These are so named because they are disposed parallel to the molar arches. There are two on each side. The superior molar gland, the most considerable, represents a narrow line of salivary lobules placed outside, and along the upper border of, the alveolo-labialis muscle. In its posterior part, where it is concealed beneath the masseter muscle, this gland is thicker and more compact than in front, where the few lobules which compose it scarcely come in contact with each other. The inferior molar gland, less lobulated and voluminous, and not so wide as the preceding, is placed at the inferior border of the buccinator, immediately beneath the mucous membrane of the mouth, and near the 370 THE DIGESTIVE APPARATUS IN MAMMALIA. point where it is reflected from the side of the cheek on to the inferior maxillary bone. It is bordered, for the whole of its extent, by the buccal nerve. Both glands poiu* their secretion into the mouth by numerous salient orifices, which can be seen arranged in line on the buccal membrane, parallel to each molar arcade. It may he remarked that these glands establish a transition between the preceding and those yet to be mentioned. Their lobules are far from representing so compact an agglomeration as that formed by the parotid or sublingual lobules ; and they tend to separate from each other to become more independent. Therefore it is that many writers regard them as distinct, and describe them as superior and inferior molar glands. 5. Labial, Lingual, and Palatine Glands. The lobules composing these glands are spread in layers more or less thick on the inner face of the mucous membrane, instead of being agglomerated in masses, as in the previous glands. Sometimes they are scattered, in consequence of their small number. In general, the excretory duct of each glandule opens independently into the mouth, without com= municating with those of the neighbouring lobules. Labial Glandidce. — These are more abundant in the upper than in the lower lip, and pass beyond the commissures to be spread for a short distance over the inner aspect of the cheeks. It is easy, in the living Horse, after turning up the lip and carefully wiping it, to see the salivary fluid secreted by these small organs escape by their excretory ducts. Lingual Glandules. — They form a layer under the mucous membrane at the base of the tongue, and adhere very closely to the fibres of the small hyo-glossus muscle, and, laterally, are continuous with the layer which covers the external face of the amygdaloid mucous membrane. They are also found on the side of the tongue, above the superior border of the hyo- glossus longus muscle ; though these are few and scattered, and look as if incrusted in the substance of the hyo-glossus muscle. Staphyline (or Palatine) glandidce. — The thick layer these form under the anterior mucous covering of the soft palate has been described with that organ. We have only to observe here, that it is continuous, laterally, with the glands at the base of the tongue, through the medium of the glandulaB of the amygdaloid cavity ; and in such a manner, that the part of the mouth immediately in front of the isthmus of the fauces, and which might bo justly considered as the isthmus itself, is enveloped in a complete glandular zone. In the dead body, we always find in this compartment a greater or less quantity of viscid fluid, which is certainly secreted by this zone. It is here, then, that the alimentary bolus is enveloped in the glutinous matters intended to favour its passage in the pharynx and oesophagus ; and it is worthy of notice that the constricted passage where this secretion is poured out in the living animal, immediately precedes the canal traversed by the bolus of food in the act of deglutition. DIPFEEENTIAL CHARACTERS IN THE SALIVARY GLANDS OF OTHER TUAX SOLIPED ANIMALS. The snlivary system of the Hcrbivcra is more extensive than that of tlie Omnivora, and especially the Carnivora. Ruminants. — 1. Parotid gland. — The paiotid glands of the Ox are distinguished by THE SALIVARY GLANDS. 371 their meagre development and red colour, which contrasts markedly with the pale yellow hue of the maxillary glands. In the Sheep and Goat, Steuou's duct passes through the masseter muscle. (In the Ox, this gland otfers, at the upper part of its anterior border, a round lobe lying on the masseter. Steuon's duct opens into the mouth at the fifih molar. It terminates in the Sheej) and Goat at the fourth molar.) 2. Maxillary gland. — In the Ox this gland is much thicker than in Solipeds, its Tolume being m inverse relation to that of the parotid. In its posterior moiety it enlarges into an oval lobe which, below the larynx, lies against that of the opposite tide. Whurlon s duct follows the same course as in the Horse ; the papilla through which it opens is hard, resisting, and notched, and is lodged in an elliptical fossette near the incisors. 3. Sublingual gland. — In the Ox, Sheep, and Goat, this gland comprises two portions : a posterior, somewhat voluminous and lobulated, provided with a special excretory duct which follows and opens near Wharton's duct (by the ductus Bartho- linianus) ; and an anterior, pouring out its secretion by many canals, and representing the gland proper. This arrangement allows the saliva to be" collected separately from this gland. 4. Molar glands. — These are more developed in Ruminants than in Solipeds, The upper one is enlarged at its posterior extremity. Pig. — The parvtid gland of tiiis animal is little developed, as in Ruminants, and Stenon's duct follows the posterior border of the lower jaw. (Leyh says that it is, pro- portionately, largely developed : that its upper end does not reach the conch of the ear, and that Steuou's tiuct opens at the sixth molar.) The sublingual gland is analogous in its disposition to that of the Ox. Cuvier, in his 'Let/ons d'Anatomie Compare'e,' indicates this: — -"ThePtj/ has two sublingual glands. One, very long and narrow, accompanies, outwardly, the excretory canal of the sub- maxillary gland, from the angle of the jaw to the second sublingual. It is composed of small lobules of a pale red colour. Its excretory duct arises near the posterior third, and passes along with, but to the outside of, the submaxillary duct. It terminates m ar tie orifice of the latter by a small opening ; its diameter is equally small. Tin- second Gub- lingual gland is placed before the first: its form is square and flattened, and the lobes of which it is composed are larger and redder. It has from eight to ten excretory ducts." (In this animal the duct of Wharton does not open into the mouth by a papilla ; consequently there is no barb.) Carnivora. — The parotid of the Dog and Cat is small, and Stenon's duct always passes through the masseter. (It opens at the fourth molar in the Dog, and tiie third in the Cat.) In the Dog the submaxillary glands are larger than the parotids. " They even havo in front, along Wharton's duct, a small accessory gland, with a distinct excretory canal opening into the same-papilla as Wiiarton's." (Leyh states that the submaxillary duct does not project into the mouth). The supplementary ghmd is absent in tlie Cat. The sahiingual gland is not present in the Dog ; it is very small in the Cat, and carried further back than in the other animals. (Leyh describes a tublmgiial gland as present in the Carnivora, and which is divided into two portions, as in the Pig: the anterior being formed of detached lobules that open into the mouth liy several ducts ; and the posterior, larger above than below, with two ducts, the smaller opening into Wharton's duct, and the larger a little in front of it.) The upper molar gland of the Dog, scarcely noticeable for the greater part of its extent, forms posteriorly, under the zygomatic arch, near the eye, an independent lobe, remarkable for its large size and its single excretory rluct. Duvernoy who first described it, proposed to name itthe subzygomatic ghmd. It is not present in the Cat. (This is doubtless the organ described by Leyh as the orbital gland, which, he says, is only foun;l in the Dog; the superior molar gland, according to him, not existing in that- animal. This orbital gland is external to the ocular muscles, has three or four excretory canals (the ductus Nuckiani) which converge into one duct that opens into the mouth above tl;e last molar.) The labial, lingual, and palatine glandulx are much less developed in the Carnivora than the Herbivora. This predominance of the salivary system in the latter i-* suffi- ciently accounted ft)r, when we consider the hard, fibrous, and coriaceous food these animals live upon, and which must be ingested in large quantity, bec.iu.-e of the small amount of nutrition it contains. For its mastication and deglutition a great amount of saliva is absolutely necessary. 372 THE DIGESTIVE APPARATUS IN MAMMALIA. COBIPAKISON OF THE SALIVABY GLANDS OF MAN WITH THOSE OF ANIMALS. As in animals, the parotid is the most voluminous of the salivary glands. Its tissue is reddish-grey and lobulated, the lobules adliering closely to each other. Its shiipe is irregular, and" it is moulded to the excavation behind the angle of the Jaw. Steuon's duct passes across the masseter, and shows on its course some salivary lobules, forming what is named the accessory parotid (or socia ;parotidis) ; it opens opposite the third uijper molar. The submaxillary gland weighs about half-an-ounce. It is partly situated beneath the deep cervical fascia, and partly within tlie boily of the lower jaw, between the mylo- hyoideus and hyo-glossus muscles. Its lobules are more loosely united than those of the parotid. Wharton's duct opens on the sides of the frsenum linguae by a small opening at the apex of a round papilla (carM?icu?a sublingualis). The sublingual gland is analogous to that of the Ox and Pig. There are, in fact, two sublinguals ; an anterior about the size of an almond, and furnished witli a single excretory canal — the ductus Bartholini, that terminates near Wharton's duct; the other, posterior, formed by several isolated lobules with multiple excretory ducts, the ductus Riviniani. There are also labial, palatine, and lingual glands: with, besides, near the frseuum, a small conglomerate gland, the gland of Nuhn, which has a special duct. Fig. 174. PHARYNGEAL AND LARYNGEAL RE- GION; THE POSTERIOR PART OF THE HEAD INCISED AND THROWN FORWARD. 1, Base of the cranium ; 2, Roof of the pharynx ; 3, Muscles of the cheek ; 4, 4, Walls of the pharynx ; 6, Septum nasi ; 7, Posterior openings of nostrils ; 8, Entrance to the mouth ; 9, Epiglottis ; 10, Posterior pillars of soft palate ; 11, Arytenoid cartilages ; 12, Opening of the oesophagus ; 13, (Esophagus ; 14, Trachea. THE PHARYNX. (FigS. 174, 175.) Preparation. — 1. Study the general disposition and situation of this vestibule in the antero- posterior vertical section of the head (fig. 175). 2. In order to examine the interior conveniently, the head sliourd be separated from the neck, leaving attached to it a certain portion of the trachea and cesophagus ; then by sawing across, either through or behind the temporo-maxillary articulations, all that portion of tlie cranium is re- moved, and the posterior parietes of the pharynx is exposed, and may be dissected to study the muscles (Fig. 178), or opened in the middle line to reach the interior of the cavity (Fig. 174). 3. The muscles should be dissected with those of the tongue, and in the same manner. Tlie pharynx is a membranous vestibule common to the digestive and air passages, and situated behind the soft palate, which separates it from the moiith ; above, it is at- tached to the base of the cranium, and, below, to the laryngeal apparatus. Form and internal disposition. — In con- sequence of the conformation of the soft palate, which, in the domesticated animals, and particularly in Solipeds, is prolonged to the base of the epiglottis, the pharynx forms a cylindrical cavity elongated from before to behind, enclosed laterally and posteriorly by vnde thin muscles, and with the soft palate for an anterior wall. At the two extremities of this cavity are openings which allow the pharynx to communicate with the other passages or cavities, and whose dis- position we will at once begin to study. At the upper extremity of the large axis of the pharyngeal cavity is to be re- marked : 1, In front, the two posterior THE PHARYNX. 373 openings of the nasal cavities ; 2, Behind, and directly opposite the pre- ceding, the two pharyngeal ojienings of the Eustachian tubes, which are closed by a cartilaginous kind of clap-valve.^ At the inferior extremity of this axis is found : 1, In the centre, a vast gaping orifice projecting into the anterior of the pharyngeal cavity, like a tap into a cask : this is the entrance to tJie larynx, the salient portions of which form, on the walls of the pharynx, two lateral gutters limited superiorly by the posterior pillars of the soft palate ; 2, In front of, and beneath this, is the isthmus of the fauces ; Behind and above, the oesophageal opening at the bottom of an infundibulum, which may be considered as a special region of the pharynx. These seven openings of the pharyngeal cavity give it the appearance of a cross road, into which abut different thoroughfares. It is necessary to note that the air and digestive passages intersect each other here, and in such a way that, during deglutition, the bolus of food passes over the entrance of the larynx to reach the oesophageal opening. This peculiarity is easily seen by referring to figure 175. Fis;. 175. MEDIAN LONGITUDINAL SECTION OF HEAD AND UPPER PART OF NECK. 1, Upper lip; 2, Premasilla ; 3, Hard palate; 4, Tongue; 5, Septum nasi; 6, Nasal bone; 7, Palate bone; 8, Soft palate; 9, Pterygoid bone; iO, Epiglottis; 11, Entrance to Eustachian tube ; 12, Arytenoid cartilage ; 13, Cricoid cartilage ; 14, (Esophagus; 15, Frontal bone and sinus; 16, Cerebrum; 17, Corpus cal- losum ; 18, Cerebellum ; 19, Sphenoid bone ; 20, Medulla oblongata ; 21, Cervical ligament ; 22, Spinal cord ; 23, Occipital bone ; 24, 24, Atlas ; 25, 25, Dentata ; 26, Trachea. Belations. — Viewed externally, for the study of its connections, it will be found that the pharynx responds, posteriorly, to the guttural pouches and guttural lymphatics ; laterally, to the large branch of the os hyoides, the 1 This reo^ion corresponds to the posterior nares (arriere fond) of Man, a diverticulum ■which cannot be distinguished from the pharynx in the domesticated animals. Under the designation of the posterior nares of the 'nasal fossae, it will be understood that we mean the posterior extremities of these cavities. (In the 'Annates de Me'decine Viterinaire.' of Brussels, for 1871 (p. 244), M. Lorge describes a pharyngeal caecum as existing in Solipeds, which he states corresponds to the naso-pharyngeal region, or posterior nares, of Man.) 27 374 THE DIGESTIVE ATTARATL'S IN' MAMMALIA. internal pterygoid and stylo-hyoid muscles, the glosso-pharyngeal, great hypoglossal, and superior laryngeal nerves, and the glosso-facial artery. Steucture. — The walls of the pharynx are composed of a mucous mem- h'ane, external to which is a muscular layer. 1. Mucous membrane. — This membrane is covered, externally, by a thin layer of yellow elastic fibres, and is much more delicate and less protected by its epidermis than the buccal mucous membrane, of which it is a con- tinuation ; it also communicates with that of the oesophagus, the larynx, the nasal fossae, and the Eustachian tubes. Its epithelium is stratified throughout ; but it is thin and ciliated in the upper part, thicker and tesselated on the inferior moiety, which more particularly belongs to the digestive apparatus. Everywhere there are racemose glands, though they are most numerous towards the roof of the pharynx. There are also some follicidar glands beneath the mucous membrane, in the neighbourhood of the guttural opening, the nasal cavities, and the Eustachian tubes. 2. Muscular layer. — This is composed of seven pairs of muscles, indicated in the following enumeration : the palato-pharynr/eus, pterygo-pharyngeus, hjo-pharyngeus, thyro-pharyngeus, crico-pharyngeus, aryteno-pharyngeus, stylo- pharyngeus. Palato-pharyngeus (Pharyngo-staphylinus). — This muscle, which has already been described as belonging to the soft palate, is prolonged back- wards on the lateral wall of the pharynx, where its fibres are mixed with those of the pterygo-pharyngeus, and go to be attached to the superior border of the thyroid cartilage by passing beneath the hyo-pharyngeal and thyro-pharyngeal muscles. It therefore also belongs to the pharynx. Pterygo-pharyngeus, OR Superior Constrictor (the pcdato-pharyngeusoi Percivall). — This muscle is thin, wide, flat, and triangular. It originates from the pterygoid process, whence its fibres diverge, some posteriorly, others inwardly. The former mix with those of the palato-pharyngeus, and comport themselves like that muscle ; and the latter are united, on the median line, with the analogous fibres of the opposite muscle, form- ing a kind of zone around the origin of the Eustachian tube. This muscle is covered, externally, by a layer of yellow elastic tissue, which is attached with it to th.e pterygoid bone ; afterwards it is fixed to the superior border of the great branch of the os hyoides, and is even prolonged on the external surface of the muscle it covers to the thyroid cartilage. The elasticity of this fibrous covering plays a certain part in the move- ments of the hyo-laryngeal apparatus, in acting as a passive antagonist of its depressors. This muscle is, and can only be, a perfect constrictor of the pharynx, as it diminishes the diameter of that cavity in every direction : the longi- tudinal diameter, by means of its posterior fibres, which draw the thyroid cartilage forward ; and its transverse diameter, by the circle thrown around the orifice of the Eustachian tubes (Figs. 149 : 176, 8). Hyo-pharyngeus, or First Middle Constrictor ; Thyro-pharyngeus, OK Second Middle Constrictor ; and Crico-pharyngeus, or Inferior Constrictor. — The two first of these muscles only form one in Man, the middle constrictor of the pharynx. They are three muscular bands which terminate above the pharynx, on a median fibrous fold sometimes wide enough to look like an aponeurosis. The first band arises from the cornu of the OS hyoides ; the second, from the external surface of the thyroid carti- lage ; the third, from the superficial face of the cricoid cartilage. THE FHAR I'.VA'. 375 These are universally regardecl as constrictors. Sometimes two fasciculi are observed in the crico-pharyngeus. The supplementary fasciculus is somewhat thin, and arises from the posterior border of the bezil of the cricoid cartilage, ascending parallel to the oeso- phagus to terminate with the principal fasciculus. Aeyteno-pharyngeus. — By this name has been described a small fasci- culus, extremely thin in Solipeds, which extends from the posterior border of the arytenoid cartilage to the origin of the oesophagus. To expose this muscle, which we do not look upon as constant, it is necessary to turn the oesophagus forward on the superior surface of the pharynx. Stylo-pharyngeus. — A narrow band which descends from the great hyoideal branch to the side of the pharynx, where it is confounded with the pterygo-pharyngeus. It elevates the pharynx in contracting, and it is also regarded as a dilator ; though the disposition of the parietes of the pharynx, and the feeble volume of this muscle, scarcely allows it to play any efficacious part in the dilatation of that cavity. It may only produce a very slight infundibulum where it is inserted. The real dilating agent of the pharyngeal cavity is the alimentary bolus, which is pushed into it by the action of the tongue (Fig. 149, 5). Fig. 176. MUSCLES OP THE PHARYNGEAL AND HYOIDEAL REGIONS. 1, Glenoid cavity of temporal bone ; 2, Superior extremity of styloid bone ; 3, Tensor palati with its pulley, 5 5 4, Stylo-pharyngeus ; 6, Palato-pharyngeus ; 7, Circumflexus palati ; 8, Pterygo-pharyngeus ; 9, Sublingual gland ; 10, Portion of hyoid bone ;r 11, Hyo-pharyngeus ; 12, Thyro-pharyngeus ; 13, Crico-pharyn- geus; 14, Portion of stylo-pharyngeus ; 15, Hyo-thyroideus ;"16, Styloid bone; 17, Crico-arytenoideus lateralis ; 18, (Esophagus ; 19, Sterno-maxillaris and hyoideus, and subscapulo hyoideus ; 20, Trachea ; 21, Hard palate ; 22, Tongue. It is not rare to meet a second stylo-pharyngeus muscle terminating on the same point as the first, but proceeding from the inferior extremity of the large branch of the os hyoides, instead of its upper part. Certain anatomists designate it the inferior kerato-pharyngeus, and con- sider it as a constrictor of the pharynx. It sometimes exists only on one side. 3. Vessels and nerves. — The blood sent to the pharynx comes from the 376 THE DIGESTIVE APPARATUS IN MAMSIALIA. pharyngeal and thyroideal arteries. Tlie nerves are supplied by the glosso- ■jjJiaryngeus, pneumogastric, and great sympathetic. Functions. — The pharynx plays a passive part in respiration, by serving as an intermediate canal between the nasal passages and the larynx. Its principal function, however, is connected with the digestive pheno- mena, by its being an active agent in the first stage of deglutition — a complex and rapid movement, which is executed in the following manner : The bolus of food, propelled by the tongue into the pharyux, is seized by the constrictor muscles, which come into action successively from before to behind, in a peristaltic and involuntary manner, to carry the mass to the entrance of the oesophagus. The food thus passes over the opening of the larynx during pliaryngeal deglutition, but it cannot enter it, because the bolus forces back the epiglottis on this aperture, which it almost exactly closes ; because, also, the passage of the food prevents pulmonary inspiration, which might, if allowed to take place, divert it from its natural course, and throw it into the nasal air-passages ; the application of the walls of the pharynx to the pellet of food during its momentary passage over the larynx, intercepts all communication between the external air and the lungs, and only permits the elevation of the ribs with the utmost difficulty. The extreme rapidity of the act of deglutition is another reason for the food escaping the larynx. (Gray concisely remarks : When deglutition is about to be performed, the pharynx is drawn upwards and dilated in different directions to receive the morsel propelled into it from the mouth. The stylo-pharyngei, which are much further removed from one another at their origin than at their insertion, draw upwards and outwards the sides of this cavity, the breadth of the pharynx, in the antero-posterior direction, being increased by the larynx and tongue being carried forwards in their ascent. As soon as the morsel is received in the pharynx, the elevator muscles relax, the bag descends, and the constrictors contract iipon the morsel and convey H gradually downwards into the oesophagus.) The deglutition of liquids is carried on in a similar manner. It is curious to remark that, in Solipeds, the food does not come into direct contact with the greater portion of the superior wall of the pharynx during its passage through that cavity. When the alimentary mass is carried back by the tongue, it raises the soft palate and bears its posterior border backwards to the entrance of the oesophagus. The extreme develop- ment of this palatine curtain, therefore, quite prevents this surface of the pliarynx from being directly applied to the food, and it is through the medium of this partition that the constrictors exercise their peristaltic action on the morsel of aliment until it reaches the oesophageal infundibulum. DIFFERENTIAL CHARACTERS OF THE PHARYNX IN OTHER THAN SOLIPED ANIMALS. The pharynx of Ruminants is lono^ and very spacious. The hyo-, thyro-, and crico- pharyngeal muscles— the first and second of the two middle constrictors, and the inferior constrictor — are less distinct from each other than in the Horse ; the last-named muscle is very small, and the fibrous raphe on which the constrictors unite is little developed. In the pharynx of the Sheep is noticed a mucous duplicaturo that descends to the middle of the posterior wall, and appears to be a continuation, posteriorly and inferiorly, of the nasal septum. In the Pi(f, the posterior part of the pharynx is narrow, and has a pouch immediately above tho glottis, between the thyro- and crico-pharyngeal muscles. In the Dog, the infundibulum is very spacious, and the pharyngeal mucous membrane, nmch finer than that of the oesophagus, is distinguished from it by a well-marked line of demarcation. The crico-pharyngeal is nut very distinct from the thyro-pharyiigeal muscle ; so that, in reality, only three constrictors can be dittinguished. THE (ESOFHAGVS. 377 compauLjOK of the pharynx of man with that of animals. In consequence of the smallness of the soft palate, the pharynx of Man is only a kind of chiinnel between the mouth and the larynx and CBS.)phagu:>. It is usually divided into three portions : a superior, the posterior nares, covered by ciliated epithelium ; a middle, or (juttund, and au iuferior, or esophageal ; tlie two latter are covered with tesselated epithelium. The muscles are almost the same as in the Dog, being a portion of the palato-pharyn- geus, the superior, middle, and inferior constrictors, and a stylo-pharyngcal muscle. Below the sides uf the pharynx, and between the pillars of the soft palate, are the amyrjdalx : almond-shaped organs, whose surface s'.ows the openings of the follicles that, witli the vessels and a little connective tissue, compose their substance. THE (ESOPHAGUS. (Figs. 178, 179.) Preparation, — Place the subject in the first or second position ; remove the subcu- taneous cervical muscle from the left side; take away the corresponding anterior limb, and proceed to tlie Fig. 177. excision of the ribs of this side, with the exception of the first. Afterwards dissect the vessels and nerves in the neighbourhood of the oesophageal canal, taking care to preserve their relations to each other. Form. — The oesophagus is a long, cyHndrical, narrow, membranous canal, easily dilated for the gi-eater part of its extent, and destined to convey the food from the pharynx to the stomach, and to complete the act of deglutition. Course. — This canal begins at the pharynx, and communicates with it by means of the pos- terior opening situated above the glottis. It afterwards descends behind the trachea to the middle of the neck, where it commences to deviate towards the left side of that tube, and enters the thoracic cavity by inclining towards the inner aspect of the first left rib. It soon after regains its situation above the trachea, passes over the base of the heart, and reaches the open- ing of the right pillar of the diaphi-agm, in passing between the two layers of the posterior mediastinum. Traversing tlais opening, it pene- trates the abdominal cavity, and immediately afterwards is inserted into the smaller curvature of the stomach by an orifice designated the cardiac, which will be studied at the same time as that viscus. Belations. — The oesophagus in its course has the following nimierous relations : At its origin, it is comprised between the guttural pouch and the posterior crico-arytenoid muscles. HniAN PHARYNX LAID OPEN FROM BEHIND. 1, Section through base of skull ; 2, 2, Walls of pha- rynx drawn aside ; 3, 3, Posterior nares, separated by the vomer ; 4, Extremity of one Eustachian tube ; 5, Soft palate; 6, Posterior pillar of soft palate ; 7, An- terior pillar ; 8, Root of the tongue, partly concealed by the uvula ; 9, Epiglottis overhanging (10) the cordi- form opening of the larynx ; 11, Posterior part of larynx ; 12, Opening of oesophagus, 13 ; 14, Trachea. In the cervical region, it is enveloped in a thick layer of cellular tissue, which unites it in a loose manner to the sm-rounding organs, its relations with these varying as we consider them superiorly or inferiorly. Superiorly, and in the median plane, it occupies the space included between the trachea and the longus-colli, being bordered on each side by the common carotid artery, with its satellite nerves — the 378 THE DIGESTIVE APPARATUS IN MAMMALIA. trunk common to the great sympatlietic and pneumogastric, and the inferior laryngeal. Inferiorly, it is related to the trachea internally; and, externally, to the inferior scalenus muscle, and the vessels and nerves of the left cervical channel, which also includes the jugular vein.^ At its entrance into the thoracic cavity, the oesophagus, still deviating to the left, and lying on the side of the trachea, responds, externally, to the inferior cervical ganglion, the afferent and emergent nervous branches of that ganglion, the vertebral arteries and veins, and the superior cervical and dorso-muscular vessels, which obliquely cross its direction. Beyond this Fig. 178. TRANSVERSE VERTICAL SECTION OF HEAD AND NECK IMMEDIATELY IN FRONT OP THE STYLOID PROCESSES, AND BEHIND THE (ESOPHAGUS. 1, (Esophagus ; 2, Inner surfacer of trachea ; 3, Common carotid artery ; 4, Recur- rent nerve ; 5, Thyroid gland ; 6, Exterior of pharynx ; 7, Crico-pharyngeal muscle; 8,9, 10, 11, Guttural pouch and objects in its interior; 12, Stylo- pharyngeus muscle; 13, Sphenoid bone; 14, Jugular ganglia; 15, Internal carotid; 16, 17, Pneumogastric nerve; 18, Parotid gland; 19, Great hypoglossal nerve ; 20, Jugular vein , 21, Subscapulo-hyoideus ; 22, Stylo-maxillaris. it regains its position between the trachea and the longus colli, passes above the left bronchus, to the right of the thoracic aorta, until it reaches between the layers of the posterior mediastinum, which bring it into relation with the internal face of the lungs ; these are channeled for its reception, and here it is accompanied by the oesophageal artery, and the oesophageal branches of the pneumogastric nerve. The very short ]portion lodged in the abdominal cavity responds, on the ' It is not rare to find the oesophagus deviate to the right below the neck ; in this case its relations will be inverted. We have never seen this canal enter the thorax in the median plane of the body. THE (ESOPHAGUS. 379 right, to a fissure in the superior border of the liver, and is enveloped by the peritoneum. Interior. — Internally, the canal whose course and relations we have just studied jwesents nothing of interest ; and it only requires to be remarked, that its walls are always shrunken and in contact when food is not passing between them. Structure. — The oesophagus has two tunics : a mucous and a muscular. The mucous membrane is continuous with that of the pharynx and the stomach ; it is white, and shows numerous longitudinal folds which allow the canal to dilate. It adheres but loosely to the muscular coat, on which it can glide with the greatest facility. It has a thick, resisting, stratified, tesselated epithelium, an unstriped muscular layer, and some racemose glands. Fig. 179. PECTORAL CAVITY AND MEDIASTINUM, SHOWING THE COURSE OF THE TRACHEA AND tESOPHAGUS. (A third or mirldle coat is sometimes mentioned by anatomists ; it is composed of the tissue connecting the latter tunic with the one to be next described.) The muscular coat commences at the posterior part of the pharynx by the aryteno-pharyngei muscles, and by two small superficial bands which are detached from the posterior portion of the crico-pharyngei muscles. This tunic is formed of superficial longitudinal fibres, often assembled in fasciculi ; and of a deeper series of spiral or circular fibres, which, towards the inferior extremity of the canal, intercross in an almost inextricable manner. This muscular layer in the cervical, and for a great part of the thoracic portion of the cesophagus, has the red colour of voluntary muscles ; but it becomes white, like the involuntary fibres, after the conduit enters the mediastinum, and acquires considerable thickness and marked rigidity. It is to be noted that this arrangement of the muscular tunic is especially 380 THE DIGESTIVE APPARATUS IN MAMMALIA. evident towards the insertion of the cesophagus into the stomach, and that the muscular tube is at this point so narrow, that it is almost exactly filled by the folds of mucous membrane it contains. For this reason it is tbat we may inflate a stomach by the pylorus, without applying a ligature to the oesophagus ; the aperture of the canal being so i^erfectly closed that it does not allow a bubble of air to escape. In describing the interior of the stomach, we will refer to the consequences resulting from this interesting anatomical fact. Vessels and nerves. — The oesophagus is supplied with blood by the divisions given off" by the common carotid artery, as well as the bronchial and oesophageal arteries. The nerves are almost exclusively derived from the pneumogastric ; the motor nerves are the superior oesophageal filaments, branches of the external pharyngeal and laryngeal ; the sensitive filaments are derived from the recurrent. Functions. — This canal conveys nutriment from the pharynx to the stomach ; it has no other uses. DIFFERENTIAL CHARACTERS OF THE (ESOPHAGTS IN OTHER THAN SOLIPED ANIJIALS. In all the other domesticated animals, the muscular coat is red-coloured throughout its whole extent, and everywhere ofters tlie same degree of thickness and the same flaccidity, The canal is also as wide towards the stomach as at the pharynx. In Ruminants and the Carnivora, it enters the stomach as a funnel-shaped (iufundi- buliform) tube. The dilatability of the cesophagus is very remaikable in these animals : Dogs swallow- large pieces of flesh; and Cows and Oxen are able to injtst large turnips, or sucii voluminous foreign bodies as shoes. (Ill Ruminants and the Carnivora the cesophagus is, proportionally, wider than in the Horse and Pig.) COMPARISON OF THE CESOPHAGUS OF MAN WITH THAT OF ANIMALS. The oesophagus oi Man resembles that of Carnivora ; its diameter is almost uniform. It also inclines to the left below the neck, but in tlie thorax is in the median line, though it again deviates to the left as it joins the stomach. As the thyroid in Man is very voluminous, it is related to tlie cesophagus in the upper part of the neck. Two small accessory fasciculi, belonging to the muscular tunic of the cesophagus, have been described : one is the broncho-oesophageal muscle, which is detached from the left bronchus ; and the other the pleuro-oesophageal muscle, detached from the left layer of the posterior mediastinum. Article II, — The Essential Organs of Digestion. These organs being all contained in the abdominal cavity, this common receptacle will first be studied ; afterwards the stomach, intestines, and their annexed organs — the liver, pancreas, and spleen — will be described, the abdominal cavity. In mammalia, the interior of the trunk is partitioned by the diaphi"agm into two gTcat cavities, that lodge the majority of the organs so vaguely termed the viscera. The anterior, the smallest, is the pectoral or thoracic cavity ; the posterior is named the abdomen, or abdominal cavity. The latter, the only one we have now to study, is a vast oval-shaped reservoir, elongated from before to behind, having for its upper wall the muscles of the sub- lumbar region, inclosed below and laterally by the muscles of the inferior abdominal region; bounded in front by the diaphragm, and prolonged behind between the bones and membranous ligaments of the pelvis. The elements composing the parietes of this cavity having been already described, we will confine oui'selves to au examination of its interior, ia THE ABDOMINAL CAVITY. 381 order to determine the various regions into wliicli it is possible to divide it : a matter of some importance, as it singularly facilitates the tojiographioal study of the contained viscera ; for to say that an organ is situated in the abdomen, is a very vague reference to its precise situation, in conse- quence of the great extent of this cavity. It is necessary, therefore, to divide the abdomen into a certain number of peripheral regions which corre- spond to the different parts of its wall, with a view to define the situation of the organs lodged therein, yet without complicating anatomical de- scription. Six princijial regions are recognised in the abdominal cavity. A. The superior, or sublumbar region, corresponds to the superior wall of the abdomen : that is, to the psoas muscles and the bodies of the lumbar vertebraB. It extends from the opening between the two pillars of the diaphragm to the entrance to the pelvis. B. The inferior region, limited, laterally, by the hypochondriacs and the flanks, commences, in front, at the xiphoid cartilage, and is prolonged to the pubis ; it comprises all that jjurtion of the abdomen which corre- sponds to the linea alba and the two recti muscles. Its great extent necessitates its subdivision into five secondary regions : The suprasternal region, named the epigastric in Man, placed above the xiphoid cartilage of the sternum ; the umbilical region, situated behind the preceding, and so named in consequence of its including that jxart of the wall which is pierced by the umbilicus ; the prepubic region — the hypogastric or pubic of Man — occupies the s^iace in front of the anterior border of the pubis ; the two inguinal regions, diverticuli of the abdominal cavity, located in the inguinal tracts, where they form the special reservoirs to be hereafter described as the vaginal sheaths (or canals). C. The lateral regions {right and left lumbar of Man) are limited : in front, by the costal attachments of the diaphragm ; behind, by the entrance to the pelvic cavity ; above, by the superior border of the small oblique muscle ; below, by the interval comprised between the inferior border of that muscle and the external border of the great rectus muscle. The designation of hypochondriac is given to the subregion which corresponds to the cartila- ginous circle of the false ribs. The flank is that section covered by the muscular portion of the small oblique muscle. D. The anterior, or diaphragmatic region, comprises the cavity formed by the posterior face of the diaphragm. Like that muscle, it is divided into two regions, a central and peripheral. E. The posterior, or pelvic region, is a special diverticulum of the abdomen described as the pelvic cavity. It is bounded, above, by the sacrum ; below, by the superior face of the pubes, the ischia, and the internal obturator muscle ; on the sides, by the constricted portions of the ossa innomiuata and the saero-ischiatic ligaments. The entrance to this diverticulum is situated above the pubes, and is of an oval form. Posteriorly, it is narrower, and is traversed by the rectum and the genito-urinary organs, which open externally. The Peritoneum. — The abdominal cavity is covered, internally, by a serous membrane, the peritoneum, which will now be briefly described. Like all the splanchnic serous membranes, the peritoneum is composed oi a parietal and a visceral layer, which together form a closed sac, so arranged that the organs contained in the abdomen are situated external to this sac. The adjoining theoretical figure (180), representing a transverse section of the abdominal ca^'ity, will show at a glance this arrangement. Let a represent the section of the small intestines floating at liberty in the interior of the 382 THE DIGESTIVE APPARATUS IN MAMMALIA. Fiff. 180. THEORETICAL ITIANSS'EH.SE SECTION OF THE ABDOMINAL CAVITY, TO SHOW THE DISPOSITION OF THE PERITONEUM. cavity, b that of the aorta, at the level of the great mesenteric artery : the peritoneal membrane, cc, covers the walls of the abdomen, and at the points DD (not inserted, but intended to be placed ivithin the cavity below, and on each side of b, the aorta) is folded around the great mesenteric artery in such a manner as to form two layers, ff, which come in contact by their adherent face, reach the intestine, and then separate to enveloj) it. We then see in this figure the parietal layer of the peritoneum, cc, the visceral layer, GG, and the two layers, ff, which establish the continuity of the parie- tal and visceral portions; the complete sac formed by these is ai^i^arent, and it could be rendered more so by the further separation and development of the layers ff ; so that there is no difficulty in under- standing how the small intestine may be at the same time in the interior of the abdominal cavity, and outside the sac formed by the serous membrane which lines that cavity. This arrangement is common to all the organs freely suspended in the abdomen. The serous folds which suspend them, in joining their peritoneal layer to that which covers the parietes of the cavity, will be studied under the names of ligaments, mesenteries, and omenta. Some organs — the kidneys, for example — have no proper visceral layer, being comjmsed between the abdominal wall and the external face of the parietal peritoneum, and are invested with none of the duplicatures just mentioned. We will briefly study the duplicatures, ligaments, mesenteries, and omenta that the peritoneum forms, starting from the mnbilicus and passing forwards and backwards (Fig. 181). On reaching the suprasternal region, the peritoneum forms a falciform duplicature, extending from the umbilicus to the middle lobe of the liver, and which is even prolonged between that lobe and the posterior face of the diaphragm ; at the free border of this fold is a thickening ^hich is regarded as the remains of the obliterated umbilical vein. In becoming doubled over the neighbouring organs, the diaphragmatic portion constitutes : 1, The ligaments of the right and left lobes of the liver ; 2, The common ligament of that gland, which surrounds the posterior vena cava : 3, The cardiac ligament that envelops the termination of the oesophagus. Behind the liver is found the hepato gastric ligament, which fixes the stomach in the posterior fissure of the liver and is, to the right and backwards, attached to the duodenum at the lower face of the right kidney ; it is then directed from right to left, and becomes continuous with the parietal peritoneum of the sublumbar region and the mesentery proper. The two laminae of the hepato-gastric ligament separate at the lesser curvature of the stomach to cover that viscus ; then join at its greater cur- vature, and pass to the interior of the abdominal cavity. This fold receives the name of the great or gastro-colic omentum ; it leaves the left tuberosity of the ventriculus, which it suspends to the sublumbar region from the whole extent of the great curvature ; to the right it goes beyond the pylorus, THE ABDOMINAL CA VITY. 383 to be continuecl on the concave curvature of the dnodcnum as far as the caecum. By its posterior border, the great omentum is spread around the termination of the large colon and the origin of the floating colon, where it is confounded with the visceral peritoneum of these organs, as well as with the parietal peritoneum. It resiilts from this arrangement that the great omentum forms behind the stomach, and in front of the adherent portion of the large colon, a space that communicates with the great peritoneal cavity by a very narrow opening, the foramen of Winsloio. This aperture is included between the vena portfe, posterior vena cava, anterior extremity of the pancreas, and the lesser ciu'vature of the stomach. To the left of the latter viscus, on the external face of the great omentimi, the spleen is suspended ; consequently, that portion extending from the spleen to the veutriculus is named the gastro-splenic omentum. The two layers composing the great omentum are very thin for the greater part of their extent, and include the blood-vessels between them. In emaciated animals these vessels are distinctly seen, owing to the trans- parency of the membranes, and they give the omentum a lace-work appear- ance ; but in fat subjects they are concealed by the adipose tissue deposited aloug their course, and which may accumulate in considerable quantity. In the sublumbar region, the parietal peritoneum forms several folds ; these are : the hepatico-renal ligament, extending from tire right lobe of the liver to the anterior border of the right kidney ; the ligament of the lohus Spigelii, the mesentery proper, the colic mesentery ; lastly, the greatly de- veloped laminae surrounding the caecum and the second flexure of the colon, which constitute the meso-ca;ciim and mesa-colon. THEORETICAL LONGITUDINAL AND MEDIAN SECTION OF THE ABDOMINAL CAVITY, TO SHOW THE REFLEXIONS OF THE PERITONEUM. 1, Liver ; 2, Stomach ; 3, Small intestine ; 4, Origin of the floating colon ; 5, Rectum; G, Vagina and uterus; 7, Bladder; 9, Posterior aorta; 10, Diaphragm; 11, Posterior vena cava; 12, Inferior abdominal wall. — Pp, Pp, Parietal perito- neum ; Pv, Pv, Visceral peritoneum. — L, Hepato-gastric ligament ; M, Mesentery. — Ge, Great omentum. The great mesentery is detached from the border of the large mesenteric artery, and projects into the abdominal cavity to reach the small intestine at its lesser curvatui'e, and enveloi) that viscus. 384 THE DIGESTIVE APPARATUS IN MAMMALIA. Its shape is that of an irregular triangle, whose summit corresponds to the mesenteric artery, the very short anterior border being continuous with the duodenal frtenum, and the posterior border, the longest, with the meso-colon, its convex festooned base being as long as the intestine itself. Between the two laminae that compose it are the blood-vessels and lymphatics, as well as the nerves, of the small intestine. The colic mesentery is constituted like the great mesentery. Its inferior border, plane or plicated, is fixed to the small curvature of the floating colon and the commencement of the rectum ; its ujoper border extends from the great mesenteric artery as far as the entrance to the jDclvic cavity. Around the cross of the cfecum, from the origin and the termina- tion of the great colon, the peritoneum is reflected to cover these viscera ; a layer passes from the anterior border of the caecum on to the ileum and the second flexure of the colon : this is the meso-ccmum ; another layer, comprised between the second and third portion of the colon, and whose shape is that of a battledore, is named the meso-colon. If, again, the peritoneum is taken at the umbilical region and followed backwards, it will be found to insinuate itself into the inguinal canals, cover the organs contained in the pelvis, and become reflected at the bottom of that cavity, to be continued either with the peritoneiim of the sublumbar region, or with that on the abdominal walls. This serous membrane covers the anterior cul de sac of the bladder, and at this point has three ligaments. The middle ligament, falciform in shape, leaves the large extremity of the bladder, is attached to the anterior border of the pubis, and insensibly disappears on the inferior abdominal wall ; on its free border is a small fibrous cord, which is supposed to be the remains of the urachus. The two lateral ligaments are more developed, and extend from the entrance to the pelvic cavity to the vesical cul-de-sac ; they have on their free border the obliterated umbilical arteries. In the male, the peri- toneum is prolonged from the upper face of the bladder to the enlargement of the deferent ducts, between which it sends a transverse fold to the anterior extremity of the vesiculae seminales, and is then reflected around the rectum. In the female, it is carried from the bladder to the terminal portion of the vagina, to the uterus, and to the cornua of that organ, where it forms three folds named the hroad ligaments, ligaments of the ovary, and the round ligament; then it re descends on the upper face of the vagina, and thence envelops the rectum, around which it is reflected from behind forwards. According to this arrangement, we see that the termination of the digestive canal, and the parts of the genito-urinary organs situated altogether at the posterior portion of the pelvic cavity, are placed outside the peri- toneal serous membrane. Structure. — Like all the serous membranes, the peritoneum is formed by a membrane of connective tissue, rich in elastic fibres, and covered on its free face by a simple tesselated layer of epithelium (the cells of which are flat and polygonal, and about yoV^ of an inch in diameter). Many hlood-vessels are found on the adherent surface, while lymphatics are abundant in the visceral layer. Its nerves come from the diaphragmatic, lumbar, and inter- costal branches, and the great sympathetic. DIFFERENTIAL CHARACTERS IN THE ABDOMINAL CAVITY OF OTHER THAN SOLIPED ANIMALS. In the Car)iivr)7'a, the ahilominal cavity is very narrow ; while in Rumiwnifs it is very vast, itd capacity being in direct relation to the volume of tlie viscera it contains. THE STOMACH. 385 The general disposition of tlie peritoneum varies but little in the different species, the only notable diversities being remarked in the great omentum. In the Ox, iiheep, and Goat, this is detached from the middle of the lower face of the rumen, and envelops the right sac of that organ, fixing the fourth compartment to its great curvature, and then passing upwards to become continuous with the mesentery. In the Dog and Fig, this fold descends in front of the intestinal mass until near the pelvis : then it asctiuls in gathering ou itself, and ultimately spreads over the colon : in the middle portion of thtJ great omentum there are, consequently, four layers placed against each other. COMPARISON OF THE ABDOMINAL CAVITY OP MAN WITH THAT OF ANIMALS. The abdominal cavity of Man is elongated vertically, and has an inferior cavity occupying the entrance to the pelvis. There is nothing particular to note in its disposi- tion, tlie difterences observed in it being allied to the external shape of the body. The peritoneum is spread over its parietes nearly in the same manner as in the Carnivora ; the great omentum is constituted by four layers, and covers the intestines like an apron ; between its two laminte is the lesser cavity of the omentum, virtually in the adult. THE STOMACH. The stomach, is a membranous sac comprised between the oesophagus and intestines, and in which are commenced the essential phenomena of digestion. 1. The Stomach in Solij^eds. (Figs. 182, 183, 184, 185, 186.) Preparation. — In order to study the relations of this organ, it suiUces to open the abdomen and remove the intestinal mass in the following manner : — Place the animal iu the first po.sition, and very slightly inrllned to the left side ; make an incision through the inferior abdominal wall, or, still better, carry it away entirely by a circular incision, taking care not to wound any part of the intestine. The entire viscera should then be withdrawn from tlio abdominal cavity, and laid on the table which suppoits the subject ; for this mass cannot be allowed to fall on the ground without risk of being pulled and torn, either in the intestine itself, or those parts which it is desired to preserve intact in the abdomen. Incise the floating colon where it joins the rectum, and the duodenum where it passes behind the great mesenteric artery ; the base of the caecum should now be detached from the sublumbar surface by the rupture of the cellular tissue which connects it to the right kidney and the pancreas; the cellular connection between the latter gland nud the terminal extremity of the fourth portion of the large colon should also be broken ; after this, it is only necessary to divide the attachment of the mesenteric bands to the sublumbar region, with the vessels contained between them. The intestinal mass is then definitively expelled from the abdominal cavity. In this way it is possible to expose, and conveniently prepare, not only the stomach, but also the spleen, liver, pancrea-, kidneys, ureters, etc. Nothing more remains than to make known the procedure to be adopted in everting the stomach, in order to study its intemal surface, or dissect its deep muscular layer. It is recommended, first, to excise the stomach with at least three inches of the oesopnagus, and eight inches of the duodenum, end cleanse the interior of the organ. Tliis may be done in several ways, but the following is the simplest : — a certain quantity of water is introduced into the stomach by fixing the duodenum to a water-tap, tl.e right hand manipulating the organ while the left closes the duodenum to prevent the escape of the liquid. The alimentary substances contained in it are in this way mixed with the water, and may be expelled from the duodenum by pressing the stomach ; this operation being repeated four or five times, thoroughly cleanses the cavity of the organ. To evert the inner surface, it is only necessary to introduce by the duodenum a loop < f wire, and make it pass through the oesophagus ; a strong waxed thread is fastened in the loop and firmly fixed around the esophagus, when, in pulling back the wire, this extremity is drawn towards the pylorus, and by carofal traction the latter is so dilated as to allow the passage of the cardiac end, and complete eversion of the stomach. Inflation will then give it its normal form and disposition ; with thii clifl'erence, that the mucous membrane is external, and the serous tunic internal. Lastly, to render the muscular layers of the stomach more evident, it is advisable to plunge the organ into boiling water for some minutes, after which it should be put into cold water. If it is desired to study the external and middle layers, the stomach should be inflated, and its serous covering removed by strips with forceps and the fingers ; if the deep layer is to be examined, the mucous membrane must be removed by means of tlie forceps and scalpel from a stomach previously everted. 386 THE DIGESTIVE APPAE ATI'S IN 3IAMMALIA. Situation. — The stomack, also designated the ventriculus, is situated in the diaphragmatic region of the abdomen, where it affects a direction transverse to the median plane of the body. Dimensions. — Its average capacity, in an ordinary-sized Horse, is from 3 to 3i gallons ; but it varies greatly according to the bulk of the animal, its breed, and the nature of its food. Eelatively, it is more considerable Cm o C3 -^ 0";=; « "-I _ o rt S o -3 .2.0 8 O C5 3 s51 ^ CO ^^ CO > o ci a ««! f- fcn " a. =-§ ^.13 »-; O' «1 -I t„ hJ P-( O .~ „■' CO (M " ■^ •- .-' S "S c '-0 J5 s- _. d in common-bred Horses, and in the Ass and Mule. When empty, its average weight is between 3 and 4 pounds. Form. — Elongated laterally, curved on itself, often constricted in its middle, and slightly depressed from before to behind, this reservoir presents, externally : 1, Two faces — an anterior and posterior, smooth and rounded ; 2, A great or convex curvature, forming the inferior border of the THE STOMACH. 387 organ, and giving attachment, throughout its extent, to the great omentum — a membranous fold which has been described as a dependency of the serous membrane ; a lesser or concave curvature, into which the oesophagus is inserted, and which is united, to the right of that canal, to the liver, by means of a frasnum known as the hepato-gastric ligament ; 4, A left ex- tremitij, dilated in the form of a large conical tuberosity, and constituting the left cul-de-sac (or fundus) of the stomach ; 5, A right extremity, narrower, curved upwards, and continued by the duodenum, from which it is separated by a marked constriction : this is named the rigid cul-de-sac of the stomach. Relations. — Studied in its connections with the neighbouring organs, the stomach is related : by its anterior face, with the diaphragm and liver ; by Fiff. 183. STOMACH OF THE HORSE. A, Cardiac extremitj' of the oesophagus ; B, Pyloric ring. its posterior face, with the diaphragmatic curvature of the colon. Its inferior border, margined to the left by the spleen, which is suspended from it by means of the great omentum, is separated from the inferior abdominal wall by the large anterior curvatures of the colon ; its distance from this wall depends upon the fulness of the organ. The left extremity, suspended to the sublumbar region by the aid of a very short serous ligament, a portion of the great omentum, responds to the base of the spleen, the left extremity of the pancreas and, less directly, to the anterior border of the left kidney. THE DIGESTIVE APPARATUS IN MAMMALIA. Fig. 184. Tho right extremity, lower than the left, touches the right lobe of the liver aucl the above-meutioned intestinal curvatures. Interior. — When a stomach is opened to study its interior, one is at first struck by the different aspect its internal membrane presents, according as it is examined to the right or left. To the left, it has all the characters of the oesophageal mucous membrane, in being white, harsh, and even resisting ; it is covered by a thick layer of ejiithelium. To the right, it is thick, wrinkled, spongy, very vascular and follicular, has a reddish-brown tint which is speckled by darker patches, loses its consistency, and is deprived of the remarkable epidermis it exhibits on the left side, to be covered by a very thin epithelial pellicle. It is not by an insensible, but a sudden transition that the mucous membrane of the stomach is thus divided into two portions ; and their separation is in- dicated by a salient, more or less sinuous, and sharply-marked ridge. This crest, then, divides the stomach into two com- partments : a division already indicated externally by the circular depression observed in the majority of subjects. The left sac or compartment is considered as a dilatation of the oesophagus. The rigid sac constitutes the true stomach of Solii^eds ; as on it alone devolves the secretory function which elaborates the gastric juice, the essential agent of diges- tion in this organ. The interior of the stomach (Fig. 184) offers for study two apertures : the cardiac and pyloric. The cardiac, or cesophageal orifice, is in the lesser curva- ture of the left sac of the stomach. Its disposition has given rise to numerous discussions, as in it has generally been sought the reason why Solipeds vomit with such extreme difficulty. At one time there has been des- cribed a semilunar or spiroidal valve, which is opposed to the retrograde movement of the food ; and at another time it was the oblique insertion of the oesophageal canal, resembling that of the ureters into the bladder, and which, by a mechanism analogous to these, proved an obstacle to the return of aliment into the oesophagus. Both suppositions are wrong. When we attentively observe the manner in which the oesophagus comports itself at its termination, it will be noticed that it is inflected downwards, after travers- ing the right pillar of the diaphragm, and is inserted almost perpendicularly into the lesser curvature of the stomach. In opening into this viscus, the oesophagus does not widen into an infundibiilum, as in other animals ; on the contrary, its calibre is here narrower than elsewhere, and its cardiac or stomachal orifice, completely obstructed by the folds of mucous membrane, only occupies an infinitely small portion of the internal surface of the stomach. With regard to the jpylorus, it represents a large aperture formed at the bottom of the right sac, and furnished with a thick circular ring; this opening can be completely closed through the action of the powerful sphincter sui'rounding it. Structure. — The parietes of the stomach are composed of three INTERIOR OF THE HORSES STOMACH, A, Left sac ; B, Right sac ; C, Duodenal dilatation. THE STOMACH. 389 membranes : an external, or serous ; a middle, or muscular ; and an internal, or mucous. 1. Serous memhraite.— This membrane, derived from the peritoneum, adheres closely to the muscular layer, except towards the lesser curvature, where it is constantly covered by an expansion of yellow elastic tissue, whose use appears to be to maintain the two extremities of the stomach near each other ; for when this is destroyed the lesser curvature becomes considerably elongated. Along the whole of the greater curvature is a triangular space occupied by connective tissue ; this space disappears more or less completely as the organ becomes distended. It has three folds, which are detached from the stomach and carried on to the adjacent parts, and which are formed in the manner indicated in the general description of the peritoneum. Those folds constitute the cardiac ligament, the gastro-liepatic ligament or omentum, and the great omentum. The cardiac ligament is a short, serous band developed around the terminal extremity of the oesophagus, and strengthened by fibres of yellow fibrous tissue. It attaches the stomach to the posterior face of the diaphragm, and is continuous, on each side, with the two folds about to be described. The g astro-hepatic (or lesser) ligament is a band composed of two layers, which leave the lesser curvature of the stomach, and are inserted into the posterior fissure of the liver. It is prolonged posteriorly, and to the right, along the duodenum, where it constitutes a peculiar serous frasnum which will be studied with the small intestine. The great, or gastro-coUc omentum, is detached from the whole extent of the great curvature, from the cardia to the pylorus, beyond which it extends to the duodenum. The portion surrounding the left cul-de-sac is excessively short, and is carried to the sublumbar wall of the abdomen, to which the stomach is fixed. For the remainder of its extent, this omentum is greatly developed, and hangs freely in the abdominal cavity, among the intestinal convolutions. The border opjiosed to the stomach is attached to the terminal portion of the large colon, and to the origin of the lesser colon. For further details, see the description of the peritoneum. These three ligaments fix the stomach in the abdominal cavity, in addition to the oesophagus and duodenum, which are continuous with it. 2. Muscular membrane. — This tunic, comprised between the serous and mucous layers, is lined internally by a covering of condensed connective tissue which adheres intimately to it, and which may be regarded as the fibrous membrane of the stomach. Dissection shows this muscular tunic to be composed of three superposed planes. The superficial plane envelops all the right sac, and the majority of the fibres composing it are spread in loops around the left cul-de-sac, their extremities being lost on the surfaces of the organ. Some of them even extend over the great curvature, to the surface of the right sac ; while others are evidently continuous with the superficial fibres of the oesophagus (Fig. 185, A). The middle plane (Fig. 185, b) is formed of circular fibres spread over the whole of the organ. In the right sac, they are placed immediately below the serous membrane ; in the left sac, they j^ass beneath the fibres of the superficial plane, and finish by becoming confounded so intimately with these, that towards the tuberosity formed by the left extremity it is impossible to distinguish them. By their aggregation around the pylorus, 28 390 THE DIGESTIVE AFFARATUS IN MAMMALIA. they constitute the sphincter (or pyloric valve) which envelops that orifice. The deep plane (Fig. 186, a), like the first, is specially destined for the left sac, and cannot be properly studied except in an everted stomach deprived of its mucous membrane. Much thicker than the superficial plane, it yet, in its general arrangement, much resembles it. Thus, its fasciculi present loops which embrace the left cul-de-sac, and whose extremities are lost on the faces of the organ, where some of them become continuous with Fig. 185. Fig. 186. MUSCULAR FIBRES OF THE STOMACH ; EXTERNAL AND MIDDLE LAYERS. A, Fibres of the external layer enveloping the left sac ; B, Fibres of the middle plane in the right sac ; c, Fibres of the ceso- phagus. DEEP AND MIDDLE MUSCULAR LAYERS EX- POSED BY REMOVING THE MUCOUS MEM- BRANE FROM AN EVERTED STOMACH. A, Deep layer of fibres enveloping the left sac ; E, Fibres of the middle plane which alone form the muscular layer of the right sac ; C, Fibres of the oesophagus. fhe circular fibres. The loops nearest the oesophagus embrace the stomachal opening of that canal like a cravat. It is to be remarked that the fibres of this deep layer intersect those of the superficial plane ; the former passing from the left to the right sac, in inclining downwards towards the great curvature, while the latter are directed to the right and slightly upwards. From this arrangement it results, as a glance at Figs. 185, 186 will show : 1, That the right sac has only a single muscular plane ; 2, That, on the • contrary, the left sac has three, all of which concur in propelling the aliment that has accumulated in the left or oesophageal compartment into the right, or true stomach. 8. Mucous membrane. — Independently of the general characters notified in the interior of the stomach, it has to be remarked that the gastric mucous membrane is united to the preceding tunic by an expansion of connective tissue ; though it adheres but feebly throughout the right sac, especially towards the greater curvature, where it is thickest ; and that it has no ridges in the left sac, though in the right they are always present, even when the organ is inflated. On the surface of this membrane are seen microscopical apertures {alveoli), the orifices of the excretory ducts of glands ; these are rare in the left sacj THE STOMACH. 391 but extremely numerous in the right. In this region they are sojiaratcd from each other by minute processes resembling papillae ; but the latter are only met in the vicinity of the pylorus. The gastric mucous membrane is composed of an epithelial layer and a corium, in which is distinguished a glandular and a muscular layer. Tho epithelium is stratified and tesselated in the left compartment, simple and cylindrical in the right sac, where it covers the little mucous processes that separate the glandulae, and penetrates more or less deeply into the interior of these. In the left side there are found some glandular organs analogous to those of the oesophagus, but the real glandular layer belongs only to the Fis. 187. Fig. 188. PEPTIC GASTRIC GLAND. a, Common trunk ; 6, 6, Its chief branches ; c, c, Terminal caeca, with spheroidal gland- cells. PORTIONS OF ONK OF THE 0.T:CA JIORE HIGHLY MAGNIFIED, AS SEEN LONGITUDI- NALLY (a), and in TRANSVERSE SEC- TION (b). a, Basement membrane; 6, Large glandular cell ; c, Small epithelial cells surrounding the cavity right side. There are found multitudes of parallel tubular glands, united by a small quantity of delicate connective tissue which is very rich in nuclei. They secrete the gastric fluid, or furnish the mucus that covers the surface of the epithelium ; they are consequently distinguished as pepsine (or peptic), and mucous glands, the former being much more numerous than the latter. They are composed of a simple straight tube at their origin (excretory ductj, which frequently divides into two or more flexunus tubes that 892 THE DIGESTIVE APPARATUS IN MAMJSIALIA. Fig. 189. terminate in culs-de-sac (or glandular cceca). The epithelium is not tho same in the two kinds of glands : the mucous glands (Fig. 189, a, h) are lined with cylinder-epithelium throughout their extent ; the peptic glands (Figs. 187,188) are lined with cylinder-epithelium at their origin (Fig. 187, a), but the secretory tubes contain round peptic cells. (Each caeca, when highly magnified, is found to consist of a delicate basement membrane (Fig. 188, a) inflected over a series of nearly globular cells (h), which occupy almost the whole cavity of the tube, and contain a finely-gi-anular matter ; the narrow passage left vacant in the centre is, however, still surrounded by a layer of epithelial cells (c), whose small size is in striking contrast to the large dimensions of the gland cells.) The muscular layer (of the mucous membrane) is immediately beneath the glandular structure, and contains two planes of intersecting fibres. Lastly, the connective layer of the corium is thick and loose, sustains the vessels (and nerves), and unites the mucous to the muscular tunic of the stomach. 4. Vessels and nerves. — The stomach receives its blood by the two branches of the gastric artery, the splenic and its terminal branch — the left epiploic artery, and by the pyloric and right epiploic arteries. The principal arterial ramifications extend be- „ , tween the mucous and muscular layers, where MUCOUS GASTRIC GLAND WITH ^^ . -i, -n ^-ix- \.xi CYLINDER EPITHELIUM. ^'^^J lumish two Capillary reticulations to the a, Wide trunk , b, b, Its cscal glandular layer : a deep network that surrounds appendage. the secretory tubes, and a superficial placed be- tween the alveoli. The blood is carried from the organ to the vena portae by the satellite venous branches. The lymphatics Fig. 190. APPEARANCE OP THE PROPER GASTRIC MEMBRANE OF THE STOMACH IN AN INJECTED PREPARATION (HUMAN). A, From the conrex surface of the folds or ruga; ; B, From the neighbourhood of the pylorus, where the orifices of the gastric follicles occupy the interspaces of the deepest portions of the vascular network. form a subserous and two deep networks at the base of the glandular layer and in the fibrous membrane. They enter small ganglia (or glands) situated along the curvatures, and from these to Pecquet's reservoir. The TEE STOMACH. 393 nerves are derived from the pneumogastrics and solar plexus, and in accom- panying the vessels show microscopic ganglia in their course ; their mode of termination is not known. Functions. — In the stomach is begun those transformations by which alimentary matters are rendered capable of being assimilated. There the food comes into contact with the gastric fluid, by whose action its principal elements, and particularly the albuminoid substances, become soluble and absorbable, after undergoing some isomeric changes. DIFFERENTIAL CHARACTERS IN THE STOMACH OF OTHER THAN SOLIPED ANIMALS. The stomacli is an organ that exhibits great differences in the various domesticated animals. In the study of these differences, we will proceed from the simple to the complex. 1. TJie Stomach of the Pig. The Pig's stomach is simple, like that of the Horse, but it is less curved on itself, and the cardia is nearer the left extremity ; the latter has also a small conical dilatation, which has been compared to a cowl curved backwards. The ojsophagus opens into the stomach by a wide infundibulum, and the mucous membrane of that conduit is prolonged over the gastric surface in a radius of from two to three inches around the cardia. Here again we find a "trace of the division into two sacs," common to Solipeds. The capacity of the Pig's stomach averages from one and a half to two gallons. (The muscular tunic is thicker in the right than the left extremity ; near the ceso- phagus the serous tunic shows some transverse folds.) 2. The Stomach of Carnivora, (Fig. 191.) In the Dog and Cat the ventriculus is but little curved, and is pear-shaped, the small extremity corresponding to the pylorus. The cardia is dilated like a Fig- 191' funnel, and is nearer the left extremity of the organ than in otlier animals. The oesophageal mucous membrane is not con- tinued beyond the margin of that orifice. The simple stomach of Carnivora forms only a single sac, whose internal mucous membrane presents, throughout its whole extent, the same organisation as the membrane lining the right sac of Soli- peds. This membrane is remarkable for the regular and undulated folds it forms when tlie stomach is empty. Nothing is more variable than the capacity of the Dog's stomach, because of the great dif- ferences in the size of this animal, accord- ing to breed. M. Colin has found the minimum to be IJ pints, and the maxi- mum If gallons ; he calculates the aver- age to be about 2 J quarts. In the Cat, the average is from 2 to 2| gills. 3. The Stomach of Ruminants. These animals are distinguised from the others by the faculty they possess of swallowing their food after imperfect comminution, and causing it to return again into the mouth to submit it to a second mastication, previous to final de- glutition. The gastric apparatus is ad- stomach of the dog. mirably arranged to effect this pliysio- A, (Esophagus ; B, Pylorus, logical finality, and is remarkable for its enormous development, as well as its division into four separate pouches, which are regarded as so many stomachs. 394 TEE DIGESTIVE APPARATUS IN MAMMALIA. These cavities represent a considerable mass that fills the greater part of the abdomiiifil cavity, and the medium capacity of which is not less than fifty-five gallons! One of them, the rumen, into which the oesophagus is inserted, constitutes nine-tenths of the total mnss. The other three, the reticulum, omasum, uud abomasum, form a short chain, continuous with the left and anterior portion of the rumen. The abomasum alone should be considered as a true stomach, analogous to that of the Dog, or the right sac of the ventriculum of Solipeds. The other three compartments only represent, like the left sac in the latter animals, oesophageal dilatations. The description about to be given of each of these divisions more particularly applies to the Ox ; care will be taken, in the proper place, to note the special peculiarities in the stomach of the Sheep and Goat. KcMEN (Fig. 192). — This reservoir, vulgarly designated the paunch, alone occupies three-fourths of the abdominal cavity, in which it alfects a direction inclined from above to below, and from left to right. Fig. 19. • STOMACH OF THE OX, SEEN OX ITS RIGHT UPPER FACE, THE ABOMASUM BEING DEPRESSED. A, Rumen, left hemisphere ; B, Rumen, right hemisphere ; c, Termination of the oesophagus ; D, Reticulum ; E, Omasum ; F, Abomasum. External conformation. — Elongated from before to behind, and depressed from above to below, it offers for study : 1. An inferior and a superior face, nearly plane, smooth, and divided into two lateral regions by traces of fissures, which are only sensible at the extremities of the organ ; 2, A left and right border, smooth, thick, and rounded ; 3, A posterior extrennty, divideol by a deep notch into two lobes, described by Chabert by the name of conical cysts ; 4, An anterior extremity, offering an analogous arrangement, and concealed, at first sight, by the stomachs (or compartments) superadded to the rumen ; the notch on the right of this extremity divides it into two unequal pouches, which will be referred to presently. It is to be remarked that theic two notches, which are prolonged on the surface by furrows that separate these into two lateral regions, divide the rumen into two sacs, a right anol left ; this olivision we will find more manifest in the interior of theviscus. The right sac, the shortest, is in great part enveloped by the serous covering which constitutes the i^reat omentum. The left sac surpasses the other by its two extremities, except in the Sheep and Goat, in which the riiiht conical cyst is longer than the 1 ft. The anterior extremity of this left sac is thrown backwards on the corresponding THE STOMACH. 395 lobe of the right sac ; above, it receives the insertion of the oesophagus, and is continuous^ in front, with the reticulum. Relations. — The external form of the rumen being rletermined, fhe study of its relations becomes easy. By its superior surface, it is in contact with the intestinal mass ; its opposite face rests on the inferior abdominal wall. Its left border, supporting the spleen, touches the most elevated part of the flank and the sublumbar region, to which it adheres by cellular tissue, as well as the vicinity of the cceliac trunk and tlie great mesenteric artery; the right bonier, margined by the abomasum, responds to the most declivitous portion of the right hypochondriac and flunk, as well as to the intestinal circumvolutions. The anterior extremity, bounded by the reticulum and omasum, advances close to the diaphragm ; the posterior occupies the entrance to the pelvic cavity, where it is more or less in contact with the genito-urinary oigans lodged there. In the pregnant female, the uterus is prolonged forwards on the upper face of the viscus just described. Interior (Fig. 193). — In the interior of the rumen are found incomplete septa, which repeat the division into two sacs already so marked externally. These septa are two in Fis. 193. INTERIOR OF THK STOMACH IN EITMINANTS ; THE UPPER PLANE OF THE RtTMEN AND RETICULUM, WITH THE OESOPHAGEAL FURROW. A, Left sac of the rumen ; B, Anterior extremity of that sac turned back on the right sac ; C, Its posterior extremity, or left conical cyst ; G, Section of the anterior pillar of the rumen ; g, g, Its two superior branches ; H, Posterior pillar of the same ; h, h, h, Its three inferior branches ; i, Cells of the reticulum ; j, (Esophageal furrow ; K, ffisophagus ; L, Abomasum. number, and represent large muscular pillars, which correspond inferiorly to the notches described at the extremities of the organ. The anterior pillar (Fig. 193, g) sends to the inferior wall of the rumen a strong prolongation, directed backwards, and to the left ; it is continued on the superior wall by two branches, which separate at an acute angle. The poderior pillar (Fig. 193, H), more voluminous than the preceding, has three branches at each of its extremities — a middle and two lateral. The middle branches are carried forwards on the limit of the two sacs, which they separate from one another ; that from above meets the corresponding branch from the anterior pillar The 396 THE DIGESTIVE APPARATUS IN 3IAMMALIA. lateral branches diverge to the right and left in describing a curve, and in circumscrib- ing the entrance to the conical cysts, which they transform into two compartments distinct from the middle portion of the sacs of the rumen; the inferior go to meet the superior branches, but do not altogether join them. The internal surface of the rumen is covered by a multitude of papillary prolongations, dependencies of the mucous membrane. To the right, and in the cids-de-sac, thcae papillae are remarkable for their number, their enormous development, and their general foliated shape. On the left side they are more rare, particularly on the superior wall, and only form very small mammiform tubercles; they are absent on the muscular columns. This papillary arrangement is still more developed in certain wild Ruminants, and it is scarcely possible to give an idea of their richness in the stomach of the Gazelle. The interior of the rumen offers for study two openings, situated at the anterior extremity of the left sac : one is the oesophageal orifice, pierced in the superior wall, dilated into an infundibulum, and prolonged into the small curvature of the reticulum by a particular furrow (or channel), which will be described after the latter compart- ment ; the other, placed below, and opposite the preceding, traverses the bottom of the cul-de-sac from before to behind, and forms the C(jmmunication between the paunch and reticulum : it is a very large opening, circuinscribid below and on the sides by a septum or semilunar valve, resulting from the jimction of the parietes of the rumen with those of the reticulum. Structure. — Like all the hollow organs in the abdomen, the rumen has three tunics : a serous, a Ttiuscular, and a mucous. The serous envelops the organ throughout, except above, in front, and to the left, the point which touches the sublumbar region, and the pillars of the diaphragm, as well as the bottom of the notches which separate the culs-de-sac from the extremities. This membrane gives origin, like that of the stomach of the Horse, to a vast duplicature — the great omentum. The arrangement of this, which is somewhat difficult to observe in the Ox, in consequence of the enormous weight of the gastric mass, is readily seen in the smaller Ruminants. It begins at the middle of the faces of the paunch and the tissure intermediate to the two conical cysts, forming a wide envelope that contains the right sac and the abomasum; it becomes attached in passing over the great curvature of the last-named cavity, and is confounded, sujjeriorly aud posteriorly, with the great mesentery. The muscular coat is very thick, and forms the internal columns of the viscus. Its fibres are disposed in several layers, whose arrangement is simple, and offers nothing really interesting to study, except in the points where the serous tunic passes from one cul-desac to another, or from the rumen to the reticulum ; there it is often accompanied by thin and wide muscular fasciculi which, like the latter membrane, stretch over the intermediate fissures, and thus become real unitive or common fibres. The muscular fibres of the rumen present an unmistakable transverse striation — a very rare physical characteristic in the muscular tissue of organic life. The mucous membrane offers some peculiarities, which deserve a few words. The corium is very thick, and probably contains some glands, but they must be extremely few. The free face of the membrane is excessively uneven, in consequence of the pajjillary apparatus mentioned above. The papillai of the rumen are foliaceous, conical, or fungiform. Those of the first description are much more numerous than the others ; they have the shape of an oval, elongated leaf, their summit is wide and rounded, and the base narrow and apparently implanted in the corium. On one face is a little rib that springs from the base and disappears on the widened portion, resembling the principal vein or nervule of a leaf. On the other face, opposite the vein, is a faint longitudinal groove. These papillae are constituted by a layer of nucleated connective tissue, covered by epithelium ; the former, in the principal papillae, has on its faces and extremities minute prolongations, resembling on a small scale the secondary papillae described as existing on the lingual mucous membrane. In the centre of the papillae are one or two main arteries, derived from the network of the corium. These pass, in a slightly flexuous manner, to the summit, and break up into several branohlets, succeeded by veins, that descend along the surface of the papilla into each of its secondary prolongations. The conical and fun^riform papillaj are few in the left sac, and resemble the papillsQ of the same name described on the tongue. The epithelium of the mucous membrane of the rumen is remarkable for its strength and cohesiveness. It belongs to the category of stratified tesselated epithelium, and forms a sheath to each papilla, covering the corium in the interpapillary spaces. There are frequently found, in opening the rumen of animals just killed, large TEE STOMACH. 397 exfoliated patches on the surface of this layer. This is a sufficient indication of the activity of the secretion of the epithelium, and the rapidity of its renovation. Reticclvm (JIONEYCOMis) (Figs. Uf2, 193). — JSitiKition—Form — Iielations. — This, the smallest compartment, is elougateJ from one side to the other, slightly curved on itself, and placed transversely betwei u the posterior face of the diaphragm, in one direction, and the anterior extremity of the left sac of the rumen in the other ; the latter onlv appearing, externally, to be a prolongation, or a diverticulum of the rumen. It has two faces, ttco curvatures, and two extremities. The anterior face adheres to the phrenic centre of the diaphragm by cellular tissue. The posterior face lies against the anterior extremity of the rumen. The great inferior or convex curvature occupies the suprasternal region. The lesser, superior, or concave curvature partly responds to the lesser curvature of the omasum. The left extremity is only separated from the rumen by a fissure, which lodges the inferior artery of the reticulum. The right extremity forms a globular cul-de-sac, in relation with the base of the abomasum. Interior (Fig. 193). — The internal surface of the reticulum is divided by ridges of the mucous membrane into polyhedral cells, which, in their regular arrangement, look like a honeycomb; they are widest and deepest in the cul-de-sac. and become gradually smaller in approaching the superior curvature. The interior of these cells is divided into smaller spaces, included one within the other, by secondary and successively-dtcreas- hig septa. The principal septa ofler on their free border a series of conical prolonga- tions, with a rough hard summit; while their faces are studded with minute, blunt, or pointed papillffi. The secondary septa also show similar prolongations; and those on their free margin are even more developed than on the chief septa. Lastly, from the bottom of the cells spring up a crowd of long, conical, and very pointed papillte, resem- bling stalagmites in the:r arrangement. It may be noted that the foreign bodies so frequently swallowed by Eimiinants, are usually lodged in the reticulum; therefore it is that at tlie bottom of the cells are found either small stones, and needles or pins, often fixed in the intermediate septa, or nails, scrajDS of iron, etc. The interior of the reticulum communicates with the left sac of the rumen by the orifice already described, and with the omasum by a particular open- ing, placed near the middle of the small curvature, though a little more to the right than the left. This opening, eight or ten times smaller than the preceding, is connected with the infundibulum of the cardia by a remarkable groove (or channel), the oesophageal, which will be described separately, as it does not properly belong to the reticulum. Structure. — The serous membrane does not cover all the anterior surface of the organ, as the latter adheres to the posterior face of the diaphragm. The muscidar tunic is much thinner than that of the pauneh, and more fasciculated. The fibres pass in the same direction. The corium of the mucous membrane sends a prolongation into each of the septa of the alveoli, and into each of the conical papillae on these septa, or to the bottom of these alveoli. The stratified pavement epithelium is very thick, and its horny layer is very developed at the summit of the papillae. Esophageal Gkoove (Fig. 193). — This gutter is so named because it appears to continue the oesophagus to the interior of the stomach. It extends on the lesser curvature of the reticulum from the cardia to the entranee of the omasum ; commencing in the rumen, it belongs to the reticulum for the remainder of its extent. Measuring from six to eight inches in length, this demi-canal is directed from above downwards, and from left to right, between two movable lips, which are fixed by their adherent border to the superior wall of the reticulum. These two lips are thickened at their free margins, which look downwards and to the left. At their origin at the oesophageal infundibulum, they are thin and but slightly elevated ; but they become thick and salient on arriving near the orifice of the omasum, which orifice they surround, though they neither meet nor become confounded with each other. The mucous memhrane covering these two lips is much corrugated outwardly and on the free border ; but in the interior of the groove it possesses all the characters of the oesophageal mucous membrane in being smooth, white, and ridged longitudinally ; near the orifice of the omasum it has some large conical papillaa If this membrane be removed to study the subjacent tissue, the following arrangement is observed : At the bottom of the channel, and in the space comprised between its two lips, are transverse muscular fibres, which belong to the rumen or reticulum. The lips themselves are entirely composed of longitudinal muscular fasciculi, particularly abun- dant towards the free border ; these fasciculi are confounded with the proper fibres of the stomach towards the extremities of the canal, and are carried from one lip to the other in forming loops around the orifices which communicate by this canal. Omasum {Fsalterium, jMany-plies, Many-leaves, or jNIanyplcs. Fig. 192). — In the 39S THE DIGESTIVE APPARATUS IN MAMMALIA Ox, this compartment id larger tlian tbe reticulum, but in the Sheep and Goat it ia smaller. Situation — Form — Relations. — Situated above the cul-de-sac of the reticulum and the anterior extremity of the right sac of the rumen, this compartment, wlien distended, has an oval form, is slightly curved in an opposite direction to the honeycomb division, and depressed from before to behind. It lias, therefore, an anterior face, applied against the diaphragm, to which it is sometimes attached by connective tissue ; a posterior face lying towards the paunch : a great curvature, turned upwards, and fixed in the posterior fissure of the liver by an omental fra?num which is continued on the lesser curvature of the abomasum and duodenum ; a lesser curvature, wiiich looks downwards and responds to the reticulum ; a left extremity, exhibiting the neck, which corresponds to the orifice of communication between tiie reticulum and many-plies ; a riglil extremity, continuous with the base of the abomasum, from which it is separated by a constriction analogous to that of the anterior extremity, but much less marked. Interior. — This compartment shows in its interior the two apertures placed at its extre- mities. The right orifice, opening into the abomasum, is much wider than the left, which Fig. 193 > Rf SECTION OF THE WALL OF THE OMASUM OF THE SHEEP: FROM THE GREAT CURVATURE, SHOWING THE ORIGIN OF THE LEAVES. P, Peritoneum ; M, The two muscular layers ; E. Epithelium ; 1, 1, Principal leaves at their origin; 2, Secondary leaf; 3, 3, Leaves of the third order; 4, Denticu- lated lamina ; 5, 5, Two planes of muscular fibres ascending into the principal leaves, some issuing from the muscular layer of the organ. communicates with the reticulum. The cavity which tliese orifices bring into communica- tion with tlie adjoining compartments, offers one of tlie most curious arrangements met with in the viscera ; it being filled by unequally-developed leaves of mucous membrane, which follow the length of the cavity. These laminae have an adherent border attached either to the great curvature or to the fac«s of the organ, and a free concave border turned towards the lesser curvature. They commence at the side of the orifice of the reticulum by denticulated ridges, between which are furrows, and which are prolonged from the base of the leaves to the entrance of the abomasum. At the latter aperture tney disappear altogether, after rapidly diminishing in height. Tlieir faces are studded by a multitude of very liard mamillai-y papillfe, resembling grains of millet, which are more developed and conical on some of the leaves than others. All these lamellar prolongations are far from bein^ of the same extent: t^velve to fifteen are so wide that th. ir free border nearly reaches the lesser curvature of the viscus, and between these principal leaves are others which, thougli regularly enough arraneed, are more or less narrower. At first there is remarked a sec mdary leaf, half the width of the chief ones, between which it is placed; then, on each of its sides, another, one-half narrower ; and, lastly, at the base of these, two denticulated laminae more or less salient. In a general way, the laminte which are inserted into the great curvature are the longest and widest ; and those attached to the faces of the viscus become shorter and narrower as they draw nearer the lesser curvature. The space comprised between these prolongations is always filled by very attenuated alimentary matters, which are usually impregnated by a very small quantity of fluid, but are also often dry, and sometimes even hardened into compact flakes. THE STOMACH. 399 Slructiire. — The gerom layer is a dependency of tlie peritoneum, and offers nothing particular ; it does not completely cover the anterior face. The muscular tunic is much fasciculated, and thin. The mucous membrane is remarkable for the thickness of its stratified pavement epithelium ; all the leaves are formed by two layers of this membrane, laid one against the other ; and as their structure is interesting, we will notice it. The principal leaves are composed of this duplicature of mucous membrane, and two layers of muscidar fibres between ; these layers are opposite each other at the commence- ment of the leaf, and separated by a transverse vessel ; in tlie remainder of their extent tliey are kept apart by the vessels thut pass towards tiie border of the leaf. Their fibre s are detached from tht- surface of the muscular tunic and, at certain points, from its deep layer. In the smaller leaves there appears to be only one layer of muscular fibres ; on all the leaves are various-sized papillae, the smallest of which are l»ue a grain of millet, Fis. 195, Fig. 196. T— SECTION OP A LEAF OF THE OMASUM. 1, 1, iluscular planes ; v, vessel ; 2, Epithe- lium ; 3, 3, Small-sized papillse, round and hard. LOXGITUDINAL SECTION OF A LARGE PA- PILLA FROM THE OMASCJI, SHOWING NERVE-CELLS IN ITS INTERIOR. and have for base a mass of condensed connective tissue, whose superficial fibres form a kind of shell (Fig. 195) ; the largest are club-shaped. They receive blood-vessels, and we have found in the connective tissue, elements with a S"mewhat irregular outline, pro- vided with nuclei, which we considered to be nerve-cells (Fig. 196.) Abomasum (Eeed or Eennet. Figs. 192, 193). — Situation — Form — Tielations. — The abomasum stand;? next to tiie rumen for capacity. It is a pyriform reservoir, curved on itself, elongated from before to behind, and situated behind the oruasum, above the right sac of the rumen. On the right it touches the diaphiaiim and tlie hypochondriac; on the left it is related to the rumen. The greater curcature, turned downwards, receives the insertion of the great omentum. Tiie lesser curvature, inclined upwards, gives attachment to the serous band already noticed when speaking of the great curvature of the omasum. Its 5a.se is in contact with the cul-de-sac of the reticulum, and is separated from the omasum by the constriction in the foiTU of a thick neck, which corresponds te the communicating orifice of the two stomachs. Its point, directed upwards and back- wards, is continued by the duodenum. Interior. — This being the true stomach of Ruminants, the mucous membrane lining its interior acquires all the characters which distinguish that of the stomach of the Carnivora, or that of the right sac of the Horse's stomach. It is soft, spongy, smooth to the touch, vascular, red-coloured, covered by a thin epithelium, and provided with numerous glands for the secretion of the gastric juice. Thinner than in monogastric animals, this tenuity is compensated for by a mtich greater extent of surface, which is still further increased by numerous lamellar folds. These latter are analogous in con- stitution to those of the omasum, cross i:i a veiy oblique manner the great axis of the abomasum, and altogether affect a kind of spiral arrangement. The abomasum has two apertures : one, situated at its base, opens into the omasum ; the other, placed opposite to the first, and much narrower, is the pylorus, which is circumscribed, as in the other animals, by a muscular ring. Structure. — The serous membrane is continuous with the omenta which abut on the great and lesser curvatures of the viscus. The muscular layer is of tlie same thickness as in the omasum. The internal tunic has already been noticed. FrxcTioss OF THE Stom.^ch in Rumin.\xts. — We cannot pretend to give here a complete history of the phenomena of rumination, but must confine ourselves to describe in a few words what are the principal attributes of each gastric dilatation. 400 THE DIGESTIVE APPARATUS IN MAMMALIA. The rumen is a sac where the aliment taken during feeding-time is kept in reserve, and whence it is again carried into the mouth during rumination, after having been more or less softened. The reticulum participates in the functions of the rumen, to which it is only a kind of diverticulum. But it is particularly with regard to liquids that it plays the part of a reservoir ; the solid substances contained in it being always diluted by a larger quantity of water. The oesophageal groove carries into the omasum the substances swallowed a second time after rumination, or even those which the animal ingests in very small quantity for the first time. The omasum completes the trituration and attenuation of the food, by pressing it between its leaves. The abomasum acts as a true stomach charged with the secretion of the gastric juice ; in this reservoir occur the essential phenomena of gastric digestion. COMPARISON OF THE STOMACH OF MAN WITH THAT OF ANIMALS, In its form, the stomach of Man much resembles that of the Carnivora. The insertion of the oesophagus, however, does not offer so large an infundibulum. The organ is situated in the left hypochondriac, and is nearly horizontal. Everywhere the mucous membrane is red and glandular ; the muscular fibres are disposed in three planes, as in Solipeds ; but the superficial and deep are particularly directed towards the left sac. THE INTESTINES. (Figs. 204, 205, 206.) The alimentary canal is continued from the stomach, in the abdominal cavity, by a long tube doubled on itself a great number of times, and which terminates at the posterior opening of the digestive apparatus. This tube is the intestine. Narrow and uniform in diameter in its ante- rior portion, which is named the small intestine, it is irregularly dilated and sacculated in its posterior part, the large intesti?ie. These two por- tions, so markedly defined in all the domesticated mammals, are but im- perfectly distinguished from one another with regard to the digestive phenomena occurring in tlieir anterior. We will study them in all the animals which interest us, and conclude by a general and comparative examination of the entire abdominal portion of the digestive canal. Preparation. — The study of the intestines does not demand, properly speaking, any special preparation ; it being sufficient to incise the inferior wall of the abdomen to expose these viscera. As their mass, however, is heavy and unmanageable, it is advisable to expel their contents in a manner similar to that recommended for the preparation of the stomach ; a puncture at the point of the Cfecum allows the escape of the substances accumulated in that I'eservoir — those which fill the large colon may be removed by an incision made toward the pelvic curvature, and those in the floating colon by the rectum. The small intestine may be evacuated by three or four openings at about equal distances in the length of the viscus. Having done this, inflate the intestines to somewhat of their natural volume ; this preparation then permits the gen- eral arrangement of the intestinal mass in the interior of the abdomen to be easily studied. It would be well to remove the entire mass altogether from the body, and lay it out on a table, so as to isolate the various parts, study them in succession, and note their form, 1, The Small Intestine. (Figs, 204, 205, 206,) Length — Diameter. — The small intestine is a long tube, which, in a horse of ordinary height, may average about 24 j'ards in length, and from 1 to If inches in diameter. This diameter is susceptible of variation, according to the state of contraction of the muscular tunic of the viscus. Form. — This tube is cylindrical, doubled on itself, presenting two cur- vatures : one convex, perfectly free ; the other concave, called the small cur- vature^ which serves as a point of insertion to the mesentery that sustains THE INTESTINES. 401 the organ. Removed from tlie abdominal cavity, freed from the serous folds which sixspend it, and distended by air or water, this disposition of tho small intestine naturally causes it to twist in a sjural manner. Course and Belations. — The small intestine commences at the right cul- de-sac of the stomach, from which it is separated by the pyloric constriction. At its origin it presents a dilatation which, in form, closely simulates a small stomach, whose cui'vatures are the inverse of those of tljc proper stomach. Placed at the posterior face of the liver, this expansion, or head, of the small intestine begins the narrower portion, which at first is directed forward, then bends suddenly backward : thus forming a loop investing the base of the caecum on the right side ; then it is carried to the left in crossing, trans- versely, the sublumbar region, beliind the great mesenteric artery ; here it is joined to the origin of the floating colon by a very short serous fr^uum. It then reaches the left flank, where it is lodged, and where it forms numerous folds that are freely suspended in the abdominal cavity among the convolu- tions of the small colon. The terminal portion of this conduit, which is easily recognised by the greater thickness of its walls and its smaller diameter, disengages itself from these convolutions to return to the right, and opens into the concavity of the cfecum, below, and a little to the inside of, the point where the large colon has its commencement. In the language of the schools, this terminal portion is named the ileum (eiActv, to heist) ; the part which is susjDended in the left flank, and which forms the principal mass of the intestine, is designated the jejunum (jejunus, empty) ; and the curvature formed by this viscera at its origin, from the pylorus to the great mesenteric artery, is termed the duodenum (twelve fingers' breadth). This classical division is, however, altogether arbitrary, and scarcely deserves to be retained. It would be better to divide the intestine into a fixed or duodenal, and a free oy floating portion. Mode of attachment. — The small intestine is maintained in its position, at its extremities, by the stomach and the caecum. But its principal means of fixation consists in a vast peritoneal fold, which, from its use, is named the mesentery {fxicrov, h'Tepov). This serous layer presents a very narrow anterior part which sustains the duodenum, and fixes it in such a manner as to prevent its experiencing any considerable displacement. Continuous, in front, with the gastro-hepatic omentum, this portion of the mesentery is successively detached from the base of tho liver, the inferior aspect of the right kidney, or even from the external contour of the base of the cfecum, and, lastly, from the sublumbar region, to be soon confounded with the principal mesentery. This becomes wider as it approaches the cfecal extremity, and arises, as from a centre, from the outline of the great mesenteric artery, to spread in every direction, and is inserted into the small curvature of the floating portion of the viscus. The great length of this insertion causes it to become extended in a spiral or screw-like manner, around its point of origin. It may be remarked that the terminal extremity of the intestine is retained between the two serous layers of the mesentery, to a certain distance from its free border. This peritoneal fold consequently forms at this point, at the side opposite to its insertion into the intestinal tube, a particular fraBnum, which is observed to be carried to the anterior face of the caecum. Interior. — The interior of the cylindrical tube formed by the small intestine offers longitudinal folds, which are effaced by distention, except towards the origin of the duodenal portion. Those met with in this situation 402 THE DIGESTIVE APPARATUS IN MAMMALIA. possess all the characters of the valvidse conniventes (valves of Kerlcring) of Man ; they resist the effects of traction exercised on the intestinal membranes, and are formed by two mucous layers laid together, with a plentiful supply of connective tissue between them. The internal surface of the small intestine also offers for study a mul- titude of villosities and glandular orifices, or follicles, which will be noticed hereafter. It communicates with the inner surface of the stomach by the pyloric orifice, and with that of the caecum by means of an opening which projects into the interior of that reservoir, like a tap into a barrel. This projection, which is not very marked, is formed by a circular mucous fold, strengthened externally by muscular fibres, and is named the ilio-coecal valve or valvula Bauhini. Two additional orifices open on the surface of the small intestine in its duodenal portion, from 5 to 8 inches from the pylorus : one is the orifice common to the biliary and principal pancreatic duct, the other that of the accessory pancreatic duct. Structure. — The wall of the small intestine, like that of the other hollow viscera in the abdominal cavity, is composed of three tunics : 1. Serous membrane. — This envelops the organ everywhere, except at its small curvature, which receives the insertion of the mesentery. 2. Muscular coat. — Covered internally by a layer of condensed connective tissue (which is sometimes designated as a fourth tunic) this middle mem- brane has two planes of fibres : one, superficial, is formed of longitudinal fibres uniformly spread over the whole surface of the viscus ; the other, deep-seated, is composed of circular fibres, which are a continuation of those of the pyloric ring. 3. Mucous membrane. — This tunic, extremely interesting to study, is soft, spongy, highly vascular, very delicate, and of a reddish-yellow colour. Its external face is loosely adherent to the muscular layer, and its free aspect exhibits the villi, and the glandular or follicular orifices already noticed. It comprises, in its structure, an epithelial covering, and a mucous derm or corium. The epithelial layer is formed by a single row of cylindrical (or columnar) cells, implanted, by their summit, on the surface of the derm, and lining the interior of the«orifices which open on the inner face of the membrane. The base of these cells has an amorphous cushion, which, when they are all united, appears like a thin layer spread on the inner surface of the intestine. The mucous derm is thick and loose in its deeper portion, and is con- Btituted by fasciculi of connective tissue mixed with elastic fibres, and lymphoid elements. On its free surface it exhibits villosities and depressions, which correspond to the glands. It has a muscular layer, whose unstriped fibres are arranged in a similar manner to those of the muscular coat of the intestine. Lastly, it contains follicles, and vascular and nervous reticulations. We will study each of these. The villi are the foliated or conical appendages which are found to be most developed in the shortest portions of the intestine. In Birds and the Carnivora they attain their maximum length ; while in Euminants they are in a rudimentary state, though, whatever may be their dimensions, they are always visible to the naked eye. Their number is considerable, and they have been justly compared to the pile of velvet. In structure, they are formed of a small spongy mass of embryonic connective tissue, in the .centre of which are one or more lymphatic (or lacteal) vessels, with a THE INTESTINES. 403 magnificent network of peripherj|,l capillary blood-vessels ; tlie whole being inclosed in a complete epithelial sheath. FiV. 197. A. VILLI OF MAX, SHOWING THE BLOOD-VESSELS AND LACTEALS.- OF A SHEEP, -B. VILLUS Fi?. 198. The orifices opening on the intestinal mucous membrane belong either to Brunner's {duodenal) glands, or to those of Lieberkiihn {simple follicles). Brunner's glands form a continuous layer beneath the duodenal mucous mem- brane. In their organisation, these small granular bodies are exactly like the acini of the salivary glands ; each acinus pos- sesses an extremely short excretory duct, that passes through the mucous mem- brane. (These racemose glands secrete a clear alkaline mucus, w^hich contains no formed elements, such as cells or nuclei.) The glands (or cryptse mucosse) of LieherhiiJin or Galeati are placed in the substance of the mucous membrane, and are distinguished by their microscopical dimensions, their considerable number, and their tubular form, which has caused each of them to be compared to the finger of a glove; they are implanted perpen- PORTION OF ONE OF BRtmNER S GLANDS. 404 THE DIGESTIVE APPARATUS IN 3IAMMALIA. dicularly in the mucous membrane, and open on its free surface. Tliey are found throughout the whole extent of the intestine, and are lined with columnar epithelium. The solitary glands {glanduloe, solitarise, or lenticular glands) are round, salient bodies, visible to the naked eye. They are somewhat rare in the small intestine, but are more abundant at the posterior portion of the large intestine. They are foi-med by a mass of lymphoid elements enveloped by some condensed fasciculi of connective tissue. Above them the mucous membrane is sliglitly umbilicated, and is destitute of villi and tubular glands, though these are arranged in a circle around the follicles, to form the coronce tuhulorum. (The solitary glands usually contain a cream-like secretion, which covers the villi on their free surface.) Fis:. 199 PERPENDICULAR SECTION THROUGH ONE OP PETER's PATCHES IN THE L0"\^ER PART OF THE ILEUM OF THE SHEEP a, a, Lacteal vessels in the villi r b. 6. Superficial layer of the lacteal vessels {rete angustum); c, c, Deep layer of the lacteals (rete arnplum); d, d, EfTerent vessels provided with valves ; e, Lieberkiihn's glands ; /, Fever's glands ; g, Circular muscular layer of the wall of intestine ; h, Longitudinal layer ; i, Peritoneal layer. The aggregated follicles (glandulae agminafoe) are nothing more than solitary glands collected together in a limited space, where they constitute what are known as the glands of Peyer or of Pecldin, or the honeycomb glands. Absent in the duodenum, and even at the commencement of the jejunum, these glands, about a hundred in number, are very irregularly placed on the internal surface of the intestine at its gi'eat curvature, on the side opposite to the mesentery. Their form is oval or circular, and the THE INTESTINES. 405 smallest scarcely measure more than some few hundredths of an inch square ; while the diameter of the largest increases to 1^ inch. (Each of these patches is composed of a group of small, roimd, whitish vesicles, covered with mucous membrane; these vesicles consist of a Fig. 200. Fis. 201. PERPENDICULAU SECTION THROUGH THE INTESTINAL WALL TO SHOW A SOLITARY FOLLICLE. a, Liebertuhnian glands ; b, Solitary follicle ; c, Lacteal vessels sui-rounding, but not penetrating, the follicles ; d, Lai-ge eiierent vessels, provided with valves. moderately-thick external capsule, having no excretory canal, and containing a similar secretion to that in the solitary follicles. They are surrounded by a zone or band of simple follicles, and the spaces between them are covered with villi. The vesicles are usually closed ; though it is supposed they open at intervals to discharge their secretion. The mucous and submucous coats of the intestine are intimately adherent and highly vascular, oppo- site the Peyerian glands.) 4. Vessels and nerves. — The small intestine receives its arteries almost exclusively from the great mesenteric artery. One, which goes to the duodenum, comes from the coeliac trunk. These arteries form a submucous network, from which branches pass inwards and outwards, the first to the muscular and serous tunics, the second to the glands and the villi. A tubular network sur- rounds each Lieberkiihnian gland, and is observed in each villus ; while a spherical reticulation sur- rounds each solitary follicle, loops being given off which penetrate nearly to the centre of the follicle. The veins have the same arrangement, and finally enter the vena portae 29 VILLI OF INTESTINE, WITH THEIR CAPILLARY PLEXUS INJECTED. 4oa THE DIGESTIVE AFFAnATUS IX MA^niALIA. The lymphatics constitute three superposed networks in the mucous membrane. The first is situated around the glandular orifices ; it receives Fig. 202, HORIZONTAL SECTION THROUGH THE MIDDLE PLANE OF THREE PEYERIAN GLANDS, SHOWING THE DISTRIBUTION OF THE BLOOD-VESSELS IN THEIR INTERIOR. the central lacteal from FiV. 203 DIAGRAMMATIC REPRESENTA- TION OF THE ORIGIN OF THE LACTEALS IN A VILLUS. e. Central lacteal ; d, Connec- tive-tissue corpuscles with communicating branches ; c, Ciliated columnar epithe- lial cells, the attached ex- tremities of which are di- rectly contiguous with the ar region by con- nective tissue. It describes the arc of a circle, in the concavity of which is lodged tie right extremity of the pancreas, and not the caicum as in Solipeds. 418 THE DIGESTIVE APPARATUS IN MAMMALIA. The small intestine proper is suspended by a mesentery somewhat similar to that of the Horse. Its length varies mufh — from IS to 26 feet. Its internal face has a large number of transverse riigse, the valvulx conniventes. It also shows from 20 to 25 Fcyer's patches, particularly in the ileo-ca3cal portion. Its structure is like that already (ieocribed. In the large intestine is recognised the csecum, colon, and rectum. The ca3cum is a small reservoir placed in the right iliac fossa, a little obliquely downwards and to the left. It commences at the ileo-cajcal valve, has an average length of about 2J inches, and terminates by a rounded extremity with a small hollow prolong- ation, averaging 3 inches in length, the cxcal or vermiform appendix. The mucous membrane is like that of animals, and the muscular tunic is the same. The human colon is regularly sacculated, like the small colon of the Horse ; it begins in the right iliac fossa, above the valvula Bauhiui; it ascends to the lower face of the liver, passes abruptly across from right to left, and, arriving at the spleen, again changes its direction downwards to the iliac fossa : it then again describes the iliac S, to reach the mesial line, where it is continued by the rectum. From this course, the colon has been divided into three portions : the ascending colon, transverse colon, and descending colon. In the ascending and transverse colon are observed three series of sacculi, separated by three muscular longitudinal bands ; the descending colon has only two. There is scarcely anything special to note in the rectum and anus, except that they, and esi^ecially the latter, are very rich in arteries and varicose veins, and that the anus is sepaiated from the rectum by small cavities open in front, and which are found ia the Dog ; these are the sinuses of Moryagni. GESEEAL AND COMPAEATIVE SURVEY OF THE ABDOMINAL OR ESSENTIAL rORTTON OF THE DIGESTIVE TUBE. We have terminated the description of the anatomical characters which distinguish the tssential portion of the alimentary canal in all the domesticated animals, and what gradations has this study revealed ! Let us recapitulate and compare them, before showing the admirable harmony which pervades these diverse arrangements, and adapts them to the variations in general organisation, habits, and instincts. In the Carnivora which subsist on flesh {Dog and Cat), we have seen a very ample stomach, secreting a gastric fluid throughout the whole extent of its mucous membrane, and intestines, (relatively) extremely short. In the Oinnivora, or mammalia which live on a mixed diet (Pig], we have found a small portion of the internal surface of the stomach occupied by a mucous membrane unfitted to secrete gastric juice, and the intestines relatively of much more considerable capacity than in Carnivora. With the Herbivora, which derive their nourishment exclusively from the vegetable kingdom ' Buminants and Solipeds), the surface destined for the production of the gastric juice also singularly diminishes in extent, although the stomach in some of these animals is remarkable for its extraordinary development. But to compensate for this, the capacity of the intestinal canal assumes considerable proportions, and in the various species is in directly inverse relation to the area of the gastric surface. This surface being relatively more extensive in Ruminants than in Solipeds, all these animals ought to be classed in an inverse order with regard to the development of the intestinal surface. Finally, in considering as the internal surface of the stomach (a point of view quite rational) only those portions of the mucous membrane organised for the secretion of the gastric juice, we are led to recognise that this surface is in inverse proportion to that of the intestine; that it reaches its highest degree of development in Carnivorous animals; and that it is reduced to the smallest dimensions in Solipeds, animals which, on the contrary, present a very great development of the intestinal surface. The nature of the aliment readily accounts for these remarkable differences. The Cainivora, living on substantial food, take it in very large quantity, because they are exposed to frequent fastings; it is, therefore, necessary that they should have a stomach Iirge enongh to contain the ingested substances, and to secrete the amount of g istric juice neeiled to transform them into assimilable materials. If these animals have a .short and nariow intestine, it is because a small surface only is required to absorb the products of digestion, these being mixed with but a minimum quantity of non-nutritive sub.stances, and readily come in contact with the absorbing membrane. With regard to the Herbivora, their food contains a trifling proportion of nutritive dementi inclosed in an extremely abundant matrix, and being compelled to ingest great ORGANS ANNEXED TO THE ABDOMINAL DIGESTIVE CANAL. 419 quantities at short iiit( rvals, the stomach, properly called, can only be a temporary receptacle for the aliment, wiiicli passes rapiiily throuuh it after being inijiregnated by the g-istiic juice. The surface which secretes that tiiiid is nho singularly reduced, because if it has to perform its functions more frequently than in Carnivora, it is nc^t required to display so much activity in a given time. If, on leaving tlie stouiach, the alimenfarv matters encounter a vast intestinal surface, it is iu order that the reparative materials dispersed in the alimentary mass may not escape the absorbent action of tiiat surface, and may be the more eftectually brdught into contact with it. We have tiiis exemplified in Kuminants ; owing to tlieir double mastication and the triturating action of the mani/- plies, their food arrives in the stomach proper more comminuted and bet'er attenuated than in the Horse ; the mas.^, more finely broken up, retains less of the assimilable and reijarative matters, and these are more easily seized by the absorbing surface : and, :is a necessary consequence, the intestinal tube, although longer tiian in fcjoiipeds, is far from offering the same capacity. Analogous considerations explain the reason for the intermediate conformation of the digestive canal in Omnivorous animals. There is, then, an admirable correlation between the conformation of the digestive tube and tlje nature of the substances which form the base of the alimentation of animals ; and this harmony is eqTially apparent when the stomacii and intestines are compared with the other apparatus of the economy, and with the natural habits and instincts of creatures. So it is tliat a creatitre furnished with an ample stomach and narrow intestine, will have sharp teeth and claws to tear its prey, strength and agility to capture it, and will also pos.-ess sanguinary instincts, while another, with its gastric surface greatly diminished, willliave inte.-'tines as developed in their length as in the'r capacity, and be distinguished by its jieaceful habits, the absence of aggressive claws, and the crushing and grinding furm of the principal pieces of its dental apparatus, etc. ORGANS ANNEXED TO THE ABDOMINAL PORTION OF THE DIGESTIVE CANAL. These organs are three in number : two glands — the Ever and 'pancreas, which pour into the small intestine two particular fluids, the hile and pan- creatic juice ; and a glandiform organ, the spleen, remarkable for its nume- rous vasctilar connections with different organs of the digestive apparatus, and which for this reason deserves to be studied with it, although it is doubtful, if not improbable, that it has anything to do with digestion. Preparation. — These three organs can readily be studied after removing the intestinal mass, as indicated at page 385. In order to examine the details of their organisation with more facility, it would be well to detach them altogetiier with the diaphragm and kidneys, and to lay out the whole on a tuble. (To study the relations of tliese three organs with tliose of the abdominal cavity, it is advisable to place the sul)Ject on its sternum after removing the intestines, and to detach the poiterior part of the body at the loins.) The Liver. (Figs. 182, 211, 216.) Sitiiaiion — Direction.- — This organ is situated in the abdominal cavity, to the right of the diaphragmatic region, and in an oblique direction down- wards and to the left. Weight. — The weight of the healthy liver, in a middle-sized Horse, is eleven pounds. Form and External Surface, — Eeleased from all its connections with the neighboiu'ing organs, and viewed externally, it is seen to be flattened before and behind, irregularly elongated in an elliptical form, thick in its centre, and thin towards its borders, which are notched in such a manner as to divide the organ into three principal lobes. This configtn-ation permits it to be studied in two faces and a circumference. The anterior face is convex, perfectly smooth, and channeled by a wide 420 THE DIGESTIVE APPARATUS IN MAMMALIA. and deep notch formed for the passage of the posterior vena cava. This fissure extends directly from behind to before, and consequently slightly crosses the general direction of the liver ; near the point where the vena cava leaves the gland to traverse the diaphragm are seen the openings of the principal suprahepatic veins. The posterior face is equally smooth and convex, and has also a fissure by which the vena portse and the hepatic artery and nerves enter, and by which the biliary ducts emerge from the liver. This groove is slightly concave towards the left, and follows the direction of the liver in proceeding obliquely downwards, backwards, and to the left. The circumference may be divided into a superior or left, and an inferior or right border, united at both extremities by the ellipsis formed by the liver. The superior border presents, in jiroceeding from right to left : 1, The insertion of the ligament of the right lobe ; 2, The origin of the fissure for the vena cava ; 3, A notch for the oesophagus ; 4, The insertion of the left ligament. The inferior border is sharp, and otfers two deep notches, which divide the liver into three lobes : a superior or right, an inferior or left, and an intermediate one. The rir/ht lobe is usually of medium volume, and has above, on its posterior face, an appendix in the shape of a small secondary lobule of a triangular form, whose base responds to the com- mencement of the portal fissures : this is the lobus Spigelii. The left lobe is nearly always the largest. The middle lobe, the smallest of the three, is itself divided by secondary notches into several digitations or lobules. Belations. — Viewing the organ in position, in order to study its general relations, it is found that the anterior face is apj^lied against the diaphragm — a disposition which augments its convexity in diminishing that of its pos- terior face ; and that the latter is in contiguity with the stomach, the duodenum, and the diaphragmatic curvature of the colon. The connections proper to each lobe are observed to be as follows : I, The middle lobe responds to the centre of the aponeurotic portion of the diaphragm ; 2, The left lobe touches the left and inferior part of this aponeurosis, and is prolonged to the cori'csponding point of the fleshy peripheral band of that muscle ; 3, The right lobe is in contact with the right and superior part of the muscle ; its upper border touches the right kidney ; the pancreas rests against its base, on the posterior face. Mode of attachment. — The liver is suspended to the sublumbar wall of the abdomen by the large blood-vessels which enter its fissures, and it is also fixed to the posterior face of the diaphragm by four particular bands. One of these is carried from the anterior face of the liver to the phrenic centre, and appears intended to oppose total displacement of the organ ; the other three belong to each particular lobe. A. The ligament of the anterior face of the liver (or coronary ligament) comprises two series of very short aponeurotic fibres, which, arising from the two borders of the vena cava fissure, go to be fixed to the posterior face of the phrenic centre. The peritoneum is folded over it on each side in passing from the diaphragm to the liver The adherence of these fibres to the walls of the vena cava is extremely close ; and the vena cava itself, being thus in a manner united to the tissue of the liver, it happens that the union of the anterior face of the viscus wdth the phrenic centre could not be more solidly established. B. The ligament of the left lobe is a wide peritoneal fold, between the two layers of which are some fasciculi of w^hite fibrous tissue. It is detached ORGANS ANNEXED TO THE ABDOMINAL DIGESTIVE CANAL. 421 from the aponeurotic centre, to the left of the oesophageal orifice, and is inserted into the left part of the superior border of the liver. C. The ligament of the right lobe is a fold analogous to the preceding, but much shorter, and whose origin, placed very high and near the sub- lumbar parietes, is partly covered by the right kidney. It is inserted into the § si « 5 s W « o Eh '^ ... ^ S3-- f. S -^ t> ^ bfl iJ (N 2 o .:; Q '- 3 ■" superior border of the viscus, and sends a small layer to the lobus Spigelii ; most frequently, hoAvever. this lobule is sustained by a special peritoneal frsenum, given off from the anterior border of tlie kidney. D. The ligament of the middle lobe (the longitudinal, broad, falciform, or suspensory ligament) is a falciform and vertical serous layer, whose adherent 30 422 THE DIGESTIVE APPARATUS IN MAMMALIA. border is attached, almost in the median plane, to the posterior face of the diaphragm, and even to the inferior abdominal parietes. At its free border is a fibrous cord (the round ligament), formed, by the obliteration of the fcetal umbilical vein. By its upper part, it penetrates a secondary notch in the middle lobe, and is prolonged on the anterior face of this to tlie point where the vena cava traverses the diaphragm. Structure. — As elements in its structure, the liver offers for study : 1 , A serous membrane ; 2, A fibrous capsule ; 3, The proper and fundamental tissue of the organ. 1. Serous Membrane. — This membrane is only an expansion of the peri- toneal bands or ligaments already described, and of which the two, on arriving at the organ, separate to become developed on its surfaces, and to completely cover it, except in the anterior and posterior fissures. 2. Fibrous, or Glisson's Capsule. — This, the proper envelope of the liver, is formed by a very fine fibrous membrane, closely adherent to the preceding layer on the one side, and to the tissue of the liver on the other. It penetrates the substance of that tissue in passing around the vessels lodged in the posterior fissure, and from its inner face it sends a multitude of lamellar partitions, which separate the hepatic granulations, and form a veritable framework in the interior of the organ. The presence of this capsule has been denied, but its existence is not to be doubted in all the domesticated animals ; it is particularly well developed in Ruminants. 3. Proper Tissue of the Liver. — The proper substance of the liver is distinguished by its bluish-brown or violet hue, the shades of which vary much according to the subjects. It is heavy, compact, and so friable that it is crushed by the most moderate pressure. It is composed of polyhedric granulations from l-20th to 1-lOth of an inch in diameter, which are readily enough distinguished from one another through the peritoneum on the surface of the organ, particularly when the septa thrown in between them from Glisson's capsule are hypertrophied from some slight chronic irritation. Sometimes the hepatic lobule is uniform in colour throughout ; often it shows a red central point, with a yellow circle around it, and an interrupted red rin" circumscribing this again, and which communicates with a similar circle belonging to the adjoining lobules, so as to compose a network at the surface of the gland ; at other times the lobules are yellow at the centre and red at the circumference. All these appearances, the study of which at one time was considered of much importance, are uncertain, and may vary in a thousand ways, in combining with one another ; so that they really demand but little attention, due as they are to the greater or less degree of plenitude of the different vessels entering the lobule. As the liver is composed of lobules placed beside each other, we will describe one ; as when its structure is well known, we will be familiar with the organisation of the entire organ. In a hepatic lobule we find : 1. Hepatic (or hiliary) cells ; 2, Biliary canal- iculi (or ducts); 3, Afferent vessels; 4, An efferent vessel; 5, Ltjmphatics ; 6, Connective tissue. Hepatic cells. — These are polygonal or round, and much resemble squamous epithelium ; their diameter varies from l-500th to l-200th of an inch. They are composed of a thin enveloping membrane and yellow- coloured contents. The latter comprise one or two nuclei with nucleoli, coloured granules, biliary matter, a small mass of a substance which has been ORGANS ANNEXED TO THE ABDOMINAL DIGESTIVE CANAL. 423 Fio;. 212. studied by Bernard and Schiflf, and named " animal amidon ;" and, lastly, adipose granules, whose volume and quantity vary with the condition of the animals, or the period of digestion at which the liver has been removed. The hepatic cells are situated in the network formed by the vessels of the lobule, and constitute its principal portion. Hepatic Ducts. — Destined to carry away the bile secreted in the interior of the hepatic lobule, the bili- ary ducts iorm around it a kind of girdle that accompanies the interlobular branches of the vena portfe. Within and with- out, this girdle sends off small pz'olongments : the first bring it into communication with the ducts of the neighbouring lobules; the second enter the substance of the lobule and are soon lost. The wall of the biliary ducts is a thin amorphous membrane, lined by polygonal cells, smaller than the hepatic cells. The origin of the biliary or hepatic ducts in the interior of the lobules is still a vexed question in histology. It was believed, and some authorities still believe, that the ducts terminate in pouches, at a short distance from the periphery of the lobule. But it has been remarked that an injection introduced by the ductus choledochus does not remain near the periphery of the lobule, but, on the contrary, penetrates to its centre by passing between the hepatic cells ; and from this it is admitted that the hepatic ducts fur- nish a very fine network around each of the cellular elements of the liver (Fig. 213). Nevertheless, there are histologists who do not share in this opinion, who assert that these terminal ducts have no proper walls, and that the supposed networks they form is only a simple system of intercellular spaces distended by the injection. Afferent vessels. — These are the branches of the portal vein and hepatic artery. The portal vein, after reaching the interior of the liver, divides into gradually decreasing vessels, until it terminates by forming the interlobular or subhepatic veins. These vessels surround the lobule, communicate with the neighbouring interlobular veins, and give off a large number of twigs to the interior of the lobule, where a, Capillaries of the biliary they anastomose, and constitute the hepatic capillary ^^^f; ^' |?^P.^,^'''J^'^p*' plexus. The hepatic artery furnishes ramuscules, piUary Wood-vessel's. which mix with the ramifications of the portal vein in the (vaginal) plexus. The principal branches of the latter are all A. Portion of a hepatic column, showing its compo- nent secreting cells ; B, Secreting cells detached ; a, In their normal state ; b, A cell more highly magnified, showing the nucleus and distinct oil- particles ; c. In various stages of fatty degenera- tion. 213. BILIARY CAPILLARIES OF THE rabbit's liver. PART OF A LOBULE, SHOWING THE ARRANGE- MENT OP THE BILIARY DUCTS IN RELATION TO THE HEPATIC CELLS. 424 THE DIGESTIVE APPAEATUS IN MAMMALIA. directed from the periphery towards the centre of the lobule, where they unite to form the aiferent vessel. It results from this arrangement that the hepatic cells which fill the spaces ^'S- 214. between the vessels are placed in radiating series. Efferent series. — Situated in the centre of the lobules, this vessel receives all the ramifications of the capillary plexus, and is named the intralobular or central supra- hepatic vein. It is voluminous, and communicates with the other intralobular veins. (These intra- lobular veins terminate in the larger trunks that run along the bases of the lobules, and are named the siiblohular veins.) Lymphatics. — In a hepatic lo- bule are found very fine lymphatic vessels that sui-round the branches of the hepatic plexus, where they form the lymphatic vaginae, or canals which contain the blood- vessels. Connective tissue. — The intra- lobular connective tissue is scanty, the lobule being almost entirely composed of cells or capillaries ; so that only some trabeculse exist around the lymphatic sheaths. There is, however, a larger quantity in the inter- lobular spaces ; and in some '^' " '■ animals — especially the Pig — Glisson's capsule sends somewhat thick lamellae of connective tissue between these lobules. ExcRETOEY Apparatus. — This is very simple in Soli- pods, and is composed of a vessel named the ductus chole- dochus, resulting from the luaion of several trunks lodged in the posterior fissure of the liver, and which come from the tliree lobes. Traced in the substance of the hepatic tissue, these branches divide into more and more attenuated ramuscules that arise from the periphery of the lobules, and are continuous with the biliary ducts that envelop and penetrate these. Course. — At its exit from the liver, the ductus choledochus is placed between the layers of the gastro-hepatic omentum, and ascends to the wall of the duodenum, which it passes through at about six inches from the pylorus, HORIZONTAL SECTION OF THREE SUPERFICIAL LOBULES, SHOWING THE TWO PRINCIPAL SYSTEMS OF BLOOD-VESSELS. a, a, Intralobular veins, terminating in the hepatic veins; b, b, Interlobular plexus, formed by branches of the portal vein. SECTION OF A SMALL PORTION OF THE LIVER OF A RABBIT, WITH THE HEPATIC OB INTRALOBULAR VEINS INJECTED. OBGANS ANNEXED TO THE ABDOMINAL DIGESTIVE CANAL. 425 along with the principal pancreatic duct. The orifices of these two canals are surrounded by a circular mucous fold {ampulla of Vafer), which is usually very prominent, and acts as a valve in preventing the entrance of alimentary substances into the apertures it encircles ; this office it fills so well, tliat it will not even allow the aii- with which the duodenum is inflated to pass mto the ducts. Fig. 216. EXCRETORY APPARATUS OF THE HORSE'S LIVER. 1, Left lobe of the liver; 2, Middle lobe; 3, Right lobe; 4, Lobule of Spi^rel ; 6, Posterior vena cava at its entrance into the liver ; 7, Vena porta; ; 8, Ductus oholedochus ; 9, Pancreatic duct ; 10, Common entrance of these two ducts into the small mtestine. There enter into the structure of the ductus choledochus: 1, A fibrous membrane, which some anatomists believe contains unstriped muscular fibres ; 2, Cylindrical epitJieUum; 3, Numerous racemose glands, opening on its inner surface by very small orifices. Vessels and Nerves of the Liver.— The blood-vessels are the hepatic artery, portal vein, and suprahepatic veins. The liepatic artenj is a branch of the coeliac, and enters the gland by the posterior fissure, in company with the portal vein and ductus choledochus. In the liver it divides into very fine ramifications which join the intra- lobular plexus, anastomose on the surface of the biliary ducts, or expand either on the serous membrane, or in the walls of the portal vein. The portal vein is the functional vessel of the liver. It reaches that organ by the posterior fissure, and Glisson's capsule accompanies its rami- fications as far as the hepatic lobules, where they form the plexus of sub- hepatic veins. The suprahepatic (or sublobular) veins are so named because they gain the antero-superior face of the viscus to open into the posterior vena cava. They carry away the blood that has been brought by the portal vein and hepatic artery. Their origin is due to the union of the intralobular veins, which make a passage through the hepatic tissue with which their walls are immediately m contact, gradually join each other, and enter the posterior vena cava on its way through the anterior fissure of the liver. The number of trunks (hepatic) entering this vessel is considerable, but the majority are very small ; the principal confluent is placed at the anterior extremity of the fissure. The lymphatics form a fine superficial plexus, easy to inject ; with deeper 426 TEE DIGESTIVE APPARATUS IlS MAMMALIA. networks placed around tlie vessels that penetrate by the posterior fissure. In the lobules they are disposed as described above. Joined to the lymphatics of the stomach, they constitute a single trunk that goes to the sublumbar receptacle. The nerves are more particularly derived from the solar plexus, although the pneumogastric and diaphragmatic also supply filaments to the liver. They interlace around the hepatic artery and portal vein ; their mode of termination is unknown. Functions. — The most important considerations are attached to the study of the functions of the liver ; but we cannot enter into them in detail with- out going beyond our subject. Besides, there is yet much to be learned respecting them. The liver is a biliary and glycogenetic gland. It secretes the bile at the expense of the blood of the portal vein, which comes from the intestinal tunics charged with the assimilable substances absorbed by the veins from the villi. This fluid is submitted to modifications in the interior of the liver, by which it is relieved of certain matters, while at the same time it furnishes the biliary secretion. The bile is, therefore, in this respect an excrementitious secretion ; though all its elements are not thrown off, some of them acting on the alimentary substances, and others being absorbed. From the most recent researches, it would appear that it has a share in the purification of the blood, in digestion, and in calorification ; in the latter especially, as its absorbed elements are very rich in carbon and hydrogen, bodies eminently adapted for the production of animal heat. The liver is also a glycogenetic gland, this function having been demon- strated to pertain to it by Bernard. The sugar formed in the liver finds its way into the blood, and leaves the organ by the suprahepatic veins. It is elaborated in the hepatic cells by the transformation of the substance known as "animal amidon," which is brought into contact with a kind of diastase that exists with it in their interior. Lastly, it is also believed that the liver is a hcematogenetic organ, the red globules being formed in its mass at the expense of the fibrine of the blood that passes through it. It will thus be seen that the liver furnishes two very different products- bile and sugar. The knowledge of this fact, combined with the internal arrangement of the organ, has led some anatomists to consider the organ as two glands reciprocally contained within each other. But this hypothesis loses its value if it be admitted that the hepatic ducts pass between the cells to the centre of the lobule, and that in this portion they are destitute of epithelium. It is therefore probable that the sugar and bile are produced in the large hepatic cells, and that the first passes into the veins, while the second is poured into the biliary ducts. In Solipeds, the secretion of bile, though most active during the digestive period, yet goes on in a continuous manner. (Certain deductions of a pathological kind are based upon the foregoing anatomical facts, and have an important bearing with regard to comparative pathology. They have been pointed out by Wilson, and are as follows : — Each lobule is a perfect gland ; its structure and colom- are uniform, and it has the same degree of vasciilarity throughout. It is the seat of a double venous circulation ; the vessels of the one (Jiepatic) being situated in the centre of the lobule, and those of the other {portal) in the circumference. Now the colour of the lobule, as of the entire liver, depends chiefly on the OBGANS AXXEXED TO THE ABDOMINAL DIGESTIVE CAXAL. 427 proportion of blood contained within these two sets of vessels ; and so long as the circulation is natural, the colour will be uniform. But the instant that any cause is developed which shall interfere with the free circuhi- tion of either, there will be an immediate diversity in the colour of the lobule. Thus, if there be any impediment to the free circulation of the venous blood through the heart or lungs, the circulation in the hepatic veins will. be retai-ded, and the sublobular (or supralubularj and intralobular veius will become congested, giving rise to a more or less extensive redness in the centre of each of the lobules; while the marginal or non-congested portion presents a distinct border of a yellowish white, yellow, or green colour, according to the quantity or quality of the bile it may contain. ■' This is ^passive conrjestion' of the liver, the usual and natural state of the organ after death ;" and, as it commences «-ith the hepatic vein, it may be called the first stage of hepatic venous congestion. But if the causes which produced this state of congestion continue, or be from the beginning of a more active kind, the congestion will extend through the lubular venous plexuses " into those branches of the portal vein situated in the interlobular jissures, but not to those in the spaces, which being larger, and giving origin to those in the fissures, are the last to be congested.'' In this second stage the liver has a mottled appearance, the non-congested substance is arranged in isolated, circular, and ramose patclies, in the centres of which the spaces and parts of the fissure are seen. This is an extended degree of hepatic venous congestion ; it is " active congestion " of the liver, and very commonly attends disease of the heai't and lungs. These are instances of partial congestion ; but there is sometimes general congestion of the organ. "In general congestion the whole liver is of a red colour, but the central portions of the lobules are usually of a deeper hue than the marginal portions.") Development — The liver of the foetus is remarkable for its enormous development. Its function commences early, for at birth the intestines are filled with meconium, a product of the biliary secretion. A more detailed description will be given when the general development of the foetus comes to be studied. 2. The Pancreas. This organ has the greatest resemblance to the salivary glands in its structure and physical properties ; and for this reason it has been named the abdominal salivary gland. Situation. — It is situated, in the sublumbar region, across the aorta and posterior vena cava, in front of the kidneys, and behind the liver and stomach. Its weight is seventeen ounces. Form and Belations. — The pancreas is rather irregular and variable in form, according to the kind of animal. Flattened from above to below, traversed obliquely from its inferior to its superior face by an opening for the passage of the portal vein, and which is named the pancreatic ring, this gland is sometimes triangidar, sometimes oblong, and curved on itself : it is under the latter form that we will notice it. It5 faces present the lobulated aspect of salivary glands. The superior adheres by cellular tissue to the aorta, posterior vena cava, coeliac trunk, solar plexus, splenic vessels, and the right kidney and supra renal capsule ; it is covered by the peritoneum for a certain portion of its extent. The inferior responds to the base of the cfecum and the foiu'th portion of the 428 THE DIGESTIVE APPARATUS IN MAMMALIA. colon, througli the medium of a thick layer of cellular tissue. The anterior border, concave and undulating, is in contact with the duodenum and the left extremity of the stomach. The posterior is very convex, especially to the right, and near its middle jiresents a notch for the reception of the portal vein before its entrance into the ring. The right extremity (or head), the thinnest, adheres to the duodenum, and shows the excretory ducts of the gland. The left is carried towards the base of the spleen, in passing between the left extremity of the stomach and the kidney of the same side. Structure. — It resembles the salivary glands, except in its epithelium. This, instead of being simple polygonal cells lining the thin, structureless membrane of the ultimate follicles, is very granular, and fills these cavities. The gland receives its blood by the hepatic and great mesenteric arteries ; the nerves come from the solar plexus. Excretory apparatus. — The liaucreas has two excretory ducts : a principal, described by Wirsung, whose name it bears, and an accessory. The duct of Wirsung, lodged in the substance of the gland, but nearer the superior than the inferior face, at first comprises two or three thick branches, which soon unite to form a single trunk that emerges from the pancreas by the left extremity of the organ. Larger than the ductus choledochus, it opens, as already stated, at the same part of the duodenal surface. The accessory duct (ductus pancreaticus minor) is much smaller ; it leaves the principal trunk, receives some branches in its passage, and opens alone into the small intestine, directly opposite the duct of Wirsung. The ductus choledochus and the duct of Wirsung do not pass directly through the wall of the intestine, but obliquely, like the entrance of the ureters into the bladder. They open in the middle of a circular valve — the ampulla of Vater. This ampulla is limited by a thick primary mucous fold, and within this is a second, thinner, beneath which the ductus chole- dochus opens ; at the bottom of the space circumscribed by this second fold, beneath a free mucous lip, is seen the duct of Wirsung. Functions. — From the researches of Bernard, it appears established that the fluid secreted by the pancreas emulsifies fatty matters and renders them absorbable. 3. The Spleen. The spleen differs from glands not only in the absence of an excretory duct, but also in the other details of its organisation. It has been consi- dered as a vascular gland, whose uses are not yet determined in a precise manner. Situation. — It is situated in the diaphragmatic region, close to the left hypochondriac, and appears as if suspended in the sublumbar region, as well as at the great curvature of the stomach. Form — Direction — Relations.— The spleen is falciform, and directed obliquely downwards and backwards. It has two faces, two borders, and a point. The external face is in relation with the muscular portion of the diaphragm, and is moulded to it. The internal, slightly concave, touches the large colon ; it has sometimes a small lobule, or offers traces of lobula- tion. The posterior border is convex, thin and sharp. The anterior, thicker, concave, and bevelled at the expense of tlie internal face, is channeled by a slight longitudinal fissure which lodges the splenic vessels and nerves ; it OBGANS ANNEXED TO TEE ABDOMINAL DIGESTIVE CANAL. 429 receives the insertion of the great mesentery, by which it is held to the greater curvature of the stomach. The base, or superior ex-fremity, is thick and wide, and responds to the left kidney and the corresponding extremity of the pancreas ; it shows the insertion of the susjjensory ligament. The point, or inferior extremity, is smooth and thin. Weight. — The average weight is 32 ounces ; but it is sometimes of enormous dimensions — as much as three or fom* times its normal volume. Mode of attachment. — The sjdeen is a floating organ, whose displacements are limited by a suspensory ligament, and the great (or gastro-splenic) omentum. The first is a peritoneal fold which proceeds from the anterior border of the left kidney and the sublumbar wall, and is strengthened by the elastic fibrous tissue comprised between its two layers. It is fixed to the base of the spleen, and is confounded, inwardly, with the great omentum. The latter is already known as proceeding to the colon, and in its passage becoming attached to the splenic fissure, whence it extends over the sur- face of the organ to form its serous covering. Structure. — The tissue of the spleen has a violet-blue coloiu-, sometimes approaching to a red hue ; it is elastic, tenacious, and soft, yields to the pressure of the finger, and retains the imprint. Enveloped externally by the peritoneum, its substance includes a fibrous frameicork, splenic pulp, Mal- pighian corpuscles, vessels, and nerves. Serous membrane. — This is developed over the whole surface of theor^an, except in the fissui'e of the anterior border Its internal face adheres most intimately to the proper tunic of the spleen. It is only an expansion of the serous bands which limit the movements of the viscus. Fibrous frameicorli. — Under the peritoneal membrane is a thick, resisting, fibrous timic, roughened and granular on its exterior, and sending from its deep face into the interior of the mass a multitude of prolongations called trabeculce, which cross in all directions, forming a cellular network whose numerous narrow meshes contain the other elements of the organ. In washing a morsel of spleen in a jet of water, the latter are removed, and the outlines of this fibrous structure are fully exposed. If a stream of water is passed through the splenic artery, the same result will be arrived at. Kolliker has found in the proper tunic of the spleen, and in its trabeculfe, a particular contractile tissue, the muscular cell-fibres, mixed with fasciculi of elastic or inelastic fibrous tissue. (The proper coat, the sheaths of the vessels, and the trabeculfe consist of a dense mesh of white and yellow elastic fibrous tissues, the latter considerably predominating. It is owing to the presence of this tissue that the spleen possesses a considerable amount of elasticity, admirably adapted for the very great variations in size that it presents imder certain circumstances. In some of the mammalia, in addition to the usual constituents of this tunic, are found numerous pale, flattened, spindle-shaped nucleated fibres, like imstriped muscular fibre. It is probably owing to this structure, that the sjdeen possesses, when acted upon by the galvanic current, faint traces of contractility.) Spjlenic pulp. — This name is given to a reddish pultaceous material, which partly occupies the aveolar framework formed by the intersections of the trabeculfe. It is sustained by a very delicate reticulum of connective tissue, and is composed of numerous elements, such as pigment granules, free nuclei, large cells with several nuclei, lymphoid elements, and blood- globules in a state of decomposition or transfoi-mation. These globules are free or enveloped in an albuminoid membrane. (The proper substance of the spleen consists of coloured and colourless elements. The coloured 430 THE DIGESTIVE APPARATUS IN MAMMALIA. Fis. 217. are composed of red blood-globules and coloured corjjuscles, either free or included in cells. Sometimes unchanged blood-discs are seen included in a cell ; but more frequently the included blood-discs are altered both in form and colour. Besides these, numerous deep-red, or red- dish-yellow, or black corpuscles and crystals, either single or aggre- gated in masses, are seen diffused throughout the pulp substance ; these, in chemical composition, are closely allied to the hsematine of the blood. The colourless ele- ments consist of granular matter; nuclei, about the size of the red blood-discs, homogeneous or gra- nular in structure ; and nucleated vesicles in small numbers. These elements form a large proportion of the entire bulk of the si^leen in well- nourished animals ; whilst they diminish in number, and occasion- ally are not found at all, in starved animals. The a2ii:)lication of chemi- cal tests shows that they are essen- tially a proteine compound.) Maljnghian corpuscles, — These are ccmtained, like the pulp, in the meshes of the fibrous framework, and are enveloped by this pulp. Scattered along the track of the small arteries, these corpuscles are visible to the naked eye, and appear as whitish closed sacs, cells, and nuclei floating in a plasma. The Malpighian corpuscles are constituted by the adven- titious tunic of the arteries, in which lymphoid ele- ments are accumulated at certain points. They are therefore allied to the closed follicles of the intestines, (These splenic or Malpighian corpuscles, are round,, whitish, semi-opaque bodies, glutinous in consistence, and disseminated throughout the sub- stance of the organ. They are more distinct in early than in adult life or old age, and vary con- siderably in size and number, From the manner CLE, FROM THE SPLEEN vo. whicli they are appended to the sheaths of the OF THE ox. smaller arteries and their branches, they resemble 1, External tunic, or mem- the buds of the moss-rose. Each consists of a mem- brana propria , 2 Gran- branous capsule, composed of fine pale fibres inter- uiar contents: o, Part ■, . • n t ,• mi i i i i -t of a small artery • 4 lacmg in all directions, i he blood-vessels ramiiy Its sheath, derived from ing on the surface of the corpuscles, are the larger the external tunic of the ramifications of the arteries to which the sacculus spleen, with which the jg connected, and also of a delicate capillary plexus, necSr^' '' "''' ^"^"l^i" *" t^^*^* surrounding the vesicles of other glands. These vesicles have also a close relation with the veins, and the vessels begin on the surface of each vesicle through- out the whole of its circumference, forming a dense venous mesh in which BRANCH OF SPLENIC ARTERY WITH ITS RAMI- FICATIONS STUDDED WITH MALPIGHIAN COR- PUSCLES, Fis, 218, A SINGLE SPLENIC CORPUS- ORGANS ANNEXED TO THE ABDOMINAL DIGESTIVE GANAL. 431 each of these bodies is inclosed. It is probable that, from the blood con- tained in the capillary network, the material is sepai'ated which is occa- sionally stored up in their cavity ; the veins being so placed as to carry off, under certain conditions, those contents that are again to be dis- cbarced into the circulation. Each capsule contains a soft, white, semi-fluid substance, consisting of granular matter, nuclei similar to those found in tlie pulp, and a few nucleated cells, the composition of which is apparently albuminous. These bodies are very large, after the early periods of diges- tion, in well-fed animals, and especially those fed upon albuminous diet. In starved animals, they disapj^ear altogether.) Arteries. — These emanate from the splenic artery at different elevations, and plunge into the tissue of the spleen, preserving their reciprocal independence. Their terminal ramifications do not open, as has been said, into venous sinuses, but into minute tufts of capillaries, wLich traverse the splenic pulp, to be continued by the venous network. Veins. — All the venous branches of the spleen open into the splenic vein, and are lodged with the corresponding artery in the fissure of the organ. Traced from their commmencement, they are seen to gradually lose their constituent membranes, and to open into sinuses which are only lined by the epithelium of the vessels. It is in these sinuses that the network of venous capillaries which succeed the arterial capillaries, originates. Lymphatic vessels. — These are found on the external surface of the organ, and along the track of the blood-vessels. (They invest these with a distinct sheath, between which and the parietes of the vessels numerous lymph corpuscles may be fomid.) Nerves. — They are derived from the solar plexus, and enveloping the splenic artery, with it enter the spleen. (They appear to be very large, but this appearance is due to the great proportion of ordinary fibrous tissue investing them.) From what has been said above respecting the arrangement of the splenic arteries and veins, it will be perceived that the areolfe formed by the trabecidae of the fibrous framework contain the pulp, and are not in direct communication with the arterial capillaries. Such an organisation belongs to erectile tissues. The arteries communicate with the veins proper by venous canals channeled in the splenic pulp, and are lined only by ellip- tical cells. These venous canals are extremely dilatable, especially in the Horse. When the splenic vein is inflated, their walls separate and press back the pulp, they become considerably enlarged, and distend the cells of the fibrous structm-e, but the air does not reach the interior of these cells. FcN'CTioys. — Nothing precise is known regarding the functions of the spleen : though they must be of very secondary importance, because animals in which the organ has been extirpated, and which have recovered from the consequences of the operation, have continued to live in apparent good health. Numerous hypotheses have been formed on this subject , two of which, foimded on the study of the anatomical peculiai'ities of the spleen tissue, and on exact physiological observations, are as follows : 1, The spleen is a diverticidura for the portal vein ; 2, The red globules are destroyed in the spleen. With regard to the first hypothesis, it is evident that, owing to the presence of the venous sinuses already mentioned, and their great dilata- bility, as well as to the elasticity and contractility of the spleen tissue, the organ is favourably constructed to act as a blood reservoir-. M. Goubaux, 432 THE DIGESTIVE APPARATUS IN MAMMALIA. on the other hand, has demonstrated that there is always an augmentation in the spleen's volume when an animal has ingested large quantities of water, the consecutive absorption of which determines a certain tension in the portal venous system. The second opinion, emitted by Kolliker, is founded on the existence in the splenic pulp of blood-globules in a state of decomposition, and in the analyses made by J. Beclard of the blood in the splenic vein, which have proved that there is a notable diminution in the proportion of globules. It is to be remarked that, in the researches undertaken to discover the functions of the spleen, account has not been taken of the connections existing between this organ and the great omentum in the majority of mammals, and which testify that the spleen is only, properly speaking, a vascular appendage placed on the track of this omentum. But the uses of this vast peritoneal fold are themselves little understood. Might they not be included with those which are presumed to belong to its appended organ '^ DIFFERENTIAL CHARACTERS IN THE ANNEXED ORGANS IN THE ABDOMINAL PORTION OF THE DIGESTIVE CANAL IN OTHER THAN SOLIPED ANIMALS. The important differences these organs offer in the domesticated mammals belong more particularly to the liver. 1. Liver. — In the domesticated mammals other than Solipeds, the liver exhibits vari- ations in form, volume, and position, which have no influence on its organisation : so tliat the study of these possesses but a mediocre attraction. This is not so, however, with re- gard to the excretory apparatus, the arrangement of which is complicated, and becomes very interesting. The biliary duct, in fact, on leaving the fissure of the portal vein, and before reaching the intestine, gives rise to a particular conduit which is detached at an acute angle, and which, after a course of variable length, according to the size of the animal, becomes dilated into a vast sac, the so-called gall-hladder. In all treatises on anatomy, the special conduit is designated the cystic duct, that portion which precedes its origin being named the hepatic duct ; while the appellation of ductus communis choledochus is reserved for the section which goes to the intestine. But these distinctions are vicious, and we limit ourselves to the recognition of : ( a) A ductus choledochus exactly like that of Solijjeds, and like it extending from the posterior fissure, where it originates by the union of several branches, to the duodenum ; and {b) a cystic duct, which branches suddenly into the choledic duct, and terminates in the gall- bladder. a. The gall-hladder is a reservoir with membranous walls, in which the bile accumu- lates during the intervals of digestion. This sac, lodged wholly, or in part, in a fossa on the posterior face of the liver, is oval or pyriform, and presents a fundus and nech. Its parietes comprise three tunics : an external, of peritoneum : a middle, formed of dartoid tissue ; and an internal, or mucous, continuous with that of the various biliary ducts. b. The cystic duct extends in a straight line from the neck of the gall-bladder to the choleilic duct. It adheres intimately to the tissue of the liver, and does not exhibit, in- ternally, the spiral valves which have been described in Man. In opening it longitudi- nally, there ai-e discovered, at least in Ruminants and the Camivora, very small orifices which pierce the wall adherent to the tissue of the liver : these are the openings of several minute but particular biliary canals, named the hepatico-cystic ducts. c. The ductus communis choledochus comports itself exactly as in Solipeds. It is much wider than the cystic duct, and opens sometimes alone, sometimes with the pan- creatic canal, into the duodenum in a manner which, up to a certain point, reminds one of the mode of termination of the ureters. Instead of passing perpendicularly across the intestinal parietes, it first pierces the muscular layer, follows for a short distance between it and the mucous membrane, and then opens on the internal face of the latter by an orifice which is encircled by a valvular fold, as in the Horse. Such is the excretory apparatus belonging to the liver in animals provided with a gall-bladder. In these animals the biliary secretion is certainly continuous, as in the Horse ; but in the intervals of digestion the bile, instead of flowing directly on to the intestinal surface, passes into the gall-bladder by the cystic duct, and there OBGANS ANNEXED TO TEE ABDOMINAL DIGESTIVE CANAL. 433 accumulates. When digestion commences again, this reserve of bile is thrown into the ductus choledochus by the contraction of the muscular fibres of the cyst, and by the pressure of the abdominal viscera ; it meets that which comes directly from the liver, and with it is carried to the duodenum. We will now glance at the particular arrangement of this viscus in each species. In the Ox, the liver is entirely confined to the right diaphragmatic region. It is thick, vohuninous, and scarcely notched at its peripheiy ; so that it is difficult, if not impossible, to distinguish three lobes in it, the lobus Spigelii alone being detached from the mass of the organ. The gall-bladder, fixed towards the superior extremity, is nearly always floating ; near its neck it receives the insertion of several large conduits, which come directly from the up^jer part of the liver. The ductus choledochus opens alone at Fis, 219. LIVER OP THE DOG, WITH ITS EXCRETORY APPARATUS. D, Duodenum and the intestinal mass; p. Pancreas; r, Spleen; e, Stomach; /, Rectum; R, Right kidney; B, Gall-bladder; ch, Cystic duct; ff. Liver; f'. Lobe of the liver, prepared to show the distribution of the vena porta; and hepatic vein ; VP, Vena portse ; Vh, Hepatic vein ; d, Diaphragm ; VC, Vena cava • C, Heart. a great distance from the pylorus ; M. Colin has found it to be 24i inches in one cow, and 29^ inches in another. In the Sheejj and Goat, the form and position of the liver diflera but little from that of the Ox. The ductus choledochus, however, imites with that of the pancreas, and terminates at 12 to 16 inches from the pylorus. In the Pig, the liver has three well-marked lobes ; the middle carries the gall- bladder. The ductus choledochus opens alone at 1 or 1 J inches only from the pylorus. In the Dog and Cat, the liver is very voluminous, is deeply notched, nnd is divided into five principal lobes. The middle lube has the gull-bladder attached to it, and gives it complete lodgment in a fossa. 434 TEE DIGESTIVE APPABATUS IN MAMMALIA. In the Dog, the ductus choledochus, joined to a small branch from the pancreatic duct, enters the intestine at a variable distance from the pylorus, depending upon the size of the animal, but usually between 1^ and 4f inches. In the portion comprised between tlie intestine and the origin of the cystic duct, it receives several biliary canals of some- what considerable diameter. In the Cat, the ductus choledochus is most frequently inserted from about 1 to l^ inches from the pyloric orifice ; it opens immediately along- side the pancreatic duct when it does not join it. 2. Pancreas. — In the Ox. the pancreas is not placed across the sublumbar parietes, but is comprised between the layers of the mesentery, to the right of tlie great mesenteric artery. The excretory duct is single, and opens into the small intestine at from 14 to 16 inches beyond the ductus choledochus. In the Sheep and Goat, there is the same general arrangement, but the excretory duct opens with that of the liver. In the Pig, this duct is inserted at from 4 to 6 inches behind the ductus choledochus. The pancreas of the Dog is extremely elongated, and included between the layers of the mesentery which sust;iin the duodenum. It is curved at its anterior extremity, behind the stomach, to one side of the median line. Its excretory du't, usually single, pierces the intestinal membranes 2 inches beyond the hepatic duct (Fig. 219, m). Except in the mode of insertion of the excretory duct, which has been described in noticing the ductus choledochus, the pancreas of the .Cat comports itself exactly like that of the Dog. 3. Spleen. — In Ruminants, the spleen is nut supported by the great omentum, but adlieres to the left side of the rumen and diaphragm. It is not falciform, and its breadth is the same througliout its extent. In the Carnivora, it is suspended to the great omentum at a certain distance from the left sac of the stomach. It is irregularly falci- form, its point is less acute than in Solipeds, and is directed upwards. COMPARISON BETWEEN THE ANNEXED ORGANS OP THE ABDOMINAL PORTION OF THE DIGESTIVE CANAL IN MAN AND TBOSE OF ANIMALS. 1. Liver. — Like that of Euminants, the human liver is situated in the right excava- tion of the lower face of the diaphragm. Its direction is nearly horizontal ; its shape is oval, and its average weight from forty-nine to fifty-three ounces. The posterior border is thick and round ; the anterior border and extremities thin and sharp. The upper lace, which in expiration asceuds to the fourth rib, is divided nito two portions or lobes — right antl left, by the falciform Fio-. 220. ligament; it is smooth and con- vex. The inferior fiice has three furrows, or fossae : two longitu- dinal, united by a transverse, re- sembling altogether the letter H. The transverse furrow represents that on the posterior aspect of the liver of animals, and its des- tination is the same. The right long tudinal furrow lodges the obliterated umbilical vein ; the left, well marked before and be- hind, lodges the gall-bladder in front, and the inferior vena cava behind. This face has four lobes, the right and left, and two middle lobes. In front of the '' transverse furrow is the lobus UNDER SURFACE OF THE HUMAN LIVER. quadratus, and behind the same 1, Right lobe; 2, Left lobe; 3, Lobus quadratiis; 4, fissure is the lobus Spigelii. Lobus Spigelii : 5, Lobus caudatus ; 6, Longitudinal On the lower face of the right fossa ; 7, Pons hepatis ; 8, Fossa of ductus venosus ; lobe are three depressions : an 9, Inferior vena cava; 10, Gall-bladder; 11, Trans- anterior or impressio colica ; a verse fossa; 12, Vena cava; 13, Depression corres- deep middle one, impressio vesicm ; ponding to the curve of the colon; 14, Double and a small posterior one, which depression produced by right kidney and supra-renal receives the supra-renal capsules, capsule. impressio renalis. 2. Pancreas. — This organ is very elongated transversely, like that of the Dog and Cat. It is closely applied against the lumbar vertebrae, as in the Horse, but its anterior face is much more enveloped by tlie peritoneum Its right extremity rests on t!ie duodenum, while the left corresponds to THE DIGESTIVE APPARATUS IN BIRDS. 435 the spleen and left kidney. Its texture is consistent, and of a greyish-white colour. The duct of Wirsung terminates along with the ductus choledochus in the ampulla of Vater. 3. Spleen. — This is not falciform, but quadrangular; its inferior extremity is larger than the superior. It is attached to the stomach by the great omentum, and its inner face is divitled into two portions by a salient ridge ; a little in front of this is a fissure the hilam lienis, by which vessels enter it. CHAPTER III. THE DIGESTIVE APPARATUS OF BIRDS. Constructed on the same plan as tliat of Mammals, the digestive apparatus of Birds nevertheless oilers in its arrangement several important peculiarities, which will be hurriedly noticed in reviewing, from the mouth to the anus, its different sections. Month — The essentially distinctive character of the mouth of birds consi.>ts in the absence of lips and teeth, these organs being replaced by a horny production fixed to each jaw, and forming the salient part termed the beak. In the GaUinacx, the beak is short, pointed, thick, and strong, the upper mandible being curved over the lower. In Palmipeds, it is longer, weaker, flattened above and below, widened at its free extremity, and furnished within the mouth, on the borders of each mandible, with a series of thin and sharp txansverse laminae to cut the herbage. Tiie muscular appendage, or tongue, lodged in the buccal cavity, is suspended to a remarkably mobile hyoidean apparatus. Covered by a horny epithelium, and provided at its base with several papillre directed backwards, this organ always affects the form of the lower jaw : in Poultry it is like the barbed head of an arrow, the point being directed forwards ; in Pigeons this saggital form is still more marked ; in Geese and Duchs, on the contrai7, and in consequeuce of the wide shape of the beak, it has not this disposition, and is softer and more flexible than in the Gallinaose. With regard to the salivary glands annexed to the mouth, they are imperfectly developed, the presence of the fluids they secrete being less necessary in birds than iii Mammals, as the food is nearly always swallowed without undergoing mastication; consequently insalivation is all but useh ss. Gurlt^ speaks of a parotid gland situated beneath the zygomatic arch, whose duct opens into the mouth behind the commissure of the jaws. Meckel names this organ the angular gland of the mouth, and says that it is difficult to regard it as representing the parotids, any morethan the glands of the cheeks and lips. Duvernoy- categorically assimilates it to the latter. The sublingual glands lie in the median line throughout nearly their whole extent, and form an apparently single and conical mass, whose apex occupies the re-entering angle formed by the union of the two braiiches of the lower maxilla. According to Duvernoy, the submaxillary glands are represented by two very small organs situated behind the preceding. Their existence, however, is far from being general ; for among common poultry, the Turkey was thii only bird in which Duvernoy observed these submaxillary glands. Pharynx (Fig. 221, 2). — This cavity is not distinct from the mouth, the soft palate being entirely absent in birds. On its sraperior wall mav be remarked the guttural orifice of the nasal cavities : a longitudinal slit divided into two by the infi rior border of the vomer. Below is another less extensive slit, the entrance to the larynx, and which is remarkable for the complete absence of the epiglottidean operculum. OESOPHAGUS. — Tills canal is distinguished by its enormous calibre and great expansi- bility. Its walls are very thin, and contain in their substance lenticular glands, easily seen in an inflated cesophagus, in consequence of the tenuity and transparency of its textures. At its origin, the oesophageal canal is not separated from the pharynx by any constriction ; in its course it lies alongside the long muscle of the neck, and the trachea ; its terminal extremity is inserted into the first compartment of the stomach, or .succentric ventricle, alter entering the thorax and passing above the origin of the bronchi, between tlieir two branches. In Palmipeds, the resophagus is dilated in its cervical portion in such a manner as to form, wheu its walls are distended, a long fusiform cavity. ' Anatomic der Hausvogel.* Berlin, 1849. Cuvier. ' Anatomic Compare'e.' 2nd Edition. Pari?, 1836. 436 THE DIGESTIVE AFPABATUS IN BIEDS. Fiff. 221. GEKEKAL VIEW OF THE DIGESTIVE APPARATUS OF A FOWL. The abdominal muscles have been removed, as well as the sternum, heart, trachea, the greater portion of the neck, and all the head except the lower jaw, which has been turned back to show the tongue, the pharynx, and the entrance to the larynx. The left lobe of the liver, succentric ven- tricle, gizzard, and in- testinal mass, have been pushed to the right to exhibit the different portions of the alimen- tary canal, and to ex- pose the ovary and ovi- duct. 1, Tongue; 2, Pharynx "j 3, First portion of the oesophagus ; 4, Crop ; 5, Second portion of the oesophagus ; 6, Succen- tric ventricle ; 7, Giz- zard ; 8, Origin of the duodenum ; 9, First branch of the duodenal flexure ; 10, Second branch of the same , 11, Origin of the float- ing portion of the small intestine ; 12, Small intestine; 12', Terminal portion of this intestine, flanked on each side by the two caeca (re- garded as the analogue of the colon of mam- mals); 13, 13, Free extremities of the ce- cums ; 14, Insertion of these two culs-de-sac into the intestinal tube; 15, Rectum ; I'i, Cloaca; 17, Anus; 18, Mtseutery ; 19, Left lobe of the liver • 20, Right lobe; 21, Gall- bladder; 22, Insertion of the pancreatic and biliary ducts ; the two pancreatic ducts are the anteriormost, the cho- ledic or hepatic is in the middle, and the cystic duct is posterior; 23, Pancreas ; 24, Dia- phragmatic aspect of the lung; 25, Ovary (in a state of atrophy ; 26, Oviduct. THE DIGESTIVE AFPABATUS IN BIRDS. 437 In Gallmacv (Fi^j. 221. 3. 4, rt >. this dilataiion does not exist; but the oesophao:us presents in its course, and ininit diately before eiit( ring tlie chest, au ovoid membranous pouch named the crop (or unjliivieg.) In the oesophagus of the.se birds, then, wp find two distinct sections, joined end to end — one superior or cervical, the other inferior or thoracic, on tlie limit of wliich is the crop. The latter does not dilier in its structure from the oesophagus, and is a temporary reservoir for the food swallowed by the animal duriuLj its meal, and where it is softened by being impregnated with a certain quantity of fluid; afttr wliich it is passed into the succentric ventricle by the contractions of the 'jxtcrnal membrane of the crop, aided by a wide subcutaneous cervical muscle which covers tliat reservoir. In Pi(]eons, the crop is also present ; but it is divided into two lateral pouches, and exhibits glandular eminences towards the common inferior opening of these sacs into the oesophagus. " Otherwise, singular changes are observed in the apparent structure of its walls in the male as well as in the female, during incubation, or during the first weeks after hatching." (Hunter was the first to observe this ; — ' Observations on Certain Parts of the Animal Economy,' London, 1792). "At this period, the membranes of the crop become thickened ; the vessels, more numerous and more apparent, are redder, and the glands mtire developed. The intern.il surface is divided by folds or ridges, which cross each other, and form triangular meshes ; while an apparently milky fluid is poured out from the secret.)ry poris into the cavity of the crop. Pigeons exclusively nourish their young with this fluid dui'ing the first three days of their existence." ' Stojiach —The stomach presents numerous variations in birds. Its simplest form is seen in the heron, pelican, petrels, etc., where it is a single tac provided with a thick zone of glands around the entrance of the oesophagus, which secrete the gastric juice. But in the majority of tlie other species, and particularly in our domesticated birds, the disposition of the stomacii is modified and complicated ; the glandular zone destined for the gastric secretion forms a special compartment — the succentric ventricle, and this is followed by a second reservoir — tlie gizzard, which is remarkable for the strong muscular constitution of its walls. The first is also named the glandular stomach, and the second the muscular stomach. Glandular str»nach, or succentric ventricle (lyrovenfrictdus) (Fig. 221, 6). — This is an ovoid sac placed in the median plane of the body, between the two lobes of the liver, and beneath the aorta. Its anteiior extremity receives the insertion of the cesophagus; the posterior is continued by the gizzard The volume of this stomach is inconsiderable, and its cavity is very narrow; the aliment does not accumulate in it, but merely passes tlirougli, carrying with it the acid juice which afterwards dissolves its protein elements. Its ■walls have three tunics : an external or peritoneal ; a middle, formed of white muscular fibres, continuous with those of the cesuphagns; and an internal, of a mucous nature, per- forated by orifices for the passage of the gastric juice. Tiiese are small cylinders placed perpendicularly to the surface of the stomach, closely laid against one- another, like the microscopic glands of Lieberkiihn, and contained in the cellular layer uniting the inner to the middle tunic. The glandular structiu-e of this receptacle sufficiently demonstrates that it should be assimilated to the right sac of the stomach in Solipeds, and therefore must be regarded as the true stomach. Gizzard, OT muscular stomdch (ventricidus Indbostis) (Fig. 221, 7). — Much more volu- minous than the preceding, this stomach is oval in form, depressed on each sitie. and situated behind the liver, being partly covered by the lateral lobes of that gland. Above, and to the right, and at a short distance from each otiier, are seen the insertion of the succentric ventricle and the origin of the duodenum. The cavity of the gizzard always contains food mixed with a large quantity of silicious pebbles, whose use will be indicated hereafter. This viscera is composed of the three tunics which form the walls of all the abdominal reservoirs. Tlie internal, or mucous, is distinguished by the thickness and extraordinary induration of its epidermic layer, which presents nearly all the characters of horny tissue, and is so easilj' detached from the mucous chorium that it is often regarded as a special membrane. On the adherent face of this corium are applied two powerful red muscles — a superior and inferior, occupying the borders of the organ, and whose fibres, disposed in flexures, pass from side to side, and are inserted into a strong, nacrous aponeurosis on the lateral surfaces of the organ. Outside this contractile apparatus is a thin peritoneal envelope. The gizzard is the triturating apparatus of birds. When the aliment reaches its cavity it has not yet submitted to any disaggregation, but here it meets with all the conditions Buvernoy. • Legons d'Anatomie Compare'e de G. Cuvier.' 2nd Edition. 31 438 THE DIGESTIVE APPARATUS IN BIRDS. indispensable to the accomplishment of thi.s act: two energetic compressor muscles, a C(inieous layer spread over the internal surface of the viscera, giving to it the rigidity necessary to r sist the enormous pressure exercised on its contents; and silicious pebbles— veritable artificial teeth — wliich an admirable instinct causes i)irds to swallow, and between which, by the efforts of the tiiturating muscles, the food is bruised. This triturating action of the gizzard is only effected in birds fed on hard coriaceous aliment, such as the various kind of grain. It would be useless in birds uf prey, in which the two gizzard muscles are replaced by a tliin fleshy membrane of uniform thickness; showing that the presence of these muscles is subordinate to the kind of alimentation. Intestine.— The length of the intestine varies, as in Mammals, according to the nature of the food : very short in birds of prey, it is notably elongated in omnivorous and granivorous birds. Its diameter is nearly UTiitbrm throughout its whole extent, and it is difficult to establish in birds the various distinctions recognised in the intestine of Mammalia. It begins by a portion curved in a loop, which represents the duodenum, and whose two branches, lying aide by side, are pirallel to each other like the colic flexure of Solipeds. Fixed by a short mesenteric fryenum to the colon, this part of the intestine includes the pancreas between its two branches. Its curvature floats freely in the pelvic portion of the abdominal cavity (fig. 221, S, 9, 10). To the duodenal loop succeed convolutions suspended to the sublumbar pnrietes by a long mesentery, and which are rolled up into a single mass, elongated from before to behind, occupying a middle position between the air sacs of tiie abdominal cavity. Tlie analogy existing between this mass of convolution.s, and the floating iiortion of the small intestine of Mammals, does not require demonstration (fig. 221, 11, J 2). The terminal part of this floating intestine lies besicle the duodenal loop, and is flanked by the two appendages disposed like cxca. 'Ihese, scarcely marked in the Piijeon by two sm dl tubercles placed on the track of the intestinal tube, do not measure less than from six to ten inches in the other domesticated birds; thiy are two narrow culs-de-sac, slightly club-shaped at their closed extremities, which are free and directed towards the origin of the intestine, while the other extremity opens into the intestinal canal near the anus. There are always alimentary matters in these sacs, tliese becoming introduced, in following a retrograde course, by the same almost unkirown mechanisn-i which presides over the accumulation of spermatic fluid in the vesiculas seminales. Ac- cording to the majority of naturalists, these two appendages, although described as cxca, do not represent the reservoir bearing that designation in Mammals. This reservoir is nothing more than a small particular appendix placed on the track of the intestine, in front of the free extremity of the ab;)ve-mentioned culs-de-sac, and which is only to be found in a small number of birds, and among these sometimes, as Gurlt affirms, is the Goose. According to tliis view, which appears to be a very rational one, the portion of intestine comprised between the two blind luhes annexed to the viscera (Hg 221, 12') corresponds to the colon, and these tubes themselves are only dependencies of this inte.^tine. The rectum (fig. 221, 15) terminates the digestive canal; it is the brief portion of intestine which follows the opening of the cajea. Placed in the sublumbar region, this viscus is terminated by a dilatation, the cloaca ffig. 221, lU), a vestibule common to the digestive and genito-urinary passages, which opens externally at the anus, lodges the penis when it exists, and serves as a confluent for the ureters, oviduct, bursa of Fabricius, and the deferent canals. Abdominal Appendages of the Digestive Canal. — Liver (Fig. 221, 19, 20). — This is a voluminous gland, divided into two principal lobes — a right and left, the former always larger than the latter ; these incompletely include, on each side, the gizzard and succentric ventricle. In the Pigeon, this gland is provided with a gall-bladder (fig. 221, 21) attached to the internal face of the right lobe. But the arrangement of the excretory apparatus is not altogether identical with that observed in Mammals ■which possess this receptacle ; as two biliary ducts open separately into the intestine towards the extremity of the second branch of the duodenal loop. One proceeding directly from the two lobes of the liver, is the hepatic or choledic duct ; the other, the cydic duct, remains independent of the Litter, and opens behind it. It carries into the digestive canal the bile accumulated in the gnll-bladder, and which arrives there by a particular duct belonging exclusively to the right lobe; the cvstic canal is a braneli of this duct (fig. 221, 22). Pancreas (Fig. 221, 23).— In the Galhnacse., this gland is very devdoped, long, and narrow, and is comprised in the duodenal loop or flexure; at the extremity next the gizzard it has two principal excretory ducts, which separately pierce the intestinal membranes, a little in front of the hepatic canal. 4 Splfen. — This is a small, red-coloured, disc-shaped bodv, placed to the right of the stomachs, on. the limit of the gizzard and buccentric ventricle. BOOK III. Kespieatory Apparatus. The maintenance of life in animals not only requires the absorption of the organisable and nutritive matters conveyed to the internal surface of the digestive canal, but demands that another principle, the oxygen of the atmo- sphere, should enter with these materials into the circulation. In animals with red blood, this element, in mixing with the nutritive fluid, commences by expelling an excrementitial gas, carbonic acid, and communicating a bright red colour to that fluid, with which it circulates ; it is brought into contact, in the general capillary system, with the minute structures of the various apparatus, exercising on the organic matter comjjosing them a special excitory influence, without which the tissues could not manifest their properties, as well as inducing a combustible action which evolves the heat proper to the animal body. This new absorption constitutes the phenomenon of respiration. In the Mammalia, this is etfccted in the lungs : parenchymatous organs hollowed out into a multitude of vesicular spaces whicli receive the atmospheric air and expel it, after depriving it of a certain quantity of oxygen, and giving, in return, a proportionate quantity of carbonic acid. These organs are lodged in the thoracic cavity, whose alternate movements of dilatation and contraction they follow. They communicate with the external air by two series of canals placed end to end : 1, A cartilaginous tube originating in the pharyngeal vestibule, and i-amifving in the lungs ; 2, The nasal cavities, two fossae opening into that vestibule, and commencing by two openings formed at the anterior extremity of the head. CHAPTER I. RESPIRATORY APPARATUS OF MAMMIFERS. In this apparatus we will first study the organs external to the thoracic cavity : the nasal cavities, and larynx and trachea ; then the chest and the organs it contains — the lungs. To this study will be added that of the two glandiform organs whose uses are unknown, but which, by their anatomical connections, belong to the respiratory apparatus. These are the thyroid bodies and the thymas gland. THE NASAL CAVITIES. These cavities are two in number, a right and left, and oiTer for study : their entrance, or nostrils — the fossse, properly called, which constitute these cavities : and the diverticuli named sinuses. 440 THE RESPIRATORY APPARATUS IN MAMMALIA. Preparation. — Remove the lower jaw from three heads. On the first of these make two transverse sections, one passing between the second and third molar tootli, the other behind the dental arcade. Saw through the second head longitudinally and vertically, a little to one side of the median line. On the third make a horizontal section in such a manner as to obtain an inferior portion analogous to that shown in figure 23. 1. The Nostrils. The nostrils are two ohlong, lateral openings, situated at the extremity of the nose, circumscribed by lij)s or movable ivings (alse) disjiosed in an oblique direction downwards and inwards, and slightly curved on them- selves, so as to present their concavity to the external side. The lips or alse of the nostril are enveloped, inwardly and outwardly, by a thin, delicate skin, covered by fine, short hairs. The external is concave on its free margin ; the internal is convex. The commissure which unites these two wings superiorly, forms a slight ci'oss curved inwards. When the finger is introduced into this commissure it does not enter the nasal cavity, but the false nostril : a conical pouch formed by the skin, extending to the angle comprised between the nasal spine and tlic elevated process of the pre- maxillary bone. In the Ass, according to Goubaux, the false nostril is areolated at the posterior extremity, which ascends beyond the summit of the re-entering angle formed by the nasal and premaxillary prolongation. The inferior commissure is round and wide, and, towards the bottom, presents an opening, sometimes double, which looks as if punched out ; this is the inferior orifice of tlie lachrymal duct, which, in the Ass and Mule, is carried to the inner face of the external wing, near the superior commissure. Structure. — The nostril is composed of a cartilaginous framework, muscles to move it, and integuments, vessels, and nerves. Cartilaginous framework (Fig. 222). — This framework is formed by a cartilage, bent like a comma, and which, in its middle part, lies against that of the opposite side, the two making a kind of figure X. Fixed in a movable manner to the inferior extremity of the middle septum of the nose, by means of short interposed fibres, this cartilage offers : a wide upper part, situated in the substance of the inner wing of the nostril, and covered by the transverse muscle of the nose (Fig. 222, 1) ; and an inferior portion, which, after passing into the lower commissure, is jirolonged, in a blunt point, to the external wing, where it receives the insertion of several fasciculi belonging to the orbicularis muscle of the lips, the pyramidal muscle of the nose, and the supernaso-labialis (Fig. 222, 2). Each wing, therefore, possesses a cartilaginous skeleton ; but that of the external wing is very incomjilete, in conse- quence of its being only formed by the inferior ex- tremity of the common cartilage. This cartilage, it will be imderstood, sustains the 2, 2, Narrow e.xtremity alaa of the nose, prevents their falling inwards, and prolonged into the ex- always keeps open the external orifices of the re- ternal wins : 3, bupenor . ■; , or anterior border of the spiratory apparatus. septum. Muscles. — The motor muscles of the alfe are all dilators in the domesticated animals. They are : the transversalis nasi (dilatator naris anterior — Percivall), or transversalis of the Ficr. 22: CARTILAGES OF THE NOSE. 1, 1, Wide portion, form- ing the base of the inter- nal wing of the nostril , THE NASAL CAVITIES. 4n nose, a single muscle placed on the widened portion of the cartilaginous pieces ; the supermaxillo-nasalis magnus (dilatator naris lateralis — Percivall), or pyramidal muscle of the nose, whose insertion occupies the wliole extent of the external wing ; the supermaxillo-nasalis parvus (nasalis hrevis lahii superioris — Percivall), fixed, by its two portions, to the skin of the false nostril; the middle anterior (depressor alse nasi — Percivall) which is con^ founded, superiorly, with the external fasciculus of the preceding muscle, it being attached to the inferior branch of the cartilaginous appendix of the maxillary turbinated bone ; and, lastly, the super naso-lahialis (levator lahii superioris aloique nasi — Percivall), whose anterior branch is inserted, in j)art, into the external wing. All these muscles having been described in the Myology (page 220), need not be further alluded to here. Integuments of the nose. — The skin covering the alfe of the nose, ex- ternally, is doubled over their free margin to line their internal face, being prolonged over the entire extent of the false nostril, and is continued, in the nasal fossae, properly called, by the pituitary membrane. This skin is fine, thin, charged with colouring pigment, often marked by leprous spots, and adheres closely to the muscles included between its duplicatures, through the medium of a very dense and resisting fibro-cellular tissue. Vessels and nerves. — The nostrils are supplied with blood by the superior coronary, the external nasal, and the palato-labial arteries ; it is returned by the glosso-facial veins, and partly by the venous network of the nasal mucous membrane. The lymphatics, large and abundant, receive those of the pituitary membrane, and join the submaxillary glands by passing over the cheeks. The nerves are very numerous, the sensory being derived from the maxillary branch of the fifth pair, and the motors from the facial nerve. FtTNCTiONS. — The nostrils permit the entrance to the nasal cavities, of the air which is to pass to the lungs. Their dilatability allows the admission of a greater or less volume, according to the demands of respiration. It is to be remarked that, in Solipeds, the nostrils constitute the only channel by which the aerial column can be introduced to the trachea, in consequence of the great development of the soft palate, which is opposed to the entrance of air by the mouth ; these orifices are also, for the same reason, relatively larger than in the other domesticated animals, in which the passage of air, by the buccal cavity, is easily accomplished. 2. The Nasal Fossx. (Figs 223,224.) Clianneled in the substance of the head, above and in front of the palate, and separated from one another, in the median plane, by a cartilaginous septum which does not exist in the skeleton, the nasal fossae extend from the nostrils to the cribriform plate of the ethmoid bone, in a direction parallel to the larger axis of the head. Their length is, therefore, exactly measured by that of the face. See Fig. 223 for the whole of these cavities. The nasal fossae are formed by two lateral imlls, a roof or arch, a floor, and two extremities. Walls. — The two walls are very close to each other, and the more so as they are examined towards the ethmoid bone and the roof of the cavity. The space separating them varies, in proportion as it is measured at the level of the turbinated bones or at the meatuses. Inner wall. — This is formed by the nasal septum, and is perfectly smooth. •142 THE RESPIRATORY APPARATUS IN MAMMALIA. Outer wall. — This is chiefly constituted by the supermaxillary bone, is very rugged, and is divided into three meatuses, or passages, by the turbinated bones — the irregular columns applied against the inner face of the before-mentioned bone. The turbinated hones have already been described, and we will only now refer to the principal features of their organisation. Each is formed of a bony plate rolled upon itself (Fig. 223, 2, 3), and is divided, internally, into two sections, the superior of which forms part of the sinus, and the in- ferior belongs to the nasal fossae ; they are continued, inferiorly, by a fibro- cartilaginous framework, which prolongs tlieir nasal section to the external orifice of the nose. The flexible appendix of tlie ethmoidal turbinated bone is usually single, sometimes double, and disappears before reaching the alee of the nose. That of the maxillary turbinated bone is always bifui-cated, Fio;. 223. TRANSVERSE SECTION OF THE HEAD OF AN OLD HORSE, SHOWING THE ARRANGEMENT OF THE NASAL CAVITIES AND MOUTH. 1, Nasal fossa ; 2, Superior turbinated bone ; 3, Inferior ditto ; 4, Median septum of the nose ; 5, Centi-al part of the buccal cavity (drawn more spacious than it really is when the two jaws are brought together) ; 6, 6, Lateral portions of the same ; 7, Section of the tongue. and its antero-superior branch is directly continued by the superior extremity of the internal wing of the nostril. The meatuses are distinguished into superior, middle, and inferior, or into anterior, middle, and posterior, as the head is inspected in a vertical or hori- zontal position. The superior passes along the corresponding border of the ethmoidal turbinated bone, and is confounded with the roof of the nasal cavity ; it is prolonged, behind, to near the cribriform plate of the ethmoid THE NASAL CAVITIES 443 bone : it is tlie narro-^est. The middle, comprised between the two tur- binated bones, presents, on arriving near the ethmoidal cells, the orifice ■which brings all the sinuses into communication with the nasal fossa. This orifice is ordinarily narrow and curved; but we have seen it sometimes converted into a foramen sufficiently wide to permit the introduction of a finger end. It is also by this meatus that the inferior compartment of the turbinated bones opens into the nasal fossa, these two bones being each rolled in a contrary direction. The inferior meatus, situated under the maxillary turbinated bone, is not distinct from the floor of the nasal cavity. See figure 224 for the arrangement of the tui'binated bones and the meatuses on the external wall of the nosp. Roof or arch. — This is formed by the nasal bone, and is only a narrow channel, confoimded, as has been said, with the superior meatus. Floor. — Wider, but not so long as the roof, which is opposite to it, but from which it is distant by the height of the cartilaginous septum, the floor is concave from side to side, and rests on the palatine arch, which separates the mouth from the nasal cavities. In front of this nasal region is remarked the canal or organ of Jacobson : a short duct terminating in a cul-de-sac in the middle of the cartilaginous Fis. 224. LOXGrrUDINAL MEDIAN SECTION OF THE HEAD AND UPPER PART OF NECK. 1, 1, Atlas ; 2, 2, Dentata ; 3, Trachea ; 4, Right stylo-thvroideus ; 5, Guttural pouch; 6, Stvlo-pharyngeus ; 8, Palato-pharyngeus ; 9, Sphenoidal sinus; 10, Cranial cavity, 11, Occiput; 12, Parietal protuberance; 13, Frontal sinus; 14, Ethmoidal turbinated bone; 15, Maxillary turbinated bone; 16, Entrance to nostril, 18, Pharyngeal cavity; 19, Inferior maxilla; 20, Premasilla; 21, Hard palate. substance which closes the incisive foramen. At the bottom of this cul-de- sac opens a second canal, longer, wider, and more remarkable, but which has not yet been described. (It has been described by Stenson, and is named " Stenson's duct.") It has sometimes the diameter of a writing quill, commences by a cul-de-sac on a level with the second molar tooth, accom- panies the inferior border of the vomer from behind to before, where it is envelojjed in a kind of cartilaginous sheath — a dependency of the nasal septum ; it terminates, as we have said, after a course of about 5 inches. 444 THE RESPIRATORY APPARATUS IN 3IAMMALIA. The structure of this duct resembles that of the excretory ducts of glands ; its walls are evidently composed of two timics— an internal or mucous, very rich in follicles, and having longitudinal folds, and an external, of a fibrous nature These membranes receive numerous vessels, as well as nervous divisions emanating from a long filament of the spheno-palatine ganglion, and which may be traced from the external side of the canal to near the incisive foramen, where it is lost. Such is the organ of Jacobson ; its uses are quite unknown. Extremities. — The anterior or inferior extremity/ of the nasal fossa is formed by the nostril already described. The posterior or superior extremity presents, above, a space occupied by the ethmoidal cells. Below and behind, this extremity communicates with the pharyngeal cavity by a wide oval opening, which is circumscribed by the vomer and palate bones : this is the guttural opening of the nasal fossa. Structure. — The nasal fossfe ofier for study in their organisation : 1, The hony framework by which these cavities are formed ; 2, The cartilaginous septum separating them ; 8, The pituitary membrane — the mucous layer covering their walls. 1. Bony Framework of the Nasal Fossae. — This comprises: 1, The nasal, maxillary, frontal, and palate bones, which together form a vast irre- gular tube circumscribing the nasal fossae ; 2, The ethmoid bone, occupying the bottom of this tubular cavity and the turbinated bones aj^plied against the latei'al walls ; 3, The vomer, j)laced in the median plane, and serving as a support for the cartilaginous partition dividing this single cavity into two compartments. All these bones having been already studied in detail, we confine oiu'selves to their simple enumeration. 2. Middle Septum of the Nose ('Fig. 223, 4). — Formed of cartilage susceptible of ossification, this partition is nothing more than the perpendi- cular lamina of the ethmoid bone prolonged to the extremity of the nose. Its elongated form permits us to recognise in it two faces, two borders, and two extremities. The faces are channeled by a multitude of furrows, which lodge the anastomosing divisions of the magnificent venous plexus of the pituitary membrane. The superior border, united to the frontal bone and median suture of the nasal bones, expands to the right and left on the inner faces of these, in forming two laminfe, thin at their free margin, the section of which is represented in Fig. 223. These laminae are wide enough in front to project b«yond the nasal spine. The inferior border is received into the mortice of the vomer. The posterior extremity is continued without any precise limitation, by the perpendicular lamina of the ethmoid bone. The anterior extremity, a little wider, supports the cartilages of the nostrils. It is joined, below, to the premaxillary bones, and is spread out on the incisive openings in a thick layer which exactly closes them. This septum is covered by a thick perichondrium, which adlieres intimately to the pituitary membrane. 3. Pituitary Membrane. — This membrane, also designated the olfactory mucous membrane, and Schneiderian membrane, is continuous with the cutaneous integument covering the inner face of the alse of the nose. Considered at first on the internal wall of the nasal fossae, the pituitary membrane is seen to cover the cartilaginous septum forming this wall, then to be spread over the floor as well as the roof of the cavity, reaching the outer wall, which it also covers in enveloping the external surface of the turbinated bones, THE NASAL CAVITIES. 445 and is insinuated, by the middle meatus, into the cells of the inferior or anterior compartment of these osteo-cartilagiuous columns. It also penetrates, by the semicircular opening of this meatus, into the sinus, to give it its mucous covering, and is likewise prolonged into the apparatus of Jacobson. Behind, it is confounded with the lining membrane of the pharyngeal cavity. Its deep face is separated by the periosteum or perichondrium, from the bony or cartilaginous walls on which it is spread ; and it is united to the two precited layers, this union being closest where it is thinnest, although it can always be easily distinguished from these two fibrous layers* through- out the whole extent of the nasal fossa. The free, or superficial face, presents numerous glandular orifices, and is constantly covered by an abundance of mucus, that prevents the desiccation to which this surface is exposed by the incessant movement of air over it. Structuke. — The organisation of the pituitary membrane resembles that of other mucous membranes, but it also presents some diflerences according as to whether it is examined near the nostrils or deeper in the cavities. It is also usual to divide it into two portions : the olfactory mucous membrane, which covers the upper part of the ethmoidal turbinated bone and cells ; and the Schneiderian memhiane covering the inferior two- thirds of the nasal cavities. The corium oi' the Schneiderian membrane is thick, soft, spongy, and rose-coloured, and contains a large number of vessels and glands. The latter are mucous, or racemose glands, and are extremely abundant in the layer covering the septum of the nose, as well as at the inner face of the cartilaginous appendices of the turbinated bones ; though they are rare or altogether absent on the Fig. 225. external face of the latter. The ejnthelium is ciliated and stratified, the deeper cells being round, those on the surface columnar. The olfactory mucous membrane differs from the preceding by its greater thinness, its delicateness, its slightly yellow tint, and the cliaracter of its epithe- lium. The corium contains straight or slightly-con- torted tubular glands — the glands of Bowman. The epithelium is columnar and stratified, and readily changes ; in animals it is destitute of cilia. The deeper cells contain some yellowish pigment granules. Schultze describes as olfactory cells, certain fusiform elements which he considers as concerned in filfaction. These cells have two prolongations : a deep one, which is connected with the fibres of the olfactory nerve ; and a superficial, tliat enters between the epithelial cells and tends to approach the free surface of the membrane. (The " olfactory cells " are than, rod-like bodies (Fig. 225, b), presenting varicose enlargements which are connected with processes of deeper-seated nerve- cells. The epithelial cylinders proper (d, e) are related at their bases with the septa of connective tissue belonging to the sub-epithelial glandular layer, and are probably in communication with the olfactory cell. Schultze describes another set of epithelial cells (a) as terminating externally by truncated flat surfaces, and to all CELLS OF THE OLFACTORY MUCOUS MEMBRANE. a, b, c, After Schultze , d, e, f, After Lockhart Clarke. 446 THE BESPIBATOBY APPAEATVS IN MAMMALIA. appearance not covered by any membrane, apart from the contents of the cell, which are a yellow, granular proto-iilasma surrounding an oval nucleus lying in colourless protoplasma. The extremity of these cells is thin, and they can be traced inwards until they expand into a flat portion that sends off pro- cesses which apj)ear to be continuous with the fibres of the submucous connective tissue. Similar cells (c) are found towaxxls the margin of the true olfactory region, but these have a band at their free extremity, which is also provided with a circle of cilia.) The pituitary membrane receives its blood by the ophthalmic and nasal arteries ; it is returned by the large anastomosing veins which form, in the deep layer, a long, close, and magnificent j)lexus that terminates in the satellite vein of the nasal artery. This i^lexuous arrangement is so marked at certain points — as at the appendices of the turbinated bones, that it gives the mucous membrane somewhat the ajipearance of erectile tissue. It will be understood that in fiivouring the stagnation of the blood, this arrangement predisposes to haemorrhage. The lymphatics of the pituitary membrane could not be injected for a long time, neither in man nor animals ; and this led several anatomists to deny their existence. Nevertheless, they do exist, and form a fine sui)erficial network on the septum of the nose, the turbinated bones, and the meatuses. The trunks passing from it go to the submaxillary glands. The nerves of this membrane are numerous, and are derived from the first and fifth pairs, and from Meckel's ganglion. The ramifications of the olfactory nerve, on emerging from the apertures of the cribriform plate of the ethmoid bone, j^ass to the inner and outer walls of the nasal cavities ; being destined for the olfactory mucous membrane, they do not descend below the upper third of these cavities. They form at first a close plexus, and afterwards terminate in a manner not quite understood. Schultze admits that they terminate on the olfactory cells mentioned above. The branches derived from Meckel's ganglion and the fifth pair are specially destined for the Schneiderian membrane, and are named the ethmoidal brandies of the palpebro-nasal and spheno-palatine nerves. They endow the nose with an acute degree of sensibility, and it is believed that they render olfaction more perfect. (It is to be remarked that the filaments composing the olfactory plexus differ from ordinary cephalic nerves in containing no white substance of Schwann, and are nucleated and finely granular in texture, resembling the gelatinous form of nerve-fibres. The surface to which they are limited is that covered with the yellowish- brown ej)ithelium.) 3. Sinuses. The sinuses are very anfractuous cavities, excavated in the substance of the bones of the head, on the limits of FIBRES OP ULTIMATE tlic cranium and face, and around the ethmoidal masses, ^^^r'^!!^!?! w^i^^i ^^^^J envelop. These cavities, diverticuli of the nasal fossae, are pairs, and are five on each side : the frontal, super- maxillary, sphenoidal, ethmoidal, and inferior maxillary sinuses. The first four communicate ; the last is usually perfectly isolated. Feontal Sinus. — This cavity, situated at the inner side of the orbit, Fig. 226. OLFACTORY OF DOG. THE NASAL CAVITIES. 447 presents very irregular walls, wliich are formed by the frontal, nasal, lachry- mal, and ethmoidal bones, and the superior portion of the ethmoidal turbinated bone. It communicates with the superior maxillary sinus by a vast opening made in a very thin bony partition. A thick vertical plate, often bent to the right or left, but always imperforate, separates this sinus from that of the opposite side. SuPERiOK Maxillary Sinus. — Channeled beneath the orbit, between the maxillary, zygomatic, ethmoid, and lachi'ymal bones, this diverticulum is the largest of all, and is divided into two compartments by the maxillo-dental canal, which traverses it. The internal compartment constitutes a kind of shallow cavity, continuous with the sphenoidal sinus, and presents a narrow slit, which penetrates to the ethmoidal sinus. The external compartment is separated, in front, from the maxillary sinus by a partition which M. Goubaux has, contrary to the generally-received opinion, demonstrated to be imperforate at all periods of life ; though he has sometimes found it so thin as only to consist of two mucous layers laid against each other. This compartment is prolonged backwards into the maxillary protuberance, and the roots of the two last molars project into its anterior. Sphenoidal Sinus. — This is the smallest, after that ot the great ethmoidal cell. Formed by the sphenoid and palate bones, this cavity is very irregular, and is subdivided by incomplete septa into several compartments, which may be always reduced to two : an anterior, comprised between the palatine laminae ; the other posterior, hollowed in the body of the sphenoid bone. In contact, on the median line, with the sinus of the opposite side, it is separated from it by a twisted plate, which is constantly perforated, even in young animals. Ethmoidal Sinus. — By this name is designated the internal cavity of the large ethmoidal cell, which constitutes a real sinus, and which a narrow slit brings into communication with the superior maxillary sinus. Inferior Maxillary Sinus. — This last diverticulum is remarkable because of its not communicating with the others. Excavated in the supermaxillary bone, and separated from the superior sinus by the imperforate septum previously mentioned, it is divided, like the latter cavity, into two compart- ments : an internal, prolonged into the superior cavity of the maxillary turbinated bones ; and an external, the smallest, showing the roots of the fourth molar, rarely those of the third. It does not d-iscend, as Rigot has asserted, above the three front molars ; but supposing the head to be vertical, it does not extend, in the adult Horse, beyond the extremity of the maxillary ridge, in front of which it would be necessary to trepan, in order to arrive at its interior. Communicating Orifice of the Sinuses with the Nasal Fossa. — All the sinuses of one side communicate with the corresponding nasal fossa by the curved slit which has been observed at the bottom of the middle meatus. This slit penetrates the superior maxillary sinus, under the septum that separates it from the frontal sinus ; it also enters the inferior maxillary sinus, which thus communicates solely with the nasal cavity, wliile the other diverticuli open in common into this cavity through the medium of the superior maxillary sinus. Mucous Membrane of the Sinuses. — In entering the sinuses to cover their walls, the pituitary membrane becomes extremely thin, and loses its great vascularity ; it is applied immediately to the bones, and serves as a periosteum. Development of the Sinuses. — These cavities begin to be developed in 448 TEE EESPIEATOEY APPARATUS IN MAMMALLi. the fcetus, and are gradually hollowed in the thickness of the bones which concur to form them. They increase during the animal's lifetime, by the thinning of the bony plates inclosing or partitioning them, and particularly by the growth of the superior molar teeth, whose roots project into these cavities. The formation of the inferior maxillary sinus is more tardy than the others ; though it is not so late as seven or eight years, as the majority of Veterinary Anatomists have asserted. M. Goubaux has proved that the sinus is already present at six months old ; and in a head which has been for several years in the museum of the Lyons School, and which belonged to a foal of very small stature, about a year old, this sinus is seen, in its external part, to be already 1^ inches in depth, and 8-lOths of an inch in width. Functions of the Sinuses. — Have the sinuses or diverticuli of the nasal cavities the same uses as these cavities? It is probable, although not absolutely certain. There is nothing to prove that they have anything to do with respiration or olfaction ; and it would seem that their exclusive function is to give increased volume to the head without increasing its weight, and in this way to furnish wide surfaces of insertion for the muscles attached to this bony region— these cavities being all the more ample as the muscles are large and numerous. DIFFERENTIAL CHARACTERS OF THE NASAL CAVITIES IN OTHER THAN SOLIPED ANIMALS. 1. Nostrils — In the Ox, the nostrils, placed on each side of the muffle, are narrower anfl less movahle than in the Horse. (The superior extremity of the ala is not horizontal ; the inferior is diviiled into two branches.) In the Puj, the end of tlie nose constitutes the snout (rostrum suis), whose anterior surface, plane and orbicular, shows the external orifices of the nostrils. This snout, a veritable tactile organ employed by tlie animal to dig up the ground, is covered by a dark-coloured skin, kept damp by a humid secretion, like the muffle of the Ox. It has for a base the scoopmg-hone, a particular piece situated at the extremity of the nasal septum, and enveloped by a layer of cartilage which extends aroimd the no.strils. It is easy to distinguish two symmetrical halves in this bone, which evidently represent the two cartilaginous pieces in the nose of Solipeds. In the Bog, the end of the no.se forms a salient region, which is roughened, naked, usually dark-coloured, damp, and sometimes divided by a median groove ; in this region the nostrils are pierced, their form resembling two commas opposed to each other by their convexities. The cartilaginous framework sustaining these orifices is not composed of separate pieces, but is only a dependance of the median septum and the appendages of the tm-binated bones. The same considerations apply to the nostrils of the Cat with the exception of the colour of the integument, which is nearly always of a ro.sy hue, like the mucous surfaces. 2. Nasal Cavities. — The nasal fossaj of the Ox, Sheep, and Goat are distinguished by the presence of a third turbinated bone— the olfactory antrum, andliy the commrmication existing between them, posteriorly, above the inferior border of the vomer. We have already seen that in these animals, as in those yet to be mentioned, the canal of Jacobson completely traverses the palatine arch. In tlie Pig, the nasal fossaj are long and narrow. They are, on the contrary, very short in the Dog and Cat, and the internal cells of the tinbinated bones, remarkable for their number and complexity, all communicate with the proper nasal I'ossaj, without concurring in the formation of the sinuses. 3. Sinuses. — In the Ox, the frontal sinuses are prolonged into the bony cores which support the horns, and into the parietal and occijjital bones ; they therefore envelop, in a most complete manner, the anterior and superior part of the cranium, and form a double wall to this bony receptacle. They are extremely diverticulated, and do not communicate with those of the great maxillary bones. They u.sually open, on each side, into the nasal cavities by four apertures pierced at the base of tiie great ethmoidal cell. According to Girard, three of these orifices lead to special comjiartments, isolated from one another, and grouped around the orliit ; in consequence of which these diverticuli of the frontal sinuses are designated the orbital sinuses. This author has denied the presence of sphenoidal sinuses ; but they exist, although email, and are in communication with the preceding. TEE LARYNX. 449 The sinus of the great ethmoidal cell comports itself as in the Horse. There is only one pair of maxillary sinmes, which are very large, anil partitioned into two compartments by a plate of bone, that bears at its superior border the siipermaxillo- deutal canal, like the superior maxillaiy sinus of .Solipeds. The external or maxillary compartment is prolonged into the lachrymal {jrotuberance ; the internal occupies the thickness of the palatine arch. A wide orifice at the base of the maxillary turbinated bone aflbrds a connnunication between this sinus and the nasal fossa. In the Sheep and Goat, there exists a similar arrangement of the sinuses of the head; but these cavities are much less spacious tlian in tlie Ox; the frontal sinus ia particular, does not extend beyond tlie superior border of the frontal bone. In the Pi(j. these latter sinuses are prolonged into the parietal bones ; though they are far from olfering the same extent as in the smaller Ruminants. It is tlie same with the others ; they present an arrangement analogous to those of the Sheep and Goat. In the Dog and Cat, there are only, on each side, a maxillary and a frontal sinus. The first scarcely merits notice ; and the second, a little more tleveloped, opens into the nasal cavity by means of a small aperture situated near the middle septum of the two frontal sinuses. (Leyh states that the Carnivora have no maxillary sinus ; consequently, the sphenoidal sinus communicates below with the nasal foss£e.) COMPAPwlSON OF THE NASAL CAVITIES IX MAX VflTH THOSE OF AXIMALS. The external orifices of the nasal cavities of Man are called nostrils ; these are fla.,..encd transversely, and prolonged in front of the lobule of the nose; their external face or ala is concave and movable. They are lined internally by a membrane that holds a middle place between the skin and mucous membranes , it has a number of little hairs, called vihrissx. The cavities or nasal fossseoSer nothing paiticular; as in animals, they show a superior, middle, and inferior meatus. On their floor, in front, is seen tlie superior orifice of the incisive foramen, which corresponds to the commencement of Jacobson's canal. The pituitary membrane has a squamous epithelium in its olfiictory, as on its Schneiderian portion. At the bottom of the nasal cavities and the upper part of the pharynx, is a kind of diverticulum named the postenor naves; it has been already alluded to when speaking of the pharynx. The sinuses are : 1, The sjjhenoidal sinus and the posterior ethmoidal cells, that open beneath the roof of the nasal fossse ; 2, The middle ethmoidal cells, opening into the superior meatus; 3, The -anterior ethmoidal cells, and frontal and maxillary sinuses, communicating with the middle meatus. All these sinuses have a proper communicating orifice with the nasal cavities. THE AIR TUBE SUCCEEDING THE NASAL CAVITIES. This single tube comi^rises : the lari/nx, which commences the trachea ; the latter forms the body or middle portion, the bronchice terminating it. . Larynx. (Figs. 227, 228, 229.) Preparation.— I. Make a longitudinal section of the head, in order to study tho general disposition of the larynx (Fig. 224'. 2. Isolate the cartilages, to examine their external conformation. 3. Remove the muscles from a third larynx, to show the mode of articulation of the various cartilages Figs. 227, 228\ 4. Prepare the muscles in conformity with the indications furnished by a glance at figure 22S). 5. Remove a larynx as carefnily as possible, so as not to injure the walls of the pharynx, in order to study the interior of the organ, and especially its pharyngeal opening. Form — Situation. — The larynx forms a very short canal, which gives passage to the air during respiration, and is at the same time the organ of the voice. It is a cartilaginous box, depressed on each side, and open from one end to the other ; the anterior orifice being situated at the bottom of the pharyngeal cavity, and the posterior continuous with the trachea. This apparatus, situated in the intermaxillary space, is suspended between the two cornua of the os hyoides, and fixed to the extremities of these appendages by one of its constituent pieces. It serves to support the 4 50 THE HESPIRA TOE Y APPARA TUS IN MAMMA LI A . pharynx, and by means of the walls of the latter is attached to the cir< cumference of the posterior openings of the nasal cavities. In order to facilitate description, this brief notice of its form, situation, general relations, and mode of attachment will be followed by a notice oi its structure ; afterwards, the study of its external and internal surfaces will receive attention. Structure of the Larynx. — It comprises in its structure : 1, A carti- laginous frameworJc, composed of five pieces; 2, Muscles which move these pieces ; 3, A mucous membrane spread over the inner surface of the organ ; 4, Vessels and nerves. 1. Cartilaginous fi-ameivorh of the larynx. — In this we find : three single median cartilages, the cricoid, thyroid, and epiglottis; and two lateral cartilages, the arytenoid. All are movable one upon the other. Cricoid Cartilage. — This cartilage, as its name indicates (KptKos, elSo?, like a ring), is exactly like a ring with a bezel looking upwards. Depressed on each side, but all the less as the animal has its respiratory apparatus well developed, this ring offers two faces, and tioo borders or circumferences. The internal face is smooth and covered by mucous membrane. The external face is provided, in the middle of the widened portion forming the bezel with a little eminence more or less prominent, elongated in the form of a crest, and separating the two posterior crico-arytenoid muscles, to which it gives attachment, from each other. On the sides of this bezel are two small, articular, concave facets, which correspond to the branches of the thyroid cartilage. Notliino' remarkable is to bo noted for the remainder of the extent of this face. The superior ■ circumference, comjirised laterally between the two branches of the thyroid cartilage, is hollowed out in the narrow part opposite the bezel, where its shows two lateral convex articular facets for articulation with the arytenoid cartilages. The inferior circumference responds to the first ring of the trachea ; it offers a small notch, often double, on the middle of the bezel. Thyroid Cartilage (^upcds, cISos, like a shield). — This is composed of two lateral plates, which have the form of an obliquangular parallelo- gram, and are united at their anterior extremity to form a thick constricted part which, in Veterinary Anatomy, is named the body of the thyroid. This body is smooth on its inferior face, where it is covered by the terminal extremity of the subscapulo-hyoideii muscles. On its siiperior face is an obtuse, rounded, and irregular protuberance, on which the epiglottis articulates. The plates, lateral branches, or alee of the thyroid present tico faces, two borders, and two extremities. The external face, slightly convex, is covered . by the hyo-thyroideus and thyro-pharyngeus muscles. The internal face, slightly concave, is covered, near the superior border, by the pharyngeal mucous membrane ; for the remainder of its extent it responds to the thyro- arytenoid and lateral crico-arytenoid muscles. The superior border is divided by a small prolongation into two parts : an anterior, giving attachment to the thyro-hyoid membrane ; the other posterior, into which is inserted the pharyngo-staphyleus (palato-pharyngeus) muscle. This appendix, the great thyroid cornu of Man, forms one of the obtuse angles of the parallelogram represented by each lateral plate of the thyroid cartilage ; it is united to the extremity of the hyoid cornu ; and at its base is an opening, or deep notch, through whicli passes tlie superior laryngeal nerve. The inferior border is also divided into two parts by the second obtuse angle of the cartilage : the anterior part forms, with that of THE LARYNX. 451 the opposite plate, a receding angle occupied by the crico-thyroid membrane ; the posterior gives attachment to the crico-thyroid muscle. The extremities constitute the acute angles of the thyroid plate. The anterior is confounded with that of the opposite branch, to form the body of the cartilage. The posterior, slightly curved downwards, is terminated by a small, convex diarthrodial facet, which articulates with the concave facets of the external lace of the cricoid cartilage. The thyroid cartilage is frequently partially, or even entirely, ossified. Epiglottis. — This piece forms a soft and flexible appendix, shaped like a sage-leaf; inferiorly, it circumscribes the entrance to the larynx, and is bent over it, so as to close it hermetically when the alimentary bolus is traversing the pharyngeal vestibule. This cartilage has two faces, two lateral borders, a ha^e, and a summit. The anterior face is convex from side to side, concave from above to below, and covered by the mucous membrane of the j)harynx ; it gives attachment to the hyo epiglottidean muscle. H^he posterior face shows an inverse configuration, and is covered by the lining membrane of the larynx, which is perforated by glandular orifices. The borders ofier a free portion, which aids in circumscribing the entrance to the larynx; as well as an adherent part fixed to the arytentiid cartilage by means of a mucous fold, and made irregular by the little cartilaginous bodies which are superadded to it. (These are the cuneiform cartilages, or cartilages of Wrisberg, placed in the aryteno-epiglottidean fold of mucous membrane which extends from the apex of the arytenoid cartilage to the side of the epiglottis.) The base is thick, and articulated with the middle part of the thyroid ; it gives origin, posteriorly, to two lateral prolongations, which pass to the inferior border of the arytenoids, but usually without joining these. The summit unites the iree portion of both borders, and is thrown forwards on the upper face of the soft i:»alate (Fig. 174, 9). Arytenoid Cartilages. — These two pieces have been so designated from their resemblance, when approximated, to the mouih of a pitcher (upvTaLva, cT8os, nice a intcher). They are situated in front of the cricoid, above the entrance to the larynx; each afiects an irregular quadrilateral form, and presents for study two faces and four borders. The internal face is smooth, almost flat, and lined by the laryngeal mucous membrane. The external face is divided by a ridge into two portions : a superior, covered by the arytenoid muscle ; and an inferior, giving attachment to the thyro- arytenoid and lateral crico-arytenoid muscles. The superior border is concave, and joined to that of the opposite cartilage. Tlie inferior border gives attachment, posteriorly, to the vocal cord. The anterior border, thick and convex, and covered by the mucous membrane, circumscribes, superiorly and laterally, the entrance to the larynx ; it is in joining above, with the homologous border of the other arytenoid cartilage, that the pitcher- beak already mentioned is formed. The posterior border projects into the larynx by its inferior portion ; superiorly, this border is very thick, and is hollowed by a small articular facet, which responds to the anterior facet of the bezel of the cricoid. Above, and to the outside of this facet, is a very prominent tubercle which terminates behind the crest of the external face, and gives attachment to the posterior crico- arytenoid muscle. Articulations of the Laryngeal Cartilages (Figs. 227, 228), — -These articulations are of the simplest kind. They are as follows : A. The thyroid cartilage is joined to the os hyoides : ] , At the 452 TEE BESPIBATORY APPARATUS IN MA3IMALIA. extremities of the cornua, by means of a short ligament interposed between that extremity and the appendix of the superior border of the thyroid ; 2, To the whole extent of the hyoid concavity, by an elastic membrane — the thyro-hyoid membrane, attached to the body of the thyroid cartilage and the superior border of the lateral plates of that cartilage (Fig. 228, 4). Fi2. 227. Fis 228. SUPERIOR FACE. INFERIOR FACE. CARTILAGINOUS PIECES OF THE LARYNX, MAINTAINED IN THEIR NATURAL POSITION BY THE ARTICULAR LIGAMENTS. a, Cricoid cartilage ; h, b. Arytenoid cartilages ; c, Body of the thyroid ; c', c', Lateral plates of the thyroid ; d, Epiglottis ; e, Body of the hyoid ; /, Trachea. — 1, Crico-arytenoid articulation ; 2, Capsule of the crico-thyroid articulation ; 3, Crico-thyroid membrane ; 4, Thyro-hyoid membrane ; 5, Crico-trachealis ligament. B. The thyroid cartilage articulates with the cricoid by two small arthrodi83, which unite the posterior extremities of the branches of the first cartilage with the facets on the external face of the second. A thin external capsule incloses this articulation (Fig. 227, 2). These two cartilages are also held together by meaus of a membranous elastic ligament — the crico- thyroid membrane, which passes from the angle comprised between the two branches of the thyroid to the anterior notch of the cricoid (Fig. 228, 3). C. The two arytenoid cartilages are united, at their superior border, by the arytenoid muscle and laryngeal mucous membrane. D. The latter cartilages are brought into contact with the anterior facets of the cricoid bezel, by means of the concave articular surface of their posterior border ; the result is a small, but very movable, arthrodial joint, inclosed by a thin external capsule and by the surrounding muscles (Fig. 227, 1). E. These cartilages are also united to the thyroid through tlie medium of the vocal cords. These are two elastic bands which project within the larynx, and between them include the triangular space termed the glottis ; their internal face is covered by the mucous membrane of the larynx ; the thyro-hyoid muscles envelop their external face ; their inferior extremity is fixed into the crico-thyroid membrane, and the angle of the thyroid cartilage ; THE LARYNX. 453 the superior is attaclied to the inferior border of the arytenoid cartilage, towards the angle which separates this from the posterior border. The articuhitiou of sounds is jirincipally due to the vibration of these cords, F. The epiglottis is fixed by amphiarthrosis to the body of the thyroid cartilage, by means of elastic fasciculi mixed with fat, which pass from the base of the first to the upper face of the second. It is not rare to find among these fasciculi small synovial bursas. G. The epiglottis is united, laterally, to the inferior border of the arytenoids, through the medium of the two mucous folds already noticed, in the substance of which are the cartilaginous prolongations annexed to the base of this fibro-cartilage. These prolongations circumscribe, anteriorly, the ventricles of the larynx, and are sometimes designated the superior vocal cords : a name we rarely give them, as they do not merit it. H. Finally, the first ring of the trachea is attached to the cricoid cartilage by a circular elastic membrane. All of these articulations have neither the same importance nor mobility. The kind of movements they permit is easily understood, aud they are suf- ficiently indicated in the description of the muscles which execute them. It is sufiicient here to state, that these movements may either produce the shortening or elongation of the larynx, its tlilatation or contraction in a transverse direction, or the occlusion of its anterior opening. 2. Muscles of the larynx. — The laryngeal ajiparatus is elevated or depressed with the hyoid bone, which it follows in all its movements. It is also moved by proper muscles, which either produceits total displacement, or cause the several pieces of its cartilaginous framework to play upon each other. Among these muscles there are three extrinsic : the i>terno-tlujroideus, lujo-thjroideus, and the hyo-epiglottideus. The others are intrinsic, or attached in their origin and termination to the different pieces of the larynx ; they are : the crico-thyroid, posterior crico-aryfenoid, lateral crico-arytenoid, thyro-ariitenoid, and the arytenoideus muscles. All are pairs, except the last and the hyo epiglottic! eus. Sterxo-thyroideus. — (See page 198.) Hyo-thyroideus. — This is a ^-ide, triangular muscle formed entirely of muscular fasciculi, which originate from the whole extent of the hyoid cornu, and terminate on the external face of the thyroid ala ; the most inferior are longest. This muscle covers the thyroid cartilage and the thyro-hyoid membrane. It is covered by the maxillary gland. In contracting, this muscle brings the thyroid cartilage within the branches of the hyoid bone, and in this way carries the larynx forward and upward. Hyo-epiglottidecs. — By this name is designated a small cylindrical fasciculus, whose fibres are buried in the middle of a mass of adipose tissue, and which extend from the superior face of the body of the hyoid bone to the antero-inferior face of the epiglottis. Partly covered by the mucous membrane of the pharynx, this muscle concurs in restoring the epiglottis to its normal position after the passage of the alimentary bolus. But it is also necessary to state that the epiglottis is carried forward more particularly by its own proper elasticity, as well as that of the ligamentous fasciculi which attach it to the thyroid cartilage. Crico-thyroideus (Fig. 229, 8). — This small muscle, applied to the external side of the cricoid cartilage, is elongated from above to below, and composed of strongly tendinous fibres which cross, more or less, the general direction of the muscle. They arise from the above-named cartilage, and pass to the posterior border of the thyroid plate. 32 454 THE BE8PIRAT0RY APPARATUS IN MAMMALIA. Fia. 229 The crico-thyroideus shortens the larynx, in bringing together the two cartilages into which it is inserted. Posterior Crico-arytenoideus (Fig. 229, 7) — This is the most powerful muscle in this region. Its fibres are directed for- wards and outwards, and originate from the bezel of the cricoid, which they cover, and from the median crest of that part. They all converge, in becoming more or less tendinous, towards the posterior tubercle of the arytenoid cartilage, on which they ter- minate. Covered by the oesophagus and the crico-pharyngeal muscular baud, this muscle is separated from that of the oppo- site side by the median crest of the cricoid bezel. The posterior crico-arytenoid muscles dilate the entrance to the larynx, as well as the glottis, in causing the arytenoid car- tilages to rotate or swing on the cricoid cartilage, and in separating them from one another by their anterior and inferior bor- ders. They act as a lever of the first order. Lateral Crico-arytenoideus (Fig. 22'J, 5). — A triangular muscle, smaller than the preceding, situated between the thyroid and arytenoid cartilages, and formed of tween the cricoid ' cartilage and fasciculi longer in front than behind ; these first ring of trachea, 10; 11, In- originate on the side of the anterior border fero-posterior extremities of crico- ^£ ^-^^ cricoid cartilage, and are directed thyroid cartilages. t ^ i • ^ i • i ^t ^ • •' * upwards to terminate outside the posterior crico-arytenoideus, on the tubercle of the arytenoid cartilage. It is a direct antagonist of the last muscle, and, consequently, a con- strictor of the larynx. Thyro ARYTENoiDETTS (Fig. 229, 6). — Lodged at the inner face of the thyroid ala, this muscle comprises two fasciculi, separated by the ventricle of the glottis. The anterior fasciculus is a long and pale band, originating on the internal surface of the ala of the thyroid cartilage, near its receding angle, and ascending to the arytenoid cartilage, bending round its external face to join, on the median line, the analogous fasciculus from the opposite side, mixing its fibres with those of the arytenoideus. By its inner face it covers the superior vocal cord and the laryngeal mucous membrane. The posterior fasciculus, wider than the anterior, comports itself in a somewhat similar manner. It commences from behind the same point, and terminates on the external crest of the arytenoid cartilage ; but its most anterior fibres pass over this crest and join the arytenoid muscle. Its internal face corresponds to the vocal cord, and its posterior border is con- founded with the fibres of the lateral crico-arytenoideus. Sometimes it happens that these fasciculi are not distinct from each other, and exist only as a wide muscular band applied against the ventricle of the glottis. It is surmised that this muscle is a constrictor of the larynx. Its POSTERO-LATERAL VIEW OF THE LARYNX I, Epiglottis ; 2, Arytenoid cartilages ; 3, Thyroid cartilage ; 4, Arytenoi- deus muscle ; 5, Crico-arj'ienoideus lateralis ; 6, Thyro-arytenoideus ; 7, Crico-arytenoideus posticus ; 8, Crico-thyroideus ; 9, Ligament be- THE LARYNX. 455 function is particularly marked in phonation, wten it modifies the length, separation, and tension of the vocal cords. Akytenoideus. — Situated beneath the pharyngeal mucous membrane, above the arytenoid cartilages, this, the smallest of the laryngeal muscles, is composed of two lateral portions whose fibres arise from a median raphe and, diverging, pass to the superior part of the external face of the before- mentioned cartilages, where they terminate by becoming inserted into the crest dividing that face, and imiting with the thyro-arytenoid muscle. The French works on Veterinary Anatomy cite this muscle — we do not know why — as a dilator of the larynx. Its position in front of the crico- arytenoid cartilages sufiiciently indicates that it cannot act otherwise than in bringing the two arytenoid cartilages together. And the continuity of a large number of its fibres with those of the thyro-arytenoideus, does not allow it to have any other action than that of this muscle. 3. Mucous membrane of the larynx. — This membrane is only a con- tinuation of the jjharyngeal mucous membrane, which, after covering the prominence formed by the opening of the larynx, is folded over the cir- cumference of that opening, to be spread on the posterior face of the epi- glottis and the internal face of the arytenoid cartilages, to dip into the ventricles, pass above the vocal cords, line the inner face of the cricoid cartOage, and, finally, to be prolonged into the tracheal tube. Its deep face adheres closely to the parts it covers, excejit in the lateral ventricles. The free face is perfectly tense, and is covered with stratified tesselated epi- theliimi at the epiglottis and vocal cords, but only with ciliated epithelium elsewhere. The glandulce of the larynx are racemose, and are numerous on the posterior face of the epiglottis, where they are lodged in the minute depres- sions of the cartilage ; they are also found on the arytenoid cartilages and the aryteno-epiglottidean folds. The mucous membrane of the larynx possesses an exquisite sensibility, owing to which admission to the air- passage is denied to the solid or liquid alimentary particles, which, dui'ing deglutition, might deviate from their normal course and pass into this opening. The slightest touch brings into play this sensibility, and deter- mines an energetic reflex excitation of the constrictor muscles of the larynx and chest ; from this results the almost complete occlusion of the laryngeal tube, and a violent cough which expels the substances whose contact has occasioned the irritation of the membrane. Everyone has experienced the effects of this reflex action, and knows by experience the great sensibility of the larynx. 4. Vessels and nerves. — Blood is carried to the larynx by the laryngeal arteries, which pass between the cricoid and the posterior border of the thyroid cartilages. Their branches spread over the ventrical of the glottis and the thyi-o-arytenoid muscle, to be expended in the substance of the miiscles and mucous membrane. The terminal ramifications form red plexuses on certain parts of the larynx. The veins are satellites of the arteries. The lymphatics form a superficial and a submucous network. The pneumogastric furnishes the larynx with its principal nerves — the superior and inferior laryngeal. The first is distributed to the upper part of the organ and to the entrance to the glottis, endowing the mucous membrane with that high degi-ee of sensibility that distinguishes it. The second is more especially a motor nerve, and supplies all the muscles, except the crico-thyroid muscle. A filament of the recurrent nerve is distributed in the mucous membrane of the subglottal portion, and to the 456 THE BESPIBATORY APPARATUS IN MAMMALIA. inferior border and inner face of the vocal cords. The presence of nervous filaments, analogous to those of the trachea, in the sub-glottal part of the larynx may explain the difference, well known to physiologists, that exists betwefen the sensibility of the entrance to the glottis and that of the inferior border of the vocal cords. External Surface of the Larynx. — It is divided into four planes : a superior, inferior, and two lateral. The superior plane, formed by the ary- tenoid and posterior crico-arytenoid muscles, is covered by the pharynx and oesophagus ; in its anterior moiety, it is directly covered by the pharyn- geal mucous membrane. The inferior plane presents, from before to behind, the thyro-hyoid membrane, the body of the thyroid cartilage, the crico-thyroid membrane, the inferior part of the cricoidxjartilage, and the crico-trachealis ligament. There is remarked, laterally, the inferior border of the thyro-hyoid muscle. This plane corresponds to the scapulo-hyoideal muscles, which entirely cover it. The lateral planes exb'bit the external faces of the thyro-hyoid and crico-thyroid muscles, that of the cricoid tiartilage, and the alse of the thyroid. They also show the opening through which passes the superior laryngeal nerve ; they are related to the crico- and thyro-pharyngeal muscles, as well as the maxillary gland. Internal Surface of the Larynx. — -This surface is divided into three perfectly distinct regions : a middle one, named the glottis ; a superior, called the supraglottic portion ; and an inferior, designated the subglottic portion. The glottis [rima glottidis) is a narrow si)ace which affects the figure of a very elongated isoscelated triangle, its base being uppermost. This irregular fissure is comprised between the elastic structures known as the vocal cords. It is the narrowest part of the larynx. The supraglottic portion, wider than the glottis, but always greatly depressed on each side, particularly in the region comprised between the arytenoids, presents: 1, The two ventricles of the larynx, lateral excavations, dilated at the bottom, and which penetrate between the anterior border of the vocal cords and the prolongations of the base of the epiglottis, insinuat- ing themselves even between the fasciculi of^he thyro-arytenoid muscle (in the Ass and Mule the ventricles are proportionately larger than in the Horse, and open close to the base of the epiglottis) ; 2, The suhepiglottic sinus, a deep depression at the base of the epiglott's, which is provided, in the Ass and Mule, with a thin membrane, capable of vibrating ; 3, The entrance of the larynx, or pharyngeal opening of the cavity, a vast, gaping aperture of an oval fi)rm, circumscribed by the anterior border of the arytenoids and the lateral border of the epiglottis, and making a remark- able projection at the bottom of the pharyngeal space. The subglottic portion of the larynx is the widest of the three ; it is directly continuous with the internal canal of the trachea. In front is seen the prominence formed by the posterior border of the vocal cords : above, a diffused and shallow excavation, placed at the point of junction of the arytenoid and cricoid cartilages, and which is named the subarytenoid sinus. Functions. — As a tube intended for the passage of a column of air during the act of respiration, the larynx does not give rise to any very interesting physiological considerations. It is, nevertheless, worthy of remark . that this organ, in imitation of the nostrils, dilates or contracts, according to the volume of the column of air introduced into, or expelled from, the lungs, and that its paralysis, during rapid movements, causes an embarrass- meni in the respiration which betrays itself in "roaring." But a physio- THE TRACHEA. 457 logical study of the larynx acquires a real interest v.lien it is examined with regard to the articulation of sounds, or as an organ of phonation. This study, however, does not come within our province ; though what has been said concerning the vocal cords will give a summary, but satisfactory, idea of the mechanism which presides over this function, and the part the larynx plays. It may also be added, that nearly all the muscles of the larynx are con- cerned in phonation ; by modifying the tension and the separation of the vocal cords they determine differences in the sounds. One only is concerned in respiration ; this is the posterior crico-arytenoideus, which is a dilator of the glottis. 2. The Trachea. (Figs. 230, 234.) Preparation. — Follow the same procedure as for the dissection of the oesophagus. The trachea is a flexible and elastic tube, formed of a series of incom- plete cartilaginous rings, which succeed the larynx, and terminate above the base of the heart by two divisions, which constitute the bronchi. Form. — This tube is cylindrical, and (slightly) flattened on both sides. Its inferior face and two borders are regularly rounded, and offer transverse grooves, which correspond to the intervals between the constituent pieces of the trachea. The superior face, nearly plane, shows the thin and widened extremities of these cartilaginous arcs. Course. — Leaving the posterior extremity of the larynx, the trachea descends backwards to the entrance of the chest, by following the inferior border of the neck below the longus colli muscle. It afterwards becomes inflected, superiorly, to pass between the two first ribs, enters the chest in traversing the anterior mediastinum, proceeds directly backwards, and finally arrives above the left auricle of the heart, to the right of the posterior aorta, where the tube presents its terminal bifurcation. Relations. — In its cervical portion, the trachea, surrounded by a loose and abundant cellular tissue, lies in a kind of muscular envelope which the majority of the muscles of this region form around it, and which are : the sterno-hyoid and steruo-thyroid, placed in front ; the sterno-maxillaries, situated at first ha. front, and afterwards on the sides towards their termina- tion ; the subscapulo-hyoideii, above and in the middle of the lateral parts ; the scalenii, altogether below and at the sides ; the longus colli, behind ; and outside all these muscles, the superficial expansion of the subcutaneous muscle of the neck. This envelope is thinnest in front of the middle portion of the neck ; and this is the place where the operation of tracheotomy should be performed. The trachea is also in relation, in its cervical portion: 1, With the oesophagus, which descends, as we know, at first in the middle of the posterior face, then to the left side of the air-tube ; 2, With- the carotid arteries, which pass along both sides of the tube, accompanied by their satellite nerves — the pneumogastric, great sympathetic, and recurrent nerves. After clearing the two first ribs, where it reaches its thoracic portion, the trachea responds, superiorly, to the longus colli and the oesophagus ; below to the brachial trunks, to the anterior aorta which fm-nishes them, to the anterior vena cava, the cardiac and recurrent nerves, and to the base of the heart ; laterally, to the inferior cervical ganglia of the great sympa- thetic, the vertebral vessels — cervical and dorso-muscular — and to the two ^•^vers of the anterior mediastinum ; to the right, the vena azygos ; to the 458 THE BESPIBATORY APPARATUS IN MAMMALIA. left, the arch of the aorta and the thoracic duct. The latter is sometimes carried to the opposite side. Stktjctuee, — The trachea comprises in its structure : the cartilaginous rings which form its base ; the ligaments which unite these rings ; the mucous membrane spread over its inner face ; a muscular layer, which only lines that membrane superiorly ; and vessels and nerves. Fiff. 230. . THE RESPIRATORY ORGANS; INFERIOR, OR FRONT VIEW. 1, Trachea ; 2, Jugular vein ; 3, Great rectus anticus muscle ; 4, Carotid artery ; 5, Longus colli muscle ; 6, Origin of the common carotids ; 7, Vertebral artery ; 8, Section of first rib; 9, Cephalic trunk of right axillary artery; 10, Anterior lobe of right lung; 11, Middle, or supplementary lobe of ditto; 12, Posterior portion or lobe of ditto ; 13, Heart ; 14, Cardiac artery ; 15, Ventricular branch of cardiac vein ; 16, Qi^sophagus. Cartilaginous rings of the trachea. — These are about fifty in number, and do not form perfect rings, being incomplete on the upper side of the trachea. Each is a kind of arc, composed of a cartilaginous plate flattened and curved on itself, whose extremities are turned towards each other, and THE TEA CHE A. 459 joined in the majority of tlie rings ; tliey even overlap in some. These extremities are thin and wide, and sometimes bifurcate and unite with the adjoining rings. In the middle part of the trachea, these rings are generally larger than at the origin or termination of the tube. The last ring, in serving as a transition between the trachea and bronchi, presents a more complicated arrangement ; being frequently completed by isolated cartilaginous plates, and is always divided by a median spur or bifurcation — directed towards the interior of the trachea, into two lateral segments, each of which corresponds to a bronchus. Ligaments. — The rings of the trachea are united at their borders by intermediate ligaments, which are composed of elastic tissue, and -permit the lengthening or shortening of the tube they concur to form. Towards the extremities of the arcs, they are confounded with a tliin cellular layer that unites these extremities. The first cartilage is received by its anterior border into the cricoid ring, and joined to it by the wide annular ligament mentioned at page 452. Owing to the elasticity of this ligament, the two cartilages it binds together can move one within the other, like two segments of a telescope, and in this way vary the length of the tube. Muscular layer. — This layer only covers the superior face of the trachea ; it is formed of pale, rose-coloured, transverse fasciculi, attached by their extremities to the internal face of the cartilages. Its action undoubtedly diminishes the diameter of the trachea, by contracting the arcs composing this cartilaginous tube. (Kolliker has found some longitudinal fibres passing across the transverse ones at the posterior part of the trachea. Leyh describes longitudinal fibres in the anterior wall of the trachea, between the mucous membrane and the cartilaginous rings, and which, he states, diminish the length of the tube.) Mucous membrane. — Continuous with that of the larynx, this membrane is prolonged, through the medium of the bronchi, and in becoming modified in character, into the air-cells. Its free or superficial surface is perforated by glandular orifices, and ex- hibits longitudinal ridges which are ineftacable by distension ; it is lined with ciliated epithelium. Its deep face is covered with yellow elastic tissue dis- posed in longitudinal fasciculi, and adheres inti- mately either to the face of the cartilages and their intermediate ligaments, or to the posterior muscular layer. An essential characteristic which distinguishes this membrane from that lining the larynx, is its slight sensibility. (The tracheal glands, whose orifices are so nume- ^' External layer oflong rous in the mucous membrane, abound towards the posterior part of the tube ; they are small, ovoid bodies, lying between the muscular and fibrous coats. Other glands, less in size, are placed between the layers of fibrous tissue uniting the cartilages at the sides of the trachea. Their secretion is poured out upon the free surface of the mucous membrane, to lubricate and protect it.) Vessels and nerves.- — The small arteries emanating from the vessels in the vicinity of the trachea — as the carotid and the collateral branches CILIATED EPITHELIUM FROM THE TRACHEA. tudinal elastic fibres ; 2, Homogeneous surface layer of the mucous membrane ; 3, Round cells ; 4, Oval and ob- long cells ; 5, Ciliated cells. 4u0 THE RESPIRATORY APPARATUS IN MAMMALIA. of the brachial arteries — supply it with blood. Its nerves come from the recurrent ; they show small ganglia on their track. Functions. — Except as a tube for the passage of the inspired and expired air, the trachea performs no other function. 3. The Bronchi. (Fig. 232.) Preparafion. — After removing the lung from the thoracic cavity, it is filled with water by fixing the tiaclica to a water-tap. The bronchi may then be dissected by tearing aiid triturating the i^ulmonaiy tissue. Each of the two bronchi — the terminal branches of the trachea — resembles a tree imbedded in the substance of the lung, and sending out a multitude of branches. Fig. 232. '^;^v^^''' ^\ '-^-z :^^^^ Bronchial Tube, with its Bronchules and Ultimate Ramifications (natural size). Disposition. — At a short distance from their origin, the bronchi enter the lobes of the lung, and pass backwards and outwards towards the superior part of the base of the organ, giving off in their course large collateral branches until they tliemselves are expended. These branches originate alternately above, within, below, and outwards ; and thiis extend in every direction. The first forms an obtuse angle with the principal trunk, and is directed forwards, to ramify in the anterior lobule of the lung ; the others are detached at an angle more or less acute. All are subdivided into gradually-decreasing branches, which soon become of a capillary diameter, and finally open into the pulmonary air-cells. (See Stkuctuke of the Lungs.) THE TRACREA. 461 Form. — The bronchial tubes are not flattened like the trachea; a transverse section shows them to be regularly cylindrical. Volume. — -The left bronchus is always smaller than the right, and both are much inferior in volume to the aggregate of their respective branches. Relations. — Each bronchus enters the pulmonary lobe along with the blood-vessels, which with it forms what is called the root of the lung. The divisions of this arborescent trunk are accompanied by the bronchial artery, vein, and nerves, which ramify in the same manner. Near their origin, the bronchi are related to the bronchial glands, above which, and to the left side, passes the oesophagus. Stetjctttre. — The structure of the bronchial tubes resembles that of the trachea ; their walls being formed by a cartilaginous framework, a muscular layer, mucous membrane, and vessels and nerves. Cartilages of the bronchi. — These only exist in tubes of a certain calibre, the minute passages being deprived of them, aud having only membranous walls. As in the trachea, this framework includes, for each tube, a series of transverse rings joined border to border ; though these are no longer formed of a single arciform piece, but each results from the union of several lozenge-shaped pieces whose extremities overlap, and which are united to each other, like the cartilaginous segments of the neighbouring rings, by means of cellular layers, and also by the membranes spread over their internal sui'face. Muscular layer. — Extended in a very thin continuous layer over the entire inner surface of the cartilaginous rings, this layer disappears in the smallest bronchial tubes. Mucous memhrane. — This membrane is dis- tinguished from that of the trachea by its great sensibility ; it alone constitutes the walls of the terminal bronchial divisions. (When the cartilages terminate, the tubes are wholly mem- branous, and the fibrous coat and longitudinal elastic fibres are continiied into the ultimate ramifications of the bronchiee. The muscular coat is disposed in the form of a continuous layer of annular fibres, and may be traced upon the smallest tubes ; it is composed of the un- striped variety of muscular fibre.) Vessels and nerves. — The vascular and ner- vous branches distributed in the tissue of the ''^^<'°^' membrane of a bron- , ■,■-,.-, r, , ,iT, 1 CHIAL TUBE, WITH THE CAPIL- broucnial tubes come from the satellite vessels laries injected. and nerves of these tubes — the hroncliial arteries, veins, and nerves. The lymphatics pass to the bronchial glands. DIFFERENTIAL CHARACTERS IN THE AIR-Tl'BE SUCCEEDING THE NASAL CAVITIES IN OTHER THAN SOLIPEU ANIMALS. EuMiNANTS.— In the Ox, Slieep, and God, the interior of the larijnx is simpler than in the Horse, and tlie lateral ventricles and vocal cnrds are almost eti'aced. The most important diiferences in its various pieces are as follows : 1, Tlie thyroid cartilage has no anterior appendices, but is provided, posteriorly, with two considerable prolongations that articulate with the cricoid cartilage it has no excavation between the two wings, and is formed by a single piece ; its inner face, in the middle, near the lower border, has a small fossette to which a round and very salient tuberosity on the extern^il face corres- ponds) ; 2, The upper border of the cricoid is not notched in front (neither is the bezel on its lower border) ; 3, The epiglottis is wider, but less acute, than iu Sulipeds '^Leyh says it 462 THE BE8PIBAT0BY APPARATUS IN MAM3IALIA. is less extensive, but thicker) ; 4, A hyo-epiglottidean muscle bifid at its origin. (There is no aryteuo-epiglottidean ligament.) The trachea of these animals does not olfer aoy important differences. The last ring is not so developed as in the Horse, and the tube detaches a supplementary bronchus to a lobe of the lung which does not exist in Solipeds. (Tlie rings of the middle portion are proportionally nariow, and their exti-emities meet behind and form a salient ridge.) Pig. — The larynx of the Pig is remarkable for its great mobility, suspended as it is to the hyoid cornua by the base of a very developed epiglottis, rather than by the wings of the thyroid cartilage. " There are wide, shallow, lateral ventricles, which have a small oblong sinus that ascends between the thyroid cartilage and the mucous membrane. These ventricles are not surrounded by the thyro-arytenoideus muscle, which is small and undivided ; above and outwardly, they are margined by a thick cord — a kind of superior vocal cord, considered by Duges as acting with the ventricles to modify the deep grunting sounds." * (Instead of a tuberosity on the external face of the thyroid cartilage, there is a median crest, and its inferior border has a small point. The cricoid appears to be drawn downwards and backwards, and its lower border is very prominent in the middle, and articulates with one or two small cartilaginous plates which have been sometimes wrongly described as belonging to the proper cartilages of the larynx. The antero-superior angles of the arytenoid cartilages are united to a small cartilaginous piece which prolongs them ; their external face has a spine, and the internal angles are separated by a small pisiform body called the ' interarticuiar cartilage.") The trachea of this animal resembles that of Ruminants. (It has about thirty rings, and has three bronchi.") Carnivora.— The larynx of the Dog and Cat is very like that of the Horse. In proportion, the epiglottis is shorter, wider at the base, and more triangular than in the other species ; the lateral ventricles are shallow. (There is an interarticuiar cartilage as in the Pig ; there is no sub-epiglottidean ventricle, and the vocal cords appear to be nearer each other. The trachea has about forty-two rings, whose extremities do not meet ; the space between them is less in the Cat than the Dog.) The larynx and trachea of Man will be compared with that of animals when we come to describe the lungs. THE THOEAX. (Figs. 230, 234.) The thorax, also called the thoracic or pectoral cavity, lodges not only the lungs, but also the heart and the large ve.ssels that spring from or pass to that organ, with a portion of the oesophagus and trachea, as well as nerves, which are as remarkable for their number as their physiological importance. Situation. — We have seen that the thorax has for its base the bony cage formed by the ribs, sternum, and bodies of the dorsal vertebraB. Suspended beneath the middle portion of the spine, this cage is transformed into a closed cavity by the intercostal muscles, which fill the spaces between the ribs ; and by the diaphragm, that vast oblique partition which separates the thorax from the abdomen. Internal conformation. — Considered as a whole, the thoracic cavity represents a hollow cone placed horizontally, depressed on each side, and particularly in front towards the summit; with its base, formed by the diaphragm, cut very obliquely, in consequence of the direction taken by that muscle. This obliquity of the diaphragm renders the antero-posterior diameter of the cavity much greater above than below ; the difference is more than double. The internal surface of this conical cavity may be divided into six regions : a superior, inferior, and two lateral planes, a base, a posterior plane, and a summit. The superior plane presents, on the middle line, a large projection resulting from the union of the vertebral bodies ; and, laterally, two deep channels — furrows — the vertehro-costal channels. These latter, wider behind than before, are formed by the superior extremities of the costal arches ; ^ Lavocat, ' Auatomie des Animaux Domestiques.' THE THORAX. 463 tliey lodge the superior border of the pulmonary lobes. The middle projectiou, or ridge, is comprised between these two lobes. Covered in front by the posterior extremity of the longus colli, this ridge responds, for the remainder of its extent, to the posterior aorta, the thoracic canal, and the vena azygos; on its sides are seen the subdorsal branches of the great' sympathetic nerve. The inferior plane, much shorter than the preceding, is, like it, narrower in front than behind ; it has for a base the superior face of the sternum, the sternal cartilages, and the triangularis sterni muscle. Posteriorly, it gives attachment to the fibrous sac containing the heart. Fio;. 234. THE PECTORAL CAVITY AND MEDIASTINUM, WITH THE COURSE OF THE TRACHEA AND (ESOPHAGUS. A, Anterior mediastinum; B, Posterior mediastinum; C, The heart and pericar- dium in the middle part of the mediastinum ; D, Diaphi-agm ; E, Trachea ; f, (Esophagus. The lateral planes, more extensive than the other two, are concave in both their diameters. Formed by the internal face of the ribs and the deep intercostal muscles, they are in contact with the external face of the lung. The base, or posterior plane, formed by the convex face of the diaphragm, is circumscribed on its exterior contour by the circle of asternal cartilages, and by the last rib. In it we see the three openings which traverse the diaphragmatic septum. The summit, or entrance of tlie tJiorax, is an oval opening, elongated vertically, comprised between the two first ribs and the longus colli muscle, and which is partly obstructed by an enormous collection of lymphatic glands ; through this opening passes the trachea, oesophagus, the axillary and carotid arteries, the anterior vena cava, and the pneumogastric, great sympathetic, inferior laryngeal, and diaphragmatic nerves. 464 THE RESPIRATORY APFARATUS IN MAMMALIA. Sucli is the thoracic cavity. Like the abdomen, it is provided witli. a serous lining, which remains to be examined. The Pleura. — The serous lining of the thprax comprises two distinct membranes, designated as the pleime, constituting two sacs placed one against the other in the median plane, and forming a septum named the mediastinum, which divides the thoracic cavity into two lateral compart- ments. Each pleura, therefore, covers one of the external or costal walls of the thorax, and the corresponding moiety of the diaphragm ; it is afterwards reflected in the vertical and antero-posterior plane of the cavity, to concur in the formation of the mediastinum, whence it is carried over the lung. This arrangement exhibits the pleura in four portions : a costal, diaphragmatic, mediastinal, together representing the parietal layer of the membrane, and a pulmonary or visceral portion. The costal pleura is ajiplied to the inner face of the ribs and the internal intercostal muscles. Strengthened on its adherent face, at each intercostal space, by a lamina of yellow elastic tissue, this membrane responds, by its free face, to the external plane of the lung, with which it does .not, in a normal condition, contract any adhesions. It is continued, jDosteriorly, with the diaphragmatic layer ; in front, above, and below, with the medias- tinal pleura. The diaphragmatic pleura adheres somewhat loosely to the fleshy portion of the muscle, but the union is more intimate on the aponeurotic portion. This layer is contiguous, by its free face, with the base of the lung ; it is confounded with the mediastinum by the internal part of its periphery. The mediastinal pleura is placed, by its adherent face, against that of the opposite side, and in this way produces the middle septum which divides the thoracic cavity into two portions. Several organs are comprised between the two layers of this partition, but most important of all is the heart. In Veterinary Anatomy, that part of the septum in front of this organ is named the anterior mediastinum ; the appellation of posterior mediastinum being reserved for the portion situated behind it. These terms have not the same signification as in hmnan anatomy, though they are retained here to prevent misunderstanding. The anterior mediastinum, thicker than the posterior, but much less extensive, contains, superiorly, the trachea, oesophagus, the anterior aorta and its divisions, the anterior vena cava, thoracic duct, the cardiac, pneumo- gastric, recurrent, and diaphragmatic nerves ; it also includes the thymus gland in the foetus and young animal. The posterior mediastinum is incomparably narrower below than above, in consequence of the oblique position of the diaphragm. Its inferior part, always deviated to the left, is extremely thin, and perforated by small openings, which give it the appearance of fine lace-work. Traversed altogether superiorly by the pos- terior aorta, the vena azygos, and the tlioracic duct, this mediastinum gives passage, a little lower between its layers, to the oesophagus, the oesophageal branches of the pneumogastric nerves, and to the left dia])hragmatic nerve. It is these layers of this mediastinum which pass to the lung to constitute the pulmonary pleura, in becoming reflected above and below, in a hori- zontal line extending from the root of the pulmonary lobe to the anterior face of the diaphragm. The pulmonary or visceral pleura, a continuation, as has been said, of the mediastinal pleura, is in contact, by its free face, with the parietal layer of the membrane. Its deep face adheres intimately, in Solipeds, to the proper tissue of the lungs. THE THORAX. 465 Independently of these four serous layers, tlie right pleura furnishes a special membranous fold, which arises from the inferior wall of the thoracic cavity, and ascends to envelop the posterior vena cava. This fold also sustains the right diaphragmatic nerve. In order to study the various portions of the pleurae collectively, with their reciprocal relations, and their connections with the organs contained in the thoracic cavity, we will suppose three transverse sections of this cavity : one passing behind the heart ; the other at the roots of the lungs, and dividing the left ventricle of the heart , the third traversing the anterior mediastinum, a little in front of the right ventricle. If. in the first section (Fig. 235), we take the costal pleura at the point a, and follow it up to 6, we will see it folded downwards to form the Ficr. 235, Fig. 236. Ficr. 237 THEOKETICAL S1::CTI0:ELs. — The lung is a very vascular organ. The nu- merous ramitications it receives divide into two orders — the functional and the nutritive vessels. Functional vessels of the lung. — We know that the blood returns from all parts of the body by the veins, after losing, along with its bright red '^' colour, the properties which render it fit to maintain the vitality of the tissues. It thus arrives at the right side of the heart, whence it is pro- pelled into the lung, there to be regenerated by mediate contact with the air. It is the pulmonary artery which conveys this fluid into the parenchyma of the organ, and by the pulmonary veins it is carried back to the heart. The artery is at first divided into two branches, which ramify and finally terminate in dense capillary plexuses upon the walls of the air-cells. The veins, innumerable and attenuated at their origin, like the arterial capillaries, terminate in from four to eight principal trunks, which open into the left auricle of the heart. These two orders of vessels, which necessarily participate in the phvsiolo- 83 AIR-CELLS OF LUNG, WCTH rSTTERVENING TISSUES. «, Epithelium ; h, Elastic trabecule ; c, Membranous wall, with fine elastic fibres. ARRAXGEIIEXT OF THE CAPILLARIES AROUND THE AIR-CELLS. 470 THE EESPIRATORY APPARATUS IN MAMMALIA. gical functions of the lung, like the vena portge with the liver, are very properly distinguished from the other arteries or veins of the organ by the designation of functional vessels. But though they are so named, it must not be inferred that they are excluded from all participation in the acts of nutrition, It is now admitted by competent authorities that the blood of these vessels concurs to sustain vitality in the tissue of the lung, in common with the nutritive fluid carried by the arteries and veins now to be described. Nutrient vessels. — By this name is designated the divisions of the hronchial arteries and veins, whose terminal ramifications anastomose with the capillaries of the pulmonary vessels at the ultimate bronchules. Lymphatics. — These vessels are divided into superficial and deep. The first form a network beneath the pleui'a , the second exist in large numbers around the lobules. They mix together, and terminate in the bronchial glands. (Lymphatics of very small size have been described as commencing in the alveolar spaces, on leaving which they gain a proper coat or internal tunic, and are subsequently supplied with valves.) Nerves. — The nervous branches supplied to tlie tissue of the lung come from the same source as those of the bronchial tubes — the pneumogastric and great sympathetic nerves. Their ramifications accompany the pulmonary vessels and bronchiae, and they show small ganglia on their course. Functions. — To know that the lung is the seat of the absorption of oxygen and the expulsion of carbonic acid from the nutritive fluid — phenomena accompanied by the transformation of the dark into red-coloured blood, and probably of several other metamorphoses yet doubtful or un- known —is the only authentic fact necessary to remember with regard to the functions of this organ. It must be added that the subtle molecular opera- tions from which all these phenomena result, take place in the lung by the mediate contact of the atmosphere introduced into the air-cells during inspiration, with the blood traversing the walls of these cells. With the intimate mechanism of these molecular actions we have nothing to do here, however Development. — Although the lung is in a state of inactivity in the foetus, yet it is one of the organs early developed. During the whole period of foetal existence, its lobular texture is much better defined than in the adult, and it then appears to be formed exactly like a racemose gland. Sections of it prepared for microscopical examination distinctly show the vesicles and their arrangement. We have already made known the differ- ences in colour and density which distinguish the pulmonary tissue of the foetus and that of the adult. It only remains to repeat what has been said as to the slight vascularity of the first, and to note that the blood of the pulmonary artery passes almost entirely into the posterior aorta by the arterial canal (or ductus arteriosus). DIFFERENTIAL CHARACTEBS IN THE LUNGS OF OTHER THAN SOLIPEB ANIMALS. The lungs of the Ox, Sheep, and Goat are remarkable for the distinctness with which the lobules are defined. They are, in fact, separated by thick layers of cellular tissue, continuous with the internal face of the visceral pleura. These thick septa are ratlier the interlobular ramifications sent off from the subserous envelope.) Dietrichs, who was the first to draw attention to this peculiarity in the larger Runnnauts. has justly remarked that it perfectly explains the altogether special characters of the lesions of pneumonia in these animals. The general figure of the lungs of Ruminants does not differ from that observed in the Horse ; the left lung, however, is divided into two lobes, and the right into four, THE LUNGS. ill of which one, an anterior, is curved in front of the heart this peculiarity. In the Pig, the lungs comport themselves like those of Kuminants. In the Dog and Cat, there is no well- marked fissure in either lung towards the Fig. 241 heart, which causes that organ to be almost completely enveloped by pulmonary tissue, *'- Tlie left lung has three lobes, and the right four, separated from one another by deep furrows, which are generally prolonged to the root. The lobules are small, very close, and the pulmonary tissue is exceedingly compact. (The pulmonary vesicles are pro- portionately largtr than in Rmninants.) COMPARISON OP THE LARYNX, TRACHEA, AND LINGS OF MAN WITH THOSE OF ANIMALS. 1. Larynx. — The human larynx is pro- portionally shorter and wider than that of animals. The principal cartilages are those which have been already studied ; but there are, besi tliH left ; consequently, the right auricle is to the right of the sternum, between the third and fourth rih.s, and the point on a level with the sixth left inter- costal space. The auricular ap- pendages, paiticularly the right, are more rounded and bulging than in animals. The pulmonary veins, four in number, open on the upper face of the left auricle. There are no essential ditfcr- HUMAN LUNGS AND HEART; FRONT VIEW. ^^^^^^ ^^ ^^ ,^^^^,1 j.^ j^^ i„t.rnal 1, Right ventricle 2, Left ventricle ; 3, Right auricle ; conformation. We may indicate 4, Left auricle ; 5, Pulmonary artery ; 6, Right the presence of a fold that passes pulmonary artery; 7, Left pulmonary artery; 8, from, the ring of Vieussens to the Ligament of ductus arteriosus; 9, Arch of aorta; opi ning of the inferior vena cava : 10, Superior vena cava ; 11, Arteria mnominata; 12, this is the Eustachian valve. We Right subclavian vein, with the artery behind it ; niay also mention tiie Thebesian 13, Right common carotid arter\ and vein, 14, Left vena innominata , 15, Left carotid artery and vein ; 16, Left subclavian vein and artery; 17, Trachea; 18, Right bronchus; 19, Left bronchus; 20, 20, Pulmonary veins; 21, Superior lobe of right lung; 22, Middle lobe ; 23, Inferior lobe ; 24, Superior lobe of left lung; 25, Inferior lobe. valve at the entrance of the coro- nary vt in. The tibious rings and muscular fiisciculi are disjiosed as in the Horse. 'I'he pericardium is a conical sac ; but instead of its base being presented upwards, it rests against the aponeurotic centre of the diaphragm ; its summit is lost among the large vestels, and it adheres to the posterior face of the sternum. SECOND SECTION. The Arteries. CHAPTER I. GENERAL CONSIDERATIONS. The name of arteries is given to the centrifugal vessels, whicli carry the blood from the heart to the various organs. These vessels proceed from the heart by two trunks, which are perfectly independent in the adult animal ; they originate, one in the right ventricle, the other in the left. The first of these trunks, destined to carry the dark blood, is the pul- monary artery. The second conveys the red blood, and is named the aorta. There exist, therefore, two groups of arteries ; the pulmonary system, and the aortic system. General Form.— -Single at their origin, the two arterial systems soon divide into less voluminous trunks, which again subdivide into successively decreasing canals, until at last their diameter becomes reduced to an extreme degree of tenuity. In a word, the arterial trunks present the ramous dis- position of dicotyledonous plants. The total volume of the secondary trunks exceeds that of the primary trunk, and the same relation exists between the respective dimensions of the branches and their ramifications, to the ultimate divisions of the artery. In tracing all the ramifications of one of these systems to a single canal, it will then be found that this canal is incessantly increas- ing from its origin to its termination, and that it represents a hollow cone whose apex corresponds to the heart. Form of the Arteries. — Each aiterial tube affects a regularly cylin- drical form, whatever its volume may be. When the diameter of these vessels is measured at their origin and their termination, between two collateral branches, no sensible difference is perceived. Mode of Origin. — The arterial ramifications are detached in an angular manner from the parent branches which give them origin. Sometimes the angle of separation is more or less acute — this is most frequently the case ; sometimes it is at a right angle, and at other times it is obtuse. It will be readily understood that the opening of this angle exercises a somewhat marked influence on the course of the blood ; for example, the blood from a principal vessel, in passing into the canal of a secondary one which springs from it at an obtuse angle, must experience a notable check in its impetus, because of the change in direction it has to encounter , on the contrary, the rapidity of the current is not modified to any appreciable degree in those vessels which separate from their trunk of origin at a very acute angle. Towards the point of separation, there is always remarked, in the interior of the vessel, a kind of spur whose sharp border is towards the heart, thus dividing the current of blood and diminishing the resistance. This spur resembles in its disposition the pier of a bridge, against which the waters are divided to pass on each side. (When a short trunk divides abruptly into several branches, proceeding in different directions, it is termed an axis. A very peculiar feature in the division of arteries, however, and one which will be 516 TEE ARTEBIES. made amply conspicuous in the following description, is their bifurcation or dichotomous arrangement, which prevails so largely.) Course. — In the course pursued by an artery, it is necessary to consider the situation occupied by the vessel, its direction, relations, and the anastomoses which establish communication between it and the neighbouring vessels. Situation. — The arteries tend constantly to recede from the superficial parts : to become lodged in the deep-seated regions, and in this way to be removed from the hurtful action of external causes, a tendency all the more marked as the arteries are more considerable in volume, and which ceases to be manifested in the less important ramuscules. These vessels, therefore, occupy either the great cavities of the trunk, or the deep interstices on the internal face of the members ; when they pass over an articulation, it is always on the side at which flexion occurs. But in the limbs, for instance, the joints are flexed alternately in opposite directions, and it then happens that the arteries in these regions have a slightly helicoid (or spiral) disposi- tion. This is evident in the case of the femoral artery, which passes round the inner face of the femur to become the popliteal artery ; and also in the luuneral artery, which is at first situated to the inner side of the scapulo- humeral articulation, then turns around the humerus to be placed in front of the elbow joint. Direction.- — The arteries are sometimes rectilinear, and at other times more or less flexous. The latter disposition is evidently intended to prevent the dilaceration of the vessels in organs susceptible of elongation and con- traction, as may be remarked in the tongue or to moderate the impetus of the blood, as in the internal carotid arteries. Belations. — In their course, the arteries may be in contact with the viscera, nerves, muscles, bones, skin, and connective tissue. a. In nearly every part of the body, the arteries maintain the most intimate relations with the veins : sometimes with two of these vessels, when the artery is placed between them ; sometimes with only one, which is always more superficial. h. The arteries are usually accompanied by nerves belonging to the cerebro-spinal or ganglionic systems. Those of the latter category are distinguished by the reticular interlacing they form around the visceral arteries ; their structure will be alluded to presently. c. Lodged for the most part in the interstices of the muscles, the arteries contract relations with these organs which it is very important to know in a surgical point of view. Some of these muscles lie parallel with important arteries, and for this reason have been designated satellite muscles; they serve to guide the surgeon in searching for the arteries, by the more or less salient relief their presence affords beneath the skin. It is worthy of remark that the arteries are not included in the fibrous sheaths enveloping the muscles ; these vessels nearly always occupy, with the nerves which accompany them, special lodgments resulting from the approximation of several aponeurotic sheaths. When they pass through the substance of a muscle, which sometimes happens, they are covered by an arch or fibrous ring, which protects them from compression during muscular contraction : the arch or ring receiving on its convexity the insertion of fibres from the muscle. d. Nothing is more common than to see the arteries in direct contact with the bones : as, for instance, the aorta, intercostals, &c. Neither is it very rare to find a more or less thick muscular layer between the arteries and portions of the skeleton. In every case, a knowledge of the connections (GENERAL COXSIDERATIONS. 517 of the arteries with the bones is important to the surgeon ; as it enables him, temporarily, to interrupt the circulation in these vessels by exercising external pressure on the points of their coui'se which correspond to the several bones, and thus diminish their calibre by flattening them. e. By virtue of their deej) situation, the arteries are, in general, distant from the skin ; there are, nevertheless, some which course immediately beneath the inner face of that membrane ; these are only fomid about the head and in the extremities. /. Lastly, all the arteries are enveloped by a layer of connective tissue, •wliich forms around them a kind of sheath, generally difficult to tear with the fingers alone, and which isolates from the neighbouring parts, but chiefly the veins. This connective tissue, more or less abundant according to the regions, is always loose enough to allow the arteries to roll and be displaced with the greatest facility, and thus to glide away from incisive bodies accidentally introduced into the tissues. Anastomosea. — Very often the arterial branches are united to each other by communications, which have received the name of anastomoses, and which assure the distribution of the blood in regulating its flow. There are distinguished : 1. Anastomoses by convergence : formed by two vessels joining at their terminal extremity in an angular manner, to form a third and more voluminous trunk. 2. Anastomoses hy arches or hy inosculation : due to the junction of two principal branches, which are inflected towards each other, meet, and unite to form a single and curvilinear canal. 3. Anastomoses by transverse communication : represented by ramifications thrown transversely between two parallel arteries. 4. 31ixed or composite anastomoses : in which are found a combination of the different types enumerated above. A knowledge of the anastomoses of vessels is of the highest practical interest ; as these communications permit the surgeon, in extreme cases, to tie the principal artery of a region without the latter experiencing any considerable nutritive disturbance ; the blood continuing to arrive by the collateral vessels which, at first very small, ■ gradually dilate from the excentric pressure to which their walls are submitted. But these anasto- moses, if they offer this immense advantage, have also their inconveniences : we allude to the difficulties experienced in arresting hfemorrhage in wounds of certain organs, owing to the relations of the principal vessel with its communicating collaterals. Mode of Distribution. — The branches an artery distributes in the neighbouring organs are distinguished as terminal and collateral. The arterial trunks, after finishing a certain course, divide into several branches — nearly always two, which, as new arteries, continue the primary vessel and take the name of terminal branches, because they really begin at the terminal extremity of that vessel. The collateral vessels originate at various distances along the course of the arteries, and proceed in a lateral direction : these collateral branches increase in number as the arteries become more superficial, the ramifications being particularly abundant around the articulations, and in the organs which are prominent on the surface of the body. This abundance of vessels is intended to maintain a moderate temperature in those parts which, by their structure or situation, are exposed to sudden chills. The distinction between the terminal and collateral branches of arteries 36 518 THE ARTERIES. is not always easy to establish, and is far from having an absolute value ; it possesses, nevertheless, some importance, as it greatly facilitates description. Termination.— The arteries terminate in the substance of the tissues by extremely fine and numerous ramuscules, which so frequently anastomose with each other as to form a plexus or microscopical network, whose meshes Fig. 266. WEB OF FROCi'S FOOT STRETCHING BETWEEN TWO TOES, SHOWING THE BLOOD- VESSELS AND THEIR ANASTOMOSES. a, a, Veins ; 6, 6, b, Arteries, the capillaries being between. Fiff. 267. are very close. These ramuscules constitute the capillanj system, which again gives rise to ramifications of gradually increasing size, the veins. The capillary system is, therefore, nothing more than a network of microscopical canals intermediate to the arteries and veins. In the erectile tissues, the mode of tefmination is different : the small arteries sometimes opening directly into the cells placed at the origin of the veins, without jjassing through a capillary plexus. In describing the genital organs we shall notice, in detail, the termination of the arteries in the cavernous tissues. Structure. — The walls of arteries offer a certain rigidity, which permits tliese vessels to remain open when they are emptied of blood. The ancients believed this was their normal condition, and that they were filled with air during life. This was a grave error, as a perfect vacuum exists throughout tlie entire circulatory system. The gaping of the arteries mtist be attributed solely to the physical properties of their walls. These wails comi>rise three superposed tunics : an internal, middle, and external. The internal tunic is continuous with the endocardium of the left heart EPITHELIAL CELLS OF BLOOD-VESSELS. a, b, From a vein ; c, From an artery, Magnified 350 dia- meters. GENERAL CONSIDERATIONS. 519 Fig. Fig. 270. FENESTRATED MEMBRANE FROM THE CAROTID ARTERY OF THE HORSE. Magnified 350 diame- ters. Fig. 269. on the one part, and on the other with the capillaries and veins. For a long time it has been assimilated to a serous membrane, but it has not absolutely the same texture. It is composed of a simple epithelial layer which is in contact with the blood, and is formed by fusiform cells that slightly bulge in the situation of their nucleus. These cells sometimes become detached, and are carried about in the nutritive fluid, in Avhich, after a certain period, they resemble more or less mis-shapen blood- globules. The epithelium lies upon a layer of amorphous elastic tissue, perforated by openings, and named the fene- strated membrane ; on its ex- ternal face are proper elastic fibres passing in a longitudinal direction. The middle tunic is remark- able for its thickness, its elas- ticity, and the yellow colour it offers in the principal vessels. It is composed of a mixture of elastic fibres, as well as smooth muscular fibres, the first constituting a kind of network, in the meshes of which the contractile fibres are disposed in a circular manner around the vessels. The proportion of these two elements varies with the size and situation of the artery. In the large trunks, such as the aorta, the elastic is more abundant than the contractile ; in the middle-sized vessels they are about equal ; but in the small arteries, in which the contractile force of the heart is lost because of their distance from it, the muscular fibres almost exclusively com- pose the middle tunic. The external tunic is only a layer of connective tissue, with some longitudinal reticu- lated elastic fibres in its deeper part. Though this tunic is very thin, yet it is strong ; as Jirgnified 35o"dYame- a ligature tied tightly around an artery will rupture ters! the other tunics, but not this. The structure of the capillaries is not the same as that just described, but is modified in proportion as they are fine. In the smallest capillaries, the walls are formed by a thin amorphous mem- brane, in which (oblong) nuclei are somewhat regularly disseminated ; in medium-sized vessels, another layer containing transverse nuclei is observed ; and in the largest capillaries — those immediately succeeding the small OP COARSE TISSUE FROM MIDDLE COAT OF PUL- MONARY ARTERY OF THE HORSE, THE FIBRES BEING PIERCED WITH ■ CIRCULAR OPENINGS. TRANSITION OF A MINUTE ARTERY OF THE BRAIN TNTO CAPILLARY VES- SELS. 1, Minute artery; 2, Tran- sitional capillary ; 3, Coarse capillary with thick coat, represented by a double contour line; 4, Fine capillary, with single contour. The nuclei are seen widely scattered in 4- and 3 ; more closely con- gregated in 2 ; and still more so in 1, where they form an epithelium. — a, Transverse elongated nuclei of muscular cells, the inci]iient muscular coat of the artery. 520 THE ARTERIES. arteries, these two nucleated layers are enveloped by a thin tunic of con- nective tissue. (Some authorities state that the walls of the very finest capillaries ai'e merely composed of closely-adhering cells, without any basement membrane, which only becomes apparent in tubes of a large diameter.) Vessels and nerves — Tlie arteries are provided with vessels termed vasa lasorum, which are furnished either by the arteries themselves, or by ueigh- bouring vessels. These vasa vasorum form a superheial network witli quad- rilateral meshes, and a deep plexus whose principal branches are helicoidal. The majority of anatomists believe that this plexus does not extend beyond the external tunic. The lymphatic vessels maintain intimate relations, in certain regions, with the capillaries. In the brain and spleen there has been discovered, around the arterial caiiillaries. a vessel that completely envelops them, and which has been named the lymphatic sheath. The nerves, designated vasa motors, accompany the vessels and penetrate the muscular tunic, for which they are naturally destined. These vaso- motor filaments join the branches of the capillary plexuses, and form, at the points where they meet each other, ganglionic enlargements, from which arise the fibres of Remak, the termination of which is unknown. Anomalies in the Arteries. — In their arrangement, the arteries very often present anomalies which the surgeon should be guarded ag-ainst. These usually belong to their number, their point of origin, and their volume. In a purely anatomical and jjliysiological point of view, however, these anomalies are of no moment ; as it matters little whether the blood comes from one source rather than another, or that a collateral vessel be- comes the principal at the expense of the parent trunk, provided its rela- tions are not altered, and the principle of immutability of connections is maintained. Preparation of the Arteries. — This requires two successive operations: 1, In- jection; 2, Dissection. Injection of the arteries. — The object to be attained in injecting these vessels, is to introduce into their interior a solidifiable substance whicli •will cause them to assiune the volume and conformation they presented during life, when they are filled witii blood. Tallow, coloured by lamp-black, is the most convenient and gL-nera'i injecting mate- rial. Sometimes a solution of gelatine, with the addiiion of a certain quantity of plaster of Paris, is used ; but this is seldom employed in the French schools. A copper or brass syringe, and a canula with a stop-cock to fit on its extremit}% are the only instru- ments necessary to propel these mutters into tlie arteries. The following are the details of the operation, when it is desired to make a general injection: — -The animal being placed on a table, the carotid artery is exposed by iin incision in the jugular cliannel, and opened longitudinally. A ligature is applied above the opening, and the tube, with the stop-cock, is firmly fixed in the cavity of the artery towards the heart by a second ligature. The injection, previously prepared, is tuken up by the syringe, which is fitted into the tube, and the piston pushed, in order to drive the contents of the instrument into the arterial canals. To perform the operation successfully, the following precautions are to be attended to: 1. Inject the vessels of an animal killed by eft'usion of blood, and yet warm. 2. If suet is employed, and which is always to be reconunended, make it so hot that the finger can scarcely endure it. When it is colder than this it solidifies too quickly, and when liotter it shrivels up the sigmoid valves, passes into the left ventricle, and from thence into the auricle and pulmonary veins; an accident generally attributed to the tOD power- ful force applied to the piston of the syringe. 3. Do not make any undue pressure on the piston, though this does not strain the sigmoid valves so frequently as is believed. 4. Cease injecting when the arteries react, by their elasticity, on the piston, so as to drive it back in the syringe. In order to insure the retention of the injected matter in the arteries, and prevent the sigmoid valves being forced a cork may be intioduced into the aoita througu the PULMONARY ARTERY. 521 left ventricle, and firmly tied there by a strong ligature ; the cork should have a traiis- verse notch for the reception of the liirature. In.itead of injecting by the carotid, a long curved canula may be fixed to the aorta itself, after making an opening' in the left side of the chest, on a level with the heart, by the ablation of two segments of the ribs, and incising the pericaiilium and left auricle to introduce it. This mode allows the tallow to be injected at a very high temperature, and gives tlie best results, lor it can then penetrate to the capillaries, if we only know how to manage it ; in certain organs the injected matter may even be made to return by the veins. But no matter what procedure may be adopted, there are several parts into which the tallow can never be made to enter by a general injection • these are the four extre- mities. So that a special operation must be resorted to, in order to fill their vessels. After separating theur from the trunk, by sawing them through ahove the knees and hocks, they should be allowed to steep for two hours in water, con.stantly kept up to a temperature of 140^ to I(3U'^ Fahr. at most ; it is then easy to inject them, either by the posterior radial artery, or the a"terior tibia!, alter tying those branches wiiich may be open at the cut extremity of the limbs. If it is desired to make partial injections in other parts of the body, it will be better not to separate them from tlie trunk ; but only to tie those vessels which anastomose between the arteries to he filled and those which are not. For example, to inject the arteries of the head, it suffices to push the mixture into one of the common carotids, after ligaturing the other in the middle of the neck, and both vertebrals in the space between the two portions of the scalenus muscle. We may give ilie tallow more fluidity, and a higher degree of penetration, by mixing with it a little spirits of turpentine ; or more consistence, in adding to it a small proportion of beeswax. The two following mixtures are borrowed from Cruveilhier's Anatomy : — Tallow 9 parts Turpentine 1 .? Ivory Black, mixed with spirits of turpentine . 2 „ For preservative injections : — Beeswax 1 part Tallow 3 „ Vermilion, indigo, or Prussian blue, previously mixed in spirits of turpentine A sufficient quantity. Of course it is well understood that these instructions are only intended for the diss -cting-room injections necessary for the study of descriptive anatomy. To inject the capillaries, it is requisite to have recourse to other substances and other procedures. Sutfice it to say that these injections are made with cold fluids, such as varnish, alcohol, or spirits of turpentine, holding in suspension extremely fine colouring matter, gum arable dissolved and coloured by a substance also in solution, etc., or, better still, colours rubbed up in oil, and mixed with spirits of turpentine. Dissection of the arteries. — There are no general rules to be given for the dissection of arteries. CHAPTER II. PULMONARY ARTERY (Fig. 258, e). Preparation. — The pulmonary artery is not filled by the general injection mentioned above. It is directly injected by propelling the tallow into the right heart by the anterior vena cava, after tying the posterior vena cava. The pulmonari/ artery springs from the infunflibulum of the right ventricle, is directed upwards and then backwards, describing a curve whose concavity is infero-posterior, and arrives above the left auricle, where it divides into two secondary arteries, one for each lung. These arteries enter the pulmonary tissue with the bronchi, and exclusively ramify in it. The pulmonary artery accompanies the trunk of the aorta on the right side, and is enveloped with it in a serous sheath, a dependency of the visceral layer of the pericardium. At its origin, it is flanked before and behind by 522 THE ARTERIES. the appendages of the auricles and the cardiac yessels. About the middle of its coui'se, it is united to the posterior aorta by means of a yellow elastic fibrous cord (the ligamentmn arteriosum), the remains of the ductus arteriosus wliich, in the foetus, establishes a large communication between these two vessels (Fig. 258, e). The walls of the pulmonary artery are much thinner than those of the aorta, and are yellow and elastic, as in the other canals of the same order. We remember, however, having seen them in an Ass, formed almost entirely of red muscular fibres, analogous to the fiisciculi of the heart. It may be repeated that the pulmonary artery conveys into the lungs the dark blood carried to the right heart by the veins of the general circulation. ' CHAPTER III. THE AORTA. If we take a general survey of the aortic trunk, we will find tliat it arises from the base of the left ventricle, ascends to beneath the dorso-lumbar column, curving backwards and downwards, and reaches the entrance to the pelvis, where it terminates by four branches. It furnishes, besides, about 2 to 2|- inches from its origin, a secondary trunk, which soon divides into two new arteries, the right and largest of which gives off a particular trunk, the common origin of the two long vessels destined for the head. This disposition permits us to recognise in the aorta seven principal sections : 1. The aortic trunh or common aorta : the source of all the arteries belonging to the red-blood system, and giving rise to the anterior and posterior aorta. It only furnishes blood directly to the heart itself. 2. The posterior aorta : the veritable continuation of the (common aorta, is distributed to the posterior moiety of the trunk and to the abdominal limbs ; it terminates by a double bifurcation. 3. The internal and, 4, external iliac arteries: branches of this bifuraxtiou which are almost entirely expended in the posterior limbs. 5. The anterior aorta: the smallest of the two trunks furnished by the common aorta, is chiefly destined to the anterior moiety of the trunk and the thoracic limbs. 6. The axillary arteries, ov brachial trnnlcs: these come from the bifurca- tion of the preceding artery, and aie continued by their terminal extremity into the fore-limbs. 7. The carotid arteries, or arteries of the head : these emanate by a common trunk from the right brachial bifurcation. Article I, — Aortic Trunk or Common Aorta. The point of departure for all the arteries carrying red blood, the aortic trunk proceeds from the left ventricle by becoming continuous with the festooned fibrous zone which circumscribes the arterial orifice of that cavity. It passes upwards and a little forwards, bifurcating, after a course of 2 or 2-i inches, into the anterior and posterior aortse. Its volume, mferior to that of its two terminal branches, is not uniform ; as at its origin, and opposite the sigmoid valves, it presents (an enlargement — the hulhus aortse — caused by) three dilatations described as the sinus of the aorta {sinus aortici, sinus Valsalvse). TEE POSTERIOR AORTA. 623 Included, on the right side, in the crescent formed by the auricular mass ; in relation, on the left side, with the pulmonary artery, which is joined to it by means of cellulo-adipose tissue traversed by the cardiac nerves, the common aorta forms, with tlie latter artery, a fasciculus enveloped by the visceral layer of the i^ericardium, which is reflected as a sheath around these two vessels. Two collateral arteries are given off directly from the aortic trunk: these are the cardiac or coronary arteries. Cardiac or Coronary Arteries. (Figs. 258, 259.) There are two cardiac arteries, a right and left, exclusively destined for the tissue of the heart. Right Cardiac Arteky (Figs. 258, 259, l). — This originates from the front and to the right of the aorta, at the free margin of the sigmoid valves, and proceeds perpendicularly, or at a right angle, from the trunk, passing forwards to the right of the pulmonary artery, beneath the anterior auricle ; then to the right and backwards, to reach the aiiriculo- ventricular groove, which it follows till near the origin of the right ventricular furrow. Here it divides into two branches : one vertical, descending in this furrow to the apex of the heart, which it bends round to the front, and anastomoses with an analogous branch of the left coronary artery ; the other is horizontal, is smaller than the first, aud follows the primitive course of the artery in the auriculo-ventricular gi'oove, also inosculating with the artery of the left side. Left Cardiac Artery (Fig. 258, 2). — This arises opposite the pre- ceding, at the same angle of incidence, passes behind the pulmonary artery, and divides, under the left or posterior auricle, into two branches similar in every respect to those of the right artery. The vertical branch descends in the left perpendicular furrow ; the horizontal is lodged in the coronary groove ; aud both anastomose with the analogous branches of the opposite vessel. From this arrangement, it results that the heart is surrounded by two arterial circles : a vertical, or ventricular, which has been compared to a meridian ; and a horizontal, or auriculo-ventricular, analogous to an equatorial circle. In tlieir course, which is more or less tortuous, the coronary arteries throw out a considerable number of ramuscules, which enter the muscular tissue of the heart. The vertical circle gives off branches which are entirely ventricular ; while from the horizontal circle come the superior or auricular, and inferior or ventricular branches. Among the latter there is one which, rising from the right artery where it bends at an angle beneath the auricle, enters the substance of the right ventricle by passing round the pulmonary infundibulum ; its ramifications anastomose with those of a similar branch from the left artery, and in this way establish another com- munication between the two vessels. Article II. — Posterior Aorta. Cuurse.^This artery is a continuation of the aortic trunk, which it neai'ly equals in volume, and from which it passes upwards and backwards, describing a curve whose convexity is antero-superior, and which is known as the arch of the aorta. It thus reaches tlie left side of the inferior face of the spine, about the 8e>^nth dorsal vertebra, behind the posterior extremity of the longus coUi muscle, and is then carried directly backwards, following 524 THE ARTERIES. the vertebral bodies, though a little to the left at first ; it gradually incliues to the right, however, and reaches the median plane at the pillars of the diaphragm. Here it passes through the opening circumscribed by these two pillars, enters the abdominal cavity, and extends to the entrance of the pelvis, under the spine, still preserving its median position. On reaching the last intervertebral articulation, the posterior aorta tei'minates by a double bifurcation, from which arises the external and internal iliac arteries. Helations. — To facilitate the study of its connections, tlie posterior aorta may be divided into two sections : one thoracic, the other abdominal. a. At its origin or arch, the thoracic aorta is crossed to the right by the trachea and oesophagus ; on the opposite side, it responds to the pulmonary artery and the left lung. For the remainder of its extent, it is comprised between the two layers of the jjosterior mediastinum, and through these is in relation with the jmlmonary lobes, which are fissured for its reception ; this fissure is much deeper in the left than the right lung. Above, it is ill contact with the bodies of the last twelve dorsal vertebrae, and is accompanied on the right by the large vena azygos and tlie tlioracic duct ; the latter is often carried to the left for the whole or a j^ortion of its extent. (Remak observed muscular fibres on the external face of the aortic arch and thoracic aorta in the Horse, Sheep, and Pig ; the fasciculi they form are so large as to be visible to the naked eye.) h. The abdominal aorta, enlaced by the abdominal nerves of the great sympathetic, corresponds, above, with the bodies of the lumbar vertebrje, the originating tendon of the diaphragmatic pillars, Pecquet's reservoir., and the common inferior vertebral ligament ; it passes above the pancreas and the peritoneum, the latter by its sublumbar layer covering the posterior two- thirds of the vessel. On the right, it is accompanied by the posterior vena cava, which perhaps it slightly pushes to the left of the median plane. Collateral branches. — The arteries emanating from the posterior aorta during its long course, very naturally form two classes; some are desig- nated parietal, because they are distributed to the jiarietes of the great splanchnic cavities; the others are the visceral branches, destined for the organs lodged in these cavities. Among the parietal branches, may be noticed : 1. The intercostal arteries, furnished by the thoracic aorta. 2. The diaghragmatic arteries, whose origin is j)laced on the limits of the two portions of the vessel. 3. The lumbar arteries, and the middle sacral artery, springing from the abdominal aorta. The visceral branches are : 1. The broncho- oesophageal ->'i« ? O EL, _^ 00 CC 0) cs I FIT- ^ -;: t-T ^ I -4= H O C - 3 3 f- o co~ ; -S •-5 > r-« THE ANTEBIOB VENA CAVA. 605 internal maxillary artery. This vein issues from the parieto-temporal conduit, behiud the supercondyloid eminence ; it receives one or two branches which escape from this conduit by the foramina in the temporal fossa, crosses the temporal muscle, and is charged with venules which arise in the interior of that muscle, as well as in the textures of the external ear. 2. The subzygomatic vein, a satellite of the homonymous artery, and like it, divided into two branches : one accompanying the transverse artery of the face, the other the masseteric artery. The latter branch com- municates by its inferior extremity with the external maxillo-muscular vein ; it joins, by its other extremity, an enormous branch which comes from the temporal muscle, and which passes into the corono-condyloid notch, after being largely anastomosed with the deep temporal branches of the internal maxillary vein. 2. Internal Maxillary Vein. Remarkable for its enormous vohnne, this vein creeps between the internal masseter muscle and the maxilla, in an oblique direction upwards and backwards. Arriving withiu the articulation of the jaw, a little below the maxillary condyle and the external pterygoid muscle, it joins the temporal trunk after being slightly inflected downwards. It, therefore, runs its course at a certain distance from the corresponding artery (Fig. 290). The interual maxillary has for its root the buccal vein, which it succeeds near the superior extremity of the alveolo-labialis muscle. Satellite of the artery and nerve of the same name, this buccal vein, re- markable for its volume, is situated beneath the masseter muscle, near the inferior border of the alveo-labialis muscle ; by its anterior extremity it communicates directly with the internal maxillary vein, nearly opposite to the embouchure of the inferior coronary vein ; its posterior extremity is continued directly with the internal maxillary. The collateral branches it receives in its course come from the masseter muscle and the parietes of the cheek. On its way it receives a great number of affluents ; these are : 1. A large lingual vein, accompanying the small hypoglossal nerve. 2. The inferior dental vein. 3. The trunh of the deep temporal veins, a large vessel situated in front and to the inside of the temporo-maxillary articulation, where it com- municates with the masseteric. This vessel arises in the texture of the temporal muscle, bixt particularly in the parieto-temporal confluent, with which it joins by the foramina in the temporal fossa. 4. The pterygoid veins (Fig. 291), numerous branches, only a portion of which come from the pterygoid muscles. The others, springing from the subsphenoidal confluent of the sinuses of the dura mater, form, on the superficial face of the external pterygoid muscle, a wide-raeshed network which communicates posteriorly with the temporal trunk, and anteriorly with the confluent of the dee}) temporal veins. But as these two vessels are bound together, outside the temporo-maxillary articulation, by means of the masseteric artery, it results that this articulation is enlaced on every side by one of the richest venous plexuses in the whole economy. 3. Sinuses of tJie Dura Mater. We will here describe not only the sinuses of the encephalic dura mater which supply the roots of the jugular vein, but also those of the spinal dura 606 , THE VEINS. mater, although these empty themselves into other veins ; in order that we may be able to consider, in their entirety, all the vessels of the nervous centres which carry dark blood. The Sinuses of the Dura Matek in General. — These are vascular spaces comprised in the texture of the external meninge, or situated between that membrane and the bones which form the walls of the cerebro-spinal sheath, or even excavated on the iuner surface of these bones. These spaces diifer more particularly from the veins, by their being generally of a prismatic form, by being continually open, by the absence of valves in their interior, and the presence, in some of them, of himellse (irabecidce), or intersecting filaments (chordce Willim) which stud their iuner surface, and make them look reticulated. Their walls are reduced to an epithelial layer that lies either on the dura mater, or on the osseous tissue. It is into these sinuses that the veins of the encej)halon and the spinal cord disgorge themselves. The Sinuses of the Cranial Dura Mater in Particular. — Four principal will be described : the sinus of the falx cerebri or median sinus, the two cavernous or sphenoidal sinuses, and the group of occipito-atloid sinuses. 1. Sinus of the Falx Cerebri, or Median Sinus. — Channeled in the substance of the falx cerebri, and becoming wider as it extends backwards, this sinus commences near the crista galli, and terminates on the internal parietal protuberance by bifurca ting. The two branches resulting from this division forna the origin of the parieto-temporal coufiuent, or ivinepress of Herophilus (torcular Herophili). 2. Cavernous or Supra-sphe n oidal Sinuses. — These are two in number — a right and a left. They occupy, on the internal face of the sphenoid bone, at each side of the sella turcica, the so-called cavernous fissures. Bordered outwardly by the superior maxillary nerve, they receive at their anterior ex- tremity the insertion of the alveolar vein. Posteriorly, they join each other, and in doing so farm a kind of arch, open in front, around the pituitary gland. Each opens widely at the lacerated foramen, into the subsi)henoidal confluent. 3. Occipito-atloid Sinuses. — By this name is designated a network of larg« irregular veins, situated beneath the external face of the dura mater, on the sides of the occijiital foramen, and on the entire internal surface of the atloidean ring. Anteriorly, these venous reservoirs communicate, through the condyloid foramen, with the posterior extremity of the sub- spheuoidal confluent. Posteriorly they are continuous with the spinal sinuses, of which we may consider them to be the origin. 4. RuDiiME>fTARY SiNUSES OF THE Ckanial Dura Mater. — Independently of the above-described reservoirs, tliere exist, on the inner wall of the cranium, some rudimentary venous sinuses which should be indicated; these are : 1, One or two veins lodged in the structure of the tentorium, designated the petrosal or transverse sinuses, communicating, below, with the cavernous sinuses, and entering, above, into the parieto-temporal confluent ; ^ 2, Some small, irregular, and reticulated cavities, very variable in their disposition, situated beneath the dura mater, on the sides of the cerebellar cavity, atid which generally empty themselves into the subsphenoidal confluent, by ' ATore frequently, perliaps, these veins arise directly from the substance of the brain, and do not communicate, below, with the cavernous sinuses. THE ANTERIOR VENA CAVA. 607 traversing the posterior part of tbe lacerated foramen, and also opening some- times into the petrosal sinus ; these cavities may be regarded as the re})resen- tatives of the lateral sinuses in Man ; 3, In some instances, an inferior •H31 SJ-5^^ §r;2 §2 * 00 a, •" > y; a rt .^^ .- a -M s « ^ fl « " Cl o t^ ■■" rH O Is "3 ~ o »2 £ ° -" > 6J a 1^ s| "wit^r P'^ © g >, ., « CU 1. „ « j3 ^ _S 3 ' ■'^ O ~ c s -« a CO , £ la— 'S ^a ^ 5 =s > •< sT-S ."t; *j Is " 1. s- a .^ c — ^ 5 !s S « o 3 1 .2 ^ S E i2-5-o3 CO C o .^ ^ -!! -° ~ •- ^ o -3 C § O )J ■5 5--:: ^ s H i. a > b ^g'M O ^ s::-^ hr l-ll o H t« ■*' s - O ;3 o) !M w bX) •- U rH CO ^i^iT &• S fl -3 S •" e-«^ " ^■3 oTS 13 C3 a tn oj *j a; 0) -g^^o: ^Sd:^^ 603 THE VEINS. median sinus, channeled near the free border of the face of the brain, passes behind into the torcular Herophili. The Spinal Sinuses in Particular. — We thns designate in Veterinary Anatomy, and with good reason, two series of venous reservoirs which are found throughout the whole extent of the vertebral column, on the sides of the roof of the si:>inal canal. Lodged in the lateral depressions of the superior face of the vertebral bodies, at the side of the common superior vertebral ligament, and covered by the dura mater, these reservoirs, continued from one vertebra to the other, are like two large, irregular, parallel veins, which commence at the atlo-axoid articulation, terminate on the first coccygeal vertebrfe, where their presence is yet well defined, and communicate with one another during their course by transversal anastomoses. Affluent Veins that open into the Sinuses of the Dura Mater. — TJiese are the vessels which carry blood either from the dura mater itself, or from the substance of the nervous centres : those of the first category are rare, but the second are numerous. Although we are unwilling to make a detailed study of the latter, we must nevertheless notice what is most remarkable in their disposition. a. On the encephalon, the veins form a much richer and closer network than that of the arterial ramifications ; from this network proceed a certain number of principal branches, which throw themselves into the sinuses of the cranial dura mater. The veins of the cerebrum, for the most part, gain the median and transverse sinuses ; a few only pass into the cavernous sinuses. Those of the isthmus and cerebellum go to the i^etrosal and occipito-atloid sinuses. With regard to the internal veins of the brain — those which, by their interlacing, constitute the choroid plexus — we see them unite into a large trunk — the great vein of the brain, or vena Galeni, which bends round the superior extremity of the corpus callosum, reaches the interlobular fissure, and" throws itself into the falciform or middle sinus, near its posterior extremity, after receiving the superficial veins from tlie inner face of the hemispheres. h. The venules arising from the spinal cord are also very remarkable for the fine network they form on the surface of the organ. They collect into a common trunk — the median spinal vein, which runs from before to behind, throughout the whole extent of the superior groove in the spinal cord ; thus occupying an analogous, though oj)posite, jiosition to that of the artery of the same name. From this vein escape, at intervals, emergent branches which open into the spinal reservoirs. Effluent Canals of the Dura Mater Sinuses. — We have to notice, under this designation, the veins which transport the blood from the sinuses, and we will consider in succession those which commence at the encephalic reservoirs, as well as those that emerge from the interspinal canals. a. To be carried from the encephalic sinuses, the blood flows into two kinds of double gulfs, known as the jparicto-iemporal and suhsphenoidal confluents. The parieto-teraporal confluents are lodged in the canals of the same name, along with the mastoid artery. Each commences at the base of the internal parietal protuberance, and terminates behind the supercondyloid eminence. The median and transverse sinuses are confounded with tlie superior extremity of these reservoirs, and empty into tliem the blood coming from the encephalic mass. This fluid is subsequently taken away by the super- THE ANTEBIOB VENA CAVA. 609 ficial and deep temporal veins, which have their principal roots in these confluents. The suhsphenoidal confluents extend on the sides of the body of the sphenoid bone and the basilar process, from the base of the subsphenoidal process to the condyloid fossa, by concurring in the obturation or closing of the occipito-spheno-temporal hiatus. They open at their middle portion into the corresponding cavernous sinus, by an oval ajierture which the in- ternal carotid artery traverses in penetrating into the cranium. The anterior extremity terminates in a cul-de-sac. Posteriorly, they communicate through the condyloid foramina with the occipito-atloid sinuses. The vessels which carry off the blood from these confluents are the pterygoid veins, and the anterior root of the occipital vein. We already know that the posterior branch of the latter vessel removes the blood directly into the occipito-atloid sinuses. b. The emergent veins of the spinal sinuses present a more simple dis- position. At each intervertebral space arise several branches, which more particularly make their exit by the intervertebral foramina to join the neighbouring veins ; in the cervical region, the vertebral veins serve as a receptacle in this way for the venous branches emanating from the spinal sinuses ; in the dorsal region, it is the spinal branches of the intercostals ; in the loins, the analogous branches of the lumbar veins ; and in the sacral region, the lateral sacral vein. AXILLARY VEINS. A general confluent of all the veins of the thoracic limb, and of some from the trunk, the axillary vein commences beneath the scapulo-humeral articulation, towards the terminal extremity of the corresponding arterial trunk, accompanying the latter to the entrance of the chest, and joining the confluent of the jugulars to constitute, with these two vessels, the inferior vena cava (293, 18). In studying, from their origin to their termination, the numerous branches which concur in the formation of this venous trunks we re- cognise : 1. That they form in the foot a very rich network, from which proceed the digital veins, satellite vessels of the homonymous arteries. 2. That to these digital veins, which are united in an arch above the larf^e sesamoids, succeed three metacarpal branches or collaterals of the cannon: two superficials, placed on each side of the flexor tendons, and a profound (or deep) vein, situated underneath the suspensory ligament, along with the interosseous arteries. 3. That the metacarpal veins also open into each other, in the superior and posterior region of the carpus, to form, on again separating, two groups of antihrachial veins : one group comprising the tdnar and the posterior or internal radials, which accompany the arteries of the same name ; the other, constituted by a single subcutaneous branch, the median vein, which receives at its superior extremity the anterior superficial radial vein. 4. That at the ulnar articulation, these two groups of antihrachial veins join the satellite vessel of the anterior radial artery, and communicate by a very complicated system of anastomoses, from which results a principal trunk, the humeral vein. 5. That the humeral vein, after receiving on its course several muscular 610 THE VEINS. brandies and the subcutaneous thoracic vein, unites near tLe shoulder-joint with the suhscajmlar trunk, to form the axillary vein. We will study all these branches in the inverse order of their enumeration. 1. Subscapular Vein. A V3ry considerable vessel, whose disposition resembles that of the subscapular artery, though presenting some special peculiarities whose study does not deserve a moment's delay ; for example, it most frequently receives the satellite vein of the prehumeral artery. 2. Humeral Vein. Placed behind and within the humeral artery, this vessel commences above the articulation of the elbow, being formed at this point by the anasto- mosing system of veins from the fore-arm, and terminates below the shoulder- joint in opening into the subscapular vein. Independently of the subcutaneous thoracic vein, which will be studied in a special manner, the humeral vein receives on its way several collateral satellites of the branches emanating from the humeral artery. One of these, the ejncondyloid, is only a continuation of the ulnar vein. Very often we find a second humeral vein in the deep region of the arm ; this is an accessory vessel, parallel to the preceding, and situated opposite it in front of the artery. 3. Subcutaneous Thoracic or Spur Vein. This vein, which is important to know, as bleeding is sometimes practised from it, commences on the flank and belly by numerous super- ficial divisions, which unite in two principal roots, and afterwards become a single trunk, placed in the substance, or on the external surface of the panniculus carnosus, where it is directed forwards in following the superior border of the large pectoral muscle, accompanied by an arterial ramuscule and a thick nerve. It insinuates itself beneath the olecranian muscles, and finally terminates in the humeral vein by opening into the branch that follows the deep muscular artery. 4. Deep Veins of the Fore-arm. A. Anterior Eadial Vein. — This follows the same track, and affects the same variations, as the corresponding artery. B. Posterior Radial Veins.— The posterior radial artery is always accompanied, and, as it were, enveloped, by a fasciculus of three or four venous branches, which frequently anastomose with each other, and are reinforced by collateral branches, among which the interosseous vein must be noted. These radial branches commence above the carpus, by continuing the metacarpal veins. They concur to form the humeral vein, in joining the other antibrachial veins at the inferior extremity of the arm. C. Ulnar Vein. — This vessel is lodged, with the nerve and small artery of the same name, in the interstice of the oblique and internal flexors of the THE ANTERIOR VENA CAVA. Cll metacarpus. A number of muscular aud subcutaneous branches enter tbis vein. It has the same origin as the posterior radial veins. Its superior or terminal extremity bonds forward, close to the trunk of the epicondyloid artery, and goes to the inferior extremity of the humeral vein. Frequently the ulnar vein is double in the latter portion of its track, and between the two branches lies the artery. It always communicates at this point, by one or more branches, with the deep muscular vein. o. Superficial Veins of the Fore-arm. Placed outside the fibrous sheath formed by the antibrachial aponeurosis, these veins, which are principally two in number, are maintained against the external face of that membrane by a thin fascia which separates them from the skin. A. Median, or Internal Subcutaneous Vein (Fig. 293, 31). — This is also one of the vessels selected for the operation of phlebotomy. It is the continuation of the internal metacarpal vein, ascends from the inner face of the carpus to the superior extremity of the fore-arm, by crossing the radius in a very oblique manner, and terminates in two very large branches, the posterior of which is the hasilic vein, and the anterior the cephalic vein. The hasilic vein traverses the sterno-aponeurotic (transverse pectoral) muscle, to aid in forming the humeral trunk (Fig. 293, S-i). The cephalic, ov plat vein, crosses the superticial band of the biceps or coraco-radial muscle, is lodged in the space comprised between the levator- humeri and small pectoral muscles, and afterwards opens into the jugular vein (Fig. 293, 35). B. Subcutaneous, or Anterior Eadial Vein (Fig. 293, 32). — Less considerable than the preceding, this vein arises at the carpal region, in its course occupies the anterior face of the fore-arm, and terminates in uniting its superior extremity either to the subcutaneous median or the cephalic vein ; the last is most frequently the case. 6. Metacarpal Veins. Three in number, as we know, these veins are distinguished into in- ternal and external collateral of the cannon, and deep or interosseous collateral. A. Internal Collateral of the Cannon. — More voluminous than the others, this vein passes from the vicinity of the fetlock along the flexor tendons, accompanied by the principal artery of the cannon and the external plantar nerve, places itself in the special sheath which envelops the common trunk of the interosseous arteries to the inside of, and behind the carpus, to be continued in the antibrachial region by the median subcutaneous vein, after communicating with the other metarcarpal veins (Fig. 293, 30). B. External Collateral op the Cannon. — Situated opposite the preceding — to the external side of the flexor tendons, in company with the corresponding plantar nerve — the external collateral of the cannon follows that nerve to near the trapezium, and then separates into several reticulated branches whicli anastomose with the internal collateral, from which proceed the ulnar and internal or posterior radial veins. G12 TEE VEINS. C. Interosseous Vein. — A tortuous, irregular, and sometimes multiple vessel, lodged with the plantar interosseous arteries between the suspensory- ligament and the posterior face of the principal metacarpal bone. Eeachiug the superior extremity of that bone, it unites largely to the right and lelt with the external and internal collaterals, sending upwards one or two small branches which traverse the carpal sheath along with the collateral artery of the cannon, and open into the posterior radial branches above the knee. 7. Digital Veins. These veins occupy, on the sides of the digital region, the same position as the homonymous arteries in front of which they are placed. They arise from the network formed on the lateral cartilages by the veins of the foot, and terminate in uniting above the fetlock, between the flexor tendons of the phalanges and the superior sesamoid ligament, so as to form an arch from which proceed the three metacarpal veins (,Fig. 293, 37). 8. Veins of the Foot or Ungual Region. The importance of the region to which these vessels belong, requires that they should be described more fully than the other veins, and as has been already done with the arteries of this part of the body. We will, therefore, borrow the exact and minute description given by M. H. Bouley.i This venous apparatus may be divided into external and internal or intra-osseous. a. External Venous Apparatus. "The external venous apparatus of the digital region is very remarkable for the number, development, superficial distribution, and reticulated disposition of the canals composing it. To give an idea of this, we cannot do better than compare its general form to a net whose irregular meshes are extended over, and moulded on, the two last phalanges which are contained in it. " This intricate reticulation of the venous apparatus of the foot is marvellously displayed in specimens injected after maceration, and then dried. " To facilitate its description, we recognise in it three parts distinct by their situation, though they only form a continuous one. They are : "1. The solar plexus. " 2. The podophyllous plexus. "3. The coronary plextis. " A. SoLAK Plexus. — The veins of the solar plexus are remarkable for the equality of their calibre throughout the whole extent of the plantar surface, and by the almost absolute absence of anastomotic communications with the deep parts. " Sustained in a special fibrous web (plantar reticulum), which replaces the periosteum at the lower surface of the phalanx, and is a continuation of the cerium of the villous tissue, these veins appear indeed to have so little communication, except with each other, that it is possible to detach the •plantar reticulum Ivom the superior face of the third phalanx without disturbing them. ' ' Traite de 'Organisation du Pied du Cheval,' p, 65. THE ANTERIOR VEX A CA VA, 613 " The general disposition of the venous canals in the texture of the reticulum supporting them, closely resembles that of the secondary ribs of the limb (or laminar merithal) of certain asymmetrical leaves. In their course they follow an irregularly-broken line, intercepting each other by joining at short intervals, so as to form unequal-sized, unsymmetric, polygonal spaces. " These venous conduits have a double canal for discharging themselves : a central, the least considerable and least constant ; the other peripheral or circumflex, corresponding to the artery of the same name,^ and whose satellite vein it is. " Central canal. — The central canal is formed by the simultaneous anastomoses of a crowd of venous ramifications converging towards the centre of the digit. It is of a parabolic shape, and embraces in the concavity of its curvature the point of the pyramidal body, whence it throws its two branches in a parallel manner on the sides of that body, into the bottom of the lateral lacunee as far as the cartilaginous bulbs, where it proceeds to the external coronary plexus. This disposition is not constant, however, as specimens are frequently met with in which this central canal is replaced by multiple veins, which are more considerable than those foi*ming the whole of the plexus, and which serve them as overfalls towards the super- ficial coronary plexus. Circumflex vein, or peripheral venous canal. — " This vein is of large calibre, and formed by divergent ramifications from the solar plexus, as well as the descending veins of the podophyllous j^lexus ; it margins the external limb of the villous tissue in following a slightly undulous line within the circumflex artery, whose satellite it is. It is sometimes broken up, at certain points of its course, into several smaller canals which are continuous with its trimks. " In its circular route, all the divergent solar and descending podo- phyllous veins are discharged into it, and it terminates, at the extremities of the crescent formed by the third phalanx, in several large branches which pass beneath the podophyllous tissue to the lateral cartilage, where they concur to form the superficial coronary plexias. " B. Podophyllous Venous Plexus or Network. — The veins of the podophyllous plexus exhibit a disposition analogous to those of the solar plexus ; like them, they are sustained in the meshes of a fibrous texture (the reticulum processigerum of Bracy Clark, the suhpodophyllous reticulum ot French Veterinarians) spread on the anterior surface of the bone, in the same way as the periosteum is on other bones, and continuous with the corium of the laminal tissue. Communicating largely between each other by multiple anastomoses, like the solar plexus, they appear to be completely isolated from the deeper parts, from which it is commonly believed they emanate. " Tortuous and split up into branches in their course, the podophyllous veins wind in a serpentine manner along the length of the laminae they cover, very close to each other, and forming narrow elongated meshes. Their confluence is such, that at certain points they appear bound together by their external walls. " The calibre of these vessels is tolerably uniform throughout the extent of the podophyllous plexus, except towards the posterior parts, where their principal canals empty themselves into the coronary plexus. " The podophyllous veins are in anastomotic communication, below, with ' The inferior circumflex artery of the foot, 42 614 THE VEINS. Fio;. 292. the circumflex vein of the solar plexus, whicli they concur to form, and above, with the coronary plexus, which is only a continuation of them. " C. Coronary Venous Plexus, — The coronary venous plexus (Fig 292, 2, 4) is arranged like a ramose garland around the second phalanx to the origin of the third, and on the surface of the cartilaginous apparatus which completes the latter. "It is supported, like the other venous networks of the digit, by a fibrous texture imme- diately subjacent to, and con- tinuous with, the corium of the coronary substance, and is juxta- posed, as well as adherent, to the expansion of the extensor tendon, the lateral cartilages, and to the bulbous enlargements of the plantar cushion. " This plexus proceeds from the intra- osseous, podophyilous, and solar networks. To facili- tate its description, we recognise in it three parts: one central and anterior, situated between the two cartilaginous plates, and two lateral, corresponding to these cartilages. " Central Part of the Coronary Plexus. — The central part of the coronary plexus (Fig. 292, 2), immediately subjacent to the substance or cushion of that name, constitutes a very close network formed by innumerable venous radicles, which rise in a tortuous manner from, and are continuations of, the podophyilous plexus, until they reach a large anastomotic vein thrown across from one cartilaginous plexus to the other, and into which they open by ten to twelve principal mouths (Fig. 292, 3'). " These veins of the central part of the coronary plexus gradually increase in calibre, and diminish in number, from the podophyllus plexus, where they take their origin, to their superior and terminating canal, which itself only appears to be the result of their successive anastomoses. " Cartilaginous Plexus, or Lateral Parts of the Coronary Plexus. — The cartilaginous plates serve to support, by their two faces and the canaliculi by which they are traversed, a mass of very close, anastomosing, and converging veins, which, from its situation, may be designated the cartUagtnous plexus. "This cartilaginous plexus is forme;! by two layers of vessels — a superficial and deep. '^Superficial cartilaginous layer or plexus. — The superficial layer (Fig. 292, 3, 4)," extended over the external surface of the cartilaginous plates and bulbs, has its origin by innumerable roots from the veins of that part of the podophyilous plexus corresponding to the superficies it occupies. These THE VEINS OF THE FOOT. THE ANTERIOR VENA CAVA. 615 roots, massed in a very dense network, converge towards the superior portions by diminishing in number and augmenting in volume, and terminate in forming themselves, by the aid of successive anastomoses, into ten or twelve principal branches which again unite into two considerable vessels (Fig. 292, G), situated at the superior limit of the plexus. These vessels, tinally, by their last fusion at the inferior extremity of the first phalanx, constitute the digital vein, the satellite of the artery of the same name (Fig. 292, 5). '' Considered from below upwards, in a foot previously prepared by injection, the digital vein, divided into two branches, subdivides itself into secondary branches and ramuscules which diverge and spread over the convex surface of the cartilage and coronary cushion, resembling somewhat the disposition of trees trained on esj)aliers, whose spreading branches are fixed to the walls on which they ramify. " The two peripheral branches of the superficial cartilaginous plexus establish communications with the opposite cartilaginous plexus, in con- tracting direct anastomoses with the branches of the plexus which aro symmetrical to them. " The anterior anastomosing canals are double and superposed. " The most inferior and superficial is constituted by the large vein (Fig. 292, 3') thrown slantingly across from one plexus to the other in the median plane, and on the external surface of the extensor tendon ; this receives a considerable multitude of venous ramuscles, which emerge from the anterior part of the podophyllous plexus. " This first communicafing vein joins the anterior branches of the carti- laginous plexus. " The second communicating vein, situated three-quarters of an inch above the first, and beneath the tendon, is thrown transversely from one anterior branch of the plexus to the other. They open into each other on each sido, at the same point where the first communicating vein enters. " Sinuous in the whole of its track, sometimes double, and sometimes formed of several confluent veins, as in Fig. 292, this anastomosing canal serves as an outlet for several deep veins. " The anastomosis between the posterior peripheral branches of the cartilaginous plexus is formed by an irregularly curved and long vein of large calibre, sinuous or broken in its course, but always considerably longer than the distance from the two cartilaginous plates between which it is extended. " This posterior communicating vein acts as a confluent to the canals emerging from the cartilaginous bulbs, and to the posterior part of the solar plexus, which throws into it five or six well-developed afferent veins. " Deep cartilaginous layer or plexus. — The deep layer of the carti- laginous plexus is formed : " 1. By somewhat large ascending branches from the posterior part of the podophyllous and solar plexuses. " 2. By the deep internal venous apparatus of the third phalanx. " 3. By the deep veins arising from the coronary bone and the liga- ments and tendons surrounding it. " The ascending branches of the podophyllous tissue are introduced by the numerous foramina which traverse the base of the cartilaginous plate and the inferior fibrous covering of the plantar cushion; they follow the canals which continue those foramina in the substance of the cartilage, and reach its internal face, along with the branches proceeding from the intra-osseous 616 TEE VEINS. venous system and those coming from the tendons and ligaments, forming a fasciculus of five or six thick converging veins which unite in two large ascending branches. These anastomose with each other before their de- finitive junction with the two peripheral branches resulting from the super- ficial cartilaginous plexus, with which they concur in constituting the digital vein." h. Internal, or Intra-osseous Venous Apparatus. " Girard, the younger, and Eigot have denied that the plantar artery had, in the interior of the phalanx, a satellite venous system. These two able anatomists committed an error. " The disposition of the venous apparatus in the interior of the phalanx is absolutely identical with that of the arterial. " The satellite radicular venules of the terminal arteries converge, by forming successive anastomoses, towards the semilunar sinus, into which they enter by the anterior interosseous canals, ascending and descending, and by which the emergent arteries from the semilunar anastomosis pass out- wards. There they join into a semicircular canal, the satellite of that anastomosis, which is continued backwards by two eiferent veins that follow the posterior canals of the semilunar sinus, emerge by the plantar foramina, pass into the fissure of the same name, ascend within the basilar process, lie at the internal face of the cartilaginous plate, in one of the infractuosities with which it is sculptured, and concur in the formation of the deep layer of the cartilaginous plexus. " Beside these veins converging towards the cartilaginous plexus, there is a small number of divergent ones which follow the track of the arteries, and pass into the podophyllous plexus through the anterior porosities of the phalanx. " The dissection of specimens injected by the veins puts this arrangement of the venous apparatus in the interior of the os pedis beyond a doubt. " But is this internal venous system limited to the group of vessels which are satellites of the arteries, or is it not rather extended over a vaster surface, and may not all the areolae of the spongy tissue of the bone be considered as a dependency of it ? " This way of viewing it would seem to be supported by the result of certain injections, in which the material introduced by the neighbouring veins has filled all the internal spongiolse of the bony tissue ; though this was probably due to an accident in the operation, and it is presumable that the direct passage of the venous injection into the areola? of the spongy tissue arose from a rupture in the VASCular walls. If the tissue of the phalanx formed a kind of diverticulum for the venous system, as the opinion just given would admit, operations performed on this part during life, when the texture of the bone is deeply involved, ought to be followed by haB- morrhage from the open orifices of these aerolaa — a circumstance which does not take place. " It does not appear, therefore, that there is in the structure of the third phalanx any departure from the general plan on which bones are constructed, and we think that its internal veinous system is limited to the vessels, very numerous as they are, which accompany the arterial divisions." TEE POSTERIOR VENA CAVA. 617 ARTICLE III.— PosTERiOK Vena Cava. (Figs. 258, v; 259,/; 293.) This vein, whose volume is uot equalled by that of any other vessel in the body, commences at the entrance to the pelvis by two large roots, the pclvi-crural trunks. From this point it is directed forward, beneath the bodies of the lumbar vertebrae, soon reaches the superior border of the liver, where it leaves the lumbar region to lodge itself in the fissure excavated on the anterior face of that gland ; passing through this, it traverses the aponeurotic centre of the diaphragm, and opens into the postero-external part of the right auricle of the heart. In this course, the posterior vena cava is naturally divided into three portions — a suhlumbar, hepatic, and thoracic. The suhlumbar portion, placed to the right of the abdominal aorta and to the left of the right kidney and suprarenal capsule, is maintained against the common inferior vertebral ligament and the left small psoas muscle by the peritoneum and the pancreas. It responds, besides, to the right renal artery, which crosses its face perpendicularly, as well as the corresponding great splanchnic nerve and the nervous divisions of the right renal and iumbo-aortic plexuses. In its hepatic portion, the posterior vena cava is only related to the liver and diaphragm, wiiich form a comj^lete canal around it. The thoracic portion is lodged between the right lung and its internal accessory lobule, and enveloped by a particular serous fold— a dependency from the right j^leura, and which has been already described (page 465)w Collateral afferents. — Those vessels which, as considerable as they are numerous, open into the posterior vena cava, are, enumerating them from before to behind : 1. The diaphragmatic veins. 2. The vena portce, a trunk into which are collected the majority of the visceral abdominal veins, and which, instead of opening directly into the vena cava, is divided in the liver like an artery, reconstituting itself into a certain number of thick branches — the suprahepatic vessels, which enter the vena cava on its way through the anterior fissure of the liver. 3. Renal veins. 4. Spermatic veins. 5. Lumbar veins. All these vessels will be studied, in the order above indicated, before the roots or pelvi-crural trunks of the vena cava. DIAPHRAGMATIC VEINS, These are two, sometimes three, enormous vessels lodged in the texture of the aponeurotic centre, commencing by several branches in the fleshy jjortion of the muscle, and entering the vena cava at the moment when it traverses the diaphragm. VENA POET^. (Figs. 293 ; 294.) The manner in which this vessel comports itself gives it an altogether peculiar physiognomy, and has caused it to be considered as a separate vascular system. After what has been already said concerning the structure of the liver, it cannot be ignored that the vena portae is distributed in that gland exactly like an artery. 618 TEE VE1^S. Fig. 293. GENERAL VIEW OF THE VEINS IN THE HORSE. THE POSTEBIOR VENA CAVA. 619 It begins in the sublumbar region, at the great mcsenteiic artery, by tho union of three large roots ; it is then directed forwards and a little to the right, traversing the pancreatic ring, below the vena cava, and is afterwards lodged in the great posterior fissure of the liver, where it ramifies by forming the subhepatic veins, whose capillary divisions themselves give rise to the sujjrahepatic vessels. Sujprahepaiic and subhepatic veins (Fig. 219, VP, V^). — These vessels having been already studied in the description of the liver, we need not again occupy ourselves with them, but refer t)nly to a peculiarity incompletely noticed in that description, with reference to the suprahepatic veins. We know that these vessels are divided into two categories, according to the arrangement of their openings. The majority enter the vena cava in forming a single confluent placed at the anterior extremity of the fissure in the liver, at the diaphragmatic veins ; the others open separately over the whole extent of the hepatic portion of the venous trunk. In carefully examining the confluent towards which all the veins of the first group converge, we recognise the embouchures of three principal veins, one coming from each of the hej^atic lobes, and furnished with three very thick, incom- plete valves. With regard to the vessels of the second group, M. Claude Bernard ^ considers them to come, for the most part, directly from the sub- hepatic veins, and not from the capillary network formed by the arborisation of these veins in the lobules of the liver. It is true that injections readily penetrate from the vena portaa into the vena cava, but they do this quite as much by passing along the large suprahepatic vessels as the canals of which we now speak ; and, besides, if the material forced into the vena portae is mixed with some imperfectly-powdered colouring matter, the injection will arrive colourless, or but slightly tinged, in the suprahepatic vessels and the vena cava. These facts, we see, do not militate in favour of M. Bernard's * Lemons de Physiolojic Expertmentale.' Paris, 1856. Anterior vena cava; 2, 2, Posterior vena cava; 3, Right pelvi-crural trunk, divided at tlie ilio-sacra) articulation ; 4, Lett pelvi-crural trunk ; 5, Femoral veiu ; 6, Obturator vein ; 7, Subsacral vein ; 8, Left testicular vein ; 9, Puste- rior abdominal vein; 10, Renal vein; 11, 11, Ascending branches of the asternal vein; 12, Vena azygos, with its intercostal branches, and in front the subdorsal venous branch, 13; 14, (Esophageal vein; 15, Dorsal, or dorso-muscular vein; 16, Cervical, or cervico-muscular veiu; 17, Vertebral vein; 18, Right axillary vein, cut at the anterior border of the first rib; 19, Substernal, or internal mammary vein ; 20, Left axillary artery ; 21, Termination of the left cephalic vein; 22, Left jugular, 23, Right jugular; 24, External maxillary, or glosso- facial vein ; 25, Coronary vein ; 26, Angular vein of the eye ; 27, Subzygomatic vein ; 28, Posterior auricular vein ; 29, Maxillo-muscular vein ; 30, Internal metacarpal vein ; 31, Median subcutaneous vein ; 32, Radial subcutaneous vein ; 33, Posterior radial vein; 34, Basilic vein; 35, Plat, or cephalic vein; 36, Coronary venous plexus , 37, Digital vein ; 38, Internal metatarsal vein ; 39, Anterior root of the internal saphena vein ; 40, Posterior root of ditto ; 41, Internal saphena; 42, Great coronary vein; 43, Small mesaraic vein; 44, Dif- ferent branches of the great mesaraic vein ; 45, Trunk of the vena porta: in its sublumbar portion, lodged in the pancreas ; 46, The same in the posterior fissure of the liver ; below it is seen entering the substance of the gland. — M, Sub- scapular hyoideus muscle cut obliquely in the direction of the trachea ; P, Cervical panniculus turned down to expose the jugular channel ; 0, Right auricle of the heart ; A, Posterior aorta ; G, Section of the right lung ; F, Left lobe of the liver behind the section of the diaphragm; R, Right kidney carried up and forward; L, CEsophagus ; v, Bladder; s, Rectum; T, Thoracic duct; t', Termination of that duct in the confiuent of the jugulars. 620 TEE VEINS. opinion ; and there is every reason to believe that the system of the vena portte and that of the vena cava do not communicate, in the adult, otherwise than p;^ 294 l^y *^® capillary network which is intermediate to the subhepatic and suprahepatic vessels. If any other means of communication exist, they must be extremely small. Constituent vessels of the vena portce. — The three roots of this vein are the great and small mesenteries and the splenic vein. The collateral affluents it re- ceives on its course are principally two : the right gastro-epiploic veins and anterior gastric. We will make a rapid survey of all these vessels. 1. Boots of the Vena Portce. A. Great Mesenteric or An- terior Mesaraic Vein (Fig. 293, 44 ; 294, 2, 7). — This is an enormous venous canal into which flows the blood that has passed through the walls of the small intestine, csecum, large colon, and the origin of the small colon, and whose divisions correspond exactly to the diflerent branches fur- nished by the great mesenteric artery. When traced from its opening to its origin, in an inverse direction to the course of the blood, it is observed to lie between the two colic arteries, and proceed beyond the fold formed by the suprasternal and diaphragmatic curvatures, beyond which it divides into two satellite branches for the colic arteries, which anastomose in arcade towards the pelvic curvature, like the arteries they accompany. It is therefore by the union of two colic veins (Fig. 294, 8, 9) that the great mesaraic vein is constituted, and in whose formation numerous collateral affluents concur ; among these may be noticed the two ccecal veins (Fig. 294, 5, 6), the ilio-ccecal vein (Fig, 294, 4) coming from the origin of the floating colon, and the veins of the small intes- tine : vessels arranged so exactly like the corresponding arteries that we may of them. THE VENA PORT^ AND ITS ROOTS; PARTLY THEORETICAL. 1, Trunk of the vena portse ; 2, Its origin ; 3, Veins of the small intestine; 4, llio- caecal vein ; 5, External cajcal vein ; 6, In- ternal caecal vein ; 7, Great mesaraic veiii ; 8, 9, Colic veins forming the roots of that vessel ; 10, Collateral vein sometimes con- tinuing the left colic, and joining the great mesaraic vein near its origin; 11, Com- mon confluent of the small mesaraic and splenic veins ; 12, Small mesaraic vein and its collateral branches ; 13, Splenic vein ; 14, Left gastro-epiploic vein; 15, Eight ditto ; 16, Posterior gastric vein. — a, Stomach ; b, Duodenum ; c, Small intes- tine ; d, Caecum ; e, Large colon ; /, Float- ing colon ; g, Rectum ; h, Portion of the great omentum ; i. Spleen ; _;", Mesentery ; k, Colic mesentery. dispense with any further description THE FOSTERIOR VENA CAVA. 621 B. Small Mesenteric or Posteuioii Mesaraic Veik (Figs. 293, 43 • 294, 12). — This vessel commences above the rectum, near the anus by- large luemorrhoidal branches which communicate with the homonymous ramuscles of the internal pudic. It is directed forwards, between the two layers of the second mesentery, along the small mesenteric artery, which it passes, and extends to the great mesenteric artery, on the left side of which It unites with the splenic vein, before opening into the anterior mesaraic to form the vena portte. In its course it receives all the satellite venous branches of the divisions of the artery of the same name, and whose arrangement is similar to that of the arterial ramifications. C. Splenic Vein (Fig. 294, 13).— This is an enormous canal which follows the splenic artery, and comports itself exactly like it. It begins by the left gastro- epiploic vein (Fig. 294, 14) anastomosing in arcade with the right gastro-epiploic, receiving on its track gastric, splenic, and epiploic branches, and joining the small mesaraic after passing above the left ex- tremity of the pancreas, and obtaining the posterior gastric vein (Fig. 294, 16). 2. Collateral Affluents of the Vena Portce. A. Right Gastro-epiploic Vein (Fig. 294, 15). — We already know that the heiJatic artery, before entering the liver, gives off pancreatic branches, a pyloric branch, and a gastro-epiploic division, which in turn detaches a small duodenal artery ; the vessel described as the right gastro-epiploic vein cor- responds, in every respect, to all these collateral ramifications of the hepatic artery. This vein, then, has its origin from around the great curvature of the stomach, but at an undetermined point, as it forms an anastomotic arch with the left gastro-epiploic vein. Posteriorly, it crosses the dilatation at the origin of the duodenum, receives the pyloric, duodenal, and pancreatic vtins, and opens into the vena porta? after traversing tlie pancreas. B. Anterior Gastric Vein. — Satellite of the homonymous artery, this vein joins the vena portfe separately, after the entrance of that vessel into the great posterior fissure of the liver, and when very near the terminal extremity of that fissure. renal veins. Two in number, like the arteries they accompany, these veins are dis- tinguished by their enormous volume and the tenuity of their walls. The left, having to cross the abdominal aorta before entering the vena cava, is longer than the right. They receive the majority of the veins from the suprarenal capsules (293, 10). SPER5IATIC VEINS. These vessels correspond to the great spermatic arteries of the male, and the utero-ovarian arteries of the female. Testicular vein. — The radicles which constitute this vein present, at their emergence from the superior border of the testicle, a flexiform and very complicated arrangement, enlacing, turning, and inflecting themselves in a thousand ways around the convolutions of the great spermatic artery, and ascending in this manner towards the neck of the vaginal sheath (abdominal ring), which they jiass through usually after joining to form two trunks. These rise towards the sublumbar region, beneath the peritoneum, in a fold of which they are at first included ; they communicate with one another in 622 THE VEINS. tlieir course by anastomosing branches, and are generally confounded into a single spermatic vein, whicb opens into the vena cava near the renal vein (Fig. 293, 8). Utero-ovarian vein. — This vein, which is very voluminous, enters the vena cava at the same point as the corresponding vessel in the male, and proceeds, as its name indicates, from the ovaries and uterus by flexuous and reticular branches, whose fusion into a single trunk only takes place near the vena cava. LUMBAR VEINS. Satellites of the arteries of the same name, these vessels enter the vena cava separately. The most anterior often open into the vena azygos. PELVI-CRUKAL TRUNKS OR COMMON ILIAC VEINS. These appellations are given to two enormous vessels, into which are col- lected all the veins of the abdominal limb and the posterior part of the trunk — very short vessels, which, by their junction, form the posterior vena cava (Fig. 293, 3, 4). _ _ The common iliac vein is lodged in the angle of separation comprised between the external and internal iliac arteries, and is a continuation of the two satellite veins of these arterial canals. The right, shorter than the other, passes above the external iliac artery to join the vena cava at its origin. The left, longer, insinuates itself between the body of the second last lumbar vertebra and the terminal extremity of the posterior aorta, to open into the other. If we trace, as was done with the veins of the anterior extremity, from the ungueal region to the pelvis, all the branches which concur in the formation of these two trunks, we will find, as the common point of de- jjarture for each, a rich siibungueal plexus, from which spring two digital veins. To these succeed three metatarsal veins, the common origin of all the vessels of the leg. These latter are distinguished as superficial and deep, and are four in number — two saphena veins in the first group, and tico tibial veins in the second — continued by the popliteal vein. This vessel is itself continued by the femoral and external iliac veins, which finally form the pelvi- crural trunk by opening into the internal iliac vein. All these vessels will be studied in an inverse order to that in which they have been enumerated, and as follows : 1. Internal iliac vein. 2 External iliac vein. 3. Femoral vein. 4. Popliteal vein. 5. Dee]) veins of the leg. 6. Superficial veins of the leg. 7. Metatarsal veins. 8. Veins of the digital region. 1. Internal Iliac Vein. This vessel is formed by the satellite veins of the branches furnished by the homonymous artery : these are the iliaco-femoral, obturator, iliaco- muscular, gluteal, lateral sacral, and internal pudic, whose distribution does not differ from that of the corresponding arterial divisions. TEE POSTERIOR VESA CAVA. 623 The trunk resulting from the union of these different branches is usually- very short ; it may even be altogether absent, and we then see its con- stituent veins open into the common iliac vein by forming two or three separate groups situated very close to each other. 2. External Iliac Vein. This vein constitutes the principal root of the pclvi-crural trunk, which is but a continuation of it, the internal iliac being only, properly speaking, a collateral affluent of the single canal represented by the external and common iliac veins. Situated behind the crural arterial trunk, this external iliac vein com- mences at the anterior border of the pubis, where it is directly continued, without any line of demarcation, by the femoral vein. The only important vessel it receives on its course is the iliac circumflex vein, which, however, opens more frequently into the common than the external iliac. 3. Femoral Vein. Continuous by its superior extremity with the external iliac vein, and inferiorly with the popliteal, this femoral vein is remarkable for its large volume, and closely follows the artery of the same name throughout its extent (Fig. 293, 5). The collateral affluents it receives in its course are distinguished by their number aud considerable volume. They are : — 1. The satellite veins of the muscular arteries. 2. The internal saphena vein, which will be again referred to in describing the superficial veins of the leg. 3. The prepubic vein, formed by i\ie posterior abdominal and the branches of the internal pudic. The latter are very numerous and large, and anas- tomose with each other, forming between the thighs, in the texture of the scrotum and sheath, and above the penis, a very rich network which com- municates behind with the cavernous veins. This network only sends a small trunk into the inguinal ring, along the external pudic artery ; in its middle part it opens into an enormous branch which traverses the ring in the sartorius muscle, and is lodged in the inferior groove of the pubis to join the femoral vein. One of these external pudic veins represents the subcutaneous abdominal vein, and communicates with the subcutaneous thoracic vessel. All these branches in the female show an analogous disposition, 4. Popliteal Vein. Satellite of the popliteal artery, this vein is formed by the union of the anterior and posterior tibial veins. Among the branches it receives on its course, the femoro-popl ileal vein may be particularly noted ; this accompanies the artery of the same name, and joins the external saphena before opening into the popliteal vein. 5. Deej) Veins of the Leg. These are two in number : the anterior and posterior tibial. A. Anterior Tibial Vein (Fig. 278, 5).— Placed beside the homo- nymous artery, often double, always very ample, this vein originates on the 624 THE VEINS. anterior face of the tarsal articulations by means of several anastomosing roots, the principal of which is formed by the deep metatarsal vein, that passes through the cuboido-cuneo-scaphoid canal from behind to before. After crossing the fibular arch with the artery, it joins the posterior tibial to constitute the popliteal vein. B. Posterior Tibial Vein. — This commences near the hollow of the hock, within the calcis, by radicular branches which principally come from the two saphena veins. It then ascends along its satellite artery, to open into the anterior vein beneath the j)opliteal muscle. 6. Superficial Veins of the Leg. These are the internal and external saphena. A. Internal Saphena Vein. — This vessel shows two roots — an anterior and posterior (Fig. 293, 39, 40). The first proceeds from the internal metatarsal vein, the second from the external. Both ascend, in converging towards each other, on the internal face of the tibia, uniting into a single branch before reaching the thigh. This single branch, always very voluminous, glides upwards on the sartorius muscle, and terminates in a variable manner on reaching the groin : sometimes it is insinuated into the interstice of the two adductors of the leg, to join the femoral vein, and at other times it ascends to the ring of the short adductor, and opens into the external j^udic veins. B. External Saphena Vein. — It rises, by a short branch, outside the OS calcis, communicates, even at its origin, with the posterior root of the internal saphena by means of a large reticular anastomosis thrown trans- versely in front of the apex of the calcis ; and with the posterior tibial, by a large branch which passes between the tibia and the perforans muscle. It follows the external saphena nerve outside the gastrocnemii tendons, behind the external gastrocnemius muscle, and enters the popliteal vein, after joining the femoro-popliteal vessel. 7. Metatarsal Veins. These veins arc three in number, and are distinguished as internal, external, and deep ; they proceed from the sesamoid arch, which is formed by the anastomosis of the two digital veins. A. Internal Metatarsal Vein (Fig. 278, 9). — This vessel, the most considerable of the three, appears more particularly to continue the digital vein of the same side. For the greater part of its extent it is placed with the internal plantar nerve, along, and a little in advance of, the flexor tendons. Arriving near the tarsus, it deviates slightly to reach the anterior face of the tarsal articulations, and there communicates, by a very large transverse branch, with the origin of the anterior tibial vein ; afterwards it rises on the internal face of the leg, where it constitutes the anterior root of the internal saphena vein. B. External Metatarsal Vein (Fig. 278, 8). — It occupies, outside the flexor tendons, a position analogous to the preceding. Towards the superior extremity of the metatarsus, it communicates, by a short thick branch, with the deep vein. It then continues its ascending course by entering the tarsal sheath along with the plantar arteries, and is prolonged in the hollow of the hock, along the great femoro-popliteal nerve, in con- stituting the posterior root of the internal saphena. C. Deep Metatarsal Vein (Fig. 278, 10).— This is placed beneath THE POSTERIOR VENA CAVA. 625 the suspensory ligament, at the inner side of the principal interosseous plantar artery. Near the tarsus, it receives a very large branch from the external vein, and then traverses the cuboido-cuueo-scaphoid canal, tu form the largest root of the anterior tibial vein. 8. Veins of the Digital Megion. As these resemble, in every respect, those belonging to the anterior limb, the same description will suffice for both (see page 613). DIFFERENTIAL CHARACTERS IK THE VEINS OF OTHER THAN SOLIPED ANIMALS. It does not come within our plan to give a complete history of the venous system of these animals, because of the small utihty of such a study. To remain faithful to the object in view, we confine ourselves to tlie indication of tlie special characters of the veins on which bleeding is usually practised, and those which may be interesting in a surgical point of view, as the digital veins of Ruminants. A. Angular Vein of the Eye. — This vessel is remarkable for its large volume in the Sheep ; and as it is well defined beneath the skin, in consequence of the fineness of that membrane, it is more frequently selected for phlebotomy than in other animals. B. Jugular Vein. — Very large m all animals, and particularly in the Ox, this vein deserves tiie preference given to it when it is proposed to abstract a certain quantity of blood from tlie system. In all non-soiiped animals there is found an accessory jugular, which sometimes exists in the Horse, but is much less in size, alongside the common carotid artery. It arises from the occipital vein, and, therefore, measures the whole length of the neck. Sometimes its diameter is small ; but it is often so large as to receive a very notable quantity of blood from the principal jugular, when compression is applied to the latter to favour the flow of blood after opening it : a circumstance which explains the difficulty sometimes experienced in obtaining a voluminous jet of blood. C. Abdominal Subcutaneous Vein. — In the Bovine species, this vessel has an enormous volume, especially in the milch-cow, in contradistinction to the subcutaneous thoracic vein, which is always very narrow. This vein is prolonged forward on the wall of the abdomen, to nearly the xiphoid cartilage, where it passes through to join the internal thoracic vein.' Behind, it is formed by multiple branches, which anastomose with each other, or with tho^e of tue opposite vein, and are in communication with the proper external pudic veins. D. Internal Saphena Vein. — This is alway smaller than in Solipeds, and is rarely selected to bleed from. E. External Saphena Vein. — This vessel is, on the contrary, more voluminous than in the Horse, and at the same time more superficial ; consequently, it is more favourably situated for phlebotomy, as well in Pigs and the Carnivora, as in Ruminants. It arises from the union, in the hollow of the hock, of the two principal roots furnished by the metatarsal veins. F. Veins of the Posterior Foot in the Ox. — As in the Horse, they commence in the subungueal nehvork of the digital region, which is double, like the region itself. a. Three digital veins leave this reticulum : 1, A median or anterior one, arising by two roots from the anterior part of each network, passing between the two digit.-, and joining the anterior superficial metatarsal vein above the fetlock ; 2, Two laterals, com- municating with one another, behind, by a transverse anastomosis which receives several venules from the ungueal plexus, and with the anterior vein by an interdigital branch, united by an arch in front of the flexor tendons, above the sesamoid groove. b. These digital veins are continued by five metatarsal veins : two deep and one superficial anterior, and two posterior. The two deep anterior veins are small vessels which accompany the collateral artery of the cannon, which is placed between them. They arise in the interdigital space from the anterior digital vein, communicating, by the inferior metatarsal foramen, with the sesamoid arch, sending off on their way transverse anastomoses, and being continued above the tarsus by the two anterior tibial veins, whose roots they constitute. The anterior superficial vein is very voluminous. It proceeds from the sesamoid arch, 1 The openings through which these vessels pass in the abdominal parietes, are commonly named the milk fountains or doors. 626 THE VEINS. receives near its origin the median digital vein, rises in front of, and a little to the outsido of, the tarsus, communicating at this point with the anterior tibial veins; it divides above the tibio-tarsal articulation into two branches : a posterior, forming the anterior root of the external sapiieua ; the other anterior, joining tlie anterior tibial vein of the external side. The two posterior veins spring from the sesamoid arch. Situated at first between the suspensory ligament of the fetlock and the posterior face of the metatarsus, and com- municating there by several anastomoses, these two veins are continued along the tarsus, the one within, the other without. Tlie interned follows the corresponding plantar artery, and is prolonged in the tibial region by the posterior tibial and internal saphena veins. The external ascends witbin the calcis, and is united to a branch of the anterior super- ficial metatarsal, to form the exttrual saphena vein. Before leaving the deep situation it occupies below the suspensory ligament of the fetlock, these two vessels concur, but especially the internal, to furm a perforating branch which traverses the cuboido-scaphoid canal to join the anterior tibial veins. G. Veins of the Anterior Foot in the Ox. — Four digital reins escape from the two subuno'ueal plexuses: an anterior, jmsterior, and two lateral. a. Tlie anterior digital vein, which is very slender, is lodged superficially between the two digits, and comports itself at its origin like the analogous vein of the posterior limb, in rising by two roots. In being prolonged above the fetlock, it constitutes a subcutaneous metacarpal branch, whicli occupies the anterior and internal plane of the cannon, and is united above the knee to the principal cutaneous vein of the fore-arm. b. The posterior digital vein, often doubled by a small accessory branch, accompanies the common digital artery, and extends along the collateral artery of the cannon, to constitute one of the posterior radial vcius. c. The internal digital vein, after passing the digital region, is lodged between the cannon bone and the "internal border of the suspensory ligament, proceeds outsido the carpal sheath with the radio-palmar artery, and divides above the knee into two branches: an anterior, the origin of the internal subcutaneous vein of the fore-arm; the otlier posterior, forming one of the posterior radial veins. d. The external digital vein occupies, on the outer side of tlie external digit and the cannon bone, a position analogous to the internal vein. It gives rise to several deep metacarpal veins which anastomose, and are mi.ved with the interosseous palm;ir arteries; the principal vein and its accessory branches are joined, below the carpus, to the internal vein. It is to be remarked that these four digital veins communicate, in the interdigitnl space, by anastomoses resembling those of the posterior limb; and that the last three, or principal veins, anastomose above tiie fetlock in forming a complicated and variably- arrano-ed sesamoid arch, on leaving which these digital veins become metacarpal vessels. COMPARISON OF THE VEINS IN MAN WITH THOSE OF ANIMALS. In Man, as in animals, the veins are grouped into those of the lesser circulation, or pulmonary veins, and those of the greater circulation. The latter open into the heart by tiiree trunks: the cardiac veins, and superior and inferior vena cam. The superior vena cava represents the anterior vena cava of animals, and receives the blood from the veins of the head, thoracic limbs, and a portion of the chest. It extends from the first costal cartilage to the heart, and commences after the junction of the two braehio-cephalic trunks (innominate veins). The superficial veins of the thoracic limb at first form, on the back of the hand, a plexus of elongated meshes from which the median, radial, and idnar veins spring. Near the bend of the elbow, the median bifurcates and gives rise to the median cephalic and median basilic. Blood is abstracted from one or other of these branches. At the arm, all the superficial veins constitute but two trunks : the cephalic and basilic veins. The deep vessels join these to form the axillary vein, which becomes the subclavian below the clavicle, then the braehio-cephalic trunk {vena innominata) when it receives the internal jugular The venous sinuses of the cranial dura mater are proportionately more developed than in Solipeds, tliough they have the same disposition. There is constantly present a median or inferior longitudinal sinus. The jugulars which carry the blood from the cranium and face to the heai-t, are four in number. The anterior jngxdar, the smallest, descends beneath the superficial cervical aponeurosis, in front of tlic sterno-mastoideus muscle, and enters the subclavian vein. The external jugxdar comiwewcei by the union of the facial and temporal vein; in its disposition it resembles the jugular of the Horse, and would be a complete representative GENERAL CONSIDERATIONS. 627 if deprived of the branches from the cranial sinuses. The infernal jugular arises nt the posterior foramen lacerum, at a dilatation of the lateral sinus mimed the hulbits veme, jugularis, and passes to the subclavian vein. Lastly, the posterior jugular (or vertebral vein) bituatud beneath tlie great coniplexus, and in relation with the cervical vertebra;, curries the blood from the spinal sinuses in this region, and which, in Solipeds, is received by the occipital and vertebral veins. The inferior vena cava corresponds to the posterior vena cava of animals, and receives the blood from all the subdiaphragmatic veins. It originates from the union of the two common iliac veins, at the third hunbar articulation, and terminates in the right auricle. In its course it receives the median sacral, lumbar, renal, suprarenal, inferior phrenic, and right spermatic veins. The latter forms on the surface of the testicle, and at the origin of the cord, a rich network — the spermatic plexus ; on the abdominal portion of the cord it constitutes the pampiniform plexus. The vena cava also receives the vena portx, which has the same disposition as in animals. It begins by three branches : the great and small mesaraic and splenic reins. For affluents, it has the pancreatic and duodenal venides, and the right gastro-omental vein. It passes behind the pancreas, and not through that gland, as in the Horse. The veins of the abdominal limb are divided into deep and superficial. The first terminate by forming the femoral vein, which, in joining the vessels of the pelvis, constitutes the common iliac vein. The superficial i^eins commence by a network on the dorsum of the foot, which gives origin to the two saphenas : external and internal. FOURTH SECTION. The Lymphatics. CHAPTER I. GENERAL CONSIDERATIONS. Charged with the absorption and transport of the chyle and lymph, the lymphaiic or absorbent vessels are convergent canals with thin and transparent walls, which originate in the texture of organs by tine reticulated radiculae ; and which, after traversing one or more ganglia (or glands) — glandiform bodies placed on their course — enter the venous system by two trunks : the thoracic duct and the great lymphatic vein. LYMPHATIC VESSELS, These canals resemble veins in so many points, as to merit the name of white-blood veins. Like these vessels, the lymphatics are directed from the periphery to the centre of the circulatory apparatus ; like them, they are nodulated cylindrical tubes ; internally, and at those points where they outwardly appear to be constricted, they show numerous valves which look towards the heart ; like the veins, again, they separate into two orders of canals : the ones deep-seated, lodged in the vasculo-nervous intei'muscular sheaths ; the others superficial, situated on the surface of containing apon- euroses ; like the veins, also, the lymj^hatics terminate in two principal trunks resembling the venae cavse ; and, finally, as the veins have three tunics, so have the lymphatics, these not difiering in any respect, except in being very much thinner. In carrying this parallel still farther, we will find other analogies whose existence was but little suspected until recently : the glands — those organs which are apparently glandular, and seem to be proper to the lymphatic system — are they not represented in the venous system by the liver — 628 TEE LYMPHATICS. that enormous gland placed on the track of the abdominal veins — as the glands are on parts of the lymphatics ? It may be added that, if we pass into the domain of physiology, it is also easy to observe characters which are common to the two anatomical systems under comparison. They, in fact, almost equally divide the absorbent function between them : a function which is accomplished in the radicular network of each ; and the dynamical process which gives impulsion to the fluids they carry, if it is not quite identical in both, is at any rate very similar in many points. We may, nevertheless, observe numerous differences between the veins and the lymphatics, and chiefly in their form, number, capacity, and structure. The form of the lymphatic canals is, as we have said, nodulated and cylindrical ; but their external nodosities are much less marked, and are closer together than in the veins, owing to the larger number and greater develop- ment of the valves. Besides, as these canals travel for considerable distances, and preserve thoir regularly-cylindrical form with undiminished capacity, if we mentally bring all the divisions of the lymphatic system to a single canal, we no longer obtain a hollow cone whose apex corresponds with the heart, although the capacity of the lymphatic vessels augments from the trunk towards the branches; this conduit only represents a series of cylinders joined end to end, and successively decreasing from its origin to its termination. The number of lymphatic vessels in a certain region is always much greater than that of the veins. But as the lymphatics are much smaller than the veins, there is not, as might at first be supposed, a proportional increase in their total capacity. Observation, indeed, demonstrates that the relation between the capacity of the lymphatics, and the corresponding veins of a region does not exceed one to two. The structure of the lymphatics differs from that of veins in that there exists, in those of average dimensions, smooth muscular fibres in the adven- titious tunic. The presence of muscular fibres in the external tunic of these vessels is rendered necessary by the absence of an impelling organ at the origin of the lymphatic system : this organ being, in reality, disseminated throughout the extent of the canals, and aids the vis a tergo that causes the lymph to circulate in their interior. We terminate this short parallel, to d\^'cll in detail on several points connected with the general history of the lymphatics, and which merit particular attention ; we allude to the origin, course, and termination of these vessels. Obigin. — For a long period after the discovery of the lymphatic vessels, a state of profound ignorance existed as to their origin. Nevertheless, the importance of the solution of the problem was well appreciated, as it was really the key to the theory of absorption ; numerous hypotheses, therefore, sprang into existence. The anatomists who occupied themselves with the question were hindered in their investigation by the imperfect means of research at their disposal. Beyond the larger branches, the lymphatics escaped attention, owing to their transparency and tenuity. Thanks, how- ever, to the patient and minute researches of Hunter, Cruikshank, Mascagni, Fohmann, Panizza, Cruveilhier, and Sappey, the lymphatics were injected by colouring matters or by mercury, and thus rendered visible to their finest ramifications. It is now known that the lymphatics arise from capillaries, which form networks or terminal cids-de-sac. GENERAL CONSIDERATIONS. 629 These terminal cids-de-sac exist in the intestinal villi ; and it is no longer maintained that the ends of these small api)endices have an opening by which the lymphatic receives the chyle that bathes the mucous membrane of the intestine. The plexuses are composed of more or less irregular meshes, and their form and volume often vary with the disposition of the tissues or organs in which they are studied. They may be superficial or deep, and exist together or separately. In many membranes the two networks are found, but then the superficial is thinner than the deep. They are mixed with, or placed above, the blood-vessel plexuses, but never communicate Avith them. Do these lympliatic plexuses exist in all the tissues, properly speaking ? Here is another question of incontestible importance, and W'hose solution is even now occupying the attention of anatomists. Judging by analogies, one is tempted to reply in the aflBrmative : why, in fact, should the lymphatics not be spread everywhere throughout the organism, when the sanguine caj)il- laries are constituent i)arts in the framework of each tissue ? It is true we may ask if lymjjhatic absorption is a necessary act in the vital movement ; and although science is far from being satisfied on this point, we know some facts which at least authorize the doubt. On the other hand, direct ob- servation has not revealed lymj^hatic plexuses in all organs ; there are even tissues in which theii" existence has been denied : though jirematurely, it is well to say, because we may always attribute the non-success of a lymphatic injection either to the imperfection of the instruments employed, the insufficiency of the measures adopted, or certain peculiar conditions as yet unknown attaching to the species of animals selected for the demonstration of the lymphatic netw^orks in a certain region. As bearing out this last assertion, we may observe that M. Sappey has not yet been able to inject the pituitary plexuses in Man or the Calf, and that he loolvs upon their existence as being at least doubtful ; while in the Horse, this lymphatic apparatus is as remarkable for its richness, as for the facility with which, it may be filled with mercury. The following are the most trustworthy notions available on this subject. The lymphatic vessels of the skin are very numerous, and form tw^o net- works : one, with extremely fine meshes, occupies the most sujierficial layer of the dermis ; the other, placed beneath the deep face of the integu- ment, includes vessels more voluminous than the first, and communicates with it by multijilied ramuscules. These lymj^hatic plexuses are far from being equally developed in every region : though it is unanimously agreed that no part is entirely destitute of them. In the internal tegument, or mucous membranes, an analogous disposition of these vessels is met with. It is more than probable that they exist throughout the whole extent of these membranes, though their positive demonstration has yet to be made in some regions. In other regions, the injection of these networks is, on the contrary, very easy, and gives the most magnificent results ; we particularly mention the lingual, intestinal, and pituitary mucous membranes. The lymphatics belonging to the latter membrane assume so beautiful an aspect in the Horse, that we would advise anatomists who desire to inject lymphatics always to choose that animal. The operation is simple and constantly pei^formed, and we are astonished that in the hands of some individuals it should fail. Not only can the two networks of the membrane be filled, but also the trunks arising from them, and which are directed towards the entrance of the nasal cavities, collect in several thick branches around the nostril, and bend up towards the free 43 630 THE LYMPHATICS. to reach the submaxillary cavity, where they enter the ganglia situated to the right and left of that space. The majority of anatomists admit the presence of lymphatic plexuses in the splanchnic or synovial serous membranes. M. Sappey, however, denies this ; he considers the vessels that can be so easily injected by pricking the external surface of a viscus, as belonging to its proper tissue, and not to the serous membrane covering it. Those on the inner face of the walls of the splanchinc or synovial cavities, and which are sometimes filled with mercury, dg not, according to him, come from the serous tunic, but from the sub- jacent tissues. The lymphatics do not exist in vessels, although some modern anatomists have admitted them to be present in the inner layer of the circulatory apparatus. The lympJiatic sheaths discovered by His, Robin, and Tomaso, around the blood-capillaries of the frog, and those of the brain and spleen of Man. ought not to be considered as the lymphatics of vessels, as they merely surround the ultimate vascular ramifications, and do not arise in the substance of their walls. In the nervous tissue lymphatics have not been discovered, though they are present in the meninges. Their existence is doubtful in hone tissue and in the muscles ; but they are abundant in the glands and glandiform organs of the animal economy, forming the finest, richest, and most easily demonstrated plexuses. It has been stated above that the lymphatics commence by capillaries arranged in networks. Are these networJcs the real, or only the apparent, origin of the lymphatics f This is a question that has been, and is still, warmly discussed. It is, however, believed that the plexuses are fed by very minute radicles lodged in the substance of the tissues. But how do these radicles originate ? In the epithelium, says Kiiss ; in the plasmatic cells of the connective tissue, asserts Virchow ; in the serous membranes, states Recklinghausen, since he observed fatty matters pene- trate the lymphatics by the abdominal face of the diaphragm. The opinion of Virchow is overthrown at present by the reseai-ches of Ranvier, which have modified the descrij^tions given of the connective tissue. According to this authority, plasmatic cells do not exist in that tissue ; what have been described as such by Virchow have been only radiating spaces limited by the fasciculi of connective fibres, in which elements analogous to lymph globules circulate. It may be added that these fasciculi are covered by large flat cells, which give these spaces the appearance of a serous cavity with septa at close intervals. These conclusions of Ranvier, then, should affirm the hypothesis of the Wurzbourg professor, and tend to prove that in the connec- tive tissue of the economy there is an infinite number of minute serous cavities into which the lymphatic vessels open, in which the lymph circulates, and which are in communication, on the other hand, with the great splanchnic cavities. It must be mentioned, however, that these deductions are only hypothetical, particularly at the period of scientific evolution through which we are now passing. Course of the Lymphatic Vessels.— ^The lymphatics follow the track of the veins, and are divided, exactly like them, into superficial and deep vessels. The latter, running parallel to each other, are grouped immediately around the corresponding veins, on which they are generally superposed. The fia-st, although situated in proximity to the superficial veins, are widely spread on each side and on the surface of the suj)erficial aponeiu'oses, by forming parallel fasciculi, like the deep lymphatics. GENERAL CONSIDERATIONS. 631 • The direction followed by tlie lymphatics in their course is nearly always somewhat rectilinear ; they never show the flexaosities which are so developed on the track of certain arteries, and even some veins. Neither do they communicate with one another by transverse or arching anastomoses, like those so commonly met with in the other two orders of canals belonging to the circulatory apparatus. They frequently, however, in their parallel course, bifurcate and join the neighbom'ing vessels. (At certain situations, as at some of the articulations, and in other jjarts, the larger stems suddenly break-up into a close interlacing plexus of small vessels or capillaries (Fig. 295), which in tiieir disposition, greatly resemble the rete mirahile of the blood-vessels. This plexus is surrounded by condensed connective tissue, and is penetrated by blood-vessels, though no communication takes place between them and these, the only points at which communication occurs being where the great lymphatic trunks empty themselves into the vena cava. This rete would appear to be the first step towards the formation of a lymphatic gland.) Fi-. 295. A SECTION OF A SIMPLE RETE MIRABILE, VIEWED FROM THE SURFACE. a, a, Affereut vessels; b, b, Efferent vessels only partially visible; from the popliteal space. But of all the considerations relative to the course of these canals, the most interesting are those which belong to the glandiform bodies 2>laced along their track, and whose abridged history we sliall give immediately. Termination. — We have already mentioned the thoracic duct and the right great lymphatic vein as being the receptacles of all the absorbent vessels of the body, and we have also stated that these two trunks enter the general venous system ; this union of the sanguine with the lymphatic system takes place at the origin of the anterior vena cava, and this vessel may be con- sidered as the general confluent for all the absorbents. The researches of Haller, Cruikshank, and Mascagni first threw light on this imjiortant fact ; and it is to those of Fohmaun, Panizza, Kossi, &c., that we owe the dedi- cation of this discovery. 632 TEE LYMPEATIC8. LYMPHATIC GLANDS. The lymphatic glands are ovoid, spherical, or discoid bodies of medium consistency, grey, rosy, or red-coloured, and sometimes quite black, and which at several points intercept the course of the lymphatic vessels. Their number is considerable, and they are rarely isolated ; most frequently they are collected in groups along the blood-vessels. They are always larger in youth than in old age. All the canals of the lymphatic system are provided with at least one gland on their course, and some even traverse two or three before opening into the thoracic duct or great lymphatic vein. On reaching these glands, they plunge into their structure in ramifications, appearing on the opposite point after being reconstituted into several principal canals, which are generally larger and less numerous than the primitive vessels. The latter take the name of afferents (vasa infer entia or afferentia) ; the others are named efferents (vasa efferentia), because they leave the gland to reach the central canal. Structure. — The structure of the glands is extremely complicated, and difficult to make out, in consequence of the delicateness of their tissue. The following is what is positively known in reference to this subject. The glands have an envelope of connective tissue (continuous with the tunics of the afferent and efferent vessels), which surrounds a substance that is readily perceived to be composed of two layers of a different aspect : one cortical, the other medullary. The first appears to be granular, the second somewhat fibrous. This proper tissue is sustained by connective laminae (or septa — continuations of the capsule) which contain smooth muscular fibres. The laminae form alveoli in the cortical layer, and a sort of minute tubes in the central layer. These alveoli are in their turn divided by reticular tissue into secondary spaces, which become smaller as they lie near the centre; at the periphery, where Fig. 296. Fig. 297. SECTION OF A LYMPHATIC GLAND. a, a, The fibrous tissue that forms its exterior ; b, b. Superficial vasa inferentia ; c, c, Larger alveoli, near the surface ; d, d, Smaller alveoli of the interior; e, e, Fibrous walls of the alveoli. SIMPLE LYMPHATIC GLAND. a, The capsule with sections of lym- phatics, d, d, passing through it ; b. Lacunar and intercommunicating passages, permeated by the lymph, and forming the superficial lymph path of Frey ; c. Nucleus, or me- dullary portion, with section of blood-vessel in the centre. they are most voluminous, they are named lymphatic sinuses. Everywhere these sinuses are filled with lymph globules. The arrangement is identical GENERAL CONSIDERATIONS. 633 Fig. 298. in the medullary substance ; in the interior are seen a gi*eat number of arterial capillaries. The nerves are derived from the sympathetic system. The atierent lymphatics, where they enter the gland, communicate with the alveoli which coiTespond to the cortical substance ; these al- veoli are connected by the/ cords of the central layer, and the latter are united, in their turn, to the alveoli of the opposite side of the cortical substance, from which the efferent ramuscules spring. The lymph, therefore, traverses every part of the gland, and during this very tortuous course becomes charged with solid particles. Certain glands have a much more simple structiu'e, being en- tirely composed of lymphatic capil- laries rolled up on themselves in clusters, and anastomosing in net- works. These capillaries arise from the divergent arborisation of the afferent vessels, and are contin- uous with the convergent branches which, by their union, form the efferent lymphatics. The organs have received the name of false glands, though they are leally lymphatic glands. In support of this assertion, it may be said that " in descending the animal series, we see the glands becoming more and more simplified, and trans- formed at a great number of points into an interlacing of vessels. In birds, they only occupy the base of the neck and the entrance to the chest, forming in all the other regions simple plexuses ; in rep- tiles and fishes, the lymphatic glands disappear altogether, and the plexuses that replace them are themselves not at all complicated." — Sappey. PREPARATToy OF THE I.YMPHATic VESSELS. — The lympliatic networks can only be studied after liaving been filled with mercury by means of injection; but as this opeia- tion is not usually practised by the pupils for wliom this book is written, the mode of performing it will only be traced in a few words. The apparatus in use consists of a glass tube continued by a flexible one, which carries at its inferior extremity an iron tap and a fine canula, also of iron, or (better) gla.-s. To apply this apparatus, the tube ought to be suspended and then filled with mercury ; the canula is then seized by the right hand, keeping it parallel to the membrane we wish to inject, and burying it in the most superficial layer of that membrane. Tlie extremity of the canula is thus introduced into the midst of the meshes of the lymphatc network, and necessarily wounds some of the capillaries which compose it. In opening the tap, the mercury is allowed to flow into the capillaries by the solutions of continuity they present, and fills them in the most perfect manner. The lymphatic plexuses being PORTION OF THE MEDULLARY SUBSTANCE OF THE MESENTERIC GLAND OF AN OX, THE ARTERY OF WHICH IS INJECTED WITH CHROJIATE OF LEAD ; MAGNIFIED 300 DIAMETERS. a, Medullary substance with capillary network, fine reticulum of connective tissue , and a few lymph corpuscles ; h, h. Superficial lymph- path, traversed by a reticulum of nucleated cells (c c), with numerous anastomosing pro- longations. The lymph corpuscles have for the most part been removed ; d, d, Trabecule composed almost exclusively of unstriped mus- cular tissue ; g, A small medullary cord, or bridge, containing a blood-vessel and numerous lymph corpuscles. (534 TEE LYMPHATICS. always superposed on the capillary blood-vessels, one is always certain of injecting them only, in taking the precaution to penetrate the membrane as superficially as possible. If the point of the canula enters too deeply, the mercury will pass into the veins, and the operation will be unsuccessful, and must be commenced again. To study the branches and lymphatic trunks, it will suffice to inflate them from their origin towards their termination. This procedure, properly conducted — and it was almost exclusively the only one adopted by the older anatomists — gives the most satis- factory results, and is even sufficient to demonstrate the texture of the glands. The latter do not require any particular precautions in their preparation. CHAPTEE II. THE LYMPHATICS IN PARTICULAE. We will commence with the examination of the thoracic dud and all its affluents, and terminate by studying the great lymphatic vein. In this description the glands and principal lymphatic vessels will be only referred to, the disposition of the networks being already noticed in speaking of the diiferent organs, and they will be further mentioned when speaking of the nervous system, the organs of sense, and those of generation Article I. — The Thoracio Duct. (Fig. 293, t t.) Preparation. — Tie the jugulars and axillary veins near their termination, as well as the anterior vena cava about the middle of its length ; expose the thoracic duct by removing the ribs on the right side ; open that canal near the pillars of the diaphragm,, and throw into its interior two injections of tallow, one forward, the other backward from the incision. The first injection will fill the canal and the venous reservoir which is intersected between the ligatures applied to the above-named vessels ; the second, although directed in opposition to the valves, overcomes the resistance offered by them, and passes into Pecquet's cistern and the principal branches which open into that confluent. Or we may select one of these branches in the abdominal cavity — for example, one of those wliich lie beside the colic arteries near their origin — and inject the entire thoracic duct from its origin to its termination. But this proceeding requires more practical ability than the first, in order to find the vessel which is tc receive the canida; and if the animal is very fat, it is im- possible. The thoracic duct is the general confluent for all the lymphatics of the body, vnth the exception of those which come from the right anterior limb and the right moiety of the head, neck, and thorax. Extent. — It extends beneath the vertebral column, from the first lumbar vertebra to beyond the entrance to the thorax. Origin. — Its origin is marked by a very irregular dilatation described as the suhlumhar reservoir, or cistern of Pecquet {receptaculum or cyster nachyli), into which open the principal affluents of the canal. This reservoir is divided, internally, by lamellfe into several incomplete compartments, and may be more or less voluminous and circumscribed, and present very variable forms. It is placed above the abdominal aorta and the posterior vena cava, at the great mesenteric artery, or more frequently a little behind it. In the Dog it is of an enormous size, oval in shape, and prolonged between the pillars of the diaphragm into the thoracic cavity. Course. — ^To this reservoir succeeds a tube whose calibre is very irregular, and appears singularly slender when compared with the diameter of the THE THORACIC DUCT. 635 initial dilatation, or that of the affluent vessels composing it. This is the thoracic duct. We see it enter between the two pillars of the diaphragm, along with the aorta, deviating more or less to the right side of that vessel, and follow it thus to about the sixth dorsal vertebra, in passing to the outside of the right intercostal arteries, which it crosses, and beneath the great vena azygos, beside which it lies. Sometimes, however, we find it carried in this first part of its course directly .above the thoracic aorta, between the double series of intercostal arteries, and to the left of the vena azygos, which is then found immediately in contact with the right side of the aorta ; or it may even creep to the right of that vein, concealing the greater part of it from sight. Leaving the above-mentioned dorsal vertebra, the thoracic duct abandons the aorta and crosses the flexure of the vena azygos to the left, to extend itself forward on the left side of the trachea, but often also on the right side. It afterwards places itself between the two axillary arteries, crosses the interval comjirised between the prepectoral glands, emerges from the chest, and terminates in a manner to be indicated hereafter. Termination. — The terminal extremity of the thoracic duct is always provided with a dilatation analogous to that which exists at its origin, though much smaller, better circumscribed, and less irregular — a dilatation which opens into the anterior vena cava sometimes by a single orifice furnished with valves, at other times by two very short branches, whose length we cannot estimate at more than the fifth part of an inch, and which are also valvular at their entrance. The point where this entrance takes place is neai'ly always at the summit of the vena cava, and precisely at the point of junc- tion of the two jugulars. The thoracic duct rarely opens elsewhere ; though the fact that it does so at times is exemplified in a specimen in the museum of the Lyons School, in which the embouchure of the duct is placed between the termination of the left jugular and that of the corresponding axillary vein. Varieties in Solipeds. — " The thoracic duct is far from always showing itself in Solipeds as I have described it, but in its com'se and insertion presents a great number of variations which we will now pass in review. " The single canal is separated sometimes, at a part of its length, into two branches, which, after proceeding parallel to each other, soon unite to form a single vessel. This division usually takes place at the base of the heart, at the place where the lymphatics of the bronchial and oesophageal glands enter ; it forms a ring whose diameter is often not more than four-tenths of an inch, or an ellipse whose larger axis is from four to eight-tenths of an inch. We see this produced once, twice, and even thrice on the anterior half of the canal, which becomes simple at its termination as it was at its origin. The spaces circumscribed by the bifurcations constitute what have been termed the insnlse. " The canal, instead of remaining single, very often becomes double from its commencement (Fig. 300). Then the two canals are sensibly equal, or one is larger than the other. If they are unequal, it is usually the right which has the advantage, though the conti*ary sometimes occurs. In any ease, the two canals are isolated, one being to the right, the other to the left of the aorta. In advancing towards the entrance to the thorax, they remain completely separated, or communicate with each other by one or two, more or less voluminous, transverse anastomosing branches. Eeaching to ten, eight, and sometimes even to two inches from their opening into the jugular gulf, the two canals approach each other, and become confounded into a single THE LYMPHATICS. Ficr. 299. Fi?. 300. Fis. 301. DIFFERENT VARIETIES OF THE THORACIC DUCT IN THE HORSE. A, Receptaculum chyli ; B, Sublumbar branches ; C, Anterior mesenteric branch ; D, Posterior mesenteric branch. In figure 299 the duct is single, the usual condition, and enters the AFFLUENTS OF THE THORACIC DUCT. C37 vessel. Their fusion generally takes place at the base of the heart, and I have never seen them remain distinct throughout their whole extent, to enter the vena cava separately. "Sometimes (Fig. 301) there emanates from the gland, at the entrance to the thorax, a long canal which proceeds parallel to the first, and joins it, after a retrograde course, near the pillars of the diaphragm. " The thoracic duct, double for the greater part of its extent, from the time it leaves the sublumbar reservoir, occasionally ends by becomino' triple. In this case, the largest of the two canals is divided into two branches ; then the three canals, after pursuing a certain coiU"se, all join at the same point, or tw'o are fii-st united into a single conduit, into which the thiixl opens at a variable distance from the confluent of the first."' The affluents of the thoracic duct. — The lymphatic branches which enter the thoracic duct are as remarkable for their number as their volume. Some empty themselves into the sublumbar reservoir ; a few vessels open into the great lymphatic vein of thft thorax, and the others terminate in that conduit, near its insertion into the venous system. The first, variable in their number, particularly the largest, are more especially regarded as the roots of the thoracic duct. Ordinarily three are fountl, with a certain number of small accessorv trupks. One of the largest branches enters the posterior part of the cistern ; very often double, and even multiple, it arises from an enormous group of ganglia placed in the sublumbar region, around the posterior extremity of the abdominal aorta and vena cava, and into which are collected all the vessels of the posterior limbs, the pelvis, abdominal walls, and the pelvi- inguinal viscera. The other two trunks reach the left side of the cistern, and result from the union of the lymphatics w^hich have their source in the abdominal digestive organs; among these lymphatics, however, there are some belonging to the parietes of the stomach and the parenchyma of the liver and spleen, and which approach the right side of the sublumbar recep- tacle, to open singly into that cavity. The affluents the thoracic duct receives on its course, proceed fi-om the viscera contained in the thoracic cavity, and from the walls of that cavitv. Those which terminate at the anterior extremity of the duct are formed by the lymphatics of the left anterior limb, and the left half of the thorax, diaphragm, neck, and head. We will now examine rapidly all the radicular branches of these affluents. Article II. — The Lymphatics which form the Affluents of the Thoracic Duct. These lymphatic vessels are divided into five groups . 1, These of the abdomiual limb, the pelvis, abdominal parietes, and the pelvi-in<^uinal organs ; 2, Those of the abdominal digestive viscera ; 3, Those of the organs contained in the chest ; 4, Those of the thorax ; 5, Those of the head, neck, and anterior limb. • G Colin. ' Traite cle Physiologie Oomparee des Aniiuaux Domestiques,' vol. ii summit of the anterior vena cava by two short branches. It is double in Figure 300 ; and in Figure 301 it has a long branch that arises at the entrance to the thorax and joins the duct, by a i-etrograde course, near the pillars of the diaphragm. 638 TEE LYMPHATICS. LYMPHATICS OP THE ABDOMINAL LIMB, PELVIS, ABDOMINAL PAMETES, AND THE PELVI-INGUINAL ORGANS. All these vessels converge towards an immense group of ganglia, named the suhlmnhar glands. Besides these, there are other groups on different parts of their track, constituting the deep inguinal, superficial inguinal, popliteal, iliac, and precrural glands. The successive description of these ganglia, and their afferent and efferent vessels, will conveniently make known the lymphatic apparatus, whose study we have in view in this paragraph. 1. Suhlumbar Glands. This group, which occupies, as its name indicates, the suhlumbar region, comprises : 1, A small single mass situated in the sinus of the angle formed between the two internal iliac arteries, and is often formed by a single large ganglion ; 2, Another mass lodged between the two iliac arteries, and a third placed without, and to the front of, the crural trunk : these two are double ; 3, A single agglomeration of glandular lobules dispersed around the origin of the small mesenteric and spermatic arteries : these are isolated from one another. These different masses receive the lymphatics of the pelvis, the emergent branches of the deep inguinal ganglia, those which come from the iliac ganglia, some ramuscules from the rectum and large colon, and those from the spermatic cord. They are bound to each other by communicating branches, and give rise to several series of emergent branches, which soon collect into one or more trunks that enter Pecquet's reservoir. 2. Deep Inguinal Glands. This is a considerable mass of glandular lobules lodged beneath the aponeurosis and the crural arches, in the interstice of the adductor muscles of the leg, along with the crural vessels, within which they are placed. The form of this group is elongated, and its length may be six to eight inches, or even more ; its superior extremity extends as high as the anterior border of the pubis. It is composed of from fifteen to twenty lobules, which rarely have an uniform colour, some being grey and others brown, or nearly black. The afferents are formed by the superficial lymphatics which accompany the internal saphena vein, whose roots may be traced beyond the fetlock, and by the deep satellite vessels of the crural artery and vein. The efferents proceed to the suhlumbar glands, by ascending in the abdomen along the external iliac artery and vein. 3. Superficial Inguinal Glands. These are placed in front of the inguinal ring, at the side of the sheath, on the track of the subcutaneous abdominal artery, where they form a small elongated mass from two and a-half to three inches in length, and are composed of a dozen principal lobules. Their afferents, which are very numerous, come from the inner aspect of the thighs, the sheath, scrotum, and the inferior abdominal wall. The efferent vessels, much larger, but less numerous — there are only five or six — ascend in the inguinal canal, accompanying the external pudic artery and AFFLUENTS OF THE THORACIC DUCT. 639 {^For Description, see p. 640. 640 THE LYMPHATICS. the inguinal nervous branches. They enter the deep inguinal glands, after traversing the crural ring, in company with the prepubic artery. 4. Popliteal Glands. These glands represent a very small mass composed of from three to five independent lobules, situated behind the great sciatic nerve and gas- trocnemii muscles, between the long vastus and semitendinous muscles, and near the femoro-popliteal artery. They receive some of the lymphatics which arise from the environs of the hock, and those coming from the posterior and inferior part of the gluteal region. Their efferents join the deep inguinal glands, by following the muscular interstices of the thigh. 5. Iliac Glands. Slightly yellow in colour, and of a soft consistence, these glands are five or six in number, and form a group which is situated in the triangular interval comprised between the two branches of the circumflex iliac artery. They receive the emergent branches of the anterior crural glands, and a great number of deep lymphatics from the abdominal wall. Their efierent branches, four or five in number, follow the circumflex iliac artery to pass to the sublumbar glands. 6. Freer ural Glands. Placed within the anterior border of the fascia lata, on the track of the circumflex iliac artery, these glands form a small elongated mass, composed of a dozen lobules lying close to each other. To this group come afferent vessels from the anterior and internal part of the thigh. It gives rise to three or four large efferent vessels, which ascend the internal face of the muscle of the fascia lata, accompanying the circumflex iliac artery, and entering the abdominal cavity near the angle of the haunch, to join the iliac glands. LYMPHATICS OF THE ABDOMINAL VISCERA. 1. Glands and Lymjpliatic Vessels of tJie Rectum and Small Colon. The glands in this portion of the intestinal tube are : at first, two or three lobules placed at the base of the tail and on each side of the sjihincter ani; in the second place, a very numerous series of small glandular bodies situated along the small cui'vature of the viscus; thirdly, some rounded A, Facial and nasal plexus whose branches pass to the subglossal glands; B, 0, Parotid lymphatic gland, sending vessels to the pharyngeal gland ; D, E, Large trunks passing towards the thorax ; F, G, H, Glands receiving the superficial lymphatics of the neclv, a portion of those of the limbs, and those of the pectoral parietes ; i, Junction of the jugulars; J, Axillary veins; K, Summit of anterior vena cava; L, Thoracic duct; M, Lymphatics of spleen — N, of stomach — 0, of large colon — S, of small colon ; R, Lac- teals of small intestine — all joining to form the two trunks, p, Q, which open directly into the receptaculum chyli ; T, Trunk which receives the branches of the sublumbar glands, U, to which the vessels of the internal iliac glands, v, the receptacles of the lymphatics of the abdominal parietes, pass ; W, Precrural glands receiving the lymph- atics of the posterior limb, and which arrive independently in the abdomen ; X, Super- ficial inguinal glands into which the lymphatics of the mamma, external generative organs, some superficial trunks of the posterior limb, etc., pass; Z, Deep inguinal glands receiving the superficial lymphatics, z, of the posterior limbs. AFFLUENTS OF TEE THORACIC DUCT. 6il lobules comprised within the two layers of the mesentery, and placed on the track of the arterial and venous divisions. Originating in the texture of the mucous and muscular tunics, the lymphatic radicles gain the glands of the small cm-vatm-e of the colon, and escape from them as efferent branches, which pass in great numbers into the mesentery. These efferents, or at least some of them, traverse the lymphatic glands placed on the course of the blood-vessels, and collect, near the origin of the posterior mesenteric artery, into several somewhat voluminous branckes, which join the divisions of the sublumbar glands, or those of the large colon. 2. Glands and Lymphatic Vessels of the Large Colon. There' is seen on this enormous viscus a double chain of glands, lying beside the colic arteries, and numerous small lobules disseminated at a short distance from the principal glands, and on the track of the collateral branches furnished l3y these two vessels, Eeceived at first, for the most part, by these lobular bodies, the lym- phatics which have emanated from the tunics of the viscus afterwards join the principal glands, from which they emerge in forming several large satellite branches for the colic vessels. Only two or three in number at the pelvic curvature, these branches are increased to ten or twelve on arriviug near the origin ef the colic arteries. It is from the union of these vessels with those of the small intestine, that the two large mesenteric trunks (Fig. 299, A, c) arise, which, with the branches emanating from the sub- lumbar glands (Fig. 299, b), form Pecquet's reservoir. 3. Glands and Lymphatic Vessels of the Ccecum. There exists, on the track of each cfecal artery, a moniliform series of glands, farther apart from one another than those of the double colic chain, to which the vessels coming from the csecal membranes are directed, and from which several long satellite branches of the blood-vessels, that proceed to the same trunk as those of the small intestine, depart. 4. Glands and Lymphatic Vessels of the Small Lntestine. The glands which receive the lymphatic vessels from the small intestine are very large and abundant. About thirty in nmnber, of a grey colour, very compact, fusiform, often bifurcated at their superior extremity, these glands are placed in the texture of the mesentery, near the origin of the great mesenteric artery, from which those belonging to the portion of intestine nearest the end of the viscus are most distant. The latter also possess, in addition, fifteen special small glandular lobules, dispersed on the track of the ileo-csecal artery. We have already noted the richness of the vascular apparatus which rises from the wall of the small intestine, towards the mesenteric glands It must be added that these glands give rise, at their superior extremity, to large emergent branches, two or three for each, which soon coalesce to make more voliuninous branches that concur in the formation of the two intestinal roots of Pecquet's reservoir. 5. Glands and Lymphatic Vessels of the Stomach. There are two classes of lymphatic glands for the stomach 1, Several large glands situated on the small curvature of the organ ; 2, A series ot 642 THE LYMPHATICS. small lobules disseminated along the great curvature to the attacliment of the great omentum. The vessels which emerge from them " gather on the track of the gastric arteries and veins, and ascend to the great tuberosity, near the trunk of the coeliac artery ; there they anastomose with the lymjihatics derived from the spleen and liver, and unite into several flexuous branches, some of which open directly into the thoracic duct, to which the others pass, after being confounded with the anterior trunk of the intestinal lymphatics." — Colin. 6. Glands and LymphattU Vessels of the Spleen and Liver. " The lymphatic vessels of the spleen, rising some from the interior of the viscus, others from its surface, pass towards the splenic artery and vein ; they traverse several groups of glands disposed on the track of these vessels, commencing from the middle of the length of the fissure, ascend, five or six in number, towards the origin of the artery in foi.'nung a sinuous mass whose divisions, anastomosing with those of the stomach and liver, open, on the one hand, with the latter in the anterior trunk of the intestinal lymphatics, and, on the other, into a magnificent plexus commimicating directly with the thoracic duct. '" Finally, the lymphatics of the liver form a very close network on the surface, and another in the interior of the parenchyma. They collect towards the posterior fissure, and first dip into a primary and very small glandular group, then into a second group of voluminous round glands, which are concealed between the trunk of the vena portse and the pancreas. They open in common with the vessels of the stomach and spleen." — Colin. GLANDS AND LYMPHATIC VESSELS OF THE ORGANS CONTAINED IN THE THORACIC CAVITY. We find annexed to these organs tliree groups of lymphatic glands : 1, A series of small granulations placed in tiie posterior mediastinum, on the course of the oesophagus ; 2, The hronckial glanfs, situated in the angle of bifurcation of the trachea, around the origin of the bronchi, which they follow for a short distance into the pulmonary parenchyma; 8, Two long strings of lobules extended on the sides of the inferior face of the trachea, from the base of the heart to near the first rib. The first group receives the posterior lymphatics of the oesophagus, the second those of the lung, and the third those of the pericardium, heart, and a portion of the trachea and cesophagus. Their efferents, unitiug into some large trunks, enter the thoracic duct at different distances. GLANDS AND LYMPHATIC VESSELS OP THE THORACIC WALLS. These glands form three series : 1, A double chain of rounded grains, situated on each side of the dorsal column, above the intercostal spaces, and beneath the costal pleura ; 2, A frequently voluminous mass, lodged at the base of the xiphoid appendix, behind the heart, and in front of the inferior part of the diaphragm ; 3, Some rudimentary granulations lying beside the internal thoracic vessels. The lymphatics of the diaphragm, after receiving those from the convex face of the liver pass to the glands placed at the base of the muscle, from which they escape in the form of several canals that accompany the internal thoracic vessels, and open into the anterior extremity of the thoracic AFFLUENTS OF THE THORACIC DUCT. 643 duct or tlie great lymphatic vein, the majority of them through the medium of the prepectoral glauds. These vessels receive, on their course, those which are brought from the inferior part of the intercostal sj)aces into the suprasternal granulations. The other lymphatic vessels of the costal wall ascend between the two muscles which close these spaces, and go to the subdorsal glauds, which afterwards eject them, near the origin of the thoracic duct, in the form of one or two long vessels proceeding in a retrograde manner on each side of the dorsal column. LYMPHATIC VESSELS OF THE HEAD, NECK, AND ANTERIOR LIMB. These vessels are all directed towards the entrance to the chest, and are gathered into a group of glands, called the prepectoral, which, with regard to the lymphatics of the anterior part of the body, play the same part as the sublumbar glands do to the vessels of the posterior region. Before arriving at this common point of convergence, they are inter- cepted on their course by other glands, which form four principal groups : 1, The guttural or pharyngeal glands ; 2, The suhmaxillary glands ; 3, The p-escapular glands ; 4, The brachial glands. In studying these different glandular groups in succession, vnth. their afferent and efferent vessels, we will give a sufficient idea of the entire lymphatic apparatus iu the region which remains for us to examine. 1. Prepectoral Glands.^ They form, on each side of the terminal extremity of the jugular, within the inferior border of the scalenus muscle, a very large mass which extends into the chest by passing beneath the axillary vessels, and ascends to the inner face of the first rib. Into these glands pass the lymphatic vessels emerging from the pre- scapular and axillary glands, those which descend along the trachea with the common carotid, and which come from the pharyngeal glands, as well as the majority of those which follow the internal thoracic vessels. They give rise to several short and voluminous branches : those from the glands of the right side form, by their junction, the great lymphatic vein ; and those from the left side join the thoracic duct, or are inserted separately beside the latter, at the summit of the anterior vena cava. 2. Pharyngeal Glands. Very numerous, soft, and loosely united to one another, these glands are disposed in an elongated mass that occupies the lateral plane of the pharynx, below the guttural pouch, and which is prolonged backwards even beyond the thyroid body. They receive all the lymphatics from the head : some come directly from the base of the tongue, the soft palate, the pharyngeal walls, and the larynx ; the others are derived from the submaxillary glands, and from a lobule lodged in the substance of the parotid gland. The efferent branches which leave it are four or five in number. Always voluminous, they descend along the trachea, some separately, but the majority are imited in a fasciculus which follows the carotid artery; ' These are glands, we believe, which ought to be regarded as the representatives of the axillary glands of Man. 644 THE LYMPHATICS. they are provided on tlieir course with several elongated glands, to which the lymiihatic radicles that arise from the cervical portion of the trachea and oisophagus pass. On arriving near the entrance to the chest, they are lost in the prepectoral glands. Some of them, however, traverse these without dividing, and directly enter, on the left, the thoracic duct, and on the right, the great lymj)hatic vein. It has been even possible for us to inject the latter vessel by one of these canals exposed on the right side. 3, Suhmaxillary or Suhglossal Glands. They represent a fusiform mass situated at the bottom of the inter- maxillary space, in the receding angle comprised between the digastricus on the one side, and the mylo-hyoideus and subscapulo-hyoideus muscles on the other, above and near to the external maxillary artery. The lymphatics of the tongue, cheeks, lips, nostrils, and nasal cavities join these glands. Their efferents reach the pharyngeal or guttural glands. 4. Prescapular Glands. By their union they form a species of chain, at least twelve inches in length, placed on the course of the ascending branch of the inferior cervical artery, beneath the internal face of the levator humeri muscle, and descend- ing close by the fixed insertion of the sterno-maxillaris muscle. The majority of the lymphatics of the neck, and those of the breast and shoulder, open into these glands. Their efferents, short and voluminous, enter the prepectoral glands. 5. Brachial Glands. Situated beneath the anterior limb, within the arm, these vessels are divided into two groups : one placed near the ulnar articulation, within the inferior extremity of the humerus ; the other disposed in a discoid mass behind the brachial vessels, near the common insertion of the adductor muscle of the arm and the great dorsal muscle. The first group receives the vessels from the foot and the fore-arm, which accompany the superficial veins, or pass with the deep arteries and veins into the muscular interstices. It sends nine or ten flexuous branches to the second group, into which open directly the lymphatics of the arm and shoulder, and from which emerge a certain number ot efferents that pass, in company with the axillary vessels, to the prepectoral glands. Abtiole III.— Gbeat Lymphatic Vein. The second large receptive trunk of the lymphatic vessels, this great vein (the ductus hjmphatinis de.r/er) leaves the prepectoral glands of the right side, and therefore becomes the general confluent of the lymphatics from the right anterior limb, the right axillary and superficial costal regions, as well as the I'ight half of the head, neck, and diaphragm. This trunk is only from three-fourths of an inch to two inches in length. " It usually opens at the junction of the jugulars, at the side of the canal, by an orifice furnished with a double semilunar valve. Sometimes one or two of the branches which concur to form it describe circumvolutions around the corresponding brachial trunks or some of its divisions, before joining the others. Lastly, it is not rare to see this lymphatic trunk anastomose GREAT LYMPHATIC VEIN. G45 with the thoracic duct by voluminous collateral branches, then unite with it in such a way as to be inserted together by a single orifice above the gulf of the jugidars." — Colin. Fig. 303. Fig. 304 THE GREAT LYMPHATIC VEIN AND ENTRANCE OP THE THORACIC DUCT. A, Thoracic duct ; B, Great lymphatic vein, or right lymphatic trunk ; c, D, Anasto- moses established between them near their insertion. DIFFERENTIAL CHARACTERS IN THE LTBIPHATIC SYSTEM OF OTHER THAN SOLIPED ANIMALS. The lympliatic system, glands and vessels, is more developed in Ruminants and the Pig than in the Carnivora. In this respect the domesticated animals may be classified in the following order : Ox, Slieep, Horse, Pig, Dog, Cat. Ruminants.—" The thoracic duct of large Ruminants, when it has entered the thorax by a special opening in the diaphragm, almost distinct from that of the aortic arch, is placed above and to the right of the aorta, between it and the spine. There, although outside the corresponding intercostal arteries, it is completely concealed by a thick layer of adipose tissue, in which are numerous subdorsal glands. Towards the fifth dorsal vertebra, it receives a large lymphatic vessel coming from the enormous gland that exists on the track of the oesophagus in the posterior mediastinum; it then crosses the direc- tion of the aorta and the esophagus, passes to the left, gains the entrance to the thorax, and opens in front of the first rib, above the junction of the left jugular with the anterior vena cava.' " The varieties it presents in the Ox are numerous and very common. The rarest disposition is that of a canal, single through- out its entire length, such as it has been described, and such as it is usually found to be in small ruminants (Fig. 309). This canal (Fig. 306), single at its origin and for the greater part of its extent, often bifur- cates towards the base of the heart, or at a short distance from its insertion. Of these two branches, one passes to the right of the cesophagus and trachea, the other to the left of these, in following the ordinary direction ; and, at the entrance to the thorax, they either terminate separately, each in t!ie "angle of union of the jugular and corresponding axil- lary vein, or togethei- at the same point — the gulf of the two jugular veins. " It happens that one of the branches of the bifurcated canal is in its turn subdivided into two smaller branches, and that the other experiences at the same time a similar Fisr 30.5. ENTRANCE OF THE THORACIC DUCT IN THE OX. (' Zundel has pointed out the curious fact, that in Ruminants, the long, special, lymphatic gland situated between Ihe layers of the mediastinum and above the cesopha- gus, sometimes becomes so voluminous that its weight impedes rumination, especially when the animal is lying. The bolus of food is prevented from ascending into the cesophagus, and this may become a frequent and periodic cause of indigestion.) 44 646 TEE LYMPHATICS. subdivision : in such a way that the trunk of the canal, at first single, becomes double, then quadruple, and consequently opens into the venous system by four distinct orifices! Fio;. 306 Fig. 307. VARIETIES OF THE THORACIC DUCT IN THE OX. If the branches of the canal, instead of remaining isolated, send off transverse anastomoses there results a complication of which Solipeds do not offer an example (Fig. 305). ' • The thoi-acic duct is oftea double throughout its extent. The two canals are then THE CIRCULATORY APPARATUS OF BIRDS. 647 detached separately from the cistern, one follows the right side, the other the left side of the aorta, describing an arch whose concavity is downward at the base of the lieart, on the lateral parts of the trachea, terminating either very near one another, and on the same transversal line, at the junction of the two jugulars, or one to the right, the other to the left, in each of these two veins, and not far from their junction with the axillaries (Fig. 307.) " When the two canals arise from the sublumbar reservoir, tliey sometimes repeatedly anastomose with each other by sinuous and curved branches, as shown in figure 308. Fi?. 309 THORACIC DUCT OF SMALL RF3IINANTS, " Then all the branches collect in the anterior mediastinum, and constitute a single canal which, near its termination, again subdivides into four vessels that open separately, two to the right and two to the left, in the usual place. " This variety is tlie most remarkable and complicated of all those observed in the domesticated animals. Pig. — " The thoracic duct of the Pig, usually single throughout its whole extent, is sometimes divided, at one to one and a-half inches from its insertion, into two branches which soon reunite in an oval dilatation ; this, after receiving the vessels from the head, neck, and limbs, opens towards tlie extremity of the left jugular. Carnivora. — " In the Dog, Pecquet's reservoir is enormous ; in shape it is ovoid, and is prolonged between the pdlars of the diaphragm into the thoracic cavity. The thoracic duct of this animal generally resembles that of the Pig. Yet it sometimes oflers in its course and termination very numerous variations : Rudbecky has noticed a bifurcation above the heart, and another bifurcation wliose branches anastomose with each other several times. Swammerdam and Stenon have figured numerous irregular anastomotic divisions towards the middle of a single canal, to its point of departure. These old authors have indicated and represented double and triple insertions of ditferent forms. Lastly, Bilsius has shown an arch, or rather a very remarkable ring, at the entrance of the conduit, and at its junction with the lymphatic vessels of tiie neck and anterior limbs, and which is more or less analogous to that which I have observed on several occasions in the Horse, Pig, and Cat."' CHAPTEE III. THE CIRCULATORY APPARATUS OF BIRDS. We will briefly examine the characteristics of the difierent portions of the circulatory apparatus — the heart, blood-vessels, and lymphatic vessels — of birds. Article I. — The Heart. The heart, in birds, is situated quite at the entrance to the chest, in the median line, and is contained in a pericardium that adheres to the posterior diaphragmatic sept'im ' G. Colin, op. cit. 648 THE CIRCULATORY APPARATUS OF BIRDS. and the cervical reservoir. In the domesticated species, it has the form of an acute cone, whose base is surmounted by a less distinct auricular mass than in the Mammalia. Internally it has four cavities. The right ventricle is more crescent-shaped tlian in Solipeds, and in a manner envelops the left ventricle in frunt and to the right ; it does not reach the point of the heart. The auricular valve is not tricuspid, and offers a very remarkable arrangement. " Tliis valve, iu fact, instead of being lormed as usual by membranous curtains whose margin is retamed by cords fixed to the walls of the ventricles is composed of a wide muscular leaf which appears to be a portion of the inner wall of the ventricle detached from the interventricular septum. This septum is convex, and the auriculo-ventricular orifice is situated in the space comprised between it and the muscular valve in question ; so that when the latter contracts at the systole, it is applied against this septum and closes the passage." ' There is notliing particular to note with regard to the left ventricle, whose walls are likewise thicker than those of the right. The auricles have a kind of diverticulum or sinus, in which tlie veins that open ioto each of these cavities imite. Article II. — The Abteeies. The aorta of Gallinaceous birds ascends beneath the lower face of the right lung, then turns abruptly backwards and a little to the left. It attains the median line towards the anterior extremity of the kidneys, and in this situation it reaches the sacral vertebrae, where it divides into three branches — the arteries of the pelvic limbs, and the middle sacral artery. Close to its origin, the aorta gives off the brachio-cephalic (or innominate) trunks. With the Fowl this name is perfectly correct, as they both furnish vessels to the winge and head. The right passes upwards and forwards, is inflected backwards at the first rib, and continued on the lower face of the wing by the humeral artery. It throws off a thoracic artery, whose volume is in relation with that of the pectoral muscles ; this artery emits superficial branches that form iu the skin of the abdomen, with other vessels, a very rich plexus named by Barkow the rete mirabile of incubation. It afterwards gives oif a cephalic trunk, from which arise the ascending cervical, vertebral, and right carotid artery. The left brachio-cephalic trunk has the same distribution as the riglit, a slight difference only being observed in its direction ; on leaving the thoracic cavity it describes a small S curvature. The carotid arteries exhibit a somewhat curious arrangement. Each springs from a corresponding brachial trunk ; and placed at first on the sides of the neck they make a curve, whose convexity is anterior, and gain the median line by passing, the right above the oesophagus, the left above the trachea. They remain beside each other, beneath the longus colli, from the second last to the second cervical vertebras, where they separate at an acute angle and reach the border of the jaw, terminating there la two branches — the internal and external carotid arteries. The other collateral branches furnished by it, are: 1, The intercostal arteries. These may arise from the subcosfcil branches which are parallel to the aorta ; thus, in the Fotvl, there is a common descending intercostal which proceeds from the vertebral, and a common ascending intercostal that leaves the aorta as it passes into the abdomen ; 2, The c(eliac trunk, which commences at the middle of the lower face of the lung, and descend- ing obliquely backward, reaches the posterior aspect of the liver. It divides into several ramuscules, of which there are three principal vessels: a very fine one goes to the spleen; a left or middle one passes to the gizzard along the proventriculus; the third, more voluminous, is directed to the right side, gives a twig to the liver, and is continued by a long pancreatico-duodenal branch that joins the extremity of the loop which the intestine forms at its origin ; 3, The anterior or superior mesenteric, which arises at a short distance behind the cceliac trunk, enters the mesentery, and is directed backwards, describing a curve whose convexity is.antero-inferior, and which emits twigs to the intestine ; 4, The spermatic or ovarian arteries. The inferior or posterior mesenteric leaves the subsacral artery, and, by some ramuscules, reaches the rectum and cloaca. Shortly before its termination in three branches, the aorta gives off an artery that crosses the middle portion of the kidneys, leaves the abdominal cavity, and becomes dis- tributed to the anterior muscles of the thigh, after detaching the epigastric artery. The latter proceeds forward, beneath the skin of the abdomen, and anastomoses with the ramifications of the thoracic artery. ' MUne Edwards — ' I.e^ons sur la Physiologie et rAnatomie Comparee de I'Hommo et des Animaux.' Vol. iii. TEE CIRCULATORY APPARATUS OF BIRDS. C49 The arteries of the pelvic limbs — the femoral or crural, in i^assiug above the kidneys, furinsh the renal arteries ; they then leave the pelvis by the great ischiatic notch im- mediately behind the coxo-femoral articulation. Haced beneath the muscles on' the posterior face of the thigh, in following the branches of the lumbo-sacral plexus as far as the femoro-tibial articulation, they are then continued by the popliteal vessels. These arteries throw off articular raniuscules, the medullary artery of the tibia, and a long branch to the muscles on the posterior aspect of the leg ; they are placed in tlie groove resulting from the junction of the tibia and fibula, and pass through the osseous inter- space to form the anterior tibial arteries. The middle sacral contiimes the aorta to the bottom of the pelvis ; when it arrives below the last coccygeal vertebra, it forms a kind of arch whose ramifications are dis- tributed among the muscles and quills of the tail. Article III. — The Veins. As in Mammals, the veins are distinguished as belonging to the great and lesser circulation. The veins of the great circulation are collected into three trunks that open into the right auricle of the heart ; there are two anterior venae cavse and one posterior vena cava. They enter a particular compartment, a kind of sinus, in the auricle. The anterior vense cava; collect the blood from the subclavian arteries and those of the head. The jugular veins, which are their principal branches, are not the satellites of the carotid arteries, as in the larger domesticated animals ; they are superficial and placed on the sides of the trachea ; while the carotids are placed in the median line, beneath the long flexor muscle of the neck. They are not of the same calibre in all species,'the right jugular being more voluminous than the left ; there is always, however, a transverse anastomosis between the two jugulars, below the base of the cranium. The posterior or inferior vena cava commences at the anterior extremity of the kidneys, and passes forwards, traversing the right portion of the liver, receiving the hepatic veins, and enters the right auricle. Among the branches forming it, there may be cited the femoral or crural veins. These vessels do not accompany the corresponding arteries; not entering the pelvic cavity by the great ischiatic notch, they pursue a course analogous to that described for these vessels in Solipeds, in passing beneath the crural arch. In birds furnished with a crest and mandibles, the skin of the head is provided with an excessively rich vascular plexus. Article IV. — The Lymphatics. Birds possess lymphatic vessels and glands. The latter are few, and are scarcely met with elsewhere than in the cervical region ; the former are abundant in the viscera, and unite in such a manner as to form iico thoracic ducts. These ducts commence at the celiac trunk, and pass along the lower face of the lung, receiving the lymphatics of that organ and those of the wings, and finally open into the jugular veins, "a little in front of their union with the axillary veins. A transverse branch forms a communication between the two thoracic ducts, towards theii.- termination. BOOK VI. Apparatus of Innervation. FIKST SECTION. THE NERVOUS SYSTEM IN GENERAL. The functions whose instruments we have just described, suffice in them- selves to maintain nutrition — that mysterious molecular movement which is the ultimate object of the activity of organs, and the essence even of life : loco- niotory acts which permit the animal to seek its food and to introduce it into its organism, lead to the elaboration and absorption of the assimilable materials of the alimentary mass in the interior of the digestive cavity, the circulation of the reparative fluids in the economy, and the depuration and revivification of these fluids by the action of the lungs and the kidneys : in brief, could anything more be required to constitute the conditions necessary for the manifestation of the nutritive phenomena ? And yet, while the anatomist conceives in his mind a vertebrate animal exclusively endowed with the apparatus destined to execute these functions ; while he supposes the breath of life and the dependent properties of that animating principle to be due to these apparatus, he could not succeed in creating an imaginary being capable of moving, digesting, keeping in circula- tion the nutritive fluids, reviving these fluids by respiration and urinary depu- ration — in a word, of executing all those acts whose concurrence is indispens- able to the maintenance of nutrition, the supreme vital act. It is because the tissues of that animal, though possessing the organic properties inherent in their structure, require an excitant capable of bringing these properties into play. Their inertia is due to the absence of this excitant ; for all motion, no matter what kind it may be, demands for its realisation, not only the motor faculty in the organ which executes it, but also an excitatory cause. But give to this mutilated organism, this creation of our fancy, white cords, ramifying by extremely slender divisions in the depth of these instruments of life, and commencing from a central axis lodged in the cranium and spinal canal ; or, in other words, add to our incomplete animal an apparatus of innervation, and, as if by enchantment, there will appear the first signs of life. Owing to the peculiar properties which dis- tinguish the tissues of this apparatus, and concerning which we will have more to say hereafter, it plays the part of an exciter and regulator with regard to the properties of the other tissues. Stimulated by the nervous system, these properties no longer remain in a latent state, but manifest themselves by their usual results — such as contraction in the muscles, and exhalation and secretion in the membranes and glands ; then the imperfect being at once begins to digest, respire, etc. — in a word, to live, and is worthy of taking rank in the animated world. THE NEBVOUS SYSTEM IX GENERAL. C51 But tlio effects of tliis radical transformation do not cease here. The animal thus rendered apt to the nutritive movement acquires, beyond this vegetative life, the common appanage of all organised beings, all the attributes of what it has become habitual, after Bichat, to term animal life,- — that is, sensibility, volition, instinct, and intelligence. The perceptive centre which receives the excitations developed at the periphery of organs, or in their structure ; the excitatory centre which induces motion in all the other tissues ; the seat of the instinctive and intellectual faculties ; in short, does not the apparatus of innervation, thus charged with the grandest physiological finality, present itself as a most attractive study ? We will commence by giving a general and succinct idea of its conformation, structure, properties, and functions, before undertaking the special description of the different parts composing it. GENERAL CONFORMATION OF THE NERVOUS SYSTEM, The apparatus of innervation comprises a central and a peripheral portion. The first represents a very elongated stalk lodged in the spinal canal, ard bulging at its anterior extremity, which occupies the cranial cavity. TLis is named the cerebrospinal axis or centre. The second consists of a double series of ramescent branches, which are given off laterally from the central stalk, to be distributed to all parts of the body ; these branches are the nerves. The Cerebro-spikal Axis. — The stalk, or axis properly so called, lodged in the spinal canal, forms the spinal marrow (or cord). .It is a large white cord, terminating in a point at its posterior extremity, and giving rise, at each intervertebral foramen, to one of those nervous branches which, collec- tively, represent the peripheral portion of the apparatus of innervation. The bulging extremity inclosed in the cranium, is named the enceplialon (or brain). More comjilicated in its conformation than the sj^inal cord, this portion is divided, as we will see, into four parts : 1, A white peduncle, the continuation of the spinal cord ; 2, Three grey-coloured ovoid masses, one of which is posterior, the other two being anterior, and placed symmetrically side by side. This medullary prolongation emits, right and left, like the cord itself, nervous branches destined almost exclusively for the head. The Nerves. — The nerves are in the form of fasciculated cords, and make their exit from the orifices at the base of the cranium, or tbrough the intervertebral foramina, passing into all the organs by ramifying like arteries, which they generally accompany. All the nerves have their origin from the medullary axis, or from its encephalic prolongation, by radicles more or less apparent. They are divided, according to the relative position of their point of emergence, into two great categories ; the superior, arising from the corresponding face of the si)inal axis ; the others, inferior, escaping from the lower face : a distinc- tion which is perfectly appreciable with regard to the cord itself, but A\hich is more difiicult to establish in the encephalic peduncle, as it is less distinct. At their emergence from the bony canals which give them passage, the radicles of each nerve always unite into a thick common trunk. In the majority of cases, there enters into the composition of this trunk the nerves or fibres of the two orders ; only a few nerves are composed of fibres of the one kind, and these all belong to the brain. 652 TEE NEBVOVS SYSTEM IN GENERAL. At the origin of the trunk into which the nerve roots are collected, there is a greyish enlargement termed a ganglion; but this peculiarity belongs exclusively to the superior fibres. After a variable course, which is generally short, this trunk divides into branches, the point of departure for all the nerves of the body. Among these branches, those which are expended in the apparatus of animal life are pairs, and perfectly alike on both sides of the body. Those of the organs of nutrition are composed at first of an almost symmetrical double chain, placed beneath the spinal column, and whose elements are borrowed from nearly all the nervous trunks emanating from the cerebro-spinal axis ; in proceeding to their destination, their distribution is most irregularly com- plicated. As they offer on their course a great number of ganglia similar to those we have already mentioned, they are called ganglionic nerves ; they are also designated the nerves of organic or vegetative life, while the others are named the nerves of animal life or of relation. STRUCTURE OF THE NERVOUS SYSTEM. Two particular substances, one grey, the other white, enter into the or<»anisation of the nervous apparatus. These two substances are formed, the first by nerve-tubes and united nerve-cells ; the second by tubes alone. The nerve-tubes are microscopic elements, composed of a proper wall and contents. The wall, named the nervous sheath [sheath of Schwann), is a thin, homogeneous, elastic membrane that contains in its substance or its inner face some nuclei of cells. It is not visible in quite fresh tubes. The contents comprise, in the centre, a solid core, the axis-cylinder Fig. 310. (^oT primitive hand of Eemak), which becomes very appa- i^ rent after the addition of certain reagents ; between the axis-cylinder and the wall is found a viscid substance, the nervous medulla or ichite substance of Schicann, which coagulates very quickly under the influence of cold. When the medulla is solidified, it is seen to be bordered by two dark lines, parallel to the walls of the ^T" nerve-tubes; this aspect has caused the latter to be named " double-contoured tubes (or nerve-fibres)." DIAGRAM OF sTRuc- ^^ ^]^g ncrvc-tubes do not possess, at the same time, FIBRE ^^ ^^^"^^ these three parts, for the medulla may be absent ; so that 1 Sheath- 2 Medul- ^^^^^^ ^^'^ distinguished medullated and non-medullated ' laiy substence of nerve-Jibres. The first, more or less thick, are met with Schwann; 3, Axis- in the nervous centres, and at the origin, and in the cylinder, or primi- ini(j(Jle portion of the nerves ; the second are found at tive band. ^j^^ termination of nerves, and in the great sympathetic. There are also observed in the nerves of organic life, elongated elements, designated fibres of Bemak, grey fibres, and nucleated nervous fibres. These are pale, flattened fibres, with parallel borders, and furnished with elliptical nuclei. Some authorities consider these to be bands of connective tissue, and not nerve elements. The nerve-cells, or corpuscles, are voluminous, and are formed by a mass of granular protoplasm without any enveloping membrane. In the ganglia they are covered by a layer of fibrous connective tissue, provided with nuclei, which appear to furnish them with a very thick enveloping membrane. The nucleus, with one or two nucleoli, is often surrounded by granulations, whose dark colour gives rise to the supposition that they are pigment cells. THE NERVOUS SYSTEM IN GENERAL. 653 The nerve-cells have prolongations or poles, whose niimber varies from one to five. Cells with only one prolongation are named unipolar ; those which have two are bipolar ; and those which have a greater number are designa- ted multipolar. These poles establish relations with the nerve-tubes, and constitute the origin of the nerves. Fio;. 311. MULTIPOLAR OR STELLATE GANGLIONIC NERVE-€ELL, WITH ONE OP ITS PROLONGATIONS — a, Becoming contmuous with the axis-cylinder of a double-contoured nerve-fibre, h. Such are the anatomical elements that enter into the structure of the nervous system. In the white substance of the cerebro-spinal axis, only medullated nerve- tubes of every size are found ; in the grey substance are tubes, and a more or less considerable number of nerve-cells are situated along their course. To these two elements is added a large quantity of blood-vessels, which are incomparably more abundant in the grey than in the white substance. In the nervous cords, the elementary tubes are alone met with ; they are disposed in long bundles, which are collected into successively increasing fasciculi. A cellulo-vascular envelope, the neurilemma (or ijerineurium), binds all these fasciculi into a single cord, and forms a special sheath around each of them. Tbe details of their organisation will be referred to hereafter.- It is admitted that the ganglionic, or nerves of organic life, possess a greater quantity of slender tubes than the others. These tubes are com monly designated as the organic nerve fibres. They also contain fibres of Remak. In the ganglia, the cells are joined to the nerve-tubes. It has been shown, by dissection and microscopical observation, that the corpuscles composing the ganglia at the origin of the trunks are all attached to the superior fibres. The other tubes have none. In the cerebro-spinal axis, the two substances are equally associated with each other, but in a variable manner, according to the region. In the cord 654 THE NERVOUS SYSTEM IN GENERAL. and its prolongation into tlie enceplialon, tlie grey substance occupies the interior, while it is spread over the exterior of the encephalic lobes and envelops the white substance. Fig. 312 Fig. 313. MICROSCOPIC GANGLIOX FROM HEART OF FROG. BIPOLAR GANGLIONIC CELI5 AND NERVE- FIBRES, FROM GANGLION OP FIFTH PAIR IN LAMPREY, (In some instances, as in the cells of various parts of the spinal cord, the prolongations subdivide and ramify in a curious manner, and form a close network that penetrates the surrounding nervous tissue. In addition to these, there are other very complex nerve- cells whose structure has only Fiff. 315. Fig. 314. STELLATE NERVE-CELL. FROM THE NUCLE0S CERVICIS CORNU (POS- TERIOR VESICULAR column) OF A FCETUS OF SIX MONTHS. MAGNIFIED 420 DIAMETERS, STRUCTURE OF GANGLIONIC NERVE-CELL. A, According to Beale ; B, According to Arnold. — «, Straight fibre ; 6, Double spiral fibre ; c, Capsule of connective tissue. recently been clearly established. These have been foimd in the sympathetic ganglia, and each is invested in a capsule of connective tissue. In shape, the cell is pyriform, and it contains a nucleus ; from the narrow end spring two fibres, that pass in opposite directions when they reach the nervous TEE NERVOUS SYSTEM IN GENERAL. 655 bundle to whicli they are distributed. This disposition has given rise to the opinion that every nerve-fibre, no matter how long its course may be, is a loop that originates in, and returns to, the same cell. One of the fibres that enters the cell, and looks like a stalk to it, is usually straight ; the other seems to arise from the outside of the cell, is sometimes double, and circles round the other in a spiral manner two or three times. Both fibres at first resemble the cylinder-axis of ordinary nerve-fibres, and may subsequently be- come dark-bordered, or remain pale fibres. The spiral fibres bear large oblong nuclei in their course. Some observers state that they have traced the straight fibre into the nucleus, and the spiral fibre into a plexus on the exterior of the cell, but which may be ultimately traced into the nucleolus ; so that the two fibres are continiious through the nucleus and nucleolus). PROPERTIES AND FUNCTIONS OF THE NERVOUS SYSTEM. It would require a long chapter to do justice to this subject, and we could not venture on it here without going beyond our domain. We will, however, ofier some remarks on those notions connected with the properties and functions of the nervous system which are strictly necessary for the comprehension of the anatomical facts to be hereafter dealt with. And first as to the properties of the nerves. We will suppose the spinal canal to be opened in the lumbar region, and the cord laid bare in a living animal. If we cut across the inferior roots of one of the spinal nerves, and if we compress with a pair of forceps one or more of these roots, by the end remaining attached to the cord, nothing results to denote that this irritation has had any influence on the organism. But if, instead of operating on the central or attached end of these divided roots, we excite the peripheral end which is continued by the trunk of the nerve, contraction of the muscles of the limb which receives the fibres coming from the irritated roots is produced. The muscular tissue comports itself as if the irritation were directly applied to it ; so that the nerve has served as the medium of communication. It has received the excitation, it has been imp-essioned by it, and it has conducted this to the muscles to which the nerve is distributed. This double reaction produced by the nervous tubes is their special attribute, their essential property. With M. Vulpian we might designate it as a whole by the name of veuriJihj ; but it is necessary to distinguish the two modes it affects by naming the property of being impressed by excitations as the excitability of the nerve, and nervous conductihility its aptitude to convey the excitations which have impressed it. The same experiment may be repeated on the upper roots. It is then perceived that the pinching, which produces no effect at the peripheral extremity, causes pain when applied to the central end. The animal testifies immediately, by cries and movements, that it feels the touch of the forceps. But, as will be mentioned in a moment, the impression resulting from this touch has only been perceived by the brain ; it has therefore been conducted to the spinal cord by the excited nervous fibres, and then to the brain by the fibres of this medullary axis. In putting to one side, for the moment, the part played by the latter in the phenomenon now analysed, it will be seen that the superior fibres of the spinal nerves enjoy the same attributes as the inferior ; neurilily is their appanage, and this property is apjiarent in its two qualities — excitahility and conductihility. Only here the latter property is exercised in a centripetal 656 TEE NERVOUS SYSTEM IN GENERAL. sense ; wliile in the first instance it acted in a centrifugal sense. But it must not be assumed that these two conductibilities are essentially distinct. The physiological diflferences by which they ajipear to be distinguished seem to belonw to the difference in the relations of the nerve-fibres with the organs to which they are distributed. In one case, that of the centrifugal nerves, the organs of reaction — the muscles — are placed at the peripheral extremity of the nerves ; in the case of the centripetal nerves, the organs of reaction — the brain and spinal cord — are found at the central extremity of the nervous fibres. This theory of the unity of nervous conductibility has, moreover, been proved to be correct by the researches of Philipeaux and Vulpian, who have utilised the experiment of Gluge and Thiernesse on the union of the central end of the lingual (centripetal) with the peripheral end of the hypoglossal nerve (centrifugal), to demonstrate that the fibres of the former then acquire centrifugal conductibility. It is easy to demonstrate that this double property of conduction belongs to all the nerve-fibres springing from the cerebro-spinal axis, centripetal conductibility being peculiar to the superior fibres, and centrifugal conducti- bility to the inferior ones. It is also demonstrated that this conduction acts in either one sense or the other, whatever may be the point on the course of the nerves so stimulated ; as the nerve-tubes possess, throughout their whole length, the property of excitability and conductibility. The fibres with centrifugal conductibility constitute the motor nerves ; those whose conductibility is centripetal are the sensitive nerves. But sensi- bility does not exist only in the filaments of the superior roots ; it has also been remarked in the lower roots, and they owe it to the filaments which are given off from the roots whose conductibility is centripetal, and which return to the nervous centres by the motor roots. The sensitiveness evinced by these motor roots is named recurrent sensibility. The anatomical and physiological characters of the nerves persist as long as they communicate with the centres. If they are divided at any part of their course, the portion attached to the spinal axis still preserves its properties ; but that situated beyond the section — the peripheral end, as it is named — degenerates, and becomes incapable of conducting the sensitive impressions, or of transmitting the voluntary motor excitations. Now as to the spinal cord. Does the medullary axis, which has apparently, in great part, the structure of a nerve, possess, like the latter, excitability and conductibility, those two essential properties of the peripheral nervous system ? Excitability is entirely absent in the grey substance. On the surface of a section of the cord, the slightest, or even the most intense irritation of this portion produces no reaction. In the white substance, this excitability can only be easily rendered evident on the surface of the upper bundles or fasciculi, where it is exquisite. With regard to the always limited reactions observed Avhen the excitations are made on the deej} part of the fasciculi, it is difficult to say if they result from the excitability of the spinal cord, or that of the nerve roots that iraverse the white substance. Nervous conductibility is certainly one of the attributes of the spinal cord ; the transmission of excitations of the sensitive nerves to the brain, and the voluntary movements tliat result from stimulation of the motor nerves, demonstrate that the necessary medium between the nerves and bi*ain — the spinal cord — possesses conductibility. But does this portion of the nervous system possess no other property? Yes; it may act as a nervous centre, and the following experiment irrefutably demonstrates it : THE NERVOUS SYSTEM IN GENERAL. 657 I will suppose that an animal lias had its spinal cord cut across in the lumbar region, and I excite, by pinching, one of the superior roots re- maining intact on the caudal portion. The stimulus cannot be conducted to the brain, as this part is isolated from it ; and yet movements take place in the muscles of the posterior members. Does it happen that, after section of the medulla, the conductive property of the nervous fibres which originate superiorly is interverted and changed into centrifugal conductibility ? No ; for after the transverse section of these roots, the irritation of their central end produces exactly the same effects. It must be, therefore, that the excitation had first reached the medulla, and was then transmitted by it to the muscles by means of the centrifugal current fibres. And this is really what occurred ; the section of the whole of these fibres on the trunk of the cord hindered the manifestation of all movement in the muscles when the superior roots were touched. There is, as has been said, reflexion in the substance of the cord, on to the inferior roots, from the irritation due to this pinching, and the property which permits the medullary axis to act in this manner is named the reflex power. It may be remarked that, if we suppose for a moment the superior and inferior nervous roots to be united in an arch in the substance of the spinal cord, this reflex property would be nothing more than the nervous conductibility itself operating precisely in the direction special to each kind of nerves. This union really takes place ; only the nerve-roots are not in communi- cation, except through the medium of the cells in the grey substance, in which the sensitive is changed into motor excitation. The reflex power is extinct immediately after death occurs in Mammals, but it may last for several hours, or even for a day, in a decapitated animal in which asphyxia has been averted by pulmonary insufilation. The extent of the movements it determines is in relation to the intensity of the stimuli;s which is the primary cause of it ; merely localised when they result from a slight irritation, these movements may take place in all the muscles of the body after an energetic stimulation. Let us now inquire into the attributes of the encephalcn. Excitability is not remarked in all parts of the brain ; it exists in several points of the medulla oblongata, and in the deep substance of the cerebellum ; but it cannot be rendered evident on the surface of the latter, nor yet in the cerebral hemispheres. The brain possesses conductibility, because the grey substance composing it is the receiver of, and the point of departure for, all the excitations. In fine, the encephalic mass should possess neurility like the nerves, but this general property is more or less modified. What more particularly distinguishes the encej)halon is its action as a sensitivo-motor centre ; in it arrive the excitations from the sensitive nerves, and there they are felt and judged. In the brain arise the motor excitations which result in spontaneous voluntary movements. In an animal paralysed by division of the cord at the occipito-atloid articulation, and in which death has been prevented by artificial respiration, observation demonstrates that sensibility and spontaneous motricity are preserved in the head, whose nerves are in direct communication with the encephalon. Pinch the upper lip, and the patient testifies by the movements of this organ that it feels pain. Pass the finger towards the eye, and the eyelids are twinkled and closed : a proof that the animal sees objects, appreciates the distance which separates it from them, and tries to remove the eye from their contact. More striking still, the animal feels hungry, and endeavours to satisfy this cra\'ing by seizing the food within its reach, and C58 THE NERVOUS SYSTEM IN GENERAL. masticating and swallowing it. After this demonstration, it is no longer possible to doubt that, if an animal /eeZs, it is by the brain, and if it loills, it is also by the brain. But sensibility and volition do not constitute the only attributes of the brain tissue ; for it is the seat of other manifestations not less interesting — those of the instincts and intelligence. If the encephalon is to be considered as the immediate instrument of all these phenomena, it would be impossible — it is impossible — to attribute the cause, properly speaking, to the activity of its physical matter ; above this hovers a mysterious power that can only be demonstrated by a methodical analysis of the manifestations produced by that activity. But we dare not venture to touch upon the nature of this power; the first word would be useless without the last, and this would carry us too far. To sum up, the nerves possess a single vital property — neurility, which is manifested by excitahility and by centripetal conduct ihility in the nerves whose roots are uppermost, centrifugal conductibility in the nerves whose roots are inferior. The spinal cord is inexcitable in its grey substance, but is excitable on the surface of its superior fasciculi, though scarcely so in the remainder of its white substance. It serves as the organ of transmission between the brain and the nerve-roots; and is, in addition, endowed with the reflex property or power. The brain has for its appanage a special activity, to which is due sensi- bility, volition, and the manifestations of instinct and intelligence. It remains to make known the nature of the influence the nervous system exercises on the other apparatus through the properties we know it to possess. But here again we must limit ourselves to principles. Since Bichat's time, it has been agreed to divide into two great classes those functions whose operation maintains the life jjroper of the individual : those of animal life or relation, and those of organic or vegetative life. The first, which are exercised with consciousness, comprise the sensorial functions and voluntary movements; the latter are provoked by the spon- taneous excitation originating in the brain, and transmitted to the muscles by the nerve-fibres whose conductibility is centrifugal ; the former have for their object the appreciation, by the brain, of tactile sensations — of heat, light, taste, and smell, by means, or through the instrumentality, of the nerve-fibres possessed of centripetal conductibility, which transmits to the encephalic mass the stimulus developed at their terminal extremity by these diverse physical agents. The functions of vegetative life — those which are executed unconsciously, we may say, in animals, and which are not the result of physico-chemical forces — are placed under the influence of the reflex power of the spinal cord. For example, the stomach is empty and its mucous and muscular membranes remain altogether passive ; there being no contractions in the first, nor secretion of gastric fluid in the second. Food arrives in its interior, and immediately its activity is develoj)ed ; the muscular tunic executes move- ments which cause the mixture of the food, and propel it towards the pyloric orifice ; while the free surface of the internal membrane pours out an abundant solvent secretion. This change is due to the stimulus exercised by the presence of the alimentary particles on the extremity of the centri- petal nerve-fibres, and which has been transmitted by them to the medul- lary axis, there reflected on the centrifugal fibres, and carried by these to the tunics of the stomach, whose special functions are thus brought into play. THE CEREBROSPINAL AXIS. 659 It is worthy of remark that the properties of the nervous system, which act in so important a manner on the organs of vegetative life, have no direct influence on nutrition itself. Destruction of the nerves in a certain region will certainly derange the nutrition of its tissues, in consequence of the paralysis of the vessels, but it is not destroyed. There is an immense category of organised beings — vegetables, for instance — in which nutrition is very active, and in which there is no nervous system. So that the property which determines the essential phenomena of nutrition is indepen- dent of nervous action : it is an attribute of livincj matter. SECOND SECTION. The Central Axis of the Nervous System. The cerebrospinal axis is resolved, as we have said, into two principal sections — the spinal cord and the encepTialon. We will study these two portions in succession, the spinal cord first, in order to facilitate our de- scription, although that organ only holds the second place in a physiological jjoint of view. The protective parts of these two a^jparatus will, however, be examined before we proceed further. CHAPTER I. THE ENVELOPING AND PROTECTING PARTS OF THE CEREBRO-SPINAL AXIS. The cerebro-spinal apparatus is lodged, as we abeady know, in a bony case — the spinal canal — which is prolonged anteriorly by the cranial cavity ; but it is protected more immediately by three envelopes, which have received the names of dura mater, arachnoid, and pia mater. THE BONY CASE THAT CONTAINS THE CEREBRO-SPINAL AXIS. A knowledge of the bones which enter into the composition of this pro- tective case, cannot be acquired without also knowing the case itself; so that we dispense with its special study here. We will allude, however, to the succinct terms already employed in describing the spinal canal, and in the same spirit of concision will also describe what has hitherto been deferred — the cranial cavity. 1. The Spinal Canal. This canal communicates, anteriorly, with the cavity of the cranium. Very wide at the atlas to receive the odontoid process, and allow those rotatory movements of the head which prevent the medulla being injured, the spinal canal suddenly contracts at the axis ; it expands again at the end of the cervical, and the commencenunt of the dorsal region, where the medulla presents a greater volume, and the movements of the spine are very extensive. Towards the middle of the back, the spinal canal offers its smallest diameter, but on leaving this portion, and as far as the lumbo -sacral 660 THE CENTRAL AXIS OF THE NERVOUS SYSTEM. articulation, it widens again ; after wliicli it rapidly lessens, and altogether disappears towards the fourth or fifth coccygeal vertebra. The lumbo- sacral dilatation coincides with the expansion the cord shows at this point, and with the enormous volume of the nerves lying beside it. 2. Tlie Cranial Cavity. (Figs. 22, 23, 175.) This is a very irregular oval box, whose walls are formed by the frontal, parietal, occipital, ethmoidal, and temporal bones. It presents for consideration four planes and two extremities. The superior plane offers on the middle line, and towards its superior third, the parietal protuberance, the two lateral crests of which concur with that eminence in dividing the cranial cavity into two compartments : one posterior, destined to contain the cerebellum ; the other anterior, incomparably larger, lodging the cerebral hemispheres, and divided by the single rudimentary crest Avhich begins at the fixlciform eminence, and joins the crista galli, into two lateral sections — one for each hemisphere. Here- after we will see that the folds of the dura mater are attached to this parietal protuberance, and to the ridges detached from it, thus rendering much more perfect the partitioning of the cranial cavity. On the lateral planes there is also noticed the division into a cerebellar and cerebral compartment, due to the lateral crests of the falciform j)rocess, which are prolonged obliquely to near the sphenoid bone : the first section is formed by the occipital and the inner face of the petrous bone ; the second by the squamous portion of the temporal, the frontal, and the great ala of the sphenoid bone. Both are concave, and marked by digital impressions, as they also are on the superior plane. The inferior plane, very irregular, offers from behind forward : 1, On the median line, the basilar channel, into which the greater portion of the encephalic isthmus is received ; the pituitary fossa, made deeper by a circular fold of the dura mater, and lodging the gland of that name ; the optic fossa, where the chiasma of the optic nerves is situated ; 2, On the sides, the foramen lacerum, partly closed by cartilaginous substance, and by the dura mater ; the cavernous sinuses and maxillary fissures, outside which is remarked a deep and wide digital impression for the reception of the mastoid lobule, or inferior lobe of the brain. The posterior extremit!/ of the cranial cavity presents the occipital foramen, by means of which this cavity communicates with the spinal canal. The anterior extremity offers, in the median plane, the crista galli process, or superior border of the perpendicular plate of the ethmoid bone ; on the sides, the two ethmoidal fossas — deep depressions containing the olfactory lobes, and at the bottom of which is observed the cribriform aspect of the transverse plate of that bone. THE ENVELOPES OF THE CEEEBRO-SPINAL AXIS. The three membranes which cover the cerebro-spinal axis, and separate it from the walls of the bony cavity inclosing it, are thus designated. Generally termed meninges, and distinguished as external, middle, and internal meninge, these membranes are better known as the dura mater, arachnoid, and pia mater — names which will be employed in our description. The dura mater, or external meninge, is a strong fibrous membrane in contact with the walls of the cranium and the spinal canal. The arachnoid, or middle meninge, is a tunic of a serous nature, which TEE CEREBBO-SPINAL AXIS. GGl resolves itself into two layers : an external, applied to the inner face of the dura mater ; and an internal, spread, through the medium of the pia mater, over the cerebro-spinal axis, from which it is again separated in a great number of points by a particular fluid, the subarachnoid. The pia mater, or internal meninge, is the proper envelope of the central nervous stalk ; it is cellulo-vascular, closely adherent to the external surface of the cord, united to the visceral layer of the arachnoid by more or less dense connective tissue, between the meshes of which is deposited the subarachnoid fluid. This arrangement of the cerebro-spinal envelopes permits the cerebro- spinal axis to be assimilated, to a certain extent, to a viscus, and the bony sheath containing them to a splanchnic cavity, whose serous membrane, the arachiuid, is covered outside its parietal layer by a fibrous expansion, the dura mater, and within its visceral layer by a cellulo-vascular tunic, the jna mater, or internal meninge. This collective view of the envelojies belonging to the nervous centres will now be followed by a special descrij)tion of each, in which their spinal and cranial portions will be successively considered, after glancing at them in a general manner. 1. The Dura Mater. This membrane is the most external and the strongest of the cerebro- spinal envelopes, and covers the walls of the cerebro-spinal cavity, whose form it exactly rej)eats. It is, therefore, a second protective sheath, which is dilated at its anterior extremity into an ovoid cavity that lodges the encephalon, and terminates in a prolonged point in the coccygeal vertebrfe. It ofiers two faces : an external, in contact with the walls of the bony case ; and an internal, adhering in the most intimate manner to the external layer of the arachnoid. In several points of its extent it is traversed by the nerves which escape from the cerebro-spinal axis, and by the vessels destined to this portion of the nervous system. Structure. — The dura mater possesses the texture of all white fibrous membranes. It is composed of parallel longitudinal fasciculi of connective tissue, mixed with some fine elastic fibres. Bourgelat thought they formed two distinct layers — an external and internal ; but nowhere is it possible to demonstrate this. It receives blood-vessels ; the arteries are derived, for the spinal portion, from the vertebral, the intercostals, lumbar, and lateral sacrals ; for the cranial portion, meningeal ramuscules, such as the ethmoidal branch of the nasal, the spheno-spinous, and tympanic, mastoideal, and cerebro-spinal arteries. Nerves have been seen passing to its cranial portion ; these have been divided into anterior, middle, and posterior. The first are furnished by the ethmoidal filament of the nasal nerve ; the second from the Gasserian ganglion ; and the third, by the ophthalmic branch of Willis. The existence of lymphatic vessels has not yet been demonstrated. Spinal Dura Mater (Theca Vertebralis). — This is a very elongated sheath, continuous at the occipital foramen with the encephalic dura mater, and terminated behind by an attenuated point lodged in the narrow channel which, in the middle coccygeal vertebrre, represents a trace of the spinal canal. As it is in shape exactly like the latter, its largest diameter is at the atlas, and at the brachial and lumbo- sacral enlargements of the spinal cord. Its capacity depends greatly on the volume of the latter, and in some of its parts it can allow the accumulation of the cerebro-spinal fluid ; this 45 G62 TEE CENTRAL AXIS OF THE NERVOUS SYSTEM. accumulation is impossible for nearly the whole extent of the cranial region. The external face of the dura mater is very slightly adherent, esijecially above, to the walls of the spinal canal ; and it is even separated from them, at the intervertebral spaces, by a certain quantity of adipose tissue which is never absent, though the animals be ever so emaciated. This face covers, inferiorly, the common superior ligament, and the veins we have described as spinal sinuses. The internal face gives attachment, between each pair of nerves, to the festoons of the dentated membrane, a dependency of the pia mater. It is rendered smooth and polished by the external layer of the arachnoid, to which it is so firmly united, that it is needless to attempt their separation. Here the external layer of the arachnoid is reduced to a simple layer formed by a row of cells with flattened nuclei. On each side, the substance of this meninge is completely traversed by a double series of orifices for the passage of the spinal nerves, around which it sends small special sheaths as far as the intervertebral foramina. Cranial or Encephalic Dura Mater. — This membrane forms a sac which is exactly moulded by its external face to the cranial parietes, and by its internal face to the superficial surface of the encephalon. The latter, therefore, completely fills the cavity of the cranium, a circumstance that explains why an accumulation of fluid is impossible in this region. External surface. — It adheres strongly, by cellulo-vascular bands, to the cranial walls, whose undulations it follows ; this adhesion is not, however, equally marked everywhere, for on the sides of the roof of the cerebral compartment it is least intimate, and it is closest on the middle plane of this roof, on the crista galli, around the parietal protuberance, on its crests, and towards the lateral faces of the cerebellar compartment at the petrous bones, where the membrane is very thin. This face gives rise to a number of prolonged sheaths, corresponding to -the nerves leaving the base of the cranium. The principal are found around the ethmoidal filaments, the optic nerves, and the two thick branches furnished by the Gasserian ganglion. Internal surface. — The internal surface of the cranial dura mater is covered by the parietal layer of the arachnoid, which is firmly attached to it only in the spinal region. It sends into the cranial cavity three pro- longations, which are distinguished as the falx cerebri (falx, a sickle), .tentorium cerebelli {tentorium, a tent), and i)iQ pituitary fold. These processes ■complete the partitioning of the cranial cavity, isolate the various external ibulgings of the encephalic mass, and protect them from the compression they might exercise on each other. a. The falx cerebri is a vertical lamina comprised between the two cerebral hemispheres, and owes its name to its sickle-like form. Its antero-superior border is adherent and very convex, and corresponds to Abe crista galli process, as well as to the median ridge on the inner face of the frontal and parietal bones. This border is very thick, and hollowed internally by a prismatic and triangular venous canal, which con- stitutes the median sinus. Towards its inferior border, which is free and concave, and corresponds to the corpus callosum, the falciform process is extremely thin, and cribbled lite lace-work. The posterior extremity, or base of the falx, rests on the parietal ; protuberance. THE CEREBROSPINAL AXIS. 663 The anterior extremity advances in a curve to near the optic fossa. In aged animals, there are sometimes found on the faces of the falx cerebri, especially towards its posterior extremity, small yellow granules, known as the Pacchionian (/lands. They are little nuclei of connective tissue that arise from the subarachnoideal tissue ; meningeal g7-anulations would be a better designation for them than that of glands. 6. The tentoritim cerebelli is composed of two lateral laminae, which form a transverse partition between the cerebellum and the posterior extremities of the cerebral lobes. Each lamina, coursed internally by one of the transverse sinuses, offers : an adherent convex border, attached to the parieto-temporal crest ; a free concave border, turned inwards and a little forwards, remarkable for its thickness and solidity, and, with the second lamina, circumscribing an oval opening through which the encephalic isthmus passes ; a superior extremity, attached to the parietal protuberance ; an inferior extremity, which disappears above the Gasserian ganglion, near the fold that surrounds the pituitary gland. Of the two faces of these laminae, the anterior corresponds to the cerebral lobes, the posterior to the cerebellum. c. The sup'osphenoidal, or pituitary fold, is a thick, slightly salient, and almost circular pad, channeled internally by the cavernous sinus, and circumscribing the sella turcica by enveloping the pituitary gland laterally and posteriorly. 2. The Arachnoid Membrane. The arachnoid presents the same disposition as all the splanchnic serous membranes, in being resolved into two layers — a parietal and a visceral, both constituting a perfectly closed sac, outside which the cerebro-spinal axis is contained. The cavity of this sac is traversed by the roots of nerves, the vessels of the brain and cord, and filaments and cellular lamellfe which pass from the pia mater to the dura mater ; around all these its layers form sheaths by becoming continuous with one another. Each of these layers exhibits an adherent and a free face. The adherent face of the parietal layer is united, as we have already seen, to the dura mater. That of the visceral layer covers the nervous axis in spreading itself over the pia mater, but without accompanying it into the anfractuosi- ties of the central mass ; it is beneath this face of the visceral layer that the cerebro-spinal (or subarachnoid) fluid is confined in spaces which will be studied hereafter. By their free face, which is smooth and moist, like that of all serous membranes, the arachnoid layers are in contact with each other. Structure. — The structure of this membrane resembles that of all others of the same nature. The meshes of elastic fibres are most abundant in the cranial portion. Everywhere the parietal layer is only composed of a simple layer of epithelium. The arachnoid has no proper vessels or nerves ; those which pass through it only accompany each other. Spinal Arachnoid Membrank — The parietal layer presents nothing of interest. The visceral layer is separated from the spinal cord, throughout its extent, by a somewhat considerable space (the subarachnoid), in which the subarachnoid fluid is collected ; this space is greatest posteriorly, around the terminal extremity of the cord and the nerves of the cauda equina. The adherent face of this membrane is only connected with the external 664 ~ TEE CENTRAL AXIS OF THE NERVOUS SYSTEM. surface of the spinal cord by thin cellular filaments detached from the pia mater. Cranial oe Encephalic Arachnoid. — There is nothing special to note in the parietal layer. If the visceral layer be traced from the occipital foramen, -nhere it is continuous with the spinal arachnoid, to the anterior extremity of the cerebral lobes, it is seen to be prolonged inferiorly on the lower face of the isthmus, as far as the pituitary stalk, to which it fui-nishes a sheath : the pituitary gland itself is not covered by the arachnoid, except on a portion of the superior or deep face ; from the isthmus it is carried forward, and extends on each side of the cerebellum and cerebral lobes. Superiorly, this internal layer sj)reads over the surface of the cerebellum, and is reflected at the bottom of the fissure between that organ and the cerebral hemisj^heres, over the posterior extremity of the latter, enveloping them separately by descending into the interlobular fissure as far as the corpus callosum. Eeaching the anterior extremity of the cerebrum, it gains the olfactory lobes, is principally prolonged on their supero-posterior face, and doubles around the ganglion of grey substance on their inferior face, to be con- tinued with the parietal layer. In covering the external surface of the encephalon, the cranial arachnoid does not adhere everywhere to the nervous substance, but is only slightly connected with it, through the medium of the pia mater, at such salient portions as the summits of the cerebral convolutions. Neither does it dip down to enter the sulci existing between these parts, but i)asses over them, and in this way forms a large number of subarachnoid spaces analogous to that developed over the whole extent of the spinal cord. These spaces, which are filled by the subarachnoid fluid, differ widely in form and dimensions. In Man, thi-ee principal have been described, and these are also found in animals ; Magendie has named them the confluents of the subarachnoid fluid. Of these three confluents, the anterior is situated in advance of the chiasma of the optic nerves, between the two cerebral lobes ; the inferior, the largest, is comprised between the pituitary stalk and the annular protuberance to the surface of the peduuculi of the cerebrum ; while the third, or posterior confluent, lies behind the cerebellum, at the calamus scriptorius. None of these spaces communicate with the internal cavities of the en- cephalon, and, consequently, the subarachnoid fluid cannot enter them. Magendie has nevertheless described a communication between the pos- terior confluent and the ventricle of the cerebellum ; though the opening he described towards the calamus scriptorius has not been found in the Horse by M. Renault, and we believe we may afiii'm, with M. Lavocat, that it does not exist in the other animals. The Subarachnoid Fluid. — The fluid contained in the subarachnoid spaces is slightly yellow or colourless, and perfectly limpid and transparent. Some authorities admit that it is secreted by the visceral layer of the arachnoid, and others by the pia mater. According to the remark made by Cruveilhier, the nervous centres are irmnersed in it, like a foetus in the liquor amnii; and this remark, which is particularly applicable to the spinal cord, gives the key to the use of this fluid, which keeps the organ away from the walls of the spinal canal, deprives it of the greater part of its weight (Foltz), and thus diminishes every kind of concussion to which it might be exposed. (This fluid, so necessary for the support and protection of the cord and THE CEREBROSPINAL AXIS. G65 brain, is alkaline, and contains but a small quantity of albumen ; it varies in quantity according to the relative size of the cerebro-sijinal axis and its containing cavity, or with the amount of blood sent to this region. By aflfording, under all cii'cumstances, an equable pressure on the brain and spinal cord, and the nerves emanating from these, its importance as a hydro- static agent is greatly enhanced.) 3. Tlie Pia Mater. The pia mater, the proper envelope of the cerebro-spinal axis, is a thin membrane whose framework, essentially connective, sustains on its external face a very abundant network of blood-vessels and nerves. Applied immediately to the surface of the encephalon and spinal cord, it adheres lirmly to that surface and follows all its inequalities, jjenetrating between the cerebral or cerebellar convolutions, and forming in each inter- mediate sulcus two layers that lie against each other. The external face of the pia mater, bathed in part of its extent by the subarachnoid fluid, adheres to the visceral layer of the arachnoid by means of a more or less dense and close filamentous connective tissue. From it arise the cellular coverings that constitute the neurilemma of the nerves. It detaches a multitude of filamentous or lamellar prolongations to the internal face of the dura mater, which traverse the arachnoid cavity in the same manner as the nerves and vessels, by being enveloped, like these, in a sheath furnished by the arachnoid membi'ane. Always very short, these prolongations simulate the adhesions established between the two layers of that membrane. The internal face is united to the nervous substance by multitudes of arterial and venous radicles or connective fi.laments, which leave the pia mater to plunge into this substance. The vessels of the pia mater form a very close network, from which are detached branches that reach the medulla and encephalon. They are ac- companied by nervous filaments, and surrounded hj perivascular canals, which are now believed to be lymphatics. Certainly, in their interior a colour- less fluid circulates, and which contains globules very like those of lymph. Spinal Pia Mater. — Less vascular than the cranial pia mater, with which it is continuous towards the medulla oblongata, this membrane is remarkable for the arrangement of the prolongations that arise from its two faces. The internal prolongations form longitudinal laminae at the fissures of the cord, and enter these fissures. The external prolongations attach, as we have said, the pia mater to the external meninge. A very large number are filamentous in form, and are dispersed over the superior and inferior surfaces of the cord. Others consti- tute, on each side of the organ, a festooned band named the dentated ligament (ligamentum dentata, or denticulatum). These ligaments exist throughout the entire length of the medullary axis, between the superior and inferior nerve- roots : theii- inner border is confounded for its whole length with the pia mater ; and their outer margin, cut into festoons, attaches itself to the dura mater by the summit of the angles separating these festoons. To complete this description of the spinal pia mater, there may be noticed a posterior or coccygeal prolongation (Jilum terminale) : a very narrow process formed by this membrane at the posterior extremity of the cord, situated in the midst of the cauda equina nerves, and attached to the bottom of the conical cul-de-sac at the termination of the dura mater. 6G6 THE CENTRAL AXIS OF THE NERVOUS SYSTEM. (This ligament, or memhrana dentata, serves to maiutain tlie position of the spinal cord in its hydrostatic bed, and to prevent the nerves proceeding from it being dragged during flexion of the spine.) Cranial, or Encephalic Pia Mater. — The vascular element pre- dominates in this portion of the internal meninge. This membrane sends scarcely any prolongations to the dura mater, except at the medulla oblongata, though it projects remarkably large ones into the cerebral mass and the sides of the cerebellum. The descrijition of the velum interpositum, and the cerebral and cerebellar plexus choroides, belongs to the encephalon. (The pia mater is extremely vascular on the surface of the cerebrum, and forms remarkable anastomosing loops in the intermediate spaces of the convolutions, which chiefly supply the grey substance. It is the nutrient membrane of the brain and spinal cord. Its nerves accompany its arterial branches, and are minute filaments from the sympathetic.) differential characters in the enveloping and protective parts of the cerebro- spinal AXIS IN OTHER THAN SOLIPED ANIMALS. The oony canal that protects the spinal cord and brain does not present any note- worthy differences in the domesticated animals, and the subject has been already sufficiently studied in the osteology of the head and vertebral column. With regard to the meninges, their number and general disposition are the same in all the species. COMPARISON OF THE ENVELOPING AND PROTECTIVE PARTS OF THE CEREBRO-SPINAL AXIS OF MAN WITH THOSE OF ANIMALS. There is nothing particular to be said respecting the cranial cavity and spinal canal, nor yet the arachnoid and pia mater. The dura mater ofifers the folds described in Solipeds, and, in addition, ufalx cerebellum, thnt extends from the tentoriuni of the same name to near the foramen magnum. The meningeal granulations, or Pacchionian glamls, are nearly constant in aged Individuals, and their volume is sometimes so considerable, that by compression they thin away, aud even perforate, the cranium at corresponding points. CHAPTER IL THE SPINAL CORD. Preparation. — Isolate the cranium and vertebral column from all the 6ther parts of the body; open the spinal canal and the cranial cavity by their superior surface, as in figure 3] 6, bv raising with a chisel (or rogne-pied, the farrier's "toe-knife") and hammer, the roof of the skull and nnnular portion of all the vertebrse. The organ may then be studied in situ in its bony case, and surrounddl by its membranes; afterwards extract the whole cerebro-spinal axis inclosed in the dura mater, and open up the latter along the course of the cord, so as to completely expose that portion of the nervous system. (The saw and farrier's pincers, or spine ratchet, will be found useful auxiliaries in the tedious and delicate operation of exposing the brain and cord ; and particularly in lay- ing open the cranial cavity. An easy mode of obtaining access to the spinal canal and its contents, is to saw through the laminse of the vertebra; on each side, at the roots of the transverse processes, and raise the arches with the chisel or toe-knife.) EXTERNAL CONFORMATION OF THE SPINAL CORD. General view. — The spinal cord is that portion of the nervous centres which occupies the spinal canal. It is a thick, white, and irregularly cylindrical cord, commencing at the occipital foramen, where it continues the medulla oblongata, terminating in a point at the upper third of the sacral canal, or a TEE SPINAL CORD III 667 -B < 668 THE CENTRAL AXIS OF THE NERVOUS SYSTEM. little beyond that, and giving rise at each side, during its course, to the superior and inferior roots of the spinal nerves. Weight.— ^In medium- sized animals the weight of the cord is represented by the following approximate numbers : for the Horse, lOJ ounces : the Ass, .5|- ounces ; Cow, Tf ounces ; Sheep and Goat, If ounce ; Pig, 2i ounces ; Dog, 1^ ounces ; Cat, 4^ drams. Figure and volume. — The medullary cord is slightly depressed above and below, throughout its whole length ; in whatever part we examine a transverse section of it, we will always find the lateral diameter greater than the vertical, and that this section appears regularly elliptical. Its volume is far from being uniform. In following it from before to behind, we at first remark that it presents the same dimensions to the fifth cervical vertebra, and that between this point and the second dorsal vertebra it forms an oblong enlargement, designated the brachial (brachio-rachidian) bulb or enlargement. Beyond this, it assumes its primitive volume, and becomes gradually smaller even than in the cervical region. Towards the middle of the loins, it again augments to constitute the crural (lumbo-rachidian) bulb or enlargement, which extends to the entrance of the sacral canal. After this dilatation comes a conical prolongation, whose point represents the terminal extremity of the coud. If we compare the diameter of this medullary axis with that of the spinal canal, we will observe, as has been already said, that the capacity of the containing r^avity is generally related to the volume of its contents, and that the former is, as a rule, most capacious at the cervical and lumbar enlarge- ments. It will even be noticed that the dilatation the spinal canal offers at these two points, is relatively more considerable than the excess in volume of the cord. This is because the mobility of the spine, which is justly very great in these two regions, requires this diiference to secure the spinal axis from contusions during the movements executed by the vertebral column. This protective combination is also found elsewhere : at the atlas, for example, where we know the motion is considerable; and in the entire extent of the cervical region, which in this respect greatly exceeds the dorsal region. External surface of the cord. — Covered by the pia mater, this surface presents an extremely simple disposition. On its superior and inferior planes, at each side, we remark the double series of sensitive and motor roots of the spinal nerves, which are implanted in the same longitudinal line to right and left of the median plane, and are collected in fasciculi opposite the intervertebral foramina. In the middle line, and throughout the entire length of the organ, there are two deep and narrow fissures : one superior (fissura longitudinalis superior), the other inferior (fissura longitudinalis inferior), into which the pia mater enters. Four other fissures have been described at the point of emergence of the nerve roots, under the names of superior and inferior collateral fissures (or sulci); but the two superior alone exist, and even these are often scarcely noticeable. INTERNAL CONFORMATION AND STRUCTURE OF THE SPINAL CORD. In making a transverse section of any portion of the cord, we may convince ourselves that it has an internal cavity. This central canal is elliptical, and lined by cylindrical ciliated epithelium, resting on a thin connective membrane, the ependymis of Virchow. This section also shows THE SPINAL COED. C69 the two median fissures mentioned in describing the exterior of the cord, the inferior of which is wider and deeper than that of the superior, whose situation is scarcely perceptible. These two fissures advance one before the other, and do not meet so as to completely divide the cord into two lateral halves, but ^* remain separated by two thin horizontal and superposed bands of nervous matter, that pass from one end to the other of the me- dullary axis. The inferior, formed of white substance, corresponds to the bottom of the inferior fissure ; while the superior, composed of grey matter, meets the superior fissure. These bands are named the ichite and fjrey commissures of the spinal cord (Fig. 318). Notwithstanding the presence of these two commissures between the lateral halves of the spinal axis, these latter do not the less con- stitute two symmetrical systems, whose structure will now be studied. Each medullary cord repre- sents a semi-cylinder of white sub- stance, in the centre of which is a mass of grey matter, that varies somewhat in quantity in different regions, but the arrangement of which is everywhere the same. Thus, inwardly, this grey matter joins the grey commissure ; above, it sends off a thin jjrolongation which traverses the thickness of the medullary cord (sujierior grey cornu), to reach the bottom of the superior collateral fissure ; below, it gives rise to an analogous, thoiTgh a thicker and a more irregular, prolongation (inferior grey cornu), which is directed well in front of the inferior roots, but does not reach the surface of the cord. In consequence of this arrange- ment, the grey substance of the medulla forms altogether a kind of capital H, whose horizontal branch is •perforated in the middle by the centra] canal. This disposition of the grey substance causes the white matter to be divided, in each lateral moiety of the spinal axis, into three cords or secondary columns ; the superior of these is perfectly isolated, and is com- prised between the middle sujierior fissure and the origin of the sensitive roots ; another, the inferior, united to that of the opposite side by the white commissure, is limited, inwardly, by the inferior median fissure, and out- wardly by the line of origin of the motor nerve-roots ; while a third, the lateral or intermediate, thicker than the others, is confounded superficially with the inferior, and formed by all that portion of the medulla situated between the lines of origin of the superior and inferior roots. Of these three columns of the medullary axis, the first is sensitive ; the other two, which in reality are only one, are motor, Steucture. — Independently of the epithelium mentioned when describing SECTION OP THE SPINAL CORD OF THE HORSE AT THE LUMBAR REGION; MAGNIFIED TWO DIAMETERS. 1, Superior median fissui-e ; 2, Inferior median fissure ; 3, 3, Superior collateral fissures ; 4, 4, Inferior ditto ; 5, Grey commissure ; 6, White commissure ; 7, 7, Superior grey cor- nua ; 8, 8, Inferior grey cornua ; 9, Central canal. G70 THE CENTRAL AXIS OF THE NERVOUS SYSTEM. the ependymis, connective tissue, nerve tubes, nerve cells, and vessels enter into the structure of the medulla. The connective tissue of the sjiinal cord is very delicate, rich in nuclei, and belongs to the variety that histologists have named '' reticular " or " adenoid." It appears to arise from the pia mater, and forms lamellfB that i)enetrate the nerve-substance to meet and anastomose with each other, and finally become confounded with the ependymis around tbe central canal. This tissue, which is also named neuroglia, has been compared to a sponge, in whose sj)aces ai-e deposited the other elements of the cord. This neuroglia exists in the white and grey substances, but is more abundant in the superior than in the inferior grey cornua. It surrounds the upper extremity of the former in becoming softer and more trausjiarent, and is here designated the gelatinous substance qf Rolando (substantia gelatinosa). It constitutes, in great part, the grey commissure, and can be deeply stained by the corminate of ammonia. Fis. 319. TKANSVERSE SECTION OF SPINAL CORD OF MAN THROUGH THE MIDDLE OF THE LUMBAR REGION, SHOWING ON THE RIGHT SIDE THE COURSE OF THE NERVE- ROOTS, AND ON THE LEF.T THE POSITION OF THE PRINCIPAL TRACTS OF VESICULAR MATTER. A, A, Anterior 01- inferior columns; P, p, Posterior or superior columns ; L, L, Lateral columns. — a, Anterior or inferior median fissure ; p, Posterior or superior median fissure ; 6, h, 5, b. Anterior or inferior i-oots of spinal nerves ; c, c. Posterior or superior roots; d, £?, 'Tracts of vesicular matter in anterior column; e, Tracts of vesicular matter in posterior column ; /, Central canal ; g, Substantia gelatiuosa. The tubes and cells form, with the neuroglia, the whole of the grey substance. The cells have at least five prolongations, and the tubes are reduced either to the axis-cylinder (axis-fibre), or to this and a very thin layer of medullary substance. The cells are not uniformly distributed in the grey substance, but are arranged in small masses that constitute three longitudinal columns : two TEE SPINAL COED. 671 Fiff. 320. in the inferior, and one in tlie superior grey coruu. The columns cor- resjiond to wliat Stilling has named the nuclei of the nerves. A foui-th mass of cells, the superior vesicular column of Clarice, or dorsal nucleus of Stilling, is observed at the point where the grey com- missure joins the cornua. The nerve-tubes (or tubules) affect longitudinal, transversal, oblique, and vertical directions. They bring the cells of one lateral moiety of the medulla into communication with : 1, The tubes of the white substance ; 2, Each other ; 3, The cells of the opposite moiety, by passing into the commissures ; 4, The tubes of the white substance of the op- posite moiety, by foHowing the same course. The neuroglia and nerve-tubes consti- tute the white substance, which is decom- posed, as we know, into three cords. All the tubes of this substance do not ascend to the brain, as was believed for a long time ; the opinion that the tubes of the spinal nerves formed the medulla and extended to the brain, has been abandoned since Volk- mann measured, comparatively, the section of all these nerves and that of the nervous spinal-axis. (Volkmaun has established the fact, that the size of the medulla corresponds with the number of nerve-tubes given off at any point. He gives the weight of four segments, each 2y^ inches in length, from the spinal cord of the Horse, and the relative extent of the grey matter in square lines ; these are as follows Area Area Grains. of Grey- of White Ma Iter. Matter. rom below 2nd Spinal Nerve, 219 13 109 Sth „ „ 293 28 142 „ 19th „ „ 163 11 89 ,, >. 30tli „ „ 2«1 25 121) LONGlTtTDINAL SECTION THROUGH CERVICAL ENLARGEMENT OF SPINAL CORD OF CAT. In the white substance the tubes are lon- gitudinal, oblique, or transversal ; the latter arise from the cells of the grey substance, and represent the roots of the nerves ac, Interior white columns ; ac', Por- emerging either by the superior or inferior tion showing the arrangement of collateral fissure. the longitudinal fibres, PC,Pos. mi J 1 1. ,1 , ' 1 , tenor white columns: G, hvej The tubes of the anterior cords pass to substance between them (the vesicles being omitted to avoid obscuring the course of the fibres) ; A, Anterior roots of the nerves , P, Posterior roots, consisting of three kinds : the first, a, crossing the posterior columns horizontally, and then pass- ing obliquely downwards, across the grey substance, into the anterior columns ; the second, 6, traversing the posterior columns horizontally, and then losing themselves in the grey substance; the third, c, for the most part becoming continuous with the longitudinal fibres of the posterior column ; all, or nearly all, ultimately entering the grey substance. 672 THE CENTRAL AXIS OF THE NERVOUS SYSTEM. the cells of the grey substance, or reach the encephalon by remaining in the corresponding moiety of the medulla ; for instance, the fibres of the right half of the medulla gain the brain without passing into the left half. Those of the lateral cords decussate, each cord sending to, and receiving from, the other, tubes which cross in the white commissures. The posterior cords contain fibres that extend directly to the brain : these are sensorial ; there are also found transverse fibres that enter the cells of the superior grey cornua, and others that pass into the cells of the inferior or motor cornua. Such is, in a few words, the disposition of the nerve-elements in the medulla. The subject is a very long and complicated one, which cannot be dealt with in a more detailed manner in a work on descriptive anatomy. Vessels. — The medulla receives arteries from the ramifications of the pia mater. The grey is richer in vessels than the white substance ; the latter is penetrated everywhere by a large number of minute arteries ; while the first is traversed by the divisions of an artery that is thrown off by the median spinal, and ascends towards the bottom of the inferior fissure. The veins follow the arteries, and constitute two somewhat voluminous vessels that pass along the grey commissure, to the right and left of the central canal. DIFFERENTIAL CHARACTERS IN THE SPINAL CORD OF OTHER THAN S0L7PED ANIJIALS. In all the species, the white and grey substances affect the disposition above de- scribed; only some slight differences in the reciprocal volume of each have been remarked. As in the Horse, the spinal medulla does not extend beyond the sacral region; its length has no relation to that of the coccygeal region, as certain anatomists would, in principle, establish; in the rabbit, for example, the tail of which is very short, the spinal cord is prolonged into the coccygeal vertebrae. COMPARISON OP THE SPINAL CORD OP MAN WITH THAT OF ANIMAI,S. The spinal medulla of the adult Man does not reach beyond the first lumbar vertebra, though in the fcetus it is in the coccyx. It is rounder than in the Horse, and the grey substance is, relative to the white, more abundant than in the spmal cord of the domes- ticated animals. The posterior grey cornua are also larger and less elongated than the superior cornua in the Horse ; and the roots of the nerves are also more voluminous. CHAPTEE III. THE ENCEPHALON. Article I. — The Encephalon as a Whole. The encephalon is that portion of the nervous system which is lodged in the cranial cavity. It succeeds, without any line of demarcation, the spinal cord, of which it may be considered, with regard to its figure, as a kind of efflorescence. General form and constitution. — In shape it is an ovoid mass, elongated from before to behind, and very slightly depressed from above to below. When it is viewed on its superior face (Fig. 321), we first see, behind, a white pedicle, the prolongation of the spinal cord, and a single lobe of a grey colour designated the cerebellum. In front of this is remarked two other lobes, separated from the first by a deep transverse fissure, into which THE ENCEPHALON. 67S the tentorium of tlio cerebellum passes. Isolated from one another on the middle line by a shallower fissure, these two lobes constitute the hrain, and are usually named the cerebral hemispheres. In turning over the encephalon Pio-, 321. to examine its inferior face, we see that the posterior peduncle of the organ — a continuation of the spinal cord — is prolonged beneath the ce- rebellum, which is joined to the lateral parts of its superior face ; this portion then enters the cere- bral hemispheres by their inferior face, behind two thick white cords — the optic nerves, which mark the anterior limit of this prolongation (Fig. 322). This is the isthmus of the encephalon : a name given to it because it actually forms an inter- mediate bond between the three enlargements which form the prin- cipal mass of the encephalon. The cranial jjortion of the cen- tral nervous mass is, then, com- posed of three apparatus : the isthmus of the encephalon, a pro- longation of the spinal cord ; and the cerebellum and cerebrum, bulbous lobes grafted on the superior face and anterior extremity of this pe- duncle. These three divisions are very well seen in their entirety and reciprocal relations in Figure 329. We will study them sepa- rately and in succession. Volume of the encephalon. — Con- trary to what is found in the spinal cord, the dimensions of the en- cephalon closely represent those of the cavity containing them : the visceral layer of the arachnoid lying everywhere immediately on the proper envelope of the nervous mass, the pia mater, excejit at the subarachnoid spaces ; and, on the other hand, the arachnoid cavity can scarcely be said to exist while the dura mater is, as it were, glued to the cranial walls, and in reality constitutes their internal periosteum. The encephalon has, therefore, no room to move in its receptacle, but is maintained in it in an almost absolutely immovable condition, which coincides exactly with that of the sutures or cranial articulations. Weight. — The total weight of the encephalon, in average-sized animals, may be inferred from the following figures : Horse, 22 oz. 15 drams ; Ass, 12 oz. 11 drams ; Ox, 16 oz. 15 drams ; Sheep and Goat, 4 oz. 9^ drams; Pig, 5 oz. 10 drams ; Dog, 6 oz, 5^ drams ; Cat, 1 oz. 1 dram. In comparing these figures with those of the sjiinal cord, it will be seen that the relative weight of the medidlary axis to that of the encephalic mass GENERAL VIEW OF THE BRAIN ; TIPPER SURFACE. 1, Medulla oblongata; 2, Middle lobe of the cerebellum ; 3, 3, Lateral lobes of ditto ; 4, 4, Cerebral hemispheres ; 5, Inteiiobular fissure ; 6, 6, Ethmoidal lobules. 674 THE CENTBAL AXIS OF THE NERVOUS SYSTEM. differs notably in tbe several animals, being bigbest in tbe Dog. Tbe relations in eacb species, between tbe two divisions, are tbe following ; Dog, 1 : 5,14 ; Cat, 1 : 3,75 ; Sbeep and Goat, 1 : 2,60 ; Ass 1 : 2,40 ; Pig, 1 : 2,30 ; Horse 1 : 2.27 ; Ox, 1 : 2,18. We give tbese numbers, as it bas always been attempted to establish in tbe predominance of tbe eucepbalon tbe cause of tbe development of intelligence, and tbat tbe best measure of tbis predominance is really tbe relation of tbe spinal axis to tbe encepbalic mass. It bas also been attempted to measure tbis predominance of tbe encepbalon by comparing its weigbt with tbat of tbe entire body ; but it is sufficient to cast one's eye over tbe tables drawn up witb tbis view in several anatomical and pbysiological works, to be convinced tbat tbis basis does not possess all the value desirable. Preparation of the encephalon. — To study the encepbalon, it is necessary to extract it from its bony receptacle ; a result acliieved in two ways. The first consists in opening the roof of the cranium by hammer ami chisel, after removing from its exterior all the parts covering it, or which are iu its vicinity. The dura mater is then excised with scissors, and the encephalon, which is thus directly reached, is completely isolated by raising its posterior extremitj', and cutting from behind to before all the nerves passing through the foramina at the base of the cranium, with the pituitary stalk, as well as the extremity of the olfactory lobes. This method is very expeditious, but it sacrifices the pituitary gland, which remains firmly incrusted in the sella turcica : an inconvenience we obviate by resorting to the second procedure. In this, the cranium is opened by its base or floor, after separating the head from the trunk, cutting away the lower jaw, tongue, and os hyoides, and excising all the soft parts so as to expose the bony surfaces. The head, thus prepared, is held by an assistant, the roof of the cranium resting on a table or block. Armed with a chisel and hammer, the operator first removes the zygomatic arches and styloid processes of the occipital bone, then the condyles of this bone, the basilar processes, and the sphenoid, palate, and ethmoid bones, returning to the lateral portions of the cranium, which are chiselled away in succession from the occipital to the ethmoid bones. The encephalon being sufficiently exposed, is relieved from its dura mater as in the first metliod, and raised in the left hand to destroy, by means of scissors held in the right hand, the attachments which yet fix it to the cranial roof, and which are cliiefly the veins that open into the sinuses of the dura mater. In afterwards ex- cavating the ethmoidal fossaj with the point of a scalpel, the olfactory lobes are detached, and the nervous mass is free. This procedure is more difficult than the first, but possesses several advantages over it ; for not only do we preserve the pituitary gland, but have the ethmoidal lobes more intact, and may also have, if desired, the ganglia of the cranial nerves, with a more or less considerable portion of tiie nerves themselves. After indicating the methods for extracting the encephalon from its bony case, we ought to say some words as to the course to be pursued in order to study it successfully. To do this it is advantageous to have two brains ; one of these should be hardened by steeping it for some weeks in alcohol (or methylated spirit), or in water to which has been added a tenth part of nitric acid. This hardening contracts the nervous substance, and causes the cavities and reliefs to appear more manifest. (It is a good plan to place the brain, base uppermost, in a suitable vessel, and if a piece of cloth be spread beneath it, its removal therefrom will be greatly facilitated.) "We commence by examining rapidly the whole apparatus, and pass immediately to the study of the isthmus, of which it is necessary to have at first a well-defined idea. We therefore take a hardened specimen, and isolate this portion of tlie encephalon in the manner represented in figure 323 ; to do this, it suffices to cut through the peduncles of the cerebellum, and excise the cerebral hemispheres upwards and backwards ; the remains of these and the cerebellum should be preserved for an analysis of their structure. The isthmus thus isolated is fitted for an examination of its external confor- mation and its internal cavities : the ventricle of the optic layers and the aqueduct of Sylvius, into which we may penetrate by a superior longitudinal incision. After the isthmus, the cerebellum is to be studied : in its external conformation, on an Intact specimen ; and in its internal conformation and structure on the incised piece. We terminate with the cerebrum, whose superficies is soon examined, and whose interior should be studied in the following manner : — It is necessary to begin by demon- strating the existence of ventricles in the olfactory lobes, and their communication with all the other internal cavities of tlie brain, which can easily be done by the in- flation of one of these organs by means of a straw (or dissecting-case tube) which TEE ISTHMUS. 675 raises the pitnitarv gland, the cerebral lobes, and the cerebellum. Then we pass to the corpus callosimi, which is exposed, as in figure 330, by a horizontal section of the hemi- spheres across the centrum ovale. The corpus callosum of each side is afterwards excised on the median line to reach the interior of the lateral ventricles, and this great commissure of the brain ought, after studjing tlie septum lucidum, tube cut across iu the middle and turned over, as in tigure 331, so as to show the cerebral trigonal , fornix). The foramen of Monro is next examinetl, then the corpus striatum, hippocampi, trenia semi- circularis, choroid plexus, and velum interpositum. which are expi sed by the ablation of the hippocampi and ti-ii a'-^ " '^ i .- ?; p.=s "^ fa ^ 3 o o ■►J . Cm C C5 . rt p " — ' a 3 t. o 3 bPj c " =" 'S > •-=; S Kr « -^ -S 'S . "s > o .s a „vo" i ■" .2 '"' 3 -2 cf:=; a ci O R a" j:; .H ° -i X ' ., —X. ® ^ 'o £ I ^ g ^- J a rt 2 5, t. '-S 'c .2 "2 ^ o ■ *; a s^ ;i £> o a 5 .S £ a ^ _ c3 ci, ^ _ " ^ a "" f= r^ 5 §c-:---^« ^ laferaZ lohes (Fig. 321, 3, 3).— These are shaped like two irregular segments of a sphere. Their surface, fissured and lobulated in every direction, presents nothing interesting externally, superiorly, or posteriorly. It is by ' This septum is represented in the rudimentary state in Man, by the vaiulx Tarini. 688 TEE CENTRAL AXIS OF THE NERVOUS SYSTEBI. their inferior part that tlie peduncles enter the substance of the cerebellum ; and behind this point, beneath their lateral parts, the cerebellar plexus choroides is applied. The cerebellar choroid plexuses. — This name is given to two small reddish granular masses, formed of vascular loops, elongated from before to behind, depressed above and below, and comprised at their internal borders between the corpora restiformia and the inferior face of the lateral lobes of the cerebellum, to which they are strongly adherent by their superior face. These two plexuses are joined together by means of Eenault's valve, which is united to them towards its base. Sulci and lobules of the cerebellum. — On examining, in a general manner, all the sulci which intersect the external surface of the cerebellum, we see that they penetrate to very uneo[ual depths in the substance of the organ, and that they divide it into successively decreasing segments, of which Figs. 324 and 327 may furnish a sufiicient idea. There is at first a certain number of princij^al lobules, which are divided into secondary lobules ; and these, again, are in their turn separated into short lamellae, representing the extreme limits of cerebellar lobulation. 2. Internal Conformation and Structure of the Cerebellum. The cerebellum concurs, by its inferior plane and the internal face of its peduncles, to form the cavity already described as the posterior or cere- bellar ventricle ; but in the mass of the organ itself there is no trace of excavation or other peculiarity. This is demonstrated in the most evident manner by sections of its substance made either in an antero-posterior or in a transverse direction. We only see in these traces of the sulci which divide the organ into lobules ; and they also afford evidence as to the structure of the cerebellum, showing that, like all the other parts of the cerebro-spinal axis, it is formed of white and grey substance. The latter, spread over the entire surface of the organ, constitutes the cortical layer of the different segments of which it is composed. It is even jirolonged into the convolutions which increase the surface-extent of the cerebellum ; in each lobule it may be decomj)osed into superposed layers, parallel to the lamina of white substance that forms the nucleus of the lobule ; between these layers of grey substance is a very thin mass of white matter. The lohite substance, enveloped on every side by the grey, forms two thick nuclei occupying the centre of the lateral lobes, and which are united and confounded on the median line in the texture of the middle lobe. These two nuclei, in continuity on each side with the cerebellar peduncles, are only their prolongations or inter cerebellar portions. They send into the middle of each principal lobule a long and thick branch, which gives off smaller divisions that ramify in the secondary lobules, and from which escape a new series of ramuscules that enter the smallest segments ; this gives to the cerebellum a beautiful arboreal aspect, justly designated by the older anatomists the arbor vitce. (See Figs. 324, 327, 329, for representations of the arbor vitce cerebelli.) In the interior of these nuclei, a little in front, there sometimes exists a small, slightly-grey spot ; this is the trace of the corpus rhomboideum (or dentatum of Man). The nuclei of the white substance of the cerebellum are constituted, like the matter of the medulla, by nerve-tubes which are continuous on one side TEE CEBEBBUM. 689 with the crura cerebelli, and on the other terminate in the cells of the grey- substance. In the grey spot that forms the corpus rhomboideum, is a great number of large nerve-cells. With regard to structure, the grey matter of the cere- pjo- 303 bellimi may be decomposed into two layers ; the super- ficial is very rich in blood-vessels, has a greyish tint, and is composed of large nerve-cells and smaller rounded ele- ments ; the deep layer is of a yellow colour, and also contains nerve-cells and round elements, though the latter are smaller than in the other layer, and have been sometimes mistaken for simple nuclei. DTFFEEEXTIAL CHARACTERS OF THE CEREBELLTJ3I IN OTHER THAN SOLIPED AXIJIALS. The external and internal conformation of the cerebellum offers the closest analogies in the domesticated niammifers. In all, its volume, compared witli that of the otiier encepiialic lobes, is not invariable. Thus, while the relation between tlie weight of the cere- bellum and that of the brain of the Horse is as 1 to 7 ; with the Ox it is as 1 to 9; with the Dog 1 to 8; with the Cat 1 to 6; and witii the Sheep 1 to 3. These are the only ditierences to be noted COMPAKISOX OF THE CEREBELLUM OF MAN WITH THAT OF ANIBIALS. In Man, the encephalic mass being enormous, the cerebellimi is absolutely more considerable in volume than in the larger domesti- cated animals ; though, in proportion to the cerebral hemispheres, it is smaller than in the Ox, its relation to the latter lobes being as 1 to. 8. It is wider than it is long, and projects much beyond the medulla oblongata. It has three lobes; but these are only visible on its lower aspect ; on the opposite face, the median lobe is depressed and concealed beneatii the lateral lobes, which are so large tliat they have been named the cerebellar hemispheres. The inferior vermis forms a free projection in which is the fourth ventricle; this is termed the uvula of the cerebellum. The uvula is connected at each side with the valves of Turin: laminae of nerve-substance lodged for the most part in tlie fourth ventricle, and hidden by the lower face of the cerebellar hemispheres. The latter constitute, on the sides of the medulla oblongata, two prominences situated one below tlie other, above the crura cerebelli; the fii'st is designated the amygdala or tcijisil, the second the pneumogastric lobule (or flocculus). aii THE SUB- Akticle IV. — The Cerebrum. SECTION OF CORTICAL STANCE OF THE CEREBELLOI. a, Medullary sub- stance, showing its fibres ; 6, Sub- stantia ferrugi- nea, composed of fibres and cell- nuclei ; c, Grey surface, granu- lar at the sur- face, and contain- ing large mul- tipolar branch- ing cells near the substantia ferrucrinea. The cerebrum, the principal portion of the encephalon, comprises the two anterior lobes or hemispheres of that apparatus : enlargements which are elongated in the direc- tion of the great diameter of the head and cranial cavity, lie beside each other on the middle line, and are united at their central part by a transverse commissure, and by the encephalic isthmus, whose anterior extremity penetrates, inferiorly, into their substance. (See Fig. 329 for a good idea of this penetra- tion.) These two lobes together represent an ovoid mass, having its thick extremity adjacent to the cerebellum ; it is depressed from above to below, deeply divided above, in front, and behind by a median antero-posterior 690 THE CENTRAL AXIS OF THE NERVOUS SYSTEM. fissure, and receiving in the middle of its inferior face the insertion of the cerebral peduncles. This mass, seven to nine times more voluminous than the cerebellum, fills the anterior compartment of the cranial cavity, and thus occu2)ies the greater portion of that space. It exliibits for study its external conformation, its internal conformation, and its structure. Fio-. 329. ANTERO-POSTERIOR AND VERTICAL SECTION OF THE ENCEPHALON TO ONE SIDE OF THE MEDIAN LINE. 1, 1, Isthmus of the encephalon ; 2, Medulla oblongata; 3, Pons Varolii; 4, Cerebral peduncle ; 5, 6, Corpora bigemiua ; 7, Optic thalamus ; 8, Pituitary gland ; 9, Pituitary stem ; 10, Optic nerve ; 11, Cerebellum ; 12, 12, Cerebral hemisphere ; 13, Ventricle of the hemisphere ; 14, Corpus striatum • 15, Cornu Ammonis ; 16, Olfiictory lobe; 17, Ventricle of the olfactory lobe. EXTERNAL CONFORMATION OF THE CEREBETJM. Instead of examining the organ in mass, with regard to its external con- formation, we will first consider the great interlobular (or longitudinal) fissure which divides it lengthways ; and afterwards study its two lateral halves, or cerebral hemispheres, which in reality constitute two symmetrical organs. 1. The Longitudinal Fissure. This fissure exists throughout the vertical and antero-posterior circum- ference of the cerebrum, but does not everywhere ofier the same disposition. On the superior aspect of the organ it is very deep, and when the two hemispheres are sejiarated to discover its extent, we see that it reaches to the upper face of the great commissure — the corpus callosum. Behind, it curves between the posterior lobes of the hemispheres, but without corres- ponding directly with the posterior thick rounded margin of the corpus callosum, above which there is a feeble adhesion established between the two halves of the cerebrum, forming a kind of bridge. But in front it passes to the anterior margin of this commissure, and is prolonged in the interval of the anterior lobes of the hemispheres to reach the inferior face of the organ. Examined inferiorly, the interlobular fissure is well defined in front, TRE CEREBRUM. G91 where it attains the anterior border of the corpus callosxim ; but behind, on leaving the chiasma of the optic nerves, and which marks the anterior limit of the isthmus, this fissure appears suddenly to stop. This is because it becomes considerably enlarged, and is changed into a vast notch which admits the anterior extremity of the isthmus : or rather, it bifurcates to pass on each side between the hemisphere and the anterior extremity of the medullary prolongation, at first crossing the optic nerve, then turning round the cerebral peduncles and corpora bigemina, above which its branches unite, and are confounded with the undivided part of the fissui'e, which separates the posterior lobes of the hemispheres. There exists, then, around the point of immergence of the isthmus in the cerebrum a well-marked line of demarcation, which constitutes, above and laterally, a very deep fissure in which is imbedded the vascular expansion known as the velum interpositum ; this aperture is designated the fissure of Bichdt, or