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ELEMENTS fh 
 
 ^fl^ub 0F O^+^W^W 
 
 PHYSIOLOGY. 
 
 IN TWO VOLUMES. 
 
 ^7 
 
 
 pO / 
 
Elements of Phy/wlogy; A M 
 
 JO. FRED. BLUMENBACH, m.d. 
 
 PROFESSOR OF MEDICINE IN ORDINARY AT GOc'TTINGEN, 
 MEMBER OF THE ROYAL SOCIETY OF SCIENCES AT 
 GOETTINGEN, AND OF SEVERAL OTHER SOCIETIES IN 
 DIFFERENT PARTS OF EUROPE. 
 
 Tr -an/lated from the Original Latin, 
 
 AND 
 
 INTERSPERSED WITH OCCASIONAL NOTES. 
 By CHARLES CALDWELL. 
 
 TO WHICH IS SUBJOINED, BY THE TRANSLATOR, 
 
 An APPENDIX, 
 
 EXHIBITING A BRIEF AND COMPENDIOUS VIEW 
 OF THE EXISTING DISCOVERIES 
 
 Relative to the Subject of 
 
 ANIMAL ELECTRICITY 
 
 VOLUME I. 
 
 PHILADELPHIA, 
 
 PRINTED BT THOMAS I) OB SON, 
 
 AT THE STONE-HOUSE, N°4I, SOUTH SF.COND-STRt ET. 
 
 M.DCC.XCY. 
 
 & 
 
T O 
 
 THE PROFESSORS 
 
 VARIOUS BRANCHES OF MEDICAL SCIENCE 
 IN THE UNIVERSITY OF PENNSYLVANIA. 
 
 GENTLEMEN, 
 
 JLiONG have you been my 
 fathers and long my attentive pre- 
 ceptors ', in the interefting fcience 
 of medicine. You juftly hold on 
 me, therefore, a twofold claim for 
 the twofold duty of a pupil and a 
 fon. In refpeclful acknowledge- 
 ment of this undeniable claim, I 
 now ftep forward and thus publicly 
 folicit your acceptance of the f?f 
 fruits of that medical education, 
 which you yourfelves were pleafed 
 
 to 
 
 275305 
 
vi. DEDICATIO N. 
 
 to patronize and direct with fuch 
 ability and care. 
 
 Avowedly to folicit an cxtenfion 
 of your immediate patronage and 
 protection to the following tranf- 
 lation, would be to offer you an 
 indignity little lhort of aclual in- 
 fult. Such a folicitation would 
 falfely reprefent you as men un^ 
 willing to become the fpontaneous 
 guardians and friends of filent, 
 un affirming truth and merit, but 
 {landing with open arms for the 
 reception even of intrufive error 
 itfelf, when ufhered to your notice 
 by a brazen front and a blanditious 
 tonbue. 
 
 The original work of Profeffor 
 Blumenbach has been already fane- 
 
 tioned 
 
DEDICATION. vii. 
 
 tioned by the applauding voice of 
 the learned and the ingenious in 
 aim oft every part of the globe to 
 which phyfical fcience has hitherto 
 found its way. On the folitary 
 bafis of its own intrinfic merit let 
 my tr (inflation alfo Hand ; or if, 
 indeed, it be deftitute of fuch bafis, 
 with difgracc let it fink into that 
 fea of oblivion which fo juftly 
 awaits its final reception. 
 
 From you, Gentlemen, it is fe- 
 cure of at leaft, a patient, and, I 
 flatter myfelf, an impartial exami- 
 nation. Should the execution of 
 the work fortunately meet with 
 your approbation and applaufe, 
 you will be its aufpicious announ- 
 cers to the medical public : but 
 mould it appear to you faulty and 
 
 even 
 
 275305 
 
viii. DEDICATION. 
 
 even wholly unworthy of further 
 attention or regard, you will not, 
 I am fure, lofe fight of that fa- 
 vourite maxim of the humane and 
 generous bofom, " primum pecca- 
 tum veniandum e/l" 
 
 Impreffed with the moil pro- 
 found fentiments of efteem and 
 gratitude for your favours of a 
 public nature, as well as for your 
 attentive acls of private friendihip, 
 I have the honour to be, 
 
 Your fmcere Friend, 
 And Pupil, 
 Tile TRANSLATOR, 
 
 PlULArELPHIA, 7 
 
 hebruary 1 1, 179;. 5 
 
Preface by the Tranjlator. 
 
 Wh AT a fafhionable letter of in- 
 troduction is to its bearer, a fafhionable pre- 
 face is to the literary performance which it 
 openly announces to the world, The former 
 procures, for the moil part, admiffion, and, 
 at leaft, a dinner ; the latter moil commonly 
 an attentive perufal. For their future conti- 
 nuance, however, in favour and eileem, both 
 the vifitant and the volume muft depend on 
 fomething more fubflantial, and of more un- 
 equivocal utility, than either the light eti- 
 quette of a letter, or the fpecious propofak 
 of a recommendatory preface. 
 
 The 
 
x PREFACE. 
 
 The reader is requefted to view the pre- 
 fent prefatory add refs as a mere peace-offering, 
 made by the tranflator to ancient and invete- 
 rate cuftom, and not as afolemn appeal to the 
 public defigned to enhance either the merit of 
 the following performance, or the uprightnefs 
 of the motives which led to its execution. For 
 with regard to the merit of the work, I flatter 
 myfelf that no character of literature and ta- 
 lents will ever refign his right of judging for 
 himfelf ; and as to the motives by which I 
 was induced to engage in its translation, they 
 are indeed at prefent nothing better than ab- 
 iblute non-entities, and will in no way elfecl: 
 its utility to man. 
 
 The want of a new and complete fyftem 
 of phyfiology has been long and very fenfi- 
 bly experienced and regretted by ail medical 
 fludents on this fide the Atlantic. As to 
 myfelf, I am fure I was led moil devoutly to 
 
 regret 
 
PREFACE. » 
 
 regret ftich a want, throughout every ftage 
 o f medical ftudies. in orJe to acquire 
 a knowledge .of the improvements which had 
 lat taken pla< e in this important branch 
 of phyfical fcience, I was obliged to range 
 with an infinitude of labour and attention, 
 through daily accumulating volumes, which 
 it was fometimes extremely difficult to pro- 
 cure. This difficulty was augmented even 
 to impoffibility itfelf with thofe unfor- 
 tunately living out of the fphere of public 
 libraries, 
 
 The mutilated abridgment of Haller's 
 phyliology, publifhed in the Fngufh lan- 
 guage, is (to ufe a common mode of expref- 
 iion) certainly nothing more than a bare apo- 
 logy for a fyftem. It is imperfect, erro- 
 neous, and, in many places, to me wholly 
 Unintelligible. In fome parts, therefore, it 
 wo doubt inculcates truth, in others implants 
 
 the 
 
*ii PREFACE. 
 
 the feeds of error, and in other places again 
 leaves the young mind at liberty to indulge 
 itfelf in all the wildnefs and revelry of con- 
 jecture. 
 
 For thefe deficiencies and faults, I am Hire 
 that at leafr. fome compenfation is made, and 
 fome degree of remedy provided in the fol- 
 lowing fheets, which I am about to ufher 
 forth to the world. But on this fu bjecT let 
 decifion be awarded, and judgment pro- 
 nounced, by the candid and intelligent rea- 
 der, and not by 
 
 His obedient humble Servant, 
 
 The TRANSLATOR. 
 
CONTENTS, 
 
 VOLUME r. 
 
 SECTION. I. Of the living Human Bodv in general i 
 
 Sect. II. Of the Fluids of the Human Body in 
 
 general, and of the Blood in particular - 3 
 
 Sect. III. Of the Solids of the Human Body in 
 general, but particularly of the Cellular Mem- 
 brane . . . . .18 
 
 Sect. IV. Of the Vital Energies in general, but par- 
 ticularly of Contractility . . 31 
 
 Sect. V. Of Sound Health, and of the Nature of 
 
 Man .... 39 
 
 Sect. VI. Of the Motion of the Blood in general 48 
 
 Sect. VII. Of the Arteries . . -54 
 
 Sect. VIII. Of the Veins which carry Blood. 62 
 
 Sect. IX. Of the Heart ... 66 
 
 Sect. X. Of the Powers by which the Blood is 
 
 kept in Motion . . . 83 
 
 Sect. XI. Of Refpiration and its Primary Ufe 97 
 
 Sect. 
 
xiv CONTENTS. 
 
 Sect. XII. Of Voice and Speech . i ro 
 
 Sect. XIII. Of Animal Heat. . . M q 
 
 Sect. XIV. Of Cutaneous Perfpiration. . 126 
 
 Sect. XV. Of the Senforium and Nerves . 142 
 
 Sect. XVI. Of the Functions of the Nervous Syftem 
 
 in general . . . . ^ 
 
 Sect. XVII. Of the External Senfes in general, but 
 
 particularly of the Touch . . . z 6 2 
 
 Sect. XVIII. OftheTafte . . 166 
 
 £ect. XIX. Of Smelling . . .169 
 
 Sect XX. Of Hearing ... 173 
 
 Sect. XXI. Of Vifion . . . .178 
 
 Sect. XXII. Of the Internal Senfes and other Facul- 
 ties of the Mind . .195 
 
 Ssct. XXIII. Of thofe Adions of the Body which 
 
 are fubject to the power of the Will . 201 
 
 S«ct. XXIV. Of Mufcular Mot'oa. . 207 
 
 Sect. XXV. Of Sleep. . . 22 j 
 
 VOLUME 
 
 - 
 
CONTENTS. .v. 
 
 VOLUME IX, 
 
 Sect. XXVI. Of Food, and the Appetite for it i 
 
 Sect. XXVII. Of Maftication and Deglutition 8 
 
 Sect. XXVIII. Of Digestion . . 16 
 
 Sect. XXX. Of the Bile . . .28 
 
 Sect. XXXI. Of the Function of the Spleen . 45 
 
 Sect. XXXII. Of the Function of the Omentum 50 
 
 Sect. XXXIII. Of the Function of the Inteftines 55 
 Sect. XXXIV. Of the Functions of the Abforbent 
 
 Syftem. . . . „ .65 
 
 Sect. XXXV. Of Sanguification . . 78 
 
 Sect. XXXVI. Of Nutrition . . S3 
 
 Sect. XXXVII. Of Secretion . . 9 o 
 
 Sect. XXXVIII. Of the Urine . • 10* 
 Sect. XXXIX. Of the Difcrimination of the Sexes 
 
 in general . . . . n 
 
 Sect. XL. Of the Genital Function of the Male Sex. 1 14 
 Sect. XLI. Of the Genital Function of the Female 
 
 Sex in general . . . .122 
 
 Sect. XLII. Of Mcnftruation . . 141 
 
 Sect. XLII1. Of the Milk . . .146 
 
 S^ct. XLIV. Of Conception and Pregnancy . 154 
 
 ? Sect. 
 
xvi CONTENTS. 
 
 Sect. XLV. Of the Nifus Formativus, or Formative 
 
 Effort. . . . . 174 
 
 Sect. XLVI. Of Parturition, and its Confcquences 184 
 
 Sect. XLVII. Of the Differences by which the 
 
 Human Subject is charaflcrifed before and after 
 Birth . . . . 191 
 
 Sect. XLVIII. Of the Increafe, Maturity, and 
 
 Decline of Man * . . 200 
 
 APPENDIX 213 
 
 ELEMENTS. 
 
ELEMENTS 
 
 OF 
 
 PHTSIOL GT. 
 
 SECTION I. 
 
 OF THE LIVING HUMAN BODY IN GENERAL. 
 
 I 
 
 § >• 
 
 N the living human body, the healthy 
 fun&ions of which conftitute the exclufive object 
 of the fcience of Phyfiology, there occur three 
 things worthy of our immediate attention and 
 regard* j namely, 
 
 The Solids, or parts containing ; 
 
 * In an ancient volume commonly ranked among the wri- 
 tings of Hippocrates, Epidemic. VI. Sect. 8. § 19, we find the 
 following remarkable claufe : " Quae continent corpora, aut 
 * intus continentur, aut in nobis cum impetu moventur 
 " contemplanda funt." This celebrated claufe furnifhed 
 Abr. Kaau Bocrhaave with the firft hints and fuggeftions 
 Vol. I. A on 
 
2 OF THE LIVING HUMAN BODY. 
 
 The Fluids, or parts contained within the folids j 
 
 And laftly, the Vital Energies, which in the 
 confideration of the fe'ence of phyfiology, confti- 
 tute the moft interefting and important object of 
 our regard. It is in confequence of thefe energies 
 that the fo'ids are rendered alive to the impulfe of 
 the fluids, endued with a power to propel the fame, 
 and alfo to perform a variety cf other motions. 
 It mud however be obferved, that thefe energies 
 are not incommunicably excluded even from fome 
 of the fluids themfelves : on the whole, they ap- 
 pear to constitute the effence or fupreme charac- 
 terise of an organifed body. 
 
 § 2. 
 But although thefe three objecls have been with 
 propriety conlidered as diftinct from each other, 
 and may therefore be feparately enumerated on 
 the prefent occafion, they are notwithstanding in 
 the living body, which is alone the exclufive fub- 
 jecl: of phyfiology, fo intimately connected toge- 
 ther, that it is fcarcely poflible to form even a 
 conception of one without at the fame time em- 
 bracing the others. 
 
 on tht {abject of his incftimable work entitled, " Impetum 
 " faciens dictum Kippocrati per corpus con&ntiens." L. B. 
 
 1745-8. 
 
 The 
 
OF THE FLUIDS, 3 
 
 The mofl pure and limpid fluids of our body 
 abound with animal earth : on the other hand, 
 though our folids may appear to us completely 
 deftitute of liquid matter, yet, befides the circum- 
 flance of their originating from the fluids as their 
 matrix or primary fource, they contain in their 
 compofition an evident quantity of moifture : 
 laftly, if we be not deceived, it is certainly true 
 that there exifls fcarcely a fibril in the living 
 body which does not poflefs, in a higher or lower 
 degree, a vital energy inherent in itfelf. 
 
 §3- 
 
 We now proceed to treat of each of thofe three 
 obje&s feparately and in order : and firft of the 
 fluids ; as conflituting by far the greatefk^ and 
 what may be emphatically called the firji-born 
 part of our bodies. 
 
 SECT. II. 
 
 OF THE FLUIDS OF THE HUMAN BODY IN GENERAL, 
 AND OF THE BLOOD IN PARTICULAR. , 
 
 §4- 
 
 XA.LL the different fluids of our body, 
 may with propriety be thrown into three leading 
 clafles. 
 
 A 2 Thcfe j 
 
4 OF THE BLOOD. 
 
 Thefe are, I. The Crude or unaflimilifed fluid, 
 confifting chiefly of the chyle contained in the 
 prima? vise, and deftined for converfion into blood; 
 to which may alfo be added, that fluid received 
 by abforption from the external fuperficies of the 
 body, and conveyed to the fame receptacle with 
 the former. 
 
 II. The blood itfelf; 
 
 And Laftly, the fecrefed fluid, or that formed 
 from the volume of blood by the animal procefs, 
 called fecretion : the fluids prepared by this pro- 
 crfs are deftined, fome of them, to be retained in 
 our body, to ferve further purpofes in the animal 
 economy ; and others, to be eliminated from our 
 f)ftem, as wholly excrementitious. 
 
 § 5- 
 
 Of the firfl: and third of thofe clafles we will 
 fpeak on a future occafion, when we come to trtat 
 of chylification, and of fecretion, together with the 
 oi!:er functions to which thofe fluids are rtfpec- 
 tively related. Let us now proceed to the confe- 
 deration of the blood, that mo ft important, that 
 prim?ry, and truly vital liquid, which may with the 
 great eft propriety be called, the living fountain 
 of all the other fluids ; as being that into which 
 the crude fluid is converted j and from which all 
 
 the 
 
OF THE BLOOB. 5 
 
 the fcrreted fluids derive their origin ; and which 
 (a few parts of the body excepted, fuch as the 
 epidermis, the tunica araebnoidea, the amnion, 
 the vitreous fubftance, or enamel, of the teeih, 
 .&•'.) fl>ws uniformly through every even the 
 iTiOff minute and fine fpun parts of the inexplicable 
 texture of our.fyftem. 
 
 § 6. 
 
 The blood is a liquid ful generis, of a well 
 known colour, more or lefs intenfe : it is glutin- 
 ous and warm to the touch : the formation of this 
 liquid has hitherto been ranked among the arcana 
 of nature, as it has never been fuccefsfully imi- 
 tated by any procefs of art. 
 
 §7- 
 
 This vital liquid when recently drawn from a 
 living fubjecl:, and received into a veffel, exhibits 
 in a very obvious manner the following remark- 
 able phenomena : 
 
 In the firft place, while it is yet warm, a fubtle 
 halitus afcends from it, which being colle&ed in a 
 receiver, forms fmail pellucid globules, fimilar in 
 appearance to drops of dew ; it is of an aqueous 
 nature, refembling not a little common fountain 
 water, except that it emits a peculiar nidorous 
 fmell, (ilill more confiderable in the blood of car- 
 A 3 niyorous 
 
6 OF THE BLOOD. 
 
 nivorous animals) and which may be aptly called 
 the animal odour ; fuch, for example, as arifcs 
 from frefh urine, or from the thoracic and abdo- 
 minal cavities of a dead fubject recently opened. 
 Cf this aqueous liquor a confiderable quantity re- 
 mains in a Mate of mixture with the other confli- 
 tuent parts of the blood, which (hall be hereafter 
 mentioned. 
 
 § 8. 
 
 In the mean while, as the blood contained in 
 the veflel fuffers a gradual redu&ion of tempera- 
 ture, it begins to feparate into two parts. A 
 coa?uhi n is firft formed, from the fapcrficies and 
 fides of which, there prefrntly exfudes a liquor 
 of an intermediate (hade between pale yellow, 
 and cvanefcent red, which they call the ferum of 
 the blood ; in proportion as this liquor accumu- 
 lates by exfudation, a correfponding diminution is 
 obfervable in the volume of the coagulum itlelf ; 
 the coa ulum thus reduced in fize has been dif- 
 tinguifhed by the name of crajfamentum, as alfo 
 by thofe of the liver, and placenta cf the blood, 
 from a refemblance, in point of colour and fran- 
 gibility of texture, fuppofed to exift between it 
 and thefc two bo lies ; it has been likewife called 
 the ijlind, from the circumflance of its being held 
 in a natant or floating date in the furrounding 
 fen: m. 
 
 § 9* 
 
OF THE ELOOB. 7 
 
 § 9- 
 This craffamentum itfelf, by a delicate treatment, 
 fuch as gentle agitation or frequent ablutions in 
 water, may be again feparated into two constituent 
 parts, viz. the cruor, which imparts the red co- 
 lour to the whole mafs of blood, and which by 
 ablution is carried off from the lymph, the other 
 and more fubftantial part, and which, therefore, 
 is called the bafis of the craffamentu n ; that the 
 cruor retains for this bafis a much ftron^er af- 
 finity than the ferum pofTelTes, is fufficientiy ob- 
 vious from this circurnftance, that the cruor and 
 bafis cannot be difparted unlefs by the interpo- 
 fition of a certain degree of force. Tlie lymph 
 itfelf beino: robbed of the cruor, becomes more and 
 more pale until it finally affumes the appearance of 
 a white and coniiderably tenaceous coagulum, 
 
 § 10. 
 Such then appears to be the four principal con- 
 ftituent parts of the blood, — viz. the watery 
 baUtus ; the ferum; the cruor, or red globules j 
 and the coagulable lymph; which fcveral parts, 
 as long as they retain their native degree of vital 
 temperature, continue in a (late of the moil 
 equable mixture, conftituting an uniform and 
 homogeneous fluid. 
 
 A 4 It 
 
8 OF THE BLOOD. 
 
 It will now be proper to enter into a more mi- 
 nute confideration of thofe three portions of the 
 blood which (land lad in the above enumeration : 
 As to the aqueous exhalation which we have men- 
 tioned, it does, not appear of fufficient importance 
 to claim any further attention ; indeed as it is alfo 
 difcovered in other parts of the body, it cannot 
 be confidered as proper to the blood alone, any 
 more than the air which this vital fluid contains, 
 and on which we will date a few obfervations in 
 a fubfequent part of this fe&ion. 
 
 § «- 
 
 The ferum is a liquid of fuch a gelatinous nature 
 as to impart to the whole mafs of the blood the 
 chief part of its vifcofity or gluey confidence : it 
 very much refembles, in all its properties, the al- 
 bumen or white of eggs ; when fubje&ed to the 
 aftion of a temperature equal to the 150th degree 
 on the fcale of Fahrenheit's thermometer, it paf- 
 fes into a coagulum, white and eafily broken 
 down, analogous to the white of eggs in a boiled 
 flate; it alfo differs a fimilar change, according 
 to the experiments of the celebrated Mofcati, if 
 it be mixed with a quantity of quick lime, though 
 in this cafe the coagulation proceeds much raore 
 flowly, and is not completed till after the twen- 
 tieth hour. But if the fcrum be dried with a 
 gentle heat, and left wholly undifturbed, it is 
 
 converted 
 
OF THE BLOOD. ' 9 
 
 converted into a firm pellucid mafs, fimilar in irs 
 external appearance to gum arabic, which in a 
 gradual manner, like the dried white of eggs, 
 cracks and forms over its furface numerous Juki 
 or fuTures running in a fomewhat fpiral direclrion, 
 and exhibiting a very lingular appearance. 
 
 § 12. 
 
 Befides thofe other properties of the ferum 
 already mentioned, there is one highly worthy 
 our confideration, to which my attention was firft 
 called by the experiments of the illuftrious 
 Prueilley * ; but my belief of which has fince 
 been fully confirmed by repeated obfervations of 
 my own, viz. the facility with which the air, fur- 
 rounding a veflcl filled with blood, is able to act 
 through the medium of the ferum or the craifa- 
 mentum, though deeply covered by the former, in 
 fuch a manner as to produce a very remarkable 
 change in the colour of the latter, whereas, on 
 the other hand, the fame a&ion of the air would 
 be very much impeded, if not entirely prevented, 
 if inflead of the ferum, the craflamentum were 
 covered with any foreign liquid, fuch as water, 
 or oil, &c. or even with any other fluid of the 
 human body kfelf, as the faliva or urine. 
 
 * Philof. Tranfatf. vol. LXVI. P. I. pag. 244, feq. 
 
 § 13- 
 
i* OF THE BLOOD. 
 
 § *3- 
 
 The cruor confcitutcs another very finking and 
 important part of the blood, and is a fource of 
 many Angularities, whether we confider the 
 colour and figure of its particles, or the elemen- 
 tary parts into which it is refolved when fubjected 
 to the acTion of an intenfe heat. It appears to 
 deferve a place among the mod elaborare juices 
 of the body, as it feldom appears in the tender 
 fcetus previoufly to the fourth week after concep- 
 tion, nor in the nafcent young of gallinaceous 
 fowls till the fortieth hour of incubation. After 
 profufe hemorrhages it like wife appears to be re- 
 placed by the powers of the fyftem, with much 
 more difficulty than the other condiment portions 
 of the blood. 
 
 § 14- 
 
 It confifts of globules, find obferved by Leen- 
 wenhbek. In blood recently drawn they are al- 
 ways prefent, of a conftant, uniform figure, and 
 of an equable magnitude ; which circumdances, 
 added to the further confideration, that in no 
 other fluid (milk alone excepted, the particles of 
 which are fo me what analogous), are fimilar 
 bodies to be met with, leave not a fliadow of 
 doubt, but that thofe globules form a part very 
 obvioufly and eilentially different from the other 
 condiment portions cf the blood, though at the 
 
 fame 
 
OF THE BLOOD. 1 1 
 
 fame time the formation of thofe globular bodies 
 thenfelves appears in reality to be much more 
 fimple than iome celebrated characters would in- 
 duce us to believe. For to pafs over in filence 
 the complexity of the fixfold form iiclitiouflv be- 
 llowed on them by Leeuwenhoek, neither the an- 
 nular figure attributed to them by the illuftrious 
 de la Torre, nor the form of veficles enclofing an 
 opaque nucleous, fuch as Hewfon apprehended he 
 difcovered in them, have appeared to me to be 
 well founded*. In my obfervations, indeed, I 
 have been able to detedl: nothing more than bodies 
 of a fimple fpherical appearance, and, if I am not 
 deceived, of a folid gelatinous confidence. I have 
 not, indeed, abfolutely denied the lenticular figure 
 bellowed on them by fome observers : I dare not, 
 however, venture to affert, that I have been fo 
 fortunate as to obferve it. 
 
 It has been a fubjeft of controverfy whether or 
 not they can alter their figure when it becomes 
 neceifary for them to pafs through a veflel of a 
 very narrow diameter. I am inclined to believe, 
 in conformity to the opinion of that accurate 
 obferver Reichel that under the above circum- 
 flances, they do actually change their fpherical 
 for an oval figure, and again refume their former 
 
 » Philof. Tranf. Vol. LXIII. P. II. p. 303. faj. tab. XII. 
 
 globular 
 
iz OF THE BLOOD. 
 
 globular fhape, when they advance into vcfTels 
 fufficien ly capaciou-s ; though I mud confvfs, I 
 never had the happinfs to be a fpc&ator of this 
 interefting phenomenon. 
 
 This fpherical figure of the globulus is never 
 perceived unlefs in the blood circulating in the 
 veffels of a living animal, or in that -which is re- 
 cently drawn ; they lofe all regularity of form in 
 procefs of time, and appear to dhTolve, as it were, 
 and again unite with each other into one uniform 
 ihapelefs mafs. 
 
 § '5- 
 
 Phyfiologifts differ in determining the fize of 
 the globules of the blood. Hales reckons them 
 equal in diameter to the -r*Wh part of an inch. 
 Senac eftimates their diameter at about the TT««th 
 part of the f ime meafure, while others again en- 
 tertain different opinions. 
 
 § .6. 
 
 Their colour is red, and therefore the beautiful 
 cri.Vifon caffc of the whole mafs of blood appears 
 to be evidently derived from them. The intenilty 
 of this colour changes with a multiplicity of vary- 
 ing circumftances ; it is more pale in animals which 
 ate too fparingly nourilhed, or in fuch as have 
 fullered profufe hemorrhages. The blood con- 
 contained 
 
OF THE BLOOD. 13 
 
 tained in the arteries is imre florid, together with 
 that which has been Subjected to the action of 
 atmofpheric, but more efpecially, that which has 
 been expofed to dephhgifticated air ; while venous 
 blood is more obflure, as well as that which has 
 been acted on by fixed or inflammable air. 
 
 § l 7- 
 Upon the whole, the caufes, which augment 
 
 the quantity of the red globules in general, and 
 alfo heighten the intenfny of their colour, are 
 fufficiently evident : but to difcover from what 
 fecret fmrce their difpofition to this crimfon dye 
 is originally derived, is a matter of Herculean 
 difficulty indeed. Haller afcribed it to the pre- 
 fence of crocus martis, becaufe the blood abounds 
 more with iron than the bones, or other parts of 
 the body, although the quantity contained, even 
 in the blood itfelf, is very fmall ; and although 
 authors differ aftonifhingly in their attempts to 
 afcertain it. Thus, for inilance, Menghinus efti- 
 inated its relative proportion to the whole mafs of 
 the blood, to be as 1 to 110; whereas, the illus- 
 trious Rhades calculated it to be only as 1 to 427 ; 
 and again, in fome future experiments, to be no 
 more than as 1 to 503, &c. 
 
 On the prefent Subject it feems proper to make 
 the following obfervation ; viz. that no iron can 
 
 be 
 
1 4 OF THE BLOOD. 
 
 be difcovered in the cruor of the blood unlefs it 
 be previoufly calcined ; whereas, on the other 
 hand, when it was dried with a gentle heat, and 
 reduced to the mod impalpable powder, I could 
 not obferve a tingle particle of it attracted by the 
 magnet, whether the experiment was made in 
 water, or in that mod fluid of all vehicles, quick- 
 filver. 
 
 § 18. 
 
 We now come to the consideration of that con- 
 diment part of the mafs of blood, which dands 
 lad; in our order of enumeration, viz. the Lymph; 
 which is by fome called the bafis of the craflamen- 
 tum, by others, the mucous or glutinous part, 
 and by others, the fibrous portion of the blood. 
 
 This, in former times, was very erroneoufly 
 confounded with the ferum, from which it is not- 
 withftanding very widely different, in all its effen- 
 tial properties. When the lymph is expofed to the 
 action of air, efpecially of fuch as is of a low tem- 
 perature, it is immediately coagulated ; but by the 
 admixture of quicklime, (which has been already 
 faid (§ 11.) to have the power of coagulating 
 ferum), it is preferved in a fluid date ; or, even 
 though it be already coagulated, yet, by the 
 addition of this fubdance, it is again immediately 
 refolved. 
 
 § 19- 
 
OF THE BLOOD. 15 
 
 We have already touched on the methods, by 
 which this part of the blood may be feparated 
 from the cruor (§ 9.). It »» alf o b y otncr artifi - 
 cial methods, fuch as whipping or agitating the 
 blood with fmall twigs, induced to aflame the 
 appearance of a membrane, which has been named 
 after Ruyfch its celebrated difcoverer. 
 
 The fimilitude which prevails between the mem- 
 brane thus formed by art, and certain remarkable 
 phenomena in difeafes, efpecially in thofe of an 
 inflammatory nature, reduces it to a certainty, 
 that fuch phenomena are to be entirely referred 
 to the coagulation of the lymph, of which we arc 
 now treating. 
 
 It may be proper on the prefent occalion to 
 mention a few of thofe numerous phenomena al- 
 luded to, which evidently derive their origin from 
 this property of the lymph ; thus we may inftance 
 in particular, the pleuritic cruji, which is formed 
 on the furface of the craffamentum of blood re- 
 ceived into a veflel and fuffered to remain fomc- 
 time at reft ; the membrane-like appearances which 
 ufually tranfude from, and completely invert the 
 furfaces of the feveral vifcera when in a flate 
 of inflammation j and alfo the membrana caduca 
 
 of 
 
16 OF THE BLOOD. 
 
 of Hunter, which exfudes from the cavity of the 
 uterus, when impregnated, and ftill under the 
 gentle alow of the venereal orgafm. From the 
 fame fource originates likewife, that production of 
 cellular m.mbrane by which we fee frequently the 
 lungs connected to the pleura in cafes of peripneu- 
 mony ; as alfo the preternatural portions of the fame 
 fubftancc often found in the cavity of the abdomen 
 after profufe hemorrhages ; and finally, to no other 
 fource can we rationally refer thofe membrane- 
 like productions, which, in that lingular fpecies 
 of difeafe, vulgarly denominated Lithopcedion, 
 firmly attach to the contiguous vifcera fuch parts 
 as are irritated to inflamation by the too long re- 
 tention of the calculus or (tone in the abdominal 
 Cavity. It feems to be alfo an opinion founded at 
 lead on probability, that polypi, and fuch like 
 preternatural coagulated excrefcences, owe their 
 exiftence to the fame caufe. 
 
 § 20. 
 Thofe phenomena juft enumerated, together 
 with a variety of others which every where occur, 
 demonfhate, in a moil ftriking manner, the fuperior 
 importance of this lymphatic portion, in which 
 the viral principle of the blood appears immedi- 
 ately to refide, if indeed the blood poflefs any fuch 
 principle, an opinion which I think both ingeni- 
 ous and highly probable. 
 
 2 Befides 
 
OF THE BLOOD. 17 
 
 § 21. 
 Befides thofe general portions of the blood al- 
 ready enumerated, we have on a former occafion 
 obferved that this fluid contains alfo, in a fhue of 
 mixture, other elementary principles. (§ 10.) 
 
 What I principally advert to at prefent is air, 
 which is commonly believed to conflitute tt part 
 of the whole mafs of blood, but which in the 
 blood of a living and healthy fubject does not 
 exifl in a free and perfectly elaftic (late, but is fo 
 intimately united and involved, and fo permanent- 
 ly fixed, as to be with difficulty extricated and 
 reflored to its native triform ftate. Indeed I 
 have learned from actual experiments, that even a 
 very fmall quantity of the moil pure air injected 
 through an artificial opening into thejugular vein 
 of a dog, has excited fymptoms of a very formida- 
 ble nature, fuch as palpitations of the heart, drowfi- 
 nefs, convulfions, and, when the quantity was flight- 
 ly increafed, even death itfelf quickly fucceeded. 
 
 § 22. 
 The elementary parts of the blood thus concife- 
 ly treated of, differ very widely in the proportion 
 they bear to each other in different fubjects, ac- 
 cording to the complex ratio of age, nourifhment, 
 and other circumflances of importance, which re- 
 gard the foiled health of each individual. 
 vol. 1. „ B § 23. 
 
fS OF THE SOLIDS. 
 
 § 23. 
 Neither has any thing more certain or decifive 
 been advanced with refpecl to the proportion which 
 the whole volume of blood bears to the entire 
 bulk of the body. Haller was of opinion, that in 
 an adult it amounts to 30 or 36 pounds by 
 weight y while the calculations of others have been 
 widely different. 
 
 SECT. IIL 
 
 OF THE SOLIDS OF THE HUMAN BODY IN GENERAL, 
 BUT PARTICULARLY OF THE CELLULAR MEM- 
 BRANE. 
 
 § 24. 
 
 
 X HE folids of the body are originally 
 derived from the fluids themfelves ; thus in the 
 firfl rudiments of the embryo, while yet in a gela- 
 tinous ftate, the folids, each in its own appropriate 
 fituation, begin in a very gradual manner to af- 
 fume their proper form and texture, infinitely dif- 
 ferent from each other in point of cohefion, from 
 the molt tender and almoft pultaceous confidence, 
 fuch as the medullary fubftance of the brain, to 
 the moft firm and durable, as the vitreous cortex, 
 or enamel of the teeth. 
 
OF THE SOLIDS. 19 
 
 § 25. 
 In all the folids of the body an earthy bafis of 
 a calcareous nature abounds more or lefs, not in- 
 deed in a fimple (late, but united to the phof- 
 phoric and faccharine acids, the former of which 
 exifts in by far the largeft: proportion. Their co- 
 hefion depends not only on the peculiarity of their 
 texture, but is alfo much promoted, as well by 
 the quantity of air contained in them in a fixed 
 date '*, (which is afcertained by the experiments 
 of the illuftrious Hales to be more abundant as the 
 parts are more folid) ; as alfo by the fubftance 
 called animal glue, which is procured in large 
 quantities from the folid parts of animal bodies, 
 and is in general ufe in fome of the mechanical arts. 
 The origin of this tenacious fubftance may be 
 very eafily explained and comprehended from 
 what has been already faid refpecYing the vifcofity 
 or gluey nature of the blood. 
 
 * " The properties and powers of air have not yet been 
 ultimately developed. It is, however, in the mean time 
 certain, that this fubftance conftitutes, at leaft, a part of the 
 gluten or cement by which all the more compact bodies 
 in nature are confolidated and bound together. Thus the 
 diflblution of metals, bones, ftones, fhells, and falts, is uni- 
 formly attended with an extrication of air." See Haller de 
 corp. hum. funclionib. Vol. III. pag. 271. 
 
 B 2 The 
 
to OF THE SOLIDS. 
 
 The elementary fubftance of iron, to which has 
 been attributed the import ant office of increafmg 
 the powers of ohefion in the diiFerent parts of 
 the human body, fcarrely deferves to be taken 
 into confiderat'.on at aU. as I have found its quan- 
 tity to be fo very minute as uot to exiil in a 
 greater proportion than one fifth part of a grain 
 to two rounds even of the bones, the hardeft and 
 mux coherent parts of the auimal fyftem. 
 
 § 26. 
 A great portion of the folids of our body very 
 evidently exhibits a fibrous texture, compofed of 
 fmall filaments running more or lefs parallel to 
 each other. Thefe filaments or fibres may be 
 evidently enough perceived in the bones, efpe- 
 cially the bones of a foetus, in the mufcular flefli, 
 in tendons, ligaments, aponeurofes, and fome mem- 
 branes, as the dura mater, &c. 
 
 § 2 7- 
 In various other parts of the animal body, the 
 texture is fo widely different from that of which 
 we have juft fpoken, that in them it is fcarcely 
 poffible to trace the appearance of a fingle fibre ; 
 their ftrudlure is indeed o r a very lingular and fpe- 
 cific nature, diftinguiflied in Greek by the name 
 parenchyma. This parenchymatous fubftance is 
 almoft exclufively confined to fome of the fecreting 
 
 vifcera 
 
OF THE SOLIDS. <u 
 
 rifcera of the fyftem ; thus it exifts in the kidncs, 
 in the liver, Szc. though afTuming a fomewhai .li- 
 ferent and peculiar appearance in each. 
 
 § 28. 
 
 Through all thofe varieties of compofkion and 
 texture, whether of a fibrous or parenchymatous 
 appearance, there is interwoven, in common, more 
 or lefs of a certain web-like fubfiance, which is 
 called cellular membrane, and which defcrves a 
 place among the primary, the molt important and 
 elTential, conftituent parts of our fyftem. 
 
 § 29. 
 For, in the firfl: place, there are feveral of the 
 -folid parts of the human body, which appear to 
 confift of little elfc than cellular membrane, in a 
 conllipated or compared (late ; of this defcription 
 are moil of the membranes and cartilages ; which, 
 by long maceration, may be again refolved into a 
 cellular web, of more or lefs laxity. It is, again, 
 fo intimately and minutely interwoven in the com- 
 pcfition of other parts, as to ferve the important 
 purpofes of a receptacle and bafis to the other 
 portions of fubftance which aflift in their formation. 
 Thus, for inftance, the hardeft bones made their 
 firfl appearance in the tenderer ftate of cartilage, 
 which, as already obferved, is nothing more than 
 condenfed cellular membrane: this cellular mem- 
 brane, yet Id a lax condition, became afterwards 
 
 B 3 diftended^ 
 
* 2 OF THE SOLIDS. 
 
 diftended, and at length completely faturated, as 
 it were, by the conftant acceilion of offeous matter, 
 till it finally aflumed the nature and appearance of 
 perfect bone. Indeed it would appear, that none 
 of the folids of our body exift, without containing 
 more or lefs of this web-like fubffance in their 
 compofnion, if we except the enamel of the teeth, 
 in which I was not able to difcover the fmallefl por- 
 tion of cellular fubltance, even when the enamel 
 was fubje&ed to the action of one of the flronger 
 acids. 
 
 § 3°- 
 This cellular Jubilance, which ferves the great 
 
 purpofe of a boundary, or partition-wall, to adja- 
 cent parts, is efpecially interwoven in, as well as 
 fpread between, mufcles and membranes. To other 
 parts, again, particularly to veffels and nerves, 
 
 it anfwers as a bed or bafis of fupport. Finally, 
 it conftiiutes one common and general bond of 
 union, which connects the neighbouring individual 
 parts to each other, and eftablifhes between the 
 whole an extenfive medium of communication, 
 
 § 3 1 - 
 From what has been already faid, two conclu- 
 sions naturally prefent themfelves, 
 
 Firft, in as much as it appears, that the cel- 
 lular membrane certainly conflitutes the ground- 
 work 
 
OF THE SOLIDS. 23 
 
 work of the ftru&ure of the whole body, if we 
 figure to ourfelves the entire removal of every 
 other fubftance which enters into, and affifts in 
 completing, ihe compofition of the fyftem, the 
 cellular membrane, (till remaining in its proper 
 fituation, unmolefled and alone, will neverthelefs 
 preferve and exhibit the complete figure of the 
 whole and every part of the body. 
 
 Secondly, as by means of this cellular founda- 
 tion, a certain connection and medium of commu- 
 nication are formed, between all the parts of the 
 body, however widely different from each other 
 they may be, in nature, or remote, in fituation ; 
 the knowledge of this fail: ferves an important end, 
 not only in deciding controverfies which refpedt. 
 the continuation of membranes, but alfo in explain- 
 ing many phenomena of difeafes which daily pre- 
 fent themfelves. 
 
 § 3 2 - 
 As the cellular membrane appears thus to afford 
 origin and foundation to moft of the folid parts of 
 the body, fo it appears itfelf to owe its own exif- 
 tence to the lymphatic part of the blood, of which 
 we have already fpoken. I am induced to enter- 
 tain this opinion from having feen the lymph, after 
 tranfuding from the lungs of pleuritic patients, 
 converted by the powers of the animal economy 
 B 4 into 
 
^4 C OF THE SOLIDS. 
 
 into real cellular fubftance, which afterwards 
 affirming the appearance of more compacted mem- 
 branes, oftentimes attaches thofe vifcera to the 
 furrounding pleura, 
 
 § 33- 
 What has been already advanced on the fubject, 
 may be fufficient to ihow the general nature, and 
 eflablifh the importance, of the cellular membrane. 
 We will now proceed to coniider fome of its 
 varieties. 
 
 And, in the firft place, its firmnefs is not always 
 uniform. 
 
 For, in general, other circumftances being alike, 
 the cellular membrane of the human body is very 
 tender indeed, when compared with that of other 
 animals. If I am not deceived, this very foftnefs 
 and pliancy of the cellular fubftance in the human 
 fyftem, deferves to be ranked among the leading 
 prerogatives of man ; becaufe, in confequence of 
 it, his fufceptibility of impreffions from the more 
 refined and fubtle ftimuli is greatly increafed, as 
 well as, his capacity to perform motions and vari- 
 ous functions, with facility and perfection. 
 
 But with regard to the more lax or firm texture 
 gf the cellular membrane., even among mankind 
 
 themfelves, 
 
OF THE SOLIDS. i S 
 
 themfelves, a very great variety occurs, depend- 
 ing on age, fex, mode of life, climate, &c. 
 
 Finally, the condition of this membrane as to 
 denfity and flrmnefs, is various, as it is found 
 exifting in different parts of the fame body : thus, 
 it is more lax on the eye-lids and prepuce, more 
 compa£l and firm about the ears, &c. 
 
 § 34- 
 We now proceed to confider another ufe or 
 office of the cellular membrane, befides that 
 which we have already faid it performs to the 
 body in general, (§ 29, 30) ; namely, that by 
 means of its numerous fmall cells, it affords con- 
 venient temporary receptacles for fluids of different 
 kinds. 
 
 That fluid, which thofe minute cells are more 
 particularly deftined to receive, is a fine halitus of 
 a ferous nature, or a very fubtle Water, by which 
 almofl all parts of the body are moiffened, and 
 lubricated, and which this cellular web appears to 
 abforb, after the manner of a fponge *. 
 
 If it be admifTible to defignate by the name of vefels, 
 thofe minute interj}iccs of the cellular membrane, by which 
 it abforbs fluids after the manner of a fponge, I readily 
 acquiefce in the opinion of William Hunter, (fee Medic. 
 
 Obf. 
 
26 OF THE SOLIDS. 
 
 § 35- 
 But, befides this, the cellular membrane, ia 
 certain parts of the body, ferves as a refervoir to 
 humours of a different and fomewhat fpecific na- 
 ture. Thus, that portion of it which conftitutes 
 the vitreous fubftance of the eye, is charged with 
 a fluid of the fame name : 
 
 That which forms the meddullary membrane 
 of the bones (commonly, though improperly, cal- 
 led the internal periofleum) contains the medulla : 
 
 and, 
 
 Finally, A large portion interwoven through 
 the foft pans of the body, furnHhes a convenient 
 receptacle for the other portions of oily fubftance. 
 
 Obf. and Inquiries, vol. ii. p. 27. feq.) that this web-like 
 expansion, now under immediate coniideration, is compofed 
 of a congeries of veffels, in like manner with the other parts 
 of the body. But if he entertained a belief, that this mem- 
 brane confifts of fmall cylindrical veins, which anatomills 
 commonly mean to reprefent by the term veffe/s, I muft 
 acknowledge, that microfcopical obfervations, conducted 
 with the utmofl degree of minutenefs, and the mofl cautious 
 circumfpecuon, have not been fufficient to furnifh me with 
 any unequivocal teitimony that fuch veflels actually exift, 
 but have rather induced me to embrace a contrary opinion. 
 
 S 36, 
 
OF THE SOLIDS. 27 
 
 § 36. 
 And here indeed a threefold variety prefents 
 
 itfelf to our confideration : 
 
 There are, in the firft place, certain parts of 
 the body, the cellular fubftance of which, though 
 of a very foft and extremely flaccid nature, is 
 notwithstanding, never filled with fat in a healthy 
 fubje-ft. ; fuch, for inftance is that which lines the 
 eyelids, and that fpread on the genital organs of 
 the male, Sec. But further, in numerous parts 
 throughout the body, there are not unfrequently 
 found irregular and tranfient collections of fat, 
 which appear to refide in the fame kind of cells, 
 which at other times aft as refervoirs to the atte- 
 nuated ferous fluid already mentioned. 
 
 But finally, in certain parts of the body, and, 
 unlefs I am deceived, in cells of a peculiar nature, 
 and given defcription, fat is found conftantly en- 
 clofed, defigned to fubferve dated, uniform, and 
 fpecific ufes in the animal economy, fuch, for ex- 
 ample, is that which, in the female fyftem, forms 
 the mom veneris, which appears to me to confti- 
 tute a very peculiar and completely circumfcribed 
 protuberance *. 
 
 * This circumftance I had an opportunity of afcertaining 
 in a much more fatisfaclory manner in the dead body of a 
 female ape. After having for fome time fubjecled the corpfe 
 %o the action of cold, I was able, by removing the fkin, to 
 
 expofp 
 
28 OE THE SOLIDS. 
 
 § 37- 
 On the fubjeft of the fit itfelf we will now pro- 
 ceed to make a few observations, this being fo 
 very proper a place for entering on the confidera- 
 tion of it. 
 
 It is an oil, not unlike the un&uous oils of ve- 
 getables ; bland, inodorous, and lighter than 
 water, confiding of phlogifton, united to phlegm 
 by means of an acid of a peculiar nature. 
 
 § $8. 
 
 It is formed at fo late a period in the foetus, 
 that fcarcely an indubitable veftage of it can be 
 difcovered earlier than the fifth month after con- 
 ception. 
 
 Its confidence is various in different parts of 
 the body. That for inftance which lines the in- 
 fide of the orbit of the eye, is more fluid, whilft 
 that on the contrary which furrounds the kidneys 
 approaches to the firmnefs and appearance of faet. 
 
 § 39- 
 A controverfy has cxifted with refpeel to the 
 fecretion of this fubflance, namely, whether it is 
 performed by a peculiar fet of glandular bodies, 
 
 expofe entire the circumfcribcd globe of fat fituated beneath 
 the pubes. 
 
 agreeably 
 
OF THE SOLIDS. 29 
 
 agreeably to the opinion of William Hunter, or 
 whether it merely tranfudes, by fimple diapedefis, 
 through the patulous mouths of arteries ? The 
 latter of thefe opinions, befides other arguments 
 which might be advanced in its favour, appears 
 the mod probable from hence, that not unfre- 
 quently preternatural collections of fat have been 
 difcovered in other parrs than thofe commonly oc- 
 cupied by this fubftance : this circumftance can be 
 much more aptly and rationally explained by at- 
 tributing fuch unufual collections of fat to an error- 
 loci, arifing from a morbid flate or difpofition of 
 the veiTels, than by referring it to an unnatural 
 and recently formed fyftem of glands : thus for 
 example, in the very ball of the eye itfelf, fat has 
 been fometimes found ; and a fubftance of a na- 
 ture like fuet, ufua'ly fills up the cavity from 
 which a teflicle has been extra&ed ; indeed there 
 fcarcely exifts a cavity in the body in which ftea- 
 tomatous collections have not made their appear- 
 ance. 
 
 But to conclude ; thofe fmall glands to which 
 certain celebrated characters have been folicitous 
 to attribute the fecretion of fat, appear as yet to 
 be in reality nothing more than mere creatures of 
 analogy. 
 
 But 
 
3 o OF THE SOLIDS. 
 
 But however this may be determined, it is in 
 the mean time very certain, that both the fecre- 
 tion and abforption of this fubftance can be per- 
 formed with the utmoft difpatch. 
 
 § 4o. 
 The ufes of the fat are numerous. It lubri- 
 cates the folids, and thus facilitates motion. It 
 obviates and prevents a morbid excefs of fenfibi- 
 lity. It a&s as a defence againft cold : and, 
 finally, by its uniform diftention of the ikin, con- 
 tributes to comelinefs and beauty. Not to men- 
 tion the peculiar ufes of the fatty matter con- 
 ftantly bellowed on certain parts of the body, as 
 the medulla of the bones, &c. 
 
 This fubftance appears, however, to contribute 
 fcarcely any thing to the nourifhment of the hu- 
 man fpecies *, when in the enjoyment of entire 
 health. 
 
 * That bloodlefs infecfts, however, derive a principal part 
 of their nourifhment from the fatty fubftance with which 
 their bodies are plentifully fupplied, is a conjecture of natu- 
 ralifts founded at lead on probability. 
 
 SECT. 
 
OF THE VITAL ENERGIES. 31 
 
 SECT. IV. 
 
 OF THE VITAL ENERGIES IN GENERAL, BUT 
 PARTICULARLY OF CONTRACTILITY. 
 
 § 41- 
 
 VVE enter now on the confideration of 
 a difficult fubjeft, namely, the living folid, and 
 fhall attempt a full account of the vital energies, 
 by which the different parts of our body appear 
 to be animated and fitted, as well to receive the 
 impulfe of ftimuli, as to perform the various mo- 
 tions which are neceffary in the economy of the 
 living fyftem. 
 
 § 42. 
 But with refpeft to the living folid, it will firfl: 
 be neceiTary to afcertain its exaft limits, and to 
 define it with precifion and accuracy ; whence it 
 will evidently appear, that it is not our intention, 
 on the prefent occafion, to treat either of thofe 
 properties, which the human body pofTeffes in 
 common with numerous other bodies in nature, 
 fuch as elaflicity (the powers of which, however, 
 are notwithftanding exhibited in various motions 
 and functions of the animal economy), nor yet of 
 thofe which refide exclufively in the mind ; tho* 
 we flatter ourfelves no one will deny the powerful 
 influence of thefc latter over the energies pofTefT- 
 
 ed 
 
32 OF THE VITAL ENERGIES. 
 
 ed by the living folid itfelf, confidercd us a mate- 
 rial body. We will confine ourfelves folely to 
 the confideration of thofe energies which refide in 
 our body as a fyftem of organifed matter, and 
 which appear to be related to each other in the 
 following order. 
 
 § 43- 
 
 The firfl: and moil univerfal fpecies of thofe vi- 
 tal energies, and which may indeed be regarded as 
 an inferior degree of the others, or rather as the 
 threfliold leading to them, is fimple contraflility, 
 i. e. a propenfity in a part to contract itfelf. As this 
 property appears in reality to refide in every part of 
 the cellular membrane, it mud be equally exten- 
 five with that membrane itfelf, and therefore may 
 be faid to pervade almofl; the whole body. Hence 
 this may be called, with perhaps fufficient propri- 
 ety, the vis celluhfa. 
 
 § 44- 
 Another of the vital energies is, the irritability 
 of Hallcr, which refides in mufcular fibres only, 
 and may therefore be called the vis mufcularis* 
 It manifefts itfelf by a very fingular, ofcillatory 
 and tremulous motion, eafily diftinguifhed from 
 limple contraction, by its being more readily ex- 
 cited to action on the application of any acrid fti- 
 mulus. 
 
 4 § 45- 
 
OF THE VITAL ENERGIES. 33 
 
 § 45- 
 The third is fenfibility, which refides folely in 
 the nervous medulla, communicating with the fen- 
 forium, called therefore vis nervea ; when any 
 part endowed with this property is acted on by 
 irritating ftimuli, an impreflion is immediately 
 made on the fenforium. 
 
 §46. 
 
 The three foregoing may be, with propriety, 
 confidered as common or general vital energies ; 
 becaufe they exift, more or lefs, in almoft all, or 
 at lead in a great many, parts of the body, which 
 the ancients called therefore Jimilarcs, i. e. parts 
 of a fimilar nature. 
 
 § 47- 
 But befides the foregoing, there exifts alfo a 
 fourth energy worthy of our confideration, namely, 
 the vita propria, or fpecijic life; under which deno- 
 mination I mean to arrange fuch powers as belong 
 to certain particular parts of the body, deftined for 
 the performance of peculiar functions, and which 
 cannot with any propriety be referred to either of 
 the claffes of coimnon energies, formerly mentioned. 
 
 Inferring fyntheticaily, or a priori, as it is 
 
 termed, it is not repugnant to found induction to 
 
 conclude, that parts differing from all others in 
 
 vol. 1. C texture, 
 
34 OF THE VITAL ENERGIES. 
 
 texture, in arrangement, and in peculiarity of 
 function, mud alfo be furnifhed by nature with 
 peculiar properties and powers, adapted to the 
 performance of fuch fpecific action. 
 
 But reafoning analytically, or a pojferiori, we 
 are likewife taught by accurate obiervations made 
 on nature herfelf, that there are certain parts of 
 the body, particularly fome of the vifcera, which 
 perform motions fo very Angular, as cannot by 
 any means be fuppofed to arife from either one or 
 other of the common energies, of which we have 
 already fpoken, but mud be referred to a vita 
 propria, or fpecific energies of their own. 
 
 Inftances of fuch figularity of action we have in 
 the motions of the iris ; the erection of the papilla 
 in the breafts of females ; the moiions of the fim- 
 bria: of the fallopian tubes ; the action of the 
 placenta ; the action of the uterus in parturition ; 
 the defcent of the teftes in the male foetus ; and, 
 if I am not deceived, in a great part, if not in the 
 whole of the procefs of fecretion. 
 
 § 4 8. 
 
 The fifth and lafl energy which claims our at- 
 tention is, the nifus format ivus, or formative pro- 
 penfity, which mould be coniidered as the efficient 
 caufe of the whole procefs of generation (taken in 
 
 fo 
 
OF THE VITAL ENERGIES. 35 
 
 fo extenfive a latitude as to include both nutrition 
 and re-produclion as modifications of itfelf). In 
 confequence of this propenfity, the matter of the 
 animal fyflem, whether appropriated to generation 
 or nutrition, being lodged in the places deftined 
 for its reception, and having acquired fufficient af- 
 fimilation and m.uurity, affumes forthwith its due 
 arrangement and figure, and enters into the com- 
 pofition of thofe p trts which are afterwards fur- 
 nifhed and enlivened either with the whole or 
 part of the energies we have, already enumerated, 
 viz. contractility, irritability, fenjibility, or finally 
 fpecijic life. 
 
 § 49- 
 
 Of this nifus formativus, or formative propen- 
 fity, more will be faid when we come to treat of 
 the proeefs of generation. 
 
 Irritability will be more fully confidered when 
 on the fubject of mufcular motion. 
 
 The fubjecT: of fenfibiliiy will be again refumed 
 when we come to confider the action of the ner- 
 vous fyflem. 
 
 Of the vita propria, or fpecific life, we will 
 every where treat, when the fubjecl: under confi- 
 deration may render it proper. 
 
 C 2 But 
 
3 <5 OF THE VITAL ENERGIES. 
 
 But with refpcct to contradility, the prefenr 
 is a very fuitable place to offer on it a few addi- 
 tional and particular obfervations. 
 
 § .'O. 
 I have already faid that this energy pervades 
 almoft the whole body, at lead, that its extent is 
 commenfurate with the extent of the cellular 
 membrane. 
 
 In the firfl place, therefore, it refides in all 
 fuch pans as confift of compacted cellular fub- 
 ftance, of which the different membranes of the 
 body ferve as examples. That thefe poffefs con- 
 tractility will not be denied by any one who re- 
 flects on the conftridtion of the dartos tunic > or 
 who calls to mind the fpafms of the fkin, or of 
 the peritoneum, which alone appears fometimes 
 to incarcerate and flrangle the inteftines in cafes 
 of hernia. 
 
 Further, It alfo exifts in fuch vifcera as are 
 compofed chiefly of this kind of membrane ; of 
 this defcription are the lungs, the external fuper- 
 ficies of which is highly contractile, as I have 
 lately learned from frequently puncturing and irri- 
 tating them in a living ft ate j but I have not found 
 them pofTeffed of any real irritability, as has been 
 lately aliened by Varnier. 
 
 Even 
 
OF THE VITAL ENERGIES. 37 
 
 Even the bones themfelves do not appear to be 
 entirely deftitute of contractility, as we learn, not 
 only from the alveoli, which are well known to 
 become narrower after the extraction or lofs of 
 the teeth, but alfo from the morbid affection term- 
 ed necrofis (/'. e. mortification), from which it ap- 
 pears, that after a lifelefs part of bone is quite re- 
 moved, the new production of bene, by which 
 the vitiated part was before furrounded, contracts 
 itfelf very gradually, almoft to the natural thick- 
 nefs and former figure of the part. 
 
 But as we cbferved on a former occallon, 
 that the vitreous fubftance of the teeth was quite 
 deftitute of cellular membrane, fo it appears to 
 me probable, that it is entirely deftitute of con- 
 tractility alfo, becaufe^ when a part of it is either 
 confumed by a caries, or broken off by accident, 
 the remaining portions or fides are not approxi- 
 mated to each other, as we have already faid takes 
 place in the alveoli, but an irreparable hiatus or 
 chaftn continues without a iliadow of diminution. 
 
 § 5'- 
 
 This very power of contraction, poffeffed by the 
 cellular membrane, iliould be ranked among the 
 primary and leading fecurities or fupports of firm- 
 nefs and health ; and to it (hould be referred that 
 tone of parts, fo highly and favourably fpoken of 
 
 C 3 by 
 
3 8 OF THE VITAL ENERGIES. 
 
 by the acute and ingenious Stahl. To advance 
 one argument in favour of the foregoing pofition, 
 from many which might be adduced, it is the cel- 
 lular fubftance which, in a healthy fubject, ab- 
 forbs, afrer the manner of a fponge the aqueous 
 liquid, of which we have already fpoken, and by 
 means of its contractility propels it forward into 
 the lymphatic veflels : on the contrary, in a dif- 
 eafed flare, being deprived of its proper tone, and 
 reduced to an atcnic condition, it becomes op- 
 prefled and diftended with a load of water, and 
 thus gives rife to cedema and other cachectic 
 fymptoms. 
 
 § s* 
 
 Finally, from the univerfal prevalence of con- 
 tractility throughout the whole body, we may 
 plainly infer its influence and contagious effect, as 
 it were, on the other vital energies ; and alfo from 
 its infinitude of modifications and degrees in dif- 
 ferent men, we learn its highly influential part in 
 the conftitution of both the proper health and pe- 
 culiar temperament of each individual. 
 
 SECT. 
 
OF SOUND HEALTH. 39 
 
 SECT. V. 
 OF SOUND HEALTH, AND OF THE NATURE OF MAM. 
 
 § S3' 
 
 THOSE three fubjefts (§ i.) in the 
 eonfideration of which we have been hitherto en- 
 gaged, perpetually act and re-act on each other in 
 the living human body. The fluids, for example, 
 aft by their ftimulus on the fclids ; while thefe 
 again, in confequence of their vital energy, are 
 fitted and prepared both to receive the action of 
 the flimulating fluids, and to re-act on them in 
 turn. In a found and healthy fubject, this whole 
 routine of action and re-action, correfponds with 
 fuch exactnefs and definitude, as to conftitute a 
 perfect and harmonious equilibrium. 
 
 § 54- 
 There further exifts in the living fyflern a won- 
 derful confent of parts, even the mod remote ; 
 this confent is derived not from one, but feems to 
 owe its origin to different fources. 
 
 One of thofe fources refides in the nerves, de- 
 pending as well on the aftonifliing net-like anaflo- 
 mofes, formed by their numerous branches, as on 
 the intricate nature of their plexus and ganglia ; 
 C 4 by 
 
4 o OF SOUND HEALTH. 
 
 by the medium of which, the impulfe of ftimuli 
 being communicated to the fenforium, may from 
 thence re-a£l on parts more remote. 
 
 Another fource of this wonderful confent mud 
 be referred to the different veffels of the fyftem, 
 as well the fanguiferous as the lymphatic. 
 
 Another, again, arifes from a certain fimilitudc 
 of ftructure, giving origin to what may be called 
 a native fympathy. 
 
 The cellular membrane, which, as has been al- 
 ready obferved, appears to conftitute a common 
 bond of union to the whole body, may be readily 
 conceived to poifefs a very ftriking and powerful 
 influence in promoting the confent of diftant parts. 
 
 § SS- 
 Finally, to this head belongs what is juftly ef- 
 teemed one of the greateft myfteries of nature, 
 namely, the connection of the mind with the 
 body, and the diverfified and aftonifhing power of 
 the one over the other. As this fubject will be 
 again refumed, and treated more fully in another 
 place, it will be fufficient on the prefent occafion 
 briefly to obferve, that befides the obvious power 
 of the will over mod of the mufcles, there are 
 alfo other faculties which exert their influence on 
 
 the 
 
OF SOUND HEALTH. 41 
 
 the body, even without the concurrence or aid of 
 the will. 
 
 Of this defcription are thofe blind and purely- 
 animal inftinfts of our nature ; fuch, for example, 
 as that which excites to the gratification of vene- 
 real enjoyments. 
 
 Further, the body is greatly under the influence 
 of the internal fenfcs, more efpecially of the ima- 
 gination, and thofe pafiions of the mind which it 
 contributes to excite. 
 
 Finally, it is by the interpofition, and through 
 the medium of thefe, that a communication and 
 reciprocal influence are preferved between the 
 powers of the body, and the more exalted facul- 
 ties of the mind. 
 
 § 56. 
 
 By this diverfified confent of the folids, of the 
 fluids, and of the vital energies (§ 53.), by this 
 fympathy of parts (§ 54.), and by this intimate 
 connection between the mind and the body, 
 (S 55-)i life an d health are preferved in vigour j 
 yet not always exifling in the fame, but in widely 
 different degrees of perfection and energy. 
 
 § 57- 
 
42 OF SOUND HEALTH. 
 
 § 57- 
 
 Between the two extremes of life there exift 
 different grades, of which one is called vita max- 
 ima, or perfect life j the other vita minima, or im- 
 perfect life. 
 
 Life is faid to be perfcel in the flower of age, 
 when the functions of the body have reached that 
 pinnacle of perfection, called by the Greeks acme ; 
 this might alfo be denominated the athletic Jlaie. 
 
 Life, on the other hand, is faid to be imperfeel 
 when the functions are performed with lefs vi- 
 gour ; although their perfection may be the mod 
 confummate, when the fituation of the f&bjeft, and 
 its mode of exigence, are taken into confedera- 
 tion : thus life is imperfect in a fcetits in utcro, 
 and that in proportion as the fcetus is tender and 
 young. Finally, life is lefs perfect in the Jlecping 
 than in the waking ftate ; lefs perfect alfo in a 
 fubject advanced in years, than in one balking in 
 the meridian blaze of manhood. 
 
 § 5«- 
 
 The varieties in point of health are no lefs nu- 
 merous and confiderable : there is indeed a cer- 
 tain flate of health which may be faid to be pecu- 
 liar to each individual. Such perfons as we fup- 
 
 pofe 
 
OF SOUND HEALTH. 43 
 
 pofe to be in the enjoyment of the mofl complete 
 health, differ, notwithstanding furprifingly from 
 each other, as well in confequence of a difference 
 in the conftitution of the blood, as of a diverfity 
 of tone, and of the other vital energies ; hence 
 different individuals are fo differently affected by 
 the fame ftimuli acting on their bodies. Perhaps 
 each individual may poffefs peculiar idiofyncra- 
 fies, though fo very inconfiderable as to be fcarce- 
 ly obfervable : the influence of cuflom is fo pow- 
 erful, as to create, in different fuhjects, an intole- 
 rance of different imprefftons, though in them- 
 felves quite innocent ; it alfo produces a facility of 
 bearing, and finally creates a defire for, fuch 
 things as appeared at firft both unnatural and dif- 
 agreeable. 
 
 § 59- 
 This appears to be the very hinge on which re- 
 volves the nature and variety of temperaments, fo 
 frequently the fubjects of phyfiological difcufion. 
 The conftitution of the temperaments depends, not 
 only on the proportion and mixture of the confti- 
 tuent parts of the blood (§ 22.), but alfo on the 
 peculiar vigour of the vital energies already treat- 
 ed of ; and likewife on the confequent variety in 
 the mode of the reciprocal action and re- action of 
 the body and mind on each other. From this 
 combination and concurrence nrifes that peculia- 
 rity 
 
44 OF SOUND HEALTH. 
 
 rity of fenfation to the impreffions of ftimuli ; and 
 alfo that lingular power of performing motions 
 with greater or lcfs facility. 
 
 _ § 60. 
 Hence the varieties of temperaments are lite- 
 rally infinite, and can never be reduced to any 
 certain and definite clafTes. But as it has been 
 the pleafure of phyfiologifts to arrange them un- 
 der certain heads, for the fake of regularity, w^ 
 may with fufHcient propriety give our aflent ro the 
 common mode of arrangement, by which they 
 have been reduced to four orders^ namely, the 
 phlegmatic, the fanguineous, the choleric, and the 
 melancholic. 
 
 § 6u 
 
 For although Galen erected this divifion on an 
 abfurd foundation, falfely fuppofed to be derived 
 from the nature and constituent parts of the 
 blood, yet if this erroneous foundation be kept 
 entirely out of view, the divifion appears in other 
 refpe&s fo confonant to nature, that the different 
 temperaments of all men generally, and of every 
 individual in the different periods of life, may be 
 with propriety referred to one or other of thefe 
 four leading claffes. Thus, in the tender age of 
 infancy the phlegmatic temperament chiefly pre- 
 vails. This in youth is exchanged for the fan- 
 guineous. 
 
OF SOUND HEALTH. 45 
 
 guineous. The choleric marks the period of man- 
 hood. And the melancholic is the temperament 
 of old age. 
 
 But, as has been already obferved, the variety 
 in the exifting degrees of the fame, and in the 
 mixtures of different temperaments, is fo un- 
 bounded, as to afford an open and a very exten- 
 five field of fpeculation to fuch as wouM with to 
 amufe themfelves with tracing out, and eftablifh- 
 ing, on this fubjecl:, more minute combinations, or 
 divifions and orders. 
 
 § 62. 
 
 This whole collective affemblage of all the fa- 
 culties and laws hitherto mentioned, by which the 
 functions of the human body are performed and 
 regulated from the opening, to the clofing pulfc 
 of life, are called human nature^ or the nature of 
 man; from whence arofe the name of phyjiology, 
 the fcience now under our immediate confidcration. 
 
 § 63- 
 
 Thofe functions of the body may be themfelves 
 properly enough divided into four claries ; which 
 divifion, although not entirely free from exception, 
 nor perfectly conformable to nature, may never- 
 thelefs be aptly enough retained a3 a ufeful afTift- 
 ant to the memory. 
 
 I. The 
 
4<S OF SOUND HEALTH. 
 
 I. The firft clafs of this divifion embraces the 
 vital f unci ions, fo called becaufe their mediant 
 and unmolefted action, is more efpecially and ef- 
 fentially neceffary to the continuance of life. To 
 this clafs belong the circulation of the blood, and 
 after birth the procefs of refpiration. 
 
 II. The fecond clafs embraces the animal func- 
 tions ; thefe ferve to diftinguifh annuals from or- 
 ganifed bodies belonging to the vegetable king- 
 dom *. This clafs in man includes the connection 
 
 * I lament it as a ferious misfortune to the fcience of na- 
 tural hijiory, that his final object did not call on the very 
 learned and ingenious profellbr to be more explicit and mi- 
 nute on that clafs of functions denominated the animal. He 
 has told us in terms very general and definite, that they are 
 filch as ferve to constitute the great barrier of distinction be- 
 tween animal and vegetable bodies. I am forry that neither 
 the object nor extent of an elementary work permitted him to 
 defcend to a more minute fpec'-fication of thof; characterises, 
 in which the difference between animals and vegetables more 
 immediately conlifts. Few points of investigation can be 
 propofed which have given rife to a greater diverfity of opi- 
 nion, than that which refpects the difference between thefe 
 two claffes of natural bodies ; and fewer ftill perhaps can be 
 advanced, with regard to which philofophers, even in the pre- 
 fent imperfect ftate of phyfical fcience, Should more unani- 
 mously agree. Be this later pofition, however, true or falie, 
 1 have ;.lways been led to confider the Strangely diveriified, 
 and even contradictory opinions, entertained by naturalifts 
 refpe&ing the difference between animals and vegetables, as 
 
 fo 
 
OF SOUND HEALTH. 47 
 
 of the mind with the body, but it regards more 
 efpecially fenfation, and mufcular motion. 
 
 fo many unanfwerable teftimonies of the equivocality of the 
 whole. The difcovery therefore of an exclufive line of dif- 
 tindYton between the animal and vegetable kingdoms, (if in- 
 deed thefupreme author and arbiter of nature permits fuch a 
 line to exift) muft ftill be confidered as a peculiar dijideratum 
 in the fcience of natural hiftory. 
 
 From all my {peculations on this interefting fubjecT: (and 
 it is with me a favourite object of purfuit) I am firmly of 
 opinion, that there exifts no incommunicable characterillic, 
 and I will venture to add, no congregation of characteriftics, 
 which ferve to conflitute a complete partition-veil between 
 the animal and vegetable kingdoms. The numerous and 
 highly diverilfied fubje&s of thefe two important kingdoms 
 of life, appear to be nothing elfe than different individuals of 
 one extenfive family, defcended from a common parent, and 
 exhibiting the mod unequivocal teftimonies of their kindred 
 nature. Like the delicate tints of light and fhade in a well fin- 
 ifhed picture, they fo gradually intermingle, and run into each 
 other fo infenfibly, that it is literally impoffible to fay with 
 definitude, where the one terminates and the other begins 
 
 All refearches therefore after an exclufively difiinctive cha- 
 racteristic between vegetables and animals, appear to me equal- 
 ly irrational and vifionary with the late enthufiadic purfuits of 
 the deluded alchemifts, after the philofopher's ftone, or their 
 more chimerical refearches after their flattering panacea. 
 Why then fliould man, prefumptucus man ! attempt the ef- 
 tablifhment of an eiTential dillinction between phyfical bodies 
 where wiler nature acknowledges none ! 
 
 2 HI. 
 
4 8 MOTION OF THE BLOOD. 
 
 III. The natural functions conftitute the third 
 clafs. Thefe are fubfervient to the nourifhment 
 of the body. 
 
 IV. The fourth and laft clafs confifts of the ge- 
 nital functions, which are deftined for, and employ- 
 ed in the propagation of the fpecies. 
 
 Let us now confider each clafs of functions in 
 order, beginning with the vital. 
 
 SECT. VI. 
 OF THE MOTION OF THE BLOOD IN GENERAL. 
 
 § 64- 
 
 ± HE blood as we have already feen, af- 
 fords the primary origin to the principal parts of 
 the body, and continues afterwards to convey to 
 them uniform and perpetual fupplies of nourifh- 
 ment, and ought therefore, with a very few ex- 
 ceptions (§ 5.) to be diftributed far and wide, 
 through even the moft fubtle and diftant receffes 
 of the whole body. That fuch a minute diftribu- 
 tion actually takes place, we learn not only from 
 a fine injection of the vefTels, but alfo from every 
 day's experience, from which it appears that very 
 
 1 few 
 
MOTION OF THE BLOOD. 49 
 
 few parts of the body can be pun&ured with the 
 point of the fmalleft pin without the occurrence 
 of a greater or lefs hemorrhagy. 
 
 § 6*- 
 
 This vital liquid does not, as was the opinion 
 of the ancients, flow and ebb like the waves of 
 Euripus *, through channels of the fame nature 
 and order, but is fo moved onward in an orbit, 
 or circulates, as they exprefs it, in fuch a manner, 
 as to be carried from the heart, by means of the 
 arteries, to every part of the body ; and being 
 there taken up by the veins, conveyed back again 
 by them to the fame original fountain, the. heart* 
 
 § 66. 
 After a few, and thofe very indefinite, expref- 
 fions j- of his predeccfTors, William Harvey efta- 
 
 * A narrow arm of the fea, extending between Bocotia and 
 Euboea, faid to ebb and flow feven times during each diurnal 
 revolution of the earth, or each term of 24 hours. In this 
 extraordinary portion of fea, Ariftotle, that celebrated anci- 
 ent philoiopher, is falfely reported to have drowned hirnfelf, 
 becaufe he was not able to develope the caufe of the conflant 
 flux and reflux of its waters. C. C. 
 
 f The unfortunate Serveius, and that truly illuftrious cha- 
 rafter Andr. Cafalpinus, appear to have advanced nearer to a 
 true knowledge of the genuine circulation of the blood, than 
 any of the other phyfiological writers who are conjrnordy 
 enumerated in the fame clafs. 
 
 rot i. D It 
 
5 MOTiON OF THE BLOOD. 
 
 blifhed, in a manner tolerably conclnfive, the cir- 
 culation of the blood, in a fmall but immortal 
 work publifhed in the year 1628. 
 
 In procefs of time, however, every fliadow of 
 doubt en this fubjeft was removed. This was 
 effected chiefly by frequent rccourfe to adtual and 
 fimple obfervations with the microfcope ; but in 
 part alfo by injections of wax and other fubftances 
 into the arteries, which were feen paffing again 
 to the heart by the route of the veins ; and, fur- 
 ther, by the elegant and fublime experiment of 
 
 It may not be improper on the prefent occafion to advert 
 to a remarkable claufe in the writings of Servetus, contained 
 in a phyfiological dilfertation, which he included in his cele- 
 brated and very fcarce work, that occafioned the death cf its 
 illuftrious author. The work is entitled " Reflitutio Chrifti- 
 anifmi," &c. (Viennx Allobrog.) 1553-8. The differ cation 
 particularly alluded to, is contained in the fifth book of the 
 abovementioned work, " de trlnitate divina, in quo ag'itur de 
 fpiritu fancto," in which we are presented with the following 
 words, " Vitalis e/t fp'tr'itus qui per anajlomofes ab arttriis com- 
 muntcatur vcnis t in quibus dicilur naturalist* 
 
 But from the memorable problem of Ccefalpinus, " de ve- 
 nit ultra vinculum tumeftentibus, non citra," it appears obvious 
 as the blaze of day, that that truly illuftrious phyfiologift 
 trod on the very confines of a complete knowledge cf the 
 circulation of the blood. See his "Qmcftionum medica- 
 rum," L. II. quseft. 17. page 234. 
 
 transfufincr 
 
MOTION OF THE BLOOD. 51 
 
 transfufing the blood of one living aiiiraa] into 
 another, or into a human fubject ; as alfo by vari- 
 ous other experiments which may be performed 
 on animals in a living (late. 
 
 § 6 7 . 
 What fliould be efteemed the definite ftandafd 
 of the celerity of this motion, in a healthy human 
 fubjecl, we are not well able to determine. In 
 this refpecl there is not only a difference between 
 one fubjecl and another, but there alfo occurs a 
 great variety relating to this point, arifing from 
 the difference of ages : there indeed exifts a dif- 
 ference in the celerity of the blood's motion, even 
 in the different parts of the fame body. 
 
 Finally, the venous blood appears to glide on 
 more flowly than the arterial ; and when flowing 
 through the trunks of veffels, its motion is more 
 rapid than when palling their fmaller ramifica- 
 tions. Former phyfiologifls, however, have not- 
 withftanding exaggerated thefe feveral diverfities, 
 in the celerity of the blood's motion, beyond their 
 natural magnitude. 
 
 The common conclufion, however, on this fub- 
 
 jeft is, that the blood, flowing through the aorta 
 
 with its mean velocity, paffes over a diftance of 
 
 about eight inches during the fpace of one pulfa- 
 
 D 2 tion ; 
 
52 MOTION OF THE BLOOD. 
 
 tion ; at which rate it would travel about fifty fee: 
 in the fird minute of time. 
 
 § 68. 
 
 The globules of the cruor appear to revolve on 
 their axes or centres of motion ; and it is faid that 
 the fame are propelled forward with greater velo- 
 city than the other conflituent parts of the blood. 
 I know not whether this conclufion be drawn 
 from actual experiment, or whether it be only an 
 inference from an abfurd application of the com- 
 mon laws of hydraulics to the circulation of the 
 blood : I call the application abfurd, becaufe it is 
 certainly the very fummit of folly, to attempt to 
 account for that motion of a vital flu'd, by which 
 it is carried through the living canals of an ani- 
 mated fyftem, on the purely mechanical principles 
 by which water is forced through hydraulic ma- 
 chines. — As to myfelf, I muft acknowledge I have 
 never been fo fortunate as to be favoured with 
 a view of this prerogative or preceffion of the 
 globules. 
 
 § 69. 
 I am fully perfuaded, that thofe globules only 
 glide forward, fufpended or fwimming in the fluid 
 formed by the other conflituent parts of the blood, 
 but that they do not at the fame time rotate on 
 their own axes at all. To conclude, it is not 
 
 fully 
 
MOTION OF THE BLOOD. 53 
 
 fully and clearly afcertained, that the blood, be- 
 fides its progreffive motion, of which we are now 
 fpeaking, is alfo fubje&ed to one of a different 
 kind, called an inteftine motion ; although there 
 can be no doubt, but that the elementary parts of 
 the blood may be occafionally affected in their 
 arrangement and combination, when they are 
 tumultuoufly ■unrated in confequence of the im- 
 menfely varied directions., the minute divifions and 
 numerous anaftomofes of the reikis through which 
 they pafs. 
 
 § 7°- 
 Thus much we thought proper to advance on 
 the motion of the blood in general. Previoufly 
 to our entering on a more dofe and minute con- 
 fideration of this fubjecl, we think it beft to treat 
 of the vclTels in which the blood is contained, and 
 alfo to confider with attention the energies, by 
 which thefe veiTels are animated, and fitted both 
 to receive and again propel the blood. 
 
 B 3 SECT. 
 
U OF THE ARTERIES. 
 
 SECT. VII. 
 
 OF THE ARTERIES. 
 
 § 7 1 - 
 
 J. HE veffcls which receive the blood 
 immediately from the heart, and convey it to all 
 the different and minute parts of the body, are 
 
 called arteries* 
 
 In their collective or aggregate dimcnfions, they 
 are lefs capacious than the veins; but their texture 
 is far more folid, more compact, very elaftic, and, 
 as appears, from the experiments of Wintringham, 
 remarkably ftrong. 
 
 § 7' 2 - 
 They are compofed of three membranous ftrata, 
 
 or coats. 
 
 I. Of an external, which Haller called a true 
 cellular coat, Albinus a nervous, Vefalius a carti- 
 laginous, others a tendinous, &c. It confifts of 
 CQndenfed cellular membrane, externally more lax, 
 but becoming by degrees more compact, as you 
 advance nearer to its internal furface, where it 
 i: overfpn ad with numerous fmall blood veffels. 
 
 To 
 
OF THE ARTERTES. 55 
 
 To this coat the artery appears to be chiefly in- 
 debted for its tone and elasticity. 
 
 II. The fecond or middle ftratum, is compofed 
 of tranfverfe fibres, afluming a lunated or falciform 
 figure and dire&ion ; its fubflance has a flefhy ap- 
 pearance, from whence it has been called the 
 mufcular coat, and in it the vital energy of the 
 arteries appears in a very particular manner, to 
 refide. 
 
 III. The laft and mod internal coat, is a mem- 
 brane of an extremely fmooth and polifhed furface, 
 which ferves as a lining to the cavity of the artery. 
 
 In the trunks and larger branches of the arte- 
 ries, thele coats may be diflin&ly obferved ; but 
 they are lefs evident in the more minute ramifica- 
 tions. 
 
 § 73- 
 All the arterial branches in the human body 
 take their origin from either one or the other of 
 two leading trunks. 
 
 The firjl of thefe trunks is the pulmonary artery, 
 which, rifing from the anterior ventricle of thr 
 heart, pafTes into the lungs. 
 
 D 4 The 
 
5 6 OF THE ARTERIES. 
 
 The fccond is the aorta, which rifes from the 
 pofterior ventricle of the heart, and fhoots its 
 ramifications into every part of the fyftem. 
 
 Thefe trunks are divided into branches, which 
 again undergo farther and more minute fubdi- 
 viiions. 
 
 § 74- 
 
 An opinion has been conceived and propa* 
 gated as an eftablifhed truth, that, throughout 
 the whole fanguiferous fyftem, the aggregate capa- 
 city of all the branches, taken together, is fuperior 
 to that of the trunk from which fuch branches 
 dircclly originate. I fear, however, that the au- 
 thors of this opinion have exprefTed tbemfelves 
 on this fubjeel: in terms by far too general, and 
 have fometimes even confounded the meafure of 
 the diameter of veffels, with that of their nrea. In 
 my inveftigations and inquiries on this fuhjecr, I 
 did not truft to the refult of a fingle experiment, 
 nor did I confine my experiments to veffels filled 
 with wax, which, however improper, were the 
 only kind ufed by fome celebrated phyfiologiits, 
 in their attempts to afcenain the matter now under 
 conlideration ; but, as the nature and importance 
 of the fubjeel: evidently demanded, I made my 
 experiments and obfervations on the found and 
 rnakered veffels of fubjecls recently dead. I took, 
 
 for 
 
OF THE ARTERIES. 57 
 
 for example, that namelefs trunk from which the 
 ri^ht carotid and fubclavian arteries diverge as 
 branches, and alfo the brachial trunk, together 
 with its branches, the radial and cubital arter'es, 
 and having formed a rectangular triangle, from 
 the di. .meter of the trunk and the diameters of its 
 appended ramifications, I found, from the well 
 known theorem of Pythagoras, that the iquare 
 of the hypothenufe was equal to the fum of the 
 fquares of the bafc and perpendicular. 
 
 Indeed, in arteries of the (mailed orders, Haller 
 himfelf acknowledged that the capacity of the 
 trunks is greater than that of their ramifications ; 
 fo that, at lead, the common calculation does not 
 apply univerfally, but, (if it be indeed ever admif- 
 fible), mud be reftri&ed to a very few orders of 
 vefTels. 
 
 S 75- 
 
 Each trunk and ramification, feparately confi- 
 dered, have been commonly believed to pofTefs 
 a conical figure, the bafe, or that part next to 
 the heart, being fuppofed more capacious than 
 the oppofite extremity. This opinion appears 
 however to be hypothetical : for, whoever will 
 take the trouble of examining the arteries with 
 accuracy and attention, will find their figure to be 
 perfectly cylindrical : indeed, on the other hand, 
 
 there 
 
5 8 OF THE ARTERIES. 
 
 there are not wanting inftanccs of fome arteries 
 which in their progrefs rather widen and expand, 
 fuch, for example, are the mammarise interna?, or 
 internal rnammaries, and even the arch of the 
 aorta itfelf is more contracted at its bafe than at 
 its apex or top. All arteries, efpecially thofe of 
 the larger orders, appear to be a little dilated and 
 enlarged, jufr before their divifion into branches. 
 
 § 7& 
 
 The number of orders, formed by the divifions 
 of the main arterial trunk into the progrellive 
 feries of uniformly decreafing ramifications, from 
 its firfl origin at the heart, to its final termination 
 in the extreme capillaries, cannot poiTibly be uni- 
 verfally afcertained and eftablifhed as a general 
 and unvarying refult. The truth of this pofition 
 will be obvious to any one who confiders, that in 
 the different parts of the body, efpecially in the 
 vifcera, the arteries are fubjecl: to great variety 
 with refpect to their divifions ; and that, on this 
 account, they fomctimes form more, fometimes 
 fewer orders of vefTels, previoufly to their fepa- 
 ration into evanefcent capillaries. 
 
 Hence the disagreement of authors who have 
 attempted to amufe themfelves with calculations 
 of this kind. Thus, for example, Keil eflimated 
 the number of the orders of arteries at fifty, while 
 
 Haller 
 
OF THE ARTERIES. $ 9 
 
 Haller contended that they amount to no more 
 than twenty. 
 
 S 77- 
 
 After numerous divifions of this kind, and va- 
 rious anaftomofes, by which the neighbouring 
 branches of arteries communicate with each other, 
 they at length arrive at their final terminations, 
 which are completely continuous with, or which 
 fairly open into, the origins of veins ; fo that, 
 (heir route being uninterrupted, they are reflected 
 from extremities that can fcarcely be difcerned, 
 and thus converted into thofe returning veffels, by 
 which the blood, lately arterial, but now become 
 venous, is conveyed back again to the heart. 
 
 § 78. 
 But although this complete continuity of the 
 arteries and veins be fo extremely evident in nu- 
 merous parts of the body, as to be obvious even 
 to the naked eye, yet it ilill remains a matter of 
 doubt, whether this be the only and exclufive 
 mode, in which arteries communicate with veins, 
 or whether there may not be, at lead in certain 
 parts of the fyflern, an intermediate and parenchy- 
 matous fu.bit.ance, which receives the blood from 
 the terminations of the arterits, and again depo- 
 fits it in the incipient mouths of the veins ? 
 
 There 
 
Co OF THE ARTERIES. 
 
 There occur certain phenomena, fuch for ex- 
 ample, as erections of the penis, and the common 
 phenomenon of blufliing, which render the ex- 
 iftence of fuch a connecting medium between 
 thofe two kinds of veffels, at lead not improbable. 
 
 § 79- 
 There are, again, veffels of a nature evidently 
 different from thofe already fpoken of, which ap- 
 pear to arife every where from the fmaller arte- 
 rial branches ; thefe veffels confift chiefly of two 
 kinds, namely, the ferous, which are fo narrow as 
 not to be able in a healthv fubject to admit the 
 globules of the cruor, but only to receive the 
 thinner fluid or vehicle in which thofe globules 
 fwira (§ 69.) ; and the fecrctory, which do not 
 appear to attract any thing from the mafs of arte- 
 rial blood, but fuch fpecific fluids as are deftined 
 for fecretion (§ 4.) 
 
 § 80. 
 
 With regard to the former kind of veffels, 
 which we denominated ferous, it is neceffary to 
 obferve, that we do not mean by them the imagi- 
 nary orders of yellow and of white veffels, fpoken 
 of by Boerhaave, which appear to have been fan- 
 cifully conceived, in conformity to the account 
 given by Lecuwenhoek of his equally imaginary 
 fixfcld conformation of the globules of the blood : 
 
 neither 
 
OF THE ARTERIES. 61 
 
 neither do we mean the neuro-lymphatic veffcls 
 of Vieuflen and Ferrein, of which thofc gentle- 
 men fuppofed the vifcera to be in a great meafure 
 compofed ; but which do not indeed appear to be 
 any better founded than the preceding conjectures 
 of Boerhaave and Leeuwenhoek. 
 
 By the ferous we mean thofe colourlefs veflfels 
 which are never vifible, unlefs in certain cafes of 
 violent inflammation, where the impetus of the 
 blood is very powerful ; and indeed in fome parts 
 of the body, even this energetic procefs of nature 
 is not of itfelf fufhciently powerful to bring them 
 into view, unlefs they be dill farther dilated by 
 means of an anatomical fyphon or injector : of this 
 latter description are, for example, the vefTels of 
 the cornea, which can fcarcely ever be filled with 
 wax, unlefs in the dead bodies of fuch fuhjects as 
 have died while labouring under a violent inflam- 
 mation of the eyes. 
 
 § Si. 
 
 The fecretory veflels, on the other hand, appear 
 to be different from thofe, and belong chiefly to 
 the fecreting vifcera and conglomerate glands •, 
 they can alfo be traced by means of a very fubtle 
 injection, which, for inflance, when thrown with 
 force into the artery of the parotid gland, flows 
 out and efcapes through the duel of Stenonius. 
 
 But 
 
61 OF THE VEINS. 
 
 But on thefe veffels we will have a ftated oppor- 
 tunity of being more pointed and particular in a 
 fubfequent fcclion. 
 
 SECT. VIII. 
 OF THE VEINS WHICH CARRY BLOOD. 
 
 § 82. 
 
 X HAT blood, which, by means of the 
 arteries has been diftributed throughout every 
 part of the fyftem, mufl be conveyed back again 
 to the heart through the medium of the veins. 
 
 Thefe veffels differ very widely from the arte- 
 ries, both in their functions and flruclaire : to this, 
 however, veins of the fmalleft orders form an ex- 
 ception, as their ftruclure does not differ from that 
 of arteries of the fame magnitude in fo wide and 
 obvious a degree. 
 
 § S3- 
 The veins (if we except the pulmonary fyftem) 
 are more capacious in their collective or aggregate 
 dimenfions than the arteries ; their ramifications 
 are alfo more numerous ; they are much more ir- 
 regular in their courfes and modes of ratifying j 
 
 their 
 
OF THE VEINS. 6j 
 
 their texture is alfo much fofter than that of the 
 arteries ; they are far lefs elaftic, but nevertheless 
 extremely tenacious, and capable of wonderful ex- 
 pa nfion. 
 
 § »s- 
 
 Their coats are considerably thinner than thofe 
 of the arreries ; whence the blood which they 
 contain appears in fome meafure through them ; 
 they are alfo lefs numerous, being no more than 
 a certain. cellular coverings fomewhat refembling 
 what has been called the nervous coat of the ar- 
 teries, and an internal membrane of a very exqui- 
 fite polilh, fimilar to that with which the arteries 
 are lined. 
 
 No part of the venous fyilem is furnifhed with 
 mufcular fibres, except the larger trunks near the 
 heart. 
 
 § 86. 
 
 In by far the greater number of the larger 
 veins, fuch, for example, as exceed in their dia- 
 meter the twelfth part of an inch, this internal 
 membrane forms, by its foldings, an immenfe num- 
 ber of valves of the moft. beautiful ftru&ure, ex- 
 ceedingly pliant or moveable, and exhibiting the 
 appearance of fmall facks : they are, for the mod 
 part, fimple and alone, frequently however, ar- 
 1 rataged 
 
64 OF THE VEINS. 
 
 ranged in pairs, and fometimes in riplets ; and 
 are fo fituatcd and difpofed, that the bottom of 
 the little fack points to the origin of the vein, 
 while its mouth or orifice opens, and is directed 
 towards the heart. 
 
 Thofe fmall valves are, neverthelefs, wanting in 
 the veins of certain pans, as in thofe of the ence- 
 pha'on, the lungs, Sec. and in the whole fyftem of 
 the vena potarum. 
 
 § 87. 
 
 The fmall ramifications of the veins (which 
 would, indeed, with more propriety be called their 
 radicles or little roots) form, by their jun&ions, 
 larger branches, and thefe unite finally into fix 
 leading trunks ; viz. the two vena cava, one cal- 
 led the fupcrior, the other the inferior, and the 
 four trunks of the pulmonary vein. 
 
 The vena portaritm alone exhibits one pheno- 
 menon peculiar to itfelf. The trunk of that vein, 
 on entering the liver is, after the manner of an 
 artery, immediately divided into branches, the 
 extreme ramifications of which become, at length, 
 radicles to the inferior cava, and finally lofe them- 
 felves in the bofom of that trunk. 
 
 1 § 83, 
 
OF THE VEINS. if 
 
 § 88. 
 We need not, on the prefent occafion, again 
 advert to the common, and by far too general, 
 opinion, that the areas of the branches are more 
 capacious than the area of the trunk from which 
 they rife, nor yet to that refpecling the conical 
 figure of fingle veffels, as what was faid on thofe 
 fubjects, when treating of the arteries (§ 74, J$.), 
 will apply with fufficient precifion to the veins. 
 
 There are alfo among the veins, a few examples 
 of veffels being more capacious at a more remote 
 distance from the heart ; fuch, for inflance, is the 
 vena poplitea, where it pafTes between the condyls 
 of the os fcmoris. 
 
 What has been already faid, with regard to the 
 final terminations of the arteries (§ 77, 78, 80.), 
 may, by making fuch obvious and neceflary 
 changes, as are adapted to the different nature 
 and circuinftances of our fubject, be fitly applied 
 to the origins of the veins. 
 
 TOL. I. 
 
 E SECT.. 
 
66 OF THE HEART. 
 
 SECT. IX. 
 
 OF THE HEART. 
 
 § 89. 
 
 1 HERE cxifls, as we have already had 
 occafion to obferve (§ 65), a two-fold communi- 
 cation between the arteries and veins: one, for 
 inftance, at the minute extremities of each kind of 
 veffels (§ 77) ; and the other at the heart, their 
 common fountain, in which the leading trunks of 
 the whole fanguiferous fyitem meet. 
 
 § 9°- 
 The heart is, as it were, the firft. active orgafc 
 and moving fpring of the whole human machine, 
 as it is by the perpetual and truly aftonifhing 
 energy of this body, that the mod important vital 
 function, namely, the circulation of the blood, it 
 performed, from fo early a date of our exiftence, 
 as the fourth week after conception, down to the 
 clofing period of tranfient life. 
 
 § 9 1 - 
 
 This active organ, by its alternate dilatation 
 and contraction, firft: receives and again ejects the 
 blood in the following manner. Into the anterior 
 venous finus, and its appendage, the anterior auri- 
 cle 
 
OF THE HEART. 67 
 
 €le of the heart, the blood is conveyed from the 
 whole body, by means of the two vena cava, viz. 
 the fuperior and inferior, and likewife from the 
 fubftance of the heart itfelf, by means of the coro- 
 nary veins, the common orifice of which is fur- 
 nifhed with a valve of a peculiar ftru&ure ; and 
 from this auricle, it is again conduced into the 
 correfponding ventricle of the fame fide^ 
 
 § 92^ 
 
 From this anterior ventricle (formerly called 
 the right ventricle, in conformity to the fituation 
 of the heart in brutes) the blood is thrown into 
 the lungs through the pulmonary artery, which 
 was called by the ancients vena arteriofa; from 
 thence, by the four pulmonary veins, called in 
 former times arteria venofa, it is conduced into 
 a common finus, formed by their conflux, and 
 thence again into the correfponding auricle ; thefe 
 were once called the left, but are now more pro- 
 perly named the pojlerior, finus and auricle. 
 
 § 93- 
 From the pofterior auricle it pafTes on to the 
 
 ventricle of the fame fide, from whence it is diftri- 
 
 buted, by means of the aorta, through the whole 
 
 arterial fyftem appropriated to the other parts of 
 
 the body, and by the coronary arteries, through 
 
 the fubftance of the heart itfelf. 
 
 E 2 §' 94. 
 
63 OF THE HEART. 
 
 § 94- 
 The blood having palled from the extreme and 
 
 ultimate branches of the arterial, into the incipient 
 
 radicles of the venous fyjlem, re-enters the two 
 
 vena? cava?, (while that from the coronary arteries 
 
 is alio returned by veins of the fame name), and 
 
 thus the whole collective volume refumes again, 
 
 and inceffantly continues, the fame circuitous route 
 
 already defcribed. 
 
 § 95- 
 This circular and regularly progrefUve motion 
 of the blood through the cavities of the heart, is 
 powerfully directed, and the regurgitations of that 
 fluid are completely prevented, by means of fmall 
 valves, which furround and ferve as portals to the 
 principal avenues which lead to the heart. Thefe 
 valves are fituated on the margins, or extreme lips, 
 of the ventricles which are adjacent to, and look 
 towards, their correfponding fmufes, and alfo at 
 the mouths of the two great arterial canals leading 
 out of thofe ventricles. 
 
 § 9 6. 
 
 Thus a fmall venous ring or tendon, which 
 forms a partition between the anterior finus and 
 ventricle, defcending into the cavity of the latter, 
 feparates into three fmall valves of a tendinous 
 appearance, each one of which was formerly be- 
 lieved to divide again into three apices or points, 
 
 from 
 
OF THE HEART. 69 
 
 from whence they received the name of valvules 
 trigiochines or tricitfpides, Thefe valves are con* 
 netted at their points to fiefhy columns, common- 
 ly called miifzull papillarcs. 
 
 § 97- 
 
 In like manner another fmall ring of the fame 
 kind, which constitutes a partition between the 
 pofterior finus and ventricle, is alfo divided into 
 two fmall valves, which, from a certain fuppofed 
 refemblance to ^facerdotal mitre, have been called 
 valvule mitralcs. 
 
 §98. 
 
 At the entrance into the pulmonary artery, as 
 alfo at the mouth of the aorta, are fituated, in an 
 annular or circular pofition, three valves much 
 fmaller indeed than thofe already defcribed, but 
 of a very elegant and beautiful figure and appear- 
 ance, and furnifhed with fiefhy fibres ; thefe have 
 been called valvule femilunares or Jigmoides. 
 
 § 99- 
 Now it evidently appears, that by means oi 
 
 thefe different kinds of fmall valves, fufficient pro- 
 vifion is made againfl: the irregular, confufed and 
 retrograde movement of the blood. They eafily 
 yield, and afford a paffage to the blood when ad- 
 vancing regularly forward in the edabliflied courfe 
 E 3 of 
 
7 © OF THE HEART. 
 
 of its circulation. But they prevent the regurgir 
 tation of this fluid, by becoming, in confeq. ence 
 of its refluent effort, fully expanded like the fwell- 
 ing of a well-filled fail, and thus completely clofing 
 the orifices round which they are arranged. 
 
 § IOO. 
 
 The valve of Euflachius which, in the fcetal 
 ftate, is {Tretched like a curtain acrofs the mouth 
 of the afcending cava, becomes after birth (fooner 
 or later in different fubjedls) fo gradually oblite- 
 rated for the mod part, as to be rendered wholly 
 unfit for the execution of its former functions; 
 neither indeed does the fyflem (land any longer in 
 need of it, as a paflage is now opened and prepa- 
 red for the blood through the lungs, and its re- 
 turn from thofe vifcera prevented by the fcmihi- 
 nar valves already fpoken of, and as each fubfe- 
 quent column of blood, prcfling from behind, mufl 
 purfue the fame route with that immediately pre- 
 ceding it. But as it does fometimes notwithfland- 
 ing happen, that the paffage of the blood from 
 the right fide of the heart into the lungs is by 
 fome means obftructed, we then learn from the 
 preternatural pulfation obfervable in the fapericr 
 cava, that the blood is repelled in a retrograde di- 
 rection from the right fmus into the two adjoining 
 great venous trunks. 
 
 § I0 Q; 
 
OF THE HEART. ?l 
 
 § 101. 
 
 It is a point of controvcrfy, whether or not the 
 femilunar valves fufFer the ventricles to be perfect- 
 ly and completely evacuated, or whether they do 
 not rather by means of their expanfion intercept 
 a part of the blood in its efcape from thofe cavi- 
 ties, and thus force it to take in fome meafure a re- 
 trograde courfe. 
 
 Obfervations made on frogs, and even on the 
 minute heart of the nafcent chick, prove that in 
 thofe animals the heart is indeed completely eva- 
 cuated ; but whether or not the fame thing takes 
 place in man himfelf, when in a found ftate of 
 health, is not yet clearly afcertained ; if, however, 
 it be admiffible, in phyfiological difcuffions to fpe- 
 culate and draw conclufions from the ftru£hire and 
 mechanifm of thofe valves themfelves, as they ap- 
 pear on the dhTe&ion of the heart, the contrary 
 opinion appears the mod probable. 
 
 § 102. 
 The texture of the heart is altogether lingular, 
 and peculiar to that organ. Ic is indeed fldiiy, 
 but remarkably clofe and compact, and widely dif- 
 ferent from the common conflitution and appear- 
 ance of mufcles. 
 
 It 
 
72 OF THE HEART. 
 
 It is compofcd of fmall bundles of fibres, more 
 or lefs oblique, frequently ramifying in a lingular 
 manner, contorted and wound fpirally in diverii- 
 lied and truly ftrange directions ; thefe fibres lie 
 over, and reft on, each other in certain orders of 
 ftrata, they are intermingled and clofely knit to- 
 gether in the feptum which feparates the two ven- 
 tricles, and are faflened and firmly connected at 
 the bafis of thofe ventricles by four cartalaginous 
 rings or bands, which (according to the accurate 
 unravelling and developement of the whole fibrous 
 texture of the heart, lately executed by the inde- 
 fatigable and illuftrious Wolff), appear to ferve as 
 a flay and fupport to the Jlefljy Jlraclure of the 
 ventricles, and alfo to feparate and difiinguiih it 
 from the fibres of the fmufes. 
 
 § 103. 
 Thofe fiefhy fibres are every where overfpread 
 with an infinitude of fmall nervous ramifications 
 of extreme foftnefs, but they are more particularly 
 fupplied with fuch an immenfe apparatus of blood 
 vefftls, aiifing from, and belonging to, the coro- 
 nary arteries and veins, that Ruyfch has declared 
 in his writings, that the whole fabric of the heart 
 appears to be compofed folely of fanguiferous 
 tubes. 
 
 § i°4- 
 
OF THE HEART. 73 
 
 § 104. 
 
 By means of the foregoing Jlruclure (§ 90. 
 feq.) and texture (§ 101. feq.) the heart is fitted 
 for the performance of thofe perpetual and uni- 
 formly equable movements, which return in fuch 
 general order, that the preliminary appendices 
 and ventricles themfelves, are alternately contrac- 
 ted and relaxed, or perforin, in alternate times, 
 thofe motions, called in phyfiological language, 
 fyftole and diajlole. 
 
 § 105. 
 
 With fuch definitude do they preferve this har- 
 monious order in their routine of contraction and 
 dilatation, that as foon as the appendices contract, 
 themfelves, to propel the blood, returning from 
 the lungs and vence cava?, into the ventricles, 
 thefe latter are at the fame inftant relaxed and 
 fitted to receive the fame advancing wave of 
 blood ; but in the fubfequent and next moment, 
 when it is the point of time for the ventricles, 
 now recently filled, to contract and force the blood 
 into the two arterial trunks, the appendices are 
 again relaxed, and their mouths rendered patulous 
 for the purpofe of drinking in a frefh tide of ve- 
 nous blood as it rolls on in its ufual courfe. 
 
 § icO. 
 
*4 OF THE HEART. 
 
 § 1 06. 
 
 This fyflole of the ventricles, which is fuppoi'ed 
 to confume about one third part of the whole time 
 of the heart's pulfation, is pt rformed in fuch a 
 manner, that the exterior fides of thofe cavities 
 are approximated and cortr cted towards the in- 
 tei-mediate feptum which feparates the right ven- 
 tricle from the left; which contrnclion, efpecially 
 if we attend to the conical h* ure of thofe cavities, 
 appears fully fufficient to evacuate them of their 
 contents. 
 
 But befides this approximation of the lateral 
 parts of the heart towards each other, the apex 
 of that organ is, during its fyflolic motion, con- 
 tracted towards, and brought nearer to its bafis ; 
 as has been frequently obfcrved not only in the 
 inferior animals both of cold*, and zuarm blood, 
 but even in man himfelf, while in a living ftatef. 
 
 * I have not in the live-di flection of any animal discover- 
 ed the heart more evidently fhortened, during its fyftolic 
 motion, than in that of coluber vatr'tx or water ferpent. 
 Throughout the forelts in the neighbourhood of our city, 
 this fpecies of ferpent may be fometimes found four feet in 
 length. Having taken one of thefe animals and fufjectcd it 
 in a living Mate to the anatomic knife, I obferved that the 
 length of its heart during the diajlolie, exceeded its length 
 during thcjjjlo/ic motion, at lead tire fpace of two lines. 
 
 f It does not, however, appear that this diminution of 
 
 the longitude of the heart during its fyftolic motion is an ab,. 
 
 4 folute 
 
OF THE HEART. 75 
 
 An argument feemingly in favour of a contrary- 
 opinion has been derived from, and founded in, 
 vulgar experience, from which it appears that the 
 apex of the heart ftrikes, during its fyftolic mo- 
 tion, againft the left mamma or bread, and feems 
 therefore to be rather elongated than contracted 
 and fhorrened ; this apparently conclufive argu- 
 ment will however have no weight with one who 
 confiders, that thofe fenfible percuffions or flrok.es 
 of the heart are to be attributed as well to the im- 
 petus of the venous blood ruining into the appen- 
 dices of that organ, as to that of the arterial blood 
 forcibly ejected from its ventricles ; by both which 
 fources of propulfion the whole heart is carried 
 towards and impinged againd that region of the 
 ribs. 
 
 § '©7- 
 The impetus, which is by this fyftolic contrac- 
 tion of the heart imparted to the blood, is coiri- 
 
 folute condition of life. I am led to the adoption of this 
 opinion from a variety of obfervations made on the heart of 
 a duck, in a grtat portion of which a complete offificatinn 
 had taken place. This heart was depolited in my anatomi- 
 cal colleftion by my very liberal and worthy friend C. F. Mi- 
 chaelis, and is marked by completely offif ed ftrice running 
 from its bafe to its apex. On its fides, however, it was {till 
 furnifhed with fkfliy fubftance fufficient to continue the late- 
 ral motion of its ventricles; and thus preferve the circulation 
 of die blood. 
 
 jmunicated 
 
-j6 OF THE HEART. 
 
 municated to the arterial fyftem, receiving the 
 blood, in fuch a manner, that every fyftole of the 
 heart may be plainly perceived in fuch arteries of 
 the other parts of the body as can be fek by the 
 touch, (of which defcription are all thofe that ex- 
 ceed in their diameters the fixth part of a line), 
 and liktwiie in fuch other arteries as can by any 
 means whatever have their pulfations rendered 
 obvious to the fenfes : this can be eafily effected, 
 for example, in the internal ear or eye, in either 
 of which a fingular kind of motion can be excited 
 and rendered fenfible, which (as well as the fame 
 kind of throbbing or pulfatory motion fo percep- 
 tible in the other parts of the arterial fyftem) is 
 called the diaftole of the arteries : of this diaftolic 
 motion we (hall have an opportunity to fpeak on 
 a future occafion, at which time we will take up 
 the inquiry, whether or not it is to be attributed 
 folely to the action of the arteries themfelves, or 
 derives its exiftence from fome other fource. 
 
 § 108. 
 In whatever manner this point may be deter- 
 mined, one thing we learn from experience, the 
 fureft guide to truth, viz. that in a healthy fub- 
 jec~t, what is called the pulfe of the arteries, is 
 precifely fynchronous with, and perfectly corref- 
 pondent to, the motions of the heart ; and like- 
 wife in a morbid intermiflion cf the pulfe, the 
 
 heart 
 
OF THE HEART. 77 
 
 heart and arteries (till harmonize in their action, 
 by eeafing from, and again commencing, motion 
 at precifely the fame moments. 
 
 § 109. 
 The frequency of the pulfations of the human 
 heart in a healthy (late, is extremely different in 
 different fubjects. This diverfity arifes principally 
 from diverfity in point of age, but partially alfo 
 from other conditions of the fyffem, which at any 
 and every period of life conftitute the health pro- 
 per to each individual ; fo that it is not pofliblc 
 to afcertain and eltablifh, on this fubjecl, any cer- 
 tain and definite rule. It may neverthelefs be pro- 
 per to mention the general refult of my obferva- 
 tions (made in our own climate) on the frequency 
 of the pulfe in the different periods of human life. 
 
 In the firft days after birth I have generally 
 found the pulf itions of the heart of the tender in- 
 fant, while found afleep, amount to about 140 in 
 the fpace of a minute. 
 
 At the expiration of the firfl year, they amount 
 to 124 iu a minute. 
 
 At the end of the fecond year to about 1 10. 
 
 At the end of the third year to about 96, &c. 
 
 At 
 
7* OF THE HEART. 
 
 At that period in which the firft fet of teeth, 
 ufually culled the milk -teeth, drop out, the pulfa- 
 tions of the heart amount to 86 in a minute. 
 
 At the age of puberty to about 80. 
 
 In the prime of life, or at the period of man- 
 hood, to about j$. 
 
 And to about 60 at the fixtieth year of human 
 life. 
 
 In fubjedls ftill farther advanced in years, I have 
 fcarcely found two in whom the number of pulfa- 
 tions were the fame, at the fame period of old 
 age. 
 
 § no. 
 All other circumftances being alike, the pulfa- 
 tions of the heart are more frequent in females 
 rhan in males. 
 
 If proper and neceffary allowance be made for 
 the habit of body, they are lefs frequent in men 
 uncommonly tall, than in fuch as are rather low. 
 This circumftance I have afcertained to be a truth 
 by comparative obfcrvations made on the pulfes 
 of dwarfs, and giants or men remarkably large. 
 
 § n i« 
 
OF THE KEARTv 79 
 
 § III. 
 
 On the fubjeft of thofe varieties in the pulfe* 
 occafioned by extraneous circumjiances, vulgarly 
 called non-naturah, it is neceffary to obferve, that 
 a Cold climate produces a flow pulfe ; thus, for 
 inftance, the heart of a Greenlander when in 
 perfect health, does not pulfate oftner than from 
 thirty to forty times in a minute. 
 
 But it is an obfervation as common as it is 
 true, that the pulfe becomes more frequent after 
 the taking in of aliment, and after an emiffion of 
 femen* The fame effect is alfo produced on the 
 pulfe by a want of deep, by bodily exercife, or 
 by paffions of the mind. 
 
 The foregoing obfervations relate to the na- 
 tural or healthy pulfe, in the confideration of 
 which it feems more confident, and agreeable to 
 nature, to direft our views to the heart, as its ex* 
 clufive fource, than to the arteries, on which 
 phyfiologifls have ufually fixed their attention 
 when engaged in the inveiligation of this fubjecT:. 
 
 In this inceffant routine, the heart continues its 
 pulfations, down to the extreme glimmerings of 
 life's perifhable flame ; and even then, all its parts 
 tlo not ceafe from a&ion at the fame moment, 
 
 but 
 
tto i)F THE HEART. 
 
 but it is the prerogative of the right ventricle 
 with its appendices, the right auricle and finous, 
 furvive the left ventricle, and its appendices. 
 
 This may be fufficiently illuftrated in the fol- 
 lowing manner : After the laft act of expiration, 
 the lungs now in a collapfed ftate, can no longer 
 admit the blood to flow through them in its cuf- 
 tomary channel, while at the fame time that wave 
 of blood which they have jult returned to the left 
 fide of the heart, is from thence forccably expel- 
 led through the aorta, and thus urges forward by 
 a ids a tergo the advancing column of venous 
 blood : from this combination and concurrence 
 of circumftances, the blood returning with preci- 
 pitation and impetuofity, ruflies violently into the 
 appendices and ventricle on the right fide of the 
 heart, in confequence of which the parietes of 
 thofe cavities are thrown into convuliive efforts, 
 and thus continue to be agitated, for fome time, 
 after the left fide of that organ is completely de- 
 prived of all vital motion. 
 
 § 1*3- 
 
 From a knowledge of this fad, viz. that 
 during the laft vital efforts of declining nature, 
 the blood is propelled into the cavities on the 
 right fide of the heart, we deduce, with the ut- 
 moft eafe, the caufe of that ftate of depletion in 
 i which 
 
OF THE HEART. Si 
 
 which the larger arteries are found after death. 
 To the fame caufe aifo Weifs, and after him the 
 illuftrious Sabatier, were defirous of attributing 
 the fuperior fize of the cavities on the right, to 
 that of thofe on the left, fide of the heart, efpe- 
 cially in the corpfe of an adult fubjecT:. 
 
 § H4- 
 
 The whole of this motion of the heart, which 
 
 has been the fubject of the preceding obferva- 
 tions, is to a very confiderable degree limited and 
 dire&ed by the pericardium, in which the heart 
 loofely hangs, and by which it is completely en- 
 clofed as in the walls of a prifon. 
 
 The pericardium is a membranous fac, confid- 
 erably capacious, and accommodated to the figure 
 of the heart which it enclofes. It takes its oricrin 
 from the membranes conftituting the mediaftinum, 
 and although, from its finenefs, it may appear fome- 
 what tender, yet we learn from the experiments 
 of Wintringham, that it is fo very tenacious and 
 firm, as far to exceed in (Irength all other mem- 
 branes of a fimilar nature in the human body. 
 
 That the pericardium is a part of the firft 
 
 importance in the animal economy, we fafely 
 
 infer from this fingle circumftance, namely, that 
 
 throughout all claffes of animals pofTefling red 
 
 voi.. i. F blood, 
 
82 OF THE HEART. 
 
 blood, it is found as conftantly and uniformly ex- 
 iting as the heart itfelf ; and records do not fur- 
 nilh more than one or two examples of the human 
 heart having been found completely deftitute of a 
 pericardium. Thefe fingular examples of fuch an 
 unnatural (late of the heart are recorded in the 
 writings of Dinkier. 
 
 § 115. 
 The internal furface of the pericardium is kept 
 conftantly humid by a dew-like ferous efTufion, 
 which appears to exhale from the fmall arteries 
 of the heart itfelf. 
 
 In like manner a fluid, of a fimilar nature, ap- 
 pears to tranfude into the very cavities of the 
 heart, and to moiften and lubricate their furround- 
 ing parities or walls. 
 
 In either cafe the efTufion during the healthy 
 flate of the part is of a ferous nature, and not ac- 
 companied by any real lymph, unlefs the heart be 
 labouring under inflammation ; but when this or- 
 gan becomes the feat of an inflammatory affection, 
 then genuine lymph tranfudes, giving rife, on the 
 external fuperficies of the heart, to fine filaments 
 of a hair-like appearance, together with thofe 
 preternatural portions of cellular membrane, 
 which in fuch cafes connect the heart to the 
 
 pericardium. 
 
POWERS, &c. 83 
 
 pericardium, but on the interior furfaces of the 
 cavities themfelves producing excrefcences of a 
 truly polypous nature. (§ 19.) 
 
 SECT. X. 
 
 OF THE POWERS BY WHICH THE BLOOD IS 
 KEPT IN MOTION. 
 
 _LlAVING thus completed the confid- 
 cration of the organs in which the blood is con- 
 tained, we now pafs on to take a view of the 
 powers, by which thofe organs are qualified and 
 fully prepared to keep that vital fluid in motion. 
 
 Let us, in the firft place, take an attentive and 
 accurate furvey of thofe powers which refide in 
 the heart itfelf, and which ought, without doubt, 
 to be confidered as by far the mod active and ef- 
 fential in the great buiinefs of circulation : we 
 will then proceed to confider what may be called 
 the fecondary and affiftant powers, which we will 
 alfo find of high importance in the animal econo- 
 my, from the concurrent and effective aid which 
 they afford to the action of the heart. 
 
 F 2 5 117. 
 
*4 POWERS WHICH KEEP 
 
 § 117- 
 It will at firft view appear obvious to even the 
 moil fuperficial obferver, that it is a matter of 
 Herculean difficulty indeed, either to afcertain by 
 accurate calculation the force of action exerted 
 by the heart, or to determine with precifion the 
 quantity of blood thrown into the aorta by that 
 organ at each pulfation ; neither will the fpecula- 
 tive phyfiologifl find himfelf belet with difficulties 
 of lefs moment, when he attempts to afcertain and 
 eftabliih with definitude, either the diftance to 
 which each projected wave of blood is carried by 
 the impetus it receives from the heart alone, or 
 yet the celerity with which fuch wave rolls for- 
 ward ; but he will be furrounded with difficulties, 
 ftill encreafing at each advancing ftep, in his at- 
 tempts to render a jufl ftatement and accurate ac- 
 count of all fuch obftacles as oppofe, and thus 
 greatly diminiih the effects of the force exerted 
 by the heart, in its action on the circulating maf> 
 of fluids. 
 
 § 118. 
 
 A certain eflimation may neverthelefs be formed 
 of the power of the heart, by collecting and com- 
 paring the mod probable conjectures which have 
 appeared on the above points of phyfiological fpe- 
 culation. Thus for inftance, if we fuppofe the 
 whole mafs of blood to amount at a mean rate to 
 
 33 
 
 
THE BLOOD IN MOTION. 8$ 
 
 ^ pounds, i. e. 396 ounces (§ 23), and eftimate 
 the number of pulfations at 75 in a minute, /. e. 
 4500 every hour (§ 109) ; and further, if we 
 adopt the opinion that at each fyftole the left ven- 
 tricle ejefts two ounces of blood, it will then fol- 
 low, that during the courfe of every hour the 
 weight of the whole volume of blood makes 11% 
 complete tranfitions through the heart. We may 
 alfo form a tolerable conception and eftimation 
 of the impetus with which the circulating blood 
 is propelled from the left ventricle of the heart, 
 by obferving with what aftonifhing violence, and 
 to what a confiderable height, the blood fpouts 
 from one of the larger arteries when wounded in 
 the neighbourhood of the heart. Thus, from 
 the wounded carotid of an adnlt fubjedl, I have 
 feen the blood, during a few of the firft contrac- 
 tions of the heart after the accident, mount in 
 jets to the height of at lead: five feet. 
 
 § JI 9« 
 But when we inftitute an enquiry for the dif- 
 
 covery of thofe unfailing fountains or fprings, 
 
 which fupply the heart with a force fo powerful, 
 
 and at the fame time fo uninterrupted and lafting, 
 
 that which firft attracts our attention, as being 
 
 foremoft both in point of time and importance is 
 
 its irritability ', (§ 44). This vital energy, as has 
 
 teen already evinced (§ 90), is much longer pof- 
 
 F 3 fefled 
 
86 POWERS WHICH KEEP 
 
 fefTed by the heart, than by any other mufcular 
 part in the whole human body. 
 
 That the parietes, or walls themfeves of the 
 cavities, are irritated and excited to contract by 
 reiterated impreffions from the circulating waves- 
 of blood, is manifeft from a well known experiment 
 of the illuftrious Haller. From this celebrated 
 experiment, of that indefatigable phyfiologift and 
 acute philofopher, it appears, that he could at 
 pleafure grant, either to the right or left fide of 
 the heart, the prerogative of a more protracted 
 vital motion, (/". c. of longer life) accordingly as 
 he firil deprived the one fide or the other of its 
 peculiar flimulus, the blood*. 
 
 § 120. 
 
 When the proportional quantity of the blood 
 is well adjufled to the fize of the containing veiTels, 
 and its quality uncontaminated by any morbid 
 change, its action on the heart, and the re-action 
 of that organ again on the blood, proceed with 
 fuch an equable, regular and happy facility, that, 
 when in a (late of reft, we are fcarcely fenfible of 
 the circulation of this vital fluid, which is the kind 
 and condant difpenfer of life and vigour to every 
 part of our bodies. 
 
 * See Haller " De motu cordis a ftimulo r.ato," in 
 Cornmentur. Soc. Sc'.ent. Goettingeas, torn. i. 
 
 Bat 
 
THE BLOOD IN MOTION. 87 
 
 But if the circulating volume of blood be either 
 too abundant, or preternaturally fcanty, but efpe- 
 cially if this vital fluid be contaminated by the 
 admixture of any foreign fubftance, as noxious 
 miafmata, air in an elaftic flate, or poifons in- 
 jected into the veins, &c. the heart, either roufed 
 immediately into excefiive action, or deprefied to 
 the oppofite extreme of proftration and debility, 
 continues no longer fit for the falutary difcharge 
 of its important function, but falls into motions 
 convu'five, irregular, and very widely different 
 from the equable tenor of its healthy action. Fo- 
 reign fubftances of the fame kind, as air blown 
 into the veins, &c. are alfo fometimes able to 
 roufe again, and excite to motion, the heart of an 
 animal recently dead. 
 
 § 121. 
 
 It has been a point of controverfy, even in very 
 modern times, whether this extreme irritability of 
 the heart be eflfentially inherent in its own fub- 
 ltance, or if it be not rather adventitious, and de- 
 rived, as fome celebrated characters would induce 
 the world to believe, from rhe myfterious influence 
 of the nerves ? We will hereafter have a fit oppor- 
 tunity of declaring our fentiments refpedting the 
 whole of this controverfy, when we come to con- 
 fider the doctrine of mufcular irritability, under 
 which head, this fubject of inquiry mod naturally 
 F 4 falls. 
 
SS POWERS WHICH KEEP 
 
 falls. On the prefent occafion it may fufficc to 
 obferve, that I am daily more and more convinced, 
 that irritability is a fpecics of vital energy altoge- 
 ther peculiar in its nature, belonging exclusively 
 to mufcular fibres, and completely diftincl: from 
 the vis nervea (§ 34, 45.) But, on the other 
 hand, it is no lefs evident and incontrovertible, 
 that the nerves do alfo polfefs a very powerful in- 
 fluence and command over the action of the heart : 
 this we learn, as well from the peculiar habit and 
 appearance of the cardiac nerves, from their foft- 
 nefs, their defect of covering, and their fingular 
 difpofition and arrangement, as from the aftoniih- 
 ing confent of the heart with by far the greater 
 number of the functions of the human body, even 
 with thofe of the mod oppofite nature. In tefli- 
 mony of the reality of this confent, it may be 
 fufficient barely to mention, the fudden and tran- 
 fient fympathy which, even in a healthy fubjec"t, 
 exifts between all the pafhons of the mind and 
 the heart, together with that, which, in a great 
 many fpecies of difeafe, manifests itfelf between 
 this organ and the prima via. 
 
 § 122. 
 
 But, befides ihofe vital energies of the heart, 
 
 it poirefTcs alfo another power, arifmg out of its 
 
 mechanical ftru&ure, which appears to contribute 
 
 not a little towards carrying on the circulation of 
 
 the 
 
THE BLOOD IN MOTION. 8 9 
 
 the blood. The cavities of this organ being 
 clofely contracted, in the time of its f) dole, and 
 the blood by this means completely expelled, a 
 vacuum is thus produced, into which, on the prin- 
 ciples of the well known law of derivation, the 
 neighbouring blood muft of neceffity flow ; for, as 
 the valves prevent the regurgitation of the wave 
 juft ejected, it follows of courfe, that the cavities 
 of the heart muft then drink in, and fwallow down, 
 with rapidity, the blood advancing in the trunks 
 of the veins. 
 
 § i 2 3- 
 We proceed now to enquire, whether or not, 
 any of the other organs through which the blood 
 pafles, befides the heart itfelf, are furnifhed with 
 powers contributary to the continuance of the 
 circulation of that fluid. Judging from firft prin- 
 ciples, or a priori, as it is termed, we are led to 
 fufpedt that fuch powers do exift ; for it appears 
 hardly probable, that the wifdom of nature has 
 entrufied fo important a function, on which the 
 life of fanguiferous animals immediately depends, 
 to one organ only, the faults and defects of which 
 might, in fuch cafe, with too much facility, be 
 attended with fatal confequences. But, reafoning 
 a po/leriori, as they term it, i. e. from actual cb- 
 fervations, made on the animal economy, we are 
 furnifhed with numerous facts fufficiem to eitablifh, 
 
 beyond 
 
po POWERS WHICH KEEP 
 
 beyond a doubt, the exiftence of fuch poweis, 
 which we may therefore term fecondary powers, 
 and which are able, not only to aid the action of 
 the heart, but, in fome cafes, to compenfate for 
 almoft the complete abfence of the influence of 
 that important organ. A finking inftance of this 
 nature, is the continued motion of the blood, in 
 certain parts of the body, on which the power of 
 the heart can have but very little effect, if indeed 
 it can extend to them at all : this phenomenon is 
 obfervable, as well in the venous fyflem of the 
 liver, ns in the placenta of the uterus ; not to 
 mention numerous instances of feetufes having 
 been born, without the fmalleft vefiige of a heart. 
 
 § i-*4- 
 
 Of thefe fecondary poivcrs, the mft to be men- 
 tioned is, the j "unci "ions of the Arteries, the influ- 
 ence of which, in promoting and continuing the 
 circulation of the blood, appears to be, indeed, 
 very confiderable ; although the true principles 
 and mode of their action, on this fluid, have not 
 yet been fully developed and eflablifhed. 
 
 Speaking in general terms, there exifls a very 
 confiderable refemblance between the arteries and 
 the heart itfclf: that the arteries, for example, 
 have a mufcular coat, is a facl of the utmoft pub- 
 hn:y(§;2.) 
 
 That 
 
THE BLOOD IN MOTION. 91 
 
 That they alfo poflefs irritability, has been very 
 generally known, fince the famous experiments of 
 the illuftrious Verfchuir. 
 
 And, further, as the afpect or difpofition of the 
 cardiac nerves on the heart itfclf is truly fingular, 
 thus alfo the larger branches of the arteries are, 
 here and there, furrounded with aflonifhing reti- 
 cular intertextures of foft nerves. 
 
 § 125. 
 Finally, It is well known to every one that the 
 arteries pulfate, and that indeed with fuch vehe- 
 mence and force, that if we fuffer one of our legs 
 to lie over the other knee, the pulfations of the 
 popliteal artery are fufficient to elevate in a fub- 
 fultory manner, the fuperincumbent leg not only 
 alone, but even with a very confiderable weight 
 appended to it. Indeed for a long time pall:, both 
 a fyftolic contraction and diaftolic relaxation have 
 been attributed to the arteries, which motions 
 have been faid to correfpond and harmonize with 
 the alternate contractions and dilatations of the 
 ventircles of the heart. 
 
 Though the truth of this laft propofition is 
 generally believed to be eftablifhed and confirmed 
 by the fimple teftimony of the fenfes themfelves, 
 the fubjeft is neverthelefs flill embarralTed with 
 
 various 
 
92 POWERS WHICH KEEP 
 
 various doubts and difficulties : thefe difficulties 
 immediately rife to view, when it is aiked, 
 whether this vibrating or pulfatory motion, 
 which is felt on examination by the ringer, is to 
 be attributed to the inherent energy of the ar- 
 teries, or to the impulfe of the heafrt ; and 
 whether the whole motion of the arteries does 
 not depend folely on the impetus with which the 
 blood is projected into the aorta, and thus im- 
 pinges againft the fides of that tube, and its rami- 
 fications ? 
 
 DifTe&ions of living animals have not been fuf- 
 ficicnt to decide this controverfy. For it fome- 
 times happens that during the live-d'nTections of 
 warm blooded animals you may difcover the lar- 
 ger arteries pulfating, while at other times again 
 they appear in a Mate of complete reft. In man 
 himfelf, while in the enjoyment of vitality, I had 
 once an occafional opportunity of obferving the 
 neighbouring trunks of the aorta and pulmonary 
 artery, to be perfectly deftitute of all motion ; 
 but it fhould not be forgotten, that this phenome- 
 non appeared in a cafe of monftrous or preterna- 
 tural formation of the parts. There are alfo ar- 
 teries which we fometimes feel in a ftate of violent 
 pulfation, and which we neverthelefs know, from 
 anatomy, are, in confequence of their fituation, 
 almoft immoveable; of this we have an example 
 
 in 
 
THE BLOOD IN MOTION. 93 
 
 in the cerebral carotid, where it pafles through 
 the canal of the os pctrofum. 
 
 § 126. 
 "When all circumftances relative to this fubj eel 
 are impartially weighed and difpaflionately consi- 
 dered, this appears to be the refult, viz. that the 
 diajlole or the larger arteries takes place in confe- 
 quence of their peculiar nature, and is to be attri- 
 buted to the impetus of the blood milling for- 
 cibly into them, and expanding their coats or tu- 
 nics, which, by means of their elafticity, imme- 
 diately return again to their natural dimenfions. 
 To the fame impulfc alfo mould be attributed 
 that lateral or curving motion of their axes, 
 which may frequently be obferved in the larger 
 arteries when they run in a ferpentine direction, 
 and lie einbedded in foft cellular membrane. 
 
 But in a found (late of the fyftem, we contend 
 that the arteries fcarcely exhibit any unequivocal 
 proofs of a true fyftole^ i. e. they do not by a ge- 
 nuine contra&ion recede from their natural^ to 
 fmaller dimenfions, as long as the heart is adequate 
 to the due performance of its momentous func- 
 tion ; but although it be certain, that the arteries 
 do not always, yet we acknowledge that they do 
 fometimes, exhibit and exercife a power of real 
 contraction : thus for mftance, when the heart is 
 
 deficient 
 
94 POWERS WHICH KEEP 
 
 deficient in its action in confequence of labouring 
 under either a morbid oillfication, or fome other 
 fpecies of difeafe, it is probable that then the 
 duties of this important organ devolve on, and 
 are difcharged by, the arteries, and that the 
 blood is thus kept in motion by the vital energy 
 of thofe animated tubes. 
 
 § * 2 7- 
 
 As it has been the decided opinion of feveral 
 celebrated phyfiologifts, efpecially the famous 
 Whytt, that the powers of the heart cannot pof- 
 fibly extend their influence to blood-veflfels of the 
 fmallefl: order, as, for example, to the extreme 
 terminations of the arteries, and to the incipient 
 radicles of the veins ; they have therefore attri- 
 buted the motion of the blood, in that part of the 
 fyftem, to a cerrain ofcillatory action of thofe mi- 
 nute veffels themfelves, by the help of which their 
 contents are propelled forward : and this fame vi- 
 bratory motion they have alio applied, with a 
 great deal of ingenuity, to explain and demon- 
 ftrate the nature of inflammation, &c. 
 
 There are indeed a variety of phenomena, as 
 well pbyfwlogical, which fhall be mentioned when 
 on the fubject of animal heat, as pathological, par- 
 ticularly obfervable in fpafmodic affections, ac- 
 companied with fever, which feena to favour the 
 
 exiftence 
 
THE BLOOD IN MOTION. 95 
 
 exiflence of fuch a power of ofcillatory motion, 
 although no fuch motion has ever been actually 
 obferved, even with the affiftance of glafles, in 
 the diffeclions of living animals. 
 
 • § 12S. 
 
 It yet remains to enquire alfo after thofe afllft- 
 ant powers, by which the other parts of the veins, 
 befides their radicles or incipient roots, are fitted 
 to complete finally the return cf the blood to the 
 heart. It appears, indeed, at the firft view of the 
 fubject, that the veins pofTefs and exert a much 
 imaller portion of the active vital energies than 
 the other parts of the fanguiferous fyftera, becaufe 
 the return of the vital fluid, contained in thofe 
 veilels, towards the heart, feems to be owing to 
 the impetus of the arterial blood urging it on b\ 
 a vis a tcrgo, as well as to the valvular dructure 
 of the veins themfelves, which effectually prevents 
 the blood from regurgitating:. That thefe minute 
 valves are of the utmoft importance in promoting 
 and continuing the regular and free circulation cf 
 the blood, is fatisfa&orily demonftratcd by the fre- 
 quent congeftioas and infarctions, which happen ia 
 thofe veins that originate in the inferior parts of 
 the abdominal cavity, and which are entirely de- 
 ftjtute of fuch valves. 
 
 But 
 
9 6 POWERS WHICH KEEP 
 
 But there arc neverthelefs a variety of argu- 
 ments which render it probable, that the trunks 
 of the veins do poflefs, and actually exert, certain 
 degrees of the vital energies ; as is well exempli- 
 fied in the veins of the liyer, and of the uterine 
 placenta (§123.), &c. 
 
 It is alfo well known to every one, that the ex- 
 periments firft inftkuted by the illuftrious Ver- 
 fchuir, are highly in favour of the exiftence of a 
 vital energy in the veins. 
 
 And, that the two leading and extreme venous 
 trunks have a ftratum of a true mufcular nature, 
 we have briefly hinted on a former occafion 
 (§ 84). 
 
 § 129. 
 
 Thefe are indeed the leading powers which are 
 aftive in promoting the circulation of the blood, 
 and which derive their origin from the very 
 ftru&ure of the veflels in which this fluid is con- 
 tained. I fay nothing of the manner or degree in 
 which the motion of this vital liquid is influenced 
 by weight, attradion, or fuch other properties as 
 are poflefled by all bodies in common. 
 
 I alfo pafs over in filence the more remote and 
 inconfiderable aids, which, in a human fubject after 
 
 birth 
 
OF RESPIRATION. 97 
 
 birth, are afforded to the circulation of the blood, 
 by the exercife of the other functionsof the fyftem, 
 fuch as refpiration, mufcular motion, £cc. 
 
 SECT. XI. 
 OF RESPIRATION, AND IT9 PRIMARY USE. 
 
 § 13°- 
 
 X HE lungs, which are very intimately 
 connected with the heart, as well from the vicinity 
 of their fituation, a* from their uniform intercourfo 
 in the performance of their important function, 
 are two vifcera, large in the human fubject after 
 birth, but of fuch fpecific lightnefs, as to float on 
 the furface of water. They confifl of a paren- 
 chymatous fubftance, of a fpungy texture, and 
 even exhibiting fomewhat the appearance of foam, 
 yet flill confiderably tenacious and flrong. 
 
 § I 3 l - 
 The lungs fill up the two cavities of the thorax, 
 
 and thus lie in perfect contact: with the facs of the 
 pleura, to which, as well as to the other parts 
 contained in the thorax, they apply and accom- 
 modate themfelves with the utmolt defmitude and 
 exact nefs. 
 
 vol. 1. G § 152. 
 
98' OF RESPIRATION'. 
 
 § ' 32. 
 
 Thefe vi fee r.i are appended to an air tube com- 
 monly called the afpera arteria y which, (befides 
 an internal membrane, lined with mucus, under 
 which is expanded a nervous intertexture of ex- 
 treme fenfibility), confifls alfo of a mufcular coat, 
 which furronnds the nervous expanfion, and on 
 the pofterior fide is eafily diftinguifhed at the ter- 
 minations of certain cartilaginous arches, which 
 aflift in the formation of the tube, but are not uni- 
 forra in their number. 
 
 § 133- 
 
 After the afpera artcria has entered the thorax 
 it firft forms, by bifurcation, the two trunks of 
 the bronchia, which as they (hoot (till deeper and 
 deeper into the lobes and lobules of the lungs, pafs 
 again, by reiterated divifions and fubdivifions, into 
 branches and ramifications, uniformly decreafmg 
 in fize. During thefe progreflive and multiplex 
 divifions into inferior orders, both the fmall carti- 
 laginous rings, and their mufcular coat gradually 
 difappear, till the evanefcent extremities of the 
 tubes finally terminate in thofe minute cells, 
 which conftitute by far the greater and more im- 
 portant part of the fubft ance of the lungs, as their 
 office is to receive, and again difcharge the vivify- 
 ing aerial element, in the procefs of refpiration. 
 
 § l 34- 
 
OF RESPIRATION. pp 
 
 Thofe fmall air cells do not appear to poiTcfs 
 uniformly, either the fame figure or dimenjions. 
 With refpect. to the former of thefe, (viz. their 
 figure), it is in general that of a polyhedron. The 
 latter, (/'. e. their dimenfions), as far as their fqper- 
 fieial extent is embraced in the confideration, can- 
 not without the utmofi difficulty, be afcertained ; 
 but, if we confider only their aggregate capacity, 
 this, in the lungs of an adult fubjecl:, whofe infpi- 
 rations are full and flrong, is fufficient to admir 
 and contain about 60 cubic inches of air. We do 
 not here fpeak of the immenfe fize, to which the 
 lungs may be expanded by inflation, after the tho- 
 rax is opened, but only of the quantity and volume 
 of air which they do actually admit in the living 
 fubjecl, when the procefs of refpiration is per- 
 formed with eafe and vigour. 
 
 § l 35- 
 Thefe vcftcles or cells, deftined for the reception 
 of air, are every where furrounded and bound 
 together by that common, but extremely tender, 
 cellular membrane, which, as we have already 
 learned, conftitutes a general vinculum or bond of 
 union to the whole body. But it is necelTary to 
 diitinguifh clearly and accurately between the two 
 kinds of cells which exiil in the pulmonic fyiterr.. 
 I have feen the air cells fo feparatc and diflin&, 
 G 2 ia 
 
106 OF RESPIRATION. 
 
 in the lungs of a healthy human fubje£t, that a per- 
 fon's breath, gently and cautioufly blown through 
 a very minute and tender ramification of the bron- 
 chia, would elevate only a fingle circumfcribed 
 ciufter or veflels or cells, and would neither pafs 
 into the neighbouring cells of the fame kind, nor 
 yet into the common cellular membrane, which is 
 every where interpofed between thofe ceils in- 
 tended for the reception of air. But, if the breath 
 be urged with confiderable force, the air cells 
 will be lacerated, and fuch a communication form- 
 ed with the furrounding cellular membrane, as to 
 give free pafTage to the fubtle elaftic fluid, and 
 thus the whole and every part, of the pulmonary 
 lobe, will appear to be inflated. 
 
 § J 3 6 - 
 This exceedingly tender cellular membrane, 
 
 which enclofes and lies between the air veficles of 
 the lungs, is every where interfperfed with innu- 
 merable fmall ramifications of both kinds of pul- 
 monary vcfTcls, viz. of the pulmonary artery, and 
 of the four pulmonary veins, the branches of 
 which accompany the branches of the bronchice, 
 and afterwards, form in their courfe, by an im- 
 mense number of divifions and fubfequent anafto- 
 mofes, reticular intertextures, and expanfiens of ex- 
 treme fmenefs and fubtilty. This truly aftonifhing 
 reticular tiiTue, running in all directions through 
 
 the 
 
OF RESPIRATION. IO i 
 
 the cellular membrane, fo completely furrounds, 
 and clofely embraces, the cells deftined for the 
 reception of air, that the whole volume of blood, 
 which paffes in an inceffant round through the 
 pulmonic fyftem, is feparated from the air taken 
 in at each infpiration, by nothing elfe than mem- 
 branes (o amazingly fine and fubtle, as fcarcely to 
 be equal in thicknefs, (according to the obferva- 
 tions and calculations of Ilalesj, to the one thou- 
 fandth part of an inch. 
 
 § "37- 
 
 As we have already obferved, that each indivi- 
 dual ramification of the bronchia;' has appended to 
 it its own peculiar clufter of air veficles (§ 135), fo 
 likewife it appears, that to every individual velicle 
 of each duller is peculiarly appropriated its own 
 fyftem of fmall blood vefTels, the minute rami- 
 fications of which communicate very frequently 
 with one another, forming thofe fiirprifmg reticu- 
 lar tifllies aleady fpoken of, but fcarcely appear to 
 anaftomofe, in any degree, with the fmall blood- 
 veffeU of the adjacent cl Lifters. That this is a 
 truth we are taught, if I am not deceived, as well 
 from microfcopical obfervations made on the lungs 
 of living frogs and ferpents, as from more minute 
 and fuccefbful injections of the lungs of human 
 fubje&s : the fame thing is alfo further evidenced 
 by certain pathological phenomena which may be 
 G 3 obferved 
 
i ©2 OF RESPIRATION. 
 
 obfervcd in vomica, and other fimilar topical affec- 
 tions of the pulmonic fyftem. 
 
 § 138- 
 
 It is neceffary to mention alfo, in the laft place, 
 that fmgular and ftriking apparatus of lymphatic 
 veffels, which fpreads and appears, in a more parti- 
 cular manner, on the external membrane by which 
 the lungs are inverted. To this apparatus of vef- 
 fels belongs that numerous affemblagc of lympha- 
 tic or conglobate glands, which, though of a quite 
 different and diftinct order, are neverthelcfs com- 
 monly confounded, through miftake, with thofe 
 glands in their neighbourhood, which are called 
 bronchialcs. 
 
 § *39- 
 
 The thorax, in which the lungs are fecurely 
 tnclofed, has for its foundation or ikeleton, bones 
 and cartilages, arranged and dilpofed fomev hat 
 like the walls or fides of a cave. Though this 
 bony cavity, taken together as an entire whole, 
 be to a considerable degree firm and fteady, 3 t 
 mod of its parts are fo pliant and moveable, as to 
 be well adapted for the performance of thofe mo- 
 tions which the bufinefs of refpiration requires. 
 
 This pliability, or facility of motion is particu- 
 larly obfervable in fix pairs of the true ribs, which 
 
 being 
 
OF RESPIRATION. 103 
 
 being placed beneath the fuperior and fird pair, 
 are more moveable in proportion as their fituation 
 is lower ; or their aptitude for motion is com- 
 mcofurate with the fuperior length of their bodies, 
 and cartilaginous appendices, which connect them 
 to the mar-ins on each fide of the fternum, by a 
 fpecies of articulation called amphiarthrojis, 
 
 § 140. 
 
 Between the edges of thofe rib? lie two drata 
 of intercoflal mufcles, the fibres of which aifume 
 indeed and pLirfue different directions, but which, 
 neverthelefs, co-operate in their action in pro- 
 ducing the fame motion in the parts to which 
 they are attached. 
 
 Acrcfs the bafis or inferior part of the whole 
 of this cavity the diaphragm is ftretched, fomewhat 
 in the form and direction of an arch. This is a 
 mufcle worthy of particular attention, and, to ufe 
 the words of Haller, next in importance to the 
 heart itfclf ; its parts appear to depend chiefly on 
 the phrenic nerve for their fitnefs to co-operate in 
 the function of refpiration, as was long fince de- 
 monftrated by the celebrated live-diiTeclions of the 
 immortal Galen. 
 
 The 
 
xo4 OF RESPIRATION. 
 
 The diaphragm alternates for the mod part, by 
 an antagonizing motion, with the mufcle> of the 
 abdomen, efpecially with the external and internal 
 oblique, and the tranjverfe mufcles. 
 
 § 141. 
 The thorax thus formed and finiflied is, in the 
 living human fubject after birth, alternately dilat- 
 ed at the time of each infpiration, and contracted 
 again to its former dimenfions in every fubfequcnt 
 act of expiration. 
 
 In infpiration, the enlargement of the tho- 
 racic cavity extends, in a more efpecial manner, 
 literally and downwards, fo that the bodies of 
 thofe ribs of which we have particularly fpoken 
 (§ 139) are elevated, and their inferior margins 
 or edges turned in fome degree outwards ; while, 
 at the fame time, the arch of the diaphragm is 
 ibmewhat depreffed, and brought nearer to the 
 portion of a plain, or level furface. 
 
 But as to what is boldly afTerted of thefternum, 
 viz. that its inferior end is at the fame time pro- 
 truded forward, this is a phenomenon which I 
 mull confefs, I have never been able to obferve in 
 the tranquil and unmolefted refpiration of a healthy 
 
 fop, 
 
OF RESPIRATION 1 . 105 
 
 This alternate motion of the thorax, which in 
 a healthy fubject is indeed performed fpontane- 
 onfly and without effort, is uniformly continued 
 from the moment of birth to the extinction of life, 
 for the following neceiiary and important pur- 
 pofes, namely, that the lungs themfcivrs may, by 
 a fimiiar viciflitude of motion, be expanded for the 
 free admiffion and convenient reception of the air 
 we infpire, and again contracted in order that the 
 fame may be forthwith expelled. 
 
 § H3- 
 For man, together with all other warm blooded 
 
 animals, is prevented, by abfolute neceiiity, from a 
 lengthy retention of the air which he infpires ; he 
 is obliged, after a very fhort period to difcharge it 
 again, and exchange it for a frefli fupply of this 
 vital pabulum ox food, as the air has been termed, 
 even from the mod remote ages. It appears in- 
 deed from the mofl common obfervation, that the 
 air which is infpired and retained any time in the 
 lungs, however great may have been its original 
 purity, fuffers, in a very (hort time, fuch remark- 
 able changes as afFecl it with the mod obvious 
 contamination, and, unlefs it be fpeedily renewed, 
 render it wholly unfit to be any farther employed 
 in the important procefs of respiration. 
 
 S 144. 
 
106 OF RESPIRATION. 
 
 § '44- 
 
 Enquiries have been inftirutcd for the purpofe 
 of afcertaining the nature of thofe changes which 
 the air we infpire undergoes in our lungs. Such 
 changes certainly do not arife, as was formerly 
 believed, from the lofs of any myfterious principle 
 of elafticity, which refides in the air, but are evi- 
 dently produced by a decompofition of its elemen- 
 tary parts. For the atmuipheric air which we 
 breathe is truly an aftonifhing mixture of elemen- 
 tary fubflances, very widely different from each 
 other in their natures. Not to mention the va- 
 rious heterogenous matters which this neceffary 
 fluid contains ; fuch, for example, as the aerial 
 feeds of the fmalleft and meft fimple plants, the 
 odorous effluvia arifing from numerous bodies, 
 volumes of dufl, and a thoufand other fimilar fub- 
 flances, which for the mod part float in the at- 
 mofphere. Not to mention, I fay, thefe hetero- 
 genous bodies at all, the air which we breathe 
 always contains aqueous exhalations in larger or 
 (mailer quantities, and is alfo more or lefs charged 
 with the matters of electricity and magnetifm. 
 But finally, though the whole of the foregoing 
 fubflances be left entirely out of view, yet even 
 then the air of our atmofphere does not conftll of 
 one fimple aeriform fluid, but is compofed of de- 
 phlogiflic.ited, phlogiidicate-, and fixed airs. 
 
 The 
 
OF RESPIRATION. 107 
 
 The proportion of thofe elementary matters, 
 efpecial'y of fuch as are organic, is varied ex- 
 tremely from diverfity of places, and by the nature 
 of the bodies which exift in thefe places. It is in 
 the mean time, however, the common eftimation, 
 that the air of our atmofphere confifts of about 
 ith part of dephlogifticated, Hths of phlogifti- 
 cated, and £th of fixed air. 
 
 § 145- 
 It appears, that at each infpiration, (in which 
 an adult fubject, breathing in a quiet and tranquil 
 manner, draws in about 30 cubic inches of air,) a 
 fourth part of the dephlogifticated air is decom- 
 pofed, and, in a great meafure, exchanged for 
 phlogifticated and fixed airs ; fo that the expired 
 fluid, being received into a proper veflel, extin- 
 guishes flume or coals when immerfed into it, pre- 
 cipitates lime from the water which fufpends it, 
 and far exceeds atmofpheric air in its fpecific gra- 
 vity, &c. 
 
 § 14-6. 
 It is probable that the igneous parts of the de- 
 phlogifticated air, i. e. thofe parts fuited to favour 
 the procefs of combufticn, being fet at liberty by 
 the decompofltion which takes place in the lungs, 
 enters the arterial blood, and is thus diilributed 
 throughout the whole body j while, on the other 
 
 hand, 
 
tc8 OF RESPIRATION. 
 
 hand, the bafis of fixed air is carried back, along 
 with the phlogifticated and venous blood, to the 
 right fide of the heart, and thence (as the an- 
 cients were pleafed to exprefs themfelves) ex- 
 creted through the lungs like foot. 
 
 The more florid dye of the arterial blood, the 
 more obfeure colour of the venous, and the fimili- 
 tude of colours imparted to both kinds of blood, 
 when expofed to the aclion of thofe fpecies of air 
 now under our confideration (§ 16), are circum- 
 ftances very much in favour of the preceding 
 opinions. 
 
 In a fcetus which has never yet received vital 
 air into its own pulmonic fyftem, there is in general 
 lefs difference between the arterial and venous 
 blood, than in an adult fubjeft, in whom the pro* 
 cefs of refpiration has already taken place. 
 
 After the infant is born, the new fenfation, ex- 
 cited by the contact of an unufual element, in an 
 animal which had hitherto led an aquatic life, and 
 the application of various other flimuli altogether 
 new, appear to afford us a happy clue for explain- 
 ing the new motions which at that period take 
 place in the body, more especially the dilatation 
 of the thorax and the firft aft of infpiration. 
 
 When 
 
OF RESPIRATION. 109 
 
 When the lungs are dilated by this firft complete 
 a& of infpiration, a new paflage is thus opened 
 through them for the blood, fo that this fluid is 
 ever after diverted from the umbilical vefTels to 
 the thorax. 
 
 But when this infpired air is, by that decompo- 
 fnion of its elementary parts, of which we have 
 already fpoken, rendered both noxious and trou- 
 blefome to the lungs, I afcribe to the mod fimple 
 prefervative efforts of nature, the immediately fub- 
 fequent motion, by which this poifonous mephitis 
 is exfpired, and profitably exchanged for a frefh 
 fupply of the foftering pabulum of life. 
 
 From all the foregoing circumftances, taken 
 collectively, (efpeciaily if we attend to the great 
 influence of refpiration on the circulation of the 
 blood, as demonftrated by the well known experi- 
 ment of Hooke), we are furnifhed with a much 
 better explanation of the celebrated problem of 
 Harvey, than has yet been given by moft of the 
 other reiterated labours of phyfiologifts, who have 
 attempted to folve that difficulty. 
 
 SECT. 
 
no OF VOICE AND SPEECH. 
 
 SECT. XII. 
 OF VOICE AND SPEECH. 
 
 § >4«- 
 
 
 1 HE leading function of refpinuion 
 has been already the fubject of our confident) on. 
 We will fpeak, in another place, of the part which 
 this fublime procefs acts, in blending and intimately 
 uniting the chyle with the blood, and alfo of the 
 fervices which it renders, in a variety of ways, to 
 almolt the whole clafs of natural functions, (§ 63. 
 1 12.) We now proceed to confider its other ufes 
 in the animal economy. 
 
 The firfr. object or phenomenon which attracts 
 our attention, in this invefligation, is the Voice, 
 which belongs to the human fubjecT: after birth, 
 and evidently proceeds from the lungs, as was 
 long fince very juftly obferved by Ariftotle, who 
 faid, that no animals are vocal, i. c. poITefs the 
 power of emitting found, but fuch as breathe 
 through lungs. For, by the denomination of voice, 
 we properly defignate that found formed, by means 
 of the exfpired air, in the larynx, which is a fmall 
 apparatus or machine of the mod exquifite {frac- 
 ture, placed on the top of the wind-pipe or afpera 
 
 arteria, 
 
OF VOICE AND SPEECH. 1 1 1 
 
 arteria, fomewha: like a capital on the furamic of 
 a column. 
 
 § H9- 
 This fmall machine is compofed of various car- 
 tilages joined together fomewhat after the form of 
 a capfula or caiket. Thefe cartilages are furniihed 
 with a great and truly admirable apparatus of muf- 
 cles, in confequence of which, not only the whole 
 are rendered fit for motion collectively, but fome 
 of them are alfo enabled to move individually and 
 alone, according to the different variations abouc 
 to be produced in the voice. 
 
 § '5 - 
 That part which is more particularly engaged hi 
 
 the immediate generation of the voice is die glottis, 
 a very narrow paffage leading into the wind-pipe 
 from above, to which is prefixed, or applied as a 
 lid, a minute cartilage called the epiglottis. That 
 found is produced by the air expelled from the 
 lungs, finking, in a proper direction and with due 
 force, agairft the edges of this llrait paffage, is a 
 matter too plain to admit of a doubt. 
 
 § i5 r - 
 Controverfies have exitted on the fubjeel of 
 
 thole changes that take place in the glottis, by 
 
 which the modulations of the voice are produced, 
 
 namely, 
 
112 OF VOICE AND SPEECH'. 
 
 namely, Whether this cartilaginous part be alter- 
 nately expanded and contracted, as was the opi- 
 nion of Galen, and afterwards of Dodart? or, 
 Whether the variations of the voice do not rather 
 depend on the tenfion and relaxation of its liga- 
 ments, as war. held by Ferrein ? 
 
 The latter of thofe, therefore, compared the 
 primary organ cf the voice to a violin, the former 
 to TLJlute — i. e. the onefet of difputants conceived 
 it to emit found on the principles of a corded^ the 
 other on thofe of a wind, injirwnent of mufic. 
 
 From a faithful collection, and impartial confi- 
 deration, of all the arguments which have been 
 advanced on this contefled point, we are of opi- 
 nion, that both kinds of changes do actually take 
 place in the glottis when employed in the emiiTion 
 of found ; but we, neverthelefs, believe, that the 
 principal and mod important of thofe changes de- 
 pend on and arife from the tenfion of the liga- 
 ments, more efpecially of the thyreo-arytonoidei 
 inferiores (which appear to have been the vocal 
 cords of Ferrein. 
 
 § 152. 
 
 That all this mobility of the glottis, of whatever 
 
 kind it may be, is influenced and wholly directed 
 
 by the numerous ir.ufcles which belong, and are 
 
 1 attached, 
 
OF VOICE AND SPEECH. ir 3 
 
 attached, to the larynx, may be fully eftablifhed 
 by the following beautiful experiment, viz. It the 
 recurrent or wandering nerves (as they are termed) 
 be either fecured in light ligatures, or completely 
 cut afunder, the voice of the animals fubjec>*d to 
 fuch experiments, will be in the former cafe, ren- 
 dered extremely weak and low, and in tne latter, 
 entirely deftroyed. 
 
 § 153- 
 The faculty of ichifiling belongs in common 
 both to the human fpecies, and to fmall birds of 
 note. To qualify them for this, fmging birds are 
 furniflied with a bifurcated larynx at each extre- 
 mity of the afpera artcria. But though human 
 fubjects be fupplied with only one plain and fimple 
 larynx, yet they learn to imitate thofe fmall ani- 
 mals, as appears to me, by a co-arftion or pucker- 
 ing up of their lips. 
 
 % 154- 
 But fong, which is compofed of fpeech and a 
 harmonious modulation of the voice, I would con - 
 fider as peculiar to man alone, and as conftituting 
 the leading prerogative of his vocal organs. The 
 faculty of whittling is, as already obferved, a part 
 of the birth-right of birds : a numerous train of 
 the feathered race, and fometimes even dogs them- 
 felves, have a!fo been taught to pronounce a va- 
 tQL. i. H riety 
 
**4 OF VOICE AND SPEECH. 
 
 riety of words. But I doubt extremely indeed,' 
 whether any brute animals have ever yet polfcffed 
 a faculty of true an.i genuine fong ; whereas, on 
 the other hand, I believe there fcarcely exifts a 
 a nation fo barbarous, where fong does not very 
 generally prevail. 
 
 § *55- 
 Speech iifelf is a peculiar modification of the 
 voice, chiefly by the aid of the tongue, but par- 
 tially alfo by that of the lips, the teeth, the palate, 
 and by the further afnftance of the nofe, combined 
 into the formation of words. 
 
 Hence the difference between voice and fpeeck 
 appears very obvious and plain : the firlt is evi 
 dently formed in the larynx itfelf ; wnereas the 
 latter is effected by the Angular mechanifm of th 
 other organs already menroned. It is but ju 
 and proper, however, to obferve, that this laft 
 pofition is not capable of univerfal application, as 
 there are a few nations (of which the Sinenfians 
 may fcrve as an example), among whom their al- 
 moil homonymous* words are diftinguiftied only 
 by a varied modulation of the voice itfelf. 
 
 1 
 
 * A word is faid to be homonymous, when it is highly- 
 equivocal, or ufed indifcriminately to reprefent a difcordant 
 variety of obje&s or things. 
 
OF VOICE AND SPEECH. *ti§ 
 
 But further, voice belongs in common to brutes 
 as well as to man ; it is poffcfled alfo by the new- 
 born babe, nor is it wholly denied to fuch unhap- 
 py infants as have patted their lives amidfr the 
 haunts, and in the gloomy fociety, of wild beads, 
 nor even to thofe that have been born without the 
 fenfe of hearing. But fpeech is not acquired till 
 after the cultivation and exercife of reafon ; it 
 conftitutes, therefore, no lefs than that operation 
 of the mind itfelf, a characteriftic privilege, and 
 diftin&ive prerogative between man and the reft 
 of the animal kingdom. To ferve all the pur- 
 pofes, and anfwer all the demands of brutes, that 
 inftincT: with which nature has beneficently fupplied 
 them, is completely adequate ; of this inftinft, 
 however, man h deftitute, as alfo of fuch other 
 aids and individual powers as might enable him to 
 preferve and fuftain life by his own folitary exer- 
 tions ; he is therefore kindly furnifhed with the 
 prerogatives of reafon and fpeech^ by means of 
 which, embracing the advantages, and difcharg- 
 ing the duties, annexed to a focial flate, he is able 
 both to difclofe his own wants, and relieve thofe 
 •f his fellow creatures. 
 
 That truly admirable mechanifm, by means of 
 
 which fpeech and the pronunciation of letters are 
 
 H 2 effected, 
 
 i 
 
ji6 OF VOICE AND SPEECH. 
 
 effe&ed, has, fince the celebrated refearches of 
 that paradoxical character, Franc. Mcrcur. Hel- 
 mont, been very much illuftrated and explained 
 by further and later enquiries, efpecially thofe of 
 Jo. Wallis and Conr. Ammanus. 
 
 That dhifion of the letters by Ammanus into 
 I. Vowels, II. Semivowels, and III. Confonants, 
 is, of all others, by far the mod fimple and na- 
 tural. 
 
 I. Vowels he again divides into Jimple, as a, e, i, 
 y, 0, u 9 and mixed, as, a, 5, ii. 
 
 II, Semivowels arc themfelves either nafals, 
 fuch as, m 9 ?i, ng, (i. e. n placed before g in the 
 German language) ; or Orals (otherwife called 
 Unguals') fuch as, r, /. 
 
 III. Finally, Confonants he divides, ift, into the 
 Sibilantes or hijfing (i. e. into thofe confonants the 
 pronunciation of which can be continued for an 
 indefinite length of time). Thefe are h, g, ch,, s, 
 fch, f, v, ph. 
 
 2dly, Explojive, as, k, q, d, /, b, p, and 
 
 3dly, Double (or Compound), fuch as, x, z. 
 
 S '57- 
 
OF VOICE AND SPEECH. u 7 
 
 S iS7- 
 
 Finally, It yet remains to mention certain other 
 modifications of the human voice, which ufually 
 occur as fymptoms, or figns of either particular 
 pafIions of the mind, or more violent affections of 
 the organs of refpiration. The greater part of 
 thefe modifications of the voice, fuch for example, 
 as laughing and crying, appear to belong exclu- 
 fively to the human race. 
 
 § i S 8. 
 
 Mod of the modifications which immediately 
 follow, are connected together by fuch a powerful 
 kindred alliance, that one of them is not unfre- 
 quently obferved to pafs into another. It mufl be 
 alfo further obferved, that the greater part of 
 them do not always afTume and exhibit the fame 
 uniform appearance, &c. 
 
 To fpeak, however, in general terms, in the 
 aft of laughing, exfpirations fhort, interrupted, and 
 in fome meafure broken, follow each other in 
 quick fuccefHon. 
 
 Crying produces deep infpirations, which fud- 
 denly alternate with lengthy exfpirations fre- 
 quently interrupted and broken. 
 
 H 3 Sighing 
 
n3 OF VOICE AND SPEECH. 
 
 Sighing confifts in a lengthy, full, and flrong in- 
 fpiration, and afubfequent flow exfpirarion, which 
 is not unfrequendy accompanied with fomewhat 
 of a groan. 
 
 Coughing is produced by quick and fonorous 
 exfpirations fucceeding a deep infpiration. 
 
 Sneezing is a more violent and fomewhat con- 
 vulfive exfpiration, which had been preceeded by 
 a fhort and forcible infpiration. 
 
 The Hickup on the other hand confifts entirely 
 of a fingle infpiration, fonorous, exireme\y fudden, 
 and at the fame time of a convulfive nature. 
 
 The prefent feems a very fuitable occafion to 
 fpeak of the phenomenon of yawning, which con- 
 fifts in a full, flow, and lengthy infpiration, -fuc- 
 ceeded again by a fimilar exfpiration, while, at 
 the fame time, the jaws are drawn fo very widely 
 afunder, that the air which is received into the 
 expanded fauces can enter with cafe the Eujia- 
 chean tubes. One thing peculiar to this pheno- 
 menon is, its being extremely contagious, i. e. it 
 very readily excites to imitation : the caufe of this 
 js, without doubt, to be fought for in the remem- 
 brance of the agreeable fenfatious produced at a 
 former time, by the languid operation of yawning. 
 
 SECT, 
 
OF ANIMAL HEAT. n^ 
 
 SECT. xin. 
 
 OF ANIMAL HEAT. 
 
 § 159. 
 
 IT is worthy of obfervation, that man in 
 a living ftate, together with the other fubje&s be- 
 longing to the clafs Mammalia, as vt ell as the whole 
 feathered race, are diftinguifhed from the reft of 
 the animal kingdom by this peculiarity, that the 
 native heat of their bodies far exceeds, in degrees 
 of temperature, the ufual heat of the medium or 
 element in which they live. With refpeft to man 
 himfelf, it is however to be remembered, that he 
 appears to be inferior, in the heat of his fyftem, 
 to thofe other kinds of animals we have juft men- 
 tioned. Thus, in our climate, the heat of the 
 human body generally ftands at about the 96th 
 degree of Fahrenheit's fcale, whereas, in other 
 animals belonging to the clafs Mammalia, the vital 
 [ temperature very confiderably exceeds this point, 
 while it afcends ftrll higher in individuals of the 
 feathered tribes. 
 
 § 1 6a. 
 
 Indeed, the degree of native heat poffefTed by a 
 
 healthy perfen is fo conftant and uniform, that in 
 
 H 4 general^ 
 
ja # OF ANIMAL HEAT. 
 
 general, (provided we make allowance for the 
 ftate of health peculiar to each individual), its 
 range will include but a very few degrees of the 
 thermometer, whether the fudject be expofed to 
 the inclemencies of the mod rigorous climate, or 
 placed beneath the fervors of a tropical fky. For 
 the opinion formerly delivered by Boerhaave, that 
 man has not a power of exifting in a medium of 
 fuch a nature as exceeds in temperature the native 
 heat of his own body, has, fince the famous ob- 
 fervations of that illuflrious traveller and former 
 governor of Georgia, H. Ellis, been refuted by a 
 great number of characters learned in the fcience 
 of phyfiology, and the reverfe completely demon- 
 flrated and eftablifhed by experiments well adapted 
 to the nature of the fubjecL In this particular, 
 indeed, appears to confift one of the great prero- 
 gatives of man, that imprifoned and confined to 
 no one climate or zone of the earth, he is able to 
 pafs his life in any feclion of the immenfe globe 
 we inhabit, and is free to fix his habitation either 
 beneath the rigors of Hudfon's ftormy channel, 
 where the quickfilver pafTes fpontaneoufly to a 
 ftate of complete congelation, am id ft the tempefts 
 of Nova Zembla, or in the bofom of thofe glaring 
 folar fires, which fcorch the glowing ihores of the 
 Senegal, 
 
 § 161. 
 
OF ANIMAL HEAT. |(j 
 
 § 161. 
 
 We proceed now to enquire into the origin and 
 fource of that aftonifhing fire, which minutely 
 pervades our bodies, and uniformly fupplies them 
 with their neccflary degrees of warmth. To pafs 
 in filence over the vifionary conjectures of the 
 ancients on this fubjeft, fome of the moderns have 
 attempted to derive animal heat, with all its phe- 
 nomena, from the matter of electricity and the 
 nerves, others from the attrition generated by the 
 circulation of the blood, others from the recipro- 
 cal friclion between the folid elementary parts of 
 living animals, while others, again, have embraced 
 and defended different opinions. 
 
 § 162. 
 But all thofe hypothefes are embarraffed with 
 infurmountable difficulties, whereas, on the other 
 hand, the utmofl fimplicity, and an entire cor- 
 refpondence to the phenomena of nature, combine 
 in recommending and confirming that doclrine, in 
 which the lungs are confidered as t\ic focus ox fire - 
 ■place where animal heat is generated, and the de- 
 phlogifticated part of the air which we breathe, 
 as the fuel that fupports the vital flame. That 
 juftly celebrated character, Jo. Mayow, fketched 
 out, formerly, the leading traces and firft great 
 outlines of this doclrine, which, in our times, has 
 been greatly improved, extended, and farther 
 
 elucidated, 
 
122 OF ANIMAL HEAT. 
 
 elucidated, by the labours of the illuftrious Craw- 
 ford. 
 
 The whole drift and tenor of Crawford's theory 
 obvioufly refults in this, that refpiration, no lefs 
 than combu/lion, belongs to fuch procefTes as are 
 called phlogiftic ; in which the phlogifton refiding 
 in, and conftituting a part of, our bodies, is ex- 
 pelled by the acceflion of free or fcnfiblc heat, 
 (which ought to be carefully diftinguifhed from 
 heat exifting in a fixed or latent date.) 
 
 For phlogifton and the matter of heat are ele- 
 ments of fuch contrary and oppofite natures, that 
 the greater quantiry of the one our bodies at any 
 rime contain, the lefs, at the fame time, is their 
 proportion of the other ; thus, fixed air, for ex- 
 ample, is not fuppofed to contain more than a Vth 
 part of the quantity of the matter of heat, which 
 belongs to an equal weight of atmofpheric air, &c. 
 
 But it appears, from experiments, that atmo- 
 fpheric air has a ftronger affinity to phlogifton 
 than to the matter of heat, fo that it unites itfelf 
 with the greateft readinefs to the former, while, at 
 the fame time, it fets at liberty the latter, which 
 had been hitherto held in a fixed and latent ftate. 
 
 § 164. 
 
OF ANIMAL HEAT. 123 
 
 § 164. 
 When we come to apply the foregoing por- 
 tions and principles to the phenomena of refpira- 
 tion, it appears highly probable, that animal heat 
 is generated by a procefs of a fimilar nature. 
 
 For, as we have already had occafion to ob- 
 ferve, the air whicli we exfpire differs, in a very 
 remarkable degree, from wh;.t we had immediately 
 before infpired ; being deprived of its igneous 
 portion, or of that part fit for contributing to the 
 fupport of flame, it is returned highly impreg- 
 nated, on the contrary, with phlogifton and the 
 bafe of fixed air. (§ 146.) 
 
 It appear?, therefore, extremely prcbable, that 
 the igneous portion of the air we breathe enters 
 thofe minute blood-vefTels, which are every where 
 difperfed throughout the fubflance of the lungs, 
 and feparated from the air-veficles themfelves by 
 nothing more than fubtle partitions of the mod 
 filmy texture (§ 136) ; that from the lungs it is 
 conveyed through the pulmonary veins to the 
 aorta, from whence it is again, by means of the 
 arterial fyftem, diftributed throughout every part 
 ©f the body. 
 
 During 
 
i2 4 OF ANIMAL HEAT. 
 
 During the whole cnurfc of this minute diftri- 
 bution, more efpecially while in the extreme ra- 
 mifications of the veffels, it appears to be ex- 
 changed for phlogifton, which it every where 
 meets with in confiderable quantities. This phlo- 
 giftic principle, being thus mixed with the blood, 
 and occupying the place juft: evacuated by the 
 mauer of heat, is conveyed back, by means of the 
 venous fyftcm to the right fide of the heart, and 
 from thence by the pulmonary artery, into the 
 lungs, where, agreeably to the fe laws of affinity 
 which we juft now hinted at, it is immediately 
 received and taken up by the volume of air 
 recently infpired. In confequence of the acceifion 
 of this quantity of ph'ogifton, and its union with 
 the air contained in the lungs, a frefh portion of 
 the element of fire or heat is fet at liberty, which 
 inflantly enters the blood and is thus inccflantly 
 diitributed throughout the fyftem in the manner 
 aheady defcribed. 
 
 § 166. 
 
 The truth of this theory is evidenced by thofe 
 diverfnics between arterial and venous blood, to 
 which we have every where adverted. It is 
 alfo farther evidenced by the difference between 
 the fpecific heat of arterial, and that of venous 
 blood ; thus the fpecific heat of the blood con- 
 tained in the arteries is to that of the blood con- 
 tained 
 
OF ANIMAL HEAT. 125 
 
 tained in the veins, as ill to 10. Finally, as an 
 additional evidence of the fame thing, we might 
 mention, in the feft place, that ofcillatory action 
 exerted by the fmalleft order of blood vefiels, 
 which was the fubjecl: of our attention on a 
 former occauon. 
 
 § 167. 
 
 For it feems altogether probable, that thofe 
 extremely minute ramifications of the fanguiferous 
 fyftem, are parts of fuch utility and importance, 
 that in proportion as their action is itronger or 
 weaker, a correfpondent increafe or diminution 
 takes place in that exchan je of the element of fire 
 for the matter of phlogifton, which goes conftanrly 
 forward in the body, and alfo in the heat of the 
 animal uniformly generated by fuch exchange. 
 
 Thofe memorable and finking phenomena, from 
 which it appears, that animal heat (if indeed the 
 matter be determined by a thermometer, and not 
 trailed to the fallacious teft of f nfation), remains 
 in general at very nearly the fame precife point of 
 temperature, little augmented by the rummer's 
 blaze, little diminimed by ths winter's blaft ; and 
 further, that on certain occafions the heat of our 
 bodies is even increafed in confequence of an im- 
 merfion in cold water — Thofe phenomena, I fay, 
 feem to. demonstrate, and reduce if to a certainty, 
 
 that 
 
ii6 OF PERSPIRATION. 
 
 that according to the variations that take place in 
 the temperature of the medium in which we live, 
 correfponding diversities immediately follow in the 
 aclion of the fmallelt vafcular ramifications of our 
 bodies. From this Angularly accommodating 
 power, refident in the minute extremities of our 
 vafcular fyftem, it follows, that on being expofed 
 to cold (which appears to aft by increafing their 
 tone), they are immediately enabled to exchange 
 a larger quantity of the principle of phlogifton for 
 the igneous pabulum, and thus generate a higher 
 degree of heat ; whereas, on the other hand, 
 they are obliged to exchange a much /mailer quan- 
 tity, as often as they are rendered inactive by be- 
 ing fubjected to the influence of a relaxing and 
 debilitating medium. 
 
 SECT. XIV. 
 
 OF CUTANEOUS PERSPIRATION. 
 
 § 1 68. 
 
 jO various, and extremely diverfined, 
 are the functions of the cutis, with which the hu- 
 man body is inverted, that an enumeration and 
 complete account of the whole of them can 
 fcarcely be comprehended with propriety under 
 
 one 
 
OF PERSPIRATION. 127 
 
 one and the fame head ; they would appear to 
 be more fitly arranged for confideration, each one 
 under that clafs of aclions to which, from its 
 nature it belongs. 
 
 For, in the firit place, the cutis is the organ of 
 touch, of which we will fpeak when treating of 
 the animal functions. 
 
 It is again the medium or inftrument of inhala- 
 tion, by which office it makes a part of the 
 abforbing fyftem of lymphatics ; this fhall be a 
 fubject of further confideration, when we come 
 to take a view of the natural funclions. 
 
 Finally, It is the laboratory or organ of perfpi- 
 ration alfo. This function agrees in a great 
 variety of refpecls with the procefs of refpiration, 
 and appears therefore to be introduced with 
 Sufficient propriety as the fubject of the prefent 
 fection. 
 
 § 169. 
 
 The cutis is faid to confifl: of a threefold mem- 
 brane, or of a membrane compofed of three 
 laminae. Thefe laminas or layers are the corium 
 or true fkin, lying on the interior fide, the cuticula, 
 or cuticle making the exterior covering, and the 
 reticulum (i. e. the rete mucofiwi), which is fpread 
 
 between 
 
128 O* ANIMAL HEAT. 
 
 between the two lamincc juft mentioned. Of each 
 of thefe we will treat feverally and in order. 
 
 § 170. 
 The cuticle, or epidermis, forms, as juft ob- 
 ferved, the external covering to the whole body : 
 It is thus, from its fituation, expofed to a free ac- 
 ceflion of the air, the immediate contact of which 
 element, fcarcely any other part of the body can 
 bear with impunity, even in a found date, except 
 the enamel of the teeth, the tubes of refpiration, 
 and the alimentary canal. 
 
 § I7 1 - 
 The texture of the epidermis is fimple to the 
 
 utmofl degree, being entirely deftitute of veffels, 
 
 of nerves and of pores. This texture, though on 
 
 the whole fcarcely organic, is neverthelefs highly 
 
 fingular and ftriking ; notwithftanding its femipel- 
 
 lucid and tender appearance, its tenacity is yet fo 
 
 very confiderable as to refill effectually, for a 
 
 great length of time, not only maceration, but 
 
 various other modes of generating putrefaction. 
 
 § I7 2 ' 
 The origin of this filmy expanfion is as yet in- 
 volved in doubts and difficulties. It is in the 
 mean time, however, probable that it fprings, 
 along with the fmall bulbs furrounding the roots 
 4 of 
 
OF PERSPIRATION. 12g 
 
 of the hairs, from the corium or true fkin expanded 
 beneath it : that this is the cafe, we are led to in- 
 fer, from the myriads of minute and extremely 
 tender fibrils, by which it and the ikin are con- 
 nected together. 
 
 When by any means deflroyed, ir is re-pro- 
 duced aq;ain with greater facility, than any of the 
 ©ther folid parts of the human body. 
 
 § l 73- 
 That this membranous lamina is of the utmoft 
 
 importance in the economy of organized bodies, 
 is inconteflibly evinced by its univerfal prevalence 
 throughout both the animal and vegetable king- 
 doms. It may be obferved already formed even 
 in the tender embryo itfelf, at fo early a period as 
 the third month after the time of conception. 
 
 § T 74- 
 
 Underneath the cuticle is expanded a thin mu- 
 cous membrane, which, from an opinion entertained 
 refpe&ing it, by its celebrated difcoverer, is called 
 reticulum Malpigbianum. 
 
 This reticulum or fubtle net-like expanfion, ex- 
 hibits the habit and appearance of mucus, ex- 
 tremely eafy of folution : it can fcarcefy in any 
 part, except in the fcrotum of ^Ethiopians, be fepa* 
 
 vol. i. I rated 
 
t2f OF PERSPIRATION. 
 
 rated entire from both the cuticle and true {kin, 
 and thus be procured in the form of a genuine and 
 complete membrane. 
 
 The part now under confideration, conftitutes 
 the primary and principal feat of colour in the 
 human race. In all men the true iKin is fair and 
 ihining ; the cuticle alfo is femipellucid and whitifh 
 in all nations, except the inhabitants of ^Ethiopia, 
 in whom it is more dufkifh and obfeure. But in 
 the human fubject after birth, the colour of the 
 reticulum mucofum is varied, in correfpondence to 
 the diverfities of age, mode of life, climate, and 
 alfo in proportion as the conftkution is more or 
 lefs found. 
 
 Thus, for example, of the five 'varieties, into 
 which the human race appears to me, to be with 
 much propriety divided, the jirjl has the reticu- 
 lum more or lefs whirifli. This defcription in- 
 cludes, befides Europeans, thofe who inhabit the 
 weft of Afia, and the north of Africa, together 
 with the natives of Greenland and Efquimaux. 
 
 idly, In the fecond variety, which includes the 
 inhabitants of all the other parts of Afia, the reti- 
 culum fomewhat tawny, inclining to an olive 
 cad. 
 
 2> dl h 
 
OF PERSPIRATION. 13 1 
 
 %dty, In the third, which embraces the inhabi- 
 tants of ^Ethiopia, it is blackifh. 
 
 Arthly, In the fourth, which confifls of the ab- 
 origines of America, it is to a certain degree cop- 
 per-coloured. 
 
 5tbly, Finally, in the fifth, which comprehends 
 the inhabitants of all the South Sea iilands, it is 
 more or lefs tawny or brown. 
 
 But all, and each one of thofe varieties of co- 
 lour, as well as all other varieties, by which man 
 differs from man, and nation from nation, appear 
 to be fo intimately blended together, and are dif- 
 pofed to run into each other with fo much facility, 
 that it feems fcarcely poffible to eftablifh any divi- 
 fions or claifes of them, but fuch as are plainly 
 arbitrary. 
 
 § *7 6 - 
 
 The Corhim or true Jkin itfelf, to which the 
 reticulum and epidermis ferve as a covering, is a 
 membrane of a peculiar nature ; it is porous, te- 
 nacious, capable of valt dilatation, varied in its de- 
 grees of thicknefs, confiding chiefly of condenfed 
 cellular membrane, and extremely clofe and com- 
 pact on its external fuperficies ; it is more lax on 
 she internal furface, which, (if you except a few 
 I 2 re ians 
 

 OF PERSPIRATION. 
 
 regions or pares cf the body) (§ 36.) contains, for 
 the moil part, a certain quantity of common fat. 
 
 § 177. 
 Befides nerves and abforbaits, of which w« will 
 fpeak particularly on a future occafion, the cor'tum 
 or true fkin is alfo plentifully fupplied with innu- 
 merable fmall blood-vejfch ', which run on its exte- 
 rior furface, and, as we learn from a fucceisful 
 injection, inveft the fame with reticular expansions 
 of the mod clofe and fubtile texture. 
 
 § 178. 
 Over the fame exterior furface is alfo inter- 
 fperfed an immenfe afRmblage of fmall febaccous 
 follicles, which thoroughly anoint the whole cutis 
 with a very fubtle and limpid oil, of fuch a nature 
 as not to be eafily evaporated and dried up. This 
 fine fluid fhould neither be confounded with the 
 common fiueat, nor yet with that fetid fuuflancc 
 which infefts only fome particular parts of the 
 body. 
 
 § x 79- 
 
 Finally, almofl the whole of the true fkin is 
 planted with hairs of various kinds. The mo ft 
 numerous and abundant of thefe are very fhort 
 and tender, inclining more or lefs to the nature of 
 down ; of hairs which fall under this defcription, 
 
 fcarcely 
 
OF PERSPIRATION. 133 
 
 fcarccly any part of the body is destitute, except 
 the eye-lids, the male penis, the palms of the 
 hands, and the foles of the feet. But, on certain 
 parts of the body, the hairs, being deflined for 
 particular ufcs, grow to much greater lengths ; 
 examples of this we have in the hair of the head, 
 in the eye-brows, in the eye-lafhcs, the hairs in 
 the noflrils, the whiikers, the beard, together with 
 fuch hairs as grow in the arm-pits, and about the 
 anus and parts of generation. 
 
 § 180. 
 In general, man is indeed lefs hairy than mod 
 other anim.ils belonging to the clafs mammalia. 
 A difference exifts, however, in this refpecl, be- 
 tween the inhabitants of different countries. For, 
 to pafs in filcnce over thofe nations who are in 
 the daily practice of plucking out, as well the 
 beard, as the hairs which appear on other parts 
 of the body, there are not wanting certain tribes, 
 who are naturally destitute of hair ; of this defcrip- 
 tion appear to be the Tungufos and the Buratce. 
 On the other hand, we are informed by travellers 
 of the higheft reputation in point of veracity, that 
 the inhabitants of Nadigfda, one of the northern 
 Kurilikian Hlatids, are remarkable for the unufual 
 quantities cf hair with which their bodies are pro- 
 tected. 
 
i 3 4 OF PERSPIRATION. 
 
 § III. 
 
 Ne'ther arc the varieties fewer, which are ex- 
 hibited by the hair, in regard to length, flexility, 
 curlinefs, and, more efpecially, in point of colour : 
 this lad property depends, in general, on the power 
 of climate, on age, and other caufes, which exert 
 their influence in perfect conformity to the efla- 
 Mifhed laws of nature ; but it fometimcs alfo de- 
 pends on a morbid and mifplaced temperament, as 
 appears to be the cafe in the white natives of 
 ./Ethiopia. The colour of the hair correfponds, 
 for the mod part, to that of the eyes. 
 
 § 182. 
 
 There is alfo a further peculiarity in the direc- 
 tion of the hairs, on certain parts of the body ; 
 thus, for example, on the vertex or crown of the 
 head, they purfue a fpiral direction ; on the pubes, 
 they diverge and point upwards ; on the pofterior 
 fide of the arm, they look, (as on the ape, and 
 contrary to their direction on the fatyr), towards 
 the elbow, (that is, they point from the fhoulder 
 downwards, and from the wrilt upwards) : of the 
 directions purfued by the eye-brows and eye-la(hes, 
 it feems unneceflary to fay any thing on the pre- 
 sent occafion. 
 
 S *fy 
 
OF PERSPIRATION. i 3S 
 
 § *H 
 
 The hairs originate from the interior furface of 
 the true (kin, which contains a quantity of fat : 
 they are fixed with confiderable firmnefs in each 
 of the fmall bulbs, which are compofed of two in- 
 volucra ; the external involucrum is vafcular, and 
 oval ; the internal is cylindrical, appears continu- 
 ous with the epidermis, and ferves as an immedi- 
 ate covering to thofe elaftic filaments of which 
 each individual hair is itfelf compofed, and which 
 are from five to ten in number. 
 
 S l8 4- 
 The hairs are always completely befmeared with 
 an oily halirus, and are almofl incorruptible. They 
 appear to pc fiefs more of the nature of original 
 ele&rics (or of eleclra per fe, as they are called), 
 than any of the other parts of the body. Their 
 nutrition is extremely fimple and eafy, as is alfo 
 their re-produ&ion after having fallen off, unlefs 
 the cutis itfelf be labouring under fome morbid 
 affecYion. 
 
 § 185- 
 
 Befides other important purpofes which thefe 
 
 common integuments of the body ferve, they are, 
 
 in a particular manner, to be reckoned among the 
 
 number of the excretory organs of the fyflem ; by 
 
 I 4 their 
 
i 3 6 OF PERSPIRATION. 
 
 their affifhmce, in this point of view, certain foreign 
 matters, which would from retention prove highly 
 noxious, are hourly eliminated and totally removed 
 from the general volume of our fluids. 
 
 The truth of the above pofition is fully demon- 
 ftrated and eftablilhed, by the well-known circum- 
 ftance of miafmata being completely removed from 
 the fyftem, under the appearance of exanthemata 
 or eruptions ; it is alfo proved by the odours of 
 garlic, mufk, and other fubftances taken into the 
 body, palling by the fkin ; it is ftill further demon- 
 ftrated and confirmed by the procefs of fweating, 
 and by other phenomena of a fimilar nature. 
 
 S 1 86. 
 But above all, thofe excretory paflages convey 
 off a certain fluid, which is called the perfpirable 
 matter of Sa?iciorii(Sy in honour of that moft acute 
 and ingenious philofopher, who infiituted the firfl 
 ferics of rational inquiries for the exprefs purpofc 
 of afcertaining its utility and importance. 
 
 It is neceflary, however, to obferve, that under 
 this appellation, phyflologifh commonly defignate 
 excrementitious matters, which, if not oppojite, arc 
 at lead exceedingly different, in their natures, and 
 which ought, therefore, to be diftinguifhed from 
 piich other with the utmcfl accuracy and care j as 
 
 the 
 
OF PERSPIRATION. 
 
 J 37 
 
 the excretion of fweat, for inftance, from the 
 genuine matter of perfpiration* 
 
 The former (/. e. the fweaty excretion) is a 
 liquid of an aqueous nature, faltifh to the tafte, 
 and which fcarcely ever iflues fpontaneoufly from 
 the healthy body when in a ftaie of tranquility 
 and reft. 
 
 But the latter, (viz. the genuine matter of per- 
 fpiration), of which alone we intend to treat on 
 the prefent occaficn, is an aeriform fluid, perman- 
 ently elaftic, and bearing a very ftriking refem- 
 blance to that which we exfpire by the lungs. 
 
 § 187. ^ 
 Like that elaftic fluid, it is highly charged with 
 the principle of phlogifton, like that, it precipitates 
 quick-lime from the water in which it was fuf- 
 pended, and, like that, it is alfo unfit both for 
 contributing to the nourifhment of flame, and alfo 
 for fupporting the procefs of refpiration, &c. 
 
 § 188. 
 The quantity of this fluid that exhales from the 
 whole fupcrficies of the body (which, in an adult 
 human fubjccl of the middle fize, amounts by 
 meafuremcnt to about fifteen fquare feet) can 
 fcarcely be reduced to accurate calculation. 
 
 For, 
 
138 OF PERSPIRATION. 
 
 For, that the fcales, which from the time of 
 San£torius have been made ufe of for afcertain- 
 ing the exact weight of the body, are not well cal- 
 culated for determining the precife quantity of this 
 elaftic fluid, may be eafily undcrftood from what 
 we have juft now faid refpecVing the different fub- 
 flances whi:h are eliminated from the fyftem by 
 the flrin, befides the true matter of perfpiration. 
 
 It was long fince difcovered, that the nature 
 and quantity of prrfpiration vary extremely, not 
 only in different pcrfons, but even in the fame 
 perfcns, at different times. It feems at prefent, 
 hovvever, to be a point too well afcertained to 
 admit of a doubt, that there does really exift, 
 with refpedt to the matter perfpired, a national 
 variety and peculiarity ; the truth of this we con- 
 fidently reft on what has been faid, by aurhors of 
 the higheft veracity, with regard to the lingular 
 and fpecific odours which are tranfpircd through 
 the fkins of the Caribeans, of the Greenlanders, 
 of the ./Ethiopians, and alfo of the individuals be- 
 longing to other barbarous tribes. 
 
 § .89. 
 
 On confidering what has been faid with refpeft 
 to the vafcularity obfervable in the texture of the 
 ikin (§ 177), and alfo with refpeft to the analogy 
 that exifts between the matter of perfpiration and 
 
 the 
 
OF PERSPIRATION. 139 
 
 the air we expire (§ 1 87); and further, on confider- 
 ing what has been advanced refpe&ing the power 
 and influence of the fmalleft vafcular ramifications, 
 in the generation of animal heat — to him, I fay, 
 who carefully weighs and attentively confiders all 
 thefe circumftances, it will appear extremely pro- 
 bable, that there exifts a ftrik'ng fimilitude indeed 
 between the action of the lungs in refpiration, and 
 that of the fkin in the procefs of perfpiration. It 
 will appear that there exifts between the cutis 
 and lungs a reciprocal confent ; fo that the one 
 may be fuppofed capable of aflitling and fome- 
 what relieving the other, and even of fupplying 
 its place, at leafl to a certain degree, in cafe of 
 any accident or derangement. 
 
 § 190- 
 In fupport of this opinion we can adduce the 
 concurrent teftimonies of a variety of phenomena, 
 obfervable not only in a found, but alfo in a 
 difeafed, itate of the fyflem. 
 
 Some of thefe phenomena are, for example, 
 thofe leading points, in which the human fceius, 
 as well as that of the other animals belon^imj to 
 the clafs mammalia, differ from the incubated 
 chick, or the young of the feathered tribes, while 
 yet enclofed in the farhtes of the egg. 
 
 A further 
 
i4« OF PERSPIRATION. 
 
 A further evidence in favour of the fame 
 opinion, is that fingular coldnefs of certain parts 
 of the body, even in warm blooded animals, (as 
 in the nofes of clogs, &c.) which appears to be 
 refcrr-d with ftlfficient propriety, to a lefs phlo- 
 giftic action of the fmall veflels, with which thofe 
 parts abound. 
 
 On the contrary, from an encreafed action of 
 the minute vcfT.ls in certain parts of the body, we 
 ex -lain, with the lumoH: fairnefs and facility, a 
 variety of morbid fymptoms, f.ich, for inilance, as 
 that lingular heat and flaming in the palms of the 
 hands, which occur fo frequem'y* and are fo 
 ftrikingly obfervable in patients labouring under 
 a hectic fever. 
 
 With regard to that vicarious action of which 
 we formerly fpoke, and by which we (aid it ap- 
 peared probable, that the functions of the lungs 
 and cutis lend mutual aid and afliftance to each 
 other ; that fuch an action does unequivocally 
 exift, we derive fome force of teftimony from thofe 
 phenomena in pathology, where human fubjeets, 
 after birth, and even after advancing to an adult 
 age, having their lungs almod totally deftroyed by 
 a confumption, or highly vitiated by fome other 
 contamination, have nevcrthelefi furvived fuch 
 melancholy misfortune?, for a long time, and in 
 
 feme 
 
OF PERSPIRATION. i 4I 
 
 fame cnfe? have even paded fever.il years, during 
 the whole of which period tlry appeared to be 
 almo't emirely -.'cprived of the ufe and advantages 
 of refpiration. 
 
 § J 9 T - 
 
 Finally, It does not appear improbable, but 
 that the interior f.iface of the alimentary canal, 
 may alfo, befides its other primary functions, be 
 perpetually engaged in the performance of a phlo- 
 giflic procefs, not unlike that conducted by the 
 Jkin and pulmonary fy/iem. 
 
 This cnnal or tube appears, indeed, to be the 
 only interior part of the body, except the lungs 
 themfelves, to which the atmofpheric air has free 
 accefs ; but that the air has really free accefs to 
 the prima vja a or firjl pafjages, as they are called, 
 and that we f wallow that elaftic fluid in con- 
 fiderable quantities, are matters, much too plain, 
 to fland in need of any proof. 
 
 Further, That the air which we fwallow 
 undergoes a change very fimilar to the change 
 fuffered by that taken by infpiration into the 
 lungs, is fatisfactorily demonftrared by the nature 
 of the air contained in the whole alimentary canal. 
 
 Finally, 
 
M2 OF THE SENSORIUM 
 
 Finally, To all thofe concurring circum(lance9 
 we may further add, that truly aftonifhing con- 
 geries of fmall blood veflels, fpread in profufion 
 over the interior furface of the inteftines, which 
 is commonly believed to be equal in extent to the 
 external fuperficies of the whole body. 
 
 SECT. XV. 
 
 OF THE SENSORIUM AND NERVES. 
 
 § I92. 
 
 VV E come now to treat of another 
 clafs of the functions of the human body, which 
 embraces what we denominated the animal fane- 
 tions (§ 63): by means of thefe, an uninterrupted 
 commerce and intercourfe are kept up between 
 the body and the various faculties of the mind. 
 They belong therefore exclufively, (as indeed the 
 name itfelf plainly imports,) to organifed and ani- 
 mated bodies ; but as they pervade the whole 
 animal kingdom more univerfally than the vital 
 functions, they appear to have an exceedingly ju ft 
 and well founded claim to the epithet, animal. 
 
 § J 93- 
 
AND NERVES- 143 
 
 § J 93« 
 The organs which are principally fubfervient to 
 
 the exercife of thefe functions are, the cerebrum, 
 the cerebellum, and their appendage the medulla 
 fpinalis, together with the nerves that originate 
 from thefe three fources. The whole of thc-fe 
 organs may, with fufficient propriety, be ar- 
 ranged under two leading claffes, namely, the Se?i- 
 forium and Nerves. The former of thefe em- 
 braces (if we except the nerves themfelves, and 
 thofe parts which conftitute their more immediate 
 origins) all the remainder of that whole fyftem, 
 which forms, more particularly, the vinculum or 
 medium of connexion, that exifts between the 
 offices or functions of the nerves and our nobler 
 part, the faculties of the mind. 
 
 § 194* 
 
 On this divifion is founded that beautiful obfer- 
 
 vation of the illuftrious Sommering, in which he 
 alledges, that the relative magnitude which the 
 two preceding clalfes of organs bear to one 
 another, correfponds fo accurately with the fa- 
 culties of the mind, that the fmaller and lefs bulky 
 the nerves of animals are, when compared to the 
 fize of the other organs or parts which we have 
 comprehended under the denomination of Sen- 
 forium, the more vigorous and active are the fa- 
 culties or their minds. In this refpeel he obferves, 
 
 that 
 
144 OF THE SEKSORIUM 
 
 that man may be faid to pfcffda the largeft cere- 
 brum or brain, it" its bulk be compared to the 
 fmall fize of the nerves that originate and proceed 
 from ir, but not if its weight be compared with 
 the relative weight of the whole body. 
 
 § x 95- 
 Befides the bony cranium or fkull, in which the 
 cerebrum iifelf is endofed, it is dill farther inverted 
 with three involucra or coverings ; thefe are the 
 dura and pia ?uatres, between which is expanded 
 the third, viz. the tunica arachnoidea* 
 
 § 196. 
 
 The dura mater, which lines, as a periofteum, 
 the cavity of the encephalon, is lengthened out 
 into a variety of partitions or proceffes. By its 
 falciform procefs, which is the mod prominent and 
 remarkable, it feparates from each other, the two 
 hemifpheres of the brain ; while, by means of that 
 procefs -called the tentorium, it forms a partition 
 between the cerebellum and the parts fituated above 
 it, and thus, by giving fupport to the pofterior 
 lobes of the brain, prevents them from making an 
 undue preflure on the fubjacent cerebellum. 
 
 Further, the dura mater, by various duplicaturcs 
 
 or doublings of its own membrane, forms what 
 
 are called the venous finufes, while it gives them at 
 
 4 the 
 
AND NERVES. 145 
 
 the fame time firmnefs and fupport, and prevents 
 them from being unduly compreiTcd. Through 
 thefe finufes the blood of the encephalon, or parts 
 contained within the cranium, glides back towards 
 the heart : this blood is faid, by phyfiologifts, to 
 poffefs properties peculiar to itfelf, and appears, 
 from attual calculation, to be fo confiderable in 
 quantity as to amount, at leaft, to one tenth part 
 of the whole mafs of blood contained in the human 
 body. 
 
 § J 97- 
 Next to the dura mater lies the tunica arachnoU 
 dea, fo called from its extreme tendernefs and filmy 
 texture. It is deftitute of blood-veilels, (§ 5.J, 
 and does not, any more than the dura mater, enter 
 the various Juki or furrows, and receive the dif- 
 ferent eminences or ridges, which mark the fur- 
 face of the cerebrum, but only expands, with uni- 
 formity, over the whole volume of that important 
 vifcus. 
 
 § 19S. 
 
 Very different from this is the ftate and fitua- 
 tion of the internal involucrum or covering of the 
 brain, on which the ancients bellowed the name 
 of pia mater. This membrane every where ac- 
 companies the cortical part of the cerebrum fo 
 clofely, that the innumerable fmall blood-veffels, 
 
 vol. 1. K with 
 
1 4 5 OF THE SENSORIUM 
 
 with which it is profufely fupplied, enter, and 
 even perforate the cortex itfelf, with their infini- 
 tude of minute ramifications ; hence, when the pia 
 mater is feparatcd by force from the cerebrum, its 
 external furface prefents a fmooth and exquifitely 
 beautiful polifh, while its internal furface, on the 
 contrary, is confiderably villous, and refembles, not 
 a little, thofe delicate radicles by which the moffe« 
 adhere to their native foil, or places of growth. 
 
 § i99- 
 
 Both the cerebrum and cerebellum are compof- 
 
 ed of a variety of parts, different from each other 
 both in texture and figure, the ufes of which have 
 been hitherto generally unknown : thefe parts are 
 particularly diftinguifhed by the four ventricles, as 
 they are called, the communication between which 
 has been of late traced and developed, with the 
 utmoft accuracy, by the illuftrious Monro : of 
 thefe ventricles, the two anterior and the fourth 
 conta'n what are denominated the plexus cboroidei, 
 the ufes and functions of which are alfo involved, 
 as yet, in intricacy and doubt. 
 
 § 2CO. 
 
 In all parts, of both the cerebrum and cerebel- 
 lum, there exiii two kinds of fubilance, one of a 
 cineritious or alh-colour, which is called the corti- 
 cal part, although it does not always form the 
 
 exterior 
 
AND NERVES. M7 
 
 exterior (tratum, the other white and mining, and 
 therefore called the medullary portion. Agree- 
 ably to the obfervations of the illuftrious Som- 
 mering, there is interpofed between the two fore- 
 going fubflances, flill a third, of a colour border- 
 ing on white ; this body is moft confpicuoufly ob- 
 fervable in the arbor vita of the cerebellum, and 
 in the poflerior lobes of the cerebrum. 
 
 § 201. 
 
 The proportion, which the cineritious fubflance 
 bears to the medullary, decreafes as life advances; 
 ^ius, in infants it is greater, in adults lefs. Almoft 
 the whole of this cineritious fubftance, is com- 
 pofed of an immenfe affembiage and contexture of 
 the fmallefl fized blood-veffels, together with veffels 
 of an order flill inferior, even (o minute as to be 
 incapable of admitting any thing except a white 
 or colourlefs fluid of the mod exquifite tenuity, 
 (§ 79.) : a fmall number of thefe veffels paffes 
 into the medullary portion, which appears to con- 
 tain in its own compofition, (befides thefe minute 
 veffels and a quantity of very tender cellular mem- 
 brane), a foft pultaceous parenchyma, in which 
 phyfiologifls, even when armed and aided by the 
 moft powerful glaffes, have not yet been able to 
 difcover any uniform and definite texture. 
 
 K 2 § 20a. 
 
t 4 8 OF THE SENSORIUM 
 
 § 202. 
 
 In the cerebrum is obfervable a perpetual but 
 very gentle motion, bearing fuch a relation and 
 exact correfpondence to the procefs of refpiration, 
 that while the lungs are collapfed, and their 
 volume diminifhed in the act of exfpiration, the 
 cerebrum is flightly elevated, but immediately 
 fubfides again, when the thorax is dilated br 
 means of a fubfequent act of infpiration. 
 
 § 203. 
 What has been called by phyfiologifts the me- 
 dulla oblongata, terminates in the medulla fpinalis, 
 which is contained in that flexible tube, formed 
 by the vertebrae of the fpine or back, and is flill 
 clothed in the fame membranes which we have 
 already feen inverting the cerebrum or brain itfelf : 
 further, as the brain, fo likewife the fpinal marrow, 
 is found to coniift of two kinds of fubflance, with 
 this ftriking circumftantial difference, however, 
 that, in the latter, the cineriuous or afh-coloured 
 fubftance forms the internal, whilft the fhining or 
 medul'ary compofes the external, part. 
 
 § 204. 
 
 From each of the foregoing fources, namely, 
 
 the cerebrum and cerebellum, together with the 
 
 medulla fpinalis, the nerves primarily derive their 
 
 origins. Thefe are fmall ropes or cords, of a 
 
 colour 
 
AND NERVES. i 49 
 
 colour more or lefs whitim, differing likewife in 
 their degree of firmnefs), which are minutely 
 diflributea throughout almoft all the other foft 
 parts of the human body. This opinion of the 
 minute, and it?iiverfal, diflribution of the nerves 
 through every part of the human fyftem,. though 
 admiJTible as a general rule, is, however, fubjeft 
 to certain well founded exceptions. 
 
 § 204. 
 
 For it appears from an infinitude of experiments 
 made by the illuflrious Haller, and other able 
 obfervers, that there are feveral of the partes 
 fimilares (or fimilar parts § 46) of our bodies, in 
 which, the knife, and powerfully armed eye of 
 the anatomift, have not been able to detect the 
 {mailed veftige of nerves, and where neither fur- 
 gical obfervations nor live diffe&ions, often re- 
 peated by the mod dextrous hand, havefucceeded 
 in difcovering even the fainted phenomena of 
 feniibility. 
 
 In an enumeration of fuch parts, as appear to 
 be deflitute of fenfation and nerves, we mud em- 
 brace, befides the naked cellular membrane, the 
 epidermis, the reticulum mucofum, the hairs, and 
 the nails. 
 
 K 3 We 
 
i 5 o OF THE SENSORIUM 
 
 We include further, the cartilages, and bones, 
 with their perioftia and marrow. 
 
 To thefe mufl be added, the tendons, the aponeu- 
 roses, and ligaments; as alfo mod of the broader 
 and more extenfive membranes, fuch, for example, 
 as the dura mater and tunica arachnoidea ; the 
 pleura, with the mediaftinas and pericardium; the 
 peritoneum; the cornea, &c. 
 
 Under the fame head we arrange mod parts of 
 the abforbent fyftem, but more efpecially the 
 thoracic duel. 
 
 Finally, This catalogue of fuch parts as neither 
 poffefs nerves, nor are endued with fenfibility, 
 fhall be clofed, by the addition of the fecundities, 
 and umbilical cord. 
 
 § 206. 
 
 The primary or nafcent origins of the nerves, 
 emerging from the fenforium itfelf, have, as yet, 
 eluded the moft zealous researches of the fubtle 
 knife and prying eye of the anatomifl : it there- 
 fore flill remains a matter of controverfy and 
 doubt, whether the nerves on each fide of the 
 body derive their origins from the cor re/ponding, 
 or from the oppofite fide of the fenforium ? Cer- 
 tain pathological phenomena appear indeed to fa- 
 vour 
 
AND NERVES. 151 
 
 vour the latter of thefe opinions. It has been alfo 
 lately eftablifhed by the illuftrious Sommering that 
 a true decufTation or eroding of the optic nerves 
 does actually exift. 
 
 § 207, 
 A certain continuation of the pia mater accom- 
 panies the medullary part of the nerves in their 
 courfe, in fuch a manner, as to form for them a 
 vafcular cortex, or covering, of extreme tender- 
 nefs. No fooner, however, do thefe cords emerge 
 from the cerebrum > or the fpinal marrow, than 
 they affume a very fmgular habit and appearance, 
 by which they may be readily diftinguiflied from 
 almoft all the other fimilar parts of the body. 
 This peculiarity of appearance is produced by 
 fmall plicae or folds, which they exhibit, running 
 in angular directions, more or lefs oblique. Thefe 
 folds were formerly defcribed by P. P. Molinel, 
 who compared them, not inconfiftently with pro- 
 priety and fitnefs, to the rugas of the Iumbricus, 
 or round worm, or to the fmall rings of the afpera 
 arteria. 
 
 § 208. 
 
 The nerves, especially thofe of the fingle or 
 unpaired orders, fuch, for inftance, as the inter- 
 coital and vagantes or wandering nerves, are 
 every where furnilhed with ganglia, i. e. fmall 
 K 4 bulbs, 
 
152 OF THE SENSORIUM 
 
 bulbs, of a texture confidcrably compart, and of 
 a cineritious colour, fomewhat inclining to a pale 
 red : the functions and ufes of thefe bodies in the 
 animal economy have not yet been fatisfaftorily 
 afcertained and demonflrated. We are, however, 
 in the mean time, mod inclined to adopt the 
 opinion formerly entertained reflecting thefe fub- 
 ftances by the ingenious Zinn. That acute phy- 
 iiologift believed the ganglia to confift entirely of 
 mazy complications and intertextures of minute 
 nervous filaments originating from di Terent fources. 
 In confequence of this intricate and uninveftigated 
 texture of thefe bodies, he conjectured, that each 
 nervous filament, or thread proceeding from them, 
 participates, or contains in its compofition, a part 
 of every filament that enters into their ftruclure, 
 however numerous thofe filaments may be, or 
 however different the fources from which they 
 originate. 
 
 § 209. 
 
 Neither does there appear to exift any very 
 material difference between the nature of ganglh, 
 as jufl: defcribed, and of what are called plexus 
 nervqfi. Thefe latter are alfo indebted, for their 
 exigence and form, to a fimilar concurrence and 
 anaftomofin.T intertexture of nerves that originate 
 from different fources. The compofition of fuch 
 nervous filaments as ramify and proceed from thefe 
 
 plexus 
 
AND NERVES. 153 
 
 plexus nervoji, appears to be alfo perfe&ly analo- 
 gous to the composition of thofe, that originate 
 from the ganglia, of which we have already 
 fpoken. 
 
 5 210. 
 
 But as the nafcent origins of the nerves, fo like- 
 wife (with a few exceptions), the final termina- 
 tions of their extreme ramuli, or remote filamentary 
 branches, are as yet involved in the depth of ob- 
 fcurity. For if we except tfcofq tew n. rves that 
 terminate in a kind of rr.edullary expanfion, as the 
 optic nerve in the retina, and the foft portion of 
 the feventh pair, in that pulpy zone, contained be- 
 tween the fpiral laminse of the cochlea of the ear 
 — If, I fay, we except thefe two nerves, the eva- 
 nefcent filaments of fuch of the others as enter the 
 vifcera, the mufcles, the fkin, &c. become fo mi- 
 nutely blended with the real parenchyma of the 
 parts on which they are diftributed, and gradually 
 aflfume fuch a pulpy confidence, that the eye of 
 the anatomifl: can no longer trace them through 
 their mazy courfes. 
 
 SECT. 
 
154 OF THE NERVOUS SYSTEM. 
 
 SECT. XVI. 
 
 OF THE FUNCTIONS OF THE NERVOUS SYSTEM 
 IN GENERAL. 
 
 § 211. 
 
 WE have thus fecn, that of the fen- 
 forium, and nerves fo generally and minutely 
 diflributed throughout moll: parts of the body, a 
 complete fyflem is beautifully conftituted, which, 
 during the continuance of life, fcrves as a medium 
 of communication and mutual intercourfe between 
 the body and the mind. 
 
 § 212. 
 Various circumftancrs and phenomena combine 
 in rendering it probable, that the mind is indeed 
 attached and clofely connected to the brain itfelf. 
 That the brain is thus honoured and dignified in 
 its alliance is very powerfully and ftrikingly 
 evidenced, by mod of the inftruments of fenfation 
 being fituated in the very vicinity of that organ ; 
 by the aftoniming conformation of its various 
 parts, confidered with regard to their figure and 
 flructurc ; but more efpeciaily by the phenomena 
 attendant on its morbid rufec'iions. 
 
 S 213. 
 
OF THE NERVOUS SYSTEM. i 5 $ 
 
 § 213. 
 With refpeft to that connexion of which we 
 have juft hinted, I would further obferve, that 
 certain phyfiologifts, wantonly fporting in the de- 
 lufive fields of imagination, have fufFered them- 
 felves to be fo far influenced by the form and 
 fituation of particular parts of the encephalon, 
 that they have confidered, and even endeavoured 
 to prove, fometimes one, fometimes another of 
 thefe parts, to be indeed the very feat, and royal 
 court, (as it were) of the mind. This honorary 
 and fublime privilege, of affording a faered feat 
 to our nobler and immortal part, fome meta- 
 phyfical phyfiologifts have been folicitous to 
 beflow on the pineal gland*, others on the 
 cerebellum, others on the corpus caliofum f, and 
 
 * In favour of the Cartefian hypothecs, fome degree of 
 teftimony appeared to be derived from the diifeftions of 
 certain maniacs, in whom the pineal gland was found in- 
 verted with calculous concretions. On more accurate ob- 
 fervation, however, it was difcovered, that not only in 
 maniacs, but alfo in numerous other fubjedts poftefling the 
 moft complete degree of mental fanity, this fame glandular 
 body was furrounded, from about the 1 2th year of life, by 
 minute fandy concretions of a pearl-like appearance. — CI. 
 Sommering de lapillis vel prope vel intra glandulam pinea- 
 lem fitis, f. de acernulo cerebri Mogunt. 1785. 8. 
 
 f Thofe fictitious prerogatives both of the cerebellum and 
 corpus caliofum are refuted in a very mafterly manner by 
 
 Zinn 
 
256 OF THE NERVOUS SYSTEM. 
 
 others, again, on that part which has been deno- 
 minated pons Varolii. 
 
 § 214. 
 
 We are not by any means to fuppofe, that the 
 whole energy of the nervous fyftem depends on 
 the encephalon alone ; it is alfo derived in part 
 from the fpinal marrow, and even the nerves 
 themfelvcs pofTcfs fuch a degree of inherent or 
 native energy, as is fufficient of itfelf to throw the 
 mufcles into a ftate of convulfion. This native or 
 exclufive energy of the nerves, appears to be 
 principally fnpported and preferved by that vaf- 
 cular cortex or covering of thofe organs, of which 
 we briefly fpoke on a former occafion (§ 205). 
 It is, however, a truth which ought not to be for- 
 gotten, that this inherent power of the nerves 
 themfelves is lefs, and that energy, on the con- 
 trary, which is derived immediately from the 
 encephalon, greater, in man, than in other 
 animals, efpecially fuch as are fupplied with cold 
 blood. 
 
 § 2I 5- 
 The onice of the nervous fyflem appears, in a 
 particuler manner, to be two-fold. Firji, by means 
 
 Zian in his " Expcrim. circa corpus callofum, cerebellum, 
 duram meningem, in vivis animalibus inftitut. Goctting. 
 3719. 4. 
 
 of 
 
OF THE NERVOUS SYSTEM. 15) 
 
 of this fyftem, other parts of the body, efpecially 
 fuch mufcles as are fubjected to the influence of 
 the will, are excited to motion ; of this function, 
 however, we will treat more fully in another 
 place. But, fecondly, the nerves are peculiarly 
 fubfervient to fenfation ; whatever fenfible impref- 
 fions are made on the body, they, like active he- 
 ralds, convey and announce immediately to the 
 fenforium, and there give rife to perception. 
 
 § 216. 
 Finally, the fenforium is evidently poffeffed of 
 the following very lingular faculty or power, viz. 
 that, having received fenfible impreffions through 
 the medium and agency of certain nerve?, it is 
 able to re-act again in its turn, not only on the 
 fame nerves, but alfo on fuch as are completely 
 different. In tellimony of the truth and authen- 
 ticity of this pofition, it will be fufficient to men- 
 tion the action of the retina, when affected by 
 light, on the fenforium, and the re-action of this 
 latter, again, in either conilricting or dilating the 
 iris. 
 
 § 217. 
 
 It is principally from this lad fource, fha't we 
 are to derive and explain mo ft of the effects of 
 the imagination, and paffion? of the mind, 0.1 
 the human body : of tlufe eiTcfts we will fpeak 
 
 more 
 
158 OF THE NERVOUS SYSTEM. 
 
 more fully on a future occafion. To the fame 
 fourcc, alfo, mud we refer that extenfive and 
 diverfified confent of the nervous fyftem, which 
 prevails throughout almoft the whole body (§ 14.), 
 and the aftonifhing power and influence of the 
 fame, over moft of the other functions of the 
 animal economy. 
 
 § 218. 
 
 That the phenomena which we have juft men- 
 tioned, proceed from certain properties effential 
 to the nervous fyftem, is a pofition, that appears, 
 from obfervation and experiment, to be founded 
 on the mod indubitable evidence. But, to eluci- 
 date and explain the manner in which this fyftem 
 atts, in the production of fuch phenomena, is, 
 indeed, a difficulty of the utmoft magnitude. 
 
 § 219. 
 When we view the fubjeel: in a general light, 
 the various opinions, which have at different times 
 been advanced on this contefled point, may be all 
 referred to two leading dalles : one of thefe 
 alleges the action of the nervous fyftem, to de- 
 pend on a certain ofcillatory motion ; while the 
 other fuppofes it to be produced by the motion of 
 a peculiar fluid, refpecting the nature of which 
 phyiiologifts, again, hold different opinions. Thus, 
 while feme believe this fluid to be animal fpirits, 
 
 contained 
 
OF THE NERVOUS SYSTEM. 159 
 
 contained in, and palling through, vefiels, others 
 contend, that it is a certain modification of matter, 
 limijar to fire, electricity, or the magnetic effluvia* 
 
 § 220. 
 
 Although I am difpofed to adopt neither of 
 the above opinions as my own, yet it is proper to 
 obferve, that moil of the arguments, by which the 
 advocates of either hypolhefis have endeavoured to 
 invalidate the other, appear to me to be as crude 
 and inconclufive, as they ought to be fubtle, inge- 
 nious and forcible. This obfervation applies, as 
 well to the arguments made ufe of to prove the 
 ofcillations of the nerves, as to thofe advanced for 
 the purpofe of efhblifhing the exigence of a ner- 
 vous fluid. 
 
 § 221. 
 If, indeed, our views of the fubjeft be not erro- 
 neous, the two foregoing opinions may, without 
 impropriety, be united, and thus a third one 
 formed, more plaufible, at Ieaft, than either of 
 the originals, namely, that a certain nervous fluid 
 does actually exiil, and that this fluid is a!fo capa- 
 ble of motion, and of being thrown into ofcillatory 
 vibrations, when fubjecled to the action and influ- 
 ence of ftimuli. 
 
 § 222. 
 
j6o OF THE NERVOUS SYSTEM. 
 
 § 222. 
 
 Not to mention various other evidences, which 
 might be obvioufly deduced, from the different 
 phenomena of the nervous fyftem, the Jiruflure of 
 the brain itfelf, which bears a ftriking refemblance 
 to that of certain fecreting vifcera, appears indeed 
 to be highly in favour of the exigence of a nervous 
 fluid. It is furely a matter too obvious to admit 
 of controverfy, that there is no more need of any 
 direft tubes and canals, for the diftribution of 
 fuch a fluid through the nerves, than there is, for 
 the conveyance of a liquid through brown paper, 
 or any other nitre. 
 
 The nugatory calculations, rendering the aflo- 
 nifliing rapidity, with which the animal fpirits have 
 been fuppofed to hurry through their nervous 
 canals, in all pans of the fyftem, are fu ! j<:ets too 
 hypothetical' and vifionary to merit our time, or 
 command our attention. 
 
 § 223. 
 That an ofcillation of the nerves does indeed 
 exift, is a pofition, powerfully fupported by a great 
 variety of very ftriking and pointed phyfiological 
 phenomena. This ofcillation mud not, however, 
 be fuppofed to bear any refemblance to the rude 
 vibrations of tenfe chords, but is fuch a fubtle, 
 tremulous motion, as may be readily conceived to 
 2 take 
 
OF THE NERVOUS SYSTEM. 10T 
 
 rake place in the tender, pulpy fubftance of the 
 brain. That hearing is excited by an ofcillation 
 of a liquid, has been reduced to fatisfa&ory de- 
 monftration. That an ofcillatory motion fomewhat 
 fimilar takes place alfo, in the act of vifion, is 
 (though we fhouid not be willing to repofe impli- 
 cit confidence in the opinions of Leon. Euler) a 
 pofition founded, at lead, on firong probabilities. 
 That the action of the other fenfes depends alfo 
 on an ofcillatory motion of a fimilar nature, is an 
 opinion, which was not only embraced by the 
 illuftrious Newton*, but has been fince ably and 
 fuccefsfully defended in the writings of the fuga- 
 cious Hartley. It is on the principle of the exis- 
 tence of fuch a motion, that this laft mentioned 
 author, has firfh happily accounted for the affoci- 
 ation of ideas, and then, by the aid of this, pro- 
 ceeded to explain, with the utmoft ingenuity, mod 
 of the functions performed by the different facul- 
 ties of the mind |. 
 
 * Vide ejus Quscftiones ad calcem optices. Qu. 23. p. 
 355. edit. Lond. iynj-8. 
 
 ■f David Hartley's Obfcrvations on man, his frame, his 
 duty, and his expectations. Lond. 1749, vol. ii. 8. 
 
 vol. i. L SEC T. 
 
1 62 THE TOUCH. 
 
 S E C T. XVII. 
 
 THE EXTERNAL SENSES IN GENERAL, BUr 
 PARTICULARLY OF THE TOUCH. 
 
 § 224. 
 
 V7NE office of the nerves, as we have 
 already had occafion ro obferve, confifts in com- 
 municating to the Tentorium, impreffions made by 
 external objects. This they do through the me- 
 dium of the external fenfes, which officiate as 
 watchful centinels to the body, and diligent in- 
 flructors to the mind. 
 
 Thefe, therefore, (hall constitute, at prefent, the 
 folc objeel of our consideration. For to arrange 
 among the fenfes, the ftimulus or propenfity which 
 animals feel to evacuate their firces, the fenfatioa 
 of hunger to which they are fuhjected, or other 
 internal calls of nature of a fimilar kind, would 
 be, as Haller formerly obferved, an unnecefiary 
 fpecies of fubtility and refinement. 
 
 225. 
 
 It ought to be remembered, that no other clafs 
 
 of functions belonging to the animal economy, is 
 
 fubjected to fuch an aftonifhing variety in different 
 
 individuals, as that of the external fenfes, which 
 
 conflirutes 
 
OF THE TOUCH. 163 
 
 constitutes the fubjec'r. of our prefect confidenuion. 
 This infinite diveriiry, which exifls between thefe 
 fenfes in different individuals, is either natural or 
 acquired, and relates to their greater or lefs acu- 
 men or fharpnefs, their fubtlety, or to the manner 
 in which they are affe&ed by fimilar applications 
 of the fame ftimuli. 
 
 § 226. 
 In giving an entire and complete account of 
 the external fmfes, it appears moll proper to 
 begin with the touch, this being the one which 
 manifests itfelf at the earlieft period in the human 
 fubjec'r. after birth. The organ of the fenfe of 
 touch is expanded over the whole fuperficies of 
 the body, and is fo conflituted and formed as to 
 be affected by much the greatefl number of the 
 properties of external objects. 
 
 § 227. 
 For we are not only made fenfible of certain 
 qualities of fubftances by means of the touch 
 alone, as of heat, hardnefs, weight, &c. but there 
 alfo exift other qualities, fuch, for inftance, as 
 figure, diflance, &c. of which we acquire, a much 
 more certain and accurate knowledge by the aid 
 of the touch, though it mad be acknowledged 
 that thefe qualities are at the fame time fuhject to 
 the cognizance of fome of the reft of our fenfes. 
 L 2 § 228, 
 
OF THE TOUCH. 
 
 § 228. 
 The touch is lefs liable to deception than the 
 other fenfes ; and is capable of becoming, by cul- 
 tivation and attention, fo exquifitely perfect and 
 refined, as to be able to compenfate, in a certain 
 degree, for any deficiency in its fifttr fenfes, more 
 efpecially in that of vifion. 
 
 § 229. 
 The organ of this fenfe is indeed the fkin in 
 general, concerning the fabric and texture of 
 which we fpoke formerly ; but thofe parts that 
 are more immediately fubfervient to the touch, 
 arc the papillae of the corium or cutis vera; thefe 
 papillae exhibit various figures in different parts of 
 the body; they are indeed, for the mod: part, ver- 
 rucofc, in other places they are fungous, in others 
 filamentous or thread-like, &c. under all which ap- 
 pearances, the extremities of the cutaneous nerves 
 terminate after the manner of fmall pulpy pencils. 
 
 § 230. 
 But by far the mod important and difiinguifhed 
 inftruments of the touch are, in particular, the 
 hands, the fkin of which is impreiTed with a great 
 number of flriking peculiarities. Thus, for ex- 
 ample, the fkin on the palms of the hands, and on 
 each ii'le of the joints of the fingers, is fr.lcated 
 and completely deftitute of hair, for the purpofe of 
 
 facilitating 
 
OF THE TOUCH. 165 
 
 facilitating the folding or doubling up of thofe 
 parrs. The extremities of the fingers, on their 
 internal, and of the toes, on their inferior, fur- 
 faces, are furrowed with flight and very elegant 
 grooves running in directions more or lefs fpiral : 
 bu rhe former, on the exterior, and the latter on 
 the fuperior, fides, of their terminations, are pro- 
 tected from injury by nails. 
 
 § *3'« 
 
 Thefe fcutiform nails are poffeffed only by man, 
 and a few other animals, (belonging to the clais 
 mammalia), which are alfo furnifhed with hands, 
 and excel in the acutenefs of their fenfe of touch. 
 Thefe nails appear to be defigned for the purpofe 
 of making a gentle refinance to the preffure of 
 the fingers when examining fubfiances, and thus 
 aiding their action. 
 
 The nails, though of a horny nature, mud 
 neverthelefs be confklered, on the whole, as pro- 
 ductions or continuations of the epidermis : for 
 immediately under them lies the reticulum muco- 
 fum, which in ./Ethiopians is black ; and finally, 
 beneath this again is expanded the corium or true 
 fkin, which is firmly attached to the perioMium of 
 the extreme phalanx of the fingers. Alfo thefe 
 conftituent parts of the nails are ftriated in a lon- 
 gitudinal direction. At their pofterior margins 
 
 L 3 (which 
 
i66 OF THE TASTE. 
 
 (which arc difHnguifhed by fmall femilunar fcg- 
 ments, of a fhinmg or fomewhat brilliant ap- 
 pearance) they arc fecurely fixed in a groove 
 formed by a reflecr.:on of the cutis, from whence 
 by a daily, but very moderate, increafe, they are 
 gradually protruded forward, in fuch a manner, as 
 to be completely renovated in every term of about 
 fix months. 
 
 SECT. XVIII. 
 
 OF THE TASTE. 
 
 § 232. 
 
 1 ASTES are certain impreffions made 
 on, and perceived by, the tongue, an J alfo, in fome 
 meafure, by the adjoining cutaneous parts of the os 
 internum (/. c. the infide cf the mouth); thefe parts 
 are, in particular, the medium palati^ the fauces, 
 the cheeks, and even the lips themieives ; with 
 refpect, however, to the whole of thefe auxiliary 
 parts, it in proper to obferve, that they have no 
 perception of any tafies except fuch as are acrid 
 or intenfely bitter. 
 
 § 233- 
 
OF THE TASTE. 167 
 
 The principal inftrument of tafte is //v tongue, 
 an organ capable of the utmoft agility in motion, 
 very pliable, and exceedingly changeable in poinj: 
 of form : it confifts of a flelliy texture, which ex- 
 hibits a (hiking appearance, fomewhat referoblJng 
 the texture of the heart. 
 
 § 234. 
 It is inverted with involucra or coverings, which 
 hear a fimilitude to the different llrata of the cutis : 
 tbefe arc, the cpithelion, which correfponds to the 
 cuticle, the reticulum Malpighianum, and laftly, 
 a papillary membrane, that differs but little in its 
 ilruiSiure from the corium or true fkin. 
 
 § *35- 
 The principal difference confifts in this, that 
 the epithelion, instead of a fine cutaneous oil, is 
 lubricated and moiftened by mucus, which exfudes 
 from that imperceptible orifice, named after Mei- 
 bomius, and alfo from the reft of that glandular 
 expanfion, difcovercd by Morgagni : another point 
 of difference is, the conformation of the papillae, 
 which are divided into the petiolated, the obii/ft, 
 and the conlzal ; of thefe, the former, being very 
 few in number, are placed in a lunated arrange- 
 ment, a: the root of the tongue, while the others,, 
 being of various fizc^, are crouded promifcuoufly 
 L 4 and 
 
ioS OF THE TASTE. 
 
 and without order, on the back of the tongue, 
 but more efpecially on its edges an J tip, -where 
 the fenfe of tulle is moll acute and exquiiite. 
 
 § 236. 
 To thefe papillce pafs the extreme filaments of 
 the lingual branch of the fifth pair of nerves, by 
 the offices and aid of which it appears probable, 
 that the fenfe of tafte is proximately generated and 
 preferved. 
 
 For the ninth pair of nerves, and alfo that 
 branch of the eighth, which is diftributed through- 
 out the tongue, appear to be fubfervient to the 
 various motions performed by that organ in chew- 
 ing, fu allowing, fpeaking, &c. rather than to its 
 function as the immediate inftruraent of tafte, 
 
 § 237. 
 That the tongue may exercife the fenfe of tafle 
 in perfection, it is fleceflary for it to be kept in a 
 ftate of complete humidity ; the fubftance to be 
 tailed flaonld alfo be a liquid, and ought to abound 
 with falts in a ftate of foiution : for if either the 
 tongue itfelf, or the fubflances applied to it be 
 dry, it may then indeed examine them by the 
 touch, which it generally poffeiTes in an exquifite 
 degree, but cannot with ftri&nefs and propriety 
 be faid to tafte them. 
 
 When 
 
OF SMELLING. itft, 
 
 When the tongue difcharges the office of 
 tailing with mod perfection and acutenefs, the 
 papillae, fituated on its apex and edges, appear to 
 be brought into a ftate of genuine, though flight, 
 erection. 
 
 SECT. XIX. 
 
 OF SMELLING. 
 
 § 238. 
 
 £)Y means of the fenfe of fmelling we 
 perceive impreffions made by the odorous effluvia 
 of ftibftances, which being inhaled in infpiration, 
 come in contact with that part, in particular, of 
 the Schneiderian membrane, which inverts each 
 fide of the feptum narium, and lines the convex 
 furfaces of the concha. 
 
 § 2 39- 
 For although the whole of the internal nares, 
 together with the adjoining finufrs, which open 
 into them, be lined with a humid membrane, 
 fimilar in appearance to the Schneiderian, it 
 neverthclefs appears to be diverfied in its nature 
 in different places. 
 
 That part of the membrane, which is fituated 
 near the opening of the external nares themfelves, 
 
 bearing 
 
r7© OF SMELLING. 
 
 bearing a ftronger refcmblance to the other part! 
 of the real cutis, is overfpread with febaceous fol- 
 licles, which are completely mantled in clutters ol 
 hair. > 
 
 But that part which lines the fepium narium, 
 and concha, is of a fungous nature, and abounds 
 with fmall muciferous cryptae or cells. 
 
 Finally, Thofe portions which invert tl 
 parictcs of the frontal, the fphenoidal, the ei 
 moidal, and the maxillary finufes, are by far 
 moil tender and delicate of all, and are complc 
 cverfpread with an infinitude of minute bio 
 vefTels, which conftantly exhale from their ex- 
 tremities a fubtle dew-hke fluid of an aqueous 
 nature. 
 
 § 240. 
 The principal, if not, indeed, the only ufe of 
 thofe finufes appears, therefore, to be, to furniih 
 a watery liquid, of fuch a nature, as has been juft 
 defcribed, which being firft conveyed into the 
 three paffages or avenues of the nares, may be 
 from thence communicated to thofe adjacent parts, 
 which, we have already faid, conftitute the imme- 
 diate inflrumtnts of the fenfe of fmelling. By 
 thus fupplying, with a due degree of humidity, 
 the parts which proximately form the olfactory 
 
 creans. 
 
OF SMELLING. 171 
 
 organs, thofe finufes contribute, not a little, to 
 preferve the a'cutenefs and perfection of this ia- 
 terefting fenfe. 
 
 For the attainment of this end, fuch a wife pro- 
 vifion is made by the very fituation of thofe feveral 
 fmufes, that in whatever pofirion the head be 
 fu tfered to reft, one or other of them may {till 
 difcharge and depofi: a quantity of this fubtle dew, 
 on the immediate feat of the fcnfe of fmelling. 
 
 § 241. 
 The fungous part of the nafal membrane, of 
 which we have already fpoktn, and which con- 
 ftitutes the proximate organ of fmelling, befides, 
 the immenfe number of minute blood-vefTcls with 
 which it is overfpread (and which are rendered in 
 a particular manner remarkable, by this circum- 
 itance, that there are no other vefiels in the whole 
 body equally liable to fpontaneons hemorrhages); 
 befides thefe fmall blood-veffels, I fay, this part 
 of the membrane is alfo furniflied with nerves, 
 efpecially from the firft pair, and alfo from both 
 branches of the fifth pair : of thefe, the firft pair 
 appears to be of itfelf folely fubfervient to the fenfe 
 of fmelling ; while the others fuppiy the parts, to 
 which they are diftributed, with branches for the 
 purpofes of common fenfation^ fuch, for example, 
 as that which gives rife to freezing, &c. 
 
 § 242. 
 
17- OF SMELLING. 
 
 § 242. 
 The extreme filaments of thi3 firft pair of nerves 
 are not, (as is the cafe in the organs of touch and 
 tafle), lengthened out and rounded into papillary 
 elongations, but appear to deliquate, or melt down, 
 as it were, into the fpongy and uniform paren- 
 chyma of the membrane in which they terminate. 
 
 § 2 43- 
 In new-born infants, the chamber deftined for 
 the immediate recep-ion of odours is narrow, 
 as yet extremely imperfect. The finufes, of which 
 we have already fpoken, have at this tim: fiercely 
 made their appearance : hence, infant do ti t ac- 
 quire the fenfe of fmelling till a late period, ; 
 expanfion and complete formation of their internal 
 nares are but gradually and very ilowly accom- 
 pllfhed. The larger thofe inflruments become, 
 and the more accurately they ate formed and 
 finifhed, the more exquifite will be the acutenefs 
 and perfection of this fenfe. 
 
 § 244. 
 Finally, it is a truth well worthy of being re- 
 membered, that there is fcarcely another external 
 fenfe, which pofTirfies fuch a powerful connection 
 with, and influence over, both the fenforium itfelf, 
 and the internal fenfes, as that of fmelling. 
 
 There 
 
OF HEARING. 173 
 
 There is none fubjett to fuch (hiking diofyn- 
 crafies ; none better calculated either to produce, 
 to prevent, or to remove, paroxyfms of fainting. 
 
 Neither is there any one fufceptible of more 
 delicate and pleafing i m predion s ; the fmell is, 
 th fore, h; !Ut termed by Roufleau the fenfc 
 of the imagination. 
 
 Nor are there, laftly, any other fpecies of fen- 
 fations that appear to excite fo clear and vivid a 
 remembrance, as that which fpecific odours recal 
 to the memory. 
 
 SECT. XX. 
 
 OF HEARING. 
 § 244. 
 
 iOOUND, which is excited by a tremu- 
 lous collifion of elaftic fubftances, and propagated 
 from fonorous bodies, through the medium of the 
 air, is at length perceived by the fenfe of hearing, 
 after having proceeded onward in the following 
 order: viz. it is firft received by a (hell-formed 
 cartilage denominated the external ear, over which 
 
 a few 
 
174 OF HEARING. 
 
 a few of the human fpecies pnfTefs a power of 
 voluntary motion: bun.; colled a d concen- 
 trated, as it were, by means of this co icha < r ,. , 
 it pafTes immediately into the meatus audit onus, 
 which is thoroughly anointed and d ftnde 1 by a 
 very bitter and fomewhat yellowifti cerumen, or 
 wax-like fubftance : at the internal extremity of 
 this meatus auditorius it ftrikes aga ; nft the mem- 
 brana tympani, which is fituat::d in an oMi'jue 
 pofition, is firmly attached to an annular groove 
 in the os temporis, and forms a complete par ; 
 between this meatus auditorius, or pafTage for 
 found, and the middle portion of the ear. 
 
 S 246. 
 Behind this membrane, the middle portion of 
 the ear, denominated the cavity of the tympanum, 
 is fo fituated as to have its fundus or bottom 
 pointing upwards and inwards. 
 
 It contains three fmall bones, belonging to the 
 organ of hearing, the external of which, called 
 the malleus, is connected by its handle to the mem- 
 brane of the tympanum ; from its fpinous procefs, 
 which runs in a forward direction, a bulb or globe 
 is formed, (efpecially in an adult fubject), with an 
 annular groove fnnounding its bafe j this finall 
 globular head refts on the body of the incus. 
 
 The 
 
OF HEARING. 173 
 
 The incus itfelf is attached to the minute knob 
 or head of the Jlapes, by its longer procefs, which 
 extends nearly to the middle of the cavity of the 
 tympanum. 
 
 Finally, the Jlapes, refting its bafis on the fenef- 
 tra oralis, looks towards the vejlibulum of the 
 labyrinth, into which, found, having percuftuted 
 agairift the membrane of the tympanum, is propa- 
 gated by means of the connections of thofe three 
 oficcula or final! bones. 
 
 S 2 47- 
 The Eufbchean tube, running from the interior 
 
 parts of the fauces, opens alfo into the cavity of 
 
 the tympanum ; the inferior winding paffage of 
 
 the cochlea enters likewife into the fame cavity \ 
 
 over the mouth or orifice of this paffage, called 
 
 the fenejira rotunda, a fine membrane of a peculiar 
 
 nature is expanded. Phyfiologifts have not yet 
 
 afcertained and demonflrated, in a clear and fatif- 
 
 factory manner, the ufes of either of thofe two lad 
 
 mentioned parts. 
 
 § 248. 
 
 Laftly, in the deep and hidden receffes of the 
 $s petrofum lies the labyrinth, or internal portion of 
 the ear, which embraces again three fevcral parts. 
 
 Thefc 
 
176 OF HEARING. 
 
 Thefe arc the veftibuhim, which is fituated in 
 the middle between rhe other two, and into which 
 open, befidcrs the feneftra ovalis, both the five 
 mouths of the femicircular canals that run in a 
 backward direction, and alfo the fuperior winding 
 paffage of the cochlea, which extends and lies 
 anteriorly. 
 
 § 2 49- 
 The labyrinth itfelf contains a very fubtle, lim- 
 pid water, which has been named after the illuf. 
 trious Cotunnius, and which that celebrated phy- 
 fiologiil difcovered to be abforbed by two very 
 minute canals : thefe fmall canals, called by Co- 
 tunnius, aqueducts, (and by Meckel diverticula), 
 arife, the one from the veftibulum itfelf, the other 
 from the inferior winding paffage of the cochlea. 
 
 § 250. 
 The foft portion of the feventh pair of nerves, 
 together with the hard, (which afterwards paffes 
 through the aquedud of Fallopius), having en- 
 tered the internal chamber of hearing, tranfmits 
 its medullary filaments through the perforated 
 bottom of that cavity. Thefe filaments pafs, in 
 part, to the vcftibulum and femicircular canals, 
 but are diftributed more efpecially over the bafe 
 of the cochlea, where their extremities are ar- 
 ranged in fuch a manner as to run between the 
 2 laminas 
 
OF HEARING. 17? 
 
 laminae or plates of the feptum of the cochlea, 
 exhibiting the appearance of a fine medullary- 
 zone, beautifully ornamented with plexiform ftria? 
 or ftreaks. 
 
 § 251. 
 The ofcillatory tremor which we formerly traced 
 and followed up, even to the feneflra ovalis, 
 (§ 246.), is from thence propagated to the vefli- 
 bulum, where, finally, through the medium of the 
 fubtle aqueous liquid already defcribed (§ 249.), 
 it ftrikes and imprefles the auditory nerves them- 
 felves, which are distributed with infinite art and 
 ingenuity throughout the mazy circumvolutions 
 of the labyrinth. 
 
 § 252. 
 
 The impetus of found, finking againft the mem- 
 brane, and being propagated through the cavity 
 of the tympanum, is thought to be modified and 
 regulated, not only by the mufcles of the malleus 
 zndjiapes, which appear, in their contraction and 
 relaxation to be fubjeft to the influence of the 
 will, but alfo by the chorda tympani, which is 
 fituated in the middle, between the handle of the 
 malleus and the longer leg of the incus. 
 
 tol. 1. M SECT. 
 
•178 OF VISION". 
 
 SECT. XXI. 
 
 OF VISION. 
 
 J- HOSE rolling or vcrfatilc globes, 
 denominated eyes, are to be considered as the im- 
 mediate inftruments of the fublime fenfe of vijion. 
 They are fixed as if on footflalks, by their optic 
 nerves (rtfpecYmg the decuflation of which we 
 have already fpoken, § 205.), in fuch a manner, 
 that their infertions are not directly oppofite to 
 the centres of the cornea and iris, but are placed 
 behind the imaginary axes of the eyes, in fnua- 
 tions fomewhat nearer to the nofe. 
 
 § 254. 
 Each orb is compofed of various tun'cs or coats, 
 which inclofe humours of different denfities, and 
 fo extremely pellucid, that the rays of light, 
 having entered the pupil or window in the ante- 
 rior fegment of the orb, can pafs through, with- 
 out the lead interruption, to its bottom or oppofite 
 fide. 
 
 § 155- 
 The external involucrum of the globe of the eye 
 is called fclerotica, the anterior hiatus or chafm ot 
 
 which 
 
OF VISION. i 79 
 
 which is clofed up by the tranfparent cornea, 
 which is a lameilated membrane, more or lefs 
 convex, and projects in a flight degree forward, 
 like a fegment of a fmaller globe protruding out 
 ©f a larger. 
 
 § IS 6 ' 
 Next to the fclerotica lies the tunica choroidea, 
 which abounds in blood-veiTels, more efpecially 
 in verticofe or circuitous veins: this coat is ftained 
 on each fide by a black pigment, which loofely 
 adheres to its concave furface after the manner, 
 and with the appearance, of mucus. 
 
 § 2 57' 
 The choroides enclofes, finally, the retina, 
 
 which is the moft internal of the common tunics 
 embracing the vifual orb. This coat confifts en- 
 tirely of the medullary fubftance of the optic 
 nerve, which having perforated the fclerotica and 
 and choroidea, is expanded on the concave fur- 
 face of this lad involucrum, and there arranged 
 with the utmoft beauty and elegance of ftru&ure. 
 
 § 258. 
 
 The anterior border of the tunica choroidea 
 terminates in a cellular ring, which is denominated 
 orbiculus ci/iaris, and by means of which the cho- 
 roides is more firmly attached to a correfponding 
 M 2 groove 
 
i8o OF VISION. 
 
 groove or depreffion in the fclerotica. From this 
 cellular girdle or attachment, two other membranes 
 of different kinds, (namely, the iris and ciliary 
 procejfts), originate and diverge from each other, 
 like two expanded circles. 
 
 § 259. 
 The iris (the pofterior furface of which, being 
 overfpread with a dark pigment, is denominated 
 uvea) is fituated anteriorly, is gently convex on 
 the furface next the cornea, and is furrounded on 
 all fides by a humour of an aqueous nature. That 
 fegment of the iris, which lies next the nofe is 
 narrower, while that which looks towards the 
 temples is poffeffed of greater expanfion. Its tex- 
 ture confifts entirely of condenfed cellular mem- 
 brane, without the fmallefl: veftige of mufcular 
 fibres ; upon the whole, it appears to be in reality 
 a membrane fid generis, as was formerly well 
 obferved by Zinn, and not by any means an ap- 
 pendage to the choroides. On its anterior furface 
 it is differently coloured in different individuals, 
 and while diftended and animated with a plenitude 
 of life, it exhibits fomewhat of a floccofe ap- 
 pearance. 
 
 § 260. 
 
 The blood-veffels of the iris run principally oa 
 its anterior furface, and, in the fcetus, arc con- 
 tinued 
 
 
OF VISION. i»i 
 
 tinued into what is called the membrana pupillaris : 
 refpe&ing the nature and ufe of this membrane, [ 
 have fpoken more fully in another place *. It 
 appears to be intended for the purpofe of pre- 
 ferving the iris, (during the rapid growth of the 
 ball of the eye), in a ftate of expanfion, and thus 
 rendering it more fit for future motion. 
 
 About the fevcnth or eighth month of preg- 
 nancy, when the ball of the eye has now acquired 
 a confiderable magnitude, this membrane begins 
 to open and give way in its centre; the elliptical 
 arches of its veffels are retra&ed in a very gradual 
 manner, and thus form, in my opinion, the J hall 
 interior ring of the iris ; it is, at lead, certain, that 
 not a lingle trait of this ring can be difcovered in 
 the eyes of a foetus previouily to the above-men- 
 tioned period. 
 
 § 261. 
 
 Thepojlerior of thofe two orbicular membranes, 
 of which we have already fpoken, (§ 258) is 
 called the ciliary body or band; it runs in a back- 
 ward direction, and therefore, in its progrefs, 
 diverges ftill farther from the iris; by its external 
 border, which is grofs and firm, it is attached to 
 "'■khe. orbiculis ciliaris (§ 258), but by its internal, 
 
 * Commentat. fociet. fcient. Goettingens. T. VII. 
 
 M 3 which 
 
1 82 OF VISION. 
 
 which is more fine and delicate, it embraces the 
 margin of the capfule of the lens: it is alfo (haded 
 with that fame dufky pigment, of which we have 
 twice already fpokcn. 
 
 Its anterior furface, lying oppofed to the uvea, 
 is fomewhat flriated. 
 
 Its pofterior furface, reding on the vitreous 
 fubllance, is diftinguifhed by about feventy plicae 
 or folds, which exhibit an extremely elegant 
 fioccofe appearance; thefe are called ciliary pro- 
 ceffes, and are remarkable for a vafcular apparatus 
 of inexpreilible fubtlety and beauty. 
 
 § 262. 
 In the eye-ball itfelf, the membranes of which 
 we have been hitherto defcribing, there are en- 
 clofed, in particular, three different humours. 
 
 The vitreous humour occupies and fills the 
 pofterior, and by far, the greateft, portion of the 
 vifual orb. It is diftributed, in a countlefs number 
 of minute drops, throughout as many minute cells 
 of the membrana hyaloidea, in fuch a manner, that 
 the whole mafs, confiding, in part, of membrane, 
 and in part, of lymph, exhibits the appearance of 
 a peculiar, tremulous jelly. 
 
 § 263. 
 
OF VISION. x« 3 
 
 263. 
 The anterior part of this vitreous fubftance, 
 has appended to hfelf, and embraces, in the ciliary 
 girdle, a capfule, in which is contained the chryf- 
 taline lens, furrounded on all fides by a very 
 fubtie water, firft difcovered and defcribed by 
 Morgagni. 
 
 This lens itfelf, is alfo compofcd of extremely 
 pellucid cellular membrane; it is by far more 
 denfe than the vitreous fubftance, and is furniflied 
 with fo minute a quantity of genuine humour, 
 that, when prefTed between the fingers, it refembles 
 glue of the mod tenacious confidence, but at the 
 fame time of aftoniihing tranfparency. 
 
 § 264. 
 The remaining portion of the internal cavity of 
 the eye, is filled up by an exceedingly limpid 
 aqueous humour, and, by the expanded orbicular 
 curtain of the iris, is divided into two chambers : 
 thefe are, the anterior, or more capacious cham- 
 ber, which feparates the cornea from the iris, and 
 the pofterior one, of finaller dimenfions, extending 
 from the uvea to the corpus ciliare, 
 
 § 265. 
 Thefe moil precious and ineftimable parts of 
 the body, as Pliny, the elder, has emphatically 
 M 4 called 
 
1 84 OF 7 . VISION. 
 
 called the eyes, arc fccurely protected from ex- 
 ternal injuries, as well by their reclufe fnuations 
 in their orbits, as by their valviform coverings, 
 the palpebral. 
 
 Between the folds of the palpebral arc planted, 
 in inmenfe profufion, the crouded febaceous fol- 
 licles of Meibomius; their extreme or lower edges, 
 ed with three or four phalanges of cilia or 
 lames, are kept in an expanded ftate by certain 
 cartilages call d tarft, which are alfo of further 
 fervice in facilitating the motion of the palpebral 
 on the eye-balls. 
 
 But (to adopt the language of the eloquent 
 Cicero) the parts fituated immediately above the 
 palbebrae, being clofely mantled in the fupercilia 
 or eye-brows intercept and turn afide the fweat 
 flowing down in ftreamlets from the he..d and face, 
 and alfo ferve to moderate, in a certain degree, 
 the exceffive effulgence of light. 
 
 § 266. 
 For the purpofes of lubricating the eyes, of 
 preferving their fplendor, and of wafhing out he- 
 terogeneous fubltances, the tears are provided : 
 the principal fource of this fluid is a fmall conglo- 
 merate gland, deeply fituated in a depreflion to- 
 wards the external part of the circumference of 
 
 the 
 
OF VISION. 185 
 
 the orbit. The excrerory duels belonging to this 
 gland are numerous, but extremely tender ; they 
 are fuppofed to convey, from both eyes, in the 
 courfe of twenty-four hours, about two ounces of 
 tears ; After having been excreted, the tears are 
 again abforbed by the puncla lacrymalia, from 
 whence they are conducted through what are 
 called the comua limacum, or /nail's boms, to the 
 lachrymal fac, and from thence finally difcharged 
 into the lowermofl: pafTage of the nares. 
 
 § 267. 
 
 Thus much it was neceffary to premife refpeft- 
 ing the admirable ftructure of the vifual organ. 
 We come now to treat of the functions of this 
 organ, or, in other words, to confider the dadrine 
 of vifion. 
 
 All the rays of light which fall on the convex 
 furface of the cornea pafs through it, provided 
 their angle of incidence be leis than that of 48 
 degrees. In confequence, not only of the den- 
 fity, but alfo the figure of the aqueous humour, 
 the rays are refracted in that medium> and turned 
 a little nearer to the real axis. 
 
 As many of the rays as, having paffed through 
 the pupil, enter the cryftalline lens, mufl necef- 
 
 farily 
 
iS6 OF VISION. 
 
 farily, in this more denfe medium, be fubjecVed 
 to a ftill higher degree of refraction. 
 
 But by means of the more attenuated and lefs 
 refractive vitreous medium, wife provifion is made 
 to prevent thefe rays from uniting in a focal point 
 at too fhort a diftance : this point, being thus 
 farther removed from the convex furface of the 
 cornea, falls on the retina, and there exhibits, in 
 an inverted pofition, the images of a!l objects 
 prefented, and that in perfect correfpondtnee to 
 the nature of furrounding and attendant circum- 
 ftances. 
 
 § 268. 
 This difference in the denfity of the refracting 
 media of the eye, exhibits a very ftriking inflance 
 of the exquifite and inimitable workmai ihip of the 
 divine creator. By means of this diverfity, fuch 
 a complete remedy is provided againft the two- 
 fold feparation or divergency of the rays of light, 
 (the one arifing from the different refrangibility 
 of the different coloured rays, the other from the 
 very figure of the lenfesj, that they are all finally 
 collected and united in the fame focal point. 
 
 § 269. 
 The celebrated problem, in which the caufe is 
 demanded, wherefore we fee thefe objects erect, 
 
 the 
 
OF VISION. i8 7 
 
 the images of which are neverthelefs exhibited in 
 an inverted pofition on the retina ? appears to 
 admit of an eafy folution, when we confider, that 
 objects are faid to be inverted, only from the 
 relation they bear to others, which are exhibited 
 in an erect pofition. 
 
 In as much then as the images, not of a few, 
 but of all objects, even of our own bodies, are 
 received by the retina in the fame relative pofition, 
 the fituations and relations of the whole of them 
 harmonize and correfpond to one another, equally 
 as well, as they could poffibly have done, had 
 their pofitions been truly erect : in coniequence 
 of this, the mind, (which does not attend to the 
 image itfelf, but to the fenfation excited by its 
 impreflion), is fufficiently guarded againff embar- 
 rafTment and miftake. 
 
 § 270. 
 
 4 
 In as much as the conditions, efTentially neccf- 
 
 fary for the purpofes of acute and diftinct vifion, 
 
 are extremely numerous and varied, the creator of 
 
 man has made the wifeft provifion for thefe, by 
 
 endowing the part, fubfervient to this fublime 
 
 fenfe, with a great variety of functions. 
 
 As a certain adequate, but yet definite, quantity, 
 and not too potent a glare, of light, is efTemial 
 
 to 
 
i88 OF VISION". 
 
 to the exiftence of clear and perfect vifion, a two- 
 fold caution is thus taken ; firft, to admit, (ac- 
 cording as the light is flronger or weaker), a 
 greater or lcfs column of rays to fall on the lens ; 
 and fecondly, that all fuperfluous rays which enter 
 the eye, and tend only to dazzle by the intenfity 
 of their fplendour, be abforbed and rendered 
 inactive. 
 
 The former of thefe purpofes is effectually ac- 
 eomplifhed by the motion of the iris j the latter, 
 by means of the black pigment. 
 
 § 2-JU 
 
 The iris poffeffes an aftonifhing mobility, by 
 which it accommodates itfelf fo perfectly to the 
 quantity of tight acting on it, that when expofed 
 to a more intenfe glare, it is immediately expanded, 
 and thus diminifhes the fize of the pupil, but when 
 fubjected to the action of a weaker light, it is 
 again retracted, and the pupil confequently en- 
 larged. 
 
 Phyfiologifts have attempted a fatisfactory ex- 
 planation of this motion, in a variety of modes, 
 founded on different principles ; by fome it has 
 been derived from diverfified impulfes of the blood 
 on the tender veffels of the moving part, while 
 others have figured to themfelves the exiftence of 
 
 certain 
 
OF VISION. 189 
 
 eertain imaginary mufcles in the irh, and have 
 committed to them the whole of the phenomenon 
 in quellion, Sec. But I have lately made it appear 
 in a feparate paper, that neither cf thefe modes 
 of explanation is well founded, but that it is much 
 more agreeable to evidence, and correfpondent to 
 the phenomena of nature, to derive the immediate 
 caufe of the motion of the iris from its vita pro- 
 pria, or fpecijic life. (§ 47.) The more remote 
 caufe of this motion, as we obferved on a former 
 occafion (§ 256), cannot be referred to any other 
 fource, than the re-action of the fenforium itfelf. 
 
 § 272. 
 The function of this dufky pigment, of which 
 we have already fo repeatedly fpoken (§ 256, 
 259, 261,) to wit, that it is deflined to abforb 
 the fuperfluous rays of light, and is hence of the 
 utmofl importance in the bufmefs of perfect vifion, 
 may, befides other arguments, be fafely inferred 
 from directions of the eyes of various animals; 
 but is more completely demonftrated and eflab- 
 limed, by the morbid conftitution of the white 
 -/Ethiopians, or Albinos, as they are called, in 
 whom, from a deficiency of this pigment, the 
 organs of vifion are painfully tender, and the im- 
 pulfe of light confequently too powerful to be 
 borne. 
 
 § *73- 
 
15?® OF VISION. 
 
 S 173- 
 It is further requifite, that the focus of re- 
 fracted rays be perfectly formed on the retina, fo 
 that it may ftrike the very point of vifion, and be 
 neither fo far extended as to fall behind it, nor fo 
 much contracted as to terminate before it, in the 
 vitreous fubftance. 
 
 The latter of thefe deviations from perfect 
 vifion is what takes place in thofe individuals 
 called ?nyopes 9 in whom the lucid cornea is rather 
 too convex and gibbous. 
 
 But the former deviation is that under which 
 the prejbyta labour, as the conformation of the 
 anterior parts of the eyes is directly the reverfe. 
 
 § 2 74- 
 But as an eye perfectly found is able to difcern, 
 with equal diitinctnefs, bodies, whether at a 
 greater or lefs diflance, it muft, without doubt, 
 be furnifhed with peculiar faculties or powers of 
 accommodating itfelf to the various diftances of 
 objects. That thefe internal and accommodating 
 changes of the eye, are in a great meafure pro- 
 duced by the preffure of the retti mufcles on the 
 ball which they embrace, is a pofition fo clear, 
 and apparently well founded, as fcarcely to admit 
 of a doubt. Befides other arguments which might 
 
 be 
 
OF VISION. 191 
 
 be advanced in favour of this opinion, I am 
 induced to adopt it in confideration of the very 
 lingular ftructure, and extreme flexility, of the 
 fclerotka, in the eye of the Greenland phoca, or 
 fea-calf. By this peculiarity of fabrication and 
 arrangement, nature has made the moll exquifite 
 provifion to enable this amphibious animal to 
 enjoy at all times, the advantages of vifion, 
 though palling its life alternately in media of very 
 different denfities. 
 
 § 2 75- 
 By means of thefe fame mufcle?, our eye?, 
 whilft we are awake, are perpetually agitated, 
 although with an almoft infenfible motion, and fo 
 directed as to have their vifual axes arranged in- 
 right lines with the objects viewed. For although 
 the whole of the retina be porTefTed of fenfibility, 
 yet it is not in every part equally well adapted to 
 receive the images of objects. 
 
 For at the genuine axis of the eye-ball, in the 
 place, for example, where the optic nerve enters, 
 it appears, from the well-known and celebrated 
 experiment of Mariotte, that the human eye is 
 deflitute of the power of vifion. 
 
 But the principal focus of the retina, and that 
 
 which ought to be confidered as the leading and 
 
 4 immediate 
 
i 9 2 OF VISION. 
 
 immediate inftrument of diftincl vifion, is fituateci 
 in an imaginary axis of the eye-ball, which is fup- 
 pofed to pafs through the centre of the cornea, 
 and to be thus continued through the centre of 
 the whole orb. It is not, however, (as was lately 
 obferved by the celebrated Kaeftner in his com- 
 ments on certain works of Boerhaave), to be 
 from hence underftood, that we are unable to fee 
 clearly and diftin&ly, more than one fingle point 
 of an object while the eye remains perfectly at 
 reft, and that we are obliged to fhift or alter its 
 axis in order to diftinguiih any other point. The 
 cafe is quite otherwife, becaufe the fenfation pro- 
 duced by one entire object, is alfo itfelf, like its 
 original, or exciting caufe, one and entire. 
 
 § 276. 
 
 The habit of directing the axis of the eye with 
 difpatch and facility towards the object of vifion, 
 is finally acquired only by ufe and daily exercife. 
 That this is a pofition founded in truth, isdemon- 
 ftrated not only by the example of fuch individuals 
 as, having been born blind, acquired afterwards 
 the power of vifion in adult age, but alfo by that 
 of tender infants, who feldom attain to this happy 
 facility of moving their eyes previoufly to the 
 third month after birth. 
 
 2 § 277. 
 
OF VISION. 193 
 
 § 277. 
 To the fame power of cudom and habit, mud 
 we alfo attribute the remarkable circumdance of 
 our feeing objects only fingle, though our eyes be 
 two in number. New-born infants appear to fee 
 objects double, and double vifion, which fre- 
 quently continues fometime after certain difeafes 
 of the eyes, may be at length overcome and re- 
 moved by ufe and exercife. 
 
 § 278. 
 The joint power cf both eyes, with regard to 
 the acumen and ftrength of vifion, does not, 
 according to the calculation of Jurin, exceed that 
 of one eye, more than a thirteenth part. 
 
 And, agreeably to an obfervation, long fince 
 made by that celebrated painter Leon, da Vinci, 
 it is much bed in judging of the didances of 
 objects to make ufe of one eye only. 
 
 § 2 79- 
 
 Finally, In treating of the ftrength and per- 
 fection of the eye, our former illudrious country- 
 man, Tob. Mayer, demondrated, by a feries of 
 very elegant and ingenious experiments, that the 
 angle of vifion ought to exceed, in dimenfions, at 
 leaft 34 feconds of a degree. From hence he at 
 the fame time illuftrated and proved the extreme 
 
 vol. I. N perfection 
 
1 94 OF VISION. 
 
 perfection of the human eye, becaufe this extent 
 of the angle of vifion may continue nearly the 
 fame, under any light whatever, whether that of 
 the meridian fun, or that of a weak lamp, fo that 
 though the window or pupil of the eye be greatly 
 contracted and diminiflied, yet the clearnefs of 
 vifion can, from that fource, be fcarcely in any 
 degree affected. 
 
 § 280. 
 
 From hence we may infer, the inconceivable 
 fmallnefs of the images of objects which are thrown 
 and delineated on the retina, and which are never- 
 thelefs impreffed with fo much force* that, under 
 certain circumftances, vefliges of them remain a 
 considerable time, even after the objects them- 
 felves have been entirely removed from the eye. 
 
 SECT. 
 
OF THE INTERNAL SENSES. 19$ 
 
 SECT. XXII. 
 
 OF THE INTERNAL SENSES, AND OTHER FACULTIES 
 OF THE MIND. 
 
 § 28l 
 
 1 HROUGH the medium of thofe ex- 
 ternal fenfes, of which we have hitherto treated, 
 ideas are conveyed to cur nobler part, the mind; 
 for, agreeably to the tenor and fpirit of a well- 
 known theorem, nothing can enter the under- 
 ftanding fave by the route or avenue of the fenfes. 
 
 § 282. 
 For the purpofes of receiving and preferv- 
 ing the ideas thus acquired, by the aid of the 
 fenfes, and alfo for making the belt ufe and im- 
 provement of the intellectual (lock received, va- 
 rious faculties of the mind contribute their united 
 exertions. Though thefe faculties be, (as we 
 have already had occalion to obferve, § 42.), 
 widely different from the vital energies which 
 refide in the body, neverthelefs, by means of the 
 nervous fyflem, they are fo clofely connected with 
 thofe corporeal energies, that an aftonifhing in- 
 tercourfc is thus eftablifhed and fupported between 
 the body and mind, (§ 211.) 
 
 N 2 § 283. 
 
i9<i OF THE INTERNAL SENSES. 
 
 § 283. 
 The firft of thofe powers, poffcfTing indeed, 
 apparently, the lowed grade, is the faculty of 
 Perception, by means of which the mind is ren- 
 dered confeious of impreffions made on the dif- 
 ferent organs of fenfe. 
 
 § 284. 
 This faculty is aided by another, of better rank 
 and higher dignity, namely, attention, which fo 
 directs and determines the mind towards any idea 
 when once excited, as to rivet its thoughts to that 
 object alone. 
 
 § 285. 
 For the important purpofes of preferving ideas, 
 which have been already perceived, of re-exciting 
 them, and aflbciiuing them into more lively and 
 piclurefque fpecies of imagery, two other faculties, 
 called internal fenfes, are brought into aclion : 
 thefe are memory and imagination, two powers, 
 which, though nearly allied to each other, may, 
 notwithftanding, be readily diftingnifhed by the 
 following characters : memory appears to be more 
 fubfervient to, and engaged in, the reception and 
 retention of arbitrary figns of things ; whereas, 
 imagination, on the contrary, wakes up rather the 
 very images of things, bellows on them form and 
 colouring, and marfhals them under the view of 
 
 the 
 
OF THE INTERNAL SENSES. 197 
 
 the mind, as if the objects themfelvcs were again 
 a&ually prefent : this faculty is mure particularly 
 and powerfully exercifed on fuch objects as are 
 calculated to excite fenfations of pleafure or difgu't. 
 
 § 2S6. 
 Upon the whole, the faculty of chafing and 
 refii/ing, and, (when we conhJer the matter a 
 little more minutely), even the foundation of the 
 whole will itfelf, appear to relt and depend en- 
 tirely on certain agreeable and difagreeable varie- 
 ties of fenfation. 
 
 § 287. 
 .From the fame prolific fource, namely, the 
 imagination, are alfo to be derived the affections 
 or commotions of the mind, to which we fee dif- 
 ferent individuals varioufly fubjecled, in confor- 
 mity to the countlefs diverfities of.exifting tempe- 
 raments (§ 59.) The very intimate and inilan- 
 taneous confent of thele affections with certain 
 functions of the body, appears flrikingly evident 
 in an infinitude of examples ; thus, for inftance, 
 there is fcarcely a fmgle pafiion of the mind, which 
 does not po fie is confiderable influence over the 
 motion of the heart, the appetite for food, and the 
 powers of ciigc/lion, — not to defcend 10 a minute 
 fpecification of particular effects, fuch, for exam- 
 ple, as the acticn of fliame in giving rife to 
 
 N 3 blujhing, 
 
198 OF THE INTERNAL SENSES. 
 
 blujhhig, the action of love or hatred on the organs 
 which ferve to diftinguifh the fexes, the action of 
 anger on the fecretion of bile, &c. &c. 
 
 While fpeaking of the effe&s produced in the 
 economy of the human body, by the commotions 
 of the mind, it is proper to obferve, that they 
 may be divided into Jtimulant and fedative, or 
 into thofe which excite, and thofe which deprefs. 
 
 Of the former defcript'o 1 are joy, love, hope, 
 anger, &c. 
 
 Of the latter, fear, forrow, noftalgia, and other 
 fpecies of permanent defire or longing, terror, 
 envy, Scq. 
 
 § 288. 
 
 Thofe faculties of the mind hitherto enume- 
 rated, are obferved to exift in brutes as well as 
 man, though the latter undoubtedly poiTeffes them 
 in by far the highefl degrees of ftrength and per- 
 fection : thus, for example, in none of the inferior 
 animals do we difcover a memory fo extenfive in 
 its range, and fo powerful in its tenacity ; in none 
 do we difcover fuch a fplendid brilliancy, and 
 glowing warmth of imagination ; in none do we 
 difcover fuch an unbounded, and fometimes fatal, 
 vehemence of mental paflions, &c. 
 
 § 289. 
 
OF THE INTERNAL SENSES. 
 
 l 99 
 
 § 289. 
 The leading prerogative of the human mind, 
 confifts in this, that it alone pofTefTes the exclufive 
 power of reafon, by means of which it is able to 
 judge, to form abftract. ideas, Sec. and which exerts 
 alfo the greatefl influence over moil cf the other 
 faculties of the mind, in place of this divine 
 power, other animals are endowed with various 
 ifi/linds, or blind and involuntary impulfcs, which 
 lead them to the performance of fuch actions, as 
 are fuitable to their feveral economies and modes 
 of life. Of thefe inftincYive impulfes man, on the 
 other hand, is furnifhed with fcarcely any, fave 
 that which prompts him to participate in venereal 
 gratifications. 
 
 § 290. 
 The immenfe and (Iriking difference between 
 animal inftinft and human reafon, will appear 
 glaring as the noon-day light to him who eonfiders: 
 
 That inftincls are faculties co-eval with birth, 
 whereas, on the other hand, the ufe of reafon is 
 acquired only by culture and education : 
 
 That inftincls remain fiationary, and admit of 
 no improvement, whereas the expanfive improve- 
 ment and exemfe of reafon, are literally free from 
 circumfcripticm : 
 
 N 4 That 
 
203 OF THE INTERNAL SENSES. 
 
 That infiincts are fuited only to the deftined 
 mode of life, to the climate, &c. of each fpecies 
 of animals, and, on this account, are not adequate 
 to the exigencies of man, who, confined to no 
 climate, exclufively reflricled to no mode of life, 
 is deftined to be an inhabitant of the world at 
 large : from which boundlcfs and fplendid prero- 
 gative, an inconceivable diverfity of wants arife, 
 which fimple inftincl: is too weak! — far too weak 
 to fupply! but which, the powers of reafon, from 
 refources equally diverfified as the emergencies 
 themfelves, are able to fatisfy, in the mod ample 
 and complete manner. 
 
 Laftly, another high prerogative of man, de- 
 pending on the powers and exercife of his reafon, 
 is the ufe of fpeech, of which we have briefly 
 fpoken on a former occafion (§ 154.) This in- 
 valuable privilege is the exclufive boaft of man 
 alone, brutes being only furnhhed with voice, or 
 a power of emitting found. 
 
 SECT. 
 
OF VOLUNTARY ACTIONS. 201 
 
 SECT. XXIII. 
 
 OF THOSE ACTIONS OF THE BODY WHICH ARE 
 SUBJECT TO THE POWER OF THE WILL. 
 
 § 29I. 
 
 JL HE nerves, as we have already feen, 
 are fo conftituted as to perform two different 
 functions (§ 215), namely, fenfation and motion. 
 The do&rine of the former we have already con- 
 sidered. It yet remains to add a few obfervations 
 on thefubject of the latter. 
 
 § 292. 
 
 The motions in general of the feveral parts 
 of the human body, are ufually divided into two 
 claffes, one of which is excited and governed by 
 the power of the will, while the other is not in 
 any meafure fubjecr. to its influence, or controul. 
 
 For examples of the latter clafs, phyfiologifts 
 commonly refer to the harmonious a£lion of the 
 heart, and likewife to the perifialtic motion of the 
 inteflines and certain other vifcera, &c. 
 
 Inftances 
 
202 OF VOLUNTARY ACTIONS. 
 
 Inftances of the former clafs we have in the 
 motions of by far the greater part of the other 
 mufcles of the body. 
 
 Doubts are flill entertained, with refpect to the 
 real nature of certain motions which take place in 
 the human fyftem ; fuch as the motions in refpira- 
 tion, in fneezing, in the tenfion of the membrana 
 tympani, &c. Thefe are by fome claffcd with the 
 voluntary, by others with the involuntary, while 
 others again refer them to a third clafs, called 
 mixed motions.- 
 
 § 293. 
 
 When this divifion, however, is confidered with 
 a little more fieadinefs and attention, it is eafily 
 perceived to be embarrafled with fuch momen- 
 tous difficulties, that it is fcarcely poffible to 
 ascertain, and mark, with definitude, the precife 
 limits between the claffes. 
 
 For, on the one hand, a few of the functions 
 of our bodies, over which the will, unaffifted by 
 other powers, may be faid to poflefs no command 
 at all, may notwithflanding be excited and brought 
 into action, when the imagination and paffions of 
 the mind act in concert with the will. 
 
 On 
 
OF VOLUNTARY ACTIONS. 203 
 
 On the other hand there are not wanting 
 inftances of mufcular functions, which, though 
 naturally fubject to the immediate command of 
 the will, have, notwithftanding, been rendered in 
 a great meafure involuntary, by the plaftic power 
 of cujlom, (the influence and energetic agency of 
 which, on animal motions, arc indeed of the 
 utmofl: moment and importance.) 
 
 § 294. 
 Of this latter defcription are thofe kinds of 
 mufcular motion, which, although at other times 
 fubjecT: to the controul of the will, yet, under 
 certain circumftances, take place not only without 
 the confeioufnefs, but even contrary to the incli- 
 nation of the mind. 
 
 Thus, for example, we wink contrary to our 
 determination, when the finger of a friend is 
 haflily approached towards our eye, although it 
 does not touch it; and in molt perfons, the flexion 
 of the little finger is ufually attended with a fyn- 
 chronous flexion of the ring finger, though a de- 
 termination had been formed to preferve the latter 
 entirely unbent. 
 
 Without the confeioufnefs of the mind we fre- 
 quently move our limbs, even when wrapt in the 
 mod: profound fleep. 
 
 There 
 
204 OF VOLUNTARY ACTIONS. 
 
 There are, on the other hand, examples of 
 mufcles, which, although for the mod part per- 
 fectly obedient to the will, yet in certain cafes 
 refufe to obey its commands. To this head we 
 may refer the difficulty of defcribing, by fyn- 
 chronous movements, circles in contrary directions, 
 with the hand and foot of the fame fide, together 
 with other motions of a fimilar nature, which, 
 although truly voluntary, and extremely eafy 
 when practifed alone, are, notwithftanding, per- 
 formed with the utmoft difficulty, if an attempt 
 be made to alfociate them with certain other 
 motions. 
 
 § 295. 
 
 With refpect to thofe motions, which phyfio- 
 logiils fuppofe to be perfectly exempt from the 
 influence of the will, I know of none which can 
 be clearly and unexceptionably referred to this 
 head, fave the fpafms of the uterus in the labour 
 of parturition. 
 
 With refpect to the pulfation of the heart, a 
 very remarkable account (lands on record of a 
 Britifn colonel, who pofTeffed a power of fuf- 
 pending, at pleafure, the motion of both the heart 
 and arteries. In confirmation of the truth of this, 
 we have the public teflimony of Baynard and 
 Cheyne, two phyficians of the higheft reputation 
 
 and 
 
OF VOLUNRARY ACTIONS. 205 
 
 and veracity, who were themfelves witneffes to 
 the afloniming phenomenon. 
 
 That the motion of the ftomach may be volun- 
 tary, (as indeed the procefs of rumination in 
 general feems to evince), I had once an oppor- 
 tunity of afcertaining, to my entire fatisfa&ion, in a 
 ruminating human fubjeft, in whom this retrogade 
 or reverted motion of the ftomach, was under the 
 mod perfeft fubjeclion to the command of the 
 will. 
 
 Although the motion of the iris be involuntary, 
 in by far the greater part of the human race, I 
 have, notwithftanding, been favoured with an 
 account, fafficiently authenticated, of a man, who 
 poffeffed a power of voluntary command over this 
 membrane, in fuch a manner, as to be able, by a 
 very lingular effort, to contract the pupil of the 
 eye even in a weak and dull light. 
 
 There are indeed a great variety of motions, 
 which, though generally performed without the 
 influence of the mind, are neverthelefs voluntary 
 in certain individuals, cfpecially if a high degree 
 of attention, and a vigorous effort of imagination 
 be excited. Thus, I have known men, who were 
 able at any moment, to produce and exhibit on 
 themfelves a fpafmodic horripilation of the fkin, 
 
 and 
 
206 OF VOLUNTARY ACTIONS. 
 
 and alfo to renew and completely revive in 
 themfelves the ideas or perception of certain difa- 
 grceable fenfations. 
 
 § 296. 
 
 Perhaps thofe phenomena may be fatisfa&orily 
 explained from the re-aclion of the fenjorium, 
 which appears to be indeed as powerfully excited 
 by means of the imagination waking up and 
 exhibiting before it, the image of an active 
 ftimulus, as by the Jlimulus it/elf, when imprefling 
 it by its a&ual prefence. There are indeed an 
 infinitude of phenomena of the animal economy, 
 which admirably correfpond to this explanation; 
 as the various caufes, for example, which excite 
 erections of the male penis, &c. 
 
 S 297. 
 
 With regard to voluntary motions in general, 
 it may be proper finally to obferve, that they are 
 among the primary and leading chara&eriftics 
 which ferve to diftinguifli the animal from the 
 vegetable kingdom ; for, as on the one hand, a 
 power of voluntary motion is never obferved to 
 be pofTefled by any plant, fo on the other, fuch a 
 power conftitutes an effential attribute of even the 
 raofl: fimple and imperfect genera of animals. 
 
 § 298, 
 
OF MUSCULAR MOTION.- 207 
 
 § 298. 
 In our own fyftems, the voluntary motions fur- 
 nifh the mod full and ftriking evidence, of that 
 intimate and truly aitonifhing harmony, which 
 fubfifts between the mind and the body. Of the 
 exiftence of this harmony every one will be con- 
 vinced, who confiders with attention, the amazing 
 celerity with which fuch diverfied motions fucceed 
 each other, in the fingers of an able and fkillful 
 performer on the violin, or in our organs of 
 fpeech, while we are engaged in converfation. 
 
 SECT. XXIV. 
 
 OF MUSCULAR MOTION. 
 
 § 299, 
 
 X HE immediate organs of by far the 
 greater number of the motions of our bodies, are 
 the mufcles, which conftitute the principal portion 
 and bulk of what are called partes fimilares. 
 
 § 3°°- 
 The mufcles are, however, diftinguifhed, in a 
 particular manner, from the reft of the fimilar 
 parts, by a two-fold characleridic j one depending 
 
 on 
 
ao8 OF MUSCULAR MOTION. 
 
 on their texture ; and the other of a very lingular 
 nature, derived from their vital energy. 
 
 § 3 OI « 
 Their texture is flefhy., compofed of a peculiar 
 
 fet of fibres, of a very pale red colour : they are 
 
 fo joined together, that every mufcle confifts, in 
 
 the firft: place, of fibrous cords, thefe cords again, 
 
 of fmaller bundles of fibres, which bundles, by a 
 
 ftill further progreflive divifion, may be finally 
 
 fepar'ated and refolved into flefhy fibres and fibrils 
 
 of inconceivable minutenefs. 
 
 § 3°2- 
 Each mufcle is inclofed in a cellular fheath or 
 covering, which, pafiing into the very fubftance 
 of the mufcle, appears to be interwoven through- 
 out the whole of its volume, and thus forms par- 
 titions, firft between the larger lacerti, then be- 
 tween the fmaller fafciculi or bundles, and laftly, 
 between the fibres and more minute fibrils them- 
 felves. 
 
 § 3°3- 
 Befides this cellular expanfion, the whole tex- 
 ture of the mufcles is alfo interfperfed with an 
 infinitude of blood-vcfiels and nervous filaments ; 
 of thefe, the latter appear to deliquate into an 
 infcrutable pulp, and to be thus very intimately 
 2 blended 
 
OT MUSCULAR MOTION. 209 
 
 blended along with the mufcular fibres ; bur the 
 former are fo extenfively and minutely interwoven 
 among thofe very tender fibres, as to paint the 
 whole of the fleihy parts with that beautiful crim- 
 fon dye, by which they are uniformly characlerifed. 
 When thefe are thoroughly wafhed, they are 
 again fcflored to their native colour, which, as 
 already obferved (§ 301.), is fomewhat pale-. 
 
 § 3°4- 
 Finally, a circumftance common to mod of the 
 
 mufcles is, that they terminate in tendons — parts, 
 which, though likewife of a fibrous texture, are 
 notwithflanding fo extremely different, with reflect 
 to colour, flruclure, eladicity, &c. that their entire 
 difagreement from both the preceding kinds of 
 fibres, is very eafily afcertained and demonftrated. 
 Hence, therefore, we are enabled fuccefsfully to 
 refute the opinion of thofe phyfiologifb, who have 
 crroneoufly fuppofed, that the tendinous ', are no- 
 thing more than mere continuations of the mufcu- 
 lar fibres. To the adoption of this opinion, they 
 have been inadvertently led by attending to the 
 following phenomenon, obfervable in the mufcles 
 of infants ; namely, if we compare the mufcular 
 parts, of thefe tender fubjects, with thofe of adults, 
 we will find the proportion of ilelh, to that of 
 ttndon, greater in the former than in the latter. 
 
 vol. i. O ?o<: 
 
210 OF MUSCULAR MOTION. 
 
 The other exclufive characteriftic of mufcle«, 
 which we have mentioned (§ 300.) is, the irrita- 
 bility of Haller. Although we endeavoured, on 
 a former occaiion, to give a general view of this 
 vital energy, and to afcertain the difference be- 
 tween it and contrattility, (§ 44.)? yet it may not 
 be improper, at prefent, to purfue the inquiry a 
 little further. 
 
 S 306. 
 
 This irritability, otherwife called vis mufcularis, 
 vis injita, or vis propria, is indeed common to 
 all the mufcular parts of our bodies, but does not 
 refide in all of them in the fame degree, fome parts 
 being obferved to poffefs a much higher propor- 
 tion of it than others. 
 
 The principal feat of this energy, where it moil 
 plentifully abounds, is the hollow mufclcs, fub- 
 fervient to the vital and natural functions : of 
 thefe mufcles, the heart, as was obferved formerly 
 (§ H9-)j poffeffes the higheft degree of the cha- 
 rafterijlic now under confideration : of this lad 
 mentioned organ, the internal furface, in parti- 
 cular, is endowed with the mofl exalted degree of 
 life, and is by far the mod tenacious of irrita- 
 bility. 
 
 Next 
 
OF MUSCULAR MOTION. 211 
 
 Next to i.he heart, in point of this prerogative, 
 is the inteilinal canal, more efpecially that portion 
 cf it which conftitutes what are called the, final! 
 inicjlines: in warm-blooded animals, this part of 
 tl e tube fomctimes contracts on bein? irritate 1, 
 <: a after the heart itfelf has become incapable of 
 .notion. 
 
 Next in degree is the flomach, — next, the uri- 
 nary bladder, &c. 
 
 Among the remaining mufcles of the fyflem, 
 irritability refides, again, in a very finking degree, 
 in thofe actively concerned in the function of 
 refpiration, as the diaphragm, the intercoftals, 
 and the triangularis Jlerni. 
 
 Next in order to thefe are the various other 
 mufcles of the body. 
 
 The arteries doubtlefs poffefs irritability, though 
 in a degree far inferior to what exiils in the parts 
 jult mentioned (§ 123.) 
 
 This vital energy refides alfo in the trunks <s£ 
 veins contained in the thorax, (§ 84.) 
 
 In a degree JIM lower, does it exift, in the other 
 
 parts of the fanguiferous veins, if, indeed, thofe 
 
 O 2 parts 
 
trz OF MUSCULAR MOTION. 
 
 parts can be faid to pofTefs any genuine irritability 
 at all (S 128.) 
 
 § 307. 
 
 Haller himfelf, that iiluflrious defender of the 
 doctrine now under confiderauon, appears to me 
 
 to have, without fuilicicnt foundation, attributed 
 irritability to certain parts of the body, which are 
 found, indeed, on experiment, to be endowed 
 with contractility (§ 50 feq.), but in which I have 
 never been able to difcover any indubitable ttiii- 
 monies of genuine irritability. 
 
 Among thefe parts may be reckoned the lacleal 
 veins, the fmall glands, the pall-bladder, the uterus, 
 the dartcs covering, and the male penis. 
 
 On no better foundation, in my opinion, is irri- 
 tability attributed, by others, to the iris, to the 
 external furface of the lun^s, &c. in all which 
 parts (if, indeed, I be capable of judging rightly), 
 there exifrs no more of this vital energy, than 
 there does in the common cellular membrane, and 
 parts compofed of it, fuch, for inftance, as the 
 common integuments, the meninges, the pleura, 
 the peritoneum, the perioileum, the medullary 
 membrane, the tendons, the aponeurofes, &c. ; 
 or than there does in thofe vifcera compofed of 
 g muine parenchyma, (§ 27.), fuch as the liver, 
 
 the 
 
OF MUSCULAR MOTION. 213 
 
 the fpleen, the kidneys, the fecundities, the brain, 
 v, : h the reft of the nervous fyftem, 8zc. all which 
 parts, as they are thr cughour, completely deftitute 
 of -nufcular fibres, (o are they likev/ife deftitute of 
 irritability, which refides in mufcular fibres alone. 
 
 S 3 oS - 
 
 As we have, thus, on the one hand, feen 
 mufcular irritability now and then confounded 
 with cellular contractility , (o on the o:her, certain 
 celebrated characters have lately been defirous of 
 ascertaining and eilablhhing an identity between 
 irritability and the vis ncr-vca. 
 
 For although we can neither deny the power- 
 ful influence of the nerves on mufcular motion^ (of 
 which we will fpeak a few words prefently), nor 
 exhibit the fmalleft fibril of mufcular flefh, per- 
 fectly deftitute of the pulp of evanefcent nerves, 
 yet thefe circumftances are not fufficiently mo- 
 mentuous to compel us to a dereliction of the 
 opinion, that irritability is, in its own nature, as 
 widely and eiTcntia'Iy different from riae vh mrve.a 
 as it is from contracliUty. On the one hand, 
 this energy is wanting in all parts not -mufjular, 
 although they be Supplied with the utmoft profu- 
 fion of nerves, as the lldn, all the nervous vifcera, 
 £ic; whereas, on the other, we are not able to 
 produce any portion of true mufcu'ar (lc(h, v»here 
 O 3 to 6 
 
214 OF MUSCULAR T-IOTIOI-:. 
 
 the genuine and obvious phenomena of irritability 
 do not exhibit themfrlves. From a clofe and 
 impartial confiJcration of the foregoing argu- 
 ments, befides a great number of others which 
 might be advanced, it appears more confonant to 
 reafon and found induction, to attribute the 
 lingular phenomena of irritability to the equally 
 fincnilar texture of mufcular fibres, than to refer 
 them to the nerves, which, in fc many other parts 
 of the body, are as minutely distributed as they are 
 through the mufcles, and yet do not generate and 
 exhibit, in thofe parts, the fainted: fhadow of real 
 irritability. I fay nothing of the weighty argu- 
 ments which might be drawn from the following 
 well-founded pofition, viz. that no fteady propor- 
 tional relation is obferved to exift, between the 
 degree of irritability in any part of the body, and 
 the quantity of nerves with which it is fupplied. 
 
 § 3°9- 
 With refpect to the extreme terminations of 
 
 the nerves, which are well known to exert an 
 influence over the mufcles, the following appears 
 to be the mod rational conclufion, viz. that they may 
 be conlldered as remote or exciting camfes of muf- 
 cular motion, but fhould not be 'confounded with 
 the proximate or efficient cnufe, which is indeed 
 irritability alone, and that refiding exclufively in 
 the mufcular fibres. - 
 
 The 
 
OF MUSCULAR MOTION. 215 
 
 The pafiions of the mind, for example, aft on 
 the fenforium, this again re-acts on the nerves of 
 the heart, in fuch a manner, as to excite its irrita- 
 bility, and thus produce palpitations and other 
 irreguiar motions of this organ. 
 
 The will acts on the fenforium, this re-acts 
 again on the nerves of the arm, thefe nerves in 
 like manner operate immediately as remote caufes 
 in exciting mufcular motion, which, notwith- 
 ftanding, depends ultimately for its exiftence on 
 irritability itfelf. 
 
 § V°- 
 This diftinction, of the two kinds of caufes 
 which concur in the production of mufcular 
 motion, is indeed fully authorifed and fanctioned 
 by actual experiments: from a variety of thefe it 
 appears, that certain parts of the animal fyftem 
 have been oftentimes rendered paralytic, by cutting, 
 or inclofing in ligatures, the nerves leading to them, 
 while they have, notwithstanding, frill continued to 
 retain their irritability for a long time afterwards. 
 
 In what degree the blood, with which the 
 mufcles are very abundantly fupplied, contributes 
 to their action, is not yet clearly and fatisfactorily 
 
 afcertained. 
 
 O4 It 
 
216 OF MUSCULAR MOTION. 
 
 It appears, however, from an experiment of 
 Steno, ih.u a paralyfh of the lower extremities 
 may be generally produced, by paffing a ligature 
 round the aorta in its defcent behind the abdo- 
 minal cavity. 
 
 Befides thefe common inherent energies of the 
 mufdes, which have hitherto been the fubjecls of 
 our confidenuion, they poffefs alio certain fpecific 
 and adventitious peculiarities, ariiing from varieties 
 in their figures, fituations, Szc. by thefe peculia- 
 rities they are adapted, and rendered completely 
 adequate, to the nice performance of their feveral 
 functions. 
 
 S 3 l 3- 
 From the contemplation of this circumflance, 
 mufcles are ufually divided into hollow and folid : 
 the former of thefe, as we have already feen, not 
 being in immediate fubjedtion to the command of 
 the will, are particularly deflined to the perfor- 
 mance of the vital and natural functions, and 
 cannot, therefore, be further treated of in this 
 place, where we are confidering what are called 
 voluntary mufcles, which are more efpecially fub- 
 fervient to tint order denominated the animal 
 fu nil ions. 
 
 § 3M- 
 
OF MUSCULAR MOTION. 217 
 
 Between thefe lad-mentioned mufcles them- 
 felves, there occur again very ftriking diverfities. 
 For to fay nothing of the varieties in their relative 
 magnitudes, they differ extremely from each other 
 in the difpofition of their lacerti and fafciculi, in 
 the direction of their fibres, but more efpecially 
 in the habit and proportional relation of their 
 fleihy and tendinous parts, and, finally in their 
 courles, their infertions, &C. 
 
 § 3 l 5- 
 Neverthelefs, in by far the greater part of the 
 
 fiifform or tapering mufcles, their figures are 
 
 more or lefs oblong, (o that their flefhy bellies 
 
 terminate at each end in tendinous cords. Thefe 
 
 cords, which are inert and perfectly deftitute of 
 
 irritability, being attached to, and infrrted in, 
 
 bones, ferve the neceffary purpofe of moving 
 
 them after the manner of levers. 
 
 § 3 l6 - 
 As there are, however, a few mufcles in the 
 
 body entirely defliture of tendons, fuch as the 
 latijjimus colli ; fo there are, in like manner, a few 
 no: attached to bones, namely, the mufcle laft 
 mentioned, the cremajler mufcle, as it is generally 
 called, the azygos uvula, and mod of thofe which 
 move the ball of the eye. 
 
 § 3*7- 
 
218 OF MUSCULAR MOTION. 
 
 § 3*7- 
 By the co-operation and combined aid of all 
 
 thofe energies, (as well the common, § 305, as 
 
 the proper, § 312), with which the mnfcles are 
 
 furnifhed thefe inftruments of motion are fitted 
 
 and completely qualified for the performance of 
 
 their feveral actions, which may, in like manner, 
 
 be alfo divided into common and proper. 
 
 §3;8 ' 
 
 During their common action, which avifes 
 immediately from irritability, and occurs in all 
 mufcles, their flefhy portions become fliorter, 
 more rigid, and, for the mofl part, unevenly and 
 fomewhat angular. It alfo appears irom the 
 celebrated experiment of Gliffon, that they fuffer 
 at the fame time a flight diminution in point of 
 magnitude. 
 
 We are indeed prevented from joining Jo. 
 and Dan. Bernouille, and other mathematical 
 phyficians, in an attempt to reduce the meafure 
 of this diminution to common calculation, firft, by 
 the immenfe difference in this refpecl, which is 
 obfervable between the hollow and folid mufcles, 
 and fecondly, by the diverfity which alfo occurs, 
 on the fame point, between thefe latter mufcles 
 themfelves; — not to mention various other diffi- 
 culties, which obflrucl the road to fuccefs. 
 
 S 3*9- 
 
OF MUSCULAR MOTION. 219 
 
 §3 I 9- 
 The proper or fpecific actions of the mufcles, 
 (§ 3 l 7-)> correfpond precifely to their fpecific 
 energies ; from whence it naturally and fponta- 
 neoufly follows, that thefe actions are marked 
 with fuch an infinitude of varieties, as to render it 
 literally impoflible to reduce them to any general 
 laws, or to arrange them under any well-defined 
 orders and genera. 
 
 With regard to the general principle, commonly 
 taught and adopted on this fubject, viz. that every 
 mufc'-j while in aciion, draws the more moveable 
 part to which it is attached, towards that which is 
 more permanent, it ought to be confidered, fas has 
 been veryjuftly obferved by the fagadous Window) 
 in a relative point of view, and is indeed fubjecl: 
 to a variety of limitations. Thus, for example, 
 the two parts to which a mufcle is attached, may 
 be rendered, each more moveable than the other, 
 in alternate vicifTnudes, accordingly as the one or 
 the other is fked and rendered ftationary, by the 
 joint aciion of other co-operating mufcles. 
 
 As to the aftion of the flexor mnfclcs, it ou^ht 
 to be cftimated on contrary principles, and a dif- 
 ferent opinion formed refpecling it. Although 
 thefe mufcles, for the moft part, predominate fo 
 much over their antagonifb, the extenfors, that 
 
 when 
 
22o OF MUSCULAR MOTION. 
 
 when the body is in a ftate of perfeft quietude 
 and reft, the arms, fingers, Sec. are under a gentle 
 degree of flexion, yet thefe parts do not appear to 
 be drawn into this ftate and pofuion by any aftual 
 force, but rather in confequence of a voluntary 
 relaxation of their extenfor mufcles, by means of 
 which, thofe mufcles, fubfervient to the flexion of 
 the parts, are left at liberty to aft without oppo- 
 fiton or refiftance. 
 
 § 3 2 °- 
 To all the foregoing confederations, it appears 
 proper to add, in the laft place, that each niufcle 
 pofTeffes a peculiar and fpecific mechanifm, by 
 means of which it is adapted, in the moft complete 
 manner, to the performance of the various motions 
 of its immediate deftination. 
 
 Befides the peculiar advantages which the 
 mufcles feverally derive from their determinate 
 figures, their aftions are alio promoted by a variety 
 of other concomitant aids, fuch, for inftance, as the 
 annular ligaments by which they are furrounded ; 
 the fat, in which a great number of them are 
 imbedded ; the lymphatic dew with which they 
 all abound ; and, what ought to have been men- 
 tioned in the very firft inftance, the confoimation 
 of the fkeleton itfelf, efpecially as far as the fame 
 relates to the ftrufturc of the apophyfes, and the 
 
 articulation 
 
OF MUSCULAR MOTION. ait 
 
 articulation of the joints : under the fame head of 
 auxiliaries to the mufcles, may be alfo arranged 
 certain entire bones, as the patella, and offa, 
 fefimoidea, of fimilar ftruchires and ufes, which 
 nature appears to have very wifely adapted and 
 deftined to facilitate the motions of particular 
 mufcles. 
 
 321. 
 
 By thefe diverfified and numerous aids, has 
 nature made compenfation for, or at leafl very 
 ccnfiderably diminifhed, that inevitable lofs of 
 power, which neceiTarily arifes from the confor- 
 mation and ftature of the whole body. The 
 acutenefs of the angles formed by the insertions 
 of a great many mufcles, and the vicinity of thefe 
 infertiens to the centres of motion, mav be brought 
 forward as incontrovertible teftimonies in favour 
 of fuch a lofs of power, which would not have 
 been fuftained, had the tendinous cords been in- 
 ferted at greater diftances from the centres of 
 motion, or in fuch directions, as to have formed 
 more obtufe angles. 
 
 § 3 22 - 
 To our bodies, thus furnifhed with about four 
 hundred and fifty mufcles, together with a few 
 occalional fupernumeraries, (arifing from fexual 
 and individual varieties), two advantages of the 
 urmofl magnitude and importance are very obvi- 
 
 oufly 
 
222 OF MUSCULAR MOTION. 
 
 oufly derived. Firft, in confequence of this beau- 
 tiful and complicated fyftem of organs, not only 
 our individual members, but alfo our whole bo- 
 dies, are rendered capable of the mod aftonifhing 
 agility, in point of motion ; and Jecondly^ from 
 the fame fource, we derive fuch remarkable de- 
 grees of ftrength, as qualify us to bear, without 
 injury, the moft arduous fpecies of labour and 
 fatigue. Thefe two momentous advantages de- 
 pend, indeed, in part, on a perfect ftate of the 
 mufcles, to which, no lefs than to a. perfect ftate 
 of the bones, we arrive by degrees, as youth 
 advances towards maturity; but they are alfo, in 
 part acquired by a frequency of ufe and exercife. 
 The powerful influence which thofe two latter 
 circumftances pofTefs and exert over the mufcles, 
 in ftrengthening them and rendering them capable 
 of the utmofl agility of motion, is flrikingly de- 
 monstrated by numerous examples of rope-walkers, 
 of dancers, of runners, of wreftlers, of boxers, 
 and of thofe robuft barbarians, who conftituted 
 the glory and boafl of former ages. 
 
 SECT. 
 
OF SLEEP. 223 
 
 SECT. XXV. 
 
 OF SLEEP. 
 
 § 3 2 3- 
 
 1 HOSE two fprcies of nervous acYion, 
 (die hiitory of which we have dow completed) 
 that have for their ultimate ends fenfation and 
 motion, are fo reduced and debilitated by the 
 divcrfified exercifes of the day, that repofe 
 by night becomes abfulutely neceiTary, for the 
 purpofe of refrefhing their declining vigour 
 and energy, which Jkcp alone, the image, or fern- 
 blanu of gelid death, is able compleiely to reftore. 
 
 § 3*4- 
 
 Sleep is a fun&ion perfectly periodical, which 
 fufpends, as it were, for a time, all intcrcourfe 
 and communication between the mind and body. 
 The various phenomena of this function, fome of 
 which (hall be immediately enumerated, appear to 
 declare, with no fmall force of evidence, in favour 
 of the exigence of a nervous fluid. 
 
 § 3*S- 
 Befides a variety of ether cirenmftances, we 
 
 may here enumerate as precurfors and harbingers 
 
 of 
 
224 OF SLEEP. 
 
 of fleep, a fluggilhncfs and gradually increafing 
 dullncfs of the external fenfes, together with a 
 relaxation of molt of the voluntary mufcles, 
 efpecially fuch as are of confiJerable length. To 
 thefe may be added a congeflion of the venous 
 blood in, and near, the heart, and an effort to 
 remove the uneafmefs thence arifing, by the aid 
 of yawning. Finally, the only additional pre- 
 cursor to be mentioned at prefent, which appears 
 to conflitute the very ijih/nus, as it were, between 
 the waking and fleeping dates, and the immediate 
 tranfition of the former into the latter, is a pecu- 
 liar fpecies of tranilent delirium. 
 
 § 326. 
 
 The following are what conflitute the principal 
 phenomena of fleep, when that flate has actually 
 occurred: the animal functions are wholly fuf- 
 pended from action, while aimed all the others are 
 at the fame time performed in a more fluggifh and 
 torpid manner; thus, in fubjecls buried in fleep, 
 all other circumftances being alike, the pulfe is 
 flower, and the heat of the body fomewhat 
 diminifhed ; perfpiration is alfo lefs plentiful ; 
 digeflion lefs powerful; and (if the occafional 
 difcharge ofthefemen mafculinutn be excepted) 
 all the excretions are fupprelTed, 8:c. 
 
 1 § 3 2 7> 
 
 
OF SLEEP. 22$ 
 
 § 3*7- 
 The remote caufes which induce fleep are very 
 plain and obvious. For to fay nothing of narcotic 
 fubftances themfelves, we may confider as very 
 energetic caufes in the production of this ftate, all 
 ivafte of the animal powers by means of preceding 
 fatigue, by watching, &c. To thefe we may fab- 
 join the influence of cuftom, together with dark- 
 nefs, filence, reft, &c. which appear indeed to 
 derive their fomnifcrous powers from the fame 
 fource; we may alfo further add, gentle, uniform, 
 and conftant impreffions acting on any of the 
 fenfes, fuch, for inftance, as the foft murmurings 
 of the rill, or the appearance of a harvefl: field, 
 agitated and thrown into wavy undulations, by the 
 mild fannings of the weftern breeze, &c. Under 
 the fame head of remote caufes we may alfo con- 
 fider, full meals, and intenfe cold acting on the 
 body, together with a variety of other circum- 
 ftances, tending to derive the blood from the 
 encephalon, as pediluvia, clyfters, and profufe 
 hemorrhages, &e. 
 
 § 3*7- 
 
 Thofe remote caufes which we have mentioned 
 in the latter part of the preceding paragraph, are, 
 of themfelves, fufficient to conduct us to the proxi- 
 mate caufe, which appears, from the beft evidence 
 
 vol. 1. P that 
 
2 26 OF SLEEP. 
 
 that can be collected on the fubjecl, to confifl in 
 a diminution of the column of blood that goes to 
 fupply the encephalon. 
 
 That this is indeed the proximate caufe of fleep, 
 is powerfully illuflrated and confirmed, by a very 
 fingular and ftriking phenomenon, which I had. 
 once an opportunity of obferving in a living 
 human fubjeft, whofe cafe has been already men- 
 tioned on another occafion. As often, and as 
 long, as this perfon indulged himfelf in fleep, his 
 brain fubfided and continued in a flate of confi- 
 derable collapfe, but during his waking hours 
 throughout the day, this organ became again 
 turgid and diflended in confequence of a more 
 copious afflux of blood. 
 
 As an additional argument in fupport of the 
 fame caufc, we may obferve, that morbid watch- 
 fulnefs, on the other hand, ufually arifes from 
 congeftions of blood in the region of the brain. 
 
 § 329. 
 The quantity of fleep neceflary, depends in a 
 great meafure on varieties in age, habit of body, 
 temperament, &c. The general refult, however, 
 of all the exifting evidences on this fubjedt, 
 appears to be, that a longer indulgence in fleep is 
 cither a concomitant of imbecility (as is the cafe 
 
 in 
 
OF SLEEP. 227 
 
 in tender infants, and fubjefts far advanced in 
 years), or a very exuberant fource of fatuity and 
 dullnefs. 
 
 § 330- 
 We rife from fleep with renovated powers, and 
 our return into the living, and completely waking 
 ftate, is accompanied with fymptoms and pheno- 
 mena very fimilar to thofc which attended our 
 tranfition from this ftate into that of fleep: we are 
 attacked, for inftance, by a yawning, accom- 
 panied for the moft part with more or lefs of a 
 ftretching, we are a!fo affected by a certain dull- 
 nefs and torpidity of the fenfes, &c. 
 
 § 33 l - 
 The caufes which roufe into wakefulness, ap- 
 pear to correfpond exactly with thofe productive 
 of fleep. 
 
 The proximate caufe will be the return of a 
 more copious column of blood into the ence- 
 phalon. 
 
 The remote caufes, befides the power of 
 cuftom, which is confeffedly very great, confift of 
 an immenfe variety of ftimuli, that may be divided 
 into external and internal. The external are 
 calculated to excite the flumbering fenfes, while 
 P 2 the 
 
228 OF SLEEP. 
 
 the internal act either immediately on the body 
 itfelf, as the didenfion of the urinary bladder; or 
 imprefs the nervous fyftem through the medium 
 of the imagination, the mode in which dreams 
 operate. 
 
 S 33 2 > 
 Dreams are light fportings of the imagination, 
 in which it recalls the images of things formerly 
 perceived, and appears to exercife and bufy itfelf 
 in arranging and combining them into the moll 
 fantaftical reprefentations. 
 
 I have never been able to difcover the flighted 
 veflige of this faculty in new-born infants pre- 
 vioufly to the third month after birth. 
 
 There are alfo various examples of adults who 
 explicitly declare, that they have no knowledge 
 cf dreams, having never been troubled by them. 
 
 Thofe vifions of the night are, for the moft 
 parr, indeed, confufed and irregular; but they 
 arc, notwithftanding, fometimes marked with 
 ailoniming veftiges of reafon. 
 
 The influence cf flimuli acting on the body is 
 
 truly great in the production of dreams: thus the 
 
 famulus of the ma'e femen gives rife to luflful 
 
 2 ideas; 
 
OF SLEEP. 229 
 
 ideas ; the ftimulus of an exceflive plethora calls up 
 images of a frightful and terrifying nature, &c. We 
 have even received a well confirmed account of a 
 man, to whom, while afleep, his friends could fug- 
 ged whatever vifions they pleafed, by communi- 
 cating to him the fubjecT: and matter of the dream 
 in a foft and gentle tone of voice. This appears 
 however, to belong rather to a preternatural (late, 
 confifting of fomnolency and wakefulnefs, ot 
 which that truly morbid affeftion of the fomnarji' 
 bulantes, or thofe who walk in their fleep, 
 conftitutes alfo another variety. 
 
 It is neceiTary previoufly to the final conclufion 
 of this fubjeft to obferve, that Locke and others 
 have thought proper to confider all dreams as 
 belonging to this mixed or compound (late. 
 
 END OF THE FIRST VOLUME. 
 
ELEMENTS 
 
 OF 
 
 PHTSIOL GT. 
 
 SECTION XXVI. 
 OF FOOD, AND THE APPETITE FOR IT, 
 
 § 33^ 
 
 AS the wafte of the animal powers is 
 again reftored by fleep, fo in like manner the in- 
 ceilant lofs of the natural powers, and even of the 
 very elementary parts of the body, is repaired by 
 frefh and repeated fupplies of food. 
 
 S 333- 
 To the acquifition and ufe of this food we are 
 
 forcibly led by the frequent and irrefiftable calls 
 of nature. Thefe calls, though widely different 
 from each other in their natures, tend notwith- 
 standing to the final accomplishment of the fame 
 end : they confift, on one hand, of the infupport- 
 vol. ii. A able 
 
2 OF FOOD AND APPETITE. 
 
 able torments of hunger and thirjl ; and on the 
 other, of the very pleafing, but no lefs powerful, 
 allurements of appetite. 
 
 § 334- 
 The ftimulus of hunger , fome phyfiologifts have 
 
 fjught for in the mutual friction between the rugae 
 
 of the ftomach when empty ; others in that which 
 
 appears, indeed, to be of primary importance in 
 
 giving birth to this potent fenfation, namely, not 
 
 only in a more copious fecretion and afflux of the 
 
 humours difcharged into the firft pafTages, mere 
 
 efpe. ially of the faliva, the pancreatic juice, and 
 
 the bile, but alfo in a certain degree of morbid 
 
 acrimony, with which thefe fame humours are apt 
 
 to be contaminated, unlefs fuch a ftate be guarded 
 
 againfl by regular fupplies of nourishment. 
 
 § 335- 
 Thirjl is a diftrefTing fenfation, arifing princi- 
 pally from a very troublefome drynefs of the fau- 
 ces and efophagus ; and alfo from a peculiar im- 
 prefiion produced by taking in acrid, but more 
 efpecially faline, fubflances. 
 
 § 33 6 - 
 With refpect to the abfolute necejjity of fatisfy- 
 
 ing and removing thele ftimuli, no fixed and pofi- 
 
 tive rule can with propriety be laid down, as fuch 
 
 neceflity 
 
OF FOOD AND APPETITE. 3 
 
 necefiity is doubtlefs rendered more or lefs urgent 
 by varieties in age, habit of body, and more efpe- 
 cially by the power of cuftom. From a general 
 confideration of this fubject, however, the refult 
 appears to be, that an adult and healthy perfon, 
 who is under no undue imprcflions or influence, 
 (in whom, for inftance, thofe aiTuafive calls of na- 
 ture are neither filenced by the louder ravings of 
 enthufiaflic fanaticifm, nor by other preternatural 
 caufes) cannot refrain from the ufe of food, for 
 even one whole day, without a very great proflra- 
 tion of ftrength ; and can feldom fad for more than 
 eight days without incurring the utmoft hazard of 
 life. 
 
 § 337- 
 With regard to drink, although a defire for 
 this appears to urge with the greater vehemence 
 and intenfity of the two, it is, notwithftanding, 
 much lefs necefTary to life and health than the ar- 
 ticle of food. This we infer, with apparently 
 ftrict. propriety and truth, not only from numerous 
 fpecies of warm-blooded animals, as mice, quails, 
 &c. that are never impelled by neceflf-ty to the ufe 
 of drink, but alfo from actual examples of certain 
 individuals of the human race, who have conti- 
 nued, through a long feries of time, in the enjoy- 
 ment of life, health, and fpirits, without recourfe- 
 to the ufe of drinks of - any kind. 
 
 A 2 § y^. 
 
4 OF FOOD AND APPETITE. 
 
 § 338- 
 
 As to food, controverfies have exifted refpe&ing 
 the kind moft proper to fatisfy the internal calls 
 of our nature : whether, for example, the frruc- 
 ture and conftitution of the human body corres- 
 pond moil: perfectly w ith food taken from the ani- 
 mal, or with that derived from the vegetable, 
 kingdom ; and which of thefe two kinds of fub- 
 ftances nature, therefore, defigned to constitute 
 the aliment of man ? 
 
 § 339- 
 That man is by nature an herbivorous animal, 
 Rouffeau attempted, with a great degree of acute- 
 nefs, to prove, not only by arguments taken from 
 the figure of his teeth, and the length of his in- 
 teftines, but by the further confideration, that wo- 
 man is naturally uniparous, and furnilhed with 
 two mammas, &c. ; to all which might be added, 
 a&ual examples of rumination having been per- 
 formed by human Subjects, a procefs well known 
 to belong exclufively to herbivorous animals. 
 
 Thofe, on the contrary, who, with Helvetius, 
 confider man as a carnivorous animal, attempt to 
 fupport their opinion by the fhortnefs of his intef- 
 tinum c<zcum, and other arguments of a fimilar 
 nature. 
 
 § 340. 
 
OF FOOD AND APPETITE. y 
 
 § 34°- 
 But from more accurate obfervation, and a 
 more minute inveftigation of the fubjeft, it ap- 
 pears, that nature did not intend to reftridt man 
 to the exclufive ufe of either the one or the other 
 of thofe kinds of aliment, but more indulgently 
 deflined him to a free participation of both. That 
 this is indeed the kind deflination of man with re- 
 flect to the nature of his food, we very naturally 
 infer from his teeth, efpecially the molarcs, and the 
 conformation of his inteftines, briefly mentioned 
 above, poflfeffing a middle (fate between the fame 
 parts, as they exift in carnivorous and in herbivo- 
 rous animals. This prerogative of man is, how- 
 ever, dill more forcibly demonftrated, by the na- 
 ture of the artieulation which connects the con- 
 dyles of the lower jaw to the ojfa temporum in hu- 
 man fubjecls. 
 
 § 341. 
 If the obfervations be true (and they furely 
 cannot be doubted) which we dated on a former 
 occafion, refpecting the high privilege of man, in 
 being by far better calculated than other animals 
 for traverfinsr an extenfive ran ire of climate on 
 the globe we inhabit, it from thence fpontane- 
 oufly follows, that he would have been indeed 
 very illy accommodated, in being folely reftric~red 
 either to the one or the other of the above kinds 
 A3 of 
 
6 OF FOOD AND APPETITE. 
 
 of food : for as fome regions of the globe afford 
 animal, and others vegetable food alone, the ob- 
 vious and unhappy refult of fnch an exclufive re- 
 ftri&ion would have been, that man, though cal- 
 culated and deftined to refide in all latitudes of 
 the earth, mull, notwithstanding, in fome of them, 
 be denied the ufe of fuch aliments as nature had 
 rendered effentially neceffary to the continuation 
 of his exigence, 
 
 § 342. 
 Of all animals, wi:h which we are in any mea- 
 fure acquainted, man may, with the ft r i 61 e ft pro- 
 priety and truth, be faid to be omnivorous. As 
 on the one hand he is calculated to banquet in 
 luxury, amidfl the mod profufe variety of delica- 
 cies that aft can prepare from the immenfe re- 
 fources of the animal and vegetable kingdoms, 
 fo, on the contrary, he is able to retain his health 
 •and vigour when fubfifling on the moft fimple and 
 frugal fare. 
 
 Thus, to produce only a very few examples, a 
 great many men even at the prefent day fubfift 
 folely on a vegetable diet, fuch as potatoes, chef- 
 nuts, dates, &c. which confHtuted alfo the food of 
 the firft progenitors of the human race : for it ap- 
 pears highly probable, that thofe fimple and hardy 
 fops of nature, fupported life firft by the fruits and 
 
 roots 
 
OF FOOD AND APPETITE. 7 
 
 roots of plants, and afterwards, by the more fub- 
 flantial and durable fare of grains and pulfe. 
 
 Some of the Moorifh tribes in Africa live aimed 
 entirely on the gum fenegal. 
 
 The inhabitants of Kamfchatka and of a great 
 many other maritime fituations fubfift on fifh. 
 
 In Europe itfelf, the Morlachi are fupported al- 
 mofl entirely on a diet of flefli. 
 
 Some nations of Barbarians fubfift even on raw 
 HeMi, a circumttance which is undoubtedly true, 
 with refpect to the Samoids, the Efquimaux, and 
 certain tribes of people inhabiting South America. 
 
 Neither are the liquids made ufe of as drinks, 
 in certain nations, lefs lingular and (biking. 
 
 Thus the inhabitants of fcveral iflands, which 
 lie between the tropics, more efpecially thofe fitu- 
 ated in the Pacific Ocean, arc entirely deftitute of 
 fvveet and pleafant water, and therefore, as a fub- 
 ftitute for this fluid, ufe the delicious juice of the 
 I a clef cent cocoa. 
 
 Others again drink the waters of the briny 
 
 ocean ; — from all which fa£h and circumftances, 
 
 A 4 taken 
 
S OF MASTICATION 
 
 taken colle&ively, together with an infinitude of 
 others that might be adduced, we need not hefitate 
 a moment to pronounce, that man is literally an 
 omnivorous animal. 
 
 SECT. XXVII. 
 OF MASTICATION AND DEGLUTITION. 
 
 § 343- 
 
 -TOR the purpofe of maflicating the 
 more folid fpecies of food, both our under, and 
 upper jaws, are armed with three different kinds 
 of teeth. 
 
 Thefe are firfl, the incifores, which, in moil: 
 men, are chifel-formed, and well calculated to bite 
 off morfels of food. 
 
 Secondly, the canini, ftrong, conical and com- 
 pletely adapted for breaking fubftances of greater 
 iirmnefs. 
 
 .And la/lly, the molares, of different fizes, exqui- 
 fkely fitted for the procefs of grinding. 
 
 § 344- 
 
AND DEGLUTITION. 9 
 
 § 344- 
 
 The mandible or lower jaw is connected to the 
 other parts of the head, by means of a very lingu- 
 lar variety of articulation, which appears to be of 
 a middle nature between arthroida and ganglimus. 
 Being furnifhed with a pair of double concave car- 
 tilages, it thus unites, to a fufficient degree of 
 flrength and firmncfs, a capacity of being eafily 
 and very confiderably moved in all directions. 
 
 The under jaw is drawn back, in opening the 
 mouth, chiefly by means of the miifculu? bivente?-, 
 but in part alfo by the geniohyoidei and the my- 
 lohyoidei. 
 
 It is brought back again, when we attempt to 
 cut any thing through with the dentes incifores, 
 and prefled with aftonifhing force againfr. the 
 oppofite jaw, during our efforts to crufh any 
 hard fubftances, by the maffeter and temporal 
 mufcles. 
 
 It is moved laterally in chewing, by the action 
 of the internal and external pterygoid mufcles ; 
 the latter of which have alfo the power of moving 
 it in a forward direction. 
 
 § 345- 
 
10 OF MASTICATION 
 
 § 345- 
 Subftances taken into the mouth for the pur- 
 
 pofe of being chewed, are retained, placed in a 
 
 proper fituation, and thus effectually fubjected to 
 
 the action of the teeth, by means of the mufculus 
 
 buccinator ) and the tongue, an organ of extreme 
 
 flexibility, and very capable of changing its form 
 
 (S 2 33> 
 
 § 34& 
 During the act of manducation we emulge, as 
 it were, a certain quantity of faliva, which is an 
 aqueous liquid, of a nature fomewhat faponace- 
 ous ; it contains a fmall quantity of earthy matter, 
 (which gives origin to tartarous incruftarions of 
 the teeth, and to fmall fublingual calculi) ; this 
 fluid, from being in perpetual contact with the 
 tongue, mafccs no fenfible impreflions of tafte on 
 that organ, although it contains a fmall quantity 
 of microcofmic fait ; it poffefles antifeptic and re- 
 folvent properties, and has alfo a power of fpee- 
 dily exciting the procefs of fermentation in vege- 
 table fubftances, efpecially in thofe of the farina- 
 ceous kind. 
 
 § 347- 
 The fources from whence this fluid is derived 
 are, fmall conglomerate glands, cf three feveral 
 
 orders, 
 
AND DEGLUTITION. n 
 
 orders, the lateral and internal, of which are fitu- 
 ated beneath the lower jaw. 
 
 The mod confulerable of thefe glands, called 
 parotids, (remarkable, on account of being ex- 
 tremely fubject to metaftafes), excrete their faliva 
 through the Stenonian duct, juft behind the middle 
 molar tooth of the upper jaw. 
 
 The faliva furnifhed by ihc/ubmaxUlary glands., 
 is difcharged through the duel: of Wharton. 
 
 That derived from the fublingual glands, which 
 are the lead of all, flows through the numerous 
 ducts of Rivinus. 
 
 s 348- 
 
 The excretion of faliva, (of which, in confor- 
 mity to the opinion of Nuck, about a pint is com- 
 monly fuppofed to be fecreted in the fpace of 
 twelve hours), is confiderably encreafed both by 
 the application of any ftimulating fubftance, and 
 alfo by mechanical prefTure, the latter of which 
 appears to aft merely by emulging the containing 
 parts. 
 
 Thus, whatever hard fubftances we chew, be- 
 come perfectly moiflened and macerated, as it 
 were, by a copious afflux of faliva produced in 
 
 confe- 
 
12 OF MASTICATION 
 
 confequence of the prcflure, to which the parotids 
 are particularly expofed from, being fituated fo 
 near to the articulation of the lower jaw. 
 
 With regard to the operation of flimuli on the 
 fecretion of this fluid, it is neceffary farther to ob- 
 ferve, that when acrid fubftances are taken into 
 the mouth, a plentiful afflux of faliva is immedi- 
 ately produced, which has the effect of diluting 
 and thus effectually counteracting the irritating 
 acrimony : an increafe of the fame fluid is alfo oc- 
 cafionally produced by the flimulus of the imagi- 
 nation ; to this caufe muft wc refer that afflux of 
 faliva, which fo frequently accompanies a itrong 
 appetite for food. 
 
 § 349- 
 With the faliva are blended a fine aqueous, 
 dew-like fluid, which tranfudes from the foft parts 
 of the mouth, and alfo a mucus, fecreted by fmall 
 glands, fituated in the lips and cheeks : it is a 
 portion of this mucus by which the tongue is lu- 
 bricated. 
 
 § 35°- 
 The morfel during maftication, being thorough- 
 ly moiftened by this mixture of faliva and other 
 animal juices, is thus, not only converted by de- 
 grees into a foft pulpy bolus, more fit for the pur- 
 
 pofc 
 
AND DEGLUTITION. 13 
 
 pofe of deglutition, but is likewife prepared, at 
 the fame time, for further digeflion and final affi- 
 milation. 
 
 § 35 1 - 
 
 The adtual bufinefs of deglutition, although it 
 appears to be of a very compound nature, and is 
 indeed performed by the co-operation of a great 
 many different parts, may be confidered as com- 
 mencing and proceeding in the following order ; 
 viz. the tongue being firft retracted towards its 
 bafis, and becoming therefore fomewhat turgid 
 and ftiff, receives on its excavated dorfum or back, 
 the lubricated and moiftened bolus, which is from 
 thence forced onwards into the fauces, where it 
 is received by the expanded infundibulum of the 
 ■pharynx , which appears, at the fame time, to ad- 
 vance fomewhat upwards ; on the reception of the 
 food the infundibulum makes a Angular and vio-. 
 lent exertion, which may be fuppofed to proceed 
 from a fpecies of vita propria ; from this funnel- 
 like entrance, the bolus is again protruded on- 
 ward, by a threefold contraction of the pharynx, 
 into the cefophagus. All the above motions fuc- 
 ceed each other with the utmoft degree of rapidi- 
 ty, and are of extremely fhort continuance. 
 
 § 35 2 - 
 For the purpofes of expanding this paiTage, and 
 
 rendering it at the fame time Heady and fecure, 
 
 nature 
 
14 OF MASTICATION 
 
 nature has made the mod ample provifion by a 
 variety of auxiliary parts. 
 
 The motion of the tongue, in this momentous 
 bufinefs, is regulated and directed by the os hyo- 
 ideum. 
 
 To prevent any of the fubftances fwallowed, 
 from palling, by miftake, either into the internal 
 nares, or into the euftachean tubes, the foft palate 
 is very wifely provided. This flcfhy curtain, de- 
 pending equally from the arched roof to which it 
 is attached, is capable of being rendered tenfe by 
 the action of a peculiar fet of mufcles, and thus 
 the above pafTages may be completely clofed. 
 
 The glottis is fecurely guarded by the tongue 
 itfelf, becaufe at the very inftant in which we at- 
 tempt to fwallow, the larynx, being drawn up- 
 ward and forward, is in a certain degree concealed 
 beneath the retracted bafis of the tongue, and is 
 fo compreffed by it, that the glottis, not only by 
 this conftriction, but alfo by the additional fecurity 
 of the epiglottis, is thus very effectually guarded 
 againft the intrufive entrance of any heterogene- 
 ous fubftances. 
 
 § 353- 
 Finally, the bufinefs of deglutition is greatly fa- 
 cilitated by means of a quantity of mucus, with 
 
 which 
 
AND DEGLUTITION. 15 
 
 "which the whole of the paffage above defcribed 
 is lubricated ; and which, befides the lingual 
 glands already mentioned (§ 235), is chiefly fur- 
 nifhed by the numerous finufes of the tonfils, and 
 by that infinitude of mucaginous cryptKi fo pro- 
 fufely beftowed on the larynx itfelf. 
 
 § 354- 
 
 "Wiih refpeft to the ccfophagas itfelf, through 
 which all fubftances fwallowed muft neceffarily 
 pafs, previoufly to their entrance into the fiomach, 
 it is a flefhy canal, rather narrow in its diameter, 
 and exceedingly firm and flrong, but at the fame 
 time pliable, di!atable,and poffeffed of a high degree 
 cf ferifibility : it is compofed of tunics or coats, 
 which, if we except the difference in their thick- 
 ntfs, bear no fmall refcmblance to the coats of the 
 other portions of the alimentary canal. 
 
 Thus, the external covering is mufcular, made 
 up of fibres running both longitudinally and in 
 tranfverfe or circular directions. 
 
 The middle coat is nervous, ending on each fide 
 in a very lax cellular membrane, by means of 
 which it is connected, as well to the preceding, as 
 to the fubfequent tunic. 
 
 Laflly, 
 
itf OF DIGESTION. 
 
 Laftly, the internal coat is lined by mucus of an 
 exquifite degree of lubricity. 
 
 § 355- 
 
 The following appears to be the mode in which 
 this canal performs its office ; as foon as it has re- 
 ceived either a draught or bolus completely within 
 its parietesy the parts immediately above prefently 
 contraft themfelves, thus forcing downwards the 
 fubftance to be fwallowed ; which, if it be a bo- 
 lus, can be protruded onward only by one uni- 
 form feries of exertions in the furrounding tube, 
 till it has palTed through the diaphragm, and been 
 finally received into the cavity of the ftomach 
 itfelf. 
 
 SECT. XXVIII. 
 
 OF DIGESTION. 
 
 1 HE chamber, or immediate feat of di- 
 geftion, is the ftomach , a vifcus more uniformly 
 pofTefled than any other, by almoft every indivi- 
 dual throughout the immenfe range of animated 
 nature : if, therefore, we eftimate the dignity of 
 the feveral vifcera from this circumftance alone, 
 the ftomach is, dcubtlefs, to be confidered as an 
 
 i organ 
 
OF DIGESTION. 17 
 
 crgan furpaffing all the others in utility and im- 
 portance to the animal economy. 
 
 § 357- 
 The human flomach refembles a leathern pouch, 
 
 of very confiderable dimenfions, fufficient, for the 
 
 mod part, in an adult, to contain three pints, or 
 
 more, of water, and furnifhed with two feparate 
 
 orifices or mouths : 
 
 Thefe are, fir/}, a fuperior orifice, called car- 
 dia, which is formed in the place where the cefo- 
 phagus, by a plaited and fomewhat oblique aper- 
 ture, opens into the flomach itfelf, and points to- 
 wards the bottom of this vifcus, or that extremity 
 which regards the left fide of the body. 
 
 Secondly, an inferior one, which conflitutes the 
 termination of the right, and lefs capacious end of 
 the flomach : this orifice is called pylorus^ and de- 
 fcends a fliort diftance into the cavity of the ad- 
 joining duodenum. 
 
 § 353. 
 
 The fituation of the flomach, when empty, is 
 different from that of the fame organ, when full : 
 thus, in the former ftate, it hangs loofe and flaccid 
 in the abdominal cavity, in fuch a manner that its 
 greater curvature looks in a backward direction - 9 
 
 vol. 11. B and 
 
1 8 OF DIGESTION. 
 
 and its pylorus, being turned fomewhat upwards-, 
 forms a plaited or twifted angle with the duode- 
 num, to which it is connected. 
 
 But in the latter ftate, when diftended with food, 
 its greater curvature is again turnrd. and looks in 
 an anterior direction, fo that the tj lorus enters 
 now, by a more direct route, into the duodenum ; 
 whereas the cardia, on the contrary, is fo folded 
 and bent as to be completely clofed, 
 
 § 359- 
 The ftomach is compofed of four principal 
 coats, diftinguifhed and feparated by three others, 
 of an entirely cellular nature, which lie between 
 them. 
 
 The mod external of thefe coverings is common 
 to the ftomach, with all the reft (fave a fmall por- 
 tion) of the alimentary canal, and is continued 
 over the omenta, which fliall be fpoken of here- 
 after. 
 
 Next to this, lies that cellulo-mufcular coat, (o 
 very ftriking in irs nature and properties, on which 
 depend both the exquifite irritability of the fto- 
 mach (§ 306.), and alfo its periftaltic motion ; the 
 latter of which fliall be a fubject of confideration 
 in another place. This coat is compofed of dif- 
 ferent 
 
OF DIGESTION. t$ 
 
 ferent ftrata of mufcular fibres, which are ufually 
 divided into three orders, one longitudinal, and 
 two circular ; the circular fibres are again divided 
 into thofe that are dtreclly* and thofe that are ob- 
 liquely, circular. It mud, however, be obferved, 
 that fo extremely variable and irregular are the fi- 
 bres of this coat, with regard to their direction 
 and diftribution, as fcarcely to admit of reduction 
 to, and arrangement under, any determinate and 
 general rules. 
 
 The third principal coat is called the nervous, 
 an appellation extremely improper, as it is compo- 
 fed wholly of condenfed cellular membrane, be- 
 coming gradually more foft and lax on each fide ; 
 by which means it is connected externally to the 
 mufcular, and internally to what we (hall prefently 
 call the villous, coat. It is, notwithstanding, fo 
 firm and robu(t, that it may be aptly enough call- 
 ed the bafts of the whole flomach. 
 
 Laftly, the internal coat, which has been very 
 improperly called vil'ous, ii exceedingly tender, 
 fomewhat fpongy, porous, and folded into a very 
 great number of rugce or wrinkles, fo that its area 
 is much more extenfive than that of any of the 
 other coats which we have juft defcribed : it every 
 where exhibits cells cf the utmoft minutenefs,fome- 
 B 2 what 
 
20 OF DIGESTION. 
 
 what fimilar in appearance to thofe larger ones, 
 with which the reticulum of ruminating animals 
 is very beautifully and elegantly characterized. 
 
 The internal furface of this coat is lined with 
 mucus, apparently fecreted by fmall mucaginous 
 cryptse, fome of which may be, indeed, readily 
 enough diftinguifhed near to the pylorus, or lower 
 orifice of this organ. 
 
 § 3 6 °- 
 The flomach is furnifhed with an aflonifliing 
 
 apparatus of nerves, whence its fenfibility is fo ex- 
 quifite, that it is capable of being very readily af- 
 fected by flimuli of almoft every kind, whether 
 they be external, as cold &c. or internal as food, 
 and even by the inquiline humours themfelves. 
 From the fame fource arifes alfo that exteniive, 
 and truly admirable confent, which exifls between 
 this important vifcus and mofl of the other func- 
 tions of the body; to which head belongs, in a 
 particular manner, the flriking effects, produced 
 on the flomach, by all mental commotions, and 
 alfo, on the other hand, the very powerful influ- 
 ence of an entirely found and healthy flate of this 
 organ, on the cheerfulnefs and ferenity of the 
 mind, 
 
 § 56i. 
 
OF DIGESTION. 2i 
 
 § 56l. 
 
 The number and functions of the blsod vejfels, 
 belonging to the ftomach, are no lefs confiderable 
 and ftriking, than thofe of the nerves. The fmall 
 arteries, (of which an infinitude of different or- 
 ders, are minutely interfperfed throughout the cel- 
 lular coats of this organ), appear to conftitute the 
 immediate fources of the gqfiric juice, a liquor 
 which flows in perpetual ftreamlets from the inter- 
 nal furface of the ftomach. 
 
 § 3 6 2- 
 
 This juice bears, on the whole, no fmall refem- 
 blance to faliva, except that, agreeably to the ex- 
 periments of the illuftrious Spalanzani, its powers 
 are counter to thofe which promote fermentation. 
 As to the reft of its properties, it is faponaceous, 
 equally antifeptic with the faliva, and is indeed, a 
 very powerful menftr-uum, fuflicient gradually to 
 dhTolve milk after it has been gently coagulated in 
 the ftomach. 
 
 § 3 6 3- 
 The gaftric juice appears to be the moft power- 
 ful and active agent in the great bufmefs of digef- 
 tion. If the food be carefully mafticated, and fuf- 
 ficiently blended with the menftruum furnifhed by 
 the falivary glands, this fluid of the ftomach com- 
 B 3 pletely 
 
12 OF DIGESTION. 
 
 pletely difTolves, and finally converts it, into a 
 foft pultaceous chyme. 
 
 § 364" 
 This momentous function is alfo further aided 
 and promoted, by a variety of acceflbry and afiif- 
 tant powers : of thcfe the molt considerable is the 
 feriftaltic motion, by means of which the food, 
 now reduced to a pulpy confidence, is thoroughly 
 agitated, and kept perpetually in a ftate of wavy 
 commotion. Although the force of the periftaltic 
 motion fall far {hort of the chimerical calculations, 
 formerly made on this fubjeft, by mathematical 
 phyficians, and although it be not itlelf the fole 
 caufe of digeftion, it is, notwithstanding, of the 
 utmofl; efficacy and influence in this important 
 procefs. 
 
 § 365- 
 
 Among the auxiliary powers, of this kind, may 
 be alfo reckoned another fpecks of motion, which 
 the preflure of the furrounding parietes of the ab- 
 domen, communicates to the ftomach : to thefe 
 we may flill farther fubjoin, the extreme warmth 
 of the fituation in which this vifcus is placed ; fo 
 very powerful was this fotus or bath, formerly 
 efteemed, in confequence of the abundant quan- 
 tity of blood contained in the neighbouring vefifels 
 
 and 
 
OK DIGESTION. 23 
 
 and vifcera, that inftead of the term digejiion, 
 that of coclion, was ufed by the greater part of 
 phyfiologifls. 
 
 § 366- 
 To determine, with precifion, the period of time 
 requifite for the converfiofi of our aliment into 
 chyme by the joint co-operation of the foregoing 
 powers (§ 361.), will appear almofl: impoffible to 
 any one, who may c mfider the great variety of 
 ciroimftances, on which fuch converlion mud de- 
 pend : thefe circumflances are, the quality and 
 quantity of the food taken in, the different degrees 
 of force in the digeftive powers, the greater or 
 lefs attention and care bellowed on the prepara- 
 tion of the food for digeftion, by previous rnafti- 
 cation, &c. 
 
 For in a healthy fubjec~t, the unimpaired fto- 
 mach does not difcharge fuch alimentary matters 
 as have been taken in, previouily to the conver- 
 fion of their digeftible parts into a perfect pulp. 
 From whence it is evident, that different periods 
 of time are requifite, for the complete digeflion of 
 different kinds of food. If, however, it be allow- 
 able to form any general conclufion on this fubjec'r, 
 it would appear, that from the third, to the fixth 
 hour, after the ufe of aliment, the flomach has, 
 for the mofl part, difcharged through the pylorus, 
 B a ia 
 
44 OF DIGESTION. 
 
 in a very gradual manner, the whole of its pul- 
 taceous contents. 
 
 § 36> 
 The pylorus is an annular rim, not formed, 
 (like the other rugce on the internal furface of the 
 flomach), by the folding of the villous coat alone, 
 but confuting, in part, alfo of a few fafciculi from 
 the fubjacent nervous^ and alfo of certain fibres 
 from the mufcular^ coat : all which parts are fo 
 organized and arranged, as to conflitute a coniform 
 termination to the flomach, that is extended into, 
 and embraced by, the duodenum, in the fame 
 manner as the os uteri is received and embraced, 
 by the fuperior part of the vagina. 
 
 SECT. XXIX. 
 
 OF THE PANCREATIC JUICE. 
 § 368. 
 
 Subsequent to the expuhion of 
 
 the chyme through the pylorus, that pulpy mafs 
 mud be fubje&ed, in the duodenum (a fhort, but 
 remarkable portion of the inteftina! tube), to new 
 and confiderable changes, previoufly to the for- 
 mation 
 
OF THE PANCREATIC JUICE. 25 
 
 mation and final reparation of complete, alimen- 
 tary chyle. Thefe neceffary changes are effe&ed 
 in the chyme by the acceffion and admixture or 
 various kinds of inquiline humours, the mod (hik- 
 ing and important of which, are, the bile and the 
 pancreatic juice. 
 
 § 369- 
 Of thefe two humours, we will fpeak in fepa- 
 rate fec"Hons. We proceed therefore, to confider 
 the liquor of the pancreas firft, becaufe it appears 
 to bear a very confiderable refemblance, both in 
 its nature and ufes, to thofe other two diffolvent 
 humours, of which we have already fpoken, name- 
 ly, the faliva and the gaftric fluid. 
 
 § 37°- 
 Athough it be indeed a matter of no fmall diffi- 
 culty, to procure the pancreatic liquor of a found 
 animal, in a pure and unadulterated date, yet the 
 obvious and unequivocal refult of all the fa£b, 
 which the moft: attentive investigation has been 
 able to fupply, with regard to its nature, is, that 
 it bears the itrongeft fimilitude to the faliva in all 
 its general properties. Were it not for the pur- 
 pofe of fhowing how mifchievous, and even de- 
 finitive, the practice of medicine may become, 
 unlefs directed by found principles of -V .logy, 
 I fhould not think it neceffary nor ev uper, at 
 
 the 
 
x6 OF THE PANCREATIC JUICE. 
 
 the prefent enlightened period, to mention the er- 
 roneous phyfiological hypothefes, entertained by 
 Franc. Sylvius, and his humble followers, Regn. 
 de Graef, Flor. Schuyl, and others, refpedting 
 the vifionary or fuppofed acidity of the pancreatic 
 liquor, efpecially as thofe opinions have been long 
 fince very ably refuted by Pechlin, Swammerdam, 
 and Brunner, characters of the firft celebrity in 
 the annals of medical fcience. 
 
 § 37 1 - 
 
 The fources from whence the lymph and faliva 
 are derived, bear no fmall refemblance to that 
 which constitutes the fubject of our prefent confi- 
 deration, namely, the pancreas : this latter is by 
 far the largefl of all the conglomerate glands of 
 the human body, and exhibits, in the whole of its 
 ftruclure, a very flriking fimilitude to the glands, 
 that give birth to the falivary fluid ; with thefc 
 laft mentioned bodies it alfo further agrees, in this 
 particular, that its excretory canals, arifing from 
 radicles of the utmoli minutenefs, run together 
 and unite by degrees, till they conftitute finally a 
 common duct, which has received its name from 
 Jo. G. Wirfung, who firfl: difcovered and de- 
 monstrated it in the human fubject, in the year 
 1642. 
 
 This 
 
OF THE PANCREATIC JUICE. 27 
 
 This duel: paffes through the coats of the duo- 
 denum, and by a conflant Jlillicidium, weeps into 
 the cavity of that inteftine, the fluid it had receiv- 
 ed from the gland to which it is appended. 
 
 § 37 2 ' 
 
 Finally, the excretion of this fluid appears to be 
 promoted by the very fame powers, which were 
 formerly faid to be fubfervient to the excretion of 
 faliva, namely, prejjiire zi\djiimulus. 
 
 By means of the former, it is emulged chiefly 
 when the ftomach is diftended and reds immedi- 
 ately on the pancreas. 
 
 The fubftances that contribute moft, by their 
 irritations, to excite a difcharge of the pancreatic 
 fluid are, firft, the chyme irfelf, as it paffes through 
 the pylorus in a crude and unaflimilated (late ; and 
 fecondly, the bile, which is difcharged through 
 the very fame orifice with the liquor of the pan- 
 creas. 
 
 § 373- 
 
 The ufe of this fluid is doubtlefs to diflblve the 
 chyme, more efpecially that part of it, which has 
 not been fufficiently digefted in the ftomach : by 
 its abundant afflux, it contributes to aflimilate this 
 
 pulpy 
 
2 8 OF THE BILE. 
 
 pulpy mafs ft ill more and more to the nature of 
 the inquiline humours, and thus finally mature it 
 for the further procefs of chylification. 
 
 SECT. XXX. 
 OF THE B I L E ». 
 
 § 374- 
 
 T 
 
 H E fecretion of bile is the pecu- 
 liar deftination of the liver, the largeft and moil 
 ponderous vifcus in man. This fuperiority of fize 
 is more especially obfervable, during the fcetal 
 
 * Dottor Maclurg, of Virginia, publifhed in the year 
 1772, an experimental treatife on the formation, the nature 
 and the ufes of the human bile, which has acquired for its 
 learned and ingenious author, no fmall degree of reputation 
 both at home and abroad. That this elaborate publication 
 pofleffes an uncommon fliare of merit, not even the avowed 
 enemies of the DocTor are themfelves able to deny. The 
 author has fliewn himfelf to be, at lead, a very patient expe- 
 rimenter, and an extremely attentive obferver. He appears 
 to have made himfelf perfectly matter of the opinions of all 
 authors of celebrity and diftindion, who had previoufly writ- 
 ten on the fame fubjecl. With regard to the literary merit of 
 the compofition itfelf, it is doubtlefs entitled to die higheft en- 
 comiums that even the moil partial eulogift can beftow. The 
 
 order 
 
OF THE BILE. 29 
 
 fhte, in which, the younger the foetus the greater 
 is the proportional magnitude of the liver, when 
 compared with that of the other vifcera of the 
 
 order is inimitably lucid, the ftyle is chafte, manly and ner- 
 vous in the higheft degree, and as to clofenefs and propriety 
 of argumentative arrangement, not even the fupercilious lo- 
 gician himfelf, can find room to fugged the fhadow of an 
 amendment. 
 
 All human compofitions are, however, like the fources 
 from whence they originate, in fome meafure faulty and im- 
 perfect. To this general maxim, humiliating as it may ap- 
 pear to the pride of the felf-adoring philofopher, the treatife 
 of the illuftrious Maclurg is by no means an exception. In 
 feveral of the Doctor's experiments there appears to be a 
 want of fufficient accuracy and definitude, in others a want 
 of object and defign. Over thefe faults, however, confider- 
 able as they are in the works of an experimentalift, we feel 
 inclined to fpread a kind mantle of palliation, when we re- 
 collect that our author experimented and wrote in the early 
 morn of fcientific chemiftry. Experimenters had not yet be- 
 come perfect adepts in their nice and momentous art ; they 
 had not yet acquired fafficient circumfpection and addrefs to 
 obviate every fource of fallacy, and to avail themfelves of 
 every circumftance that might pave the way to fatisfactory 
 and unequivocal refults. 
 
 But another charge of a more weighty and important na- 
 ture, lies againft our learned and ingenious author. He has 
 certainly built, on nothing more fubftantial than the flimfy 
 bails of deceptious analogy, fome of the leading principles ot 
 his favourite doctrine. Thus, for example, he fuppofes the 
 
 bile 
 
30 OF THE BILE. 
 
 body. The dignity and high importance of this 
 vifcus in the animal economy may be fairly de- 
 duced, from the univerfality of its prefence ; thus 
 
 bile to be a fluid, the direct refult of a putrefactive degene- 
 racy in a portion of the circulating volume of the blood. 
 His moft plaufible reafons in fupportof this opinion a.re,J;r/l, 
 that the parts, from whence the incipient radicles of the vena 
 portarum immediately originate, contain, and communicate 
 with, matter already in a femiputrefcent ftate. And ficond- 
 ly> that the bile is moft abundant in quantity and moft active 
 with regard to its quality, at that feafon, and under thofe 
 circumftances, which arc moft favourable to the commence- 
 ment and progrefs of putrefaction in the living fytlem, a? 
 well as in all other phyfical bodies. 
 
 Plaufible as thofe arguments may, on firft view appear, 
 they are certainly, as already obferved, founded on nothing 
 better than fair, but fallacious analogy. The principle 
 which they tend to efiablifh ftands in the moft direct opposi- 
 tion to the refult of experiment — facred experiment ! the on- 
 ly unerring guide to conduft the candid enquirer to the erer- 
 lafting temple of truth. Did our learned author (I would 
 beg leave to afk) ever faithfully experiment on feparate por- 
 tions of the blo^d, drawn from different parts of the body, in 
 order to determine the comparative proximity of each portion, 
 to the putrefactive Mate ? I prefume he never did, otherwife 
 his opinion on this fuhject would have been, dcubtlefs, very 
 different from what we find in his ingenious publication. 
 For it is a truth, nothing the lefs facred and refpectable on 
 account of its novelty, that if equal quantities of blood be 
 taken from the venapcrtarum, and from the lungs or any part 
 of the arterial fyftem, and expofed to the fame incumbent 
 
 circum- 
 
OF THE BILE. 32 
 
 in all animals poiTeffing red blood, it exifts no lefs 
 generally and uniformly than the heart itfelf. 
 
 circumftances, the pulmonic or arterial, will affume the putre- 
 factive procefs, much fooner than the hepatic, blood. The 
 caufe of this phenomenon muft be r i f Kciently obvious to any- 
 one acquainted with the late dilLoveries, in the divine fciencc 
 of chemiftry. We would attempt its folution in the follow- 
 ing manner. 
 
 Vital air (which is indeed the genuine feptic principle, if 
 any fuch principle exift) is in all cafes e/Tential to the progrefs 
 of putrefaction. This air, or rather its bafe (termed oxygene 
 by the ingenious chemifts of France) is, as we have the firong- 
 eft reafons to believe, from the experiments cf Goodwyn, 
 Beddoes, Girtanner, and others, intimately blended with the 
 circulating blood in its paflage through the lungs. As the 
 blood proceeds in its mazy route through the different parts 
 of the arterial fyftem, it is gradually robbed of its concommi- 
 tant oxygene or bafe of vital air, by the myfterious aflion of 
 the animal fyltem. The confequence of this fpoliation i», 
 that the florid arterial, affumes a much darker colour, and fuf- 
 fers finally a complete tranfmutation into venous blood. In 
 this latter ftate the putrefactive proccfs is lefs apt to com- 
 mence, becaufe the blood contains lefs oxygene in a ftate of 
 intimate mixture, or perhaps I might with more propriety 
 fay, in a ftate of combination. For in proportion as the bafe 
 of vital air is more intimately blended with, and therefore 
 more nearly approximated to, the conftituent parts of the 
 blood, the more powerfully can it co-operate with other aux- 
 iliary agents, in inducing thefe parts to affume that intcftine 
 motion, which conftitutes the putrefactive procefs. Although 
 our learned author is decidedly of opinion, that putrefaction 
 commences more readily, if vital air be excluded altogether 
 
 from 
 
32 OF THE BILE. 
 
 § 375- 
 The fubfhnce of the liver is of a nature, fid 
 generis, and may be readily diftinguifhed, at firft 
 
 from the putrefying fubftances, yet it is now well known, 
 that the very reverfe of this is true. Exclude vital air from 
 a body, in the compofition of which none of this energetic 
 fluid exifts, and you thereby embalm that body in a degree 
 equal, if not fuperior to the embalmment of the unperifhable 
 mummies of the Eaft. 
 
 No body, whatever, is capable of taking on the putrefac- 
 tive procefs, that does not contain in its compofition more 
 or lefs of thofe fimple fubftances that belong to the clafs of 
 inflammables. Reafoning therefore a priori, or climbing the 
 arduous fteeps of fcience by the more laborious fteps of expe- 
 riment and obfervation, we are warranted in either cafe to 
 conclude, that putrefaction confifts, in a very considerable 
 degree, in the intimate combination of the bafe of vital air to 
 certain fubftances of an inflammable nature. Both the pri- 
 mary elements of which putrcfiablc bodies are compofed, and 
 alfo the refuhs of actual putrefaction, co-operate in the efta- 
 blifliment of the fame conclufion. 
 
 It is certainly a truth, that vital air is as eflential to the 
 putrefactive procefs as it is to the fupport of combuftion, or 
 the continuance of animal life. 
 
 Upon the whole, we may without the fmalleft hefitation 
 conclude, that the former opinions of phyfiologiits refpecting 
 the fuppofed putrefcent difpofition of the hepatic blood, are 
 wholly infupportable by argument or fact, being indeed di- 
 rectly oppofed to the literal refult of pofitive experiment; 
 2 and 
 
OF THE BILE. 33 
 
 light, from that of all the other vifcera of the 
 body : it confiits of .1 parenchyma of a well known 
 colour and very tender texture : this parenchyma 
 is abundantly fupplied with nerves, with lympha- 
 tic vefTels (very vifible on both furfaces), with bi- 
 liferous dufh, and finally with blood-veffels, from 
 whence thefe duels originate : with refpecl to 
 thefe blood-veffels, fome of which are remarkably 
 large, we will immediately (late a few obfervations 
 on each of their feveral orders. 
 
 § 376- 
 
 The firft vefTel which here prefents itfelf for 
 our confideration is, the vena port arum ^ which 
 diners very widely from every other portion of 
 the venous fyflem, not only in its fingular appear- 
 ance, but alfo in the peculiarity of its courfe and 
 diflribution, of which a few words were fpoken 
 on a former occafion (§ 87). This large vefTel 
 is formed by the conflux of by far the greater 
 number of the venous branches that originate and 
 run from the vifcera, £ mated in the lower part of 
 the abdomen, and is invented and ftrengthened by 
 
 and therefore, that the pious eulogia fo profufely beflowed 
 on the powers of the animal economy, in being able to form 
 an antifeptic out of a highly putrefcent fluid, appear to be as 
 rifionary and hypothetical, as nature's final intention in the 
 preparation o r this fluid was thought to be beneficent, and hzt, 
 procefs itfelf beautiful, and interefting. 
 
 vol. 11. G a ecl- 
 
3* OF THE BILE. 
 
 a cellular covering, commonly known by the name 
 of capfula GUJfunil. No fooncr does this trunk 
 make its entrance into the liver, than it is divided 
 into feveral branches, which as they run in vari- 
 ous directions through its fubftance, fuffer flill far- 
 ther divifions, till they are finally encreafed to a 
 countlefs number of the molt fubtle ramifications, 
 which pervade, with the utmofl minutenefs, every 
 portion of this vifcus. This whole fyllem of the 
 vena portarum was formerly compared, by Galen, 
 to a tree, the roots of which are difperfed through- 
 out the whole cavity of the abdomen, while its 
 branches are encloied in the more contracted vo- 
 lume of the liver. 
 
 § 377- 
 
 Another blooJ-vefTel of a different kind, with 
 which the liver is furnillied, is the artcria hepatica. 
 This veiTel originates from the caeliac artery, and 
 although far inferior to the vena portarum, both 
 in its capacity and in the number of its branches, 
 is, notwithstanding, divided into ramifications of 
 aftonifiimg fubtility, and is alfo diftributed with a 
 great deal of minutenefs throughout every part of 
 the liver. 
 
 s 37»- 
 
 The extreme terminations of both the forego- 
 ing kinds of vcllels, end in genuine veins, which 
 
 gradually 
 
OF THE BILE, 3 ; 
 
 gradually uniting, form by their general conflux, 
 certain large venous trunks, that lofe themfelves 
 finally in the inferior vena cava. 
 
 § 379- 
 Thofe extreme terminations, by which thefe 
 
 fmall branches of the vena portarum and arteria 
 hepatica become radicles to the vena cava, form 
 a very fubtle vafcular texture, exhibiting a fingu- 
 lar and ftriking appearance, as if the veifels were 
 convoluted, or wound up into globes of incon- 
 ceivable minutenefs. Thefe globular bodies im- 
 pofed fo effectually on Malpighi, as to induce that 
 illuftrioas phyfiologift to confider them as glandu- 
 lar, hexagonal, and hollow kernels, deitined to 
 conflitute the immediate chambers of fecretion. 
 
 § 38o. 
 From thofe fame globular convolutions of blood- 
 veffels arife, laitiy, the port blliarii. Thefe are 
 very tender ducts, which convey the galliih liquid 
 from the blood, and completely eliminate the fame 
 from the fyftem of the liver, through the duclus 
 hepaticus communis, a canal which they form by 
 their general conflux. 
 
 § 3 8l « 
 
 It is common for phyfiologiits to enquire, 
 
 from what kind of blood the bile is immediately 
 
 G 2 fecrcted ; 
 
id OF THE BILE. 
 
 i'ccrctcd ; whether from arterial, or from that con- 
 tained in the vena poriarum ? 
 
 Although the former of thefe opinions appears, 
 on the firfb view of the fubjelt, to be rendered 
 mod probable from the analogy of other fecre- 
 tions, which are evidently the refult of arterial 
 aftion, yet from a more accurate invefligation of 
 the matter we will readily be convinced, that by far 
 the greater part, if not indeed the whole, of the bi- 
 liary fecretion, is derived from the vena portarum : 
 the blood of this vefTel being lurid, and highly im- 
 pregnated with phlogidon, correfponds precifely 
 with the nature of the bile ; but how extremely 
 difFerent, on the o:her hand, are the habit and 
 conftitution of the florid and fiery arterial blood, 
 which the cseliac artery tranfmits from the aorta 
 immediately to the liver ! 
 
 "With refpecl: to arguments drawn from analogy 
 we may obferve, that as the vena portarum is fub- 
 jctfted to an arterial diflribution, fo it may, in like 
 manner, poffefs the power of performing an arte- 
 rial fun&ion : this fame opinion, for which we con- 
 tend, appears alfo to derive additional fupport 
 from the analogy which exifts between the liver 
 and the lungs : to perform the leading function of 
 thefe laft mentioned vifcera, is dcubtlefs the imme- 
 diate defoliation of the large pulmonary arteries j 
 
 whereas, 
 
OF THE BILE. 3? 
 
 whereas, on the other hand, the bronchial artery- 
 is only fubfervient to the nourifhment of the parts, 
 on which it is diftributed : — the difcharge of an 
 office, fimilar to this latter, is alfo, if we be net 
 greatly deceived, the more immediate deflinaiiou 
 of the arteria hepatlca. Notwithflanding what 
 we have here advanced, we. are (till ready to ac- 
 knowledge, that the hepatic artery may poffibly 
 contribute fome what towards the fecretion of bile ; 
 but, that its influence, in this refpecT:, is indeed 
 very inconfiderable, and not yet fufficiently afcer- 
 tained and demonftrated, are pofitions-to which 
 we fubferibe with the utmeff. confidence. 
 
 382. 
 
 The biliary hepatic liquor, when once fecreted, 
 flows in a gentle but uninterrupted ftreamlet 
 through the hepatic duel ; and, when the intejli- 
 num duodenum is empty, glides directly onward, 
 through the common duel us cboledocus, into the 
 cavity of that vifcus ; but when the duodenum is 
 diftended with chyme, it becomes necefTary for 
 this fluid to purfue a different route, whence it 
 regurgitates from the hepatic, and flows through 
 the cyjlic duel into the gall-bladder, where it is 
 retained a certain time, and thence derives the 
 name of cjftlc bile. 
 
 C 3 §3** 
 
3« OF THE BILE. 
 
 § S«3- 
 
 The gall-bladder is an oblong fack, fomewbat 
 pyriform in its figure, attached to the concave fu- 
 pcrficies of the liver, and compofed of three mem- 
 branes or coats. 
 
 Thcfe are, firft, the external, which does not 
 invert the whole of the cyfl, and is derived from 
 the peritoneum. 
 
 Secondly, the middle, ufually called the nervous 
 coat, which, as in the flomach, the inteftinal tube 
 and the urinary bladder, conflirutes here likewife 
 the principal part of the tone and firmnefs of the 
 fac. 
 
 And, laflly, the internal, which bears a certain 
 fimilirude to the internal membrane of the flomach 
 (§ 3590 » 1'ke tnat n * s interfperfed with an infi- 
 nitude of minute blood-veffels, and like that it is 
 alfo marked by rugas or wrinkles, which form, 
 here and there, fine net-like checkerings, that ex- 
 hibit the appearance of the mod exojuifitely ele- 
 gant lattice-work. 
 
 § 384- 
 
 The neck of the gall-bladder is conical, and 
 forms, by its termination, the cjjiic duel, which 
 
 purfues 
 
OF THE BILE. i9 
 
 purines not a direct, but fomewhat circuitous or 
 terpentine route, and is furnifhed with a few mi- 
 nute valves of alunated or falciform figure. 
 
 § 385- 
 
 The gall-bladder retains the bile, when once 
 received, til! that liquor either flows out fpontane- 
 ouflyj in confequtnee of being favoured by a re- 
 cline. i and fomewhat fupirie pofition of the body, 
 or till it is emulged from the cyfl by the prefllire 
 of the neighbouring inteftines, namely, the jeju- 
 num and ileum, or by the occafional pa flag e of 
 hardened fecces through the tranfverfe colon. 
 
 Different ftimuli acting on the duodenum have 
 alfo the effect of folieiting a more copious effuflfn 
 of bile into the cavity of that intefline. 
 
 The remarkable contractility of the gall-blad- 
 der, evidenced and fatisfactorily eftablifhed by live 
 diflecTions and certain pathological phenomena, 
 (although this fac be indeed completely deftitute 
 of all genuine irratibUity \) ', (§ o°7-)-> w '^ appear 
 to contribute, not a little, to the excretion of the 
 bile ; efpecially when wc confider the ftimulant 
 impreflion which this fluid, after retention in the 
 cyfl, rnufl make on its furrounding parietes or 
 walls. 
 
 Q 4. $ 3S6. 
 
4* OF THE BILE. 
 
 § 386. 
 
 For although the cyjlic exhibits, in its general 
 properties, the mcfl finking fimilitude to the he- 
 ■patl: bile (§ 382.), it is notwithstanding concen- 
 trated, as it were, by reft and ftagnation, and 
 thence rendered more tenacious and bitter : this 
 effect appears to be owing, in a particular man- 
 ner, to the lymphatic veifcls of the cyft, which 
 flowly abforb the aqueous parts of the bile, while 
 thus enclofed and retained in a quiefcent (late. 
 
 § 387- 
 
 We proceed now to the confideration of the 
 bile itfelf. This is an animal fluid of the higheft 
 dignity and importance in the living fyftem : its na- 
 ture and ufes have, for twenty pears pad, laid a 
 foundation for more literary controverfies among 
 phyfiologifts, than have exifted refpecling any 
 other fluid that belongs to the body of man. 
 
 What we fhall advance on this fubjeft will re- 
 late immediately to the cyftic bile, as this is to be 
 efteemed the more perfeel of the two, and is there- 
 fore in a ftate more favourable for fuccefsful in- 
 vefligation. 
 
 § 38s. 
 
 Bile, taken from the recent corpfe of an adult 
 fubjedfc, who had not previoufly laboured under 
 
 any 
 
OF TH£ BILE. 41 
 
 any difeafe, is a liquor fomewhat vifcid, of a faint 
 green colour, inclining towards a brown, inodo- 
 rous, and, if compared with the gall of brutes, of 
 a llightly bitterilh tafte. 
 
 § 389- 
 
 Although the condiment parts of this fluid nei- 
 ther feparate from each other fpontaneoufly, nor 
 yet by fo fimple a mode of treatment as is fufficient 
 to produce that effect on the parts that compofe 
 the blood, they may, notwithstanding, be fabje<ft- 
 cd, without much difficulty, to fuch an examina- 
 tion as will make it appear, that they doubtlefs 
 pofTefs and exhibit a certain analogy to the ele- 
 mentary parts of the blood, though this analogy 
 fliould not be purfued to too great an extent. 
 
 The bile contains, in the firft place, an aqueous 
 menflruum, which has been denominated by fome 
 late phyfiologiils, its falroary part : this may be 
 aptly enough compared to the aqueous portion, 
 and refembles alio, though not in every particu- 
 lar, the ferum of the blood. 
 
 From the bile we can alfo feparate and procure 
 a fmall portion of a white and grumous fubftance, 
 which may be faid to pofTefs a certain, though re- 
 mote refemblance to the plaflic lyrftph of the 
 
 blood. 
 
 Finally, 
 
42 OF THE BILE. 
 
 Finally, the mod flriking and important princi- 
 ple which the bile contains is the nutter of phlo- 
 glfton^ derived in large quantities from the blood 
 of the vena portarum, which is highly impreg- 
 nated with this fubtle element. 
 
 § 39°- 
 This active inflammable part evidently manifefts 
 its exiftence in dried bile, but more efpecially in 
 gall ftones, by burfting immediately inco flame, 
 when placed in contact with a burning fubicance. 
 To the action and influence of this principle inuflj 
 we attribute thofe ftriking and lingular qualities, 
 formerly enumerated, fuch as colour, taife, &c. 
 which ferve to diilinguilh the bile from the other 
 inquiline humours belonging to the fyftem ; and 
 from the fame fource muff we a'.fo derive the other 
 remarkable properties of this fluid, which fliall be 
 mentioned hereafter. 
 
 1,39V 
 
 The bile is not of fuch a nature as to polTefs, 
 like foap, an equal affinity to oil and water, and 
 thus ferve to mix and intimately combine thefe 
 two elements together. The contrary opinion 
 (which was crroneoufly entertained on this fubjecl 
 by Boerhaave, and afterwards by Schroder) was 
 formerly invalidated and refuted by certain re- 
 markable experiments of my own (fmce confirmed 
 
 and 
 
OF THE BILE. 43 
 
 and further increafed by other writers), and is 
 now entirely repudiated by the greater number of 
 phyfiologifts. On the other hand, if bile be ap- 
 plied to the two foregoing elements, i. e. oil and 
 water, when in a {late of intimate mixture and 
 combination, it produces an evident difunion and 
 feparation of them from each other. This fluid 
 pofTefTcs indeed no alkaline properties, but is, not- 
 withstanding, equally unfriendly to the exigence 
 of acid acrimony, to fermentation, and to putre* 
 faction, 
 
 § 39 2 - 
 
 By confidcring with due attention the foregoing 
 obfervations, we may eafily afcertain the true, the 
 important, and the diversified ufes of the bile, in 
 the procefs of chylification. 
 
 For in the firil place, from that equable and 
 uniform chymous pulp which the {lomach has dis- 
 charged into the duodenum, which the pancreas 
 has diluted by an eflufion of its own juice, and 
 which moves fpontancouily onward to the cavity 
 of the fmall inteftincs, it gradually precipitates the 
 faeces, and thus feparatcs from them that crearn- 
 jike fluid denominated cbvle. 
 
 The 
 
44 OF THE BILE. 
 
 The bile itfclf differs, at the fame time, a divi- 
 sion into two parts, the one aqueous, the other 
 phlogiftic. The latter part adheres to the faeces, 
 tinges them, and is afterwards difcharged, along 
 with them, out of the body ; whereas the former 
 appears to be mixed with the chyle, and re-con- 
 dufted back to the mafs of blood. 
 
 Thus the abundant phlogift.cn, now become 
 troublefome and noxious to the blood, is firft di- 
 rected to the liver, where it is rendered fubfcrvient 
 to the formation of a fragular and very important 
 humour : After this humour has fully anfwered 
 the end of its deftination, its fuperfluous, or rather 
 noxious part is included among the excrements, 
 and finally eliminated' from the fyftem. 
 
 A further ufe of the bile is, to evolve and ex- 
 terminate from the alimentary canal, the fixed air, 
 which had been hitherto confined among the chy- 
 mous mafs : it appears alfo to act on, and aid, the 
 inteflinal tube, by means of its (limulus, thus ex- 
 citing it to perform its periftaltic motion with 
 greater vigour and energy. 
 
 I filently pretermit a variety of other ufes, com- 
 monly attributed to the bile, which appear to me 
 to reft: on more doubtful 3nd equivocal evidence, 
 
 fuel), 
 
OF THE SPLEEN. 45 
 
 fuch, for inftance, as its power of regurgitating 
 into the ftomach when empty, and thus exciting 
 appetite, a phenomenon that, in my opinion, can 
 very fddom occur in a well formed and healthy 
 human fubject. 
 
 SECT. xxxr. 
 
 OF THE FUNCTION OF THE SPLEEN. 
 § 393' 
 
 1 HE fpleen is very intimately connect- 
 ed with the liver, not only by an intercourfe of 
 veffels, but alfo by the affinity and fubferviency of 
 its function : it is iituated in the left hypochon- 
 driac region, oppofite to the liver ; its figure is 
 oblong, generally, indeed, accommodated to the 
 fituation of the neighbouring vifcera with which it 
 lies in contact : it is fubjedl however, to multiplex 
 varieties with regard to form, number, and other 
 fpecies of lufi nature, or preternatural pheno- 
 mena. 
 
 § 394- 
 Its colour is livid, its texture altogether lingu- 
 lar, being foft, friable, eafily lacerated, and there- 
 fore 
 
4 3 OF THE SPLEEN. 
 
 fore fecurely protected by two membranous cover-* 
 ings, the internal of which belongs properly to 
 the fpleen itfelf, while the external appears to be 
 derived from the omentum. 
 
 § 395- 
 The fituation and fize of the fpleen are now and 
 
 then, no lefs than its figure, fubject to finking 
 
 and lingular variations, arifing in a great meafure 
 
 from the different {fates of the ftomach, with re- 
 
 fpect to fulnefs and depletion : thus, for example, 
 
 when the ftomach is empty, and hangs in a loofe 
 
 and depending pofition, the fpleen is diflended 
 
 with blood ; but when the former vifcus becomes 
 
 turgid again, the latter is emulged, and confe- 
 
 quently diminifhed in bulk by the preffure to 
 
 which it is fubjected. 
 
 The fpleen is alfo agitated by another perpetual, 
 though gentle and uniform motion, in confequence 
 of refpiration, being fubjectcd to the immediate 
 action of a primary inflrument of that function, 
 namely, the diaphragm. 
 
 § 396. 
 The texture of the fpleen, phyfiologtfls former- 
 ly fuppofed to be cellular, and uniformly compared 
 it to the corpora cavernofa of the penis : this opi- 
 nion, however, is evidently founded in error, and 
 
 haa 
 
OF THE SPLEEN. 
 
 41 
 
 has been very fatisfaclorily refuted by a more ac- 
 curate examination of the human fpleen. For, 
 from fuch examination we learn, that almoft the 
 whole volume of this vifcus is compofed of blood 
 veil els, extremely large in proportion to its fize ; 
 fo that it is fupplied with a greater profufion ol 
 blood, than any other part belonging to the body 
 of man. 
 
 § 397- 
 The fplenic artery, confpicuous (agreeably to 
 the experiments of Wintringham) on account of 
 the aftonifhing finenefs and drength of its coats, 
 is divided into an infinitude of minute ramifica- 
 tions, which conftitute finally, by their evanefcent 
 extremities, very fmall pulpy pencils : thefe pencils 
 afford origin, again, to fine filiform veins, that 
 conftitute by their gradual confluence, large and 
 lax trunks highly capable of dilatation. 
 
 < § 39 8 - 
 
 This vaft congeries of blood veffels, is, how- 
 ever, knit together and fupported by a fmall quan- 
 tity of cellular parenchyma, from whence the ab- 
 forbent vtffels arife, the trunks of which run on 
 the plain or flat fide of the fpleen, between the 
 two membranous coverings, of which we have al- 
 ready fpoken. 
 
 § 399- 
 
4$ OF THE SPLEEN. 
 
 § 399- 
 This texture of the fpleen, fo very lax and high- 
 ly capable of admitting blood, correfponds admi- 
 rably with what we formerly faid refpecting the 
 fanguineons difteniion of this vifcus (§ 395) : and 
 we may further obferve, that the phenomena of 
 the congeftion, and tardy progrtffive motion of this 
 crimfon fluid in the fpleen, confidered in conjunc- 
 tion with the nature of the furrounding and conti- 
 guous vifcera, tend not a little to illuftrate the pe- 
 culiar flate and condition of the fplenic blood, 
 which of themfelves appear to ftied confiderable 
 light on the function of this myfterious vifcus, a 
 fubject of fuch repeated controverfies among phy- 
 lioiogifte. 
 
 § 4°°- 
 The blood contained in the veins of the fpleen 
 is very fluid, diflblved, coagulated with the utmofl: 
 difficulty, and admits of but a flight and partial 
 reparation of the ferum from the crafiamentum ; 
 its colour is alfo livid and obfcure, as in the foe- 
 tus ; all which phenomena appear evidently to 
 combine in ascertaining and even demonftrating 
 the prefence of an abundant quantity of the phlo- 
 giflic element. That this element is, however, 
 unequivocally prefent in large quantities, I further 
 afcertained to my entire fatisf action, by the follow- 
 ing fi;np!e and conclufive experiment : to the ac- 
 
 1 tion 
 
OF THE SPLEEN. 4 y 
 
 tion of pure dephlogifticated air, I expofed recent 
 fections and ilices of the fpleen of a human fubject; 
 no fooner were thefe pieces brought in contact 
 with this vital fluid, than they were overfpread 
 with a very florid and beautiful crinifon blufh, 
 while the air itfelf, thus dcipoi'ed of its native 
 fire, was on the other hand, contaminated by the 
 fplenic phlogifton. 
 
 § 4-OI- 
 When we contemplate the foregoing circum- 
 ftances collectively, and conllder in the laft place, 
 that the fpleen is the only vifeus of a fimilar nature 
 wholly unfurnimed with any veflige of an excre- 
 tory duct, fave thofe vtffels which we have alrea- 
 dy laid run to the liver, we are obliged from the 
 force of concurring telUmony to conclude, that 
 the fole office of the organ now under confidera- 
 tion, is to act in fubferviency to the function of the 
 liver, and contribute towards the formation of 
 bile by the co-operation of its phlogiftic parts. 
 
 § 4 02 - 
 This opinion is flill farther fubitantiated by a 
 Very curious and ufefui oMervation, made on fuch 
 individuals of the animal kingdom, as have been 
 deprived of the fpleen by excifion. It appears 
 that in animals fubjected to this operation (v/hich, 
 however Angular and feemingly barbarous, has 
 vol, ii, D been, 
 
$o OF THE OMENTUM. 
 
 been, notwithstanding, very frequently performed 
 from remote periods of time) the cyftic biie has 
 been uniformly afterwards found to be pale, weak- 
 ly impregnated with phlogifton, and difpofed to a 
 grume-like coagulation of its lymphatic portion. 
 
 SECT. XXXII. 
 OF THE FUNCTION OF THE OMENTUM. 
 
 § 4°3- 
 
 JL H E omentum gafkrocolium, or omentum 
 magnum, (fo called to diftinguiih it from the par- 
 *uum or hepaticogaftricwii), is indeed a very lingu- 
 lar produ&ion of the peritoneum, originating im- 
 mediately from the external coat of the llomach. 
 
 § 4 G 4- 
 For notwithftanding the continuations of the 
 peritoneum, in the abdominal cavity, be almofl innu- 
 merable, and although all the parts contained in 
 this cavity, whether viewed collectively or indivi- 
 dually, be fo uniformly invefteg by it, that, on 
 opening the abdomen, it is impbfTible to difcovcr 
 a lingle vifcus which this membrane does not em- 
 brace, yet the modes in which it furnimes this 
 
 covering 
 
OF THE OMENTUM. $f 
 
 covering to the feveral vifcera, are fo diverfnied, 
 as to merit a divilion into different claffes. 
 
 Thus, for example, the abdominal cavity con- 
 tains certain parts, over which the peritoneum is 
 only fpread in fuch a partial and Ample manner, 
 as to invell but one of their furfaces ; this obfer- 
 vation may be applied particularly to the kidneys, 
 the inteflinum rcclum, the veftca urinaria, and in 
 fome meafure alfo, to the pancreas and gall- 
 bladder. 
 
 There are alfo other vifcera, which, notwith- 
 {landing their attachment and adhefion to the fur- 
 rounding parietes of the abdomen, yet projeft alfo 
 to a conliderable diftance into the abdominal ca- 
 vity itfelf, and derive from the peritoneum a co- 
 vering, which inverts, by far, the greater part of 
 their external furfaces : of this defcription are the 
 liver, the fpleen, and even the fromach and female 
 uterus, to which we may add, finally, the teftes 
 of a male foetus, previoufly to their defcent into 
 the ferotum. 
 
 Confiderably different again, (in point of peri- 
 toneal covering), from both the foregoing claffes 
 of vifcera, is the whole of the inteftinal tube, ex- 
 cept that portion which is denominated intejiinum 
 rectum. This tube paffes through the adommal 
 D z cavity 
 
§i O'F THE OMENTUM. 
 
 cavity in fuch a manner, as to carry along with it, 
 two remarkably broad proceffes of the peritoneum, 
 namely the mefentery and mefocolon, to which it 
 adheres in a ftate of fufpenfion : under the fame 
 clafs with the two preceding proceffes, may we 
 alfo arrange thofe fmgular peritoneal productions, 
 denominated the broad ligaments of the uterus. 
 
 But fmally, the moft extenfive of all is that pe- 
 culiar continuation of the peritoneum called the 
 omentum. This production is a large empty fac 
 of a very delicate texture, that hangs in a depend- 
 ing pofition from the great curvature of the flo- 
 mach ; it is fpread over the region of the fmall in^ 
 tejiines in particular, nicely adapts itfelf to their 
 irregular convexities, and dips down, in fome 
 meafure, into their numerous interfaces. 
 
 § 4° 6 - 
 Befides the blood veffels by which the omen- 
 tum is painted, it is alfo marked by numerous 
 ,fir'uz or broad lines of adipofe fubflance, which 
 meet, interfecl:, and thus form a variety of reticu- 
 lar intertextures, from whence the membrane has 
 received the name vernaculwn. In perfons dif- 
 pofed to obefity this adipofe fubflance encreafes 
 now and then to fuch a fize, as to become not only 
 troublefome but even dangerous : it is alfo this 
 
 adipofe 
 
OF THE OMENTUM. 
 
 53 
 
 adipofe portion that affords origin to that oily 
 haliius by which the omentum is conftanrfy fur- 
 rounded and moiftened. 
 
 § 4°7- 
 It has been the opinion of certain celebrated 
 
 characters, and a further attempt was made by 
 the illuftrious Haller to prove, that the fat con- 
 tained in the omentum is deftined to be taken up 
 by abforption and conveyed to the liver, for the 
 purpcfe of fupplying the bile with its oily portion, 
 8zc. With refpefi to the truth of this opinion, 
 however, I mud fti'l be permitted to entertain and 
 exprefs a ferious doubt, having never yet been 
 convinced that found, uncontaminated, bile con- 
 tains any oil ; nor have I ever been able to difco- 
 ver any orifices fubfervient to fuch an abforption, 
 not even in frogs themfelves, where Malpighi al- 
 leged, and even attempted to prove, their exif- 
 tence ; much lefs in that part which is the fubject 
 of our prefect confideration, namely, the omentum 
 of man. 
 
 § 408. 
 What appear?, from the nature and fituation of 
 the part, as well as from the concurring belief of 
 all phyfiologifts of the prefent day, to be a much 
 more unequivocal ufc of the omentum, is, to lu- 
 bricate the inteflines, and by that means aid and 
 D 3 facili- 
 
54 OF THE OMENTUM. 
 
 facilitate their perpetual motion. The fame ap- 
 pear alfo to be the ufe and deftjnaticn of certain 
 fimilar, but fmall, adipofe bur/a, by which tne 
 colon and reclwn are inverted. 
 
 The omentum alfo further ferves to prevent the 
 occurrence of an adhefion between the inteftines 
 and peritoneum, by which the whole oitice of the 
 primse viae would be fubverted. 
 
 § 4°9- 
 That this adipofe curiam is dfftined to fcrve as 
 a defence againft cold, (though an opinion very 
 generally received), appears, notwithstanding, to 
 reft on evidence of a more qqeftionable nature : 
 the omentum of a man in perfect health, which 
 ought by no means to be burrhened with an accu- 
 mulation of fat, is indeed, but very illy calculated 
 to anfwer fuch an intention. 
 
 When we confider, in the mean time, the An- 
 gular ft rucTure of the two omenta, more efpecially 
 of that denominated omentum parvum or gaftrohc- 
 paticum, it appears fufEciently probable, that be- 
 fides the ufes already enumerated, the latter is ftill 
 deftined for another, of, perhaps, even fupremc 
 importance, which is as yet unknown to us, and 
 which future refearches in comparative anatomy 
 •■•■ ;:1 be alone able to develope. 
 
 SECT, 
 
OF THE INTESTINES. 55 
 
 SECT. XXXIII. 
 OF THE FUNCTIONS OF THE INTESTINES. 
 
 § 4 10 - 
 
 JL HE inteftinal tube itfelf (before which 
 the omentum is fpread, and into which we have 
 already feen the chyme conveyed, in order to be 
 further elaborated and fufficiently fitted for the 
 feparation of chyle), is divided into two leading 
 portions, namely, the fmall and great ; of the 
 functions of which we will now treat feparately 
 and in order. 
 
 § 411- 
 The fmall portion of inteftines is again fubdi- 
 vided into three parts, namely, the duodenum, je- 
 junum, and ileum. 
 
 The duodenum derives its name from the cir- 
 cumilance of its lencrth. 
 
 O 
 
 The jejunum from that of its general habit, be- 
 caufe, in a recent cprpfe, it appears collapfed and 
 empty as it were, even although it contain at the 
 fame time a quantity of pulpy chyme. In the 
 third divifion, called ileum, the chyme depofits its 
 faeces, and fuffers an evolution of its air, which 
 D 4 had 
 
56 OF THE INTESTINES. 
 
 had been hitherto fixed, fo that this laft of the 
 fmall inteflines, being at the fame time the longeft, 
 and deriving its name from its circumvolutions, 
 appears more turgid, fomewhat inflated, and mark- 
 ed here and there with fmall bubble-like emi- 
 nences, af:er the manner of the large portion of 
 tms tube. 
 
 § 412. 
 
 The coats of the fmall inteflines are perfectly 
 fimilar to thofe compofing the flcmach, of which 
 we have already fpoken (§ 359.) 
 
 The external is a production of the mefentcry. 
 
 The mufcular coat confifts of two orders of 
 ■fibres, to wit, longitudinal, which are interrupted 
 in their courfe, and run rather externally, efpeci* 
 ally on that fide of the intefline that looks in a 
 contrary direction from the mefemery ; and more 
 internal, annular, or falciform fibres, which are 
 calculated to contra& or narrow the diameter of 
 the tube ; whereas the former are intended to di- 
 ininifh its longitudinal extent. On both the pre- 
 ceding orders of fibres depends that exquifitely 
 energetic and pertinacious irritability of the intes- 
 tines, of which we have fpoken on a former occa- 
 sion (§ 3 o6 
 
 The 
 
OF THE INTESTINES. 57 
 
 The nervous coat confifts of compared cellular 
 membrane ; and may, by a very fimple mode of 
 treatment, efpecially by blowing into it, be again 
 reduced to a fpongy, foam-like untie : throughout 
 this coat a variety of blood-veffels, detached from 
 the mefenteric, are diflributed in the form of ar- 
 borets or branching fhrubs, of inimitable elegance 
 and beauty. As in the (lomach, fo likewife in the 
 interlines, the nervous coat is the principal feat of 
 tenacity and flrength. 
 
 Finally, the internal coat (which merits more 
 unequivocally, in the fmali inteflines, than in any 
 other part of the alimentary canal, the name vil- 
 lous J, is continued here and there, in conjunction 
 with the internal furface cf the preceding mem- 
 brane, into wave-like productions and rugous 
 folds, that in the inteflines, when inflated and 
 dried, exhibit a falciform appearance, and are de- 
 nominated valvules Kerkringii. 
 
 § 4*3- 
 Of the villi themfeives, an immenfe number 
 overfpread, in the clofeft order, the whole inter- 
 nal farface of the fmaH inteflines : their fubtle and 
 exquifitely elegant vafcular flructure, was firft dif- 
 covered and demonflrated by the labours of the 
 indefatigable Lcibcrkuhn. While the inteftines 
 are deftimte of chyle, the vilU may be compared 
 
 in 
 
5 8 OF THE INTESTINES. 
 
 in fome meafure to fmall purfes hanging in a loofe 
 and flaccid pofition, and confifting internally of a 
 foft fpongy texture ; but when they become tur- 
 gid, in confequence of the abforption of this 
 milky fluid from the inteflinal canal, their figure 
 undergoes fuch a flriking change, as to bear no 
 frnall refemblance to the phallus efculentus *. 
 
 § 414- 
 Thofe villi are furrounded, at their bafes, by 
 
 an infinitude of fmall glandular follicles^ which are 
 lodged principally in the nervous coat, and com- 
 municate by very minute orifices with the intefli- 
 nal cavity, into which they difcharge a mucus that 
 ferves to line and lubricate the whole internal fur- 
 face of that tube. 
 
 Thefe minute glands are commonly fuppofed to 
 confiil of three orders. Firji, the Brunnerian or 
 larger glands, which are feparate from each other, 
 and fituatcd principally on that part of the duode- 
 num, which lies next to the pylorus. 
 
 Secondly the Peyerian, which are confiderably 
 fmaller, planted in clufters, a>nd lodged, in parti- 
 cular, on the other extremity of the fmall intef- 
 
 * A fpecies of 'fungus, denominated phallus, from its ftrik- 
 
 tines, 
 
 ing fimilitude to the male penis. 
 
OF THE INTESTINES. 59 
 
 tines, which looks towards, and is contiguous to, 
 the valve of the colon. 
 
 And, Iq/l/y, the glands of Leiberkuhn, the mod 
 minute of all, of which about eight are faid to be- 
 long to each villus. 
 
 It ought to be obferved, however, that this di- 
 vifion of the fources of mucus appears to reft on 
 very equivocal evidence. For if I be not greatly 
 deceived, both the Brunnerian and Peyerian 
 glands, as commonly exhibited in plates, are the 
 refult of a vitiated and difeafed (late of the intefti- 
 nal tube. I am induced to entertain this opinion 
 from having never been able to difcover, in the 
 found fmaJl inteftines of fubje&s carefully exami- 
 ned in different periods of life, the fmallefl veflige 
 of fuch fungous papilla?, perforated with orifices ; 
 whereas, on the other hand, I have frequently 
 feen, in cafes of aphtha, almofl the whole intefti- 
 nal canal planted with countlefs numbers of them, 
 partly (landing alone, and partly arranged in 
 crouded duffers. From confiderin^ the forerointr 
 circumftances, I feel a confidence in concluding, 
 that none can be accounted true muciferous 
 glands, except thofe extremely minute miliary bo- 
 dies, which, on gently feparating the •villous lining, 
 may be readily detected on its averted fur/arc, but 
 
 cannot, 
 
<?o OF THE INTESTINES. 
 
 cannot, without great difficulty, be diilinguifhed 
 on the fide next to the eye. 
 
 § 4*5- 
 It has been incontrovertibly eftablifhed, not 
 
 only from that well known experiment fir ft infli- 
 tuted (if I miitake not) by Pechlin, but alfo from 
 feveral others, that as the ftorr.acb, fo in like 
 manner the cavity of the fmall inteflines, is fup- 
 plied with a conftant influx of a liquid, denomi- 
 nated, from the place into which it is cifchargcd, 
 inte/iinal juice. It appears probable that this fluid 
 is fimilar in its nature to the gauric liqucr, al- 
 though a more accurate inveftigation of it is, cer- 
 tainly as yet, a defideratum in phyficlogy : nei- 
 ther can I venture to fay any thing decifive re- 
 fpecling the quantity of this liquid fecreted : I am, 
 however, fully of opinion, that Haller has been 
 too profufe in his ellimate, where he alleges, 
 that this fecretion amounts to eight pounds in the 
 fpace of twenty-four hours. 
 
 § 416. 
 Further, it is alfo common to the inteflines with 
 the ftomach, to be agitated by a fimi/ar, but far 
 more lively and vigorous fcrijlaltic motion^ which, 
 In particular, while the chymous pulp is advancing, 
 cfcwsrdp throws the fame into gentle commotion, 
 
 by 
 
OF THE INTESTINES. 6\ 
 
 by a wavy and progrdftve ccnftriction, and thus 
 propels it forward ficm the duodenum towards 
 the great inredincs. For although we cannot ab- 
 folutely deny the phenomenon of an anti-periftal- 
 tic commotion, in confequence of which the intef- 
 tines are fubje&ed to a retrograde action, it mud', 
 notwithftanding, be acknowledged, that this, in a 
 healthy fubjecl:, is much feebler than the former, 
 that it occurs more rarely, and pofTefks a more 
 precarious and (liort-lived exigence. 
 
 § 4*7- 
 
 In confequence of the co-operation of thofc 
 energetic caufes, hitherto enumerated (viz. both 
 the principles of ?uotim, of which we have jiiil 
 fpoken, and likewife the folvent and alterative 
 powers of the inquiline humours that are every 
 where blended in abundance with the chyme), the 
 following remarkable changes are produced in this 
 heterogeneous mafs : — in the jejunum it exhibits 
 the appearance of a more liquid pulp, poiTeiling a 
 colour fomewhat grey, and an odour flightly acid : 
 alter its entrance into the ileum it begins to fepa- 
 rate into two portions ; thefe are, /Srft, the faces, 
 marked by a pale yellow colour, inclining more 
 or left towards a brown, and poffeffing a fetid 
 odour; and, fecondlj^ a white milk-like fluid, de- 
 nominated true chile, whkh floats on the furface 
 of the J , and is I .' from them by the 
 
62 OF THE INTESTINES. 
 
 a&ioti of the hepatic liquor or bile. This chy- 
 mous emulfion, designated by the name of chyle, 
 is defined to be received by abforption into the 
 lacleal veffcls, through which mazy tubes we will 
 accompany it farther in the following feclion ; and 
 iliall, in the mean time, clofe the prefent, by tra- 
 cing, in as brief and intelligible a manner as pof- 
 fible, the route purfued by the refiduary faxes. 
 
 § 41S. 
 
 Thefe, therefore, after having become more and 
 more infpiffated, in confequence of a tedious courfe 
 through the ileum, are obliged at length to pafs 
 the vaive of the colon, and thus enter the tratt of 
 the great intejlines ; for which purpofe the neigh- 
 bouring extremity of the ileum is furr.ifh.ed, and 
 lubricated internally, by a more copious quantity 
 ef mucus, deflined to deitroy the friction of the 
 fasces, and confequently facilitate their tranfition 
 through the foregoing valve. 
 
 § 4I9- 
 The valve of the colon (denominated very juftly 
 
 in honour of its real and illuftrious difcoverer, 
 
 valvula FallopiiJ, is a mort continuation or procefs 
 
 of the ileum projecting into the cavity of the great 
 
 intejlinal portion, by uhich it is furrounded and 
 
 ciofely embraced : the more exterior labia of this 
 
 procefs are fo condituted, by means of a more 
 
 prominent 
 
OF THE INTESTINES. 63 
 
 prominent or extenfive ruga of the great Intejliiie^ 
 as to confifl: not only of its internal and nervous 
 coats (as is the cafe with the greater number of 
 fuch plicae), but to contain alfo in its compofition 
 feme fibres from the mufcular coat. Hence the 
 function of this valve appears to be twofold, to 
 prevent the premature paflage of the fceces from 
 the f. nail into the great interlines., and alfo to ob- 
 ftruct their regurgitation from the latter into the 
 former. 
 
 § 42o. 
 The great inteftinnl portion, which in like mari- 
 ner with the fmall, is alfo divided into three fec- 
 tions, begins from the ceecum (to which is append- 
 ed the 'vermiform proeefs, a part indeed of equivo- 
 cal ufe in the economy of an adult iubject), and 
 conftitutes collectively a canal fo capacious, as to 
 admit the infpiifated fasces to be gradually collected 
 and retained in its cavity, till a convenient oppor- 
 tunity for their evacuation. 
 
 § 421. 
 As the great is fuperior to the fmall portion of 
 the interlines in diameter, fo it lifoewife exceeds it 
 in the thicknefs and ftrength of its coats. The 
 mufcular coat, in particular, poffeflfes this peculia- 
 rity, that its longitudinal fibres (if we except 
 lower part of the rectum) are collected into tl 
 
 faiuculi 
 
($ OF THE INTESTINES. 
 
 fafciculi or bundles, called ligamenta coll ; aud the 
 colon itfelf is thus divided into diftinct fcgments of 
 a velicular or cyftiform appearance. The internal 
 coat in the great, is not of fuch a beautiful and 
 elegantly" floccofe appearance as in the fmall in- 
 teflincs 4 but poffeiTes a nearer refemblance to that 
 which inverts the cavity of the ftomach. 
 
 § 4 22 - 
 The periflaltic motion appears to be lefs vivid 
 and active in the great, than in the fmall inteflines. 
 On the other hand, the abdominal pre (fare is con- 
 fiderably greater on the former than on the latter, 
 in as much as the whole colon is fubjecled to its 
 immediate action and influence. 
 
 § 4 2 3- 
 The infpiflated and hardened feces contained in 
 the large inteflines, are protruded {lowly onward, 
 till having at length reached the rectum, they ex- 
 cite, by their ftimulus on the internal furface of 
 that tube, a propennty to an evacuation. For the 
 purpofe of facilitating this evacuation, ample and 
 wife provifion is made, partly by a defect or inter- 
 ruption iu the tranfverfe rugae, but more efpeci- 
 ally by a. profufe quantity of mucus, that lubri- 
 cates the internal furface of the rectum near to its 
 extremity* 
 
 a The 
 
OF THE ABSORBENT SYSTEM. 65- 
 
 The evacuation of the fasces is, however, prin- 
 cipally accomplished by a downward dire£tion of 
 the abdominal preffure, overcoming the refiftance 
 of the coccyx and both the fphincters, the interior 
 of which is a very fingular fafcifculus or bundle 
 of annular fibres, but the exterior, a genuine cuta- 
 neous mufcle : thefe ends being quite completed, 
 there fucceeds an entire remiffion of the abdominal 
 effort, the inteftine is retracted by the levator ani 
 in particular, and finally clofed a^ain by the con- 
 traction of the fphindters. 
 
 SECT. XXXIV. 
 OF THE FUNCTIONS OF THE ABSORBENT SYSTEM. 
 
 § 4H- 
 
 . -T ROM obfervations delivered in a for- 
 mer fe&ion it is fufficiently evident, that the chyle, 
 which we left in the inte/iinum ileum, completely 
 difen^aged from its fasces, is a compound of feve- 
 ral different humours. Although it be almoft li- 
 terally impoflible to calculate, with accuracy and 
 definitude, the precife quantity of inquiline hu- 
 mours, fuch as faliva, gaflric juice, pancreatic juice, 
 inteflinal juice, bile, &c. that is mixed and blended 
 vol. ii. E with 
 
66 OF THE ABSORBENT SYSTEM. 
 
 with the chyme, it appears, notwithstanding, a 
 mutter of the higheft credibility, that thefe feveral 
 humours, taken collectively, very far exceed, in 
 quantity, the other conftituent part of the cfy'le, 
 which is derived immediately from alimentary fub- 
 ftances, recently taken as nutriment. Hence we 
 may derive a folution of that problem in phyfio- 
 logy, by what means alimentary matters, though 
 of the mofl different and even oppofite kinds, may, 
 notwithflanding, be converted into the fame aflimi- 
 lized, homogeneous, and milk-like chyle, equally 
 adapted to the nature, and calculated to ferve as 
 the nutriment, of animals ? 
 
 § 4-5- 
 
 The channels through which the chyle rnufl 
 flow, in its paffage from the inteflines jto the mafs 
 of blood, (the refervoir deftined for its ultimate re- 
 ception), conflitute a part of the abforbent fyjlem, 
 which we have hitherto mentioned only occafion- 
 ally, and in a very curfory manner, but will now 
 affume as the profeiTed object of our prefent at- 
 tention. This fyflem is divided generally into 
 four parts, viz. lacteal veins ; lymphatic veins ; 
 conglobate glands ; and finally, the thoracic duel;, 
 each of which fhall conftkute a fubject of exclu- 
 five confideration. 
 
 -§426. 
 
OF THE ABSORBENT SYSTEM. 67 
 
 With refpect to the nafcent origin of the lac- 
 teals from the inteftines, there exilts fcarccly a 
 doubt, but that this is conftituted by the innume- 
 rable villi of the internal inteftinal coat, of which 
 we have already fpoken. It is, however, dill a 
 matter of controverfy, whether the lacleals origi- 
 nate immediately from thofe villi themfelve?, or 
 only preferve a more diftant intcrcourfe and com- 
 munication with them, by means of interjacent 
 cellular fubftance. As far as my information has 
 extended, no one has hitherto been able, more 
 than myfelf, to trace the evanefcent radicles of the 
 lacteal veifels to the villi themfelves, with fuch 
 clearnefs and definitude, as to difcover an imme- 
 diate and unequivocal connexion between the 
 parts ; on the other hand, the lacleals appear here 
 and there, throughout the coats of the inuftines, 
 to form trunks of coniiderable fize, immediately 
 after their orgin, and, (if a conjecture be allow- 
 able), to abforb from the cellular fubftance of the 
 adjacent parts, that chyle which had been origi- 
 nally taken up from the cavity of the inreflines by 
 means of the villi themfelves. This phenomenon 
 I think I have frequently obferved, in young pup- 
 pies, into which I had poured, according to the 
 celebrated experiment of Lifter, a foluti m of In- 
 dian blue, one or two hours before fubje&ing 
 them to the operation of livs-difleftion. 
 
 E 2 § 427* 
 
58 OF THE ABSORBENT SYSTEM. 
 
 § 4 2 7- 
 Thofe trunks, of which we have juft fpoken, 
 frequently run the diflance of feveral inches, and 
 fometimes even wind about in angling or mean- 
 der-like directions, immediately under the external 
 coat of the inteftine, previoufly to their entrance 
 into the mefentery. 
 
 § 4^8- 
 During their paffage through the mefentery, 
 thefe trunks make frequent entrances into fmall 
 vis/enteric g/ands, which may be divided into two 
 different feries or orders. Thofe of the firfl order 
 are fituated in the vicinity of the inteftinal tube, 
 and referable, in their appearance, fmall beans ly- 
 ing feparate from each other. The glands of the 
 other order, lie nearer to the receptacle of the 
 chyle, are fuperior in magnitude, and planted in 
 collective clutters. 
 
 § 4 2 9- 
 Both the foregoing kinds of glands appear to 
 be in reality nothing elfe, than round compacted 
 convolutions of the lacteal veffels themfelves, co- 
 vered and interfperfed with an infinitude of minute 
 blood-veffels : their deflination appears to be, to 
 retard the progreffive motion of the chyle, in or- 
 der, perhaps, that, by fuch delay, it may be more 
 fully and perfectly animalifed and matured, previ- 
 oufly 
 
OF THE ABSORBENT SYSTEM. 6 9 
 
 oufly to its entrance into the thoracic duct, and 
 fubfequent admixture with the circulating volume 
 of the blood. 
 
 § 43°- 
 It has been propofed as a phyfiological queflion, 
 whether or not the large, poffefs alfo Ia&eal veins, 
 in common with the fmall intcftines ? The affirma- 
 tive of this has been zealcufly advocated, and its 
 defence attempted by arguments drawn from the 
 influence and efficacy of fpecific enemas, of ene- 
 mas compofed of nutrimental fubftances, of ine- 
 briating fubftances, &c. and alfo from the follow- 
 ing well known circumftance, viz. that the longer 
 infpiiTated fasces are retained in the large portion 
 of the alimentary canal, the more indurated and 
 infucculent they are uniformly found. But al- 
 though thefe arguments do not fatisfaclorily de- 
 monftrate that any genuine chyle is abforbed from 
 the faeces after their tranlition over the valve of 
 Fallopius, they furnim, notwithftanding, additional 
 evidence in confirmation of that, which has indeed 
 been long fince eftabliihed on the teftimony of 
 the fenfe of vifion itfelf, namely, that the great in- 
 terlines abound with a fufficiently plentiful appa- 
 ratus of lymphatic veins, perfectly fimilar to the 
 lacttals both in their ftructure and functions : in 
 teftimony of this entire ilmilarity, it may be proper 
 to obferve, that when the inteftines are deftitute 
 E 3 of 
 
7© OF THE ABSORBENT SYSTEM. 
 
 of chyle, the lacVals of the mefentery are then 
 eng iged in the afeforption of lymph. 
 
 § 43 1 - 
 Another qucftion, more important and difficult 
 
 of folution than the former, is, whether or not 
 
 the whole of the chyle, abforbed from the cavity 
 
 of the fmall inieftines, be conveyed to the blood 
 
 through the fame public, and royal route, as it is 
 
 termed, or whether there do not ex id certain fe- 
 
 cret channels, through which it may glide furrep- 
 
 titioufly onward, to mingle its flreamlets with the 
 
 general current of circulating blood ? 
 
 It mull indeed, be confeffed, that mod: of the 
 arguments, by which phyfiologifts have endea- 
 voured to prove a private abforption and convey- 
 ance of chyle through the fanguiferous veins, do 
 not appear to reft on a very folid foundation : 
 thus the affenion of Ruyfch, that on the approach 
 of old age the mefenteric glands become fo indu- 
 rated and conRricted, as to be rendered unfit for 
 performing their functions, has been long fmce re- 
 futed, and it has, on the other hand, been fatif- 
 faclorily demonftrated that, different affections of 
 thefe glands, fuch as fwellings, &c. very errone- 
 ously pafs under the common name of ob/lruclions, 
 while, at the fame time, their veffels remain in a 
 ftate fufneiently pervious to afford a very eafy en- 
 trance 
 
OF THE ABSORBENT SYSTEM. 71 
 
 trance and tranfition to injections of quick filver. 
 That well known phenomenon, from which it is 
 afcertained, that tepid water, thrown into the inert 
 mefenteric veins of a dead fubject, tranfudes into 
 rhe cavity of the imeftines, appears to contribute 
 but very little towards the fatisfactory elucidation 
 of any function of the human body while in a 
 living ftate ; much lefs can we repofe confidence 
 in the evidence derived from that bicrural and two 
 branched tube of copper, which was invented by 
 Lieberkuhn, for the purpofe of confirming the 
 fame opinion. As to the aflertion, that chyle has 
 been unequivocally detected in the red veins of 
 the mefentery, it appears to me to (land in need 
 of farther evidence for its unquestionable confir- 
 mation ; on the whole, I have never yet been 
 convinced, that thofe veins convey any thing elfe 
 than blood very highly charged with phlogifton, 
 -deftined for the fecretion of bile. 
 
 S 432. 
 "Finally, the ultimate trunks of the lacteal veins, 
 (with certain other tubes very fimilar in appear- 
 ance and function, which are formed by the con- 
 fluence of a great number of minute lymphatic vef- 
 fels), unite and conftimte by their junction, the 
 receptacle or cijiern of the chyle, which is a name 
 given by phyfiolc-gifls to the inferior and larger 
 E 4 portion 
 
72 OF THE ABSORBENT SYSTEM. 
 
 portion of the thoracic duel, called alfo the duel of 
 Pecquet. 
 
 § 433- 
 This duct is a membranous canal, of a delicate 
 appearance and texture, yet fufficiently robuft and 
 ftrong, more or lefs circuitous in its courfe, and 
 not unfrequently fubject to very flriking diverfities 
 W'i h regard to the direction in which it runs, and 
 the divifions it occafionallv undergoes : it is equal- 
 ly deflitute of mufcular fir-res and nerves, is fur- 
 nifhed here and therewith fmall valves, and, after 
 having paffed over the left fubci 'avian vein, is again 
 reflected towards, and finally inferted into, the 
 fame, and, at the very point of infertion, has its 
 entrance guarded by a valve of a peculiar ftruc- 
 ture. 
 
 § 434- 
 The powers which produce and continue the 
 onward motion of the chyle, both in the lacteal 
 veins, and through the thoracic duel, are to be 
 attributed, indeed, principally to the contractility 
 of thefe veifels themfelves, but, in part alfo, to 
 the valves with which they are furniftied, to a 
 propulfive vis a tergo, and to the uninterrupted 
 pulfation of neighbouring arteries, 
 
 § 435- 
 
OF THE ABSORBENT SYSTEM. 73 
 
 § 435- 
 
 It appears probable, that the principal deitina- 
 tion of the valve, which is fixed, as has been al- 
 ready obferved, in the entrance of the chyliferous 
 duel: into the fubclavian vein, is not fo much to 
 obflruct. the lateral paffage of blood into this duct, 
 as to regulate the neceffary difcharge of chyle in- 
 to the vein, and prevent its admiflion in any other 
 manner than by a flow and gradual flillicidium. 
 
 By this means, adequate provifion is made 
 againft the fimultaneous entrance of too large a 
 quantity of recent chyle, into the mafs of blood. 
 Such an exceflive influx of this crude fluid would 
 necefiarily ftimulate the parietes of the heart to ex- 
 ertions too violent and laborious, and would be 
 blended and aflimilated by the fame, with the ut- 
 moft difficulty, and in an imperfect manner ; that 
 this would be the refulr, we judge from the nature 
 of recent chyle, which is a compound of hetero- 
 geneous elements, derived net only from the pri- 
 ma via, by means of the lacleal, but alfo from 
 all the other parts of the body, through the ave- 
 nues of the lymphatic vejfels. 
 
 § 436. 
 The lymphatic veins the.nfelves, which confti- 
 tute a third part of the abforbent fyftem, and bear 
 
 a very 
 
74 OF THE ABSORBENT SYSTEM. 
 
 a very clofe refemblancc to the la&eals, both in 
 flruelure and in function, are fo considerable, in 
 point of extenfion, as to pervade, perhaps, every 
 part of the human body ; but originate, in parti- 
 cular, from the common external integuments, 
 from the pleura, the peritoneum, and vifcera, 
 contained in the thorax and abdomen. 
 
 S 437- 
 The manner in which they arife, is fimilar to 
 
 the origin of the la&eals from the inteitines, of 
 which we have already fpoken. Thus each radi- 
 cle of each lymphatic veflel, is deftined to abforb 
 from a neighbouring portion of cellular membrane, 
 (as from a territory of its own), the moifture it 
 contains, and propel it onward to the general cif- 
 tern of the chyle. 
 
 § 43S. 
 Thefe lymphatic vejfels are furnifhed in their 
 courfe, fomctimes more frequently, fometimes 
 more rarely, with valves fituated in biga or pairs. 
 By far the greater part of them enter conglobate 
 glands - y thofe in the vicinity of each other fre- 
 quently anaftomofe ; and fuch of them as over- 
 fpread the furface of certain vifcera, as that of the 
 lungs, the liver, &c. form exquiiitely elegant reti- 
 cular expanfions. 
 
 § 439- 
 
OF THE ABSORBENT SYSTEM. 75 
 
 § 439- 
 To pafs filently over certain other aids, fuffici- 
 ently evident from former obfervations, the func- 
 tion of the lymphatics is greatly promoted by their 
 remarkable contractility, and the Jlrength of their 
 delicate coats, which is fufficient, in proceffes for 
 anatomical preparations, to refill: the prefiure from 
 a ponderous column of quick filver : this function 
 is a!fo further aided, efpecially in the joints, by 
 mufcular motion, in confequence of which, the 
 lymphatics being compreffed and clofely embraced 
 on all fides, have their tone remarkably aug- 
 mented. 
 
 § 44°- 
 With refpect to the terminations of the lym- 
 phatics, various controverfies have lately exifled 
 among phyfiological writers. Thus, while fome 
 contend, that all thofe veflels unite in the thoracic 
 duel:, (in like manner as the fanguiferous veins 
 unite in the venae cavas), others, on the contrary, 
 exempt from this general confluence, at lead the 
 lymphatics of the right arm, and right fide of the 
 neck, which they allege are not inferted into the 
 fame duct, but into the right fubclavian vein : 
 others again affert that in the conglobate glands, 
 the lymphatics communicate immediately with fan- 
 guiferous veins ; and laftly, others maintain (not 
 indeed without an appearance of probability) that 
 
 certain 
 
76 OF THE ABSORBENT SYSTEM. 
 
 certain lymphatic vcffcls *, actually cxift, which 
 form a direct and free communication between the 
 inteilinal tube and uropoietic organs. 
 
 5 44 1 - 
 Seeing therefore, the lymphatic vefTds are 
 extended far and wide throughout almoft the 
 whole fyftem, and, cfpecially, in us much as an 
 immenfe profundi of them originate on the cuta- 
 neous furface of the body, and may confequently 
 abforb fuch fluids as arc applied from without, it 
 is fufficiently evident, that the lymph, when re- 
 cently abforbed, muff, be, indeed, a liquid eompo- 
 fitipn extremely heterogeneous and diverfified as 
 
 * For a great number of truly important cbfervations 
 and highly interefling {peculations on this fubjecT, the reader 
 is referred to a fhori treatife, written by Charles Darwin, 
 " On the retrograde motion of the lymphatics," and pub- 
 lifhed at Litchfield in the year 1780, a confiderable period 
 of time after the premature death of its ingenious author. 
 This young philofopher and phyiician appears to have been 
 peculiarly formed by nature, and happily fmiflied by edu- 
 cation, to fhed unequivocal light on fubjefts of a dark and 
 difficult nature in the fcience of medicine. He experimented 
 with accuracy and dsfinitude, he obferved with the utmoft 
 attention, and he fpeculated with the higheft ingenuity and 
 force. Unhappily for the healing art, and (perhaps I may 
 add) for fcler.ee in all its aarious branches, this amiable 
 young philofopher was haftily fummoned away, ere yet his 
 mind was perfectly expanded, or his plenitude of merit 
 announced to the wo; Id. 
 
 to 
 
OF THE ABSORBENT SYSTEM. 77 
 
 to its nature and elementary parts : this diverfity 
 is fully afcenained and eftabltfhed, by a more 
 careful and accurate examination of dead fubjecls, 
 where, for inftance, the liquid contained in the 
 abforbents of the liver and fpleen, appears to be 
 evidently different from that difcovered in thofe 
 which run to the uterus. 
 
 § 44 2 - 
 Of the conglobate glands, (which conftitute the 
 laft branch of the lymphatic fyftem), the prin- 
 cipal ufe and defoliation appear to be, to aflimi- 
 late to the animal nature this fubtle and hetero- 
 geneous fluid, efpecially that portion of it which 
 is abforbed by the lymphatics of the fkin : this 
 afTimilation they accomplifh by retarding and in 
 fome meafure'obftrucrjng the motion of the lymph, 
 and perhaps alfo by the addition of a new fluid, 
 derived from the minute arteries, with which they 
 very plentifully abound. Hence a wife and ade- 
 quate provifion is made, to prevent the humours, 
 while in too crude a ftate, from effecting a prema- 
 ture mixture with the blood, and thus the heart 
 is guarded in perfect fecurity from their noxious 
 imprefiions. 
 
 5 443- 
 With refpect to thofe other glands of the fame 
 nature, which are niinutelv difprqad throughout 
 
 by 
 
78 OF SANGUIFICATION. 
 
 by far the greater part of the fyftem, and planted 
 here and there in collected clutters, as in the 
 groin, beneath the axilla, &x. they bear, in every 
 refpecl, the mod perfect refemblance to the me- 
 fenteric glands, of which we have already fpoken ; 
 like them they are compofed, in a great meafure, 
 of the mazy convolutions of abforbent veins ; like 
 them they are furnifhed with a vaft profufion of 
 minute blood veffels ; and finally, they are fubject 
 to be readily invaded by the fame difeafes that 
 attack the glands of the mefentery. 
 
 SECT. XXXV. 
 OF SANGUIFICATION. 
 
 § 444- 
 
 -T is fcarcely neceffary to obferve, that 
 by the term fanguification, we mean the affimila- 
 tion of chyle to blood, and the conftant and uni- 
 form restitution made by means of the former, for 
 the equally conftant and uniform lofs which is fuf- 
 tained by the latter. 
 
 § 445*- 
 For on this principle depends that divifion of all 
 the humours of our body, into the three clafles 
 
 (§4- 
 
OF SANGUIFICATION. 19 
 
 (§ 4' 5') °^ crude, fanguineous, and fecreted ; viz. 
 that the middle clafs embrace the whole circula- 
 ting volume of blood, from which the different fe- 
 creted humours are derived in conflant ftreamlets, 
 and to which the countlefs channels of the abfor- 
 bent fyftem convey their chyle, and the infinitude 
 of lymphatic tubes return their abforbed fluids in 
 currents equally conftanr and uniform. 
 
 § 446. 
 Seeing the blood is an animal humour of fo very 
 fingular and exclufive a kind, as to be wholly dif- 
 fimilar to every other fluid yet difcovered in any 
 department of nature, it is a proportion fufficiently 
 felf-evident, that there mud be a variety of afUfl:- 
 ant powers which contribute, by their joint co- 
 operation, to incorporate and affimilize with the 
 blood, the heterogeneous and adventitious hu- 
 mours, which it is conftantly deriving from the 
 thoracic duel:. 
 
 § 447- 
 The procefs of fanguification we may confider, 
 then, as firlt commencing under the action and 
 influence of thofe mazy circumvolutions (frequent- 
 ly fpoken of already), which both the lacteal and 
 lymphatic veins exhibit occafionally in their courfes 
 (more efpecially in the mefenteric and other con- 
 globate 
 
80 OF SANGUIFICATION*. 
 
 globate glands), and which are, at the fame time, 
 furn idled with coufijerable quantities of what may 
 be called animal and inquiline contagion, 
 
 § 44 8 - 
 It is neceffary further to confider, that a great 
 part of the lymph, which enters the fubclavian 
 vein (after having firft effe&ed a mixture with the 
 inteftinal chyle in the thoracic du&), is derived 
 from the interior recedes of the vifcera and other 
 foft parts of the body, and was formerly fecreted 
 from the blood itfelf ; from whence it necefLrily 
 follows, that fuch portion of the lymphatic fluid 
 mud: doubtlefs poflefs, already, the animal nature 
 entire, and be very readily mlfcible with the mafs 
 of blood to which it is returned. 
 
 § 449- 
 To thcfe w r e may add another circumdance, of 
 which we fpoke on a former occafion, naniely, 
 the dow and dillicidious tranfition of the chyle into 
 its refervoir, the blood — that fluid not being ad- 
 mitted to pafs through the ultimate valve of the 
 thoracic du& into the fubclavian vein, in any 
 other manner than by drops, in order that thofe 
 minute portions may, by this means, be more inti- 
 mately mixed and incorporated with the circu- 
 
 lating blood. 
 
 § 45°- 
 
OF SANGUIFICATION. 81 
 
 450 
 The internal ftru&ure of the heart itfelf appears 
 alfo to contribute, not a little, towards the im- 
 portant procefs of fanguification. Thns, by means 
 of thofe aftonifliing mufcular papilla?, with which 
 the ventricles of the heart are plentifully fur- 
 nifhed, the blood and chyle (having recently met 
 together), are thoroughly agitated, and brought 
 into a ftate of more intimate combination. 
 
 § 45 1 - 
 That the lungs, receiving the blood, recently 
 
 impregnated with chyle, perform, by the fun&ion 
 
 of refpiration, an important part in the farther 
 
 afiimilation of this crude fluid, will appear fuffici- 
 
 ently evident to any one who confiders the aflo- 
 
 mining vafcular ftru£hire of thefe vifcera (§ 1 ?6.) 
 
 in conjunction with the equable alternate motion 
 
 to which they are perpetually fubje&ed, during 
 
 the continuance of human life. 
 
 § 45 2 - 
 The remaining part of the procefs of fanguifica- 
 tion is finally completed by the more exten five 
 circuitous journey of the blood throughout the 
 whole body, and by thofe powers which con- 
 tribute towards the continuance of the fame, 
 more cfpecially mufcular motion, Sec. 
 
 vol. 11. F § 453. 
 
Si OF SANGUIFICATION. 
 
 § 453- 
 But although potent provifion be made, by 
 fuch powerful and diverfified apparatus, for blend- 
 ing and intimately incorporating the chyle with 
 the blood, it appears, notwithftanding, that there 
 exifts a certain fimilarity between the condiment 
 parts of thofe two fluids. It is very commonly 
 aflerted, that a great many hours mud elapfe be- 
 fore the chyle can be completely diverted of its 
 own milky colour, and perfectly affimilated to that 
 of the crimfon fluid into which it is deftined to be 
 converted : in teftimony of the truth of this afler- 
 tion, medical philofophers ufually adduce (befides 
 other arguments) the following fingular patholo- 
 gical phenomenon, namely, that feveral hours after 
 the clofe of digeftion, genuine chyle has been fre- 
 quently obferved to flow from an orifice made ia 
 a vein of the human body : this phenomenon I 
 have indeed had an opportunity of obferving rny- 
 felf ; but it was at the fame time extremely evi- 
 dent, that the blood was then highly charged with 
 phlogifton (a condition of this fluid very un- 
 friendly to the regular aflimilation of chyle), fo 
 that from hence fcarcely any inference can be 
 drawn relative to the healthy ft ate of the fyftem, 
 which is alone the exclufive fubjeft of the fcience 
 &f physiology. 
 
 SECT. 
 
Of nutrition* &3 
 
 sect: xxxvi. 
 
 OF NUTRITION. 
 
 § 454* 
 
 xJeSIDES that funflion (which we at- 
 tributed to the blood in a former fedYion) of dif- 
 tributing the element ofjire throughout the whole 
 body, and in its place wafting that of fhlogijlon 
 back to the lungs, two of its primary and leading 
 offices appear to be, to convey to the body nou- 
 rifhir.ent, and to rhe fecretory organs the matter 
 of thofe peculiar fluids which they are feverally 
 deft ned to extract. Of this twofold function we 
 wi I next treat ; and firjl of the function of nu* 
 trition. 
 
 § 455- 
 Nutrition is the fupreme privilege of nature. 
 It is a common and leading prerogative of all or- 
 ganized bodies, whether animal or vegetable, by 
 which they are inftamly difcovered, on firft view, 
 to furpafs, in an immeafureable degree, all ma- 
 chines and automatons conftru&ed by human ar- 
 tifice : becaufe on none of thefe latter has any 
 artift ever been able to confer a power (I will not 
 fay of actual growth, of progreffing toward matu- 
 rity, and of acquiring gradually higher and higher 
 F 2 degree** 
 
$4 OF NUTRITION. 
 
 degrees of perfection J, but not even of preferring 
 themfelves in a ftate of Jlationary exiftence by their 
 own inherent powers, nor of repairing the gradual 
 lofles to which they are fubjecled by attrition, by 
 incidental cafualties, &c. 
 
 § 45& 
 
 Nutrition is that faculty of our bodies, on which 
 all the fublime and aftonifhing functions of our na- 
 ture depend. By means of this faculty we increafe 
 in magnitude from the earlieft dawnings of our 
 exiftence, we advance through the expanding 
 period of youth, and finally arrive at our acme, 
 or point of complete maturity. It is alfo through 
 the inftrumentality of this fame faculty that a com- 
 petent remedy is applied, and fufficient reftitution 
 made, for that uniform wade and lofs of the body, 
 by which (while in a living (late) it deftroys and 
 in fome meafure cenfumes itfelf, by its own necef- 
 fary action. 
 
 § 457- 
 With refpect to the nature and mode of this 
 zuajiing or lofs, various controverfies have exifted 
 among phyfiologifts. The more immediate point 
 of difputation has been, whether fuch wafle occurs 
 in the folid parts of our bodies, or whether it be 
 not more probable, that thofe parts, when once 
 formed and completed, remain ftationary, without 
 
 being 
 
OF NUTRITION. g 5 
 
 being fubjecl: either to vitiation or change ? which 
 latter is indeed an opinion embraced and taught 
 by feveral characters of the utmoft: acumen and 
 ingenuity. 
 
 § 45 & 
 With refpecl to fome particular folid parts of 
 die body, fuch, for example, as the epidermis, 
 the nails, &c. there exifts indeed not a madow of 
 doubt, but that they are gradually deftroyed and 
 again repaired ; and with regard to the deftru&ion 
 or wafte and fubfequcnt reparation of the bones 
 themfelves, the teftimony will appear equally plain 
 and conelufive, to any one who may confider with 
 attention the refult of the well known experiments 
 made by feeding warm-blooded animals, for fome 
 time, on the root of the rubia tinfiorum, or who 
 may take the further trouble of contemplating 
 attentively the phenomena exhibited by certain 
 large plain bones, efpecially thofe of the cranium, 
 which in extreme old age become remarkably 
 attenuated, or diminiihed in thickncfs, in confe- 
 rence of the fcanty nourifliment with which they 
 are fupplied at that period of life. 
 
 S 45°- 
 
 Upon the whole, if I be capable of judging 
 
 rightly, thofe folid parts appear to be not only 
 
 gradually confumed, and again repaired, by the 
 
 f 3 faculty 
 
86 OF NUTRITION. 
 
 faculty of nutrition, but poffefs alfo a vis repro- 
 ducliva, or power of re-produ&ion. This latter 
 is indeed a furprifmg faculty, deflined not only 
 to make reftitution for the uniform removal of 
 minute atoms by the neceflary action of the animal 
 economy, but alfo to repair the incidental lofs of 
 larger parts (fuffered in confequence of external 
 injuries, wounds, &c), by a perfeft restoration of 
 the fubftance of which the body has been thus 
 forcibly deprived. That fuch a power does un- 
 equivocally refide in the bones, and a few other 
 parts, of which we have jufl fpoken, is with me 
 too well afcertained and fubftantiatcd to admit of 
 a doubt* 
 
 § 460. 
 
 But on the other hand, from a variety of obfer- 
 vations and experiments which I have made both 
 on man and other warm-blooded animals, this 
 power of reproduclion appears to refide in fcarcely 
 any other folid parts of the body than fuch as are 
 endowed with contraclility alone ', without poffcfj'ing 
 at the fame time any of the other vital energies, 
 fuch as irritability, fenfibility, or finally, fpecific lift, 
 
 § 461. 
 
 Of thofe parts of the fyftem therefore (which 
 poiTefs the more exalted kinds of vital energy), 
 ;he flaminal bafis appears to me to confift oi a pe- 
 rennial 
 
OF NUTRITION. S 7 
 
 rennlal parenchyma, which is fubjeft neither to 
 genuine mutation nor decay, but only liable to 
 certain viciffitudes in point of bulk, that are pro- 
 duced in the following manner, namely, when 
 the procefs of nutrition is conducted with fuffi- 
 cient activity and vigour, the cellular interfaces of 
 the parenchyma, being uniformly filled with the rich 
 and plallic lymph of the blood, are, of courfe, dif- 
 tended, and the parenchyma neceiTarily enlarged - 9 
 but when, on the other hand, nutrition goes on 
 lefs favourably, thefe fame interfaces, being in a 
 great meafure deprived of this nutritious lymph, 
 fall into a ft ate of collapfe, and the parts become 
 eonfequently diminiihed in fize. 
 
 § 462. 
 
 With refpecr. to this plaftic lymph (of the dig- 
 nity and importance of which we have fpoken 
 fully on a former occafion), as it alTumes with 
 great facility the appearance and nature of genuine 
 cellular membrane, fo it appears to conftitute ge- 
 nerally the principal nutritious matter of the 
 whole fyftem, and is conveyed to every part of the 
 body by means of that infinitude of minute blood- 
 velTels, to which we have fo often called the 
 leader's attention. 
 
 F 4 § 463. 
 
SS OF NUTRITION. 
 
 § 463- 
 
 During the time of the body's advancement in 
 growth, it appears to poflefs certain peculiar or 
 fpecific powers, by the aid of which the lymph, 
 being depofited from the evanefcent extremities 
 of the fanguiferous vefTels, into the furrounding 
 cellular membrane, is duly arranged, and com- 
 pletely aflimilated to each particular portion, and 
 kind of parenchyma. To the head of thefe fpecific 
 powers, mufl we in part refer that particular law 
 of affinity, by means of w T hich the partes fimilares 
 of the fyftem attract and appropriate to themfelves, 
 the homogeneous elements of the nutritious lymph, 
 more efpecially fuch of them, as poflefs reciprocal 
 and kindred propenfities ; and to the fame head 
 may We alfo in part refer that nlfas formativus, of 
 which we v/ill have occafion to fpeak more fully 
 hereafter, and to which mud be attributed, the 
 jufl and fpecific application of the rude, and hi- 
 therto formlefs, elementary mat<:er ? and its fubfe- 
 qisent organifation and arrangement into the form 
 and figure of its peculiar deflination. 
 
 § 464. 
 It is, I prefume, from the joint co-operation of 
 both the preceding powers, that we miift princi- 
 pally derive the nutrition of thofe parts of the 
 body, which are not proximately fupplied with any 
 
 bipod 
 
OF NUTRITION. 89 
 
 "blood veffels at all ; fuch as the nails, hairs, &c. 
 and which are, notwithstanding, generated at firfl, 
 by a very powerful and truly infallible nifus or ex- 
 ertion, are afterwards advanced in magnitude, and 
 regularly fupported by nutriment throughout the 
 whole of life, and, finally, if by accident removed, 
 are again readily reftored by the adoniihing 
 efforts of the vis reproduclroa. 
 
 § 465- 
 Although the preceding appears to be a general 
 breviate account of the prccefs cf nutrition, yet, 
 on the other hand, it is evident that there exifts, 
 in different individuals, a great many varieties, 
 with regard to the degrees and modes in which 
 this function is difcharged. Thus, for example, 
 in proportion as a more lax or more clofe appofition 
 and unior. of the nutritious matter are effected, the 
 texture of the parts themfclves is rendered more 
 denfe or delicate, and hence alfo feems to origi- 
 nate the difference between the fpecific weight cf 
 human bodies j in which refpeft it is well known, 
 not only that man differs from man, but even 
 nation from nation : in tedimony of this truth it 
 may be fufBcient to adduce even a folitary example 
 from among certain northern tribes, namely, the 
 Jukutas, the Buratse, Sec. people highly con.fpi- 
 cuous on account of the remarkable and truly fin- 
 gtilar levity of their Jjpdies. 
 
 SECT, 
 
9® OF SECRETION, 
 
 SECT. XXXVII. 
 OF SECRETION. 
 
 -DESIDES thofe juices deflined for 
 the important procefs of nutrition, there are alfo 
 in the animal fyftem other humours, of a very 
 different order and character, which are extracted 
 for various purpofes from the exuberant fountain 
 of the blood. Thefe humours owe their exis- 
 tence to the procefs of fecretion, than which no 
 function is lefs underftood by phyfiologifts ; a 
 truth mentioned as a fubjecl: of juft regret, both 
 by the immortal Haller and other preceding 
 writers. 
 
 § 467- 
 
 The fecreted humours, appear, in one point of 
 view, to be fo extremely diverfified in their na- 
 tures, and, in another, to bear fo ftriking an affi- 
 nity to each ether, that it is not poffible to reduce 
 them to any, fave highly arbitrary, clajfes. If, 
 however, in treating of thefe humours, we found 
 our divifions of them on the lefs and greater 
 changes to which their elementary parts, (con- 
 tained 
 
OF SECRETION. t?i 
 
 tained in the mafs of blood), are fubjected in the 
 fecretory organs, they may be aptly enough enu- 
 merated in the following order. 
 
 Firft, the milk, a fluid which we think proper 
 to place at the head of our cenfus or enumeration, 
 becaufe it may be confidered, in fome meafure, as 
 renovated chyle, and appears to be fecreted, by 
 the moft funpie procefs, from the blood, to which 
 die chyle had been recently united. 
 
 Secondly, the aqueous fluids ; fuch, for exam- 
 ple, as the humours of the eye, and the tears : 
 to the fame head mufl we refer in like manner, 
 the fweat ; and alfo, (if our opinion be not un- 
 founded), that halitus which is contained gene- 
 rally in the interfaces of the cellular membrane, 
 as well as in the cavities of the thorax and abdo- 
 men i this vapour appears to differ but very little 
 either from the liquor of the pericardium, or from 
 that fubtle halitus by which the ventricles of the 
 brain, and the pituitary flnufes of the cranium are 
 preferved in a (late of perpetual humidity. 
 
 Under the fame head of aqueous fluids, it is 
 liktwife common to arrange the urine, although 
 this is doubtlefs a liquid poflcfled of fome fingu- 
 Jarly finking and peculiar properties. 
 
 Cf 
 
 
f% OF SECRETION. 
 
 Of a Iefs compound nature are the fativarj 
 humours, which, in office, are fubfervient to maf- 
 tication, to digeftion, and to cbyliikation. 
 
 Thirdly, the tnucagenous fluids, which inveft 
 and lubricate the cavities of mod of the vifcera, 
 that are deflined to the performance of the natural 
 and genital functions, and alfo the internal furfaces 
 of all the aerial avenues belonging to the fyflem, 
 fuch as the nares, the larynx, and the a/pent 
 artcria* 
 
 Of a nature not widely different from the fore- 
 going, is that portion of mucus which covers the 
 internal fegment of the eyeball j as well as that 
 which is fpread immediately beneath the epi- 
 dermis. 
 
 Fourthly, the adipofe humours are, in particular, 
 (befides the common fat itfelf), the medulla of 
 the bones, and the fmegma or oily covering of the 
 ikin, to which may be added the cerumen aurlum, 
 or waxlike fubftance inverting the external ave- 
 nues of the ears. 
 
 Of a nature nearly related to the foregoing, is 
 that un&uous fecretion, fo evident on the glans 
 penis of the male, and about the rima or os exter- 
 num y in the genital organs of the female. 
 
 ynder 
 
OF SECRETION. 93 
 
 Under the fame clafs may we alfo arrange that 
 oily fubftance, with which the glands of Meibo- 
 mius furnifh and anoint the eyelids. 
 
 Fifthly, what are commonly denominated by 
 phyfiologifts gelatinous fluids, examples of which 
 we have in the liquor amnii, and ur.guen of the 
 joints. Reflecting the nature of thefe fluids, 
 however, we are not yet pofleffed of a fuflicient 
 number of well authenticated' facts to give birth 
 to unequivocal and fatisfactory conclufions: a 
 fimilar obfervation may alfo be made, refpe&ing 
 that uninveftigated and anonymous humour, which 
 the female uterus difcharges during the ardent 
 glow of the venereal orgafm. 
 
 We remain alfo as yet, in a ftate cf equal un- 
 certainty refpe£ting the nature of that fluid, which 
 is lodged, during the firfl months after conception, 
 between the chorion and amnios ; of that which 
 is contained in the umbilical vc/icula or pQv.ch of 
 the embryo in its tenderer!: ftate ; and alfo of that 
 which is interpofed between the three veiTcls tha: 
 conftitute the umbilical cord. 
 
 The liquid enclofed in the "ueficttfts grajfiafia of 
 the female ovary, and alfo the liquor of the prof- 
 tare gland, appear to be of a irvhy ferffls or albu* 
 ?nhwu; nature* 
 
94 OF SECRETION. 
 
 Sixthlly, the male feme n appears to be a hiimour 
 io remarkably lingular in its nature, as not to 
 admit of clarification, nor even of comparifon^ 
 with any other. 
 
 And laftly, with regard to the bile, there is 
 equal room for the admiiTion of a fimilar obfer- 
 vation. 
 
 § 4 5S. 
 
 That the foregoing fecreted humours, fo ex«- 
 tremely diverfified in their natures and habits, can 
 neither be derived from the mafs of blood by the 
 fame individual procefs, nor by organs of the fame 
 kind, is a propofition too felf-evident to (land in 
 need of, or indeed leave room for, any farther 
 confirmation. Among thefe humours, there ob- 
 vioufly exifts this memorable variety, namely, that 
 while fome of them are fecreted and conveyed 
 from the blood through a fljortcr route, others 
 again, are more elaborately prepared, by being 
 carried onward through tubes of greater longitu- 
 dinal extenfion. 
 
 § 469. 
 
 Of all the modes of fecretion, that mud doubt- 
 Iefs be confidered as the moft fimple, in which the 
 fecreted humour appears to tranfude immediately 
 through the coats of the arteries, by what phyfi- 
 
 ologifts 
 
OF SECRETION, $| 
 
 elogifts call diapedefis. Tnftances of this mode we 
 have in the fecretion of the fat, and of the medulla 
 refiding in the bones, &c. ; and, finally, it appears 
 to be by a modification of the fecretory procefs, 
 not greatly diflimilar to the foregoing, that the 
 gaftric liquor, the inteftinal liquor, &c. are pre- 
 pared and difcharged into the cavities of their 
 refpe&ive vifcera. 
 
 § 47°' 
 The mechanifm of fecretion appears to be more 
 
 compound, where that procefs is performed by 
 means of glands, under which denomination we 
 generally include even follicles and crypto them- 
 felves ; fuch, for example, as are eafily difcover- 
 able in the fauces ; and which phyfiologifts gene- 
 rally defignate by the name of glandula Jim- 
 H/Jima, 
 
 We bellow, with propriety, the denomination 
 of fecreting glands, on thofe bodies which, (to 
 diflinguifh them from the conglobate, belonging to 
 the lymphatic fyflem), are called conglomerate ; ex- 
 amples of which we have in the falivary glands, in 
 the pancreas, in the lachrymal glands, and in the 
 mamma, or breads of females. The foregoing 
 glandular bodies are furniflied with excretory 
 duels, which are compofed of tubes or canals 
 running imraediatelv from their larger lob^s : thefe 
 
 lobes, 
 
96 OF SECRETION. 
 
 lobes, on being fubmitrcd to farther examination, 
 are found to be made up of fmaller lobules, re- 
 fpc&itig the internal (lru£lure of which, there for- 
 merly exiled very warm controverfies in fome of 
 the moil celebrated fchools of medicine. Malpighi 
 confidered the fmall miliary globules, which may 
 be readily demonlrated in the greater part of 
 them, to be nothing elfe than genuine acini or 
 kernels^ containing, each cnc, a minute cavity in 
 its centre. While Ruyfch contended, on the 
 other hand, that thofe hypothetical excavated 
 kernels were nothing more than globular convo- 
 lutions of extremely fine blood veiTels ; which lat- 
 ter opinion, is doubtlefs founded on by far the 
 moll unequivocal and fubftantial teftimony, as 
 we readily learn from well conduced anatomical 
 invefligations, more efpecially from fuccefsful 
 injections, and the aUhlance of glaffes. 
 
 § 47 1 ' 
 Nor does this ftruclure (if indeed we keep cut 
 of view the peculiar parenchyma of each parti- 
 cular vifcus), differ much from, but appears rather 
 to fned a confidefable gleam of light on, the flruc- 
 ture of certain other fecreting vifcera, particularly 
 en that of the liver and kidneys, in which late ex- 
 perimenters have been able to demonstrate, with 
 the utmdft pcrfpicuity, certain fpherical bodies 
 entirely firnilar to the globular convolutions of 
 4 Ruyfch, 
 
OF SECRETION. 97 
 
 Ruyfch, or the kernel-like fubftances of the cele- 
 brated Malpighi. For, in what is called the cortical 
 portion of thofe vifcera, minute ramifications emerg- 
 ing from the fides of the fmall capillary arteries, be- 
 come prefently convoluted, in fuch a manner, as to 
 form little vafcular balls, which thus appear to hang 
 by thofe ramifications of which they are compofed, 
 like fo many fmall berries or grapes fupported by 
 their footflalks. From thefe minute vafcular balls 
 originate firji t that very fubtle and colourlefs 
 order of veffels immediately deftined for the bufi- 
 nefs of fecretion, (refpe&ing the origin of which, 
 from the evanefcent terminations of arteries, we 
 tranfiently fpoke on a former occafion, (§ 79. 
 8 1.) j andfecond/y, the incipient radicles of veins, 
 into which the minute arteries are themfelves 
 continuoufly reflected, and which conduct back 
 to the venous trunks, the refidue of the blood 
 now deprived of thofe elementary particles necef- 
 fary to conditute the fluid recently fecreted. 
 
 § 47 2 - 
 Finally, certain other parts of the body, appro- 
 priated entirely to the bufinefs of fecretion, are 
 diftinguifhed again by different and remarkably 
 peculiar, fpecies of organization ; thus the male 
 teftes, for example, are wholly compofed of no- 
 thing elfe than clofe and mazy convolutions of 
 very lengthy and numerous blood vefTels, &c. 
 
 vol. n. G § 47 
 
 ,■>* 
 
OF SECRETION 
 
 § 473- 
 We come now to the confideration of the pe- 
 culiar caufes, by the operation and efficacy of 
 which thofe determinate and fpecifk humours are 
 fecreted in thefe correfponding determinate and 
 fpeciflc organs : this is indeed the Gordian knot — 
 this is by far the mofl difficult point of difquifition 
 in the whole doctrine of fecretion — that point 
 which numerous doubts and difficulties yet invert. 
 
 § 474- 
 It appears indeed to be a truth afcertained and 
 
 eftablifhed beyond the faintefl fhadow of a doubt, 
 that the leading, and what may be called the 
 proximate caufe of mod of the fecretions, mult 
 be fought for in the internal ftru&ure of the fe- 
 treting organs themfelves : under this head we 
 mufh particularly confider, in the conglomerate 
 glands and other fecreting vifcera, not only the 
 peculiar diilribution and direction of the extreme 
 blood-velTels, from which the humours are fe- 
 creted, but alfo the parenchyma^ fo uniformly 
 proper to each fecreting vifcus, that in many of 
 them it can be inftantly known and diftinguifhed 
 at firft fight from all other kinds or fpecies of 
 fiem (§ 27). 
 
 § 475- 
 It is alfo an opinion extremely probable (in 
 fupport of which we have advanced, on former 
 
 occafions, 
 
 
OF SECRETION. 9 
 
 cccafions, feveral arguments not eafily refuted)* 
 that the fecreting vifcera, befides their peculiar 
 parenchyma, poffefs alfo what we have taken the 
 lilxrry to call a vita propria, i. e. a fpecific or 
 exclufive kind of vital energy, effentially different 
 from what we denominated the three commo?i 
 energies, namely, contractility, irritability, and fen- 
 Ubility. 
 
 § 47 6 - 
 But further, if my views of the fubject be in 
 any meafure juft, the abforbent fyjlem appears to 
 contribute alfo a very important part towards the 
 promotion of the feveral fecretions : thus, from 
 each of the fecreting vifcera certain appropriate 
 branches of this fyftem abforb and re-convey to 
 the blood-veffels larger or fmaller portions of each 
 of the feveral humours to which thefe vifcera give 
 origin \ the uniform cenfequence of which is* 
 that the blood becomes literally impregnated with 
 the contagion of every humour fecreted in the 
 different parts of the body, e. g. with bile from 
 the liver, Wnhfemen from the telles, &c. 
 
 Thus there appears to exift, in the fyftem de- 
 fined for the bufinefs of fecretion, a perpetual 
 routine or circulation, fo that the elementary 
 parts of the humours already fecreted being in- 
 ceffantly conveyed from the fecreting organs 
 G 2 them- 
 
jdo OF SECRETION. 
 
 themfelves, are united afrefh to the mafs of blood, 
 and on their fubfrquent return to their parent 
 organs, in conjunction with the fanguineous cur- 
 rent, are again more eafily attracted by the fe- 
 creting veffels, in confequence of a peculiar law 
 of affinity, and have alfo a power of drawing 
 along with them thofe parts of the blood that 
 are mod homogeneous in their nature, and for 
 which they confequently poflefs the higheft de- 
 cree of attraction. 
 
 § 477- 
 
 To facilitate the fecretion of certain hianours 
 of the body, adequate provifion is made by the 
 production of fpecific qualities, in thofe particular 
 portions cf the blood from which they are to be 
 proximately derived : thus the bile is fecreted 
 from the blood of the vena portarum, a portion 
 of fluid highly impregnated with phlogifton, fur- 
 niflied in profufion by the abdominal fourccs, from 
 which this blood immediately originates. 
 
 § 478. 
 
 I pafs in filence over certain other co-operating 
 aids, which act in fubfervience to particular fecre- 
 tions, as congejiion and derivation, fo evidently 
 efficacious in the fecretion of milk, with other in- 
 stances of a fimilar nature. 
 
 S 479- 
 
OF SECRETION, io£ 
 
 § 479- 
 Among the humours thus fecreted by the or- 
 gans which we have juft defcribed, and by the 
 powers or caufes jufl: enumerated, it may be ob- 
 fcrved that the following difference afterwards 
 exifts, namely, while fome of them drop imme- 
 diately from their fecreting organs into the places 
 of their ultimate deftination, in which they are to 
 perform their fpecific functions, others again are 
 conveyed to appropriated receptacles, in which 
 they are retained for fome time, and thus farther 
 matured previoufly to their final elimination from 
 the fyftem : of this laft defcription is the milk 
 which ftagnates in the lactiferous ducts, the urine, 
 the bile, and the femen mafculinum, which are 
 fubjected to retention in their veficular receptacles, 
 and finally, the ferum contained in thofe veficles 
 which were firfl: difcovered by de GraafF in the 
 ovaria of the female. 
 
 G 3 SECT, 
 
foj OF THE URINE, / 
 
 SECT. XXXVIII. 
 OF THE URINE. 
 
 JjE SIDES the nutritions juices and the 
 fecreted humours deftined for further fervices in 
 the animal economy (§ 4.), the blood furniihes 
 alfo materials for the formation of certain ufelefs 
 and fuperfluous liquids, that are intended to be 
 entirely eliminated from the fyftem, and are from 
 thence vulgarly called excrements of ihe fecond di- 
 gejlion. Thtfe excrementitious liquids are of two 
 kinds, one of which is exhaled by the procefs of 
 perfpiration, and has already engaged our parti- 
 cular attention ; the other is the ufine, a liquid 
 fecreted in thofe glands denominated kidneys. 
 
 § 481- 
 The kidneys are two vifcera fituated behind the 
 peritoneum, on each fide of the fpine, and in the 
 upper part of the lumbar region : Although their 
 figure is generally fomewhat flatted, yet it is pro- 
 per to obferve, that both in this refpecl, and alfo 
 in point of number, they are fubject. to more va- 
 rieties than any other vifcus belonging to the hu- 
 #nan body : they hang by vefTels commonly called 
 
 emulgents 
 
OF THE URINE. 103 
 
 emulgents (remarkably large in proportion to the 
 magnitude of the parts on which they are distri- 
 buted), and are cufhioned round by fat of a feba- 
 ceous confidence (§ 38). 
 
 § 4S2. 
 They are inverted by a proper membrane, of 
 an elegant vafcular ftru&ure : each one of them, 
 efpecially during the period of infancy, appears to 
 be compofed of about eight, or fomewhat more, 
 kidney-form lobes or fubdivifions ; each of which 
 confifts again (according to an opinion formerly en- 
 tertained and taught by Ferrein), of about feventy 
 or eighty fiefhy radii, which that phyfiologift 
 called white pyramids. 
 
 § 483- 
 If the kidney be differed or divided from its 
 convex dorfum towards its concave pelvis, it ex- 
 hibits in its compofition two kinds of fubftance ; 
 one forming its circumference, and therefore de- 
 nominated its cortical, the other conflicting its 
 centre, and hence called its medullary, portion. 
 
 Each portion abounds with Sanguiferous arte- 
 ries and veins ; befides which, the external cortex 
 is alfo furniihed with an additional order of very 
 minute colourlefs vefTels, deftined to fccrete the 
 urine : while the medulla contains alfo veffds of 
 G 4 a fimilar 
 
• •4 OF THE URINE. 
 
 a fimilar description, intended to carry it onward 
 when fecreted. 
 
 Thofe fecretory ducts originate, in the manner 
 already defcribed (§ 47 1.), from the fmall glo- 
 bular convolutions of capillary arteries that are, 
 every where interfperfed throughout the cortex 
 of the kidney : thofe duels conftitute indeed by 
 far the greater portion of the cortical fubftance 
 of the kidney, and may be very eafily diftinguifhed 
 by their fmgular meanderings and intricate mazes, 
 from the fmall conducting tubes of Bellini, in which 
 they finally terminate. Thefe tubuli Belliriiani 
 (as they are frequently termed) pafs by a direct 
 route from the cortical, and enter the medullary 
 fubftance, of which they conflirute bv Br the 
 greater part ; and uniting afterwards by reiterated 
 coalitions into a fmall number of narrow trunks, 
 finally perforate, by their extreme orifices, in a 
 fieve-like manner ,the feveral papilla, contained in 
 the renal pelvis, 
 
 § 484- 
 
 The papillx correfpond for the moft part to the 
 number of lobes, of which we already faid each 
 kidney is compofed. The urine that is fecreted 
 in the colourlefs veiTcls of the cortex, and after- 
 wards conduced through the tubuli Belliniani oi 
 she medulla, thefe papilla? difcharge into their 
 
 £orrcfpoiid;n^ 
 
OF THE URINE. 105 
 
 correfponding infundibula, which form by their 
 fubfequent confluence the common pelvis, 
 
 § 485- 
 The pelvis is continued into the ureters, which 
 are membranous canals, exquifitely fenfible, and 
 defended internally by a complete inveftiture or 
 lining of mucus j they are capable of extreme di- 
 latation ; in man they are here and there uneven 
 in the width of their cavities, and are at length 
 inferted into the pofterior furface, not far from 
 the neck of the urinary bladder. This infertion 
 is effected in fuch a manner, that the ureters do 
 not immediately perforate the parietes of the uri- 
 nary cyft, but defcend a fhort diRance between 
 its mufcular and nervous coats (which are here 
 poffefTed of more than ordinary thicknefs), and 
 open finally into the cavity of this organ by ob- 
 lique orifices. By means of this ilrufture, ade- 
 quate provifion is made to prevent the urine, that 
 has once entered the cavity of the bladder, from 
 being forced to return again into the ureters by 
 an inverted or retrograde motion. 
 
 § 486, 
 
 In an adult fubject, the urinary bladder is in 
 
 general fufficiently capacious to contain about two 
 
 pounds of urine ; its fundus or bottom, which in 
 
 fetal (late terminates in the uracbus, and alfo 
 
ic<5 OF THE URINE. 
 
 its pofterior fide, are inverted by the peritoneum ; 
 as to its remaining membranes or coats, they bear 
 a general refcmblance to thofe of the ftomach, of 
 which we have already fpoken. 
 
 The mufcular coat confifts indeed of interrupted 
 bands of flefhy fibres, that furround the cy.t, 
 forming at the fame time various irregular decuf- 
 fations or interferons, which are different in dif- 
 ferent fubje&s : this mufcular coat phyfiologifts 
 denominated detrufor urinte, while they defignate 
 by the name of fp hinder vc/tca, thofe orbicular 
 fibres that partially furround the neck of the blad- 
 der, though they are very inconftant and irregu- 
 lar, both with refpecl to their figure and origin. 
 
 The nervous coat bellows on this membranous 
 vifcus alfo the principal part of its flrength and 
 firmnefs. 
 
 Finally, the internal coat, which is confidered 
 by phyfiologifts as a procefs or continuation of the 
 epidermis, is defended by a complete covering of 
 mucus, efpecially round the neck of the bladder. 
 
 § 4^7- 
 Befides thofe public and well known routes of 
 the urine, of which we have already fpoken, it 
 appears probable from feveral phenomena, that 
 
 there 
 
OF THE TJRINE. 107 
 
 there exifl alfo certain fecret avenues, which lead 
 immediately from the interlines to the nropoietic 
 organs. For the fpeedy difcharge of certain 
 drinks from the urinary emun&ory, fo frequently 
 imbued with the odour, tinctured with the colour, 
 and characterized by other fpecific qualities of the 
 aliments recently taken in, will fcarcely admit the 
 belief, that thefe liquids had performed, in fo (liort 
 a time, the cuftomary long and circuitous route 
 through the thoracic duel and fanguiferous fyf- 
 tem : to the foregoing circumftance we may add 
 an account we have read, of the urine having 
 been found covered with oil, that entered into the 
 compofition of an enema, which had been previ- 
 oufly and recently thrown into the inteftinum rec- 
 tum. It is, on the other hand, a circumftance 
 well known to phyfiologifts of the prefent day, 
 that very ftriking and numerous anaftomofes oc- 
 cur between the lymphatic veflels of the intef- 
 tines, and thofe of the kidneys. Laflly, it is now 
 unequivocally afcertained and confirmed by live 
 directions, that if both ureters of a dog be tightly 
 enclofed in ligatures, and his bladder perfectly 
 evacuated of its contents, this latter organ will, 
 notwithstanding, in the term of three hours after- 
 wards, contain a certain quantity of urine ; while 
 •at the fame ti;re the ufual avenues of this fluid, 
 namely, the ureters, are completely obftructed, as 
 is evident from this circumftance, that above the 
 
 ligatures 
 
foft OF THE URINE. 
 
 ligatures thefe tubes fuffer vaft diftention from the 
 accumulated urine. 
 
 § 488. 
 But through whatever avenues the urine has 
 been conveyed to the bladder, its gradual accu- 
 mulation in that organ excites an uneafy fenfation, 
 which becoming urgent and troublefome (§ 331.) 
 potently folicits its final elimination, through an 
 emiffary or fewer deftined for that particular pur- 
 pofe, namely, the urethra. This excretory canal 
 16 fubje&ed to a variety in its conformation, found- 
 ed on the diverfity of the fexes, of which we will 
 fpeak more amply when treating profeffedly of 
 the fexual functions. 
 
 § 4 S 9- 
 In order to evacuate the bladder, it is neceffary 
 to overcome the contraction of its fphin&er, by 
 the exertion of its own detrufor (of which we for- 
 merly fpoke) (§ 486.), aided by the co-operation 
 of the abdominal mufcles, and thofe fubiervient 
 to the procefs of refpiration ; to which, in males 
 of the human fpecies, we may add, laftly, the 
 action of the mufculi accc!a\itores, which forcibly 
 ejaculate, perfaltum t as it were, even the refiduary 
 drops of urine that may be occafionally lodged in 
 the bulb of the urethra. 
 
 S 49^ 
 
OF URINE. to? 
 
 § 49°- 
 
 As to the nature of the urine itfelf, it is fubjeft 
 indeed, to an infinitude of varieties generated by 
 the circumftances of age, and feafon, but, above 
 all, by the longer or fhorter term of time, fubfe- 
 quent to the previous ufe of food and drink, the 
 difcharoje of this fluid occurs ; to which may be 
 alfo added, the quality of the aliment previonfly 
 ufed, Sec. In general, however, when we exa- 
 mine the urine which is difcharged by a healthy 
 human adult, immediately after found and tran- 
 quil fleep, we difcover it to be a watery liquid, of 
 a nidorous faiell, and citron colour, containing in 
 its aqueous medium, (as in a common vehicle} 
 various elementary fubilances, efpecially earthy 
 and filine, which bear different proportions to 
 each other in different individuals, and even in 
 the fame individual at different times and under 
 the influence of different circumftances. Of the 
 terrene elements the moil abundant is, in general, 
 calcareous earth, which is not unfrequently found 
 in the urinary parages under the form of calculi, 
 but which is, notwithstanding, extremely variable 
 and inconftant in its quantity. Of all the falins 
 matters, that mod worthy of being mentioned, is 
 the effcntial and native fait of urine — called alfo, 
 microcofmic fait, fuf.ble fait , &c. This faline fub- 
 ftance contains, in a greater proportion than any 
 
 othcr 
 
j ra 6F SEXUAL DISCRIMINATION. 
 
 other part of the human body, the celebrated 
 phofphoric acid chemically efpoufed to the volatile 
 alkali. 
 
 SECT. XXXIX. 
 
 OF THE DISCRIMINATION OF THE SEXES IN 
 GENERAL. 
 
 § 49 T - 
 
 1 HOSE functions of the human body, 
 in the confideration of which we have been hi- 
 therto engaged, are indeed poflefTed, and exercifed 
 in common, by the individuals of each fex : with 
 refpccl: to the mode, however, in which fome of 
 them are performed, there occur between the 
 two fexes no inconfiderable degrees of difference. 
 Of this difference, it may be proper briefly to 
 enumerate the leading points, previoufly to our 
 entrance on the confideration of what are denomi- 
 nated the fexual functions. 
 
 § 49 2 - 
 To fpeak, then, in general terms, each fex 
 
 poffefTes and exhibits its own peculiar habit, which 
 differs conMerably from that of the other. In 
 
 the 
 
OF SEXUAL DISCRIMINATION. n* 
 
 the human fubjeft after birth, this difference of 
 habit is diftinttly obfervable ; but during the. ten- 
 der fcetal (late, is fcarcely to be diflinguifhed, 
 unlefs by more clofe and pointed attention j 
 neither indeed, in this ftate, can the external 
 organs of generation themfelves be difcriminated, 
 on a tranfient and fuperficial view, owing to the 
 extraordinary magnitude and prominency of the 
 female clitoris, and the very diminutive fize of the 
 male fcrotum. 
 
 § 493- 
 During the period of infancy this difference of 
 the general habit, depending on the diverfity of 
 fex, makes only a flight impreffion on the ob- 
 ferver ; but becomes gradually more and more 
 obvious and ffriking till the full completion of the 
 years of puberty, at which period, the general 
 conformation of the female body, its tendernefs, 
 its foftnefs, and the ufual inferiority of its ffature, 
 contrafted with the athletic and robuft body of 
 die male, exhibit this general habitual difference 
 in the mod ftriking point of view. 
 
 § 494- 
 Similar to the difference that occurs between 
 
 the external habits of body, that chara&erife the 
 two fexes, is that which is obfervable in the bones 
 
 them- 
 
ri2 OF SEXUAL DISCRIMINATION*. 
 
 thcmfelves. Thefe folid portions (all other cir- 
 cumftances being alike) are evidently much more 
 fmooth and round in females than in males ; the 
 cylindrical bones, in particular, are more flender 
 and delicate, and the plane ones more attenuated 
 or thin, in the former, than in the latter fex ; not 
 to mention the peculiar diverfities of certain re- 
 markable bones, particularly thofe of the thorax 
 and pelvis, with the clavicles, the femora, &c. 
 
 § 495- 
 With refpec"r. to the foft parts of the body, we 
 
 may obferve in general, that in females, the cel- 
 lular membrane is more lax, more pliable, and 
 confequently more readily dilatable in the ftate of 
 pregnancy : while the fkin is more tender, fair 
 and beautiful, in confequence of the immediate 
 fubftratum of fat. 
 
 The hair of the head is generally of a greater 
 length in females than in males ^ while at the fame 
 time, certain other parts of the body which in the 
 latter are rough and hairy, are in the former' 
 either perfectly fmooth, as the chin and bread ; 
 lefs hairy, as the perineum ; or planted with only 
 a very tender and foft down, as the arms and 
 legs, 
 
 x % 496. 
 
OF SEXUAL DISCRIMINATION. 113 
 
 § 49 6 - 
 
 When fpeaking of the diverfities of particular 
 functions, we mull not filently pretermit the pulfe, 
 which (other circumftances being alike) is more 
 frequent in females than in males, (§ 109). In 
 the former, the thorax is Subjected to a greater 
 degree of motion, (especially at its fuperior part,) 
 than in the latter ; the os hyoides is much fmaller, 
 the larynx is lefs capacious, and hence the voice 
 more drill. 
 
 S 497- 
 
 With regard to the animal functions, it is ne- 
 ceflary to obferve in general, that in females the 
 mobility of the nervous fyftem is much greater 
 than in males, the irritability is more exquiiite ; 
 and the propenfity to commotions of the mind, 
 more prompt and Spontaneous. 
 
 § 498- 
 
 As to the natural functions, the appetite for 
 food is weaker in the female, than in the male 
 fex ; while, en the other hand, the increafe of the 
 body is more rapid in the former, and the (late of 
 puberty and mature growth attained at an earlier 
 period. 
 
 vol. II. H § 409. 
 
n 4 OF THE GENITAL FUNCTION 
 
 § 499- 
 But by far the greateit and mod important 
 
 cHfJinftion of the fexes is derived from the genital 
 functions themfelves, the male being furnimed 
 with a power of fecundation, and the female with 
 that of conccbtimi. A farther inveftiijation of thefe 
 powers (hall engage the greater part of our atten- 
 tion, throughout the remaining pages of this 
 work. 
 
 SECT. XL. 
 OF THE GENITAL FUNCTION OF THE MALE SEX. 
 
 § 5 00 ' 
 
 
 -a. HE genital liquor of the male is 
 prepared by the tefles, two bodies fufpended in 
 the fcrotum by their fpermatic cords, and (befides 
 the lymphatic veins with which they abound in 
 profufion), compofed chiefly of three kinds of 
 veffels. 
 
 Thefe are firji, the fpermatic artery, which in 
 proportion to its {lender diameter is faid to be the 
 longeft of all the arteries belonging to the human 
 
 body ; 
 
OF THE MALE SEX. 115 
 
 body : it in general conveys the blood immedi- 
 ately from the abdominal portion of the uona 
 itfelf, to the body of the teflis. 
 
 Secondly, the duel us deferens, which carries to 
 the vificula feminales, the femen when once fe- 
 crcted from the arterial blood. 
 
 And, laftly, what is commonly denominated the 
 pampiniform plexus of veins, the function of which 
 is to receive and convey to the cava or emulgent 
 vein, the blood that remains after the procefs of 
 fecretion is accomplifned. 
 
 § 501. 
 The teftes are not, from the time of their 
 earlieft forms tion, fufpended in the fcrotum, as 
 reprefented in the above defcription : thus in the 
 male fectus, while yet in a very tender and imma- 
 ture ftate, thofe gtandular bodies occupy indeed 
 a very different fituation, the reafon and fuccelllve 
 changes of which were firQ: accurately inveftigated 
 and detailed by Hal!er, at Gottengen in the year 
 1749, but were afterwards explained by other 
 writers on principles fo different from each other, 
 as to have given rife to various controvcrfies of 
 fomc weight and importance. Of the fituation 
 and changes of the teftes in the fecial ftate, I am 
 prepared to lay before the reader a brief, though 
 H 2 compre- 
 
n6 OF THE GENITAL FUNCTION 
 
 comprehenfive account, — the fpontaneous refult 
 of numerous obfervations made on nature herfelf, 
 during a remarkable feries of difleclions of male 
 embryo's, in which 1 engaged for the exprefs 
 purpofe of (liedding light on this fubject fo inte- 
 resting to phyfiologifts. 
 
 § 5 02 - 
 On opening the lower abdominal region of an 
 immature foetus, we difcover in each groin, near 
 what is called the ring of the oblique mufcles, a 
 very narrow orifice in the membrane denominated 
 peritoneum ; this orifice is the threshold to a (trait 
 avenue or alley, as it were, that leads through the 
 abdominal ring itfelf, and terminates afterwards 
 in a peculiar bullous or bubble like fack : this 
 fack extends without the abdominal cavity, looks 
 towards the fcrotum, is interwoven with cellular 
 fibres, and deftined for the future reception of 
 the teftis. 
 
 § 5°3> 
 At the very pofterior margin of this fmall 
 abdominal orifice, the peritoneum fends off an- 
 other procefs, which mounts upwards, and in the 
 tender foetus reprcfents, in the greater part of its 
 courfe, a longitudinal fold : from the bails of this 
 procefs a (lender cylinder, or rather inverted cone 
 afcends, and forms at its fummit, which regards 
 
 the 
 
OF THE MALE SEX. 117 
 
 the inferior margin of the kidney, a fmall blifter 
 or fack-Iike termination ; in this fack the teflis 
 and epididymis are enclofed ; fo as to refemble, 
 at firft fight, a fmall berry reding on its footflalk, 
 and appear, at the fame time, to hang loofeiy into 
 the abdominal cavity fomewhat like the liver or 
 fpleen (§ 404). 
 
 § 5°4- 
 The veffels which are afterwards to conftitute 
 the fpermatic cord, are, at this very early period, 
 feen running behind the extremely tender and 
 pellucid peritoneum, (o that the fpermatic artery 
 and vein run in a defcending dire&ion along the 
 fides of the fpine, while the vas deferens bending 
 fomewhat inwardly towards the neck of the uri- 
 nary bladder, ftretches along the loofe cellular 
 membrane, which is fituated behind the perito- 
 neum, and both enter the body of the teftis in 
 that peritoneal plica or fold of which we have 
 already fpoken. 
 
 § 5^5- 
 From about the middle liage of pregnancy, the 
 teftes begin to fink downward by degrees, fo as 
 gradually to approach the narrow orifice of the 
 peritoneum, which has been already mentioned. 
 At the fame time, the foregoing peritoneal fold, 
 with its cylindrical attachment, are wrapped up 
 H 3 by 
 
ii3 OF THE GENITAL FUNCTION 
 
 by decrees, till the teflis finally refrs on the very- 
 mouth of the preceding canal. 
 
 § 506, 
 When in the fcetus, now advanced to a higher 
 flage of maturity, the teflis is fully prepared for 
 a final defcent, the orifice, hitherto fo contracted 
 cr narrow, fuffers fuch a remarkable dilatation, 
 that the teftis is at full liberty to enter with facility 
 the opening that leads out of the abdomen as well 
 as the ring by which this opening is furrounced, 
 to pafs onward through the whole length of the 
 canal, and thus plunge headlong, as it were, into 
 the bliiler-like fac of which we have already fpo- 
 ktn. The teftis having finally accomplished its 
 defcent, the peritoneal opening is foon after clofed 
 in the molt: complete manner, and even fubjected 
 in a fhort time to a perfect, adheilon of its fides, (o 
 that in the flage of infancy, fcarcely a wreck of 
 it is left, to point the enquirer to the place of its 
 former exigence. 
 
 § S07- 
 The more gradual and flow the movement of 
 the teflis (while yet in the abdominal cavity) to- 
 wards the orifice of its egreflion, the more fud- 
 den and inftantaneous appears to be its act of 
 tranfition through the abdominal ring. For in 
 the difTeclions of mature fcetufes, it is by no means 
 
 uncom- 
 
OF THE MALE SEX. 119 
 
 uncommon to difcover the tedis either as yet in- 
 cumbent on the peritoneal opening, or elfe ftatio- 
 nary in the groin, after having recently paffed the 
 abdominal ring : but once only was 1 fo fortunate 
 as to have an opportunity of obferving the right 
 tedicle of a twin-fcetus (of which a complete 
 drawing has been given), at the very moment ot 
 its pafTage through the abdominal ring : the gland 
 appeared to have been very tightly embraced and 
 drangled, as it were, by the furrounding parts, 
 and was apparently in complete readinefs to 
 emerge from the abdomen into its deflined lack ; 
 a tranfition already accomplished by the left tef- 
 ticle, that had juft efcaped from the ring, the ori- 
 fice of which had again refumed its former imper- 
 vious (late. 
 
 § 5°S- 
 This remarkable defcent of the tedes along the 
 groins, does not appear to be exclufively confined 
 to any particular period of time : it occurs for 
 the mod part, however, about the lad month of 
 pregnancy : although thefe glandular bodies are 
 not unfrcquently found either in the abdominal 
 cavity itfelf, or in the fuperior part of their in- 
 guinal route, even in infants after birth. For the 
 teflicle, after its entire efcape from the abdomen, 
 has dill a further ftage of its journey to perform, 
 namely, its final defcent along the groin into the 
 II 4 fcrotum, 
 
i2o OF THE GENITAL FUNCTION 
 
 fcrotum, in company with the fmall fa'c by which 
 it is enveloped. 
 
 § 509. 
 
 That the foregoing is indeed a true account of' 
 the progreiTive movement of the teftcs in their 
 defcent from the abdomen into the fcrotum, I 
 have had fufficient opportunities of ascertaining 
 from repeated observation. To develope the 
 caufes and energies by which this aftonifhing de- 
 fcent is accomplished, appears to be indeed attend- 
 ed with difficulties of the utmoft magnitude* For I 
 am daily more and more convinced, that neither of 
 thofe powers to which this defcent has been hither- 
 to afcribed (fuch, for example, a^ the action of the 
 cremafter mufcle, the action of the diaphragm, or 
 the contractility alone of that cellular and tendi- 
 nous intertexturc, which adheres to the proceiles 
 of the peritoneum, and is ufually denominated 
 gubernaculum Hunterii, &c), is fufficient to ex- 
 plain a movement of fuch extreme Angularity, 
 efpecialiy that part of it relating to the immediate 
 tranfition of the teflis through the narrow abdo- 
 minal ring, to which the reader's attention has 
 been fo frequently folicited : while I am imprefled, 
 on the other hand, by a thorough conviction, 
 that this whole procefs exhibits the moft unequi- 
 vocal aud ftriking example of what we have de- 
 nominated fpecific life, without the peculiar opera- 
 tion 
 
OF THE MALE SEX. 121 
 
 lion and aid of which, it is fcarcely poflible to 
 folve the feveral phenomena of a tranfition fo ex- 
 tremely fingular in its nature, and fo widely diffi- 
 miiar to all other movements and functions that 
 occur in the whole animal economy. 
 
 The involucra by which the tefles are invefted, 
 after their final completion of the foregoing route, 
 may be aptly enough divided into common and 
 proper. 
 
 The only involucrum common to both thefe 
 glandular bodies is the fcrotum. This is a fac, 
 confiiling of a tender portion of cutis expanded 
 over a thin fubilratum of fat, and pofTefTing a pe- 
 culiarity that does not refide in any other part of 
 the common integuments of the body, namely, a 
 power of changing, in a very remarkable degree, 
 its ufual habit and appearance : thus, it fometimes 
 depends loofe and flaccid, and again (efpecially 
 under the impreffion of the venereal ceflrum, or 
 in cafe of expofure to cold), becomes conftricled 
 and rigid, as it were, and is then particularly 
 marked by furrows and divernfied rugofities. 
 
 § 5 11 - 
 Of thofe involucra which are proper to each 
 
 teftis, that placed immediately beneath and within 
 
 the 
 
122 OF THE GENITAL FUNCTION 
 
 the fcrotum, is called the tunica dartos : this coat 
 poffefTes a very peculiar and vivid contractility, by 
 which Window, Haller, and other celebrated cha- 
 racters have been fo far deceived, as to beftow on 
 it the nature and energy of a mufcle. 
 
 § 5 12 - 
 This is fucceeded (after a voluminous and foft 
 flratum of cellular membrane), by three feparate 
 •vaginal coverings, which were firffc accurately 
 traced and diftinguiihed by the ingenious and in- 
 defatigable Neubauer. 
 
 Of thefe vaginal coats, the exterior is common 
 to the teilicle and fpermatic cord, and has the cre- 
 mafter mufcle attached to it by feparate bundled 
 of fibres. 
 
 But the two interior are proper, one to the fper- 
 matic cord, and the other to the teftis itfelf ; of 
 thefe the latter adheres, for the moli part,by its 
 fundus to the common tunic, while its internal 
 furface is moiftcned by a lubricant fluid, fome- 
 what after the manner of the pericardium. 
 
 § 5 J 3- 
 The origin of thofe vagina] tunics which has 
 given rife to fuch a variety of controverfies among 
 phyfiologifts, can, (if I be not greatly deceived), 
 
 be 
 
OF THE MALE SEX. 123 
 
 be without difficulty afcertained, from what has 
 been already faid, when treating of the defcent of 
 
 the teftes. 
 
 Thus, the tunica communis, for example, origi- 
 nates from the defcending (§ 502.) blifter-likc 
 fac or procefs of the peritoneum. 
 
 The propria tejiis, from that production of the 
 peritoneum, which mounting upward in the form 
 of a cylinder (§ 503.), invcfts the teftis itfclf from 
 its earlieft formation. 
 
 And, finally, the propria funiculi, from that 
 fold of the peritoneum, of which we have already 
 fpoken, and the {hort cylinder in which it termi- 
 nates previoufly to its embracing the teftis itfelf. 
 
 § 5*4- 
 Immediately to the teftis itfelf the tunica albu- 
 «inea is very clofcly attached, fomewhat after the 
 manner of a cortical covering. From this tunic, 
 blood-vefTels pafs into the pulp or body of the 
 tefticle, which confifts indeed entirely of innume- 
 rable vcffels, about a fpan in length, wound up 
 into fmall conglomerate lobules : thefe vefTels, of 
 which the fubftance of the tefticle is compofed, 
 are both fanguifefous and fecretinc - . the latter of 
 
 which 
 
i 24 OF THE GENITAL FUNCTION 
 
 which conduct the femen, when prepared, through 
 the vafcular net-work of Haller, and the vafa 
 defferentia of Graaf, into the beginnings of thofe 
 cones that form the epididymis. 
 
 § 5 l S- 
 That body which ranges along the fide of the 
 
 teflis, namely, the epididymis, confifts indeed of a 
 fingle veffel, about thirty feet in length, which at 
 one end (that for inftance denominated its head), 
 is diftinguiihed into about twenty fmall rolls or 
 cones, and at its other (inferior) extremity, called 
 therefore its tail, increafes gradually in thicknefs, 
 and thus forms by its continuation the vas de- 
 ferens. 
 
 § 5>6. 
 
 The two vafa deferentia afcending towards the 
 neck of the urinary bladder, and forming a junc- 
 tion beneath, or near to, the proftate gland, are 
 from hence bent backward, and expanded into 
 the vefizula feminales ; in fuch a mariner, how- 
 ever, that thefe veficulse, and the vafa deferentia 
 themfelves, open by two common orifices into the 
 urethra, jufl behind the caput gallinaginis. 
 
 < § 5*7- 
 Finally, the veficula fcminales themfelves, are 
 
 attached to the pofterior furface of the urinary 
 
 cyft, 
 
OF THE MALE SEX. 125 
 
 cyft, near to the inferior extremity, or neck, of 
 that organ : they are imbedded in a profufe quan- 
 tity of fat, and from their diverfified flexuofities 
 and numerous blind appendicula that moot oft 
 fomewhat in the form of ramifications, refemble, 
 in their general appearance, two fmall inteftines. 
 
 Thefe veficula? confifl of two coats, almoft of 
 the fame kind with thofe that enter, as formerly 
 mentioned, into the ccmpofuion of the gall blad- 
 der ; thus, the firft or external coat is more ro- 
 bufl:, and fimilar in its nature to fuch as are com- 
 monly denominated nervous ; while the fecond or 
 internal abounds with minute cells and pits, and 
 is every where divided, by means of proje&ing 
 eminences, into minute purfe-like cavities, per- 
 fectly fimilar to thofe that are fo confpicuous 
 about the neck of the gall-bladder. 
 
 § 5 i8. 
 
 In thofe organs and vefTels hitherto enume- 
 rated and defcribed, there is, even from the ear- 
 lieit years of puberty, a certain fluid fecreted 
 ilowly, and retained in fmall quantity, namely, 
 l\\efe?nen mafculinum ; a liquor extremely fingular 
 in its nature, and of the utmoft dignity and im- 
 portance in the animal economy : it exhibits to 
 the eye a milky colour, emits an odour entirely 
 peculiar, pofTefles a mucoid vifcofity, and is of 
 
 fuch 
 
n6 OF THE GENITAL FUNCTION 
 
 fuch remarkable fpecific gravity, as to furpafs, in 
 this refpeft, all other fecrcted humours belonging 
 to the animal body. 
 
 § 5*9- 
 
 A peculiarity of this fluid, which mud not be 
 paffed over in filenee, is, (as was fir A: obferved by 
 Lud. Ham at Dantzic, in the year 1677), tnat ic 
 is peopled by a countlefs multitude of microfcopic 
 animalcule, belonging to the fame order with 
 thofe called i??fufvria, and pofiefling different 
 figures, as they appear in the feminal fluids of dif- 
 ferent animals. In man (and alfo in the male 
 afs) the feminal animalcules exhibit oval figures, 
 furnilhed with tails of extreme minutenefs : thefe 
 animalcules are faidnot to be found in any, fave 
 found and prolific femen, fo that they appear to 
 conflitute a certain adventitious criterion of the 
 fertilizing maturity of this important fluid : we 
 have called the criterion derived from thefe ani- 
 malcules adventitious , and prefume it is fcarcely 
 neceffary, at this enlightened period, to repeat, 
 that they iliould not be accounted the refervoirs 
 of the fecundating principle, much lefs fhould they 
 be coniidered as the germs of future bomunculi, 
 fince fo many, and fuch weighty arguments and 
 obfervations have been lately advanced in fup- 
 port of a different do&rinc. 
 
 § 5 20 - 
 
OF THE MALE SEX. 127 
 
 This genital liquid being gradually collected in 
 the veficulse, which we have already defcribed, is 
 there retained till a future act. of excretion. By 
 fuch retention it fuffers changes very nearly re- 
 fembling thofe to which the bile is fubje&ed in 
 confequence of a flate of ftagnancy in its cyftic 
 refervoir ; thus, being gradually robbed of its 
 aqueous portion, it is more and more infpiflated 
 and approximated, as it were, towards a ftate of 
 concentration. 
 
 § 521. 
 
 For as the tgfles generally, together with the 
 cords by which they are fufpended, abound with 
 an aftoniihing aflemblage of lymphatic vefTels, 
 which ferve to re-convey from thence to the 
 blood a portion of fluid, impregnated with the 
 fpermatic contagion, and by this means aid and 
 facilitate the further fecretion of femen, on the 
 principle, and in the manner formerly laid down 
 (§ 476.), fo are the veficula feminaks themfelves 
 alfo provided with veffels of the fame kind, which 
 by abforbing the fubtle, though inert water, ren- 
 der the refidue of the feminal fluid more active 
 and efficacious. 
 
 § 5 22 - 
 
ii8 OF THE GENITAL FUNCTION 
 
 § 5 22 - 
 On this fubjett I doubt much whether or not, 
 
 in a healthy man, any genuine femen be ever ab- 
 forbed from the veficuls? feminales : — more dill, 
 whether or not, as is fometimes alleged, femen 
 thus abforbed could be carried immediately into 
 the neighbouring fanguiferous veins : — but mod 
 of all, whether or not fuch a feminal abforption 
 (admitting its real exigence) could poilibly aft as 
 an antidote againd exceflive venereal propenfities, 
 fince it appears evidently, on the other hand, that 
 this fame abforption would neceffarily operate as 
 an exciting caufe of unbridled and almod infuriate 
 luft : in quell of tefrimony to eftablifli the truth of 
 this latter proportion, we need only attend to the 
 phenomena of fuch animals as experience the ve- 
 nereal propenfity only at dated feafons of the 
 year, and compare them with the conditution of 
 thofe that have been reduced to the date of cas- 
 tration. 
 
 § 5*3' 
 To me indeed it appe.irs probable, that, for the 
 purpofe of moderating libidinous defires, man is 
 endowed with a far different prerogative (not 
 conferred on any other fpecies of animals with 
 which we are hitherto acquainted), namely, that 
 of nzfiurnal pollutions : thefe evacuations I there- 
 fore confider among the natural excretions of man 
 i — e vacua- 
 
OF THE MALE SEX. 129 
 
 ' — evacuations by which (as they occur at longer 
 or fhorter intervals, according to the varieties of 
 temperament and conftitution), he is relieved from 
 a troublefome and orhenvife urgent impreflion 
 produced by an abundant accumulation of femen. 
 
 § 5H- 
 
 It miift be obferved, however, that the femen 
 mafculinum is never excreted in a ftate of entire 
 purity, but is always blended with more or lefs of 
 what is ufually denominated liquor projlaia (i. e. 
 the liquor of the proftate"). With regard to the 
 external habit and appearance of this laft men- 
 tioned liquid, it bears a very ftriking fimilitude to 
 the albumen or white of eggs. This peculiar 
 liquor derives its name from its immediate birth- 
 place or fource, which is a body of confiderable 
 magnitude, and of a fingular and very compact 
 parenchymatous texture, fituated between the ve- 
 fuula fcminalcs and the bulb of the urethra, and 
 is ufually defignated by the name of glandula pro- 
 f.aia. The excretory avenues of this liquor have 
 not yet been fatisfaclorily inveftigatcd and afcer- 
 tained, unlefs (as appears probable) they commu- 
 nicate with the duel: of the caruncula feminalis, 
 the orifice of which opens into the urethra be- 
 tween the two mouths of the avenues leading 
 from thofe minute veficles deftined for the recep- 
 
 vol. 11. I tion 
 
i~o OF THE GENITAL FUNCTION 
 
 tion and temporary retention of the fertilizing 
 fenen, (§ 516). 
 
 525. 
 The urethra in man is dellined as a common 
 conduit or emiffary duct, to three different kinds 
 of fluids, namely, the urine, the femen, and the 
 liquor of the proftate gland. It is lined internally 
 with a mucus which originates from an immenfe 
 number of finufes, that are every where difperfed 
 throughout its canal. It is furrounded by a fub- 
 ftance of a fpongy texture, to which are fubjoined 
 two other bodies, fimilar in ftrutlure but far fnpe- 
 rior in fize, (called corpora caverno/a), that con- 
 ftitute the principal part of the male penis ; an 
 organ which is terminated anteriorly by the glans, 
 and wholly invefted by a very tender and pliable 
 portion of ikin entirely deilkute of all appearance 
 of fat. This Ikin forms the prepuce by its at- 
 tachment round the corona^ or circular bafe of the 
 glans, and plays over this body with a free motion, 
 fomewhat like the palpebrce over the ball of the 
 eye. The interior duplicative of the prepuce, 
 having affumed a different appearance, is reflected 
 over the glans itfelf, (fomewhat like the adnata 
 over the eye) and is furniihed around the corona, 
 with an immenfe number of the finall glands of 
 Liitrius, (analogous to the Meibomian glands of 
 
 the 
 
OF THE MALE SEX. 13 i 
 
 the palpebrce) that give birth to a matter of an 
 un&uous but very lingular nature. 
 
 § 5 2 6- 
 The male penis, thus organifed and conftructed 
 agreeably to the preceding defcription, pofTefifes a 
 faculty of ere&ion, /. c. in confequence of an 
 encreafed conge/lion and impetuous effufion (for 
 congeftion alone will not explain the phenomenon) 
 of blood into the corpora cavernofa, the penis 
 fwells, becomes rigid, and changes its former 
 pofition, but fuffers again a deturrefcence and 
 collapfe by a reabforption of the fuperfluous por- 
 tion of this diftending fluid. 
 
 § 5*7' 
 When the penis rcfumes its flaccid condition, 
 it fuffers a Angularly circuitous flexion, at the 
 place where it originates from the neck of the 
 bladder. In this Mate it is, indeed, extremely 
 well calculated for the excretion of real urine, but 
 quite unqualified for the emiffion of femen, as the 
 beginning of the urethra forms now a more acute 
 an^le with the fmall orifices of tie veficulse femi- 
 nales. 
 
 § 5*8- 
 When a gradual intumefcence of the penis com- 
 mences, there occurs firft an effufion of the liquor 
 I 2 furn ifhed 
 
! ;2 OF THE GENITAL l 7 UNCTION, &c. 
 
 furnifhed by the proflate gland, which is often- 
 times eliminated unmixed, but fcarely ever along 
 with the urine. Of this liquor the primary defti- 
 nation is, to be ejected, in conjunction with the 
 fcmlnal fluid itfelf ; either, that it may, by its 
 albuminoid lubricity, qualify the fluggifli tenacity 
 of the latter fluid, and thus facilitate and promote 
 its ejection ; or that it may itfelf contribute, in a 
 certain degree, towards the procefs of generation. 
 
 § 5*9- 
 The emiffion itfelf of the male femen is excited 
 
 as well by the immediate impreffion aiifmg from 
 an abundant accumulation of this fluid in its ap- 
 propriated receptacles, as by the genuine fexual 
 injiincl ; it is accomplifljed, firft, by a very flrong 
 ereclion of the penis, which, while it obftructs the 
 paflage of the urine, paves as it were, on the 
 other hand, a more direct and ready way for the 
 tranfition of the femen ; to which we may fubjoin, 
 as co-operating caufes, a certain fpafmodic con- 
 traclion of the veficulce feminales, a convulflvc 
 action of the levator ani, and accelcratorcs tiring, 
 and finally, a general fuccujfion, of the whole ner- 
 vous fyflcm, gentle indeed in degree, and tranfient 
 in exiftence, but yet of an epileptic nature, and 
 confiderably deprefling, in its effects, on the ener- 
 gies of the fyftem. 
 
 SECT. 
 
OF THE GENITAL FUNCTION, fc?V. 133 
 
 SECT. XLI. 
 
 OF THE GENITAL FUNCTION OF THE FEMALE SEX 
 IN GENERAL. 
 
 § 53°' 
 
 l\.S the male organs of generation are 
 naturally calculated to give, f ) are the female to 
 receive, and in the two fexes thefe organs are, in 
 a general point of view, widely different from 
 each other. It mud be ohferved, however, that 
 in the general flruclure of certain parts, thefe two 
 kinds of organs exhibit no fraall degree of reci- 
 procal fimilitude. Thus beneath the pubes (the 
 llruclure of which has been already a fubject of 
 tranfient attention (§ 36.) the clitoris which lies 
 concealed in the fuperior commiflure of the labia., 
 refembles the male penis in more refpe&s thau 
 one, but is not furnilhed with a urethra, is there- 
 fore imperforate, and, (when not of a preter- 
 natural proportion,) is remarkably fmall. It is 
 faid, however, that this organ preferves, occafion- 
 ally, even in adults, the fame proportional Cze, 
 which, as formerly obferved, is fo extremely 
 confpicuous in the clitoris of the female embryo, 
 ($ 492.) Hence appears, in all probability, to 
 have originated mod of thofe obfeene and fabulous 
 I 3 dories, 
 
i 3 4 OF THE GENITAL FUNCTION 
 
 ftoricSj refpetting the exigence of hermaphrodites. 
 This organ confifls alfo, like the male penis, o? 
 corpora cavernofa, like it, is capable of erection, 
 like it, is invefled by a prepuce, and furnifhes, 
 finally, an unctuous matter not diffimilar to that 
 ofLittrius, (§ 525). 
 
 § SV- 
 From the clitoris defcend the nymph a, acquiring, 
 
 alfo, occafionally, an enormous and preternatural 
 magnitude, (which excefs has, in like manner, not 
 unfrequently given rife to extraordinary and fabu- 
 lous reports) : they poflefs, in common with the 
 clitoris the mod exquifite degree of fenfibility; 
 and appear to give direction to the ftream of urine 
 when discharged, as the orifice of the urethra, 
 (a tube extremely inert in the fema'e fex, and, in 
 the moil highly fmimed and perfect examples, 
 ciliated or fiinged in a very Angular manner), lies 
 hid, as it were, in a fojfla formed by their two 
 bafes, 
 
 § S3 2 - 
 Beneath this orifice is fituated the opening of 
 the vagina itfelf, environed by crypta of various 
 kinds, fucli, for example, as the urethral lacuna 
 of Graaf, and the mouths of what are improperly 
 and even abfurdly termed, the proilare glands of 
 Cafp. Bartholin, &c, with the unguen-Iike mucus 
 
 of 
 
OF THE FEMALE SEX. 135 
 
 of which, thefe obfcene parts are moiftened and 
 lubricated. 
 
 § 533- 
 Over the very threshold or entrance of the 
 vagina is expanded a weblike production denomi- 
 nated the hymen. This is a membrane, the exis- 
 tence of which in an unlacerarcd condition, is 
 confidered as a fure badge of fpotlefs virginity — 
 a membrane beftowed exclufively on the female 
 of the human fpecies, and of which no phyfical 
 deflination has been yet unequivocally afcertained. 
 
 The fringes or refidual fragments of this mem- 
 brane, after laceration, are gradually converted 
 into what are denominated caruncula myrtiformes 9 
 bodies quite indefinite in point of number. 
 
 § 534- 
 From the immediate feat of thefe minute myrti- 
 form bodies afcends, between the urinary cyfl and 
 inteflinum rectum, the vagina, a tube compofed 
 of a cellular parenchyma, interfperfed with an 
 infinitude of fmall blood-vefiels. At its inferior 
 extremity the vagina is encircled by a mufcle 
 denominated conftriclor cunni ; more internally it 
 is lined by a very (oft and delicate coat, which is 
 characterifed by two extremely elegant columns of 
 ruga or wrinkles, namely, the anterior and pofie- 
 I 4 rio.r ; 
 
i 3 6 OF THE GENITAL FUNCTION 
 
 rior ; from thefe columns a fine mucus is con- 
 flantly difcharged, deflined to lubricate the cavity 
 of this highly important canal. 
 
 § 535- 
 The vagina, at its upper and interior end, re- 
 ceives and embraces, finally, the uterus, an organ 
 attached on each fide to, and thus fufpended by, 
 the Ugammta laia. 
 
 The cylindrical neck of this organ being thus 
 embraced, as it were, by the vagina, is perforated 
 by a narrow canal, which, like that of the vagina, 
 is impreffed by a fiiuular apparatus or arrange- 
 ment of rugefirics, designated by the name of 
 arbor vit<s : of thi s canal the two extreme orifices, 
 more efpecially the fuperior or internal, are over- 
 fpreacl, for the mod part, with a quantity of tena- 
 cious mucus. 
 
 § $36- 
 
 The fubflance of the uterus is altogether fin- 
 gular in its nature, confuting of a peculiar paren- 
 chyma, very denfe and compact, and interwoven 
 wah an infumude of blood-vefiels (running in 
 ferpentine mazes of aitonifhing intricacy) of which, 
 the veins are wholly deftitute of valves. This 
 organ is doubtlefs furnifhed, in like manner, with 
 an apparatus of lymphatic vefTels : it abounds 
 
 with 
 
OF THE FEMALE SEX. 137 
 
 with a countlefs number of nerves, through the 
 medium of which, it preferves fuch a» aftonifliing 
 fympathy with the other parts of the fyftem. 
 
 § 537- 
 Externally the uterus is invefted by the perito- 
 neum, while its minute internal cavity is lined, 
 efpecially at its fundus^ by a very foft and tender 
 membrane, of a fpbngy texture, which, as fome 
 phyfiologifts allege, confifts of colourlefs veffels, 
 while others pronounce it to be compofed of lym- 
 phatic abforbents. 
 
 s 538- 
 
 With regard to the mufcular texture attributed 
 to this organ by fome phyfiologifts, and ftrenu- 
 cufly denied again by others, I muft take the 
 liberty of obferving, that notwithstanding the 
 number of uteri which I have examined with the 
 utmoft care and attention, both in an impregnated 
 and an unimpregnated (late, (in each of which I 
 have had repeated opportunities of examining this 
 organ, not only in a prepared condition, but alfo 
 in fubjecls recently dead), I have never yet been 
 able to deteft, in them, any portion that exhibited 
 obvious and unequivocal figns of mufcularity. On 
 the other hand, I am daily more and more per- 
 fcaded, that the uterus, poiTeffing no mufcular 
 fibres, is deflitute alfo of true irritability (§ 307), 
 
 and 
 
tjS OF THE GENITAL FUNCTION 
 
 and owe:, entirely to a vita propria, or fpecifk life 
 (§ 47. ), all its peculiar motions and functions, 
 which cannot, indeed, with the fmalleft femblance 
 of propriety, be derived from any of thofe ener- 
 gies that are common to what we formerly term- 
 ed the paries fimilares^ or fimiiar parts of the 
 body (§ 43, 46). So very fingular and unac- 
 countable did the motions and functions of the 
 uterus appear to the phyficians and phiiefopfv --. 
 of ancient times, that they were led to coufidei 
 this organ as a fmaller animal contained within a 
 larger. 
 
 5 539- 
 
 From the ancles on each fide of the lacunar- 
 or fundus uteri, arife what are called the Fallopian 
 lubes. Thefe are two very narrow and tortuous 
 canals, that run in the fuperior duplicature of the 
 ligavienUi lata : they are fimiiar in texture to the 
 vagina iifelf, except, that being internally deffitute 
 of valves, they are lined with a kind of fpongy 
 fiefli, of a very foft and tender confidence. 
 
 ^ § 54°- 
 The extreme orifices of thefe tubes, that regard 
 the abdominal cavity, befides being much more 
 capacious than thofe which open into the uterus, 
 are alfo edged round by fringe or finger-like_yf;«- 
 J?ria, of a truly fingular and elegant flruclure. 
 
 The 
 
OF THE EEMALE SEX. 139 
 
 The offices which thefe fimbria? are deftined to 
 perform, in the bufmefs of conception, appear to 
 be indeed of no fmall degree of importance ; thus 
 bein?; rendered, during the venereal orgafm, 
 equally turgid with the tubes themfelves, they 
 evi lenrly embrace, in this fcate, the ovaria that 
 are fituated in fome meafure beneath them. 
 
 § 54*. 
 The ovaria themfelves, or (he female te/ies, as 
 
 they were called previoufly to the time of Steno, 
 befides a tenacious and fomewhat tendon-like in- 
 volucrum, confift alfo of a denfe and decuflating 
 cellular membrane, which inclofes in each ova- 
 rium about fifteen of thofe minute bodies denomi- 
 nated the ovida, or little eggs of Graaf : thefe 
 ovula contain each a fmall veficle, or rather drop 
 of ferum, faintly yellowiih in its colour, and of an 
 albuminous nature, which, if the recent ovarium 
 be immerfed in boiling water, is reduced, like the 
 genuine white of eggs, to a ftate of complete co- 
 agulation. 
 
 § 542. 
 An albuminoid drop of this kind appears to be 
 indeed the principal fluid which the female con- 
 tributes towards the procefs of conception ; for it 
 appears extremely probable, that, throughout the 
 progreffive courfe of what are termed the prime 
 
 or 
 
f 4 o OF THE GENITAL FUNCTION, fefr. 
 
 or better years of life, thefe final! drops arrive at 
 complete maturity in gradual fucceflion, fo that 
 each one, in its turn, looks as it were through the 
 involucrum, by which the ovarium is enveioped, 
 till it is able finally to burfl the parietes of its 
 prifon, and thus be received by the abdominal 
 orifice of the Fallopian tube. 
 
 § 543- 
 But befides this minute albuminous drop that 
 thus bnrfts from the volume of the ovarium, it 
 appears that there occurs alfo, during the vene- 
 real ceftrum, an effufion of another liquor, which 
 ancient phyfiologifts very improperly and errone- 
 ously denominated the female femen. Refpecling 
 the nature, however, the fources, and the univer- 
 ial prefence of this humour, we are able to pro- 
 pcfc nothing more determinate or faiisfaftory than 
 we can advance with regard to its deftination 
 and ufes. 
 
 SECT, 
 
OF MENSTRUATION. 141 
 
 SECT. XLII. 
 OF MENSTRUATION. 
 
 § 544- 
 
 xjl VERY frequent and highly import- 
 ant function of the uterus in the female of the hu- 
 man fpecies is, to difcharge monthly a tributary 
 effufion (called therefore caiamema), during the 
 tedious and momentous term of about thirty years. 
 This is a painful condition of evidence, to which 
 nature has not fubje&ed any other genus of her 
 fubje&s, throughout the wide and diverfified range 
 of the whole animal kingdom ; fo that to ufe the 
 words of the eloquent Pliny " the only mcnjlruous 
 " animal in nature is woman." From this con- 
 dition, on the other hand, painful as it is, nature 
 has not exempted the females of any of the known 
 nations of the globe, but has ftamped it with 
 the facred character of an effential requifite — of 
 a genuine fine qua ?ion, in rendering the female 
 fex competent to the propagation of their fpecies. 
 
 § 545- 
 
 The commencement of this lingular function 
 
 generally takes place, in our climate, about the 
 
 fifteenth year of life, and is, for the mod part, 
 
 preceded by various and unequivocal fymptoms 
 
 of 
 
142 OF MENSTRUATION 1 . 
 
 of plethora, fuch as congeftion and anxiety about 
 the bread, fenfe of tenfion and weight in the lum- 
 bar region, hffitude or wearinefs of the limbs, &:c. 
 Cn the firft appearance of the catamenia, the ge- 
 nital organs, in the beginning of the attack, ufu- 
 ally difcharge a humour of a pale reddifh cad ; 
 this is gradually fuceeeded by a liquid of a more 
 intenfely florid and finguineous colour, which 
 terminates, at length, in an effufion of genuine 
 cruor or red blood. This fpontaneous, though 
 gentle difcharge of blood, is kept up for the 
 term of feveral days, and is, in the mean time, 
 accompanied by a gradual ceffation of all thofe 
 diftreffing fymptoms of which we have juft exhi- 
 bited a partial detail. 
 
 § 546. 
 
 From the time of its firfl occurrence, this con* 
 ftitutional hemorrhagy (as it may, with fufHcient 
 propriety, be denominated) becomes regularly pe- 
 riodical : thus its future paroxyfms return uni- 
 formly about the expiration of every fourth week, 
 and at each recurrence, the evacuation continues, 
 at a mean calculation, about fix days j during 
 which term, a healthy female is fuppofed to dif- 
 charge from eight ounces to an entire pound of 
 blood. 
 
 § 547- 
 

 OF MENSTRUATION. 143 
 
 § 547- 
 It is proper, however, to obferve, that this func- 
 tion is fubjeft, for the moft part, to an entire in- 
 termiffion, during the ftate of female pregnancy, 
 and the term of maternal lactation. 
 
 The final cejfation of the catamenia occurs after 
 their difcharge has continued, at ftated periods, 
 about the fpace of thirty years, which term of 
 lime is completed, in our climate, about the 45th 
 year of life. 
 
 § 548. 
 The fources of the catamenial dsfciiafge have 
 been referred by fome to the veffels of the vagina, 
 and by others (with fuperior weight of evidence 
 on their fide) to thofe of the uterus : for with 
 regard to thofe examples commonly adduced in 
 fupport of the former opinion, where women, 
 although pregnant, poffefling an imperforated 
 uterus, or diftrehed by a prolapfus of that organ 
 in "an inverted ftate, have notwithstanding men- 
 flruated with uniform regularity, they tend to 
 prove nothing tlfe than the powerful efforts of 
 the vis medicatrix natures t which in cafes where 
 the main llreet is obftru&ed, is (to adopt a vulgar 
 mode of expreffion) fortunately acquainted with 
 the routes through lanes and alleys. There are 
 on record, on the other hand, numerous diffe&iom 
 
 of 
 
r 4 4 of menstruation: 
 
 of females who died during the term of a£hial 
 menftruation, from which it was unequivocally 
 afcertained, that the catamenial difcharge had 
 been wept out of, or difcharged in a flillicidious 
 manner from, the uterine cavity of thefe fubjects : 
 not to mention the arguments drawn a priori (as 
 metaphyficians exprefs themfelves), from which it 
 appears highly probable, that the end and deto- 
 nation of the menfes are, to prepare the uterus 
 for a date of future pregnancy, and render it more 
 fit for the regular nutrition of the foetus. For 
 the very fame reafons alfo this hemorrhagy ap- 
 pears to be attributed, with more propriety, to 
 the arterial than to the venous veffels of the 
 uterus. 
 
 § 549- 
 With regard to the caufes of this periodical and 
 perennial hemorrhagy, they are ftirouded by fo 
 thick a curtain of obfeurity, and their invefligation 
 is attended with fuch momentous difficulties, that 
 in the profecuticn of this fubjecl, we have not a 
 fufficient power of evidence to conduct us over 
 the arduous mound which divides the twilight- 
 region of probability from the more luminous realm 
 of demonjl ration^ and certainty. 
 
 The proximate caufe phyfiologifts fuppofe to be 
 a certain topical congeflion or plethora, to which 
 
 i opinion, 
 
OF MENSTRUATION. 145, 
 
 opinion, indeed, the fymptoms of the impending 
 catamenia, together with the profufion and nature 
 of the uterine blood-veffels fitly enough correfpond, 
 and in favour of the truth of which they exhibit 
 a degree of teftimony fufficiently refpectable. 
 
 Among its remote caufes it will be proper to 
 enumerate, the ereft pofition of the body (a pofi- 
 tion that ferves as a char acleri flic diftinttion be- 
 tween the human fpecies and moil other defcrip- 
 tions of animals) ; to which we mud add, the 
 fmgular parenchyma of the uterus itfelf, and, 
 finally, the vita propria or fpecific life of that 
 important organ. 
 
 With regard to the caufe of the periodical re- 
 currence of the catamenia, it will here be better, 
 much better to acknowledge our ignorance, than 
 to indulge ourfelves in vague and vifionary con- 
 jectures, and fportively range through the fair but 
 fallacious fields of mere fpeCulative hypothefis. 
 For I am, indeed, perfuaded, that all thofe peri- 
 odical phenomena which occur in the animal body, 
 whether in health or difeafe, (provided their in- 
 terval extend beyond the term of 24 hours) mud: 
 be ranked with thofe latent myjleries of animal 
 nature, which nothing but time; talents, and in- 
 duftry, will be ever able to develope. 
 
 vol. 11. K SECT. 
 
i 4 <6 OF THE MILK. 
 
 SECT. XLIII. 
 OF THE MILK. 
 
 § 55°- 
 
 JjETWEEN the female mamma and 
 uterus (the former of which were, by the philo- 
 fopher Favorinus in his communications to Gellius, 
 elegantly and emphatically denominated, the fa- 
 cred fountains that nouriJJj the human race, there 
 exifts fuch an extremely potent fympathetic con- 
 ne£tion, that thefe two organs may be faid to be 
 iiidiiTolubly aifociated, or to accompany each other 
 hand in hand, in their phenomena and functions. 
 Thus, during the tender period of infancy, fo 
 great is their imbecility and want of action, that 
 they are capable of performing fcarcely any func- 
 tion at all : as the years of puberty advance, 
 they begin, at the fame time, to acquire vigour 
 and activity, fo that on the firft eruption of the 
 catamenia, a fwclling of the mamma? or breads 
 mes alfo evident to the fenfes. Throughout 
 riie fubfequent periods of life thofe two organs 
 are either fubjectcd to fimultaneous and fimilar 
 changes, as when the breads become turgid and 
 difcharge mil!: during the progrefs of pregnancy ; 
 or experience alternate and oppofite aifeftions, 
 
 inftances 
 
OF THE MILK. 147 
 
 inftances of which we have in the fufpenfion of 
 the catamenia during the term of lactation, a more 
 copious effullon of the lochia when the fecretion. 
 of milk does not commence at the ufual period, 
 §cc. And, laftly, on the unwelcome acceffion of 
 old age, both the preceding functions fail at the 
 fame time, fo that when the catamenia finally 
 retreat, never again to return, the uterus and 
 mammae become equally flaccid, inert and wholly 
 incapable of their former action. A great variety 
 of pathological phenomena, eafily obfervable in 
 cafes of irregular menflruation, mfltfor albus, and 
 other fimilar affections, (hall be in filence preter- 
 mitted, although they furnifh the molt potent and 
 unequivocal teftimony in confirmation of the 
 fympathy now finder consideration, namely, that 
 which exifls between the uterus and mammas. 
 
 § S5 1 - 
 
 Nor will this intimate fympathetic connection, 
 which fublifts between the uterus and ma ma?, 
 appear in any meafure extraordinary or furprifing, 
 when we confider, that all thofe diveriified jburces 
 of phyiiological confent, particularly enumerated 
 on a former occafion (§ 54), jointjy co-operate in 
 the eflablimment of fuch connection between thefe 
 organs of the female thorax and abdomen. 
 
 K 2 § 552. 
 
t 4 8 OF THE MILK. 
 
 The anaftomofis obfervable between the internal 
 mammary and epigaftric arteries, was formerly 
 efteemcd a circumftance of the higheft importance 
 in the explication of the foregoing confent. Al- 
 though phyfiologifts have hitherto attributed by 
 far too much to this remarkable anaftomofis, yet 
 that it ought not to be entirely excepted from the 
 number of co-operating caulks will appear ex- 
 tremely probable to any one who confiders the 
 obvious and wide difference which exifts between 
 the diameter of the epigaftric artery in a (late of 
 pregnancy, and that of the fame vefTel during the 
 period of laclation. 
 
 § 553- 
 The two preceding organs, namely, the uterm 
 
 and mammae, pofTefs alfo, in common with each 
 other, this further property, that they both retain 
 and exhibit a friendly affinity or attraction for the 
 chyle, by which means they folicit that fluid to 
 themfelves, efpecially during the term of preg- 
 nancy, and thus convert it to peculiar ufes. 
 
 § 554- 
 The female mamma? confifts of a placentoid con- 
 geries of fmall conglomerate glands, diftinguiflied 
 by numerous Juki into lobes of confiderable mag- 
 nitude, and completely embedded in a mafs of 
 
 adipofe 
 
OF THE MILK. 149 
 
 adipofe fubftance. On the anterior part, in particu- 
 lar, a protuberance is formed by a more firm feba- 
 cious cufhion, which is covered and protected by 
 a cutis of a very tender and delicate texture. 
 
 S 555- 
 Each one of thefe lobes is compofed of a num- 
 ber of inferior lobuli, and thefe a^ain of what are 
 denominated acini or kernels, in which the incipi- 
 ent radicles of the lacliferous duels originate, and 
 from the extreme ra?nuli or branches of the in- 
 ternal mammary artery extract a chyliform fluid, 
 which they are particularly deflined to convey. 
 
 §556- 
 
 Tb? fine filiform radicles uniting fucceffively 
 in their onward palfage, terminate finally in lead- 
 ing trunks, correfponding in number to the prin- 
 cipal lobes ; fo that they generally amount, in 
 each mamma, to about fifteen or perhaps a few 
 more. Thefe trunks are frequently dilated into 
 more fpacious finufes, but never appear to be con- 
 nected by genuine anaftomofes. 
 
 § 557' 
 
 Thefe trunks terminate in excretory canals of 
 
 exquifite delicacy and tendernefs, which, being 
 
 collected and clofely approximated towards the 
 
 centre of the mamma, form, by the co-operation 
 
 K 3 of 
 
150 OF THE MILK. 
 
 of cellular membrane, the patilla or nipple. This 
 projecting papilla being interfperfed and minutely 
 pervaded by an infinitude of blood-veffels and 
 nerves of extreme finenefs and fubtlety, is ful je£l 
 to a very Angular fpecies of erection on the accef- 
 fion of certain external (limuli. 
 
 § 558. 
 
 The nipple is furrounded by an areola or fmall 
 circle, which is confpicuous, as well as the pa- 
 pilla itfelf, on account of the fingular colour of 
 the reticulum mucofum expanded immediately be- 
 neath the epidermis or cuticle. This areola is 
 further diftinguifhed by fmall ftbaceous follicles, 
 and likewife by a few minute lactiferous ducts with 
 which it is in fome inllances pervaded. 
 
 § 559- 
 
 The human mV.h which is fecreted in the glan- 
 dular organs hi frert'o defcribed, is a fluid of a 
 well known coloiir, fomewhat watery, and con- 
 taining alfo a fmall portion of oil : this liquid is 
 fweetilh to the t ;fte, extremely mild, and refem- 
 bles, in its general properties, the milk of do- 
 meftic animals belonging to the clafs mammalia, 
 except that it is nor, like the latter, fubjtel to co- 
 agulation from the action of acids, nor does it ex- 
 feifcit, to the moll attentive obfervation, the flight- 
 eft veflige of volatile alkali. 
 
OF THE MILK. 151 
 
 When coagulated, however, by the influence 
 of fpirits of wine, it exhibits the fame component 
 elements of which the milk of thofe other animals 
 already mentioned is known to coniifl. For be- 
 sides the watery halites which human milk emits 
 when recently drawn, and yet in a tepid (late, its 
 Jerum, feparating from the cafeous or cheezy por- 
 tion, contains alfo the fugar of milk, which is 
 compofed of the faccharine acid united to a calca- 
 reous earth, together with certain additional parts 
 oily and mucaginous in their natures. Laftly, it 
 contains alfo a crtam or butter-like portion, the 
 globules of which are* extremely various and 
 changeable in their magnitudes, ihus vibrating in 
 their diameters from the T J.th to the »2vth part 
 of a line. 
 
 ^ 561. 
 
 The analogy which is obferved to exifl between 
 chyle and blood, and between each of thefe 
 liquids and milk itfelf, renders it fufliciently pro- 
 bable, that this laft humour, (which conttitutes 
 at prefent the more immediate object of our con- 
 fideration), is a fpecies of chyle renovated from 
 the volume of b/osd, or rather feparated from this 
 crimfon fluid (with which it had jufl formed a 
 'junction) previouily to its final and complete afli- 
 milation. This opinion, befides other arguments 
 K 4 win 
 
 r r 
 
1 52 OF THE MILK. 
 
 which might be advanced in its favour, derives 
 powerful testimony from the fpecific taftes of feve- 
 ral kinds of aliment being not unfrequently per- 
 ceptible in the milk of nurfes ; and alfo from the 
 chyle-like habit and conftitution of that watery 
 milk, which not unfrequently exudes from the 
 breafts of females during the term of pregnancy, 
 and for a fhort time after the period of parturition. 
 
 § 5^2. 
 The reafon why, during the progrefiive con- 
 tinuance of lactation, this bland food of the 
 foetus becomes gradually more and more infpif- 
 fated, rich and oily, mufl be referred chiefly to 
 the lymphatic veins, with which the mammae 
 plentifully abound : Thus the more profufe the 
 afflux of milk, and the greater length of time this 
 afflux has continued, with the more power and 
 uniformity do thtfe lymphatics abforb its ferous 
 parts, and convey them back to the mafs of cir- 
 culating blood, by which means they furnifh the 
 moil effective aid to the whole procefs of this fe- 
 cretion (§ 476). 
 
 § 563- 
 
 During the firft days after parturition, a very 
 
 profufe fecretion of milk occurs, and (provided 
 
 the mother /aflates, i. e. fuckles her child) is pro- 
 
 * moted and kept up by the faction of the infant 
 
 itfelf, 
 
OF THE MILK. 153 
 
 itfelf, Until i-he catamenia return, which had for 
 a long lime ceafed to flow (^ 547). The exig- 
 ence of milk in the breads of virgins truly invio- 
 late, in the breads of new-born infants of each 
 fex, and even in the breads of men themfelves, 
 as well as in thofe of other male animals belong- 
 ing to the clafs mammalia, is a phenomenon which 
 not unfrequently prefents itfelf to our obfervation. 
 
 § 564- 
 
 A profufe quantity or accumulation of milk in 
 the breads effectually fohens its own final excre- 
 tion, whence a fpont neous difcharge of that fluid 
 is obferved frequency to occur ; this difcharge 
 is further promoted by the external preflure of 
 the marnmce, as well as by the faction of the 
 tender infant. 
 
 SECT. 
 
154 OF CONCEPTION 
 
 SECT. XLIV. 
 OF CONCEPTION AND PREGNANCY. 
 
 § 565. 
 
 AVING hitherto confident! the 
 ftrufture of the genital organs peculiarly belong- 
 ing to each fex, we come now to treat of thofe 
 functions or proceffcs which conftitute the imme- 
 diate end and destination of thefe organs, namely, 
 conception and the propagation of the human race. 
 In the order and progrefs of our enquiries into 
 thefe abflrufe and interefting fubje&s, we will firhV 
 give a plain and fimple narrative of the feveral 
 phenomena obfervable in this admirable and truly 
 divine procefs ; and then attempt an inveftigation 
 of the energies from which thefe phenomena 
 appear to originate. 
 
 § 566. 
 
 It is, in the firfl place, neceffary to obferve, 
 that the fubjetls of the human race have not, like 
 mod: other animals (all thofe, if I be not deceived, 
 belonging to the clafs mammalia, man alone ex- 
 cepted), any peculiar feafon of the year in which 
 they are unufually prone to venereal enjoyments, 
 
 but 
 
AND PREGNANCY. 155 
 
 but are equally liable to experience, at every pe- 
 riod and under every varying temperature, the 
 gentle glow of love's diffufive fires. 
 
 § 567- 
 
 When therefore, the female of the human fpe- 
 cies a ;m.ts r he embraces of the male, and while 
 they are thus mutually enwrapt in the ardour of 
 th.u animal inlfinct. which far furpafTes every other 
 both in the univerfaliiy and the potency of its fway, 
 the uterus (if we be not greatly dectived) being 
 rendered turgid by a fpecies of inflammatory or- 
 gafm, and animated at the fame time by its own 
 fpecifie life, (§ 538.) drinks in, as it were, the 
 feminai fluid emitted by the male, and effects a 
 fvnehronous difcharge of that which is proper to 
 itfeh (§ 543) ; the fallopian tubes become at the 
 fame time rigid, and with their fimbricated extre- 
 mities embrace the adjacent ovaria : in one or the 
 other of thefe ovaria one of the veficula? GraafRante 
 is lacerated or burn 1 , fomewhat after the manner 
 cf an abfeefs advanced to a (late of complete ma- 
 turity, and the albuminoid liquid which this rup- 
 tured veficula contained, being abforbed by the 
 orifice of the embracing tube, is thus conveyed 
 onward into the cavity of the uterus. 
 
 § 568. 
 

 1)5 OF CONCEPTION 
 
 §568. 
 This liquid being difcharged from the ovary, 
 ihe external lips of the final 1 and recent wound 
 through which it was emitted, are again united 
 by a fine cicatrix, while the remaining delicate 
 vafcular membrane in which the liquid had been 
 enclofed, conrtitutes what is called corpus luteian. 
 This body appears to be at firft hollow and filled 
 with a quantity of plallic lymph, that in procefs 
 of time is converted into a flefhy nucleus, inverted 
 by a firm cortex or membrane, which is inter- 
 fperfed by a variety of minute, yet remarkable 
 blood-veffcls. 
 
 § 5^9- 
 The uterus being thus impregnated, the canal 
 leading through the cervex or neck of that organ, 
 efpecially towards its fuperior or internal orifice, 
 (§ 535-) ls completely obftructed, in fuch a man- 
 ner, that according to the common courfe of 
 nature there is no room left for fuperfcetation. 
 
 § 57°- 
 The internal fuperfices of the uterus appears to 
 
 be inverted with a flight inflammatory cruft of 
 
 plaftic or coagulable lymph, (§ 19.) which forms 
 
 the membrana caduca, (called alfo membrana de- 
 
 eidua), of Hunter. 
 
 This 
 
AND PREGNANCY. 157 
 
 This membrane-like cruft phyfiologifts diflin- 
 guifli into two laminse or layers; one of which, 
 denominated lamina crajfa, inverts the whole 
 internal cavity of the uterus, except the imme- 
 diate openings into the fallopian tubes, and the 
 internal orifice of the cervical canal; while the. 
 other is the growth of a later period, and appears 
 to be generated in the following manner, viz. 
 after the formation of the ovulum is fairly com- 
 menced, and this miuute body begins to ftrike its 
 roots into the decidua, already mentioned, this 
 fecond lamina begins gradually to expand, and is 
 thus continued from the place where thofe minute 
 roots begin to pullulate, over the remaining 
 fuperficies of the ovum, whence it has been 
 diftinguilhed by the name of caduca reficxa. 
 
 § 57 1 - 
 
 Although the ovulum be formed itfelf at an 
 earlier period than the embryo which it is deftined 
 to contain, yet the real organization of the former 
 feldom commences earlier than the termination of 
 the firft week after conception. For I very much 
 doubt, whether or not, at an earlier period than 
 this, any unequivocal veftige of an organifed body 
 has been ever obferved in the impregnated uterus 
 •f the human fubjeft. 
 
 S 57*< 
 
158 OF CONCEPTION. 
 
 § 57 2 - 
 This ovulum, or little egg, is compofed of two 
 proper membranes, befides that external adven- 
 titious covering, which it derives from the caduca 
 of Hunter. 
 
 The proper membranes are, firft, an external 
 one, apparently deftitute of bloo.l vcffcls, which 
 forms the chorion of modern writrrs. From the 
 earlieft origin of this membrane :; great part < f its 
 external fuperficies is beautifully f t with kn t like 
 flocculi or minute piles of inconreiv • 'e elegance, 
 from whence it has been called, chorion mufeofum 
 feu frondofum, i. e. the mo fs -like, or leaf-like, 
 chorion. By means of thofe delicate piles, which 
 conftitute the rudiments of the foetal part of t e 
 future placenta, the ovulum is inferted (as if by 
 roots) into the decidua uterina. (§ 569. J 
 
 The other membrane, lying interiorly, is deno*- 
 minated the amnion, which is alfo defliture of 
 blood-vefTels, (§ 5.) it is indeed delicate and ten- 
 der, but yet of remarkable tenacity and ftrength. 
 
 § 573' 
 For a few weeks after the firfl formation of the 
 
 ovulum, its two proper membranes differ v<ry 
 widely from each other in point of fize, the 
 chorion exhibiting the appearance of a larger 
 
 bladder, 
 
 
AND PREGNANCY. 159 
 
 bladder, to the infide of which the amnion 
 adheres under the form of a /mailer one, and is 
 attached in particular to that part which is 
 oppofite to the centre of the external floccofe 
 fuperficies of the chorion. 
 
 The interftice which then exifts between the 
 chorion and amnion is filled with a very fnbtle 
 chryilaline water, of doubtful origin, and tranfient 
 continuance. 
 
 For when the amnion begins, during the firffc 
 months after conception, to increafe with greater 
 rapidity tkin the chorion, and to gain on the 
 latter mem 1 rane in point of magnitude, this chryf- 
 taline liquor mud neceilarily undergo a fynchro- 
 nous, and perfectly correfpondent, diminution. 
 
 S 574- 
 
 The internal membrane of the ovum, from the 
 earlied period of its formation (§ 570), till the 
 final clofe of parturition itfelf, is conftantly filled 
 with a fluid, denominated by phyfiologifts, liquor 
 amnii. This liquid is aqueous, and of a pale 
 yellowifli colour; it emits icarcely any odour, and 
 is to the tafte bland, with a flight faline impreg- 
 nation hardly perceptible; phyfiologifts generally 
 fuppofe it to be a fource of nourifhment, and 
 compare it to the white of an egg;, from which it 
 
 notwithstanding, 
 
:do OF CONCEPTION 
 
 notwithstanding, differs in a very obvious and 
 efLntial manner, as may be eafily >U monftrated by 
 an attentive experimental inveftigation. 
 
 The fources of this fluid are as yet doubtful: It 
 is certainly, however, neither derived from the 
 fcetus nor the urn ti'ical cord, as it is not unfre- 
 quenily found in abortive ovula, which contaiu 
 neither of thefe bodies. 
 
 The quantity of this fluid is in an inverfe pro- 
 portion to the bulk of the foetus. Thus the 
 fmaller and more tender the embryo, the more 
 profufe is the volume of liquor amnii, and vice 
 verfa. 
 
 Hence we are at liberty to hazard a conjecture 
 refpe&ing the primary life of ti.is liquor, which 
 appears to be fubfervienr, not fo much to the 
 nutrition, as to the protection and defence of the 
 minute body of the tenckr embryo, as yet in a 
 gelatinous flare, and, therefore, wholly unable to 
 bear the violence of external injuries. With 
 :£l to that fmall portion of the liquor anmii, 
 which has been fometimes (though fo rarely as to 
 deferve to be efleemed a preternatural occurrence) 
 found in the fiomach of the foetus, it cannot 
 poflibly be deflined for the purpofe of its nutrition, 
 as will be obvious to any one who confiders how 
 2 extremely 
 
 
AND PREGNANCY. 161 
 
 extremely inert and empty the chyliferous fyftem 
 of even a more mature foetus appears, Low unfit 
 for, and even how averfe from, the arduous and 
 important procefs of cl ylification. To the forego- 
 ing circumfiances we might (if necefTary) fubioin 
 various examples of fcetufes deftitute of heads, 
 with diverfe other arguments of a flmilar nature, 
 and tending to the eilabliiliment of a fimilar refult. 
 
 § 57S- 
 The embryo itfelf, which (fufpended by the 
 
 umbilical cord, as fruit appended to its foot-ftalk), 
 
 floats in this liquor, begins to be formed about 
 
 the third week after conception : it appears firft 
 
 under the very fimple globe-like figure of a final! 
 
 bean or kidney, to which the rudiments of the 
 
 extremities are gradually fubjoined, the fymmetry 
 
 and fpecific form farther completed, &c. 
 
 § 57 6 ' 
 According to the ufual courfe of nature, the 
 
 female of the human fpecies is uhiparous, and con- 
 ceives only one foetus at a time. She not un fre- 
 quently, however, bears twins, the proportion of 
 which to folitary births is, according to the calcu- 
 lations of SufTmiich, as one to feven. In a cafe 
 of twins each foetus has its own amnion, but they 
 are both enveloped in a common chorion. 
 
 vol. if. L Thar 
 
1 62 OF CONCEPTION 
 
 S 577- 
 That medium, by the aid of which a recipro- 
 cal intercovirfe is preferred between the embryo 
 and mother, are the umbilical cord, and the pla- 
 centa through which this cord is minutely dif- 
 tribured. 
 
 § 578- 
 
 The umbilical cord, which appears to be co- 
 eval with the embryo itfelf, is indeed very ftrik- 
 ingly diverfified, not only in point of length and 
 thicknefs, but alfo with refpect to the place of 
 its infertion into the placenta, its varicoie protu- 
 berances, &c. In general, however, it is formed 
 of the fpiral contortions of three blood-vefiels, 
 namely, a vein running to the liver of the fcetus, 
 and two arteries which originate from the inter- 
 nal iliacs or hypogaflrics. Thefe vefTels are fe- 
 parated and diftinguifhed from each other by cel- 
 lular partitions, running in various directions, and 
 have their lights or diameters frequently flraitened 
 by the fmall nodes or valve-like bodies of Ho- 
 boken. 
 
 Thefe veffcls are collected and compacted to- 
 gether into a cord by means of cellular membrane, 
 which being filled with a lingular and very limpid 
 humour, exhibits the appearance of jelly, but is in- 
 veiled externally by a continuation of the amnion. 
 
 S 579' 
 
AND PREGNANCY. 163 
 
 § 579- 
 At the place where the fetus is attached to 
 this cord, the latter is joined by a peculiar body, 
 which originates from the bottom of the vefica 
 urinaria (§ 486.), and purfues a middle courfe 
 between the two umbilical arteries, namely, the 
 urachus. This body is, in the human fpecies, 
 pervious, for at lead a {hort fpace, and afterwards 
 totally difappears ; but in other animals belong- 
 ing to the clafs mammalia, leads onward to what 
 is called the allaniois. Of this allantois the human 
 foetus appears to be entirely deftitute, unlefs we 
 be inclined to defignate by this name that myfte- 
 rious and tranfient veficuia umbiiicalis, uniformly 
 obfervable in the human ovula, between the cho- 
 rion and amnion, which (if I be not greatly de- 
 ceived) Ifbr. de Diemerbroek firil difcovered long 
 before it was feen by Albums or Zinn. But in 
 more modern times it is difcovered too frequently, 
 and with too uniform an afpe£l in unvitiated and 
 fruitful human ovula, (even to fo late a period as 
 the third month after conception), to be any 
 longer confidered as an accidental, a morbid, or 
 amonftrous conformation of the part. 
 
 § 580. 
 
 The blood-vefTels of the cord, of which we 
 
 have already fpoken, pafs into the placenta, which 
 
 was formerly faid to originate from the leaf-like 
 
 L 2 fuperficies 
 
ftf-4 OF CONCEPTION 
 
 fuperficics of the chorion, a membrane attached 
 to, and even inferted in, the dccidua craffa : 
 Hence we perceive that the placenta is a body 
 compofed of two different kinds of fubftance, re- 
 ceived from an equal number of fources. Thus, 
 for example, one kind called the uterine, from its 
 immediate apportion to that organ, is derived 
 from the decidua, and conftjtntes the fpongy pa- 
 renchymatous portion of the placenta; while the 
 ether belonging to the foetus-, and therefore call- 
 ed, the fatal part, is derived from the umbilical 
 vefTels distributed throughout the chorion. 
 
 At this time the increafe of the tender ovum 
 is unequal, fo that the growth of the fmooth por- 
 tion of the chorion is greater and more rapid 
 than that of the mufecfum or mofs-like ; hence 
 it, is evident, that the relative magnitude of the 
 placenta to that of the whole volume of the egg, 
 is greater in proportion as the conception is more 
 recent* and lefs, on the other hand, accordingly 
 le period of parturition is nearer. 
 
 As pregnancy gradually advances, the placenta 
 becomes more and mere clofe and compact in its 
 texture; it is impreffed with grooves, and diftjn- 
 hed into lobes on its external furface which 
 refpects the u:cru:., bnf is fmooth and highly po- 
 lifiied on its internal, which, looking towards the 
 
 tus, 
 
AND PREGNANCY. 165 
 
 foetus, is invelted or lined by the amnios. Witfe 
 regard to magnitude, thicknefs, figure, and fitua- 
 tion or point of cohe/ion to the uterus, it is fub- 
 jec! to a multitude of diverfities ; it is attached, 
 however, for the moft part," to the fundus or bot- 
 tom of that organ ; and is, upon the v hole, 
 equally destitute of both feniibiiity (§ 205.) and 
 genuine irritability (§ 307). 
 
 § 581. 
 
 Although all phyiiologiih uniformly concur in 
 this, that the placenta is the principal organ 
 through the medium of which the tender foetus 
 is fupplied with nutriment, yet various contro- 
 verlies have latterly exifted among them refpect- 
 ing the genuine mode of its ofticial action, and its 
 reciprocal relation, as well to the uterus as to the 
 foetus. From an attentive and impartial confide- 
 ration of all the tetlimony that can be collected 
 on this fubjecl, the refult appears to be, that there 
 exifts no dirccl: anaftomofis between the blood- 
 veffe'.s of the maternal uterus and thofe of the 
 umbilical cord ; but the arterial blood which paffes 
 by a continuous route from the uterus of the 
 mother to that portion of the placenta that owes 
 its origin to the decidua craiTa,' is there abforbed 
 by the incipient radicles of the umbilical veins, 
 that are distributed throughout the mofs-like por- 
 tion of the chorion, and thus conducted into the 
 L 3 venous 
 
1 66 OF CONCEPTION 
 
 venous trunk of the funis umbilicalis : while, on 
 the other hand, the blood which is conveyed 
 back from the fceius by the umbilical arteries, 
 being in like manner effufed into the parenchyma 
 of the placenta, is taken up by the venous radi- 
 cles of its uterine portion, and thus finally re-con- 
 veyed into the fubftance of the uterus itfelf. 
 
 The foregoing opinions receive additional con- 
 firmation from the many well guarded but fruit- 
 lefs attempts that have been made by different 
 phyfiologiils to inject, the veffels of the umbilical 
 cord through thofe of the uterus, or, on the other 
 hand, to fill the veffels of the latter organ by in- 
 jections forced through thofe of the former. As 
 a further evidence in fupport of the fame prin- 
 ciples, we may mention the difference which is 
 obferved to exift between the pulfe of the mother 
 and that of the foetus before their final difen- 
 gagement from each other; and laftly, it may 
 not be improper to add, as a circumflance tend- 
 ing to the eftablifhmcnt of the fame rcfulr, the 
 obfervations which we formerly delivered refpecl- 
 ing the difference between the nature of the 
 fceral and that of the maternal blood (§ 147). 
 
 But further, it appears probable that a portion 
 of chyle is alio conveyed to the foetus along with 
 the blood of the mother. For befides the confide- 
 
 ration 3 
 
AND PREGNANCY. 167 
 
 ration, that the blood of the mother is not at all 
 times equally pure and unmixed, bur, for fome 
 hours after every meal, carries along with it, in 
 an unafiimilated ftate, that portion of chyle re- 
 cently received from the thoracic duel, it has 
 been demonilrated, on a former occafion, that the 
 uterus itfelf polTeffes a fmgular and ftrong affinity 
 to the chyle and milk (§ 550. SS3-)'f anc * tnere 
 are alfo on record a great variety of obfervations, 
 from which it appears, that a milky juice has been 
 actually difcovered in the uterine portion of the 
 placenta. 
 
 § 582. 
 
 During the progreflive advancement of preg- 
 nancy, while the foetus and fecundities increafe fo 
 very remarkably in magnitude, it is obvious that 
 the uterus mud be alfo fubjected to ftriking and 
 remarkable changes. Befides the augmentation 
 of its bulk, fo extremely evident at firft view, 
 thofe changes refpect alfo its fiiuation and figure, 
 but affeel: more efpecially the texture of this An- 
 gular and important vifcus. Thus, in confequence 
 of the uniform and weighty congeftion of humours 
 which the gravid uterus is obliged to fuflain, it 
 is likewife fubjetfted to extreme alteration, both 
 with regard to the ftate of its blood-veffels, and 
 L 4 alfo 
 
i<58 OF CONCEPTION 
 
 alfo with rcfpeft to that of its parenchymatous 
 portion, throughout which thofe veilcls are inter- 
 woven. 
 
 On the prefent occifion it may not be impro- 
 per to observe, that in proportion as the impreg- 
 nate ]• uterus advances in magnitude, its blood- 
 veffe s i i at mazy and convoluted appearance, 
 for which they are ar other times fo very remark- 
 able, and affume courfes much more rectilineal or 
 dire ft ; while at the fame time they are fubjefted 
 to a confi derable extenfion of their diameters, and 
 a confequent increafe of their real capacities. 
 Thus, even the uterine Teins have become {o ex- 
 tremely capacious and prominent, as to har? been 
 piiftaken by numerous anatomifts for true finufes. 
 
 With regard to the parenchymatous portion of 
 the impregnated uterus, it becomes gradually 
 mere and more lax and fpongy, efpecially where 
 it is in contaft with the ovum contained ; fo that 
 towards its fundus or bottom it becomes confider- 
 ably thick, and in a living and healthy female, is 
 greatly diftended with blood, and poifeiles the 
 powers of life in a very high degree. This or- 
 gan is, 'notwithstanding, (oft at the fame time, 
 and very widely di.Terent in its general habit and 
 appearance from the firm and compact flefh of the 
 
 uterus 
 
AND PREGNANCY. i6 9 
 
 uterus in ^n uoi tpregnated ffcate: this difference 
 is ftill ro r,i '• king if the fubjcfi containing t! e 
 gravid uterus be dead, in which cafe, provided 
 pregnancy be coi.fiderably advanced, this organ 
 falfcJy aflupies in its texture (as was formerly well 
 obferved by Arantius), a lamellated appearance. 
 
 It may not be amifs, on the prcfent occafion, 
 briefly to enumerate a few more of the moil 
 imporrant changes to which the gravid uteru is 
 jfubje&ed, to ether with the moll remaikable i v.ci 
 that occur in the ovum and foetus. Thefe changes 
 we will confider in the fucceffive order in which 
 they appear throughout the feries of ten lunar 
 months, which period of time is now, with fuffi- 
 cient propriety, fuppofed to conftitute the moil 
 natural term of pregnancy. 
 
 § 583- 
 
 As we uniformly obferve the uterus beginning 
 to fwell fhortly after the time of impregnations 
 (§ 567-) fo being from that period incre.ifed both 
 in bulk and weight, it defcends a little deeper into 
 the fnperior part of the vagina; notwithstanding 
 this defcent it Mill retains its former figure in all, 
 except the following, refpe&s, viz. its fundus 
 becomes a little more convex, its anterior paries 
 or wall, recedes a little farther from the pojlcrior, 
 and its cavity, which was before very narrow and 
 
 aim oft 
 
i-jo OF CONCEPTION 
 
 almofl: triangular, now accommodates itfelf to the 
 globofe figure of the ovulum it enclofes. 
 
 About the end of the firft month, the ovulum 
 itfelf amounts to the fize of a pigeon's egg, and 
 has the two defciduae feparated from each other, 
 and alfo the fraall amnion fituated at a diftance 
 from the larger chorion: about the termination of 
 the third month it attains the fize of a goofe's 
 egg, the caduca reflexa becomes approximated to 
 the crafla, and the amnion approaches nearer to 
 the chorion. The amnion abounds, at this time, 
 with a profufe volume of fluid denominated liquor 
 amnii. In this liquor the embryo, as yet very 
 tender, and extremely fmall in proportion to the 
 quantity of the furrounding fluid (being at this 
 time fcarcely equal in magnitude to a fmall moufe) 
 appears to iiu&uate in a loofe and unfteady 
 manner, and is even now in a precipitate pofition. 
 
 § 584- 
 
 About the fourth month after conception, the 
 uterus begins to aiTume more of an oval or fome- 
 what globe-like appearance; its neck being more 
 and more foftencd, gradually fhortened, and as it 
 were, deftroyed, or rather latterly diftended, it 
 again protrudes upwards, and begins to afcend 
 from the fmaller into the larger pelvis. At the 
 fame time the fallopian tubes themfelves, with the 
 
 convex 
 
AND PREGNANCY. 171 
 
 convex bottom of the uterus being elevated or 
 borne upwards, are thus extended and elongated; 
 thefe tubes are, however, attached and connected 
 fo clofely to the fides of the uterus, that they 
 cannot recede from them, more than one half of 
 their own length; hence, when only viewed 
 fuperficially, they appear to originate and proceed 
 from the middle of the uterus, which has given 
 birth to a very erroneous opinion refpecling the 
 aftonifhing increafe of the fundus uteri. 
 
 From this time alfo the foetus acquires by 
 degrees fuch an increafed magnitude, as renders 
 it more proportionate to the capacity of the ovum, 
 and begins about the fame period to fix itfelf in a 
 more fteady and firm pofition, which it preferves 
 till the very clofe of parturition : in this pofition 
 its head is placed in a downward direction, and 
 and its face turned towards the lumbar region of 
 the mother, inclining, for the mod part, fo me what 
 obliquely towards the left fide. 
 
 § s#- 
 
 In the middle ftage of pregnancy, which occurs 
 about the end of the fifth month, the uterus has 
 attained fuch a magnitude, that its fundus is 
 elevated to a point half-way between the pubes 
 and umbilicus, and the pregnant (late becomes now 
 
 obfervable 
 
172 OF CONCEPTION 
 
 obfervable from the external appearance of the 
 abdomen. 
 
 About lite fame time, the fceius becomes more 
 perceptible to the mother from the agitative mo- 
 tion of its body, though we are not able to deter- 
 mine, with accuracy and dtfmitude the preciie 
 period of time at which this motion takes place. 
 It appears now, however, to be more vigorous 
 and aclive, fo that, according to the common ufe 
 and acceptation of fpeech, it may be faid to be 
 the unequivocal action of life. 
 
 § 586. 
 
 Throughout the five remaining lunar months 
 the uterus, with the foetus which it contains, make 
 gradually dill farther advancements in point of 
 magnitude. Thus, at the end of the fixth month 
 they reach nearly to the umbilicus or navel ; and 
 about the termination of the eighth approach 
 even the fcrobiculus cordis, in confequence of 
 farther protrufion upwards. The cervix uteri is 
 in the mean time more and more obliterated, re- 
 duced nearer to a level with the adjacent parts of 
 that organ, and its parietes or walls confiderably 
 diminhh in thicknefs. 
 
 §587- 
 
AND PREGNANCY. 173 
 
 § 587- 
 
 Finally, about the end of the tenth month after 
 conception, the uterus being opprefTed and over- 
 powered as it were, by its own bulk and weight, 
 (its longitudinal axis, amounting in general to n, 
 and its tranfverfe to 9 inches in length) begins 
 again to fubfide, and as the period of parturition 
 approaches, its oftium or mouth is gradually ex- 
 panded, and thus exhibits an orbicular or ring-like 
 opening. 
 
 Each membrana caduca, more efpecially the 
 reflected one, which adheres to the chorion, 
 having been gradually attenuated for feveral 
 months immediately preceding, exhibits now a 
 kind of net-like appearance diftinetly marked by 
 fliort fibres of a whitiih colour. 
 
 Such is the fize of the placenta at this advanced 
 period, that its greatfefl: diameter or breadth 
 amounts to about 9 inches, its lead diameter or 
 thicknef; to about one inch ; and its weight 10 
 about one pound, and fometimes more. 
 
 The length of the umbilical cord for the moil 
 part equals, and fometimes even exceeds, eighteen 
 inches. 
 
 The 
 
i 7 4 OF THE NISUS FORMATIVUS. 
 
 The weight of a mature and wejl grown fcetus 
 is nearly feven pounds, its length about twenty- 
 inches. 
 
 The quantity of the liquor amnii is fo extremely 
 variable, that it cannot poffibly be ascertained 
 with any degree of definitude ; in general, how- 
 ever, it fcarcely amounts to a pound, provided the 
 fcetus be healthy and robuft. 
 
 SECT. XLV. 
 
 OF THE NISUS FORM ATI VUS. 
 
 § 588- 
 
 AVING thus enumerated and de- 
 fcribed, in a plain and fimple manner, the mofl 
 obvious and unequivocal phenomena of concep- 
 tions, together with fuch changes as are difcovered 
 by attentive obfervation to fucceed each other, 
 during the progrefiive courfe of pregnancy, not 
 only in the human ovum itfelf, but alfo in the 
 fcetus which it embraces, and contains, we now 
 proceed to an inveftigation of thofe phyfical pow- 
 ers, by the influence and efficacy of which the 
 
 fublime 
 
OF THE NISUS FORMATIVUS. 17c 
 
 fublime and truly aftonifhing procefs of generation 
 appears to be mod probably accomplifhed. 
 
 § 589- 
 
 There are not wanting certain characters of 
 high celebrity and diftinclion who attempt, even 
 in our own times, to explain the divine procefs, in 
 the following brief and fummary manner ; they 
 contend that the genuine work of actual generation 
 has not, at the prcfent time, any real exigence at 
 all ; on the contrary, they allege, that the whole 
 human race pofTeffed, under the form of original 
 germs, a joint pre-exftence in the genital fydem of 
 one or other of our iirlt parents, and that thefe 
 germs have ever been, and are yet, fubjecled to 
 gradual evolutions, according as the progreflive 
 lapfe of time, aided by the co-operation of fpecific 
 caufes, has contributed to awaken them to the 
 enjoyment of open and actual life. 
 
 Unfortunately, however, for «the advocates of 
 the foregoing hypothefis, an effential difference 
 of opinion prevails among them on a point of 
 confiderable magnitude and importance ; thus, 
 while fome of them are anxiouily in quell of thofe 
 original germs among the animalculae that peoplr 
 the femen of the male ; others are fearching for 
 thofe microfcopic animals with no lefs induftry and 
 zeal in the ovaria of the female. 
 
r 7 £ CF THE NISUS F0RMATIVU5. 
 
 § 59°- 
 To the latter of thcfe feels in phyfiology, I mult 
 acknowledge that I myfelf was formerly an adhe- 
 rent. 1 was lead to adopt the opinion of this 
 learned body not only by the refpeetable autho- 
 rity of its numerous advocates, but alfo by the 
 want of another more rational and fatisfattory. 
 At prefect, however, I am obliged to repudiate 
 this do&rine entirely, to confefs my errrors, and 
 endeavour if poflible to correct them ; having"- 
 been fully convinced, from a more clofe and mi- 
 nute attention to the phenomena of generation, 
 that nature performs this procefs in a manner quite 
 different from that contemplated and embraced in 
 the theory now under confideration. 
 
 § 59 1 - 
 
 For I am indeed duly more and more con- 
 vinced, that all living organized bodies pofiVfs, 
 from their earlieft! effort at organization to the 
 cloiing glafs of their exiflence, a peculiar power 
 perpetually active, perpetually efficacious, the 
 immediate dedication of which is, hrit, to mould 
 the bodies in which it refides into their native and 
 Ipecific forms by the myderious procefs of gene- 
 ration, to preferve them afterwards from deduc- 
 tion by the cealelefs function of nutrition, and, in 
 cafe of accidental mutilation, to reftore their parrs 
 agLiin, as far as confident with the regular efta- 
 2 bliihments 
 
OF THE NISUS FORM ATI V US. 177 
 
 blifhments of nature, by the procefs of repro- 
 duction. That this energy may not be confounded 
 with the other kinds of vital energy, let it be 
 diltinguifhed by the name of nifus formal ivus. 
 By this name, however, we mean to defignate not 
 fo much a caufe as a perpetual and uniform effect, 
 the exigence and reality of which are deduced 
 from actual observations made on the condant and 
 univerfal occurrence of certain phyfical pheno- 
 mena. It is thus, with views, and on principles 
 entirely fimilar, that we make ufe of the terms 
 attraction and gravitation^ to denote certain ener- 
 gies or fources of action, the caufes of which 
 are notwithstanding Hill involved in more than 
 Cimmerian darknefs. 
 
 § 59 2 - t 
 
 To me it appears, indeed, highly probable, that 
 a dated period of time is requilite for accomplish- 
 ing the intimate mixture, the union and complete 
 concoction or maturity of thofe various inquiline 
 humours, belonging to each frx, (§ 518. 524. 
 542. 543.) which are doubtlefs dif<. harged into 
 the cavity of the uterus, during every act of fruitful 
 coition. This term of preparation having at length 
 elapfed* and the liquors being fully matured and 
 brought into the mod perfect (late of union and 
 reciprocal influence, the nifus formativus is forth- 
 with excited into action, by means, of which the 
 
 vol. 11. M fpercaatic 
 
i 7 8 OF THE NISUS FORMATTVUS. 
 
 fpermatic mafs, hitherto formlefs and chaotic, fa 
 partly arranged and organized into the elegant 
 and beautiful envelopes of the nafcent ovulum, 
 and partly moulded into the figure of the living 
 embryo which this minute bodies enclofes. Fron. 
 this theory we can aflign a fatisfactory re;i' 
 why the uterus, for the two firft weeks after cc; 
 ception, appears to contain a mafs of crude and 
 fhapelefs humours alone, and does not exhibit, 
 even to our bed glaffes (now brought to very 
 high perfection), the fmalleft veftige of an or- 
 ganized embryo, which, notwithstanding burfts 
 into view aim oft inftantaneoufly about the end of 
 the third week, and is, even on its firft appear- 
 ance, of confiderable magnitude. 
 
 § 593- 
 
 Of the 7iif us format ivus we are prefentcd with 
 more remote veftiges throughout every department 
 of natural bodies, not excluding even the moft 
 fimple elements of matter, where original germs 
 cannot poflibly be fuppofed to have the fhadow of 
 an exiftence. Thus, the clouds themfelves affume 
 their own determinate forms, and even the ftream- 
 ing torrents or veins of the electric fluid preferve 
 fpecific figures. There are, again, in the mineral 
 kingdom, fpecimens of metallic chryftallization, 
 which, if indeed the form alone be confidered, and 
 
 . . the 
 
OF THE NISUS FORMA TIVUS. 179 
 
 the prerogative of life kept entirely out of view, 
 bear the mod ftriking refemblance to truly orga- 
 nized bodies. 
 
 In teftimony of the truth of this, we need only 
 mention the curious hypniform cryftals into which 
 refined or depurated copper fhoots when firft 
 reduced to a ftate of fufion, or that exquifitely 
 beautiful fpecimen of native peruvian filver which 
 they call filicinum or fern-like, from the refem- 
 blance of its figure to that of the plant denomi- 
 nated fern. 
 
 § 594* 
 
 In like manner both the animal and vegetable 
 kingdoms afford numerous examples of organized 
 bodies, in which, from their magnitude being fuf- 
 ficient to render them vifible, from their beautiful 
 and unclouded tranfparency and from the extreme 
 rapidity of their progreflive growth, the whole 
 procefs of generation is completely unmafked as it 
 were, and may be fubjected to the examination of 
 the naked eye. The refult of attentive and minute 
 obfervations made on this procefs Li fuch fuhje&s 
 as thefe, will be fivfficient to evince, on the autho- 
 rity of the mod indubitable teftimony that, at leaft 
 in thefe bodies, no germs pre-exift. In illuftration 
 of the above pofition it will be fufficient to mention 
 M 2 from 
 
i3o OF THE NISUS FORMATIVUS. 
 
 from among the different individuals of the vege- 
 table kingdom, the conferra fontinaUs. And from 
 thofe of the animal, the hydra viridis. 
 
 § 595- 
 I mould far exceed the limits prefcribed to thefe 
 
 inftitutions were I to attempt a minute and circum- 
 stantial detail of the various arguments which, in 
 my view, nature herfelf furnifhes to prove the 
 potent influence of the nifus formativus in the 
 procefs of generation. It may be proper, how- 
 ever, briefly to (late a few of them, the force and 
 efficacy of which will appear fufficiently evident 
 on the flight eft examination. 
 
 § 59 6 - 
 The firft argument I fhall further propofe on 
 
 this fubjeft is taken from the hiftory of thofe 
 curious and interefting fubje&s of organized nature 
 denominated hybrids. From a very beautiful and 
 celebrated experiment it appears, that, if prolific 
 female hybrids be fucceilively through feveral 
 fenerations impregnated by males of any given 
 fpecies different from the fpecies of the females, 
 the new offspring will gradually deviate fo widely 
 from the original form of the mother, and make 
 fuch evident and effectual ftrides towards that of 
 the father, as to lofe at length every veftige of 
 fimilitude to the former, and become finally, (by a 
 
 fpecies 
 
OF THE NISUS FORMATIVUS. til 
 
 fpecies of arbitrary metamorphofis) completely 
 affimikted to the external figure and appearance 
 of the latter. 
 
 § 597- 
 
 There exists a phenomenon or fa<ft relative to 
 the hiflory and production of monjiers, (the truth 
 of which is too well afcertained and eftabllfhed 
 to admit of a doubt), that merits our attention 
 while on the consideration of the prefent intereil- 
 ing and intricate fubjecl. It is a circumftanee well 
 known to naturalifls, that thofe animal produc- 
 tions denominated monjlers (moft of which are 
 fuppofed, by the advocates for the celebrated 
 doctrine of evolution, to have pre-exifted in a 
 monftrous germiform date from their original crea- 
 tion) — it is, I fay, well known, that fuch preter- 
 natural productions, though very frequent among 
 certain fpecies of animals in a fubjugated or do- 
 mestic flare (more efpecially among fwine), are 
 notwiihfhnding very rarely found among the ori- 
 ginal and free-born animals of the very fame fpe- 
 cies, that have never been reduced to an humble 
 ftate of domeftication, but ftill range the com- 
 mons and wilds of nature, wholly exempt from 
 the tyrannic controul of man. 
 
 M 3 § 59 S. 
 
i8z of the nisus formativus. 
 
 § 598- 
 
 It is neceffary further to obferve, that not only 
 monftrofities co-eval with the birth of animals, 
 but alfo fubfequent adventitious mutilations and 
 other /pedes of deformity, whether produced on 
 the animal fyftem by accident or defign, become 
 now and then completely hereditary ; and thus, 
 what was at firft the effect of art alone, may be 
 faid to become at length the actual work of nature 
 herfelf. 
 
 § 599* 
 
 The phenomena of re-produftion in general are 
 much more eafily and rationally accounted for, by 
 confidering them as the refult of a nifus forma- 
 tivus, than by referring them to the pre-exiftence 
 of partial or .local germs. This obfervation is 
 more fully and clearly illuflrated, and its truth 
 more forcibly exhibited by an application of it to 
 fome particular inftances of re-production, as that 
 of the nails, for example, which after the entire 
 lofs of the Jir/t, are well known to be frequently 
 regenerated on the fecond phalanx of the fingers. 
 
 § 600. 
 Again, in certain parts of the body where no 
 pre-exiftence of germs can poflibly be fufpected, 
 wt not unfreqnently fee organic parts of a pre- 
 ternatural 
 
OF THE NISUS FORM ATI VU& 183 
 
 ternatural order produced by rhe wis medicatrix 
 natures, when roufed into action in confequencc 
 of accidental difeafes : As an example, and in 
 illuftration of this, we may mention thofe fmall 
 ofiifications known by the name of ojficula Wor~ 
 miana, which, in cafes of hydrocephalus internus y 
 are formed by the provident powers of the ani- 
 mal fyftem, for the purpofe of arching over and 
 thus completely clofmg the enlarged fontanel. 
 
 Finally, on comparing with candour, and weigh- 
 ing with impartiality, the various arguments on 
 each fide of the queftion, it very evidently ap- 
 pears, that befides a power of exciting to motion 
 and action, which the advocates for the pfe-ex- 
 iftence of germs attribute to the male femen, in 
 order to render their favourite theory more fpc- 
 cious and plaufible, they mud alio beftow on that 
 fluid plajlic or formative powers of the utmoft 
 extent and influence : Whence it is obvious, that 
 the do&rine for which they fo zealoully contend, 
 is of itfelf wholly inadequate to the explanation 
 of the numerous and intricate phenomena of ge- 
 neration, unlefs it be aided by the powerful con- 
 currence of a nifus formativus: Whereas, en the 
 other hand, the fyftem which we have j nil pro- 
 pofed on the fubjecl is, without the bold pre- 
 emption of prc-exijicnt germs, fully fuflicient to 
 explain all the multiplicity of phenomena attend- 
 ed 4 ant 
 
xfi4 OF PARTURITION. 
 
 ant on this divine procefe. Let us then on the 
 prefent, as we fhonld on every other point of ccn- 
 troverfy, adhere to that doctrine which is raoft 
 fimple in its nature, and mod condufive in its end, 
 from a thorough conviction, that an unneceffary 
 multiplication of entities or caufes is no lefs repug- 
 nant to real and practical utility, than to the tenor 
 and fpirit of found philofophy. 
 
 SECT. XLVI. 
 
 OF PARTURITION, AND ITS CONSEQUENCES. 
 § 602> 
 
 JL HE foetus being regularly formed and 
 faihioned by the energies of which we have hi- 
 therto treated, and advanced through the pro- 
 greffive ftages of its fubfequent growth, till it be 
 brought to a ftate of fcetal perfection, rauft, after 
 arriving at this particular period of maturity, be 
 finally ufhered into the enjoyment of light and en- 
 tire life, by the painful bufinefs of parturition. 
 
 § 603. 
 This critical and important period arrives, agree- 
 ably to the ufual order of fpontaneous nature, 
 (which is the only object contemplated in phyfio- 
 
OF PARTURITION. 185 
 
 logy), about the termination of the tenth lunar 
 month, i. e. about the 39th or 40th week after 
 conception. 
 
 § 604. 
 When a pregnant female finally arrives at this 
 eventful crifis, Ihe is forcibly impelled to the la- 
 bour of parturition by an infuperable neceffity, 
 already faid (§ 295.) to be lefs fubjett to the con- 
 troul of the will than that which urges to the per- 
 formance of any other function belonging to the 
 human body. 
 
 § 605, 
 
 With refpeft to the caufes of a revolution fo 
 determinate and hidden, different and even oppo- 
 fite opinions have been entertained by different 
 phyfiologifts. When we view, and take into at- 
 tentive confideration, all the attendant circum- 
 ftances, it appears neceffary to refer the caufe, 
 which immediately impels to parturition, to an 
 eternal law of nature, which has hitherto received 
 no better explanation than has been given to a 
 great many other phyfical phenomena, which take 
 place in like manner at regular and Jlated periods ; 
 fuch, for example, as the metamorphofis of infers, 
 the progreffive ftages of eruptive fevers, their 
 crifes, &c. &c .Without fubje&ing themfelves to 
 the juft charge of fancifully entering on an abfurd 
 
 fpeculation, 
 
1 86 OF PARTURITION. 
 
 fpeculation, certain phyfiologifts have compared a 
 mature ovum, in the uterus of the human fubjeft, 
 to the healthy fruit of vegetables, which when 
 completely ripened, fall fpontaneoufly from their 
 parent plants, in confequence of a felf-conjlriclion 
 of the vdTels through which rheir nourilhment 
 was conveyed. It has been in like manner ob- 
 ferved, that as the period of parturition ap- 
 proaches, the human placenta fuffers a flight de- 
 gree of conftri&ion, and becomes thus prepared, 
 as it were, for its impending reparation from the 
 furrounding uterus. 
 
 With regard to the opinion entertained on this 
 fubjecT by phyfiologifts in general, namely, that 
 the amazing expanfion to which the impregnated 
 uterus is fubje&ed, with a multitude of other im- 
 preffions or impulfive powers of a like nature, acT 
 as the genuine exciting caufes of parturition, it 
 appears to be very clearly and effectually invali- 
 dated by a great variety of arguments, which may 
 be fairly deduced from the unequivocal pheno- 
 mena of the animal economy itfelf : of thefe argu- 
 ments we think proper to mention the following, 
 namely, in numberlefs genuine cafes of extra- 
 uterine conception, where the fcetufes have been 
 contained, for example, in the Fallopian tubes, or 
 in the ovaria, the uterus has notwithftanding been 
 attacked by painful and convulfive throws, about 
 
 the 
 
OF PARTURITION. 187 
 
 the termination of the tenth lunar month after the 
 occurrence of fuch preternatural conception. 
 
 § 606. 
 
 Befides the exciting, it is evident that there 
 mufl be alfo the joint co-operation of very pow- 
 erful efficient caufes, arifing from the nature and 
 properties of the uterus itfelf, and of the contents 
 which it enclofes. 
 
 The proximate or immediate and primary caufe 
 mufl be doubtlefs referred folely to the vita pro- 
 pria, or fpecific life of the uterus itfelf (§ 47.) 
 
 Of the remote caufes the leading and moft con- 
 fiderable appear to be, the powerful efforts which 
 are made by the afMance of the procefs of refpi- 
 ration, and the extenfive confent or co-operation 
 of the intercoflal nerve with the other portions 
 of the nervous fyftem. 
 
 § 607. 
 "When finally the labour of genuine parturition 
 is excited, its phenomena obferve a determinate 
 and regular order with regard to their commence- 
 ment and fubfequent progreffive courfe. In con- 
 fequence of this, they have been divided by ac- 
 coucheurs into different Jiages, of which four 
 have been enumerated by the lateft writers on the 
 pbfletric art. 
 
 § 608. 
 
i88 OF PARTURITION. 
 
 § 608. 
 
 In the jirft ftage, the parturient patient expe- 
 riences a flight attack of thofe peculiar and well- 
 known pains, called in that (late prccurfors 01 
 ivarnings, which (hoot in a direction from the 
 loin? to the lower parts of the uterus, and which 
 are indeed felt at intervals, (though with dimi- 
 nifhed frequency and force), throughout the whole 
 period of parturition : the orifice of the uterus 
 begins, at the fame time, to be confiderably di- 
 lated, the abdominal tumor fubf des, an inciina- 
 tion to pafs urine becomes urgent and trouble- 
 fome, and a copious difcharge of mucus takes 
 place from the genital organs, now in a Hate of 
 diflenfion and laxity. 
 
 § 609. 
 In the fecond ftage, the pains increafe, and are 
 now diflinguifhed by the name of preparantes, or 
 preparatory efforts : the inferior fegment of the 
 coverings or membranes of the ovum are, at the 
 fame time, protruded through the uterine orifice 
 into the vagina. 
 
 § 610. 
 
 In the third ftage the pains Mill continue greatly 
 augmented in their violence, and are now denomi- 
 nated dolor -es ad par turn *. They aft againft the 
 
 * i. e. The genuine pains of parturition. 
 
 uterus 
 
OF PARTURITION. 189 
 
 uterus with a more violent impetus, and thus 
 potently protrude it downwards, while, a r the fame 
 time the uterus prefTes with fuch aftonifliing force 
 on the encarcerated foetus, as to occafion a rup- 
 ture in the membranes by which it is inclofed. 
 
 § 6n. 
 
 During the fourth and laft flage of parturition, 
 while the patient i ited vvith convulfive throws, 
 
 and tortured with the mod excruciating pain, (lie 
 makes, at length, a violent exertion, (not un- 
 frequently accompanied with horripilation, grind- 
 ing of the teeth, trembling of the knees, &o), by 
 the impuifive force of which, the head of the 
 emerging iniant is urged forward, and finally pro- 
 truded quite through the external orifice with its 
 face foremoft : in this unlooked for pofition it is 
 forced to advance, in confequence of the vertex 
 or crown of the head becoming lodged againft the 
 arch of the pubes, while its other parts are urged 
 onward, and obliged to revolve on the flationary 
 vertex, as on an axis, or centre of motion. Thus, 
 amidft a profufe difcharge of blood, the infant is 
 finally excluded from its place of confinement, and 
 introduced to the enjoyment of light and life. 
 
 § 612. 
 
 The foetus being thus happily excluded, the 
 birth of the fecundines fuxceeds, after a fhort in- 
 terval, 
 
9» OF PARTURITION. 
 
 terval, accompanied, in like manner, with painful, 
 though much lefs violent, throws : this latter birth 
 is, as well as the former, followed by a difcharge 
 of blood, from that part of the uterine cavity to 
 which the placenta adheres by means of the 
 crajfa or grofs membrana decidua. 
 
 § 613. 
 
 The uterus, being thus, at once delivered of 
 its two-fold birth, by which it had been encum- 
 bered and oppreffed, is now contracted by little 
 and little, till it is finally reftored to its former 
 figure, and reduced almoft to its former fize. 
 
 § 614. 
 
 During the firft week after the birth of the 
 child, there exifls, from the genital organs of the 
 mother, an uninterrupted eifufion of the lochia, 
 a difcharge very much refembling the catamenia, 
 except that it is more profufe in quantity, efpe- 
 cially when not in any meafure checked or dimi- 
 nifhed, by the commencement of laflation. The 
 bloody or florid colour of the liquid difcharged by 
 this evacuation is, notwithstanding, changed about 
 the fourth day to a pale red, and from thence 
 pafles on to afTume a white appearance. 
 
 As foon as the uterus is thoroughly cleanfed 
 of all remaining fragments of its deciduous mem- 
 brane, 
 
OF THE HUMAN SUBJECT, &c. 191 
 
 brane, and has thus finally completed the painful 
 and tedious tafk of propagation, it may again 
 refume the natural procefs of mcnJiruaUon^ or 
 even return to the performance of frefh immola- 
 tions on the altar of conception itfelf. 
 
 SECT. XLVIII. 
 
 OF THE DIFFERENCES BY WHICH THE HUMAN 
 SUBJECT IS CHARACTERISED BEFORE AND AFTER 
 BIRTH. 
 
 § 615. 
 
 Jf ROM what has been already faid 
 refpe&ing the mode of life enjoyed by the fcetus, 
 while yet encarcerated within the parietes, and 
 immerfed in the warm-bath of the maternal uterus, 
 it is extremely obvious that an immenfe difference 
 mud exift, between the functions of the animal 
 economy in this (late, and that which Ihortly fuc- 
 ceeds, when the infant is finally introduced, by 
 birth, into entire life, and is poffeffed of a power 
 of fpontaneous motion. An enumeration and 
 ftatement of the leading points or circumftances 
 of this difference, conftitutes the defign of the 
 prefent fe&ion. 
 
 S 616. 
 
i 5 ;2 OF THE HUMAN SUBJECT 
 
 § 616. 
 To begin then with the circulation of the blood, 
 it mud be obferved, that the route of this crimfon 
 fluid is different in the festal dare, from what it is 
 in that which immediately fucceeds paturition or 
 birth. During the continuance of the former 
 ftate, the fcetus is connected, and preferves a cir- 
 cular intercourfe with the uterine placenta, by 
 means of the umbilical cord ; it has never, as yet, 
 infpired air for the purpofe of fupplying the blood 
 with that vital pabulum, a procefs which immedi- 
 ately commences and is uniformly continued after 
 birth, when this reciprocal connection between 
 the mother and child, is finally deftroyed. 
 
 § 6*7. 
 
 The umbilical vein originating from the placenta 
 of the mother, and paffing through what is called 
 the umbilical ring of the fcetus, directs its courfe 
 towards the liver, where it difcharges its blood 
 into the fmus of the vena portarum ; from thence 
 the blood is diftributed in part, by the ramifica- 
 tions of this memorable vein, throughout the liver, 
 and in part, conveyed by a direct route through 
 the ducltis venofus Arantii, to the inferior or 
 afcending vena cava. 
 
 The two foregoing canals, namely, both that 
 
 portion of the umbilical cord which is contained 
 
 1 in 
 
BEFORE AND AFTER BIRTH. 193 
 
 in the abdomen of the foetus, and alfo the ductus 
 venofus mentioned above, fuller after birth an 
 entire obliteration of their cavities, and afTumethe 
 nature and appearance of folid cords, jnfomuch 
 that the former conftitutes what is denominated 
 the round lhament of the liver. 
 
 a 
 
 § 618. 
 
 When, in the foetus, the blood is conveyed 
 from the inferior vena cava to the right fide of the 
 heart, the greater part of it is denied a paffage 
 from thence through the lungs, and is therefore 
 directed towards the left or pofterior auricle of 
 the heart, by the valve of Euftachius, and admit- 
 'ted into that cavity through the foramen ovale* 
 
 § 619. 
 
 For over the mouth of the inferior vena cava, 
 after its afcent from the cavity of the abdomen in 
 the foetal (late, a valve of alunated figure is extended, 
 which, in honour of its immortal difcoverer, has 
 been called the valve of Euftachius. This luni- 
 form body is, for the mod part, gradually oblite- 
 rated as life advances, although in the fcetal (late it 
 appears to perforin the important office of directing 
 the blood, emerging from the abdominal cavity, 
 towards an orifice to be fpoken of prefently, which 
 penetrates the feptum fituated between the two 
 auricles of the heart. 
 
 vol. u. N § 620. 
 
i£4 OF THE HUMAN SUBJECT 
 
 § 620. 
 The orifice referred to in the preceding para- 
 graph is called the foramen ovale, through which 
 by far the greater part of the afcending column of 
 blood, derived immediately from the inferior vena 
 cava, is conducted into the left auris of the heart 
 during each diaftole of the auricles : of this blood 
 the regurgitation is effectually prevented, by the 
 elegant falciform valve formerly mentioned, which 
 is clofely fpread over the foramen, and appears to 
 clofe that orifice completely, during each fyftolic 
 motion of the auricles. During the firfl: years of 
 infancy the foramen ovale is in part clofed by means 
 of this frnall valve, and partly obliterated by the # 
 gradual but flow adhefion of its fides : in cor- 
 refpondence to fuch adhefion, the valve of Eufta- 
 chius itfelf undergoes alfo a flow and gradual 
 diminution in point of fize, till fcarcely a wreck of 
 it is left behind. 
 
 § 621. 
 
 Of that blood which, at the fame time, enters 
 the right auricle of the heart from the fuperior 
 vena cava, a veryfmall portion only can be received 
 by the lungs of the lcetus, as yet in a weak and in- 
 active condition : it is therefore taken up by the 
 duclus arteribfus, from the trunk of the pulmonary 
 aitery (of which this duct is indeed the leading 
 branch) and conveyed by a direct and fpeedy route 
 
 to 
 
BEFORE AND AFTER BIRTH. i$$ 
 
 to the arch of the aorta, without paffing through 
 the lungs at all. Within the courfe of a few weeks 
 after the birth of the infant, the cavity of the 
 du&us arteriofus is, for the moft part obliterated, 
 and its parietes or walls converted into the nature 
 and appearance of a denfe and firm ligament. 
 
 § 622. 
 The blood being propelled through the trunk 
 of the aorta, that portion of it, deftined to be 
 re-conveyed to the fyftem of the mother, enters 
 the umbilical arteries (§ 5^8.) which pafs through 
 the annulus wnbilicalis, on each fide of the urachus^ 
 and are, in like manner, after the birth of the 
 infant, converted into folid imperforated cords. 
 
 § 623. 
 As the lungs perform in the fcetus fcarcely any 
 fun&ion at all, their general habit and appearance 
 differ very materially from thofe which they aflume 
 after the infant has commenced the procefs of 
 refpiration. Thus, their bulk is proportionably 
 much lefs, their colour more dark, their fubftance 
 more compact, and hence their fpecific gravity (o 
 much greater, that when immerfed, recent and 
 free from putrefaction, into a vefTel of water, they 
 fink inftantly to the bottom ; whereas, on the 
 other hand, if the infant has been born in a living 
 Itate, and taken in air by infpiration, thcfe vifcera, 
 N 2 ' tlic 
 
OF THE HUMAN SUBJECT 
 
 for the mod parr, float on the furface of water, or 
 of any ether fluid equally ponderous. The right 
 lobe of the lungs appears to polTefs the peculiar 
 prerogative of being dilated a little fooner than 
 the, left by the incipient influx of air in the fir(t act 
 of infpiration. With regard to the other pheno- 
 mena of this new function of life, they were 
 enumerated formerly, when we were treating 
 particularly or the procefs of refpiration. 
 
 § 624. 
 
 From the obfervations which were formerly 
 propofed on the nutrition of the foetus (§ 574, 
 581.), it may be very eafily perceived that the 
 ftate and condition of the alimentary tube and cby- 
 lopoietic fyftem 9 are extremely different before, 
 from what they are after, the birth of the infant, 
 thtfe vifcera being in the firft cafe inert and 
 wholly incapable of action. Thus, for inflance, 
 in the render embryo of only a very few months 
 ejeiftence, the larger, are perfectly fimilar in habit 
 and appearance to the /mailer, intejlines; but 
 during the clofiflg months of pregnancy the former 
 portion of the inteftinal canal (being confiderably 
 #ftended with meconium') appears to merit unequi- 
 vocally that name by which it is afterwards d\{- 
 tinguHhed from the latter. 
 
 § 625. 
 
BEFORE AND AFTER BIRTH. 197 
 
 § 625. 
 
 The meconium is a peculiar fpecies of faburra, 
 of a green colour, (haded with more or lefs of a 
 brownifh caffc. It is douhtlefs derived from the 
 inquiline humours of the foetus itfeU, more efpe- 
 cially from the bile: that it is indeed of a bilious 
 origin we are induced to believe from the follow- 
 ing conliderations: — Firji, becaufe the earlicfi 
 appearance of this excrementious fubftance cocref* 
 ponds exactly, in point of time, with the com- 
 mencement of the biliary fecretion; and, Secondly > 
 becaufe we learn from accurate obfervation, that 
 ftich monPters as are deftitute of a liver, have their 
 inteftines fupplied with nothing elfe but a final! 
 quantity of colourlefs mucus ioftead of the more 
 common and natural meconium. 
 
 § 626. 
 In the new-born infant the form of the ccccum 
 is a'fo very widely different from what it is in rhe- 
 future periods of life; and this inteftine is then 
 continued in a direct line with the appendicula 
 vermiformis* 
 
 § 627. 
 Several other differences and peculiarities, of a 
 fnnikir nature, we have already fpoken of on parti- 
 cular occafions, and ihall here, therefore, only 
 N t. glance 
 
io8 OF THE HITMAN SUBJECT 
 
 glance an them in the moft brief and tranfienj; 
 manner : 
 
 They are the Urachus (§ 579.) the membrana 
 pupillaris (§ 259.) and, in the male foetus, the 
 defcent of the tejies (§ 501.) 
 
 A few additional peculiarities will be fpoken of 
 with more propriety in the following fection. 
 Others, as being of lefs importance, we volun- 
 tarily pretermit in perfect filence. 
 
 § 628. 
 The prefent appears to be indeed a very fit 
 and favourable opportunity for calling the attention 
 of the reader to three parts of the human body, 
 altogether peculiar in their nature and obfeure in 
 their destination, which are of a greater propor- 
 tional fize in the fcetus than in the adult, and 
 appear to be in a fpecial manner fubfervient to 
 the economy of the former. The true and une- 
 quivocal ufes of the parts now in contemplation 
 have not as yet, however, been clearly and fatif- 
 fa&orily afcertained, although, anxioufly fought 
 after by the combined labours of numerous and 
 very refpeclable anatomifls. Thefe parts ~ are 
 designated by the name of glands, although their 
 parenchy?na is far, very far, different from the 
 g'andular, and they have never been difcovered 
 
 to 
 
BEFORE AND AFTER BIRTH. 199 
 
 to pofiefs the fainted: veftige of an excretory duel:. 
 They are denominated the thyroid glands the 
 thymus, and the rencs fuccenturiatati. 
 
 § 629. 
 The thyroid gland is fituated on the anterior 
 fide of a cartilage of the fame name, which enters 
 into the conformation of the larynx. It confifts 
 of two lobes, and is of a lunated or falciform 
 figure; in the fcetus it is diftended with a lympha- 
 tic fluid, but, as life advances, becomes gradually 
 more and more fpoliated of its diftending liquid. 
 
 § 630. 
 
 The thymus confifts of a mafs of fhining and 
 very tender fle(h, is, in like manner with the pre- 
 ceding fubftance, bilobular, now and then divided 
 into two diftincl: portions, and contains alfo occa- 
 sionally a cavity of conilderable dimenfions. This 
 body is fituated beneath the middle and upper 
 part of the fternum, and afcends on each fide even 
 to the throat itfelf; in the fcems it is large, 
 irregular in its figure, and abounds with a juice of 
 a milk-like nature; but as youth advances it gra- 
 dually diminiihes in fize, until, finally, on the 
 acceffion of old age, it is fo completely obliterated 
 as to exhibit fcarcely a fhadow of its former 
 exigence. 
 
 N 4 § 631, 
 
206 0E THE INCREASE, MATURITY, 
 
 § 631. 
 Laflly, The Irenes fucccnturlatali^ (called like- 
 wife glandula fuprarenalcs^ capful a airabiliati<2 y 
 &c.) are fuuated beneath the diaphragm, reding 
 on the upper extremities of the kidneys. In adults 
 they are not only diminifhed in fize, but are alfo 
 removed to a fmall diflance from the contact of 
 the kidneys, and contain a dark coloured fluid, 
 which in the fcetus is more inclined to a pale red. 
 
 SECT. XLVIII. 
 
 OF THE INCREASE, MATURITY, AND DECLINE 
 OP MAN. 
 
 § 632. 
 
 JriAVING hitherto minutely confidered 
 the human economy, in detail, agreeably to the 
 feveral claffes into which its phyfical functions arc 
 divided, nothing further remains at prefent than 
 to take a general, brief, and comprehensive furvey 
 of man in his tranfit over the diverfifled fhge of 
 life, and thus accompany him, from his earlieft 
 vital pulfe in an embriotic (late, throughout the 
 
 leading, 
 
AND DECLINE, OF MAN. 201 
 
 leading revolutions and eras in his economy, down 
 to the final termination of his exiftence. 
 
 § 6 33- 
 Firji, then, about the third week after concep- 
 tion, the rudi menial organization of the embryo 
 appears to take place f§ S7S')'- about tne fourth 
 week afterwards, while the embryo flill enjoys an 
 extremely low and languid degree of life, border- 
 ing even on that of a vegetable, it is fupplied with 
 the frit portion of genuine red blood (§ 13.) 
 The motion of the corculum or minute heart, has 
 been but very feldom obferved by pbyfiologifts in 
 the incipient human embryo, but was long fince 
 difcovered by Ariftotle in the incubated chick, and 
 has been, from that period, defignated by the 
 name of the punclu?n fallens. 
 
 § 634. 
 
 About the feventh or eighth week after con- 
 ception, the momentous procefs of q/ieogeny, or 
 the generation of bone, commences in the human 
 fubjeft. Thofe parts where offeous, or bony 
 matter makes the fird depofuions for the formation 
 of its nuclei, are the clavicles, the ribs, the verte- 
 brae, the long cylindrical bones of the extremities, 
 the mandible or lower jaw, and certain other- 
 bones of the face, &c. Thcfe parts again where 
 the offeous depoihiens are fecondary in point of 
 
 time, 
 
202 OF THE INCREASE, MATURITY, 
 
 time, are fome of the plain bones of the lkull, 
 fuch, for example, as the frontal and occipital: — 
 while the bones of the neck, &:c. are formed at a 
 flill later period. 
 
 The younger the embryo is, in particular, or to 
 proceed on a more extenfive and general fcale, 
 the younger the human fubjett is, whether before 
 or after birth, with the greater rapidity does its 
 growth advance, and vice verfa. 
 
 § 635- 
 
 About the middle period of pregnancy, the 
 foetus becomes what may be called a genuine fub- 
 je& of vitality or life, agreeably to the rule of 
 difcrimination laid down on that particular point in 
 a former part of this work (§ 585.) About the 
 fame time, the fecretion of certain humours make 
 their firft appearance, fuch, for example, as the 
 fat (§ 38) and the bile. 
 
 § 6 3 6. 
 As the fcetus advances towards maturity the 
 tender hair begins to pullulate, the nails emerge 
 into view, the membrana pupillaris gives way 
 (§ 260), and in the male fex the tejles begin to 
 defcend (§ 505). 
 
 § 6 37- 
 
AND DECLINE, OF MAN. 203 
 
 § 637. 
 About the clofe of the tenth lunar month, the 
 infant is finally releafed from its imprifonment by 
 means of parturition (§ 603); after which, befides 
 the aftoniihing revolutions in almoft the whole 
 economy of its fyflem, detailed more amply and 
 minutely above, it is alfo fubjected to various 
 changes in its external habit and appearance; 
 thus, for inftance, that delicate lanuginous hair, 
 with which the face of the new-born infant is 
 overfpread, difappears by degrees, its wrinkles are 
 gradually obliterated, its anus retires within the 
 nates, which now begin to be flowly protruded, 
 &c. &c. &c. 
 
 § 638. 
 
 The infant alfo learns, (though indeed by very 
 flow degrees), the exercife of the various faculties 
 of the mind, fuch, for example, as thofe of per- 
 ception, of attention, of reminifcence, of defiring, 
 &c. &c. from whence, in a very few months after 
 birth, it is fubjected to dreams, &c. 
 
 § 639. 
 
 The organs of the external fenfes undergo alfo 
 gradual or progreffive improvements, and are 
 advanced to (till higher and higher degrees of 
 perfection, fuch as the external ears, the internal 
 
 nares, 
 
2o 4 OF THE INCREASE, MATURITY, 
 
 nares, alfo the coverings of the eyes, fuch as 
 ihtirfupra- orbital arches, their fnpercilia, &c. 
 
 § 640. 
 
 The bones of the cranium acquire, in the mean 
 
 time, an augmented degree of firmnefs. The 
 
 fonticuli or chafms between the different bones 
 
 are gradually arched over, and about the eighth 
 
 month the procefs of dentition commences. 
 
 § 641. 
 
 The infant is now ready to undergo abluchition 
 
 or weaning, being furniflied with teeth for the 
 
 exprefs purpofe of fubduing more folic! food, and 
 
 not to injure the papilla, or nipple of the mother. 
 
 § 642. 
 About the clofe of the firft year, the infant 
 learns to (land alone, and fupport i'felf in an < 
 pofition, the greateft and mod enviable prerogative 
 with which the human body is dignified. 
 
 § 643. 
 The infant being thus removed from its mother's 
 breail, and poflefUng the ufe and command of its 
 feet, makes daily advances in growth, and im- 
 proves in the power of fpontaneous motion, while 
 it acquires, at the fame time, another very import- 
 ant privilege conferred on the human race, namely, 
 the ufe of fpccch. Ideas which have become 
 
 familiar 
 
AND DECLINE OF MAN. 205 
 
 familiar to its mind it now begins to make attempts 
 to exprefs by the aid of that important organ the 
 tongup* 
 
 § 644. 
 About the feventh year of life, the milk-teeth, 
 or firfl fet, being twenty in number, drop out by 
 degrees, and are replaced in a feries of years by 
 a fecond dentition, confuting of thirty-two peren- 
 nial or permanent teeth. 
 
 § 645. 
 During this period of infancy the memory far 
 furpafies in ftrength and perfection the other pow- 
 ers of the mind, and appears to be indeed in a 
 very peculiar manner adapted for receiving and 
 retaining the figns of things ; whereas after the 
 fifteenth year of life, the glowing powers of the 
 imagination ufually gain the afcendency. 
 
 § 646. 
 
 This fuperior ftrength and activity of the ima- 
 gination very happily manifefls itfclf throughout 
 thofe years of life in which the human fubjeft is, 
 by a variety of (Inking and very important 
 changes in the body, gradually prepared for the 
 future performance of fuch functions as conftitute 
 the ciiaracteriftic diftindtions between the two 
 fexes. 
 
 § 647- 
 
2o<5 OF THE INCREASE, MATURITY, 
 
 § 647. 
 Shortly after this period the mamma; or breads 
 of the female fubject begin to fwell, the chin of 
 the male becomes clothed in a mantle of coarfer 
 down, and a variety of other phenomenon occur 
 in each fex, which ferve in like manner to an- 
 nounce the gradual approach of puberty : thus, 
 in the female the catamenia begin to flow ; while 
 in the male the fecretion of a true femen com- 
 mences, which is uniformly accompanied by a 
 more luxuriant crop of beards and a very ftriking 
 change in the voice from a fliriller to a graver 
 tone. 
 
 About the fame time the fexual injlincl (§ 289.) 
 that fpontaneous and potent call of nature, is firfi: 
 awakened into a&ion, and man, now in the blof- 
 fom of life, is fitted and inclined to venereal en- 
 joyments. 
 
 § 648. 
 
 The crifis or precife period of puberty cannot 
 by any means be accurately afcertained. It is 
 much varied by diverfities of climate and of tem- 
 perament. In general, however, it occurs earlier 
 in the female than in the male fex ; thus, in our 
 climate females may be faid to have arrived at 
 this interefting period againfl the fifteenth, but 
 males not before the twentieth year of life. 
 
 § 649. 
 
AND DECLINE OF MAN. 207 
 
 § 649. 
 
 Shortly after the above period the human body- 
 finally ceafes to increafe mjiature ; this particular 
 is alfo influenced and greatly diverfified by differ- 
 ence of climate, not to mention the countlefs va- 
 rieties that are exhibited relative to this point, 
 not only by different individuals, but even by 
 whole families. 
 
 § 650. 
 About this period alfo the epiphyfes, which had 
 been hitherto diftinguifhed from the bones to 
 which they were attached by very vifible lines of 
 feparation, become fo intimately united to, and fo 
 completely coalefce with thefe bones, that not a 
 veftige is left to ferve as a memento of their for- 
 mer didinc'tion. 
 
 § 65I. 
 With refpect to the term of perfect manhood, 
 which conditutes indeed the mod lengthy, as well 
 as mod ufeful and important period of human 
 life, we find it charaSerifed by the higheft de- 
 grees of vigour and uniformity, when we examine 
 the function? of the body, and by that moft inva- 
 luable prerogative, maturity of judgment, when 
 we take into confideration the faculties of the 
 mind. Throughout this imereding period the 
 
 lamp 
 
:o8 Of THE INCREASE, MATURITY, 
 
 lamp of human life blazes with the higheft degree 
 of intenfity and fplendor. 
 
 § 652. 
 The heralds which unerringly announce the in- 
 trufive approach of old age are, in females, the 
 cefTation of the catamenia, (§ 547. ), in males, a 
 languid propenfity to venereal gratifications, and 
 in both an invafion of what is called the rigidity 
 or drynefs of old age, with a flow but fenfible de- 
 clination of the vis vita, or aggregate power of 
 performing the various functions of life. 
 
 Finally, the frigid reign of the ultimate degree 
 of old age is ftrcngly characterifed by the follow- 
 ing concomitant phenomena, namely, a fluggifh* 
 nefs and increafmg dulnefs of the fenfes, both ex- 
 ternal and internal, an irrefiftible call for longer 
 indulgence in fleep, and a torpidity and languor 
 in all the functions of the animal economy. The 
 hairs aifume a filvery gray, and fall in part from 
 their exalted fituation. The teeth themfelves 
 drop fpontaneoufly from their declining fockets. 
 The neck is no longer able to fupport the head, 
 nor the tottering legs to fultain the weight of the 
 incumbent body. Even the bones themfelves, 
 thofe indifpenfible fulcra of the whole machine, 
 1 are 
 
AND DECLINE OF MAN. 209 
 
 are obliged to bear a part in this irremediable 
 and univerfal decay. 
 
 § 654. 
 We have thus arrived at length to the remote 
 ultimatum of phyfiology, namely, death without 
 difeafc, or the cuthanafia of old age. To conduct 
 and protract human life to this only natural ter- 
 mination (the caufes of which are fufticiently ob- 
 vious from what has been already laid down) con- 
 ftitutes indeed the alpha and omega, i. e. the fole 
 and exclufive end and object of the healing art. 
 
 § 655. 
 
 The phenomena of this natural death (as obferved 
 in man when about to refign himfelf to its potent 
 grafp), are, a coldnefs of the extremities, a lofs 
 of the brilliancy of the eyes, a very fmall and 
 flow pulfe, accompanied with intermiflions pro- 
 greffively increafmg in frequency, and laftly a flow 
 refpiration, which by a more forcible act of ex- 
 fpiration, is at length clofed for ever. 
 
 In the live-diflections of animals belonging to 
 the clafs mammalia, there is a convenient oppor- 
 tunity for obferving the lad exertions of the heart, 
 from which it appears, that the right ventricle 
 and auricle of that vifcus refill the encroachments 
 
 vol. 11. O of 
 
2io OF THE INCREASE, MATURITY, 
 
 of death longer, and continue the motions of life 
 to a later period, than the left. 
 
 § 656. 
 
 Coiclnefs accompanied by rigidity, a cadaverous 
 flench, but more efpecially a flaccidity of the cor- 
 nea, and a hiatus or gaping of the anus afcertain 
 in the mod unequivocal manner the complete death 
 of the body. When in the corpfe an aggregate 
 collection of all thefe figns occur at once, not even 
 the fceptical Pliny himfelf could find room to inrer- 
 pofe the fhadow of a doubt reflecting the complete 
 extinction of animal life. 
 
 § 657. 
 
 To afcertain with definitude the natural term of 
 the life of man, (or to point out that period 
 which nny be confidered as the more frequent and 
 regular goal or ne plus ultra of human exigence), 
 is, indeed, a matter attended with the utmoft diffi- 
 culty. 1 have notwithftanding learnt, from exa- 
 mining with care and comparing with accuracy, a 
 great number of bills of mortality, that a confider- 
 able proportion of fuch Europeans as are advanced 
 ia years reach, but that very few of them pafs, 
 1 :ie eightieth and fourth year of life. 
 
 § 658. 
 
AND DECLINE OF MAN. 211 
 
 § 658. 
 We may obferve upon the whole, that in con- 
 fequence of the weaknefs and tender fufceptfbility 
 of infancy and childhood, the intemperance and 
 irregularity of an infinitude of adults, the incon- 
 trolable violence of difeafes, and a countlefs 
 multitude of fatal cafualties, not more of mankind 
 than feventy eight in a thoufand refign their lives 
 to that fpecies of death now under confideration, 
 namely, death without difeafe. Notwithstanding 
 the truth and authenticity of the preceding obfer- 
 vation, yet on making a genuine eftimate of human 
 longevity and comparing it, under fimilar circum- 
 ftances, with that of the other fubjefts belonging 
 to the clafs mammalia, whofe natural term of 
 exigence is known to us, it will evidently appear, 
 that, except the bafelefs declamations of fop hi/is 
 regarding the miferies of human life, nothing can 
 be more unfounded and irrational than their fplen- 
 did and verbofe effufions refpe&ing its brevity. 
 
 O o. 
 
APPENDIX, 
 
 IN WHICH IS EXHIBITED A 
 
 Condenfed and Summary View 
 
 OF THE 
 
 EXISTING DISCOVERIES AND SPECULATIONS 
 
 Relative to the Subject of, what is ufually denominated, 
 
 ANIMAL ELECTRICITY. 
 
 STEADY and uniform as the lapfe of 
 time itfelf, are the exertions made by the enter- 
 prize and induftry of man, to fhed light on the 
 arcana or fecret proceffes of nature. In proportion 
 as fuch laudable attempts are profecuted with 
 boldnefs and crowned with fuccefs, revolutions and 
 improvements take place in the various branches 
 of phyfical fcience. Revolutions derive birth from 
 the detection of error, while improvements refult 
 from the difcovery of truth. On the repudiation 
 of falfe principles in fcience, as well as on the 
 developement of new ones deduced from the reci- 
 O 3 procal 
 
214 APPENDIX. 
 
 procal concurrence of numerous and unequivocal 
 facts, it is not without the Sanction of reafon and 
 propriety that new fyftems are forthwith compiled, 
 digefted. and ufhcred into the world. 
 
 For, to be complete and fatisfadtory, a fyftem 
 in any branch of fcience, Should embrace and ar- 
 range in order all the well authenticated principles 
 fpontaneoufly refulting from facts already afcer- 
 tained and obfervations already made, relative to 
 that particular branch. A fyftem lefs general and 
 comprehenfive in its fcope than this, fhould be 
 deemed, at beft, but defective and partial, and 
 received as the abortive production of a mind 
 deficient in point of information. 
 
 Of the former defcription was the famous phy- 
 siological fyftem of Baron Haller, at the time its 
 iliuftrious author firft fubmittcd it to the eye of the 
 world. That excellent phyfician and philofopher 
 grafped in his acute and comprehenfive mind, and 
 detailed at large, in the work to which I here 
 allude, all the authentic and well defined princi- 
 ples refulting from the infinitude of facts with 
 which the fcience of phyfiology was at that time 
 enriched. 
 
 But all fyftems are Stationary and have been as 
 yet imperfect, while, happily for the intereft of 
 
 man, 
 
APPENDIX 2t$ 
 
 man, improvements in fcience are progreffive and 
 advancing towards perfection. In the courfe of a 
 few years, fuch a blaze of phyfical light was dif- 
 fufed abroad by the induflry and ingenuity of 
 philofophers in general, but of phyficians and 
 cheittifts in particular, that the deficiencies and 
 errors of the Baron's elaborate fyftem were ren- 
 dered obvious to the mod weak and inattentive 
 obferver. In the important doclrines refpe&ing 
 the caufes of animal heat and the nature and 
 purpofes of refpiration, in particular, entire revolu- 
 tions were efft&ed by the numerous and ingenious 
 difcoveries of chemhts in that branch of fcience 
 denominated aerology. 
 
 To fupply, as far as poflible, the deficiencies 
 of this fyftem of Haller, and to circumvent the 
 errors which the authority of fo celebrated a cha- 
 racter might tend to diffnfe throughout the minds 
 of his numerous readers, became defiderata of no 
 fmall moment in the fcience of phyfiology. 
 
 The mod effectual method of accompliihing thefe 
 defirable ends was too obvious to efcape difcovery. 
 For as violence is mod effectually repelled by 
 counter violence, and one difeafe not ^infrequently 
 removed from the animal fyftem by the impetuous 
 invafion of another, fo in like manner., in fcience, 
 the defects of one fyftem are moft advanrageoufly 
 O 4 fupplicd 
 
ii6 APPENDIX. 
 
 fupplied, and its errors moft effectually contrc- 
 verted and expoftd, by the plenitude and unequi- 
 vocal certainty cf the principles of a rival fyftem. 
 
 This truth did not efcape the obfervation of that 
 learned and acute profeffbr, of Goettingen, who 
 new fills the chair which was formerly rendered 
 vocal by the eloquence of the immortal Haller. 
 Need I add, that profeffor Blumenbach is the man 
 to whom I allude — a man, for the completion of 
 whofe greatnefs and utility in phylical fcience, 
 nature and art appear to have all but exhaufted 
 their abundant refources ! For induitry and perfe- 
 verance in the collection of materials, for powers 
 to combine and arrange materials when thus col- 
 lected, and for ingenuity and acumen to deduce 
 and fpeculate from fuch combination and arrange- 
 ment, the prefent age certainly boafts few-r-too 
 few phyfioiogifts who may be fee in competition 
 with the illuftrious Blumenbach. 
 
 For this phyfician and philofopher was referved 
 the honourable and important taH: of collecting, 
 digefting and consigning to publicity, a fyftem of 
 phyfiology clefiined to fupply the deficiencies and 
 correct the errors of that which had already 
 refulted from the labours or hi-j celebrated friend 
 :kpA predeceiTor. The fyftem of profeifor Blumen- 
 bach. was, like that of Baton Haller, perfect: and 
 
 complete 
 
APPENDIX. 217 
 
 complete at the time in which it was handed to 
 the world. There exifted not, at that period, an 
 eftabli fned principle, nor fcarcely even a probable 
 conjecture in phyfiology, with which he was not 
 minutely acquainted, and which he did not draw 
 into the extenfive and powerful vortex of his 
 fyflem. 
 
 Had the fcience of phyfiology been finally com- 
 plete at the time in which proieflbr Blumenbach 
 wrote, the induftry, the immenfe refources and 
 the ccmprehenfive talents of that philrfopher 
 would, no doubt, have quire precluded the necef- 
 fity of future fy (terns in this branch of fcience. 
 But in the unfathomed depths of the animal 
 economy more arcana yet exifted — more terra 
 incognita lay yet unexplored, and further re- 
 fearches of enterprise were therefore effenthiLi 
 
 By the combined labours of experimental phyfi- 
 ologids in different parts of the world, this branch 
 of fcience was at length matured for giving birth 
 to another difcovery, which will probably be found 
 of equal importance, in explaining the phenomena, 
 and in removing the difeafes of the animal fyflem, 
 with that which consigned to immortality the name 
 of the illuftrious Harvey. The difcevcry to which 
 I wifli at prefent to direct the attention of the 
 reader is that of, what is ufua'.ly called animal 
 
 > V'7; Icity. 
 
t\% APPENDIX. 
 
 elcclricity, or, of the exigence and operation of a 
 fluid extremely fimilar to electricity in the living 
 animal fyftem. For the fortunate Galvani pro- 
 felfor of anatomy at Bologna, was referved the 
 honour of lighting by accident on this beautiful 
 and divine difcovery — a difcovcry which entitles 
 its author to be ranked with the great promoters 
 fcience and the enential benefactors of man. 
 
 That fuch a fluid did actually exiit in the bo- 
 dies of animals, had been long fufpe&ed by phy- 
 fiologifts and other fpeculative philofophers. The 
 matter refted however on pure conjecture alone, 
 and was yet unfan&ioned by the tefls of experi- 
 ment and obfervation. The apparent intricacy 
 of the fubject deprelfed the hopes of the boldefl 
 experimenters, and the fubtlety of the investiga- 
 tion feemed to throw an infurmountable bar in the 
 road to fuccefs. But accident not unfrequently 
 does more for the real advancement of fcience, 
 than boafled genius and induftry are able to ac- 
 complifh. It was accident that firft fuggefted to 
 the celebrated Gallileo the conftruction and ufe 
 of that optical inftrument denominated the tele- 
 fcope—It was accident which firft led the immortal 
 Newton to the original conception of that prin- 
 ciple of gravitation, by which he afterwards ex- 
 plained, with fuch facility, the movements and ex- 
 quifite balance of the material univerfe. And it 
 
 was* 
 
APPENDIX. 219 
 
 wis, in like manner, accident — fortunate accident, 
 that firft fuggefted to the induftrious and acute 
 Galvani the mode of experimenting, with effect, 
 on the intricate fubjecl of animal eledricity—2. 
 fubje<ft which may poffibly be deftined as the only 
 proper clue to conduct future phyfiologifts to the 
 genuine fprings and principles of life itfelf. 
 
 " Whilfl the profeflbr (alluding to Galvani) 
 was engaged in drfTe&ing a frog in a room where 
 fome of his friends were amufing themfelves with 
 an electrical machine, one of them drew a fpark 
 from the conductor, at the fame time that the 
 profeffor touched one of the nerves of the animal. 
 In an jnftant the whole body of the frog was 
 fhook by a violent convulfion. The profeiTor 
 was aftonifhed at the phenomenon, and believed 
 it owing to his having wounded the nerve ; to 
 affure himfelf whether this was really the cafe, 
 he pricked it with the point of his knife, without 
 any motion of the body being produced ; he how 
 touched the nerve with the inftrument as at firft, 
 and ordered a fpark to be taken from the machine, 
 on which the contractions were renewed. The 
 experiment was repeated a third time, but the 
 animal remained motionlefs ; however, upon per- 
 ceiving he held his fcalpel by the handle, which 
 was of ivory (a bad conductor), he changed it 
 
 for 
 
— APPENDIX. 
 
 for a metallic one, and re-excited the movements,- 
 which he conftantly failed of doing whilft: ufing 
 an electric fubftance. 
 
 " After having made a number of experiments 
 with the elect ical machine, he refolved to profe- 
 cute the fubject with atmofpheric electricity. To 
 this end he raifed a conductor upon the roof of 
 his houfe, from which he brought an iron wire 
 into his room, and to this attached metal con- 
 ductors, connected with the nerves of the animals 
 defined to be the fubjects of his experiments, 
 and to their legs he tied wires, which reached the 
 floor. Confiderable movements were obferved in 
 the animals, whether of cold or warm blood, 
 whenever it lightened. Thefe preceded thun- 
 der, and corrtfponded with irs intenfity and re- 
 petition, and even when it did not lighten the 
 movements took place when any florniy cloud 
 palled over the apparatus." 
 
 " Profeffor Galvani one day lufpended fome 
 frogs, perhaps with fimilar views, on metal hooks, 
 fixed in the fpiric of the back, upon the iron rail- 
 ing of his garden ; feveral times he remarked that 
 thefe animals contracted, and appeared to receive 
 fhocks ; at firft he conceived the movements were 
 owing to changes in the atmofphere, but a more 
 
 fcrupulous 
 
APPENDIX. 22} 
 
 icrupulous examination undeceived him* Having 
 placed a prepared frog * upo:i an iron plate in his 
 room, and happening with his differing forceps to 
 prefs it againfl the plate, he obferved the move- 
 ments to take place. This experiment fuccecded 
 with all metallic bodies, but more particularly well 
 with filver ; non-conducing fubftances were not 
 proper for it. From this period our author began 
 to fuipeft the animal pofTefTcd an electricity of its 
 own ; and in this fufpicion he was further con- 
 firmed by the following circumftance : — He held 
 
 * That the reader may not be entirely ignorant of what is 
 meant by a prepared frog, I take the liberty of prefenting 
 him with the following brief extract from the firft experi- 
 ment detailed in Dr. Valli's publication : " My firft experi- 
 ment was made on a frog, in the following manner : I opened 
 the abdomen in order to lay bare the fpine of the back, and 
 difcover the crural nerves which i.Tue from it ; a few lines 
 above this point I cut the animal in two, and by p ailing my 
 fciilars immediately under the origin of thefe nerves, re- 
 moved the remaining portion of the vertebral column, fo 
 as only to leave the vertebra: which united the bundle of 
 nerves. Having enveloped this portion of the vertebra with 
 a piece cf ftiee'; lead, with one end of a metal conduflor, I 
 touched the coated part, and with the other the furface of 
 the thighs, which had been previously ftripped of the fkir. 
 The movements were violent, and continued for a long time," 
 &c. In general, throughout the whole of tlvs phyfician's 
 expertmental treatife, when one cr more of the nerves of an 
 animal arc coated with (heet-lcad or any ether metal, that 
 animal is faid to be prepared, 
 
 to 
 
it* APPENDIX. 
 
 a prepared frog by a hook with one hand, (o as 
 to let its feet reft upon the bottom of a fraall fil- 
 ver cup, which he happened unintentionally to 
 ftrike with the other ; at the inftant the body of 
 the animal fell into violent convulfions. If one 
 perfoa held the prepared frog, and another touch- 
 ed the cup, no movements were excited. The 
 profeflbr being now aware of the neceffity of a 
 communication, undertook a feiies of experiments 
 for the farther investigation of this fubject. He 
 firft placed a prepared frog upon a non-conduct- 
 ing furface, and brought one end of a conductor 
 in contact with the hook which fecured the ani- 
 mal, and with the other touched its feet, on which 
 the contractions took place. When the conduct- 
 ing arch was interrupted by a non-conducting 
 fubftance, the frog remained motionlefs, &c." 
 
 No fooner hadproftlTor Galvani publifhed to 
 the world his experiments en animal electricity, 
 than their fame difpread, fwift us the intangible 
 fluid which they regarded, throughout the differ- 
 ent parts of Europe. Animal electricity became, 
 in a fhort time, a fubject of very interefting fpecu- 
 lation to medical philofophers. Among the feve- 
 ral phyfiologifts who entered the lifts in this in* 
 veftigation, the molt diftinguifhed whofe writings 
 have fallen into my hands, are Dr. Valli, an Italian 
 phyfician, from whofe publication the preceding 
 
 account 
 
APPENDIX. 223 
 
 account refpe&ing the firft difcoveries of Galvani 
 is extracted, and Mr. Fowler, a native of the 
 ifland of Great Britain. 
 
 Do£tor Valli appears to have led the van of 
 thofe philofophical characters who firft co-ope- 
 rated with the celebrated Galvani in inveftigating 
 that animal fluid, the exigence of which had been 
 {o long fufpefled, but fo lately realifed by actual 
 experiment. After repeating mod of the experi- 
 ments of his predeceffor in this branch of phyfics, 
 the Doclor proceeded to a feries of new experi- 
 ments, moftly conceived and inftituted by himfelf. 
 
 The objects which he appears to have kept flea- 
 dily in view throughout the whole courfe of his 
 experiments and obfervarions were, to afcertain 
 the nature of the animal fluid difcovered by the 
 profeflbr of Bologna, and to determine its influ- 
 ence and medium of operation in the animal eco- 
 nomy. In the profecution of thefe ends the Doc- 
 tor has doubtlefs difplayed all that iuduftry and 
 patient perfeverance, (o eflentially requisite in the 
 character who would fuccefsfully inquire of na- 
 ture, through the medium of experiment. I am 
 forry ,however, to obferve, that all his experiments 
 were not conceived and inflituted with equal in- 
 genuity, and perhaps I may add, not executed 
 •with equal accuracy and defmitude. Many of 
 
 many 
 
224 APPENDIX. 
 
 them appear to have been indituted without a di- 
 rect reference to any fpecific or particular end — 
 Equally unhappy with regard to conception, inde- 
 finite with refpeft to their nature, and inconclu- 
 sive in point of refult, they leave no imprefflons 
 on the mind of the reader, five thofe of d'tfap- 
 poiniment and regret — regret that a character of 
 fuch learning and induftry ihould, notwithdand- 
 ing, interrogate nature with fo little meaning, and 
 (I am forry to add) with fo little fuccefs. 
 
 The preceding obfervations mud be confidered 
 only in the light of general rules, and as fuch, 
 are liable to numerous exceptions. Many of the 
 experiments of Dr. Valli are, doubtkfs, both in- 
 genious and valuable ; and I even entertain the 
 utmoft confidence, that the period will yet arrive, 
 when the whole of them, that are afcertained 
 and related with juflnefs and definitude, will be 
 made fubfervient to the eilablifhment of general 
 and ufeful remits. At prefer) t, however, they 
 (land in an infalaled date, completely detached 
 from practical conclufions, and difconnected from 
 all known principles in phyfical feience. 
 
 After a feries of experiments fufliciently lengthy 
 and tedious, the Doctor conceived himfeif une- 
 quivocally authorifed to conclude, that the animal 
 fluid of Galvani, was entirely the fame with the 
 4 fu 1 — I 
 
 
APPENDIX. 225 
 
 fubtle matter of electricity. This conclufion he 
 alleges to be the fpontaneous and necefiary refult 
 of the following pofitions, which he delivers as 
 fubftantiated and confirmed by actual experiment. 
 
 " Firft, fubftances which conduct electricity, 
 are conductors likewife of the nervous fluid." 
 
 " idly, Subftances which are not conductors 
 of electricity, do not conduct the nervous fluid.'* 
 
 " 3^//y, Non-conducting bodies, which acquire 
 by heat the property of conducting electricity, 
 preferve it likewife for the nervous fluid." 
 
 " Atbly, Cold at a certain degree, renders water 
 a non-conductor of electricity, as well as of the 
 nervous fluid." 
 
 " $thly, The velocity of the nervous fluid is, 
 as far as we can calculate, the fame with that of 
 electricity." 
 
 " 6thly, The obflacles which the nerves, under 
 certain circumflances, oppofe to electricity, they 
 prefent likewife to the nervous fluid." 
 
 " ytbly, Attraction is a property of the electric 
 fluid, and this property has been difcovered in the 
 nervous fluid." 
 
 vol. 11. P Having 
 
226 APPENDIX. 
 
 Having enumerated and detailed the foregoing 
 arguments, the Doctor, in an erfufion of triumph, 
 fubjoins, " We here fee the greateft analogy be- 
 tween thefe fluids ; nay, I may even add, the cha- 
 racters of their identity." 
 
 As an additional fupport to the fame opinion, 
 Dr Valli adduces the peculiar and ftriking pheno- 
 mena exhibited by the torpedo, the gyninotus elec- 
 trieus, the Jilurus, &c. which proceed, as he 
 alleges, from a fluid in every refpect the fame 
 with that which was difcovered in frogs, by the 
 profeflfor of anatomy at Bologna. As the Doctor, 
 however, has advanced nothing in confirmation of 
 fuch entire famenefs, fave a certain remote analogy 
 which he fays he has difcovered between the muf- 
 cles of animals, and the electrical apparatus of the 
 torpedo, the gymnotus, &c. it is obvious that this 
 latter argument will but very flightly imprefs the 
 philofophical phyfiologift, who founds his belief 
 of principles on facls, rather than on vague and 
 vifionary conjectures. 
 
 Having thus, as he fuppofed, fatisfactorily afcer- 
 tained the identity of the nervous with the electric 
 fluid, he next proceeds to fpeculations on its in- 
 fluence in the diverfified movements and functions 
 of the animal economy. To me, however, I mud 
 confefs, the greater part of this fpeculative invef- 
 ligation, appears to be rather the eflervefcent 
 
 effufions 
 
APPENDIX. 227 
 
 effufions of an imagination, heated to excefs in a 
 favourite purfuir, than the folemn decifions of a 
 tranquil and unbiafTed under/landing. I acknow-> 
 ledge myfelf unable, in many inftances, to difcern 
 the necefTary nexus or affinity between his con- 
 clufions, and the fa&s from which they are de- 
 duced : — or perhaps I may fpeak my fentiments 
 more fully when 1 fay, that the learned author 
 appears not unfrequcntly to have fubftitutcd mere 
 hypothetical allegations, for fair and logical conclu- 
 fions — the vacant refults of his own conjectures, 
 for genuine principles developed by experiment, 
 and afcertained by obfervation. It very often 
 happens, that by attempting to embrace too much 
 under a fingle caufe, we extend the tortured 
 principle beyond its natural limits, and thus,- to 
 appearance, weaken or render doubtful its influ- 
 ence, even on thofe phenomena which it immedi- 
 ately regards. This obfervation applies with too 
 much propriety and force, to the fpeculations of 
 the indefatigable Valli. By attempting to explain 
 all, he has in fa£t explained none, of the pheno- 
 mena of the animal economy, by that fubtle fluid 
 on which he fo patiently experimented. Many of 
 his phyfiological fatts and fpeculations are indeed 
 ingenious and interesting, but, in my view, they are 
 equally deducible from any other feries of experi- 
 ments, as from that by which they are preceded 
 in the Doctor's publication. Many of the learned 
 author's fafts may be, no doubt, true and well 
 P 2 defined 
 
228 APPENDIX. 
 
 defined, and forne of his principles and refults to 
 a certain degree interefting to the phyfician and 
 philofopher, but, taken in the aggregate, they 
 are too diljointed to conftitute any thing like a 
 fyftem, too difconne&ed to form a regular chain 
 of investigation. On my mind, his /peculations 
 on the caufes of mufcular motion, fenfation fecre- 
 tion and nutrition, imprefs no more folid convic- 
 tion than do ihofe of Stahl on the fubjeft of his 
 anima medica, of Van Helmont refpe&ing his 
 fubtle Archeus, or of the airy Paracelfus with re- 
 gard to his planetary influence, Notwithftanding 
 the apparent feverity of the foregoing obferva- 
 lions, I am fiiil obliged to declare it as my 
 opinion, that the novelty and importance of the 
 fubject on which Dr Valli has experimented and 
 written, entitle his work to the particular atten- 
 tion of the learned and ingenious of every na- 
 tion. 
 
 For the want of fyftem and requifite decifion in 
 the writings of the preceding author, compenfation 
 is, in a great meafure, made by a fubfequent pub- 
 lication of the accurate and ingenious Fowler. The 
 
 experiments and fpeculations of this young philofo- 
 pher, on what he terms, the " influence difcovered 
 by Gahani," made their firft public appearance 
 at Edinburgh, in the courfe of the year 1793 : 
 they are not, indeed, fo numerous as thofe of the 
 Italian phyfician, but they appear to have been 
 
 conceived 
 
APPENDIX. 229 
 
 conceived with more defign, and executed with 
 more judgment. Mr. Fowler feems to have been 
 among the firfl who controverted the opinion of 
 Galvani and Valli, reflecting the identity of the 
 nervous and electric fluids: and he has, doubtlcfs, 
 controverted it with ability and effect. 
 
 Mr. Fowler preliminates his obfervations, with 
 a lucid and forcible Statement of a certain previous 
 combination of circumftances, which he alleges, 
 muff haveftrongly prepoflfefTed the mind of profeffor 
 Galvani, with a belief of the famenefs of the pre- 
 ceding fluids. 
 
 That fuch a prepoffeflion mufl have had, indeed, 
 a powerful effect on the ifubfequent dedu&ions and 
 conclufions of the Profeffor, will be readily ac- 
 knowledged, by every one who has experienced 
 the influence of preconceived opinions — an influ- 
 ence pregnant with error, and leading countlefs 
 evils in its train. 
 
 Mr. Fowler proceeds then to mention the firft 
 object which engaged his attention, in the com- 
 mencement of his interesting inquiry, and which 
 appears well calculated to pave the way, for the 
 more eafy and effectual accomplishment of his 
 experimental courfe. This, to make ufe of his 
 cwn words, was, " to afcertain, as well the va- 
 P 3 rious 
 
23® APPENDIX 
 
 rious circumftances, effentially requisite to the 
 production of thefe new phenomena, as thofe in 
 which they can be rendered moft obvious." The 
 iflue of his enquiry on this fubj £t, 1 will alfo lay 
 before the reader in his own words. " After" 
 fays he, " a great variety of experiments, of which 
 it wonld be unneceffary here, to relate more than 
 the refult, I found, that I could not excite in an 
 animal the appearances defcribed by Galvani, with 
 any fubftances whatever, whether folid or fluid, 
 except the metals : and that the mutual contact of 
 two different metals with each other, fo far as I 
 was able to determine, was in every cafe neceffary 
 to the effcc~t." 
 
 After a fatisfa&ory attainment of this object, 
 the ingenious author next proceeds to a judicious 
 feries of experiments, with a view to difcover the 
 genuine nature of the animal fluid, firft realifed by 
 the fortunate profeflfor of Bologna. Of thofe ex- 
 periments he does not give us a minute fpecifka- 
 tion, but only furnifhes fhiternents of their moft 
 obvious and linking refults. Thefe Abatements he 
 alfo occafionally interfperfes with intertfting and 
 important remarks, and fome very ingenious fpe- 
 culations. 
 
 Having flnifned his feries of experiments, (a 
 feries fufiiciently numerous and diverfified for the 
 
 eftablifhment 
 
APPENDIX. 231 
 
 flablifhment of general principles) relative to the 
 nature of the nervous fluid, and its affinity to the 
 matter of electricity, Mr. Fowler at length favours 
 us on this fubject with the following conclusions, 
 which I fhall take the liberty of preferring to the 
 reader in the words of their ingenious anthor. 
 
 After having ftated a few analogies between the 
 animal fluid of Galvani, and that pofLflfed by the 
 torpedo, he then reverfes the comparifon, and 
 lays down feveral points of effential difference, 
 not only between the two preceding fluids, but 
 alfo between the former of them, namely the fluid 
 of Galvani, and the matter of electricity. 
 
 " This influence, (fays he, referring to the 
 nervous fluid of animals) differs, both from that 
 of the torpedo, &c. and from electricity, in pro- 
 ducing no fenfation (in man at lead) at all fimilar 
 to that of an electrical {hock." 
 
 " That fome kind of difaereeable fenfation 
 
 is occafioned by it, even in frogs, independent of 
 that which mud neceffarily arife from irritation 
 and the contractions of their mufcles, is evident 
 from their reflleffnefs and expreffions of uneafinefs. 
 In other animals, as I mall afterwards have occa- 
 fion to fhew, thefe expreffions are (till lefs equi- 
 vocal : and in man we can afcertain both their 
 P 4 degree 
 
232 APPENDIX. 
 
 degree and their kind. That they differ confider- 
 ably from fuch as are produced by electricity will 
 be proved when I come to fpeak of the effects of 
 this influence upon our fenfes." 
 
 <c But the mod: important, and characteristic 
 difference which I have yet been able to difcover, 
 between this new influence and electricity, confifts 
 in their effects upon the contractile power of 
 auimals and of plants. The contractions of ani- 
 mals excited by electricity have a tendency to 
 deftroy that power upon which contractions de- 
 pend. But the contractions excited, by the appli- 
 cation of the metals, have, in all my experiments, 
 had the directly oppofite effect. The more fre- 
 quently contractions have been in this way excited, 
 the longer do they continue excitable : and the 
 longer are the parts upon which fuch experiments 
 are made, preferved from putridity. An influ- 
 ence, capable of exciting contractions without 
 occafioning exhauflion, was a thing I fo little 
 expected to find, and fo contrary to the character 
 which had been given of this both by Galvani 
 and by Doctor Valli, that I at flrfl diftrufted my 
 own observation of the fact : but the number of 
 comparative experiments which I had afterwards 
 cccafion to make, though with views different 
 from that of afcertaining the point in queftion, 
 convinced me that this influence, fo far from 
 
 deftroyjng 
 
APPENDIX. 233 
 
 deftroying the contractility of mufclcs, has a ten- 
 dency to preferve it. Oxygene is, fo far as I 
 know, the only ftimulus in nature, whofe effects 
 are at all analogous." 
 
 " When a frog has been long dead, I have 
 been fometimes more than a quarter of an hour 
 without being able to excite a fingle contraction 
 by the application of the metals : but after this, 
 without at all varying the means employed, con- 
 tractions have appeared, and have become gradu- 
 ally more and more vigorous. " 
 
 " It is laid (for I have never had an opportunity 
 of making the experiment), that a dream of elec- 
 tricity, palTed through a fenfitive plant, produces 
 an almoft immediate collapfe of its leaves. But 
 the influence difcovered by Galvani produced no 
 fuch effect in the following experiment. Having 
 feparated the leg of a frog from its body, I freed 
 its crural nerves from furrounding parts, and with 
 one hand held it fupported upon the end of a 
 probe. An afliftant placed a piece of filver under 
 its foot, and held the zinc with which it was to 
 be touched, A fenfative plant formed the medium 
 of communication between us. He held the bot- 
 tom of its (tern between his fingers, while I held 
 the top ; fo that when the filver was touched by 
 the zinc, the influence paffed tip the plant, and 
 
 through 
 
234 APPENDIX. 
 
 through the whole of its ftem. The frog's teg 
 inftantly contracted, and repeated its contractions 
 every time the filver and zinc were brought in 
 contact : but the leaves of the plant did not col- 
 lapfe ; neither did they when any of its branches 
 formed part of the circuit." 
 
 I mufl however, confefs that the plant, upon 
 which this experiment was made, had been kept 
 through the winter. With a young one the refult 
 might poflibly be different ; but fuch an one I 
 have not yet had in my power to procure. 
 
 " The torpedo does not appear at all affected 
 by the influence which itfelf produces. Animals 
 in which Galvani's phenomena are produced, are 
 ftrongly affected." 
 
 The very ingenious author paffes on next to 
 report the refult of certain experiments which he 
 inflituted, in order to refute the opinion of thofe, 
 who allege, that the fluid of Galvani proceeds 
 entirely from the metallic fubftances ufcd, and 
 does not refide at all in any part of the animal 
 fyftem. In his enquiry refpecting this point he 
 difplays the fame fertility in devifing, the fame 
 fagacity in judging, and the fame ingenuity in 
 deducing, which fo forcibly imprefs the reader 
 throughout every part of his experimental invefti- 
 
 gation. 
 
APPENDIX. 235 
 
 gation. He alfo farther {hows, that the nervous 
 influence of Galvani, and the fubtle fluid of elec- 
 tricity differ very materially from each other in 
 the following particular, namely, that againft the 
 effects of the former, animals are able to guard 
 thcmfelves by means of a certain voluntary exer- 
 tion, whereas the operation of the latter is not in 
 the fmalleft degree fubjeft to the controul or in- 
 fluence of the will. 
 
 Having fmifhed the confederation of the nature, 
 Mr. Fowler proceeds to make fome ufetul appli- 
 cations ^ of the influence difcovered by the profeflfor 
 of anatomy at Bologna. In his attempts to ftied 
 light on certain controverted points, and to folve 
 certain abflrufe qneftions, in phyfiology, by means 
 of this fluid, he appears no lefs ingenious and 
 fatisfa&ory than in the former parts of his 
 enquiry. 
 
 He appears peculiarly happy and conclufive in 
 his refearches after the fource from whence the 
 nerves and mufcles derive their refpe&ive powers. 
 I beg leave to lay before the reader two of the 
 author's experiments, inflituted for the purpofe ot 
 afcertaining this interefting particular — a particular 
 which has fo long furnifhed a fubjeft of Gontro- 
 verfy among fpeculative phyGologifts. The latter 
 of the two experiments, (to which the former 
 
 ferves 
 
2^6 APPENDIX. 
 
 ferves only as a necefTary introdu&ion) is of itfelf 
 more than equal to all that has ever been ad- 
 vanced on the oppofke fide of the queltion. 
 
 Experiment I. 
 " I divided (fays Mr. Fowler) the fciatic nerve 
 of one leg, and tied the crural artery of the other 
 in a large frog. Scarcely any blood was loft in 
 doing either. Two days after this I ftrangled it. 
 During the firft 24 hours, the leg in which the 
 nerve had been divided, appeared to contract with 
 the mod vigour; after this period the difference 
 between them became more doubtful; but the 
 contractions were at no time ftronger in the leg 
 whofe artery was tied, than in that whofe nerve 
 was divided. 
 
 Experiment II. 
 
 " The fame operations were performed upon a 
 large female frog full of fpawn. Four hours 
 afterwards {he was covered by a male, who had 
 been treated in a fimilar manner. I mention this 
 circumftance, as it tends to prove, that the pain 
 occafioned by the operation was probably not fo 
 great as to produce much fallacy. 
 
 " On the day following, (lie had fpawned, and 
 on the fixth day from the operations, me was 
 Wrangled. When laid upon a plate of zinc, and 
 
 excited 
 
APPENDIX. 237 
 
 excited by means of a rod of filver, the contrac- 
 tions were found extremely feeble in the leg 
 whofe artery had been tied, and ceafed altogether 
 in about twenty-two hours after her death. 
 
 In the leg, whofe nerve had been divided, they 
 appeared as vigorous as they ufually are in legs 
 to which no injury has been previoufly done, and 
 continued excitable upwards of two days after 
 they had ceafed to be fo in the other.'* 
 
 It may be proper on the prefent occafion briefly 
 to obferve, that the influence difcovered by Gal- 
 vani was the tefl ufed by Mr. Fowler to determine 
 the exiftence or ceffation of irritability in the 
 mufcles of the animals fubje&ed to the preceding 
 experiment. For this influence, as our author 
 judicioufly obferves, appears to be indeed by far 
 the beft and moft delicate tefl: that has ever yet 
 been difcovered for afcertaining the loweft poflible 
 degrees of mufcular irritablility. After having 
 become wholly infenflble to the impreflions of all 
 other flimuli, mufcles flill continue to vibrate to 
 the kindred touches of this fubtle fluid, to which 
 nature appears to have given them fuch a nice, 
 and, perhaps I may fay, fpeciflc correfpondence. 
 
 Mr. Fowler, after having tranfiently glanced 
 on the fubjeft of inflammation, pafles on to the 
 
 attack 
 
238 APPENDIX. 
 
 attack of a phyfiological doctrine, propagated with 
 zeal, and fupported with ability by that celebrated 
 experimentalift, the Abbe Fontina. The doctrine 
 alluded to, embraces the exiftence or refidence of 
 a certain vital principle in the volume of the 
 blood. On this principle, as the induftrious 
 Abbe alleges, poifons produce their inflantaneous 
 effect, when introduced into the vafcular fyftems 
 of living animals. To all the different parts of 
 this phyfical doctrine I could never yet be induced 
 to fubfcribe, notwithstanding the refpectability of 
 its learned and numerons advocates. 
 
 By attacking and vanquifhing one of its mofl 
 powerful champions, Mr. Fowler has doubtlefs 
 contributed much to its final demolition. For, in 
 the conteft now under our immediate confide- 
 ration, I mud confefs, that to me the laurels of 
 victory appear to be fairly wrefted from the 
 filvered temples of the Italia?i, and planted over 
 the youthful brow of the BritiJJj Philofopher. 
 
 I have thus exhibited a view, fomewhat general 
 indeed, though confeffedly very fuccinct, of the 
 refults laid down, and of the opinions entertained, 
 by the ingenious Fowler, on the fubjeet of the 
 animal influence difcovered by ProfefTor Galvani. 
 To lay before the reader a full account of all that 
 is ufeful and important in the obfervations of this 
 
 imereflin<s 
 
APPENDIX. 239 
 
 interefting author, would be to tranfcribe and re- 
 print his whole publication. 
 
 The only productions in the Englifh language, 
 whirh this country now furnifhes, profefLdly on 
 the fubjeft of the animal fluid difcovered by Gal- 
 vani, are (as formerly obferved) thofe of Fowler 
 and Va Hi. On the comparative merit of thofe 
 two authors I will here take the liberty of 
 advancing a few general, and, I flatter myfelf, 
 impartial, obfervations : 
 
 The experiments of Doctor Valli are more 
 numerous and pompous — thofe of Mr. Fowler 
 more definite and intelligible. The former aurhor 
 appears often, the latter, never, to have experi- 
 mented without fome determinate end in view. 
 The experiments of the Italian may be compared 
 to the promiscuous plants of the foreft, ftrewn at 
 random by the fportive and irregular hand of 
 nature — thofe of the young Briton, to choice and 
 valuable coI't£tions, arranged with order and 
 elegance, in a well regulated and beautiful garden. 
 The experiments of Valli appear to throw into 
 Jhade, thofe of Fowler into light, the objects 
 which they immediately regard. From the for- 
 mer, the reader collects information with diffi- 
 culty, from the latter, without labour or painful 
 attention. 
 
 In 
 
24o APPENDIX. 
 
 In their deductions and fpeculations, the two 
 preceding authors are no lefs diflimilar, than with 
 regard to their experiments themfelves. Valli is 
 more diffafe and often hypothetical — Fowler more 
 pointed and generally conclufive. Valli appears 
 to give loofened reins to a glowing imagination — 
 Fowler to be conftantly under the fteady guidance 
 of a powerful and well-cultivated underftanding. 
 The former makes a greater difplay of learning, 
 and, therefore, too frequently views objects 
 through the more obfeure media of previous 
 publications — the latter exhibits a higher degree 
 of ingenuity, and derives the principal part of his 
 information, not from pages, fan&ioned only by 
 the names of celebrated, yet fallible, authors, but 
 from the great /b/zo-volume of nature, imprefled 
 with her own fignature. On the whole, Valli 
 has experimented and written in the mod lengthy 
 and profufe — Fowler in the moil definite and 
 conclufive manner. In many parts of the writings 
 of the former, nothing elfe than the fiat of an 
 almighty genius would be able to bring order out 
 of confufion — in thofe of the latter, lucidity, con- 
 nection, and regularity, fhine pre-eminent through 
 almofl: every page. 
 
 Having thus, without referve, delivered my 
 
 fentiments on the publications of others ', I hope I 
 
 may be allowed to trefpafs on the reader's attention 
 
 4 while 
 
APPENDIX. 241 
 
 while I make a few obfervations relating to my 
 
 own. 
 
 1 
 
 Nothing could have induced me thus haftily to 
 forfake the humble, but fecure, retreats of obfcu- 
 rity, and rifk myfelf before the eye of the world 
 in the hazardous character of an author, fave a 
 folicitous wifh to contribute to the advancement 
 of medical fcience, and thus aid in acquiring for 
 man a more effectual exemption from mifery and 
 pain. I faw with regret the literary trcafures of 
 a Blumenbach concealed from the view of my 
 fellow-citizens beneath the drapery of an ancient 
 and an obfolete language. I was anxioufly 
 defirous to fee the phyfiological fyftem of that 
 illuftrious character completely clothed in the 
 language of ray country. I engaged in the tranf- 
 lation of this work, not becaufe I conceived my- 
 felf better qualified for its execution than others, 
 but becaufe others appeared to me unpardonably 
 remifs with regard to the undertaking. The 
 execution proved laborious aud difficult beyond 
 my expectations. The difficulty of detecting an 
 author's precife meaning through the dulky 
 medium of a Latin expreffion, can be fully nnder- 
 ftood and realifed only by him who has made the 
 arduous experiment. 
 
 vol. 11. Q^ Even 
 
i# APPENDIX. 
 
 Even after the ideas and opinions in the original 
 are fully embraced and completely comprehended, 
 another difficulty of no fmall magnitude ftill 
 remains, namely, to convey them to the reader 
 with unequivocal definitude, through the indefinite 
 medium of a different language. It is well known 
 how extremely liable we are to mifapprehend the 
 precife meaning of an author who even writes in 
 our own vernacular tongue, much more {o of one 
 who publiihes in a language but little ufed in con- 
 verfaiion, and, at bed, but imperfectly underftood 
 by any man living. 
 
 Should the foregoing tranilation ever fall into 
 the hands of the celebrated profeffor of Geottingen, 
 I hope he will receive, with candour and indul- 
 gence, a well meant attempt to extend the empire 
 of his utility and his fame, by increafing the 
 number of his admiring readers. If the tranila- 
 tion be in any part erroneous, in any part defi- 
 cient, ftvietures and corrections will be thankfully 
 received, and punctually attended to in a fecond 
 edition of the work, fhould a fecond be demanded 
 by a patrcHifmg public. * 
 
 To preferve as far as poflible the firm and 
 energetic fpirit which characterizes the writings 
 of the illufirious profefTor of Goettingen, and to 
 
 convey 
 
APPENDIX. 143 
 
 convey to my readers the facts, the principles, the 
 fpeculations, and the opinions contained in his 
 original work, without even the (hadow of altera- 
 tion, diminution, or acMition, has been my (teady 
 and uniform aim throughout the whole of the 
 foregoing tranflation. Owing, however, to the 
 different conjlituiions or idioms, as they ate more 
 generally termed, of the Latin and Englifh lan- 
 guages, my tranflation is in many places far — very 
 far from Deng ftriftiy literal. Phrafcology I con- 
 fider, at beft, as the mere trappings or drapery of 
 compofifion, Vs'\\\\c facls and principles conditute its 
 more fubitantial and important part. To preferve 
 the latter, therefore, inviolate, and to communicate 
 them with the utmoft definitude, is the indifpen- 
 fible duty of a tranflator, from a principle of 
 juflice to the original author, to the public, and 
 to himfelf *, but in my opinion, he is not bound, 
 by any principle whatever, to make an entire 
 facrifice of all elegance and beauty, to mere puncti- 
 lious literality of expreffion. ImprefTed with the 
 propriety and truth of thefe femiments, I have, 
 throughout the whole of the foregoing work, 
 been fometimes literal and fometimes free, 
 •accordingly as the one or the other mode of 
 tranflation gave birth to a phrafeology or ftile 
 mod: agreeable to my ear, and raoft accordant to 
 the fpirit of the original compofition. 
 
 (^2 Witt 
 
244 APPENDIX. 
 
 With refpedt to the appendix itfelf, it may not 
 be amifs to make it the fubjedt of a few tranfient 
 obfervations. The principle which thefe additi- 
 onal pages regard, and are intended to commu- 
 nicate, is juftly becoming, among medical philofo- 
 phers, an object of primary importance. M his 
 principle opens to the view of the fpeculative mind 
 a rich and fpacious field, never yet printed, fave 
 by the adventurous fteps of a few pre eminently 
 active and enterprifing phyfiologifts — A field, the 
 falutary fruits of which will, no doubt, at a future 
 day, ferve to elucidate the nature, to develope 
 the compofition, and to alleviate the complicated 
 mifery of man. 
 
 My whole defign in this appendix is to give a 
 condenfed, but fomewhat general view, of this 
 principle or influence difcovered by profeflbr Gal- 
 vani. 
 
 By far the greater number of medical charac- 
 ters in the immenfe tract of country embraced 
 within the limits of the United States, are, in con- 
 fequence of their diftances from literary inftitu- 
 tions, excluded from accefs to public libraries, 
 and fruated quite beyond the free circulation of 
 phyfical fcience. To fuch my appendix will ferve 
 the humble purpofe of a literary chronicle ; it will 
 convey to them a brief account of the difcoveries 
 2 which 
 
APPENDIX. 24s 
 
 which are now going forward in the delightful 
 and important fcience of phyfiology. 
 
 On the fubject of the influence difcovered by 
 Galvani I have myfelf inftituted and performed 
 a confiderable number of experiments * ; fome of 
 
 * That the reader may be acquainted with an eafy, cheap 
 and familiar method of experimenting on this fubject, with- 
 out having his feelings hurt by the agonizing pangs of tor- 
 tured and dying animals, I will here take the liberty of in- 
 ferring, in form of notes, a few extracts taken from a com- 
 munication tranfmitted to Mr. Fowler, by his learned friend 
 Mr. Robifon, profdfor of natural philofophy in the univer- 
 fity of Edinburgh. 
 
 I. " I find (fays the profeflor) that if a piece of zinc be 
 applied to the tongue, and be in contact with a piece of fil- 
 ver, which touches any part of the lining of the mouth, 
 noftrils, ears, urethra, or anus, the fenfation refembling tafte 
 is felt on the tongue. If the experiment be inserted, by ap- 
 plying the filver to the tongue, the irritation produced by 
 the zinc is not fenfible, except in the mouth and the urethra, 
 and is very flight. 
 
 II. " If the zinc (finely poliflied) be applied to the ball 
 of the eye, the brightness of the flafh feems to correfpond with 
 the furface of contact of the filver with the tongue, palate, 
 fauces, or cheek. The fame tiling happens when the filver 
 is applied to the eye." 
 
 III. " When a rod of zinc and one of filver are applied 
 to the roof of the mouth, as far back as poffiblc, the irrita- 
 tions 
 
246 APPENDIX. 
 
 my reful ts hare appeared flriking and new, but my 
 experiments have been neither fufficiently nume- 
 rous nor varied to warrant the deduction and efta- 
 blimment of general principles. My prefent in- 
 tention is ((hould heaven indulge me in life and 
 health), to profecute to fome extent this highly 
 
 tions produced by bringing their outer ends into contact, are 
 very flrong, and that by the zinc reiembles tafte, in the ,ame 
 manner as when applied to the tongue." 
 
 IV. " I had been paring my toenails with fciffars, and 
 had cut off a confiderable portion of the th'cic fkin, fo that 
 the blood began to ooze through in the middle of the wound. 
 I applied the zinc there, and an extenfive furface of filver 
 to the tongue. Every time I brought the metals into con- 
 tact, I felt a finait irritation by the zinc at the wound," &c. 
 
 A variety of other experiments of a fimilar nature are 
 contained in the fame communication from Mr. Robifon 
 to Mr. Fowler ; but a further detail of them I conceive un- 
 necefiaxy, as the ingenious reader, being acquainted with 
 the foregoing, can with facility devife other experiments 
 for himfelf. Thus I have frequently conveyed to my eye 
 the luminous flafh mentioned by Mr. Robifon, not only 
 from die internal veftments of the mouth, the nofe, the ure- 
 thra, &c. but alfo from between my fingers, from the cu- 
 bital flexure of my arm, and from various other parts of 
 my body, where the texture of the cuticle and fkin is more 
 fine and foft than ordinary ; always taking care, however, 
 to moiftcn the part previoufly to the application of the 
 metals. 
 
 intercfling 
 
APPENDIX. 347 
 
 interefting fubject. Should my inveftigation be 
 favoured with the difcovery of any thing curious 
 in fcience, or ufeful in practice, a detail of it may 
 be expected in a future communication. 
 
 To my folemn audit before the bar of the pub- 
 lic, I now ha^en in tremulous anxiety, " with all 
 my imperfections on my head," — imperfections 
 which will no doubt awaken the cenfure of the 
 critic, but receive, I flatter myfelf, the indulgence 
 of the liberal and candid. The approbation of 
 the former I neither court nor regard ; that of 
 the latter it (hall be my conflant ambition to de- 
 ferve. The profeffed buiinefs of moft modern 
 critics appears to be, to condemn — promifcuoufly 
 condemn, too frequently without the fainteft (ha- 
 dow of either inclination or talents to difcriminate 
 merit from its reverfe. 
 
 In my view the approbation of a profeffed critic 
 is perfectly fynonymous with the cenfure of the 
 liberal and the ingenious, to whofe candid exami- 
 nation the preceding pages are fubmitted with all 
 that refpect and deference due from an inexperi- 
 enced writer. 
 
 THE END. 
 

612 B056C 
 
 275305 
 
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