AcS43| 
 
FIRST LINES 
 
 OF 
 
 PHYSIOLOGY. /S'/^ 
 
 BY 
 
 ALBERT VON HALLER. 
 
 TRANSLATED FROM THE 
 
 THIRD LATIN EDITION. 
 
 TO WHICH IS ADDED, 
 
 A TRANSLATION OF THE 
 
 INDEX, 
 
 COMPOSED FOR THE EDINBURGH EDITION, 
 PRINTED UNDER THE INSPECTION 
 OF DR. WILLIAM CULLEN. 
 
 FIRST AMERICAN EDITION. 
 
 TROY ; 
 
 PRINTED BY OBADIAH PENNIMAN & CO. 
 
 SOLD BY THEM AT THEIR STORE, RIVER-STREET ; BY C. R. 
 & G. WEBSTER, AND D. & S. WHITING, ALBANY ; THO- 
 MAS & ANDREWS, 'WEST & GREENLEAF, J. WEST, W. P. & 
 L. BLAKE, C. BINGHAM, AND MANNING & LORING, BOS- 
 TON ; AND P. BYRNE, PHILADELPHIA. 
 
 1803. 
 
Digitized by the Internet Archive 
 in 2016 
 
 https://archive.org/details/firstlinesofphys02hall 
 
ADVERTISEMENT 
 
 TO THE EDINBURGH EDITION^ 
 
 1 HE correftlon of this volume for the prefs was un- 
 iSertaken at the defire of the Publilhers. Having already under- 
 gone three editions, the prelent Editor believed, that a careful 
 perufal of the proof-lheets, and attention to the typographical 
 accuracy of die work, would chiefly conllitute his fliare in the 
 publication. On collating, however, the laft edition with the 
 original of Haller, it appeared, that few fentences, and fcarce- 
 ly one paragraph, conveyed the true meaning of the Author. 
 In many places, the fenfe was totally miftaken, fometimes per- 
 verted, and the omiffions and interpolations were both fo nu- 
 merous, and lb prejudicial to the work, that thofe who have 
 formed their opinion of the value of Haller’s Firfl; Lines, 
 from any tranflation in the Englilh language, mull have form- 
 ed an opinion of them, highly detrimental to the well deferved 
 reputation of the Author. In die prefent edition, with much 
 labour, the Editor has endeavoured to corredl thefe miftakes, 
 to fupply what was omitted, and to expunge the interpolations ; 
 in Ihort, to give Haller’s Firh Lines in Englilh. 
 
 The very great deviations made by the original Tranllator 
 from the meaning of the Author, have betrayed the prefent 
 Editor into an oppolite fault, that of making his edition more 
 literal than perhaps is confillent with the true idiom of die 
 Englilh language. For this imperfection he has no other apol- 
 ogy to offer : but for the omilTion of Dr. Wrisberg’s Notes, 
 one is neceflary. Of thefe notes, many are excellent ; but as 
 moft of them are literary, fome controverfial, and others but 
 add a new conjedlure upon points not yet underftood, and, final- 
 ly, as they do not now fulfil their original Intention of fupply- 
 ing every difcovery made in Phyfiology fince Haller’s time, 
 it was thought proper not to increafe the fize and price of the 
 volume by their infertion. 
 
 CONTENTS. 
 
CONTENTS. 
 
 ChAp. Pace. 
 
 l. Of fibre and cellular fubftance, i 
 
 II. Of the veflhls, ii 
 
 m. Of the motion of the blood tlirough the veins and 
 
 arteries, or circulation, 26 
 
 IV. Of the hearty 32 
 
 V. Of the nature of tlie blood and humours of the 
 
 human body, 60 
 
 VI. Of the common oifices of arteries, 69 
 
 VII. Of fecretion, 85 
 
 VIII. Of refpiration, 104 
 
 IX. Of voice and fpeech, ; . 132 
 
 X. Of the brain and nerves, . 142 
 
 XI. Of mufcular motion, 186 
 
 XII. Of the fenfe of touch, 201 
 
 XIII. Oftafie, 215 
 
 XIV. Offinell, 22 r 
 
 XV. Of hearing, 227 
 
 XVI. Of fight, 242 
 
 XVII. Of the internal fenfes, 269 
 
 XVIII. Of maflication, faliva, and deglutition, . . 288 
 
 XIX. Of the aftion of the ftomach on the food, . . 305 
 
 XX. Of the omentum, . . 321 
 
 XXL Of the fpleen, . . 329 
 
 XXII. Of the pancreas, 334 
 
 XXIII. Of the liver, gall bladder, and bile, . . . 336 
 
 XXIV. Of the linall inteftines, 354 
 
 XXV. Of the large inteftines, 365 
 
 XXV. * Of the chyliferous velTels, 374 
 
 XXVI. Of the kidneys^, bladder, and urine, . . . 380 
 
 XXVII. Of the male organs of generation, . . . 395 
 
 XXVIII. Of the virgin uterus, 412 
 
 XXIX. Of conception, 424 
 
 XXX. Of nutrition, growth, life and death, . . . 462 
 
 FIRST 
 
f 
 
 FIRST LINES 
 
 OF 
 
 PHYSIOLOGY, 
 
 CHAP. I. 
 
 FIBRE. CELLULAR SUBSTANCE. 
 
 1. ^ I 'HE moft fimple parts of the human body, 
 § are either fluid or folid. As the fluids 
 are of different kinds, we fhall conflder each of 
 them in its proper place ; and premife the hiffory 
 of the folids, which are moft fimple, and the true 
 bafis of the body, to the confideration of the other 
 parts. 
 
 II. The folid parts of animals and vegetables 
 have this fabric in common ; that their elements, 
 as feen by the moft powerful microfcopes, are ei- 
 ther fibres, or laminae, or unorganized gluten. 
 
 III. Fibres for the moft part, refernble lines of 
 very minute breadth, or rather flender cylinders. 
 Their moft permianent particles are demonftrated to 
 
 B be 
 
 / 6 3ii / 
 
FIBRE 
 
 Chap. I. 
 
 be earthy, by combuftion, or long continued pu- 
 trefaclion. 
 
 IV. Thefe earthy particles derive conneclion and 
 the power of coheiion, not from themfelvcs, but 
 from interpofed gluten. We know this from the 
 preceding obfervations, (iii.) and the eafy experi- 
 ment, in which a burnt hair, whofe parts hang fthl 
 together, recovers a certain degree of firmnefs by 
 being dipped in water or oil. Ivory and bones alfo 
 become friable, by the extraction of their gelly. 
 Long expofure to weather elFecls a hmilar change, 
 rendering bones a true earth, abforbent and bibu- 
 lous. But even bone, become friable from having 
 its gelly extracted, reacquires its olleous hardr.efs, 
 when that geily is reftored. I’he more fimple an- 
 imals conllft entirely of this gluten. 
 
 v. Laitly, the chemical analyhs of bone, and hair, 
 the geily of bone, ivory, and horn, the nature of 
 our aliments, &c. prove, that this gluten is com- 
 poied of water, incorporated with oil by animal life, 
 blor does any other kind of gluten unite the parts 
 of animals more ilrongly, as we fee in hze and 
 comm.on glue. 
 
 VI. The primary fimiple fibre, fuch as we rather 
 comprehend from reafon than fenfe, is compofed of 
 earthy particles, adhering longitudinally, and con- 
 nefled by intervening and cohefive gluten. 
 
 VII. But the fibres v hich appear primary to the 
 fight, are of two kinds. The lirft is linear, wliole 
 length is coniiderable in proportion to its breadth, 
 .and whofe elementary particles lie in a flraight line, 
 and thus generally parallel to thofe contiguous. 
 W e fee examples of this kind of fibre in bone, 
 mofl eafily in thofe of the fetus, and alfo in ten- 
 dons, ligaments and mufcles, always recoilefblng 
 that the eye fees not the m.cfi; minute fibres, but 
 only the larger ones compofed of tliefe, and fimi- 
 lar to them in flraiglitnefs and flcndernefs. That 
 
 the 
 
Chap. I. CELLULAR SUBSTANCE. 
 
 3 
 
 the ultimate fibres are perfectly fimilar, we are 
 convinced by the microfcopes of Muys and Lecu- 
 wenhoeck, in which the mufcular fibres, even the 
 molt minute, appear exactly like the larger ones, 
 and perfectly linear. 
 
 VIII. The fecond kind confifts of laminae, in 
 which, a breadth often greater, is conjoined with a 
 Ihorter length. A loole web of thefe has got the 
 name of Cellular Tunic, though the term Tunic is 
 on many accounts improper. 
 
 IX. This cellular fubftance is compofed of an in- 
 finite number of fmall laminae, which, by their 
 various dire<5tions, inclofe fmall fpaces and cavities, 
 and join all the parts of the human body, afford- 
 ing an extenfive and firm union, with fufficient 
 mobility. But in this web there is the greatefi; di- 
 verfity in the proportion of the folids to the cavi- 
 ties; in the breadth and firmnefs of the laminae; in 
 the nature of the- contained liquor, which is either 
 more watery or more oily ; and in the admixture 
 of fibres and filaments, of which there is a great 
 quantity in fome places, as in the coats of the ar- 
 teries, in others almofi; none, as under the fkin. 
 
 x. Of this cellular fubilance when compacted, 
 from the laminse concreting, and being compreffed 
 by the a<5iion of the incumbent mufcles, diftend- 
 ing liquid, or other caufe, broad plates are formed, 
 which are either rectilineal in general, and more 
 properly called Membranes ; or convoluted into 
 cylinders and cones, vcith liquids flowing through 
 their cavities, and denominated Veffels ; or extend- 
 ing round fome place in a plane parallel to it, get 
 the name of Tunics. That tunics are formed of 
 cellular fubftance, is proved in the aorta, fkin, pe- 
 ricardium, and dura mater, by ocular infpection, 
 and efpecially by maceration. The coats of the 
 mufcles, are alfo evidently cellular, and fimilar to 
 other tunics. The fame thing is alfo proved from 
 the eafy change of the dartQS, and the nervous 
 II 2 meinbrane 
 
4 
 
 FIBRE. 
 
 CllAP. I. 
 
 membrane of the intelHnes, into cellular fubftance, 
 l>y inhation ; and from the hard and thick mem- 
 branes formed in enc)dled tumors, which are mere 
 productions of cellular texture. In the integu- 
 ments, being very clofely compacted in continued 
 n;radation, it forms the true fkin lyinG: under the 
 epidermis j and being thence continued, it is at 
 laft partly refolved into the fubcutaneous cellular 
 texture fiUed with fat. 
 
 XI. The veffels which colour the tunics are an 
 addition to tlie cellular fubftance, and in no wile 
 cll'ential to the nature of membrane, but fupcr- 
 addcd to the membrane formed of the cellular 
 fubhance. Betvceen the meihes of the intefdnal 
 netv/ork of veffels, when moll perfectly fiUed by 
 the Ruyfcliian art, white cellular fubffance re- 
 mains, e\'en then greatly exceeding the bulk of 
 the veffels, although being preternaturally diitend- 
 ed, they occupy a. greater fpace. But I do not 
 knov/ any membranes compofed of fibres mterv/o- 
 ven with, and decuflating each other ; unlefs you 
 conhder as fach the ligamentary or tendinous hbres 
 which are fpread over true membranes. 
 
 XII. Cellular fubffance is found in the human 
 body, wdierever there is a v^efl'cl or mufcular fibre, 
 without exception, as far as I know. 
 
 XIII. The other elementary fubftance of the 
 human body, (ii.) which cannot be truly called 
 cither a fibre or cellular lamince, is a mere extra- 
 vafited gluten, concreted, not into fibres, but in 
 the fnaces betwixt them. This is manifeft in the 
 
 A 
 
 bones, whofe fibres are feen v^ery diftincHy in tlie 
 foetus, with veffels running in the intervals be- 
 i W'cen them ; fo that the fkull in every part, re- 
 fcmbles a comb. This fabric is fo altered in the 
 adult, that tlie intervals being filled up by fluid, 
 cxtras'afcitcd in the fnaces betveixt the fibres, as 
 liappens with the juice of madder, and the edges 
 
 being 
 
Chap. I. CELLULAR SUBST.\I>TCE. 
 
 5 
 
 being agglutinated, laminoe are formed. The car- 
 tilages feem to be fcarcely any thing elfe than con- 
 creted gluten. 
 
 XIV. But here the order of nature fcems to be, 
 that the fibres above mentioned (in.) are all ori- 
 ginally formed of this gluten. That the cellu- 
 lar fubftance (vii.) is thus formed, appears from 
 thofe cellular fibres, produced in the thorax from 
 concreted vapour, which joins the furface of the 
 lungs to the pleura, and perfectly refembling the * 
 true and natural cellular fubftance, even though 
 compacted of infpiflated pus. The fame appears 
 alfo from a comparifon of the foetus with the 
 adult ; for, inftead of the abundant fubcutaneous 
 cellular fubftance, the foetus has a mere jelly inter- 
 pofed betwixt the fkin and mufcles, which have 
 already acquired greater firmnefs ; from the mor- 
 bid diflblution of the membranes of the mufcles 
 into a mere gluten ; and from a fimilar change 
 into glue of the fkin, tendons, and ligaments of 
 animals, by means of boiling water. Clots of 
 coagulated blood ; the fanguineous membranes of 
 Ruyfch ; Albinus’s membranes formed of mucus, 
 polypus, filk and glue, alfo illuftrate this theory. 
 Laftly,that the bony fibres themfelves are formed of 
 compacted gluten, is fhown from difeafes in which 
 the hardeft bones, by a liquefaction of their gluten , 
 return into cartilage, flefli, and jelly. Similar 
 changes are made on the bones of fifties and other 
 fdbftances by Papin’s digefter. 
 
 XV. It feems, then, that an albuminous fiui'l, 
 with a fmaU portion of earth, faTi concretes in- 
 to filam.ents, from fome preflure, whofe caufes we 
 now pafs over. Thefe by the mutual attraction 
 of cohefion, leaving, however, fpaces between 
 them, compofe the cellular texture, after hav- 
 ing acquired fomc firmnefs from the clofenefs of 
 the earthy rarticics, which follows the expul- 
 
6 
 
 FIBRE. 
 
 Chap. E 
 
 lion of the too aqueous gluten. This fubftance, 
 wherever its laminae are lubjected to greater prcf- 
 fure, turns into fibres and tunics ; and, laftly, with 
 unorganized gluten (xiv.) concretes into bone, 
 (xv.) Hence, in general, all parts of the body, 
 from the foftefi; to the hardeft, feem to differ on- 
 ly in the latter having more of the earthy par- 
 ticles, and thefe more clofely compacted, with lefs 
 aqueous gluten ; vchile in the foft parts there is 
 lefs earth and more gluten. 
 
 XVI. The cellular texture is made up of fibres 
 and laminae (viii.) which are neither hollow nor 
 vafcular, although it is coloured by acceffor^" vef- 
 fels, but folid. The following are its chief va- 
 rieties. In fome parts it is loofe, and formed 
 of long and diftant liminas ; in others thin, and 
 compofed of llrort fibres. I find it fherteft be- 
 twixt the fclerotica and choroides of the eye, 
 efpeciaHy of animals, and betwixt the arachnoides 
 and pia mater of the brain. I alfo find it tender, 
 but more confpicuous, betwixt every two coats of 
 the intefiines, fiomach, bladder, and ureters ; in 
 the veficles of the lungs, under the pulp of the 
 glans penis ; and between the ftnall kernels of the 
 vifeera and glands. It is compofed of ftill longer 
 fibres, where it accompanies the veffels, under the 
 name cf Vagina, through the vifeera, and particu- 
 larly the liver and lungs ; and is vaftly firmer in 
 the veffels which go to the head and limbs. Its 
 principal ufe is to bind together the contiguous 
 membranes, vclfcls, and fibres, in fuch a manner as 
 to allow them a due des;ree of motion. But the 
 cellular fubftance, as hitherto deferibed, hardly 
 ever contains any fat ; but is moiftened by a w^a- 
 tery, gelatinous and fomewhat oily vapour, exhaled 
 from the arteries, and received again into the 
 veins. The truth of this is eafily dcmonftrable 
 from injections of water, ifinglafs or oil, made in 
 ah parts of the body. When this vapour is want- 
 
Chap. I. CELLULAR SUBSTANCE. 
 
 7 
 
 ing, the filaments cohere, and the contiguous 
 membranes are united, with lofs of motion. 
 
 XVII. The cellular texture is more lax, and form- 
 ed of laminx rather than fibres, where it divides 
 the mufcular fibres, even the moft minute ; wLere 
 it loofely accompanies and fuftains the veffels ; and 
 within the cavities of the bones, where it is com- 
 pofed of bony as w'ell as membranous laminae. 
 That is likewife very lax, which, under the fur- 
 face of the body, is every where interpofed be- 
 twixt the mufcles and the Ikin ; but theiaxeft of 
 all is that which furrounds with very wide cells 
 the genital parts of the male. 
 
 XVIII. Into the empty meflies of this cellular 
 texture (xvii.) there is poured almofi; every where, 
 in the foetus, firft a gelly, then a grumous, and laft- 
 ly, under the whole Ikin, and in its pits, a clotted 
 fat. This fubftance is lighter than water, infipid, 
 inflammable, becomes folid in the cold, is found 
 in greater quantity about the kidneys and in gra- 
 minivorous animals ; in fillies, v/hile alive, and 
 probably alfo in man, nearly fluid, though apt to 
 coagulate. In it an acid fait, almofl in the pro- 
 portion of one-fixth, is united with oil. 
 
 XIX. Through this cellular texture the blood- 
 veffels run and are divided ; from the arterial ex- 
 tremities of which, the fat is depofited and a^- 
 forbed by the venous. The paflage, from the ar- 
 teries into the adipofe cells, is fo immediate and 
 free; that they mull open by very large mouths, 
 fmee they admit injeffed mercury, air, water, fize, 
 and oil, which is always very fluggilh, even in liv- 
 ing animals. It is not fecreted by any long duels 
 of particular fabric, but tranfudes on all • fides 
 through the whole extent of the artery ; infomuch 
 that, when an artery is filled with water, there is no 
 part of the furrounding cellular fubftance which is 
 not moiflened. The warm fat, during the pulfation 
 of i^je arteries, eaiily finds out the iarne paffages. 
 
 How 
 
8 
 
 FIBRE. 
 
 Chap. I. 
 
 Hov/ ^ickly it is collected, appears from the 
 ipeedy renovation of fatnefs after acute difeafes. 
 
 XX. But that this fat is abforbed by the veins, 
 we are taught from the fudden effects which muf- 
 cular exercife has in confuming the fat, more ef- 
 pecially of animals in which it abounds ; alfo 
 from its confumption in fevers ; from the cure of 
 droplies, v/here the water effufed into the ceUu- 
 lar fubftance is in a manner abforbed and thrown 
 out by the inteftinal tube ; and, lafdy, from the 
 venous tranfudation of water and oil, when inject- 
 ed by the fyringe, obferved in every part of the 
 body. Are nerves diftributed upon the adipofe 
 cells ? It is certain they run through this fub- 
 fcance, and every where divide in it, into the mi- 
 nuteft filaments, fo that they can no longer be 
 traced by the knife. That they terminate in it, is 
 not probable j for the fat is both infenfible and 
 unirritable. 
 
 XXI. The rneflies betwdxt the laminae of the 
 cellular" membrane, are every where open, and 
 unite in forming one continuous cavity through- 
 out the whole body. This appears from the infla- 
 tion of the &in over all the body, which butchers, 
 and likevvile the furgeons of Ethiopia, efTecl; by a 
 finglc wound ; from ernphyfema, in wdiich the air 
 received by a wound of the fldn, being retained, 
 caufes a fwellin?: throughout the whole bodv ; 
 from the paffage of bodies, put under the Ikin, to 
 a place remote from that at which they entered ; 
 from the paffage of pus, from an inflamed place 
 10 remote ulcers ; and, finally, from difeafes, in 
 v/hich water depofited in ail the cellular fub- 
 ftance of the body, is comipletely evacuated by 
 a fingle incifion. That none of the cellular tex- 
 ture is excepted, appears from a cafe of emphy- 
 fema in v/hich the vitreous body of tlie eye itfclf 
 was inflated ; and from a difeafe, in which the 
 
 gelatinous 
 
Chap. I. CELLULAR SUBSTxlNCE. 'g 
 
 gelatinous ferum of a dropfy was transfufed even, 
 into the cavernous homes or the penis. 
 
 XXII. The great importance of this cellular 
 flibftance will be evident to all who confider, that 
 from it alone proceeds the due firmnefs and fta- 
 bility of all the arteries, nerves, and mufcular 
 fibres, and confequently of all the ileili and vifcera 
 formed of thefe ; but even the figures of the parts, 
 their juft length, cavities, curvatures, flexures, 
 depend entirely on the cellular membrane, being 
 in fome places of a laxer, and in others of a denfer 
 fabric : for when divided, every part is lengthened 
 and collapfes. Of this fubftance, with veftels, 
 nerves, mufcular and tendinous fibres, (a great 
 part of which are however formed of it,) all the 
 vifcera, all the mufcles, glands, ligaments and cap- 
 fules, are compofed ; on it alone, and its different 
 length, tenfion, quantity or proportion, the diver- 
 fity of our glands and vifcera depends ; and, laft- 
 ly, it certainly conftitutes by far the greateft part 
 of the body itfelf, if indeed the whole be not 
 formed of cellular filaments of this kind. 
 
 XXIII. It poffeffes a contracUIc power, different 
 from irritability, which, thougli not demonftrable 
 by experiments, difpofes the cellular fibre to ftiort- 
 en itfelf, though for the moft part flowly, after 
 having been ftretched. This power, eycited by 
 cold, renders the fldn rigid ; raifes the hairs ; 
 draws up tlie ferotum ; and, after geftation, rc- 
 ftores the Ikin of the abdomen, and the uterus, to 
 their former fize. The fame force, by a gentle 
 but continual contraftion, promotes the fecretion 
 of fat of the liquors of the fubcutaneous and oth- 
 er glands, and of pus : in the veins and recepta- 
 cles, it refifts dilatation ; and, when that is taken 
 off, it regains its former fiiortnefs. In tlie foetus, 
 this gentle force is among the principal caufes of 
 the changes that liappen to the body. 
 
FIBRE. 
 
 Chap. I. 
 
 to 
 
 XXIV. The ufes of the fat are various ; it every- 
 where facilitates the motions of the mufcles, Icf- 
 fens their attrition, and prevents rigidity : it fils 
 up the fpaces between the mufcles, and the cavi- 
 ties about many of the vifeera, in fuch a manner, 
 that it readily yields to their motions, and yet 
 fupports them when at reft : it principally confti- 
 tutes the weight of the body ; conducts and de- 
 fends the veflels ; it uniformly diftends the fkin ; 
 ferves as a cuftiion to the body, and renders the 
 whole comely : it probably, by mbdng with fome 
 humours, abates their acrimony : it has a princi- 
 pal fliare in forming the bile ; and, by tranluding 
 through the cartilaginous incruftations of the 
 bones, it mixes with the articular liquid, and by 
 abforption, it lubricates their fibres : by exhaling 
 through the pores of the Ikin, it refifts the dr) ing 
 fharpnefs of the air ; alfo, by exhaling in a living 
 perfon from the mefentery, mefocolon, omentum, 
 and round the kidneys, it lubricates the furfaces 
 of the vifeera with a bland vapour ; and, by being 
 interpofed, prevents their concretion. 
 
 XXV. The fat is depofited into the cells during 
 lleep, reft of body and mind, and dimaniflied force 
 of circulation. When collected in too great a quan- 
 tity, it proves injurious ; by comprefling the veins ; 
 and, impeding the action of the heart, it produces 
 afthma, apoplexy and dropfy. The fame humour 
 is taken up by the veins ; and, being more rapidly 
 moved along the arteries, by violent exercife, ve- 
 nery, watchings, cares of the mind, falhation, 
 diarrhoea, fever, falling, it is carried beyond the 
 excretory pores : it is confumed by fuppuration. 
 When reftored to the blood, it increafes acute 
 difeafes, tinges the urine, and forms a part of its 
 fediment. After being fuddenly confumed, it is 
 foon renewed again from healthy humours : but, 
 in a languid habit, a gelly, inllead of fat, is depo- 
 fited into the cells, caufing auafiirca, and external 
 hydrocele. 
 
Chap. II. 
 
 VESSELS. 
 
 It 
 
 ; C K A P. II. 
 
 VESSELS. 
 
 XXVI. ^'1 ‘'HE membranes will be better defcribed 
 fingly. There are many things common 
 to the arteries. They are long extended cones, de- 
 crealing according to the number of their branches. 
 But where arteries run for fome length, without 
 fending off large branches, their convergency is 
 not very evident, if any ; and at length, where 
 they are called capillaries, and wherever they give 
 palTage to a lingle globule, they are either cylin- 
 drical, or diminifli very imperceptibly ; their tranf- 
 verfe fecUons are every Vv^here and without excep- 
 tion circular, when the artery is full. Where they 
 fend off large branches, the caliber is fuddeniy 
 diminiflied, infomuch that they may be reckoned a 
 chain of cylinders, of which every one is narrower 
 than the preceding. If you reckon them cones, 
 then the balls of the cone, common to all the arteries 
 is in one or other of the ventricles of the heart ; 
 and the apex of the cone, either in the beginning 
 of a vein, or in the beginning of the cylindrical 
 part of the artery, or unlefs it is cylindrical, in an 
 exhaling veffel. In fome places they feem to di- 
 late ; at leaft they certainly become wider, after 
 they have been filled and difcended with wax ; 
 poffibly from fome obftruflion which caufes the in- 
 jected vrax to diftend that part of the artery more 
 than the reft. Examples of this kind we have in 
 the vertebral artery, at the bafts of the fkull ; in the 
 fplenic ; in the flexure of the carotid, according to 
 Mr. Cowper’s injeClions ; and, laftiy, unlefs 1 be 
 much deceived, in the fpermatic arteries. In all 
 places, iikewife, where the ramifications begin, the 
 diameter of the artery is a little increafed. 
 
 XXVII. 
 
si 
 
 VESSELS. 
 
 Chap. IL 
 
 XXVII. There is no external coat proper and 
 common to all arteries. Tliey derive an exter- 
 nal and merely incum.bentintegument,inthe thorax 
 from the pleura, and in the abdomen from the pe- 
 ritonxum. In the neck, arm, and thigh, a fort of 
 thicker cellular fubftance furrounds the arteries. 
 The membrane of the pericardium, v.hich on all 
 itdes encircles the aorta, returns back with the 
 veifels to the heart. The dura mater imparts a 
 capfule to the carotid, as it paiies out of the ikull. 
 But the fiiTt true membrane of the arterial tube, is 
 every where cellular, and fometimes adipofe as in 
 the thorax. 
 
 XXVIII. Tlie external furface of this cellular coat 
 is of a ioofer texture, coloured by a great many 
 fmall veins andarteries,and permeated by nervesnot 
 very minute. It is fometimes fo abundant, that its 
 external layers feem hardly to belong to the arte- 
 ry, but appear like an extraneous texture added to 
 it. It is of this appearance in the neck, and round 
 the inguinal, fubciavian, mefenteric, coeliac, and 
 hepatic arteries, being chiefly compofed of long 
 iilaments. Thefe are the Vaginx of the Arteries, of 
 iome eminent men. 
 
 XXIX. As this cellular coat advances more inward- 
 ly, and nearer to the cavity of the artery, it becomes 
 more denie, folia, and flbrous, and may be called a 
 proper coat of the artery. That there is no tendi- 
 nous coat of the arteries dlfcincf from tliis cellular 
 fubflancc, is evident from maceration, by which tiic 
 inmofl; ftratum of this arterial tunic becomes cel- 
 lular. 
 
 XXX, Within the former, and nearer the cavity 
 of the artery, we And libres,in general orbicular ; re- 
 coliecfing, however, that no flbre anywhere makes 
 a complete circle ; but that many of them conjoin- 
 ed, v/ith their extremities turned ofl 'fldeways, feem 
 to form one ring. Tliefe fibres, in the larger 
 tranks,%-m many fliu.ta.fufliciently apparent from 
 
 thciv 
 
Chap. IL 
 
 VESSELS. 
 
 their reddifli colour and folidity *, but in tlie fmall- 
 er arteries they are by degrees more diflicult to 
 demonftrate, and feem to be wanting in the arteries 
 of fmall animals. I have never obferved them 
 longitudinal. Under this membrane, but more 
 diflicult to demonftrate, is an exceedingly ftiort 
 cellular texture, into which the tophaceous matter 
 is poured when an artery offifies. 
 
 XXXI. The innermoft coat of the artery is 
 thin, and finely poliftied by the current of blood ; 
 it covers with an uninterrupted lining the flefiiy 
 fibres, which are not fufficiently continuous, and 
 prevents the blood from infinuating itfelf into 
 the intervals. It is every where fmooth and with- 
 out valves ; although, from a fort of mechanical 
 necefiity, fometimes certain folds, railed into a fe- 
 mi circle at the origin of branches, project, as we 
 fee, at the branches fent off from the arch of the 
 aorta. Yet, in arteries of the vifcera, the inner- 
 moft coat is fofter, lax, wrinkled, and almoft fri- 
 able, efpecially in the ductus arteriofus. 
 
 xxxii. The arteries themfelves have arteries, 
 particularly in their external cellular coat, fpring- 
 ing on all fides from the adjacent fmall arteries, 
 num.erous, branchy, reticular, all very minute, even 
 in the fmtus, without injection, very numerous. 
 Nerves every where delcend, for a great way along 
 hhe farface of the arteries, and vanifih in the cellu- 
 lar fubftance ; of which we have examples in the 
 external and internal carotids, and arch of the 
 aorta. From thefe, do not the arteries derive a 
 contractile fpaftic force, different from fimple elaf- 
 ticity ? Do not fevers, faintings, palfy with atro- 
 phy, and the paffions of the mind, prove fomething 
 like this ? But arteries are infenfible and unirrita- 
 ble ; and if they are conftricted by poifons, they 
 have that property in common with the dead fkin. 
 
 xxxni. The fections of arteries are circular, be- 
 eaufe they are elaftic j this is the reafon why, even 
 
 from 
 
*4 
 
 VESSELS. 
 
 Chap. If. 
 
 fi'om the fmaU arteries of the teeth, haemorrhages 
 are fometimes fatal. The aorta, indeed, in the 
 thorax and abdomen, the carotids in the neck, and 
 fome other arteries of the dead body, when not 
 diftended, appear flat ; but their round figure, 
 and circular feedion, are always reftored by injec- 
 tion. By their elafticity, arteries fiirongly com- 
 prefs the finger that dilates them, and more tight- 
 ly in the dea.d than in the living body. In the 
 living body, indeed, it yields to the action of the 
 heart ; but vrhen the heart is relaxed, inftantly 
 contracts, and regains its former diamieter ; this 
 conflitutes the pulfe, whofe full explication will 
 properly follov'- the hiftory of the heart ; at pre- 
 ient, it is fufiicient to fay, that all arteries pulfate, 
 although the fyftole and diaftole can be perceived 
 by the finger, only in the larger, not in the fmaller 
 ones ; and though in the ultimate inflections of the 
 arteries, it almoft vanifhes ; for, by an increafed 
 motion of the blood, even the fmaller arteries beat 
 violently, as we fee in inflammations. They con- 
 tract lengthvdfc ftrongly, and are rendered ihorter 
 when cut entirely acrofs. 
 
 XXXIV. The ftremrth of the arteries is confider- 
 
 O 
 
 able enough : but the denfe, hard texture of the 
 outer cellular coat, as it refufes to yield to a dif- 
 tending force, breaks without much difficulty, al- 
 moft more eafiiy than the coats of the veins ; hence 
 arife aneurifms. The trunks are almoft every 
 where weaker, and the branches ftronger, fo that 
 the impulfe of the blood may have confiderable ef- 
 feef upon the former, while in the limbs it has ve- 
 ry little. Hence, aneurifm.s, are moft frequent 
 near the heart. In the lower extremities, the 
 flrength of the arteries, and of the veins, is increaf- 
 ed, as well as in the fecretintr ora;ans. 
 
 XXXV. Nature has diilributed arteries over the 
 whole animal body, excepting a membranes, 
 where they iirc/e not yet been.demonftrateJ. But 
 
 fhe 
 
Chap. II. 
 
 VESSELS. 
 
 15 
 
 Ihe has difpofed of the trunks every where in pla- 
 ces of fafety, becaufe wounds cannot happen to 
 the fmaU ones without danger, or to the large ones 
 without lofs of life. The Ikin has numerous fliort 
 and fmaU tvdgs ; but the larger trunks, defended 
 by the fldn and mufcles, creep near the bones. 
 In general, the arteries are in proportion to the 
 parts of the body to which they are fent, yet lar- 
 ger branches go to the fecretory organs, fpleen and 
 brain *, and finaller ones to the mufcular parts. 
 
 XXXVI. The proportion of the folid part of an 
 artery to its cavity, is not every where the fame, 
 nor is it conftant even in the fame artery. This 
 proportion, in the firft place, is leaf: of all at the 
 heart, and increafes as the arteries remove farther 
 from it. Secondly, in a fuU fed plethoric animal, 
 whofe blood paifes freely, and with great force, 
 through its arteries, the proportion of the folid 
 part is lefs than in a familhed extenuated creature, 
 whofe blood moves feebly. 
 
 XXXVII. From each arterial trunk, branches are 
 fent forth, and from thefe again proceed fmaUer 
 ramifications by repeated divifions, of which you 
 will fcarcely find the end, though you may, per- 
 haps, trace a feries of twenty. The calibers of 
 any two branches taken together, always exceed 
 that of the trunk from whence they come, in 
 nearly a fefquilateral proportion, or fomewhat 
 lefs. In the capillaries this law does not obtain, 
 and the fum of the calibers of the branches, does 
 not exceed that of the trunk. The fmaUeft ar- 
 teries v/hich tranfmit a fingle globule, have near- 
 ly the fame diameter with a globule, that is, the 
 three thoufandth part of an inch. Every trunk, 
 above its divifion, expands a little. The angles, 
 at which the branches go out, are generally a- 
 cute, either half right angles or nearly fo j which 
 angle, even in mechanics, carries projefililes far- 
 theft. Inftances of their going off at right angles, 
 
 or 
 
VESSELS. 
 
 Chap. IL 
 
 i6 
 
 or nearly fo, we have in the lumbar and intercof- 
 tal arteries ; of a retrogade courfc, we have one 
 iidtance in the coronaries of the heart, and another 
 in the fpinal arteries, which are produced by the 
 a^ertebrals, and feveral in thofe of the limbs, as in 
 the tibial and brachial. But nioft of thofe v hich 
 are efLceined retrograde, are fent oft, at their ori- 
 gin, at acute angles ; fuch as the afeending artery 
 of the pharynx, the defeending one of the palate, 
 the umbilical and mammary arteries, and the nu- 
 tritious ones of the large bones. Befides, it is com- 
 mon for larger branches to arife under lefs angles, 
 and fmaller ones under greater angles. It is rare 
 that two arteries of a large diameter run together 
 into one trunk. An example of this, liowever, 
 odds in the artery formed of the vertebrals. In 
 the fmaller ones it is frequent, as in both the fpi- 
 nal arteries, and that of the fincipital foramen. 
 In many parts, they have repeated flexures, fo that 
 the artery undulates around a ftraight line, in al- 
 ternate obtufe angles. This happens moft fre- 
 quently vcherever the diameter of the part to which 
 the artery goes, is occaflonally much increafed, as 
 in the large intcftincs, womb, face, fpleen, lips, 
 and iris. Even the ftraight arteries in other pla- 
 ces, if too much diftended, fall into ferpentine 
 flexures. Sometim.es they are fuddenly twifted 
 into a Idnd of circle, as the carotids under the 
 mammillary prccefs. 
 
 XXXVIII. They are frequently conjoined by in- 
 termediate branches, in fuch a manner, that the 
 twig of one artery lhall run to meet one of the 
 fame kind, from a neighbouring artery, and 
 unite with it into one trunk. Wc find inltanccs 
 of this, in large trunks in the inteftines, among 
 the middling ores in the kidneys, womb, <kc. 
 and amon<r the fmaller ones in ail narts of the 
 body; fo tliat there is no part of the human 
 body, in whicli tlie neighbouring arterial branches, 
 
 whether 
 
Chap. IL 
 
 VESSELS. 
 
 17 
 
 whether of the fame or of different denominations, 
 are not joined by intermediate branches. Of cir- 
 cles formed by arteries diverging laterally, and 
 uniting again with each other, we have inftances 
 in the eye and brain. The extremeties of the arte- 
 ries which are either cylindrical or nearly fo, fend 
 off fmaller branches, which, in the fame extent, 
 are more numerous, and are generally reticular ; 
 fo that each branch, by its fmaller twigs, forms ana- 
 ftomofes with thofe of its neighbouring branches : 
 and thus we find it in aU membranes. By this 
 means it happens, that, though the paffage from the 
 heart to any part of an artery be obftrufted, the 
 blood may neverthelefs flowthrough the neighbour- 
 ing arteries into all the branches of the obfl;ru(S:ed 
 one. Thus, gangrene and langour are very power- 
 fully prevented, and obftrucflions are more eafily 
 refolved by the repulfion of the obftacles into the 
 larger part of the trunk. 
 
 XXXIX. Laftly, the minute arteries terminate in 
 veins, either by a continuation of their canals, fo 
 that the ultimate little artery, which is general- 
 ly refledfed, having pafled the angle of its re- 
 flection, has now become a fmall vein ; or elfe a 
 branch, fent out at right angles from the artery, is 
 inferred under a like angle into the branch of a fmall 
 vein. Both thefe kinds of mechanifm are demon- 
 ftrated to us by the microfcope, and by the eafy re- 
 turn through the veins,of injedlions thrown into the 
 arteries. Thefe veflels are fometimes large enough 
 to receive feveral globules, and fometimes admit on- 
 ly one. A large artery never terminates in a vein. 
 
 XL. In the vifcera we do not find their diftribu- 
 tion fo truly reticular but varied, the fmall branches 
 defcending, crov/ded together, brufhy, arbufcular, 
 parallel to the trunk, ferpentine or villous, accord- 
 ing to the various natures of the parts. 
 
 XLi. Sometimes the arteries end in another man- 
 ner, namely, by being converted into veflels of fmall- 
 C er 
 
VESSELS. 
 
 Chap. II. 
 
 er orders. Thefe are fometimes continuous with 
 the arteries and are real trunks, as in the oph- 
 thalmic artery, if you examine the arteries of the 
 tunica choroides, then the circle of the uvea, 
 and laftly, the colourlefs ones of the iris. That a 
 netveork of pellucid arteries is continuous with the 
 red branches in the tunica conjunctiva, is evident 
 from inflammation, and the rednefs of the part 
 when relaxed by vapour, or by cupping, from in- 
 jection, and the microfcopical obfertutions of Lie- 
 berkuhn upon frogs, in which colourlefs globules 
 Vv'ere feen to pafs from red arteries into lateral 
 velfels. In a fabric of this kind, the red blood is 
 eafily forced into the fmaller vefl’els. 
 
 XLii. In other places the fmaller velfels feem to 
 proceed laterally from the trunks of the lc?dt fan- 
 guiferous arteries, as brandies fmaller than the 
 trunks. Thefe are called Excretory Duclrs. It is 
 with difliculty that thefe are filled through the red 
 velfels ; of this Ave hai'e, however, examples in the 
 kidneys, tli.e liver, and breaks. And the blood, 
 wEen vitiated, penetrates the excretory duds of 
 the whole body without hurting the velfels, lince 
 tliat aberration has no bad confequence. 
 
 XLiii. Another termination of arteries is in ex- 
 haling A^eflels ; and this is frequent in ali parts of 
 the body. Tlie whole Ikin, all the membranes of 
 the human body vdiich inclofe any cavity, all the 
 ventricles of the brain, both chambers of the eye, 
 all the adipofe cells and pulmonary A^elicles, the 
 whole cavity of the ftomach and inteftinal tube 
 and air pafl'ages, are all of them rcpleniflied with 
 exhaling arteries of this kind. Thefe emit a thin, 
 Avatery, gelatinous humour, A\'hich, by ftagna- 
 tion, congeftion, and accumulation, from difeafe or 
 death, is conA’^erted into a AAutery, but coagulable 
 lymph. The truth of this is eanly demonftrable 
 from the exudatioii that enfues from injecting the 
 arteries AA'itli A\ann AA'ater. In feme places, in- 
 deed, 
 
Chap. II. 
 
 VESSELS. 
 
 19 
 
 ‘ deed, they pour out, not a thin, vapour, but blood 
 itfelf, as we fee in the heart, the cells of the penis, 
 urethra, clitoris, and nipple of the female breaft j 
 in all which the blood itfelf is poured out in its 
 natural ftate. Is not every fecretion in true glands 
 or cryptse, analogous to this exhaling fabric ? 
 
 XLiv. In every part of the human body, do vef- 
 fels arifmg from the fanguiferous ones, but carry- 
 ing a humour thinner than blood, again fend out 
 other fmalier veffels, to be fubdivided into ftill 
 lefs orders ? We feem, indeed, not to want ex- 
 amples of this, as pointed out by men of eminence. 
 That the aqueous humour is fecreted by minute 
 veifels, generated from the colourlefs arteries of 
 the iris, is very probable. That the red coloured 
 veifels in the cortical fubftance of the brain, by 
 the intervention of another order of veifels, fepa- 
 rate a juice pervading the medullary fubftance, is 
 almoft certain. Eryftpelas, and the yellow inflam- 
 mation, arifmg from the yellow or ferous globules 
 impafled into fmalier veifels, fuggeft the fame 
 opinion. 
 
 XLv. Are there then yellow arterial veifels of a 
 fecond order, which fend off" lymphatic ones of a 
 third, from whence, by degrees, ftill lefs kinds of 
 veifels branch out ? Such a fabric does not feem 
 agreeable to the eafy tranfition of blood, mercury, 
 or wax, into the exhaling, perfpirative, uriniferous 
 and adipofe veifels and pulmonary cells ; nor is it 
 very difficult for the blood to ftray into the laftif- 
 erous, lymphatic, and lachrymal veifels, whither 
 it fliould feem not able to penetrate, if it went 
 through any other intermediate vafcular fyftem, 
 fmalier than the blood-globules. Nor is this opi- 
 nion admiffible, from the great retardation which 
 muft arife to the humours in a third, and much 
 more in inferior orders of veffels. 
 
 XL VI. The Veins, in many particulars, rcfem- 
 ble the arteries. There are fix, of which two an- 
 fwer to the aorta, and the remaining four to the 
 c 2 pulmonary 
 
20 
 
 VESSELS. 
 
 Chap. II. 
 
 pulmonary artery. Their balls is in the ventricles ' 
 of the heart, and their apices in the extremity of 
 each branch, through all p^rts of the body, ex- 
 cepting one inftance, in the liver. In moft parts, 
 they run parallel with the arteries, contiguous to 
 them ; but they differ in various refpects. 
 
 XLvn. The fabric of the veins is thin, every 
 where fmooth, difficultly feparable into membranes ; 
 of which the inmofl; is like that of the arteries, 
 and round it is a condenfed, but very eaffiy dif- 
 tended, cellular membrane, furrounded in a fingle 
 inftance, above and below the heart, with tranf- 
 verfe mufcular fibres. The cellular lubftance, 
 which connects them to the reft of the body, is, 
 however, like that of the arteries, every vffiere very 
 lax. Notwithftanding this ftender fabric, the veins 
 are every where fufficiently firm, and do not eaffiy 
 burft when inflated with air ; being, in mmft in- 
 ftanceS, ftronuer than the arteries themfelves. But 
 they burft more eaffiy in man while alive, as ap- 
 pears from morbid inftances in the leg, arm, face, 
 &c. Nor do they fupport themfelves after being 
 divided, but collapfe fo as to make their apertures 
 appear like hits ; unlefs they be prevented by 
 fome ftrong cellular fubftance placed round them, 
 as we fee in the liver and womb. They are mod- 
 erately irritable, and not by ftimuli alone, unlefs 
 they be chemical ; but, in that cafe, they contract 
 more than the arteries. They have no pulfation, 
 unlefs, if we may truft ail accounts, when the ve- 
 nous channel is fomewhere obftrudfed; or when, in 
 dying people, the blood is thrown back again from 
 the rig^ht auricle into the defeendinsr and afeend- 
 mg cava, or falls back from the brain. 
 
 XLviii. The veins are much larger than their cor- 
 refponding arteries, having the fquare of their dia- 
 meter often double or triple that of the latter ; and 
 fometimes almoft quadruple, as near the root of, and 
 in the veficls of the kidneys. In general, however, 
 
 tlie 
 
Chap. II. 
 
 VESSELS. 
 
 21 
 
 tiie diameter of the veins is to that of the arteries as 
 nine to four ; yet the capacity of the capiliary 
 veins but little exceeds that of the arteries which 
 accompany them. They differ iikev/ife from the 
 arteries in their divifion, having more numerous 
 trunks and branches ; for to one artery in the 
 limbs we ufually meet with two veins. The lar- 
 ger veins are alfo more reticulated, and unite by 
 more frequent anaftom.ofes, not only of the fmall 
 branches, but even of the large trunks, occurring 
 every where amongft the neighbouring veins, up- 
 per with lower, and right with left. They prefer 
 the furface of the body ; and through the limbs, 
 neck, and head, they run a long way, perfectly cu- 
 taneous, which is very rarely the cafe with arte- 
 ries ; from which, on that account, they feparate. 
 Then the veins follow the furface, without a cor- 
 refponding artery, which, in the mean time, runs 
 at a coniiderable depth, attended by fome frnaller 
 venous branch. In the frnaller branches, and 
 membranous reticulations, and in the internal fa- 
 bric of the vifcera, the veins and arteries common- 
 ly run contiguous. The veins are generally iefs 
 tortuous. 
 
 xLix. In the larger fanguiferous veins, valves 
 are found in great numbers. The innermoft mem- 
 brane rifes double into the cavity of the vein, in 
 the manner of a curtain, and being on either hde 
 extended deeper along the courfe of the vein, 
 forms what may be called its cornicles : but the 
 bafis, where it arifes from the vein in the lhape of 
 a fegment of a circle, is ftronger, and confdtutes 
 its agger. With the lides of the vein as it pro- 
 ceeds, they inclofe a curtained fpace, of which the 
 exterior fide is the vein itfelf, and the interior the 
 valve, which by its convexity projects into the cav- 
 ity of the vein. The bafis of this almoil parabo- 
 lic fpace, or the mouth of the valvular cavity of 
 the veins, ahvays looks towards the heart. They 
 . a:e 
 
22 
 
 Chap. II. 
 
 are fonrd in all the habcutancous veins of the 
 limbs, in tnofc of the neck, face, tcng'ue, and in 
 the veins of the penis : at the origin of the larger 
 branches, there a.re two, three, four, and fometinies 
 five of them together, which, however, is rare : 
 in the fmaller branches they are ilngle. There 
 are none in the veins of the deep feated vifeera ; 
 and, therefore, none in the brain, lungs, heart, or 
 liver, or in the whole lyftem of the vena portarum, 
 or in the kidneys or womb, (except one or two 
 valves in the fpermatic vein ;) or, laftly, in thofe 
 fmalier veins, which a,re lefs than a line in diame- 
 ter. Sometimes, though rarely, they have been 
 feen in the vena azygos. In the cava, at the 
 mouths of the hepatic and renal veins, I have 
 obferved a fort of wrinkles in their place. In the 
 fmaller branches, the folitary valves are long and 
 very acutely parabolical, almoll proportionately 
 longer as the vein is fmaller. Thefe feem to op- 
 pofe the rehux of the blood more powerfully than 
 the larger ones. 
 
 L. The origin of the veins we noticed in fpeak- 
 ing of the arteries. They arife continuous from 
 minute arteries, by inferred branches, or the re- 
 fieclion of a trunk. Others, again, are cither 
 continued from veins of inferior orders, or receive 
 additions and roots from them ; as, for inftance, in 
 the lymphatic veilcls and thoracic duel. Others of 
 a bibulous kind take their origin from the ab- 
 forbing veins difperfed over the whole bodv, in 
 the cavities of the eyes, inteftines, breaft, perito- 
 naeum, pericardium, and ventricles of the brain. 
 Hence the venous exudation, eafilyirnitablcover the 
 whole human body, by injecting the venous trunks 
 with an aqueous liquor ; hence water, jelly, or oil, 
 pals from the vena portarum into the cavity of the 
 inteftines ; hence water, iniccled into the abdomen 
 of a li ving animal j quickly difappears. But of thefe 
 
Chap II. 
 
 VI 
 
 23 
 
 things we liiall fpeak again more fully in their 
 pioper places. 
 
 LI. Little different are thofe veins which arife 
 from every part of the cellular membrane, and car- 
 ry back to the mafs of blood, dropfical waters, moift 
 vapours, diffolved fat, extravafated and corrupting 
 blood, and the poifon of opium introduced into the 
 cellular texture ; or bring back the blood itfelf 
 from the cellular fabric of the penis, clitoris, or 
 nipples of the breaks, after the venereal orgafm. 
 That, into all the glands, veins of this kind open, 
 is highly probable, which, by abforbing the thin- 
 ner humour, leave the remaining mafs of a thicker 
 confiftence, as, for example, the bile, fperm, mu- 
 cus, &c. 
 
 Lii. That there are fmaller orders of veins, as 
 of arteries, refembling thofe which convey blood, 
 appears from experiments. Thus, in the eye there 
 are the fmall veins of the iris, and not a few trunks 
 in the adnata ; and, without doubt, veins return 
 from the vitreous humour, which, in health, are 
 pellucid. 
 
 Liii. But, in moft parts of the human body, other 
 veins are found, full of a reddirn, yellowifh, or al- 
 moft pellucid liquor, coagulable by heat ; formed 
 of a very tender coat, and excitable by chemical fti- 
 muli. They are intercepted by double valves, for the 
 moft part fo very frequently, that they ahnoft feem 
 jointed when they are turgid. By degrees uniting, 
 either the whole or greateft part of them meet in 
 the thoracic duel. They arife from the cellular 
 texture throughout the whole body, as I had long 
 ago learned of the lactiferous veflels of the breafts, 
 the vafa efferentia of the tefticles, and, laftly, of the 
 lymphatics originating from the mefenteric glands ; 
 and is now ftiewn of the lymphatic veflels of the tef- 
 ticles, fpleen, and other parts. From analogy, and 
 from the analogy of difeafes, efpecially of clrop- 
 fy, we are induced to believe, tiiat they arife like- 
 
 r* 
 
 wiie 
 
24 
 
 VESSELS. 
 
 Chap. II. 
 
 wife from the large cavities of the body ; nor is it 
 contradiftory to iuppofe. that titis kind of vcffels 
 receive a thin hmnonr from very minute veins. 
 But all the lymphatics, in their courfe, meet with 
 a peculiar kind of glands, called Conglobate, into 
 which they enter, having become arterial by the 
 convergence of the venous cones, and dividing into 
 branches ; and again iuue from them, to unite into 
 new trunks. 
 
 Liv. Thefe glands themfelves confift of lympha- 
 tic veffels, connected by cellular texture, into which 
 a fluid brought by the arteries, exfudes, and from 
 which it is taken up by the veflels which carry 
 away the lymph. They are covered with a contin- 
 uous mem.brane, generally of an oval fliape, wheth- 
 er they are Ample or compound; and they follow 
 the courfe of the larger blood-veflels ; efpecially of 
 the veins, through the whole trunk of the body, 
 to the infertions of the limbs ; running along the 
 jugular and fubclavian veins, the vena cava fupe- 
 rior, the afpera arteria, gullet, lumbal vena cava, 
 vena porta, the iliac, hypogaftric, crural and popli- 
 teal veins, and likewife the veflels of the ftomach, 
 fpleen, n^efentery, and mefocolon. 
 
 Lv. They are found on the furface of the vifee- 
 ra, in the thorax and abdomen : and more eaAly in 
 brutes : in the lower part of the face, mufcles of 
 the tongue and parts adjacent, in the neck, and 
 thofe parts of the upper limbs which are nearefl; 
 the trunk, as far as the bending of’ the elbow ; 
 throu2:hout the whole lens;th of the anterior and 
 pofterior inediaftinum, and wherever we And con- 
 globate glandules, either in the neck or thorax ; in 
 th'e whole lumbal region that is contio;uous to the 
 aorta; in the mefocolon ^pelvis, vcffels and furface ot 
 the teflicle ; and in the lower limbs, wherever they 
 are fupplied with conglobate glandules, as far as the 
 knees. Whether thev extend further, and exift in 
 every part of the body, in the brain, eye, hand, 
 
 3 
 
Chap. II. 
 
 VESSELS. 
 
 25 
 
 foot, back, fore part of the perlton3euiTi, &c. is not 
 confirmed by fuiliciently accurate or numerous ob- 
 fervations on the human body. They are every 
 where found on the furfaces of the vifcera. They 
 are almofi; every where collected into bundles, 
 which lie not far from the large blood-veflTels. Thofe 
 from the inferior limbs, pelvis, and loins, run into 
 one duel, which is joined by another bundle coming 
 from the liver, fpleen, and ftomach ; and that trunk, 
 at length, becomes the thoracic du£l. The fuperior 
 veiTels, from the whole extent of the breaft, the 
 • head, and fuperior limbs, empty themfelves into the 
 fame duct towards its upper extremity. They 
 feem, however, likewife to terminate in the red 
 veins. 
 
 Lvi. Of what fervice thefe glands are to the lym- 
 phatic vefiTels is not yet well known. In the foetus, 
 as well as the thymus and glandulas renales, they 
 are turgid with a milky liquor ; but it is not certain 
 that this fluid is poured out into the cellular 
 fpaces. It is however rendered probable by late 
 experiments, that in thefe glands fome kind of fluid 
 is prepared which is mixed with the lymph ; fince 
 thin fluids, injefted into the a.rteris, enter the lym- 
 phatic veflels. In the progrefs of life, this fluid van- 
 ifhes ; and the glands themfelves, being dried up, 
 almoft difappear. The very frequent fchirrofities 
 in thefe glands feem to indicate, that the motion 
 of the fluid paffing through them is retarded. 
 
 Lvii. Their valves (liii.) are compofed of two 
 femicircular membranes, which give way to the 
 fluid that goes toward the 1 vrger trunks ; and by 
 applying themfelves to the fides of the veffel, leave 
 a free pafiTage. But the fame valves, if the liquor 
 return from a larger trunk towards the fmaller 
 branches, being filled, fwell, expamd, and fliut up 
 the tube. 
 
 CHAP. 
 
2 $ 
 
 CIRCULATION. 
 
 Chap. III. 
 
 CHAP. III. 
 
 OF TPIE CIRCULATION OR MOTION OF THE BLttOD 
 TI-IROUGII THE ARTERIES AND VEINS. 
 
 Lviii. I ''HE arteries and veins hitherto deferi- 
 I bed, contain either blood or lymph. 
 The red blood, v.diofe nature v'e Ihall explain when 
 we treat of fecretion, fills the arteries and veins 
 commonly known, which we call red, or thofe of 
 the hrll order, and which have their origin in the • 
 heart. Thefe it fills, in a living perfon, in fuch a 
 manner that at one time they are very loofely and 
 imperfectly difiiended by it, and at another, they 
 are rendered very full and turgid. After death, 
 the veins are found very full of blood ; but occa- 
 fionally, the fmall veins, chiefly feme time after 
 death, have been found diftended with air. The 
 arteries in the dead body, commonly contain only 
 a fmafl quantity of blood. 
 
 Lix. This blood is rapidly moved through all the 
 veffels of the living body. The truth of which is 
 demonftrated by wounds, from which, even a mor- 
 tal lofs of as much blood as is neceflai*^' for the main- 
 tenance of life quickly enfues, almoft inftantly from 
 the larger arteries, and fometimes very fuddcnly 
 from the fmaller ones, but more diflicultly from the 
 veins, unlefs very large ; yet are there not want- 
 ing inflances of fatal hemorrhages from wounds 
 of the vein in the inner corner of the eve, or of 
 that under the tongue. Laftly, experiments made 
 upon liHng animals, fufliciently prove the power- 
 ful impulfe with which the blood is moved, partic- 
 ularly through the arteries. In the large arteries 
 it runs moft fwiftly ; in the fmall ones, fomewhat 
 flower. In the large veins, the blood moves more 
 flowly than in the arteries, in the lame proportion 
 as the calibers of the arteries are ieis tlian thofe of 
 
Chap. III. 
 
 CIRCULATION. 
 
 ^7 
 
 the veins, almoft twice or thrice. Another argu- 
 ment is derived from the compreliion and relaxa- 
 tion of a vein, by which the motion of the blood is 
 promoted from valve to valve. This motion in the 
 veins, is equable enough ; but, in the arteries, it is 
 alternately greater, fo that the veffel at one inftant 
 rebounds llrongly, and at the next is relaxed. This 
 is confirmed in living animals by ocular infpeclion. 
 
 LX. The direction of the motion of the blood 
 through the red veflTels, is Iliewn by experiments 
 of this kind. Firft, it is certain, that all the arte- 
 ries and veins communicate ; becaufe, from one, 
 and often a fmall artery, and fometimes alfo from 
 a vein, all the blood ihall be difcharged, even cauf- 
 ing death and extreme pallidity of the whole flefli, 
 not only of the limb wounded, but of the whole 
 body. Fatal examples have occurred from arteries 
 of the noftrils, gums, fingers, teeth, from a cuta- 
 neous pore, lachrymal point, cupping, and the bite 
 of a leech. There miufl; therefore be pafifages by 
 which the blood fpeedily flows from the venous 
 into the arterial fyfcem. 
 
 Lxi. That the blood, again, in the arteries, flows 
 from the heart toward the extreme parts of the 
 body, is proved by the microfcope, and by tying 
 up the artery of a living animal. For if an artery 
 be flopped by a ligature, a fwelling enfues in that 
 part betwixt the heart and the ligature, whilft 
 the other part beyond the ligature, and more re- 
 mote from the heart, becomes empty, has no pul- 
 fation, nor, if wounded, bleeds. The effect of a 
 ligature is alfo produced by difeafe ; as when fome 
 tumor, by ccmprefiion, or an aneurifm, intercepts 
 the motion of the heart. Experiments have been 
 made on moft of the arteries even by myfelf. 
 Sometimes anaflomofes, or the efcape of the blood 
 by fome channel into a neighbouring branch, and 
 the retrocefiion of the blood in a dying animal, 
 feeni exceptions» 
 
CIRCULATION. 
 
 Chap. III. 
 
 2S 
 
 Lxii. Tliere have been doubts with regard to 
 the motion of the venous blood, and all the an- 
 cients were perfuaded, that the blood flow'ed alfo 
 in the veins from the heart, or certainly from the 
 liver, to all parts of the body. Few have difeovered 
 the error : feveral, indeed, in the pulmonary vein : 
 in the vena cava, fewer ; perhaps only Andreas Cse- 
 falpinus, and as an uncommon appearance, Vefalius. 
 
 Lxiii. Hai'vey firft eftabliilied, by experiments, 
 the courfe of the venous blood which returns from 
 every part to the heart, fo as to remove every 
 doubt. And, firft, the valves point out this truth ; 
 for the common ofiice of thefe valves is, that every 
 prefliire, however applied to the veins, determines 
 the blood towards the heart, fince they take away 
 the pofiibility of its returning into the branches, 
 after having once entered a trunk. For, fince the 
 valvular portions are concave upwards, towards the 
 heart, the refluent blood enters into and expands 
 them. Thus, that part of the valve which projects 
 loofely within the cavity of the vein, approaches 
 towards the axis, until it meet the eppofite fide, 
 and ihut up the tube. This we know from infla- 
 tion, ligatures, and injections ; for we never can 
 force a liquor eafily into the veins againft the valves. 
 They do not, indeed, every where fliut up the 
 cavity entirely ; but they always do it in a great 
 meafare. 
 
 LXiv. Another olnce of the valves in the veins 
 feems to be to fuftain the weight of the blood, that 
 its upper columns may not gravitate upon the lower, 
 nor the blood, flowing through the trunks, impede 
 that comino: throuarh the branches. For if, from 
 the flower motion of the blood, it flrall happen that 
 its weight flrall bear too great a proportion to the 
 impullive force, and any part of the fangaiineous col- 
 umn begin to deicend by its weight, the ncareft 
 valve fupports it in its relapfe, prevents it from 
 preifing on the lucceeding column, and affords time 
 
Chap. IH. 
 
 CIRCULATION. 
 
 29 
 
 for fome contiguous mufcle, by its preffurs, to free 
 the valve, and propel the column. This is the rea- 
 fon for the lituation of valves in the veins of the 
 limbs and neck ; in which parts they are both more 
 numerousand more robuft thanelfewhere. Thisalfo 
 explains the caufe of varices, when the blood, enter- 
 in the valves, preffes their folid convexity down- 
 wards, and forces them to defcend and dilate. Like- 
 wife, in mufcular motion, the valves occafion the 
 whole preffure which the veins then fuftain, to for- 
 ward the due courfe of the blood towards the heart. 
 
 Lxv. Moreover, the valves placed in the right fide 
 of the heart, are fo conftrufted, as we fhall here- 
 after fee, that they freely permit blood, air, or wax, 
 to pafs from the venous trunks of the cava into the 
 heart, but allow nothing to efcape from the heart. 
 
 Lxvi. Befides, in a living perfon, ligatures make 
 the thing evident. When either by defign or ac- 
 cident, the veins of the ham, arm, or leg, are tied 
 with the limb jitfelf, the limb every where below 
 the ligature fwells, the veins become diftended and 
 turgid, and, when opened, freely difcharge blood ; 
 nothing of this kind happens above the ligature, 
 nor are any veins to be feen there. The fame hap- 
 pens when the veins are compreffed by fchirrous 
 vifcera, or enlarged glans ; and from polypi, tumors 
 of the large veins are frequent. Ligatures retain 
 the blood in any limb round which they are tied,, 
 and prevent it from returning to the heart, and 
 from being loft through a wound in another part. 
 
 LXVI I. The experiments which have been made 
 on living animals, are ftill more accurate. From 
 them, even from our own, it appears, that, by tying, 
 in a living animal, any vein, whether belonging to 
 the cava or to the pulmonary veins, that part al- 
 ways fwells which ismoft remote from the heart, and 
 is diftended with the blood retained by the obftacle, 
 while that next the heart becomes pale and flaccid. 
 Laftly, if both the arteries and veins be tied, the 
 
 veins 
 
CIRCULATIDN. 
 
 Chap. III. 
 
 veins coilapfe ; but, upon removing the ligature, 
 the veins are immediately filled. 
 
 Lxviii. In like manner, the injection of poifons 
 or medicines fhews, that, into whatever vein you 
 inject chemical acid fpirits, the blood even to the 
 heart is coagulated by the force of the poifon. But 
 the affection of the brain by the narcotic power of 
 opium, of the inteftines by purgatives, and of the 
 Ilomach by emetics, clearly proved that the blood, 
 with which thefe fubftances were mixed, had paff- 
 ed from the venous branch to the heart, and from 
 thence through the whole body. 
 
 Lxix. Moreover, from the transfufion of blood, 
 it appears that the living blood of one animal, in- 
 jected into the vein of another, completely emptied 
 of blood, replenilhes its heart, arteries and veins, 
 fo as to reftore vigour, turgidity, and even to 
 produce plethora. 
 
 Lxx. But that the blood palfes from the minute 
 arteries into the minute veins, we .are taught by 
 injection ; filling, without much difficulty, by one 
 arterial trunk, the arteries and veins throughout 
 the whole body, provid..ed the liquor be watery and 
 fiuid ; and with very great eafe thofe of the head, 
 mefentery, heart and lungs. 
 
 Lxxi. Laftly, microfcopical obfervations on the 
 pellucid tails, feet and mefenteries, of animals, 
 prove, beyond all doubt, that the blood, carried to 
 the extreme parts by the arteries, is poured either 
 into fmall veins, continuous with the reflected ar- 
 teries, or through communicating branches from 
 an arterial trunk into a parallel vein, and that it 
 returns by the veins to the parts nearer the heart. 
 This tranfition happens both in the moft minute 
 veins, which are capable of receiving only one glo- 
 bule, and in thofe fomewhat larger, which admit 
 two globules. That there is nowhere any fpongy 
 or parenchymatous fubflance interpofed betw’ecn 
 the arteries and veins, is proved both by the mi- 
 
 crofeope 
 
Cpiap. III. 
 
 CIRCULATION. 
 
 3 * 
 
 crofcope and by injeftions, which, if there were 
 any cellular fpace betwixt the arteries and veins, 
 would be extravafated in fliapelefs mafles. 
 
 Lxxii. The circulation of the blood, is, there- 
 fore, nov/ received as a medical truth by every 
 one ; namely, all the blood of the humian body is 
 carried through the aorta, from the left cavity of 
 the heart towards the extremities of the arterial 
 branches ; whence it is entirely tranfmitted into 
 the minute veins ; from thence it returns to the 
 large veins, the cava and heart itfelf; in which 
 courfe it perpetually circulates. 
 
 Lxxiii. Yet inftances occur, when, from pallions 
 of the mind, from a fudden great revulhon by 
 blood-letting, or from convulhon, the blood has 
 retroteded from the fmaUer into the larger arte- 
 ries. And, in like manner, from an obilruclion 
 being formed in the venous branches above the 
 valves, the blood has been knowm to return into 
 the extreme branches. But thefe deviations, are, 
 for the moft part, tranlitory, and the blood foon 
 returns into its natural courfe. They may be fup- 
 pofed to happen moft frequently in the abdomen 
 and vena portarum. 
 
 Lxxiv. The courfe of the humours in the val- 
 vular lymphatic veins, appears from ligatures and 
 from the valves : for every lymphatic vein when 
 tied, fweUs between its fmaller extremities and the 
 thoracic duCt ; but grows flaccid betwixt the duft 
 and ligature. All the valves, like thofe of the 
 veins, allow air and mercury to flow freely into 
 the thoracic duct ; but they refift, and often obfti- 
 nately, the contrary courfe, although fometimes 
 in the dead body they have given way. 
 
 Lxxv. The vapour that moiftens the cellular fub- 
 ftance, the halitus of the abdomen and other cavi- 
 ties are conveyed from the pellucid into the red 
 veins, that thefe may tranfmit their contents to the 
 heart. Hence, v'hen a vein is comprefled or tied, 
 
 oedema 
 
CIRCULATION. 
 
 Chap. III. 
 
 32 
 
 cedema enfues, the fluid flagnating, from its paf- 
 fage being interrupted. In the otlicr fmaller vef- 
 fels, experiments cannot be made ; but reafoning 
 and analogy fupport the fame concluflon. Experi- 
 ments concerning the fluid, reabforbed from the 
 inteftines, pulmonary veficles and Ikin, fliail be 
 mentioned in their proper places. 
 
 jLxxvi. Therefore all the fluids in the human 
 body are expelled from the heart into the aorta ; 
 and except thofe which are exhaled out of the cav- 
 ity of the body, or are excreted, they all return to 
 the heart through the minute veins. It remains 
 to difcover a palfage by which the blood may re- 
 turn from the right to the left fide of the heart ; 
 but this paflage luppofes an acquaintance with the 
 hiflory of the heart and pulmonary veflels. 
 
 CHAP. IV. 
 
 HEART. 
 
 Lxxvii. ^ g ■'HE thorax, compofed of bones and 
 I cartilages, on the whole, refembles 
 a truncated cone, as we fliall hereafter mention. 
 The lateral parts of this cone, are two membranous 
 bags, having at their upper end an obtufe termina- 
 tion, above the firfl; rib, at which place they are con- 
 tiguous, and feparated only by fome cellular fub- 
 ftance. Their obliquity is fuch, that the right bag 
 is wideft, and adheres to the middle of the fternum, 
 but as it defcends it inclines to the left fide, and 
 comes from the very margin of the fternum. The 
 left bag defcends not from the fternum, but from 
 the cartilages of the ribs. The inner and oppofite 
 fides of each bag, form what anatomifts call the 
 mediaftinum. Tliefe bags have no communication 
 whatever, and the right may be opened and its 
 luna; dcliroycd, without irdurins; the left. But the 
 
 membrane 
 
Chap. IV, 
 
 HEART* 
 
 33 
 
 membrane which forms them, is fimple, denfe, ex* 
 ternally furrounded by ceUular fubftance, is called 
 the pleura, is harder than the peritonaeum efpe- 
 ciaUy towards the back^ fofter anteriorly, and is 
 naturally infenfible. The cavity of the mediafti- 
 num, or interval between the right and left bags, 
 broadeft above, but alfo confiderable below, con* 
 tains the thymus, conglobate glands, fat, velfels, 
 and in fome difeafes, pus. 
 
 Lxxviii. Below, the fame bags diverging, re- 
 cede from each other, and leave a cavity central 
 in all its dimenlions, which feparates them. This 
 cavity is the pericardium. But the bags of the 
 pleura, defcending at the lides of the pericardium, 
 and before and behind it, terminate hnally, about 
 the fifth or fixth rib, upon the diaphragm, and on 
 it have their bafis, which is truncated obliquely, 
 fo that anteriorly it is fliort, but pofteriorly de- 
 fcends farther, and is arched upwards* Within 
 thefe bags are the lungs. Pofteriorly, thefe bags 
 are more tender, contiguous and feparated in the 
 fame manner by cellular fubftance, which termi* 
 nates on the pericardium, and includes, in fome 
 meafure, the aorta, but more evidently the trachea 
 and cefophagus* This is the pofterior mediaftinum. 
 Triangular productions of each lamina of the me- 
 diaftinum form the ligaments of the lungs, one on 
 each fide. 
 
 Lxxix. The pericardium, or third bag, which is 
 loofely furrounded, firft by cellular fubftarice, and 
 then on aU fides by the contiguous pleura, as an ex- 
 terior lamina, touches the fternum by a very fmall 
 part indeed ; fince the lungs when diftended, cover 
 the heart almoft wholly before, and interpofe 
 themfelves betwixt the fternum, and pericardium 
 below ; and the mediaftinum, by gradually diverg- 
 ing towards the left fide, has an interval, narrow 
 indeed, under the lower end of the thymus, to each 
 fide of which, the lungs extend : but this fituation 
 D is 
 
HEART. 
 
 Chap. IV. 
 
 34 
 
 is dircurbed, iinlefs you are careful in tlie manner 
 of opening the thorax. The pericardium has a 
 broad, fomewhat round bafis, adhering to the ten- 
 dinous, and by a fmaUer part on the left fide, about 
 the fifth or fixth rib, to the fielliy part of the dia- 
 phragan ; in young fubjects by loofe, but in adults 
 by very firm, cellular fubftance. Towards the right 
 it is broader, and towards the left it grows imalier. 
 It is fomewhat larger than the heart, that it may 
 move freely in it. It never certainly was wanting. 
 
 Lxxx. Upwards, the pericardium grows gradu- 
 ally narrower, ending above the heart in an obtufe 
 conical appendix, which adheres to the coats of the 
 large blood-veffels almoft to the upper edge of the 
 fternum ■, iirfi; to the inferior branch of the right 
 fuperior pulmonary vein ; then to the vena cava ; 
 after that to the aorta, on its acceffion to wliich it 
 is higheft ; then dovenwards to the fame velfel, and 
 the ducfus arteriofus ; hence to the left branch of 
 the pulm.onary artery, and at laft to both branches 
 of the left fuperior pulmonary vein. On the back 
 part it is again attached to the right pulmonaiy 
 vein ; then to the left fmus, to both left pulmonary 
 veins, and to the auricle of the fame fide ; then a 
 long way from the pulmonary vein to the inferior 
 cava, then to the feptum of the fmufes, then to the 
 inferior cava. Befides, it adheres to the pulmonary 
 artery, its right branch, and the aorta below the 
 origin of its great branches, furrounding each ar- 
 tery with a cylindrical production, fo that it ap- 
 pears like a kind of partition between every two 
 neighbouring veiTels. Thus alfo it contains the 
 vena cava fuperior in a ring ; and the anterior and 
 pofterior cavities of the pericardium are loofely 
 continued between that vein and the aorta. In 
 like manner it furrounds the inferior cava. But 
 this fireath, by which the velTels are furrounded, 
 preferves its nature only for a flrort fpace, and 
 immediately returns to the lieart with thofe large 
 
 vellels 
 
Chap. IV. 
 
 HEART. 
 
 35 
 
 veffels which it there ferves as an external coat. 
 But it fends cellular fubilance like a Iheath, along 
 with the great arteries and veins, to the lungs. 
 
 Lxxxi. The pericardium has its arteries either 
 from thofe of the thymus, from thofe which ac- 
 company the phrenic nerve above and below, from 
 the larger phrenic arteries, from the mediaftinal 
 branches of the mammary, from the bronchial, oefo- 
 phageal and polterior m.ediaftinal arteries, or from 
 the coronaries which inofculate with the bronchiais 
 and others. The trunks of the veins are analogous, 
 but with more evident anafcomofes between thofe 
 of the right and left fides. The nerves are from 
 the fuperficial cardiacs. 
 
 Lxxxii. The membrane which properly confd- 
 tutes the pericardium, is ftrong, white, compact, 
 more robuft than the aorta itfelf, and through its 
 fubftance the nerves of the heart and forne final! 
 vefl'els defcend. The furrounding cellular lub- 
 flance makes its outer furface fomewhat rough, 
 while internally, where it is in contacl with the 
 heart, it is very fmooth, and moillened on aU fides 
 by a watery vapour. This halitus, which we have 
 always obferved in the living animal, conhitutes 
 the water of the pericardium, fmall in quantity, 
 but always prefent, limpid, or tinged with yellow 
 or red, fomewhat vifcid, erroneoully denied by 
 fome ; and in fome difeafes immenfely increafecl. 
 The nature of this fluid is lymphatic, becaufe it 
 thickens into a gelly by heat, and in difeafes, mix- 
 ed with the mucus Vv^hich every where exudes from 
 the heart and its pericardium, it concretes into 
 villi and cellular fubftance. This liquor is fecreted, 
 without any glands or viftble pores, from the ex- 
 haling arteries of the heart, auricles and pericar- 
 dium ; as may be proved by the tranfudation of 
 water or ftze injected into the large arteries. 
 
 i.xxxiii. The ufe of the pericardium is to con- 
 tain this vapour, and the heart, fo that it may have 
 D 2 a fixed 
 
HEART. 
 
 Chap. IV, 
 
 3 ^ 
 
 a fixed point, to which, when in motion, as to a 
 fulcrum, it may draw its fibres, without ftretching 
 the large veffels, and that it may not fhift, pendu- 
 lous, on changing the pofition of the body. For 
 thefe reafons, we find it in all animals that have a 
 true heart. A watery vapour bedews the very 
 hot and very rapidly moved heart. It prevents 
 fricfion, and its cohefion with the pericardium ; 
 for, when this vapour is dried up, the pericardium 
 adheres to the heart, either in fome particular 
 place, or over its whole furface, fo that it may 
 feem to be wanting. 
 
 Lxxxiv. Nature has g-Iven to moft animals, and 
 even to many infefts and vermes, a heart ; flie has 
 denied it to others, and indeed to the moft fimple 
 animals, beins; thofe which are irritable over their 
 whole body,hov/ever large,as the holothuria hydra. 
 
 Lxxxv. The veins which carry back the blood 
 from the whole body to the heart, if we except 
 thoie of the lungs, are two. Anatomifrs call them 
 the cava, but they either never form one finglc 
 trunk, or for a very fliort fpace. Of thefe large veins, 
 the inferior is the largeft, and in man afcends in the 
 right fide direftly above the diaphragm. Towards 
 the right it is fomewhat gibbous, that it may meet 
 the fuperior cava, and pofteriorly it forms the 
 feptum, which interv'^enes between the right and 
 left finufes. But the left fide of the vein unites 
 with the right auricle, whofe fibres are continuous 
 with thofe of the cava. The fame is true of the 
 fuperior cava. 
 
 Lxxxvi. A cavity is thus produced, whofe right 
 fide is free, convex, and compofed by the union of 
 the tvm venae cavae, and which is filled vath flefhy 
 fibres, varioufly intersvoven between the two limplc 
 membranes. The fam.e cavity, at its anterior and 
 left partds perpendicularly oblong, and almoft oval ; 
 anteriorly it is dilated ; and, laftly, upwards, it has 
 an acute blind termination, detached from the heart, 
 
 and 
 
Chap. IV. 
 
 HEART. 
 
 37 
 
 and refting upon the aorta. This cavity evei'y 
 where between the external membrane of the heart 
 and its own very thin internal membrane, has very 
 copious fibres, fiefhy, detached, almoft parallel, yet 
 obliquely interfecting each other, v/hich arifing 
 from the right fide of the whole cavity, and from 
 the left, are extended round its anterior femicylin- 
 der, in the manner of parallel arches. Very minute 
 oblique fibres conned: thefe mufcular arches. This 
 anterior and ftringy part is called the auricle, but 
 the right and pofterior portion is called the finus, 
 which is fmooth along the feptum of the auricles, 
 and between the anulus ovalis and mouth of the 
 heart to the left of the vena cava. In the auricle 
 are three confiderable mufcles, the anterior, pofte- 
 rior, and inferior. 
 
 Lxxxvii. Towards the left of the feptum, which 
 divides the two auricles, almoft in the middle be- 
 tween the two venas cavae, there is a depreffion, as 
 if imprinted, deeper above, lefs deep below, in 
 which the feptum is exceedingly thin. I fliall call 
 it the fofla ovalis. A fleftiy column bounds it on 
 each fide, by the junction of which, is formed an 
 arch, convex upwards, whofe ftefliy fibres are 
 ftretched around in the form of arches, while their 
 lower and thinner roots are turned backwards to- 
 wards each other. This I call the anulus ovalis ; 
 others, the ifthmus. 
 
 Lxxxviii. Where the afcending cava opens in- 
 to the right auricle, froih the left tumid column of 
 the foramen ovale arifes a membrane of a crefcent 
 fliape, naturally entire, but from its thinnefs fome- 
 times reticular in adults ; which being extended 
 round the lower edge of the auricle, always grow- 
 ing thinner as it returns incurvated to the right, 
 circumfcribes almoft half the circumference of the 
 auricle, and feparates it from the vena cava, in the 
 manner of a feptum, It is called the valve of Eu- 
 
 ftadiius. 
 
HEART. 
 
 38 
 
 Chap. IV, 
 
 ftacliius. The foianien ovale we fliall defcribe 
 hereafter. 
 
 Lxxxix, Into this linus and auricle, which, how- 
 ever, compofe but one porch of the heart, the 
 blood of the two venae cavae is impelled by the 
 niufcular power which refides in each of thefe 
 veins ; for as far as they lie within the breaft, they 
 are endov'-ed vAth ftrong and irritable mufcular 
 fibres, by whofe contraction the blood is driven 
 into the neiehbourins: auricle. 
 
 O ^ 
 
 xc. In like manner the auricle, when irritated, 
 contracts in every dimenfion. Firft, by the con- 
 Itriction of tlie mufcular lacerti of the auricle, its 
 anterior femicylinder is reduced to a plane, while, 
 by contracting at the anterior extremity or begin- 
 ning of the heart, and at the poflerior, or finus, 
 they draw the middle of the arch backwards. Then 
 the appendix of the auricle defeends and contracts 
 tranfverfely, while the lower part afeends ; and 
 thus the auricle is lliortened. Laftly, the left hde 
 approaches evidently to the right, and the right 
 fornewhat to the left, and thus the auricle is ren- 
 dered narrower. Into' the mouth of the heart, 
 now free, the blood is impelled like a wedge 
 through the aperture cf the valves, fo that the flat 
 fides of the valves in the right ventricle are every 
 where applied to tlie fidcs of the heart. The blood 
 is now hindered from returning again into the 
 loveer ca\ a, cn the ccntraclion cf the aui'iclc, bqth 
 by the reliftance of the fucceeding blood from the 
 abdomen, and by the Euftachian valve ; and from 
 returning upwards it is prevented, both by the 
 iubfequent blood and its gravity. It is driven 
 back, however, both ways, if there be any obflacle 
 in the lun 2 ;s. 
 
 xci. The heart itfelf, in feme meafure, refembles 
 half a cone. The fecdon, palling through the axis 
 of the cone, and dhdding it, is almofl triangular, 
 ]3ut with an obtufe nearly bifid point, and flattened 
 
 tp 
 
Chap. IV. 
 
 HEART. 
 
 39 
 
 to the form of the diaphragm, refls upon, and is 
 fuilained by it. But the convex furface of the cone 
 is fo inclined within the pericardium, under the 
 great blood-veffels, that its thicker lemicircular 
 cavity lies in the fuperior and left fide, the obtufe 
 margin of the moderns *, while below, and anteri- 
 orly, it is extenuated into a kind of edge, or the 
 acute margin. The point is turned a little forwards. 
 This is the fituation in man ; for, in brutes, the 
 heart being almoft parallel to the larger axis of the 
 thorax, its apex only touches the diaphragm. 
 
 xcii. The whole heart is hollow ; and continuous 
 with the right auricle and finus, as they are called, 
 it has its properly anterior, though formerly called 
 its right ventricle, broad, refembling the fourth 
 part of a cone, not fo long as the left ventricle^ but 
 larger, and terminating in the fiiorter tip of the 
 bifurcated apex. The mouth of this ventricle, where 
 it opens into the auricle, is elliptical, and termina- 
 ted by a white margin, not fo much tendinous, as 
 callous and glutinous, on which a ftratum of flelhy 
 fib res refts, and externally fome fat. 
 
 xciii. From this margin is extended, within the 
 heart, a membranous ring, formed by a reduplica- 
 tion of the internal membrane of the auricle, float- 
 ing within the auricle and fo far entire. But this 
 fame ring, in that part which hangs within the 
 ventricle, is divided into three unequal trapezic 
 portions, in fuch a manner, that you may, in ibme 
 meafure, give them the name of valves ; and reckon 
 three of them. They are, however, continued 
 parts of one ring, only broader here. Thefe were, 
 by the ancients, named triglochines. 
 
 xciv. The furface of thefe valves which lies next 
 to the fides of the heart is flrengtliened by tendi- 
 nous fibres, which, m.eeting together in their courfc, 
 are inferted by fome very ftrong cords, lying in 
 rows on each other, partly into the fides of the 
 heart, and partly into papillary or cylindrical 
 
 mufcleSs 
 
40 
 
 HEART. 
 
 Chap. IV. 
 
 mufcles, ariling towards the right from the left 
 part of the right ventricle, bifid, trifid, or even 
 branchy. The largeft is that which anfwers to 
 the biggeft of the valves, which is both the upr 
 permoit and that which anfwers to the adjacent 
 mouth of the pulmonary artery. The middle 
 valve lies next the feptum of the heart. The 
 leaft of them is the loweft, and moft anterior in 
 the acute margin, 
 
 xcv. The uie of this valve is evident; for, on the 
 contraftion of the right auricle (xc.) the blood 
 contained in the right porch of the heart being 
 forced into the open extremity of the auricle, that 
 is, the mouth of the heart, feparates, in the manner 
 of a wedge, the pendulous portions of the ring, call- 
 ed valves, and prefles them to the fidcs of the heart. 
 Thus the right ventricle of the heart is filled, while 
 the uppermoft valve (xciv.) fliuts the pulmonary 
 artery, left the blood, with the weak impulfe of the 
 auricle, fhould enter that artery ; but that being firft 
 received into the heart, by its flrong contraction it 
 may be more powerfully expelled into the artery. 
 
 xcvi. Ey this blood, copious, warm and hea^y, 
 the fenfible flelli of the heart is irritated and ex- 
 cited to contraction : for that the heart, on being 
 irritated, will contract itfelf in a moribund, or re- 
 cently dead animal, is proved by the injection of 
 water, and inllation of air, renewing the motions 
 of a heart after having become quiefcent. 
 
 xcvn. The motion of the heart is performed by 
 mufcuiar fibres ; the origins of which, in general, 
 are from rings formed of firm cellular fubftance, 
 iuch as I have defcribed in xcii. and with which 
 all the large blood-vefiels cf the heart are furround- 
 ed. The fibres from thence defcend gradually in 
 an oblique courfe towards the left fide, and to the 
 apex, in many itrata, fometimes a little decutfating, 
 of which the m.iddle ones are more tranfverfe, the 
 outer molt and innermolt more direcT. In the flat fide 
 
 of 
 
Chap. IV. 
 
 HEART. 
 
 41 
 
 of the heart (xci.) the fibres are few ; and fo thin, 
 that next to the fat, the cavity is found aimoft un- 
 covered, The ventricle, which is denominated the 
 left, is furrounded by very firm fibres ; which, in 
 the feptum, flightly decuffating, are interwoven 
 with thofe of the right fide. Many of thefe fibres, 
 in their progrefs towards the apex,defcend into the 
 cavities of the heart, and being interwoven, even 
 repeatedly, in the manner of a net, intercept mefities 
 hid amongft the mmfcular lacerti, and form the 
 flelhy columns mentioned at xciv. Others, at the 
 apex, convoluted in a fpiral direction, terminate the 
 bifid ventricles with a firm mafs. A very thin and 
 fmooth membrane covers both the external and 
 internal furface of thefe fibres ; but the external 
 membrane, efpeciaily about the coronary veflels, 
 contains much fat. I have not been able to obferve 
 with fufficient precifion, any thing further in the 
 human heart ; becaufe it is the peculiar property 
 of the fibres of the heart to be joined by branchy 
 appendices, fo that they cannot be feparated any 
 where without laceration. 
 
 xcviii. But eminent anatomifi;s,whofe ingenuity 
 and candour I refpect, have publilhed the evolution 
 and defcription of thofe fibres. They allege, that 
 the external fibres of the heart defcend to the apex, 
 common to both ventricles ; that in their couffe, 
 fome infert themfelves into the feptum, while others 
 perforate the left ventricle near the point, and be- 
 ing reflected, return along the inner furface of that 
 ventricle, to the bafis, in a contrary direction. But 
 there are other middle fibres, betwixt the aforefaid 
 inner and outermofi: ones, which being varioufly in- 
 clined, and towards the bafis principally traniverfe, 
 form the feptum. Other anatomifts have given fig- 
 ures and defcriptions of many layers of fibres, of 
 which the external and internal have contrary di- 
 rections, and the intermediate are tranfverfe. As 
 thefe do not differ very much from my own obfer- 
 
 yations, 
 
43 
 
 HEART. 
 
 Chap. IV. 
 
 vations, I by no means undertake to deny them, al- 
 though I have never feen this difpofition fufiiciently 
 manifeft, and am acquainted mth great anatomifts 
 who have not been more fuccefsful than myfelf. 
 
 xcix. Thefe fibres of the heart, like other mufcles, 
 are furaiflied with nerves of their own, numerous 
 and of various origin. The firft and uppermoft, on 
 the left fide, come from the uppermoft cervical 
 ganglion of the intercoflal nen^e. With it are join- 
 ed others from the pharyngeal plexus, formed of 
 the foft nerves, proceeding from that ganglion, and 
 from the glolfo-pharyngeal nerve; others are added 
 from the trunk of the intercoftal nerve ; others 
 from the middle ganglion feated on the ftraight 
 mufcle about the paflage of the thyroid artciy, 
 which has branches both from tliat uppermoft 
 nerve, and from the trunk of the intercoftal and 
 phrenic nerves ; and others from the recurrent 
 neiwe of the eighth pair. The nerves of the heart, 
 originating from thefe fources, woven togetlier into 
 a plexus, partly before the aorta, on which thofe, 
 hereafter mentioned, are alfo added ; and partly 
 after forming feveral fmall plexufes between the 
 trachea and the large arteries iffuing from the 
 heart, form one or more plexufes, in which the 
 neiwes of the right and left lide arc united, though 
 fometimes they remain diftinct. From this plexus, 
 or plexufes, fome branches pafs between the aorta 
 and pulmonary’ artery'' to the right artery of tlie 
 heart ; others crofs the pulmonary artery, and go 
 between it and the auricle of the i'ame fide to tne 
 left coronary artery ; others behind the pulmonary 
 arrteiy to the fame coronary’ ; and others, again, dc- 
 feend very deeply behind the right pulmonary ar- 
 tery to tlie left finus and fiat furface of the heart. 
 To the plexus, above deferibed, other large nerves 
 are added from the fifth and lower cervicals, and 
 idmetimes from the phrenic nerve, and from tlie 
 iewefi cervical ganglion of the inter: ofial, with 
 
Chap. IV. 
 
 HEART. 
 
 43 
 
 which are united very large roots from the loweil 
 cervical nerves. Thefe, larger, very foft, and tranf- 
 vcTic, are partly mixed with the former plexus, 
 and partly go to the lungs. Lafdy, fome fmaii 
 branches, uncertain as to courfe and number, come 
 from the recurrent and eighth pair of nerves, vari- 
 ouhy inofculated with the intercoilals, and blended 
 with the eighth pair. Thofe nerves, which fome 
 eminent anatomifts have leen afcending through 
 the foramen of the vena cava, from the great ab^ 
 domirial plexus, to the heart, I have never been 
 able to find ; althousrh it is eafy to difeover the di- 
 aphragmatics arifing in that place,of which, though 
 having ganglions peculiar to themfelves, thofe 
 anatomifts make no mention. 
 
 c. That thefe nerves conduce povrerfully to the 
 ' motion of the heart, is the opinion of eminent anat- 
 omifts, from a confideration of the common nature 
 of mufcles ; and from the increafe of motion in the 
 heart, on irritating the eighth pair of nerves, or 
 brain, or fpinal marrow , ?,nd from the languor that 
 enfues upon tying thofe nerves, for the moft part 
 either immediately fatal, or certainly within a few 
 days, although it is poflible to tie only a few of 
 them , for the intercoftal, and ftill more thofe from 
 the uppermoft thoracic garnglion, cannot be tied. 
 
 ci. But that fomethins: elfe is comnrehended in 
 the caufe, appears from the motion of the heart re- 
 maining undifturbed in the living animal, after ex- 
 ceilive irritation of the nerves ; from its continuing 
 after the moft extenfive wounds of the head, and 
 even of the cerebellum and medulla fpinalis, nay, 
 even in the heart, v/hen torn out of thebreaft, chiefly 
 in thofe animals in which the lungs, being pervious, 
 make no refiftance to the powers of the heart ; 
 moreover, from the lively aftion of the heart in tlie 
 foetus before the brain is completed, and in anim.als 
 wanting the head. And all our experiments agree, 
 that the quiefeent heart, in moribund, and finally 
 
44 
 
 HEART. 
 
 Chap. IV. 
 
 in dead animals, when irritated by warmth, vapour, 
 cold, poifon, and efpecially by a current of air, wa- 
 tery liquors, wax, or blood, or by an electric fpark, 
 is immediately contracted, and all its fibres excited 
 to quick and violent motion, fometimes general 
 throughout the whole heart, and fometimes con- 
 fined to one part of it. 
 
 cii. Thus, then, there relldes in the fibres of the 
 heart an impatience of ftimulus ; fo that in various 
 places of the vifcus, even when almoft dead, 
 wrinkles, and motions, appear to be propagated 
 through it, as if from radiating points : again, the 
 heart, when torn out and cold, on being pricked, 
 inflated, or irritated, contracts itfelf *, and the fi- 
 bres of a dilTecled heart, corrugate themfeives orbi- 
 cularly, when it is no longer fupplied either with 
 nerve or artery. This irritability exifts in a great- 
 er degree, and remains longer in the heart than in. 
 any other part of the body ; fo that, by flimulating 
 it, the motion of the heart may be renewed at a 
 time when that or no other mufcle can. I'hc heart 
 of the foetus is more irritable, as well as larger, in 
 proportion, than in adults ; and very tenacious of 
 its mobility, even in the cold. This mobility is in- 
 herent in the heart, and is neither derived from the 
 brain, nor the foul ; fince it remains in the dead 
 animal, and in the heart when torn out of the 
 breafl ; and cannot be accelerated or retarded by 
 volition. 
 
 CHI. The heart, therefore, when ftimulatcd by 
 the venous blood thrown into it, contracls. Tliis 
 convulilve contraction is made with great celerity, 
 and a manifck corrugation of the fibres ; and the 
 whole heart becomes fhorter, thicker, and harder. 
 Idle left ventricle is drawn fomewhat towards the 
 feptum of the heart, and the right one more fo. 
 Ike bafe aifo advances towards the apex ; but tlie 
 apex more evidently towards the bafis. This I 
 have Qften obferved with the greatefl certa.i]'ty in 
 
Chap. IV. 
 
 HEART. 
 
 45 
 
 dilTecliing living animals ; fo that thofe learned 
 gentlemen mull have been fome how deceived, who 
 have afferted, that the heart is elongated during 
 its contraftion. But the heart does not feem to 
 turn pale in warm blooded animals. Even the fep- 
 turn of the heart is rendered Ihorter, and draws 
 itfelf towards the balls. By this adion, the flelhy 
 parts of the heart fwell inwardly, and comprefs the 
 blood, as they do the finger when introduced udth- 
 in it. But that the heart is completely enough 
 emptied, appears both from the event ; from the 
 -evident palenefs in animals whofe heart is white, 
 as frogs and chickens ; and from the uneven inter- 
 nal furface, which has everywhere eminences and 
 correfpondent hollows, and thick reticular columns 
 interrupted by furrows. Befides, the apex of the 
 heart, being turned a little forwards, like the radius 
 of a circle, and being, moreover, driven forwards 
 by the left venal finus, which is at that time, par- 
 ticularly filled, ftrilces againfi: that part of the peri- 
 cardium next the thorax, about the fifth or fixth 
 rib. In ftrong exfpiration, it is carried with con- 
 fiderable force upwards and forwards. Both fads 
 are proved by experiment. 
 
 CIV. The blood, prefled by the contradied heart, 
 (cm.) endeavours to efcape in all diredrions ; but 
 fince the contraflion begnin in the fides of the heart 
 drives the blood towards the axis of the ventricle, 
 that part of the blood which lay betwixt the ve- 
 nous ring (xciii.) and fides of the heart, carries 
 the ring before it, and extends its loofe extremities 
 inwards. As this happens to the whole. circum- 
 ference of the ring, it becomes extended, throws 
 back a part of that blood which had defeended into 
 the cone of the open valve, into the right auricle 5 
 and, laftly, fhuts up the venous orifice more clofely 
 as the heart contrails more firongiy, and without 
 doubt would force the tricufpid valves, as they are 
 called, invertedly into the auricle, if the papillary 
 mufcles (xciv.) did not keep down their edges, and 
 
HEART. 
 
 Chap. IV. 
 
 46 
 
 by their contraction, which is the fame with that 
 of the heart, retain them firmly in thatpolition in 
 vchich the chords connected with the valve are ex- 
 tended, without being injured. 
 
 cv. But the fame effort of the blood opens to it 
 another paflage. Whilft the right larger valve 
 (xciv.) approaches towards the axis of the heart, 
 it leaves the mouth of the pulmonary artery, which 
 it clofed, and the blood opens it, preffes the valves 
 placed in the artery clofe to its fides, and ruflies 
 into the artery. 
 
 cvi. From the upper part of thepofterior, or, as 
 it is caUed, the right ventricle, a paffage leads into 
 the artery, received as it were between producfions 
 of the fleili of the heart, and ftrongly ccnnecled to 
 the heart by a cellular, callous ring, from whence 
 the artery afcends to the left and backwards, and 
 paffes behind the arch of the aorta. The ftrength of 
 this artery is moderate, being much weaker than the 
 aorta. From the inner furface of the artciy, where 
 it is joined to the heart, the femilunar valves arife. 
 Each of thefe is formed by a reduplication of the 
 arterial membrane, extended from the part of the 
 artery next the heart, upv'ards, in an obtufe and 
 tuiUcientiy hat arch. On the whole, they are par- 
 abolical v/ith a loofe and moveable margin. The 
 middle of the edge is generally divided, fometimes 
 in the foetus itfeli, by a fmall callous body, almoft 
 conical, but made up of inclined planes ; fo that 
 the margin, which would otherwife have the lliape 
 of a crefeent, is now divided into two crefeents. 
 Betwixt the two membranes of the valve, arihng 
 from the edge and hrm root of the valve, appear 
 fome mufcular of tendinous fibres, partly tranfverfe, 
 feme of which even bind the \ -alve to the conti^fu- 
 
 O 
 
 ous fide of the heart, leaving fometimes fpaces be- 
 twixt tiicm in a reticular manner. Other fibres 
 afeend from the bafii of the vaivcj and adliereto 
 
 the 
 
HEART. 
 
 Chap. IV. 
 
 47 
 
 the callous corpufcle. Thefe draw back the valve, 
 and open it. 
 
 evil. Each of thefe valves wdth the fide of the ar- 
 tery at this part fomewhat enlarged, intercept a par- 
 abolical fpace, which towards the heart is impervi- 
 ous; but open upavards,as we obferved of the valves 
 in the veins (xnix.) When, therefore, the blood is 
 impelled towards the axis by the contraction of the 
 heart, it efcapes in the diredion of that axis ; pen- 
 etrates like a wedge, betwixt the valves, preffes 
 their loofe membranous edges againft tlie fides of 
 the pulmonary artery, and flows out freely. This 
 appears from the mechanifm, from injection, from 
 ligatures, and from the increafed fize of tlie cavities 
 of the right fide of the heart, when the lungs, be- 
 ing obftruded, prevent them from being emptied. 
 
 cviii. The blood received into the pulmonary 
 artery, circulates through the lungs. That artery is 
 firfl divided into two branches ; of which the left 
 is lefs and fiiorter, and enters immediately into the 
 lungs of that fide: but the right branch, larger and 
 longer, pafles tranfverfely behind the arch of the 
 aorta to its correfponding lungs. From each of 
 thefe, by fucceflive fabdivifions, very minute twigs 
 are produced, of which, a part exhale a watery 
 liquor into the cells of the lungs, and a part are 
 continued into the veins. That the blood flows in 
 this diredion, is proved by the mechanifm, by the 
 application of a ligature, which, intercepting the 
 blood between the heart and lungs, dilates the ar- 
 tery ; by polypufes obftruding the mouth of the 
 pulmonary artery, in which cafe the right cavities 
 of the heart become monftroufly enlarged, and at 
 length burft, while the left remain empty; and by 
 injedion ; for water, fize and milk, are very eafily 
 thrown from the pulmonary artery into the vein^ 
 and into the left fide of the heart. But in frogs, 
 the anaftomofes themfelves of the arteries with the 
 veins, are feen by means of the microfeope. 
 
 CIS. 
 
Heart. 
 
 Chap. IV. 
 
 4S 
 
 cix. Nor can the bloody which has once entered 
 the pulmonary artery, return into the heart ; be- 
 caufe the valves (cvi.) are of fuch dimenfions, 
 that, v/hen diftended, they perfectly fliut up the 
 opening at the heart ; and are fo flrong, that they 
 are able to reiift a much greater force than the con- 
 tradtion of the pulmonary artery. However, fome- 
 times, from the great preffure of the contracted ar- 
 tery, they grow callous ; or one of the membranes 
 is lacerated, and ofleous matter is poured in be- 
 twixt the duplicature of the valves. For, when the 
 blood, by the contraction of the artery returns to- 
 v/ards the heart, it ftrikes againft the open mouths 
 of. the valvular fpaces, (cvn.) enters them, expands 
 thevalves,and forces them towards the central axis ; 
 when expanded, they fliut up the paflagc, fo that 
 not even a flit remains, for that is prevented by 
 the hard corpufcles (cvi.) 
 
 cx. The pulmonary veins, of which we fliall fay 
 more hereafter, are gathered into branches, and, at 
 laft, into four, feldom two, and ftill more rarely in- 
 to five trunks ; to which cuflom has aflixed the An- 
 gular name of pulmonary vein. Thefe trunks en- 
 ter the cavity of the pericardium, from whence they 
 receive an external covering ; and are then infert* 
 ed into the corners of the fquare, left, or pofterior, 
 or as it is fometimes called the pulmonary Anus. 
 The upper veins defeend, the lower ones afeend. 
 That thefe veins bring their blood in that direction 
 which leads to the Anus, is proved by ligatures, 
 v/hich, by impeding the blood, caufe a turgefcence 
 of the vein betwixt the ligature and lungs. 
 
 CXI. This left Anus, almofl; cubical, firmly con- 
 ftructed of various fefciculi of fibres rurning be- 
 tween twomembranes, has, onthe anteriorand right 
 fide, the feptum, common to it and the right Anus, 
 (licxxvi.) but, at its anterior and left edge, it ter- 
 minates in a conical appendix, notched and creAed 
 with proceffes, v.'hich, making two or three ferpen- 
 
Chap. IV. 
 
 HEART. 
 
 49 
 
 tine turnings, is cailed the left auricle, and with its 
 point direfted forwards refts upon the left ventricle^ 
 As iji the right auricle, fome of its fibres being bent 
 into the form of an arch, contract the auricle ; 
 others, coming from the origin of the appendix, 
 and inferted into its apex, deprefs it. This finus, 
 with the left auricle, are fomewhat lefs than the 
 right finus and auricle. 
 
 cxii. In this finus, the blood waits for the relax- 
 ation of the heart ; at which time the nifiis of the 
 blood acting againft the venous valves, and ftronger 
 than the adtion of the finus, remits. Then the left 
 finus ftretches itfelf forward acrofs the heart, and at 
 the fame time is contradfed tranfverfeiy, and the ap- 
 pendix becomes evidently fliorter and narrower. 
 Thus the left porch impels the blood into the left 
 ventricle of the heart, in the fame manner as the 
 right auricle impelled its blood into the right ven- 
 tricle (xcv.) For, as in that, there is a valvular 
 oval membranous ring, which has fimilar produc- 
 tions, called mitral valves, and which are ufually 
 reckoned two in number. Thefe are longer and 
 ftronger than thofe of the right fide. They have, 
 in like manner, ftefliy mufcles, one and one only to 
 each, but much ftronger. And, more frequently 
 than in the valves of the right fide, the valves, be- 
 ing fubjedted to the powerful action of the heart, 
 abound every where at the beginning of the ten- 
 dinous chords with cartilamnous tumours. 
 
 cxiii. Therefore there comes into the left ven- 
 tricle the blood, which the venae cavas had fent in- 
 to the right auricle (lxxxix.) this auricle had 
 poured into the correfponding ventricle (xcv.) the 
 ventricle had propelled into the pulmonary artery 
 (cv.) and from it, being received into the pulmo- 
 nary veins, \vas conveyed into the left finus (cx.) 
 and driven by it into the left ventricle (cxii.) This 
 conftitutes the lefs circulation, aiid was known to 
 many of the ancients (lxii.) It is proved, by the 
 E increafed 
 
HEART. 
 
 Chap. IV« 
 
 increafed bulk of the left pulmonary veins, and of 
 the veffels of the right cavities of the heart, on the 
 entrance into the left ventricle being obftruclcd. 
 
 cxiv. The left, or pofterior, or upper ventricle, 
 the firft formed, and in many animals the only one, 
 occupies that part of the half conical heart, which 
 v.^e called obtufe (xci.) It is narrovcer than the 
 right ventricle, a little longer and rounder, and its 
 cavity, on the whole, hnaller. For, the capacity of 
 this ventricle is about two ounces, while that of the 
 right amounts even to three. Its texture internal- 
 ly is in like manner reticular, but more minute ; 
 and alfo at the mouth of the artery fmooth. Its 
 force is greater, as the mufcular flelh, with which it 
 is furrounded, is much, almoft three times, ftronger. 
 The feptum of the heart belongs moftly to the left, 
 but fome part of it alfo to the right ventricle : the 
 whole of it is equally reticulated ; but folid, and 
 does notfuffer any injected liquid to pals from one 
 ventricle to the other. 
 
 cxv. The left ventricle, from the fame irritable 
 nature, already fpoken of, (cm.) being ftimulated 
 by the blood thrown into it, contracts, and with 
 great energy forces the blood contained in it to- 
 v/ards the axis and balls, while the cone of the heart 
 is retracted nearer to the bafe. And lince there is 
 the fame apparatus of valves, the blood diltends the 
 venous ring, and removes the right divilion of the 
 valve from the mouth of the aorta which it Ihut 
 up, opens to itfelf that mouth, preffes thefemilunar 
 valves, there placed, againlt the fides of the aorta, 
 and rullies into that artery with a violent impetus. 
 This is proved by ocular demonllration in living 
 animals, and by the enlargement of the left ventri- 
 cle on obftrufting the palfagc into the aorta. 
 
 cxvi. Tlie valves of the aorta are not verj^ dif- 
 ferent from thofe in the pulm.onary artery. Only as 
 the aperture is here greater, fo the valves them- 
 felvcs are larger and ftronger, and are fcldomer 
 
 without 
 
Chap. IV. 
 
 HEART. 
 
 5 * 
 
 without thofe callous globule^. The fibres too of 
 the valves, both tranfverfe and afcending, are fome- 
 what more confpicuous. 
 
 cxvm After the contraftion of the heart, fol- 
 lows its relaxation or diaftole, in which it becomes 
 empty , lax, and foft, recovers its former length, the 
 ventricles dilate from the feptum, and the b'afis re- 
 cedes from the apex. But as the blood dillending 
 the auricles, lies immediately at the orifices of the 
 ventricles, it rufhes through the valvular apertures, 
 and feparatcs the oppofite fides of the heart, which 
 is thus rendered both larger and longer. After the 
 auricles have emptied themfelves of the blood they 
 contained, they become in like manner relaxed, and 
 their oppofite fides feparate from each other. Thefe 
 ventricles are then filled with the blood, coliecled 
 in the venae cavse and pulmonary veins, by the con- 
 traction of the veins ; and, like the ventricles, are 
 increafed in every dimenfion, and even the pro- 
 ceffes of the crefied margin are diftended and ex- 
 panded. That there are in the heart dilating fibres, 
 is contradicted by the connection of its fibres, which, 
 being bound together by intermediate branches, can- 
 not be feparateiy moved, and by the difleCtions of 
 living animals which Ihow that the whole heart is 
 contracted at the fame time. 
 
 Gxviii. But it mull be obferved, that thefe mo- 
 tions of the right and left auricles, and of the right 
 and left ventricles, are not performed in that fuc- 
 celfion in which, for the fake of method, we have 
 defcribed them ; for both the auricles are contract- 
 ed, while the ventricles are relaxed, and the con- 
 traction of the auricles precedes the contraction of 
 the ventricles ; as we are convinced, from manifeft 
 experiments on dying and on cold blooded animals. 
 But both auricles are filled in the firit inflant, and 
 both of them are emptied in the fecond inllant ; 
 and both the ventricles are contracted in the third 
 inftant, which however correfponds to the firit ; 
 
 £ z and 
 
HEART. 
 
 Chap. IV. 
 
 52 
 
 and bofth ventricles, being evacuated, are relaxed in 
 the fourth inftant, which correfponds to the fecond. 
 Thofe who have taught otherwife, have not taken 
 fufScient affiftance from experiments on living ani- 
 mals. That the auricle, near death, makes frequent 
 palpitations, before the ventricle of the heart per- 
 forms one contraftion, and that the motion of the 
 right continues after the left has ceafed, is certainly 
 true. The auricle, with its Gnus, forms one cavity, 
 and both are filled at one time, and both emptied 
 in the fame inftant, 
 
 cxix. But it may be alked, why the heart, with 
 inceflant motion during fo many years as there are 
 in a lifetime, during fo many days as there are 
 in a year, and when, in each hour, in a healthy per- 
 fon, it contradfs not much lefs than 5000 times, nev- 
 er refts, but contraction perpetually fucceeds re- 
 pletion, and repletion contraction, in conftant fuc- 
 ceffion ; nor is the heart fatigued or pained by fo ex- 
 ceflive an action, that no other mufcle could endure 
 it even for a few hours ? To this queftion, different 
 profeffors have given different anfwers, founded up- 
 on a compreffure of the nerves betwfixt the large 
 arteries ; upon an alternate repletion of the coro- 
 nary arteries and heart, &c. 
 
 cxx. But to me the fimplicity of nature feems 
 very confpicuous. When the auricle is relaxed, it 
 is filled by the mufcular force of the contiguous 
 veins, and fo the heimt in like manner contracts it- 
 felf, when it is irritated by the blood conveyed 
 through the auricle. Therefore, the heart, when it 
 has received the blood, in confequence of that irri- 
 tability and ftimulus by which its fibres are excit- 
 ed to adtion, contradts, empties itfelf of the blood, 
 and, being freed from the ftimulus, refts and be- 
 comes relaxed. But being now relaxed, it is again 
 filled by the contradtion of the auricle, which the 
 fame ftimulus of the venous blood excites, fince the 
 jneeffant adlion of tlie heart and 'arteries continual- 
 
 Iv 
 
 * 
 
HEART. 
 
 Chap. IV. 
 
 53 
 
 ly fupply blood to the auricle. That this is the 
 fact, is proved from obfervation ; which readily dif- 
 covers the fucceffion of repletion and contraction in 
 the vein, auricle, ventricle, and artery, in an exhauft- 
 ed animal ; but more evidently, in thofe animals 
 which have but one ventricle ; as the tortoife, frog, 
 fnake, fiflies ; and in the chick in ovo, which, in- 
 ftead of a heart, has only a crooked canal. The 
 fame is alfo confirmed by the quiefcence of the 
 heart, upon tying the veins ; and by its motion, on 
 removing the ligatures, if this observation be cor- 
 rect, but more certainly on the injeCtion of air or 
 fluids ; and laitly, by the perpetual contraction of 
 the heart of a frog, upon a veficle of air blown in- 
 to it ; which, it will force into the auricle, and re- 
 ceive, alternately, for many hours. The left ven- 
 tricle firlt ceafes its motion ; then the auricle of 
 that fide 5 then the right ventricle ; after that, the 
 right auricle ; and, lafl: of all, the pulmonary veins, 
 and venae cavae. The motion afcribed to the venae 
 cavae, proceeds from the auricle, repelling into both 
 thefe veins the bipod, which the heart, when dead, 
 does not receive. 
 
 cxxi, Nor do I believe any thing more required^ 
 than a continual ftimulus applied to a part irri- 
 table in the higheft degree. For, even in the arti- 
 cle of death, the very coldnefs of the limbs, which 
 the warmth of life has left, conftriCls the veins, and 
 drives the blood to the heart ; at which time the 
 lungs, being impermeable for want of refpiration, 
 tranfmit no blood to the cavities of the left fide. 
 On the other hand, the heart, thoroughly emptied, 
 remains at reft. It is, therefore, poflible to tranf- 
 fer the prerogative of dying laft from the venae 
 cavae and right auricle, to the left auricle, and ven- 
 tricle ; if you contrive that the right cavities be 
 emptied, and that the left be irritated by blood. 
 But' thofe, who attribute the quiefcence of the heart 
 to the coxnpreftion of its nerves, are refuted by the 
 
 appearances 
 
HEART. 
 
 Chap. IV. 
 
 54 
 
 appearances in thofe auricles, whofe nerves are not 
 comprelied ; as, for example, in filhes, and in the 
 chick in ovo, where there is no fuch comprelhon. 
 If you deduce the quiefcencc of heart from the co- 
 ronary arteries, this is contrary to experience; fince 
 tliey are not covered by the valves of the aorta, 
 and fince, from the coronaries, when divided, the 
 blood fprir.gs to the greateft height during the fyf- 
 tole of the heart. 
 
 cxxii. Nor, with the powers of the heart, do I 
 conicin the ofcillation of the minute veflels, which 
 is refuted by experiments ; nor the influence of ex- 
 ternal heat ; flnce animals are found to live and 
 thrive in the coldeft regions of thenorth : and though 
 the contracfile force of the artery, and the w’eight 
 of the parts and of the atmcfphcre, aflift the mo- 
 tion of the blood clurinQ- the diaftole of the heart, 
 the fame powers refill it during the fyftole ; fo that 
 the blood is not moved more eaffiy through the 
 contractile arteries, than even through the rigid 
 arteries of the fmaller animals. 
 
 cxxm. But the celerity and force with w hich 
 the heart propels the blood, are varioufly comput- 
 ed. Tlie more modern writers have calculated 
 upon the following pofitions. In determining the 
 celerity, they luppole two ounces of blood to iiTue 
 out of the heart w ith fuch a celerity, tliat tliat part 
 of the pulfe, called its fyllolc, is finiflred within the 
 third part of a wiiole pulfation, or within ? of a 
 minute : and the area of the month of the aorta, 
 they have eflimated at 0.4187 parts of an inch : fo, 
 by dividing 3.318 inches, the fpace filled by tv/o 
 ounces of blood, by the area of the aorta at its mouth, 
 and by multiplying by 225, or number of puifa- 
 tions, this quotient inches, or length of cy- 
 
 linder of the aorta which is filed bv tw o ounces 
 of blood, they And 149 feet and tw'o-tenths of an 
 inch for the fpace througli whicli the blood would 
 run in a minute, if it proceeded and paiTcd through 
 
Chap. IV. 
 
 HEART. 
 
 55 
 
 the cylindrical aorta with the fame velocity with 
 which it was expelled from the heart. But -the 
 weight of blood preffing upon the heart, they have 
 computed by the jet with which the blood fprings 
 from the aorta in a living animal, being feven feet 
 five-tenths ; and from the area of the ventricle, 1 5 
 inches ; which produce 1350 cubical inches of 
 blood, or 51*- pounds five ounces, w'hich prefs a- 
 gainft the ventricle of the contradling heart. The 
 heart, therefore, propels a weight of 51 pounds, 
 with a velocity by which it may run through 149 
 feet in a minute ; and this four thoufand eight 
 hundred times in an hour. 
 
 cxxiv. Although into thefe calculations many 
 things enter, which are neither eftabliilied, nor 
 perhaps ever to be cleared up ; although the mouth 
 of the diftended aorta is wider in a living animal ; 
 thousfh the menfuration of the area of the ventricle 
 IS uncertain, and the jet of blood perhaps too low, 
 if we confider, that, in the living animal, the blood 
 iffues with violence from very minute arteries ; laft- 
 ly, although we cannot determine what part of an 
 entire pulfation the fyftole of the heart takes up, 
 variations in which will, however, greatly alter the 
 whole computation ; yet, in the mean time, it will 
 plainly appear, that the machine we call the heart 
 is very powerful. This opinion is fupported by 
 experiment, which fliews, that by anatomical injec- 
 tion, it is very difficult to fill aU the red blood- 
 velfels, and impoffible to fill all the fmaller ones ; 
 while the heart not only gradually diftends wntli 
 blood all the large, fmall and minute veffels, but 
 befides, propels the blood with great rapidity. 
 Even into the moft minute arteries, the blood is 
 driven by the heart with fuch force, as to make its 
 alternate m.otions perceptible. Likewife in the 
 veins, and laftly, in the fmaller veffels, both in cold 
 blooded animals, and in the chick in ovo, there is 
 no other force befides that of the heart, by which 
 
HEART. 
 
 5 ^ 
 
 Chap. IV, 
 
 the blood is driven through thefe veffels. And, 
 from very fmall arteries, I have feen the bicod pro- 
 jected feveral feet, defcribing a parabola, whofe 
 height was four, and its extent feven feet • and 
 forne abert, they have feen the blood thrown out 
 of the aorta to the height of twelve feet. 
 
 exxv. Moreover, in eftimating the force of the 
 heart in living animals, we muft confider the pow- 
 erful obliacles it overcomes : v/e muft compute the 
 enormous weight of the whole blood ; for the en- 
 tire mats, weighing fifty pounds and upavards. when 
 at reft, is eafiiy fet in motion by the heart alone, as 
 in the inftances of fainting and refuicitaticn from 
 drovening. We muft, moreover, confider the great 
 decreafe of velocity, arifing from the greater capa- 
 city of the branches, which, even in the inteftines, 
 it feems we might conipute at the 24th or 30th 
 power of the root And yet fluids are carried 
 with velocity through the fmrlleft veflels, of w’hich 
 we haa^e examples in the Sancloiian perfpiration, 
 w'hich in fubterraneous caverns I have feen rifing 
 with great velocity, in the manner of fmoke ; and 
 in the motion of the blood in fifties, Befidcs, as 
 friction in every machine confumes the greateft 
 part of its powers, it will be readily conceived, 
 tliat, in the human body, in which a liquid, much 
 more vifeid than water, flows in canals fo narrowy 
 that they admut but one globule at a time, and not 
 even that, without a change of figure, an excef- 
 five retardation muft arife from friftion, and that 
 the power muft be immenfe, w^hich moves fuch a 
 mafs, in fpite of fuch obftacles and diminutions of 
 its force. But even aneurifms and arteries are burft 
 by the force of the heart ; and great w’eights along 
 with tlie human body are elevated by the force of 
 its f}dtole. 
 
 exxvi. The blood, when driven into the aorta, 
 finds the mouths of the two coronary arteries near 
 to the valves of the artery, but higher up and not 
 
 covered 
 
HEART. 
 
 Chap. IV. 
 
 57 
 
 covered by them. Into thefe, firft of all, it ruflies, 
 and thus the heart fupplies itfelf with blood. Thefe 
 arteries are almoll conftantly two, and arife from 
 the heart at an obtufe angle with the trunk ; the 
 right goes oiT between the aorta and pulmonary 
 artery, and the upper and left one between the left 
 auricle and the aorta. All the external branches 
 are furrounded with m.uch fat. Their cavity is not 
 intercepted with valves any more than other arte- 
 ries. Thefe arteries communicate, by fmaU branches, 
 every where about the feptum and tip of the heart ; 
 but they do not make a complete ring round the 
 heart. They terminate in two ways. 
 
 cxxvii. Their firft termination is in the veins, of 
 which the branches accompany the arteries, but the 
 trunks neceffarily feparate. The left artery is there- 
 fore accompanied by the great coronary vein, which 
 is inferred by a large opening, fecured with a valve, 
 or feveral little m.embranes, into the auricle to the 
 left of the Euftachian valve. It is diftributed on 
 the bafe of the left auricle, and accompanies the 
 fuperficial branches of the left artery. 
 
 cxxviii. The fecond vein (which you may make 
 a part of the former, fince they have both one 
 common infertion,) defcencls along upon the fep- 
 tum of the heart on its flat furface ; and may be 
 properly called the median coronary. The third 
 tranfverfely feeks the root of the right auricle, and 
 terminates within, or at leaft very near, the large 
 opening of the coronary vein, (cxxvii.) or in an 
 anterior vein. It fupplies that part of the right 
 ventricle which lies in the flat fide of the heart ; 
 and often receives the vena innominata, immediate- 
 ly to be defer ibed, 
 
 cxxix. There are ftill fome other anterior veins 
 of the heart ; but one, more confiderabie, which 
 runs along that part of the right ventricle next to 
 the margin, and winding in an oblique courfe, fome- 
 tiraes between the membranes, is inferted into the 
 
 mofl: 
 
^8 
 
 HEART. 
 
 Chap. IT. 
 
 mofl anterior part of the right auricle, and fomc- 
 times into the trunk of the upper vena cava. Ikis 
 anterior vein fends off along the root of the right 
 linus, another which runs concealed through the 
 very fubftance of the heart, and beincir asrain infer t- 
 ed. into the great coronary vein, completes the ve- 
 nous- cii’cle round the heart, like the arterial circle 
 wdiich fome have deferibed, but wdiich to me is un- 
 known. 
 
 ex XX. But there are a great many mcji'c veins, 
 uncertain in their number and polition, whidi, hid 
 ainong’ft the origins of the large veffels, belong to 
 the deep fcated and difhcultly acceffible parts of 
 the bafis of the heart. Thefe open by numerous 
 fmall mouths into the right finus and auricle , and, 
 though more rarely, into the left finus. Thus I 
 have feen a particular vein, -which, from a latent 
 finus in the flefli of the right auricle, h-as afeended 
 towards- the aorta and pulmonary artery, and in- 
 ferted itfslf on the other fide into the greater coro- 
 nary vein. I have feen anothev concealed bctv.hxt 
 the mouth of the coronary vein and the -aorta, in- 
 ferted into the right finus ; and another along the 
 remains of the foramen ovale, and feptum of the 
 two finufes, inferting itfclf into the right finus ; 
 and others again belonging to the venous valves ; 
 fcefides which, there are kill others too numerous 
 to deferibe. I have alfo feen a vein arifins: from 
 the left finus, inferted into the vena cava. 
 
 cxxxr. There are other fmaller veins, whofe 
 little trunks are fliort, and cannot eafily be traced 
 by dilTeftion. Thefe open by oblique fliort mouths, 
 through all thofc innumerable pits of the right and 
 left ventricles, and into the feptum of the heart, 
 and into both auricles. Tlicfe are demonflrated by 
 injeciir.g -water, air, or mercury, efpeci'aily into the 
 coronary arteries, after ha-^fing tied all the corre- 
 fponding veins ; or even into the veins themfeh es, 
 after having fecured the infertion of the Lirgeft 
 
 truiflis. 
 
Chap. IV. 
 
 HEART. 
 
 59 
 
 trunks. For, drops of coloured water, bubbles of 
 air, fpherules of mercury, exude through the whole 
 extent of both ventricles ; and this, without any 
 violence that can be fuppofed to have burft the vef- 
 fels. The paffage from the arteries into the ca^dties 
 of the left nde, is, hov^^ever, more difficult. 
 
 cxxxii. There are fome who fuppofe that the co.. 
 ronary arteries are filled vAth blood, not by the 
 contraction of the heart, but of the aorta. Their 
 opinion is founded on the retrograde angle of their 
 origin, on their mouths being covered by the valves, 
 and on the palenefs of the heart when contracted. 
 But the two lafi; of thcfe are contrary to fact ; and 
 the firfi; perhaps fomewhat retards or ieffens, but 
 certainly does not obftruti; the entrance of the 
 blood ; for the injections of air or mercury into the 
 feminal and biliary veffeis every v/here, demonftrate, 
 that in a diftended yeffel, even more retrograde 
 angles do not prevent fluids from entering the 
 branches. Moreover, in the coronary artery, the 
 pulfe is fynchronous with the other arteries in 
 the animal body, and the blood, during the con- 
 traction of the heart, fp rings to a greater height 
 (cxxi.) 
 
 cxxxiii. Concerning the reflux, there is lefs 
 room for doubt : into the ventricles and auricles 
 of the heart, right and left, but more into the lat- 
 ter, all the blood of the coronary veffeis is difcharg- 
 ed, both by the large orifices, (cxxvii. cxxviii.- 
 cxxix.) and by the ImaU ones, (cxxx.) and by 
 thofe minute ones, (cxxxi.) which, when the large 
 veins are tied, readily tranfmit injections. This 
 circulation feems to be completed in a very fliort 
 fpace of time, on account of the very great veloci- 
 ty the blood receives from the immediate action of 
 the heart itfelf. I do not, however, think that 
 it is effected during one pulfation ; for the blood- 
 \^effels of the heart neither lofe their colour, nor 
 are eompletely evacuated, There is a very free 
 
BLOOD, 
 
 60- 
 
 Chap. V. 
 
 paflage from the arteries of the heart into the fat. 
 What are the ufes of the minute veins r (cxxxi.) 
 They return the blood of thofe deeply feated arte- 
 ries, which have no larger correfponding veins. 
 
 . cxxxiv. The humours of the heart, which are 
 thinner than blood, return by the valvular lymphat- 
 ic veins, which accom.pany the coronary vefl'els, and 
 afcend towards the thoracic duct and fubclavian 
 vein ; they are very rarely to be feen, but 1 have 
 ©bferved them in brute animals. 
 
 CHAP. V. 
 
 NATURE OF THE BLOOD AND HUMOURS OF THE 
 HUMAN BODY.. 
 
 exxxv. ^ I ' HAT liquid which is contained in the 
 I pulfating arteries and their corre- 
 fponding veins, is called, by one comxm.on name, 
 the blood. When fuperficially viewed, it appears 
 homogeneous, coagulable throughout, and redder 
 in proportion as the animal is ftronger and fuller 
 fed j in a weak and famiflied one it inclines to a 
 yellow. Any admixture of white generally pro- 
 ceeds from chyle. But experim.ents of various 
 kinds have demonftrated the compound nature of 
 this liquid. 
 
 cxxxvi. That fire is contained in the blood is 
 proved from its heat, which, in man and fimilar 
 animals, is from 93 to 100 degrees, which is higher 
 than the mean degree of atmofpherical heat, but 
 lefs than the greateft. Befides, from blood, when 
 di’awn, fomething volatile or halituous, with a pecu- 
 liar odour, intermediate between that of the fweat 
 and urme, efcapes. When collected in proper vef- 
 fels, it appears aqueous, v.ith a flight tincture of an 
 alkaline nature. 
 
 cxxxvii. 
 
BLOOD. 
 
 Chap. V. 
 
 6i 
 
 cxxxvii. After the cfcape of this vapour, the 
 blood of a healthy perfon, fpontaneoufly congeals 
 into a tremulous fcifiile mafs ; but with a degree 
 of heat lefs than that of boiling water, (and indeed 
 at 150°) it coagulates more completely even when 
 perfedly healthy, though more efpedally when tak- 
 en from a febrile perfon. It fometimes coagulates 
 in the veins of a living perfon, and is found clot- 
 ted in wounds of arteries. Even in a living per- 
 fon, and in one dying from the violence of fever, 
 the blood has been coagulated into a tremulous 
 jelly throughout all the veins. The principal part 
 of this coagulum is the cruor, which has the red 
 colour peculiar to itfelf, and imparts it to the 
 other parts of the blood. This, condenlible by- 
 reft, or a moderate degree of cold, and coagulable 
 into a liver-like mafs by a heat of 150°, alcohol* 
 or the mineral acids, is, ho-vvever, foft, unlefs hard- 
 ened by the attrition of life, or equivalent agita- 
 tion. It is ponderous, and heavier than water by 
 nearly an eleventh part ; and, when freed from 
 its water, it is wholly inflammable. In the mafs 
 of blood, one half or upwards is cruor ; and, in. 
 ftrong I'obuft people, the ferum makes only a third 
 part ; in fevers, it is diminiflied to a fourth or 
 fifth part j and in difeafes from debility, it is in- 
 creafed. 
 
 cxxxviii. From this coagulum there feparates* 
 as it were fweating out of its pores, but afterwards 
 colledling in fufhcient quantity to allow the coagu- 
 lum to fink in it, another part of the blood which 
 is white or fomewhat yellowiih, and alfo feemingly 
 homogeneous, though it is not fo. This part o£ 
 the blood is, in general, one thirty-eighth part heav- 
 ier than water, and almoft a twelfth part lighter than 
 the red globular mafs ; coagulable by a heat of 150® 
 or the addition of mineral acids or alcohol, or by 
 agitation ; it produces a firm.er coagulum than the 
 red cruor (cxxxvn.) and concretes into an in- 
 
 foluble 
 
62 
 
 BLOOD. 
 
 Chap. V. 
 
 foluble gluten, acquires a membranous appearance, 
 and finally a horny hardnefs, with a friability like 
 that of gum. Of it are formed the pleuritic crufts, 
 polypufes, and artificial membranes. In the ferum, 
 befides this coagulable albumen, there is contained 
 fimple water, which conlUtutes the principal part 
 of the whole ; and fome mucous matter, capable 
 of being drawn into finer threads than the red cru- 
 or ; and not coagulable by fire or by acids as the 
 albumen. 
 
 cxxxix. Putrefaction alone, and the influence 
 of a temperature of 96" diffolves into a fetid liquor 
 the whole blood, but efpecially the ferum ; fir ft 
 the ferum, and then the cruor more flowly ; till, 
 at length, tire whole, both cruor and lymph, is 
 changed into a volatile and feted exhalation ; leav- 
 ing very few feces behind. The blood, when fome- 
 what diffolved by putrefaction, both before it be- 
 comes fetid, and while fetid, evinces an alkaline 
 nature, and efi'ervefees with acids. Thence, in 
 confequence of putrefaction, it furiliflies lefs alka- 
 line fait. When putrid, it cannot by any art be 
 infpift’ated ; it is alfo very difficult to refolve it af- 
 ter it has been coagulated by fpirit of wne. By 
 too fevere exercife, heat of the atmofphere, and ma- 
 lignant diforders, the cohefion of the blood is dif- 
 folved, and it aiTumes an alkaline nature almoft as 
 if from putrefaction. 
 
 GXL. Befides thefe conftituents of the blood, 
 which are demonftrated without fabjecTing it to 
 any violence, it alfo contains a quantity of fea-falt, 
 wliich is difcernible by llie tafte, and fornctimes by 
 the microfeope. Both nutrition and chemical an- 
 alyfis deinonftrate, that the blood alfo contains 
 earth, which is contained in the meft nuid parts, 
 and efpecially united with the oil. By fome very 
 late experiments, it appears, that a conliderable 
 quantity of ferrugineous calx, eallly reducible into 
 a true metal by the addition of any infiainmalde 
 
 body. 
 
Chap. V. 
 
 BLOOD. 
 
 63 
 
 body, is contained in calcined cruor. Laftly, there 
 is mixed with the blood condenfed air, and that 
 in a very confiderable quantity ; the exigence of 
 which in the blood and ferum is proved by putre- 
 faction, or by removing the prelTure of the ambi- 
 ent air. The blood globules are not, on this ac- 
 count, air bubbles, for they are fpecihcaily heavier 
 than the ferum. 
 
 cxLi. By the admixture of neutral fklts,tlie col- 
 our of the blood becomes deeper and brighter, as 
 by them it is neither diffolved nor thickened. It 
 is fcarcely altered by weak acids. By ftrong ones 
 it is coagulated. Tixed alkaline falts have aknoft 
 the fame effects as the neutrals. The volatile alka- 
 lies rather turn it larown, and coagulate it. Alco- 
 hol and diltilied oils coagulate it like krong acids. 
 It does not eflervefce with any fait. 
 
 cxLii. Chemiftry has opened various ways for 
 iriveftio:atLn<y the nature of the blood. From blood 
 recently drawn and perfeftly frelh, by expofure 
 to a gentle degree of heat, there is diltilied a large 
 quantity of water, compoling five-fixths of the 
 whole or more, almoft inlipid, though impregnat- 
 ed with feme fetid oil, more krongly as the dif- 
 tillation proceeds. 
 
 The reliduum, expofed to a kronger kre, yields 
 various alkaline liquors ; of which the firk, acrid, 
 fetid, and of a reddiki colour, is ufualiy called the 
 ipirit of blood ; it conliks of volatile fait and oil, 
 dilfolved in water, and amounts to one-twentieth 
 part of the original mafs of blood. There is, more- 
 over, an acid in fat, and in kelh even when putrid, 
 and in blood. 
 
 Both before, and along with the oil, that next 
 afcends in the dikillation, a dry volatile fait arifes, 
 and adheres in branchy keeces to the neck of the 
 retort ; its quantity is fmali, about an eightieth part. 
 
 Another kuid, gradually thicker and heavier, at 
 firk yellow, then black, and iakly of a pitch)'- te- 
 nacity. 
 
BLOOD. 
 
 Chap. V.. 
 
 64 
 
 nacity, acrid and inflammable, is the oil of human 
 blood. - Its quantity is fmall, about the fiftieth part. 
 There now remains, in the bottom of the retort, 
 the fpongy and inflaminable cinder of the blood, 
 which, being kindled, deflagrates, and leaves aflies 
 behind. From thefe, by lixiviaiion, is obtained a 
 fait, confifting of fea-falt, mixed with fixed alkali, 
 and a fmall quantity of infipid earth. This fixed 
 fait is fcarcely the five hundredth part of the firft 
 mafs, and of this almoft one-fourth is alkaline : 
 when fubjedted to an intenfe degree of fire, it af- 
 fords a little acid, which we fappofe to arife partly 
 from the fea-falt, fimilar to that demonftrable in 
 the fpirit of blood; and partly from the vegetable 
 nature of our aliments, not yet completely ar.ima- 
 iyzed. Hence it is found in herbivorous animals, 
 as well as in man. But the earth, which is about 
 the hundred and fiftieth part, contains feme parti- 
 cles which are attracted by the loadflone. 
 
 cxLiii. This analyfis fliews that the blood con- 
 tains various fluids, feme more heavy and tenacious 
 than others, feme aqueous, others inflammable, and 
 that moft of them impart to the blood a putrid or 
 alkalefcent tendency. For, the blood, when heal- 
 thy, and not injured by putrefacHon, or too vio- 
 lent a degree of heat, is neither alkaline nor acid ; 
 but bland, and fomewhat fait, although, in fome 
 difeafes, it is very acrid and almoft putrid ; as, for 
 inftance, in feurvey, where it corrodes its contain- 
 ing vefiels ; and in dropfies, the waters of which 
 are nearly alkaline. In infecls, there is found an 
 alkalefcent calx which eftervefees with acids. 
 
 cxLiv. By viewing with the microicope frefli 
 blood in a fmall glafs tube, or while it is yet 
 movinu in the veins of a warm blooded livincf ani- 
 
 O O 
 
 mal, as a cliicken, or of a cold one, as a frog, we 
 perceive in it red globules ; which doubtlcfs, con- 
 ftitute the cruor mentioned in cxxxvii. Or are 
 
 they 
 
BLOOD. 
 
 Chap. V. 
 
 
 they rather lenticular particles of the fame kind 
 withlhofe obferved by Leeuwenhoeck in filhes, and 
 lately difcovered in our own fpecies ; it is difficult 
 to determine i nor, often as I have ufed the mi- 
 crofcope^ have I ever miffed thofe fliadows in the 
 globules which indicate thicknd^s and convexity. 
 
 cxLv; The colour of thefe globules is red; and 
 fo much the deeper, and more inclined to fcarlet, 
 the llronger the animal is ; and in the fame propor- 
 tion, their number increafes, when compared with 
 the yellow ferum. Their diameter is fmall, being 
 between ^boo and Tsbo of an inch. They are faid 
 to change their figure into an oblong egg like 
 lliape, v/hich I have never been able to obferve 
 with fufficient certainty. They are ajfo faid to 
 break down into other leffer globules of a yellow 
 colour, which I have neither obferved myfelf, nor 
 can eafily admit. 
 
 cxLVJ. Fibres are obtained in great quantity 
 from the blood, and more fparingly from the fe- 
 rum, by gradually waffling it, when poured on a 
 linen cloth, with much water ; or by beating with 
 rods, blood poured into water : they will amount 
 to one eighty-fifth part of the whole. Thefe are 
 formed of the gluten, and do not exift in the liv- 
 ing animal ; fince they neither are perceived by the 
 microfcope, which yet fo eafily renders vifible the 
 red globules, although fo much fmaller, nor is theii* 
 long thread like figure adapted for receiving mo- 
 tion. 
 
 cxLvii. From the preceding experiments com- 
 pared together, arifes that knowledge, which wc 
 at prefent have of the blood; namely, that the 
 cruor is compofed of globules. The inflammable 
 nature of thefe globules is proved by the inflam- 
 mation of dried cruor, and the preparation of py- 
 rophorus from human blood ; and, from thele, 
 moil probably, proceeds the greater part of the 
 F pitchy 
 
66 
 
 BLOOD. 
 
 Chap. V. 
 
 pitchy oil that is obtained frOm blood by the acUon 
 of lire. 
 
 cxLviii. The ferum of the blood, fubjecled to 
 the aclion of fire, yields almoft the fame principles 
 with the red blood, viz. fait, oil, and earth, but 
 more water and n6 iron. Similar principles, but 
 with a lefs proportion of oil and fait, are obtained 
 from tlie aqueous humours formed from the blood ; 
 as the faliva, and mucus. 
 
 cxLix. The quantity of blood, contained in the 
 wliole body, cannot be very certainly computed. 
 I he weight of the fluids, however, is much greater 
 than that of the lolids ; but many of them, as the 
 gluten in various parts, and the fat, do not circu- 
 late. But if we may be allowed to form a judgment, 
 from thofe profufe hemorrhages that have been fuf- 
 tained without deflroying the life of the patient ; 
 from experiments made on living animals by ex- 
 iracfino; all their blood ; and from the canacitv of 
 the arteries and veins ; there will be at leaf! fifty 
 pounds of fluids vdiich circulate, of which about 
 twenty-eight will be true blood : the arteries con- 
 tain about one-fifth, and the veins the other four 
 parts. 
 
 CL. Nor are the proportions of the elements, 
 which we have hitherto m.entioned, conftant ; for, 
 an active life, manhood, and fever, increafe the 
 cruor, rednefs, coagulability, cohefion of the parts, 
 firmncfs of the coagulated ferum, weight and alka- 
 line principles. The ferum, and the mucus if con- 
 tains, are increafed by the contrary caufes ; a lefs 
 mature age, inactive life, and a watery and vegeta- 
 ble diet ; by all which, the crahamentum of the 
 blood is lefiened, and its watery part increafed. 
 Old ac-e, affain, auerments the cruor, and diminiflies 
 the gelatinous part. 
 
 CLi. On tLefe principles, conjoined vdth a con- 
 fideration of the folid ftruclure, the divcrlity of 
 temperaments depends. For plethora arifes from 
 
Chap. V. 
 
 BLOOD. 
 
 67 
 
 an abundance of the red globules ; a phlegmatic 
 temperature, from a redundancy of the watery part 
 of the blood ; a choleric difpofition in the fluids 
 feems to proceed from a more acrid and alkalefcent 
 nature of the blood ; as in thofe who live on flefh^ 
 and in anthropophagi, who appear to be more fierce 
 than thofe who live on vegetable food. In the fol- 
 ids, greater irritability, and hardnefs, with mobili- 
 ty, are attributed to a choleric habit ; a lefs irrita- 
 bility, with a more moderate denfity, to a fanguine 
 habit ; and lefs denfity, and lefs irritabilty, to a 
 phlegmatic temperament. There is alfo a fluggifh 
 temperament, in which remarkable ftrength of body 
 is joined with little irritability. In the melancho- 
 lic, exceffive irritability feems united with debility. 
 But we mufl; be cautious not to clafs too fyftemat- 
 ically the temperaments, which in nature are not 
 four or eight, but infinite in their varieties. 
 
 CLii. The generation of heat feems to be the 
 principal ufe of the red cruor, as its quantity is in 
 proportion to the temperature of the blood. Being 
 confined, by the largenefs of the globules, within 
 the firfl: order of veflels, it hinders them from col- 
 lapfing ; and, in receiving the common impulfe from 
 the heart, on account of the greater denfity of its 
 parts, it acquires a greater impetus, and fets in 
 motion the inferior orders of hum.ours. Nor is it 
 improbable, that the heart is more duly excited by 
 the ponderous cruor. The globular figure of its 
 parts, imparts to it fluidity conneded with denfity ; 
 that quality, and perhaps the power of generating 
 heat, are increafed by the quantity of iron and of 
 oil. Hence, when the red part of the blood.is too 
 much diminifhed by bleedings, there follows a 
 flagnation in the fmaller veflels ; fatnefs and dropfy. 
 From the fame reafoning, a due proportion Of cru- 
 or feems neceflary for the generation of new blood. 
 For, in confequence of hemorrhages, the blood de- 
 generates 
 
blood: 
 
 ^ 8 ^ 
 
 Chap. V , 
 
 generates from its red and denfe nature, into a pale 
 and ferous ftate. 
 
 CLiii. The coa-gulable ferum is more efpecially 
 deligned for the nutrition of the parts, as will be 
 hereafter fliewn, chap. xxx. The thinner fluids 
 ferve various purpofes ; as, the diflblution of the 
 aliments, the moiflening the external furface, and 
 furfaces of the internal cavities of the human body, 
 to preferve the flexibility of the folids, and conduce 
 to the motion of the nerves, the fight, &c. The 
 faline particles feem proper for diflblving the -ali- 
 ment, and llimulating the veffels. The properties 
 of the aerial part are not yet fufficiently known. 
 The heat produces its fluidity, and is not eafily 
 raifed to fuch a degi'ee as to coagulate the fluids of 
 the human body. 
 
 cniv. Therefore, health can neither fubfifi; with- 
 out the thick blood, and a diminution of its quan- 
 tity caufes a ftagnation in all the fmaller veiTels, 
 and univerfal palenefs, coldnefs and debilty : nor 
 can the functions of human life or health fublifl: 
 without the fluids of the inferior orders, fince the 
 cruor, deprived of its watery part, congeals and 
 obftructs the paflages of the veffels, and produces 
 too great a heat. 
 
 CLv. Is there any difference betwixt the arte- 
 rial and venous blood ? It feems probable, as the 
 former has lately fuffered the action of the lungs. 
 But, in experiments, I fcarcely find any difference 
 obfcrvable, either in colour, denfity, or any other 
 property 5 although, in other fituations, I have feen 
 it very apparently, for the bright red colour of the 
 art crial blood feems to diffinguHh it from the dulky 
 dark coloured blood in the veins ; but this, in the 
 plain example of the chick in ovo, arifes only from 
 the feries of stlobules beinsr deeoer in the thicker 
 vein. Nor is there any eftabliflied difference in the 
 blood of different arteries. 
 
 CLVIr 
 
Chap. VI. 
 
 ARTERIES. 
 
 J&9 
 
 cLvi. From the fame blood, driven Into, the 
 aorta, are generated all the fluids of the human 
 body. Thefe are red.ucible to certain claffes. The 
 means by which they are feparated, ought to be 
 accounted for by the fabric of the glands. But 
 muft firft confider what the blood fuffers from its 
 containing veflels. 
 
 CHAP. VT. 
 
 OF THE COMMON FUNCTIONS OF ARTERIES. 
 
 CLVii. ^ g '•HE blood, driven from the left ventri- 
 1 cle of the heart into the aorta, which, 
 at its origin from the heart, bends firfl; a little to- 
 wards the right, and then to the left, and back- 
 wards, in a very acute arch, ftrikes, in a mafs, firft 
 againft the right fide of the aorta, and is then re- 
 flecled to the left- fide ; whence, with a rotatory 
 motion, as much as their fulnefs permits, it pro- 
 ceeds through the arteries, alternately ftri-king and 
 rebounding from their fides. The fize of the aorta 
 is a little increafed, where it arifes from the heart, 
 CLviii. The arteries are, in a living perfon, always 
 full of blood 5 fince the blood fpringing from an 
 artery, is not interrupted by alternate flops during 
 the relaxation of the heart, but flows on in a con- 
 tinued ftream, and the microfcope fliews the arte- 
 ries, in living animals, to be full, both in their fyf- 
 tole and diaftole ; nor can the circular fibres of the 
 arteries contracl themfelves completely, or entirely 
 evacuate thefe tubes. Therefore, when into the 
 full arteries there comes a new wave of blood, al- 
 though it fcarcely exceeds two ounces, and bears 
 a fmall proportion to the arterial fyftem tlirougli- 
 out the body ; it, however, overtakes the preceding 
 wave, which being farther from the heart, moves 
 flower j it confequently drives tlic iame forwards, 
 
 IpncrflirnfSi 
 
 O 
 
ARTERIES. 
 
 CiiAP. YL 
 
 70 
 
 lengthens the cylindrical artery, augments its di- 
 ameter, preffes the membranes clofer to one another, 
 urges the convex parts of its flexures outwards, and 
 produces more ferpentine turns, as injections de- 
 monftrate. This dilatation of the artery, and change 
 of its caliber, from a lefs to a greater circle, is call- 
 ed the pulfe ; the diaftole of which, is an expan- 
 flon of the artery beyond its natural diameter. It 
 is peculiar to life, and refults from the heart only, 
 and is not naturA to arteries left to themfelves. 
 Hence, yrhen the motion of the heart is intercep- 
 ted, whether its im.pulfe be obftimcled by aneurifin, 
 or ligature, there is no pulfation ; and hence, the 
 flidden ceflation of the pulfe, in a living animal, 
 on the heart being perforated. The artery is 
 proportionally more dilated, the more flowly the 
 preceding wave of blood efcapes, and the more 
 the velocitv of the new wave exceeds that of the 
 former. 
 
 CL IX. The contraction of the artery fucceeds its 
 dilatation. For the heart, having emptied itfelf, 
 and removed the fcimulus of the blood, becomes 
 quiefeent. Eut the artery, at that inftant, by the 
 innate elafticity refiding in its circular fibres, 
 being irritated by the fame ftimulus of blood 
 thrown into it, contracts ilfelf, and expels as much 
 of the blood as it had received above its mean ca- 
 pacity ; the whole of this quantity pafles either into 
 the fmallcr vcflcls, or into the veins ; for the femi- 
 lunar vah es of the aorta prevent its reflux into the 
 heart. So foon as the arteiy has freed itfelf from 
 this wave, being no longer ftiinulated, it remits its 
 contracl'ile aftion, and immediately yields to a new 
 wave, propelled by the heart ; and a new diaftole 
 enfues. 
 
 CLX. That the arteries contract, and by that 
 means propel the blood, is proved by their contrac- 
 tile nature ; by the evident remifnon of the dilata- 
 tion caufed by the heart ; by the fpontaneous eva- 
 cuation 
 
Chap. VI. ARTERIES. 71 
 
 cuation of an artery through its lateral hranches, 
 included between two ligatures ; by the return of 
 the blood to the heart, after its artery is tied, which 
 blood, therefore, is not propelled by the heart ; by 
 the jet of blood from arteries being greater during 
 the relaxation of the heart, as obferved by emi- 
 nent anatomifts; by the vigorous projection of blood 
 from the aorta when tied, below the ligature ; by 
 the evacuation of the arteries during the perfeft 
 quiefcence of the heart ; by the veins being fuller 
 than the arteries after death ; by the coniiderabie 
 jet of blood, to the extent of two feet, from the 
 aorta in an animal after death ; by the fmail cali- 
 ber of the ill filled arteries in a famiflied animal ; 
 by the clofing of their orifices in wounds ; and by 
 the fphacelation of limbs, whofe arteries are ofiifi- 
 ed, and the veins being in that cafe diftended with 
 blood. 
 
 CLxi. The mean velocity of the blood may be 
 computed, by diminifliing its velocity during the 
 fyftole, as much as we increafe what remains of it 
 during the diaftole, to be nearly fuch, as to move at 
 the rate of two feet in a fecond. The conftaiit 
 plenitude of the arteries, is the reafon why we can- 
 not perceive any fucceflion in the pulfations of dif- 
 ferent arteries, and that in the Iiuman body they 
 all feem to beat at one inftant, and at the fame time 
 that the heart ftrikes againft the breaft. However, 
 there certainly is a fucceflion, and the contractions 
 of the aorta appear to follow in the fame order, as 
 its repletion with the blood, expelled by the heart, 
 fo that the part of the artery next to the heart con- 
 trafls firft, and that thus the contraHions proceed 
 gradually to the ultimate arteries. This is appar- 
 ent in the example of the inteftines, and may be 
 feen in infecfs, whofe long and knotty heart mani- 
 feftly contraHs fucceflively from the beginning to 
 the end. But the mind of the obferver cannot dif- 
 
ARTERIES. 
 
 
 Chap.. VI. 
 
 tingullh the minute portion of time, which amountsi 
 only to a few thirds. 
 
 CLxii. Where does thepulfe ceafe ? In my opin- 
 ion, in the uitima.te and cylindrical arteries. We 
 have noticed v/ith what velocity the blood iffues 
 from the heart. But that velocity continually de- 
 cre?.fes. It is certain, that the aggregate capacity 
 , of the fmali arteries, always bears a larger propor- 
 tion to the capacity of the aorta, as their divihcn 
 proceeds farther ; and thus, notwithftanding the dif- 
 ference in the proportion between the trunks and 
 their branches a'vaays decreases, this proportion 
 will be greatell, although it may be variable, be- 
 tween the aggregate capacity of the fmall arteries 
 in their ultimate divilion, and the capacity of the 
 aojta at its origin ; and there wall be a fimilar re- 
 tardation of blood to that which occurs in aneu- 
 rifms. Beiides, the proportion of the coats of the 
 arteries to their calibers always increafes as they 
 are fmaller, until it is greateft v'here they tranfmit 
 the glol'/iilcs fmgly. This is proved from di flec- 
 tion ; from inflation, by which every thing bcin^ 
 reckoned, they arc always more difficultly ruptured 
 as they are fmaller ; and by calculation, which efti- 
 mates tlie fize of the globules by the cylindrical 
 membranes of the. ultimate arteries. Add to tliis, 
 the friction of a liquid pafling through minute and 
 long tubes, bent and uniting at angles ; which kind 
 of friclion diminilhcs remarkably the velocity even 
 of fluid water pafling through Ample and merely 
 long tubes, and this always in proportion to their 
 fmallnefs ; and befldes, the fmaller an artery is, the 
 greater number of globules come in contact with 
 its tides, and rub againfl: them. In confequence of 
 the conical form of the arteries, the broader wave 
 of blood coming from the trunk cannot pafs with- 
 out rcfiftance through the linaller aperture of the 
 bran.h, and without endeavouring to diftend the 
 branch ; but alfo, t|ie influctiens and folds retard 
 
 the 
 
Chap. VT. 
 
 ARTERIES. 
 
 73 
 
 the blood ; fince feme part of the impelling force 
 is always fpent in impinging on the convex part of 
 the fold, and in the change of the figure of the in- 
 flected veffel. Large angles likewife diminifli the 
 velocity, in proportion as they are more obtufe, and 
 recede from a ftraight line. Moreover, the vifeid- 
 ity of the blood itl'elf muft be taken into confider- 
 ation ; fince, by reft alone, it immediately con- 
 cretes into clots ; and fince it is from the circula- 
 tory motion only that this mutual attraction of co- 
 hefion in its parts is overcome, fo as to prevent it 
 from adhering to the fides of the arteries, as it ad- 
 heres in aneuriims and wounds ; and the globules 
 from concreting together, as they ufually do after 
 death. The oppofition it meets with in the branch- 
 es, leffens the velocity of the blood likewdfe in 
 the trunk : the oppofite currents of blood in anai- 
 tomofes alfo deftroy fome part of its motion. Hence 
 the immenfe retardation of the blood in the minute 
 veflels. . We may eafily perceive that it is very 
 confiderable, although it is difiicult to eftimate it. 
 In the living animal, the blood flows in the trunk 
 wdth the rapidity of a torrent ; in the minute ar- 
 teries, it for the moft part begins to move flowly, 
 and then to be coagulated. It is alfo well known 
 to furgeons, that a flnall branch of a.n artery near 
 the heart or aorta, bleeds more dangeroufly than a 
 much larger one that lies at a greater diftance. The 
 v/eight of the incumbent atmofpherc, of the mufcles 
 and flefliy parts lying above the arteries, and the 
 contractile power of the veflels, make a refiftance 
 indeed to the heart, but do not lelfen the velocity 
 of the blood, for they add as m.uch during the diaf- 
 tole of the heart, as they take away from its powers 
 during the tidtole. . 
 
 CLxiii. It ip certain, hovrever, from incifions 
 m.ade in living animals, that the globules of bloodj 
 which move fingly, do not iofe fo much of their ve- 
 locity as, by calculation, they ought to do. There 
 
 muft. 
 
ARTERIES. 
 
 Chap. VI. 
 
 74 
 
 rnufl, therefore, exift feme caufes, which diminlfh 
 the powers impeding their motion. And, indeed, it 
 is certain, that, in the minute velfeis, the calibers of 
 the branches do not bear fo great a proportion to 
 the trunk j their great fmoothnefs alfo diminifhes 
 the friction. The facility, likewife, with which the 
 blood returns through the veins, expedites its paf- 
 fage through the ultimate arteries which imme- 
 <liately communicate with thefe veins. No great 
 effed: can be expected from the weight of the 
 blood, from the action of the nerves, or from their 
 plexufes, of which the firft may both retard and 
 accelei'ate occalionally, and in living animals, the 
 two laft have no effect whate^'er. The power of 
 derivation, whatever that is, and mufcular adion, 
 are capable of producing an increafe of vel'^- ity. 
 
 CLxiv. The pulfe is therefore generated by the 
 anterior wave of blood Sovung more howly, while 
 the fabfequent wave hows fafter ; fo that the form- 
 er is an obftacle to the latter (cnviii.) But iince 
 the motion imparted to the blood by the heart 
 weakens in its progrefs, and the contradile power 
 of the arteries increafes, therefore the cxcefs of 
 celerity of the pofterior veave, which comes from 
 the heart, above that moved by the contraefion of 
 tiie minute veffels, \rill be continually Icffening, 
 till, arriving at a part where tliere is no excels, 
 the pulfe will there ccafc, from tlic anterior and 
 pofterior waves both flowing with the fame ve- 
 locity, and therefore in one ftream. I'his place 
 will not be in the larger branches ; for in them, 
 the wave, laft coming from the heart, moves quick- 
 er than what goes before ; as is evident from the 
 inflammatory pulfation, efpecially of the fmali ar- 
 teries of the eye. But, in the ultimate arteries, the 
 pulfe vaniflies. This is evident from the equable 
 motion of the blood in the minute arteries, often 
 feen by the microfeope in frogs. Even in vef- 
 fels fomewhat larger, the flxth part of a line in 
 
Chap. VI. 
 
 ARTERIES. 
 
 75 
 
 diameter, the ptslfe ceafes to be perceptible iii’the 
 living arximal. In the veins vifible by the micro- 
 fcope, there is no puHation or acceleration of the 
 blood, whilft the heart contracts, demonftrable ei- 
 ther by the microfcope or in any other way. 
 
 CLxv. Even in the veins, the blood preffes 
 againit their fides, as appears from the furrows 
 hollowed out in the bones, and the fwelling of the 
 veins on being tied. AVhy do not the veins beat ? 
 for we do not allow that to be a pulfe which is 
 caufed by refpiration, or by the regurgitation of 
 blood from the right auricle, or mufcular part of 
 the, vena cava. The reafon feems to be, that the 
 blood, when it immediately leaves the heart, is 
 more retarded, and in the ultimate arteries, lefc. 
 Hence the Ihort fpace of time by vchich the ve- 
 locity of the laft wave exceeds the foregoing, is 
 greateft at the heart, and groves gradually lefs, till 
 •at laft it totally vanilhes. The following experi- 
 ment is appolite. Water forced in jets through a 
 leathern tube, by means of a fyringe, flows out of 
 a bit of fponge fixed at the end of the tube in one 
 uniform and continued ftream ; and alfo the anal- 
 ogous experiment, where the fame happens when 
 water is thrown, in alternate jets, into the mefen- 
 teric' arteries ; for even then the water Sows cut of 
 the veins in one continued fiream. 
 
 CLXvi, The pulfe is the meafure of the powers 
 exerted by the heart, becaufe it is the immediate 
 and full efFefl of thofe powers. Hence, all things 
 confidered as alike, the pulfe is flow in the Rate 
 of perfefl health, where there is no ftimulus, no 
 refiflance acting as a ftimulus, and the heart pro- 
 pels the blood freely and eafJy, except whern 
 there is fome obffacle, by which the blood is pre.- 
 vented from entering the aorta. From that caufe, 
 the pulfe in afthmatic people is flow : and alfo 
 from the debility or infenfibility of the heart, the 
 ufual ftimulus is 
 
 incapable or ftxcitme: it 
 
 i o 
 
 to con-i 
 tradion. 
 
ARTERIES. 
 
 Chap. \T. 
 
 7S 
 
 traiTion. A full pulfe is caufed by the fuUnefs of 
 the artery, joined with a ftrong force of the heart ; 
 » fmall pulfe by the emptinefs of the artery, and 
 a fmaUer wave of blood fent from the heart. A 
 hard pulfe denotes forne obllacle or ftimulus, or 
 increafed aftion of the heart, with a greater thick- 
 nefs of blood, or a greater rigidity or obftruclion 
 of the artery. A quick pulfe denotes feme ftimu- 
 lus, obllacle, or greater fenlibility and irritability 
 of the heart. The pulfe is bell felt where the ar- 
 tery lies expofed and fupported by bone ; but ob- 
 Ilruclions fometimes render the pulfe perceptible in 
 the moft oppofite fitu^tions. 
 
 cnxvii. The pulfe is ilower in animals as they 
 are larger ; becaufe the heart is proportionably lefs 
 than ill fmaller animals, and, as well as the other 
 parts of the body, is lefs irritable, and propels the 
 blood to a greater diftarxe ; and becaufe there feems 
 to be a greater increafe of friction, than of power 
 in the heart. Hence fmall animals are more vora- 
 cious ; and large ones, as the whale and elephant, 
 eat lefs. The pulfes of a healthy adult in the 
 morning, are at leaft 65 in a minute ; in the even- 
 ing they amount to 80 ; during the night they a- 
 gain become lefs frequent^ and gradually return to 
 the morning number. For mufcular motion, the 
 action of the external and internal fenfes, the 
 warmth of the atmofphere, and food and drink, 
 urge the venous blood to the heart, which being 
 thereby oftner fUmulated, makes more frequent 
 contractions. This is the caufe of tlie evening pa- 
 roxyfms obfervable in all fevers. Sleep retards the 
 blood and every other motion. 
 
 CLxviii. A frequent pulfe is different from a quick 
 one ; and it is poffible for the pulfe to be at the 
 fame time quick and unfrequent. But it is diffi- 
 cult to pbferve a quick pulfe. The frequent pulfe 
 is what is commonly called a quick one. It 13 fre- 
 quent in ghiidren,*and becomes lefs frequent in the 
 
 progrei's 
 
Chap. VI. 
 
 ARTERIES. 
 
 77 
 
 progrefs of life. In the falient point, the puLfes are 
 134 ; in new born infants, 120 ; and in old people, 
 they decreafe to 60. The febrile pxilfe begins from 
 96. In fevers, or in an adult after mufcular action, 
 no or 120 is a moderate frequency : but it is ex- 
 ceffive at 130 or 140, with which number people 
 feldom recover ; nor have I ever obferved it ex- 
 ceed that number. The pulfe beats flower in win- 
 ter, and quicker in fummer, often by 10 flrokes ; 
 and under (he torrid zone, it increafes to 1 20. The 
 pafiions of the mind difturb the pulfe in various 
 ways. ■ Whatever obftructs the circulation, accele- 
 rates the pulfe 5 not from the laws of hydroftatics, 
 or on account of the canal being made narro^ver, 
 or from the aflion of the foul ; but Amply becaufe 
 the heart being with more difficulty freed from the 
 ftimulating blood, contradfs itfelf more ftrongiy, 
 and at fliorter intervals. Irritation from acrid 
 blood is frequently the caufe of the febrile pulfe. 
 
 CL XIX. Through the minute veins the blood 
 moves flowly, partly by the force of the heart, and 
 partly by the contradtiiity of the arteries. The Arfl: 
 is proved by a renewal of the motion of the blood, 
 in perfons drowned, which is effected folely by the 
 excitation of the heart. But the contradlile force 
 of the arteries is proved by what we faid in clx. 
 
 . After death, the blood is moved by its own gravity, 
 and by the elaftic air, generated during its putre- 
 fadtion. 
 
 CLXX. The blood moves faffer in the larger 
 veins. For wherever the impelling powers fuffice, 
 and the conveying tubes are rendered narrower, the 
 motion muff be accelerated ; for venous trunks arc 
 fmaller than the branches of wffiich they are form- 
 ed, in the fame m.anner as arteries are lefs than the 
 branches into which they divide. Therefore, if 
 the motion of the venous blood loft nothing in its 
 W'ay, the proportion of its celerity in the vena cava, 
 to its celerity in the veins of the thirtieth diviflon, 
 
 would 
 
ARTERIES. 
 
 78 
 
 Chap. VI. 
 
 would be exacHy the thirtieth power of the pro- 
 portion of the funi of the calibers of all the ulti- 
 mate veins, to the caliber of the vena cava. At the 
 fame time the friction is diminished, and the ccn- 
 taft of the blood with their hides. 
 
 CL XXI. But since the blood moves very flowly in 
 the ultimate arteries and incipient veins, and as tlie 
 weight of the blood itfelf, in many places, impedes 
 its return remarkably, and as, from the very thin 
 coats of the veins, but little contractile power can 
 be expected, nature has ufed various precautions, 
 left, from the flownefs of its motion, the venous 
 blood fhould ftamate or concrete. Therefore Ihe 
 
 O ^ • • 
 
 has reft or ed to the veins, the halitus and fluid 
 lymph, in larger quantity, as it feems, than v'hat 
 the arteries loft, on account of the great exhalation 
 from the lungs. 
 
 CLXxii. She has likewife placed the veins near 
 the mufcles, which, by their fwelling, comprefs the 
 interpofed veins ; and fince ea^^ery preiTure of the 
 veins, on account of their valves, determines the 
 blood towards the heart (lxih.) therefore all this 
 force is entirely employed in accelerating the re- 
 turn of the blood to the heart. Hence that won- 
 derful quicknefs of the pulfe (cLxvii.) heat, red- 
 nefs, and quick refpiraticn after mufcular action. 
 
 CLXXiii. Moreover, thofe mufcles, which ftrong- 
 iy comprefs on every fide all the parts contained in 
 any of the common cavities, powerfully promote 
 the motion of the venous blood. In the abdomen,, 
 this is effected by the conjunft preffure of the dia- 
 phragm and abdominal mufcles. Laftly, the pu Ra- 
 tions of the arteries, every where contiguous and 
 parallel with the veins, promote the return of the 
 venous blood ; ftnce, as we have before ihewn, every 
 impulfe acting on the veins can determine their 
 blood to the heart ordy. 
 
 ci.xxiv. To thei’e is added the p'ower, not yet 
 fufiiciently Iviiown, of derivation, by which the 
 
 blcoil 
 
Chap. VI. 
 
 ARTERIES. 
 
 79 
 
 blood is brought from a place where it is more 
 compreffed, to one more lax, and where it meets 
 with lefs refiftance. Laitly, refpiration is of great 
 efficacy •, in which the blood is ^dternateiy brought 
 by the power of derivation from all parts of the 
 body into the fpongy lungs ; and again, in exfpi- 
 ration, is driven into the trunks of the veins in the 
 head and abdomen. Hence the fwelling of tlie 
 veins, even of the brain, in the tim.e of exlpiration. 
 The circulation is not indeed affifted by thefe cauf- 
 es, but the blood is agitated and prelTed forvvards. 
 The anallomofes have the fame effiecls as in the ar- 
 teries ; for they facilitate the paffage of the blood 
 from places where it is obftrudted, to thofe which 
 are pervious. 
 
 - cLxxv. By thefe means, the blood in a healthy 
 perron, ufing fufficient exercife of body, moves with 
 a velocity, which is fufficient to reftore, in each pul- 
 fation, to the heart, by the vena cava, as much blood 
 as the aorta carried away. But corporeal inaftioii 
 and debility of the contracting fibres of the heart 
 and m.ufcles, frequently render the m.otion of the 
 venous blood more difficult. Hence the varices in 
 pregnant women ; and hemorrhoids, to which the 
 abfence of valves in the vena porta contributes much. 
 Hence the rnenfes themfelves. And when the veins 
 .return their blood too flowly to the heart, the fubtle 
 vapours being unable to return from the minute vef- 
 fels to the heart, flagnate and occafion that fre- 
 quency of cedema in weak people. 
 
 chxxvi. The time in which an ounce of blood, 
 fent out from the left ventricle, returns to the right, 
 and which is commonly reckoned the time in which 
 the greater circulation is performed, is uncertain, 
 and different in every different portion of the body. 
 If, however, you inquire concerning the ounce of 
 blood, when propelled in the quantity we have 
 mentioned, with 4500 pulfations, about feven and a 
 
 half 
 
ARTERIES. 
 
 8o 
 
 Chap. \T. 
 
 half ounces will perform in an hour nearly twenty- 
 three complpte circulations and a half. 
 
 CLXxvii. The effects of the action of the heart 
 and arteries upon the blood, which follow from 
 what has been mentioned, are various, and are efti- 
 mated by comparing the blood of living vcidi dead, 
 of healthy with difeaied, and of inactive with active 
 animals. For the blood of a Imng animal is warm, 
 is of a fcariet colour, feems homogeneous, although 
 compofed of mixed principles, is entirely globular, 
 flows very readily through the molt minute veffels, 
 and exhales the volatile halitus, which we have al- 
 ready defcribed particularly. In the dead animal, 
 before it is tainted by putrefaction, it lofes much 
 of its red colour ; it feparates into heavier and ligiit- 
 fer principles ; exhales no vapour, and when drawn 
 out from the veins, coUgeals either entirely or near- 
 ly fa. But even in living animals, when weak, in 
 which there is fome pulfe or refpiration, though 
 very fmall, the blood cools to a confiderable de- 
 gree. If, again, you compare the blood of a perfon 
 inactive both in body and mind, with that of one 
 addidled to violent exercife, you will obferve in the 
 latter, a greater heat, intenfe rednels, greater com- 
 paclnefs, fpecific gravity, and very great abundance 
 of the volatile principles. Ail which appearances 
 feem rnanifeftly the effects of the action of the 
 heart and arteries, fmee, with its incrcafe, they in- 
 creafe, with its diminution, diminifli, and with its 
 ceffation difappear. 
 
 CLxxviii. That we may underftand the manner ' 
 in which thefe appearances are produced in the 
 blood, we muff confider what are the effects of 
 the heart in expelling it, and of the arteries in - 
 alternately comprelling it. And, indeed, the 
 heart propels the blood with very great velocity 
 (cxxiii.) The heart throws the blood into the 
 crooked arteries, in a confufed manner, fo tiut the 
 ri'jrht ttlobiilcs, expelled into the mouth of the 
 
 aorta. 
 
Chap. VI. 
 
 ARTERIES. 
 
 8i 
 
 aorta, ftrike againft the left fide of the artery ^ 
 from whence being repelled, they incline towards 
 the right fide, and thus all the particles of the 
 blood are agitated with a confufed and whirling 
 motion. It necelfarily follows, that the blood, im- 
 pelled into curved canals, muft impinge on their 
 lides, dilate them and increafe their convexity ; and 
 laftly, in the fmalier veflels, capable of receiving 
 but few or only one of the blood globules, in which 
 the greatefi; number or all the globules come into 
 contact with the fides of the artery, they fo exactly 
 rub againft them, that they are even obliged to 
 change their figure in order to pafs. 
 
 CLXxix. But the arteries, by their elaftic force, 
 repel the blood from their fides towards the axis 
 of their cavities, and readl upon it pr effing againft 
 them, and laftly tranfmit the globules, fingly, into 
 arteries through the circular mouths of the uiti- 
 
 ^ O 
 
 mate feries. 
 
 CLXxx. In the arteries there is, therefore, a very 
 great degree of friction ; of the blood globules a- 
 gainft the arteries ; of the arteries contracting round 
 the btood like an obftacle ; and of the particles of 
 the blood amongft each other by the confufed and 
 vorticle manner in which they are propelled. The 
 efiedts of this fridtion are computed from the vif- 
 cid and inflammable nature of the blood, from the 
 narrownefs of the veflels through which it runs, 
 from the ftrong impulfeof the heart, from the power- 
 ful readtion of the arteries, and from the weio'ht of 
 the incumbent parts raifed by the force of the arte- 
 rial blood. This fridlion generates fluidity, by per- 
 petually removing the points of contadt between 
 its globules, refilling their force of attradlion, mix- 
 ing together the particles of different kinds, which 
 become more fluid upon mixture, as in the inftance 
 of oil triturated with water. Then their rotation 
 and mutual attrition difpofe the particles to afiume 
 a fpherical figure j fop by breaking off their pro- 
 tuberances, 
 
 G 
 
Al^TERIES. 
 
 Chap. YT. 
 
 tuberances, it renders tliofe that are ill formed or 
 branxhy inore fphericaL But even the fragments 
 broken from the projecting furiaces of the ill formed 
 globules, acquire a round iha}?e from the fame ro- 
 tation, attrition, and circular caliber of the minute 
 velfels.i- Hence blood coagulates in the vdTels be- 
 fore death ; and regains its loif fluidity by reftor- 
 inp; the motion of the heart, as are tauorht by 
 experiments made on li\dng animals. Does the 
 motion of the blood, and the denflty proceeding 
 from it, produce the red colour, flnee it is nearly 
 in proportion to the denflty, and incrcafes or de- 
 creafes from the fame caufes ? It feems to de- 
 pend on the calx of iron triturated with the oil. 
 
 CLxxxi. Does the motion of the blood alfo gen- 
 erate its heat, as in experiments with all kinds of 
 fluids, and even air, but more efpecially in a com- 
 buftible animal fluid, denfer than water, com- 
 prefi'ed by contractile tubes, and rubbed in con- 
 fequence of rapid inflection and extenflon of 
 the canals themfelves ? Is this proved by the 
 blood belnsc warm in flflies which ha^■e a lar'T;c 
 heart, and cold in thofe which have a fmall one, as 
 if the heat generated were in the proportion of the 
 flze of the heart to the body ; by the great heat of 
 birds, whofe hearts are large; by the increafe of 
 heat by every motion, even friction ; by the cer- 
 tain congelation of all the human fluids, at a de- 
 gree of cold in which man freezes and retains his 
 blood warm as long as he lives ; and by the cold- 
 nefs of perfons whofe pulfe is weak and obfeure I 
 Nor docs the heat proceed from any incipient pu- 
 trefaction in the blood, flnee the fluids, when per- 
 fe-5lly at reft, do not generate that degree of heat 
 nor is the evident phenomenon explicable from the 
 action of fuch an obfeure thing as the vital power ; 
 and though fometimes the heat may be greater 
 when tlie pulfe is flow, and lefs when it is more- 
 frequent, tlie difference may arile from the differ- 
 
Cha?. Vi. 
 
 ARTERIES. 
 
 fent nature of tEe blood, from the different den- 
 fities of the veffels, or from the abundance or fcan- 
 tinefs of the perfpiration. 
 
 CLxxxii. The fame caufe alfo checks putre- 
 fadlion, by not fuffering the inteftine motion to 
 be diminifhed, by admixing antifeptic pai^ticleSi 
 and by diffipating others which have already be- 
 gun to be corrupted. 
 
 CLXxxiii. But in confequence of the different 
 natures of the particles themfelves, which con- 
 jundtiy conftitute the blood, the impetus of the 
 heart produces different effects on the different 
 particles of the blood. Namely, thofe particles 
 move more quickly, v/hofe greater denfity makes 
 them receive a greater impetus, and wliofe apt fig- 
 ure and lefs extended furface meets with lefs re- 
 fiitance in the fluid in which they move. Thofe 
 alfo move more quickly, which, either from their 
 weight, or from the direction in which they pafs 
 out from the heart, move in the axis of the veffeL 
 Befides, thofe which have the greateft projeftilc 
 motion vnU ftrike asrainft the convexities of the 
 nexures ; while thofe which, from their greater 
 gravity or lentor, have lefs projectile motion, will 
 move fluggifhly along the concavity of the veffeL 
 In this manner is the blood difpofed for the fe- 
 cretions. 
 
 CL XXXIV. In the firft place, the fyfcole of the 
 arteries produces compaftnefs 5 fince, by contract- 
 ing round the blood as round an obftacle, they 
 comprefs it where vifcid and comprefiible, they 
 expel the more liquid parts into the lateral mouths^ 
 increafe the points of contact betwixt the globules, 
 unite the larger, and compact the flat particles 
 into denfer bodies. But the denfity of the blood 
 is partly as the number of globules, and partly 
 as the denfity of the fubftance of thefe globules. 
 
 CLXxxv. Befides, thefe very minute mouths, 
 perviou? to one globule, feem to be the meafures 
 G a lu 
 
ARTERIES. 
 
 Chap. VI. 
 
 8-4 
 
 in which the fanguineous particles, being approxi- 
 mated to a fpherical figure by having their points 
 rubbed off, now affunie it and become perfect 
 fpheres. This is another fource of denfity, lince, 
 of all figures, the fphere is the moft capacious. 
 
 CLxxxvi. The anaftomofes of the arteries re- 
 move every danger of obftrucHon, for to any part 
 of an artery where there may be an incipient ob- 
 ftruction or coagulation of the blood, they admit 
 an oppofite current, by which the obftacle is re- 
 pelled in a contrary direction into a larger part of 
 the trunk, and is comminuted between it and the 
 direct current of blood. The irremoveable obftruc- 
 tion or the lofs of any veffel, is alfo fuppiied by the 
 fubfequent enlargem.ent of fome contiguous branch, 
 as is proved by furgical fa<Ts, in which the princi- 
 pal artery has been cut or tied. The collilion of 
 thefe oppofite torrents of blood takes fomething 
 f rom its velocity ; and the reticular diftribution 
 augments the friction of the globules. 
 
 CLXx^cvii. In like manner as the velocity, fothc 
 flow motion of the blood in the ultimate velfels Las 
 its peculiar effects. In the larger arteries, the m.oft 
 heterogeneous particles are whirled about amongft 
 each other ; in the fmaller branches, the progref- 
 live motion of the blood being diminiflied, the 
 lighter particles feparate from the very ponderous 
 and red globules, and are forced towards the cir- 
 cumference and branches, while the compact glo- 
 bules rem.ain in the axis. The attraftive powers 
 of the particles of the blood are alfo increafed ; 
 hence, the oily particles which are both fluggifli 
 and large, attract each other, and feparate by open 
 lateral mouths ; and other thinner fluids are lent 
 off through lateral branches of a fmaller orifiee, till 
 at length little more than the red blood alone pafl- 
 es into the incipient vein. Heterogeneous particles 
 arc alfo mixed in a Angle vein, that the blood may 
 be prepared for certain ufes, as in the. vena porta- 
 
 rum. 
 
Chap. 
 
 SECRETION. 
 
 ^5 
 
 rum. But all thefe particulars which prepare the 
 blood for the fecretions, we lhall conlider in the 
 following chapter. 
 
 CHAP. VII. 
 
 SECRETION. 
 
 CLXXxviii. ^ I '’HE fluids which, being depofited 
 § from the blood into other veflels, 
 are faid to be fecreted, feem reducible to four clalT- 
 es. The jirjl confifts of vifcid fluids, coagulable 
 by a heat of about 150 degrees, by alcohol, and by 
 ftrong acids ; although generally, in the living ani- 
 mal, they efcape in the form of vapour, and after 
 death are compared into a gelatinous fubftance. 
 To this clafs belong the liquor and halitus of the 
 ventricles of the brain, of the pericardium, pleura, 
 peritoneum, tunica vaginalis, amnois, joints, renal 
 capfules, and probably of the womb, with the juices 
 of the ftomach and inteftines, and laftly the lymph 
 generally known. 
 
 CLXxxix. The fccond clafs confifts of fluids, of 
 which fome, in like manner, are exhaled, but 
 more Ample than the former (clxxxviii.) and 
 more aqueous, are not coagulable by fire or by fpir- 
 its of wine ; and others are not exhaled, but, being 
 depofited in their refpedtive excretory ducts, are 
 excreted in their proper places by the common out- 
 let of fome gland. To the former of this clafs be- 
 long the perfpirable matter of Sanftorius, part of 
 the tears, and the v/atery humour of the eye. To 
 the latter of this clafs belong the remaining 
 part of the tears, the faliva, pancreatic juice, 
 and the urine. The fweat feems to be a mix- 
 ture of the perfpirable matter and the fubcuta- 
 neous oil. 
 
 cxc. 
 
86 
 
 SECRETION. 
 
 Chap. YIL 
 
 cxc. The third clafs differs from both the pre- 
 ceding, being heavier than water, fluggilh and 
 vifcid, but of an aqueous nature, not congealable 
 into a jelly, but hardening into dry crufts by ex- 
 haling their water. Thole do not eflervefce with 
 any fait, but are contracted and made thicker by 
 acids. By lixivial falts they are diflblved. By fire 
 they are refolved into water, a little volatile fait, 
 and a little oil. Of this kind are the whole mucus- 
 in the human body, extended over all the internal 
 pafiages for air, aliments, or urine, and the cavities 
 of the genital parts ; and femen. 
 
 cxc I. The clafs is that of the inftammable 
 juices, which, when recent, are indeed thin 'and 
 Vv^atery, but, byftagnation and by evaporatmg their 
 water, become thick, oily, inflammable, and often 
 bitter liniments. To this clafs we refer the bile,, 
 earWax, tallovc, the oily liniment of the fkin, the 
 marrow in the bones, and all the fat throughout 
 the human body ; and caftor, and the yolk of the 
 egg. The milk itfelf, fo far as it contains butter, 
 belongs to this clafs. 
 
 cxcii. Other humiours are compounded of thefe 
 which we have deferibed as Ample ; as the mik, of 
 butter and water ; and the liniment of the joints, of 
 lymph and fat. 
 
 cxciii. Whoever confiders, that in the blood are 
 found a coagulable ferum (^cxxxvii.) an exhaling 
 water (cxi.ii.) a fort of vikid mucus (cxxxviii.) 
 and iaftly an oil (cxlii.) wiU begin to perceive 
 the perfecl poflibility of the foregoing clafl'es 
 (cLxxxviii. to cxci.) of humours being feparated 
 from the blood, fince their principles exift in the 
 fanguineous mafs. But in what manner it is brought 
 about, that oil is feparated from the blood in one 
 part, water in another, and mucus in a third, re- 
 mains to be explained, and requires a defeription 
 of tlie fccretorv organs. 
 
 QXCIV, 
 
Chap. Ylt 
 
 SECRETION. 
 
 7 
 
 cxciv. The coagulable juices are feparated al- 
 moft every where, from the arteries themfeives, in- 
 to excretory canals, continuous with the arteries, 
 without any intermediate organ. The proof of this 
 we have from injections of glue, water, and thin 
 oils, which very readily exude from the red arte- 
 ries, and are poured out into all the cavities in which 
 that coagulable vapour is naturally found, with- 
 out meeting vdth any intermediate knots or retard- 
 ing cells. Finally, the blood itfelf, being poured out 
 into moft of thefe .cavities, without any permanent 
 kfion, in confequence of ftagnation, retardation, 
 or fmall increafe of impetus, Ihows plainly that the 
 paffage betwixt the red blood-veffels and thofe ex- 
 cretory du<Ts is neither long nor difficult, and that 
 the yellow ferum does not differ much from blood. 
 
 cxcv. Another liquid, coagulable by acid fpirits 
 and alcohol, is the albuminous humour of the joints, 
 w'hich being compofed of fat, medullary oil, and 
 watery exhalation, ccnfiitutes an exceedingly foft 
 liniment, very fit for lubricating the cartilages, and 
 leffening friction. For fecreting this, there are def- 
 tined certain conglomerate glands of a peculiar 
 ftructure, which are fo fituated in the rough pits of 
 the articulations of the bones, that they may be 
 moderately compreffed, but cannot be crufhed. 
 
 cxcvi. The ftrufture of thefe glands is peculiar. 
 The larger cluflers of glandular acini adhere, for 
 the molt part, to the bone by a broad bafis wrap- 
 ped up in fat. Thence, being extenuated into a 
 crefted edge, they pour out their liquor from an ex- 
 ceedingly thin border, by open ducts, which how- 
 ever I do not find very evident. Other fmaller 
 ones, placed every where in the capfules of the ten- 
 dons, and between the diverging fibres of the liga- 
 mentary capfules of the joints, feem to be ahnoft of 
 the nature of fimple glands, and are turgid with 
 yellow mucous ferum. 
 
 'CXCVII, 
 
88 
 
 SECRETION. 
 
 Cfup. ■^TI, 
 
 cxcvii. The imcoagulable juices (clxxxix.) of 
 the firft fort are fecreted in the fame manner ^vnth 
 the coagulable ones (clxxxviii.) to wit, from ex- 
 haling arteries, which arife from the red arteries, 
 without any intermediate follicle. In the velfcls, 
 which exhale the cutaneous perfpiration, and in 
 the lachrymal veiTeis of the firft fort having a wa- 
 tery ftuid ; injections of water, or thin fize exude 
 from the arteries, fo as to remove every doubt of 
 this. Thefe arteries are alfo irritable, fo that, from 
 the contact of an acrid fubftance, they difcharge 
 more juice in a given time, than in a ftate of health. 
 
 cxcviii. But in the latter kind, the falival, the 
 fecretion is made by means of conglomerate glands, 
 which the ancients firft diftinguifiied by their cluf- 
 ter like fabric, and efteemed glands. Thefe are 
 compofed of acini or roundifh lobules, conjoined 
 together into a larger mafs, by loofe cellular fub- 
 ftance, which is often covered externally by fome 
 denfe cellular membrane, as a common envelope, 
 as in the parotid and maxiUary glands. Through 
 the intervals, betwixt the clufters, run the arteries 
 vchich are here pretty large, and the veins. But 
 moft of the conglomerate glands feparate their 
 fiuids from the blood, and difcharge it in the fol- 
 lowing manner : Each acinus fends out an excre- 
 tory duel, which ioins with others of the fame kind, 
 into a larger trunk, forming at laft, in the manner 
 of veins, one canal, which conveys the humour, 
 feparated by the gland, to the part for which it is 
 defigned, as the cavity of the mouth, inteftines, fur- 
 face of the eyes, &c. There are, indeed, fome in- 
 ftanccs in which either there are no excretory 
 durfts, or they have not hitherto been diicovered ; 
 as the thyroid gland, capfuls renales, and thymus, 
 unlefs thefe approach to the nature of conglobate 
 crlands. 
 
 CXCIX. 1 
 lilvjted by 
 
 he acini themfelves are furreunded and 
 fome firm cellular fubftance 3 and are 
 
Chap. VII. 
 
 SECRETION. 
 
 89 
 
 alfo fubdivided into leffer acinuli, as is evident to 
 the eye, and by tlie microfcope. How does this 
 fubdivilion end ? Is every fimpie acinus hollow in 
 its middle, receiving the humour tranfuding from 
 the arteries in a follicle, and fending it out by an 
 excretory duft ? Is this ftruclure rendered probable 
 by eruptions, hydatids, and the kidneys filled with 
 round fchirri ? Are the larger vifcera, appointed 
 for fecretion, conglomerated glands ? Is this opin- 
 ion made probable from the morbid round concre- 
 tions formed in the liver, fpleen, kidneys, tefticles, 
 and cortical fubftance of the brain ; or from the 
 bunch like appearance which thofe vifcera have in 
 fmailer animals ? In the cellular fubftance that fur- 
 rounds every part of the human body, even the 
 extreme vafcules, are there hollow fpaces and cells, 
 into which a fecreted humour is poured ? 
 
 cc. Nothing of this kind feems to be the cafe. 
 For, indeed, the acini compofing the vifcera of ani- 
 mals, are .not elementary, but compofite lobes, and 
 large in proportion to the animals. The morbid 
 concretions are almoft all of them feated in the cel- 
 lular fubftance, and in the limbs themfelves, where 
 there is not the leaft room to fufpecl any thing of 
 a glandular fabric ; and are compofed of oil, earth, 
 and vaporous particles, extravafated into fome of the 
 cellular cavities, where, ftagnating and compreliing 
 the adjacent foUicles, they form to themfelves proper 
 membranous tunics, Befides, the watery and fluid 
 nature, of the juice fecreted in thefeglands (clxxxix.) 
 is an argument that, during its fecretion, it met 
 with no retardation, no place in which it ftagnated. 
 For the fluids ‘which remain at reft in the warm 
 cavities of the human body, which are full of ab- 
 forbing vefiels, are all .infpilTated, and approach, 
 either towards a mucous or an oily nature. More- 
 over, anatomical injections would meet with more 
 difficulty in paffing from the arteries into the ex- 
 cretory ducts } which would be impervious to thick 
 ' injections. 
 
SECRETION. 
 
 Chap. 
 
 injections, and tliiii ones would be exhaled into the 
 cellular fubftance. Yet we fee, that the fuperiative 
 art of great anatomifts has conveyed thick injec- 
 tions, like wax, directly from the arteries of the 
 falivary glands, liver, &c. into continuous excretory 
 dufts ; and this without filling up any intermediate 
 cavities, which, according to the foregoing hypo- 
 thefis (cxcix.) fhould happen. 
 
 cci. Therefore, the acini appear to be compofed 
 of arteries and veins, divided and fubdivided, part- 
 ed and connected by the intervention of a good 
 deal of cellular fubftance, which, becoming gi'adual- 
 ly more compact, alfumes a fpheroidal figure. Tliis 
 is fupported, by analogy in the lobes of the lungs, 
 in the lobules of the thymus, in the ftnicture of in- 
 fects ; but more efpecially in the tefticle, of which 
 the lobules are evidently formed of excretory dueds, 
 connected together into fafciculi by a very foft 
 membrane. The glands do not feem to pour their 
 fluids into cellular fubftance, as by it the paflage to 
 the excretory ducts would be obftructed or prevent- 
 ed. The induftry of anatomifts has lately difeovered 
 very fmall, white, cylindric veffels, the real elements 
 of the vifeera ; and it is to be hoped that this dif- 
 covery will be confirmed by future obfervations. 
 
 cell. Thin fluids, neither coagulable nor exhal- 
 ing, but aqueous, are likewife generated in other 
 parts, without the affiftance of conglomerate aci- 
 nous glands. Thus, the urine is depofited from 
 the red arteries into membranous tubes, manifeftly 
 continuous, in a manner which readily admits the 
 paflage of air, water, or mercury. The nervous 
 fluid feems to be fecrcted in the brain, in a fimilar, 
 though lefs apparent manner. 
 
 cciii. The third clafs of fluids, the mucous, (cxc.) 
 is almoft every where fecreted from fmufes or liol- 
 lovr glands. The ftruchire of true glands or folli- 
 cles, in general, confifts of an ample cavity, every 
 wll$re circumfci'ibcd by a membrane ■, but in fuch 
 
 a mamier, 
 
Chap. VII. 
 
 SECRETION. 
 
 9 * 
 
 a manner, that the flefli itfelf of the part, to which, 
 the gland adheres, ioraetimes forms, the one fide, 
 and completes the hemilphere of the follicle. In 
 other places, a continued membrane forms the whole 
 of the round or oval receptacle of the gland. The 
 cavity is in general round ; but fometimes it is ob- 
 long, and lituated obliquely betwixt the adjacent 
 parts ; as, for example, in the urethra of the male, 
 and in the foUicles of the linus muliebris. They 
 are irritable ; and, v/hen ftimukted by acrid fub- 
 liances, accelerate their fecretions. 
 
 cciv. Into thefe follicles minute arteries, either 
 from the flefli in which it is feated, or from the 
 membrane ivhich conftitutes its convex fide, open 
 by extremities extended into the cavity of each 
 crypta, into which they pour their refpeTive juice ; 
 after being received into the follicle, it is detained 
 from the narrownefs of the excretory duff, and 
 infpiflated, the more watery parts being abforbed 
 by the veins, which correfpond to the exhaling ar- 
 teries. The truth of this we are taught from the 
 ftrufture of the Ample follicles obfervable in the 
 tongue, in which both the importing pores, and the 
 excretory ducts, are even vifible to the eye ; and 
 from the tubuli of the ftomach of birds, in which 
 the fecreting villi manifeftly protrude into the cav-. 
 ity ; and laftly, from injeftions, which force wax 
 colourlefs into the Ample glands. 
 
 ccv. The long mucous Anufes, and round 
 glands, are both furniflied with excretory duffs, 
 which, for the moA part, are fulAciently large ; al- 
 though, in the round glands, they bear no great 
 proportion to the cavity of the gland, Thefe ori- 
 fices often open into the common large cavity, into 
 which the mucus is poured, without any interme- 
 diate duff; as in the back of the tongue, and in 
 the Ample glands of the ftomach and inteftines. 
 Thefe have been denominated cryptae by Ruyfcli.. 
 The Anufes have pfcen a Amilar ftruffure, and, 
 
 open. 
 
SECRETION. 
 
 9 ^ 
 
 Chap. \TI. 
 
 open, without an intervening duel, as in the ure- 
 thra of the male, 
 
 ccvi. In another kind of thefe glands, there 
 are many limple follicles contained in one common 
 covering, which open with ample orifices into one 
 common finus, without any true excretory duct, 
 as in the tonfils. Thefe are called conglutinated 
 glands. < 
 
 ccvii. Other Ample glands have an excretoiy 
 duct, by -which they excrete their mucus ; namely, 
 a membranous, cylindric, narrow veffel, opening 
 with its pofterior orifice into the cavity of the 
 gland, and with its anterior orifice into the com- 
 mon cavity for which its mucus is defigned. Thefe 
 excretory du£ls are of confiderable length in the 
 fubcutaneous and febaceous glands, and in thofe of 
 the palate and windpipe. In fome parts, the pore 
 and duct are more eafily demonftrable than the fol- 
 licle, as in the noftrils, larynx, reclum, &c. 
 
 ccviii. . In other places, feveral of thefe duds, 
 arifing each from its refpedive follicle, run togeth- 
 er like the branches of a vein, fo as to form one 
 confiderable excretory canal, com.inon to a number 
 of follicles. To this kind belong the compound 
 glands of the inteftines, and the blind finus at the 
 root of the tongue, of the clafs of glands ; and of 
 the finufes, fome compound finufes of the urethra, 
 and the tubulous fibres of the ftomachs of filhes 
 and of birds. Glands of this fort may be faid to 
 he compounded of Ample ones ; but where they lie 
 only contiguous, they may be called aggregate or 
 congregated glands ; as are thofe of the tauces, fto- 
 mach, inteftines. See. 
 
 ccix. The inflammable juices (cxcix.) are fepa- 
 rated by organs diftering in their fabric. The fat 
 and marrou'^ are depofited into cellular fubftance, 
 without the intervention of ^ands, from the finall 
 mouths of the arteries. The fubcutaneous fat 
 every where exudes through fmall duels and pores, 
 
 \t'ithout 
 
Chap, VII. 
 
 SECRETION. 
 
 93 
 
 without any glandular follicles. - But the -earw 2 LX 
 and cutaneous fuet are fecreted by glands of differ- 
 ent kinds. Many of the febaceous glan,ds are vifi- 
 ble, \Auth a naked mouth in the ficin, and without 
 a duel of any length ; as we fee in the ears, ai'eolac 
 of the nipples, in the female nymphse, and the 
 groove betwixt them and the labia, and in the pre- 
 puce of the penis and clitoris. Thefe differ but 
 little from the cryptse (ccv.) except in the matter 
 which they fecrete. 
 
 ccx. There are others of the febaceous glands^ 
 W'hich have an excretory du6l of fome length ^ as 
 almofl ail the cutaneous ones, which, being feated 
 in the cellular fubfcance, are neceffarily prowded 
 with a dudl to perforate the Ikin. This is moll 
 evident in the face, where the length of the duel is 
 indicated by maggot like fubflance preffed out ; 
 the bulk of which demonftrates, that a follicle lies 
 under the flender pore. 
 
 ccxi. There are hill other febaceous glands of 
 the kind, mentioned ccviii. in which the fmail 
 du(ils of many cryptse meet together in one larger 
 excretory du6l. Thus, in the face, in feveral places, 
 the large pores are in common to a number of 
 cryptae. Of this kind, alfo, are thofe febaceous 
 du(Ts in the eyelids ; and the unguinous glands in 
 the fecretory organ of the mufk-goat, beaver, hy- 
 aena, civet-cat, and mufk-rat, which pour their fe- 
 baceous matter into one common receptacle. 
 
 ccxii. The milk, which is compofed of water 
 and oil, and perhaps of abforbed fat, and is a fluid 
 of a peculiar nature, is fecreted in a conglomerate 
 gland, fuch as we deferibed at cxcviii. The bile 
 is a matter of controverfy ; but there are many ar- 
 guments in favour of the vafcular flruclure, and of 
 the bile being depofited in the pori biliarii, from the 
 vena portarum, without intermediate follicles; efpe- 
 cially the Ruyfehian art of inje<5lion, in which the 
 wax paffes dire^iy from the porta into the biliary 
 
 pores. 
 
SEC^ETIOl'^. 
 
 Chap. \1L 
 
 §4 
 
 pores, witliout meeting with any intermediate knots 
 retarding it. The milk and bile are both of them 
 however much thinner, and more watery, than the 
 fat, or the febaceous m.atter in follicles. 
 
 ccxiii. It remains for us to inquire, how it hap- 
 pens, that from one common mafs of the blood, the 
 fame variety of peculiar fluids are conftantly fepa- 
 rated, each in its refpective place, and that milk is 
 never ferreted in the kidneys, bile in the thymus, 
 or mucus in the febaceous glands. This problem 
 will be at laft perfe<5fly folved by one who lhall be 
 intimately acquainted with the internal ftruchire 
 of the fecreting organs. In the mean time, I fliall 
 notice what is hitherto known with fulHcient cer- 
 tainty. 
 
 ccxiv. In the firfl: place, the blood itfelf, from 
 which any liquid is to be fecreted, aflumes in vari- 
 ous places, that peculiarity of character, that it con- 
 tains more particles, of a like nature with thofe 
 which nature wilhes to predominate in the fluid to 
 be fecreted. In the liver, the venous blood arrives 
 witli a flow motion, loaded with oil, and the femi- 
 putrid vapours of the inteftines. To the tefticles, 
 the blood is brought flowly, through long, {lender 
 and inflected canals, arifing at very fmall angles, 
 under the ikin, in a cold fltuation. In the carotids, 
 it is probable that the ftronger, fpirituous, and denfe 
 parts of the blood afeend ; fo that that is more wa- 
 tery, which defeends into the abdomen and to the 
 kidneys, and forms the faliva of the pancreas, and 
 the gaftric and inteftinal juices. 
 
 eexv. Befidcs, the blood is prepared for fecre- 
 tion, by its retardation in the minute velfels, in con- 
 fequence of which, the red and denfer parts alone 
 occupy the axis of the canal ; while the other. light- 
 er, m.ore iluggifh, and lefs quickly moved particles, 
 recede to the lateral branches, impinge on the iecre- 
 tory mouths ariiing from the fldes of th.e veliels, 
 and adhere to them by their vifcofity. 
 
 ccxyi. 
 
Chap. VII. SECRETION. 9^ 
 
 ccxvi. Thefe orifices, though poffibly of dif- 
 ferent diameters, are always too fmall to admit the 
 lalood in their natural ftate. As from an increaf- 
 ed aclion of the heart, many of them admit blood, 
 we may conclude, with probability, that they arife 
 continuous with the red arteries, and are not much 
 fmaller than the red globules. Hence the fame 
 fecretory orifices refufe thick injeftions of wax or 
 fuet, and generally admit thinner liquors injected 
 into the arteries. Therefore, this is the firft and 
 mod; hmple mechanifm of fecretion, viz. that the 
 caliber of the excretory ducd admits only thofe par- 
 tides, of which the greateft diameter is lefs than 
 the diam.eter of the duct. It is only in this way 
 that the yellow arteries convey a pure liquor from 
 the blood, and that the uriniferous dudls exclude 
 the red blood and coagulable ferum. But this is not 
 the foie caufe, fince limilar fluids are generated by 
 large, as well as by fmall animals. 
 
 cGxvii. Merely according to this law, the fecret- 
 ed juices may be of many different kinds : for the 
 very minute orifices will only admit fluids of ex- 
 treme tenuity, as in the fmall veflels of the brain ; 
 while the larger will admit water and jelly ; and 
 tlie largeft of all, fat. Moreover, if a number of 
 fecretory organs arife, in fucceflion from one fecern- 
 ing artery, and be provided with large orifices, thofe 
 which arife laft from the artery will admit only 
 the thinneft fluids. If, on the contrary, thofe which 
 arife firft in order from the fecreting artery, be 
 fmail, the laft ones v/ill receive only the groffer li- 
 quids. It may be objefled, that though the veflels 
 in the foetus are vaftly lefs than in an adult, yet the 
 humours are the fame. But thefe humours, which 
 are called fat, bile, lymph, and urine, in the foetus, 
 are very different from the fat, bile, lymph, and 
 urine of an adult. 
 
 ccxviii. It is altogether in this way, that moft 
 fecrctions are made by veflels ajiflng immediately 
 
 from 
 
SECRETION. 
 
 Chap. VIL 
 
 g6 
 
 from fangiiiferous arteries (xlv.) Thefe feparate 
 grofs juices ; thick, coagulable, or watery j as the 
 fat, urine, juice of the ftomach and inteifines, &;c. 
 But other fecretions of thinner juices are perform* 
 cd by veflels ariling from the inferior orders of ar- 
 teries, not fanguiferous ; to the orifices of which, 
 not only no red blood, but no ferum, fat, or other 
 grofs fluids, can have admittance. Thus the more 
 thin and pure humours muft neceflarily be feparat- 
 ed ; as, for example, in the eye. 
 
 ccxix. Perhaps the angle, which the fecretory 
 branch forms with its trunk, contributes fom.ething 
 to fecretion. For it is eafily demonftrated, that 
 at right and reflefted angles, only the \dfcid and 
 fluggifh juices are expelled, in confequence of the 
 ftronger force of the particles keeping the middle 
 of the canal ; and that the liquids which prefervc 
 their velocity, are thofe fent off at acute angles. 
 For men of credit have obfcrved, that, in liwing 
 animals, the velocity is greater in acute angles, 
 and lefs in right angles. The very ftruclure of 
 the body convinces us, that thefe angles have 
 fomie effect on fecretion, fincc in difl'erent parts we 
 find the angles at which the branches proceed from 
 the trunks different, and the reticulations different. 
 For the ultimate veffels are, in general, arbufcular, 
 the trunks fending out branches on eveiy fide, but 
 at difierent angles ; thus, at fmall angles in the 
 larsre inteflines, and lar2;e antrles in the fmall in- 
 teftines. Thus in the fpleen, the fmallcr red arte- 
 ries arife fo tlnck from tlieir trunks, that theyre- 
 femble a fprinkler ; in the inteflines, they refemblc 
 pencil brufhes ; in the kidneys they are ferpentine ; 
 in the liver radiated ; in the tefticle, they are curl- 
 ed up like a lock of hair ; and in the uvea they arc 
 anular. But it is no improbable conjecture, that 
 the Creator never made this diverfity of fabric in 
 vain. "VVe have not as yet, however, any account of 
 thefe reticulations that is fulEciently accurate ; nor 
 
 docs 
 
Chap. VII. 
 
 SECRETION. 
 
 97 
 
 does a fimilarity in the fluids fecreted feem to be 
 connefted with a fimilarity of ftrufture. The veins 
 too have fimilar reticulations, for the purpofe of fa- 
 cilitating the motion of the blood, and not for di- 
 verfifying the nature of the fecretions. 
 
 ccxx. The inflexions of the fmaller veiTels, as 
 well arteries as excretories, greatly retard the mo- 
 tion of the blood ; in which the greater part of the 
 force received from the heart is evidently fpent in 
 the change of figure in the veflel. The repeated 
 inflexions, therefore, of the fecretory arteries colleX 
 the vifcid parts of the fluids, by giving them time 
 to attraX each other. A ftrais^ht courfe of the vef- 
 lels is favourable to celerity of motion, rendering 
 the fecretion copious and eafy, but impure, as we 
 fee in the urine. 
 
 ccxxi. That the ultimate arteries, and in like 
 manner the fecretory orifices, have different degrees 
 of denfity, is not improbable, fince we aXually find 
 it fo by experiments in the larger branches. But 
 the denfer the capillary arteries are, the more will 
 they adm.it only the ftrong, and at the fame time 
 minute particles, and exclude thofe that are lighter, 
 moved with lefs velocity, and groffer. Irritability 
 produces almoft the fame effeXs j for if the fecre- 
 tory orifice be irritated, it will rejeX the grofs hu- 
 mours, and tranfmit the more fluid ones : inftead 
 of mucus in the urethra, it will feparate a thin yel- 
 low ferum ; and a fimilar fluid, inftead of the fub- 
 cutaneous fat : the quantity of fecreted liquor will 
 alfo be increafed ; as, for example, in the tears. 
 
 CCXXI I. Laftly, the velocity is greatly increafed, if 
 the heart be near, if the artery be ftraight, if it go off 
 at a fmall angle, or if the excretory duX arife near 
 the extremity of a confiderable arterial branch. 
 The velocity is diminifhed, if the fecreting artery 
 run a long way capillary, loofing the greater part of 
 the motion of its blood, from friXion, if it arife at 
 a diftance from the heart, and at a large angle. 
 
 H Finally, 
 
SECRETION. 
 
 Chap. VR. 
 
 Finally, from whatever caufe the dlverhty may pro- 
 ceed, an increafe of velocity increafes the quantity of 
 fluid fecreted, carries off the heavy liquids, and ren- 
 ders the fecretions thicker and more impure, though 
 fluid, as it prevents llagnation, by which they con- 
 tract vifcidity ; but flownefs facilitates attraction 
 and vifcidity, and renders the fecreted juice more 
 pure ; as the fimilar particles, when brought togeth- 
 er, can better attraft and join each other, under a 
 flow motion, fo as to retain the larger canal, while 
 the thinner parts go off by the leffer lateral branch- 
 es. Hence, from the impetus of the heart alone 
 being too much increafed, all the fecretions become 
 confounded. 
 
 ccxxiii. Thefe conditions, nature is able vari- 
 oufly to unite or feparate, and to impart to each or- 
 gan, in greater or lefs degrees ; and thus, to modi- 
 fy the fecreted humours in various vuys. Anat- 
 omy furnifhes examples, if you compare the fecret- 
 ing apparatus of the bile or femen, which are thick 
 juices, v/ith thofe of the urine and tears, whicli are 
 fluid ones, 
 
 ccxxiv. From all that has been advanced, we 
 may perceive, that, fince the blood contains parti- 
 cles of various kinds ; tome fluggifla and mucous j 
 fome coagulable, but fluid ; fome denfe and red ; 
 fome watery and thin ; and others fat and aufeid 
 (cLxxxviii, et fcq.') among all thefe particles, thofe 
 which are the iai'geft and moll denfe, fuch as the 
 cruor, will continue in the axis of the veffel, and 
 in the trunk, fo as to pafs on in a continued courfe 
 into the fanguiferous vein (xxxix.) 
 
 ccxxv. Ihofe particles which are grofs and fiug- 
 gifh, fuch as the fat, muft go off by the larger ori- 
 fices ariling laterally from the fanguineous arter^g 
 by fhort dufts ; for in long dufts the oil would 
 ftagnate, from its fluggiflmels. The phenomena of 
 the fecretion of fat (xix.) agree with this deferip- 
 tlon. Such as are coagulable, but fpecificaily heav- 
 
Chap. VIL 
 
 SECRETION. 
 
 99 
 
 rer than thofe which are merely watery, and which 
 continue fluid in the living animal, pafs from the 
 red arteries, into others which are pellucid, but con- 
 tinuous to the red ones, and fmaller ; whether thefe 
 pellucid ones be continued on as trunks, fending off 
 other fmaller branches, fuch as the arteries of the 
 inferior orders (xli.) or whether they exhale 
 their contents by a fliort extremity, like the vefl’els 
 of CLXX. 
 
 ccxxvi. Thin watery fluids may evidently pafs 
 off by any veflels continuous with the fanguiferous, 
 or inferior orders of velfels (xliv.) provided they 
 be only fmail enough to exclude the grofler juices : 
 whether thefe proceed from the fldes of the larger 
 veflels ; or whether all the proper fluids being fent 
 Oif through the larger canals, the fmaller canal be 
 continued as the trunk, as in the eye. To the pro- 
 dudlion of thefe fluids, the moft Ample fabric, even 
 the direct continuation of the fecretory artery itfelf 
 into the excretory du£l, is fuflicient, as feems prob- 
 able in the urine. Therefore, in this cafe, the 
 ftru6ture is direct and Ample, with few infle<3:ions, 
 and with little diminution of velocity. 
 
 Such juices as, being watery^ are lights but vif- 
 cid at the fame time, and confequently fluggifli 
 and tardy, efcape eafily by fliort tubes append- 
 ed to the fanguiferous arteries, and lefs than the 
 adipofe veflels ; and, therefore, it is evident, that 
 thefe will be feparated from the blood more abun- 
 dantly in fome parts of the body, where the veloc- 
 ity derived from the heart is lefs, the flexures of 
 the artery more frequent, and the length of the ca- 
 pillaries greater. 
 
 cc XXVII. Has each part its particular ferments, 
 form of pores, fpeciAc weight, and Alters Ailed 
 with their own peculiar humour, and refuAng what- 
 ever is not analagous to it, which determine the 
 nature of the fluids to be generated? Let thofe 
 who adopt thefe ideas, conAder the great varieties 
 li 3 there 
 
foo 
 
 SECRETION. 
 
 Chap. VIT. 
 
 there are in fluids, feparated in the fame part of the 
 body, according to the difference of age, courfe of 
 life, &c. In the foetus, the bile is fweet ; the fe- 
 men thin, and without animalcules ; the milk wa- 
 tery or abfent ; the urine watery, mucous, and in- 
 fipid ; the uterine mucus very white ; the cuta- 
 neous velfels full of a red fluid ; the aqueous hu- 
 mour red ; and the fat gelatinous. In the fame or- 
 gans, in an adult perfon, the bile fecretcd is acrid ; 
 the femen thick ; the milk but)Taceous ; the urine, 
 yellow, tiiin, and aikalefcent ; the menftrual blood, 
 and the aqueous liumour, very limpid. But, even 
 in the adult perfon, how different the aqueous urine, 
 the concocted urine, and the heavy febrile urine, 
 replete with falts and oils ? The paflions of the 
 mind, v/hich make no change in the body except up- 
 on thetenflon of the nerves, yet wonderfully change 
 the fecretions, and expel even the blood and bile 
 tlirough the velfels of the flein. Add to this, the 
 frequent diflurbance and alteration of the fecre- 
 tions from flight caufes ; fo that, different augmen- 
 tations of velocity fltall caufe different liquors to be 
 fecreted by the fame organ : for blood has been 
 laiown to pafs into almoll all the paffages of all the 
 fluids ; of the fweat, tears, mucus of the noftrils, 
 and of the womb, milk, femen, urine, and fat. A 
 true milk has been feen feparated by glands in 
 the thig;h. VvTien the urine is not excreted, on ac- 
 count of fome dcfecl of the kidneys, ureters, or 
 bladder, it has been exhaled into the fkin, ventricles 
 of the brain, or into the whole cellular fabric. The 
 pcrfpirable matter of Saneforius, though fo fluid, 
 by cold is fent off by the urinary paflages ; and by 
 fear, or by medicines, through the excretory' villi 
 of the inteftines. That exhalin<x A'ifcid matter of 
 the celluiar fubftance is fecreted and abforbed, and 
 by the fame organs, alternately with the fat, fo dif- 
 ferent from it (xviii.) Salivation fupplies the 
 place of the exhaling fluid of Sanctorius, the cxhal- 
 
Chap. 
 
 SECRETION. 
 
 loi 
 
 ing fluid fupplies the internal. The bile, when 
 abforbed, evidently pafles into the vefl’els of the 
 eyes. It appears, that there is not any thing in the 
 particular fabric of any of the vifcera or glands, 
 that can fo fix or maintain the nature of the fectet- 
 ed fluid ; that in perfectly entire organs, different 
 fluids may not be feparated, by an increafe or di- 
 minution of velocity, or alteration of the ftricture 
 of the nerves. The fpecific gravities of the vifcera 
 and ftrainers do not correfpond, even according to 
 their authors, to the fpecific gravity of the huiuour^ 
 which they fecrete ; nor are they at all known by 
 experiments that can be depended on. 
 
 ccxxviii. It now remains for us to diicover, how 
 the pure fecretions are formed in a healthy perfon. 
 For aU the fluids, when recently fecreted, without 
 excepting any, not even the oil, are mixed v/ith a 
 great deal of water ; nor does it feem pofllble, that 
 any of the thicker juices could be formed, without 
 having a mixture of the thinner ones : how then 
 do the femen, bile, oil, and mucus, get rid of their 
 fiaperabundant water, and acquire their proper vif- 
 cidity and other qualities ? 
 
 ccxxix. For this end, nature has framed glands 
 and follicles, large and fmall, for thoie fluids from 
 which the watery paits are to be feparated, in or- 
 der to render the remaining part more ftrong and 
 vifcid. A flightly mucous water, differing at firfi: 
 very little from the perfpirable vapour or from tears, 
 is depofited in the follicles of the noftrils, windpipe, 
 and inteftines. This is not continually difcharging, 
 becaufe the excretory orifice being lefs than the 
 follicle (cxcvi.) and the excretory duct being 
 fometimes long and flender, at others repeatedly 
 bent, and inffecied or tranfmitted through hard 
 cellular texture, or clofed by fome force equivalent 
 to a fphincter, the fluid is fo retarded that it can 
 fcarcely efcape without tlie afliftance of extrinfic 
 preflure j unlefs perhaps the follicle being irritated 
 
!02 
 
 SECRETION. 
 
 Chap. VIT. 
 
 by its quantity or acrimony, prels out the liquor 
 incommoding it, by a kind of periftalic motion. 
 I’his appears from the miorning difeharges of mu- 
 cus by blowing the nofe, coughing up from the 
 lungs, and by fneezing after the nocturnal ftagna- 
 tion. In the mean time, the patulent veins, ex- 
 tended into the cavity of the follicle, abforb the 
 more aqueous parts from the thin mucus, fo that it 
 becomes thicker as it is retained longer ; but if, by 
 the force of fome ftimulus, it be directly difeharg- 
 ed after it is fecreted, it comes out thin and wa- 
 tery. Examples of this we have in the urethra, 
 in the noftrils, and in the earwax ; as alfo in the 
 bile, which, at its firft feparation in the liver, is 
 ■watery, and has but little yeUownefs or bitternefs. 
 It is therefore detained in a bladder, and there 
 digeiled by the vital heat ; its thinner parts are 
 abforbed by the veins, or exude through the mem- 
 branes themfelves ; whence the remainder becom.es 
 more thick, bitter, and oily. The fame mechanifm 
 takes place in the femen ; which, being preferved 
 in the feminal velicle, is there thickened, fo as to 
 be very vifeid after long chaftity ; while after re- 
 peated venery it is expelled very fluid. In fome 
 places nature has made this recepticle double or 
 triple in the fame organ, that tlie fluid might at- 
 tain the utmoft degree of vifeidity. In the femi- 
 nal palTages, the rete teftis and termination of the 
 epididymis, confrirute a large canal, and a large 
 veiicle ; while the vefleis of the teflicle, vas deie- 
 rens and proflate dudl, are narrow. Hence there 
 are ncw'here real glands, except for fecreting a vif- 
 eid liquor. And if a vifeid liquor be feparated 
 from arteries without a follicle, it always ftagnates 
 in fome conflderabie follicle. The femen, bile, 
 liquor of the joints, and fat, afford examiples of 
 this, 
 
 ccxxx. The fluids may be likewife changed in 
 their receptacles by the afluflon of fome new li- 
 quor. 
 
Chap. VH. 
 
 SECRETION. 
 
 103 
 
 qnor. Thus the femen is thickened by the addition 
 of the liquor of the proilate ; the chyle is attenua- 
 ted by mixture with the faliva of the pancreas and 
 the gaftric and inteftinal juices, and by theaffuHon 
 of the bile it becomes alkaleicent ; the albumen 
 of the joints is tempered by the tvco kinds of fat 
 (cxcv.) 
 
 ccxxxi. Laftly, what is abforbed, may have its 
 ufes in the animal economy, after it is taken into the 
 blood ; thus the femen gives a furprifing ftrength 
 to male animals. For the moft part, likewife, in 
 fluids which are detained, an acrimony of an al- 
 kalefcent nature is generated, which alfo hath its 
 ufes, as in the bile and femen. 
 
 ccxxxii. But the moft important ufe of the 
 follicles and receptacles is to preferve their peculiar 
 fluids, for thofe times in which alone they are fubfer- 
 vient to life, and that a large quantity of them may 
 be collected to correfpond with their ufes at certain 
 periods. Thus the bile is referved for the time of 
 digeftion, the femen for due venery, and the mu- 
 cus of the noftrils is accumulated in the night to 
 moderate the force of the air palling through them 
 in the day. 
 
 ccxxxiii. Therefore, as nature has framed ma- 
 chines which retard the fluids in large or fmall 
 follicles, fo flie has made others to expel them at 
 proper times. To fome glands fhe has given par- 
 ticular mufcles ; as in the tefticles of brutes, the 
 urinary bladder, and the gaU bladder, and in the 
 inteftines, and ftom.ach *, or flie has fubjoined 
 contiguous mufcles to promote the difcharge, as 
 the biventer, malfeter, mufcles of the abdomen 
 and diaphragm ; or elfe Ihe has given them a kind 
 of nervous irritability, which, being excited to 
 aftion by an indefcribable ftimulus, opens the Ihut 
 paflages to the milk, femen, tears, &c. or from 
 the contact of any thing acrid, as already mention- 
 ed, accelerates the difcharge of the fluid ■, as hap- 
 pens 
 
RESPIRATION. 
 
 104 
 
 Chap. MH. 
 
 pens to the bile, liquor of the ftomach and intef- 
 tineSj and to the febaceous matter. 
 
 CHAP. vni. 
 
 RESPIRATION. 
 
 ccxxxiv. p ’TIE bags of the pleura (lxxvii. 
 
 Lxxviii.) are fiUed by the lungs ; by 
 which we underhand two vifcera, one right and 
 another left, in figure correfponding with the bags 
 themfelves which they fill, having a broad balls 
 below, and being terminated above at the firft rib 
 by an obtufe cone. Anteriorly their furface is flat, 
 laterally convex, and pofterioiiy it is rounded ; in- 
 ternally it is concave, efpecialiy that of the left 
 lungs, for the purpofe of containing the heart. 
 The right lung is the largeft, and is moft frequent- 
 ly divided into three lobes ; which is feldom the 
 cafe with the left. They are freely fufpended by 
 the great blood-vcffels ; unlefs you call that a liga- 
 ment which is formed at the bafis of the dia- 
 phragm by the external membrane of the pleura 
 going off to the lungs. Between the lungs and 
 pleura is found a watery vapour, of a coagulable 
 nature, like that of the pericardium (lxxxii.) 
 which tranfudes from the lurface of the lungs and 
 of the pleura, continually in the foetus, and not un- 
 frequentlp in the adult. In dropfy, this vapour 
 is increafed, or thickens to a kind of febaceous 
 matter ; or, iaftly, it concretes into fibres, forming 
 adiiefions of the lungs. 
 
 ccxxxv. The external membrane of the lungs 
 is fimple, and thinner than the pleura, although 
 continuous with it. It fprcads, from the adiiellon 
 of the great blood-vefiels of the heart, over the 
 lungs in every direction, and, when entire, may 
 be eafily inilated, even after being feparated from 
 
Chap. Vm. 
 
 RESPIRATION. 
 
 105 
 
 the lungs. The fame membrane paffes over the 
 intervals between the lobules, like a bridge. It is 
 joined to the lungs by cellular texture. 
 
 ccxxxvi. The lungs are made up of lobes fepa- 
 rated by intermediate intervals, in which there is 
 loofe cellular fubftance. Their firft divifion is in- 
 to two large lobes, and one middle one of a fmall- 
 er fize ; which, however, cohere together : they 
 are afterv/ards repeatedly fubdivided into fuccef- 
 fively fmaller lobes, always furrounded by cellular 
 membrane, till at lad the lobules are refolved into 
 very fmall membranous cells, which, in adults, are 
 filled with air, are of various figures, and com- 
 municate on aU fides with each other. The ele- 
 mentary parts of the lungs, therefore, are not oval 
 bags, furrounded by mufcular texture, with a fin- 
 gle orifice which receive the air from the windpipe, 
 but they admit the air exhaling from the ultimate 
 branches of the trachea, fo that being effufed into 
 irregular fpaces, it paffes and repaffes freely from 
 any one portion of the lungs into all the others. 
 This is demonftrated by inflation, for air blown 
 into any, even the moft minute lobule, through its 
 branch of the trachea, paffes into all the reft. In 
 man and in the fmaller animals, the cellular fabric 
 of the intervals is neither fhut up from the veficies 
 of the lungs, nor are the lobes furrounded by- any 
 peculiar membrane •, in the largeft animals, there 
 is no communication between the air veficies and 
 the cellular fpaces which furround the lobules. 
 
 ccxxxvii. The air paffes into thefe veficies 
 through the windpipe. The windpipe arifes from 
 the larynx (hereafter to be defcribed,) and receives 
 the air through it alone. Its firft part fingle and 
 fimple, partly flefliy and partly cartilaginous, the 
 cefophagus lying below it and to its left, is fup- 
 ported on the broad and flat vertebrs of the neck ; 
 in other vcords, within the cellular fubftance that 
 
 furrounds 
 
Iq6 
 
 RESPIRATION. 
 
 Chap. VTIT. 
 
 farrounds the v.dndpipe, there is fituated a canal, 
 compofed of alternate cartilaginous and mufcular 
 rings. The cartilaginous rings, thin and elaftic, 
 anteriorly fomewhat fiat and thick, are joined to- 
 gether by their pofterior extremities, which are 
 thinner ; and the cirple is completed by ftrong tranf- 
 verfe mufcular fibres, adhering to both the loofe 
 extremities of the cartilage. The lower circles arc 
 lefs ; the uppermoft is often augm.ented by an ap- 
 pendix, that next to the divifion is perpendicular. 
 
 ccxxxviii. The flefhy rings, fituated alternately 
 with the cartilaginous ones, are compofed of red 
 mufcular fibres. Some of thefe are tranfverfe, con- 
 nefting the detached ends of the annular cartil- 
 ages 5 others defeend from each upper to the next 
 lower ring. But other mufcular fibres again, de- 
 feend from the cricoid cartilage, and having reach- 
 ed" below the divifion of the bronchia, vanifh upon 
 the lungs. The tranfv'erfe fibres contract the 
 windpipe ; the longitudinal ones fhorten it. 
 Within the lungs, between the imperfect rings, 
 there is a fort of mufcular fabric, but lefs uniform- 
 ly difpofed. 
 
 ccxxxix. In the cellular coat which furrounds the 
 mufcular one, but efpecially behind, in the inter- 
 val between the cartilages (ccxxxvi.) are placed 
 numberlefs fimple glands, which, by very fnvall 
 ducts, like pores, opening into the ca\dty of the 
 windpipe, depofitc within that cavity a watery 
 and pellucid mucus, not coagulable into films, and 
 xery bland, which is of the greatefl ufe in defend- 
 ing the exceedingly fenfible membrane from the 
 impurities of the air, which is loaded with particles, 
 irritating by their mechanical figure or chemical 
 acrimony. Numerous conglobate glands are fitua- 
 ted around the trachea and its bronchia, but thefe 
 are of the lymphatic kind, although their black 
 fluid frequently penetrates into the trachea, l.aft- 
 
Chap. VIII. 
 
 RESPIRATION. 
 
 loy 
 
 ly, the internal tube of the windpipe is lined by a 
 membrane, covered by epidermis, continuous with 
 the fidn and miembranes of the mouth, fmooth, 
 foft, and very irritable. It is connected with the 
 mufcular coat by cellular fubftance. 
 
 ccxL. The veffels of this entire part of the 
 windpipe, in the neck, come from the lower thy- 
 roids ; in the thorax, from other fmall branches 
 of the fubclavian trunks, or the mammaries, or the 
 bronchials properly fo called. Its nerves, ariling 
 from the recurrent and intercoftals, are numer- 
 ous. 
 
 CCXL I. In the upper part of the thorax, the 
 windpipe is received between the laminse of the 
 pofterior mediaftinum ; and at the third vertebra, 
 or a little above, is divided into two branches limi- 
 lar to the trunk, formed in like manner of imper- 
 fect cartilages, and furniflied with limilar glands ; 
 each of thefe enters the lung to which it corre- 
 fponds, and the right is fomething Ihorter and larg- 
 er than the left. Having entered the lungs, the 
 cartilaginous rings gradually degenerate into frag- 
 ments, become more difform, gnomonic, angular, 
 triangular, and intermixed with a larger portion of 
 membrane, till at length, by the diminution of the 
 cartilages, the ultim.ate branches of the bronchia 
 become membranous. 
 
 ccxLii. Its ultimate branches are invilible, and 
 exhale air into the cellular fpaces of the lungs in 
 adults, and from the fame fpaces receive the arterial 
 expired vapour. 
 
 ccxLiii. The veffels of the bronchia, are the 
 bronchial veins and arteries. The latter are gen- 
 erally two ; one coming from the upper intercof- 
 tal of the aorta, which is diftributed either to the 
 right only, or to both the lungs ; the other, from 
 the trunk of the aorta, goes to the left lung. Some- 
 times there are m.ore ; as when there are three, by 
 the addition of a fecond from the aorta. At other 
 
 tiinesj 
 
RESPIRATION. 
 
 Chap. VIH. 
 
 loS- 
 
 times, there is only one artery common to both 
 lungs. The thoracic part of the bronchia, fituated 
 without the lungs, has its proper veffels from the 
 ao.rta, or from the fubclavian, or the mammary, 
 or the intercoftal. The bronchial veins are very 
 commonly two ; the right from the vena azygos, 
 the left from a peculiar branch of the fubclavian 
 vein, the left faperior intercoftal. Thefe blood- 
 veffels accompany the branches of the trachea ; and 
 defcend into their membranes, the arteries inofcu- 
 late with the pulmonary arteries, and the veins with 
 the veins, forming a vafcular web in the internal 
 cellular fubftance. There are forne inftances where 
 the pulmonary vein itfelf has given fmall branches 
 to the lungs, to the windpipe, and to the furface 
 of the lungs. 
 
 ccxLTv. But there are other largrer veffels belone:- 
 ing to the lungs, the pulmonary artery (cvi. cviii.) 
 and the vein (cx.) The great artery, in the foetus 
 larger than the aorta, and in the adult but little 
 lefs, has two branches ; the right lai'ger but Ihorter, 
 the left narrower and longer. In the foetus, the 
 trunk itfelf is continued into the defeending aorta, 
 and is known by the name of duclus arteriofas. In 
 the adult, that trunk degenerates into a folid liga- 
 ment. The four pulmonary veins accompany the 
 branches of the artery and of the trachea, through 
 the lungs, fiarrounded by a good deal of cellular fub- 
 ftance ; which fubftance, being increafed, at laft 
 compofes the lungs themfelves. Witlftn this cellular 
 fabric, the air-veff'els and blood-veffels are fubdivid- 
 tsd, and in the ultimate cellular fpaces, the ultimate 
 veins and arteries fpread, reticularly interwoven ; 
 and here the fmall arteries exhale a plentiful vapour 
 into the aerial cells of the lungs, and the veins ab- 
 forb a watery vapour from them. Hence coloured 
 v/ater, the whey of milk, or thin wax, being inieef- 
 cd into the pulmonary artery, flow' with troth into 
 the windpipe 5 or, on the contrary, penetrate from 
 
Chap. VIH. 
 
 RESPIRATION. 
 
 tog 
 
 the bronchia into the ptilmonary artery. In like 
 manner, injedions pafs from the pulmonary vein 
 into the bronchia ; or from thence, into the veins- 
 Laftly, they readily pafs from the arteries into the 
 pulmonary veins j or return from the veins into the 
 arteries. 
 
 ccxLv. The lymphatic veffels, as in other parts, 
 form a network upon the furface of the lungs, 
 from whence branches run to the cavity of the 
 pofterior mediallinUm, to the glands feated on the 
 cefophagus, and to the thoracic dud. The nerves 
 are fmaJl, efpecially the anterior, the pofterior ones 
 being fomewhat larger : they come from a nerve 
 of the eiglrth pair ; but they receive fome addition, 
 accompanying the large blood- vefiels, from the re- 
 current, and likewife from the cardiac plexus. 
 Hence the lungs have but little fenfation ; but that 
 of the little nerves, divided upon the fubftance of 
 the bronchia, is very acute. Nor are the lungs of 
 an irritable nature. 
 
 ccxLvi. The quantity of blood which enters into 
 the lungs is exceedingly great, equal to (or even 
 perhaps greater than) that which is fent in the fame 
 time throughout the reft of the body ; which, there- 
 fore, indicates this vifcus to be fubfervient to fome 
 very important purpofe. That this ufe depends 
 manifeftly upon the air, appears from the univerial 
 confent of nature, in which we fcarcely find an ani- 
 mal which does not refpire ; alfo from the ftrudure 
 of the lungs in the foetus, in which being ufelefs, 
 on account of the abfence of air, they receive only 
 a very fmall portion of that blood, which the pul- 
 monary artery conveys from the heart. We come. 
 Therefore, to ipeak of refpiration, or the inhalation 
 and expulfion of air by the lungs. 
 
 ccxLvii. Air, phyfically confidered, is an ele- 
 ment, fluid, invifible, elaftic, with an indeftrudible 
 fpring, and foniferous. But the air, which we com- 
 monly receive into the lungs, is impure, fiUed with 
 a great quantity of watery and other vapours, alfo 
 
 with 
 
tio 
 
 RESPIRAllOI'T. 
 
 Chap. \TII. 
 
 wth falls, and the univerfal acid, with the feeds* of 
 |jlants and animals, and other foreign particles ; and 
 is ponderous *, weighing, however, 8 50 times lefs 
 than water, a cubic foot of air being between 610 
 and 694 grains. This air, which furrounds the earth 
 on all lides, being compreiTed by its incumbent col- 
 umns, perpendicularly and laterally, enters with 
 great force wherever it meets with lefs reirftance, 
 as appears from experiments made in vacuo, and 
 from the phenomena of the air-pump ; fo that its 
 preillire on the human body is not lefs than 30,000 
 pounds. It is repelled chiehy by the pores of mem- 
 branes, though thefe are permeable by water ; it 
 likewife penetrates oil or mucus with difficulty. 
 
 ccxjLviii. The ambient air is excluded from all 
 parts of the human body, by denfe Ikin, which, 
 even when dry, is impervious to the air ; by the fat 
 lying under it ; by the narrownefs of the abforbent 
 yeffels, and by the equability of the refiftance. We 
 muft inveftigate why the air enters the lungs, which 
 in an adult are always filled with air, and therefore 
 refill the prefiure of the whole atmofphere with an 
 equivalent force. That' the lungs always contain air, 
 is e\ddent ; becaufe, however you comprefs them, 
 they are ftill lighter than w*ater ; and even after 
 they have been inflated but a few times, they always 
 fwim ; whereas, in the foetus, before air has been 
 admitted into them, they fink to the bottom. 
 
 ccxLix. On the equilibrium being deftroyed, the 
 air invariably defeends in ev^ery direction to that place 
 where it meets with kail refiftance (ccxnvii.) But 
 air that is denfe and heaay defeends more eafily 
 than that which is light, whofe force fcarcely ex- 
 ceeds that of the air in the lungs, nor is able by the 
 fame force to overcome the refillance of the bron- 
 chia, and of the force by which the air contained 
 in the lungs is compreiTed. Hence an animal lives 
 with greater eafe in a denfe than in a light atmof- 
 phere : although that air is alwavs better tolerated. 
 
 wluch 
 
Chap. VIII. 
 
 RESPIRATION. 
 
 iij 
 
 which is pure in proportion to its levity ; fuch as 
 that of the higheft mountains of the Alps. There- 
 fore, that the air may enter the lungs, they muR 
 make a lefs refiftance to it than before ; namely, 
 the air, wfiich is already in the cellular fabric of 
 the lungs, muft be rarefied : but this effeft will be 
 produced, if the cavity of the breaft, which is filled 
 by the lungs, be dilated. The air, which is always 
 in the lungs, expands into this increafed fpace, by 
 which, being weakened in its fpring, it makes lefs 
 refinance to the external air ; confequently a por- 
 tion of external air defcends into the lungs, fuffi- 
 cient to reftore to the air, now contained in the 
 lungs, the fame denfity with that of the external 
 air. 
 
 ccL. We muft, therefore, defcribe the powers 
 \yhich dilate the breaft. The breaft or thorax is 
 compofed of bones, mufcles, and cartilages ^ being 
 almoft of the Ihape of an elliptic barrel, fomewhat 
 comprefled before, but behind divided by an emi- 
 nence, whofe hoops are the ribs, and of remarkable 
 ftrength. In the lateral parts of this ftruclure, tlie 
 lungs are fituated ; the central and lower parts con- 
 tain firft the pericardium, and then fome of the 
 abdominal vifcera. 
 
 ccLi. The bafis of the thorax is formed by a 
 column, a little curved, at the upper part gibbous 
 backwards, fo that its fummit is fituated moft be- 
 hind. To this twelve vertebrae are affixed. But 
 they alfo coalefce, by the union of their bodies into 
 a fingle column, which projefts forwards between 
 the two cavities of the breaft ; divides the right 
 from the left ; and is plain in the forepart, and 
 broad towards the fides. A flight finuofity receives 
 the ribs into that place where the arch feparates 
 from the body. They are bound together into one 
 column, both by the elaftic plate interpofed be- 
 tween the bodies of every two, and coalefcing with 
 both ; and by other ligaments and fpines lying up- 
 
RLSPIRATIOI^. 
 
 Chap. YUl, 
 
 it2 
 
 on one another, and by the junclion of the ribs ; 
 on which accounts they fcarcely admit of motion 
 amongft themfelves. The fides of the brcaft are 
 formed of twelve ribs. Thefe are in general bent 
 in the form of an irregular arch, having a conlider- 
 abie curvature laterally and backwards, but extend- 
 ing in their forepart towards a right line. I'he 
 bony parts of the ribs are, however, parallel with 
 each other. The greateft part of the rib is bony ; 
 of which the pofterior portion is round and thick, 
 and the anterior thin and flat. The anterior remain- 
 ing part of the rib confifls of a cartilage ; which in 
 general preferves the ligure of the rib, broad, flat, 
 adhering to an irregular hoUow of the bony part ; 
 and which does not change into bone, unlcfs in ex- 
 treme old zg;e. 
 
 ccLii. The poflerior, bony, and thick part of 
 each rib terminates in a head. Thefe are inferted 
 into pits fcooped out of the bodies of the upper- 
 moft and two iowermoft vertebrae, and in the con- 
 tiguous margins of each of the other two. The 
 vertebrae are tied to the ribs by flrong ligaments, of 
 which the principal is diftributed upon each adja- 
 cent vertebra, in a radiated manner from each rib ; 
 other ligaments tic the tranfverfe procefs to the tu- 
 bercle of the rib, and others connect the contiguous 
 ribs, and alfo the tranfverfe procefles, with each 
 other. Moreover, between the angle of incurva- 
 llon and the articulation with the vertebrae, each of 
 the ten upper ribs has a tubercle, wliich, being con- 
 nefted with the plain fide of the tranfverfe procefs 
 of the correfponding vertebra, are tied by fiiort and 
 flrong ligaments to that procefs, in fuch a manner, 
 that, w'hilc the juncture is very flrong, the rib can 
 afeend and defeend for a fliort way. 
 
 ccLiii. Of the anterior cartilages, the feven upper- 
 iTiofl; reach to the fternum,andfl;rengthcncd hy Ihort 
 ligaments, they enter with a double head into lateral 
 dcpvcflions in that bone, which are incrufled with 
 
 cartilage. 
 
Chap. VIII. 
 
 respiration. 
 
 1^3 
 
 cartilasce. Of the five remainins: ribs, the ucner- 
 moft is agglutinated by Rrong cellular fubftance to 
 the ieveii!:h, and each lower one to the one imme- 
 diately above it, fo t-hat they form a continuous 
 margin, which is itfelf faiiered to the fternurn. 
 The cartilages are connected with each otheiv both 
 by proper ligaments, and by cartilaginous appen- 
 dages joined by cellular fubftance: the two low-er- 
 moft are free, and connected only with the muf- 
 cles. Thefe inferior cartilages are united to one 
 another and to the fternum by ftrong ligaments. 
 ccLiv. The firft rib is the ftiorteft and moft Iblid. 
 
 As they follow in ftacceilion to the feventh and 
 eighth, every two of them form larger and more 
 moveable circles. The eighth is the longeft of all ; 
 and below it, they always become Ihorter, the 
 lower they are. 
 
 ccLv. The upper rib defcends ; the fecond joins 
 the fternum alrnoft at a right angle, while the 
 others afcend both to the vertebrae and to the fter- 
 tium, but more to the latter. The bony part or 
 the ribs is placed in fiach a direftionj that the up- 
 permoft have their anterior furface declined for- 
 wards, alrnoft tranfverfely. About the third rib 
 it is placed alrnoft perpendicularly ; and below' the 
 middle ones, it prcjecls a little forwards. Eefides, 
 the ftrength of the ribs is very different. The'up^ 
 permoft, being lliort, tranfverfe, rather united than 
 articulated with the fternum, and, laftly, often con- 
 folidated, make the greateft reftftance. Tlie mo-* 
 bility of the lower ribs increafes fucceffively to the 
 loweft, which, adhering only to mufdes, moves 
 moft freely of ail. 
 
 ccLvi. The fternum in general is a thin fpongy 
 bone, in adults of a fmgle piece, but in the f-retus 
 varioufly multiplicate. Its upper part is broader, 
 oefagonai, and ftipported by the cla’N ides, vchich 
 are united with it by a triangular head, and very 
 ftrong articulation, and by the firft rib cn each fide. 
 
 I 
 
RESPIRATION. 
 
 Chap. VUE 
 
 II 4 
 
 The next part which is longer and narrower, grows 
 broader downwards, and its lides receive the ribs 
 into proper angular cavities. The lower part, 
 which is iefs and Ihorter, is obtufely fliaped like a 
 tongue. This is continued into a detached appen- 
 dage, partly bony, and partly cartilaginous, which 
 is called the enliform cartilage ; of various Ihapes, 
 being foinetimes obtufe like a little tongue, fonie- 
 times pointed, fometimes bifid, and foinetimes per- 
 forated. 
 
 ccLvii. In order, therefore, to dilate the feat of 
 the lungs, and thus to produce that condition which 
 caufes the external air to defcend into the lunjis, 
 the thorax muft be elevated. For thus all the fec- 
 tions of the thorax form right angles, and its ca- 
 pacity is increafed. This motion is performed by 
 various mufcles, v.'hich either operate conftantly, 
 or only at certain times. The whole of the in- 
 tercofial mufcles, always elevate the ribs. Under 
 this name we comprehend 22 mufcles; of which 
 1 1 are external or I'ubcutaneous ; and as many in- 
 ternal, leparated from the pleura only by fat and 
 cellular fubfiance. The origin of the external in- 
 tercoilals is at the pofterior articulation of the ribs 
 (ccLii.) their anterior termination is in the bony 
 part of each rib, at fame diftance from the carti- 
 lage, fo that the remaining fpace between the car- 
 tilages, all the way to the fternum, in place of the 
 mufcles, is filled with an aponeurofis. Their di- 
 recfion is fuch, that they defcend obliquely for- 
 v/ards, from the lower edge of the upper rib to the 
 upper edge of the lower rib. Almoft all authors 
 agree, that they elevate the ribs ; becaufc they de- 
 fcend from the upper and more fixed, to the lower 
 and more moveable rib, in fuch a manner, that 
 their lower point lies more diftant from the verte- 
 bral articulation, or fulcrum of the lever of the 
 ribs. 
 
 ccnviii. 
 
RESPIRATION. 
 
 Chap. VIIl. 
 
 
 ccLviii. But the internal intercoftals arife at 
 fome diftance from the vertebrse, near the on tilde 
 of the tubercles (cclii.) From thence they pro- 
 ceed as far as the fternum., into which the firfc of 
 this kind are inierted above. Except the anterior 
 part of the firft internal mufcles, their direction is 
 contrary to that of the former ; fo that they de- 
 fcend backwards, from the lower margin of the up- 
 per rib, to the upper edge of the lower rib. There- 
 fore their action is difputed, becrmfe their lower 
 infertion is made into a point of the rib, nearer its 
 articulation with the vertebras, which, therefore, 
 feems to be the leaft moveable : however, they el- 
 evate the ribs notwithftanding this ; for the immo-* 
 bility of the upper rib, arihng from its articulation, 
 weight, and ligaments, far exceeds the mobility 
 produced by its greater diftance from the fulcrum. 
 This is proved by the difledtion of living animals ; 
 in which it appears, that the internal mufcles act 
 during the elevation of the ribs, and reft when 
 they are dcprefled ; by threads fixed to a flexible 
 human Ikelcton, and drawn in the direction of the 
 internal intercoftal mufcles, which always and in- 
 variably raife the inferior rib towards the fuperior ; 
 and by the firmnefs of the upper ribs, which ferve 
 as a fixed point to the lower ones : for the firft ribs 
 are from eight to twelve times lefs moveable than 
 the other true ribs ; while the difference of diftance 
 from the centre of motion, is fcarcely the twentieth 
 part of the whole lever. And laftly, by experi- 
 ment on the dead fubjeft ; for, on raifing its tho- 
 rax, the internal intercoftals fwell. 
 
 ccLix. By the action, therefore, of thefe mufcles, 
 the thorax is elevated, not altogether as one ma- 
 chine, nor would refpiration be aflifted by fuch a 
 motion ; but the ribs, turning upon their articu- 
 lations, behind are but little moved, while with 
 their anterior extremities, they defcend and form 
 larger angles both with the fternum and vertebne ; 
 
 J 2 .and 
 
ti6 
 
 RESPIRATION. 
 
 Chap. Vllt 
 
 and in the middle of their arches, they afcend and 
 raife their lower edges forv.^ards. At the fame 
 time, the Rernum is thruft forward from the verte- 
 bras and from fhe junctures with the ribs. Thus 
 the ribs are both farther from the vertebrx, and 
 the right ribs recede from the left ; and both diam-. 
 eters, from the right to the left, and from the 
 fternum to the vertebrx, are increafed by almoR 
 two lines each ; and as this occurs in every imagin- 
 able fection of the thorax, the cavity of the breall 
 will be fufficiently dilated. This happens efpecial- 
 ly in women, and in men whofe breathing is fome- 
 what laborious. Thefe effects are produced leafl 
 of all by the nrft ribs, but more by the fucceeding 
 ones. In ftrong infpirations, the ribs defeendboth 
 behind and before, and, along with thefe, the fter- 
 num ; and the fpaces between the cartilages are 
 leffened. But this dilatation is neither futlicient 
 for healthy refpiration, nor is it almofl obfeiA^abie 
 in men ; although even tlien, the intercoftal mufcleSy 
 by retaining and elevating the ribs, very much aflifl 
 the infpiration in a fccondary way, by affording a 
 fixed point to the diaphragm, fo that the whole 
 force of that rnufcle may be fpent, not in deprefllng 
 the ribs, but in lov.^ering itfelf. The greater part, 
 therefore, of the fpace which the thorax gains in 
 infpiration, arifes from the action of the diaphragm. 
 
 ccLX. By the diaphragm we underhand a 
 mufeie expanded in a curvilineal plate, which, in 
 general, feparates the pulmonary bags from the 
 abdomen in fuch a manner, that the middle and 
 tendinous part is the higheft, and fupports the peri- 
 cardium ; that the lateral portions, which arife from 
 the folid parts of the thorax and loins, are every 
 W'here lower j and that its pofterior portions are 
 lovreft of all. The flefhy fibres of this rnufcle arife 
 from the internal or pofterior furface of the cnli- 
 form cartilage to the very point, and from the 
 fixth, feventh, eighth, ninth, tenth, eleventh ribs. 
 
Chap. Vni. 
 
 RESPIRATION. 
 
 117 
 
 and apex of the twelfth ; after which follows an 
 interval, in which the naked pleura is contiguous 
 to the peritonaeum. Thereafter mufcular appen- 
 dages of the diaphragm, much ftronger, collected 
 into two, three, or four round mufcles on each 
 lide, arife flefliy from the tranft^erfe procefs of the 
 fiift lumbal vertebra, and from the lide of the body 
 of the fecOnd ; and tendinous from the middle 
 of the body of the fecond, third, and fourth, and 
 from the cartilages placed between them, on the 
 whole higher up in the left fide, and lower down 
 in the right. 
 
 ccLxi. All thefe fibres (cclx.) becoming ten- 
 dinous, form the centre of the diaphragm, which 
 refembles, in figure, an obtufe gnomon, and fupports 
 the pericardium .with its middle and broader angle, 
 while the lateral wings, of which the left is nar- 
 rower, defcend backv^^ards. This central portion is 
 more moveable than the reft ; but in the middle 
 tendinous part, and neighbouring mufcular fub- 
 ftance, it is refifted by the heart ; the lateral wings 
 and contiguous portions are the mmft moveable. 
 The fibres of this tendon form a moft beautiful 
 w'eb, principally indeed on the upper part ; which 
 ftretches from each mufcular portion, to the muf- 
 cular portion oppofite to it : and then they form re- 
 markable inferior fafciculi, tranfverfe, right, left, 
 and pofterior, which laft portion is the uppermoft. 
 
 ccLxii. There are two holes in the diaphragm ; 
 of which the right, in the right fide of its tendon, 
 is obtufely fquare, and circumfcribed by four 
 ftrong tendinous fafciculi ; the left, which is ellip- 
 tical, lies betwixt the right and left fleftiy portions, 
 arifing from the middle of the bodies of the lumbal 
 vertebrae : under this opening they deculfate and 
 crofs each other once and again, but above they 
 end in the tendon. Therefore it is probable that 
 the latter is contrafted during; the action of the 
 diaphragm, and that the former remains immovc- 
 
 able. 
 
RESPIRATION. 
 
 ii8 
 
 Chap, Vni. 
 
 able. For tendons are but little changed during 
 inuibular motion. 
 
 ccLxiii. The ftruclure of the parts, and the dif- 
 feclion of living animals, demonllrate, that the 
 fieihy portions of the diaphragm, by afcending on 
 all lides from fixed points to middle and moveable 
 parts, deprefs thefe, and by that means draw down- 
 ward the lateral bags (lxxvii.) of the thorax, 
 which contain the lungs *, and thus augment the 
 perpendicular diameter of the breaft. The muf- 
 cular portions are more depreffed ; the tendon lefs, 
 both becauie it is fixed to the pericardium, and 
 becaufe its own fubftance does not contract. The 
 cefophagus and even the vena cava are compreffed, 
 while the diaphragm acts. The diaphragm almoft 
 alone performs the oflice of rcfpiration in a healthy 
 man who is at reft ; and alfo in thofe whofe ribs 
 are fractured, or the fternum burft, or where the 
 perfon will not make ufc of his ribs on account of 
 pain. The force of the diaphragm alfo, in dilating 
 the breaft, is greater, according to calculation, than 
 all the reft of the powers which contribute to ref- 
 piration. The extent of an infpiration is thus far 
 limited, becaufe, during the extreme action of the 
 diaphragm, the lovcer ribs are drawn inwards, and 
 the breaft is fo far ftraitened. To oppofe this, the 
 intercoflal niufclcs interfere in a moderate infpi- 
 ration j in an exceflive one they are not equal to 
 the diaphragm. The phrenic nerve, when irrita- 
 ted, more evidently than in moft other mufcles, 
 forces the diaphragm to perform its office. The 
 lungs themielves are entirely governed by the air, 
 ribs, and diaphragm ; being in immediate contact 
 with thefe, as appears through a large incifion, or 
 through the pleura, or pellucid part of the dia- 
 phragm, when the containing parts remain en- 
 tire. 
 
 ccLxiv. In violent infpirations, occafioncd by 
 an increafed quantity of blood driven into the 
 
 lungs, 
 
Chap. VIH. 
 
 RESPIRATION. 
 
 I If 
 
 lungs, or by any obftacle occuriiig in them, fcveral 
 other powers elevating the thorax, allift in dilating 
 the breaft, which are inferted into the thorax, cla- 
 vicles, or fcapultE ; fuch as the fcaleni mufcles, 
 malloidei, trapezii, cervicales defcendentes, ferrati 
 fuperiores, peclorales, and levatores parvi, for which 
 anatomy mull Ijp confulted. 
 
 ccLXv. Thus, there are powers which increafe 
 the capacity of the thorax in all its three diinen- 
 lions (ccLxiii. and cclix.) By thefe the cavity 
 of the breaft is dilated, fo that it compreftes the 
 lungs lefs than before ; into that fpace the lungs 
 ftrive to extend themfelves, ftnce they are never 
 deftitute of air, which, as foon as the preffure is 
 taken off, becomes rarefied, and expands itfelf. 
 Independent of the action of the mufcles, the lungs 
 poftefs no peculiar inherent power of attracting air ; 
 and, even when they are moft full of air, on clofing 
 the trachea, the animal, however, attempts to in- 
 fpire, by the efforts of its intercoftal mufcles and 
 diaphragm. It follows, that the air (ccxlvii.) 
 gravitating, and preffed on all fides by the incum- 
 bent columns of the atmofphere, rnuft enter the 
 thorax ; and with greater force the lefs air is in 
 the lungs ; and with the greateft, if they contain no 
 air ; but air will not enter the thorax, if the air, 
 beinsj admitted to the lurms throusfh a wound in the 
 breait, comprefs their iurface. In this action, 
 therefore, which is called infpiration, the bronchia 
 are every way increafed, both in length and 
 breadth ; becaufe all the diameters of the thorax 
 are increafed, and the inftated lungs remain imme- 
 diately contiguous to the pleura. At the fame 
 time, the veffeis, which are joined with the bron- 
 chia by a cellular flieath, becomie longer and are 
 extended, and the fmall angles become larger; by 
 which means, the circulation is facilitated. Be- 
 lides, when the veficular fubftance of the lungs is 
 hiied with air, the ipace through which the capil- 
 lary 
 
120 
 
 RESPIRATION. 
 
 Chap. VIII. 
 
 lary veflels of the hangs run, is increafcd, the 
 branches of the arteries and veins are ftretcKcd out 
 at greater angles, the lobes prefs lefs upon each 
 other, the comprefilon of the neighbouring parts is 
 JefTened, and, therefore, the blood fent from the 
 heart will ilow with greater eafe and celerity 
 through the large and fmall arteries of the lungs. 
 Hence, by inflating the lungs, and by that means 
 facilitating the paflage of the blood to the left ven- 
 tricle, moribund animals are refufeitated, and in 
 the fame way perfons who are taken out of the 
 water apparently drowned. But, on account of its 
 great levicy, tlio preiTure of tlie air upon the blood 
 does not deferve notice, as being three hundred 
 times iefs than the force of the lieart ; and in- 
 jiifiicient to force the air againft the blood, M'hich 
 may eafily be done by a lyphon. 
 
 CCLX7I. Is air contained between the lungs and 
 the thorax ? Is this air rarciied in infplration, and af- 
 terwards becoming condenfed, and comprdTing the - 
 lungs, does it caufc exfpiration ? Is this opinion con- 
 firmed by the analogy of birds, of which it is firicl- 
 ly true ? Every thing concurs to confute this opin- 
 ion : bcliir.d the pleura, in living quadrupeds, as 
 well as in dead human bodies, llic naked lungs arc 
 ^ vifible, v.'idiout any intermediate fpace betwixt 
 them : on perforating the pleura, the lungs retract 
 themfelves towards the vertebrae, as foon as the air 
 conies in contact with them. In birds, the lungs, 
 being pervious, admit the air tlirough large holes 
 into the caiity of the thorax. But in thefe there 
 is a rnanifeit fpace betwixt the lungs and the 
 pleura, which would be equally manifeft in quad- 
 rupeds, if the lungs were not contiguous with the 
 pleura. Large wounds, admitting the air into one 
 cavity of the thorax only, dirninifli the rel'piration ; 
 but fuch wounds, as let the air into both cavities, 
 fupprefs it. When the thorax i:/ opened under 
 v/ater, it emits no bubbles of air ilu'ough the faid 
 
 water j 
 
Chap. VIII. 
 
 RESPIRATION. 
 
 I2I 
 
 water ; but in birds, in whofe thorax there is air, 
 it does. The imaginable fpace betwixt the lungs 
 and the thorax is filled by vapour, or a very little 
 water. Adhefions of the lungs injure the refpira- 
 tion but in a fmali degree ; which ought entirely 
 to ceafe, if any intermediate air betwixt the lungs 
 and thorax were neceffary to refpiration. Finally, 
 the external air, being admitted to any of the m.em- 
 branes of the human bodp, infiames them, if they 
 be not defended by plentiful mucus, and of this the 
 pleura is deftitute. 
 
 ccLxvii. Refpiration, whether by the admix- 
 ture of a fubputrid vapour, or in fome other way, 
 certainly vitiates the air, and renders it unfit eith- 
 er for inflating the lungs or fupporting flame ; 
 and laflly, it deprives that element of its elafticity. 
 It is probable that this happens from putrefaction, 
 fince, by a crowd of men the air is rendered pefli- 
 lenti^, and fevers of the molt malignant kind are 
 generated in a few hours. In whatever way it hap- 
 pens, we are certain, that, in the lungs, the air is 
 vitiated ; lofes its elafticity ; and cannot keep the 
 lungs diftended, fo as to tranfmit the quantity of 
 blood now increafed by the dilatation of the pul- 
 monary arteries, into the veins. Nor can the wdll 
 dilate the breafl; beyond certain bounds, or aflift the 
 pafiage of the blood. A ftate therefore wall take 
 place, in which the blood cannot pafs through the 
 lungs. 
 
 ccLxviH. Thus a nev/ refiflance to the blood con- 
 tinually coming from the heart is generated : and 
 in long retentions of the breath, as in making vio- 
 lent efforts, the venous blood, efpecially of the head, 
 flagnates before the right ventricle of the heart, 
 which is clofed up, becauie it cannot evacuate it- 
 felf into the lungs ; and tumefies the face with red- 
 nefs, and fomietimes burfts the veins of the brain, 
 neck, intellines, kidneys, or lungs, and even the 
 right auricle of the heart. This is the caufe of 
 
 exceffive 
 
1^2 
 
 RESPIRATION. 
 
 Chap. VIII. 
 
 excellive anxiety of mind ; this is the caufe of death 
 in compreffed air, in perfons drowned or ftrangled, 
 which is much more hidden than is commonly im- 
 agined v/ith regard to drowned people. A living 
 perfbn therefore, that he may remove thofe incon- 
 veniencies which arife from the palfage of the 
 blood being ouftructed, Ilackens the powers of in- 
 fpiration, and excites to action thofe of exfpiration, 
 in order to free the breaft from the too greatly 
 rarefied air. 
 
 cci>xix. Thefe powers are, firft, the elafticity of 
 the ribs, which being drawn upwards out of their 
 natural fituation, as foon as the elevating powers 
 eeafc to acf, fpontaneoully replace therafelves at 
 more acute angles with the fternum and vertebrae. 
 There is alfo the claftic force of the bronchia and 
 veficles diftended with air, by which they endeav- 
 our to contract. Elence exfpiration is performed 
 more eafily and quickly than infpiration j and hence 
 it is the lail acition of dying people. 
 
 ccLxx. Thefe are alTiited by the abdomdnal muf- 
 cles ; the oblique, Itraight and tranfverfe. The 
 former of thefe are faftened by one part to tlie 
 lower ribs ; and by another part, they are attached 
 to the os pubis and ilium, which are immoveable, 
 v/hen compared with the breaft. Therefore, t-ic 
 ftraight mufcles, being contracted, flatten the arcli 
 into which the abdominal vifeera were protruded 
 by the depreflion of the diaphragm, reduce tlie con- 
 vexity of the abdomen nearer to a ftraight line ; 
 force the abdominal vifeera up^rards and backwards 
 againft the diaphragm, which alone can give way ; 
 and prefs it up into the thorax, v'hich is thus ren- 
 dered fliorter. The oblique mufcles, for the fame 
 reafons, comprefs the lateral parts of the abdomen, 
 carry the liver and ftomach backwards, and prefs 
 them towards that place vEere there is the Icaft 
 rcflftance. Laftlv, all of them draw down the ribs 
 which \vere elevated by the intercoftals. The 
 
 trantieiTe 
 
Chap. VIII. 
 
 RESPIRATION. 
 
 tranfverfe mufcles, indeed, do not draw down the 
 ribs ; but they pull the cartilages of the falfe ribs 
 a little inwards, render the whole abdomen much 
 narrower, and force the fame vifcera againft the 
 diaphragm. As acceiTory powers may be reckoned 
 the fternocoftal, and the long internal intercoftal 
 mufcles, which are called depreffors. By this joint 
 force the elevated ribs defcend ; the middle ones 
 more, the uppermoft lefs, the loweft moft of all ; 
 their margins are drawn inwards : the cartilages 
 afcend, and return into acute angles with the fter- 
 num 5 and the fternum itfelf recedes backv/ards 
 with the ribs. By thefe means the thorax, by the 
 converfe of cclix. is rendered narrower in every 
 direftion and fhorter, and expels as much air out 
 of the lungs as is faihcicnt to remove the uneah- 
 nefs (ccLxviii.) 
 
 ccLXXi. In violent refpiration, when the infpira- 
 tions are fuller, the more powerful expirations de- 
 rive afliftance from fome other caufes, as the facro- 
 lumbalis, longiffimus and quadratus mufcles. By 
 this force, leaden bullets, weighing above a dram, 
 may be blown to the diftance of 363 feet ; which 
 force is equal to a third part of the preffure of the 
 atmofphere. But, in a healthy perfon, the mufcles 
 of the abdomen alone faflice, and the lunns are not 
 fo much emptied as in blowing. 
 
 ccLxxii. The effects of exfpiration are the com- 
 preflion of the blood- veffels of the lungs ; the dimi- 
 nution of the angles of the bronchia ; the reitino- 
 the weight of the adjacent veffels on the reticular 
 veffels ; the expulfion of the corrupted air from the 
 lungs ; the propulfion through tlie veir.s of that 
 part of the blood which is impacted in the capil- 
 lary arteries, to the left fide of the heart, and the 
 impeding that part of the blood which is coming 
 from the right ventricle. Exfpiration, therefore, 
 flops the ready entrance of the blood into the lungs ; 
 and as the \vhole thorax is cornpreifed at the fame 
 
 time^ 
 
124 
 
 RESPIRATION. 
 
 Chap. MU. 
 
 time, it repels the venous blood into the veins of 
 the head, and nils the brain and its finufes. 
 
 cci,xxiii. In this manner the necefuty for refpi- 
 ration arifes anew, as often as the collapfed vellels 
 of the lungs relilf the blood expelled from the right 
 ventricle of the heart : this is one caufe of death 
 in thofe animals which expire in velTels exhaulled 
 of air. The lunes in thole which have remained 
 long in vacuo, from having the air drawn out from 
 them, become denfe, folid, and heavier than water ; 
 and, therefore, impervious to the blood. Of the 
 fame kind is the death of thofe who are killed by 
 lightning, and perhaps by the noxious vapours of 
 caverns. Therefore, in confequence of a moll in- 
 telligent ftruclure, at the hrft perception of the un- 
 eafinefs ariling from the oppofition to the paffage 
 of the blood through the lungs, the exfpiring pow- 
 ers become relaxed, the infpiring powers are ex- 
 cited into action, and the motion of the blood 
 through the lungs is. rendered free and accelerated. 
 
 ccLxxiv. Are there other caufes of alternate 
 refpiration ? Is any thing, to be derived from the 
 compreffion of the vena fine pari, of the plirenic 
 nerve, or from the blood not being fent to the 
 brain ? But thefe are difproved by comparative 
 anatomy ; which, where there is no fuch nerve or 
 vein, finds the fame alteration in refpiration every 
 where. Does it proceed from the alternate con- 
 tradlicn of antagoniil mufcles, among vTdch, thofe 
 of exfpiration relax thofe of infpira-tion, and the 
 reverfe ? But, according to this argument, aU the 
 jnufcles of the hum.an body would be perpetually 
 alternating in their motions. 
 
 ccLxxv. From what has been faid, it fufficiently 
 appears, that refpiration is abfolutely neceffary to 
 a healthy adult ; becaufe, whether the lungs re- 
 main long in a Hate either of exfpiration or of 
 jnfpiratioii (cclxxiii. cci^viii.) death will be the 
 
 confequence. 
 
Chap. VnL 
 
 IRESPIRATION. 
 
 i-25 
 
 confequence. Therefore, no animal, that lias lungs 
 like ourfelves, after it has breathed for forne time, 
 fo that the air ihall have penetrated into the in- 
 Inoft parts of the lungs, and the pulmonary artery 
 fliall have brought a new quantity of blood to that 
 vifcus, can fubfift longer than a few minutes with- 
 out the ufe of air, without perifliing, or at lead: 
 falling into a ftate which differs from death only in 
 the poffibility of recovery. In an animal recently 
 born, this neceffity’for air does not take place very 
 inftantaneoufly. 
 
 ccLxxvi. But the ufe of refpiration Is different 
 from this necefGty ; which nature might have avoid- 
 ed, either by forming no lungs at all, or by con- 
 ftruftiiig them fimiiar to thofe of the fetus. The 
 ufe, therefore, of refpiration, muft be very confid- 
 erable, fince all animials are furniflied either with 
 lungs, or with gills, or with a windpipe diftributed 
 through all parts of the body. 
 
 ccLxxvii. To inveftigate this utility, let us com- 
 pare the blood of the adult with that of the fetus, 
 and with the vital ftuid in fillies. It appears, that in 
 the foetus the blood is deftitute of its fiorid rednefs 
 and folid denfity ; that the blood of filh is cold, 
 and has lefs denfity, and a tender craffamentum. It 
 is therefore probable, that the blood acquires both 
 thefe properties in tlie lungs. 
 
 ccLxxviii. Is animal heat generated principally 
 in the lungs ? Does it arife from the alternate ex- 
 tenfion and contraftion, relaxation and compreffion, 
 of the veflels (cclxv. and ccuxxii.) by which the 
 folid parts of the blood are perpetually rubbed to- 
 gether, and fuu'er attrition from their conftriftion ? 
 Ihe lungs, therefore, will add to the office of the 
 reft of the arteries, becaufe in them the blood is al- 
 ternately relaxed and comprexTed more than in any 
 other part of the body. But when the lungs are 
 obflrufted, ulcerated, and ahnoft deftroyed, morbid 
 heat is increafeci in the human body ; and in the 
 
 lungs^ 
 
RESPIRATION. 
 
 1:26 
 
 Chap. VIII, 
 
 lungs, the cold air comes moil nearly in contact 
 with the blood. 
 
 ccLXxix. The deniity is, indeed, promoted by 
 the copious difcharge of watery vapour from the 
 VelTels of the lungs, by which the reft of the m.afs 
 becomes fpscifically heavier. In the fame manner 
 as in other arteries, the blood, being alternately re- 
 tarded and accelerated, is figured by the moulds of 
 the ultimate arteries, becomes fpherical, and there- 
 fore denfer, having more ponderous globules, and 
 iefs light fluid. I’he pulmonary vein alfo being 
 fmaller than its correfponding artery, is of confider- 
 able ufe in compreffmg the globules, and in increaf- 
 ing their attraction. Neverthelefs, cold animals, 
 with very fmall lungs, have denfe and coagulable 
 blood ; as alfo the chick in ovo. The courfe of 
 the blood through the lungs is fhortcr : through the 
 whole body the courfe is longer, and the artery 
 weaker ; the ventricle, by wdiich the blood is pro- 
 pelled, is aifo weaker. 
 
 ccLxxx. Is the air itfelf received into the blood 
 in the lungs, and docs it there produce neceflary 
 vibrations ? Is this demonftrated from the refiftance 
 of the body to the weight of the external air ; from 
 the air found in the biood-vcfiels, in the cellular 
 fubftance, and in the cavities of the human body ; 
 from the cracking produced by extending the joints ; 
 from air being manifeftly poured from the trachea 
 into the hearts of many animals, as thelocuft ; from 
 the cfcape of air from the blood and animal fluids 
 in Mr. Boyle’s vacuum ; from the necefllty of a 
 \utal ofeiilation in the blood ; and from the increaf- 
 ed rednefs of the pulmonary blood ? 
 
 ccLxxxi. That no elaftic air is here received in- 
 to the blood, is demonftrated from its not being 
 able to enter into the blood, if it retain its elaftici- 
 ty ; from the inutility of its reception, if its elafti- 
 city be loft in the blood ; from the perfecT immu- 
 tability ox the blood by cold ; from the minuteneft 
 
Ghap. VIII. 
 
 RESPIRATION. 
 
 t'l’] 
 
 of the inhaling velTels ; from the lides of the veiides 
 being perpetually covered with mucus ; from the 
 elaftic nature of air being unfit to pafs through ca- 
 pillary veffels ; and from its repulfion by water, 
 that hinders it from paffing through moiftened pa- 
 per, linen, or leather. Again, air thrown into the 
 trachea never pafi’es 'into the heart ; or only when 
 it is driven with exceffive force. In the veffels and 
 humours of the human body, air, from a ftate of in- 
 elafticity, becomes elaftic in confequence of putre- 
 fadion, froft, or an external vacuum. But fuch air 
 exifts in every liquid, and is taken into our bodies 
 with the aliments, and with vapours, mixing flowly 
 and difficultly. There never were any elaftic bubbles 
 of air obferved in the blood of a living animal, un- 
 lefs after wounds ; air being inSated into the blood- 
 veffels of any animal, kiUs it certainly and fpeedily. 
 Nor is there any thing fufficiently certain in the in- 
 creafed rednefs of the blood in the pulmonary veins.- 
 Laftly, air indeed is abforbed by moft fluids, and by 
 water, but flowly, and only at the end of feveral 
 days after the former air has been exhaufted by the 
 pump. It then likewife lays aftde its elaftic nature ; 
 and no reafon has been advanced why the air lliould 
 either be more fpeedily abforbed by the blood, or 
 why it fliould retain its elafticity after its abforp- 
 tion. 
 
 ccLxxxii. Is the blood cooled in the lungs ? Is 
 this proved from the death of animals in air heated 
 to the fame degree with the animal, as is believed 
 to have happened from very fultry fummer weath- 
 er, and fcorching eaft winds ? Are the pulmonary 
 veins, therefore, lefs than the arteries ? Does the 
 deftre of cold in hard working people arife from 
 thence ? That the blood is cooled in the lungs, is 
 thus far true, that it warms the contiguous air, and 
 therefore imparts to it fomething of its own heat. 
 But that this was not the defign of nature, is evi- 
 dent \ ftnee no one has faid, that the venous blood 
 
 is 
 
128 
 
 RESPIRATION. 
 
 Chap. VIIL 
 
 is hotter than the arterial, although fome affert that 
 it is colder ; and nobody ever obferved the left ven- 
 tricle of the heart colder than the rig^ht. But the 
 venous blood enters the luns^s. If it be cooled 
 there, it follows that the arteries muit receive it 
 ftill colder. Therefore, the blood recovers that 
 heat which it lofc, and even niore : and bdides, a 
 perfon may live in an air much hotter than the 
 blood itfeif, of which we have a familiar example 
 in baths, and warm climates. The fize of the 
 pulmonary artdry in the foetus, which does not re- 
 Ipire, is greater j and the larger area of the right 
 auricle and ventricle of the heart, which is likewife 
 much greater in the foetus, feems to be a receptacle 
 fubfervient to frequently neceiTary retardations, and 
 the narrowneis of the vein contributes to the accel- 
 eration of the blood. 
 
 ccLxxxiii. Does the blood derive its rednefs from 
 the air ? This is contradicted by what we fee in 
 cold animals, which, though they make aimoft no 
 ufe of the air, have blood equally red with that of 
 warm animals ; by the certain connection of red- 
 nefs in the blood of frogs, with their having plenty 
 of food, and of paleneis with want of food ; and 
 by the air, as we have jufc now faid, having no ac- 
 cefs to the blood. Neverthelefs, rednefs is produ- 
 ced, and reftored to the blood by the contact of air, 
 and is deftroycd by its removal. Does fomc fubtle 
 element from the air penetrate the blood, and caufe 
 its colour, as light is required for the colours of 
 plants ? 
 
 ccLxxxiv. Is the ufe of the lungs, to abforb 
 nitre from the air to the blood ? Is this the 
 caufe of the florid colour, obfervable on the furface 
 of a cake of blood, while the bottom part is black. 
 Does this preferve the animal from putrefaction ? 
 It is certain, that fome volatile principle of acidity 
 exifts in the air, which, with a luitable earth, forms 
 nitre j for nitrous earth, after being exhaufted, 
 
 when 
 
Chap. VIIL RESPIRATION; ' 129 
 
 when expofed again to the air, becomes reimpreg- 
 nated with nitre. But the fame principle of acid- 
 ity, we kno\X" by certain experiments, with differ- 
 ent earths, forms a vitriolic fait, or alum, or fea- 
 falt. For the caput mortuum of fea-falt, which, 
 remains after the dillillation of the acid, recovers 
 from the air the property of furniiliing more acid 
 by dillillation ; and in fnow, there is cubical fait i 
 from marcafites, true vitriol exudes ; and colco- 
 thar recovers the acid, which was drawn from 
 it, and alkali becomes vitriolated tartar. Is this, 
 therefore, the ufe of refpiration ? The quantity of 
 thefe falts, which exifts in the air, is too fmall ; and 
 refpiration ismoft falutary on the higheft mountains, 
 where they are moft rare ; nor have any m^arks of 
 a nitrous fait ever been detefted in our blood. 
 
 ccnxxxvi. Why do tortoifes, frogs, lizards, fnailsj 
 earwigs, and many other infedlsj live long without 
 air ? In them, the lungs arc given;, not fo much for 
 the preparation of the blood, of which they have 
 but a iinall quantity, as for affifting them in fwim- 
 ming ; hence their lungs are fuppiied with veins 
 from the cava, and with arteries froHi the aorta^ 
 Infects inhale and exhale air, through points in the 
 fkin. Why do ail animals, however fmall, fucli as 
 little birds, periflr in air that is not renewed ? Be- 
 caufe the air, which has once entered the lungs, is 
 contaminated by inelaftic, watery, and alkaline va- 
 pours, and therefore it becomes noxious 1 not be- 
 caufe it becomes lighter ; for the mercury falls but 
 little in air, which has not been renewed, and which 
 has killed an animal. Hence, on the other hand, 
 animals furvive loiter in air which is more com- 
 prelfed than that or the atmofphere" ; for in that 
 cafe, the proportion of the elaftic element is great- 
 er, and therefore the air isTnore fiowly contami- 
 nated. But, even in other cafes, confined air becomes 
 deleterious, and filled with vapours, by ftagnation 
 alone. Vv^hy do animals fweii in an exhaufted re- 
 R ceiver ? 
 
RESPIRATION. 
 
 150 
 
 Chap. VIII. 
 
 ceiver ? From the expanfion of the air, which ex- 
 ifted in an inelaftic ftate in the blood. 
 
 ccLxxxvii. There is a certain connexion be- 
 tween the pulfe and refpiration. According to the 
 common cmirfe of nature, three or four pulfations 
 are reckoned to one refpiration. If the quantity of 
 blood fent to the heart be increafed, the frequency, 
 both of the puhe and refpiration, are increafed. 
 This is the reafon of the panting in a perfon, tak- 
 ing exercife, vchich accelerates the motion of the 
 venous blood (cxlii.) If the blood meet with 
 much refiftance in the lungs, and do not pafs freely 
 from the right into the left ventricle of the heart ; 
 to accelerate its courfe, both the number and mag- 
 nitude of the refpirations are increafed. This is the 
 caufe of fighing, yawning, and panting ; of which 
 the firft is a deep infpiration ; the fecond flow, and 
 very great ; and the third, frequent and imperfeef. 
 The number of refpirations, however, does not al- 
 vrays increafe with the pulfe ; of which vee have an 
 example in fevers, in which the lungs are not af- 
 fefeed. 
 
 ccLxxxviii. The mucus, which lines the fcnflblc 
 membrane of the bronchia, may become trouble- 
 fome, both by its quantity and acrimony ; it has 
 been even known to caufe fuffocation in a dropfy 
 of the lungs. Therefore, its fuperabundance, adhe- 
 fion, or acrimony, is removed by coughing ; name- 
 ly, by irritating the refpirative fyftein, the mucus 
 or concretions are loofened and expelled by large- 
 infpirations, and exfpirations, alternately fucceed- 
 ing each other with rapidity, and by ftrokes of the 
 abdominal mufcles. 
 
 ccLxxxix. Laughter diners from coughing in its 
 caufe, which refldes commonly in the mind, or at 
 leaft conliiLS in the titillation of fome of the cuta- 
 neous nerves ; and ahb, becaufe, after one deep in- 
 fpiration, there are frequent but imperfecl: exfpira- 
 tions, through the contrafted glottis, and the air is 
 
 not 
 
Chap. VIIL 
 
 RESPIRATION. 
 
 131 
 
 not totally evacuated from the lungs. Hence laugh- 
 ter, in a moderate degree, conduces to health ; be- 
 caufe, in place of one full infpiration, fever al infpi- 
 rations and exfpirations happen in the fame time, 
 and thus the concuffion is greater. Hence its dan- 
 ger, from ftagnation of the blood ; becaufe the ex- 
 Ipiration is not full, and therefore the blood is ad- 
 mitted into the pulmonaiy artery, but is not fuffer- 
 ed to pafs through it. Weeping begins with a deep 
 infpiration, after which follow fhort alternate infpi- 
 rations and exfpirations 5 and it is finifhed with a 
 deep exfpiration, which is immediately followed 
 by an infpiration : hence it has nearly the fame 
 good and bad effe6ls ; and, when moderate, it re- 
 lieves the diflrefs arifing from grief. Hiccough is 
 a very great, fonorous, and fudden infpiration. 
 Sneezing confifts of one deep infpiration, fucceed- 
 ed by a Angle powerful exfpiration ; and by the 
 torrent excited, the acrid matter, irritating the nof- 
 trils, is blown away. 
 
 ccxc. The fecondary ufes of refpiration are very 
 numerous. It exhales copioufly, and removes from 
 the blood fomething highly noxious ; for by remain- 
 ing in the air, it will caufe fuffocation ; and the 
 breath of many people, crowded in a clofe and fmali 
 place, impregnates the air with a fuffocating quali- 
 ty. On the other hand, it abforbs from the air a 
 thin vapour, of which the ufe is perhaps not fuih- 
 ciently known. It is alfo a force, which perpetu- 
 ally Gompreffes the abdomen, and all its vifeera ; it 
 evacuates the ftomach, inteftines, gaU bladder, re- 
 ceptacle of the chyle, urinary bladder, inteftinum 
 re6tum, and the womb ; it comminutes the aliments, 
 and forces the blood through the liver, fpleen, and 
 mefentery. It caufes a kind of flux and rehux in 
 the blood, fo that it is alternately prelfed back to- 
 wards the extremities of the veins, and a little af- 
 ter is propelled towards the heart by an accelerated 
 velocity, as into an empty fpaee. Moreover, infpi- 
 k 2 ration 
 
tp VOICE AND SPEECH. Chap. IX. 
 
 ration attracts the odoriferous particles from the 
 air, and conveys them to the fenforiuin. But even 
 fucking, fo necelfary to the new born infant, is ef- 
 fected by infpiration, and by forming a larger fpace, 
 in which the air contained in the mouth is rare- 
 fied, fo that the prelTure of the external air forces 
 the milk into that part where it is leaft refifted. 
 Eaftly, the voice itfelf depends upon the air, and 
 feems to be the principal manifeft effect of refpira- 
 tion. This, therefore, appears a proper opportuni- 
 ty for defcribing it. 
 
 C H A P. IX. 
 
 VOICE AND SPEECH. 
 
 ccxci. ^ I 'HE principal organ of the voice is the 
 I larynx ; for, when it is injured, the 
 air paffes through the windpipe, without yielding 
 any found. By the larynx, we underhand an af- 
 femblage of cartilages, joined into a hollow ma- 
 chine, which receives the air from the fauces, and 
 tranfmits it into the windpipe, connected with it by 
 ligaments and mufcular fibres. Among the larger 
 of thefe cartilages, the annular and fcutiform in 
 adults offify internally. The anterior and larger 
 part of the larjmx, which lies almolt immediately 
 under the Ikin,. is compofed of two cartilages ; the 
 thyroid and cricoid, to which the lateral parts of 
 the larynx alfo belong in fuch a manner, that the 
 portions of the cricoid cartilage always become 
 larger, as they are higher feated. The back part of 
 the larynx is compofed firff of the faid annular car-^ 
 tilage, and afterwards of the ai*ytenoid cartilages, 
 connecled by mufcles. The epiglottis, loofely con- 
 nected with the thyroid cartilage, is either raifed 
 or inclined over the larynx. The veffels arife from 
 the upper and lower thyroids j the nerves are nu- 
 merous ; 
 
Chap. IX. VOICE AND SPEECH. 
 
 ^33 
 
 merous ; the inferior ones come from the recur- 
 rents ; the fuperior ones from the eighth pair, inof- 
 culating in various ways ; fome alfo from the inter- 
 coftal. The former of thefe nerves is remarkable 
 for its origin in the thorax ; for its reflection round 
 the aorta and right fubclavian ; for its giving rife 
 to fome of the nerves of the heart, and for the ex- 
 periment, which proves, that the voice is deftroyed, 
 by tying this nerve. 
 
 ccxcii. All thefe cartilages are connected togeth- 
 er by various mufcles and ligaments, fo that the 
 whole may poflefs mobility, while fome of its parts 
 are firm, and others extremely moveable. The 
 feutiform or thyroid cartilage, fituated on the fore- 
 part, is compofed of two, alm.oft quadrangular 
 plates, inclined to each other in an obtufe angle, 
 projecting forwards. In thefe plates, two apertures, 
 one on each fide for the internal veflels of the 
 larynx, are found fometimes, though rarely. The 
 upper procefles of this cartilage, terminating in a 
 thick point, inclining upwards and backwards, are 
 connected with the horns of the os hyoides, by 
 ftrong ligaments, fometimes mixed with bone. The 
 lower procefles are ihortcr, are adapted to the flight- 
 ly hollowed, and almofl: fiat furfaces of the cricoid 
 cartilage ; and are connected by a very firm artic- 
 ulation, on account of the fliortnefs and ftrength 
 of the cellular fubftance, which unites them. The 
 middle anterior part is joined by ftrong perforated 
 ligaments, to the m.iddle of the annular cartilage ; 
 and likewife by other fuperior ligaments, proceed- 
 ing from the defeending horn of the feutiform 
 cartilage, to the upper part of the annular carti- 
 laa;e. 
 
 O 
 
 ccxciii. The cricoid cartilage, anteriorly thick 
 and hard, is increafed backwards, in form of a ring 
 unequally truncated ; and, in the middle, it is di- 
 vided into two cavities by a protuberant line. It 
 j-s firmer than the refl of the cartilages, and forms 
 
 their 
 
VOICE AND SPEECH. 
 
 Chap. IX. 
 
 ^34 
 
 their bahs. From it longitudinal mufcular fibres 
 and ligaments defcend to the windpipe (ccxxxviii.) 
 The pharynx connecled with each of thefe cartila- 
 ges by many mufcular layers, receives the larjmx 
 into its cavity. From this cartilage a fliort liga- 
 ment proceeds to the arytenoid cartilage on each 
 fide. 
 
 ccxciv. The fis'ure of the two arvtenoid cartila- 
 
 A-/ 4 
 
 ges is very complex. It fpontaneoufly divides in- 
 to two parts, of which the lower is larger, and 
 is connected by a moderately concave bafe wdth tlie 
 thick cricoid cartilage, forming a moveable articu- 
 lation. It fends a procefs forwards, which fepa- 
 rates the glottis, and fuflains the inferior part of 
 the ventricle of the larynx. They afcend upwards, 
 of a triangular figure : the pofterior bafe is hollow, 
 and the anterior fide is convex, and divided by 
 three furrows. They are extenuated upwards, till 
 they are at lafi: terminated by a pretty thick, oval, 
 cartilaginous head fixed on them. I'he lower part 
 of thefe cartilages is connected by numerous muf- 
 cular fibres, partly tianlverfe, and partly oblique ; 
 of which the different directions are evident, though 
 they cannot be feparated, Thefe are called the 
 arytenoid mufcles. In their upper part, the aryte- 
 noid cartilages are feparated by a perpendicular 
 chinlc, which has been improperly by fome called 
 the Q'lottis. 
 
 ccxcv. The arytenoid cartilages are connected 
 with the thyroid by tranfverfe ligaments, for the 
 molt part fufficiently ftrong and elaftic, but cover- 
 ed with the common mucous membrane of the la- 
 rynx. Thefe ligaments arife below the middle of 
 the arytenoid cartilages, and are inferted into the 
 fiat angle of the thyroid cartilage (ccxcii.) and 
 may be feparated from each other, by remoHng the 
 arytenoid cartilages from being in mutual contacf, 
 apid may be again brought into contiguity' by' the 
 
 cartilages 
 
Chap. IX. 
 
 VOICE AND SPEECH. 
 
 135 
 
 cartilages approaching each other. This conftitutes 
 the true glottis, and is continuous, but at right an- 
 gles with the above mentioned chink (ccxciv.) 
 
 ccxcvi. From the fame angle of the thyroid car- 
 tilage, under a notch, from a firm ligament, a car- 
 tilage arifes, with an ere£t flender ftalk, of an oval 
 flaape, convex before, behind cohcave, and with its 
 fuperior extremity reflefted backwards and con- 
 cave. It is kept erect by its own elafticity, fo that 
 it rifes upright behind the tongue ; but it can be 
 fo inclined whenever the root of the tongue is preff- 
 ed backward, that, having become tranfverle, it 
 completely fhuts up and protedls the paffage into 
 the larynx, which defcends between this, the epi- 
 glottis, and the arytenoid cartilages. The epiglot- 
 tis is joined to the tongue by pale m.embranous fi- 
 bres, and to the os hyoides by much membranous 
 expanfion. It either has no fibres from the thyroj 
 arytenoidal and arytenoidal mufcles, or they are 
 too minute to counteracf its elaflicity. 
 
 ccxcvii. At the fides of the lioaments of the 
 glottis (ccxcv.) two other upper and fofter liga- 
 ments, lefs tendinous or elaflic, proceed parallel 
 from each arytenoid cartilage to the thyroid. Be- 
 twixt thefe two (ccxcvii. and ccxcv.) ligaments of 
 each fide, a peculiar cavity or ventricle defcends, 
 having the figure of a compreffed parabolic fpacc, 
 extending downwards betwixt the double mem- 
 brane of the larynx, with its faperior orifice, of an 
 elliptic form, conftantly open into the larynx. 
 
 ccxcviii. Laflly, all the internal cavity of the la- 
 rynx is lined with the fame foft, irritable, mucous 
 membrane, we before deferibed in the windpipe 
 (ccxxxix.) This membrane is moifiened by a great 
 number of glands. The uppermofi; are fmah, and 
 compofed of fimple glands (ccviii.) They are 
 feated on the anterior convex part of the epiglottis, 
 and fend prolongations through its various perfo- 
 rations and larger fmufes, to its concave'’ fide, 
 
 which 
 
VOICE AND SPEECH. 
 
 Chap. IX, 
 
 136 
 
 which arc there contin-ued into fimilar nrm glands. 
 Moreover, upon the anterior furrowed furface of 
 the arytenoid cartilages (ccxciv.) there is on each 
 lide a gland, of a loofe conglomerate fabric, refem- 
 bling much a gnomon, compofed of round acini, 
 doubtlefs mucous, of which a loofe portion defcends 
 on each fide as far as the annular cartilafxe. In 
 the ventricles, there are numerous m.ucous finufes. 
 Laftly, all the internal furface of the larynx is full of 
 large mucous pores. All thefe glands fecrete a thin 
 and watery, but at the lam.e time, \dfcid mucus. 
 
 ccxcix. Has the thyroid gland any lim.ilar ufe ? 
 It is of the conglomerate kind, but foft, the cover- 
 ings of the lobules being much more tender than in 
 the falival glands, it is very large, is anteriorly feat- 
 ed upon the thyroid and cricoid cartilages and 
 windpipe, lurrounding vvith lateral produclions the 
 hides of the thyroid, is joined to its companion by 
 an iilhmus, which is narrow and emarginated be- 
 low ; and by a middle very thin procels it afcends 
 on the forepart, almoil to the os hyoides. This gland 
 is fuU of a ferous, yellowiCi, and fomewhat vifcid 
 humour : Does it difcharge this fluid into the wind- 
 pipe, or into the cefophagus ? Into neither are duels 
 certainly knov/n to open. Does it retain its fluid 
 entirely, and afterwards reftore it to the veins, like 
 the thymus, which is analogous in its ftrucnire ? Is 
 it a conglobate gland ? That the ufe of this gland is 
 very coniidcrablc, appears from the remarkable fize 
 of the arteries which it receives from the carotids, 
 and of its inferior ones from the fubclavians. The 
 veins return into the jugulars and fubclavians. It 
 has a peculiar mufcle, not however conflant, arifing 
 from the maruin of the os hyoides, and fometimes 
 from the low'Cr edge of the thyroid cartilage to- 
 wards the left, which defcends without a fellow, 
 and fpreads its tendinous fibres over the gland, 
 upon which alfo the fccrnchycidei and fterno.thy- 
 loiuci piufcles arc incumbent, 
 
 ccc, 
 
Chap. IX. 
 
 VOICE Aim SPEECH. 
 
 137 
 
 ccc. The whole larynx is fufpended from the os 
 hyoides, both by ligaments inferted into the fupe- 
 fior horns of the thyroid cartilage, and by the 
 middle of its balls, united to the junction of the 
 plates, conftituting that cartilage. The larynx, and 
 os hyoides connefted with it, may be raifed con- 
 liderably, even half an inch above its mean alti- 
 tude. This is performed by the biventer mufcles, 
 together v/ith the geniohyoidei, geniogloffi, llylo- 
 glolli, ftylohyoidei, ftylopharyngei, thyropalatini, 
 hyothyroidei ; either conjunftly or partially. Dur- 
 ing its elevation, the glottis is rendered narrower, 
 and the ligaments before mentioned (ccxcv.) ap- 
 proach nearer together. Thus, by the affiilance of 
 the ad:ion of the arytenoid mufcles, both oblique and 
 tranfverfe, the glottis may be accurately clofed, fo 
 as to relift with and incredible force the preliure of 
 the v/hole atmofphere. 
 
 ccci. The whole larynx may aifo be deprelTed 
 about half an inch beneath its ordinary lituation, 
 by the fternohycidei, fternothyroidei, and coraco- 
 hyoidei, as they are called ; and, when thefe are 
 in action, by the anterior and pofterior cricothyroi- 
 dei. By this motion the arytenoid cartilages re- 
 move from each other, and the glottis becomes 
 wider, v/hich is alfo drawn open by the mufcles 
 laterally inferted into the aiytenoid cartilages, and 
 by the cricoarytenoidei poftici and laterales, and 
 thyroarytenoidei ; thefe alfo, by refting upon the 
 ventricles of tlie larynx (ccxcvn.) are capable of 
 compreffing them. The particular cartilages which 
 form the larynx, can fcarcely be mioved feparately. 
 
 cccii. From the larynx the air comes into the 
 mouth and noftrils. By the m.outh, we here mean 
 that large and irregularly fliaped cavity, fituated 
 between the foft and hard palates, both concave in 
 the middle,, and the mufcles lying under them, and 
 the lower jaw. The noftrils afcend forwards above 
 
VOICE AND SPEECH. 
 
 Chap. IX. 
 
 135 
 
 the foft palate ; they are two broad cavities, in- 
 cluded between the feptum medium, and the oiTa 
 cavernofa, and fome other parts. They are every 
 where bony and cartilaginous. 
 
 ccGiii. The tongue lies in the middle of the 
 mouth ; it is a broad piece of flelli eafily change- 
 able into any kind of figure, and readily moved 
 without delay to any part of the mouth ; by its own 
 fielhy fibres, and by the mufclcs attached either to 
 itfelf or to the os hyoides, which is joined to it by 
 many flelhy fibres and membranes, it may with 
 great facility be made to affume any pofition or 
 figure. It is drawn forwards by the genioglolTi and 
 geniohyoidei mufcles ; backwards by the fiyloglofii, 
 fiylohyoidei, ceratogiofii, bafiogloffi, chondroglofii, 
 and biventer ; downwards, by tlie fiernoliyoidei, 
 and ceratohyoidei ; and upwards, by the ityloglofli, 
 fiylohyoidei, by the biventers, and likewife by the 
 mylohyoidei. 
 
 ccciv. So much for the anatomy. It remains 
 that we demon (Irate what efiecds are produced by 
 air, when expelled, during exfpiration, by the pow- 
 ers above defcribed (cclxix. cclxx.) from the 
 lungs through the windpipe into the larynx, and 
 from thence forced through the glottis into the 
 mouth varioully configured. Thefe effects are, 
 voice, fpeedr, and finging. Sound only is produ- 
 ced when the air is expelled with fo great a veloci- 
 ty through the contracted glottis, that it impinges 
 on the ligaments of the glottis, and thus produces 
 in the larynx that tremor, which, being vibratory 
 on account of its elafticity, it continues and in- 
 creafes. Therefore, from the united vibrations of 
 the ligaments (ccxcv.) and of the cartilages of the 
 larynx, a found is produced, vrhich we call tlie 
 voice, peculiar in every clafs of animals, and wliidi 
 depends entirely on the larynx and glottis. When 
 there are no vibrations, a wliifper is- produced. 
 
 ccev. 
 
Chap. IX. 
 
 VOICE AND SPEECH. 
 
 139 
 
 cccv. The ftrength of the voice depends upon the 
 quantity of air exfpired, and the narrownefs of the 
 glottis ; and, therefore, upon capacious lungs ealily 
 dilatable, an ample, cartilaginous and elaftic larynx 
 and windpipe, the free refonance of the noftrils, 
 and a powerful exfpiration. But the acutenefs or 
 gravity of the tones, we obferve to arife from va- 
 rious caufcs. The former proceeds partly from the 
 narrownefs, and partly from the tenlion of the 
 glottis, and the latter from its relaxation and dila- 
 tation. For hence, the air, in a given time, im- 
 pinges upon the ligaments of the contrafted glot- 
 tis with more numerous undulations, and caufes 
 more frequent vibrations ; but when the glottis 
 is dilated, the contrary of all this follows. And 
 from the greater tenlion of the ligaments, the tre- 
 mors in like manner become more numerous from 
 the fame ftroke. Therefore, to produce an acute 
 found, the whole larynx is drawn upwards and 
 forwards ; and with greater force as the vo;ce is 
 required to be iharper, infomuch that the head it- 
 felf is fometimes inclined backwards, that the 
 mufcles elevating the larynx may exert their full 
 powers. The truth of this is conjlrmed by experi- 
 ment, for by applying the fingers to the larynx 
 when acute founds are emitted, the elevation of the 
 larynx, which is about half an inch for the octave, 
 is ealily felt : and by comparative anatomy, which 
 demonllrates the glottis to be very narrow and car- 
 tilaginous in finging birds, and wide in hoarfe ani- 
 mals, and fuch as are low or mute. This is alfo 
 illuftrated by whiffling, where the llrarpnefs of the 
 found evidently proceeds from the contraction of 
 the mouth : and by mufical inltruments, in which 
 the narrownefs of the opening admitting the air, 
 and the celerity with which it is impelled, are the 
 caufes of an acute tone. 
 
 cccvi. Gravity of the voice is produced by op- 
 ppfite drcumltances, the deprellion of the larynx 
 
VOICE AND SPEECH. 
 
 Chap. IV 
 
 T4®' 
 
 by the caufes (ccci.) already defcribed ; a wide 
 glottis and a very ample larynx. This is proved 
 by the touch, which eaiily perceives the defeent 
 o£ the larynx in perfons hnging, in like manner 
 about half an inch for every oclave ; by the great- 
 er gravity of the voice in males, and by the loweft 
 tones of the voice degenerating into a filent breath- 
 ing. 
 
 cccvii. Does every diverhty of tone proceed 
 from the length of the ligaments of the glot- 
 tis, which is augmented when the feutiform car- 
 tilage is drawn forwards, and the arytenoid one's 
 backwards ? Is it according to this rule, that the 
 moil acute tones are produced, by the. ligaments 
 being rendered very tenfe, and therefore vibrating 
 with great celerity ? This- is afl'erted by fonie 
 late anatomifts, from experiments, which have been 
 alfo repeated by^ fome eminent men ; they^ have 
 obferved, that, when the chords or ligaments of 
 the glottis are tenfe, the peculiar voice of every 
 kind of animal is produced by blowing air into its 
 trachea ; that this voice was rendered more acute 
 by ftretching the ligaments, and more grave by 
 loofening them ; that by Ihutting the whole liga- 
 ment, the voice was fupprelTed ; by lliutting the 
 half, the voice was rendered an octave higher ; by 
 flmtting a third part, a fifth higher, See. Ihcre 
 are not wanting, however, doubts concerning this 
 new theory, arifing from the cartilaginous and 
 bony, and confequently immoveable and inexten- 
 iibie, glottis of birds ^ from the certain production 
 of more acute founds, ip whiftling, from the mere 
 contraction of the lips ; from the etmmple of wo- 
 men, in which the larynx is fofter, but the voice 
 more acute, than in men ; from experiments which 
 lliow, that more acute founds are produced by 
 bringing the ligaments of the glottis nearer into con- 
 tacc with each other ; and from the total abfence of 
 machinery for llretching the lig-aments, and draw- 
 ing the thyroid cartilage forwards from the annular 
 
 one. 
 
Chap. IX. 
 
 VOICE AND SPEECH. 
 
 44 * 
 
 one. But fince it appears from experiments, that 
 the tenfion of the ligaments fufiices for producing 
 acute founds, without the contraction of the glottis, 
 it is probable that difference of tenfion in the glot- 
 tis contributes more than a difference of its diame- 
 ter to the diverfity of voice. 
 
 cccvm. Singing, is when the voice, modulated 
 through various degTees of acutenefs and gravity, 
 is expelled through the lar^mx, while vibrating and 
 fufpended between contrary powers, which chiefiy 
 diftingnifhes it from fpeech. It is a laborious addon, 
 on account of the perpetual a<ffion of the mufcles 
 poifing the larynx ; and it increafes the animal 
 heat, becaufe acute tones require a contracted glot- 
 tis, vchich retards the exfpiration, and at the fame 
 time a great deal of air to give them ffrength 
 (cccv.) and, therefore, deep infpirations are necef- 
 Hry. it tends very much to dry the windpipe, 
 from the accelerated paffage of the air ; and ren- 
 ders a ^eat deal of mucus neceffary, which is the 
 reafon why there are fuch numbers of mucous re- 
 ceptacles in the larjmx, amongft which I very much 
 fufpedt the ventricles before defcribed (ccxcvii.} 
 ought to be numbered. 
 
 cccix. Speech is performed when the larynx is 
 at reft, in tones differing but little in acutenefs and 
 gravity : by varioully modifying the voice by the 
 organs of the mouth. Canorous fpeech has both 
 valuations in the tone, and modifications of the 
 voice by the organs of the mouth. 
 
 cccx. All fpeech is reducible to the pronuncia- 
 tion of letters, which differ m various nations, ai.— 
 though they agree in the greateft number over the 
 whole world. Of thefe, fome are called vowels^ 
 which are expreffed by the mere emifiioii of the 
 voice through the mouth, without the application 
 of the tongue to any part of the mouth. But con- 
 fonants are formed by a coliificn of the tongue 
 againft fome part of the mouth, lips, or teeth. The 
 
 nature 
 
142 
 
 BRAIN AND NERVES. 
 
 Chap. X, 
 
 nature of our work forbids us to be more particu- 
 lar, and prevents us from explaining a moil inge- 
 nious art, which, a rare occurrence in phyiics, has 
 fo clearly determined all the corporeal caufes of 
 each letter, that, by mere infpeclion and touch of 
 the organs during their pronunciation, it has 
 taught fpeech by imitation. 
 
 CHAP. X. 
 
 BRAIN AND NERVES. 
 
 cccxi. ^"I'^HE remaining actions of the human 
 i body we fliall confider according to 
 the order in which they receive the blood. Of the 
 coronary arteries we fpoke, when we gave the hif- 
 tory of the heart. Next to thofe, the catotids arife 
 from the aorta. 
 
 CCCXI I. The aorta, which comes out from the an- 
 terior part of the heart (clvii.) in order to bend it- 
 felf towards the vertebne of the thorax, inclines 
 backwards, and to the left, in an angle that is round 
 indeed, but not very large, forming a confiderable 
 arch. From the convexity of this arch, three 
 branches arife. The firft afcends towards the right 
 fide, and is immediately fubdivided into two large 
 arteries, of which the lowermoft proceeds in the di- 
 redlion of its trunk, under the denomination of the 
 fubclavian. The other afcends along the wind- 
 pipe to the head, and is called the right carotid. 
 The left carotid fprings next from the fame arch, a 
 little inclined to the left fide ; and the third, which 
 is ftill more inclined to that fide, is called the left 
 fubclavian, and is fomewhat lefs than the. right. 
 At tlie origins of thefe branches, the continuous 
 fide of the aorta is a little thicker, and projecls a 
 little to the left. Variations from this courfe are 
 rarely obferved. 
 
 GCCXIII, 
 
Chap. X. 
 
 BRAIN AI'ID NERVES. 
 
 243 
 
 cccxiii. The carotid artery, inclofed alorigwitii 
 the jugular vein and nerve of the eighth pair, in 
 copious and denfe cellular fubftance, commonly ar- 
 rives at the upper part of the thyroid cartilage, 
 without fending off any branches. There it divides 
 into two trunks. The anterior, which is called the 
 external carotid, is more in the direction of its 
 trunk, and rather larger. It fends off the thyroidea 
 fuperior, the tortuous lingualis,and then the labialis; 
 and from its poherior part, clofe by its divifion, the 
 pharyngea afcendens, which, behdes the pharynx 
 and mufcles of the velum palati, fupplies to the 
 dura mater, through the foramen common to the 
 jugular vein and nerve of the eighth pair, a confid- 
 erable branch, fent off at the bafis of the os petrc- 
 fum, near to the foramen magnum, and cuneiform 
 procefs of the fphenoid bone. 
 
 cccxiv. Then, from the exterior fide of the ex- 
 ternal carotid, fprings the occipital artery ; whic^ 
 alfo fends a branch to the dura mater, which is d^.-. 
 tributed, at the bafis of the cerebellum, through a. 
 peculiar foramen of the dura mater in the angle 
 which the os petrofum forms by departing from the 
 mamillary procefs ; another branch paffes over the 
 atlas to the dura mater, both under and into the 
 fkull ; and a third fometimes goes through the foffa 
 jugularis to the dura mater. The next artery, the 
 auricularis, goes to the back part of the ear, to the 
 membrane of the tympanum, and to the temples. 
 
 cccxv. What remains of the external carotid ar- 
 tery, afcends through the parotid gland, to which 
 having given fome branches, as well as to the face 
 and eyelids, it fends out, in the firft place, the tem- 
 poralis, which is confiderable. The trunk of the 
 carotid, being inclined behind the lower jaw, lofes 
 itfelf under the denomination of maxillaris interna. 
 In that place, it directly fends off a large trunk 
 to the dura maters which paffes through a pe- 
 culiar opening of the broad pterygoid wings, to 
 
 the 
 
BRAIN AND NERVES. 
 
 Chap. X * 
 
 144 
 
 the vicinity of the middle foITa of the brain ; and is 
 largely diftributed upon the dura naater, in the re- 
 gion of the temples and forehead, as far as the falci- 
 form linns. Sometimes this artery is double, and 
 often fends a confpicuous branch to the lachrymal 
 gland of the eye. Moreover, the fame maxillary 
 artery enters the upper part of the noftrils by a 
 triple trunk, where it is fpent, after having given 
 off branches to the teeth of the lower and upper 
 iaws, the infra orbitalis, a branch to part of the 
 face and eyelids, and the palatine to the bone of 
 the palate, with fmall twigs to the dura mater, both 
 through the fmaller pores of the great wings, and 
 accompanying the third and fecond branch of the 
 fifth pair of nerves, and the dura mater filling up 
 the lower orbital fiffure. 
 
 ceexvi. But the other trunk, which is pofferior, 
 and com.mcnly called the internal cai'otid (cccxni.) 
 afeends without a branch. This artery, having 
 firft made a remarkable ferpentine flexure, enters 
 through a peculiar forauien in the os petrofum, 
 where it is lurfounded with a vagina from the du- 
 ra mater, like that which comes out through all 
 the openings of the flcull : afcer.ding upwards, then 
 inclining forwards, it penetrates into the cavity of 
 the fltull, and afeends tortuoufly bent along the leila 
 equina, in the middle of the blood of the cavernous 
 finus, having given fmall branches to the fifth pair 
 of nerves, dura mater, and infundibulum, with 
 one larger to the eye, part of which returns Agatin 
 through a peculiar hole into that part of the dura 
 mater, which lies upon the middle of the orbit. 
 The rete mirabile is'psculiar to fome anim.als, and 
 does not exift in man. 
 
 cccxvii. But the trunk of this internal carotid 
 paiTes over tiic anterior part of the felia equina ; 
 and being incurvated backwards, and received with- 
 in the arachnoid membrane, after giwng branches 
 to the pons and crura of the brain, and a twig to 
 
Chap. 1. BRAIN AND NERVES. 
 
 H5 
 
 the choroid plexus, and a branch that accompanies 
 the optic nerve, it then divides into an anterior and 
 pofterior branch. The former being conjoined 
 with its fellow artery of the other fide by a fiiort 
 anaftomofis, is then incurvated backwards and up- 
 wards, along the corpus callofum, and goes to the 
 middle and pollerior part of the brain, and fome- 
 times fends branches to the falciform procefs, and 
 at its very origin to the third ventricle, the fornix 
 and thalaini. The latter, being joined by a mode- 
 rate anafiomofis with a branch of the vertebral ar- 
 tery, unlefs that arife from the undivided trunk of 
 the carotid, afterwards afcends a long way through 
 the foffa of Sylvius to the lateral part of the brain ; 
 and alfo fends branches to the choroid plexus. AH 
 the branches of the carotid, contained within the 
 Ikull, have a thin, folid, and more brittle fubftance 
 than the other arteries of the body. 
 
 ccc'xviii. The vertebral artery commonly arifes 
 from the fubclavian of the fame fide, (though the 
 left has been fometimes feen to fpring from the 
 trunk of the aorta,) in a deep fituation, and without 
 giving branches, it enters the foramen in the tranf- 
 verfe procefs of the fixth vertebra of the neck ; af- 
 ter which, it afcends with alternate flexures through 
 the proceffes of the other vertebrae of the neck ; 
 through each interval, it fends off fmall branches to 
 the mufcles of the neck, and communicates with 
 the lower thyroidal : with other branches, fome- 
 what larger and pofterior, it accompanies each 
 nerve to the pia mater of the fpinal marrow ; and 
 by anterior branches, not fo numerous, but larger, 
 it communicates in the fpinal marrow with its an- 
 terior artery. Laftly, having becom.e tranfverfe by 
 a fmall flexure at the fecond vertel^ra, and by a 
 large one round the procefs of the firft, having 
 there given oft' two confiderable branches to the 
 mufcles of the neck, and during its palfage through 
 the foramen magnum, having lent fmall ones to the 
 L dura 
 
BRAIN AND NERVES. 
 
 Chap. X , 
 
 146 
 
 dura mater of the foramen magnum and neighbour- 
 ing cavity of the cerebeilum, it finally enters the 
 cavity of the ikull through that foramen. There, 
 while it afcends along the medulla oblongata, the 
 right trunk gradually approaching the left, unites 
 with it at a very acute angle (a moil uncom.mon' 
 circumftance) into one artery, the bafilary, which 
 being ftretched under the pons Varolii, is fufpcnded 
 in the pia mater. From the vertebral arteries, be- 
 fore they are conjoined, or from their common 
 trunk juft formed, arteries both going to the lower 
 furface of the cerebeilum, and entering deeply into' 
 the fourth ventricle and the internal fubftance of 
 the cerebellum, arife. Thefe fend off the fpinal ar- 
 teries. There are inftances where thefe arife from 
 the united trunk ; or from the trunk in one fide, ‘ 
 and from a branch in the other. Then the bafila- 
 ris, belides branches to the medulla oblongata and 
 crura of the brain, fends off other lower arteries of 
 the cerebellum. Amonoft thefe branches alfo arifes 
 
 O 
 
 the artery, which accompanies the auditory nerve. 
 Finally, the bafilaris, at the forepart of the pons, 
 divides on each fide into two brandies. One of 
 thefe goes to the upper part of the cerebellum, to 
 the fourth ventricle, to the crura of the medulla of 
 the cerebellum, the nates, teftes, and pineal gland : 
 in place of this, aifo, there are two trunks. The 
 other, the profunda cerebri, is diffributed to the 
 pofterior lobe of the brain, the choroid plexus, the 
 plexus lying on the pineal gland, that gland itfelf, 
 the thalami, corpora ffriata, fornix, and whole an- 
 terior ventricle. 
 
 cccxix. Fro;.n the foregoing hiffory of the ar- 
 teries belonging to the brain, it appears, tliat in ' 
 every pulfation a great quantity of blood is fent to 
 this organ, equal to a fixth part or more of the 
 whole blood in the human body, and conveyed by 
 trunks which arife very near the liearf, and from 
 the convexity of the aorta. It is therefore not im- 
 probable. 
 
BRxlIN AND NERVES. 
 
 Chap. X. 
 
 147 
 
 probable, that the fcroingeft parts of the blood, and 
 thofe moll retentive of motion, goto the head. Is 
 not this evident from the elFedls of mercurials being 
 almoll confined to the head ; from the fpdden ac- 
 tion of inebriating'fpirits upon the head ; from the 
 fpeedy llupor excited by camphor ; from the face 
 being oftner affected by heat and fweat, than any 
 other part of the body ; and from the eruption of 
 highly volatile miafmata upon the face ? The fafe 
 lituation in which the arteries of the head afcend, 
 defends the large and important veffels from injury. 
 The frequent reciprocal inofculati-oiis of the trunks 
 going to the head, as well as of their branches, di- 
 minifli the danger of obftrudion. Hence, when 
 the carotids are tied, aninials neither die, nor feem 
 to be very uneafy. The conliderable flexures of 
 the vertebral and carotid arteries, ferve to mode- 
 rate the impulfe of the blood coming to the brain, 
 flnce a great part of the velocity, which it receives 
 from the heart, is thus fpent in changing the figure 
 of the infleftions. Some reputable authors have 
 obferved, that the arteries are fomewhat large! at 
 this place. 
 
 cccxx. The hiftory of the brain ptoperly co^'n'- 
 mences with its integuments. A part fo tender and 
 fo neceffary to life, is, in the firft place, furrounded 
 by an offeous fphere compofed of many pieces, 
 which, therefore, admits of extenfion, while it ef- 
 feflually refills external preffure. To every part 
 of the internal furface of this fphere, a very llrong 
 membrane adheres, compofed of two plates fuffi- 
 ciently dillincl. It is firmly attached by an infinite 
 number of fmall veflels, even penetrating to the ex- 
 terior parts of the head, as by fo many footllalks ; 
 in a healthy perfon it is no where detached, but 
 adheres fomewhat lefs firmly to the very fmooth 
 bones, but with exceflive ftrength to the commif- 
 fures of the bones of the Ikull, whicli, from their 
 figure, are called futures. In young lubjefts, the 
 h 2 adhelion 
 
BRAIN AND NERVES. Chap. X, 
 
 145' 
 
 adheilon of the dura mater to the fkuU is fo great, 
 that the fibres to v/hich it fs connected are fepa- 
 rated at the fame time with it. In adults, many 
 of the veiTels being effaced, the dura mater becomes 
 lefs infeparable ; but yet it cannot be detaclred from 
 the ficull without forae violence. Hence thofe 
 bloody drops which appear on remo'/ing tlie cra- 
 nium. tience all that has been advanced concern- 
 ing the motion of the dura mater is erroneous. As 
 
 O ^ ^ 
 
 to the motion, which has been remarked in wounds 
 by fome obfervers, it arofe either from the puffa- 
 tion of the arteries, in a place whence the refiffancc 
 was removed, vchile the reff of the cranium afford- 
 ed iniuperable refiftance to the action of the heart, 
 or from the turgefcence of the brain. The dura 
 mater lias neither irritability nor fenfibility, and is 
 dellitute of nerves, though thofe going to other 
 parts have been, by fome, uferibed to this mem- 
 brane. 
 
 cccxxi. It is the external lamina of the dura 
 mater, which adheres to the bones, and ferves 
 them for a perloffeum. It paffes out of all the 
 holes of the Ikuil along the nerves and veffels, and 
 coheres vcitli the perioffeum of the head, vertebrae, 
 and, laftiy, of the whole body ; from which cir- 
 cumffance, the name of mater given to it by the 
 barbarians, is derived. The internal plate of the 
 dura mater is, in moft pai'ts, continuous with the 
 former : but, in fome, it recedes a little from it, as 
 in the great fphenoidal wings ; at the fides of the 
 i'ella equina, where a good deal of blood is poured 
 lietw ixt them ; and upon the fella equina itfelf : 
 liaviilg left tire external laiuina, which adheres 
 hrmly to the bones, it defeends double to form the 
 falx, which arifes hrft from the multiform bone 
 behind the criihi galli, then from the enfta, after- 
 wards from the whole juncture of the two frontal 
 2md parietal bones, and, lauly, from the middle 
 and back part of the occipital bone ; it becomes 
 
 broader 
 
Chap. X . 
 
 BRAIN AND NERVES. 
 
 14-9 
 
 ■broader as it proceeds backwards ; it is interpofed 
 betwixt the heinifpheres of the brain ; and hangs 
 over the corpus caliofuin, at a greater diftance in 
 the forepart, but very near behind, where it ahb is 
 extenuated to an edge. That there are fhining 
 fibres in this part, difperfed towards the longitudi- 
 nal finus, from its junction with the tentorium, in 
 the lhape of palm branches, is certain •, but it does 
 not therefore follow, that they have any mmfcular 
 motion : betwixt thefe fibres frequently there is no 
 membrane, "fo that they form natural foramina. The 
 falx is joined to the middle of the tentorium, and is 
 continuous with it. In the fame manner, but in a 
 different fituation, the fame lamina forms the fiiort 
 falx of the cerebellum, feparating its lobes, togeth- 
 er with the ftrong tentoria, wltich, arifiiig from 
 the cruciform protuberance of the occiput, are in- 
 terpofed tranfverfely betvdxt the brain and cere- 
 bellum, and, at lail, adhering to the petrous bones 
 and anterior clinoid procefi’es, leave an aperture 
 nearly oval for the medulla oblongata. Thefe pro- 
 ductions of the dura mater, prevent any part of the 
 brain from preffing on the reft, in any fituation of 
 the body j and, iikewdfe, one lobe from compref- 
 fing another, in concufiions of the brain. Hence, 
 in the fwifteft quadrupeds, where the danger from 
 concuffion is greater, the bra,in and cerebellum are 
 divided by a bony partition. 
 
 cccxxii. Upon the external furface of the pia 
 mater, not far from the finus of the falx, are placed 
 glands, feated in the reticular texture of the dura 
 mater, which partly are inclined towards the finus 
 and its cavity, fo that fome of them are contiguous 
 to the cavity of the finus, while others are fo plac- 
 ed at the infertion of the larsfe veins into the pia 
 
 X 
 
 mater, that, together with the former jufi mention- 
 ed, they make up a continued ferics ; thefe are 
 fometimes foft, oval, and white, fornetimes red, and 
 hal'd, like warts. They have alfo been noticed in 
 
Chap. X, 
 
 150 BRAIN AND NERVES, 
 
 the tentorium cerebelli. But the vapou-r, which 
 exhales from the furface of tbe pia mater, is not 
 fecreted by thefe glands ; for every v/here, even 
 where there are none of thofe glands, as. in the 
 ventricles, a copious vapour tranfpires from thf 
 ultimate arteries, as is proved by injections of wa- 
 ter or iise, which exude from every part of the 
 furface of the pia mater. 
 
 cccxxiii. The next covering of the brain, m.uch 
 clofer to it, and exprelhng its figure, as the former 
 does that of the cavity of the fkull, has been de- 
 nominated, from its tenuity, arachnoid. Pellucid 
 as water, very thin, and as far as its thinnefs petr 
 mils, firm, it completely envelopes the brain, paff, 
 ing over its larger and fmaller furrows, and in- 
 clofing the larger vefTels, fo that they lie between 
 the arachnoides and pia mater. It is not a lamina of 
 the pia mater, from which it differs in fituation, 
 in being connecled with it by cellular fabflance, 
 and in the exarnple of the fpinal marrow, although 
 it is refolved into a cehular nature between the 
 hemifpheres of the brain. 
 
 cccxxrv. The third covering of the brain, is 
 the pia mater, or foft membrane of the brain. 
 This immediately inr efts the whole furface of the 
 brain and fpinal marroAV on all fides, is tender, and 
 compofed of a vaft number of fniall veftels joined 
 together, by cellular texture: but thefe veiiels it 
 fends into the brain in a regular order, like little 
 roots. It defeends into all the finuofities, and in- 
 fmuates itfelf into the fiffures of the brain, cere- 
 bellum, and fpinal marrow, and is the bond by 
 which the lobules of the brain are joined together, 
 being pollefled of confiderable firmnefs in propor- 
 tion to its tenuity.^ Being received into the caw- 
 ties of the brain, it changes its fabric, and becomes 
 foft and aim oft of a micdullary comlftence, efpe- 
 cially \\ hen the fubjeci is dilTcc^ed fame time after 
 death, although the veftels itiil point it ou^ 
 
 ccex;j;v, 
 
Chap. X. BRAIN AND NERVES. 151 
 
 cccxxv. The veins in the brain are not con- 
 hrucled as in other parts of the body. For neither 
 have they any valves, nor do they accompany the 
 arteries, nor have their trunks the common ftruc- 
 ture which prevails in other veins. Therefore, 
 from the innermoft cavities of the -brain, the veins 
 which reft upon the ridges of the ftriated bodies, 
 the veins of the choroid plexus, of the lucid fep- 
 tum and of the anterior ventricles, are colleffed 
 into trunks, which at laft meet in one great vein, 
 or often two, which, being accompanied with m.any 
 fmall arteries of the choroid plexus, defcends back- 
 wards to the partition of the brain and cerebellum. 
 In that place, it receives veins ariftng from the 
 pofterior and lower part of the brain, and lome of 
 the cerebellum, and meets with a fmus or vein, in- 
 cluded in a reduplication of the inner lamina of 
 the dura mater, and being changed into this finus, 
 it generally defcends into the lefs tranfverfe fmus, 
 moft frequently of the left fide, though fometimes 
 dividing, it fends a branch to each fide. This is 
 called the fourth ftnus. 
 
 cccxxvi. The fuperior and fuperficial veins of 
 the brain are large, and fpread in the windings 
 with which the brain on all fides abounds. Into 
 thofe veins, over the whole ftirface of the brain, 
 are infer ted fome veins of the dura mater ; while 
 others of them enter by peculiar orifices into the 
 falciform finus. Then the veins being gradually 
 collefled into trunks, proceed, the greateft number 
 of them forwards, a few either directly, or back- 
 wards, and thefe moft efpecially from the forepart, 
 .and infert themfelves, vcith their terminations ob- 
 liquely truncated, into the long falciform finus 
 which is form.ed by the internal lamina of the dura 
 mater, from the right and left fide miceting togeth- 
 er below in the upper edge of the falx. There- 
 fore it is of a triangular figure, convex in its upper 
 fide. It begins with a ilender origin at the foramen 
 
 caecum. 
 
152 BRAIN AND NERVES. Cka?. X. 
 
 cfficum, which lies before the criRa galli ; it af- 
 cends and follows the courfe of the falx ; where 
 that joins the tentcrinm, being generally inclined 
 to the right, it takes the name of the right tranf- 
 verfe finus, and goes by a peculiar channel impreff- 
 ed in the occipital and temporal bones, firft tranf- 
 verfely, then incurvated, to the foramen jugulare, 
 where, becoming very large, it receives the inferior 
 petrous and the occipital finufes, and empties itfelf 
 into the jugular vein. But the left tranfverfe iinus, 
 refembling the former, and alfo leading to the ju- 
 gular vein, is rather inferred into its riglit lide, 
 than continued as its trunk. Into it the fourth 
 finus (cccxxv.) and the occipital one, ufoaily infert 
 tliemfclvcs. But there are fome infcances of a re- 
 verfe arrangement, lb thc^t the longitudinal fmus 
 terminates in the left tranfverfe fmus ; and then 
 the right tranfverfe linns receives the fourth and 
 the occipital one. At other times it is equally di- 
 vided into tveo tranfoerfe trunks ; and fometimes 
 a middle linns joins the tranfverfe ones. There 
 even have been found two fimilar fmufes parallel to 
 each other. 
 
 cccx:cvii. Irregularly parallel with the lower and 
 tl'dckcr margin of the falx, runs a llendcr and 
 rounder hnus, more refembling a vein ; it receives 
 veins from the folx itfelf, Vvdaich alfo communicate 
 with the npper fmus ; and from the adjacent hem- 
 ifphcres cf the brain, and from the corpus callo- 
 fum. Vt^hcre the falx joins with the forepart of 
 the tentorium, it is inferted into the fourth finus. 
 
 cccxxviii. The lower veins of the brain, which 
 lie next to the bafis of the Ikull, are variouliy in- 
 ferled. The anterior veins coming from tlie folia 
 Sylvii, collected into fome trunks, are inferted into 
 the cavernoa-s. fmus, or that triangular interval, be- 
 tween the external and internal plates of the dura 
 mater, which is at the fide of the fella equina. 
 
 Other 
 
BRAm AND NERVES. 
 
 Chap. X. 
 
 5 53 
 
 OLiier veins, from the pons itfelf, lead into the up- 
 per finus petrofus. Other pofterior veins, which 
 come from the pofterior lobes of the brain, are in- 
 ferted in great numbers into the tranfverfe linufes 
 in the tentorium. 
 
 cccxjiix. The upper veins of the cerebellum, 
 meeting together in large trunks, partly terminate 
 in the fourth finus, and partly in the tranfverfe 
 finufcs. The lower veins, from the cerebellum and 
 meduUa oblongata, infert themfelves into the upper 
 finus petrofus ; and fome of thefe alfo into the 
 tranfverfe finus very near the place where it goes 
 out. 
 
 cccxxx. There are many finufes, befides thofe 
 now mentioned. The moft anterior of them, which 
 commonly has a circular appearance, furrounds the 
 pituitary gland, and betrveen the clinoid procefies, 
 communicates witfi the cavernous finufes ; and be- 
 tw’een thefe proceffes and the carotid, with the low- 
 er petrous finufes, and laitly, by the way of the 
 fixth pair, with the upper petrous finufes behind 
 the fifth nerve. There are fome inftances where 
 this finus receives the ophthalmic vein ; and fome- 
 times the tranfverfe, joining to the cavernous finus, 
 fupphes the place of this circular finus, or elfe co> 
 exilis with it. 
 
 cccxxxi. The upper petrous finus runs back- 
 wards in a groove of the os petrofum. It arifes 
 from the anterior extremity of the falcus of the os 
 petrofum, where it communicates v/ith the caver- 
 nous finus ; it receives veins of the dura mater 
 which are inferted into it, and fometimes ante- 
 rior veins of the brain itfeif, mentioned before 
 (cccxxviii.) and is inferted into the angle of the 
 tranfverfe finus, where it begins to be bent, and 
 fometim.es into the inferior petrous finus. Another 
 vein, paffing along the top of the os petrofum, is in 
 like manner inferted into the angle of the tranfverfe 
 finus. The io'wer finus petrofus, which is fiiorter 
 
BRAm AOT NERVES. 
 
 Chap. X, 
 
 554 
 
 and larger, goes round the root of the bone of this 
 name, and communicates with is fellow behind the 
 clinoid procefs ; after twice communicating with 
 the cavernous iinus, and with the upper linus, un- 
 der the nerve of the fifth pair, it is finally inferted 
 into the jugular foifa ; it alfo receha^s fome veins 
 of the dura mater from the region of the verte- 
 brae. To the fame outlet alfo, the nofterior occi- 
 pital finus on each fide leads. Thefe are pretty 
 large, go round the margin of the foramen mag- 
 num, till, arriving at the falx of the cerebellum, 
 {cccxxi.) they are fooner or later inferted, gener- 
 ally after being conjoined into the fourth finus, 
 and with that into the left tranfverfe one, or imme- 
 diately into this finus itfelf, or lafdy, by a divided 
 extremity into each of the tranfverfe finufes. It re- 
 ceives the lower and pofterior veins of the dura 
 mater, and feune from the vertebrae. 
 
 cccxxxii. The anterior occipital finus, irregular 
 and multiform, partly tranfverfe, and partly de- 
 feending to the great foramen, is united in various 
 ways with the lower petrous finufes ; from whence 
 branches either accompanying the nerves of the 
 ninth pair, or pafiing through a peculiar foramen, 
 communicate with the external vertebral vein ; 
 while otlier branches, going downwards, open into 
 the venous circles of the fpinal marrow. But the 
 cavernous finus of the dura mater, (cccxxv.) which 
 is furrounded with a good deal of cellular fubftance, 
 befides the finufes (cccxxix. cccxxx.) and large 
 veins already deferibed, alfo receives the ophthalmic 
 and principal vein of the dura mater ; it likevnfe 
 tranfmits peculiar veins, accompanying the firft, and 
 fecond, and third branches of the fifth pair, the prin- 
 cipal artery of the dura mater, (ceexvi.) and the in- 
 ternal carotid, (ceexvi.) and alfo through a foramen 
 in the great wing, which is not conftant ; it fends 
 branches which inofculate evith veins on the outfide 
 of the Ikuil belonging to the jugulars, and efpeciaily 
 with the large pterygoid plexus of the nafal veins. 
 
Chap. X. 
 
 BRAIN AND NERVES. 
 
 155 
 
 In the fame manner, the veins of the pericranium 
 pafs through foramina in the parietal bones into the 
 longitudinal fmus, the occipital veins through the 
 maftoid hole into the tranfverfe fmus, and the ex- 
 ternal vertebral veins through the anterior canal of 
 the occipital bone, into the folfa jugularis ; and 
 others from the anterior occipital veins accompany 
 the nerve of the ninth pair. Thus there are an in- 
 finite number of ways open to the blood, by which 
 it may efcape from the linufes, wherein it is often 
 collected in too great quantity, in various directions, 
 according to the laxity or declivity of the part. 
 Hence no violent fymptoms follow upon tying a 
 vein, hov/ever large, or even both the jugulars. 
 
 cccxxxiii. The quantity of blood which goes to 
 the brain, the great impulfe with which it is fent 
 into the carotid arteries, (cccxix.) the immunity of 
 a part defended by bones from every kind of pref- 
 fure ; the flow motion of the blood through the 
 abdominal vifcera and lower extremities 5 the per- 
 petual exerciie of the brain and fenfes, which de- 
 termines an influx of blood to thefe parts, and 
 other circumftances, caufe the head to be furprif- 
 ingly filled v/ith blood, immediately on any increafe 
 of the circulation. Hence the rednefs of the face, 
 the turgefcen.ee of the eyes, the fparkling, the head- 
 ach, the throbbing, the haemorrhages from the nofe, 
 which are fo frequently produced by violent exer- 
 cife. Therefore, it is evidgnt, that, if the veins in. 
 the brain were thin and round, the imminent dan- 
 ger of rupture and apoplexy, even now frequent, 
 could not poflibly be avoided. On this account, 
 to the veins which carry out the blood from the 
 brain, nature has given another form more eafily 
 dilatable, becaule it makes an unequal refiflance 5 
 and another texmre, of great firmnefs, and more 
 difficultly ruptured, efpeciaUy in the large finufes, 
 which perform the office of trunks ; for the fmall- 
 er finufes are either rounder, half cylindrical, or 
 
BRAIN AND NERVES. 
 
 Chap. X. 
 
 ts& 
 
 of an irregular figjire. Within, nature has furnifhed 
 thehnufes with crofs braces, formed of ftrong mem- 
 brane, palling from the right fide of the bottom of 
 the finus-to the left, w^hich, in excefilve difientions, 
 ftrengthen the acute angle wdiich is moft diftended, 
 and fecure it from rupture. She has likewife, in 
 thefe veins, provided numberlcfs inofculations, both 
 mutually amongft themfelves, and with the external 
 veflels of the head, and with thoie of the fpinal 
 marrow, that they m^ay, wfith greater facility, dif- 
 cliarge their fuperabundant blood, (cccxxxii.) 
 
 cccxxxiv. Is arterial blood aJfo poured into the 
 finuics of the brain ? Do they pulfate, by being ex- 
 cited by that blood ? It is alloveed, that they have 
 no pulfiition ; becaufe the dura mater every way 
 adheres to the fnui], and moft firmly in the regions 
 of the finufes. They certainly receive liquors in- 
 jccfed by tlie aiteries. Whether are thcfc exhaled 
 through the fmalL vcfiels, or do they, in the find 
 place, circulate through the veins ? The latter opin- 
 ion is much more probable. 
 
 cccxxxv. Ail the blood of the brain is finally 
 conveyed into the jugular veins, which are very 
 dilatable, and for that reafon protected by valves, 
 againfe the regurgitation of blood from the auricle, 
 and furrounded with a great quantity of cellular 
 fubfiance. For the blood, which comes from tlic 
 head to the vertebral veins, is very inconfiderable. 
 The jugulars, fo direffly correfpond with each of 
 the principal branches of the vena cava fuperior, 
 tha,t they bring back the blood to the heart in the 
 fliortefi; way, and that the right one proceeds in a 
 ftraight line from the right auricle. They feparate 
 nearly as the arteries, into a facial and cerebral 
 branch. 
 
 ccacxxvi. The external jugular is a cutaneous 
 vein of the neck, which gives off the temporal one : 
 it is united by a broad anafiomofis with the internal 
 jugular at the bans of the loveer jaw } and fends a 
 
 biTtUcii 
 
Chap. X. 
 
 BRAIN AND NERVES. 
 
 257 
 
 branch through the os mamillare into the tranf- 
 X’^erfe finus. The internal vertebral empties itfelf 
 through the tranfverfe proceiles of the neck into 
 the tranfverfe finus, -when the canal belonging to it 
 is open. 
 
 cccxxxvii. The firtufes of the fpinal marrow, 
 which are two in number, and lateral, run along 
 its whole length, are joined at each vertebra by a 
 femicircular arch, and are finally united with the 
 jugular and occipital finufes ; they fend branches, 
 however, to the fpinal marrow, communicatingwith, 
 the anterior and pofterior fpinal veins. 
 
 cccxxxviii. In confequencc of the innumerable 
 anaftomofes of the veins, tlie blood returns with the 
 greatefi; facility from the head, of which the reple- 
 tion is attended with much danger. During infpi- 
 ration, the brain is alfo more eafily evacuated, and 
 fubfides when the fkull is opened ; during exfpira- 
 tion, on the contrary, it fwells. Hence, blowing 
 the nofe, fneezing, and coughing, are dangerous to 
 thofe whofe brain is turgid with retained blood. 
 
 cccxxxix. Have lymphatic vefl'els been feen with 
 certainty in the brain ? They have been defcribed 
 in the large choroidal plexus, amongil the fibres of 
 the olfaHory nerve, and in the pia mater. For my 
 ov/n part, I have never feen them, and it is prob- 
 able that there are none, fince there are no conglo- 
 bate glands in the brain, which are always found 
 near thefe veffels. As for the various accounts 
 which are given of the pituitary gland, of the in- 
 fundibulum, and of the ducts which lead from 
 thence into the veins of the head, abforbine' water 
 from the ventricles, they are not fupported by any 
 anatomdcal demonftration : which makes it proba- 
 ble, that the vapour, which is fecreted into the ven- 
 tricles of a healthy perfon, is, in like proportion, 
 abforbed again by the inhaling veins ; and that if 
 there be any excels, it defcends through the bottom 
 of the ventricles to the bafis of the fkull, and into 
 
 the 
 
BRAIN AND NERVES. 
 
 Chap. N. 
 
 '158 
 
 ' the loofe cavity of the fpinal marrow. That this 
 is the cafe, appears from paliies, which cnfue after 
 apoplexies ; and from the v/atery tumours in the 
 lower part of the fpinal marrow, in hydrocephalic 
 patients. 
 
 cccxL. It now remains for us to fpeak of the en- 
 cephalon itfelf. There are feveral parts included 
 under this general denomination. By the brain, 
 properly fo called, v/e underhand the upper part of 
 that viicus, which is contained in the Ikull, and 
 which alone occupies its anterior portion ; but be- 
 hind, it lies above another part, called the cerebel- 
 lum, which is htuated in the pofterior and lower 
 cavity of the occipital bone, under the tentorium. 
 Its lower, middle, and white portion, lying under 
 the brain, and before the cerebellum, is in part call- 
 ed the pons, and in part the medulla oblongata. 
 
 CCCXL I. The figure of the brain refembles that 
 of half an egg, which is deeply divided longitudi- 
 nally, not through the whole, but through more 
 than the half of its length, into hemifpheres, re- 
 fcmbllng the quarters of an egg. Both the upper 
 and lower furfaces in man, are full of convolutions, 
 v/hich, with alternate round angles, pretty deeply 
 divide the brain into undulated lobes. But .the 
 largeft is, that which afcends on both fides out- 
 wards from the fides of the fella turcica, and di- 
 vides the hemifpliere into two lobes. Upon the fur- 
 face of thefe lobes, lies the cortex, which is ex- 
 tremely foft, and of an afh colour, tinged with yel- 
 low or red. It is the moft tender of all the parts in 
 the human body. The internal parts are occupied 
 by the medulla, which is almoft white, but redder 
 in the foetus ; perforated by very numerous, recH- 
 lineai and firnple arteries, more folid and more ca- 
 pable of fufcaining its hgure, notwithfeanding it is 
 very foft, and in greater quantity than the cortex. 
 The greater pofierior branch of the carotid artery 
 (cccxvii.) divides each hemifphereof the brain in- 
 to a fmailu' aiiterior lobe, raid a lamer nollerior lobe. 
 
 CCCXLII. 
 
Chap. X. 
 
 BRAIN AND NERVES. 
 
 159 
 
 cccxLii. The fabric of the cortex was long a 
 fubject of controverfy ; but it is now fafficientiy 
 evident, from anatomical injections, that* much the 
 greater part of it conhfts of veliels, which arife in 
 every part from the branches of the pia mater, like 
 footftalks, enter into the cortical fubftance, and 
 convey a fluid thinner than blood ; and fometimcs, 
 in difeafes from ftranguiation, and in animals, efpe- 
 ciaily in birds, they receive even the true blood- 
 The remaining part of the cortex which is not fill- 
 ed by any injection, is probably either an affemblage 
 of veins, or of yet more tender veffels ; for no 
 diffimilarity, which would lead us to conjecture one 
 part of it to be tubular, and the other part folid, 
 is apparent in the cortex, in its healthy hate. Be- 
 fides, of the apparently uniform cortex, a greater 
 portion becomes vafcular j the greater the induftry 
 which has been employed in filling the veffels, and 
 the greater the tenuity of the injection. The idea 
 of its being glandular, has been difcarded by uni- 
 verfal confent ; nor indeed was there ever any opin- 
 ion received with lefs probability than this. 
 
 cccxLiii. In order to underftand the nature of 
 the medulla, we are to confider the internal ftruc- 
 ture of the brain, compared with the brains of brute 
 animals and filh. That part of the brain which lies 
 immediately under the external convolutions, is of a 
 white colour, and becomes gradually broader and 
 more abundant ; fo that at length, it compofes the 
 whole oval feclion of the brain, except only corti- 
 cal covolutions on* its furface. In this part, the 
 two hemifpheres of the brain, which I before ob- 
 ferved were not entirely divided, are united by a 
 central portion of medulla. That part of the me- 
 dulla which lies under the falciform proceis, but at 
 fome diftance from it, is called the corpus callo- 
 fum ; in the upper furface of which run two paral- 
 lel white ftripes, formed by the puKation of the ar- 
 teries, diverging forwards, and terminated at the 
 
 anterior 
 
BRAIN Mm NERVES. 
 
 Chap. S. 
 
 i6o 
 
 ^interior commifiure, and in like manner divided 
 backwards. The anterior extremity of the corpus 
 callofum, is loft in the fubftance of the crura cere- 
 bri, comirtg from the anterior lobes of the brain : 
 the pofterior extremity, which is broader, vdth its 
 ihorter termination bent in the fliape of a talon, pen- 
 etrates inwards, and defcends with another por» 
 tion into the inferior horn of the ventricle ; and 
 with its longer termination is continued into the 
 hippocampus. Moreover, the whole ftirface of this 
 fubftance is ftreaked with tranfverfe fibres, which 
 are continued, but extenuated, into the adjacent 
 medulla of the brain. Even its interior fubftance 
 is of a ftriated nature, and its lower furface has its 
 raphe and tranfverfe fibres. 
 
 cccxLiv. What follows is more difficult to be 
 underftood ; for the brain is not folid, but from the 
 bottom of its medullary portion, which is incum- 
 bent UDon the multiform bone, where the jrreater 
 crus of the brain pafles out from it, a cavity com- 
 mences, covered only with the pia mater, which 
 gradually afcends backwards, and then turriing, con- 
 tinues its courfe forwards and upwards. Then it 
 divides itfelf near the pofterior extremity of the 
 corpus callofum ; and vdth its fliorter pofterior por- 
 tion it ends in the pofterior lobe of the brain, 
 with its extremity directed inwards, and filled vath 
 the talon mentioned above ; but its anterior portion 
 is extended along the fide of the corpus callofum, 
 parallel to the horizon, and with a horn incrcafing 
 in breadth outwards, it terminates in the anterior 
 lobe of the brain. The cavity thus formed, of 
 which there is one in each hemdfphere of the brain, 
 and which do not communicate, is called the ven- 
 triculus anterior or tricornis. It is naturally filled 
 with vapour, which is frequently condenied into 
 water or ieliy. 
 
 cccxLv. This cavity has no vacuity, for the upper 
 and lower portions of the brajn mutually touch each 
 
 other. 
 
Chap. X. BRAIN AND NERVES. i6i 
 
 other. Below, its floor is varioufly figured. Ante- 
 riorly, it confifts of a horn, having in its lov/er part 
 an eminence, which is flightly convex, long, diver- 
 ges backwards, is covered with an extremely vafcu- 
 lar membrane, and is outwardly cinereous. They 
 are called the corpora ftriata ; becaufe inwardly 
 they exhibit, intermixed with much cortical fub- 
 flance, alternate white oval ftreaks, parallel to one 
 another, and longer behind, befides lefler fpots and 
 points, as if of medullary fubftance. More inwardly 
 and pofteriorly, two other fimilar eminences, more 
 of an egg like fliape, towards the third ventricle 
 and other parts in a great meafure cinereous on the 
 outfide, and obfcurely ftriated, incline towards each 
 other, fo that they frequently cohere on the upper 
 part, by the intermixture of their cortical fubflance : 
 thefe, going inwards and defcending through the 
 horn of each anterior ventricle to the bails of the 
 Ikull, generate the optic nerves, of which they are 
 called the thalami. Between the corpora ftriata 
 and thalami, there is an intermiediate, parallel, and 
 white band of medullary fubftance, which is called 
 the centrum femicirculare geminum, produced from 
 the anterior commiffure, and frequently from the 
 crura of the fornix ; but efpecially from the me- 
 dulla of the brain itfelf, before the thalami. This 
 commiflure, which is broad and ftrong, joins togeth- 
 er the anterior part of the brain before the thalami. 
 The centrum geminum, wdiich is broadeft behind, 
 arifes with many fibres from the jundlion of the pes 
 hippocampi with the medulla of the brain. The 
 corpora ftriata, with the thalami, conftitute the 
 medullary crura of the brain ; which, in the bafts 
 of the cerebrum, pafs over the medulla of the cere- 
 bellum, and are joined together at the anterior ex- 
 tremity of the bridge, to be defcrlbed hereafter. 
 Where they approach neareft to one another, each 
 fends out an hemifpherical eminence, called mtamil- 
 lary. The fibres of the medulla of tlie brain itfelf, 
 M interwoven 
 
i62 brain and nerves. Chap. X. 
 
 interwoven with the medulla of the cerebellum, 
 defcend into the medulla oblongata ; and, being- 
 then collected into a bundle, they go to the corpo- 
 ra pyramidalia. 
 
 cccxLvi. The corpus callofum projects in the 
 middle over the common axis of thofe ventricles. 
 Behind, it refts contiguoufly upon the fornix. Be- 
 fore, two fimilar medullary partitions, v'hich are 
 called the feptum lucidum, triangular, united be- 
 low, with their vertex inclined backwards, and in- 
 cluding an anonymous central cavity, defcend from 
 this body along the corpora ftriata, even to the 
 union of the thalami. This feptum below is con- 
 tinued to the fornix, which is a ceiling fupported on 
 four pillars, having its anterior origin from the 
 medulla of the brain, and fometimes from the ma- 
 millary protuberances, and the cornmiflure which 
 we have mentioned ; and behind that, particularly 
 under the thalami, often both from the centrum ge- 
 rninurn and curved line of the thalami. This fornix 
 is incumbent upon the interval between the corpora 
 feriata, and upon the interval between the thalami ; 
 and degenerates partly into a broad thin fimbria, the 
 pes hippocampi, where it is divided into toes ; and 
 partly into other tubercles, which are continuous 
 both with the fornix and corpus callofum, but more 
 evidently continued from the latter, as larger, and 
 are femi-cylindrical, having the fimbria attached to 
 them. Thefe defcend into the lower anterior horns 
 of the ventricles ; and at lafi: terminate in an arch, 
 convex outwards, and commonly divided by ten fur- 
 rows, imprinted on it by the convolutions of the 
 brain, and in a four toed hoof, whence the name of 
 hippocampus, which is externally covered by an ex- 
 ceedingly thin medullary lamina, but internally 
 confihs of cortical fubftance. At the beginning of 
 the divifion of the pes hippocampi, the taenia ends 
 in two white ftriee, a long and a fliort one, inferted 
 into this foot and into the brain, or in one inferted 
 
 into 
 
Chap. X. 
 
 BRAIN AND NERVES. 
 
 163 
 
 into the moft internal unguis. A like protuberance, 
 continuous with the corpus callofum, enters into 
 the pofterior horn of the ventricle, crooked imvards 
 at its extremity, like the fpur of a bird, the pofterior 
 part of the defcending horn of the ventricle being 
 occupied by a column continuous with it. Between 
 the diverging pofterior crura of the fornix, the me- 
 dullary portion, which is behind the middle plexus 
 of the ventricles, and marked generally with tranf. 
 verfe and palmated ftreaks, is called the pfalterium. 
 
 cccxLvii. In the anterior and lower part of the 
 ventricles, on each fide, begins the choroid plexus, 
 included in the pia mater only, lying naked in the 
 reft of the ca\nty of the fkull, made up of a great 
 many fmall arteries (cccxvii. cccxviii.) and veins 
 originating from the large trunk, (cccxxv.) all 
 which numerous veflels, joined together by the pia 
 mater, refemble a curtain varioufly folded. It is 
 often, but not always, intermixed with many pel- 
 lucid glands of a round figure, refembling hydatids. 
 It afcends from the bafis of the brain, through the 
 defcending horn of the ventricle, and becomes dilat- 
 ed as it proceeds upwards ; but afterwards becom- 
 ing narrower, it goes along the optic thalamus, to 
 the pofterior extremity of the feptum luciduin. 
 When thefe plexufes have reached the anterior ex- 
 tremity of the thalami, they cohere, and are continu- 
 ed with a remarkable vafcular plexus, which gradu- 
 ally defcends along the roof of the third ventricle 
 as far as the pineal gland, and is continued into the 
 pia mater of the pofterior lobes of the brain. From 
 this proceeds the internal warmth of the brain, and 
 it undoubtedly exhales and inhales. The choroid 
 plexufes are very broad where the anterior ventri- 
 cles begin to defcend ; contracting gradually down- 
 wards, they projeff in the inferior anterior end of 
 the ventricle, covered only by the pia mater. 
 
 cccXLviii. Between the thalami, applied to each 
 other almoft with a plain furface, there is a natural 
 ra 2 fiffure. 
 
BRAIN AND NERVES. 
 
 Chap. X. 
 
 i64 
 
 liffure, wnich is terminated by the crura of the 
 brain meeting together in the bafis of the fkuU r 
 this is called the third ventricle. It leads by a per- 
 pendicular funnel, forwards into a cortical column 
 it is hollow in brutes, lefs evidently tubular in man> 
 and connected to the pituitary gland. 
 
 cccxLix. This gland, flattened on both fides^ 
 Ample, of uncertain ftruclurej in the Interior larger 
 part, almoft round, and of a reddifli colour ; in the 
 poiterioF part lefs, cinereous, tranfverfely broad ; 
 covered with the pia mater of the brain ; lies upon 
 a proper deprefiion of the feUa turcica, and feems 
 to be a kind of appendix to the brain. 
 
 cccL. Backwards, the thalami, are conjoined in 
 
 the bottom of the ventricle, by a central medullary 
 
 fafeia, or pofterior commiflure, and by a fmaller 
 
 trarifverfe chord ; from which, on each Ade, an 
 
 arched white band goes out in the upper part, which 
 
 lofes itfelf in the centrum geminum, and in the- 
 
 anterior commiflure, and fometimes in the crus 
 
 ©f the fornix. On the fore and upper part, the 
 
 thalami have a protuberance, which is formed by 
 
 the triansfular fornix Atuated between the two tha- 
 o 
 
 lami. 
 
 cccLi. This eminence feparates the upper trian- 
 gular cavity of the third ventricle. Ailed up with 
 the fornix, from the inferior calamus feriptorius^ 
 fo that the cavity is continued both to the anterior 
 and poflerior extremity of the third ventricle, from 
 the top to the bottom. But the anterior commif- 
 fure is alfo a medullary band which unites the tha- 
 lami before the anterior crura of the fornix. 
 
 cccLii. For a pofterior, tranfv'erfe, Agured emi- 
 nence is applied to the thalami, which conjoins the 
 medulla of the right and left pofterior lobes of the 
 brain. It is marked behind by four oval emi- 
 nences, v'hich are outwardly fmaller, called the 
 nates and teftes, and which confift externally of 
 fome medulla, and internallv of cortical fubftance. 
 
 The 
 
'Chap. X. 
 
 BRAIN AND NERVES. 
 
 155 
 
 The {iiperior ones in man are the largeft, and are 
 called the nates. Upon thefe is feated a cortical 
 gland, ovally conical, fupplied with many velTels,, 
 into which the choroid plexus degenerates ; this is 
 the celebrated pineal gland fo frequently difeafed, 
 which is joined to the brain by fmail footftalks fent 
 into the linea alba through the thalami in their pat- 
 fage forwards. Between this eminence, marked 
 with thefe four protuberances, and the crura of the 
 medulla oblongata, a canal refembling an aqueduct, 
 and manifeftly open, paffes from the third to the 
 fourth ventricle. 
 
 cccLiii. The whole medulla of the brain below, 
 is collected together in its bahs, into two very thick 
 compreffed columns, having their furface longitu- 
 dinally marked with lines, and conlifting exter- 
 nally of medulla with fome cortical fubfiance in- 
 ternally. Thefe are the crura of the brain. Thefe, 
 meeting together backwards, are covered by the 
 fubjacent crura of the cerebellum, and are infert.- 
 ed by apparent ftrata of fibres into the pyramidal 
 bodies of the medulla oblongata ; and with other 
 deeper tranfverfe fibres, which feparate the inner 
 fibres that come from the cerebellum from the 
 preceding, conftitute, together with the medulla 
 cerebelli, the beginning of the medulla oblongata, 
 
 cccLiv. The cerebellum, as it is lefs, fo it is 
 more fimpie than the brain. It has two lobes, but 
 no where deeply parted, united above and below 
 by a central ring of the fame fabric with itfelf, 
 ealled the vermis, at the fide of which there is a 
 broad fmooth eminence of the fame nature with 
 the cerebellum. This part of the encephalon con- 
 tains a great deal of the cortical, and little of the 
 medullary fubfiance. And here, likewife, the cor- 
 tex is placed in the circumference, but marked 
 with furrows, which are mofdy parallel, fo as to 
 form circular arclies. Thus the lobules are defin- 
 ed. 
 
BRAIN AND NERVES. 
 
 Chap. X. 
 
 1 66 
 
 ed. but not deeply, each of which contains its 
 medulla, and by tlie gradual union of many of thefe 
 medullary branches into one trunk, an arbufcular 
 appearance is produced. This luedulla, coHecled 
 together into the large crura of the cerebellum, and 
 internally marked with ferrated and intricate cor- 
 tical lines, has a threefold termination. One part 
 afcends towards the bafis of the nates, where it 
 joins the medulla of the brain under the teftes ; 
 and the right is alfo joined to the left by a tranf- 
 verfe medullary band behind the nates. From 
 this, fome dillinct fibres afcend outwards, and join 
 themfelves to the tranfverfe ones of the bridge. 
 Between thefe firft prccelies of the cerebellum, is 
 flretched a medullai-y lamina, behind the fourth 
 ventricle, fending forth fibres beyond the procefs. 
 The fecond portion defeends into the fpinal mar- 
 row, and terminates in peculiar ftudded protuber- 
 ances, having other cortical protuberances adjacent, 
 both of which are anonymous. The third portion, 
 which is larger, and fituated in the middle, going 
 tranfverfely dovmwards, pafles under the crura of 
 the brain, which it embraces ; and being twice 
 alternated with their medullary fibres, (ccclii.) by 
 its own tranfverfe fibres, it is in a great meafure 
 blended with them. 
 
 cccLv. Thus, from the crura of the brain dc- 
 feending over thofe of the cerebellum, and from the 
 medulla of tlie cerebellum tranfverfely furround- 
 ing that of the cerebrum, there is produced, in the 
 firft place, the pons, vrhich is almofi; oval, but more 
 flattened on both fides, deprefled in the middle, 
 and every where marked with tranfverfe fibres. 
 Then, continuous v.ith the pons, the medulla ob- 
 longata is formed, vTiich is internally variegated 
 and fireaked with feme cortical fubftance, is of a 
 conical fliape, and defeends directly to the great 
 foramen. This meduila has two pairs of tubercles 
 before the pons j the outerinofi; of the figure of 
 
 an 
 
Chap. X. 
 
 BRAIN AND NERVES. 
 
 167 
 
 an olive, and the innermoft of a pyramidal flrape, 
 diminilhing conically downwards : thcfe are divid- 
 ed in the middle by a furrow, into which the pia 
 mater enters. But betwixt this medulla and the 
 vermiform procefs of the cerebellum, is formed a 
 cavity, limited by the four lelfer proceifes, which 
 afeend and defeend ; at firft it is narrower, but above 
 the tubercles (cccliv.) it grows broader, and is of 
 a rhomboidal figure : it is called the fourth ven- 
 tricle, and is fhut behind by the valvula magna, or 
 medullary velum, which unites the procefles going 
 from the cerebellum to the nates, and the vermis, 
 with the tranfverfe band lying under the teftes, 
 and fliuts the ventricle behind, (cccliv.) This 
 ventricle has a moderate furrow, bounded on each 
 fide by tumiid edges, inferibed on the medulla ob- 
 longata, and correfponding to a canal which is 
 covered by the nates and teftes, and is called the 
 aqueduct, (cccxlviii.) In this laft ventricle, as in 
 the foregoing, there is a plexus choroides,onlylefs, 
 and a fulcus called calam.us. Each of thefe fulci is 
 continued down along the m.edulla fpinalis, the 
 anterior moft evidently, the pofterior lefs fo. In 
 the former, tranfverfe fibres are detached from the 
 right to the left fide, both in the medulla oblon- 
 gata and fpinalis. But two or three of the trlnf- 
 verfe ftreaks of the fourth ventricle, terminating 
 in the foft nerve, arife from the eminences inclof- 
 ing the fulcus ; others go to the eighth pair, and 
 others of the fame kind afeend to the crus of the 
 cerebellum. 
 
 cccLvi. All the medulla of the brain and cere- 
 bellum paftes out from the flcull, through different 
 openings, to the places for which it is deftined. 
 The fmaller bundles of this medulla we call nerves ; 
 but the larger, Avhich is a continuation of the ob- 
 longata, we call the medulla fpinalis. The nerves 
 are medullary fafciculi, very foft in their origin, 
 and compofed of chords of fibres meeting from the 
 
 brain, 
 
i68 
 
 BRAIN AI'JD NERVES. 
 
 Cmap. X, 
 
 brain, even there in fome examples, dihinct, ftraight 
 and parallel in the nerve. Thele chords, after hav- 
 ing proceeded fome way, and being covered with 
 the pia mater, which is fomewhat red and firm, 
 are united into a more conftant fafcia ; and then, 
 conjoined with others of the fame kind by cellular 
 membrane, divided, and contiguous, go on to their 
 proper opening in the dura mater, and run along 
 its canals and intervals, till they meet with an open- 
 ing in the ikull, out of which they pals through a 
 funnel of the dura mater. The nerve, having ar- 
 rived without the ficull, is commonly furrounded 
 by the dura mater, and becomes folid and firm. 
 This is the cafe in the optic nerve, in the fifth pair, 
 and in others ; but in fome again there does not 
 appear to be any dura mater furrounding the nerve, 
 as in the olfacfory nerves, in the foft portion of the 
 auditory nerve, and the intercofcal. The nerves, 
 now naked and lefs defended, amongft the mufcles, 
 are compofed of chords, each of which has its medul- 
 la, and its flreath of pia mater. The ultimate cht>rds 
 of this kind unite into other larger chords, furround- 
 ed by much ceilular fubflance, through which run 
 many frnall arteries and veins ; and fometimcs fat 
 itfelf is depofited. But the general covering, com- 
 mon to the whole nervous bundle, is formed by 
 fome indurated cellular fubftance, often refembling 
 a true membrane, which envelopes them all, and 
 combines them into one nerve. 
 
 cccLvii. I'he whole of the nerves of the head 
 arife from the lower part of the medulla of the brain 
 or cerebellum. The olfacfory nerve arifes by a lat- 
 eral fibre from the interval betwixt the anterior 
 lobes of the brain, and by a direct fibre from the 
 medulla of the anterior lobe itfelf. A great part of 
 the optic nerve fprings from the thalami, (cccxlv.) 
 but fome part likewife from the. crus of the brain, 
 v/hiie the nerves decullate it. The third pair arifes 
 from the bottom of the crus of the medulla of tlic 
 
 brain. 
 
Chap. X. 
 
 BRAIN AND NERVES. 
 
 169 
 
 brain, behind the mamillary proceffes. The fourth, 
 whether funple or bifid, proceeds from the fide of 
 the procefs of the cerebellum to, the teftes. The 
 fifth arifes plainly from the peduncles of the cere- 
 bellum. The fixth from the bottom of the pons, 
 from the deep fulcus (cccliv.) between it and the 
 meduUa oblongata. The feventh arifes with one 
 portion, which is fofter, pofterior and larger, from 
 the medulla oblongata, and by two tranfverfe ftriae, 
 from the fourth ventricle itfelf ; and with another 
 harder portion, from that part of the crus of the 
 cerebellum next the pons. The eighth from the 
 interval between the corpora olivaria and pyrami- 
 dalia, out of a furrow of the medulla oblongata ; 
 and, according to the obfervation of other eminent 
 anatomifts, from the fourth ventricle itfelf. The 
 ninth arifes from the corpora olivaria and pyrami- 
 dalia. The tenth is a nerve of the neck, as appears 
 from its double root, its conjunclion with the up- 
 per and lower adjacent nerves, and its place of ori- 
 gin. Therefore, no nerves arife properly from 
 the cerebellum, unlefs the fifth and fourth ; for the 
 anterior nerves, the olfactory, optic, and third 
 pair, come from the brain only ; and all the reft 
 from thofe parts where the medulla, both of the 
 brain and cerebellum, are conjoined. 
 
 cccLviii. The fpinal marrow is a veiy foft me- 
 dullary rope, which defcends from the medulla 
 oblongata, as low as the fecond vertebra of the 
 loins. In the neck it is fiat before and behind, and 
 gibbous at the fides ; in the back it is almofl; qua- 
 drangular. It is largefi where it goes out from the 
 head ; from thence it becomes fmaller in the top 
 of the neck, then larger at its lower part ; again it 
 is fmaller throughout almofi: the whole back, but 
 thicker at bottom ; and laftly, it ends in tubercles, 
 one conical, another oval. Like the brain, it is in- 
 vcfied with its own pia mater, which enters deeply 
 into its anterior filfare, and almofi: divides the me- 
 dulla 
 
BRAIN AND NER v^S. 
 
 Chap, X. 
 
 170 
 
 dulla into two. Within it has fome obfcure cortical 
 fubftanee ; its anterior artery arifes in the Ccull, 
 from the branches of the vertebrals ; it is retro- 
 grade, defcending through the whole length of the 
 pia mater, perpetually making alternate hnuous 
 flexures, forming inofculations about many, but not 
 all of the nerves, with branches of the vertebral, 
 intercoftal, lumbar, and facral arteries ; till at laft, 
 covered v/ith a peculiar coat from the pia mater, it 
 goes out at the coccyx and difappears. Two pof- 
 terior arteries, flmilar, but fmaller, arife from the 
 lower arteries of the cerebellum : thefe are more 
 ferpentine, and have frequent mutual inofculations. 
 The fpinal veins accompany the arteries in their 
 defeent from the brain itfelf, and fend out branches 
 m like manner, accompanying the nerves into as 
 many circular iinufes, fituated in the dura mater, 
 as there are vertebree, all of which fo communicate 
 one with another, that each communicates with 
 thofe above and below it, by a flraight duct, in each 
 direction, and, by a branch fent outwards, unites 
 with the vertebral, intercoflal, lumbar, and facral 
 veins. The uppermoft of thefe fmufes inofeuiates 
 with the anterior occipital finufes, (ccclii.) 
 
 cccLix. But the fpinal marrovr is furrounded 
 by another covering, loofely and at fome diflance, 
 which is not vaicular, but pellucid like water, tol- 
 erably firm and continued from the brain. It is 
 called arachnoid, is longer than the pia mater, be- 
 ing extended to the bottom of the os facrum, and 
 there it alone includes the bundle of contiguous 
 nerves. But in what manner it accompanies the 
 nerves in their paffage out, has not been hitherto 
 deferibed. Between that membrane and the dura 
 mater, there is a vapour, which is frequently con- 
 denfed into a reddifh water, and produces a true 
 dropfy. 
 
 cccLx. Lafdy, the dura mater of the fpinal mar- 
 row is continuous with that of the brain, furrounds 
 
Chap. X, 
 
 BRAIN AND NERVES. 
 
 171 
 
 the araclinoides, in like manner defcends to the bot- 
 tom of the os facrum, larger at its beginning, at the 
 bottom of the neck, and at the loins, but flenderer 
 in the back, and at laft terminates in a llender 
 cone, attached by many ligaments to the periof- 
 teum of the os facrum. As the nerves pafs 
 through this membrane, it gives them an external 
 covering, which direclly enlarges with them into a 
 ganglion, or hard, oval, reddilh knot. To this dura 
 mater in the intervals between ail the nerves, a den- 
 ticulated ligam.ent internally adheres, which arifes 
 from the Ikull near the paffage of the ninth pair of 
 nerves, and connects the arachnoid to the dura ma- 
 ter by triangular produftions, in each of the inter- 
 vals, between the anterior and potter ior bundles of 
 the nerves down to the bottom, and twelfth verte- 
 bra of the back. Externally, the dura mater is 
 furrounded by fome lubricating fatty matter, and 
 then by the internal covering of the vertebrae, which 
 are themfelves fo conttrucfed into a canal, that the 
 fpinal marrow is not compretted by it in any of its 
 flexions. 
 
 cccLxi. The fibres of the fpinal marrow appear 
 diftincl in dropfical fubjetts, and in brute animals. 
 Thefe arife from the whole anterior and potterior 
 furfaces of the fpinal marrow ; and commonly the 
 anterior chords included in the pia mater, converge 
 like rays into a larger fafciculus ; to which a fimilar 
 falciculus of the potterior filaments accedes, form- 
 ing one nerve, which, patting out through a hole of 
 the dura mater, between every two vertebrae, pro- 
 duces a nerve. The vertebral nerves are about 30 
 in number. In the neck, numerous radiated ner- 
 vous fibres compofe one large and almott tranfverfe 
 nerve. In the back, they defcend, in general, 
 fmaller j but 10 that the lower and larger ones are 
 commonly contiguous to one another. The large 
 and long lumbar ones join to form the cauda equina. 
 The lowett nerves of the os facrum are very fraall. 
 
BRAIN AND NERVES. 
 
 Chap. X. 
 
 172 
 
 the uppermoll ones large. Many of the dorfal 
 nerves, together with the lumbar and facral ones, 
 covered v/ith their proper pia mater, accompanied 
 by their arteries, and inciofed in the arachnoid 
 membrane, conftitute that chord which is called the 
 cauda equina. 
 
 cccLxii. Thofe nerves are dlftributed to all parts 
 of the body in a very complicated manner, which 
 does not admit of a defeription in this place. But 
 the following particulars cannot be palled over. All 
 the fpinal nerves, except one or two in the neck, 
 after palling out of the vertebrae, have botli an 
 anterior and pofterior trunk. The former is fent 
 tO" the mufdes only. The latter forms a ner- 
 vous root, which joining with its fellows, and vvitli 
 a fmall accelfory branch, which comes through the 
 pterygoid canal, from the fixth nerve of the brain, 
 and the fecond branch of the fifth, forms one of t!ie 
 principal nerves of the humian body ; which, com- 
 municating; with almofl ail tlie other nerves of the 
 whole fyftem, fends out nervous branches to the 
 heart, and to all the vifeera of the abdomen. It has 
 as many ganglia as it has roots from the fpinal mar- 
 row, unlefs when feveral of them join into one gan- 
 glion. It communicates varicully with the crural, 
 braclaial, and diaphragmatic nerves, alfo with the 
 par vagum and ninth pair. Another principal nerve 
 is the eighth or par vagum, arifing from the brain, 
 and joining iifelf to the intercoftal in the bottom 
 of the neck, in the thorax, and in the abdomen ; 
 this paffes out of the Ikuil in three chords, of which 
 the larger fends branches to the larynx, throat, the 
 cardiac plexufes themTelves, (xcix.) lungs, cefopha- 
 g*us, ftomach, and liver. The third of thefe is the 
 phrenic nerve, arifing from mod of the lower nerves 
 of the neck, and having received an augmentation 
 from the brachial nerves, and fometimes from the 
 root of the ninth, it delcends along the pericar- 
 dium, and inferts itfelf into the upper furtacc of 
 the diaphragm j below, it is iiippiied from tlie 
 
Chap. X. 
 
 BRAIN AND NERVES. 
 
 173 
 
 great plexus of the intercoftal nerve. Laflly, the 
 acceffory nerve, arifing by many fmali roots from 
 the fix or feven uppermoft pofterior cervical nerves, 
 and from the medulla oblongata, returning into the 
 fkull, joins the eighth pair and feems to produce 
 fome Sympathy betvdxt that important nerve and 
 the fpinal marrow: Finally, tlie nerves of the 
 
 limbs originate from plexufes, and are on account 
 of their length, harder and larger, than the nerves 
 %vhich go to the vifcera ; thofe which go to tlie 
 hand, arife from the four lower nerves of the neck, 
 and firft and fecond of the back ; thofe of the low- 
 er extremities from the nerves of the loins and os 
 facrum. 
 
 cccLxiv. The nerves divide into branches like the 
 blood-^veilels, but in acute, and often manifeftly ret- 
 rograde, angles, growing gradually fofter and fmall- 
 er, though fometirnes they become thicker, as tliey 
 recede from the brain ; at length, with their ulti- 
 mate extremities, which are INdom vifibie, feem to 
 terminate in a pulp, by depofiting the firm integu- 
 ments with which they were covered, after the man- 
 ner which we obferve in the optic nerve. But the 
 rectilineal courfe of the fibres, continued from the 
 brain -itfelf, is fuch, that they are never divided in 
 any ramification, but only recede from each other, 
 where they had been connected by cellular fub- 
 llance. This appears from diforders, confined to 
 fome particular parts, not extended to the whole, 
 produced by affections of the brain ; as a lofs of 
 the voice, deafnefs, dumbnefs, and palfies of par- 
 ticular mufcles. They are connefted by cellular 
 fubffance to the adjacent parts, have hardly any 
 elafticity ; do not contrad on being divided, but 
 only expel their medulla by the contradion of their 
 integuments. In whatever way they are irritated, 
 they do not contrad, nor are they rendered fhorter 
 during the motion of the mufcles which they ex- 
 cite. A great many nerves are fent into the muf- 
 
 des j 
 
BRAIN AND NERVES. 
 
 Chap. X. 
 
 m 
 
 cles ; many to the Ikin ; fewer to the vifcera ; very 
 few to the lungs ; and none to the dura or pia ma- 
 ter, arachnoides, tendons, capfules, ligaments, and 
 lailly the whole fecondary membranes. Like the 
 veffels, they make frequent anaftomofes with each 
 ether, or out of one trunk they are divided into ma- 
 ny branches : and it is principally in the concourfe 
 of branches, arihng from different trunks, that 
 the ganglia are found. Thefe are hard nervous 
 tumors, for the moil: part vafcular, and included in 
 a iirm membrane, of which the ufe and ftructure are 
 uncertain, and in which the ftraight courfe of the 
 nervous fibres is interrupted. They are not found 
 in the nerves of the fenfes, or in the eighth pair ; 
 or in the phrenic nerves ; or in the nerves of the 
 extremities ; but are peculiar to the fpinal nerves, 
 to the intercoftal, which is in fact a fpinal nerve, 
 and to the fifth pair. 
 
 cccLxv. Theie are nearly what we have learned 
 from anatomy concerning the brain and nerves ; 
 the phyfxological ufes of thefe parts remain to be 
 inveffigated. Every nerve which is irritated, by 
 whatever caufe, produces an acute fenfe of pain. 
 Senfation is a change of the miind, produced by a 
 change of the body. It is the medullary part of 
 the nerve which feels. If a nerve be appropriated 
 to any peculiar fenfe, that fenfe perifhes when the 
 nerve is compreffed or divided ; and the fenhbility 
 of the whole body is deftroyed, when the brain is 
 compreffed ; or of thofe parts whofe nerves origi- 
 nate below the feat of preffure, if you comprefs the 
 fpina.1 marrov/. If certain parts of the brain, from 
 which particular nerves arife, be compreffed, then 
 thefe fenfes only are loff, as the fight or hearing. 
 Thofe parts of the body which receive nerves, pol- 
 fefs fenfibility moft acutely, when they receive 
 many, as the eyes and penis ; obtufely, when they 
 receive few nerves, as the vifcera ; and thofe which 
 have no nerves, as the dura mater, tendons, liga- 
 ments, 
 
Chap. X, BRAI^T AND NERVES. 175 
 
 ments, fecundlnes, the broad bones, and cartilages, 
 have no fenfation. 
 
 ccci-xvi. It is extremely probable, that all fen- 
 fation arifes from the imprefiion of a fenllble objeS: 
 on fome nerve of the human body ; and that the 
 fame being tranfmitted to the brain along that 
 nerve, is at laft reprefented to the mind, after it 
 has reached the brain. It therefore feems to be 
 falfe, that the mind perceives immiediately by means 
 of the fenforia and branches of the nerves. For 
 this opinion is refuted, by the pains felt after am- 
 putation, by the entire ceffation of pain when a 
 nerve is compreffed, and by the difeafes of the 
 fenfes from injuries of the brain. That the effe& 
 of the fenfes is preferved in the brain, is evident 
 from the lofe of memory which fucceeds compref- 
 fions or injuries of the brain ^ alfo from the deli- 
 rium which happens in fome difeafes, and the ftu- 
 por and lleepinefs which happen in others. We 
 have already obferved, that the dura mater has no 
 fenfation. 
 
 cccLXvii. Another office of the nerves is to ex- 
 cite the mufcles into powerful action. When a 
 nerve is irritated, the mufcle to which it goes is 
 immediately convulfed ; or the mufcles, if it fend 
 branches to feveral. This happens during the life 
 of the animal, and a little after its death w'hile 
 all the parts are Rill moift. By great irritation, 
 other mufcles are thrown into convullions, and 
 even the whole body. Nor is it necelTary that 
 the nerve fhould be entire ; for even when it is 
 cut, on being irritated, it will excite limilar mo- 
 tions in the mufcles. On the other hand, when a 
 nerve is compreffed or tied, a palfy follows ; for 
 the mufcles which have their nerves from that one, 
 lie unmoved, when they are commanded by the 
 will to act. They again recover their mobility, 
 when the compreffion is removed, provided the 
 nerve has received no injury. 
 
 CCCLXVIII* 
 
BRAIj^J Al'JD NERVES. 
 
 Chap. X. 
 
 1‘jG 
 
 cccL XVIII. When the medulla of the brain is 
 deeply wounded or irritated in its crura, dreadful 
 convulsions enliie throughout the whole body ; the 
 difference of the part irritated produces no ex- 
 ception ; nor does the brain, cerebellum, or corpus 
 callofum, enjoy any perogative in this rcfpcct. 
 The fame confequences follow, if the fpinal mar- 
 row be irritated. But if the encephalon itfelf be 
 compreffed, in any part whatever, there enfues a 
 lofs of lenfe and motion in fome part of the body, 
 which appears to be exactly that which has its 
 nerves from the part compreffed, according to ob- 
 servations of injuries of particular portions of the 
 brain, in which the orivinof the nerves beinsr com- 
 preffed, the voice is loft ; or the motion of one arm 
 or leg, or of one fide of the pharynx. In injuries of 
 the fpinal marrow, it is ftiU more evident, that thofe 
 parts v/hich receive their nerves from the place in- 
 jured, are convulfed if that be irritated, or rendered 
 paralytic if it be comprefled. But when any more 
 confiderable portion of the braiti is compreffed, 
 cither from blood, water, feirrhus, an impacted 
 bone, or other mechanical caufe, the greateft part, 
 or the whole of the body, lofes its power of mo- 
 tion ; the voluntaiy organs, if the lefion be in a 
 lefs degree, and all of them vv'hen it is greater ; ail 
 theie diforders ceafe upon removing the compref- 
 fing caufe. Laftly, if the fpinal marrow in the 
 neck be injured, death quickly enfues ; bccaufe, 
 from that part the nerves of the heart (xcix.) prin- 
 cipally arife. 
 
 cccLxix. Thefe things being confidered, there 
 feems to be no doubt, that ail motion in the human 
 body, proceeds in a great meafure from thebrain,and 
 its annexed cerebellum and fpinal marrow ; and that 
 it is thence conveyed through the nerves, to all the 
 mufcles and parts of the body. Befides, the caufe 
 of motion cannot rchde in the parts themfelves, fince 
 it would then remain after the brain is deftroyed, 
 
 and 
 
Chap.X. brain and nerves. 177 
 
 and would not be increafed by irritating the brain, 
 or weakened by comprehing it. 
 
 cccLxx. Is there in the brain any principal part, 
 which is the origin of ail motion, the end of all 
 fenfation, and where the foul has its feat ? Is this 
 proved by the frequent obfervation of the integrity 
 of the fenfes, and power of motion remaining after 
 fevere injuries of the brain ? Is it in the corpus 
 callofum ? Is this fhewn by the greater mortality of 
 wounds or difeafes in the corpus callofum ? Is this 
 body fufficiently connected with the nerves ? Are 
 there any experiments which derive from it the 
 fifth, feventh, and other nerves ? Does not the 
 fame, or even greater mortality, accompany wounds 
 of the medulla fpinaiis ? Yet this is not the feat of 
 the foul, fince, though it is compreffed or even de- 
 firoyed, the perfon will furvive a long time, with 
 the perfect ufe of all his fenfes. Nay this opinion 
 is oppofed by numerous fafts ; birds have no cor- 
 pus callofum 5 and wounds in that body, are not 
 in the leaft more mortal than thofe in other parts of 
 the brain, as appears from undoubted experiments. 
 
 cccLxxi. Nor does the cerebellum enjoy the 
 prerogative of exciting the vital aftions, nor are 
 the provinces of vitality and animality diftinct ; 
 nor does the cerebellum generate the nerves of the 
 heart and other vital organs, and the brain thofe 
 which go to the organs of fenfe and voluntary mo- 
 tion. From the cerebellum the fifth nerve is moil 
 evidently produced ; but that goes to the tongue, 
 pterygoid, buccinator, temporal, and frontal mufcles, 
 the ear, the eye, the noftrils, all which are parts 
 either moved by the will, or deftined for fenfe. 
 Again, the fame nerve, as the eighth, fends vital 
 branches to the heart and lungs, animal and volun- 
 tary ones to the larynx, and fenfitive ones to the 
 ftomach. Laftly, it is not even true, that diforders 
 of the cerebellum occafion death fo certainly and 
 fpeedily. For, from certain obfervations, even of 
 N our 
 
178 BRAIN AND NERVES. Chap. X. 
 
 our own making, it has borne wounds and fcirrhi, 
 without taking away life ; nor is it very different 
 from the brain, being only fofter and more tender ; 
 and, laftly, we read, and that not very rarely, of 
 wounds of the cerebellum being cured. The power, 
 however, of this part, in exciting convulfions, is 
 fomewhat greater. 
 
 cccLxxii. Concerning the feat of the foul, we 
 mufl inquire experimentally. In the firft place, it 
 muft be in the head, and not in the fpinal marrow. 
 For though the latter be affected, the integrity of 
 the mind remains the fame. Again, it appears, 
 from the experiment of con%nilfions arifing v/hen 
 the inmolt parts of the brain are irritated, that it 
 lies not in the cortex, but in the meduUa ; and not 
 improbably, in the crura of the medulla, the cor- 
 pora ftriata, thalami, pons, medulla oblongata, and 
 cerebellum. Finally, by another not abfurd con- 
 iecture, it lies at the origin of every nerve, fo that 
 the concurrence of the firft origins of all the nerves, 
 makes up the cenforium commune. Are the fen- 
 fations of the mind reprefented there, and do the 
 voluntary and neceffary motions arife in thatpkce? 
 This feems very probable. For it does not feem 
 pofiible, that the origin of motion can lie below 
 that of the nerve ; for that would be a gratuitous 
 fuppofition of immobility or infenfibility, in fome 
 part of the nerve, though perfectly ftmilar to the 
 reft. Nor can the origin of motion (cccnxix.) be 
 placed higher in the arteries, for they neither have 
 feeling, nor are excited to voluntary motion. It 
 therefore follows, that the feat of the mind, muft 
 be where the nerves firft begin. 
 
 O , - 
 
 cccLxxiii. We come now to the explanation of 
 the manner in which the nerves are the organs of 
 fenfe or motion ; which, as it lies hid in the ulti- 
 mate elementary fabric of the medullary fibres, 
 feems to be placed above the reach both of our 
 fenfes and rcafon : but we fhaii endeavour to make 
 
Chap. X. BRAIN AND NERVES. 
 
 179 
 
 as great an approximatfon to the truth as polhble, 
 by experiments. Firft, it is demonilrated, that 
 fenfation does not come through the membranes 
 from the fentient organ to the brain, and that mo- 
 tion is not tranfmitted through the coverings from 
 the brain into the mufcle. For the brain itfelf, 
 deeper than thefe membranes, receives the impref- 
 lions of fenfe, and when injured throws the mufcles 
 into convulhcns. Moreover, it is certain, that the 
 nerves arife from the medulla of the brain ; the 
 truth of which is manifeft in all the nerves of the 
 brain, more efpecially in the olfaflory, optic, fourth 
 and feventh pair, which continue their m.edullary 
 fabric a long way before they receive the covering 
 of the pia mater. 
 
 cccLXxiv. We muft, therefore, Inquire into the 
 nature of this medulla. It is a very foft pulp, 
 harder in infects and idiots ; in other refpects every 
 where alike. It is difpofed, however, to be formed 
 into fibres, or parallel threads, lying upon one an- 
 other lengthwifej This appears from innumerable 
 obfervations, efpecially in the corpus callofum, cor- 
 pus ftriatum, thalami of the optic nerves, fpinal 
 marrow, in the brains of filhes, and efpecially in 
 their thalami opticL Again, that the fibres of the 
 brain are continuous with thofe of the nerves, fo 
 as to form one continued fubftance, appears very 
 evidently in the feventh, fourth and fifth pair of 
 nerves. There is a great deal of oil in the medul- 
 la, upwards of a tenth part of its whole weight. 
 
 cccLxxv. But here a controverfy begins con- 
 cerning the nature of this fibre, which, with other 
 fimilar fibres, compofes the fubftance of the medul- 
 la and of the nerves. Many recent philofophers 
 have fuppofed it to be a folid thread, and only moif- 
 tened by vapour exhaling into the cellular fabric 
 which furrounds the nervous fibres, and that, when 
 it is ftruck by a fenfible body, the vibration excit- 
 ed is conveyed to the brain. 
 
 N 2 
 
 CCOLXXVI, 
 
BRAIN AITD NER\^S. 
 
 Chap. X, 
 
 ?8o’ 
 
 cccLxxvi. But the phenomena of wounded 
 nerves will not allow us to imagine the nervous 
 fibres to be folid. For, if a nerve when irritated, 
 vibrate, (after the manner of an elaftic chord, which 
 trembles when it is taken hold of,) the nerve 
 ought to confiil of hard fibres, fixed by their ex- 
 tremities to hard bodies, and tenfe ; for chords 
 which are foft, or not tenfe, or not fixed, do not 
 vibrate. But all the nerves, at their orign, are 
 medullary, and very foft, and exceedingly far from 
 any kind of tenfion ; and they retain the fame foft 
 texture, and arc not covered with membranes, 
 where they pafs through w^ell protected channels, 
 as the intercoftal nerve and the fecond branch of 
 the fifth pair ; fome alfo are foft throughout their 
 whole length, whatever fize they may be of ; . as, 
 for example, the foft olfactory and acouftic nerves, 
 in w^hich laft we would molt readily expect tre- 
 mor ; as in found. Agadn, although the nerves be 
 hard, they become foft in the vifeera, mufdes, and 
 fenfogia, before they act. Therefore, the nervous 
 fibres, being neither tenfe in their origin, nor in 
 their termination, cannot pofilbly vibrate in an 
 elaftic manner. But alfo, in particular and moft 
 important cafes, they cannot vibrate ; becaufe, 
 through their whole length, they are firmly tied 
 to folid parts, by means of cellular fubftance ; for 
 example, the neiwes of the heart are tied to the 
 great arteries, and to the pericardium. Finally, 
 that the nerves are totally devoid of elafticity, is 
 demonftrated by the experiment, in \vhich the 
 nerves, cut in two, neither become fhorter, nor 
 draw back their divided ends to the folid parts ^ 
 but are rather elongated from their laxity, and ex- 
 pel their medulla in form of a protuberance. Be- 
 lides, the extremely foft medulla of the brain ex- 
 hibits aU the phenomena of pain and convulfions, 
 which are produced by nerves, without any pofli- 
 bilitv of tenfion. 
 
 cccLssvn. 
 
Chap.X. brain and nerves, I8i 
 
 cccLxxvii. Add to this, that the motion of an 
 irritated nerve is propagated downwards, and that 
 mufcles that are feated above the place of irrita- 
 tion, are never convulfed. This is altogether in- 
 confiftent with elafticity j for an elaftic chord prop- 
 agates its tremors from the point of percuffion, to 
 both extremities. Bnt, if the phenomena of fenfe 
 and motion cannot be explained from the nature of 
 elafticity, the only probable fuppofition that re- 
 mains is, that there is a liquor which comes from the 
 brain, defcends into the nerves, and flows out to the 
 extreme parts of the body ; the motion of which 
 liquor, accelerated by irritation, operates only ac- 
 cording- to the direction in which it flows ; and the 
 convulfions cannot afcend upwards, becaufe of the 
 reftftance made by the frefh afflux of the fluid from 
 the brain. But the fame liquid being put in mo- 
 tion in an organ of fenfe, by a fenftble body, tranf- 
 mits its motion upwards to the brain ; for then it is 
 not refifted by a contrary fenforial torrent coming 
 from the brain. 
 
 cccLxxviii. It is therefore probable, that the 
 nervous fibrils, and the medullary fibres of the 
 brain, which have the fame nature, are hollow. 
 Nor is the fmallnefs of thefc tubes, which are not 
 vifible by any microfcope, of any force againft the 
 propofed arguments j nor the abfence of fwelling 
 in a tied nerve, which is not exaflly true ; with 
 other arguments of the like kind, v/hich indeed 
 fliow the weaknefs of our fenfes, but have not any 
 validity againft the real exiftence of nervous fluids. 
 If they are tubes, it is very probable that they de- 
 rive their fluids from the arteries of the brain. 
 
 cccLxxix. Eut the nature of this fluid is dif- 
 puted. Many, efpecially the moderns, will have 
 it to be extremely hard or elaftic, ethereal, or even 
 electrical ; but the more ancient opinion is, that 
 it is rather aqueous, incompreflible, and albumi- 
 nous. Indeed it is not to be denied, that there are 
 
 many 
 
i 82 
 
 BRAIN AND NERVES. 
 
 Chap. X. 
 
 many arguments againfl admitting either of thefe 
 opiaions. An eledrical matter is, indeed, the moft 
 po'^terful, and litteft for exeiting motion ; but then 
 it cannot be confined within the nerves, but pene- 
 trates throughout the whole animal to vhich it is 
 commuuicated, and fiUs with its energy the flelh 
 and fat, as well as the nerves. But, in a living 
 animal, the nerves only, or fuch parts as are pej’- 
 vadcd by nerves, tremble when irritated ; and, 
 therefore, this liquid muft be of a nature which 
 permits it to flow through the nerves, and yet con- 
 fines it within their tubes. Alfo a ligature on a 
 nerve takes away fcnfe and motion, but does not 
 flop an elecirical current. 
 
 cccLXXX. A watery and albuminous nature is 
 common to miofl of tlie juices in the human body, 
 and may be therefore readily imagined to exift in 
 the nervous fluid, as indicated by the water which 
 exudes into the ventricles of the brain from the 
 fame veflels ; by the gelatinous fluid, which flows 
 out in cutting through the brain in fifh, and the 
 larger nerves of animals ; and by the tumor which 
 a riles in tied nerves* But is fuch a nature capable 
 of explaining the wonderful force of commlfed 
 nerves, obfervable in the difleclions of living ani- 
 mals, even the fmalleft, and in the great ftrength 
 of mad and liyfterical people ? Is the hydroflatic 
 example of capillary tubes of any n'eight ; which, 
 althougli it may explain the ftrength in the mo- 
 ticHi, is neverthclefs inconiiflent with the celeri- 
 
 ... 
 
 cccLxxxi. For, the nervous fluid, which is the 
 inflrement of fenfe and motion, muft, be exceed- 
 ingly moveable, fo as to carry the impreflions of 
 feiife, or commands of the mill, to the places of 
 their ddti nation, without any imaginable lofs of 
 time, and cannot receive the caufe of its motions 
 only from the heart. Moreover, it is very thin and 
 invlfible, and dcititute of all tafte and fmcll ; yet 
 
 reparable 
 
• Chap. X. 
 
 BRAIN AND NERVES. 
 
 •183 
 
 reparable from the aliments. It is not on any ac- 
 count to be confounded with that vifible, vifcid 
 liquor exhaling into the intervals of the nervous 
 chords. 
 
 cccLxxxii. That this liquor moves through 
 tubes rather than through the fpongy and folid 
 fubftance of the nerves, we are perfuaded from its 
 celerity, and from the analogy of the whole body ; 
 of which all the liquids, the fat excepted, how 
 through their proper veffels. 
 
 cccLxxxiii. Therefore, upon the whole, it feems 
 to be certain, that, from the veffels of the cortex, 
 a liquor is fecreted into the hollow tubes of the 
 medulla, which, being continued into the fmall 
 tubes of the nerves, and propelled to their extremi- 
 ties, is the caufe both of fenfe and motion. But 
 there will be a twofold motion in that humour ; 
 the one how and conftant, from the heart ; the 
 other not continual, but exceedingly fwift, which 
 is excited either by fenfe, or any caufe, as motions 
 arifmg in the brain. 
 
 cccLxxxiv. The fame nerves moh evidently 
 are fubfervient both to fenfe and motion ; fo that 
 we are not allowed to adopt two diftinfl: fyhems of 
 nerves, one motory, the other fenfitive. If fenfe 
 fometimes remains after motion is deftroycd, this 
 feems to be becaufe much more hrength is required 
 for the latter. Dying people hear and fee, when 
 incapable of motion. 
 
 cccLxxxv. What becomes of this nervous huid, 
 which cannot but be fecreted in very great abun^ 
 dance, from fo large a quantity of blood moved 
 with fuch velocity, if you compare it with the very 
 copious fecretion from more ffuggihi blood, and at 
 a greater dihance from the heart, in the fmall re- 
 nal and mefenteric arteries ? It is not improbable 
 that it exhales through the cutaneous nerves ; the 
 laffitude, fupervneing in a few hours both to fen- 
 fation and motion, and its removal by fpirituous 
 
 medicines, 
 
BRAIN AND NERVES. 
 
 Chap. X. 
 
 184 
 
 inedicines, fhew that this liquid may both be loft 
 and repaired. Many have thought that it alfo 
 exhales into various cavities of the body ; as that 
 of the ftomach, and inteftines. Vfe may expect 
 fomc part of it to be abforbed, that the nobleft 
 fluid of the body may not be too quickly diflipated. 
 That it nourifhes the body, is improbable : it is 
 too moveable to expect adhelion from it : that is 
 the office of flow and vifcid fluids. 
 
 cccLxxxvi. What is the purpofe of fo many 
 protuberances in the brain ; of the ventricles, nates, 
 and teftes ; of the diftinction of the brain from the 
 cerebellum ; and of fo many tranfverfe chords com- 
 municating from one fide of the brain, cerebellum, 
 and fpinal medulla, to the oppofite fide ? 
 
 cccLXXxvii. The diftindion of parts neceflary 
 for important ufes, feems to have produced the ne- 
 ceffity of the ventricles. That the corpora ftriata 
 and thalami might keep their medulla diftinct, it 
 was neceflary for a vapour to be interpofed be- 
 tween them ; and the fame reafoning is true with 
 regard to the brain and cerebellum. Perhaps, like- 
 wife, the ncceiiity of introducing warmth into the 
 thick medulla of the brain, may have produced the 
 neceffity of a cavity through whicli the arteries 
 may enter in great numbers and crowded together. 
 Perhans alfo it was proper, that, into the inmoft 
 parts of the brain, fmall veffels only, without any 
 large ones, hiould enter. We may alfo fufpect, 
 that the foftnefs of the fibres of the brain requires 
 fiiortnefs, in order to fuftain their own weight. 
 
 cccLxxxviii. We are not yet acquainted vith 
 the ufes of moft of the protuberances, and we ought 
 to learn them from difeafes, and from anatomical ex- 
 periments made on animals refembiing man. But we 
 have little hopes of fuccefs, in parts that are fo 
 final], fo deeply fituated, and hardly ever to be 
 touched, without inflicling a fatal wound. Do fo 
 many diftince provinces of ideas exift in them j as. 
 
Chap. X. brain and nerves. 185 
 
 in the optic thalami ? But moft of thefe protuber- 
 ances produce no nerves. 
 
 cccLXXxix. The internal bands and duels feem 
 to make fome communication of motions, and per- 
 haps of fenfations. Some of thefe join the brain 
 with the cerebellum ; others join the fpinal mar- 
 row with the nerves of the brain, as the accelfory 
 nerve ; and moft of them join the right and left 
 parts together, as the anterior commilTure (cccxlv.) 
 and the two pofterior (cccl.) the corpus callofum 
 (cccxniii.) the flrias between the procefs from the 
 cerebellum to the teftes (cccliv.) and the medullary 
 crofs bars, in the bottom of the third ventricle, and 
 in the medulla oblongata and fpinalis (ccclv.) For 
 this manifeilly feems to be the reafon why, as in 
 inlinite examples, from an injury of the right fide 
 of the brain, the \vhole mufcles of the left fide of 
 the body become paralytic, and the reverfe al- 
 though it feems unaccountable, that this decuflation 
 does not ahvays happen. Moreover, by this con- 
 trivance, nature feems to have provided, that, when 
 any part of the brain is injured, the nerve arifing 
 from it is not always rendered ufelefs. For if a 
 nerve receive its fibres, both from its own hemifi. 
 phere of the brain, and from the oppofite one, by 
 communicating bundles, its office* may, in fome 
 meafure, be continued entire by the fibres which 
 it receives from the oppofite fide, after thofe of its 
 own fide are defiroyed. Accordingly, we have 
 numberlefs infiances of wounds of the brain, even 
 attended with a confiderable lofs of fubfiance, which 
 yet have not been followed with permanent injury 
 to any nerve, or to any of the mental faculties. 
 Many of the other appearances, fuch as the fmaller 
 firipes, refemblances of nerves, and even protuber- 
 ances, are produced in the brain from mechanical 
 neceffity, the pulfation of the veffels, and the figure 
 of the incumbent parts. 
 
 cccxc. 
 
i86 
 
 MUSCULAR MOTION. Chap. XL 
 
 cccxc. We have faid, that the nerves are the or- 
 gans of fenfe and motion ; we fliall therefore pro- 
 ceed firft to explain motion, becaufe it is more 
 fimple, uniform and perpetual, as it exills in the 
 foetus before moll of the fenfes. 
 
 C H A P. XI. 
 
 MUSCULAR MOTION. 
 
 cccxci.' I ‘HE organ of motion in the human 
 ^ body is not hngle. And, in the firft 
 place, in every animal and vegetable fibre, in hair, 
 feathers, membranes, cellular fubftance, in the hu- 
 mid mufcular fibre, and, laftly, in animal and vege- 
 table gluten, there is acontracfilc power, by which 
 they both refill extenfion, and, w'hen the extending 
 power is taken away, acquire their former Ihortnefs ; 
 nor does this power ever ceafe endeavouring to 
 bring the elementary particles into the clofeft con- 
 ta<T the mechanifm of the part can admit. After 
 death, even for many days, it does the fame, fo that 
 the fibres of a divided mufcle contract towards each 
 extremity, and leave a wide gap in the middle ; al- 
 fo arteries, when divided, contract themfeives in 
 length. 
 
 O 
 
 cccxcii. I call this force dead, becaufe it con- 
 tinues to acl after death, and fo far is difierent from 
 the po^vers of life. In the living animal indeed it 
 is fomewhat more lively ; for, both from cold and 
 fear, the fein is Ilimulatcd, fo that it grows harder, 
 and erefled, and along with this hardnefs contracts 
 itfeif in length. Again, the cellular fibres are per- 
 petually endeavouring to iliorten themfeives, and 
 always tend to their own contraflion. Hence, when 
 the Hun or any other membrane is extended, as 
 foon as the caufe of extenfion is taken off, it returns 
 by a gentle effort to its former Ihortnefs. But it 
 
 allb 
 
Chap. XI. MUSCULAR MOTION. 
 
 187 
 
 alfo refills diflention in another way, -with a perpe- 
 tual effort ; and, by a gentle but continual approxi- 
 mation of its own elements, it propels the contain- 
 ed fat or M^ater, or other bodies accidentally intro- 
 duced. The fame power alfo feems to limit the 
 excretion of vapour ; for when the fibres and plates 
 of the cellular texture are preternaturally relaxed, 
 an immenfe quantity either of fat or of watery hu- 
 mour is depofited in that texture. This debility 
 feems to be the principal caufe of a true dropfy. 
 The fame caufe being always efficacious, and at 
 work in the heart, joints, and every where through- 
 out the body of the embryo, brings into nearer 
 contact tlie arteries, auricles, and ventricles j pro- 
 duces flexures ; and contrails the heart, when in a 
 manner diffolved, into a cone. By an unknown or 
 hidden power, it alfo feems to determine the fhape 
 of mofi; parts of the human body ; by expelling the 
 gluten received into the cells,, bringing the terreflrial 
 particles nearer to one another, and giving the pro- 
 per folidity, curvature, and fituation, to the differ- 
 ent parts. 
 
 cccxciii. It Is the nature of this power to afl 
 continually, by a gentle but uninterrupted effort. 
 It is common for it alfo to be excited by poifons, in 
 every membrane, fibre, and^ cellular texture ; but 
 never by cutting or punfluring with a lharp inffru- 
 ment. Thefe are the proper charafleriffics of the 
 red mufcular fibre. The ftrufture of this fibre it 
 is now neceffary for us to confider. 
 
 cccxciv, Mufcular fibres in the human body, 
 are bundles of red threads, by which manifeft mo- 
 tion is performed. When many of thefe fibres are 
 collected together, and are evidently red, they are 
 called a mufcle. The extreme fimpiicity of the 
 fabric has been the caufe of the obfcurity that pre- 
 vails in underffanding how fmall and foft flefliy 
 fibres can produce, with fuch ftrength, moft cxten- 
 
 five 
 
m 
 
 MUSCULAR MOTION. Chap. XL 
 
 five motions, both in man, and moft efpecially in 
 the cruftaceous infects. 
 
 cccxcv. In every mufcle there are fibres, which 
 are long, flender, foft, fomewhat eiaftic, aimoft con- 
 ftantly parallel on the whole, and, furrounded with 
 a good deal of cellular fubftance, are collected into 
 lacertuli. Thefe bound together, by loofe cellular 
 fubftance, generally with fome fat, unite into larger 
 bundles, which are always divided by cellular bands, 
 and membranous partitions, till at laft a number 
 of them, either parallel or inclined, furrounded 
 with a thin cellular membrane, continuous with 
 their partitions, and feparated from the neighbour- 
 ing mufcles by fome coarfer cellular fubftance, con- 
 flitute a lingle mufcle. In every vifible fibre there 
 appears a feries of filaments, which, by oblique 
 extremities being mixed and agglutinated with oth- 
 ers of the fame kind, are combined into one larger 
 fibre. 
 
 cccxcvi. The generality of mufcles, but efpe- 
 cially all thofe which are inferted into bones, and 
 all which are preffed ftrongly by other flefliy in- 
 cumbent parts,' do not confift of fibres of one kind. 
 For the flefhy fibres (cccxcv.) being collected to- 
 gether, commonly compofe the fwelling in the 
 middle of the mufcle, which is called its belly : 
 thefe fibres degenerate by degrees at each end of 
 the mufcle, become more flender and hard, and 
 having laid afide their red colour, acquire a filveiy 
 fplendor, and being compreffed clofer together, are 
 included in a fmaU quantity of fnort cellular fub- 
 ftance, are coloured with fewer veflels, and become 
 indolent and fcarcely irritable : they are denominat- 
 ed tendons if they arc collected into a narrow round 
 chord, but if into a broad flat furface, aponeuroles. 
 The cellular texture which covers the whole ten- 
 don is called its vagina, and refembles the coat of 
 a mufcle. That flefliy fibres actually change into 
 tendinous, is rendered probable by comparing the 
 
 foetus, 
 
Chap. XL MUSCULAR MOTION. l^ 
 
 foetus, in which there are very few tendons, with a 
 young perfon, in whom there are many more ; and 
 with an adult or old perfon, in whom are the great- 
 eft number. Mufcles which are not inferted into 
 any bone, have commonly no tendons, as the heart, 
 the fphinclers, the tongue, and mufcular membranes 
 of the vifcera and veffels. But thofe commonly 
 end in long tendons, which are required to pafs 
 round the joints and heads of the bones, and in 
 that extremity which is njoft moveable. In the 
 foetus the mul'cles are evidently inferted into the 
 periofteum only ; but in adults, where the periof- 
 teum is intimately united with the bone, the ten- 
 dons being blended with the periofteum, adhere 
 into the pits of the bone itfelf. 
 
 cccxcvii. The tendinous fibres indeed often lie 
 in a ftraight line with the fieftiy ones, and are, as 
 it were, a continuation of them. But it is not at 
 all rare for the flelhy fibres to be obliquely inclined 
 to the tendon, and to adhere to it, fo that it grows 
 thicker in its progrefs by continually receiving new 
 fibres. This is called a pennated mufcle. Other 
 tendons lie in the middle betwixt two plates of 
 fibres, one on each fide, meeting together in an ob- 
 tufe angle downwards. There are jnftances of fev- 
 eral tendons pennated on each fide, being conjoin- 
 ed into one- mufcle. There are alfo other modes 
 of union of the tendinous with the fieftiy fibres. 
 
 cccxcviii. Within the cellular tunic that fur- 
 rounds the fibres, the arteries and veins are fubdi- 
 vided into rectangular reticulations, for the mofl 
 part accompanying and contiguous to each other ; 
 thence the vapour and fat effufed into the coarfe 
 and fine cellular fubftance ; thence their abforption. 
 Lymphatic veffels run along the mufcles of the 
 tongue, neck and face, but are difficultly demon- 
 ftrated in the limbs. Along with the blood-veffels, 
 nerves are alfo diftributed throusch the cellular lub- 
 ftance of the mufcles, more numeroufly than to 
 
 other 
 
MUSCULAR MOTION. Chap. XI. 
 
 X90 
 
 other parts of the body, except the eye ; they lay 
 afide their hard involucrum, become fofter and van- 
 ifh before they can be traced to their ultimate ex- 
 tremities. They enter the fame mufcle in many 
 parts, without preference to any particular one. 
 in the tendons they cannot be demonftrated. Nor 
 are there any nervous fibres which furround and 
 conftrinffe the mufcular lacerti. Thofe who have 
 defcribed them faw nothing but cellular fubilance. 
 
 cccxcix. The ftrucfure of the ultimate fibre, 
 confidered as the elements of a mufcle, vrhen in- 
 veftigated by the microfcope in man and other an- 
 imals, has always appeared fimilar to the liruclure 
 of the larger fibres ; and except very minute fila- 
 ments, connefted by cellular fabftance, nothing up- 
 on which we can rely has been obferved. There 
 is no feries of veficles or chain of rhombs. Are 
 thefe fibres hollow ? Are they continuous Avith the 
 arteries ? Does the difference betwixt mufcular and 
 tendinous fibres confift in the latter being rendered 
 folid by being comprefied and having their fluids 
 expelled ? That the blood is not concerned, is prov- 
 ed by the flendernefs of the fibres, vffiich are 
 fmaller than the blood globules, by the whitenefs of 
 the mufcles, after the blood is waflaed from them, 
 and by phyfiological reafons (ccccxr.) And, in gen- 
 eral, more ftrength may be expected from a folid 
 fibre. 
 
 cccc. A mufcle is endowed at leaft with a three- 
 fold power. Firft, the dead one, common to it 
 with other animal fibres. Then another, which 
 vre have called the vis infita, poffTefiing different 
 plienomena. For, in the firft place, it is peculiar 
 to life, and to the firff: hours after death, and it dif- 
 appcars much fooncr than the dead one. Again, 
 in moll cafes, its action confifts in alternate ofcilla- 
 tions ; fo that moving to and fro, at one moment 
 it contracts itfelf towards the middle ; and at the 
 
 next, 
 
Chap. XI. MUSCULAR MOTION. 
 
 191 
 
 next, extends itfelf from the middle towards the ex- . 
 tremities, and fo on fucceffively for feveral times. 
 Moreover, it is manifeft, quick, and performs veiy 
 confiderable motions ; the dead force, only fuch 
 as are linail and fcarcely apparent. It is excited 
 both by the touch of a lharp inftrument, and in the 
 hollow m.ufcles by inflated air, by water, and every 
 kind of acrimony, but more powerfully than by 
 any other ftimulus by electricity. Laftly, it is pe- 
 culiar to the mufcular fibre, and in no other part 
 of the human body is it found pofieiTed of the qual- 
 ities above mentioned. But its phenomena deferva 
 to be more particularly explained. 
 
 cccci. It is natural to every mufcle to flrorten it- 
 felf, by retracting its extremities towards its belly 
 or middle. In order to difcover the moving power 
 from the fabric which we have defcribed, it will 
 be of ufe to coniider the phenomena of mufcular 
 contraction. Every mufcle when in action becomes 
 fliorter and thicker. This contraction of its length 
 is various ; lefs in fome, more in others 5 and in 
 particular inftances very confiderable, for example, 
 in fome of the fphinfters*, iris, diaphragm and inter- 
 coftals, infomuch that it appears that the length of 
 a mufcle may be contracted much miore than one 
 third, which computation was derived from an er- 
 roneous hypothefis. 
 
 ccccii. The inteftines are exceedingly tenadoms 
 of their vis infita ; they continue to contract, after 
 they are taken out of the body, and even after they 
 are cold. The heart is even more tenacious than 
 thefe, if you confider all things ; as is molt evident 
 in the chick, and in cold blooded animals.. Differ- 
 ent mufcles are moff readily excited, by different 
 ftimuli ; as the bladder by urine, the heart by the 
 blood, and the inteftines by air. Though their 
 nerves are removed, on their Connexion with the 
 brain cut off, mufcles lofe but little of their irri- 
 table nature. It appears alfo, that this irritable 
 
 difpofitioa 
 
MUSCULAR MOTION. Chap. XL 
 
 ig2 
 
 difpofition is very widely extended through the an- 
 imal fibre, from the e:?iamp]es of polypi and other 
 infefts, which have neither brain nor nerves, and 
 yet are exceedingly impatient of any fcimulus ; and 
 from the analogy of plants, of which very many 
 flowers and leaves open or eontraU, according to 
 the various degrees of heat and cold, fome even fo 
 quickly, that they are nothing inferior in this refpecl 
 to animals. This power is totally different from 
 any other known property of matter, and is new. 
 It does not depend cither upon gravity, or attrac- 
 tion, or elafticity, for it is inherent in foft fibres, 
 and is deftroyed, when they become indurated. 
 
 cccciii. But that a caufe of motion is conveyed 
 through the nerves into the mufcles, is certain from 
 the obfervations, already noticed (ccclxvii. et feq.) 
 For the nerve alone pollefies feeling ; alone conveys 
 the dictates of the mind ; and neither retains any 
 influence over, nor receives any perceptions from 
 any part, whofe nerve is either tied or cut, or which 
 lias no nerve. On irritating the nerve or fpinal 
 marrow, even in a dead animal, the mufcle or muf- 
 cles, which have nervous branches from thoie parts, 
 are moll violently convulfed. When the nerve of 
 any mufcle is cut or tied, or the part of the fpinal 
 marrow, or brain, from whence the nerve has its 
 origin, is compreffed, the mufcle becomes paralytic 
 and feeble, and cannot by -any power be recalled 
 into action fimilar to the vital one. But if the com- 
 preffion be removed from the nerve, the mufcle re- 
 covers the power by which it is put into action. 
 When the nerve is irritated below the place where 
 it is cut, the mufcle to which that nerve belongs is 
 contracted. Numerous experiments liave been made, 
 to prove this, efpsdally on the phrenic and recur- 
 rent nerves. 
 
 cccciv. This power is not the fame with the vis 
 infita. The former is adventitious to the mufcle ; 
 whereas the latter is inherent in it. The tnrmer 
 
 ceafes 
 
Chap. XL MUSCULAR MOTION. 
 
 193 
 
 ceafes along with life whereas the latter, accord^ 
 ing to certain experiments, fubfifts long after it. 
 Th^e former is fupprexTed-, by tying a ligature upon 
 the nerve, by injuring the brain, or by the exhibi- 
 tion of opium. The latter is not affeded by thefe 
 circumftances, but continues after the nerve is tied 
 or cut, and even in the intehines, though taken out 
 of the body ; it alfo exiils in animals deftitute of 
 brain : parts of the body poffefs motion, which are 
 deftitute of fenfation, while others poffefs fenfation ^ 
 which are deftitute of motion. The will excites 
 and removes the nervous action, but has no power 
 over the vis inftta. 
 
 ccccv. In mufcular action, whether proceeding 
 from the vis inftta, or from the nervous power, the 
 fibres are contraded towards the middle of its 
 belly, and expand outwards : they are varied by 
 tranfverfe wrinkles, and the whole mufcle becomes 
 fliorter, and draws its extremities towards its 
 centre, and therefore carries tow'ards each other 
 thofe parts with which ' it is conneded, in the re- 
 ciprocal proportion of their firmnefs. Mufcles, dur- 
 ing their contradion, fwell, and at the fame time 
 become hard, and, as it were, increafe their cir-* 
 cumference every where. I have never obferved 
 them to turn pale. Whether, on the whole, they 
 are increafed in bulk, and acquire more in breadth 
 than they lofe in length, is difficult to be known. 
 They draw after them the paffive tendons, which 
 of themfelves are neither moveable or irritable. 
 The whole of a mufcle may be moved at once, or 
 only a part of it : if one extremity is ftxed to an 
 immoveable part, that only is moved, which is ca- 
 pable of yielding. 
 
 ccccvi. Do the arteries contribute in anyway to 
 mufcular motion, as indicated by the paralyfts of the 
 lower extremities, produced by tying the aorta? 
 Not at all, unlefs by prefer ving the integrity of the 
 mufcles, and mutual relation of the parts, by fecret- 
 ing vapour and fat, aijd by ngurilhing them. For 
 Q , by 
 
MUSCULAR MOTION. Chap. II. 
 
 194 
 
 by dividing or tying its art9,r)% a mufcle does not 
 become paralyfed, unlefs aftbr a conLderable time, 
 when the mufcles begin to be dellroyed by gan- 
 grene. The irritation of the artery has no effect 
 on the mufcles. Moreover, it is impracticabie to 
 explain the motion of peculiar mufcles from a caufe, 
 which, proceeding from the heart, operates with 
 equal force on all parts of the body. Laftly, the in- 
 iiuence of the will is confined to the nerves, and 
 does not extend to the arteries or other folid parts 
 of the body. 
 
 ccccvii. But the manner in which the nerves 
 excite motion in the mufcles, is fo obfeure, that we 
 may aim.off defpair of difeovering it. And we do 
 not even attempt to inveftigate the vis infita, which 
 feems to be an increafed attraction of the elementa- 
 ry parts of the fibre, by which they mutually ap- 
 proach each other, and accumulate contortions in 
 the middle of the fibre. This force of attraction, 
 which is implanted by nature in the mo^'ing fibre, 
 is excited and increafed by ftimuli. The reft is 
 mere hypothefis. As to nervous vcficles fwelling 
 by a quicker infiux of the nervous fluid, they are 
 inconfiftent with anatomical truth, which demon- 
 flrates the fibres to be cylindrical, and in no part 
 veficular ; and likewife with the celerity with wlrich 
 mufcular mmtion is perform.ed, and with the bulk 
 of a mufcle being rather diminiflred than increafed 
 during its action. The chains and rhombs of the 
 inflated fibres are in the fame manner repugnant 
 to anatomical infpection, and to the celerity ; they 
 Vvmuld alfo occafion an immenfe wafle of power, 
 and render the mufcle but little fhorter. The 
 nerves want that irritable nature which is obferved 
 in the mufcular fibre ; and befides, it is by no means 
 demonftrable, that the fibres, fo numerous, can arife 
 from nerves, fo few and diffributed in a different 
 direction, almoffti'anfverfelywith refpeetto the muf- 
 cular fibres. The idea of nerves being difpofed round 
 
 arterial 
 
Chap. XI. MUSCULAR MOTION. 
 
 195 
 
 arterial fibres, compreffing them by their elafticity, 
 is founded upon a falfe ftruflure of the fibre, which 
 is gratuitoufly aflumed to be filled with blood, and 
 fuppofes nerves, where cellular fibres only can be 
 demonftrated. Moreover, the phenomena of ani- 
 hials, which have neither brain or nerves, and ai'e 
 yet very capable of motion, demonftrate the fabric 
 of the mufcles to be fufficient for their motion, even 
 without nerves. Blood globules, filled with air, and 
 the explanations derived therefrom, fuppofe a falfe 
 nature of that fluid ; namely, that elaftic air exifts, 
 where it does not (cclxXxi.) The animal fpirits 
 are not of the nature of eledlricity. 
 
 ccccviii. If we may add any thing to the phe- 
 nomena, we may fuppofe the nervous liquor to be 
 of a ftimulating nature, forcing the elementary par- 
 ticles of the mufcular fibre to approach nearer to 
 each other. The motive caufe which occafions the 
 influx of the fpirits into the mufcle, fo as to excite 
 it into adfion, feems not to be the foul, but a law 
 eftablifhed by the Creator. For animals, newly 
 born, or newly transformed, without any attempt, 
 or exercife, know how to perform compound mo- 
 tions, very difficult to be defined by calculation. 
 But the foul learns thofe things, which it performs, 
 flowly, imperfectly, and experimentally. Mufcles, 
 therefore, contraft, which in a given time receive 
 more of the nervous fluid, whether that be occa- 
 fioned by the will, or by fome irritating caufe arif- 
 ing in the brain, or applied to the nerve. 
 
 ccccix. Though the foul may be fuppofed to adt 
 in nervous motions, it cannot be admitted in thofe 
 arifing from the vis infita. The heart and intef- 
 tines, alfo fome organs of the venereal appetite, are 
 governed by the vis infita, and by ftimuli. Thefe 
 powers do not arife from the will ; nor are they lefl- 
 ened, or excited, or fupprefled, or changed by it. 
 No cuftom or art can fubjedf thefe organs of inhe- 
 rent motion to the will, or caufe a fateliitc of vbl- 
 0 4 untary 
 
MUSCULAR MOTION. Chap. XL 
 
 tg6 ■ 
 
 Hntary motion to forget to obey the commands of 
 the foul. It is fo certain, that motion is produced 
 by tlie body alone, that we cannot even fufpsct any 
 motion to arife from a fpiritual caufe, except that 
 which the will feems to excite in animals ; and, 
 even in the very organs of animal volition, a ftim- 
 ulus will accafion the mofc excellive aCdons, in di- 
 recL oppofition to the will. 
 
 cccGx. There feems to be this difference between 
 the mufcles obeying the will, and thofe which are 
 govei’ned by the vis infita, that the latter are more 
 irritable, and are very eafily excited into action by 
 a gentle flimulus ; as, for inftance, the heart and 
 inteftines ; \ehich organs are moft manifeflly, and 
 greatly, and Gonhantly, irritable. On the other 
 hand, the mufcles which obey the will, are Icfs ea- 
 lily, and lefs durably irritable. Hence, they either 
 need the agency of the will, or of a powerful ftim- 
 ulus ; by which, indeed, even tliefe may be excited 
 to action, independent of the'wiU. Thus, it hap- 
 pens, that, in apoplexy, the mufcles which obey the 
 will, being deprived of all influx from the brain, 
 lang'uifh, and become paralytic ; while the vital 
 mufcles, having no occafion for the operation of 
 the brain, continue to be excited into contraction 
 by their Itimivli ; the heart by the blood, and the 
 inteftines by the air and aliments. 
 
 ccccxh The ftrength of this action is very con- 
 ficlerable in all perfons, but more efpecially in mad- 
 men, and in feme ftrong men ; fince frequently, 
 with a few mufcles only, they wall raife a weight, 
 much greater than that of the whole human body. 
 But even in healthy people, very flender mufcles 
 have elevated 2co or 300 pounds. The mufcles of 
 the back will even fuftain 3000. Notwithflanding 
 this, much the greater part of the force or power 
 exerted by a mufcle, is always loft, without produ- 
 cing any vifible effect. For aU mufcles are inferted 
 nearer the fulcrum, than the weights are append- 
 
Chap. XL MUSCULAR MOTION. 
 
 19.7 
 
 cd ; and therefore their action is lellened. In pro- 
 portion as their lever is Ihorter than that of the 
 weight. Moreover, moft of the mufcles are infert- 
 ed into the bones, elpecially in the limbs, at very 
 acute angles ; whence, again, the eflFed; which a 
 mufcle exerts in aftion, is proportionably lefs than 
 the effort which it exerts, as the fine of the angle 
 intercepted betwixt the bone and the mufcle, is lefs 
 than the whole fine. Again, the half of every 
 mufcular effort is loft, becaufe it may be confidered 
 as an elevating cord, drawing an oppoftte weight 
 to its fixed point. Beftdes, many of the mufcles 
 are feated in the angle between two bones, arifing 
 from the one, and moving the other ; and therefore, 
 on that bone being moved, they are bent, and, like 
 inflefted cords, require a new force to extend 
 them. Many of them pafs over feveral joints, each, 
 of which they bend in feme degree, fo that only a 
 fmall part of their effort remains to bend their prop- 
 er joint. The fiefhy fibres themfelves of the muf- 
 cles very often form angles with their common 
 tendon, whence a great part of their force is again 
 loft, and only that proportion cf the whole remains,- 
 which is as the line of the angle of their infertion 
 to the whole. Tinaily, the mufcles move their op- 
 pofed weights with very great velocity and eafe, fo 
 that they not only overcome the equilibrium, but 
 likewife add a confiderable excefs of velocity; 
 
 ccccxii. Allthefe Ioffes of power being compu- 
 ted, make it evident, that the force exerted by 
 mufcles in aftion, is exceedingly great, and totally 
 different from any mechanical proportion ; fince 
 the effecl is fcarce -go of the whole force exerted 
 by the mufcle, and yet a few mufcles, weighing 
 but a few pounds, are able not only to raife fome 
 thoufands cf pounds, but aifo with very great ve- 
 locity. Nor is this to be reputed any defefl: of 
 wifdom in the Creator : for all thefe lofl'es of 
 power were rendered neceflary, on account of the 
 
 fymmetry 
 
MUSCULAR MOTION. Chap. XL 
 
 198 
 
 fymmetry of the body, of mufcular motion, and of 
 the requifite celerity and direction ; whereas the 
 contrary of all thefe is required in the mechanifm 
 of machinery. We may, however, certainly con- 
 clude from hence, that the action of animal motion 
 is very powerful, fince, in a fmall organ, it can 
 exert a force equal to fome thoufand pounds for a 
 conliderable time, or even for entire days ; nor does 
 this feem to be otherwife explicable, than by the 
 incredible celerity with which the influx of this fluid 
 obeys the command of the wiU. But from whence 
 this velocity proceeds, we are unable to fay, and 
 muft rell fatislied with knotting that there exifts a 
 law, by which, at a given volition, a given celerity 
 is produced anew in the nervous fluid. 
 
 ccccxiii. The equilibration of imifcular motion 
 is aflifted by the action of antagonift powers. 
 Namely, in all parts of the human body evcry 
 inufcle is counterpoifed by fome counteracting 
 weight, or by elafticity, or by mufcles, or by 
 a fluid which reacts upon hollow mufcles, by 
 which it is expelled, This caufe is the vis infita, 
 and operates continually, even vchile the mufcle 
 adts ; and fo foon as the additional celerity derived 
 from the brain remits, its aftion reftores the limb 
 or other part immediately to its former Rate, in 
 which tliere is an equilbrium betwixt the mufcle 
 and its oppofing caufe. Whenever mufcles confli- 
 tute the antagonift power, none of them can con- 
 tract without extending their antagonifts, by which 
 the nerves being diftended, and a fenfe of uneafl- 
 nefs produced, a ftill ftronger endeavour towards 
 reftoring the equilibrium is excited. Hence, when 
 a flex or mufcle is divided, the extenfor operates 
 even in the dead body ; and the reverfe. 
 
 ccccxiv. But there are acceflbry means, by which 
 the motions of the mufcles are rendered fafe, cer- 
 tain and -eafy. The large long mufcles, by which 
 the greater flexions are performed, are included in 
 
 firm 
 
Chap. XI. MUSCULAR MOTION. 
 
 199 
 
 firm tendinous Iheaths, which are drawn and tight- 
 ened by other mufcles ; for thus, while the joint 
 is bent, the mufcle, though in a ftate of contraction, 
 remains preiied againft the bone, and a confiderable 
 lofs of power is avoided. But the long tendons, 
 which are incurvated or extended over joints which 
 are bent when they are moved, are received with- 
 in proper braces, which have lubricated canals hol- 
 lowed out in them, and which, at the fame time 
 that they do not interrupt their motion, keep the 
 tendons fteady, fo that they neither can be difplac- 
 ed, nor get rigid under the Ikin, with pain and 
 lofs of motion. In thefe tubular braces, a proper 
 liniment is poured around the tendons. The fame 
 oiEce is performed in Tome lituations by perforated 
 -mufcles themfelves. In other parts, the tendons 
 are either carried round eminences of bone, in or- 
 der that they may be inferted at greater angles 
 into the bone which they move ; or they are in- 
 ferted into another bone, from whence a different 
 tendon defcends under a much larger angle into 
 the bone to be moved. In other parts, nature has 
 carried the mufcles derived from convenient litua- 
 tions, in a contrary direclion into the part to be 
 moved, as it were round a pully. She has likewifc 
 furrounded the mufcles on all lides with lubrica- 
 ting fat, both the fibrils, fibres, lacerti and mufcles ; 
 which fat, being compreffed and effufed amongfl; 
 the tumid mufcles and fibres, anoints the fibres, 
 and prefcrves their flexibility. 
 
 ccccxvi. Moreover, the effeiT of one mufcle is 
 determined by the co-operation or oppofltion of 
 others, which either hold firm the part from which 
 the mufcle arifes, or bend it, or elfe, by the concur- 
 rence of their action, change the action of the 
 mufcle from its flraight courfe to its diagonal, 
 Mufcles alfo affift each other, even though fituated 
 at a confiderable diftance, by the one keeping the 
 bone fteady, out of wlijch the other arifes. There- 
 fore, 
 
soo 
 
 MUSCULAR MOTION. Chap. XL. 
 
 fore, the aclion of no mv.fcle can be underftood 
 from confidering it alone ; but all the others muft 
 likewife be confidered at the fame time, which are 
 either inferted into the rnufcle itfelf, or into any 
 of the parts to which the faid rnufcle adheres. 
 
 ccccxAHi. By thefe mufcles varioufly confpiring 
 and oppofing each other, are performed walking, 
 handing, flexion, extenfion, deglutition, and all the 
 other functions of human life. But the actions of 
 the mufcles are alfo generally ufeful. They ac- 
 celerate the return of the venous blood, by com- 
 prciiing both the contiguous veins between the tu- 
 mid mufcles, and the veins proper to the mufcles 
 between their turgid lacerti, and by the force of that 
 preffure being determined by the valves towards the 
 heart only, they afilfc the powers of the heart : they 
 likewife return the fat to the blood ; and agitate, 
 and triturate the arterial blood, and fupply it more 
 quickly to the lungs. They influence the fecretions 
 and excretions, retarding or accelerating them ; 
 in the liver, mefentery, womb, &c. they promote 
 the courfe of tlie contained blood, bile, and other 
 juices, and Icffen the danger of their flagnation : 
 they increafe the flrength of the ftomach, by the 
 addition of their own, whereby digeftion is pro- 
 moted ; infomuch that aU fcdentary and inactive 
 courfes of life are contrary to the appointment of 
 nature, and predifpofe to difeafcs arifing from ftag- 
 nation of the fluids, and crudity of the aliaments. 
 The large mufcles, which are placed round the 
 belly, propel the blood contained in that cavity, 
 and prefs it towards the heart. But by mucii ac- 
 tion, the inufcles themfelves become indurated and 
 tendinous, and they convert the cartilaginous and 
 membranous parts upon which they are incumbent, 
 into a bony nature ; they increafe the inequalities 
 and procefles of the bones, and excavate the fides 
 contiguous to them j they obliterate the cells feat- 
 
Chap. XII, 
 
 TOUCH. 
 
 20J 
 
 ed in the diploe, and bend the bones towards them-, 
 felves. 
 
 ccccxviii. Mufcles which are not excited by a 
 ftimulus, or for which the mind has no occafion, 
 become relaxed and foft ; their wrinides are fmooth- 
 ed out, their fibres are rendered longer, receding 
 from the middle towards the fixed extremities ; 
 and the whole mufcle collapfes the accefibry caufe 
 of contradion, whatever it is, is removed ; while 
 that remains without which the mufcle never is, as 
 long as it is alive. Nor is there any occafion for 
 antagonifl; mufcles, although they may afiift. It has 
 been alked. What becomies of the fpirit that is fent 
 from the brain ? A part of it perhaps is exhaled ; 
 I fufped'a part to adhere to the fibre; and that 
 this is the reafon, that by exercife the mmfcles grow 
 ftronger, and the limbs become thicker. 
 
 ecccxix. HE other office of the nerves and 
 
 fer changes from the impreflions of external fub-. 
 fiances in the parts of the body affected by them, 
 and to undergo analagous changes in the reprefem 
 tations in the mind. We lhall, therefore, firft ex- 
 amine each of the fenfes in particular ; and then 
 confider what is common to all of them, and what 
 happens in the mind from the changes in the or- 
 gans of fenfe. 
 
 ccccxx. Touch is underftood in a twofold man- 
 ner. For, by this term, in general, we call every 
 change of the nerves, arifing from heat, cold, 
 roughnefs, fmoothnefs, weight, moifture, or drynefs 
 in external bodies, in whatever part of the body that 
 change may arife. In this acgeptation, touch is afi 
 
 CHAP. XII, 
 
 TOUCH, 
 
 brain is fenfation ; that is, to fuf- 
 
402 
 
 TOUCH. 
 
 Chap. XII. 
 
 cribed to almoft all parts of the human body, in 
 a greater or lefs degree ; as in different places of 
 the body the nerves are more numerous, bare, or 
 covered with thinner membranes , and in this fenfe 
 pain, pleafure, hunger, thirft, anxiety, itching, 
 and the other fenfations, belong to the fenfe of 
 touch. 
 
 ccccxxi. But, in a fomewhat different and more 
 proper acceptation, the feiife of touch is faid to be 
 the change from external bodies which is produ- 
 ced in the fkin, more efpecially at the ends of the 
 fingers, and is rcprefented to the mind. For, by 
 the fingers, we mofl accurately difUnguiffi the tan- 
 gible qualities of bodies, 
 
 ccccxxii. Indeed, in the fkin we do not eafily 
 diftingulfli any particle which does not feel. But 
 fince the touch is commonly afcribcd in a peculiar 
 manner to the papillse, the ftructure of the fkin 
 muft be defcribed. What is ftrictly called the 
 fldn, is compofed of a denfe web of very compact 
 cellular fubflance, whofe fibres are intermixed and 
 interwoven, which renders it highly extenfible, con- 
 tractile, and porous. Its ftrata, which are expof- 
 ed to the air, and next to the epidermis, are more 
 clofely compacted ; as they approach the fat, they 
 are gradually relaxed, and refolved into a fofter cel- 
 lular texture. It is more tender in fome places, 
 and in others firmer. It is pervaded by many fmall 
 arteries, which come from the fubcutaneous ones : 
 they are neither large nor long, but are numerous 
 in forne parts where the fkin is red, as in the 
 cheeks ; in other parts they are fewer in number, 
 d’he veins arife in great numbers from the fubcu- 
 taneous reticulations : the nerves likewife in the fkin 
 are very numerous ; but they vanifir fo fuddenly, 
 that it is very difhcult to trace their ultimate ex- 
 tremities. Betwixt the fkin and mufcles, there is 
 cellular fubflance, into which the fkin infenfibly 
 refolved, degenerates,^ in mofl, parts repieniflied 
 
 witii 
 
Chap. XII. 
 
 TOUCH. 
 
 203 
 
 with fat, of which the little eminences form pits 
 in the Ikin ; but in fome parts, as the penis, red 
 part of the lips, &c. it is deftitute of fat. There 
 are very few parts in the human body where muf- 
 cular fibres are immediately contiguous to the Ikin, 
 without any feparation by fat ; for the dartos is 
 only cellular fubftance, and has no mufcular fibres. 
 There are fome places where tendinous fibres are 
 inferred into the fein ; as in the palms of the hands, 
 and foies of the feet. 
 
 ccccxxiii. Throughout the Ikin in general, in 
 mofi: parts of the body of man or of the larger ani- 
 mals, on removing the epidermis, fcarcely an une- 
 vennefs is perceptible, unlefs very minute granula- 
 tions, raifed hardly any vifible height, and obtufe. 
 But in the ends of the fingers, papillae, fomewhat 
 larger, but Hill very difficult of demonllration to 
 the fight, are feated in cavities of the cuticle, and 
 receive nerves fcarcely vifible ; they are minute 
 projeftions, formed of velfels with one or more 
 linall nerves, wrapped up in cellular fubftance. 
 In the lips, after maceration, they appear long and 
 villous ; in the penis they are flaky ; and in the 
 tongue they are moll evident, from the fabric of 
 which we conclude, by analogy, with refpecl to 
 the other cutaneous papillae. 
 
 ccccxxiv. The Ikin is furrounded by another 
 covering, which refills completely the adlion of the 
 air, and which coheres with the Ikin by an infi- 
 nite numiber of frnall veffels, and by hairs palling 
 through it. The outer furface of this covering, 
 of a corneous nature, dry, infenlible, not fubje<T to 
 putrefadlion, dellitute of veflels and nerves, wrink- 
 led in a particular manner, and reticular towards 
 the Ikin, is called the epidermis. It is perforated 
 by an infinite number of pores, of which the larger 
 ones are perfpirative, and the fmaUer vaporiferous, 
 and is connedled with the Ikin by numerous mi- 
 nute vefl'els refembling down. By preflure or burn- 
 ing, 
 
204 
 
 TOUCH. 
 
 Ci-iAr. XIL 
 
 ing, the cutkle grows thicker, by the addition o£ 
 new plates, formed between it and the fs:in ; and is 
 then faid to be callous. But even without difeafe, 
 in negroes the two plates are diftincc. 
 
 ccccxxv. The inner furface of the cuticle, more 
 foft, pulpy, half fluid, refembling concreted mucus,, 
 is feparated with dilliculty in Europeans, but eafily 
 in the African negro, in whom it is truly mem-, 
 branaceous, folia, and feparable ; and in the palate 
 of brutes. It is incumbent on the lldn, of v Inch 
 it receives the papillae into foft pits. It is called 
 the rete Malpighianum, although it be certain that 
 it is not perforated in a confpicuous manner, as a 
 lieve. 
 
 ccccxxvi. That this reticular body is compofed 
 by the concretion of fome fluid, tranfuding from 
 the fldn, feems very probable. The fabric of the 
 cuticle is ftiil uncertain ; for fince it is defiitute of 
 veffels, is regenerated, and is infeniible, it does not 
 feem to belong to the organical parts of the body. 
 Is it the outer part of the Malpighian mucus 
 (ccccxxv.) coagulated and conclenfed by the air 
 and by prefllire ; which is perforated in many 
 places by exhaling and inhaling ducts, the mouths 
 of which are cemented together by the interpofed 
 condenfed glue ? Is this opinion fupported by the 
 mucous expanfion upon the membrane of the tym- 
 panum j by its diffolution in water, as obfervxd by 
 eminent anatomills, though by others denied, in 
 .the cuticle of negroes ? 
 
 ccccxxvii. Moreover, to the hiftory of the fkin 
 belong the firaple glands, which are feated in very 
 •many places under the fkin in the cellular fub- 
 ■llance, and perforate it by their excretory ducts, 
 and pour out upon the cuticle, in the hair)’ fcalp, 
 and in the convex furface of the ear, a fat foft 
 half fluid liniment. Other febaceous glands, partly 
 fimple, and partly compound, generate in the face, 
 though more fiO'.vly, a dry vdiite liniment, but in 
 
Chap. XU. 
 
 TOUCH. 
 
 so5 
 
 the groins and armpits one more oily, with which 
 the &in being anointed, Ihines, and is defended both 
 from the air and from friftion. They are found in 
 all parts of the human body tha.t are under the ne- 
 ceffity of being more immediately expofed to the 
 air, as in the face, where there are a great number 
 of the compound fort ; or wherever the Ikin is li- 
 able to great friclion, as in the breails, armpits, 
 groins, glans penis, nymphae, anus and hams. They 
 frequently fend out hairs. Are follicles of this kind 
 feated -in all parts of the fkin ? Although anatomy 
 does not demonftrate them, yet it feems probable 
 that they are prefent every where, as appears from 
 the fordes, coUecled about the whole furface of the 
 body, feemingiy of the febaceous kind. But anoth- 
 er fort of oily ointment (ccix.) is pOured out up- 
 on the Ikin, through its pores, from the fat itfeif, 
 without the intervention of glands, efpecially where 
 the Ikin is clothed with hair, 
 
 ccccxxviii. The hair and nails are alfo appen- 
 dages to the Ikin. The former are icattered over 
 aimoft the whole furface of the body, the palms of 
 the hands and foies of the feet excepted ; in moft 
 parts fiiort and foft ; but longer upon the Ikin of 
 the head, cheek, chin, and break in men ; alfo, up- 
 on the forepart of the limbs, in the armpits, groins, 
 and pubis. They arife from the fubcutaneous cel- 
 lular fubkance, originating from a little bulb, which 
 is membranous, krong, vafcular, of an oval fhape, 
 and more lax towards the cellular texture, at which 
 part it is alfo furnifhed with vekels ; in which little 
 bulb another bulb lies hid, roundiki at its begin- 
 ning, but afterwards cylindrical, and furrounded 
 v/ith blood. In this fecond bulb lies the hair, cov- 
 ered with a fatty humour. The hair, with both its 
 cylindrical Iheaths, arrives at a cutaneous pore, goes 
 out through it, and forces the epidermis into afimilar 
 flieath ; whence the very great kability of the hair : 
 after this the iheath cannot be any longer feparated 
 
 from 
 
2o6 
 
 TOUCH. 
 
 Chap. XIL 
 
 from the cortex ; the filaments, and fpongy and 
 cellular matter, are continued throughout the whole 
 length of the hair. The hairs grow naturally in 
 the fubcutaneous cellular fubftance; but,by difeafe, 
 they are fometimes formed in other fituations with- 
 in the fat. They grow continually ; and when cut, 
 are renewed by the protrulion of their medullary 
 fubftance from the fkin outwardly, and by the pro- 
 longation of the cuticle. In old age, the hairs, def- 
 titute of this medulla, dry up, fplit, and fall off. 
 Their colour is from the juice, which fills the inter- ' 
 nal cellular texture. They feem to exhale through 
 their extremities, and pofiibly throughout their 
 whole furface, as we may conclude from the con- 
 ftant protrufion of their medulla, which ought to 
 have an end from the plica Polonica, and from the 
 luminous rays that come out from .the hairs of an 
 animal elecfrified. The fubcutaneous fat follows the 
 courfe of the hairs, and is exhaled. 
 
 ccccxxix. The nails are of the nature and fabric 
 of the cuticle, and fall off along with it, being in 
 like manner infenfible, and capable of reproduc- 
 tion. They are found upon the end of the fingers 
 and toes, occupying their upper and back part, 
 and correfpond to the tactile papillary apex, which 
 they fupport, and retain applied to the object felt. 
 They arife from a fquare root, between an inter- 
 nal ftratum of the fldn, mixed with periofteum, 
 and another external ftratum, a little beyond the 
 laft articulation : they go out by a lunar cleft in the 
 external plate of the fkin, where the cuticle partly 
 returns back towards the root of the nail, to which 
 it adheres, and is partly laid over the outfide of 
 the nail, and extended forward vith it, forming its 
 outer covering. The nail itfelf is foft when it is 
 firft produced, and in the part covered by the 
 fkin ; but, by age, and contacl; with the air, it be- 
 comes harder, corneous, folid, and elaftic, compofed 
 of long fibres cemented by gluten, feparated by 
 
 fulci. 
 
Chap. XIL TOUCH. 207 
 
 fulci, fiiiile, and of many layers. The nail thus 
 formed, extends itfelf to the extremity of the lin- 
 ger ; and, through its whole extent, its inlernal 
 ftriated furface is lined by furrowed Ikin, blended 
 with periofteum, of which the filaments are hrli; 
 fliort, afterwards longer, and thofe which adhere 
 near the point of the nail are the longeft of ail. 
 Thefe are moft intimately connected with the root 
 of the nail. Beyond the adhering part of the nail, 
 the fldn asrain becomes free and unconneded with 
 
 O 
 
 the nail, and has its own epidermis. A furrowed 
 network is interpofed betwixt the lldn and nail, 
 which is feparabie and foft, for the protection of 
 the papillae ; where the furrows are, it becomes 
 gradually harder, fo that at laft it can fcarcely be 
 diflinguifhed from the nail. The tendons do no^ 
 reach fo far as the nail. 
 
 ccccxxx. The fubcutaneous cellular fubfcance in 
 very few places is without fat, on account of the 
 neceffary motion of the fkin. Wliere it is replen- 
 iflied with fat, it defends the warmth of the internal 
 parts from the air ; it renders the Ikin moveable 
 upon the mufcles ; it fills up the cavities between 
 the mufcles themfelves ; and contributes to the 
 W'hitenefs and beauty of the body. The fkin, Mal- 
 pighian mucus and cuticle, not only cover the exter- 
 nal furface of the body every where, but likewife, 
 where they feem to be perforated, returning inwards 
 they gradually change their appearance. For the 
 cuticle is manifeft in the anus, urethra, vagina, cor- 
 nea of the eye, auditory paffage, mouth and tongue ; 
 nor is it wanting even in the ftomach itfelf and in- 
 teftines j although, by the perpetual emoliition, its- 
 fabric be altered, and relaxed into their villous 
 coat. Thus the true fkin, being continuous with 
 the internal fabric of the palate, tongue, pharynx, 
 noftrils, vagina, &c. changes every where into the 
 wlute, thick, pulpy, commonly called nervous, coat 
 of thofe parts. 
 
 ccccxxxi. 
 
2o8 
 
 TOUCH. 
 
 Chap. XII. 
 
 ccccxxxi. What has been hitherto advanced, is 
 fufficient to enable ns to iinderftand the nature of 
 touch. The papillae at the ends of the lingers, 
 fomewhat larger in the infide, beautifully difpofed 
 in fpiral folds, probably fomewhat erecled by the 
 attention of the mind, as appears from flriverings, 
 from the nipples of women, from the prolapfus of an 
 intelline, from the handling of tangible objects, and 
 from gentle friction, receive the impreflion of the 
 object on their nervous fabric, and tranfmit it to the 
 trunks of the nerves, and to the brain. This is the 
 fenfe of toueh. It enables us to diftinguifh chiefly 
 the roughnefs of objects ; and has been poflefled to 
 fo exquilite a degree by feme perrons, that they have 
 been known to diftinguilh coloured furfaces by the 
 touch alone. We perceive heat, when external bo- 
 dies are warmer than our lingers ; and weight like- 
 wife, when they gravitate more in comparifon with 
 their bulk than ufual. Humidity we . judge of by 
 the prefence of adhering water ; foftnefs, by the 
 yielding of the object ; hardnefs, by the }delding 
 of the finger ; figure, by the hard limits circum- 
 feribing them ; diitance, by an inaccurate calcula- 
 tion derived from experience, to which the length 
 of the arm ferves as a meafure, &c. Touch cor- 
 rects the errors of our other fenfes, although it 
 fometimes errs itfelf, and though other fenfes, in- 
 dependent of touch, furnilli animals with juft per- 
 ceptions. 
 
 ccccxxxii. The mucous body of Malpighius- 
 moderates the action of the object touched, and pre- 
 ferves the integrity and fofeneis of the papiilce. The 
 cuticle excludes the air from the defanictiblc fldn ; 
 moderates the imprellions of bodies, fo that they 
 may be only fufficient to affect the touch, without 
 cauling pain ; and, therefore, when thickened by 
 life, the fenfe of feeling is loft ; but, if it be too 
 foft, the touch becomes painful. The hairs defend 
 the cuticle from friction, generate and preferve the 
 
Chap. XII. 
 
 TOUCH. 
 
 209 
 
 heat, conceal fome parts, and render the membra.nes 
 of others irritable, which require to be defended 
 againft the entrance of infers ; and perhaps they 
 excrete fomething excrementitious, and afford a paf- 
 fage to the exhaled oil. The nails are fubfervient 
 to the touch, by refilling the object touched, fo as to 
 prevent the papillae from yielding, and being bent 
 back ; they increafe the power of apprehenfion, and 
 affift in the handling of minute objects. In molt ani- 
 mals, they ferve as weapons of offence ; and would 
 be of the fame ufe to man, if they were not cut. 
 
 cc OCX XXIII. Thefe are not aU the ufes of the 
 Ikin. For a moll important ofSce of that covering 
 is to exhale from the body a large quantity of hu- 
 mours, and to abforb others from the air. Accord- 
 ingly, the whole furface of the fkin, by an infinite 
 number of fmall arteries, both prolonged into the 
 papillae, and feated in the fkin itfelf, exhales a va- 
 pour which exudes through correfponding pores 
 of the cuticle ; but when the polition of the velfels 
 is changed, it is eflufed between the cuticle and 
 fkin. Thefe arteries are ealily demonftrated by in- 
 jecting water or ilinglafs into the arteries ; for then, 
 from all' parts of the fkin, an infinite number of 
 fmall drops exude, which being effufed under the 
 cuticle, rendered impervious by death, raife it up 
 in blifters. 
 
 ccccxxxiv. During life, this exhalation is de- 
 monftrated in many ways. A bright mirror, when 
 held near the warm and naked fkin, is quickly ob- 
 fcured by a moift vapour. In fubterraneous cav- 
 erns, where the air is denfer, it moft evidently 
 efcapes into the air, from the whole furface of the 
 body, in the form of vifible and thick clouds. 
 
 ccccxxxv. In man, and in fome, though not in 
 all animals, whenever the motion of the blood is 
 increafed, while at the fame time the fldn is hot 
 and relaxed, from the fmall cutaneous pores, in- 
 ftead of an invifible vapour, fweat exudes in the 
 P form 
 
^210 
 
 TOUCH. 
 
 Chap. XB. 
 
 form of minute, but vifible drops, which, with oth- 
 ers of the fame kind, run together into larger drops. 
 The hotteft parts are moil fubjecl to fweat, as the 
 head, breaft, and folds of the body. The experi- 
 ment before mentioned (ccccxxxiii.) together with 
 the fimplicity of nature, the viuble denfity of the 
 cutaneous and pulmonary exhalation (ccccxxxiv.) 
 perfuades us, that fweat is difcha.rged through the 
 fame vefiels which are the organs of perfpiration, 
 and that it differs only in its quantity and celerity, 
 and by the admixture of the liquor of the febaceous 
 glands (ccccxxvii.) and the fubcutaneous oil, 
 w'hich being diluted by the more plentifully fecre- 
 ted arterial fluid, exude of an oily and yellow con- 
 fiflence, and chieiiy caufe the fmell and colour of 
 the fweat. Hence, it is more fetid and yellower in 
 the armpits and groins, where thofe glands are 
 moft numerous. Both blood and fmall fand have 
 efcaped from the fkin along with the fweat. 
 
 ccccxxxvi. The nature of perfpiration mufl be 
 invefdgated by experiments, and by its analogy 
 with the pulmonary exhalation, which, in like man- 
 ner, but more frequently becomes vifible in a cold 
 air. That this exhalation is chiefly water, has been 
 proved by experiments, in which the breath, being 
 received into large veffels, has condenfed into wa- 
 tery drops. This is confirmed by the tenuity of 
 the cloud on the mirror, and its volatility, and by 
 the familiar change of the perfpired matter, when 
 obflrucled, into a diurefis or diarrhoea, and from the 
 eafy determination of wT.rm liquors to affume the 
 form of perfpiration by heat, or of urine by cold. 
 This w^ater is derived from our drink, which fur- 
 nifhes a great part of the perfpiration, and from in- 
 halation. Frequently, even the odours of our ali- 
 ments may be plainly perceived in the perfpiration j 
 there is alfo an admixture of the electrical mat- 
 ter in every perfon, and in fome it is cHdently lu- 
 cid. 
 
 CCCCXXXVII. 
 
Chap. XIL 
 
 TOUCH* 
 
 2ii 
 
 ccccxxxvii. That it alfo contains fome volatile 
 particles of an alkaline nature, is evident, both from 
 the nature of our blood, and from the confiderable 
 evils whiclf fucceed the retention of the perfpira- 
 tion, moft confpicuouily in acute difeafes, when, by 
 being repelled inward, it renders the urine pale, 
 and from the corruption of the air by refpiration. 
 This volatile alkadine matter arifes from the parti- 
 cles of the blood, attenuated by perpetual heat and 
 trituration, and changed into an acrimonious na- 
 ture. Dogs trace thefe odours, and could not know 
 their mafters unlefs fomething of a particular nature 
 were perfpired from each perfon. 
 
 ccccxxxviii. The quantity of the matter perfpir- 
 ed is very large, whether we conlider the extent 
 of the organ fecreting it, the quantity of vapour 
 exhaled by the lungs alone, or the experiments of 
 Sandtorius, by v/hich it would feem, that of eight 
 pounds of food and drink, five pounds, or, according 
 to other experiments in a colder country, from thir- 
 ty to fifty-fix ounces areperfpired, which neither add 
 to the weight of the body, nor efcape by any vifible 
 excretion, except the fall va, fweat, and mucus of 
 the nofe. But the cutaneous exhalation is even 
 much larger than this ; fince it not only throws off 
 fuch a proportion of the alimentary matters, but 
 likewife redifcharges what the blood acquires by 
 inhalation (ccccxlii.) In this, however, the dif- 
 ferent fiates of the air, and of the body, have great 
 influence. In warm countries, in the fummer 
 months, and in young active perfons, more goes off 
 by tranfpiration, and lefs by the urine. But in 
 cold climates, during the temperate and winter fea- 
 fons, in aged Or inactive perfons, more goes off by 
 the urine than by the infenfible perfpiration. In tem- 
 perate countries, making a computation throughout 
 the whole year, fomething more is perfpired than 
 what pafles oft by urine ; and, by collating all the 
 experiments m.ade in different countries, both ex- 
 
0.12 
 
 TOUCH. 
 
 Chap. XII. 
 
 cretions are almoll alike. It is alfo fomewhat af- 
 fected by the difference of time after eating ; and 
 the law which feems to obtain, is, that the perfpi- 
 ration is moft copious at that time when the ali- 
 mentary matters, being moftly digefted, and receiv- 
 ed into the blood, are fitted for exhalation. It is 
 naturally diminifhed during fleep,even in the warm- 
 er climates ; but it is increafed by the heat of the 
 bedclothes. 
 
 ccccxxxix. In general, a plentiful and equable 
 perfpiration, at the fame time that the body is 
 ftrong, are good figns of health ; for exceffive perf- 
 piration, when conjoined with debility, is obferved 
 to do more mifchief than its entire fuppreflion, if 
 what has been written on this fubjecl is fufficicnt- 
 ly to be depended on. It is a fign of health, be- 
 caufe it denotes the pervioufnefs of the velfcls dif- 
 perfed throughout the whole body, and the com- 
 plete digellion of the aliments, of which a great 
 part is refolved into halitus. When it is diminifli- 
 ed, it indicates conftridion of the fkin, weaknefs of 
 the heart, and imperfe(5f digellion. When excef- 
 five, it perhaps waftes the nervous fpirits. This dif- 
 charge is, by moderate exercife, increafed to fix 
 times that of a perfon at reft, to the extent of a 
 pound in an hour, or even in half an hour. It is 
 farther increafed, if aided by ftrong and open vef- 
 fels, by warm, watery, and cordial drinks, by food of 
 eafy digellion, by a denfe and temperate atmofphere, 
 and by cheerfulnefs. It is diminiflied or fupprefl'ed 
 by the contrary caufes ; as a denfe fkin, a mioift, or 
 a cold and dry atmofphere, reft, an increafed flow of 
 urine, the fupervention of a diarrhoea ; and hilly, 
 nervous aritation, from a difaereeable affeclion of 
 the m.ind. Hocvever, the continuance of life does 
 not depend fo intimately on this difcharge, which 
 is fo eafily, and without bad confequences, increal- 
 cd or diminiflied by flight caufes ; and is lb incon- 
 fiderable, in many nations,anointing their fl?:ins with 
 
Chap. XII. 
 
 TOUCH. 
 
 213 
 
 oil, and in many animals. When by being fup- 
 preffed, it produces fuch bad elFecls in fevers of a 
 bad kind, it hurts chiefly by the putrefcent par- 
 ticles, which are retained by the perfpiration being 
 fupprelfed. 
 
 ccccxL. The fweat is evidently of a faline na- 
 ture ; as appears both from its tafte, and from the 
 cryftals which form upon the clothes of glafs blow- 
 ers ; and by diftillation, which demonftrates its al- 
 kaline nature. Hence, by this difcharge, the mi- 
 afmata of the moft peftilential dileafes are frequent- 
 ly expelled. But, in reality, fweat is always a pre- 
 ternatural difcharge, and ought never to exift in a 
 healthy perfon, unlefs by violent bodily exerciie, 
 he have induced a temporary difeafe. It alfo is fre- 
 quently injurious in acute difeafes ; by wafting the 
 water of the blood, fo that the reft becomes thick- 
 er, and the falts more acrimonious. By violent ex- 
 ercife, or the heat of the climate, the fweat is ren- 
 dered extremely fetid, and even fanguineous ; be- 
 ing elecftrical, it fometimes is lucid. 
 
 ccccxLi. The ufes of perfpiration are, to free the 
 blood of its redundant water, of its alkaline im- 
 purities, rendered more acrid by repeated circula- 
 tions ; and of an extremely volatile oil, probably 
 prepared from the fame blood. The fame perfpi- 
 ration likewife qualifies and foftens the cuticle, and 
 preferves the neceflary foftnefs of the p^pills. 
 
 ccccxLii. But the fame Ikin, w'hich has veiTels 
 exhaling into the air, is likewife replenifhed with 
 veflels, which abforb thin vapours from the air, 
 either perpetually, or at leaft in a moderate degree 
 of cold ; in a moift atmofphere ; in the night time, 
 when the body is at reft, the mind deprefled, and 
 under circumftances, contrary to thofe mentioned 
 above, (ccccxxxviii.) which increafe perfpiration. 
 Thefe veins are demonftrated by anatomical injec- 
 tions, which, if thin or watery, exude through them 
 in the fame manner as through the arteries : 
 
 moreover. 
 
214 
 
 TOUCH. 
 
 Chap. XII. 
 
 moreover, by the manifeft operations of medicines, 
 diiTufed in the air, or applied to the fkin ; of 
 vapours, mercury, turpentine, faffron ; of baths, 
 mercurial plafters, tobacco, coloquintida, opium, 
 cantharides, arfenic ; by the fatal effecls of poifons, 
 abforbed by the Ikin ; as the venereal poifon ; by 
 the living of animals, without drink, in hot but hu- 
 mid illands ; by the perfpiration and urine being 
 fulliciently copious in fuch fituations, without much 
 drink ; and laftly, by extraordinary morbid cafes, 
 in which the quantity of urine difeharged has far 
 exceeded the drink taken in ; in which it is proba- 
 ble, that the inlialing pores were more open ; for 
 that new ones were generated, is not credible. It 
 is dilhcult to afeertain its quantity ; that it is very 
 great in plants, in* the night time, is proved by cer- 
 tain experiments. 
 
 ccccxLiii. Both the exhaling and inhaling vef- 
 fels, may be contracted and relaxed by the nervous 
 power. This appears from the effects of the paffions 
 of the mind ; which, if lively and exhilirating, relax 
 the exhaling veffels, by increafmg the impulfe of 
 the influx of blood ; and by the remiflion of the 
 nerves ; hence rednefs, moilture, and turgefcence 
 of the fldn. Thofe paflions which are languid and 
 deprefling, contract the exhaling veffels ; as appears 
 from the drynefs of the fldn, produced by them ; 
 from the goofe fldn, by terror ; and from diarrhoea, 
 caufed by fear. They alfo feem to dilate the inhal- 
 insr veffels, whence fear facilitates the action of the 
 fmaliuox and the nlasrue. 
 
 * A O 
 
 CHAP, 
 
Chap. XIII. 
 
 TASTE. 
 
 2^5 
 
 CHAP. XIII. 
 
 TASTE. 
 
 CcccxLiv. I “'HE organ of talle differs but Illght- 
 ly from that of touch. It appears, 
 by certain experiments, to be feated in the tongue 
 chiefly ; for neither does fugar, applied to any other 
 part of the mouth, excite the leaf! fenfe of tafte in 
 the mind 5 nor any other fapid body, unlefs it con- 
 tain fomething vehemently penetrating ; in which 
 cafe, the palate, root of the tongue, uvula, and even 
 the cefophagus, are affecfled by the fapid acrimony. 
 That fenfation, which is fometimes excited in the 
 ftomach, cefophagus, and fauces, by the regurgita- 
 tion of the aliments, feems alfo to belong to the 
 tongue, to which the fapid vapours are applied. 
 
 ccccxLv. Onlythe upper furface andlateral edges 
 of the tongue are fitted by nature to exercife the fenfe 
 of tafle. By the tongue we underhand a mufcular 
 body, lodged in the mouth, obtufe, very broad in 
 man, and divided in the middle by an obfcure fulcus. 
 Its poilerior and lower parts are varioufly connect- 
 ed to the adjacent bones and mufcles ; its anterior 
 and upper parts are moveable. In that portion 
 which conftitutes the organ of tafce, the fkin con- 
 tinuous with that of the face and mouth, adheres to 
 the mufcular flelh, but is pulpy and foft, from the 
 perpetual warmth and moiflure. From this fkin 
 arife innumerable nervous papillae, of a more con- 
 fiderable fize here than in other parts. Of thefe 
 there are fever al kinds ; the firft kind confifls of 
 nine or ten, at the back part of the tongue, difpof- 
 ed in a line on each fide of the foramen caecum. 
 Thefe, furrounded by a circular groove, for the 
 mofl part refemble an inverted cone, and have a deep 
 finus in their middle ; but are otherwife hard, and 
 but indifferently adapted for tafdng, although you 
 
 can 
 
2i6 
 
 TASTE. 
 
 Chap. XIH. 
 
 can eafily trace nerves into them. There are fome 
 other papillae of the fame kind found fcattered be- 
 fore thefe upon the back of the tongue. 
 
 ccccxLvi. Thefe degenerate into the fungiform 
 clafs of papillae, which are found diftributed over 
 the upper furface of the tongue, lefs and flenderer 
 than the former, always becoming more pointed as 
 they proceed forwards, till around the edges of the 
 tongue they are crowded together, and difpofed in 
 diverging lines. The third fort of papillae are co- 
 nical. Thefe are by far the moft numerous ; are 
 difperfed among the former, and are fpread copioufly 
 over the tongue. The moft anterior of them in 
 the apex of the tongue, are more inclined and fluc- 
 tuate ; they are moft remarkably numerous in the 
 edges of the tongue ; there are even fome behind 
 the foramen cxcum. They are highly fenfible, and 
 conftitute the true organ of tafte ; other papillae arc 
 intermixed, partly conical, and partly filiform ; and 
 of the conical ones fome are larger, and others fuc- 
 ceflively fmaller. 
 
 ccccxLvii. Thefe papillae, befides numerous vef- 
 feis, are fapplied with nerves which may be traced 
 into the larger papillae, and with which the tongue 
 is more largely fupplied than almoft any other 
 part. For, befides a nerve of the eighth pair, 
 which, with one of its principal three branches, 
 enters deeply into the bafis of the tongue, covered 
 by the cerato-glofliis, near the os hyoides ; there 
 is alfo a confiderable nerve that goes to the mufcles 
 of the tongue, from the ninth pair ; which having 
 inofculated with the firft nerve of the neck, and 
 with the large cervical ganglion, and having fent a 
 branch downwards, often uniting with the eighth 
 pair, and conftantly with the fecond and third of 
 the neck, and fupplying the mufcles arifing from 
 the fternum, and frequently communicating with 
 the phrenic nerve, proceeds with the reft of its 
 trunk to the tongue. This communicates in the ce- 
 
 rato-glolTus, 
 
Chap. XIII. 
 
 TASTE. 
 
 217 
 
 rato-gloffus, by many branches, with the fifth pair, 
 and is chiefly fpent upon the genio-gloffus. Lafl- 
 ly, the third branch of the fifth pair having fent 
 upwards or received the cord of the tympanum, 
 and given other branches to the internal pterygoid, 
 and biventer ; to the maxillary gland, forming 
 with thefe a ganglion ; to the fublingual gland, 
 and crofling with its principal trunk the cerato- 
 glofius, where it is united with the ninth pair, 
 comes to the tongue, in company with the deep 
 feated artery, with which it penetrates to the tip 
 of the tongue, where it becomes cutaneous. To 
 this nerve, therefore, if there be any preference, 
 the fenfe of tafte is to be efpecially afcribed, which 
 is even confirmed by morbid examples. Laftly, 
 the papillse of the tongue are of a hard texture ; a 
 firm, pulpy, cellular fubfiance uniting the arteries, 
 veins and nerves into malTes, of which many com- 
 pofe one large papilla. 
 
 ccccxLviii. The arterial and venous villi, which 
 run between the papillae, are for the purpofes of 
 exhalation and inhalation, and have nothing to do 
 with tafte, farther than that they feparate from the 
 blood, a liquor proper for diffolving falts, and for 
 keeping moift the papillae, which they pour out on 
 the back of the tongue. On the upper and back 
 part of the tongue, are feated many fimple mucife- 
 rous glands, opening by one or more outlets, and of 
 a round lhape, formed by an hemifpherical mem- 
 brane, and the flefliy part of the tongue. Some of 
 thefe open into an obfcure blind cavity, of an un- 
 certain figure, -which is placed in the middle of the 
 largeft papillae, (ccccxlv.) and commonly contains 
 fome of them. 
 
 ccccxLix. The papillae of the human tongue are 
 covered only by a mucous, femipellucid m.embranc, 
 which adheres clofely to them, and ferves them as 
 a cuticle. But, in animals, a perforated network 
 
 receives 
 
21 8 TASTE. Chap. XIII. 
 
 recehTS the papilis, which enter into hoUow cor- 
 nuted Iheaths. 
 
 ccccL. Under the papiUa: lies the mufcular fub- 
 ftance of the tongue, compofed of various mufcles, 
 but in man hardly extricable. The lower part is 
 in a great meafure made up of the genio-gloiius 
 mufcle extended outwards from the commiflure of 
 the chin, and diftributcd like ra.ys upon the tongue. 
 The upper and lateral parts are compofed of the 
 ftyio-glolfus, whole fibres run to the tip of the 
 tongue. Its middle part between thefe is compofed 
 of the proper lingual mufcle, which arifing from it- 
 felf before the pharynx, and from the ftylo-gloffus, 
 but deeper, proceeding forwards, is terminated 
 there, and in the genio-glofius mufcle, and between 
 that and the ftylo-glofius, conftitutes a confiderabie 
 part of the tongue. The back part is formed by 
 the cerato-giofius, of which the fibres afeend up- 
 v/ards and backv.^ards, and which is included be- 
 tween the ftylo-gloffus and lingualis, and by the 
 chondro-gloftus, an entirely different mufcle, which 
 arifes from the fmall bones of the os hyoides, and 
 the neareft part of its bafts, from whence palling 
 outwards, covered by lateral layers of the genio- 
 glofius, and joining the ftylo-gloffus, it difappears 
 in the tongue. By the action of thefe mufcles, the 
 whole tongue is moveable in all directions, and is 
 capable of varying its own figure, becoming con- 
 cave when elevated by the ftylo-giofii, being again 
 flattened by the cerato-glofTi, being rendered nar- 
 rower and almoft cylindrical, by the tranfverfe fibres 
 of the tongue ; befides which, there are other or- 
 ders in the human tong-ue inextricable and inter- 
 
 . r 
 
 mixed vcith much tenacious rat. 
 
 ccccLi. The arteries of the tongue are numerous. 
 The largeft, which is deep feated and ferpentinc, 
 comes from the external carotid, a.nd extends along 
 the lower part to the tip of the tongue ; a fmallcr 
 iuperfidal artery, incumbent on the fublingual 
 
 gland. 
 
Chap. XIII. 
 
 TASTE. 
 
 219 
 
 • 
 
 gland, and inofculating with the preceding, arifes 
 either from it, or from the labial. Other fmall polle- 
 rior arteries arife either from branches of the labial, 
 or from the tonfiilaris. The veins of the tongue 
 are varioully intricated, and difficult to defcribe ; 
 one, lying deep, accompanies the nerve of the ninth 
 pair ; another, fuperficial, accompanies the mental 
 arter}’-, and, inofculating with the former, forms 
 the ranular vein ; but all of them tend towards 
 that large vein, which is a different branch of the 
 internal jugular, from the cerebral one. They va- 
 rioufly communicate with the adjacent tonlillary, 
 thyroid, pharyngeal, and cutaneous plexufes ; and 
 on the back of the tongue, before the epiglottis, 
 thofe of the right and left lides are interwoven 
 with ’ each other. I find lymphatic veffels rather 
 in the neighbourhood of the tongue, than in the 
 tongue itfelf. 
 
 ccccini. The papillce of the tongue, being larger 
 and fofter than thofe of the fldn, and perpetually 
 moift, perform the office of touch more exquifitely 
 than thofe of the Ikin, which are dry and fmall ; 
 hence the tongue fuffers more acute pain : more- 
 over, the cutaneous papillce receive no other fenfa- 
 tions from falts than thofe of nioiffure or pain. But 
 the papillae of the tongue being ereded and fqme-' 
 what protuberant, to perform the office of tafte, are 
 affefted in fuch a manner by falts diffolved in water, 
 or faliva, and applied to their fummits, that the 
 mind diftinguiffies certain claffes of tafte, as four, 
 fweet, rough, bitter, fait, urinous, fpirituous, aro- 
 matic, pungent of various kinds, infipid, putrid, 
 and others partly purely faline, and partly changed, 
 and compounded by the admixture of fubtile ani- 
 mal or vegetable oils. All very acrid falts excite 
 pain inftead of tafte. Does the diverfity of fla- 
 vours arife from the different figures of the falts ? 
 Does this appear from the cubical figure of fea- 
 falt, the pri&i.aticai figure of ifftre, or the particu- 
 lar 
 
720 
 
 TASTE. 
 
 Chap. XIII. 
 
 lar configuration of vitriol, fugar, &c. ? It does not 
 fcem probable, for even infipid cryftals have their 
 particular figures ; and in falts, very different in 
 tafte and other properties, the figures are too much 
 the fame, and again are inconftant in the fame fait, 
 as for example, in nitre, which may by art be ren- 
 dered cubical. The caufe of tafte feems therefore 
 to refide in the internal ftruclure of the elements, 
 not perceptible by our fenfes. 
 
 ccccLiii. But the nature of the covering of the 
 papillae, of the faliva, of the fluids, and of the ali- 
 ments lodged in the ftomach, have great influence 
 on the perception of taftes ; infomuch, that the 
 fame flavours do not affect all ages alike, nor all 
 temperatures ; nor even the fame perfon, according 
 as he may be in health, difeafed, or habituated to 
 it. In general, whatever contains lefs fait than the 
 faliva does, feems infipid. 
 
 ccccLiv. The fpirituous parts, more efpecially of 
 vegetables, are received either into the papillae them- 
 felves, or into the abforbing villi of the tongue ; as 
 appears from the fpeedy renovation of ftrength by 
 liciuors of this kind, even when they are not taken 
 into the ftomach. 
 
 ccccnv. Nature defigned the diverfity of fla- 
 vours, that animals might know thofe things moft 
 proper for their food : for in general, there is no 
 aliment unhealthy, that is of an agreeable tafte ; 
 nor is any thing ill tailed that is fit for the food 
 of man. We here take no notice of excefs, by 
 which the moft healthy food may become prejudi- 
 cial, or of minerals, which are not furniflied by na- 
 ture, but prepared by art. Thus nature has invit- 
 ed man to take the food necelfary for his fubfdt- 
 ence, both by the pain called hunger, and by the 
 pleafure arifing from tafte. But animals, which 
 do not learn from example and the inftruction of 
 others, diftinguifla flavours more accurately, and, 
 admoniflied by that teft, abftain cautioufly from 
 
 unhealthy 
 
Chap. XIV. 
 
 SMELL. 
 
 
 unhealthy food ; and, therefore herbiverous ani- 
 mals efpecially, to which a very great diverfity of 
 aliments mixed with noxious plants are offerol, 
 are furniilied with fuch long papillae, and fo ele- 
 gant a ftruclure of the tongue, for which man has 
 lefs occafion. 
 
 CHAP. XIV. 
 
 SMELL. 
 
 ccccLvi. i the fame ufe of difcerning preju- 
 I dicial food, the fenfe of fmelling is 
 fubfervient ; by which we both perceive their nox- 
 ious nature, before they be tailed, which might be 
 dangerous ; and efpecially avoid putridity in our 
 vi duals, which to us is exceedingly hurtful ; and 
 difcover what is grateful and wholefome ; although 
 by habit, this advantage of fmell is more confpicu- 
 oiis in animals than in man. But men who have 
 been left to themfelves, and whofe fenfe of fmell has 
 not been corrupted by variety, have been obferved 
 moll certainly to retain that fagacious faculty in 
 dillinguilhing food in an eminent degree. Final- 
 ly, the powers of medicinal plants are hardly to be 
 eftimated better than by the limple tellimonies of 
 talle and fmell. Hence, in all animals the organ 
 of fmell is placed near the mouth ; and hence the 
 fmell is ftronger, and the organs larger, in thofe 
 animals which have to feek their prey at a conlid- 
 erable dillance, or to rejed deleterious plants from 
 among their food. 
 
 ccccLvii. The fenfe of fmelling is performed by 
 means of a foft, pulpy, vafcular, papillous, porous 
 membrane, which lines the whole internal cavity 
 of the nollrils, and is thicker upon the feptum and 
 principal cavity of the nofe, but thinner in the 
 hnufes. It is plentifully fupplied with very foft 
 
 nerves. 
 
222 
 
 SMELL. 
 
 Chap. XIV. 
 
 nerves, the middle ones of which defcend from the 
 firft pair, (ccclvii.) through the holes of the os cri- 
 brofum to the leptum narium ; but in fuch a man- 
 ner that it is very difficult to trace them to their 
 extremities and into the feptum. Other lateral 
 nerves come from the fecond branch of the fifth 
 pair and its branches, from that which crofTes the 
 pterygoid canal, and from another which defcends 
 through the canals of the palate ; and in the max- 
 illary linus from the infra-orbital branch, from the 
 dental branch, and from the anterior nerve of the 
 palate. Moreover, the anterior part of the feptum 
 has a twig from the ophthalmic of the firft branch 
 of the fifth pair. 
 
 ccccLviii. The noftrils are fupplicd wath very 
 numerous arteries ; from the three nafal branches 
 of the internal maxillary, above from both the eth- 
 moidal branches, and the frontal and nafal branch- 
 es, with lateral arteries from the fmaller ophthalmic 
 branch of the internal carotid, and from branches 
 of the palatine artery, and in the finufes from the 
 ihfra-orbitrd, and from the fuperior dental one. 
 Thefe arteries have the property of exuding blood 
 eafiiy, and in great quantity, Avithout any lefion of 
 confequence. The correfpondent veins form a ve- 
 ry large plexus upon the external pterygoid muf- 
 cle ; then communicate with the finufes of the du- 
 ra mater ; and, laftly, meet in the external branch 
 of the internal iugular. The arteries fupply nour- 
 ifiiment, warmth, and mucus. 
 
 ccccLix. The head, efpeciaily in man, being of 
 a fpherical figure, confines the organ of fmell with- 
 in a fmall fpace. That it may be extended inter- 
 nally, the noftrils have been made complicated and 
 cavernous in a furprifihg manner. In the firft 
 place, the noftrils are thaTpiultiform cavity which 
 begins at the anterior openings of the nofe, and, 
 extending tranfverfely backwards over the roof of 
 the palate under the ethmoid bone, terminatCvS at 
 
 the 
 
Chap. XIV. 
 
 SMELL. 
 
 the cavity of the fauces. This cavity is divided by 
 a feptum, often unequally, which is bony in the 
 upper part, and defcends from the plate of the eth- 
 moid ; below, it is formed by the vomer, and in its 
 forepart it conlifts of a triangular cartilage, whofe 
 furface is large and very fenfible. 
 
 ccccLX. Moreover, the lateral furfaces of the 
 nares are increafed by the fpiral convolutions of 
 the offa turbinata ; the uppermoft of which are the 
 fmall faperior and pofterior convolutions of the eth- 
 moid bone. The muddle ones belong to the fame 
 bone, are of a long conchoid form, convex inwards, 
 externally concave, pointed at both ends, covered all 
 over with pits, and internally filed with fpongy 
 cells fufpended tranfverfely, and fupported by par- 
 ticular eminences of tlie palate and maxillary bones. 
 The low^eil turbinata are fxmilar to the middle 
 ones ; like them refemble in figure a limpet flieli, 
 but longer ; are for the moft part divided from the 
 former, but fiometimes conjoined by a bony plate 
 which is m.ofi; frequently of a membranous nature. 
 This appendix, being extended upwards in a fquare 
 form, completes the maxillary finus. 
 
 ccccLxi. The cavity of the noftrils is ftill fur- 
 ther enlarged, by means of the various finufes, 
 which are recefles or a kind of appendages to the 
 noftrils. The uppermoft of thefe are the frontal 
 finufes, wLich are inconftant and irregular, feated 
 in the fuperciliary ridge, and fituated betwixt the 
 anterior and pofterior plates of the frontal bone. 
 T"hey are not found in the foetus, and feem to arife 
 from the action of the corrugator and other mufcles, 
 which draw the anterior plate outw*ards, and in- 
 creafe the diploe into cells, in the fame manner as 
 in the maftoid procefs. Thefe open in the upper 
 part of the noftrils into the anterior cell of the os 
 papyraceum. There are inftances of their being 
 totally w^anting, and growing after birth. 
 
 CCCCLXIL. 
 
124 
 
 SMELL. 
 
 Chap. XIV. 
 
 ccccLxn. The fecond in order are the ethmoi- 
 dal finufes ; of which four or more on each fide 
 are found in the outer part of the os cribofum,like 
 the cells of an honey comb ; above, they are com- 
 pleted by the cellular diploe of the os frontis, be- 
 fore by the os unguis, and behind by the palate and 
 fphenoidal bone ; they open into the upper part of 
 the noftrils in a tranfverfe line, by many fmall tubes, 
 even placed one above another. With thefe are 
 continuous the cells in the bottom of the orbit, and 
 thofe excavated in the os planum and maxillare 
 are outwardly continued from them. In the third 
 place, the large cavity of the multiform bone on 
 each fide is alfo contiguous, and in fome meafure 
 belongs to the ethmoid and palate bones. By the 
 drying up of the cartilage, which is here of large 
 extent in the foetus, it gradually is formed in the 
 folid bone, under the fella turcica, is capacious, 
 either fingle or divided, and opens forwards by its 
 aperture into the upper paflage of the noftrils. 
 
 ccccLxiii. The laft, loweft, and largeft of the 
 finufes, which in the foetus exifts in fome degree, 
 but in the adult, by the attenuation of the bony 
 laminae, becomes very large, is chiefly excavated in 
 the upper maxillary bone. Its opening into the 
 noftrils is bounded by the os unguis, bone of the 
 palate, proper lamella of the loweft os turbinatum, 
 and by membranes, fo that it enters by a round 
 aperture between the middle and loweft fpongy 
 bones. But it likewife fends forth an hollow ap- 
 pendix, ftretching forwards under the orbits, which 
 is formed by the os planum, unguis, and papyra- 
 ceum, communicating likewife with the ethmoidal 
 cells, and opening behind the oftium lachr)"male. 
 
 ccccLxiv. The nerves of the nofe, being almoft 
 naked, require a defence from the air, which is 
 continually infpired and expired through the nof- 
 trils, for the purpofes of refpiration. Nature has 
 
 therefore 
 
Chap. XIV. 
 
 SMELL. 
 
 225 
 
 therefore fupplied the noftrils, in place of a thicker 
 cuticle, with a vifcid, bland, inlipid mucus, fluid 
 at its firft feparation, but by the air condenling in- 
 to thick dry crufts, and more confiftent here than 
 in other parts of the body. By this mucus the 
 nerves are defended from drying and from pain. 
 It is poured out from the very numerous fmall ar- 
 teries of the noftrils ; and is depofited partly into 
 numerous cylindrical du6ts, and partly into round 
 vilible cryptse, fcattered throughout the noftrils. 
 The fame mucus exudes over the furface of the 
 whole olfadlory membrane, and every where anoints 
 it. In the feptum, a long finus, common to many 
 muciferous pores, runs forwards a confiderable way. 
 The mucus accumulated in the night time, in too 
 great quantity, is expelled during the day by com- 
 prelEng the noftrils, and forcing the breath through 
 them ; or by its drynefs and acrimony, it irritates 
 the very fenfible nerves, and is then expelled by the 
 fneezing excited. But the finufes which abound 
 Vvdth mucus, evacuate it according to the different 
 poftures of the body ; by fome of them always be- 
 ing at liberty to difcharge it, whether the head be 
 erect or inclined forwards, or to the fide ; yet fo, 
 that generally the maxiUary and fphenoidal finufes 
 are more difficultly emptied than the reft. More- 
 over, the tears defcend through a proper duct into 
 the noftrils, and moiften them, and dilute the mucus. 
 
 ccccLxv. The extremities of the noftrils are cov- 
 ered by the nofe, which is lined inwardly with a 
 membrane of the fame nature, and is com.pofed of 
 two bones, and ufually fix cartilages, two of which 
 are continuous vfith the middle feptum (cccclix.) 
 The nofe may be moved by its mufcles, fo as to 
 be raifed and dilated by a mufcle common to it and 
 the upper ftp, and to be contracted by its proper 
 deprellor and compreffor, and depreffor of the lep- 
 tum. Thus the organ of fmell is prominent; and 
 cxpofed to the aCtion of odours, and may be dilated 
 Q for 
 
smUll. 
 
 Chap. XIV. 
 
 226 
 
 for taking in a larger quantity of air, and again be 
 coiitracled, when the fuperabundance is expelled. 
 
 ccccLxvi. The air, therefore, filled with the 
 very fubtile, invifible, pungent, oily, faline, and vol- 
 atile effluvia, which exhale from almoft every 
 known body, being received into the noftrils, by 
 the aclion of refpiration, (cclxv.) and by a pecu- 
 liar effort for drawing the air into them, carries 
 thefe particles to the nerves, widely naked, and 
 conftantly foft. By thefe there is excited in thefe 
 nerves a kind of fenfation which we call fmeil, by 
 which we diftinguifh the feveral kinds of oils and 
 falts, in a manner fomewhat indiffinef, diflicultly 
 reducible to claffes, difficultly recalled to the mem- 
 ory, neverthelcfs fufficiently for our purpofes. 
 This fenfe informs us of unwliolefome putridity, of 
 exceffive acrimony, and of the bland and ufeful na- 
 ture of fubftances. And as fait, united with oil, is 
 an object of tafte, and as oils, combined with falts, 
 conftitute odours, the affinity of the two fenfes, 
 which was neceffary to derive utility from either, 
 is apparent. But volatile particles chiefly are 
 diffinguiflied by fmeil, and fixed ones by the tafte ; 
 perhaps becaufe the thick mucous cuticle, fpread 
 over the tongue, intercepts the aclion of the more 
 fubtile falts, which eafily affecl: the fofter and lefs 
 covered nerves of the noftrils. Wc are ignorant 
 of the reafons why fome fmeils pleafe, and others 
 difpleafe ; perhaps cuftom may have fome influ- 
 ence in this refpecl. 
 
 ccccLxvii. The action of fmeils is ftrong,but of 
 fhort continuance ; becaufe particles in a very mi- 
 nute ftate are applied to naked nerves, in the im- 
 mediate vicinity of the brain. Hence the delete- 
 rious and refrefiiing actions of odours, by which 
 people are refufeitated from faintings, and even from 
 drovming. Hence the violent fneezing, excited by 
 acrid particles, the evacuation of the bowels, by the 
 fmeli of purgatives, and the power of antipathies. 
 
 Hcncc 
 
HEARING. 
 
 Chap. XV. 
 
 227 
 
 Hence the pernicious effects of exceffive fneezing, 
 more efpecially blindnefs, from the great fympathy 
 of the nerves. Amongft the various parts of the 
 noftrils, the feptum, and the offa turbinata, and 
 their anterior portions, efpecially form the organ 
 of fmell : fince thefe parts are multiplied in quick 
 fcented animals, forming beautiful fpires in quadru- 
 peds ; and in fifli, being diftributed in parallel la- 
 minae elegantly toothed. 
 
 CHAP. XV. 
 
 HEARINGi 
 
 ccccLxviii. A S the fenfe of fmelling diftinguifh- 
 es the fmall bodies which float in 
 the air, hearing perceives the tremors of the elafdc 
 air itfelf. Therefore, the fenfltive organ of the 
 ear is compofed in a different manner from that of 
 any of the other fenfes ; as it is in a great part 
 made up, either of elaftic cartilages, or hard bones, 
 that it may communicate with accuracy the tre- 
 mors received. 
 
 ccccLxix. The external organ of this fenfe is 
 the ear, or that cartilage which is connected before 
 and- behind to the bones of the temple, by ftrong 
 cellular fubftance and proper ligaments, with fome 
 degree of mobility, which is diminifhed by habit. 
 This cartilage is of a compound figure ; in its general 
 fhape, oval, but divided by projecting convolutions 
 and intermediate grooves, to which other hollows 
 and ridges correfpond in the oppofite furface. The 
 outer eminence, called helix, arifes above the loofe 
 lobe, and furrounding the ear, terminates in a pro- 
 jedting line dividing the concha; Below it, lies the 
 anthelix, a bifurcated eminence, forming a ridge 
 Contained within the former, and terminating in a 
 ftiort tongue called the antitragus. The remaining 
 0^ 2 part 
 
Chap. XV. 
 
 HEARING, 
 
 part of tlie ear hollow before, and convex behind, 
 growing gradually deeper, having a projecting line 
 running through its middle, is called the concha, 
 and is joined with the meatus auditorious, which is 
 protected by a neai'ly round moveable appendix, 
 called the tragus. 
 
 ccccLxx. All this part of the ear is only cover- 
 ed by a thin fkin, and lean cellular fubftance ; and 
 is replenillied with many febaceous glands, fupply- 
 ing an ointment. It is moved by certain mufcles, 
 ■ivhich generally become ufelefs, from habit and 
 the cuftom of binding them, which, however, it is 
 probable were appointed by nature to perform 
 certain ofSces; The uppermoft of thefe mufcles 
 arifes thin from the frontal and from the aponeu- 
 rofis of the cranium ; whence it is broadly fpread 
 over the aponeurohs of the temporal mufcle, and 
 is inferted into the anthelix, or neighbouring helix, 
 at the anonymous cavity. The pofterior mufcles, 
 which are two or three, or more or lefs, are more 
 robuft than the former, almoft trahfverfe, and arif- 
 ing from the aponeurohs of the cervical mufcles, and 
 from the membraites adhering to the maftoid pro- 
 cefs, are inferted into the convex part of the conch, 
 and without doubt dilate it. The anterior mufcle 
 is the leaft j this alfo is fpread upon the aponeurolis 
 of the temporal mufcle, and is inferted almoft train- ; 
 verfely into the origin of the helix and into tlie j 
 neighbouring concha. But fmaller, fliort mufcles, | 
 hardly diftinguifhable, though fomewhat red , proba- 
 bly make fome change in the ear itfelf. The tranf- < 
 verfe mufcle of the ear, joining the concha with I 
 the concave back part of the anthelix, opens the ear. ^ 
 The antitragicus, defeending from the root of the 
 anthelix to the upper part of the antitragus, widens 
 the entrance of the conch. The tragicus, which lies 
 upon tlie tragus, and is almoft fquarc, dilates the i 
 aperture ; the mufculus inciftirie majoris, lies be- I 
 tween the middle and third cartilages of the nudi- i 
 
 torr 
 
HEARING. 
 
 22 § 
 
 Chap. XV. 
 
 tory paffage, brings them nearer together, and ren, 
 ders the meatus itfelf more elaftic. The remaining 
 mufcles, the longer or larger, and the leffer of the 
 helix, have hardly any great ufe ; perhaps they 
 have fome influence when we wifh to hear weak 
 founds more accurately, and tighten the organ of 
 hearinir, and render the meatus auditorious firmer 
 by drawing together the cartilages, 
 ccccLXXi. With the concha is connected the mea- 
 tus auditorious, of a round compreffed figure, in.; 
 dined inwards, leffening as it proceeds, about the 
 middle bent forwards, and for a confiderable part 
 bony. But, in its anterior and outer part, it is 
 partly formed of three imperfec): rings, the firft 
 arifing from the tragus, the fecond from the 
 concha, and the third from the other two, con- 
 neded with each other by intermediate mufcle, 
 memibrane, and cartilage, and finally adhering to 
 the bone itfelf. The upper and back parts of the 
 meatus are formed by mere membrane. This 
 is the ftate of it in adidts ; for, in the foetus and, 
 new born infant, the meatus is wholly cartilaginous, 
 and its olTeous part is gradually formed. 
 
 ccccLxxii. Into this auditory pafiage are con, 
 tinued the cuticle and true fkin, which are gradu- 
 ally extenuated and exactly ftretched over the 
 bone, and are therefore very fenfible of any irrita- 
 tion, pleafure or pain ; and by the irritable hairs 
 with which it is furnifhed, intimation is given of 
 the accumulation of any fordes, and of the entrance 
 of infeds. In the cellular fubftance, which is 
 fomewhat indurated and reticulated, efpecially in 
 the membranous portion, (cccclxxi.) there are nu- 
 merous yellow round follicles, which, by fliort duds, 
 depofite into the cavity of the auditory paffage a 
 liquid, at firft oily, but afterwards becoming gra- 
 dually thick, bitter, and inflammable, which lines 
 the fenfible fkin and membrane of the tymna- 
 tipm, and defends them from the air, and drives 
 
 away 
 
HEARING. 
 
 Cha:?. XV. 
 
 230 
 
 away or keeps back infects ; but, when accumula- 
 ted in flothful or uncleanly perfons, it caufes deaf- 
 ncfs. 
 
 ccccLXxiii. Into the ear the fonorous waves of 
 the air flow, which, from the principles of me- 
 chanics, it collects. The elaftic air receives fono- 
 rous vibrations ; and particularly tranfmits them, 
 although fome other bodies alfo propagate fonorous 
 vibrations, either alone, or at leaf! in the greateft 
 degree, if indeed water deprived of air be capable 
 of vibrating. Hence, found is increafed in air that 
 is condenfed, and is loft in vacuo. The air receives 
 thefe tremors, either from fome body ftriking a- 
 gainft it, or from fome body againft which it rufh* 
 es, or laftly from the mutual coUifion of bodies. 
 But a body which produces found, muft vibrate 
 and ofcillate in all, even in the leaft of its particles, 
 fo as to form alternate arches riling up from the for- 
 mer ftraight furface, and returning beyond the fame. 
 This fpecies of curved line is called the excedens of 
 the founding body. The tremor impels the neareft 
 wave of air, and thus the anterior portion of air 
 being comprefled, as foon as its elafticity over- 
 comes the impelled trem.or, rebounds and repels the 
 air towards the founding body, where the air is now 
 more rarefied and thin, and cempreffes it. The fame 
 portion of air, ftruck by the founding body, in like 
 manner impels the portion of air contiguous to it, 
 which alfo reacting in due time, repels the tremu- 
 lous air backwards towards the body, and for- 
 wards to produce a new wave. Thefe ofcillations 
 muft thus fucceed each other quickly, to render 
 them audible, and iiiuft not be fewer than 30 in 
 a fecend. 
 
 ccccLXxiv. Acute founds are, in general, emit- 
 ted from bodies that are hard, brittle, and very 
 tenfe : grave founds are connected with the contra- 
 ry properties. Thofe founds .in general are called 
 
 acute 
 
Chap. XV. 
 
 HEARING. 
 
 231 
 
 acute, which are produced by more frequent vibra- 
 tions in a given time ; and thofe obtufe, which are 
 produced by lefs frequent vibrations. There is no 
 limit between acute and grave founds, but what is 
 arbitrary. Cords, or other bodies, that yield the 
 fame number of vibrations in a given time, are faid 
 to be in unifon. Octaves are produced when the 
 one makes double the number of ofcillations that 
 the other does ; other proportions have different 
 names affigned to them. The fhorter cords pro- 
 duce the fliarpeft tones, and the reverfe, in the in- 
 verfe proportion of their lengths ; they are alfo 
 more acute as they are tenfer in the fubduplieate 
 proportion of their tenlion, or the weights by which 
 they are ftretched. Experiments to this purpofe 
 are very eafily made vdth a monocord, or a feries 
 of cords ftretched by weights. 
 
 ccccLxxv. Sound, however produced, whether 
 acute or grave, ftrong or weak, is carried through 
 the air with a velocity equal to about 1038 Paris 
 feet in a fecond, and that with an uniform velocity, 
 without being diminiflied by great diftances. But 
 a contrary wind, although much flower, retards in 
 fom.e degree the progrefs of found, and takes away 
 about of its velocity. So likewife denfity and 
 drynefs of the air increafe found ; rarefaction and 
 moifture diminifti it. The heat of fummer augments 
 its velocity ; in Guinea, it has been tranfmitted at 
 the rate of 1098 Pariftan feet in a fecond. 
 
 ccccLxxvi. Every found meets with particles in- 
 all adjacent bodies, even in \vater and mercury, in 
 which it excites fimilar vibrations, not only in fuch 
 as are in unifon, which yield a more evident found, 
 but alfo in other particles, which vibrate in a dif- 
 ferent ratio. Hence every found which vx hear, 
 is a mixture of the primitive tone, produced by the 
 vibrating body, and of the fecondary tones gene- 
 rated by the elaftic tremors of the furrounding bo- 
 dies, The ftrength of found is increafed, if the fe- 
 
 eondarjy 
 

 HEARESTG. 
 
 Ghap. XV. 
 
 condary founds fucceed the primary one fo quickly, 
 that they cannot be difcriminated by tlie ear ; but 
 if fo llowly as to be diftinguifhable by the ear, they 
 produce an echo ; but this requires an interval of 
 fix thirds of time, or the diftance of 55 feet betwixt 
 the body returning the found and the ear. 
 
 ccccLxxvii. Sound is reflected from hard bodie*^ 
 in angles equal to thofe of its incidence. But found 
 emitted into the open air, being diffufed through 
 an immenfe fphere, grows weaker ; when fent 
 through a cylinder, it retains its ftrength, and when 
 coiiecfed into the focus of an ellipfe, as in th.e fpeak- 
 ing trumpet, it is increafed, as it ifl'ues from the fo- 
 cus of the parabola in parallel, not in diverging 
 lines. 
 
 ccccLXxviii. Therefore the fonorous undulations, 
 propagated through the air, ftrike upon our ear, 
 placed in an elevated fituation, and naturally in- 
 clined forwards and outwards. As that is elaftic, 
 they arc reverberated ; and by alternate refleclions, 
 they are collected into the concha, and into the 
 meatus auditorious, where they become as much 
 flronger, as the furface of the car is larger than the 
 caliber of the meatus. Through that paflage, in 
 fomc mcafure cylindrical, they proceed inwards un- 
 diminifhed, and increafed by new rcfonances, ex- 
 cited by the percufiion of the elaftic cartilages 
 and hard bones, and blended with the primitive 
 found. 
 
 ccccLxxix. The internal end of the meatus au- 
 ditorious is terminated by the membrana tympani ; 
 in adults it is obliquely applied, of a roundifh figure 
 but having an appendix above, projects inwards 
 like a flrield, fo that the lower half, concave to- 
 wards the meatus, projects as the bofs into the 
 cavity of the tympanum, and the upper half is con- 
 cave towards the tympanum, and convex towards 
 the meatus. This m^embrane is compofed of leve- 
 ral plates ; the firft is v.-hiteand mucous, net a per- 
 
•HEARING. 
 
 Chap. XV. 
 
 n ^ H 
 
 feet membrane, and in the foetus only ; then the epi- 
 dermis ; and then the true Ikin, continuous with 
 the membrane of the meatus, and vafcular ; the 
 third is dry, rattling, ihining, pellucid, and with- 
 put blood-veffels. It is formed from the periofteuni 
 of the meatus, and of the tympanum. Some tender 
 cellular texture intervenes between thefe. This 
 membrane is not naturally perforated with any 
 opening, fo far as I have been able to difeover, and 
 the tranfmiffion of fmoke is fabulous. It is con- 
 ftantly ftretched in the groove of the ring in which 
 it is contained, which is proper to the foetus, but 
 after the birth coalefces with the reft of the os pe- 
 trofum, fo that there is no part of the human body 
 more tenfe or more tremulous than this. Upon 
 the furface of this membrane, and more efpecially 
 upon its conical cavity pointing inv/ards, the fono- 
 rous waves ftrike, after their laft refledlion in the 
 auditory paflage, and on account of its elafticity, 
 force it to vibrate. 
 
 ccccLxxx. This membrane is ftretched over a 
 cavity of the os petrofum, called the tympanum ; 
 which is in general of an irregularly roundifli fig- 
 ure. It is divided in its middle by a promontory, 
 and in the adult it is increafed' backwards by the 
 cells of the maftoid bone, which in the foetus are 
 wanting. The tympanum is cellular alfo before, 
 above and behind. ' It is lined with a vafcular 
 membrane, receiving fmail branches from the in- 
 ternal carotid, from the branch of the artery of the 
 dura mater, which paffes through the fiffure in the 
 aqueduff, and from the external arteries of the 
 tympanum, and from the llylo-maftoidea. It is 
 commonly full of mucus, poured into it from the 
 Euftachian tube, and is divided into a kind of cells 
 by different membranes, which are productions of 
 tile periofteum to the ollicula auditus. 
 
 cccci-xxxr. Within this cavity, the little bones 
 of hearing are fituated, three of them being lar- 
 ger. 
 
HEARING. 
 
 Chap, TV. 
 
 234 
 
 ger, and the fourth lefs. The round head of the 
 malleus, its upper part, is fituted in the roof of the 
 tympanum, from whence its long handle defeends 
 between the laminae of the membrane of the tym- 
 panum, as far as its middle, accurately, tied to it, 
 with a broad extremity a little incurvated outwards. 
 It is alfo connected with the long crus of the incus 
 by a peculiar ligament ; another membrane, near its 
 long procefs, fattens the malleus. A Ihort and co- 
 nical procefs above its handle, prefles the membrane 
 of the tympanum outwards. From the fame place, 
 a procefs, very long, comprefied, and fomewhat 
 broad, but of a variable figure, extends forwards in- 
 to a fulcus of the tube. The head of the malleus is 
 articulated with the incus by two protuberant lines, 
 and an intervening fulcus, all of them oblique. 
 
 ccccLxxxii. Three mufcles are commonly deferi- 
 bed, as belonging to the malleus ; the firtt and lar- 
 gett, the tenfer tympani, is internal, and is lodged 
 in a particular canal of the tube, to which it runs 
 parallel, arifing from a procefs of the multiform 
 bone between the pattage of the cerebral carotid and 
 the hole of the artery of the dura mater ; it is infec- 
 ted by its tendon rcttecled downwards and out- 
 wards, around a pully, into the beginning of the han- 
 dle. The fecond mufcle arifes from a fulcus, con- 
 neetted with the fame tube, but external to it, ftiorter 
 than the former ; and carried backwards almoft in 
 the fame manner, but without being reflected, it ad- 
 heres by a confiderable extent to the longer pro- 
 cefs ; its luufcularity is doubted, not being re- 
 markably different from red pulpy membrane. 
 The third, which is faid to arife from the auditory 
 paflage, to enter the. tytnpanum, through a notch 
 in the imperfect ring, to be infected juft by' the 
 flrorter procefs into the malleus, and to relax the 
 membrane, has never been feen with fuflicient cer- 
 tainty', either by myfelf, or by the mott eminent 
 anaiomitts. The tenfor, by means of the mallcu>, 
 
 ■ada^t:^ 
 
HEARING. 
 
 Chap. XV. 
 
 235 
 
 adapts the membrane of the tympanum for the 
 hearing of weak founds ; the fecond mufcle, if it 
 exift, moderates thofe that are too powerful, by 
 drawing the malleus from the incus, and in that 
 way, interrupting the propagation of the fono- 
 rous tremors. If the membrane of the tympanum 
 be broken, or the fmall bones difplaced, the hear- 
 ing firft becomes dull, and afterwards perfect deaf- 
 nefs enfues ; that part of hearing only being left, 
 which is propagated through the bones of the 
 Ikull. 
 
 ccccLxxxiii. The malleus imparts the tremors 
 which it receives from the membrane of the tympa- 
 num, to the incus, which is a fhort thick little bone, 
 articulated with it behind by a broad furface, with 
 two fulci and a middle eminence. The Ihorter leg of 
 this bone, whofe little body is bifurcated, is notch- 
 ed, fufpended by a ligament, and is held firm in 
 a peculiar fulcus of bone. The other leg defcends 
 farther, parallel to the malleus ; and, by its ex- 
 tremity bent inwards, is adapted to the fourth 
 bone, which it receives, being convex on that fide, 
 and flat on the other, and refts upon the frapes,' to 
 which it communicates its vibrations. 
 
 ccccJLXxxiv. The ftapes, aptly fo called from its 
 figure, lies in an inclined pofition, with a hollow 
 head which receives the incus, with curved crura, ef- 
 pecially the pofterior one, and with an oval bafis, but 
 flatter below, with which it fills a hole correfponding 
 to it, commonly called the feneftra ovalis. The cru- 
 ra, which are fulcated inwardly, are joined by a 
 denfe membrane affixed to the flightly hollow bafis. 
 The ftapes is governed by its own mufcle, which be- 
 ing included in a bony papilla, fends out a fmall ten- 
 don, which proceeds forwards, and is inferted under 
 the incus into the head of the ftapes. It feems to draw 
 the ftapes fo that its pofterior part may enter deep- 
 er into the feneftra ovalis, and its anterior part ad- 
 yance outwards. Thus the nervous pulp of the 
 
 veftibulum 
 
HEARING. 
 
 Chap. XV. 
 
 236 
 
 veftibuliim is compreffed, both by the bafis of the 
 ftapes, and by the air of the tympaniim. The whole 
 feat of the ftapes is feparated from the reft of the 
 tympanum by a peculiar membrane. 
 
 ccccLxxxv. A fmaU roundifti oval bone, flightly 
 excavated on both ftdes, is connected by one fide 
 with the longer leg of the incus, and by the other 
 with the head of the ftapes. 
 
 ccccLXxxvi. Various canals pafs out from the 
 cavity of the tympanum. Above the two larger 
 bones, behind the pofterior leg of the incus, is a 
 fmall cell, a kind of appendix to the tympanum, of 
 the figure of a gnomon. Behind it, the cells in the 
 os petrofum begin above the mamillary procefs. 
 Below thefe, that procefs is excavated in the adult 
 with various cells. 
 
 ccccLxxxvii. Bcfides, a peculiar canal, proceed- 
 ing forwards from the anterior extremity of the 
 tympanum, emerges from the bones between the 
 fphenoid and temporal bones, and correfponds ufith 
 an elliptical diverging cone, partly cartilaginous, 
 of uncertain ftructure, and partly membranous, 
 which opens behind the noftrils into the ca^'ity of 
 the fauces, by a very large elliptical aperture, turn- 
 ed inwards and forwards ; it is lined with a porous 
 membrane, full of cryptae, continuous, and fimilar to 
 the membrane of the nares. This forms the Eufta- 
 chian tube, whicli by the aclic^ of the circumjacent 
 mufcles, may be comprefied, and probably a little 
 relaxed and opened again, by the circumflex mufcle 
 of the moveable palate. By this canal, the air, dur- 
 ing infpiration, enters int© the tympanum to l>e 
 changed, and the mucus is poured around the little 
 bones to defend them : nor is it improbable, that 
 the air iiTues out of this tube, when the tympanum 
 is prefled inwards by powerful founds ; likewife, 
 founds received into tlie mouth, are conveyed by it 
 to the organ of hearing. In infpiration, the air 
 prefles the membrane of the tympanum outwards •, 
 
 hcnQ<^ 
 
Chap. XV. 
 
 HEARING. 
 
 ^ 3 ^ 
 
 hence the humming and dulnefs of hearing in 
 yawning ; for then the air entering in greater quan- 
 tity into the tube and tympanum, refifts the tre- 
 mors of the external air. 
 
 ccccLXxxviii. Two other paflages lead from the 
 tympanum to the labyrinth, or innermoft part of 
 the ear. The feneftra ovalis, (cccclxxxiv.) not 
 covered by any membrane, leads into the veftibu^ 
 ium ; which is a round cavity, excavated in the 
 very hard petrous bone, and lies near the inner 
 part of the tympanum^ In that cavity there is a 
 fuperior elliptical recefs, an inferior circular one, 
 and a third refembling a groove. There is a ner- 
 vous pulp in the veftibulum, feparated from its 
 bony fides by vapour furrounding it. Into this the 
 five mouths of the three femicircular canals, the 
 foramen ovale, and the paflages of the nerves and 
 arteries open. 
 
 ccccLxxxix. In the foetus, the canals are formed of 
 a diftind: hard fhell, which is furrounded with fpon- 
 gy bone ^ in adults, they are excavated in the excef- 
 fively hard petrous bone, fomething larger than fe- 
 micircles, and have ample openings. The larger pof- 
 terior and lower of thefe is perpendicular ; alfo 
 the middle and upper one is placed perpendicular- 
 ly j but the outermofl; and leafl: is horizontal. The 
 inner mouth of the uppermoft unites with the up- 
 per opening of the pofterior. 
 
 ccccxc. But the cochlea is ftill more wonderful. 
 It is feated in an inclined pofition in the anterior 
 portion of the os petrofum. Into its one cavity the 
 veftibulum opens, and into the other the feneftra 
 rotunda of the tympanum, which being covered by 
 the promontory, lies hid in the bottom of the tym- 
 panum. The cochlea itfelf is compofed of a nu- 
 cleus of bone, of a conical figure, with its apex in- 
 clined inwards ; divided into tubes, which are call- 
 ed fcalae, by a middle fulcus, which is perforated,, 
 both in its bafis, and through its whole length, by 
 
 innumerable 
 
HEARING. 
 
 Chap. XV. 
 
 23S 
 
 inmimerable fmall foramina, and terminates in the 
 middle of the fecond fpiral. About this nucleus 
 are wrapt two turns and a half of a canal ; %vhich, 
 in the foetus, is diftincl, and has its own flaell ; but, 
 in the adult, is united with the adjacent bone, and 
 diminiflies conically from the two openings men- 
 tioned above, towards the apex of the nucleus. 
 This canal is bilocular, and divided by a partition 
 called lamina fpiralis, of which the greateft part is 
 bony, and arifes from the nucleus, projecting from 
 it at right angles into the hollow canal, is ftriated, 
 and included on both fides in the internal periof- 
 teum as in a capfule. The remaining and exterior 
 portion is membranous, which completes the divi- 
 lion of the canal : thus there are formed two dif- 
 tinct femicanals, called fcalse. The interior and pofte- 
 rior of thefe begins from the fcneltra rotunda, where 
 it is firut by a membrane, and is called the fcala 
 tympani ; the other anterior one arifes from the 
 vellibulum, from which it has its name. From the 
 apex of the nucleus a third cavity originates, fhap- 
 cd like a funnel. Into this the fpiral lamina ter- 
 minates by a membranaceous extremity, but fo that 
 the funnel comiRumicates with each fcala, by one 
 fmall hole on each fide, and by many ^\’ith the cav- 
 itv of the modiolus, which is filled with nerve. 
 
 ccccxci. The blood-velTels of the outer ear come 
 from the tanporal, and proper auricular branches ; 
 thofe of the membrane of the tympanum from the 
 temporal, from the ftylo-maftoideal, or from both j 
 thole of the meatus auditorius come from the fame ; 
 thofe of the tympanum were defcribed (cccclxxx.) 
 and the velTels belonging to the veftibulum, cochlea, 
 and femicircular canals, are from the vcrtebralis and 
 ftylo-maftoidealis and meningea. The induftry of 
 late anatomifts has traced abfcrbent veflels of a par- 
 ticular kind, from the veftibulum into the tranf- 
 verfe finusj from, the cochlea into the cavity of the 
 Ikull. 
 
 CCCCXCI I. 
 
HEARING. 
 
 Chap. XV. 
 
 23$ 
 
 ccccxcii. It now remains that we defcribe the 
 nerves fubfervient to the fenfe of hearing, of which 
 the principal is that called the feventh, (ccclvii.) 
 This nerve enters into the internal auditory fmus 
 of the os petrofum, in the blind end of which it 
 divides. The fmaller part of the nerve enters 
 through the upper opening in the linus, into a ca^ 
 nal, which is at firft tranfverfe, and afterwards re- 
 fledfed behind the tympanum. While it defcends 
 there, it gives off a branch through a peculiar ca- 
 nal to the tympanum, which afcends betwixt the 
 malleus and incus, goes out of the tympanum, 
 through a fiffure behind the articulation of the 
 lower jaw, and inferts itfclf into the nerve of the 
 tongue, (ccccLvii.) the reafon of which fecret com- 
 munication is obfcure, but ferves to explain the 
 fympathy between the teeth and lliarp founds, and 
 burning of the ear, &c. The reft of the nerve, 
 efcaping by the fide of the ftyloid procefs, is diftri- 
 buted on the external ear, the parotid gland, a large 
 part of the face, and upper part of the neck, both 
 cutaneous and mufcular ; and in the face, forms 
 numerous inofculations, both betwixt its own 
 branches, and wdth thofe of the firft, fecond, and 
 third of the fifth pair ; with the eighth pair, and 
 with the third cervical pair. To the organs of 
 hearing, it fends either no branches, or very fmall 
 ones. The anterior part of the outer ear receives 
 other nerves from the third branch of the fifth pair, 
 and the pofterior part, from the fecond and third 
 cervicals. 
 
 ccccXciil. But the foft portion, which is larger, 
 but more obfcure, arifes by very minute filaments, 
 from the fourth ventricle of the brain itfelf, 
 (ccclvii.) and enters through exceeding fmaU holes 
 of the inner auditory finus, in part with from three 
 to five branches, into the veftibulum, and in part 
 into the fulcus of the cochlea. Thefe branches in 
 the veftibulum form three pulpy maffes, which com.^ 
 
 bine 
 
240 
 
 HEARING. 
 
 Chap. XV. 
 
 birxC to form the membrane fufpended in the vefti- 
 bulum, and which is continued through the whole 
 of the femicircular canals. The other part, which 
 enters the fulcus of the cochlea, has an obfcure ter- 
 mination. 
 
 ccccixciv. With refpccl to the nerve which is 
 diftributed upon the veftibulum and femicircular 
 canals, there is no doubt that it is affected by tlie 
 tremors of the external air, propagated to the Rapes ; 
 which reach the pulp of the naked nerve, through 
 the feneftra ovalis. That part of the neiwe, which 
 enters the cochlea, is altogether lefs underftood. 
 ft is probable, that fmall branches from thence pafs 
 through the little foramina, (ccccxc.) to the peri- 
 ofteum of the cochlea, and to the membranous part 
 of the lamina fpiralis. Do tranfverfe nervous fila- 
 ments, fucceflively lliorter, pafs out from the nu- 
 cleus of the cochlea, along the lamina fpiralis? 
 Is it the organ of hearing ? Thefe are queftions, 
 which we are yet hardly able to refolve from anat- 
 omy ; though the example of birds and fiflies, 
 which hear exquifltely without a cochlea, feems tp 
 negative them. However this may be, it is pro- 
 bable, that the fpiral plate, full of nerves, is ex- 
 cited to vibration by the ofcillations of the mem- 
 brane of the tympanum, which agitate the air in 
 the cavity of the tympanum, fo that it impinges on 
 the membrane of the round feneftra, which again 
 agitates the air contained in the cochlea. 
 
 ccccxcv. It is an elegant conjechire, that fince 
 the lamina* fpiralis forms a true triangle, of which 
 the apex is a very acute angle, it may be fuppol- 
 cd to contain an infinite number of cords, fuc- 
 cefTively flicrter, which correfpond harmonically, 
 (ccccjLXxiv.) with the various acute and grave 
 tones, fo that tliey vibrate in unifon with the greateft 
 number of founds ; the longeft cords in the bafisof 
 tlie cochlea, with the graveft founds •, and the flrort- 
 
Chap. XV. 
 
 HEARING. 
 
 241 
 
 efl cords neareft the apex, with the fliarpeh founds. 
 Are founds perceived in the middle femicircular 
 canals, fince thefe alone are found in all clalfes of 
 animals ? Or are they perceived in thefe canals, in 
 the cochlea, and in the membrane fufpended in the 
 veftibulum ? This feems probable. 
 
 ccccxcvi. It appears that the audable elaftic un- 
 dulations of the air, pafs through the outer ear 
 and auditory paffage, to the membrane of the tym- 
 panum ; for when it is injured, and not repaired, 
 the hearing is totally deftroyed. It feems to be 
 ftretched, for hearing w'eak founds, by the mufcles 
 of the malleus; From this membrane, the found 
 is propagated through the fmall bones to the vefti- 
 bulum ; for thefe bones being deftroyed, the hear- 
 ing is again aboliftied. The bony fides of the vef- 
 tibulum vibrate, and agitate the aqueous fluid fur- 
 rounding the nervous pulp* By it, the nervous pulp 
 fufpended in the veftibulum, feems to be affeded, 
 and that tremor to be continued through the con- 
 tinuous pulp of the cochlea and femicircular canals. 
 Nothing farther is known : but, by undoubted ex- 
 periments, elaftic fonorous tremors affect the audi- 
 tory nerve, through the intervention of the Eufta- 
 chian tube, of the teeth, and of ail the bones of the 
 IkulL 
 
 ccccxcvm The diftinftion of founds, without 
 doubt, proceeds from the velocity of the tremors 
 excited in the auditory nerve, according as they 
 fuceed each other more fwiftly or flowly ; it is not 
 neceffary the mind Ihould number them ; it is fuf- 
 ficient that the different numbers excite different 
 changes in the mind. Does the gratefulnefs of 
 founds arife from the number of confonances ? Does 
 the mind, inconfdcufly, number the degrees of con- 
 fonance, and derive pieafure from their facility and 
 frquency ? Thefe are denied by the moft expert 
 mufidans, vho prove, that much pieafure proceeds 
 R from 
 
242 
 
 SIGHT. 
 
 Chap. XVI. 
 
 from founds having very little concordance, and re- 
 lated in very difficult proportions. Why are too 
 acute founds intolerable ? They feem to ftrctch 
 our nerves in the lamina fpiralis to fach a degree, 
 that they are even ruptured, as glaffes are broken by 
 acute founds, and the Ihrill whifilino; of canarv 
 birds almoll deftroys the power of hearing. 
 
 CHAP. XVI. 
 
 SIGHT. 
 
 CCCCXCVIII. 
 
 ’TEARING is the perception of the 
 J. vibrations of the air ; fight per- 
 ceives thofe of light : the organ of hearing is bony, 
 that it may admit of refonance ; the organ of vi- 
 fion chiefly confifls of humours, which refract : the 
 complex nature of this organ was rendered necef- 
 fary for the defence of parts, fo very tender, and 
 by the diverfity of the humours, to be contained 
 each in its proper integuments. 
 
 ccccxcix. The moft external defence of the eye 
 is afforded by the eyebrow, which is a protuber- 
 ance of the fkin, fuftained by mufcles, at the bot- 
 tom of the forehead, full of thick imbricated hairs, 
 and along with the frontal mufcle, capable of being 
 pulled down by the action of the corrugator, and 
 orbicular mufcles, fo as to afford a ffiade to the eye 
 in too ftrong a light. After the eyebrow has com- 
 pleted its functions, it is again raifed by the frontal 
 mufcle, which is inferted into it, thin and flefhy, 
 immediately under the continuous fkin, faflened to 
 the cellular membrane of the fkull, which is finn- 
 ing, not very unlike an aponeurofis, and is drawn 
 back\vards by the rectangular occipital mufcle. The 
 deprefiion of the eyebrow denotes care, its eleva- 
 tion, tranquillity and ferenity of mind. It alfo turns 
 
 afidc 
 
Chap. XVI. SIGHT. 243 
 
 alide the courfe of the fweat, and keeps off infects 
 from the eye. 
 
 D. The eyelids furnifti a nearer protection to 
 the eye. Thefe are folds of the Ikin, proceeding 
 from that of the face, extenuated, lengthened out 
 into an edge, as if divided, reflected upon itfelf, 
 and retracing the courfe of the former lamina, 
 from which it is feparated by fome cellular fub- 
 ftance ; then having become membranous, vafcular, 
 and therefore red, and thin, it is carried over the 
 ball of the eye, under the denomination of con- 
 junctiva tunica, and covers the anterior portion of 
 the fclerotica, and finally the cornea. The epider- 
 mis accompanies it in its whole courfe, even where 
 it adheres to the cornea. The upper eyelid is larg- 
 er, and more moveable : the lower is fmaller ; and 
 rather paflive, than moved by any power of its 
 own. The nerves, which give fenfibility to the 
 eyelids, are numerous, from the firft and fecond 
 branches of the fifth pair, and from the portio dura 
 of the feventh ; they abound with arteries from 
 the ophthalmics, temporals, branches of the inter- 
 nal maxillaries, infra orbitals, and facials. 
 
 Di. That the eyelids may fhut together more 
 exactly, each of them has a cartilaginous arch, call- 
 ed tarfus, upon that margin which touches tlie 
 other. It is flender, of a lunar figure, extenuated 
 outwards, and ftretches the eyelid, preventing the 
 formation of folds while it is elevated or depreffed. 
 The elevation of the upper eyelid is performed by 
 a peculiar mufcle, arifing from the involucrum of 
 the Optic nerve gradually fpreading, and continued 
 by its expanfion to the tarfus. This is confiderably 
 affifted in its aClion by the frontalis, which is vari- 
 oufly connected with the orbicularis, and draws it 
 upwards. The upper eyelid is depreffed by the 
 orbicularis, as it is called ; a broad mufcle, both 
 widely expanded around the orbit, and contained 
 in the eyelids, carried as far as both angles of the 
 R 2 eye. 
 
SIGHT. 
 
 Chap. XVI. 
 
 ^44 
 
 eye, and having, as fixed points, the ligament ad- 
 hering to the procefs of the maxillary bone, and 
 fome fibres inferred into the frontal and upper jaw 
 bone. The fame mufcle elevates the lower eyelid, 
 and covers the eye in fach a manner that no dull 
 or light can enter it during fleep. The lower eye- 
 lid is depreffed by two bundles of fibres, inferred 
 into the upper lip. 
 
 Dll. Finally, that the tumid m.argins of the eye- 
 lids may not flint too clofely, they are provided 
 with eyelaflies, or fringes of hair fpreading out- 
 wards, proceeding in many rows from the edges 
 of the eyelids, which, by decuffating each other, 
 increafe the fhade and obfeurity. Thefe are of ufe 
 in more difUncf vifion, by excluding the extrane- 
 ous rays, when we require a diftincf reprefentation 
 of any objeci:. 
 
 Din. The eyelids are prevented fi’om hurting 
 each other by the febaceous glands of Meibomius, 
 confifling of thirty or more follicles in each eyelid, 
 which arc fimple, bifid or trifid ; placed in general 
 according to the length of the lid, and compofed of 
 peculiar blind roundifli cavities, which unite into 
 one larger ferpentine duel, of which the orifice is 
 in the margin of tlie evelid itfelf. Thefe difcharjje 
 a fort unctuous liniment, which mixes and waflies 
 off with tlie tears. 
 
 Div. But the perpetual attrition caufed by the 
 eyelids afeending and defeending againft the globe 
 of the eye is prevented, the delicacy of the cornea 
 is preferved, and any infects or other irritating fub- 
 Itances which may have got into the eye, are wafli- 
 ed away by the tears ; a faline, pellucid, and evap- 
 orable liquor, which never ceafes to be poured over 
 the anterior furface of the eye, but never runs 
 over the cheeks, unlcfs accumulated from fome 
 caufe. This liquor is exhaled partly from the ar- 
 teries of the conjunctiva, as we fee from an imita- 
 tion of nature by injecting water j and in part it is 
 
 believed 
 
Chap. XYl. 
 
 SIGHT. 
 
 245 
 
 believed to proceed from a gland feated in a hollow 
 recefs of the os frontis, fomewhat hard, and of the 
 conglomerate kind : divided into many lobes, inter- 
 mixed with fat, and fupplied with many blood-vef- 
 fels from the ophthalmics and internal maxillaries ; 
 and pervaded by many nerves arifing from a pecu- 
 liar branch of the firft trunk of the fifth pair. 
 
 Dv. From this lachrymal gland, fix or more vi- 
 fible ducts defcend, which open on the inner fide of 
 the conjunctiva of the eyelid. In man thefe dufts 
 have been lately difcovered by credible authors. 
 The fecretion of the tears is increafed by the re- 
 peated contractions of the orbicular mufcle, either 
 from irritation, or fome depreffing paflion, by 
 which means the tears are conveyed over the whole 
 eye, and the furface of the conjunctiva is waflied. 
 
 Dvi. After the tears have performed their oflice, 
 fome part of them being evaporated by the air, the 
 reft, that they may not prove injurious by their ac- 
 cumulation, are propelled by the orbicular mufcle, 
 towards its origin next the nofe, and to the inner- 
 moft part of the commiffure of the eyelids ; which 
 from not having any tarfus, does not meet exactly 
 together. There a caruncle, full of febaceous, hairy 
 follicles, oblong, and conical outwards, interpofes 
 itfelf between the eyelids, and prevents them from 
 meeting, and anoints with its liniment thofe parts 
 of the eyelids which have no Meibomian ducts, 
 Before it, a fmall third eyelid defeends perpendicu- 
 larly, and joins the true eyelids ; it is larger in 
 beafts. At the beginning of this fpace interpofed 
 between the eyelids, in which the tears are collect- 
 ed, in each margin a little papilla projects, having 
 one orifice, furrounded by callous cellular fubftance, 
 and perpetually open, unlefs when convulfively 
 clofed. This orifice, which is called the punctum 
 lachrymale, abforbs the tears from the finus in 
 which they are collected, partly by attraction, and 
 partly by the impulfe of the orbicular mufcle. If 
 
 thefc 
 
SIGHT. 
 
 246 
 
 Chap. XVI. 
 
 thefe points are obllrucled, the tears run over and 
 excoriate the cheek. 
 
 Dvii, From each point, a peculiar duel, much 
 wider, thin, and included in the Ikin, proceeds, the 
 one downwards above the caruncle, and the other 
 more tranfverfely inwards, and under it ; which ap- 
 proach each other, and are inferted by two mouths 
 into the lachrymal fac, not quite at the top ; which 
 name is given to a cavity formed in the groove of 
 the os unguis and upper jaw, lined firll with a hard 
 cellular, and as it were aponeurotic membrane ; 
 then by another, red and pulpy, continued from 
 the membrane of the nares, pervious to the exhaling 
 moifture, and fomewhat of an oval figure. From 
 this veficle the nafal du(5i; defeends a little backwards 
 into the nares, and opens by an obliquely oblong 
 aperture, covered by the lower os fpongiofum, into 
 their loweft meatus. Through this the fuperfluous 
 tears defeend into the nofe, which they in part moifi- 
 en, (ccccLxiv.) A mufcle is by fome aferibed to 
 this fac ; but it is not yet fuliiciently afeertained. 
 
 Dviii. The eye, of a globular fhape, comprelied 
 before, though not always in the fame manner, 
 longer from the brain to the cornea than from the 
 right fide to the left, is fituated in the orbit, \^ hich is 
 an offeous cavity, almofl; conical, compofed of fe\ en 
 bones, interrupted in the back and outer fides by 
 larger fififures, and widening forwards, and by which 
 it is defended on all fides. But as this is larger than 
 the eye, it is filled by mmch very foft fat, furrounding 
 the globe of the eye, and allowing it free motion. 
 
 Dix. The eye begins from a nerve, by the ex- 
 panfion of whofe coats thofc of the eye are formed. 
 Its origin we have already deferibed, (ccclvii.) 
 Having paiTed acrofs the crus of the brain, it joins 
 with its fellow from the other fide, and coheres 
 with it for a confiderabie way, by much medullary 
 fubftance ; yet fo that the right goes to the right 
 eye, and the left to the left, though not without 
 
 fomc 
 
Chap. XVI. 
 
 SIGHT. 
 
 247 
 
 fome reciprocal intermixture of medulla. The 
 nerve then enters the orbit, a little infledled, and of 
 a round form, fomewhat comprefled ; and is infert- 
 ed, not into the middle of the globe of the eye, but 
 a little nearer to the nofe. 
 
 Dx. The nerve having reached the eye, the inner 
 plate of its dura mater, which it received in the 
 opening of the fphenoidal bone, is detached : or 
 having become thicker, is extended around the 
 eye, as its firft coat, called the fclerotic, or adheres 
 to the fclerotic, which perfetlly refembles it, and 
 always arifes from it. The other plate of the dura 
 mater, the external, recedes and forms the periof- 
 teum of the orbit : the pia mater, which is in this 
 nerve very diflin£l and full of veffels, having be- 
 come entirely dark coloured and thin, lines the in- 
 lide of the fclerotic. The remaining medullary 
 central part of the nerve, continued from the brain, 
 but divided by cellular plates, contrafts into a 
 deprelTed white conical papilla ; which entering 
 through the holes in the white circle of the cho- 
 roid coat, and again expanding, produces the moft 
 internal membrane of the eye, the retina. 
 
 Dxi. The fclerotica is in general white, furnifli- 
 ed with few veffels, tough and compact, refembling 
 the nature of Ikin, of a figure very nearly globular, 
 but compreffed before, and is thicker at the back 
 part. Before this coat, which is perforated by cir- 
 cular holes in its forepart, is placed, and oblique- 
 ly connected v/ith it, a more convex portion of a 
 fphere ; pellucid, compofed of many plates, whofe 
 veffels are filled with pellucid water, and are diffi- 
 cult of demonftration, infenfible, and almoft circu- 
 lar, circular towards the nofe, and oval towards the 
 temples : it is termed the cornea, and through it 
 the light paffes into the infide of the eye. It readi- 
 ly imbibes and exudes water. Before the anterior 
 and flatter part of the fclerotica, and before the 
 cornea, the conjundiva is detached from each of 
 
 the 
 
SIGHT. 
 
 Chap. XVI. 
 
 248 
 
 the e^'^elids, and is joined to the fclerotica by pro- 
 per cellular fubftance, which may be inflated, (d.) 
 and is replenifhed, partly with red veffels, and 
 partly with their pellucid continuations. 
 
 Dxii. The origin of the choroid coat, is from the 
 circumference of the white cellular circle, termina- 
 ting the fubflance of the optic nerve, and through 
 whofe numerous foramina, and from which the re- 
 tina and arteria centralis retinae proceeds. At that 
 place the choroides adheres to the iclerotic, and to 
 the circle above defcribed. Then it is expanded 
 concentrically, within the fclerotic, with v'hich it is 
 united, perhaps by fome cellular fiibftance, and by 
 many veffels, which come from it to the choroides. 
 Outwardly it is of a brown colour, but inv^ardly of 
 a deep ruffet or alraoff black, and at the fame time 
 villous ; the two furfaces are feparable by macera- 
 tion ; and the inncrmoff may be diftinguiflied by 
 the name of Ruyfch ; but it grows white through 
 age. When it has reached the beginning of the 
 pellucid cornea, it there becomes clofely connected 
 with the fclerotica, by much cellular fubftance, hav- 
 ing the appearance of a white circle, called orbicu- 
 lus ciliaris, and then turns off in another direction ; 
 namely, the coat, which was before fpherically ex- 
 panded, is now ftrctched under the arch of the 
 cornea, in the form of a circle, a little convex ff)r- 
 wards, and incomplete, having in its centre a circu- 
 lar foramen called the pupil, which is feated nearer 
 to the nofe, and is larger towards the temple. I'he 
 anterior part of this ring is called the iris ; and the 
 back part, feparable from the former in the human 
 body, by maceration, in fome animals even by the 
 knife, is, from the black pigment with which it is 
 covered, called the uvea. On the anterior furface 
 of the iris appear numerous radiated and branching 
 ffreaks, of various colours in different people, and 
 entirely covered with liocculi. Thcfe terminate 
 
 on 
 
SIGHT. 
 
 249 
 
 Ghap. XVI, 
 
 on this fide of the pupil in a ferrated circle, front 
 which other fimilar ftreaks extend, even to the 
 edge of the iris. They are ferpentine when the 
 pupil is dilated, and ftraight when it is contracted. 
 On the poflerior furface of the uvea is much black 
 pigment ; which being v/aflied off, ftraight radiated 
 ftreaks appear, extending to the pupil, and not 
 flocculent. Orbicular fibres, concentrical with the 
 pupil, I have not been able to obferve, either with 
 the naked eye, or with the microfcope, even in the 
 ox ; but only in the uvea, an internal circle diftin- 
 guifhed by obfcurer rays, and lefs villous. In the 
 human foetus, the pupil is fliut up, and the iris be- 
 ing continued, makes a complete circle. That part 
 of it which extends acrofs the pupil is of a vafcular 
 texture. 
 
 Dxiii. Though the iris has little fenfibility, and 
 is not endowed with any mechanical irritability j 
 yet during life, in man, quadrupeds, and birds, 
 the pupil is contracfted by every greater degree of 
 light, and is dilated by every fmaller one ; hence 
 it is alfo rendered broader for viewing diftant ob- 
 jects, and narrower for viewing fucli as are near. 
 The caufe of this dilatation feems to be a remiffion 
 of the powers refifting the aqueous humour ; as 
 proved by the dilatation of the pupil, from debil- 
 ity, fyncope and death. The contraftion is lefs un- 
 derftood, and perhaps only depends on the ftrong- 
 er afilux of humours into the colouriefs veffels of 
 the iris, by which thefe veffels are extended ; and, 
 at the fame time, the iris is rendered longer, and 
 fliuts up the greater part of the pupil : fo that this 
 motion has fomething in common with inflamma- 
 tion, as agreeing in their caufe. In young people, 
 the pupil is more evidently moved and contracted ; 
 as the eye gradually grows callous in old people, it 
 becomes almoft immoveable. In an animal twenty- 
 three hours after death, I have feen the iris extend- 
 ed by heat fo as to ftiut the pupil. 
 
 DXIV. 
 
SIGHT. 
 
 Chap. XVI. 
 
 2.50 
 
 Dxiv. Behind the uvea, from the fame circle in 
 which the choroides unites with the fclerotica, 
 more externally than the cornea, thick ftrise, ele- 
 gantly plaited, ariling from the choroides, white, 
 with parallel veffels running under them, with plu- 
 mous, pendulous extremities, joined to the loofe 
 and thin retina, and every where covered with a 
 good deal of black pigment, depart, in the form of 
 a. perforated ring, inwards from the tunica choroi- 
 dea, and proceed forwards behind the ciliary circle, 
 and reft upon the vitreous humour ; and, laftly, 
 upon the capfule of the cryftalline lens, but do not 
 adliere to them. They are denominated the cil- 
 iary ligaments. The origin of the pigment is not 
 known ; nor liave the fecreting glands, which fomc 
 Iiave fuppofed, been found. Among its ufes, one 
 feems to be, to keep the cryftalline lens firm. In 
 infants, this ftme mucus, behind the ciliary pro- 
 ceifes, exprelles the figure of a radiated flower. 
 
 Dxv. The retina, which is a true continuation 
 of the meduUa of the optic nerve, and therefore 
 very tender, mucous, and evaporable, is expanded 
 within the choroides into a fimilar fphere, concen- 
 tric with it ; and immediately inclofes the vitreous 
 humour. But when the retina has reached the 
 ciliary proceftes, it follows their courfe, fupporting 
 their arteries and ftrise, and proceeds to the cr)dtal- 
 line lens, adhering to and covering its capfule, if 
 the obfervations of fomc other anatomifts, as well 
 as my own are to be relied on ; for in quadrupeds 
 this termination of it is not perfccUy certain, al- 
 though in birds the internal lamina of the retina, 
 covered with the ciliary body, is evidently contin- 
 ued to the cryftalline lens ; to the circumference 
 of which it alfo adheres in man. The fabric of the 
 retina is inch, that externally its foft and medulla- 
 ry globules form a thick and pulpy membrane, 
 within which radiated fibres proceeding from the 
 lamina cribrofa, and continued forwards, conftituie 
 
 a thinnci' 
 
Chap. 
 
 SIGHT. 
 
 251 
 
 a thinner involucrum, very readily obferved in 
 fiflres, and alfo in fome birds and quadrupeds, but 
 not in nian, Arterial and venous veffels with red 
 trunks, form a net in the internal furface of the re^^ 
 tina, which when accurately filled with coloured 
 water compofe a membrane. 
 
 Dxvi. Thefe coats, refembling the coats of a 
 bulbous root, are fupported, and the fpherical fig- 
 ure of the eye is preferved by its humours ; of 
 which one is a foiid, another a foft body, and a 
 third truly a liquor. Firft, then, the concave fur- 
 face of the. retina is every where filled by the prin- 
 cipal or vitreous humour, of which the flructure 
 confifls of a peculiar thin, pellucid, cellular mem- 
 brane, in whofe cellular intervals is contained a 
 very pellucid liquid, very rarely altering even in 
 old age, completely evaporable by heat, nearly al- 
 lied to the aqueous humour, and fomewhat denfer 
 than water. Its veffels, which are moft manifeft 
 in fifli, lie in the back part, moft beautifully radi- 
 ated from the central trunk of the retina, embrac- 
 ing the convexity of the vitreous humour j and 
 inferred into a circle formed not far from the lens 
 by other arteries coming from the choroides, and 
 which I have feen in the fheep. The vitreous mem- 
 brane, which is tender confidering its body, ad- 
 heres to the lens in two places, before and behind ; 
 fo that a hollow fpace is intercepted in the middle 
 between the two infections, around the cryftalline 
 lens. This fpace is divided in different places by 
 fome fibres. On its anterior furface the ftriae of 
 the ciliary body imprint their marks. 
 
 Dxvii. But, in the forepart of the vitreous body, 
 behind the uvea, there is an orbicular depreflion 
 of confiderable depth, into the cavity of which the 
 cryftalline lens, (alfo, though improperly, ranked 
 amongft the humours,) is received. The figure of 
 this lens, refembling frozen jelly, is compofed of 
 
 two 
 
SIGHT. 
 
 Chap. XVI. 
 
 252 
 
 two elliptical convex fegments, the anterior of 
 which is flatter, and the pofterior more gibbous. 
 It is conftrufted of concentric laminae, connected 
 by cellular fibres, which themfelves are compofed 
 of fibres elegantly difpofed through fine cellular 
 membrane. Betwixt the plates of the cryftaliine 
 lens, is alfo contained a peUucid liquor, but which, 
 in old age, naturally acquires a yellow colour. 
 The innermoft fcales are more clofely compacted ; 
 and form as it were a harder nucleus ; externally 
 it adheres fo very loofely to the capfule, that when 
 tlis«s broken, it very .^readily fprings out ; and 
 f(3«ie /^^ fay, that a littih. water is eflufcd around 
 it. It i^upplied with an artery from the retina, 
 which perforates the middle of the vitreous hu- 
 mour, and enters behind ; for veffels have not 
 yet been difeovered on the anterior furface. The 
 'vfiole lens is contained in a ftrong, thick, elaftic 
 capfule of, a pellucid membrane, more firm in the 
 forepart, and which is lined poflerioidy by the vit- 
 reous tunic. ^ 
 
 Dxviii. Laftly, the aqueous humour, which is 
 extremely pellucid and fluid, “and wliich is renew- 
 ed again if it be let out, ^nms in the fmall trian- 
 gular curvilinear fpace betwixt the uvea and cryf- 
 taliine lens, anchin that larger fegment of a hollow 
 fphere which lies betwixt the iris and the cornea. 
 This humour feems to exhale from the fmall arte- 
 ries of the iris, uvea, and ciliary procelTes ; being 
 again abforbed by the correfponding veins, while 
 fome portion of it is abforbed by and exhaled 
 throuTn the cornea. This humour alfo moiftens 
 the uvea and capfule of the lens. About the be- 
 ginning of the prefent century, the fpaces filled 
 with this liquor were called the chambers of the 
 eye ; that between the cornea and iris the anterior 
 one, and that fmall one between the furface ot the 
 cryftaliine lens and the uvea the pofterior. 
 
 DXIX.- 
 
Chap. XVI. 
 
 SIGHT. 
 
 253 
 
 Dxix. The eye, thus conftructed, is provided 
 with mufcies externally inferted into it, by which 
 it is governed. Namely, into the circle of the 
 fclerotica, which is contiguous to the cornea, are 
 inferted four flraight mufcies, ariling almoft in one 
 circle from the dura mater of the optic nerve ; 
 where, departing from the nerve, it coheres with 
 the periofteum of the orbit, and proceeding for- 
 wards with their bellies round the bulb of the eye, 
 they terminate again by their aponeurofes, meeting 
 together in another circle. Of thefe, the elevator 
 is the leall, and the abductor rather the longeft. 
 The office of each of thefe mufcies appears very 
 plainly ; fince, being bent round the convex bulb 
 of the eye, as about a pulley, they mull, of courfe,- 
 elevate, deprefs, or turn the eye either to the nofe 
 or to the temples. Moreover, two of them acting 
 together may move the eye diagonally ; as up- 
 wards and outwards, upwards and inwards, &c* 
 Laftly, when all the four ftraight mufcies contract 
 together, there is fcarcely a doubt that they draw 
 back the whole eye within the head towards their 
 origin, and thus bring the cryltalline lens nearer to 
 the retina. 
 
 Dxx. But the fabric of the two oblique mufcies 
 of the eye is more compound. The upper of thefe, 
 arifmg together with the recli, is long and flender, 
 afeending forwards to a notch in the os frontis, 
 which is completed into a hole by a double liga- 
 ment, which on each fide fuftains a cartilage, ex- 
 cavated in the middle, and almoft quadrangulaiv 
 Through this canal pafles the tendon of the obli- 
 quus, which being reftefted backwards and out- 
 wards, included in a capfule of its own, is infert- 
 ed into the globe of the eye behind the ftraight 
 mufcies. This draws the globe forwards, as if out 
 of the orbit, and inwards, and turns the pupil in- 
 wards and downw'ards. The other, the obliquus 
 minor from the finus of the lachrymal foramen in 
 
 the 
 
SIGHT. 
 
 Chap. XVI. 
 
 254 
 
 the upper jaw, afcends immediately outwards from 
 the os ungiiis round the globe of the eye, and is 
 inferted by its tendon into the fclerotica behind the 
 external reclus : v.Tence it appears to turn the 
 point of its infertion into the eye downwards and 
 outwards ; and, therefore, the oppofite pupil up- 
 wards and inwards. 
 
 Dxxi. But there are other minute mufcular mo- 
 tions performed in the eye, which prefuppoie a 
 knowledge of its nerves. Of the optic nerve we 
 have already treated (mx. dx.) The fourth pair 
 goes only to the larger oblique mufcle, and the 
 fixth pair to the recfus externus. The third and 
 fifth pair produce the principal nerves in the eye ; 
 the firft or ophthalmic branch of the fifth fends off 
 a nerve at its entrance into the orbit, to the eyelid 
 and lachrymal gland, which joins with the fecond 
 branch of the fifth pair, and with the teniporal 
 branch of the third of the fifth pair. On entering 
 the orbit, its trunk divides into two. The upper 
 branch, larger and bifid, is expended on the fore- 
 head and eyelids : but the lower, penetrating in- 
 wards above the optic nerve, fends off a long ilen- 
 der filament at the outer part of that nerve, which, 
 joining with another filament of tlie third pair 
 forms the ophthalmic ganglion, and fends off one 
 or two ciliary nerves. Finally, after having given 
 off the recurrent nerve of the nofe (cccclvii.) it 
 is then fpent upon different parts in the internal 
 angle of the eye. 
 
 Dxxii. But the third pair is of moft importance. 
 After giving ofl’ a branch upwards to the Itraight 
 mufcles of the eye, and to the eyelids, it pi'oceeds 
 with its trunk under the optic nerve, and at the 
 fame time fends out three branches to the inferior, 
 obliquus minor and interims ; after this, or before, 
 from its trunk, or fometimes from the branch of 
 the obliquus minor, it fends off another Ihorf 
 nerve, much thicker than the root from the fifth, 
 
 (dxxi.'! 
 
Chap. XVI. 
 
 SIGHT. 
 
 ^SS 
 
 (dxxi.) which, under the abdu<ftor mufcle upon 
 the optic nerve, forms the ophthalmic ganglion, 
 which is oval and conftant, and fometimes arifes 
 from the third alone. From that ganglion, and 
 fometimes from the trunk of the third or fifth, four 
 or five ciliary nerves playing around the optic nerve 
 in a flexuous courle, go to the globe of the eye, 
 perforate the fclerotica almoft in its middle, in 
 company with its longer fmall arteries or veins, 
 run ftraight forwards along the choroides, and vi- 
 fibly proceed to the iris, and feemingly to the cili- 
 ary proceiTes. Other very fmall nerves, originat- 
 ing from the fame ganglion, remain in the tunica 
 fclerotica. 
 
 Dxxiii. The motion of the ciliary proceffes is 
 obfcure and difficult of demonftration, (dxiv.) ly- 
 ing incumbent upon the furrows of the vitreous 
 membrane, by their action they are believed to 
 prefs back that body, fo as to bring the lens for- 
 wards, and remove it farther from the retina. But 
 I have never feen, in all the animals I have differ- 
 ed, any thing like a mufcle in this ciliary body, 
 but only a membrane which fupports fmall veflels. 
 The fphinder of the pupil and conffridor of the 
 cornea, mentioned by fome writers of eminence, 
 and the moving fibres, which others have imagined 
 proper to the cryffalline lens, are not confirmed by 
 anatomy, nor are they confiftent with the conftant 
 hardnefs of the lens and cornea in moft animals. 
 
 Dxxiv. The hiftory of the eye alfo comprehends 
 its veflels, which have a moft beautiful fabric. Ail 
 thofe which belong properly to the eye itfelf come 
 from the ophthalmic artery, a branch of the inter- 
 nal carotid, (cccxvi.) This, creeping under the 
 optic nerve, fends off, as principal branches, the 
 upper ciliary, one or more inferior ciliaries ; the 
 lachrymalis, from whence the nafalis recnrrens pof- 
 terior, and internal part of the arch of'the tarfus ; 
 afterwards the mufcularis inferior, the nafalis re- 
 
 currens. 
 
SIGHT. 
 
 Chap. XIV: 
 
 currens, anterior and pofterior, the mufculares fu- 
 periores, and the palpebralis, which, with the form- 
 er branch, forms the arch of the tarfus. Laftly, it 
 goes to the face, nofe and adjacent parts. But the 
 ophthalmic branches, belonging to the inner parts 
 of the eye, are called the ciiiaries ; which, arillng 
 from the trunks now . mentioned, and playing 
 around the optic nerve, in four or more branches, 
 in a ferpentine courfc, partly clofe by the entrance 
 of the optic nerve, go to the choroides with forty 
 or more branches, and make upon its external fur- 
 face, ramifications divided at acute angles, which 
 proceed forwards to the circle of the uvea. 
 
 Dxxv. But molt of the fmall arteries of the tu- 
 nica choroides gradually incline towards the inte- 
 rior parts of the eye ; and, being covered with a 
 kind of cellular down, go to the ciliary procefles, 
 along each of which two fmall arteries run, giving 
 off on every fide, vafcular flocculi, and inofculating 
 at their apex. 
 
 Dxxvi. Other fmall arteries alfo, likewife arifing 
 from the ciliary ones, but few in number, moll 
 commonly two, go to the place, from which the 
 uvea originates. There, fpreading in various di- 
 reclions, they furround the root of the uvea with 
 their branches, and join to form a circle, into 
 which the anterior ciliaries inofculate ; which are 
 fmall arteries arifing from the mufcular branches of 
 the ophthalmic ; and are inferred into the circle 
 generally by twelve fmall trunks, near the origin 
 of the cornea. From that circle, and likewife from 
 the above mentioned anterior ciliaiy arteries, with- 
 out the intervention of the circle, llraight, branch- 
 ed veflTels, arc diftributed, both on the iris, and on 
 the uvea 5 the former full of a blue or dark colour- 
 «d fiuid ; and the latter naturally white, but cov- 
 ered with a good deal of a black paint. In the 
 uvea, at fome diftance from the pupil, they fre- 
 quently form an imperfect circle. 
 
 DXXVIT. 
 
SIGHT. 
 
 Chap. XVI. 
 
 257 
 
 Dxxvii. But from the fame ophthalmic artery, 
 from its trunk, or from the lachrymal branch, or 
 from one of the ciliaries, one or more branches en- 
 ter into the optic nerve ; the principal, the central 
 artery of the retina, penetrates into the medulla of 
 the nerve, and palling through the apex of the pa- 
 pilla, (dx.) enters the centre of the retina ; from 
 thence it fpreads every way through the retina- it- 
 felf, by fo many branches, when traced by a Ikilful 
 anatomill j that that vafcular network has been taken 
 for a peculiar membrane. Sometimes a fmall branch 
 goes along the centre of the nerve to the retina, and 
 is in like manner ramified through it. From com- 
 parative anatomy, it is certain, that from thefe 
 branches the vafcular branches of the vitreous tu- 
 nic are produced, as well as the pofterior artery of 
 the lens. The moft internal of thefe arteries, is the 
 celebrated porus opticus of the ancients. 
 
 Dxxviii. The veins of the eye, in general, arlfe 
 from the ophthalmic vein, which on the one fide 
 comes from the facial vein, entering the orbit ; 
 and on the other, is inferted into the cavernous 
 finus. The internal veins of the eye perforate 
 the middle of the fclerotica, with fewer and larger 
 trunks than the arteries, and form larger and more 
 anterior reticulations, of a roundifli figure, which 
 commonly occupy the middle of the tunica cho- 
 roides ; fome, which are long, are continued to the 
 origin of the uvea : others anterior, fimilar to the 
 arteries ; and another, the centralis nervi optici, cor- 
 refponding with the artery, goes to the retina. The 
 pellucid veffels do not differ from the fanguiferous. 
 Lymphatic veffels are faid to have been feen in the 
 retina ; but the obfervation has not been fufiiciently 
 repeated. 
 
 Dxxix. So far with refpecL to the anatomy ; but 
 the aftion of the eye is entirely elucidated by phy- 
 fical experiments, from which it has been afcer- 
 tained, in the moft incontrovertible manner, except 
 S a few 
 
SIGHT, 
 
 Chap. XVI. 
 
 25S 
 
 a few doubtful points. Light is the fame matter 
 with heat, or very nearly the fame, poffelling ex- 
 treme fluidity and fubtiity, penetrating through 
 all bodies, very rigid, not exhaufted by any dif- 
 tance of its paffage, and moving with exceffive ve- 
 locity, fo as to arrive at the earth from the fun in 
 eight minutes and thirteen feconds. Light in our 
 planet proceeds either from the fun, which feems 
 to have the power of arranging in ftraight lines, the 
 matter of light, otherwife confufedly fcattered ; 
 or from fome other lucid point. From it, as from 
 a centre, the light is diftributcd like rays, to all parts 
 of the fphere, fo as to fall upon the furfaces of all 
 bodies ; from whence again it is reflected, and im- 
 pinges on the eye, at angles equal to the angle of 
 incidence, and renders the bodies, from which it 
 comes, coloured and vifble. 
 
 Dxxx. It is afcertained, from experiments, that 
 light is compofed of rays in right lines, almofl vdth- 
 cut any phyf cal breadth ; and yet, each of which 
 may be feparated into feven more minute, perma- 
 nent and immutable rays. The known properties 
 of thefe rays are. that all of theiUj conjoined togeth- 
 er, confiitute a white beam ; but when refracted, 
 and feparated by the minute furfaces of bodies, 
 they are fubdivided into red rays, which are the 
 molt conflant, hard, and leaft refrangible ; and af- 
 terwards into orange, yellow, green, blue, indigo, 
 and violet ; which are always weaker and more rc- 
 franmbie, as thev are farther diftant in order from 
 the red rays. Shade arifes from a deficiency of re- 
 flected rays. Colours are compounded of fltade 
 united with various rays. 
 
 Dxxxi. The peculiar colours of bodies arife from 
 the minute furfaces of their folid particles, by which 
 their pores are limited, which refraCt the rays of 
 light, according to the difference of their thicknefs, 
 reflecting one kind of ra.ys moft copioufly, and in a 
 great meafure fuffocating by repeated internal refrac- 
 tions, the others admitted into their fubftance: fothat 
 
SIGHT; 
 
 Ghap. xvi. 
 
 259 
 
 the thickeft and denfeft particles reflect a white col- 
 our ; the next red ; and the thihneft violet. Bodies 
 are opaque, which retain all the rays, and tranfmit 
 none, from the largenefs of their pores, to the tides 
 of which the light is attracted ; and which are fill- 
 ed with fome matter that has a power of refraction, 
 different from that of the particles of the body. 
 Thefe principles we embrace, till a new theory, 
 which afcribes the diverfity of colours to vibra- 
 tions of different celerities, ihall be better eftablifh- 
 ed ; for it is not our bufinefs to afcertain thefe mat- 
 ters. 
 
 Dxxxii. Thefe rays, when they fall obliquely up- 
 on liquors of various denfities, in palling through 
 them, varioufly recede from, or incline towards the 
 perpendicular : this is called refradlion. In gen- 
 eral, the denfer the medium^ the more are the rays 
 bent towards the perpendicular ; excepting only in- 
 flammable liquors, which, by a peculiar property, 
 attradl the rays more to the perpendicular, than in 
 proportion to their denfity. The proportions of 
 the angles of incidence to thofe of refraftion, are 
 conftant ; fo that the fine of the angle of refrac- 
 tion of rays palling from air into water, is to the 
 fine of the angle of incidence, as 3 to 4 : and of 
 rays, palling from air into glafs, the fine of the in- 
 cidence is to that of refradion, as 1 7 to 1 1 5 and 
 from water into glafs, as 5 1 to 44. 
 
 Dxxxiii. Rays, which come through the air with 
 but little divergency, as thofe of the fun on ac- 
 count of its immenfe diftance ; or as, in general, 
 any rays that come from a diftance of above 100 
 feet, when they fall upon a body, fpherically con- 
 vex, and denfer than the air, at a large angle, as at 
 48 i degrees, are refle<fted, and do not penetrate it. 
 If the angles are fmaller, they penetrate the refra<ft-i 
 ing medium, and are refrafted in it, fo as to meet 
 together in one point, which is called their focus^ 
 This point lies in the axis, or in the ray, falling 
 s 2 perpendicularly 
 
SIGHT. 
 
 Chap. XVl. 
 
 i6o 
 
 perpendicularly on the furface, and therefore not 
 inhered ; and in a fpherkal globule of water, the 
 focus of rays coming from the atmofphere, is at 
 the diilance of one iemidiameter from the fphere j 
 and in a fphere of glafs, a fourth part of the diam- 
 eter, and in a convex lens of glafs, that is, a part of 
 a fphere not lefs than thirty degrees, and equally 
 convex, it is alfo one femidiameter ; but fo that the 
 rays meet, not in a point, but in a little circle. 
 
 Dxxxiv. Therefore the rays of light, whether di- 
 rect or reflected, fall in fuch a manner upon the 
 cornea of the eye, as to form a very acute cone, 
 from the lucid point to the furface of the mem- 
 brane : the balls of which is the furface of the cor- 
 nea, and the apex the radiant point ; yet fo, that 
 the rays of the cone may be confidered parallel, 
 without any fenfible error. Of thefe rays, all thofe 
 which fall upon the cornea at a greater angle than 
 forty degrees, are reflecled from the cornea with-^ 
 out penetrating its furface. Others which enter 
 the cornea, but ftill at large angles, fall in betwixt 
 the uvea and fides of the cryltalline lens, and are 
 I'ufi'ocated in the black paint that lines the uvea, 
 (dxii.) and the ciliary procefles, (dxiv.) and thofe 
 rays only fall upon the furface of the lens, which 
 enter the cornea at fmall angles, not much diHant 
 ii'om the perpendicular, or at about twenty-eight 
 degrees. By this means, all thofe rays are exclud- 
 ed, which the refracting power of the humours in 
 the eye could not have been able to collect into one 
 point of the retina ; and which, therefore, would 
 have painted the image on the retina too broad and 
 confufed. 
 
 Dxxxv. Thofe rays, therefore, coming from the 
 air, which is fo thin, and palling through the cor- 
 nea, wliich is the fegment of a fphere, thick, denfer 
 than water, and therefore almoft a fourth part more 
 refracting, are remarkably inclined towards the 
 perpendicular. By the aqueous humour, which is 
 
 linalJ 
 
Chap. XVI. 
 
 SIGHT. 
 
 261 
 
 fmall in quantity, and almofl like water, but rather 
 lighter, they are not altered, and fall upon the fur- 
 face of the tranfparent lens, before they have form- 
 ed a focus, becaufe of its nearnefs, nearly parallel, 
 or rather converging ; becaufe their divergency 
 was abundantly corre6led by the refrading power 
 of the cornea. Moreover, the cornea being convex, 
 and more prominent than the hemifphere of the 
 fclerotica, receives and collects a greater number of 
 rays than if its furface were flatter, and therefore 
 fmaller. 
 
 Dxxxvi. That the refradUng power of the cryf- 
 talline lens, exceeds that of water, may be under., 
 flood from its hardnefs and weight, although we 
 have no fufficiently certain meafure. In this lens, 
 therefore, and more efpecially in its poflerior very 
 convex furface, the rays converge very much, and 
 pafs thence into the vitreous body. 
 
 Dxxxviii. This fubflance is denfer than water, 
 fince it finks in it ; but rarer than the cryflaliine 
 lens ; bends the rays a little more gently towards 
 the perpendicular, till at length the rays, coming 
 from a point of diflinft vifion, are concentrated in- 
 to the fmalleft poflible point of the retina, where 
 they paint an image of the obje6l from which they 
 come ; but inverted, on account of the neceffary 
 decufl'ations, The manner in which the images of 
 objects are thus painted, may be feen in an artifi- 
 cial eye, or in a natural eye, when the back part of 
 the fclerotica is removed. But the image is paint- 
 ed on the outer fide of the entrance of the optic 
 nerve, at the termination of the axis of vifion, 
 which is not limited to a mere point, but has fome 
 breadth ; fince we fee many objedls at once, v/hofe 
 images mufl be reprefented in different points. 
 Vifion is there moft diflinft, becaiafe the rays ar- 
 rive thither nearly perpendicular. But frequently 
 it does not fill on the fame place in both eyes of 
 the fame individual. When the lens is deftroyed. 
 
SIGHT. 
 
 262 
 
 Chap. X\T. 
 
 the vitreous humour alone collecls the rays, though 
 lefs powerfully. 
 
 Dxxxix. Is it entirely falfe that the objecl is 
 painted on the retina ? Is the picture reprefented 
 on the choroides ? Is this new opinion confirmed 
 by the experiment, by which it appears, that the 
 place where the optic nerve enters is infenfible ? 
 and which is thus explained, that there is in that 
 place no choroides but only the bare retina, and 
 that therefore, it does not poffefs vifion. But this 
 is repugnant to a very well known obfervation, 
 that the retina is a mofi: fenfible nervous medulla ; 
 and that the choroides almoft entirely confifts of a 
 few fmaU nerves, and of veflels which are moft cer- 
 tainly blind. This is likewife contradicted by the 
 very great variety of the choroides in animals ; by 
 the equally great uniformity of the retina ; and by 
 the black fpots, which, even in man, obfeure the 
 exterior furface of the retina. But, by this experi- 
 ment, we perceive the reafon why the optic nerve 
 is not inferred into the axis of the eye, but to- 
 wards one fide. For thus, except only in the 
 fingle cafe, where an impediment is fituated in the 
 point of interfeftion of lines drawn through the 
 centre of the optic nerves, the one eye fees and 
 afiiids that v/hofe blind portion is directed to the 
 object. 
 
 DXL. But fince the ncceflary functions of human 
 life require that a diftincl: object be painted upon 
 the retina, not only by the rays which come from 
 one certain diftance, but likewdfe that rays w'hich 
 come from various and very dififerent fituations, 
 more or lefs difiant, fliould excite a diftinct idea of 
 the objeft from which they come : therefore, it is 
 believed, that the necefiary change is produced in 
 the eye by proper means. Some celebrated anato- 
 mifts have fuppofed the lens moveable by the pow- 
 ers before mentioned, (nxix. nxxiii.) They afl'ert 
 this art of changing the eye is learned by experi- 
 ence, 
 
Chap. XVI. 
 
 SIGHT. 
 
 263 
 
 ence, and is not poITeffed by thofe on whom the 
 operation of couching the catarafl has been lately 
 performed. Alfo in an artificial eye, the advantages 
 and neceffity of this motion, it is faid, may be plain- 
 Jy perceived. Therefore, too great a divergency of 
 the rays, as in thofe which come from objefls very 
 clofe to the eye, is corre6led by the removal of the 
 lens farther from the retina, by which means the 
 focus, which is more diftant, on account of the di- 
 vergence of the rays, falls upon the retina itfelf, 
 which would otherwife have fallen behind the reti^ 
 na ; for the refrafting power of the eye being fupr 
 pofed to be fuch, as will caufe the focus of rays 
 coming from the diftance of three feet, to fall exacts 
 ly upon the retina, it will not be able to collect to- 
 gether into the fame point, rays which come from 
 the diftance of three inches ; and the more diverg.- 
 ing rays, when not collefted by more powerful 
 means, will be too late of uniting. 
 
 DXLi. But thofe rays, which come from very 
 remote fituations, and may be therefore reckoned 
 parallel, would meet in the vitreous humour before 
 they reached the retina ; and would again feparate 
 as rays from the point of concourfe, as if from a 
 lucid point : it is therefore believed, that the pow- 
 ers, (dxxiii.) remove the cryftalline lens from the 
 cornea, and carry it nearer to the retina, that the 
 rays may meet at a greater diftance from the lens, 
 and that that diftance may be accommodated fo as 
 to fall upon the retina. For an eye, that will col- 
 le<ft the rays coming from a diftance of feven inch- 
 es, on the retina, will collect thofe which come from 
 a diftance of three feet too foon, and before they 
 reach the retina. So that it feems perfectly necef- 
 fary for the eye to be made thus changeable, fince 
 we fee diftinftly at various diftances. The point 
 of diftinct vifion is that in which the given object 
 is painted on the retina in the leaft fpace poflible. 
 The powers colleding the rays, are often very dif- 
 ferent 
 
SIGHT. 
 
 Chap. XVT. 
 
 264 
 
 ferent in the two eyes of the fame perfon, fo that 
 the one eye is rather long fighted, and the other 
 Ihort fighted. 
 
 DXLii. Thefe and other fimllar opinions, com- 
 naonly received, are taught, more efpecially by the 
 mathematical phyficians, who more obvioufly per- 
 ceive the neceflitv of thefe changes. Yet there is 
 no power in the human eye which can either moA^e 
 the cryftalline humour from its place, or comprefs 
 it. And v/e do not perceive this faculty in our- 
 felves : for we m.ove a book, which by being too 
 far off we fee confiifedly. nearer to our eyes, which 
 we would not do, if by an internal change in the 
 eye we could correct the fault of the diftance : and, 
 through a frnall hole, we perceive an objecl:’only 
 fingle in the point of difiincf vifion, but double in 
 every other. Perhaps the contradlion of the pupil 
 may have fome effect in enabling us to fee near ob- 
 jects more dictinclly. 
 
 DXLiii. But this adaptation is not fufficient in 
 all perfons : for there are, and now more com- 
 monly than formerly, perfons leading a fedentary 
 life, and occupied with the obfervation of very 
 minute obje(fts, in vdiom the cornea is more con- 
 vex and denfe ; the cryftalline lens more convex 
 and folid ; the eye itlelf, by the weight of the 
 humours, more elongated ; and the reft of the hu- 
 mours themfeives probably more denfe ; and in 
 whofe eyes one, or levcrsJ, or all of thefe difeafes 
 occur. In thefe perfons, the iris is fenfible in a 
 fmall light ; and therefore from their winking, 
 they are denominated myopes. In thefe, the point 
 of diftinCL vifion is very near to the eye, from one 
 to feven inches from the eye j they fee remoter ob- 
 jeffs obfcurely, without being able to diftinguilh 
 their parts. The reafon of this is evident ; iince, 
 from the caufes jufi mentioned, the too great re- 
 frafling power of the humours, caufes the diftant 
 and confequently parallel rays to m.eet before the 
 
 retina ; 
 
SIGHT. 
 
 Chap. XVI. 
 
 265 
 
 retina ; and therefore diverging again from their 
 focus, they faU upon the retina in many points. 
 Thus alfo to a found eye, the perception of near 
 objeds is confufed ; becaufe the rays coming from 
 thefe are fpread all over the retina, without being 
 coUefted. 
 
 DXLiv. The remedy, in the commencement of 
 this difeafe, is to view diftant places, to abftain 
 from minute obje6ts, and concave glaffes, and to 
 look through a fmall aperture, by which the light 
 is weakened. V/hen the diforder is confirmed, it 
 is alleviated by the ufe of a concave lens, which 
 diminiflies the refrafting power in the humours, 
 cornea, and cryftalline lens, in proportion to its 
 concavity ; and thus removes the focus of diftant 
 objeds farther from the cornea, fo as to fall upon 
 the retina. This glafs ought to be a portion of a 
 fphere, whofe diameter is equal to the diftance of 
 diftind vifion by the naked eye, fquared by the 
 diftance of diftind vifion in the eye furniihed with 
 a glafs, and divided by the difference betwixt 
 them. Short fighted people may hope for fome 
 relief from the progrefs of life ; for children are 
 almoft all myopes : but, as they grow older, the 
 eye becomes flatter from the ftrength of the folids, 
 it becomes ftiorter, and the converging powers, of 
 the lens and cornea are diminiftied. 
 
 DXLV. Another defed, the oppofite of the form- 
 er, troubles people who are in the habit of look- 
 ing much at very diftant objeds, and is efpecially 
 frequent and incurable in old people. In it, the 
 cornea and cryftalline lens are flatter, and the hu- 
 mours of the eye have a lefs refrading power. 
 Hence near objeds, whofe rays fall very diverging 
 upon the cornea, appear to them confufed ; becaufe 
 the converging powers of the eye are not fufiicient 
 to colled the rays into a focus upon the retina, and 
 the rays arrive at it fcattered, and have their focus 
 behind the eye ; hence their vifion is confufed. 
 
 The 
 
SIGHT. 
 
 266 
 
 Chap. XVf. 
 
 The point of diftincf vifion among prefbyopi, is 
 from fifteen inches to three feet. 
 
 DXLvi. Such perfons are, in fome meafure, re- 
 lieved by'looking through black tubes, by the ufe 
 of which the retina grows tenderer, and the rays 
 come to the eye in a parallel direction. The re- 
 medy here is a convex lens of glafs, which may 
 caufe the rays to converge, fo as to meet fooner in 
 a focus, and upon the retina. The diameter of the 
 fphere, of which fuch a lens ought to be a portion, 
 is exactly as before (dxliv.) There is no hope 
 from age, which increafes the malady. 
 
 DXLvii. The medium betwixt the fhort and 
 long lighted eye is the belt, with which a perfon 
 can fee diftinctly objects that are both tolerably 
 near and tolerably remote, and therefore may af. 
 fume the properties both of the myopes and pref- 
 byopi ; of this kind we reckon an eye that is able 
 to read diftinctly at the diftance of one foot. But 
 other conditions are neceflary, fuch as perfect clear- 
 nefs of the humours ; great mobility of the eyes ; 
 fenfibility of the pupil ; and a retina, neither too 
 fenfible nor callous. 
 
 DXLviii. But by means of the eye, the mind does 
 not receive a ftmple reprefentation of the image 
 of the object on the retina, which is transferred to 
 the feat of the foul ; but many things are added 
 from experience, f*. w'hich the eye does not really 
 fee, and other things are interpreted differently 
 by the mind, from what they arp reprefented by 
 the eyes. And, firft, the magnitude of an objed 
 is judged of by the optical angle intercepted be- 
 tween the radiating object as the vertical point, 
 and the cornea as the bafe. From hence, things 
 very near feem large, and remote objects fmall. 
 To this may be referred the power of the micro- 
 fcope, by which objects are made to appear to us 
 fo much larger, as the diftance of the focus of the 
 glafs lens is left than the diftance of diftincft vifion ; 
 
SIGHT. 
 
 Chap. XVI, 
 
 267 
 
 and, in reality, they do not appear larger, but only 
 more diftin£t and lucid ; whence the mind judges 
 them to be nearer. 
 
 Dxnix. In the fame external light, the ftrength 
 of illumination depends upon the fame angle, and 
 upon the number of rays, joined with the fmallnefs 
 of the point which they affeft in the retina ; near 
 obiects therefore appear brighter, and diftant ob- 
 ieds more obfcure ; or if remote objefls appear 
 bright by their own light, the mind reprefents them 
 as large, or near, or both. 
 
 DL. The place of a vilible objefl is eftimated by 
 one eye, to be in a line comprehended by two 
 other ftraight lines drawn to the extremities of the 
 body. If the fame body is beheld with both eyes, 
 it will then feem to be in the concourfe of two 
 lines drawn through the axis of each eye to the 
 pbjeft. 
 
 DLi. We do not fee diftance ; and a blind man, 
 who has never feen, on acquiring the ufe of fight, 
 imagines every thing he fees to touch him. After 
 much experience, we at laft make conjectures about 
 diftances, though always fallacious : but we judge 
 of them both from the diminution of the known 
 bulk of the body, and from the diminifhed ftrength 
 of the light, and faint image of the objeft whofe 
 parts we diftinguifh lefs evidently, and from the 
 number of bodies interpofed, v/hofe diftance is 
 known to us. 
 
 DLii. Convexity is not feen ; but from expe- 
 rience, a body is reckoned convex, after we have 
 learned, that a body, which is convex to the feel- 
 ing, caufes . light and fhadow to be difpofed in a 
 certain manner. It is convex if the lhade be in 
 the fide correfponding to the left hand, and con- 
 cave if in the right. Hence it is, that microfcopes 
 frequently pervert the judgment, by tranfpofing or 
 changing the fhadows. The fame alfo happens in 
 that phenomenon .which is not yet fufSciently un- 
 
 derftood. 
 
268 
 
 SIGHT. 
 
 Chap. XVI. 
 
 derftood, by which the concave parts of a feal are 
 made to feem convex, and the contrary. 
 
 DLiii. The parts of a vifible object are judged 
 by the mind to have the fame fituation which they 
 have in the object, and not inverted as they are on 
 the retina. The mind poffeffes this power of cor- 
 rection, previous to experience in men who have 
 been born blind, and in animals at birth, as appears 
 by indubitable experiments upon men, who had 
 been blind from birth, and acquired the power of 
 viiion fuddenly by the operation of couching. 
 
 DLiv. Another falfe perception of the mind a- 
 rifes from this circumftance, that external fenfa- 
 tions conveyed to the feat of the foul by the eyes, 
 are reprefented during almoft the fpace of a fecond 
 of a minute, to the mind as objeCts really pre- 
 fent. Hence proceeds the idea of a fiery circle 
 from the circumrotation of a lucid body ; and 
 hence the continuance of the image of the fun, and 
 fometimes alfo of opaque bodies. 
 
 DLv. Do wc perceive only that objeCl diftincUy 
 which is directly before that part of the retina 
 which fees moft diftincUy ? And does the mind 
 perfuade itfelf, that it fees many objeCts at a time, 
 partly from the duration of the ideas, and partly 
 from the quicknefs of the motions in the eye ? Con- 
 cerning perfectly diftinCt Aufion, this is moft cer- 
 tain ; but we can hardly affirm it of that which is 
 lefs diftinCt. Why do we fee only one objeCt with 
 two eyes ? Becaufe the fenfation is fingle, and with- 
 out difference, when we have ftmilar impreffions 
 of two objects. For, even without the decuffation 
 of the optic nerves, infects who have numerous 
 eyes perceive objects fingle. Hence the images of 
 two objects excite only one fenfation in the mind, 
 when they fall upon the fame point of the retina ; 
 but two fenfations arife from one object, when the 
 images fall upon difterent parts of the retina of 
 qach eye. Whence proceed diurnal and nocturnal 
 
 blindnefs ? 
 
Chap. XVII. INTERNAL SENSES. 
 
 d6g 
 
 blindnefs ? The latter is common to many nations 
 living in the very warm climates, and under the 
 vertical fun, and to old men. The former happens 
 in inflamed eyes, and in young men of a hot tem- 
 perament, and hence furnifhed with eyes vaftly fen- 
 Able. For great fenfibility of the retina produces 
 diurnal blindnefs ; infenfibility produces nodurnal 
 blindnefs. How do animals fee in the dark ? From 
 a large dilatable pupil, tender retina, and refulgent 
 and very lucid choroides. Why do we become 
 blind when brought out of a ftrong light into a 
 weak one ? Becaufe the optic nerve, having fuffer- 
 ed the action of ftronger caufes, is not affedted by 
 weaker ones. Why is the fudden tranflation from 
 a dark place into the light painful ? Becaufe the 
 pupil, being widely dilated, fuddenly admits una- 
 ^Wares too great a quantity of light, and the retina 
 having been but flightly affedbed by the weak light, 
 now feels the ftronger impreffions very acutely. 
 Do we fee with one eye, or with both ? Moft fre- 
 quently with one, efpecially and generally the right 
 eye : but by the afliftance of the other, we fee more 
 objedts, and more plainly j and we alfo diftinguifti 
 more points of the fame objedb, and judge better 
 of diftances. 
 
 CHAP. XVII. 
 
 INTERNAL SENSES. 
 
 DLvi. have confidered the fenfes apart. 
 
 V V It is common to them all, that the 
 medulla of the tender and pulpy nerve, being af- 
 fedbed by external objedts, tranfmits fome change 
 by the nervous fpirits, to that part of the brain 
 where the fibres of the nerve afledbed firft arife 
 from the arteries of the brain (ccclxxxii.) We 
 know nothing more, than that new thoughts are 
 
 excited 
 
INTERNAL SENSES. CriAp. XVII. 
 
 57 e> 
 
 excited in the mind, as often as a change of this 
 kind, originating in any organ of fenfe, is tranfmit- 
 ted to the origin of the nerve affefted. For this 
 perception is not an adual reprefentation of the ob- 
 ject, by which the fentient nerve is affected. The 
 idea of rednefs has nothing in common with ravs 
 little refrangible, and feparated from the feven por- 
 tions of the total ray ; and much lefs is it confiftent 
 with optical principles, for an image painted by 
 rays upon a foft wEite nerve, to be conveyed for a 
 long way, in perfect darknefs, through a complete- 
 ly opaque body, to the origin of the thalami optici. 
 There is nothing in the pain of burning that can 
 reprefent to the mind the violent motion of a fwift 
 and fubtile matter, by W'hich the particles of the 
 nerves are removed from mutual contact. There is 
 nothing in the idea of a lharp found from a cord^ 
 of a certain length, that can inform the mind that 
 the faid cord vibrates 5000 times in the fpace of a 
 fecond. Neither does the tafte teach us that the 
 cryftals of fea fait are of a cubical figure. Laftly, 
 motion imparted by a body perceived by the fenfes, 
 is indeed propagated to the brain, but the mind 
 neither perceives this motion, nor the tremors of 
 found, nor the percuffion of the rays of light, but 
 fomething perfeftiy diftindl from motion. It is 
 ehablilhed as a reciprocal law by the Creator, that 
 with certain changes, produced firh in the nerve, 
 and then in the fenforium commune, new' and defi- 
 nite thoughts fhall arife in the mind, invariably 
 connected ; and that cur perceptions of external ob- 
 jefls are arbitrary, yet that they are not falfe, ap- 
 pears plainly from the perpetual agreement of fim- 
 ilar ideas with fimilar affections of the fentient 
 nerves, in all perions at the fame timCj and in one 
 perfon at different times. 
 
 DLVii. Therefore, when w^e feel, fi\*e very differ- 
 ent exiftences are conjoined : the thing which w'e 
 p"vreiv'e ; the affc<Tlon of the organ of fenfe by that 
 
 body ; 
 
Chap. XVIL INTERNAL SENSES. 271 
 
 body ; the afFeftion of the brain, arihng from the 
 percuffion of that fenfory ; the change produced in 
 the mind j and, laftly, the confcioufnefs of the 
 mind, and perception of the fenfation. 
 
 DLvni. It appears from certain experiments, that 
 the firft origin of every fentient nerve is always dif- 
 tinft from all the others j and that the change 
 which is firft excited by external objedls in that 
 nerve (dlvi.) continues long in its origin ; and 
 that thofe changes are generally fo arranged in the 
 faid part of the brain, that, being difpofed accord- 
 ing to the order of time, thofe are neareft together, 
 which were either c.otemporary, or occurred in im- 
 mediate fucceflion ; or, laftly, thofe which have a 
 relation to the famefubjeft, or were excited by fim- 
 ilar objefts j infomuch, that it is certain, that new 
 ideas are conveyed to the fame part of the brain 
 where others of the like kind are referved: for 
 otherwife, neither would the arbitrary figns of 
 words and letters recall to the memory paft ideas ; 
 or difagreeable ideas, returning into the mind, with- 
 out the aftiftance of external objefls, reproduce the 
 fame effedls, as objefts themfelves ; nor, otherwife, 
 could there be fo conftant and manifeft a connection 
 of analogous ideas, which fupervene moft remark- 
 ably in dreaming, to the corporeal impreffions, a<ft- 
 ing at that time moft powerfully. Imagination 
 and memory depend on this confervation of ideas. 
 Thofe changes conferved in the fenforium, which 
 many term ideas, are, for the fake of diftinClion, by 
 us called the impreffions of things, as they do not ex- 
 ift in the mind, but are imprefled in the body itfelf, 
 and indeed in the medulla of the brain, in an in- 
 comprehenfible manner, by certain characters, in- 
 credible in their minutenefs, and infinite in their 
 number. Amongft thefe the impreffions received 
 by the fight are the moft remarkable, and moft dif- 
 tinCtly preferved, and next, thofe of hearing j thofe 
 of the other organs are more confufed, and lefs re- 
 vocable 
 
INTERNAL SENSES. Chap. X\TI. 
 
 £72 
 
 vocable by the will. Both the imprefllons and their 
 figns are preferved ; the latter more eafily ; the 
 former, however, fo far, that a painter can exprefs 
 with his pencil upon canvas, a face fimiiar to the 
 image of a familiar face, imprehed upon his mind. 
 
 DUX. We are faid to imagine, when, by means of 
 any image preferved in the fenforial part of the brain, 
 the fame ideas are excited in the mind which would 
 arife if the fentient nerve that firft produced the 
 faid image itfelf fuffered that change. This we term 
 recalling an image. This definition is confirmed 
 by the example of the great ftrength of fancy in 
 certain perfons, and in thofe who are delirious, and 
 in every perfon, in the inftance of dreams, in which 
 thoughts arife in the mind, occafioned by the images 
 preferved in the brain, not at all weaker than thofe 
 which are primarily produced by the change in the 
 fentient nerve, from the external objects, and in 
 which the perfect refemblances of perfons and things 
 v/ith which we are occupied, are reprefented to 
 the mind. Attention^ quiet, and the abfence of 
 other objects, even obtain a ftronger affent of the 
 mind to thefe traces imprefl’ed on the brain, than 
 to thofe perceptions which are excited in the m.ind 
 by external objects : for the will is much more 
 powerfully determined in thofe who dream, than 
 in thofe who are awake ; and fome voluntary muf- 
 cles perform, during lleep, funftions, which, while 
 awake, they never could perform, even when their 
 nerves were moft ilrongly affected by the fame ob* 
 jeft. From hence we may underftand, how it is 
 pofiible, that a very vivid internal impreiiion in de- 
 lirium, may fo impofe upon the mind, as to be 
 roiftaken for the perception of an external objedl j 
 which is evident in the fparks which are excited by 
 rubbing the optic nerve ; in the rednefs feen by 
 the eye when Ihut ; in the vertigo that arifes from 
 a miotion of the retina, which we afcribe to the ex- 
 ternal objects themfelves j in double vifion, &c. 
 
 DLX. 
 
Chap. XVII. INTERNAL SENSES. 275 
 
 DLX. Memory is faid to be exerclfed, when any 
 thought of the mind, or image of an external ob- 
 jed: preferred in the fentient part of the brain, 
 (cccLXXii.) excites any perception in the mind. 
 This is commonly weaker than in imagination, and 
 almoft confined to certain arbitrary figns, which 
 the mind conjoined with that idea at its firfi: per- 
 ception. For memory hardly reprefents the images 
 and pidlures of things to the mind, but almoft only 
 words, and certain attributes, and abftrad ideas ; 
 for which reafon, it excites volition lefs pow'erful- 
 ly. But it appears from the obfervation of the phe- 
 nomena of memory, that thofe changes which arife 
 from the external ienfes, remain long in the brain ; 
 and fometimes, if they made a ftrong imprelfionj 
 are reprefented to the mind for a long period, al- 
 moft forever ; but that they are gradually weaken- 
 ed and impaired ; unlefs they be renewed, either by 
 the objed being reprefented again to the mind, or 
 by the mind itfelf recalling the fame change again 
 into memory ; and that at laft the change will be 
 in a manner erafe'd, and entirely loft, and the idea 
 which was conneded with that change by the law 
 of nature, will never again recur to the mind. This 
 annihilation is gradually effeded by new and dif- 
 ferent impreffions made on the fenforium, and not 
 from time only, or the circulation of the blood, as 
 in cataleptic patients, who fometimes, after a con- 
 fiderable interval of time, return to the fame train 
 of thought which the difeafe had interrupted. But 
 fometimes all of them will be fuddenly deftroyed 
 by fome difeafe, in which the brain is in fome way 
 com.prefled, either by the blood or any other caufe. 
 Such a caufe, ading on part of the common fenfory, 
 blots out a part of the impreffions from the memo- 
 ry, fuch as certain words, or all of them, the cha- 
 raders by which we exprefs words, or our friends, 
 and even the necelfaries of life : yet all thefe im- 
 preffions may often be rene’wed by removing the 
 T compreffing 
 
INTERNAL SENSES. Chap. XVII. 
 
 274 
 
 compreiling caufe. But the ftrength and duration 
 of an idea depend upon its being unuiual, exceffive, 
 or greatly conducing either to increafe or leffen our 
 felicity ; and, lafdy, upon our attention to it, and 
 repetition ; which laft renders the impreflions fo 
 vivid, that their perception is at length miftaken by 
 the mind for the perception of external objects, as 
 in the cafe of maniacs. 
 
 DLxi. Moreover, if we review the hiftory' of hu- 
 man life, it appears, that in early infancy, we have 
 hardly any memory ; only fimple perceptions, that 
 foon vanilh : which, nevertheless, excite ftrong ideas 
 in the mind, as we fee from the crying of infants. 
 The memory is perfected by degrees ; and the ideas 
 received from favorite objects, and familiar perfons, 
 remain imprelTed in the mind of the infant ; while, 
 at the fame time, the imagination likewife increafes, 
 which is often very powerful in young children ; 
 as, for example, in terror, which in no age produces 
 more violent or deplorable effects. Afterwards, as 
 the number of our ideas increafes, the facility of 
 preferving paft ideas is impaired, and, at the fame 
 time, the power of the imagination becomes torpid : 
 till at laft the former almoit perifhes, and the ideas 
 whicii are received efcape from the brain in a fhort 
 time ; while, at the fame time, the imagination, 
 which is a kind of memory, languiflres. 
 
 DLxii. But lince thefe perceptions produce vari- 
 ous changes in the mind itfelf, which are perfectly 
 diftiilff from any corporeal faculty, we fliall briefly 
 add fom.ething concerning them, fo far as may fuf- 
 fice for the purpofes of medicine. Thought re- 
 fides in the foul, it attends to the fenfations which 
 are either brought by the fenfes, or recalled by the- 
 imagination ; frequently alfo to the mere figns 
 which recur into the mind. Attention is when one 
 idea occupies the mind principally or folely for any 
 length of time. The coraparifon of two ideas, in- 
 fdtuted by the mind, is called judgment or genius, 
 
 when 
 
Chap. XVIL INTERNAL SENSES. 275 
 
 icvhen the mind, by comparing them, difcovers them 
 to be alike or diffimilar. Genius confifts in a vivid 
 fenfation conjoined with rapidity of thought, fo as 
 inftantly to abftraft from notions their points of 
 fimilitude and diffimilitude. The principal fource 
 of judgment, invention, and wifdom, conhfts in the 
 flow examination of ideas, by which they are con- 
 fldered by the mind in every point of view, and in 
 the attention of the mind being confined to one ob- 
 ject, to the exclufion of all other ideas. Kence the 
 efficacy of darknefs in making difficult calculations ; 
 the exquifite attention of blind people to the na- 
 ture of founds j and of thofe who are deaf, to col- 
 burs. The fources of error, are negligence in con= 
 templating the whole idea, the eftimating it from a 
 partial view, and the connection of ideas vrith oth- 
 ers that are diftihCt, and only related by accident, 
 or external caufes; 
 
 DLXiii; The integrity of the judgment depends 
 upon a healthy conftitution of the brain- For when 
 that is comprefled, irritated, exhaufted of blood, or 
 changed in its fabric, the ufe of reafon is totally 
 difturbed ; the ftrong internal impreffions on the 
 brain are reprefented to the mind as external or 
 real objeCts ; the chain of ideas is broken, fo that 
 the mind does not. compare them, or perceive their 
 refemblance or diverfity, but pafles abruptly from 
 one idea to another totally different ; or, laftly, the 
 actions of the feiifes being impaired or interrupted, 
 and all impreffions being in a manner erafed from 
 the brain, man is reduced to a ftate of imbe- 
 cility or vegetation. But external caufes alfo 
 have confiderable influence in changing the rela- 
 tion of the mind to the impreffions of the fenfes ; 
 the air. Way of life, food, and habit, either affift 
 or diminifli the foundnefs of the judgment, the 
 force of the imagination, and the ftrcngth of the 
 memory. 
 
 T 2 
 
 DLXIV.. 
 
mXERNAL SENSES. Chap. TYlt 
 
 276 
 
 DLXiv. Finally, as thefe ideas are either indifTer- 
 ent, or have foine relation to our happinefs, they 
 produce different determinations in the will. Some 
 of the caufes by which the felicity of our mind is 
 either incrcafed or diminiffied, proceed entirely 
 from the body, and are purely mechanical ; amongll 
 thefe are pain, difagreeable fenfations, \\hich feem 
 to be produced by every fenfation in a nerve that 
 is too ftrong, and pleafure, in which the nerve is 
 irritated beyond what is ufual, but in a moderate 
 degree; Itching is akin to pleafure, and in both 
 the flow of blood is increafed into the part in 
 v\'hich either pleafure or titillation is perceived ; 
 but, when farther increafed, it degenerates into 
 pain, or exceflive fenfation in the nerve. Anxiety 
 is from the blood being retarded in its paffage 
 through the lungs. Other ideas which affect the 
 mind, are either entirely unconnected with the 
 properties of m.atter, or certainly lefs Ample, under- 
 Itood, or mechanical, than the foregoing. The pre- 
 fence of good conftitutes joy ; the deAre of good, 
 love ; the expeftation of good, hope : the prefence 
 of evil, forrow, terror, or defpair ; the diflike of 
 evil, hatred ; and the expeftation of evil, fear. 
 Hope, curioAty, and glory, feem to be affections of 
 the human mind, which neither belong to the bo- 
 dy, nor exift in beafts. 
 
 DLXV. From thefe affections of the mind, not 
 only the pure will appears to direct the actions of 
 the body to a forefeen purpofe, in order to attain 
 good, and avoid evil, but allb in the body itfelf, 
 neitiier willing tliem nor capable of oppoAng them, 
 various changes happen in the pulfe, refpiration, 
 appetite, ftrength, and other functions of the heart, 
 nerves, ftomach, and other parts, which both im- 
 medi.ttelv follow and indicate the paflions of the 
 mind. Thus anger violently excites the m.otion 
 of the fpirits, increafes the motion of the heart, 
 the frequency of the pulfe, and the ftrength of the 
 
 mufcles j 
 
Chap. XVII. INTERNAL SENSES. 
 
 277 
 
 mufcles ; forces the blood into the ultimate and 
 pellucid veffels, and even out of the vefTels ; accele- 
 rates the excretion of bile, terminates chronic dif- 
 eafes, and removes obftruclions. Grief weakens 
 the ftrength of the nerves, and action of the heart ; 
 retards the pulfe ; deftroys the appetite ; and pro^ 
 duces palenefs, cachexy, diarrhoea, jaundice, fcir- 
 rholities, and difeafes ariling from a ftagnation of 
 the humours. Fear diminiflres the force of the 
 heart, fo as to occafion polypufes, and palenefs 
 weakens the mufcular motions, relaxes the fphinc- 
 ters, increafes inhalation, and diminillies exhala- 
 tion. Exceffive terror increafes the ftrength even 
 to convulfion ; excites the pulfe ; removes obftruc- 
 tions, palftes ; interrupts the courfe of the blood, 
 and produces fudden death. Love, hope, and joy, 
 promote perfpiration, quicken the pulfe, promote 
 the circulation, increafe the appetite, and facilitate 
 the cure of difeafes. Exceffive and fudden joy often 
 kills, by increafing the miotion of the blood, and 
 exciting a true apoplexy. Shame, in a peculiar 
 manner, retains the blood in the face, as if the 
 veins were tied ; and alfo fuppreftes the menfes, 
 and has been even known to kill. 
 
 DLXVi. In what manner are thefe changes pro.- 
 duced by the refpecfive paffions of the mind ? Do 
 nervous fphinflers regulate the veflels, and at one 
 time comprefs them fubfultorily, and increafe the 
 motion of the blood, and at another relax them 
 and deftroy their tone ? That fomething like this 
 obtains in the fmaller veflels, appears evidently 
 from the very fimilar effefts produced by fear and 
 cold upon the nerves of the Ikin, In the genital 
 parts, we manifeftly fee the veins, under particular 
 circumftances, conftricled, and a confequent accu^ 
 mulation of blood : and it feemed probable, that 
 in the larger veflels, the nervous noofes furrounding 
 tnany of them produced the fame eflecls ; for, in 
 
INTERNAL SENSES. Chap. XVII. 
 
 278 
 
 various parts, they furround and include the me- 
 ningeal, temporal, vertebral, carrotid, fubclavian, 
 cceliac, mefenteric, renal, and other arteries. But 
 after it was fliewn by our experiments, that the 
 nerves are at reft during the action of the mufcles, 
 and cannot be rendered Ihorter by any irritation, 
 we were obliged to defert this elegant theory. Nor 
 would it feem far from the truth, that the arteries 
 are rendered more or lefs irritable from the various 
 fenfibility of the nerves, and thus may be con- 
 traded more vehemently or languidly by the fame 
 quantity of blood, and that thus the motion of the 
 blood is either quickened or retarded, if it were at 
 all certain that the fmaller arteries have the fame 
 irritable nature with the large ones. Thus the ap- 
 petite and periftaltic m.otion of the ftomach and 
 inteftines, are manifcftly deftroyed by the affections 
 of the mind. 
 
 DLxvii. It cannot be denied that the Creator 
 has affixed charaderiftic marks to the paffiions of 
 the mind, that in focial life man might not eafily 
 impofe on man. For the refpedive mufcles, more 
 efpecially of the voice, face, and eyes, exprefs the 
 feveral paffions of the mind fo faithfully, that they 
 may be even reprefented in painting. To invei- 
 tigate each of them, would indeed be an elegant 
 taffi, but too long for this compendium. From 
 the adion of thefe mufcles being often repeated, 
 phyftognomy arifes, fo that the conftant expreffion 
 of the face retains fomethino; of the adion of the 
 prevailing mufcles ; and fome charader of frequent 
 anger often remains in the countenance, after the 
 paffion itfelf is gone off. 
 
 DLXviii. Whence proceeds the fympathy of parts, 
 fo fanaous in the pradice of phyfic ? In fome of 
 them it appears to depend upon the connedion of 
 the blood-veftels ; by which tlie blood, being repelled 
 from one part, prelTes more hea\ ily upon another, 
 which has its vtffds from the fame common trunk, 
 
 i'his 
 
Chap. XVH. INTERNAL SENSES. 
 
 279 
 
 This comprehends reyulfions made by blood let- 
 ting j headach, from cold feet, &c. In other parts, 
 the fympathy arifes from a fimilitude in their fab- 
 ric, by which they fuffer like effects from the fame 
 caufes ariiing in the body, fuch as the fympathy 
 betwixt the womb and the bpeafts. Another caufe 
 is, the continuity of membranes, from hence the 
 itching in the glans of the penis from calculus, the 
 cure of deafnefs by diarrhoea. Another caufe ex- 
 ifts in the nerves themfelves, and their anaftomofes, 
 as fatisfaclorily appears from the teeth being fet on 
 edge by certain founds, a diiagreeable fenfation be- 
 ing produced in the maxillary nerve, on account 
 of its various communications with the portio du.- 
 ra. Thus the fympathy of the eyes, which is not 
 obfervable in like manner in the ears, proceeds 
 from the decuffation of the optic nerves 5 and vom- 
 iting is excited by nephritis. Laftly, another caufe 
 is referred to the common fenfory, and beginnings 
 of the nerves, which is demcnftrated from generaj 
 convulfions being produced by the irritation of a 
 fingle nerve, and univerfal epilepfy by a local dife 
 order, &c. Some fympathies in difeafes arife from 
 a tranllation of the matter to other parts through 
 the cellular fubftance, or by the aftion of the mufe 
 cles, arteries, or gravity, 
 
 DLxix. But that important fympathy remains to 
 be explained, which fubfifts betwixt the body and 
 the mind. For that the nature of the mind is dif- 
 ferent from that of the body, is proved by an in.? 
 finity of circumftances, efpecially by ideas and afe 
 feclions of the mind, to which nothing in fenfation 
 is analogous, For what is the colour of pride? or 
 what the magnitude of envy or curioiity ? to which 
 there is nothing fimilar in animals ; neither can 
 that good which is delired by it, glory and the acr 
 quihtion as it were of new ideas, be referred to any 
 corporeal pleafure. Is it poffible that the body 
 can poffefs two kinds of forces, fo that its infinite 
 
 particles 
 
INTERNAL SENSES. Chap. XVII. 
 
 2§o 
 
 particles fliould unite into one mafs, which do net 
 preferye their own affections only, and reprefent 
 them to themfelves, but alfo join together into one 
 common thinking whole, differing from the attri- 
 butes of all, and yet capable both of receiving and 
 comparing thefe attributes ? Is there any inftance 
 of a body, which, without an external caufe, paffes 
 from reft to motion, changes or reverfes the direc- 
 tion of motion, without the action of feme other 
 caufe, as is very eafily obferved with regard to the 
 mind ? 
 
 DLXX. Yet this m.ind, fo different from the body, 
 is connected with it by the molt intimate ties, be- 
 ing both obliged to think upon thofe impreffions 
 which the body prefents to it, and not feeming to 
 poffefs memory or judgment, independent of the 
 corporeal imprellions on the brain ; and, laftly, by 
 means of volition being the caufe or occafion of the 
 greateft and fwiteft motions of the body. 
 
 DLXxi. Thofe have acted circumfpeedy vko, con- 
 feffmg themfelves ignorant of the manner in which 
 the body and mind are united, have contented 
 themfelves with the laws effablilhed by the Creator, 
 which they have afeertained, and not conjectured. 
 They are manifeftiy excufed by the obfervation, 
 (onvn) that even in optics, it is very certain that 
 the affections of the body are connected with the 
 thoughts of the mind, by an arbitrary relation, and 
 that other ideas evould have been fuu'Sfefted, if the 
 Creator had altered the figure, the refracting pow- 
 er, or colours of the parts of the eye. As there is 
 a law, which effabliffres a perpetual connection be- 
 tween the leak refrangible rays and the idea of a 
 red colour ; there is alio a law which conftitutes 
 the conneciion betwixt the iixxpreflicn of thofe rays 
 upon the retina, and the cerrefponding idea. Nor 
 need we be more afham.ed of our ignorance of the 
 mechanifm. of the latter law, than of cur ignorance 
 of the nature of the former. 
 
 ELrerni. 
 
Chap. XVII. INTERNAL SENSES. 
 
 281 
 
 DLXxii. Does the mind govern the body ? Do 
 all the motions and adions in the body arife from 
 the mind, as the immediate fource and origin of 
 motion ? Do the motions of the heart, arteries, and 
 refpiration, arife from the mind, willing them and 
 folicitous for the common good of the whole fyf- 
 tem ? Is this power of the mind demonhrated by 
 the ftrudure of polypi form.ed in wounds, by the 
 paffions of the mind, and by the nsevi materni ? Is 
 the abfenee of confdpufnefs accounted for by the 
 well known example of the obfcure perceptions 
 we have in refpiration, winking, and mufcular mo- 
 tion, all of which are effeded by the will, although 
 we do not know the organs, or attend, that we 
 will, when we breathe, wink, or walk, when occur 
 pied in thought ? Is it therefore certain, that all 
 motions arife from the mind, becaufe there is no 
 other evident caufe perpetually conneded with the 
 body, to which they can be referred ? 
 
 DuxxHi. There are many reafons which do not 
 yet permit us to adopt this opinion. And, lirft, the 
 conilrudion and government of the body itfelf ap- 
 pear greatly to exceed the wifdom of the mind. 
 Our mind fees one point diftindly, (dlv.) and 
 thinks one thought diftindly ; but if it endeavours 
 to fee two objects at the fame time, to contemplate 
 two ideas at the fame timely or to read two letters at 
 once, it always becomes confufed, commits mif. 
 takes, and comprehends neither rightly ; and con- 
 fcious of its own powers, whenever it applies feriouf- 
 ly and diligently to any objed, it withdraws itfelf 
 as it were from the impreflions of fenfe, and nei- 
 ther fees, nor hears, nor fmells, nor performs muf- 
 cular adions. But the mind ought to be capable 
 of infinite and diftind thoughts, in order to be able 
 to govern fuch an infinite variety of mufcles, veft 
 fels, and fibres, in a manner accommodated to the 
 moft exad geometry ; and to refolve and conftrud 
 pccafional problems in the diredion of the muf- 
 cles, 
 
2^2 
 
 INTERNAL SENSES. Chap. XVIf, 
 
 cles, fcarcely foluble by the higheft geometry ; and 
 yet we muft conclude the mind ignorant of this im- 
 menfe talk, and at the fame time, over and above 
 all thofe works, capable of contemplating the moft 
 difficult and abftracf ideas ; fo that neither the care 
 of the body difturbs its meditations, nor its medita- 
 tions interfere with the necefl'ary motions of the 
 body. 
 
 DLxxiv. Moreover, if, without being confcious 
 of volition, we can will to refpire, or vdnk, and 
 with effecl : we neverthelefs retain our control, 
 and can fufpend refpiration, and keep the eyelids 
 firm, and alternately excite their actions, and there- 
 fore we never lofe either the confcioufnefs of our 
 control, or the ufe of it, But we are not able to 
 perform any thing of this kind in the heart or in- 
 teftines ; we cannot reftrain their motion, when too 
 quick, or excite them when languid. Amongfi. ail 
 mankind, why does eveiy one govern his refpira- 
 ton ? why in all ages no one his heart ? If cuftom 
 only is the caufe of our inconfcioufnefs of this pov'- 
 er, wffiy is not the mind fenfible of its action, in 
 moving the heart, or in exercifing the periftaltic 
 motion, after being fufpended for hours, or even 
 whole days, in fwoons, in hyfteric fits, and in af- 
 phyxia ? 
 
 DLXxv. But it is evidently falfe, that all mo- 
 tions arife from the mind, and that without it 
 matter would be an immoveable inert mafs : for 
 the contractility excitable by every ftimulus, to 
 which the motion of the heart, inteftines, and per- 
 haps all the other motions in the human body, be- 
 long, (ccccxci.) does not require the prefence of 
 the mind ; it continues in the dead body ; it is ex- 
 cited by mechanical caufes, heat, and inflation ; 
 and it does not defert the fibres, until they become 
 ftiff and cold, although the mind, which perceives 
 and w’ills, may have been a long time expelled by 
 the deftruCtion of the brain and heart, and even 
 
 althougli 
 
Chap. XVII. INTERNAL SENSES. 283 
 
 although the mufcle, by being taken out of the bo- 
 dy, has been feparated from every imaginable con- 
 nexion with the mind. 
 
 DLXxvi. Little, if any, reliance is to be put in 
 the nsevi materni, as is noticed in another place. 
 That the direXion of the vital motions, in difeafes, 
 is not regulated by prudence, but almott entirely 
 by the power of ftimulus ; we are explicitly taught 
 by the moft ancient and only certain pf aXice, which 
 reftrains the exceilive motions in acute and inter- 
 mitting febrile difeafes, by the ufe of blood letting, 
 opium, nitre, Peruvian bark, &c. The fage has 
 no prerogative in the government of his body, over 
 the mereft ideot ; and that the foetus, which even 
 at birth is ignorant of the motions of its mufcles, 
 and learns by experience to walk, to fwallow and 
 to fee, conftruXs its body, fabricated with fuch in- 
 credible art, is an affirmation fo repugnant to prob- 
 ability, and fo abfard, that of itffiif alone it is faf- 
 bcient to refute the hypothelis. 
 
 DLxxvii. The ftate of aptitude for exercifing the 
 fenfes and voluntary motion, in healthy organs, is 
 called wakefulnefs. Indifpofition to fuch exercife, 
 and their perfeX reft, with healthy organs, is called 
 deep. 
 
 DLXxviii. In deep, the mind either thinks not at 
 all of what fhe knows or retains in memory ; or 
 only attends to the traces of paft objeXs repofited 
 in the common fenfory, (dlviii.) the vivid repre- 
 fentations of which excite altogether the fame per- 
 ceptions in the mind as are made by the impreffion 
 of external objeXs upon the organs of fenfe. Thefe 
 reprefentations are called dreams ; and have the ef- 
 feX, that while the reft of the emporium of the 
 fenfes and mufcular motion is at reft, fome part 
 remains open, is pervaded by the fpirits and 
 watches. Sometimes certain voluntary motions are 
 conjoined with thefe perceptions of the mind, fo 
 that the organs of fpeech, many, or all of the 
 
 limbs, 
 
i86 
 
 mXERNAL SENSES. Chap. XML 
 
 ways from the motion of the fpirits through the 
 brain being impeded. 
 
 DLxxxvi. This theory is confirmed by the caufes 
 of vigilance : for all thofe things prevent ileep 
 which produce plenty of fpirits ; more efpecially 
 warm aromatic drinks, which fend minute Simula- 
 ting particles to the head ; by which the motion 
 of the blood is moderately quickened through the 
 brain, and, being at the fame time more diluted^ 
 it fecretes more fpirits in a given time. 
 
 DLXxxvii. Sleep, again, is prevented by cares of 
 the mind, attentive and interefting meditation, and 
 pain of body and mind ; all of which prevent the 
 fpirits in the fenforium commune from refting, and 
 the nerves from collapfing. Therefore, the rormer 
 caufes increafe the quantity of the fpirits, thefe in- 
 creafe their motion. And, therefore, we return to 
 our former conclufion (dlxxxv.) namely, that the 
 nature of fleep confifts in the collapfe of the nerves,- 
 proceeding from the fenforium commune. 
 
 DLXxxviii. Is the region of lleep, therefore, in 
 the ventricles of the brain ? It is inconfiftent with 
 the univerfality of lleep, which extends to animals 
 which have no ventricles in their brain. Do the 
 vital aftions continue during Seep, becaufe it is an 
 affection peculiar to the brain, and independent of 
 the cerebellum ? And what is the caufe of this di- 
 Verfity, which occafions the animal functions to reft 
 during lleep, and the %dtal functions to continue ? 
 it is that already mentioned, that vital motions are 
 prevented from refting by perpetual ftimuli, and 
 perpetually exciting caufes, (cccxcii.) 
 
 DLXxxix. The effe<Tt of lleep is the abatement of 
 all the motions in the human body. For now the 
 action of the heart alone remains to propel aU the' 
 humours, while rdl the motions of tlie mufcles and 
 fentient nerves, and thofe originating from the pal- 
 lions of the mind and volition, are removed ; by 
 which, while awake, the courfc of the blood and 
 
 fpirits 
 
Chap. XVII. INTERNAL SENSES. 2S7 
 
 fpirits was promoted, as well as by the heart (dlxv* 
 ccccxvii.) The heart gradually returns from its 
 quick and almoft feverifli pulfation, to its morning 
 flownefs ; the breathing becomes lels and flower, 
 the pcrillaltic motion of the ftomach and inteftines, 
 hunger, digeftion, and the progreflion of the feces, 
 are aU diminiflied ; the thinner juices move more 
 flowly, while the more fluggifli are coUecf ed togeth- 
 er, and the effuied fat is accumulated ; the nour- 
 ifliing jelly adheres more plentifully to its fibres 
 and cavities ; the confum.ption of the fpirits, the at- 
 trition of the blood, and the quantity of perfpira- 
 tion, are all diminiflied. Thus, while the nervous 
 fluid continues to be fecreted, and its confumption 
 to be diminiflied, it is by degrees accumulated in 
 the brain, fo as to diflend and fill the collapfed 
 nerves^ and from the acceflion of the flighteft flim- 
 ulus, both the internal and external fenfes are ex- 
 cited to aftion, and the fyftem is awakened. Sleep, 
 continued for too great a length of time, difpofes 
 to all the diforders that attend flownefs of circula- 
 tion, to fatnefs, drowflnefs, and cachexies j and is 
 highly detrimental to the memory. 
 
 Dxc. Whence the yawning of thofe about to 
 fleep ? To promote the paflage of the blood through 
 the lungs, which is now'- flower. Whence the 
 ilretching of the limbs ? To overbalance, by the 
 influx of the fpirits, the natural contraction of the 
 mufcles, by which all the limbs are put in a mod- 
 erate degree of flexion, and fo to reftore ftrength to 
 the extenfor mufcles. Whence the opinion, that, 
 during fleep, the motion of the heart becomes ftrong- 
 er, and the perfpiratron more plentiful ? From the 
 heat of the tedclothes, by which the perfpirable mat- 
 ter being confined, foftens and relaxes the Ikin. But 
 any one that fleeps in his ufual garments, grows cold- 
 er ; and animals which fleep through the winter, be- 
 come exceflively cold, as dormice and hedge-hogs. 
 Why do all animals grow fleepy after taking food ? 
 
 Not 
 
MASTICATION. Chap. X\Tli. 
 
 Not from preffure upon the aorta, or congeftion of 
 blood in the brain ; for even animals which have 
 fcarcely any brain, Ileep after food. Do the indigef- 
 tible particles of our aliments, by palling lefs eafily 
 through the brain, and comprefling its medulla, ren- 
 der the fleep lefs refrefliing ? Is dreaming perpetual 
 and infeparable from fleep ? Is it fo far natural, and 
 a kind of fubftitute for fenfation to the mind, that 
 it may never be without thought ? This does not 
 feem probable. We rather aferibe dreams to fome 
 morbid ftate, or to fome ftimulating caufe, inter- 
 rupting the perfect reft of the fenforium. Hence 
 that fleep refreflies moft which is without dreams, 
 or at leaft wdthout the remembrance of them. 
 Hence they are generally wanting in the firft fleep, 
 at which time the fpirits are moft exhaufted, and 
 return in the morning when thefe are in fome 
 meafure repaired. Hence care, the ftrong impref- 
 Con of fome idea upon the memory, indigeftible 
 food, excefs, or any uneafy pofture of the body, oc- 
 caflon dreams ; for they are ufually generated by 
 fome fenfation, vcith which, according to the laws 
 of the aflbeiation of ideas, the whole coUedtion of 
 fimilar impreflions connect themfelves. 
 
 CHAP. XVIII. 
 
 OF MASTICATION, SALIVA, AND DEGLUTITION.' 
 
 Dxci. T_T ARD and tough articles of food, con* 
 fifting of long parallel fibres, or cover- 
 ed with a bony Ihell or cartilaginous integuments, 
 and friable fubftances, generally require maftica- 
 tion, to divide them into fmaUer and lefs coherin 
 parts, that they may the more eafily yield to th 
 dilfolving powers of the ftomach. The more com- 
 pletely they are fubdivided in the mouth, they be- 
 come 
 
 bn 
 
Chap. XVIIL 
 
 MASTICATION; 
 
 2 
 
 come the more fapid, approach the nearer to the 
 nature of a fluid, and are digefted the more ea-' 
 Jily. 
 
 Dxcn. Therefore mofl: animals are provided with 
 extremely hard teeth, each having a bony, hollow 
 root receiving, through a fmall hole in the apex of 
 its cone, little blood-veflels, and a nerve, which go 
 to its internal periofteum ; fixed by the whole root 
 into the alveolus adapted to it, and, in the upper 
 part of its crown, ftrongly tied down by the ad- 
 hering gum. But the upper part of the teeth pla- 
 ced above the gums, is not bony, but of a peculiar 
 jflrufture, much harder and denfer, refifting putre- 
 faftion in the dead body, and almofl; vitreous, com- 
 pofed of flraight fibres vertical towards the root, 
 and running together in the middle. This portion 
 has neither periofteum nor veflels, and being per- 
 petually wafted, feems to be as often repaired by 
 fome fluid which afcends from the follicle of the 
 root. The teeth are therefore well adapted for 
 overcoming the hardnefs of other bodies, and for 
 Comminuting the food. 
 
 Dxciii. As the materials of our food are various 
 in their texture and firmnefs, nature has according- 
 ly diverfified the ftrucfure of the teeth. In man, 
 the anterior teeth, four in each jaw, are weaker 
 than the reft, have a Angle root, and a crovrn in- 
 wardly concave, outwardly convex, extenuated like 
 a wedge, and terminated by a reftilineal edge. They 
 are deftined for dividing, into fmaller portions, the 
 fofter foods, which are merely tough, and for com- 
 minuting the fibres and membranes of animals and 
 vegetables, and the kernels of fruits. 
 
 Dxciv. The fecond fpecies is the canine teeth, 
 of which there are two in each jaw, fixed by a 
 longer and ftronger, but Angle roof, with a crown 
 of a conical lhape. Thefe lacerate tough aliments, 
 and hold faft thofe which require much tritura- 
 tion. 
 
 IJ 
 
 DXCV. 
 
290 
 
 MASTICATION. 
 
 Chap. XVUh 
 
 Dxcv. The third order is the grinders, whicJ^ 
 in general have feveral roots, and a quadrangular 
 crown, with a fiat furface, but divided by che- 
 quered afperities. The two anterior ones are weak- 
 er, have one or two roots, with the furface of their 
 crown parted into two ; the three pofterior grind- 
 ers are larger, fixed by three, four, and fometimes 
 five roots, but generally by one lefs in the lower 
 jaw, with a flat furface, quadrangular, and com- 
 monly divided into as many eminences as there are 
 roots. Betwixt thefe teeth, the bony articles of 
 food are interpofed and broken, the hard are bruif- 
 ed, while the lower teeth, being moved obliquely 
 and laterally, are rubbed againfl; the immoveable 
 upper ones : by thefe the functions of the teeth arc 
 principaiiy performed. 
 
 Dxcvi. That the teeth might polfefs mobility 
 combined with ftrength and firmnefs, the upper 
 ones are fixed into the fockets of the immoveable 
 upper jaw, the lower ones into the lower moveable 
 jaw, which is a Angle bone, and articulated with 
 the temporals, in fuch a manner that it may be 
 drawn down from the upper jaw, and raifed up 
 againfl them with great force ; and may be moved 
 laterally to the right and left, and forwards be- 
 yond the upper jaw, and backwards to its firft fitu- 
 ation. Thefe motions depend upon the articula- 
 tion of its condyles, (in which the lateral parts of 
 the loveer jaw terminate, and which are broadefl 
 tranfverfely, and convex in the middle,) with the 
 oblique tubercles of the temporal bones, which 
 are hollowed at the root of the jugal procefs, deep- 
 er in the middle, and increafed by a little fi;it 
 furface of the fame kind, before the auditory paf- 
 fige, from which it is feparated by a peculiar fif- 
 fure. M'his joint has greater liberty in moving, 
 and a durable cartilaginous crufl, from a cartilage 
 interpofed between the condyle of the lower jaw 
 and the tubercle of the temporal bone, on both fides 
 
 concave 
 
Chap. XVIII. MASTICATION. ^gt 
 
 toncave in its middle, with raifed edges, corre= 
 fponding by the former to the tubercle of the tem- 
 poral bone, and by the latter to the adjacent de- 
 preffions. 
 
 Dxcvn. The mufcies moving the lower jaW, 
 which in man are weaker, but very ftrong in 
 brutes, are the temporalis, an elevator, arifmg from 
 a large part of the fide of the ikull, and from its 
 aponeurofis, collecling its tendinous fibres, inter- 
 mixed vith mufcular fibres, in a ftellated manner, 
 into the {harp procefs of the jaw ; the malTetef, an 
 elevator, defcending double or triple from the ju- 
 gum and margin of the cheek bone backwards into 
 the coronoid procefs. Thefe act in concert ; but 
 the temporal mufcle carries the jaw more back- 
 wardsj the maffeter more forwards. The pterygoi- 
 deus internus deicends from the pterygoid foITa, 
 and from the palate bone and root of the little 
 pterygoid procefs, and its internal wingj into the 
 angle of the lower ja.w, which it elevates when de- 
 prefled by its antagonifts, or draws to one fide. 
 The pterygoideus externus has a double origin ; 
 the one tranfverfe from the inner wing and adja- 
 cent bone of the palate, and pofterior convexity of 
 the upper jaw : the other, defcending, arifes from 
 the hollow temporal part of the great wing of the 
 fphenoides ; thence it proceeds backwards and down- 
 ■wards into the outer part of the condyle of the low- 
 er jaw, which it draws forw^ards before the upper 
 jaw, and to one fide. 
 
 Dxcviii. The lower jaw is deprefled, and the 
 mouth opened by the digaftric m.ufcle, arifing from 
 a hollow of the mamillary procefs, tied by its mid- 
 dle tendon wfith much firm cellular fubilance, of a 
 tendinous nature, to the os hyoides ; likewife con- 
 neffed to the mylohyoideus, and pafiing through 
 the defcending fibres of the fiylohyoideus, increaf- 
 ed by another flelhy belly, and inferted at the fym- 
 phyfis of the two halves of the lower jaw. More- 
 u 2 over. 
 
MASTICATION. 
 
 Chap. XVIII. 
 
 292 
 
 over, the mouth may be opened by all the other 
 mufcles, inferted into the inferior maxilla, os hy- 
 oides and larynx, as the gciiiohyoideus, mylohyoi- 
 detis, geniogloITus, Ilernohyoideus, Ilernothyroide- 
 las, coracohyoideusy and latiffimus colli ; although 
 the latter rather draws the ikin of the neck and 
 face downwards. The gcniohyoidcus and digaftric 
 mufcles draw the jaw backwai'ds. 
 
 Dxeix. The lower jaw is elevated with great 
 force, and the lower teeth being carried up againft 
 tiie upper teeth, divide the food, by the aclion of 
 the temporal, maffeter, and internal ptery goid muf- 
 cles ; which appears by undoubted experiments to 
 be very powerful, and iuflicient to raife fever al hun- 
 dred weight. The lateral motions of the jaw, and 
 its circular motion around one condyle as a fixed 
 point, are performed by the external and internal^ 
 ptcrygoidei, and by the former mufcles acting fin- 
 gly and alternately^ Thus the food is cut, broken 
 and bruifed ; and if the mallication be rightly per- 
 formed, it is reduced into a kind of pulp. 
 
 DC. Before the teeth there is placed a cutaneous 
 and flellry fack, which is every where produced 
 from the integuments of the face ; and inclofes a 
 hollow fpace with both rows of teeth when fhut. 
 The lateral parts are called the cheeks, the middle 
 the lips. From this cavity there is a paflage, be- 
 twixt the teeth, into the mouth, which on the up- 
 per part is bounded by the bony and foft palate, 
 underneath by the mufcles lying under the tongue, 
 and on the forepart by the teeth. On the back 
 part it opens between the foft palate and tongue 
 into the fauces, d'he tongue divides the cavity of 
 the mouth in the middle, and is eafily moveable to- 
 every part of it. 
 
 Dci. During the trituration of the food in the 
 mouth, there is continually poured to it a large 
 quantity (;f a watery clear liquor, cvaporablc, inii- 
 
 pid. 
 
CfiAP. xviir. 
 
 SALIVA. 
 
 293 
 
 pid, or very little faline, containing a very fmall 
 quantity of earth, and neither acid nor alkaline, al- 
 though from it a very fmall portion of lixivial fait 
 may be obtained ; of which all around are numer, 
 ous fources. A large quantity of this faliva is fe- 
 creted by innumerable oval glands in the lips and 
 cheeks, and by fome larger ones which are placed 
 round the mouth of the parotid du6l ; and laftly, 
 by the pores of the hard palate, pouring out the 
 liquor, which they fecrete, through a little fhort 
 duel and hole. The fluid efTufed by the exhaling 
 veffels of the cheeks, and back of the tongue, is 
 ftmilar, or more watery. It is now afeertained, that 
 the duclus incifivus is impervious, and tranfmits 
 nothing but the artery, w'hich goes from the palate 
 to the noftrils. 
 
 Dcii. The faliva is a watery liquor, with a fmall 
 quantity of fait, partly lixivial, and partly culi- 
 nary ; with fome oil and earth, evaporable by the 
 fire ; with fcarcely any tafte, unlefs when fharpened 
 by difeafe or hunger. The quantity produced is 
 confiderable, as twelve ounces have been known to 
 flow out from wounds in the fpace of an hour. By 
 well bred people, it is for the mofc part fwallowed; 
 and ufefully, as it cannot be thrown av/ay without 
 hurting^ the dia;efl:ion. 
 
 Dciii. The falivary glands efpecially fupply the 
 faliva. Of thefe, the principal is the parotid, exten- 
 flvely filling up the interval between the auditory 
 paflage and the lower jaw, and covering the jaw- 
 bone where naked, and part of the mafieter. It is 
 a conglomerate gland, with round acini, connected 
 by cellular fubllance ; which more denfely com- 
 pacted, forms a kind of involucrum, almoft tendi- 
 nous, to the whole gland. Its du<T is white, vafeu- 
 lar, and capacious, afeending from the bottom of 
 the gland to the jugum, from whence it is tranf- 
 verfely inclined, and receives the du6l of a gland, 
 feated on the top of the maffeter, which is either 
 
 continuous 
 
SALIVA. 
 
 Chap. XYllL 
 
 £94 
 
 continuous with the parotid, or diftinct from it, 
 and rarely double ; after this, bending round the 
 tumid edge of the malfeter, it opens with an ab- 
 rupt termination, without a papilla, through the 
 feparatjng fibres of the buccinator, furrounded by 
 many little glands of the cheek. The bulk of this 
 gland, and the number of its arteries, render it the 
 chief fource of the faliva. 
 
 Dciv. Another fmall gland, adjacent to the pa- 
 rotid, but twice as fmall, coinpofed of fofter and 
 larger acini, connected by a fimilar membrane, is 
 contiguous to the corner of the lower ja»"-bone, 
 and being in part fabcutanepus, terminates upon it, 
 and in part fends off an appendix over the inylohy- 
 oideus rnufcle, which running along the long con- 
 cave fide of the lower jaw, of a granular fabric, and 
 fpread under the membrane of the mouth, is called 
 the fublingual gland. From the larger maxillary 
 gland, a duct pafies out along with this appendix, 
 cov^ered by the middle part of the fublingualis, from 
 which it receives one, two, or three branches ; by 
 whofe infertion being increafed, it opens into a pro- 
 jecting membranous cylinder, feated on the bridle 
 of the tongue. But other fmall and fhort ducts 
 from the fublingual gland, three, four, or more, 
 even to the number of twenty, perforate the edge 
 of the tongue in the line continued backwards from 
 the frenum, with fhort little ducts and points, and 
 fecrete faliva. There are inftances where the lar- 
 ger anterior branch of this gland, which ufually 
 joins itfelf to the duct of the maxillary gland, goes 
 on fingle, and parallel to it, and opens by itlelr. 
 Some other glands alfo, fimilar to thofe of the 
 cheeks, which however may be reckoned among 
 the fubiinguals, by their proper ducts perforate the 
 membrane of the mouth where it departs from the 
 tongue. Various other falival ducts have been in- 
 timated by difierent perlons, but they are not con- 
 firmed by anatomy. 
 
 Dcy- 
 
Chap. XVIII. 
 
 SALIVA. 
 
 29 s 
 
 Dcv. The Creator has wifely provided, that maf- 
 tication cannot be performed, without the falival 
 glands being comprelfed by mechanical neceflity, fo 
 as to difcharge their fluids in an increafed quanti- 
 ty. For, when the mouth is opened, the maxillary 
 gland, being preffed by the digaftric and mylohyoi- 
 deus, throws forth a fountain of faliva ; the parotid 
 gland is compreffed by the maffeter, when fwelled, 
 and by the cutaneous mufcle of the neck which lies 
 over it : hunger has the fame effects with mufcular 
 preffure, and caufes a flow of faliva into the mouth. 
 
 Dcvi. The food, therefore, being ground be- 
 tween the teeth, with the watery faliva and air, 
 is broken down into a foft fucculent, figurable 
 pulp, replete with elaflic air, which being heated 
 by its fituation, on account of its elafticity, perpet- 
 ually tends to the dilfolution of the particles 
 of the food between which it is included. By 
 this procefs, the oily and aqueous parts of the 
 food are intermixed ; the fmell and tafle of differ- 
 ent ingredients are blended together ; and, at the 
 fame time that the faliva dilutes the filine parts, 
 the food becomes fapid. Such particles as are vor 
 latile, are directly abiorbed by the bibulous vef- 
 fels of the tongue and cheeks, and recruit the 
 ftrength, by being reflored to the blood-veffels and 
 nerves. 
 
 Dcvii. But the motions which are neceffary for 
 turning round the food in the cavity of the mouth 
 that it may be introduced between the teeth, are 
 effected by the tongue, cheeks, and lips. And ef- 
 pecially, the tongue being at one time expanded, re^ 
 ceives the food into the fmall concavity in its fur- 
 face ; and being moved by its proper powers, 
 (ccccL.) conveys its load to the part dehgned. At 
 another time, the tongue contrafted, and narrow, 
 fearches every part of the mouth with its tip, and 
 collects together the food into one heap. At anoth- 
 er time, by applying itfelf to the teeth, it draws 
 
 froai 
 
SALIVA. 
 
 Chap. XVIII. 
 
 296 
 
 from the cavity of the cheeks the fluids or chewed 
 aliments, and conveys them to the pofterior cavity 
 of the mouth, fituated behind the teeth. 
 
 Dcviii. But thefe motions of the tongue are like- 
 wife governed by the os hyoides, which is exten- 
 flvely connected with it by mufcles and membranes, 
 and is compofed of a bafis, concave inwardly, of 
 horns extending outwardly, and terminated by a 
 thicker knob, and of oval cornicles. When drawn 
 dovrn by its refpeftive mufcles, it carries back the 
 tongue at the fame time, and alfo deprefles the low- 
 er jaw, if the mufcles of that be relaxed. Thefe 
 powers are the fternohyoideus, but arifing alfo in 
 part from the clavicle, which is extenuated up- 
 wards, and flriped with tendinous lines : the fter- 
 nothyroideus, which is broader, and arifes from the 
 fame place, and alfo from the upper rib j on deprelf- 
 ing the cartilage, into which it is inferted, it necef- 
 faiily forces the os hyoides connected with it, to de- 
 feend : it is intermixed wirh the hyothyroideus and 
 thyreo-pharyngeus, and every where intermixed 
 with the fternohyoideus : the coracohyoideus, but 
 M'hich arifes obliquely from the upper and fliorter 
 fide of the fcapula, near its notch ; where eroded by 
 the jugular vein, it becomes tendinous ; with its 
 upper belly, it is ftraight, and pulls the os hyoides 
 directly downwards; it is every where blended with 
 the fternohyoideus, and the hyothyroideus, which 
 is governed by the former mufcles. 
 
 Dcix. Other powers elevate the os hyoides, to- 
 rether with the tona;ue. 'fhe ftvlotrloflus mufcle, 
 luflained by a peculiar ligament from the upper 
 jaw*, which is fometimes fiefiry. The ftylohyoideus, 
 a weak mufcle, often fplit for the palTagc of the bi- 
 venter, and again collecded into two portions, ad- 
 hering to the tendinous expanfion of the biventer, 
 and inferted by the one portion into the bafis ot 
 the os hyoides, and by the other portion into the 
 horn, and mixed vvith the tendinous expanfion of 
 
Chav. XVIII. DEGLUTITION. <297 
 
 jlie mylohyoideus. The ftylohyoideus alter, when 
 it is prefent, refembles the former, behind which it 
 is placed ; arifing from the tip of the ftyloid procefs, 
 and inferted into the offa triticea, it anfwers the 
 pnrpofe of a ligament to fuftain the os hyoides. All 
 thefe mufcles draw the tongue back, and elevate its 
 lides. The mylohyoideus, ar4fing from the whole 
 length of the jaw, combining into one with its com- 
 panion, elevates the tongue, and gives it firmnefs 
 for various motions, or elfe it depreffes the jaw. 
 The geniohyoideus, accompanying the genioglof- 
 fus, pulls the tongue forwards out of the mouth. 
 
 OCX. But, moreover, the mufcles of the cheeks 
 varioufly move and comprefs the food in the mouth. 
 Some carry it from the cavity of the cheeks into 
 the cavity of the mouth behind the teeth, as the 
 buccinator when the mouth is fhut. Others open 
 the mouth for receiving the food ; fuch as the 
 double headed proper elevator of the upper lip, and 
 the elevator communis in part, the nafalis labii fu- 
 perioris, both zygomatici, the riforius, tariangularis 
 menti, and the depreffor proprius anguli oris, which, 
 arifing on each fide from an excavation near the 
 locket of the canine tooth, is inferted into the orbi- 
 cularis. Others, again, fhut the mouth, that the 
 food received may not fall out ; fuch as the orbi- 
 cularis of each lip, the proper depreflTor of the up- 
 per lip, and the proper elevator of the lower lip, 
 - and the elevator communis in part. Of thefe, more 
 particular defcriptions may be had from profelfed 
 fyftems of anatomy. 
 
 DC XI. By thefe means the food, mixed with and 
 foftened by the faliva, is collected from all fides, 
 behind the teeth, and is committed to the tongue, 
 expanded by the ceratoglofli and geniogloffi, and 
 rendered a little concave by the ftylogloffus, from 
 thence it is next conveyed to the fauces. 
 
 Dcxii. The tongue being raifed by the hylo- 
 glofii, and extenfively applied to the palate, firft 
 
 with 
 
DEGLUTITION. 
 
 Chap. XVIII. 
 
 5.98 
 
 with its apex, then gradually with its pofterior ex- 
 tremity, preffes the food towards the fauces, at that 
 time the only open paffage. After this, the thick 
 root of the tongue itfelf refifts the larynx, which is 
 drawn upwards, and preffes down the approaching 
 epiglottis, which Hands up behind the tongue, and 
 is connefted with it by numerous membranes, and 
 perhaps by fome muicular fibres. At the fame 
 time, all the mufcles elevating the pharynx ad; to- 
 gether } the biventer, geniohyoideus, geniogloffus, 
 ftylohyoideus, ftylogloffus, ftylopharyngeus, and 
 others, and draw the larynx upwards and fonvards, 
 fo that the epiglottis prefents itfelf oppofite to the 
 tongue, and is more eafily inclined. Hence it is 
 neceffary for deglutition, that the jaws be clofed, or 
 at leaft that the lower one be raffed, and fixed in 
 that pofition, that the biventer, and the other muf- 
 cles already mentioned, may derive ftability, from 
 it, and elevate the os hyoides. Thus tl»e epiglottis, 
 being turned down, fhuts up the pail'age to the 
 larynx fufficiently and largely, and over it, as over 
 a bridge, the food paffes into the fauces. 
 
 Dcxiii. By the pharynx we underhand an ample 
 Ihapelefs cavity, bounded behind by all the vertebr'e 
 of the neck, and the occipital bone before the hm.i- 
 men magnum, in the middle by the cuneiform bo^ e, 
 and before by the opening of the nares, the move- 
 able velum of the palate, tlie niouth, ' he tongue, 
 and the larynx : below it is continued int-' tlie cUb- 
 phagus. Its fides are formed by the low . i.;w, the 
 cheeks, the velum of the palate, the pterygoid pro- 
 ccfs, the ftiliform appendix, the tongue, os hyoides, 
 and larger cartilages of the larynx. It forms one 
 foft membranous bag, outwardlv furrounded on all 
 fiaes by mufcular fibres. Its internal meiribrane is 
 continuous with the cuticle, and renewable, but 
 more moiff . Outwardly the pharynx is covered by 
 a good deal of cellular fubftance, more efpecial'iy in 
 its pofterior and bteral parts. Therefore it is lax 
 
Chap. XVIII. 
 
 DEGLUTITION. 
 
 299 
 
 and dilatable, and fitted for receiving all bodies 
 that are prefled by the tongue over the larynx. 
 
 Dcxiv. It is dilated in the action (dcxii.) by the 
 powers elevating it, by the ftylopharyngeus, which 
 defcends fometimes double into the membrane of 
 the larynx, under the os hyoides, and into the mar- 
 gin of the thyroid cartilage, and is largely diftribu- 
 ted over the internal furface of the pharynx, togeth- 
 er with the following mufcle ; the thyreopalatinus, 
 fpread in the form of an arch round the moveable 
 palate, and forming two columns, which defcend 
 along the fides of the pharynx, and form a confid- 
 erable part of that bag, being alfo connefled by 
 broad fibres to the thyroid cartilage. That the 
 falpingopharyngeus is a true mufcle, I am ready to 
 believe, rather from the obfervations of eminent 
 anatomifts than from my own. Of the cephalo- 
 pharyngeus, I am doubtful, unlefs you reckon the 
 ftrong white cellular fubftance, which occupies the 
 tipper part of the pharynx, as a mufcle. Drink 
 pafles round the larynx on each fide of the epiglot- 
 tis, and falls into the oefophagus. 
 
 Dcxv. The aliments are prevented from regurgi- 
 tating into the noftrils when they arrive at the dila- 
 ted pharynx (dcxiv.) by the palatum mobile, which 
 is interpofed. Anteriorly from the bony palate, and 
 laterally from the pterygoid wings, is continued a 
 moveable velum, compoied of the membranes of the 
 mouth and noftrils, with intervening mufcles and 
 glands, almoft of a fquare figure, and hanging be- 
 twixt the cavity of the nares and mouth, into the 
 hollow fauces, in fuch a manner that it naturally 
 Reaves the former open, and is concave towards the 
 mouth : the middle lower portion of this, extended 
 into a conical lhape, pendulous, before the epiglot- 
 tis, and replete with many glands, from its appear- 
 ance in a difeafed ftate, is called the uvula. At each 
 fide of the velum, two arches defcend from the ve- 
 lum palati, of which the fmaller and thinner goes 
 
 to 
 
DEGLUTITION. Chap. XVIIL 
 
 to the tongue, the larger to the pharynx. The ele- 
 vator of this velum, which is llrong, arifes from 
 the afperities and plane furface of the os petrofum, 
 behind the fpinal foramen, and alfo from the cartil- 
 age of the Euftachian tube, defcends inwards with 
 its companion, forms an arch in the velum mobile, 
 between the two plates of the thyreopalatinusmufcle. 
 It may therefore draw that velum to the nares and 
 tubes, that the food may not enter either of them. 
 But, during deglutition, it does not feem to have 
 any confiderablc acHon. At this time regurgitation 
 into the noftrils is prevented by the conftri&on of 
 the mufcles of the pharynx, together with the de- 
 preffion of the thyreopalatinus, which manifeftly 
 draws the moveable velum downwards, and applies 
 it to the tongue and pharynx, and of the circum- 
 flcxus palati mollis, which arifing a little more for- 
 wards from the fame petrous bone, and from the 
 Iharp procefs of the cuneiform wing, and from the 
 interval between the wings and iiinermoft wing, 
 and from the cartilage of the Euftachian tube, dc- 
 fcends broader ; and, pahlng through the notch of 
 the pterygoid hook, it changes its direction, and 
 afcends with a radiated tendon, difperfed through 
 the upper membrane of the velum palati, and, join- 
 ing with its fellow, forms the balls of the other 
 niufcles, and adheres to the fmooth edge of the pal- 
 ate bone. This is able both to open the tube, and 
 Jeprefs the velum mobile, Thus t;\e pharynx be- 
 ing contracted like a fphincter, fo xes down the 
 food, without permitting any part to regurgitate in- 
 to the nares. Hence, when the veiu:n of the palate 
 is injured, the aliments regurgitate into the noftrils, 
 and deafnefs enfues. 
 
 Dcxvi. During the effort to deprefs the food 
 (dcxvii.) the velum being placed upon it, and 
 depreffed, is drawn down towards the tongue by 
 the palatopharyngei, and by the circumflcxus pa- 
 lati mollis. Thefe mufclcs, together wdth the glof- 
 
 fopalatiuus. 
 
Chap. XVIH. DEGLUTITION. 30! 
 
 fopalatinus, (which laft is indeed weak, is received 
 into the lelfer arch of the fauces, and on the one 
 lide fs united with its companion into an arch in 
 the velum of the palate, and on the other is inferr- 
 ed into the tongue,) prefs the velum againk the 
 protuberant root of the tongue, and intercept any 
 return to the mouth. After the danger of any part 
 falling into the windpipe is over, the epiglottis is 
 raifed up again, both by its own elafticity, and by 
 the tongue itfelf being again drawn forwards. Laft- 
 ly, the deprefled uvula is raifed by the azygos, which 
 arifes from the tendons of the circumflexus, and by 
 the levator of the foft palate. 
 
 Dcxvii. A little after this, follows an effort to 
 urge the food downwards, which is exerted by the 
 conftridtors of the pharynx, which draw the back 
 part forwards ; thefe mufcles are partly tranfverfe, 
 and partly afcend. into the pofterior furface of the 
 pharynx. The principal is the pterygopharyngeus, 
 arifing from the whole hook, and from the edge of 
 the internal wing, and from the tendon of the cir- 
 cumflex mufcle ; from whence forming an arch, 
 it is extended upwards and backwards, and, largely 
 furrounding the upper part of the pharynx, it unites 
 with its cognominal companion. The mylopharyn- 
 geus is partly continuous with the fibres of the 
 buccinator, in the middle betwixt its two adhefions 
 to the bones, and partly arifes from an origin of its 
 own, above the laft of the grinders in the lower 
 jaw. Thefe being almoft tranfverfe, and furround- 
 ing the pharynx, draw its back part forwards. 
 Next follow the afcending mufcles in two ftrata, 
 the geniopharyngei, of w'hich the obfcure and con- 
 fufed fibres originate from the tongue ; the chon- 
 dropharyngei, of a triangular figure, arifing from 
 the officula trkicea ; the ceratopharyngei, which 
 afcend radiated from half of the horn ; the fyn- 
 defmopharyngei, arifing from the horn of the thy- 
 roid cartilage, and diftindl from the following ; the 
 
 double 
 
5^2 DEGLUTITION. Chap. XVIII. 
 
 double thyreopharyngei, increafed by fibres of the 
 ilernothyroideus and cricothyroideus, and the tranf- 
 verfe, the afcending, and the defcending crycbpha- 
 ryngei. Thefe mufcles act focceffively, the upper- 
 moft firft, and then according to their fituation, 
 and force the food into the cefophagus. At the 
 fame time, the depreffing mufcles of the larynx, 
 the coracobyoideus, fternohyoideus, and fternothy- 
 roideus, draw down the larynx backwards, com- 
 prefs the pharynx and urge the food downwards. 
 The arytenoidsei contract the perpendicular chink 
 of the larynx as the food pafl’es near it. 
 
 Dcxviii. As various dry and rough bodies are 
 fometimes fwaUowed, and as it was neceffary for 
 the pharynx to be dilatable and indolent, the great 
 quantity of mucus, which is collected in all parts 
 of the fauces, is of great importance. Therefore, 
 in general, betwixt the nervous and innermoft coat 
 of the pharynx, are placed a very great number of 
 limple oval follicles, which pour out through Ihort 
 mouths a bland, aqueous, but vifcid and ropy mu- 
 cus, having a greater quantity of oil, volatile fait 
 and earth, than the faliva. They are molt plenti- 
 ful in that part of the pharynx which is extended 
 under the occipital bone, where they are difpofed 
 in a fort of radiated right lines ; and about the ton- 
 fil towards the Euftachian tube, where commonly 
 the fecond tonlil lies on each fide adjacent to the 
 large one, and in that portion of mufele which is 
 called falpingopharyngeus. But likewife many flat 
 and circular follicles of this kind are feated on the 
 back part of the tongue, as far as the foramen cae- 
 cum (cGocxLvin.) Other pores from the pulpy 
 flefli of the palate, and from the numerous glands 
 lituated there, difeharge a llmilar mueus. JNIore- 
 over, the whole moveable palate is of a glandular 
 nature like the pharynx ; only compofed of more 
 numerous and thickly diftributed follicles. Nor, 
 
 iaftly. 
 
Chap. XVIIL DEGLUTITION. 303 
 
 laftly, are lacunx wanting, into each of which ma- 
 ny fimple glands unite. 
 
 DC XIX. Where the pharynx defcends from the 
 pterygoidal hook betwixt the two arches of the 
 fauces, diat is between the gloffopalatinus and pha- 
 ringopalatinus, are feated the tonfils, one on each 
 fide, of an oval figure, convex behind, and thicker 
 on the upper part, perforated inwardly with ten or 
 more large finufes, which open through the mem- 
 branous velum, and by the preflure of the adjacent 
 mufcles difcharge a great quantity of a very vifcid 
 mucus from their finufes. In like manner, the ad- 
 jacent parts of the nares, and tumid ring of the 
 tubes, and the furface of the epiglottis next to the 
 larynx, and the back of the arytenoid cartilages, 
 are replenifhed with mucous organs. Laftly, the 
 cefophagus itfelf, on all fides, abounds with fimple 
 follicles, from which a mucus more fluid is poured. 
 The glandulx oefophagex are of the conglobate 
 kind, and contribute nothing to this mucus. The 
 blood- veflels of the tonfils come from thofe of .the 
 tongue and lips ; thofe of the pharynx from thefe 
 and from the pharyngea ; thofe of the cefophagus 
 from the pharyngeals, upper and lower thyreoi- 
 dals, the bronchials and aorta. The numerous veins 
 of the palate and tonfils, after forming plexufes, 
 meet in the fuperficial branch of the internal jugu- 
 lar. 
 
 Dcxix. The cefophagus is a double tube, of which 
 the interior is feparated from the exterior, by much 
 inflatable cellular fubftance. The interior is ner- 
 vous and ftrong, continuous with the membranes 
 of the mouth and nares, and feparated from the 
 innermoft, (which is the epidermis, plaited and po- 
 rous, but not villous, exhaling a thin fluid and pul- 
 py,) by peculiar fliort cellular fubftance, in which 
 veflels are reticulated, and glands are interfperfed, 
 which are continuous, and fimilar to thofe of the 
 pharynx. The exterior tube, the mufcular, is alfo 
 
 ftrong,- 
 
DEGLUTITION. 
 
 Chap. XVIII. 
 
 ftrong, with fibres continued backwards and down- 
 wards from the cricoid cartilage, changing from 
 annular into external longitudinal fibres, railing 
 the cefophagus againft the food, and dilating it 
 that the mouthful may be received. But other 
 internal circular fibres, which are alfo ftrong, arife 
 in like manner from the cricoid cartilage, and by 
 their fuccefiive contraction, force the food down 
 through the long tube of the cefophagus, which de- 
 fcends firft in a direct courfe, a little to the left fide 
 of the windpipe ; in the breaft, it paftes behind the 
 heart, through the pofterior interval between the 
 two bags of the pleura (lxxvii.) from whence it in- 
 clines by degrees a little to the right, and then for- 
 wards, that it may pafs through the appointed 
 opening in the diaphragm (cclxii.) in the inter- 
 val between exfpiration and infpiration. The 
 whole cefophagus is furrounded externally by cel- 
 lular fabftance, by which it is loofely tied to the 
 neighbouring parts. 
 
 ncxx. The aliments are moved tlirough the cefo- 
 phagus as through an inteftinc. The longitudinal 
 fibres, afcending to the cartilages of the larjmx, 
 dilate the gullet, to receive the dcfcending morfel. 
 But when it is received into the gullet, the longi- 
 tudinal fibres in like manner dilate and elevate the 
 gullet to that place which has received it. Then 
 that part of the cefophagus, where the morfel is 
 feated, being irritated, contracts, and propels the 
 food downwards. Its mufcularity is ftrong, and 
 very irritable. 
 
 Dcxxi. This upper opening of the ftomach is 
 contracted, by the action of both the lower mufcles 
 of the diaphragm, in infpiration, and the food is 
 confined within the ftomach, fo that every preflure 
 of the diaphragm fends it naturally towards the 
 pylorus. By this means, the ftomach is fo clofely 
 ftaut, that in perfect health, even vapours are con- 
 
STOMACH. 
 
 Chap. XIX. 
 
 30s 
 
 fined within the ftomach j and do not afc£nd but 
 from a morbid afFedion. 
 
 CHAP. XIX. 
 
 ACTION OF THE STOMACH ON THE FOOD. 
 
 Dcxxii. ^T^HE ftomich is a membranous bag, def- 
 I tined for the reception of the food ; 
 placed within the abdomen, behind the liver, dia- 
 phragm and left falfe ribs ; of a figure fomewhat 
 Oval, or like a calk ; longeft tranfverfely, and the 
 more fo the more aged the perfon is. In the foetus, 
 it is altogether round and fliort. But if we confid- 
 er its figure more accurately, every fedion of it is 
 circular j but fo, that, in its left extremity, there 
 is an an impervious cavity obtufely conical, from 
 whence the ftomach gradually grows wider, and its 
 fedions increafe tov/ards the cefophagus, at whofe 
 infertion is its largeft fedion ; from thence it di- 
 miniflies flowiy, till being refleded towards itfelf, it 
 ends in the pylorus. Its bulk depends in a great 
 meafure on the quantity of food, by which the ca- 
 vity of the ftomach is augmented ; and, on tlie 
 contrary, it is diminiftied by falling. Its fituation 
 in general is tranfverfe ; yet fo that the entrance of 
 the cefophagus is pofterior, and its right termina- 
 tion anterior. The middle of the human body, or 
 enfiform cartilage, correfponds nearly to the centre 
 of the ftomach ; but alfo to its right fide, and laft- 
 ly to the pylorus : to the latter the umbilical fif- 
 fure correfponds. Since its figure is round, but in- 
 curvated ; when empty, its larger convex arch is 
 pendulous ; but when full, it appears prominent 
 forwards within the peritonaeum. At that time, 
 the leffer arch, interpofed between the two orifices, 
 is direded perfedly backwards, and includes the 
 W fmail 
 
STOMACH. 
 
 Chap. XIX. 
 
 306 
 
 fmall lobe of the liver. The infertlon of the oefo- 
 phagus in the full ftomach is more horizontal ; but 
 in the empty ftomach, more perpendicular ; the 
 right extremity of the ftomach, when empty, is 
 bent upwards to the pylorus ; in the fuU ftomach, 
 it is bent backwards, and therefore defcends in per- 
 fons lying on their back. In man, when alive, the 
 fituation of the ftomach, approaches nearer to that 
 which we have attributed to the full one. 
 
 Dcxxiii. The vifcera, contiguous to the ftomach, 
 are the fpleen, contiguous to its left imperforated 
 extremity, and connected with it by much omen- 
 tum ; the lobule of Spigelius, filling up its Idler 
 curvature ; the left lobe of the liver, largely inter- 
 pohng itfelf betwixt the ftomach and the dia- 
 phragm, and comprefling the anterior part of the 
 ftomach ; after which, below the liver, a moderate 
 portion of the ftomach is immediately contiguous 
 to the diaphragm, which there lies under the falfe 
 ribs, or it is entirely covered : behind, the pan- 
 creas lies under it ; below it when empty, the tranf- 
 verfe portion of the colon is contiguous for a con- 
 liderable way ; laftly, from the leffer curvature, arifes 
 the little omentum, from which a continuous, but 
 Itronger membrane, connects the oefophagus with 
 the diaphragm : and the larger omentum rs not 
 connected to the whole length of the ftomach, but 
 is wanting on the right fide near the pylorus ; and 
 on the left, it is continued, into a ligament, which 
 connects the fpleen and alfo the diaphragm with the 
 ftomach. The ligaments are productions of the 
 peritonxmn, receding from the diaphragm, thrown 
 over the ftomach, and forming is outermoft coat. 
 Of the orifices, the pylorus lies farther forwards, 
 more to the right fide, and a little lower. 
 
 Dcxxiv. The fabric of the ftomach, in general, 
 is the fame with that of the oefophagus ; of which , 
 it is a kind of expanfion ; and, in fome animals, 
 perfectly fimihr. The outermoft coat is from the 
 
 peritonceum j 
 
Cpiap. XIX. 
 
 STOMACH. 
 
 307 
 
 peritonseum ; is ftrong, limits the reft, and affords 
 fupport to the fubjacent mufcular fibres : it is ex- 
 panded into both omcntums ; and in that place, the 
 ftomach is without its outermoft coat. Then fol- 
 lows the firft cellular coat, more abundant at the 
 origin of the little omentum, where it contains con- 
 globate and lymphatic glands, and alfo in the re- 
 gion of the great omentum j it is thinner and fliort- 
 er in the intermediate planes, fo that the outer and 
 mufcular tunic in them cohere together : in this 
 fubftance, the large branches of the veflels are dii- 
 tributed. 
 
 Dcxxv. The mufcular coat is next in order, which 
 is complex and difficult to defcribe or prepare. 
 The longitudinal fibres of the oefophagus, when 
 they arrive at the ftomach, diftribute themfelves 
 along all the fides of the ftomach. Some of them, 
 of confiderable ftrength, run on to the pylorus, 
 along the fmaller curvature ; part of which, by de- 
 grees declining, and following the length of the 
 ftomach, defeend into the planes of each fide, and 
 part of them proceed along the pylorus into the 
 duodenum itielf, and gradually disappear. Other 
 fimilar fibres^ which are lefs ftrong, defeend to the 
 blind fack on the left fide of the ftomach. Befides, 
 other fibres furround that blind fack, w'hich being 
 gradually increafed, are continued with the circu- 
 lar fibres of the reft of the ftomach. This fecond 
 ftratum of fibres is the moft confiderable. Laftly, 
 the fphinder of the cefophagus, is the moft inter- 
 nal, and is a continuation of the annular fibres of 
 the cefophagus. It is compofed of fibres, arifing 
 from the left of the cefophagus, and running to the 
 right, on each fide of the gullet, which they nearly 
 furround ; and gradually becoming longitudinal, 
 they terminate, covered by the fecond ftratum., near 
 the pylorus. The ligaments of the pylorus are two 
 bands, lying betwixt the two curvatures, which 
 cor.trad: the pylorus. They are formed of longi- 
 w 2 tudinal 
 
STOMACH. 
 
 Chap. XIX. 
 
 3°S 
 
 tudinal fibres, and run from the ftomach to the py- 
 lorus, intimately connected with the external mem- 
 brane. 
 
 DC XXVI. Next to the mufcular fibres, there is 
 the fecond cellular coat, larger than the firft, eafily 
 inflatable, fofter, and confifting of larger cells than 
 is common in the inteflines. Into it, the veflels, 
 which perforate the mufcular coat, enter with large 
 trunks, and are divided into an angular network. 
 Under this, lies the nervous coat, which is thick, 
 white, and firm ; and, like other nersmus coats, 
 properly conftitutes the true fubftance of the fto- 
 roach. Then the third cellular ftratum, which is 
 fufficiently evident, and whofe vafcular network 
 is compofed of fmaller velfels than the former re- 
 ticulation. Then the villous coat, continuous with 
 the external cuticle, reparable ; mucous and foft, 
 with very lliort villi, but folded into large wrin- 
 kles, ftellated under the oefophagus, and in the mid- 
 dle of the ftomach almoft parallel vdth the ftomach 
 itfelf. But, at the extremity of the pylorus, there 
 is a more confiderable fold, commonly called its 
 valve, formed of tranfverfe fibres, and of a redu- 
 plication of the nervous coat thickened, and of the 
 villous, fo that a kind of tumid ring is produced, 
 flippery and flefliy, which is furrounded by the du- 
 odenum for a conftderaljie length. The large wrin- 
 kles of the villous membrane are finally fubdivided 
 into fmaller ones, refembling a reticulation, of a 
 quadrangular figure, flvallow, eafily difappearing, 
 and more obfcure than thofe in the biliary duels. 
 Tliroucrhout the whole of this villous coat, but 
 more efpecially towards the pylorus, I have certain- 
 ly obferved fome pores, not always to be perceived, 
 which terminate in fimple follicles, feated in the 
 third cellular ftratum. 
 
 Dcxxvii. The veflels of the ftomach are numer- 
 ous, and derived from many trunks, that the alflux 
 of the blood might not be intercepted by any prel- 
 
 fure. 
 
Chap. XIX. 
 
 STOMACH. 
 
 309 
 
 fure, which might ealily have happened if there had 
 been a fingle trunk. The common fource of all 
 thefe is the cceliaca ; from its tripod, or above the 
 faid diviiion, arifes its firft and largeft artery, the 
 upper coronary, with one branch furrounding the 
 ceiophagus ; to which, and to the diaphragm, and 
 alfo to the liver, it gives branches ; with another 
 following the fmaller curvature, it inofculates, by 
 an anterior and pofterior trunk, with the lefTer co- 
 ronary on the right fide, which arifes from the 
 right branch of the cceliac in the vena portarum it- 
 felf, and returns along the fmaUer curvature. But 
 the fame right branch of the cceliac, after defcend- 
 ing behind the origin of the duodenum, gives off a 
 confiderable artery to the great arch of the ftomach, 
 the right gaftro-epiploica, which being fufpended 
 in the omentum, fupplies both furfaces of the fto- 
 mach, and furrounding the greater part of it, it is 
 inferted into the left gaftro-epiploica. Namely, the 
 left trunk of the cceliac, as it paffes along the du<ft 
 of the pancreas and finuofity of the fpleen, fuccef- 
 fively fends off many branches to the ftomach : of 
 which the firft are commonly namelefs ; and of 
 the following, one branch, called the left gaftro- 
 epiploica, fends off one confiderable branch, and 
 other fmaller branches, to the omentum, and re- 
 turns round the ftomach to the right fide, to inof- 
 culate with its companion of the right fide. Other 
 fmaller twigs, coming from thofe of the fpleen, are 
 fpread upon the remaining part of the greater curve 
 of the ftomach, as far as the diaphragm, and are 
 called the vafa brevia. Frequently, alfo, one or 
 two arteries come from the fplenic one, to the pof- 
 terior furface of the ftomach under the cefophagus, 
 in a different direction from the gaftro-epiploics. 
 The other arteries are fmaller, the upper pylorics 
 from the hepatics, and the lower from the gaftro- 
 epiploics, and thofe of the loweft part of the cefo- 
 phagus from the phrenic arteries. 
 
 DCXXVIII. 
 
310 
 
 STOMACH. 
 
 Chap. XIX. 
 
 Dcxxviii. Thofe arteries are diftributed in the 
 following manner ; the external and mufcular mem- 
 
 O 
 
 branes receive Ihort branches ; the trunks are ar- 
 ranged in the firft cellular ftratum, and with little 
 diminution penetrate the mufcular coat ; and be- 
 tween that and the nervous membrane, they com- 
 pofe a larger and true network ; in which aU the 
 fmall arteries of the different trunks are united, by 
 an infinity of inofculations. From this reticulation, 
 again, other fliort, but numerous and fmall ramifi- 
 cations, go to the third cellular and villous coat of 
 the ftomach. 
 
 Dcxxix. The branches of the veins accom.pany 
 the arteries. The greater coronary generally goes 
 to the left trunk of the porta, together vdth the 
 brevia and left gaftro-epiploic ; while the right A'ein 
 of the fame denomination joins with the middle 
 vena colica, and is inferted along with it into the 
 mefenteric branch of the A’’ena portarum. Finally, 
 the right coronary vein belongs to the trunk of the 
 vena portarum itfelf. All thefe veins are without 
 valves ; and the upper coronary veins inofculate 
 with the branches of the vena fine pari, in like mian- 
 ner as the arteries inofculate with the thoracic cefo- 
 phagei. 
 
 Dcxxx. The nerves of the ftomach are large and 
 numerous, produced from the eighth pair, which 
 forms two plexufes on the oefophagus, of which the 
 anterior and fmaller goes from the oefophagus to 
 the greater curvature and anterior furface ; and the 
 pofterior and larger to the fmaller curvature, and 
 along with the arteries to the liver, and to the pan- 
 creas and diaphragm itfelf. Thefe nerves m.ay be 
 traced into the fecond cellular ftmtum. Beyond 
 this, efpecially the papillae, are more obfcure. From 
 their very great number, the, ftomach is extremely 
 fenfible, efpecially about the entrance of the gullet, 
 infomuch, that acrimonies, wiiich are not perceived 
 by the tongue, turn the ftom.ich j the inteftines are 
 
STOMACH. 
 
 Chap. XIX. 
 
 3 ” 
 
 alfo known, by certain morbid obfervations, to be 
 much more indolent ; even the naked fkin itfelf is 
 lefs fenfible than the ftomach. By making a liga- 
 ture upon the nerves of the eighth pair, the adion 
 of the ftomach and the digehion of food are de- 
 ftroyed. 
 
 DC XXXI. I have feen confiderable lymphatic vef- 
 fels in the fmaller curvature of the ftomach, ariftng 
 from its glands, and infer ted by a very large trunk 
 into the thoracic du6l. Others, without doubt, 
 arife from the glands of the fame kind in the great- 
 er curve 5 and eminent anatomifts have obferved 
 lymphatic glands over the whole ftomach. Other 
 lacteal veflels, I have not feen, and wall not readily 
 admit thofe lately defcribed, which are faid to pafs 
 from the ftomach through the omentum to the liv- 
 er, filled with true chyle. 
 
 DC XX XII. All bags in man are perforated by in- 
 organic pores ; through thefe, water poured into the 
 ftomach exudes through it when ftiut, and, on the 
 contrary, penetrates into the cavity of the ftomach 
 when put under water. But we cannot for this 
 reafon conclude, that during life this paffage is per- 
 vious to moifture. 
 
 Dcxxxiii. Within the human ftomach, we firft 
 meet with a great quantity of mucus, anointing its 
 villous coat, derived from the pores before defcrib- 
 ed (dcxxvi.) which mucus is not unfrequently ting* 
 ed by regurgitated bile. Befides, from the fto- 
 mach, after fafting, upon bending the body, a lim- 
 pid humour will frequently flow, poflefilng all the 
 properties of the faliva, but more mucous, which it 
 is very difficult to obtain pure in the ftomach. It 
 is entirely without any acidity, when it can be had 
 unmixed with food. When feparated from the 
 acid impregnations of the food, and left to itfelf, it 
 changes, both in man and brutes, rather to an alka- 
 line nature, more efpecially in a fafting animal. 
 This liquor diftils from the arteries of the ftomach, 
 
 through 
 
DIGESTION. 
 
 Chap. XIX. 
 
 3*12 
 
 through its villous coat, as is proved by anatomical 
 injections ; by which water, glue, and oil, may be 
 thrown into the ftomach, through numberlefs pores. 
 
 Dcxxxiv. Then it muft be rem.embered, that 
 the ftomach is comprefled as in a prefs in the ab- 
 domen, which is perfedly full, between the dia- 
 phragm, of which the concave left wing lies before 
 and above the liver, and therefore over the fto- 
 mach, and the renfting mufcles of the abdomen, 
 the rectus and obliqui, but chiefly the tranfverfe. 
 The more the ftomach is filled, the more it ex- 
 periences this preflure of the abdomdnal mufcles j 
 becaufe, at that time, it is in contact with the perU 
 tonasum at a rio;ht angle. 
 
 O O 
 
 Dcxxxv. Now we muft explain v'hat is received 
 into the ftomach, and why it is received. The 
 Creator has giv'en to man pain (dlxiv.) and plea- 
 fure, for his prefervation ; the one to incite him to 
 avoid evil, the other to imdte him to ufeful actions. 
 But the taking of aliment is of the greateft necef- 
 ftty to man. For fince every day there is much 
 perfpired, much wafted of his real fubftance, he 
 alfo ftands in need of reparation ; as the body is 
 manifeftly wafted by fafting. But the neceflity 
 of taking food is promoted by the natural tendency 
 of the blood to an alkaline ^fpofition, making it 
 always approach more nearly to a putrid acrimony, 
 by the natural and neceflary motions of the heart 
 and arteries, and by the heat which very much 
 promotes the putrefadion of animal humours. 
 Moreover, the coagulable difpofition of the blood, 
 continually iofing a great part of its water by in- 
 fenfible perfpiration, requires a fupply of its 
 aqueous element to feparaie the globules and pre- 
 vent it from coagulation. 
 
 ncxxxvi. Thefe truths are proved not only from 
 their caufes, but likewife by the appearances exhibit- 
 ed in men and other animals killed by hunger. For 
 it is common for thefe to have an acrid fetid breath, 
 
 for 
 
Chap. XIX. ^ DIGESTION. 313 
 
 for their teeth to become loofe from the faline acri- 
 mony corroding them, and to fuffer violent pains 
 in the ftomach, acute fever, and actual madnefs. 
 Thefe diforders are the more rapid in their pro- 
 grefs, the more violently the body is exercifed, and 
 the more robuft and younger it is. They en- 
 fue very Ilowly in people who are phlegmatic and 
 unaftive, who perfpire little, and whofe blood cir- 
 culates feebly. Finally, thofe who have lived with- 
 out food, have alfo lived without bodily exercife, 
 and for the moft part laboured under a difeafe of 
 the nerves. 
 
 Dcxxxvn. The frefli chyle, compofed, for the 
 moft part, of the acefcent clafs of vegetables, and 
 always thinner than the blood, being received into 
 the circulation, tem-perates its putrefcent acrimony, 
 dilutes its impending coagulation, and reduces the 
 whole mafs to that moderate degree of faltnefs 
 which is natural to man : and finally, the chyle, 
 but more efpecially that derived from the flelh of 
 animals, and from the farinaceous grains, furniflies 
 a new gelatinous lymph, which being applied by 
 proper caufes (dcccclix.) to the vacuities of the 
 wafted folids, repairs that wafte. The drink di- 
 lutes the coagulable blood, and hinders its putre- 
 faction, by feparating its putrefcent particleSj 
 Hence a perfon may live for a long time vdthcut 
 food, if fupplied with drink ; but without drinkj 
 life fubfifts but a few days. 
 
 Dcxxxviii. We are induced to take food, both 
 from the fenfe of pain which we call hunger, and 
 from that of the pleafure imparted by the fenfe of 
 tafte (ccccLV.) The firft of thefe proceeds undoubt- 
 edly from the folds of the ftomach, which poffefs 
 great fenfibility, being rubbed againft each other, 
 by the periftaltic motion, and by the prelTure of 
 the diaphragm and abdominal mufcles, fo that 
 naked nerves being rubbed againft naked nerves 
 excite an intolerabk degree of pain. Thus man 
 
 is 
 
DIGESTION. 
 
 Chap. XIX. 
 
 314 
 
 is both efFecluaUy admonilhed of the dangers of 
 abftinence, and excited to procure food by his la- 
 bours. It is perhaps increafed by the gaftric juice 
 having become more acrid, unlefs it putrefies. 
 
 Dcxxxix. Thirfi; is feated in the tongue, fauces, 
 cefoplragus, and ftomach. For whenever thefe parts, 
 which are very fenfible, and naturally are moif- 
 tened by their mucous and falival juices, grow 
 dry from a deficiency in the fecretion of thofe hu- 
 mours, or from muriatic or alkalefcent fiilts adher- 
 ing to them, a much more intolerable fenfation is 
 produced, as thirfi: is attended by much greater 
 danger, and does not abate until the abundance of 
 water, being refiored to the blood, and the obfiruc- 
 tion removed from the fecreting veffels in the parts 
 mentioned, they are again moiftened. From hence 
 v.'-e learn, why thirfi attends labour, which exhales 
 the water by perfpiration ; and why it is a fymp- 
 toiTi of fevers, where the exhaling veffels belong., 
 ing to the tongue and fauces are obfirucled ; why 
 limple water is lefs efficacious in allaying thirfi ; 
 why fubacid liquors are more efficacious, which 
 not only moifien by their fluidity, but alfo, by a 
 mild irritation of the tongue and mouth, excite a 
 flow of the retained humours, and at the fame time 
 correct putrefcency. 
 
 DcxL. From thefe caufes, mankind being com- 
 pelled to take food, has in all ages felecfied thefe 
 fupports of life from the vegetable and animal king- 
 doms, fo that of the third, water and fait alone 
 are added. It is probable, that the original choice 
 efi our foods was made by experiments, as fuggeft- 
 ed by the fmell and flavour of certain vegetables, 
 and as their utility was confirmed by the renewal 
 of flrength. By degrees, as animals became incom- 
 modious to hufbandmen, and v'egetables alone were 
 not fufficient for fupporting them under their la- 
 bours, the flefli of animals was afterwards added. 
 At prefent, the number of •ubfiances is almo’l 
 
Chap. XIX DIGESTION. 315 
 
 infinite, which we take either as food or feafon- 
 ing. 
 
 DcxLi. Although there are inftances of particu- 
 lar perfons, and even of nations, who have lived 
 entirely upon food taken from one clafs, as upon 
 vegetables alone, or animals alone, and fometimes 
 upon a few individuals of one clafs ; and laftly, 
 upon milk alone or its whey ; yet it feems to be 
 neceffary, both from the nature of the hum.an bod}', 
 and to be indifpenfable according to certain experi- 
 ments, that we ought to fupport life efpecially by 
 two kinds of food, fo intermixed, that neither may 
 exceed ; which mediocrity we are taught from the 
 loathing itfelf, which is excited by any one kind 
 of food that has been continued too long. 
 
 DcxLii. The flelh of animals appears neceffary, 
 from the teeth in both jaws, and from the fabric 
 of the human ftomach itfelf refembling that of car- 
 nivorous animals ; from the fmallnefs and fhortnefs 
 of the inteftinum caecum, and from the ftrength 
 which w'e require. For the flefli of animals alone 
 contains the gelatinous lymph ready prepared, 
 which, being extradled from the broken veffels, 
 pafles eafily and in great abundance into the blood. 
 Abftinence from animal food caufes gfeat weakneis 
 both in the body and ftomach, and is ufually at- 
 tended by a troublefome diarrhoea. Man agrees 
 with the herbivorous animals in the fize and length 
 of the large inteftines. 
 
 DcxLiii. Efculent vegetables are generally of the 
 acefcent kind ; a few of them only are either alka- 
 lefcent or aromatic. Few of them have that gluten 
 which is fpontaneoufly changeable into blood, and 
 they only nourifh by means of their farina, a fmall 
 part of which, after repeated circulations, is at laft 
 con-^terted into the natural juices. Yet they are ne- 
 cefl'ary to avoid over repletion with blood, and of 
 too putrefcent a kind, from the ufe of animal food 
 alone, fuch as moft certainly occurs in the anthro- 
 pophagi. 
 
DIGESTION. 
 
 Chap. XIX. 
 
 pophagi, and produces fcurvy, ferocity, fetor, lep- 
 rofy, and every kind of alkaline corruption, all 
 which evils are cured by change of diet, and the 
 excluhve ufe of acid vegetables. Hence we are 
 furnilhed with few. canine teeth ; and our appetite 
 in health, but more efpecially in difeale, is ftronger 
 for acidulous vegetables, in proportion to the 
 warmth of our temperament, of the feafon of the 
 year, and of the country. Hence, in the hotteft 
 climates, people Live almoft altogether upon vege- 
 tables, and ufe flefh very rarely, and with danger ; 
 while, in the colder countries, it is eaten freely 
 with lefs danger. Hence bread, or a farinaceous 
 aliment fimilar to it, is eaten in every part of the 
 world. 
 
 DCXLiv. The beft drink is pure water, free from 
 every kind of fait, and not impregnated with air, 
 which excites, fermentations. That from a moun- 
 tainous fpring, which runs through a fandy bed, 
 and is cold, clear, light, and iniipid, is juftly pre- 
 ferred, Whenever there is a deficiency of pure 
 water, as is frequently the cafe in fiat countries, or 
 when any power ftimulating the ftom.ach to con- 
 traction, or any aromatic is required, it is fupplied 
 by vinous liquors, efpecially thofe prepared from 
 grapes, but alfo from apples and pears ; which, af. 
 ter fermentation, become clear, and contain alco- 
 hol and an acid fait diluted with water. Liquors 
 of the fame kind, not deftitute of alcohol, but more 
 flatulent, vapid and colder, are prepared by fermen- 
 tation from grain toafled, and boiled in water, in 
 thofe countries where the grape does not ripen. 
 
 DCXLv. Men have invented various condiments. 
 They have added fait, vinegar, and acids of various 
 kinds, to correcL the putrefcence of flefh ; pepper, 
 hot fpices, and alliaceous fubftances, to ftrengthen 
 the ftomach, which is weakend by die conflant 
 ufe of vegetables ; and fugar, lalt and aromatics, 
 for the fake of flavouring or preferring our food. 
 
Chap. XIX. 
 
 DIGESnON. 
 
 3^7 
 
 But none of thefe nourifh, being deftitute of gela- 
 tinous lymph, and nourilhing farina. The fpirits 
 of wine and of corn may be of fome ufe as medi- 
 cines, but are unfit for drinking. 
 
 DcxLvi. According to the difference of country, 
 climate, or feafon, the aliments undergo various 
 preparations, by which crudity is removed, folid 
 fibres foftened, exceflive air expelled, difagfeeable 
 acrimony diminiflied, or a pleafant flavour impart- 
 ed. But many vegetable foods, and more efpecial- 
 ly flefh meats, require fome trituration, particular- 
 ly in man, whofe flomach is but little flefhy, nor 
 ought the articles of food to become putrid by re- 
 maining too long in the flomach. 
 
 DcxLvii. The meafure of our food is determined 
 by the ceafing of our hungei*, which is different ac- 
 cording to the difference of aliments. Animal and 
 farinaceous food nourifhes moil : other aliments 
 ought to fupply by their quantity, what they want 
 in powers of nourifhment. In general, we are 
 nourifhed bed by a fomewhat fpare diet, unlefs fub- 
 jefted to much labour. 
 
 DcxLviii. Into the flomach, therefore, the ali- 
 ments are let down, often almoft crude, and little 
 chewed ; of various kinds, as alkalefcent flefh, ran- 
 cefcent fat, or acefcent vegetables, bread and milk, 
 and glutinous fubflances. Here they are digefled 
 in an heat equal to that of incubation, imparted by 
 the contiguous heart, liver, and fpleen ; and in a 
 cavity fhut above (dcxxi.) and alfo below by the 
 afcent of the pylorus, the narrownefs of the valve 
 placed there, and the a<Tion of the fibres, conflridt- 
 ing the pylorus, fo that even milk itfelf remains en- 
 tirely in thellomach of healthy animals feveral hours 
 after meals, without paffmg into the inteflines. Be- 
 fides,the aliments are macerated in a moifl place with 
 much air, either fwallowed during deglutition, or 
 mixed with the aliments. This air, therefore, ex- 
 panding by the force of heat, putrefadion, or fer- 
 mentation. 
 
DIGESTION. 
 
 Chap. XIX. 
 
 318 
 
 mentation, biirfts the cells in which it is included, 
 divides the vifcid liquors, weakens the I'olid hbres, 
 prepares fpace for the fluid which is to enter into 
 them. But this air alfo, which is the principal ce- 
 ment of animal folids, emerges from their fubltance, 
 and leaves the other elements without a vinculum, 
 as we fee from the phenomena in Papin’s digefter, 
 in the ftomachs of animals, and even in that of 
 man. This air, fet at liberty, diftends the Itomach 
 more than the food itfelf, and is termed flatus. At 
 the fame time, the aliments begin to corrupt into 
 a naufeous liquid, often acefcent ; at other times 
 putrefcent, but lefs fo in man from the influence of 
 bread and fait ; or rancefcent, as appears from the 
 flatus and eruftations, varioufly fetid, and even in- 
 flammable. This is the foie caufe of digeftion in 
 fifli and ferpents, and almoft in carnivorous birds* 
 Hence, in man, metals themfelves, by long flay in 
 the ftomach, grow foft, and are eroded. At the 
 fame time hunger is removed, the nervous folds of 
 the ftomach being removed from mutual contact 
 by the aliments interpofed, the acrid gaftric fluid 
 being neutralized, and perhaps from the very pre- 
 fence of this naufeous liquid being difagveeable to 
 the nerves. 
 
 ECXLix. But they are prevented from degener- 
 ating into complete acidity, by the heat inducing 
 putrefaction, by the action of the gaftric juice, and 
 of the faliva, which is fwallowed to the amount of 
 half an ounce in an hour, both inclined to alka- 
 lefcency, and by the bile which certainly regurgi- 
 tates frequently into the ftomach. Thefe fluids, 
 being incorporated with the aliment, macerate and 
 foften it, divide the membranes, refolve the cellu- 
 lar bands, liquefy the pulps, as warm water and 
 time do in other fltuations, extract their juice, and 
 mingle it with themfelves. There is, therefore, no 
 kind of fermentation in the ftomach, from whieJi 
 the nature of the fluid, and the defign of r.atur;:. 
 
DIGESTION. 
 
 Chap. XDC. 
 
 3^9 
 
 are diftincl. And yet the juice of the ftomach 
 alone, by a continuance of its aftion, in filhes, dif- 
 folves the bones which they devour. 
 
 DCL. For, the flefhy fibres in the ftomach being 
 now irritated by the flatus, wei^t, and acrimony 
 of the food, begin to contraft themfelves more 
 powerfully than when the ftomach is empty, and 
 with greater force in proportion as it is more full, 
 its round fwelling ftretching the fibres. And, firft, 
 the plane of the fmaller curvature draws the pylo- 
 rus to the oefephagus ; and, being inferted only in- 
 to its left furface, it draws that to the right. The 
 principal ftratum of the circular fibres, diminilhes 
 the cavity of the ftomach, incorporates the aliments 
 with the juices, (ncxxxiii.) and comprefies them 
 flightly as if between the hands on oppofite fides 
 and gradually determines them towards the pylo- 
 rus : but it is not im.mediately permitted to efcape, 
 both on account of the reafon before afligned, 
 (dcxxvi.) and alfo becaufe this motion begins 
 from the part that is moft irritated ; and, there- 
 fore, impels the aliment upwards, as at other times 
 it forces it downwards. The contracted portion of 
 the ftomach. propels the food into the neighbour- 
 ing dilated part, and is in its turn relaxed when 
 that other is contracted. Thefe alternate contrac- 
 tions at laft terminate in complete evacuation. In 
 this action, there is nothing which refembles the 
 trituration made by the ftrong gizzards of granivo- 
 rous fowls, which fome anatomifts have afcribed to 
 the human ftomach ; yet it has a confiderable de- 
 gree of ftrength, and afibrds an example of fibres 
 contracted to more than a third part of their length; 
 for the ftomach is frequently reduced to much lefs 
 than a third of its diameter, even to the breadth of an 
 inch ; and, laftly, is capable of difcharging needles. 
 Yet it neither bruifes berries, nor the fofteft worms. 
 
 DC LI. The action exerted by the diaphragm and 
 mufcles of the abdomen, is ftronger than the peri- 
 ftaltic force of the ftomach ; for, by this, it is ca- 
 pable 
 
DIGESTION. 
 
 Chap. XIX. 
 
 pable of perfectly evacuating the ftomach, and of 
 bringing its anterior and pofterior fides into actual 
 contaft. For this force, principally, expels tlie 
 fluids immediately, but the folids only when they 
 ave foftened, ancf rendered fmall enough for the 
 valve of the pylorus, through that pylorus into the 
 duodenum, which is inclined when the ftomach is 
 full ; for the aliments do not feem to leave the 
 ftomach, before they have loft their fibrous or other 
 texture, and are refolved into a mucous, yellow- 
 ifti, cineritior^, fomewhat fetid, pultaceous liquid. 
 That which is firft prepared and liquefied, goes 
 firft, and, therefore, water and milk, firft of all ; 
 then pot herbs ; and, laftly, flefli. The harder, 
 tougher, and longer fkins or fibres, pafs at the 
 fame time unchanged : and fuch things as are hard 
 and too large to pafs the pylorus, are retained in 
 the ftomach for a long time. 
 
 DCLii. But the moll confidcrable portion of the 
 drink is abforbed by the pendulous patulent veins 
 of the ftomach itfeif, correfponding to the exhaling 
 arteries (ccxxxiii.) and is carried by a fhorter way 
 to the blood, as plainly appears from injecUons. Does 
 any thing enter the lymphatic veffels (dcxxxi.) ? 
 
 Dcniii. The ftomach, being irritated by too great 
 a quantity or acrimony of the food, or elfe by nau- 
 fea from regurgitation of the bile, or other caufe, 
 V/ith an antiperiftaltic motion repels its contents up- 
 wards, and difcharges them through the open and 
 relaxed cefophagus, by vomiting. But this is allift. 
 ed by the aftion of the abdominal mufcles, which 
 comprefs the belly, draw in the ribs, and, as the 
 defcending diaphragm a<ft;s againft them, they eva- 
 cuate the ftomach with very great force, fqueezed 
 as if in a prefs. 
 
 DCLiv. But the aliments tranfmitted in their na- 
 tural ccurfe to the duodenum, meet there with the 
 bile which frequently regurgitates into the ftomach 
 itfeif, and with the pancreatic juice. The nature 
 
 of 
 
Chap. XX, OMENTUM. 32 x 
 
 of the former of thefe, the principal fluid of cligeE 
 tion, requires a previous hiftory of the vifcera^ 
 ^'hieh tranfmit their blood to the vena portarum,' 
 
 C H A P. XX. 
 
 THE OMENTUM. 
 
 bcLV, "'HE perltonteum is a ftrorig hmpie mem- 
 i brane, by which all the vifeera of the 
 abdomen are furronnded. It has an exceedingly 
 fmooth, exhaling, and moifl internal furface 5 out- 
 wardly, it is every where furrounded by cellular 
 fubftance ; which, towards the kidneys, is very 
 loofe and very fat ; but is extremely fliort at the 
 lower tendon of the tranfverfe mufcles* It begins 
 from the diaphragm, which it completely lines ; 
 and at the laft flelhy fibre's of the ribs, and the ex- 
 ternal lumbar fibres, it completes the feptum, in 
 eonjunftion with the pleura, Vvuth which it is con- 
 tinuous through the various intervals of the dia- 
 phragm, It defcehds behind, before the kidneys ; 
 before, behind the abdominal mufcles ; it dips into 
 the pelvis ; from the bones of the pubes, pafies over 
 the bladder, and defcends behind it ; and being 
 again carried backwards at the entrance of the ure- 
 ters in two lunar folds, it rejoins upon the intefli- 
 num rectum, that part of itfelf which invefts the 
 loins, and in this fituation lies- before the reftum. 
 
 DCLvi. The cellular texture, which covers the 
 peritonaeum on the outfide, is continued into fheaths 
 in very many places ; of which one receives the tef- 
 ticle, on each fide ; another the iliac veffels j others 
 the inteftinUm reftum, the large veffels of the pel- 
 vis, the obturatoria, penis, bladder, and aorta, and 
 afcending, into the breaft, accompany the gullet and 
 vertebr;s j by means of which, there is a commu- 
 X nication 
 
322 OMENTUM. Chap. XX. 
 
 nicatlon between the whole body and the peritonaea 
 um, well known in dropfical people. 
 
 DCLvii. It has various prolongations for covers 
 ing the vifeera. The fliorter productions of this 
 membrane are called ligaments ; and are formed by 
 a continuous reduplication of the peritonaeum, re- 
 ceding from its inner furface, inclofmg cellular fub- 
 ilancc, and extending to fome vifeus, where its 
 plates feparate ; and having diverged, emibrace the 
 vifeus ; but the intermediate cellular lubftance al- 
 ways accoiripanies this membranous coat, and joins 
 it with the true fubftance of the vifeus. Of this 
 Utort kind of production, three belong to the liver, 
 one or two to the fpleen, and others tothelddneys 
 and to the fides of the uterus and vagina. By this 
 means, the tender fubftance of the vifeera is defend- 
 ed from injury by any motion or concuilion, and 
 their whole mafs is prevented from being mifplaccd 
 by their own weight, and from injuring themfelves, 
 being fecurely connected with the firm fides of the 
 peritonaeum. 
 
 DCLviii. But the moft important of all thefe 
 productions of the peritonaeum, are thofe called the 
 mefentery and mefocolon ; and the defeription of 
 which, although very difficult, ought not to be fe- 
 parated. We fliall, therefore, begin firfl; with the 
 mefocolon, as being the moft fimple. In the pel- 
 vis, the peritonasum fpreads itfelf Ihortly before the 
 reftura. But where that inteftinc becomes loofe, 
 and forms the femilunar curve, the peritonxum 
 there rifes confiderably from the middle iliac vef- 
 fels and region of the pfoas- mufcle, double (dclvii.) 
 and with a figure adapted for receiving the hol- 
 low colon. But above, on the left fide, the co- 
 lon is connected with almoit no intermediate 
 loofe production to the peritonxum, fpread upon 
 the pfoas mufcle, as high as the fpleen, where this 
 part of the peritonxum, which gave a coat to the 
 colon, being extended under the fpleen,. receive* 
 
Chap. XX. OMENTUM. 3-3 
 
 and fuftains that vifcusj in a hollow fiiperior re- 
 cefs. 
 
 DCLix. Afterwards the peritonaeum, from the 
 left kidney, from the interval between the kidneys, 
 from the large veffels, and from the right kidney, 
 emerges forwards, under the pancreas ; and forms 
 the broad and fufficiently long continuous produc- 
 tion, called the tranfverfe mefocolon, which, like a 
 partition, divides the upper part of the abdomen, 
 containing the ftomach, liver, fpleen, and pancreas, 
 from the lower part. The lower plate of this tranf- 
 verfe production, is continued hngly from the right 
 mefocolon to the left, and ferves as an external coat 
 1,0 a pretty large portion of the lower and defcend^- 
 ing part of the duodenum; But the upper plate, 
 lefs hmple in its courfe, departs from the lumbar 
 peritoneum at the kidney and -region of the vena 
 cava, farther to the right than the duodenum, to 
 which it gives an external membrane, not quite to 
 the valve of the pylorus ; and, beyond this intef- 
 tine, and beyond the colon, it is joined with the 
 lower plate, fo that a large part of the duodenum 
 lies within the cavity of the mefocolon. After- 
 wards, in the region of the liver, the mefocolon is 
 infleCfed, and defeending over the kidney of the 
 fame hde, much fhorter, it includes the right of the 
 colon, as far as the inteftinum caecum, which refts 
 upon the iliac mufcle, and the appendix, which is 
 provided with a peculiar, long, curved mefentery. 
 There the mefocolon terminates, almoft at the bi- 
 furcation of the aorta. 
 
 DC LX. The whole of the mefocolon, and of the 
 mefentery, is hollow ; fo that air may be forced in 
 between its two limilar plates, in fuch a manner as 
 to expand it into a bag; At the place where it fuf- 
 tains the colon, and alfo from part of the intelUnum 
 rectum, the mefocolon, continuous with the outer 
 membrane of the intclline, forms itfelf into fmall 
 flender bags, refembling the omentum, for the moft 
 x 2 part 
 
OMENTUM. 
 
 Chap. XN.- 
 
 P'4 
 
 part in pairs, with their loofe extremities thicker 
 and bifid, and capable of admitting air, blown in 
 between the plates of the mefocolon. 
 
 Dci.xi. In the next place, vv*e come to the me- 
 fentery, a very large, folded production of the pe- 
 ritonaeum, continuous with the tranfverfe and right 
 mefocolon, at the right fide of the emerging duo- 
 denum ; and then proceeding for a long way vath 
 both mefocolons, even as low as the pelvis. The 
 mefentery, under the right' portion of the tranfverfe 
 mefocolon, defeending from that part of the perito- 
 naeum, which lies upon the aorta, under the pan- 
 creas, and having numberlefs folds in its edge, con- 
 tains the very long feries of the fmall inteftines. 
 
 DCLxii. Every part of the mefentery and mefo- 
 colon contains fat, collected in the neceilary inter- 
 val of the plates ; generally in greater quantit)', 
 where they are loirger ; and interpofed vefl'els dif- 
 tributed around the fat, which the arteries fccrete, 
 •and the veins, as already mentioned, abford ; and 
 ahb very numerous glands,, which are moft confpi- 
 cuous in a young fubjeef. 
 
 Dcnxim The nature of the omentum is very 
 analogous to that of the mefenteiy. But there arc 
 many membranes that come under this general de- 
 nomination, of the fame ftructure and utility, all 
 eompofed of a tender membrane, very eafily lace- 
 rated, through which reticulated velTels are dif- 
 tributed, with fat depofited in ftreaks along their 
 courfe. This membrane is always double ; and be- 
 tween its lamellee, clofely connecled by very ten- 
 der cellular fubftance, the veflels are diftributed, 
 and the fat collected. And, firll, where the top of 
 the right kidney, and the lobulus caudatus of the 
 liver, with the fubjacent large veflels, form an an- 
 gle with the duodenum, there the external mem- 
 brane of the colon which comes from the peritn- 
 nasum, joining with the membrane of the duode- 
 num, which alfo avifes immediately from the perk 
 
 tona^um. 
 
Chap. XX. 
 
 OMENTUM. 
 
 325 
 
 tonasum lying upon the kidney, enters backwards 
 into the tranfverfe fiffure of the liver for a confid- 
 erable fpace, is continuous vath its external coat, 
 contains the gall bladder, fupports the hepatic vef- 
 feis, and is very yellow and llippery. Behind this 
 membranous production, betwixt the right lobe of 
 the liver, hepatic veffels, vena portarum, biliary 
 ducts, aorta, and adjacent duodenum, there is a nat- 
 ural opening, by which air may be blown extenlively 
 into all that cavity of the omentum, which we fliall 
 prefently defcribe ; and, laftly, into the bags of the 
 reft of the omentum. 
 
 DCLXiv. From thence, in a courfe continuous 
 with this membrane (dclkiii.) from the pylorus and 
 the fmaller curvature of the ftomach, the external 
 membrane of the liver joins in fueh a manner with 
 that of the ftomach, that the thin membrane of the 
 liver is continued out of the folTa of the venal duft, 
 acrofs the little lobe, into the ftomach, ftretched 
 before the lobe and before the pancreas. This is the 
 little omentum or hepatieo gaftricum ; which, when 
 inflated, refembles a cone ; and gradually becoming 
 harder, and emaciated, it changes into a true liga- 
 ment, by which the oefophagus is connecled to the 
 diaphragm (dcxxiii.) 
 
 DCLXv. But the larger omentum, the gaftrocoll- 
 cum, is of a much greater extent. It begins at the 
 flrft aceeflion of the right gaftro-epiploic artery to 
 the ftom.ach, being continued there from the upper 
 plate of the tranfverfe mefocolon (dclix.) ; and 
 then from the whole great curve of the ftomach, 
 as far as the fpleen, and alfo from the right convex 
 end of the ftomach towards the fpleen, until it alfo 
 terminates in a ligament that ties the upper and 
 back part of the fpleen to the ftomach. This is the 
 anterior lamina. 
 
 DCLXvi. Being continued downwards, fometimes 
 to the navel, fometimes to the pelvis, it hangs be- 
 fore the inteftines, and behind the inufdes of the 
 
 abdomen, 
 
OMENTUM. 
 
 Chap. XX. 
 
 326 
 
 abdomen, until, from its lower edge being reflected 
 upon itfelf, it afcends, leaving an intermediate va- 
 cuity between it and the anterior lamdna, and is 
 continued for a very great extent into the external 
 membrane of the tranfverfe colon, and laftly into 
 the Jlnus of the ipleen, by which the large blood- 
 vefl’els are received, and it ends finally on the oefo- 
 phagus, under the diaphragm. Behind the ftomach, 
 and before the pancreas, its cavity is continuous 
 with that of the fmaller omentum. 
 
 DCLxvii. To this the om.entum colicum is con- 
 nected, which arifcs farther to the right than the 
 firft origin of the omentum gaftrocolicum from the 
 meibcolon, with the cavity of which it is contin- 
 uous, but produced folely from tlie colon and its 
 external membrane, which departs double from the 
 intcfline ; it is prolonged, and terminates by a co- 
 nical extremity, fometimes of longer, fometimes of 
 fliorter extent, above the inteflinum cxcum. 
 
 DCLXviii. The ufes of the omentum are many. 
 In common with the mefentery, it forms loofe fpa- 
 ces, into ayhich the fat may be poured, and pre- 
 ferved during fleep and inactivity, that it may be 
 afterwards diiTolved by increaie of motion, reftored 
 by the abforbent veins, and conftitute a principal 
 ingredient of the bile. Hence it is fometimes found 
 very thick, even an inch thick, and at others thin, 
 and more tranfparent than paper. For that the fat 
 returns ao-ain into the veins, is demonftratcd from 
 human omenta being found of very difierent bulks 
 and fatnefs, according as they belonged to indolent, 
 laborious, or difeafed fubjects ; from the phenomena 
 in animals ; from the analogy of all the reft of the 
 fat of the human body (xx.) ; from experiments in 
 frogs, where this reabforption of the fat may be 
 made evident to the eye ; and, laftly, from the evi- 
 dently inflammable nature of the bile. Hither I 
 alto refer the diforders of digcftion, the crudities 
 
Chap. XX. OMENTUM. 327 
 
 and coldnefs of the ftomach, obferved from cutting 
 out the omentum. 
 
 DCLXix. For all the blood which returns from 
 the omentum and mefocolon, goes into the vena 
 portarum, and by that into the liver itfelf. The 
 omentum gaftrocolieum is furnifhed with blood 
 from each of the gaftro-epiploic arteries, by many 
 defcending reticulated branches : of which the moft 
 lateral are the longeft, and the loweft anaftomofe 
 by minute twigs with thofe of the colon. It alfo 
 has branches from the fplenic, duodenal, and adi- 
 pofe arteries. The omentum colicum has its arte^ 
 ries from the colon, as alfo the fmaller appendices, 
 (dclx.) and from the duodenal and right epiploic, 
 'fhe arteries of the fmaller omentum come from the 
 hepatics, and from the right and left coronaries. 
 
 Dci.xx. The omentum, being fat and indolent, 
 has very fmall nerves. They arife from the nerves 
 of the eighth pair, both in the greater and in the 
 leffer curvatures of the ftomach. 
 
 DCLXxi. The arteries of the mefentery are, in 
 general, the fame with thofe which go to the in-^ 
 teftines, and of which the fmaller branches remain 
 in the glands and fat of the mefentery. Various 
 fmall acceflbry arteries go to both mefocolons, from 
 the intercoftals, fpermatics, lumbars and capfulary, to 
 the tranfverfe portion, from the fplenic artery and 
 pancreatico duodenalis, and to the left mefocolon, 
 from the branches of the aorta going to the lumbar 
 glands. 
 
 DCLxxii. The veins of the omentum, in general, 
 accompany the arteries, and unite into ftmilar 
 trunks : thofe of the left part of the gaftrocolic 
 omentum into the fplenic, and alfo thofe of the he- 
 paticogaftric, which likewife fends its blood to the 
 trunk of the vena portarum : thofe from the larger 
 and right- part of the gaftrocolic omentum, from the 
 omentum colicum, and from the appendices epiplo^ 
 ides, into the mefenteric trunk. All the veins of the 
 
 mefenterv 
 
OMENTUM. 
 
 Chap. XX. 
 
 528 
 
 mefentery meet together in one, which is the true 
 trunk of the vena portarum : being collected firft 
 into two large branches ; of which the one, the me- 
 lenteric, receives the gaftro-epiploic vein, the colicse 
 mediae, the iliocolica, and all thofe of the fmall in- 
 teftines as far as the duodenum ; the other, which 
 going tranfverfely inferts itfelf into the former, 
 above the origin of the duodenum, carries back the 
 blood of the left colic veins, and thofe of the rec- 
 tum, except the lowermoft, which belong partly to 
 thofe of the bladder, and partly to the hypogaftric 
 branches of the pelvis. The vein which is called 
 haemorrhoidalis interna, is fometimes inferted rath- 
 er into the fplenic than into the mefenteric vein. 
 Idas the omentum alfo lymphatic vefiels ? Certain- 
 ly there are conglobate glands, both in the little 
 omentum and in the gaftrocolicum ; and ancient 
 anatomifts have obfeiu'ed pellucid velfels in the 
 omentum ; and a modern has defcribed them for 
 lacleals of the flomach. 
 
 DCLXxiii. The other ufes of the omentum are, to 
 interpofe itfelf betwixt the inteftines and perito- 
 naeum, which are very apt to adhere ; to preferve 
 the mobility of the former entire,both among them- 
 fclves and upon tlie peritonaeum ; to lelfen friction ; 
 and to lubrica.te the mufcular fibres with a very bland 
 oil. Therefore, even in infects, there is a great 
 deal of fat around the inteftines. In the large in- 
 teftincs, there are a great many appendices, becaufe 
 they have larger lacerti, and cannot be altogether 
 covered by the omentum'. The omentum aUb ar- 
 ranges the vefiels, conducts and fupports them, con- 
 necls the contiguous vifcera, and exhales a foft va- 
 pour, which, mixing with watery abdominal exha- 
 lations, anoints and lubricates all the vifcera. 
 
 DC I, XXIV. The mefentery fuftains the inteftines 
 in fuch a manner, that they poflefs both mobility 
 and firmnefs : it fupports and conduces with fafety 
 the blood-veffels, ladeals and nerves 3 it fixes tlie 
 
 eland'-- 
 
SPLEEN. 
 
 Chap. XXL 
 
 329 
 
 glands, as ftiall be noticed hereafter, gives an exter- 
 nal coat to the inteftines, and forms moft of the 
 omenta. 
 
 D c L X X V. But befides , theblood, returning through 
 the mefenteric and mefocolic veins, brings with it 
 to the liver a fecond principal conftituent of the 
 bile ; namely, a copious fubalkaline humour, which 
 is abforbed from all the fmall inteftines, as will be 
 demonftrated in its proper place. Moreover, from 
 the large inteftines, it conveys to the liver another 
 fluid, but more putrid, fetid, and nearly approach- 
 ing to the nature of volatile alkali, abforbed from 
 the alvine faeces, that now begin to fmell ftrong ; 
 which is eaftly proved, both from proper experi- 
 ments, and from the induration of the faeces when too 
 long retained in the bowels. For this water is nat- 
 urally fluid, and rendered more fo by incipient pu- 
 trefaction ; it moderates the tenacity of the oil from 
 the omentum and mefentery, and keeps it from co- 
 agulation. But it efpecially imparts to the bile that 
 alkaline rancidity with which it abounds, and on 
 which the great tenuity, and dyeing and fapona- 
 ceous powers of the bile almoft folely depend. 
 
 DCLXXvi, HE fpleen is alfo one of thofe vifcera. 
 
 It is pulpy, bloody, livid, and fomewhat thick ; of 
 an oval circumference, often notched on the mar- 
 gin, or even divided into lobes ; on one fide, to- 
 wards the ribs, convex, on the other concave ; with 
 two furfaces, one anterior towards the ftomach, and 
 another pofterior towards the diaphragm ; divided 
 by the entrance of its veflels ; and with two extrem- 
 Uie;3, of which the inferior and anterior is the 
 
 CHAP, XXL 
 
 SPLEEN, 
 
 which fend their blood to the liver. 
 
 lharpeft. 
 
SPLEEN. 
 
 Chap. XaI, 
 
 S3® 
 
 fharpeft. It is connected to the ftomach by the 
 little omentum and upper ligament, fupported from 
 the adjacent colon by the ligament (dclviii.) be- 
 hind, it is contiguous to the renal capfule ; and it 
 is connected to the kidney by the peritonaeum. It 
 alfo receives the peritonaeum from the diaphragm, 
 under the denomination of a ligament, in the back 
 part of its hollow hnus, behind its veffels. Its fit- 
 uation is variable, and depends on the ftomach. 
 When that is empty, the fpleen is placed more 
 perpendicularly, and its extremities become fu- 
 perior and inferior ; but when the ftomach is full, 
 and its middle curv'ature arifes forwards (dcxxii.) 
 then the fpleen at the fame time changes its fit- 
 uation, and its extremities become anterior and 
 pofterior, fo as to lie almoft tranfverfely. Alfo, 
 being of a very foft texture, it is more fpongy 
 and larger when the ftomach is empty ; and when 
 the ftomach is full, being prefled by it againft the 
 ribs, it is emptied. Hence, in weak fubjecfts, it is 
 large ; but in thofe who die fuddenly, and in full 
 health, it is fmall. It alfo defccnds with the dia- 
 phragm in inipiraticn, and afcends with it in exfjft- 
 ration ; and befldes, it frequently varies its fltua- 
 tion with the colon. Frequently there is a fecond 
 acceffory fpleen, or even fcveral. 
 
 DCLXxvii. The blood -veflels of the fpleen are 
 large, in proportion to its weight. The arterial 
 trunk comes from the cceliac ; the left branch of 
 which proceeds in a Terpentine courfc, above and 
 behind the pancreas, to which it gives branches, 
 and to the inefocolon, ftomach, and omentum, iur 
 curvated along the fulcus of the fpleen, and being 
 fupported by the right end of the gaftrocolic omen- 
 tum, it in a manner perforates the fpleen by many 
 branches. The thicknefs of this artery is greater 
 than that of the aorta. The fplenic vein is remark- 
 ably foft, almoft more fo than any other vein ot the 
 body j it forms the principal kft branch of the vena 
 
 portarum. 
 
SPLEEN. 
 
 Chap. XXL 
 
 331 
 
 portarum, and, befides the branches accompanying 
 the arteries, it receives the great coronary, defcend- 
 ing behind the pancreas, and fometimes the internal 
 hsemorrhoidal. The vafa brevia, arifing from thofe 
 of the fpleen, we have mentioned elfewhere ; and 
 laftly, fmall twigs from the lumbars, phrenics, in- 
 tercoftals, and thofe of th^ renal capfules, go to tho 
 ligaments and membranes. In like manner, the 
 fplenic and fliort veins communicate with the renal 
 capfulary, renal and phrenics. 
 
 DCLXxviii. The lymphatic velTels which are de- 
 fcribed in the duplicature of the membrane of the 
 fpleen, which, however, does not exift, and are faid 
 to proceed on to the receptacle of the chyle, are 
 very evident in the calf; and in mankind are ren- 
 dered confpicuous by blowing air under the mem- 
 brane, or by maceration, or by injecHng water in- 
 to the artery. 
 
 DCLxxix. The nerves of the fpleen are fmall ; fo 
 that it is little fufceptible of pain, and is very rarely 
 inflamed. They arife from a particular plexus of 
 the pofterior branches of the eighth pair, (dcxxX.) 
 and of peculiar branches from the large gangliform 
 plexus, which the fplenic trunk of the intercoftal 
 nerve produces ; and they furround the fplenic ar- 
 tery with branches. 
 
 DCLxxx. The fabric of the fpleen appears to be 
 much more fimple than is commonly believed. For 
 it is compofed, both in man and in calves, entirely 
 of arteries and of veins ; the former of which are 
 remarkably branchy, and fubdivided into fewer 
 large branches, but into very numerous minute 
 ones, terminating finally in very tender twigs, very 
 difficult of injedlion, and arifing very crowded to- 
 gether ; from which there is a ready paffage into 
 the correfponding veins. Various authors have 
 confidered thefe pencils, with their parallel branch- 
 es, being fomewhat round, as glands. Injeftion, 
 rightly managed, never efcapes into any intervals ; 
 
 noy 
 
SPLEEN. 
 
 Chap. XXI. 
 
 332 
 
 nor have hollow glands ever been demonftrated 
 with certainty. Each little arterial trunk, with the 
 fmaller t wigs that proceed from it, is furrounded 
 by a very fine cellular web, in the fame manner as 
 in all the vifcera, but here rather fofter. The 
 whole body of the fpleen is externally furrounded 
 by a lingle membrane, hmple and not very firm, 
 continued from the peritonaeum, and joined to the 
 fubftance of the fpleen by thicker cellular fub- 
 flance. 
 
 DCLXxxi. Obfervation alfo teaches us, that the 
 fpleen contains more blood, in proportion, than any 
 other vifcus •, lince it has no mufcles, fat, air veffels, 
 or excretory duels, interpofed between its blood- 
 vellels. Its blood is fcarcely ever coagulated, has 
 a fomewhat dark colour, and from its dilution, col- 
 our, and greater proportion of water, ma) be al- 
 moll compared to the foetal blood. It abounds with 
 water and volatile fait’, but has lefs oil. 
 
 DCLXxxii. The want of an excretory duel to the 
 fpleen, has occafioned, in all ages, inquiries, doubts, 
 and controverfies, about its ufe. The following 
 feems to us to correfpond with its fabric ; al- 
 though, perhaps, all the ufes of the fpleen are not 
 comprehended by it. A great quantity of blood is 
 carried to the fpleen, (dclxxvii.) and, from the 
 denfity and ferpentine courfe of the artery, its mo- 
 tion is flow ; but, when the flomach is empty, at 
 which time it arrives in greater quantity, ar.d being 
 lefs compreffed, is retained in the fpleen, it in fome 
 meafure ftagnates, from the very great proportion 
 of branches to the trunks in this part ; and the dif- 
 hcult circulation of the blood of the fpleen through 
 the llraits of the liver. Hence the very frequent 
 fchirrofities of the fpleen ; hence that immenfc 
 quaiitity of blood with which the wliole fpleen is 
 dillended, and which is not found in any other vil- 
 cus in fuch epantity. Therefore the blood, in tins 
 warm ftuation, and fomented by the putrid faces 
 
Chap. XXI. 
 
 SPLEEN. 
 
 333 
 
 of the adjacent colon, is refolved, and afterwards 
 advances, in a certain degree, towards putrefac. 
 tion, as appears from its colour and fluidity. But 
 it is the more fluid, becaufe the fpleen has no fc- 
 cretory veflels, and therefore the whole quantity 
 of water enters the vein, which was brought by the 
 artery. 
 
 DC LX XXIII. Then, when the ftomach is filled 
 with food or flatus, the fpleen is comprefled into a 
 narrower compafs, againll the reflfting ribs and fu- 
 perincumbent diaphragm, and the blood which 
 was returning through the fplenic vein, flowly and 
 in fmall quantity, is fuddenly prefled out of the 
 ipleen, returns with celerity to the liver ; mixes 
 with the fluggifli blood loaded with the fat of the 
 omentum and mefentery, (dclxix.) dilutes it, pre- 
 ferves it from coagulation and ftagnation ; and, at 
 the fame time, it conduces to increafe the fecretion' 
 of bile, at the time when it is moft wanted, for the 
 procefs of digeftion which is then going on. The 
 Ipleen, tlierefore, feems to fupply to the bile fome 
 aqueous principle, but probably of a fubalkaline na- 
 ture, and acrid from its ftagnation. 
 
 DCLxxxiv. Is the fabric of the fpleen cellular ? 
 Does the blood poured out into thofe cells ftagnate ? 
 Is it diluted with fome juice fecreted by peculiar 
 glands ? Nothing of this is demonftrated by anat- 
 omy ; nor do liquids or wax ever efcape from the 
 arteries, unlefs injefted with two great violence. Is- 
 an acid juice prepared in the fpleen for the ftomach ? 
 That opinion is difcarded, as repugnant to the na- 
 ture of all the animal juices, and inadmiflible, from 
 the want of a paflage. Is the fpleen ufelefs ? Is this 
 proved, by the little injury animals fuftain from its- 
 extirpation ? The lofs even of a confiderable part does 
 not injure a robuft animal ; and yet there are exam- 
 ples, where, from its extirpation, the liver became 
 fwelled and difeafed,the bile more fcanty and darker,-^ 
 and troublefome flatulencies fucceeded, which are re- 
 ferable' 
 
PAITCREAS. 
 
 Chap. XAH; 
 
 ferable to the vitiated nature of the bile, the ob- 
 ftruflion of the liver, and diminillied powers of di- 
 geifion ; if they were confirmed by repeated ex- 
 periments. 
 
 CHAP. xxn. 
 
 PANCREAS. 
 
 DCLXXXv. pancreatic juice, which is wa~ 
 
 i tery, infipid, thin, neither acrid 
 nor alkaline, is excreted at the fame place into 
 which the bile is difcharged. 
 
 DCLXXXV I. The pancreas, the largefi; of the fali- 
 vary glands, is of great length, is fituated before the 
 left renal capfule and the aorta, above the inferior 
 lamina of the tranfverfe mefocolon ; (which beyond 
 the pancreas, behind its fuperior lamina, behind the 
 ftomach, before the fpleen, under and behind the 
 liver, joins wdth the inferior lamina ;) is of a flattifii 
 triangular fhape, with a light deprefiion on the up- 
 per part, and is covered with the peritonaeum. Up- 
 on it, being pofterior and inferior, the -pofteriof 
 fide of the empty firomach refts. The pancreas be- 
 gins at the fpleen itfelf ; extends almoft tranfverfe- 
 ly towards the right fide, acrofs the vertebrae, at the 
 light of which it grows broader, being received be- 
 twixt the fuperior and inferior plates of the tranf- 
 verfe mefocolon (dclix.) and is, finally, fo con- 
 nected by its round head to the duodenum, as to 
 ferve it for a mefenterjn It is like the falivary 
 glands, compofed of round, hardifli acini, connected 
 by a good deal of cellular fubftance. Its veflfels 
 are rather numerous than large, and are derived 
 chiefly from the fplenics ; but on the right fide it 
 is fupplied by thefirfi; artery of the duodenum, and 
 from another which is inferior, and is common to 
 
 the 
 
Ghap. XXII. 
 
 P^UnCREAS. 
 
 33 ^ 
 
 the duodenum and pancreas ; both of v/hich arife 
 from the hepatic artery, and of which the former 
 inofculates with the latter, and both with the me- 
 fenteric artery, which alfo fupplies conliderable 
 twigs to this gland 5 and minute branches come 
 from the phrenic and capfular arteries.* The nerves 
 are not conliderable, whence it is little fenlible ; 
 they are derived from the pofterlor gaftric, the he- 
 patic and fplenic plexufes, &c. 
 
 DCLxxxvii. The du6t runs through the middle 
 of this gland, white and tender, arifing every where 
 from an infinite number of roots, by which, being 
 gradually increafed, it emerges before the vena por- 
 tarum and mefenteric artery, having received a larg- 
 er branch from the larger part of the pancreas ; fol- 
 lowing the courfe of the duodenum, it arrives at 
 the fame part of the duodenum into which the bil- 
 iary du(T proceeds ; where, changing its courfe, it 
 defcends, and being extended into a finus, betwixt 
 the coats of the inteftine, internally fmooth ; and, 
 being continued, after having received the du^lus 
 choledochus, it opens in a particular fold in the 
 bottom of the descending part of the duodenum. 
 But it not unfrequently happens, that it opens by 
 an orifice diftind: from that of the biliary dud and 
 fometimes by two, of which the one, the lower, is 
 diftind and lefs ; but in man, and in moft other 
 animals, it always opens near the biliary dud. In 
 its orifice there is no valve. 
 
 DCLxxxviii. The quantity of fluid fecreted is 
 uncertain : but it mull be very conliderable, if we 
 compare it with the weight of the faliva, the pan- 
 creas being three times larger, and feated in a 
 warmer place. It is expelled by the force of the 
 circulating blood, and of the incumbent vifeera in 
 the full abdomen ; as the liver, llomach, fpleen,- 
 mefenteric and fplenic arteries, and the aorta. Its 
 great utility appears from its conflancy, being 
 found in almofl all animals : nor is it refuted by 
 
 the 
 
LIVER. 
 
 , Chap. XXIIL 
 
 the few experiments, in which a part of it was cut 
 out from a robuft animal without occahoning 
 death ; bccaufe the whole pancreas cannot be re- 
 moved without the duodenum ; for even a part 
 of the lungs may be cut out, without producing 
 death, but they are not therefore ufelefs. Its cf- 
 fcrvefcence with the bile arifes from the elfecl of 
 the ligature, and of air mixed with the inteftinal 
 liumour. 
 
 DCLXxxviii. It feems principally to dilute the 
 vifcid cyftic bile, to mitigate its acrimony, and to 
 mix it with the food. Hence it is poured into a 
 place remote from the cyftic duel as often as there 
 is no srall bladder. Like the reft of the inteftinal hu- 
 
 O 
 
 mour, it dilutes and refolves the mafs of aliments^ 
 and performs every other office of the faliva. 
 
 C H A P. XXIII. 
 
 LIVER, GALL BLADDER, AND BILE. 
 
 Dci.xxxix. liver, the largeft of all the 
 
 I vifeera, occupies a large part of 
 the abdomen, above the mefocolon ; and in the 
 foetus one ftill larger. Both above, and behind, and 
 before, and to the right, it is covered by the dia-. 
 phragm, from which it receives the peritonieum, 
 under the denomination of ligaments, chiefly in 
 three places. For on the convex part of the liver, 
 from the pallagc of the vena cava to the tranfvcrfe 
 furrow of the liver, the peritoneum defeends 
 double, growing broader anteriorly, under the 
 name of ligamentum fufpenforium, which dmdes- 
 the greater right lobe from the fmaller left lobe ; 
 and diverging, it expands into a membrane of the 
 liver, (dcxxiii.) white. Ample, thin, like the ex- 
 ternal coat of the ftomach, having cellular fub- 
 ftance under it, by which it is ioined to the fub- 
 
 ftaiu* 
 
Chap. XXIIL 
 
 LIVER. 
 
 xj -J i 
 
 fiance of the liver. To the lower margin of this, 
 the umbilical vein is United ; which, in the adult, 
 having almoft difapipeared, leaves a fibrous appear- 
 ance, with much fat. In the extremity of the left 
 lobe, and on the convex part, and not unfrequently 
 at its edge, a membrane goes to the liver from the 
 diaphragm ; which in children, ^nd in other in- 
 ftances, is frequently to the left fide of the cefo- 
 phagus, but in adults to the right fide ; and always 
 conjoined both to the gullet and to the fpleen, when 
 the liver is large. This is the left ligament. The 
 right ligament ties the diaphragm' very far back to 
 the very thick right lobe. Befides, but without any 
 apparent length, the membrane of the right lobe 
 of the liver is often conjoined with the diaphragm 
 by cellular fubftance in the right lobe, behind and 
 to the right of the oval lobule, more efpecially in 
 bid fubjects, for in the foetus it is eafily feparated ; 
 and betwixt the fufpenfory and left ligament, there 
 intervenes a production of peritonaeum, in like man- 
 ner continuous, refembling a ligament. But alfo 
 from the kidney, the peritonaeum going to the liv- 
 er makes a reduplication like a ligament ; and the 
 fmaller omentum, and the continuous loofe produc- 
 tions of the mefocolon (dclxiii.) unite the liver 
 with the ftomach, duodenum and colon ; and the 
 mefocolon alfo unites it to the pancreas. Thus 
 the liver is fufpended in the body with firmnefs, 
 and yet with confiderable mobility, fo that it may 
 be varioufly agitated and depreffed by the dia- 
 phragm. The fame ligaments form the common 
 membrane, which covers the liver as well as other 
 vifcera. 
 
 Dcxc. Moreover, the inner concave furface of 
 the right lobe of the liver, correfponds with its fore- 
 part to the colon ; and with its back part to the 
 right kidney and renal capfale, to which it is cor- 
 neCled by cellular fubftance. The middle finus is 
 contiguous to the duodenum, which touches the 
 Y gall 
 
LiVER, 
 
 Chap. XXIII. 
 
 33 ^ 
 
 gall bladder, and that part which conducls the great 
 blood-velTels. The left lobe extends largely over 
 the ftomach ; and frequently, efpecially in younger 
 fubjecls, is extended beyond the oefophagus into 
 the left hypochondrium. The lobule adapts itfelf 
 to the fmaller curvature of the ftomach. But, 
 moreover, the pancreas lies under the liver, and the 
 right venal capfule is tied to the part of the liver 
 fartheft to the right by much cellular texture. 
 
 Dcxci. The figure of the liver is difficult to de- 
 fcribe. It begins in the cavity of the right h) po- 
 chondrium, by a very thick folid protuberance, 
 convex towards the diaphragm, and hollow towards 
 tlie colon and kidney ; having a protuberant line 
 dividing thefe concave furfaces, which is continued 
 into the longer appendix of the lobule. After 
 this, the liver grows gradually flenderer and thin- 
 ner, and is extenuated, with an almoft triangular 
 ftiapc, into a tip, which palTes into the left hypo- 
 chondrium, acrofs the oefophagus, in young fubjeds, 
 as far as the fpleen ; but in adults, it is often fhort- 
 cr, and ends at the oefophagus. The edge, in which 
 the convex part of the liver meets with the con- 
 cave one, is wholly in the anterior and lower part. 
 The wliole obtufe margin lies backwards, d'he 
 upper and back part of the liver is every where 
 convex ; fuftains the diaphragm ; and with a large 
 portion, which is fomevvhat flatter towards the left 
 fide, it lies under the heart : but the lower furface, 
 varioufly figured, refts upon the duodenum, colon, 
 ftomach, pancreas, and right renal capfule. For 
 there are leveral fiflures which divide the furface 
 into different regions, which did not efcape the no- 
 tice of the ancients. 
 
 Dcxcii. The principal of thefe, the tranfverfe, 
 extends from right to left, and divides a third part 
 of the liver, beginning flender in the right lobe, 
 and growing broader towards the left. Before this 
 traniveric fifture, there is an excavation in the right 
 
Chap. XXIII. 
 
 LIVER. 
 
 339 
 
 lobe for the gall bladder ; then there is the convex 
 anonymous lobe ; and then the foffa of the umbilical 
 vein, extending tranfverfely backwards^ often cov- 
 ered with the bridge that joins the anonymous to 
 the left lobe. Behind the great fulcus in the right 
 fide, there is a tranfverfe eminence, {lender at its 
 commencement, growing broader tov/ards the right 
 and moderately hollow, by which the great blood- 
 velTels are conduced into the liver : the holknv 
 was by the ancients denominated the portae. This 
 joins the lobe, which I Ihall next defcribe, with the 
 right lobe. Then the pollerior lobule, papillary, 
 obtufely conical, projects into the little curvature of 
 the ftoma'chi The thick roOt of this and of the 
 former excavated eminence, begins from the con- 
 vex part of the liver, at the diaphragm ; and in 
 the right fide, is impreffed with an oblique furrow, 
 inclined to the right fide, fOr the trunk of the vena 
 cava, defcending from the heart to the lumbar ver- 
 tebrae, and frequently covered by a confiderable 
 portion of the fubftance of the liver, as by a bridge, 
 fo as to form a tube. The left end of the lobule 
 is terminated by another foffa almoft ftraight back- 
 wards, but alfo inclined to the left ; which begin- 
 ning at the extremity of the tranfverfe one, termi- 
 nates at the paffage of the vena cava through the 
 diaphragm. In this was lodged the duclus venoms 
 in the foetus, of which there are ftill fome remains 
 to be perceived in the adult. All that lies beyond 
 this is the left lobe, which is fimple, uniformly con- 
 cave below, fo as to lie upon the ffomach, and ex- 
 tenuated to an edsre. 
 
 Dcxciii. This very large vifcus is proportion- 
 ably fupplied with vefl'els, and of various kinds. 
 The artery, which is indeed confiderable, being the 
 greater and right portion of the caeliac, emerging 
 forwards and to the right, goes tranfverfely before 
 the vena portarum • and after giving off the fm.all 
 coronary and the pancreatico duodenalis, the latter 
 Y 2 of 
 
LIVER. 
 
 Chap. XXIIL 
 
 i4o 
 
 of which is pretty large, the reft enters the liver,- 
 commonly by two branches ; of which the left 
 fupplies the umbilical foffa, the venal duel, pofte- 
 rior lobule, with the left and the anonymous lobes, 
 and th& fufpenfory ligament ; this branch inofeu- 
 lates with the phrenic and epigaftric arteries. The 
 right lies deeper, covered by the biliary duels y 
 goes to the right and anonymous lobes, and fends 
 off, in one fmall trunk, the cyflic artery, which im- 
 mediately dividing into two, is fpread both under 
 and over the gall bladder, covered by its external 
 coat, and fupplies branches to the gall bladder and 
 biliary ducts, and likewife many to the liver. From 
 the left branch, or fom.etimes from the trunk, a- 
 fuperficial artery goes to the biliary duels, anony- 
 mous lobe, and glands of the portae. Befides the 
 caeliac artery, not very rarely,- a large right branch 
 is produced from the mefenterica major, creeping 
 behind the pancreas ; this ferves inftead of the 
 right hepatic branch of tlie caeliac. But, like^^dfe, 
 the greater coronary, which is the firfl twig of the 
 cadiac, always gives fome ramifications to the left 
 lobe, and to the foffa of the duftus venofus ; which 
 is often very confiderable. Thofe fent to the liver 
 from the phrenic, mammaries, renal and capfulary 
 arteries are fmaller.- They communicate alfo with 
 the epigaftrics.- 
 
 Dcxciv. In the foetus, the umbilical vein brings 
 a great deal of blood to the liver, at which time the 
 vein going, to the portse is but fmall. It fends 
 forth, while it flretches backwards through its foffa, 
 numerous and very large branches, each of them 
 equalling the vena porfarum in bignel's ; at this 
 place it is dilated into a tumor, which unites with 
 the left branch of the vena portarum. But it fends 
 a fingle branch through the poflerior part of the 
 horizontal foiTa into the vena cava, or into fomc of 
 its hepatic branches ; this is called the duclus veno- 
 fus. In the adult, indeed, this duel is obliterated, 
 
 and 
 
Chap. XXIII. 
 
 LIVER. 
 
 341 
 
 ^ind the vena portarum, which has now grown lar- 
 ger, fupplies the hepatic branches. 
 
 Dcxcv. The vena portarum receives all the blood 
 of the ftomach (dcxxix.) of the inteftines and me- 
 fentery (dcxxxi.) of the fpleen (dclxxvh.) omen- 
 tum (dccxix.) and, laftly, of the pancreas, at firft 
 into two trunks, the tranfverfe fplenic and amend- 
 ing mefenteric, and then into one, which is conti- 
 nued with the mefenterics. It is large,^ compofed 
 of ftrong membranes, ftronger than thofe of the 
 vena cava, afcends behind the firft flexure of the 
 duodenum, receives the veins from the right fide 
 of the duodenum, and the fmaller coronary, afcends 
 to the right in the finus of the lobule of the liver 
 (dcxcii.) and is afterwards again divided into two 
 large trunks. The right, which is fliorter, larger, 
 and bifurcated, having received the cyftic vein, goes 
 to its own lobe. The left proceeds through ‘the re- 
 maining part of the tranfverfe furrow of the liv^er, 
 and fupplies the lobule, the anonymous and left 
 lobe, and being refleffed, enters the umbilical fofla, 
 about the middle of which, it penetrates branchy 
 into the liver. There are inftances in which the 
 branch of the pofterior lobule rather proceeds from 
 the trunk of the vena portarum. 
 
 Dcxcvi. The vena portarum is furrounded on 
 every fide with a good deal of cellular fubftance, 
 wMch it brings with it from the mefentery and 
 fpleen ; and which being denfe and flrort,ftrengthens 
 the membranes, which are firmer than thofe of the 
 aorta itfelf. Intermixed with this cellular fubftance, 
 are alfo many fmall yelfels and the hepatic nerves, 
 which are all comprehended under the denomina- 
 tion of capfule, which is nothing more than the 
 cellular fubftance, and never has a Angle truly 
 flefliy fibre. The vena portarum carries this along 
 with it, through the liver, and is fuftained by it ; 
 infomuch, that the branches, when cut, being fup- 
 ported, preferve the roundnefs of their fedion. 
 
 Each 
 
LIVER. 
 
 Chap. XXIH. 
 
 34 ^ 
 
 Each branch of the vena portarum is divided into 
 many others, again divided and fabdivided, e\'en 
 to the fmalleft capillaries, as arteries commonly are. 
 Every branch of the vena portarum is accompanied 
 by a branch of the hepatic artery, creeping upon its 
 furface, and upon the hepatic duels, almolt in the 
 fame manner as the bronchial arteries ufually creep 
 along the bronchia ; and by a branch of the biliary 
 duct, which are both connecled by thin cellular 
 fubftance. Some go out of the liver, being divided 
 on the ligaments, and inofculating with the fur- 
 rounding veins. The fum of the branches in the 
 vena portarum is alv/ays greater than the trunk ; 
 hence the calibers of all the branches together, 
 greatly exceed that of the trunk (xxxva.') Hence ; 
 there is a great degree of friclion, (clxxx. and 
 CLXii.} exactly as in the arteries. 
 
 Dcxcvii. But as the blood is conveyed to the liver 
 by the vena portarum, as well as by the hepatic ar- 
 tery, it muft of courfe be conveyed away by fome 
 other vein. Therefore, the extreme branches of 
 the vena portarum and hepatic artery inofculate 
 ultimately with other veins, which are branches of 
 the cava ; arifing from the whole circumference of 
 the liver, they run towards the pofterior gibbous 
 part of the liver, unite into branches and trunks, 
 which at laft terminate in ten or more large velfels. 
 'I'he fmaller and more numerous of thefe, arife from 
 the pofterior lobule and liver, and go to the cava, 
 where it afeends towards the left, to the diaphragm, 
 through the fulcus, that lies on the right fide of the 
 lobule, and is often included by a bridge thrown 
 over it. The remaining two or three, which are 
 much larger, are inferred into the fune cava, cirfe 
 to the diaphragm, whofe veins they often receive. 
 The branches of the vena cava are, in the adult, on 
 the whole, fewer than thofe of the vena portarum ; ' 
 
 which is an argument that the blood moves more 
 quieddy through thefe branches, on account of the 
 
 dinunuti'^u 
 
Chap. XXIII. 
 
 LIVER. 
 
 343 
 
 diminution of the friction, (clxx.) and of the very 
 colleftion of the blood into a lefs caliber, which 
 always accelerates its courfe, when there is a fufh- 
 cient compreffing force (clxx.) I know not of 
 any valves in the mouth of thefe veins, which de- 
 ferve to be remembered. The trunk of the vena 
 cava afcends through a foramen of the diaphragm, 
 obtufely quadrangular, included by mere tendons 
 furrounding it ; and therefore (cclxii.) not eafily 
 variable : and immediately expands into the right 
 auricle. The fmaller veins of the ^iver, creeping 
 upon its furface, are fent from the phrenica, rena- 
 lis and azygos ; or at leaft there is a communication 
 betwixt thefe and the hepatic veins coming from 
 the portae. 
 
 Dcxcvin. That the blood comes from all parts 
 (dcxcv.) by the vena portarum to the portae, is 
 proved by ligatures, by which the veins fwell be- 
 twixt thefe parts and the ligatures ; while the vena 
 portarum itfeif grows flaccid and empty. But that 
 it afterwards goes through the liver to the cava, 
 is proved by anatomical injections, which fhow the 
 anaftomofes, and open communication betwixt the 
 vena portarum and the cava, and by the common 
 nature of the veins going to the cava. Again, the 
 difliculty of the arterial diftribution of the vena por- 
 tarum, as being remote from the heart, and the 
 oily nature of its blood, occafion it to fcagnate, accu- 
 mulate and form fcirrhous fwellings in the liver 
 oftener than in any other part. But this danger is 
 diminilhed by mufcular action, and refpiration ; 
 and is increafed by reft, indolence, and four and vif- 
 cid aliments. Elitherto, we have been fpeaking of 
 the adult liver, in which both the umbilical vein 
 and the duclus venofus are empty, although they 
 cohere with the left branch of the vena porta- 
 rum. 
 
 Dcxcix. The nerves of the liver are rather nu- 
 merous than large ; hence, when wounded or in- 
 
 flapaed. 
 
LIVER. 
 
 Chap. XXIII. 
 
 344 
 
 flamed, it caufes a moderate degree of pain. They 
 have a twofold origin. Moft of them arife from 
 the large gangliform plexus of the fplenic branch 
 of the intercoftal nerve, with the addition of a 
 branch from the pofterior plexus of the eighth 
 pair ; they accompany the hepatic artery, and, 
 playing around its trunk, go to the liver, with that 
 and the branches of the , vena portarum. Anoth- 
 er fafci'culus of nerves ufually enters with the duc- 
 tus venofus, and arifes from the pofterior plexus 
 of the eighth'pair, but fometimes, from the great 
 plexus. 
 
 Dcc. The lymphatic veflels of the liver are nu- 
 merous, and may be conftantly and eaftly feen about 
 the portae. They arife from the whole concave fur-; 
 face of the liver, and from the furface of the gall 
 bladder, run together into a plexus, furrounding 
 the vena portarum, and go to the conglobate glands, 
 feated before and behind the faid vein j from whence 
 they meet together in one large trunk, wdrich is one 
 of the roots of the thoracic duct. L^pon the con- 
 vex part of the liver, are deferibed other lymphat- 
 ics, v/hofe infertion is not well known ; for it is 
 hardly probable that they enter the cava, nor have 
 they been fufticiently often traced to the receptacle 
 of the chyle. 
 
 Dcci. The interior fabric of the liver is more ob- 
 feure. Through the whole liver, bundles of bil- 
 iary veflels, of branches of the vena portarum, and 
 of the hepatic artery, are diftributed. Each vef- 
 fel has both its proper cellular texture furrounding 
 it, and ligaments of the fame fubftance, by which 
 it is tied to its fellow veflels ; and, laftly, the whole 
 bundle is furrounded by cellular texture. The 
 branches of the vena cava lie on the cutflde of the 
 others, being lefs accurately received into the fame 
 bundle. Laftly, the ultimate branches of the ve- 
 na portarum, cava, and hepatic artery, and of the 
 biliary du<5ts, which we Ihall foon deferibe, are uni- 
 
LIVER. 
 
 Chap. XXIII. 
 
 345 
 
 ted together by means of cellular fubftance (dcxcvi.) 
 into a fort of acini of a fomewhat hexagonal fliape, 
 ifurrounded with lax cellular fubftance. In thefe 
 bunches, likewife, there are mutual anaftomofes of 
 the branches of the vena portarum, and of the he- 
 patic artery, with the roots of the vena cava, and of 
 the branches of the vena portarum, with the firft 
 origins of the pori biliarii ; which laft connexion is 
 demonftrated by anatomical injeftions ; for liquors 
 injected into the vena portarum, at laft return 
 through the porus choledochus. 
 
 Dccii. Many eminent anatomifts have taught, 
 that thefe acini are hollo^vvhaving arteries and 
 veins fpread upon their external furface, and that 
 the bile, fecreted from the branches of the vena 
 portarum, is depoftted into their cavities. They 
 derive their arguments from the anatomy of brutes, 
 in whofe liver the acini are round, and more de- 
 fined than in man ; and from difeafes, which exr 
 hibit cells and round tubercles, filled with lymph, 
 chalk, and various kinds of concreted matter. I'q 
 this, they might have added the lentor of the bile, 
 by which it refembles mucus, and the analogy of 
 the follicles of the gall bladder. 
 
 Dcciii. But greater accuracy in anatomy does not 
 admit thefe follicles into which the fmall fecretory 
 veflels are faid to open ; for fuch would intercept the 
 courfe of wax injecftions, and would occafton inter- 
 mediate knots betwixt thefe veflels and the biliary 
 pores, which have never yet been feen ; for the wax 
 flows in one continued thread, without any retar- 
 dation, effufion into a cavity, or diminution of its 
 impetus, from the vena portarum into the biliary 
 du<fts. Nor could the great length of the biliary 
 duels admit of a glandular fabric. For all follicles 
 depoflte, at no great diftance, their fluid, which is 
 not fitted for a long courfe, as they deftroy fo great 
 a part of the velocity received from the arteries. 
 
 Laftly, 
 
346 
 
 LIVER. 
 
 Cha?. xxm. 
 
 Laflly, the very common preffure, would fo crufh 
 thefe bundles of acini, which vx mull fuppofe, that 
 the motion of the excretory duel could derive no 
 affiftance from thence. The concretions and hy- 
 datids are formed in the cellular fubfrance ; and, 
 laftly, the bile, when lirft fecreted, is fufficientiy 
 fluid. 
 
 DC CIV. Again, we are convinced, that no bile is 
 feparated from the hepatic artery, by the peculiar 
 ftruebare of the vena portarum, which would be 
 ufelefs if it fecreted nothing ; by the continuity 
 of its branches with the biliary dufts, which is 
 much more evident than in the arteries ; by the 
 experiment, in which it appears that the biliary fe- 
 cretion continues after the hepatic arter)’- is tied ; 
 by the great fize of the biliary ducts, in proportion 
 to fo fmall an artery, and by the peculiar nature of 
 the blood collected in the vena portarum, which is 
 perfectly adapted for the iecretion of bile. For it 
 contains both oil, which abounds m.ore in the bile 
 than in any other humour of the body ; and a fa- 
 ponaceous fluid, abforbed from the ftomach, and 
 the alkalefcent fiibfetid vapour of the abdomen, 
 i'lought back from the whole furface of the intef- 
 tines, flomach, omentum, liver, fpleen, and mefen- 
 ter%', as we know by evident anatomical experi- 
 ments ; and, finally, the alkalefcent femiputrid, ac- 
 rimonious humidity, abforbed from the alvine fe- 
 ces themfelves, while they are indurated in the large 
 inteftines, and brought thither by the internal he- 
 morrhoidal veins, from whence that bitternefs, al- 
 kalefcent and putrefeent difpofition of the bile is 
 derived. But in the blood of the hepatic arter}', 
 there is nothing which renders it peculiarly fitted 
 for the fecretion of bile, or analogous to it. 
 
 Dccv. Since, therefore, the vena portarum con- 
 veys the blood, in its fitteft Rate, for the fecretion of 
 bile, to the ultimate acini of the liver, (neen'-,' 
 as there the paflage, from each branch of the 
 
 ve:.a 
 
Chap.XXIII. 
 
 LIVER. 
 
 347 
 
 vena portarum, into the beginning of the biliaiy 
 du<fts, is diredf without any intermediate follicle, 
 and as fluids injefted into the vena portarum read- 
 ily take this courfe, the bile vdll be propelled that 
 way by the force of the blood furrounding it, and 
 urging it from behind, and alfo by the accefibry force 
 of the diaphragm prefling the liver againfl; the refl: 
 of the vifcera in the very full abdomen, (dclxxxix.) 
 and again of the thorax, contracled in exfpiration, 
 it will be forced into the larger branches, and laft- 
 ly into the two trunks of the hepatic biliary duff ; 
 which trunks meet together in one on the vena 
 portarum, and in the tranfverfe folfa of the liver, 
 near the anonymous lobe. 
 
 Dccvi. This duel is compofed of a ftrong nervous 
 membrane, like that of the inteftines, and of an 
 external and internal cellular coat, and of a villous 
 coat, loofe, elegantly reticulated, but afperated v/itli 
 many fmall pores and flnufes, and continuous wdth 
 that of the inteftine. There is no certainty of any 
 mufcularity. From experiments, it appears to have 
 3 moderate degree of irritability. That it is vaftly 
 dilatable, is flaown from difeafes. They feem alfo 
 to flaow that this duel is pofl'effed of great fenfibil- 
 ity. _ 
 
 DC evil. The hepatic duel, thus formed, goes 
 along the vena portarum, more to the right than 
 the artety, towards the pancreas ; and then defeend- 
 ing obliquely, covered by fome part of that gland, 
 it comes in contadl with the back and lower part 
 of the fecond flexure of the duodenum, about fix 
 inches from the pylorus ; paffes through an interval 
 in its flslhy fibres ; meets vdtli an oblique oblong 
 liiius, made by the pancreatic du6l, and opens into 
 it by a narrow orifice. This finus defeends oblique- 
 ly a long way through the fecond cellular coat, of 
 the duodenum, pertprates the nervous coat, and 
 again runs obliquely between it and the villous tu- 
 nic 5 and, laflly, opens into a protuberant long tail- 
 ed 
 
LIVER. 
 
 Chap. XXIII. 
 
 34S 
 
 ed wrinkle of the duodenum. Between the firft ar- 
 rival of this duel at the duodenum and its orifice, 
 a finus, almofi; an inch long, which receives the 
 duflus choledochus, is inclofed between the mem- 
 branes of the inteftines, fo that when this inteftine 
 is filled, or diftended by flatus, or clofely contracl- 
 ed by a violent periflaltic motion, it muft be confe- 
 quently compreffed and fhut ; but when the duode- 
 num is relaxed, and moderately empty, it difeharges 
 itfelf. Any regurgitation from the duodenum is 
 hindered by this obliquity, and by the wrinkle, 
 which is eafily prelTed together, or clofed, and by 
 the very eafy defeeut of frefh bile through the duel. 
 Even air does not find its way from the inteftine in- 
 to tlie duel. 
 
 Dccviii. But in the very portae, this duel receives 
 the addition of another lefs canal of the fame kind, 
 for a good way parallel, and adhering to it, and 
 inferted into it in a very acute angle. This is 
 called the cyflic duel, from its origin, and is 
 fometimes firfl increafed by another duct from 
 the liver. It arifes from the gjall bladder, which is 
 found in moil animals ; but is abient in fome, efpe-r 
 dally the fwift footed, and perhaps only the herbi- 
 vorous. It is contained in an excavation of the 
 right lobe of the liver, (dccxcii.) to the right of 
 the anonymous lobule, in fuch a mamner, that in 
 young people, it lies entirely vnthin the edge of 
 the liver, but in adults projeds confiderably be^ 
 yond it, lying upon the colon. Its fituation is tranf- 
 verfe, from before backwards ; its neck afeends a 
 little. 
 
 Dccix. The fismre of the trail bladder is variable, 
 but in general like that of a pear ; it is terminat- 
 ed before by an obtufe, hemifpherical, imperdous 
 end ; and gradually diminifhes backwards ; the neck 
 or tip of this truncated cone being refiecled againll 
 itfelf once or twice, and tied together by proper 
 cellular fubftance ; and having made another flex- 
 ure upwards, ends in the cyflic dud 5 which from 
 
 thence 
 
LIVER. 
 
 Chap. XXIII. 
 
 349 ' 
 
 thence goes towards the left fide of the hepatic du<d:. 
 But this dud, being alfo contraded by many cellu- 
 lar bands, is internally marked with many protu- 
 berant wrinkles, which, conjundly in the dried gall 
 bladder, reprefent a kind of fpiral valve ; but be- 
 ing foft and alternate in the living body, they re- 
 tard, but do not entirely obftrud, the courfe of the 
 bile either way, as is proved by experiments, made 
 with air and prelTure. Befides, it is reticulated like’ 
 the gall bladder itfelf. 
 
 Dccx. The outermoft coat of the gall bladder cov- 
 ers only its lower fide, being the common covering 
 of the liver itfelf, ftretched over the gall bladder, 
 and retaining it in its fituation. The fecond is 
 a loofe cellular coat. The third coat has fome- 
 times fplendent longitudinal fibres, in different di- 
 rections, fo as obliquely to interfect each other. At 
 other times, it has none j fo that w^e may doubt of 
 its mufcular nature, efpecially as the irritability of 
 the gall bladder is flow and obfeure. The nervous, 
 fecond cellular, and villous coats, are found as in 
 the inteftines, except that the laft, as in the biliary 
 duds, is reticulated and full of cells. In the gall 
 bladder, efpecially about its neck, but even as far as 
 its middle, we obferve muciferous pores, capable of 
 receiving a briftle ; and arteries, as in other places, 
 difeharge fome watery humour into the cavity of 
 the gall bladder, and bile eafily tranfudes through 
 inorganic pores to the furface of the gall bladder, 
 and neighbouring membranes. 
 
 DC CXI. Ail animals, between their gall bladder 
 and liver, or between their duds, have alfo fome 
 peculiar openings into the gall bladder, into which 
 fome duds, originating from, the liver, or from the 
 hepatic biliary dud, open. In man, fimilar duds 
 have not been fhowm by any certain experiment, and 
 the gall bladder, when full of bile, is eafily fepara- 
 ted from the liver, wdthout a drop of bile efcaping 
 either from it or from the liver. There is alfo a 
 
LIVER. 
 
 3 5-5 
 
 Chap. XXIII. 
 
 thin water in the bladder as ofterx as the cyftic dudt 
 is obftrucced. 
 
 Dcexii The bile naturally flows both out of the 
 bladder and liver, whenever there is no impediment 
 in its courfe ; fo that both duels fwell when tlie paf- 
 fage is obftru6led, and the cyftic lies in a ftraight 
 line with the choledochus. Nor is it probable that 
 the whole of the bile is fent into the gall blad- 
 der before it flows into the duodenum. There is 
 not a perpetual obftacle which hinders its efilux, 
 and peculiarly obftrucls the hepatic bile, and ad- 
 mits the cyftic ; the paflage into the duclus chole- 
 dochus is larger and ftraighter, the duclus cyfticus 
 much lefs than the hepatic, and therefore not form- 
 ed for receiving all the bile ; the choledochus, much 
 larger than the cyftic, and therefore not appointed 
 for the reception of its bile only. There are many 
 animals in which the hepatic duel enters the in- 
 teftine without any communication with the cyf- 
 tic. In living animals, even when the cyftic dueft 
 is free, the bile appears to defeend into the duode- 
 num with a perpetual current. That the quantity 
 is very confiderable, appears from the magnitude of 
 the fecretory organ, and of the excretory duel, 
 which is fo many times larger than the fdivary 
 ones ; from difeafes, in whicli four ounces of cyftic 
 bile only have flowed out daily through an ulcer of 
 the ftde. But the hepatic bile goes into the gall 
 bladder, as often as there is any obftruclion in the 
 duodenal iinus, from flatus, or any other caufe ccm.- 
 prefling the orifice of the duclus choledochus. Ac- 
 cordingly, it is found- extremely full, whenever the 
 common biliary duel is comprefted by any feirrho- 
 fity or tum-our, and it is fometimes enlarged beyond 
 all belief ; if the cyftic dull be tied, it fwells be- 
 twixt the ligature and its union with tlie hepatic 
 duel ; and in living animals, the hepatic bile has 
 been feen to diftU into the wounded gall bladder. 
 This is not inconuftent with tlic retrograde angle- 
 
 t T 
 
Chap. XXIIL 
 
 LIVER. 
 
 351 
 
 foP a very flight preflure urges the bile from the 
 liver into the gall bladder ; and air eafily takes the 
 fame way, more efpecially if the duodenum be firtl 
 inflated. Nor does there fcem to be any other bile 
 fecreted by the gall bladder. Whenever the cyftic 
 dud is obftruded by a calculus, or by a ligature 
 made upon it, we find nothing in the gall bladder, 
 except a fmall quantity of iniipid mucus, fecreted 
 from the follicles, (dccx.) or fome watery exhala- 
 tion. In many animals, we meet with no appear- 
 ance of a gall bladder, when, neverthelefs, plenty 
 of acrid and falutary bile is difcharged into the in- 
 teftines. It does not feem probable, that any bile is 
 fecreted in the gall bladder from the cyftic branch 
 of the vena portarum, for that is a mere returning 
 veflel ; nor from the hepatic artery, for it is fcarce- 
 ly probable, that the very acrid cyfiic bile fhould 
 be feparated from a milder blood than milder hepa- 
 tic bile prepared from appropriated blood (ncciv.) 
 
 Dccxii. Laftly, the bile flows aifo from the gali 
 bladder to the liver, and at length returns into the 
 blood, when its pafl’age into the inteftines is totally 
 intercepted, fometimes alfo from a latent caufe exift- 
 ing in the nerves. This courfe is morbid, and pro- 
 duces the jaundice ; which, therefore, is cured by 
 the paiTage of the calculi, and by reftoring its free 
 courfe. 
 
 Dccxiii. Therefore, a portion of the hepatic bile 
 being received into the gall bladder, ftagnates, be- 
 ing only gently agitated by refpiration, and there 
 exhales its thinner parts, which we fee extenfively 
 diffufed over the adjacent membranes. The re- 
 mainder, being oily and fubalkaline, from its warm 
 situation, grows acrid and rancid, and its thicknefs, 
 bitternefs, and colour are increafed ; nor is there 
 any other difference betwixt the cyfUc and hepatic 
 bile, which lafl: we find in the duels, lefs bitter, lefs 
 dark coloured, and lefs vifeid. That this difference 
 proceeds only from ftagnation, appears from fuch 
 
 animals 
 
LIVER. 
 
 Chap. XXIIL 
 
 352 
 
 animals as have only a larger porus hepaticus, in- 
 ftead of a gall bladder ; for the bile which ftagnates 
 there, is remarkably more bitter than that in the liv- 
 er ; as, for example, in the elephant. But the 
 gall bladder gives this particular advantage, that it 
 receives the bile, when, the ftomach being empty, 
 it is of no ufe, and fupplies it more quickly when 
 we principally Want it for the digeftion of the ali- 
 mcnts, now flowing in great quantity into the duo- 
 denum. This quicknefs is greater in proportion as 
 the cylfic duel is fmaller than the gall bladder. 
 
 Dccxiv. The gall bladder, indeed, does not touch 
 the flomach, but the beginning of the defeending 
 duodenum. But when the ftomach is diftended, 
 and occupies a confiderable fpace in the very full 
 abdomen, it both preftes the liver and duodenum, 
 and comprefles the gall bladder, and empties it. 
 Thus the bile flows through a free paflage, from 
 the gall bladder into the biliary duel, and into the 
 duodenum 5 moft eafily in perfons lying on their 
 back, for then the bottom of the gall bladder is up- 
 permoft. Hence the gall bladder becomes turgid 
 after fafting. There is fcarcely any other evacua- 
 ting power than the ftomach and diaphragm ; for 
 that reflding in the proper mufcular and contractile 
 membrane of the gall bladder, is very inconlidcr- 
 able. 
 
 Dccxv. The hepatic bile is always bitter, but 
 the cyftic more fo ; always vifeid ; of a full yellow 
 colour, with a tinflure of green ; mifciblc, by tritu- 
 ration, with wa'ter and oil, and with \dnous fpiritsr 
 coagulable by the mineral acids ; foluble in the 
 alkalies, efpecially the volatile alkali ; well adapted 
 for diflblving oily, refinous, or gummy fubftances j 
 of a lixivial and faponaceous nature ; quickly pu- 
 trefying, and by putrefadlion fpontaneoufly acquir- 
 ing the odour of muik. Its chemical analyfls, and 
 experiments of mixture with various fabftances, de- 
 monftrate, that it contains a large portion of water. 
 
Chap. XXIIL 
 
 LIVER. 
 
 353 
 
 and a confiderable quantity of the inflammable oil, 
 which is fo evident in cyflic calculi. It therefore, 
 is a foap ; but of that fort which is compofed of a 
 volatile alkaline fait, m.ixed with oil, and retains its 
 water. Therefore, being intermixed with the ali- 
 ment, reduced to a pulp and exprefled from the 
 ftomach by the periftaltic motion of the duodenum, 
 and preflure of the abdominal mufcles, it in a great 
 meafure overcomes the acefcent qualities of the 
 food ; it diflblves the coagulum of milk, and dif- 
 pofes the aliment more to putrefcency ; it diflblves 
 the oily matters, fo that, by freely incorporating 
 with the watery parts, they may form chyle, and 
 enter the lacteals ; it abflerges and attenuates the 
 mucus ; and, laftly, excites the periftaltic motion 
 ty its acrimony ; all which offices are confirmed, 
 by obferving the oppofite difeafes to arife from a 
 want of bile. Nor is the hepatic bile ftifficient to 
 evacuate the inteftines, if the cyftic is wanting. So 
 great is its utility, that perfe<ftly robuft animals 
 have been found to die in a few days, by prevent- 
 ing the afflux of bile to the inteftines, or deftroying 
 the gall bladder. 
 
 Dccxvi, The bile gradually defcends along with 
 the food, and is evacuated along with the faeces, 
 fomewhat changed, its bitternefs being deftroyed 
 by putridity. Perhaps fome of the watery, leaft 
 bitter, and thinneft parts, are again taken up by the 
 vena portarum. Its regurgitation into the ftomach 
 is impeded by the afcent of the duodenum, at the 
 bottom oif which it enters, by the valve of the py- 
 lorus, and by the accefs of new chyle which the fto- 
 mach adds to the former : in man, however, it fre- 
 quently happens, and in birds always. The bile in 
 the foetus is bland and fweet ; for in them no fetid 
 fasces fupply acrid alkaline vapours, nor is there 
 any oil abforbed. As the bile is vifcid in fluggilh 
 and fat animals, and in man from the fame caufes, 
 and from grief, it readily forms hard coagulums, 
 Z either 
 
INTESTINES. 
 
 Ghap. XXIV- 
 
 354 
 
 either calcareous or refinous, and much more fre- 
 quently than the urine, according to our experi- 
 ments. Its ufe is manifeft, as, by trituration with the 
 aliments, it dilfolves oil, refifts acidity, and ftimu- 
 lates the inteftines to contraction. 
 
 uccxvii. In the fetus, behdes fecreting the bile, 
 the ufe of the liver is evidently to tranfmit the blood 
 returning from the placenta, and, as it feems, to 
 moderate its impetus. Even in the adult, it has the 
 fame ufe, though lefs manifeftly, in retarding the 
 return of the blood coming back from the chylo- 
 poetic vifcera. 
 
 CHAP. XXIV. 
 
 SMALL INTESTINES. 
 
 Dccxviii. 1 ~) Y the fmall inteftines, anatomifts un- 
 
 derftand one continued, and almoft 
 cylindrical tube, whofe tranfverfe fecHon is nearly 
 oval, the obtufe end being towards the unconnecled 
 fide of the inteftine. This tube being continued for 
 a long w^ay from the end of the ftomach, the right 
 orifice of wEich it embraces, (dcxxv.) terminates by 
 expanding into a larger inteftine. Anatomifts have 
 uftially reckoned three fmall inteftines, though na- 
 ture has formed but one. However, the duodenum 
 has a tolerable fixed limit, at the bottom of that 
 part of the abdomen which is above the tranfverfe 
 mefecolon (dclix.) But that fmall inteftine which 
 lies below this mefocolon, has no certain mark of 
 diftinclion, by which the jejunum, commonly fo 
 called, is feparated from the ileum : for although 
 
 the former abounds more with valves and blood-vef- 
 fels, and is furniflied with longer villi, and there 
 fore appears fomewhat redder ; and the ileum again ! 
 rather contains glands, and has fewer vafcular ram- 
 ifications j thefe differences inienfibly occur, with- 
 out 
 
I^TTESTINES. 
 
 Chap. XXIV. 
 
 out any certain limits, being great in tlieir extremcj 
 and obfcure in their contiguous terminations. 
 
 DccxiXi The duodenum is denominated from its 
 length. It is lax and large, efpecially in its firft 
 flexures^ becaufe in part it has no external mem- 
 brane, and in part is not completely furrounded by 
 it. It is florid and tender, and has flefhy fibres of 
 confiderable thicknefs. It begins by adhering round 
 the annular orifice of the pylorus ; then it proceeds 
 undulating, but on the whole tranfverfe, to the right 
 and backwards in the empty flomach, to the gall 
 bladder, to the neck of which it becomes conti- 
 guous (dccXiv.) From thence it defcends oblique= 
 ly to the right, and backwards as far as the lower 
 plate of the mefocolon, and the entrance of the bil- 
 iary duct, and in that courfe is received betwixt 
 the upper and lower plates of the mefocolon. From 
 thence it again returns, tranfverfely, but at the fame 
 time afcCnding, behind the pancreas and large me- 
 fenteric veffels, to the left, along with the left renal 
 vein ; it goes out from the duplicature of the plates 
 of the mefocolon ; and making a turn^ it defcends 
 on the right of the faid veffels, through a peculiar 
 foramen, in which the mefentery, left and tranf- 
 verfe mefocolon, adhere to it, to the lower part of 
 the abdomen, which it enters, and becomes the je- 
 junum. The largenefs of this intefline, its afcent 
 from the infertion of the biliary duff, its fucceeding 
 flexure around the root of the mefentery, caufe fome 
 delay, by which the bile and pancreatic juice are 
 here efpecially mixed with the alimentary mafs. 
 
 Dccxx. In the reft of the fmall inteftine there Is 
 no certain point ; but with uncertain and infinite 
 convolutions, not to be defcribed, it fills the lower 
 part of the abdomen and the pelvis, furrounded by 
 the colon, and alfo lies between the bladder and 
 
 I 
 
 I uterus. 
 
 Dccxxi. The fabric of the fmall inteftine is aft 
 moil the fame with that of the ftomach and cefo- 
 z 2 phagus. 
 
INTESTINES. 
 
 Chap. XXIV' 
 
 35 ^ 
 
 phagus. Excepting part of the duodenum, it re- 
 ceives an external coat from the peritonaeum, or 
 mefenter}g applied to the acute vertex of the intef- 
 tine, double, and feparated there by fome cellular 
 fubftance, often by fat, but clofely embracing the 
 reft of the inteftine, fo that its mufcular fibres ad- 
 here to the external membrane, which does not at 
 all differ from that of the ftomach. By this exter- 
 nal membrane, and by the mefentery (dclxi.) the 
 inteftines are fupported as firmly as is neceffary, 
 and with very great mobility. 
 
 Dccxxin But the mufcular coat is different, from 
 the difference of figure. The moft confiderable 
 ftratum of fibres in the inteftines is circular ; they 
 furround the tube on every fide, and are uniform, 
 parallel, formed of imperfecl arches, cemented into 
 circles, pale, and yet remarkably contractile. The 
 longitudinal fibres are, in the I'mall inteftines, few 
 in number, and fcattered round their whole extent, 
 but efpecially laid over the others on the obtufe 
 vertex of the inteftine. 
 
 occ XXIII. Within the mufcular coat, is feated 
 the fecond cellular, larger, as in the ftomach, fpread 
 on all fides round the nervous coat, and in man 
 rarely fat. But the nervous coat, as in the ftomach, 
 ferves as the foundation for the v'hole inteftinal 
 tube ; it is compofed of compacted fibres, which, by 
 inflation, may be feparated and difunited, fo as to 
 afl'ume a cellular appearance. Next follows the 
 third cellular coat, which is almoft like the fecond. 
 The innermoft, the villous, differs from that which 
 we defcribed in the ftomach : for, firft, it is every 
 where folded into wrinkles, generally femicircular, 
 but alfo into others joining the femicircular ones 
 obliquely, and into others varioufly irregular, into 
 which the nervous coat flightly enters, but the third 
 cellular enters deeply, lying between the doubled 
 villous coat, and fiUing up the duplicature. Thefe 
 folds begin within one inch of the pylorus, and are 
 
 moft 
 
Chap. XXIV. 
 
 INTESTINES. 
 
 357 
 
 moft numerous in the firft half of the inteftines, 
 dut gradually diminilh in number. In each of thefe 
 a fmall artery and vein lie upon the convex furface 
 of its fecond cellular coat. The firft plicae in the 
 duodenum are confufed, and lie nearly in the di- 
 rection of the inteftine. They are changed into 
 acute circles and valves by anatomical preparation. 
 They are indeed foft, and eafily inverted, and yield 
 to the paflage of the alimentary pulp either way, 
 but by their number they retard it, and enlarge the 
 furface of the villous membrane. 
 
 Dccxxiv. Laftly, the membrane is here truly vil- 
 lous, which in other parts is fo named from analo- 
 gy. Namely, the whole internal furface of the in- 
 teftine, both the valves, and the intervening hol- 
 lows, fend out every where innumerable pendulous 
 flocculi, refembling filk velvet, which are conical, 
 but fomev/hat obtufe, produflions of the inner coat 
 of the inteftine, containing cellular fubftance be- 
 tween the duplicature, and veflels and nerves wrap- 
 ped up in that fubftance, and likewife a lafteal vef- 
 fel, fuch as we lhall afterwards defcribe, fo as very 
 much to refemble the papillae of the tongue, except 
 in being fofter. 
 
 Dccxxv. The chief veflTel of each of the villi is 
 an oval vcflel, opening by a flender duct in the fur- 
 face of the villous coat, often filled with a milky 
 fluid, and furrounded by neighbouring veffels. 
 
 Dccxxvi. In the internal furface of this villous 
 coat, open an infinite number of pores ; fome larg- 
 er, others fmaUer. The former lead to confpicuous 
 fimple mucous glands, featcd in the third cellular 
 ftratum, fimilar to thofe feated in the mouth and 
 pharynx, having a very vafcular follicle, and an ori- 
 fice opening into the inteftine, In the duodenum 
 there are feveral of them which are contiguous, but 
 do not run together, and cannot always be demon- 
 ftrated ; in the ileum they are very numerous, both 
 folitary, a few joined together, and in confiderable 
 
 numbers 
 
INTESTINES. 
 
 35S 
 
 Chap. XXIV. 
 
 numbers collecled into an elliptical figure. They 
 are furroundecj by villous membrane. 
 
 Dccxxvii. The fmaller pores are found through- 
 out the whole inteftines, and furround the bafis of 
 the yiili ; they are moft confpicuous in the large 
 Inteftines, where they have been long known, but 
 have been lately difcovered in the fmall inteftines 
 Tkewife. Thefe alfo feem to depoftte a liquor of 
 the mucous kind. 
 
 Dccxxviii. The veftels of the fmall inteftines are 
 very num.erous. The common larger trunk belongr 
 ing to that part of the inteftine that lies below the 
 mefocolon, is called the mefenteric artery, which is 
 the largeft of thofe produced by the aorta, and fit- 
 uated above the renal arteries. Defcending behind 
 the pancreas, to the riglit of the beginning of the 
 jejunum, and beftdes the colic branches, being efpe- 
 cially produced in a long trunk towards the right, 
 to the bottom of the mefentery and termination of 
 the ileum, it fends numerous branches from its left 
 lide, the firft and laft being fliorter, the middle ones 
 longer. Thefe, fubdividing into fmaUer, join with 
 thofe adjacent into convex arches ; which again 
 fend out other branches, united in like manner, 
 forming almoft five feries of arches, until the laft 
 fend, from their convexities, ftraight and very nu- 
 merous branches to the inteftine. 
 
 Dccxxix. The diyifion of thefe branches on the 
 inteftine, is very uniform ; fo that from the mefen- 
 tery, through the firft cellular coat, there is fent 
 one anterior, and another pofterior, which, having 
 given fmaU branches to the outermoft and flefhy 
 coats, penetrate to tlic feccnd cellular one : there 
 the anterior trunk, running out towards the obtufe 
 vertex of the inteftinal ellipiis, is continued ftraight 
 into the correfponding pofterior branch ; and, ac- 
 cording to its fize, gradually fends off fmaller ar- 
 bufcuiar branches, inofculating with the contiguous 
 and oppofite branches, by innumerable twigs. From 
 
INTESTINES. 
 
 Chap. XXIV. 
 
 359 
 
 this reticulation, branches penetrate through the 
 nervous tunic into the third cellular ftratum, and 
 laftly into the cavities of the villi, which finally, 
 with open orifices, exhale their contents into the 
 inteftine. This courfe is eafily imitated, by injec- 
 tions of water, fize, or mercury. From recent ob- 
 fervations, it has been added, that the arterial ex- 
 tremities open into an hollow veficle, and there de- 
 pofite their liquor, which exudes through the com- 
 mon orifice of the veficle. Befides, the reticular 
 difpofition of the arteries, and their numerous anaf- 
 tomofes, have the effedl, that the inteftines are as 
 little fubjefl to obftru6lions as poffible, and that 
 any obftrucling matter may eafily return, by means 
 of fo many inofculations, into the larger arterial 
 trunks. 
 
 bccxxx. Thelaft trunk of the mefenteric artery 
 ihofculates with the ileo-colic. The duodenum has 
 various arteries. The firft, the uppermofi: from the 
 hepatic, on the right, goes round the convexity of 
 the curvature of this inteftine, in the pancreas, and 
 fupplies this inteftine, and inofculates with another 
 on the left, and inferior, the pancreatico duodenalis 
 which makes a fimilar arch in the pancreas, in the 
 hollow of the curvature of the duodenum, and is 
 at laft inferted into the lower duodenal arteries, pro- 
 duced by the mefenteric in its pafiage before this 
 inteftine. I willingly pafs over the fmall arteries, 
 which go from the fpermatics to the duodenum, 
 and from thofe of the renal capfule. 
 
 Dccxxxi. The veins, exaftly correfponding with 
 the arteries, meet all together, into the mefenteric 
 trunk of the vena portarum ; except the right duo- 
 denal vein, which goes immediately into the trunk 
 of the vena portarum itfelf ; and thofe fmall veins 
 which accompany the fmaU arteries, (dccxxx.) and 
 are inferted into the fpermatics and luinbals. Nor 
 have I hitherto been able to difcover any other veins 
 of the mefentery, arifing from the cava. It is a pro- 
 perty 
 
INTESTINES. 
 
 Chap. XXIV. 
 
 36© 
 
 perty common to all thefe veins to be without 
 valves, and to communicate freely with the arte- 
 ries. In the villous coat, which is for the moft part 
 compofed of veins, as the venous trunks are fewer 
 and larger, they abforb from the inteftines a thin 
 humour ; as appears from the inieclion of waterv’’ li- 
 quors, which readily take that courfe ; and, from 
 analogy, in aged perfons, in whom the mefenteric 
 glands, and confequently the palTage of the lacteals, 
 are frequently obliterated, and from the analogy of 
 birds, which have no lacteals, and from the celerity 
 with which watery liquors pafs to the blood and 
 through the kidneys, compared with the fmallnefs 
 of the thoracic du(T, and chiefly from thofe experi- 
 ments which have confirmed by ocular demonflra- 
 tion the pafTage of water from the cavity of the in- 
 teftine into the vena portarum. 
 
 Dcc:i:xxii. The nerves, numerous and fmall, im- 
 part to the inteftines a confiderable degree of fenfi- 
 bility ; they arife from the middle plexus of the 
 fplenic nerves, which embraces the mefenteric ar- 
 tery, and play round it in great numbers, wrapped 
 up in a very denfe cellular fubftance. The duode- 
 num has llkewifc nerves from the pofterior hepatic 
 plexus of the eighth pair. From the acute fenfibil- 
 ity of the inteftines, it is probable, that the ulti- 
 mate branches of the nerves penetrate into the third 
 cellular coat. 
 
 Dccxxxiii. From the exhaling arteries, a thin 
 aqueous liquor diflils into the cavity of the intef- 
 tines, refembling the gaflric juice, not acrid, but 
 faltifli. The very great quantity of this liquor is 
 computed from the great fize of the excretory ori- 
 fices, and of the fecreting arteries, which are not 
 larger in any part of the body ; and from the lax- 
 ity of parts perpetually kept warm and moifl, and 
 from the copious diarrhoeas or watery difeharges 
 that often follow the ufe of purgative medicines. 
 
 Pi;: 
 
INTESTINES. 
 
 .Chap. XXIV. 
 
 361 
 
 But the mucus arihng from the fources, dccxxvi. 
 Dccxxyii. lubricates the internal furface of the vil- 
 lous membrane, and defends the fenlible nerves from 
 acrid or fpirituous alimentary matters. Hence, it 
 is more abundant at the beginning of the large in- 
 teftines, becaufe there the mafs of aliment begins 
 to be feculent, acrid, and tenacious. 
 
 Dccxxxiv. This liquor is mixed with the pul- 
 py mafs of the aliment, with the bile, and with 
 the pancreatic juice, by the external motion of the 
 mufcles furrounding the abdomen ; but this force 
 is quite fmall, and unfit for moving forwards the 
 aliments. And in the firft place, the periftaltic mo- 
 tion is' not any where llronger, or miore evident, 
 than in the fmaU inteflines. For any part of the 
 inteftine, irritated by flatus, or any fliarp or rough 
 body, contra(Ts itfelf, even after death, very vio- 
 lently in that part where the ftimulus is applied, 
 frees itfelf from the offending or diftending body, 
 and expels it into the contiguous part of the lax in- 
 teftine ; which alfo contracting from the fame ftim- 
 ulus, repels what it received, either way. This 
 motion occurs in various parts of the inteftines, 
 without any certain order, wherever flatus or ali- 
 mentary matter act as ftimuli. So great, however, 
 is the aptitude of the inteftines, for motion, that 
 they emulate, and even exceed, the irritability of 
 the heart, or at leaft are fcarcely exceeded by it. 
 When not irritated, they remain at reft, as I have 
 often obferved ; and we may fuppofe this to be the 
 caufe why fat retards the belly. The air is the prin- 
 cipal ftimulus of the inteftines, next the aliment, 
 and laftly the bile. This m.otion is performed by a 
 wonderful fort of alternate creeping and revolution 
 of the inteftines, which difledion eafily demon- 
 ftrates in living animals, and unfortunate cafes of 
 wounds in the abdomen, and ruptures, have fhowii 
 in the human fpecies. And fince, here, among fo 
 many inflexions, gravity can have no effect, the in- 
 teftine 
 
DH'ESTINES. 
 
 Chap. XXIV. 
 
 3 ^ 2 . 
 
 teiline when irritated, evacuates itfelf equally up- 
 wards and downwards. From this, the antiperifrai- 
 1-ie motion is underftood, by which the pulp of the 
 aKmentary mafs is longer expofed to the gentle trit- 
 uration of the inteftine, and to the action of the di- 
 luent liquor, and of the abforbing veins. All the 
 contents of the inteftines are at laft determined to 
 the large inteftines, becaufe every' ftimulus begins 
 in the left orifice of the ftomach ; and the conftant 
 fuccefiion of food excites a new contraction in the 
 parts above, by irritating them, while no contrac- 
 tion of the colon propagates a ftimulus backwards 
 to the lower part of the ileum ; hence the loofe co- 
 lon receives what defeends into it, and unloads it- 
 felf into the large unactive caecum more ealily, than 
 it can repel upwards the aliments it has ^ecei^'ed, 
 and which are refifted by the preffure of the inteftine 
 propelling frelh matter. Anatomifts obferve, that 
 this motion acts more ftrongly downwards than up- 
 wards, and that the fuperior parts of the inteftines 
 are more irritable. But as often as any infupcrable 
 cbftacle refifts the paffage of the aliment, the feat 
 of the principal contraction will be there, and the 
 aliment will be repelled upwards, even from the 
 valve of the colon, through the whole length of the 
 inteftines, into the ftomach, and laftiy into the mouth 
 itfelf. 
 
 Dccxxxv. This periftaltic motion, in which the 
 inteftine is conftricted, is performed by the circular 
 fibres, which are capable of moft exaflly emptying 
 the tube, fo as to propel downwards the moft mi- 
 nute bodies, fucli as needles or powders. But the 
 revolutions of the inteftines, drawn upwards or 
 downwards, and the bending of the ftraight, and 
 the ftraightening of the crooked portions, which are 
 fo confpicuous in animals, are pei'formed by the long 
 fibres, and which, moreover, when they contract 
 themfelves towards the feat of the prefent, ftiinuia- 
 
Chap. XXIV, INTESTINES. 363 
 
 ting food, we fee dilate the fucceeding portion of 
 inteftine, and fit it for receiving. The fame con- 
 traftion, forces the villous membrane into the cavity 
 of the intellines, and renders the folds longer ; and 
 exprelTes the mucus, fo that luch a quantity is ap- 
 plied to the alimentary mafs, as is required by the 
 irritation and degree of the ftimulus. They alfo 
 produce frequent, and generally harmlefs, introfuf- 
 ceptions, by drawing up the fucceeding portion of 
 inteftine, againft that which is contrafted, in fuch 
 a manner, that the former is received within the 
 latter, which is relaxed, 
 
 Dccxxxvi. The alimentary pulp, therefore, dilu^ 
 ted with the pancreatic juice and that of the intef- 
 tines, intimately mixed with the faponaceous bile, 
 and covered with mucus, is accurately triturated, 
 and more efticacioufty than in the ftornach, in pro- 
 portion as the fides of the fmall inteftines approach 
 nearer together, and to the length of the feries of 
 the periftaltic motion afling, and to the quantity 
 of animal juices affufed. The vifcid pulp, inter- 
 mixed with air, becomes frothy, without fermenta- 
 tion, and the air continues to have the fame effects 
 as in the ftornach, but fo that every acid tendency 
 within the inteftines is counterafted. But the oily 
 or fat parts of the food, diflblved by the bile, 
 
 I (dccxv.) and mixed with the watery juices, ac- 
 j quire ufually a bright white colour, like an emul- 
 1 fion, firft viftble in the duodenum, below the en- 
 trance of the biliary du6t ; and afterwards adher- 
 ; irig clofely to the villous coat, throughout the whole 
 ' length of the fmall inteftines. But the gelatinous 
 ! juices of flefti meats, diluted by copious affufion of 
 water, and being of themfelves of a fubvifcid na- 
 ture, adhere to the villous coat, and are prepared for 
 i! abforption. The water and watery liquors are all 
 \\ very greedily abforbed by the veins : and yet the 
 [I faeces never grow thick in the fmall inteftines, as far 
 I as I have obferved, becaufe the water abforbed is 
 ! { repaired 
 
 ' 1 
 
INTESTINES. 
 
 364 
 
 Chap. XXIV. 
 
 repaired by the arterial vapour and the mucus ; nor 
 do they becoipe fetid in any confiderabLe degree, 
 both on account of the great quantity of diluting 
 juices, and becadfe their quick progrelEon does not 
 allow them time for putrefaction. In the beginning 
 of the jejunum, the white mafs is coloured with 
 bile ; in the end of the ileum, it is entirely mu- 
 cous. Thofe remains, which are more earthy, grofs, 
 coarfe, and acrid, and were excluded by the abforb- 
 ing orifices, either by their own weight, or by fome 
 power acting as a fphincler, defcend into the large j 
 inteftines, being gradually, forced down, fo as to 
 complete their whole courfe in the fpace of about 
 twenty-four hours. But within three or four 
 hours, or a little more, almoft all the chyle is ex- 
 tracted. 
 
 Dccxxxvn. The confiderable length of the fmall 
 intelline, which is live times longer than the body, 
 or more, the great furface of the villous membrane 
 increafed by folds, the incredible number of exhal- 
 ing and abforbing veffels, the flow progrefs of the 
 food through the large inteftines, and the gi’eat 
 quantity of the inteftinal juice, poured to the ali- 
 mentary mafs, have the eflect of providing abun- 
 dantly, in the fmall inteftines, every requilite for 
 diluting the food with our juices ; for their abforp- 
 tion into the lacfteals and the mefenteric veins ; for 
 the abfterfton of vifcidities from the inteftine ; for 
 preventing adhefions and coagulations : for the fup- 
 prefllon of any acidity, not yet fubdued ; and for 
 the deftruction of the deleterious qualities in many 
 juices, which, being direcftly mixed uith the blood, 
 inftantly kill, but are without injury received by 
 the mouth. Hence the inteftines are long in ani- 
 mals that feed upon any hard food, but Ihorter in 
 carnivorous ones, and Ihortell in thofe that live up- 
 on juices alone ; and, in man, an uncommon Ihort- 
 nefs of the inteftines has been attended with hun- 
 ger, and fetid and fluid fteces. 
 
 Dccxxxvin, 
 
INTESTINES. 
 
 Chap, XXV. 
 
 3^5 
 
 Dccxxxviii. The heat, by which the aliment is 
 fomented, and which is well fitted for the folution 
 of the gelatinous matter, and for exciting the be- 
 ginning of putrefaffion, is therefore the principal 
 caufe of the fetor, which is gradually produced in 
 the aliment ; and alfo of that thinnefs by which the 
 ufeful part of the aliment is fitted for abforption. 
 But the air alfo, inclofed in the vifdd aliment, ope- 
 rates, as in the ftomach, by breaking the cohefion 
 of the aliments, if any yet remain entire. The in- 
 teftinal water dilutes the mafles of aliment ; and if 
 any hard part remains, foftens it by maceration. 
 The bile being intimately mixed with oil, diflblves 
 it, and renders it mifcible with water. 
 
 CHAP. XXV. 
 
 LARGE INTESTINES. 
 
 Dccxxxix. "T'TTHAT remains, after the chyle 
 V V been abftraded, confifts of 
 fome portion of the bile, but mucous and degene- 
 rate ; fome part of the human mucilage ; mofl; of 
 the earthy parts that were in the food 5 all thofe 
 parts, which by their acrimony were rejeded by 
 the abforbing mouths, changed, however, by putre- 
 faction, (dccxxxvi.) with all the folid fibres and 
 membranes, which refilled the powers of macera<< 
 tion and the periftaltic motion. 
 
 DccxL. All thefe remains pafs from the extrem- 
 ity of the ileum into the caecum, in which they 
 ftagnate ; namely, the extremity of the fmall in- 
 teftine applies itfelf obliquely to the right fide of 
 the colon, refting upon the right ileum and iliac 
 -mufcle, fo that, upon the whole, it afcends, but 
 more with its lower fide, and lefs with its upper^ 
 which is aim oft tranfverfe. But the extremity of 
 
INTESTINES. 
 
 Chap. XXV. 
 
 ^66 
 
 the nervous and villous coats, and tranfverfe flefliy 
 fibres of the ileum, are fo extended betwixt the 
 departing flefhy fibres and nervous coat of the co- 
 lon, that there hangs within the cavity of this 
 large intelline, a moveable, foft, double prelecting 
 fold, compofed of the villous and nervous coats of 
 the large inteftine, and of the villous and nervous 
 coats of the fmall inteftine, and of the interpofed 
 fleftiy fibres of the ileum and colon, connected by 
 much cellular fubftance. The upper fold is tranf- 
 verfe and fhorter, the low'-er is larger, longer, and 
 afeending. They are conjoined by a fmall pro- 
 dudtian of the fame kind, more efpedally where 
 they approach in the right fide. Betwixt thefe 
 two folds, the mouth of the ileum opens, like a 
 tranfverfe flit. By inflation, this ftructure is much 
 altered, afl’uming the appearance of membranes and 
 hard valves. After the cellular fubftance is en- 
 tirely removed, and the interpofed flefhy fibres are 
 cut, the ileum, Comes out from the colon, and the 
 valvular appearance difappears ; but if a large part 
 of it only be removed, fo that it ftill remoins infert- 
 ed by fome, it refembles a fphincler. 
 
 DccxLi. Below the entrance of the ileum, at the 
 diftance of fome inches, the great inteftine defeends 
 and refts with an impervious extremity, upon the 
 ileum. From the lower part of this, towards the 
 light fide, a very acutely conical fmall inteftine 
 extends, in adults flender, in the foetus proportion- 
 ally larger, varioufly incurvated upwards, fome- 
 times downwards, and full of fmall mucous glands,- 
 which pour out a glutinous matter to the frees ; 
 in the foetus, the colon itfelf is continued wdth a 
 conical termination into the appendix. But the 
 weight of the fuperincumbent fcybalse, deprefllng 
 the fpaoe on the right fide of the appendix ; the 
 ftrength of the cellular texture uniting the left 
 part of the caecum with the ileum ; the ftrength of 
 the flcfliy fibres uniting both inteftines ; the very 
 
 contractile 
 
Chap. XXV. 
 
 INTESTINES. 
 
 3^7 
 
 contracHle force of the ligaments ; the fitnefs of 
 the anterior fac of the oecum, for eafily receiving 
 the faeces fi'om the ileum 5 all contribute to remove 
 the appendix from the middle, fo that it arifes from 
 the left lide of the extremity of the colon : and to 
 form the thick and pendulous bag of the colon 
 lying fartheft to the right fide, and which is pecu- 
 liar to adults. When, therefore, the remains of the 
 alimentary mafs come from the ileum into the 
 colon, they fall by their weight into this impervi- 
 ous bag, and ftagnate there, and become putrid^ 
 both from the warmth of the place and their own 
 nature ; and here, efpecially, the fetor of the ex- 
 crements begins. 
 
 DccxLii. The inteftine which is continuous with 
 the caecum, and indeed the fame, is named the co- 
 lon. This thick and very large inteftine, which is 
 much ftronger than the fmali inteftines, begins in 
 the right ileum, (dccxl.) afcends along the kid- 
 ney, lies in the angle of the right hypochondriuna 
 under the liver, and is connedred to both vifcera 
 by the peritonaeum. Then it paffes under the liver 
 and ftomach, for the moft part tranfverfely, to the 
 fpleen, under which it lies, (dclxxvi.) and in a 
 deep recefs under the left ribs, it is often reflected 
 upon itfelf. Then it defcends again, and having 
 made a large flexure to the left ileum, (ncnviii.) it 
 is continued with the lower part of this flexure in- 
 to the pelvis, and becomes the reftum. 
 
 DccxLiii. The ftructure is, on the whole, the 
 fame with that of the fmali inteftines, but it differs 
 in feveral particulars. And firft, all the longitudi- 
 nal fibres are collected into three bundles, which 
 run through the whole extent of the inteftine ; 
 and of thefe one, and that the largeft, lies naked j 
 another, at its origin, is concealed by the omentum, 
 and the third by the mefocolon. Thefe are fliorter 
 than the inteftine, and contradt it fo that the ner- 
 vous and villous membranes (dcxliv.) projeft in- 
 wardly. 
 
INTESTINES. 
 
 Chap. XXV. 
 
 368 
 
 wardly. Thefe fibres are connected mofl accurately 
 with the external coat of the inteftine ; but in tlie 
 intermediate places, and chiefly at the mefocolon, 
 is feated the firft cellular coat replenifhed with fat. 
 Being dilated at their origin, they adhere to the 
 vermiform appendix. In the extremity of the co- 
 lon, there are often only two ligaments, the two 
 fmaller joining into one. They diffufe themfelves 
 upon the rectum fo as to cover it entirely. 
 
 DccxLiv; Again, the flefhy and nervous coat, 
 third cellular and villous tunics of the colon, are 
 extended into much larger wrinkles in the parts 
 betwixt the ligaments, often projecting in a three- 
 fold rank, which being fuftained by the ligaments, 
 are able to fupport a little the fcybalae, and refift 
 their relapfe. In the beginning of the colon, they 
 are very exactly threefold ; but in its progrefs, they 
 vary more and more, being lefs, and double, and 
 folitary, and fmall and large intermixed, and entire- 
 ly abfent. Where the ligaments which contrad: tha 
 colon, difappear, thefe valves difappear almoft en- 
 tirely. Laftly, the villous coat is thinner, and 
 vnthout villi, but wrinkled and porous, furnifhed 
 both with large pores leading to proper, large, 
 round, folitary follicles, and with innumerable 
 fmall pores leading to fmaller follicles. Both kinds 
 fupply a great quantity of mucus. 
 
 Dccxi-v. The blood-veffels of the large inteftines 
 are partly from the greater and left mefenterics, 
 and partly from the hypogaftrics. The middle 
 colic artery arifes from the large mefenteric trunk, 
 as that defcends behind the tranfverfe mefocolon. It 
 rifes upwards with one, two, and fometimes three 
 branches to the tranfverfe mefocolon, and unites 
 on the right fldc with the ileo-colic ; and on the 
 left, with the lower mefenteric, in a very large 
 arch, which ir the largeft of all the arterial inofcu- 
 lations in the numan bodyn Again, under the me- 
 focolon, from the fame large mefenteric artery, a 
 
 larger 
 
Chap. XXV. 
 
 INTESTINES. 
 
 3^9 
 
 larger branch goes dire6lly to the valve of the ile- 
 um with the colon, and inofculates upwards at the 
 right of the colon with the middle colic ; and to the 
 left with the mefenteric ; but from the middle of 
 the mefentery it gives a branch that runs along the 
 mefocolon of the appendix verraiformis, and ter- 
 minates with two branches in the two folds of the 
 ileum and colon, both the anterior and pofterior. 
 Laltly, the lower mefenteric, arifes by its proper 
 trunk from the aorta, betwixt its bifurcation and 
 the renal arteries, and goes to the left part of the 
 colon : upwards it forms a large arch, with the 
 middle colic j downwards in three or four trunks, 
 it fpreads over the iliac flexure of the colon, and 
 defcends even into the rectum. There tire reftum 
 receives various branches from the middle hemor- 
 rhoidal, ariling from the laft trunk of the hypo- 
 gaftricsj and conjoined with the former. The ul- 
 timate arteries are from the fame trunk, but arife 
 without the pelvis. I pafs over the fmaller colics, 
 ariling from the fpermatics, intercoftal, omental, 
 capfulary, and lumbar arteries. The veins, like the 
 arteries, run together into the gaftrocolic, and the 
 internal hemorrhoidal, and thence into the vena 
 oortarum : and into the middle and external he- 
 morrhoidals, and the trunks of the iliacs. 
 
 DccxLvi. The divilion of the veflels to the large 
 inteftines, differs much front that of the fmall in- 
 teftines. Their arches are lefs frequent and lefs of- 
 ten fubdivided ; the trunks follow the courfe of the 
 inteftines a long way ; the glands feated on them 
 are fewer ; the branches on the inteftines lefs ar- 
 bufcular, divided at lefs angles, and more tortuous ; 
 and the reticulation in the cellular fubftance is 
 loofer. An exhaling moifture diftils into the cavi- 
 ty of the inteftines, and the veins likewife abforb a 
 thin fetid vapour from the faeces. The external, 
 and perhaps alfo the internal veins, fwelling into 
 varices, pour out the hemorrhoidal blood j which 
 A a is 
 
INTESTINES. 
 
 
 Chap. XXV. 
 
 is always unnatural, although fometlmes infracHons 
 of the veffels of the porta are relieved by that eva- 
 cuation. 
 
 DccxLvii. But there are alfo lymphatic veffels, 
 arifing from the whole tract of the colon, and from 
 the rectum, which unite with thofe of the loins. 
 We are not without examples of chyle having been 
 found inftead of lymph, in thefe lymphatics, arifing 
 from the colon ; a proof, that even in this place 
 fomething ftill remains, which may be added to the 
 blood with advantage. 
 
 DccxLviii, The nerves proceed from the left co- 
 lic plexus compofed by the defeending branches of 
 each renal plexus, and others arifing from the in- 
 tercoftal trunk in the thorax and loins, and others 
 from the large mefenteric plexus. Thefe accom- 
 pany the lower mefenteric artery, and go to the co- 
 lon. The lowermoft nerves arife from the plexus 
 juft mentioned, and go to the rectum, vithin the 
 pelvis others go to the fame inteftine from the low- 
 er intercoflals, and from the nerves of the facrum. 
 Thefe nerves are not numerous, and the inteftine is 
 not very fenfible, that it may endure the hard and 
 acrid faeces.- 
 
 Dccxnix. Tlie inteftinal faeces, therefore, retain- 
 ed in the blind beginning of the large inteftines, 
 (dccxl.) become dry by the abforption of their 
 fluid parts, fliaped by the round and contracted co- 
 lon, afeend from the bottom of the caecum, being 
 elevated by the long ligaments, which unite in the 
 v'orm like appendix. And here the manner in 
 w'hich the faeces are propelled by the contraction of 
 the circular fibres, appears better than in the fmall 
 inteftines. The longitudinal fibres being drawn to- 
 wards the contracted portion of the inteftine, as to • 
 a fixed point, draw the lower part of the inteftine 
 upwards, and dilate it ; then the next part of the 
 inteftine, to which the faeces are brought, being 
 irritated in like manner, contracts the long fibres 
 
 toward? 
 
Chap. XXV. 
 
 INTESTINES. 
 
 37 ^ 
 
 towards it ; by a fiiccellive repetition of which 
 adion, the faeces finifli their courfe through the 
 whole large inteftine j for the moft part within 
 twenty-four hours in a healthy perfon. For this 
 periftaltic motion of the large inteftines may be feen 
 in living animalsj and in the human body from 
 wounds ; it is alfo confirmed by the antiperiflaltic 
 motion, and by the phenomenon of giyfters being 
 difcharged through the mouth. The fame fibres 
 refill the air contained in the inteftines ; and flatu- 
 lence is faid to be generated as often as they are 
 overcome and yieidj and the inteftine is dilated. 
 
 DCCL. While the grofs faeces afcendfrom the cae- 
 cum along the folds (dccxl.) or valves, at the en- 
 trance of the ileum, they incline the lower fold to 
 the left, and backwards, and draw down the liga- 
 ment common to both valves, and thus deprefs the 
 upper fold downwards : thus the paflage is accurate- 
 ly Ihut, fo that nothing may return info the ileum ; 
 which, however, cannot be done fo accurately in a 
 fluid ftate of the faeces. The faeces, when falling 
 down from the upper parts, deprefs the upper valve, 
 and thus accurately exclude themfelves. This hap- 
 pens very exacftly with hardened faeces, but not fo 
 accurately with fluid fasces. From thence, becoming 
 more and more dry and figured, they continue to 
 move flowly forwards by the fame caufes (dccxlix.) 
 through the whole colon, which is repeatedly bent, 
 and of five or feven feet in length, in fuch a fpace 
 of time as is fufficient to give no interruption to 
 the affairs of human life ; and which is lefs than 
 twenty-four hours, by the time the alimentary mafs 
 remained in the fmall inteftines. 
 
 DccLi. At length the hardened excrement falls 
 into the return, which is at firft inclined down- 
 wards, and then alfo forwards, of a broad and flat 
 figure, at firft contiguous to, and afterwards fpread 
 under the bladder, or vagina, but connedted more 
 with the latter than with the former. Here the fsecej 
 A a 3 are 
 
INTESTINES. 
 
 Chap. XXV. 
 
 37 ^ 
 
 are colleclcd for a great while, and often to a great 
 quantity, being a part which is loofe, or furround- 
 cd with foft vifcera and mufcles, and much fat. 
 
 DccLii. The ftrufture of the reclum differs very 
 much from that of the other inteftines. The ex- 
 ternal membrane or peritonseum covers it only be- 
 fore, while behind it is connected to the region of 
 the os facrum, by a very broad ftratum of cellu- 
 lar fubftance, replenilhed with fat, and many con- 
 globate glands. The rnufcular fibres are much 
 itronger than in the other inteftines, efpecially the 
 longitudinal ones, wEich being compofed of the 
 three ligaments, expanded and feparated, firft oc- 
 cupy the anterior face, and then the w'hole intef- 
 tine : they dilate it againft the advancing faeces, 
 and draw it back after tliey are excluded. But the 
 tranfverfc fibres are alfo ftrong, and their laft oval, 
 tumid ring, is the internal fphincler by which the 
 opening of the anus is accurately clofed. 
 
 DCCLiii. Moreover, the villous tunic, wiiich is 
 extremely full of pores, and rough with polygonous 
 and tender wrinkles, has likewife fome finufes pe- 
 culiar to itfelf. Namely, the part of the inteftine 
 next to the fkin and inferior orifice, forms a white 
 firm valvular circle, into >vhich defcend longitudinal 
 folds, but incurvated and approacliing to each oth- 
 er on the circle itfelf. Betwixt thofe folds, there- 
 fore, finufes are interpofed, hollow upw^ards, and 
 of a greater depth towurds^the bottom. Into their 
 cavities open mouths from large m.ucous glands ; 
 while the mara.in of the anus itfelf is defended bv 
 
 O , * 
 
 febaceous glands, that it may not be excoriated by 
 the hard and acrid faeces. 
 
 DcciJv. There are allb proper mufcles which 
 govern the anus. The external fphincler is broad 
 and ftefhy, and confifts of tw'O plates of femi-elliptic 
 fibres, which crofs each other towards the cocc) X, 
 and towTii'ds the genital parts. And, in the form- 
 er place, thev are inferted by fleflay bundles into a 
 
 callous 
 
Chap. XXV. 
 
 INTESTINES. 
 
 373 
 
 Cculous cellular fabric defcending from the coccyx. 
 In the latter, in like manner, they are attached by 
 fimiiar bundles to the fkin of the perinaeum ; but 
 by three ftronger than the others, one middle, and 
 two lateral into the accelerator and bulb of the ure- 
 thra, the lateral ones partaking both of the nature 
 of a fphincter and levator. The fibres, therefore, 
 of the fphinfter, approaching to a ftraight line be- 
 tween their anterior and pofterior fixed extremities, 
 clofe the opening of the anus, which lies between 
 them. With the internal fphincler, the external 
 one is conjoined by a liefhy portion, that they may 
 operate together. Their affion is voluntary and 
 not perpetual ; for the anus feems to be clofed nat- 
 urally, by the narrownefs of its orifice, compared 
 with the largenefs of the inteftine, by the wrinkles 
 correfponding to the other (dccliii.) by the ftrength 
 of the tranfverfe fibres of the internal fphincler, and 
 by the incumbent bladder. 
 
 DCCLV. But the office of the levators is different. 
 They are large and complicated mufcles. They 
 defcend betwixt the oppofite ofl'a ifchia, are placed 
 under the reclum and bladder, and fullain both, 
 and prevent the reclum from defcending and gap- 
 ing difgullingly. Moreover, by their fibres fpread- 
 ing extenfively in the manner of a fphincler, and 
 being joined to that mufcle, they can dilate its fibres, 
 and open the anus ; but, at the fame time, they el- 
 evate and fullain the inteftine from prolapfing wJrile 
 the fteces are palling. They arife, as is weft known, 
 from the fpine of the ifchium, os ileum, and fyn- 
 chondrolis of the offa pubis, terminating the mar- 
 gin of the great foramen of the pubes, and from 
 that part of the ifchium, wffiich is above the tuber- 
 cle. Finally, they meet together under the coc- 
 cyx, into which they are inferted by numerous fi- 
 bres. 
 
 DccLvi. Therefore, whenever the fteces are col- 
 Icftcd \vithin the reftum in any great quantity, 
 
 and 
 
CHYLIFEROUS Chap. XXV.- 
 
 374 
 
 and become troublefome by the irritation of their 
 weight, or acrimony, even to the adjacent vifcera ; 
 they are forced by the power of the will through 
 the llraits of the coUapfed inteftine (dccliw) by 
 the force of the incumbent diaphragm, exerting an 
 effort ; which being drawn downwards with great 
 force, preffes downwards the vifcera of the abdo- 
 men, which arc alfo refifted by the contraction of 
 the abdominal mufcles, and forces the contents of 
 the bladder or reclum through the inferior opening 
 between the bones of the pelvis, where the refin- 
 ance is leaft. When the refiflance of the anus is 
 thus overcome, the force of the diaphragm abates, 
 and the fgeces are difeharged from the body, by the 
 periftaltic motion of the inteftine itfclf. After the 
 ibsces are expelled, the inteftine is drawn back by 
 its longitudinal fibres ; and the anus being con- 
 tracted by both its fphinclers, fliuts its orifice as 
 before. 
 
 DCCLvii. Thefe faeces in man, and carnivorous 
 animals, are very fetid, almoft: putrid, fubalkaline, 
 foft, and contain much oil mixed with faiine mat-, 
 ter, which are the remains both of the aliments and 
 of the bile and other humours of the human body. 
 An acrid and fetid water returns from the faeces 
 into the blood ; hence, coflivenefs in fevers is hurt? 
 ful, as by its addition it promotes putrefcency. 
 
 CHAP. XXV.* 
 
 CHYLIFEROUS VESSELS. 
 
 uccLvili. ^ S HE chyle is a white juice (dccxxxvi.) 
 
 § extracted from the aliments, which 
 is poured into the blood. It feems to be compofed 
 of water and oil, as appears from its tafte, being 
 fweet with fome mixture of faltnefs, from its acci- 
 
 cent 
 
Chap. XXV.* 
 
 VESSELS. 
 
 375 
 
 cent nature, from the whitenefs of its colour, 
 from its fpontaneous reparation and coagulabili- 
 ty, and from its lightnefs, by which it fwims on 
 the blood : in all which properties it very much 
 refembles an emulfion. It is compofed of vege- 
 table farina, with lymph and animal oil. It every 
 where retains the properties of the volatile and oily 
 aliments. It changes into milk with very little al- 
 teration. But then, the glutinous pellucid ferum 
 which it contains, becomes more manlfeft, being 
 coagulable into a kind of a jelly, by expofure to a 
 high temperature, or by evaporating its water. 
 
 DccLix. That the chyle is abforbed into the 
 lacteal veflels from the villous coat of the inteftines, 
 to which it adheres, has been long known, by ex- 
 periments with coloured liquids, which defcribed 
 the fame courfe ; from the hmilitude of the white 
 liquor, as feen in the lacteals, and out of them and 
 from the venous nature of ladleal veifels. But late 
 experiments have given us better information on 
 many particulars. The chyle is abforbed by the 
 patulent orifice in the extremity of each of the villi, 
 by a force fimilar to that of capillary tubes ; is re- 
 ceived into the hollow villi, which are relaxed 
 when the inteftine kfeif is relaxed 5 but the veficle, 
 being compreffed by the fucceeding confiriftion of 
 the mufcular fibres of the inteftine, the chyle k 
 preiTed on into the du(ft, which begins to appear 
 in the fecond cellular ftratum. But there is a dou- 
 ble feries of thefe trunks, one anterior, the other 
 pofterior, as we obferved of the blood-veft’els, 
 (dccxxix.) From thence the lafteal veflel, already 
 united into a larger canal, pafles into the firft cel- 
 lular ftratum, and, in general, follows the courfe of 
 the arteries, and likewife accompanies their arches, 
 being conjoined with others of the fame kind into 
 a very obliquely angled netv/ork. This kind of 
 vefTels hitherto has been obferved only in quadru- 
 peds, In the large inteftine they arife without the 
 
 veficle. 
 
CHYLIFEROUS 
 
 Chap. XXV.* 
 
 376 
 
 veficle. Very many arife from tlie firft part of the 
 fmall inteftines under the mefocolon ; fome from 
 the duodenum, and a few from the large inteftines 
 themfelves. 
 
 Dcci-x. The lacteal veffels are valvular in the 
 very firft cellular texture of the inteftine, being 
 provided, like the lymphatics, with very frequent, 
 double, lunated valves, (lvii.) which admit the 
 chyle paffing from the inteftines but prevent its re- 
 turn. Through this whole courfe, the chyle is 
 propelled by the periftaltic motion of the inteftines; 
 by the periftaltic aftiion of the velTels themfelves, 
 which are certainly irritable, even after death pro- 
 pelling the chyle ; and by the confiderable prelture 
 of the abdominal mufcles, directed by the valves. 
 
 DCCLXi. But betvixt the plates of the mefentery, 
 at the divifions of the veftels, are found an infinite 
 number of glands, of the conglobate kind, but fofter 
 and fpongy, conlifting of cellular texture full of 
 juices, covered with an external membrane, lefs 
 hard than in other parts, and variegated with num- 
 berlcfs fmall biood-vefiels. Some lacteal veftels feem 
 to pafs by thefe glands : the greateft number enter 
 them ; and, being divided and fubdivided through 
 their cellular fabric, compofe the greateft part of 
 the gland. On the other hand, other lacteal veftels 
 originate in every gland ; and, being mutually join- 
 ed, compofe trunks, of which the ultimate and 
 iargeft go out from tlie gland. In the fame man- 
 ner the chyle enters two, three, or four glands, in 
 fticceftlon ; nor does any laefteal veflel arrive at the 
 thoracic duff without entering fome of thefe glands, 
 although it may occafionally pafs by fome without 
 entering them. That tliis is the true courfe of the 
 chyle, and that it paftes from the inteftines to the 
 mefenteric glands, appears from tying them, by the 
 veftels growing turgid betwixt the ligature and the 
 jmeftine ; from fchirrofities in the glands, by which 
 they are rendered confpicuous , and from the na- 
 ture 
 
VESSELS. 
 
 CiAp. XXV.* 
 
 3J / 
 
 ture of the valves preventing any return to the in- 
 teftines. 
 
 DCCLXii. What happens to the chyle in thefe 
 cellular I'paces is not fufficiently known ; but it ap- 
 pears that fome thin liquor is fecreted from the ar- 
 teries in thefe glands, by the aftufion of w'hich the 
 chyle is diluted. For it is obferved, that after the 
 chyle has paffed all the glands, it appears more wa- 
 tery ; and thin liquors, injecled through the arte- 
 ries, exude into the cells of the glands, and mix 
 with the chyle, lince the laftcal vcflels may be filled 
 through the arteries. Laftly, this milky fluid ap- 
 pears manifeftly in the glands of infants. 
 
 DccLxin. From the laft glands, which are col- 
 lected together in the centre of the mefentery, a 
 few very large lacteal veflels go out, to the number 
 of four, five, or more, which afcend with the me- 
 fenteric artery, and intermix with the lymphatic 
 plexus, which arifing from the lower parts of the 
 body, creeps over the renal vein, and afterwards 
 with that which comes behind the aorta from the 
 lumbar glands, and with the hepatic. A duft is 
 thus produced, fubject to great varieties, but which 
 niofl: frequently expands into a veficle of conlider- 
 able breadth at the fide of the aorta, lying between 
 that and the right appendix of the diaphragm, two 
 or more inches long ; and mofi: commonly contin- 
 ued above the diaphragm into the thorax, coni- 
 cal both ways : it is called the receptacle of the 
 chyle. In this the gelatinous lymph of the iimbs, 
 and of the abdomen, mixes with the chyle, and 
 dilutes its white colour ; fo that fometimes it ap- 
 pears filled with a pellucid or reddifli humour, 
 but frequently alfo with a w'hite milk. But there 
 are fome inftances where there are two or three 
 fmall and narrow duels, inftead of this recep- 
 tacle. This, how'ever, is moft frequent, and being 
 comprefled by the diaphragm and aorta, propels 
 the chyle with greater velocity, in proportion 
 
 as 
 
378 ' CHYLIFEROUS Chap. 
 
 as its caliber is larger than that of the duel jnto 
 which it empties itfelf. This receptacle is rarely 
 fo fhort, that it may be compared with an egg ; but 
 for the moft part it is broadeft in the middle, and 
 decreafes conically towards each end. 
 
 DCCLxiv. That the chyle comes from the intef- 
 tines into this duel, is fliewn from injeclions, by 
 which quickfilver has fometimes been puflied from 
 the firft lacleal veffels into the thoracic duel ; from 
 ligatures made on the duel itfelf, or the red veins 
 which receive it, by which the firft and fecond 
 la<fteal veffels fwell ; and from the manifecl flux of 
 the chyle into the thoracic du<ft when the ligatures 
 are removed. 
 
 DCCLXv. The thoracic du<ft, as it is called from 
 its courfe, is generally Angle ; or, if double for fome 
 part of its courfe, it foon unites into one, which 
 afeends in a waving courfe behind the pleura, be- 
 twixt the vena azygos and the aorta ; and receives 
 in its way the lymphatic veffels of the ftomach, 
 cefophagus, and lungs, palling through the conglo- 
 bate glands, of which there are many incumbent on 
 it, and coUecled into large bunches. It is, on the 
 whole, cylindrical ; and often forms iflands, by 
 fplitting and uniting again, more efpecially in its 
 upper part. It has few valves, and thofe lefs con- 
 fpicuous. About the fifth vertebra of the back, it 
 generally goes to the left, behind the cefophagus, 
 and then afeends along the left fide of the thorax, 
 behind the fubclavian veffels, till it arrives near the 
 lixth vertebra of the neck. 
 
 DCCLXvi. Then, being refleded and often didd- 
 ed, it defeends with each branch dilated into a fort 
 of veficle, and enters, either \sdth diftincl or united 
 openings, into the junction of the fubclavian and 
 internal jugular vein, by an oblique courfe from the 
 upper, pofterior, and right fide, downwards, to the 
 left, and forwards ; or going on v.ath one or other 
 branch, it enters the fubclavian, on the outiide of 
 
 that 
 
Chap. XXV.* 
 
 VESSELS. 
 
 373 
 
 that junftion. It is guarded by a true, moveable, 
 and almoft circular valve ; alfo by its defcent the 
 blood is prevented from entering it. It is rarely 
 otherwife difpofed ; and very rarely fplit into two, 
 with one branch entering each fubclavian ; and 
 yet more rarely does it fend a branch into the vena 
 azygos. Near its infertion it receives a large lym- 
 phatic veffel, coming tranfverfely from the arm ; 
 and another defcending from the head, in one or 
 more trunks. 
 
 DccLXvii. It appears that the chyle flows through 
 the thoracic duct into the blood ; becaufe, on tying 
 the red veins, both the thoracic duct and lafteal 
 veflels which are inferted into it fwell. 
 
 DCCLxviii. I have attributed the firft caufe of 
 motion in the chyle, and of its abforption, to the 
 attradion of the capillary veflels, alternated with 
 the periftaltic contraction of the inteftines. The 
 attraction fills the villi ; the periftaltic force emp- 
 ties them, and moves the chyle farther forwards. 
 The reft of its motion feems to depend on the force 
 of the membrane of the lacteal veflel itfelf, v/hich, 
 even after death, expels the chyle, fo that the veflels 
 become pellucid, which before were milky. The 
 alternate ccmprefling force of the diaphragm alfo 
 has fome efleft ; and the motion of the chyle 
 through the thorax is fomewhat accelerated by the 
 receptacle, which, being comprefled, propels the 
 chyle fo much the more quickly, as it is larger than 
 the thoracic du<ft. 
 
 DccLxix. The chyle, mixed with the blood, does 
 not immediately change its nature ; as is proved 
 from the milk produced from it. But five hours or 
 more after a meal, almoft to twelve, during ail 
 which time a woman can afford milk j having cir- 
 culated near 80,000 times through the body, fo- 
 mented with the heat of the body, and mixed with 
 the animal juices, it is changed, fo that its fat feems 
 to be partly depofited in the cellular fubftance, 
 
 partly 
 
 ( 
 
KIDNEYS. 
 
 Chap. XKV!. 
 
 280 
 
 partly figured into the red globules, (cxlvii.) the 
 gelatinous part changes into the feruni of the blood ; 
 and the watery parts go off, partly by urine and 
 perfpiration, and in part dilute the blood. Nor is 
 it uncommon for a pellucid liquor to be in place of 
 the chyle in the lacteals in a dying animal, or for a 
 white liquor to be in one part of the mefentery, and 
 limpid liquor in another, in veffels which perfectly 
 agree in their fabric. There are not, therefore, two 
 kinds of veffels from the inteflines ; of which the 
 one carries chyle only, and the other lymph. 
 
 DCCLXX. When digeftion is not going on, the 
 lacteal veffels abforb water from the inteflines, and 
 are tranfparent, and the thoracic duel conveys the 
 lymph of the abdomen, and of mofl parts of the 
 body, to the blood (liii.) 
 
 CHAP. XXVI. 
 
 KIDNEYS, BLADDER, AND URINE. 
 
 DccLxxi. ^ 8 ''HE chyle, when taken into the blood, 
 I contains a great deal of water ; the 
 proportion of which in the blood would be too 
 great, and its feparation into the cellular fubftance 
 too eafy, if it were not excreted. A part of it ex- 
 hales through the fkin, (ccccxxxvi.) and another 
 part, as large, or often larger, is flrained through 
 the Iddneys, and ejected from the body. 
 
 DCCLXxii. The kidneys are tv^o vifeera, placed 
 behind the peritonseum,one on each fide of the fpine, 
 incumbent upon the diaphragm, and upon the pfoas 
 and quadratus mufcles of the loins, but fo that the 
 right kidney is commonly placed lower and more 
 backwards. Before the right kidney are placed the 
 liver upon its upper part, (dcxc.) and then the co- 
 lon and inteftines ; before the lelt kidney arc tl'.e 
 fpleen, ftomach, pancreas, and alfo the colon. 1 hey 
 
 are 
 
KIDNEYS. 
 
 Chap. XXVL 
 
 
 are tied by reduplications of the peritonjeum to the 
 colon, duodenum, liver, and fpleen. Their figure 
 externally is convex, and femi-elliptical ; laterally 
 they are flat, and inwardly concave ; they are un- 
 equally divided into an upper, longer and thicker 
 extremity, and into a lower, flat, flender extremity. 
 They are firmly invefted by a ftrong external denfe 
 membrane, which does not come from the perito- 
 nscTam. Betwixt that membrane and the perito- 
 naeum of the loins, there is always interpofed a 
 great quantity of fat, by which the whole furface 
 of the kidney is furrounded on all fides, and the 
 nidus is completed, which, though prepared for it, 
 the kidneys would not totally fill. From the kid- 
 ney the peritonaeum afcends to the liver, fpleen, co- 
 lon, and diaphragm, and forms as it were ligaments 
 for the kidney. 
 
 DC CL XXIII. The veflels of the kidneys are very 
 large, both the arteries, which together exceed the 
 mefenterica, and the veins. The arteries arife froiti 
 the aorta under that of the mefentery, not always 
 in the fame manner, yet fo that the left is common- 
 ly fhortcr than the right, and each of them fre- 
 quently in two, three, or four trunks. From thefe 
 arife the lower capfular arteries, and the adipofe 
 ones belonging to the fat cortex of the kidney 
 (dcclxxii.) and not unfrequently the fpermatics. 
 
 ; The fat, rather than the kidneys, receives fmaller 
 branches from the fpermatic and lumbar arteries. 
 
 I The arteries are thick, fo /that the proportion of 
 i their coats to their caliber is great ; that they are 
 among the flrongeft of the body ; 'and that they 
 exceed the ftrength of the aorta by one third. 
 
 DccLxxiv. The x^eins are large, efpecially the 
 left, and lefs inconftant than the arteries : the right, 
 which is often without a branch, is fliott and con- 
 cealed ; the left always receives one of the fperma- 
 tics, and the capfular, and the laft branch on that 
 fide of the vena fine pari. It is a very large vein, 
 
 and 
 
KIDNEYS. 
 
 Chap. XXVI^ 
 
 3S2 
 
 and accompanies the duodenum, being extended 
 tranfverl'ely a conliderable way to the left, before 
 the aorta. Both the arteries and veins of the kid- 
 neys arife from the great trunks in an angle, acute 
 downwards, and both divide themfelves into feve- 
 ral branches before they enter the kidney. That 
 the pafi'age of the blood from the renal arteries into 
 the veins is very quick, appears from the facility 
 with which water, wax, or air pafs that way. The 
 uppermoft veins of the fat of the kidneys come from 
 the capfular veffels, the middle from the renal ones, 
 and the lowermoft from the fpermatics. 
 
 DccLXxv. There are lymphatic veins, of confider- 
 able fize, found near the renal veins, where they 
 form the beginning of the receptacle of the chyle 
 (dcclxiii.) and which are faid to receive the 
 branches that are divided under the external coat 
 of the kidney, and are rendered manifeft by putre- 
 faftion, or by the injedfion of a fluid into the renal 
 arteries, or even into the ureter. 
 
 DCCLXxvi. The nerves of the kidneys are fmall^ 
 but numerous ; arifing from a confiderable plexus, 
 mixed on each fide with ganglions, which is gen- 
 erated by branches of the great femilunar gan- 
 glion, joined with others coming from the intercof- 
 Eii trunk, from within the thorax itfelf. They en-* 
 ter the kidney, along with the artery, and fend off 
 the middle mefenteric, (dccxlviii.) and the fperma- 
 tic nerves. As thefe nerves are fmall, they give but 
 a fmall degree of fenfibility to the kidney. 
 
 DccLxxvii. Upon the top of each kidney Is feat- 
 ed the renal capfule ; which in the foetus is large, 
 even larger than the kidney itfelf, but does not af- 
 terwards increafe in the adult : it is glandular, of 
 the conglomerate kind, divided into lobes, of an 
 oval lhape in the foetus, and triangular in the adult ; 
 that on the ris^ht fide is connecled to the 'iver : the 
 left to the fpleen and pancreas ; and both to the dia- 
 pliragm and kidney, by as many fides. From care- 
 
Chap. XXVI. 
 
 KIDNEYS. 
 
 383 
 
 ful obfervation, it feems to be hollow within,- fepa- 
 rable like a ventricle, with the internal furfaces 
 I'mooth, as if cut, full of a liquor of a yellowifh red 
 colour, and fluid, almoft like blood. The arteries 
 of thefe capfules are many, and of three kinds ; the 
 uppermoft from the phrenics, the middle ones from 
 the aorta, and the lower ones from the renals ; the 
 veins are one on each flde, the right one going to 
 the cava, and the left to the renal vein. The faid 
 vein creeps almoft naked through the very fmooth 
 ventricle, in the fulcus dividing the capfule, and 
 fends branches through its internal furfaces. Its 
 ufes are as yet unknown ; although we are led to 
 believe, that it is fubfervient to the kidney, efpe- 
 eially in the foetus, from their conftant vicinity in 
 fo many animals. It has no excretory du(ft, nor 
 does it difcharge any juice, by vifible pores, into 
 the vein. 
 
 DccjLxxviii. The internal fabric of the kidney 
 is fimple, and known. The veflels enter the inter- 
 val between the upper and lower portions of the 
 kidney, and penetrate into its fubftance, furround- 
 ed with a cellular flieath, and divide into branches, 
 which run between the branches of what is called 
 the pelvis, along the columns interpofed betwixt 
 the papillae. From thence, having formed arches 
 both in the papillae and between them, they fur- 
 round the origin of the papillae, nearer to the peri- 
 phery, fometimes joined, but by fmall branches : 
 from whence proceed innumerable little twigs, of 
 which fome return by the intervals between the pa- 
 pillx into the columns, and into the papillae ; and 
 others tend towards the external furface of the kid- 
 ney, and fometimes pafs through the coat of the 
 kidney, enter into its adipofe covering, and are 
 there changed into minute ferpentine twigs, which 
 being reflected towards the fame portion of the kid- 
 ney from whence their trunk arofe, they are grad- 
 ually extended, and intermixed with the urinifer- 
 
 ous 
 
KIDNEYS. 
 
 Chap. XX\T 
 
 ous tubes. But from the cortex, bundles of urlnif- 
 erous tubuli arife in feveral rays, collected in great 
 numbers into threads, of which each contains many 
 tubuli. That they are continuous with the arteries, 
 or at lead; that tliey receive their branches into 
 them, we know, from experiments which Iliew that 
 water, or even air, palfes eafily from the arteries of 
 the Iddneys into the ureter ; and, laftly^ from dif- 
 cafes, in which the blood itfelf takes the fame courfe. 
 Between thefc papillae, and about their origin, arc 
 lituated fome roundifla knots, which the lateil anat- 
 omifts conlider as arterial glands, producing the 
 proper and more narrow urinary du(5ls. Between 
 thefe dufts many arteries run parallel. It is pro- 
 bable, that the cortex conhfts of curved veffels, 
 which eminent anatomifts have fuppofed to be fmall- 
 er than the red ones. 
 
 DCCLXxix. Thofe uriniferous vcfiels gradually 
 converge, being joined together like rays, and in- 
 fected in great numbers into one blind duel, which 
 duels complete the reft of the papilla, and terminate 
 Cngly in its convex extremity by confpicuous pores. 
 The number of thefe papillse is not altogether cer- 
 tain ; but thirteen or more of them, fimple, triple, 
 and even quadruple, have been feen. Thefe were 
 in the foetus fo dlfdncl, that the kidney then appear- 
 ed to confift of as many diftin<T fmaller kidneys, 
 connecled together by loofe cellular membrane, 
 each of which was furnifhed with its proper cortex- 
 of ferpentine veffels, and its compages of ftraiglit 
 uriniferous du6ls ; the bafis of all of tltcm lay 
 in the circumference of the kidney, and their ver- 
 tices converged towards the centre. The oppofitc 
 cortices of two of thefe little kidneys make a col- 
 umn, which feparates the two papillse. In the 
 adult, the cellular fubftance being condenfed, draws 
 the papllke clofer, and unites them into one kid- 
 ney ; however, it again almoll recovers the condi- 
 tion which it had in the fcctus. if the cellular plates 
 
KiDNEYSa 
 
 Chap. XXVI. 
 
 3 ^ 
 
 are relaxed by injecUng water into the veffels. The 
 kidney is alfo larger in the foetus than in the adult. 
 
 DCCJLXXX, Around the protuberant furface of each 
 papilla, a loofe membranous diftind; covering, of 
 larger lize, adheres ; fo that the papilla, or fome- 
 times two contiguous ones, projed into the hollow 
 tube of this cylindrical funnel. Two or three of 
 the tubes unite together, and form by that union 
 three hollow trunks, an upper, middle, and lower, 
 which again unite, but on the outfide of the kid- 
 ney, into one conical canal, called the pelvis. 
 
 DCCLxxxi. The blood of the renal artery being 
 lefs moveable, as is generally believed, than that 
 of the brain, and probably containing more water, 
 and being brought by the ferpentine arteries of the 
 kidneys, depolites into the redilineal tubes of the 
 papillae a great portion of its water, and the oil in- 
 corporated with it, and the falts, and any thin fluid 
 it may contain. But the fmaU diameter of each 
 Uriniferous dud at its origin, and its firm refiftance 
 feem to exclude the grois oil, and the chyle, and 
 the coagulable lymph. Hence, the increafed celerity 
 of the blood fo eaflly forces the red globules through 
 thefe tubes, and, by morbid relaxation, thej tranf- 
 mdt the true fat and the chyle, and the falts of the 
 meat and drink. But when the frrength of the kid- 
 ney is reftored by aftringent medicines, the urine 
 returns to its natural ftate. The nerves likewife 
 have a pov/er of contrading or relaxing thefe pafla- 
 ges ; and thus the urine, which was of a yellow col- 
 our, fuddenly becomes watery from violent affec- 
 tions of the mind. A vaft quantity is prepared ; 
 equal to that of perfpiration, o^r fomewhat greater. 
 
 DCCLXxxii. The urine, by heat or putrefadion, 
 fometimes by difeafe, and in fome animals more eafl- 
 ly, changes into a volatile alkaline fllbftance, inti- 
 mately mixed with oil ; partly empyreumatic, yel- 
 lov/, and volatile ; and partly very fixed, feparable 
 only by the laft degrees of fire, called phofphorus, 
 B b a congealing 
 
KIDNEYS. 
 
 Chap. XXVI, 
 
 386 
 
 a congealing fubftance, fpontaneoufly emitting light, 
 and taking fire in the air : and with earth in greater 
 quantity than any other human fluid, both creta- 
 ceous and fparry ; the latter coming chiefly from 
 the drink, the former alfo from the folid parts of 
 the body themfelves, diiTolved and mixed with the 
 blood. But there is alfo fea-falt in frefh urine, and 
 even after long putrefaftion it is found in the phof- 
 phorus, although a great part of it is changed into 
 volatile alkali. Nor is the urine wholly deftitute 
 of an acid, flmilar to the vitriolic, both in man and 
 in animals. There is alfo a fait obtained from 
 urine, which is fufible by heat, cooling and analo- 
 gous to nitre. In fevers, the oily and faline parts 
 of the urine are augmented in quantity and acri- 
 monv. 
 
 4 
 
 DCCLXxxiii. The ureter, continuous with the 
 pelvis, carries on the urine received from the kid- 
 ney, by the preflure of the incumbent vifcera, and 
 of the abdominal and lumbar mufcles, and by the 
 blood circulating and giving impulfe from behind ; 
 and, laftly, by the weight of the urine. The ure- 
 ter, covered by the peritongeum, is compofed of cel- 
 lular membrane ; then of a weak and obfcure muf- 
 cuiar coat, if any : then a fecond cellular coat ; a 
 firm, white, nervous one ; a third cellular coat, and 
 an innermoft very fniooth memibrane, porous and 
 glandular internally ; and it is in general moderately 
 irritable. It is of diflerent diameters in different 
 places, and every where fwells into veficles. It de- 
 fcoids along the pfoas mufcle, acrofs the great iliac 
 vclfels, arrives into the pelvis behind the urinary 
 bladder ; and, at the union of the defcending and 
 tranfverfe portions of the bladder, enters obliquely 
 betwixt the mufcular fibres and nervous coat ; and 
 dcfcends betwixt the nervous and villous coats, for 
 a conflderable way inwardly, fo that the mouths of 
 the two ureters are near each other, and open by a 
 truncated orifice. They have no valves, cither at 
 
 their 
 
Chap. XXVL 
 
 KIDNEYS. 
 
 3S7 
 
 their orifice, or in any part of their courfe. From 
 their infertion, a protuberant line of the thickened 
 nervous coat defcends towards the caput gaUinagx» 
 nis. 
 
 DccLkxxiVi That the urine is feparated in the 
 kidneys, is a matter of fact, as it can be emulged 
 from its canals by preffure. That it defcends by 
 the ureter, is fiiewn by the furprifing fw'eiling of 
 the kidney, and of that part of the ureter which is 
 above a ligature, and by the emptinefs of that part 
 which is below it. That it paiTes into the bladder, 
 is alfo proved, by the immenfe fwelling of the ure- 
 ters and kidneys, as often as the bladder cannot re-^ 
 ceive the urine, or cannot emit it ; in confequence 
 of an obftacle in either place. 
 
 bccLxxxv. Nor does the urine feem to come 
 in any other way. For although it be certain, that 
 the llomach, like all other membranes, exhales ; al- 
 though it be not improbable, from experiments, that 
 the bladder alfo abforbs ; and although the palTage 
 of acidulous waters be extremely quick ; it does not 
 follow, that there is a way, different from the ure- 
 ters, to convey the water from the food to the blad- 
 der. For the bladder is, on all fides, feparated from 
 the cavity of the abdomen by the peritonaeum ; nor 
 is it afcertained that vapours, either exuding from 
 the bladder, or tending towards it, can here find 
 open pores in the peritonaeum ; and membranes 
 which are already wetted and faturated with moif- 
 ture, do not imbibe much. But the urine alfo which 
 is contained in the bladder, diftends it even fo as 
 to occafion death ; and does not find any paffage 
 through which it can efcape into the pelvis ; and on 
 the other hand, when the ureters are obftrufted with 
 ftones, fo that the bladder receives nothing from 
 them, it is either quite empty, or contains a very 
 acrid and thick urine, m.anifeftly indicating that the 
 water can find no way from the pelvis into the 
 bladder. And a careful attention to the manner in 
 B b 2 vdiich 
 
BLADDER. 
 
 Chap. 
 
 383 
 
 which mineral waters are difcharged by urine, de- 
 monftrates, that there is no fuch rapidity therein as 
 is commonly imagined 5 but that the cold of the 
 water drunk, like external cold applied to the Ikin, 
 ftimulates tlie bladder, fo as to make it difchar^e 
 immediately the urine it contains already fecreted, 
 and not that derived from the drink juft taken. 
 Again, the largenefs of the renal veflels demon- 
 ftrates, that not much lefs than an eighth part of 
 the blood of the whole body is fent to the kidneys ; 
 and, confequentiy, above 1000 ounces of blood in 
 an hour ; fo that it is not farprifing that 20, or even 
 50 ounces of water, are feparated from the blood in 
 that fpace of time. Finally, it is certain, that both 
 man and animals perifh if the ureters be tied or ob- 
 ftruLfted ; nor, in thefe circumftances, is any urine 
 found in the bladder. 
 
 nccLXXxvi. The urinary bladder is feated in the 
 cavity of the pelvis, which is an appendix to the 
 abdomen, furrounded almoft on aU fides by bones ; 
 but laterally, and at the bottom, only inclofed by 
 mufcles ; and in every dimenfion, larger in women 
 than in men. it is fo fituated in it, as to cohere 
 with the oflli pubis by much cellular fubftance ; 
 then it receives from them the peritonseum, which 
 is applied to a fmall part of it before ; but Behind 
 the bladder, it defeends for a great way, almoft as 
 far as the infertions of the ureters ; from whence it 
 proceeds ta the re<ftum, or to the uterus in women.. 
 Behind the bladder, the feminal veficies, proftate 
 gland, reefum, and levatores ani, lie under it. In 
 the foetus, the bladder being very long, and coni- 
 cal, extends above the ofla pubis ; but in adults, it 
 hardly ariies above thofe bones, even when inflat- 
 ed, becaufe, in them, the pelvis is much larger and 
 deeper in proportion to the body. 
 
 DccLxxxvii. The figure of the bladder is, in gen- 
 eral, oval, but its anterior furface is flatter, its pof- 
 terior more convex, and its inferior obtufe vertex, 
 
 which 
 
Chap. XXVI. 
 
 BLADDER. 
 
 3S9 
 
 which refts upon the rectum, is very flat and broad. 
 Such is the figure of it in the male adult : in the 
 foetus it is almofl: cylindrical ; and, in women, who 
 have had many children, it is fo much flattened lat- 
 erally, that it refembles a roundifli tetrahedral fig- 
 ure, of which the fections are triangular. This 
 change feems to arife from the weight of the urine, 
 which deprefles the lower parts of the bladder, and 
 extends it in breadth, fo as to render it fliorter and 
 broader. It is of different magnitudes ; fo that, in 
 fome difeafes, from irritation, and habitual contrac- 
 tion, it becomes very fmall, 
 
 DCCLXxxviii. The fabric of the bladder is much 
 like that of all large membranous receptacles. The 
 firft membrane is cellular ; in its forepart lax, and 
 replenifhed with fat ; behind, it is lefs fo, where it 
 alfo unites with the redum. In this, there is a net- 
 work of veffels, chiefly of veins. Next to this fol- 
 lows the mufcular coat, which is very difixcult to 
 deferibe, conflfting of pale contracHle fibres, difpof- 
 ed in various reticulated bundles, not continuous, 
 but with intervening fpaces, in which the nervous 
 coat lies uncovered. The principal ftratum of thefe 
 is longitudinal ; which, arifmg before from the prof- 
 tate gland, and frequently, though not always, fo 
 connected to the fynchondrofis of the offa pubis, or 
 the membranes covering it, as feemingly to arife 
 from thence, afeend towards the conical fuperior 
 extremity of the bladder ; defeend over it, along the 
 pofterior furface, become at that place very broad, 
 and again terminate at the proftate ; but at the fides 
 they diverge, varioufly palmated, and are blended 
 from the anterior and pofterior planes. Thefe fi- 
 bres muft deprefs the bladder, and confequentiy 
 propel the urine towards its lower part. 
 
 DccLxxxix. The remaining fibres are very difii- 
 eultiy reduced to any order. They fill the inter- 
 vals of the former ; arifing from the proftate, then 
 infleded, they afeend, and form a ftratum, partly 
 
 oblique, 
 
390 
 
 BLADDER. 
 
 Chap. XXVL 
 
 oblique, and partly tranfverfe, the interior ones 
 more fo than the others, both in the forepart and 
 back part of the bladder. 
 
 Dccxc. The contracfile force of th? bladder is 
 gentle, but perpetual ; fo that it contracts from its 
 greateft dilatation to its fmaileft diameter, without 
 any alternate relaxation, and remains long in its 
 Rate of greateft contraction. The urine is its leaft 
 uneafy fdmulus ; water injected is more fo ; and 
 calculus, and every kind of irritation, the molt in- 
 fufferable. When immoderately diftended, it lofes 
 its powers ; fo that either it cannot expel, or it can- 
 not retain the urine. 
 
 Dccxci. Within the mufcular coat is fpread the 
 fecond cellular ftratum, of an elegant fabric, inflat- 
 able, more tender, and fofter than in the intcftines. 
 Next follows the nervous coat, continuous with the 
 fkin, and acutely fenfible ; the innermoft, refem- 
 bling that of the fhomach, is lafl: ; more obfcui'e ; 
 diflicultly feparable from the nervous one ; conti- 
 nuous with the epidermis ; and, like it, eafily re- 
 parable, extremely mucous, and folded into various 
 wrinldes, without any certain order. In it, the 
 pores of the cryptse fometirnes appear, but not al- 
 ways eaflly, pouring out a vifcid and bland gluten. 
 The mucus itfeif is very manifeft, and is prepared 
 in greater quantity in proportion to the irritation 
 of the bladder. It is of the greateft importance for 
 diminilhing the irritation of the acrid urine. 
 
 Dccxcii. The veflels and nerves of the bladder 
 coincide with thcfe which go to the genital parts, 
 where we Ihall defer ibe them. Thofe which come 
 from the epigaftrics are fmall. Their principal re- 
 ticulation is in the ftrft cellular ftratum, and there 
 is another in the fecond. Through the villous coat 
 the exhaling arteries exhale, as we learn by experi- 
 ment, from anatomical injeclions ; and the abforb- 
 ing veins open, to which are owing the greater 
 conftftence and higher colour of the urine, wJicn 
 
 retained. 
 
Chap. XXVI. 
 
 BLADDER. 
 
 391 
 
 retained. The lymphatic veffels in the outer cellular 
 ftratum, are eahly demonftrated ; but their origin 
 is probably foreign from the adjacent inteftine. 
 
 Dccxcm. The urinary bladder is of the fame 
 nature with other membranous facs, fo that it both 
 tranfmits water from its cavity through the inor- 
 ganic pores of its membranes, and abforbs water 
 when immerfed in it. 
 
 Dccxciv. Into this bladder, the urine flows, in 
 one uniform ftream, as has been proved, in morbid 
 and uncommon cafes, in which the extremities of 
 the ureters were vilible to the eye, and there re- 
 mains, and becomes more acrid and higher colour- 
 ed, from the abforption of its water. We are not 
 fully acquainted with the caufe, which retains the 
 urine in the bladder. The fphinfler is obfcure ; the 
 deprellion of the bladder feems to affifl, which be- 
 ing convex, defcends upon the recfum, behind the 
 fphincfler, below its orifice, fo that the urine does 
 not reach the orifice of the urethra till collected in 
 fome quantity. It is certain, that the urine does 
 not efcape fpontaneoufly even from the dead body. 
 
 Dccxcv. At length, the urine, by its bulk and 
 acrimony, irritating the fenfible fabric of the blad- 
 der, is expelled, firft by the motion of the dia- 
 phragm and abdominal mufcles, by the preflure of 
 which, impelling the inteftines againfl; the bladde? 
 in the ere6f pofture, the urine makes itfelf a way 
 through the narrow and impeded paflage ; and fec- 
 ondly, by the periftaltic motion of the bladder it- 
 felf, arifing from the contraction of its mufcular 
 fabric (dcclxxxviii. et feq.) 
 
 Dccxcvi. By the urine, befides the water, and 
 part of our food, much matter, that is noxious to 
 the human body, feems to pafs off ; efpecially cal- 
 careous earth reforbed from the bones and folid 
 parts, and which would produce bony crufts and 
 calculi wherever it was retained ; the fparry earth 
 of waters j an acrid oil mixed with fait, fo as to af- 
 
 fume 
 
392 
 
 BLADDER. 
 
 Chap. XXVI. 
 
 fume a volatile nature. The urine, by its retention, 
 difpofes to the generation of calculi, and to gout : 
 when fuppreffed, it produces acute fev^ers ; and laft- 
 ly, flows back to the brain, and is depofited on it, 
 and deftroys it. 
 
 Dccxcvii. From the obtufe vertex of the bladder, 
 not exactly from its bottom., but further forwards, 
 a canal with a fmall orifice, continuous with the 
 bladder, arifes. It is denominated the urethra, and 
 is compofed of an internal membrane, which is evi- 
 dently continuous with the epidermis, of furround-r 
 ing cellular fubftance, and of a firm nervous coat. 
 It is variable in its diameter and direction ; in wo^ 
 men, it is ftraight, tranfverfe, and flrort. I do not 
 find a valve in its orifice, 
 
 Dccxcviii. The urethra is at firfi: furroundcd on 
 all fides, by the profiate gland ; it then proceeds 
 naked, for a fmall fpace ; it is then embraced by the 
 bulb immediately attached to it, firft below, and 
 then above ; it is then received in the interval be- 
 tween the corpora cavernofa of the penis, contigu- 
 ous to it above, and laterally, and acquires ftrength 
 and the ftate of an open tube from them. I'he 
 urethra is widefi; where it arifes from the bladder ; 
 it contracts itfelf conically in the profiate ; in its 
 naked part it is cylindrical ; it enlarges at the firft 
 accefiion of the bulb ; in the penis it is alfo cylin- 
 drical, and again dilates itfelf a little before its ter- 
 mination. 
 
 Dccxcix. This canal is governed by various muf- 
 cies, either proper or contiguous, And firft, in 
 women, there are manifeftly fibres placed round 
 the egrefs of the incipient urethra, which are, on 
 tlie v/hole, tranfverfe, but varioufly decufl'ating each 
 other ; of which the fixed point is in the vagina, 
 and the office is evidently that of a fphincTer, to 
 deprefs the canal, about the opening of which they 
 are clifpofed, and to clofe it againft the refilling 
 contracted vagina, and fphinfler of the anus. In 
 
 man, 
 
Chap. XXVI. 
 
 BLADDER. 
 
 393 
 
 man, fimilar tranfverfe fibres, but forming an arch 
 upwards, run into the conjunction of the bladder, 
 with the proftate ; both covering a longitudinal 
 bundle of fibres and the proftate, and covered by 
 thefe fibres, they are to a certain degree fitted for 
 contracting the orifice of the bladder. 
 
 Dccc. The firft tranfverfe mufcle proceeding tranf- 
 veriely from that branch of the ifchium which fends 
 forth the ereCtor mufcle of the penis, towards the 
 other os ifchium, partly paffes into it, partly is inferr- 
 ed into the middle of die bulb of the urethra, and 
 partly degenerates into the accelerator. It preffes 
 upon, fhakes, and draws backwards the bulb of the 
 urethra. The other, produced from the branch of 
 the os ifchium, is inferred into the ifihmus of the 
 urethra before the bulb, and dilates it. 
 
 DCCC I. But like wife the levator of the anus feems 
 to ralfe the urethra againfi; the os pubis, and to 
 fhut the exit from the bladder ; and the conftric- 
 tion of the accelerator, together with the fphinfter, 
 ’is eafily perceived in the living body, as it per- 
 fectly clofes the mouth of the bladder, and checks 
 the urine even while it is flowing ; whence there 
 is no doubt, that the moderate tenfion of this muf- 
 cle contributes towards retaining the urine. 
 
 Dcccii. An effort being now made, (dccxcv.) by 
 the prefi’ure of the diaphragm, the urine is ejedted 
 with greater celerity, as it com.es from a large re- 
 ceptacle, through a narrow canal ; and, being dif- 
 charged, the body is freed from the uneafy fenfa- 
 tion. The laft drops, which remain in the loweft part 
 of the bulb, and are retained there by their weight, 
 are expelled by the accelerator mufcle, which is 4 
 ftrong mufcular expanlion, placed round the bulb 
 of the urethra, with pennated fibres, meeting in the 
 bottom middle part of the bulb, faftened before by 
 two tendons to the cavernous bodies of the penis 
 behind, and connected by three mufcular portions 
 to the fphincter of the anus, of which two are lateral, 
 
 and 
 
BLADDER. 
 
 Chap. TlYt 
 
 394 
 
 and one central, with fome acceillon from the tranf- 
 verfe mufcles. This mufcle, when the fphincter is 
 fteady and ihut, draws the bulb upwards ; and, 
 acting upon the urethra alternately, with confider- 
 able force, expels the laft drops of the urine. 
 
 Dccciii. We cannot admit, that the pyramidal 
 mufcle of the abdomen, draws the bladder down- 
 wards from the bundle of umbilical veffels, and re- 
 laxes it, and fits it for the action of the long muf- 
 cular fibres, as the mufcle itfelf is often wanting ; 
 as it cannot deprefs the bladder, and very rarely 
 reaches the navel. 
 
 Dccciv. But as the urine is acrid, and the mem- 
 brane of the urethra very fenfible, and as the air 
 can be admitted into it, nature has fupplied this 
 canal with a large quantity of mucus. Befides its 
 fources in the bladder, this mucus is generated, in 
 the firfi: place, by two conglomerate glands ; one 
 of which is feated on each fide, in the angle be- 
 twixt the bulb of the urethra and the cavernous 
 body of the penis, and fends out a duel, running 
 for a confiderable way obliquely along the urethra, 
 and inferted before its bulb. I am ignorant of any 
 gland of the ifthmus different from the cellular tex- 
 ture. Moreover, the whole urethra is full of cy- 
 lindrieal mucous finufes, moft of which defeend 
 towards the glans, though fome run in a contrary 
 dii'eclion, into whofe fides minute cryptee depofite 
 a fluid and bland mucus. The iargeft of thefe 
 fmufes are difpofed in a feries along the upper fide 
 of the urethra, beginning before the bulb, and ex- 
 tending to the origin of the glans. The fmall 
 ones are both mixed with thefe large ones, and dif- 
 pofed on the lides. In women, they are numerous 
 and large in their , fliort urethra, efpeciaUy at its 
 opening. 
 
 Dcccv. The neceffary propriety of human life 
 requires the detention of the urine. But this very 
 utility is attended with the danger of difeafe, finte 
 
 the 
 
Chap. XXVII. MALE GENITALS.. 
 
 395 
 
 the urine when at reft, immediately depohtes its 
 earthy particles, which by the acceffion of new ftrata, 
 form calculi. But the great number of people free 
 from calculi, ihow, that the very lubricous mucus 
 of the bladder is a fullicient protection, unlefs the 
 ufe of fabulous and tophaceous water, of wine, or of 
 vifcid aliments, exceflive inactivity, preternatural re- 
 tention of the urine, the prefence of fome vifcid 
 body to attract the calculous earth, and, finally, ne- 
 phritic difeafes, afford a fuperabundance of calcu.? 
 lous earth, or a nucleus for its adhefion. 
 
 CHAP. XXVII. 
 
 MALE ORGANS OF GENERATION. 
 
 Dcccvi. '' I 'HE veffels belonging to the genitals 
 § arife near the kidneys, almoif in ev- 
 ery kind of animals. This is occafioned by the op- 
 portunity of deriving a double ufe from one organ, 
 w'hich might difcharge both the urine and the fe- 
 men, and by the relation of the genital parts to the 
 interval between the tops of the thighs, which is 
 fubfervient to cleanlinefs, modefly, the facility of 
 parturition, of making water, and to the effed. of 
 the efforts employed in thefe. 
 
 Dcccvii. The male femen is formed in the tef- 
 ticle ; is depofited in the feminal veficles ; is eject- 
 ed from the penis ; is injected into the uterus, and 
 fecundates the ovum. Such is the arrangement we 
 fliall follow. The human tefticles, fmaU in pro- 
 portion to the body, in the foetus, when very young, 
 are lodged within the peritonaeum, and gradually 
 defcend under it into the groins, and when it has 
 arrived at maturity, they lie below the groins ; 
 their fituation being changed, perhaps by the fimple 
 force of their weight, and of the influx of blood ; 
 yet fometimes they remain in the groin, even in 
 
 adults. 
 
MALE GENITALS. Chap. XXW. 
 
 adults. They defcend by a cellular paflage, which 
 in the fetus is open, and called the proccfs leading 
 from the cavity of th^ peritonaeum into the fcro- 
 tum ; and the fame paffage, after the tehicle is 
 tranfmittcd, is contracted and obliterated by a law 
 of nature. 
 
 Dcccviii. The tefcicles are defended by various 
 integuments. In the firft place, they are iurrour.d- 
 ed by the fcrotum, which is formed of a denfe cel- 
 lular coat, vafcular and compacled into a folid mem- 
 brane, clofely adhering to the Ikin, which pofTefTes 
 fome elaftic motion from cold and during venery, 
 but without any mufcular fabric, although when it 
 acts it becomes corrugated, and draw^ up the tef- 
 ticles. This cellular coat, commonly called the 
 dartos, is placed round each of the tefticles feparate- 
 ly ; therefore, at their union, they form a kind of 
 feptum, in a dry preparation ; this feptum is often 
 imperfect in its upper part, near the penis. 
 
 Dcccix. The dartos is interiorly relaxed into cel- 
 lular fubftance, which is inflatable as in other pla-. 
 ces, but without fat, except in the lower part of 
 the fcrotum. Next follovrs a mufcle, from its oL 
 lice called crem after ; which arifes from the degen- 
 erating fibres of the lefs oblique mufcle of the ab- 
 domen, and from the tendon of the obliquus ex- 
 ternus, which has got the name of a ligament, and 
 fometimes from other fibres defcending from the 
 os pubis, and being expanded into a vagina, and 
 furrounding the tefticle behind, and then on all 
 fidcs, it comprefles, elevates, and emulges it. 
 
 Dcccx. Next to this follows the fecond cellular • 
 ftratum, v/hicli is continuous with the exterior 
 fpongy web, which furrounds the pcritonxum ; 
 this is called the tunica vaginalis. It is compofed 
 of lonsrer cells than clfewliere, wliich may be inflat- 
 ed one after another. At the beginning of the 
 tefticie, above the epididymis, part of the va- 
 ginal coat, which furrounds the tefticle, is lb fepa- 
 
Chap. SXVIL MALE GENITALS. jpf 
 
 rated from the rell, which lies higher than the tefti»= 
 cle towards the ring of the abdominal muicles, as 
 almoft to prevent the tranfmiffion of air. Betwixt 
 this membrane and the following, there is a fpace, 
 into which vapour is exhaled, and fometimes a little 
 water is cohered. The innermoft coat of the tef- 
 ticle, called the albuginea, is a Itrong, white, com- 
 pa£t membrane, wliich immediately invefls the fub- 
 ftance of the tellicle. 
 
 Dcccxi. The tefticle properly fo called, is of an 
 oval figure, with an acute vertex, directed up^ 
 wards and a little outwards. The epididymis is a 
 kind of addition to the tefticle ; a flat thick tape, 
 which goes round the pofterior margin of the teft 
 tide, to which it is conneded by cellular texture, 
 and by veflels. Below it is flatter ; on the upper 
 part it adheres to the tefticle by a thick and con- 
 vex head, as it alio does at the very bottom. In 
 the middle, it is partly attached, and being partly 
 loofe, forms a Ihut cavity. 
 
 DcccxiL To the tefticle the fpermatic arteries 
 defcend, one on each fide, arifing from the aorta 
 below the renal arteries ; but not unfrequently 
 from the renals themfelves, or from one of the cap- 
 fulary, or from the aorta itfelf above the renal. 
 This artery, the fmalleft in the body in proportion 
 to its length, defcends outwards before the pfoas 
 mufde, and gives frnali branches to the liver, the 
 fat of the kidney, the ureter, lumbar glands, mefo- 
 colon, peritonseurn, and efpecially a remarkable 
 adipofe branch, bent around the bottom of the kid- 
 ney : and, without becoming lefs, it proceeds be- 
 hind the peritonaeum, as far as the ring of the 
 abdomen. This ring is formed entirely of the ten- 
 dinous fibres, defcending from the external oblique 
 mufcle, interrupted by a long aperture, grov/ing 
 wider downwards ; a great many of which, ftender 
 and interior, are partly inferted extenfively into 
 the middle of the os pubis, and partly decuflate 
 
MALE GENITALS. Chap. XXVIL 
 
 55S 
 
 and unite with the fibres of the mufcle of the op^ 
 polite fide ; thefe are called the inner coluinni 
 Other external ftronger fibres, feparated from the 
 former by the aperture, are inferred in a thick bun- 
 dle into the outer fide of the os pubis, under the 
 denomination of the external column : from it va- 
 rious fibres run off to the fafcia lata and groin. 
 The upper part of this opening is in fome meafure 
 clofed up by fibres, arifing from the outer column j 
 ihllefted and afcending along the inner and weaker 
 column. Below thefe fibres, through the fmall 
 opening left, which is often divided b}" tendinous 
 fibres, the fpermatic artery defcends, along with 
 the vein, and vas deferens, formed into a cylindrical 
 cord, with a good deal of cellular fubftance, before 
 the external column, but does not perforate the 
 peritonaeum, which lies before it through its whole 
 extent. At this ring, the duclus deferens is joined 
 wnth the rope of vefl'els, and the whole bundle pro- 
 ceeds into the groin, and afterwards into the fcro- 
 tum. The fpermatic artery gives many branches 
 to the cremafter, to the cellular coat, and to the 
 feptum of the fcrotum ; and defcends in two plex- 
 ufes to the tefticle ; of which the principal palfes 
 betwixt the epididymis and origin of the vas de- 
 ferens, to the middle and lower part of the tefticle, 
 and is diftributed in tranfverfe branches, through 
 the albuginea : the other plexus goes to the tefticle 
 in company with the vas deferens, has a like termi- 
 nation, and is varioufly inofculated with the former. 
 Other fmall arteries go to the coverings of the tef- 
 ticle from the epigaftrics, and others from thofe of 
 the bladder, accompanying the vas deferens ; both 
 of which communicate with the fpermatic veffels. 
 
 Dcccxiii. Thefe very numerous arteries play a- 
 bout the epididymis ; but the larger of them fpread 
 tranfverfely through the albuginea, which they per- 
 forate in fevcral places, and enter into the inner- 
 moft fubftance of the tefticle, through v hich they 
 
 are 
 
Chap. XSVII. MALE GENITALS. 399 
 
 are every where diftributed upon the numerous 
 membranous feptuia. There is no larger anafto- 
 moiis or communication betwixt the fpermatic ar^. 
 tery and vein here, than in other parts, nor are the 
 branches .within the albuginea, received into the 
 tefticle, without blood. But the long courfe of this 
 artery, the fmallnefs of its diameter, the ferpentine 
 flexures, the great proportion of the branches to 
 the trunk, and their cold fituation, demonftrate, 
 that the blood arrives at the tefticle flowly, and in 
 final! quantity. 
 
 Dcccxiv. The right fpermatic vein carries its 
 blood to the cava ; the left to the emulgent vein, 
 or to both : it is enormoufly larger than the artery, 
 both in its trunk and branches and accompanies 
 it, but more plentifully, having feveral trunks in- 
 terwoven into a very long reticulated "web within 
 the abdomen, which furrounds the artery, and is 
 continued into the tefticle, by degrees dividing in- 
 to two like the artery. There are fome valves in 
 this vein, though few. 
 
 ncccxv. The external coverings of the tefticle 
 have their arteries from the epigaftrics ; the fcro- 
 tum from the crural arteries, and from the internal 
 branch of them, v/hich is called the external pu- 
 denda ; the core efpondent veins go to the faplnena, 
 and to the crural veins. 
 
 Dcccxvi. The nerves of the tefticle are many, 
 whence its fenftbility is peculiarly acute, fo that 
 injuries of the tefticle are immediately followed by 
 faintings and convulfions, and particularly by lock- 
 ed jaw. Some of them arife deep from the renal 
 plexus, from the great mefenteric plexus, from the 
 trunk of the intercoftal nerve, and laftly from the 
 mefocolic plexus, and follow the courfe of the 
 fpermatic veffels. Others, more fuperficial, defeend 
 to the coverings of the tefticle, from the fecond, 
 tliird, and fourth pair of the lumbar nerves. 
 
 DCCCXVII. 
 
MALE GENITALS. Chap. XX^TL 
 
 3.9 S 
 
 and unite with the fibres of the mufcle of the op- 
 pofite fide ; thefe are called the inner column. 
 Other external ftronger fibres, feparated from the 
 former Iry the aperture, are inferted in a thick bun^ 
 die into the outer fide of the os pubis, under the 
 denomination of the external column ; from it va- 
 rious fibres run off to the fafcia lata and groin. 
 The upper part of this opening is in fome meafure 
 clofedup by fibres, arifing from the outer column, 
 inflected and afcendihg along the inner and weaker 
 column. Below thefe fibres, through the fmall 
 opening left, which is often divided by tendinous 
 fibres, the fpermatic artery defcends, along with 
 the vein, andvas deferens, formed into a cylindrical 
 cord, v/ith a good deal of cellular fubftance, before 
 the external column, but does not perforate the 
 peritdnseum, which lies before it through its whole 
 extent. At this ring, the ductus deferens is joined 
 with the rope of veflcls, and the Vv*hole bundle pro- 
 ceeds into the groin, and afterwards into the fcro- 
 tum. The fpermatic artery gives many branches 
 to the cremafler, to the cellular coat, and to the 
 feptum of the fcrotum ; and defcends in two plex- 
 ufes to the tefiicle ; of which the principal pafles 
 betwixt the epididymis and origin of the vas de- 
 ferens, to the iTiiddle and lower part of the tefticle, 
 and is diftributed in tranfverfe branches, through 
 the albuginea : the other plexus goes to the tefticle 
 in company with the vas deferens, has a like termi- 
 nation, and is varioufly inofculated with the former. 
 Other ftnall arteries go to the coverings of the tef- 
 ticle from the epigaflrics, and others from thofe of 
 the bladder, accompanying the vas deferens ; both 
 of which communicate with the fpermatic velTels. 
 
 Dcccxiii. Thefe very numerous arteries play a- 
 bout the epididymis ; but the larger of them fpread 
 tranfverfely througlt the albuginea, which they per- 
 forate in fevered places, and enter into the inncr- 
 mofl fubftance of the tefticle, through which they 
 
Chap. XXVII. MALE GEmXALS. 
 
 399 
 
 are every where diflributed upon the numerous 
 membranous feptula. There is no larger anafto- 
 mofis or communication betvdxt the fpermatic ar- 
 tery and vein here, than in other parts, nor are the 
 branches within the albuginea, received into the 
 tefticle, without blood. But the long courfe of this 
 artery, the fmallnefs of its diameter, the ferpentine 
 flexures, the great proportion of the branches to 
 the trunk, and their cold lituation, demonftratCj 
 that the blood arrives at the tefticle flowly, and in 
 fmali quantity. 
 
 Dcccxiv. The right fpermatic vein carries its 
 blood to the cava ; the left to the emulgent vein, 
 or to both : it is enormoufly larger than the artery, 
 both in its trunk and branches ; and accompanies 
 it, but more plentifully, having feveral trunks in- 
 terwoven into a very long reticulated w^eb within 
 the abdomen, v/hich furrounds the artery, and is 
 continued into the tefticle, by degrees dividing in- 
 to two like the artery. There are fome valves in 
 this vein, though few. 
 
 Dcccxv. The external coverings of the tefticle 
 have their arteries from the epigaftrics ; the fcro- 
 tum from the crural arteries, and from the internal 
 branch of them, which is called the external pm 
 denda ; the correfpondent veins go to the faphaena, 
 and to the crural veins. 
 
 Dcccxvi. The nerves of the tefticle are many, 
 whence its fenftbility is peculiarly acute, fo that 
 injuries of the tefticle are immediately followed by 
 faintings and convulftons, and particularly by lock- 
 ed jaw. Some of them arife deep from the renal 
 plexus, from the great mcfenteric plexus, from the 
 trunk of the intercoftal nerve, and laftly from the 
 mefocolic plexus, and follow the courfe of the 
 fpermatic veffels. Others, more fuperficial, defcend 
 to the coverings of the tefticle, from the fecond, 
 third, and fourth pair of the lumbar nerves. 
 
 Daccxvii. 
 
MALE GENITALS. Chap. XXm 
 
 460 
 
 Dcccxvii. I hare frequently obferved lymphatic 
 veffels in the fpermatic cord, which are belie^^ed 
 to arife from the tefticle itfelf, and which unite 
 with thofe that accompany the inguinal blood- 
 velTels. The induftry of late anatomifts has tra- 
 ced fome of them even to the network of the tefti- 
 de itfelf. 
 
 Dcccxvjii. The blood, moved flow'ly and in a 
 fmall quantity, brought by its arteries into the in- 
 ner fabric of the tefticle, (dcccxiii.) is diftributed 
 into minute veffels, which carry their fluids to the 
 feminal veffels, although we are ignorant of the 
 manner by which the arteries communicate with 
 thefe tubes, bundles of which form the whole fub- 
 ftance of the tefticle. Thefe are fmall, ferpentine, 
 fomew^hat firm, and have a very fmall caliber in 
 proportion to their membranes j they are not, how- 
 ever, fo impervious as to prevent them from being 
 ftlled through the vas deferens. They are collect- 
 ed together into bundles, above tw^enty in number, 
 feparated by cellular partitions, which defcend 
 from the albuginea into the tefticle, and condud 
 the arteries and veins. In each cell there is a duct 
 which receives the femen from the feminiferous 
 veflels. Thefe ducts, twenty or more in numberj 
 form a network of longitudinal veffels adhering 
 to the albuginea, and inofculate wdtll each other ; 
 and readily permit quickfilver to efcape into the 
 furrounding cellular fubftance. From this net 
 twenty or thirty ducts afeend to the upper part of 
 the epididymis, which being wonderfully convolu- 
 ted, form as many vafcular cones. Thefe, joined 
 together by intermediate cellular fubftance, and ly-» 
 ing upon each other, form the head of the epididy- 
 mis, and in that head foon meet together into one 
 dudl on the outfide of the tefticle. 
 
 Dcccxix. This finsrle duct beins^ convoluted into 
 an infinite numher of folds and ferpentine flexures. 
 In a manner not found in any other part of the 
 
 body, 
 
Chap. XXVII. MALE GENITALS. 
 
 4c<J ' 
 
 body, and connected together by much loofe cel- 
 lular fubftance, and being collected by one con- 
 tinuous membrane produced from the albuginea, 
 conftitutes the epididymis. But the du6l of which 
 the epididymis is compofed, grows larger as it de- 
 fcends ; from whence being reflected, it again af- 
 cends along the pofterior furface of the tefticle, and 
 by degrees unfolding its fpiral convolutions, which 
 are now much larger, it gets the name of ductus 
 deferens. Almoft always, however, a fmall veffel 
 feparates fomewhere from the du<5tus deferens, and 
 afcends along with the chord, having an uncertain 
 termination. 
 
 Dcccxx. This is the courfe defcribed by the fe- 
 men, moved forwards by the fluid fuccellively 
 coming from the tefticle, and perhaps by the cre- 
 mafter ; but very flowly, as we may conclude from 
 the numberlefs convolutions of the epididymis, ob- 
 ftru(fLing almoft every kind of injeftion ; and from 
 the length of time that is required to repair the 
 femen, after the feminal veftcles have been ex- 
 haufted. 
 
 Dcccxxi. The cylindric du(ftus deferens being 
 compofed of very thick fpongy fubftance, included 
 betwixt two firm membranes, perforated by a very 
 fmall tube, begins at the bottom of the epididymis, 
 afcends in the chord of the fperm.atic veffels, pafles 
 through the ring of the abdomen (dcccxii.) de- 
 fcends into the pelvis, applies itfelf to the bladder 
 between the ureters, and there meets with its fab- 
 jacent receptacle, which is called the veficula femi- 
 nalis, of which there are two, one right and one 
 left. Here the vas deferens lies on the inner fide 
 of the veficle, as far as the proftate gland ; and be- 
 ing dilated in its courfe, and bent in a ferpentine 
 direction, it appears cellular. But very near the 
 proftate, the duct, being continued from thefe cel- 
 lular windings, unites with a conical du6t coming 
 from the veficle, in a very acute angle, into one 
 C c duct, 
 
402 
 
 MALE GENITALS. Chap. XXVIL 
 
 du(T, alfo conicalj which is continued rather from 
 the vas deferens, and penetrates through the prof- 
 tate gland, there forms a great flexure, diverges 
 outwardly at right angles from its companion of 
 the other fide, and, becoming contracted, opens in- 
 to the urethra in one of the two very fmall lateral 
 orifices of the tumid, long beaked, hollow protu- 
 berance. By injecting a liquor into the ductus de- 
 ferens of a dead fubject, we perceive that it flows 
 both into the urethra and into the feminal veficle, 
 but more readily into the former : but in a living 
 perfon the femen never Slows out but in the act of 
 venery ; and confequently the ductus deferens con- 
 veys all its femen, notwithftanding the retrograde 
 angle, to the feminal veficle. 
 
 Dcccxxii. By this laft denomination we under- 
 ftand a membranaceous, firm inteftine lying under 
 the bladder, connected with it by much cellular 
 fubflance : from which ten or more impervious cells 
 proceed, fome of which are alfo ramified and divid- 
 ed, but which end in impervious conical extremi- 
 ties. This inteftine, with a great deal of firm cel- 
 lular fubftance and intervening veffels, and perito- 
 naeum lying under it, is fo contracted, as to be col- 
 lected into a fhort ferpentine mafs. Befides, its ex- 
 ternal fabric is pulpy and thick, and is fomething 
 analogous to the ductus deferens.. Its external fab- 
 ric is wrinkled like the villous and reticulated coats 
 of the biliary veffels, villous with minute flocculi ; 
 and is faid to have fmaU pores and glands, with 
 which I am unacquainted, though it certainly has 
 various, and hoUow cells. 
 
 Dcccxxiii. The liquor depofited in it,, in the 
 telticle is yellowifh, thin, and watery and retains 
 the fame nature in the veficle, though it becomes 
 there more vifcid and yellow ; and laftly, in man 
 it becomes white, when it is mixed with the liquor 
 of the proflate. It has a peculiar hea\w fmell, in 
 every kind of animal j and it is the heaviefl fluid 
 
Chap. XXVII. MALE GENITALS, 403 
 
 in the body* In water, part of it forms a thin, 
 fwimming pellicle, but the greater part, which is 
 feemingly of a pulpy nature, links to the bottom ; 
 and in the femen which has been long retained by 
 continent people, Ihining globules mixed with a 
 whiter liquor are ealily feen with the naked eye., 
 It agrees in many particulars with mucus< 
 
 DcccxxiVi Without the conveyance of this into 
 the womb, no animal which is of two fexes can be 
 fecundated. The reafon of this was unknown, till 
 the microfcope fhewed, that in man, and in every 
 other animal, the feminal liquor is full of living 
 animalcules, refembling eels, having in man a thick 
 liead, and a long and flender but confpicuous tail ; 
 which are always found in healthy femen, from 
 the period of puberty ; but, before that time, and 
 in thofe who are fterile from ficknefs, they are ab^ 
 fent, and they are not found in any other animal 
 fluid; That they are animalcules, appears evident- 
 ly from their various motions, avoiding obftacles, 
 retrogreflion, and change of velocity. 
 
 Dcccxxv. The real ufe of thefe animalcules has 
 been much doubted ; and we flhall have another 
 opportunity of confldering the received opinion, 
 that they are as it were the firft appearance of the 
 future animal; To me, in the mean time, the na- 
 ture of the feminal animalcules feems to be the 
 fame with that of the eels in vinegar or other in- 
 fufory animals. 
 
 Dcccxxvi. That the femen is produced from the 
 lymph of the blood, and that the chyle is added to 
 the lymph appears probable from the difpofltion to 
 venery quickly fupervening after eating, and be- 
 ing leflened by falling. It is compounded of the 
 liquor of the tefticles, and of the feminal veficles, 
 which in fome animals is more evident, and of the 
 coagulable milky fluid of the proftate gland; That 
 liquor, however, only fecundates which is generat- 
 ed in the tefticles 5 as we fee from cafcrated ani- 
 c c 2 mals. 
 
404 
 
 MALE GENITALS. Chap. XXVII. 
 
 mals, which, though they have the feminal veficles 
 and proftate, are yet unprolific. 
 
 Dcccxxvii. The feminal fluid is retained in the 
 veficles, excepting in the venereal act and in the 
 illufions of dreams. Being prefent during that 
 whole time, according to its quantity, it ftimulates 
 the animal to venery. But a conliderahle part of 
 the femen, and that the moft volatile and odorous, 
 is abforbed into the blood, and by its addition to 
 it produces wonderful changes. Impregnating the 
 whole animal with its fmeU, caufing the beard, and 
 hair upon the pubes, and horns to grow, changing 
 the voice and difpofitions. For thefe do not hap- 
 pen in confequence of the age of the animal, but 
 of the femen, and never occur in eunichs. The 
 growth and ftrengtli of caftrated animals are di- 
 miniflied ; but in uncut animals, the ferocity and 
 llrong fmell, diffufed through the w'hole fiefli, in- 
 creafes. And from fome examples o£ anim.als, and 
 even of men, it has evinced a fatal irritating pow- 
 er, by exciting convulfions. Retention of the femen 
 feems to proceed from the narrownefs of the femi- 
 nal duel, excretory duft, a feirrhofity of the prof- 
 tate, and other .caufes not fufficiently known. * 
 
 Dcccxxviii. The quantity of femen expelled at 
 one time from the veiicles in man is but fmall, 
 efpeciaUy if the abftinence from venery has been 
 iiiort ; and it is natural that it fliould be but flowly 
 produced from fo fmall, and that a fubcutaneous 
 artery. Its generation is accelerated by love, by 
 the prefence of the beloved objefl ; fo that it dif- 
 tends its veffels with a fenfe of pain. Nature her- 
 felf, therefore, enjoins venery for the prefervation 
 of the human race, and likewife of the health of 
 every found man. That it paffes from the tefticle 
 into the veficles, is fhewn by difeafes, in which the 
 duffus deferens being obftruCfed, a fweUing of the 
 tefticle has enfued. From the veficle it does not 
 efcape, except during the venereal act. 
 
 DCCCXXIX. 
 
Chap. XXVIT. MALE GENITALS. 405 
 
 Dcccxxix. As the femen is fmall in quantity, 
 that it might be proje^Ied with greater force, and 
 to a further diftance, another humour, which is 
 generated by the proftate, is added to it. This 
 gland, fliaped like a heart, with the fmall end fore- 
 moft, furrounds the origin of the urethra, and con- 
 tains it, though moft contiguous to the upper fur- 
 face of the gland. It is a very hard and compadl 
 gland, of a peculiar fabric, not evidently conglom- 
 erate ; it prepares a thick, white, bland, copious 
 fluid, which is projected at the fame time and from 
 the fame caufes (dcccxl.) with the femen itfelf, 
 into the excavations at each fide of the openings of 
 the feminal veficles, through numerous duels, and 
 in the femen its white colour and vifeidity are pre- 
 dominant. 
 
 The urethra, although cylindrical upon the whole, 
 has three confiderable dilatations. The firft in the 
 proftate at the caput gallinaginis, the fecond in the 
 bulb, and the third in the beginning of the glans. 
 Its courfe at firft is generally horizontal, afterwards 
 it afeends along the ofiTa pubis, and in the male it 
 is finally pendulous, except in the time of venery. 
 It is a continuation of the nervous coat of the blad- 
 der, and is internally lined with a very fmooth epi- 
 dermis ; between which and the nervous coat there 
 is cellular fubftance. 
 
 Dcccxxx. But is was neceflary for this urethra 
 to be firm and ftraight, that the femen might be 
 thrown with fome force into the diftant womb j 
 therefore it is furrounded by a triple cavernous bo- 
 dy. The firft, the proper cavernous body of the 
 urethra, begins, as foon as that canal has pafled the 
 proftate, with a thick origin, almoft like a heart j 
 at firft it lies under the urethra, but afterwards fur- 
 rounds it alfo above, but is there thinner, and ac- 
 companies it through the whole length of the pe- 
 nis, till the lower part terminates in the glans, while 
 the upper part is refteded back from the extremity 
 
 of 
 
MALE GENITALS. Chap. XXVII. 
 
 406 
 
 of the urethra, and, being dilated, returns in a con., 
 trary direftion along the penis, and, being termi- 
 nated by a broad, thinner, and round extremity, it 
 refts upon the corpora cavernofa penis, and for the 
 moft part communicates with them by an imperfect 
 feptum. The fabric of this body is cellular, but 
 lax, and compofed rather of plates, interwoven like 
 a net, than of fibres, and inclofed between two firm 
 membranes. 
 
 Dcccxxxi. Into this cavernous body of the ure- 
 thra, the blood is poured out from the deep feated 
 arteries, which come from the external hemorrhoi- 
 dals (dcccxxxvi.) This is demonftrated by the 
 injed:ion of any kind of fluid, which eafily flows 
 from thefe arteries into the cellular fpaces fur- 
 rounding the urethra. But they are not fponta- 
 neoufly turgid with blood, becaufe there are veins 
 equally open, fufficient to carry av^ay the effufed 
 blood. But when thefe veins are coinprefled by 
 the powers mentioned in dcccxxxix. the blood is 
 then retained within the cellular fpaces, while the 
 arteries, being ftronger, continue to pour it in. 
 Thus the blood ftagnating, diftends the bulb of the 
 urethra, together with its cavernous body, and the 
 glans itfelf. But this is performed generally when 
 the other cavernous bodies of the penis, with which 
 this of the urethra has no communication, are pre- 
 vioufly diftended. 
 
 Dcccxxxii. The cavernous bodies of the penis 
 arife from the ofia ifehii, almofl: from their bottom, 
 with which they are joined by a white, cellular, 
 but very denfe and firm fubftance ; from whence 
 inclining inwards and towards each other, they in- 
 clofe the urethra, a little before its bulb, where, 
 changing their direction, they go on parallel, and 
 conjoined together, with the urethra lying below 
 and between them, and terminate in the glans with 
 an acute end, laterally furrounded by the cavernous 
 body of the urethra. They confifl; of a veiw firm 
 
 integument, 
 
Chap. XXYII. MALE GENITALS. 
 
 407 
 
 integument, and Ipongy internal flefli, as in the 
 urethra, (dcccxxx.) like it aifo capable of being 
 diftended with blood. Between thefe cavernous 
 bodies, there is a middle feptum, compofed of 
 firm parallel tendinous fibres, growing narrower 
 downwards, and not continuous ; fo that the inter- 
 mediate fpaces are larger and more numerous, as 
 they are more forward j and a free communication 
 is left between the right and left fpongy body. 
 Other fibres of this kind run through the cavernous 
 bodies, as well as the feptum, and are inferted in- 
 to the very firm involucrum : they prevent over- 
 diftention and aneurifms of the penis. 
 
 Dcccxxxiii. Thefe cavernous bodies are fur- 
 rounded by much very fine cellular fubftance ; of 
 which the part lying next the cavernous bodies is 
 tenfe and firm, like a membrane j without it the 
 cellular fubftance is very tender, continuous with 
 that of the fcrotum, and included within a thin 
 fkin without any fat, and always the more tender 
 the nearer the fkin it is. By inflation, it affumes 
 a beautiful fiiky texture. But the glans (dcccxxx.) 
 is covered in the following manner by the fkin : be- 
 ing continued from the penis, and reflecled againft 
 itfelf, as in the eyelids ; covered on both fides with 
 its proper cuticle, and filled with intermediate cel- 
 lular fubftance, it is called the preputium, and may 
 be drawn back, and laftly, it is continued forwards 
 again to the glans penis, and is there changed into 
 a tender, foft, fpongy, flocculent body, acutely fen- 
 fible, covered with its proper cuticle, and with a 
 depreffed pulpy reticulum, fpread over the refledted 
 cavernous body of the urethra, (dcccxxx.) and, 
 finally, continuous with the membrane of the ure- 
 thra itfelf. The prepuce is tied by a double trian- 
 gular frsenulum, by which the fkin is joined to the 
 cellular involucrum of the penis, as far as the mouth 
 of the urethra. In the hollow which lies under the 
 crown of the glans, and in that circle itfelf, are 
 
 feated 
 
MALE GENITALS. Chap. XXVIL 
 
 408 
 
 feated limple febaceous follicles, v/hich feparate a 
 liniment, which, from the nature of the place, is 
 fetid, as in other parts of the body expofed to fric- 
 tion. The whole penis is fuftained by a firm cel- 
 lular fubftance, compadfed into a kind of triangular 
 ligament, which defcends from the fynchondrofis of 
 the ofia pubis, and is continuous with the denfe 
 and hard cellular ftratum that furrounds the caver- 
 nous bodies. 
 
 ncccxxxiv. The whole human penis forms a 
 cylindrical body, deprelTed on the upper part, of 
 variable magnitude, whofe ufe is to be received into 
 the female parts of generation, and to carry thither 
 the prolific femen. 
 
 Dcccxxxv. Thcfe cavernous bodies of the penis, 
 during coition, by the blood impelled through the 
 arteries, and retained in the veins, become turgid, 
 diftended and ftilF, and fuftain the flaccid, or if it 
 alone were filled, the weak urethra, in fuch a man- 
 ner that the femen may arrive at the diftant womb. 
 This is demonftrated from the difleclion of animals 
 killed in the acf of venery, from artificial eredion, 
 from the injedion of liquid fubftances into the vef- 
 fels of the penis. It is produced by love, the defire 
 of enjoyment, the fridion of the glans, and various 
 irritations of the bladder, tefticles, feminal veflels, 
 and urethra, from urine, from abundance of good 
 femen, from the venereal poifon,from cantharides, 
 whipping with rods, or nervous convmlfion. But 
 the caufe of this diftention is not yet evident. The 
 defcription of the diftribution of the blood-veflels 
 into the genital parts is therefore now neceflary, to 
 Ciow how little it is adapted for promoting the 
 caufe tvhich coinpreflTes the veins. 
 
 Dcccxxxvi. The aorta at the fourth vertebra of 
 the loins, and the vena cava at the fifth, are didd- 
 cd ; of thefe the latter is pofterior, the former an- 
 terior. The common iliac branches, before they 
 arrive at the middle interval at the beginning of 
 
Chap. XXVII. MALE GENITALS. 
 
 409 
 
 the thighs, fend off inwards and downwards a con- 
 fiderable artery, called the hypogaftric, which in 
 the foetus is larger than the femoral artery, and in 
 tire adult is equal to it. This defcends into the 
 pelvis, and divides into four, five, or fix principal 
 branches ; of which the firfl: is the iliaca anterior, 
 which alfo fends branches to the dura mater and 
 cauda equina, upwards to the loins, and downwards 
 to the os facrum. The next, the facra lateralis, 
 goes to the fame os facrum and cauda equina, when 
 it does not arife from the former. The third, the 
 iliaca pofterior, is almoft confined to the glutei 
 mufcles. The fourth, the ifchiadica defcendens, 
 fupplies feveral mufcles, the nerves, and the leva- 
 tor ani. The fifth, or the trunk, is the hsemorrhoi- 
 dea infirna or pudenda communis, which, within 
 the pelvis itfelf, fends confiderable branches to the 
 bladder, and to the rectum the middle hsemorrhoi- 
 dal, which anaftomofes with the mefenterics ; after 
 which, going out of the pelvis, it creeps by the fide 
 of the obturator, and gives off the external hiemor- 
 rhoidals to the fphincler and fkin of the anus : 
 then dividing, its internal branch fupplies the bulb 
 of the urethra and the proftate ; the external is 
 again divided, and with one branch enters deeply 
 into the cavernous body of the penis, and runs 
 through its whole length ; while, the other branch 
 often joined with the veffels of the bladder, runs 
 along the back of the penis, and terminates in 
 branches fent to its corpora, and to the fkin. The 
 fixth is the obturatrix, fpent upon the joint of the 
 femur and adjacent mufcles. The laft, the umbil- 
 ical artery, wiU be defcribed in treating of the foe- 
 tus ; in the adult it fends fome branches- to the 
 bladder, from its thick callous vagina. Sometimes 
 feveral of thefe arteries arife from one common 
 trunk. The fkin of the penis and fcrotum have 
 their arteries from the epigaftric, from the crural, 
 and from its internal branch. Thefe external ar- 
 teries 
 
410 MALE GENITALS. Chap. XXW. 
 
 terles communicate in m.any places with the inter- 
 nal. 
 
 Dcccxxxv'ri. The veins, in general, correfpond 
 with the arteries. They often come off from the 
 iliacs in two trunks, forming a plexus with each 
 other ; then the haemorrhoidal vein,' returning a- 
 round the os pubis, forms a very large plexus upon 
 the proftate gland, wnth the veins of the bladder 
 arifmg in the pelvis : from which the vena penis 
 arifes, which is often lingle, and is furnilhed with 
 valves, determining the return of the blood to the 
 cava. The external veins of the penis and fcrotum 
 go to the faphsena and crural, and communicate in 
 feveral places with the internal veins, more efpecial- 
 ly at the balls of the prepuce. 
 
 Dcccxxxviii. The lymphatic veflels of the penis, 
 feen by very eminent anatomifts, are faid to run 
 under the Ikin of the penis. The nerves, \vhich 
 are very numerous, and very large, and accompany 
 the arteries of the penis, arife from the great trunk 
 of the fciatic nerve. But the bladder, rectum, and 
 uterus, are fupplied by the lower mefenteric plex- 
 us, which arifes from the middle one, and defcends 
 into the pelvis. 
 
 iMZCcxxxix. To dillend the penis, It is neceflar)'- 
 that the veins (dcccxxxvii.) carryung back the 
 blood from the cavernous bodies of the penis or ure- 
 thra, be compreffed, or, at leaft, that a power be ap- 
 plied to the ultimate veins, which open ever)^ where 
 into the cavernous bodies, hindering them from ab- 
 forbing the blood brought there by the arteries. 
 The firft may be in fome degree effected by the le- 
 vator, drawing up the proftate and bladder ; but, 
 from the analog^'' of the nipples of the female breaft, 
 of the gills of the peacock, of the blulliing of the 
 face produced by the paftions of the mind, and of 
 animals, all of w^hich copulate in the fame manner, 
 without any erector mufcle ; of the erection in ani- 
 mals totally dift'erent in their ftrufture from man. 
 
Chap. XXVII. MALE GENITALS. 411 
 
 and efpecially of the very fudden ereftions in birds j 
 from the very inadion of the erector mufcles them- 
 felves during libidinous erection, and from their 
 unfitnefs for compreffing the veins j it is probable, 
 that, independently of the mufcles, the abforption 
 of the blood by the veins may be retarded, and that 
 it is affected by the multitude of deep feated ner- 
 vous noofes, which being conflricted by the force 
 of pleafure, comprefs the veins, fo that, being ren- 
 dered narrower, they return lefs blood to the trunks 
 than what is imported by the arteries, which are 
 not only free from any ftrifture, but at the fame 
 time, by the increafe of the pulfe, are bringing the 
 blood more quickly, which is an acceffory caufe. 
 But the caufe of this convulfion feems to exift in 
 the nervous fphinfters, fince the penis becomes 
 erected, both from mechanical irritation of the 
 nerves, and that more fubtile irritation caufed by 
 the imagination. 
 
 DcccxL. To a continued and violent erection, 
 an expulfion of femen at laft fucceeds, which 
 requires much greater force than fimple erection. 
 For the femen is emitted when the irritation of the 
 nerves is arrived at its greateft height ; and in nat- 
 ural venery, when the cellular fpaces of the urethra, 
 which are later of being filled, and the continuous 
 glands at laft become turgid with blood, fo that be- 
 ing diftended with a large quantity of warm blood, 
 they become ftiff, and therefore the nervous pa- 
 pillae, being erected, are violently affefted by the 
 caufe of pleafure. The feminal veficles are evacua- 
 ted by the levator mufcles of the anus, which prefs 
 them againft the refifting bladder, being excited 
 either by voluptuous imagination alone, or by the 
 exceflive pruritus of the nerves of the glans, efpe- 
 cially of its lower part, in the neighbourhood of the 
 frenum. The femen is never difcharged along with 
 the urine, in a healthy man ; becaufe the expulfion 
 of it requires the bladder to be fhut ; for, while 
 
 lax, 
 
VIRGIN UTERUS. Chap. XX^TR. 
 
 412 
 
 lax, it affords no refiftance to the feminal veficles. 
 The tranfverfe mufcles feem to dilate the canal of 
 the urethra for the reception of the femen expreffed 
 from the veficles. 
 
 DCCCXLi. Soon afterwards, the fenfible urethra 
 being irritated by the femen, the powers conftrict- 
 ing it are called into action. This is principally ef- 
 fected by the accelerator, (dccch.) which ftrongly 
 comprefling the bulb and adjacent part of the ure- 
 thra, propels the contents more fwaftly, in propor- 
 tion as the bulb exceeds in diameter the urethra. 
 That this may act firmly ■, the fphincter of the anus, 
 and therefore alfo that of the bladder, mult be con- 
 tracted. The accelerator feems alfo to be the prin- 
 cipal mufcle of erection, by compreffmg the veins 
 of the corpus cavernofum of the urethra. At the 
 fame time, the ereCtores penis, as they are common- 
 ly called, arifing from the above tubercles of the 
 ifchium, being ftrong, and inferted into the ca- 
 venious bodies, fupport the penis, in a direction in- 
 termediate betwixt the tranfverfe and perpendicu- 
 lar. Thus the femen is projected into the vagina, 
 and into the uterus itfelf, in prolific coition. This 
 action is very violent, and comes near to a convul- 
 fion ; whence it is wonderfully debilitating, and 
 very much injures the nervous fyltem principally, 
 as the maladies arifing from thence feem to indi- 
 cate, from the affection of the nerves, without which 
 the femen cannot be expelled. 
 
 C El A P. XXVIII. 
 
 VIRGIN UTERUS. 
 
 DCCcxLii. ^HE uterus in woman is feated in the 
 I upper part of the pelvis, wdth the 
 bladder before, and the rettum behind it, without 
 adhering to either of them, and with its mouth in- 
 clining 
 
Chap. XXVIII. VIRGIN UTERUS. 413 
 
 dining a little forwards. In the female adult, it Is 
 contained within the pelvis ; but in the infant, it rifes 
 above it. In women, the peritonaeum defcends from 
 the os pubis into the pelvis, and proceeds for a con* 
 fiderable way behind the bladder, to the bottom of 
 the uterus. Then it afcends along the uterus ; and 
 a fecond time defcends on its oppolite fide, applied 
 to it as far as the vagina, and the tranfverfe portion 
 of the uterus, from whence, including the redum 
 with lunated folds, it ceafes to differ from the ftruc- 
 ture in man. But this fame peritonaeum, coming 
 into the pelvis from the iliac veffels, and being 
 broader than the uterus, and adhering to its fides, 
 and to the vagina ; and being refieded along itfelf, 
 divides the pelvis into two regions, the anterior and 
 pofterior, like a partition, and is called the ligamen- 
 tum latum. It is accurately conneded with the 
 uterus, without any intermediate fat, fo as to ferve 
 it on all fides as an external coat. It does not hin- 
 der the uterus from being totally moveable. 
 
 DcccxLiii. Th^ body of the uterus is ufuaRy dif- 
 tinguilhed from its neck. The figure of the body 
 is convex before and behind, with a degree of flat- 
 nefs, with acute edges, where itsfurfaces meet, con- 
 verging at the fides, and moderately convex at the 
 top. It has a peculiar fabric, of a clofe compad, 
 firm, but fom.ewhat fucculent, cellular fubftance, in 
 which we perceive mufcular fibres, efpecially in 
 puerperal women. They are flat, and reticularly 
 interwoven with each other, fome longitudinally 
 difpofed along the uterus from the fundus to the 
 os uteri, others arranged in various circles, and par- 
 ticularly in the fundus, and betwixt the tubes, and 
 likewife in the neck near the mouth. In beafts, the 
 , uterus is manifeftly mufcular ; and in women, like- 
 wife, it gives evident figns of a contradile nature. 
 Its outer coat is received from the peritonaeum. 
 After repeated examinations, I have not found any 
 mucous finufes, branching and varioufly dividing 
 
 within 
 
VIRGIN UTERUS. Chap. XXVIIL 
 
 414 
 
 within the fabft an ce of theuterus,but veinsfurround- 
 ed with cellular fubftance, which do not collapfe. The 
 internal membrane of the uterus is continuous with 
 the cuticle ; within the cavity, it is pulpy, and cov- 
 * ered with fliort flocculi ; in the cervix, it is callous 
 and valvular. The cavity of the uterus is fmall, al- 
 moft triangular, but bounded by lines convex in- 
 wardly ; in the remaining part, it is a comprefl'ed 
 cylinder. This part, which is called the cervix uteri, 
 is cylindrical, compreffed, and thick, and has alfo 
 a cylindric cavity within. It is entirely rough, with 
 callous wrinkles, extenuated to an edge, and inclin- 
 ed towards the vamna. Thefe recede from an an- 
 
 O 
 
 terior and pofterior line towards the fides, and are 
 joined by fmaller wrinkles, in the intervals of which 
 are mucous linufes, as round globules are every 
 where found in the upper part of the neck of the 
 womb, filled with a very pellucid liquor, differing 
 both in number and magnitude. It is not uncom- 
 mon for the uterus to be divided by a middle pro- 
 jecting line. I’he cervix is terminated by the os 
 internum uteri, having a ti'anfverfe flit, furrounded 
 with tumid lips, drawn out into the vagina, and re- 
 ceived within its blind extremity, projecting into it 
 obliquely and forwards. It is full of mucus, and 
 has mucous fmufes in its tumid edges. 
 
 DcccxLiv. The triangular part of the uterus fends 
 out, from its lateral angles, canals, folded together 
 by means of cellular fubftance, growing gradually 
 broader, and, again a little contracted towards the 
 extremity : their direction is at firft tranfverfe to- 
 wards the ovarium, and afterwards defeending, but 
 with fome variation : they are termed the Fallopi- 
 an tubes. Their external membrane is from the pe- 
 ritonseum ; for they are included within tlie dupli- 
 cature of the broad lig^ament : their internal mem- 
 brane is wrinkled almoft reticularly, mucous, and is 
 extended to a greater length, in tlie form of fpread 
 fringes, folded longitudinally, which crown the ori- 
 
Chap. XXVIII. VIRGIN UTERUS. 
 
 415 
 
 fice of the ovarium, and are conneded to the ovary. 
 Betwixt the two membranes, is fome fpongy cellu- 
 lar fubftance, of a more Gender texture than in the 
 vas deferens. They ufuaUy contain mucus, the 
 origin of which is not known. There are alfo a 
 great number of veffels interpofed, and perhaps fome 
 mufcular Gbres, but the latter are more obfcure. 
 They are fupported by a proper fold of the pe- 
 ritonaeum, which proceeds from the broad liga- 
 ment. 
 
 DcccxLv. The ovaries are tranfverfely Gtuated in 
 the fame broad ligament, included in its duplica- 
 ture behind the tubes, and conjoined to thefe tubes 
 by a peculiar expanGon of the broad ligament, 
 which is long enough to allow them a free motion. 
 They are of an oblong figure, comprelled on each 
 fide ; their unconneifed edge is convex, and femi- 
 elliptical ; but that which is connefted with the 
 ligament is ftraight. Their peritonaeal membrane 
 is thick, and almoft cartilaginous. Their fabric 
 very much refembles that of the uterus itfelf ; be- 
 ing clofe, white, and cellular, and without fat. The 
 margin of the broad ligament, where it recedes 
 from the uterus, becoming thicker, to fuftain the 
 ovary, has fomething of a folid fubfiance, refem- 
 bling a ligament, but is not hoUow, or a true ca- 
 nal. 
 
 DcccxLvi. In the ovary even of a young girl, 
 there are round veficles, confifiing of a pretty ftrong 
 pulpy membrane, and connected every where to 
 the ovarium by cellular threads, which are filled 
 with coaguiable lymph ; uncertain in their num- 
 ber, fifteen or more being found in one ovary 5 nor 
 uniform in their fize. They are remarkable bo- 
 dies, being found very widely diffufed through all 
 animals, even in thofe which have but one fex. 
 
 DcccxLvii. Laftly, the uterus fends forwards, 
 from the fame lateral angles of its triangular body, 
 a fafciculus, compofed of long cellular fibres and 
 
 veffels. 
 
416 \1RGIN UTERUS. Chap. XX\TIL 
 
 veffels, which, becoming fmaller in its progrefs, 
 goes out of the pelvis through the ring of the ab- 
 domen (dcccxii.) into the groin, where it fplits 
 into branches, and feparates into fmall veffels, which 
 communicate with the epigaftrics. Has it alfo long 
 fibres propagated from the uterus itfelf ? I have 
 not feen them fufficiently diftincfly. 
 
 DcccxLviii. The arteries of the uterus are from 
 the hypogaftrics ; a conliderable branch of which 
 the uterine, like the loweft to the bladder in men, 
 arifes from the umbilical trunk, or immediately be- 
 low that trunk. It goes to the lower part of the 
 uterus, almoft at the termination of its neck, giwng 
 branches to the uterus, bladder, and rectum, and 
 afeending upwards, it fends tranfverfe inflected 
 branches to the uterus, makes numerous anoftamo- 
 fes with the fpermatics, and often gives arteries to 
 the tube itfelf. Another plexus of branches tends 
 downwards to the vagina, running along it a con- 
 fiderable way, although there is alfo a proper vagi- 
 nal artery originating likewife in the pelvis, and 
 fometimes acceffory branches from the mefocolic. 
 There are alfo feminal veffels which have the fame 
 origin as in men, and defeend with a pampiniform 
 plexus over the pfoas mufcle into the pelvis, and di- 
 vide into two plexufes. The pofterior goes to the 
 ovary itfelf, with many twifted furculi diftributed 
 throusfh its fubftance and among the ova. The ante- 
 rior both fupplies the tube, and defeends to the ute- 
 rus, in which it is divided into winding branches up- 
 wards and downwards, fome going to the bladder. 
 Another artery, the middle hsemorrhoidal, from 
 the trunk of the pudenda communis, accompanies 
 the vagina a confiderable way forwards, to which, 
 and to the bladder and reefum, it is diftributed. 
 Moreover, the beginning of the vagina and the cli- 
 toris, have arteries from the external haemorrhoidal, 
 and the clitoris, like the penis, has both deep feated 
 
Chap. XXVIII. VIRGIN UTERUS. 
 
 417 
 
 and fuperficlal arteries, alfo inofculating with a 
 branch from the bladder. 
 
 DcccxLix; The uterine veins oft the whole cor- 
 refpond with the arteries, originating from the 
 trunks of the hypogaftrics ; they are both internal 
 as the uterine, the vaginal, and middle hemorrhoi- 
 dal^ and external as the circumflex, and thofe of 
 the clitoriSi But they form a remarkable plexus 
 on each fide, which occupies the fides of the vagi- 
 na below the clitoris. Below that, it is joined in^ 
 to a continued plexus with its companion on the 
 Other fide. A plexus alfo from the external he- 
 morrhoidal and vefical velfels, goes to the clitoris, 
 as in men to the penis. They have no valves, ex- 
 cept a few in the fpermatics, which alfo, in a very 
 large bundle, go to the ovarium, and the alse vef- 
 pertilionis. 
 
 DcccL. Within the uterus itfelf the arteries ter- 
 minate in exhaling branches on its internal furface. 
 In the puerperal Rate they are elongated into pen- 
 dulous tubes. Thus the' veins of the uterus become 
 at that time very large finufes ; for they are enor- 
 moufly enlarged, and open with very large mouths 
 into the cavity of the uterus. 
 
 DcccLi. Lymphatic veffels are found in the ute- 
 rus of brutesj and in women more rarely, though 
 by very eminent anatomifts. 
 
 DcccLii. The nerves are fupplied from the loweft 
 mefocolic plexus, united wdth thofe of the facrum, 
 and fending large branches to the bladder, womb, 
 and reftum ; befides which, fome pafs through the 
 ‘broad ligament to the ovarium, and others from 
 the nerve that goes with the veffels to the clitoris, 
 arifing from the fciatic trunk. But the ovary has 
 alfo its proper nerves from the renal plexus, fimi- 
 lar to thofe which go to the teflicles of the male. 
 Thus all thefe organs, from the great number of 
 their nerves, are extremely fenfible. 
 
 Dd 
 
 DCCCLIII, 
 
VIRGIN UTERUS. Chap. XX^TH, 
 
 418 
 
 DcccLiii. What we have hitherto defcribed is 
 common to all ages of the female ; but about the 
 13th years or fomewhat later, neai'ly at the fame 
 time when femen begins to be form.ed in the male, 
 a confiderable change aifo takes place in the female. 
 For, at this time, the whole mafs of blood in the 
 female begins to circulate with an increafed force, 
 the breads fwell, the pubes becomes covered ; and 
 at the fame time the menfes begin to flow, by a 
 common law of nature ; although in different coun- 
 tries, the time and quantity of blood difcharged is 
 different. 
 
 DcccLiv. This difcharge is preceded by various 
 fymptoms in the loins, heavy pains, fometimes like 
 colic pains, with an increafed pulfe, headachs and 
 cutaneous puftules, and a white fluid commonly 
 flows from the uterus. For now the fleecy vefl'els 
 of the uterus, which have hitherto depofited into 
 the uterus a milky fluid, of a very white colour in 
 the foetus, and in young girls ferous, now begin to 
 be turgid with blood ; and at lafl; to pour out the 
 red cruor itfelf into the cavity of the uterus. This 
 continues fome days, while, in the mean time, the 
 flrft troublefome fymptoms abate, and the orifices 
 of the uterine veflels again gradually contracfing, 
 diftil only a little ferous moifture as before. But 
 at uncertain intervals in young girls, gradually, 
 however, fhortening to the end of the fourth week, 
 the fame pains return, the fame flow of blood takes 
 place, and this period is obferved to about the 50th 
 year ; though the diet, country, and conftitution, 
 have much influence in this refpecf. Pregnancy 
 commmonly produces a ceflation of the menftrual 
 difcharge. 
 
 EcccLv. That this blood is difcharged from the 
 veflels of the uterus itfelf, is demonftrated by acfual 
 infpedion of women who have died during their 
 courfes ; of living women, in whom the uterus 
 being inverted, has diflilled the blood from the os 
 
 internum : 
 
Chap. XXVIIL VIRGIN UTERUS. 
 
 419 
 
 internum : and of others, in whom, from obflmc- 
 tion of the menfes, the uterus has been filled with 
 concreted blood ; and by comparing the nature of 
 the uterus itfelf, replete with foft veffels, and fpon- 
 gy with the thin, by no means villous, and callous 
 vagina. Obfervation alfo fhews, that this is good 
 blood in an healthy and clean woman. However, 
 there is nothing to prevent the blood from being 
 difcharged through the vagina, when the uterus is 
 obftruHed, as in other inftances it is through the 
 in'teftinum rectum, and laftly through the remoteft 
 parts of the body. 
 
 DcccLvi. Since no animal certainly menftruates 
 in the fame manner as the human fpecies, (although 
 fome animals diftil blood from their genitals, in the 
 feafon of their annual venery) and fince the body of 
 the male is free from this periodical difcharge, the 
 caufe of this hemorrhagy, peculiar to the female fex 
 of the human fpecies, has been an objedl of inquiry 
 in all ages. From the remoteft periods, it has been 
 afcribed to the attraction of the moon, which is 
 known to raife the tides ; by others, to a fliarp fti- 
 mulating fluid fecreted in the female parts, alfo the 
 caufe of the venereal appetite. But its being caufed 
 by the moon is difproved, fince there is not a day 
 in which there are not many women ftibjefted to 
 this evacuation, and there are not fewer in the de- 
 creafe than the inereafe of the moon. There is no 
 fuch thing as any ferment near the uterus, but every 
 thing is bland and mucous ; and venery, which ex- 
 pels all thofe juices, neither increafes nor lelfens the 
 menftrual flux ; and women deny, that, during the 
 time of their menfes, they have any increafed defire 
 of venery, many of them at that time being rather 
 affected by pain and languor 5 and the feat of vene- 
 real pleafure is rather in the entrance-of the puden- 
 dum than in the uterus, from which laft the menfes 
 flow. Laftly, that the menftrual blood is forced 
 out by fome caufe exciting the motion of the blood 
 D D 2 againft 
 
420 
 
 VIRGIN UTERUS. Chap. XXVin. 
 
 againft tte veffels, appears from hence, that, when 
 retained, it has been known to break through all 
 the other organs of the body, where no ferments 
 were acting, the veins being even ruptured ; nor is 
 the effedl of the retained blood confined to thofe 
 parts which pour out the venereal humour. 
 
 DCCCLvii. Nature has, in general, given women 
 a fofter body, lefs elaftic folids, fmaller mufcles,. 
 with a greater quantity of fat interpofed betwixt 
 their fibres, and ilenderer bones, with fmaller pro- 
 cefl'es. Moreover, the pelvis of the female is, in all 
 its dimenfions, larger ; the offa ilia more diftant 
 from each other ; and the os facrum turned more 
 backwards from the bones of the pubes, while the 
 offa ifchii are feparated by a longer line ; but above 
 all, the angles in which the bones of the pubes 
 meet is much larger : which differences are con- 
 firmed by the obfervations of the greateft anato- 
 mifts ; and from neceffity itfelf, which requires a 
 greater fpace for the greater number of vifcera in 
 the pelvis. Moreover, the arteries fupplying the 
 uterus are very large, more fo than in men ; and 
 their caliber is larger in proportion to their coats, and 
 they are more lax in proportion to the veins : but 
 the veins are, in proportion, lefs ample in the men,^ 
 and of a more firm texture than in other parts of 
 the body. From hence it follows, in the firft place, 
 that, in women, the blood is brought to the womb 
 in greater quantity, and more quickly, through lax 
 and ample arteries ; and, in the fecond place, that,, 
 on account of the rigidity and narrownefs of the- 
 veins, it returns with difficulty from the uterus, 
 and diftends its veffels. 
 
 DcccLiK. The female infant, when firft born, has 
 fmall lower extremities ; and the greater part of 
 the blood of the iliac arteries goes to the umbilicals, 
 a fmall portion only enters the pelvis. Hence the 
 pelvis is fmall, and little concave ; and the bladder 
 and uterus itfelf, with the ovaries, rife above the 
 
 pelvis. 
 
Chap. XXVm. VIRGIN UTERUS. 
 
 421 
 
 pelvis. But, when the foetus is born, and the um- 
 bilical artery is tied, all the blood of the iliac arte- 
 yy defcends into the lower limbs and pelvis, which 
 grow larger, and the pelvis becomes deeper and 
 wider ; fo that by degrees, the womb and bladder 
 fink into its cavity, and are not fo much compreffed 
 by the intefiines and peritonseum, when the abdo- 
 minal mufcles central the lower parts of the belly. 
 Then, when the grov/th is completed, or nearly fo, 
 the arteries of the uterus, and of the pelvis in gen- 
 eral, which in the foetus were very fmall, have be- 
 come very large, and are eafily injefted with wax j 
 and all things are fo changed, that the hemorrhoi- 
 dal artery now forms the trunk of the hypogaftric 
 (dcccxxxvi.) as formeiiy the umbilical had done. 
 More blood, therefore, at this time goes into the 
 uterus, vagina, and clitoris, than formerly. 
 
 DcccLx. At the time when the growth of the bo- 
 dy has almoft ceafed, and a large quantity of blood 
 is prepared in found vifeera and in healthy confti- 
 tutions, plethora takes place in both lexes of the 
 human fpecies. In the male, it vents itfelf fre- 
 quently by the noftrils, from the exhaling veffels 
 of the pituitary membrane (ccccnviii.) being di- 
 lated to fo great a degree, as to pour out the red 
 blood, and now the femen firfl: begins to be fecre- 
 ted, and the beard to grow. But in the female, 
 the fame plethora finds a more eafy paffage, be- 
 caufe the very weight of the blood carries it down- 
 wards, and becaufe the uterine veffels, now much 
 enlarged, being placed in a lax fituation in the fuc- 
 culent and foft cellular fubftance of the uterus, and 
 being therefore very extenfile and exhaling by very 
 foft flocculi, open into the empty uterus, and the 
 blood finds almoft a more eafy paffage that way, than 
 into the correfponding veins ; while in the fame fe- 
 males, the arteries of the head are firmer and 
 fmaller in proportion. The return of the blood 
 is alfo retarded, both becaufe the flexures of the 
 
 arteries 
 
422 
 
 VIRGIN UTERUS. Chap. XXVIII, 
 
 arteries, from the increafed afflux of the blood, be-f 
 come more ferpentine and fitter for retarding the 
 m.otion of the blood, and bccaufe it now returns 
 with difficulty through the "eins. The blood is, 
 therefore, firil coliecled in the veiTels of the uterus, 
 which at this time, according- to difi'eclions, are 
 turgid ; then in the arteries of the loins and in the 
 aorta itfelf ; now when the heart fends a new tor- 
 rent of blood into the veffels already diftended, its 
 force is at laft propagated to the ferous veffels of 
 the uterus, fo that they difcil at firft a copious warm 
 mucus, then red ferum, and laftly pure blood. The 
 fame determination of the blood to the genital parts, 
 forces out the hitherto latent hairs, ihcreafes the 
 bulk of the clitoris, dilates the cavernous plexufes 
 of the vagina, and excites the appetite towards ve- 
 nery, Accordingly, the quantity of the mcnftrual 
 diicharge is increafed, and its firft appearance haf- 
 tened by every thing that either increafes the quan- 
 tity of blood in general, or determines it particu- 
 larly to the uterus ; fuch as joy, defire, pediluvia, 
 a full diet, warm climate, and lively temperament 
 of body. It is diminiffied by thofe things which 
 diirnniflr plethora and the motion of the blood, as 
 want, grief, cold atmofphere, inactivity and pre- 
 ceding difeafes. 
 
 DcccLxi. When fix or eight ounces of blood 
 have been thus evacuated, the unloaded arteries 
 now exert their elaftic force as all arteries do, and 
 their diameters being contracted, they only tranf- 
 mit a thin fluid as at firft. But the quantity of 
 blood wffiich the uterus difcharged, being repro- 
 duced by the fame caufes, it is again excreted 
 through thefe fame paffages, rather than througii 
 any other. Nor is it neceifary to inquire, why this 
 period is nearly menftrual ; for this depends upon 
 the proportion which fubfifts between the quantity 
 and miomentum of the blood coUcched, and tlie re- 
 fiftance of the uterus, which v'ill at laft uraduahv 
 
Chap. XXVIH. VIRGIN UTERUS. 
 
 423 
 
 yield. Therefore this difcharge of blood returns 
 Iboner and does not wait for' the interval of a 
 month, whenever a greater quantity of blood is 
 determined to the uterus in plethoric or libidinous 
 women. They ceafe entirely to flow, when the 
 uterus, like all the other folid parts of the body, has 
 acquired fo great a degree of hardnefs, as cannot 
 be overcome by the force of the heart propelling 
 the arterial blood. This hardnefs in the uterus, 
 in the arteries and ovaries, is fhewn by the knife 
 and by injections. Animals in general have no 
 menfes ; on account of their uteri being membra- 
 nous rather than flefhy, and if the firmnefs of their 
 veifels, which is fo great, that in thefe animals no 
 hemorrhage, either from the noftrils, or any other 
 part, ever occurs. In men they do not occur, 
 becaufe in their pelvis there is no fpongy organ fit 
 for retaining the blood ; and becaufe the arteries 
 of the pelvis are both harder and fmaller in pro- 
 portion than the veins, and thus the impetus of the 
 blood is turned aflde into the lower extremities, of 
 which in men, the growth is greater, as that of the 
 pelvis is lefs. 
 
 DcccLxii. Why do the breafts fwell at the fame 
 time ? Their fabric in many refpeCts is analogous to 
 that of the uterus ; as appears from the fecretion of 
 the milk in the breafts, which fticceeds the birth of 
 the foetus, and which increafes or diminifties in pro- 
 portion as the lochial flux diminiflies or increafes ; 
 from the fimilitude of the ferous liquor, found in 
 the uterus, to the thin whitifli milk, in thofe, who 
 are not laClefeent, which is very apparent in ani- 
 mals ; and from the erection of the nipples by 
 friction, analogous to the erection of the clitoris. 
 Therefore, the fame caufes which diftend the vef- 
 fels of the uterus, Ijkewife determine the blood 
 more plentifully to the breafts j the confequence of 
 which is an increafe of the conglomerate gland of 
 the breaft, and of the furrounding fat. 
 
 CHAR 
 
4?4 
 
 CONCEPTION. 
 
 Chap. XXIX, 
 
 CHAP. XXIX. 
 
 CONCEPTION, 
 
 DcccLxiii. TE now enter upon a ver^' difficult 
 
 V V ffibject ; to inveftigate what in- 
 ternal changes take place in woman, when the 
 germination of the life of a new being begins udth- 
 in her, whom, in proper time, fhe is to bring forth. 
 We Ihall relate, in the firft place, therefore, thofe 
 things which obfervation has proved ; and then 
 fliall add thofe hypothefes by which learned men 
 have endeavoured to fupply whatever is not learnt 
 from experience. How few things are afcertain- 
 ed on this fubject, and how difficult they are to 
 be afcertained, I have learned too much by expe- 
 rience. 
 
 DcccLxiv. That fome light may appear amidft 
 this darknefs, we fliall begin with the mofl; Ample 
 animals, and afterwards notice what nature has add- 
 ed in others wffiofe fabric is more compounded. 
 The fmallcft animals then, w'hich have very few or 
 no limbs, very little diflinclion of parts, very fliort 
 period of life, the vital funftions both few and very 
 limilar to each other ; thefe animals bring forth 
 young ones like themfclves, with no diftincHon of 
 iexes, all of them being fruitful, and none fecun- 
 dating the reft. Some of them exclude their young 
 whom they have conceived in their bodies, through 
 fome opening in their bodies ; from others, fome 
 limbs fall oft', which are completed into animals of 
 a kind Amilar to thofe from -which they have fallen. 
 This kdnd of generation is extended very widely, 
 and comprehends the greater part of animal life. 
 
 DcccLxv. The next, wdiich are a little more com- 
 pounded, all parturiate ; yet in fuch a manner, that 
 in their bodies is generated a certain particle, dil- 
 
 fimilai' 
 
Chap. XXIX. 
 
 CONCEPTION. 
 
 425 
 
 iimilar to the whole animal, and contained in fome 
 involucra, within v/hich lies the animalcule that is 
 afterwards to become fimilar to that within which 
 it is produced ; thefe are called eggs. A great part 
 of thefe animals is immoveable. 
 
 DCCCLxvi. The animals which follow, which are 
 not indeed numerous, have both eggs and alfo male 
 femen ; fo that both fexes are joined in the fame in- 
 dividual. By the m.ale femen we underhand that 
 with which it is neceiTary for the eggs to be fprink- 
 led, in order to become prolific, although alone it 
 never becomes a new animal. In this clafs, there- 
 fore, a juice is prepared by its own proper organs, 
 which is poured on the eggs generated in like man- 
 ner, in proper, but different organs. 
 
 DcccLxvii. Thofe animals are much more numer- 
 ous which have both a male juice and female eggs ; 
 and yet are not capable of fecundating themfelves, 
 but ftand in need of real venery. For of this kind 
 two individuals concur in the work of fecundation, 
 in fuch a manner, that each impregnates the other 
 with its male organs, and reciprocally has its fe^ 
 jnale organs impregnated by the male parts of the 
 other. 
 
 DcccLxviii, And now the nature of animals ap- 
 proaches nearer and nearer to that of the human 
 race ; amongft the individuals of which, though in 
 other refpefts fimilar, fome have only male organs, 
 ;and thefe males fprinkle their femen on the fe^ 
 male eggs of others. Many cold blooded animals 
 affufe their feed upon the eggs after they are ex-, 
 eluded from the body of the mother. Warm ank 
 mals injeef their femen into the very uterus of the 
 female. But now, whether eggs be generated with- 
 in the body of the female, and the feetufes be pro-, 
 duced inclofed in coverings, or whether the female 
 carry the live foetus fo long in its uterus, until it 
 produce them without any involucrum ; the dif- 
 ference between thefe oviparous and viviparous an- 
 imals 
 
426 CONCEPTION. Chap. XXIX. 
 
 imals is fo fmall, that in the fame clafs, and in the 
 fame genus, fome animals lay <iggs, and others Ih e 
 fcetufes ; and, laftly, the fame animal fometimes 
 lays eggs, and fometimes brings forth live young. 
 
 DcccLxix. From this review of animals it ap- 
 pears, that all of them are produced from an ani- 
 mal hmilar to themfelves ; many of them from a 
 part of it fimilar to the whole j others from an egg 
 of a peculiar ftrucfure ; but that all thefe do not 
 hand in need of male femen. Laftly, the locomo- 
 tive and more lively animals, having a compound 
 ftrufhire, only are endowed with a double fyftem 
 for generation ; and the difference of fexes feems 
 to be added for the bond of focial life, and for the 
 prefervation of a lefs numerous progeny. 
 
 DcccLxx. To this effufion of the male juice into 
 the female ors^ans, both fexes are excited bv the 
 moft vehement delires : the male indeed moft ftrong- 
 ly ; the female being always ready to fuffer the ve- 
 nereal congrefs, it behoves the male to be animated 
 with a defire of venery, when he has abundance 
 of good and prolific femen. Therefore, this cir- 
 cumhance itfelf is the gneateff caufe of venereal 
 dehre in him ; but in females, of the brute kind 
 efpecially, it is a certain degree of inflammation in 
 tlie vagina, which excites an intolerable itching. 
 
 DCCCLXxi. But nature has added, for combining 
 the energy of both, in women and in quadrupeds, 
 to the uterus, a vagina or round membranous canal, 
 very dilatable, which, embracing the mouth of the 
 uterus, (dcccxi.iii.) defcends downwards, and then 
 downw’ards and forwards, lying under the bladder, 
 add refling upon the rectum to which it adheres, 
 and, laftly, opens under the urethra with an orifice 
 a little contracted. This orifice, in the foetus and 
 in virgins, is protected from the action of the air or 
 water, by a remarkable valvular fold, denominated 
 the hymen, formed of the fkin and cuticle of 
 the vagina, probably for fome moral purpofe, as 
 
 amongft 
 
 O 
 
Chap. XXIX. 
 
 CONCEPTION. 
 
 427 
 
 amongft all the animals I have examined, it exifts 
 only in the human fpecies. It would be circubr, 
 if it were not incomplete under the urethra and 
 even there it is not always deficient ; toward the 
 anus it is broader. Being gradually worn away 
 by copulation, and lacerated, it at laft difappears. 
 The caruncles, which are called myrtiformes, are 
 partly the remains of the lacerated hymen, and 
 partly the indurated extremities of the columnse of 
 the vagina ; and, laftly, the valves of the mucous 
 lacunae hardened into a kind of fiefh. 
 
 DCCCLXXii. The fabric of the vagina in women 
 is cutaneous, and is compofed of a firm callous cuti- 
 cle, and a thick, white, nervous fkin, in which, more 
 efpecially at its extremity, fleflry fibres appear. Its 
 internal furface is, in a great meafiire, rough with 
 callous verrucas, which, though hard, are fenfible, 
 and with inclined laminae,terminated by a projecting 
 edge,pointing downwards, and arrangedfo that they 
 are collefted into two principal columns, ftudded 
 as it were with thefe verrucae, of which the upper- 
 moft and largefi: is extended under the urethra, and 
 the loweft is incumbent on the anus. From each 
 of thefe, a valvular feries of fmaller papillae, va- 
 rioufly infleded into arches, is continued till they 
 mutually meet on both fides. This fabric feems to 
 be defigned for the purpofes of enjoyment, and for 
 facilitating its expanfion. It is furnifhed with a 
 peculiar mucus, from finufes fituated all over it, 
 but more efpecially in its pofterior and fmoother 
 fide. 
 
 DcccLxxiii. At the entrance of the vagina are 
 prefixed two cutaneous appendages, called nymphae, 
 continued from the cutis of the clitoris, and from 
 its glans itfelf, full of intermediate cellular fub- 
 ftance, of a diftendible fabric, jagged and furnifhed 
 on both fides with febaceous glands, fuch as are 
 alfo found in the folds of the prepuce of the clitoris, 
 'llieir chief ufe, it is fuppofed, is to dired the urine, 
 
 which 
 
CONCEPTION. 
 
 428 
 
 Chap, XXIX, 
 
 which flows betwixt them from the urethra, fo aa 
 to turn it off from the body, which office is attended 
 with a certain ereclion of the nymphae. Thefe 
 membranes defcend from a cutaneous arch fur- 
 rounding the clitoris, which is a part extremely 
 fenfible, and wonderfully prurient, and, like the 
 penis, is compofed of two cavernous bodies, arifing 
 from the fame bones, and joined together, but vnth- 
 out including any urethra. It is furnifhed with 
 blood-veflels, nerves, and levator mufcles, and a 
 ligament fent down from the fynchondrofis of the 
 olfa pubis, analogous, to thofe in men : and in like 
 manner from venery, the clitoris grows turgid and 
 ere£l, but lefs in raodeft women j but from friction 
 always. 
 
 DcccLxxiv. The mufcle, termed oftii vaginze 
 conftriftor, arifes on each lide from the fphincter 
 of the anus, and being increafed by an acceflion 
 from the as ifehium, covers the vafcular plexus, 
 and proceeds broadly fonvards, along the begin- 
 ning of the labia externa, and is inferred into the 
 crura ditoridis ; it feems to comprefs the lateral 
 plexufes of the vagina, and to retard the return of 
 the venous blood in both ways. The tranfverfe 
 mufcle of the urethra, and the bundle from the 
 fphincter inferred into it, have the fame fituation as 
 in men. 
 
 DCCCLxxv. The female being invited either by 
 moral love, or the delire of pleafure, admits the 
 male, whofe penis being introduced into the vagi- 
 na, is rubbed againft its fides, until the male femen 
 h ejefted and thrown into the uterus. Thus, as 
 we have obfeiwed of the male, (dcccxl.) the fric- 
 tion of parts fo tender and exquilitely fenfible, ex- 
 cites a convulfive conftriction of all the parts fur- 
 rounding the vagina. By thefe means, the return 
 of the venous blood being fuppreffed, the clitoris, 
 both the nymphze, and the plexus furrounding al- 
 mofl all the vagina, become turgid, more efpcciaily 
 
Chap. XXIX. CONCEPTION. 429 
 
 in libidinous women ; the pleafure is raifed to the 
 higheft pitch : and, laftly, though not always^ or in 
 all women, there is expelled, by mufcular force, 
 {dccccxxiv.) a mucous lubricating liquor of va- 
 rious origin. The principal fources of this are, 
 in the firft place, in the entrance of the urethra, 
 where large mucous finufes are placed in the tumid 
 extremity of this uriniferous canal. Then, at the 
 fides of the urethra, in the bottom of the linufes 
 which are formed by the membranous valves being 
 concave upwards, two or three large mucous finuf. 
 es penetrate into the fubftance of the urethra itfel£ 
 Laftly, at the fides of the vagina, betwixt the bot- 
 toms of the nymphse and the hymen, there is one 
 opening, on each fide, from a very long dudl ; 
 which, defcending towards the anus receives mu- 
 cus from fmall follicles. 
 
 DcccLxxvi. But, by the fame aflion which in- 
 creafes the pleafure to the higheft degree, and, 
 therefore, caufes a conflux of blood to the whole 
 genital fyftem of the female, (dlxiii.) a much more 
 important change is produced in the internal parts 
 of the female : for, when the hot femen of the male 
 penetrates into the fenfible cavity of the uterus, 
 which is itfelf turgid and heated with influent blood, 
 the Fallopian tubes at the fame time fwell, being 
 very full of diftended veflels, creeping betwixt their 
 two coats, and now filled with a very great quan- 
 tity of blood. In this ftate, thefe tubes become red 
 and rigid, and the fringed mouth of the tube af- 
 cends, and is applied to the ovarium. All thefe 
 changes are confirmed by difleflions of women, and 
 other animals, and by morbid cafes. 
 
 DCCCLXxvii. But, in a female of ripe years, the 
 ovary is extremely turgid, with a lymphatic coagu- 
 iable fluid, with which the veficles are diftended. 
 In a prolific copulation, fome one of the riper of 
 thefe veficles burfts, and opens with a manifeft cleft, 
 and at length effufes a clot of blood. Within this 
 
 veficle. 
 
CONCEPTION. 
 
 Chap. XXIX. 
 
 43.6 
 
 velicle, after copulation, a kind of flelli is formed, 
 at firft flocculent, then granulous, and like a con- 
 glomerate gland, confiiling of many acini joined to- 
 gether by cellular fubftance ; which, by degrees, 
 becoming larger and harder, fills the whole cavity 
 of the veficle, and is indurated till it acquire a fcir- 
 rhous appearance, in which, for a long time, a cleft, 
 or the veftage of one, remains. This is the corpus 
 iuteum, common to all warm blooded quadrupeds, 
 in which fome late anatomifts have aflerted, that 
 there is a fluid before defloration ; which, however 
 experience does not admit, fince there is no corpus 
 Iuteum at that age. Nor is the veficle, which be- 
 comes the human ovum, contained in the corpus as 
 in a calyx. 
 
 DcccLxxviii. Moreover, in a prolific congrefs, 
 the tube, comprefling the ovarium, is fuppofed to 
 exprefs through a fifl'ure in the outer membrane, a 
 mature ovulum, and to abforb it, and then to tranf- 
 mit it to the uterus by a periftaltic contraction, 
 which begins from the firft point of contact, and 
 gradually forces the ovulum towards the uterus, 
 as is very manifeft in animals. The truth of this 
 is certainly fupported by the fiffure produced in 
 the ovarium after conception ; by foetufes being 
 certainly found in quadrupeds and in women, both 
 in the ovarium and in the tube ; and by the anal- 
 ogy of birds, in which the defeent of the o\'um 
 from the ovarium is very manifeft. Yet we muft 
 acknowledge, that a true ovum was never found, 
 vdth certainty, in quadrupeds, unlefs after a long 
 time. It is probable, that at the time of concep- 
 tion, the true ovum being almoft fluid, very foft 
 and pellucid, cannot be diftinguiflied from the mu- 
 cus with which the tube is filled ; like-.\ ife, that 
 it is very fmall, on account of the narrownefs of 
 the tube. The veficle itfelf which was in the 
 ovary, remains fixed in it, and becomes the covering 
 of the corpus Iuteum. But the accounts of ova, 
 
 faid 
 
Chap. XXIX. CONCEPTION. 431 
 
 faid to have fallen from women during the 
 days, are not certain, and are contradicted by the 
 fmallnefs of the foetus obferved many days after 
 conception ; by the fhape which it was lirft ob= 
 ferved to have, which is always oblong, and in 
 brutes even cylindrical ; and likewife by the linali- 
 nefs of the tube. 
 
 DGCcLxxix. Thefe things are performed with 
 pleafure to the future mother, and not without a 
 peculiar fenfation of internal motion in the tube, 
 and of a tendency to faint. Neither is the place 
 of conception in the uterus, into which accurate 
 experiments Ihow that the male femen reach- 
 es. For the power of the male femen fecundates 
 the ovum in the ovarium itfelf, as is proved by 
 the foetufes being found in the ovaries and tubes 5 
 by the analogy of birds, in which, by copulation, 
 one egg indeed falls into the uterus, but many are 
 fecundated at once in the ovarium. Nor is this 
 inconfiftent with the fmall quantity of the male 
 femen, or its fluggifh nature, which, by eminent 
 anatomifts, has been thought unadapted for per- 
 forming fuch a journey. For it is certain, that tlie 
 male femen has filled the tubes themfelves after re- 
 cent impregnation, both in women and other ani- 
 mals. 
 
 DcccLxxx. The uterus Indeed, certainly in ani- 
 mals, and in women probably, is clofed after con- 
 ception, left the very fmall ovum, together with 
 the hope of the new progeny, fliould perifli. At 
 that time the new mother fuffers many difagreeable 
 affeflions, which probably arife from the abforp- 
 tion of the fubputrid and fubalkaline male femen. 
 Conception, almoft like the fwallowing fome rancid 
 egg, caufes naufea, efpecially of flefti meat, vom- 
 iting, the eruption of fome puftules, and pains in the 
 teeth. The greater inconveniences I afcribe to 
 the fwelling of the uterus, compreffing the vifcera 
 
43^ CONCEPTION. Chap. XXIX. 
 
 of the abdomen, and to the retention of the men^ 
 fes. 
 
 DCCCLXxxi. What we have hitherto hated, can 
 certainly be confirmed or corrected by the teftimo- 
 ny of our fenfes. W hat follows is more conjectural, 
 and more difficult, on account of the paucity of ex- 
 periments, and their little agreement with each 
 other. And, in the firfl place, it is a difficult quef- 
 tion, from whence do the rudiments of the new 
 animal proceed ? Are they derived from both pa- 
 rents, and mixed into one animal by a conjunction 
 of feminal matter coming from the whole body J 
 as indeed there is a refemblance of the foetus to both 
 parents in animals, but efpeciaUy in plants, as con- 
 firmed by numerous experiments, and as the dif- 
 eafes of parents are propagated to their children. 
 But no femen has ever been obfcrved with certain- 
 ty in females ; and innumerable examples of ani- 
 mals fliow, that the fpecies may be propagated with- 
 out any mixture of feeds. Laflly, the refemblance 
 to the father feems only to fhow, that in the male 
 femen there is fome power, which can influence the 
 form of the foft fubftance of the very minute em- 
 bry-o, jufl as the fame power adds length to the pel- 
 vis in the body itfelf, dilates the larynx, and caufes 
 the horns to grow. 
 
 DCccnxxxiT. To the father fome hare attribu- 
 ted every thing ; chiefly after the feminal worms, 
 now fo wellknowm, were firfl: obferved in the male 
 femen by the help of the microfcope, which are ob- 
 ferved, with truth, to agree in figure with the form 
 of the firfl: embryos of all animals. But thefe ani- 
 malcules are not proportionate to the number of 
 the fcetufes, and are not perpetual in the different 
 tribes of animals ; and they have too great a re- 
 femblance to thofe animalcules that are every where 
 produced in other juices, which, though always te- 
 nacious of their owm genus, are never found to grow 
 
 up 
 
Chap. XXIX. 
 
 CONCEPTION. 
 
 433 
 
 up into a totally different kind of animal, poffeding 
 limbs. 
 
 DcccJLXxxili. Again, other anatomills, not lefs 
 celebrated or lefs worthy of credit, have taught that 
 the foetus exifted in the mother and maternal ova- 
 ry ; that the male femen excites it into a more ac- 
 tive life, and likewife influences it varioufly, but that 
 it finds it already exifting and prefent. For yolks 
 are manifeftly found in the female ovary, even al- 
 though they have not been fubjecfed to any male 
 influence. But the yolk is an appendix to the in- 
 teftine of the chick ; and derives its arteries from 
 the mefenteric artery, and the' membrane of the 
 yolk is continued from the nervous membrane of 
 the intefline, which is continuous with the fkin of 
 the animal. In the hen, therefore, the foetus feems 
 to be prefent along with the yolk, which is a part 
 of it, and receives veflels from it. Laftly, the ana- 
 logy of nature fliows, that many animals generate 
 eggs without any connection with a male of the 
 fame fpecies, but that no male animal is ever pro- 
 lific without a female. There is a continued pro- 
 greflion from the female quadruped to the ovipa- 
 rous, and from that to the non-oviparous. But the 
 old animal produces the new one from part of it- 
 felf. It is therefore certain, that the male is an ap- 
 pendage to that fex which produces the foetus from 
 its own body ; which addition is neceffary in feme 
 tribes of animals, but in the greateft number, and 
 moft fruitful, may be wanted. Nor can any kind 
 of ingrafting be admitted with any degree of pro- 
 bability, by which the dilated navel of the male- 
 born animal fhouid cohere with the vefTels of the 
 female. For this navel is much too fmall at the 
 time when the yolk is of confiderable fize ; nor 
 could the very fmall umbilical arteries be applied 
 to the very large yolk with any hope of a continu- 
 ance of the circulation,- 
 E e 
 
 DCCCLXXXIV. 
 
CONCEP'riON. 
 
 Cbiap. XXIX. 
 
 434 
 
 DccCLXXxiv. Thus luUcIi concerning the mate- 
 rials. But there is as mucli difficulty concerning 
 the trieans by which the rude and ffiapelefs mafs of 
 the firft embryo is fafhioned into the beautiful fhape 
 of the hunaan body. We readily reject fuch caufes 
 as the fortuitous concourfe of atoms, the blind at- 
 tradlions of nutritive particles, and the action of 
 ferments in confcious of their effects. The foul is 
 certainly unequal to the talk of producing fuch a 
 beautiful fabric ; and internal moulds, of v.diich I 
 never could conceive any clear idea, are to be re- 
 ferred to thofe hypothefes which the defire of ex- 
 plaining thofe things, of which we are unwillingly 
 ignorant, has produced. 
 
 DccGLXxxv. To me, indeed, the tell of experi- 
 ment feems to coincide with thofe things which the 
 mind itfelf forefecs will arife from their own caufes. 
 For hence, indeed, it appears to me certain, that the 
 beautiful ftrucfture of animals, fo various, that it is 
 always perfectly adapted to the proper and diftinct 
 habits and functions and manner of life of each j 
 calculated by rules more perfect than thofe of hu- 
 man geometry, and molt evidently accommodated 
 to forefeen purpofes, in the eye, the ear, and the 
 hand, and finally, every where ; can be aferibed to 
 no caufe below' the infinite wifdom of the Creator. 
 Again, the more frequently, and the more minute- 
 ly, we obferve the long feries of increafe through 
 which the fliapelefs embryo is brought to the per- 
 fection neceffary for animal life, the more certainly 
 does it appear, that thofe things, which are obferv- 
 ed in the more perfect foetus, exifted in the tender 
 embryo, although the lituation, figure, and compo- 
 fition, feem at firft exceedingly different from wdiat 
 they appear at laft ; for an unwearied and labori- 
 ous patience difeovers the intermediate degrees by 
 which the fituation, figure, and fymmetry, are in- 
 fenfibly correefed. Even the tranfparency of the 
 primary feetus alone conceals many things, w'hich 
 
Chap. XXIX. CONCEPTION. 435 
 
 the colour aftei'vcards added does not generate, but 
 renders manifeft to the eye. And it fufiiciently ap- 
 pears that thofe parts, which eminent anatornilts 
 have fuppofed to be generated at a later period, and 
 to be added to the primeval ones, were connate 
 with thefe,, though fmall, foft, and colourlefs. 
 
 DcccLxxxvi. It does not feem improbable, that 
 the embryo, lying dormant during a long period, 
 neither increafes, nor is agitated, except by a very 
 gentle motion of the humours, which we may fup- 
 pofe to ofcillate from the heart into the neighbour- 
 ing arteries, and from thefe back again into the 
 heart. But it is alfo probable, that the ftimulus of 
 the male femen excites the heart of the foetus to 
 greater contraflions ; fo that it infenlibly evolves 
 the complicated vefl'els of the reft of the body by 
 the impulfe of the fluid, and propagates vital mo- 
 tion through all the canals of the animal em.bryo ; 
 more quickly into fome parts, and more flowly into 
 others ; and that from thence it happens, that fome 
 parts of the body of the animal feem to be produc- 
 ed very early, and others to fupervene afterwards ; 
 and laftiy, that fome do not fhew themfelves until a 
 long time after birth, as the veficles of the ovaries, 
 the veffcls of the male tefticles, the teeth, hairs of 
 the beard, and horns of animals. In aU animals, 
 heat aflifts this evolution ; in the more Ample ones, 
 Vv^hofe vefl'els are few, and lefs complicated in the 
 Variety of their origin j it alone effe& it. 
 
 Dccci.xxxvii. Of the objecftions which are ufu- 
 ally brought, fome are not true, as the difference of 
 ftruclure caufed by nsevi ; others feem to belong 
 to caufes depending on fome accident, fuch as moil 
 inftances of monfters ; fome to the increafe of fome 
 particular parts, occaAoned by the powers of the 
 male femen ; fome to the cellular texture varioufly 
 relaxed, fo that it feems to form new parts ; fome to 
 indurated juices. Although it is not eafy to explain 
 every thing mechanically, yet we ought to remeni- 
 E E 2 ber. 
 
CONCEPTION. 
 
 Chap. XXIN. 
 
 436 
 
 ber, tbat if indeed the new animal actually, and ac- 
 cording to obfervation, exifts in the egg, thofe diffi- 
 culties which are made cannot overturn things 
 which have been truly demonftrated, although per- 
 haps foine things may remain, to which, in the pre- 
 lent infancy of human knowledge, we cannot yet 
 give a fatisfaclory anfwer. 
 
 DcccLXXxviii. Some days after the human ovum 
 is brought dov/n into the uterus, \fe become more 
 lenlible of its changes. The ovum itfelf fends out, 
 from every part of the furface of its membrane hith- 
 erto fmooth, foft branchy flocculi, which adhere 
 to and iiiofculate with the exhalinsf and abforbins; 
 fiocculi of the uterus (dcccxliii.) This adhelion. 
 takes place in every part of the uterus ; but chiefly 
 in that thick part which lies between the tubes, 
 and is commonly called the fundus uteri. Thus, 
 the thin ferous humour of the uterus, oroceedinar 
 from its arterial villi, is received into the flender 
 venous veflels of the otnim, and nouriflies it togeth- 
 er with the foetus- Before adhefion, it is either 
 nourifned by its proper fluid, or by abforption, if 
 indeed there is a time when it does not adhere. 
 
 DcccLxxxix. At this time, in the ovum, there 
 are contained a great proportion of a watery fluid, 
 coagulable by heat or alcohol, and limpid, and the 
 foetus, which is long invifible, as I have never obferv- 
 cd it before the 1 7th day, at firfl: a lhapelefs mafs,con- 
 fifting of mere mucus, and then cylindrical. When 
 now fome diflindtion of parts fucceeds, it has a very 
 great head, a final! body, no limbs, and is fixed by 
 a flat ample navel to the obtufe end of the ovum. 
 
 Dcccxc. From this minutenefs the o%nim increafes 
 in fize, and alfo the foetus, but in unequal propor- 
 tions ; for while the arterial ferum is conveyed by 
 pafifages, gradually more open, into the veflels of the 
 ovum, the foetus itfelf grows the fafteft, to which 
 the greatefl; part of the nourifliment feems to pafs 
 
 through 
 
Chap. XXIX. 
 
 CONCEPTION. 
 
 437 
 
 through the very large umbilical vein. At the fame 
 time, the ovum itfelf alfo grows, but flower, fo that 
 the proportion of the ovum, and the waters which 
 it includes, to the foetus, is perpetually diminifliing. 
 The flocculi of the ovum gradually diminifli and 
 occupy a fmaller portion of the ovum, and are in- 
 fenflbly fpread over with a continuous membrane, 
 and only thofe which fprout out from the obtufe 
 end of the ovum increafe, and are by degrees form- 
 ed into a round circumfcribed placenta. 
 
 Dcccxci. Such is the appearance of the ovum in 
 the fecond month ; and after that period, it chan- 
 ges only in bulk. That portion of the ovum, in its 
 upper part, next the uterus, making about a third 
 of its whole bulk, conflfts of a round, flat, fuccu- 
 lent, fibrous, tuberous and perfectly vafcular difc, 
 changed into equal and fimilar tubercles, accurate- 
 ly, and often infeparably connected, generally with 
 the uppermoft part of the uterus remarkable for its 
 large veflTels, by thin cellular fubftance without fat 
 collefting the veflels, both generally, but chiefly in , 
 the circumference of the greateft circle, and alfo by 
 the exhaling arteries of the uterus, anfwering to 
 the veins of the placenta, and by the arteries of the 
 placenta, inofculating with the large veins of the 
 uterus. There, in the furface common to the ute- 
 rus and placenta, a communication exifts, by which 
 the uterus tranfmits to the foetus, both that ferous 
 liquor not unlike milk, and laftly, as it feems, blood 
 itfelf. This communication of fluids between the 
 uterus and placenta, feems to be demonftrated by 
 the fuppreflion of the menfes in pregnant women, 
 whofe blood muft be turned into another channel ; 
 from the lofs of blood which follows from the fep- 
 aration of the placenta, efpecially in a mifcarriage ; 
 and from the blood of the foetus being exhaufled 
 by haemorrhagies from the mother ; from haeinor- 
 rhagies that enfue from the unfecured navel-ftring, 
 while the placenta remains in the uterus, killing 
 
 the 
 
CONCEPTION. 
 
 438 
 
 Chap. XXIX, 
 
 the mother ; and, laftly, from the paffage of water, 
 quickfilver, tailow, or v/ax, from the uterine arte- 
 ries of the mother into the veffels of the placenta, 
 as obferved, and lately confirmed by eminent anjt- 
 omifts. But that it is blood which is fent into the 
 foetus, is evinced by the magnitude of the finufes 
 of the uterus and placenta •, the diameter of the 
 ferpentine arteries of the uterus ; the haemorrhagy 
 that follows the feparation, even the moll gentle, 
 of the placenta, and efpecially by the motion of the 
 blood, which, in a foetus deftitute of a heart, could 
 only be given to the humours of the foetus by the 
 blood of the mother. 
 
 Dcccxcn. Ihe remaining part of the body of the 
 ovum, and likewife the convex furface of the pla- 
 centa, are covered by an external m.einbrane, which 
 is villous, fiocculent, reticulated, porous, cafily lac- 
 erable, and vafcular, refembling a fine placenta, and 
 is called the chorion. This alfo is connected to the 
 fiocculent and very fimiiar but fofter furface of the 
 uterus, by veffels fmaller than thofe of the placen- 
 ta, but mjnifeftly inofculated from the chorion in- 
 to the veffels of the uterus. 
 
 Dcccxciii. Under the chorion lies a continuous 
 white, opaque, and firm membrane, not vafcular, 
 which does not cover the part of the placenta con- 
 tiguous to the uterus, but its concave furface con- 
 tiguous to the foetus. It coheres by cellular tex- 
 ture both with the chorion and amnios. The 
 moft limple name we can give it, is the middle 
 membrane. 
 
 Dcccxciv. The innermoft coat of the foetus, the 
 amnios, is a watery pellucid membrane, veiw rarely 
 liaving any confpicuous veffels, which, however, I 
 have obferved even in the human fubjecd ; extreme- 
 ly fmooth, and in all parts alike ; alfo extended 
 under the placenta along with the former, and 
 every where in contact with the waters. If there 
 be more foetufes than one, either in woman or 
 
 in 
 
Chap. XXIX. CONCEPTION. 439 
 
 in any other female, each of them has its proper 
 amnios. 
 
 Dcccxcv. The nourifhment of the fetns from the 
 beginning to the end of the conception, is without 
 doubt conveyed through the umbilical vein. This 
 gathering its roots from the exhaling vefTels of the 
 uterus, (dcccliv.) and from the umbilical artery, 
 with which it is manifeftly continuous, and form- 
 ing venous linufes under the furface of the placen- 
 ta, unites into a large trunk, which being twifted 
 in various folds, but lefs than its cprrefppnding ar- 
 teries, and being of fufScient length to allow of a 
 free motion j furrounded with cellular fubftance 
 full of mucus ; feparated by three partitions, and by 
 the membrane which is continued from the amnios, 
 but firmer, and known by the name of the um- 
 bilical rope ; and fwelling into feveral knots, en- 
 ters the navel between diverging arches of the (kin 
 and abdominal mufcles, and proceeding to a pro- 
 per finus of the liver, (ocxcii.) fends the fmaller 
 portion of its blood through the ductus venofus, 
 which is fmaU and feated in the pofterior foffa of 
 the liver, to the vena cava ; and tranfmits to the 
 heart the greater part through the large hepatic 
 branches which conftantly arife from its fulcus, 
 and remain even in the adult, (ncxcv.) and 
 through the branches of the cava, (dcxcvii.) con- 
 tinuous with thefe. The finus of the vena porto- 
 rum, or left branch, is alfp a part of the umbilical 
 vein, and its branches bring the blood from the 
 placenta to the cava, while the right branch alone 
 (ncxcv.) carries the mefenteric and fplenic blood 
 through the liver. 
 
 Dcccxcvi. But this is not the only ufe of the pla- 
 centa ; for the foetus fends great part of its blood 
 to the placenta, through twp very large umbilical 
 arteries, which are the continuation of the aorta ; 
 and after giving off flender feinorals, and very fmall 
 arteries into the pelvis, they afcend refle<Ted along 
 
440 
 
 CONCEPTION. 
 
 Chap. XXIX. 
 
 the bladder, furrounded by the cellular plate of the 
 peritonaeum, and fome fibres feparated from the 
 bladder and urachus, and on the outfide of the pe- 
 ritonaeum enter into the umbilical cord, in which, 
 alternately ftraight and contorted, veith various 
 windings, fomcwhat fliarper than thofe of the vein 
 around which they play, they arrive at the placen- 
 ta, whofe fubflance is entirely made up of their 
 branches, and the correfponding veins, and lubri- 
 cous cellular fubftance accompanying both vefTels ; 
 fo that the acini themfelves, confpicuous in the 
 placenta, are convolutions of vefTels. This blood 
 leems to pafs out through the arterial vefTels of the 
 placenta into the bibulous veins of the uterus, fo that 
 after undergoing the action of the lungs of the 
 mother, it returns ameliorated to the foetus : For 
 what other reafon can be affigned for fuch large ar- 
 teries, which carry off above a third part of the blood 
 of the foetus ? 
 
 Dcccxcvii. Is the foetus alfo nouriflied by the 
 mouth ? Does it drink from the cavity of the amniv.)S, 
 the lymphatic lubricating liquor, which is coagu- 
 lable, unlefs when putrid, in which the fmtus fwims, 
 and whofe origin is not fufliciently knovm ? Is this 
 opinion confrmed by the analogy of chickens, 
 which are necefiarily nouriflred from the contents 
 of the egg only ; by the abfence of a navel-ftring in 
 fome feetufes ; by the meconium filling the large, 
 and part of the fmaii inteftines ; by the liquor 
 found in the flomach of the feetufes of birds, and 
 even of the human fpecies, fimilar to that which 
 fills the amnios ; by the proportionable decreafe of 
 the liquor amnii, to the growth of tire foetus ; by co- 
 agulated fibres, found continued from the amnios, 
 through the mouth and gullet, into the ftomach of 
 the foetus ; by hairs and true faeces being found in 
 the ftomach of the feetufes of quadrupeds ; by the 
 open mouth of the foetus, which we have certainly 
 obferved : the gaping of the chicken, fwimmingin 
 this liquor, and its attemnts as if to fwallow it ? 
 
 Yv'hat 
 
441 
 
 Chap. XXIX. CONCEPTION. 
 
 What are the fources of this lymph of the amnios ? 
 Does it tranfiide through the invifible velTels of the 
 amnios ? Is it tranfmitted to it through certain pores 
 from the fucculent chorion, which is itfelf fupplied 
 from the uterus ? On every point, numberlefs diili- 
 culties occur ; but it feems more probable, that this 
 liquor is nutritious, efpecially in the early ftages of 
 the foetus, and that it is derived from the uterus. 
 
 Dcccxcviii. The excrements of the foetus are col- 
 lected during that whole time in fmall quantity, on 
 account of the great tenuity of the nutritious fluid, 
 percolated through the very fmall veflels of the 
 uterus. I frequently obferve, that the bladder is al- 
 ' moft empty in the foetus. However, there is gen- 
 erally fome quantity of urine, collected in the large 
 and very long urinary bladder. But in a great por- 
 tion of the inteftines, there is collected a green 
 pulp, poffibiy the remains of the exhaling juices ; 
 for I have feen a flmilar fubftance in other cavities, 
 that are filled with exhaling juices, and in the vagi- 
 nal coat of the tefiicle. 
 
 Dcccxcix. Is there, then, no allantois ? fince it is 
 certain, that from the top of the bladder the ura- 
 chus pafles out, which is a tender canal, at firft 
 broad, covered by the longitudinal fibres of the 
 bladder as with a capfule ; and afterwards, when 
 thofe fibres have receded from it, it is continued 
 {lender, but hollow, for fome way along the umbil- 
 ical cord ; in which, how'ever, it vaniflies. Are 
 not the other parts, though not yet feen in the hu- 
 man fpecies, fupported by the very ilrong analogy 
 of brute animals, which have both an urachus and 
 an allantois ? But a proper receptacle, continuous 
 with the hollow urachus, fo large in quadrupeds, 
 has not yet been obferved in man with fufficient 
 certainty, or not fufliciently often ; and thofe emi- 
 nent anatomifts, who have obferved a kind of fourth 
 veffei, continued along the umbilical cord into a 
 proper veficle, do not confidcr that veflel to be the 
 
 urachus^ 
 
443 
 
 CONCEPTION. 
 
 Chap. XXIX. 
 
 urachus, and very lately have referred it to the om- 
 phalomefenteric genus ; and in the human foetus, 
 the urine is feparated in a very fmall quantity : nor 
 perhaps would it be an improbable conjecture, that 
 lome portion of the urine is conveyed from the 
 urachus into the funiculus umbilicalis, and its fpon- 
 gy cellular fabric, and there effufed ; and therefore, 
 that, of all animals, man has the longeft umbilical 
 cord, becaufe he alone has no allantois. It is cer- 
 tainly fhort, and enters into the cord, but does not 
 feem to reach the placenta. Sometimes, in the 
 adult, it has remained open, and has contained 
 urine even as far as the navel. 
 
 Dcccc. In the mean time, the foetus grows ; the 
 tubercles of the limbs gradually fhoot from the 
 trunk ; and the further moh beautiful evolution of 
 the child advances to perfection, in a manner which 
 cannot be defcribed here, and not yet fufficiently 
 by anatomifts ; of which, however, we muft premife 
 a ilrort account. 
 
 Dcccci- The embryo which we firft faw in tl)C 
 uterus of the mother, was gelatinous, having fcarce- 
 ly a definite form, of which one part could not be 
 cllftinguiflied from anotlicr. There was, however, 
 in that gluten, a heart, the fource of life and mo- 
 tion ; there v/ere veffels which generated the li- 
 quor of the amnios ; there were therefore umbilical 
 veffels, and the trunks of the yolk, which it re- 
 ceives from the foetus, are largeff when they fir if 
 become vilible. There was both a head and fpi- 
 nal column, each of them very large, and larger in 
 proportion than at any other time. There were 
 likewife, without doubt, the reft of the vifc^ra, but 
 in a mucous and pellucid ftate ; for which reafon , 
 they may be obferved fooner than is to be expecbed 
 naturally, by rendering them opaque. 
 
 Dccccii. But in every part of the foetus, a very 
 large proportion of water is mixed with a very lit- 
 tle earth, fo that the verv cellular texture is in an 
 
 intermediate 
 
Chap. XXIX, 
 
 CONCEPTION. 
 
 443 
 
 intermediate Hate between fluid and folid ; from 
 large drops of water being interpofed between dif,- 
 tant folid elements. 
 
 Dcccciii. In birds, befldes this living gluten, 
 there is the albumen, which is of a lymphatic na- 
 ture ; and the yoik, which is oleaginous : in man, 
 there is a lafteous fluid, not very unlike the yolk, 
 and coagulable lymph. That the blood is prepared 
 from the fat by the proper powers of the foetus, we 
 are perfaaded from the example of birds. From 
 it, are gradually prepared the other humours, and 
 all of them are at firft mild, void of take, colour and 
 fmell, and of a glutinous nature* The peculiar na- 
 ture of each fupervenes, at a later period, in fome 
 of them not till many years after birth, for inftance 
 in the femen. 
 
 Dcccciv. The elementary folids, even in the 
 adult, conftitute much the fmalleft portion even of 
 the harder parts of the human body ; in the foetus 
 they differ from the fluids, only by a fomewhat 
 greater degree of cohefion, refembling, as yet a 
 gluten, at firft fluid, and afterwards of greater con- 
 fiftence. In this, the fibres, of which none were to 
 be diftinguiflied in the primeval embryo, are by de- 
 grees produced, by the gluten, as it feems, being 
 compreffed between the neighbouring veffels, part 
 of the water exprelfed, and the earthy elements at- 
 tracling each other. Thefe fibres varioufly com- 
 prehend one another, and form cellular texture, 
 even morbidly, and intercept little fpaces, in which 
 a fluid is contained. Of this cellular fubftance, are 
 formed the membranes and veffels, and almoft the 
 whole body. 
 
 Dccccv. The veffels are prior, and exift, formed 
 in the firft appearance of the embryo. What firft 
 appears diftinft, and formed in an egg during in- 
 cubation, are venous circles : but thefe veins fuppofe 
 arteries, by which they both receive their fluid, and 
 the motion of that fluid. They are not generated 
 
 mechanically, 
 
444 
 
 CONCEPTION. Chap. XXIX. 
 
 mechanically, from any obftacle to the courfe of 
 the arterial blood. The trunks of the veins are firft 
 vifible, and afterwards the branches which lead to 
 thefe trunks. If they were produced from reflect- 
 ed arteries, the branches wmuld firft be feen, and 
 the trunks formed in the laft place. Nor could the 
 arterial blood, if repelled by an obftacle, form thofe 
 moft beautiful circles, and vefiels ret.urning into the 
 heart ; but it v/ould rather be irregularly diffufed 
 through the cellular texture. And the primeval 
 heart would foon lofe its vitality, unlefs as much 
 fluid returned to the heart by the veins, as was fuf- 
 ficient to maintain its pulfations. 
 
 Dccccvi. There are, therefore, in the primeval foe- 
 tus, when it firft becomes vifible, fome things more 
 perfect and confpicuous ; others involved, invifible, 
 and very fmall. The heart is the moft perfect, and 
 the only moveable and irritable part ; although it is 
 in many refpects different from what it is in the 
 adult. The brain is la^^e and fluid ; the vefl'els 
 formed, which appear in the back, next to the 
 heart. We cannot yet diftinguifh the vifcera, muf- 
 des, nerves, limbs ; the bones themfelves, of which 
 the firft appearance is mucous, or the veffels of the 
 reft of the body. The other portion is the abdo- 
 men, of which the umbilical capfule is an immenfe 
 hernia. 
 
 Dccccvii. To this embryo is fuperadded motion, 
 in man almoft of the heart alone ; and aifo in birds, 
 Vvdiofe formation does not take place without a heat 
 rather greater than that of the human body : yet, 
 without the heart, heat deftroys, inftead of forming 
 the foetus. The heart is proportionally largeft at 
 the very firft, and afterwards decreafcs more and 
 more in comparifon with the reft of the body. Its 
 pulfations are alfo at this time very frequent, and 
 in the very foft foetus extremely powerful, in impell- 
 ing the humours, and diftending and producing 
 the vefl'els. 
 
 DCCCCVIII. 
 
Chap. XXIX. 
 
 CONCEPTION. 
 
 445 
 
 Dccccviir. To the force of the heart is oppofed, 
 what neverthelefs is of fervice in the formation of 
 the foetus, the vifcidity of the vital humours which 
 unite the earthy elements. There is therefore in 
 the embryo both an impelling force, which increafes 
 the longitudinal growth ; and a reiifting force, 
 which moderates that increafe, and increafes the 
 lateral preffure, and thus the diftention. By the 
 force of the heart all the arteries, or for ealinels of 
 expreffion the artery, which reprefents all the reft, 
 with ail the furrounding cellular texture, is length- 
 ened out ; its folds are fmoothed out. It is alfo di- 
 lated. And the blood by its lateral preffure makes 
 an effort againft the almoft impervious branches of 
 the arteries, fills and involves them, and fets them 
 off at more obtufe angles : thus are produced fpaces, 
 having little refiftance, into Which the gluten is de- 
 pofited. In the very fubftance of the artery, while 
 it is every where dilated, between its imaginable 
 folid threads, are prepared little reticulated fpaces 
 like the interftices of a diftended net, which are 
 alfo adapted for receiving humours. Thefe are 
 larger round the heart and in the head, whither 
 the impulfe of the heart is more direft, and in the 
 placenta : they are fmaller in the inferior part of 
 the body, from which the umbilical arteries , fub- 
 traft the greateft part of the blood. 
 
 Dccccix. The foetus increafes very quickly, as 
 is moft evident in the example of the chick in ovo, 
 whofe length on the twenty fecond day is to its 
 length the firft day at leaft as 1,000,000 to i ; and 
 the whole increafe of bulk in the bird during the 
 remainder of its life does not exceed the fifth part 
 of its increafe in the egg during the firft day. For 
 the fcetus has a larger and more irritable heart, 
 veffels larger in proportion, and likewife more nu- 
 merous and relaxed, and its folid parts are mucous 
 and diftenfible. The breaft is later formed, and 
 
 furrounded 
 
44S CONCEPTION. Chap. XXIX. 
 
 farrounded with membranes fo foft, that they can- 
 not be feen^ 
 
 Dccccx. The embryo does not only increafe in 
 bulk, but is remarkably altered in every particular, 
 fo that it is brought forth totally di/hmilar frcna 
 what it was, v/hen it firll became vifible. And lirft 
 it is probable, that from the produclion of the arte- 
 ries of the limbs, the limbs connected to tire fides 
 by fome gluten are feparately evolved, and that at 
 firft they fprout out very fhort, but afterwards be- 
 come gradually longer, and divided into diltinct ar- 
 ticulations, as the wings of a butterfly are expand- 
 ed by the extenflon of a network of veffels. Thus 
 likewife the right ventricle of the heart is expand- 
 ed by the blood coming to it in greater quantity ; 
 and, being increafccl by degrees, becomes equal to 
 the left. 
 
 Dccccxi. On the other hand, the cellular texture, 
 from its glutinous aqueous nature, becoming grad- 
 ually harder by the addition of earthy particles ; 
 by a gentle attraction contracts the parts, which 
 were before ftraight, into various flexures ; and 
 unites the auricles to the heart, from which they 
 were hitherto feparate. Thus the mufcles, by their 
 action, draw out tlie proceffes from the bones, and 
 dilate the fmail cavities into large cells ; and like- 
 wife incurvate the bones, and varioufly modif)^ their 
 fiiape. 
 
 Dccccxii. Preflure has much influence : to it 
 is attributed the defeent of the tefticles into the 
 ferotum, after the abdominal mufcles acquire irrita- 
 bility ; to it the repuliion of the heart into the 
 breaft, when the integuments of the breaft become 
 larger : to it alfo the lengthening of the breaft, the 
 flrortening of the abdomen, and the leffeiung of its 
 vifeera, when the air received into the lungs dilates 
 the cavity of the thorax. But even the bones arc 
 varioufly deprefied by the preflure of the mufcles, 
 blood-vefl'els, and even of the very foft brain itfelf ; 
 
CONCEPTION. 
 
 Chap. XXIX. 
 
 447 
 
 and by the fame means flelli is changed into ten« 
 don. 
 
 Dccccxiii. The power of derivation brings the 
 blood into the pelvis and lower extremities, from 
 the clofed umbilical arteries : when the foramen 
 Gvale is contra<Ted by the auricles drawn towards 
 the heart, it evolves the right ventricle of the heart : 
 when the veffels of the yolk have occupied the 
 whole length of the egg, and can receive no further 
 elongation, it dilates the umbilical arteries of the 
 chick, and produces a new membrane with incred- 
 ible celerity. On the contrary, but by the fame 
 power, after the blood has acquired a new facility 
 of admifion into any veffels, the other parts, to 
 which its paffage is not equally eafy, inereafe lefs 
 quickly. The growth of the head is flower after 
 the lower limbs have begun to inereafe. 
 
 Dccccxiv. By the evaporation of the thinner part 
 of a fluid, a membrane may be formed, as in the 
 example of the epidermis ; or cartilage, as hap- 
 pens in the bones : or bone itfelf, or fomething of a 
 ftony nature, which happens very frequently in the 
 fliells of aquatic animals. The bones at firft are 
 foft, and of a mucous nature ; then they acquire 
 the conflftence of jelly j and this afterwards be- 
 comes a cartilage, without any change of parts, as 
 far as can be obferved. 
 
 Dccccxv. Cartilage, however, is not fo imper- 
 ceptibly converted into bone. It never happens, 
 without lines and furrows having previoufly mark- 
 ed the cartilage ; without the red blood making a 
 paffage for itfelf into the veffels of the bones ; with- 
 out thefe veffels manifeftly penetrating from the 
 nutritious trunks into the interior of the bone, and 
 impinging as it were in right lines on the cartilagi- 
 nous extremity of the body of the bone, which they 
 remove farther and farther from its middle. Round 
 thefe veffels are formed cellular texture and lami- 
 nse, which the veffels themleives feem to comprefs 
 
 into 
 
CONCEPTION. 
 
 Chap. XXIT. 
 
 448 
 
 into a medullary tube. Laflly, in the epiphylls, 
 which both remains cartilaginous, and denies en- 
 trance to the blood much longer, the red veffels ]>en- 
 etrate through the extreme cruft, as alfo others 
 which come from the exterior veflels of the limbs. 
 Thus alfo in the epiphyfts is produced a red vafcu- 
 lar nucleus, v/hich, being gradually increafed by 
 veffels fent out from its furface, converts the reft of 
 the cartilage into a bony nature. 
 
 Dccccxvi. In thefe long bones, it feems evident, 
 that their growth is owing to the arteries being 
 elongated by the force of the heart, and gradually 
 extended to the extremities of the bones : and that 
 the hardnefs is owing to grofler particles, depofited 
 in the cartilage, after its veflels have admitted the 
 red blood* But even a bony callus never becomes 
 found, till newly formed red veffels have penetrated 
 its fubftance. 
 
 Dccccxvii. The flat bones originate from a kind 
 of membrane. Over this, the fibres fpread them- 
 felves, at firft in a loofe network, and afteiwards 
 more denfely, having a membrane for their bafts ; 
 the pores and intervals between thefe fibres being 
 gradually contrafled and filled wuth a bony juice, 
 at laft convert it into perfect bone. In thefe bones 
 alfo, ftraight red veffels, are diftributed between the 
 fibres. 
 
 Dccccxviii.- The phenomena of the formation of 
 callus, prove, that, between the primeval fibres, an. 
 offeous fluid, replete with groffer particles, is depof- 
 ited, as it exudes in fmall drops, not from the pe- 
 riofteum, but from the inmoft fubftance of the bone, 
 and gradually becomes indurated. But even che- 
 mical analyfis extraifts that gluten from the bones j 
 and in anchylofis, it appears poured around in the 
 manner of confiftent fluid, and manifeftly fills up 
 the chinks of the bones and intervals of the futures. 
 It contains grofs earthy particles, which have been 
 difeovered bv various experiments j and the juice 
 
 of 
 
Chap. XXIX. CONCEPTION.- 449 
 
 of madder adhering to it, manifeftly diftinguifhes 
 it by its colour. 
 
 Dccccxix. The periofteum covers the bones, as 
 membranes the vifcera ; and from it cellular pro- 
 ductions follow the interior veffels of the bones : 
 but the periofteum has neither ftraight fibres, nor 
 the habit of alveoli or laminoe, nor red veffels, while 
 the bone in the egg is indurating ; nor does the 
 periofteum at all adhere to the bone, except in the 
 epiphyfis, when its bony nature is fpreading from 
 the middle ; and it is thinneft when the bone is in 
 a cartilaginous ftate, afterwards it becomes every 
 where complete. In the flat bones, it every where 
 affords a bafis for the bony fibres. 
 
 Dccccxx. Therefore the head is large, every where 
 membranaceous, and, in the firft days of geftation. 
 Cartilaginous in few places, the mouth deep, and 
 the jaws long ; alfo, in the mature foetus, there are 
 the rudiments of the teeth, to which a great deal of 
 membrane is attached ‘ the brain is at firft fluid, 
 and always foft ; it is alfo large ; and the nerves 
 are large ; the eyes are large, and the pupil is Ihut 
 by a membrane ; the breaft is very ftiort, but ex- 
 panfile, on account of the great quantity of cartil- 
 age ; the belly is large, and inclofed with mem- 
 branes : the liver very large ; the bile is inert and 
 mucous : the inteftines are flowly irritable, and, 
 when the foetus is ripe, are full of green foft fasces ; 
 the kidneys are divided into lobes, and large, and 
 renal capfules very large : the pelvis is very fmall, 
 fo that the ovaries, the bladder, and Fallopian tubes 
 project above it ; the genital fyftem is denfe, not 
 yet evolved, or fecreting its fluids : all the glands 
 are large, efpecially the conglobate glands, and full 
 of ferous fluid : the fkin is at firft peUucid, and af- 
 terwards covered with a foft cuticle, and febaceous 
 ointment : the fat is gelatinous, and afterwards 
 grumous ; and the tendons foft, fucculent, and not 
 yet fliining, 
 
 F f DCCCCXXI. 
 
45 ^ 
 
 CONCEPTION. 
 
 Chap. XXIX. 
 
 Dccccxxi. There is a great difference betM'ixt 
 the circulation of the blood in the foetus and in the 
 adult : that this may be underftood, it is neceffary 
 to defcribe the organs by which it is preformed. 
 The firft is the th)unus, a fort loofe gland, confift- 
 ing of many lobes, colleffed into two larger upper 
 procellcs, and two inferior fhorter ones, which are, 
 however, joined together by a great deal of long 
 and lax cellular texture : this gland is large in the 
 foetus, and occupies a great part of the breaft ; it is 
 feated in the cavity of the mediaftinum, and in part 
 of the neck ; and is wholly filled, in its very inmofl 
 ftruclurc, with a white ferous liquor, which cannot 
 be difeovered without wounding it. In the adult, 
 being comprefled by the enlarged lungs, and by 
 the aorta now become larger, it gradually difap- 
 pears. Of the ufe of this gland or its liquid, we are 
 altogether ignorant ; although all the other glands, 
 efpecially the conglobate ones, are alfo larger in the 
 foetus, as we have juft now obferved. 
 
 Dccccxxii. We have faid, that the cavity of the 
 breaft is flrort, being compreffed by the enormous 
 bulk of the liver j the lungs are fmall in propor- 
 tion to the heart, and folid fo as to ftnk in water, 
 vdien completely excluded from the air, by being 
 furrounded with water. Since, therefore, previous 
 to reipii'ation, the lungs cannot tranfmit fo great a 
 quantity of blood as they do in the adult (ccxcii. 
 ccxcYii,) in the foetus there are therefore other ways 
 prepared, by v'hich the greateft part of the blood 
 palfes from tlie umbilical vein and lower cava, into 
 the ?.orta, without entering the lungs. In the pri- 
 m.eval foetus there is no right ventricle of the heart ; 
 and the communication between the right auricle 
 and the left is fo large, that all the blood which 
 comes by the vena cava paffes immediately into the 
 aorta, a very fmall quantity excepted, which goes 
 to the very fmall and invifible lungs. Afterwards, 
 in the foetus, now grown bigger, the lungs are in- 
 
Chap. XXIX. 
 
 CONCEPTION. 
 
 451 
 
 deed larger, and the paflTage from the right part of 
 the auricle into the left is narrower, fmce the auri- 
 cular canal is now taken entirely within the heart, 
 and the auricles themfeNes are become much lliort- 
 er. But yet the feptum, which is common to the 
 right and left auricles, is perforated with a large 
 foramen ovale, throus^h which the blood coming 
 from the abdomen, and a little repelled by the val- 
 vular margin of the right auricle, (lxxxiii.) flows 
 in a full ftream into the left finus. But by degrees 
 the membrane of each finus is elevated backwards, 
 and is connefted with the pulmonary finus, above 
 the oval foramen, by an upper fibre on each fide, 
 and then by many lower palmated ones in fuccef- 
 fion, fo as to clofe up at firft a fmall part, and after- 
 wards the greater part of this foramen ; fo that on- 
 ly a tranfverfely oval oblique paflage is left, whicli 
 remains free betwixt the round margin of the faid 
 oval foramen, and the increafing veflel in the ma- 
 ture foetus, equal to about a fifteenth part of the 
 mouth of the vena cava. 
 
 Dccccxxiii. That the blood takes this courfe, 
 and that no part of it, on the contrary, flows from 
 the left finus into the right, is confident with ^eve- 
 ry fact. For, the column of blood in the right finus 
 is very large ; for it is impofiible there fliould be a 
 larger, as it brings back the blood from the whole 
 body ; and the left auricle contains lefs blood than 
 the right, as part of it flows through the duclus ar- 
 teriofus, whence it is alfo much lefs than the right : 
 moreover, the valve in the mature foetus is fo large, 
 and placed fo much to the left of the ifthmus or 
 mufcular arch (dccccxxii.) that when impelled from 
 the left fide, the valve, like a Ihutter, clofes up the 
 foramen ; but being impelled from the right fide, 
 it readily gives way, and tranfmits either blood or 
 flatus, and even retains flatus itfelf, when blown 
 from the right, and does not fuffer it to return to 
 the right fide. 
 
 F F 2 
 
 DCCCCXXIV. 
 
CONCEPTION. Chap. XXIX. 
 
 452 
 
 Dccccxxiv. Moreover, but a fmall portion of that 
 blood which entered the right ventricle paffes to 
 the lungs ; for the pulmonary artery, being in the 
 fcetus much larger than the aorta, is continued in 
 a ftraight line into the duclus arteriofus ; which is 
 larger than the joint caliber of both the pulmonary 
 branches, and greatly larger than the opening of 
 the foramen ovale, and which enters into that part 
 of the aorta which firft comes in conta^ with tlie 
 fpine, under its fubclavian branch ; by which means 
 it transfers more than half the blood of the pulmo- 
 nary artery to the defcending aorta, which mult 
 otherwife have palTed through the left ventricle in- 
 to the afcending branches of the aorta ; and this is 
 the reafon why the aorta in the foetus is fo fmall at 
 its coming out from the heart. By this mechan- 
 ifm, therefore, the lungs are relieved from preffurc, 
 and a great part of the blood flows in a more direft 
 courfe to the umbilical arteries, and the powers of 
 both fidcs of the heart are united in propelling the 
 blood of the aorta. 
 
 Dccccxxv. Thofe who have aflerted that the foe- 
 tus refpires in the uterus, having made ver\' few 
 obfervations, have neglected that moft eafy one 
 which is derived from the water, in tlie middle of 
 which the foetus fwims, and likewife of the lungs, 
 which in a foetus are conftantly heavy, and fink in 
 water ; and, laftly, the evident fliortnefs of the 
 breaft, and fmallnefs of the lungs. Whether it can 
 take in air during its fhort paflage through the va- 
 gina, is more diflicult to determine ; and I fufpect, 
 that in a certain fituation, a healthy foetus, not too 
 much comprefled, may fometimes infpire, while it 
 is in part ftill impacted between the parts of the 
 mother. 
 
 Dccccxxvi. The uterus increafes conftantly along 
 with the foetus ; the ferpentine arteries of which it 
 is compofed being extended, and rendered ftraight, 
 bv the blood impelled into them ; the veins being 
 
 unable 
 
Chap. XXIX. 
 
 CONCEPTION. 
 
 453 
 
 unable to return the blood into their trunks com- 
 preffed by the great bulk of the uterus, and fweiling 
 out into immenfe finufes ; and laftly, the menftrual 
 blood, being retained in the uterus, and not entire- 
 ly fpent on the ftill fmaU foetus. Its thicknefs con- 
 tinues the fame,becaufe the greater quantity of blood 
 in the arteries and veins coinpenfates for the exten- 
 uation of its folid parts. The fundus or upper 
 part, efpecially, increafes ; fo the tubes now defcend 
 from the middle of the gravid uterus. The ute- 
 rus, therefore, rifes out of the pelvis, even as high 
 as the colon and ftomach itfelf, and compreffes 
 the abdominal vifcera, and the bladder and redum. 
 The os uteri in the firft months of geftation is drawn 
 upwards along with the uterus, and recedes from 
 the entrance of the vagina : after the third month, 
 however, it again defcends and immerges into the 
 vagina. The fame becoming perpetually Iliort- 
 er, projects into the impervious extremity of the 
 vagina : for it is conftantly becoming more ten- 
 der ; and, from that cartilaginous hardnefs which 
 it has in the virgin womb, it is relaxed into a mu- 
 cous foftnefs. Never perfectly clofed together, it is 
 covered and defended from the air by the mucus of 
 the f nufes, and perhaps by that of the veiicles which 
 are feated in the cervix uteri. Finally, the cervix, 
 which remains long unchanged, at length, during 
 the laft months of geftation, becomes likewife fhort, 
 and its opening becomes flat and broad, without 
 length ; and towards the time of delivery, is always, 
 more open. At the fame time, the foetus increafing, 
 which in the firft months had no certain fituation, 
 and about the middle of the time of geftation, was 
 often rolled together into a globe, fo that the head 
 lay betwixt the knees, finks its ponderous head more 
 and more into the pelvis, and direds it towards the 
 cervix uteri. , — 
 
 Dccccxxvii. The various complaints in the ute- 
 rus are now increafed to the higheft degree. Being 
 
 diftended 
 
454 
 
 CONCEPTION. 
 
 Chap. XXIX. 
 
 diftended by the blood retained in it, all its nerves 
 are irritated ; for nothing is more difagreeable to 
 man, than exceffive tenfion, unlefs it occurs very 
 gradually. From the head of the foetus, funk into 
 the pelvis, the rectum, bladder, and that part of the 
 uterus next to the neck, and the moft fenfible, are 
 prelfed, and become painful ; the foetus, having ac- 
 cjuired its full bulk, diftends the uterus everyway ; 
 and with greater uneafmefs, becaufe, the waters be- 
 ing now taken away, the projecting limbs, and the 
 head, prefs much more Itrongly on the uterus. It 
 is alfo thought, that the placenta itfelf, now very 
 large, diftends the naked internal furface of the ute- 
 rus. From thefe caufes, arife at firft tranfient ef- 
 forts of the irritated uterus, to free itfelf ; and at 
 laft, vehen thefe caufes have got to their utmoft 
 height, an uneafy fenfation is occaftoned by the im- 
 pacfed head of the foetus, like that which arifes from 
 a collection of faeces in the reclum ; by \^'hich pain, 
 therefore, the mother is forced to attempt the birth 
 of the child. The time of delivery arrives at the 
 expiration of nine folar months, and is in the fame 
 manner defined in every fpecies of animals, although 
 by particular caufes it may be accelerated or retard- 
 ed for fome v^eeks, provided thefe caufes be afeer- 
 tained, and their power not extended too far. 
 
 nccccxxvin. 'formented by tenefmus, now be- 
 come intolerable, the mother exerts the whole ef- 
 fort of a veiy deep infpiration, by which the vif- 
 cera of the abdomen being forced downwards, prefs 
 upon the uterus, (dcclvi.) while, at the fame time, 
 the v'omb itfelf, being contraded by its contractile 
 force, urges the foetus, fo as fometimes to exclude it, 
 vithout any efforts of the mother. The difficulties 
 of the birth, however, are evidently overcome prin- 
 cipally by the efforts of the mother, when the mouth 
 of the uterus, now very foft, fuffer« itfelf to be dif- 
 tended by the head of the foetus. For the amnios, 
 filled with water, protruded in the form of a cone, 
 
Chap. XXIX. 
 
 CONCEPTION. 
 
 455 
 
 by the head of the foetus, dilates the os internum 
 uteri, becomes extenuated, and diftended,and burlts ; 
 the waters efcape, which lubricate the paffage of the 
 ■vagina, and relax , all the parts. Then the naked 
 head of the foetus, with the face turned towards 
 the os facrum on account of its weight, and being 
 urged forwards, like a wedge, dilates the os uteri ; 
 till, by a very powerful effort of the mother, the 
 bones of the pubes being often fomewhat loofened 
 with intolerable pain to the mother, and tremor of 
 the whole body, the head is preffed out, and advan- 
 ces through the dilatable vagina, which is not very 
 much comprelfed by any bone ; and the foetus is 
 brought forth, with difficulty even in quadrupeds, 
 but moft difficultly in the human race, whofe foetus 
 has the largeft head. 
 
 Dccccxxix. It is natural for women to have but 
 one child at a birth, which law they have in com- 
 mon with all the larger animals, except the carniv- 
 orous. Frequently, however, they have two, more 
 rarely three, and never more than five. It is not 
 to be doubted, that a fecond foetus may be conceiv- 
 ed, while the firft remains in the uterus : fince wo- 
 men have frequently iDorn children, in whofe ute- 
 rus a hard and offified foetus had been long re- 
 tained. 
 
 Dccccxxx. The placenta, connefted with the 
 fundus uteri, (dccclxxxviii.) is generally fepara- 
 ted without difficulty in a mature birth, by weaker 
 throes of the mother, and by the art of the mid- 
 wife. Thus the fiocculi of the placenta are drawn 
 out from the villi of the womb, a confiderable flow 
 of blood takes place, and the mother is delivered 
 of the fecundines. At the fame time, the umbil- 
 ical cord is tied ; for it cannot be left open in a 
 healthy and lively child without danger ; and is cut. 
 ^riius the umbilical vein is deprived of its fupply of 
 blood, and an infuperable obftacle is oppofed to the 
 arteries of the fame name. 
 
 DCCCCXXXI. 
 
45 ^ 
 
 CONCEPTION. 
 
 Chap. XXIX, 
 
 Dccccxxxi. The uterus, which hitherto had 
 been exceffively diftended, now contracts itfelf by 
 the power of its elaftic fibres, (dcccxliii.) fo fud- 
 denly and powerfully, as often to catch the hand 
 of the deliverer, and the placenta, if it be not foon 
 loofened. Thus, the veffels are compreffed, alfb con- 
 tracting to a lefs fize by their own pov^er ; whence 
 the large quantity of blood that was collected in 
 the uterus, is expreffed and flows out under the de-r 
 nomination of the lochia ; at firft pure blood, but 
 afterwards, as the veffels contract themfelves more 
 clofely, it becomes yellow, and afterwards white ; 
 and the extenfive wound of the uterus is healed, 
 which foon fhrinks to a bulk not much exceeding 
 that of the viroin uterus. 
 
 O 
 
 DccccxLiv. But two or three days after delivery, 
 when the firft violence of the lochial difchara;e lias 
 abated, the breafts fwell confiderably ; and as in 
 the time of geftation they yielded a little ferum, 
 they now become turgid, at iirft with a ferous, thin 
 fluid, which is foon followed by tlie chyle itfelf. 
 For milk very much refembles chyle, but human 
 milk lefs than that of other aniinals. It is white, 
 thickifh, fweet, and replete with a very fweet ef- 
 fential fflt, grorvs four fpontaneoufly, but is tem- 
 pered by the addition of oil and lymph, and is com- 
 pofed of an odorous volatile halitus, a good deal of 
 fat, water, vifeid cheefy matter, and an earthy fub- 
 ftance rather alkalefcent ; by fafting fame time, from 
 the chyle being then converted into ferum, the milk 
 becomes fait, alkalefcent, and difpleafmg to the in- 
 fant. Like the chyle, it frequently retains the nature 
 of feme kinds of aliments and medicines. The caufe 
 of this increafed fecretion in the breafts, feems to de- 
 pend on revulfion, and to fucceed the fupprefllon 
 of that plentiful uterine fecretion by which the 
 feetus was nouriflied ; as diarrhoea fucceeds fuppref- 
 fed perfpiration. For it has been obferved, that 
 true milk has been difeharged from other parts. 
 
Chap^ XXIX. 
 
 CONCEPTION. 
 
 45 ? 
 
 ;ind even through wounds. And there is belides 
 between the uterus and breafts, fome kind of ner- 
 vous fympathy, and a fimilar fitnefs for generating 
 a white liquor. For the uterus in infancy, and dur- 
 ing pregnancy, manifeftly generates it. But the 
 inofculations betwixt the mammary and epigaftric 
 arteries, though true, are fo fmall, that in this 
 nothing is to be afcribed to them, 
 
 DccccxLv. The breafts are compofed of a very 
 large quantity of very foft and very white fur- 
 rounding fat and of a conglomerate convex gland, 
 confifting of round, hard kernels, of a reddifli blue 
 colour, furrounded externally, and connected to- 
 gether, by firm cellular fubftance, feparating into 
 fmaller acini ; which ftrucfure is common to men 
 and women. To thefe glands many veffels are 
 diftributed from the internal mammaries, from the 
 external thoracics, and laftly from the humeral ar- 
 tery, all which mutually inofculate near the nipple. 
 The trunks of the mammary arteries, but not the 
 mammales, inofculate with the epigaftric velfels ; 
 the veins more evidently. The nerves, both large 
 and numerous, as in cutaneous parts, are derived 
 from the nerves placed between the upper ribs. 
 
 DCcccxLvi. From the middle of this gland of 
 the breaft, and likewife from the furrounding fat, 
 from an infinite number of roots, numerous, very 
 flender, foft, white, and dilatable dufts arife, which 
 converge on all fides to the nipple in the centre, both 
 into the circle which lubtends its bafe, and into the 
 area of that circle, and emerge into the root of the 
 nipple. This is a cavernous cellular body, into 
 which the blood may be effuied, fo as to caufc 
 ereclion, as in the penis. This papilla is perfora- 
 ted by twenty or more excretory duels from the 
 breaft, called la<ftiferous ; between which there is 
 not any inofculation, and which are much narrow- 
 er in the nipple, than before : and in the flaccid 
 ftate of the nipple, are compreiied, wrinkled, coL 
 
 lapfed. 
 
45S CONCEPTION. Chap. XXIX, 
 
 lapfed, and fliut ; but when the nipple is erected 
 by any kind of titihation, they become ftraight and 
 have patulent mouths, lying betwixt the cutaneous 
 wrinkles. This papilla is furrounded by a circle 
 furnilhed with febaceous glands, which defend the 
 tender fkin againft attrition and perpetual moif- 
 ture. 
 
 DCcccxLVii. This is the firft food of the infant, 
 and at other times alfo is exceedingly falutary to 
 man. This the infant knows how' to take, before 
 it has attempted to perform any other function of 
 the body. Taking the nipple in its mouth, it 
 carufes it to fiveU by gentle vellications, and prelTes 
 it wdth the lips, that no air may enter betw'ixt 
 them ; at the fame time, it infpires and forms a 
 fpace in its mouth, in w'hich the air is rarelied ; 
 and thus, the preffure of the air, and the compref- 
 fing force of the lips of the infant, emulges the 
 milk from the nipple, from which, on account of 
 its quantity, it is moreover difpofed to flow fpon- 
 taneoufly ; and the infant fucks, and is nourilhed. 
 The firft ferous milk, termed coloftra, loofens the 
 bow^els of the young infant, and evacuates the me- 
 conium, (dcccxcviii.) to the great advantage of 
 the child. Yet, even independent of the foetus. 
 Ample titillation erecting the nipples, and increaf- 
 ing the afflux of blood, has produced a flow of 
 milk, even from virgins, old women, and men. 
 Milk is only generated after puberty ; befewe that 
 time a ferous humour flows from the breaft ; and 
 for the moft part it is nrft generated about the mid- 
 dle of pregnancy. After the menfes have ceafed, 
 the breads, as well as the uterus, being grown 
 effete, ceafe to perform their office. 
 
 DccccxLviii. But great changes happen to the ir^ 
 fant when born. The Arft is refpiration, which it 
 attempts even wdthin the vagina of the mother ; be- 
 ing probably excited, by various pain and anxiety, 
 to thofe cries with which it falutes the light, and 
 
 perhaps 
 
Chap. XXIX. CONCEPTION. 
 
 459 
 
 perliaps by the delire of food which Is obtained from 
 the {lore of the amnios : therefore, it draws air into 
 its lungs, and dilates them, till now, fmall and full 
 of ferous humours, and changes them from being of 
 a deep red colour, fmall, folid, and linking even in 
 fait water, into a fubftance, which is light, fpongy 
 and floating, large, full of air, and almoil of a 
 white colour : therefore, the blood enters more ea- 
 fily into thefe enlarged and loofe lungs, (cclxv.) 
 in confequence of which, a large portion of the 
 blood of the pulmonary artery, that went through 
 the canalis arteriofus into the aorta, no\v pall’es into 
 the lungs by the other branches of that artery. 
 And the duel is hill more deferted, as there is a 
 new obhacle to the defeent of the blood into the 
 abdomen ; for the very large umbilical arteries are 
 now tied, fo that the blood of the defeending aorta 
 cannot now find its way, but by an effort with which 
 it dilates all the arteries of the pelvis and lower ex- 
 tremities. Finally, as the lungs receive more blood, 
 the aorta arifing from the heart alfo receives a great- 
 er quantity, and the intermediate duflus arteriofus 
 is comprefl'ed between the tumid aorta and the pul- 
 monary artery, fo that in the adult it is found not 
 only empty but flaortened ; in other refpecls it is 
 • fingularly red within, foft, and very apt to concrete 
 with hagnating blood. This courfe of the blood, 
 therefore, is foon aboliflied, commonly within a 
 year. 
 
 DccccxLix. Then the foramen ovale is, by the 
 fame caufes, alfo gradually clofed up. For as foon 
 as the paffage into the lungs is rendered eafier, the 
 palfage into the right fide of the heart alfo becomes 
 eafier ; whence the blood of both cavas flows 
 thither more plentifully, as it is invited by the lax 
 pulmonary artery, and therefore does not need that 
 paffage excavated in the feptum of finufes. Again, 
 the umbilical vein, being now almoft deilitute of 
 any fupply of blood, on account of the umbilicus 
 
 being 
 
CONCEPTION. Chap. XXIX. 
 
 460 
 
 being tied, (dccccxxx.) lefs blood will flow into 
 tlielower cava, and confequently the preflure againit 
 tlie foramen ovale will be diminilhed ; into which, 
 moreover, the blood of the upper cava, on account 
 of the ifthmus, will be fcarcely able to penetrate. 
 Laftly, as more blood is conveyed through the 
 lungs into the left fmus, it is dilated, and, along 
 with the whole flnus, the cornicles of the oval valve, 
 which are fixed to it, are extended, and elevate tlie 
 valve ; fo that, in the mature foetus, being drawn 
 over the ifthmus, it entirely fhuts up the paflage, 
 and is clofely applied to the ifthmus, while, at the 
 fame time, the blood, within the left flnus, fupports 
 the valve againft the impulfe of the blood within 
 the right flnus. Thus, by the acceflion of a little 
 friclion of the uppermoft margin of the valve againft 
 the fuperior ifthmus, the foramen ovale clofes up 
 by degrees, and the upper margin of the valve is 
 agglutinated and coheres to the pofterior furface of 
 the ifthmus. But this takes place very flowly ; fo 
 that, very frequently, even at an advanced age, a 
 fmall aperture ftill remains between the ifthmus 
 and upper part of the valve ; and where there is no 
 aperture, yet there are the remains of the whole 
 foramen, hollow to the left flde, and of a paflage at 
 the upper part, open towards the right flde, and 
 clofed to the left, becaufe the power of the blood 
 in the right fide is always either greater than its 
 reflftance on the left, or certainly not lefs, even in 
 the advance of life. 
 
 Dcccci^ The umbilical vein, being deprived of 
 blood, foon clofes up. I'he blood of the vena porta- 
 rum, being no longer impeded by an oppoflte force 
 .coming from the umbilicus, occupies the left flnus 
 and curve of the umbilical fofla, (ncxcv.) and 
 tranfmits blood through thofe branches by wliich 
 the umbilical vein formerly fer t blood into the cas a. 
 The duefus venofus being neglected, clofes by tlic 
 new compreflion which the diaphragm, defce;idi;ig 
 
Chap. XXIX, CONCEPTION. 4^4 
 
 in infpiration, makes againft -the liver ; by v/hicli 
 the left lobe -of the liver is preffed towards the lo*- 
 buk, and, perhaps too from the obtnfe angle which 
 it makes with the left finus of the vena portarum 5 
 for it is certainly firfl: clofed next the vena porta- 
 rum. 
 
 DccccLi. The umbilical arteries are clofed up in 
 the fame way as other arteries ufually are when 
 tied, by part of the blood being coagulated into a 
 polypus, which fills up the impervious extremity, 
 and by the blood, which meets with refilling mem- 
 branes, diverging into the adjacent lefs reflfting 
 branches. Nor do I overlook the force of the ab- 
 dominal mufcles, by which thofe arteries are com- 
 preffed againft the full abdomen in refpiration 5 or 
 the very acute angle in which the umbilicalis, arif- 
 ing from the iliac artery, and now incurvated with 
 it along the bladder, makes ; or the ftraight direc- 
 tion in which the thighs, which in the foetus- made 
 an acute fold with the body, are now extended. 
 Thus, thefe arteries are foon fhut up, leaving only 
 a very fmall tube, that leads to two or three arteries 
 of the bladder. The urachus is very quickly oblit- 
 erated, from its afcending directly from the bladder, 
 being a very flender tube, having no outlet, and 
 now negle&ed on account of the defcent and per- 
 me-ability of the urethra. 
 
 DccccLii. From limilar caufes the liver is grad- 
 ually diminifhed, and contrafts itfelf within the 
 ribs ; and the inteftina crafla, from their flender 
 condition in the foetus, dilate to a confiderable di- 
 ameter, and the ftomach is elongated j and the cx- 
 cum is formed by the weight of the faeces prefling 
 downwards on the right of the appendix ; and the' 
 lower extremities are remarkably enlarged by the 
 repulfion of the blood, from the umbilical arteries 
 now tied ; and the other changes take place, by 
 which the foetus infenfibly advances to the nature 
 of a perfed adult. 
 
 CHAP. 
 
NUTRITION. 
 
 Chap. XX^!. 
 
 462 
 
 CHAP. XXX. 
 
 NUTRITION, GROWTH, LIFE, AND DEATH. 
 
 DCCCCLIH. |P VEN after ths child is borrij it con- 
 j tinues to grow, but always more 
 Ilowly in proportion to its age. There are many 
 caufes for the perpetual diminution of its grow'thi 
 Many veffels feem to be obliterated, both becaufe 
 they are comprefTed by the neighbouring torrent 
 of fome large artery, and becaufe the blood, now be- 
 come more vifeid, coagulates. Befides, the food 
 being now coarfer, accumulates in the blood more 
 earth, which, being carried through the whole body 
 with the nutritious fluid, renders every part of it 
 harder, bones, teeth, cartilages, tendons, ligaments, 
 veffels, mufcles, membranes, and cellular fubftance ; 
 lb that an Increafe of hardnefs may be perceived, 
 even by the touch. Wherefore, fince the blood 
 flows from the heart through fewer canals, and 
 fince all the parts which flaould be lengthened or 
 diftended have become harder, it necdlarily follows, 
 that thofe which ought to increafe in bulk, will 
 yield lefs and lefs to the impulfe of the , heart. 
 
 DCCccLiv. But the heart likewife, which is the 
 part that is lirlt cOnfolidated of all the foft ones, 
 increafes lefs than any other part of the whole body; 
 and while the mucli more tender limbs and Ibfter 
 vifeera are diftended, the heart itfelf grows more 
 flowly, and continually bears a lefs, and at laft an 
 eight times fmaller, proportion to the reft of the 
 body in the adult. At the fame time, from that 
 very denftty which it has fo quickly acquired, it 
 becomes lefs irritable, and is contracled lei's fre- 
 quently within a given time. I'hus, while tlie re- 
 fifting powers are augmented, the diftending ones 
 are at the fame time diminiflied. 
 
 DCCCCLV. 
 
Chap. XXXi 
 
 GROWm 
 
 4^3 
 
 DccccLv. There will, therefore, fooner or later, 
 be an end of increafe ; and this will happen fooner, 
 in proportion to the quicknefs and frequency of the 
 contra<d:ions of the heart, and will approach when 
 the cartilaginous crufts of all the bones are now be- 
 come fo thin that they cannot yield or give way to 
 the increafe of the bony part. In women, the men- 
 fes feem to put an earlier ftop to the growth- In 
 cartilaginous fifties the growth is perpetual. 
 
 DccccLvi. There is no durable ftate j for, nature 
 from the firft conception, tends, by a perpetual pro- 
 grefs, towards decreafe. It is faid, however, to take 
 place, when there is neither any increafe of bulk, 
 nor yet any very vifible decreafe. 
 
 DccccLvii. For we are all perpetually confumlng 
 (ccccxxxiv.) Nor do v/e only lofe the fluid parts 
 of our bodies, but even thofe which are reckoned 
 the moft folid. For even the bones are changed ; 
 and the teeth, which are harder than the bones, 
 increafe in bulk when the attrition of the oppofite 
 teeth ceafes to wear them away, and, therefore, 
 their elements are changed : even the fibres of 
 ivory in the elephant’s tooth have given way, and 
 furrounded on each fide, in curved lines, a leaden 
 ftiot ; the bony juice likewife is changed ; fince in 
 fome cafes the bones grow foft ; in others, it forms 
 bony tumors : even cicatrices themfelves have a 
 manifeft growth, for otherwiie they would not be 
 fufficient, in an adult, to fill up a wound received 
 in infancy ; and a great quantity of the earthy, cer- 
 tainly of the animal part of our bodies, goes off" by 
 urine, as is proved by fome difeafes. 
 
 DCcccLviii. The caufes of the deftruflion of the 
 folids confift in the perpetual extenfion and retrac- 
 tion, which happens at every pulfation of the heart, 
 of which there are an hundred thoufand every day, 
 a degree of motion by which metals themfelves are 
 worn ; then in the friftion of the fluids againft the 
 folids 3 the wearing away of all the membranes, 
 
 which 
 
GROWTH. 
 
 Chap. XXX. 
 
 4C4 
 
 which termlmate with a loofe extremity, either on 
 the furface or in the internal cavities of the body, 
 ■i^ hich are fupported folely by the reft of the canal ; 
 in the alternate fwelling and collapfe of the mufcles ; 
 and in the attraction and preffure which our mufcles 
 exert. But the parts of our body are the fooner 
 worn away, that they conftft of a great deal of 
 gluten combined with a fmall quantity of earth ; 
 and that gluten, when it is extended, if the exten- 
 fion has been a little fuperior to the force of co- 
 hehon, muft of neceffity fall away and be carried 
 off from the earthy parts. Thus, deficiencies are 
 generated, fuch as are vilible in the arteries of old 
 men. The cellular texture, which otherwife would 
 be difft)lved in water, into a jelly, is worn away by 
 the friftion produced by the impetus of the blood 
 preffing againft the neighbouring blood-vclVels and 
 mufcles, and by the perpetual alternation of flexion 
 and extenflon. 
 
 DccccLix. This decreafe would be very quick 
 and indeed there would be no great diftance be- 
 tween the end of our hfe and its besinnins;, unlefs 
 thefe Ioffes were repaired. The fluid parts are re- 
 ftored by the aliments, and that pretty quickly ; as 
 appears from the example of a chicken, in which 
 blood is generated from its aliment within two days. 
 The fat, however, and red globules of the blood, 
 are formed out of the fat, as is fhov.m elfewhere ; 
 the lymphatic juice from the jelly ; the mucus, 
 from mucus 5 and the reft of the humours, Irom 
 thefe and water. The lolids are repaired aimoil 
 by the fame means which we have deferibed in 
 the hiftory of the foetus. A gelatinous juice is con- 
 veyed from the aliments, through the arteries, to 
 all parts of the body, and exudes into the cellular 
 texture every where. The furrows, vchich we im- 
 agine to be made in the inmoft arterial membrane 
 by the impetus of the blcoi, are filled up by a 
 vifeid matter, applied to them by the lateral prd- 
 
 lurc; 
 
Chap. XXX. GROWTH. 465 
 
 fure ; never in too great quantity, becaufe the 
 exuberant parts of the nutritious particles muft ne- 
 ceffarily be abraded by the current of the blood. 
 Nor will it be deficient while there is a fufficient 
 quantity of aliment, fince there is more reft, and 
 lefs refiftance in the bottom of the furrow, which is 
 farther removed from the motion of the blood 
 through the centre of the veffel. There feem to 
 be certain powers in the ain, by which the aliment 
 is attached to the folid patts, although we are ig- 
 norant of the manner in which they aft:. 
 
 DccccLx. The decreafe of the cellular texture 
 arifing from attraftidn or preffure is repaired by 
 the vifcid vapour exhaling from the artery, and ap- 
 plied to the wafted places by the force of the neigh- 
 bouring arteries and comprefling mufcles, its aque- 
 ous part being exprefled and abforbed. The glu- 
 ten repairs moft of the organic parts, tendons, and 
 membranes ; being formed into new cellular fub- 
 ftance, as in the foetus. 
 
 DccccLxi; The wafte, which takes place in the 
 linconnefted extremities of parts adhering by their 
 Other extremity to the reft of the body, can be re- 
 paired by protrufion alone, while the lymph fills up 
 the intervals produced. 
 
 DccccLXii. When the growth of the body can 
 proceed no further, fatnefs fupervenes, which is a 
 kind of imitation of real growth. This proceeds 
 from the fat generated by the aliment ; which, 
 from the impetus of*t^e blood being now leflened 
 as it enters the fmall vefiels with more difficulty, is 
 removed to the fides of the vefiels ; enters the 
 lateral vefiels, and inorganic pores of the arteries ; 
 exudes into the cellular texture ; and there is ac- 
 cumulated, in confequence of the diminution of the 
 compreffing power of the blood, and likewife of the 
 abforption by the veins. 
 
 DccccLxiii. The beginnings of decay are percep- 
 tible even in youth itfelf. Even in that blooming 
 G g feafon 
 
LIFE. 
 
 Chap. XXS. 
 
 feafon the folid elements of the body are augmented, 
 the apertures through which the humours flow are 
 leflened, the veflels are obliterated, and the greater 
 attraction of the cellular fubflance has condenfed 
 the whole body. In every part of the body the in- 
 duration produced by age becomes confpicuous, in 
 the bones now wholly brittle, in the Ikin, in the 
 tendons, in the conglobate glands, in the arteries, 
 and in the weight of every part, and of the brain 
 itfelf. But thoie parts grow fooneft rigid, which are 
 moft exercifed by motion ; as thofe in every work- 
 man, which he chiefly employs in his profeffion. 
 
 DccccLXiv. Moreover, the arteries continue to 
 become denfer, narrower,and even impervious, both 
 by the internal prefliire of the blood flowing through 
 the large arterial tube, and by the attraction of the 
 cellular texture of which the greateft part of the 
 artery is compofed. An infinite number of parts of 
 the cellular texture therefore ceafe to be nourilhed ; 
 to which the minute arteries hitherto conveyed nou- 
 rifhment ; but which being now flopped up, bring 
 none. The extending force being removed, the cel- 
 lular flocculi attract each other, leflen the interflices 
 between them, degenerate into membranes, or fub- 
 flances of a hard texture, which inclofe, and, as it 
 were flrangulate other veflels. The gelatinous \"a» 
 pour.likewife concretes in the interflices of the cellu- 
 lar texture, and forms a hard folid with its fides. The 
 mufcles, by the expulfion of their blood, and the 
 concretion of their fibres, degenerate into hard denfe 
 tendons, deflitute of irritability. 
 
 DccccLxv. At the fame time, the nerves become 
 more and more callous, and infenfible to the im- 
 prefiions of the fenfes, and the mufcles to irritation : 
 thus the contractile force of the heart, and the fre- 
 quency of its pulfations, is diminiflied, and there- 
 fore every force which impels the blood into the 
 ultimate veflels. 
 
 DC CC CL XVI. 
 
LIFE. 
 
 Chap. XXX; 
 
 467 
 
 DccccLxvi. The quantity of humours is dimin- 
 ifhed in the denfer body, as the perlpiration, femen, 
 humours of the eye, and of the conglobate glands ; 
 the vapour, which moiftens the folid parts of the 
 body, every where manifeftly decreafes. For this 
 reafon, nutrition now languifhes, becaufe there is 
 more which requires nouriflxment, and lefs nutri- 
 tious juice. 
 
 DccccLxvil. Nor is the quantity of humours on- 
 ly diminifhed : they themfelveS likewife become vi- 
 tiated. They were mild and vifcid in children : 
 but thefe fame humours are now acrid, fait, fetid, 
 loaded with a great quantity of earth, in old men. 
 This is produced by the ufe of fait and putrefcent 
 aliments, the bad effects of which increafe, being 
 collected through a great length of time ; alfo, by 
 the diminution of the cutaneous perfpiration, and 
 the coftivenefs of the belly, on account of the di- 
 minifhed irritability, and by the reforption of the 
 putrid liquamen, thus increafed. Hence the fetor 
 of the urine, of the breath, and the difficult healing 
 of wounds; 
 
 DCcccLxviii. But the greateft fault of the hu- 
 mours, is, that they abound with earthy particles, 
 both collected infenfibly from the aliments after the 
 fecretions have become lefs eafy, and partly abftract- 
 ed from the folids themfelves, and returned into 
 the blood : for this earth is demonftrated in fome 
 difeafes, and by the nature of the gouty concretions. 
 From this abundance of earth, the proportion of 
 that element through the whole body, is again aug- 
 mented, becaufe the nutritious liquor brings too 
 m.uch of it along with it ; whence the brittlenefs of 
 the bones, and the hardnefs of all the parts increaf- 
 es ; it is likewife every v/here depofited in the cel- 
 lular texture, and produces every where crufts, at 
 firft callous, and then bony or ftony, chiefly in the 
 coats of the arteries. 
 
 DccccLxix. The rigidity of the whole body, the 
 decreafe of the mufcular powers, and the diminu- 
 G G 2 tion 
 
DEATH. 
 
 Chap. XXX. 
 
 468 
 
 tion of the fenfes, conftitute old age ; which, fooner 
 or later, opprefles mortals feverely : fooner, if fub- 
 jected to violent labour, or addicted to pleafure, or 
 fed upon an unwholfome diet ; but more flowly, if 
 they have lived quietly and temperately, or if they 
 have removed from a cold to a warm climate. 
 
 Dccccnxx. But as thofe caufes incelTantly conti- 
 nue to operate in rendering the matter of the body 
 more denfe, in diminifhing its irritability, and in 
 augm.enting the quantity of earth, it is not polSble 
 but decrepit old age muft fucceed. In it, the fenfes 
 are almoft deftroyed, and the*vis infita of the muf- 
 cles becomes exceedingly weak, fo that the limbs 
 lofe their ftrength, and become, efpecially the legs> 
 unable to direct the body ; that the callous infenfi- 
 bility of the nerves cannot be excited to perform 
 the office of generation ; that the very inteftines, 
 becoming torpid, do not obey the habitual ftimuli ; 
 that, by the induration of the intervertebral carti- 
 lages, the body bends forward ; that by the falling 
 out of the teeth, the jaws, now rendered fliorter, 
 do not fupport the lips fufficiently ; and laftly, that' 
 the pulfations of the heart become one half lefs fre- 
 quent than in the infant hate. 
 
 DccccLxxi. Thus at laft, the neceffity of natu- 
 ral death approaches, although the greateft number 
 of mortals are carried off prematurely by difeafes. 
 One in a thoufand exceeds the age of 90 ; and one 
 or two perhaps in a century live to the age of 150, 
 Man is long lived, when compared with other ani- 
 mals ; he is alfo more tender than any of them, has 
 loofer flefh, and lefs hard bones. It is not eafy to 
 fay what was the caufe, in long lived people, of 
 their longevity. England feems to exceed all other 
 nations in the number of thofe who live to an ad- 
 vanced age ; and in general, the temperate coun- 
 tries are remarkable in this refpedt. Among the 
 claiTes of men, the commonalty has almoft folely 
 afforded thefe rare examples j ^though, irom its 
 
 being 
 
Chap. XXX. 
 
 DEATH. 
 
 469 
 
 being the moft numerous, we may expect a greater 
 number of examples. Some prerogative feems to 
 belong to fobriety, at leafl in a moderate degree ; 
 temperate diet ; peaceable difpofition ; a mind not 
 endowed with very great vivacity, but cheerful, and 
 little fubjed to care. Among animals, birds are 
 longer lived : and filhes, whole heart is very fmall, 
 growth very flow, and whofe bones never harden, 
 are the longeft lived. 
 
 DccccjLxxii. Death from old age happens fome-. 
 times, but rarely. It may be faid to occur, when 
 the powers gradually decay, firft; of the voluntary 
 mufcles, then of the vital mufcles, and laftly, of the 
 heart itfelf ; fo that, in an advanced age, life ceafes 
 through mere weaknefs, rather than through the' 
 oppreflion of any difeafe. I have often obferved the 
 fame kind of death in animals. The heart becomes 
 unable to propel the blood to the extremities, the 
 pulfe and heat defert the feet and hands ; yet the 
 blood continues to be fent from the heart into thofe 
 arteries neareft to it, and to be carried back from 
 thence : the flame of life is thus fupported for a 
 little while, which foon after we perceive to be ex- 
 tinguifhed ; when now the heart itfelf, being totally 
 deprived of its powers, and not irritable by the 
 blood to any effectual motion, cannot propel the 
 blood through the lungs, that the aorta may receive 
 its due quantity. The laff efforts of refpiration are 
 now exerted to open a paffage for the blood through 
 the lungs, until even the powers given by nature 
 for performing the aaion of infpiration, becoming 
 unequal to their talk, ceafe. Then, the left fide of 
 the heart neither receives blood nor is irritated, 
 and therefore remains at reft ; while yet, for a little 
 time, the right ventricle, and laftly the auricle of 
 the fame fide, receive the blood brought by the 
 veins from the cold and contracted limbs, and being 
 irritated by it, continue to beat weakly. But at laft, 
 when the reft of the body has become perfectly cold. 
 
470 DEATH. Chap. XXX, 
 
 and the fat itfelf congealed, even this motion ceafes, 
 and the death becomes complete. 
 
 DccccLxxiii. I fliall call that death, when the 
 heart has become totally deprived of irritability. 
 For the mere quiefcence of the heart is not without 
 hope of refufeitation : neither does the putrefaction, 
 or infenfibility, or coldnefs of any part of the ani- 
 mal body, demonftrate the death of the whole ani- 
 mal : but all thefe things, when joined together, 
 and perpetually increaiing, with the rigidity pro- 
 duced by the congelation of the fat, in confequence 
 of reft and cold, afford the ftgns of death in any 
 doubtful cafe. 
 
 DC cc CL XXIV. The body after death is deftroyed 
 by putrefaction. Thus the fat, and the w^ater, and 
 the gluten, being refolved, are diflipated ; the earth, 
 deprived of its bonds of union, infcnftbly moulders 
 avray, and mixes itfelf wdth the duft. The foul 
 goes to that place which God hath appointed it : 
 its indeftructibiiity by death is proved by a very 
 common phenomenon ; for many people, when 
 their bodily powers are w'^afted and fpent, give evi- 
 dent proofs of a highly ferene, vigorous, and even 
 cheerful mind. 
 
 INDEX. 
 
I N D 
 
 E X. 
 
 CHAP. I. 
 
 FIBRE. CELLULAR SUBSTANCE. 
 
 I. T^LEMENTARY parts. 
 
 Jlj 2. General ftru(Sture of the 
 the folids. 
 
 3. Fibres. 
 
 Their mofl: fixed particles earthy. 
 
 4. The earthy particles cohere by 
 
 means of interpofed gluten. 
 
 5. Gluten is formed of oil and wa- 
 
 ter. 
 
 6. Simple fibres. 
 
 7. Vifible linear fibres. 
 
 8. Laminx. 
 
 Cellular Substance. 
 
 9. General flrutSure of cellular fub- 
 
 llance. 
 
 10. Membranes, vefibls, t^d tunics, 
 
 are formed of cellular fub- 
 ftance. 
 
 II. The veflels of the tunics are an 
 
 acceffion to the cellular fub- 
 Itance. 
 
 12. Cellular fubftance is found eve- 
 
 ry where. 
 
 13. Inorganic gluten. 
 
 14. Fibres and cellular fubftance 
 
 are formed of gluten. 
 
 15. In what manner the folids are 
 
 formed of gluten. 
 
 16. Varieties of cellular texture. 
 Where llrort and tender. 
 
 17. Where lax. 
 
 18. The fat is effufed into the lat- 
 
 ter. 
 
 19. The fanguiferous veffels of the 
 
 cellular fubftance. 
 
 The fat is depofited by the ex- 
 tremities of the arteries. 
 
 It alfo exudes through their 
 fides. 
 
 20. It is abforbed by the veins. 
 
 Do nerves terminate in the cel- 
 lular fubftance 
 
 21. All the cells communicate with 
 
 each other. 
 
 22. The great importance of cellu- 
 
 lar fubftance ? 
 
 23. The contraiftility of cellular 
 
 fubftance is different from 
 irritability. 
 
 24. The various ufes of fat. 
 
 25. The caufes and effefts of the ac- 
 
 cumulation of fat in the cel- 
 lular fubftaBce, and of its re- 
 forption. 
 
 CHAP. 
 
472 
 
 INDEX. 
 
 CHAP. II. 
 VESSELS. 
 
 a6. The figure of the arteries. 
 
 27. They have no peculiar and con- 
 ftant external membrane. 
 Their firft true membrane is 
 every where cellular. 
 a8. Externally, this is more lax, and 
 perforated with blood-velTels 
 and nerves. 
 
 29. Internally it is more denfe, and 
 
 forms the proper coat of the 
 artery. 
 
 30. The mufcular cojt is formed of 
 
 circular fibres. 
 
 There are no longitudinal ones. 
 Under the mufcular coat there 
 is llrort cellular fubllance. 
 
 31. The innermoft membrane of 
 
 the artery. 
 
 Its nature in the arteries of the 
 vifcera. 
 
 32. The arteries of the arteries. 
 
 The nerves of the arteries. 
 
 Do they derive from tliem a 
 contradllle power, different 
 from fimple elaflicity ? 
 
 33. The fection of the arteries is 
 
 round. 
 
 The pulfation of the arteries. 
 
 34. T,rc llrength of the arteries. 
 The trunks are weaker, and the 
 
 branches ftronger. 
 
 33. Arteries go to all parts. 
 
 The proportion of arteries to 
 the parts which they fup- 
 ply. 
 
 36. The proportion of the folid 
 
 part of the artery to its cali- 
 ber. 
 
 37. The divifion of the arteries in- 
 
 to branches. 
 
 The proportion of the caliber 
 of the branches to that of 
 the trunk. 
 
 The angles at wliich the branch- 
 es go off. 
 
 The flexions of the arteries. 
 
 38. The anaftomofes and reticula^ 
 
 dons of the veflels. 
 
 39. The tranfition of the ultimate 
 
 arteries into veins. 
 
 40. The various difpofition of the 
 
 arteries in the vifcera. 
 
 41. The arteries terminate in vef- 
 
 fels of a fmalier denomina- 
 tion. 
 
 42. Or in excretory dudls. 
 
 43. Or in exhaling canals. 
 
 44. Are veflels every where pro- 
 
 duced from the red ones ? 
 
 45. Are fmalier orders of veffels 
 
 produced by a multiplied di- 
 vifion ? 
 
 46. The veins are fimilar to the ar- 
 
 teries in many rcfpecis, but 
 in others are different. 
 
 47. The ftruchire of the veins. 
 
 48. The fize and divifion of the 
 
 veins. 
 
 They affedt the furface of the 
 body. 
 
 49. The valves of the veins. 
 
 50. The veins originate from arte^ 
 
 ries ; from veins of inferior 
 orders ; from the abforbing 
 veins of the w’hole circumfe- 
 rence, and of every cavity of 
 the body. 
 
 51. Other abforbing veffels from 
 
 the cellular texture are little 
 diflerent from thefe. 
 
 5 2. There are veins as well as arte- 
 ries of fmalier kinds. 
 
 53. The IjTnphatic veffels. 
 
 J4. The conglobate glands. 
 
 55. Where the lymphatic veffels are 
 found. 
 
 They unite in the thoracic du< 2 . 
 36. The office of the conglobate 
 glands. 
 
 57. The valves of the lymphatics. 
 
 CILM-. 
 
INDEX. 
 
 All 
 
 CHAP. III. 
 
 CIRCULATION, or the MOTION of the BLOOD 
 THROUGH THE ARTERIES ANB VEINS. 
 
 j8. In what manner the blood fills 
 the arteries and veins. 
 
 59. The blood moves rapidly 
 
 through all the veflels. 
 
 60 — 76. The diretStion of the mo- 
 tion of the blood. 
 
 60. Proofs that all the arteries and 
 
 veins communicate. 
 
 61. The bloopd flows through the 
 
 arteries from the heart to the 
 extremities. 
 
 ,6a. The motion of the venous blood 
 was doubted. 
 
 Who have difcovered their er- 
 ror. 
 
 63. Harvey firfl fliowed, that the 
 
 venous blood every where 
 returned from the extremi- 
 ties to the heart. 
 
 This is proved by the valves 
 which prevent the reflux of 
 the blood into the branches. 
 
 64. The valves alfo fuftain the 
 
 weight of the blood. 
 
 They alfo caufe the prefTure of 
 the mufcles upon the veins 
 to diredt the blood towards 
 the heart. 
 
 65 — 70. Proofs of the courfe of 
 the venous blood. 
 
 63. The valves of the right fide of 
 the heart. 
 
 66. Ligatures and compreflion in a 
 
 living perfon. 
 
 67. More accurate experiments on 
 
 living animals. 
 
 68. InjetSlions into the veins. 
 
 69. Transfufion of blood. 
 
 70. InjeeSHons prove, that the blood 
 
 palTes from the arteries into 
 the veins. 
 
 71. The fame paflage is lliown by 
 
 the microfeope. 
 
 There is no parenchyma be- 
 tween the arteries and veins. 
 
 72. The nature of that circulation 
 
 of the blood, which is prov- 
 ed by what is already faid. 
 
 73. There are inftances, however, 
 
 where the palTage is for a 
 little in a contrary diretSllon. 
 
 74. In the lymphatic velTels the 
 
 courfe of the liquor is from 
 their roots to the thoracic 
 du(fi. 
 
 73. The reforbed vapours are car- 
 ried tow'ards the heart. 
 
 76. A palTage muflbe found for the 
 blood from the right ventri- 
 cle of the heart into the left. 
 
 C H:,A P. IV, 
 
 HEART. 
 
 77, 78. The bags of the pleura. 
 
 77. The mediaftinum. 
 
 The pleura. 
 
 78. The fituation of the pericardi- 
 
 um. 
 
 The mediaftinum pofterius. 
 
 The ligaments of the lungs. 
 
 79. 80. The pericardium. 
 
 81. The arteries of the pericardi- 
 um. 
 
 Its veins. 
 
 Herves. 
 
 82. The ftrutfture of the pericardi- 
 
 um. 
 
 The water contained in it. 
 
 83. The ufe of the pericardium. 
 
 84. What animals have a heart. 
 
 83. In what manner the vena cava 
 
 terminates in the heart. 
 
 86. The right finus venofus. 
 
 The right auricle. 
 
 87. The foflaovalis. 
 
 The anulus ovalis. 
 
 88. The valve of Euftachius. 
 
 89. By 
 
INDEX. 
 
 47^ 
 
 89. By what powers the blood is 
 
 forced into the right porch 
 of the heart. 
 
 90. The contratftion of the right 
 
 auricle, and its effedls. 
 
 91. The figure and fituation of the 
 
 heart- 
 
 9a. The anterior or right ventricle 
 of the heart. 
 
 93. The valvulae triglochines. 
 
 94. Their papillary mufcles. 
 
 95. The ufe of the triglochines. 
 
 96. The heart is IHmulated to con- 
 
 fra<Tion,by the blood thrown 
 into it. 
 
 97. The mufcular fibres of the heart, 
 
 according to the author. 
 
 98. The fame deferibed by others. 
 
 99. The nerves of the heart. 
 
 XQO. Thefe nerves contribute to the 
 motion of the heart. 
 lOl. There is, however, fome other 
 caufe. 
 
 loa. The irritability inherent in the 
 heart. 
 
 103. How the contraction of the 
 ventricle is performed. 
 
 X04.. Bythe contradtion ofthe heart, 
 the blood does not return 
 into the auricle and veins. 
 
 105. By the contradlion of the right 
 
 ventricle the blood is driven 
 into the pulmonary artery. 
 
 106. The origin and beginning of 
 
 the pulmonary artery. 
 
 Its femilunar valves. 
 
 107. The pafl'age of the blood from 
 
 the right ventricle into the 
 pv.hnohary artery. 
 
 3c8. The palTage of the blood 
 through the lungs. 
 
 109. The blood cannot retvrm from 
 the pulmonary artery into 
 the heart. 
 
 no. The pulmonary veins. 
 
 The courfeof the bloodthrough 
 thefe. 
 
 III. The left fmus venofus. 
 
 The left auricle. 
 
 1 1 3. The contradlicn of the left 
 porch forces the blood into 
 the left ventricle. 
 
 The valvulx mitralcs. 
 
 113. The courfc of the blood from 
 the right ventricle into the 
 left, or the fmaller circula- 
 tion. 
 
 114- The left ventricle. 
 
 1 15. The blood is forced info the 
 
 aorta by the contraiTion of 
 the left ventricle. 
 
 116. The valves of the aorta. 
 
 1 1 7. The diaftole of the heart, 
 
 118. In what manner the motions 
 
 of the auricles and ventricles 
 alternately follow one anoth- 
 er. 
 
 119. “Why are thefe motions contin- 
 
 ued fo long, and fin conllantly. 
 
 120. This quefbon is explained, by 
 
 the Ibmulus of the blood 
 driven into irritable ca\T- 
 ties. 
 
 121. Nothing more is necellary. 
 The realbn cannot be found 
 
 cither in the comprcllion of 
 the nerves, or in the corona- 
 ry arteries. 
 
 122. The powers of the heart are 
 
 not aflilled by the ofcillation 
 of the ultimate vcflcls. 
 
 Or by the power of external 
 heat. 
 
 Or by the contradtilc force of 
 the arteries. 
 
 123. The velocity with which the 
 
 blood ilTues from the heart. 
 The weight of the blood in- 
 cumbent on the heart. 
 
 The force of tlie heart. 
 
 124. Many things on tliis fubjedt 
 
 are uncertain. 
 
 The powers of the heart are, 
 however, very flrong. 
 
 125. This is proved by the refinan- 
 
 ces which the heart over- 
 comes. 
 
 126. The entrance of the blood in- 
 
 to the coronary arteries. 
 Tbe two coronary arteries. 
 
 127. They terminate in veins. 
 
 I nc great coronary vein. 
 
 128. The middle veiu. 
 
 The third vein. 
 
 129. The anteri.>r veins. 
 
 130. The middle lized veins. 
 
 131. The minute veins. 
 
 132. At what time the coronary ar- 
 
 teries receive the blood. 
 
 133. The blood returns from the 
 
 coronary arteries into the 
 cavities of the heart through 
 the veins. 
 
 134. The hmipliatic veflcls of the 
 
 heart. 
 
 CH-\P. 
 
INDEX. 
 
 47S 
 
 CHAP. V. 
 
 NATURE OF THE BLOOD, and HUMOURS of ths 
 HUMAN BODY. 
 
 135. The blood in general. 
 
 136. The warmth of the blood. 
 
 The halitus ifTuing from blood 
 
 when drawn. 
 
 137. The blood coagulates when 
 
 the halitus is difcharged. 
 The cruor is the principal part 
 of the coagulum. 
 
 138. The ferum of the blood. 
 
 139. How the blood is changed by 
 
 putrefaction. 
 
 140. Befides thefe, there are in the 
 
 blood, fea-falt, earth, calx of 
 iron, and air in an inelaflic 
 Hate. 
 
 141. What changes are produced 
 
 in the blood by the admix- 
 ture of halts. • 
 
 14a. The chemical analyfis of the 
 blood. 
 
 143. Refult of the information de- 
 
 rived from it. 
 
 144. Red globules are diftinguiflied 
 
 in the blood by the help of 
 the microfcope. 
 
 Their figure. 
 
 145. The colour of the globules, 
 
 their number, magnitude, 
 and variable figure. 
 
 Do they break down into oth- 
 « er fmaller globules ? 
 
 146. Fibres are produced from 
 
 waflied blood, which did not 
 exift in the living animaL 
 
 147. The cruor is compofed of glo- 
 
 bules, which are inflamma- 
 ble. 
 
 148. The chemical analyfis of the 
 
 ferum. 
 
 The aqueous humours, the fal- 
 iva and mucus, afford near- 
 ly the fame prodiuEts. 
 
 149. The quantity of blood in the 
 
 whole body. 
 
 ijo. The proportions of the ele- 
 ments of the blood are not 
 always the fame. 
 
 The caufes which vary tlieiy 
 proportion, 
 
 151. On the different proportion of 
 the elements, and the coa- 
 fidcration of the ftrudlure of 
 the folids, depend the differ- 
 ences of temperaments. 
 
 Tja. The ufe of the red cruor. 
 
 1J3. The coagulable ferum, thinner 
 liquids, faline particles, air 
 and fire ; the effeCls of each. 
 
 154. The thick blood and more 
 
 thin liquids are equally ne- 
 ceffary for health. 
 
 155. The difference between the ar- 
 
 terial and venous blood. 
 
 156. All the reft of the humours are 
 
 produced from the . bloo4 
 alone. 
 
 CHAP. VI. 
 
 COMMON FUNCTIONS of the ARTERIES. 
 
 157. The blood propelled from the 
 
 left ventricle into the aorta. 
 
 158. The arteries are conftantly 
 
 full. 
 
 The pulfation of the arteries, 
 and its caufe. 
 
 3:59. The contraction of the arte- 
 ries. 
 
 160. How is it proved that the ar- 
 
 tery is contracted, and tha^ 
 the blood is driven forwards 
 by that means ? 
 
 161. No fucceffion can be perceiv- 
 
 ed in the pulfation of differ- 
 ent arteries, although we arc 
 
 certaia 
 
INDEX, 
 
 475 
 
 l6j. 
 
 163. 
 
 164. 
 163. 
 
 z 66 . 
 
 167. 
 
 j68. 
 
 J69. 
 
 X70. 
 
 >71- 
 
 188. 
 
 189. 
 
 certain that it ac);ully takes 
 place. 
 
 The velocity of the blood 
 coming from the heart muft 
 continually be diminillied as 
 it proceeds farther through 
 the arteries. 
 
 What circumltance's feem to 
 diminilli its velocity, with- 
 out adlually diminilliing it. 
 
 The blood does not feem to 
 lofe fo much of its velocity 
 as, according to calculation, 
 it ought to do. 
 
 The caufes of this. 
 
 Why the pulfe vaniflies in the 
 ultimate arteries. 
 
 The blood prefTes againfl; the 
 fides of the veins. 
 
 W'’hy the veins do not beat like 
 the arteries. 
 
 The pall'e is the meafure of the 
 powers of the heart. 
 
 What is meant by a flow, full, 
 hard, or quicjc pulfe. 
 
 Where it is bcft felt. 
 
 The pulfe is flower in propor- 
 tion to the bulk of the ani- 
 mal. 
 
 The diflTerence of the pulfe in 
 men, according to the time 
 of the day. 
 
 A frequent pulfe is dilFerent 
 from a quick one. 
 
 DiflTerent caufes of a frequent 
 pulfe. 
 
 By what powers the venous 
 blood is moved. 
 
 It moves more quickly in the 
 trunks than in the branches. 
 
 By what means the blood is 
 prevented from flagnating 
 and coagulating in the veins. 
 
 171. The venous blood is propelled 
 by the aAion of the muf- 
 cles. 
 
 173. Other powers comprefling the 
 
 veins. 
 
 174. The power of derivation. 
 What are the efFedb of anaf- 
 
 tomofes. 
 
 175. The velocity of the venous 
 
 blood. 
 
 What caufes render its motion 
 s more difEcult. 
 
 176. The time in which the circu- 
 
 lation is performed. 
 
 177. The efFedts of the motion of 
 
 the heart and arteries upon 
 the blood,and by what means 
 they are eftimated. 
 
 178. 179. The means bv which we 
 
 underftand the manner in 
 which thefe clTedls are pro- 
 duced. 
 
 180. The fridtion which takes place 
 in the arteries. 
 
 Its efledts, how calculated. 
 Whence the rednefs of the 
 blood. 
 
 18 r. Does the heat of the blood 
 arife from its motion f 
 1S2. The progreflive motion of the 
 blood hinders putrefadlion. 
 
 183. It is various in different parti- 
 
 cles of different natures. 
 
 184. The effedts of the fyftole of the 
 
 arteries. 
 
 185. The fmallcft mouths of the ar- 
 
 • tcries arethemouldsinwhich 
 
 the particles of blood are 
 formed. • 
 
 186. WTat is the ufe of the reticu- 
 
 lations of the arteries. 
 
 187. The cffedls of a retarded mo- 
 
 tion of the bhiod. 
 
 CHAP. VII. 
 
 SECRETION. 
 
 Four clalTes of fecreted hu- 
 mours. 
 
 The fird confifls of the coagu- 
 iable ones, which for the 
 moft part exhale. 
 
 The fecond are not coagulable, 
 and partly exhale, and part- 
 ly do not. 
 
 The third are mucous. 
 
 The fourth inflammable. 
 
 The other humours are com- 
 pofed of thefe. 
 
 A defeription of the fecretorv 
 organs is required, in order 
 to Jifeover the reafen of the 
 
 diverhty 
 
 190. 
 
 191. 
 19a. 
 
 193- 
 
INDEX. 
 
 diverlity of the fecreted flu- 
 ids in the different organs. 
 
 194. The fecretion of coagulable 
 
 liquors is performed with- 
 out glands. 
 
 195. What glands fecrete the albu- 
 
 minous fluid of the joints. 
 
 196. The feat of thefe glands. 
 
 197. The exhaling liquors which are 
 
 not coagulable are fecreted 
 without glands. 
 
 198. Such liquors as are neither co- 
 
 agulable nor exhaling, are 
 fecreted by conglomerate 
 glands. 
 
 Thefe are compofed of acini. 
 
 199. aoo, 201. The flrudture of thefe 
 
 acini. 
 
 202. Some liquors of the nature of 
 198 are even fecreted with- 
 out thefe kernelly glands. 
 
 303. The mucus is every where fe- 
 
 creted by glands. 
 
 The ftrudfure of a true gland, 
 
 304. How the fecretion is perform- 
 
 ed in thefe glands. 
 
 30 J. The excretory orifices. 
 
 The cryptJE. 
 
 306. The conglutinated glands. 
 
 207. The excretory dudfs. 
 
 308. The compound glands. 
 
 The agminated or congregate 
 glands. 
 
 309. The various fecretlons of In- 
 
 flammable liquors. 
 
 There are many febaceous 
 glands without a dudh 
 
 310. Other febaceous ones have a 
 
 dudh 
 
 31 1. Compound febaceous ones. 
 
 212. The milk is fecreted in con- 
 
 glomerate glands. 
 
 313. The organs being deferibed, 
 
 we return to the queftion 
 
 193- 
 
 314. The blood going to the fecre- 
 
 tories is already of a partic- 
 ular nature. 
 
 213. The retardation of the blood 
 
 in the- minute veffels fepa- 
 rates the more denfe hu- 
 mours from thofe that are 
 lighter and more fluggidi. 
 216. The mouths of the fecretory 
 veffels are of very different 
 diameters. 
 
 317. This inequality may alter the 
 
 All 
 
 fecretlons in many different 
 ways. 
 
 318. Mofl fecretlons are performed 
 
 by veffels arifing from fan- 
 guiferous arteries. 
 
 Others, however, by veffels 
 which arife from an inferior 
 order of arteries. 
 
 319. The angle at which the fecre- 
 
 tory branch goes off is per- 
 haps of fome confequence. 
 What things render this pro- 
 bable. 
 
 What things render it doubt- 
 ful. 
 
 220. The flexions of veffels contri- 
 bute to fecretion. 
 
 321 . The denfity of the arteries 
 may do the fame. 
 
 Their irritability has nearly 
 fimilar effedts. 
 
 222. Various circumflances which 
 augment or diminifli the ve- 
 locity of the blood have great 
 effedi on the fecretlons. 
 
 323. The fecreted humours are va- 
 ried by a variation of thefe 
 conditions. 
 
 224. The largefl and denfeft parti- 
 
 cles of the blood pafs into 
 the veins. 
 
 225. What becomes of the large, 
 
 flow, and fluggifh particles. 
 And of the coagulable ones. 
 
 226. In what veffels the thin and 
 
 aqueous liquors are fecreted. 
 In what veffels the light aque- 
 ous but vifeid and flow hu- 
 mours. 
 
 327. Various hypothefes are form- 
 ed concerning fecretion. 
 
 228. It remains to be difeovered 
 how the pure fecretlons arc 
 made. 
 
 AJl recent fecretlons have au 
 admixture of water. 
 
 329. All of them become vifeid by 
 flagnating in follicles. 
 
 230. The fluids may be changed in 
 their receptacle by the ad- 
 mixture of a new liquid. 
 
 331. The reforbed humours are al- 
 fo of life. 
 
 232. The ufe of receptacles. 
 
 233. The powers by which the re- 
 
 tained humours are at laft 
 ejedted. 
 
 CHAP, 
 
INDEX. 
 
 CHAP. VIII. 
 RESPIRATION. 
 
 234. Tlie figure of the lungs. 
 
 335. The external membrane of the 
 lungs. 
 
 236. The firucture of the lungs. 
 
 237. The flrudlure of the afperia 
 
 arteria. 
 
 238. Its mufcular fibres. 
 
 239. Its mucous glands. 
 
 The conglobate glands conti- 
 guous to it. 
 
 240. The veffels and nerves of the 
 
 afperia arteria. 
 
 341. Its divifion into bronchia. 
 
 342. Their ultimate branches ter- 
 
 minate in cellular texture. 
 
 343. The bronchial arteries & veins. 
 
 244. The pulmonary artery. 
 
 The pulmonary veins. 
 
 245. The lymphatic vefl'cls of the 
 
 lungs. 
 
 The nerves of the lungs. 
 
 346. A very large portion of the 
 blood enters the lungs. 
 
 The utility of this vifeus de- 
 pends on the air. 
 
 247. The nature of atmofpherical 
 
 air. 
 
 248. In what manner it is excluded 
 
 from the body. 
 
 We muft invelligate why it 
 enters the lungs. 
 
 349. The reafon why it enters them. 
 
 250. The general fabric of the tho- 
 
 rax. 
 
 251. The vertebrx of the back. 
 2 J2. The articulation of the ribs 
 
 with the vertebrae. 
 
 The ligaments of this articula- 
 tion. 
 
 253. How the ribs are joined with 
 the fternum. 
 
 334. The length of the ribs. 
 
 235. The direction of the ribs. 
 Their Ilrength various. 
 
 236. The fternum. 
 
 237. The thorax muft be raifed in 
 
 order to dilate the feat of 
 the lungs. 
 
 This is performed by the ex- 
 ternal intercoftal mufcles. 
 
 238. The internal intercoftals. 
 There are doubts concerning 
 
 the aiStion of thefe, but it is 
 certain that they elevate. 
 
 239. In what manner the thorax is 
 
 enlarged by' thefe. 
 
 But tins dilation is not, how- 
 ever, fufticient. 
 
 260, 261. The diaphragm. 
 
 262. The two holes of the dia- 
 
 phragm. 
 
 263. The contradlion of the fep- 
 
 tum augments the capacity 
 of the thorax. 
 
 Alone, it almoft performs reC- 
 piration. 
 
 264. By what powers it is aflifted 
 
 in deep infpirations. 
 
 263. Infpiration, how performed. 
 
 Its efl'ccls on the air and blood- 
 veflels. 
 
 266. Is air contained between the 
 
 lungs and thorax ? 
 
 267. The air is vitiated by refpifa- 
 
 tion. 
 
 268. The inconvenienciesof too long 
 
 an infpiration. 
 
 269. The powers of expiration. 
 
 270. The abdominal mufcles con- 
 
 fpire to produce this cffeift. 
 The fternocoftals and others 
 alfo alllft. 
 
 271. What powers afllft the muf- 
 
 cles in ftronger refpirations. 
 
 272. The effeifts of expiration. 
 
 273. From thence there arifes a 
 
 new nccellity for infpiratu.n. 
 
 274. Other caufes for alternate ref- 
 
 plritioD are fcarcely afeer- 
 tained. 
 
 273. Refpiration is neceffary for 
 adults. 
 
 276. The utility' of refpiration is 
 
 different from that necelEty. 
 
 277. How that is afccrt.iined. 
 
 278. Is heat generated in the lungs ? 
 
 279. Is the blood coadenfed in the 
 
 lungs ? 
 
 280. Is the air itfclf received into 
 
 the blood in the lungs ? 
 
 What 
 
INDEX. 
 
 479 
 
 What clrcnmftances render 
 this probable. 
 
 s8x. What I'eem to prove the con- 
 trary. 
 
 %%%. Is the blood cooled in the lungs? 
 
 485. Does the red colour of the 
 blood proceed from the air? 
 
 285. Is the ufe of the blood to ab- 
 forb nitre from the air ? 
 
 485. What animals live long v/ith- 
 out air. 
 
 Why every animal dies in air 
 that is not renewed. 
 
 287. What is the conhecflon be- 
 
 tween the puife and refpira- 
 tion. 
 
 288. Cough. 
 
 289. Laughter. 
 
 Weeping. 
 
 Hickup. 
 
 Sneezing. 
 
 290. The acceflbry ufes of refpirai 
 
 tion. 
 
 CHAP. IX. 
 
 VOICE AND SPEECH; 
 
 4 §S. The larynx is compofed of car- 
 tilages. 
 
 Its veffels and nerves. 
 
 292. The fcrutiform cartilage. 
 
 293. The annular cartilage. 
 
 294. The arytenoid cartilages. 
 
 295. The glottis. 
 
 296. The epiglottiE. 
 
 297. The ventricles of the larynx. 
 
 298. The mucous glands of the la- 
 
 rynx. 
 
 299. The thyroid gland. 
 
 36b. The connedtion of the larynx 
 with the os hyoides. 
 
 The elevation of the larynx, 
 and contradlion of the glot- 
 tis. 
 
 joi. The depreffion of the larynf:^ 
 and dilatation of the glottis. 
 
 302. The cavity of the mouth. 
 
 The noftrils. 
 
 303. The tongue. 
 
 304. The voice. 
 
 Whifpering. 
 
 305. The ftrength of the voloe. . 
 What circumflances produce 
 
 an acute tone. 
 
 306. A grave tone is produced by 
 
 the oppofite caufes. 
 
 307. The caufes of diverfity of tone. 
 
 308. Singing. 
 
 309. Speech. 
 
 310. The pronunciation of letters. 
 
 CHAP. X. 
 
 BRAIN AND NERVES. 
 
 311. The nature of the arrange- 
 
 ment. 
 
 312 — 319. The arteries which be- 
 long to the brain. 
 
 312. The arch of the aorta, and the 
 
 branches produced from it, 
 
 313. The diviiion of the carotid. 
 The external carotid. From 
 
 it proceeds. 
 
 The fuperior thyroid artery. 
 The lingual. 
 
 The labial. 
 
 The afeeading pharyngea. 
 
 314. The occipital artery. 
 
 The auricular. 
 
 315. The temporal artery. 
 
 The internal maxillary. 
 
 The principal branch to the 
 dura mater. 
 
 Other branches of the internal 
 maxillary. 
 
 316. The internal carotid. 
 
 Its flexures. 
 
 Its paffage through the fora- 
 men of the os petrofum. 
 
 The 
 
4S0 
 
 INDEX, 
 
 Tlie branches produced from 
 it in the receptacle. 
 
 317. The branches of the internal 
 
 carotid on the bridge and 
 crura of the brain. 
 
 Tire branch to the plexus cho- 
 roides, and accompanying 
 the optic nerve. 
 
 The anterior and poflerior 
 branch. 
 
 The (IrniElure of the branches 
 of the carotid artery which 
 be within the fkull. 
 
 318. The vertebral artery. 
 
 The bafilaris. 
 
 The profunda cerebri. 
 
 319. The conclulions which may be 
 
 deduced from the hiftory of 
 the arteries of the brain. 
 
 320 — 324. The coverings of the 
 brain. 
 
 320. The ofleous fhell of the ence- 
 
 phalon. 
 
 The dura mater in general. 
 
 321. The external and internal la- 
 
 mina of the dura mater. 
 
 The falx and tentoria proceed 
 from thefe ; their ufe. 
 
 322. The glands. 
 
 323. The arachnoid membrane. 
 
 324. The pia mater. 
 
 325 — 339. The veins of the ence- 
 phalon. 
 
 325. The fourth finus. 
 
 326. The fuperior finus of the falx. 
 The tranfverfe finufes. 
 
 327. The inferior finus of the falx. 
 
 328. The inferior, anterior, and pof- 
 
 terior veins of the brain. 
 
 329. The veins of the cerebellum. 
 The fuperior veins terminate 
 
 in the fourth finus ; the in- 
 ferior ones in the fuperior 
 petrous andtranfverfe fiauf- 
 es. 
 
 530. Circular finus. 
 
 The tranfverfe finus joining 
 the cavernous ones. 
 
 331. ‘The fuperior finus petrofus. 
 
 The inferior finus petrofus. 
 The pofierior occipital finus. 
 
 332. The anterior occipital finus. 
 The cavernous finus. 
 
 The conjundlion of the finufes 
 and external veins of the 
 cranium with each other, 
 and its eiFetSfs. 
 
 333. The ufe of the finufes. 
 
 334. The connedlion between the 
 
 arteries and the finufes. 
 
 335. The blood chiefly flows into 
 
 the jugular veins. 
 
 Their cerebral and facial 
 branches. 
 
 336. The external jugular vein. 
 
 The internal vertebral vein. 
 
 337. The finufes of the medulla fpi- 
 
 nalis. 
 
 338. The iifes of the venous anafto- 
 
 mofes. 
 
 339. The l)'mphatic vefTels of the 
 
 brain. 
 
 The reforption of what is ex- 
 haled in the brain. 
 
 340. A great number of parts are 
 
 comprehended under the 
 name of encephalon. 
 
 The cerebrum, cerebellum, 
 bridge, and medulla oblon- 
 gata, what they are. 
 
 341. The figure of the brain. 
 
 Its circumvolutions. 
 
 — cortex. 
 
 — ^medulla. 
 
 — lobes. 
 
 342. The minute ftruclure of the 
 
 brain. 
 
 343 — 53. The interior anatomy of 
 the brain. 
 
 343. The oval fecHon of the brain. 
 The corpus callofum. 
 
 344. The anterior or three-horned 
 
 ventricle. 
 
 345. The corpora ftrlata. 
 
 The thalami of the optic 
 nerves. 
 
 The double femicircular cea- 
 tre. ^ 
 
 The anterior comminure. 
 
 The mamillary eminences. 
 
 346. The pellucid feptum. 
 
 The fornix. 
 
 The fimbria:. 
 
 The hippocam.pi. 
 
 The pfalterium. 
 
 347. The choroid plexus. 
 
 348. The, third ventricle. 
 
 349. The pituitary gland. 
 
 3jO. The poflerior double commif- 
 fure. 
 
 351. The ftparat'on of the third 
 ventricle from the calamus 
 feriptorius. 
 
 The anterior commiiTure. 
 
 2Si. The 
 
INDEX. 481 
 
 5J2. The nates. 
 
 The teftes. 
 
 The pineal gland. 
 
 S53. The crura of the brain. 
 
 354. Tlie cerebellum. 
 
 3J5. The bridge. 
 
 The medulla oblongata. 
 
 The olive fhaped and pyrami- 
 dal bodies. 
 
 The fourth ventricle. 
 
 The great valve. 
 
 The aquedudt. 
 
 The calamus. 
 
 356. The common properties of the 
 
 nerves of the brain. 
 
 357. The origins of each of the 
 
 nerves of the brain. 
 
 358. The medulla fpinalis. 
 
 Its pia mater, arteries, and 
 veins. 
 
 359. The arachnoid membrane of 
 
 the medulla fpinalis. 
 
 360. The hard membrane of the 
 
 medulla fpinalis. 
 
 The denticulated ligament. 
 
 361. The common properties of the 
 
 fpinal nerves. 
 
 362. The anterior and poflerior 
 
 trunks of the fpinal nerves. 
 The intercoftal nerve. 
 
 ^'he eighth pair. 
 
 The phrenic nerve. 
 
 The acceflbry nerve. 
 
 364. The extremity of the nerves. 
 The ftraightnefs of the fibres 
 
 of the nerves. 
 
 The nerves are fcarcely elafr 
 tic, and not at all irritable. 
 The number of nerves is iri 
 proportion to the parts to 
 which they are fent. 
 
 The anaftomofes of the nerves. 
 Ganglions. 
 
 365. How it is proved that fenfa- 
 
 tlon is owing to the nerves. 
 It is the medullary part of the 
 nerve which feels. 
 
 366. The foul perceives in the brain; 
 
 not immediately by the fen- 
 foria and branches of the 
 nerves. 
 
 367. How the mufcles are affedted 
 
 by compreffing or irritating 
 the nerves. 
 
 368. What derangements of the an- 
 
 imal motions happen on in- 
 
 Hh 
 
 juring the brain or fpinal 
 marrow. 
 
 369. From what is laid down in. 
 
 367 and 368, the nerves are 
 proved hkewife to be the 
 organs of motion. 
 
 370. Is there in the brain any prin- 
 
 cipal feat in which is the 
 origin of all motions, and the 
 end of all fenfatioh, where 
 the foul reftdes ? 
 
 It is not in the corpus callo- 
 fum. 
 
 371. Neither is it the proper prov- 
 
 ince of the cerebellum to 
 carry on the vital motions. 
 Nor are the motions called 
 animal and vital to be refer- 
 red to different fources. 
 
 372. The feat of the foul is where 
 
 the nerves firft begin. 
 
 373. The nerves are the organs of 
 
 fenfation and motion, not 
 by their membranes, but by 
 their medullary part. 
 
 374. What the medulla is. 
 
 21 S- Whether the medullary fibres 
 are folid. 
 
 376. The nerves are entirely devoid 
 
 of elaflicity. ' 
 
 377. Motion can only be propagat- 
 
 ed downwards. 
 
 From what is faid, it follows, 
 that the medullary fibre 
 feems to be hollow. 
 
 378. Refutation of the objedlions 
 
 againft this. 
 
 379. The nature of the nervous flu- 
 
 id. 
 
 Hov/ proved not to be elec- 
 trical. 
 
 380. The nature of that fluid is nei- 
 
 ther aqueous nor albuminous. 
 3S1. Of what kind the nervous flu- 
 id ought to be. 
 
 382. How it is rendered more pro- 
 
 bable that the nervous fluid 
 pafl'es through hollow tubes 
 than through the fpongy and 
 folid fubftance of the nervu. 
 
 383. The motion of the nervous 
 
 juice is twofold. 
 
 384. The fame nerves moft evident- 
 
 ly ferve both for feufe and 
 motion. 
 
 38J. What 
 
 r 
 
4S2 
 
 INDEX. 
 
 385. what becomes of the nervous 
 
 fluid. 
 
 Whether it nouriflies. 
 
 386. Qucftions concerning the ufes 
 
 of the parts of the brain. 
 
 387. The offices of the ventricles. 
 
 388. What is known concerning th< 
 
 ufe of the tubercles. 
 
 389. The offices of the ftriae and of 
 
 the internal du<£b. 
 
 390. The reafon for the arrange- 
 
 ment of wliat follows. 
 
 CHAP. XI. 
 
 MUSCULAR MOTION. 
 
 391. The dead power of the fibre. 
 
 392. 'I'he reafon why it is called 
 
 dead. 
 
 Its effehbs. 
 
 393. The characters of the dead 
 
 power. 
 
 The charadlers which arc pe- 
 culiar to the red mufcular 
 fibre. 
 
 It is necefifary to examine its 
 ftrudlure. 
 
 394. What nuifculaf fibres and muf- 
 
 cles are. 
 
 393. The fibres treated more fully. 
 
 396. The belly, tendon, aponcuro- 
 
 lis, and capfule of a mufcle, 
 what. 
 
 Whether the fibres of the ten- 
 dons are of a dilFerent genus 
 from the mufcular fibres. 
 Mufcles which commonlyhave 
 no tendons. 
 
 The parts in which the muf- 
 cles chiefly terminate in long 
 tendons, and thofe to w'hich 
 they affix themfelves. 
 
 397. The modes in which the ten- 
 
 dons unite themfelves with 
 the flelh. 
 
 A pmnated mufcle, what. 
 
 398. The arteries, veins, h-mphat- 
 
 ics, and nerves, of the muf- 
 cles. 
 
 399. The fcrudlure of the ultimate 
 
 fibre, which is the elementa- 
 ry part of the mufcle. 
 
 400. There is a threefold force in 
 
 the mufcle. 
 
 The vis infita of the mufcle. 
 
 401. The meafure of the fliortening 
 
 of the mtrfcles when they 
 contract. 
 
 402. Other things tvhich relate to 
 
 tJie vis infita. 
 
 403. The nervous power of the 
 
 mufcle. 
 
 404. In what the nervous power 
 
 and vis infita differ. 
 
 405. The phenomena in the motion 
 
 of the mufcles arifing from 
 the nervous power and vis 
 infita. 
 
 406. What the arteries contribute 
 
 to the motion of the mufcles. 
 
 407. A refutation of the manner in 
 
 which the nerves are faid to 
 move the mufcles. 
 
 408. The nervous fluid feems to 
 
 perform the oflice of a ftnn- 
 uius ; and its moving caufe 
 is not the foul, but a law de- 
 rivc*d from the Creator. 
 
 409. What things fliow that in the 
 
 motion arifing from the vis 
 Infita, the foul does not in- 
 terfere. 
 
 410. The difference between the 
 
 mufcles obeying the will, 
 and thofe which are govern- 
 ed bv the vis infita. 
 
 411. The magnitude and lofs of the 
 
 powers which the mufcles 
 exert in their contradhons. 
 
 41 2. The reafon of thefc lofl'cs. 
 
 413. The effedts of antagonifls, as 
 
 they are called, in mufcular 
 motion. 
 
 414. Other helps to this motion. 
 
 416. The co-operation of the muf- 
 
 cles. 
 
 417. The effedis produced by the 
 
 adlion of the mufcles. 
 
 418. The relaxation of a mufcle at 
 
 refl. 
 
 What becomes of the fpirit 
 fent from the brain. 
 
 CHAP. 
 
INDEX. 
 
 4S3 
 
 CHAP. XII, 
 TOUCH. 
 
 419. Senfation. 
 
 Account of the arrangement. 
 440. Touch in general. 
 
 431. Touch in another and more 
 proper fenfe. 
 
 433. The true Ikin. 
 
 433. The granulation and papillse 
 
 of the fkin. 
 
 434. The epidermis. 
 
 435. The rete Malpighianum. 
 
 436. Of what the network and epi- 
 
 dermis confift. 
 
 437. The glands of the Ikin. 
 
 There is another fource of oily 
 
 liquor ; what it is. 
 
 438. The hairs. 
 
 439. The nails. 
 
 430. The fubcutaneous cellular tex- 
 
 ture in very few places is 
 without fat. 
 
 What purpofe it ferves after 
 it has received the fat. 
 
 The Ikin and Malpighian mu- 
 cus, and epidermis, where 
 they feem perforated, are 
 drawn inwards, and degen- 
 erate. 
 
 431. The mode of touch, and the 
 
 qualities whieh are known 
 by it. 
 
 433. The Malpighian mucus, hairs 
 and nails, what purpofe? 
 they ferve. 
 
 433. Thevapour perfpiring through 
 
 infinite little arteries of the 
 Ikin. 
 
 434. The ways of demonftrating 
 
 this exhalation. 
 
 435. Sweat. 
 
 436. The elements of perfpiration. 
 Water. 
 
 The odours of aliments. 
 
 The eledtric matter. 
 
 437. Another element of perfpira- 
 
 tion, fomething' volatile, of 
 an alkaline nature. 
 
 438. The quantity of perfpiring li- 
 
 quid, 
 
 439. The indication from the quan- 
 
 tity of perfpiring liquid. 
 What things augment or di- 
 minifli it, and what follows 
 from thence. 
 
 440. How fweat benefits or hurts 
 
 the body. 
 
 441. The ufe of perfpiration.' 
 
 443. Inhalation, by what arguments 
 
 it is proved. 
 
 443. How it is proved that both the 
 exhaling and inhaling veflels 
 may be contradfed and re- 
 laxed by the power of the 
 nerves. 
 
 CHAP. XIII. 
 TASTE. 
 
 444. Tafte Is chiefly exercifed by 
 
 the tongue. 
 
 445. The tongue in general. 
 
 Firfl Idnd of its papills. 
 
 446. The fungiform papillce. 
 
 The conical ones. 
 
 Others which intervene. 
 
 447. The nerves of the tongue. 
 
 448. The arterious and nervous vil- 
 
 li which run between tliem. 
 
 449. The covering of the tongue. 
 
 430. The mufcles of the tongue, 
 451. The veffcls of the tongue. 
 
 453. The manner of exerciling the 
 
 tafle. 
 
 Flavours, and their caufe. 
 
 453- What things contribute to the 
 perception of taftes. 
 
 454. The fpirits are refumed either 
 
 into the papilla; or the ab 
 forking villi of the tongue, 
 45 j. The ufe of the fenfe of tafte. 
 
 CHAP, 
 
484. 
 
 INDEX. 
 
 CHAP. XIV. 
 SMELL. 
 
 456. The life of firell. 
 
 457. Smell is exercifed by the help 
 
 of the membrane of the nof- 
 trils. 
 
 The nerves of that membrane. 
 
 458. The arteries and veins of the 
 
 membrane of the noftrils. 
 
 459. Whaf the noftrils are. 
 
 'i'he feptum of the noftrils. 
 
 460. The uppermoft, middle, and 
 
 lowcft ofta fpongiofa. 
 
 461. The finufes in general, T.vhat 
 
 they are. 
 
 The frontal finufes. 
 
 462. The ethmoidal finufes. 
 
 The finus of the multiform 
 bone. 
 
 463. The finus of the maxillary 
 
 bone. 
 
 464. The mucus of the noftrils. 
 
 The finufes abounding in mur 
 
 cus can evacuate it in the 
 dilFerent fituations of the 
 body, fo that feme of thtin 
 can alvrays empty them- 
 felves. 
 
 465. The nofe and its mufcles. 
 
 466. The m.anner of exerciung the 
 
 fenfe of fmell. 
 
 In what it agrees or difagrees 
 ■with the fenfe of tafte. 
 
 467. Tlie ftrength of odours. 
 
 The parts t'f the noftrils -which 
 principally belong to the 
 fenfe of Imelliug. 
 
 CHAP. XV. 
 HEARING. 
 
 468. The reafon of the difference 
 
 between the organ of hear- 
 ing and that of the other 
 fenles. 
 
 469. The external ear and its parts. 
 
 470. The glands and mufcles of the 
 
 ear. 
 
 471. The meatus auditorius. 
 
 472. The ftcin and cuticle of the 
 
 meatus. 
 
 The glands for feparating its 
 wax ; the xyax. 
 
 473 — 477. The phyfical properties 
 of the air. 
 
 474. Tones. 
 
 475. The velocity of found. 
 
 476. Sym.pathetic trem.ors. 
 
 1 he ftrength of found. 
 
 Echo.' 
 
 .477. How found rebounds from 
 hard bodic§. 
 
 The caufe of the inrreafe and 
 diminution of founds. 
 
 478. The coUedfion of founds in the 
 meatus auditorius; 
 
 479. The membrane of the tt-mpa- 
 
 num. 
 
 The founds ftrike upon it after 
 their iiltim-ate refledfion in 
 the meatus auditorius. 
 
 480. The tvmpanum. 
 
 481. The four little bones of hear- 
 
 ing are placed in the tym- 
 panum. 
 
 The malleu.s. 
 
 482. The mufcles of the malleus. 
 The effedfs of the rupture of 
 
 the membrane of the tpnpa- 
 num. 
 
 483. The incus. 
 
 • 484. The Rapes and its mufcle. 
 
 483. The little round bone. 
 
 486. Various canals go out of the 
 cavity of the ttTnpanum. 
 The appendix to the tympa^ 
 num, of the figure of a gno- 
 mon. 
 
 The cells above the mamillary 
 procefs, and in the procels 
 itftlf. 
 
 487- The 
 
INDEX. 485 
 
 487. The tube. 
 
 488. Two other pafTages lead from 
 
 the tympanum into the lab- 
 yrinth. 
 
 The oval fencflra. 
 
 The velKbulum. 
 
 489. The femicircular canals. 
 
 490. The round feneftra. 
 
 The cochlea. 
 
 491. The velTels of the organ of 
 , hearing. 
 
 49Z. The nerves belonging to this 
 organ remain to be defcrib- 
 ed. ■ 
 
 The feventh pair of nerves, 
 and its hard portion. 
 
 The nerves of the external car. 
 493. The foft branch of the feventh 
 pair of nerves. 
 
 494 — 5. Various remarks concern- 
 ing the feat of hearing. 
 
 496. What things are" known with 
 
 more certainty concerning 
 this matter. 
 
 497. The dlllindion and agreeable? 
 
 nefs of founds. 
 
 CHAP. XYL 
 SIGHT. 
 
 498. The difference between light 
 
 and hearing. 
 
 The organ of light is neceffa- 
 rily compounded- 
 
 499. The eyebrow, 
 joo. The eyelids. 
 
 The conjundtiya. 
 
 The nerves and arteries of the 
 palpebrse. 
 
 501. The tarfas. 
 
 The levator mufcle of the up- 
 per eyelid. 
 
 The orbicularis palpebrarum. 
 501. The eyelallies. 
 
 503. The Meibomian febaceous 
 
 glands. 
 
 504. The tears and their fources. 
 
 505. The dudt of the lachrymal 
 
 gland. 
 
 The effedts of the contradlion 
 of the orbicular mufcle. 
 
 506. What becomes of the tears. 
 The caruncula lachrymalis. 
 The third palpebra. 
 
 The pundtum lachrymale. 
 
 507. The dudlus lachrymalis. 
 
 The lachrymal fac. 
 
 The nafal dudl. 
 
 508. The figure of the eye. 
 
 The orbit. 
 
 The furrounding fat. 
 
 509. The optic nerve. 
 
 Its courfe. 
 
 510. What becomes of it, after it 
 
 touches the eye. 
 
 The fclerotica. 
 
 The cornea. 
 
 513. The choroides. 
 
 The Ruyfchian lamina, 
 
 The ciliary circle. 
 
 The pupil. 
 
 The iris. 
 
 The uvea. 
 
 The membrane lliutting the 
 pupil in the foetus. 
 
 513. The motion of the iris. 
 
 514. The ciliary ligaments. 
 
 515. The retina. 
 
 516. The humours of the eye. 
 
 The vitreous humour. 
 
 517. The cryltalline lens. 
 
 318. The aqueous humour. 
 
 The chambers of the eye. 
 
 519. The llraight mufcles of the 
 
 eye. 
 
 520. The oblique mufcles of the 
 
 eye. 
 
 521. 522. The nerves of the eye. 
 
 321. The ophthalmic branch of the 
 
 fifth pair. 
 
 322. The branches of the third 
 
 pair. 
 
 323. The motion of the ciliary pro-- 
 
 ceffes. 
 
 324 — 527. The arteries of the eye- 
 
 328. The veins of the eye. 
 
 329. Light in general. 
 
 330. Light confills of rays of differ- 
 
 ent colours. 
 
 531. Whence the colours proper to 
 every body arife. 
 
 Opaque bodies, what. 
 
 532. What 
 
486 INDEX. 
 
 53 j. Wliat refradklon is, and its 
 laws. 
 
 S 3 3 ' When rays fall on a convex 
 fpheric body, which of them 
 are refradcd, and which re- 
 fieifted. 
 
 The focus of refracted rays. 
 
 534. What rays falling upon the 
 
 cornea are refledted, or being 
 refracted are fufFocated, or 
 reach the lens. 
 
 535. How the rays are refradted in 
 
 their pafTage through the 
 cornea and aqueous humour. 
 
 536. How they are refradted by the 
 
 cryftalline humour. 
 
 538. How they are refracted bje the 
 
 vitreous humour, and are at 
 laft colledtcd upon the reti- 
 na. 
 
 539. Whether objedts are rather 
 
 painted on the choroides. 
 
 540. 541. How the eye is thought 
 
 to accommodate itfelf to the 
 variotts diftances of objedts. 
 
 542. But nothing of this kiud hap- 
 pens. 
 
 543. Myopia. 
 
 544. The cure for this difordcr. 
 
 545. Prefbyopia. 
 
 546. The remedy for prefbyopia. 
 
 547. A medium between fliort and 
 
 long fightednefs is l>efl. 
 
 548. In what manner we judge o£ 
 
 • the magnitude of objeefe. 
 
 549. The force of the light, and its 
 
 effects. 
 
 550. How the place of an objedl is 
 
 ellimated. 
 
 551. Diflance. 
 
 552. How we perceive objjedb to be 
 
 gibbous. 
 
 553. In what manner we judge of 
 
 the fituation of the parts of 
 objedts. 
 
 554. The images of objedts remain 
 
 for a little time, even after 
 the objedts themfelves arc 
 removed. 
 
 555. Various queltions concerning 
 
 vihon. 
 
 CHAP. XVII. 
 
 INTERNAL SENSES. 
 
 556. Senfation takes place when a 
 
 new perception arifes in the 
 mind by the pcrcullion of a 
 nerve. 
 
 The perception is not the im-. 
 age of the objedt affecting 
 tlie nerve. 
 
 The connedtion between the 
 changes in the nerves and 
 the perceptions produced by 
 them in the mind, is arbi- 
 trary. 
 
 Why, notwithflanding this, 
 what we perceive of this 
 world is not falfe. 
 
 557. What things are combined 
 
 wlien we perceive. 
 
 558. The changes produced by ob- 
 
 jedts in the nerves remain a 
 long time in their origin. 
 The prefervation and order of 
 thefe ideas. 
 
 559. Imagination, what it is, 
 
 ■/ 
 
 560. Memory. 
 
 561. At what times of life the mem- 
 
 ory and imagination flour- 
 ith, and when they decay. 
 
 562. Thought ; attention. 
 
 Judgment ; genius. 
 
 The fources of error. 
 
 563. Soundnefs of judgment, on 
 
 what it depends, and by 
 what it is impaired. 
 
 564. What ideas molUy affedl: the 
 
 will. 
 
 565. The affedtious of the mind. 
 Effects of the affedtious of the 
 
 mind. 
 
 566. The caufes of tltcfe effedts. 
 
 567. The pathons of the mind are 
 
 faithfully expreffed in the 
 countenance. 
 
 Phyhognomy, whence It arifes, 
 
 568. Cec-.fent of parts, whence it 
 
 arifes. 
 
 569. The 
 
INDEX. 
 
 ^69. The nature of the foul is dif- 
 ferent from the body. 
 
 570. The foul, however, is mod in- 
 
 timately connected with the 
 body. 
 
 571. We have no reafon to be 
 
 adiamed of our ignorance 
 of the manner of this con- 
 nedlion. 
 
 572. By what arguments thofc are 
 
 chieflyperfoaded who derive 
 the origin of all the motions 
 and actions ia the body 
 from the foul. 
 
 S 73 j 576- What circumftances do 
 not permit us yet to adopt 
 that opinion. 
 
 577. Watching. 
 
 Sleep. 
 
 578. Dreams. 
 
 With thefe, fome voluntary 
 motions are fometimes coi^- 
 joined. 
 
 4S7 
 
 579, What acShions continue to be 
 carried on during fleep. 
 
 58a Plow the mechanical caufe ef 
 deep is to be difcovered. 
 The phenomena of watching 
 and of fleep. 
 
 581, 584. What things contribute 
 towards fleep, or produce 
 it. 
 
 585. The proximate caufe of fleep. 
 
 586, 587. This is confirmed by the 
 
 caufes of watching, and what 
 thefe caufes are. 
 
 588. The feat of fleep is not in the 
 
 ’ . ventricles of the brain. 
 
 Why the vital adlions go on 
 in the time of fleep. 
 
 589. The effedts of fleep. 
 
 590. Various queftions concerning 
 
 fleep. 
 
 CHAP. XVIII. 
 
 MANDUCATION, SALIVA, and DEGLUTITION.- 
 
 591. Moll: kinds of food need man- 
 
 ducation. 
 
 592. Therefore mod animals are 
 
 furniflied with teeth. 
 
 Their drudlure in general. 
 
 593. In man, on account of their 
 
 diverlity of food, there are 
 different kinds of teeth. 
 
 The incifors. 
 
 594. The eanine teeth. 
 
 595. The grinders. 
 
 596. The teeth are fixed in the jaw- 
 
 bones. 
 
 The various motions and ar- 
 ticulations of the lower jaw. 
 
 597. The levators of the jaw. 
 
 The pterygoideus externHs. 
 
 598. Hew the jaw is deprelfed. 
 
 599. The powers of the levator 
 
 mufcles. 
 
 The mufcles producing a late- 
 ral and circular motion of 
 the jaw. 
 
 600. The cheeks. 
 
 The lips. 
 
 The mouth. 
 
 The fituation and mobility of 
 the tongue in the mouth. 
 
 ^01. The liquor poured upon the 
 aliments during madication. 
 Its fources. 
 
 The dudtus incilivus is imper- 
 vious. 
 
 602. The fallva. 
 
 603. The parotid gland. 
 
 The gland called the accefibfy 
 gland. 
 
 604. The maxillary gland. 
 
 The fublingual gland. 
 
 60J. Thefe being comprefled in 
 madication, pour out their 
 liquor. 
 
 Appetite alone alfo produces 
 the fame effedts with com- 
 preffion. 
 
 606. The aliments are triturated 
 
 with faliva and air into a 
 pade. 
 
 They are rendered fapid. 
 
 The volatile parts are reforbed. 
 
 607. The motions of the tongue for 
 
 revolving the aliment with- 
 in the cavity of the mouth. 
 
 608. The tongue is diredted by the 
 
 os hyoides. 
 
 The 
 
488 
 
 INDEX. 
 
 TRe mufclcs deprefEng the os 
 hyoides. 
 
 609. The miifcles raihng the os hy- 
 
 oides. 
 
 610. The mufcles of the cheeks and 
 
 lips. 
 
 611. The aliment being che^ved is 
 
 applied to the tongue, and 
 carried towards the fauces. 
 61Z. How the food is carried from 
 the mouth into the fauces. 
 How the'accefs into the larynx 
 is doled. 
 
 613. The pharynx. 
 
 614. The mufcles dilating the 
 
 pharynx. 
 
 €15. How food is prevented from 
 falling into the larynx. 
 
 The velum of the palate. 
 
 The uvula. 
 
 616. How the return of the aliment 
 into the mouth is prevented. 
 How tl>e epiglottis and uvula 
 
 are erected after thev hav^ 
 been deprefl'ed. 
 
 617. The powers which prefs the 
 
 aliments downwards through 
 the pharynx. 
 
 The action of the arytenoid 
 mufcles. 
 
 618. The mucus of the pharvnx, 
 
 and its various fources. 
 
 619. The tonhls. 
 
 The mucus of them Is very 
 vifcid. 
 
 The neighbotiring fiarts arc 
 full of mucous organs. 
 
 The mucus of the cefophagus 
 is more fluid. 
 
 The veflcls of the tonfils, 
 pharynx, and ccfophagus. 
 619.* The oefophagus. 
 
 6zo. The paffage of the aliment 
 through the oefophagus. 
 
 6zi. The conftriction of the upper 
 orifice of the ilomach. 
 
 CHAP. IX. 
 
 The action of the STOMACH on the ALIMENTS. 
 
 fzz. Tlie fituation, figure, and &ze 
 of the Ilomach. 
 
 6Z3. The vilcera in the neighbour- 
 hood of tlie ftom.ach. 
 
 6z 4. The external membrane of the 
 flomach. 
 
 The firft cellular coat. 
 
 6zy. The mufcular coat of the fto- 
 mach. 
 
 The ligaments of the pydonis. 
 
 6z6. The fecond cellular coat. 
 
 The nervous coat of the fto- 
 mach. 
 
 The third cellular coat. 
 
 The villous coat. 
 
 The valve of the pylorus. 
 
 The pores of the villous coat. 
 
 6zy. The arteries of the flomach. 
 
 628. The diftribution of the arteries 
 through the coats of the flo- 
 mach. 
 
 619. The veins of the flomach. 
 
 630. The nerves of the flomach. 
 
 631. The lymphatic veflcls of the 
 
 flomach. 
 
 632. The inorganic pores. 
 
 623. The mucus anointing the vil- 
 lous membrane. 
 
 The limpid humour which the 
 arteries diflii. 
 
 634. The prefl'ure of the diaphratm 
 
 and mufcles of the abdomen 
 on the itcmach. 
 
 635. The necefiity of meat and 
 
 drink. 
 
 636. The phenomena of hanger. 
 
 63 7. New chyle, its ufes. 
 
 638. The caufe of hunger. 
 
 639. The feat of third. 
 
 How it is excited. 
 
 How quenched. 
 
 640. The pleafure of taking food. 
 
 641. Our diet ought to conllft of 
 
 two kinds of t.li.mentE blen- 
 ded together. 
 
 642. Why flefti is required. 
 
 643. Why vegetables. 
 
 644. Drink. 
 
 645. Condiments. 
 
 646. Preparations of aliments. 
 
 647. The meafure of footl. 
 
 648. The changes which happen to 
 
 the food in the flomach. 
 
 649. What hinders the food from 
 
 degenerating into complete 
 acidity in the flomach. 
 
 There 
 
INDEX. 
 
 't'liere Is no kind of ferment 
 here. 
 
 650. The Deriftaltic motion of the 
 
 llomach propelling the ali- 
 ment into the inteftincs. 
 
 651. The more powerful force of 
 
 the diapliragm and abdomi- 
 nal mufcles. 
 
 489 
 
 In what order and time the 
 aliments go out of the fto- 
 niach. 
 
 654. A certain portion of drink is 
 abforbed in the llomach In- 
 to the veins. 
 
 653. Vomiting. 
 
 654. Order of arrangement. 
 
 CHAP. XX. 
 
 The omentum. 
 
 655. The peritoneum and its ex- 
 tent. 
 
 6j6. The cellular texture placed 
 round the peritoneum is con- 
 tinued into the capfules. 
 
 Its connexion with other parts. 
 
 657. The produdlions and ligaments 
 
 of the peritonseum. 
 
 By the feparated lamihse of 
 the peritoneum the vifcera 
 ate furrounded, and kept 
 firm and defended in motions 
 and concuflions of the body. 
 
 658, 659. The mefocolon. 
 
 660. The mefocolon and mefentery 
 are hollow. 
 
 The (lender purfes of the me- 
 focolon. 
 
 66 r. The mefentery. 
 
 662. What things are found in all 
 
 parts of the mefentery and 
 mefocolon. 
 
 663. M.anv parts are comprehended 
 
 under the name of omen- 
 tum. 
 
 Their nature in general. 
 
 The membrane from the ex- 
 ternal membrane of the co- 
 lon inferring itfelf into the 
 Sflure of the liver. 
 
 The natural orifice, and com- 
 mon porta of the omentum. 
 
 664. The lefler hepatico-gallric o- 
 
 mentum. 
 
 665. The anterior lamina of the 
 
 greater gallro-colic omen- 
 tum. 
 
 666. Its poflerlor lamina. 
 
 667. The omentum colicum. 
 
 668. It is common both to the o- 
 
 mentum and mefentery to 
 . accumulate fat. 
 
 How it Is proved that this fat 
 is received into the veins. 
 
 669. The arteries of the omenta. 
 
 676. The nerves of the omenta. 
 
 671. The arteries of the mefentery 
 
 and mefocolon. 
 
 672. The veins of the omentum and 
 
 mefentery. 
 
 The lymphatic veffels of the 
 omentum. 
 
 673. Other ufes of the omentum. 
 
 674. The ufe of the mefentery. 
 
 675. The nature of the water ab- 
 
 forbed by the veins of the 
 mefentery, and what it con- 
 tributes towards the bile. 
 
 CHAP. XXI. 
 
 The spleen. 
 
 676. The fubflance of the fpleen. 
 Its figure. 
 
 Connedlion. 
 
 Its fituation, bulk, and num- 
 ber. 
 
 I i 
 
 677. The arteries and veins of the 
 
 fpleen. 
 
 678. The lymphatic velTels of the 
 
 fpleen. 
 
 679. Its nerves. 
 
 6 So. Its 
 
INDEX. 
 
 49 ^ 
 
 680. Its internal flru^ure. Its nature. 
 
 Its furrounding ineDibrane. 682 — 3. The ufe of the fpleen. 
 
 681. The fpleen contains a great 684. ConjeiTurcs ccuceruing it. 
 
 deal of blood. 
 
 CHAP. XXII. 
 
 The pancreas. 
 
 685. The pancreatic juice. 
 
 686. The fituation and figure of the 
 
 pancreas. 
 
 Its Ilrudfure. 
 
 Its ve'fcls. 
 
 Ils nerves. 
 
 687. The pancreatic duiT. 
 
 683 . The quantity of pancreatic 
 juice. 
 
 The powers by which it is ex- 
 pelled. 
 
 1 he univerfality of the pan- 
 creas is an argument of its 
 utility. 
 
 Whence the efFervefcence with 
 the bile arifes. 
 
 688.* The utility of the pancreatic 
 juice. 
 
 CHAP. XXIII. 
 
 The liver, GALL BLADDER, and BILE. 
 
 6S9. The bulk of the liver. 
 
 The fituation of the liver in 
 refpedf to the diaphragm. 
 The ligaments from it. 
 
 Other ligaments. 
 
 How it can be moved. 
 
 Its common membrane. 
 
 690. How the liver is fituated with 
 
 refpecl to the colon, kid- 
 neys, duodenum, flomach, 
 and pancreas. 
 
 691. The ihape of the liver. 
 
 692. The furrows of the liver. 
 
 Its lobes. 
 
 693. The arteries of the liver. 
 
 694. The umbilical vein. 
 
 The ductus venofus. 
 
 695. The large trunks of the vena 
 
 portarum. 
 
 696. The capfule of the vena por- 
 
 tarum. 
 
 The divifions of its branches. 
 Thefe are perpetually accom- 
 panied by branches of the 
 hepatic artery. 
 
 The proportion of the branch- 
 es of the vena portarum to 
 the trunks. 
 
 697. The branches of the cava. 
 
 Theproportio.nof its branch- 
 
 es to thofe of the vena por- 
 tarum. 
 
 The trunk of the vena cava. 
 The fmaller veins creeping 
 over the furface of the liver. 
 
 698. The palTage of the blood 
 
 through the vena portarum. 
 
 699. The nerves of the liver. 
 
 700. The hmphatic velTcls of the 
 
 liver. 
 
 701 — 3. The internal Ilrmflure of 
 the liver. 
 
 704. How it happens that the bile 
 is not fecreted from the hep- 
 atic artery, but from the Ve- 
 na portarum. 
 
 703. How the fecreted bile is fent 
 into the biliary duels and 
 through them. 
 
 706. The ftructure of the bUiary 
 
 duct 
 
 Its irritability and fenfibllity. 
 
 707. The dudlus choledochus. 
 
 708. The dudVus cvllicus. 
 
 The gall bladder. 
 
 Its fituation. 
 
 709. The fhape of the gall bladder. 
 The wrinkles of the dudlus 
 
 cylHcus. 
 
 710. The 
 
INDEX. 49! 
 
 yio. Tliecoatsandmuciferouspores 
 of the gall bladder. 
 
 The exhalation of the arteries 
 into the gal! bladder. 
 
 The bile exudes through in- 
 organic pores. 
 
 Ill, In man, no dudts come from 
 the liver into the gall blad- 
 der. 
 
 711.’*' The bile flows into the in- 
 teftine both from the liver 
 and from the gaU bladder. 
 
 All the bile is not firll con- 
 veyed to the gall bladder. 
 
 The quantity of bile. 
 
 How often the bile flows into 
 the bladder. 
 
 The gall bladder does not fe- 
 Crete its proper bile. 
 
 713. The return of bile into the 
 blood is morbid. 
 
 713. The change which the bile un- 
 
 deigoes in the cyftis. 
 
 It is directed into the gall 
 bladder, when there is no 
 ufe for it in the intellines. 
 
 714. The powers which exprefs the 
 
 bile from the gall bladder. 
 
 715. The qualities, elements, and 
 
 offices of the bile. 
 
 716. Whither the bile goes. 
 
 It fometimes comes into the 
 Ilomach. 
 
 The bile of the foetus. 
 
 Its coagulation and ufes. 
 
 717. The proper ufe of the hver in 
 
 the fetus. 
 
 C H A P. XXIV. 
 
 The small INTESTINES. 
 
 718. The fmaU intellines in general. 
 Their divifion. 
 
 719. The duodenum. 
 
 In it chiefly tlte bile and pan- 
 creatic juice are mixed with 
 the aliments. 
 
 730. The fituation of the reft of the 
 
 frnall intellines in general. 
 
 731, 37. The ftrudture of the fmaU 
 
 intellines. 
 
 731. The external coat. 
 
 The firll cellular coat. 
 
 733. The mufcular coat. 
 
 733. The fecond cellulai coat. 
 
 The nervous coat. 
 
 The third cellular coat. 
 
 The villous coat. 
 
 Its folds. 
 
 734. The villi of the intellines. 
 
 735. The veficles of the villi. 
 
 736. The larger pores of the villous 
 
 coat leading to the mucous 
 glands. 
 
 737. The leflcr pores Ilkewife de- 
 
 politing mucus. 
 
 738, 730. The arteries of the fmall 
 intellines. 
 
 730. The arteries of the duodenum. 
 
 731. The veins .of the fmall intef- 
 
 tines. 
 
 How it is proved that thefe 
 abforb a thin humour from 
 the intellines. 
 
 733. The nerves of the fmall intef- 
 tines. 
 
 733. The liquid flowing from the 
 arteries into the cavity of 
 the inl^ftiues. 
 
 Its quantity. 
 
 The ides of the mucus of the 
 fmall intellines. 
 
 734 — 5 - The pcriftaltic motion. 
 
 736. The changes which the food 
 
 undergoes in the fmall in- 
 tellines. 
 
 737. The office of the fmall latef- 
 
 tines in general. 
 
 738. The principal caufes which 
 
 chaiige the aliments in the 
 fmall intellines. 
 
 CHAP. 
 
INDEX. 
 
 4!J2 
 
 CHAP. XXV. 
 
 The large intestines. 
 
 739. The remains of the food after 
 
 the chyle is extraiSed. 
 
 740. How the ileum applies itfelf 
 
 to the colon. 
 
 The valve of the colon. 
 
 741. The blind extremity of the co- 
 
 lon. 
 
 The appendix. 
 
 How the change from the 
 flruefture of the ca;cum in 
 the foetus to that of the adult 
 takes place. 
 
 The fetor of the inteflines be- 
 gins chiefly there. 
 
 74Z. The fituation and conneclions 
 of the colon. 
 
 743. The flriidture of the colon in 
 
 general. 
 
 Its ligaments. 
 
 744. The cells of the colon. 
 
 Ike wrinkles, follicles, and 
 pores of its villous mem- 
 brane. 
 
 745. The vefl’els of the large intef- 
 
 tine. 
 
 746. The diviiion of the veffels to 
 
 the large inteflines. 
 
 The exhalation and reforption 
 from ihefc. 
 
 The hemorrhoids. 
 
 747. The lymphatic vefTels of the 
 
 large inteflines. 
 
 Chvlc is fometimes cbferved 
 in thefe. 
 
 748. The nerves of the large intef- 
 
 tincs. 
 
 749. The faeces of the inteflinum 
 
 colon. 
 
 The perifkaltic and antiperif- 
 taltic motion of the colon. 
 Flatus. 
 
 750. How the ileum is Unit. 
 
 The paffage of the fatces thro’ 
 the colon. 
 
 751. The fituation and courfe of 
 
 the rectum. 
 
 752. The external and mufcular 
 
 coat of the reelum. 
 
 The internal Iphincler of the 
 anus. 
 
 753. The villous coat of the reiSlum. 
 Its folds, and mucous glands. 
 
 * The febaceous glands of the 
 anus. 
 
 754. The external fphimTtcr of the 
 
 anus, and its aclion. 
 
 ITo-yv- the anus is naturally clo- 
 fed. 
 
 753. The levator mufclcs of the 
 anus. 
 
 756. The excretion of the ficet, 
 
 73 7. I'hc fxces themfclves. 
 
 CHAP. XXV.* 
 
 The CHYLIFEROUS VESSELS. 
 
 738. The nature of the chyle. 
 
 JJ9. The ubforption of the chyle, 
 and its paffage through the 
 ladleal vefTels. 
 
 In what aniraals latfteal vefTels 
 are. found. 
 
 How they are difpofei in the 
 dixFerent inteftines. 
 
 760. The valves of the laifteals. 
 
 The caufes of the motion of 
 the chyle tlirough the coats 
 of the inteflines. 
 
 776. The glands of the mefentery. 
 
 The chyle proceeds from the 
 inteflines to thefe glands. 
 
 762. What happens to the chyle in 
 
 the glands of the mefenterv. 
 
 763. The courfe of the lacTtals from 
 
 the mefentcric glands to the 
 receptacle of the chyle. 
 
 764. How the paffage of the chyle 
 
 into the receptacle is de- 
 monflrated. 
 
 763 — 6. 1 he thoracic duff. 
 
 767. The chyle paffes to the hlocd 
 through the th^r cic du« 51 . 
 
 768. The 
 
INDEX. 
 
 y6S. The caufes of the motion of 
 the chyle in general. 
 
 J'69. The change of the chyle dur- 
 ing its circulation with the 
 blood. 
 
 In the inteflines there are not 
 lacteal and lymphatic veffels 
 of difl'erent kinds. 
 
 495 
 
 770. The lacteal veflels abforb wa- 
 ter when digeftion does not 
 go on. 
 
 The thoracic dui5t brings bact 
 the lymph of the whole bp- 
 dy. 
 
 CHAP. XXri. 
 
 P 
 
 The kidneys, BLADDER, and URINE. 
 
 771. A part of the water brought 
 
 into the blood with the chyle 
 is ftrained through the kid- 
 neys. 
 
 772. The liuiation and connection 
 
 of the kidneys. 
 
 Their figure. 
 
 External membrane. 
 
 Their fat. 
 
 Ligaments. 
 
 773. The arteries of the kidney’s. 
 
 774. The veins of the kidneys. 
 
 The quick pafiage of the blood 
 
 from the arteries into the 
 veins. 
 
 The veins of the renal fat. 
 
 77j. The lymphatic veins of the 
 kidneys. 
 
 776. The nerves of the kidney's. 
 
 777. The renal capfule. 
 
 778 — 8a The internal flrudture of 
 the kidney'. 
 
 778. The Itructure of the cortical 
 
 part. 
 
 The uriniferous vefTels. 
 
 The gland,s. 
 
 779. The papillx of the kidneys. 
 
 780. The infundibula. 
 
 The pelvis. 
 
 781. The lecretion of urine. 
 
 The quantity of the urine. 
 
 782. The elements of the urine. 
 
 783. How the ureter carries the u- 
 
 rine forwards. 
 
 The ureter itl'elf. 
 
 784. How it is proved that the urine 
 
 is fecreted in the kidneys, 
 and defeends by the ureter 
 into the bladder. 
 
 7§r. The urine cannot defeend by 
 other palTages. 
 
 786. The lituation of the urinary 
 bladder. 
 
 787. The figure and magnitude of 
 
 the bladder. 
 
 788. The lirtt cellular coat of the 
 
 bladder. 
 
 Itsiongitudinalmufcular fibres. 
 
 789. Its other mufcular fibres. 
 
 790. The contractile power of the 
 
 bladder. 
 
 791. The fecond cellular coat of the 
 
 bladder. 
 
 The nervous coat. 
 
 The innermoft coat of the 
 bladder. 
 
 The mucus of the bladder, and 
 its fources. 
 
 79a. The veffels ai>d_nerves of the 
 bladder. 
 
 The lymphatic, 
 
 793. The bladder tranfmits and ab» 
 
 forbs water through its ip- 
 organic pores. 
 
 794. The urine flows through tki: 
 
 tireter into the bladder. 
 
 It remains there. 
 
 The caufes retaining the urine. 
 
 795. How the urine is expelled 
 
 796. Various noxious matters TC 
 
 thrown off by the urine- 
 The confequences of a reten- 
 tion or fuppreflion of urine. 
 
 797. The urethra in general 
 
 798. The parts receiving and eup- 
 
 porting the urethra. 
 
 The various capacity and fig-, 
 lire of the urethra. 
 
 799 — S02. The muicles governing 
 the urethra. 
 
 803. The pyramidal mufclc has no 
 
 cffeiT in drawing the blad- 
 der downwards. 
 
 804. The mucus of the urethra, and 
 
 its various fources. 
 
 80J. Theffone in the urinary bladder. 
 
 CILVP. 
 
*94 
 
 INDEX, 
 
 CHAR xxvir. 
 
 The male GENITALS. 
 
 806. The reafon of the lltuation of 
 
 the genital parts. 
 
 807. The order of the arrangement. 
 The various utuations. of die 
 
 tefticles. 
 
 808. The ferotunu 
 The dartos. 
 
 809. Hie cellular texture of the 
 
 ferotnm. 
 
 The cremafler. 
 
 810. The vaginal coat of the tefticlc. 
 1 he tunica albuginea. 
 
 8 1 1. The figure and fituation of the 
 
 epididymis. 
 
 812. The fpermatic arterj-. 
 
 The abdominal ring. 
 
 The courfe of the fpermatic 
 cord from thence to tlie tel- 
 ticle. 
 
 The fmall arteries to the cov- 
 erings of the teftlcle. 
 
 813. The dilhribution of the fmall 
 
 arteries tlirough the teflicle. 
 The arteries have no anailo- 
 mofes with th% fpermatic 
 vein. 
 
 The motion and quantity of 
 the blood in the tefticle. 
 
 8t 4. The fpermatic vein. 
 
 815. The vefiTels of the external cov- 
 
 erings of the tefticle. 
 
 816. The nerves of the tefticle. 
 
 817. The lymphatic veftels of the 
 
 tefticle. 
 
 818. 'I'hc internal ftruclure of the 
 
 tefticle. 
 
 819. The ftruclure of the epididy- 
 
 mis, and the vafcula aber- 
 rans. 
 
 820. The motion ©f the femen. 
 
 821. The vas deferens. 
 
 822. The veficula feminalis. 
 
 823. The'fcmen. 
 
 824. The animalcules of the femen. 
 
 825. How thefe feem to be in the 
 
 femen. 
 
 826. Whence the femen proceeds. 
 
 Of what humours it is compof- 
 
 ed. 
 
 What is generated in the tefti- 
 cles only is prolific. 
 
 How long the femen is pre- 
 ferved in the vcficks. 
 
 827. A part of the femen is abforb- 
 
 ed, and its effcdls. 
 
 How the femen is retained in 
 the veficles. 
 
 828. The quantitj' of femen. 
 
 The femen proceeds from the 
 tefticle into the velicle. 
 
 829. The proftate gland. 
 
 Its liquor. 
 
 S29.* The three dilatations of the 
 urethra ; its various direc- 
 tioiis ; its coats. 
 
 830. The cavernous body of the 
 
 urethra. 
 
 831. How it is proved that the blood 
 
 is poured into this body. 
 
 832. The cavernous bodies of the 
 
 penis. 
 
 833. Tlie teguments of the penis. 
 The prepuce. 
 
 The odoriferous g'ands. 
 
 Tiie fufpr.dory ligament. 
 
 834. The ufc of the penis. 
 
 S35. T;:e creclion of the penis. 
 
 Its exciting caufes. 
 
 836. The arteries of the genital 
 
 parts. 
 
 837. The veins of the fame parts. 
 .838. The hunphatic veffcls of the 
 
 penis. 
 
 The nerves of the genital parts 
 
 839. The i iimediate caufe of the 
 
 ercdlion of the penis. 
 
 840. The cxpullion of die femen 
 
 into the urethra. 
 
 841. Its expuhion from the urethra. 
 This adtion is verv violent, 
 
 and aunoft convulftve. 
 
 ChL^J’. 
 
INDEX. 
 
 <95: 
 
 CHAP. XXVIII. 
 The virgin WOMB. 
 
 84a. The fituatioTi of the uterus in 
 the pelvis. 
 
 How the uterus is tied to the 
 peritoneum. 
 
 ' The broad ligaments. 
 
 843. The body, neck and internal 
 
 mouth of the uterus. 
 
 844. The tubes of the uterus. 
 
 845. The ovaries. 
 
 846. The eggs in the ovaries. 
 
 847. The round ligament of the ute* 
 
 rus. 
 
 848. The arteries of the uterus. 
 
 849. Its veins. 
 
 850. The internal veflels of the ute- 
 
 rus. 
 
 831. The lymphatic vefTels of the 
 uterus. 
 
 85a. The nerves of the uterus. 
 
 8 33. The age at which the menfes 
 begin to flow. 
 
 834. The phenomena of the men- 
 fes. 
 
 The duration of the flux. 
 
 The periods at which they re- 
 turn. 
 
 833. The menftrual blood flows 
 from the veflels of the ute- 
 rus itfelf. 
 
 The nature of the menflrual 
 blood. 
 
 The uterus being obflrudled, 
 the blood flows out through 
 the vagina, and through oth- 
 er parts. 
 
 836. Whether the moon, ferments, 
 
 or the venereal defire, be the 
 caufes of the menfes. 
 
 837. The female body in general. 
 
 The pelvis and its vefl*els,in as 
 far as they differ from the 
 fabric in the male. 
 
 How the paffage of the blood 
 through the uterus is thence 
 afFe< 3 :ed. 
 
 839. The inferior limbs, pelvis, and 
 uterus, of a female child 
 newly born. 
 
 How the flrudlure of thefe is 
 changed in the adult. 
 
 The effedls of thefe changes. 
 
 860. Plethora is generated in both 
 
 fexes when the growth of 
 the body ceafes. 
 
 This, in males, goes off by the 
 noflxils. 
 
 In women it finds an eafier 
 paflage by the uterine vef- 
 fels. 
 
 There are other effedls of this 
 determination of the blood. 
 
 How the quantity of the men- 
 fes is increafed or diminifli- 
 ed. 
 
 861. The quantity of the blood fent 
 
 out. 
 
 The remiflion and return of 
 the period. 
 
 Why the period is commonly 
 fixed to a month. 
 
 Why the menfes ceafe to flow 
 altogether. 
 
 Why brute animals have no 
 menfes. 
 
 Why men want them. 
 
 86 a. Why the brealls fwell at the 
 fame time. 
 
 CHAP. XXIX. 
 
 CONCEPTION. 
 
 863. The difficulty of this fubject. How they produce their young 
 
 The order of treating it. "ones. 
 
 864. The molt Ample animals of no 863. Oviparous animals of a lingle 
 
 fei. fex. 
 
 866 — 7. Animals 
 
49<> INDEX. 
 
 866 — 7. Animils of two fexes exift- 
 ing in the fame individual. 
 
 866. Whatauimalsimpregnatetherti- 
 
 felves. 
 
 867. Animals of this kind which 
 
 mutually ftand hi ^jccd of 
 one another’s affiftaiice. 
 
 8'68. Animals with two fexes divid- 
 ed. 
 
 yC'p. Confequences which follow 
 from what has been faid 
 concerning the origin and 
 fexes of anim-als. 
 
 870. Caufes of the venereal defire. 
 
 871. The vagina, and its fituation. 
 
 The hvmen. 
 
 The carunculas myrtifoimes. 
 
 872. The ftrudture of the vagina. 
 
 873. The nymphac. 
 
 The clitoris. 
 
 Z~4. The confiricfor mufele of the 
 mouth of the vagina. 
 
 Eys- Coition. 
 
 What happens to women dur- 
 ing the time of coition. 
 
 876. The fources of the muc'bus li- 
 quor ejected. 
 
 The tubes are eredted in coi- 
 tion, and applied to the ova- 
 lium. 
 
 877 — 8. What changes take place 
 in the ovarium at that time. 
 
 The corpus luteum. 
 
 878. How it is proved that the tube 
 prefies out the egg, abforbs 
 it, and carries it to the uterus. 
 
 S79. The feelings of the future mo- 
 tlier while thefe things are 
 performed. 
 
 How It Is proved that concep- 
 tion takes place in the ova- 
 rium. 
 
 28 o. Why the uterus Is thought to 
 be Unit after conception. 
 
 Whence the complaints after 
 conception arife. 
 
 S81. The original femlna of the 
 new animal ; whether they 
 are from b.ith parents, and 
 the mixture of femeii furuifli- 
 ed from all parts of the bodv. 
 
 882. Whether they proceed only 
 
 from the male and liis femi- 
 nal animalcules. 
 
 883. Whether the foetus proceeds 
 
 ratlier from the mother. 
 
 884. Hypothefes concerning the for- 
 
 mation of the nesv animal. 
 
 885. What feems to he more cer- 
 tainly known concerning this 
 matter. 
 
 806. The ftate of the embryo before 
 conception. 
 
 How it is changed by the male 
 femen. 
 
 887. Objedtions derived from moles, 
 
 of no weight. 
 
 888. The change of the egg when 
 
 brought into the uterus. 
 
 Its inofculatiou with the uterus. 
 
 889. The contents of the egg at that 
 
 time. 
 
 The foetus during the firft days 
 of conception. 
 
 890. The incrcafe of the egg and of 
 
 the foetus until the placenta 
 is completed. 
 
 Defeription of tlic completing 
 of the placenta. 
 
 891. The placenta, and its connec- 
 
 tion with the uterus. 
 
 892. TIic chorion. 
 
 893. The middle membrane. 
 
 894. The amnion. 
 
 893. The umbilical vein, by which 
 nouriihmctit is conveyed to 
 the fetus-. 
 
 The cord. 
 
 896. The umbilical arteries. 
 
 Thefe, with tlu ir veins and 
 
 cellular texture form the pla- 
 centa. 
 
 The blood flows from the pl.i- 
 centa into the veina of the 
 uterus; 
 
 897. Whether the fetus takes in 
 
 the liquor of the amnion by 
 the mouth, and is nourilhed 
 by it. 
 
 What is the fource of this li- 
 quor. 
 
 898. The excrements of the foetus. 
 
 899. Whether there i- .my allantois 
 
 in the human race. 
 
 They certainly have an ura- 
 chus. 
 
 The urine is perhaps depofited 
 in the cellular texture of the 
 cord. 
 
 90c. A compendium of the forma- 
 tion of the fatus mufl be giv- 
 en. 
 
 901. What parts arc formed at the 
 very firlf beginning of the 
 fetus. 
 
 902. The 
 
INDEX, 
 
 497 
 
 902. The proportion of the fluid to 
 
 the folid parts at that time. 
 
 903. The acceflbry nutritious juices. 
 How the blood and reft of the 
 
 humours are perfedted. 
 
 904. How the folid parts in general 
 
 are formed. 
 
 90J. The veffels are firft formed. 
 How they are produced. 
 
 906. What parts are at firft com- 
 
 pleted and become confpicu- 
 ous in the primeval foetus. 
 What are as yet involved and 
 lie hid. 
 
 907. The motion of the heart is ap- 
 
 pended to this kind of em- 
 bryo. 
 
 The heart at firft bears the 
 largeft proportion to the reft 
 of the body. 
 
 Its pulfations are very power- 
 ful in diftending and length- 
 ening the veffels. 
 
 908. What is oppofed to this power 
 
 of the heart. 
 
 How the arteries are then af- 
 fetfted. 
 
 909. The foetus, grows very quickly. 
 The caufe of this quick in- 
 
 creafe. 
 
 910. The embryo is altered during 
 
 its growth. 
 
 910 — 14. By what caufes this is 
 chiefly produced. 
 
 910. Expanfion. 
 
 91 1. Attradfion. 
 
 912. Preffure. 
 
 913. The power of derivation. 
 
 Of revulfion. 
 
 914. The change of the humours. 
 
 915. How bone fucceeds cartilage 
 
 and epiphyfis. 
 
 916. How the long bones are form- 
 
 ed. 
 
 917. How the flat bones are formed. 
 
 918. Plow bone is produced from 
 
 gluten. 
 
 It is depofited from the inmoft 
 fubftance of the bone, and 
 not from the periofteum. 
 
 919. The periofteum. 
 
 920. The foetus during the firft days 
 
 of pregnancy. 
 
 921. The thymus. 
 
 921 — 24. The circulation of the 
 
 blood peculiar to the foetus, 
 and the organs by which it 
 is performed. 
 
 92J. Whether the foetus breathes in 
 the womb. 
 
 Whether it docs fo in the va- 
 gina. 
 
 926. The changes which happen to 
 
 the uterus during pregnancy. 
 The different fituations of the 
 foetus. 
 
 927. The complaints attending preg- 
 
 nancy. 
 
 The time of delivery. 
 
 928. Parturition, 
 
 929. The number of foetufes. 
 Superfetation. 
 
 930. The loofening of the placenta. 
 — of the umbilicus. 
 
 931. The contradtion of the uterus 
 
 after delivery. 
 
 The lochia. 
 
 The fwelling of the breafts. 
 
 944. * The milk. 
 
 Sympathy between the breafts 
 and uterus. 
 
 945. The breafts. 
 
 Their veffels. 
 
 Nerves. 
 
 946. The ladtiferous dudls In the 
 
 breaft. 
 
 The nipple and its ladtiferous 
 dudts. 
 
 The areola of the nipple. 
 
 947. Sudtion. 
 
 The coloftra. 
 
 Milk may be produced with- 
 out a child. 
 
 The breafts, after the menfes 
 have ceafed, become effete. 
 948 — 52. The changes which hap- 
 pen to the child after birth. 
 
 948. Refpiration. 
 
 The deflexion of the courfe of 
 the blood from the dudlus 
 arteriofus. 
 
 949. The flmtting up of the foramen 
 
 ovale. 
 
 9JO. The flrutting up of the umbili- 
 cal vein and dudtus venofus. 
 
 951. The contradtion of the umbili- 
 
 cal veins, and abolition of 
 the urachus. 
 
 952. Other changes. 
 
 K k 
 
 CHAP, 
 
45S 
 
 INDEX, 
 
 CHAP. XXX. 
 
 NUTRITION, GROWTH, LIFE, and DEATH. 
 
 953. The growth of a child is (low- 
 
 er as it advances in age. 
 
 The caufes why the growth is 
 continually lefTened. 
 
 954. The heart grows lefs in pro- 
 
 portion than any other part 
 of the body. 
 
 And becomes lefs irritable. 
 
 955. The end of the inci^fe of the 
 
 body. 
 
 93 6. When this is faid to occur. 
 
 957. Hqw it is proved that all parts, 
 
 even the moft folid, are 
 continually confuming and 
 changing.^ 
 
 958. The caufes of the deftrucUon 
 
 of the folid parts. 
 
 959. How the wade of the folids is 
 
 repaired. 
 
 960. How the wade of the cellular 
 
 fubdance and mod organic 
 parts is repaired. 
 
 961. How the free extremities of 
 
 parts are repaired. 
 
 962. Fatnefs. 
 
 963. The beginnings of decay. 
 
 964. The progrefs of decay. 
 
 965. The diminution of the vis inli- 
 
 ta and nervous power. 
 
 966 — 8. The change of the fluids. 
 
 966. The decreafe of the fluids. 
 
 967. The corruption of the fluids. 
 
 968. The increafe of the qu^tity 
 
 of earth in the fluids. 
 
 969. Old age. 
 
 970. Decrepit old age. 
 
 '97X. iaOngcnrity. 
 
 972. Death from old age. 
 
 973. The figns of death. 
 
 974. The body is dedroyed by pu-* 
 
 trefatdion. 
 
 The foul furvives after death, 
 and goes to the place appoint- 
 ed for it by the Almighty. 
 
 FINIS. 
 

 

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 copy 2