■ 'Vi 
 
FIRST LINES 
 
 I 
 
 O F 
 
 t 
 
 PHYSIOLOGY, 
 
 BY THE CELEBRATED 
 
 Baron ALBERTUS HALLER, M. D. ^c. 
 
 TRANSLATED FROM THE 
 
 CORRECT LATIN EDITION 
 Printed under the Inspection of 
 
 WILLIAM C U L L E N, M. D. 
 
 To which is added, A Translation of 
 The Laborious INDEX compofed for that Edition. 
 
 EDINBURGH: 
 
 Printed for Charles Elliot, Parliament Square,’ 
 
 M, D C C, L X X I X. 
 
t 
 
 ADVERTISEMENT. 
 
 T H E firft edition of this work was publifh- 
 ed in 1747. It was defigned as a correc- 
 tion and improvement of Boerhaave’s Inftitu- . 
 dons, by adding the new difcoveries of Mor- 
 gagni, Window, Albinus, Douglas, See. 
 
 In 1751, another edition was publifhed; in 
 which ibme things were treated more fully, and 
 others more briefly, than before. The ana- 
 tomical deferiptions, particularly, were here 
 abridged ; fome new phyfiological difcoveries 
 added j and a great number of typographical 
 errors corrected. 
 
 A THIRD edition was publilhed in 1 764. Here 
 the. author conformed the order of his fubjects 
 treated of in his Firft Lines to thofe of his larger 
 work, and made the number of books contain- 
 ed in both equal ; but did not think proper to 
 abridge his Firft Lines any farther, left they 
 fhould thus have become lefs fit for the pur- 
 pofes of a text-book. 
 
 The demand for this work foon became fo 
 great, that an edition was printed at Edinburgh 
 in 1766, under the infpedlion of the then Pro- 
 feflTor of the Inftitutions of Medicine ; who had 
 formed the phyfiological part of his ledlures 
 upon a fimilar plan. The greateft care was 
 taken to have this edition as exadl and free 
 from typographical errors as poflible; and it 
 was farther improved by the addition of an 
 
 Index, 
 
 
[ vi ] 
 
 Index, which may be confidered as an elegant 
 compend of the whole. It was thought proper, 
 however, to retain the erroneous numbers of the 
 paragraphs which had efcaped in the original 
 editions, for the more eafily referring from one 
 place to another, and that no confulion might 
 arife from tiling the different editions. 
 
 Of the laft mentioned valuable edition tlie 
 prefent is an exaeff tranllation, in which ail 
 poffible care has been taken to give the tine 
 meaning of the author, in a plain and eafy 
 manner : An undertaking to wliich the publillier 
 was incited by the conffderation, that the tranf- 
 lation with which Undents have been hither- 
 to furnilhed, not only was done from an old 
 edition, exceedingly imperfect; in comparifon 
 with the laft one; but is alfo unneceffarily ex- 
 tended in the printing to double the fize of the 
 original, and of courfe proportionably enhanced 
 in the price. 
 
TABLE OP CONTENTS. 
 
 Chap. Page. 
 
 I. Of the animal fibres^ i 
 
 II. Of the cellular fubjlance, 6 
 
 III. Of the arteries and veins^ 1 1 
 
 IV. Of the circulation of the blood, 26 
 
 V. Of the heart, 33 
 
 VI. Of the nature of the blood and juices of 
 
 the human body, 62 
 
 VII. Of the common offices of the arteries, 7 1 
 
 VIII. Of the fecretions, 88 
 
 IX. Of refpiration, 108 
 
 X. Of the voice and fpeecb. 13^ 
 
 XI. Of the brain and nerves, 146 
 
 XII. Of mufcular motion, 189 
 
 XIII. Of the fenfe of touch, 204 
 
 XIV. Of the tafte, 218 
 
 XV. Of fmelUng, 224 
 
 XVI. Of hearing, 248 
 
 XVII. Of the fight, 264 
 
 XVIII. Of the internal jenfes. 290 
 
 XIX. Of maflicationffaliva, and deglutition, 3 1 1 
 
 XX. Of the adion of the flomach on the food, 328 
 
 XXL Of the omentum, 345 
 
 XXII. Of the fpleen, 354 
 
 XXIII. Of the pancreas, 358 
 
 XXIV. Of the liver, gall-bladder, and bile, 361 
 
 XXV. Of the fmall inteflineS, 379 
 
 XXVI. Of the large inteflines, 390 
 
 XXVII. Of the chyliferous vejfels, 3 99 
 
 XXVIII. Of the kidneys, bladder, and urine, 405 
 
 XXIX. JDf the genital parts in man, 420 
 
 XXX. Of the virgin uterus, 435 
 
 XXXI. Of conception, 449 
 
 XXXII, Of nutrition, growth, life, and death, 487 
 
 FIRST 
 
 
Digitized by the Internet Archive 
 in 2016 
 
 htt|is://archive.org/details/firstlinesofphys01hall 
 
FIRST LINES 
 
 O F 
 
 PHYSIOLOGY. 
 
 CHAP. I. 
 
 Of the Animal Fibres. 
 
 I. HE moft fimple parts of the human body 
 
 S are either fluid or folid. The fluid parts, 
 ffi being of divers kinds, we Ihall hereafter 
 M. confider in their moft convenient places. 
 But here the folids, which make the moft Ample and 
 true balls of the body, come firft to be confidered be- 
 fore the hiftory of the other parts. 
 
 2. The yo/zV parts of animals and vegetables have 
 this fabric in common, that their elements, or the 
 fmalleft parts we can fee by the fineft microfcrope, are 
 either fibres, or an unorganized concrete. 
 
 g, A fibre in general may be confidered as re- 
 fembling a line made of points, having a moderate 
 breadth ; or rather as a flender cylinder. And tha£ 
 the more conftant or permanent parts thereof are 
 earth, is demonftratcd from a calcination, or a long 
 continued putrefadtion. 
 
 4. Thefe earthy particles have their connexion and 
 power of cohcfion, not from themfclves or a mere con-* 
 B tadf, 
 
2 ANIMAL FIBRES. Chap. I. 
 
 ta£l, but from the intermediate glue placed betwixt 
 them. This we know from the experiments mention- 
 ed above (3.); and from the eafy experiment by which 
 a burnt hair, whofe parts yet hang together, recovers 
 a degree of firmnefs by dipping in water or oil. Alfo 
 the remains of ivory or bone ihavings, whofe jelly has 
 been extrafted, become friable, like bones which, by 
 long expofure to the weather, are converted into a true 
 earth very ready to imbibe water. But even bones 
 rendered friable by having their gluten extracted, will 
 recover their hardnefs when the gluten is redored. 
 It is this gluten alone which holds together the more 
 fimple parts of animals. 
 
 5. That this glue is compofed of oil combined with 
 v/ater by the vital attrition in animals, appears again 
 from the chemical analyfis of bones and hair ; from 
 the jelly of bones, ivory, and horns ; and from the 
 nature of our aliments themfelves. Nor is there any 
 kind of glue that could more powerfully join the parts 
 of animals together ; as we experience in fifii-glue, 
 and that of joiners or cabinet-makers, &c. 
 
 6. Earthy particles then(g.) cohering longitudinally, and 
 tied together by an intervening cohefive glue (5.'), com- 
 pofe firfimne of the lead or mod fimple fibres, fuch as we 
 have a knowledge of rather from reafon than fenfe. 
 
 7. But the fibres which appear fird to the fight arc 
 of two kinds. The fird kind of thefe fibres is lineal ; 
 namely, fuch as have their length confiderably large in 
 proportion to their breadth ; and which, by difpofing ot 
 the elementary particles in a right line, mud of courl'e 
 lay them generally parallel with the contiguous fibres. 
 Examples of fuch fibres we fee in the bones, and molt 
 eafily in thofe of a foetus ; and likewife in the tendons, 
 ligaments, and mufcles : only we mud always remem- 
 ber, that the eye never reaches to the finalled fibres, 
 but to larger ones made up of the fmalled, and like to 
 them in dendernefs, placed together in a reidiliner-l 
 courl'e. That thefe are not different from the fmalled 
 fibres, we arc perfuaded by the mod accurate micro- 
 
 fcope> 
 
Chap. I. ANIMAL FIBRES. 5 
 
 fcopes of Muyfe and Lewenhoeck ; by which the muf- 
 cular fibres, divided even to the laft, appear fimilar to 
 the larger, till at length they feem mere lines. 
 
 8. The fecond kind of fibres (7.) are thofe in which 
 the breadth is frequently larger than their length. 
 Thefe, when loofely interwoven with each other, are 
 called the cellular tunic ; though the name tunic or 
 membrane is on many accounts very improper. 
 
 9. This cellular fubftance is made up of an infinite 
 number of little plates or fcales, which, by their va- 
 rious direflions, intercept fmall cells and web-like 
 fpaces j and join together all parts of the human body 
 in fuch a manner, as not only fufiains, but allows them 
 a free and ample motion at the fame time. But in this 
 web-like fubfiance there is the greateft diverfity ,in refpedl 
 of the proportion betwixt the folid parts and intercepted 
 cells, as well as the breadth and ftrength of the little 
 plates, and the nature of the contained liquor, which 
 is foinetimes more watery, and fometimes more oily : 
 and likewife in the mixture of fibres and threads; of 
 which in fome parts, as in the coats of the arteries, 
 there is a great number ; in others, as under the Ikin, 
 fcarce any. 
 
 10. Out of this net-like cellular fubftance, com- 
 pared by the little plates concreting and prefied together 
 by the force of the incumbent mufcles and diftending 
 fluids, or from other caufes, arife broad and flat plates 
 or fldns in various parts of the body, which, being ge- 
 nerally difpofed in a rerilineal diredtion, are more 
 properly called membranes ; or, being convoluted into 
 cones and cylinders, pervaded by a flux of fome juice 
 or liquors through their cavities, put on the name of 
 vejfels ; or elfe, being extended round fome fpace that 
 is in a plane parallel to itfelf, we call it a tunic or coat. 
 But that tunics or coats are formed out of the cellular 
 fubftance is proved by ocular infpedlion, efpecially in 
 the aorta, fkin, pericardium, or dura mater, by mace- 
 ration ; and the coats of the mufcles are thus evidently 
 of a cellular fabric, fimilar to that of other tunics. 
 
 B 2 The 
 
4 ANIMAL FIBRES. Chap. I. 
 
 The fame thing is alfo proved from the eafy change of tlie 
 dartos, and the nervous membrane of the inteftines, 
 by inflation, into a cellular fubftance ; from the hard 
 and thick membranes about encyfted tumors, and 
 which have their origin only in the cellular texture ; 
 and, laftly, from that membrane which, being gra- 
 dually compaded mod firmly together, forms the true 
 Ikin lying under the epidermis, and being thence con 
 tinned is partly refolved into the fubcutaneous cellular 
 texture which is filled with fat. 
 
 1 1 . All the veflels with which we fee tunics com- 
 monly painted, arc an addition to the cellular net- 
 work, and in nowife conftitute the nature of a mem- 
 brane, but are fuperadded to the membrane itfclf, 
 which is fird formed of the cellular net-like fubdance. 
 Betwixt the maflres or fpaces of the intedinal net-work 
 of velfels, perfedly well filled by the Ruyfchian art of 
 injedion, we dill fee that the white cellular fubdance 
 which remains greatly exceeds the bulk of the vtlTels, 
 although, by their preternatural didendon, they take 
 up more room by dlling more of the fjjace. But for 
 membranes compounded of fibres interwoven with or 
 decuffating each other, I know of none fuch ; unlefs 
 you will take ligamentary or tendinous fibres for them, 
 which yet are fpread only over the face of fome true 
 membrane. 
 
 12. This cellular webdike fubdance in the human 
 body is found throughout the whole, namely, where- 
 ever any vefl'el or moving mufcular fibre can betraeed ; 
 and this without the leafh exception that I know of. 
 
 i:^. The other elementary fubdance of the human 
 body (2.) which cannot be truly called cither a fibrous 
 or cellular plate, is a mere glue evafared and concreted, 
 not within the fibres, but in fpaces betwixt them. In 
 the bones this extravafated fubdance is manifed 
 enough : for you fee the fibres very diftind in the 
 bones of a foetus, in the intervals betwixt which you 
 perceive the veflels running ; fo that every bone in the 
 ikull, on all fides, refemblcs the teeth of a comb. But 
 
Chap. I. ANIMAL FIBRES. 5 
 
 this fabric is fo altered in an adult perfon, that the juice 
 being extravafated in the fpaces betwixt the fibres, and 
 the intervals thereby filled up, as happens with the juice 
 of madder, plates are then formed of the teeth above 
 mentioned cemented together. The cartilages feem 
 to be fcarce any thing befides this glue concreted. 
 
 14. But here the courfe of nature feems to be fuch, 
 that even the filamentary fibres ( 3.) are all firft formed 
 of fuch a transfufed glue. And that the membranous 
 or fcaly fibres of the cellular fubftance (7.) are thus 
 formed, appears from thofe cellular fibres produced in 
 the thorax from a concreted vapour, v/hich joins the 
 furface of the lungs to the pleura ; for thefe perfedtly 
 refemble the true and natural cellular fubftance. The 
 fame appears alfo from a comparifon of the foetus 
 with an adult ; for the large fubcutancous cellular fub- 
 ftance has in a foetus a mere jelly in its ftead inter- 
 pofed betwixt the Ikin and mufcles, wftiich laft we ob- 
 ierve very firm in a foetus : from the morbid diftblution 
 of the membranes of the mufcles into a mere glue : 
 and from a fimdlar change into glue or fize, made on 
 the fkin, tendons, and ligaments of animals, by means 
 of boiling water. This theory is alfo illuftrated from 
 clots of coagulated blood, the fanguineous membranes 
 of Ruyfch, Albinus’s membranes formed of mucus, 
 polypus, filk, and glue. Laftly, that the bones 
 themfelves are formed of compared gluten, is fhown 
 from difeafes in which the hardeft bones, by a lique- 
 faction of their gluten, return into cartilage, flefh, and 
 jelly : fimilar changes are made on the bones of fifties 
 and other animals by Papin’s digefter. 
 
 1 5 . It feems, then, that a gelatinous water, like the white 
 of an egg, with a fmall portion of fine cretaceous earth, 
 firft runs together into threads, from fome preiTure, the 
 caufes of w'hich are not our prefent concern. Such a 
 filament, by the mutual attraction of cohefion, inter- 
 cepting fpaces betwixt itfelf and others, helps to form 
 a part of the cellular net-like fubftance, after having 
 acquired fpme toughnefs from the neighbouring earthy 
 
 particles. 
 
6 
 
 CELLULAR SUBSTANCE. Chap.I. 
 
 particles, which remain after an expulfion of the re- 
 dundant aqueous glue. And in this net-like fubftance, 
 wherever a greater prelfurc is impofed on its fcales or 
 fades, they turn into fibres and membranes or tunics ; 
 and in the bones, laftly, they concrete with an unor- 
 ganifed glue (4.) Hence, in general, all parts of the 
 body, from the fofteft to the hardefl, feem to differ no 
 otherwife than as the latter have more of the earthy 
 particles more clofely compacted together, with lefs of 
 the aqueous glue ; while in the fofteff parts there is 
 lefs earth and more glue. 
 
 CHAP. II. 
 
 Of the Cellular Substance and its Fat. 
 
 16. I HE cellular fabric is made up of fibres and 
 A plates (9.), which are neither hollow nor vaf- 
 cular, but folid; although they are afterwards painted 
 by an acceffion of veffels. But the principal differences 
 of this fabric are the following. In fome parts of the 
 body it is open and loofe, being formed of long and di- 
 ftant plates ; in others, it is thin and compact, being 
 made up of fhort fibres concreted together. I find it 
 fhorteft betwixt the fclerotica and choroides of the eye, 
 and betwixt the arachnoides and pia mater of the brain. 
 I aifo find it tender, but more conipicuous, betwixt every 
 two coats of the inteflines, ftomach, bladder, and ure- 
 ters ; in the lungs, where it obtains the name of veficies ; 
 under the pulp of the glans penis ; and between the fmall 
 kernels of the vifeera and glands. It is cornpofed of 
 longer fibres, where it is extended over the larger vef- 
 fels, under the name of capjule or vagina ; as through 
 the vifeera, and particularly the liver and lungs ; and is 
 vaflly firmer in the veffels which go to the head and 
 joints. Its principal ufe is to bind together the contigu- 
 ous membranes, veffels, and fibres, in fuch a manner as 
 to allow them a due or limited motion. But the cellu- 
 lar 
 
Chap. II. CELLULAR SUBSTANCE. 7 
 
 iar fubftance, fo far as we have hitherto defcribed it, 
 hardly ever receives any fat; it is moiftened by a wa- 
 tery vapour, gelatinous and foinewhat oily, exhaled out 
 of the arteries and received again into the veins. The 
 truth of this is eafily deinonilrable from injedions of 
 oil and water, either alone or with fifh-glue, made in all 
 parts of the body. When this vapour is wanting, the 
 iinall hbres grow one to another, and the contiguous 
 membranes or plates are cemented into one, with a lofs 
 of their motion. 
 
 1 7. The cellular texture is more lax, and formed of 
 plates rather than fibres, where it divides the mufcles 
 and all their fibres, even to the ultimate fibre ; where it 
 furrounds and fufcains the leafl vefTels with their free 
 motion ; and within the cavities of the bones, where it 
 is alfo made up of bony plates, with membranous ones 
 intermixed. That is Jikewife very lax, which, under the 
 furface of the body, is every where interpofed betwixt 
 the mufcles and the fkin ; but the laxefl of all is that 
 which furrounds the genital parts of the male with very 
 wide cells. 
 
 18. Into the empty fpaces of this cellular texture 
 (17.) is poured almofl every where in the foetus, firfl a 
 gelly, then a grumous, and laftly a clotted fat, ail under 
 the fein, and in its fmall hollows. It is compofed of an 
 infipid inflammable liquid, lighter than water, which in 
 a cold air concretes into a folid, efpecially about the 
 kidneys ; and in graminivorous animals, in fiflaes, pro- 
 bably alfo in man, while they are alive, it is very nearly 
 fluid, although apt to be indurated. In it, along with 
 the oil, is united an acid fait in quantity almofl equal to 
 the fixth part of the oil. 
 
 19. Through this cellular texture the blood-vefiels 
 run and are divided ; from the arterial extremities of 
 which the fat is depohted and abforbed by the veins. 
 This paffage, from the arteries into the adipofe cells, is 
 fo free and fhort, that there muil needs be very large 
 mouths by which they open, and by which they give 
 admittance to, iniedted mercury, air, water, diSblved 
 
 fifh- 
 
8 CELLULAR SUBSTANCE. Chap. II. 
 
 fifh-glue or jelly, and oil not excepted, which is always 
 very fluggilh in paffing through the veiTels even of li- 
 ving animals. Thefe are I'ecreted not by any long ducts, 
 but by tranfuding on all fides through the whole extent 
 of the velTel j infomuch that, when an artery is filled or 
 injected with water, there is no part of the furrounding 
 cellular fubflance but what fwells with the moifiure. 
 The warm fat, during the pulfation of the arteries, ea- 
 fily finds out the fame paflages. How quickly it is col- 
 lected, appears from the fpeedy renovation of it, by a 
 returning fatnefs after acute difeafes. 
 
 2 0. But that this fat is abforbed by the veins, we are 
 taught from the hidden effects which exercife of the 
 mufcles more efpecially has in confuming the oil of very 
 fat animals ; alfo from the confumption of our fat in 
 fevers ; from the cure of dropfies, where the water 
 transfufed into the cellular fubflance is in a manner 
 abforbed and thrown out by the inteflinal tube ; and, 
 laftly, from the tranfuding of water and oil from the 
 venous orifices, when injefted by the fyringe. Whe- 
 ther the nerves are fpread upon the adipofe cells, is a 
 queflion. But it is certain they in mofl parts run through 
 this fubflance, and hereby divide, in their courfe, into 
 the minutefl filaments, fo fmall that you can no longer 
 trace them by the knife. But then the fat is both infen- 
 fible and unirritable. 
 
 2 I . The intervals or fpaces betwixt the plates or 
 fcales of the cellular membrane, are every where open, 
 and agree in forming one continuous cavity throughout 
 the whole body. This appears from the inflation which 
 butchers, and likewife the lurgeons of Ethiopia, make by 
 a wound of the Ikin, and which raifes the fkin all over 
 the body ; alfo from an ephyfema, in which the air re- 
 ceived by a wound of the fkin, being retained, caufes 
 a fw'clling throughout the whole furface of the body ; 
 the paffage of bodies, put under the fkin, to a place re- 
 mote from that at which they entered ; the paffage of 
 pus, from an inflamed place to remote ulcers ; and, fi- 
 nally, from difeafes, in which a watery or ferous humour 
 
Chap.il cellular substance. ^ 
 
 is depofited into all the cells of this net-like fubftance 
 throughout the body, and is emptied from them all by 
 a fingle incifion. That none of the cellular fabric is ex- 
 cepted from this communication, appears from cafes 
 wherein the vitreous body of the eye has received the 
 flatus of an emphyfema; and again from difeafe, in 
 which the gelatinous ferum of a dropfy has been found, 
 transfufed even into the cavernous bodies of the penis. 
 
 2 2. The great importance and ufe of this cellular 
 fubftance, in the animal fabric, muft be evident to all 
 who confider, that from this part alone proceeds the due 
 ftrmnefs and ftability of all the arteries, nerves, and 
 mufeuiar fibres of the body, and confequently of all the 
 flefhy parts and vifeera formed from thence ; and even 
 the figures of the parts, their juft length, cavities, 
 curvatures, flexures, and motions, depend entirely on 
 the cellular membrane, in fome places of a lax and in 
 others of a more denfe and hard fabric ; That out of 
 this fubftance, joined with veffels, nerves, mufeuiar and 
 tendinous fibres (a great part of all which are before 
 formed of this fubftance only), all the vifeera, all the 
 mufcles and glands^ with their ligaments and capfules, 
 are entirely compofed *, and that only from the different 
 length, tenfion, quantity or proportion of this the di- 
 verfity of our glands and vifeera arifes ; and laftly, that 
 this alone makes up by far the greateft part of the 
 whole body, as we are certain, although the whole be 
 not formed out of cellular filaments of this kind. 
 
 2^. This fubftance hath a contradlile power, diffe- 
 rent from that of irritability, which, though not de- 
 monftrable by experiments, for the moft part difpofes 
 the cellular fibre to fhorten itfelf after having been 
 ftretched. This power, excited by cold, renders the 
 fkin rigid ; raifss the hairs ; draws up the ferotum ; and, 
 after geftation, reftores the fkin of the abdomen, and 
 the uterus, to their former fize. The fame force, by a 
 gentle but continual contradion, promotes the fecretion 
 of the fat, the liquors of the fubcutaneous and other 
 glands, and pus : in the veins and receptacles, it refills 
 
 C dilatation j 
 
io CELLULAR SUBSTANCE. Chap. II. 
 
 dilatation; and, when that is taken ofF, it reflores the 
 part to its former fize. In the foetus, this gentle force 
 is among the principal caufes of the change that hap- 
 pens to the body. 
 
 24. The ufes of the fat are various ; as to facilitate 
 the motions of the mufcles in all parts, leffen their at- 
 'trition againft each other, and prevent a ftiffnefs or 
 
 rigidity: it fills up the intermediate fpaces betwixt the 
 mufcles, with the cavities about many of the vifcera, in 
 fuch a manner, that it readily yields to their motions, 
 and yet fupports them when at reft : it principally con- 
 ftitutes the weight of the body ; conducts and defends 
 the veffels : it gives an uniform extenfion to the fkin ; 
 and, ferving as a cuftiion to eafe the weight of the body, 
 renders the whole of a comely, agreeable ftiape : it pro- 
 bably, by mixing with many of the humours, abates 
 their acrimony : it has a principal ftiare in forming the 
 matter of the bile; and, by tranfuding through the car- 
 tilaginous incruftations of the bones, it mixes with the 
 articular liquid, and by abforption ferves to fmear 
 their fibres : by exhaling through the pores of the Ikin, 
 it keeps off the inclement drying quality of the air : alfo, 
 by exhaling in a living perfon from the mefentery, me- 
 focolon, omentum, and round the kidneys, it lubricates 
 the furfaces of the vifcera with an oily emollient vapour; 
 and, by interpofing betwixt their integuments, prevents 
 their growing one to another. 
 
 25. The fat is depofited into the cells of this fub- 
 ftance by fleep, reft of body and mind, and a diminilh- 
 ed force of circulation ; whence, being collected in too 
 great a quantity, it proves injurious by comprdfing the 
 veins ; and, by caufing too great a refiftance to the heart, 
 it makes a perfon fhort-breathed, and liable to an apo- 
 plexy or dropfy. The fame humour is taken up by the 
 veins ; and, being rapidly moved along the arteries, is 
 confumed by violent exercife, venery, watchings, cares 
 of^ the mind, a falivation, diarrhcea, fever, fafting, or 
 fuppuration. When reftored to the blood, it increafes 
 acute difeafes, tinges the urine, and forms a part of its 
 
 fediment. 
 
II 
 
 Chap. III. ARTERIES. 
 
 fediment. After a fudden confumption of it, it is foon 
 renewed again from good juices, or healthy humours : 
 but, in a languid habit, a gelly, inftead of fat, is depo- 
 fited into the cells ; and this caufes the dropfy we call 
 anafarca, together with an external hydrocele or watery 
 fwelling. 
 
 CHAP. III. 
 
 Of the Arteries and Veins. 
 
 26. HE membranes we fhall hereafter better de- 
 X fcribe, each in its refpeftive place. Of 
 thefe membranes there are feveral common to the ar~ 
 teries ; which are long extended cones, whofe dia- 
 meters decreafe as they divide into more numerous 
 branches. But where the arteries run for fome length, 
 without fending off large branches, their convergency is 
 not very evident ; and at length, where they are called 
 capillaries, and wherever they give paffage to only a fmgle 
 red globule, they are either cylindrical, or very nearly 
 fo, from the imperceptible diminution ; but their tranf- 
 verfe fedlions are every where and without exception 
 circular, when the artery is full. Where they fend off 
 large branches, the light or cavity is there fuddenly di- 
 minifhed, infomuch that they might be taken for a 
 chain of cylinders, of which every one is narrower 
 than the preceding. If you reckon them cones, then 
 the common bafis of the cone in all arteries is either in 
 one or the other ventricle of the heart ; and the apex 
 of the cone terminates either in the beginning of the 
 veins, or in the beginning of the cylindrical part of the 
 artery, or in the exhaling veffel, unlefs it is cylindrical. 
 In fome places they feem to diverge or dilate ; at lead: 
 they become there of a larger diameter, after they have 
 been filled or dillended with wax ; which poffibly may 
 arife from fome ftoppage of the wax, by whofe impulfe 
 that part of the length of the artery becomes more di- 
 
 C 2 ftended 
 
12 
 
 ARTERIES. Chap. IIT. 
 
 {tended than the reft. Examples of this kind we have 
 in the vertebral artery, at the bafts of the Ikull, in the 
 fplenic artery, in the flexure of the carotid artery, ac- 
 cording to Mr Cowper’s injections ; and, laftly, unlefs 
 all my experiments deceive me, in the fpermatic arte- 
 ries. In all places, likewife, where the ramifications be- 
 gin, the diameter of the artery is a little increafed. 
 
 27. There is indeed no external coat perpetual and 
 proper to all the arteries ; but the office of fuch a coat 
 is fupplied to fome of them by one fingle external and 
 incumbent integument, which in the thorax is the 
 pleura, and in the abdomen the peritonseum. In the 
 neck, arm, and thigh, a fort of thicker cellular fub- 
 ftance furrounds the arteries. The membrane of the 
 pericardium, which on all Tides clofes round the aorta, 
 returns back with the veflfels to the heart. The dura 
 mater imparts a capfule that furrounds the carotid ar- 
 tery as it pafles out through a hole in the fkull. But 
 the firft true external membrane common to the arte- 
 rial tube in all parts of the body, is the cellular fub- 
 ftance, which in fome parts (as in the thorax) we fee 
 replenifhed with fat. 
 
 28. This cellular coat is, in its external furface, of a 
 more lax texture, painted with a great many fmall arte- 
 ries and veins ; and it has nerves running through its 
 fubftance, which are none of the fmalleft. There is 
 fometimes fo much of this cellular fubftance about the 
 artery as might occafion one to think it hardly belonged 
 to it as an external coat or lamella, but rather as fome 
 foreign net-work added to this veffel. Thus we find it 
 in the arteries of the neck, groins, and fubclavians ; in 
 the mefenteric, coeliac, and hepatic arteries ; where it is 
 chiefly interwoven with long fibres. And thefe are the 
 vaginae or capfules of the arteries, formerly obferved 
 by fome eminent anatomifts. 
 
 29. As this cellular coat advances more inward, and 
 nearer to the light and capacity of the artery, it be- 
 comes more denfe^ folid, and is tied more clofely toge- 
 ther by a kind of wool, and may be called the proper 
 
 coat 
 
Chap. III. ARTERIES. 13 
 
 ceat of the artery. That there is no tendinous coat of 
 the arteries diftinft from this laft part of the cellular 
 fubftance, is evident from maceration, whereby the in- 
 ner ftratum of this arterious tunic changes into a cel- 
 lular fabric. 
 
 30. Within the former, and nearer the light or ca- 
 pacity of the artery, it has a coat of mufcular fibres^ 
 which are in general imperfecl circles : that is to fay, 
 no fibre any where makes a complete circle round the 
 veffel ; but a number of fegments conjoined together, 
 with their extremities turned off fideways, feem to form 
 one ring round the artery. Thefe fibres, in the larger 
 arterial trunks, form many firata, appear of a reddilh 
 colour, and are remarkably firm and folid ; but in the 
 fmaller arteries they are by degrees more difficult to 
 demonftrate, and feem to be wanting in the arteries of 
 fmall animals. 1 have never obferved them to run along 
 the vefl'el lengthwife. Under thefe membranes, but 
 pretty difficult to demonftrate, is an exceeding ffiort 
 cellular texture, into which a chalky concreting matter 
 is poured when an artery offifies. 
 
 31. The innermofl coat of the artery is thin, and fine- 
 ly poliffied by the influent blood ; fo as to form a Angle 
 incruftation that every where lines the fleffiy fibres, 
 which are not very continuous one to the other, and 
 prevents the blood from infinuating into the fpaces be- 
 twixt them. It is every where fmooth and without 
 valves ; although, from a fort of mechanical neceffity, 
 fdinetimes certain folds, raifed into a femicircle at the 
 origination of branches, form a projefting eminence ; 
 as we fee at the branches produced by the arch of the 
 aorta. Yet, in arteries of the vifcera, the innermofl 
 coat is fofter, lax, wrinkled, and almofl friable, efpe- 
 cially in the dudus arteriofus. 
 
 32. The arteries themfelves have arteries which are 
 more particularly fpread through their external cellular 
 coat ; and, fpringing on all fides from the next adjacent 
 fmall arterial trunks, form numerous branchy net- 
 \vorks, which are all of them indeed very minute, but 
 
 plainly 
 
14 ARTERIES. Chap. III. 
 
 plainly appear, even in the foetus without injection, to 
 be very numerous. There are alfo nerves which de- 
 fcend for a long way together through the furface of the 
 artery, and at Tall vanifh in the cellular fubftance of the 
 veffel ; of which we have a fpecimen in the external 
 and internal carotids, and arch of the aorta. And from 
 thefe, do not the arteries feem to derive a mufcular and 
 eonvulfive force, very different from that of their fimple 
 elafticity ? Does not this force fhow itfelf plainly e- 
 nough in fevers, faintings, palfy, and confumption, and 
 paffions of the mind ? But the artery is in a manner 
 infenfible and unirritable ; and if it is conftricfed by the 
 application of poifons, it has this in common with the 
 dead fkin. 
 
 The fedions, or divifions, of arteries (howthem- 
 felves with a round light, or hollow capacity, becaufe 
 they are elallic ; and this is the reafon why, from the 
 fmall arteries of the teeth, haemorrhages are fometimes 
 fatal. The aorta, indeed, of the thorax and abdomen, 
 the carotids of the neck, and fome other arteries of the 
 dead body, from their leffened extenfion, appear fome- 
 what fiat or depreffed ; but their round figure, or cir- 
 cular feftion, is every where reftored by injedlion. 
 Their elajiicity is alfo evident in that powerful com- 
 preffure, which a fegment of a large artery makes upon 
 the finger that diftends it, and which is much ftronger 
 in a dead than in a living body. In the living body, 
 indeed, this force yields to that of the heart ; but in- 
 ffantly recovers itfelf, when the heart is relaxed, and 
 reffores the artery to its former diameter ; and this 
 makes the pulfe, whofe full explication ought to be 
 preceded by an hiftory of the heart : at prefent, it may 
 fufiSce for us to fay, that all the arteries have this pul- 
 fation, although the fyftole and diaftole thereof can be 
 perceived by the finger, only in the larger, not in the 
 fmaller ones naturally ; and in the ultimate inflexion of 
 the arteries, the pulfe totally vaniliies ; but, by an in- 
 creafed motion of the blood, even the leffer arteries 
 niake a violent pulfation, as we fee in an inflammation. 
 
 Thefe 
 
Chap. III. ARTERIES. 15 
 
 Thefe veffds ftrongly contrad lengthwife, and are ren» 
 dered fl^orter on dilfedion. 
 
 3^. The Jlrength of the arteries is confiderablc 
 enough : but as the denfe, hard net-work of the outer 
 cellular coat refufes to yield to a dillending force, it 
 breaks without much difficulty, almoU ealier than the 
 coats of the veins ; and from thence arife aneurifms. 
 But, in general, the trunks are, in all parts of the bod)'-, 
 weaker, and the branches llronger, in their coats ; 
 whence the impulfe of the blood may exert a conli- 
 derable elfed upon the former, but leaf! of all on thofe 
 of the limbs. From hence it is, that aneurifms are moll 
 frequently formed near the heart ; for, in the lower ex- 
 tremities, the llrength of the arteries, and of the veins 
 too, is much increafed, as well as in the fecreting or- 
 gans. 
 
 35. With regard to the courfe and general diftribution 
 of the arteries, nature has every where concealed them, 
 except in a few' membranes. But ffie hath difpofed of 
 the trunks every where in places of fafety, becaufe 
 wounds cannot happen to the fmaller of them without 
 danger, nor to the larger without lofs of life. The Ikin 
 is fpread with numerous ffiort and fmall arterial trunks ; 
 but the larger ones, defended by the fkin and mufcles, 
 creep along near the bones. In general, the arteries 
 are in proportion to the parts of the body to which 
 they are fent. The largell go to the fecretory organs, 
 the brain, and fpieen ; the lefler ones to the mufcular 
 parts. 
 
 36. The proportion of the light or cavity of the ar- 
 tery to its folid part is not every where the fame, nor is 
 it conflant even in the fame artery. This proportion, 
 in the firft place, is leall of all at the heart, and in- 
 creafes as the arteries remove farther from it. Second- 
 ly, in a full-fed plethoric animal, whofe blood paffes 
 freely, and with great force, through its arteries, the 
 proportion of the folid parts of thefe velfels is lefs than 
 in a familhed extenuated creature, whofe blood hath a 
 feeble motion. 
 
 37. From 
 
i 6 ARTERIES. Chap. III. 
 
 37. From the trunks of all the arteries branches are 
 fent forth, and from thefe again proceed lelfer twigs 
 by a numerous divifion, of which you can fcarce find 
 the end, though you may perhaps count twenty fubdi- 
 vifions of this kind. Here the lights or feclions of any 
 two branches, taken together, always exceed the light 
 of the trunk from whence they come, in nearly a fcf- 
 quialteral proportion, or as one and a half to one, or 
 fomewhat lefs. Alfo every trunk, juft above its divi- 
 fion, is fomewhat broader or more expanded. The 
 angles, at which the branches go out from their trunks, 
 are generally acute, either half right angles or nearly 
 fo ; to the forming of which angles, as we fee in me- 
 chanics, there is required thelongeft projcftion. In- 
 ftances of their going off at right angles, or nearly fo, 
 we have in the lumbal or intercoftal arteries ; of their 
 going off in a retrograde or reflefted courfe, we have 
 one inftance in the coronaries of the heart, and ano- 
 ther inftance in the fpinal arteries, which are produced 
 by the vertebrals. But, generally fpeaking, thofe 
 which are efteemed retrograde or reflexed were fent 
 off, at their origin, in acute angles; fuch as the afcend- 
 ing artery of the pharynx, the defcending one of the 
 palate, the umbilical mammary arteries, and the nutri- 
 tious ones of the large bones. Laftly, we often ob- 
 ferve large branches arifing under leffer angles, and 
 fmaller ones under greater angles : but it is rarely that 
 we obferve two arteries of a large diameter run toge- 
 ther into one trunk. An example of this, however, 
 we have in that artery which is formed out of the ver- 
 tebrals ; in the fmaller ones it is frequent, as in both 
 the fpinal arteries, and that of the fincipital foramen. 
 In many parts, the arteries have repeated alternate un- 
 dulations or flexures, as they run on in a fpiral courfe, 
 wherein we fee their diameter often confiderably en- 
 larged, as in the large inteftines, womb, face, fpleen, 
 lips, and iris. Even the ftraight arteries in other 
 places, if too much diftended, fall into ferpentine 
 flexures. Sometimes they are fuddenly twifted into a 
 
 kind 
 
Chap. III. ARTERIES. 17 
 
 kind of circles, as the carotids under the mammillary 
 procefs. 
 
 3 8. The arteries are frequently conjoined one to 
 another by intermediate branches, in fuch a manner, 
 that the twig of fome certain artery fliall run to meet 
 one of the fame kind from anodier neighbouring arte- 
 ry, and, by joining together with that, form one trunk. 
 Inllances of this kind we have among the large trunks 
 in the inteflines, among the middling ones in the kid- 
 neys, womb, &c. and among the fmaller ih all parts of 
 the body ; infomuch that there is no part of the human 
 body wherein the neighbouring arterial trunks, whe- 
 ther of the fame or of different denominations, do not 
 form anaftomofes or joinings one to the other by in- 
 termediate branches. Of rings diverging laterally 
 from the arteries, and returning again into themfelves, 
 we have inllances in the eye and brain. The extremi- 
 ties of the arteries, which are either cylindrical or near- 
 ly fo, fend off fmaller branches, which, for their ex- 
 tent, are more numerous, and generally difpofed like 
 a net ; fo that each branch, by its fmaller twigs, forms 
 anaftomofes with thofe of its neighbouring branches : 
 and thus we find it in all membranes. By this means it 
 happens, that, though the palfage from the heart to 
 any part of an artery is obftrudled, the blood may ne- 
 vertheiefs flow through the neighbouring arteries into 
 ail the branches of the obftrudled one. Thus a gan- 
 grene or languor of the part is very ftrongly prevent- 
 ed, and the obftruftion is more eafily refolved by the 
 repulfion of the obftacle into the larger part of the 
 trunk. 
 
 39. Laftly, one of the leaft arteries is either chan- 
 ged by a continuation of its canal into a vein, in fuch 
 a manner, that the ultimate little artery, which is ge- 
 nerally reflected, having furpaffed the angle of its re- 
 flgction, becomes now a fmall vein ; or elfe a branch, 
 fent out at right angles from the artery, is inferted un- 
 der a like angle into the branch of a fmall vein. Both 
 thefe kinds of mechanifm are demonftrated to us by 
 
 D the 
 
28 ARTERIES. Chap. III. 
 
 the microfcope, and the eafy return of injeclions thro’ 
 the veins into the arteries. And thefe vafcules we fee 
 fometimes large enough to receive only one, and fome- 
 times feveral blood-globules at a time. A large artery 
 is never obferved to open into a vein. 
 
 40. In the vifcera, we find the fmall arteries difpo- 
 fed not ib much in net-works as in a dilferent fabrica- 
 ture, wherein the fmall branches defcend very thick, 
 or in clufters, parallel to the trunk, fo as to refemble 
 brufh-pencils, a variety of little trees or bufhes, fmall 
 ferpents, or threads, according to the various difpofi- 
 tion of the parts. 
 
 41. Sometimes the arteries end in another manner, 
 namely, by being converted into veffels of the fmaller 
 kinds. Thefe are fometimes continuous to the arte- 
 ries and real arterial trunks, as will be obferved in the 
 ophthalmic artery, upon tracing the arteries of the tu- 
 nica choroides, or the colourlefs ones of the circle of 
 the uvea and iris. That a net-work of pellucid arteries 
 is continuous with the red branches of the ophthalmic 
 one, is evident from inflammations, and the rednefs of 
 the parts when relaxed by vapour or by cupping ; 
 from repletion, and the microfcopical experiments of 
 Lieberkuhnius upon frogs, in which colourlefs glo- 
 bules were feen to pafs from a red artery into a lateral 
 velfel. In a fabric of this kind the red blood is eafily 
 forced into the fmaller vefl'els. 
 
 42. In other places the fmaller veffels feem to pro- 
 ceed laterally as branches from the trunks of the leafl 
 fanguineous arteries, and are drawn out into trunks 
 {till fmaller. Thefe are called excretory duds. It is 
 with difficulty that thefe veffels are filled with red 
 blood ; of this, however, we have examples in the 
 kidneys, the liver, and breafts. Indeed the blood, 
 when vitiated, penetrates the excretory duffs of the 
 whole body, even without hurting the veffels, nor is 
 that aberration found to be productive of any evil con- 
 fequence after the diforder of the blood is cured. 
 
 43. Another 
 
Chap. III. ARTERIES. ig 
 
 43. Another termination of the arterial extremities 
 is i}ito the exhaling vejfels ; and this is a manner of their 
 ending very frequently to be obferved in all parts of the 
 body. The whole fldn, all membranes of the human 
 body which form any clofe cavity, all the ventrides of 
 the brain, the anterior and poflerior chambers of the 
 eyes, all the adlpofe cells and pulmonary veficles, the 
 whole cavity of the ftomach and inteflinal tube, thro’ 
 which the air has a paffage, are all of them replenifhed 
 with exhaling arteries of this kind. Thefe breathe ou6 
 a thin, watery, gelatinous humour, which, being col- 
 lected together by (landing, fometimes makes no in- 
 confiderable quantity; and, particularly by difcafe or 
 death, is converted into a watery, but coagulable 
 lymph. The truth of this is eafily demonflrable from 
 the watery fweat that enfues after injeCling the arteries 
 with that liquor warm. In fonre places, indeed, they 
 exhale, not a thin vapour, but blood itfelf, as we fee 
 in the heart, the cellular fabric of the penis, urethra, 
 clitoris, and nipple of the female breaft ; in all which 
 the blood itfelf is naturally poured out.' Does not eve- 
 ry fecretion that is made in true glands or hollow cryp- 
 tas bear fome analogy to this exhaling fabric ? 
 
 44. Whether or no, in all parts of the human body, 
 do the pellucid veffels arifmgfrom the fanguineones, and 
 carrying a humour thinner than blood, again fend out 
 other fmaller veffels to be fubdivided into ftill leffer or- 
 ders? ~We feem, indeed, not to want examples of 
 this in the manner propofed to us by the moft cele- 
 brated profeffors. That the aqueous humour is fepa- 
 rated by very fine veffels, generated from the colour- 
 lefs arteries of the iris, is very probable. That the red- 
 coloured veffels in the cortical fubftance of the brain 
 feparate a juice, pervading the medullary fubftance, by 
 the intermediation of another order of veffels, we are 
 almoft certain. And the like we are perfuaded from 
 an eryftpelas or yellow inflammation, arifing from the 
 yellow or ferous globules impaCled into fmaller vef- 
 fels. 
 
 D 2 
 
 45. It 
 
20 
 
 ARTERIES. Chap. IR. 
 
 45. It may be then afked, If there are not yellow 
 arterious veffels of a fecond order, which fend off lym- 
 phatic ones of a third order, from whence by degrees 
 If ill leffer kinds of veffels branch out? Such a fabric 
 does not feem agreeable to the very eafy tranfuion that 
 is made by the blood, mercury, or \vax, into the ex- 
 haling and perfpiratory veffels, or into the uriniferous tu- 
 buli, with the adipofe and pulmonary cells ; nor is it 
 very difficult for the blood to ftray into the lactiferous, 
 lymphatic, and lachrymal duCts, whither it ffiould 
 feem not able to penetrate, if it went through any ’ 
 other intermediate vafcular fyffem, fmaller than the 
 blood-globules, which make the fame journey. Nor 
 can this fyffem be allowed by the great impediment or 
 retardation that muif arife to the humours in a third, 
 and much more in the leffer orders of veffels, 
 
 46. The Veins, in many particulars, rcfemble 
 the arteries. There are fix, of which two anfwer to the 
 aorta, and the remaining four to the pulmonary artery. 
 Their bafis is in the ventricles of the heart, and their 
 apices in the extremity of each branch, through ail parts 
 of the body, excepting one inftance in the liver. And, 
 in a great number of parts, they run parallel with the 
 arteries, one by the fide of the other ; but yet they 
 differ from the arteries in various refpeCfs. 
 
 47. The fabric of the veins is flender, every where 
 finooth, difficultly feparable into diffincf coats or mem- 
 branes, like tli« arteries; and the cellular texture fur- 
 rounding this fabric is very eafily diftend^d. This fa- 
 bric, both above and below the heart, is furrounded, 
 except in one place, with mufcular fibres. Every 
 where, however, it is lax, like the cellular texture of 
 the arteries by which they are joined to the other parts 
 of the body. Notwithlfanding this {lender fabric, the 
 veins are every where fufficiently firm, and do not 
 eafily burft with inflated air ; being, in inofl inftances, 
 ftronger than the arteries themfelves. But they bura 
 much more eafily in living than in dead animals, as 
 appears from morbid inftances in the arm, face, leg, 
 
 thigh, 
 
Chap. III. VEINS. 21 
 
 thigh, &c. Nor do they fupport themfelves like cy- 
 linders after being divided, but they collapfe together, 
 lb as to make their light or capacity appear like a flit ; 
 except they are fuflained and hindered from collapfing 
 thus by fome ftronger cellular fubftance placed round 
 them, as we fee in the liver and womb. They are but 
 nightly irritable, unlefs the ftimulus be of the chemical 
 or more acrid clalTes ; for, in that cafe, they contrad 
 themfelves with a convulfive force greater than that 
 of the arteries. They have no pulfation, if we may 
 trull all accounts, unlefs the venous channel is fome- 
 where obftrufted ; or when, in dying people, the 
 blood is thrown back again from the right apricle into 
 the defeending and afeending cava, or when falling 
 back from the brain. 
 
 48. The veins are m.uch larger than their corre- 
 fponding arteries, having the fquare of their diameter 
 often double or triple that of the latter ; and, in fome 
 places, almofl quadruple ; as near as the emulgents 
 and veffels of the kidneys. In general, however, the 
 diameter of the veins is to that of the arteries as nine 
 to four ; yet the capacity of the capillary veins but 
 little exceeds that of the arteries which accompany 
 them. They differ likewife 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 larger veins are alfo branched in a 
 more net-like difpofition, by forming more frequent 
 anaftomofes one with another ; for not only the fmall- 
 er branches, but even the larger trunks, of the veins, 
 are conjoined one to the other within its neighbour- 
 hood, upper with lower, and right with left, by appa- 
 rent inlets or inofculations. They affedl to run near 
 the furface of the body ; and through the limbs, neck, 
 and head ; they run a long way covered with little 
 more than the bare fkin, which is a circumftance we 
 very rarely obferve in arteries ; and, for the fame rea- 
 fon, they often go out, in their courfe, to a confiderable 
 diftance from the arteries. For, in this cafe, the veins 
 
 follow 
 
2 2 VEINS. Chap. III. 
 
 follow the furface of the parts next the without 
 their correfponding artery, which, in the mean time, 
 dcfcends to a confidcrable depth, attended in its courfc 
 by fomefmaller venous branch. In the fmaller branches 
 of the velfels, where they make net-like difpofitions 
 in the membranes and the internal fabric of the vifce- 
 ra, the veins and arteries commonly run contiguous 
 one with the other ; but here the veins have generally 
 a lefs ferpentine or inflected courfe. 
 
 49. In the larger fanguineous veins, little valves are 
 found in great plenty. The innermofl; membrane of 
 the vein, being double, rifes into the cavity of the vef- 
 fel like a curtain, ftretching itfelf farther along the 
 vein every way, fo as to form what may be cafled a 
 a kind of little horns ; but the bafls, which is the part 
 that fuftains the weight of the blood, is llrongefl, and 
 grows out of the vein in the fhape of a circular feg- 
 ment. Thefe, joined with the fide of the proceeding 
 vein, intercept a fpace, of w^hich the outer fide is the 
 vein itfelf, and the inner the valve, which, by its con- 
 vexity, {lands out within the bore of the vein ; fo that 
 the parabolic fpace or hollow mouth of the valves al- 
 ways looks towards the heart : they are found in all the 
 fubcutaneous veins of the limbs, in thofe of the neck, 
 face, tongue, and in the veins of the penis : at the 
 origin of the larger branches there are two, three, 
 four, and fometimes five of them together, while in 
 their fmaller branches they are only fingle. There are 
 none of thefe valves in the deep running veins of the 
 vifeera ; and, therefore, none in thofe of the brain, lungs, 
 heart, or liver, or through the whole fyilem of the ve- 
 na pertarum, nor in the kidneys or womb (except one 
 or tw'O valves in the fpermatic vein); nor, laftly, are 
 there any in thofe fmaller blood-veins, which are of a 
 lefs diameter than the twelfth part of an inch. Some- 
 times, though rarely, they are found in the vena azy- 
 gos, and at the mouths of the hepatic and renal veins : 
 there I have feveral tunes obferved a fort of wrinkles in 
 the place of valve's. In the fmaller venous branches 
 
 there 
 
Chap. III. VEINS. 25 
 
 there are a fet of long, fliarp-pointed or parabolical 
 valves, of a more extended figure as the vein is fmall- 
 er ; and thefe make a greater refiftance than the larger 
 valves, to hinder the blood from returning back upon 
 the parts. 
 
 50. I'he veins have their origin, as we faid before, 
 from the terminations of the arteries. They fome- 
 times arife by a continuation from the inferted branches, 
 or from a refleftion of recurved trunks of the fmalleft 
 arteries. Others again are either continued from veins 
 lefs than thofe which carry blood, or elfe receive addi- 
 tions and roots from them ; as we fee, for inftance, in 
 the lymphatic veins of the thoracic dudi. Others of a 
 bibulous kind take their origin from the abforbing 
 veins that are difperfed all over the furface of the 
 body, as in the chambers of the eyes, the cavities of 
 the inteflines, bladder, womb, breaft, peritonaeum, 
 pericardium, and ventricles of the brain. From thefe 
 iffue a watery fweat, by injeding the venous trunks with 
 that kind of liquor, which may be eafily imitated 
 throughout the whole human body : hence water, jel- 
 ly, or oil, diftil from the the vena portarum into the 
 cavity of the inteftines ; hence alfo water, injeded into 
 the abdomen of a living animal, quickly vaniflies : but 
 of thefe things we fliall fpeak more largely in a proper 
 place. 
 
 51. Not much differing from the former are thofe 
 veins which, arifing in all parts of the cellular mem- 
 brane, return thin vapours, dropfical waters, diffolved 
 fat, or extravafated and corrupting blood, and the poi- 
 fon of opium introduced into the cellular texture, 
 again into the mafs of the blood ; or which take up 
 again and return the blood itfelf from the cellular fa- 
 bric of the penis, clitoris, or nipples of the breads, af- 
 ter the venereal ad. And that inhaling veins of this 
 kind open into all the glands, is highly probable ; 
 where, by abforbing the thinner humour, they leave 
 the remaining mafs of a thicker confidence, of which 
 we have indanccs in the bile, fperm, mucus, &c. 
 
 52. That 
 
24 
 
 VEINS. Chap. IIL 
 
 52. That there are veins of a fmaller clafs, but re- 
 fembling tliofe which convey blood, appears from the 
 fame experiments which deraonftrate the pellucid arte- 
 ries : thus, in the iris of the eye there are fmall veins, 
 and not a few in the adnata tunica of that organ j nor 
 is it to be doubted that, in a healthy body, fmall pellu- 
 cid veins may be found in the vitreous body of the eye 
 itfelf. 
 
 55. But, in mofi; parts of the human body, are 
 found other veins, full of a reddilh, yellowifii, or al- 
 moft pellucid liquor, cpagulable by heat ; which veins, 
 being formed of very tender coats, have a degree of 
 irritability from any chemical or very acrid Itimulus. 
 They have very frequent valves or partitions, which 
 make them in thofe places feem jointed or knotted 
 like a reed w'hen they are turgid ; thefe, by degrees, 
 meeting together, either all or molt part of them empty 
 their contents into the thoracic duel. They arife from 
 the cellular texture throughout the whole body, as I 
 long ago learned concerning the laftiferous veficls of 
 the breafts, the vafa efferentia of the tefticles, the lynv 
 phatics which originate from the mefenteric glands ; 
 and as is now fKown to be the cafe with the lymphatic 
 veifels of tlie tefticles, fpleen, and other parts. From 
 analogy, efpecially from hydropical appearances, it is 
 very probable that they arife likewife from the large 
 cavities of the body; nor is it improbable that this kind 
 of veffels receive a thin humour from veins of the 
 fmalleft fize. But all the lymphatics, in their courfe, 
 meet together in a peculiar kind of conglobate glands, 
 into which they enter ; and, from the lhape of veins, 
 becoming arterial, or like converging cones, they di- 
 vide into fmall branches, and then proceed to meet to- 
 gether again in other little trunks. 
 
 54. Thefe glands themfelves are only as it were 
 fmall clues of lymphatic veffels, connecled together by 
 a cellular texture, into which the arterial liquour ex- 
 fudes, and is conveyed from the fame bv the veffels 
 which ferve to bring back the lymph. They are co- 
 vered 
 
Chap.IIL veins. 25 
 
 vered with a continuous membrane, almofl; of an oval 
 lhape, and this whether they are Angle or heaped to- 
 gether : and they chiefly follow the courfe of the veins 
 through the whole trunk of the body, even to the tops 
 of the limbs ; running along the jugular and fubclavian 
 veins, the vena cava fuperior, the afpera arteria, gullet, 
 lumbal vena cava, vena porta, the iliac, hypogaflric, and 
 crural veins, the veins of the thigh, and likewife the 
 vcflels of, the ilomach, fpleen, mefentery, and mefo-» 
 colon. 
 
 55. They are found feated on all the furfaces of the 
 vifcera, in the thorax and abdomen ; but are more 
 eafily difcovered in brutes. They run through the 
 lower part of the face, mufclcs of the tongue, the ad- 
 jacent parts of the neck, and thofe parts of the upper 
 limbs v/hich are nearefl; the trunk, as far as the bend- 
 ing of the elbow ; throughout the whole length of the 
 mediaftinum, before and behind, and wherever we 
 find conglobate glandules, either in the neck or tho- 
 rax : the lymphatic veins are alfo fpread through the 
 whole lumbal region that is contiguous to the aorta, 
 the mefocolon and pelvis, velfels and furface of the 
 teilicle ; and in the lower limbs, wherever they are 
 fupplied with conglobate glandules, even to the knees. 
 Whether they extend further into other parts through- 
 out the whole body, or through the brain, eyes, hands, 
 feet, back, fore part of the peritonseum, &c. remains as yet 
 undetermined ; at leaft, there are not examples enough 
 in the human body upon which one can depend to 
 evince the truth of their exiftence. But they are eve- 
 ry where to be found upon the furfaces of the vifcera. 
 They are almofl: every where collefted into bundles, 
 not far from the large blood-veflels. Thofe from the 
 inferior limbs, pelvis, and loins, run into one duft, 
 which is joined by another bundle coming from the li- 
 ver, fpleen, and ftomach ; and that trunk, at length, 
 becomes the thoracic du£l. The fuperior veflels, from 
 the whole extent of the breaft, the head, and fuperior 
 limbs, empty themfelves into the fame du^l towards its 
 
 E upper 
 
upper extremity. They feem, however, likewife to 
 termuiate in the red veins. 
 
 56. Of what fervice thcfe glands are to the Ivm- 
 phatic veffels is not well known. In the fetus they 
 are fwelled with a milky liquor, as alfo the thymus and 
 glandulae renales ; but it is not certain whether this 
 juice is poured out into the cellular texture. It is ren- 
 dered probable by late experiments, that fome kind of 
 juice is prepared in thefe glands, which is mixed with 
 the lymph ; and that a thin humour, injedted into the 
 arteries, likewife enters the lymphatic veiTels. By age, this 
 juice vaniflies ; and the glands themfelves, being dried 
 up, almofl totally difappear. A very fudden feirrhus 
 happening to thefe glands feems to be the caufe of their 
 decay. 
 
 57. The vahes of thefe pellucid veffels (53-) are 
 compofed of two femicircular membranes, which give 
 way to the fluid that goes towards the larger trunks ; 
 fo that, by applying themfelves clofe to the fides of the 
 veffel, they leave a free light or capacity through it. 
 But the fame valves, if the contained liquor is preffed 
 back towards the fmaller branches of the veffel, being 
 filled out therewith, fwcll or expand, fo as to (hut up 
 the light of the canal. 
 
 Of the Circulation or Motion of the Bi.ood 
 through the Arteries and Veins. 
 
 HE arteries and veins, whieh we have hitherto 
 
 deferibed, contain either blood or lymph. The 
 
 red blood, whofe nature we Ihall explain when we come 
 to treat of fecretion, fills the arteries and veins com- 
 monly known, which we call red, or thufe of the firft 
 order, and which have their origin in the heart. Thefe 
 it fo fills in a living perfon, that at fome times they 
 are very loofely and imperfedly diftended by it, and 
 
 CHAP. IV 
 
Chap. IV. CIRCULATION, &c. 27 
 
 at other times they are rendered very full and turgid. 
 After death, the veins are found fuller of blood than 
 the arteries ; but fometimes, when the perfon has been 
 dead a confiderable time, the fmall veins have been 
 found diftended with air. But the arteries of a dead 
 body commonly contain only a fmall quantity of blood. 
 
 59. This diftending blood, then, is rapidly moved 
 through all the veflels of a living body. The truth of 
 which is demonftrated to us from wounds, by 'which 
 the patient foon expires, from the lofs of fo much blood 
 as was necelfary for the maintenance of life j which 
 lofs of blood happens almoft inilantly from the larger 
 arteries, and fometimes very fuddenly from the fmaller 
 ones : but from the veins, unlefs they are fome of the 
 largeft, this lofs of blood is more How and difficult ; yet 
 are there not wanting inftance's of fatal haemorrhages 
 from wounds of the veins, in the inner corners of the 
 eyes, and thofe under the tongue. Experiments made 
 upon living animals, fufficientiy evidence the impulfe 
 and rapidity with which the blood is moved, particu- 
 larly through the arteries. In the larger trunks, it runs 
 moft fwiftly ; but, in the lead: of them, fomewhat flower. 
 And, in the larger veins, the blood’s celerity is lefs thaa 
 in the arterial trunks, in the fame proportion as the 
 lights or feftions of the arteries are lefs than thofe of 
 the veins, i. e. twice or almofl; thrice flower. Another 
 argument of the circulation, is the compreffure and re- 
 laxation of a vein, whereby the motion of the blood is 
 promoted from one valve to another This motion of 
 the blood is, in the veins, uniform or equable enough ; 
 but, in the arteries, it is alternately greater when the 
 veffel is more dilated, and lefs when it is contracted. 
 This is proved by ocular infpedion in living animals. 
 
 60. That the motion the blood deferibes is a courfc 
 through the fanguineous arteries into the veins, is dif- 
 covered from experience. For, firfl, it is certain, that 
 all the arteries and veins communicate or open one in- 
 to the other ; becaufe often, from one, and that a fmall 
 artery, all the blood fhall run even until death, and 
 
 E 2 make 
 
28 CIRCULATION, &c. Chap. IV. 
 
 make all the flefh exceedingly pale ; and this not only 
 out of the wounded limb, but from the whole body. 
 Of fuch fatal examples we have a number, from an in- 
 ner artery of the nofe, from the gums, a finger, tooth, 
 cutaneous pore enlarged, from the lachrymal point, 
 from the wound of cupping on the fkin, and even the 
 bite of a leach. There are, therefore, of courfe, open 
 ways by which the blood fpeedily flows from the venous 
 into the arterial fyftem. 
 
 6 £ . That the blood, again, in the arteries, flows from 
 the heart toward the extreme parts of the body, is 
 proved by the microfcope, an-d by a ligature on the ar- 
 tery of a living animal. For whatever artery fliall be 
 flopped by a ligature, a fwelling enfues in that part be- 
 twixt the heart and the ligature, whilfl; the other part 
 is emptied beyond the ligature, which is the part of the 
 artery more remote from the heart: neither has it there 
 any pulfation; nor, if it be there wounded, will it yield 
 any blood. The fame eftecls which we fee follow from 
 a ligature, are likewife often produced by difeafe ; as 
 when fome tumour, by cornpreffure, or an aneurifm, in- 
 tercepts the motion from the heart. Experiments of 
 this kind have been made by us on moft of the arte- 
 ries ; anaflomofes, however, or the blood flowing 
 through a neighbouring branch, or the retroceffion of 
 the blood in a dying animal, form exceptions to this 
 rule. 
 
 62. But for the courfe or motion of the venous blood, 
 it has been always more doubted of ; almofl all the an- 
 cients have been perfuaded, that the blood in the veins 
 flowed through them, either from the heart or from 
 the liver, to all parts of the body. Very few of them 
 have known, that this was an error. Several of them 
 have, indeed, acknowledged it to be falfe in the pulmo- 
 nary vein. But that the blood did not move from the 
 heart in the vena cava was known to flill fewer anato- 
 mifls of the ancients ; perhaps only to Andreas, Cte- 
 falpinus, and (from an extraordinary accident) to Vefa- 
 
 lius. 
 
 ^3. 
 
Chap. IV. CIRCULATION, kc. 29 
 
 63. Dr William Harvey is the firft who experi- 
 mentally aflerted the motion of the blood returning in' 
 the veihs to the heart, in fuch a manner as to render 
 the whole intelligible, and leave no room to doubt of 
 it. And, firft, the valves of the veins lead us to this 
 truth : for the common ufe or office of thefe valves is, 
 to determine the preflure that is given from any quar- 
 ter upon the veins, towards the heart, by allowing no 
 opportunity to the venous blood,'that has once entered 
 the trunk, wffiich they intercept, to flow back to the 
 branches. For, fince the covering fpaccs of the valves 
 open upwards towards the heart, the blood enters into 
 and expands them. Thus thofe parts of the valves 
 which ftand out with a free motion within the light of 
 the vein, approach each other towards the axis, until 
 the oppofite fides, by meeting together, fiiut up the 
 tube. This we know from inflations, ligatures, and 
 injeftions of the veins ; for you never can force a li- 
 quor eafily into the veins by urging it againft, or con- 
 trary to, their valves. They do not, indeed, every 
 where fliut up the whole cavity of the veins ; but where 
 they ffiut not clofe, they always intercept the greateft 
 part of the light. 
 
 64. Another office of the valves in the veins feems 
 to be for fuftaining the weight of the blood, that its 
 upper columns may not gravitate upon the lower ; nor 
 the blood, flowing through the trunks, make too great 
 a refiftance againft that which follows it through the 
 branches. For if, from the flower return of the blood 
 into the veins, its weight or preflure fhall, in any part, 
 much exceed the impulfe that drives it on, fo as to caufe 
 fome part of the column to defeend by its weight ; it is, 
 in that cafe, immediately catched, and fuftained in its 
 relapfe by the next adjacent valve, which hinders it 
 from urging againft the next fucceeding column, and 
 affbrd:s time and opportunity for fome contiguous 
 mufcle, by its preflure or concuffion, to fend forward 
 the faid column. And this is the reafon why valves 
 _are placed in veins of. the limbs and neck; in which 
 
 parts 
 
30 CIRCULATTON, &c. Chap. IV. 
 
 parts they are both more numerous and more robufl: 
 than elfewhere. And this is the caufe of varices, when 
 the blood, entering the hollow valves, urges their folid 
 convexity downwards, and makes the vein dilate in that 
 part. Likewife, in mufcular motion, the valves occa- 
 fion the whole prelTure which the veins then fulfain, 
 to forward the due courfe of the blood towards the 
 heart. 
 
 65. Moreover, the valves, placed in the right ven- 
 tricle of the hearty have fuch a fabric, as we {hall here- 
 after fee, that they freely permit blood, flatus, or w'ax, 
 to pafs from the venous trunks of the cava into the heart, 
 but deny any paffage from the heart again into the 
 veins. 
 
 66. Again, ligatures^ in a living perfon, may make 
 the thing more evident. When the veins of the limbs 
 are tied, either by defign or accident, with the limb it- 
 felf about the hams, arms, ancles, or wrifts, the limb be- 
 low the ligature fweils, the veins fill and diftend them- 
 themfelves, and when opened make a free difeharge of 
 blood : but, at the fame time, nothing of this kind hap- 
 pens above the ligature, nor are any of the veins to be 
 feen there. The fame phenomenon happens when the 
 veins are compreffed by fwelled and feirrhous glandules 
 in the vifeera ; and from polypufes the veins are often 
 largely fwelled, or enlarged into tumours. Thefe liga- 
 tures will ferve to keep the blood in any limb round 
 which they are tied, that it may not return to the heart 
 and be loft through a wound in another part. 
 
 67. The experiments to prove this courfe of the 
 blood, which have been made in living animals, are Hill 
 more accurate. From them, even from our own, it 
 appears, that, by tying any vein, in a living animal, near 
 the cava, or belonging to the pulmonary veins, that part 
 always fweils which is moft remote from the heart, all 
 below' the ligature appearing diftended with the retained 
 blood, white above and next the heart they are pale and 
 flaccid. Laftly, if the arteries are tied at the fame t’.miC 
 with the veins, thefe laft remain flaccid and empty ; but, 
 
 upon 
 
Chap. IV. CIRCULATION, &c. gt 
 
 upon removing the ligature from the arteries, the veins 
 are immediately filled. In like manner, the infufion of 
 poifons or medicinal liquors fhew, that, into whatever 
 vein you injed chemical acid fpirits, the blood is driven 
 •along with the force of the poifon to the heart itfelf. 
 But when, from this caufe, the brain is affedted with the 
 narcotic virtue of opium, and the inteftines and ftomach 
 with the virtue of purgatives and emetics, this is a de- 
 monflration that the blood, with which thefe fubftances 
 were mixed, had paffed through the ramifications of 
 the veins to the heart, and from thence through the 
 whole body. 
 
 69. Another proof we have in the transfufions of 
 - blood ; in which all the vital gore from the arteries of 
 
 one animal is urged into the veins of another exhaufted 
 of blood, whereby the heart, arteries, and empty veins 
 of the latter become fo turgid and well replenilhed, 
 that they work the whole machine of the animal with 
 a remarkable degree of vivacity, or even caufe it to la- 
 bour by a plethora. 
 
 70. But that the blood pafles from the leaf! arteries 
 into the lead veins, we are clearly taught by anatomical 
 injedion ; where, by one arterial trunk, we eafily fill all 
 the arteries and veins, almoft throughout the whole bo- 
 dy ; provided the liquor be watery or very fluxile, fo 
 as to pafs eafily in the veffels of the head, mefentery, 
 heart, and lungs. 
 
 71. Laftly, the 7 mcrofcope has put the matter beyond 
 all doubt in the pellucid tails, feet, and raefenteries, of 
 animals ; where we fee, that the blood, brought to the 
 extreme parts by the arteries, is poured either into fmali 
 veins, continuous with the refiexed artery, or elfe goes 
 through branches of the arterial trunk into the parallel 
 communicating vein, by which it goes on to the parts 
 neareft the heart. This is the way in which the blood 
 pafles, as well into the lead: veins, which are capable of 
 receiving only one globule, as into thofe that are fome- 
 what larger, being able to admit two or more globules 
 to advance forward in a bread. Bat, that there is no 
 
 fpongy 
 
32 CIRCULATION, kc. Chap. IV. 
 
 fpongy or parenchymous interpofition betwixt the ar- ' 
 teries and veins, in the general courfe of the circula- 
 tion, is proved both from microfcopes and injections. 
 For, if there w^ere any fuch parenchyma or fpongy inai's 
 betwixt the arteries and veins, the hardening injections 
 would fhow it, by appearing extravafated in a like un- 
 fliapen mafs. 
 
 72. The circulation of the blood is, therefore, now 
 received as a medical truth by every one ; namely, that 
 all the blood of the human body is carried through the 
 aorta, from the left cavity of the heart, to the extreme 
 parts or converging ends of the arterial branches ; from 
 whence the whole mafs is again tranfmitted into tlie 
 lead veins, which convey it to the larger, and from 
 them into the cava and heart itfelf ; in which courfe it 
 perpetually goes and returns during life. 
 
 73. Yet there are fome inftaiices where, by pallions 
 of the mind, a fudden revulfion by copious blood-let- 
 ting, or a vafcular convulfion, the blood has been forced 
 to recede back from- the fmaller into the larger arteries. 
 And, on the other fide, where an obflrudtion being 
 formed above the valves, the blood has been known to 
 Aide back from the venous trunks into their fmaller 
 branches. But then thefe accidents are very momen- 
 taneous or fudoen, nd the blood foon returns into its 
 natural courfe. Thefe things happen mod frequently 
 in the abdomen and vena portarum. 
 
 7q. The courfe of the humours in the lymphatic 
 veins which have valves, appears both from the nature 
 of thole veins, and from ligatures ; for every lymphatic 
 vein tied, fwells betwixt the fmaller extremities of it 
 and the thoracic du£t ; but grows fiac-cid betwixt the 
 faid duct and the ligature. All the valves in thefe, like 
 thofe of the blood-veins, give a free pafiage for flatus 
 and mercury to flow to the thoracic duct : but they 
 make a refidance, and often an obdinate one, to any 
 return the other way 5 although fometimes they have 
 been known to yield. 
 
 75. The vapours that moiden the whole cellular fub- 
 
 ftance, 
 
Chap. V. HEART. 33 
 
 ftance, the fleams of the abdomen and other venters, 
 are ail thus drank up by the leafl pellucid veins, and fo 
 conveyed along to the blood-veins, that their contained 
 juices may pafs on to the heart : and from thence it is, 
 that an oedema enfues when a vein is compreifed by a 
 ligature ; becaufe, by intercepting the courfe of the ab- 
 forbing veins by the ligature, the vapours ftagnate un- 
 abforbed. In the other fmaller veffels, we can make 
 no experiments : but they appear conformable to what 
 we have faid, both by reafon and analogy ; and are like- 
 wife fupported by the experiments of water or other li- 
 quors, abforbed out of the cavity of the inteftines, tho- 
 rax, and pulmonary veficles. 
 
 76. All juices, therefore, in the human body, are 
 drove out of the heart into the aorta ; from whence they 
 are all returned again to the heart by the lead veins ; 
 thofe humours only excepted, which are exhaled or 
 difcharged without fide the cavities of the body. To 
 complete this circle, it only remains for us to find out a 
 courfe for the blood, from the right to the left cavities 
 of the heart : but then this fuppofes us to be firft ac- 
 quainted with the hiftory of the heart, and the pulmo- 
 nary veffels. 
 
 CHAP. V. 
 
 Of the Heart. 
 
 77. ^ I H E fabric of the thorax^ compofed of bones 
 X and cartilages, in general refembles a trun- 
 cated cone, as we (hall hereafter declare more at large. 
 The lateral parts of this cone are two membranous 
 bags, terminated above by an obtsfe end at the firft rib, 
 where they lie very near together, and are diftinguifli- 
 ed only by the interpofed cellular fubftance. The ob- 
 liquity of the plane, dividing thefe two bags, is fuch, 
 that the right is much the broadeft, and adheres in its 
 defcent all along to the whole middle of ths fternum ; 
 
 F butj 
 
34 HEART. Chap. V. 
 
 but, in its defcent, is inclined to the left fide, and comes 
 from the margin of the fternum itfelf; while the left 
 bag defcends, not from the fternum, but from the car- 
 tilaginous ends of the ribs. The inner central fides of 
 thefe bags, oppofed one againft the other, make up 
 what anatomifts call the mediaftinum. Thefe bags have 
 no where any communication one with the other ; fo 
 that the right may be opened, and the lungs therein 
 may be .deftroyed, without injuring the left. But the 
 fimple denfe membrane, which forms thefe bags, out- 
 wardly invefled with the cellular fubflance, is called the 
 pleura ; being harder than the peritoneum, efpecially 
 where it adheres to the back ; but is fomewhat fofter 
 in its fore part, and is ahnoft deftltute of feeling. The 
 capacity of the mediaftinum, or that interval which lies 
 betwixt the right and left bag, broadeft above, and 
 likewife below, contains the thymus, and fome conglo- 
 bate glandules, fat, and veffels, and, in fome difeafes, 
 pus. 
 
 78. Below, the fame bags, growing broader, depart 
 one from the other, and leave a capacity through the 
 whole middle part of their extent, by which the faid 
 bags are divided one from the other. And this capacity 
 is that of the pericardium. But the bags of the pleura 
 on each fide the pericardium, defcending both before 
 and behind it, terminate finally on the diaphragm, a- 
 bout the fifth or fixth rib ; and on this their bafe is cut 
 off obliquely, fo that each cavity is before fhorter in the 
 fore part, as behind they defcend longer and lower, in 
 fuch a manner as to be hollow in the upper part. With- 
 in thefe bags, then, play the dilatable lungs. The back 
 parts likewife of thefe bags are more tender ; and tho’ 
 they ly near to each other, are yet feparated by the cel- 
 lular fubftance, which terminates in the pericardium, 
 and includes the aorta, together with the oefophagus ; 
 and this we call the pojlerior mediaflinum. The trian- 
 gular produdions of the fides of the mediaftinum form 
 the ligaments of both lobes of the lungs. 
 
 79. The pericardium.^ or third bag, which firft the 
 
 cellular 
 
Chap. V. HEART. 35 
 
 cellular fubftance, and then the conjoined pleura, loofe- 
 ly cover on all fides as an outer coat, touches the fter- 
 num indeed but by a very fmall part ; Imce the lungs, 
 when diftended, cover the heart almoft wholly before, 
 and interpofe betwixt the fternum and pericardium in 
 their lower part ; and the mediaftinum, gradually de- 
 parting towards the left fide, forms altogether a narrow 
 interval under the lower end of the thymus, clofe to 
 which the lungs meet on each fide : but this vital litu- 
 ation you will alter or corrupt, unlefs you are very care- 
 ful in your manner of opening the thorax. The peri- 
 cardium has a broad, but fomewhat rounding, bafis, 
 adhering to the tendinous part of the diaphragm, and 
 by a fmall part to the flefhy fubftance of the fcptum on 
 the left fide, about the fifth or fixth rib. In young fub- 
 jeds it adheres more laxly ; but, in adults, very firmly, 
 by the cellular fubftance fpreading broader to the right, 
 and narrower towards the left. It is fom.ewhat larger 
 than the heart; which, therefore, may move freely 
 therein. This membranous' capfule, or fence of the 
 heart, was never known to be abfent. 
 
 80. Upwards the pericardium grows gradually nar- 
 rower, ending above the heart in an obtufe conical ap- 
 pendix, extended over the coats of the large blood- 
 veftels almoft to the upper edge of the fternum. It 
 adheres firft to the inferior branch of the right fupe- 
 rior pulmonary vein ; then to the vena cava ; after 
 that to the aorta, on its acceflion to which it rifes high- 
 er up ; then it adheres to the defeending trunk of the 
 fame veflel, and to the duftus arteriofus ; from hence 
 it is fpread upon the left branch of the pulmonary 
 artery, then on both branches of the left fuperior pul- 
 monary vein. On the back part it is again attached 
 to the right pulmonary vein ; then to the left finus, to 
 both pulmonary veins on the left fide, and to the auri- 
 cle of the fame fide ; from thence it proceeds a long 
 Avay from the pulmonary vein even to the inferior ca- 
 va, then to the feptum of the finufes, then to the in- 
 ferior cava. Befides, it goes to the pulmonary arte- 
 
 F 2 ry, 
 
H E A R T. Chap.V. 
 
 ry, its right branch, and the aorta under the origin of 
 the large branches, in fuch a manner as to furround 
 both arteries with a cylindrical production of its fub- 
 ftance, whence it appears like a kind of partition be- 
 tween every two neighbouring veffels. Thus alfo it 
 contains the vena cava fuperior as in a ring, the ante- 
 rior and pofterior cavities of the pericardium being 
 freely continued between that vein and the aorta. In 
 like manner it furrounds the inferior cava. But this 
 flieath, by which the veffels are furrounded, preferves 
 its nature only for a fliort fpace, and immediately re- 
 turns to the heart with thofe large veffels to which it 
 ferved as an external coat. It alfo fends a cellular fa- 
 bric like a Iheath, along with the great arteries and 
 veins, to the lungs. 
 
 81. The arteries of the pericardium are either from 
 thofe of the thymus, which accompany the upper and 
 lower phrenic nerves, or from the larger phrenic arte- 
 ries, from the branches of the mammaries and media- 
 ffinals, the bronchial, oefophageal and pofterior me- 
 diaftinal arteries, or from the coronaries which inofcu- 
 late with the bronchials and others. The venous trunks 
 of the pericardium have a like origination, but appear 
 with mofl evident anaftomofes from thofe of the right 
 into the others of the left fide. The nerves of the pe- 
 ricardium are from the fuperficial branches of the car- 
 diacs. 
 
 82. That which makes the proper fubflance of the 
 pericardium, is a ftrong, white, compact membrane, 
 more robufl than the aorta itfelf, through which the 
 nerves of the heart and fome fmall veffels defeend. 
 Its outer furface, being fpread with the cellular fub- 
 flance, gives it there a foraewhat rough appearance, 
 while internally it appears highly poliflied, and nioi- 
 flened on all Tides by a watery vapour. This vapour, 
 which we have, times without number, obferved in 
 the living animal, compofes fome, though naturally a 
 very fmall quantity, of a water within the pericar- 
 dium j which is either limpid, yellowiff, or reddifh, 
 
Chap. V. HEART, 37 
 
 and fubvifcid or gelatinous ; by difeafe, it is fometimes 
 increal'ed to an immenfe quantity ; yet the exillence of 
 fuch a water here is injudicioufly denied by fome. 
 The water of the pericardium is of a lymphatic na- 
 ture ; becaufe, by the heat of fire, it hardens into a 
 jelly ; and from hence finall fibres and a cellular fub- 
 fiance are often found, in fome difeafes, mixed with 
 the natural vifcous humour which every where exfudes 
 from the heart and its pericardium. This liquor is fe- 
 parated, without any intermediate glandules, or any vi- 
 fible pores, from the fmall exhaling arteries of the 
 heart, auricles, and pericardium ; as may be proved 
 by a fimilar tranfudatjon of water or filh-glue injeded 
 into the large arteries. 
 
 83. The uje of the pericardium is to contain the 
 heart, along with this vapour ; and to fupport and 
 ftrengthen it as a fulcrum or prop, that, in contradion, 
 the fibres of the heart may be drawn together without 
 diftorting the large blood-veflels, and that it may lefs 
 fluduate like a pendulum every way by altering the pofi- 
 tion of the body. For thefe reafons, we find it in all ani- 
 mals that have a true heart. A watery vapour here be- 
 dews the heart, hotter and quicker moved than other 
 parts, fo as to hinder attrition and cohefion betwixt it and 
 the pericardium ; but, when this vapour is dried up or 
 deficient, the pericardium adheres either to fome one 
 part only of the heart, or to its whole furface, fo that 
 it fometimes feems to be entirely wanting. 
 
 84. Nature hath given a heart to moft animals, even to 
 many infeds and worms ; to others ftie hath denied it ; and 
 thefe are the moft fimplc of all animals, although large, 
 feeing they are irritable throughout their whole body, 
 as, for inftance, the prickly hydra. To thofe animals 
 who have no heart, veftels are alfo denied. 
 
 85. The veins which carry back the blood from the 
 whole body to the heart, if we except thofe of the 
 lungs, are reducible to two. The cava is improperly 
 named in the fingular by anatomifts, fince it is no 
 where, or for a very fhort fpace, one fingle trunk. 
 
 The 
 
33 HEART. Chap. V. 
 
 The lower of the two large veins, which is the biggeft 
 of them in man, afcends immediately above the dia- 
 phragm Irom the right fide, towards which it is a little 
 convex or gibbous, to its union with the upper cava, 
 and, together wdth that in its back part, forms a mid- 
 dle partition betwixt the right and left finus ; but the 
 left fide of the venous tube degenerates into the right 
 auricle, whofe fibres are a continuation from thofe of 
 the cava. What we have here faid of the lov/er cava 
 is alfo true of the upper. 
 
 86. Thus, by the meeting of the upper and lower 
 cava, a finus or cavity is formed with a convexity to 
 the right, and inwardly filled with ftrong, flefhy fibres, 
 detached betwixt the two finiple membranes, and va- 
 rioufly interwove. But the fame cavity, to the left 
 and fore part, dilates forwards into an almoft perpendi- 
 cularly oblong or oval form, and terminates above with 
 a blind-pointed end, which is free from adhcfion with 
 the heart, and lies incumbent on the great artery. 
 This cavity alfo, like the former, has plenty of flefhy 
 fibres placed betwixt two very thin membranes, almoft 
 in a parallel pofition ; and thefe form a kind of arch 
 extended from the right to the left edge of the w hole 
 cavity, and round the anterior half cylinder of this 
 cavity; and thefe mufcular arches are connected toge- 
 ther by fome of the leaft fibres. This anterior and 
 ftringy part of the cavity is called the auricle ; but that 
 to the right and poftcrior part is called the finus: it is 
 thin at the partition of the auricles, and likewife be- 
 tween the oval ring and where the vena cava enters the 
 heart. In this appendix there feem to be three large 
 mufcles, the anterior, poflerior, and inferior. 
 
 87. In the partition which feparates the two auricles, 
 the bafis lying in the middle between the two venae 
 cavte is depreffed to the left fide, more on the upper, 
 and lefs on the under part; and, at its bafis, the par- 
 tition is exceedingly thin. Ifliall call it the oval fojfa. It 
 is bounded on both fides by a flefhy column, by the 
 union of which an arch is formed at top, while the 
 thinner parts at bottom are turned backwards to meet 
 
 one 
 
Chap. V. HEART. 39 
 
 one another. This I call the oval ring ; others, the 
 ijlhmus. 
 
 88. Where the lower cava opens into the right au- 
 ricle, from the tumid column of the left fide of the fo- 
 ramen ovale arifes a moon-like membrane, naturally 
 complete in its figure, and from its thinnefs in adults 
 fometimes net-like : and this being extended round the 
 lower edge of the auricule, grows thinner all the way 
 as it is incurvated to the right; but does not quite fur- 
 round half of the auricular circumference, the cavity 
 of which it fervesTike a partition to divide from the 
 vena cava. This is called Eujlachnis’ s valve. The 
 oval foramen we (hall deferibe hereafter. 
 
 89. The blood of the two venae cavae is propelled by 
 a mufcular force, in either vein, into this atrium or porch 
 of the heart, compofed of the finus and auricle. Thefe 
 veins, as far as they lie within the breaft, are endowed 
 with flrong and irritable mufcular fibres, by whofe con- 
 tradlion the blood is driven into the neighbouring auricle. 
 
 90. In like m.anner, the auricle, being irritated, is con- 
 traftedonall fides. And firft,by aconffriftion of its muf- 
 cular fibres, the anterior femicylinder of the auricle is 
 reduced to a plane ; while the fame fibres, by their con- 
 tradion, bring back the middle arch towards the ante- 
 rior extremity or beginning of the heart, and likewife 
 towards its poflerior extremity or finus. • Then the ap- 
 pendix to the auricle defeends, and is contraded tranf- 
 verfely by itfelf, while the lower part afeends ; and thus 
 the auricle becomes fhorter. Again, the left edge turns 
 evidently to the right, and the right edge a little to 
 the left ; and thus the auricle is rendered narrower. 
 Thus the blood of both cavse, being mixed toge- 
 ther in the beginning of the heart now difincumber- 
 ed, is drove through the edges of the open valve, in 
 fuch a manner as to urge the valves of the right ven- 
 tricle clofe to the fides of the heart. But the blood is 
 now hindered from returning again into the lower ca- 
 va, both by the contradVion of the auricle, the re- 
 fiflance of the fucceeding blood from the abdomen, 
 
 and 
 
HEAR T. Chap. V. 
 
 and of the Eujlachian valve ; and upwards it is hinder- 
 ed from afeending, both by the motion and weight of 
 the confequent blood. Jt is driven back, however, on 
 both fides, if there happens to be any oblfacle in the 
 lungs. 
 
 91. The figure of the heart itftlf, in fome meafure, 
 refembles half a cone, if the cone be fplit into two 
 longitudinally in the dlreftion of its axis. It is almofi: 
 triangular ; only the end of it is obtufe, and the lower 
 fide of it is flattened in proportion to the diaphragm on 
 which it lies incumbent, and is thereby fuftained. But 
 the convex furface of the cone is fo inclined within 
 the pericardium, under the great blood-velTcls, as fuf- 
 fices to place its thicker femicircular curvature, which 
 modern anatomills call its obtufe margin^ diredted to the 
 upper and to the left fide of the breah ; in its lower 
 and anterior part, the heart is alfo extenuated into a 
 kind of edge, which is called its acute margin ; but the 
 point is turned a little forewards. This is the general 
 fituation of it in mankind ; but, in brutes, the heart be- 
 ing almoft parallel to the larger axis of the thorax, its 
 apex or tips only extend to touch the diaphragm. 
 
 92. The whole heart is hollow, having its anterior, 
 formerly called its right ventricle, communicating into 
 the right auricle and fmus, which is broad, and Iha- 
 ped like the fourth part of a cone ; not fo long as 
 the pofterior left ventricle, but larger ; and it terminates 
 in the fliorter tip of the bifurcated apex of the heart. 
 The mouth of this ventricle, where it opens into the 
 auricle, is elliptical ; and terminated by a white gluti- 
 nous margin, more callous than tendinous : over this, 
 plates of mufcular fibres are fpread, and fome fat lies 
 outw'ardly upon thefe. 
 
 93. From this callous margin is extended, within the 
 heart, a membranous ring, formed by a reduplication 
 of the internal membrane of the auricle, extended fo 
 as to float wdthin the ventricle, to which it was before 
 continuous. But this fame ring, in that part which 
 fluctuates in the ventricle, is fo fplit or divided into 
 
 three 
 
HEART. 
 
 Chap. V. 
 
 41 
 
 three unequal triangular portions, that you may, in 
 fome meafure, give them the name of valves, and 
 count three of them in number, although they are, iii 
 faft, only continued parts from one broader ring. 
 Thefe were, by the ancients, named triglochines, or tri^ 
 citfpid valves. 
 
 94. That part of thefe valves which lies next to the 
 fides of the heart is ftrengthened by tendinous fibres, 
 which, meeting together in their courfe, are inferted 
 by very ftrong cords, partly into the fides of the hearty 
 and partly into papillary or cylindric mufcles, which 
 arife upward from the left fide of the right ventricle 
 towards its right fide. The largeft of thefe mufcular 
 columns is that which anfwers to the biggefl of the 
 valves, which is both the uppermofl and that which 
 anfwers to the adjacent mouth of the pulmonary arte- 
 ry. The lead: of them is the loweft, and is fituated 
 before the acute margin. 
 
 95. The ufefulnefs of this valve is evident enough * 
 for the right auricle (90.) being contraded, the blood 
 contained in the right porch of the heart, at the loofe ex- 
 tremity of the auricle, being impelled from the circum- 
 ference towards the axis, like a wedge, feparates the 
 pendulous portions of the ring, called tricujfid valves, 
 and preffes them to the fides of the heart. Thus is 
 filled the right ventricle of the heart, while the upper- 
 moft valve (94.) fhuts the pulmonary artery,' left the 
 blood, by the weak impulfe of the auricle, fliould flow 
 into that artery ; the blood thus received, and con- 
 fined within the right ventricle of the heart, is, by the 
 ftrong contradion thereof, more powerfully expelled 
 into the artery. 
 
 96. The fenfible flefh of the heart, being irritated 
 by the quantity and weight of this warm blood, is 
 thereby folicited to a contradion : for that the heart, 
 being irritated, will contrad itfelf in a perfon dying, 
 or even lately dead, is proved by injedions of water, 
 and inflations of air, whereby the heart, then quiefeent, 
 is recalled to its motion. 
 
 97. The 
 
 G 
 
42 
 
 heart. Chap.V, 
 
 97. The heart’s motion is performed by mufcular 
 fibres ; the originations of which, in genera!, are from 
 rings formed of the cellular fubftance, compared into 
 a callous ligament, agreeable to the defcription given 
 in 92. and with which all the larger blood-veffels, at 
 their opening into the heart, are furrounded. From 
 thence the fibres which arife defcend gradually in an 
 oblique winding courfe towards the left fide, and for- 
 ward to the apex, in many diftindf plates, and fome- 
 times a little traverfing each other, the middle ones 
 being the mod tranfverfe, while the outermofl and in- 
 nermoft defcend in a flraighter line. In the flat fide 
 of the heart (91.) there are few fibres; and fo thin, 
 that, when you have removed the fat, the cavity ap- 
 pears almofl: uncovered. That which is called the left 
 ventricle is, however, very firmly invefted by the 
 fibres ; which, after furrounding the fame ventricle, 
 form a flight decuffation in the feptuin cordis with the 
 fibres of the right ventricle, and are interwoven with 
 them. Some of thefe fibres defcend into the cavities 
 of the ventricles, and form there the flefhy columns 
 mentioned at 94. Others, at the tip of the heart, are 
 wound in a vortical or whirling pofition, the two horns 
 ending by a ftrong fafciculus or bunch in each ventricle. 
 A very thin and finooth membrane covers the external 
 and internal furface of thefe fibres ; but the external 
 membrane, efpeeially where it is fpread over the coro- 
 nary vefiels, contains much fat beneath it. I have, for 
 my own part, not been able to diflinguifh any thing 
 more particular in the mufcular fabric of the heart, 
 with any tolerable degree of evidence ; becaufe it is 
 the peculiar property of the fibres in the heart to join 
 together in branchy appendices or heaps, in fo flrict 
 union, that they cannot be feparated without lacera- 
 tion. 
 
 98. But there are feveral eminent anatomifls, whofe 
 ingenuity and communicative freedom I refpect, who 
 have reprefented apd deferibed thofe fibres difplayed 
 and feparated : namely, the external fibres of the 
 
 heart. 
 
Chap. V, HEART. 45 
 
 heart, common to both ventricles, defcending to the 
 tip, and then, taking another courfe, to infert them- 
 felves into the feptum ; others again, at the tip, to 
 perforate the left ventricle, and return, in a contrary 
 courfe, to the bafis, along the inner furface of the faid 
 ventricle. But the middle fibres, betwixt the afore- 
 faid inner and outermoft ones, being varioufly inclined 
 towards the bafis, they form the feptum. And others 
 have given us figures and deferiptions of flill different 
 orders of fibres, of which the outermoft run counter 
 to the innermoft, while the intermediate are tranf- 
 verfe. Which deferiptions, as they are not much dif- 
 ferent from my own obfervations, I fliall make no op- 
 pofition to, although I have never been able to fee this 
 difpofition of them fufficiently manifeft, and am ac- 
 quainted with great anatomifts who have not herein 
 been more happy than myfelf. 
 
 99. Thefe fibres of the heart, like other mufcles, 
 are furnifhed with nerves of their own, very numerous 
 and of various origin. The fir ft and uppermoft are 
 on the left fide from the ganglion of the intercoftal 
 with the uppermoft cervical nerve. With thefe are 
 joined others from the pharyngeal plexus of foft 
 nerves ; others, produced from the pharyngeal and 
 gloifo-pharyngeal ganglions, are mixed with them ; 
 others alfo are added from the trunk of the intercoftal 
 nerves ; and others from the middle ganglion feated 
 on the ftraight mufcle about the paffage of the thyroid 
 artery, which has branches both from that uppermoft 
 nerve, and from the trunk of the intercoftal and phre- 
 nic nerves. Others come from the recurrent nerve of 
 the eighth pair. The nerves of the heart, originating 
 from thefe fources, (wove together into a plexus, part- 
 ly before the great arteiy, in which the following ones 
 are mixed together; and partly forming feveral fmall 
 plexufes between the afpera arteria and the large arteries 
 going out of the heart,) form one or more plexufes out of 
 the nerves of the right and left fide ; which plexufes are 
 
 G 2 commonly 
 
44 HEART. Chap. V. 
 
 commonly joined together, though fometlmes they arc 
 diftinft. From this fame plexus, or plexufes, other 
 nervous twigs pafs betwixt the aorta and pulmonary 
 artery to the right artery of the heart ; others crofs the 
 pulmonary artery, and go betwixt it and the left auricle 
 to the coronary artery of the fame fide ; others behind 
 the pulmonary artery to the fame coronary ; and 
 others, again, defccnd very deeply behind the pulmo- 
 nary artery to the left finus and flat furface of the heart. 
 To the cardiac plexus, above defcribed, other large 
 nerves accede from the fifth and lower cervicals, and 
 fometimes from the phrenic nerve, and from a gang- 
 lion of the lowefl: cervical with the intercoftal, to w hich 
 join large roots from the lowefl; cervical nerves. The 
 lafl; defcribed nerves, which are larger, fofter, and 
 more tranfverfely difpofcd, are partly mixed with the 
 foregoing plexus, and partly go to the lungs. Laftly, 
 there are fome fmall branches, uncertain as to courfe 
 and number, which join the cardiac plexus from the 
 recurrent and eighth pair of nerves ; and, making various 
 inofculations with the intercoflals, are confounded 
 with thofe of the eighth pair. As for thcfe nerves^ 
 which fome enrinent anatomifls have feen afcending 
 from the great abdominal plexus to the heart, through 
 the foramen of the vena cava, I have, never been able 
 to find fuch ; although it is eafy enough to difcover 
 the diaphragmatics in that place, having ganglions pe- 
 culiar to themfelves, of which thofe anatomifls make 
 no mention. 
 
 100. That thefe nerves conduce powerfully to move 
 the heart, is the opinion of eminent anatomifls, from 
 a confideration of the common nature of mufcles; and 
 from the increafe which follows in the heart’s motion, 
 by irritating the eighth pair of nerves, either at the 
 brain, or the fpinal medulla ; and from the languors 
 that enfue upon tying thofe nerves, which proves fatal, 
 either fuddenly or within a few days, even though you 
 happen to make the ligature on but a few of the nerves 
 that com^ to the heart j for the intercoflal, and efpe- 
 
 cially 
 
Chap. V. HE AR T. 45 
 
 dally thofc from the ganglion of the upper thoracic, 
 cannot be tied. 
 
 10 1. But that there are flill other caufes, befides 
 that of the nerves, conducing to the motion of the 
 heart, we are perfuaded from obferving its motion un- 
 difturbed. by the irritation of all the nerves in the living 
 animal ; from its remaining after the greateft wounds 
 of the head, and even of the cerebellum and medulla 
 fpinalis ; likewife from its motion w'hen torn out of the 
 bread ; moftly in thofe animals in which the lungs, be- 
 ing impermeable, make no refiftance to the heart’s mo- 
 tion ; for the motion of the heart is obferved to be ve- 
 ry vigorous in the foetus before the brain is well form- 
 ed, and likewife in animals wanting the head. And 
 all our experiments agree in this, that the quiefcent 
 heart, in dead or dying animals, when irritated by 
 heat, cold, vapours, poifons, and efpecially the force 
 of impelled flatus, watery liquors, wax, or blood, or 
 on receiving an eledric fpark, immediately contrads 
 itfelf, by putting all its fibres into a rapid motion, by a 
 force fometinies common throughout the whole heart, 
 and fometimes affefling only a particular part of it. 
 
 102. Thus then we fee, that there refides in the heart 
 a kind of impatience of ftimulus ; fo that even in the 
 vifcus, when almoft dead, wrinkles, and motions of dif- 
 ferent kinds, appear to be propagated along its furface, 
 from places as it were irradiating from points : again, 
 the heart, when torn out and cold, on being pricked, 
 inflated, or irritated, contrails itfelf; and its fibres, when 
 diffedled, corrugate themfelves orbicularly, when there 
 is neither nerve nor artery to bring it fupplies of any 
 kind. This irritability is greater, and remains longer, 
 in the heart than in any other part of the body ; feeing, by 
 Simulating it, the motion of the heart may be renewed 
 at a time when that of no other mufcle can. The heart 
 of the foetus is moft irritable, as well as larger, in pro- 
 portion, than in adults ; and moft tenacious of its mo- 
 tion, even in the cold. That motion is peculiar to the 
 heart itfelf ; coming neither from the brain, nor the 
 
 foul 5 
 
4^ HEART. Chap. V. 
 
 foui ; feeing It remains In a dead animal, even when 
 the heart is torn out of the breaft ; neither can it, by 
 any a£l; of the will, be made either quicker or flower. 
 
 log. It is, therefore, evident, that the flimulus, oc- 
 cafioned by the impulfe of the venous blood, caufes the 
 heart contraft itfelf ; and that this contraftion is con- 
 vulfive, made with great celerity, and a manifeft cor- 
 rugation of the fibres ; whereby the whole heart be- 
 comes fhorter, thicker, and harder, fo that the left 
 ventricle is drawn fomewhat towards the feptum of the 
 heart, and the right one much more. The bafe alfo 
 advances towards the apex ; but the apex more evi- 
 dently towards the bafis. This -I have often obferved 
 with the greatefl certainty in difl'ecting brute animals ; 
 fo that thofe learned gentlemen muff have feme w'ay or 
 other been deceived, w'ho have afl'erted, that the heart 
 is elongated during its contraftion. But the heart does 
 not feem to turn pale in fuch animals as have warm 
 blood. Even the feptum of the heart is rendered fhorter, 
 and draws itfelf towards the bafis. By this aftion, the 
 flefhy parts of the heart fw'ell inwardly, and comprefs 
 the blood, as they do the finger, when introduced into 
 its cavities. But that the heart is confiderably enough 
 emptied in this adion, appears both from the event ; the 
 evident palenefs of animals whofe heart is white, as frogs 
 and chickens ; and from the internal furface being full 
 of eminences, which exadfly anfwer to oppofite cavi- 
 ties, and to the thick reticular arms or columns inter- 
 rupted by finufes. Finally, the apex of the heart, be- 
 ing contrafted a little like a hook, ftrikes againft that 
 part of the pericardium next the thorax. Forwards, 
 there is alfo a pulfation from the left venal finus ; which 
 is, at ^hat time, particularly filled. In exfpiration, the 
 heart flrikes violently more upw'ards and forwards. 
 The truth of both thefe we know^ by experiment. 
 
 104. The blood, wdiich is prefl'ed by the contracted 
 heart (log), endeavours to efcape in all diredlions ; but 
 being driven from the mufcular Tides, tow^ards the axis 
 of the ventricle, by the reaftion of what is lodged be- 
 twixt 
 
Chap. V, HEART. 47 
 
 twixt the venal ring (93 .) and Tides of the heart, the loofer 
 ends of the faid ring are driven forwards and extend- 
 ed inward at the fame time. By this action upon the 
 whole circumference of the ring,, it not only becomes 
 extended itfelf, but, at the fame time, throws back a 
 part of that blood into the right auricle whicli had 
 before defcended into the cone of the open valve, 
 whole fides, now approaching, (hut up the venous ori- 
 fice more dofely as the heart contrafts more ftrongly, 
 by whole force the tricufpid valves, as they are called, 
 would be preffed reduplicated into the auricle, if the 
 mufcular nipples (94.) or columns did not keep down 
 their edges, and hold them firmly by their contraftion 
 (which is the fame with that of the heart) in fuch a 
 fhape, as will extend the annexed chords of the valve, 
 without injuring them. 
 
 105. But the nifus of the remaining blood, now re- 
 filled by the tricufpids, feeks another courfe ; and, 
 whilfl it derives the larger of thofe valves that is feated 
 to the right (94.), from the fide towards the axis of the 
 heart, this leaves open the mouth of the pulmonary ar- 
 tery, which it before coverfed ; whereupon the blood 
 prefling the valves in the mouth of the faid artery clofe 
 to its fides, it thus rufhes into it. 
 
 106. To defcribe this more particularly; from the up- 
 per and pollerior part of the right ventricle, a way leads 
 into the artery, taken in as it were between the flefliy 
 parts of the heart produced, and ftrongly connected to 
 it by a cellulous, callous ring, from whence the artery 
 afcends to the left backward, and difplays itfelf behind 
 the arch of the aorta. The ftrength of this artery is 
 not extraordinary, being much weaker than that of the 
 aorta. But from the inner furface of the artery, where 
 it is joined to the heart, three femilunar valves arife, by 
 a reduplication of the arterial membranes extended up- 
 wards, and towards the axis, in an arch that is flat or 
 obtufe enough ; and thefe valves always ftucluate with 
 their edges at free liberty, in a parabolical fhape. The 
 middle of the edges, in each of thefe valves, is gene- 
 rally 
 
48 HEART. Chap. V. 
 
 rally divided, fometimes in the foetus itfelf, by a fmall, 
 denfe, callous body, of a conical fhape, but made up of 
 inclined planes ; whereby each whole valve, in itfelf re- 
 fembling an half-moon, is thereby again fubdivided into 
 two lefs half-moons. Betwixt the two membranes of 
 the valve, appear fome mufcular or tcndmous fibres, 
 partly in a tranfverfe pofition ; fome of which hold fait 
 the valve to the next contiguous fide ot the heart, leav- 
 ing fometimes fpaces betwixt them in a reticular man- 
 ner. Other fibres afeend from the bafis of the valve j 
 and, by growing to the callous corpufcle, draw back 
 the laid valve, and open its concavity. 
 
 107. Each of thefe valves, in conjundion with the 
 fides of the artery here diverging, intercept a fpace, 
 which is blind or impervious downward ; but open up- 
 ward in a parabolical fhape, as we obferved of the 
 valves in the veins (49.) When, therefore, the blood 
 is impelled from the fides towards the axis of the con- 
 tracling heart, it endeavours to efcape in the diredlion 
 of the faid axis ; and, by rufhing forth like a wedge, 
 betwixt the valves, preffes their loofe fail-like edges 
 againft the fides of the pulmonary artery, fo as to run 
 freely out of the heart. The truth of this appears from 
 the plain fabric, from injections, and from ligatures, 
 which, by obflrudting the lungs, will not fulfer the large 
 cavities in the right fide of the heart to be emptied. 
 
 108. The blood now received into the pulmonary 
 artery, goes on then to make its circulation through the 
 lungs. That artery is firfl: divided into twm branches ; 
 of which the left, being lefs and fhorter, enters dircdfly 
 into the fubflance of the lungs : but the right branch, 
 being larger and longer, paffes tranfverfely through the 
 arch of the aorta; and, after going a little way behind 
 the faid aorta, enters the correfponding lungs of the 
 fame fide. From each of thefe branches, by a multi- 
 plied fubdivifion, arife the very lead arteries, fome of 
 which tranfmit the blood directly into the continued 
 fmall veins, and others exhale part of its aqueous juices 
 into the pulmonary cells. That the blood goes thus di- 
 
 reaiv 
 
HEART. 
 
 Chap. V. 
 
 49 
 
 leQily from the arteries into the pulmonary veins, ap- 
 pears evidently from their ftrufture ; alfo from a liga- 
 ture, which, intercepting the blood’s courfe, while the 
 heart and lungs flill urge it, caufes an aneurifmatic di- 
 latation of the artery ; and from polypufes, by which, 
 the mouth of the pulmonary artery being obftrudted, 
 the right cavities of the heart become monftroufly en- 
 larged, and at length burft, while the left remain empty. 
 Laftly, from injeftions ; for water, fifh‘glue, and milk, 
 are very eafily forced from the pulmonary artery into 
 the vein, and from thence into the left cavity of the 
 heart. But the diredt anaflomofes or final openings 
 of the arteries into the veins in the lungs, is proved 
 even to the fight by the microfcope, in frogs, &c. 
 
 109. Nor can the blood, which has once entered the 
 pulmonary artery, return back again upon the heart ; 
 becaufe the valves therein (106.) are of fuch dimen- 
 fions, that, when diflended, they perfeftly fliut up the 
 opening at the heart ; and are fo ftrong, that they refifl 
 a much greater force than the contradion of the pul- 
 monary artery, without being conftrained to yield. 
 However, fometimes, from a greater contradile force 
 of the artery, they grow fomewhat callous ; or, from a 
 laceration of their outer membrane, a bony matter is 
 poured in betwixt the duplicature of the valves. For, 
 when the blood, by the contradion of the artery, re- 
 turns towards the heart, it meets and enters the open 
 fail-like concavities of the valves (107.), which are, by 
 that means, expanded, and driven together towards an 
 axis in the middle : whence the valves, once expanded, 
 quite fhut up the mouth of the artery, fo as to leave not 
 the lead flit open ; for any opening that might be left, 
 is precluded by the fmall callous bodies remarked at 106. 
 
 1 1 o. The pulmonary veins ^ of which we lhall fay more 
 hereafter, gather into larger branches, which, at laft, 
 terminate in four (feldom two, and flill more rarely in- 
 to five) trunks ; to which it has been cuftomary ta 
 affix a name in the fingular, by calling them the pul- 
 monary vein. Thefe enter the cavity of the pericar- 
 . H dium. 
 
50 HEART. Chap. V. 
 
 dium, From whence they receive an external covering ; 
 and are then inferted at angles into the fquare left or 
 ■pojlerior finus^ which is fometimes likewife called the 
 pulmonary finus. In this courfe the upper veins de- 
 fcend, as the lower ones afcend. But that thefe veins 
 bring their blood towards the heart, in the fame direc- 
 tion with the fmus into which they open, is proved by 
 a ligature, which caufes a turgefcence or fwelling, from 
 the blood retained, betwixt the ligature and the lungs. 
 
 111. This pulmonary fmus, which is almofl of a cu- 
 bical figure, being firmly built of divers bundles of 
 fibres running betwixt two membranes, has, forward 
 and to the right, one fingle fide or partition, in com- 
 mon to itfclf and the right finus (86.); but, forward 
 and to the left fide, it goes into a conical appendix, 
 which is divided into proceffes, or indentations, like a 
 cock’s comb ; and, after two or three ferpentine turn- 
 ings, makes what is called the left auricle^ incumbent 
 on the left ventricle, and pointing forwards. Some of 
 its fibres, as in the right auricle, by their bending, con- 
 traft it into the form of an arch ; others, coming from 
 the origin of the appendix, and inferted into its apex, 
 deprefs it. This finus, with the left auricle, are fome- 
 what lefs than the right finus and auricle. 
 
 112. In this left finus, the blood waits for the heart’s 
 relaxation ; at w'hich time the nifus of the blood im- 
 pelled againft the venous valves, and the contrading 
 Ilronger force of the finus, grow lefs. Then the left 
 finus ftretches itfelf forward acrofs the heart, is contraft- 
 ed tranfverfely along with it, and the appendix becomes 
 evidently fliorter and narrower. Thus the blood is 
 driven into the left ventricle, in like manner as the right 
 auricle impelled its blood into the right ventricle, (95.) 
 For here, as before, a like membranous oval ring forms 
 productions called mitral valves, of which there are u- 
 fually two only counted. Thefe valves are longer and 
 Ilronger than thofe of the right ventricle. They have 
 each a mufcular column, often fingle only, and joined 
 to the tendinous threads of each valve : but they are 
 
 much 
 
Chap. V. HEART. 51 
 
 much ftrongcr than thofe of the tricufpids. And here, 
 more frequently than in the valves on the right fide, 
 callous knots, or cartilaginous humours, are found in 
 the tendinous ftrings, at their originations from the 
 membranous ring. 
 
 1 1 3. From what has been faid, then, it appears, that 
 the fame blood is now arrived into the left ventricle of 
 the heart, which was a little before fent from the venae 
 cavae into the right auricle (89.), which drove it into the 
 correfponding or right ventricle (95.) ; by which, again, 
 it was urged into the pulmonary artery (105.); and, 
 from thence, palling into the pulmonary veins, was 
 conveyed into the left fmus (no.); and, out of this, 
 we here find it driven into the left ventricle (112.). 
 This courfe of the blood, from one fide of the heart to 
 the other, through the lungs, is called the pulmonary 
 or leffer circulation, and was known to many of the an- 
 cients. It is proved by the increafed bulk of the pulmo- 
 nary veins on the left fide ; and likewife of the right 
 cavities of the heart, on an obftrudion of the entrance 
 into the left ventricle. 
 
 1 14. The left, or pofterior, and upper ventricle of 
 the heart, which is always firft formed, and in a great 
 number of animals the only one, makes up that part of 
 its half-cone-like body, which we before called obtufe, 
 (91.) It is fomewhat narrower than the right ven- 
 tricle, a little longer, rounder, and generally of a lefs 
 capacity within. For the contents of this ventricle are 
 about two ounces, while thofe of the right advance up 
 to three. Its fabric internally is reticular, but more 
 nicely wrought than in the right ventricle ; and with- 
 in the mouth of the artery it is fmooth : but irs force 
 is confiderably greater, as the mufcular flefii that fur- 
 rounds it is much thicker, and almofh 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 reticulated in like manner ; but folid, 
 and incapable of fulfering any injeded liquid to pafs 
 from one ventricle to another. 
 
 H 2 
 
 1 15. Again, 
 
52 
 
 HEART. Chap. V. 
 
 1 1 5. Again, this left ventricle, being inftigated to 
 motion by the impelled blood, does, from the fame ir- 
 ritable nature before mentioned (103.) contraQ:, and 
 drive its contained blood with a violent motion in the 
 direftion of its axis, and determine it towards the bafis, 
 at the time when the tip or cone of the heart is drawn 
 nearer to its bafis. And fmce the apparatus of the 
 mitral valves is here the fame as before in the tricuf- 
 pids, the venous blood, now expanding the ring from 
 w'hence they arif^, removes that valve which lay againfl 
 the mouth of the aorta, fo as to open a way for itfelf to 
 the artery ; in dilating the mouth of which, the faid 
 blood preffes the femilunar valves, there placed, againfl 
 the fides of the aorta, into which it rufhes with a vio- 
 lent impetus. This is proved by ocular demonflration 
 in living animals, where the left ventricle fwxlls upon 
 fhutting the paffage into the aorta. 
 
 116. The femilunar valves of the aorta differ little 
 from thofe in the pulmonary artery : only as the open- 
 ing is here greater, fo the valves are propoitionably 
 larger and flronger, and are not fo often dilUnguiflied 
 in the middle by thofe callous globules or little round 
 bodies. The fibres too of the valves, both tranfverfe 
 and afcending, are here fomewhat more confpicuous. 
 
 1 1 7. After the contraftion of the heart, follows its rela- 
 xation or diaflole, in which it becomes empty, lax, and 
 foft, recovers its former length, the ventricles recede 
 from the feptum, and the bafis from the apex. But, 
 while it is in this (late, the blood in the auricles, having 
 been as it were in a flate of expectation, rufhe s through 
 the openings of the valves of the veins, dilates the op- 
 pofite fides of the heart, and makes it at once longer and 
 larger. After the auricles have freed themfelvcs of the 
 blood they contained, they are in like manner relaxed, 
 and their oppofite fides remove from each other. Then 
 the blood, collected in the venm cavse and pulmonary 
 veins, fills the auricles by the contraction of the veins ; 
 renders them long, bread, and thick, like the ven- 
 tricles ; and even di fiends and fills the tooth-like pro- 
 
 cclfes 
 
Chap. V. HEART.. 53 
 
 ceffes of the crefted margin. That the fibres of the 
 heart are not dilated, is proved from the jundfion of 
 thofe fibres ; which, being tied together by their mid- 
 dle branches, cannot be feparated : alfo, by the diffec- 
 tions of live animals, in which the whole heart is fiiown 
 to be contraded. 
 
 118. But we mufl; now confider, that thefe motions 
 of the right and left auricle, with the right and left ven- 
 tricle, are not performed in that fucceffion in which, 
 for the fake of method, we have here defcribed them ; 
 for both the auricles are contraded, while the ventricles 
 are relaxed ; fo that the contradion of the auricles pre- 
 cedes the contradion of the ventricles ; as we are af- 
 fured from manifefl experiments on dying animals, and 
 on thofe whofe living blood is cold. But both auricles 
 are filled together in the firft inftant, as both of them 
 are emptied together in the fecond inftant ; and both 
 the ventricles, are contraded together in the third in- 
 ftant, which is the fame with the firft ; and both ven- 
 tricles, being evacuated, are relaxed in the fourth in- 
 ftant, which is the fame with the fecond. Thofe who 
 have miftakenly taught otherwife, have not taken the 
 advantage of making a fufficient number of experi- 
 ments on living animals. That the auricle, near death, 
 makes frequent palpitations, before the ventricle of the 
 heart performs one contradion, is true enough. The 
 auricle wnth its finus forms one cavity, and both are fill- 
 ed and both emptied in the fame inftant. 
 
 I ip. But it may be afked, why the heart never ceafes 
 from its perpetual motion, through fuch a number of 
 years as there are in one’s life, through fo many days 
 as there are in a year, and through, fo many hours as 
 there are in a day ; when, in each hour, the heart of a 
 healthy perfon contrads not much lefs than 5000 times; 
 fo often are there fucceffive repletions followed with 
 new contradions, perpetually in the fame conftant or- 
 der. Nor is there any other mufcle, befides the heart 
 and diaphragm, but what becomes tired and painful, 
 by ading incelfantly, even for a few hours. Different 
 
 anfwers 
 
54 HEART. Chap. V. 
 
 anfwers have been given to this queftion by different 
 profeffbrs, founded either upon a compreflure of the 
 cardiac nerves betwixt the large arteries, or upon an 
 alternate repletion of the coronary arteries and cavities 
 of the heart, &c. 
 
 12 0. But to me the fimplicity of nature feems very 
 great in this matter. When the auricle is relaxed, it 
 is diredlly filled by the mufcular force of the continu- 
 ous great vein ; and fo the heart alfo contracts itfelf, 
 when, in like manner, it is irritated by the blood driven 
 into it from the auricle. Therefore, the heart, having 
 once received the blood, is contraded by that ftimulus 
 or irritable force, whereby mufcular fibres are excited 
 into contradion *, whereupon it empties itfelf of the 
 blood, and, being freed from the ftimulus thereof, im- 
 mediately refts or relaxes itfelf. But the heart being 
 now relaxed, the auricle is in like manner irritated by 
 its contained blood, and by contrading fills it again ; 
 while the inceffant adions of the heart and arteries con- 
 tinually urge new blood into the right finus and au- 
 ricle. That this is the true flate of the heart’s mo- 
 tions, is proved from adual experiment or obfervation ; 
 whereby we plainly difcern the fucceflive repletions and 
 conflridions made in the great vein, auricle, ventricle, 
 and artery, eafily feen in a weak or expiring animal j 
 but more efpecially, and more evidently, in thofe ani- 
 mals which have but one ventricle in the heart ; as the 
 tortoife, frog, fnake, fiflies ; and in the chick hatching 
 in the egg, which, inftead of a heart, has only one 
 crooked canal. The fame is alfo confirmed from the 
 refting of the heart, which follows upon tying the veins ; 
 and from the return of its motion, by removing the li- 
 gatures, or by the impulfe of wind or liquors injeded ; 
 and, lafily, from the perpetual contradion of a frog’s 
 heart, round or upon a veficle of air inflating it ; which 
 air, urged into it by the veficle, it will alternately re- 
 ceive, and for many hours tranfmit into the common 
 air. The left ventricle firfl ceafes its motion ; then the 
 auricle of that fide j then the right ventricle j after that. 
 
Chap. V. HEART. 55 
 
 the right auricle ; and, laft of all, the pulmonary vein$, 
 and venss cavse. Whatever motion is in the vense ca- 
 vae, ought to be attributed to the auricle repelling the 
 blood into both thefe veins, and which the heart, when 
 dead, is not capable of receiving. 
 
 121. Nor do I believe there is any thing more re- 
 quired to the heart’s motion, than a continual ftimulus 
 applied to a very irritable part. For, even in the ar- 
 ticle of death itfelf, the very coldnefs of the limbs, which 
 the warmth of life has left, contracts the veins, and. 
 drives the blood to the heart ; when the lungs, being 
 impermeable for want of refpiration, tranfmit no blood 
 to the cavities of the left hde. And, on the other 
 hand, the heart, after it is thoroughly emptied, re- 
 mains at reft. It may thus happen, that, inftead of 
 the vena cava and right auricle, the laft appearance of 
 life may be transferred to the left auricle and ventricle ; 
 if we fuppofe the right cavities to be empty, the left 
 may be irritated by the blood contained in them. But 
 if you derive the refting of the heart from the compref- 
 fion of its nerves, the motion of the auricles will be an 
 obje£lion, becaufe their nerves are not comprefled. An 
 example alfo we have in filh, and little chicklings in the 
 egg, where there can be no room for a compreflure of 
 the nerves. If, again, you deduce the heart’s reft from 
 a compreflure or occlufion of the coronary arteries, 
 this is contrary to experience ; fince they are not co- 
 vered by the valves of the aorta, and from a wound of 
 the faid arteries, during the fyftole of the heart, the 
 blood ftarts out to a great height. 
 
 122. Nor, with the ftrength of the heart, do I join 
 the ofcillations of the very fmall veflels, which is refuted 
 by experiments : nor the force of external heat ; feeing 
 animals are found to live and thrive in the coldeft re- 
 gions of the north : and though the contradlile force 
 of the artery, and the weight of the parts and of the 
 atmofphere, alTift the motion of the blood during the 
 diaftole of the heart, the fame powers refill it during 
 the fyftole j fo that, indeed, by thefe means, the blood 
 
5^ HEART. Chap. V, 
 
 is moved no farther through the contractile arteries, 
 than even through the rigid arteries of the fmaller ani- 
 mals. 
 
 123. But with what celerity, and with what force, the 
 heart drives forward the blood, is controverted, and 
 varioufly computed. The more modern writers have 
 raifed their calculations upon a fuppofition that, for the 
 celerity to be determined, we are to admit two ounces 
 of blood to ilTue out of the heart with fuch a celerity, 
 that the part of the pulfe, called its fyjlole, makes one 
 third of the whole pulfation, and is hnilhed within a 
 VTT part of a minute j but the area of the mouth of 
 the aorta, they have eftimated 0.4187 parts of an inch : 
 fo, by dividing the fpace filled by two ounces of blood, 
 (3.318 inches) by the area or feftion of the aorta at its 
 mouth, (^and length of its cylinder filled by two ounces, 
 viz.=7ff^], the number thence produced divided by 
 
 the time in which the heart contratfs, they find 
 149 feet and two tenths of an inch for the fpace thro’ which 
 the blood runs in a minute, if it goes on in a cylinder 
 with the fame velocity it firft had from the heart. But 
 the incumbent weight of blood moved by the heart, 
 they have computed by the jet wherein the blood (tarts 
 forth from the larger arteries in a living animal, being 
 feven feet five tenths; and from the furface of the ven- 
 tricle, whofe area make 15 inches; which produce 
 1 350 cubical inches of blood, or 5 1 pounds five ounces, 
 which prefs againfl the ventricle of the contracting 
 heart. The heart, therefore, thus drives forward a 
 weight of 5 1 pounds, with a velocity by which it may 
 run through 1 49 feet in a minute ; which force it 
 exerts four thoufand eight hundred times in an hour. 
 
 1 24. Although there are many particulars here un- 
 thought of, which may render the eftimate incomplete, 
 and l^uch perhaps as we may never get over ; and 
 although the mouth of the diftended aorta may be wi- 
 der in a living animal, though the area of the ventricle 
 is of uncertain dimenfions, and the jet of blood com- 
 puted from an infufficient height ; yet, if we confider 
 
Chap. V. HEART. 5? 
 
 the violence with which the blood ftarts from lome of 
 the lead; fanguine arteries in the living animal, although 
 we cannot eafily determine how much of the heart’s 
 fyftole it affutnes to itfelf, variations in which will great- 
 ly alter the computation ; yet, in the mean time, it 
 will plainly appear, that the machine we call the heart 
 is a very powerful one. The truth of this is evident 
 from experiments, in which it appears to be very diffi- 
 cult to fill all the red blood-velfels by anatomical in- 
 jedions, and quite impoffible to fill all the fmaller of 
 them : yet the heart, we fee, not only gradually diflends 
 all the larger, the fmaller, and even the lead veffels, with 
 blood, but alfo drives it forward through them with a 
 confiderable celerity. Even in the leaft arteries, the 
 blood is urged forward by the heart with fuch a force 
 as to make the alternate motions of that mufcle per- 
 ceptible. Likewife, in the veins and fmaller veffels of 
 cold animals, even while contained in the infcfts egg, 
 there is no other force befides that of the heart, by 
 which the blood is driven through their fmall veffels. 
 And, from fome of the lead arteries, I have feen the 
 blood dart forth feveral feet, the jet defcribing a para- 
 bola, whofe height was four feet, and amplitude of the 
 projefliion feven feet ; and fome affert, they have feen 
 the blood afcend from the aorta to the height of twelve 
 feet. 
 
 125. Moreover, that we may make a jud edimate 
 of the heart’s force in living animals, we mud confider 
 what great refidances that complex mufcle overcomes : 
 we mud compute the enormous weight there is of the 
 whole blood; a mafs, perhaps, of fifty pounds and 
 npwards : for all that quantity of fluids, once dagnant 
 in a perfon lately drowned or fainted away, are eafily 
 put into their former motion by the heart only. We 
 mud again confider the great decreafe of the blood’s 
 velocity, arifing from the greater light or capacity of 
 the dividing branches, (from whence the ratio of its ce- 
 lerity, even in the intedines, may be computed to on- 
 ly a 24th or a 30th part of its original impulfe), abates 
 
 I two- 
 
58 HEART. Chap. V. 
 
 two-thirds from the heart’s force. And yet we fee 
 there are humours fwiftly moved through much fmall- 
 er velfels ; as, for example, in thofe of the Sancforian 
 perfpiration, which, in a fubterraneous cavern, I have 
 obferved to afcend fwiftly in form of fmoke or vapour ; 
 and the fame celerity of the blood in the leafl veflels of 
 little fifhes, &c. is apparent to the eye by a microfcope. 
 Now, fince the fridions, in every machine, always 
 confume the greateft part of the moving forces ; much 
 more do they in the human body, whofe blood and 
 juices are fo much more vifcid or clammy than water, 
 and driven through' veifels fo fmall, that they permit 
 only a globule at a time to pafs through, and even 
 hardly allow that without changing their figure : but from 
 fo ftrong and extended a fri£Hon there mufl neceffarily 
 follow a very great hindrance to the motion ; whence 
 we may eafily underftand, that the force muft be very 
 great which drives fo fwiftly fuch a prodigious mafs of 
 fluids over fo many refiftances and decrements of the 
 moving forces. But aneurifms, andlikewife arteries, are 
 burfl by the force of the heart ; and great weights are 
 elevated along with the human body by the force of 
 its fyftole. 
 
 126. The blood, being driven into the aorta, imme- 
 diately finds the two openings of the coronary arte- 
 ries, which lie next the arterial valves, but above them, 
 or within the aorta ; and, in confequence of this, it 
 ruflies firfl of all into the faid coronary arteries, by 
 which the heart fupplies icfelf with blood. Thefe arte- 
 ries are almoft conftantly two ; which going off from 
 the aorta next the heart at an obtufe angle, the right 
 goes off between the aorta and pulmonary artery, and 
 the upper and left one between the left auricle and the 
 aorta. All the external arteries are furrounded with 
 much fat ; but their cavity is more intercepted with 
 valves than that of other arteries. Thefe arteries com- 
 municate, by inofculations of the fmall branches, every 
 where about the feptum and tip of the heart ; but they 
 
 no 
 
Chap. V. HEART. 5p 
 
 no where make a complete ring round the heart. They 
 terminate in a two-fold manner. 
 
 127. The firfl termination of them is into the coro- 
 nary veins, whofe branches running in company with 
 thole of the arteries, have their trunks of neceffity dif- 
 pofed in a different courfe. The great coronary vein is, 
 therefore, a companion of the left coronary artery ; 
 and is inferted with a large opening, fecured with 
 valves, or a number of little membranes, on the left 
 fide of the Euftachian valve of the right auricle : the 
 root of this furrounds the left auricle externally, and 
 then accompanies the fuperficial branches of the left 
 artery. 
 
 128. The other coronary vein (which you may 
 make a part of the former, fince they have both one 
 common infertion) defeends along upon the feptum of 
 the heart to its flat fide ; and may be properly called 
 the median coronary. The third bends tranfverfly round 
 the furface of the right auricle ; and then terminates 
 within, or at leafl; very near, the large opening of the 
 edronary vein (i 2 7.) anteriorly. This vein fupplics that 
 part of the right ventricle which lies in the flat fide of 
 the heart ; and often receives thofe namelefs veins we 
 fhall hereafter deferibe. 
 
 129. There are ftill fome other anterior veins of the 
 heart ; but one, more particularly large, goes along 
 the adjacent edge of the right ventricle, and, running 
 for fome length obliquely betwixt the membranes, is 
 inferted into the mofl: anterior part of the right auricle, 
 and fometimes into the trunk of the upper vena cava. 
 This anterior vein fends off another concealed one 
 through the root of the right finus ; and, being again 
 inferted into the great coronary vein, it makes a com- 
 plete circle round the heart, like the arterial circle 
 which fome have deferibed, but has not yet been feen 
 by me. 
 
 1 30. But there are a great many more veins, un- 
 certain in their number, which belong to the bafis and 
 internal parts of the heart, to which the anatomift has 
 
 I 2 feldona 
 
6o 
 
 HEART. Chap. V. 
 
 feldom any accefs, becaufe they lie concealed betwixt 
 the origins of the large veffels : and thefe open by num- 
 berlefs fmall mouths into the right finus and auricle ; 
 and fome, but a few only, into the left finus. Thus 
 I have feen a particular vein, which, from a latent fi- 
 nus in the flefh of the right auricle, has afcended to- 
 wards the aorta and pulmonary artery, and inferred it- 
 felf on one fide into the greater coronary vein. Ano- 
 ther I have obferved, concealed betwixt the mouth of 
 the coronary vein and the aorta, inferred into the right 
 finus ; and another through the remains of the oval 
 foramen, and feptum of the two finufes, inferring itfelf 
 into the right finus ; and others again belonging to the 
 venous valves ; befides which, there are ftill others too 
 numerous to deferibe. I have obferved alfo a vein 
 arifing from the left finus, and inferred into the vena 
 cava. 
 
 I 31. There are ftill more, and much fmaller, veins 
 in the heart, whofe little trunks, being very lliort, can- 
 not eafily be traced by diffeftion ; and thefe open them- 
 felves by an infinite number of oblique fmall mouths, 
 through all the numerous fovas or little finuofities and 
 excavations obfervable throughout the furface of the 
 right and left ventricle. Thefe are demonftrated by 
 injedions of water, wind, or mercury, made by the coro- 
 nary arteries, after you have firft tied their correfponding 
 or accompanying coronary veins ; or even bv injecting 
 into the great coronary veins, after you have firft inter- 
 cepted the openings of their largeft trunks. For, in 
 cither of thefe cafes, there are drops of the tinctured 
 water, bubbles of air, fpherulcs of mercurv, rulhing 
 out through the w'ho.le extended furfaces of both the 
 ventricles of the heart: and this, without any violence 
 that can be fuppofed fufficient to break the velTeis. 
 But the paftage from the arteries into the cavities of 
 the left fide is more difficult. 
 
 132. There are fome wdio will have the coronary 
 arteries filled with blood, not by the contracting of the 
 heart, but of the aorta in its fyftole ; which they think 
 
 muft 
 
Chap.V. heart. 6 i 
 
 muft be a confequence of the retrograde angle of the 
 blood’s courfe here, and the palenels of the contraded 
 heart, with a fuppofition that the valves of the aorta 
 cover or clofe the mouths of the coronary arteries. 
 But the two laft of thefe are difproved by experience ; 
 and the firft, or retrograde courfe, can only impede 
 or leffen, and not intercept, the flux into the heart : 
 for the injeftions of wind or mercury, into all the fe- 
 minal and biliary veflels, demonftrate, that the large 
 retrograde angles, which the veflels often there make, 
 do not hinder the fluids from taking their natural 
 courfe, though they retard it. But a proof, ftill more 
 evident, is, that the coronary artery has a pulfe at the 
 fame time with all the other arteries in the body, and 
 the blood darting from it makes a higher faltus at the 
 time when the heart is contra£fing( 121.) 
 
 153. Concerning the reflux or return of blood from 
 the mufcular fubftance of the heart, there is ftill lefs 
 room to doubt : for all the coronary veflTcls difeharge 
 their blood into the auricles and ventricles, either right 
 or left, (but lefs into the latter), by thofe larger (127, 
 128, 129.), and by the fmaller orifices (130.), as well 
 as by the leaft (131.), which fo eafily tranfmit the in- 
 jections, after you have firft tied the larger coronary 
 veins. The circulation through thefe veflels feems to 
 be compleated in the ftiorteft fpace of time that can be 
 in any part, from the great velocity the blood receives 
 from the heart itfelf, urging the fame through its own 
 fubftance. But that the whole contents of the veflels 
 are cleared in each contraction, does not feem to me 
 probable ; for the blood-veflels of the heart do not 
 look pale enough in that aCtion to produce fuch an ef- 
 fect as an entire evacuation. There is a very free or 
 open paflage from the arteries of the heart into the cel- 
 lular fubftance, or fat, which furrounds it. If you afk. 
 What are the ufes of thofe leaft or ftiorteft veins which 
 open obliquely through the furface of both the ven- 
 tricles ( 1 3 1 .) ? they ferve to return the blood of thofe 
 
 deeply 
 
62 BLOOD. Chap. VI. 
 
 deeply feated fmall arteries, which have no correfpond- 
 ing veins. 
 
 1 34. The humours of the heart, which are thinner 
 than blood, return by the valvular lymphatic ■veins, 
 which accompany the coronary blood - velTels, and 
 afcend towards the thoracic du6t and fubclavian vein ; 
 but are very rarely to be feen, although 1 have obferved 
 them in brute animals. 
 
 CHAP. VI. 
 
 Of the Nature of the Blood and Juices of the Human 
 
 Body. 
 
 135. I ^ H E liquor which is contained in the beat- 
 JL ing arteries and their correfponding veins, 
 is called, by one general name, the blood ; which, to aloofe 
 examination, appears homogeneous, or of fimilar parts, 
 red and coagulating throughout ; and is obferved to 
 be redder in proportion to the ftrength of the animal ; 
 in a weak and fciinlfhed one, the blood inclines to a 
 yellow : it hath a whitenefs mixed with it, which 
 comes almoil totally from the chyle. But experiments 
 of diverfe kinds have Ihown us, that diffimilar parts of 
 various natures refide in the compofition of this animal 
 liquor. 
 
 1 36. That fire is contained in the blood may be 
 proved from its heat, which, in human blood and that 
 of fome other animals, is from 92 to 100 degrees 01* 
 Fahrenheit’s thermometer, more than the mean de- 
 gree of atmofpherical heat, but lefs than the greateft. 
 Again, a kind of volatile vapour or exhalation conti- 
 nually flies off from the warm juice, with a fort of 
 fetid odour coming betw'ixt that of thefweatand urine. 
 This vapour, being catched and condenfed in proper 
 veffels, appears of a watery nature, joined with a fmall 
 tinfture of an alkaline difpofition. 
 
 137. After this vapour is gone off, the blood of a 
 
 healthy 
 
Chap. VI. BLOOD. 6 ^ 
 
 healthy perfon fpontaneoufly congeals into a fciffile 
 trembling mafs j and, with a lefs degree of heat than 
 that of boiling water, (viz. 150 deg.), it grows more 
 tough, like to a boiled egg. This toughnefs is greater 
 in feveriili perfons than in fuch as are in health. It forae- 
 times coagulates in the veins of a living perfon, and is 
 found clotted in wounds of the arteries. But even 
 within the velfels of a living perfon, and in one dying 
 of a fever, the blood has been feen, by the violence of 
 that diftemper, changed into a concreted tremulous jelly 
 throughout all the veins. The principal part of this 
 coagulated mafs is the crajfamentum or cruor, which 
 has the red colour peculiar to itfelf, and gives it to the 
 other parts of the blood. This, if it be not kept fluid 
 by the attrition of a vital circulation, or fome fimilar 
 concuffion, runs confufedly into a compact, but foft 
 mafs, like liver, merely by reft and a moderate degree 
 of cold ; as it alfo does by the addition of alcohol, by 
 mineral acids, or by a heat of 150 degrees, of 
 which 98 is the blood’s heat in robuft people. It 
 is, either as a fluid or a folid, fpecifically heavier than 
 water by near an eleventh part j and, when freed 
 from its water, it is wholly inflammable. In a mafs of 
 healthy blood, one half or upwards is red cruor: and, 
 in ftrong laborious people, the feruni makes only a 
 third part ; and is ftill more diminilhed in fevers, often 
 to a fourth or fifth part of the mafs. 
 
 I 38. From this coagulum there feparates, at firft as 
 it were fweating out of its pores, but which afterwards 
 collefts in fufficient quantity to allow the concrete to 
 fink in it, another white, fomewhat yellowifli, part 
 of ,the blood ; which again feems to be a liquor, con- 
 fifting of homogeneous or fimilar parts, when it is not 
 really fo. This part of the blood is, in general, one 
 thirty-eighth part heavier than water, and almoft a 
 twelfth part lighter than the red globular mafs of craf- 
 famentum: this too, by an heat of 150 deg. or by mix- 
 ture of mineral acids or alcohol, and by a concuflive 
 motion, is congealable into a much harder coagulum 
 
 than 
 
64 BLOOD. Chap. VI. 
 
 than the red cruor (137.); and forms an undiflfolvablc 
 glue, a flefli-like membrane, which at length fhrinks 
 up to a horn-like fubftance, or friable gum. From 
 thence are formed the pleuritic crufts or ficins, polv- 
 pufes, and artificial membranes. In this ferum of the 
 blood, befides the albumen, which will harden like 
 the white of an egg, there is concealed a great deal of 
 fimple water ^ which even makes the bigger part of the 
 whole ; and fome quantity of a ropy mucus^ capable of 
 being drawn into threads better than the red cruor ; 
 which lafl, however, is not coagulable like the albu- 
 men, neither by fire nor by acids. 
 
 139. But, by putrefaftion only, or the dilTolving 
 power of the air hot to 96 deg. equal to the blood’s na- 
 tural heat, the whole mafs, but efpecially the ferum, 
 diiTolves or melts into a fetid liquor ; firll the ferum, 
 and then the cruor more flowly ; till, at length, the 
 whole mafs, both of ferum and cruor, is turned into 
 a volatile and fetid exhalation ; leaving very few feces 
 behind. The blood being a little diffolved by putre- 
 faftion, and even before that, becomes fetid ; with 
 the fetor, affumes an alkaline nature ; and eftervefees 
 with acids. This property it afterwards lofes, the al- 
 kaline fait being deflroyed by putrefaction. The pu- 
 trid blood cannot by any art be infpifi'ated, as it is al- 
 fo very difficult to be relblved after it has been coagu- 
 lated by fpirit of wine. By too fevere exercife, heat, 
 and malignant diforders, the cohefion of the blood is 
 diffolved, and it affumes an alkaline nature ahnofi; as if 
 from putrefaction. 
 
 140. Befides thefe parts of which the blood appears 
 to confift, without fubjeCting it to any violence, it 
 contains in its fubftance a quantity of fea fait, which 
 is difcernable to the tafte, and fometimes vifible by the 
 microfeope. That there is earth lodged in the blood, 
 is demonflrated from nutrition ; and from a chemical 
 analyfis, whereby the earth appears to lodge in the molt 
 fluid, and efpecially in the oily, parts of the blood. 
 By fome very late experiments, it appears, that a con- 
 
 fiderablc 
 
Chap. VL BLOOD/ 65 
 
 liderable quantity of ferruginous earth, eafily reducible 
 into metal by the addition of phlogifton, is contained 
 in the blood when calcined. Laftly, another part in 
 the blood is air in an unelaftic flate, and that in a very 
 confiderable quantity 5 the exiflence of which air in the 
 blood and feruin is proved by their putrefadlion and 
 diftillation, or by removing the ambient air from them 
 by the pump. But we are not to think, from hence, 
 that the blood-globules are bubbles full of air, for they 
 are fpecifically heavier than the ferum. 
 
 14T. By the admixture of neutral falts, the colour 
 of the blood becomes deeper and brighter, as by them 
 it is neither ditfolved nor thickened. It is fcarcely al- 
 tered by a weak acid. By fermented liquors it is coagu- 
 lated. Fixed alkaline falts have almoft the fame effedls 
 as the neutrals. The volatile alkalies rather turn it 
 brown, and coagulate it. Alcohol and diftilled oils 
 coagulate it, as alfo vinegar. It does not effervefee 
 with any fait. 
 
 142. Chemiflry has, by various ways, Ihowed us 
 the nature of the blood. (i.)When frefh drawn, before 
 it has time to putrefy, the blood, diftilled with a flow 
 heat, yields a water to the quantity of five parts in fix: 
 of the whole mafs ; which water has little or no tafte 
 or fmell, till you come towards the end of the opera- 
 tion, when it is proportionably more charged with a 
 fetid oil, as it draws nearer to a conclufion. (2.) The 
 refiduum, expofed to a ftronger fire, yields various al- 
 kaline liquors ; of which the firft, being acrid, fetid, 
 and of a reddifh colour, is ufually called the ffirit of 
 blood ; confifting of a volatile fait, with fome little oil, 
 diflblved in water, to the amount of one twentieth part 
 of the original mafs of blood. There is an acid obfer- 
 vable in the fat, and likewife in putrid flefh and blood. 
 (3.) A little before, and together with the oil, that 
 next afeends in the diftillation, a dry volatile fait arifes, 
 and adheres in branchy fleeces to the neck and fides 
 of the glafs ; and this in but a fmall proportion, lefs 
 than an eightieth part of the firft mafs, (4.) The next 
 
 K liquor 
 
66 BLOOD. Chap. VI. 
 
 liquor is that called oil of human blood, which afcends 
 gradually thicker and heavier, is at firft yellow, and 
 afterwards black, till at lad it refembles pitch, being 
 very acrid and inflammable, but in a fmall quantity, 
 about a fiftieth of the whole mafs. (5.) There now re- 
 mains, in the bottom of the retort, a fpongy inflammable 
 coal or cinder of the blood, which, being kindled, burns 
 away, and leaves aflies behind. From thefe, by lixi- 
 viation with water, is obtained a mixed fait, partly fea- 
 falt, and partly fixed alkali, together with a fmall quan- 
 tity of fixed earth. This fixed fait is fcarce the five 
 hundredth part of the firfl mafs, and of this only one 
 fourth part is alkaline : but, being urged with the mofl 
 intenfe degrees of fire, the whole fait affords fome por- 
 tion of an acid fpirit ; which we judge to arife partly 
 from the fea-falt in the blood, fome of which isdemon- 
 ftrable even in the fpirit of blood ; and partly from the 
 vegetable kind of the aliments, not yet digefted into an 
 animal nature. For which lafl; reafon, an acid is pro- 
 curable from the blood of graminivorous animals, as 
 well as from that of man. But the earth, feparated 
 from the lixivium by filtration, will, perhaps, make a- 
 bout an hundred and fiftieth part of the original mafs ; 
 and contains fome particles which are attrafted by the 
 loadflone. 
 
 143. From the preceding analyfis of the blood, it 
 evidently contains a variety of particles, difiering in 
 bulk, weight, figure, and tenacity ; fome watery, 
 others inflammable, and mofl; of them inclined greatly 
 to putrefaciion or to an alkaline nature. For the blood, 
 in a found healthy flate, not injured by putrefadlion, or 
 too violent a degree of heat, is neither alkaline nor acid ; 
 but mild or gelatinous, and a little faltifh to the tafte : 
 yet, in fome difeafes, it is fliarp enough, and comes near 
 to a flate of putrefaflion ; as, for inftance, in the feurvy, 
 where it corrodes through its containing veffels ; and in 
 dropfies, the waters of which are often next to alkaline. 
 But the calx of the blood of infers is alkaline, and 
 effervefees with acids. 
 
 By 
 
Chap. VI BLOOD. 67 
 
 1 44. By viewing frefli blood in a fmall glafs tube by 
 a microfcope, or by applying the fame inftrument while 
 it is yet moving in the veins of a warm living animal, 
 as a hen-chicken, or a cold one, as a frog, we perceive 
 in it red globules ; which, doubtlefs, make that part 
 called cruor or craffamentum, mentioned in 137. If it 
 be queftioned, whether thefe are not rather lenticular 
 particles of the fame kind with thofe obferved by Lew- 
 cnhock in filh, and lately difcovered in our own fpecies ; 
 we confefs it is a point difficult to ’determine : nor have 
 I ever made a fufficient number of microfcopical expe- 
 jiments on thofe globules which feem moft denfe and 
 convex. 
 
 145. The colour of thefe globules is red; and fo 
 much the deeper, and more inclined to fcarlet, the 
 ftronger the animal is : and, in the fame proportion, their 
 number increafes, when compared with the quantity of 
 yellow ferum. Their diameter is very fmall, being be- 
 tween and of an inch. They are faid to 
 change their figure into an oblong egg-like ffiape, 
 which I could never obferve with fufficient certainty. 
 They are alfo faid to diflblve into other leffer globules 
 of a yellow colour, which I have neither obferved my- 
 felf, nor can eafily admit. 
 
 146. From the red part of the blood, fibres are ge- 
 nerated in abundance ; from the ferum, in fmaller quan- 
 tities. They are procured by pouring the blood into a 
 linen cloth, and wafliing it gradually with a great deal 
 of water, or by beating it with a rod. In quantity, they 
 equal the 28th part of the whole mafs. Thefe are 
 formed of the gluten, and are not generated in a living 
 animal ; feeing they are neither to be perceived by the 
 microfcope, which yet fo eafily renders vifible the red 
 globules, nor yet does their long thread-like figure feera 
 adapted for receiving motion. 
 
 147. From the preceding experiments compared to- 
 gether, arifes that knowledge which we, at prefent, 
 have of the blood ; namely, that the craflamentum or 
 cruor is compofed of globules. The inflammable or 
 
 K 2 ' com- 
 
58 BLOOD. Chap.VI: 
 
 combuftiblc nature of thefe globules is proved from 
 dried blood, which takes flame and burns ; as alfo from 
 the pyrophorus, which is generated from the human 
 blood ; and from thefe, mod probably, arifcs the greater, 
 part of the pitchy oil that is obtained from blood by the 
 violence of fire. 
 
 148. The ferum of the blood, diftilled with a ftrong 
 fire, gives over almod the fame principles with the cru- 
 or, viz. fait, oil, and earth. It yields, however, much 
 more water, but no iron at all. Similar principles, but 
 with a lefs proportion of oil and fait, are obtained from 
 the aqueous humours prepared from the blood; as the 
 faliva, and mucus. 
 
 149. The exadf mafs or quantity of blood, contained 
 in the whole body, cannot be certainly computed. The 
 weight of the mafs of humours, however, is much 
 greater than that of the folids ; but many of them do 
 not flow currently in the circulation, as the glue or jel- 
 ly that lodges in mod parts, and the fat. But if we 
 may be allowed to form a judgment from thofe profufe 
 haemorrhages that have been fudained without de- 
 droying the life of the patient, with experiments made 
 on living animals by drawing out all their blood, join- 
 ed with the bulk ot the arteries and veins themfelves : 
 from thefe principles, the mafs of circulating humours 
 will be at lead fifty pounds ; whereof about 28 will be 
 true red blood, current in the arteries and yeins ; of 
 which the arteries contain only one fifth, and the veins 
 the other four. 
 
 150. Nor does the blood always contain the fame, or 
 a like proportion, of thofe elements or principles above- 
 mentioned ; for an increafed celerity, whether by labori- 
 ous and drong exercifes, a full age, fever, or other- 
 wife, augments the craflTamentum, with the rednefs, con- 
 gealing force, and cohefion of the particles ; and the hard- 
 nefs and weight of the concreted ferum with the alkaline 
 principles are, by the fame means, increafed. On the 
 other hand, the ferum, and the mucus it contains, are 
 Inpreafed by the contrary caufes, the more as the animal 
 
BLOOD. 
 
 Chap. VI. 
 
 .^9 
 
 is younger, lefs aftive, and fed more on a watery ve- 
 getable diet ; by all which, the craflamentum of the 
 blood is leflened, and its watery part increafed. Old 
 age, again, lelfens the cralfamentum, and the gelatinous 
 part likewife. 
 
 1 5 ! . • From thefe principles, but with a conjunft con- 
 fideration of the folid fibres and veifels, the different 
 temperaments of people are derived. For a flsthonc 
 or /anguine habit arifes from an abundance of the red 
 globules ; a phlegmatic temperature, from a redundancy 
 of the watery parts of the blood : a choleric difpofition 
 of the humours feems to arife from a more acrid, acid, 
 and alkalefcent property of the blood ; as appears from 
 thofe who live on fiefh, and on the human fpecies, being 
 fo much fiercer and more palTionate than thofe who 
 live on plants or on vegetable food. In the folid parts, 
 a great firmnefs, joined with an exquifite fenfibility, or 
 nervous irritability, difpofes to a choleric habit ; a lefs 
 irritability, with a moderate denfity, to a fanguine ha- 
 bit ; and a lelfer degree both of denfity and irritability 
 are to be referred to a phlegmatic temperament. There 
 is alfo a kind of dull heavy temperament, in which there 
 is the greateft ftrength of body, joined with no great 
 degree of irritability. In the melancholy, again, a 
 weaknefs of the folids is joined with the higheft degree 
 of nervous irritation or fenfibility. But you muft be 
 careful not to take thefe temperaments as the foie and 
 limited fyftems or clalfes of conftitutions ; which, in the 
 courfe of nature, are found to be not only four, or 
 eight, but are really diftindl in numberlefs degrees. 
 
 152. The red part of the blood feems chiefly of ufc 
 to generate heat, fince its quantity is always in pro- 
 portion to the heat of the blood. This being confined, 
 by the largenefs of the globules, within the red and firft 
 order of veffels, hinders them from collapfing ; and, in 
 receiving the common motion of the heart, by the 
 greater denfity of its parts, it has a greater impetus, and 
 fets in motion the leffer ordeYs of humours. Nor is it 
 improbable, that the heart is more flrongly irritated by 
 
7* BLOOD. Chap. VI, 
 
 the ponderous cruor of the blood. The globular figure 
 of its parts, together with their denfity, makes it eafily 
 pervade the vefiels ; and the quantity of iron it con- 
 tains, as well as of oil, perhaps increafes its power of 
 generating heat. And hence it is, that the red part of 
 the blood being too much diminilhed by profufe bleed- 
 ings, there follows a ftagnation or leffened motion of 
 the humours in the fmaller vefiels j whence fatnefs, and 
 dropfy. By the fame rule alfo, a due proportion of 
 cruor is necefiary within the habit, to generate and re- 
 pair new blood. For, by large haemorrhages, w'e fee 
 the blood lofes its red or denfe nature, and degenerates 
 into a pale, ferous, or watery fiate. 
 
 I5g. The coagulable ferum is more efpecially de- 
 figned for the nutrition of the parts, as will be hereafter 
 more apparent. Chap. XXXI. The thinner juices ferve 
 various purpofes; as the difiblution of the aliments, the 
 inoiftening of the external furface of the body, and fur- 
 faces of the internal cavities, to preferve the flexibility 
 of the folids, and conduce to the motion of the nerves, 
 the fight, &c. The laliiie particles feem proper tor dif- 
 folving the'aliment, and ftimulating the vefiels. The 
 properties of the aerial part are not yet well known. 
 The heat produces fluidity, and is not eafily raifed to 
 fuch a degree as to coagulate the humours. 
 
 1 54. Therefore, health cannot fubfifl: without a denfe 
 and red blood, whofe quantity too much diminithed 
 caufes a ftagnation of the juices within the fmaller vef- 
 fels ; whence all parts of the body become cold and 
 weak. Nor can life or health fubfift w'ithout a fufiiciency 
 of thinner juices intermixed with the red blood ; fee- 
 ing the cruor, deprived of its watery part, congeals and 
 obftrucls the finalleft paffages of the veffels, and kindles 
 too great a heat. 
 
 155. If it is afked, whether there be any difference 
 betwixt the arterial and venous blood ? we anfwer, that 
 fome difference there feems to be ; the former having 
 lately fuffered the action of the lungs. But, in experi- 
 rqents, I fcarce find any obfervable difference either in 
 
 colour. 
 
Ch’Ap. VII. ARTERIES. 71 
 
 colour, denfity, or any other known diverfity. Other- 
 wife, however, I have found a moft evident difference ; 
 for the bright red colour of the arterial blood feems to 
 diflinguifh it from the dufky dark-coloured blood in 
 the veins ; but this, in the plain example of the hatch- 
 ing of a chicken, arifes only from the deeper feries of 
 globules in the thicker vein. But we have not fuffi- 
 cient certainty of a difference in the blood of different 
 arteries. However, the arterial blood is apparently of 
 a more bright or fplendid red ; and having a greater 
 degree of fluidity and proportion of watery parts, may 
 fo far differ from the venous darker-coloured blood. But, 
 in this refpe^:, it remains that we make further experi- 
 ments. 
 
 156. From one and the fame mafs of blood, driven 
 into the aorta, are generated all the fluids of the human 
 body ; which, from their affinity one to another, are 
 reducible to certain claffes. The manner by which they 
 are feparated, ought to be accounted for by the fabric 
 or mechanifm of the glands themfelves. But we mufl 
 firft confider what the blood fuffers from its containing 
 veffels. 
 
 CHAP. VII. 
 
 Of the Common Offices of the Arteries. 
 
 157. ^ I ’’HE blood is driven from the left ventricle of 
 A the heart into the aOrta ; which takes its courie 
 firft a little towards the right, and then to the left, in 
 an arch that is very fharply bent : and here the mafs of 
 this purple fluid ftrikes firft againft the right fide, and 
 is then reflefled to the left fide again of the aorta ; 
 whence, flowing in a vortical or whirling motion, as 
 mach as that full veffel will permit, it goes on through 
 the arteries, with an alternate collifion againft, and re- 
 percuffion from, their fides. The aorta fwells a little in 
 bulk at the place where it proceeds from the heart. 
 
 158. The 
 
72 
 
 ARTERIES. Chap. VIE 
 
 158. The arteries are, in a living perfon, always full 
 of blood ; fince the jet or ftream that harts from an ar- 
 tery, is not interrupted by alternate hops, while the 
 heart rehs or relaxes itfelf, but it hows on in a continu- 
 ed thread : add to this, that the microfcope fhews the 
 arteries, in living animals, to be full, both in their fyhole 
 and diahole ; nor can the circular fibres of the arteries 
 fo far contradl thernleives, as entirely to evacuate thefe 
 tubes. Since, therefore, a new wave or column of 
 blood is fent into the arteries, already full, although it 
 bear a fmall proportion to the whole mafs contained in 
 the arterial fyhem throughout the body, hardly ever 
 exceeding two ounces ; yet, by its immediate contact 
 •with the precedent wave or column, which moves hower 
 as it gets farther from the heart, it confcquently drives 
 the fame forwards, lengthens the artery, and makes it af- 
 fume a cylindric form, augments its diameter, preffes the 
 membranes clofer to one another, urges the convex parts 
 of the arterial flexures outwards, and caufes their fpiral 
 waves to be more ferpentine, as injections demonftrate 
 to us. This dilatation of the artery, w'hereby its light 
 or capacity is changed from a lefs to a greater circle, is 
 called the pulfe ; the diajlole of which, is an expanfion 
 of the artery beyond its natural diameter. This being 
 the proper or charaCteriftic aCtion of life, refults from 
 the heart only, and is in nowife natural to the arteries 
 left to themfelves. Hence, w'hen the motion- of the 
 heart is intercepted, whether by aneurifm, ligature, or 
 otherwife, there is no pulfation of the arteries to be felt ; 
 and from hence, too, there is a fudden ceflTation of the 
 pulfe, by a wound through the heart, in a living animal. 
 But the artery is proportionally more dilated, as the 
 wave of blood flows on before more flowly, and the 
 more the velocity of the new wave exceeds that of the 
 former one. 
 
 1 5 9 . The fyjlole or contraction of the artery follows the 
 dilatation of it. For the heart, having emptied itfelf, and 
 removed the ftimulus of the blood, comes into a ftate 
 ®f relaxation and reft. But the artery, at this fame 
 
 time. 
 
Chap. VII. ARTERIES. 73 
 
 time, by its innate elafticity, and contraftlle power re- 
 ading in its circular fibres, irritated likewife by the fti- 
 mulus of the blood, contracts itfelf, and expels as 
 much blood as ferved to dilate it beyond its mean or 
 middle diameter : this quantity of blood is either for- 
 ced into the fmalier and fcarce-beating arteriolae, or elfe 
 returned into the veins, from the refiiting femiiunar 
 valves of the aorta, which oppofe the reaction of the 
 blood from the neighbouring parts of that veffel. So 
 foon as the artery has freed itfelf from this wave or co- 
 lumn of blood, being no longer ftimulated by dillen- 
 tion, it directly collapfes by its own proper contractile 
 force, and is now again ready to yield to a new wave 
 or column of blood, fent into it from the heart ; 
 whence follows a repeated diaftole. 
 
 160- That the arteries thus contraft, and, by that 
 force, drive forward their contained blood, is proved 
 evidently from their ftrongly-ContraCtile nature; front 
 the apparent diminution of the diameter or dilatation 
 they receive from the heart ; from the evacuation that 
 follows, by the proper force of the artery itfelf, driving' 
 out all the blood that is contained in the lateral branches, 
 betwixt two ligatures ; from the return of the blood to 
 the heart through veins whofe artery is tied, and fo can- 
 not propel the blood to the heart ; from the jet of blood 
 being greateft when the heart is in its diaftole, as ob- 
 ferved by fome eminent anatomifts ; from the firength 
 with which the blood is thrown out of the tied aorta, 
 below the ligature ; from the evacuation which the ar- 
 teries make of their contained blood, even after death, 
 into the veins, whereby thefe latter appear much fuller 
 than the arteries ; and, lafily, from the confiderable jetf 
 or faltus of blood, that iffues from a large artery in an 
 animal, even after death, mounting to the height of 
 two feet : to which add, the convulfive contraftions of 
 the animal in which the artery is thus wounded, and 
 the remarkable clofings of the mouths of divided arte- 
 ries in wounds, and a fphacelation of the limbs from 
 
 L an 
 
74 A R T E R t E S. Chap. VII. 
 
 an offification of the artery ; whence the veins become 
 diftended. 
 
 161. The mean fwiftnefs of the blood’s motion be- 
 ing diminifhed in the time of the heart’s fyflole, but in- 
 creafed during its diaftole, is fuch as carries it through 
 a fpace fomewhat lefs than one foot in the fpace of a 
 fecond of time ; and the conflant plenitude of the ar- 
 teries renders it impoffible for us to perceive any fuc- 
 ceflion in the pulfes of different arteries ; whence all the 
 arteries of the body feem to beat at one and the fame 
 inftant, whiKt the heart ftrikes againd the bread : and 
 yet there is certainly a fucceffion in the fydole of the 
 arteries, by which the aorta feems to contract in the 
 fame order fucceffively, as it is filled by the blood ex- 
 pelled from the heart ; fo that the pait of the artery 
 next the heart is fird condringed, and thence, gradu- 
 ally, the arterial contrafting force proceeds to the ex- 
 tremities. An indance of this we have in the intef- 
 tines; and the fame is evident to the eye in iufeds, who 
 have a long fidulous and knotted heart, maniftlUy con- 
 trafting in a fucceffion from the beginning to the end. 
 But the mind cannot didinguiflr the lead points of time, 
 which are the mea.^ures of this fucceffion, and amount 
 only to a few thirds of a fecond. 
 
 162. If it be afked. Where this pulfation ends: 
 we anfvver, In the lead arteries, and cylindrical origi- 
 nations of the veins. We have already mentioned the 
 velocity with which the blood comes from the heart. 
 But that velocity continually decreafes. Certain we 
 are, ( i .)That the lights or feftions of the arteries, com- 
 pofed by the aggregation or fum of their tranfverfe fec- 
 tions, as they divide farther, in their ccurfe, from the 
 heart, greatly exceed that of the aorta ; fo that fince 
 the ratio, or lefs proportion of the trunks to their 
 branches, continually diminiflies as they make lefs ra- 
 mifications, and this in a variable or uncertain pro- 
 portion ; the difference of that ratio or proportion will 
 be the greated betwixt the light of the aorta at the 
 heart, and the fum of the fe6;ions of all the fmall ar- 
 teries. 
 
Chap.' VII. ARTERIES. 75 
 
 teries, where they are leaft, in the extreme parts of 
 the body. Again, (2.) The proportion of the arterial 
 membranes or coats in thicknefs, with refpedl to their 
 bores or capacities, is greater as the arteries grow 
 lefs ; and is larged: in the lead: of them, which tranf- 
 mit only one globule at a time. The truth of this is 
 proved from anatomy, and the forcing of air into the 
 arteries, by which they burd: always more difficultly as 
 they are lefs ; and from the calculation itfelf, by which 
 the magnitude of the lead: arteries is determined from 
 the globules difiending their two femicylindric mem- 
 branes'. Add to this, (3.) The friction of the juices 
 through the lead: vedels, infected and meeting toge- 
 ther in angles ; which fridtion, even in the molt duid 
 water, running through long pipes that are fingle, and 
 in a direct courfe, greatly diminidies the velocity, and 
 more in proportion as the tube is of a lefs bore ; while 
 again, as the artery is lefs, there are a great number 
 of globules rubbing and grating againd: its membra- 
 nous converging fades. And by the conical figure of 
 the artery, it happens, that the broader wave of blood 
 coming from the trunk is rdifled in its paffage through 
 the narrower branch, and fo mud: diflend it by force. 
 But moreover, (^j.) The inflections and folds, or plates, 
 of the veffels, greatly^ dacken the blood’s motion j 
 fince always fome part of the impelling force is fpent 
 and loft in removing the convex parts of the folds, 
 and changing the figure of the indedled vedel. The 
 angles likewife take off more from this force in propor- 
 tion to their acutenefs, or the more they recede from a 
 ftraight line. I.,ad]y, (5.) The great vifcidity or tenaci- 
 ty of the blood itfelf mud: be confiderably allowed for j 
 fince, by reft only, it direiStly hardens into clots ; and 
 fince it is from the circulatory motion only of the blood, 
 that this mutual attraction of cohefion in its parts is over- 
 come, fo as to hinder it from adhering together, or to 
 the fades of the arteries ; for fo we find it adhere in 
 aneurifms and wounds of the arteries, or elfe the glo- 
 bules clot together, as we fee ufually after death. 
 
 L 2 Erpm 
 
76 ARTERIES. Chap. VII. 
 
 From all which coiifiderations, you will obferve, that 
 the blood meets with the greateft retardation, in its 
 courfe, in the leaft velTels. And the oppofition it meets 
 with in the branches leffens the velocity of the blood 
 alfo in the trunk : the oppofition of torrents of blood 
 to one another in the anaflomofes of veffels alfo de- 
 flroys fome part of its motion. We may eafily per- 
 ceive the amounts of this retardation will be very con- 
 fiderable, although it be difficult to make a juli efli- 
 inate of it. In the larger trunks, the blood of a living 
 animal flows with the rapidity of a torrent : but, in the 
 leaft branches, it creeps along very flowly ; fo that, in 
 thefe, it begins to put on a ftate of coagulation. 
 It is alfo well known to furgeons, that a fmall branch 
 of an artery near the heart or aorta bleeds more dan- 
 geroufly than a much larger one that lies at a greater 
 diftance. The weight of the incumbent atmcfphere, 
 of the mufcles and flefliy parts lying above the artery, 
 and the contractile power of the veflel irftlf, make a 
 refiftance indeed to the heart, but do not leflTen the ve- 
 locity of the blood, feeing they give as much in the dia- 
 flole as they take away in the fyftole. 
 
 163. It is certain, however, from incifions made in 
 living animals, that the Angle globules of blood, which 
 move feparately in the fmall veffels, do not lofe fo 
 much of their velocity as, by calculation, they ought 
 to do. We muft therefore give fome other caufes by 
 which this deftruCtive power of the blood’s motion is 
 leffened. And, in the firfl place, it is certain, that 
 the lights of the branches do not bear fuch a propor- 
 tion to the trunk in the fmallefl veffeh- ; ti;Cir great 
 Imoothnefs diminiflres the friftion. The facility, like- 
 wife, with which the blood flows through the veins, 
 expedites its paffage through the little arteries which 
 immediately communicate with thefe veins. No great 
 effect, indeed, can be expected from the weight of the 
 blood, or the force of the nerves, which are both ca- 
 pable of diminilhing and accelerating the motion we 
 fpeakofj but, in live animals, thefe have very little 
 
 ftrength. 
 
Chap. VII. ARTERIES. 77 
 
 ftrength. The power of derivation, whatever that is, 
 and the motion of the mufcles, are capable of pro- 
 ducing a new velocity. 
 
 164. The pulfe therefore enfues, becaufe the ante- 
 rior wave or column of blood moves on flower, while 
 the fubfequent or pofterior wave comes fader ; fo that 
 the precedent is an obllacle to the confequent blood 
 (158.) But fince the force of the heart weakens as the 
 blood goes on, and the contraftile power of the arte- 
 ries increafes, therefore the difproportion of celerity, 
 betwixt the antecedent and confequent waves or co- 
 lumns of blood coming from the heart, will be conti- 
 nually lelTening, with refpeft to the blood that is urged 
 on by the contradfion of the fmaller veffels, till, arri- 
 ving at a part where there is no excefs or difference, 
 it will there ceafe to make any pulfation of the artery ; 
 becaufe here the anterior and confequent blood flow 
 evenly, or with the fame celerity. But this place of 
 equality, in motion, cannot be in the larger and more 
 confpicuous arterial branches ; for in them, the wave, 
 laft coming from the heart, moves quicker than what 
 went before ; as is evident from the inflammatory pul- 
 fation of them, efpecially in the fmall arteries of the 
 eye.' But, in the leaft red arteries, the pulfe at length 
 begins to vanilh. This is evident from the equable 
 motion of the blood, often feen by a microfcope, thro’^ 
 the arteries of a frog. In the larger veflels, however, 
 fuch as may be about the fixth part of a line in 
 diameter, the pulfe is perceptible. But in the lead 
 veins vifible to the eye there is no fenfible pulfation 
 or accelerated motion of the blood, whilll the heart 
 contracts, demonflrable either by the microfcope or any 
 other experiment. 
 
 165. Even in the veins, the blood preffes againfl; 
 their Tides, as appears from the furrows hollowed out 
 of the bones, and the fwelling of the veins on being 
 tied. If it is afked, why the veins do not beat? (for we 
 do not allow that to be a pulfe which happens from re- 
 fpiration, from the rejeftion of the blood from the right 
 
 auricle, 
 
^8 ARTERIES. Chap. VII, 
 
 auricle, or from the mufcular part of the vena cava) ; 
 the reafon of this feems to be, that the blood, when it 
 immediately leaves the heart, is more retarded in its 
 motion, than when it paffes into the fmalleft veffels. 
 Hence, the lliort fpace of time by which the velocity of 
 the laft wave exceeds the foregoing, is greateft at the 
 heart, and grows gradually Id's, till at lafl it totaliv 
 Vanilhes. This is illuftrated by the experiment, in 
 which a pipe, fixed in a leathern tube, and driving 
 forth water in a continual, but llarting dream, does, 
 by a fponge fixed round the mouth of the faid tube, 
 caufethe water to iffue forth in an even dream, without 
 leaping, through the fponge : and the fame is evident 
 from another experiment, in whicli the fame thing 
 happens, by injedting the mefenteric arteries with an 
 alternate impulfion of water ; for then the water flows 
 out through the veins, in one continued even dream. 
 
 1 66. The pulje is, therefore, the meafure of the 
 powers which the heart fpends on the blood ; becaufe 
 it is the immediate and full efiedl of thofe powers. 
 Hence, all things confidered as alike, tlie pulfe is 
 in the mod healthy people, where there is no dimuUis, 
 nor any unnatural rcfidance to caufe the effccl; of a di- 
 mulus, but the heart is at liberty to fend forwards the 
 blood wfith eafe. You mud except thofe cafes where 
 there is fome obdacle, by which the blood is prevented 
 from entering the aorta. For this reafon, the pulfe in 
 adhmatic people is flow ; the fame thing alfo happens 
 from a debility or infenfibility of the heart, which the 
 ufual dimulus is not capable of exciting to contradfion. 
 A large pulfe is caufed by fulnefs of the artery, joined 
 v/ith a drong force of the heart ; a fmall pull'e by the 
 emptinefs of the artery, and a leffer wave of blood fent 
 from the heart. A hard pulfe denotes fome obdacle or 
 dimulus ; or elfe, that the heart’s force is increafed 
 with a greater thicknefs of blood, or a greater rigidity 
 of the artery. A quick pulfe denotes fome dimulus, 
 obdacle, or greater fenfibility or irritability of the heart. 
 It is bed felt where the artery lies expofed bare to the 
 
 touch. 
 
Chap. VII. ARTERIES. 79 
 
 touch, upon fome refifting bone ; but obflrudions 
 fometimes render the pulfe perceptible, where it is ne- 
 ver fo naturally. 
 
 167. The pulfe is flower in animals as they are 
 larger or more bulky; becaufe the heart is prpportion- 
 abiy bigger in the fmaller than in the larger animals, 
 and, as well as the other parts of the body, is more ir- 
 ritable in the former than in the latter ; and becaufe 
 the heart is obliged to drive the blood to a greater di- 
 flance ; whence the refiftances or friclions feem to be 
 increafed, in the more bulky, over the force of the 
 heart. Hence, fmall animals are more voracious ; and 
 large ones, as the whale and elephant, eat lefs. The 
 pulfe of a healthy perfon rifling in the morning, beats 
 65 in a minute ; but, after the fatigue of the day, it 
 will beat 80 in that time ; and again, by the night’s reft 
 or fleep, it will become gradually lefs frequent, till in 
 the morning you will find it returned to its primi- 
 tive number of 65. For the motions of the mufcles, 
 and actions of the external and internal fenfes, the 
 warmth of the atmofphere, and the action of the ali- 
 ments taken into the ftomach, urge the venal blood on 
 to the heart, which, being thereby oftener flimulated, 
 makes more frequent dontraftions. This is the caufe 
 of thofe paroxyfms or fits of increafe obfervable in all 
 fevers towards the evening. For fleep not only re- 
 tards the motion of the blood, but of all the other hu- 
 mours and actions in the body whatever. 
 
 168. A frequent pulfe is different from afwift one; 
 and it is poffible for the pulfe to be at the fame time 
 fwift and unfrequent. But it is difficult to obferve a 
 fwift pulfe. The frequent pulfe is what is commonly 
 called a fwift one. It takes place in children, and be- 
 comes afterwards flower in perfons as they grow older. 
 The falient point beats 1 34 in a minute : new-born in- 
 fants have their pulfe 1 20 in that time; and from thence 
 down to old age it grovvs flower, to 60 in a minute. A 
 feverifli pulfe begins from 96 per minute ; and we count 
 the pulfe has but a moderate celerity in fevers, or labo- 
 rious 
 
8o 
 
 ARTERIES. Chap. VI!. 
 
 rious exercifes of adult perfons, if it does not exceed 
 above i lo or 120 in a minute : but it is excelTive at 
 130 or 140, with which number people feldom reco- 
 ver ; nor have 1 ever obferved it exceed that number. 
 The pulfe beats flower in winter, and quicker in fum- 
 mer, by about 10 ftrokes per minute; and under the 
 torrid zone, it grows quicker to 120. The different 
 pafTions of the mind varioully accelerate, retard, and di- 
 flurb the pulfe. Vv^hatever obltructs the circulation is 
 alfo found to accelerate the pulfe-; not from the laws of 
 hydroftatics, or on account of the canal being mace 
 narrower, nor from the action of the tbul ; only the 
 heart being with more difficulty freed from the ftimu- 
 lating blood, contracts itfelf more flrongly,, and at 
 fhorter intervals. An irritation from an acrid blood is 
 the caufe of the frequent pulfe in fevers. 
 
 169. Through the leafl veins the blood moves on 
 very flowly, partly by force of the heart, and partly 
 by the contractile force of the arteries. The firfl is 
 proved by a renewal of the motion of the blood, in per- 
 fons drowned ; where, merely by exciting the adtion of 
 the heart, the whole mafs is driven forwards. But the 
 contractile force of the artery is proved by what is faid 
 (160.) But, after death, the blood continues to move, 
 in part, alfo by its own gravitv, and by the elaflicitv of 
 the air generated or extricated by putrefadtion. 
 
 170. But the blood moves on falter in the larger 
 veins. For whenever the impelling powers remain fuf- 
 ficient, and the conveying finall vefl'els are rendered 
 narrower, the motion of their contained fluids mufl: of 
 courfe be accelerated ; fmce the fection of the venal 
 trunk is much lefs than that of ail its branches, in the 
 fame manner as that of an artery is lefs than the fum of 
 the branches into which it divides. Therefore, if the 
 motion of the venal blood lofes nothing in its way, the 
 proportion of its celerity in the vena cava, to its cele- 
 rity in the veins of the thirtieth divifion, will be thirty 
 times greater in the former, in proportion as the con- 
 jundl lights of all the fmall veins exceed the light of the 
 
 cava. 
 
8r 
 
 Chap. VII. ARTERIES. 
 
 cava. In like manner too, the friftion or attrition of 
 the blood in the veins, and its contaft with their fides, 
 diminifli. 
 
 171. But fince the blood moves thus flowly in the 
 lead arterial veflels and incipient veins, and as the weight 
 of the blood, itfclf, in many places, wonderfully hinders 
 its return to the heart, while, at the fame time, the very 
 thin coats of the veins have but little contraftile power 
 to be expected from them ; therefore, nature has ufed 
 various precautions, left, from the llownefs of its mo- 
 tion, it Ihould any where ftagnate or concrete. To 
 obviate this, ftie has fupplied the veins with more watery 
 vapours and fluxile lymph than Ihe probably fent by 
 the arteries, if we confider the great exhalation that is 
 made from the arterial blood in the lungs. 
 
 172. She has, therefore, likewife placed the veins 
 near the mufcles, that, by the turgefcence or contrac- 
 tions of the latter, the veins may be preffed ; and fince 
 any preffure upon the veins muft be determined to- 
 wards the heart (<53.), therefore all this force muft be en- 
 tirely employed in accelerating the return of the blood 
 to the heart. From hence proceeds that wonderful 
 quicknefs of the pulfe (167.), heat, and rednefs of the 
 body, with a fhort and laborious breathing, that attend 
 mufcular motions or violent exercifes. 
 
 173. Moreover, thofe mufcles, which coiiftantly urge 
 or prefs violently the contiguous vifeera on all fides, 
 that are contained in any of the common cavities, do 
 all of them powerfully promote the return of the venal 
 blood to the heart. Such an effeft has the conjqnd: 
 preffure of the diaphragm with the abdominal mufcles, 
 in refped to the abdomen. Laftly, the pulfations of 
 the arteries, which run every where contiguous and pa- 
 rallel by the lides of the veins, have no inconfiderable 
 effect in promoting the return of the venal blood j fince, 
 as we have before fliewn, any impulfe adling on the 
 veins can determine their blood to the heart only. 
 
 174. To thefe is added a force not yet fufficiently 
 known, by which the blood is brought from a place 
 
 M where 
 
82 
 
 ARTERIES. Chap. VII. 
 
 where it is more compreffed to one more lax, and 
 where it meets with lefs refiftance. In this matter alfo 
 refpiration is of great efficacy; in which the motion of 
 the blood into the lungs when relaxed is accelerated by 
 the power of derivation from all parts of the body: and 
 again, in exfpiration, it is driven into the trunks of the 
 veins in the head and abdomen. Hence the fwelling 
 _of the veins, and likewife of the brain, in the time of 
 exfpiration. The circulation is not indeed affifled by 
 thefe caufes, but the blood is agitated and prefled. The 
 anaftomofes of the arteries contribute to the fame end ; 
 for they render the paflage of the blood more eafy from 
 thofe places where it is obflruded, to fuch as are more 
 free. 
 
 175. By thefe means, the blood in a healthy perfon, 
 uflng fufficient exercife of body, moves on with fuch a 
 velocity, as fuffices to deliver as much of the purple 
 fluid in every pulfe by the vena cava to the heart, as is 
 equal to what is fent out by that great artery the aorta. 
 But reft or inaftivity of body, and a weaknefs of the 
 contracting fibres of the heart and other mufcles, fre- 
 quently render this motion of the venal blood more dif- 
 ficult. Hence follow varices and the piles in women 
 with child ; which latter is much occafioned from the 
 deficiency of valves in the vena porta. And from hence 
 fpring even the menfes themfelves. And when the 
 veins too flowly return their blood to the heart, the 
 fubtle vapours from the lead veflels irrigating the parts^ 
 being thus refilled, or fcarce able to return to the heart, 
 are obliged to ftagnate; whence proceeds that frequen- 
 cy of cedematous and pitting fwellings of weak people, 
 
 176. The time in which an ounce of blood, fent out 
 from the left ventricle of the heart, returns to the right, 
 and which is commonly reckoned the time in which the 
 greater circulation is performed, is uncertain, and dif- 
 ferent in every different portion of the body. If, how- 
 ever, you want to know about the ounce of blood pro- 
 pelled in that quantity which we have mentioned, the 
 amount of it will be about 7^ ounces in an hour, with 
 
 4500 
 
Chap. VII. ARTERIES. 83 
 
 4500 pulfes; and the amount of the perfect circulations 
 will be about 2 j,-. 
 
 177. The elFcdis which follow from the motion of the 
 heart and arteries upon the blood are various, which 
 may be deduced and eftimated from the caufes them- 
 felvcs of thofe effects, if we compare together the blood 
 of a living and of a dead animal, that which is healthy 
 with that which is difeafedj and that which is inert or 
 too little moved, with that which circulates too fwiftly. 
 For we obferve, that, in the living, the blood is, (1 .) Con- 
 fiderably warm or hot. (2.) It looks red, with a fort 
 of purple florid hue. (3.) It feems to be homogene- 
 ous or uniform, and alike in its parts ; though they are 
 really mixed, and pf different principles. (4.) It is 
 made up almoft entirely of globules. (5 .) It flows very 
 readily through the leafl; velfels ; from whence being 
 drawn, ,(6.) It exhales a volatile vapour, which we 
 have already defcribed particularly. In the dead ani- 
 mal, which has not yet begun to corrupt or putrefy, we 
 obferve, ( \ .) That it has loft a great deal of its rednefs. 
 (2.) That it feparates into a more denfe and a more thin 
 fubftance. (3.) That it exhales no vapour. (4.) Be- 
 ing drawn out from the veins, it congeals either all or 
 the greateft part. But even in the living animal, when 
 very weak, where there is fome pulfe or refpiration, 
 though fmall, we find the blood cold, even to a confi- 
 derable degree. If, again, you compare the blood of 
 a human perfon unaftive both in body and mind, with 
 the blood of one that is addicted to violent exercife, 
 you will obferve the latter has, ( i .) A greater heat. 
 (2.) A more intenfe rednefs. (3.) A fubftance more 
 compact, and fpecifically heavier. And, (4.) The vo- 
 latile parts more abundant. All which appearances 
 feem manifeftly the effects of the motion of the heart 
 and arteries, fmce they proportionably increafe and di- 
 minifli with that motion, and difappear when that ceafes. 
 
 178. That we may underftand the manner in which 
 thefe appearances are produced in the blood, we muft 
 confider what are the effeds of the heart impelling the 
 
 M 2 fame, 
 
84 ARTERIES. Chap. VII. 
 
 fame, aad of the arteries alternately comprefling and 
 urging it forward. And firh we fee, that the heart 
 drives the blood into the arteries with a very great ce- 
 lerity (123.) With a confufed or vortical motion, the 
 heart thus throws the blood into the crooked or inflec- 
 ted arteries, in fuch a manner, that the right globules, 
 expelled through the opening of the aorta, ftrike againft 
 the left fide of the artery ; from whence being repelled, 
 they incline towards the right fide, whereby all the par- 
 ticles of the blood are agitated with a confufed or tur- 
 bulent and whirling motion. The blood thus impelled 
 againft the flexile and curved fides of the arteries, of 
 neceffity dilates or diftends them into a greater con- 
 vexity ; and laftly, in the fmaller veflels, capable of re- 
 ceiving only one or a few of the blood-globules, all the 
 faid globules come fo intimately into contadl with, and 
 grate againft, the fides of the faid artery in all their 
 points, that they are even obliged to change their fi- 
 gure in gaining a paflTage into the veins. 
 
 179. But the arteries, by their elaftic force, reacting 
 upon the impinging blood, repel the fame from their 
 fides towards the axis of their light or capacity ; and, 
 at laft, tranfmit every fingle particle of it through the 
 circular mouths of the leaft veflels, by which the arte- 
 ries and veins join together. 
 
 180. There is, therefore, a moft prodigious degree 
 of friftion, as well of the blood-globules againft the. 
 fides of the arteries, as of the arteries themfelves, con- 
 trading round the blood like an obftacle ; to which add, 
 the attrition of the particles of the blood amongft each 
 other by the confufed and vortical motion with which 
 they are propelled. The efFefts of this friction may be 
 computed from the vifcid and inflammable nature of 
 the blood itfelf, from rhe narrownefs of the veffels thro’ 
 w'hich it runs, and from the ftrong impulfion of the 
 heart, joined with the powerful reaction of the arteries; 
 to which add, the weight of the incumbent parts raifed 
 by the force of the arterial blood. This fridion gene- 
 rates a fluidity in the blood, by perpetually removing 
 
Chap. VII. ARTERIES. 85 
 
 the points of contaft in its globules, refilling their at- 
 traction of cohefion, mixing together particles of dif- 
 ferent kinds, which become more fluid upon mixture, 
 as we have an inftance in oil when triturated with wa- 
 ter. It alfo augments the fphericity of the particles, by 
 breaking off their protuberances and little branchings. 
 But even thefe very fmall particles themfelves, which 
 are broken off from the large particles of the blood, 
 put on a round figure by their friClion againft the fides 
 of the canals, and their rotatory motion among the 
 reft. By deficiency herein, the blood coagulates in 
 the velfels before death ; and from hence, the lofl flui- 
 dity of the blood is again reftored, by recovering the 
 motion of the heart, as we are taught' by experiments 
 made on living animals. It is a queflion w^hether this 
 motion of the blood, and the denfity proceeding from 
 it, is the catife of the red colour of the«blood, feeing the 
 rednefs is in proportion to the denfity, and increafes or 
 decreafes from the fame caufes. This feems.to arife 
 from a mixture of the ferruginous with the oily part of 
 the blood. 
 
 1 8 1 . We may alfo afk, whether the heat of the blood 
 does not alfo proceed from its motion ; feeing we ob- 
 ferve heat to arife from the motion of all kinds of fluids, 
 even of air itfelf, in our experiments ; but much more 
 does this attrition produce heat in the elaflic and com- 
 buftible animal juices, which are denfer than water, and 
 compreiTed with a confiderable force by contraClile 
 and converging tubes. Is not the truth of this fuf- 
 ficiently evidenced, by the blood’s being warm in thofe 
 fifli which have a large heart, and cold in fuch as have 
 a fmall one? the generation of heat being in propor- 
 tion to the fize of their bodies : from the more in- 
 tenfe heat of birds that have a larger heart, and more 
 frequent or quick pulfations ? from the increafe of a- 
 nimal heat, that enfues from exercife of all kinds, 
 and even from bare fridlion of the parts ? from the 
 congelation of all the humours of the human body in a 
 certain degree of cold, in which a man grows ftilF, 
 
 though 
 
86 
 
 ARTERIES. Chap. VIL 
 
 though he yet retains fome warm blood and is alive ? 
 and from the coldnefs of fuch people as have their pulfe 
 weak and obfcure? Nor does the heat at all arife at firfl; 
 from any degree of putrefadlion in the blood, feeing 
 the humours themfelves, when left at reft, generate no 
 heat. Nor muft we explain an evident appearance 
 from the adlion of fuch an obfcure being as the vital 
 ■power; and though fometimes the heat may be greater 
 when the pulfe is flow, and lefs when it is more fre- 
 quent, the difference may arife from the different dif- 
 pofition of the blood, from the different denfities of the 
 veffels, or the increafc or diminution of perfpiration. 
 
 182. The fame caufe alfo hinders putrefadion, by 
 not fuffering the inteftine motion to be diminifhed, and 
 by diffipating fuch particles as have already begun to 
 be corrupted. 
 
 183. But the different natures of the feveral parti- 
 cles themfelves, which conjunftly make up the mafs of 
 blood, are the caufes whereby, from one and the fame 
 impetus of the heart, different effects or confequences 
 are produced indifferent particles of the blood. Name- 
 ly, thofe particles move quicker, whofe greater den- 
 fity makes them receive a greater impetus, and whofe 
 apt figure or lefs extended furface makes them meet 
 with lefs refiftance in the fluid in which they move. 
 Thofe alfo are driven along more fwiftly, which, either 
 from their weight, or from the direction in which they 
 pafs out from the heart, are urged chiefly into the axis 
 of the veffel. Thofe again will ftrike againft the con- 
 vexities of the flexures in the arteries, which have the 
 greateft projefHle motion ; while the other parts of 
 greater bulk and tenacity, having lefs projectile mo- 
 tion, will move fluggiflily along the concavity of the 
 veffel. And in this manner is the blood prepared or 
 difpofed for the feveral fecretions. 
 
 1 84. 'I'ht fyflole of the arteries renders the parts of 
 their contained fluids more denfe or compact, while 
 they contract round the blood as round a folid ob- 
 ftacle, which being in fome parts vifeid and compref- 
 
 fible 
 
Chap. VII. ARTERIES. 87 
 
 fible, they drive and expel the mere liquid parts into 
 the lateral mouths or du£ls, at the fame time increafmg 
 the points of contatl betwixt the globules themfelves, 
 uniting together their more large and denfe fpherules, 
 and compading 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 materials 
 whereof thefe globules are compofed. 
 
 1 85 . Moreover, the mouths of the leafl; veflels, per- 
 vious to only one globule at a time, feem to be a fort 
 of moulds to figure and break off the angular eminences 
 of the particles in the blood, and bring them to a fphe- 
 rical figure ; which at length they put on, and change 
 into perfed fpherules. Laftly, from hence arifes the 
 denfity of thofe particles ; fince, of all figures, fpheres 
 contain the moll within a given furface. 
 
 186. The reticular diftributions and inofculations of 
 arteries remove any danger of obllrudion ; fince in any 
 part of the artery, where the blood cohering begins to 
 form an obftrudion, a contrary flux is admitted, where- 
 by the obftructing matter is repelled to a larger part of 
 the trunk, and thus betwixt the reflux and the dired 
 torrent of the blood the faid matter is broke and atte- 
 nuated. This mechanifm alfo fupplies the deficiency 
 from an irremoveable obftrudion or the lofs of a veffel, 
 by caufing a greater diftenfion or enlargement of the 
 next adjoining or anaftomofing veflel ; as is proved by 
 experience in furgery, after tying and cutting a great 
 artery. The collifion of thefe oppofite torrents of blood 
 take fomething from its velocity; and the reticular di- 
 ftribution augments the fridion of the globules. 
 
 187. As the quicker motions of the blood in the 
 trunks conduce to fanguification, fo the flower motions 
 of it, in the leafl; veflfels, have their effeds towards the 
 fecretions. In the larger arteries, we fee the different 
 particles of the blood are whirled about amongfl each 
 other, with a rapid and confufed motion ; but, in the 
 leflfer ramifications, the progreflive motion of the blood 
 being diininifhed, the more loofe colourlefs particles 
 
 depart 
 
88 
 
 ARTERIES. Chap. VIII. 
 
 depart laterally from the more denfe and red globules, 
 while the latter, keeping on their courfe more firmly 
 along the axis of the veil’d, expel the former laterally 
 and to the circumference. Thus the attradive powers 
 of the particles in the blood increafe, as their progref- 
 five motion abates hence, the oily or fat particles are 
 drawn one to another, and go off by the open lateral 
 du£ts which lead to the cellular fubltance, which par- 
 ticles we know are both grofs and lluggilh : and again, 
 other thinner juices are fent olF through lateral branches 
 of a much fmaller orifice, till at length little more than 
 the red blood alone remains to pafs through the eva- 
 nefcent artery into the incipient vein. But all thefc 
 particulars, whereby the blood is difpofed for the fe- 
 cretions, we fliall confider diflinctly in the following 
 chapter. 
 
 CHAP. VIII. 
 
 Of the Secretions. 
 
 188. B ’♦HE claffes or tribes of humours which, bc- 
 _L ing depofited or {trained off from the blood 
 into other vdl'els, are faid to be fecerned or fecreted, 
 feem reducible to four: of which the frft includes all 
 the vifcid and lymphatic juices, which are coagulated 
 by a heat of about 150 degrees, by alcohol, and by a- 
 cids; although generally, in the living animal, they 
 are capable of flying off in form of a vapour, and after 
 death are within the fame veffels compacted into a ge- 
 latinous thicknefs. To this clafs belong the vaporous 
 juices of the ventricles of the brain, of the pericar- 
 dium, pleura, peritoneum, vaginal tunic of the teflicle, 
 of the amnios, joints, and probably of the womb, with 
 the juice of the ftomach and inteflines, of the renal 
 capfules, and laflly the lymph itfelf commonly known 
 and called by that name. 
 
 i8p. The fecond clafs is of thofe juices, of which 
 
 feme 
 
Chap. VIII. SECRETIONS. gp 
 
 fome are exhalable, like the former (i8o.), but, be- 
 ing more fimple and aqueous, are neither to be coa- 
 gulated by fire nor by redificd fpirits of wine; and 
 others do not exhale, but, being depofited in their 
 rel'pedive excretory duds, are expelled by fome com- 
 mon outlet, proper to a part of fome gland. To the 
 former of this clafs belong the perfpirable matter of 
 Sandorius, and probably the internal perfpirable mat- 
 ter of the epithelium and cellular fnbftance, with part 
 of the tears and watery humours of the eyes. To the 
 latter of this clafs belong the remaining part of the 
 tears, the faliva and pancreatic juice, that of the renal 
 capfules, and the urine. The fweat feems to be a mix- 
 ture of the perfpirable matter and the fubcutaneous oil. 
 
 190. The third clafs, differing from both the prece- 
 ding, includes the vifeid, fluggifh, or ropy juices; but 
 fuch as are of a watery difpofition, and not congealable 
 into a jelly, but hardening into a cruft-like or fcaly 
 fubftance, by exhaling their water. Thefe do not ef- 
 fervefee with any fait, and are contraded and made 
 thicker by acids. By lixivial falts they are diffolved. 
 By fire they are refolved into water, a little volatile 
 fait, and a little oil. Of this fort are all the kinds of 
 mucus in the human body, fpread through all the inter- 
 nal paffages for air, aliments, or urine, and the cavities 
 of the genital parts, liquor of the proftates, and feed. 
 
 191. The fourth and lafl clafs is that of the inflam- 
 mable juices, which, at their firft formation, are indeed 
 thin and watery, but, by time, ftagnating and exhaling 
 their more watery parts, become a thick, oily, inflam- 
 mable liniment, often very bitter. To this clafs we re- 
 fer the bile, ear-wax, febaceous and oily liniment of 
 the fkin, the marrow in the bones, and all the fat of 
 whatever confiftence or in whatever part feated through- 
 out the human body. To this clafs alfo belong caftor 
 and the yolk of an egg. And the milk itfelf, fo far 
 as it is butyraceous and inflammable, belongs to this 
 clafs. 
 
 192. Other humours, which we have deferibed as 
 
 N Ample, 
 
SECRETIONS. 
 
 Chap. VIII. 
 
 fimple, arc compounded of the foregoing ones ; as 
 milk is compofed of butter and water, and the lini- 
 ment of the joints of lymph and fat. 
 
 193. Thofe who confider, that in the blood arc 
 found a coagulating ferum (i 37.), an exhaling water 
 
 a fort of vifcid mucus (138.), and laftly an 
 oil (142.), may thence begin to perceive the poffibility 
 of a feparation to be made from the blood of all the 
 foregoing clafles (188. to 191.) of humours; in as 
 much as we thus fee their conftituent principles are al- 
 ready in the mafs of blood itfelf. But in what manner it 
 is brought about, that oil is feparated from the blood in 
 one part, a watery liquor in another, or a gummy mu- 
 cus in a third, is a talk that Hill remains to be explain- 
 ed, and requires a previous defcription of the fccre- 
 tory organs themfelves. 
 
 194. The coagulable juices are feparated almoft 
 every where, from the arteries themfelves, into conti- 
 nuous excretory canals, without any intermediate or- 
 gan or machine betwixt them. The proof of this we 
 have from injedlions of filh-glue, water, and thin oils, 
 which very readily pafs the red arteries, and are pour- 
 ed out like unto fweat into all the cavities of the body 
 in which that coagulable vapour is naturally found ; nor 
 do the injedlions in this courfe meet wdth any interme- 
 diate knots or flops from any hollow cavities or cells. 
 Finally, the blood itfelf, being fo readily poured out 
 into moll of thefe cavities, without any permanent da- 
 fnage, when its courfe is either much obftrucled, re- 
 tarded, or urged with a greater impetus through the 
 arteries, fhows plainly that there is a fhort and open 
 way betwixt the red blood-veffels and thofe excretory 
 dufts, 
 
 195. Another liquid, coagulable by acid fpirits and 
 alcohol, is the albuminous humour of the joints. This 
 being compofed of fat, medullary oil, and the exha- 
 ling liquor, conflitutes an exceeding foft liniment, very 
 fit for lubricating the cartilages, and leffening the fric- 
 tion. For fecreting this, there arc appointed certain 
 
 conglo- 
 
Chap. VIII. SECRETIONS. pi 
 
 conglomerate glands of a peculiar ftrufturc, which arc 
 fituated in the articulations of the bones, fo that they 
 may be moderately comprelTed, but cannot be crufbed. 
 
 196. The ftrufture of thefe glands is peculiar to 
 themfelves. The larger clufters of glandular kernels 
 adhere, for the moft part, to the bone by a broad balls 
 wrapped up in fat. From thence, being drawn out 
 into a kind of crefted edge, they pour out their liquor 
 from an exceedingly thin border, by open dudts, which 
 however I do not find very evident. Other lelfer ones, 
 placed every where in the capfules of the tendons, and 
 between the diverging fibres of the ligamentary cap- 
 fules of the joints, feem to be much of the nature of 
 fimple glands, and are turgid with yellow mucous ferum. 
 
 197. The uncoagulable juices (1 89.) of the firft fort 
 are fecreted in the fame manner with thofe which hard- 
 en (188.); to wit, from the exhaling arteries, which 
 arife from the red fanguineous arteries, without any 
 intermediate follicle or cavity betwixt them. Thus the 
 veffels, which pour out the perfpirable matter through 
 the (kin and lachrymal dufts of the firft fort, fuffer a 
 watery or thin gluey injeflion to tranfude fo readily 
 from the arteries, as leaves no room to doubt of this 
 truth. And thefe fecretory dudfs have alfo a confider- 
 able degree of irritability ; whence, by any ftimulus 
 or contadl of acrid particles, they difeharge more 
 juice in a given time, than what they diftil in a ftate 
 of health. 
 
 198. But in the latter falival kind of that clafs, the 
 fecretion is made by means of conglomerate glandules, 
 which the ancients fo called from their clufter-like fa- 
 bric, and efteemed them ahnoft the only proper glands. 
 Thefe are compofed of roundilh lobules or clufters 
 (fomewhat like thofe in bunches of grapes, currants, 
 barberries, &c.) loofely conjoined together into larger 
 maffes by the yielding cellular fubftance, which, at 
 laft, often forms a denfer coat or covering to the whole, 
 like as we fee in the parotid and maxillary glandules. 
 Through the intervals, betwixt thefe glandular clufters 
 
 N 2 
 
9^ SECRETIONS. Chap. VIII. 
 
 or grape-like bunches, run the arteries and veins, 
 which are here large or confiderable enough. But 
 moll of the conglomerate glandules feparate their juices 
 in fuch a manner from the blood, and from thence dif- 
 charge it fo, that each kernel fends out an excretory 
 du(St, which, joining v/ith others of the fame kind, 
 form larger trunks, which at laft, in the manner of a 
 vein, end in one canal, which conveys the humour, 
 feparated by the gland, to the part for which it is de- 
 figned, as the cavity of the mouth, inteftines, furface 
 of the eyes, &c. There are, indeed, fome of thefe 
 glands in which the faid excretory ducts are either not 
 prefent, or at lead not yet difeovered ; as we obferve in 
 the thyreoideal glandules, thofe called capfuliz renales^ 
 and the thymus, unlefs we fuppofe thefe to approach to 
 the nature of conglobate glands. 
 
 199. The acim or kernels of thefe conglomerate 
 glands are each of them circumferibed and limited by 
 a harder ftratum of the cellular fubftance ; by which 
 fubftance they are alfo fubdivided into leffer acinuli, as 
 is evident to the eye and by the microfeope. But it 
 may be queftioned. How does this fubdivifion end ? 
 Whether or no is every hmple acinus or kernel hollow 
 in its middle, that, by receiving the humour tran- 
 fuding from the arteries into the follicle or cell, it may 
 be fent out thence by the excretory du£l ? Whether 
 or no are we perfuaded to believe fuch a fabric obtains 
 from the fmall fliot-hke Hones and hydatides bred in 
 thefe glands, with the round feirri that fometimes fill 
 the kidneys ? Whether are the larger vifeera, appointed 
 for fecretion, of the nature of conglomerated glands? 
 Whether is this opinion made probable from the morbid 
 round concretions formed in the liver, fpleen, kidneys, 
 tefticles, and cortex of the brain ; or from the bunch- 
 like divifion or appearance which thofe vilcera have 
 in younger animals ? Whether the cellular fubftance, 
 that furrounds the extreme vafcules in all parts, does 
 not communicate by open areolae or cells, in which a 
 fecreted humour is poured by thefe glandules? 
 
 2CO. In 
 
Chap. VIII. SECRETIONS. 93 
 
 200. In fliort, none of thefe arguments appear true 
 or conclufive. For the acini, which are found in the 
 vifeera of brute animals, are component lobules, and 
 not elementary parts ; but are large and compounded, 
 for the conveniency of each beaft. The morbid con- 
 cretions are almofl: all of them a fort of placentulsc 
 formed in the loculi of the cellular fubftance, and take 
 up their fear even in the limbs themfelves, where there 
 is not the leafl room to fufpeft any thing of a glandular 
 fabric ; and are compofed, as to their matter, of oil, 
 earth, and vaporous particles, extravafated into fomc 
 of the lead interftices of the cellular fubftance, where, 
 ftagnating and comprefling the adjacent follicles, they 
 form to themfelves proper membranous tunics. On 
 the contrary, the watery and fluid nature of the juice 
 fecreted in thefe glands (189.) is an argument that it 
 meets with no arreftment in the feparation, nor places 
 of ftagnation in its way. For all the juices that reft 
 any time in the warm cavities of the human bo- 
 dy, which are full of abforbing veffels, are each of 
 them more or lefs infpiffated, and approach either to- 
 wards a mucous or an oily difpofition. Moreover, if 
 there were any fuch arreftments, anatomical inje6;ions 
 would meet with more difficulty in paffing from the ar- 
 teries into the excretory dutls of thofe glands ; which, 
 under fuch ciicumftances, would be impervious to 
 thick injecHons, and thin ones they would exhale into 
 their cellular fabric. Yet we fee that the fuperlative art 
 of great anatomifts has not only conveyed injections, but 
 even thick ones like wax, direCtly from the arteries of 
 the falival glands, liver, &c. into their excretory duCts ; 
 and this without filling up any intermediat<^ knot-like 
 cavities, which, according to the foregoing hypothefis 
 -(199.), they ought to exhibit. 
 
 201. Therefore the acini or kernels of thefe glan- 
 dules appear compofed merely of arteries and veins di- 
 vided and fubdivided, parted and connected by the in- 
 tervention of a good deal of cellular fubftance, whofe 
 ftrata growing gradually more compaCt or firm as they 
 
 enlarge 
 
94 SECRETIONS. Chap. VRI. 
 
 enlarge, at length fhow their contents moulded into a 
 fort of globular nut-like figure. In the belief of this, 
 we are confirmed by analogy in the lobes of the lungs, 
 the lobules of the thymus, and from the ftrufture of 
 infects; but more efpecially the fabric of the tefticle, in 
 which we plainly fee, that the lobules are formed of 
 excretory dufts, connected together in fafciculi by a 
 very foft membrane. But they feem not to pour their 
 juices into a cellular fabric, which would intercept or 
 make difficult the paffage to an excretory du£t. The 
 late experiments alfo of very eminent anatomifts have 
 fhown very fmall, white, cylindric vcflels, to be the real 
 elements of the vifeera; and it is to be hoped that this 
 difeovery will be confirmed by future obfervations. 
 
 202. Thin watery juices, neither coagulable nor 
 wholly evaporating, are likewife in other parts genera- 
 ted without the ailiftance of conglomerate or kemelly 
 glandules. For thus the urine is depofited from the red 
 or fanguineous arteries into membranous pipes, with 
 which they are manifeftly continuous, and form an 
 cafy way, admitting air, water, and mercury, to pafs 
 in like manner. And after the fame manner, though 
 lefs evidently, the nervous juice feems to be feparated 
 in the brain. 
 
 203. The third clafs, or mucous juices (190.) are in- 
 deed almoft every where feparated into, and difeharged 
 from, finufes or hollow glands. Thefe true glands or 
 follicles have, in general, fuch a fabric as makes up an 
 ample cavity, every where circumferibed by a mem- 
 brane ; but in fuch a manner, that the fleffi itfelf of the 
 part, to which the gland adheres, is often taken for 
 another clofe hemifphere of the follicle. The faid ca- 
 vity or follicle is for the generality round : but fome- 
 times it is oblong, and obliquely creeping betwixt the 
 adjacent parts ; as for example, in the urethra of the 
 male, and in the follicles of the finus muliebris. They 
 are irritable ; and when ftimulated by acrid fubftan- 
 ecs, increafe the quantity of their fecretions. 
 
 }P 4 . Into thefe follicles or cells the leaft arteries (or 
 
 the 
 
Chap. VIII. SECRETIONS. 55 
 
 the vafcular flefh furrounding each crypta or cell, and 
 compleating its convexity) open by produced extremi- 
 ties within the cavity of each crypta, into which they 
 diftil or exhale their refpedtive juice; where, being re- 
 tained from the narrownefs of the excretory duct, the 
 more watery parts are drawn up by the abforbing veins, 
 which correfpond to and refemble the exhaling arte- 
 ries ; and thus the follicular or cryptal juices receive 
 a confiderable degree of thicknefs. The truth of this 
 we are taught from the ftrufture of the fimple follicles, 
 obfervable in the tongue, in which both the importing 
 arterial du£fs or pores, and likewife the excretory 
 mouths, are vifible to the eye ; and from the velvet-like 
 tubuli lining the ftomach of birds, in which a fecretory 
 villofity manifeftly hangs in the cavity ; and laftly, from 
 injections, which difcharge a colouriefs wax into the 
 fimple glands. 
 
 205. Whether the mucous cavity of fuch a glandule 
 be long or round, it has always an excretory du£t, 
 which, for the moft part, is none of the leaft ; altho’, 
 in the round mucous glandules, the difcharging du£l or 
 orifice be lefs, in refpeCt to the referving cavity, than in 
 others. This difcharging orifice often opens into the 
 common large cavity, into which the mucus is to be 
 poured, without any intermediate duft ; for thus it is 
 in the back of the tongue, and in the fimple glands of 
 the ftomach and inteftines, where they have been de- 
 nominated crypta or cells by Ruyfch. The finufes have 
 often the like fabric, opening without an intervening 
 duCl, as in the urethra of the male. 
 
 206. Another k^ind of thefe glandules is, where 
 fimple follicles are folded up together in one common 
 covering, and open with their gaping orifices into one 
 common finus, without forming any true excretory 
 duCf. This fabric we obferve in the tonfils. — Thefe are 
 called conglutinated glands. 
 
 207. Other fimple glands of this clafs have an excre- 
 tory duSly by which they expel their mucus ; namely, a 
 narrow, membranous, cylindric, fmall veffel, opening 
 
 with 
 
96 SECRETIONS. Chap. VIIL 
 
 with its poflerior orifice into the cavity of the glandule, 
 and with its a'nterior orifice opening into the common 
 cavity for which its mucus is defigned. Thefe excre- 
 tory dudts are of confiderable length in the fubcutaneous 
 and febaceous glands, and in thofe of the palate and 
 wind-pipe. In ibme parts alfo, the pore or orifice, and 
 its duft, are more eafiiy demonltrable, than the follicle 
 or body of the gland itfelf; as in the nofirils, larynx, 
 reSum, &c. 
 
 208. In others, again, an affemblage of thefe duels, 
 arifing each from its refpeclive lollicle, run together 
 into one, like the branches of a vein, fo as to form a 
 confiderable excretory canal, common to a number of 
 follicles. To this kind belong the compound mucous 
 glands of the intefeines, fome of the larger in the cavity 
 of the urethra, with the blind or impervious duel or ft- 
 nus at the root of the tongue ; to which, in brutes and 
 birds, add the fringe-hke tubuli of the ftomach. The 
 glands of this fort may be called fnnple ones compounded 
 or continuous : but where they lie only contiguous one 
 to another, they may be called Jimple aggregate or con- 
 gregated glandules ; as are thofe of the fauces, flo- 
 mach, inteflines, &c. 
 
 209. The inflammable juices (196.) are feparated 
 by organs differing in their fabric. The fat and mar- 
 row are depofited, without the intervention of glands, 
 from the fmall mouths of the leafl arteries into the cel- 
 lular coat or rather fubflance ; and the fame fat again 
 efcapes from under the fkin by fmall pores or duels, 
 without the afliflance of any glandular follicles. But 
 the ear-wax, and the waxen or fuety liniment of the 
 fldn, are feparated by glands of divers kinds, Moft of 
 the febaceous glandules are vilible enough, wdth an 
 open or naked mouth in the fkin, that leads immediate- 
 Iv into the follicle, without any duel of confiderable 
 length ; as we fee in the external ears, nofe, rings about 
 the nipples, in the female nympha, and the valley or 
 groove that runs betwixt them and the external labia, in 
 the clitoris, and in the male glans and prepuce. Thefe 
 
 differ 
 
Chap. VIIL SECRETIONS. 97 
 
 differ but little from the cryptse (205.), except lii their 
 contained matter, which they feparate. 
 
 2 10. There are others of the febaceous glands, which 
 have an excretory du£t of a confiderable length, like 
 moft oPthofe in the fkin, which, being feated in the 
 cellular fubflancc, have confequently a duft long enough 
 to perforate the fkin. Thus we fee it is in the face 
 more evidently, where the length of the dud is often 
 to be meafured by the concreted maggot-like fubflance 
 preffed out; the bulk of which demonftrates, that a fol- 
 licle or cell lies under the narrower pore. 
 
 2 1 r . There are ftiil other febaceous glands of the 
 kind mentioned 208. in which many cryptae by fmall 
 ducts meet together in one larger excretory dud. Thus 
 in the face, in feveral places, there are large pores in 
 common to a number of fubjacent cryptse. And of 
 this kind are thofe febaceous finks or little inteflines in 
 the eye-lids : and thus it is in the fecretory organs of the 
 mufk-goat, beaver, hyaena, civet-cat, and mufk-rat, 
 which gather their febaceous matter into one common 
 receptacle. 
 
 212. The milk, being a humour of its own particu- 
 lar kind, formed of oil and watery juices intermixed, is 
 feparated by conglomerated glandules, whofe fabric we 
 deferibed at 198. Whether the fecretion of the bile be 
 glandular, is controverted ; but there are many argu- 
 ments to perfuade us, that the liver is a mere vafcular 
 fabric, whence the bile distils immediately from the 
 extremities of the porta into the port bUiarii, or roots 
 of the biliary duds, without paffing any cells or fol- 
 licles by the way : and in this we are more efpecially 
 confirmed by the Ruyfehian art of injedion, in which 
 the wax palfes diredly from the porta into the biliary 
 duds, without exhibiting any intermediate knots or 
 ftoppages ; and therefore we fee the milk and bile are 
 both of them much thinner and more watery than the 
 fat, or the febaceous matter which thickens in follicles. 
 
 213. It now remains for us to inquire, how, from 
 ®ne common mafs of the blood, the fame variety of pe- 
 
 O culiar 
 
$9 SECRETIONS. Chap. VIII. 
 
 culiar juices are conftantly fcparated, each in its re- 
 fpeft)ve place ; fo that we never fee milk fecreted in 
 the kidneys, bile in the thymus, or mucus in the feba- 
 ceous glandules. This problem, indeed, maybe folved 
 by one who lhail have previoufiy acquired a thorough 
 knowledge of the intrinfic fabric that obtains in each 
 fecreiory organ. In the mean time, we fiiall here pro- 
 pofe what has been hitherto advanced with certainty on 
 that fubjtcl from any known principles whofe truth 
 we are convinced of. 
 
 214. And, firft, the blood itfelf, from whence any 
 liquid is to be fecreted, in the various parts, puts on 
 fuch a charafter or difpofition there peculiar to itfelf, 
 that more particles, of a like nature with the humour, 
 abound in that portion of the blood, which nature in- 
 tends to feparate from it. In the liver, the venous 
 blood arrives with a very flow motion, full of oil, anil 
 full of the femiputrid vapours of the inteflines. To the 
 teflicles, the blood is brought flowly through very long 
 llender and infledled canals, arifing at very fmall angles, 
 and palTing out of the abdomen through a cold tract 
 under the fkin. In the carotids, it is probable that the 
 ftronger, fpirituous, and denfe parts of the blood a- 
 feend ; while whatever is more watery defeends into the 
 abdomen and to the kidneys ; alfo to the forming of 
 the falival juice of the pancreas, and the liquor of the 
 ftomach and inteflines. 
 
 215. Another preparation of the blood, towards fe- 
 cretion, is from its retardation in the leaf!: veffels: 
 whereby the red and denfer parts go on by themfelves 
 along the axis of the canal ; while the other lighter 
 and more fluggifh or lefs moving particles recede to 
 the lateral openings or branches, fo as to enter the fe- 
 cretory orifices, which pafs out from the hides of the 
 faid veffels ; and to thefe they adhere by their vifeo- 
 fity. 
 
 216. Thefe orifices, though of different diameters, 
 are yet always fmall enough, in their healthy and natu- 
 ral flate, to refufe the red blood. Hence, therefore. 
 
Chap. VIII. SECRETIONS. 
 
 ' 99 
 
 we may conclude, that, being enlarged by an increafed 
 force of the heart, they every where admit a good deal 
 of the red blood from the fanguineous artery, which 
 they arife from, and open into, as we cannot with pro- 
 bability fuppol'e them to be much lei's than the red glo- 
 bules. And hence the fame fecretory orifices or duels, 
 which refufe thick injeftions ot wax Or fuet, do ne- 
 verthelefs generally admit thinner liquors injected into 
 the arteries. 7 herefore this is the fir (I and moil fimple 
 mechanifm of fecretion ; viz. that the light or open- 
 ing of the excretory du£l may admit only fuch par- 
 ticles as have their greateft diameter lefs than the 
 diameter of the faid opening. From this reafon only 
 it is, that the yellow arteries convey off a pure liquor 
 from the blood, and that the uriniferous dudts exclude 
 both the red blood and coagulable ferum. But this is 
 not the foie caufe, fince the fame juices are generated 
 by large as by fmall animals. 
 
 217. Merely by this law, the fecreted juices may be 
 of many different forts : for thofe whofe lights or tranf- 
 verfe feclions are the leait, will receive only the thinneil 
 juices, as in the fmall veffels of the brain ; and the 
 larger duds will admit water and jelly, while the thick- 
 eft fat will enter the biggefl of all. Moreover, if a 
 number of fecretory organs are formed in a fucceffion 
 from one fecerning artery, each of them having large 
 mouths or duds ; in that cafe, the lafl which come out 
 from the faid artery will receive only the thinneft 
 juices. But if thofe, which are firfl formed in order 
 from the fecerning artery, have fmaller duds, then the 
 lafl only will receive the groffeft juices. It may be ob- 
 jeded, that though the veffels in a 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 vafliy different from the fat, 
 bile, lymph, and water, of a man. 
 
 218. From hence only it is, that the fecretions are 
 generally made immediately from fanguineous arteries, 
 without palling the ferous lateral ones, (45.) Thefe 
 
 O 2 all 
 
100 
 
 SECRETIONS. Chap. VIII. 
 
 all feparate grofs juices ; thick, coagulable, or watery ; 
 as the fat, urine, juice of the ftomach and inteftines, &c. 
 But the fecretions of the other thinner juices are made 
 not from fanguineous, but from fmaller pellucid arteries 
 arifing from the former ; to the fecerning mouths of 
 which, not only no red blood, but no ferum, fat, or o- 
 ther grofs juices, can have admittance. Thus the more 
 thin and pure humours mull neceifarily be feparated ; 
 as for example, in the eye. 
 
 219. Perhaps the angle, which the fecretory branch 
 intercepts with its trunk, contributes fomething to fe- 
 cretion. For it is eafily demonftrated, that at right and 
 retrograde angles, only the vifcid andfluggilh juices are 
 expelled by the ftronger force of the particles keeping 
 the middle of the canal ; but the liquids which are 
 about to go off at half-right angles, are thofe which 
 preferve their velocity. For, in living animals, the ve- 
 locity of the blood is greateft in veflels of the acutefl 
 angles, and lefs in thofe of right angles, as men of ve- 
 racity have obferved. That the effect of thefe angles 
 in the veffels is confiderable, with regard to the fecre- 
 tion, we are perfuaded from the ffructure of the body 
 itfelf; fince they form different angles in different parts 
 with refpecl to their trunks, and in fome parts com- 
 pofe net-w'orks. For the fmalleft veffels, in general, 
 refemble the branchings of little trees or flirubs, the 
 trunks and arms of them every way fending out branch- 
 es, but in different angles ; fmall in the large intelfines, 
 but larger in the fmaller inteftines. Thus, in the fpleen, 
 the fmaller red arteries arife fo thick from their trunks, 
 that they relemble a wifp or fprinkler ; in the intef- 
 tines, they refemble pencil-brufiies ; ferpents, in the 
 kidneys ; ftars, in the liver ; a radiated circle in the 
 uvea ; and, in the tefticle, a lock of hair curled up into 
 a button. But we defervedly receive it as a rule, that 
 the Creator never made this diverfity of fabric to no 
 purpofe. We have not as yet, however, any account 
 of thefe net- works that can be fufticientlv depended up- 
 on. Neither does there feem to be any affinity between 
 
Tor 
 
 Chap. Vllf. SECRETIONS. 
 
 the fabric of the veffel, and the nature of the liquor 
 which it fecretes : and, indeed, thefe net-works are al- 
 moft fimilar to the veins, as if made rather for fhorten- 
 ing the paffage of the blood in fome meafure, than for 
 diverfifying the nature of the fecretion. 
 
 2 20. The inflexions of the fmaller veffels, as well 
 arteries as excretory duds, greatly retard the motion 
 of the blood ; in which, therefore, the greater part of 
 the force received from the heart is evidently fpent in 
 changing the figure of the veffels. The repeated in- 
 flexions, therefore, of the fecretory arteries increafe the 
 vilcidity of the juice, by delaying the flux, and giving 
 the parts more time to cohere or attrad each other. 
 But a ftraight courfe of the veffels increafes the celerity 
 of their fluid, whence a copious and eafy fecretion ; but 
 then it makes the fecretion more impure, as we fee in 
 the urine. 
 
 22 1. That the fmaller arteries have different de- 
 grees of denfity or firmnefs, there is no reafon to doubt; 
 fince we adually find it fo by experiments in the larger 
 branches. But the denfer the capillary arteries, the 
 more they refifh the light and flowly moving particles, 
 and yield only to the more denfe ones that have a 
 greater impetus. Irritability produces almofl the fame 
 efleds ; for if the fecretory flrainer has a very acute 
 fenfation, it will rejed the grofs humours, and tranfmit 
 the more fluid ones : inflead of mucus in the urethra, 
 it will feparate a thin yellow ferum ; and almofl the fame, 
 inflead of the febaceous matter that lies under the fkin : 
 the quantity of fecreted liquor will alfo be increafed ; 
 as for example, in the tears. 
 
 222. Again, the velocity is greatly increafed, if the 
 heart is near ; if the artery is ftraight, or if it is pro- 
 duced with a fmall angle ; alfo, when the excretory dud 
 arifes before the extremity of a larger arterial branch : 
 and it is diminiflied, when the fmall fecretory artery 
 runs a long way capillary, whereby the blood lofes the 
 greater part of its motion in fridion. Finally, from 
 whatever caufe the diverfity may arife, a greater velo- 
 
102 
 
 SECRETIONS. Chap. VIII. 
 
 city increafes the quantity of fecreted liquor, and pro- 
 duces heavy, more grofs, impure liquids ; it alfo gives 
 a degree of fluidity to the fecreted liquors, as it pre- 
 vents the ftagnation, by which they might contraft a 
 vifcofity : but flownefs increafes the attraction and vif- 
 cidity, and renders the fecreted juice more pure ; as the 
 fimilar particles, when brought together, can better at- 
 tract 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 branches. From hence it is, that, 
 only the impuh'e of the heart being too much increafed, 
 all the fecretions are confufed. 
 
 223. Thefe conditions nature is able varioufly to join 
 together or feparate, and impart to every (trainer in 
 greater or leffer degrees ; and thus, by various me- 
 thods, to modify the fecreted humours. Anatomy fur- 
 nifhes an example, if you fliall compare the ftrainer of 
 the bile or femen, which are thick juices, with the 
 ftrainer of the urine and tears, w'hich are fluid ones. 
 
 224. From all that has been b.itherto advanced, we 
 may now begin to perceive, that, fince the blood con- 
 tains particles of various kinds ; (bme fluggifli ; others 
 mucous ; ethers coagulable, but fluid ; fome denfe 
 and red ; fome watery and thin ; others fat and grofs 
 (188. et /eq.)”. among all thefe particles, thofe which 
 are the largeft and mod denfe, as the cruor, will go 
 on moft towards the axis of the veffel, fo as to pafs 
 on in a continued courfe from the artery into the trunk 
 of the fanguineous vein (39.) 
 
 2 25. Thofe particles w'hich are grofs and fluggifh, 
 as the fat, muff needs go oft' laterally by larger orifices 
 from the fanguineous artery, by fliort du£ls ; for long 
 dufts would make a (top to fuch a fluggifh juice as oil. 
 The phenomena of the adipofe fecretion (19.) agree 
 with this defeription. Such parts as are coagulable, 
 but fpeciftcaiiy heavier than thofe which are merely w^a- 
 tery, kept fluid only while the powers of life are in ac- 
 tion ; thefe pafs off laterally from the red arteries, into 
 the arteries w’hich are not red, but continuous to the 
 
 red 
 
Chap. VIII. SECRETIONS. 103 
 
 red ones, and fmaller ; whether thefe pellucid ones are 
 continued on in the nature of trunks, fending off other 
 fmaller branches, like the leaft arteries (41 .) ; or whe- 
 ther they exhale their contents by a fliort extremity, like 
 the veffels of 170. 
 
 226. Thin watery juices may evidently pafs off by 
 any veffels continuous with the fanguineous ones, or the 
 leffer ones (44.), provided they be only fmall enough 
 to refufe the groffer juices : and this, wEether they 
 come out from the Tides of the larger arteries; or whe- 
 ther by a long continued courfe, and fending off all the 
 groffer juices by large lateral branches, they, at length, 
 end in a fmaller pellucid canal inftead of a trunk ; as for 
 example, in the eye. To the produdlion of thefe juices, 
 the moff Timple fabric is fufficient ; even a dired con- 
 tinuation of the fecretory artery itfelf into an excretory 
 dud, as we fee in the urine. Therefore, the duds and 
 veffels have here a ftraight and fimple courfe, with few 
 or no inflexions ; and a proportionable velocity as yet 
 holds in the courfe of their contained juices. 
 
 226*. Such juices as, being watery, light, but vifcid 
 at the fame time, are confequently fluggifli and lefs 
 moveable ; thefe may be eafily fecreted by fliort nar- 
 row duds of a lefs diameter than to admit the fat, and 
 appended to the fanguineous arteries : and, therefore, 
 it is evident, thefe will be feparated from the blood 
 more abundantly in fome parts of the body than others ; 
 namely, where the velocity received from the heart’s 
 impulfe is lefs, the flexures of the artery more frequent, 
 and where the extent of the capillary artery lhall be car- 
 ried to a greater length. 
 
 227. Whether or no ought we to afcribe to each 
 particular part, the ferments, pores, fpecific weights, or 
 filters filled -with their own peculiar humour, and ad- 
 mitting nothing that is analagous to it, which deter- 
 mine the nature of the humours to be generated? 
 One who admits of thefe, ought to confider the great 
 difference there is in one and the fame juice, feparated 
 in the fame part of the body, according to the difference 
 
 of 
 
104 SECRETIONS. Chap. VIIL 
 
 of age, courfe of life, &c. The bile in a foetus is ge- 
 nerated fweet ; the femen thin, and without vermicles ; 
 the milk cither none or watery ; the urine watery, mu- 
 cous, and infipld ; the uterine mucus very white ; tiie 
 cutaneous vcffels toll of red juices ; the watery juices 
 reddifh ; and the fat gelatinous. By the fame organs, 
 in an adult perfon, the bile feparated is (harp or acrid ; 
 the femen thick ; the milk butyraceous ; the urine yel- 
 low, thin, and alkalefcent j the womb dilcharges a m.en- 
 flrual blood, and the aqueous humour very clear. But, 
 even in the adult perfon, how different is the urine ? 
 at one time watery ; at another, thick or concocted ; 
 in a fever, high-coloured and heavier, full of falts and 
 oils. The paffions of the mind, which make no other 
 change in the body than that of ftridfures in the nerves, 
 yet wonderfully change the face of the fecretions, and 
 expel even the blood and bile through the vcffels of the 
 fkin. Add to this, the frequent diflurbance of the fe- 
 cretions, and the changes to which they are liable from 
 flight caufes ; fo that only an increafed celerity (hall 
 caufe feveral differing liquors to be fecreted by one and 
 the fame organ : for blood has been known to pals into 
 almofl all the paffages of the fecreted juices ; into thofe 
 of the fweat, tears, mucus of the noftrils and of the 
 womb ; and into the lactiferous, feminal, and urinary 
 duels, as well as the fat. A true milk has been feen 
 feparated by glands in the thigh. When the urine has 
 not been excreted by its natural courfe through fome 
 defeCl of the kidneys, ureters, or bladder, it has pafl'ed 
 by the fkin, exhaled into the ventricles of the brain, or 
 even into the whole cellular fabric. The perfpirable 
 matter of SanCtorius, however thin, is often by cold 
 driven through the nofe or kidneys ; or, by the fame 
 caufe, by fear, or by medicines, is depofited through 
 the excretory villi of the inteflines. That exhaling vif- 
 cid juice, fecreted by the fame organ with the fat, from 
 which it fo much differs, into the cellular fubflance, is 
 depofited, takes place of the fat, is re-abforbed, and 
 alternates again with the fame, (i8, &c.) A falivation 
 
 fupplies 
 
Chap.VIIL secretions. ioj 
 
 fupplies the place of the Sandborlan or cutaneous exha- 
 lation externally, and of the cuticular exhalation inter- 
 nally. The bile, re-abforbed, appears evidently flow- 
 ing in the veiTels of the eyes. Nor does there appear 
 any thing in the fabric of any of the vifcera or glandules 
 that can fix or maintain the nature of the fecerned 
 fluid. The fpecific gravities of the vifcera and (trainers 
 neither aiifwer, according to the authors who treat of 
 of them, to the fpecific gravity of the humours which 
 they fecrete ; nor are they at all known by experi- 
 ments that can be depended on. 
 
 228. It now remains for us to difcover, how the fe- 
 cretions, in a healthy perfon, become pure or uniform. 
 For all the juices that have been lately fecreted (with- 
 out excepting any, even the oil or fat itfelf) have a great 
 many watery particles intermixed ; fo that none of the 
 thicker juices feem capable of being formed, without 
 having a mixture of the thinner watery ones : how then 
 do the femen, bile, fat, mucus ,and other thick juices, 
 depofite their firfl: watery flate, and acquire their proper 
 vifcid condition and other qualities? 
 
 229. For this end, therefore, nature has framed 
 glands, with large and fmall follicles or refervoirs, for 
 retaining the fecerned juices, from which the watery 
 parts are required to be feparated, to render the re- 
 maining part more ftrong and vifcid. The mucus, at 
 its firfl depofition, is thin and watery as yet, but little 
 differing from the perfpirable vapours or tears, in whicli 
 flare it diftils into the cavity of the noflrils, wind-pipe, 
 and inteflines. This is not continually difcharging, be- 
 caufe the excretory orifice is lefs than the retaining cell 
 or follicle (196.); and the excretory du£l being fome- 
 times long and (lender, at others repeatedly bent, and 
 turning backwards and forwards, or traufmitted thro' 
 a hard cellular texture, or clofed by fome force equi- 
 valent to a fphin£ler, fo retards the juice that it cannot 
 pafs out but by the afliflance of a preffure ; or perhaps, 
 not without being irritated by the quantity or acrimony 
 of the juice, the follicle preffes out the liquor which 
 
 P incom,' 
 
io6 SECRETIONS. Chap. Vin. 
 
 incommodes it, by a kind of periflaltic motion. This 
 appears from the morning difcharges of mucus by blow- 
 ing the nofe, coughing up from the lungs, and by fneez- 
 ing after the noclurnal ftagnation. In the mean time, 
 the patulent veins, extended into the cavity of the fol- 
 licle, abforb the more aqueous parts from tlie thin mu- 
 cus, that it may become thicker as it is retained lon- 
 ger ; but if, by the force of fome ftimulus, it be dire£lly 
 difeharged after it is fecreted, it comes out thin and 
 watery. Examples of this we have in the urethra, in 
 the noftrils, and in the ear-wax; as alfo in the bile, 
 which, at its fird reparation in the liver, is watery, and 
 has but little yellownefs or bitternefs. It is, therefore, 
 retained by a large follicle or gall-bladder ; and there 
 digeiled or exalted by the vital heat, and its more thin 
 or watery parts exhaled or abforbed by the veins ; 
 whence the remainder becomes more thick, bitter, and 
 oily. The fame mechanifin takes place in the femen ; 
 which, being referved in the feminal veficle, is there 
 thickened, fo as to be very vifeid after long chadity ; 
 but in repeated venery it is expelled very fluid. In fome 
 places nature has made this receptacle two or three 
 times folded together in one and the fame organ, when 
 her defign was to form a very thick juice. Thus the fe- 
 minal paflfage is in the tedicles reticular; in the end of 
 the epididymis, one large canal ending in a larger ve- 
 ficle: w'hence the velTels at the tedicle are narrow, and 
 fo again are the vas deferens and the prodatic duel. 
 Hence there are nowhere real glandules, except for 
 fecreting a vifeid liquor. And if a vifeid liquor has 
 been fcpai ated from the arteries without a follicle, it al- 
 ways dagnates in a large follicle. The femen, bile, li- 
 quor of the joints, and fat, afford examples of this. 
 
 230. A fecerned juice may be likewife changed in 
 its receptacle by the adudon of fome new liquor.. 
 Thus the femen thickens by an affudon of the proda- 
 tic liquor; the chyle is thinned by mixture w-ith the fa- 
 liva and pancreatic juice and that which didils from 
 the villi of the doraach and intediaes, and by an affu- 
 
 fion 
 
CHAP.Vni. SECRETIONS. 107 
 
 fion of the bile it becomes alkalefcent ; and again the 
 fynovia or albumen of the joints is tempered by the two 
 kinds of fat (195.) 
 
 231. Laftly, whatever is abforbed, can be of ufe 
 to the animal according to its nature, after it is taken 
 into the blood ; as the femen gives a furprifing ftrength 
 to male animals. For the moll part, likcwife, an a- 
 crimony fimilar to that of lixivium is generated, and 
 which alfo hath its ufes, as in the bile and femen. 
 
 232. But the great ufe of the follicles and receptacles 
 of glands is to preferve the juice, of whatever kind it 
 
 'be, for thofe times in which it is moll neceffary to be 
 employed in the actions of life. Thus the bile is re- 
 ferved for the time of digellion, the femen for due 
 and lawful venery, and the mucus of the nofe is accu- 
 mulated in the night to temperate the force of the re- 
 fluent air in the day. 
 
 233. Therefore, as nature has in this way framed 
 machines by which the juices are retarded in the large 
 and fmall follicles, fo {lie has made others to expel 
 them at fuch convenient times. To fome glands Ihc 
 has given particular mufcles for this ufe; as in the te- 
 fticles of brutes, the urinary bladder, and the gall- 
 bladder : or elfe Ihe has placed other mufcular ma- 
 chines round them, which, by ading at convenient 
 times, expel their contained fluids ; as, for example, 
 in the mufcular coat of the llomach and intellines. 
 In other parts llie has added contiguous and incumbent 
 mufcles to promote the difcharge, as in the biventcrs 
 and mafleters of the lower jaw: or elfe flie has again 
 joined to them a kind of nervous irritability, which, 
 being excited to action by an unavoidable Itimulus, 
 opens the Ihut palTages to the milk, feed, tears, &c. ; 
 or being touched by fomething acrid, as already men- 
 tioned, dillils the liquor more quickly ; as happens to 
 the bile, liquor of the flomach and intellines, and to 
 the febaceous matter. 
 
RESPIRATION, 
 
 Chap. IX. 
 
 . io8 
 
 CHAP. IX. 
 
 Of Respiration. 
 
 234. ^ I ' HE bags of the pleura (77, 78.) are exactly 
 X filled by the lungs ; for fo we call the two 
 vlfcera, which are difiinguifhed into right and left, in 
 figure anfwerable to that of the bags theinfelves which 
 they fill, having a broad bafis below, and being termi- 
 nated above at the firfl rib by an obtufe point or cone. 
 The anterior face of them is flat, their fitles convex or 
 round, internally or in the middle concave, forming a 
 concavity fufficient to contain the heart. The right 
 lung is larger than the left ; and more frequently di- 
 vided, or half cut tlv-ough, into three diflincl: lobes or 
 portions ; but the left lung is not fo often divided into 
 three. They are freely fufpended by the great blood- 
 veffels, at liberty on all fides ; unlefs you call that a li- 
 gament which is made by the external membrane of 
 the pleura, departing to the lungs and to the bafis of 
 the diaphragm. Betwixt the lungs and pleura is found 
 a watery or rather ferous vapour, of a coagulable na- 
 ture, like that of the pericardium (82.) ; which vapour 
 tranfudes from the furface of the lungs, continually in 
 the fetus, and not unfrcquently in the adult. This is 
 fometimes increafed to a dropfy, or thickens to a kind 
 of febaceous matter ; or laftly, concreting into fibres, 
 joins the lungs to the pleura. 
 
 235. The external membrane of the lungs is fimple, 
 and thinner than the pleura, although continuous to 
 it. It is fpread all over them, from the adhefion of the 
 great blood-veffels of the heart ; yet fo as to be capable 
 'of retaining wind eafily, without breaking, after being 
 I'eparated from the lungs. The fiune membrane covers 
 the interftice or mediaftinum of the lungs, like a 
 bridge. It is joined to the lungs by a cellular tex- 
 ture. 
 
 236. The 
 
Chap. IX. KESPIRATION. loc? 
 
 236. The ftrufture of the lungs is a heap of lobes 
 feparated from each other by intermediate intervals, in 
 which is extended a loofe cellular fubllance. The 
 firft divifion of them is into two extreme lobes, 
 which are larger ; and one middle one, which is lefs ; 
 yet cohering together : although afterwards they are 
 again fubdivided internally, through a long feries, into 
 leifer lobules down to the lead, till at lad the fmall lo- 
 bules terminate in very fmall membranous cells, 
 which, in adults, are varioufly figured, and full of air, 
 and communicate on all fides with one another. 
 Thefe veficles of the lungs, therefore, do not receive 
 the air by a fingle orifice from the wind-pipe, as into 
 an oval grape or vial ; but the air, exhaling from the 
 lead branches of the faid wind-artery, is admitted in 
 fuch a manner into their irregular fpaces, that it freely 
 fpreads through them from any one part of tiie lungs 
 into all the red, and returns again in like manner. 
 This is demondrated by inflation, which drives the air 
 even through the lead branches of the wind-pipe into 
 the fmalled lobes ; from whence it readily paffes into 
 all the red. Nor, in man and fmaller animals, is the 
 cellular fabric of the intervals lliut up from the veficles 
 of the lungs, nor are the lobes furrounded by any pe- 
 culiar membrane ; for in the larged, as between the 
 air-veficles and thofe cellular fpaces furrounded with 
 lobules, there is no commerce. 
 
 237. The air is driven into thefe veficles thro’ the wind- 
 pipe, which arifes from the larynx (hereafter to be de- 
 feribed), and from that only receives its air. The fird part 
 of this wind-pipe is fingle, and defeends along the fmooth 
 bodies of the vertebrae of the neck^ partly flefliy and 
 partly cartilaginous ; namely, within the cellular fub- 
 dance that furrounds the wind-pipe, follows a canal, 
 made up by a fucceflion of cartilaginous and mufcular 
 rings. Thefe are thin and cladic ; flatter and thicker 
 in their foremod part, but thinner in their poderior 
 extremities, which are conjoined together by drong 
 
 tranfverfc 
 
lid RESPin ATION. Chap. n. 
 
 tranfverfe mufcular fibres, which, adhering firmly to 
 each extremity of the cartilage, complete the circle. 
 But the lowermoft circles are lefs ; the uppermofi; of- 
 ten augmented by an appendix, the next again perpen- 
 dicular to the divifion. 
 
 2^8. The flcfiiy rings, alternately placed with the 
 cartilaginous ones, are made up of red mufcular fibres. 
 Some of thefe are tranfverfe, connecting the detached 
 ends of the annular cartilages ; others defeend from 
 each upper to the next lower ring. But other muf- 
 cular fibres again, defeending downwards from the cri- 
 coide cartilage, and having reached below the firft di- 
 vifion of the bronchia, vanifh within the luns[s. The 
 tranfverfe fibres contract or leffen the diameter of the 
 wind-pipe ; the hingitudinal ones render it fhorter. 
 Alfo within the lungs, betwixt the imperfect rings, 
 is found a fort of mufcular fabric, but lefs uniform. 
 
 2 In the cellular coat which furrounds the muf- 
 cular one, but efpecially in the back part of it, a- 
 long the pofterior interval that is betw'ixt the carti- 
 lages, are placed numberlefs fimple glands, which 
 open by very fmall ducts, like pores, into the cavi- 
 ty of the wind-pipe : by which pores they depofite a 
 watery and pellucid mucus into that cavity ; which 
 mucus, being without the leaft acrimony, not coagu- 
 lable into a hard fubftance like the humour of the eye, 
 is of the greatefl; ufe in defending thefe moft fenfible 
 membranes from being injured by an impure air, full 
 of particles, which, by their mechanical figure or che- 
 mical acrimony, might be very troubkfome. Laftly, 
 the internal tube of the wind- pipe is compleated or 
 lined by a membrane, which is continuous with that 
 of the mouth, fmooth, foft, and very irritable. The 
 fame cellular texture furrounds it which anfwers to the 
 mufcular coat. 
 
 240. The veflels of this part of the whole wind- 
 pipe, in the neck, come from thofc of the lower tlty- 
 reoids ; in the thorax, from other fmall branrh;, s of 
 the fubdavian trunks, or the mammaries, or the 
 
 (htah 
 
Chap. IX. RESPIRATION. ni 
 
 chlah properly fo called. Its nerves are numerous 
 from the recurrent and intercoflal ones. 
 
 241. In the upper part of the thorax, the wind-pipe 
 is received between the laminae of the pofterior part 
 of the mediaftinum ; and at the third vertebra, or a little 
 above, is divided into two fimilar branches refeinbling 
 the trunk itfelf, and formed like that of imperfeft carti- 
 lages, alfo furnlfhed wirh fimilar glandules ; each of 
 which branches enters the lung to which it correfponds, 
 only the right is fomething Ihorter and larger than tlie 
 left. Having entered the lungs, the cartilaginous rings 
 change into fragments, which become more and more 
 difform, gnomonic, angular, triangular, and inter- 
 mixed with a larger portion of the membrane, till, 
 at length, the cartilages decreafing, the laR branches 
 of the bronchia become merely membranaceous. 
 
 242. Its lad branches are invifible, w'hich exhale 
 the air into the cellular fpaces of adult lungs, and like- 
 wife receive the watery vapours exhaling from the ar- 
 teries into the faid fpaces ; from whence they arc 
 thrown out by exfpiration. 
 
 243. The blood- veflels of the bronchia are the arte- 
 r'uz & vena bronchiales. The former are almofl con- 
 ftantly two j one coming from the upper intercoflal of 
 the aorta, which is diftributed either to the right only, 
 or to both the lungs ; the other, from the trunk of the 
 aorta itfelf, goes to the left lung. Sometimes there are 
 more than two bronchial arteries to be feen ; as w’hen 
 there are three, by the addition of a fecond from the 
 aorta. But fometimes again there is only one artery 
 in common. The thoracic part of the bronchi fituated 
 without the lungs, has its proper velTels from the aorta, 
 the fubclavian, mammary, or intercoflal. The bron- 
 chial veins are mod commonly two ; the right from the 
 vena azygos, the left from a peculiar branch of the 
 fubclavian vein and the left fuperior intercodal. Thefe 
 blood-veffels travel together with the branches of the 
 wind-pipe ; and defeend into their membranes in fuch 
 a raantierj that the pulmonary arteries, irj their way. 
 
112 
 
 RESPIRATION. Chap. IX. 
 
 inofculate with their contiguous arteries, as the veins 
 iikewlfe communicate with each other. There are feme 
 inftances where the pulmonary vein itfelf has given fmall 
 branches to the lungs, to the wind-pipe, and to the fur- 
 face of the lungs. 
 
 24 ^^. But there are other larger veflels belonging to 
 the lungs, called the pulmonary artery (deferibed io6. 
 108.), and the pulmonary vein (i 10.) The great ar- 
 tery, in the fetus larger than the aorta, and in the a- 
 dult but little lefs, has two branches ; the right larger 
 but fhort, the left narrower and longer. In the fetus, 
 the trunk itfelf is continued into the defeending aorta, 
 and is known by the name of dudus arteriojus. In an 
 adult, that trunk degenerates into afolid ligament. The 
 four pulmonary veins accompany the arterial branches 
 and the afpera arteria of the wind-pipe in their courfe 
 through the lungs, furrounded with a good deal of 
 cellular fubftance ; which fubftance, being increafed, at 
 iaft compofes the lungs themfelves. Within this cellu- 
 lar fabric, and likewife upon the ultimate fpaces or 
 cells, the air-veflels and blood-veflels are fubdivided, 
 ipread, and interwoven like the mefhes of a net ; and here 
 the fmall arteries exhale a plentiful vapour into their 
 cells, and the veins abforb a w’atery vapour from the 
 fame cells. Hence water tinctured, the whey of milk, 
 or a thin waxen injeftion, being urged into the pulmo- 
 nary artery, flows w'ith a froth into the wind-pipe ; or, 
 on the contrary, being urged from the wind-pipe into 
 the lungs, they penetrate into the pulmonary arter)'. 
 In like manner, injeftions pafs from the pulmonary 
 vein to the wind-pipe ; or from thence again, they may 
 be forced into the veins. Laftly, a liquor injected by 
 the arteries, readily enters the pulmonary veins ; and, 
 the reverfe. 
 
 2^5. The lymphatic veflels, as in other parts, form 
 a net-work upon the furface of the lungs, from whence 
 there are branches conveying the lymph to the cavity 
 at the back part of the mediaftinum, and to the fmall 
 glands which lie behiod the oefophagus, opening at 
 
Chap.IX. respiration. 113 
 
 laft into the thoracic du£t. The anterior pulmonary 
 nerves are fmall, but the pofterior ones fomewhat lar- 
 ger : they come from a nerve of the eighth pair ; and 
 there are alfo fome fmall nerves to the lungs from the 
 recurrent, and likewife from the cardiac plexus, which 
 enter together with the large blood-veffels. Hence the 
 lungs have but little fenfation ; that of the little nerves, 
 how^ever, divided after the manner of the bronchia, is 
 very acute. Nor are the lungs of an irritable nature. 
 
 246. The quantity of blood which enters into the 
 lungs is exceeding great, equal to (or even perhaps 
 greater than) that which is fent in the fame time through- 
 out the reft of the whole body ; which, therefore, de- 
 monftrates fome very confiderable ufe proper to this 
 vifeus. And that this ufe depends manifeftly upon the 
 air, appears from the univerfal confent of nature, ia 
 which we fcarce find any animal without breathing; al- 
 fo from the ftrudure of the lungs in the fetus, in 
 which, for want of air, they are ufelefs, receiving only 
 a fmall portion of the blood, which the pulmonary ar- 
 tery condufts from the heart. We are now, therefore, 
 to fpeak of refpiration, by which the air is drawn into 
 and expelled from the lungs. 
 
 247. The element of air appears, from the principles 
 of philofophy, to be an elaftic and fonorous fluid, 
 with a fpring which cannot be deftroyed. But the at- 
 mofpherical air, which we commonly receive into the 
 lungs, is impure, filled with a great quantity of watery 
 and other vapours, alfo with falts and the univerfal acid, 
 with the feeds of plants and animals, and other foreign 
 matters, but in very minute particles ; fo that it weighs 
 859 times lefs than water, and a cubic foot of air weighs 
 between 6 10 and 694 grains. This air, which furrounds 
 the earth on all fides, being prefled by the incumbent 
 columns of its own mafs, perpendicularly, laterally, 
 and in all diredions, enters wherever it meets a lefs 
 refiftance, and with a confiderable force, as appears 
 from experiments made with empty or exhaufted vef- 
 fels, and by the air-pump, fo that its preffure on the hu- 
 man body is not lefs than 3000 pounds weight. It is 
 
II4 RESPIRATION. Chap. IX, 
 
 repelled chiefly by the pores of the membranes, which 
 yet are permeable by water : it likewife penetrates oil 
 or mucus with difiiculty. 
 
 248. This air is excluded from all parts of the hu- 
 man body by the furrounding clofe fliin, which, even 
 when dried or tanned, is impervious to the air; but 
 more fo, as under the ikin is placed the fat, making an 
 equal refiftance to the narrow openings of the abforb- 
 ing veflfels. It, therefore, now remains for us to in- 
 quire, why the air enters the lungs of an adult perfon ; 
 for with this they are in a manner conflantly full, 
 and of courfe are equally preffed, and refilling againft 
 the weight of the whole atmofphere : but that the lungs 
 always contain air, is evident; becaufe, however clofe 
 you comprefs them, they will be llill lighter than wa- 
 ter ; and even in the fetus, after they have been infla- 
 ted but a few times, they always fwim ; vrhereas, before 
 breathing, they fink to the bottom of water, if they 
 have as yet not given admittance to the air. 
 
 249. The equilibrium of the air’s preflfure being re- 
 moved in any ^ace, it conflantly defcends or flows that 
 way where it is leafl refilled (247.) But air that is 
 denfe and heavy will defcend more eafily than fuch as 
 is light, whofe force fcarce overcomes that of the air 
 which is already in the lungs, nor is able by the fame 
 force to overcome the refiflance of the bronchia and 
 force by which the lungs comprefs the air contained in 
 them. Hence an animal lives better in a denfe than in 
 a light air : although that kind of air is always moll 
 tolerable, which is pure at the fame time that it is light; 
 fuch as that of the highefl mountains of the Alps. 
 Therefore, for the air to enter the lungs, they mull 
 make a lefs refiflance to it than before ; namely, the 
 air, which is already in the cellular fabric of the lungs, 
 mull be ratified : but this elFed will follow, if the ca- 
 vity of the thorax, in which the lungs are contained, 
 and which they exaflly fill, be dilated. Thus the air, 
 which is always in the lungs, expands into a larger 
 fpace, by which, being weakened in its fpring, it 
 
 u^es 
 
Chap.IX. respiration. 115 
 
 makes a lefs refiftance to the external air ; and confe- 
 quently a portion of the faid external air defcends into 
 the lungs, fulficient to reftore the confined and rarefied 
 air, filling the lungs to the fame denfity with that of the 
 external air. 
 
 250. We mull therefore defcribe'the pov/ers which 
 dilate the thorax to produce this effeft. The bread or 
 thorax is a fort of cage made up of bones, mufcles, and 
 cartilages ; being almoft of the lhape of an oval tub, 
 fomewhat comprefled before, but behind divided by an 
 eminence, whofe hoops are the ribs, which are of a re- 
 markable ftrength. In the lateral parts of this cage are 
 placed the lungs ; in the middle and lower part lie the 
 pericardium and heart ; after which it is taken up by 
 ibme of the abdominal vifeera. 
 
 251. The bafis of the thorax is formed by a column, 
 a little crooked, and gibbous on the upper and back 
 part ; and likewife, in that part of the bafis which is up- 
 permoft, the fame is very much behind the others into 
 which twelve vertebree coalefce. They coalefce, how- 
 ever, by the union of their bodies into a fingle column, 
 which is prominent in the forepart between the two ca- 
 vities of the bread; divides the right from the left; and 
 is plane in the forepart, and broad towards the fides. 
 A {light finuolity receives the ribs in that place where 
 the arch feparates from the body. They are bound to- 
 gether into one column, as well by the eladic plate in- 
 terpofed between every two bodies, and coalefcing with 
 both 5 as by other ligaments and fpines lying upon 
 one another, and the joining of the ribs, by which 
 means no motion can happen among thevi without the 
 greated difficulty. The fides of the bread are made 
 up of twelve ribs. Thefe are in general bent in the 
 form of an irregular arch, having a great curvature la- 
 terally and backwards, but extending in their forepart 
 towards a right line. The bony parts of the ribs lie 
 
 - fufficiently parallel with each other; the greated part 
 of the rib is bony, round, and thick backward, but 
 thin and flat forw’ard. The other part forward is com- 
 
 0^ 2 pleted 
 
ji6 RESPIRATION. Chap.IX. 
 
 pleted by a cartilage ; which in general continues the 
 figure of the rib, growing in a flat broad concavity of a 
 nature different from the bony part ; and which does 
 not change in*o bone, unlefs in extreme old age. 
 
 252. The pofterior and bony thick part of each rib 
 terminates in a head ; along from which, in the body of 
 the uppermoft and two lowermofl; ribs, runs a cavity or 
 groove, formed in the other ribs, betwixt every two ad- 
 jacent margins, which lie one towards the other. The 
 vertebrae are tied to the ribs by ftrong ligaments, of 
 which the principal fpread from each rib like rays into 
 the next adjacent vertebra, other ligaments tie the tranf- 
 verfe procefs to the tubercle of the rib, and others tie 
 the ribs one to another and to the tranfverfe procefles 
 at the fame time. Moreover, betwixt the angle of in- 
 curvation and the juncture with the vertebrie, each of the 
 ten upper ribs fend out a protuberance, which, being 
 articulated with the plain fide of the tranfverfe procefs 
 of each vertebra, are fo tied by fliort and ftrong liga- 
 ments to that procefs, that the rib has liberty to make 
 a fmall afeending and defeending motion, but with a 
 confiderable degree of firmnefs. 
 
 253. Among thefe anterior cartilages, the feven up- 
 permoft: reach to the fternum, and enter into the lateral 
 cavities, which are incrufted with a cartilage in that 
 bone, to which they are alfo made faft by fhort liga- 
 ments. Of the five remaining ribs, the uppermoft is 
 faftened to the feventh preceding, and that to the next 
 lower, by a ftrong cellular texture, by which they form 
 a continuous margin, which is at laft alfo faftened to 
 the fternum. The fame are connected to one another 
 both by proper ligaments, and cartilaginous appendiees 
 joined with them through the cellulofuy : the two lower- 
 inoft are free, and connedled only with tlse mufcles. 
 Thefe inferior cartilages are united to one another and 
 to the fternum by ftrong ligaments. 
 
 254. The firft rib is the fliortcft, but more folid 
 than any of the reft. As they follow in fuccefTion to 
 the feventh and eighth,every two and two ftretch them- 
 
 felvcs 
 
Chap. IX. RESPIRATION. 117 
 
 felves into longer and more moveable circles. The 
 eighth is the longefl of all ; and from thence, the lower 
 down they are, they grow continually fhorter. 
 
 255. The direftion of the upper rib is defeending; 
 but the fecond rib joins the fternum almoft in a right 
 angle, while the others afeend both to the vertebrae and 
 t-o the fternum, but more to the latter. But the bony 
 part of the ribs is placed in fuch a direction, that the 
 uppermoft have their fides in the fore part very much 
 declined forward, almoft tranfverfely. In the third ribs 
 it is placed almoft perpendicularly; in the middle ones, 
 it projeds a little outward in the lower part. Befides, 
 the ftrength of the different ribs is very different. The 
 uppermoft, being fhort, rather grow into the fternum 
 than form a joint with it; and being tranfverfe, and 
 often as it were welded together, they make a very 
 ftrong refiftance. From thence the mobility increafes 
 downwards, till the loweft rib, adhering only to muf- 
 cles, has the moft eafv motion. 
 
 256. The fternum in general is a thin fpungy bone 
 altogether, one in adults, but is varioufly divided in the 
 fetus. Its upper and broader part refembles an octa- 
 gon ; and is articulated with the clavicles, which are 
 jointed very clofely with the triangular head of the fter- 
 num, and with the firft rib on each fide. The other 
 part which is longer and narrower grows broad down- 
 wards, and its fides receive the ribs each into its pro- 
 per angular cavities. The lower part, which is leffer and 
 Ihorter, imitates the obtufe figure of a tongue. This 
 is continued into a detached appendix, partly bony, and 
 partly cartilaginous, of a changeable figure, which they 
 call the enjiform cartilage ; and which is found of va- 
 rious fhapes, fometimes being obtufe like a little tongue, 
 fometimes pointed like a fword, fometimes bifid, and 
 fometimes perforated. 
 
 257. In order, therefore, to dilate the feat of the 
 lungs, and thus to put the body in fuch a ftate that the 
 external air may rufh into the lungs, it is neceffary for 
 the thorax to be elevated. For thus all the fe£tions of 
 
 the 
 
ii8 RESPIRATION. Chap. IX. 
 
 the thorax form right angles, and its capacity is increa- 
 fed. This motion is performed by various mufcles, 
 •which either operate conftantly, or only at certain times. 
 The intercoftal mufcles, therefore, all of them a£t per- 
 petually in elevating the ribs. By this name "we un- 
 derfland 22 mufcles; of which 1 1 are external, or next 
 the fkin; and as many internal, feparated from the pleura 
 only by fat or cellular fubftance. The beginning of the 
 cuter intercofials is at the poilerior articulation of the 
 ribs (252.); but the termination of them is in the ante- 
 rior bony part of each rib, at fome diftance from the 
 cartilage, in fuch a manner, that the remaining fpace 
 betwixt the cartilage and flernum to the mufcle is filled 
 by a tendinous expanfion. The diredlion of thefe muf- 
 cles is fuch, that the fibres defeend obliquely forward, 
 from the lower edge of the upper rib to the upper edge 
 of the lower rib. And that their aftion is to elevate the 
 ribs, all authors unanitnoufly agree; becaufe they thus 
 defeend from the upper lefs moveable to the lower and 
 more eafily moveable rib, in fuch a manner, that their 
 lower point lies more diflant or remote from the hypo- 
 mochlion or point of motion, which is in the coftal arti- 
 culation with the vertebrae, confidering the rib as a lever. 
 
 258. But the internal intercofials arife at fome di- 
 flance from the vertebrae, almofl at the outer tubercles 
 of the ribs beforementioned (252.). From thence they 
 proceed as far as the flernum, into which the upper- 
 mofl of thefe mufcles are inferted above. The diretlion 
 of thefe is contrary to that of the former, except the 
 anterior part of the firfl or uppermofl of them ; fo that 
 they defeend from the lower margin of the upper rib 
 backward, to the upper edge of the lower rib forwards. 
 Therefore fome doubt of their a«flion, becaufe their 
 lower part is inferted into that portion of the rib which 
 is nearefl its articulation with the vertebrae, and which 
 therefore feems to be the leafl moveable : however, they 
 elevate the ribs notwithflanding this ; for the great firm- 
 nefs or immobility of the upper rib, exceeding that of 
 the lower, is evident from the articulation, weight, and 
 
 H- 
 
Chap. IX. RESPIRATION. 119 
 
 ligaments there formed, which furpafles that mobility, 
 arifmg from the greater diftance of the center of mo- 
 tion. This appears from the diifedion of living animals ; 
 in which we fee the inner intercoflal mufcles operate in 
 the elevation of the ribs, and reft in the depreffion of 
 them ; alfo from a flexible thread fixed to the rib of 
 fome human fkeleton, and drawn in the fame direction 
 with that of the fibres of the inner intercoflal mufcles, 
 by which means the lower rib will be always approxi- 
 mated towards the upper. The greater firmnefs alfo of 
 the upper ribs proves this, as they ferve for a fixed 
 point to the lower ones ; for the fir ft or upper moft ribs 
 are from eight to twelve times firmer and lefs moveable 
 than the lower true ribs ; but the difference of diflance 
 in them, from the center of motion, is fcarcely the twen- 
 tieth part of the length of their whole lever. Laftly, 
 the elevating power of the internal intercoflal mufcles 
 appears plainly by experiment in a dead fubjedl, whofe 
 thorax, being raifed or inflated, thofe mufcles fwell or 
 contraft. 
 
 259. By the aftion, therefore, of thefe mufcles, the 
 thorax is elevated, not altogether as one machine, nor 
 would refpiration be affifted by fuch a motion ; but the 
 ribs turning upon their articulations, though behind 
 they are but little moved, yet the fore-part of their ex- 
 tremities thereby defeend and form larger angles both 
 with the flernum and vertebra ; but from thence in the- 
 middle of their arches, by afeending, their lower edges 
 are drawn upward. At the fame time, the flernum is 
 thrufl out forward more from the vertebra and from 
 the ribs. Thus the ribs are both removed farther from 
 the vertebra, and the right ribs depart from the left; 
 and the diameter on both fides, betwixt the right and 
 left ribs, betwixt the fternum and the vertebra, is in- 
 creafed almofl to two lines ; and therefore this enlarge- 
 ment, following in every imaginable feftion of the tho- 
 rax, will fufficiently dilate the cavity of the breafl. This 
 aftion of the ribs is more particularly complete in wo- 
 men, &nd in men who have no fhortnefs of breath. 
 
 Thefe 
 
120 
 
 respiration. Chap. IX. 
 
 Thefe effcfts are produced leaft of all by the firft ribs, 
 but more by the following ones. In very flrong in- 
 fpiration,the ribs defcend both behind and before ; and, 
 along with thefe, the fternum and the fpaces between 
 the cartilage are leffened. But this dilatation alone is 
 not fufficient for healthy breathing ; nor is it fo confpi- 
 cuous or evident in men ; although, in them, the in- 
 tercollal mufcles, by retaining and elevating the ribs, 
 very much affift the infpiration in a tacit manner, while 
 they afford a fixed point to the diaphragm, that the 
 whole force of that mufcle may be fpent, not fo much in 
 depreffmg the ribs, as in urging down the abdomen. 
 The greater part, therefore, of the fpace which the 
 thorax gains in infpiration, arifes from the adion of the 
 diaphragm. 
 
 260. By the diaphragm we underlland a mufcle 
 expanded in a curvilineal plate, by which, in general, 
 the pulmonary bags are feparated from the abdomen in 
 fuch a manner, that the middle and tendinous part of 
 the feptum is nearly the higheft, and fupports the peri- 
 cardium : its lateral parts, which arife from the folid 
 parts of the thorax and loins, are every where lower ; 
 but the lowed of all are thofe which lie moll backward. 
 The ilefliy portions of this mufcle arife before from the 
 inner or pofterior face of the enfiform cartilage, and 
 ifrom the feventh, eighth, ninth, tenth, eleventh, and 
 apex of the twelfth, rib ; after which follows an interval, 
 in which the naked pleura lies contiguous to the peri- 
 tonaeum. From thence the mufcular appendices of the 
 diaphragm, which are much the ftrongeft part of it, 
 being colleded on each fide into two, three, or four 
 round mufcular portions, arife fielhy from the tranf- 
 verfe procefs on each fide of the firff vertebra of the 
 loins, and from the fide of the body of the fecond ; 
 tendinous from the middle of the body of the fecond, 
 third, and fourth, and with cartilages placed between 
 them, always higher up in the left fide, but lower down 
 in the right. 
 
 261. All thefe fibres (26c.), becoming tendinous, 
 
 form 
 
Chap. IX. RESPIRATION. izt 
 
 form the centre of the diaphragm, which refembles, in 
 figure, an obtufe index of a fun-dial, having the middle 
 of the larger angle fupporting the pericardium, while 
 the lateral angles or wings defcend backward, the left 
 being narrower than the right. This centre of the dia- 
 phragm is more moveable and at liberty than the reft; 
 except in the middle of its tendinous part, near the 
 flelhy margin, where the incumbent heart makes a re- 
 liftance; but the lateral parts and the flefhy portions 
 belonging to them are the molt moveable. The fibres 
 of this tendon form a moll beautiful web, principally 
 indeed on the upper part; which ftretches from the 
 flelhy part of each mufcle to the flelhy part of the op- 
 pofite one : thence remarkable inferior fafciculi are fent 
 off tranfverfely to the right and left, and alfo back- 
 wards, which lall portion is the uppermoft. 
 
 262. There are two holes in the diaphragm; of 
 which that on the right fide of its tendinous part is 
 fomewhat fquare, and circumfcribed by four llrong ten- 
 dinous portions ; the left, which is elliptical, lies betwixt 
 the right and left flefhy portions, which arife from the 
 middle of the bodies of the vertebrae of the loins : un- 
 der this opening they deculfate and crofs each other 
 once or twice, but above they end in the tendon. 
 This left opening is therefore drawn clofe together 
 in the contradion of the diaphragm, while it is pro- 
 bable that the other opening remains immoveable. 
 The tendons are but little changed in the motion of the 
 mufcles. 
 
 26 g. The llrucfure of the parts, and the difledion 
 of living animals, demonllrate, that the flelhy portions 
 of the diaphragm, which on all fides afcend from the 
 firm parts to the middle and more moveable portion of 
 it, do, by their contradion, deprefs the fame, and by 
 that means draw downward the lateral bags of the tho- 
 rax, which contain the lungs (77.) ; and, by this means, 
 the perpendicular diameter of the thorax is confiderably 
 increafed. The flelhy parts are more deprelTed ; the 
 tendon lefs, both becaufe it is fixed to the pericardi- 
 
 R um, 
 
122 
 
 RESPIRATION. Chap. IX. 
 
 um, and becaufe its own fubftance doej not contract. 
 Even the oefophagus and vena cava are contracted, 
 while the diaphragm exerts its adion. So that the dia- 
 phragm almoft alone performs the office of refpiration 
 in a healthy man who is at reft •, as alfo in that thorax 
 whofe ribs are fradured, or the fternuin burll, or where 
 the perfon will not make ufe of his ribs by reafon of 
 pain. The force of the diaphragm alfo, in dilating the 
 bread, is greater, according to the calculations that have 
 been made, than all the reft of the powers which con- 
 tribute to refpiration. A ftrong infpiration is confined 
 to this place ; becaufe, during the height of the exer- 
 tions of the diaphragm, the lowermoft ribs are brought 
 inwards, and thus far the thorax is ftraitened. Left 
 this fhould always happen, the intercoftal mufcles inter- 
 fere in ordinary infpirations ; in very great ones, they 
 are inferior to the diaphragm. The phrenic nerve, 
 which is more eafily irritated than in moft other 
 mufcles, forces the diaphragm to perform its office. 
 The lungs theinfelves are altogether paffive or obedient 
 to the adion of the air, ribs, and diaphragm ; to which 
 they are preffed into clofe contad on all fides, as thro’ 
 a large wound ; and when the thorax is denudated by 
 the knife, leaving its capacity entire, the lungs appear 
 filling out the pellucid pleura and diaphragm. 
 
 264. But in larger infpirations, which receive a greater 
 quantity of blood driven into the lungs, and when there 
 is any obftacle or difficulty oppofed to the adion of the 
 lungs themfelves ; in thofe cafes, feveral other powers 
 confpire to elevate the thorax ; which powers are in- 
 ferted either into the thorax, clavicles, or fcapulas ; fuch 
 as the fcaleni mufcles, trapezii, cervicales defcendentes, 
 ferrati fuperiores, and pedorales ; together with the 
 fmall elevators, of which a more ample defcription may 
 be had from profdfed fyftems of anatomy. 
 
 265. We have hitherto furveyed the powers which 
 are able to increafe the capacity of the thorax in all its 
 three dimenfions (263 and 259.) By thefe the cavity 
 of the breaft is dilated, fo that it comprefles the lungs 
 
 left 
 
Chap.IX. respiration. 123 
 
 lefs than before : the lungs then flrive to diffufe them- 
 felves over that fpace, feeing they are never deftitute of 
 air, which expands itfelf by its elafticity as foon as the 
 prelfure is taken off. Without that mufcular force, the 
 lungs have no proper power of their own by which they 
 are capable of attrading air : and, even when they are 
 moll full of air, by having the afpera arteria clofed, the 
 animal vehemently attempts to infpire, by the efforts of 
 its intercoflal mufcles and diaphragm. It therefore re- 
 mains, that the air (247.), which is a heavy fluid, and 
 preffed on all Tides by the incumbent columns of the at- 
 mofphere, muft now enter the thorax by that greater 
 force which it has over the little rarefied air already in 
 the lungs ; or yet more powerfully, if they contain no 
 air at all ; but none if the air admitted through a wound 
 in the breafl; preffes upon the lurface of the lungs. In. 
 this adion, therefore, which is called infpiration, the 
 bronchia are every way increafed, both in length and 
 diameter ; becaufe all the diameters of the thorax are 
 increafed t but, in this aft, the inflated lungs always 
 follow clofely contiguous to the pleura, without leaving 
 any intermediate fpace. At the fame time, the pulmo- 
 nary blood-veffels, which are wrapped up, together with 
 the bronchia, in a covering of the cellular fubftance, 
 are likewife with them extended in length, and fpread 
 out from fmaller into larger angles ; by which means, 
 the circulation is rendered eafier through them. While 
 this is performing, the velicular fubftance, or flefli of 
 the lungs themfelves, filled out with air, increafes thofe 
 fpaces through which the capillary blood-veffels of the 
 lungs make their progrefs ; whereby the veficular pref- 
 fure, upon each other, and upon thofe veffels adjacent, 
 is leffened; thus, therefore, the blood will flow with 
 greater eafe and celerity into and through the larger 
 and fmaller veffels of the lungs. Hence, a dying ani- 
 mal is revived by inflating its lungs, and facilitating the 
 paffage of the blood to the left ventricle of the heart ; 
 and thus people feemingly dead by being kept a long 
 time under water, are again recovered. But as for the 
 
 R 2 preffurc 
 
124 RESPIRATION. Chap. IX. 
 
 preffure of the air upon the blood in the lungs in this 
 adion, it is fo inconfiderable as not to deferve our no- 
 tice, as being goo times lefs than the force of the heart ; 
 nor can it ever urge the air into the blood, as it eafily 
 may be forced by art with a fyringe. 
 
 266 . It is by fome queftioned, whether there be not 
 air betwixt the lungs and the thorax ? and whether this 
 air, being rarefied in infpiration, is not afterwards con- 
 denfed, fo as to comprefs the lungs, and caufe exfpira- 
 tion ? And they again alk, whether this opinion be not 
 confirmed by the inftances of birds, in which we find 
 this matter to be truly fo ? But we fee every thing con- 
 curs to confute this opinion : for, immediately behind 
 the pleura, in living quadrupeds, as well as in dead hu- 
 man bodies, the lungs are contiguoufly vifible to the 
 naked eye, without any intermediate fpace betwixt 
 them; but the pleura being perforated, the lungs are 
 immediately, by the contiguous air that enters, prelTed 
 together towards the vertebrae. In birds, indeed, the 
 lungs, being pervious to the air, admit it into the cavity 
 of the thorax through large holes in their fubftance. 
 But in thefe there is a manlfefi: fpace betwixt the lungs 
 and the pleura. Large wounds, admitting the air only 
 into one cavity of the thorax, diminifh the refpiration ; 
 but fuch wounds, as let the air into both cavities, 
 quite fuffocate or fupprefs the refpiration. The thorax 
 being opened under water, fends out no bubbles of air 
 through the faid w'ater ; but in birds it does, becaufe 
 they have air in their thorax. The imaginable fpace 
 betwixt the lungs and the thorax is always filled up by 
 a watery or ferous vapour, or elfe by the fanm vapour 
 condenfed into a w'atery lymph. If the lungs adhere, 
 they injure the refpiration but in a final! degree ; which 
 ought entirely to ceafe, if it required an intermediate 
 air betwixt the lungs and thorax. Finally, the exter- 
 nal air, being admitted to any of the internal mem- 
 branes of the human body, deftroys their texture, if 
 they are not defended by a plentiful mucus; of which 
 we can find none upon the furface of the pleura. 
 
 267. But 
 
Chap. IX. RESPIRATION. 125 
 
 267. But refpiration, whether by the admixture of 
 a fubputrid vapour, or by fome other method, cer- 
 tainly vitiates the air, and renders it unfit either for in- 
 flating the lungs or fupporting flame ; and laflly, it de- 
 prives that element of its elaflicity. It is probable that 
 this happens from putrefaction, feeing the air is ren- 
 dered peflilential by a crowd, and fevers of the moft 
 malignant kind are thus generated in a few hours. 
 Seeing this is the cafe, we are certain that the air is vi- 
 tiated in the lungs; lofes its elaflicity; and thus cannot 
 keep the lungs diflended, fo as to tranfmit an increafed 
 quantity of blood through the dilated pulmonary arte- 
 ries into the veins. Nor can the will dilate the breafl 
 beyond certain bounds, or afTifl tflat paflTage of the 
 blood in an unlimited manner. A ftate of body there- 
 fore wiil take place, in w^hich the blood cannot pafs 
 through the lungs. 
 
 .268. Thus a new refiflance to the blood continually 
 coming from the heart is generated ; and in long re- 
 tentions of the breath, as in making violent efforts, the 
 venous blood, efpecially of the head, flagnates before 
 the right ventricle of the heart when fhut, becaufe it 
 cannot evacuate itfelf into the lungs ; and thus fwells up 
 the face with rednefs, fometimes burfts the veins of 
 the brain, neck, inteftines, kidneys, and laflly of the 
 lungs, and right auricle of the heart. This is thecaufe 
 of prodigious anxiety of mind ; this alfo is the caufe 
 of death in compreffed air, in drowned people, and 
 fuch as are firangled, which is much more fudden than 
 is commonly imagined. A living perfon therefore, 
 that he may remove thofe inconveniences v.'hich flow 
 from an obflrudlion of the paflage of the blood, flack- 
 ens the powers of infpiration, and excites thofe of ex- 
 fpiration, which free the breafl from an air too greatly 
 rarefied. 
 
 269. Thefe powers are, firfl, the elaflicity of the 
 ribs, which being drawn upwards out of their natural 
 fituation, as foon as the powers which elevated them 
 ceafe to ad, fpontaneoufly place themfelves fo as to 
 
 make 
 
126 RESPIRATION. Chap.IX. 
 
 make more acute angles with the fternum and verte- 
 brae. To this end conduces likewife the elaflic force 
 of the bronchia and veficles dillended with air, which 
 ftriveto contrad theinfelves. Hence exfpiration is per- 
 formed more eafily and quickly than infpiration ; and 
 hence it is the laft aftion of dying people. 
 
 270. To this alfo contribute the oblique mufcles of 
 the abdomen, together with the flraight and tranfverfe 
 ones. The former of thefe are, in one part of them, 
 faftened to the lower ribs ; and, in another part, they 
 are attached to the os pubis and ilium, as a fixed point 
 with refpect tothebreall. Therefore the ftraight mufcles, 
 being contracted, deprefs the arch or convexity into 
 which the abdominal vifcera are thrufl by the dia- 
 phragm, and bring the fame nearer to a ftraight line : 
 at the fame time, the abdominal vifcera are prefled 
 by thofe mufcles upward and backward againft the dia- 
 phragm, which alone is able to give way ; and yield 
 up into the thorax, which at that time is rendered 
 fliorter. The oblique mufcles, for the fame reafons, 
 comprefs the lateral parts of the abdomen, and urge 
 the liver and ftomach backwards, and prefs them to- 
 wards that place where there is the leaft refiftance. 
 Laftly, they draw down the ribs, which were before 
 elevated by the intercoftals. The tranfverfe mufcles, 
 indeed, do not draw down the ribs ; but they pull the 
 cartilages of the falfe ribs a little inward, and render 
 the whole capacity of the abdomen lefs, while at the 
 fame time they prefs the vifcera againft the diaphragm. 
 Along with thefe we may reckon the powers of the 
 fternocoftal and long intercoftal mufcles, which are 
 called depreffors. By this joint force the fuperior ribs 
 defcend; but the middle ones more, the uppermoft 
 lefs, the loweft moft of all ; and the fame are brought 
 inwards by their margin ; the cartilages afccnd, and 
 return into acute angles with the fternum ; and the 
 fternum itfelf returns backw^ards with the ribs. By 
 thefe means the thorax, contrary to its former ftate 
 (259.), is every where rendered narrower and {hotter. 
 
Chap.IX. respiration. 227 
 
 fo 9S to expel as much air out of the lungs as is fulE- 
 cient to relieve the uneafmefs caufed by its retention 
 (268.) 
 
 271. In more powerful refpirations, when the infpi- 
 rations are made greater, the exfpirations are likewife 
 increafed by the afliftance of fome other powers, as of 
 the facrolumbalis, longiflimus and quadratus raufcles 
 of the back and loins. This force, by which the air 
 is blown out of the lungs through a tube, is fufficient 
 to carry a leaden bullet, weighing above a dram, to 
 the diftance of 365 feet ; which force is equal to a third 
 part of the preffure of the atmofphere. Bat, in a 
 healthy perfon, the mufcles of the abdomen alone fuf- 
 fice to an eafy exfpiration, in which the lungs are not 
 fo much emptied of air as they are by a violent effla- 
 tion. 
 
 272. The effeds of exfpiration are a compreffure of 
 the blood-veffels in the lungs, a redudion of the bron- 
 chia into more acute angles, a preffure of the reticular 
 fmall veffels by the weight and contad of the adjacent 
 larger veffels, an expulfion of the corrupted blood from 
 the lungs; by which means part of the blood, hefita- 
 ting in the capillary arteries, is urged forward through 
 the veins to the left fide of the heart, while at the 
 fame time that part of the blood is refilled which 
 flows in by the artery from the right ventricle. Ex- 
 fpiration, therefore, will flop the eafy paffage of the 
 blood through the lungs ; and, when the whole thorax 
 is compreffed together, repels the venous blood into 
 the veins of the head, and fills the brain and its fi- 
 nufes. 
 
 273. In this manner a frelli neceffity follows for re- 
 peating the refpiration ; becaufe the collapfed veffels of 
 the lungs refill the blood repeatedly expelled from the 
 right ventricle of the heart. And this makes another 
 caufe of death, in thofe animals w'hich expire in veffels 
 cxhaulled of air: for, in fuch, the lungs having the air 
 drawn out from them, appear denfe, folid, and heavier 
 than water , whence they arc rendered impervious to 
 
128 
 
 RESPIRATION. Cha? . IX. 
 
 the blood. Of the fame kind is the death of thofe who 
 are killed by lightning, and perhaps by the noxious va- 
 pours of caverns. Thus, therefore, by the power of 
 a moft wife fabricature, the organs of cxfpiration are 
 relaxed fo foon as that uneafinefs is perceived which 
 arifes from the hindrance of the blood’s courfe thro’ 
 the lungs ; and thereupon the powers of infplration arc 
 excited into aftion, whereby the courfe of the blood 
 through the lungs is rendered free and quicker. 
 
 274. It is by fome queflioned, whether or no there 
 are not other caufes of alternate refpiration ? whether 
 or no we may hope for any difeovery in this matter, by 
 compreffing the vena fine pari, the phrenic nerve, or 
 intercepting the blood fent to the brain ? But thofe are 
 repugnant to comparative anatomy ; by which we al- 
 ways find the fame alternation in the breathing of the 
 animal, independent of any fuch nerve or vein. Whe- 
 ther or no refpiration is from the alternate contraction 
 of the antagonill mufcles, among which thofe of ex- 
 fpiration rela.x the others of infpiration, and the reverfe? 
 But in this manner, all the mufcles of the human body 
 are perpetually in an alternate motion. 
 
 275. From what has been hitherto faid, it appears, 
 that refpiration is unavoidably and abfolutely neceffary 
 to life in a healthy adult perfon ; becaufe, whether the 
 lungs remain long in a ftate either of exfpiration or in- 
 fpiration (273. 278.), we fee death will be the confe- 
 quence. Therefore no animal, that has lungs like our- 
 felves, after it has once breathed, and received the air 
 into the inmoft parts of the lungs, and by that means 
 brought a new and large quantity of blood to that vif- 
 cus, can fubfifl longer than a few minutes without the 
 ufe and benefit of a free air ; but it will either perifh, 
 or at lead fall into fuch a date as differs from death 
 only in its being recoverable again by certain powers or 
 aCfions. In an animal lately born, this necellity for air 
 does not take place fo fuddenly. 
 
 276. But the ufe of refpiration is different from this 
 neceffity j w'hich nature might have avoided, either by 
 
 - ufmg 
 
Chap. IX; RESPIRATION; 129 
 
 ufing no lungs at all, or elfe by difpofing them in a man- 
 ner refembling thofe of the fetus. This ufe, therefore, 
 of refpiration muff be very conhderable, fince all ani- 
 mals are either made with lungs, or with gills as in fifli, 
 or elfe with a windpipe difperfcd through all parts of 
 the body. 
 
 277. In order to difcover this ufefulnefs of refpira- 
 tion, let us compare the blood of an adult perfon to that 
 of a fetus, and alfo with the fame vital fluid in fifli. It 
 appears then in a fetus, that the blood is defliitute of 
 its florid rednefs and folid denfity ; and in the blood of 
 fifli, we obferve, there is neither heat nor denfity, and 
 but little craffamentuni contained in it| and, therefore, 
 all thefe properties, we are, by the nature of things, 
 perfuaded, the blood acquires in the lungs. 
 
 278. It may be afked therefore. Whether the blood 
 does not acquire its heat principally in the lungs? But 
 does not this arife from the alternate extenfion and con- 
 traftion, relaxation and compreflion, of the pulmonary 
 veflfels (265. and 272.), by which the folid parts of the 
 blood are perpetually rubbed together, and clofely com- 
 prefled and ground together? The lungs therefore wdlf 
 add to the office of the reft of the arteries, becaufe in 
 them the blood is alternately relaxed and comprefled 
 more than in any other part of the body. But even 
 when the lungs are obftrudted, ulcerated, and alnioft 
 deftroyed, a morbid heat feizes upon the body : but in 
 the lungs the cold air very nearly touches the blood. 
 
 279. The denfity of the blood is, indeed, again pro- 
 moted in the lungs, partly by the copious difcharge of 
 the watery vapour which is there feparated, by which 
 the reft of the mafs becomes fpecifically heavier. But 
 the fame efteft feems to follow here, as in other arte- 
 ries, namely, from the attrition and preffure which the 
 blood here fuffers in being alternately retarded, acce- 
 lerated, and figured in its courfe through the modula- 
 ting tubes of the leaft veffels, which give a fphericity 
 and denfity to the particles ; hence it becomes denfer, 
 as having more of the weighty globules, and lefs of the 
 
 S lighter 
 
130 RESPIRATION. Chap. IX. 
 
 lighter fluid. And, in this refpecl:, the pulmonary vein, 
 being fmaller than its correfponding artery, is ot no 
 fmall ufe towards increafing the attraftion of cohefion 
 betwixt the parts of the globules, fo as to comprefs and 
 bring them clofer to each other. Neveithelefs, cold a- 
 nimals, which have very fmall lungs, have denl'e and coa- 
 gulable biood ; as alfo a chicken before it is hatched. 
 The blood alfo has a fliort paflage through the lungs : 
 through the whole body the palTage is longer, and the 
 artery weaker; the heart, by which the blood is driven 
 forward, is alfo weaker. 
 
 280. It is, therefore, queried by fome. Whether the 
 air itf.lf is not received by the blood in the lungs, fo as 
 to excite neceffary vibrations therein ? Whether this does 
 nor appear from the refiftance of bodies to the heavy ex- 
 ternal air ; and from the air found in the blood-veflels, 
 in the cellular fubfrance, and in certain cavities of the 
 human body ; alfo, from thecraking obfervedbyan ex- 
 tenfion of the joints; to which add, the air manifcftly 
 extravafated from the windpipes into the hearts of 
 certain animals, as in the locuPc; from air coming out 
 of the blood and humours of animals in Mr Boyle’s va- 
 cuum; together with a neceiTity of a vital ofcillation in 
 the blood itfelf; and, laftly, the increafed rednefs of the 
 pulmonary blood ? 
 
 281. But that no elaflic air is here received into the 
 blood, is demonftrated from the iinpoffibility of forcing 
 air into blood, if it retains its eiaflicity ; from the inutili- 
 ty of its reception, if the fpi ing of it fhbuld be lofl in the 
 blood ; from the perfect immutability of the biood by 
 cold; from the nhnutenefs of the inhaling velfels, with 
 the mucus that perpetually lines the Tides of the veflcles 
 in the lungs : to which add, the nature of the elaflic air 
 itfelf, which is very unapt to pafs through capillary vef- 
 fels ; with a repulfion of it by water, that hinders it 
 from pafllng through paper, linen cloth, or fkins that 
 are wetted by water. Again, the air being driven into 
 the windpipe, never palfes to the heart; or whenever 
 it does, it is forced thither by fome great or unnatural 
 
 violence; 
 
Chap.IX. respiration. 131 
 
 violence : but the permanent air in the veffels and hu- 
 mours of the human body, from a ftate of inelalficity, 
 may become elaftic by putrefaftion, froft, or an exter- 
 nal vacuum. But fuch permanent unelaftic air is in- 
 t;orporated with all liquors ; and taken into our bodies 
 with the aliments, and with abforbed. vapours, mixing 
 flgwly and with fome difficulty. But there never were 
 any elaftic bubbles of air obferved in the blood of a li- 
 ving animal; and fuch air being inflated into the blood- 
 veffels of any living animal, kills it certainly and fpeedi- 
 ly. Nor is there any great certainty of the blood in the 
 pulmonary veins being of a brighter red colour. Laft- 
 ly, though air indeed is abforbed by moft of our hu- 
 mours, yet that abforption is performed flowly, and 
 takes up the fpace of feveral days after the former air 
 has been exhaufted by the pump. It then likewife lays 
 afide its elaftic nature ; nor is there any reafon produced 
 why the air ftiould either be more fpeedily abforbed by 
 the blood, or why it fhould retain its elafticity after it 
 is fo abforbed. 
 
 282. Whether or not the blood is cooled in the 
 lungs ; and whether or no this feems to be true from 
 the death of animals in air which is hot to fuch a de- 
 gree as equals the heat of the hotteft breezes in the 
 moft fultry dog-days ? Whether the pulmonary veins 
 are not, therefore, lefs than the arteries ; and whe- 
 ther the defire of cold in people that are working 
 hard does not arife from thence? That the blood is 
 cooled in the lungs, is thus far true, in that it there 
 warms the contiguous air, and therefore lofes fome- 
 thing of its own heat. But that this was not the prin- 
 cipal defign of nature here, upon the blood, is evi- 
 dent ; fince no one will fay, that the venous blood 
 is hotter than the arterial, although fome pronounce 
 the former to be fomewhat cooler; but nobody ever 
 obferved the left ventricle of the heart cooler than the 
 right. Since, therefore, the venous blood enters the 
 lungs; if it be there cold, it will follow, that the arte- 
 ries muft receive it ftill colder. But then here the de- 
 
 S 2 grees 
 
132 RESPIRATION. Chap. IS. 
 
 grees of heat, which the blood communicated to the 
 air, are again recovered by it. And, indeed, a perfon 
 may live in an air much hotter than the blood itfelf, of 
 which we have a familiar example in baths, and the 
 warm countries. The pulmonary artery in a fetus, 
 which does not refpire, is greater ; and the larger area 
 of the right auricle and ventricle of the heart is like- 
 wife much greater in a fetus ; which feems neceffary to 
 referve and retard the blood, as the pulmonary vein, 
 being narrower, accelerates it. 
 
 2B3. Whether or not is the rednefs of the blood 
 from the air ? This is contradided by what we fee in 
 cold animals, which, though they are almoll entirely de- 
 prived of the ufe of air, have blood equally red with 
 that of warm animals ; from the certain connexion of 
 rednefs in the blood of frogs with their having plenty of 
 food, and a palenefs of it with a want of food ; and from 
 the air, as we have juft now faid, being denied accefs to 
 the blood. Neverthelefs, rednefs is produced when the 
 air has accefs to the blood, by which means it is alfo 
 reftored after it has been loft ; and, on the other hand, 
 it is deftroyed by the denial of the accefs of air. Whe- 
 ther or not may not a more fubtle element from the air 
 penetrate the blood, and be the caufe of its colour, as 
 light is required for the colours of plants ? 
 
 285. Whether the ufe of the lungs is to abforb a 
 nitre from the air to the blood ? or whether the florid 
 colour, obfervable in the furface of a cake of blood, be 
 owing to the fame caufe, while the bottom part looks 
 of a dark and blackiih colour? and whether or not this 
 is a prefervative againft the putrefaftion of the animal? 
 remain as queftions with foine. That tliere is a kind 
 of volatile acid in the air is certain, fince that meeting 
 with a fuitable earth forms nitre; for a nitrous earth, 
 being exhaufted of its fait, and expofed again to the 
 air, becomes re-impregnated with more nitre. But 
 the fame univerfal acid, we know by certain experi- 
 ments, meeting v/ith a different fort of earth, forms a 
 vitriolic fait, or alum, or elfe fea-falt. For the caput 
 
 mor-r 
 
Chap.IX, respiration. 133 
 
 mortuum of fea*falt, which remains after the diftillation 
 of the fpirit, recovers fo much ftrength from the air, as 
 enables it to yield more fpirit by diftillation ; even in 
 fnow there is a cubical fait : but marcafite fweats out a 
 true vitriol ; and colcothar recovers again the acid fpi- 
 rit, which was drawn from it ; alfo fixed alkali, expofed 
 to the air, turns into a vitriolated tartar. This, there- 
 fore, cannot be the ufe of refpiration, becaufe thofe 
 falts abound in too fmall a quantity in the air for fuch 
 ufes; and air is fitteft for breathing when pure in high 
 mountains, where thofe falts are the leaft to be found ; 
 nor is there any nitrous fait as yet known to be found 
 in our blood. 
 
 286. If it be afkedjWhy tortoifes, frogs, lizards, fnails, 
 ear-wigs, and other infedls, live long without air? we 
 anfwer, That in them the lungs are given not fo much 
 for the preparation of the blood, which they receive 
 but in a very fmall quantity, as for the ufe of fvvimming 
 in the water: and from hence it is that their lungs are 
 immediately joined with the venia cava and aorta. But 
 infedts, we know, draw the air in, and exhale it again, 
 through points in the fkin. If it be alked, why all a- 
 nimals periffi in air that is confined or not renewed, 
 although the animal be fmall, fuch as little birds? we 
 anfwer, Becaufe the air, which has once entered the 
 lungs, and been fouled by watery vapours, is rendered 
 lefs elaftic, and unfit for refpiration, by alkaline vapours : 
 not becaufe it becomes lighter ; for the mercury falls 
 but little in air which has not been renewed, and which 
 has killed an animal. Hence it is that the animal fur- 
 vives longer in air that is more comprelTed than that 
 of the atmofphere ; for in that cafe there is a greater 
 proportion of the elaftic element, which takes up a 
 longer time to corrupt it. But, even in other cafes, 
 confined air is rendered deftruftive only by ffagnation, 
 and filling it with vapours. But the reafon why animals 
 fwell in an exhaufted veffel, is, from the extrication 
 and expanfion of the unelaftic air lodged in the blood 
 and other juices. 
 
 287. There 
 
134 RESPIRATION. Chap. IX. 
 
 287. There is a certain confent or proportion be- 
 tween the pulfe and refpi ration; fo that, according 
 to the common courfe of nature, there are three or 
 four pulfes counted to one refpiration. But if more 
 blood is fent to the heart in a given time, the num- 
 bers both of the pulfe and refpiration are increafed. 
 This is the reafon of the panting or fhort breathing in 
 a perfon that exercifes his body with any confiderable 
 motion ; whereby the venous blood is returned fafter 
 to the heart (142.) But if the blood meets with a 
 greater refilfance in the lungs, fo that it cannot pafs 
 frpely from the right into the left ventricle of the heart ; 
 then the refpiration is increafed, both in the number 
 and magnitude, to forward its courfe : and this is the 
 caufe of fighing, yawning, and wheezing; of which the 
 hrfl is a deep infpiration ; the fecond flow, and very 
 great ; and the third, a frequent and imperfeft one. 
 The number of refpirations, however, does not alwavs 
 increafe with the pulfe; of which we have an example 
 in thofe fevers where the lungs are not affeefed. 
 
 288. The mucus, which lines the fenfible mem- 
 branes of the air-veffels in the lungs, may become 
 troublefome both by its quantity and acrimony ; it has 
 been even known to caufe fulfocation in a dropfy of 
 the lungs. Therefore its quantity, adhefion, or acri- 
 mony, excites a cough ; namely, an irritation of the 
 refpirative fyftem, by alternate large infpirations, fuc- 
 ceeded by large and quick exfpirations, together with 
 fudden Ihocks of the abdominal mufcles ; by which the 
 mucus, and fometimes calculous matters, are expelled 
 from the lungs. 
 
 289. Laughter differs from coughing in its caufe, 
 which refides commonly in the mind, or at lead con- 
 fifts in a certain titillation of fome of the cutaneous 
 nerves ; and, moreover, becaufe it is made up of im- 
 perfedl quick exfpirations through the contracted glot- 
 tis, left the air fhould be totally evacuated from the 
 lungs. Hence laughter, in a moderate degree, con- 
 duces to health ; becaufe, in the time of one full in- 
 fpiration, 
 
Chap.IX. respiration. 155 
 
 fpiration, many fliort infpirations and exfplraticns hap* 
 pen, and thus the concuffion is greater. Hence its dan- 
 ger of Ifagnating the blood ; becaufe the exfpiration is 
 not full or entire, whereby the blood is admitted into 
 the pulmonary artery without being fufFered to pafs 
 through it. Weeping begins with a great infpiration, 
 after which follow Ihort alternate infpirations and ex- 
 fpirations ; and the fame is finiflied with a deep exfpira- 
 tion, that is immediately joined by a large infpiration : 
 hence it has nearly the fame good and bad effects ; and, 
 when moderate, it conduces to relieve the anguifli ari- 
 fing from grief. An hickup is a very great, fonorous, 
 and fudden infpiration. Sneezing confifts of one large 
 or deep infpiration, which is followed immediately with 
 a powerful and fudden exfpiration ; and the acrid mat- 
 ter is blown out by it in fome quantity from the no- 
 ftrils. 
 
 290. The additional or fecondary ufes of refpiration 
 are very many. It exhales, as an emunftory, parts re- 
 dundant, or even noxious, from the blood, which would 
 fuffocate if they remained in the air ; and the breath of 
 many people fhut up in a clofe place, impregnates the 
 air with a fuffocating quality. On the other hand, it 
 abforbs from the air a thin vapour, of which the ufe is 
 perhaps not fufficiently known. It is by this force that 
 the abdomen and all its vifeera are continually com- 
 preffed ; by virtue of this, the ftomach, inteflines, gall- 
 bladder, receptacle of the chyle, bladder of urine, intef- 
 tinum redtum, and the womb itfelf, difeharge their 
 contents ; by this adfion the aliments are principally 
 ground or diffolved, and the blood is urged through 
 the fluggifh veffels of the liver, fpieen, and mefentery. 
 It excites a kind of flux and reflux in the blood, fo that 
 it is alternately preffed back towards the extremities of 
 the veins, and a little after is propelled towards the 
 heart by an accelerated velocity, as into an empty fpace. 
 Moreover, infpiration ferves to convey odours with the 
 air to the organs of fmelling. Bv this, the air is mixed 
 with the aliments j which it conduces very much to 
 
 break 
 
136 VOICE AND SPEECH. Chap.XL 
 
 break and diffolve towards a perfect dlgeftion. But 
 even fucking, fo neceflary to the new-born infant, is 
 made by the ufe of refpiration, and forming a larger 
 • fpace in the mouth, in which the air is rarefied ; fo that, 
 by the greater preffure of the outward air, the milk is 
 driven into that part where it is lefs refified. Laftly, 
 the voice itfelf is owing to the air winch we breatlie ; 
 therefore it may not be inconvenient for us, in this 
 place, to defcribe it more particularly. 
 
 CHAP. XI. 
 
 Of the Voice and Speech. 
 
 291.^ I "^HE principal organ of the voice is the larynx ; 
 
 JL for, that being injured, the air palfes through 
 the windpipe without yielding any found. By the la- 
 rynx, we underhand an affeinblage of cartilages, joined 
 into a hollow machine, which receives the air from the 
 fauces, and tranfniits it into the windpipe, having its 
 parts connedted together by ligaments an(^ mufcular 
 fibres. Among thefe cartilages of the larger kind, 
 thofe called the annular and fcutiform are, in adults, 
 frequently changed into bone. The anterior and lar- 
 ger part of this larynx, which lies almoft immediately 
 next to the fkin, is compofed of two cartilages; one cal- 
 led tbyreoides, the other cricoides ; to which laft, the la- 
 teral parts of the larynx arc fo joined, that the portions 
 of the cricoide cartilage are always fo much larger as 
 they are higher feated. The back part of the larynx is 
 firfi; made up by the faid annular cartilage, after con- 
 nefted by the arytgenoide mufcles. The epiglottis is 
 loofely connedled above the larynx with the thyreoide 
 cartilage, in fuch a manner, that it may be able to rife 
 up and fhut down. The blood-veffels of this part are 
 from the upper thyreoids ; and the nerves, below, are 
 numerous from the recurrents ; as above, alfo, there 
 are nerves coming from the eighth pair varioufly inofcu- 
 
 lating i 
 
CuAP.Xt. VOICE AND SPEECH. 137 
 
 lating ; fome alfo from the intercoftal. The former of 
 thefe nerves is remarkably famous for its arifmg in the 
 thorax, and being afterwards inflefted round the aorta 
 and right fubclavian ; and for the origin which it gives 
 to fome of the nerves of the heart, as well as for the 
 experiment by which a ligature upon the recurrent is 
 found to deftroy the voice. 
 
 292. All thefe cartilages are connefted together by 
 various mufcles and ligaments, with a certain degree 
 of firmnefs, to the adjacent parts ; and yet fo that the 
 whole is eafily moveable together, as are alfo its feveral 
 parts upon each other. Particularly the fcuUform car- 
 tilage, or the thyroidea anterior, is compofed of two 
 plates, which are almofl; quadrangular, and inclined to 
 each other in an obtufe angle, which is foremofl. Up- 
 on thefe cartilaginous plates are fometimes found two 
 apertures, one on each fide for the blood-velfcls of the 
 larynx ; but are not very often to be obferved. The 
 upper proceffes of this cartilage, terminating without 
 any protuberance, are inclined upward and backward, 
 to their connexion with the horns of the os hyoidcs, 
 by flrong ligapients, fometimes mixed with bone. The 
 lower parts of thefe cartilages are fhorter, and adapted 
 almofl with a flat furface to thofe of the cricoide carti- 
 lage ; to which they are connected with a very firm ar- 
 ticulation, by a flrong and fhort cellular fubflance, u- 
 niting them on each fide. The middle parts before, 
 being perforated with flrong ligaments, are connected 
 by the infertion of them to the middle of the annular 
 cartilage ; and likewife by other ligaments above, de- 
 feending from the horn of the feutiform cartilage into 
 the upper part of the annular cartilage. 
 
 293. The croicoide cartilage is before thick, and 
 flrong: it is increafed backwards, in form of a ring un- 
 equally truncated or cut through ; and, in its middle part, 
 is divided into two cavities by a protuberant line. This 
 is firmer than the reft of the cartilages, and, in a manner, 
 the foundation of them : from this there are longitudi- 
 nal mufcular fibres and ligaments, which defeend into 
 
 T the 
 
138 VOICE AND SPEECH. Chap.XE 
 
 the windpipe (238.) The pharynx likewife is con- 
 nected to the furface of thefe cartilages by many muf- 
 cular plates, and receives the larynx as it were into its 
 bag. From this a (hort ligament comes in both Tides 
 to the arytasnoide cartilage. 
 
 294. The two arytaenoide cartilages are of a very 
 complex figure, fpontaneoufly dividing into two parts. 
 Of thefe the lower is larger ; and is connected by a 
 moveable junCture with the protuberant cricoide carti- 
 lage, by a bafis moderately hollow j and the fame fends 
 forth a procefs forwards, which feparates the glottis, and 
 fuflains the inferior part of the ventricle of the larynx. 
 They afeend upwards, of a triangular figure, with the 
 polterior angle hollow, the anterior convex, divided by 
 three furrows or fulci, and extenuated upwards, till 
 they are at laft finiflied or terminated by a pretty thick, 
 oval, cartilaginous head fixed on them. The lower part 
 of thefe cartilages is connected by numerous mufcular 
 fibres, partly tranfverfe, and partly oblique ; of which 
 the different directions are vifible enough, but the fepa- 
 ration of them impracticable. Thefe are called arytte- 
 noide mufcles. In the upper part, the arytaenoide car- 
 tilage departs from its companion or fellow cartilage, 
 leaving a cleft perpendicularly betwixt them, which has 
 been (not very properly) by fome called the glottis. 
 
 295. The arytaenoide cartilage is connected with the 
 thyreoideal by tranfverfe ligaments, fufficiently ftrong 
 and elaflic, but covered with the common mucous 
 membrane of the larynx, wdiich ligaments are inferted 
 into the flat angle of the thyreoid cartilage (292.) 
 Thefe ligaments may be drawn out or ftretched from 
 each other, by removing the contaCt of their arytae- 
 noide cartilages, and may be again conjoined together 
 by placing the cartilages one to another : and this is 
 the true glottis, which is continuous, but at a right 
 angle with the above-mentioned cleft (294.) 
 
 296. From the fame angle of the thyreoid cartilage, 
 under a notch, from a firm ligament, and an ereCl 
 flender ftalk, is extended an oval cartilage, in its fore- 
 part 
 
Chap.XI. voice and speech. 139 
 
 part convex, behind concave, and railed up in fuch a 
 manner, by its elafticity, as to project confiderably 
 behind the tongue ; but is fo flexible or inclinable down- 
 ward, whenever the root of the tongue is prelTed back- 
 ward, that, by its tranfverfe pofition, it fiiuts up all 
 paflTage into the larynx, and defends it in fuch a man- 
 ner, that whatever is contained betwixt this part, called 
 the epiglottis, and the arytsenoide cartilages, palfes over 
 downward into the pharynx. The epiglottis is con- 
 joined to the tongue by pale membranous fibres, and 
 to the os hyoides it is connedted by many membra- 
 nous expanfions. But as for mufcular fibres from the 
 thyreo-arytsenoidal and arytasnoidal mufcles, it has ei- 
 ther none at all, or elfe fuch as are too minute to have 
 any effect upon its elafticity. 
 
 297. By the fides of the ligaments of the glottis 
 (295.), there are two other upper and fofter liga- 
 ments, which go out parallel from the arytsenoide 
 cartilage to the fcutiform one, which ligaments are 
 fomewhat lefs tendinous and lefs claflic. Betwixt thefe 
 two ligaments, on each fide (295.), a peculiar ca- 
 vity or ventricle defcends, having the figure of a com- 
 preffed parabolic finus extended downward betwixt 
 the doable membrane of the larynx, opening con- 
 flantly with an elliptical mouth by the fide of the glot- 
 tis in the larynx. 
 
 298. Laftly, all the internal cavity of the larynx is 
 lined with the fame foft, fenfible, or irritable and mu- 
 cous membrane, as we before defcribed in the wind- 
 pipe (239.) But this membrane is watered by a great 
 number of fmall glands. The uppermofl are fmall 
 fimple glands, affembled together in a heap (208.), 
 feated on the anterior and convex part- of the epiglottis, 
 upon the hollow furface of which they fend out various 
 openings, large finufes, and produftions ; and others 
 are, in like manner, continued there in fmall hard 
 kernels. Moreover, upon the hollow anterior furface 
 and back of the arytsenoide cartilages (294.), there are 
 fmall glandules placed on each fide of a loofe conglo- 
 
 T ? merate 
 
140 VOICE AND SPEECH. Chap. X. 
 
 merate fabric, compofed of little round kernels, doubt- 
 lefs muciferous, having fome of their loofer parts ex- 
 tended on each fide as low as the annular cartilage. In 
 the cavity of the ventricles, there are very many mu- 
 cous finufes. Laftly, all the internal furface of the la- 
 rynx is full of large mucous pores. All thefe glan- 
 dules feparate a thin watery mucus, which yet has a 
 confiderable degree of vifcidity. 
 
 299. It may be afked, If the thyreoide glandule has 
 a like ufe, and is of the conglomerate kind, but 
 foft and lobular, with many coverings, confiderably 
 large or broad in its extent, but of a more tender fub- 
 flance than the falival glands, feated upon the thy- 
 reoide cartilage, and in part upon the cricoide carti- 
 lage and windpipe, along their fore-part, fo as to in- 
 compafs the lateral horns and Tides of the thyreoides, 
 joined to its companion, which is narrower, by an 
 ifthmus, which is emarginated on the lower part, but 
 afcending upwards by a very thin procefs before, in its 
 middle part, as far as the os hyoides ? This gland is 
 full of a fcrous, yellowifii, and fomewhat vifcid hu- 
 mour : but whether it emits the fame into the wind- 
 pipe or into the cefophagus, is a queftion ; at lead; 
 there are no dufts certainly known to open into either 
 of them. Whether or not the juices are altogether re- 
 tained in this gland, and afterwards poured into the 
 veins in a manner refembling the fabric of the thy- 
 mus, or whether it is of the conglobate kind, is uncer- 
 tain. Yet that the ufe of this gland is very confider- 
 able, may appear from the largenefs of the arteries 
 ■which it receives from the carotids and lower fubcla- 
 vians. The veins thereof return their blood into the 
 jugulars and fubclavians. It has a peculiar mufcle, 
 not conftantly to be found, arifing from the edge of 
 the os hyoides, and fometimes from the lower margin 
 to the left of the thyreoide cartilage, which defcends 
 without a fellow, fpreading its tendinous fibres over 
 the gland. Upon which alfo the llernohyoidei and 
 
 flerno- 
 
Chap. XI. VOICE and SPEECH. 
 
 fternothyreodei mufcles are likewife fpread or incum- 
 bent, 
 
 300. The whole larynx is fufpended from the os hy- 
 oides by the ligaments proceeding towards the fuperior 
 horns of the thyreoide cartilage, and perfefting that car- 
 tilage from the middle of its bafis to the conjunction of 
 its plates. The fame, together with the conjoined os 
 hyoides, is capable of being raifed confiderably, at leaft 
 half an inch above its mean altitude. This is performed 
 by the biventer mufcles, together with the geniohyoidei, 
 geniogloffi, ftylogloffi, ftylohyoidei, flylopharyngei, thy- 
 reopalatini, hyothyreoidei ; all or fome of which con- 
 fpire together in that a6tion. In this elevation the glot- 
 tis is prelfed together or made narrower, and the liga- 
 ments beforementioned (295.) approach nearer toge- 
 ther. But thus, by the affiflance of the adlion of the 
 arytaenoide mufcles, together with the oblique and tranf- 
 verfe ones, the glottis may be accurately clofcd, fo as 
 refill with an incredible force the prelTure of the whole 
 atmofphere. 
 
 301. The fame larynx may be, in like manner, de- 
 prelfed to about half an inch beneath its ordinary fitua- 
 tion, by the flernohyoidei, llernothyreoidei, and cora- 
 cohyoidei, as they are called; and, when thefe are in 
 a£tion, alfo by the joint force of the anterior and polle- 
 rior cricothyreoidei. In this motion the arytaenoide car- 
 tilages depart from each other, and render the glottis 
 wider, which is alfo drawn open laterally by the muf- 
 cles inferted into the Tides of the arytaenoide cartilages, 
 together with the crico-arytaenoidei poftici and laterales, 
 and thyreo-arytaenoidei : thefe may alfo compreTs the 
 ventricles of the larynx (297.) on which they are incum- 
 bent; the particular cartilages which make up the la- 
 rynx can fcarce be moved feparately. 
 
 302. From the larynx the air comes into the mouth 
 and noflrils. By the mouth, we mean that large and 
 irregularly lhaped cavity between the foft and hard pa- 
 late, both concave in the middle, and lower down parted 
 between the mufcles which lie under, and the lower 
 
 jaw. 
 
142 VOICE AND SPEECH. Chap. XL 
 
 jaw. The noltrils afcend forv/ards above the foft pa- 
 late; they are two broad cavities intercepted between 
 the feptum medium, the offa cavernofa, and various o- 
 ther bones. They are every where bony and cartilagi- 
 nous. 
 
 303. The tongue lies in the middle of the mouth; 
 and is a broad piece of flelli eafily changeable into any 
 kind of figure, and thus readily moved without delay to 
 every part of the mouth; molt expeditioufly directed 
 into every fituation, and made to affume any fhape, by 
 its own flefhy fibres, and by the mufcles attached either 
 to itfelf or to the os hyoides w'hich is joined to it by 
 many flefiiy fibres and membranes. In the fore-part 
 thefe come from the genioglofii and geniohyoidei muf- 
 cles ; backwards from the ft) loglofii, ftylohyoidei, cera- 
 togloffi, bafioglofii, chondroglofii, and biventer; down- 
 wards, from the llernohyoidei and ceratohyoidei ; up- 
 wards, from the ftyloglofil, ftylohyoidei, from the bi- 
 venters, and likewife from the mylohycidei. 
 
 304. Hitherto we have given the anatomy. It re- 
 mains, therefore, that w’C demonftrate what action the 
 air produces wdien it is driven by the forefaid powers 
 (269, 270.) from the lungs in exfpiration through the 
 windpipe into the larynx, and from them urged out 
 through the glottis into the mouth varioufty configured. 
 The confequences or effedls of this are, voice, fpeech, 
 and finging. The voice, indeed, is only formed, when 
 the air is expelled with fo great a velocity through the 
 contrafted glottis, that it fplits or makes a coHifion up- 
 on the glottid ligaments, fo as to put the larynx into a 
 tremor, which tremor is returned and continued or in- 
 creafed by the elafticitv of thefe parts. Sound, there- 
 fore, arifes from the conjunct trembling of the liga- 
 ments (295-) together with the cartilages of the larynx 
 at one and the fame time, which we then call the voice, 
 and is of a peculiar kind or modulation in every fingle 
 clafs of animals, depending entirely upon the difference 
 of the larynx and glottis. But when a trembling is not 
 excited, the exfpired air caufes a whifper. 
 
 305. The 
 
Chap. XL VOICE and SPEECH. 143 
 
 305. The ftrength of the voice is proportionable to 
 the quantity of air blown out, together with the narrow- 
 nefs of the glottis; and, therefore, a large pair of lungs 
 eafily dilatable, with an ample cartilaginous and elaflic 
 larynx and windpipe, and the free echo of the nollrils, 
 joined with a powerful exfpiration, all conduce to this 
 cffeft. But acute and grave tones of the voice, we ob- 
 ferve to arife from various caufes. The former proceeds 
 from a tenfion and narrownefs of the glottis, and the 
 latter from a relaxation and expanfion of it. For thus, 
 in the former, a greater number of air-waves are fplin 
 in the fame time upon the ligaments of the glottis, 
 whence the tremors excited at the fame time are more 
 numerous; 'but when the glottis is dilated, the con- 
 trary of all this follows. And from the greater tenfion 
 of the ligaments, the tremors in like manner become 
 more numerous from the fame llroke. Therefore, to 
 produce an acu*«: and Ihrill voice, the whole larynx is 
 drawn upwards and forwards ; and fo much the more 
 as the voice is required to be fharper, infomuch that the 
 head itfelf is inclined backwards, by which the powers 
 of the mufcles elevating the larynx are rendered more 
 full and effeftual. The truth of this is confirmed by 
 experience, by applying the fingers to the larynx when 
 it forms an acute found; for then, to raife the voice an 
 oftave, you will eafily perceive it to afeend near half an 
 inch. Alfo the fame is evident from comparative ana- 
 tomy, which demonftrates the narrowed glottis and the 
 clofefl; approximation of cartilages in finging birds, but 
 an ample or broad glottis in hoarfe animals and fuch as 
 bellow or bleat. An inftance of this we have in whiff- 
 ling, where the voice manifeffly becomes more acute 
 by a contradlion or narrownefs at the mouth : alfo in 
 mufical inftruments, in which a narrowmefs of the 
 mouth or opening that expels the air, with a celerity of 
 the wind blown out, are the caufes of an acute or fhrill 
 tone. 
 
 306. Gravity of the voice, on the contrary, follows 
 from a depreffion of the larynx by the caufes (301.) al- 
 ready 
 
144 VOICE AND SPEECH. Chap. XI. 
 
 ready defcribed ; to which add a broad glottis and a 
 very ample larynx. This is evident to the touch of the 
 finger applied to the larynx when a perfon lings, by 
 which the defcent of it is inanifeftly perceived to be a- 
 bout an inch for every oftave ; hence the voice of 
 males is more grave; and hence the loweft degrees of 
 the voice degenerate into a mutenefs or whifpering. 
 
 307. Is the whole difference of tone owing to the 
 length of the ligaments of the glottis, which is aug- 
 mented when the feutiform cartilage is drawn forward, 
 and the arytsnoide ones backward ? Is it according to 
 this rule, that the moll acute tones are produced, which 
 arife from the ligaments being exceedingly ftretched, 
 and thus vibrating with great celerity ? This has been 
 confirmed by repeated experiments made by eminent 
 men ; and fome late anatomifts 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 larynx: that this voice was more 
 acute as the ligaments were more tenfe, and more 
 grave as they were llackened : that by fhutting the 
 whole ligament, the voice was fuppreffed ; by lliutting 
 the half, the voice was rendered an o£tave higher ; by 
 Ihutting a third part, a fifth higher, &c. There are not 
 wanting, however, doubts concerning this new theory, 
 arifmg from the cartilaginous and bony firuefure of the 
 glottis of birds, which of confequence mult be im- 
 moveable, and not extenfible ; from the voice moll cer- 
 tainly becoming more acute, in whittling, from the mere 
 contraftion of the lips ; from the example of women, 
 in which the larynx is fofter, but the voice more acute, 
 than in men ; from experiments which Ihow, that more 
 acute founds are produced by bringing the ligaments 
 of the glottis nearer into contact with each other; from 
 the perfect want of machines, by w'hich the ligaments 
 can be Itretched, and which may bring the feutiform 
 cartilage forward from the annular one. But feeing it 
 appears from experiments, that a tenfion of the liga- 
 ments fuffices for producing acute founds, without the 
 
 con- 
 
Chap.X. voice and speech. ,145 
 
 contraftion of the glottis, we may believe that the dif- 
 ferent tenfion of the glottis contributes more to the di- 
 verfity of voice than the different diameter of it. 
 
 308. Singing is when the voice, modulated through 
 various degrees of acutencfs and gravity, is expelled 
 through the larynx, while it is trembling and fufpeuded 
 betwixt two contrary powers ; and herein lies the prin- 
 cipal difference betwixt the chanting of fimple notes, 
 and the expreffion of words. Hence it appears to be a 
 laborious aftion, by reafon of the continual contrac- 
 tions of the mufcles, which keep the larynx at an equi- 
 librium; and hence it is, that finging makes a perfon 
 hot ; becaufe in acute tones the narrow^er glottis much 
 retards the exfpiration, while at the fame time a great 
 deal of air is required to give ftrength to the voice 
 (305.); towards which, again, deep infpirations arene- 
 ceffary. Hence likewife the windpipe is rendered very 
 dry,fiom the quicker paffage or current of air: to pre- 
 vent w'hich, a great deal of mucus is required ; and 
 therefore it is that there are fuch numbers of mucous 
 receptacles in the larynx, amongft which I am firmly 
 of opinion the ventricles before defcribed (297.) ought 
 to be numbered. 
 
 309. Speech is performed by the larynx at refl, or 
 held in the fame place, in tones of voice differing but 
 little in acutenefs and gravity ; but then the voice is 
 varioufly changed or modulated by the organs of the 
 mouth. Canorous fpeech has a variation in the tone or 
 cadence of the voice, together with a modulation of it 
 by the organs of the mouth at the fame time. 
 
 310. All fpeech is reducible to the pronunciation of 
 letters, which differ in various nations ; but mofl of 
 them are alike all the world over. Of thefe, fome are 
 called vowels, which are made only by an expreffion of 
 the voice through the mouth, without any application 
 of the tongue to certain parts of the mouth. But con- 
 fonants are formed by a coHifion of the tongue againfl 
 certain parts of the mouth, lips, and teeth. But to be 
 more particular in thd’e matters is befide our purpofe, 
 
 U which 
 
14<» BRAIN AND NERVES. Chap. XI. 
 
 which will not permit us to expatiate upon the beautiful 
 art of pronunciation. That art, as an extraordinary in- 
 ftance of mechanical knowledge, has fo accurately de- 
 termined all the corporeal caufes concurring to each 
 letter, that, by infpeflion only, with the affidance of 
 touch, letters pronounced are underflood without hear- 
 ing them, and the attentive perfon is thereby taught to 
 imitate the fame fpeech by a like ufe of the organs. 
 
 CHAP. XI. 
 
 Of the Brain and Nerves. 
 
 gii.np'HE remaining adions of the human body 
 X we fhall confider according to the order by 
 which they receive the blood. The coronary arteries 
 we fpoke of before, when we gave the hiflory of the 
 heart. Next to thofe, the carotids pafs out from the 
 aorta. 
 
 312. The aorta, which comes out from the anterior 
 part of the heart (i57.)5 in order to bend itfelf tow'ards 
 the vertebrae of the thorax, forms there a confiderable 
 arch, by which it is bent backward, and towards the 
 left, in an angle that is round, but not very large. 
 From the convexity of this arch, three confiderable 
 branches arife. The firfl afeends tow'ards the right 
 fide, and is immediately fnbdivided into tw'o large ar- 
 teries, of which the lowermoft goes on in the diredion 
 of its trunk, under the denomination of the Jubclarc'ian. 
 The other afeends according to the courfe of the wind- 
 pipe to the head, and is called the right carotid. The 
 left carotid fprings next from the fame arch, a little in- 
 clined to the left fide ; and the third, w'hich is flill more 
 inclined to that fide, is called the left fubclavian, which 
 is fomething lefs than the right. About the origina- 
 tion of thefe arteries, the next continuous margin of the 
 aorta is a little thicker and more protuberant. But va- 
 riations fronithis courfe are rarely obferved. 
 
 313. The 
 
Chap. XI. BRAIN and NERVES. 147 
 
 513. The carotid artery, furrounded with a great 
 deal of denfe cellulofity, together with the jugular vein 
 and nerve of the eighth pair, commonly afcends as 
 high as the upper part of the thyreoide cartilage, with- 
 out fending off any branches. There it divides into 
 two trunks. The anterior, called the carotid, 
 
 which is rather larger and more in the diredfion of its 
 trunk, fends off a branch called the fuperior thyreoidea, 
 alfo the infledled arteria lingualis, and then the labialis; 
 and from the poflerior face of the carotid, the next ar- 
 tery which arifes is the pharyngea afcendens, which, 
 befides the pharynx and mufcles of the moveable palate, 
 fends likewife a confiderable branch in common with 
 the nerve of the eighth pair through the foramen of the 
 jugular vein to the dura mater, very near to the great 
 foramen of the occiput, at the bafis of the os petrofum, 
 and which is divided at the cuneiform procefs of the 
 multiform bone. 
 
 314. Again, from the edge of the external carotid, 
 fprings the occipital artery ; which fends branches not 
 only to the mufcles which give it a name, but like- 
 wife fends a branch through a peculiar foramen of the 
 dura mater in the angle which the os petrofum forms 
 by departing from the mamillary procefs, which artery 
 is fpread through the feat of the cerebellum ; another 
 branch palfes over the atlas to the dura mater under or 
 into the Ikull ; and a third fometimes goes through the 
 foffajugularis to the dura mater. The next artery, which 
 is the auricularis, goes to the back part of the ear, to 
 the temple, and to the membrane of the tympanum. 
 
 315. What remains of the external carotid artery, 
 afcends through the parotid gland, to which having 
 given fome branches, as well as to the face and eye*lids, 
 it fends out the temporalis, which is confiderable. The 
 trunk of the carotid, being inclined, conceals itfelf be- 
 hind the lower jaw, under the denomination of maxiU 
 laris interna. 
 
 316. In that place, it direftly fends off a large trunk, 
 which pafles to the dura mater through a peculiar open- 
 
 TJ 2 ing 
 
245 BRAIN AND NERVES. Chap. XT. 
 
 ing of the broad and pterygoide wings, feated at the 
 middle fofla of the brain ; from whence they are large- 
 ly fpread through the temple’s and forehead within the 
 dura mater, as far as the falciform finus. Sometimes 
 this artery is double, and often gives out a branch 
 that is confpicuous to the lachrymal gland of the eye. 
 In the fame place, likewife, the maxillary artery enters 
 the upper part of the nares, by a threefold trunk, where 
 it is fpent, after having given off the branches call- 
 ed maxi Hares inferior and fuperior to the teeth, with 
 the infra orbitalis to part of the face and eye-lids, and 
 the palatina to the bone of the palate, with fmall 
 branches to the dura mater, and others through the 
 fmaller pores of the great wings, with fuch as accom- 
 pany the third and fecond branch of the fifth pair of 
 nerves ; and laftly, together with the dura mater, hiling 
 up the lower orbital fiffure. 
 
 316. But the other pofterior trunk, commonly cal- 
 led the internal carotid (31 3-)» ^feends without a branch. 
 This artery, having firft made a confiderable ferpentine 
 flexure, enters through a peculiar foramen in the os 
 petrofum, where it is furrounded with a capfule from 
 the dura mater, like that which comes out through all 
 the openings of the fkull : from thence it afeends up- 
 wards and inclined forwards, till, having penetrated in- 
 to the cavity of the fkull, it rifes up inflected and in a 
 curvature, according to the dlreftion of the fella equi- 
 na, in the middle of which there is a cavernous or hol- 
 low finus retarding the blood : from thence, having 
 given fmall branches to the fifth pair of nerves, it fends 
 others to the infundibulum and dura mater, with one 
 larger to the eye ; part whereof returns again through 
 a peculiar hole into the dura mater, which lies upon 
 the middle of the orbit. This is the rete inirabilc of 
 beafts, but not of man. 
 
 317. But the trunk of this internal carotid palTes o- 
 ver the anterior part of the fella equina ; and being in- 
 curvated backward, and received by the arachnoide 
 membrane, giving branches to the pons and crura of the 
 
 brain, 
 
Chap. XL BRAIN and NERVES. 149 
 
 brain, with a circle to the choroide plexus, and one tha^ 
 accompanies the optic nerve, it then divides into an an- 
 terior and pofterior branch. The former, being con- 
 joined with its fellow artery of the other fade by a 
 diort inofculating branch, which foraetimes fprings 
 from the trunk itfelf, is then incurvated backward and 
 upward, according to the diredtion of the os cailofum, 
 and fpreads itfelf about the middle and hinder part of 
 the brain ; where it fometimes fends branches to the 
 falciform procefs, and from the very origin of the third 
 ventricle to the fornix and thalami. Tlie latter, being 
 conjoined by a fmall inofculating branch with the ver- 
 tebral artery, unit Is that arifes from the undivided trunk 
 of the carotid artery, afterwards afcends a long way up- 
 on the fide of the brain through the Sylvian fofl'a ; and 
 the fame fends branches to the choroide plexus. All 
 the branches of the carotid, contained witfiin the fkull, 
 are made up of more thin, folid, and britde membranes, 
 than the other arteries of the body. 
 
 31 8. But the vertebral artery^ commonly ai'ifing from 
 the fubclavian of the fame fide, (though the left has 
 been fometimes feen to fpring from the trunk of the 
 aorta,) palfes on without giving branches, through a 
 place of fecurity, till it enters a foramen in the tranf- 
 verfe procefs of the fixth vertebra of the neck; after 
 which, it continues with alternate flexures to afcend 
 through the oblique proceffes of the other vertebrae of 
 the neck ; from whence, at each interval, it fends off 
 fmaller branches to the mufcles of the neck, and com- 
 municates with the lower thyreoideal : other branches, 
 again, -fomewhat larger, go from it backward, together 
 with each of the nerves, to the pia mater of the fpinal 
 medulla; but before, the branches are larger, though 
 lefs numerous, to the fame fpinal medulla, and commu- 
 nicate by an anaffomofis with its fpinal artery anterior- 
 ly. Laflly, growing lefs about the fecond vertebra, and 
 being inflecfed with a large curvature round the tranf- 
 verfc procefs of the firft vertebra, it there fends off con- 
 fiderable branches to two of the mufcles of the neck : 
 
 alfo 
 
150 BRAIN AND NERVES. Chap. XI, 
 
 alfo fmall branches it fends off in its courfe through the 
 great foramen of the occiput or ikull to the dura mater, 
 and the adjacent cavities that contain the cerebellum j 
 after which, it goes on through the faid foramen into 
 the cavity of the fkull. There afeending, according to 
 the courfe of the medulla oblongata, the right trunk by 
 degrees approaches nearer to the left, and is conjoined 
 together with it (in an extraordinary manner, hardly to 
 be found in other parts) into an artery called the baftli- 
 aris, which is fufpended in the pia mater all along under 
 the pons Varolii. From the vertebral arteries, before 
 they are conjoined together, or from the trunk produ- 
 ced after the common manner, pafs out branches, which 
 go to the lower furface of the cerebellum, and are deep- 
 ly inferted under the fourth ventricle to the inner fub- 
 flance of the cerebellum. Thefe fend off the fpinal ar- 
 teries. But there are fome inftances where they arife 
 conjunclly from a fingle trunk ; or from the trunk in 
 one fide, and a branch in the other. Then the bafifia- 
 ris, befides branches to the medulla oblongata and 
 crura of the brain, gives the other lower arteries of 
 the cerebellum. Amongfl the forefaid branches alfo 
 arifes an artery, which accompanies the auditory nerve. 
 Finally, the bafiliaris, at the forepart of the pons, di- 
 vides into two branches. One of thefe goes to the up- 
 per part of the cerebellum, to the fourth ventricle, to 
 the crura of the medulla of the cerebellum, the nates, 
 teffes, and pineal gland ; in place of this, alfo, there are 
 two trunks. The other is divided to the lowelt part of 
 the brain at its poflerior lobe, the choroide plexus, the 
 plexus incumbent on the pineal gland, that gland itfelf, 
 the thalami, corpora ftriata, fornix, and whole anterior 
 ventricle of the brain. 
 
 1519. From the foregoing hiftory of the arteries be- 
 longing to the brain, it appears, that a very great quan- 
 tity of blood is in every pulfation lent to this organ, in- 
 fomuch that it makes above a fixth part of the whole 
 blood that goes throughout the body, and derived from 
 trunks that are very near the heart, fpringing from the 
 
 con- 
 
Chap.XI. brain and NERVES. 151 
 
 convexity of the aorta. From hence it is probable, that 
 the ftrongefl parts of the blood go to the head, and 
 fuch as are mod retentive of inotion. Is not this evi- 
 dent from the effefts of mercurials exerting thenifelves 
 almoft in the head only ; from thefuddcn force and aflion 
 of inebriating fpirits upon the head ; from the ll';<?^t Ru- 
 por which camphor excites ; from the heat, rednefs, 
 and fvveat, which happen oftener in the face than other 
 parts of the body ; to which add, the more eafy erup- 
 ruption of volatile and contagious puflules in the face? 
 The well guarded paffage of thefe great and important 
 veffels, in their afcent to the head, defends them from 
 any great injury. The frequent inofculations of one 
 trunk, with the other going to the head, as well as the 
 frequent communications of their branches among 
 themfelves, leflcn any danger that might enfue from ob- 
 ftrudfion. Hence, when the carotids are tied, the ani- 
 mal neither dies, nor feems to be very uneafy. The 
 confiderable flexures of the vertebral and carotid artery 
 ferve to moderate the impulfe of the blood coming to 
 the brain, fmce a great part of the velocity, which it re- 
 ceives from the heart, is thus fpent in changing the fi- 
 gure of the inflexions. To which add, that fome au- 
 thors do not improperly obferve that the arteries here 
 grow larger or lomewhat wider. 
 
 320. The hiftory of the brain defervedly begins from 
 its integuments. Such a tender part, fo neceflary to life, 
 we obferve providently furrounded on all fides, firft by 
 a fphere of bones, confifting of many diftinX portions; 
 by which means it is rendered extenfible, at the fame 
 time that it is effeXually guarded againft external pref- 
 fure. To the internal furface of this bony fphere, on 
 all fides, grows a very ftrong membrane, compofed of 
 two plates fufficiently diftinX, which are firmly attached 
 by an infinite number of fmall veflels, as by fo many 
 foot-ftalks,to the whole furface of the faid bones, fo as 
 to be nowhere eafily feparable in a healthy perfon ; 
 thefe, being very thin and fmooth, adhere lefs firmly to 
 the bones, but more ftrongly to the futures, fo called 
 
 from 
 
152 BPvAlN AND NERVES. Chap. XI. 
 
 from their figure, which join the bones of the (kull one 
 to another. In younger fubjeds, the adhcfion of the 
 dura mater to the {ku!l is fuch, that the reparation of 
 it pulls off the fibres of the bones to which it is con- 
 neded. In adults, many of the veffels which it inferts, 
 being effaced, renders it more eafily feparable : yet it 
 is not without fome force, even in thofe, that the dura 
 mater can be feparated from the Ikull. From the rup- 
 ture of thefe vefleis, which enter the bones of the fkull, 
 appear thofe bloody drops which are obfervable after 
 removing the cranium. Hence appears the vanity of 
 all that has been advanced concerning the motion of 
 the dura mater. As to the motion which is remarked 
 by the writers of obfervations upon wounds in this part; 
 that, being preternatural, was the confequence of the 
 beating of the arteries, (in a part where the refiftance 
 of the bone was now removed, while the reft of the dura 
 mater next to the fivull fuftained the force of the heart 
 without motion ;) or of the brain fwelling during exfpira- 
 tion. Alfo that part, which is properly the dura mater, 
 has neither nerves, nor fenfation or irritability. 
 
 '321. The of the dura mater, which ad- 
 
 heres to the bones of the fkull, is to them inftead 
 of a periofteum, and fupplied with finail nerves and 
 blood-veflcls coming through all the holes of the 
 Ikull ; from whence, and from its cohefion with the 
 perioftia of the head, fpine, and whole body, it has 
 received the name mater. The internal plate of the 
 dura mater is, in molt parts, continuous with the for- 
 mer; but, in fome fubjefts, it recedes a little from it, as 
 in the great fphenoidal wings; and at the Tides of the 
 fella equina, where a good deal of blood is poured be- 
 twixt them ; and they likewife recede thus upon the 
 fella equina itfelf ; the fame plate, having left the outer- 
 moft, adhering firmly to the bones of the fkull, de- 
 feends doubled together to form the falx, which arifes 
 firft frexn behind the procefles criftas-galli of the multi- 
 form bone, afterwards from the crifta itfelf, and from 
 the whole junctures of the bones of the forehead and 
 
 the 
 
Chap. XL BRAIN ahd NERVES. I53 
 
 the parietals ; and laftly, it arifcs from the middle of the- 
 back part of the occipital bone, and, growing broader 
 backwards, is interpofed betwixt the hemifpheres of the 
 brain ; the more remote part of it forward hangs over 
 the corpus cailofum, and that which is next in the back- 
 part is extenuated to an edge in the fame place. That 
 there are fliining fibres in this part, difperfed towards 
 the longitudinal finus from the conjunction of the ten- 
 torium, in the (liape of branches and palm-twigs, is cer- 
 tain ; but it does not therefore follow, that they have 
 any mufcular motion ; and betwixt thefe fibres frequent- 
 ly, there is no membrane, only natural foramina are in- 
 terpofed. The falx is both joined to, and continued 
 from, the middle tentorium, which is extended laterally. 
 In the fame manner, with fome difference of fituation, 
 the faid falx fends out a fliort plate downward, which 
 divides the cerebellum, together with the ft rong tento- 
 ria or lateral produdtions, which, irifing from the cru- 
 ciform protuberance of the occiput, are interpofed tranf- 
 verfely betwixt the brain and cerebellum, extended as 
 far as the limits of the os petrofum, and connected to 
 the anterior clinoide proceffes, leaving an oval aperture 
 for the medulla oblongata to defeend freely. Thefe 
 produftions of the dura mater ferve to prevent the parts 
 of the brain from preffing one another, in all fituations 
 and poftures of the bodyj and they likewife hinder one 
 part of the brain from bruifing the other, by any ftiock 
 or concuflion. Hence it is, that in the more adtive 
 quadrupeds, where a concuffion is more likely to hap- 
 en, the brain and cerebellum are divided by a bony 
 ,^artition. 
 
 322. In the external furface of the pia mater, not 
 far from the finus of the falx, are placed fmall glandules, 
 feated in the reticular texture of the hard membrane, 
 partly looking towards the finus, to whofe cavity they 
 are oppofed, in fuch a manner, that fome of them are 
 contiguous to the hollow of the finus ; others arc fo pla- 
 ced at the infertion of the larger veins into the pia ma- 
 ter, that, together with the former, they make up a 
 
 X con- 
 
154 BRAIN AND NERVES. Chap. XI. 
 
 continued range or fcrics ; fome are alfo obferved in 
 the tentorium of the cerebellum, which are fometimcs 
 foft, oval, and white, fometimes red, hard, and in ap- 
 pearance like wrinkles. But the vapour, which exhales 
 from the furface of the pia mater, is not feparated by 
 thefe glands : for it is every where exhaled, even into 
 the ventricles, where there are none of thofe glandules ; 
 and it plentifully tranfpires every where from the 
 mouths of the leaft arteries, as we fee, by experience, 
 when water or fifli-glue are injeOied, which fweat out 
 through every point in the furface of the dura mater. 
 
 323. The next covering of the brain, which is more 
 clofe to it, and prefles the whole furface of the brain, 
 as that does the cavity of the fkull, has been denomi- 
 nated from its tenuity, arachmides, i. e. like a I'pider’s 
 web. This very thin or tender membrane, being pel- 
 lucid like water, every way furrounds the brain, whofe 
 inequalities it climbs over, and according to its ex- 
 treme thinnefs is pretty ftrong, and furrounds the lar- 
 ger veffels in fuch a manner that the faid veffels feem 
 to run betwixt the pia mater and arachnoides ; which 
 laft is, therefore, no part or lamella of the pia mater, 
 from which it differs by fituation, and is connected to 
 it by a cellular texture after the manner of the fpinal 
 marrow, although it is refolved into a cellular nature 
 between the hemifpheres of the brain. 
 
 324. The third or innermoft covering of the brain, 
 which is foft and cellular, is properly the pia mater. 
 This immediately invefts the whole furface of the brain 
 and fpinal marrow on all Tides, is tender, and made up 
 of a vaft number of fmall veffels which are joined toge- 
 ther by a cellular texture; but thefe veffels it fends into 
 the brain in a regular order, like little roots. This de- 
 fcends betwixt every furrow and fiffu*^ of the brain and 
 cerebellum, and even infmuates itfelf into the fpinal 
 medulla, and is the bond by which the little protube- 
 rances of the brain are joined together. This, being re- 
 ceived into the cavities of the brain, changes its fabric, 
 fo as to become foft and almoft of a medullary confift- 
 
 ence, 
 
 i 
 
Chap. XI. BRAIN and NERVES. 555 
 
 ence, more efpecially when the fubjed that comes un- 
 der the examination of the knife has lain dead fome 
 confiderable time, yet then it is able enough to demon- 
 Rrate the velTels themfelves in its fabric. 
 
 525. The veins of the brain are not difpofed in the 
 fame manner with thofe in other parts of the body. 
 For neither have they any valves, nor do they run to- 
 gether in company with the arteries, nor have their 
 trunks the ftrudure which is commonly obferved in the 
 other veins. The veins, therefore, which come out of 
 the innermoft cavities of the brain, thofe which are 
 fpread upon the ftriated bodies, the veins of the cho- 
 riode plexus, with the lucid feptuin and the anterior 
 ventricles, are colleded together into trunks which at 
 laR meet in one great vein, or often two, which, being 
 accompanied with many fmall arteries of the choroide 
 plexus, defeends backward to the partition of the brain 
 and cerebellum. In that place, it receives veins arifing 
 from the pollerior and lower part of the brain, and 
 fome of the cerebellum, from whence the blood paffes 
 into a fmus, which is a kind of vein included in a re- 
 duplication of the inner plate or membrane of the brain, 
 into which the Veins, to (horten their length, are gene- 
 rally inferred ; and this fmuousvein generally defeends 
 to the greater fmus on the left fide, though fometimes 
 it ends bifurcated, one branch on each fide. This is 
 called ihc fourth ftnus. 
 
 326. The upper and fuperficial veins of the brain are 
 large, and fpread in the windings with which the brain 
 on all fides abounds. With thofe veins, through the 
 whole furface of the brain, arc inferted other veins of 
 the dura mater ; and others, which enter by peculiar 
 orifices into the falciform fmus. From thence the veins, 
 gradually coliedted together, pafs along, mofl of them 
 forward, fome few of them in a flraight diredlion, and 
 others backwards ; of which thofe forward are the largeft, 
 and open themfelves, their extremitief being obliquely 
 cut off, into falciform fmus which is formed by 
 
 the right and left plate of the internal membrane of the 
 
 X 2 dura 
 
3S6 brain and nerves. Chap.'xI. 
 
 dura mater, which meet together below upon the upper 
 part of the back of the falx. From thence it is of a trian- 
 gular figure, convex in its upper fide, beginning with 
 a flender origin at the feat of the foramen csecum, that 
 is placed above the criftagalli ; from whence it afcends 
 and follows in the courfe of the falx, until ti>at joins the 
 tentorium : it is generally inclined to the right fide, and 
 takes the name of the right tranfuerfe fuius^ which then 
 goes by a peculiar channel in the occipital and tempo- 
 ral bone, tranfverfely to its incurvation at the opening 
 of the jugular vein; in which place being much enlar- 
 ged, it receives the lower finus petrofus, together with 
 the occipital ones, which are hereby difeharged into the 
 jugular vein. But the left tranfverfe finus refeinbles 
 the former; and is, like that, conveyed in a fimilar 
 courfe to the jugular vein, into which it is rather infert- 
 ted on the right fide, than continued as it were in a 
 trunk. Into it the fourth finus (325.), together Miih 
 the occipital one, ufually infert thcmfelvcs. But there 
 are fome inftances, where all thefe are difpofed in a dif- 
 ferent manner, by an infertion of the longitudinal into 
 the left tranfverfe finus ; and then the right tranfverfe 
 iinus receives the fourth and the occipital one. At o- 
 ther times it is equally divided into two tranfi’erfe 
 trunks; and fometimes the middle finus joins the tranf- 
 verfe ones. The two finufes alfo have been found fi- 
 milar and parallel to each other. 
 
 327. There is a flender and rounder finus, which 
 runs along the lower and thicker margin of the falx, 
 fomewhat of an irregular figure, more refeinbling a 
 vein, receiving veins from the falx itfelf, and conmiu- 
 jiicating likewife with the upper finus ; it alio receives 
 veins from the adjacent hfemifpheres of the brain, and 
 from the corpus callofum. Where the tentorium joins 
 with the fore-part of the falx, this is commonly there 
 inferred into the fourth finus. 
 
 328. lower veins of the brain, which lie next 
 to the bafis of the fkull, are varioufly inferred. Ihe 
 foreniofl of them coming from the foifa fvlviana, col- 
 
 let^cd 
 
Chap.XI. brain and NERVES. 157 
 
 kcled together into fome trunks, are inferted into th'e 
 cavernous finus, or triangular interval, that lies at the 
 fide of the fella equina, betwixt the external and inter- 
 nal plate of the dura mater. Other veins, from the 
 pons itfelf, lead into the upper finus petrofus. O- 
 ther pofterior veins, which come from the pofterior 
 lobes of the brain, are inferted in great numbers in- 
 to the tranfverfe fmus that is feated within the tento- 
 rium. 
 
 22 9. The upper veins of the cerebellum, meeting to- 
 gether in large trunks, partly open themfelves into the 
 fourth finus, and in part into the tranfverfe finus. The 
 fewer veins, from the cerebellum and medulla oblonga- 
 ta, infert themfelves into the upper fmus petrofus ; the 
 latter alfo into the tranfverfe procefs very near the place 
 where it goes out. 
 
 J530. There are rnany finufes, befides thofe before- 
 mentioned. The mod anterior of them, which is com- 
 monly like a circle, is larger behind than in its fore-part, 
 w^hich is flenderer, and furrounds the pituitary glan- 
 dule betwixt theclinoide proceffes, communicating with 
 the cavernous and with the lower petrofe finufes ; like- 
 wife communicating betwixt thofe proceffes and the ca- 
 rotid artery, and again, by the way of the fixth pair, 
 with the upper petrofe finufes behind the fifth nerve. 
 There are fome inftances where this fmus receives 
 the ophthalmic vein ; and fometimes the tranfverfe, 
 joining to the cavernous finus, fupplies the place of 
 this circular fmus, or elfe is prefent with it at the fame 
 time. 
 
 33 T. Tht upper petrofe finus \s conveyed backwards 
 in a cavity of the os petrofum, and takes its origin from 
 the extremity of the anterior fulcus of the os petrofum, 
 where it communicates with the cavernous finus, and 
 receives the infertions of the veins of the dura mater, 
 and fometimes of the anterior veins of the brain itfelf, 
 mentioned before (328.); then it is inferted into the 
 angle of the tranfverfe fmus, where it begins to be 
 bent j fometimes alio it joins the inferior fmus of the 
 
 pe- 
 
158 BRAIN AND NERVES. Chap. XI. 
 
 os petrofum. Another vein, likewife defcending by 
 the os petrofum, is in like manner inferted into the 
 angle of the tranfverfe finus. The lower firms pe- 
 trofus, which is larger, goes round the root of the 
 bone of this name, and communicates with its fellow 
 behind the clinoide procefs ; alfo twice it communicates 
 with the cavernous finus, and with the upper fmus, 
 and is conjoined under the nerve of the fifth pair, 
 being finally inferted into the jugular foffa or cavity. 
 Moreover, it receives fome veins of the dura mater 
 from the bafis of the vertebras. To the fame outlet 
 alfo the occipital fmus leads on each fide, which being 
 pretty large, goes round the margin of the foramen, 
 till, arriving at the falx of the cerebellum (g2i.), it is 
 fooner or later inferted, together with its fellow, for 
 the moft part into the fourth fmus, and with that into 
 the left tranfverfe one, or into the longitudinal finus it- 
 felf, or .laflly by a divided extremity into each of the 
 tranfverfe finufcs. This finus receives the lower and 
 pofterior veins of the dura mater, and fome others from 
 the vertebras. 
 
 332. The anterior occipital fmus is irregular or mul- 
 tiform, partly tranfverfe, and partly defcending to the 
 great foramen, being varioufly conjoined with the lower 
 petrofe finufes: from whence it pafi'cs with the nerves 
 of the ninth pair; and either communicates, through a 
 peculiar foramen, by emiffaries into die outer vertebral 
 vein; or other branches, paffing out below, open into 
 the venous circles of the fpinal medulla. But the ca- 
 vernous fmus of the dura mater (325.), being furround- 
 ed with a good deal of cellular fubftance, receives, be- 
 fides the forementioned finus (329, 330.), large veins 
 already deferibed ; alfo the ophthalmic, and principal 
 vein of the dura mater ; and tranfmits them with pecu- 
 liar veins, together with the fii ft and fecond nerve, and 
 third branch of the fifth pair, with a large artery of the 
 dura mater (316.) and the internal carotid (316.^ : al- 
 fo it fends out other emiffaries through a foramen, 
 ■which is not conftant in the great wing, which fo;m 
 
Chap.XI. brain and nerves. 15a 
 
 inofculations with veins placed on the outfide of the 
 Ikull leading to the jugulars, and efpecially with the 
 largeft pterygoidal plexus of veins belonging to the 
 nofe. in the fame manner, the veins of the pericra- 
 nium pafs through fmall holes in the parietal bones into 
 the longitudinal fmus, as the occipital veins pafs thro’ 
 the malioide hole into the tranfverfe fmus through the 
 anterior channel of the occipital bone, and the external 
 vertebral veins are inferted into the jugular fmus ; and 
 others of the anterior occipital veins accompany the 
 nerve of the ninth pair. Thus there are an infinite 
 number of ways open to the blood ; by which it may 
 pafs from the fmufes, wherein it is often colleded in 
 too great quantity, by various direftions, according as 
 the part is more lax, or has a greater declivity. Hence 
 no violent fymptoms follow upon tying either or both 
 of the jugulars or other large veins. 
 
 533. The great quantity of blood which goes to the 
 brain, the greater impulfe with which it is fent into the 
 carotid arteries (3i9.)» the immunity of this part 
 from every kind of preflure by a ftrong bony fence, 
 joined with the flower motion of the blood through the 
 abdominal vifeera and lower extremities, alfo the perpe- 
 tual exercife of the brain and fenfes, do all determine a 
 copious flux of blood to thefe parts, and fome other caufes 
 ferve to fill the head furprifingly with blood. Hence it is 
 that a rednefs of the face, a turgefcence and fparklrng 
 of the eyes, with a pain and pulfation or throbbing of 
 the arteries in the head, are fo frequently followed with 
 a bleeding at the nofe, by violent exercifes or motions 
 of the body. From hence, therefore, it is evident, 
 that, if the veins were of a thin and round flrudure in 
 the brain, they would be unavoidably in greater danger 
 of breaking, whereby apoplexies (to which, in their 
 prefent ftate, they are often liable) would be much 
 more frequent. To avoid this, therefore, nature has 
 given a different figure to the veins which carry out the 
 blood from the brain, by which they are more eafily 
 -and largely dilatable, becaufe they make an unequal re- 
 
 fiflance ; 
 
i 6 o BRAIN AND NERVES. Chap. XT. 
 
 fiftance ; their texture is likewife very firm, and more 
 difficultly broken, efpecially in the larger finufes, which 
 perform the office of trunks ; for as to the finufes of 
 the leffier fort, they are either round, half cylindrical, 
 or of an irregular figure. Befides this, nature has 
 guarded the finufes by crofs-beams, internally made of 
 ftrong membranes, and detached from the right to the 
 left fide within the finus, which, in greater dillenticns, 
 they draw towards a more acute angle, which is ca- 
 pable of a larger dilatation, flrengthening and guarding 
 it from a rupture at the fame time. She has likewife, in 
 thefe veins, provided numberleis inofculaticns,by which 
 they open mutually one into another, and openly com- 
 municate with the external veffels of the head and with 
 thofe of the fpinal medulla, by which means they are 
 capable of freeing themfelves more eafily whenever 
 they are overcharged with blood, ^52.) 
 
 334. It is by fome queried. Whether a part of the 
 arterial blood is not poured into the finufes of the 
 brain ; and whether they have not a pulfation excited 
 from that blood ? That they have no pulfation, is pafl 
 doubt ; becaufe the dura mater every way adheres firm- 
 ly to the iknll, but much more firmly in thofe parts 
 which are the feats of the finufes. Indeed they receive 
 liquors injeefed by the arteries ; but whether thofe 1 
 tranfude through the fmall exhaling arterial veffels, or 
 whether they firfl make a complete circle through the 
 veins, as indeed is much more probable, we are not yet 
 furnilhed with experiments enough to determine. 
 
 333. Thus all the blood of the brain is finally con- 
 veyed into the jugular veins, wffiich are very dilatable, 
 and for that reafon guarded with valves to prevent a 
 return of the venous blood from the right auricle, 
 being at the fame time furrounded w'ith a good deal 
 of cellular fubflance. For as to the blood which goes 
 to the head by the vertebral veins, it is a very incon- 
 fiderable quantity ; but the ample jugulars anfwer in 
 fuch a manner to the great upper vena cava in a di- 
 reft courfe, that they afford the highway for the blood 
 
 to 
 
Chap. XI. BRAIN and NERVES. i 6 i 
 
 to return back to the heart. The branches of thefe 
 are commonly the fame with thofe of the brain ; name- 
 ly, the veins of the brain, and thofe of the face. 
 
 336. The external jugular is a cutaneous vein of the 
 neck, w'hich produces the temporal one, and is united 
 with the internal jugular at the bafis of the lower jaw ; 
 and the fame fends a branch through the os maxillare 
 into the tranfverfe fmus. The internal vertebral empties 
 itfelf through the tranfverfe procelTes of the neck into 
 the tranfverfe fmus as often as the canal belonging to 
 it is opened. 
 
 337. The two lateral finufes of the fpinal marrow 
 run along its whole length, are joined to each ver- 
 tebra by a femicircular arch, and at lafl are united with 
 the jugular and occipital finufes : they fend branches, 
 however, to the fpinal marrow, joined W'ith the ante- 
 rior and pofterior fpinal vein. 
 
 338. The veins form innumerable anaftomofes with 
 one another, that the blood may return with the great- 
 eft eafe from the head, of which the repletion is very 
 dangerous. The brain is alfo more eafily evacuated 
 in the time of infpiration, and fubftdes during that 
 period when the ficull is opened, but fwelk during 
 the time of exfpiration. Hence, blowing the nofe, 
 fneezing, and coughing, are dangerous to thofe whofe 
 brain is fwelled by retained blood. 
 
 339. Whether or not there are lymphatic veffels to 
 be feen in the brain, is by fome queftioned. Indeed, 
 we read defcriptions of them in the pia mater, and in 
 the larger choraidal plexus ; but, for my own part, 
 I have never been able to fee them, and poflibly there 
 are none to be feen, fmce there are no conglobate 
 glands in the bran, which are always near at hand 
 wherever any of thefe veffels are to be found. As for 
 the various accomts wiiich are given of the pituitary 
 glandule, of the iniundibulum, and of the duds which 
 lead from thence iito the veins of the head, abforbing 
 and tranfmitting a water from the ventricles of the 
 brain, they are no fupported by anatomical experi- 
 
 Y ments : 
 
i62 brain and nerves. Chap. XL 
 
 ments : which make it more probable, that the vapour 
 which is fecreted into the ventricles of a healthy perfon 
 is, in like proportion, abforbed again by the inhaling 
 veins ; or, if any part abounds, that it defcends through 
 the bottom of the ventricles to the bafis of the Ikull, 
 and from thence into the loofe cavity of the fpinal me- 
 dulla. That this is the cafe, appears from palfies which 
 enfue on one fide of the body after apoplexies ; and 
 from the bifid fpines or watery tumours in the lower 
 part of the fpinal medulla, following in thofe who have 
 an hydrocephalus. 
 
 340. It now remains for us to fpeak of the encepha- 
 lon itfelf. But many are the parts included under this 
 general denomination. By the brain, properly fo call- 
 ed, we underftand that upper and foft vifcus which is 
 contained in the fkull, and which is lodged by itfelf in 
 its fore-part; but backward it is incumbent over ano- 
 ther confiderable part, called the cerebellum, which lies 
 in the pollerior and lower cavities of the occipital bone, 
 under the membranous tentorium, which parts it from 
 the brain. Its lower, middle, and white portion, de- 
 fcending before the cerebellum, is in part called xhtpons, 
 and in part the medulla oblongata. 
 
 341. The figure of the brain refembbs that of half 
 an egg, which is deeply divided longitudinally, but not 
 cut through above half way, into hemifpheres refem- 
 bling the fourth part of an egg. Both the upper and 
 lower furfaces are full of many gyri dr convolutions, 
 which pretty deeply cut or divide the l^ain with round 
 ends or angles into undulated portionSf But the largeft 
 is that which afcends on both fides outwards from the 
 fidcs of the fella turcica, and divide? the hemifphere 
 into two lobes. Upon the furface the faid lobules 
 or portions lies the cortex, extremel)yfoft, and inclined 
 from a yellow or red to a grey or alh colour, being the 
 mod tender of all parts in the hunan body : this in- 
 wardly is filled with the medulla, v^ich is almoft per- 
 fedly white, but redder in the fctu^, in many places, it 
 is perforated by red arteries, whioi are more fimplc 
 
 I and 
 
Chap. XI. BRAIN and NERVES. 163 
 
 and perpendicular, or ftraight, than in other parts. 
 This medulla is more folid and more capable of fu- 
 ftaining its figure, notwithftanding it is very foft, and 
 abounds in a greater quantity than that of the cortex. 
 The greater pofterior branch of the carotid artery 
 (317.) firft divides the right and afterwards the left 
 hemifphere of the brain into an anterior lobe, which 
 is the larger; and a pofterior lobe, which is the lefs. 
 
 342. The fabric of the cortex has been a long time 
 controverted ; but it is now fufficiently evident, from 
 anatomical injeftions, that much the greater part of 
 it confifts of mere veflels, which are every way in- 
 ferted from the fmall branches of the pia mater, de- 
 tached like little roots into the cortical fubftance, and 
 conveying a juice much thinner than blood in their 
 natural ftate, although in fome difeafes, and by ftran- 
 gling, they often receive even the red parts of the 
 blood, more efpecially in brutes and birds. The re- 
 maining part of the cortex, which is not filled by any 
 injection, is probably either an aflemblage of veins, or 
 of yet more tender veflels ; for no other diflimilar parts are 
 apparent in the cortex, whilft it is in an entire or natu- 
 ral ftate ; from whence one may conjedture fome part 
 of it to be tubular, and the other part folid. As to 
 glandules making the fabric of the brain, that notion 
 has been difcarded by univerfal confent ; nor indeed 
 has there been any other opinion received with lefs pro- 
 bability than this. 
 
 343. In order to gain a knowledge of the nature of 
 medulla, we are to confider the anatomical ftrmfture 
 of this part of the human brain, compared with the 
 brains of brute animals and fiih. Therefore this part 
 of the brain, which follows immediately under the 
 outer gyri or convolutions of the cortex, is of a white 
 colour, and becomes gradually broader and more a- 
 bundant ; fo that, at length, it makes up the whole 
 oval fection of the brain, except only the gyri in the 
 furface, which makes the cortex. In this part, the 
 two hemifpheres of the brain, as before obferved, are 
 
 y 2 divided 
 
164 BRAIN AND NERVES. Chap. XL 
 
 divided but half way through ; which hemifpheres here 
 continue their cohefion with the medulla in the mid- 
 dle. That part of the medulla which is extended un- 
 der the falciform procefs, but at fome diftance from it, 
 is called corpus callofum ; in the furface of which run 
 two parallel white (tripes, formed by the pulfation of the 
 arteries : thefe (tripes diverging forwards, and termi- 
 nated at the place where they mingle together in the 
 fore-part, are thence divided backwards. But the an- 
 terior extremity of this callous body is loft in the fub- 
 (tance of the crura, coming from the anterior lobes of 
 the brain : the polterior, w'hich is broader, with a 
 firorter curvature in the (liape of a nail, is brought in- 
 wards ; and the other column defeends into the inferior 
 horn of the ventricle, whence it is continued along w'ith 
 the longer one into the hippocampus. Moreover, the 
 W'hole furface of this callous body is (treaked with tranf- 
 verfe fibres, which are continued, but extenuated, into 
 the next adjacent medulla of the brain itfelf. Even the 
 interior fubfiance of this body is of a ftriated nature, 
 and its lower furface has its future and fibres tranfverfe. 
 
 344. x\s to the remaining parts of the brain, a feru- 
 tlny is more difficult to be made into them : for the 
 brain is not a folid body, but begins to be hollow in- 
 ternally from the lower part of its medulla, which is 
 incumbent upon the multiform bone, at which place 
 the greater crus of the brain paffes out from it ; and 
 in this cavity the medulla is only covered wnth the pia 
 mater, which afeends backward, and then turning 
 continues its courfe forward and upward. Next, the 
 brain divides itfelf near the pofterior extremity of its 
 callous body; and, at the fame time, fends one of its 
 firorter pofterior portions into the pofteriqr lobe of the 
 brain, turning its extremity inward. But the anterior por- 
 tion is continued a long w'ay by the fide of the callous bo- 
 dy, parallel to the horizon ; and turning its horn outward, 
 which there grows broader, it is terminated in the anterior 
 lobe of the brain. This cavity, of w'hich t'lere is one 
 in each hemifphcre of the brain, is called its triangular 
 
Chap. XI. BRAIN and NERVES. 1^5 
 
 or anterior ventricle; and it is naturally filled with a 
 vapour, which is frequently condenfed into water or 
 
 345. This cavity is full,- without any intermediate 
 fpace, by the clofe meeting together of the fides of the 
 upper and lower medulla. The lower fide or pavement 
 of this part is varioufiy figured. In its forepart, it forms 
 a horn ; below which there is a rifing moderately con- 
 vex, and of confiderable length, diverging backwards, 
 covered with a membrane that is extremely vafcular ; 
 and, being outwardly of an afli or grey colour, is called 
 the corpora Jlriata ; becaufe inwardly they exhibit to 
 the view, together with much cortex, alternate white 
 oval (freaks, parallel to one another, longer on the 
 back part ; befides, as it were, lefTer medullary fpots 
 and micse. More inwardly and backward, there are 
 two other fimilar eminences, more of an egg-like 
 fhape, towards the third ventricle and other parts, 
 moffly cinereous on the outfide, obfeurely (friated, 
 and fo incumbent together, that they frequently co- 
 here on the upper part, where they are confounded 
 with the cortex ; and thefe, .continuing their courfe 
 through the horn of each anterior ventricle, defeend to 
 the bafis of the (1-tull, and there generate the optic 
 nerves, of which they are called the thalami. Betwixt 
 the faid (friated bodies and thofe thalami, lies an inter- 
 mediate, parallel, white, and (freaked medullary por- 
 tion, called the double femicircular centre, produced 
 from the anterior commixture, and frequently from the 
 crura of the fornix ; but efpecially from the medulla it- 
 felf, before the thalami of the brain. This commixture 
 is broad, (frong, and joins together the anterior part of 
 the brain before the thalami. The double centre, 
 which is broadeff behind, arifes with many fibres, from 
 the junction of the foot of the hippocampus with the 
 medulla of the brain. But-the corpora (friata, with the 
 thalami, conlfitute the medullary crura of the brain ; 
 which, in the bafis of the cerebrum, lie over the me- 
 dulla of the cerebellum, and are joined together at the 
 
 extremity 
 
t 66 BRAIN AND NERVES. Chap. XI. 
 
 extremity of the bridge above-mentioned. At the 
 place where they approach neareft to one another, each 
 fends out an hemifpherical mamillary eminence. The 
 fibres of the medulla of the brain itfelf, mixed together 
 with the medulla of the cerebellum, defeend into the 
 medulla oblongata ; and, being then collefted into a 
 bundle, they go to the corpora pyramidalia. 
 
 546. It is to be obferved, that the corpus callofum me- 
 dium projects or rifes up in the common axis or middle 
 of thofe ventricles. Behind, this body lies contiguous and 
 incumbent on the fornix ; but, before, there are two fi- 
 milar medullary partitions, which defeend from this body 
 the whole length of the corpora ftriata ; and this part, 
 which in its middle includes an anonymous cavity, goes 
 under the name of feptum pellucidwn. This feptum is con- 
 tinued to the fornix ; that is to fay, the four-horned me- 
 dullary trafts, which take their anterior origin from the 
 medulla of the brain, and fometimes the mamillary pro- 
 tuberances, and the commixture which we have mention- 
 ed : and behind that, particularly under the thalami, and 
 often from the double centre and crooked line of the tha- 
 lami. This fornix is incumbent upon an interval of the 
 flriated bodies, and upon another interval of the thala- 
 mi : from whence it degenerates partly into a broad 
 thin fimbria; and partly into another tubercle, which is 
 evidently continuous with the fornix and callous body 
 of an half cylindrical figure, and furnifhed with an ap- 
 pofite fimhria. Thefe defeend into the lower anterior 
 horns of the ventricles ; and at laft: terminate outwards 
 by a fort of convex fulcated end, imprinted by the gyri 
 of the brain, and terminated by a foot, having as it 
 were four furrows ; whence the name of hippocampus^ 
 which externally are covered by exceeding thin medul- 
 lary plates, but are inwardly of a cortical fubftance. At 
 the beginning of the divifion of the foot of the hippo- 
 campus, the tecnia ends in two white ftriEC, a long and 
 a fhort one, inferted into this foot and into the brain, or 
 one inferted into the inmoft part of the unguis. A like 
 protuberance is continued in the poftcrior horn of the 
 
 ventricle. 
 
Chap. XL BRAIN and NERVES. 167 
 
 ventricle, crooked inwards at its extremity like the claw 
 of a bird, to which a continuous column occupies the 
 hinder part of the bafis of the horn of the defcending 
 ventricle, which is continued with the corpus callofum. 
 Betwixt the departing poflerior crura of the fornix, the 
 medullary portion, which is behind the middle plexus 
 of the ventricles, and painted with tranfverfe and pal- 
 mated ftreaks, is called the pfalteriim or harp, 
 
 347. Within the anterior or lower part of each of the 
 ventricles, begins the vafcular plems^ called choroides, 
 included in the pia mater only, it lying naked in the 
 reft of the cavity of the fkull, made up of a great many 
 fmall arteries (3 17, 318.), together with little veins ori- 
 
 ' ginating from the larger trunk (325.); all which nu- 
 merous veflels, joined together by the pia mater, re- 
 femble a curtain varioufly folded. With thefe are in- 
 termixed many fmall pellucid glandules of a round fi- 
 gure, refembling hydatids. It afeends from the bafis 
 of the brain, through the defcending horn of the ven- 
 tricle, and thus is dilated as it goes upward ; but, thence, 
 becoming narrower, it goes on with the optic thala- 
 mus, to the pofterior extremity of the feptum lucidum. 
 When thofe plexufes have reached the anterior extre- 
 mity of the thalami, being afterwards reflected and u- 
 nited together into one very large vafcular plexus, they 
 gradually defeend through the crevice of the third ven- 
 tricle as far as the pineal glandule, and then are conti- 
 nued into the pia mater of the pofterior lobes of the 
 brain. From this plexus, doubtlefs, proceeds the inter- 
 nal warmth of the brain, with its exhalation and inha- 
 lation. But the choroidal plexufes become very broad 
 where the anterior ventricles of the brain begin to de- 
 feend ; and thence, contrafting gradually downward, 
 they project their extremities to the ends of the anterior 
 ventricles, covered only with the pia mater. 
 
 348. Betwixt the thalami, applied one to the other 
 almoft with a plain furface, there is a natural fiflure ter- 
 minating the crura of the brain, which meet together 
 ill the bafis of the fkull j and this is called the third ven^ 
 
 trick. 
 
i 6 S BRAIN AND NERVES. Chap. XI. 
 
 tricle. It leads by a declivity, like a funnel, forward 
 into a concave column ; which, though hollow in brutes, 
 is yet evidently lefs tubular in man, and connefted to 
 the pituitary glandule. 
 
 349. This is compreffed on both Tides, fimple, of un- 
 certain flrufture ; in the anterior part almolt round, and 
 of a reddiTn colour 5 the pofterior part lefs, cinereous, 
 broad tranfvcrfely, covered with the pia maier of the 
 brain : it lies upon the proper impreiiion of the fella 
 turcica, and feems to be a kind of appendix to the 
 brain. 
 
 350. Backward, the thalami are conjoined together 
 in the bottom of the ventricle, by a medullary fafcia, or 
 poflerior commixture, and by a fmaller tranfvcrfe chord ; 
 from which a crooked white ftreak goes out on both 
 fides in the upper part, which lofes itfelf in the double 
 centre, in the anterior commixture, and fometimes in 
 the crus of the fornix. On the fore and upper part, 
 the thalami fpring out of a protuberance, which is form- 
 ed by the triangular fornix lying between the two tha- 
 lami. 
 
 351. This little eminence feparates the upper trian- 
 gular cavity of the third ventricle, filled up with the for- 
 nix in fuch a manner, from the inferior calamus fcrip- 
 torius, that the cavity is continued both from the ante- 
 rior and pofterior extremity of the third ventricle, from 
 the top to the bottom. But even the anterior com- 
 mixture is a medullary ftreak which unites the thalami 
 before the anterior crura of the fornix. 
 
 352. Again, behind the thalami, thofe tranfverfe fi- 
 gured eminences of the medulla meet together, which 
 conjoin the medulla of the right and left pofterior lobes 
 of the brain. In this part, backward, are cut out four 
 oval eminences, which are outwardly fmaller, called the 
 nates and teftes^ and which are of a fubftance inwardly 
 cortical, but outwardly medullary. Upon thefe is feated 
 a cortical glandule, fomewhat oval and conical, fpread 
 with many fmall »effels, into which the choroide plexus 
 here degeijerates ; this is the pneal glandule fo much 
 
 cele- 
 
Chap. XI. BRAIN and NBRVES. 
 
 celebrated, and fo frequently difeafed, and joined to the 
 brain by fmall foot-ftalks fent into the linea alba thro’ 
 the thalami in their paffage forwards. Between this 
 eminence, on which thefe four protuberances are cut 
 out, and the crura of the oblong medulla, palfes a groove 
 or channel in the fame direction from the third to the 
 fourth ventricle, manifeftly open, refembling an aque- 
 duct. 
 
 35^. The whole medulla of the brain is, in its lower 
 part or bafis, collected together into two very thick 
 compreffed columns, dilHnguidied in their furface by a 
 line running according to their length ; which have in- 
 ternally a cortical fubflance, and are the crura of the 
 brain. Thefe, meeting together backwards, are cover- 
 ed by the fubjacent crura of the cerebellum, and are 
 inferted by apparent ftrata of fibres into the pyramidal 
 bodies of the medulla oblongata ; and with the other 
 deeper fibres, which feparate the inner tranfverfe fibres 
 that come from the cerebellum from the preceding, 
 meet together with the medulla cerebelli to make up 
 the beginning of the medulla oblongata. 
 
 354. The cerebellum^ as it is lefs, fo it is more fimple 
 than the brain. It has two lobes, but no where deeply 
 parted, united above and below in their centre to a ring 
 of the fame fabric with itfelf, called the vermis, at the fide 
 of which there is a fmooth eminence of the fame na- 
 ture with the cerebellum itfelf. This part of the ence- 
 phalon contains a great deal of the cortex, with a lefs 
 proportion of medullary fubftance. And here, like- 
 wife, the cortex is placed in the circumference, but 
 marked with gyri or convolutions, which are rather pa- 
 rallel to each other, fo as to form circles. Thus the 
 fmall lobules or portions are diftinguilhed, but not deep- 
 ly, and afterwards fend out each of them their medulla; 
 which is, by degrees, lb collefted together in rays or 
 branches, meeting in one trunk, that the whole re- 
 fembles the figure of little trees. This medulla, col- 
 lected together into the large crura of the cerebellum, 
 and marked in the inner part with ferratcd cortical lines, 
 
 Z inter- 
 
170 BRAIN AND NERVES. Chap. XI. 
 
 interwoven with one anoiher, bath a threefold termina- 
 tion. One part afcends towards the bans of the nates, 
 where it joins with the medulla of the brain under the 
 teRes ; but the right and left parts of it are joined to 
 each other by a trardVerfe medullary ftria behind the 
 nates. From this, forne diftinct fibres afcend outwards, 
 and ioin thernfeives to the tranfverfe ones of the bridge. 
 Between thefe firR proceffes of the cerebellum, is 
 ftretched a medullary lamina, behind the fourth ven- 
 tricle, lending forth fibres beyond the procefs. Ano- 
 ther portion defeends into the fpinal medulla, and ter- 
 minates in peculiar nail-like protuberances, which are 
 both anonymous, and have other cortical portions near 
 them, A third portion, which is larger, and fituated 
 in the middle, goes tranfverfely downward under the 
 crura of the brain, which it embraces ; and by twice 
 intermixing alternately with tlieir tranfverfe medullary 
 fibres (^52.), it is in a great meafure confounded toge- 
 tlier with them. 
 
 t;5 5. Thus is produced from the crura of the brain 
 defeending above thofe of the cerebellum, and from, 
 the medulla of the cerebellum tranfverfely furrounding 
 that of the cerebrum, the pons^ at firR almoR oval, 
 but more blunted on both lides, deprefled in the mid- 
 dle, and inferibed on all fides with tranfverfe fibres. 
 Then the meduJla oblongata, continuous to the pons, 
 is internally variegated and Rreaked with a fubRance 
 like the cortex, and defeends of a conical fliape, in- 
 clined to the great foramen in .the occiput. This me- 
 dulla has two pair of tubercles before the pons ; the 
 outermoR of the figure of an olive, and the innermoR 
 of a pyramidal fliape, for they lefl'en downward like 
 a cone; and thefe are immediately divided by a fulcus, 
 through which the pia mater enters. But betwixt that 
 medulla and the worm-like procefs of the cerebellum,, 
 is formed a cavity, limited by the four leffer proceffes, 
 which as they afcend or defeend is at firR narrower ; 
 but above the tubercles (354-) it grows broader, and 
 is of a rhomboidal figure : it is called the fourth ven^ 
 
 tricky 
 
Chap.XI. brain AMD NERVES. iji 
 
 trick. It is Ihut in its back-part by the valvula magna, 
 dr a medullary velum, uniting the procclTes going from 
 the cerebellum to the nates and vermis, and tranfrcrfe 
 ftria lying under the idles, and Ihurting the ventricle 
 behind, (354.) I'his ventricle has a moderately large 
 fulcus or furrow, having fwelled lips on each fide inferi- 
 bed on the medulla oblongata, and anl'wcring to the 
 canal that is covered by the nates and telles, called the 
 In this iaft ventricle, as well as in the 
 foregoing, is lodged the plexus choroides, only lefs in 
 bulk, together with an upper fulcus called calamus. 
 Each of thefe fulci is continued down along the me- 
 dulla fpinalis, both in its anterior and pollerior fide j 
 more evidently in the former, but lefs fo in the latter. 
 Tranfverfe fibres are detached in its upper part from 
 the right to the left fide, both of the medulla oblonga- 
 ta and fpinalis. But two or three of the tranfverfe 
 {freaks that arife from the eminences which intercept 
 a fulcus, are inferted into the foft part of the acouflic 
 nerve ; others go to the eighth pair, and others of the 
 fame kind afeend to the crus of the cerebellum. 
 
 356. All the medulla of the brain and cerebellum 
 goes out from the fkull, through particular openings 
 towards certain parts to which it is deftined. The 
 fmaller bundles of this medulla we call nerves ; but 
 the larger, defeending through the fpine, we call the 
 medulla fpinalis^ which is a continuation of that called 
 oblongata But the nerves, wdiich are bundles 
 
 of the medulla, and very foft in their origin, are com- 
 pofed of ftraight parallel fibres in diftindl threads. 
 Thefe nervous cords, after they have gone forward 
 fome length, covered with the firm pia mater of a red- 
 difh colour, are afterwards united into a more tougfi or 
 permanent firing ; and then, conjoined, divided, and 
 in the neighbourhood of others like themfelves, they 
 haften through a cellular texture to their proper open- 
 ing in the dura mater, and thence run down through 
 the intervals of the channels formed by that mem- 
 brane, till they meet with an opening in the fkull, out 
 
 Z 2 of 
 
BRAIN AND NERVES. Chap. XL 
 
 of which they pafs through the membranous funnel of 
 the dura mater. The nerve, having arrived without 
 the Ikull, is commonly furrounded by the dura mater, 
 fo as to become very folid and firm. Thus it is 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 olfactory nerves, in 
 the foft portion of the auditory nerve, and the interco- 
 ftal. The nerves now defcend naked or lefs fenced 
 betwixt the mufcles, detaching their cords or threads 
 of which they are compofed, and are ftill made up of 
 the medulla covered by the pia mater. Many fmall 
 threads of this kind are joined together into larger, 
 by the union of the cellular fubftance that furrounds 
 them, through which run many fmall arteries and veins 
 intermixed ; and fometimes fat itfelf is therein lodged. 
 But in general the outer covering, common to the 
 whole nervous bundle, is either derived from the dura 
 mater, or at lead is a hard plate of the cellular fub- 
 ftance, wherein all the fmaller threads are contained 
 and united into one nerve, often refeinbling a true 
 membrane. 
 
 g57. It is common to all the nerves of the head to arife 
 and pafs out from the lower part of the medulla of the 
 brain or cerebellum. The o^'t?^(5/;ywerx;earifes with lateral 
 fibres from the interval betwixt the anterior lobe of the 
 brain, but with direct fibres from the medulla of the 
 anterior lobe itfelf. A great part of the optic nerve 
 fprings from the thalami (345.), but fome part hkewife 
 from the crus of the brain, while the nerves decullate 
 through its fubftance. The third arifes from the loweft 
 crus or the medulla of the brain behind the mammillary 
 bodies. The fourth, which is either fnnple or tntid, 
 fends a procefs from the fide of the cerebellum to the 
 teltes. The fifth arifes plainly Irom the peduncles of 
 the cerebellum itfelf. The fixth out of a fulcus (354.), 
 deep from the bottom of the pons betwixt that and the 
 medulla oblongata. The feventh arifes with one part 
 fpfter from the medulla oblongata, and by two tranf- 
 
Chap. XL BRAIN and NERVES. 173 
 
 verfe ftrise, from the fourth ventricle itfelf ; and with 
 another part harder from that portion of the crus of the 
 cerebellum which lies next the pons. The eighth nerve 
 arifes from the interval betwixt the olivary and pyrami- 
 dal bodies or protuberances ; and, according to the 
 obfervation of other eminent anatomifts, from the 
 fourth ventricle likewife. The ninth arifes from the 
 corpora olivaria and pyramidalia. The tenth, by rea- 
 fon of its double root, is reckoned a nerve of the neck, 
 going out with an arch, in company with the upper 
 and lower adjacent nerve. There is, therefore, no 
 nervous branch that arifes properly from the cerebel- 
 lum, unlefs it be the fifth ; for the anterior nerves, the 
 clfaftories, optics, and third nerve, come from the 
 brain only ; and all the reft from thofe parts where the 
 medulla, both of the brain and cerebellum, are con- 
 joined together. 
 
 358. The fplnal medulla is a kind of very foft me- 
 dullary rope or appendix to the encephalon, continued 
 down from the medulla oblongata, as low as the fecond 
 vertebrae of the loins. In the neck its anterior and po- 
 fterior fides are flat, laterally convex, but in the back 
 it is four-fquare. It is largeft where it goes out from 
 the head ; from thence it is fmaller in the top of the neck ; 
 in the lower part it is larger ; but fmaller again through 
 almoft the whole back ; thicker in the lower, oval, and 
 conical part of it ; and laftly it ends in tubercles. The 
 pia mater is a proper integument to this part as well as 
 to the brain, fince it enters the foremoft fiflTure deep- 
 ly, and divides the medulla almoft into two. The cor- 
 tical fubftance which lies within it is obfcure. It has 
 its anterior artery produced in the fkull, from the 
 branches of the vertebrals. This artery is retrograde, 
 and defeends through the whole length of the pia ma- 
 ter, perpetually making alternate finuous flexures, which 
 form inofculations about many but not all of the 
 nerves, with branches of the vertebral, intercoftal, 
 lumbar, and facrolumbar arteries j till at laft, being 
 covered with a peculiar coat from the pia mater, it 
 
 goes 
 
174 BRAIN AND NERVES. Chap. Xf. 
 
 goes out and difappears at the coccyx. In like man- 
 ner the two pofterior arteries, which are lefs, arife and 
 are diftributed from the lower arteries of the cerebel- 
 lum, and are more ferpentine, and frcqua;)tly inofeu- 
 lated among themfelves. The fpinal veins defeend, to- 
 gether with the arteries, from the brain itfelf, fending 
 out branches in like manner on each fide, which ac- 
 company ^'he nerves like fo man/ circular fmufes, fixed 
 in the dura mater, and correfponding to the number 
 of the vertebrae, all which fo communicate one with 
 another, that each has on all fides a dircdl confent 
 both with the uppermoft and lowermoft ; and, after 
 having fent out branches that join the vertebral, inter- 
 coflal, and lumbal veins, they unite with thofe of the 
 facrum. The uppermofl; of thefe fmufes inofculates 
 with the anterior occipital fmufes (332.) 
 
 ^59. But there is another covering, not fpread with 
 any veffels, which furrounds the fpinal medulla lool'ely 
 and at a diftance, and is pretty firm, of a w'atery clear- 
 nefs, called arachnoides ; and which being longer than 
 the pia mater, is extended to the bottom of the os fa- 
 crum, w'here the nerves, only defeending from the 
 medulla, are collcded by it into a fafciculus. But in 
 what manner it goes out, together with the nerves, has 
 not been hitherto deferibed. Betw'een that membrane 
 and the dura mater there exhales a vapour, w'hich is 
 frequently condenfed into a reddilh water, and produces 
 a true dropfy. 
 
 360. Laftly, the dura viater, belonging to the fpinal 
 medulla, and continued from that of the cerebellum, fur- 
 rounding the arachnoides, and from thence defeending 
 to the bottom of the os facrum, being larger at its begin- 
 ning, at the bottom of the neck, and at the loins, 
 but flenderer in the back, and being conneded ulti- 
 mately by many ligaments to the os facrum, it at laft 
 difappears in a llender cone. As the nerves pafs cut 
 through this membrane, it gives them an external co- 
 vering ; and diredly thickens or fwells with them into 
 ■ 3 i ganglion, or bard, oval, reddifli-coloured knot. To 
 
Chap. XL BRAIN and NERVES. 175 
 
 this hard covering of the dura mater internally adheres 
 a ligament denticulated at the interval of each of the 
 nerves, which arifes from the Ikull near the courfe or' 
 paffage of the ninth pair of nerves, tying the arach- 
 noidcs to the dura mater by triangular produdions in 
 each of the intervals of the nerves, and betwixt the 
 anterior and pofterior bundles of the fpinal nerves down 
 to the bottom, and twelfth vertebra of the back. Ex- 
 ternally there is a fort of fat furrounds the dura ma- 
 ter, and alfo lines internally the covering of the verte- 
 bras of the fpine, which by this means are fo adapted 
 like a tube to the medulla fpinalis, that the latter is 
 not liable to be comprelfed by the bending of it in any 
 pofition. 
 
 361. The fibres of the fpinal medulla, in dropfical 
 fubjeds and in brute animals, appear very difiind. 
 Thefe medullary fibres go out from the whole anterior 
 and pofterior fides of this long appendix ; after which, 
 the anterior cords are commonly wrapt up in the pia 
 mater, in which they converge together Idee rays into 
 a larger fafciculus ; to which alfo join fimilar threads in 
 another bundle from the pofterior fafciculi joining to- 
 gether into one nerve, which, pafiing out through the 
 holes of the dura mater, produces a nerve betwixt each 
 two vertebrae. Thefe vertebrae are about 30 in num- 
 ber. In the neck, numerous radiated nervous fibres 
 compofe one large and almoft tranfverfe nerve. In the 
 back they defeend, in general, of a fmaller fize ; but fo 
 that the lower and larger ones are commonly joined 
 clofe to one another. The large and long lumbal ones 
 join to form the cauda equina. The loweft nerves of 
 the os facrum are the leaft, the uppermoft ones large. 
 Many of the dorfal nerves, together with the lumbal 
 ones, and thofe of the os facrum, covered with their 
 proper membrane from the pia mater, accompanied 
 with their arteries, and inclofed in the arachnoides, 
 make up that rope which is called the cauda equina. 
 
 362. Thofe nerves are afterwards diftributed to all 
 parts of the body in a manner very complex, and not 
 
 here 
 
17<5 brain and nerves. Chap.XE 
 
 here to be defcribed. But we muft not omit to ob- 
 fervc, that all the fpinal nerves, except one or two in the 
 neck, have both an anterior and poRerior trunk. Ihis 
 is only fent to the mufcles. It produces a nervous root, 
 which joining the other adjacent nerves, and having gi- 
 ven a fmall circle that proceeds from the fixth nerve of 
 the brain and the fecond branch of the fifth, comes 
 through the pterygoide canal, and forms one of the prin- 
 cipal nerves of the human body; which, communicat- 
 ing with almolt all the other nerves of the whole fyftem, 
 fends out nervous branches to the heart and all the vif- 
 cera of the abdomen. The fame has as many ganglia 
 as roots from the medulla, unlefs where many of them 
 join into one ganglion. It communicates in various 
 places with the crural, brachial, and diaphragmatical 
 nerves, alfo with thepar vagum and ninth pair of nerves. 
 The other primary or capital nerv^e is the eighth or 
 n^ague nerve, arifing from the brain, and joining itfelf to 
 the intercoftal in the bottom of the neck, in the thorax, 
 and in the abdomen ; this palfes out of the fkull in 
 three cords, of which the larger fends branches to the 
 larynx, gula, lungs, and the cardiac plexus itfelf (99.) 
 alfo to the oefophagus, ftomach, and liver. The third 
 of thefe is the phrenic nerve, arifing from molt of the 
 lower nerves of the neck and arms ; and fometimes, be- 
 ing increafed from the root of the fpinal nerve, it de- 
 feends by the fide of the pericardium, and inferts itfelf 
 into the upper face of the diaphragm; but below it re- 
 ceives nerves from the great plexus of the intcrcoftal 
 nerve. Lafily, the accejfory nerve, arifing by many 
 fmall roots from the fix or feven uppermolt pofterior 
 nerves at the neck, and from the medulla oblongata, 
 joins the nerve of the eighth pair going back again into 
 the Ikull, and feems, by this means, to make a confent 
 betwixt that important nerve and the fpinal medulla. 
 Moreover, the nerves of the limbs have at their origin 
 plexufes or knots, and are, on account of their length, 
 harder and firmer in their fBbftance, and much larger, 
 than the great nerves which go to the vifeera : thofe 
 
 which 
 
Chap.XI. brain and NERVES. 177 
 
 which go to the hand, arife from the four lower nerves 
 of the neck and firfl of the back 5 but thofe of the lower 
 extremity from the nerves of the loins and os facrum. 
 
 -^6^. The nerves divide into branches like the blood- 
 vefl'els, but in acute angles, and often in a courfe ina- 
 nifeftly retrograde, growing gradually fofter and Icfs in 
 bulk, though fometimes they become thicker as they 
 recede from the brain, till at length their ultimate ex- 
 tremities, which are feldom vifible, feem to terminate 
 in a pulp, by depofiting the firm integuments with 
 which they were covered, after the manner which we 
 obferve in the optic nerve. But the rectilineal courfe 
 of the fibres, continued from the brain itfelf, is fuch, 
 that it is never broken off by the divilion or fplitting of 
 a nerve into fmaller threads, which only recede from 
 each other by an opening of the cellular fubftance that 
 tied them together. This appears from the diforders, 
 which are determined not to ail, but only to fome fingle 
 parts by injuries of the brain ; as a lofs of the voice, 
 deafnefs, dumbnefs, and palfies of particular mufcles. 
 They are connecled in their courfe by the cellular fub- 
 ftance to the adjacent parts, but have hardly any elafti- 
 city ; whence they do not fly back after being divided, 
 but only expel, by the contradlion of their integuments, 
 the foft medulla w^hich they include. But though they 
 are irritated ever fo much, they are neither contracted 
 nor are they rendered flrorter during the motion of the 
 mufcles which they produce. A great many nerves are 
 fent into the mufcles ;■ many of them go to the ikin ; but 
 fewer to the vifcera, and feweft of all to the lungs; none 
 at all to the dura and pia mater, arachnoides, tendons, 
 capfules, and ligaments, and laftly the whole fecon- 
 dary membranes. They make frequent inofculations 
 with each other, or out of one trunk are parted into 
 many branches ; and it is principally in thefe meetings 
 of their branches, arifing from different trunks, that 
 the nervous ganglia are formed ; namely, hard nervous 
 tumours, for the moft part replenifned with blood-vef- 
 fels, and included in a firm membrane, but of a ufe and 
 A a ftruCture 
 
173 BRAIN AND NERVES. Chap.XL 
 
 ftrudture as yet not certainly known, in which the 
 ftraight courfe of the nervous fibres is interrupted. The 
 nerves of the fenfes only are excepted from thefe gan- 
 glia or knots, together with the eighth pair; but they 
 feein in a manner efiential to the phrenic nerves, to the 
 fifth pair, to thofe of the limbs, to the fpinal and to the 
 intercofial nerves, which lafi dre truly fpinal nerves. 
 
 365. Thus far we are taught by anatomy concern- 
 ing the brain and nerves ; it remains from hence, that 
 we explain the phyfiological ufes of thefe parts. Every 
 nerve, therefore, that is irritated by any caufe, produ- 
 ces a fitarp fenfe of pain. But -we mufi; reckon the 
 mind to be changed when any change happens to the 
 body. It is the medullary part of the nerve which feels 
 the pain. If the nerve was endued with any peculiar 
 fenfe, that fenfe perifiies when the nerve is comprciTed 
 or diflefted ; the fenfes of the whole body are loft by a 
 Gompreffion of the brain ; and of thofe parts whofc 
 nerves originate below the feat of preflure, if you com- 
 prefs the fpinal marrow. If certain parts of the brain 
 are comprefled from which particular nerves arife, then 
 thefe fenfes only are loft which depend on the nerves, 
 as the fight or hearing. Thofe parts of the body which 
 receive many nerves, as the eyes and penis, have the 
 moft acute fenfation ; thofe have leaft fenfibility which re- 
 ceive few nerves, as the vifeera; and thofe which have 
 no nerves, as the dura mater, tendons, ligaments, fecun- 
 dines, broad bones, and ligaments, have no fenfation. 
 
 366. It is not verv obfeure, that all fenfation arifes 
 from the impreflion of a fenfible object on fome nerve of 
 the human body ; and that the fame is then reprefented 
 to the mind by means of that nerve’s coimedion with 
 the brain. But this feems to be falfc, that the mind 
 perceives immediately by means of the fenforia and 
 branches of the nerves. For this opinion is refuted, 
 by the pains felt after amputation, the ceflation of all 
 pain when the nerve is comprefled, and the deftruefion 
 of the fenfes by difeafes of the brain. And that the cf- 
 fed of the fenfes is preferved in the brain, is evident 
 
 from 
 
Chap. XI. BRAIN and NERVES. 179 
 
 from the lofs of memory which follows when the brain 
 is injured or compreffed ; alfo from the delirium which 
 happens infome difeafes, and the Ifupor and fleepinefs 
 which happen in others. We have already obferved, 
 that the dura mater has no fenfation. 
 
 367. Another otEce of the nerves is to excite mo- 
 tions, even the moft violent ones, in the mufcles. 
 When a nerve is irritated, the mufcle to which it goes 
 is immediately convulfed ; or if it fends branches to fe- 
 A^eral mufcles, they are all convulfed at the fame time. 
 This happens during the life of the animal, and a little 
 after its death while all the parts are moift. By a great 
 irritation other mufcles are thrown into convulfions, 
 and afterwards the whole body. Nor is it neceffary 
 that the nerve fliould be whole ; for even when it is cut, 
 an irritation of it will excite fimilar motions in the muf- 
 cles. 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 
 commandediDy the will to a£l. They alfo recover their 
 motion when the compreffion is removed, provided the 
 nerve has received no hurt. 
 
 368. But the medulla of the brain, being vellicated 
 or irritated deeply in its crura, dreadful convulfions en- 
 fue throughout the whole ; and this without any excep- 
 tion, whatever be the part of the brain fo affedled ; nor 
 is there any difference in the brain, cerebellum, or corpus 
 callofum. The fame confequences alfo follow, if the 
 fpinal medulla be irritated. But if the encephalon it- 
 felf be compreffed in any part whatever, there follows 
 thence a lofs of fenfe and motion in fome part of the 
 body, which muff be the part whofe nerves are de- 
 tached from the affefted or compreffed quarter of the 
 brain. This is clearly evidenced from experiments 
 which have been made on particular parts of the brain 
 difordered : as from thofe, for inftance, in which the 
 origin of the nerves are compreffed, the voice is loft ; 
 or the motion of one arm or leg, or one fide of the 
 pharynx, is abolilhed. But in the injuries of the fpinal 
 
 A a 2 medul!a_j 
 
i8o BRAIN AND NERVES. Chap.XI. 
 
 medulla, it is ftill more evident, that thofe parts, which 
 receive their nerves arifing from the place injured in 
 the medulla, are either convulfed if that be irritated, 
 or rendered paralytic if it be comprelfed. But when 
 any more confiderable or large portion of the brain fuf- 
 fers a comprelTure, either from blood, water, fcirrhus, 
 an impadled bone, or other mechanical caufes, the 
 greateft part, and. then the whole, of the body lofes its 
 power of motion ; of thofe organs which obey the will 
 ■when the majady is in a Iclfer degree, and of them all 
 when it is greater ; all which diforders ceafe upon re- 
 moving the compreffing caufe. Lallly, if tlie fpinal 
 medulla, entering the neck, be injured, death imme- 
 diately follows ; becaufe from thofe parts principally 
 arife almoft all the nerves of the heart (99.) 
 
 369. Thefe things being conhdered, there feems to 
 be no doubt, but the caufe of a.il motion in the Iruman 
 body arifes from the brain .vidu its annexed cerebellum 
 and fpinal marrow ; and that it thence proceeds thro’ 
 the nerves to all the mufcular parts of the body. The 
 caufe, therefore, of this motion cannot refide in the 
 parts themfelves, becaufe otherwife the moving caufe 
 W'ould continue to adt after being feparated from the 
 brain; nor would it be increafed by irritating the brain, 
 or weakened by a contpreffure of it. 
 
 370. V/hether or not is there in the brain any principal 
 part, in which refides the origin of all ntotion,the end of 
 all the fenfations, and where the foul has its feat? Whether 
 is this proved by the frequent obfervation, that the fciifes 
 are fometimes entire, and that motion likewife remains 
 tho’ the brain is grievoufly hurt. Is it in the corpus cal- 
 iofum? Or is this fhewn by the greater fatality of wounds 
 or difeafes in the corpus callofum ? Is this body fuffi- 
 ciently connected with the nerves? Are there any ex- 
 periments which deduce from thence the fifth, feventh, 
 and other nerves ? Doth not the fame or even greater 
 mortality of wounds in tlie medulla fpinalis prove the 
 fame thing ? Yet this is not the feat of the foul, feeing, 
 though it is compreffed or even deftroyed, the perfon 
 
Chap. XL BRAIN and NERVES. i8i 
 
 will furvive a long time, with the perfe£l ufe of all his 
 fenl'es. Nay, this opinion is oppofed by very many facls : 
 birds have no corpus callofum ; and wounds in that bo- 
 dy are not in the leaft more mortal than thofe in other 
 parts of the brain, as appears from undoubted experi- 
 ments. 
 
 371. But neither is the pov/er of the cerebellum 
 greater in exciting the vital motions, nor are the pro- 
 provinces of vitality and animality diftindl ; nor does 
 the cerebellum produce the nerves of the heart and o- 
 ther vital organs, and the brain thofe which go to the 
 organs of fenfeand voluntary motion. From the cere- 
 bellum the fifth nerve is mofi; evidently produced ; but 
 that gpes to the tongue, pterygoide, buccinator, tem- 
 poral, and frontal, mufcles, the lap of the ear, the eye, 
 the nofirils, all which are parts either moved by the 
 will, or deftined for fenfe. Again, the fame nerve, like 
 the eighth, fends vital branches to the heart and lungs, 
 animal and voluntary ones to the larynx, and fenfitive 
 ones to the ftomach. Again, it is not even true, that 
 diforders of the cerebellum bring on fo certain and 
 fpeedy death. For certain experiments, even of our 
 own making, Ihew that it has borne wounds and fcirrhi, 
 without taking away life ; nor is it much different from 
 the brain, only that it is fofter and more tender; and 
 laflly, w'e have known, and that not very rarely, 
 wounds of the cerebellum cured. The power, how- 
 ever, of this part, in exciting convulfions, is fomewhat 
 greater. 
 
 372. Concerning the feat of the foul, we muft en- 
 quire experimentally. In the firft place, it muft be in 
 the head, and not in the fpinal marrow. For though 
 this is obftrudled, the conftancy of the mind remains 
 the fame. Again, it appears, from the experiment of 
 convulfions arifing when the inmoft parts of the brain 
 are irritated, that it lies not in the cortex, but in the 
 medulla ; and, by a probable conjedture, in the cru- 
 ra of the medulla, the corpora ftriata/ thalami, pons, 
 medulla oblongata, and cerebellum. And again, by 
 
 ' another 
 
282 BRAIN AND NERVES. Chap.XL 
 
 another not abfurd conjecture, where the origin of e- 
 very nerve lies, as the firfl; origins of all the nerves ta- 
 ken together make up the fenforium commune. Are 
 the fenfations of the mind reprefented there, or do the 
 voluntary and neceffary motions arife in that place? 
 This feems very probable. For it does not feem pof- 
 fible, that the origin of motion can lie below that of 
 the nerve ; for although it fhould be affumed gratis, that 
 fome part of the nerve is immoveable, or infenfible, 
 ■yet that is altogether fimilar to the remainder of the 
 nerve. Nor can the origin of motion (569,) be placed 
 higher than this ; for fo it will fall within the arteries, 
 which have neither the faculty of fenfation nor of vo- 
 luntary motion. It, therefore, follows, that the feat of 
 the mind mult be where the nerve firft begins its for- 
 mation or origin. 
 
 373. We come now to explain the manner In which 
 the nerves become the organs of fenfe or motion ; 
 which, as it lies hid in the ultimate elementary fabric 
 of the medullary fibres, feems to be placed above the 
 reach both of fenfe and reafon: but we fliall, notwith- 
 Ilanding, endeavour to make this as plain as experi- 
 ments will enable us. And firft, it is demonftrated, 
 that the fenfation does not come through the mem- 
 branes from the fentient organ to the brain, nor that 
 motion is fent through the coverings from the brain in- 
 to the mufcle. For the brain itfelf lies deeper than thefe 
 membranes, and receives the impreffions of fenfe, and 
 when hurt throws the mufcles into convulfions. More- 
 over, it is certain, that the nerves arife from the medul- 
 la of the brain ; the truth of which is manifeft to the eye 
 in all the nerves of the brain, more efpeciaily in the ol- 
 faCfory, optic, fourth and feventh pair of nerves, which 
 continue their medullary fabric a long way before they 
 put on the covering of the pia mater. 
 
 374. We mufl, therefore, next inquire into this me- 
 dulla, what it is. It is a very foft pulp, harder in in- 
 fers and foolilli animals; but every where fimilar to 
 itfelf. It affeClSj however, to be formed into fibres, or 
 
 parallel 
 
Chap. XL BRAIN and NERVES. i8j 
 
 parallel threads, lying upon one another lengthwife. 
 That the coinpofition of it is fibrous, appears from in- 
 numerable arguments ; more efpecially to the eye in 
 the corpus callofum, in the ftriatum, and thalami of the 
 optic nerves ; but (till more evidently in the brains of 
 filh, and efpecially in their thalami optici. Again, 
 that the fibres of the brain are continuous with thofe of 
 the nerves, fo as to form one extended and open conti- 
 nuation, appears, by obfervation, very evidently in the 
 feventh, fourth, and fifth pair of nerves. There is a 
 great deal of oil in the medulla, upwards of a tenth part 
 of its whole weight. 
 
 375. But here a controverfy begins concerning the 
 nature of this fibril, which, with others of the like kind, 
 compofes the fubftance of the medulla and of the nerves. 
 That this is a mere folid thread, and only watered by a 
 vapour exhaling into the cellular fabric which fur- 
 rounds the nervous fibres, has been aflerted by many 
 of the moderns ; but that, when it is flruck by a fen- 
 fible body, a vibration is excited, which is then con- 
 veyed to the brain. 
 
 376. But the phenomena of wounded nerves will 
 not allow us to imagine the nervous fibres to be folid. 
 For if an irritated nerve is lhaken, (and that happens af- 
 ter the manner of an elaflic chord, which trembles 
 when it is taken hold of,) the nerve ought to be made 
 of hard fibres, and tied by their extremities to hard bo- 
 dies : they ought alfo to be tenfe ; for neither foft chords, 
 nor fuch as are not tenfe, or fuch as are not well faften- 
 cd, are ever obferved to tremulate. But all the nerves, 
 at their origin, are medullary, and very foft, and ex- 
 ceedingly far from any kind of tenfion : where they 
 pafs through channels where they are well guarded, 
 they retain the fame foft texture, and are not covered 
 with membranes, as in the intercoftal nerves and the fe- 
 cond nerves of the fifth pair ; fome alfo are foft through- 
 out their whole length, whatever fize they may be of : 
 for example, the foft olfaftory and acoufuc nerves, from 
 which we would moll readily expect a tremor j as in 
 
 the 
 
i 84 brain and nerves. Chap. XL 
 
 the cafe of found. Agafn, though the nerves are hard, 
 they are foftened in the vifcera, mufcles, and fenforia, 
 before they exert their operations. Therefore, the 
 nervous fibres cannot poflibly treinulate in an eladic 
 manner, neither at their origin, nor where they are 
 tenfe. But the fame, even in the proper and moit fa- 
 vourable cafes, cannot treinulate ; becaufe, through 
 their whole length, they are firmly tied to the folid 
 parts by means of the cellular fabric ; for example, the 
 nerves of the heart are tied to the great arteries, and to 
 the pericardium. Finally, that the nerves are very far 
 from all elaflicity, is demonftrated by experiments, in 
 which the nerves, cut in two, neither fhorten nor draw 
 back their divided ends to the folid parts ; but are ra- 
 ther more elongated by their laxity, and expel their 
 contained medulla in form of a protuberance. Again, 
 the extreme foftnefs of the medulla in the brain, with 
 all the phenomena of pain and convulfion, leave no 
 room to fufpeft any fort of tenfion concerned in the 
 effedts or operations produced by the nerves. 
 
 377. Add to this, that the force of an irritated nerve 
 is never propagated upward, fo as to convulfe the 
 mufcles that are feated above the place of irritation. 
 This is a confequence altogether disagreeing with ela- 
 fticity ; for an elaftic cord propagates its tremors every 
 way, from the point of percuffion, to both extremi- 
 ties. But if neither the phenomena of fenfe nor mo- 
 tion can be explained from the nature of elafiicity, the 
 onl)' probable fuppofition that remains is, that there is 
 a liquor fent through the brain, which, defeending from 
 thence through the nerves, flows out to all the extreme 
 parts of the body ; the motion of which liquor, quick- 
 ened by irritation, operates only according to the direc- 
 tion in which it flows through the nerve : fo that con- 
 vulfions cannot thereby afeend upwards, becaufe of the 
 refiftance made by the frefli afflux of the fluid from the 
 brain. But the fame liquid being put in motion in an 
 organ of fenfe, can carry that fenfation upwards to the 
 
 brain 5 
 
Chap.XI. brain and nerves. 185 
 
 brain ; feeing it is refifted by no fenfitive torrent com- 
 ing from the brain in a contrary direction. 
 
 378. It is therefore probable^ that the nervous fibres, 
 and the medullary ones of the brain, which have the 
 fame nature, are hollow. Nor is the objedlion which 
 arifes from the fmallnefs of thefe tubes, not vifible by 
 any microfcope, of any force againft the propofed ar- 
 guments ; to which add the abfence of a fwelling in a 
 tied nerve, which, in reality, is not fufficiently true 
 with other arguments of the like kind, which indeed 
 Iliow the weaknefs of thefenfes, but have not any vali- 
 dity againfl the real exiftence of a juice or fpirit in the 
 nerves. If they are tubes, it is very probable that 
 they have their humours from the'arteries of the brain. 
 
 379. But concerning the nature of this nervous li- 
 quid, there are many doubts. ’ Many of the moderns 
 will have it to be extremely elallic, of an etherial or of 
 an electrical matter ; but the more reafonable part 
 malce it to be incompreflible and watery, but of a lym- 
 phatic or albuminous nature. Indeed it is not to be de- 
 nied, that we have many arguments againft admitting 
 either of thefe opinions. An eleClrical matter is, in- 
 deed, very powerful, and fit for motion ; but then it is 
 not confinable within the nerves, fince it penetrates 
 throughout the whole animal to which it is communi- 
 cated, exerting its force upon the flefli and fat, as well 
 as upon the nerves. But, in a living animal, the nerves 
 only, or fuch parts as have nerves running through 
 them, are affefted by irritation ; and, therefore, this li- 
 quid muft be of a nature that will make it flow through, 
 and be contained within the fmall pipes of the nerves. 
 And a ligature on the nerve takes away fenfe and mo- 
 tion, but could not ftop the motion of a torrent of elec- 
 trical matter. 
 
 380. A watery and albuminous nature is common to 
 moft of the juices in the human body, and may be 
 therefore readily granted to the juice of the nerves j 
 like the water which exhales into the ventricles of the 
 brain from the fame veflels ; alfo, from the example of 
 
 B b a 
 
iS 6 BRAIN AND NERVES. Chap. XL 
 
 a gelatinous or lymphatic juice, which flows out in cut- 
 ting through the brain in fifli, and the nerves of larger 
 animals ; to which add, the tumour which arifes in tied 
 nerves. But are thefe properties fufflcient to explain 
 the wonderful force of convulfed nerves, obfervable in 
 the dilTeftions of living animals, and even in the lefler 
 infecls, with the great ftrength of mad and hyltcricalf 
 people ? Whether or no is not this difficulty fomcwhat 
 leffencd from the hydroffiatical experiments of attrac- 
 tion in fmall tubes ; which, although it may explain the 
 ffirength and motion, is nevertheiefs inconfiffient with 
 the celerity ? 
 
 381. The nervous liquor then, which is the inftru- 
 ment of fcnfe and motion, mufl; be exceedingly move- 
 able, fo as to carry the imprellions of fenfe, or com- 
 mands of the will, to the places of their deftination, 
 without any remarkable delay : nor can it receive its 
 motions only from the heart. Moreover, it is very thin 
 and inviflble, and deliitute of all take and fmell ; yet 
 reptTvable from the aliments. It is carefully to be di- 
 ftinguilhed from that vifible, vifcid liquor exhaling from 
 the veffels in the intervals between the nervous cords. 
 
 382. That this liquor moves through tubes rather 
 than through a fpongy folid, we are perfuaded from its 
 celerity, and the analogy of the whole body ; of which 
 all the liquids, the fat excepted, run through their pro- 
 per veffels, 
 
 383. Therefore, upon the whole, rt feems to be cer- 
 tain, that, from the veffels of the cortex, a liquor is fe- 
 parated into the hollow pipes of the medulla, which are 
 continued w'ith the fmall tubes of the nerves, even to 
 their foft, pulpy extremities, fo as to be the caufe both 
 of fenfe and motion. But there will be a twofold mo- 
 tion in that humour; the one flow and conffiant, from 
 the heart ; the other not continual, but exceedingly 
 fwift, wTich is excited either by fenfe, or any other 
 caufe of motidn arifing in the brain. 
 
 384. The fame nerves moft: evidently prefide over 
 both fenfe and motion ; as we are not allowed the two 
 
 fvftems 
 
Chap. XL BRAIN and NERVES. 187 
 
 fyftems of motory nerves dlftin£l from fenfitive ones. 
 If fenfe foraetimes remains after motion is deftroyed, 
 this feems to be becaufe much more ftrength is requi- 
 red for the latter. Dying people hear and fee, when in- 
 capable of motion. 
 
 385. If it be aflced, What becomes of this nervous 
 juice, which cannot but be feparated and diftributed in 
 great abundance, from fo large a quantity of blood 
 paffing the brain very fwiftly, in comparifon of the 
 flower moving blood, from whence the milk is fepa- 
 rated in the bread:, and the urine in the lefler renal 
 artery, or by a comparifon with the mefentei'ic artery ? 
 It may be anfwered, It -exhales probably through the 
 cutaneous nerves ; the laflitude both with refpedt to 
 fenfe and motion, which may be overcome by fpiritu- 
 ous medicines, fhews that this liquid may be both loft and 
 repaired. Many have judged, that it alfo exhales into 
 the various cavities of the body ; as that of the ftomach, 
 and inteftines. We may exped: fome part of it to be 
 reforbed, that the nobleft humour of the body may not 
 be too quickly diflipated. That it nouriflies the body, 
 is incredible : it is too moveable to expedt adhefion 
 from it; that is the oflice of a flow and vifcid hu- 
 mour. 
 
 386. But then, what is the defign of fo many protu- 
 berances in the brain ? what are the particular ufes of 
 the ventricles, nates, and teftes ; with the diftindtion of 
 the brain from the cerebellum; and the communication 
 betwixt one fide of the brain, cerebellum, and fpinal 
 medulla, with their oppofite fides, by fo many tranf- 
 verfe bundles of fibres ? 
 
 387. The ventricles feem to be made of neceffary 
 confequence, and towards the greater ufe and diftinc- 
 tion of the parts. And that the corpora ftriata or tha- 
 lami might keep their medullary parts from cohering 
 one to another, it was neceffary for a vapour to be 
 poured betwixt them ; and the fame is true with re- 
 gard to the brain and cerebellum. Perhaps, likewife, 
 she neceflity of adminiftring a degree of warmth to the 
 
 B b 2 clofe 
 
l88 
 
 BRAIN AND NERVES. Chap. XI. 
 
 clofe medulla of the brain may be one reafon for thefe 
 cavities, by which the arteries enter, and are diitribu- 
 ted in great numbers. Perhaps alfo it was proper, that, 
 in the inmoft parts of the brain, fmall veffels only, with- 
 out any large ones, (hould enter. We may alfo fufpect, 
 that the foftnefs of the fibres of the brain requires fhort- 
 nefs, in order to fuftain their own weight. 
 
 388. The ufes of mod of the protuberances we are 
 rot acquainted with, but have them yet to learn from 
 difeafes, and from anatomical experiments made on ani- 
 mals having a brain like that of mankind.. But, in 
 thefe refpefts, we have little hopes of fuccefs, in parts 
 that are fo fmall, fo deeply, and fo difficultly fituated, 
 and hardly ever to be approached but by a wound foon 
 fatal. Whether thefe parts are fo many diftincl pro- 
 vinces in which our ideas are ftpred up, and w'hether 
 this be confirmed by the protuberant thalami of the op- 
 tic nerve, are indeed queftions. But then mod of thefe 
 protuberances fend out no nerves at all. 
 
 389. As to the internal communication of one part 
 with the other by drim or duels; that feems to conduce 
 to the advantage of motion, and probably of fenfe like- 
 wife. Some of thefe communications join the brain 
 with the cerebellum ; others join the fpinal medulla with 
 the nerves of the brain itfelf, as in the acceffory nerve ; 
 and mod of them join the right and left parts together, 
 as in the anterior commixture (345.), and in the tw’o 
 poderior (350.), in that of the corpus callofum (343.), 
 in the driae betwixt a procefs of the cerebellum and 
 tedes (354.); to w'hich add the medullary crofs- bars in 
 the medulla oblongata and fpinalis (:?55.) For, from 
 this drudlure, it feems inanifedly to follow, as well as 
 from numberlefs experiments and obfervations, that, 
 W'hen the right fide of the brain is injured, all the nerves, 
 which belong on the contrary to the left fide of the 
 body become difeafed or paralytic, and the reverfe. 
 Moreover, by this contrivance, nature feems to have 
 provided, that, in whatever part of the brain any injury 
 may happen, the nerve that arifes from thence is, by 
 
Chap. XI. BRAIN and NERVES. 
 
 this means, not always deprived of its ufe. For if the 
 faid nerve receives its fibres by communicating bundles, 
 as well from the oppofite as from its own hemifphere 
 of the brain, its office may, in fome meafure, be conti- 
 nued entire by the fibres which it receives from the 
 oppofite fide, even after thofe of its own fide are de- 
 flroyed. Accordingly we have numberlefs inflances of 
 wounds, and with a confiderable lofs of fubftance from 
 the brain, which yet have not been followed with in- 
 jury to any nerve, or to any of the mental faculties. 
 Many other lefs inequalities, ftripes, protuberances, and 
 nerve-like iinpreffions, appear in the brain from mecha- 
 nical necefiity, with the pulfation of the veffels, and the 
 prelTure or figure of the continuous incumbent parts. 
 
 390. We have before declared, that the nerves arc 
 -the organs of fcnfe and motion ; we- fhal! therefore 
 proceed firfl to explain that motion before we defcribe 
 the organs of fenfe ; becaufe it is more fimple, uniform, 
 and perpetually exercifed, even in the fetus, before any 
 of the fenfes. 
 
 CHAP. xn. 
 
 Of Muscular Motion. 
 
 391. ^ I HE organ of motion in the human body is 
 X not fingle. And firfl, in every animal and 
 vegetable fibre, alfo in hair, feathers, in membranes, 
 the cellular texture, and in the humid mufcular fibre j 
 again, in animal and vegetable gluten; there is a con- 
 traflile power, which both refifls the lengthening out 
 of its fubftance, and, when the extending power is ta- 
 ken away, reftores the fibre, to its former fize; nor 
 does this power ever ceafe endeavouring to bring the 
 elementary particles into the clofeft contadl the mecha- 
 nifm of the part can admit. After death, even for 
 many days, it does the fame, fo that the fibres of a dir 
 vided mufde contrafl towards each extremity, fo as to 
 
 leave 
 
190 MUSCULAR MOTION. Chap. XII. 
 
 leave a wide gap in the middle. An artery, when cut, 
 iikewife contradhs itfelf in length. 
 
 392, I call this force becaufe it continues to 
 
 be efficacious after death, and fo is different from the 
 powers of life. In the living animal indeed it is forne- 
 what briflcer : for, both from cold and fear, the Ikin 
 is moved, fo that it grows harder, and has its papillae 
 erected, and along with this hardnefs contracts itfelf in 
 length. Again, the cellular fibres are animated with 
 this perpetual nifus to fnorten themfelves, and always 
 tend to their own'contraftion. Hence, when the Ikin 
 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 ffiortnefs. But it even fomewhat 
 refills the attempt to perpetual dillention ; and by a 
 gentle but continual acceffion of its ovm elements, pro- 
 pels the contained fat or water, or otiier bodies acci- 
 dentally introduced. The fame power alfo feems to 
 limit the excretion of vapour ; for the fibres and plates 
 of the cellular texture being preternaturaJly relaxed, 
 an immenfe quantity either of fat or of wmtery humour 
 is depofited in that texture. And this debility feems 
 to be the principal caufe of a true drcpfy. The fame 
 caufe being always efficacious, and at work in the 
 heart, joints, and every w’here throughout the body of 
 the embryo, brings into nearer contadl the arteries, 
 auricles, and ventricles ; produces flexures ; and contracts 
 the heart, when in a manner diffolved, into a cone. The 
 fame, by an unknown or hidden power, feems to form 
 the lhape of molt parts of the human body ; and while 
 it expels the gluten received into the cells, brings the 
 terreftrial particles nearer to one another, and gives 
 the proper folidity, curvature, and fituation, to the dif- 
 ferent parts. 
 
 393. It is the nature of this power to aft continual- 
 ly by a gentle but uninterrupted eftort. It is common 
 for it alfo to be excited by poifons, in every membrane, 
 fibre, and cellular texture ; but never by cutting or 
 punfturing with an iron inllrument. Thefe are the 
 
 knowm 
 
Chap. XII. MUSCULAR MOtlON. 
 
 known properties of the red mufcular fibre. The 
 ftrudtureof this fibre, then, it is nowneceffary for us to 
 confider. 
 
 39.^. By the name of mufcular .fibres in the human 
 body, we call bundles of reddifii -coloured threadsj 
 which perform all the motions of which we are fenfible. 
 When many of thefe 'fibres are collected together, and 
 appear more evidently red, they are called a mufcle. 
 The extreme fimplicity of the fabric in thefe parts has 
 been the caufe of the obfcurity that prevails in under- 
 ftanding how a fmall, foft, flefiiy portion can produce 
 fuch flrong and ample motions as we fee in man, but 
 more efpecially in the cruftaceous infects. 
 
 395. In every mufcle we meet with long foft threads 
 or fibres, fomewhat elaftic or extenfible, and almoft 
 conllantly difpofed parallel with each other ; and thefe, 
 being furrounded with a good deal of cellular fubftance, 
 are by that fattened together into little bundles. Thofe 
 bundles, called lacertuli, are again tied together into 
 larger bundles, by a more loofe cellular net- work, which 
 contains fome fat ; and betwixt thefe we conllantly 
 perceive membranous partitions and ftripes of the cel- 
 lular fubftance, removing them farther from each o- 
 ther, till at laft a number of them, combined together 
 in a pofture either parallel or inclined, are furrounded 
 with a more thin and denfe cellular membrane, conti- 
 nuous with that of their partitions ; and this being a- 
 gain furrounded by a thicker plate of the cellular fub- 
 ftance, externally parts the whole from the adjacent 
 flelh, and gives it the denomination of a fingle or entire 
 mufcle. In every one of thefe threads there appears a 
 lelfer feries of filaments, which, by oblique extremities, 
 are cemented to others of the fame kind, forming toge- 
 ther a larger fibre. 
 
 396. The generality of the mufcles, but more efpe- 
 cially thofe which are inferred into the bones, and fuch 
 as are prefled ftrongly by other flefhy incumbent parts, 
 do not confift of fibres altogether of one kind. For 
 the fielhy fibres (395 •)? being collefled together, caufe 
 
 the 
 
192 MUSCULAR MOTION. Chap. XII. 
 
 the mufcle to be thicker in the middle, which is called 
 its belly : and the fame fibres, degenerating by degrees 
 obliquely at each end of the mufcle into a more fiender, 
 hard, and fliining fubllance of a filver colour, in which, 
 meeting clofer together, the . cellular fubftance inter- 
 pofed is thinner, Ihorter, and painted with fewer vef- 
 fels ; they then become indolent and difficultly irritable, 
 and receive the denomination of a tendon, by being col- 
 lected together into a round fiender bundle ; or clfc, 
 if it expands into a broad flat furface, it is called an apo- 
 neurofis. The cellular texture which covers the whole 
 tendon is called its vagina or fheath, and refembles the 
 coat of a mufcle. For that the flefhy fibres truly change 
 into fuch as are tendinous, is evident from comparing a 
 fetus (in which there are very few tendons) wdth a child 
 of fome years growth, in which there are many more ; 
 and both with an adult or old perfon, in which are the 
 greatefl number. Mufcles, which are not inferted in- 
 to any of the bones, have commonly no tendons, as 
 the fphinCers and mufcular membranes of the vifeera 
 and vefiels. But thofe commonly end in long tendons, 
 which are required to pafs round the joints and heads 
 of the bones, to be inferted in thofe extremiities w’hich 
 are more moveable. In a fetus the mufcles are evi- 
 dently inferted into the periofteum only ; but in adults, 
 w'here the periofleum is more clofely joined with the 
 bone itfelf, the tendons, being confufed with the peri- 
 ofleum, pafs together with that even into the foveoli 
 of the bone. 
 
 397. The tendinous fibres indeed often lie in a 
 flraight line with the flefliy ones, and are as it were a 
 continuation of them. But it is not at all rare for the 
 flefliy fibres to be obliquely inclined to the tendon, and 
 to adhere to it, as the tendon itfelf grows thicker in 
 its progrefs by continually receiving new fibres. This 
 is called a tendinous mufcle. Other tendons lie in the 
 middle- betwixt two plates of fibres, forming an obtufe 
 angle with one another, at irregular diflances, in their 
 defeent. There are inflances of numerous tendons 
 
 pennated 
 
Chai>. XII. MUSCULAR MOtlOJ^. 19^ 
 
 pennated in different places formed into one mufele. 
 There are alfo other methods by which the tendinous 
 ftbres are joined with the flefliy ones. 
 
 gp8. Within the cellular tunic that furrounds the 
 fibres, the arteries and veins are fubdivided into net- 
 works, which commonly form right angles, run in com- 
 pany, and moftly contiguous with each other ; and from 
 the fmaller of thefe veffels a vapour is exhaled into the 
 thinner cellular fubftance, as the fat is alfotransfufed into 
 the thicker cellular fubftance ; from whence again they 
 are both abforbed. The lymphatic veffels, which run be- 
 twixt the mufcles of the tongue, with thofe of the neck, 
 face, and limbs, are difficultly demonftrated. But there 
 are alfo nerves more numerous than in other parts, di- 
 ftributed together with the blood-veffels throughout the 
 cellular fabric of the mufele ; which nerves, however, 
 depofite their harder covering, and become foft, and 
 difappear before they can be traced to their ultimate 
 extremities. Thofe enter the mufele in many parts, 
 without keeping to the fame place or fituation. In the 
 tendons they cannot be demonftrated. Nor are there 
 any nervous fibres invefting the mufcular bundles or 
 portions fo as to conftringe them ; for they, who have 
 given fuch a defeription, have feen nothing but the 
 cellular fubftance. 
 
 399. The fabric of the leaft, which are as the ele- 
 ments of a mufele, being inveftigated by the microfeope 
 in man and other animals, has always appeared fimilar 
 to the fabric of the larger fibres ; nor do they yield any 
 other appearance, upon which we can rely, than that 
 of the leaft threads joined one to the other by the in- 
 termediate cellular fubftance. There is, therefore, no 
 foundation here for a feries of veficles, nor for a chain 
 of rhombs. It may be afked, whether thefe fibres are 
 hollow, whether they are continued with the arteries, 
 or whether the difference betwixt mufcular and tendi- 
 nous fibres lies in the latter being rendered more denfe 
 and beat clofer together by an expulfion of the fluids ? 
 That thefe are not probable, appears from the minute- 
 
 C c nefs 
 
194 MUSCULAR MOTION- Chap. XIL 
 
 nefs of the fibres, which are found lefs than the red- 
 blood globules, and from the whitenefs of a mufcle af- 
 ter the blood is walhed out of it ; to which add the phy- 
 fiological reafons following, (41 1 .) And, in general, 
 more ftrength may be expeSed from a folid fibre. 
 
 400. A mufcle therefore is endowed at lead with a 
 threefold force. Firft, the dead one, in common to it 
 with other animal fibres. Another, which we have call- 
 ed the vis infita^ and which has different phenomena 
 from the former. For it is more proper to life, and the 
 firft hours after death, and difappears much fooner than 
 the dead one. Again, in moft cafes, it afts by alternate 
 ofcillatioris ; fo that, being driven hither and thither, it 
 fometimes contrails the mufcle towards the middle : 
 fometimes again it extends the mufcle from the middle 
 towards the extremities, and fometimes alfo it has a rei- 
 terated motion. Moreover, it is manifeftly quicker, and 
 performs the greateft motions ; the dead force, only 
 fuch as are finall and not eafily obferved. It is excited 
 both by the pricking of an iron inftrument, and in the 
 hollow mufcles by inflated air, by water, and every 
 kind of acrimony, but moft powerfully of all by a tor- 
 rent of eleftrical matter. Laftly, it is proper to the 
 mufcular fibre, and is found in no other part of the 
 human body with the qualities abovementioned. But 
 we muft give a more particular explication of its phe- 
 nomena. 
 
 401. It is natural to every mufcle to fhorten itfelf, by 
 drawing the extremities towards its belly or middle. 
 But to difeover the moving power of a mufcle from the 
 fabric which we have deferibed, it will be of ufe to 
 confider the appearances obfervable in the mufcular 
 contra( 3 ;ion. Every mufcle then becomes fhorter and 
 broader in its action. But this contraction of its length 
 is various ; in fome more, in others lefs ; and is very 
 confiderable, for example, in fome of the fphinfters, in- 
 fomuch that they appear to be contracted more than 
 one third of their extent, though this computation be 
 taken from an erroneous hypothefis. 
 
 402. The 
 
Chap. XIL MUSCULAR MOTION. ip5 
 
 402. The inteftines are exceedingly tenacious of 
 their vis infita, as they continue to contradl themfelves 
 long after they are taken out of the body, and even af- 
 ter they are cold. The heart is even more tenacious 
 thart thefe, if you confider all things ; as is moft evident 
 in a young chicken, and in cold animals. Different 
 mufcles are beft excited into adlion by different flimu- 
 li ; as the bladder by urine, the heart by the blood, and 
 the inteftines by air. Though the nerves are removed, 
 or the conne< 9 :ion made by them between the mufcles 
 and the brain cut off, the mufcles lofe but little of their 
 irritable nature. It appears alfo from tbe example of 
 polypi and other infeds, that the fame irritable difpofi- 
 tion extends very widely through the animal fibres. 
 Thefe creatures have neither brain nor nerves, yet are 
 exceedingly impatient of ftimulus, Laftly, we may ga- 
 ther this from the affinity of plants ; of which very many 
 flowers and leaves open or contrad according to the 
 various degrees of heat and cold, feme even very quick- 
 ly, fo that they are nothing inferior in this refped to 
 animals. Neither does this depend upon weight, at- 
 tradion, or elaftlcity, feeing it is feated in a foft fibre, 
 and vanifhes when the fame grows hard. 
 
 403. But that the caufe of motion is conveyed thro* 
 the nerves into the mufcles, is certain from the experi- 
 ments before-mentioned (367. et feq.) For the nerve a- 
 lone has any feeling ; this alone carries the commands of 
 the foul ; and of thefe commands there is neither intima- 
 tion nor perception in that part whofe nerve is either tied 
 or cut, or which has no nerve. Moreover, on irritating 
 the nerve or fpinal marrow, even in a dead animal, the 
 mufcle or mufcles which have nervous branches from 
 thofe parts are moft vehemently convulfed. When the 
 nerve of any mufcle is cut or tied, or the bafis of the 
 fpinal marrow compreffed, or that part of the brain 
 from whence the nerve has its origin, the mufcle be- 
 eomes paralytic, and languiffies, and cannot by any force 
 be recalled into adion fimilar to the vital one. But if 
 the ligature be taken off from the nerve, the force 
 
 C c 2 by 
 
196 MUSCULAR MOTION. Chap. XII. 
 
 by which the mufcle is put into action is again reco- 
 vered by it. The nerve being irritated below the 
 place where it is cut, the mufcle to which that nerve 
 goes is contraded. This appears from numerous ex- 
 periments, efpecially thofe made on the phrenic and 
 recurrent nerves. 
 
 404. This force is not the fame with the vis infita. 
 The former comes to the mufcle from without ; where- 
 as the other refides conflantly in the mufcle itfelf. The 
 nervous power ceafes when life is deftroyed j after which 
 the other, from certain experiments, appears to remain a 
 long time : it is alfo fuppreffed by tying a ligature upon 
 the nerve, by hurting the brain, or by drinking opium. 
 The vis infita lulfers nothing from all thefe ; it remains 
 alter the nerve is tied ; and continues in the inteftincs 
 though taken out of the body, and cut in pieces; it 
 appears with great flrength in fuch animals as are defli- 
 t'lte of brain : that part of the body is moved which has 
 no feeling ; and the parts of the body feel which are 
 without motion. The will excites and removes the ner- 
 vous power, but has no power over the vis infita. 
 
 405. In the motion of the mufdes, whether owing 
 to the vis infita or the nervous power, the fibres are 
 contracted towards the middle of its belly, and recede 
 from one another outwards : they are alfo diverfified 
 with various tranfverfe wrinkles : the whole mufcle al- 
 fo becomes Ihorter, and draws its extremities towards 
 the middle ; hence it draws towards each other thofe 
 parts with which it was connedled, in the reciprocal ra- 
 tio of their flrength ; the mufcle alfo fwells by its con- 
 tradion, becoming hard at the fame time, and as it 
 were increafes its circumference on every fide. I have 
 never obferved it to turn pale. Whether on the whole 
 it is increafed in bulk, or acquires more in breadth than 
 it lofes in length, is difficult to be known. It draws al- 
 ter it the tendons, which are obfequious to its motions, 
 though of themfelves neither moveable nor irritable. 
 The whole mufcle is alfo capable of being moved at 
 once, or only a part of it : if one extremity is fixed to 
 
 an 
 
Chap. XII. MUSCULAR MOTION. 197 
 
 an immoveable part, that only , is moved which is capable 
 of yielding. 
 
 z}o6. If it be demanded, Whether the arteries' con- 
 duce any thing to mufcular motion ? and whether the 
 palfy, which falls upon the lower limbs after a ligature 
 upon the aorta, be not an argument thereof? we an- 
 fwer, Not at all, further than as they conduce to the 
 integrity of a raufde, or to. the, confervation of the mu- 
 tual ftrufture and. habit of the parts, which they fupply 
 with vapour, fat, &c : for the irritation of an artery 
 does not affe<T or convulfe the mufcle to which it be- 
 longs ; nor does a ligature thereof caufe a palfy, unlefs 
 after a confiderable time, when the mufcles begin to be 
 deftroyed by a gangrene. Moreover, it is impracti- 
 cable to explain the motion of peculiar mufcles from a 
 caufe derived with an equal force from the heart to all 
 parts of the body. Laltly, the influence of the will is 
 confined to the nerves, without refiding in the arteries 
 or other folid parts of the body. 
 
 407. But the diredt manner by which the nerves 
 excite motion in the mufcles, is fo obfeure, that we may 
 almofl: for ever defpair of its difeovery. And firft, con- 
 cerning the vis infita, we do not indeed inquire ; as this 
 feems to be a more brifk attradion of the elementary 
 parts of the fibre by which they mutually approach each 
 other, and produce as it were little knots in the middle 
 of the fibre. A flimulus excites and augments this at- 
 tractive force, which is placed in the very nature of the 
 moving fibre. The other explanations are hypothefes. 
 
 As to nervous veficles fwelling by a quicker flux of the 
 nervous fpirits, they are inconfiflent with anatomical 
 truth, which demonftrates the leafi vifible fibres to be 
 cylindrical, and in no part veficular ; and likewife repug- 
 nant to the celerity with which mufcular motion is per- 
 formed, and with the bulk of a mufcle being rather di- > 
 
 minifhed than increafed during its adion. Again, 
 the inflation of rhomboidal chains in the fibres is e- 
 qually repugnant to the celerity, to infpedion, and to 
 anatomy ; they would alfo occafion an immenfe wafle 
 
 of 
 
198 MUSCULAR MOTION. Chap. XII. 
 
 of ftrength, and after all render the mufcle but little 
 fhorter. The nerves want that irritable nature which 
 is obl’erved in the mufcular fibre. Finally, it is by no 
 means demonftrable,that the fibres, from fo few nerves, 
 can be fo munerous, or dillributed info many different 
 tranfverfe direftions, with refpect to the mufcular 
 threads, as thofe hypothefes require to be allowed. A 
 complication of the nerves round the extremities or fi- 
 bres, fo as to contract them by their elafficity, is found- 
 ed upon a falfe ftrufture of the mufcular fibre, fuppo- 
 fmg the nerves to be diftributed, where filaments of the 
 cellular fubftance only can be demonllrated. More- 
 over, the phenomena of animals which, having neither 
 brain or nerves, are yet very apt for motion, apparent- 
 ly demonlfrate the intrinfic fabric of the mufclcs to be 
 fufficient for their motion, without other affiftance from 
 the nerves. Other explanations, derived from fphe- 
 rules full of air in the blood, fuppofe a falfe nature of 
 that fluid ; namely, a repletion of it with elaftic air, of 
 which it has none, (281.) The animal fpirits are not 
 of the nature of an electric torrent. 
 
 408. If we may add any thing to thefe phenomena, 
 you may fuppofe the nervous liquor to be ofa flimulating 
 nature, by which means it forces the elementary par- 
 ticles of the mufcular fibre to approach nearer to each 
 other. The motive caufe which occafions the influx of 
 the animal fpirits into the mufcle fo as to excite it into 
 action, feems not to be the foul, but a law derived im- 
 mediately from God. For animals newly born, or 
 newly transformed, without any attempt, or exercife, 
 know how to execute compound motions very difficult- 
 ly to be defined by calculation. But the foul learns 
 thofe things which it does, very flowly, iinperfecfly, 
 and by making experiments. That mufcle then is con- 
 trafted which in a given time receives more of the ner- 
 vous fluid, whether that be occafioned by the will, or 
 by fome irritating caufe arifing in the brain, or applied 
 to the nerve. 
 
 409. But, tho’ you may conjedure the foul to be the 
 
 caufe 
 
Chap.XIL muscular MOTION. 199 
 
 caufe of the nervous motion, you cannot do the fame 
 with regard to that arifing trom the vis infita. The 
 heart and inteftines, alfo the organs of generation, are 
 governed by a vis infita, and by ftimuli. Thefe pov/ers 
 do not arife from the will; nor are they lelfened, or ex- 
 cited, or fuppreffcd, or changed by the fame. No cuf- 
 tom nor art can make thefe organs fubjedl to the will, 
 which have their motions from a vis infita ; nor can it 
 be brought about, that they fliould obey the commands 
 of the foul, like attendants on voluntary motion. It is 
 fo certain that motion is produced by the body alone, 
 that we cannot even fufpeft any motion to arife from a 
 fpiritual caufe, befides that which we fee is occafioned 
 by the will ; and, even in that motion which is occa- 
 fioned by the will, a ftimulus will occafion the greateft 
 exertions when the mind is very unwilling. 
 
 410. There feems to be this difference between the 
 mufcles obeying the will, and thofe which are gover- 
 ned by a vis infita ; namely, that the latter, being more 
 irritable, are very eafily excited into motion by a gentle 
 ftimulus; as for inftance, the heart and inteftines; 
 which organs are moft manifeftly, and greatly, and 
 conftantly, irritable. On the other hand, the mufcles 
 which obey the will, are neither endowed with fo great 
 nor fo durable a power of this kind. Hence, they ei- 
 ther ftand in need of the power of the will, or a ftronger 
 ftimulus ; by which, indeed, when they are excited, 
 even thefe are animated to motion againft the will. 
 Thus it happens, that, in apoplexies, the mufcles which 
 obey the will, languifh, and become paralytic, as being 
 deftitute of all influx from the brain ; while the vital 
 mufcles, having no occafion for the operation of the 
 brain, continue to be excited into contraftion by their 
 ftimuli ; the heart by the blood, and the inteftines 
 by the air and aliments. 
 
 411. The ftrength of this adion in the mufcles is ve- 
 ry confiderable in all perfons, but more efpecially in 
 thofe who are phrenetic, and fome who are called ftrong 
 men ; fince frequently, with the ufe of a few mufcles 
 
 only. 
 
200 
 
 MUSCULAR MOTION. Chap. XIL 
 
 only, they will eafily raife a weight equal to, or much 
 greater than, that of the whole human body itfeif. For 
 even in one who is in his fenfes, very {lender mufoles 
 fuffice to elevate 200 or 300 pounds. The mufcles of 
 the back will even fuftain 3000. Notwithftanding this, 
 we fee, that much the greater part of the force or 
 power exerted by a mufcle is always loil without pro- 
 ducing any vifiblc efFed;. For all the mufcles are in- 
 ferted nearer the point or centre of motion, than the 
 weights they are applied to ; and therefore their aclion 
 is weaker, in the fame proportion as they move a Ihor- 
 ter part of the lever, than that to which the weight is 
 applied. Moreover, in moft of the bones, efpecially 
 thofe of the limbs, the mufcles are inferred at very acute 
 angles; whence again the effect which a mufcle exerts 
 in aefion, is proportionably lefs as the fine of the angle 
 intercepted betwixt the bone and the mufcle is lefs than 
 the whole fine. Again, the middle part of all mufeu- 
 lar force is loft, becaufe it may be reckoned as a cord 
 extended, and drawing ah oppofite weight to its fixed 
 point. Again, many of the mufcles are feated in the 
 angle of two bones, from one of which arifing they 
 move the other ; and therefore, that bone being moved, 
 they are bent, and of courfe, like an inflectsd cord, re- 
 quire a new force to extend, them. Many of them pafs 
 over certain joints, each of which they bend in fome de- 
 gree, wkereby a lefs part of their remaining force goes 
 to bend the joint to which they are particularly defti- 
 ned. The flefliy fibres themfelves of the mufcles fre- 
 quently intercept angles with the tendon in wdiich they 
 terminate ; from whence a great part of their force is 
 loft, as much as is equal to the difference or deviation 
 betwixt the fine of the angle of their infertion and the 
 whole fine. Finally, the mufcles move their oppofed 
 weights with the greateft velocity and expedition, fo as 
 not only to overcome the equilibrium, but likewife to 
 add a confiderable celerity to the weight. 
 
 412. Ail thefe Ioffes of power being computed, make 
 it evident, that the force exerted by mufcles in their 
 
 con- 
 
2Qi 
 
 Chap. XII. MUSCULAR MOTION. 
 
 contraction, is exceeding great beyond any mechanical 
 ratio or proportion whatever ; fmce the effedl is fcarce 
 ia of the whole force exerted by the mufcle, and yet 
 only a ftnall number of thefe mufcles, weighing but a 
 few pounds, are able not only to raife fome thoufands 
 of pounds, but alio with a confiderable celerity. Nor 
 is this to be reputed any defeft of wifdom in the Crea- 
 tor. For all thofe Ioffes of power were neceffary to- 
 wards a juft fymmetry or proportion of the parts, with 
 the various motions and celerities required by the muf- 
 cles to afl in different diredtions ; all which have no 
 fliare in the compofition of engines mechanically. But 
 we may, however, conclude from hence, that the adlion 
 of the nervous or animal fluid is very powerful, fmce, 
 in an engine fo fniall, it can exert a force equal to fome 
 thoufand pounds for a confiderable time, or even for 
 many days together ; nor does this feem to be otherwife 
 explainable, than by the incredible celerity by which 
 the influx of this fluid obeys the command of the will. 
 But how, or from whence, it acquires fuch a velocity, 
 is not in our power to fay ; it is fufficient, that we know 
 the laws of its motion are fuch, that a given adfion of 
 the will produces a new and determinate celerity in the 
 nervous fluid or juice. 
 
 413. The eafy and fudden relaxations of mufcles in, 
 their motion are aflifted by the adtions of their antago- 
 nijl mufcles. Namely, in all parts of the body every 
 mufcle is counterpoifed by fome weight, elaflicity, an 
 oppofite mufcle, or a humour adting againfl the cavity 
 of a mufcle, by which it is expelled. This caufe, which 
 is a vis infita, continually operates as long as the mufcle 
 adls; and fo foon as the additional celerity derived from 
 the brain abates, it reflores the limb or other part im- 
 mediately to its former eafy flate, in which there is an 
 equilibrium betwixt the mufcle and its oppofmg caufe. 
 Whenever the antagonift power is removed from the 
 mufcle, there are none of them but muff contradf, ex- 
 tending their oppofites, by which the diflended nerves 
 excite an uneafy fenfe, and caufe a ftronger endeavour 
 
 D d towards 
 
202 MUSCULAR MOTION. Chap. XII, 
 
 towards recovering the equilibrium. Hence one of the 
 flexor mufcles being cut in two, the extenfor operates 
 even in a dead body ; and the reverfe. 
 
 414. But there are other means, by which the mo- 
 tions of the mufcles are rendered more fafe, certain, and 
 eafy. The large long mufcles, by which the greater 
 motions of flexure are performed, being included in 
 tendinous capfules or cafes, drawn and tightened by o- 
 ther mufcles, are thus fecured and ftrengthened ; for fo 
 the mufcle remains prelTed againfl: the bone, in a ftatc 
 of contraftion, all the time that the limb is bent, and 
 avoids a confiderable lofs of its power. But the long 
 tendons, which are incurvated or extended over joints 
 in their motion, are received and confined by peculiar 
 bands, which retain them within their flippery channels, 
 and keep them from flipping out under the fkin ; which 
 diflocation of the tendon, whenever it happens, is at- 
 tended with a cramp of the mufcle, fevere pain, arid lofs 
 of motion. The fame kind of guidance or direftion is 
 received by fomc of the mufcles, which perforate others 
 in their courfe. In other parts, the tendons are cither 
 carried round certain eminences of the bone, in order 
 that they may be inferted at greater angles into the 
 bone which they inove; or elfe they are inferted into 
 another bone, from whence a different tendon defeends 
 under a larger angle into the bone to be moved. In 
 other parts, the mufcles which are derived from conve- 
 nient fituations, have their tendons carried round in a 
 contrary diredlion by nature, fo that they pafs into the 
 part to be moved as it were round a pully. Nature has 
 likewife furrounded the mufcles on all fides with fat, 
 which is fpread alfo betwixt their bundles of fibres and 
 the fmall fibres themfelves which lie contiguous toge- 
 ther ; which fat, being prefled out by the turgefcencc 
 of the mufcles and fibres, renders them foft, flexible, 
 flippery, and fit for motion. 
 
 4 1 6. Moreover, the pow’er and action of one mufcle 
 is determined by the co-operations or oppofitions of o- 
 thers, which ferve either to hold firm feme part from 
 
 whence 
 
Chap. XII. MUSCULAR MOTION. 203 
 
 whence the mufcle arifes, or to bend it together with 
 the mufcle, or elfe to change its aiftion from the per- 
 pendicular to the diagonal, by concurring to affift its 
 force at the fame time. The mufcles alfo affiil one a- 
 nother, even thofe which are feparated at a confider- 
 able diftance, the firfl keeping the bone firm which is 
 not to be moved, and out of which the fecond arlfe. 
 Therefore, the adlion of no one mufcle can be under- 
 ftood from confidering it alone ; but all the others mufl 
 likewife be brought into the confideration, which are 
 either inferted into the mufcle itfelf, or into any of the 
 parts to which the faid mufcle adheres. 
 
 417. By thefe mufcles, varioufly confpiring and op- 
 pofing each other, are performed walking, (landing, 
 flexion, extenfion, deglutition, and all the other ge- 
 ftures and offices of the feveral parts in the living body. 
 But the mufcles have likewife fome common or public 
 actions, by which they are of ufe to the whole animal. 
 They haften the return of the venous blood, by pfefs- 
 ing it out from the veins both of the mufcles them- 
 felves as well as of the veins which lie betwixt them ; 
 for the blood in thefe velTels, diftributed betwixt the 
 turgid bundles of a contradled mufcle, is, by the valves, 
 determined towards the heart only : they likewife re- 
 turn the fat to the blood ; and (hake, grind, or denfi- 
 fy the arterial blood, and return it quicker to the 
 lungs. Again, in the liver, mefentery, womb, &c, 
 they promote the courfe of the contained blood, bile, 
 and other juices, fo as to leffen the danger of their ftag- 
 nation : they ferve alfo to incrfeafe the (Irength of the 
 (tomach, by adding their own (Irength to it, whereby 
 digeftion is prorqoted; infomuch that ail fedentary and 
 inadive courfes of life are contrary to nature, and pave 
 the way to difeafes from a (lagnation of the humours, 
 or from a corruption or crudity of the aliments. The 
 large mufcles, which are generally placed round any 
 of the cavities of the body, propel the blood con- 
 tained in that cavity, and prefs it towards the heart. 
 But by too much exercife or ai^ion, the mufcles 
 D d 2 them- 
 
204 MUSCULAR MOTION. Chap. XII. 
 
 themfelves grow hard and tendinous on all fides ; render 
 the parts upon which they are incumbent cartilaginous, 
 or elfe change thofe which are membranous into a 
 bony nature ; increafe the roughnefs, protuberances, 
 and procefles, of the bones which lie next to them, 
 and excavate their flat parts ; dilate the cells feated in 
 the diploe; and bend the bones towards thefe parts. 
 
 418. The mufcle which the (limulus has ceafed to 
 irritate, or for the action of which the mind has no oc- 
 cafion, is relaxed, and grows foft ; its wrinkles are fill- 
 ed up, and grow plain ; its fibres are rendered longer, 
 receding from the middle towards the fixed extremi- 
 ties ; and its fwelling falls. Whatever is the caufe of 
 additional contraftion is then taken away ; but that re- 
 mains without which the mufcle never is as long as it is 
 alive. Nor is this the work of an antagonifl: mufcle, 
 although it may be aflifled by it. It may be alked. 
 What becomes of the fpirit that is fent forth from the 
 brain ? A part of it perhaps exhales ; I fufped a part to 
 adhere to the fibre ; and that thus it happens that the 
 mufcles grow ftrong with exercife, and their brawny 
 parts become thicker. 
 
 CHAP. XIII. 
 
 '' Of the Senfe ^ T o u c H. 
 
 4^9* T^UE other oflice of the brain and nerves is 
 X to perceive ; that is, to fuflPer a change from 
 the a£tions or impreflions of external bodies, and there- 
 by excite other correfponding changes or reprefcnta- 
 tions in the mind. We fhall, therefore, fir ft lead our 
 examination to each of the fenfes in particular; and 
 then confider what is common to all of them, with 
 the changes which follow from thence in the common 
 fenfory and in the mind. 
 
 4’o. The fenfe of touch is underftood in a twofold 
 manner. For, by this term, in general, we call all 
 
 changes 
 
Chap. XIII. TOUCH. 205 
 
 changes of the nerves, arifing from heat, cold, rough- 
 nefs, fmoothnefs, weight,, moifture, drynefs, or other 
 affections of external bodies, in whatever part or organ 
 they are applied to caufe a change. In this fenfe, the 
 touch is afcribed to almoft all parts of the human bo- 
 dy, tofome more, toothers lefs; as in different places 
 of the body the nerves are more numerous and bare, or 
 covered with more tender membranes ; and thus even 
 pain, pleafure, hunger, third, anguifh, itching, and 
 the other fenfations, belong to the fenfe of feeling. 
 
 42 i. But, in a fomewhat different and more proper 
 acceptation, the fenfe of touch is faid to be the change 
 arifing in the mind from external bodies applied to the 
 fkin, more efpecially at the ends of the fingers. For, 
 by the fingers, we more accurately diftinguifli the tan- 
 gible qualities of things than by other parts of our body. 
 
 422. Indeed, this fenfe does not eafily diftinguifli 
 any particles by the fkin, which it does not touch. But 
 fince the touch is more peculiarly afcribed to the cuta- 
 neous papillae, therefore the ftrudure of the fkin is to 
 be firft defcribed. That part, then, which is called the 
 true jk'in, is compofed of a thick cellular net-work, 
 whofe fibres and plates are clofely compared and in- 
 terwove together in an intricate manner, which renders 
 }t porous, and capable of contradling or dilating to a 
 furprifmg degree. Its ftrata, when expofed to the air 
 by turning up the epidermis, become more clofely 
 compared together ; the fame is infenfibly relaxed to- 
 wards fat, and is refolved into a fofter cellular texture. 
 It is more tender in fome places, and in others more 
 hard. Within this fubftance run many fmall arteries, 
 which come from the fubcutaneous ones, which, tho’ 
 neither large nor of a very great length, are yet nu- 
 merous in fome parts of the fkin, which look red, as 
 in the cheeks ; but in other parts they are fewer in 
 number. The veins arife in great numbers from the 
 fubcutaneous net-work, and the nerves likewife in the 
 fkin are very numerous ; but they vanifh fo fuddenly, 
 that it is very difficult to trace the ultimate extremities 
 
 of 
 
2o6 touch. Chap. XIII. 
 
 of them. Betwixt the (kin and mufcles is placed the 
 cellular fabric, into which the fkin is infenfibly refolved, 
 in molt parts repleniflied with fat, the little eminences 
 of which prefs upon the fmall hollows of the fkin ; but 
 in fome, as the penis, red part of the lips, See. it is de- 
 ftitute of fat. There are very few parts in the body of 
 man where the fkin is immediately joined to the muf- 
 cular fibres without any feparatton by fat or cellular 
 fubflance ; for, though the dartos of the teflide has no 
 mufcular fibres, it is not without the cellular fubflance. 
 There are fome places, indeed, where tendinous fibres 
 are inferted into the fkin ; as in the neck, in the palms 
 of the hands, and foies of the feet. 
 
 423. Throughout the whole furface of the fkin in/ 
 tnofl parts of the body, but with fome difficulty, you 
 will find it to have a rough appearance after the cuticle 
 is taken off ; but in the human body thefe are fo ob- 
 tufe, that, unlefs you underfland them to be very mi- 
 nute granulations, they are raifed hardly any vifible 
 height above the fkin. But in the ends of the fingers 
 there are larger round fapillez feated in cavities of the 
 cuticle, and receiving nerves very difficultly feen ; 
 namely, a little mount or protuberance formed of fmall 
 veffels, with one or more fmall nerves wrapped up to- 
 gether in the cellular fubflance. Thefe, in the lips 
 and glans penis, after long maceration, appear villous 
 or down-like ; and are feen mofl evidently of all in the 
 tongue, from the fabric of w'hich we conclude, by a- 
 nalogy, with refped to the other cutaneous papillte. 
 
 424. Over the furface of the fkin is placed another 
 covering, which is not fo liable to be injured by the 
 air, and which coheres with the fubjacent fkin by an infi- 
 nite number of fmall bloodlefs veffels, and by hairs which 
 pafs through its fubflance. The outer furface of this 
 covering, as it were of an horny fabric, is dry, infen- 
 fible, and not fubjed to putrefadion ; but, being defli- 
 tute of veffels and nerves, it appears in a particular 
 manner wrinkled and fcaly, and is joined to the fkin by 
 a kind of net-work. This is called the epidermis or 
 
 cuticle^ 
 
TOUCH. 
 
 Chap. XIII. 
 
 2C7 
 
 tuticle^ which is perforated by an infinite number of 
 pores, fome larger for the fweat, and others fmaller 
 for the perfpirable vapours, out of whofe duds, ex- 
 panded and cemented by the interpofition of a con- 
 denfed glue, the fubftance of the cuticle is probably 
 compofed. By preffure or burning, the cuticle grows 
 thicker, by the addition of new plates or fcales, form- 
 ed betwixt the fldn and thofe which lie outermoft ; and 
 this is called a callus. But even naturally, in Blacks, 
 the cuticle has two diflind plates. 
 
 425. The inner furface of the cuticle is more foft 
 and like a pulp, fomewhat like an half fluid or a con- 
 creted mucus j whence, by macerating fome time in 
 water, it feparates from the former, difficultly in Eu- 
 ropeans, but eafily in the Blacks, where it is truly mem- 
 branaceous, folid, and feparable, as in the palate of 
 brutes. This furface of the cuticle lies incumbent on 
 the fkin itfelf, whofe papillae, in thofe parts where they arc 
 to be found, are received into the foft cuticular alveoli 
 or fockets. This is commonly called rete Malpighianurrif 
 although it be certain there are no perforations vifible 
 through it, like thofe of a fieve. 
 
 426. That this reticular body is compofed of a hu- 
 mour, tranfuding from the furface of the true fkin, 
 feems very probable. As to the fabric of the cuticle 
 itfelf, it is obfcure ; for fince it is both cafl off, or re- 
 generated, infenfible, and deflitute of veflels, it does 
 not feem to belong to the organical parts of the body. 
 Whether is it the outer part of the Malpighian mucus 
 (425.), coagulated and condenfed by the air and by 
 preffure ; after being perforated with a number of ex- 
 haling and inhaling duds, the mouths of which are 
 cemented together by the interpofed condenfed glue ? 
 and whether or not are we perfuaded to this opi- 
 nion by the mucous expanfion upon the membrane of 
 the tympanum ? to which add, the diffolution of it 
 in water, obferved by the more eminent anatomifts ; 
 which experiment is by others denied in the cuticle of 
 Blacks. 
 
 427. More- 
 
2 o8 touch. CHAp.Xm. 
 
 427. Moreover, to the hillory of the fKin belong 
 the fimple glandules, which are feated in very many 
 places under the (kin in the cellular fabric ; from 
 whence perforating the Ikin by their excretory duct, 
 they pour out a foft half fluid liniment. Other feba- 
 ceous glandules, partly fimple and partly compound, 
 generate a dry white liniment, of an harder confiltence 
 in the face, but more oily in the groins and arm-pits, 
 with which the fldn being anointed, fliines, and is de- 
 fended both from the air and outward attrition. They 
 are found feated in all parts of the body that are under 
 a necefiity 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 fkin is liable to 
 any great attrition, as in the arm-pits, nipples, groins, 
 glans penis, nymphae, anus, and hams. They fre- 
 quently fend out hairs. If it be afked. Whether thefe 
 follicles are feated in all parts of the fkin ? we anfwer. 
 That, although anatomy does not every where demon- 
 ftrate them, yet it feems probable that they are in no 
 part abfent, as may appear from the fordes collected 
 about the whole furface of the body, feemingly of the 
 febaceous kind. But there is another fort of liniment 
 or oily ointment poured out upon the fkin from the fat 
 itfelf, by its particular pores, without the intervention 
 of glands (209.) ; and this more efpecially where the 
 fkin is clothed with hair, as in the fcalp. 
 
 428. Again, both the hair^nd nails are appendages 
 to the fkin. The former are fcattered over almoft the 
 whole furface of the body, the palms of the hands and 
 foies of the feet excepted ; in mofl parts fhort and fo't; 
 but longer upon the head, mouth, cheeks, and chin, 
 with the breafl in men ; alfo, upon the forepart of the 
 limbs, in the arm-pits, groins, and pubes. They arifc 
 from the cellular texture lying under the fivin, originat- 
 ing from a little bulb which is membranous, flrong, vaf- 
 cular, and of an oval fhape, and more lax towards the 
 cellular texture, (and from this bafis the hairs are aug- 
 mented by veffds)j in which little bulb another bulb 
 
Chap. Xlir. I? O U C H. 209 
 
 lies hid, at firfl; roundifb, but afterwards cylindrical, 
 and furrounded with blood. In that fecond bulb lies 
 the hair, laid over with a fat humour. The hair, 
 with both its cylindrical fheaths, comes to the cutaneous 
 hole, goes out through the fame paffage, and forces the 
 epidermis into a fimilar flieath ; from whence the in- 
 corruptibility of the hair : and then the cover cannot be 
 feparated farther from the cortex ; but the filaments, 
 and fpongy and cellular matter, are continued throughout 
 the whole length of the hair. The hairs grow natu- 
 rally in the cellular fubllance under the fkin ; but, by 
 difeafe, they are fometimes formed within the fat of o- 
 ther parts. They grow continually ; and are renewed 
 again, after being cut, by a protrufion of their medul- 
 lary fubftance from the fkin outward, under a produc- 
 tion of the cuticle. When the hairs are deflitute of this 
 medulla in old people, they dry up, fplit, and fall off. 
 Their colour is from the juice, which fills the internal 
 cellular texture. They feem to perfpire through their 
 extremities, and poffibly throughout their whole fur- 
 face ; as we may conclude from the conftant force of 
 protrufion in their medulla, which, in the plica Poloni- 
 ca, wants a boundary to terminate it. To which add, 
 the luminous (freaks or rays that come out from the 
 hairs of an animal eledlrified. The fubcutaneous fat, or 
 oil, feems to follow, and tranfude through the medul- 
 lary traft and pores of the hairs. 
 
 429. The nails are of the nature and fabric of the 
 cuticle ; like which they are alfo infenfible, and renew- 
 able after being cut or fallen off. They are found 
 placed upon the backs of the ends of the fingers and 
 toes, which they fupport, to make a due refiftance in 
 the apprehenfioinof objects, having the nervous papil- 
 lary bodies, that ferve the organ of touch, placed under 
 their lower furface. They arife with a fquare root, in- 
 termixed with the periofleum, a little before the laff 
 joints, from betwixt the outer and inner flratum of the 
 fkin ; and paffing on foft, go out by a lunar cleft in the 
 external plate of the fkin, where the cuticle returns 
 
 E e back. 
 
210 
 
 TOUCH, Chap. XIII. 
 
 back, and is partly laid over the outfide of the nail, to- 
 gether with which it is extended forward as an outer 
 covering. The nail itfelf is of a foft tender fabric where 
 it firil; arifes, partly covered by the fkin ; but, by age 
 and contadf with the air, it in time hardens into a folid, 
 horny, and efailic body, compofed of long hair-like 
 threads, cemented together by interpofed glue, and di- 
 ftinguiflrable from each other by intervening fulci or 
 furrows, by which one may be able to fplit them into a 
 number of leffer orders. The nail thus formed, ex- 
 tends itfelf to the extremity of the finger •, and is, in 
 this traft, lined all along internally within its concave 
 furface, by an expanfion of the true fkin, and fabjacent 
 periofteum intermixed ; the filaments of which arife 
 firfl fhort, and are afterwards continued of a greater 
 length, till they become longeft of all at the extremity 
 of the nail to which they cohere. Thefe are mofl inti- 
 mately connected into the root of the nail. Over the , 
 outer furface of the nail, fame part of the fkin is again 
 at liberty, and lies under the nail, and diflinft from it,, 
 and has its own epidermis. A furrowed net-work is 
 interpofed betwixt the fkin and nail, which is alfo eafily 
 feparable and foft, for the protection of the papillae ; 
 from thence the furrows grow gradually harder, fo that 
 at laft they can fcarce be diftinguiflied from the nail. 
 The tendons do not reach quite fo far as the nail. 
 
 430. The cellular fubftance is v/ithout fat, e.xcept in 
 a few places to allow a neceffary motion to the fkin. 
 Where it is replcnilhed with the fat, it ferves to defend 
 the warmth of internal parts from the cold air ; to ren- 
 der the fkin moveable upon the mufcles ; to fill up the 
 cavities betwixt the mufcles themfelves ; and to render 
 the whole body white and uniform. The Ikin, cuticle, 
 and its Malpighian mucus, ferve not only to limit the 
 external bounds of the body every where ; but likewife, 
 where they feem to be perforated, pafTing inward, they 
 degenerate by degrees. For the cuticle is manifeflly 
 extended into the anus, urethra, vagina, cornea of the 
 eye, auditory paffage, mouth, and tongue ; nor is it 
 
 wanting 
 
2II 
 
 Chap. XIII. TOUCH. 
 
 ■wanting even in the ftomach itfelf and inteftines; al- 
 though, by the perpetual warmth and moifture, its fa- 
 bric be altered, and extended or relaxed into their vil- 
 lous covering. Thus the true (Idn is continued into 
 the internal fabric of the palate, tongue, pharynx, no- 
 ftrils, vagina, &c. where it degenerates always into a 
 white, thick, pulpy, commonly called nervous, coat of 
 thofe parts. 
 
 431. What has been hitherto advanced, is fufficient 
 to enable us to underftand the nature of touch. The 
 papillte, feated in the larger winding ridges at the ends 
 of the fingers, regularly difpofed in fpiral folds, are, by 
 the attention of the mind, a little raifod or eredled ; as 
 appears from frights or fliiverings ; as we fee in the 
 nipples of women, in the handling of tangible obje£ls, 
 and by light friftion ; whereby, receiving the impreflion 
 of the objedl into their nervous fabric, it is thence con- 
 veyed, by the trunks of the nerves, to the brain. This 
 is what we call the touch, whereby we become fenfible 
 chiefly of the roughnefs of objefts ; in which fome per- 
 fons have fo fharp a fenfation, that they have been 
 known to diflinguifh colours by touching the furface 
 only. By this fenfation we perceive, heat, when it ex- 
 ceeds in bodies the heat of our fingers ; and weight 
 likewife, when it preflfes more than is ufual. Humidity 
 we judge of by the prefence of water ; foftnefs, by a 
 yielding of the obje£l ; hardnefs, from a yielding of the 
 finger ; figure, from the limits or rough circumfcribed 
 furface ; diftance, from a rude calculation or ellimate 
 made by experience, to which the length of the arm 
 ferves as a meafure : fo the touch ferves to corredl the 
 miftakes of our other fenfes ; but yet it fometimes errs 
 itfelf, and then the other fenfes fliew themfelves to be 
 true guides, to the animal without that of touch. 
 
 432. The mucous body of Malpighius moderates the 
 aftion of the taftile obje£l, and preferves the foftnefs 
 and found ftate of the papilla. The cuticle excludes 
 the air from withering and deflroying the fldn ; quali- 
 fies the imprelfions of bodies, fo that they may be only 
 
 , E e 2 fufficient 
 
2t2 
 
 T O U C H. Chap. XIII. 
 
 fuffident to afFed the touch, without caufing pain : and, 
 therefore, when it is become too thick by ufe, the fenfe 
 of feeling is either lofl. or leffened ; but if it be too thin 
 and foft, the touch becomes painful. The hairs ferve 
 to defend the cuticle from abrafion ; to preferve and in- 
 creafe the heat ; to cover and conceal fome parts, and 
 render the membranes of others irritable, which nature 
 required to be guarded from the entrance of infects j 
 and perhaps they may ferve to exhale fome ufelefs va- 
 pours, or afford a palfage to the exhaling oil. The 
 nails ferve to guard the touch, that the papillae and ends 
 of the fingers may not be bent back by the refiftance 
 of tangible objeds : at the fame time they increafe the 
 power of apprehenfion, and affifl in the handling mi- 
 nute objeds. In brute animals, they generally ferve as 
 weapons of offence ; and might be of the fame ufe to 
 man, if they were not cut off. 
 
 433. But thefe are not all the ufes of (he fkin. 
 For one mofl important office of that covering is 
 to exhale from the body a large quantity of humours 
 and other matters to be carried off by the air. Ac- 
 cordingly, the whole furface of the fkin fweats out a 
 vapour by an infinite number of fmall arteries, either 
 coiled up into papillae, or fpread on the fkin itfelf, which 
 pafs out, and exhale through correfponding pores of 
 the cuticle •, although the courfe or diredion of the 
 veffels which pour out this vapour be changed in paffing 
 from the fkin to the cuticle. Thefe exhaling veffels or 
 arteries are eafily demonftrated by an injedion of wa- 
 ter or fifh-glue into the arteries ; for then they fweat 
 out from all parts of the flcin an infinite number of fmall 
 drops, which being transfufed under the cuticle, ren- 
 dered impervious by death, raife it up into a blifter. 
 
 434. In a living perfon, this exhalation is many ways 
 demonflrable. A clean looking-glafs, placed againfl 
 ^he warm and naked fkin, is quickly obfcured by the 
 moifl vapour. In fubterraneous caverns, where the 
 air is more denfe, it more plainly goes off into the ai. , 
 
 from 
 
Chap. XIII. TOUCH. 213 
 
 from the whole furface of the body, in the form of a 
 vifible and thick cloud. 
 
 435. Whenever the motion of the blood is increa- 
 fed, while at the fame time the fkin is hot and relaxed, 
 the fmall cutaneous pores, inftead of an invifible va- 
 }X)ur, difcharge fweat, conhfting of minute, but vifible 
 drops, which run together into larger drops by joining 
 with others of the fame kind. But thofe parts chiefly 
 are fubjecl to fweat which are hotteft ; that is to fay, 
 where the fubcutaneous arteries are largeft, and have 
 a greater adion from their refiftance, as in the head, 
 breaft, and foldings of the fkin. The experiment be- 
 fore mentioned (433.), together with the fimplicity of 
 nature herfelf, joining with the vifible thicknefs or 
 cloudinefs of the cutaneous and pulmonary exhalation 
 (434.), fufficiently perfuades us, that the perfpirable 
 matter and fweat are difcharged through one and the 
 fame kind of vefTels, and differ only by the quantity and 
 celerity of the matter. But together with the fweat is 
 intermixed the humour of the febaceous glands (427.) 
 and the fubcutaneous oil, which being more plentifully 
 fecreted, and diluted with the arterial juice, flows out 
 of an oily and yellow confiftence, and chiefly gives 
 that fmell and colour to the fweat for which it is remark- 
 able. Hence we find it more fetid in the arm-pits, 
 groins, and other parts, where thofe glandules are moft 
 numerous or abundant. Both blood and fmall fand 
 have been known to proceed from the fkin along with 
 the fweat. 
 
 436. Concerning the nature of perjpiration, we are 
 to inquire by experiments, and by analogy with the 
 pulmonary exhalation, which more frequently and a- 
 bundantly perfpires a vaporous cloud of the fame kind, 
 more efpecially vifible in a cold air. That what flies 
 off from the body in this exhalation is chiefly water, 
 appears from experiments, by which the breath, being 
 condenfed in large veffels, forms into watery drops. 
 Agreeable with this, we find the obfcuring vapour 
 PQndenfed by a looking-glafs to be extremely fubtle, fo 
 
 as 
 
214 TOUCH. Chap. Xin. 
 
 as "wholly to fly off* again from it ; and the fame is con- 
 firmed by the obftrufted matter of perfpiration pafling 
 off* by urine, or frequently changing into a diarrhoea ; 
 and from the eafy paffage of warm liquors in the form 
 of perfpiration by a hot air, or elfe by the urinary paf- 
 fages in a cold air. The water of thefe vapours is 
 chiefly from what we drink, but is in part fupplied 
 from the inhalation of the (kin. Frequently, even the 
 particular fmell of the aliments may be plainly percei- 
 ved in the perfpiration ; and there is alfo an admixture 
 of the eledrical matter in every perfon, but in fome 
 it is more evidently lucid. 
 
 437. But that there are, befides water, fome volatile 
 particles intermixed of an alkaline nature, is evident, 
 as well from the nature of our blood, as the confider- 
 able mifehiefs which follow from a retained perfpira- 
 tion. This volatile alkaline matter arifes from the 
 finer particles of the blood, attenuated by perpetual 
 heat and triture, and changed into an acrimonious na- 
 ture, Thefe afford the feent which is clofely followed 
 by dogs, who would not know their mafters unlefs fome- 
 thing of a particular nature perfpired from each perfon. 
 
 438. The quantity of our perfpiring moifture is ve- 
 ry large, whether we confider the extent of the organ 
 by which it is feparated, the abundance of vapours de- 
 rived from the lungs only ; or barely take a review of 
 the experiments made by Sanftorius, in which five 
 pounds out of eight, but by other experiments in a colder 
 country from fifty-fix to thirty ounces, of the food and 
 drink taken into the body in a natural day,were found to 
 fly off by perfpiration only, exclufive of any of the vi- 
 fible difeharges, and without making any addition to the 
 weight of the body; but from this weight you muff de- 
 duce that of the faliva, mucus of the nofe, and fweat. 
 But the cutaneous exhalation is even much larger than 
 this ; fince it is not only throws off fuch a quantity of the 
 indigefled food and drink, but likewife what is added to 
 the blood by the way of inhalation (442.), which enter- 
 ing, often in a very confiderable quantity, is thus again 
 
 expelled. 
 
Chap.XIIL touch. 215 
 
 1 
 
 expelled. But different difpofitions of the air, and of 
 the human body, caufe great variations in thofe mat- 
 ters. In warm countries, in the fummer-months, and 
 in young exercifed perfons, more goes off by tranfpi- 
 ration from the body, and lefs by the urine. But in 
 cold climates, during the temperate or winter feafons, 
 in aged or inactive perfons, more goes off by the urine 
 than by the infenfible difcharge. But in temperate 
 countries, making a computation throughout the whole 
 year, fomething more is perfpired than what pafles off” 
 by urine ; and joining together all the experiments 
 made in different countries, both excretions are almoff: 
 alike. The difference of time after feeding does alfo 
 in foine meafure vary the quantity tranfpired ; but in 
 general it is moft copious at that time when the greater 
 part of the digefted nourifhment is conveyed into the 
 blood, and therewith attenuated fo as to be fit for ex- 
 halation. It is naturally diminilhed in ffeep, even in 
 the warmer climates j but it is increafed by the heat of 
 bed-cloaths. 
 
 439. In general, a plentiful and uniform perfpira- 
 tion, with ftrength of body, are good figns of health ; 
 for whenever it abounds from too great weaknefs, it is 
 obferved to do more mifehief than none at all, if the 
 writings on that head are fufficiently to be depended 
 on. It is thus a fign of health, becaufe it denotes a 
 free pervious difpofition of the veflels difperfed through- 
 out the whole body, together with a complete digeftion 
 of the nourifllment, the. greater part of which is per- 
 feflly attenuated into a vapour. When it is dlminifh- 
 cd, it indicates either a conftriction of the Ikin, a 
 weaknefs of the heart, or an imperfeft digeftion of the 
 aliments. Perhaps in too great a perfpiration the 
 nervous fpirits themfelves are evaporated. This dif- 
 charge is, by moderate exercife, increafed to fix times 
 that of an idle perfon, even to an half or whole pound 
 in an hour, aided by ftrong and open veflels, by warm, 
 watery, and vinous drinks, with animal food of an eafy 
 digeftion, and a heavy, temperate, or m'oderately warm 
 
 air. 
 
2i6 
 
 TOUCH. Chap. Xin. 
 
 air, affifteJ with joyful affections of the mind. The 
 contrary of thefe either leffen or fupprefs the perfpi ra- 
 tion ; as thick fkin, a inoift air, or a cold and dry one, 
 with reft, more frequent bathing than ufual, or from 
 a diarrhoea fuddenly arifing, and laflly from a nervous 
 concuffion from a difagreeable affedtion of the mind. 
 However, the continuance of life does not depend on 
 afcrupulous exactnefs in the quantity of this difcharge, 
 which is fo eafily increafed or diininifhed by flight 
 caufes ; which is fhut up by paints in many Indian na- 
 tions, and is inconfiderable in many animals without 
 any fenfible injury. When it is fupprefied, it does a 
 prodigious deal of mifchief in fevers of a bad kind j 
 it hurts chiefly by its putrefcent qualities, which are re- 
 tained by fupprefled perfpiration. 
 
 440. 1 he fweat is evidently of a faline nature ; as 
 appears both from the tafte, and from the minute cry- 
 ftals which fhoot upon the cloaths of fuch as work in 
 glafs-houfes ; as well as by diftillation, which fliows the 
 fweat to be of an alkaline nature. Hence it is, that by 
 this difcharge the mofl malignant matter of many dif- 
 eafes is thrown off from the body. But, in reality, 
 fweat is always a preternatural or morbid difcharge, 
 from which a perfon ought always to be free ; unlefs 
 by violent exercife, or other accidents, his conftitution 
 is for a fliort time thrown into a difeafed flate. l\or is 
 it unfrequent for fweats to do confiderable mifchief in 
 acute difeafes ; by wafting the watery parts, and thick- 
 ening the reft of the blood, at the fame time that it 
 renders the falts more acrimonious. By a too violent 
 motion of the blood, the fweat is rendered extremely 
 fetid ; and is fometimes even red, or mixed with blood 
 itfelf: being eleclrized, it fometimes is lucid. 
 
 441. The ufes of perfpiration are, to free the blood 
 from its redundant water, and throw out thofe par- 
 ticles which, by repeated circulations, have become 
 alkaline or otherwife acrimonious ; and poflibly to ex- 
 hale therewith an extremely volatile oil, prepared from 
 the fame blood. The fame perfpiration likewife quali- 
 
Chap. XIII. TOUCH. 217 
 
 fies and foftens the cuticle, which is a neceflary medi- 
 um extended before the tender fenfible papillae. 
 
 442. But the fame flcin that makes this exhalation 
 into the air, is likewife full of fmall veffels, which in- 
 hale or abforb thin vapours from the air, either perpe- 
 tually, or at lead when it is not very cold ; more efpe- 
 cially when the air is damp, the body unexercifed, the 
 mind opprelfed with grief, or both under conditions 
 contrary to thofe which increafe perfpiration before- 
 mentioned (438.) Thefe veins are demonftrated by 
 anatomical injections, which, if thin or watery, fweat 
 through them in the fame manner as through the ar- 
 teries, if it was watery and thin ; moreover, the ma- 
 nifeft operation of medicines in the blood, which were 
 exhaled into the air, or applied to the Ikin, prove the 
 fame ; fuch as the vapours of mercury, turpentine, faf- 
 fron. Bath-waters, mercurial plafters, tobacco, colo- 
 quintida, opium, cantharides, arfenic, with the fatal ef- 
 fects of contagious or other poifons entering through 
 the Ikin ; as in the venereal infection : to which add, 
 the living of animals almofl; without drink in hot iflands, 
 which abound with moift vapours ; from which, how- 
 ever, they fweat and pifs plentifully enough. Laftly, 
 fome extraordinary morbid cafes have demonftrated 
 thisf in which a much greater quantity of urine has 
 been difcharged than the quantity of drink taken in ; 
 in which you may believe that the moft open paffages 
 ferved for inhalation ; that new ones were generated, is 
 not credible. The proportion of this inhalation is diffi- 
 cult to affign ; but that it is very great in plants, more 
 efpecially in the night-time, appears evidently from cer- 
 tain experiments. 
 
 443. Thefe cutaneous veffels, both exhaling and in- 
 haling, are capable of contraftion and relaxation by 
 the power of the nerves. The truth of this appears 
 from the effects of paffions of the mind ; which, if joy- 
 ful, increafe the circulation, and relax the exhaling 
 veffels, fo as to yield eafier to the impulfeof the blood ; 
 from whence, with a Ihortening of the nerves, there 
 
 F f follows 
 
■21 8 TASTE. Ghap.XIV, 
 
 follows a rednefs, moifture, and turgefcence of the 
 Ikin. Thole paflions, on the contrary, which are for- 
 rowful, and retard the circulation, contrail the exha- 
 ling veffels; as appears from the drynefs and corruga- 
 tion of the fkin, like a goofe-Jhm^ after frights ; and from 
 a diarrhoea caufed by fear. But the fame affections 
 feem to open and increafe the power of the inhaling 
 veffels, whence the variolous or peftilential contagions 
 are eafily contracted by fear. 
 
 CHAP. XIV. 
 
 Of the Taste. 
 
 444. T^ROM the fenfe of touch, and Its organ, there 
 is but a finall difference or tranfition to that 
 of the tajle ; which appears by certain experiments to 
 be feated in the tongue chiefly ; for even fugar applied 
 to any other part of the mouth, excites fcarce the leaft 
 fenfe of tafte in the mind ; neither will any other fapid 
 body, unlefs it contains fomething vehemently penetra- 
 ting ; in which cafe the palate, root of the tongue, u- 
 vula, and likewife the oefophagus, are affected with the 
 tafle. That fenfation which is fometimes excited in the 
 flomach, oefophagus, and fauces, by the regurgitation 
 of tire aliments, feems alfo to belong to the tongue, to- 
 which the fapid vapours are fent back, uncommonly 
 acrid and penetrating: and even that fenfe which is 
 fometimes occafioned in the flomach, eefophagus, and 
 fauces, from a rifing of the aliments, feems alfo to be 
 owing to the tongue, to which the taflable vapours are 
 conveyed. 
 
 445. Onlj^ the upper and lateral edges of the tongue 
 are fitted to exercife the fenfe of tafle. But by the 
 tongue we underfland a mufcular body, broad and ful- 
 cated in man, and lodged in the mouth, whofe pofle- 
 rior and lower parts are varioufly conneCled to the ad- 
 jacent bones and cartilages, while it remains moveable 
 
Chap. XIV. TASTE. 219 
 
 in its anterior and upper part. In tbofe portions of the 
 tongue, which make the organ of tafte, the fkin grows 
 to the adjacent mufcular fibres, b^ng continued from 
 the fldn of the face and mouth ; here it is always 
 foft and pulp-like, from the perpetual warmth and 
 moifture. From this fkin arife innumerable nervous 
 papllce, of a more confiderable bulk here than in other 
 parts. Of thefe there are feveral kinds : the firfi; of 
 •them are difpofed in a rank on the back part of the 
 tongue, on each fide of the foramen ctecum. Thefe, 
 furrounding that opening like a circle, are for the moft 
 part like an inverted cone, having a deep finus in their 
 middle; but are otherwife hard, and but indifferently 
 difpofed for taftlng, although you can eafily trace the 
 nerves to them. There are fome other papilla of the 
 fame kind found fcattered before thefe upon the back 
 -of the tongue. 
 
 446. Thefe degenerate into a klud of papillae like 
 muflirooms, lefs and tenderer than the former, of a 
 very cylindric and fomewhat oval figure, placed at 
 fome fmall diftance from -each other, upon the upper 
 furface of the tongue, v/here they' grow fharper point- 
 ed as they lie more forwards, and are moll numerous 
 on the Tides of the tongue. The third fort of papillae 
 are of a conical figure, which abound m.ofi; in number 
 among the former, and are fpread largely over the 
 'tongue. Thefe have their apices fomewhat inclined and 
 fiudluating before, towards the tip of the tongue; thefe 
 are likewife moft numerous in the fides of the tongue, 
 though there are fome alfo behind the blind foramen. 
 They are highly fenfible, and make the true organ of 
 tafte : other papillaa lie between, which are partly coni- 
 cal, and partly fliaped like threads ; and fome of the co- 
 nical ones are greater, and the others grow always lefs 
 and lefs. 
 
 447. Thefe papillae have doubtlefs fmall nerves de- 
 tached into them, befides numerous velfels, although 
 they are difficult to trace ; for we obferve, that larger 
 nerves go to the tongue, than almoft in any inftance 
 
 F f 2 which 
 
220 
 
 TASTE. 
 
 Chap. XIV. 
 
 which we have in other parts. For befides the nerve 
 of the eighth pair, which, being one of the principal of 
 the three branches, deeply enters the bafis of the tongue, 
 covered by the cerato-gloflus, near the os hyoides, 
 there is alfo a confiderable nerve that goes to the 
 tongue and its mufcles, from the ninth pair ; w'hich ha- 
 ving inofculated with the fird nerve of the neck, and 
 with the large cervical ganglion, it fends a branch 
 downward, and frequently joins the eighth pair; but 
 conftantly communicates with the fecond and third of 
 the neck, from whence its branches afeend to the muf- 
 cles arifing from the fternum, and frequently commu- 
 nicate with the phrenic nerve; after which, the red of 
 its trunk goes to the tongue. This communicates, by 
 many branches, with the fifth pair in the cerato-glof- 
 fus, and is more efpecially fpent in the genio-glolTus. 
 Ladly, the third branch of the fifth pair having fent up 
 or received the cord of the tympanum, and given other 
 branches to the internal pterygoides, with the maxil- 
 lary and fublingual glands, paffes with its principal 
 trunk behind the cerato-gloffus, W’here it joins the ninth 
 pair, and enters the tongue deeply, in company with 
 the artery ; together with which it is extended to the 
 tip of the tongue, where it becomes cutaneous. To 
 this nerve, therefore, if there be any prerogative or 
 preference, the fenfe of tade is to be more efpecially af- 
 feribed, which is confirmed from obfervations on fome 
 difeafes. Ladly, the nipples or papillte of the tongue 
 are of a hard texture, each papilla having its pulpy fa- 
 bric made up by a number of fmall nerves, arteries, and 
 veins, conjoined or wound up together by a firm cel- 
 lular fubdance into a button, or protuberance, of 
 which many are required to make up one large papilla. 
 
 448. The arterial and venous down which runs be- 
 tw'^een the papillae are for the purpofes of exhalation ; 
 and have nothing to do with the tade, farther than that 
 they feparate from the blood a liquor fit for diffblving 
 falts, and keeping moid the papillte proper for tade : 
 this liquor they pour out on the back of the tongue. 
 
 On 
 
221 
 
 Chap. XIV. T A S T E. 
 
 On the upper and back part of the tongue are feated 
 many fimple, round, muciferous glands, having one or 
 more open outlets, which are completed by an hemi- 
 fpherical membrane, and the fleftiy part of the tongue. 
 Some of thefe open into the obfcure, blind, and uncer- 
 tain figured hollow, which is placed in the middle be- 
 tween the largefl papillae (445.), and commonly con- 
 tains fome of them. 
 
 449. Over the papilla? of the human tongue is fpread 
 only a Tingle mucous and femipellucid covering, which 
 ftridly adheres to them, and ferves them as a cuticle. 
 But, in brute animals, a perforated mucous network 
 receives the papillae, which are in a manner wrapped 
 up in cafes or capfules of this mucous body covered 
 with the cuticle. 
 
 450. Under thofe papillae are fpread the mufcles 
 which make the flefliy body of the tongue; which are very 
 numerous, and hardly extricable in the human tongue: 
 in the lower part, it is in a great meafure made up of 
 the genio-gloffus mufcle extended outwards from the 
 meeting of the chin, and diftributed like rays inter the 
 fubftance of the tongue. The upper and lateral parts 
 are compofed of the ftylo-gloffus, whofe fibres run to 
 the tip of the tongue ; which in its middle part, betwixt 
 the former mufcles, is compofed of one proper to itfelf, 
 called Rngualis; which arifing from before the pharynx 
 and origin of the ftylo-gloffus, only lower, goes out 
 forward, and, terminating betwixt the faid genio-glof- 
 fus and ftylo-gloffus, makes up a very confiderable 
 part of the tongue. The back part of the tongue 
 is made up of the fibres of the cerato-gloffus, which 
 afeend upward and backward; which ends between 
 the ftylo-gloffus and lingualis, being included between 
 them: and to this is joined the chondro-gloffus, a 
 mufcle entirely different, which arifes from the fmall 
 bones, and next adjacent bafis of the os hyoides ; 
 from whence paffing outward, with its lateral portions, 
 covered by the genio-gloffus, it joins the ftylo-gloffus, 
 and difappears in the tongue. By the adion of thefe 
 
 ' mufcles. 
 
S^2 
 
 TASTE. Chap. XIV. 
 
 mufcles, the whole tongue is moveable in all direclions, 
 and capable of figuring its own fubftance, fo as to form 
 a hollow, by the elevation of the ftylo-gloffi, which it 
 again flattens by the cerato-gloffi, but contrafts itfelf 
 into a narrow and almofl: cylindrical figure, by the tranf- 
 verfe fibres from one fide to the other, together with 
 which there are many other orders of fibres, intermixed 
 with a thick fat ; fo that they cannot be traced in the 
 human tongue. 
 
 45 1 . The arteries of the tongue are numerous. One 
 that is larger and deeper afcends in a ferpentine courfe 
 from the outer carotid, and extends to the tip of the 
 tongue ; and a lefler fuperficial artery, incumbent on 
 the fubiingual gland, either arifes from, or inofculates 
 with, the preceding. Behind, there are various fmall 
 branches derived from the pofterior labials ; and from 
 the branches proper to the lips, or thofc of the tonfils. 
 The veins of the tongue are varioufly wove, and diffi- 
 cult to deferibe; fome of which, lying deep, accompany 
 the nerve of the ninth pair; and others, that are fuper- 
 ficial, accompany the mental artery, and, inofculating 
 wnth the former, fends out the ranular vein : but all of 
 them meet together in a large vein, w'hich is one branch 
 of the internal jugular coming from the brain. Thefe 
 veins varioufly communicate with the adjacent net- 
 works belonging to the tonfils, pharynx, thyroide gland, 
 and fldn; and in the back of the tongue, before the e- 
 piglottis, there is a communication betwixt the right 
 and left fide of the venal plexus. I find lymphatic vef- 
 fels rather in the neighbourhood of the tongue, than in. 
 the tongue itfelf. 
 
 452. Tht papilla of the tongue, which arc larger 
 andfofter thanthofe of the fldn, perpetually moift, per- 
 form the office of touch more exquifitely than thofe of 
 the fmall and dry cutaneous papillse ; and from hence 
 the tongue is liable to a fharper degree of pain : more- 
 over, naked falts are not otherwife perceived than under 
 afenfe of moifture, or of pain. But the papilla of the 
 tongue being raifed a little protuberant, to perform the 
 
 office 
 
TASTE. 
 
 Chap. XIV. 
 
 
 office of tafte, from falts diffolved in! water, or faliva, 
 and applied againft their tips or fummits, are affedted 
 in a particular manner ; which being diflinguiffied by 
 the mind, and referred to certain clalTes, are called fla~ 
 ■vours or tajies, either four, fweet, rough, bitter, fa- 
 line, urinous, fpirituous, aromatic, or pungent and a- 
 crid, of various kinds, infipid, putrid, and others re- 
 fulting partly from pure faits, and in part from an in- 
 termixture of the fubtile animal or vegetable oils, va-^ 
 rioufly compounded and changing each other. If it 
 be inquired. Whether the diverfity of flavours arifes 
 from the different figures which are natural to falts ? 
 and whether this does not appear from the cubical 
 figure in which fea-falt flioots, the prifmatical figure of 
 nitre, or the particular configuration of vitriol, fugar, 
 &c. ? we anfwer. That this does not feem probable, 
 for even taftelefs cryllals have their particular configu- 
 rations ; and the tafte arifing from very different falts^ 
 and differently qualified objefts of this fenfe, are too 
 much alike each other, and at the fame time too incon- 
 inconftant or changeablej to allow fuch a theory ; as for 
 example, in nitre, i’he mechanical reafon, therefore, 
 of the diverfity of flavours, feems to refide in the intrin- 
 fic fabric or appofition of their elements, which do not 
 fall under the fcrutiny of our fenfes. 
 
 455. But the nature or difpofition of the covering 
 with which the papillae are clothed, together with that 
 of the juices, and of the aliments lodged in the fto- 
 mach, have a confiderable fliare in determining the 
 fenfe of tafte ; infomuch, that the fame flavour does not 
 equally pleafe or affeft the organ in all ages alike, nor 
 in perfons of all temperatures j nor even in one and the 
 fame perfon at different times, who fliall be differently 
 accuftomed in health or varioufiy difeafed. In general, 
 whatever contains lefs fait than the faliva itfelf, feems in- 
 fipid. 
 
 454. The fpirituous parts, more efpecially of vege- 
 tables, either penetrate into the papillae themfelves, or 
 elfe are abforbed by the adjacent pile or villi of the 
 
 tongue j 
 
224 TASTE. Chap. XIV, 
 
 tongue ; as may appear from the fpeedy recruifal of the 
 ftrength by vinous or aromatic liquors of this kind, even 
 before they are received into the ftomach. 
 
 455. Nature defigned the difference of tafles to be 
 felt by the tongue, that we might know and diftinguidt 
 fuch foods as are moll falutary : for in general, there is 
 not any one kind of aliment healthy, that is of a difa- 
 greeable tafte ; nor are there any ill tailed that are fit 
 for our nourifhment. For it muft be obferved, that we 
 here take no notice of excels, by which the moll 
 healthy food may be prejudicial. In this manner na- 
 ture has invited us to take necelfary food, as well by 
 the pain called hunger, as by the pleafure arifing from 
 the fenfe of tafle. But brute animals, who have not 
 like ourfelves the advantage of learning from each other 
 by inflruftion, have the faculty of diftinguifhing fla- 
 vours more accurately, by which they are admonifhed 
 to abflain cautioufly from poifonous or unhealthy food ; 
 and therefore it is that herbivorous cattle, to which 
 a great diverfity of noxious plants is offered amongft 
 their food, are furnifhed with fuch large and long pa- 
 pillae of fo elegant a flrudlure in the tongue, of w'hich 
 we have lefs need. 
 
 CHAP. XV. 
 
 Gf Smelling. 
 
 4^6. O the fame ufe, likewife, of diflinguifhing 
 prejudicial from falutary food, the fenfe of 
 fmelling conduces; by which w'c even difeern and are 
 admoniflied to avoid, before it comes to our tafle, 
 what might be otherwife dangerous: and thus we are 
 efpecially enabled to avoid any thing of a putrid ten- 
 dency in our victuals, which is to us of a mofl peflilent 
 nature, and likewife find out what are grateful and 
 wholefome aliments ; although continual praftice, even 
 in this faculty, has alfo rendered it more ufeful and ac- 
 quitted 
 
Chap. XV. S M E L 1 I N G. 243 
 
 curate among brute animals than in ourfelves. For 
 men who have been brought up wild by themfelves, 
 without debauching the fcent by a variety of fmells, 
 have been obferved molt certainly to retain that faculty. 
 Finally, the powers and virtues of medicinal plants are 
 hardly to be better known than by the fnnple tefliinony 
 of tailing and fmclling. From hence it is, that in all 
 animals thefe organs are placed together ; and from 
 hence the fmelling is ftronger, and the organs larger, 
 in thofe animals which are to feek their prey at a con- 
 fiderable dillance, or to rcjedl malignant plants from 
 among thofe that are fit for food. 
 
 457. The fenfe of fmelling is performed by means of 
 a foft pulpy membrane, full of pores and fmall veffels, 
 which lines the whole internal cavity of the noftrils, be- 
 ing thicker upon the feptum and principal convolu- 
 tions, but thinner in the finufes. Within this mem- 
 brane are diftributed abundance of foft nerves through- 
 out the middle of its fabric, from the firft pair (357.), 
 which defcend through the holes of the os cribrofum 
 into the feptum narium ; but in fuch a manner, 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 lies tranfverfe in the pterygoide canal, and 
 from another which defcends through the canals of the 
 palate ; and foine from the infra-orbital-branch in the 
 maxillary finus, from the dental branch, and from the 
 anterior nerve of the palate. Moreover, the fore-part 
 of the feptum has a fmall twig from the ophthalmic of 
 the firfl branch belonging to the fifth pair. 
 
 ^58. The arteries which go to the nofe are manyt 
 from the internal maxillary branches; from the three 
 nafal ones, to wit, the upper and both ethmoidal 
 branches; alfo from the frontal, nafal, and fide 
 branches ; from the lefler ophthalmic branch of the 
 internal carotid ; from branches of the palatine artery ; 
 from the infra-orbital within the finufes ; and from 
 the fuperlor dental one. It is proper to thefe arteries 
 
 G g very 
 
244 smelling. Chap. XV. 
 
 very cafily and very plentifully to fweat out blood, 
 without any confiderable injury to the velTels them- 
 felves. The veins run together in company with arte- 
 ries, and form a large plexus, by uniting upon the ex- 
 ternal pterygoide inufcle, and communicate with the 
 fmufes of the dura mater ; from w'hence they open to- 
 gether into the outer branch of the internal jugular. ' 
 The arteries fupply the nourUhment, warmth, and mu- 
 cus, neceffary ta thefe parts. 
 
 459. The neceffary reduction of the human head to 
 that of a round figure, has in us given to the organ of 
 fmelling but a fmall extent of furface ; but to enlarge 
 this the more, nature has made the internal parts of the 
 nofe varioufly hollow' and complicated, in a furprifing 
 manner. Firft then, by the jiares we underhand the 
 multiform cavity which begins before from the noftrils, 
 and, extending tranfverfely backw'ard over the roof 
 of the palate under the os cribrofum, terminates at 
 the cavity of the fauces. This cavity is divided into 
 two by a feptum or partition of bone, which defcends 
 above from the plate of the cribrofum, but below is 
 formed by the vomer, and in its fore-part is completed 
 by a triangular cartilage, w'hofe furface is largely extend- 
 ed and very fenfible. 
 
 460. Moreover, the lateral furfaces of the nares are 
 increafed by ‘the fpiral volution of the cjfa turhinata ; 
 the uppermoft of which are fmall turns or folds of a 
 fpiral figure from the upper part of the os cribrofum. 
 The middle fold belongs to the fame, fomewhat ob- 
 long like a fhell, internally convex, externally con- 
 cave, rifing into an edge on each fide ; all over rough 
 with little finuofities or excavations, and inwardly fill- 
 ed with fpungy cells or receffes ; the whole being fuf- 
 pended in a tranfverfe pofition, and fupported by par- 
 ticular eminences in the bones of the palate and upper 
 jaw. The lowermoft turbina, fomewhat like the mid- 
 dle ones, do like them refemble the figure of a limpet 
 fhell, but longer ; for the moft part divided from the 
 former, but foinetimes conjoined by a bony plate, 
 
 which 
 
Chap. XV. SMELLING. 245 
 
 which is mon: frequently of a membranous nature. 
 This bony appendix, being extended upwards in a 
 fquare form, ferves to complete the maxillary fmus. 
 
 461. From hence the cavity of the nares is enlarged 
 or dilated by various fmufes, which are a fort of re- 
 ceffes or appendages to the whole. And firll, the: 
 frontal or uppermoil fmufes, which are not always pre- 
 fent, are of an irregular figure, intercepted betwixt 
 the anterior and pofterior plate of the frontal bone, 
 where it forms the fuperciliary protuberances ; and 
 thefe, being not found in a fetus, feem to arife from 
 the aftion of the corrugator and other mufcles, which 
 draw the anterior plate of this bone outward, fo as to 
 increafe the diploe into large cells, in the fame manner 
 as we obferve in the maftoide procefs. Thefe open in 
 the upper part of the nares into the interior cell of the 
 cs papyraceum. There are inffances of their being 
 totally wanting, and growing after the birth. 
 
 462. In the fecond place come the ethmoidal fmufes; 
 which are four or more on each fide, in the outer part 
 of the os cribrofum, like the cells of an honey-comb^ 
 completed above by the cellular middle part of the os 
 frontis, and before by the os unguis ; behind by the 
 bone of the palate and fphenoid bone ; from whence 
 they open by many ftnall tubes, placed one above ano- 
 ther in a tranfverfe pofition, into the upper part of the 
 nares. With thefe are continuous the cells in the pave- 
 ment or bottom of the orbit, and thofe engraved in the 
 os planum and maxillare are continued from them 
 outward. In a third place, this finus is contiguous on 
 each fide with the cavity or firms of the multiform bone, 
 extending largely on each fide towards the os cribrofum 
 and palatinum, which is itfelf formed in a dry prepara- 
 tion, by a cartilage of large extent in the fetus, and 
 by a folid bone, which gradually widens under the 
 fella turcica, with an ample cell, either fingle or di- 
 vided ; and opening forward, by its aperture or fora- 
 men, into the fuperior part of the meatus narium. 
 
 463. The laft, lowermoft, and biggeft hnus, which 
 
 G g 2 in 
 
246 SMELLING. Chap. XV. 
 
 in a fetus is inconfiderable, but in an adult very large, 
 is that formed in the bone of the upper jaw by feveral 
 thin bony plates. The opening of this into the nofe 
 is betwixt the os unguis, bone of the palate, and the 
 proper lamella or plate which accedes to it from the 
 bottom of the os turbinatum. Which opening is fo 
 much leifened by the furrounding mem.branes, as to 
 form only a moderate round aperture in the fpace be- 
 twixt the middle and bottom of the os fpongiofum. 
 But it hkew'ife fends forth an hollow appendix, tending 
 forwards, under the orbits which the os planum, un- 
 guis, and papyraceum complete, communicating like- 
 wife with the ethmoidal cells, and open behind the o- 
 ftium lachrymale. 
 
 464. The nerves of the nofe, being almoft naked, 
 required 'a defence from the air, which is continually 
 drawn through the noflrils and blown out again by the 
 ufe of refpiration. Nature has therefore fupplied this 
 part, which is the organ of fmelling, w'ith a thick in- 
 fipid mucus, very Iluid in its firO; feparation, and not 
 at all faline, but by the air condenling into a thick dry 
 cruft, more confiftent here than in other parts of the 
 body. By this mucus tlie nerves are defended from 
 drying and from pain. It is poured out from many final 1 
 arteries of the noftrils; and depofited partly into nu- 
 merous cylindrical duels, and partly into round vifible 
 cryptm or cells fcattered all over the noftrils. The fame 
 flows out all over the furface of the olfactory mem- 
 brane, which is therewith anointed on all fides. In 
 the feptum runs down forward a long finus to a confi- 
 derable length, which is common to many muciferous 
 pores; this mucus is accumulated in the night-time; 
 but, in the day, expelled by blowing the nofe, or fomc- 
 times more powerfully by fneezing ; and may oflend by 
 its excefs or tenuity, or irritate by too great thicknefs 
 the very fenfible nerves, from whence a fneezing is 
 excited for its removal. But the fmufes of this part, 
 which abound with mucus, are this way varioufly eva- 
 cuated, agreeable to the different pcftures of the body; 
 
Chap. XV. S M E L L I N G. 247 
 
 by which always fome of them are at liberty to free 
 themfelves, whether. the head be ere£l:, or inclined for- 
 ward, or laterally ; yet fo, that generally the maxillary 
 and fphenoldal linufes are more difficultly emptied than 
 the reft. Moreover, the tears defcend, by a channel 
 proper to themfelves, into the cavity of the nofe, by 
 which they moiften and dilute the mucus. 
 
 465. To the extreme parts of the nares or organs of 
 fmelling, is prefixed the nofe ; lined inwardly with a 
 membrane of the fame nature ; and compofed of two 
 bones, and ufually fix cartilages, two of vs hich are continu- 
 ed together into the middle feptum (459.) Thefe carti- 
 lages render the nofe moveable by its proper mufcles, 
 fo as to be raifed and dilated by a mufcle common to 
 the upper lip, and to be contracted together into a nar- 
 rower compafs by the proper depreflbr and comprelfor 
 mufcle pulling down the feptum. Thus it forms an 
 air-engine, which, for the reception of fmells, can take 
 air in a larger quantity by dilating ; then contracting 
 again by elafticity, when the air is afterwards abundant- 
 ly thrown out. 
 
 466. The air, therefore, filled with the fubtle and 
 invifible effluvia of bodies, confifting of their volatile, 
 oily, and faline particles, is, by the powers of refpira- 
 tion (265.), urged through the nofe, fo as to apply the 
 faid particles to the almoft naked and conllantly foft ol- 
 factory nerves, in which a kind of feeling is excited, 
 w'hich we call fyneUlng : and by this fenfe we diftinguifti 
 the feveral kinds of oils, falts, and other matters, diffi- 
 cultly reducible to daffes, which hereby we perceive in^ 
 diftinctly ; whence they are diflicultly recalled to me- 
 mory, though the odours already eftabliffied are fuffi- 
 cient enough for our purpofes. This fenfe ferves to 
 admonifh us of any pernicious putrefaction ; of any 
 violent acrimony ; or of a mild, foapy, and ufeful dif- 
 pofition in bodies. And as fait, joined with an oil, is 
 the object of tafte ; fo a volatile oil, aided with falts, 
 ferves to excite fmells ; whence the affinity of the two 
 fenfes, which conjunCtly affift and move each other, may 
 
24« SMELLING. Chap. XV. 
 
 be eafily underftood. But volatile particles chiefly 
 are dillinguiflied by frnell, and fixed ones by the tafle ; 
 perhaps becaufe the thick mucous cuticle, fpread over 
 the tongue, intercepts the action of the more fubtle fa- 
 line effluvia from acting upon the tafle, which yet eafily 
 affedt the fofter and lefs covered nerves of the internal 
 nofe. We are ignorant of the reafon why fome fmells 
 pleafe, and others difpleafe ; and perhaps cuftom may 
 have fbme effedt in this cafe. 
 
 467. Smells have a very ftrong adtion, but of fliort 
 continuance ; becaufe they are applied immediately, by 
 the moft minute particles, to nerves which are very near 
 to the brain itfelf, and almoft naked ; from thence too 
 proceeds the force of poifonous vapours, and the re- 
 frefliment from agreeable odours, by which fome per- 
 rons are effedtually recalled to themfclves out of a dead 
 fwoon, or even after drowning. From hence comes 
 that violent fneezing, which often arifes from acrid par- 
 ticles ; and a loofenefs or purging of the bowels, from 
 the fmell of fome medicines, with the power of particu- 
 lar antipathies. From hence is derived the pernicious 
 effedfs of exceflive fneezing, more efpecially blindnefs, 
 from the near confent or fociety of the nerves. But 
 amongft the various parts of the nofe, the feptum, and 
 more efpecially the os turbinatum, have a confiderable 
 lhare in the organ of fmelling : fince thefe are parts 
 multiplied in quick-feented animals, fo as to form beau- 
 tiful fpires in hounds and other quadrupeds ; and in 
 filh, wdio fmell by water, they are formed like the teeth 
 of a comb, in an elegant manner. 
 
 CHAP. XVI. 
 
 0 /" H E A R I N G. 
 
 468. A S the fenfe of fmelling diftinguifhes the final} 
 Jl\. bodies which float in the air, fo that of hear- 
 ing perceives the elaftic tremors or impulfions of the air 
 
 itfelf. 
 
HEARING. 
 
 Chap. XVI. 
 
 249 
 
 itfelf. Therefore, we obferve the fenfitive organ of the 
 ear to be compofed in a different manner from that of 
 any of the other fenfes ; as it is made up, for the mofl 
 part, either of hard bones, or elaftic cartilages and mem- 
 branes, which are the mofl exquifitely enabled to re- 
 ceive and communicate the neceffary tremors. 
 
 469. The external part of this organ, called the au- 
 ricle or outer ear, is a cartilaginous funnel, conneded, 
 but with a fort of mobility, before and behind, to the 
 bones of the temple, by means of a flrong cellular 
 plate, and likewife by its own proper ligaments and 
 inufcles ; but the mobility of this partis diminifhedby cuf- 
 toni. This cartilage is of a very compound figure j in 
 general of a kind of oval figure, yet marked with fpi- 
 rals Handing up, and hollows interpofed, to which o- 
 ther hollows and ridges correfpond in the oppofite fur- 
 face. The outer eminence, called helix, begins above 
 by a loofe tape, is carried round at liberty about the 
 edge of the upper part of the cartilage, upon the pofle- 
 rior fide of which it terminates in the fame loofe man- 
 ner. Within the body of the cartilage, furrounded by 
 the former, arifes a bifurcated eminence, meeting toge- 
 ther in one, called the anthelix, which terminates in a 
 fmall and fhort tongue called the antitragus. The re- 
 maining part of the ear, called the concha or fhell, is, 
 before, hollow ; behind, convex ; growing gradually 
 deeper, with a crooked line or ridge running through 
 its middle, under the denomination of the concha, 
 which is immediately joined with the meatus auditori- 
 us ; before which Hands a round moveable appendix of 
 the cartilage, as a defence, called the tragus. 
 
 470. This whole cartilaginous body of the outer eaf 
 is only furrounded by a thin fkin, and an empty cellular 
 fubHance ; it is repleniflied with many febaceous glan- 
 dules, which fupply an ointment. This part is gover- 
 ned or diredled by certain mufcles, which generally lofe 
 their ufe and aftion, from the cuHom of binding the 
 head in children, which we are otherwife to fuppofe they 
 were defigned by nature to perform. The uppermoH 
 
25a 
 
 H E A R I N G. 
 
 Chap. XVI. 
 
 of thefe mufcles arifes thin from the frontal and from 
 the aponeurofis of the cranium j whence it is broadly 
 fpread over the aponeurofis of the temporal mufcle, and 
 is inferred into the anthelix, or neighbouring helix, at 
 the fide of the anonymous cavity. The polterior 
 mufcles, which are two or three, more or lefs, arc more 
 robull than the former in a tranfverfe pofiiion ; and, 
 arifing from the fame aponeurofis, are inferred into the 
 convex part of the conch near the maftoidal bone ; the 
 cavity of which conch they, doubtlefs, are defigned to 
 open or enlarge. The anterior mufcle is one of the 
 leaft, which, being fpread upon the aponeurofis of the 
 temporal, is inferred almoft tranfverfely into the origin 
 of the helix and neighbouring concha. Eut the lefier 
 mufcular portions, which, though fhort, and not very 
 confpicuous, look of a red colour, are probably of ufe 
 to make fome change in the figure of this part. The 
 tranfverfe mufcle of the outer ear, which, for a long 
 way, conjoins the helix with the anthelix, ferves to 
 open the auricle. The antitragic mufcle, defeending 
 from the root of the anthelix to the antitragiis, ferves 
 to widen the entrance of the conch. The tragicus, 
 which lies upon the tragus, opens the entrance to the 
 auditory pafl'age ; and the fmall mufcle of the larger 
 notch or incifure, that lies betwixt the two cartilages of 
 the auditory paffage, forming the tragus and antitra- 
 gus, ferves to bring them nearer together, and to ren- 
 der the meatus itfelf more tenfe and elaftic. The re- 
 maining mufcles, the longer or larger, and the lefier of 
 the helix, have hardly any great ufe ; unlefs it be to 
 tighten or brace up the cartilages whenever we attend 
 or liflen to the hearing of weak founds ; and, by draw- 
 ing together the cartilages, they likewife render the 
 auditory paffage more firm. 
 
 471. To the concha is connecled the meatus audito- 
 rius, fomewhat of a round comprefifed figure, lefiening 
 as it bends inward ; for a confiderable part bony, and 
 bent forward in its middle. But, in its anterior and 
 outer part, it is, in fome meafure, made up by three 
 
 imperfed 
 
Ch.^. XVI. HEARING. 251: 
 
 imperfedl rings, arifing from the concha and tragus, 
 and united together, and to the bone itfelt, by interme- 
 diate flefh, membrane, and cartilage. Upward and 
 backward, the meatus is completed by a mere mem- 
 brane. This is the (late of it in adult perfons ; for, in 
 the fetus and new-born infants, the meatus is wholly 
 cartilage, and becomes afterwards, in part, a bone by 
 degrees. 
 
 472. Through the auditory palfage are continued 
 the cuticle and true fkin, gradually extenuated and ex- 
 adUy ftretched over the furface of the bone, by which 
 it is rendered extremely fenfible of any itching pleafure 
 or pain ; and, being repleniflied with irritable hairs, is 
 by them admonifhed of any fordes or wax abounding, 
 and guarding from the entrance of fmall infedis. But, 
 in the cellular fubftance under the Ikin, which is here 
 more firm, and makes up the greater part of the mem- 
 brane (47 1 in a fort of reticular manner, are feated 
 numberlefs round follicles or cells of a yellow colour, 
 which pour out their contents by fliort dudts into the 
 cavity of the auditory paffage ; at firft of an oily con- 
 fiftence, but afterwards it becomes more thick, bitter, 
 and inflammable like wax. This liniment defends the 
 fenfible fkin and membrane of the tympanum from in- 
 juries of the air, and keeps out or catches any fmall in- 
 fers j hut, when accumulated in too great abundance 
 m-thofe who are flothful or uncleanly, it may be the 
 caufe of deafnefs, or a difficulty of hearing. 
 
 473. Into this funnel of the ear the fonorous waves 
 of the air flow, which, from principles of mechanics, it 
 muff of courfe collect together. The elaftic air only 
 receives fonorous tremors or impulfions ; and transfers 
 them, either alone or principally, much after the fame 
 manner as we fee water, without air, transfer any im- 
 pulfe that is given to it. From hence, the found is in- 
 creafed in air that is condenfed, and is loft in a veflTel 
 emptied of its air. But the medium receives thefe tre- 
 mors, either from fome body ftriking againft it, or from 
 the air itfelf colliding againft another body, or laftly 
 
 H h from 
 
252 HEARING. Chap. XVf. 
 
 from the collifion of two bodies againft each other in 
 the air. But the body which produces found, ought to 
 tremble or vibrate in all, even the leaft of its particles, 
 fo as to form alternate arches riling up from the former 
 ftraight furface, and returning beyond the fame ; the 
 curve line of the fame exceeding that of the founding 
 body. From fuch a tremor, the contiguous air is beat 
 into waves, whereby the parts of the air that lie outer- 
 moll are comprelTed and fly back again fo foon as 
 their elallicity gets over the impulfe-, whence the air flies 
 again towards the fonorous body, where it is now more 
 loofe and rarefied, to be there again comprelTed by im- 
 pulfion ; and in the fame manner the anterior and outer 
 portion of air, furrounding that which is impelled, is, 
 by the action of the latter, comprelTed and removed far- 
 ther from the trembling body, yet fo as to return again 
 in its proper time by the force of elallicity, driving its 
 contents to the tremulous body for the exciting of a 
 new wave. Thefe ofcillations or impulfions of the air 
 are required to fucceed each other with a certain velo- 
 city; and, in order to render them audible, they mull 
 not be fewer than 30 in a fecond of time. 
 
 4.74. Acute founds are, in general, yielded from bo- 
 dies that are hard, brittle, and violently Ihook or llruck; 
 but grave founds are from the contrary. Thofe founds 
 in general are called acute, which are produced from 
 more numerous tremorjs in an equal time ; and thofe ob~ 
 tufe, which are produced from few tremors. As to any 
 medium betwixt acute and grave founds, there is none 
 but what is arbitrary. Cords, or other bodies, that 
 yield the fame number of vibrations in a given time, are 
 laid to be unifon; as thofe which make double the num- 
 ber of ofcillations in that time, are faid to yield a tone 
 that is an o£lave or eight notes higher; and other pro- 
 portions betwixt the numbers of the vibrations have 
 different names affigned to them. The Ihorter cords 
 produce lliarper tones, and the reverfe, in a proportion 
 diredlly as their lengths ; as thofe which are more 
 ilretched afford lharper founds in a fubduplicate pro- 
 portion 
 
Chap. XVI. HEARING. 253 
 
 portion to their tenuity, or to the weights or powers 
 by which they are ftretched. Experiments to this pur- 
 pofe are very eafily made with a monochord, or a feries 
 of chords ftretched with weights. 
 
 475. The found, thus produced, whether acute or 
 grave, ftrong or weak, is carried through the air with 
 a celerity equal to about 1038 Paris feet in a fecond, 
 and that with an uniform velocity, without abating in 
 the larger diftances. But a contrary wind, caufmg the 
 vibrations to extend more flowly, retards the progref- 
 fion of found about A of its velocity. So likewife den- 
 fity and drynefs of the air increafe the found, as a rare- 
 faction and moifture of the air leflen it. Hence, in fum- 
 iner time, founds move fwifter ; and in Guinea, it has 
 been obferved to pafs at the rate of 1 098 Pariftan feet 
 in one fecond of time. 
 
 476. The found, thus every way extended, meets 
 with certain particles in all adjacent bodies, even in wa- 
 ter and mercury, to which it communicates funilar tre- 
 mors or vibrations, not only fuch as are in unifon with 
 the original tone, and which yield a found in a more 
 particular manner fenfible, but alfo it excites tremors 
 lefs fenfibly, even in the other parts of bodies, which vi- 
 brate in the various proportions of the fcale. From 
 hence it is, that every found, which we hear, is a mix- 
 ture of the original tone, produced by the . trembling 
 body, in conjunction with fecondary tones generated 
 from the elaftic tremors of the furrounding bodies. 
 The ftrength of found is increafed, if one audible or 
 primary tone follows the other fo clofely, that their fuc- 
 ceflion cannot be diftinguiflred by the ear ; but if they 
 follow each ocher fo fiowly as to be diftinguifhable by the 
 ear, they produce an echo ; but to produce this, re- 
 quires an interval of fix thirds of a fecond of time, or 
 the diftance of 55 feet betwixt the refleCling or echoing 
 body and the ear. 
 
 477. Sounds, being elaftic, are reflected from hard 
 bodies in angles equal to thofe of their incidence. But 
 Che fame found, uftiered into the open air, and dilating 
 
 • H h 2 thro’ 
 
254 HEARING. Chap. XVI. 
 
 through an immenfe fphere, grows proportionably 
 weaker: but if it be ufhered through a tube, in a cy- 
 lindrical fhape, the ftrength of it is more confined toge- 
 'ther ; or elfe, by being colleflied into the focus of a pa- 
 rabola or ellipfis, it becomes increafed, as we obferve 
 in fpeaking-trumpets, from which the voice goes out 
 parallel to the focus of the parabola, without fcattering 
 the fonorous rays. 
 
 478. Therefore the fonorous waves of the elafllcair, 
 being driven into the cartilaginous funnel of our ear, 
 which is naturally inclined forward and outward in an 
 high fituation, are repelled and collected together, by 
 alternate reflections from its elaflic fidcs, into the cavi- 
 ty of the concha, from whence it proceeds through the 
 auditory pafTage, with a force fo much ftronger as the 
 furface of the outer ear is larger than the light or fec- 
 tion of the auditory pafTage. Through this pafTage, 
 however cylindrical, the fame force is continued en- 
 tire forward, and ineneafed by new refonances, excited 
 from the percuflion of the elaflic cartilages and hard 
 bones, fo as to mix imperceptibly w’ith the primitive 
 found. 
 
 479. Moreover, the bottom or end of the faid audi- 
 tory pafTage is terminated internally by a thin mem- 
 brane, called the membrana tympani ; which, in adults, 
 is of a roundifh figure, and placed with an obliquity ; 
 but fo that from its upper appendix it projeds in- 
 ward like a fhield, whilfl the part which lies above its 
 middle projeds into the cavity of the meatus like a 
 lliield. This membrane of the tympanum is compoTed 
 of feveral plates, the firfl or outermofl of which is white 
 and mucous ; the other is a true fkin, continued from 
 the membrane of the meatus, and of avafcular texture; 
 the third is a dry, rattling, fplendid, and pellucid 
 membrane or plate, without blood-veflels ; and thein- 
 siermofl is the vafcular periofleum of the auditory paf- 
 fage and tympanum, with a tender cellular texture ly- 
 ing between. This membrane is not naturally perfo- 
 rated with any opening, fo far as I have been able to 
 
Chap, XVI. HEARING. 255 
 
 difcover, and the tranfmifTion of fmoke is fabulous. It 
 is conftantly fo flretched in the fulcus or groove of the 
 bony ring, in which it is contained, proper to the fetus, 
 and after the birth coalefcing with the reft of the os pe- 
 trofum, that there is no part of the human body to be 
 found more tenfe or more tremulous than this. Upon 
 the furface of this membrane, and more efpeclally upon 
 its conical cavity pointing inward, the fonorous waves 
 ftrike, after they have received their laft refteftions 
 from the auditory paffage, by which the elaftic fabric of 
 this membrane is forced into ofcillation. 
 
 480. This membrane is ftretched over a cavity of 
 the os petrofum, called the tympanum; which is, for the 
 moft part, of a roundifli figure, but not regularly fo ; 
 being divided in its middle into two by a promontory, 
 and in the adult is increafed backward by the cells of 
 the maftoide bone, which are abfent in the fetus. But 
 alfo, in its upper and anterior and pofterior part, the 
 tympanum has hollow cells, and, is lined with a vafcular 
 membrane, receiving fmall branches from the internal 
 carotid, and from a branch of the artery of the dura 
 mater, which laft pafl'es through a fiffure in the aque- 
 dudl, and it has others from the external arteries of the 
 tympanum and from the ftylo-maftoidea. It is common- 
 ly full of a mucus, poured into it from the Euftachian 
 tube, and i$ divided by various membranes into a kind 
 of cells, namely, by produdions of the periofteum to 
 the little bones. 
 
 481. Within this cavity, three of the larger hones of 
 hearings together with a fourth which is lefs, are ful- 
 pended moveably. And firft, the malleus or hammer 
 lies with its upper round head refting upon the conca- 
 vity of the tympanum, from whence the handle of it 
 is extended down, along the membrane of the tympa- 
 num, betwixt the plates of it: having reached as low as 
 the middle of the membrane, it terminates by a very 
 clofe cohefion, with a broad extremity a little incurva- 
 ted outwards. The fame bone is, moreover, connec- 
 ted and fuftained by a peculiar ligament of its own, 
 
 joining 
 
H E A R I N G. Chap. XVT. 
 
 joining it to the longer leg of the incus ; and another 
 membrane ferves as a fecurity near the longer procefs 
 of the malleus. This bone drives outwards the mem- 
 brane of the tympanum, which is fpread over the 
 fhorter and conical procefs of its handle. From the 
 fame place of this bone a broad, long, and flat procefs, 
 goes out forward into a fulcus of the tube. It is articu- 
 lated with the incus by two heads, having protuberant 
 lines with a fulcus in the middle, and all of them ob- 
 lique. 
 
 In the malleus are commonly defcribed three 
 mufcles: the firfl; and internal of which, called tenfcr 
 tympanic being the largeft, is lodged in a particular 
 groove within the tube, with w'hich it proceeds paral- 
 lel ; and, rifing from the procefs of the multiform bone 
 betv/een the paflTage of the cerebral carotid and the hole 
 of the artery of the dura mater, bending round a pully, 
 is inferred by its tendon reflected outward and downward 
 into the beginning of the handle. The fecond inufcle arifcs 
 from a fulcus in the fame tube, but externally fhorter 
 than the former, and carried back almoft in the fame 
 manner, but without being reflected : it adheres by a 
 confiderable extent to the longer procefs ; and the 
 fame is fufpected to be but little different from the red 
 pulpy membrane. The third mufcle of the malleus, 
 which arifes from the auditory paffage, paffes through 
 a notch in the broken or interrupted ring of the tym- 
 panum, and is inferted juft by the fhorter procefs into 
 the malleus ; and this, which is by fome faid to relax 
 the membrane of the tympanum, has never been feen 
 with fufficient certainty neither by myfelf, nor by the 
 mofl eminent anatomifls. For the reft, by means of 
 the tenfor of the malleus, the membrane of the tym- 
 panum is difpofed for the hearing of weak founds ; 
 as the other mufcle ferves to moderate in too violent 
 founds, by drawing the malleus from the incus ; by 
 which therefore the propagation of the fonorous tre- 
 mors is interrupted. If the membrane of the tym.pa- 
 num be broke, or the bones of hearing diflocated, the 
 
 perfon 
 
HEARING. 
 
 Chap. XVI. 
 
 257 
 
 perfon becomes at firft hard of hearing, and afterwards 
 perfeftly deaf ; this part being the feat of that flight 
 hearing which is propagated through the bones of the 
 fkull. 
 
 483. The malleus returns the tremors imprefled 
 upon the membrane of the tympanum to the incus, 
 which is a fliort thick little bone, articulated with the 
 former behind by a broad furface, with two fulci and 
 a middle eminence. The flrorter leg of this bone, whofe 
 little body is bifurcated, being fufpended by a liga- 
 ment, is held firm into a fulcus proper to the bone. 
 Another longer one defcends parallel to the malleus ; 
 and, by a fomewhat crooked extremity, is adapted to 
 to the fourth orbicular bone which it receives, convex 
 on one fide, flatter on the other, and refting upon the 
 Rapes, to which its protuberances are imparted. 
 
 484. The fiapes, aptly enough fo called from its fi- 
 gure, lies inclined, but more backward than forward, 
 with a hollow head that receives the incus, from whence 
 proceed two little crooked legs, the pofierior one of 
 which is largefl; : but below, its oval bafts is occupied 
 by an aperture of a correfponding figure, commonly 
 called the fenejlra ovalls. Here the legs, which are 
 fulcated inwardly, are conjoined by a tenfe membrane 
 affixed to the hollow bafts. This bone of the (tapes is 
 covered by its own mufcle, which being included in a 
 bony papilla or cafe, fends out a fmall tendon, which 
 is inferted under the incus into the head of the Rapes. 
 Hence it feems to draw the Rapes, that it may lie higher 
 up, under the back part of the feneRra ovalis, and pafs 
 out of it before. Thus the nervous pulp of the veRi- 
 bulum is preffed by the bafts of the Rapes, and by the 
 air of the tympanum. The whole courfe or feat of the 
 Rapes is feparated from the reR of the tympanum, by a 
 membrane proper to itfelf. 
 
 485. A fmall roundifli oval-fliaped bone, here and 
 there greatly excavated, is here fixed to the longer leg 
 of the incus, and from thence goes to the fmall head of 
 the Rapes. 
 
 486, There 
 
258 HEARING. Chap. XVI. 
 
 486. There are various channels wliich 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 that, the fmall cells begin in the 
 os petrofum, above the mamillary procefs. Below 
 thefe, that procefs is excavated in an adult by various 
 fmall caverns. 
 
 487. From thence the proper canal, going out for- 
 wards from the anterior extremity of the tympanum, 
 emerges from the bones lying between the os multifor- 
 me and the olfa teraporum ; and is joined into a corre- 
 fponding elliptical and diverging cone, partly membra- 
 nous, and in part made up of cartilages of a variable 
 ftrufture : it opens by a very ample elliptical aperture, 
 turning inward and forward behind the nares, into the 
 cavity of the fauces : it is lined w'ith a porous mem- 
 brane, full of cryptae and mucous cells, continued from 
 and like unto the membrane of the nares. This is the 
 tube which, by the aftion of the circumjacent mufcles, 
 may be compreffed and clofed, and probably a little re- 
 laxed and opened again, by the circumflex niufcle of 
 the moveable 'palate. By this canal the infpired air 
 enters into the tympanum to be changed or renew'ed, 
 and the furrounding mucus of the little bones and o- 
 ther parts are this way depofited : nor is it at all impro- 
 bable, that the air enters by this tube, to fupport the 
 tympanum, when it is prefTcd inward by the more vio- 
 lent founds ; for founds themfelves, received into the 
 mouth, are this way conveyed to the organ of hearing. 
 In infpiration, the air prefies the membrane of the tym- 
 panum outward : and from thence proceeds that clafh- 
 ing or whifpering noife, by wdiich the heaving is obfeu- 
 red, when the mouth is held wide open in yawning ; 
 for then the air entering more abundantly through the 
 cavity of the tube, to the tympanum, refills the tremors 
 of the external air. 
 
 488. Two other paffages lead from the tympanum 
 to the labyrinth^ or innermofl chamber of the ear. 
 
 And, 
 
Chap. XVI. HEARING. iS9 
 
 And, again, the feneflra ovalis (484,) not covered by 
 any membrane, leads into the vefUbulum'; which is a 
 round cavity, formed in a very hard part of the os pe- 
 trofum, that lies near the inner part of the tympanum. 
 In that cavity are three receffes ; of which the upper 
 one is elliptical, the lower one circular, and the third 
 like a furrow. There is a nervous pulp in the veflibu- 
 lum, diftinguilhed from the parietal bone by the vapour 
 furrounding it. Into this open the five mouths of the 
 three femicircular canals, the foramen ovalOj and the 
 paffages of the nerves and arteries. 
 
 489. In the fetus, thefe are formed of a diftincl hard 
 fhell, which, being furrounded with a fpungy bone, are 
 lodged in a cavity of the os petrofum ; which, in adults* 
 is extremely hard, extended into fegments fomething" 
 larger than femicircles, which have an ample opening 
 betwixt them. The larger pofterior and lower of thefe 
 circles, is perpendicular ; alfo the middle and upper one 
 Is placed towards the perpendicular : but the outermofi: 
 and lead is horizontal. The inner mouth or aperture 
 of the uppermofi; of thefe meets with the upper open- 
 ing of the pofterior ring, and both join into one. 
 
 490. But the cochlea is a part ftill more wonderful* 
 feated in an inclined pofture within the anterior por- 
 tion of the os petrofum. Into one part of this cavity 
 opens the veftibulum; and into the other the feneflra 
 rotunda of the tympanum, which is concealed behind a 
 protuberance in the bottom of the tympanum. The 
 cochlea itfelf is made up of a nucleus of bone, of a co- 
 nical figure, with its apex inclined inward ; divided by a 
 middle fulcus, both through its bafis, and through its 
 whole length ; and perforated with innumerable fmall 
 foramina into the tubes, which are fcalce^ termi- 
 nating in the middle of the fecond fpiral. About this 
 nucleus are wrapt two turns and a half of a canal ; which, 
 in the fetus, is made up of a diltindl fhell-like fubftance, 
 peculiar to itfelf; and, in the adult, is united into one, 
 with the adjacent bone : and this winding canal dimi- 
 nilhes gradually in a conical figure, from the two fore- 
 
 I i mentioned 
 
26o rearing. Chap. XVL 
 
 mentioned openings towards the tip of the nucleus. It 
 is bilocular, or made up of two apartments, divided by 
 a partition called lamella fpiralis. This, at its larger 
 end, is bony, and extended out of the nucleus, at right 
 angles, into a cavity j is ftriated, and every way wrapt 
 up by the internal periofteum as in a capfule. Ano- 
 ther external part hereto belonging, is a membrane^ 
 which likewife divides tht canal : thus there are formed 
 two diftincl femicanals, called fcala. The interior and 
 pofterior of thefe canals begins from the feneflra rotun- 
 da, where it is (hut by a membrane, and is called the 
 fcala tympani; the other begins before, from the vefti- 
 bulum, from which it has its name. In the tip of the 
 cochlea is formed a' third cavity, fliaped like a funnel. 
 Into this the fpiral lamina terminates by a membrana- 
 ceous extremity, but fo that the funnel communicates 
 with them by a fmall hole on each fide ; but, in many 
 bodies, it alfo communicates with the cavity of the buc- 
 ket that is filled v/ith the nerve. 
 
 49 1 . The blood-veffcls of the outer ear come from 
 the temporal, or proper auricular branches; thofe to the 
 membrane of the tympanum are either from the tem- 
 poral, from the flylo-maftoideal, or from both ; thofe of 
 the meatus auditorius come from the former ; thofe to 
 the tympanum were deferibed (480.); and the velfels 
 belonging to the vellibulum, cochlea, and femicircular 
 canals, are from the vertebrals and ftylo-maftoideals. 
 The indullry of late anatomifis has difeovered veffels 
 of a particular kind, proper for carrying back liquids 
 from the veflibulum into the tranfverfe finus, from the 
 cochlea into the cavity, of the flcull. 
 
 492. It now remains that we deferibe the nerves de- 
 ftined to the fenfe of hearing, of which the principal is 
 that called the feventh (557-) This nerve enters into 
 the internal auditory finus of the os petrofum, in the 
 blind end of which it divides. The fmaller part of the 
 nerve is fent upward, through the opening of a canal 
 in the finus; whence palling tranfverfcly, it is after- 
 wards bent behind the tympanum. In this part defeend- 
 
21^1 
 
 Chap. XVI. HEARING. 
 
 ing, it gives ofF_a branch through a peculiar channel to 
 the tymparium, which afcends betwixt the malleus' and 
 incus, and goes out of the tympanum, through a fiflure 
 behind the articulation of the lower jaw, afterwards in- 
 ferting itfelf into the nerve of the tongue (457.); the 
 reafon of which fecret communication is oblcure, but 
 ferves to explain the confent of the teeth fet on an 
 edge by fliarp founds, a remo\'al of their pain by burn- 
 ing the ear, &c. The reft of the nerve, elcaping by the 
 fides of the ftyloide procefs, is diftributed through the 
 external ear, the parotid gland, a large part of the face, 
 and upper part of the neck, both cutaneous and muf- 
 cular ; and in the face forms nuntberlefs inofculations, 
 both betwixt its own branches, as well as with thofe of 
 the firft, fecond, third, and fifth pair ; and it likewdfe 
 communicates with the eighth pair, and the third cer- 
 vical pair. But to the immediate organ of hearing it 
 fends either no branches, or at leaft very fmall ones. 
 The outer ear again receives other nerves in its fore 
 part from the third branch of the fifth pair, and in its 
 back part to the fecond and third of the cervicals. 
 
 493. But the foft portion of the auditory nerves arifes 
 larger, but more oblcure, from the fourth ventricle of 
 the brain itfelf (357-) and enters by very minute threads 
 through exceeding fmall holes of the inner auditory fi- 
 nus, which go in part to the veftibulum, and in part to 
 the furrow of the cochlea. The branches in the vefti- 
 bulum form a pulp-like tender membrane, which is e- 
 very way extended thro’ the femicircular canals. The 
 other part entering the furrow of the cochlea, has an 
 obfcure termination. 
 
 494. With refpedl to the nerve which is diftributed 
 through the veftibulum and femicircular canals, there 
 is no doubt but it is ftruck by the tremors of the ex- 
 ternal air, propagated to the ftapesj from whence the 
 tremors immediately pafs through th^oval feneftra, to 
 prefs upon the naked pulp of the nerve. That part of 
 the nerve which enters the cochlea, is altogether ob- 
 fcure in its termination. It is probable, that fmall 
 
 I i 2 brancheSj 
 
26a HEARING. Chap. XVI, 
 
 branches from thence pafs through the little foramina 
 (490.) to the periofteum of the cochlea, and to the 
 membranous part of the fpiral partition. Do the tranf- 
 verfe nervous filaments pafs out from the nucleus of the 
 cochlea, all the way fucceffively fhortcr through the fpi- 
 ral plates? Is it the organ of hearing? Thefe are que- 
 {lions, which we are yet hardly able to refolve from a- 
 natomy; though this feems repugnant to the courfe 
 v/hich we obferve nature takes in brute animals, in 
 birds, and in fifhes, who all hear very exquifitely with- 
 out any cochlea. However this may be in the human 
 body, it is there probable, that the fpiral plate, fpread 
 full of nerves, is agitated with tremors from the ofcilla- 
 tions of the membrane of the tympanum, by which the 
 air in the cavity of the tympanum is agjtated, fo as to 
 prefs the membrane of the round feneflra, which again 
 agitates the air contained in the cochlea. 
 
 495. The preceding conjecture is indeed elegant; 
 fince the fpiral plates make up a triangle, ending in a 
 {liort point towards the tip, by which it may be concei- 
 ved to contain an infinite number of nervous cords, 
 continually fiiortening in their length ; and by that 
 means adapted to aii harmonical unifon or confonance 
 (474.) according to the variety of acute and grave 
 founds, fo as to tremble together at the fame time with 
 moll of them ; namely, the longeft cords in the bafis of 
 the cochlea, with grave founds ; and the fhortefl cords 
 nearer the tip or apex, with the fliarper founds. "Whe- 
 ther are founds perceived in the middle femicircular 
 canals, when thefe alone are found in all clalfcs of ani- 
 mals? Are they detained in thefe canals, in the cochlea, 
 and by the membrane fufpended through the veftibu- 
 luin? This feems probably the cafe. 
 
 496. From what has been faid, it appears, that the 
 elaflic wavps or tremors of the air arrive through the 
 outer ear and auditory pa{fage,to the membrane of the 
 tympanum; which being injured, and not repaired, the 
 hearing is totally deftroyed. This feems to be ftretched, 
 for hearing weak founds, bv the mufcles ot the malleus. 
 
 From 
 
Chap. XVI. HEARING. 
 
 From this membrane the found is conveyed through 
 the fmall bones to the veflibulum ; for thefe bones be- 
 ing deflroyed, the hearing is again aboljfhed. The 
 bony (ides of the veflibulum, by their tremulation, agi- 
 tate the fmall quantity of aqueous fluid furrounding the 
 nervous pulp. It feems to be (truck by the nervous 
 pulp fufpended in the veflibulum, and that tremor to 
 be continued through the continuous pulp of the 
 cochlea and femicircular canals. Of more than this 
 we are not certain : but, by undoubted experiments, 
 tremors, and even elaftic founds, communicate them- 
 felves by the internal Euflachian tube, and through all 
 the bones of the (kull, fo as to imprefs their force upon 
 the auditory nerve. 
 
 q97. The diftindion of founds, doubtlefs, proceeds 
 from the celerity of the tremors excited in the hearing 
 nerve, according as they fucceed each other more fwift- 
 ly or (lowly, in a (liort time ; in order to which, it is 
 not neceffary the mind (hould number them ; it is fuffl- 
 cient that (he perceive their numbers to be different, and 
 that this difference excites a variation in her thoughts 
 and ideas thence arifing. Whether the harmony or 
 agreeablenefs of founds arifes from the number of parts 
 founding together in unifon ? and whether the mind, 
 ignorant of herfelf, numbers the degrees of confo- 
 nance, fo as to pleafe herfelf in a majority of them ? 
 thefe are quedions denied by the mofl expert mufi- 
 cians, who make it appear, that there is an agrqeable- 
 nefs, and that very confiderable, in founds approach- 
 ing the lead to a confonance, and which lies in a pro- 
 portion very difficult to determine. Why do founds 
 often become too (harp for the ear ? Our auditory 
 nerves feem to be drained upon the fpiral plates, in 
 fuch degrees as to be in danger of breaking, after the 
 manner drinking-glafles may be broke by fliarp founds, 
 and as the hearing is fometimes almod lod for a while 
 by the violently flirill whidlings of the inhabitants of the 
 Canary iflands. 
 
 CHAP. 
 
264 
 
 SIGHT. Chap. XVII. 
 
 CHAP. XVII. 
 
 Of the Sight. 
 
 498. AS the organ of hearing perceives the tremors 
 Jl\. of the air, fo the fight perceives thofe of 
 light ; and as the firft confifted chiefly of bony organs 
 capable of making a refonance ; here, on the contrary, 
 the greater part of the eye is compofed of pellucid hu- 
 rnours capable of refrafting the more fubtle medium of 
 light : but the complexity of this organ was neceflary 
 for the defence of its tender parts, and from the diver- 
 fity of the feveral humours, to be contained each in 
 their proper integuments. 
 
 499. Outwardly, a defence is afforded to this organ 
 by the eye-brow or fuperciHum, which is a protube- 
 rance of the fkin, fuflained by mufcles, at the bottom 
 of the forehead, full of thick hairs, lying over one an- 
 other like the tiles of a houfe ; and capable of being 
 pulled down by the adion of the frontal, corrugator, 
 and orbicular mufcles, fo as to afford a fliade to the eye 
 in too flrong a light. After this office is finifhed, the 
 eye-brow is raifed again, by the infertion of the frontal 
 mufcle, thin and flefliv, immediatelv under the conti- 
 nuous fkin, faftened to the cellular membrane of the 
 fkull, which is of a fliining fubflance, and not far diffe- 
 rent from the nature of an aponeurofis, which, being 
 of a long quadrangular figure, is drawn backward by 
 the occipital mufcle. A depreflion of the eye-brow 
 ferves alfo to exprefs concern of the mind ; as an ele- 
 vation of it denotes the mind to be in a ferene quiet 
 ftate. This guard alfo conduces to throw off the fwcat 
 and retained duff, or the infedts which might fall into 
 the eye. 
 
 500. I'he eye-lids, or palpebrse, are placed ffill nearer 
 guards before the eye. Here the folds of the fkin, 
 which are thinly extended, from that of the face, run 
 
 out 
 
Chap. XVII. SIGHT.' 265 
 
 out in a confiderable length, and are reflected back 
 with the cellular fubftance interpofed betwixt the outer 
 and inner plate ; the latter of which becomes then a thin 
 vafcular membrane, and therefore of a red colour, ex- 
 tended before the globe of the eye, and fpread in its 
 foremoft part upon the fclerotica, under the denomi- 
 nation of co7ijundiva tunica. This production of the 
 fkin is every where covered by another of the cuticle, 
 even where it is clofely conjoined with the cornea. The 
 upper eye-lid is larger and more moveable : the lower 
 is fmaller ; and rather obfequious to the motion of the 
 other parts, than moved by any particular forces of its 
 own. The nerves., which give fenfibtiity to the eye-lids, 
 are numerous, from the firft. branch of the fifth pair, 
 and likewife from the fecond, and from the hard branch 
 of the feventh pair ; they abound with arteries from the 
 ophthalmics, and from the branches of the tempo- 
 rals, internal maxillaries, infra-orbitals, and others of 
 the face. 
 
 501. That the eye-lids might (hut together more 
 exactly, they have each of them a cartilaginous arch, 
 called tarfus., upon their margins, w'hich meet toge- 
 ther. It is flender, of a lunar figure, extenuated 
 outward, and ferves to hinder the eye-lid from falling 
 into wrinkles while it is elevated or deprelfed. The 
 elevation of the upper eye-lid is performed by a mufcle 
 arifing from the involucrum of the optic nerve gradual- 
 ly fpreading, and extended by its expanfion to the tar- 
 fus. This elevator is confiderably affifled in its aClion 
 by the frontalis, and by various connections with the 
 orbicularis drawn up or dilated by the former. The 
 upper eye-lid is deprelfed by the orbicularis mufcle ; 
 which is broad and thinly fpread round the orbit, under 
 the fkin of the eye-lids, to each angle of the eye, which 
 ferve as fixed points to this mufcle ; and it adheres to 
 the os frontis, where that bone joins the upper jaw, 
 and then its fibres are inferted into the os frontis and 
 nearefl parts of the upper jaw. The fame mufcle ferves 
 to elevate the lower eye-lid, and covers the eye in fuch 
 
266 SIGHT. CHAP.Xyif; 
 
 a manner that no duH. or light can enter it in fleep. 
 The lower eye-lid is depreffed by a double portion of 
 fibres, inferted into the upper lip. 
 
 502. Finally, that the protuberant margins of the eye- 
 lids might not injurioufly beat againft each other, the 
 ci/ia or rails of hair are placed fpreading outwards, in a 
 row, from the edges of the eye-lids, of dilFerent lengths, 
 which by croffing each other make a blind or (hade. Thefe 
 are of ufe in more diftinct vifion, by excluding the ex- 
 traneous rays, when we require a diftincl reprefenta- 
 tion of any objedl. 
 
 503. That the eye-lids rubbing againll each other 
 might not grow together, they are fupplied with a row 
 of febaceous glandules^ firfl; noticed by Meibomius ; 
 namely, about thirty little gut-like cells or more in each 
 eye-lid ; placed in general according to the length of 
 the lid, without ever branching, but compofed of pe- 
 culiar blind finufes, which end at laft in one larger fer- 
 pentine duft, opening by a mouth in the margin of the 
 eye-lid itfelf. Thefe difehargt a foft liniment, which 
 mixes and walhes off with the tears. 
 
 504. But the perpetual attrition of the eye-lids a- 
 feending and defeending againft the globe of the eye, 
 is prevented by the diftilling humour called tears ; 
 which preferve alfo the tendernefs of the membranes 
 and of the cornea, and ferve to wafli out any infects 
 or other lharp corpufcles. -Thefe form a faline pellucid 
 liquor, that may be evaporated, and never ceafes to 
 be poured over the anterior furface of the eye ; but ne- 
 ver runs over the cheeks, unlcfs collefted together in 
 a larger quantity from foine caufe. This liquor is ex- 
 haled partly from the arteries of the conjunftiva, as we 
 fee from an imitation of nature by injediing water : and it 
 is in part believed to proceed from a gland feated in a 
 recefs of the orbit of the os frontis,fomewhat hard, and of 
 the conglomerate kind ; intermixed with fat, and paint- 
 ed with many blood-veffels from the ophthalmics and 
 internal maxillaries 5 and interfperfed with many fmall 
 
 netves 
 
Chap. XVII. SIGHT. 
 
 nerves arifing from a peculiar branch of the firft trunk 
 of the fifth pair. 
 
 505. From this lachrymal glandule in horned cat- 
 tle defcend three, four, or more vifible dufts, which 
 open on the inner fide of the conjundiva, upon the 
 eye-lid. In man theie dudls are lately found out, ac- 
 cording to credible authors. The feparation of the 
 tears is increafed by the more frequent contraftion 
 of the orbicular mufcle, either from irritation, or fome 
 forrowful paffion, by which means the tears are urged 
 over the whole furface of the eye and conjundliva, which 
 they walh, 
 
 506. After the tears have performed their office, 
 fome part of them flying off into the air, the reft, that 
 they might not offend by their quantity, are propelled 
 by the orbicular mufcle, towards its origination next 
 the nofe, to a part which is the loweft of the palpebral 
 margins ; which not being furrounded by the tarfus, 
 does therefore not meet exactly together. Here a ca~ 
 runcle full of febaceous hairy follicles, of an oblong 
 figure, interpofes and feparates the meeting of the 
 eye-lids, at the fame time furnifhing a liniment to thofe 
 parts which have none of the Meibomian duds. Be- 
 fore this part is extended a fmall portion, like a little 
 eye-lid; which, defcending perpendicularly, joins the • 
 true eye-lids, and is larger in beafts than in men : but 
 at the beginning of this fpace, betwixt the eye-lids, in 
 which the tears are colleded, both in the upper and 
 lower margin, a little papilla ftands out, having each 
 of them one opening, furrounded by callous flefli, 
 which are perpetually open, unlefs when convulfively 
 clofed. This opening, which is called the punBum la- 
 chrymale^ drinks up the tears from the finus in which 
 they are colleded ; and this partly by tubular at- 
 tradion, and partly by impulfe from the orbicular 
 mufcle. If thefe points or openings are obftruded, the 
 tears run over and excoriate the cheek, 
 
 507. From both points proceeds a fmall dud, both 
 from the upper and the lower eye-lid, much- wider than 
 
 K k the 
 
268 SIGH T. Chap. XVIL 
 
 the opening itfelf, but thin, and included in the Ikin ; 
 one of which goes downward above the caruncle, and 
 the other goes more tranfverfely inward and under 
 it ; thefe both join together, and are inferted by two 
 mouths near the uppermofl; part of the lachrymal Jack: 
 thus it is called a cavity, formed in the os unguis and up- 
 per jaw, lined with a membrane, which is at firft cellu- 
 lar, but harder, and as it were of the nature of an apo- 
 neurofis ; then by another red and pulpy one, continu- 
 ed from the membrane of the nares, pervious to the 
 exhaling dew, and fomewhat of an oval figure. From 
 the fame facculus is continued a duft, which defeends 
 a little backward into the nares, opening there by an 
 oblique oblong aperture at the bottom of the meatus, 
 covered by the lower os fpongeofuin. Through this 
 paffage the fuperfluous tears defeend into the nofe, 
 which they in part moiften (464.) A mufcle is by fome 
 aferibed to this fack j but it is not yet fufficiently con- 
 firmed. 
 
 508. The globe of the eye, comprefl'ed before, but 
 longer than it is broad, is feated in the cavity of a bony 
 orbit, which is almofl of a conical figure, made up by 
 feven bones which are in the back part ; and on the 
 inner-fide perforated or interrupted by larger fifl'ures, 
 from whence the bones, widening forward, defend the 
 cavity on all fides. But as this is larger than the eye 
 itfelf, the excefs is on all fides occupied by a very foft 
 fat, furrounding the globe of the eye, that it may both 
 fill and have a free motion within the orbit. 
 
 509. The eye begins from a confiderable nerve, by 
 the expanfion of whofe coats thole of the eye itfelf are 
 compofed. The origin of this optical nerve we have 
 already deferibed (^57.) Its progrefs is acrofs the 
 crus of the brain, where it joins with its fellow nerve 
 from the other fide, and coheres therewith for a confi- 
 derable length by a large portion of medullary fub- 
 flance ; fo that the right goes to the right eye, and the 
 left to the left eye, yet not without fome conjunction of 
 ef both medullary fubftances. The nerve, therefore, 
 
Chap. XVII. SIGHT. a 69 
 
 thus enters the orbit a little infle£led, of a figure fomc- 
 what round, but comprefled ; and is inferted into the 
 globe of the eye, not in the middle, but a little near- 
 er to the nofe. 
 
 510. The nerve having reached the eye, depofitsthe 
 inner plate of its dura mater, which it received in the 
 opening of the fphenoidal bone : and this being ex- 
 panded and rendered thicker, makes up the firft coat of 
 the eye, called fclerotka. The other outer plate of the 
 dura mater, receding from the former, makes up the 
 periofteum of the orbit ; but the pia mater, which is 
 in this nerve very diflinft and full of veffels, expands 
 itfelf as before, fo as to form a thin dark-coloured li- 
 ning to the fclerotica. The remaining inner medul- 
 lary part of the nerve, continued from the brain, but 
 divided into filaments by the cellular fubftance, is con- 
 trafted into a depreffed white conical papilla ; after 
 which it is again expanded upon the inner membrane 
 of the eye, fo as to form the retina. 
 
 51 r. The fcelerotlca is in general white, tough, and 
 furniflied with few veffels, refembling the nature of the 
 cutis or fkin, of a figure completely enough globular, 
 but compreffed or flattened before, and of a greater 
 thicknefs backward. To the fore-part of this globe, cut 
 off circularly, is prefixed obliquely a portion of a more 
 eonvex but lefs fphere ; pellucid, and made up of many 
 fcales or plates, repleniflied with a clear water and pel- 
 lucid veffels, very difficult to demonffrate ; infenfible, 
 and almofl circular, yet broader at the nofe than to- 
 wards the temples : it is termed the ccrnea^thvo’ which 
 the light paffesinto theinmoft part of the eye. This greedi- 
 ly imbibes water, and fweats it out again. Before the an- 
 terior and flatter part of the fclerotica,and alfo before the 
 cornea, the conjun^iva is detached from each of the 
 eye-lids, and clofely conjoined to the fclerotica by a 
 proper cellular fubftance, that may be inflated (500.); 
 which is repleniflied with veffels, partly red, and part- 
 ly pellucid continuations of red ones. 
 
 y 1 2- The origination of the cboroides is from the cir- 
 K k 2 cum- 
 
SIGH T. 
 
 ,870 
 
 Chap. XVII. 
 
 eumference of a white circle, terminating the fubftance 
 of the optic nerve, in that part where the retina and 
 the central artery are expanded from it, and perforate 
 it by many fmall foramina. From hence it fpreads 
 within the fclerotica, concentrically adhering thereto 
 by a cellular fubftance and many veflels, which enter 
 from the choroides into the fclerotica. This membrane 
 is outwardly of a brown colour, but inwardly of a more 
 ruftet brown or almoft black, both which colour ancT 
 furface are feparable by maceration : the innermoft may 
 be diftinguifhed by the name of Riiyfch ; but grows 
 white through age. When this has extended itfelf 
 as far as the beginning of the pellucid cornea, it there 
 joins itfelf more accurately to the fclerotica, by a cellular 
 fubftance; from whence going off almoft circularly in 
 a different courfe, it forms a kind of rim, called orhi- 
 culus ciliaris: namely, the coat, which was before fphe- 
 rically expanded, now fubtends circularly from the arch 
 of the cornea, a little convex outwardly, and with a 
 deficiency in its middle ; from whence a circular paral- 
 lel portion is taken out, fo as to form a foramen or hole, 
 called xhz pupil, wdiich is feated nearer toward the nofe, 
 and is larger toward the temple. The anterior part of this 
 round rim, is called the iris ; and the back-part, feparable 
 from the former by maceration, is, from the black colour 
 with which it is painted, called uvea. On the anterior fur- 
 face of the iris appear numerous ftripes, extended like 
 rays, of various colours in different people, the whole 
 covered as it were with little locks of wool. Thefe go 
 off beyond the pupil into a ferrated circle, from which 
 tend other fimilar ftreaks, even to the edge of the iris. 
 They are ferpentine in a broad pupil, but ftraight in a 
 narrow one. On the pofterior face of the uvea is 
 much black pigment; wdiich being w'aflied off, ftraight 
 radiated ftreaks appear, produced into the pupil, but not 
 woolly. Orbicular fibres, concentrical w'ith the pupil, I 
 have not been able to obferve, neither with the naked eye, 
 nor with amicrofcope, even in an ox ; but only in the u- 
 vea, an internal circle diftinguiflied bv obfcurer ravs, but 
 
 lefs 
 
Chap.XVH. sight. 271 
 
 lefs woolly. In the human fetus, the pupil and the iris 
 being produced, makes a complete circle. That part 
 of it which is drawn over the pupil is of a vafcular 
 texture. 
 
 513. Though the iris has little fenfation, and is not 
 endowed with any mechanical irritability ; yet in a living 
 man, quadruped, or bird, it is conftritled on every 
 greater degree of light, and is dilated on every fmaller 
 one ; hence it is rendered broader for viewing diftant 
 objefts, and narrov^er for viewing fuch as are near. 
 The caufe of this' dilatation feems to be a reiniffion of 
 the powers refilling the aqueous humour; an argu- 
 ment of which, is the dilatation of the pupil, occafioned 
 by debility, and which fucceeds fyncope and death. 
 The contradion is more obfeure,' and perhaps only de- 
 pends on the (Ironger _ afPiux of humours into the co- 
 lourlefs vcffels of the iris, into which thefe veffels are 
 extended ; and, along with thefe, the iris is rendered 
 longer, and Ihuts the greater part of the pupil : \'o that 
 this motion has fomething in common with a begin- 
 ning inflammation. The pupil is more evidently mo- 
 ved and contrafted ; as the eye gradually grows callous 
 in old people, it is rendered aimoll; immoveable. In 
 an animal twenty or thirty hours dead, I have feen the 
 iris extend by heat, and fhut the pupil. 
 
 5 14. Behind the uvea, from the fame circle by which 
 the choroides and fclerotica join together, and outward- 
 ly adhere to the cornea, arife thick ftripes, extended 
 from the choroides, elegantly wrinkled with parallel 
 veflels, fpread under them, which are conjoined by fea- 
 ther-like loofe and thin footftalks, into the retina, every 
 way fpread with a good deal of black paint ; and de- 
 parting, after the manner of a perforated ring, inward 
 from the tunica choroidea, they fpread upon the vitre- 
 ous humour ; and, laftly, are laid on the capfule of the 
 cryftalline lens, but do not adhere to it, and are called 
 by the name of the ciliary ligaments. The origin of the 
 black pigment we are as yet unacquainted v/ith ; nor 
 fan any glandules be found, which fome have alTigned 
 
372 SIGHT. Chap. XVIf. 
 
 for its reparation. Among its other ufes, one feems to 
 be to keep firm the cryftalline lens. In infants, this 
 fame mucus has the image of a radiated flower, behind 
 the ciliary procefs. 
 
 515. But the retina, which is truly a continuation of 
 the medulla from the optic nerve, is next expanded in- 
 to a fphere concentric with the choroides, extremely 
 tender, and almoft of a mucous confiftence, diflblvable 
 by a blaft ; and this immediately embraces the vitreous 
 body. But when the retina has extended itfelf as far 
 as the ciliary proceflfes, it follows their courfe, making 
 their ftripes and fmall arteries its foundation or fup- 
 port in its courfe to the cryftalline lens, to the capfule 
 of which it adheres ; and, if we may believe the olDfer- 
 vations of fome anatomifts, as well as our own, fpreads 
 upon its furface. 
 
 516. Thefc coats of the eye, which inveft and fup- 
 port each other, after the manner ^of an onion or other 
 bulbous root, give a fpherical figure to the eye, and 
 include its humours : by which name are underftood 
 commonly three fubftances ; the one a folid, the other 
 a foft body, and the third truly a liquor. Firft, then, 
 the common furface of the retina is, on all Tides, filled 
 by the principal or vitreous humour, which is contained 
 in a thin pellucid membrane of its own, of a cellular 
 fabric, in the intervals of which is confined a moft 
 clear liquor, a little denfer than water, which entirely 
 evaporates by heat, like the aqueous humour ; from 
 which nature it does not eafily degenerate, even in 
 old people. Its velfels, which are moft manifeft in 
 filh, lie in the back part ; are moft beautifully radiated 
 from the central trunk of the retina, embracing the 
 convexity of the vitreous humour ; and are inferted 
 into a circle formed by other arteries coming from the 
 choroides, not far from the lens, and which I have feen 
 in a flieep. The vitreous membrane, which is tender 
 confidering its body, is yet grown to the lens in two 
 places, before and behind ; fo that the middle hollow 
 ring is intercepted between both infections, round the 
 
 cryftalline 
 
 4 
 
Chap. XVII. SIGHT. 27^ 
 
 cryftalline lens. Afterwards it Is divided by feme little 
 ropes. The ftreaks of the ciliary body imprint their 
 marks on the anterior face of it. 
 
 517. But, in the fore-part of the vitreous body, be- 
 hind the uvea, there is an orbicular depreffion or finus 
 confiderably deep, into the cavity of which the cryjlal- 
 line lens is received, though that be lefs properly ranked 
 in the clafs of humours. The figure of this lens is 
 made up of two elliptical convex portions or fides, the 
 foremofl of which is flatter, and the pofterior more gib- 
 bous. The ftrufture of it is that of concentric plates 
 or fcales, fucceeding each other, and compofed by the 
 fibres themfelves, elegantly figured and contorted, and 
 connected together by cellular fibres, fo as to form a 
 tender cellular texture. Betwixt the cryftalline leaves 
 is.alfo contained a pellucid liquor, which, in old age, 
 turns of its own accord to a yellow colour. The in- 
 nermoft fcales lie clofer together; and form at laft a fort 
 of continued nucleus, harder than the reft of the lens : 
 it does not fo adhere to the capfule, but, when that is 
 broke, it very readily leaps out ; and fome fay that a 
 little water is effufed around it. Its artery is from the 
 retina, which perforates the middle of the vitreous hu- 
 mour ; that is, the pofterior one ; for the veflfels in the 
 fore-part are not yet known. This whole lens is con- 
 tained in a ftrong, thick, elaftic capfule of a pellucid 
 membrane, more firm in the fore-part, which is lined 
 backward by the vitreous tunic. 
 
 5 iB. Laftly, the aqueous humour, which is extremely 
 clear and fluid, and renewed again if it be let out, is 
 feated in a fmall fpace of a curve-lined triangular figure 
 betwixt the uvea and cryftalline lens, and in a larger 
 chamber that is before betwixt the iris and the cornea. 
 This humour feems to exhale from the fmall arteries of 
 the iris, uvea, and ciliary proceffes ; being again ab- 
 forbed into fmall veins of the fame parts, while fome 
 portion of it is drunk up and exhaled through the cor- 
 nea. This humour alfo waters the uvea and capfule of 
 the lens. About the beginning of the prefent century. 
 
2 74 SIGH T. Chap. XVII. 
 
 the fpaces filled with this liquor w'ere called the camera 
 of the eye ; the fore one between the cornea and iris ; 
 the pofterior one, which is finall, between the circum- 
 ference of the cryftalline lens and the uvea. 
 
 519, The eye, thus framed, is outwardly furrounded 
 with mufcles, for its government and direftion. Name- 
 ly, into the circle of the fclerotica, which is next to the 
 cornea, are inferted four ftraight mufcles, arifing from 
 the dura mater of the optic nerve at the bottom of the 
 orbit ; where, departing from the nerve, they cohere 
 with the periofteum, forming, as it were, one circle ; 
 from whence, going forward, their bellies lie round the 
 bulb of the eye, and terminate again by their aponeu- 
 rofes, meeting together in another circle into the fcle- 
 rotica. Of thefe, the elevator is the lead, and the ab- 
 duSor the longeft. The office of thefe mufcles appears 
 very plainly rn each of them apart ; fince, being bent 
 round the convex bulb of the eye, as about a pulley, 
 they muft , of courfe, elevate, deprefs, or turn the globe 
 of the eye either to the nofe or to the temple. More- 
 over, two of them acting together may turn the eye in 
 a diagonal -betwixt the former directions; as upw'ards 
 and outw^ards, upwards and inwards, &c. Laftly, 
 when all the four ftraight mufcles are contracted toge- 
 ther, there is no doubt but they draw the whole eye 
 towards its origin within the orbit, by which means the 
 cryftalline lens is moved nearer to the retina. 
 
 520. But the two oblique mufcles of the eye are of a 
 more compound fabric. The upper of thefe, arifing 
 together with the recti, is long and flender, afeending 
 forw-ard to a notch in the os frontis, which is completed 
 by a double ligament, cartilaginous on each fide, and 
 hollow in the middle, almoft quadrangular, for fuftain- 
 ing the tendon of the mufcle. Through this canal paf- 
 fes the tendon of the obliquus fuperior ; which being 
 again reflected backward and downward, included in a 
 capfule of its own, is inferted into the globe of the eye 
 behind the ftraight mufcles. This draws the globe for- 
 ward and upward, in a manner out of the orbit, that the 
 
 eye 
 
Chap. XVII. SIGHT. 275 
 
 eye may take in a larger field of vlfion ; it alfo turns 
 the pupil inward and downward. The other leffer 
 oblique mufcle, arifing from a finus of the lachrymal fo- 
 ramen in the upper jaw, afcends immediately outwards 
 from the os unguis round the globe of the eye, and is 
 inferted by its tendon into the fclerotica behind the ex- 
 ternal rectus ; whence it appears, on its part, to turn the 
 eye downward and outward j and of courfe, contrary to 
 the former, to direct the pupil upward and inward. 
 
 521. But there are other more minute mufcular mo- 
 tions performed in the eye, which prefuppofe a know- 
 ledge of the nerves belonging to this organ. And, 
 firft, we have already fpoken of the optic nerve (509, 
 510.) The fourth pair goes only to the larger oblique 
 mufcle, and the fixth pair belongs to the external rec- 
 tus. The third and fifth pair produce the principal 
 nerves in the eye ; and of thefe, the firft branch of the 
 fifth produces the ophthalmic nerve, and fends off a 
 fmall nerve from its entrance into the orbit, to the eye- 
 lid and lachrymal glandule; it then conjoins with the 
 fecond branch of the fifth pair, and with the temporal 
 branch of the third and fifth pair. After having en- 
 tered into the orbit, its trunk divides into two. The 
 upper and larger fubdivides into two, which are fpent 
 upon the forehead and eye-lids : but the lower, going 
 inwards above the optic nerve, fends out long llender 
 filaments to the outer part of that nerve, which, joining 
 with another filament of the third pair, makes up the 
 ophthalmic ganglion, and fends off one or two ciliary 
 nerves. Finally, having given off a nerve, running to 
 that of the nofe (457.), it is then fpent upon the diffe- 
 rent parts of the internal angle of the eye. 
 
 522. But the principal dignity of the third pair lies 
 in giving off a branch upwards to the ftraight mufcles 
 of the eye, and to the eye-lids ; and then, going for- 
 ward with its trunk under the optic nerve, it fends out 
 three branches together to the lower and lefs oblique, 
 and to the internal mufcle ; after this, or often before, 
 (from its trunk, and fometimes from a branch of the 
 
 L 1 lower 
 
'276 SIGHT. Chap. XVII. 
 
 lower obliquus), afcends out another fhort and much 
 thicker nerve, which fometimes joins the root of the 
 fifth (521 .), or is fometimes folitary ; which, under the 
 abduftor mufcle, conftantly forms the oval ophthalmic 
 ganglion. From that ganglion, and fometimes from the 
 trunk of the third or fifth, go out four or five ciliary 
 nerves in a crooked courfe, playing round the optic 
 nerve in their courfe to the globe of the eye, where 
 they enter the fclerotica almoll in its middle, in com- 
 pany with its longer fmall arteries or veins ; and run- 
 ning thence ftraight forward through the choroides, 
 they pafs vifibly to the iris, and feemingly to the ciliary 
 proceffes. Other very fmall nerves, originating from 
 the fame ganglion, remain in the tunica fclerotica. 
 
 523. Another more obfcure and lefs eafily demon- 
 ftrable motion in the eye, is that of the ciliary proceffes 
 (514.); which, lying incumbent upon the furrows of 
 the vitreous membrane, feem, by their action, to prefs 
 back that body, fo as to bring the lens forward, and fe- 
 parate or remove it farther from the retina. But I have 
 never feen, in all the animals 1 have diffeded, any thing 
 like a mufcle in this ciliary body ; but a membrane 
 which fupports the fmall veffels. As for any fphinder 
 of the pupil, or a conflridor of the cornea, mentioned 
 by fome writers of note, or even moving fibres, which 
 others have imagined proper to the cryftaliine lens, they 
 are in nowife fupported by anatomy, nor are they con- 
 fident with the perpetual hardnefs of texture obfer- 
 vable in the lens and cornea of molt animals. 
 
 524. Moreover, to the hiflory of the eye belongs a 
 defcription of the veffels, which, in this part, have a 
 beautiful fabric. But all of thofe which belong pro- 
 perly to the fcveral parts of the eye itfelf come from 
 the ophthalmic artery, a branch of the internal carotid 
 (3 1 6.) This, creeping along under the optic nerve, 
 fends out, as principal branches, the upper and lower 
 ciliaries, one or more; the lachrymalis, from whence 
 the pofterior running to the nofe, and internal part of 
 that belonging to the arch of the tarfus ; afterwards the 
 
 mufcularis 
 
Chap. XVII. SIGHT. 27? 
 
 inufcularis inferior, the anterior recurrent to the nofej 
 the uppermoft mufcularis, and the palpebralis ; from 
 whence, with the former branch, fprings the arch of 
 the tarfus. Laftly, it goes out forward to the face^ 
 and adjacent parts of the nofe. But the ophthalmic 
 branches, belonging to the inner fabric of the eye, are 
 the pofterior and middle ciliaries j which, arifing from 
 the trunks before-mentioned, and playing rotind the 
 optic nerve, in four or more branches, in a Terpentine 
 courfe, go partly in with the optic nerve at its firft en- 
 trance, and are partly extended further to near the 
 middle of the fclcrotica, where they fend in forty or 
 more little arteries to the choroides, which make firfl: 
 beautiful ramifications upon the external furface of that 
 membrane, round, and like the branches of trees ; from 
 whence they proceed inwardly in a more direct courfcj 
 and at laft go to the circle of the uvea. 
 
 525. But feveral of the fmall arteries of the tunica 
 choroides gradually decline towards the interior parts 
 of the eye ; and, being covered with a kind of cellular 
 woolly matter, go to the ciliary procefles, through each 
 of which run out two fmall arteries, fcattering vafcular 
 woolly-like locks, united by an handle at their apex. 
 
 526. Other fmall arteries alfo, likewife arifing from 
 the ciliary ones, but few in number, moft commonly 
 two, come to the fame bafis from which the membrane 
 of the uvea originates. There, fpreading in various di- 
 regions, they furround the root of the uvea with their 
 branches, and are joined into a circle, into which the 
 anterior ciliaries mix themfelves ; which are fmall ar- 
 teries arifing from the mufcular branches of the oph- 
 thalmic, near the origin of the pellucid cornea ; perfo- 
 rate the fclerotica by twelve or more branches, and to- 
 gether make up the circle of the pupil. From that 
 circle, and likewife from the fore-mentioned anterior 
 ciliary arteries, independent of the middle circle, are 
 difiributed veflels, both on the anterior face, which 
 makes the iris, and on the pofterior face of the uvea, 
 together with the ciliary procefTes ; the vefiels are dif- 
 
 L 1 2 ^ ttibuted, 
 
278 SIGHT. Chap. XVII. 
 
 tributed, both ftralght and ramified ; the iris is full of a 
 liquor of a bluilh colour, otherwife brown ; and the 
 uvea is fpread with a good deal of a black paint, with- 
 out which it is naturally white. In the uvea, at fome 
 dihance from the pupil, they frequently form an im- 
 perfeft circle. 
 
 527. But from the fame ophthalmic and its trunk, or 
 from the lachrymal branch, or from one of the ciliari'es,one 
 or more branches enter into the optic nerve ; the prin- 
 cipal central artery of the retina penetrates through the 
 medulla of the nerve, and, going out of the apex of the 
 papilla (5 1 o.), divides in the centre of the retina ; from 
 thence fpreading every way in company with the retina 
 itfelf, by lb many branches, when traced by a fkilful a- 
 natomift, that that vafcular net-work is taken for a pro- 
 per membrane. Sometimes a lelfer branch goes along 
 the centre of the nerve to the retina, and is in like 
 manner ramified through it. It is certain, that from 
 thefe branches the minute pellucid ones of the vitreous 
 tunic are produced, as well as the pofterior artery of 
 the lens. The centre of thefe arteries, entering the re- 
 tina, is the celebrated opticus of the ancients. 
 
 528. The veins of the eye, in general, arife from the 
 ophthalmic vein, which here comes from the vein of 
 the face ; and, going out of the bony orbit, is infcrted 
 into the cavernous fmus. The internal veins of the 
 eye are fewer in the middle of the fclerotica, which 
 they perforate with larger trunks, and form bulhes or 
 trees of a roundifh figure, which commonly keep the 
 middle of the bafis of the tunica choroides ; fome of 
 them, which are long, reach even to the origin of the 
 uvea : others, in the fore-part, are fimilar to arteries : 
 another central vein, like an artery, goes to the retina 
 of the optic nerve. The pellucid or watery velTels dif- 
 fer not in their courfe from thofe which convey blood. 
 There are alfo lymphatic velfels faid to have been feen 
 by fome in the retina ; but the obfervation has not been 
 often enough repeated for us to depend on it. 
 
 529. So far with refped to the anatomy of the eye j 
 
 but 
 
Chap. XVII. SIGHT. 27? 
 
 but that the acHon of this organ lies wholly in the re- 
 ception of light, excepting only a few doubts, appears 
 very plainly from phyfical and mechanical experiments. 
 Light then is a matter either the fame with, or very nearly 
 approaching to, that of fire ; extremely fluid and fubtile, 
 penetrating through all even the hardefl; bodies, without 
 receiving alteration from any length or diflance in its 
 courfe ; moving with fuch a very great velocity, as to 
 run through the diflance between the fun and earth in 
 the fpace of about eight minutes and thirteen feconds. 
 The light we have in our atmofphere proceeds either 
 from that of the fun, whofe body feems to have the 
 power of impelling to us, in right lines, the matter of 
 light, which is confufedly fpread around ; or elfe it pro- 
 ceeds from fome other ignited point or lucid body ; 
 from whence the rays fpread every way, as from a cen- 
 tre to all points of a large fphere, fo as to fall upon the 
 furfaces of bodies ; from whence again it is refleded 
 into the eye, from the enlightened furfaces, in angles 
 equal to that of their incidence, fo as to render the bo- 
 dies from whence it thus flows to the eye, both vifible 
 and of fome colour. 
 
 530. It is now fufficiently evidenced from experi- 
 ments, that light is compofed of rays in right lines, al- 
 moft without any phyfical breadth or thicknefs ; and 
 yet, that each of thefe rays is again feparable into fe- 
 ven other permanent and immutable rays of a leflTer 
 kind. The known properties of thefe rays are, that all 
 of them, conjoined together, conflitute a white beam ; 
 which, being refraded by the minute furfaces of bo- 
 dies, are fubdivided into rays of a red colour, which are 
 more conftant or permanent, hard, and lefs refrangible j 
 next to which follow thofe of an orange, of a yellow, 
 green, blue, and indigo or violet colour ; of which 
 thofe are always weaker and more refrangible, which 
 are farther diflant in order from the red rays. A flia- 
 dow arifes from a deficiency in the refleded rays. 
 Thofe primitive rays, varioufly compounded together 
 with fliade, make up all the variety of colours. 
 
 531. The 
 
2 So SIGHT. Chap.XVIL 
 
 531. The colours, then, which feem proper to bo- 
 dies, arife hence ; that the minute furfaces of their con- 
 ftituent folid particles, by which their pores or vacui- 
 ties are limited, do, according to the difference of 
 their thicknefs, denfity, &c. refled or feparate the rays 
 of light, fo as to fend more of one kind or colour to 
 the eye than another ; whilfl mofl part of the remain- 
 ing rays are lofl; by repeated reflections within the pores 
 of the fubitance: fo that the flrongefl and thickeffc 
 particles reflect a white colour ; thofe next in denfity 
 and fize, a red colour ; till at lalt the minutefl furfaces 
 refled a violet colour. Thofe bodies are opake, which 
 retain the rays within their fubflance, without permit- 
 ting any to pafs through them : which feems to follow 
 from the largenefs and the number of the pores, to the 
 fides of which the light is attraded ; which pores are 
 filled with fome matter that has a power of refradion, 
 different from that which the light fuffers from the 
 parts of the body itfelf. Thefe principles we embrace, 
 till a new theory that places the diverfity of colours in 
 vibrations of different celerities fhall be better efla- 
 bliflied ; neither is it our bufmefs to concern ourfelves 
 with this matter. 
 
 532. Thefe rays, falling obliquely upon the furface 
 of liquors of various denfities, pafs through them with 
 a change in their diredion, by varioufly receding from 
 or approaching nearer to a perpendicular : and this is 
 called their refradion. In general, the denfer the me- 
 dium, the more are the rays bent towards the perpen- 
 dicular ; excepting only inflammable liquors, which, 
 by a peculiar property, draw the rays more to a per- 
 pendicular than in proportion to the denfity of the li- 
 quor. The proportions of the angles of incidence to 
 thofe of refradion are obferved to be conftant enough ; 
 fo that the fine of the radius of refradion from air in- 
 to water is to the fine of the angle of incidence, as 3 
 to 4 : and in the radius, paffmg from air into glafs, the 
 fine of the incidence is to that of refradion, as 17 to 
 1 1 j and from water into glafs, as 5 1 to 44. 
 
 533. Rays, 
 
Chap. XVII. SIGHT. 281 
 
 533. Rays, which come through the air with but 
 little divergency, (as do thofe of the fun on account of 
 their immenfe diftance ; or . as, in general, do any rays 
 that come from the diftance of above loo feet), falling 
 out of the air upon denfer bodies, fpherically convex, 
 are refleded to greater angles, as of 48-I degrees ; nor 
 are they under that meafure. If the angles are fmall- 
 er, and they penetrate the refrading medium, they are 
 there fo refraded, as to meet together in one point, 
 which is called their focus. This point always falls 
 within the axis or radius that is perpendicular to the 
 furface ; whence it becomes permanent and unchange- 
 able. So that the focus of rays, paffing from air into a 
 fphere of water, will be diftant from the axis one femi- 
 diameter of the fphere ; and in a globular glafs, it 
 will be diftant a fourth part of the diameter ; but in a 
 convex lens of glafs, that is part of a fphere not lefs 
 than thirty degrees, and equally convex, the focus will 
 be likewdfe diftant one femidiameter ; yet fo that the 
 rays will meet, not in a Angle point, but in a little 
 circle. 
 
 524. Therefore the rays of light, whether dlred or 
 infleded, fall in fuch a manner upon the tunica cornea 
 of the eye, as to form a moft fharp cone betwixt the 
 lucid point and the membrane upon which they are 
 fpread : the bafts of which cone will be the furface of 
 the cornea, and the apex in the radiant point ; yet fo 
 that all rays in this cone may, without any fenftble er- 
 ror, be reckoned parallel with each other. Among 
 thefe, there are forae rays refleded back from the cor- 
 nea, without ever penetrating the furface ; namely, 
 all fuch as fall upon that membrane in a greater angle 
 than that of forty degrees. Others, which enter the 
 cornea at very large angles, but lefs than the former, 
 and fall in betwixt the uvea and ftdes of the cryftalline 
 lens, are fuffbeated or loft in the black paint that lines 
 the uvea (512.) and the ciliary procefles (5 14.) ; but 
 thofe rays only fall upon the furface of the lens, which 
 (enter the cornea, at fmall angles, not much diftant 
 
 from 
 
202 
 
 SIGHT. 
 
 Chap. XYll. 
 
 from the perpendicular, or at mofl; not exceeding 
 twenty*eight degrees. By this means, all thofe rays 
 are excluded which the refracl:ing power of the hu- 
 mours in the eye could not be able to concentrate or 
 bring together upon the retina ; without which they 
 would paint the objecl too large and confufedly. 
 
 535. Thofe llender rays, therefore, coming thus to 
 the thick cornea, w'hich is denfer than water, and forms 
 the fegment of a fphere, fuifer thus a greater power of 
 refraftion, and pafs through it in a more confiderable 
 degree towards the perpendicular ; namely, about a 
 fourth part : but thefe rays falling with but little con- 
 vergency upon the aqueous humour, which is finall in 
 quantity and almoft like water, making there no fo- 
 cus becaufe of the nearnefs of the humour to the cor- 
 nea, go on nearly parallel, or little converging, to the 
 next adjacent furface of the very pellucid or cryftalline 
 lens; becaufe their divergency was confiderably cor- 
 reded by the refrading power of the cornea. More- 
 over, the cornea, being convex and part of a lefs 
 fphere than that of the fclerotica, receives and collects 
 a greater number of rays than if it was flatter with a 
 lefs furface. 
 
 536. The refrading power of the cryffalline lens, 
 which exceeds that of water, may be underftood from 
 its greater hardnefs and w'cight ; although we have no 
 certain meafure. In this lens therefore, and more ef- 
 pecially in its pofterior very convex fide, the rays will 
 converge much together, and pafs thence into the vi- 
 treous body. 
 
 538. This vitreous body is denfer than water, in 
 which it finks to the bottom ; but rarer than the cry- 
 ftalline lens ; and continues to bend the ravs a little 
 more gently towards the perpendicular, til! at length 
 the rays, coming from the point of diftind vifion, are 
 concentrated into a very fmall part of the retina, where 
 they paint an image of that objed from whence they 
 come ; but in a pofition inverted, from the neceffary 
 4 ecufTation or crofling of the rays. The manner in 
 
 which 
 
Chap. XVII. SIGHT* 283 
 
 which the images of objects are thus painted, may be 
 feen experimentally in an artificial eye, or by a natural 
 eye when the back-part of the fderotica is cut off, and 
 a piece of paper placed to receive the objed. But the 
 image we fee is painted on the outer fide from the op- 
 tic nerve, within the bounds of the vifual axis; yet fo 
 that it is not a mere point, but has fome degrees of 
 breadth ; fince we fee many objects at once, whofe 
 images mufl: be in di'dinct points of the painted field. 
 And there an objeft is feen moil diftindly, becaufe 
 the rays arrive thither nearly perpendicular. But fre- 
 quently this point of vifion does not fall on the fame 
 place in both of the eyes. When the lens has been 
 couched or difplaced, the vitreous body, with a weak- 
 er refracting power, ufually fuffices to bring the vifual 
 rays together to a focus. 
 
 539. Is it altogether falfe that the object is painted 
 on the retina ? Or is this picture made on the choroi- 
 des ? Is this new opinion confirmed by an experiment, 
 by which it is found that the place where the optic 
 nerve enters is blind ? and which is thus explained, 
 that there is in that place no choroides but the bare re- 
 tina, and that thence there is no vifion. But this is 
 repugnant to a very well known obfervation, namely, 
 that the retina is a niofi: fenfible nervous medulla ; and 
 that the choroides confifls almofi; entirely of a few 
 fmall nerves, and of veflels moll certainly blind. This 
 is likewife contradicted by the very great variety of the 
 choroides in animals ; the equally great conliancy of 
 the retina ; and the black fpots, which, even in man, 
 obfcure the exterior furface of the retina. But by 
 this experiment we know the reafon why the optic 
 nerve is not inferred into the axis of the eye, but into 
 its fide. For thus, except only in one fingle cafe, where 
 there is an impediment in the concourfe of lines drawn 
 through the centre of the optic nerves,- the one eye 
 fees and aflills that whofe blind fide is turned towards 
 the object. 
 
 540. But fince the neceflary offices of human life 
 
 M m require 
 
284 SIGHT. Chap. XVIT, 
 
 require a diftinft object to be painted upon the retina, 
 not only by the rays which come from one certain di- 
 ftance, but likewife by rays which come from very dif- 
 ferent parts more or lefs diftant; therefore, it is to 
 be believed, that the necelfary change is produced in 
 the eye by its own proper caufes. Other famous ana- 
 tomifts have fuppofed the lens moveable by the powers 
 before mentioned (519. 523.) This art of feeing di- 
 ftindly is faid to be learned by experience, it being 
 unknown to an eye lately couched of a cataraft. Alfo, 
 in an artificial eye, the ufe and neceffity of this motion, 
 it is faid, may be plainly perceived. Therefore too 
 great a divergency of the rays, as in thofe which come 
 from objefts very clofe to the eye, is corrected by a 
 removal of the lens farther from the retina, fo as to 
 bring the focus of the diverging rays upon the retina 
 itfelf, which would otherwife have fallen behind the 
 eye ; for the refracting power of the eye being deter- 
 mined, that which will unite the focus of rays co- 
 ming from the diftance of three feet, fo as to make 
 them fall perfectly upon the retina, will not be able 
 to colledt together into the fame point thofe rays which 
 come from the diftance of three inches j and rays ftill 
 more diverging will meet together yet farther behind 
 the eye, if they are not collected together by a greater 
 refracting power. 
 
 541. But thofe rays, which come from parts very 
 remote, and which may be therefore counted parallel, 
 will meet together before the retina, in the vitreous bo- 
 dy ; and again feparate according to the nature of rays 
 from the point of concourfe, as if it was a lucid point : 
 to remedy which, therefore, it is probable that thofe 
 powers (523.) remove the cryftalline lens back from 
 the cornea, nearer to the retina ; that the rays, ^hich 
 come together from a certain diftance to the lens, may 
 be alfo united together at a certain proportionable di- 
 ftance on the retina. For an eye, that will collect the 
 rays coming from feven inches, fo as to unite them on 
 the retina, will colleCl thofe together before the re- 
 
Chap. XVn. SIGHT. 285 
 
 tina which come from a diftance of three feet. It was 
 therefore perfedlly neceflary for the eye to be made 
 thus changeable, that we might be able to fee diftinft- 
 ly at various diflances. But the point of diftindl vi- 
 fion is in that part of the retina where the given object 
 is painted in the leaft compafs* poflible. The powers 
 caufmg the vifual rays to unite or converge together on 
 the retina, are often very different in the two eyes of 
 one and the fame perfon, fo as to render one eye near- 
 ly prefbyoptical or long-fighted, and the other myopti- 
 cal or fhort-fiffhted. 
 
 O 
 
 542. Thefe and other things fimilar are commonly 
 •received and taught, more efpecially by the mathemati- 
 cians, who more readily perceive the neceflity of thefe 
 changes. But yet there is no power in the human 
 eye which can either move the cryftalline humour out 
 of its place, or comprefs it. But we do not perceive 
 this faculty in ourfelves ; for we move a book nearer 
 to our eyes w'hen it is too far off, fo as to appear con- 
 fufed ; which we would have no occafion to do, if by 
 changing the internal figure of the eye we could cor- 
 rect the fault of the diftance : and, through a fmall 
 hole, we perceive an objeQ: only fingle in the point 
 of diftinft vifion, but double in every other. Perhaps 
 the contradtion of the pupil may do fomething, by 
 w'hich we can perceive more diflindlly fuch objedts as 
 are near. 
 
 543. But this artifice of the eye is not fufficient in 
 all perfons : for there are now a greater number of 
 people than formerly employed in a fludious or feden- 
 tary life, and taken up wath the obfcrvation of more 
 minute objedts ; by which the cornea is rendered more 
 convex and denfe, and the cryftalline lens more folid 
 and of lefs fegments ; while the eye itfelf, by the 
 weight of the humours, is more elongated, and the 
 reft of the humours themfelves are probably more den- 
 fified : many or all of which circumltances attend the 
 eyes of one perfon. In fuch, the iris is fenfible in a 
 fmall light ; whence, by winking or (training the eye- 
 
 M m 2 lids. 
 
226 
 
 SIGHT. Chap. XVII. 
 
 lid, they are denominated ?nyopes, flrort or near fighted. 
 In thefe, the point of diftinci; vifion is very near- to the 
 eye, from one to feven inches from before the cornea; 
 but they fee remoter objects more obfcurely, without 
 being able to diftinguifli their parts. The reafon of 
 this is evident ; fince, from the forementioncd caufes, 
 there is a greater refracting power of the humours, by 
 which the diflant and confequently parallel rays arc 
 obliged to meet in their focus before the retina ; from 
 whence, fpreading again, they fall upon the retina in 
 many points. Thus alfo to a good eye, the fenfe ol 
 objects which are too near the cornea is confufed ; be- 
 caufe the rays coming from thence are fpread all over 
 the retina, without being collected towards the cen- 
 tre. 
 
 544. The remedy for this fault in the fight is to cor- 
 rect it in its beginning, by viewing diftant places, by 
 .keeping the eyes from minute or near objeds, and by 
 the ufe of concave glafies ; or by viewing things through 
 a fmall hole, by which the light is weakened. When 
 the diforder is confirmed, the remedy is a concave 
 lens, which takes off a degree of the refracting power 
 in the humours, cornea, and cryfialline lens, in pro- 
 portion as it is more concave ; by which means the fo- 
 cus of rays from remote objects is removed farther be- 
 hind the cornea, fo as to fall upon the retina. This 
 glafs ought to be a portion of a fphere, wliofe diame- 
 ter is equal to the dillance of diftind vifion from the 
 naked eye, fquared by the diftance of diftind vifion in 
 the armed eye^ and divided by the difference betwixt 
 them. Age itfelf advancing, gives fome relief to the 
 Hiort-fighted ; for children are in a manner naturally 
 myoptical : but, as the eye grows older, it becomes 
 flatter, in proportion as the folids grow flronger; and, 
 contrading to a fliorter axis, the converging powers ol 
 the lens and cornea are diminifiicd. 
 
 545, Another diforder of the light, contrary to the 
 former, troubles people who are often looking upon 
 very diftant objeds, and is more efpccially familiar and 
 
 incurable 
 
Chap. XVIL SIGHT. 287 
 
 incurable in old people. In fuch, the cornea and cry- 
 ftalline lens are flatter, and the humours of the eye 
 have a lefs refrading power. Hence near objects, whole 
 rays fall very diverging upon the cornea, appear con- 
 fufedly ; becaufe the converging or refrading powers 
 of the eye are not fufficient to bring the rays together 
 in a focus upon the retina, but the rays go on fcattered 
 through the retina, and through the point of their pencil 
 behind the eye ; from whence vifion is confufed. The 
 point of diftind vifion among prefbyopi, or old or long- 
 fighted people, is from the diflance of fifteen inches to 
 three feet. 
 
 546. Such perfons are, jn feme meafure, relieved 
 by looking through a black tube held before the eye, 
 by the ufe of which the retina grows tenderer, and the 
 rays come to the eye in a parallel diredion. The re- 
 medy here is a convex lens of glafs, which may caufe 
 the rays to converge and unite together fooner in a fo- 
 cus, that it may not fall behind the eye, but upon the 
 retina. The diameter of the fphere, of which fuch a 
 lens ought to be a portion, is determined as before 
 (544.) There is no hope from age, which increafes 
 the malady. 
 
 547. The medium betwixt fliort and long fighted is 
 the beft, by which a perfon can fee diffindly enough 
 objeds that are both near and remote ; and of this kind 
 we reckon an eye that is able to read diftindly at the 
 diflance of one foot. But to this are to be added other 
 neceffary conditions ; fuch as a perfed clearnefs of the 
 humours ; a due mobility of the eye itfelf, and its parts ; 
 a fenfibility of the pupil and retina, neither too tender 
 nor too tough. 
 
 548. But the mind not only receives a reprefenta- 
 tion of the image of the objed by the eye, imprefled on 
 the retina, and transferred to the common fenfory or 
 feat of the foul ; but flie learns or adds many things 
 from mere experience, whiclr the eye itfelf does not 
 
 \ really fee, and other tilings the mind confiders or inter- 
 prets to be difierent from what they appear to her by 
 
 the 
 
288 SIGHT. Chap.XVII; 
 
 the eye. And, firO:, the magnitude of an object is 
 judged of by an optical angle intercepted ; as the bafts 
 of a triangle betwixt the cornea, and as the point of a 
 cone betwixt the radiant object. From hence, things 
 very near feem large, and remote objefts feem fmall. 
 Hitherto may be referred the power of microfcopes, by 
 which objects are made to appear to us fo much larger, 
 as the diftance of the focus of the lens or magnifter is 
 lefs than the diftance of diftinct vifton ; when, in reali- 
 ty, they do not appear larger, only more diftindt and 
 lucid ; whence the mind judges them to be nearer. 
 
 549. The ftrength of vifual light likewife is propor- 
 tionable to the fame angle, in the external day-light ; 
 and the multitude or number of the rays, joined with 
 the fmallnefs of the feat which they affeft in the retina, 
 occaftons near objects to appear brighter, and diftant 
 objects more obfcure ; or if remote objects appear 
 bright by their own light, the mind reprefents them 
 as large, near at hand, or both. 
 
 550. The place of a diftant object appearing to one 
 eye, is reckoned to be in a line comprehended by two 
 other ftraight lines drawn to the extremities of the bo- 
 dy. If the fame body is looked upon with both eyes, 
 it will then feem to be in the concourfe ot two lines 
 drawn through the axis of both eyes to that object. 
 
 551. Diftance we cannot perceive ; and if a blind man, 
 who never faw, fliould by any means be reftored to 
 fight, he w'ould imagine every thing he faw to touch 
 his eyes. Even we who are accuftomed to judge by 
 fight, make many fallacious conjectures concerning the 
 diftance of objects : but concerning this w'e judge as well 
 from the known diminution of the bulk of the body, as 
 from the lelfer ftrength of the light, and faint image of 
 the object whofe parts we are lefs capable of diftin- 
 guUliing, and from the number of bodies interpofed, 
 whofe diftance is knov/n. 
 
 552. The convexity or protuberance of a body is not 
 feen ; but is afterwards judged of by experience, after 
 we have learned, that a body, w'hich is convex to the 
 
 feeling, 
 
Chap. XVII. SIGHT. 289 
 
 feeling, caufes light and fliadow to be difpofed in a cer- 
 tain manner. Hence it is, that microfcopes frequently 
 pervert the judgment, by tranfpofmg or changing the 
 fliadows. The fame alfo happens in that phenomenon 
 which is not yet fufficiently underftood, by which the 
 concave parts of a feal are made to fe?m convex, and 
 the contrary. 
 
 555. The y\Wo\e fttuation of the parts of an obje£l, 
 are judged by the mind to be the fame with that which 
 they naturally have in the objeft, and not the inverted 
 pofition in which they are painted upon the retina. But 
 it is certainly a faculty innate or born with the eye, to 
 reprefent objeds upright to the mind, whenever they 
 are painted inverted upon the retina ; for new-born a- 
 nimals always fee things upright. And men who have 
 been born with catarafts, without ever being able to 
 fee, are obferved, upon couching the cataracts, to fee 
 every thing in its natural fituation, without the ufe of 
 any feeling, or previous experiences. 
 
 554. One thing which impofes upon the mind, is the 
 continuance which external fenfations make, during al- 
 mofl the fpace of a fecond of a minute, after they have 
 been conveyed to the fenforium by the eyes ; whence 
 they are reprefented to the mind as objects really pre- 
 fent. From hence proceeds the idea of a fiery circle 
 from the circumrotation of a lucid body ; and from 
 hence proceeds the continuance of the lliining image of 
 the fun, and fometimes of other bodies, after they have 
 been viewed by the eye. 
 
 555. Do we perceive only that obje£l diftinftly which 
 is direftly before that part of the retina which fees moll 
 diftindly ? And does the eye 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 
 of the eye ? Concerning the moil diltincl; vihon, this 
 is moll certain ; but we cannot affirm it of that which 
 is lefs dillind. Why do we fee only one objed with 
 two eyes? Becaufe the fenfation becomes one, and 
 without difference, when we have fimilar impreffions of 
 
 two 
 
 I 
 
290 SIGHT. Chap. XVU. 
 
 two objedls. For, even without the concourfe of op- 
 tic nerves, infers who have numerous eyes perceive 
 objefts fingle. Hence the images of two objefts ex- 
 cite only one fenfation, when they fall upon the fame 
 point of the retina ; but two fenfations arife from one 
 object, when the images fail upon different parts of the 
 retina. Whence proceed diurnal and nocturnal blind- 
 nefs ? The former is common to many nations living in 
 the warmeft climates, under the brighteft rays of the fun, 
 and to old men. The other happens in inflamed eyes, and 
 young men of a hot temperament, and hence endowed 
 with eyes vaftly fenfible. Whence do animals fee in 
 the dark? From a large dilatable pupil, and tender 
 retina; a fhining choroides, and one which rcfledts the 
 light very ftrongly. Why are we blind when brought 
 out of a ftrong light into a weak one ? Becaufe the 
 optic nerve, having fuffered the action of ftronger cau- 
 fes, is incapable of being moved by weaker ones. 
 Whence have we a pain, by paffing fuddenly from a 
 dark place into the light? “Becaufe the pupil, being 
 widely dilated in the dark, fuddenly admits too great a 
 quantity of light before it can contraft ; whence the 
 tender retina, which is eafily affected by a fmall light, 
 feels, for a time, an imprelfion too lharp and ftrong. 
 Whether fee we with one eye, or with both ? Moll 
 frequently with one, and more efpecially the right eye : 
 but when both are employed together, w'e fee more ob- 
 je£ts, and more plainly ; and we alfo dUlinguilh more 
 points of the fame object, and judge better of their dif- 
 tances. 
 
 CHAP. XVIII. 
 
 Of the Internal Senses. 
 
 556. T TITHERT O we have confidered the fenfes 
 XJL as they are, each of them apart. It is now 
 common to them all, that the tender pulp of the nerve, 
 
 being 
 
Chap. XVIII. SENSES. 
 
 being ftruck or imprefled by external objects, conveys 
 a change by the nervous fpirits, to that part of the brain 
 where the Impreifed fibres of the nerve firfl arife from 
 the arteries (372.) We know nothing more, than that 
 new thougnts are thus excited in the mind : which we 
 call perceptions^ with refpect to the thinking mind her- 
 felf ; and ideas, ysixih refpeft to the objects from whence 
 they arife. Perception is therefore excited whenever 
 any of the forementioned changes, in fome of the fen- 
 fible organs, are transferred to their firft origin ; for the 
 thought or fenfe by which the perceiving nerve itfelf is 
 affefted, is no exprefs image or idea of the objedt. The 
 idea of rednefs has nothing in common with rays but 
 little refrangible, and feparated from the feven portions 
 of which rays of light are compofed ; and much lefs is 
 it confiflcnt with optical principles, for the image paint- 
 ed by rays, upon a foft white nerve, to be conveyed 
 through a mod opaque body, in a long courfe of perfect 
 darknefs, to the origin within the thalami. There is 
 nothing in the pain of burning that can reprefent to the 
 mind its fwift and fubtile matter violently moved, by 
 the particles of which the continuity of the nervous 
 threads is broken or deftroyed. There is nothing in the 
 idea of a fharp found, from a chord of a certain length, 
 that can inform the mind the faid chord trembles 5000 
 times in the fpace of a fecond. Neither does a fait tafte 
 teach us that the cryflals of fea-falt are of a cubical fi- 
 gure. Again,' though a motion is impreffed on the 
 brain, from the fenfation perceived by the body, the 
 mind neither perceives this motion, nor the tremors of 
 founds, nor the percuffions of the rays of light, but 
 fomething perfeftly diftinct from this motion. But it 
 is eftablilhed as a perpetual law by the Creator, that 
 certain changes, made fird in the nerve, and then in the 
 conimon fenfory, diall produce certain new correfpond- 
 ing thoughts in the mind, which have an indiffolvable 
 conne£liion with each other ;■ fo that, although what we' 
 perceive in the world be arbitrary, yet that it is real, and 
 not falfe, appears plainly from the perpetual agreement 
 
 N n of 
 
igt INTERNAL Chap-XVIII. 
 
 of fimilar thoughts arifing from fimilar affections of the 
 fenfitive nerves, in all perfons at the fame time, from 
 one objeft, or in one perfon at different times. 
 
 557. During the time of our perceptions, therefore, 
 five very different beings are joined together : the body 
 which we perceive ; the affeftion of the organ of the 
 fenfory by that body ; the affection of the brain, arifing 
 from the percuffion of that fenfory ; the change pro- 
 duced in the mind ; and, laftly, the mind’s confeiouf- 
 nefs and perception of the fenfation. 
 
 558. It appears from certain experiments, that the 
 firft origin of every perceiving nerve is always diftincl; 
 and that the change which is firfl; excited by the exter- 
 nal objeft in the faid nerve (556.) continues in the ori- 
 gin of that nerve for a confiderable time ; and alfo that 
 thofe changes are fo claffed and laid up within the faid 
 part of the brain, that thofe are neareft together, which 
 were either contemporary, or nearly fo, or which have 
 fucceeded next in courfe; or laflly, which have a rela- 
 tion to the fame fubjeO;, or were excited by fimilar ob- 
 jedls ; infomuch, that it is certain, new fpecies or ideas 
 are always conveyed again to the fame part of the brain 
 where others of the like kind are referved : for other- 
 wife the arbitrary figns of words and letters would ne- 
 ver be able to renew the fame old ideas again in the 
 memory ; nor could difagreeable ideas, returning into 
 the mind, without the affiftance of external objedts, re- 
 produce the fame effedts, as would the difagreeable ob- 
 jects themfelves ; nor, otherwife, could there- be fo con- 
 ftant and manifeft a connection of analogous ideas, 
 which moft powerfully occur in dreams, according to 
 the corporeal caufes which then remarkably a£l in the 
 brain. Whether or no do imagination and memory 
 depend on this confervation of ideas ? Finally, thofe 
 changes in the fenforium, which many term part; 
 or referved ideas, are, for diftiiuffion’s fake, by us cal- 
 led the footjleps or traces of things, which are lodged or 
 engraved not in the mind, but in the body itfelf, by 
 certain notes or charaO:ers, incredible in their minute- 
 
 nefs. 
 
Chap. XVIII. SENSES. 293 
 
 ncfs, and infinite in their number, recorded after an in- 
 expreflible manner in the medulla of the brain, A-. 
 mongft thefe charafters, fuch are more eminently and 
 diftindly preferved as were received, firft by the fight, 
 and next by the hearing ; for thofe of the other organs 
 are more confufed and irrevocable by the will. And 
 both the traces and their figns are preferved ; the latter 
 more eafily; the former, however, fo far, that a painter 
 can eafily exprefs with his pencil upon canvas, an image 
 of a face fimilar to one which he is accuftomed with, 
 and which is impreffed on his mind. 
 
 559. Imagination, then, is whenever any fpecies, 
 preferved in the common fenfory, and in prefent per- 
 ception, excites fuch other thoughts in the mind as 
 would arife if the perceiving nerve that gave the firft 
 birth to the faid fpecies was itfelf affeCled or changed. 
 This definition is confirmed by examples of the great 
 ftrength of fancy in certain perfons, and thofe who are 
 delirious ; but in every body, in the inftance of dreams, 
 in which thoughts arife in the mind, occafioned by the 
 corporeal fpecies referved in the brain, fo as to be not at 
 all weaker than thofe which were firft formed by the 
 chang^'in the fentient nerve, from the external objedts. 
 Even more, the attention and reft of the mind, with 
 the abfence of all external objedts, will often obtain a 
 ftronger alfent from dreaming, towards the traces im- 
 prcfled in the brain, than that which is given from the 
 mind by the perceptions which are excited from exter- 
 nal objedls : for the will is more powerfully determined 
 in thofe who dream, than in thofe who are awake, fo 
 as often to perform certain adlions by the voluntary 
 mufcles, while they arc aflcep, which they never can 
 perform aw’ake, even though the fame nerves were 
 more ftrongly affedfed by the real objedls. From 
 hence we may underftand, how it is poflible the inter- 
 nal fpecies, which are very ftrong in a delirium, may fo 
 impofe upon the mind, as to make her miftake them 
 for the perceptions of external objedls ; as, for example, 
 in the fiery fparks which are excited by prefling the 
 N n 2 eye 
 
<194 INTERNAL Chap. XVIII. 
 
 eye and optic nerve ; in the rednefs feen by the eye 
 .when it is fhut; in the vertigo or rotation that arifes 
 from a motion of the retina, which we aferibe to the 
 the external objedls themfelves ; in the duplicity of 
 f]ght, &c. 
 
 560. But memory is, when any internal former 
 thought of the mind, or the fpecies perceived and pre- 
 ferved in the brain, from external objects (372.), re- 
 peat or excite again other perceptions in the mind. 
 And here the perceptions are commonly weaker than 
 in the imagination, being almoft only certain arbitrary 
 figns conjoined together, with the idea that was firlt 
 perceived in the mind : for the memory hardly repre- 
 fents the images and pictures of things to the mind ; 
 only the words or figns, and certain attributes, together 
 with the general heads of ideas ; lor which reafon, they 
 move the will with lefs force ; but it appears from the 
 obfervation of thofe changes which happen in the me- 
 mory, that fuch as arife Irotn the external fenfes, re- 
 main longed in the brain ; and fometimes, if they made 
 a drong imprellion, they may for ever, and in all ages 
 pf life, be repeated to the mind ; but they arc weaken- 
 ed, and in a manner blotted out in time, by degrees, 
 unlefs the reprefentation be renewed again to the mind, 
 either from an external objedt, or from the mind itfclf 
 recalling the fame change again into memory : fo that, 
 without this repetition, at lad the change or imprefliori 
 will be in a manner erafed and quite lod ; and will 
 never be able to be drawn in again to the mind, 
 whenever die repeats fuch other thoughts as had 
 naturally any connection with the former. This de- 
 drudtion of new and different fpccies, conveyed to 
 the fenforium, is evident, not only from th,e effect 
 of time, but likewife from cataleptic diforders : which 
 fometimes, after a confiderable interval of time, go 
 on with the fame train of thoiuTht which the difeafe 
 
 O 
 
 had interrupted. But fometimes all of them will be 
 fuddenly dedroyed by difeafe, in which the brain is any 
 lipw comprefled, eithfr from the blood or other caufes. 
 
Chap. XVIII. SENSES. 295 
 
 Such a compreffing caufe, afting on fome part of the 
 common fenfory, blots out a cprrefponding number of 
 the fpecies.froin the mind or memory, whether they be 
 certain or all kinds of words, or even the charaSers by 
 which we exprefs words ; or, laftly, the characters of 
 our friends, and necelfaries of life : yet all thefe fpecies 
 are often again renewable to the mind, whenever the 
 compreffing caufe is removed. But the Iirength and 
 duration of an idea depends upon its being either un- 
 ufual, of a ftrong aCfion, or greatly conducing either to 
 increafe or leflen our felicity ; or, laftly, from being 
 joined with great attention from the mind, and often 
 repeated : all which circumftances being conjoined, 
 may render the fpecies fo ftrong to the mind, that ffie 
 will afterwards receive the perception of them, as if 
 they came from external objects, in the manner we ob- 
 ferve in mad people. 
 
 561. Moreover, if we review the liiflory of human 
 life, it will appear, that in the beginning of our infancy, 
 we have hardly any memory ; only fimple perceptions, 
 that foon vanilh ; which, neverthelefs, do for the pre- 
 fent excite ftrong thoughts or impreffions in the mind, 
 as we learn from the clamours of infants. But, after- 
 w'ards, /he memory is perfected by degrees, and the 
 ideas received from perfons moft beloved and familiar 
 to the infant remain imprefled in the mind ; while, at 
 the fame time, the imagination likewife increafes in 
 proportion, fo as to be often very pow'erful in young 
 children ; as we fee, for example, in frights, which 
 in no age producp more violent or fatal effeCts, 
 From thence forward, as the number of our ideas in- 
 creafes, the faculty of preferving thofe paft, weakens ; 
 and, at the fame time, the power of the imagination is 
 more torpid or fluggiffi : till at laft the former almoft pe- 
 riffies, and the ideas, which are received but a ffiort 
 time, efcape from the brain ; while, at the fame time, 
 the imagination, which is a kind of memory, languiffies 
 in proportion. 
 
 562. But fince the perceptions thus formed in the mind, 
 
 produce 
 
INTERNAL Chap. XVIR. 
 
 produce in her various changes, which are perfedly 
 free, and diftind from any corporeal faculty, we fhall 
 briefly add fomething concerning them, fo far as may 
 fuffice to the purpofes of phyfic. The office of cogita~ 
 tion in the foul, is to attend to the fenfations which arc 
 either brought by the fenfes, or recalled by the imagi- 
 nation ; frequently alfo to the figns alone which recur 
 into the mind. Attention^ then, is fald to operate when 
 the mind obferves one and the fame idea alone, and for 
 a longer time together. The comparifon of two or 
 more ideas brought to the mind, is called reafon; as 
 the fimilitude, diverfity, or relation perceived by the 
 comparifon, is judgment. The principal caufe of 
 •wlfdom and. invention lies in a flow examination of the 
 ideas, confidered in the relation of all their parts one to 
 another in the mind, while, negleding all other objeds, 
 fhe is employed with a flrong attention only upon that 
 which is under examination. From hence proceeds 
 that efficacy of folitude and darknefs in making difficult 
 calculation ; with the more exquifite attention of blind 
 people to the nature of founds ; and of thofe who are 
 deaf, to colours. The fource of error, is fome negled 
 in contemplating the whole idea, or the making an efli- 
 mate of it from only a part of its note or charader, or 
 from a lefs congruous connedion of fome ideas with o- 
 thers that arc diftind, but only related by accident, 
 external caufes, or affedions. 
 
 563. The integrity or foundnefs of the judgment 
 depends upon a perfed and healthy conftitution of the 
 brain. For the fabric of the encephalon being chan- 
 ged, either by compreflure, irritation, or a deficiency 
 of blood, confounds all the ufe of reafon ; occafions 
 the flrong internal fpecies of the brain to be reprefent- 
 ed to the mind as if they came from external or real 
 objeds ; breaks the connedion of the ideas, fo that 
 the mind cannot compare them together ; and is con- 
 fequently unable to judge of, or forefee, their propor- 
 tions, differences, or confequences ; darting imme- 
 diately from one idea to another that has no kind of 
 
 rela- 
 
SENSES. 
 
 Chap. XVIII. 
 
 597 
 
 relation; or laftly, the aftions of the fenfes being either 
 weakened or abolilhed, and the brain in a manner de- 
 prived of its corporeal fpecies, the man is reduced to 
 the date of an ideot or a plant. But the powers of 
 external bodies alfo have a confiderable influence in 
 changing the fpecies of objeds, which the mind ac- 
 quires by the fenfes ; for the air, way of life, food, 
 and cudoms, either help or diminifh the foundnefs of 
 the judgment, the force of the imagination, and the 
 drength of the memory. 
 
 564. Finally, as thefe ideas are either indifferent to 
 us, or elfe conduce to the lofs or increafe of our feli- 
 city, fo they produce different determinations in the 
 %vill. Some of thefe ideas, by which the felicity of our 
 mind is either increafed or diminifhed, arife merely 
 from the mechanifm of the perfed body ; and amongd 
 thefe corporal pain is a forrowful fenfe or perception in 
 the mind, to which every violence or over-drong fen- 
 fation in any nerve feems to ferve as a foundation ; 
 while pleafure confids only in the nerve’s being irritated 
 beyond what is ufual, but in a moderate degree. 
 Itching dands related to pleafure, inafmuch as both of 
 them have an increafed flux of blood into the parts in 
 which either the pleafure or the titillation is per- 
 ceived ; but, when increafed, it tends towards pain, 
 or to an over violent fenfe of the nerve. Anguifh 
 or anxiety is from an over didenfion of the veffels, be- 
 caufe the blood is hindered from paffmg freely through 
 the lungs. The other ideas with which the mind is 
 affeded, are either wholly abdraded from the proper- 
 ties of matter or body, or are at lead much lefs fnnple 
 than the foregoing, which arife either from fenfe or 
 mechanifm. The perception of good ideas excites 
 joy ; the defire of polfefling good excites love, as the 
 expedation of it is the caufe of hope : on the contrary, 
 prefent evil caules forrowfulnefs, terror, or defpair ; 
 the defire of fliunning evil excites hatred ; and the ex- 
 pedation of a future evil excites fear. Hope, curio- 
 fity, and glory, feem to be affedions of the human 
 
 mind, 
 
2 p8 INTERNAL Chap. XVIIL 
 
 mind, which neither belong to the body, nor are to 
 be found in beads. 
 
 565. From thefe affections of the mind, the mere 
 will appears not only to be determined to fome lore- 
 feen parpofe, to which it directs the actions of the bo- 
 dy, in order to poflefs good and avoid evil j but alfo 
 in the body itfelf, unconfulted, "and making no great 
 reffftance, it exercifes an equal dominion over the puife, 
 refpiration, appetite, ffrength, affedions of the heart, 
 nerves, and ftomach ; with the changes which arife in 
 the other parts, ferving as figns of the pafiions in the 
 mind, from which they immediately fofow. Thus 
 anger excites a violent motion of the fpirits, caufes a 
 a palpitation in the heart, a frequency of the puife, a 
 greater ffrength of the mufcles ; urges the blood into 
 the fmaller pellucid and improper velfels ; and, laffly, 
 haffens the expulfion of the bile from its veffels ; by 
 which means it frequently removes obffrudions, or 
 eafes chronical difeafes. Grief, on the contrary, weak- 
 ens the ffrength of the nerves, and the adion of the 
 heart ; retards the motion of the puife ; deffroys the 
 appetite and digeffion ; whence it produces a palenefs, 
 cachexy, diarrhoeas, jaundice, fcirrhofities of the glands, 
 and other flow difeafes, ariffng from a ffagnation of the 
 humours. Thus, alfo, fear fo much diminifhes the force 
 of the heart, as to occafion polypufes, palenefs, and 
 weaknefs of the mufcular motions, a palfy or relaxation 
 of the fphinders, an increafe of the inhalation of va- 
 pours, but a diminution of thole difcharged by perfpi- 
 ration. Terror from a prefent evil, will alfo increafe 
 the ffrength to fo great a degree, as to caufe convul- 
 fions and a ffrong puife ; whence it fometimes removes 
 obffrudions in palffes, or, by intercepting the courfe of 
 the blood, it kills fuddenly. Love, hope, and joy, 
 promote the perfpiration, quicken the puife, and give 
 the blood a free circulation ; whence thev increafe 
 the appetite, and render difeafes curable. But excef- 
 five and fudden joy often kills, by increaffng the mo- 
 tion of the blood, and exciting a true apoplexy. 
 
 Shame, 
 
Chap. XVIII. SENSES. 25.9 
 
 Shame, after a peculiar manner, retains the blood in 
 the face, as if the veins were tied ; it will alfo fupprefs 
 the menfes or other fecretions, and has been even 
 known to kill. 
 
 566. But in what manner are thefe changes pro- 
 duced, from the commotion of thofe pallions in the 
 mind ? Do not the nerves cover the velTcls like fphinft- 
 er mufcles, fo as, by contracting them fuddenly, to 
 increafe the courfe of the blood, or, by relaxing and 
 weakening their tone, retard and vitiate the circulating 
 juices ? That this is the cafe in the fmaller yeffels, ap- 
 pears evidently from the near fimilitude of effects in 
 fear and cold upon the nerves of the fldn. Eut in the 
 genital parts, from a conflridtion of the veins, under 
 particular circumflances, we perceive that the blood is 
 manifeflly collefted or accumulated in the parts : and 
 it is no lefs. probable, that, even in the larger veffels, 
 the nervous bridles with which many of them are fur- 
 rounded produce the fame effects : for thus, in feveral 
 parts, they furround and include the meningal, tempo- 
 ral,^ vertebral, carotid, fubclavian, cceliac, mefenteric, 
 renal, and other arteries. But after it is fhewn by 
 our experiments, that the nerves are at reft during the 
 action of the mufcles, nor can be rendered fhorter by 
 any irritation, we muft defert this elegant theory. 
 Nor does 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 contrafted 
 more vehemently or languidly by the fame quantity of 
 blood ; and thus the motion of the blood is either 
 quickened or flackened, if it is at all certain that the 
 fmaller arteries have the fame irritable nature which 
 is common , to the large ones. And thus it is that 
 the appetite and periftaltic motions of the alimentary 
 tube are manifeflly deftroyed or depraved by the paf- 
 fions of the mind. 
 
 567. Nor is it to be denied, that the Creator has 
 affxed certain chara6terlftic marks or evident figns to 
 the paflions of the mind, that in mutual fociety one 
 
 O o man 
 
gao INTERNAL Chap. X\TIL 
 
 man might not impofc upon another. For the refpeC' 
 tive mufclcs, more efpecially of the voice^ face, and 
 eyes, do naturally exprefs the feveral paflions of the 
 mind, fo faithfully, that they may be even reprefcnted 
 by a painter. To run through them all would indeed 
 be an elegant theme, but too long for this Compen- 
 dium. From the atfions of thefe inufcles, often re- 
 peated by the alFedfions, follows the features or phy- 
 fiognomy of a perfon’s face, which is a perpetual in- 
 dex to the ftate of the mind, and retains fomething of 
 the afliion of the prevailing mufeles fo that the ap- 
 pearance of anger often remains in the countenance, 
 after the paflion itfelf is gone off. 
 
 568. From whence proceeds the confent of parts^ 
 which is fo famous and often repeated by writers on 
 the pradlice of phyfic? Some of them appear to de- 
 pend upon the conjunction or inofculation of the blood- 
 veffcls ; by which the blood, being driven out of one, 
 is more ftrongly urged into another veffel, which has its 
 branches from the fame common trunk. Hitherto belong 
 the revulfrons made by blood-letting, the pains of the 
 head, which enfue from a cold in the feet. See. In 
 other parts, the confent arifes from a fimilitude in their 
 fabric, by which they fuffer like effedls from the fame 
 caufes in the body : hitherto we refer the confent that 
 is betwdxt the womb and the breafts. Another caufe 
 of this confent is, a continuity of the membranes, ex- 
 tending from one part to another : from hence a Hone 
 in the bladder excites an itching in the glans of the 
 penis, a diarrheea cures a deafnefs arifing from a de- 
 fluftion. Another caufe of confent lies in the nerves 
 themfelves, and their anaftomofes or communications 
 one with another, as appears plainly from the teeth be- 
 ing flupified or fet on an edge by certain founds, be- 
 caufe the various communications which the hard portion 
 of the auditory makes with the maxillary nerve transfer 
 the difagreeable fenfe to the latter. Thus alfo, the fympa- 
 thy of the eyes, which is not obfervable in like manner 
 in the ears, proceeds from the mutual conjuntlion of the 
 
 optic 
 
CHAP.XVm. SENSES. gef 
 
 optic nerves within the fkull ; and thus a ftone in the 
 kidney excites vomiting. Laftly, the confent may 
 proceed from fome caufe afting on the common fen- 
 fory, and beginning of the nerves, whence the irrita- 
 tion of a Tingle nerve manifelUy excites ample convul- 
 fions, fpreading through the other parts ; fo an univer- 
 fal epilepfy will proceed from a local diforder, &c. A 
 confent is obferved, in fome difeafes, from a tranflation 
 of the matter of a difeafe by filtration through the 
 cellular fubftance of one part to another ; and another 
 kind proceeds from the incumbent weight or a£lionsof 
 the adjacent mufeks and arteries. 
 
 569. But there is flill another remarkable confent 
 to be explained betwixt the body and the mind. For 
 that the nature of the mind is different from that of the 
 body, appears from numberlefs obfervations ; more efpe- 
 cially from thofe abftraiQ; ideas and affections of the 
 mind which have no correfpondence with the organs 
 of fenfe ? For what is the colour of pride ? or' what the 
 magnitude of envy or curiofity ? to which laft there is 
 nothing fimilar in brute animals ; neither can that hap- 
 pinefs which is defired by it, viz. the glory of new 
 ideas, be referred as an acquifuion to any corporeal 
 pleafure. For is it poflible, that a body can acquire 
 -two kinds of forces, by the uniting of an infinite num- 
 ber of fmaller parts into one mafs ; each of which 
 fhall not only preferve their own particular properties 
 and affeCfions, and reprefent themfelves, but alfo join 
 together into one confeious whole, differing from all 
 the charaCferiftics of its component parts, and yet be 
 capable both of perceiving and comparing the attri- 
 butes of thofe parts ? Is there any one inftance of a 
 body, which, without an external caufe, can, like the 
 mind, pafs of itfelf from reft to motion ; or is there 
 any body that can change the direction of its motion, 
 without the action of fome other caufe ? Let thofe con- 
 fider who have well obferved the voluntary aCtions of 
 •the human body from the mind. 
 
 570. Yet the mind, however different from the na- 
 
 (5 o 2 tui e 
 
302 INTERNAL Chap. XVIII. 
 
 nature of the body, is clofely tied to the fame, under 
 certain conditions : fo that (he is obliged to think upon 
 thofe fpecies which the body offers to her perception ; 
 and again, fo that die cannot perceive, remember, 
 nor judge, without the ufe or reprefentation of thofe 
 corporeal fpecies, which are lodged in the brain ; and 
 again, by her will, is the caufe of the greatefl and fwift- 
 efl motions in the body. 
 
 571. Thofe have behaved modefUy who, confefling 
 themfelves ignorant as to the manner in which the bo- 
 dy and mind are united, have contented themfelves with 
 proceeding no farther than the known laws which the 
 Creator himfelf has preferibed, without inventing and fup- 
 plying us with conjectures not fupported by experience. 
 We may be manifefUy excufed in this refpedt, from the 
 obfervation (556.), which is here equally certain as in 
 optics, that the affedtions of bodies cohere with the 
 thoughts of the mind, by an arbitrary relation or con- 
 nedtion ; in fuch a manner, that they would produce 
 other thoughts of a different kind, if the Creator was 
 to alter the figure of the refradfing power, or colours 
 of the parts of the eye. Thus he has eftabliflied a law, 
 which obtains always, betwixt the leaft refrangible 
 rays and the connexion of a red colour or idea in the 
 mind : thus there is a law betwixt the imprefiion of 
 thofe rays upon the retina, and the connedlion which 
 he has appointed of the correfponding thought. Nor 
 need we be more afliamed to confefs our ignorance in 
 the mechanifm of this ultimate law in the effedfs of 
 nature, than we are to own ourfelves unacquainted 
 with the firlt caufes of our being. 
 
 572. But it will perhaps be demanded of us. Whe- 
 ther the mind does not govern the whole body ? and 
 whether or no all the motions and adtions in the body 
 do not arife from the mind, as the immediate fpring and 
 principle of motion ? Whether even the motion of 
 the heart, arteries, and refpi ration, does not arife from 
 the niind, confeious and folicitous for the common 
 
 good 
 
Chap. XVIIL SENSES. 303 
 
 good of the whole fyftem ? Whether this power of 
 the mind does not appear in the flopping of hemor- 
 rhages from W'ounds, by grumous concretions ; to 
 which add, the force of paffions of the mind,, and the 
 power of the mother’s imagination, in the marking 
 or other blemifiics of infants ? Whether the ab- 
 fence of confcioufnefs in the mind, with refpefl to thefe 
 defedts, be not excu fable, from the known obfcurity of 
 attention which flae gives to the refpiration, the motion 
 of the eye-lids, and raufcles of the eye itfelf, the ear, or 
 tongue ; all which motions, we know’, are effedled by 
 the will, although we know not the organs, nor take 
 any notice of the aftion of the will, when we breathe, 
 look, hear, or even w’alk, while w’e are taken up with 
 other thoughts? Whether or no is it certain, that all 
 bodily motions arife from the mind, on the account of 
 our being unable to find out any other caufe, con- 
 fiantly united to the body, to which we can manifefllv 
 refer them ? 
 
 573. There are indeed many reafons which will not 
 permit us to confent to this opinion. And, firfl, the 
 conflruftion and government of the body itfelf appear 
 greatly to exceed all the power and wifdom of the 
 mind. The mind is able to fee but one point diflinclly 
 at a time (555.), and it can think only one thought or 
 idea at once : for if it endeavours to fee two objedts at 
 a time, to contemplate two different ideas together, or 
 read two letters at once, the fenfe of both is immediately 
 confufed, the mind flrays in her reafoning, and makes 
 no right judgment of either object ; infomuch, that be- 
 ing fenfible of this her weaknefs, whenever Ihe endea- 
 vours to make a ferious and diligent inquiry into any 
 object or intended work, flie w’ithdraws herfelf, and 
 (huts up all the ports of fenfe, without taking any im- 
 prefiions either by the fight, hearing, fmelling, &c. or 
 without exercifing any of the voluntary motions of the 
 mufcles. But the mind ought to be capable, not only 
 of infinite thoughts, but alfo diftindt ones, for her to be 
 able to perform and govern fo many hundred mufcles, 
 
 organSj 
 
304 INTERNAL Chap. XVIH. 
 
 organs, veffels, and moving fibres, in fuch a variety of 
 ways, and with fo great an exaftnefs, as is difficult to, 
 or even above all the folutions that can be given by the 
 working of geometrical problems : and yet, by this hy- 
 pothefis, the mind, ignorant both of herfelf and of her 
 works, ought not only to be equal to fo immenfe a talk ; 
 but likewife, at the fame time, the muft, over and above 
 thofe works, be capable of contemplating the inofl diffi- 
 cult and abdradfed ideas, without either difturbing her 
 meditations by the cares which concern the body, or 
 neglefting any of her neceflary corporeal offices by the 
 variety of her mental operations. 
 
 574. Moreover, if, without being confcious of our 
 will, we are neverthelefs able, by that faculty, to influ- 
 ence the refpiration, the winking of the eyes, &c. and 
 even to be able not only to govern, but alfo to fufpend 
 our breathing, ffiut or dofe our e3^es, and open them 
 again ; it follows from thence, that we never lofe either 
 the confcioufnefs or the ufe of thofe aftions, and con- 
 fequently neither the government of them. But we 
 are able to perform nothing of this kind in the heart or 
 inteftines ; we cannot reftrain the motion of thofe parts 
 when they are too quick, nor excite them when they 
 are too languid. In fuch a number of perfons as inha- 
 bit the world, why do we not meet with fome who can 
 govern the motion of their guts? or why, in all the 
 ages of the world, not one who could govern the con- 
 tradtions of the heart? If cuftom only is the caufe of 
 this unknown power, why does not the mind receive a 
 fenfe of her adion, in moving the heart, after it has 
 ■fiood ftill for whole hours, or even days, in fwoons, in 
 hyfteric fits, and in perfons drowned ? 
 
 575. But it is evidently a falfe pofition, that all the 
 motions of the body arife from the mind, without which 
 the body would be an immoveable unaftive mafs : for 
 the force of niufcular contradion, by any kind of fti- 
 mulus, to which the motion of the heart, intefiines, and 
 perhaps all the other motions in the human body are 
 obedient (49iO> i^ot require the prefence of the 
 
 mind ; 
 
Chap. XVIII. SENSES. 305 
 
 mind ; fince that power continues a conliderable time 
 in a dead body, and may be recalled again into aftion 
 by mechanical caufes, as heat, inflation, &c. Nor does this 
 power defert the fibres fo long as they continue unflif- 
 fened by cold, although the mind may have been a long^ 
 time feparated from the body by a deftruction of the 
 brain : and this action we fee more evidently in the 
 heart, after that mufcle has been taken out of the body 
 for fome time, fo as to be feparated from any imagi- 
 nable connexion with the mind. 
 
 576. As to the blemifhes of infants, we have decla- 
 red in another place, how little that article is to be de- 
 pended on. The adminiftration of the vital motions, 
 in difeafes, is not under the rule of any prudence, but 
 governed ahnofl entirely by the power of ftimulus ; as. 
 we are manifeftly taught from the inoft ancient and 
 only certain praftice, by which wu are direfted to re- 
 ftrain the too great violence of thefe motions in acute 
 and intermitting febrile difeafes, by the ufe of blood- 
 letting, with the poppy, nitre, Peruvian bark, &c. The 
 wifefl philofopher in the world has no more privilege 
 or advantage in the government of his body, than the 
 merefl ideot ; and that even infants fliould build up the 
 fabric of their own body, before they know that they 
 have any niufcular motions, is an affertion fo far from 
 being credible, or even moderately probable, that of 
 itfelf alone it is fufficient to refute the hypothefis. 
 
 577. A ready difpofition to the exercife of fenfe and 
 voluntary motion, in healthy organs, is called vigilance 
 or voakefulnejs ; but an indifpofition to fuch an exercife 
 of them, with an inclination to reft, in all the laid or- 
 gans, while they remain healthy and entire, is called 
 fieep. 
 
 578. In lleep, the mind either thinks not at all of 
 what Ihe knows or retains in memory ; or elfe lire only 
 attends to the traces of paft objects repofited in the 
 common fenfory (558.), the vivid reprefentations of 
 w'hich excite altogether the fame perceptions as are 
 made by the impreflion of external objedls upon the 
 
 organs 
 
3 o 6 I N T E R N a L Chap. XVIII. 
 
 organs of fenfe, by which they were firfl received. 
 Thefe reprefentations of fpecies to the mind are called 
 dr emits ; and happen whenever a finail portion of the 
 brain or common fenfory is, by the refluent motion of 
 the fpirits, kept in a flats of vigilance, while all the re It 
 of the empire of fenfe and voluntary motion is blent 
 and at reft. Sometimes there are certain voluntary 
 motions, following of courfe from the perceptions thus 
 perceived by the mind, fuch asfpeech, or motion of all 
 or fome of the lim.bs, conformable to the nature of 
 •what the mind perceives ; and hitherto are to be refer- 
 red thofe who walk in their flecp. 
 
 579. But, during the time of flecp, the motion of 
 the heart, with the diflribution and circulation of all the 
 other humours in the body, are regularly continued, 
 together with the periftaltic one of the flomach and in- 
 teflines ; and, finally, the action of the fpinfter mufcles, 
 with the refpiration, are continued in a like manner. 
 This compolition, in which a certain number of the or- 
 gans are at reft, while others continue their motions, 
 renders a knowledge of the mechanical caufe of fleep 
 fomevvhat difficult to attain. 
 
 580. Therefore, in order to make this difcovery, 
 with all its caufes, we fliall confider all the appearances 
 both of fleep and vigilance, and trace them in all kinds 
 of animals; for that condition which appears conflantly 
 to follow from all thofe caufes and appearances, will be 
 the true and mechanical caufe of fleep. Sleep natu- 
 rally follows after the vigilance and labour winch are 
 joined to human life. For when a perfon is awake, 
 there is a continual motion or exercife of the voluntary 
 mufcles, of the parts which guard the fenfes, and of the 
 affections of the mind ; all which continually add a new 
 ftimulus to the nerves, blood-veffcls, and heart itfelf. 
 Thus the blood, by continual motion and triture, 
 changes its fmooth albuminous nature, to a rough al- 
 kaline, and in fome degree putrid, fliarpnefs ; while, 
 at the fame time, its more fluid parts, efpecially thofe 
 fubtile ones which compofe the nervous fpirits, are diffi- 
 
Chap. XVIlI. SENSES. 307 
 
 pated farter than they are fecreted ; whence gradually 
 enfues both a weaknefs and a wearinefs of the body : 
 and, if the vigilance be continued longer than ufual, 
 there is alfo a feverilh heat, a greater acrimony of the 
 humours, and a fenfible lofs of rtrength. As the night 
 advances, a weight or heavinefs feizes all the large 
 mufcles and their tendons, the mind becomes' unfit for 
 any accurate thought or ftudy, and feeks after reft. 
 ^Hereupon the powers which hold the body ereft, 
 rtirink from their office, the eye-lids clofe, the lower 
 jaw falls down, a neceffity of yawning comes on, the 
 head nods forward, and by degrees we take lefs notice 
 of the external objecls, which alfo affeft us lefs, till at 
 length all the thoughts and ideas are in confufion, and 
 a fort of delirium enfues ; from whence there is a tran- 
 fition to fleep not known to us, v/hich however always 
 precedes fleep. In this natural fleep, which is common 
 to all animals, the caufe feems to be a deficiency of the 
 nervous fpirits, which have been every where largely 
 confumed by the exercifes of the mufcles arid fenfes, in 
 whofe a£lions there is probably a great quantity of this 
 fluid exhaled. 
 
 581. A perfect reft or compofure of the mind and 
 external fenfes, with the abfence of all ftimulus or irri- 
 tation in the head and other parts of the body, joined 
 with darknefs, promote and haften the forementioned 
 fteps of fleep, and render it more quiet or pro- 
 found. 
 
 582. Again, it is obfervable, that a variety of caufes, 
 which weaken the powers, incline to and increafe fleep 5 
 fuch as great Ioffes of blood from any caufe, bleeding 
 from a vein, the ufe of cooling medicines or thofe 
 prepared from the poppy, and cold of the external air ; 
 to which add, fuch as call off the quantity of blood flow- 
 ing to the head, as warm-bathing of the feet, a plenti- 
 ful ingeftion of food into the ftomach, which is found 
 to produce fleep in all kinds of animals. 
 
 583. On the contrary, again, there are various hot 
 medicines which induce fleep, by exciting a greater af- 
 
 P p - ffus 
 
3-o8 internal Chap. XVItL 
 
 flux of blood to the brain ; fuch as wine, alcohol, or 
 vinous fpirits of all forts, but more efpecially when re- 
 folved into vapour, opium, hyofcyamus, the indi- 
 geftible particles of our aliments ; to which add, acute 
 and malignant fevers of various kinds, or elfe fuch 
 things as retard the return of the venous blood, as fat- 
 nefs. All thefe caufes feem to concur in this, that the 
 blood being colleded in the head, compreffes the brain, 
 fo as, in a degree, to intercept the courfe of the fpirits 
 from thence into the nerves. 
 
 584. But likewife mechanical caufes produce a fleepi- 
 nefs; namely, a compreffure of the dura mater and 
 brain, whether from extravafated blood, a deprelfed 
 part of fome bone, or a collection of ferous water with- 
 in the ventricles of the brain itfelf. 
 
 585. Sleep, therefore, arifes either from a Ample de- 
 ficiency of the quantity and mobility of the fpirits, or a 
 compreffure of the nerves ; but always from a more 
 difficult motion of the fpirits through the brain. 
 
 586. This theory is likewife confirmed by the caufes 
 of vigilance : for all thofe things prevent fleep which 
 produce plenty of fpirits; more efpecially warm aroma- 
 tic drinks, which fend plenty of minute ftimulating par- 
 ticles to the head, by which the motion or courfe of the 
 blood is moderately quickened through the brain ; and, 
 being at the fame time more dilated, makes a larger 
 fecretion of fpirits in a given time. 
 
 387. Sleep, again, is hindered by cares of the mind, 
 meditation, fludy, and paflions of a llronger degree, 
 with pains of the body and mind ; all which hinder the 
 fpirits from refling in the common fenfory, or urge 
 them fo as to preveht the nerves from collapfing. 
 Therefore, as the former increafe the quantity of the 
 fpirits, thefe caufes increafe their motion. And there- 
 fore, again, the fame conclufions are to be made from 
 hence as before (585.); namely, that the nature of 
 fleep lies in a collapfing of the nerves which go out 
 from the common fenfory. 
 
 388. If it be inquired, Whether the feat of fleep be 
 
 not 
 
Chap. XVIII. SENSES. - 309 
 
 not in the ventricles of the brain ? we anfwer, that it 
 is not confident with the ample bounds or dominions 
 of deep, which extends itfelf even to fuch animals as 
 have no ventricles in the brain. Whether the vital 
 adions continue to be carried on in deep, as it is only 
 an affeftion of the brain independent of the cerebel- 
 lum ? and what may be the caufe of this difference, by 
 which the animal offices red in deep, while the vital 
 operations are continued? We know not of any other 
 reafons, befides thofe before given, that the vital mo- 
 tions are perpetually dimulated into action, from the 
 caufes urging a neceffity of keeping them from red: 
 
 (392-) 
 
 389. The effedl of deep is a moderation or abater 
 ment of all the motions in the human body. For now 
 the adlion of the heart only remains, by which all the 
 humours are fent through the vedels, at the fame time 
 that all the mufcles and perceiving nerves, with the pad- 
 fions of the mind and voluntary motions, are removed ; 
 by which the courfe of the fpirits was quickened not 
 only to the heart, but to all the other organs, fo as to 
 caufe wakefulnefs (565, 417.) Thus the heart is gra- 
 dually redored from its quick and almod feverifh pulfa- 
 tion, to the dow and calm condition in which we find it 
 in the morning ; the breathing in deep becomes dower 
 and fmaller, the peridaltic motion of the domach and 
 intedines, the digedion of the aliments, the fenfe of 
 hunger, and the progreffion of the fseces, are all dimi- 
 nidied ; at the fame time, the thinner juices move more 
 dowly on, while the more grofs and duggidi are col- 
 lected together, and the fat being poured out is accumu- 
 ' lated in the cellular fubdance ; the vifeid albuminous 
 humour, for the nourifhment of parts, adheres more 
 plentifully to all Tides of the fibres and fmall vedels 5 the 
 confumption of the fpirits, the attrition of the blood, 
 and the quantity of perfpiration, are all diminidied. 
 Thus, while the quantity of the nervous fpirits conti- 
 nues to be fecreted, with a lefs confumption, it is by de- 
 grees accumulated in the brain, fo as to didend and fill 
 P p 2 the 
 
gi9 INTERNAL Chap. XVIII. 
 
 the collapfed nerves, which, both in the internal and 
 external -organs, return again to adion^by the approach 
 of fome fmall ftimulus, by which they are again redo- 
 red to vigilance. Sleep, continued for too great a 
 length of time, difpofes to all the diforders that attend 
 a flow circulation, to fatnefs, drowfmefs, weaknefs, and 
 cachexies j and ;s, at the fame time, highly detrimental 
 to the memory. 
 
 590. From whence does yawning attend thofe that 
 are about to go to fleep ? We anfwer. To promote the 
 pafl’age of the blood through the lungs, which is now 
 flower. Whence the firetching of the limbs? To in- 
 creafethe motion of the fpirits, that they may oyer-ba- 
 lance the natural contradion of the mufcles, by which 
 all the limbs are drawn into a moderate degree of con- 
 tradion. If it be demanded. From whence came the 
 unjuft opinion, which has been fo well received, that 
 the motion of the heart becomes ftronger in fleep, and 
 the perfpiration more plentiful ? we anfwer. That the 
 miftake arofe from the increafed heat arifing from the 
 bed-cloaths, by which the perfpirable matter being con- 
 fined, every where conduces to warm, foften, and relax 
 the fkin. But any one that fleeps in his ufual garments, 
 grows colder ; and animals which fleep for a long fea- 
 fon together grow cold externally to the higheft de- 
 gree, as field-mice and hedge-hogs. From whence 
 is it that all animals grow fleepy after taking food ? 
 Not from a compreffure of the aorta, or from a reple- 
 tion of the head with blood j for even animals which 
 have fcarce any brain, fleep after food. Whether or not 
 do the indigeftible particles of our aliments, by pafTmg 
 lefseafily through the brain, and comprefling its medulla, 
 produce fleep of a lefs benign kind ? Whether or not 
 there is a perpetual dreaming, fo as to be infeparable 
 from fleep? and whether this be natural, fo that the mind 
 never ceafes to be without thought, as a confequence 
 following from fenfation ? We anfwer. This does not 
 feein to be the true Hate of nature ; for dreams we 
 judge to be rather referable to difeafe, or to fome fti- 
 
 inulating 
 
Chap.XIX. mastication. ' 3it 
 
 mulating caufe that interrupts the perfed reft of the 
 fenforium. Hence that fleep refreflies moft where 
 there are no dreams, dr at leaft that where we have 
 no remembrance of any. Hence they are generally 
 wanting in the firft fleep, at which time the fpirits are 
 moft exhaufted, and return in the morning when thefc 
 are in fome meafure repaired. Hence we fee, that in- 
 tenfe cares of the mind, or the ftrong impreffion of 
 fome violent idea received in the memory, hard indi- 
 geftible food abounding in its quantity, with any un- 
 eafy pofture of the body, are the moft ufual caufes that 
 excite dreams ; for they are ufually generated by fome 
 fenfation which, by the law of aflbeiation of ideas, joins 
 with itfelf a whole collection of fpecies having an affinity 
 with that one. 
 
 CHAP. XIX. 
 
 Of Mastication, Saliva, and Deglutition. 
 
 591. C? UCH hard and tough foods as confift of long 
 parallel fibres, or are covered with a bony fheli 
 or cartilaginous fkin, generally require maftication, to 
 divide them into lefs cohering parts, that they may 
 more eafily yield their nourilhment to the diffolving 
 powers of the ftomach. The more diligently they are 
 fubdivided in the mouth, the more reliffiing and agree- 
 able they become to the ftomach ; the nearer do they 
 approach to the nature of a fluid, and the more eafily 
 are they digefted or affimilated. 
 
 592. Therefore moft animals are provided with 
 teeth, extremely hard, :but planted with a root that is 
 indeed bony and hollow ; fince it receives, through a 
 final] hole in the tip or point of each fang, little blood- 
 veflels, and a nerve, which go to form its internal peri- 
 ofteum ; and this whole root, being fixed into a focket 
 of the jaw conformable to itfelf, is, in the upper part 
 mwards its crown, ftrongly furrounded and tied down 
 
 by 
 
312 MASTICATION. Chap.XIX; 
 
 by the adhering gum-. But the crown, or upper part 
 of the tooth, placed above the gums, is not bony ; but 
 a peculiar fort of enamel, of a harder, denfer fubftancc, 
 and almoft of a glaffy texture, compofed of ftraight fi- 
 bres vertical with its root, and running together towards 
 the middle. This lad portion of the tooth, having nei- 
 ther periofteum nor veflels, perpetually grinds away, 
 and is as often repaired again by a kind of petrifying 
 juice, that afcends or filters from the cells of the root, 
 by which mechanifm they are therefore fupplied with 
 a great degree of hardnefs, very fit to overcome that of 
 other bodies, and to grind the food with their unequal 
 furfaces. 
 
 593. As the materials of our food are various in 
 their texture and firmnefs, nature has accordingly 
 made our teeth varioufly figured. In us, the anterior 
 or incifive teeth are four in each jaw, weaker than the 
 reft, and fixed by a fingle root, upon which (lands a 
 crown inwardly concave, outwardly convex, and ter- 
 minated by a gradual extenuation, like a wedge or 
 chifel, with a redilineal edge. The office of thefe is 
 only, in the fofter foods, to cut thofe which are tougher 
 than the reft into fmaller portions ; fuch as the fibres 
 and membranes of animals and vegetables, with the 
 brittle feeds and kernels of fruits. 
 
 594. The fecond fpecies is the canine teeth, which 
 are two only in each jaw, fixed by a longer and 
 llronger, but fingle root ; from whence their crown is 
 extenuated into a cone. Thefe lacerate tough ali- 
 ments, and hold faft fuch as require a longer triturc 
 by the grinders. 
 
 595. The third order of the teeth is that of the mo- 
 lares, which in general are compofed of feveral roots, 
 with a quadrangular crown, fomewhat flat furfaced, 
 but more or lefs divided by rocky afperities. The two 
 foremoft of thefe are weaker than the reft, inferred by 
 two, or often but one root, with the furfacc of their 
 crown parted into two ; but the three pofterior gi ind- 
 ers are larger, fixed by three, four, and fometimes 
 
Chap. XIX. MASTICATION. 313 
 
 five roots, but terminated in their crown by only one 
 furface, fomewhat fquare and flat, but lefs in the lower 
 than upper jaw, and is fubdivided into a number of 
 eminences correfponding to that of their roots. Be- 
 twixt thefe teeth, the moft; compa'dl or bony foods are 
 interpofed and broke, as the more tough 3 bd hard are 
 ground fmaller, while the lower teeth are urged ob- 
 liquely and laterally againfl; the moveable upper ones ; 
 and thefe are the teeth which perforin principally what 
 we are to expert from maflication of food. 
 
 596. That the teeth might break or grind the food 
 with due ftrength and firmnefs, the uppermoft are fix- 
 ed into the fockets of the immoveable upper jaw, as the 
 lower ones are into the lower moveable jaw, which is a 
 Angle bone, and fo joined with the temporals, that it 
 may be drawn down from the upper jaws, and pulled 
 up againfl them with a great force ; and may be mo- 
 ved laterally to the right or left, forward and back- 
 ward. Thofe various motions of the lower jaw depend 
 upon the articulation of its oval heads, in which the 
 lateral parts of the jaw terminate, convex or higheft in 
 the middle, and received betwixt the oblique protu- 
 berances of the temporal bones, in a fhallow excava- 
 tion, at the root of the jugal procefs, deeper in its mid- 
 dle; and increafed by a little excavation of the fame 
 kind before the auditory paffage, from which it is fc- 
 parated by a peculiar fiffure. This joint has the freer 
 liberty in moving, and its incrufted cartilages have a 
 longer duration, by the interpofition of a fmall cartila- 
 ginous plate, betwixt the condyle of the jaw and tu- 
 bercle of the temporal bone ; concave in its middle 
 above and below, with rifmg fides, which furround the 
 tubercle of the temporal bone upward, the condyle of 
 the jaw downward, and correfponds to the adjacent 
 inequalities. 
 
 597. The mufcles moving the lower jaw, which are 
 weak in man, but very flrong in brute animals, are 
 the temporalis and elevator, arifing from a large part 
 of the fide of the fkull, and from the outward tendi- 
 nous 
 
314 MASTICATION. Chap. XIX. 
 
 nous expanfion of it the ftellated fibres run together 
 into a tendon fixed to the fharp procefs of the jaw * 
 the jnajfeter elevator, having two or three diftinft parts 
 or lefs mufdes, defcends from the os jugalis and mar- 
 gin of the upper jaw backward into the angle of the 
 lower jaw. Both thefe aft in concert ; but the tem- 
 poral mufcle brings the jaw more backwards, and the 
 maifeter forwards. The pterygoideiis intenius defcends 
 from the pterygoide folTa, and from the palate bone and 
 root of the little pterygoidal hook, with the internal 
 wing, into the angle of the lower jaw, which it elevates 
 or draws to one fide or the other alternately. The 
 pterygoideus externus has a double origin ; one tranf- 
 verfe from the inner wing and adjacent bone of the pa- 
 late, with the pofterior convexity of the upper jaw : 
 the other, defeending, arifes from the hollow tempo- 
 ral part of the great wing of the fphenoides ; thence it 
 proceeds backward and downward into the outer part 
 of the condyle of the lower jaw, \vhich it moves late- 
 rally, and draws forward before the upper jaw. 
 
 598. The lower jaw is depreffed, fo as to open the 
 mouth by the digraftric or biventer mufcle, ariiing 
 from an hollow of the mamillary bone ; from whence 
 defeending, its middle tendon is tied by a firm cellular 
 fubftance of a tendinous nature to the os hyoides; and 
 being likewife connefted to the mylohyoideus, and 
 then palling through the divided fibres of the ftylo- 
 hyoideus, it is increafed by another flelliy belly, in- 
 ferted at the fymphyfis of the two halves of the lower 
 jaw, within the chin. Moreover, the mouth may be 
 partly opened by all the other lower mufdes of the jaw, 
 os hyoides, and the larynx, as the geniohyoideus, genio- 
 glolTus, llernohyoideus, llernothyroideus, coracohyoi- 
 deus, and latiflimus colli ; although the latter rather 
 draws the fkin of the neck and face downward than the 
 jaw itfelf. The geniohyoideus and digaftric mufdes 
 have a power of drawing the jaw backwards. 
 
 599. The lower jaw is elevated with a great force, 
 fo as to divide the food by the prdTure of the upper 
 
 and 
 
Chap.xix. mastication. 
 
 3^5 
 
 and lower teeth againfl each other, by the a£lion of the 
 temporal, maffeter, and internal pterygoide mufcles ; 
 the contraction of which appears by experiments to be 
 very powerful, and fufhcient to raife feveral hundred 
 weight. The lateral and circular motions of the jaw 
 upon one of its immoveable condyles are performed 
 by the external and internal pterygoidei, acting either 
 alone or together with the former. Thus the food is 
 cut, lacerated, and ground to pieces ; and if the ma- 
 ftication be continued diligently, it is, together with 
 the liquors of the mouth, reduced into a kind of 
 pulp. 
 
 600. The fore-part of the teeth is covered with a 
 cutaneous and flefhy fack, which is every where pro- 
 duced from the integuments of the face ; and miakes a 
 hollow, in which both rows of teeth are fhut up. The 
 fides are called the cheeks^ the middle parts the Ups, 
 From this cavity there lies a paffage, betwixt the teethj 
 into the mouth; which on the upper part is bounded 
 by the bony and foft palate, underneath by the flefliy 
 parts lying under the tongue, and on the fore-part by 
 the teeth. On the back part it opens between the foft 
 palate and tongue into the fauces. The tongue di- 
 vides the cavity of the mouth in the middle, and is 
 eafily moveable to every part of it. 
 
 601. During the trituration of the food in the 
 mouth, there is continually poured to it a large 
 quantity of a watery clear liquor, evaporable or 
 infipid, or at leaft but very little faline, and Con- 
 taining but little earth ; neither acid nor alkaline, 
 although from thence may be obtained a very fmall 
 portion of lixivial fait ; of which there are nume- 
 rous fprings in the neighbourhood. A large quan- 
 tity of this faliva is feparated by numberlefs fmall glan- 
 dules of the lips and cheeks, of an oval figure, and 
 fome larger ones which are placed round the mouth of 
 the duft of the parotid gland ; and lafUy, the pores 
 of the hard palate pour out this liquor, which they fe- 
 crete, through a little fliort duil and hole. The juice, 
 
 Q^q poured 
 
3i6 a L I V a. Chap. XIX. 
 
 poured out from the exhaling veifels of the tongue, 
 mouth, and cheeks, is of the like kind, or rather more 
 watery. As for the ductus incifivus, we are now fuf- 
 ficiently certain that it is blind, or difcharges nothing 
 into the mouth, only gives palfage to an artery from 
 that of the palate into the nares. 
 
 6oJ. The faliva is a watery liquor, w'ith a moderate 
 quantity of fait, partly lixivial, and partly culinary j 
 with fome oil and earth, diffipable by the fire ; with 
 fcarce any tafte, unlefs given to it by difeafe or famine. 
 The quantity produced is very confiuerable, as twelve 
 ounces have been known to flow out from wounds in thofe 
 parts in the fpace of an hour. By good-mannered peo- 
 ple it is for the mofl; part fwallowed ; and ufefully, as 
 it cannot be throwm away without hurting the di- 
 geflion. 
 
 603. But the falival glands efpecially fupply the wa- 
 tery humour called after their owm name. Of thefe 
 the principal is the parotid, filling up a large interval 
 betwixt the auditory pafiage and the lower jaw, to 
 which it is immediately contiguous in the part unco- 
 vered and to the maflfeter. It is a conglomerate gland, 
 made up of round or grape-like clufters, connecled by 
 the cellular fubftance ; which lafl, being denfified and 
 reticulated, forms an almofl tendinous covering that 
 furrounds and connects the w'hole gland. Its duel is 
 white, vafcular, and capacious, afeending from the 
 bottom of the gland to the os jugale, from whence it 
 is tranfverfely inclined, and takes in by the way a fmall 
 du(Sl of a folitary glandule on the top of the maiTeter, 
 or elfe lodged diftindl, or continued upon the parotid 
 itfelf, and is rarely double ; after this the duel, bend- 
 ing round the convex edge of the mafl'eter, opens with 
 an oblique or cut aperture, without, a papilla, through 
 the departing fibres of the buccinator mufcle, in the 
 midfl; of many little glandules of the cheek. The bulk 
 of this gland, and the number of its arteries, make it 
 the chief fpring from whence the faliva flows. 
 
 604. Another fmall gland, adjacent to the parotid, 
 
 but 
 
Chap. XIX. SALIVA. 317 
 
 but twice as little, compofed of fofter and larger ker- 
 nels, connected by the like cellular membrane, is, 
 from its fituation at the lower angle of the jaw, called 
 maxillary ; being in part terminated only by the Ikm, 
 but in part fends off an appendix over the mylo-hyoide 
 mufcle, which, following the long hollow fide ot the 
 lower jaw, of a granular fabric, is fpread under the 
 membrane of the mouth, by the name of fublbigualis. 
 From the larger maxillary, together with this appen- 
 dix, a du£l paffes out, which, being a long way co- 
 vered in its middle part by the fublingualis, receives 
 one, two, or three branches ; by whofe infertion being 
 increafed, it opens into a projecting membranous cy- 
 linder under the bridle of the tongue. But other fmall 
 and fhort duCts from the fublingual gland, from the 
 number of three, four, or more, to twenty ; with 
 fliort little duCts and points in the line continued back- 
 wards from the fmall frenum, perforate the edge of 
 the tongue, and fecrete faliva. There are fome in- 
 flances where the larger anterior branch of the duCl 
 of the appendix, which ufually joins itfelf to the maxil- 
 lary gland, goes on fingle, parallel, and opens by it- 
 felt. Other glands alfo, hmilar to thofe of the 
 cheeks, which likewife may be reckoned among the 
 fublingual ones, by their proper duels perforate the 
 membrane of the mouth where it departs from the 
 tongue. Various other falival duCls have been publifh- 
 ed by different profeffors, which are not confirmed by 
 anatomy. 
 
 605. The Creator has wifely provided, that, by the 
 motion of the jaw in maftication, the falival glands 
 fhall be compreffed by mechanical neceflity, fo as to 
 difeharge their juices then to the mouth in greater 
 plenty. For, when the mouth is opened, the maxillary 
 gland, being preffed by the digaflric and mylo-hyoi- 
 deus, throws forth a fountain of faliva ; the maffeter 
 when fwelled preffes the parotid gland, as does alfo 
 the cutaneous mufcle of the neck which lies over it ; 
 
 q 2 and 
 
318 MASTICATION. Chap.XIX. 
 
 and it is this mufcular prelTure that excites the appetite, 
 and pours the faliva into the mouth. 
 
 606. The food therefore, being in this manner 
 ground betwixt the teeth, and intermixed with the wa- 
 tery faliva and air, is broken down into a foft juicy 
 pulp, pliable into any figure, and replete with elaftic 
 air, which by the aftion of the latter undergoes a far- 
 ther dilfolution, by the warmth of the parts exciting 
 the elafticity of the air to expand and burll afunder 
 the confining particles of the food, betwixt which it is 
 included. In this aft of maftication, the oily, aqueous, 
 and faline parts of the food are intermixed the one with 
 the other ; the fmell and tafte of. different ingredients 
 arc loft in one, which by the dilution of the faline parts 
 with faliva renders the food flavourable : but fuch par- 
 ticles as are more volatile and penetrating, being di- 
 reftly abforbed by the bibulous veffels of the tongue 
 and cheeks, enter ftraight into the blood - veffels 
 and nerves, fo as to caufe an immediate recruit of 
 the faculties. 
 
 607. But the motions which are neccffary for turn- 
 ing round the food, applying it to the teeth, and con- 
 veying it through the different parts of the mouth in 
 maftication, are adminiftered by the tongue, cheeks, 
 and lips. And firft, the tongue being expanded fo as 
 to form a fmall concavity in its back or furface, takes 
 up the food thus prepared, and conveys the charge by 
 its moving powers (450.) to the parts for which it is 
 defigned. At one time the tongue, rendered narrow 
 by lateral contraftion, fearches . every part of the 
 mouth with its tip, and turns out the latent food into 
 a heap on its common concavity. At another time, 
 applying its extremity to the fore-teeth, and raifing it- 
 felf up fucceffively, it draws from the cavity ot the 
 mouth the fluids or chew'ed aliments, and conveys 
 them to the fauces or back part of the mouth behind 
 the teeth. 
 
 608. But thefe motions of the tongue are likewife 
 governed by the mufclcs and membranes, largely in- 
 
 ferted 
 
Ghap. XIX. SALIVA. 319 
 
 ferted into the os hyoides, the bafis of which is inter- 
 nally concave ; from whence are extended horns late- 
 rally and outwards, terminated by more protuberant 
 heads, and completed with little oval cornices ; and 
 this bone being drawn down by its rcfpeftive mufcles, 
 depreifes the tongue at the fame time, and the lower 
 jaw likewife, if the mufcles of that be relaxed. Thefe 
 power's are the Jlernohyoideus, but arifmg alfo in part 
 from the clavicle, extenuated upwards, and ftriped with 
 tendinous lines ; the Jlernothyroideus^ arifmg as the for- 
 mer, and broader from the upper rib ; which mufcle, 
 depreffing the cartilage to which it is inferted, is under 
 a neceffity of pulling down the os hyoides^ to which it is 
 joined : this is partly intermixed with the hyothy- 
 roideus and thyreo-pharyngeus, and every where con- 
 fufed with the flernohyoideus. Next the coracohyoi- 
 deus, arifing from the upper and fliorter fide of the fca- 
 pula, near its notch, afcends obliquely, and at the crof- 
 fing the jugular vein changes into a tendon ; from 
 whence the other belly of the mufcle afcends direfl; to 
 its infertion into the os hyoides, which it depreifes, be- 
 ing every where 'confounded with the flernohyoideus. 
 The hyothyroideus is determined by the former mufcles. 
 
 609. The other powers which elevate the os hyoi- 
 des, together with the tongue, are its Jlyloglojffus 
 mufcle, fuftained by a peculiar ligament of the upper 
 jaw. The Jlylohyoideus , a weak mufcle, often fplit for 
 the paifage of the biventer, and again united into one 
 portion, after adhering to the tendinous expanfion of 
 the biventer, is inferted, together with its fellow, into 
 the angle of the bafis, and often into the horn of the os 
 hyoides : the fecond flylohyoidcus, when it is prefent, 
 refembles the former, behind which it is placed ; arifing 
 from the tip of the ilyloide procefs, it is inferted into the 
 fmall oifa triticea, and anfwers the purpofe of a liga- 
 ment to fuilain the os hyoides. All thefe mufcles draw 
 the tongue back, but laterally they elevate it. The 
 mylohyoideus^ arifmg from the whole length of the jaw^, 
 running into one with its companion, elevates the 
 
 tongue. 
 
320 DEGLUTITION. Chap. XIX. 
 
 tongue, and fixes it in making various motions, or in like 
 manner depreffes the jaw. The geniohyoideus ^ being a 
 companion of the geniogloflus, pulls the tongue forward 
 out of the mouth. 
 
 6 1 o . But, moreover, the mufcles of the cheeks varioufly 
 move and prefs the food in the mouth. Others move 
 it from the cavity of the cheeks into the inner cavity of 
 the mouth behind the teeth, as we fee in the buccina- 
 tor when the mouth is fhut. Others open the mouth 
 for receiving the food ; fuch as the double-headed pro- 
 per elevator of the upper lip, and the elevator which 
 is partly common ; to which add, the zygomaticus, up- 
 per and lower ; the riforius, triangularis menti, and the 
 depreflbr proper to the angle of the mouth ; which 
 arifing from an excavation on each fide, near the focket 
 of the canine tooth, are inferred into the orbicularis of 
 the lips. Others, again, clofe the lips, that the food 
 received may not return out of the mouth ; fuch as the 
 orbicularis of each lip, the proper depreflbr of the up- 
 per lip, and the proper elevator of the lower lip, and 
 that which ferves in common for the elevation of both. 
 Of thefe, more particular defcriptions may be had from 
 profefled fyftems of anatomy. 
 
 611. By thefe means the food, ground and mixed 
 ■with the faliva into a foft pulp, collefted from all parts 
 of the mouth by the tongue into the arched fpace be- 
 twixt the teeth, is afterward, by the expanfion and fuc- 
 ceflive preflure of the tongue, conveyed backward be- 
 hind the teeth ; and, in this action, the tongue is ex- 
 panded by the ceratoglofli and geniogloffi, and rendered 
 a little concave by the Ilylogloflus. And from thence 
 it is next conveyed into the fauces. 
 
 612. For the tongue being raifed by the ftyloglolTi, 
 and broadly applied to the palate, firft: by its apex, then 
 alfo ini'enfibly by its poflierior extremity, prefles the food 
 fuccelTively towards the fauces, which at that time only 
 afford an open paflage. After this, the thick root and 
 back part of the tongue itfelf, by the forementioned 
 mufcles, and by the ftylobyoidei and biventers carried 
 
 back^ 
 
Chap.XIX. deglutition. 321 
 
 backward, preffes down the epiglottis, which ftands up 
 behind the tongue, conneded therewith by numerous 
 membranes, and perhaps by fome mul'cular fibres. At 
 the fame time, the mufcles elevating the pharynx all 
 ad together ; fuch as the biventer, geniohyoideus, ge- 
 nioglolTus, ftylohyoideus, flylogloiTus, ftylopharyngeus, 
 and the other elevators, which now draw the larynx 
 upward and forward, that the epiglottis, being brought 
 nearer to the convex root of the tongue, may be better 
 clofed or depreffed. Hence it is neceflary towards de- 
 glutition for the jaws to be clofed, that by this means 
 the biventer may have a firm fupport ; and, together 
 with the mufcles already deferibed, elevate the os hyoi- 
 des. Thus the epiglottis, being inverted, fiiuts up and 
 covers the paflage very exadiy, into the larynx, over 
 which it is extended like a bridge for the aliment to 
 pafs over into the fauces. 
 
 613. By the pharynx we underfiand an ample fltape- 
 lefs cavity, extended from the occipital bone before the 
 great opening of the fleull downward, along the bodies 
 of the cervical vertebrse, covered above by the middle 
 cuneiform bone, the opening of the nares, and move- 
 able velum of the palate, receiving the tongue and la- 
 rynx before, and continued into the oefophagus below. 
 Its Tides are formed by the lower jaw, the cheek, the 
 velum of the palate, the pterygoid procefs, the ffiliform 
 appendix, the tongue, os hyoides, and larger cartilages 
 of the larynx. It forms one foft membranous bag, 
 outwardly furrounded on all Tides by mufcular fibres. 
 Internally it is lined with a membrane continuous to the 
 cuticle, like which it is renewable, but more moift. 
 Outwardly it is joined to the pharynx with a good deal 
 of cellular fubftance, more efpecially in its pofterior and 
 lateral parts. By this ftrudlure it becomes lax and di- 
 latable, fo as to receive all bodies that are preffed by 
 the tongue over the larynx. 
 
 614. It is dilated in its adlion (612.) by the powers 
 ferving to its elevation ; fuch as the Jlylopharyngeus, 
 fometimes double, from the procefs of its name ; w hence 
 
 defeend- 
 
322 DEGLUTITION. Chap. XIX. 
 
 defcending, it is inferted into the membrane of the la- 
 rynx, under the os hyoides, and into the cartilaginous 
 edge of the defcending thyroideus ; after which, it is 
 broadly fpread through the internal face o'f the pharynx, 
 together with the following. The thyreopalafiniis^ be- 
 ing fpread in the form of an arch round the m.ovcable 
 palate, is from thence extended downwards in two co- 
 lumns, on each fide the pharynx, which form a confi- 
 derable part of that bag, being alfo connedted by broad 
 fibres to the thyreoid cartilage. That the falpingapha- 
 ryngeus is a true or diftincl mufcle, I am ready to be- 
 lieve, rather from the obfervations of eminent anatomifts, 
 than any of my own. As to the cepbalopharyngew. ^ I 
 almofi; dcfpair of finding any, unlefs you will reckon the 
 flrong white plate of the cellular fubflance, which fur- 
 rounds the upper part of the pharynx, for a mufcle. 
 This bag clofely furrounds and follows the drink, on 
 each fide the epiglottis, above the lar)mx, that it may 
 from thence fall into the oefophagus, 
 
 615. That the aliments might not regurgitate into 
 the noftrils at the time when they are prelTcd into the 
 dilated pharynx (614.), a moveable velum or palate is 
 interpofed ; namely, from the bony palate anteriorly, 
 and laterally from the pterygoide wings, is continued a 
 moveable velum, compounded of the membranes from 
 the mouth and nares, betwixt which membranes are 
 fpread mufcles and glandules ; being almoft of a fquare 
 figure, and pendulous betwixt the cavity of the nares 
 and fauces, in fuch a manner, that they naturally leave 
 the former open, and form a concave arch towards the 
 mouth : and from the middle of this is extended a fmall 
 portion, pendulous, and of a conical fliape, before the 
 epiglottis, replete with many fmall glands ; which, from 
 its appearance in a difeafed ftate, is called uvula. The 
 elevator of this velum, which is ftrong, arifes from the 
 afperities and plane face of the os petrofum, behind the 
 fpinal foramen ; and from a cartilage of the tube de- 
 fcending inward, does, with its companion, form an 
 arch, which is moveable with the palate itfelf, between 
 
 the 
 
CHAi>. XIX. DEGLUTITION. 32? 
 
 O j 
 
 the two plates of the thyreopalatinus mufcle, fo as to 
 brought into a ciofe contaft with the fides of the nares 
 and with the tubes, that none' of the aliment may enter 
 into either of them. But this elevator does not feem 
 to have any confiderabie adion in fwallowing. At this 
 time regurgitation into the nolfrils is prevented by a 
 conftriction of the mufcles of the pharynx, together with 
 a deprelTure of the thyreopalatinus, which then mani- 
 feftly draws the moveable velum downward and to- 
 wards the tongue and pharynx. Add to thefe, the cir- 
 cumflexus palati mollis^ which arifes a little more for- 
 ward from the fame cuneiform bone, from the internal 
 fide of its wings, and from the inner wing, with the 
 cartilaginous end of the tube, broad ; and then, palling 
 through a notch of the pterygoide hook, changes its 
 direflion, and afcends with a radiated tendon through 
 the upper membrane that covers the velum of the pa- 
 late, joins with its fellow, fpreads over the other mufcles, 
 and adheres to the edge of the palate bone. This is 
 able both to open the tube, and to prefs down the 
 moveable velum of the palate. Thus the pharynx be- 
 ing contracted like a fphin£ler, drives down the food, 
 without permitting any part to return back into the ca- 
 vity of the nares. tience, when the velum of the pa- 
 late is vitiated, the aliments regurgitate into the noftrils, 
 and a deafnefs enfues. 
 
 616. During this endeavour to deprefs the food by 
 the pharynx (617.), the velum, drawn back and ex- 
 panded over, is pulled down towards the tongue, by 
 the aflion of the palatopharyngei, and by the circum- 
 flex mufcles of the foft palate. Thefe mufcles, toge- 
 ther with the glolfopalatinus, (which lafl; is indeed weak, 
 being received into the lefler arch of the fauces, and 
 here united with its companion into the arch by the 
 velum of the palate, and from thence fent to the tongue,) 
 prefs the velum againft the protuberant root of the 
 tongue, and intercept any return to the mouth and no- 
 ftrils. After there is no further danger of any part 
 falling into the windpipe, the epiglottis is raifed up a- 
 
 R r gain. 
 
DEGLUTITION. Chap. XIX, 
 
 gain, as well by its own elafticity, as by the elevation of 
 the tongue itl'elf, by which it is drawm forward. Laft- 
 ly, the depreflcd uvula is railed by the azvgos, which 
 arifes from the tendons of the circumflexi niufcles and 
 levator of the foft palate. 
 
 617. A little after this follows an attempt to urge 
 the food downward, which is exerted by the conftrictor . 
 inufcles of the pharynx which draw the fore parts to- 
 wards the back, and the mufcies which are partly tranf- 
 verfe and partly afcend into the poherior furface of the 
 pharynx. Of thefe the principal is the pterygopha- 
 ryngeus, arifing from the whole hook and internal edge 
 of the wing, and from the tendon of the circumflex 
 mufcle ; from whence forming an arch, it is extended 
 upward and backward, and, largely furrounding the up- 
 per part of the pharynx, it joins into one with its com- 
 panion, which has the fame name. The mylopharyn- 
 geus, partly continuous w'ith the fibres of the buccina- 
 tor, in the middle betwixt its two adhefions to the 
 bones, arifes alfo in part from an origin of its own, 
 above the laft of the grinding teeth in the lower jaw. 
 Thefe having a courfe almofl tranfverfe, furrounding 
 the pharynx, draw it back towards the fore part. Next 
 to thefe follow the geniopharyngei, afeending in tw’o 
 flrata of obfeure and confufed fibres which originate 
 from the tongue ; next the chondropharyngei, of a trian- 
 gular figure, arifing from the oflicula triticea ; the ce- 
 ratopharyngei, which afcend radiated from half of the 
 horn; the fyndefmopharyngei, arifing from the horn 
 * of the thyreoide cartilage, and diftincl from the former; 
 to which add, the thyropharymgei of both kinds, in- 
 creafed by the fibres of the flernothyroideus and cricc- 
 thyroideus, with the cricopharyngei, the tranfverfe, the 
 afeending, and the defeending. Thefe inufcles ading fuc- 
 cefhvely from above downward, according to their fi- 
 tuation, drive the aliment into the cafophagus. At the 
 fame time, the deprefling mufcies of the larynx, cora- 
 Gohyoideus, flernohyoideus, and fternothyreoideus, 
 draw down the larynx forward, and leffening the capa- 
 city 
 
Chap, XIX. DEGLUTITION. 325 
 
 •city of the pharynx urge the food downward. Butin 
 •this adlion, as the aliment pafles by the pofterior rima 
 ■of the glottis, the aryttenoidei contrafl: the larynx per- 
 pendicularly. 
 
 618. As various dry and rough bodies are frequently 
 fwallowed, it was neceffary for the pharynx to be dila- 
 table, and not very fenfible of pain ; to which end the 
 great quantity of mucus, which is colle6:ed in all parts 
 of the fauces, greatly conduces. Therefore, in gene- 
 ral, betwixt the nervous and innennolt coat of the pha- 
 rynx, are placed a great number of fimple mucous fol- 
 licles or cells, of an oval figure, pouring out their mu- 
 cus through fhort mouths ; of a foft, vifcid, and fome- 
 what watery nature ; but ropy, or drawing out into 
 threads, not without oil, and abounding more with vo- 
 latile fait and earth than the faliva itfelf. Thefe mucous 
 receptacles are mofl plentiful in that part of the pharynx 
 which is immediately extended under the occipital 
 bone, where they are difpofed in a fort of radiated right 
 lines ; and they are likewife numerous about the tonfil 
 towards its tube, where commonly the fecond tonfil on 
 each fide lies, adjacent to the large one, and in that 
 portion of the pharynx which is called falpingopharyn- 
 geus. But there are likewife other flat and circular 
 follicles, feated in great numbers about 'the back part 
 of the tongue, as far as its foramen cmcum (448.) O- 
 ther follicles and pores of the fame kind are every 
 where feated in the pulpy flefh of the palate, where nu- 
 merous fmall glands difcharge fuch a .vifcid mucus. 
 Moreover, the whole furface of the moveable palate is 
 of a glandular nature, like that of the pharynx ; only 
 the follicles and glandular corpufcles are here more 
 numerous and thickly fet together. Nor, laftly, are 
 lacunse wanting, into each of which are joined many 
 fimple glandules. 
 
 619. Where the pharynx defcends laterally from the 
 little pterygoidal hook betwixt the two arches of the 
 fauces, namely, between the gloflbpalatinus and pha- 
 ringopalatiniis, are feated. the tonfils, of an oval figure, 
 
 R r 2 convex 
 
32 ^ DEGLUTITION. Chap. XIX. 
 
 convex behind, and thick on the upper part, perforated 
 , inward with ten or more large fmufes, which open 
 through the membranous covering of the velum exten- 
 ded over them, and by the preilure of the adjacent 
 mufcles difcharge a great quantity of a mod thick mu- 
 cus from their fmufes. In like manner, the adjacent 
 parts of the nares, and projefting ring of the tubes, and 
 that fide of the epiglottis which lies next to the larynx 
 and the back of the arytasnoide cartilages, are alfo re- 
 plenilhed with mucous organs. Laftly, the oefophagus 
 itfelf, on all fides, abounds with fnnple follicles, from 
 whence a mucus is poured out fomewhat more fluid. 
 But the larger gland ulae oefophagaete are of the conglo- 
 bate kind, and conduce nothing to this mucus. The 
 blood-veflels of the tonfils are fupplied from thofe of 
 the tongue, lips, and pharynx itfelf ; as thofe of the 
 oefophagus are derived from the branches of the pha- 
 rynx, upper and lower thyreoidais, from the bronchiais 
 and aorta. The veins of the palate and tonfils being 
 numerous, run together into a net-work, ending in the 
 fuperficial branch of the internal jugular. 
 
 619. The afophagus^ then, is a double tube, of 
 which the innermoft is feparated from the outer bv a 
 good deal of cellular fubftance, that may be inflated. 
 The innermoft tube of the oefophagus is nervous and 
 ftrong, being continued from the membranes of the" 
 mouth and nares, on its inner fide plaited and porous, 
 having an epidermis which is not villous, but pulpy, and 
 exhaling a thin humour ; it is diftinguilhed by a thin 
 cellular fubftance, in which the fmall veffels are reticu- 
 lated with minute glands interfperfed, which are conti- 
 nuous, and fimilar ,to thofe of the pharynx. The outer 
 tube is mufcular, and in itfelf confiderably ftrong, com- 
 pofed of fibres internally continued from the lower and 
 back part of the cricoide cartilage, which, by degrees, 
 change from annular to fibres that are externally lon- 
 gitudinal, and ferve to draw up and dilate the cefopha- 
 gus againft the food, that the mouthful may be re- 
 ceived. But the other internal circular fibres, which 
 
Chap. XIX. DEGLUTITION. 527 
 
 are ftronger than the former, arife in like manner from 
 the top of the cricoide cartilage ; and by their fuccef- 
 five contraftion againft the food, drive it down through 
 the whole long tube of the oefophagus, which defcends 
 firfl; in a direft courfe, a little to the left fide of the 
 windpipe ; but having reached the cavity of the breaft, 
 it paffes behind the heart, through the cellular interval 
 that lies behind the bag of each pleura (77.); from 
 whence, inclining by degrees a little to the right, it af- 
 terwards bends again forwards to its proper opening, 
 by which its included food paffes through the dia- 
 phragm ( 7 . 62 .) in the interval of time that is betwixt 
 exfpiration and infpiration. Outwardly, the whole 
 tube of the oefophagus is furrounded by the cellular 
 fubftance, by which it is loofely tied to the neighbour- 
 ing parts. 
 
 620 . The aliments are moved through the oefopha- 
 gus as through an inteftine. The longitudinal fibres, 
 afcending to the cartilages of the larynx, dilate the gul- 
 let, oppofite to the defcending morfel. But when it is 
 received, the longitudinal fibres equally dilate and ele- 
 vate the gullet at that place which receives it. Then 
 that part of the oefophagus where the morfel is feated, 
 being irritated, contrads, and moves the food down- 
 wards. The mufcle is ftrong, and very irritable. 
 
 621 . This upper opening of the ftomach is con- 
 tradled or corapreffed in fuch a manner, by the lower 
 mufcle of the diaphragm, in every infpiration, as to 
 confine the food within the ftomach, and diredl it in 
 every refpiration, by preffure, naturally towards the 
 pylorus. By this means, the ftomach is fo clofely lliut, 
 that in the moft healthy man even wind or vapours are 
 confined within the ftomach ; nor do they ever afcend 
 but by a morbid affeftion. 
 
 chap. 
 
STOMACH. 
 
 Chap. XX. 
 
 g2S 
 
 CHAP. XX. 
 
 Of the Action of the Stomach on theYoon. 
 
 ^2 2.T> Y the fomach we underftand a membra- 
 JL# nous bag, deftined for the reception of 
 the food ; ^ placed within the cavity of the abdomen, 
 behind the lower diaphragm and left falfe ribs j 
 in general of an oval figure, or like a cafk ; of a 
 larger diameter tranfverfely, and this more fo as 
 the pcrfon is more adult ; but in the fetus it is 
 altogether fhort and round. But if we confider 
 more accurately every feftion of its figure, thev will 
 appear circular ; although there be a blind or obtufe 
 concavity in its left extremity, from whence it grows 
 wider towards the oefophagus, at whofe infertion its 
 light or fecfion is the largefi of all ; from thence it di- 
 minifhes by degrees, till, bending in a contrary direction 
 to itfelf, it ends in the pylorus. Its bulk depends 
 on the quantity of food, by which the cavity of the 
 flomach is augmented ; and, on the contrary, it is di- 
 minifhed by famine. Its fituation in general is tranf- 
 verfe ; yet fo that the oefophagus enters its pofterior 
 fide, and the pylorus goes out from it forward to the 
 right fide. The middle of the human body, or enfi- 
 form cartilage, thus covers or anfwers nearly to the cen- 
 ter of the flomach ; but alfo to the right fide, and lafl- 
 }y to the pylorus ; to the latter anfwers the umbilical 
 fiffure. Since its figure is round but incurvated, its 
 lower convexity will form a larger pendulous arch 
 when empty ; but when full, it fhow’s itfelf prominent 
 before, and in contadl with the peritonseum. On the 
 other hand, the leffer arch, intercepted betwixt the 
 two orifices, w'ill in this ftate of the flomach lie per- 
 fe£lly backward towards the fpine, fo as to include the 
 fmall lobe of the liver. Thus the infertion of the cefo- 
 phagus into the full flomach will be in an obtufe angle, 
 
 in 
 
Chap. XX. STOMACH. 529 
 
 in a manner parallel with the horizon ; but in the emp- 
 ty ftomach it will be almoft perpendicular : and at the 
 lame time, the right extremity of the ftomach forming 
 the pylorus, which in an empty ftate lies bent upward, 
 will in the full ftomach be bent more backward, fo as 
 to defcend in perfons lying on their back. In a living 
 man, that fituation of the ftomach which we have 
 attributed to the full one is nearefl; the truth. 
 
 623. In the neighbourhood of the ftomach lie the 
 vifcera : and particularly to its large Imperforated extre- 
 mity is connefted the fpleen, by a confiderable portion 
 of the omentum ; the lefler arch or curvature of the fto- 
 mach receiving the little lobe of Spigelius, as likewife 
 the left lobe of the liver, largely interpofmg betwixt the 
 ftomach and the diaphragm ; which lobe compreiTes the 
 forepart of the ftomach ; below the margin of which, a 
 portion of the ftomach lies immediately contiguous to 
 the diaphragm itfdf ; yet fo as, by a moderate exten- 
 fion, to lie hid within the bounds of the falfe ribs. Un- 
 der and behind the ftomach, lies the pancreas, extended 
 for a confiderable length in an empty fpace, upon the 
 tranfverfe portion of the colon. Again, from the lefler 
 curvature arifes the little omentum, to which is conti- 
 nued the ftronger membrane that connedls the cefopha- 
 gus with the diaphragm : nor is the large omentum 
 connefted to the whole length of the ftomach ; but, 
 leaving a deficiency to the right fide near the pylorus, 
 it is continued on beyond the left extremity, into a liga- 
 ment which connedts the ftomach and fpleen together. 
 The ligaments, in thefe parts, are produdlions of the 
 peritoneum ; which, receding from the diaphragm, 
 fpreads itfelf over the ftomach, fo as to form its outer- 
 moft coat. The pylorus lies between its mouths, on 
 the forepart, more to the right fide, and a little lower 
 down. 
 
 624. The fabric of the ftomach anfwers in general to 
 that of the oefophagus : of which, indeed, it is aa expan- 
 fion ; and, in fome animals, has in all its parts the fame 
 appearance. The outermoft coat is from the peritonae- 
 um. 
 
330 S T O M A C II. Chap. XX. 
 
 um, of confiderable ftrength, fo as to limit the reil, and 
 aftbrd a fupport to the fubjacent mufcular fibres : this is 
 expanded into the little and great omentum, and in that 
 place the ftomach is without its outermod coat. Then 
 follows the cellular coat, more abundant in the origin 
 of the little omentum, where it contains little conglo- 
 bate lymphatic glandules, which alfo holds true of the 
 cellular fubftance in the great omentum but it is thin- 
 ner and much lefs confiderable. betwixt the coats of the 
 ftomach itfelf, whence the outer and mufcular tunic 
 clofely cohere together: in this fubftance the larger 
 branches of the veffels are diftributed. 
 
 625. Next in order appears the mufcular coat, 
 neither eafy to defcribe or prepare. Here, indeed, we 
 fee the longitudinal fibres of the oefophagus, coming to 
 the ftomach, are detached one from another, along all 
 the fides of the ftomach. Some of them, of more confi- 
 derable ftrength, run on to the pylorus, along the lelfer 
 curvature ; which, by degrees declining from their lon- 
 gitudinal courfe, following the length of the ftomach, 
 defcend into a plain of each fide, and are in part ftretched 
 out through the pylorus into the duodenum itfelf, 
 v/hcre they gradually difappear. Other fibres defcend 
 to the blind fack of the ftomach, featcd on the left fide. 
 And, finally, through every fcdion of the ftomach, 
 from its blind or left extremity, to the the pylorus, are 
 fpread concentric circular fibres, which, by degrees in- 
 creafing in their thicknefs or number, are continued on 
 with the reft of the circular fibres belonging to the fto- 
 mach : this laft makes the moft confiderable order of 
 the mufcular fibres. Laftly, the fphinefter of the cardia 
 and oefophagus is compofed internally of fibres, arifing 
 from the left fide of the oefophagus, and running to the 
 right, pafs on each fide the gula, which they thus clofely 
 embrace, and then degenerate longitudinally till they 
 are loft under the circular or fecond ftratum near the 
 pylorus. But the ligaments of the pylorus fo called, 
 are two conftridfions, betwixt the two incurvations into 
 which the pylorus is bent, formed by the forefaid lon- 
 gitudinal 
 
Chap. XX. STOMACH. 331 
 
 gitudinal fibres, which run along from the ftomach to 
 the pylorus, and are very clofely joined to the internal 
 coat in their way. 
 
 626 . Immediately under the mufcular fibres, follows 
 another cellular flratum, larger than the outermoft, 
 fofter, more eafily inflatable, and confiding of larger 
 cells or veficles than what we ufually obferve in the in- 
 teftines. Within this cellular fubftance are fpread the 
 veffels which, eoming from the larger trunks, perforate 
 the mufcular coat, and are divided into an angular net- 
 work. Under this lies the nervous coatj which is thick, 
 white, and firm, and properly makes up the true nature 
 or fubftance of the ftomach itfelf, after the manner of 
 other nervous parts : and this is again lined internally 
 with a third cellular ftratum, evidently enough to be 
 perceived, whofe vafcular net-work is much more mi- 
 nute than that of the former, from whence it is derived. 
 Immediately within this lies the villous coat, that lines 
 the cavity of the ftomach itfelf, continuous with the ex- 
 ternal cuticle, like which it is renewable ; but of a 
 foft mucous texture, and extended into a very fhort 
 pile, and folded into large plates, \yhich form a ftar un- 
 der the cefophagus ; but in the middle of the ftomach, 
 thefe folds are almoft parallel with the ftomach itfelf. 
 But, at the extremity of the pylorus, there is a more 
 confiderable fold, commonly called valvula pylori, 
 which is formed by a production both of the tranfverfe 
 mufcular fibres, and of the thicker nervous coat, ex- 
 tended together in the fhape of an unequal loofe ring, 
 produced towards the duodenum ; this forms a flippery 
 flefhy protuberance, which furrounds the duodenum for 
 a confiderable length. The large wrinkles of the vil- 
 lous membrane are afterwards fubdivided more minute- 
 ly into others of a quadrangular or net-like figure ; but 
 very ftiallow, and eafily difappearing, being much more 
 obfcure than thofe in the biliary duCts. Within this 
 , villous coat of the ftomach throughout, but more efpe- 
 cially towards the pylorus, I have truly obferved fome 
 
 S f pores. 
 
S'P S’T'O MACH. Cnkp. Xf 5 t 
 
 pore’s, not always to be perceived, which terminate in 
 fimple follicles, feated in the next cellular ftratum. 
 
 627. The vejfels of the ftomach are both numerous 
 and derived from many trunks or various quarters, that 
 the courfe of the blood through them might not be in- 
 tercepted by any kind of prefl'ure, as it might eafily have 
 been if the veffels of the ftomach had come from' a 
 fingle trunk. The common mother ol all thefe gaftric 
 arteries is the coeliac ; frbrn the threefold divifion of . 
 which, or above the faid divifion, arifes tlie upper co- 
 ronary, which is the firft^^d largeft artery that paflcs 
 in a fingle branch round the ed^e of the oefophagus in- 
 to the ftdmach ; to which, firft, and -afterwards to the 
 diaphragm and to the liver, it fends off fome ramifica- 
 tions ; and then running on the leffer arch or curve of 
 the ftomach, it inofculates by more than one branch 
 with the leffer coronary of the right fide, arifing from 
 the right branch of the coeliac at the vena portarura, 
 and is diftributed along the Idler curve of the ftomach. 
 But the fame right branch of the coeliac, arifing behind 
 the duodenum, along which it defcends, gives off a very 
 confiderable artery that runs contrary to the great arch 
 or curve of the ftomach, the right ga flro-epiploica, which 
 being fufpended in the omentum, it fpreads itfelf both 
 upon each fide of the ftomach, and upon the greater 
 part of the omentum itfelf, being at laft inferred into the 
 left gajlro-epiploica. Namely, the left trunk of the coe- 
 liac, paffmg along in the direftion of the pancreas and 
 finuofity of the fpleen, there fends off many branches to 
 the ftomach : of which the firft are commonly namelefs ; 
 and among the following, one branch, more confider- 
 able than the reft, is called the left gajlre-eplploica^ 
 which fends off a confiderable twig to the omentum, 
 with fome others that are fmaller ; from whence, de- 
 feending round the ftomach towards the right fide, it 
 inofculates with the right artery, which is its compa- 
 nion. Other fmaller ones, coming from thofe of the 
 fpleen, are fpread upon the greater curve of the fto- 
 mach, even as far as the diaphragm, under the deno- 
 mination 
 
Chap. XX. STOMACH. 333 
 
 iBin^tlon of the vafa hrevia. Frequently, alfo, one or 
 arteries come from the fplenic one, to the pofterior 
 llJlate of the ftomach under the cefophagus, in another 
 line from the gaftro-epiploics. The other fmaller arte- 
 ries 'are the upper ones of the pylorus from the hepa- 
 lics, and the lower ones from the gaftro-epiploics : but 
 thofc of the lower part of the cefophagus, are from the 
 phrenic arteries. 
 
 628. Thofe arteries are diftributed in fuch a manner, 
 that firft they fend off fliort twigs to the external and 
 to the mufcular membranes, of the ftomach; their trunks 
 are fet in order in the firft cellular ftratum ; from whence, 
 diminifliing, a little in fize, they penetrate through the 
 mufcular coat ; and between that and the nervous mem- 
 brane, they compofe a larger and true net-work ; in 
 which all the fmall arteries, coming from a great variety 
 of trunks, join one with another, by an infinity of ino- 
 fculations. From this plexus, again, other Ihort, but 
 numerous and very fmall ramifications, pafs through 
 the nervous coat to the third or inner cellular ftratum, 
 and are loft in the villous lining of the ftomach. 
 
 629. The veins have their branches diftributed in 
 company with the correfponding arteries. The greater 
 coronary from the left fide of the ftomach, generally 
 goes t(^ the trunk of the porta, together with the brevia 
 and left gaftro-epiploic ; while the right vein of the laft 
 denomination joins with the middle vena colica, and, 
 together w'ith a branch from the mefentery, pours its 
 contents into the vena portarum. Finally, the right 
 coronary vein belongs to the trunk of the vena porta- 
 rum itfelf. All thefe veins are without valves ; and, 
 like the arteries, there are upper coronary veins, with 
 others of the cefophagus from the thorax, all commu- 
 nicating together by inofculations, in fuch a manner, 
 that there is a free paflage for the blood thence into the 
 vena azygos, with which they inofculate. 
 
 A 30. The nerves of the ftomach are both large and 
 numerous, produced from the eighth pair, forming two 
 complications about the cefophagus, of which the ante- 
 
 S f 2 rior 
 
334 STOMACH. Chap. XX. 
 
 rior and lefs plexus defcends through the upper or outer 
 fide of the ftomach to its greater curve ; and the pofte- 
 rior plexus, which is larger, is diftributed through the 
 lefler arch of the ftomach ; from whence it pafles, to- 
 gether with the arteries, to the liver, pancreas, and dia- 
 phragm itfelf. Thefe nerves may be every where tra- 
 ced into the fecond cellular ftratum. The remainder, 
 but efpecially the papillae, are more obfcure. From 
 their number, the ftomach is extremely fenfible, info- 
 much, that things which make no impreflion upon the 
 tongue, will naufeate and pervert this organ, which is 
 capable of much feverer pain than the inteftines ; as 
 we know from infallible experience in difeafes : even 
 the fkin itfelf, when naked by a blifter, is lefs fenfible 
 than the ftomach. By making a ligature upon the 
 nerves of the eighth pair, both the action of the fto- 
 mach and the digeftion of the food ceafe. 
 
 631. Lymphatic vejfels I have obferved, fometimes 
 very confiderable, about the lefler curve of the ftomach, 
 arifing from the glandules of that part, and inferted by 
 a very large trunk into the thoracic du£l. Others, no 
 doubt, arife from fmall glandules of the fame kind in 
 the greater curve ; and fome famous anatomifts have 
 obferved lymphatic glands over the whole ftomach. 
 Other lacteal veffels, I have neither feen, nor am ready 
 to admit; fuch as thofe lately deferibed, which are faid 
 to pafs from the ftomach through the omentum to the 
 liver, filled with a true chyle. 
 
 632. All parts of the human ftomach are perforated 
 by inorganic pores, through which water inje(fted both 
 exhales through the ftomach when fliut, and, on the 
 contrary, penetrates the cavity of the ftomach when put 
 under water. But we cannot for this reafon conclude, 
 that in a living perfon this paflTage lies open for moi- 
 fture. 
 
 633. Within the human ftomach, we firft meet with 
 a great quantity of mucus, fpiead upon its villous lining, 
 from the pores before deferibed (626.); which mucus 
 is not unfrequently tinged, by fome of the bile return- 
 
DIGESTION. 
 
 Chap. XX. 
 
 33 S 
 
 ing into the ftomach. Befides this, in an empty 
 mach after fading, upon bending the body, a great 
 quantity of a limpid hu 7 nour will arife into the mouth, 
 altogether of the fame nature with the faliva, but more 
 mucous ; which liquor is very rarely to be found 
 pure or unmixed in the domach. It is very far from 
 poffeffing any acid acrimony, when it can be had 
 pure from the food. Left to itfelf, it changes, both 
 in man and brutes, rather to a lixivial or alkaline na- 
 ture, when it is feparated from the acid illuvies of the 
 aliments, more efpecially in an hungry animal. This 
 liquor didils from the arteries of the domach, through 
 its villous coat, after the manner we fee by anatomical 
 inje<dions ; by which water, fifli-glue, and oil, may be 
 eafily urged into the veffels of the domach, fo as to 
 fweat through its numberlefs pores. ' 
 
 634. The domach then, contained within the abdo- 
 men, which is perfeftly full, will from thence, as in a 
 prefs, receive a force or compreifure upon its fides, 
 which lie betwixt the diaphragm; the concavity of 
 whofe right wing is filled by the liver, under which, 
 and within the left wing, lies the domach, extended 
 almod tranfverfely behind the redding mufcles of the 
 abdomen, viz. the refti and obliqui, but chiefly tlm 
 tranfverfe. The more the domach is dlled, the more 
 it is urged by this preffure of the abdominal mufcles ; 
 becaufe, at the fame time, it rifes upward in a right 
 angle to the conta£f of the peritonseum. 
 
 635. Now we mud fpeak of what is received into 
 the domach, and why it is received. The Creator has 
 given to man the two faithful guards of pleafure and 
 pain (564.) for his prefervation ; the one to avert evil, 
 the other to invite him to ufeful adlions. But the ta- 
 king of aliment is an aftion very neceflary and ufeful 
 to our fupport. For dnce every day there is a great 
 quantity waded from the body, by a diflblution of its 
 true fubdance thrown off by perfpiration, a repairing 
 of this lofs is every way neceffary, as the body is ma- 
 nifedly waded by fading. But this neceffity of taking 
 
3'3<5 'DIGESTION. Chap.XS. 
 
 food recurs the more quickly from the nature of the 
 blood itfelf, which is ftrongly inclined to a fharp, fa- 
 line, lixivial quality, and to a putrid acrimonious ftate ; 
 to which laft it is continually folicited, and approaches, 
 from the putrefcent difpofition of all the more ftagnant 
 humours of the animal, promoted by the inceffant and 
 natural motion of the heart and arteries, and by-the 
 heat which very much promotes the pUtrefaftion of all 
 the animal humours. Moreover, the coagulable dif- 
 polition of the blood, continually lofing d’ great part 
 of its diluting water by infenfible petfpiration, calls 
 ftrenuoufly for a recruit of the watery element, in the 
 way of drink, by which its cohefive globules 'are fepa- 
 rated from each other, and hindered from running to- 
 gether into a confiftent mafs. 
 
 <536. Thefe truths are proved not only from their caufes, 
 but likewife by the appearances which they exhibit in 
 men and other animals killed by hunger. For, in fuch, 
 we commonly obferve a fliarp ftinking breath, a loofe- 
 nefs of the teeth from the diflblving acrimony of the 
 juices, violent pains in the ftomach, lharp fevers, and 
 even a true madnefs. All thefe diforders arife fooner 
 and ftronger, as the perfon is more robuft and more 
 violently exercifed with motion of body ; but they en- 
 fue very flowly in phlegmatic people, who are unadive, 
 perfpire little, and put the blood into no great motion. 
 Laftly, thofe who have been without food, have alfo 
 lived without bodily exercife, and for the moll part la- 
 boured under a difeafe of the nerves. 
 
 637. The frelh chyle, compofed, for the moft part, 
 out of the acefcent clafs of vegetables, and of a con- 
 fiftence always thinner than that of the blood itfelf, be- 
 ing received into its torrent of circulation, temperates 
 the putrefcent acrimony, dilutes the coagulation threat- 
 ened, and reduces the whole mafs to that moderate degree 
 of faline nature which is natural to man ; and finally, 
 the chyle, but more efpecially that derived from the 
 flelh of animals, and likewife what is formed of fari- 
 naceous vegetables, being repleniflied with gelatinous 
 
 lymph, 
 
Chap. XX. DIGESTION. 337 
 
 lymph, ferves to repair the confumption or wafle 
 wihb'h is made from the body itfelf, to the vacuities 
 of -Whdfe broken folids it is applied by the caufes men- 
 tioned (959.) The drink dilutes the cohefive or gru- 
 mous inclination of the blood, hinders its putrefaction, 
 and carries off by the emunftories fuch particles as are 
 already putrid : and hence it is, that a perfon may live 
 for a long time without folid food, if he is fupplied. 
 with drink j but’ without drink, life fubfifts but a few 
 days. 
 
 638. We are folicited to take food, as well from the 
 fenfe of pain we call hunger, as from that of pleafure, 
 which is received by the tafte (455.) The firft of thefe 
 proceeds doubtlefs from the fenfible folds or wrinkles of 
 the ftomach rubbing againft each other by the periftaltic 
 motion, of which there is an acute fenfation, joined with 
 a prelfure from the diaphragm and abdominal mufcles, 
 by which the naked yilli of the nerves on one fide grate 
 againft thofe of the othety after a manner intolerable. 
 Thus we are effeblually admoniflied of the dangers en- 
 fuing from too long abftinence or falling, and excited 
 to procure food or nourilhment by labour and induftry. 
 To this fenfe perhaps the gaftric liquor or juice of the 
 ftomach, collebled and lharpened after feeding, does in 
 fome meafure conduce, unlefs it becomes putrefcent. 
 
 639. Thirji is feated in the tongue, fauces, oefo- 
 phagus, and ftomach. For whenever thefe very fen- 
 fible parts, which are conftantly and naturally moiften- 
 cd by mucous and falival juices, grow dry from a de- 
 ficiency of thofe or the like humours, or are irritated 
 by a redundancy of muriatic or alkalefcent falts here 
 lodged, there arifes a fenfe much more intolerable than 
 the former, as thlrft is more dangerous ; whofe uneafy 
 fenfe continues until the proportion of diluting water 
 in the blood, being recruited, reftores the neceflary 
 moifture and free fecretion required in the parts before 
 mentioned. From hence we learn, why thirft attends 
 labour, which exhales a greater proportion of the wa- 
 tery perfpiration j and why it is a fymptom of fevers, 
 
 where 
 
338 DIGESTION. Chap. XX. 
 
 where there is an obftrudion of the exhaling veffcls 
 belonging to the tongue and fauces ; why fimple wa- 
 ter is Icfs efficacious in abating thirlf, which yields nc- 
 verthelefs eafily to fome acid liquors, that not only moi- 
 flen and render fluid, but alfo, by their mild irritation 
 of the tongue and mouth, provoke forward the humours, 
 and at the fame time corredt their putrid tendency. 
 
 640. From thefe caufes, mortals, being under a ne- 
 ceffity of feeking food for the fuppqrt of life, have in all 
 ages determined their choice to the fucculcnt parts of 
 vegetables and animals, in fuch a manner, that water 
 and fait fee m to be added only as third affiflants. And 
 firft, it is probable, that the primitive choice of our 
 foods was made by experiments, according as the 
 variety of fmells and flavours in vegetables and their 
 feveral parts invited, and as the ftrength or recruit of 
 our faculties thence following confirmed their utility. 
 But by degrees, animals increafing fo much as to be in- 
 commodious to the hufbandmen, and vegetables alone 
 not being fufficient for fupporting them under their la- 
 bours, the flelh of animals was afterwards added. At 
 prefent, both the number and variety of fubftances are 
 almofl; infinite, which we take either as food or feafon- 
 ing for our nourifliment. 
 
 641. Although there are many inftances of particu- 
 lar perfons, and even of whole nations, w'ho have fup- 
 ported life only with one kind of food, either vegetable 
 or animal, or even from a fmall clafs of either of them ; 
 and lafUy, though fome have lived altogether upon 
 milk or its whey; yet it feems to be neceffiary, both 
 from the nature and fabric of the human body itfelf, as 
 well as from certain experiment, that we ought to fup- 
 port life by the two kinds of food, fo intermixed, that 
 neither of them may exceed their reafonable bounds ; 
 and this mediocrity we are taught from the loathing it- 
 felf, which follows to any one kind of food that has 
 been continued for too long a time together. 
 
 642. The flefli of animals appears a neceflary part 
 of our nourifhment, even from the fabric of the hu- 
 man 
 
eHAP.XX. DIGESTION. 339 
 
 man ftomach itfelf, refembling that of carnivorous ani- 
 mals ; and from the two rows of teeth, with the canine 
 teeth in each jaw ; alfo from the fmallnefs and Ihort- 
 nefs of the inteftinum caecum, and from the necelfary 
 vigour which we require. For the flefti of animals alone 
 contain the gelatinous lymph ready prepared for the 
 recruit both of our fluids and folids, which, being ex- 
 tradfed from the broken veffels and fibres, eafily paffes 
 in great abundance into the blood. An abftinence from 
 animal-food generally caufes great weaknefs both to the 
 body and ftomach, being perpetually attended with a 
 troublefome diarrhoea. But in the amplitude and length 
 of the inteflina cralfa, man agrees with herbivorous 
 animals. 
 
 643. Efculent vegetables are generally of the ace- 
 fcent kind ; only fome few of them are either alkale- 
 fcent, or elfe repleniflied with a fpicynefs. But few of 
 them have that animal glue which is fpontaneoufly 
 changeable into blood ; for it is only the fmall portion 
 of jelly which is drawn from their farinaceous parts, 
 that, after many repeated circulations, is converted 
 into the nature of our indigenous juices. Yet thefe 
 are neceffary to avoid over repletion with blood, and of 
 too putrefcent a kind from the ufe of animal food alone, 
 which, from the moft creditable accounts of the an- 
 thropophagi, prevails to fo great a degree, as to breed 
 the hot alkalefcent fcurvy, a fierce or favage temperj 
 a flinking and leprofy of the body, with a lixivial cor- 
 ruption of all the juices ; which are only to be cured 
 by change of diet, in which a vegetable acidity abounds. 
 Hence it is, that we are furnifhed but with few canine 
 teeth ; and that our appetite in health, but more efpecially 
 in difeafe, is flronger for acidulous vegetables, in propor- 
 tion to our warmer temperature of body, and greater 
 heat of the country or the feafon of the year. Hence 
 we fee, that, in the hotteft climates, people live either 
 altogether upon vegetables, or ufe flefh meats but very 
 rarely, and not without danger of acute difeafes; while, in 
 the colder countries, flefh is eaten freely with lefs danger? 
 
 T t and 
 
340 DIGESTION. Chap. XX. 
 
 and hence bread, or a farinaceous aliment fimilar to 
 it, is made a ftanding part of our food throughout the 
 world. 
 
 644. The belt drink is afforded by pure water, not 
 incorporated with falts nor with air, which may excite 
 fermentations. Of this kind wt juftly prefer that from 
 a mountainous fpring, which runs through a fandy bed, 
 being very cold, clear, light, and infipid. Whenever 
 we are unprovided with fuch pure water, as is fre- 
 quently the cafe in the lower flat countries, or when 
 any increafe of the ftrength and mufcular conflriiEtion 
 of the flomach is required from a fpicy flimulus, its 
 place may be very well fupplied by wine, prepared 
 chiefly from grapes ; but, in defe£f of thofe, from apples 
 and pears ; which, after a due fermentation, becomes 
 clear, and is replenifhed with an acid fait, and oily or 
 inflammable fpirit, well diluted in water. . Liquors of 
 the fame kind, replenifhed with a vinous or inflam- 
 mable fpirit, but more flatulent, heavy, and lefs pala- 
 table, are prepared from corns roafted, afterwards ex- 
 tracted with boiling water, and prepared by fermenta- 
 tion, as a fubflitute for wine in thofe countries where 
 the grape does not ripen. 
 
 645. But mankind have invented various pickles 
 and fauces, fuch as fait, vinegar, and acids of various 
 kinds, to correCl the putrefcent difpofition of flefli- 
 meats; with pepper, muftard, and other hot fpices, to 
 ftrengthen the aftion of the flomach, which is perpe- 
 tually weakened by the ufe of vegetables : and to thefc 
 add, fugar, fait, and the eaflern fpices, which are gene- 
 rally added either for the fake of flavouring or prefer- 
 ving our food. But all thefe yield no nourifhment, be- 
 ing deflitute of all gelatinous lymph, or any farinace- 
 ous quality. The fpirits of w'ine and corn may be of 
 fome ufe as' medicines, but are unfit for drinking. 
 
 646. The aliments are varioufly prepared, according 
 to the difference of country, climate, or feafon, by 
 which their crudity is removed, their folid fibres foft- 
 cned or opened, their too much incorporated air expel- 
 led. 
 
Chap. XX. DIGESTION. 341 
 
 Jed, or their difagreesble acrimony reduced or changed 
 to a. flavour that is agreeable. But, even after this, ma- 
 ny vegetable foods, and more efpecially flelh- meats, 
 require to be divided, in fome degree, by a previous 
 t?ifufe in the mouth, which is particularly neceffary 
 iii niati, whofe flomach is but little flefhy, and liJcewife 
 that the food may not flay fo long upon the flomach as 
 to become putrid. 
 
 647. The meafure of our food is determined by hun- 
 ger, which is different according to the difference of bo- 
 dies. Animal and farinaceous food nouriflies mofl : other 
 aliments ought to fupply by their quantity, what they 
 ■want in their powers of nourifhment. In general, we 
 are nouriffied beft by a fomewhat fpare diet, unlefs fub- 
 jeded to much labour. 
 
 648. Into this flomach, therefore, the aliments are 
 let ffowiiv T 5 ften almofl crude, and but little chewed, of 
 .faridhs Itinds ; fome of them being alkalefcent, as flefli- 
 meat-s.-; rancefcent, as oily or fat fubflances ; or acef- 
 tien't^ as bread, milk, and mofl of the vegetable kind. 
 Thefe, we obferve, are digefted in an heat equal to that 
 of an hatching egg, adminiflred to the flomach by the 
 contiguous fplecn, liver, and heart ; and this in a cavity 
 altogether clofe or confined above (621.), as it alfo is 
 below, by the afcent of the incurvated pylorus, and in 
 a great meafure by a fliutting valve, and likewife con- 
 ftringed by a mufcular force of the fibres ; from whence 
 we obferve, that even milk itfelf is often retained in the 
 flomach of flrong animals feveral hours after a meal, 
 without pafling into the inteflines, Obferve, again, 
 that thefe aliments are continually cohobated or moi- 
 flened with watery juices,- and at the fame time are 
 replenilhed v/ith a good deal of air incorporated with 
 them, either naturally or in the maflication. This air, 
 therefore, expanding by the force of heat, putrefaflion, 
 or fermentation, breaks open the cells by which it was 
 included, divides the vifcid liquors, and foftens or opens 
 the folid fibres, fo as to make a way for difcharging 
 their juices. But the fame fubflance of the air, turning 
 
 T t 2 to 
 
342 , DIGESTION. Chap. XX, 
 
 to a folid, makes the principal glue or cement by which 
 the animal folids and other bodies receive their firm- 
 nefs ; and this, being extricated by heat, leaves the o- 
 ther elementary parts friable, or without a vinculum, 
 as we fee from the change which happens in Papin’s di- 
 gefter, in the ftomachs of many animals, and even in 
 that of ourfelves. This air, fet at liberty by the dige- 
 ftion, often diftends the ftomach more than the food 
 itfelf, under the denomination of flatus. While this 
 air is extricated, the aliments by long flay begin to cor- 
 rupt or change into a naufeous liquid, often acefcent ; 
 or otherwife putrefcent, which however happens lefs in 
 mankind from our ufe of bread and fait ; or rancefcent, as 
 appears from the flatus and matters eructated, often of 
 a mofl: fetid, cauflic, and inflammable nature, from fub- 
 ftances of the like difpofition. This putrefcency, or 
 imperfeft putrefaction, is almoft the only caufe of di- 
 geftion in fifh, ferpents, and carnivorous birds. Hence, 
 in mankind, metals themfelves, by long ftay in the fto- 
 mach, grow foft, and are eroded. At this time hunger is 
 abfent, the nervous plates of the ftomach being remo- 
 ved and defended from their contafts with each other 
 by the interpofed aliment, at the fame time that the 
 juice of the ftomach itfelf is lefs (harp, and freer from 
 a mixture with the old remains of the laft food, which 
 often excite a naufeating uneafmefs in the nerves of the 
 ftomach. 
 
 649. But, that the aliment might not degenerate into 
 a complete acidity, there is a check from the putrefcent 
 degree of the heat, the power of the juices diftilling 
 from the ftomach, and that of the faliva itfelf fwallowed 
 to the amount of half an ounce in an hour, and rather 
 inclined to an alkalefcency : alfo thefe juices, being 
 ground together with the aliment, macerate, foften, and 
 diflblve the fibres themfelves and their cellular bands, 
 leaving them a foft pulp like w'hat we fee by letting 
 them ftand for a long time in warm water, extrad their 
 juice, and mingle it with themfelves. There is, there- 
 fore, no particular kind of ferment in the ftomach ; 
 
 from 
 
Chap. XX. DIGESTION. 345 
 
 from which the defign of nature, the difpofition of the 
 ftomach, and its ufc, are all very remote. And yet the 
 juice of the ftomach alone, by its longer ftay in fifties, 
 diflblves the bones which they had devoured. 
 
 650. For the flefhy fibres in the ftomach being now 
 irritated by the flatus, weight, and acrimony of the 
 food, begin to contrail themfelves more powerfully 
 than when the ftomach is empty, and with a greater 
 force in proportion as it is more full, the round fwel- 
 ling of which ftretches thefe fibres. And, firft, the 
 mufcular ftratum, which paflTes along the lefler curva- 
 ture, conneds the pylorus with the oefophagus ; and, 
 'being inferted only into the left face of the former, 
 draws it to the right. The principal ftratum of the 
 circular fibres contracts the capacity of the ftomach, 
 according to its length; grinds or intermixes its con- 
 tents, together with the liquors (633.); and determines 
 them both, like the preflure of two hands placed oppo- 
 fite, to flow towards the pylorus : but this flux through 
 the pylorus is not made continually, for reafons before 
 aflTigned (626.), as well as becaufe this motion begins 
 from fome part that is more irritated ; and from thence 
 the aliment is driven here upward, as in other parts 
 downward. Thefe alternate contradions at laft termi- 
 nate in a full evacuation. In this adion of the fto- 
 mach, there is nothing which refembles the triture made 
 by the ftrong gizzards of granivorous fowls, which fome 
 anatomifts have afcribed t@ the human ftomach ; which 
 yet has a confiderable degree of ftrength, fince the 
 contradion of its fibres is often more than a third part 
 of their length ; for we frequently fee the ftomach re- 
 duced to lefs than a third of its diameter : frequently 
 alfo the ftomach is obferved to be diminifhed to much 
 lefs than a third part, even to the breadth of an inch ; 
 which, laftly, makes it fit for moving forward fliarp 
 pointed fubftances. Yet it neither bruifes berries, nor 
 the fofteft worms. 
 
 651. But that motion which it receives from the 
 diaphragm and mufcles of the abdomen, is ftronger 
 
 than 
 
344 DIGESTION. Chap. XX; 
 
 than the periftaltic force of the ftomach ; for, by this, 
 the ftomach Is more perfedly emptied by a clofe ap- 
 proximation of its anterior and pofterior Tides. For it 
 is principally by this force, that the drinks are urged on 
 continually, but the foods only when they are diifolved, 
 left thofe parts which are too grofs fhould be expelled 
 through the pylorus into the duodenum, when the fto- 
 much is more that way inclined by repletion ; for the 
 folid aliments do not feem^to leave the ftomach, before 
 they have changed their fibrous or other texture for 
 that of a mucous, as it were cineritious, yellowifh, fome- 
 what fetid, mucilaginous, and liquid pulp. That which 
 is firft prepared and turned fluid, goes before the reft 
 out of the ftomach ; firft water ; then milk, pot-herbs, 
 bread; and laft of all, flefh-meats, the harder, tougher, 
 and longer fkins or fibres of which pafs unchanged : but 
 fuch things as are hard, or too large to pafs the pylorus, 
 are retained in the ftomach for a long time. 
 
 652. But a confiderable portion of the drink is ab- 
 forbed by the pendulous inhaling veins of the ftomach 
 itfelf, gaping like the exhaling arteries of the fame part 
 (633.); fo their contents take a fhorter way into the 
 blood, as plainly appears from repeated experiments of 
 injecting the veins. Does any thing pafs into the lym- 
 phatic veflfels (631.)? 
 
 653. The ftomach, being irritated by too great a 
 quantity or acrimony of the food, or elfe by ficknefs, a 
 repulfion of the bile, or other caufe, does, by an anti- 
 periftaltic or reverted motion of its fibres, drive its con- 
 tents upward, through the open and relaxed oefopha- 
 gus, in the a£l of vomiting. But then this effeift is 
 partly from the preflTure of the abdominal mufcles, de- 
 prefling the falfe ribs, and urging the contents of the 
 abdomen againft the diaphragm ; which, at the fame 
 time, contracting itfelf to a plain downwards, forces the 
 ftomach, as betwixt the Tides of a prefs, to throw up its 
 contents. 
 
 654. But the aliments, driven in their natural courfe 
 to the duodenum, meet there with the influent bile and 
 
 pan- 
 
OMENTUM. 
 
 Chap. XXL 
 
 345 
 
 pancreatic juice, which often flow back into the flo- 
 mach. But the former of thefe being the principal ba- 
 fis of ch)^ification, will require from us a previous hif- 
 tory of tfle y-ifcera, which convey their blood through 
 the vena potta. 
 
 CHAP. XXI. - 
 
 Of the Omentum. 
 
 ^55.T)Y perltonceum, we underftand a ftrong fim- 
 X) pie membrane, by which all the vifcera of the 
 abdomen are furrounded,* and in a meafure fuftained. 
 Internally this membrane is exceedingly fmooth, and 
 moiflened with exhaling vapours : but outwardly it ad- 
 heres- to all the parts by the loofe cellular fubftance; 
 wfliich, towards the kidneys, contains a good deal of fat ; 
 but is extremely thin and fhort before, betwixt the 
 peritonaeum and tendons of the tranfverfe mufcles of 
 the abdomen. It begins from the lower fide of the 
 diaphragm, which it lines ; and in certain intervals, join- 
 ing with the correfponding pleura above, it completes 
 what would be othcrwife deficiencies in the diaphragm, 
 as betwixt the ultimate flefhy fibres next the ribs and 
 at the loins ; to which add, its continuations upward, 
 through the foramina of the diaphragm. From thence 
 this membrane defcends, in its fore-part, behind the 
 abdominal mufcles ; in its back-part, before the kid- 
 neys ; and, going into the pelvis, from the bones of the 
 pubes, it paflfes over the bladder obliquely backward ; 
 and then reafcends back again over the ureters by two 
 lunar folds or plates, rejoining upon the inteflinum rec- 
 tum with that part of itfelf which inverted the loins, 
 and in the fame place goes before the redlum. 
 
 656. The cellular texture which covers the perito- 
 naeum on the outfide, is continued into flieaths in very 
 many places ;• of which one receives the terticle on each 
 fide f another the iliac veflels j others the intertinura 
 
 redum. 
 
34^ OMENTUM. Chap. XXI. 
 
 rectum, the larger veffels of the pelvis, the obturatoria, 
 penis, bladder, and aorta, and accompany the gullet, 
 afcending into the bread, and along the vertebrae; by 
 means of which, there is a communication between the 
 whole body and the peritonaeum, very remarkable in 
 dropfical people. 
 
 657. But through this general extent, it fends out 
 various productions for covering the vifcera. The 
 Ihorter productions of this membrane are called liga- 
 ments ; and are all of them formed by a continuous re- 
 duplication of the peritonaeum, coming from its inner 
 furface, together with a cellular fubdance, interpofed 
 and extending to fome one or other of its vifcera, where 
 its plates feparate again from each other to embrace the 
 organ, which they are to furround and furnilh with a 
 coat ; but the cellular fubdance always intervenes be- 
 twixt this membranous coat of the peritonaeum, and 
 joins with it the true flefhy fubdance of the vifcus. Of 
 productions of this kind, there are three fhort ones be- 
 longing to the liver, one or twm to the fpleen, and o- 
 thers to the kidneys, lateral parts of the uterus and va- 
 gina. By this means the tender fubdance of the vifcera 
 is defended from injury by any motion or conculTion, 
 and their whole mafs is prevented from being mifplaced 
 by their own weight, as they receive a fure connexion 
 to the firm Tides of the peritonaeum. 
 
 658. But the mod ample and moveable of all thefe 
 productions from the peritonaeum, are thofe called the 
 mefentery and mefocolon; the defcription of both which, 
 although difficult in words, ought not to be fcpaiated 
 from that of the peritonaeum itfelf. We fliall, there- 
 fore, begin fird with a defcription of the mefocolon, as 
 being the more fimple. In the pelvis, the peritonaeum 
 fpreads itfelf within a fhort compafs before the reClum ; 
 but where that intedine bends into a femilunar curve, 
 the peritoneum there departs out far from the iliac vef- 
 fels and feat of the pfoas mufcle which lie upon the 
 mufcles of the loins, and arifes as if duplicated (657.), 
 fpreading itfelf in fuch a form as is fitted to receive the 
 
 colon 
 
Chap. XXL OMENTUM. 347 
 
 colon into its capacity. But above, on the left fide, 
 that the colon might be at liberty, it is conjoined to the 
 peritonseum, with little or none of this middle produc- 
 tion ; fpreading itfelf upon the body of the pfoas mufcle, 
 as high as the fpieen, where this part of the peritonae- 
 um, that gave a coat to the colon fpread under the 
 fpieen, receives and fuflains that vifcus, by taking it in- 
 to Its capacity or folds, 
 
 659. From thence the peritonaeum, at the pelvis, a- 
 fcends upward, expanded before the left kidney, and 
 ftretched outward on each fide, forwards from that and 
 from the right kidney, before the great blood-veffels, 
 under the pancreas ; to which being continuous, it 
 forms a long produftion, called the tranfverfe mefocolon, 
 which, like a partition, divides the upper part of the ab- 
 domen, containing the ftomach, liver, fpieen, and pan- 
 creas, from its lower cavity. The lower plate of this 
 tranfverfe produdion is fingle, continued from the right 
 to the left mefocolon, and ferves as an external coat to 
 a large portion of the lower and defcending part of the 
 duodenum. But the upper plate, taking a more ob- 
 flrufted courfe, departs from the lumbar peritonaeum 
 at the kidiiey and feat 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 inteftine and the colon, is joined with the 
 lower plate in fuch a manner, that a large part of the 
 duodenum lies within the capacity of the mefocolon* 
 Afterwards, near the liver, the mefocolon bends itfelf 
 inward, and defcends laterally over the kidney of the 
 fame fide, fo as to include the right colon, which is 
 much Ihorter than the left, even as far as the inteftinum 
 ciEcum, refting upon the iliac mufcle ; to the appendicle 
 of which, a peculiar long detachment adheres, as a be- 
 ginning to the mefentery. There the mefocolon ter- 
 minates, almolt at the bifurcation of the aorta. 
 
 660. The whole mefocolon, and the whole mefen- 
 tery, is hollow ; fo that air may be forced in between 
 its two fimilar plates in fuch a manner as to expand it 
 
 U u into 
 
34 ^^ U M. Ch.Cp. XXt> 
 
 into a bag. At the place where the colon fuRains it, 
 and alfo from part of the inteftinum reftum, the mefo- 
 colon, which is cominudns with the outer membrane of 
 the inteftine, forms itfelf-into fmall flender bags, for the 
 moft part double, thicltv.,dhd bifid, free at their extre- 
 mities, and capable of admitting air driven in between 
 the plates of the mefocolon. 
 
 661. From thence forward the inefentery follows, as 
 a broad plaited production of the peritonaeum, conti- 
 nuous with the tranfverfe mefocolon,' and extended on 
 the right fide forward, and downward from the emer- 
 ging duodenum ; and then from the left or long mefo- 
 colon, even as low as the pelvis. Thus the mefentery 
 is formed by the plates of the peritonmum, which lie 
 upon the aorta, extended forward and together, under 
 the right portion of the tranfverfe mefocolon ; and, de- 
 feending obliquely under the pancreas, it contains the 
 long feries of the fmall inteftines, within its capacity, 
 difpofed in numberlefs folds. 
 
 662. The whole feat and extent of the mefentery and 
 mefocolon hold a portion of fat, collecbed commonly 
 more in proportion as they go longer within the capaci- 
 ty that is neceifarily formed by the reduplication of 
 their membranes and veffels interfperfed and furround- 
 ing the fat, which the arteries feparatc, and the veins, 
 as already mentioned, reforb; there are alfo very nu- 
 merous glands, which are moftly confpicuous in a 
 young perfon. 
 
 663. The ftruclure of the omentum anfw'ers very 
 nearly to that of the mefentery. But there are many 
 membranes that come under this general denomination, 
 of the fame ftruClure and utility, all compofed of very 
 tender and fine membranes, eafily lacerated, betwixt 
 which the blood-veffels are difpofed reticularly, with fat 
 depofited in ftreaks near the fides, and in the fame di- 
 reftions with the reticulated veffels themfelves. This 
 membrane is always double ; the two plates of which 
 are joined together clofely by a very tender cellular fub- 
 ftance, within which the veffels are diffributed, and the 
 
 fat 
 
Chap. XXL G.M E N T U M. 349 
 
 fat collected. And, firft, where the top of the right 
 kidney .arid' the infulc^ated lobe of the liver, together 
 with the Subjacent blood-veffels, meet with the duode- 
 iiurn intb'aifangie, there the external membrane of the 
 coloti,' which comes from the peritonaeum, joining with 
 the other membrane of the duodenum, v/hich is alfo 
 from the adjacent peritonaeum, they go together overthe 
 left kidney backward, and enter into the tranfverfe fif- 
 fure of the liver, for a confiderable length ; from which 
 the external membrane is continued over the gall- 
 bladder which it contains, confining the vafcular fabric 
 of the liver, very flippery, and tinged of a yellow co- 
 lour. Behind this membranous produftion, betwixt 
 the adjacent duodenum, right lobe of the liver, hepatic 
 vefiels, vena portarum, and biliary duels and artery, 
 lies a fmall natural opening, by which inflated air is 
 largely received into all that cavity of the omentum 
 which we (hall prefently deferibe as a bag ; and, lafily, 
 into the bags of the rell of the omentum. 
 
 664. Erom thence, in a courfe continuous with this 
 membrane (663.) from the pylorus and the lefs curve 
 of the ftomach, the outer membrane of the liver joins 
 jn fuch a manner with that of the ilomach, that the 
 thin membrane of the liver is continued out of the foffa 
 -of the venal duft, before the little lobule, into the fto- 
 mach itfelf, ftretched both before the lobule and before 
 the pancreas. This is called the little omentum hepa- 
 tico-gajlricum ; which, inflated, refcmbles a cone; and, 
 hardening by degrees when it is without fat, changes 
 into a true ligament, by which the ■cefophagus and liver 
 are conjoined together (623.) 
 
 66 jjg But the great gaJlrocoUc-omentum is of a much 
 large^xtent. It begins at the firft joining of the right 
 gaftro-epiploic artery to the ftomach, where it is conti- 
 nued from the upper plate of the tranfverfe mefocolon 
 (659.) ; and from thence it proceeds forward along the 
 great arch or curve of the (lomach to the fpleen, and 
 in part is continued alfo from the right convex end of 
 •the ftomach towards the fpleen, even till it degenerates 
 U u 2 . into 
 
350 OMENTUM. Chap. XXI. 
 
 into a ligament that ties the upper and back part of the 
 fpleen to the ftomach. This is the anterior leaf of the 
 omentum. 
 
 66S. This anterior leaf or lamina of the omentum floats 
 loofely downward before the inteflines, fometimes to the 
 navel, fometimes to the pelvis, behind the mufcles of the 
 abdomen ; and, making a thin edge, is folded back again 
 in a diredtion contrary to itfelf, and afcends fo as to leave 
 an intermediate vacuity, by which the fore leaf is remo- 
 ved from the pofterior ; and being at length continued for 
 a confiderable extent into the outer membrane of the 
 tranfverfe colon, and laflly continued in the finus of the 
 fpleen by which the large blood-veffels are received, it 
 ends in the oefophagus, under the diaphragm. Behind 
 the ftomach, and before the pancreas, the cavity of this 
 is continued into that of the leffer omentum. 
 
 667. To this is continued the omentum colicum, 
 which arifes on the right fide only from the colon and 
 its external membrane, immediately after the origin of 
 the omentum gaflrocoUcum from the mefocolon, with 
 whofe cavity it is continuous, but produced by the co- 
 lon and its membrane, which departs doubled from the 
 intefline, forms a produdfion ending conically, and is ter- 
 minated by a longer or fhorter extent above the intef- 
 tinum cascum. 
 
 668. The ufes of the omentum are many. Its com- 
 mon ufe is, together wdth that of the mefentery, to form 
 an ample fpace, of a loofe texture, into which the fat 
 may be poured from the arteries, at the time of fleep 
 and inadfivity of body, to be afterwards dilTolved by 
 motion, and returned again into the blood by the infor- 
 bent veins, fo as to make a conflituent principle of the 
 bile. Accordingly, you will feel the fat of the omen- 
 tum to be very tenacious or vifcid betwixt the fingers, 
 although of a thin confidence, and in its w'hole body 
 more pellucid than paper. For that the fat of this part 
 returns again into the veins, appears from the ditferent 
 bulk and w'eight of fat obfervable in the various omen- 
 ta of different perfons, according as they lead either an 
 
 t 
 
Chap. XXL OMENTUM, 351 
 
 idle, laborious, or morbid courfe of life; to which 
 add, its appearances in various brute animals, with the 
 relation it bears to all the reft of the fat of the whole 
 body (20.): from experiments in frogs, where this 
 re-abforption of the fat may be made evident to the 
 eye : and, laftly, from the apparently inflammable na- 
 ture of the bile itfelf. Hither we muft alfo refer the 
 diforders and crudities of digeftion, together with the 
 coldnefs of the ftomach, obferved to follow after cut- 
 ting out the omentum. 
 
 66 9. For all the blood which returns from the omentum 
 and mefoeolon, goes into the trunk of the vena portarum, 
 and by that into the liver itfelf. The omentum is furniflied 
 with blood by the gaftrocolic and by each of the gaftro- 
 epiploic arteries, defeending in many fmall branches, 
 and fubdivided in a reticular manner : of thefe, the ar- 
 teries on each fide run to the greateft length ; but the 
 inner or pofterior leaf of the omentum has fmall arte- 
 ries, which go out from thofe of the colon. Branches 
 alfo come to it from the fplenic, duodenal, and adipofe 
 arteries. The omentum colicum has alfo its arteries 
 from the colon, in the fame manner as the fmaller ap- 
 pendices (660.) The arteries of the leflTer omentum 
 come from the hepatics, alfo from the right and left co- 
 ronaries of the ftomach. 
 
 670. The nerves of the omentum are very fmall, as 
 being a fat and indolent body ; yet it receives fome 
 little branches from the nerves of the eighth pair, 
 both in the greater and in the lefler curve of the fto- 
 mach. 
 
 671. The arteries of the mefentery are, in general, 
 the fame with thofe that go to the inteftines ; the fmal- 
 ler branches of which go to the fmall glandules and cel- 
 lular fat, included within the mefentery. But, to the 
 mefoeolon, fmall arteries are diftributed on all fides 
 from thofe of the various parts conneded to it ; as the 
 intercoftals, fpermatics, lumbals of the renal capfules, 
 and tranfverfely from the fplenic artery, with the pan- 
 creatic branch of the duodenum : but, in the left me- 
 
 focolon, 
 
352 OMENTUM. Chap. XXI. 
 
 focolon, there are alfo fmall arteries detached from the 
 aorta itfelf to the glandulae lumbales. 
 
 672. '^The veins of the omentum, in general, accom- 
 pany the arteries, and unite into fimilar trunks : thofe 
 of the gaftrocolic omentum from the left fide open into 
 the fplenic, as do thofe of the hepaticogaftric, which 
 likewife fends its blood to the trunk of the vena porta- 
 rum : thofe from the larger part of the right gaftrocolic 
 omentum go to the mefenteric trunk ; as do thofe of the 
 omentum colicum, with thofe of the appendices epi- 
 ploides. All the veins of the mefentery meet together 
 in one, which is truly’ the trunk of the vena portarum : 
 in forming which, 'tney are firft collefted into two large 
 arms; of which one receives the gaftro-epiplgica, with 
 the middle colic and iliocolic veins, and all thofe of 
 the fmall inteftines as far as the duodenpm ; the other 
 arm, which goes tranfverfely acrofs the former^* which 
 arifes above it, is embraced by the duodenum, "and re- 
 turns the blood of the left colic veins, with thofe of the 
 rectum, except the lowermoft, which belong partly to 
 thofe of the bladder, and partly to the hypogaftric 
 branches of the pelvis. The vein which is commonly 
 called ha 7 norrhoidalis intertia^ is fometimes inferred ra- 
 ther into the fplenic than into the mefenteric vein. If 
 it be demanded. Whether the omentum has any lym- 
 phatic veflels ? we anfwer in the affirmative : fince there 
 are conglobate or lymphatic glandules, both in the little 
 omentum and in the galtrocolicum ; alfo the ancient 
 anatomifts have obferved pellucid vefiels in the omen- 
 tum ; and, lately, a modern has deferibed them for lac- 
 teals of the ftomach. 
 
 673. Other ufes of the omentum are, to interpofc 
 betwixt the inteftines and peritonaeum, which, by in- 
 flammation, are very apt to grow together ; to keep 
 the former in a ftate of free motion, as well among 
 themfelves as againft the peritonaeum, with but little 
 attrition ; and to anoint the mufcular and membranous 
 fibres with a very foft oil. For thefe reafons, even in 
 mfefts, there is a great deal of fat placed round the in- 
 teftines. 
 
Chap. XXL OMENTUM. 355 
 
 teftines. In the large inteftinf^s, there are a great ma- 
 ny appendices, which likewife are produced from the 
 large branches, and cannot altogether cover the omen- 
 tum. But th6 fame fets the vcffels in order; condudsand 
 gives them ftrength ; and exhales a foft vapour, which, 
 mixed with the exhaling abdominal water, anoints and 
 lubricates dll the vifcera. 
 
 674. The mefentery ferves to fufpend and dtfplay the 
 inteftines in fuch a manner, that they may move freely, 
 and with a degree of firmnefs ; it ferves as a bed to 
 fuftain, and fafely conduft the numerous velfels, nerves, 
 and glandules ; of which laft we lliall fpeak hereafter : 
 it alfo gives an external coat to the inteftines, and forms 
 moft of the omenta. 
 
 675. But, befides, the blood, returning through the 
 mefenteric and mefocolic veins, brings with it another 
 principal. conftituent part of the bile; namely, a fub- 
 alkaline watery humour, which is abforbed by the veins 
 from all theimall inteftines, as will be demonftrated in 
 its proper ’^lace. Befides this, it gives to the liver a 
 more putrid water from the large inteftines, which is 
 fetid, and nearly approaches to a volatile alkaline nature, 
 abforbed from the fasces, that now begin to fmell ftrong ; 
 the exiftence of which is eafily proved, both from our 
 own experiments, and the drying of the fasces when too 
 long retained. This water is, therefore, a fluid in it- 
 felf, and rendered more fo by an incipient putrefadion ; 
 and, confequently, it ferves to reduce the tenacity of 
 the oil belonging to the omentum and mefentery, fo as 
 to keep it from congealing. But more efpecially in 
 the bile, it conftitutes the acrid alkaline quality, with 
 which this humour abounds ; and from thence comes 
 the great tenuity and faponaceous force of the bile, fo 
 ufeful to dyers and painters. 
 
 CHAP. 
 
^54 
 
 SPLEEN. 
 
 Chap, XXII. 
 
 
 CHAP. XXII. 
 Of the S p L E E i-r. 
 
 676. ^T^HE fpleen itfelf is one of thofe intermediate 
 A vifcera, which fend their blood to the liver. 
 It is a blueifli, pulpy, fomewhat oval vifcus, fomething 
 like a mafs of congealed blood in its confiflence, having 
 frequently a notch or incifure in its oval circumference; 
 whence it is convex towards the ribs, concave inward- 
 ly, and circumfcribed with two margins or edges, of 
 which the inferior and anterior is the fharpefl;. It is 
 connected to the ftomach by the little omentum; and 
 above that, by the upper ligament, fupported by the 
 fubjacent colon, and by another ligament (638.) be- 
 hind the renal capfule ; to which, and to the kidneys, it 
 adheres by the peritonaeum. It alfo receives the perito- 
 aeum from the diaphragm, under the denomination of a 
 ligament, in the back-part of its hollow finus, behind its 
 velfels. The fituation of it varies with that of the ftomach 
 itfelf, which it follows. When that is empty, the fpleen 
 is raifed perpendicularly, fo as to place its extremities 
 right up and down : but when the ftomach is full, the 
 middle curve or arch of it arifes upward and fore-ward 
 (622.); and at the fame time obliges the fpleen to 
 change its fituation, fo as to lie almoft tranfverfely with 
 its lower end forward, and its upper end backward. 
 Thus, being of a very foft and loofe texture, it grows 
 larger by diftention w'hen the ftomach is empty, and 
 becomes lefs again when its blood is prefled out by the 
 diftention of the full ftomach againlt the ribs. From 
 hence the fpleen is found large in thofe who die of lin- 
 gering difeafes ; but in thofe who die fuddenly, and in 
 full health of body, it is fmall. Another motion of the 
 fpleen is, that of defeending with the diaphragm in in- 
 fpiration, and afeending again in exfpiration ; and be- 
 fides this, the fpleen frequently varies in its fituation 
 
 with 
 
CHAr. xxn. SPLEEN. 355 
 
 with that of the colon. Frequently there is a fecond 
 or lefs fpleen placed upon the former. 
 
 677. The blood-veffels of the fpleen are large, In 
 proportion to its weight. The arterial trunk comes 
 from the cceliac ; the upper branch of which, proceed- 
 ing in a ferpentine courfe above and behind the pancre- 
 as, to which it gives branches, as well as to the mefo- 
 colon, ftomach, and omentum, is at length incurvated 
 in the direftion of the fulcus or notch of the fpleen, 
 which it, after a manner, perforates by feveral diftinct 
 branches, fuflained at the right extremity by the omen- 
 tum gaftrocolicum. The thicknefs of this artery is 
 greater than that of the aorta. The fplenic vein, which 
 accompanies the artery, is confiderably fofter than any 
 other veins of the body; it forms the principal left 
 branch of the vena portarum. Befides thefe, the fpleen 
 receives fmall arteries from the great coronary, de- 
 fcending behind the pancreas, and fometimes from the 
 internal hasmorrhoidal. The vafa brevia of the fpleen 
 and ftomach we have mentioned elfewhere ; and its liga- 
 ments and membranes receive fmall arterial twigs from 
 the lumbar arteries, phrenics, intercoftals, and thofe of 
 the renal capfules. In like manner alfo the veins in the 
 fpleen, and thofe which join it to the ftomach, commu- 
 nicate with the phrenics, and with the veins of the re- 
 nal capfules. 
 
 678. The lymphatic vejfels of the fpleen are defcribed 
 to arife in the duplicature of the fplenic coat or mem- 
 brane (of which there is none at all), and from thence 
 to proceed on to the receptacles of the chyle, very evi- 
 dent in a calf ; in mankind they are rendered conipicu- 
 ous by blowing air under the membrane, by inacera-* 
 tion, or water injefted into the arteries. 
 
 679. The nerves of the fpleen are very fmall; frorn 
 whence it is capable of but little pain, and is very rarely 
 inflamed* They arife from a particular plexus, com- 
 pofed out of the pofterior branches of the eighth pair 
 at the ftomach (630.), and of certain branches from the 
 latge gangliform plexus, which produces the fplenic 
 
 X X trunk 
 
I 
 
 ^ 5 ^ S"-P 1 E E N. ChXp. xnr. 
 
 trunk of the interccftatnerve, from whence the branches 
 furround the artery- into the fpleen. 
 
 680. The fabric pf’.the fpleen appears to be much 
 niore fimple than hast)©en commonly believed. For it 
 IS compofed, both m us and in calves, altogether of ar- 
 teries and of veins; the-former of which, after fpend- 
 ing themfelves in a great number of fmall branches, are 
 at length thickly fubdivided into very foft brufli-like 
 bunches, very difficult to fill with injeci’poh, terminating 
 in circles ; by w'hich there is a ready pafpg^.fqr liquors 
 into the correfponding veins. Thefe circles, wdth their 
 parallel branches, form a fort of bunches like a pencil 
 bruffi, but of a ffiorter rounder kind ; whence many 
 have miltaken them for glands.: ' Nor does, the injec- 
 tion, rightly managed, ever efcape from the velfels into the 
 intervals ; nor were any hollow glandules ever difcovered 
 by certain obfervation. Every little arterial trunk, with 
 the fmaller twigs that proceed from it, are each of them 
 furrounded by a very fine cellular fubfiance or web- 
 work, in the fame manner with the fmall velTels of all 
 the other vifcera, but here rather fofter. The whole 
 body of the fpleen is outwardly furrounded by a fingle 
 membrane, which is not very tough, continued from 
 the peritonaeum, and joined to the flelhy part of the 
 Ipleen by a pretty thick cellular texture. 
 
 681. Hence we obferve, that the fpleen contains 
 more blood, in proportion, than any of the other vifce- 
 ra ; fince it has no mufcles, fat, air-veffels, or excretory 
 duffs, interpofed betwixt its blood-vefiels. We learn 
 alfo from obfervation, that the blood of this part hardly 
 ever congeals, from the abundance of its volatile or bi- 
 lious falts : but it looks of a dark-brown colour, and 
 may be eafily diluted ; whence one may compare it 
 almofl to the blood of a foetus. 
 
 682. The want of an excretory duff to the fpleen, 
 has occafioned the ufe of it to be doubtful, and contro- 
 verted throughout all ages of anatomy. To us the fa- 
 bric itfelf feems to lead to the following ufes ; although, 
 perhaps, they do not comprehend all the ufes of the 
 
 fpleeu> 
 
■Chap. XXII. SPLEEN. 357 
 
 fpleen. A great quantity of blood is imported to the 
 fpleen (677,), and with a flower motion, from the fer- 
 pentinis eourfe and hardnefs of the artery : but, at the 
 time whqn the flomach is empty, this blood comes, and 
 is received in a greater quantity by the fpleen, not now 
 fo much compreflTed, therein to flagnate, as it would, 
 feem plainly from the great proportion of branches to 
 the trunks in this part ; to which add, the difficult 
 courfe or flow circulation which the blood meets with 
 in pafling from the fpleen through the liver.: from 
 hence the frequent fcirrhofities of the fpleen ; and from 
 hence the immenfe quantity of blood with which the 
 fpleen is in every point diftended, the like of which we 
 do not fee in any other part. Here, then, the almofl 
 ftagnant blood, fomented with heat, attenuated, and in 
 a manner diflTolved by the putrid feces of the adjacent 
 colon., enters thus upon the firfl fteps of a begun putre- 
 faction, as we learn by experiments, both from its co- 
 lour and confiflence. But the greater fluidity of the 
 blood herein, proceeds not only from this diflfolution, 
 but becaufe all its watery juices that enter by the artery 
 return alfo again by the vein j for there are no fecreto- 
 ry duds in the fpleen. 
 
 683. Moreover, when the flomach is full -of food or 
 flatus, the fpleen is thereby compreflTed into a narrower 
 compafs, againfl the ribs and fupcrincumbent dia- 
 phragm, by which means the blood, that before was 
 fcarce able to creep along through the fplenic veins, be- 
 ing now preflTed out more plentifully, returns with a 
 greater celerity towards the liver ; till mixing with the 
 fluggifh blood in the trunk of the porta, replenifhed 
 with the fat or oil of the omentum and mefentery (669.), 
 it dilutes or thins the fame, and renders it lefs apt to 
 flagnate or congeal ; and, at the fame time, it conduces 
 to form a larger fecretion of bile at a time when it is 
 mofl wanted, viz. to flow plentifully to the food now 
 ■under digeflion. The fpleen, therefore, feems to pre- 
 .pare the blood, that it may fupply a fort of watery juice 
 to the bile 5 but fuch as is probably of a fubalkaline na- 
 X X 2 ture. 
 
35^ P A N C R E A S. Chap. XXIII. 
 
 ture, and rendered fomewhat fharp by the remora of 
 the blood. 
 
 684. Whether is the fpleen of a cellular fabric? Is 
 the blood poured out into thofe cells fo as to ftagnate ? 
 or is it diluted with fome juice fecreted by peculiar 
 glands? We fee nothing of this is demonflrable by 
 anatomy ; nor does the liquor or wax injected ever cx- 
 travafate into the cellular fubftance, unlefs urged with 
 much greater violence than nature ever ufes or intend- 
 ed. As to the old queftion, Whether the fpleen brews 
 up an acid to whet or (harpen the ftomach ; that opi- 
 nion has been long difearded, as repugnant to the na- 
 ture of all the animal juices. If it be alked whether 
 the fpleen be not an ufelefs mafs, as it might feem to 
 be, from the little damage an animal fuftains after it has 
 been cut out? we anfwer, That a robuft animal, fuffer- 
 ing but little injury from the lofs of a part, does not 
 prove it to be ufelefs ; and yet there are examples, after 
 fuch an experiment has been made, that the liver be- 
 comes fwelled and difordered, makes a lefs quantity of 
 bile, and of a darker brown colour ; while the animal 
 is perpetually troubled with flatulencies, gripes, or indi- 
 geftion: all which are to be aferibed to the vitiated na- 
 ture of the bile, an obftrudtion of the liver, and an im- 
 perfedf or weak digeflion ; at the fame time they are 
 confirmed by repeated experiments. 
 
 CHAP. XXIII. 
 
 Of the Pancreas. 
 
 ^85. H E pancreatic juice^ which is watery, infi- 
 A pid, thin, neither acid nor alkaline, is poured 
 into the fame place into which the bile difeharges it- 
 'felf. 
 
 686. The pancreas is then a very long glandule, the 
 largefl of the falival kind, extended over the inferior la- 
 mina of the tranfverfe mefocolon ; which, beyond the 
 
 pancreas. 
 
Chap. XXIII. PANCREAS. 359 
 
 pancreas, behind its fuperior lamina, behind the fto- 
 mach, before the fpleen, under and behind the liver, 
 meets with the inferior lamina : it lies before the left 
 capfule and the aorta ; is plain, and of a triangular fhape, 
 with a light ftroke on the upper part, and covered with 
 the peritonaeum, upon which the pofterior flat fide of 
 the empty ftomach is fupported ; for that fide of the 
 ftomach is both lower as well as pofterior. The pan- 
 creas begins fmall from the fpleen itfelf ; and extending 
 almoft tranfverfely towards the right fide, it emerges 
 forwards to the peritonaeum, acrofs the vertebrae, to the 
 right fide of which it grows confiderably broad, being 
 received betwixt the fuperior and inferior plate of the 
 tranfverfe mefocolon (659.); and is, finally, fo con- 
 nefted by its round head to the duodenum, that this 
 inteftine ferves it for a mefentery. The ftrudfure of it 
 is,. like that of the falival glands, made up by a -great 
 number of fmall kernels of a firm texture, connefted to 
 each other by a good deal of cellular fubftance. The 
 pancreatic blood-vejfels are rather numerous than large, 
 derived chiefly from the fplenic branches : but on the 
 right fide it is fupplied by the firft artery of the duode- 
 num, and from that other which is lower down, and is 
 in common both to the duodenum and pancreas ; both, 
 of which arife from the hepatic artery, and of which tfie 
 former inofculates with the latter, and both with the 
 mefenteric artery, which fupplies conliderable twigs to 
 this gland ; but the fmaller ramifications come from the 
 phrenic and capfular arteries. The nerves of this gland 
 are not of any confidcrable fize ; whence it is but little 
 fenfible : they are derived from the pofterior gaftric and 
 the hepatic plexus, from that of the fpleen, &c. 
 
 687. The excretory duil of this gland runs almofi: 
 through its middle, white and tender, arifing every 
 where from a great number of roots ; by which, being 
 gradually increafed, it emerges before the vena porta- 
 rum and mefenteric artery, and receives a large branch 
 from the lateral pancreatic portion ; from whence it ad- 
 vances to the fame part of the duodenum into which 
 
 the 
 
g<5o PANCREAS. Chap. XXIIL 
 
 the biliary dud opens ; where, changing its courfc 
 downward, it enters through the finus that lies betwixt 
 the coats of the inteftine, internally fmooth ; and here, 
 receiving the dudus choledochus, it opens together with 
 that into a certain fold of the fame duodenum, defcend- 
 ing towards its lowed; part. But not unfrequently it 
 opens diflind, both in its dud and orifice, from that of 
 the biliary dud; and fometimes it is infcrted by two 
 duds, of which the lower one only is diftind and lefs ; 
 but in man, and mod other animals, it always opens 
 near the dud of the bile. In its mouth there is no 
 bile. 
 
 688. The quantity of juice fecreted by this gland is 
 uncertain : but it muft be very confiderable, if we com- 
 pare the bulk or weight of it with that of the falival 
 glands ; than which it is three times larger, and feated 
 in a warmer place. It is expelled by the force of the 
 circulating blood, with an alternate preffure from the 
 incumbent and furrounding vifcera ; as the liver, fto- 
 mach, fpleen, mefenteric and fplenic arteries, with the 
 aorta. The great ufefulnefs of this gland may appear 
 from its being found not only in man, but almofi; in all 
 animals : nor is its ufe the lefs from that experiment 
 which fhows a great part of it may be cut out from a 
 robuft animal without occafioning death ; becaufe, in 
 the experiment, a part of the pancreas mult be left with 
 the duodenum. Its effervefcence with the bile arifes 
 from the effed of a ligature, and air mixed with the 
 inteftinal humour. 
 
 688. The pancreatic juice feems principally of ufe to 
 dilute the vifcid cyftic juice, to mitigate its acrimony, 
 and mix it with the food. Hence it is poured into a 
 place remote from the cyftic dud as often as there is no 
 cyftis. Like the reft of the inteftinal humours, this 
 juice dilutes the mafs of aliments, refolves them, and 
 does every other office of the faliva. 
 
 CHAP, 
 
Chap. XXIV. 
 
 LIVE R, 
 
 3^1 
 
 CHAP. XXIV. 
 
 Of the Liver, Gall-Bladder, and Bile. 
 
 689. n|^HE UveKy being the largeft of all the vifcera, 
 jL fills up a very large part of the abdomen in 
 its upper chamber, above the mefocolon ; and is yet ftill 
 larger in proportion in the fetus. Above, behind, and 
 to the right fide, it is covered by the fuperincumbent 
 diaphragm, from u'hich it receives the peritoneum for 
 a covering, under the denomination of ligaments, chiefly 
 in three places : for on the convex part of the liver, 
 from the paflage of the vena cava to the tranfverfe fur- 
 row of the liver, the peritoneum defcends double, 
 growing broader in the forepart, under the name of 
 Ugamentum fufpenforium, which divides the greater right 
 lobe from the lefler left lobe of the liver ; and then 
 parting from its duplication, it expands into the proper 
 coat of this vifcus (623.), which is white, Ample, and 
 thin, like the external coat of the fiomach ; and under 
 this is fpread the cellular fubftance, by which it is inti- 
 mately conjoined with the flelh of the liver. To the 
 lower margin of this, joins the umbilical vein ; which, 
 in an adult, being dried up, leaves only a fmall cord, 
 furrounded with much fat. In the extremity of the left 
 lobe, and on the convex part, not unfrequently at its 
 edge, a membrane goes to the liver from the diaphragm j 
 which in children, and other young fubje£ts, is fre- 
 quently to the left fide of the oefophagus, but in adults 
 to the right fide ; yet always conjoined both to the gu- 
 la and to the fpleen, whenever the liver or the left li- 
 gament is very large. The right ligament ties the dia- 
 phragm in its hinder part to the thickeft; part of the 
 right lobe. Befides, but without any apparent length, 
 the membrane of the right lobe of the liver is often 
 conjoined by the cellular fubftance with the diaphragm ; 
 more efpecially in old fubjefts, for in the fetus it is 
 
 eafily 
 
3<$2 LIVER. Chap. XXIV. 
 
 eafily feparated ; and then it continues its courfe be- 
 twixt the fufpenfory and left ligament, joined as before 
 with the peritonaeum, fo as to refemble a ligament. 
 But alfo from the right kidney, the peritoneum going 
 off to the liver, makes a reduplication like a ligament, 
 and conjoins together the lefs omentum with the con- 
 tinued loofe productions of the inefocolon (663.) with 
 the liver, fforaach, and duodenum ; and hkewife the 
 fame inefocolon to the pancreas. Thus the liver is 
 fufpended in the body, with a confiderable degree of 
 firmnefs ; yet fo as to be allowed a confiderable liberty 
 to move and be varioufly agitated, raifed, and depreffed, 
 by the actions of the diaphragm. The fame ligaments 
 form a common membrane, which covers the liver as 
 well as other vlfcera. 
 
 • 690. Moreover, the inner concave face of the right 
 liver lies with its forepart before the colon; and in 
 its back part correfponds to the right kidney and re- 
 nal capfule, to w^hich it is conneded by the cellular fub- 
 ffance. The middle finus lies near the duodenum, 
 which touches the gall-bladder ; and alfo lies contigu- 
 ous with that part that conduds the great blood-veffds. 
 The left lobe extends largely over the ftomach ; and 
 frequently, efpecially in younger fubjects, goes beyond 
 the oefophagus into the left hypochondrium. The lo- 
 bule, in the mean time, adapts itfelf to the leffer curve 
 of the ftomach. But, moreover, the pancreas is co- 
 vered by the liver, and the right renal capfule is tied to 
 the part of the liver fartheft to the right fide by much 
 cellular texture. 
 
 691. The figure of the liver is difficult to defcribe. 
 It begins in the cavity of the right hypochondrium, 
 by a very thick folid protuberance, convex towards 
 the diaphragm, and hollow towards the colon and 
 kidney ; having a protuberant line dividing the faces of 
 thefe Imall hollows, w'hich is continued to the longer 
 appendix of the lobule. After this, the liver grows 
 flenderer and thinner, and is at laft terminated or exte- 
 nuated into a tip, almoft triangular ; which, paffing into 
 
Chap. XXIV. LIVER. 3^3 
 
 the left hypochondrium, goes before the oefophagus, in 
 young fubjeds, as far as the fpleen ; but in adults, it is 
 often fliorter, and ends at the oefophagus. The edge, 
 in which the convex part of the liver meets with the 
 concave one, is wholly in the fore and lower part. The 
 whole obtufe margin lies backward. The upper and 
 back part of the liver is every where convex ; fuftains 
 the diaphragm ; and in a large part, which is fomewhat 
 flatter, towards the left fide, it is placed under the 
 heart ; but the lower furface, being varioufly figured, 
 refis itfelf upon the duodenum, colon, ftomach, pan- 
 creas, and right renal capfule. For there are feveral 
 little furrows which divide the furface into different re- 
 gions, and which did not efcape the notice of the an- 
 cients. 
 
 692. The principal of thefe furrows is extended 
 tranfverfely, from the right fide to the left, and divides a 
 third part of the liver, beginning flender in the right 
 lobe, and growing broader towards the left. Before 
 this tranfverfe fulcus, there is an excavation in the right 
 lobe for the gall-bladder, and then the anonymous con- 
 vex lobule ; after which comes the foflfa of the umbili- 
 cal vein, extending tranfverfely backward, often cover- 
 ed with a procefs or bridge that joins the anonymous to 
 the left lobe ; but behind the great fulcus, firfl towards 
 the right fide, there is a flender tranfverfe eminence 
 growing broader to the right, and moderately hollow, 
 by which the great blood-velfels are conducted into the 
 liver : and this little valley was by the ancients deno- 
 minated the porta or gates of the liver. This joins the 
 lobule, which I lhall defcribe, with the right lobe. Then 
 the pofterior lobule, fhaped like a nipple, obtufely co- 
 nical, projects into the lefs curvature of the ftomach. 
 The thick root of this and the former excavated emi- 
 nence, begins from the convex part of the liver, at the 
 diaphragm ; and from thence, on the right fide, is im- 
 preflTed with an oblique furrow, inclined to the right 
 fide, for the paflage of the trunk of the vena cava, de- 
 fending from the heart to the lumbal vertebrte j and is 
 
 Y y fre- 
 
364 LIVER. Chap. XXIV. 
 
 frequently furrounded by a great part of the flefh of the 
 liver, like a bridge, or even fo as to complete the circle, 
 and form a tube. The left end of the lobule is termi- 
 nated by another foffa almoil llraight backwards, but 
 inclined to the left ; which, taking its origin from the 
 extremity of the tranfverfe one, terminates at the paf- 
 fage of the vena cava through the diaphragm. In this 
 fmus was lodged the ductus venofus in the fetus, of 
 which there are fome remains to be perceived alfo in 
 the adult. All that lies beyond this is the left lobe, 
 which is Tingle, equally concave below, fo that it may 
 lie upon the ftomach, and is extenuated to a thin 
 edge. 
 
 693. This fo large vifcus is proportionably fupplied 
 with veffels, and of various kinds. The artery, which 
 is indeed confiderable, being the greater right portion 
 of the csliac, emerges from the trunk forward, and to 
 the right, going tranfverfely before the vena portarum ; 
 and alter giving olf a fraall coronary with the pancreatic 
 and duodenal artery, the lafl of which is pretty large, 
 it goes on and enters the liver, commonly by two 
 branches ; of which the left is betwixt the umbilical fof- 
 fa, the venal duel, pofterior lobule, with the left and 
 the anonymous lobe, alfo the furpenfory ligament ; and 
 this branch inofculates with the phrenic and epigaftric 
 arteries. The right enters the liver lower, covered by 
 the biliary duels ; and having reached the right with 
 the anonymous lobe, there fends off, in one fmall trunk, 
 the cyftic artery, which foon after divides into two, and 
 is fpread both under and upon the gall-bladder, cover- 
 ed by the common coat of the liver, and fupplies not 
 only the gall-bladder and biliary du£ls with its branches, 
 but likewife fome part of the liver itfelf. From the 
 left branch, or fometimes from the trunk of this, arifes 
 a fuperficial artery to the biliary dulls, anonymous lobe, 
 and glandules of the portae. Befides the cceliac artery, 
 there is frequently a large right branch produced from 
 the mefenterica major, creeping behind the pancreas ; 
 and this ferves inftcad of the eighth branch of the he- 
 patic 
 
Chap. XXIV. LIVER. 3^5 
 
 patic artery from the caeliac. But, llkewife, the greater 
 coronary, which is the firft twig of the cseliac, always 
 gives fome ramifications to the left lobe, and to the foffa 
 of the ductus venofus ; which laft branch is often very 
 confiderable. The leffer arteries are thofe fent to the 
 liver from the phrenic, mammaries, renal and capfulary 
 arteries. They communicate alfo with the epigaftrics. 
 
 694. In the fetus, the umbilical vein brings much 
 blood to the liver, at which time the vein ftretching to 
 the portae is but fmall. It fends forth branches while 
 it flretches backwards through its foffa ; thefe branches 
 are numerous, and very large; fo that one of them e- 
 (|uals the vena portarum in bignefs, in that place where 
 it is dilated into a tumour, which unites with the left 
 branch of the vena portarum. But it fends one branch 
 through the poflerior part of the horizontal fofla into 
 the vena cava, or fome of its hepatic branches : this is 
 called the dudus venofus. In an adult perfon, indeed, 
 this duQ: is filled up; and the vena portarum, which 
 now grows larger, fills the hepatic branches. 
 
 695. The vena portarum receives all the blood of the 
 floinach (62 9.),oftheinteflines and mefentery (631.), of 
 the fpleen (677.), omentum (669.), and, laftly, of the 
 pancreas, at firft into two trunks, the tranfverfe fplenic 
 and afeending mefenteric ; then into one, which is con- 
 tinued with the mefenterics. This is large, compofed 
 of ftrong membranes, firft a little bent behind the duo- 
 denum, where it receives the veins from its right fide, 
 together with the leffer coronary ; wdience going higher 
 to the right fide, it again divides into two large trunks 
 in the finus of the lobule of the liver (692.), and imme- 
 diately after is again divided into two large trunks. Of 
 thefe two, the right, being fliorter, larger, and bifur- 
 cated, having received the cyftic vein, goes to its own 
 lobe. The left runs on through the remaining part of 
 the tranfverfe furrow of the liver ; and, after giving 
 veins to the lobule, with the anonymous and left lobe, 
 it is incurvated and enters the umbilical foffa ; from 
 whence, about the middle, it immerges and ramifies 
 
 y y 2 through 
 
366 LIVER. Chap. XXIV. 
 
 through the liver. There are fome inftances in which 
 the venous branch of the pofterior lobule has been fent 
 diftin£t from the vena portarum. 
 
 696. The vena portarum is on every fide furrounded 
 with a good deal of cellular fubftance, derived to it from 
 the mefentery and fpleen, denfe, fhort, and adding 
 flrength to the membranes ; thofe with which it is fur- 
 nifhed being harder than the aorta itfelf. Intermixed 
 with this cellular fubllance, are alfo many of the fmal- 
 ler veffels and hepatic nerves, which all come together 
 under the denomination of a capfula, which is nothing 
 more than the cellular fubftance, and never has truly a 
 fingle flefhy fibre. By this the vena portarum is con- 
 duced to the liver, and firmly fuftained ; infoinuch, 
 that the branches, being cut, maintain the round lights 
 of their feCions. But each branch of this veflcl is di- 
 
 ' vided into many others, again divided and fubdivided, 
 after the manner of arteries, till they at length produce 
 the fmalleft capillaries. In this courfe, every branch of 
 the vena portarum is accompanied with a focial branch 
 of the hepatic artery, creeping upon the furface of the 
 vein, and the contiguous hepatic duCs, ahnoft in the 
 fame manner as the bronchial arteries ufually creep 
 along the ramifications of the windpipe in the lungs; 
 while, in the mean time, both the artery and the vein 
 are conneCed to the branches of the biliary duCs by a 
 thin cellular fubftance like a fpider’s w-eb. Some go 
 out of the liver, being divided to the ligaments, and 
 inofculating with the furrouncling veins. And the fum 
 of the branches in the vena portarum is always greater 
 than the trunk ; whence the lights of all the branches 
 together greatly exceed that of the trunk (37.): from 
 whence follows a great friction or refiftance (iBo and 
 162.), after the fame manner as we obferve in the ar- 
 teries. 
 
 697. But, fince the blood is in this manner conveyed 
 through the liver to the branches of the vena portarum, 
 together w'ith the hepatic artery, it muft of courfe be 
 conveyed back again by fome other veins: and, there- 
 fore. 
 
Chap. XXIV. LIVER. 3^7 
 
 fore, the extreme branches of the vena portarum and 
 hepatic artery inofculate ultimately into other veins, 
 which are branches of the cava ; which arifmg from the 
 whole circumference of the liver, run together towards 
 the pofterior gibbous part of the liver into branches and 
 trunks, which at laft go off into ten or more large vef- 
 fel^. The leffer of thefe trunks, and greater number of 
 them, pafs out through the pofterior lobule of the liver, 
 and go to the cava through the fulcus, that lies on the 
 right fide of the lobule, often completed into a circle 
 by a fort of bridge or produdllon of the liver; from 
 whence they afcend together through the diaphragm to- 
 wards the left fide. Two or three trunks, much larger 
 than the former, are inferted into the fame cava, clofe 
 to the diaphragm, whofe veins they often take in by the 
 way. The branches of the vena cava are, in the adult, 
 generally fewer and lefs than thofe of the vena porta- 
 rum ; which is an argument that the blood moves 
 quicker, becaufe of the lefs fridlion (lyo.j, and of the 
 very colleftion of the blood into a lefs light or capacity, 
 by which it is always accelerated when there is a fuffi- 
 cient comprefling force (i 70.) As to any valves at the 
 openings of thefe branches into the cava, 1 know not of 
 any which deferve to be regarded. The trunk of the 
 vena cava, palling through a foramen of the diaphragm, 
 obtufely quadrangular, furrounded and terminated by 
 mere tendons (262.), is thereby rendered not eafily 
 changeable: and having furmounted this opening of 
 the diaphragm, it then immediately expands into the 
 right auricle. The fmaller veins of the liver creeping 
 about its furface, are fent forth from the phrenics, re- 
 nals, and azygos ; or at leaft there is certainly a com- 
 munication betwixt thefe and the hepatic veins coming 
 from the portse. 
 
 698. That the blood comes from all parts (6p^.) by 
 the vena portarum to the portae, is proved by a ligature, 
 by which any vein betwixt thefe parts and the ligature 
 fwells ; but the porta itfelf, above the ligature, grows 
 flaccid and'^mpty. But that it afterwards goes through 
 
LIVER. 
 
 Chap. XXIV. 
 
 the liver to the cava, appears by anatomical injeclions, 
 which Ihow open and free anaftomofes or communica- 
 tions betwixt the vena portarum and the cava, together 
 with the common nature of the veins going to the cava. 
 Again, the difficult dihribution or paffiage through the 
 vena portarum, like to that of an artery, together with 
 its remotenefs from the heart, and the oily or fluggiffi 
 nature of the blood itfelf, occafion it to ftagnate, accu- 
 mulate, and form fcirrhous fwellings in no part oftener 
 than the liver. But this danger is diminiffied by the 
 motion of the adjacent mufcles, and by the refpiration ; 
 as it is increafed by inactivity, with four and vifcid ali- 
 ments. But, hitherto, we have been fpeaking of the 
 adult liver, in which both the umbilical vein and the 
 du£lus venofus are empty and clofed up, although they 
 continue to cohere with the left branch of the vena por- 
 tarum. 
 
 699. The nerves of the liver are rather numerous 
 than large; hence, when wounded or inflamed, it is 
 capable of no very great pain. They have a twofold 
 origin. Molt of them arife from the large gangliform 
 plexus, made by the fplenic branch of the intercoflal 
 nerve, with the addition of a branch from the pofterior 
 plexus of the eighth pair ; they accompany the hepatic 
 artery, and, playing round its trunk, are diftributed 
 with that and the portal branches throughout the liver. 
 Another fafciculus of nerves ufually enters w'ith the 
 du£lus venofus, and arifes from the poflcrior plexus 
 of the eighth pair, but fometimes from the great 
 plexus. 
 
 700. The lymphatic vejfels of the liver are nume- 
 rous, being conltantly and eafily to be feen about the 
 portae. They arife from the whole concave furface of 
 the liver and gall-bladder, and run together into a 
 plexus, furrounding the vena portarum, going after- 
 wards to the fmall conglobate glandules, feated before 
 and behind the faid vein ; from whence they meet to- 
 gether in one large trunk, which is one of the roots of 
 the thoracic duft. Upon the convex part of the liver 
 
 are 
 
LIVER. 
 
 Chap. XXIV. 
 
 3^9 
 
 are defcribed other lymphatics, whole infertion is not 
 well known ; but it is hardly probable that they enter 
 the cava, nor have I been able to find that they lead to 
 the ciflern of the chyle. 
 
 70 1 . The interior fabric of the liver is more obfcure. 
 Through the whole fubftance of the liver go bundles 
 of biliary veffels, of branches of the vena portarum, and 
 of the hepatic artery. Each vefl’el has both its proper 
 cellular texture furrounding it, and fimilar ligaments, 
 by which it is tied to its fellow-veffels ; and, laflly, the 
 whole bundle has its cellular texture placed round it. 
 The branches of the vena cava lie on the outfide of the 
 reft, being lefs accurately received into the fame bundle. 
 Laftly, the ultimate fmall branches of the vena porta- 
 rum, cava, and hepatic artery, together with the bilious 
 duels, which we fhall foon deferibe, are united together 
 by means of the cellular fubftance (696.), into a fort of 
 mulberry-like bunches, of an hexagonal fhape, fur- 
 rounded with a lax cellular texture. In thefe bunches, 
 likewife, there are mutual anaftomofes betwixt the por- 
 tal branches and hepatic artery, with the roots of the 
 vena cava on one fide, and the firft origins of the pori 
 biliarii of the liver on the other fide ; which laft demon- 
 ftrate their inofculations by anatomical injedlions, for 
 liquors injedled by the vena portarum return again 
 through the porus choledochus. 
 
 702. Many eminent anatomifts have taught that the 
 fore-mentioned bunches are hollow, having arteries and 
 veins fpread upon their external furface, and depofite 
 the bile into their cavity, after it has been fecreted from 
 the branches of the vena portarum. For this they al- 
 lege arguments taken from the comparative anatomy 
 of brutes, whofe liver is made up of more round and 
 definite bunches ; and from thofe difeafes which de- 
 monftrate cells and round tubercles, filled with lymph, 
 chalk, and various kinds of concreted matter. To this 
 they might have added the thick fluggifh nature of the 
 bile itfelf, by which it is related to mucus, and the ana- 
 logy of the follicles of the gall-bladder. 
 
 703. But 
 
370 LIVER. Chap. XXIV. 
 
 703. But greater acuracy in anatomy will not allow 
 any follicles into which the Imali fecretory veffels open ; 
 for fuch would intercept the courfe of anatomical in- 
 jections, and give us the appearance of knots interme- 
 diate, betwixt the fecretory velTels and the biliary pores, 
 which we have never yet been able to fee: for the wax 
 flows immediately, without any interruption or effufion, 
 into a cavity in a continued thread from the vena por- 
 tarum into the biliary ducts. But, again, a follicular 
 or glandular fabric is not allowable in the liver, from 
 the great length of the biliary ducts. For all follicles 
 depofite their contents into fome fpace immediately ad- 
 jacent ; and are unfit to convey their fecerned fluid to 
 any length of courfe, as they deftroy fo great a part of 
 the velocity received from the arteries. Laftly, the ve- 
 ry common prelfure which we mud fuppofe to be on 
 thefe bunches of kernels would fo crufh them-, that no 
 alTiftance could from thence be brought to promote the 
 motion of the excretory duCls. Concretions and hydatids 
 are formed in the cellular fubflance ; and, laftly, the 
 bile, when firft fecreted, is fufliciently fluid. 
 
 704. Again, we are perfuaded that no bile is fepa- 
 rated from the hepatic artery, becaufe the peculiar 
 ftruffure of the vena portarum would be ufelefs if it fe- 
 creted nothing. Its office in fecretion appears plainly 
 by the continuations of its branches with the biliary 
 duffs, in a manner more evident than that of the artery: 
 but it appears by experiments, alfo, that the biliary fe- 
 cretion continues to be carried on after the hepatic ar- 
 tery is tied ; add to this the largenefs of the biliary 
 dufls, in proportion to fo fmall an artery, with the pe- 
 culiar nature of the blood collefled in the vena porta- 
 rum, fo extremely well fitted for the formation of the 
 bile. For w’e have already feen that it contains oil, 
 which abounds more in the bile than in any other hu- 
 mour of the body; for it takes in the faponaceous wa- 
 ter of the ftomach by the abforbing veins, together with 
 the fubfetid alkalefcent vapours of the abdomen, which 
 tranfpire through the whole furface of the inteftines, fto- 
 mach, 
 
Chap.XXIV. liver. 371 
 
 mach, omentum, liver, fpleen, and mefentery, which 
 are abforbed again by the veins, as we know by incon- 
 teftable experiments of anatomy ; and, finally, the alka- 
 lefeent femiputrid acrimonious humidity from the fasces 
 while they continue to thicken in the large inteftines, 
 which is taken up by the internal haemorrhoidal veins, 
 from whence that bitternefs, alkalefcent and putrefeent 
 difpofition of the bile is derived. But in the blood of the 
 hepatic artery, we can find nothing peculiarly fit for the 
 fecretion of bile, or analagous to its nature. 
 
 705. Since, therefore, the vena portarum conveys 
 the blood ready charged with biliary matter, fit to be 
 fecreted in the leaft acini (704.), and from thence there 
 is an open free paffage, y/ithout any intermediate fol- 
 licles, from the ultimate branches of the vena porta- 
 rum into the beginning roots of the biliary dudls, and 
 that the humours driven into the vena portarum may 
 eafily chufh this paffage, the bile will be expelled from 
 thence by the force of the blood urging behind, as well 
 as by the auxiliary force of the diaphragm prefling the 
 liver againfl the reft of the vifeera in the very full ab- 
 domen (689.), and again, contraded in exfpiration, it 
 will be forced into the larger branches, and laftly into 
 two trunks of the larger biliary du£t of the liver ; which 
 trunks meet together in one upon the vena portarum, 
 in the tranfverfe foffa of the liver, near the anonymous 
 lobule. 
 
 706. The fabric of this dudl is made up by a ftrong 
 nervous membrane like that of the inteftines, over which 
 is fpread an external and internal cellular membrane, 
 and is internally lined with a loofe villous tunic, elegant- 
 ly reticulated, but afperated with many fmall pores and 
 finufes, and continued with that of the inteftine itfelr. 
 But there is here no mufcular fabric apparent. From 
 experiments it appears to be endowed with a moderate 
 degree of irritability. That it is vaftly dilatable, is fhewn 
 from difeafes. The fame feem alfo to fhow that this dudt 
 is endowed with a very (harp fenfation. 
 
 707. The hepatic dud, thus formed, goes on upon 
 
 Z z th?i 
 
^72 LIVER. Chap.XXIV-, 
 
 the vena portarum, more to the right than the artery, 
 towards the pancreas ; and then defcending obliquely, | 
 covered by fome part of that gland, it goes to the lower 
 part of the fecond flexure’ of the duodenum, and is in- 
 serted backward about fix inches from the pylorus, 
 through. an oblique oblong fmus made by the pancre- 
 atic diidl, into which it opens by a narrov; orifice. The 
 faid finus runs a great way through the fecond cellular 
 coat of the duodenum obliquely downward ; then it 
 perforates the nervous coat, and goes on again oblique- 
 ly betwixt it and the villous tunic ; and, laftly, it opens 
 into a protuberant long wrinkle of the duodenum. 
 Thus there is almofl; the length of an inch taken up be- 
 twixt the firfl; infertion and the egrefs of this duff 
 through the coats of the duodenum, by a finus which 
 Surrounds and receives the dudtus choledochus, in fuch a 
 manner, that -when the coats of this inteftine are di- 
 ftended by flatus, or clofely contracted by a more vio- 
 lent perillaltic motion, the opening of the du£t mull be 
 consequently comprefled or fliut ; but when the duo- 
 denum is relaxed and moderately empty, the bile then 
 has a free exit. Any regurgitation from the duode- 
 num is hindered by this obliquity and wrinkling of the 
 duft, eafily preflfed together or clofed and joined with 
 a quick fucceflion of frefli bile defcending perpendicu- 
 larly from the liver. Nor does wind inflated into the 
 inteftine find any paflfage into the duct. 
 
 708. But, in the portae themfelves, this common duft 
 receives another lefs canal of the fame kind, which lies 
 for a good w’ay parallel wdth itfelf from the gall-bladder, 
 making its infertion in a very acute angle ; and this, 
 V'hich is called the cyftic duft, from its origin, is fome- 
 times firft increafed by another fmall dud from the he- 
 patic before its common infertion. This dud is form- 
 ed by the gall-bladder as a peculiar receptacle for the 
 bile given to mo ft animals ; but is abfent in fome, efpe- 
 cially thofe of a fwifter foot, and perhaps only in fuch 
 of thefe as are herbivorous : it is placed in an excava- 
 tion of the right lobe of the liver (6^2.), to the right 
 
Chap. XXIV, LIVER, 373 
 
 fide of the anonymous lobule, in fuch a manner, that 
 in infants or children it lies wholly within the edge of 
 the liver, but in adults projedls confiderably beyond, 
 lying upon the intellinum colon. Its fituation is almoft 
 tranfverfe from the fore to the back parts j its neck 
 afcends a little upwards. 
 
 709. The figure of the gall-bladder is variable, but 
 in general like that of a pear, terminated in its forepart 
 by an obtufe hemifpherical end, which is impervious, 
 gradually diminilhing backward ; the neck or tip of this 
 truncated cone being infleded upwards againft itfelf 
 once or twice, and tied together by the cellular fub- 
 fiance belonging to it, makes then another fmall flexure 
 upward, and begins the cyftic dud ; which from thence 
 goes on towards the left fide to the hepatic dud. With- 
 in this dud there are many protuberant wrinkles, for- 
 med by the numerous cellular bridles which tie them 
 together ; and thefe wrinkles, conjundly in the dry 
 gall-bladder, reprefent a kind of fpiral valve ; but being 
 altogether foft and alternate in a living perfon, they do 
 not flop, only lelfen the courfe of the bile, as we are af- 
 fured from experiments, by prelTing the gall-bladder, 
 and by inflations. Bcfides, it is reticulated like the 
 gall-bladder itfelf. 
 
 710. The outermofl coat of the gall-bladder covers 
 only.its lower fide, being the common covering of the 
 liver itfelf ftretched over the gall-bladder, and confin- 
 ing it to the liver within its proper finus. The fecond 
 coat is the cellular fubftance, and of a ioofe texture. 
 The third coat has fometimes fplendcnt fibres, chiefly 
 longitudinal; but fome obliquely interfering each o- 
 ther in various direrions. At other times it has none 
 at all ; fo that we may doubt of its mufcular nature, 
 efpecially as the irritability of the gall-bladder is flow 
 and obfcure. Next to thefe come the nervous coat, 
 then the fecond cellular, and lafl; the villous tunic; 
 which are all found here as in the inteftines, . except that 
 the lafl, in the gall-bladder, as well as in the biliary 
 durs, is reticulated and full of cells. Within the gall- 
 
 Z z 2 bladder. 
 
374 LIVER. Chap. XXIV. 
 
 bladder, but more efpecially about its neck and middle 
 part, we obferve muciferous pores, capable of receiving 
 a horfe-hair ; and befides thefe, the exhaling arteries 
 difcharge fome quantity of a watery humour into the 
 cavity of the gall-bladder, as we obferve in other cavi- 
 ties. 
 
 7 1 1 . All animals, between their gall-bladder and 
 liver, or between the duels coming from both, have, 
 befides fome peculiar openings in the gall-bladder, into 
 which fome dudls originating from the liver, or tue 
 hepatic biliary duft, difcharge their contents. In man- 
 kind thefe du£ls have not been fhown by any certain 
 experiment, and the gall-bladder is eafily looled from 
 the liver, without a drop of bile diltilling either from 
 it or from the liver. There is alfo a thin v/ater in the 
 bladder as often as the cyftic du£l is obftrufted. 
 
 71 1. The bile flows both out of the bladder and 
 liver, according to its nature, as long as there is no 
 impediment in its way ; fo that both duds fwell when 
 that paflfage is obftruded, and the cyflic lies in a firaight 
 line with the choledochus. Nor is it credible that all 
 the bile fhould be diverted into the gall-bladder before 
 it flows into the duodenum. There is not a perpetual 
 obftacle which hinders the efflux, and peculiarly refills 
 the hepatic bile, and admits the cyflic ; the paflfage into 
 the dudus choledochus is larger and ftraighter, the 
 dudus cyfticus much lefs than the hepatic, nor is that 
 dud fo well formed for receiving all the bile ; the 
 choledochus being much larger than the cyflic dud, 
 cannot therefore be made only for the reception of its 
 bile. There are many animals in which the hepatic 
 dud difeharges its contents into the intefline without 
 any communication with the cyftic. In living animals, 
 even when the cyftic dud is free, the bill appears to de- 
 feend into the duodenum with a perpetual current. 
 That the quantity is very confiderable, appears from 
 the magnitude of the fecretory organ, and the excre- 
 tory dud, fo many times larger than the falival ones ; 
 from difeafes, in which four“ounces of the cyftic bile 
 
 only 
 
Chap.XZJV. L I V E II. - 375 
 
 only have flowed out duly through an ulcer of the 
 fide. But the hepatic bile goes into the bladder, as 
 often as there is any obftruclion in the duodenal finus, 
 from flatus or any other caufe comprefling the exit of 
 the duftus choledochus. Accordingly, we find it ex- 
 tremely full, whenever the common biliary du£l is ob- 
 flrufted or compreffed by fome feirrhous tumour, 
 whence the gall-bladder is fometimes enlarged beyond 
 all belief; and if the cyftic du£t be tied, it fwells be- 
 twixt the ligature and hepatic du£t ; and' in living ani- 
 mals, the hepatic bile vifibly diftils into the wounded 
 gall-bladder, even to the naked eye. The retrograde 
 angle, or dire£lion of this duQ:, is not repugnant to 
 fuch a courfe of the bile; for a very flight preflure 
 urges it from the liver into the gall-bladder ; and even 
 wind may be eafily drove the fome way, more efpeci- 
 ally if the duodenum be firft; inflated. Nor does there 
 feem to be any fort of bile feparated by the gall-blad- 
 der itfelf. Whenever the cyftic duct is obftrucled by 
 a fmall ftone, or a ligature made upon it, we find 
 nothing feparated into the gall-bladder more than the 
 exhaling moifture, and a fmall quantity of infipid mu- 
 cus fecreted from the follicles (710). In many ani- 
 mals, we meet with no appearance of any gall-bladder, 
 when at the fame time there is a plentiful flux of ftrong 
 well prepared and falutary bile difeharged into their 
 inteftines. Again, it does not feem probable, that the 
 cyftic branch of the vena portarum can feparate bile 
 into the gall-bladder; for that vein in itfelf is a mere re- 
 condudory veflTel : nor can any be feparated from the 
 hepatic artery ; for it muft be vaftly beyond probabi- 
 lity, that fuch a ftrong bile as that of the gall-bladder 
 fliould be feparated from a milder blood than the more 
 foft hepatic bile prepared from the blood which is moft 
 fit for that purpofe (704). 
 
 712. Laftly, the bile flows alfo from the gall-bladder 
 to the liver, and at length returns into the blood when 
 its paflage into the inteftines is totally intercepted, 
 fometimes alfo from a caufe latent in the nerves. This 
 
 paflage 
 
37^ LIVER. Chap. XXIV. 
 
 paffage Is pernicious, and produces the jaundice ; which, 
 therefore, ftones thrown out of the inteftines cure, by 
 reftoring its free courfe into the duodenum. 
 
 713. Therefore a portion of the hepatic bile being 
 received into the gall-bladder, there ftagnates, only a 
 little fhook by the refpiration ; and there, by degrees, ex- 
 hales its thinner parts, which, as we fee, filtrate through 
 and largely penetrate the adjacent membranes. The 
 remainder, as being a fluid of an oily fubalkaline nature, 
 digefting in a warm place, grows fliarp, rancid, more 
 thick, bitter, and of a higher colour : for this is all the 
 difference betwixt the cyftic and hepatic bile; which laft 
 we find weaker, lefs bitter, lighter coloured, aiid of a 
 thinner confidence, while it remains within its proper 
 hepatic duels. That this difference betwixt them pro- 
 ceeds only from flagnation, appears from fuch animals 
 as have only a larger porus hepaticus, inllead of a gall- 
 bladder ; for here we find the bile, which ftagnates in 
 the larger hepatic pore, is confiderably more bitter 
 than that in the fmaller pores of the liver; as for ex- 
 ample, in the elephant. But the gall-bladder gives 
 this particular advantage, that it receives the bile when 
 the ftomach, being empty, has no call for it, that after- 
 wards it may be able to return it in greater plenty, when 
 we principally want it for the digeftion of the aliments 
 now flowing in great quantity into the duodenum. 
 This flow of the bile is quicker in proportion through 
 the cyftic du6l, as the fedion of that dud is lefs than 
 the feclion of the gall-bladder. 
 
 714. The gall-bladder, indeed, hardly touches the 
 ftomach, but the beginning of the defeending duode- 
 num. But when the ftomach is extremely diftended, 
 and in a very full abdomen, it makes a confiderable 
 preffure both upon the liver and duodenum; by which 
 the gall-bladder is urged, and its bile expreffed. Thus 
 the bile flows through a free paffage, from the gall- 
 bladder into the common duel, and the duodenum ; 
 and this it does more eafily in perfons lying on their 
 back; in which pofture the gall-bladder is inverted, 
 
 with 
 
Chap. XXIV. LIVER. 377 
 
 with its bottom upward. Hence it is that the gall- 
 bladder becomes fo full and turgid after falling. The 
 cxpulfive force of the bile is but little more than that 
 of the preffure received from the ftoinach and dia- 
 phragm ; for as to any mufcular force refiding in the 
 fibres of the proper membrane, which may be thought 
 to contrad; the gall-bladder, it mull be very weak and 
 inconfiderable. 
 
 715. The hepatic bile is always bitter, but the cyftic 
 is more fo ; always vifcid ; of a full yellow colour, with 
 a tindure of green ; mifcible, by triture, either with 
 water, oil, or vinous fpirits ; coagulable by mineral acid 
 liquors ; dilfoluble by alkalies, efpecially the volatile 
 kinds ; and extremely well adapted to diffolve oily, re- 
 finous, or gummy fubllances ; quickly putrefying, and 
 by putrefadion i'pontaneoufly degenerating to a mufk- 
 like odour. Its chemical analyfis, and experiments of 
 mixture with various fubftances, demonftrate, that it 
 contains a large portion of water, and a confiderable 
 quantity of inflammable, oil, which, in (tones of a gall- 
 bladder, appears very evidently. The bile, therefore, 
 is a natural foap ; but of that fort which is made from a 
 volatile faline lixivium, mixed with oil, and has its wa- 
 ter along with it. This, therefore, being intermixed 
 with the aliment, reduced to a pulp, and flowly ex- 
 preffed from the ftomach by the periftaltic force of the 
 duodenum and preffure of the abdominal mufcles, in- 
 corporates them all together; and the acid or acefcent 
 qualities of the food are in fome meafure thus fubdu- 
 ed, the curd of milk is again diflblved by it into a 
 liquid, and the whole mafs of aliment inclined more to 
 a putrid alkalefcent difpofition : it dilfolves the oily 
 matters, fo that they may freely incorporate with the 
 watery parts, and make up an unifoi-m mafs of chyle to 
 enter the ladleals ; the furrounding mucus in the in- 
 teftines is hereby abflerged and attenuated, and their 
 periftaltic motion is excited by its acrimony ; all which 
 offices are confirmed, by obferving the contrary effedls 
 from a want or defe^l of the bile. Nor is the hepatic 
 
 bile 
 
S?8 LIVER. Chap. XXIV. 
 
 bile fufficient to excite the neceffary motion of the in- 
 teftines, if the cyflic is wanting ; both which are of fo 
 muchufe and importance to the animal, that we find, 
 by experiment, even the ftrongefl will perilh in a few 
 days, if the flux of bile to the inteftines be intercepted, 
 by wounding the gall-bladder. 
 
 716. Thus it flowly defcends along with the ali- 
 mentary mafs ; and having fpent its force, or changed 
 its bitternefs by putrefaction, moll of it is afterwards 
 excluded together with the faeces ; but probably fome 
 of the more fubtle, watery, and lefs bitter parts, are a- 
 gain taken up by the vena portarum. It returns the 
 lefs into the ftomach, becaufe of the afcenc of the duo- 
 denum, which goes under the ftomach, with the re- 
 fiftance it meets with from the valvula pylori, and the 
 advancement of the new chyle which the ftomach 
 adds to the former : in man, however, it frequently 
 enters ; and always in birds. The bile is of a fweet foft 
 nature in the fetus ; for in them the faeces are not very 
 fetid to fupply putrid alkaline vapours to the liver, nor 
 are there any oily or fat fubftances abforbed from the 
 inteftines. As the bile is a vifcid fluid, and thickens 
 by inaftivity of body in fat animals, and in us from the 
 fame caufes, efpecially when the blood moves languid 
 from grief ; fo it eafily coagulates into an hard, fome- 
 what reftnous, and often ftony fubftance, infomuch 
 that ftones of the gall are much more frequent than 
 thofe of the urinary bladder, as we are taught by our 
 owm experiments. Its ufe is manifeft, as, being tritura- 
 ted with the aliments, it diflblves oil, rcfifts acidity, 
 and thus ftimulates the inteftines to contraction. 
 
 717. The ufe of the liver, befides fecreting the bile, 
 
 is manifeft in the fetus. It feenis to tranfmit the blood 
 brought back from the placenta, and to break its 
 force. Even in an adult perfon it has the fame ufe 
 though lefs manifeft, namely, to retard the return of 
 the blood coming back from the vifcera appointed for 
 preparing the chyle, v 
 
 CHAP. 
 
Chap. XXV. INTESTINES. 
 
 379 
 
 CHAP. XXV. 
 
 Of the Small Intestines. 
 
 7i 8."|3 Y the /mail mtejlines^ anatomifts underftand 
 one continued almoft cylindrical tube, but 
 vvhofe tranfverfc fcclion is nearly oval, the obtufe end 
 being towards the unconneded fide of the inteftine. 
 This tube is continued from the end of the ftomach, 
 the right orifice of which it embraces (6 25. ) ; and, being 
 produced thro’ a long trail, ends by an expanfion into a 
 a much larger intefiine. Anatomifts have ufually rec- 
 koned three fmall inteftines, tho’ nature has formed but 
 one. However, the duodenum has generally pretty cer- 
 tain bounds, terminating with its end in that part of the 
 abdomen which is above the tranfverfe mefocolon 
 (659.) But that finall inteftine which lies below this 
 mefocolon, commonly called jejunum, has no cer- 
 tain mark or boundary to feparate it from the lower 
 portion, which is commonly called the ilium : although 
 the former, abounding more with valves and blood- 
 veffels, has, in general, a more florid appearance, and 
 is furniflied with longer villi internally ; and the ilium 
 again, having fewer of thofe vafcular ramifications, like 
 little trees, abounds more with a fort of minute glan- 
 dules : however, thefe diflerences infenfibly difappear 
 one in another, without affording any certain limits be- 
 twixt the two inteftines ; but is great in the extreme 
 terminations, but obfcure in the neighbouring parts. 
 
 719. The duodenum feems to be denominated from 
 its length. It is larger, and more lax or open, than fhe 
 other fmall inteftines, more efpecially in its firft flexures 5 
 which is partly owing to its not being circumfcribed in 
 fome places with any external membrane, and in other 
 places only for a fmall compafs. It is florid and ten- 
 der, having its flefliy fibres fometimes of a confider- 
 able thicknefs. Its origination begins round the ring- 
 
 3 A like 
 
3^0 INTESTINES. Chap. XXV, 
 
 like valve at the mouth of the pylorus ; from whence 
 being undulated or inflefted, but generally in a tranf- 
 verfe courfe, to the right downward and backward in 
 an empty ftomach, it goes under the gall-bladder, to 
 the neck of which it is contiguous (7 14.) From thence 
 it defcends obliquely and backwards to the right fide as 
 far as the lov/er plate of the inefocolon, where it is per- 
 forated by the biliary duft, and in that courfe is intercep- 
 ted betwixt the upper and lower plate of the inefocolon. 
 From thence at laft it proceeds tranfverfely, but a little 
 afcending behind the pancreas and large mefenteric vef- 
 fels, and goes on to the left fide along with the left renal 
 vein, where, going out from the duplicature of the me- 
 focolon, and bending round before and to the right of 
 the faid veffels, it palfes through a peculiar foramen, in 
 which the mefentery and left part of the tranfverfe me- 
 focolon adhere to the intefline itfelf j from thence it de- 
 fcends forward, towards the lower part of the abdo- 
 men, into which it advances under the denomination 
 of the. jejunum. The largenefs of this intefline, with 
 its afcent from the infertion of the biliary duel, joined 
 with the confequent fold about the root of the mefen- 
 tery, caufe a remora of its contents, by which the bile, 
 pancreatic juice, and alimentary pulp, are here firfl in- 
 timately blended together. 
 
 720. The reft of the fmall intefline, having no cer- 
 tain feat or divifion, is continued by innumerable and 
 uncertain convolutions, not to be deferibed, fo as to fill 
 out the lower part of the abdomen and pelvis fur- 
 rounded by the colon on each fide, and lies between 
 the bladder and uterus below. 
 
 721. The fabric of the fmall intefline is almoft the 
 fame with that of the ftomach and oefophagus. Its ex- 
 ternal coat, excepting part of the duodenum, is recei- 
 ved from the peritoneum or mefentery, applied on each 
 fide to the obtufe end of the oval intefline, and fepa- 
 rated by the intervening cellular fubflance, which is 
 often repleniflied with fat, but more clofely embraces 
 or adheres to the mufcular fibres in the unconnected 
 
 fide 
 
Chap. XXV. INTESTINES. 381 
 
 fide of the inteiline ; where the outer and mufcular coats 
 flridly cohere, without (hewing any remarkable diffe- 
 rence from what we have obferved of them in the (lo- 
 mach. By this external membrane, and by the me- 
 fentery (661.), the inteftines are fupported with a 
 confiderable degree of firmnefs, at the fame time that 
 they are allowed every way a free liberty for motion. 
 
 7-2 2, But the fabric of the ?nufcular coat differs from 
 that of the ftomach, in the figure of its fibres. The 
 larged and mod confiderable body of thefe fibres is 
 circular, cloathing the tube on each fide, refembling 
 each other both in their parallel difpofition and appear- 
 ance, which is that of imperfeft arches or fegments of 
 circles, cemented one to another, paler than other muf- 
 jcular fibres, and yet remarkably contradfile. The 
 longitudinal fibres are, in the fmall intedines, much 
 fewer in number, fcattered round their whole extent, 
 interfperfed with the former, and are more efpecially 
 fpread upon the loofe or unconnedled fide of the in- 
 tedine. 
 
 72:^. Within the mufcular coat, is feated the fecond 
 cellular, of a larger or loofer extent here, as it was in 
 the domach ; and this being fpread on all fides round 
 the nervous coat, which it includes, is, in us, feldom 
 replenifhed with fat. But the nervous coat, being like 
 that of the domach, ferves as an internal foundation or 
 fupport to the whole intedinal tube ; being compofed 
 chiefly of compadled fibres, which, by iiiflation, may 
 be parted one from another, fo as to refemble a web- 
 like or cellular fubdance. Next to this, follows the 
 third cellular coat, which is almod like the fecond ; 
 and then the innermod or villous coat, which differs, 
 in feveral refpefts, from that which we deferibed in the 
 ilomach : for fird it is folded on all fides into wrinkles 
 that are femicircular,the extremities of which correfpond 
 one to another oppofitely, but uncertain in their pro- 
 portions ; into which wrinkles the nervous coat (light- 
 ly enters, whild the red of the intermediate fpace be- 
 twixt the folds of the villous tunic is filled up by the 
 
 3 A 2 third 
 
382 INTESTINES. Chap.XXV. 
 
 third cellular ftratum. Thtk plica or folds of the in- 
 teftine begin within one inch of the pylorus, and are 
 mod numerous in the fir ft and middle part of the inte- 
 ftines, but gradually grow fewer in number downward. 
 Here each fmall twig of the artery, which is fpread in 
 the cellular fubftance, upon the convexity of the inte- 
 ftine on one fide, is anfwered by another twig, difpo- 
 fed in the fame manner, on the oppofite fide. The pli- 
 cae are, at firft, confufed in the duodenum, and after- 
 wards become more confpicuous as the inteftine ad- 
 vances ; but the appearance of acute imperfect circles 
 or valves is given to them by anatomical prepijration, 
 in which their natural ftate is altered. They are indeed 
 foft, and eafily inverted, fo as to give way, in any di- 
 rection, to the courfe of the alimentary pulp; upon 
 which, however, their number has fufficient influence 
 to retard the motion, while, at the fame tierje, they en- 
 large the furface of the villous membrane. 
 
 724. We come now to the true villous coat, which 
 we call fo in other parts by analogy. Namely, the 
 whole internal furface of the inteftine and its valves, 
 together with the fmall cavities interpofed betwixt 
 them, fend out on all fides innumerable fmall fluctua- 
 ting fleeces like a piece of velvet, the extremities of 
 which are obtufely conical productions of the inner 
 coat of the inteftine, and from the cellular fubftance, 
 intercepted between the duplicature, and from the 
 fmall veffels and nerves wrapped up in that cellulofity, 
 and likewife from the laCleal veifel which we fliall after- 
 wards fpeak of, fo as very much to refemble the papil- 
 lae of the tongue, only of a fofter texture. 
 
 725. The chief fmall veffel of each villofity is an 
 oval veflfel opening by a flender duCl in the furface of 
 the villous coat, often filled with milk, which the neigh- 
 bouring fmall veffels every where furround. 
 
 726- In the internal furface of this villous coat, open 
 an infinite number of pores ; fome larger, others fmal- 
 Jer. The former lead to fmall confpicuous fim )le glan- 
 dules of the mucous kind, feated in the fecond cellular 
 
 ftratum, 
 
Chap. XXI. INTESTINES. 383 
 
 ftratum, and like to thofe of the vafcular follicles feated 
 in the mouth and pharynx, which like wife open with 
 numerous patulent orifices into the inteflines. In the 
 duodenum thefe are affembled together in feveral 
 places, without running together ; nor can they always 
 be demonllrated ; but many of them are quite folitary 
 or afunder in the ilium, or often affembled only a few 
 together ; though, in many places, a confiderable num- 
 ber of the fame kind are affembled together, into a 
 little army of an elliptical figure. They have every 
 where a villous membrane. 
 
 727. 'Throughout the whole tract of the inteflines 
 are found pores of a lefs kind furrounding the bafis of 
 the villi, and mofl ample or confpicuous in the large 
 inteflines, where they were firfl obferved; but have 
 been lately difcovered, by a more careful inquiry, in 
 the feali inteflines likewife. Thefe alfo feem to depofite 
 a liquor of the mucous kind. 
 
 728. The vejfels of the fmall inteflines are very nu- 
 merous. The common larger trunk belonging to the 
 intefline that occupies the fpace below the mefocolon 
 is called the mefenteric artery ^ being the largefl of thofe 
 produced by the aorta above the renal arteries. This, 
 defcending behind the pancreas to the right fide of the 
 jejunum, and before the colic branches, fends out more 
 especially a long trunk to the bottom of the mefentery 
 and termination of the ilium towards the right fide ; as 
 on the left fide it fends out numerous branches, the 
 firfl and lafl being fhorter, the middle ones longefl. 
 Thefe lafl, fubdividing into fnialler, join with thofe in 
 their neighbourhood in fhape of convex arches j which 
 again fend out other branches united in like man- 
 ner, to the repetition of almofl the fifth feries-of arches, 
 until the lafl fend flraight and very numerous branches 
 to the intefline ; where, forming their lafl convexity, 
 their numerous fmall branches are detached on each 
 fide the intefline. 
 
 729. The divifion of thefe branches in the intefline, 
 is much after the fame regular manner j fo that one 
 
 comes 
 
384 INTESTINES. Chap. XXV. 
 
 comes out from the mefentery, through the cellular 
 fubftance, on the forefide of the inteftlne, as the other 
 does, in the like manner, upon the lower fide ; which, 
 having given fmall branches to the outermoft and flefliy 
 coat, come to the fecond cellular one : there the ante- 
 rior trunk, running out towards the obtufe vertex of the 
 inteftinal ellipfis, is continued ftraight into the pofterior 
 branch fimilar to itfelf; and, according to its fize, gra- 
 dually fends olf fmaller fhrub-like twigs, inofculating 
 with each other, and with their oppofites, by innume- 
 rable circles. From this arterial net-work, fmaller 
 twigs penetrate from the nervous tunic into the third 
 cellular ftratum, and are, with that, continued to the 
 ultimate extremities of the villi, where they at laft open 
 by exhaling orifices, and difcharge a w'atery humour 
 into the inteftine ; for this continued courfe is eafily 
 imitated and fliown, by injedling water, fifii-glue, or 
 mercury. But late induflry has difcovered, that thefe 
 arterial extremities firfl; open into an hollow veficle ; 
 from whence their depofited juice flows out through 
 one common orifice. For the reft, the arteries in this 
 part form numerous reticular inofculations, that, by a- 
 voiding all obftructions, they may be able to fuppiy the 
 inteftines equally on all fides ; and that any obftruding 
 matter may, upon occafion, be eafily removed back 
 from the narrower extremities to the larger arterial 
 trunks. 
 
 730. The laft trunk of the mefenteric artery inofcu- 
 lates with the ilio-colic. The duodenum has various 
 arteries. The firft and uppermoft from the right he- 
 patic goes round to the convexity of the inflexure of 
 this inteftine, which it fupplies in its way to the pan- 
 creas, and inofculates together with the lower or left 
 pancreatico-duodenal artery, which makes a like arch 
 round the curvature of the duodenum into the pancrer 
 as ; being, at laft, inferted into the lower duodenal ar- 
 teries, produced by the mefenteric in its paflTage before 
 this inteftine. As to the fmall arteries which go from 
 the fpermatics to the duodenum, and from thofe of the 
 
 renal 
 
Chap. XXV. INTESTINES. 385 
 
 renal capfule, we defignedly omit any further notice of 
 them. 
 
 731. The mefenteric veins meet all together, in the 
 fame courfe or difpofition with the arteries, in the rae- 
 fenteric trank of the vena portarum ; except the right 
 duodenal vein, which goes immediately into the trunk 
 of the vena portarum itfelf; and except thofe fmali 
 veins which run in company with the fmall arteries 
 f7 3o.) and are inferted into the fpermatics and lum- 
 bals. Nor have I been able to difcover any other veins 
 of the mefentery arihng from the cava. It is a property 
 in common to all thefe veins to be without valves, and 
 to make free communications with the arteries. Thofe 
 veins in the villous coat, which is for the moll part 
 compofed of veins, abforb thin humours from the in- 
 tefline ; as appears from the injeftion of watery liquors, 
 which readily run through the fame way ; and, from 
 analogy, in aged perfons, in whom the mefenteric 
 glands, and confequently the ladeals that pafs through 
 them, are frequently doled up ; add to this, that birds 
 have no ladeal veffels, and the celerity with which wa- 
 tery liquors pafs to the blood and through the kidneys, 
 compared with the fmallnefs of the thoracic dud, chiefly 
 from thofe experiments which have confirmed by ocular 
 demonllration the paflage of water from the cavity of 
 the inteftine into the vena portarum. 
 
 732. The nerves, tho’ fmall, are numerous, whence 
 the intellines receive no little degree of fenfibility ; they 
 arife from the middle plexus of the fplenic nerves, and, 
 embracing the mefenteric artery, play round it in great 
 numbers, wrapped up in a very denfe cellular plate. 
 The duodenum has likevvife fmall nerves from the po- 
 fterior hepatic plexus of the eighth pair. From this 
 great fenfibility of the intellines it is probable, that the 
 ultimate branches of the nerves penetrate into the third 
 cellular coat. 
 
 733. From the exhaling arteries dillils a thin watery 
 liquor into the cavity of the intellines, like the juice of 
 the^ftomach, not acrid, but faltifli. The quantity of this 
 
 liquor 
 
386 INTESTINES. Chap.XXV. 
 
 liquor may be computed from the large extent or fum 
 of all the excretory orifices, and from the feftion or 
 light of the fecretory artery, larger than which we fee 
 no where in the body ; add to this, the laxity of the 
 parts perpetually kept warm and moift, and the copi- 
 ous diarrhoea or watery difcharge that often follows the 
 ufe of purgative medicines. But the mucus arifing 
 from the pores or cells before-mentioned (726, 7:7.) 
 ferves to lubricate and defend the internal furface of 
 the villous membrane, and to guard the fenfible nerves 
 from ftrongly acrid or pungent particles. Hence we 
 fee, it is more abundant at the beginning of the larger 
 inteilines, becaufe there the mafs of aliment begins to 
 be more feculent, acrid, and tenacious. 
 
 734. The mixture of this liquor with the pulp-like 
 mafs of the aliment, together with the bile and pancrea- 
 tic juice, is made by the motion of the furrounding 
 mufcles of the abdomen; but this force is quite fmall, 
 and unfit for moving forward the aliments. But for 
 this purpofe ferves efpecially the perijlaltlc motion, which 
 is more particularly firong and evident in the fmall in- 
 teftines. For any part of the intefline, irritated by 
 flatus or any fharp or rough body, contracts itfelf, even 
 after death, molt violently in that part where the fti- 
 mulus is applied, in order to free itfelf from the offend- 
 ing or diftending body, which it expels into the next 
 open part of the lax intefline ; where, being received, 
 it is again propelled forward, by exciting a like flimu- 
 lus and contraction as before. This contracting mo- 
 tion of the inteflines is made in various parts of the gut, 
 either fucceffively or at the fame time, wherever the flatus 
 or aliment excite a flimulus ; and this, without obfer- 
 ving any certain order. So well fitted, however, are the 
 inteflines for this motion, that they emulate, and even ex- 
 ceed, the irritability of the heart, or at leafl are fcarcely 
 exceeded by it. When they are not irritated, they re- 
 main at refl, as 1 have often obferved ; and we may 
 fuppofe this to be the caufe why the fat remains in the 
 belly. The air ads chiefly as a flimulus to the intef- 
 
 tines. 
 
Chap. XXV. INTESTINES. 387 
 
 tines, next to it is the aliment, and laftly the bile. This 
 motion is performed by a v.'onderful fort of alternate 
 creeping and revolution of the inteilines, which diffec- 
 tion eafily demonftrates in living brute animals, and 
 unhappy cafes of wounds in the abdomen and ruptures 
 have manifefted in the human fpecies. And lince 
 here, among fo many inflexions, the v.'eight of the 
 aliment is but of little force, it eafily afcends or de- 
 fcends through the irritated inteltine, which thus emp- 
 ties itfelf. From hence the antiperijlaltic motion is in- 
 telligible, by which the pulp of the alimentary mafs is 
 oftener or longer applied with a gentle force to the 
 triture of the intefline, to the exhaling diluent liquor, 
 and to the mouths of the abforbing veins. But all the 
 contents of the intefline are determined downward to 
 the large inteflines, becaufe the flimulus begins above, 
 from the left opening of the ftomach ; and fo, by the 
 fucceflion of new chyle, repeating the flimulus above 
 the contraflion, it defcends, when there is no refiflance 
 made to it, into the lower part of the ileum, at its open- 
 ing into the colon : here the loofe part of this intefline 
 readily receives what is preffed into it by the con- 
 traftion from above, and as eafily unloads itfelf into the 
 large unaflive caecum ; from whence it is again- repel- 
 led upward, and in part urged on by the preflTure of 
 the fucceeding mafs. Anatomifls obferve, that this 
 motion is made flronger downward than upward, and 
 that the fuperior parts of the inteflines are more irri- 
 table than the lower. But as often as an infuperable 
 obflacle refills the paffage of the aliment, there will 
 be the feat of the principal contraftion, and the ali- 
 ment likewife is driven upward from the valve of the 
 colon through the whole length of the inteflines, into 
 the flomach, and laflly into the mouth. 
 
 735. This periflaltic motion of the inteflines is per- 
 formed by the conflridlion of their circular fibres, 
 which exadlly know how to empty the tube, without 
 injuring the intefline againfl pins, needles, or any other 
 fharp bodies lodged within their contents, which they 
 3 B tenderly 
 
388 INTESTINES. Chap. XXV. 
 
 tenderly promote forward. But the revolutions of the 
 inteftines, drawn upv/ard and downward, and the 
 Itraightening of crooked parts of them one before an- 
 other, which is fo remarkably confpicuous in brute 
 animals, are performed by the long fibres, which we 
 fee contradt thernfelves at the feat of the prefent ftimu- 
 lus, and dilate the following portion of them to receive 
 what enfues. By the fame contraction, the villous 
 membrane of the intefiines, within their cavity, is urged 
 and reduced into longer folds ; whence the mucus is 
 expreffed and applied to that part of the alimentary 
 mafs, where it was requiied by the force of irritation 
 and ftimulus. Thefe long fibres frequently make 
 intro-fufeeprions of the Inteftines, and generally w'ithout 
 any bad confequences, by drawing up the contradfed 
 portion of the inteftine into that which is loofe, in fuch 
 a manner, that the former is furrounded by the latter, 
 which is relaxed. 
 
 736. The alimentary pulp, therefore, diluted with 
 the pancreatic juice and that of the inteftines, intimate- 
 ly mixed with the faponaceous bile and circumjacent 
 mucus, is more perfectly diftblved than by the effi- 
 cacy of the flomach, in proportion as the fides of the 
 inteftines come into a larger contact, and approach 
 nearer together ; to which add, tiie longer feries of 
 the periftaltic motions, and the greater quantity of dif- 
 folving juices. In this manner, the alimentary pulp, 
 intermixed with air, forms a froth, without any kind 
 of fermentation, wfiich air is the fame with what we 
 commonly eruftate from the ftomach ; but yet, at the 
 fame time, the acid or acefeent force is fubdued, while 
 the oily or fat parts, diftblved by the bile (715.), inter- 
 mix with the watery juices, and put on the chyle its 
 ufual milky appearance, like an emulfion, of a bright 
 colour in the duodenum, at the firft entrance of the bi- 
 liary duct ; from whence downward it clofely adheres 
 to the villous coat of the fmall inteftines. But the ge- 
 latinous juices of flefti meats, diluted with a large por- 
 tion of water, and likewife from their own fubviftid na- 
 ture. 
 
Chap. XXV. INTESTINES. 389 
 
 ture, do more particularly adhere to the villous coat, 
 and enter it in the way of abforption. So water and 
 watery liquors are all very greedily drank up by the 
 veins; and yet the feculent remains never grow thick 
 in the fmall intdfines, as far as I have been able to ob- 
 ferve, becaufe the watery part is repaired by the arte- 
 rial vapour and mucus ; nor do they become fetid in any 
 confiderable degree, as well becaufe of the great quan- 
 tity of diluting juices, as becaufe the quick progreffion 
 will not allow them time enough for a putrefadion. 
 Thofe remains, which are of a mure earthy, grofs, and 
 acrid difpofition, which were excluded by the mouths of 
 the absorbing lacfeal orifices, do, by their weight, or 
 by the mufcular contractions, defcend flowly into the 
 large inteftines, fo as to complete their whole courfe in 
 the fpace of about twenty-four hours. But within three, 
 four, or a few more hours time, all the chyle of the 
 aliment is commonly extraCled. 
 
 737. The confiderable length of the fmall inteftine, 
 which is five or more times longer than that of the bo- 
 dy, the great furface of the villous membrane increafed 
 'by folds, the incredible number of exhaling or abforb- 
 ing veffels, the flow courfe of what remains through 
 the large inteflines, and the great quantity of the inte- 
 fcinal juice poured into the alimentary mafs, do all of 
 them concur, in the fmall intefline, abundantly to per- 
 form vdiat is required in the emulfions of the food for 
 our healthy juices, and for their abforption into the 
 lafteals and the mefenteric veins ; alfo for abfterfion of 
 vifcidities from the intefline; for the avoiding adhefions 
 and coagulations ; for the deflruCtion of any acid difpo- 
 fition not yet fubdued ; and for the fubduing any veno- 
 mous quality in many juices, w'hich, being direClly 
 mixed with the blood, inflantly kill, but are thus fent 
 in by the mouth without damage. Hence, in general, 
 the inteflines are long in animals that feed upon any 
 hard diet, but fliorter in carnivorous ones, and fhortefl 
 in all thofe that live upon juices ; and, even in man, 
 an uncommon fhortnefs dt the inteflines has been 
 
 3 B 2 known 
 
390 INTESTINES. Chap. XXV. 
 
 known to be attended with hunger, and a flux or dif- 
 charge of fetid and fluid faeces. 
 
 738. The heat by which the aliment is fomented, 
 and which is exceedingly proper for the folution of the 
 gelatinous matter, and exciting a beginning putrefac- 
 tion, is hence the principal caufe of the fetor which is 
 gradually produced in the aliment ; thence alfo is the 
 caufe of that thinnefs by which the ufeful part of the a- 
 iiment is fitted for abforption. But the air alfo, inclofed 
 in the vifcid aliment, operates here, as in the flomach, 
 by breaking the cohefion of the aliments, if any yet re- 
 main whole. The inteflinal water dilutes the little 
 maflfes of aliment ; and if any hard part remains, this 
 liquor foftens it by maceration. The bile being inti- 
 mately mixed with oil, diffolves the fame, and renders 
 it mifcible with water. 
 
 CHAP. XXVI. 
 
 Of the Large Intestines. 
 
 739.‘TTTH AT remains, after the chyle has been 
 VV abftrafted, confifts of fome portion of the 
 bile, but mucilaginous and degenerate ; fome part of 
 the human mucilages ; mofl: of the earthy parts that were 
 lodged in the food ; and all thofe parts which by their 
 acrimony were rejected by the abforbing mouths of 
 the ladleals, yet changed by means of putrefaction 
 (736.); with all the folid fibres and membranes, whofe 
 cohefion was too great to be overcome by the macera- 
 tion and periftaltic motion in the inteftines. 
 
 740. All thefe remains pafs from the extremity of 
 the ileum into the caecum, in which they are collected 
 and. flagnate ; namely, the extremity of the fmall in- 
 tefline, called the ileu?n^ applies itfelf obliquely, in fuch 
 a manner, to the right fide of the colon, refting upon 
 tli6 right ileum and its mufcle, that, in general, it a- 
 feends in a curve, but more in its lower fide, and lefs 
 
Chap.XXVI. intestines. 391 
 
 in its upper, which is almoft tranfverfe. But finally, 
 the nervous and villous parts of the ileum are fo ex- 
 tended betwixt the departing fibres of the mufcular 
 and nervous coat of the colon, as to hang pendulous 
 within the cavity of this large inteftiiie, with a double 
 eminent wrinkle or foft fold, compofed of the villous 
 and nervous coat of the thick inteftine, and of the final! 
 inteftine likewife, and of the interpofed flefliy fibres of 
 the ileum and colon, joined together by a good deal of 
 the cellular fubftance. The upper tranfverfe fold is 
 Ihorter, as the lower is broader and more afeending, 
 being conjoined together by a frnall production of the 
 fame kind, more efpecially in the right fide, adjacent 
 to them. Betwixt thefe two folds, the mouth of the i- 
 leum opens, like a tranfverfe flit. But when this inte- 
 fiine is inflated, the ftrufture of it changes very much, 
 reprefenting thefe parts to us under the figure of mem- 
 branes and hard valves. After the cellular plate has 
 been entirely removed from them, the ileum comes 
 clean out from the colon, and the valvular appearance 
 is no more to be feen ; but if a large part of it only be 
 drawn out, leaving a fmall portion inferted behind, it 
 refembles a fphinfter. 
 
 741. Below the entrance of the ileum, at the diftance 
 of fome inches, the great intefline defeends and forms 
 a blind or impervious extremity, called the cacum, 
 refting upon the ileum. From the lower part of this, 
 towards the right fide, extends a fmall worm-like pro- 
 cefs, in adults of confiderable length, like a long ex- 
 tended cone or little, intefline, varioufly incurvated, 
 fometimes downward, and full of fmall mucous glands, 
 which pour out a gluey mucilage to the fmces ; but, in 
 the fetus, the colon itfelf is extended into a conical ap~ 
 pendix. But the weight of the fuperincumbent faeces, 
 depreffing the fpace on the right fide of the appendix ; 
 the ftrength of the cellular texture uniting the left part 
 of the caecum with the ileum, of the flefliy fibres uni- 
 ting both inteflines ; the very contraftile force of the 
 ligamients j the fitnefs of the anterior fac of the caecum, 
 
 which 
 
592 INTESTINES. Chap.XX\T. 
 
 which eafily receives the faeces from the inteftinum 
 -ileum; all contribute to remove the appendix from the 
 middle, and make it to go out from the left extremity 
 of the colon: and thus is produced the thick and pen- 
 dulous globe of the colon lying farthefl to the right 
 fide, and which is proper to adult perfons. When, 
 therefore, the remains of the alimentary mafs are fent 
 from the ileum into the colon, they fall by their weight 
 firll into the cavity of the caecum, or impervious bag- 
 like appendix ; here, by ftagnating, and the warmth 
 of the parts, they begin to putrefy, according to their 
 particular nature ; and here, efpecially, the fetid fmell, 
 obfervable in the execrements, begins. 
 
 742. The colon fs an inteftine altogether continu- 
 ous, as one and the fame with the caecum ; namely, the 
 largefi; of the great inteflines, and by much the ftrong- 
 eft. Beginning upon the ileum (740.), it afcends over 
 the right kidney, and lies under the liver, with an angle 
 in the right hypochondrium ; being connected to the 
 vifcera, on each fide, by the peritonsum. From thence 
 it paffes under the liver and itomach, for the moft part, 
 tranfverfely to the fpleen, under which it ftretches 
 (676.), and in the deep recefs under the left ribs is of- 
 ten twilled upon itfelf. From thence, again, continu- 
 ing its defcent to the left ileum, it forms a large flex- 
 ure (658.); from which flexure it is continued, in its 
 lower part, through the pelvis, under the denomina- 
 tion of redum. 
 
 743. The llru6ture of the colon is in general the 
 fame with that of the fmall inteflines, but it has feveral 
 things peculiarly differing from them. And firll, all the 
 longitudinal fibres are collefted together into three 
 bundles which run through the whole extent of the in- 
 tefline ; and of thefe one, and that the largell, lies na- 
 ked, the other arifes from the omentum ; and the third 
 is contained in the mefocolon. Thefe are Ihorter than 
 the inteftine, and contrad it fo that the nervous and 
 villous membrane (744.) protuberates inwardly. Thefe 
 fibres are conneded moll accurately with the external 
 
 coat 
 
Chap. XXV. INTESTINES. 393 
 
 coat of the inteftines ; but in the intermediate places, 
 and chiefly at the mefocolon, is feated the firfl cellular 
 ftratum repleniftied with fat. At firft, being dilated, 
 they adhere to the vermiform appendage. In the ex- 
 tremity of the colon there are often only two ligaments, 
 where the two leiTer join into one. They diffufe them- 
 felves upon the redtum in fuch a manner as to occupy 
 the whole. 
 
 744. Again, the flefliy and nervous coat, and third 
 cellular llratum, with the villous tunic of the colon, are 
 extended into much larger wrinkles in the parts be- 
 twixt the ligaments, often proje<Ting in a threefold 
 rank, fuflained by the ligaments, that they may be able 
 to refill and fupport any Ihock or prelfure from the 
 motion of the fasces. In the beginning of the colon, 
 they obferve their three-fold order, exactly enough, at 
 regular dillances ; but in their progrefs they vary more 
 by degrees, being lefs, fometimes double, often foli- 
 tary, fmall and large intermixed, or none at all. Where 
 the ligaments which contract the colon difappear, thefe 
 valves almoll difappear entirely. Lallly, the villous 
 coat is thinner, without villi, but porous and wrinkled, 
 furnilhed as well with large peculiar pores of its own 
 leading to round folicles or cells which are folitary, as 
 with innumerable fmall pores leading to fmaller follicles, 
 both which fupply a great quantity of mucus. 
 
 745. The blood-vejfels 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 be- 
 hind the tranfverfe mefocolon, where it arifes up with 
 one, two, and fometimes three branches, going to the 
 right fide with the ilio-colic ; and to the left, where, 
 with the lower mefenteric, it meets it in a very large arch, 
 which makes the moft confiderable arterial inofculation 
 in the whole body. Again, under the mefocolon, from 
 the fame large mefenteric artery, arifes a confiderable 
 branch that goes diredly to the fold of the ileum with 
 the colon, and upward to the right colon with the middle 
 
 colic j 
 
394 INTESTINES. Chap. XXV. 
 
 colic ; but to the left it runs together with the mefcn- 
 teric, out of the middle of which it gives a branch that 
 runs along the worm-like appendix of the inefocolon, 
 and terminates itfeif in both the anterior and pollerior 
 fold, by which the ileum is inferted into the colon. 
 Laftly, the low'er mefenteric, ariling by its proper 
 trunk from the aorta, betwixt its bifurcation and the 
 renal arteries, goes to the left colon ; above, it runs by 
 a large arch, together with the middle colic, and being 
 bent dovvnw'ard in three or four trunks, it f})reads over 
 the flexure of the colon, and defeends even iiuo the 
 reftum. tiere the redum receives various branches 
 from the middle hemorrhoidal, arifing from the lafl; 
 trunk of the hypogaflrics, and conjoined with the for- 
 mer. The ultimate arteries are from the fame trunk, 
 but diftributed without the pelvis. V/e neglect here 
 the fmaller colics, arifing from the fpermatics, interco- 
 flal, omental, capfulary, and lumbal arteries. The 
 veins, taking the fame courfe with the arteries, run to- 
 gether into the gaftrocolic, and the internal hemorrhoi- 
 dal, and hence into the vena portae ; laftly, they unite 
 with the middle and external hemorrhoidais, and the 
 trunks of the iliacs. 
 
 746. The divifion of the velTels to the large intef- 
 tines, differs much from that of the fmall inteilines. 
 The arches the trunks fend oS", are neither fo frequent 
 nor fo often fubdivided ; they run further entire upon 
 the inteflinal tube, accompanied with fewer glands, and 
 their branches are diftributed not fo much like trees ; 
 they are divided by lefler angles, more flexible, and 
 form fewer net-works in the cellular fubflance ; but 
 they diflil an exhaling moiflure into the cavity of the 
 inteftines, as the veins likewife abforb a thin fetid va- 
 pour from the faeces. The external, and perhaps alfo 
 the internal ones, fvvelling into varices, pour out the he- 
 morrhoidal blood; which is always preternatural, al- 
 though fometimes infarctions of the veffels of the porta 
 are relieved by that evacuation. 
 
 747. But there are alfo lymphatic veffels, arifing 
 
 from 
 
Chap. XXVI. INTESTINES. 395 
 
 from the whole trad of the colon and redum, which 
 conjoin with thofe of the loins. We are not without 
 examples of the chyle entering thefe lymphatics from 
 the colon inftead of lymph ; which is an argument that 
 they are of fome further ufe in this part, by conveying 
 nourifhment to the blood. 
 
 748. The nerves of the large inteftines are, from the 
 left colic plexus, compofed by the defeending branches of 
 each renal plexus, and others arifing from the interco- 
 ftal trunk of the thorax and loins, with others produ- 
 ced from the large mefenteric plexus. Thefe nerves 
 accompany the lower mefenteric artery, and pafs with 
 them to the colon. The lowermofl nerves arife from 
 the plexus juft mentioned, and go to the redum, with- 
 in the pelvis ; others are from the lower intercoftals, and 
 the nerves of the facrum, which terminate likewife in 
 the redum. Thefe nerves are of the fmaller kind; 
 which renders the inteftine lefs fenfible, that it might 
 better fuftain the preflure of the hard and acrid feces. 
 
 748. The inteftinal feces, therefore, retained in the 
 blind beginning of the colon or large inteftine (740.), 
 there grow dry by the abforption of moift vapours, fo 
 as to be capable of receiving a figure from the round 
 contraded parts of the colon ; they afeend from the 
 bottom of the csecum, elevated by the long ligaments, 
 which end in the worm-like appendix. And here the 
 manner in which the feces are propelled by the con- 
 tradion of the circular fibres, appears better than in the 
 fmall ones. The longitudinal fibres of the inteftine, 
 being attached to the contraded parts as fixed points, 
 draw up and dilate the lower parts of the inteftine ; then, 
 the next parts of the inteftine, to which the feces are 
 brought, being irritated and contraded in like manner, 
 are immediately after drawn together by th^ round and 
 long fibres, by a fucceffive repetition of which the feces 
 finifh their courfe entirely, through the whole large in- 
 teftine, for the moft part in 24 hours in a healthy per- 
 fon. For wounds in mankind, and the comparative 
 anatomy of brute animals, demonftrate this periftaltic 
 
 3 C ■ motion 
 
39^ .INTESTINES. Chap. XXVI. 
 
 motion of the inteftines to the eye •, which is alfo con- 
 firmed by the antiperiftaltic motion, and its confequen- 
 ces, by which the matter of glyfters is returned up 
 through the mouth. The fame fibres refift the air 
 contained in the inteftines; and wind isfaid to be ge- 
 nerated as often as thefe fibres being overcome by its 
 impulfe yield, and the mteftine is dilated. 
 
 750. While the grofs Iseces afeend by the folds (740.) 
 or valves of the ileum, the weight of them deprefs the 
 lower fold to the left fide, which draws back the liga- 
 ment common to each valve, in fuch a manner as to 
 comprefs and exadlly clofe the upper fold downward, 
 that nothing may return back into the ileum ; which 
 might eafily happen in a fluid ftate of the faeces, if this 
 port was not fo accurately flnit up. 'I’he faeces, when 
 in danger of falling down from the upper parts, deprefs 
 the upper valve, and thus accurately exclude them- 
 felves. This happens very exactly with the faeces, but 
 not fo accurately with water. From thence they con- 
 tinue to move flowly forward, more dry, confiftent, and 
 figured by the fame caufes (749.) through the whole 
 trafl; and repeated flexures of the colon, which is fome- 
 times of five or feven feet in length, fo as to retain the 
 faeces a fpace of time fufficient to give no interruption to' 
 the affairs of human life; which time is lefs in propor- 
 tion than twenty-four hours, as the fmall inteftines re- 
 tain their contents a fliorter interval of the fame fpace. 
 
 751. At length the figured excrement falls into the 
 reSlum, which is infletfed firft a little dowmwards and 
 then forw'ard, of a broad depreffed figure, at firft de- 
 feending contiguous to, and afterwards fpread under, 
 the bladder, or vagina, but connefted more with the 
 former than the latter. Here, for a great while, and 
 often to a great quantity, the faeces are collefted to- 
 gether, in a part which is loofe, or openly furrounded 
 with foft vifeera and mufcles, with a good deal of fat. 
 
 752. The ftrutfure of the re£tum differs very much 
 from that of the other inteftines. The external mem- 
 brane or peritonaeum is only fpread before it, while 
 
 behind 
 
Chap. XXVI. INTESTINE S. 397 
 
 behind it is fupported. by a broad flratum of the cel- 
 lular fubftance, replenilhed with fat, and many conglo- 
 bate glandules, conneding this inteftine all the way to 
 the os facrum. The mufcular fibres in this inteftine 
 are much ftronger and more numerous, more efpeci- 
 ally the longitudinal ones, than in the other inteffines ; 
 being compofed of the three ligaments of the colon, 
 expanded and feparated firft over the anterior face, and 
 then over the whole inteftine ; which they dilate a- 
 gainft the advancing feces, and draw back the in- 
 teftine after it has excluded them. But the tranfverfe 
 fibres are alfo ftrong ; and the laft of them are oval, 
 forming a protuberant ring, which is the internal 
 fpincter itfelf, by which the opening of the anus is 
 clofed. 
 
 753. Moreover, the villous tunic, extremely full of 
 pores, and of a rough furface, full of reticulated poly- 
 gonous and tender wrinkles, has likewife fome finufes 
 peculiar to itfelf. Namely, that part of the inteftine 
 which is next to the fkin or outward opening, forms a 
 white firm circle like a valve, into which defcend the 
 longitudinal folds, but incurvated and approaching one 
 to another in the circle itfelf. Betwixt thofe folds, 
 are intercepted finufes, hollow upwards, and of a greater 
 depth towards the lower extremity of the inteftine. 
 Into the cavity of thefe open the mouths of the large 
 mucous glandules; while the margin of the anus itfelf 
 is defended by febaceous glandules, that it might not 
 be excoriated by the harder acrid feces. 
 
 754. There are alfo proper mufcles which govern 
 the anus. Of thefe the outermoft is the ffinder^ which 
 is broad and flefhy, confifting of two plates of half- 
 elliptic fibres, which crofs each other towards the coc- 
 cyx, and towards the genital parts. And there they 
 are inferted by flefliy bundles into a callous cellular 
 fabric defcending from the coccyx. But forward, they 
 are firmly attached, by denfe portions of the fame kind, 
 to the fkin of the perinseum ; but by three ftronger 
 portions in the middle, and two in the fides, they are 
 
 3 C 2 inferted 
 
398 INTESTINES. Chap. XXVI, 
 
 inferted Into the bulb of the uretha, whofe lateral parts 
 they furround, betwixt the fphincter and levator. The 
 fibres, therefore, of the fphiu6ter, placed betwixt the 
 anterior and pofterior face of the rectum, afcending in 
 a direct courfe, clofe the opening of the anus, which 
 they furround. With the intemal fpincter, the external 
 one is conjoined by flefhy portions, that they may co- 
 operate together. The conftriction of them is not 
 perpetual but voluntary ; for the anus feems to clofe 
 itfelf naturally, if the fmallnefs of its opening be com- 
 pared with the largenefs of the intedine above, and 
 •with the correfponding wrinkles (753-), aided by the 
 flrength of the tranfverfe fibres of the internal fpinder, 
 and the incumbent bladder, 
 
 755. But there is another office belonging to the 
 levators, which are broad complicated mufcles. They 
 defeend broadly from betwixt the oppofite protube- 
 rances of the ofla ifehia, placed under the reftum and 
 bladder; and ferve to (uflain the rectum on each fide, 
 and prevent it from fubfiding, or from an unfightly 
 everfion. Moreover, the fame fibres of the levator, 
 declining broadly from each other, in the nature of a 
 fphinfter, to which they join, ferve to dilate its orbicu- 
 lar fibres, and open the anus ; but, at the fame time, 
 they both elevate and fuftain the intefiine from pro- 
 lapfing downward by the prefiure of the hard fasces. 
 They arife, as is well known, from the fpine of the 
 ifchium,os ileum, and fynchondrofis of the ofla pubis, 
 terminated by the margin of the great foramen of the 
 pubes, and that part of the ifehium, which is above the 
 tubercle. Finally, they meet together in one above 
 the coccyx, into which they arc inferted by numerous 
 fibres. 
 
 756. Therefore, whenever the feces are collected 
 to feme quantity, within the re<flum,fo as to betrouble- 
 fome by their weight, irritation, or acrimony, they 
 excite an uneafinefs through the adjacent vifeera ; and 
 are then urged downward, by a voluntary prelTure 
 through the ftraits of the collapfed intefiine (754.), by 
 
Chap. XXVI. INTESTINES. 395 
 
 the force of the incumbent diaphragm, exciting an 
 effort; which urging downward with great force, the 
 vifcera of the abdomen, which is always full, are deter- 
 mined downward, through the inner rim of the pulvis, 
 fo as to urge upon the contents of the lefs refifting 
 bladder and redlum. When the refiftance of the anus 
 is thus overcome, the compreffing forces of the dia- 
 phragm abate, and the faeces continue to difcharge 
 from the body, urged only by the periflaltic motion 
 itfelf of the inteftine. After the faeces are expelled, 
 the inteftine is drawn back or up into the body, by its 
 longitudinal fibres ; after which, the opening of the 
 anus itfelf is clofely contracted by the two proper 
 fphinCters, as at firft. 
 
 757. Thefe faeces in man, and carnivorous animals, 
 are very fetid, almoft putrid, fubalkaline, foft, and 
 contain much oil intimately mixed with falts, which 
 are left both by the aliments, as well as by the bile and 
 other humours of the human body. An acrid and 
 fetid water returns from the faeces into the blood; 
 hence, coftivenefs in fevers is hurtful, as it increafes 
 putrefaction by the effufion of the above-mentioned 
 matter. 
 
 CHAP. XXVII. 
 
 Of the Chy lifer oils Vessels. 
 
 758. chyle is a white oily juice (73d.) cx- 
 
 X traded from the aliments, which is after- 
 wards poured into the blood. That its principal com- 
 pofition is of water and oil, feems evident, from the 
 fw'cetnefs of its tafte, from the whitenefs of its colour, 
 from its acefcent and coagulable nature, 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 a vegetable farina, with animal lymph and 
 oil. It every w'here retains the properties of the vo- 
 latile 
 
400 CHYLIFEROUS Chap. XXVH. 
 
 latile and oily aliments. It changes into milk with very 
 little alteration. But afterwards it becomes more ma- 
 nifeftly glutinous; fince the pellucid ferumit contains, 
 either by exhaling the watery part, or by applying an 
 intenfe heat, coagulates into a kind of jelly. 
 
 759. That the chyle is abforbed into the lacteal vef- 
 fels, by the adhering villous coat, has been a long time 
 known, by experiments of injeding tindured liquors, 
 which readily defcribe the fame courfe ; from the white 
 liquor of the ladeals, let out from blood-veffels ; and 
 from the venous nature of them. But late experiments 
 have taught us this in a much better manner. The 
 chyle is abforbed by a fmall opening in the extremity 
 of each of the villi, by the fame force which is com- 
 mon to all capillary tubes, by which it is taken up into 
 the cavity of the abforbing dud at the time when the 
 jnteftine is relaxed ; but the veficle, by w'hich the ab- 
 forbing dud begins in the inteftine, being preffed by 
 the fucceeding conftridion of the mufcular fibres in the 
 periftaltic motion, urges the contents further on into 
 the dud, which begins to appear within the fecond cel- 
 lular ftratum. But there is a two-fold ftratum of thefe 
 abforbing veflels, one anterior, the other poftcrior, as 
 we obferved before of the blood-veflels (729.). From 
 thence, uniting into a larger canal in the firft cellular 
 ftratum, the abforbed liquor enters into the ladeal vef- 
 fel, which, in general, follows the courfe of the arte- 
 ries, and likewife accompanies their arches, but con- 
 joined with others fimilar to it into a very obliquely 
 angled net-work. This kind of veflels hitherto has been 
 obferved only in quadrupeds. In the large inteftine 
 they arife without the above-mentioned veficle. Very 
 many arife from the firft part of the fmall inteftines un- 
 der the mefocolon ; fome from the duodenum, and 
 fome from the large inteftines themfelves. 
 
 760. The ladeal velTels are furnii'hed with valves in 
 the very firft cellular texture of the inteftine, like thofe 
 of the lymphatics, joined together by pairs, of a femi- 
 lunar figure (57-), which admit the chyle pafling from 
 
 the 
 
CHAP.XXVir. VESSELS. 4oi 
 
 the inteftines, but prevent its return, and fuftain its 
 weight. Through this whole courfe, the chyle is ur- 
 ged on by the periftaltic motion of the intellines, as 
 well as by the contradile force of the velfels themfelves, 
 which, even after death, is ftrong enough to propel the 
 chyle ; to which add, the confiderable prelfure of the 
 abdominal mufcles, and other parts, determined by the 
 valves. 
 
 761. But betwixt the plates of the mefentery, at the 
 divifions of the velfels, are found an infinite number of 
 fmall conglobate glandules, but fomewhat fofter and 
 more fpungy, made of a cellular texture, full of juices, 
 covered with an external membrane, lefs hard than in 
 other parts, and painted with numberlefs fmall blood- 
 velfels. Some ladeal velfels are feen to pafs thefe 
 glands; mofl part enter them ; and, being divided and 
 fubdivided through their cellular fabric, compofe the 
 greatell part of the gland. And, again, other ladteal 
 velfels are produced out of every gland ; and, being 
 mutually joined among themfelves, go olf in little 
 trunks, of which the ultimate and largelt ones go out 
 from the gland. In the fame manner the chyle enters 
 other glandules twice, thrice, or four times ; nor does 
 any lafteal velfel arrive at the thoracic du(T without en- 
 tering fome of thefe glandules, although it always palfcs 
 by fome without entering them. But that this is the 
 true courfe of the chyle, by which it palfes from the 
 intellines to the mefenteric glands, appears from a liga- 
 ture, by the velfel growing turgid betwixt the faid liga- 
 ture and the intelline ; and from feirrhofities in the 
 glands, by which they are rendered more confpicuous ; 
 and from the nature of the valves themfelves hindering 
 any return back to the intellines. 
 
 762. What alteration the chyle undergoes within the 
 cellular fabric of thefe glands is not yet fuflSciently 
 known ; but it appears, in general, that fome thin liquor 
 dillils from the arteries in this part, ferving to dilute the 
 chyle, into which it is poured. For it is obferved, that 
 after the chyle has furmounted all the glands, it appears 
 
 more 
 
402 CHYlIFEROUS Ciiap.XXVIE 
 
 more watery ; and thin liquors, injedled through the ar- 
 teries, pafs out into the cellular fabric of the glands, and 
 mix with the chyle. Laftly, that kind of cream appears 
 manifeflly in the glandules of infants. 
 
 763. From the laft glandules, which are collected to- 
 gether in the centre of the mefentery, the lacteal veflels 
 go out very large, and few, to the number of four, five, 
 or more, which afeend together with the mefenteric ar- 
 tery, and intermix with the lymphatic plexus, that 
 afeends from all the lower parts of the body, creeps o- 
 ver the renal vein, and then goes along with that which 
 takes its courfe behind the aorta from the lumbal glan- 
 dules, and with the hepatics. Here the lymphatics take 
 a variable courfe, but moft frequently terminate in a 
 veficle of confiderable breadth at the fide of the aorta, 
 betwixt that and the right appendix of the diaphragm : 
 there it ufually appears fomewhat turgid, two or more 
 inches long; and often afeends above the diaphragm 
 into the thorax, conical both above and below : it is 
 called the receptacle of the chyle. In this the gelati- 
 nous lymph of the lower limbs, and of the abdominal 
 vifeera, mixes with the chyle, and dilutes its white co- 
 lour; thus fometimes it appears filled with a pellucid or 
 reddifh humour, but frequently alfo with a white milk. 
 But there are fome inftances where there are only two 
 or three fmall and narrow dufts, inftead of this recep- 
 tacle or cifiern of the chyle. This, however, is moft 
 frequent, and fuffers a confiderable alternate preflure 
 from the diaphragm and aorta, by which the chyle is 
 moved fafter through it, in proportion as the light of 
 the ciftern is greater than that of the thoracic du( 5 t, into 
 which it empties itfelf. Yet fometimes, though rarely, 
 this veficle is fo fliort, 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. 
 
 764. That the chyle comes from the inteftines into 
 this duft, is Ihewn from injeftions, by which quick- 
 filver has fometimes been driven from the firft lafteal 
 veffels to the thoracic dud ; from ligatures made on 
 
 the 
 
Ch. XXVII. VESSELS. 403 
 
 the duft itfelf, or the red veins which receive it, and 
 by which the firfl and fecond lafteal veffels fweli ; and 
 from the manifeft flux of the chyle into the thoracic 
 dud when the ligatures are removed. 
 
 765. The thoracic dud^ as it is called from itscourfe, 
 is generally fmgle ; or, if it be double for fome part of 
 i’s couiTe, it foon after unites into one again, which 
 goes behind the pleura, betwixt the vena azygos and 
 the aorta ; and, afcending in an infleded courfe, it re- 
 ceives in its way the lymphatic veffels of the ftomach, 
 oefophagus, and lungs, and paffes through the conglo- 
 bate glands, of which there are many incumbent on ' 
 and about it ; and thefe lymphatics, as they advance 
 towards the dud, are colleded into large bunches. It 
 is, in general, cylindrical; and often forms infulations, 
 by fplitting or dividing into two or more ; after which 
 
 it unites into one again, more efpecially in its upper 
 part. It has few valves, and thofe not very confpicuous. 
 About the fifth vertebra of the back, it generally croffes 
 behind the oefophagus, and then afcends along the right 
 fide of the thorax, behind the fubclavian blood-veffels, 
 till it has arrived near the fixth vertebra of the neck. 
 
 766. There, bending down, it often divides jnto 
 two, and each defcending branch dilates into a fort of 
 veficle that enters, either with diflind or united open- 
 ings, into the jundure of the fubclavian and jugular 
 vein internally, by an oblique courfe from the upper, 
 pofterior, and lateral part downward towards the left, 
 and forward, going either with one or with two branches 
 .under the fubclavian, on the outer fide of that jundure. 
 
 It has a true circular fluduating valve placed over it, 
 which keeps off the blood by its defcent. It is rarely 
 otherwife difpofed ; and more rarely fplit into two, 
 lengthwife, for diflind infertions into the fubclavian ; 
 and yet more rarely apt to fend off a branch into the 
 vena azygos. Near its infertion it receives the opening 
 of a large lymphatic veffel, tranfverfely from the arm; 
 and another defcending from the head, in one or more 
 trunks. 
 
 3 D 
 
 7<$7. That 
 
404 CHYLIFEROUS Ch.XXVH, 
 
 767. It appears that the chyle flows through the 
 thoracic du6l into the blood ; becaufe, on tying the red 
 veins, both the thoracic du6l and lacteal veflels which are 
 inferred into it fwell up. 
 
 768. I have attributed the firfl caufe of motion in 
 the chyle, and of its abforption, efpecially to the attrac- 
 tion of the capillary veffels, which obferves alternate 
 pulfes with the periftaltic contradlion of the inteftine. 
 The attradlile force fills the villofity ; the periftaltic 
 force empties the villofity, and moves the chyle farther 
 forward. The reft of its motions feem to depend on 
 the ftrength of the membrane of the lacteal veflel it- 
 felf, which, even after the death of the animal, expels 
 the chyle, fo that the veflels become pellucid, which be- 
 fore were milky. The alternate coinpreffing force of 
 the diaphragm alfo is of fonae efticacy in this cafe, and 
 the motion of the chyle through the thorax is fomewhat 
 accelerated by the conduit itfelf ; which being preffed, 
 moves the chyle fo much the more quickly forward, as 
 itfelf is larger than the thoracic dudl. 
 
 769. The chyle, mixed with the blood, does not 
 immediately change its nature; as we learn from the 
 milk, which is afterwards made of it. But after five 
 or more hours have palled from the meal, almoft to 
 the twelfth hour, during all which fpace a w'oman w'ill 
 afford milk ; after it has circulated near 80,000 times 
 through the body, fomented with heat, and mixed with 
 a variety of animal juices, it is, at length, fo changed, 
 that a part of it is depofited into the cellular fubftance, 
 under the denomination of fat ; a part of it is again 
 configured into the red-blood globules (147.); another 
 part, that is of a mucous or gelatinous nature, changes 
 into ferum ; and the watery parts go off, in fome mea- 
 fure, by urine, in fome meafure exhaled by perfpira- 
 tion ; while a fmall part is retained in the habit, to 
 dilute the blood. Nor is it any thing uncommon for a 
 pellucid lymphatic liquor to fill the la£teals, in a dying 
 animal, inftead of chyle; or for fome of them to ap- 
 pear milky in one part of the mefentery, and limpid or 
 
 pellucid 
 

 Ch. XXVII. 
 
 VESSELS 
 
 pellucid in another ; fince, as to their fabric and ufe, 
 they alfo agree to anfwer the end of lymphatics. There 
 are not, therefore, two kinds of velfels from the in- 
 teftines ; one to carry the chyle only, and another pe- 
 culiarly for the conveyance of lymph. 
 
 770. After the digeftion has been completed fome 
 time, the la^eal velfels abforb pellucid watery juices 
 from the intefUnes, whence they appear themfelves 
 diaphanous ; but the thoracic dud is more efpecially 
 a lymphatic of the largeft order, conveying all the 
 lymph of the abdomen, lower extremities, and moft 
 parts of the body, to the blood (53.J 
 
 Of the Kidneys, Bladder, and Urine. 
 
 771. I ^ he chyle which is taken into the blood, 
 A contains a good deal of w'ater ; the propor- 
 tion of which would be too great in the velfels, lb as to 
 pafs into the cellular fubllance, if it was not expelled 
 again from the body. Therefore a part of this is ex- 
 haled through the flein (43d.); and another part, as 
 large, or often larger than the former, is drained 
 through the kidneys, and is expelled out of the body. 
 
 772. Thefe kidneys are two vifeera, placed on each 
 fide the fpine of the back, behind the peritonaeum, in- 
 cumbent upon the diaphragm, and upon the pfoas and 
 quadratus mufcles of the loins ; but in fuch a manner, 
 that the right kidney is commonly placed lower and 
 more backward than the left. Before the right kid- 
 ney is placed the liver, upon its upper part (690.), and 
 then the colon covers the reft of its anterior face ; and 
 the left kidney is alfo covered by the fpleen, ftomach, 
 part of the pancreas, and the colon. They are tied by 
 reduplications of the peritonaeum to the colon, duode- 
 num, liver, and fpleen. Their figure is externally con- 
 vex, with a feniielliptic deficiency in their inner fide ; 
 
 CHAP. XXVIII. 
 
 7T3" 
 
 laterally 
 
4 e><S KIDNEYS. Ch. XXVll!. 
 
 laterally they are flat or depreflied, inwardly hollow, 
 unequally divided into one upper, or longer and thicker^ 
 plane, and lower flenderer extremity. They are firm- 
 ly invelted by a flrong external membrane, which is 
 denfe, adheres very clofely, and does not come from 
 the peritonaeum. Betwixt that membrane and the 
 peritonaeum of the loins, there is always interpofed a 
 confiderable quantity of fat, by which the whole fur- 
 face of the kidney is furrounded on all fidcs, and a 
 nelh is completed, which the kidney does not totally 
 fill, though anfwering to its fhape. From the kidney 
 the peritoneum afcends to the liver, fpleen, colon, and 
 diaphragm, and prepares as it were ligaments for the 
 kidney. 
 
 773. The blood-vejfels of the kidneys are very large, 
 as well the arteries, which together exceed the me- 
 fenteric, as the veins. And firfl:,the renal arteries 
 out from the aorta under that of the mefentery, not 
 always in the fame manner, yet fo that the left is com- 
 monly fhorter than the right, and each of them fre- 
 quently in two, three, or four diftinct trunks. From 
 thofe trunks arife the renal arteries of the lower fort, 
 with the adipofe ones belonging to the fat cortex 
 or capfule of the kidney (772.) ; and not unfrequently 
 they give origin to the fpermatics. I'he fat, rather 
 than the kidney, receives the fmaller branches from 
 the fpermatics, and arteries of the loins. The arteries 
 are thick, fo that there is a great quantity of mem- 
 branes in proportion to their light ; they are alfo made 
 of very flrong ones, and exceed the flrength of the 
 aorta by a third part. 
 
 774. The renal veins are very large, more efpecial- 
 ly the left, and more inconflant in their courfe than 
 the arteries : for the right is often without a branch, 
 Ihort and concealed ; while the left always generates the 
 fpermatic and capfular vein of the fanre fide, and al- 
 mofl conflantly receives the lafl branch of the vena fine 
 pari ; and being of a confiderable breadth, it extends a 
 long way tranfverfdy, and produced to the left, before ' 
 
Ch. XXVIII. KIDNEYS. 
 
 the aorta, with the duodenum incumbent upon it* 
 Both the arteries and veins of the kidneys arife from 
 the great trunks laterally, a little defcending in an ob- 
 tufe angle ; and divide themfelves into many branches, 
 a little before they enter the kidney. That the paffage 
 of the blood through the renal arteries into the veins is 
 very expeditious, readily appears from the eafy courfe 
 that is afforded to water, wax, or even air, injeded. 
 The uppennoft veins of the fat of the kidneys come from 
 the capfular veffels, the middle from the renal ones, 
 and the lowermoft from the fpermatics. 
 
 775. ’ThcrtdLxe lymphatic veins, confiderably large, 
 found about the renal blood-velfels, which give origin 
 to the ciftern of the chyle (763.), which are faidto re- 
 ceive the difperfed branches that are fpread under the 
 
 , cellular coat of the kidney, and which are rendered 
 manifefl by putrefadion, or liquor injeded into the re- 
 nal arteries, or even into the ureter. 
 
 776. The nerves of the kidneys are fmall, but nu- 
 merous ; arifing from a confiderable plexus, mixed on 
 each fide with ganglions which are generated by the - 
 branches of the great femilunar ganglion, conjoined 
 with others from the intercoflal trunk, creeping along 
 from the thorax itfelf. They enter the kidney, toge- 
 ther with the artery, and fend off the middle mefente- 
 ric (748.), and likewife the fpermatic nerves. As thefe 
 nerves are fmall, they afford but a moderate degree of 
 fenfibility to the kidney. 
 
 777. Upon the top of each kidney is feated the re- 
 nal capfule; which in the fetus is large, even larger than 
 the kidney itfelf, but not afterwards increafing in the 
 adult ; it is glandulous, of the conglomerate kind, di- 
 vided into lobes, of an oval fhape in the fetus, and tri- 
 angular in the adult ; and conneded on the right fide 
 to the liver, fpleen, pancreas, on both fides to the dia- 
 phragm and kidney ; to all which it adheres by as ma- 
 ny conneding twigs. From a careful obfervation, it 
 feems to be inwardly hollow, feparable like a ventricle, 
 of a finooth furface, and terminating inwardly, as if 
 
 cut 
 
4o8 kidneys. Ch. XXVIII. 
 
 cut with a razor, full of a liquor of a yellowilh red co- 
 lour, and of a fluid confiftence, almofl like blood. The 
 arteries of thefe capfules are many, chiefly of three 
 kinds ; the uppermofl from the phrenics, the middle 
 ones from the aorta, and the lower ones from the renals ; 
 but the veins are only a large one on each fide, that of 
 the right to the cava, and the left to the renal vein of 
 the fame fide. The faid vein creeps almofl naked, in 
 branches, through the tender ventricle, in a fulcus, di- 
 viding the capfule, and fends branches through its in- 
 ternal fuperficies. The ufes of this gland are as yet 
 unknown ; although we are led to believe, from the 
 fituation, that it is fubfervient to the kidney, and of 
 greater ufe to the fetus ; fince it is conflantly found 
 near the kidneys, and info many different animals. It 
 has no vifible excretory du£l, nor does it difeharge any 
 juice, by vifible pores, into the vein. 
 
 778. The internal fabric of the kidney is Ample e- 
 nough, and fufficiently known. The blood-veffels ha- 
 ving entered the interval betwixt the upper and lower 
 ftratum of the kidney, fpread into its I'ubflance, fur- 
 rounded with a cellular fheath, and divide into branches 
 which go out between the branches of that which is 
 called the artery of the pelvis, by columns interpofed 
 betwixt the papillae. From thence, both in the papillae 
 and among them, making arches, they furround the 
 origin of the papillae, nearer to the circumference; but 
 fometimes joined by fmall branches : from whence pro- 
 ceed innumerable little twigs, of which fome return 
 into the papillae by the intervals between them and the 
 columns ; others tend towards the external furface of 
 the kidney, and fometimes, paffing through the proper 
 coat of the kidney itfelf, enter into its adipofe cover- 
 ing, where being changed into minute Terpentine curls, 
 refle£led again towards the trunk of the artery from 
 whence they rofe, they form a boundary to the kid- 
 ney, and are then gradually ftretched out and mix 
 themfelves among the uriniferous tubes. But from the 
 cortex, as it were by fome little flames, are produced 
 
 bundles 
 
Ch. XXVm. KIDNEYS. 409 
 
 bundles of the uniferous tubes collected in great num- 
 bers into threads, of which every one contains very 
 many little tubes. That they are continuous with the 
 arteries, or at lead that they receive their branches in- 
 to them, we know, from experiments which Ihew that 
 water, or even air, paffes ealily from the arteries of the 
 kidneys into the ureter ; and laftly from difeafes, in 
 which the blood takes the fame courfe. Between thefe 
 papillae, and about their origin, are fituated fome round- 
 ilh knots, which the latefl anatomifts take to be the ar- 
 terial glands, producing the proper jnd more narrow 
 urinary du£ts. Between thefe fmall du6:s run many 
 arteries parallel to one another. It is probable, that the 
 cortex conlifts of curved veffels, which eminent anato- 
 mifts have fuppofed to be fmaller than the red ones. 
 
 779. Thofe uriniferous du6ls^ gradually converging 
 towards the middle of the kidney, are joined together 
 like rays ; and are inferred in great numbers into one 
 blind dud, fuch as pcrfed the reft of the papilla ; and 
 each of which is terminated in its convex extremity 
 by confpicuous pores. The number of thefe papilla is 
 not altogether certain, but there are thirteen or more 
 of them; fome of which are obferved to be fimple, 
 fome triple, and fome quadruple. Thefe were in the 
 fetus fo diftind, that the kidney then appeared to con- 
 fift of as many diftind or fmaller kidneys, as there are 
 of thefe papilla, conneded together by a loofe cellular, 
 membrane ; and furnifhed every one with its proper 
 cortex of ferpentine veffels, and its compages of ftraight 
 uriniferous duds, the bafts of all which is in the cir- 
 cumference of the kidney, and their vertices con- 
 verge towards the centre. The oppofttc cortices 'bf 
 two of thefe little kidneys make a column, becaufe 
 it feparates two papilla. In adults, the , cellular fub- 
 ftance being condenfed, unites the renal portions and 
 their papilla into one even kidney ; however, it again 
 almoft recovers the condition which it had in the fetus, 
 if the intervening cellular plates are relaxed by often 
 
 injeding 
 
410 KIDNEYS. Ch.XXVIII. 
 
 injecting of water. The kidney is alfo remarkably larger 
 in the fetus than in the adult. 
 
 780. Round the protuberant furface of the f^id pa- 
 pillae, is extended a loofe membranous covering, in 
 fuch a manner, diftinct from the papillae itfelf, as to 
 form a larger fpace, like a cylindrical tube or funnel, 
 for receiving the papillae into its cavity, and fometimes 
 there are two in the neighbourhood of each pther. 
 Two or three of thefe tubes meet together in one j and 
 with others of the fame kind, they at lafl form by that 
 union three hollqw trunks, the upper, middle, and 
 lower, which again unite and open, but without the 
 kidney, into one conical canal, called iht pelvis. 
 
 781. The blood of the renal artery being Icfs fluid, 
 as is generally believed, than that of thebrain, and pro- 
 bably ftored with more water, brought by the ferpen- 
 tine circles of the arteries, depofits great part of its wa- 
 ter into thofe reclilineal tubes of the papillae ; a great 
 portion of which water contains oils and falts, inter- 
 mixed with earthy particles, or fuch other matters as 
 are thin enough to pafs through with it. But the fmall 
 diameter of each uriniferous duft itfelf at its origin, 
 and its firm refiftance, feem to exclude the milk or 
 chyle and the coagulable lymph. Hence, therefore, it 
 is, that the blood paflfes fo eafily through the open uri- 
 niferous tubes, whenever it is urged with an increafed 
 •celerity; or that, by a morbid relaxation, they tranf- 
 mit not only the oily parts of the blood, but even the 
 milk and felts of the meat and drink. But when the 
 flrength of the kidney is reftored by aftringent medi- 
 cines, the urine returns to its natural ftate. The nerves 
 likewife have a power of contracting or relaxing thefe 
 pafl'ages ; and thus w'e fee that urine, which in health 
 is of a yellow colour, becomes watery from hidden 
 grief of mind. A vail quantity is prepared; equal to 
 that of perfpiration, and fometimes even more. 
 
 782. The urine, by fire or putrefaction, fometimes 
 by difeafe, and in fome animals <nore eafily, changes 
 into a volatile alkaline nature, intimately mixed wdth a 
 
 fetid 
 
Ch.XXVIII. kidneys. 411 
 
 fetid oil, partly empyreuinatic, yellow, and volatile, and 
 in part very tenacious, to be feparated only by the lafh 
 degrees of fire, under the denomination of phofphorus ; 
 a fubflance fhining of itfelf, and taking fire in the air: 
 and Jaftly, it abounds more with earth than any other 
 juice of the human body, both of a cretaceous and 
 fparry nature ; the latter coming chiefly from the drink, 
 the former alfo from the folid parts of the body theni- 
 felves diffolved and mixed with the blood. But there 
 is alfo a confiderable proportion of fea-falt refiding in 
 frefh urine ; from which it is even feparable, after a long 
 putr^efaffion, in the making of phofphorus j in which 
 procefs a very great part of the urine is changed into 
 volatile alkali. Nor is the urine wholly deflitute of a 
 vitriolic acid, or at leaft one much a-kin to it; both in 
 that taken from men, as well as in the ftale of cattle. 
 There is, again, a fort of fufible fait feparable in the 
 urine, which is cooling, and a-kin to nitre. In fevers, the 
 oily and faline parts of the urine are greatly augmented 
 both in bulk and acrimony. 
 
 783. The ureter being a continuation of the pelvis, 
 carries on the urine received from the kidney, by pref- 
 fure from the incumbent vifeera, the contraftion of the 
 abdominal mufcles with thofc of the loins, and the 
 force of the circulation urging the blood behind the fe- 
 cerned fluid, and laftly the weight of the urine itfelf. 
 Firft, the ureter is covered by the peritonaeum and cel- 
 lular membrane ; but its mufcular coat is weak, ob- 
 feure, if any : it has then a fccond cellular coat ; a 
 firm, white, nervous one ; a third cellular one, lined 
 with the innermoft, which is of a fmooth membranous 
 fabric, porous and glandular internally, and in gene- 
 ral moderately irritable. It is of different diameters in 
 different places, and every where fwelis into veficles. 
 It defeends over the pfoas mufcle, croffes over the great 
 iliac blood-veffels into the pelvis ; goes behind the urinary 
 bladder; and in the conjundtion of the defeending and 
 tranfverfe portions of the bladder, enters obliquely 
 betwixt the mufcular fibres and nervous coat ; and fo 
 , 3 E again. 
 
412 BLADDER. Ch. XXVIir. 
 
 again, betwixt the nervous and villous coat, in fuch a 
 manner that the mouths of the two ureters are in the 
 neighbourhood of each other, and open by an orifice 
 obliquely cut off; but they have no valves, neither at 
 their opening in the bladder, nor in any part of their 
 courfe. From their oblique infertion into the bladder, 
 a protuberant line is formed, by the greater thicknefs 
 of the nervous coat, which defcends to the caput gal- 
 linaginis. ■ 
 
 784. That the urine is feparated in the kidneys is 
 fhown by the very nature of the thing, as it can be 
 drawn out by preffing on its fmall canals. That it de- 
 fcends by the ureter is fliewn by the furprifmg fwelling 
 of the kidney, and that part of the ureter which is a- 
 bove the ligature, as well as the emptinefs of that part 
 which is below' it. In the bladder alfo, as well as in the 
 kidneys and ureters, there is an immenfe fvveHing as 
 often as the bladder cannot receive the urine, or can- 
 not emit it; an obftacle being generated in either 
 place. 
 
 785. Nor does there feem to be any other way for 
 the urine to pafs. For although it is certain, that the 
 flomach, like all other membranes, exhales a moifture 
 through its coats; though it is not improbable, from 
 experiments, that the bladder alfo abforbs ; and al- 
 though the paffage of mineral fpaw waters, by urine, 
 be extremely quick ; yet it does not thence followq that 
 there muff be ways, different from that of the ureters, 
 to convey the water from the food to the bladder. For 
 the bladder is, on all fides, feparated from the cavity of 
 the abdomen by the peritonseum ; nor is it very likely, 
 that the vapours, which either go out from the bladder, 
 or which are derived towards it from other parts, can 
 here find open pores through the peritonseum ; nor do 
 membranes imbibe much that are already wetted, fo 
 as to fill their pores with humours. But the urine alfo 
 which is contained in the bladder, diftends it even to 
 death ; nor does it find any paffage through which it 
 can efcape into the pelvis ; and on die other hand, 
 
 when 
 
Ch, XXVIII. BLADDER. 413 
 
 ■when the ureters are obftrutled with flones, fo that the 
 bladder receives nothing from them, it is either quite 
 empty, or contains a very acrimonious and thick urine, 
 manifeftly indicating that the water can find no other 
 way from the pelvis into the bladder. And a careful 
 attention to the manner in which mineral waters are 
 difeharged by urine, fufficiently demondrates, that there 
 is no fuch rapidity therein as is commonly imagined ; 
 but the itimulus of the cold water drank, does, like the 
 external cold applied to the Ikin, caufe a concufiion of 
 the bladder and urinary parts, by which they are foli- 
 cited to repeated difeharges of the old urine which was 
 before in the body, and not immediately of that which 
 was lad drank. Again, the largenefs of the renal vef- 
 fels demondrates, that not much lefs than an eighth 
 part of the blood fent to the body is received at a time, 
 and confequently there are above 1 000 ounces of blood 
 conveyed through the kidneys in an hour ; whence it 
 will appear but a moderate allowance, for 20, or even 
 50, ounces of water to didil from that quantity of blood 
 driven through the kidneys in the fame time. Finally, 
 it is certain, that both man and brute animals pevifh if 
 the ureters are clofed up by a ligature ; we then ob- 
 ferve alfo, that no urine can be found in the bladder. 
 
 786. The urinary bladder is feated in the cavity or 
 bowl of the pelvis, w'hich is an appendix to the abdo- 
 men, furrounded on all fides by bones ; but laterally, 
 and at the bottom, only inclofed by mufclesj; and is al- 
 ways larger in women than in men. It is fituated, fo 
 as to cohere with the os pubis by a large portion of cel- 
 lular fubdance, by which it is connected to the perito- 
 naeum,. from thence backward, and for a fmall part of 
 its furface before ; but behind, it is extended to a great- 
 er length over the bladder, defeending almod as far as 
 the infertions of the ureters ; from whence it returns 
 back again, either over the reflurn or uterus in women. 
 Behind the bladder lies the rectum, the feminal vefi- 
 -cles, and prodate gland, with the levatores ani. In the 
 fetus, the bladder is very long, and fomewhat conical, 
 3 E 2 extending 
 
4 t4 BLADDER. Ch. XXVIIL 
 
 extending itfelf much above the offa pubis ; but in the 
 adult, it hardly arifes above thofe bones, even when in- 
 flated, becaufe, in them, the pelvis is much larger and 
 deeper in proportion. 
 
 787. The figure of the bladder is, in general, oval, 
 flatter before, more convex behind, terminated at bot- 
 tom by a very obtufe or flat head, that lies incumbent 
 upon the re£tum. Such is the figure of it in an adult 
 man: but, in the fetus, it is almoll cylindrical ; and, in 
 women who have had many children, fo much fatten- 
 ed laterally by preflure, that it rcfembles a fort of trian- 
 gular cone. This change of the figure of the bladder 
 feems to arife from the weight of the urine, gradually 
 extending more the lower parts of the bladder, which 
 are mofl prefled; by which means the Tides are drawn 
 together from above, fo as to render it fhorter and 
 broader. It is of different magnitudes; fo that, in dif- 
 eafes, by frequent irritation and contradion, it fome- 
 times becomes very fmall. 
 
 788. The fabric of the bladder is much like that of 
 all large membranous receptacles. The firfl membrane 
 is cellular ; in its forepart lax, and replenifhed with fat ; 
 but backward it is thinner, where it unites with the 
 redium. In this there is a net-work of veffels, chiefly 
 of veins. Next to this follows a raufcular coat, very 
 difficult to deferibe, confifting of pale contractile fibres, 
 difpofed in various reticulated bundles, not continued 
 one to another, but interrupted with net-like fpaces, in 
 which the nervous coat lies uncovered. The principal 
 flratum of thefe is longitudinal ; which, arifing before 
 from the proftate, is frequently, though not always, fo 
 connedted to the fynchondrofis of the ofl'a pubis, or the 
 membranes covering it, as feemingly to arife from 
 thence ; thence, afeending and growing broad, they 
 fpread towards the conical extremity of the upper fide 
 of the bladder : here palling on, they dtfeend over the 
 pofterior furface, and grow there confiderably broader, 
 till at length they are finally terminated in the proflate ; 
 but laterally they go off like the palms of one’s hands, 
 
Ch. XXVIll. BLADDER. 415 
 
 and are mixed from the anterior and pofterior planes. 
 Thefe fibres muft ncceflarily deprefs the bladder, and 
 confequently propel the urine towards its bottom part. 
 
 789. The remaining fibres are very difficultly redu- 
 ced to any order. They fill the intervals of the former; 
 by arifing from the proftate backward, and afeending 
 infiefled, they form a Ilratuin, partly oblique, and partly 
 tranfverfe, the interior ones more than the others, both 
 in the forward and back part of the bladder. 
 
 790. The contradile force of the bladder is gentle, 
 but perpetual ; fo that it contrafts from its greatefi; di- 
 latation to its very leafl fize, without any alternate re- 
 laxation, and remains long in its ftate of greatefi: con- 
 traftidn. The urine is the leafl uneafy ftimulus ; wa- 
 ter injefted is more fo, and a (lone the inofl of any 
 kind of irritating fubftance. When diftended beyond 
 meafure, it lofts its powers ; fo that either it cannot ex- 
 pel, or cannot retain, the urine. 
 
 791. Within the mufcular coat is fpread the fecond 
 cellular ftratum, of a tender elegant fabric, that may be 
 inflated, and fofter than that obferved in the inteftines. 
 Next follows the nervous coat, as a continuation of the 
 fkin, and refembling the nervous coat of the ftomach : 
 the inner one is more obfeure ; difficultly feparable from 
 the nervous one ; continuous with the epidermis; and, 
 like it, eafily feparable, having a great deal of mucus, 
 and folded into various wrinkles, without any certain 
 order. In the furface of this laft, the pores of the mu- 
 cous cryptas fometimes appear confpicuous, but not al- 
 ways without difficulty, pouring out a vifeid foft glue. 
 The mucus itfelf is very manifeft, and is prepared in 
 the greater quantity in proportion to the irritation of 
 the bladder. For this mucus there is the highefl necef- 
 fity, to diminifh the fenfation of the acrimony of the 
 urine. 
 
 792. The vejfels and nerves of the bladder are in 
 common with thofe which go to the genital parts, 
 where we fhall deferibe them. Thofe which come 
 from the epigaflrics are but fmalJ. They form princi- 
 pally 
 
4i6 bladder. Ch. xxvin. 
 
 pally a net- work in the firfl; or outer cellular ftratum, 
 and then another in the fecond ftratum of the fame fub- 
 ftance. The arteries exhale through the villous coat, 
 as we learn by experiment from anatomical injections ; 
 and the veins likewife abforb again, to which is owing 
 the greater confiftence and higher colour of the urine 
 by a long retention of it. The lymphatic veffels in the 
 outer cellular ftratum, are eafily demonftratcd ; but 
 their origin is from another part, probably from the ad- 
 jacent reftum. 
 
 7 9 3. The fame urinary bladder is of the nature of other 
 membranous facs-, fo that it both tranfmits water through 
 the inorganic pores of its membranes, and through the 
 fame abforbs the water in which it is immerfed. 
 
 794. Into this bladder the urine conftantly flows, in 
 a continued thread, as we are aflurcd, from experi- 
 ence, in morbid and uncommon cafes, in which the 
 extremities of the ureters have appeared to the eye. 
 By ftaying fome time in the bladder, and from the ab- 
 forption of the more watery part, the urine acquires an 
 higher colour, becomes (harper and reddifli-coloured. 
 Nor are we fully acquainted with the caufe which re- 
 tains the urine in the bladder. The fpinder is ob- 
 fcure ; the depreflion of the bladder feems to a(Tift, 
 as it defcends convex below its mouth upon the in- 
 teftinum reftum, fo that at laft the urine arrives at 
 the entrance of the urethra when any quantity of it is 
 collefted. Certain it is, that the urine does not flow' 
 fpontaneoufly even from a dead carcafe. 
 
 795. At length, by its bulk and acrimony, irritating 
 the fenfible fabric of the bladder, it is thence expelled, 
 firft by the motion of the diaphragm and abdominal 
 mufcles, by which the inteftines are urged againft the 
 bladder in a perfon who is erect, whereby the urine 
 makes itfelf a way through a narrow' and impeded paf- 
 fage ; and again, by the periftaltic motion of the bladder 
 itfelf, arifing from the contraction of its mufcular fabric 
 (788, et feq.) 
 
 796. There feems by the urine, befides the particles 
 
 of 
 
Gh. XXVIII. BLADDER. 417 
 
 of food and water, much matter to pafs off that is 
 noxious to the human body ; efpecially calcareous 
 earth reforbed from the bones and folid parts, and 
 which would not fall to produce bony crufts and cal- 
 culi wherever it was ftopped ; the fparry or gypfeous 
 earth of fountains ; an acrid oil mixed with fait, fo as 
 to aflume a volatile nature. The urine, by its reten- 
 tion, difpofes to the generation of the ftone and gout : 
 when fupprefled, it produces fharp fevers ; and at lafl: 
 flows back to the brain, and overflows and deftroys it. 
 
 797. From the anterior vertex of the.obtufe or 
 greater end of the bladder, not from its bottom, goes 
 out a flender canal with a fmall orifice, as a continua- 
 tion of the bladder itfelf, under the denomination of 
 the urethra ; and in this, there is a manifeft continua- 
 tion of the cuticle of the internal coat of the bladder, 
 with its furrounding cellular fubftance, and more efpe- 
 cially a folid nervous coat, of which it is principally 
 compofed. It is variable in its diameter and direction ; 
 in women, it is ftraight, tranfverfe, and fhort. I do not 
 find a valve in its mouth. 
 
 798. This canal of the urethra isfirfl furrounded, on 
 all fides, by the proftate gland ; from whence it goes 
 out naked, for a fmall fpace, that is immediately con- 
 tinuous below with the incipient bulb of the uretha, 
 which likewife furrounds it on all fides above ; but the 
 cavernous bodies of the penis chiefly cover it above 
 and laterally, fo as to form a common groove for its 
 reception, and add ftrength or firmnefs to this other- 
 wife lax tube. It begins wide from the bladder, and 
 contrafts itfelf conically in the proftate j from which, 
 being at liberty, it becomes cylindrical, and enlarges 
 at the firft acceflion of the bulb ; in the penis it is 
 almoft cylindrical, and again dilates itfelf a little before 
 its termination. 
 
 799. This canal is governed by various mufcles, 
 cither proper to itfelf, or belonging to the parts adja- 
 cent. And firft, in women, there are manifeftly fibres 
 placed round the egrefs of the incipient urethra, which 
 
 are 
 
41 8 BLADDER. Ch. XXVIII. 
 
 are moftly tranfverfe, but fome varioufly decuflating 
 each other; whole office, and fupport iiitlic vagina, ma- 
 nifeftly appear ; namely, to deprefs the urethra, like 
 the fpindler, about the opening of which they are dii- 
 pofed, and by this means to ciofe its opening againit 
 the refilling contrafled vagina and fpinfter of the anus. 
 In man there are tranfverfe fibres of the fame kind ; 
 but, forming an arch that opens upward, they run 
 into the conjunction of the bladder with the proftate, 
 covering the longitudinal bundle of fibres and proilatc 
 itfelf, w'hich covering of fibres thus becomes fit for 
 contrafting the orifice of the bladder. 
 
 800. The firfl tranfverfe mufcle proceeding from 
 that bunch of the ifcliium which fends forth the erector 
 mufcle of the penis, goes tranfverfely towards the other 
 os ifehium, partly pafles into it, is partly inferted into 
 the middle bulb of the urethra, and partly degenerates 
 into the accelerator. It prefles upon, ffiakes, and draws 
 backward, the bulb of the urethra. The other, pro- 
 duced from a branch of the os ifehium, is inferted into 
 the ifthmus of the urethra before the bulb, and di- 
 lates it. 
 
 801. But likewife the levator of the anus feems to 
 raife the urethra againll the os pubis, fo as to ciofe the 
 opening of the bladder into it ; and, in ourfelves living, 
 we may perceive the accelerator conftringed, together 
 with the fpindter, at the root of the penis, fo as perfectly 
 to ciofe the opening of the urethra, and prefs back the 
 urine even while it is flowing ; whence there is no 
 room to doubt, but this mufcle gives a moderate tight- 
 nefs for retaining the urine. 
 
 802. An effort being now made (7 9 5.) by the preffure 
 of the diaphragm, the urine runs forth with a greater ce- 
 lerity, in proportion as it comes through a canal fmaller 
 than the diameter of its large receptacle ; and, being once 
 difeharged, frees the body from uneafy fenfation. The lafl: 
 drops, which remain in the lower part of the bulb, irritat- 
 ing by their weight, are expelled by the accelerator muf- 
 cle ; namely, a ftrong mufcular expanfion, placed round 
 
Ch. XXVIII. BLADDER. 419 
 
 the bulbjwhofe fibres are difpofed in the fhape of a feather^ 
 meeting together in the middle of the bottom-part of 
 the bulb, and in their fore-part fixed by two tendons 
 into the cavernous bodies of the penis, and in their 
 back-part connected by three fnufcular portions to the 
 fpinfler of the anus, two of which portions may be 
 alfo referred to the levators of the anus. This mufcle, 
 when the fpinder is firmly fhut, draws the bulb up- 
 ward; and, with a confiderable force, alternately con- 
 trails or Ihakes the urethra, fo as to expel the laft drops 
 of the urine. 
 
 803. The pyramidal mufcle of the abdomen maybe 
 thought to draw the bladder downwards by the rope of 
 umbilical veffels, and likewife to relax it, and fit it for 
 the ailion of the long mufcular fibres. But this cannot 
 be admitted, feeing the mufcle itfelf is often wanting; 
 neither can it bring down the bladder, and very rarely 
 comes to the navel. 
 
 804. But as the urine is fliarp, and the membrane of 
 the urethra very fenfible, and becaufe the air will like- 
 wife enter it ; for thefe reafons nature has fupplied this 
 canal with a large quantity of mucus. This mucus is 
 not only generated from the fources in the bladder, but 
 more efpecially from two conglomerate glandules ; one 
 of which is feated on each fide in the angle, betwixt the 
 bulb of the urethra and the cavernous body of the pe- 
 nis ; from whence it fends out a flendcr dud, running 
 for a confiderable length through the urethra. I am 
 ignorant of any glandule of the ifthmus different from 
 the cellular texture. Moreover, the whole urethra is 
 full of mucous finufes, of a cylindrical figure ; very 
 many of which defcend towards the glans, though 
 feme run in a contrary djredion, having fmall mucous 
 cryptse placed at their fides, which depofite there a 
 fluid mucus, and difeharge it into the urethra. A larger 
 fort of thefe mucous cryptse are difpofed along the up- 
 per fide of th6 urethra, beginning before the bulb, at 
 the origin of the glans. There are others, ftill fmaller, 
 mixed with thefe large ones, and placed laterally, and 
 
 3 F abaut 
 
420 BLADDER. Ch. XXVIIT. 
 
 about the urethra. In women alfo there are many 
 and larger of thefe mucous cifterns, which open into 
 their much Ihorter urethra, more efpecially at its open- 
 
 ing- 
 
 805. The neceflary cleanlinefs and avocations of hu- 
 man life require the urine collefted to be difcharged on- 
 ly at certain times. But thefe advantages could not be 
 obtained without fome* danger of difeafe, from the de- 
 pofition of the earthy parts of the urine continually 
 confined and at reft ; fo that, by repeated additions of 
 the like matter cemented together, a ftone may be at 
 length formed. But the plenty of mucus, with which 
 the urinary paflages are commonly defended, is, for the 
 mofl part, a fufficient guard againft this diforder, as 
 we fee the generality of people are free from the ftone ; 
 unlefs the urine is more than commonly charged with 
 an earthy, tartareous, or chalky matter, increafed by 
 the ufe of hard water full of f|lenitic matter, drinking 
 wine ; very vifcid food, inaftivity of body, and a reten- 
 tion of the urine beyond the calls of nature ; or fome 
 vifcid body capable of attrafting the calculous mat- 
 ter; or finally, a diforder of the kidneys, laying a 
 foundation for the earthy matter firft to adhere toge- 
 ther. 
 
 C H A P. XXIX. 
 
 Of the Genital Parts in Man. 
 
 806 .^ I '' HE veflels belonging to the genitals con- 
 X ftantly arife near thofe of the kidneys, and al- 
 moft in all kinds of animals ; by which nature feems to 
 have intended a double ufcfulnefs in one organ, which 
 might be able fo difcharge the urine, and bear a rela- 
 tion likewife to the genital parts, though placed at a 
 confiderable diftance, in a fpace betwixt the tops of the 
 thighs, and fubfervient to cleanlinefs, modefty, eafinefs 
 of the birth, and the force of throes in delivery. 
 
 807. The 
 
Ch.XXIX. male genitals. 4 U 
 
 807. The femen mafcuUnum is firft formed in the 
 tefticle ; then repofited in the feininal veficles 5 after- 
 wards ejeded from the penis, into the uterus, where it 
 renders the female ovum prolific : and therefore this 
 muft be the order of our inquiry into thefe particulars. 
 The human teJHcles, but fmall in proportion to the 
 bulk of the body, are, in the fetus, lodged within the 
 abdomen behind the peritonjeum ; from whence, by de- 
 grees, they defeend into the groins ; and are at laft, in 
 a more advanced age, thruft down below the groin, 
 perhaps partly by their weight, and partly by the im- 
 pulfe of the influent blood ; yet fometimes they are ob- 
 lerved to remain behind in the groin of adults. They 
 defeend by a paffage, which in the fetus is open, cel- 
 lular, and called iht procefs, leading from the cavity of 
 the peritonsum into the ferotum ; and the fame paf- 
 fage, after the tefticle is tranfmitted, is contradted by a 
 law of nature, and preferves the tefticle. 
 
 808. The tefticle is defended by various integu- 
 ments ; of which the firft and outermoft is that of the 
 ferotum, made up of a clofe cellular ftratum, replenifh- 
 cd with veflels, and clofely adhering to the fein : which 
 laft has a kind of elaftic or contractile motion at the 
 approach of cold and in the aCl of venery, altho’ with- 
 out any mufcular fabric ; yet it has commonly aClion 
 enough to wrinkle the ferotum, and draw up the te- 
 fticles. This cellular coat, commonly called dartos, is 
 placed round each of the tefticles feparately, by the 
 conjunction of which together in the middle, is form- 
 ed a kind of feptum, which appears more remarkable 
 in a dry preparation; and this feptum is often imperfeCt 
 in its upper part, towards the penis. 
 
 809. Within the dartos is fpread a loofe cellular ftra- 
 tum, without any fat, except in the lower part of the 
 ferotum, and may be inflated like the fame fubftance in 
 other parts. Next follows a mufcle, from its office 
 called cremafler ; which arifes from the degenerating 
 fibres of the lefs oblique mufcle of the abdomen, and 
 from the tendon of the external obliquus, called by 
 
 3 F 2 fome 
 
422 MALE GENITALS. Ch.XXIX 
 
 fome a ligament, and by others fibres, defcending 
 from the os pubis backward into a vagina or capfule, 
 which, every way furrounding the teTticle, ferves to 
 comprefs, elevate, and forward its contents. 
 
 810. Next to this follows the fecond cellular ftra- 
 tum, whofe fpungy fabric is continued with the outer- 
 mod, that lies round the peritoneum ; and this fecond 
 flratumis called tunica vaginalis. In this the veficlesor 
 cells of its fabric appear larger than elfewhere, and 
 may be inflated one after another. At the begin- 
 ning of the tefticle, above the epididymis, it is, in 
 a manner fo feparated from the reft above the tefticle, 
 towards the rings of the abdominal mufcles, that the 
 inflation can hardly be continued through. Betwixt 
 this laft membrane and the following is a fpace, into 
 which are exhaled thin vapours, and fonfctimes a wa- 
 ter is collefted. The inner coat, called albuginea, is a 
 ftrong, white, compaff membrane, which immediately 
 invefts and confines the proper fubftance of the tefticle 
 itfelf. 
 
 8 1 1. The tefticle more properly fo called, is of an o- 
 val figure, with an acute vertex, looking upwards and a 
 little outwards. The epididymis is a kind of addita- 
 ment to the tefticle ; and is a flat fubftance, refembling 
 thick tape, w'hich goes round the pofterior margin of 
 the tefticle, to which it is conne<fted by the cellular tex- 
 ture, and by blood-veffels. In the lower part it is 
 plain ; on the upper part it adheres to the tefticle by a 
 thick and convex head, as it does alfo on the lower 
 part. In the middle, it is partly attached by its bafis, 
 and being partly free makes a blind fac. 
 
 812. To the tefticle the fpermatic arteries defeend, 
 one on each fide, generated by the aorta below the re- 
 nal arteries; but not unfrequently from the renal arte- 
 ries thcmfelves, from thofe of the capfules, or from the 
 aorta itfelf above the emulgents. This artery, the fmall- 
 eft in the body in proportion to its length, defeends a 
 long way outward before the pfoas mufcle, and gives 
 fmall branches to the fat of the kidney, to the ureter, 
 
 mefocolon, 
 
Ch.XXIX. male genitals. 423 
 
 mefocolon, glandules of the loins, and to the perito- 
 nseum ; but more efpecially towards the bottom of the 
 kidney, it gives a remarkable branch inflected and co- 
 vered with fat, yet leffenlng itfelf, that takes a ferpen- 
 tine courfe behind the peritonaeum, as far as the ring 
 of the abdomen. This ring is formed entirely of the 
 tendinous fibres, defeending from the external oblique 
 mufcle, interrupted in their oblique defeent by a long 
 aperture, growing wider downward ; from this aper- 
 ture part of the fmaller inner fibres are broadly detach- 
 ed to the os pubis, and others eroding cohere with the 
 fibres belonging to the other fide of the mufcle, which, 
 being colletted together, is called the inner column. 
 Other rtronger external fibres, diftinguilhed from the- 
 former by the aperture, are broadly inferted by a thick 
 bundle into the outer fide of the os pubis, under the 
 denomination of the external column; from, whence va- 
 rious fibres run od to the fafeia lata and groin. The 
 upper part of this opening is in fome-meafure clofed 
 up by fibres, arifing from the outer column, and a- 
 feending in a curve diredion round the inner and 
 weaker column. Below thefe fibres there is often a 
 fmall opening left, parted off by tendinous fibres, thro* 
 which defeends the fpermatic artery, with the vein, and 
 vas deferens, with a good deal of cellular fubftance by 
 which they are wrapt together into a cylindrical cord ; 
 before the external column, through no perforation of 
 the peritoneum, which it has every where lying on this 
 fore part of it. At the bafis of this ring, the dudus de- 
 ferens is joined with the rope of veffels, and the whole 
 bundle arrives at the groin, and thence at the ferotum. 
 Th'e fpermatic artery gives many fmall branches to the 
 cremafter, to the cellular coat, and to the feptum of the 
 ferotum; and then defeends in a double plexus, to the 
 tefticle ; of which the principal comes from betwixt the 
 ppididymis and origin of the vas deferens, at the mid- 
 dle and lower part of the tefticle, and then goes, by 
 tranfverfe branches, through the albuginea; the other 
 plexus, that accompanies the vas deferens in the upper 
 
 part 
 
424 MALE GENITALS. Ch.XXIX. 
 
 part of the tefticle, has a like termination, and is va- 
 rioufly inofculated with the former. There are other 
 fmall arteries, which go to the coverings of the te- 
 fticle from the epigaftrics, and others from thofe of 
 the bladder, which follow the courfe of the vas de- 
 ferens, both which communicate with the fpermatic 
 veffels. 
 
 813. Many of thefe fmall arteries play about the e- 
 pididymis j but the larger of them fprcad tranfverfely 
 through the albuginea, which they perforate in feveral 
 places, to enter the innermoft fabric of the tellicle, 
 through which they are minutely ramified in all points, 
 and feparated by numberlefs membranous partitions. 
 There is no large anaftomofis or communication be- 
 twixt the fpermatic artery and vein here, any more than 
 in other parts of the body ; but fome red blood is re- 
 ceived into thofe branches that pals through the albu- 
 ginea to the innermoft fubftance of the tefticle. But 
 from the long courfe of thi« artery, the fmallnefs of its 
 diameter, the number of ferpentine flexures, the great 
 ratio of the dividing branches to their trunk, and the 
 coldnefs of their fubcutaneous diftribution, demonftrate, 
 that the blood flows not only in a fmall quantity, but 
 very flowly, to the tefticle. 
 
 814. The fpermatic vein of the right fide, is inferted 
 into the cava ; but that of the left pours its blood into 
 the emulgent vein, or into both : it is enormoully lar- 
 ger than the artery, and takes the fame courfe in com- 
 pany with that ; but both its trunk and branches are 
 much larger and more numerous, very ferpentine, and 
 formed into a bunchy plexus of confiderable length, 
 which is interwove with the artery, and continued as 
 low as the tefticle, there by degrees dividing into two 
 like the artery. There are fome valves in this vein, 
 but rare. 
 
 815. Thefe external coverings of the tefticle have 
 fmall arteries from the epigaftrics ; the fcrotum from 
 the crural arteries, and thofe of the trunk, with an in- 
 ternal branch, which is called the external pudenda ; 
 
 the 
 
Ch.XXIX. male genitals, 42s 
 
 the fellow veins go to the faphena, and to the crural 
 trunks. 
 
 816. The nerves of the tefticle are many, whence it 
 has a peculiar tendernefs of fenfation ; infomuch that 
 faintings and convulfions follow from bruifing or inju- 
 ring the tefticle, and particularly a conftricftion of the 
 jaws. Some of them arife deep from the renal plexus, 
 from the mefenteric plexus, from the trunk of the in- 
 tercoftal nerve, and laftly from the mefocolic plexus, 
 and follow the courfe of the fpermatic veflels. Others 
 are proper to the furface of the coverings of the tefticle, 
 from the fecpnd, third, and fourth pair of the nerves 
 of the loins. 
 
 817. I have frequently obferved lymphatic veflels in 
 the fpermatic cord, which are judged to arife from the 
 tefticle itfelf, and mix themfelves with thofe that ac- 
 company the inguinal blood-veflels. The induftry of 
 late anatomifts has traced them even to the network of 
 the tefticle itfelf. 
 
 818. The blood, moved flowly and in a fmall quan- 
 tity through the fpermatic artery, by which it is brought 
 to the inner fabric of the tefticle (8 1 3.), is there drain- 
 ed into very fmall veflels, which carry their fluids to the 
 feminal vejfels^ although we are ignorant of the manner 
 by which the arteries communicate with thefe canals, 
 the bundles of which form the whole fubftance of the 
 tefticle. Thefe feminiferous veflels are exceeding fmall, 
 ferpentine, firm, or folid, and havfe a very fmall light in 
 proportion to their membranes ; they are not, however, 
 blind, as I have feveral times filled them through the 
 vas deferens. They are colleded together into bundles, 
 above twenty in number, divided by diftind cells or 
 partitions, which defcend from the albuginea to con- 
 dudl the arteries and veins. In each of thefe cells there 
 is a feminiferous dud, to convey the fecreted humour 
 from the feminiferous vafcules. Twenty or more of 
 thefe duds form a net-work^ adhering to the furface of 
 the albuginea, and forming inofculations one with ano- 
 ther j and quickfilver is very eafily poured from them 
 
 into 
 
426 MALE GENITALS. Ch. XXIX. 
 
 into the furrounding cellular texture. From that net 
 in the upper part of the epididymis, afcend 20 or 30 
 dudts, which, being" contorted together into folds, form 
 as many vafcular cones, that are joined together by an 
 intermediate cellular fubftancej and lying incumbent 
 one upon another, then form the head of the epididy- 
 mis, and in that head foon meet together into one duel 
 without the tellicle. 
 
 819. This du£l being intricately wove by an infinite 
 number of folds and ferpentine flexures, after a manner 
 not imitated in any other part of the body, and con- 
 nefted together by a great number of loofe cellular 
 ftrata, is afterwards colledfed by a membrane of the al- 
 buginea into one bundle, called the epididymis. But 
 the dudt of which it is compofed, grows larger as it de- 
 feends, being largeft at the bottom of the teflicle ; from 
 whence again afeending along the poflerior face of the 
 teflicle, in a direflion contrary to itfelf, it by degrees 
 fpreads open its fpiral convolutions, and comes out 
 much larger, under the denomination of dudius defe- 
 rens. Almofl always, however, a fmall veffel feparates 
 fomewhere from the duftus deferens, and afeends along 
 with the cord, having an uncertain termination. 
 
 820. This is the courfe deferibed by the femen, pro- 
 pelled forward by the motion of the fucceeding juices in 
 the teflicle ; and perhaps, in fomc meafure, though flowly, 
 by the contraftion of the cremafler : as we may reafonably 
 fuppofe, from the numberlefs fpires and convolutions 
 formed by the epididymis, obftru6ling almofl every kind 
 of injedlion ; and, as we may conclude, from the length 
 of time that is required to fill the feminal veficles again, 
 after they have been once exhaufled. 
 
 821. The cylindric dudtus deferens being made of a 
 very thick fpungy fubflance, included betwixt tw’o 
 firm membranes, bored through with a very fmall tube, 
 afeends in company with the cord of the fpermatic 
 veffcls, and together with them pafles through the 
 ring of the abdomen (812.): thence it defeends into 
 the pelvis j and applying itfelf to the bladder betwixt 
 
Ch.XXIX. male genitals. 427 
 
 the ureters, it foon after meets the fubjacent recep- 
 tacles, called the right and left neficula feminales. Here 
 it goes along the inner fide of the veficle, as far as the 
 proftate glandule ; and dilating in its palfage, forms a 
 ferpentine flexure, that begins itfelf to put on a cellular 
 appearance. But very near the proftate, being conti- 
 nued from thefe cellular bendings, with a conical dudl 
 coming out from the veficle, it unites in a very acute 
 angle, which does at the fame time itfelf form a conical 
 dudl ; which being continued rather with the vas de- 
 ferens, and finking through the proftate gland, is 
 there wrinkled intd a large fold, and going off out- 
 wards at right angles from its companion on the other 
 fide, and afterwards ftraitened, it opens into the ure- 
 thra, through a little hollow protuberance, which has 
 a long tail or defcent, and is laterally perforated with 
 two very fmall openings, one on each fide. By in- 
 jeding a liquor into the dudus deferens of a dead fub- 
 jed, we perceive that it flows both into the urethra and 
 into the feminal veficle, but more readily into the for- 
 mer : but in a living perfon the femen never flows out 
 but in the ad of vencry ; and confequently the dudus 
 deferens conveys all its femen, without further delay, 
 over a retrograde angle, to the feminal vejicles, 
 
 822. By this laft denomination we call a fort of 
 ftrong convoluted inteftine-like membrane, placed un- 
 der the bafis of the bladder, conneded towards its 
 neck by a good deal of cellular fubftance : from this 
 ten or more blind gut-like cells or inteftinuli go off 
 laterally, in fome meafure ramified and divided, but 
 ending in impervious conical extremities. This kind 
 of inteftine, intermixed with a great deal of firm cellu- 
 lar fubftance and fmall veflTels, is fo contraded toge- 
 ther, as to lie within a fhort ferpentine heap. For the 
 reft of its fabric, it feems to have externally a pulpy and 
 thick membrane, and likewife fomcthing fimilar to the 
 dudus deferens. Intesrnally it is wrinkled, having a 
 fort of villous appearance j and is befides faid to have 
 fmall pores and glandules, with which I am unac- 
 3 G quainted. 
 
420 MALE GENITALS. Ch.XXIX. 
 
 quainted, but various and hollow cells it certainly 
 has. 
 
 823. The liquor depofited into this refervoir, is in 
 the tefticle yellowifh, thin, and watery : and the fame 
 nature it retains in the veficle, only becomes there 
 fomewhat thicker and higher coloured ; and laftly, it 
 is white in mankind, when it goes oft' mixed into one 
 with the liquor of the proftate. It has a fort of heavy 
 or ftrong fmell, of a peculiar kind in each clafs of animals ; 
 and it is the heavieft humour in the human body. In 
 water, however, a part goes off into a kind of cuticle, 
 like a cobweb, that fwims in the liquid ; the greater 
 part, which is feemingly of a pulpy nature, falls to the 
 bottom. In the femen which is long kept by chafte 
 people, Aiming globules mixed with the white liquor are 
 eafily to be feen. It has a very great quantity of mucus. 
 
 824. "Without the conveyance of this into the 
 womb, no clafs of animals, of which there are two 
 fexes, can be fecundated fo as to propagate their fpe- 
 
 ^ cies. The reafon of this was concealed from us, till the 
 microfeope taught, that in man, as w'ell as in all other 
 male animals, the feminal liquor is full of living ani- 
 malcules, refembling eels, only with a thicker head ; 
 and that thefe are always prefent in healthy femen, 
 from the time that a perfon comes of age ; but, before 
 that time, and in thofe who are fterile from a go- 
 norrhasa, they are abfent. That they are animacules, 
 appears evidently from their various motions, reftings, 
 and geftures of body. 
 
 825. It has been much doubted what could be the 
 ufe of thefe animalcules ; and in another place we fhall 
 confider the difpute concerning the opinion that they 
 are as it were the firfl; appearance of the future animal. 
 To me, in the mean time, the nature of the feminal 
 animalcules feems to be the fame with that of the eels 
 in vinegar or pafte. 
 
 826. That the femen is produced from the lymph of 
 the blood, and that the chyle is added to the lymph, 
 will appear probable from the hidden alacrity to venery 
 
 that 
 
Ch.XXIX. male genitals. 42p 
 
 that happens after eating, and which is leflened by fail- 
 ing. It is compounded of the liquor of the teftides 
 and feminal velfels, the former indeed being more evi- 
 dent in fome animals, and the coagulable milk of the 
 proftate gland. That liquor, however, only fecundates 
 which is generated in the teftides ; as we fee from gel- 
 dings, which, though they have the feminal veflels and 
 proftate, are yet barren. 
 
 827. The feminal fluid is retained in the veficles as 
 long as a man neither exercifes venery, nor fports in 
 imaginary dreams. But it is always a ftimulus to the 
 animal appetite of venery, as long as it is there prefent 
 in any quantity. But befides this, there is a confiderable 
 ftrong, volatile, and odorous part of the femen abforbed 
 again into the blood, where it produces wonderful 
 changes as foon as it begins to be formed ; fuch as the 
 protrufion of the beard, the covering of the pubes, a 
 change of the voice and paflions, horns in cattle, &c. 
 for thefe changes in the animal are not the confequences 
 of age, but of the feminal fluid, and are always abfent 
 in eunuchs. The growth and ftrength of caftrated a- 
 nimals are cqnftantly diminllhed ; and in like manner 
 the fiercenefs of their temper, and the ftrong fmell of 
 their whole body, are remarkably weakened. And 
 from the examples of fome animals, and even of man- 
 kind, it appears, that the irritation of this fluid has oc- 
 casioned death, by exciting convulflons. A retention 
 of the femen may follow from a narrownefs of the ex- 
 cretory duift, a fcirrhofity of the proftate, and other 
 caufes not fufficiently known. 
 
 828. The quantity of femen expelled at one time 
 from the human veficles is but fmall, more efpecially in 
 a man who has not long abftained from venery ; and it 
 is natural to think that the liquor can- be but flowly 
 produced from I’o fmall a fubcutaneous artery. Its ge- 
 neration is accelerated by love, by the prefence of the 
 beloved woman ; fo that it diftends its veffels with a fenfe 
 of pain. Nature herfelf, therefore, enjoins venery, 
 both for preferving the human race, and likewife the 
 
 3 G 2 health 
 
436 MALE GENITALS. Ch.XXIX. 
 
 health of every found man. !Sut that it comes from 
 the tefticle, is (hewn by difeafes, in which the dudlus 
 deferens being obftru£led, a fwelling of the tefticle has 
 enfued. From the veficle it does not go out, except by 
 the venereal adl. 
 
 829. Seeing the femen is in fmall quantity, that it 
 might be projefted with a greater force, and to a fur- 
 ther diftance, nature has joined another humour, which 
 is generated by the frojlate. This is a gland, ftiaped 
 like a heart, with the fmall end foremoft, fo as to fur- 
 round the origin of the urethra, but moft round its up- 
 per fide. This is one of the hardeft and moft^compacl 
 glands, of a peculiar fabric, yet not evidently conglo- 
 merate ; it prepares a thick, white, foft, or cream-like 
 liquor in a large quantity, which is poured out at the 
 fame time and from the fame caufes (840.) with the 
 femen itfelf, into a little valley or channel at each fide 
 of the openings of the feminal veficles, where, mixing 
 with the feminal fluid, it imparts thereto the white co- 
 lour and vifeidity with w'hich it is predominant. 
 
 830. But it was neceflTary for this canal of the ure- 
 thra to be firm and capable of a direct figure, that it 
 might be able to throw the femen with fome ftrength 
 into the diftant womb ; and therefore a three-fold ca- 
 vernous body furrounds it. The firft and proper ca- 
 vernous body of the urethra begins, as foon a? that ca- 
 nal has pafled the proftate, with a thick origin, almoft 
 like a heart, firft under the urethra, and then above 
 it, but thinner ; from thence it furrounds the whole ca- 
 nal, through the whole length of the penis, till the 
 lower part terminates in the glans, while the upper 
 part isreflefted back from the extremity of the urethra, 
 and, being dilated, returns in a direftion contrary to 
 that of the penis, which being circumferibed by a bread 
 circumference, gradually extenuated, and fomewhat 
 round, terminates the extremities of the cavernous bo- 
 dies, upon which it is incumbent, and with thofe for 
 the moft part communicates by an imperfeif feptum. 
 The fabric of this body is cellular, but of a larger fort 
 
 than 
 
Ch.XXIX. male genitals. 431 
 
 than the cells of the cavernous bodies, being compofed 
 rather of plates than fibres, interwoven like a net, and 
 intercepted betwixt two firm membranes. 
 
 831. Into this cavernous body of the urethra, the 
 blood is poured out from the arteries, which come from 
 deep branches fent off from the external hasmorrhoi- 
 dals (836.); the truth of which is demonflrated by the 
 injedion of any kind of fluid, which, being urged into 
 the faid arteries, eafily flows into thefe cellular fpaces, 
 furrounding the urethra. But thefe are not naturally 
 turgid with blood, becaufe there are veins open and 
 numerous enough in proportion to drink up and re- 
 turn what is poured in by the arteries ; but if the re^ 
 turn is impeded by comprefling thofe veins from the 
 powers hereafter mentioned (839.), the blood is then 
 retained within the cellular fpaces, while the arteries 
 continue to import it more fwiftlyand flrongly than the 
 veins return it. Thus the ftagnant blood diftends the 
 bulb of the urethra, together with its cavernous body, 
 and the glans itfelf. But this is performed generally 
 at the fame time when the other cavernous bodies of 
 the penis, with which this of the urethra has no com- 
 munication, are likewife rigidly diftended. 
 
 832. But the cavernous bodies of the penis arife 
 from the ofla ifchii and pubis, where they are conjoin- 
 ed by a white, cellular, very denfe, and firm fubftance ; 
 from whence inclining inward towards each other, they 
 take betwixt them the urethra, a little before its bulb, 
 where, changing their diredion, they go on parallel, 
 conjoined together, and with the urethra extended for- 
 ward along their middle, and terminate with an obtufe 
 end in the glans, and laterally they are comprehended 
 by the cavernous body of the urethra. Thefe bodies 
 are covered with a very firm integument, and their in- 
 ternal flefh is fpungy, like that of the urethra (830.), 
 like which it is capable of being diftended by the recep- 
 tion of the blood. Betwixt both cavernous facs there is 
 a middle feptum or partition, compofed of firm parallel 
 tendinous fibres, growing narrower downward j but 
 
 not 
 
432 MALE GENITALS. Ch. XXIX. 
 
 not continuous one to another, that the intermediate 
 fpaces might be larger and more numerous, as they are 
 more forward ; and that they might leave a free com- 
 munication betwixt the right and left fpungy body. O- 
 ther fuch robufl fibres run through the cavernous bo- 
 dies, and are very firmly inferted into the fides of their 
 membranous fac, fo as to prevent an aneurifm or over- 
 diftention of the penis. 
 
 833. Thefe cavernous bodies are furrounded with a 
 good deal of very tender cellular fubftance; of which 
 that fide lying next the cavernous bodies is denfe and 
 firm, like a membrane ; but from thence outward, to- 
 wards the Ikin, its fabric is cellular and very tender, 
 without including any fat, and continuous with the cel- 
 lular membrane of the ferotum, but always the more 
 tender the nearer the fkin it is ; and, by blowing air 
 into it, it appears to have a fine filky texture. But the 
 glans (830.) is naturally covered in fuch a manner, that 
 the Ikin is continued from the penis, and folded back 
 againft itfelf, as we obferve in the eye-lids; both folds 
 of the Ikin being covered with its proper cuticle, and 
 fluffed, each with its proper cellular flratum, under the 
 name ofy>re/)wt/w7«, or prepuce; which may be, like a cap, 
 drawn back from, and again brought over, the glans ; 
 at which it changes into a tender papillary body, vehe- 
 mently fenfible, covered w'ith its proper cuticle and 
 cellular fubftance, fpread over the reflected cavernous 
 body of the urethra (830.); and, finally, is continued 
 with the membrane of the urethra itfelf. The faid pre- 
 puce is tied by a double triangular ligament, by which 
 the common Akin is conjoined to that which makes the 
 covering of the glans. Upon the excavation that fur- 
 rounds the crown of the glans, as w-ell as upon the 
 crown itfelf, are.feated fimple febaceous follicles, which 
 feparate a liniment of a peculiar, fomew-hat fetid fmell, 
 from the nature of their feat, ferving to abate the attri- 
 tion of the fkin, as in other parts of the body. Finally, 
 the whole body of the penis is fuftained by a firm cel- 
 lular plate, compared into a kind of triangular liga- 
 ment. 
 
Ch. XXIX. MALE GENITALS. , 433 
 
 nient, which defcends from the fynchondrofis of the ofla 
 pubis, and is from thence continued into the denfe 
 cellular ftratum that furrounds the hard cavernous bo- 
 dies. 
 
 834. The whole human penis forms a cylindrical 
 body, deprefled on the upper part, of variable magni- 
 tude, whofe ofe is to be received into the female parts 
 of generation, and to carry thither prolific femen. - 
 
 835. Thefe cavernous bodies then of the penis, ha- 
 ving their fpungy fabric dillended in coition by the 
 blood retained by the veins, and Hill propelled by the 
 arteries, become rigidly turgid, and fuftain the other- 
 wife flaccid or but weakly filled urethra, in fuch a man- 
 ner that it may be able to condu£l the femen into the 
 diflant womb. All this is demonftrated from the diffec- 
 tion of brute animals in the ad of venery, from an ar- 
 tificial eredion, and from the injcdion of liquid mat- 
 ters into the veflels of the penis. The caufe is in love, 
 in the defire of pleafure, the fridion of the glans, va- 
 rious irritations of the bladder, teflicles, feminal veflfels, 
 urethra, from the urine, from abundance of good feed, 
 from the venereal poifon, from cantharides, whipping 
 with rods, or convulfion of the nerves. But the caufe 
 of this diflention remains ftill to be explained. The 
 dillribution of the blood-veflfels into the genital parts 
 are therefore to be here defcribed, to make it evident 
 how ready the comprefling caufe conllantly is to ad 
 upon the veins. 
 
 836. The aorta at the fourth vertebra of the loins, 
 and the vena cava at the fifth, are divided, the former 
 before the latter. The common iliac branches, not yet 
 arrived to the middle of the interval in the thighs, fend 
 off inward and downward a confiderable artery, call- 
 ed the hypogajlric^ which in the fetus is larger than the 
 femoral artery, and in the adult is equal to it. This 
 defcending into the pelvis, divides into four, five, or 
 fix principal branches ; of which the firlt is the iliacus 
 anterior^ which fupplies branches upward to the dura 
 mater, cauda equina, and loins, and afterwards in- 
 to 
 
434 MALE GENITALS. Ch. XXIX. 
 
 to the os facrum. The next, or facro-lateral artery, 
 goes off from the bone of that name, when it does not 
 arife from the former ; and the third, or Ulaca-pofte- 
 rlor^ is diftributed to the glutei mufcles. The fourth 
 is the ifchiatica defcendens, to feveral mufcles, nerves, 
 and levators of the anus, riie fifth trunk is that of 
 the hamorrhoidea injima or pudenda communis, which 
 in the cavity of the pelvis fends confiderable branch- 
 . es to the bladder, and to the redtum gives the middle 
 hemorrhoidal joined with the mefenterics; after which, 
 going out of the pelvis, it creeps by the fide of 
 the obturator, and gives off the external heemorr hoi- 
 deals to the fphindler and Ikin of the anus : then 
 dividing, it goes with an internal branch to the bulb 
 of the urethra and furface of the proftate, where 
 the external is again divided: here it enters deep- 
 ly the cavernous body of the penis, and runs through 
 its whole length ; while by another branch often joined 
 with the veffels of the bladder, it runs along the back 
 of the penis, according to the direction of its bodies, 
 and terminates with them by ramifications into the Ikin. 
 The fixth is the obturatrix, fpent upon the joint of the 
 femnr and adjacent mufcles. The laff is the umbili- 
 cal artery, to be defcribed in treating of the fetus ; 
 although in adults it fends off fome branches to the 
 bladder, from its thick callous vagina. Sometimes one 
 or more of thefe arteries come from the common trunk. 
 The fkin of the penis and ferotum have their arteries 
 from the epigaflric, and from the internal branch of 
 the crural. Thefe external arteries communicate in 
 many places with the internal. 
 
 837 . The veins are, in general, diftributed in like 
 order with the arteries. They come off in two trunks 
 from the iliacs, joining together into a net ; and then 
 the hcemorrboidai vein, bending round under the os 
 pubis, forms a large plexus, fpread with the veins of 
 the pelvis upon the proftate and feminal veficles : from 
 hence the vena penis arifes, which is often fingle, and 
 furnifhed with valves to forward the return of the 
 
 blood. 
 
Ch. XXIX. MALE GENITALS. 435 
 
 blood. The external veins of the penis and fcrotum 
 go to the faphena and crural, communicating in feveral 
 places with the internal veins, more efpecially at the ba- 
 fis of the prepuce. 
 
 838. Lymphaiic veffels oi the penis are, by moH; e- 
 minent anatomills, faid to run under the Ikin towards 
 the groins. The nerves of this part are both numerous 
 and very large, and accompany the arteries of the pe- 
 nis from the trunk of the great fciatic nerve. But the 
 bladder, rertum, and uterus, are fupplied by the lower 
 mefenterk plexus, which arifes from the middle one, de- 
 fcending into the pelvis. 
 
 839. In order to dillend the penis, there mull be ei- 
 ther a comprelTure of the vein (837.), bringing back 
 the blood from the cavernous bodies of the penis or 
 urethra; or at Icaft it is neceffary that there be a con- 
 ftriftion of the leffer veins that every where open with- 
 in the cavernous bodies, to hinder them from abforbing 
 and returning the blood from the arteries. The firft, 
 however, may be effefted by the levator, drawing up 
 the proftate and bladder : but it is very probable, that, 
 as we fee in the nipples of the fuckling mother, in 
 the gills of the peacock, and in the blulhing or rednefs 
 of the face from paffions of the mind, as well as from 
 brute animals, which all couple without the ufe of any 
 erector mufcle ; from the erections which take place in 
 animals totally different from man, and efpecially thofe 
 which take place in birds very fwiftly ; from the libidi- 
 nous reft of the ereftor mufcles themfelves in the erec- 
 tion of the penis, and from their unfitnefs for compref- 
 fmg the veins ; from all thefe it is probable, that the 
 courfe of the blood through the vein may be retarded, 
 without the immediate ufe of any mufcle ; and that by 
 the power of the latent multitude of fmall nervous 
 bridles, by whofe conftriftion, from the force of plea- 
 fure, the veins are coinpreffed and ftraitened, fo as to 
 return lefs blood to the trunks, at that time, than what 
 is imported by the arteries, which are not only free 
 from any ftridure, but, by the increafe of the pulfe, 
 
 3 H bring 
 
43^ MALE GENITALS. Ch. XXIX. 
 
 bring a greater quantity of blood, which caufe alfo con- 
 tributes to produce the erection. But the caufe of this 
 conftriftion in the nervous bridles or fphinjfters them- 
 felves depends upon a mechanical irritation of the nerves^ 
 and from fomething more fubtile, by which means the 
 penis is immediately erefted. 
 
 840. A long continued and violent erection is com,- 
 monly joined, at lad, with an expulfion of the femen ; 
 and this requires much greater force than is requifite 
 for the erection only. For the femen follows at that 
 time when the irritation of the nerves is arrived at its- 
 greateft height: and in natural venery indeed, when 
 at length the cellular fpaces of the urethra and its con- 
 tinuous glands, w'hich are at lall filled, become fo far 
 diilended w'ith a large quantity of warm blood, that 
 the nervous papillae, ftretched out in the latter, be- 
 come violently affcfted from the irritating or plea- 
 furable caufe ; the feminal veficles are evacuated by 
 the levator mufcles of the anus, which prefs them a- 
 gainft the refilling bladder wfith a convulfive motion, 
 excited either by a voluptuous imagination, or from the 
 pruritus that is exquifite in the nerves of the glans, 
 principally in its lower part, which is in the neighbour- 
 hood of the frenum. Hence the femen is never dif- 
 charged with any of the urine, in an healthy man ; be- 
 caule the expulfion of it requires the bladder to be do- 
 led or drawn up firmly together; for, while lax, it af- 
 fords little or no refifiance to the feminal veficles. The 
 tranfverfe mufcles feem to dilate the canal of the ure- 
 thra for the reception of the femen expreffed from the 
 veficles. 
 
 841. Soon afterwards the powers conftringing the 
 urethra are, from the irritation of the very fenfible fa- 
 bric of that canal, put into action. To this conftriclion 
 conduce principallv the acceleratbr (802.), which makes 
 a powerful concullion of the bulb and adjacent part of 
 the urethra, fo as to propel the contents more fwiftly, 
 in proportion as the bulb has a larger diameter than 
 that of the urethra. But that this may ad firmly, the 
 
 fphinder 
 
Ch.XXIX. male genitals. 
 
 437 
 
 •fphinfter of the anus, together with that of the bladder, 
 muft be well Ihut. The accelerator mufcle feems alfo 
 principally concerned in the erection, by compreffing 
 the veins of the corpus cavernofum of the urethra. At 
 the fame time the eredores -penis, as they are called, 
 arifing from the tubercles of the ifchium, become 
 flrong, and are inferted into the cavernous bodies, fu- 
 liaining the penis as a fort of medium betwixt the 
 tranfverfe and perpendicular direftion. Thus the fe- 
 men is drove into the vagina and into the uterus itfelf, 
 in a prolific coition ; the whole adtion of which is very 
 impetuous, and comes near to a convulfion ; whence it 
 wonderfully weakens the habit, and largely injures the 
 whole nervous fyftem, as the maladies arifmg from 
 thence feem to indicate, which come from the affedlion 
 of the nerves, without which the femen cannot be ex- 
 pelled. 
 
 ■842.^ I HE uterus is feated in the upper part of the 
 JL pelvis, v/ith the bladder before, and the rec- 
 tum behind it, without adhering to either of them, and 
 has its mouth turned a little forwards. In an adult wo- 
 man, it is contained within the pelvis; but in an infant, 
 k lies above it. In women, the ‘peritonaeum defcends 
 from the os pubis into the pelvis, over the pofterior 
 face of the bladder, down to the bottom or mouth of 
 the uterus : from whence again it afcends over the fore- 
 fide of the uterus ; and paffing round its convexity, de- 
 fcends on the pofterior fide down to the vagina, from 
 whence it extends laterally or tranfverfely on each fide, 
 including the redlum with lunated folds, which is all the 
 difference betwixt the female and male peritonaeum. 
 But this fame peritonaeum, coming into the pelvis from 
 the iliac velfels, and broadly adhering to the fides of 
 
 CHAP. XXX. 
 
 Of the Virgin Uterus. 
 
 the 
 
VIRGIN UTERUS. Ch. XXX. 
 
 438 
 
 the uterus and vagina, is folded back over itfelf, and 
 divides the pelvis into two parts, the anterior and polle- 
 rior, like a partition, under the denomination of liga- 
 mentum latum. Thus the pcritonseum accurately con- 
 ne£ls the uterus, without the intervention of any fat, fo 
 as to ferve it on all fades as an external coat or cover- 
 ing. It does not, however, hinder the uterus from be- 
 ing totally free and moveable, 
 
 843. The body of the uterus is ufually dillinguifh- 
 ed from its neck. The body is flatly convex bcfoie 
 and behind, with acute edges on each fide and at the 
 meeting of its convexities, but converging gradually 
 afterwards for fome way ; in its upper part, moderately 
 convex. It has a peculiar fabric, being made up of a 
 clofe, firm, but fomewhat fucculent and cellular flelh, in 
 which we perceive the appearance of muiEular fibres, 
 more efpecially in thofe women that have born chil- 
 dren : fome of which fibres are flat, and mixed with 
 one another into a kiifd of net-work ; others run along 
 the uterus longitudinally, from the bottom to the mouth 
 of the uterus, difpofed in various circles, and particu- 
 larly at the fundus betwixt the tubes, and hkewife in 
 the neck near the mouth. In beads, the uterus is ma- 
 nifedly mufcular; and in women, likewife, gives evident 
 figns of a contraftile power. Its outer coat is received 
 from the peritonaeum. As for any mucous finufes- 
 varioully branching and dividing within the flefli of the 
 uterus, after repeated inquiries we now declare, that 
 we have not been able to find any; only feme veins, 
 furrounded with cellular fubdance, by which their dia- 
 meters are fudained. The internal membrane of the 
 uterus is continued from the cuticle; in the upper part 
 of the cavity, fleecy ; and in the lower part, callous, 
 like valves. The cavity of the uterus is finall, for the 
 mod part triangular upward, and below like a com- 
 preffed cylinder. I'he cylindric part, which is called 
 the cervix or rieck.^ is compreffed, thick, and has alfo 
 a cylindric cavity within. It is altogether rough, with 
 callous wrinldes rifing up into an edge, whence they 
 
 incline 
 
Ch.XXX. virgin uterus. 439 
 
 incline towards the vagina. Thefe recede laterally from 
 the anterior and pofterior margin, joining together by 
 fmall wrinkles, in the intervals of which are fmall 
 mucous finufes, with finall pellucid fpherules, filled 
 with a very clear liquor, in fome parts interfperfed 
 through the upper region of the cervix uteri, differing 
 both in their number and magnitude. It is not un- 
 common for the uterus to be difiinguifiied by a line or 
 protuberance extended through its middle. The cer- 
 vix is terminated by the os internum uteri, with a 
 tranfverfe rim, forming protuberant lips, which projeQ; 
 for fome length into the vagina, are received by 
 its blind extremity, and projeft into it obliquely for- 
 ward. But it is full of mucus, and mucous finufes 
 fituated in its fwelling lip. 
 
 844. 'I’he triangular part of the uterus fends out, 
 from its lateral angles, canals, in feme meafure folded 
 together by the cellular fubltance, growing gradually 
 broader, and, being again a little contracled towards 
 their extremity, they proceed towards the ovary, firft in 
 a tranfverfe direction, and afterwards a little defeend- 
 ing, but with fome variation, under the denomination 
 of the uterine tubes. Their external membrane is from 
 the peritonaeum : for they are included within the du- 
 plicature pf the broad ligament, which is a produdion 
 of that membrane ; internally they are wrinkled aimoft 
 reticularly, lined with mucus, extended to a confide- 
 rable length by intervening plates or folds ’which broad- 
 ly crowm the opening of the tube, wdiich is alfo con- 
 neded to the ovary. Betwixt the two membranes is 
 fomething of a fpungy cellular fubilance, of a {lender 
 texture. They alfo contain ufually a mucus, the ori- 
 gin of w’hich is not known. There are alfo great num- 
 bers of veffels, and perhaps fome mufcular fibres, but 
 the latter are more obfeure. They are fupported by 
 the proper fold of the peritonaeum which goes out 
 from the broad ligament. 
 
 845. But the ovaries., included in the fame duplica- 
 ture of the broad ligament behind the tubes, are feated 
 
 tranfverfely, 
 
440 VIRGIN UTERUS. Ch.XXX. 
 
 tranfverfely, and conjoined to thefe tubes by a ligamen- 
 tary expanfion of their own, which is long enough to 
 allow them a free motion. They are fomewhat of an 
 oblong or oval figure, deprelfed on each fide, convex 
 upon their unconnedled fide, and- half elliptical ; but that 
 which is conneded with the ligament is ftraight. 
 Their membrane, which comes from the peritonaeum, is 
 thick, and almofl cartilaginous. Their fabric nearly 
 enough refembles that of the uterus itfelf ; being a clofe, 
 white, cellular fubftance, compared together, without 
 any fat. The margin of the broad ligament, receding 
 from the uterus to fuftain the ovary, has fomcthing of 
 a more folid and thick fubftance, refembling a liga- 
 ment, yet is not a hollow or true canal. 
 
 846. But, in the ovary even of a tender virgin, are 
 fituated round veficles made of a pretty ftrong pulpy 
 membrane, connected every whei«e to the ovarium 
 by cellular threads, which are filled with coagulable 
 lymph ; of an uncertain number and magnitude, being 
 found in one ovary to 15 and upwards. Thefe 
 remarkable bodies are found very widely dilfufed 
 through all animals, even fuch as have but one fex. 
 
 847. Laftly, the uterus fends out from the fame 
 lateral angles of its triangular body downward, a kind 
 of fafciculus, compofed of long cellular fibres and fmall 
 veffels, which, becoming fmall in its progrefs, goes 
 out of the pelvis through the ring of the abdomen 
 (812.) into the groin, where it fplits into branches, and 
 diffolves into fmall velfels, w'hich communicate with the 
 epigaflrics. Whether or no it has any long fibres pro- 
 pagated from the uterus itfelf, does not plainly appear, 
 
 848. The arteries of the uterus are from the hypo- 
 gaftrics ; a confiderable branch of which goes off, like 
 that to the bottom of the bladder in men ; or at leaft it 
 arifes from the umbilical trunk, or immediately below 
 that trunk, and makes the common artery belonging 
 to the uterus, bladder, and reftum. It fpreads on the 
 lower parts of the uterus, almofl at the extremity of its 
 neck: and, afcending upwards, fends tranfverfe in- 
 flected 
 
Gh.XXX. virgin uterus. 44.1 
 
 fleeted branches to the uterus, makes numerous anaf- 
 tomofes with the fpermatics, and often gives arteries 
 to the tube itfelf. Another plexus of branches tends 
 downwards to the vagina, and follows it a long way ; 
 although there is otherwife a proper vaginal artery ori- 
 ginating in the pelvis, and branches fometimes come 
 from the mefocolic. There are alfo femlnal veiTels 
 which have the fame origin as in men ; and form a 
 plexus, which, from its fimilitude to the tendrils of a 
 vine, is called pampiniformis. This "plexus, defcending 
 over the pfoas mufcle into the pelvis, divides into two 
 plexufes. The pofterior furrounds the ovary itfelf, 
 with many circles, elegantly diflributed through its fub- 
 fiance and the ova themfelves. The anterior both fup- 
 plies the tube, and defcends to the uterus itfelf, in which 
 it fends out winding branches upward and downward, 
 and fome branches that are detached to the bladder. 
 Another artery is the middle hamorrhoidal^ coming 
 from the common trunk of the pundendeal, a confide- 
 rable way forward with the vagina ; to which, and to 
 the bladder and re£tum, it is diflributed. The begin- 
 ning of the vagina likewife, and the clitoris, have arte- 
 ries from the external hemorrhoidal, which are diflri- 
 buted like thofe of the penis, fome inwardly, others 
 fuperficially, both of which inofculate with the vefical 
 branch. 
 
 849. The courfe of the uterine veins is like to that 
 of the arteries, originating from the trunks of the hy- 
 pogallrics ; they are the internal uterine, the vaginal, 
 the middle hemorrhoidal, the external circumflex, and 
 thofe of the clitoris. But they make a remarkable 
 plexus on each fide, which occupies the fides of the va- 
 gina below the clitoris. Below that, it is joined into a 
 continued plexus with its companion on the other fide. 
 A plexus alfo from the external hemorrhoidal, and 
 joined with the vefical veffels, goes to the clitoris, as 
 well as to the penis. It has no valves, except a few in 
 the fpermatics. Thefe, in a very large bundle, go to 
 the ovarium, and wings of a bat. 
 
 850. Within 
 
442 VIRGIN UTERUS. Ch.XXX. 
 
 850. Within the uterus itl'elf the arteries terminate 
 in exhaling branches on its internal cavity. By child- 
 birth thefe go off into little pendulous productions, like 
 very finall eels. Thus the veins of the utrrus are at the 
 fame time very large finufes ; for the veins are cnor- 
 moufly augmented, and open with very large mouths 
 into their cavity. 
 
 851. Lymphatic "jcJlels are found in the uterus of 
 brutes, but more rarely in the human ; they have been 
 obferved, however, by very eminent anatomids. 
 
 852. ,The nerves are fupplied from the lower mefo- 
 colic plexus, united with thofe of the facrum, which 
 fends out large branches to the bladder, 'womb, and 
 redlum ; befides which, there are a few nervous twigs 
 that defeend through the broad ligament to the ova- 
 ries, and others from the nerve that goes with the vef- 
 fels to the clitoris. But the ovary has alfo its proper 
 nerves from the renal plexus, hmilar to thofe which go 
 to the tefticles of the male. The great number of the 
 nerves, therefore, make thefe parts extremely fen- 
 fible. 
 
 853. The deferiptions we have hitherto given, are 
 in common to all ages of the female ; but about the 
 13th year, or fomewhat later, nearly at the fame time 
 when femen begins to form itfelf in the male, there are 
 likewife confiderable changes produced in the female. 
 For, at this time, the whole mafs of blood begins to 
 circulate with an increafed force, the breads are 
 filled out, and the pubes begins to be cloathed ; at the 
 fame time the nienfes in fome meafure make their 
 appearance ; by a common law of nature, although in 
 different countries both the time and quantity of the 
 flux is different. 
 
 Sqq. But, before the menftrual flux, there are vari- 
 ous fymptoms excited in the loins, heavy pains, fome- 
 times like colic pains, with an increafed pulfe, head- 
 achs ; and cutaneous puflules commonly precede, and 
 a white juice commonly flows from the uterus. For 
 now the fleecy veffels of the uterus, which in the ftate 
 
Ch.XXX. virgin uterus. 443 
 
 of the fetus, were white, and tranfuded a fort of milk, 
 as in the young girl they tranfuded a ferous liquor, do 
 now begin to fwell with blood ; the red parts of which 
 are depofued through the veflels into the cavity of the 
 uterus. This continues fome days, while, in the mean 
 time, the firft troublefome fymptoms abate, and the ute- 
 rine veffels, gradually contratling their openings, again 
 diftil only a little ferous moifture as before. But then 
 the fame efforts return again at uncertain intervals in 
 tender virgins ; till at length, by degrees, they keep 
 near to the end of the fourth week ; at which time fol- 
 lows the flux of blood, as before, which is periodically 
 continued to about the 30.th year; though the diet, 
 country, conflitution, and way of life, caufe a great va- 
 riation in this difcharge. Pregnancy commonly pro- 
 duces a ffoppage of the menfes. 
 
 855. This difcharge of blood from the veffels of the 
 uterus itfelf, is demonftrated by infpedlion in women 
 who have died in the midft. of their courfes ; and in 
 living women, having an inverfion of the uterus, the 
 blood has been feen plainly to diftil from the open 
 orifices : in others, in whom, when the menfes have 
 been deficient, the uterus has appeared full of con- 
 creted blood. It alfo appears from the nature of the 
 uterus itfelf, full of foft fpungy veffels, compared with 
 the thin, callous, little fleecy, and almofl; bloodlefs fub- 
 fiance of the vagina. But that this is a good and found 
 blood in an healthy woman, appears both from the 
 foregoing and innumerable other obfervations. For 
 nothing hinders the blood from being fent forth thro* 
 the vagina, as in other cafes it is through the inteffinura 
 redlum, and laffly through the remoteft parts of the 
 body. 
 
 856. Since none but the human fpecies are properly 
 fubje6l to this menftrual flux of blood, (although there 
 are fome animals who, at the time of their vernal copu- 
 lation, diffil a fmall quantity of blood from their geni- 
 tals), and fince the body of the male is always free from 
 the like difcharge, it has been a great inquiry in all 
 
 3 I ages. 
 
444 VIRGIN UTERUS. Ch. XXX. 
 
 ages, what fliould be the caufe of this fanguine excre- 
 tion peculiar to the fair fex. To this effect the attrac- 
 tion of the moon, which is known to raife the tides of 
 the fea, has been accufed in all ages ; others have re- 
 ferred it to a ffiarp ftiinulating humour, fecreted in the 
 genital parts themfclves, the fame which is the caufe of 
 the venereal defire. But if the moon was the parent of 
 this effect, it would appear in all women at the fame 
 time ; which is contrary to experience, fince there is 
 never a day in which there are not many women feized 
 with this flux ; nor arc there fewer in the decreafe than 
 the increafe of the moon. As to any ffiarp ferment 
 feated in the uterus or its parts, it will be always in- 
 quired for in vain ; where there are none but mild mu- 
 cous juices, and where venery, which expels all thofe 
 juices, neither increafes nor lefl'ens the menftrual flux r 
 and women deny, that, during the time of their menfes, 
 they have any increafed delire of venery ; feeing at 
 that time moll of the parts are rather pained, and lan- 
 guid ; and the feat of venereal pleafure is rather in the 
 entrance of the pudendum than in the uterus, from 
 which lall the menfes flow. But, laffly, that the nven- 
 ftrual blood is forced out by fome caufe exciting the 
 motion of the blood againfl the veffels, appears from 
 hence, that, by a retention, the courfes have been 
 known to break through all the other organs of the 
 body, where no vellicating ferment could be feated, 
 even fo as to burft: open the veffels of each organ ; nor 
 is toe effe£l of the retained blood circumferibed by 
 thofe parts which pour out the venereal humour. 
 
 857. Nature has, in general, given women a body 
 with fofter or loofer veffels, and folids that are lefs ela- 
 ffic ; their mufcles are alfo fmaller, with a greater quan- 
 tity of fat interpofed both betwixt them and their fibres; 
 the bones too are ffenderer and lefs folid, and their 
 furfaces have fewer procelTes and afperities. Moreover, 
 the pelvis of the female is, in all its dimenfions, lar- 
 ger ; the offa ilia fpread farther from each other ; and 
 the os facruni recedes more backward from the bones 
 
 of 
 
Ch.XXX. virgin uterus. 445 
 
 of the pubes, while the ofia ifchii depart more from 
 each other below ; but, above all, the angle in which 
 the bones of the pubes meet together to form an arch, 
 is in the female remarkably more large or obtufe : 
 which differences are confirmed by the obfervations of 
 the greateft anatomifts ; and from neceffity itfelf, which 
 requires a greater fpace for a greater number of vifcera 
 in the pelvis. Moreover, the uterine arteries are con- 
 fiderably large, more fo than in men ; and have a great- 
 er proportion of light, with refpect to the thicknefs of 
 their coats : but the veins are, in proportion, lefs ample 
 than in the men ; and of more firm refifting texture, 
 than in other parts of the body. From hence it follows, 
 that the blood, brought by the arterial trunk to the 
 womb, by paffing from a weaker artery into a narrow 
 and more refifting vein, will meet with a more difficult 
 return, and confequently endeavour to efcape or go off 
 by the lateral veffels. 
 
 859. The female infant new-born has her lower 
 limbs very fmall; and the greater part of the blood, be- 
 longing to the iliac arteries, goes to the umbilicals, 
 fending down only a fmall portion to the pelvis. Flence 
 the pelvis is fmall, and but little concave ; fo that the 
 bladder and uterus itfelf, with the ovaries, projeft be- 
 yond the rim of the pelvis. But when the fetus is born, 
 and the umbilical artery is tied, all the blood of the 
 iliac artery defcends to the pelvis and lower limbs, 
 which of courfe grow larger, and the pelvis fpreads 
 wider and deeper: fo that, by degrees, the womb and 
 bladder are received into its cavity, without being any 
 longer compreffed by the inteftines and peritonasum, 
 when the abdominal mufcles urge down upon the lower 
 parts of the abdomen. When now the increafe is per- 
 fect, or next to it, then in general we find thofe arte- 
 ries of the uterus largeft, which in the fetus were lead:, 
 and eafily injefted with wax ; and all things are chan- 
 ged in fuch a manner, that the hemorrhoidal artery is 
 now in place of the hypogaftric (836.), when formerly 
 the umbilical had been the trunk of that artery. More 
 
 3 I 2 blood. 
 
44^ VIRGIN UTERUS. Ch. XXX. 
 
 blood, therefore, at that time comes into the uterus, 
 vagina, and clitoris, than was formerly in ufe to do. 
 
 860. At the fame time, when the growth of the body 
 begins confiderably to diminilh, the blood, finding eafy 
 admittance into the completed vifcera, is made in a 
 greater quantity, the appetite being now very fiiarp in 
 either fex, in both which a plethora from thence fol- 
 lows. In the male, it vents itfeif frequently by the 
 nofe, from the exhaling vclfels of the pituitary mem- 
 brane being dilated to fo great a degree without a rup- 
 ture, as to let the red blood diftil through them (458.)-, 
 and now the femen fir 11 begins to be fecreted, and tlie 
 beard to grow. But in the female, the fame plethora 
 finds a more eafy vent downw^ard ; being that way di- 
 redled partly by the weight of the blood itfeif, to the 
 the uterine veffels now much enlarged, of a foft fleecy 
 fabric, feated in a loofe hollow part, with a great deal 
 of cellular fabric interfperfed, which is very yielding 
 and fucculent, as we obferve in the womb : for ihcie 
 caufes, the veffels being eafily diftendible, the blood finds 
 a more eafy paffage through the very loft fleecy exha- 
 ling veffels, which open into the cavity of the uterus, 
 as being there lefs refilled than' in its return by the 
 veins, or in taking a courfe through any other part ; 
 becaufe, in females, we obferve the arteries of the head 
 are both fmaller in proportion, and of a more firm re- 
 fifting texture. The return of the fame is there- 
 fore more flow, both becaufe the flexures of the arte- 
 ries, from the increafed afflux of the blood, beconre 
 more ferpentine and fit for retarding the blood’s mo- 
 tion, and likew'ife becaufe it now returns with difficulty 
 through the veins. The blood is, therefore, firfl col- 
 lected in the veffels of the uterus, which at this time, 
 by repeated difleCtions, are obferved turgid or fwellcd ; 
 next it is accumulated in the arteries of the loins and 
 the aorta itfeif, which, urging on a new torrent of blood, 
 impelled from the heart by degrees, augments the 
 force, fo far as to open and w'edge the red blood into 
 the ferous veffels, which at firfl tranfmit an increafed 
 
 quantity 
 
Ch.XXX. virgin uterus. 4^7 
 
 quantity of warm mucus, afterward a reddifh-coloured 
 ferum ; and by further opening, they at laft emit the 
 red blood itfelf, which, however, in this difcharge, has 
 ufually a greater proportion of ferum. The fame greater 
 impulfe of blood, determined to the genital parts, drives 
 out the hitherto latent hairs, increafes the bulk of the 
 clitoris, dilates the cavernous plexus of the vagina, and 
 whets the female app'rtite towards venery. According- 
 ly we find, that the quantity of the menfirual fiux, and 
 the earlinefs of their appearance, are promoted by every 
 thing that either increafes the quantity or momentum 
 of the blood with refpect to the body in general, or 
 which diredf the courfe of the blood more particularly 
 towards the uterus ; fuch as joy, luff, bathing of the 
 feet, a rich diet, warm air, and lively temperam.ent of 
 body. It is diminifhed by thofe things which diminifli 
 plethora and the motion of the blood, as want, grief, 
 cold air, floth, and difeafcs which have gone before. 
 
 86 1 . When fix or eight ounces of blood have been 
 thus evacuated, the unloaded arteries now’ exert a great- 
 er force of elafticity, and, like all arteries that have 
 been overcharged with blood, contract themfelves by 
 degrees to a lefs diameter, fo as at length to give paf- 
 fage only to the former thin exhaling moiflure ; but 
 the plethora or quantity of blood, being again increa- 
 fed from the fame caufes, a like difcharge will always 
 more eafiiy enfue through the veflels of the uterus, af- 
 ter they have been once thus opened, than through any 
 other part. Nor is there any occafion to perplex our- 
 felves about the caufe, why this periodical difcharge is, 
 for the mofl part, nearly regular or menfirual ; for this 
 depends upon the proportion of the quantity and mo- 
 mentum of the blood daily colledled, together with the 
 refinance of the uterus, which is to yield again gradu- 
 ally to the firfl courfe. Therefore this critical difcharge 
 of blood never waits for the interval of a month, but 
 flows fooner or later, according as the greater quantity 
 of blood in plethoric women is determined, by lull or 
 other caufes, towards the uterus. Finally, they ceafe 
 
 to 
 
448 VIRGIN UTERUS. Ch. XXX. 
 
 to flow altogether, when the uterus, like all the other 
 folid parts of the body, has acquired fo great a degree 
 of hardnefs and reflftance, as cannot be overcome by 
 the declining force of the heart and arteries, by which 
 the blood and juices are driven on through all the vef- 
 fels. This increafed hardnefs in the old uterus is fo 
 remarkable in the arteries and ovaries, that it eafily dif- 
 covers itfelf both to the knife and the injeftions of the 
 anatomifl. But, in general, brute animals have no 
 menfes ; becaufe, in them, the womb is in a manner 
 rather membranous than flefhy, with very firm or re- 
 filling veflels, which, with the difference of their po- 
 flure, never permit a natural hemorrhage from the no- 
 ftrils or other parts. They are wanting in men, be- 
 caufe in that fex there is no fpongy organ fit for re- 
 taining the blood; and likcwife becaufe the arteries of 
 the pelvis are both harder in proportion than the veins 
 and lefs, and thus the impetus of the blood in the lower 
 limbs is turned away, and which veflels in men are lar- 
 ger, as thofe of the pelvis are fraaller. 
 
 862. It will, perhaps, be demanded, why the breafts 
 fill out at the fame time with the approach of the menfes ? 
 We are to obferve, that the breads have many particu- 
 lars in their fabric, common to that of the uterus ; as 
 appears from the fecretion of the miik in them after the 
 birth of the fetus, which increafes or diminiflies in 
 proportion as the lochial flux is either increafed or di- 
 miniflied ; from the fimilitude of the ferous liquor, like 
 whey, found in the uterus, fo as to refeinble milk, in 
 thofe who do not fuckle their children, being of a thin 
 and white confidence, appearing very evidently in 
 brute animals ; alfo from the turgefcence or ereftion of 
 the papillae or nipples of the bread by friction, analo- 
 gous to the erediion of the clitoris. Therefore, the 
 lame caufes which didend the velTels of the uterus, 
 likewife determine the blood more plentifully to the 
 breads; the confequence of which is an increafed bulk 
 and turgefcence of the conglomerate glandules and cel- 
 lular fabric which compofe the breads. 
 
 C H A P. 
 
449 
 
 Ch.XXXI. conception. 
 
 CHAP. XXXI. 
 
 Of Conception. 
 
 863. TT is very difficult to difcufs this fubjedl, as 
 X we have to fearch out what happens in the 
 inward parts of a woman, when in her begins to 
 germinate the life of a new man, whom, in pro- 
 per time, file brings forth into the light. We fhall re- 
 late, in the firft place, therefore, thofe things which 
 experience fhewsto be true; and then add thofe hypo- 
 thefes by which learned men have endeavoured to fup- 
 ply fuch things as .are not evident from the fubjeft it- 
 felf. How few things are afcertained on this fubjedt, 
 and how difficultly they are afcertained, I have learned 
 by too much experience. 
 
 864. That fome light may be thrown on fuch a dark 
 fubjed, we fliall begin with the mofl fimple animals, 
 and afterwards take notice of what nature has added in 
 others whofe fabric is more compounded. The fmall- 
 eft animals then, which have very few or no limbs, the 
 leafl diflindion of parts, the fhorteft life, the vital func- 
 tions both few and very fimilar to one another ; thefe 
 animals bring forth young ones like themfelves, with 
 no diftindion of fexes, as all of them are fruitful, and 
 none imparts fecundity to the reft. Some of them ex- 
 clude their young whom they have conceived in their 
 body, through a certain cleft ; from others, fome limbs 
 fall off, which are completed into animals of a kind fi- 
 milar to thofe from which they have fallen off. This 
 kind of generation is extended very wide, and compre- 
 hends the greater part of animal life. 
 
 865. The next to thefe, which are a little more 
 compounded, all bring forth their young ; yet in fuch 
 a manner, that in their bodies is generated a certain 
 particle peculiar to themfelves, dilfimilar to the whole a- 
 nimal, and contained in fome involucra, within which 
 
 lies 
 
450 CONCEPTION. Ch. XXXI. 
 
 lies the animalcule that is afterwards to become fitnilar 
 to that within which it is produced ; this is commonly- 
 called an A great part of thefe animals is im- 
 
 moveable. 
 
 866. The animals which follow are not indeed nu- 
 merous, but have both eggs, and male fr.men befides ; 
 fo that both fexes are joined in the fame animal. But 
 we call it ma/e femen, becaufe it is neceffary for fprink- 
 ling the eggs in order to render them prolihc, although 
 it never grows alone in the new animal. In this clafs, 
 therefore, a juice is prepared by its own proper or- 
 gans, which is likewife poured on the eggs through or- 
 gans proper to itfelf, but different from the former, in 
 order to generation. 
 
 867. Thofe animals are much more numerous which 
 have both a male juice and female eggs; yet fuch as 
 cannot fecundate themfelves, but Hand in need of real 
 venery. For two animals of this kind agree in the 
 work of fecundation, in fuch a manner, that each im- 
 pregnates the other with its male organs, and again fuf- 
 fers itfelf to be impregnated in its female ones by the 
 male parts of the other. 
 
 868. And now the nature of animals approaches 
 nearer and nearer to that of the human race; of which, 
 namely, fome individuals of a fimiliar kind have only 
 male organs, and the fame males fprinkle their feed on 
 the female eggs of others. Very many cold ones 
 fprinkle their feed upon the eggs after they are poured 
 out of the body of the mother. Warm animals injeft 
 their femen into the uterus of the female. But now, if 
 eggs are generated within the body of the female, they 
 are brought forth covered with Ihells or membranes ; 
 but if the female has a live fetus in its uterus, it is born 
 quite free of any involucrum; but the difference be- 
 tween thefe oviparous and viviparous animals is but 
 fmall ; fo that in the fame clafs, and the fame genus, 
 fome animals lay eggs, others produce live fetufes ; 
 and lafUy, the fame animal fometimes lays eggs, and 
 fometimes brings forth live young. 
 
 685?. From 
 
Ch. XXXI. CONCEPTION^. 451 
 
 869. From this review of animals it appears, that all 
 animals are produced from others fimilar to them- 
 felves ; many from a part of it Ifmilar to the whole ; 
 others from an egg of a peculiar ftrudure ; but that 
 all thefe do not ftand in need of male femen. Laftly, 
 the more moveable and lively animals only,whofe bodies 
 are of a more complicated ftridure, are endowed with 
 a double fyfliem for generation ; and the difference of 
 fexes feems to be added for the bond of focial life, and 
 for the fafety of a lefs numerous progeny. 
 
 870. For the certain effufion of this male juice into 
 the female organs, both fexes are inflamed with the 
 mofl; vehement defires : the male indeed has the moft 
 lively ones, becaufe the female is at all times ready to 
 fuffer the venereal congrefs ; and thence it behoves the 
 male to be animated with a defire of venery, when he 
 has plenty of good feed, and fuch as is of a prolific 
 nature. Therefore this is the greatefl caufe of vene- 
 real defire in him ; but in females, of the brute kind 
 efpecially, fome kind of inflammation in the vagina, 
 which excites an intolerable itching. 
 
 871. But nature has firft added to the womb, 
 both in women and in quadrupeds, a vagina or 
 round membranous cavity, eafily dilatable, which, as 
 we have already feen (843.), embraces and furrounds 
 the proje£fing mouth of the uterus ; from whence it 
 defeends obliquely forward under the bladder, and 
 refting upon the redlum with which it adheres, and 
 laftly opens under the urethra with an orifice a little 
 contracted. This opening, in the fetus and in virgins, 
 has a remarkable wrinkled valve, formed as a produc- 
 tion of the fkin and cuticle, under the denomination of 
 hymen, which ferves to exclude the air or water; not 
 perhaps without fome kind of moral ufe, feeing this 
 membrane, as far as I know, is given to women alone. 
 It is circular, excepting a fmall deficiency under the 
 urethra, which yet is not always conftant, but fpreads 
 itfelf very broadly below towards the anus. This 
 membrane being infenfibly worn away by copulation, 
 
 3 K its- 
 
452 CONCEPTION. Ch.XXXI. 
 
 its lacerated portions at laft difappear. The caruncles, 
 which are called myrtiformes, are partly the remains of 
 the flrattered hymen, and laftly the valves of the mu- 
 cous lacuntE hardened into a kind of fldh. 
 
 872. The fabric of the vagina is fomewhat like that 
 t)f the fidn, compofed of a firm, dciife, or callous cuti- 
 cle, covering a thick, white, nervous fkin, in which, 
 more efpecially at its end, appear fielhy fibres. Its in- 
 ternal furface is, in a great meafure, rough, befet with 
 many callous warts, which, though hard, are fenfible : 
 befides which, there are thin plates, terminated with a 
 protuberant inclined edge, pointing downward, fo as to 
 form two principal rows, fpreading betwixt thofe 
 warts ; and of thefs, the uppermoft are extended un- 
 der the urethra, where they are larger, as- the lower 
 are incumbent on the anus. From each of thefe to 
 the other are continued, on both fules, feveral rows of 
 leffer valve-like papillte, varioufly inflefted into arches, 
 and which feem to be defigned for increafing the plea- 
 fure, and facilitating the expanlion when it is called for. 
 It is furnifhed with a proper mucus of its own, fepa- 
 rated from particular finufes in feveral parts, but more 
 efpecially in its polferior and fmoother lide. 
 
 873. At the entrance of the vagina are prefixed two 
 cutaneous prodaclions or appendages, called nymphcE^ 
 continued from the cutis of the clitoris, and from the 
 glans itfelf of that part ; and thefe, being full of cellular 
 lubftance in their middle, are of a turgefeent or dilfen- 
 dible fabric, jagged and replenilhed with febaceous 
 glandules on each fide, fuch as are alfo found in the 
 folds of the prepuce belonging to the clitoris. Their 
 ufe is principally to direct die urine, which flows be- 
 twixt them both from the urethra, that in its defeent it 
 may be turned oft' from clinging to the body, in which 
 oftice the nymphm are drawn together with a fort of 
 erection. Thefe membranous produftions defeend 
 from the cutaneous arch furrounding the clitoris, which 
 -is a part extremely fenfible, and wonderfully influenced 
 by titillation j for which it is made up, like the penis. 
 
Ch. XXXI. CONCEPTION.- 453 
 
 of two cavernous bodies, arifing in like manner from 
 the fame bones, and afterwai'ds conjoining together in 
 one body, but without including any urethra. It is 
 furnilhed with blood-veifels, nerves, and levator muf- 
 cles, and a ligament fent down from the fynchondro- 
 fis of the os pubis, like thofe in men, like unto which 
 the clitoris grows turgid and ered in the venereal con- 
 grcfs, but lefs in thofe who are very modeft ; but from 
 friction, the clitoris always fwells up and is erected. 
 
 874. The mufcle, termed ojlii vagina confhidor, a- 
 rifmg on each fide from the fphincter of the atius, and 
 increafed by the acceffion of a branch from the os ifchi- 
 um, covers the vafcular plexus, from whence it pro- 
 ceeds outward in the direction of the labia externa, 
 and is inferted into the crura clitoridis ; thus it feems 
 to comprefs the lateral venal plexufes of the vagina, 
 whence it every way conduces to retard the return of 
 the venal blood. The tranfverfe mufcle of the ure- 
 thra, and the bundle from the fphinder inferted into it, 
 have the fame fituation as in men. 
 
 875. When a woman is invited either by moral 
 lov6, or a luflful dehre of pleafure, and admits the em- 
 braces of the male, whofe penis, entering the vagina, is 
 rubbed againfl its fides, until the male feed breaks oup 
 and is poured out into the uterus. It then excites a 
 convulfive conftridion and attrition of the very fenfible 
 and tender parts, which lie within the contiguity of the 
 external opening of the vagina, after the fame manner 
 as we obferved before of the male (840,). By thefe 
 means the return of the venous blood being fupprefled; 
 the clitoris grows turgid and ereft, more efpecially in 
 luftful women ; the nymphte fwell on each fide, as well 
 zs the venal plexus, which almoft furrounds the whole 
 vagina, fo as to raife the pleafure to the higheft pitch : 
 in confequence of which there is expelled, by the muf- 
 cular form of the conhriclor (874.), but not perpetual- 
 ly, nor in all women, a quantity of lubricating mucous 
 liquor, of various kinds. The principal fountains of 
 ;his are feated at the firll beginning or opening of the 
 
 3 K 2 urethra. 
 
^54 CONCEPTION. Ch.XXXI. 
 
 urethra, where there are large mucous finufes placed 
 in the protuberant margin of this uriniferous canal. 
 Moreover, there are two or three large mucous finufes, 
 which open themfelves into the cavity of the vagina it- 
 felf, at the fides of the urethra, in the bottom of the fi- 
 nufes which are formed by the membranous valves 
 fulcated upward. Laftly, at the fides of the vagina, 
 betwixt the bottoms of the nymphs and the hymen, 
 there is one opening, on each fide, from a very long 
 duel; which, defeending towards the anus, receives its 
 mucus from a number of very fmall follicles. 
 
 876. But the fame a6lion which, by increafing the 
 pleafure to the higheft degree, caufes a greater con- 
 flux of blood to the whole genital fyftem of the female 
 (563.), occafions a much more important alteration in 
 the interior parts. For the hot male femen, penetrating 
 the tender and fenfible cavity of the uterus, which is 
 itfelf now turgid with influent blood, does there excite, 
 at the fame time, a turgefcence and diflcntion of the 
 lateral tubes, which are very full of veflels, creeping 
 betwixt their two coats, and now ftilf with the great 
 quantity of blood they contain ; and thefe tubes, thus 
 copioufly filled and florid with the red blood, become 
 ere£l, and afeend, fo as to apply the ruffle or fingered 
 opening of the tube to the ovary. In the truth of all 
 thefe particular changes, we are confirmed by diflec- 
 tions of gravid or pregnant women, under various cir- 
 cumftances ; alfo from the comparative anatomy of 
 brute animals, and from the appearances of the parts 
 when difeafed. 
 
 877. But, in a female of ripe years, the ovary is ex- 
 tremely turgid, with a lymphatic fluid, which will har- 
 den like the white of an egg, and with which little 
 bladders are diftended. In a prolific copulation, fome 
 one of the more ripe veficles is burft, a cleft manifcflly 
 appears, and at length pours out a clot of blood. 
 Within this veficle, after copulation, a kind of flefn 
 grows up, at firfl: flocculent, then granulated, and like 
 a conglomerate gland, confifting of many kernels join- 
 
Ch. XXXI. CONCEPTION. 455 
 
 ed together by a cellular fubftance ; which flefli by. de- 
 grees becoming larger and harder fills the whole cavity 
 of the veficle, and is hardened into the nature of a fcir- 
 rhus, in which, for a long time, remains a cleft, or a ve- 
 ftige of one. This is the corpus luteum, common to all 
 warm quadrupeds, in which fome late anatomifts have 
 found a fort of juice before copulation ; which, how- 
 ever, experience does not admit, feeing there is no 
 corpus luteum at that age. But neither is the veficle, 
 which is ttie human ovum, contained in a body like a 
 cup. The extremity ot the tube, therefore, furround- 
 ing and comprelfing the ovarium in a prolific congrefs, 
 is thought to prefs out and fwallow a mature ovum, 
 from a fiflure in the outer membrane, from whence it 
 is continued down by the periftaltic motion of the tube, 
 to the uterus itfelf ; which periftaltic motion begins from 
 the firft point of contadi with the ovum, and urges the 
 ovum downward fucceftively to the opening into the 
 fundus uteri, which is very manifeft in brute animals. 
 The truth of this appears from the conftant obfervation 
 of a fear or fiflure in the ovarium, which is produced 
 there after conception ; from a fetus being certainly 
 found in quadrupeds, both in the ovarium of the fe- 
 male, and in the tube ; from the analogy of birds, in 
 which the defeent of the ovum from the ovarium is 
 very manifeft. Yet we muft acknowledge, that a true 
 ovum was never found in quadrupeds, unlefs after a 
 long time. It is probable, that at the time of concep-' 
 tion, the true ovum is almoft fluid, very foft and pel- 
 lucid, and cannot be diftinguilhed from the mucus with 
 which the tube is filled ; likewife, that it is very fmall, 
 on account of the narrownefs of the tube. The veficle 
 itfelf which was in the ovary remains in it fixed, and 
 becomes the covering of the corpus luteum. But the 
 accounts of ova faid to have fallen from women du- 
 ring the firft days are not certain, and are contradided 
 by the fmallnefs of the fetus obferved many days after 
 conception j by the ftiape in which it is firft obferved, 
 
 which 
 
45^ CONCEPTION. Ch. XXXI. 
 
 which is always oblong, and in brutes even cylindrical ; 
 and likewife by the fmallnefs of the tube. 
 
 879. Thefe things are performed, not without plea- 
 fure to the future mother, nor without a peculiar 
 fort of fenfation of the internal parts of the tube, 
 threatening to induce a fwoon. Neither is the place 
 of conception in the uterus, whither certain expe- 
 rience fhews that the male femen comes. For the 
 power of the male femen fecundates the ovum in the o- 
 varia themfelves, as we fee in the cafe of fetufes found 
 in the ovaries and tubes ; from the analogy of birds, in 
 which by copulation one egg indeed falls into the ute- 
 rus, but very many are fecundated at once in the ovaria. 
 Nor is the fmall quantity of the male femen, or its 
 fluggifh nature, any objedlion to this, which by eminent 
 anatomills has been thought to render it lefs fit for per- 
 forming fuch a journey. For it is certain that the male 
 femen fills the tubes themfelves at the firil impregna- 
 tion, both in women and brute animals. 
 
 880. The uterus indeed, in animals certainly, and in 
 women probably, is clofed, left the very final! ovum, 
 together with the hope of the new progeny, fliould pe- 
 rifti. At that time the new mother fuffers many dif- 
 agreeable .affeftions ; which probably arife from the 
 fubputrid a'nd fubalkaline male femen reforbed into the 
 blood. A naufea is occafioned by conception, almoft 
 in the fame manner as by fwallowing a bit of a rotten 
 egg. Flefli is at this time chiefly naufeated ; a vomit- 
 ing alfo occurs ; fome puftules break out, and the 
 teeth ach. The moft of thefe complaints 1 reckon to 
 be owing to the fwelling of the uterus, and the reten- 
 tion of the menfes. 
 
 88 1 . Thefe things as yet are either certainly evinced 
 by the teftimony of our fenfes, or can be confirmed or 
 corrected by them. Thofe which follow are more con- 
 jectural ; and the more difficult on account of the pau- 
 city of experiments, and their difagreement with one 
 another. And in the firft place, it is a difficult que- 
 ftion, From whence proceed the firft Itamina of the new 
 
 animal ? 
 
Ch.XXXI. conception. 457 
 
 animal ? Whether are they from both parents, and mix- 
 ed into one animal by a conjunction of feminal matter 
 coming from the whole body ; as indeed there is a re- 
 femblance of the fetus to both parents in animals, but 
 efpecially in plants, as confirmed by very many experi- 
 ments: the fame thing alfo feems confirmed by the 
 faults of parents being conveyed to their children. But 
 no feed has ever certainly been obferved in females ; 
 and innumerable examples fhew, that the fpecies of 
 animals may be propagated without any mixture of 
 feeds. Laftly, the refemblance of the young animal 
 to its father feems only to flaew, that in the male feed 
 there is fome power, which only can form the foft 
 matter of the embryo in its lead ftate ; juft in the fame 
 manner as that power adds length to the pelvis in cer- 
 tain bodies, dilates the larynx, and caufes the horns ap- 
 pear. 
 
 882. To the father fome have attributed every thing j 
 chiefly after the feminal worms, now fo well known, 
 were firfl obferved in the male feed by the help of the 
 microfcope, which are obferved with truth to agree in 
 figure with the firfl; embryos of all animals. But in'fhefe 
 animals there is wanting a proportion betwixt their 
 number, and that of the fetufes ; they are alfo not to 
 be conftantly obferved through all the different tribes 
 of animals; they have too great a refemblanhe to thofe 
 animalcules that are every where fpontaneoufly pro- 
 duced in other juices, which yet are always tenacious 
 of their own genus, and are never found to grow in the 
 moft diflimilar kinds of animals that have limbs. 
 
 883. Again, other anatomifts, not lefs celebrated or 
 lefs worthy of credit, have taught that the fetus cxifled 
 in the mother and maternal ovary; which the male fe- 
 men excites into a mere aftive life, and likewife forms 
 it varioufly, fo as to flrew it jufl brought into life, and 
 make its prefence manifelt. Yolks are alfo inanifeftly 
 found in the female ovaries, even although they have 
 not been impregnated with any male femen. But a 
 yolk is known to be an appendix to the inteftine of 
 
 fowls ; 
 
458 CONCEPTION. Ch.XXXI. 
 
 fowls; and to have its arteries from the mefenteric ar- 
 tery, and the covering of the yolk to be continued with 
 the nervous membrane of the intefline, which is con- 
 tinuous with the Ikin of the animal. Along with the 
 yolk, therefore, the fetus feems to be prcfent in the 
 mother hen, of whom the yolk is a part, and which 
 gives veflels to the yolk. Laltly, that the analogy of 
 nature (hews that many animals generate eggs without 
 any connexion with a male of the fame fpecies, but 
 that a male animal never becomes prolinc without a fe- 
 male. That the progrcflions are continued from a fe- 
 male quadruped to an oviparous animal, and from that 
 to one which is not oviparous. But the young animal 
 proceeds from a part of the old one from w'hich it is 
 generated. Certainly, therefore, the males mufl; give 
 fome addition to that fex which produces the fetus from 
 its own body ; which addition is neceflary in fome tribes 
 of animals, but in others may be wanted. But neither 
 is it poffible that with any kind of truth we can admit 
 of an infertion by which the open navel of the male a- 
 niiual when conceived fhould adhere to the velTcls of 
 the female. For this navel would be by far too fmall 
 at the time when the yolk is of a conhderable bignefs; 
 neither could the very fmall umbilical arteries be ap- 
 plied to the very large yolk w'ith any hope of a conti- 
 nuance of the circulation. 
 
 884. Thus much concerning the materials: but we 
 are again difficulced concerning the formation, by what 
 means the rude and lhapelefs mafs of the firll embryo 
 is falliioned into the beautiful lhape of the human body. 
 We readily rejeft fuch caufes as a fortuitous concourfe 
 of atoms, the blind attradlions betw’een the particles of 
 the nutritious juices, and the ftrength of ferments in- 
 confcious of the reafons why they operate ; the foul is 
 certainly an architect unequal to the talk of producing 
 fuch a beautiful fabric ; as for internal models, of which 
 I never could conceive one clear idea in my mind, we 
 Ihall refer them to thofe hypothefcs which the defire of 
 
 explaining 
 
Ch.XXXI. conception. 45^ 
 
 explaining thofe things of which we are unwillingly ig- 
 norant has given rife to. 
 
 885. To me, indeed, experience feems to agree with 
 thofe things which the mind forefees will follow from 
 their own caufes. Namely, that this mofi: beautiful 
 frame of animals is fo various, and fo exquifitely fitted 
 for its proper and diftinfl fundtions of every kind, and 
 the offices and manner of life for which the animal is 
 defigned ; that it is calculated according to law's more 
 perfed: than any human geometry ; that the ends have 
 been forefeen in the eye, in the ear, and the hand, fo 
 that to thefe ends every thing is mod evidently accom- 
 modated ; it appears, therefore, certain to me, that no 
 caufe can be alfigned for it below the infinite wifdom 
 of the Creator himfelf. Again, the more frequent- 
 ly, or the more minutely, we obferve the long fe- 
 ries of increafe through which the ffiapelefs embryo is 
 brought to the perfection neceflary for animal life, fo 
 much the more certainly does it appear, that thofe 
 things which are obferved in the more perfe£t fetus 
 have been prefent in the tender embryo, although the 
 fituation, figure and compofition feem at firft to have 
 been exceedingly different from what they ffiew_ them- 
 felves to be at laft for an unwearied and laborious 
 patience has difeovered the intermediate degrees by 
 which the fituation, figure, and fymmetry, are infenfibly 
 reformed. Even the tranfparency of the primary fetus 
 alone conceals many things which the colour added a 
 little after does not generate, but renders confpicuous 
 to the eye. And it fufficiently appears that thofe parts 
 which eminent anatomiffs have fuppofed to be gene- 
 rated in after times, and to be added to the primeval 
 ones, have been all cotemporary with the primeval 
 parts, only fmall, foft, and colourlefs. 
 
 886, It is highly probable, that for a long time the 
 latent embryo neither increafes nor is agitated, except 
 by a very gentle motion of the humours, which we may 
 fuppofe to librate from the heart into the neighbouring 
 arteries, and from thefe into the heart of the fetus. 
 
 3 L But 
 
46 a CONCEPTION. Ch.XXXI. 
 
 But we may alfo fuppofe, that the ftimulus of the male 
 femen excites the heart of the fetus to greater contrac- 
 tions, fo that it infenfibly evolves the complicated velfels 
 of the reft of the body by the impulfe of the humours, 
 and propagates the vital motion through all the canals 
 of the little body of the anim.al ; that it is more quick 
 in fome parts, and more flow in others ; and that from 
 thence it happens that fome parts of the body of the 
 animal feem to be produced very early, and others to 
 fupervene afterwards ; and laftly, that fome do not 
 fhew themfelves until a long time after birth, as the 
 veficles of the ovaries, the veffels of the male tefticles, 
 the teeth, hairs of the beard, and horns of brute ani- 
 mals, In all animals, heat afiifts this evolution ; in the 
 more fimple ones whofe vefl'els are few, and lefs com- 
 plicated in their various origins, it is the foie inftru- 
 ment of bringing it to perfeftion. 
 
 887. Of the objedtions which are ufually brought, 
 fome are not true, fuch as the fuppofitions of an excref- 
 cence of a different ftrufture from the reft of the body ; 
 others feem to belong to caufes depending on fome ac- 
 cident, fuch as moft kinds of monfters ; fome to the 
 increafc of fome particular parts, occafioned by the 
 powers of the male feed ; fome to the cellular texture 
 varioufly relaxed, as it feems to increafe in the parts 
 newly produced, or to be occafioned by indurated 
 juices. Although it is not eafy to explain every thing 
 mechanically, yet we ought to remember, that if in- 
 deed the new animal is truely, and lliewn by experi- 
 ence to be, prefent in the egg,thofe difficulties which are 
 moved cannot overturn fuch things as have been truely 
 demonftrated, although perhaps fame things may re- 
 main, to which, in fo great an infancy of human know- 
 ledge, we cannot yet give a full anfwer. 
 
 888. When the human ovum is brought down into 
 the uterus, we become more fenfible of its change of 
 fhape after the interval of a few days. The ovum 
 itfelf fends out every where foft branchy flocculi from 
 the fuperficies of its membrane hitherto fmooth, which 
 
 adhere 
 
♦ 
 
 Ch. XXXI. CONCEPTION. 461 
 
 adhere to and inofculate with the exhaling and re- 
 forbing flocculi of the uterus (843.) This adhefion 
 happens every where in the uterus ; but chiefly in that 
 thick part which is interpofed between the tubes, and 
 is called the fundus uteri. Thus the thin ferous hu- 
 mour of the uterus, proceeding from its arterial villi, 
 is received into the flender venous veflTels of the ovum, 
 and nourifhes it together with the fetus. But before 
 this adhefion, it is either nourifhed by the matter it 
 already contains, or elfe by fuch juices as it abforbs 
 from the furrounding humours, if indeed there is any 
 time when it does not adhere. 
 
 889. At this time, in the ovum, there is a great pro- 
 portion of a limpid watery liquor, which, like the white 
 of an egg, hardens by the heat of fire, or a mixture 
 with alcohol ; and now the fetus, for a long time invi- 
 fible, as I have never obferved it before the 17th day,> 
 makes its appearance at firft a lhapelefs mafs, confiding 
 of mere mucus, and as yet feemingly of a cylindrical 
 fhape. When fome diftindion of parts is next to be 
 feen, it has a very great head, a fmall flender body, no 
 limbs, fixed by a very broad flat navel to the obtufe end 
 of the ovum. 
 
 890. From hence forward the fetus continually iii- 
 creafes as well as the ovum, but in an unequal pro- 
 portion : for while the arterial ferum is conveyed by 
 more open pafiages into the fmaller veflTels of the ovum, 
 the fetus itfelf grows the faftefl ; becaufe now the 
 greatefl; part of its nourifhment feems to pafs through 
 the very large umbilical vein. At the fame time the 
 ovum itfelf alfo grows, but lefs in proportion ; and the 
 waters, which it includes, gradually diminifli from their 
 firft proportion, in refped of the bulk of the fetus. 
 The fleecy productions of the veflTels from the ovum are 
 gradually fpread over with a continued membrane, and 
 only thofe which fprout out from the obtufe end of the 
 ovum take root, or increafe fo as to form a round cir- 
 cumfcribed placenta or cake. 
 
 891. Such is the appearance of the ovum, as we 
 
 3 L 2 have 
 
 > 
 
4(J2 CONCEPTION. Ch. XXXI. 
 
 have here defcribed it, commonly in the fecond month ; 
 from whence forward it changes only by increafmg in 
 bulk. That part of the ovum next the fundus uteri is 
 commonly uppermofl;, making about a third of its whole 
 furface, in form of a flat round difli or plate ; fucculent, 
 fibrous, full of protuberances, but throughout perfeftly 
 vafcular; changing into other tubercles of the fame 
 kind, for the moft part accurately, and often infcparably, 
 connetfled with the uppermoft part of the uterus, re- 
 markable for its large vefl'els, of a thin cellular texture, 
 colledling the velfels every where, but chiefly in the cir- 
 cumference of the greatefl; circle, as well the exhaling 
 arteries anfwering to fuch as come from the uterus into 
 the veins of the placenta, as the arteries of the placenta 
 opening into the large veins of the uterus. There, in the 
 common furface of the uterus and placenta, a communi- 
 cation is made, by which the uterus fends to tlie fetus, flrfl; 
 that white ferous liquor not unlike milk, and laftly, as it 
 feems, red blood itfelf. This communication of the 
 humours feems to be demonflrated by the fuppreflion 
 of the menfes in women with child, whofe blood mud 
 be turned into another channel ; from the lofs of blood 
 which follows from a reparation of the placenta in a 
 mifearriage ; and from the blood of the fetus being ex- 
 hauded from an hemorrhage in the mother ; from he- 
 morrhages that enfue from the navel-llring, fo as to kill 
 the mother when the placenta has been left adhering to 
 the uterus ; and, ladly, from the paffage of water, 
 quickfilver, tallow, or wax, injedled from the uterine 
 arteries of the mother into the vcifcls of the placenta, 
 as is confirmed by the mod faithful obfervations. But 
 that it is blood which is fent into the fetus, is evinced 
 by the magnitude of the fmufes of the uterus and pla- 
 centa ; the diameter of the ferpentine arteries of the 
 uterus ; the hemorrhage that follows, even when the 
 placenta is very flightly liurt ; but efpecially by the mo- 
 tion of the blood, which, in a fetus deditute of a heart, 
 could only be given to the humours of the fetus by the 
 blood of the mother. 
 
 892. The 
 
Ch.XXXI. conception. 463 
 
 892. The remaining part of the ovum, and likewife 
 the furface or the placenta, are covered b)'^ an external 
 villous and fleecy membrane, full of pores and fmall 
 veflfels, of a reticular fabric, eafily lacerable, fo as to re- 
 femble a fine placenta, and is called the chorion. But 
 even this is connefted to the' flocculent furface of the 
 uterus, which is very like to itfclf, but fofter, by velTels 
 fmaller than thofe of the placenta, but manifeftly inof- 
 culated from the chorion into the veflels of the utCr 
 rus. 
 
 893. Under the chorion lies a continuous, white, 
 opaque, and firm membrane, not vafcular, which does 
 not cover the part of the placenta turned towards the 
 uterus, but is concave, and turned to the fetus. It co- 
 heres by a cellular texture both to the chorion and am- 
 nios. The mofl; fimple name we can give it, is the 
 middle membrane. 
 
 894. The innermofl; coat of the fetus, which is cal- 
 led amnios., is a watery pellucid membrane, very rarely 
 fpread with any confpicuous veflfels, which yet I have 
 obferved in an human fubjeft ; extremely fmooth, 
 and in all parts alike ; alfo extended under the placenta 
 with the former, the furface of which is every way in 
 contaft with the waters. If there are more fetufes than 
 one, either in man or beafl;, each of them has their pro- 
 per amnios. 
 
 895. The nourifhment of the fetus from the begin- 
 ning to the end of the conception, is without doubt 
 conveyed to it through the umbilical vein. This ga- 
 thers its roots from the exhaling veflTels of the uterus 
 (854.), and has manifeft communications by fome roots 
 with the umbilical artery, from whence it in part rifes, 
 and, meeting together in a large trunk, is twilled in 
 a circular manner through a number of folds to a fuf- 
 ficient length, that may allow of a free motion ; and in 
 this courfe it is furrounded with a cellular fubllance full 
 of mucus, dillinguiflied by three partitions, and the 
 membrane which is continued to the amnios, but 
 known by the name of the umbilical rope ; and alter 
 
 forming 
 
4^4 CONCEPTION. Ch. XXXI. 
 
 forming fome protuberances, it enters through the na- 
 vel, in an arch made by a parting of the Ikin and ab- 
 dominal mufcles, and goes on through a proper fmus 
 of the liver (692.), into which the fmaller portion of 
 the blood that it conveys is poured through the flender 
 ductus venofus into the vena cava feated in the po- 
 fterior foffa of the liver: but the greater part of its 
 blood goes through the large hepatic branches, which 
 conflantly arife from its fulcus, and remain even in the 
 adult (695.); but it goes thence to the heart by the 
 continuous branches of the vena cava (697.) The 11 - 
 nus or left branch of the vena portarum itfelf is a part 
 of the umbilical vein, and its branches bring the blood 
 from the placenta to the cava, while the right branch 
 alone carries the mefenteric and fplenic blood through 
 the liver. 
 
 896. But this is not all the ufe of the placenta: for 
 the fetus fends great part of its blood again into the 
 fubftance thereof, by two large umbilical arteries, 
 which are continued on in the direftion of the aorta ; 
 and after giving fome flender twigs to the femorals, 
 with ftill fmaller arteries into the pelvis, they afcend re- 
 flected back with the bladder on each fide of it, fur- 
 rounded with the cellular plate of the peritonaum, with 
 fome fibres fpreading to them from the bladder and u- 
 rachus, in which manner they proceed on the outfide 
 of the peritonaeum into the cord at the navel, in which 
 palling alternately in a llraight and contorted courfe, 
 they form various twifhings or windings, fomewhat 
 fharper than thofe of the vein which they play round ; 
 in which manner they at lall arrive at the placenta, 
 whofe fubftance is entirely made up of their branches, 
 in conjunction with thofe of their correfponding veins, 
 and a llippery cellular fubftance following both veflels ; 
 fo that the kernels themfelves that are confpicuous in 
 the placenta, are convolutions of thofe veflels. By 
 thefe branches the blood teems to pafs out through the 
 minute arteries of the placenta into the bibulous veins 
 of the maternal uterus, that after undergoing the aClion 
 
Ch.XXXI. conception. 465 
 
 of the lungs by the mother’s refpiration, it may return 
 again in an improved ftate to the fetus ; for what other 
 reafon can be afligned for fuch large arteries, which 
 carry off above a third part of the blood of the fetus ? 
 
 897. But it will perhaps be demanded, Whether the 
 fetus is not nouriflied by the mouth likewife? Whether 
 it does not drink of the lymphatic liquor contained in 
 the cavity of the amnios, which is coagulable, unlefs 
 putrefied, and in the middle of which the fetus fwims, 
 and whofe origin is not fufficiently known ? Whether 
 this opinion is not in fome meafure confirmed by the 
 open mouth of the fetus, and the analogy of chickens, 
 which are under a neceffity of being nourilhed from the 
 contents of the egg only : to which add the abfence of 
 a navel- firing in fomefetufes; the quantity of meco- 
 nium filling the large, and part of the fmall, intefiines ; 
 the fimilitude of the liquor found in the cavity of the 
 fiomach to that which fills the amnios ; the propor- 
 tionable decreafe of the liquor amnii, as the fetus en- 
 larges ; the glutinous threads which are found con- 
 tinued from the amnios, through the mouth and gu- 
 la, into the fiomach of the fetus ; the true feces 
 found in the fiomach of the fetus of quadrupeds ; the 
 open mouth of the fetus, which we have certainly ob- 
 ferved ; the gaping of a chicken fwimming in this li- 
 quor, and its attempts as it were to drink it up ? Again, 
 what are the fountains or fprings from whence this 
 lymph of the amnios flows ? whether it tranfudes thro* 
 the invifible veflfels of the amnios, or through certain 
 pores from the fucculent chorion, which is itfelf fupplied 
 from the uterus ? It mufi be confeffed, that thefe in- 
 quiries labour under obfeurities on all fides ; notwith- 
 fianding which, there feems more probability for them 
 than otherwife, fince the liquor is of a nutritious kind, 
 at leafi in the firfi beginnings of the fetus, and derived 
 from the uterus. 
 
 898. All the excremental feces, which are collefled 
 in the fetus during the whole time of its refidence in 
 the womb, amount to no great quantity, a« they are 
 
 the, 
 
4<55 C O N C E P T I O N. Ch. XXXI. 
 
 the remains of fuch thin nutritious juices, percolated 
 through the fmalleft veffels of the uterus. 1 frequent- 
 ly obierve, that the bladder is almofl empty in the 
 fetus. However, there is generally foine quantity of 
 urine, collecred in a very long conical bladder. But 
 in the cavity of the inteflines, there is collected together 
 a large quantity of a dark green pulp, which may 
 poflibly be the remains of the exhaling juices, like rhe 
 feculent remains, which are fometimes left in the other 
 cavities of the body that are filled with exhaling juices, 
 and fuch as I have fometimes obferved even in the va- 
 ginal coat of the teflicle, 
 
 899 . It may then be demanded, whether there is any 
 allantois fince it is certain, that there paffes out from 
 the top of the bladder a duel called the urachus^ which 
 is a tender canal, firft broad, covered by the longitudi- 
 nal fibres of the bladder as with a capfule ; and after- 
 wards, when thofe fibres have departed from each 
 other, it is continued thin, but hollow, for a con- 
 fiderable way over the umbilical cord, yet fo that it 
 vanifhes in the cord itfelf. Whether this, although it 
 be not yet evident in the human fpecics, is not' con- 
 firmed by the analogy of brute animals, which have 
 both an urachus and an allantois.? But as for any pro- 
 per receptacle continuous with the hollow urachus, it 
 cither has not yet been obferved with fufficient certain- 
 ty, or elfe the experiment has not been often enough 
 repeated, to become general in the human Ipccies ; 
 and thofe eminent anatomifis who have obferved a 
 fourth kind of veffel to be continued along the umbi- 
 lical rope into its proper veficle, will not allow that 
 vcflel to be called the urachus, and very lately have 
 referred it to the omphalomefenteric genus ; and in the 
 human fetus, the urine is feparated in a very fmall 
 quantity: but it perhaps may be no improbable con- 
 jeclure, that fome portion of the urine is conveyed to a 
 certain extent into the funiculus umbilicalis, and there 
 is transfufed into the fpungy cellular fabric that fur- 
 rounds it ; and therefore, that, of ail animals, man has the 
 
 longeft 
 
Ch. XXXI. CONCEPTION. 467 
 
 longeft umbilical cord, becaufe he alone has no allantois. 
 But then this can take up but a fmall fpace, termina- 
 ting in the funis, and hardly ever feems to reach as far 
 as the placenta. Sometimes, even in an adult perfon, 
 this open duct has brought the urine to the navel. 
 
 900. In the mean time, the fetus continues to ad- 
 vance in growth ; the limbs by degrees fprout from the 
 trunk, under the form of tubercles ; and the other out- 
 works of the human fabricature are by degrees beauti- 
 fully finilhed, and added to the reft ; in a manner not 
 here to be at large deferibed, as indeed it has not been 
 as yet by anatomifts in general; of which, however, we 
 muft premife fome compendium. 
 
 901. The embryo which we firft obferved in the 
 uterus of the mother was a gelatinous matter, having 
 fcarce any proper fliape, and of which one part could 
 not be diftinguiflied from another. There was, how- 
 ever, in that gluten, a heart, which was the caufe of life 
 and motion ; there were veflcls which generated the 
 humour of the amnios ; there were therefore veffels of 
 the umbilicus and yolk, the little trunks of which, be- 
 ing received from the fetus, are at that time very large, 
 feeing they have lately begun to be obferved. There 
 was both a head and fpinal column, both parts very 
 large, and larger in proportion to the reft than ever. 
 There were likewife, without doubt, all the reft of the 
 vifeera, but pellucid and of a mucous nature ; for 
 which reafon, they may be obferved fome days fooner 
 than can be hoped for from nature alone, if you render 
 them opaque. 
 
 902. But in the whole fetus, an immenfe quantity of 
 water is mixed together with a very little earth, as the 
 very cellular texture furrounds it in a ftate between 
 fluid and folid ; feeing large drops of water are inter- 
 pofed betwixt the remote elements of the folid parts. 
 
 903. In birds there is added to this the vivifying 
 gluten or white of the egg, which is of the nature of 
 lymph ; and the yolk, which is of an oily nature ; in 
 man, fomething of a milky nature, not altogether un- 
 
 3 M like 
 
4<58 C O N C E P T I O N. Ch. XXXi. 
 
 like the yolk of an egg, and the coagulable lymphs 
 That the blood is perfcfted from the fat by the proper 
 powers of the fetus, we are perfuaded from the example 
 of birds. From it are infenfibly prepared all the other 
 humours, but all of them at firft mild, void of tade, co- 
 lour and fmell, and of a glutinous nature.. The proper 
 nature of every one of them approaches to that of fe- 
 rum ; but fome of them are not produced till many 
 years after birth, for inflance the femen. 
 
 904. The firm parts, even in a grown perfon, make 
 much the fmalleft portion even of the harder parts of 
 the human body ^ in the fetus they differ from the 
 fluids, by a fomewhat greater degree of cchefion; as 
 yet, however, they are like a gluten, at flid fluid, and 
 aftervv'ards more conftdent. In thefe the fibres which 
 we could not diflinguifh in the primeval embryo are 
 by degrees produced ; the gluten, as k would feem, be- 
 ing fhaken between the neighbouring veffels, part of 
 the water exprefled, and the terredrial parts attracting 
 one another. Thefe fibres varioufly comprehend one 
 another, and form a cellular texture, even in difeafes, 
 and intercept little fpaces, in which there is a kind of 
 humour. From this cellular fubftance are formed the 
 membranes and velfels, and almoft the w'hole body. 
 
 905. The veffels are the oldeft parts of the body, 
 and are prepared in the firff delineation of the embryo. 
 What firff appears in an egg during the time of incu- 
 bation, having any diffinft form, are venous circles : 
 but thefe veins fabricate the arteries, by which they both 
 receive their juice, and the motion of that juice. They 
 are not generated mechanically from an obffacle, as 
 the arterial blood is found at that time. At firff the 
 trunks of the veins are confpicuous, afterwards the 
 branches which convey the humours to the trunks. If 
 they w'ere produced from the arteries reflected, the 
 branches would firff be feen, and the trunks formed in 
 the laff place. Neither could the arterial blood, driven 
 back by an obffacle, form thofe moff beautiful circles, 
 and bring back the veffels into the heart. It would ra- 
 ther 
 
Ch.XXXI. conception. 469 
 
 ther flow irregularly through the cellular texture. And 
 the primeval heart would foon lofe its life, unlefs as 
 much of the humours -returned to the heart as was fuf- 
 iicient to keep up its pulfations. 
 
 906. There are, therefore, in the primeval fetus, 
 fuch as we firft obferve it, fome things more perfeft 
 and confpicuous ; others involved, invifible, and very 
 fmall. The heart is the molt perfect ; it is the only 
 moveable and irritable part; althotigh it is in many re- 
 fpe£ts different from what it is in an adult perfon. The 
 brain is large and fluid; the velfels formed which ap- 
 pear in the back next to the heart. The vifcera, muf- 
 cles, nerves, and limbs, are not yet to be feen ; the 
 bones theml'elves are prefent, of which the firft appear- 
 ance is a mucus, as are the veffels of the reft of the 
 body. The other portion is that of the abdomen, the 
 umbilical capCule of which is an immenfe hernia. 
 
 907. To this embryo is fuperadded motion, in man 
 almoft of the heart alone ; as alfo in birds, wbofe for- 
 mation does not take place without heat rather greater 
 than that of the human body: yet, without the heart, 
 heat deftroys, inftead of forming the fetus. , It is the 
 largeft in proportion to the reft in thefe beginnings ; 
 afterwards its proportion to the other parts of the body 
 grows gradually lefs and lefs. its pulfations are alfo at 
 this time the moft frequent, and in the fofteft fetus the 
 moft powerful for impelling the humours, and diftend- 
 ing and producing the veflels. 
 
 908. To the force of the heart is oppofed what is 
 yet of fervice in forming the fetus, namely, the vifcidity 
 of the vital humours which collect the earthy elements. 
 There is therefore in the embryo both an impelling 
 force, which increafes the parts longitudinally ; and a re- 
 filling force, which moderates the increafe,and increafes 
 the lateral prelfure, and thus the diftention. By the 
 force of the heart all the arteries, but for eafinefs of 
 expreflion we fhall fay only one artery, which reprefents 
 all the reft, with all its furrounding cellular texture, is 
 lengthened out ; its folds are ftretched out, and the 
 
 3 M 2 fame 
 
470 CONCEPTION. Ch.XXXI. 
 
 fame artery is dilated. And the blood by its lateral 
 preffure makes an effort againft the almofl; blind branch- 
 es of the arteries, fills and evolves them, and fets them 
 off at more obtufe angles : thus are produced fpaces 
 which make very little refill ance, in which the gluten 
 is depofited. In the very fubflance of the artery itfelf, 
 while it is every where dilated, between its imaginable 
 folid threads are prepared little reticulated fpaces like a 
 flretched-out net, which are equally fit for receiving 
 humours. The largeft of thefe are formed round the 
 heart and in the head, whither the impulfe of the heart 
 drives the humours in a llraight direction, and in the 
 placenta: the leffer ones are in the inferior part of the 
 body, from which the umbilical arteries fubtradl the 
 greatefl part of the blood. 
 
 909. The fetus increafes very quickly, as is mod e- 
 vident in the example of a chicken, whofe length the 
 twenty-fecond day is to its length the firfl day at leaf! as 
 1,000,000 to 1 ; and the whole increafe of bulk in the 
 bird during the remainder of its life does not exceed the 
 fifth part of the increafe of the egg the firft day. For 
 the fetus has a larger and more irritable heart, velfels 
 larger in proportion, and likewife more numerous and 
 relaxed, and the folid parts are mucous and diflenfible. 
 The bread is later of coming to perfeclion, furrounded 
 with membranes fo foft, that they cannot be feen. 
 
 910. The embryo does not only increafe in bulk, 
 but is fo remarkably altered in fliape, that it comes 
 forth into the light totally diflimilar from any thing that 
 could be obferved in it at its fird formation. Andfird 
 it is probable, that the articulations of the limbs are 
 produced from the elongated arteries, that they are la- 
 terally knit together by a certain gluten, feparately e- 
 volved,and at fird that they fprout out very fhort, but 
 afterwards increafe by infenfible degrees, and appear 
 divided into didinft articulations, as the wings of a bat 
 are formed from an open vafcular net- work. Thus 
 likewife the right ventricle of the heart is expanded by 
 
 the 
 
Ch. XXXr. CONCEPTION. 471 
 
 the blood coming to it in greater quantity ; and, being 
 increafed by degrees, equals the left. 
 
 pit. On the other hand, the cellular texture, from 
 its glutinous aqueous nature, by which earthy particles 
 are continually brought to it, becomes infenfibly har- 
 der j by a gentle attraftion contracts its parts, which 
 were before ftraight, into various flexures ; and ties 
 the auricles to the heart, from which they were as yet 
 at a diftance. So the muicles draw out procefles from 
 the bones by their continual pulling, and open fmall 
 cavities into large cells : the fame likewife incurvate the 
 bones, and varioufly figure them. 
 
 912. Prefliire can do a great deal : to it we muft at- 
 tribute the defcent of the tefticles into the fcrotum, 
 after the irritable force of the abdominal raufcles has 
 taken place : to this alfo we mull afcribe the repulfion 
 of the heart into the brealt, when the integuments of 
 the breall are larger ; to it we are to afcribe the length 
 of the breall and the Ihortnefs of the abdomen, and the 
 fmaller fize of the vifcera of the latter ; becaufe the air 
 received into the lungs, dilates the cavity of the thorax. 
 But even the bones are varioufly hollowed out by the 
 prelTure of the mufcles, blood-veffels, and even of the 
 very foft brain itfelf ; and by the fame means flelh is 
 changed into a tendinous fubllance. 
 
 913. The power of derivation brings the blood into 
 the pelvis and lower extremities from the clofed umbi- 
 lical arteries : the fame, when the foramen ovale is con- 
 tracted by the auricles drawn towards the heart, evolves 
 the right ventricle of the heart : when the veflels of 
 the yolk have taken up the whole length of the egg, 
 and can receive no farther elongation, it dilates the 
 umbilical arteries of the chick, and produces a new 
 membrane with incredible celerity. On the other 
 hand, but by the fame power, after the blood has got 
 
 - an eafy paffage through fome veflels of any part, the 
 other parts which do not aflford a like eafy paflage in- 
 creafe the lefs. The head grows lefs after the lower 
 limbs have begun to increafe in bulk. 
 
 914. A 
 
472 CONCEPTION. Ch. XXXI. 
 
 914. A membrane may be formed from a humour 
 of which the thinneft part is exhaled, as we have an 
 example in the epidermis : from the fame may be 
 formed a cartilage as happens in the bones, or even a 
 bone itfelf, or fomething of a ftony nature, which is 
 very frequent in the tefticles of aquatic animals. The 
 bones at firft are foft, and of a mucous nature ; then 
 they become of the confiftence of jelly ; this afterwards 
 becomes a cartilage ; without any change made on the 
 parts, as far as can be obferved. 
 
 915. A cartilage, however, is not afterwards fecretly 
 changed into a bone. That never happens, unlefs lines 
 and furrows have at firft run along the cartilage : nay, 
 the red blood has made a paffage to itfelf through the 
 veflels of the bones ; but thefe veflels manifeftly come 
 from the nutritious trunks in the interior parts -of the 
 bone, and ftrike as it were in right lines on the cartila- 
 ginous extremity of the body of the bone, which they 
 remove farther and farther from its middle. Round 
 thefe veftels is formed a cellular texture and laminae, 
 which feem to prefs the veffels themfelves towards the 
 medullary tube. Laftly, in the epiphyfis, which both 
 remains much longer cartilaginous, and denies entrance 
 to the blood, the red veffels penetrate through the cruft 
 which covers the extremity, as well as the others which 
 come from the exterior veffels of the limbs. Thus alfo 
 in the epiphyfis is produced a red nucleus of a vafcular 
 texture, which, being gradually increafed by veffels fenc 
 out from its furface, changes the reft of the cartilage 
 into a bony nature. 
 
 916. In thefe long bones it feems evident, that the 
 increafe is owing to the arteries elongated by the force 
 of the heart, and gradually extended to the extremities 
 of the bones ; but that the hardnefs is owing to grofs 
 particles at laft depofited in the cartilage when its vef- 
 fels admit the red blood. But even a bony callus ne- 
 ver becomes found till the newly formed red veffels have 
 penetrated its fubftance. 
 
 917. The flat bones originate from fomething of a 
 
 mem- 
 
Ch.XXXI. conception. 473 
 
 membranaceous nature. Over this the fibres fpread 
 themfelves, at firft in a loofe net-work, but afterwards 
 they become more denfe, having the membrane for 
 their bafis ; the pores and clefts between thefe fibres 
 being gradually contradled and filled with a bony juice, 
 at laft perfect the nature of the bones. 
 
 918. That a heavy bony juice, confifting ofgrofler 
 particles, is depofited between the primeval fibres, is 
 proved by the phenomena of the growing callus, w'hich 
 exfudes in fmall drops, not from the periofteum, but 
 from the inmofl fubftance of the bone, and is hardened 
 by degrees. But even a chemical analyfis extrafts that 
 gluten from the bones ; and in an anchylofis it appears 
 poured round the joint in a fluid, and manifeftly fills up 
 the chinks of the bones and intervals of the futures. 
 It contains grofs earthy particles, which have been dif- 
 covered by various experiments ; and the juice of mad- 
 der which adheres to it, manifeflly diflinguifhes it by 
 its colour. 
 
 919. The periofteum covers the bones, as a mem- 
 brane does any of the vifeera; and from it cellular pro- 
 ductions follow the interior veffels of the bones : but, 
 in the periofteum, there are neither ftraight fibres, nor 
 an appearance of alveoli or lamince, nor red veffels, 
 while the bone grows hard in the egg ; nor does the 
 periofteum at all adhere to the bone, except in the epi- 
 phyfis, when it has affumed a bony nature in the mid- 
 dle ; and it is thinneft when the bone is in a cartilagi- 
 nous ftate, but every where complete. In the flat 
 bones it every where affords a bafts for the bony 
 fibres. 
 
 920. Therefore the head is large, every where mem- 
 branaceous, in a few places cartilaginous on thefe firft days 
 of geftation, with a mouth deeply cut, and long jaws. 
 In the fetus come to maturity, there are alfo rudiments 
 of the teeth, which have a great deal of membrane as an 
 appendage : the brain, at firft fluid, and always foft, is 
 rtfelf very large, with large nerves : the eyes are big, 
 and the pupil fhut by a membrane : the breaft is very 
 
 fliort, 
 
474 CONCEPTION. Ch. XXXI. 
 
 fhort, but capable of extenlion, on account of a great 
 quantity of cartilage : the abdomen is large, furround- 
 ed with membranes, with a very large liver : the bile is 
 innocent and mucous : the inteftines are at laft irritable, 
 and full of foft, green, excrement, when the fetus has 
 now arrived at its ftate of maturity : the kidneys are 
 divided into lobes, are large, and have very big cap- 
 fules : the pelvis is very fmall, fo that the bladder, ova- 
 ries, and tubes, projeti out from it : the genital fyftem 
 is denfe, not yet evolved, nor preparing its juices : all 
 the glands are large, particularly the conglobate ones, 
 and full of a ferous juice : the Ikin is at firft pellucid, 
 then gelatinous, and at laft covered with a foft cuticle, 
 and febaceous ointment ; the fat is firft gelatinous, and 
 then grumous : the tendons foft, fucculent, and not yet 
 fhining. 
 
 921. There is a great difference betwixt the circu- 
 lation of the blood in the fetus and in the adult : that 
 this may be underftood, it is neceflary to deferibe the 
 organs by which it is performed. The firft is the thy- 
 mus^ a foft loofe gland, confifting of very many lobes, 
 colledled into two large upper horns, 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 fetus, and occupies a great part of the 
 breaft : it is feated in the cavity of the mediaftinum, 
 and part of the neck; and is wholly filled in its very in- 
 moft ftruclure wuth a white ferous liquor, which cannot 
 be difeovered without wounding it. This gland, in an 
 adult, being continually leffened by the increafe of the 
 lungs, and by the aorta now become larger, gradually 
 difappears. What is the ufe of this gland or its liquid, 
 we are altogether ignorant ; but even all the other 
 glands, efpecially the conglobate ones, are larger in the 
 fetus than the adult, as we have juft now obferved. 
 
 922. The cavity of the breaft is fhort in the fetus, 
 and greatly depreffed by the enormous bulk of the 
 liver ; the lungs are fmall in proportion to the heart, 
 and fo folid as to fink iia water, if they are every way 
 
 excluded 
 
Ch. XXXI. CONCEPTION. 475 
 
 excluded from taking the atmofphere into their fpungy 
 fubftance, in making the experiment. Since therefore 
 the like quantity of blood (292, 297.), which palTes 
 the lungs by refpiration in adults, cannot be tranfmit- 
 ted through the unaftive lungs of the fetus, who has 
 no refpiration ; there are therefore other ways prepared 
 in the fetus, by which the greater part of the blood 
 can pafs direftly into the aorta, from the lower cava 
 and umbilical vein, without entering the lungs. In 
 the primeval fetus there is no right ventricle of the 
 heart ; and therefore there is fuch a large opening of 
 the right auricle into the left, that all the blood which 
 comes by the vena cava immediately pafles into the 
 aorta, a very fmall quantity excepted, which goes to the 
 inconfiderable and inconfpicuous lungs. Afterwards 
 in the fetus, now grown bigger, the lungs are indeed 
 larger, and the palfage from the right part of the auri- 
 cle into the left is narrower, feeing the auricular canal 
 is now taken into the heart, and the auricles them- 
 felves are become much fliorter. But yet the feptum 
 betwixt the right and left auricle, conjoining them to- 
 gether, is perforated with a broad oval foramen j 
 through which the blood coming from the abdomen, 
 and a little directed or repelled by the valvular fides of 
 the right auricle (88.j, flows in a full ftream into the 
 cavity of the left auricle. But it is by degrees that the 
 membranes of each finus depart from each other, up- 
 ward and backward, above the oval foramen into the 
 pulmonary finus, where they are conneded on each fide 
 above, by feveral orders of fibres, which below are pal- 
 mated or like fingers, fo as to clofe up at firfl a fmall 
 part, and afterwards a greater part, of this foramen, fo 
 as to leave only a fmall oval portion of it at liberty ; 
 which lies free betwixt the round margin of the faid 
 oval foramen and the increafing valve, making in the 
 mature fetus about a fifteenth part of the area or capa- 
 city of the mouth of the vena cava. 
 
 923. That the blood takes this courfe in the fetus, 
 and that it does not on the contrary flow from the finus 
 
 3 N of 
 
47 ^ CONCEPTION. Ch. XXXI. 
 
 of the left to that of the right auricle, is evident, from 
 all manner of experiments and obfervations. For, firft, 
 the column of blood in the right fmus, is of all the 
 largeft ; and, as it is the returning one from the whole 
 body, cannot be exceeded by any other; but the left 
 auricle has fo much lefs blood in proportion than that 
 of the right, inafmuch as part of it flows throw the duft 
 or canalis artcriofus into the aorta, whence its con- 
 tents will be much lefs than that of the right auricle : 
 moreover, the valve of the oval foramen, in a mature 
 fetus, is fo large, and placed fo much to the left of the 
 mufcular arch or iftmus (92 2.), that when it is impelled 
 by the blood from the left fide, the valve, like a palate 
 or fliutter, clofes up the foramen •, but being impelled 
 from the right fide, it readily gives way fo as eafily to 
 tranfmit either blood or flatus, but it will retain even 
 flatus itfelf when injefted from the right, nor will it 
 fuffer it to pafs back again to the right fide. 
 
 924. Moreover, there is but a fmall portion of the 
 fame blood, which firfl; entered the right auricle and 
 ventricle of the heart, that takes its courfe through the 
 lungs ; for the pulmonary artery, being in the fetus 
 much larger than the aorta, is direftly continued into 
 the duQus arteriofus ; which is larger than the light 
 of both the pulmonary branches together, and greatly 
 larger than the opening of the foramen ovale, and en- 
 ters that part of the aorta which comes firft in contaft 
 with the fpine^ under its left fubclavian branch ; by 
 w'hich means it transfers more than half the blood to 
 the defeending aorta, which muft otherwife have pafl'ed 
 through the left auricle and ventricle into the amend- 
 ing branches of the aorta ; and this is the reafon why 
 the aorta in the fetus is fo fmall at its coming' out from 
 the heart. By this mechanifm an overcharge of blood 
 is turned oft' from the lungs, by direding a great part 
 of that fluid in a ftraight courfe to the umbilical arteries, 
 and the powers of both fides of the heart are united in 
 propelling the blood. 
 
 925. Thofe who have alTerted that the fetus refpires 
 
 in 
 
€u. XXXI. CONCEPTION. 477 
 
 in the uterus, having made very few experiments, have 
 neglefted that moft eafy one which is made by water, 
 in which the fetus will fwim ; and likewife from the 
 lungs, which in a fetus are conftantly heavy, and fink 
 in water: laftly, they do not attend to the evident fhort- 
 nefs of the hreaft, and fmallnefs of the lungs. Whe- 
 ther or not it can take in air through the vagina of the 
 mother, is very difficult to be determined : and I fuf- 
 pe£l it to be poffible in a certain fituation, that a well- 
 grown fetus, which is not too much compreffed, may 
 foinetimes draw in air, while it flicks by a part of its 
 body between the parts of its mother. 
 
 926. As the fetus grows larger, fo the uterus in- 
 creafes proportionably ; the ferpentine arteries of which 
 it is compofed being extended by the impelled blood, 
 and ilretched into a more diredl courfe ; while the veins 
 having their trunks compreffed by the great bulk of 
 the uterus, and being unable to return the blood, 
 fwell out into immenfe fmufes ; and laftly, from the 
 menftrual blood retained in the uterus, and not yet quite 
 fpent on the fetus. Thus its thicknefs continues the 
 fame,becaufe the greater quantity of blood and dilatation 
 of the arteries and veins make up for the extenuation 
 of its folid parts. But more efpecially the fundus, or 
 upper part of the womb, increafes beyond the reft j 
 fo that, by dilating the above tubes, thefe laft feem thus 
 to defcend from the middle of the uterus, which now 
 by degrees goes out of the pelvis, even as high as the 
 colon and ftomach itfelf, fo as to compafs all the abdo- 
 minal vifera, more efpecially the bladder and redtum. 
 The os uteri in the firft months of geftation is drawn 
 upwards with the uterus itfelf, and recedes from the 
 entrance of the vagina: after the third month, howe- 
 ver, it again defcends, and ftretches into the vagina. 
 The fame becoming perpetually fhorter, projedts upon 
 the clofe extremity of the vagina : it is, however, con- 
 ftantly tender ; and, from that cartilaginous hardnefs 
 W'hich is obferved in the virgin womb, is relaxed Into a 
 mucous foftnefs. It is never perfedlly clofed or fhut 
 3 N 2 together, 
 
47S CONCEPTION. Ch. XXXI. 
 
 together, but only flopped up and defended from the 
 air by thick mucus from the fmufes, and perhaps from 
 the veficles which are feated in the cervix uteri. 
 Moreover, the cervix or neck of the womb itfelf, 
 which has long remained unchanged^ during the lafl 
 months of geflation becomes likewife fhort, and forms a 
 broad flat opening, of no length ; which, towards the 
 time of delivery, is always more or lefs relaxed and 
 gaping. As thefe matters advance, the fetus, which in 
 the firfl months had no certain fituation, being now 
 grown to a confiderable bulk, is, about the middle of 
 the time of geflation, folded together into a globe, in 
 fuch a manner that the head lies betwixt the knees ; 
 and being the heavier part, it fubfides by degrees 
 more and more into the pelvis towards the cervix 
 uteri. 
 
 927. The various complaints in the uterus are now 
 increafed to the highefl degree, being diflended by 
 the great quantity of blood retained in it ; for nothing 
 is more difagreeable to a human creature than a violent 
 tenfion, unlcfs it is done very gradually. From the head 
 of the fetus finking down into the pelvis, the reclum, 
 bladder, and that part of the uterus next the neck, 
 and which is the mod fenfible, are prefTed,and become 
 painful : the fetus, having received its full increafe of 
 bulk, diflends the uterus every way ; and that with the 
 greater uneafinefs, becaufe, the waters being now taken 
 a\vay, the limbs w'hich arc fully formed, and the head, 
 prefs much more vehemently on the uterus. It is 
 thought alfo that the placenta itfelf, now very large, 
 diflrafts the internal and naked furface of the uterus. 
 From thefe caufes arife at firfl ‘flight endeavours of the 
 uterus to free itfelf ; and at lafl, when thefe caufes are 
 now got to their utmofl height, fuch an uneafy fenfa- 
 tion is occafioned by the impafted head of the fetus 
 as arifes from a colle£tion of fasces in the re£lum ; by 
 which pain, therefore, the mother is conflrained to at- 
 tempt the birth of the child. The time of delivery 
 comes on after the expiration of nine folar months, and 
 
Ch.XXXI. conception. 479 
 
 is kept pretty cxadly in every fpecies of animals, al- 
 though by fome caufes it may be accelerated or re- 
 tarded for fome weeks, according to the nature of 
 thefe caufea, wh^fe power, however, we muft not ex- 
 tend too far. 
 
 928. The tenefmus thus increafing till it is no longer 
 tolerable, the mother ufes all her efforts by very deep 
 infpirations, which prefs downwards the uterus and vif- 
 cera of the abdomen (756.) ; and at the fame timenihe 
 womb itfelf,by its contractile vital force, conftringes itfelf 
 fo powerfully about the fetus, as fometimes to exclude 
 it, without further efforts from the mother. The diffi- 
 culties of the birth, however, are evidently overcome 
 principally by the efforts of the mother, while the mouth 
 of the uterus, now very foft, fuffers itfelf to be diftended 
 by the head of the fetus. Here then the amnios, fill- 
 ed out with the waters, is firft protruded vertically, be- 
 fore the head of the fetus, fo as to dilate the os inter- 
 num uteri ; in which, the membranes being by de- 
 grees extenuated and dilated, eafily break, and pour 
 out their waters, which lubricate the paffages, and re- 
 lax all the parts of the vagina. The naked head of the 
 fetus now prefdhts naturally with the face to the os fa- 
 crum, direfled that way by its weight: and being ur- 
 ged forward, like a wedge or cone, it further dilates 
 the os uteri ; till at length, by the more powerful ef- 
 forts of the mother, which often loofen the bones of 
 the pubes in young w-omen, the head is thruftout thro* 
 the diftraftile vagina, with intolerable pain to the mo- 
 ther, and an univerfal tremor of body ; and if none of 
 the bones of the pelvis happen to prefs unequally, the 
 infant eafily advances, and is delivered into the world. 
 This happens difficultly even in quadrupeds; but moft 
 of all in the human race, whofe fetus has the largeft 
 head in proportion to its body. 
 
 929. It is natural for women to have but one child 
 at a birth, which law they have in common with all the 
 larger animals, unlefs they are of the carnivorous kind. 
 Frequently, however, they have two, more rarely three, 
 
 and 
 
48o conception. Ch. XXXI. 
 
 and fcarce ever five. It is not to be doubted, however, 
 that a fecond fetus may be conceived, while the firft re- 
 mains in the uterus ; feeing women have frequently 
 born children, when a hard and offified fetus had been 
 for a long time retained in their uterus. 
 
 930. The placenta, or after-burthen, of the fetus, 
 conne&ed with the fundus uteri (888.) is, in the next 
 place, feparated from the womb, without much diffi- 
 culty in a mature birth, partly by the weaker throes of 
 the mother, and partly by the extracting force of the 
 deliverer ; by which the fleecy or villous furface of the 
 placenta being withdrawn from that of the womb, is 
 immediately followed with a confiderable flow of blood ; 
 and thus is the mother delivered from the fecundines 
 or after-birth. The umbilical chord of the fetus is next 
 tied with a ligature before it is cut off ; for it cannot 
 be left open, without danger of a fatal hemorrhage. 
 Thus the umbilical vein is deprived of all the fupplies 
 of blood which it ufed to receive, and at the fame 
 time an infuperable obftacle is oppofed to the expor- 
 tation that was made by the arteries of the fame name. 
 
 931. The uterus, which hitherto had been diflend- 
 ed beyond imagination, now contracts itfelf by the e- 
 laftic power of its fibres (843.), fo fuddenly and power- 
 fully, as often to catch and embarrafs the hand of the 
 deliverer, and frequently retain the placenta, if it be 
 not foon loofened and withdrawn. By this contradfion of 
 the womb, the bleeding veffels are comprelTed, no lefs 
 than by the contradion of their own coats ; whence the 
 large quantity of blood that was collefted in the uterine 
 fubftance abundantly flows out, under the denomina- 
 tion of the lochia ; at firft: a mere gore, but afterwards, 
 as the openings of the veflels more contracf themfelves, 
 they firft; become yellow, at length become of a whitifh 
 or wheyifli complexion ; and then the ample wound 
 of the uterus is foon healed, and (brinks up to a bulk 
 not much exceeding that of the virgin uterus. 
 
 944. But after two or three days are elapfed from 
 the birth, when the lochial difeharge has almoft fpent 
 
 itfelf, 
 
Ch. XXXI. CONCEPTION. 481 
 
 itfelf, the breajls begin to fwell confiderably ; and their 
 du^ls, which in the time of geftation often diftil a little 
 thin ferum from the nipple, become now very turgid 
 with a liquor, which is at firft thin or like whey, but is 
 foon after followed by the thicker chyle itfelf. For milk 
 very much refembles chyle, but human milk lefs than 
 that of other animals. It is white, thickifli, fweet, and 
 replete with a very fweet effential fait, which grows four 
 fpontaneoufly, but is tempered by the oil and. lymph ad- 
 ded to it. It has alfo a volatile and fomewhat odorous 
 vapour, a good deal of fat or oily parts, a larger por- 
 tion of a white craflamentum or cheefy curd, and ftill 
 more of a diluting water ; and again, in the craflamen- 
 tum, are contained parts of a more earthy, alkalefcent, 
 or animal nature. But when the chyle is once changed 
 into ferum, by faffing a confiderable time, the milk be- 
 comes brackilli, alkalefcent, and difpleafing to the in- 
 fant. As the chyle, fo the milk frequently retains the 
 nature of the aliments and medicines taken into the 
 ftomach. The caufe of this increafed fecretion in the 
 breafls, feems owing to the revolution, in confequence 
 of the plentiful uterine fecretion being fupprelTed, by 
 \yhich the fetus was nourifhed ; in the fame manner as 
 a diarrhaea is fupprefled by increafing the perfpiration. 
 For it has been obferved, that true milk will fometimes 
 make its way through other parts befides the breaffs, 
 and even efcape through wounds. And there is other- 
 wife between the uterus and breaffs, fome kind of ner- 
 vous fympathy, and a fimilar fitnefs for generating a 
 white liquor. For the uterus in infancy, and during the 
 time of pregnancy, manifeffly generates it. But the in- 
 ofculations betwixt the mammary and epigaffric arte- 
 ries, though true, are fo fmall, that they can have but 
 a very little fhare in this account. 
 
 945. The breajls are made up with a very large 
 quantity of foft furrounding cellular fat, of a white co- 
 lour; and conglomerate glandules, of a convex figure, 
 aflembled into bunches fomewhat round and hard, of a 
 reddifh blue colour, outwardly furrounded and connec- 
 ted 
 
482 CONCEPTION. Ch.XXXT. 
 
 ted together by a firm web of the cellular fubftance, fe- 
 parating off into leffer kernels, which are common both 
 to men and women. To thefe glandules a great num- 
 ber of blood-veffels are diflributed from the internal 
 mammaries, from the external vellels of the thorax, and 
 fometimes from thofe of the fhoulders, all which inof- 
 culate together around the nipple. The trunks of the 
 mammary arteries, but not the mammales, inofculate 
 with the epigaflric veffels, but the veins more evident- 
 ly. The nerves are both large and numerous, like 
 thofe of the more fenfible cutaneous parts, being de- 
 rived from the fuperior intercoflals. 
 
 946. From the middle of this gland of the breafl, and 
 likewife from the furrounding fat, an infinite number 
 of fmall duds or roots arife, very flender, foft, white, 
 and dilatable, which come from all Tides to the middle 
 of the nipple, and likewife into the circle which fub- 
 tends its bafis, and then run together on the area of 
 that circle, and emerge at the root of the nipple, which 
 they perforate round its margin, in a circular figure, 
 after emerging through the root of the faid papilla or 
 nipple ; for by this denomination we call a cavernous 
 or fpungy cellular body, into which the blood may pals 
 out from its velTels, fo as to caufe a kind of erection, 
 as in the penis. Through this papilla open about 
 twenty or more of the excretory duds from the breafl, 
 called laEliferous ; none of which inofculate or join with 
 the others, but are greatly contraded at their opening 
 in the nipple, to what they were in the breafl : and 
 thefe, in a loofe or flaccid flate of the nipple, are com- 
 preffed, wrinkled, and collapfed together ; but when 
 the nipple is ereded by any kind of titillation, they 
 become flraight and open, with patulent mouths, lurking 
 betwixt the cutaneous wrinkles. This papilla or nipple 
 is furrounded by a circle, planted with febaceous fmall 
 glandules, which defend the tender fkin againfl the re- 
 peated attrition and perpetual moiflure. 
 
 947. Thus the infant is naturally provided with its 
 firft food, which is otherwife exceedingly falutary to 
 
 man. 
 
Ch. XXXI. CONCEPTION. 483 
 
 man. This the infant by inftintl; knows how to re- 
 ceive, although it is as yet a flranger to all the other 
 offices of human life. Taking the nipple in its mouth, 
 it caufes it to fwell by gentle vellications ; the lips are 
 preffed clofe to the bread:, that no air may enter be- 
 twixt; at the fame time the infpiration is deep, and a 
 fpace formed in the back part of the mouth, in which 
 the air is more dilated or rarefied ; and thus, by the 
 preffure of the external air, joined with that from the' 
 lips of the infant, the milk is urged from the bread thro’ 
 the nipple, in which it would otherwifc be colledled in 
 fo great a quantity, as fometiraes to difiii fpontaneoufly 
 and be very ready to flow out; and thus the infant fucks, 
 and is nouriffied. The firft milk, which is like whey, 
 termed colojlra, loofens the tender bowels of the infant, 
 and purges out the meconium (898.), to the great ad- 
 vantage of the infant. Yet it is alio obfervable, the 
 laftiferOus duds are fo open, that when the nipples of 
 the bread are didended by titillation, and a greater 
 quantity of blood fent into the breads, they have yield- 
 ed milk, even from virgins, fometimes from old wo- 
 men, or even from men. Milk is only generated after 
 puberty ; before that time a ferous humour flows from 
 the bread ; and for the mod part it is generated only 
 about the middle of the pregnancy. After the menfes 
 have ceafed, the breads, as well as the Uterus, being 
 grow effete, ceafe to perform their office. 
 
 948. But great changes now happen to the little new- 
 born infant; and the fird is refpiration, which it en- 
 deavours to exert, even before it is well fet at liberty 
 from the vagina of the mother, being probably ex- 
 cited, from the pain or anguifh it feels, to thofe cries 
 with which it falutes the light, and perhaps from the 
 defire of food which it had hitherto taken in from the 
 liquor of the amnios. At fird, therefore, a portion of 
 the air is admitted into the lungs, which are as yet finall 
 and full of moid vapours ; but being dilated from the 
 air, change from a fmall denfe body, finking even in 
 fait water, into a light fpungy floating fabric, extended 
 
 3 O to 
 
484 CONCEPTION. Ch. XXXI. 
 
 to a confiderable bulk with air, and of a white colour 
 Now, therefore, the blood palfes more eafily into the 
 enlarged and loofe fabric of the lungs (265.) ; in confe- 
 quence of which, a large portion of the blood that went 
 before from the pulmonary artery, through the canalis 
 arteriofus, into the aorta, goes now into and through 
 the lungs themfelves, by the other branches of the faid 
 pulmonary artery. And fo much the more is the ar- 
 terial duct or canal defected, inaftnuch as there is made 
 a new obftacle to the defcent of the blood into the ab- 
 domen ; for the umbilical arteries being now very ftrait- 
 ly tied, the blood of the defcending aorta cannot now 
 find its way but by the fame force with which it dilates 
 all the arteries of the pelvis and lower extremities. 
 Finally, as the lungs now receive more blood, fo the 
 aorta itfelf receives a greater quantity, and with greater 
 force likewife from the heart ; whereupon the interme- 
 diate canal, betwixt the protuberant part of the aorta 
 and pulmonary artery, clofes up or llninks to fuch a 
 degree, that, in adults, it is not only an empty ligament, 
 but likewife of very little length ; and otherwife it is 
 fingularly red in the inner part, foft, and very fit for 
 concreting with the flagnating blood. This courfe of 
 the blood, therefore, is foon abolifhed, commonly in a- 
 bout the compafs of a year. 
 
 949. In the like manner alfo, the foramen ovale is, 
 from the fame caufes, gradually clofed up. For when 
 the way is rendered more free and pervious into the 
 lungs, it will likewife be more free into the right fide 
 of the heart; whence the blood, both of the afeending 
 and defcending cava, will flow thither more plentifully 
 as it is invited by the more lax pulmonary artery, into 
 which it will rather move on, than through the palTage 
 through the feptum of the finufes. Again, the umbi- 
 lical vein, being now almoft dellitute of any fupply with 
 blood from the ligature of the navel (930.), lefs blood 
 will from thence flow into the lower cava, and confequent- 
 lythe preflTure againfl: the oval mouth will be diminifli- 
 ed, by which means the blood of the upper cava, being 
 
 turned 
 
€h.XXXI. conception. 485 
 
 turned off by the ifthmus, will be fcarce able to pene- 
 trate the obliquity of the foramen ovale. Thence again, 
 as more blood is derived through the lungs into the 
 left finus and auricle, its greater dilatation and exten- 
 fion will ftrain the little horns of the oval valve, fo as 
 to draw up and prefs the valve, together with the 
 ifthmus, whereby it is extended fo far, as wholly to ftiut 
 up the opening in the mature infant, while, at the fame 
 time, the blood, within the left finus, props up the faid 
 valve, fo as to fuftain the impulfe of the blood on the 
 the other fide within the right finus. Thus, by the ac- 
 celTion of a little fridion of the uppermoft margin of 
 the valve againft the upper part of the ifthmus, the fo- 
 ramen ovale clofes up by degrees, and the upper mar- 
 gin of the valve forms a concretion to the pofterior face 
 of the ifthmus. But this is performed very flowly ; in- 
 fomuch that frequently, in an advanced age, there will 
 be fome fmall aperture or tube ftill remaining; and 
 where there is none of this tube, yet there are the re- 
 mains of one, as a kind of finus, hollow to the left fide, 
 that makes a tube opening upward to the right fide, 
 and blind or clofed to the left, becaufe the power of 
 the blood in the right fide is always greater than its re- 
 fiftance on the left, or certainly not lefs, even in the ad- 
 vance of lifej 
 
 950. The umbilical vein, being deprived of blood, 
 foon clofes up. The blood of the vena portarum, ha- 
 ving no oppofition from that which formerly flowed 
 through the umbilical vein, occupies the left finus and 
 curve of the umbilical folTa (695.), and fends its blood 
 through thofe- branches by which that of the umbilical 
 vein before paflTed. Thence the du6lus venofus being 
 negle£led, fhrinks up and clofes, by the new compref- 
 fure which the defcending diaphragm makes upon the 
 liver by infpiration ; and by which the left lobe of the 
 liver is prelfed towards the lobule, and perhaps too from 
 the obtufe angle which it makes with the left finus of 
 the vena portarum ; for it is certainly firft clofed in that 
 .part which lies next the vena portarum. 
 
 3 O 2 
 
 951, The 
 
CONCEPTION. Ch. XXXI. 
 
 951. The umbilical arteries are alfo clofed up from 
 the fame caufes, as other arteries ufually are after a li- 
 gature, when fome of the blood being at the fame time 
 compared into a polypus, fills up the blind void part, 
 while the other blood, flowing above, whofe impulfe 
 was fuftained by the refilling membranes, fpreads itfclf 
 through the adjacent lefs refilling branches, which are 
 thereby rendered more open or diverging. Nor do I 
 overlook the force of the abdominal mufcles towards 
 this eifecl, by which thofe arteries are coinprefled a- 
 gainlt the full abdomen in each refpiration ; and, again, 
 the very acute angle in which the umbilicalis goes off 
 from the iliac artery, now becomes a curve, by de- 
 fcending with the fides of the bladder, and is then di- 
 redly extended into an acute fold, which the thighs 
 make with the body of the fetus. Thus the capacity 
 of thefe arteries is foon fhut up, leaving only a fmall 
 tube, that gives palfage into two or three arteries of the 
 bladder. The urachus being likewife a very thin tube, 
 extended perpendicularly upward from the bladder, is 
 therefore eafily clofed up ; fo that the contents of the 
 bladder make no endeavours to pafs that way, finding 
 a ready outlet by the defeending urethra. 
 
 952. From the like caufes the bulk of the liver it- 
 felf is leflTened, and by degrees contrafts itfelf within 
 the capacity of the ribs ; in the mean time the intellina 
 cralfa, from the flender condition in which they are ob- 
 ferved in the fetus, dilate to a confiderable diameter, 
 and the llomach itfelf is gradually elongated ; the large 
 convexity of the caecum forms itfelf by the force of the 
 feces prelTing perpendicularly downward to the right 
 fide of the vermicular appendix ; and the lower limbs 
 are likewife confiderably enlarged by the return of the 
 blood, fent back from the umbilical arteries now tied ; 
 and by degrees all the other changes are made, by 
 which a fetus infcnfibly advances to the nature and per- 
 fedlion of an adult perfon. 
 
 C H A P. 
 
Ch. XXXII. NUTRITION. 
 
 487 
 
 CHAP. XXXII. 
 
 Nutrition, Growth, Life, and Death. 
 
 5*5 T LT' V E N after the child is born, it continues to 
 grow, but always flowly, and in lefs propor- 
 tion the older it is. There are many concurring caufes 
 by which the growth is continually rendered lefs and 
 lefs. Many veflels feem to be flopped up, both becaufe 
 they are compreffed by the neighbouring torrent of 
 blood flowing through the great arterious tube, and 
 becaufe the blood being now become more vifcid runs 
 into clots. But the harder kind of food that is now 
 made ufe of, throws into the blood more terreflrial 
 parts, which being carried through the whole body a- 
 long with the nutritious parts, renders them all harder, 
 as the bones, teeth, cartilages, tendons, ligaments, vef- 
 fels, mufcles, membranes, and cellular texture ; fo that 
 an increafe of hardnefs may be perceived in them, even 
 by touching them with the finger. Wherefore, feeing 
 the blood flows from the heart through fewer canals, 
 and feeing all parts are grown harder which fliould be 
 lengthened or diftended, it neceflarily follows, that thofe 
 which ought to increafe in bulk, wall yield lefs and lefs 
 to the impulfe of the heart. 
 
 954. But the heart likewife, which is the part that is 
 firft confolidated among all the foft ones, increafes lefs 
 than any other part of the whole body ; and while the 
 much more tender limbs and fofter vifeera are diftended, 
 /the proportional bulk of the heart to the reft of the bo- 
 dy grows continually lefs and lefs, till at laft its propor- 
 tion to the body of the adult becomes eight times lefs 
 than what it was in the new-born infant. At the fame 
 time, from that very denfity which it has fo quickly 
 acquired,’ it becomes lefs irritable, and is contraded 
 lefs frequently within a given time. Thus, while the 
 
 refifting 
 
4S8 G R O W T H. Ch.XXXIL 
 
 refifting forces are augmented, the diftending ones are 
 at the fame time dlminifhed. 
 
 955. There will therefore, fooner or later, be an end of 
 the increafe of bulk ; and that will happen fo much the 
 fooner as the heart has had the more frequent and vivid 
 contradlions : but this ceffation of growth will take place 
 when the cartilaginous crufts of all the bones are now 
 become fo thin that they cannot yield to the increafe of 
 the bony part. In wmmen the menfes feem to put a 
 flop to the growth fooner than in men. In cartilagi- 
 nous fifhes, there is perpetual growth. 
 
 956. There is no flate in which nature by a peren- 
 nial progrefs induces a continual decreafe from the firfl 
 
 ‘ conception. It is faid however to take place, when 
 there is neither any increafe of bulk, nor yet does any 
 vifible decreafe take place. 
 
 957. For we are all perpetually confuming (434). 
 Nor do we only lofe the fluid parts of our bodies, but 
 even thofe which are at lafl reckoned to be the moft fo- 
 lid. 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 has ceafed to wear 
 them away, and therefore their elements are changed : 
 even the fibres of ivory in the elephant’s teeth, have 
 quitted their places, and furrounded on each fide in 
 curve lines a leaden fhot : the bony juice likewife is 
 changed ; feeing in fome cafes the bones grow foft, in 
 others they fwell out in bony tumours : even cicatri- 
 ces themfelves have a manifefl growth, otherwife they 
 would not be fufficient in an adult perfon to clofe up a 
 wound which he had received w'hen a boy; and a great 
 quantity of the earthy part of our bodies goes off by u- 
 rine, as is proved by fome difeafes. 
 
 958. The caufe of the deflruclion of the folid parts 
 lies in their perpetual extenfion and retradion, which 
 happens at every pulfe of the heart : this occurs an hun- 
 dred thoufand times everyday, and by this motion even 
 metals themfelves are worn. Other caufes are from the 
 friclion of the fluid againft the folid parts ; from the 
 
Ch. XXXII. GROWTH. 489 
 
 wearing away of all the membranes, which termi- 
 nate with a moveable extremity, either on the fur- 
 face or in the internal cavities of the body, the firm- 
 nefs of which only belongs to the reft of the canal ; 
 in the alternate fwelling and decreafe of the mufclcs ; 
 and in the attraction and preflure which at firft 
 form our flelhy parts. But all parts of our body are 
 the fooner worn away, that they confift of a great 
 deal of gluten combined with a fmall quantity of earth ; 
 and that gluten when it is extended, if the extenfion 
 has been a little fuperior to the force of its cohefion, 
 muft of neceffity fall away and be carried off" from the 
 earthy parts. Thus w'rinldes or furrows are generated ; 
 fuch as arc viftble in the arteries of old men. The cel- 
 lular texture, which otherwife would be diffolved into 
 water or gelly, is worn away by the impetus of the 
 blood prefling againft the neighbouring blood-veffels 
 and mufcles, by friCtion, and by perpetual flexion and 
 extenfion. 
 
 959. The decreafe would be very quick, and indeed 
 there would be no great diftance between the end of 
 our life and its beginning, unlefs thefe lofles were re- 
 paired. The fluid parts are reftored by the aliments, 
 and that pretty quickly ; as appears from the example 
 of a chicken, in which blood is generated out of its ali- 
 ment within two days. The fat, however, and red 
 globules of blood, are formed out of the fat, as is fhewn 
 elfewhere ; the lymphatic juice from jelly ; the mucus 
 from mucus ; and the reft of the humours from thefe 
 and water. The folid parts are repaired almoft by the 
 fame methods which we have defcribed in the hiftory 
 of the fetus. A gelatinous juice is brought from the 
 aliments, through the arteries, to all parts of the body, 
 and exfudes into all parts of the cellular texture. The 
 furrows, which we might imagine to be made in the in- 
 moft arterial membrane by the impetus of the blood, are 
 filled up by a vifeid matter brought into them by the 
 lateral preflure ; nor is it polTible that thefe furrows can 
 be overfilled, becaufe every exuberant particle of nu- 
 tritious 
 
490 G R O W T H. Ch. XXXII. 
 
 tritious juice mufl neceffarlly be carried off by the cur- 
 rent of the blood. This will not be wanting while 
 there is a fufficient quantity of aliment ; while there is 
 more reft, and lefs refiftance, in the bottom of the fur- 
 row than elfewhere, which always niuft be the cafe, 
 becaufe the bottom is farther removed from the motion 
 of the blood by the depth of its cavity. There feem 
 to be certain powers in the air, by which the aliment 
 is attached to the folid parts, although we are ignorant 
 of the manner in which they aft. 
 
 960. The decreafe of the cellular texture arifing 
 from attraftion or preffure, will be repaired by the vif- 
 cid vapour exhaling from the artery, and preffed to- 
 wards thofe places which ftand in need of reparation by 
 the force of the neighbouring arteries and coinprclling 
 mufcles, its aqueous part being preffed out and reforb- 
 ed. The gluten repairs moft of the organic parts, ten- 
 dons, and membranes ; being formed into a new cel- 
 lular texture, as in the fetus. 
 
 961. The wafte which takes place in moveable parts 
 adhering by their other extremity to the reft of the body, 
 can be repaired by protrufion alone, while the lymph 
 fills up the intervals or hollows that are thus produced. 
 
 962. At that time when the growth of the body can 
 proceed no further, fatnefs is produced, which is a kind 
 of imitation of real growth. This proceeds from the 
 fat generated by the aliment; which by reafon of the 
 impetus of the blood being leffened, and its entering 
 the fmalleft veffcls with more difficulty, is carried to the 
 fides of the veffels ; enters the lateral ones and the in- 
 organic pores of the arteries ; exfudes into the cellular 
 texture ; and there, the power of conquaffation of the 
 blood being now diminifhed, and likewife the abforption 
 by the veins, the fat is confequently collcfted. 
 
 963. We feel the beginnings of decay even in youth 
 itfelf. Even in that blooming feafon the folid elements 
 of the body are augmented, the chinks through which 
 the humours flow are leffened, fmall veffels filled up, 
 and the greater attraftion of the cellular texture has 
 
 added 
 
GROWTH. 
 
 Ch. XXXII. 
 
 491 
 
 added a denfity to the whole body. Throughout the 
 whole body that hardnefs occafioned by age is very 
 confpicuous, in the bones now wholly brittle, in the 
 fkin, in the tendons, in the conglobate glands, in the 
 arteries, and hkewife in the weight of all the parts, 
 and of the brain itfelf. But thefe parts grow ftiff 
 ibonefl which are moft exercifed by motion ; as thofe in 
 every mechanic, which he chiefly makes ufe of in his 
 bufmefs. 
 
 964. Moreover, the arteries alfo continue to become 
 more denfe, more narrow, and even to be quite filled 
 up, as well by the internal prcffure of the blood flow- 
 ing through the large arterial tube, as from the attrac- 
 tion of the cellular texture of which the greatefl; part of 
 ttie artery is made up. An infinite number of parts of 
 the cellular texture thereof ceafe to be nourifhed ; to 
 which the fmalleft arteries hitherto brought their 
 nourifliment, but now when flopped up can bring 
 none. The extending force being removed, the cellu- 
 lar fleeces draw themfelves together, contraft the little 
 fpaces intercepted between them, degenerate into 
 membranes, or fubflances of a hard texture, which in- 
 tercept and as it were choak up other vefTels, But the 
 gelatinous vapour like wife concretes in the fmall hol- 
 lows of the cellular texture, and unites into a hard folid 
 with its Tides. The mufcles, having expelled the blood 
 they contained, and condenfed their fibres, degene- 
 rate into hard denfe tendons deflitute of all irritable 
 power. 
 
 965. At the fame time the nerves become more and 
 more callous to the imprefTions of the fenfes, and the 
 mufcles grow lefs fenfible to the folicitations of the 
 vital powers : thus the contraftile force of the heart, 
 and the frequency of its pulfations, is diminiflied, and 
 therefore the whole force which drives the blood into 
 the finallefl veffels. 
 
 966. The quantity of humours is diminiflied in a 
 denfe body, as is evident in the perfpiration, femen, 
 humours of the eye, and of the conglobate glands ; the 
 
 3 P vapour 
 
492 G R O W T H. Ch. XXXII. 
 
 vapour alfo which bedews the folid parts of the body, 
 every where decreafes. For this reafon nutrition now 
 languiflies, becaufe there are more parts of the body 
 which require nourifliment, and lefs nutritious juice. 
 
 967. Nor is the quantity of humours only dimi- 
 niftied ; they themfelves are likewife corrupted. They 
 were mild and vifcid in children : but thefe fame hu- 
 mours are now acrid, fait, fetid, with a great quantity 
 of earth, in old men. This happens through the ufe of 
 fait or putrid aliments, the fault of which grows Wronger 
 by being collefted through a great length of time; 
 alfo through the fault of a lefs perfpirable Ikin, a coftive 
 belly on account of the diminilhed irritability, and 
 thus the increafed reforption of the putrid liquamen. 
 Hence the fetor of the urine, of the breath, and the 
 difficult healing of wounds. 
 
 968. But the greateft fault of the humours is, that 
 they abound with earthy particles, as well thofe col- 
 lected infenfibly from the aliments after the fecretions 
 have become lefs free, as from thofe which more are off 
 from the folid parts and returned into the blood : of 
 this confifts the earth collected in fome difeafes, and 
 which is of the nature of the gouty earth. By this 
 quantity of earth, the portion of that element through 
 the whole body is augmented, becaufe the nutritious 
 liquor brings too much of that along with it ; whence 
 the brittlenefs of the bones, and the hardnefs of all the 
 other parts, increafes ; the fame is likewife every where 
 depofited in the cellular texture, and produces crufts, 
 which are at firft callous, then of a bony or ftony na- 
 ture, and that chiefly in the coats of the arteries. 
 
 969. The hardnefs or rigidity of the whole body, 
 the decreafe of the mufcular powers, and the weaken- 
 ing of the fenfes, conftitute old age ; which happens to 
 mankind fometimes fooner, and fometimes later : foon- 
 er if they have been fubjeCted to violent labour, or 
 given themfelves up to pleafure, or lived upon un- 
 wholefome diet ; but more flowly if they have followed 
 a moderate way of life, and uled temperance in their 
 
LIFE. 
 
 Ch. XXXII. 
 
 493 
 
 diet, or if they have removed from a cold to a warm 
 country. 
 
 970. But when thofe caufes continue to operate by 
 rendering the matter of the body more denfe, by dimi- 
 nifliing its irritability, and augmenting the quantity of 
 earth, it is not pofllble but decrepit old age muft fuc- 
 ceed. In it the fenfes are almofi: deftroyed,the natural 
 power of the mufcles is exceedingly weak, the limbs 
 lofe their ftrength, the feet efpecially are not fufhcient 
 for fupporting and direding the body. Thus the 
 callous infenfibility of the nerves cannot be incited to 
 perform the office of generation ; thus the very intef- 
 tines becoming inadive, refufe to anfwer to the accuf- 
 tomed felicitations : thus alfo, by the induration of the 
 cartilages interpofed betwixt the vertebrae, the body 
 bends foreward ; by the falling out of the teeth, the 
 jaws now rendered fhorter cannot fupport the lips as 
 ufual ; and laftly, the heart lofes one half of the fre- 
 quency of its pulfation which it had in the infant ftate. 
 
 971. Thus at laft natural death neceffarily follows; 
 but very many people are carried off before their time 
 by difeafes. Scarce one in a thoufand exceeds the age 
 of 90; but one or two perhaps may be found in a cen- 
 tury that live to the age of 150. Man is long lived 
 when compared with other animals ; he is alfo more 
 tender than any of them, has loofer fleffi, and lefs hard 
 bones. Among the long-lived people, it is not eafy to 
 fay what was the caufe of that privilege. England feems 
 to excel all other nations in the long-lived people ; and 
 generally the temperate countries are remarkable in 
 this refped. Among all the different profeffions, the 
 commonalty has almofl; folely afforded thefe rare ex- 
 amples of longevity already mentioned ; although from 
 the more numerous clafs; we might expert a greater 
 number of examples. Some prerogatives to long life 
 feem to be fobriety, at lead in a moderate degree; not 
 very rich food ; a mild behaviour ; a mind not endow- 
 ed with very great vivacity, but cheerful, and little fub- 
 ject to care. Among animals, fowls are longer lived 
 
 3 P 2 than 
 
494 DEATH. Ch. XXXIE 
 
 than many others, but fifhes the moft of all ; the latter 
 have the fmalleft heart, and the flowed growth, and 
 their bones are never hardened. 
 
 972. Death happens fometimes, but rarely, from 
 mere old age. This we fay happens when the powers 
 are gradually loft, firft of the mufcles fubjedl to the 
 will, then of thofe that are fubfervient to the vital func- 
 tions, and laftly of the heart itfelf; fo that old men ceafe 
 to live through mere weaknefs, rather than through the 
 oppreflTion of any difeafe. I have often obferved the 
 fame kind of death in brutes. The heart becomes un- 
 able to propel the blood to the extremities, the pulfe 
 and heat defert the feet and hands; yet the blood con- 
 tinues to be fent forth from the heart into thofe arte- 
 ries that are next to it, and to be carried back from 
 thence ; thus the flame of life is fupported for a little 
 while ; which we foon perceive to be extinguifhed, when 
 now the heart itfelf being totally deprived of its powers, 
 and not irritable by the blood to any effeftual motion, 
 cannot drive the blood through the lungs, that the 
 aorta may receive its due quantity. Thus the utmoft 
 force of refpiration is exerted in order to open a paf- 
 fage to the blood through the lungs, until even the 
 powers given by nature for performing the action of 
 infpiration, becoming unequal to their talk, ceafe alto- 
 gether. Thus 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 by this means being irritated they continue 
 to beat weakly. But laftly, when the reft of the body 
 has become perfediy cold, and the fat itfelf congealed, 
 even this motion ceales, and the death becomes com- 
 plete. 
 
 973. I fliall call that death, when the whole irritable 
 power has left the heart. For the mere refting of the 
 heart is not without hope of a revival ; neither does the 
 putrefadion of any part of the animal body demonftrate 
 
 the 
 
Ch. XXXU. DEATH. 495 
 
 the death of the whole animal ; nor does its infenfibi- 
 lity or coldnefs do fo : but all thefe things when joined 
 together, and perpetually increafing, with the ftiffnefs 
 which follows the coagulation of the fat by reft and 
 cold, afford the figns of death in any doubtful cafe. 
 
 974. The body of a dead perfon is committed to pu- 
 trefaction . Thus the fat, and the water, and gluten, be- 
 ing diffolved, fly off; the earthy part being deftitute of 
 its bonds of union, infenfibly moulders away, and mixes 
 itfelf with the dull. The fpirit goes to that place which 
 God hath appointed it : which we may know to be in- 
 deftruCtible by death, from a very common phenome- 
 non; namely, that very many people, while their bodily 
 powers are wafted by a confumption, give evident proofs 
 of a moft ferene, vigorous, and joyful mind. 
 
 
 INDEX. 
 
I N 
 
 D 
 
 E X 
 
 CHAP. I. 
 
 The fibres. 
 
 J. ' T ""H E mod Ample parts. 
 
 J- 2. The common fabric of 
 the foHds. 
 
 3. The fibres. 
 
 Their more permanent parti- 
 cles are earthy. 
 
 4. The earthy particles cohere 
 
 by means of a gluten inter- 
 pofed betwixt them. 
 
 5. The gluten is compofed of oil 
 
 and water. 
 
 6. The fimple fibre. 
 
 7. A confpicuous linear fibre. 
 
 8. Laminae or plates. 
 
 9. Common fabric of the cellu- 
 
 lar texture. 
 
 Its diverfity in general. 
 
 I o. Membranes formed of the 
 cellular texture. 
 
 Veffels. 
 
 Tunics or coats. 
 
 1 1. That the veflcls of the tunics 
 
 are an acceffiou to the cel- 
 lular texture. 
 
 12. That the cellular texture is 
 
 every where to be found. 
 
 13. The inorganic concrete. 
 
 14. That the fibres and cellular 
 
 texture are formed of the 
 gluten. 
 
 15. After what manner the fo- 
 
 lids are formed of the glu- 
 ten. 
 
 CHAP. II. 
 
 \ 
 
 The cellular TEXTURE. 
 
 16. The differences of cellular 
 
 texture. 
 
 In what parts it is (hort and 
 tender. 
 
 17. In what parts it is more lax. 
 
 1 8. That the fat is poured out 
 
 in thefe. 
 
 19. The fmall fanguineous vef- 
 
 fels of the cellular texture. 
 That the fat is depofited 
 from the extremities of 
 the arteries. 
 
 That it exfudes alfo longitu- 
 dinally through them. 
 
 20. That the fame is reforbed in- 
 
 to the veins. 
 
 Whether the veins remain In 
 the cellular texture. 
 
 21. That all the cells mutually 
 
 open into one another. 
 
 22. The very great dignity or 
 
 importance of the cellular 
 texture. 
 
 23. The contraftlle force of the 
 
 cellular texture different 
 the irritable one. 
 
 24. The various ufes of the fat. 
 
 25. The caufes and effefts of the 
 
 fat being collefted in the 
 cells, or abforbed by them. 
 
 3 0^ CHAP. 
 
49 ^ 
 
 I N D 
 
 E X. 
 
 CHAP. III. 
 
 The vessels. 
 
 26. The figure of the arteries. 
 
 27. That they have no external 
 
 and conllant common 
 membrane. 
 
 That their firft true mem- 
 brane is every where cel- 
 lular. 
 
 28. That the exterior one is more 
 
 lax, and perforated with 
 blood-veflels and nerves. 
 
 29. The inner more denfe and 
 
 proper coat of the artery. 
 
 30. The mufcular coat formed 
 
 of circular fibres. 
 
 That there are no longitudi- 
 nal ones. 
 
 A Ihort cellular texture un- 
 der the mufcular coat. 
 
 31. The innermoll membrane of 
 
 the artery. 
 
 How this is formed in the 
 arteries of the vifcera. 
 
 32. The arteries of the arteries. 
 The nerves of the arteries. 
 If there is thence a contrac- 
 tile power diftinft from 
 the Ample elafticity. 
 
 33. The round light of the arte- 
 
 ries. 
 
 The pulfe of the arteries. 
 
 34. The itrengthof the arteries. 
 That the trunk is weakeft, 
 
 the branches more ftrong. 
 
 35. That the arteries go to all 
 
 parts. 
 
 The proportion of the arte- 
 ries to the parts which 
 they enter. 
 
 36. The proportion of the folid 
 
 part of the artery to its 
 light or cavity. 
 
 37. The divifion of the arteries 
 
 into branches. 
 
 The proportion of the light 
 of the branches to that of 
 the trunk. 
 
 The angles at which the 
 branches go off. 
 
 The flexions of the arteries. 
 
 38. The anaftomofes and net- 
 
 works of the veflels. 
 
 39. How the fmallell artery goes 
 
 off into a vein. 
 
 40. The various difpofition of 
 
 the arteries in the vif- 
 cera. 
 
 41. That the arteries go out in- 
 
 to vefielsof the leffer kinds. 
 
 42. Otherwife they go off into 
 
 excretory dufts. 
 
 43. Otherwife that they at Ia(l 
 
 terminate into exhaling 
 canals. 
 
 44. Whether every where there 
 
 are veflels produced from 
 the red ones. 
 
 45. Whether the fmaller vefltls 
 
 are ufually produced by a 
 multiplied divifion. 
 
 46. That the veins belonging to 
 
 many arteries are iimilar, 
 to various others are diffe- 
 rent. 
 
 47. The ftruiflure of the veins. 
 
 48. The amplitude and divifion 
 
 of the veins. 
 
 That they affeft the furface 
 of the body. 
 
 49. The valves of the veins. 
 
 50. That the origins of the veins 
 
 are from the arteries, from 
 the veins of the lefler ge- 
 nera, from the reforbing 
 veins of the whole circum- 
 ference, and from every 
 cavity of the body. 
 
 51. That 
 
.1 
 
 INDEX, 
 
 51. That other veflels reforbing 
 
 from the cellular texture 
 are little different from 
 thefe. 
 
 52. That there are veins as well 
 
 as arteries of fmaller kinds. 
 
 53. The lymphatic veffels. 
 
 54. The conglobate glands. 
 
 499 
 
 53. Where the lymphatic veffels 
 are found. 
 
 That they unite in the tho- 
 racic duft. 
 
 56. The orifice of the conglo- 
 
 bate glands, 
 
 57. The valves of the lym- 
 
 phatics. 
 
 CHAP. IV. 
 
 The motion ov the BLOOD through the ARTERIES 
 AND VEINS, OR THE CIRCULATION. 
 
 58. In what manner the blood 
 
 fills the arteries and veins. 
 
 59. That the blood moves rapid- 
 
 ly through all the veffels, 
 
 60. - 76. The diredtion of the 
 
 motion of the blood. 
 
 60. Proofs of the communication 
 
 of the arteries and veins. 
 
 61. That the blood flows thro’ 
 
 the arteries from the heart 
 to the extremities, 
 
 62. That fome have doubted 
 
 concerning the motions of 
 the venous blood. 
 
 Who have acknowledged 
 their error. 
 
 63. That Harvey firfl fhewed the 
 
 venal blood to return from 
 the extremities to the 
 heart. 
 
 This is proved by the valves 
 which prevent the reflux 
 of the blood into the 
 branches. 
 
 64. That the valves alfo fiiftain 
 
 the weight of the blood. 
 That thefe alfo caufe the 
 preffure of the mufcles to 
 drive the blood into the 
 veins towards the heart. 
 
 65. — 70. Which things (hew the 
 
 courfeof thevenous blood. 
 65. The valves of the right fide 
 of the heart. 
 
 66. Ligatures andcompreflion in 
 
 a living perfon. 
 
 67. More accurate experiments 
 
 on living animals. 
 
 67. Injecftions into the veins. 
 
 69. Transfufion of blood. 
 
 70. That the blood pafles from 
 
 the arteries into the veins, 
 proved by Injedllon, 
 
 71. That the fame paflage is 
 
 fhown by the microfeope. 
 That there is no parenchy- 
 ma between the arteries 
 and veins. 
 
 72. Which circulation of the 
 
 blood is proved by what is 
 already faid. 
 
 73. That there are fome places, 
 
 however, vvhere the paf- 
 fage is for a little contrary 
 to the abovementioned 
 one. 
 
 74. That in the lymphatic vef- 
 
 fels the paflage of the li- 
 quor is from their roots to 
 the thoracic du6l. 
 
 75. That all the reforbed va- 
 
 pours are carried towards 
 the heart. 
 
 76. That apaffage mull be found 
 
 for the blood from the 
 right ventricle of the heart 
 into the left. 
 
 3 Ct.2 
 
 CHAP. 
 
500. 
 
 INDEX. 
 
 CHAP. V. 
 The heart. 
 
 77, 78. The bags of the pleura. 
 
 77. The mediaftinum. 
 
 The pleura. 
 
 78. The place of the pericar- 
 
 dium. 
 
 The hinder part of the mc- 
 diallinum. 
 
 The ligaments of the lungs. 
 
 79. 80. The pericardium. 
 
 81. The arteries of the pericar- 
 
 dium. 
 
 Its veins. 
 
 Nerves. 
 
 82. The ftrufture of the pericar- 
 
 dium. 
 
 The water contained in it. 
 
 83. The ufe of the pericardium. 
 
 84. What animals have a heart. 
 
 85. In what manner the vena 
 
 cava terminates in the 
 heart. 
 
 86. The right finus venofus. 
 The right auricle. 
 
 87. The oval foffa. 
 
 The oval ring. 
 
 88. Euftachius’s valve. 
 
 89. By what powers the blood 
 
 is forced into the cavities 
 of the heart, lying on the 
 right fide. 
 
 90. The contraftion of the right 
 
 auricle of the heart, and 
 what follows from thence. 
 
 91. The figure and fituation of 
 
 the heart. 
 
 92. The anterior or right ven- 
 
 tricle of the heart. 
 
 93* The valvulce triglochines. 
 
 94. Their papillary mufcles. 
 
 95. The ufe of the triglochines. 
 
 96. That the heart is llimulated 
 
 to contraftion by the 
 blood forced into it. 
 
 97. The mufcular fibres of the 
 
 heart according to the au- 
 thor. 
 
 98. The fame deferibed by o- 
 
 thers. 
 
 99. The nerves of the heart, 
 too. That thefe nerves give the 
 
 heart its power of mo- 
 tion. 
 
 1 01. But that there is alfo fome 
 
 other caufe. 
 
 102. The irritable power placed 
 
 in the heart. 
 
 103. How the contraffion of the 
 
 ventricle is performed. 
 
 104. By the contraftion of the 
 
 heart the return of the 
 blood into the auricle 
 and veins is prevented, 
 toy. By the contraftion of the 
 right ventricle the blood 
 is driven into the pulmo- 
 nary artery. 
 
 106. The origin and beginning 
 
 of the pulmonary artery. 
 Its femilunar valves. 
 
 107. The going out of the blood 
 
 from the right ventricle 
 into the pulmonary ar- 
 ter}’. 
 
 108. The paflage of the blood 
 
 through the lungs. 
 
 109. That the blood cannot flow 
 
 back from the pulmo- 
 nary artery into the 
 heart. 
 
 no. The pulmonar}’ veins. 
 
 The courfe of the blood 
 through thefe. 
 
 1 11. The left finus venofus. 
 
 The left auricle. 
 
 1 12. That the contraftion of the 
 
 left atritm forces the 
 blood 
 
E X. 
 
 I N D 
 
 blood into the left ven- 
 tricle. 
 
 The vahula initrales. 
 
 XI 3. The courfe of the blood 
 from the right ventricle 
 into the left, or the lef- 
 fer circulation. 
 
 1 14. The left ventricle. 
 
 1 15. That the blood is forced 
 
 into the aorta by the 
 contraftion of the left 
 , ventricle. 
 
 1 1 6. The valves of the aorta. 
 
 1 17. The diaftole of the heart. 
 
 1 1 8. In what manner the mo- 
 
 tions of the auricles and 
 ventricles alternately fol- 
 low one another. 
 
 119. Why thefe motions for fuch 
 
 a long time, and fo con- 
 ftantly, follow one ano- 
 ther. 
 
 120. The queftion anfwered, 
 
 that this is explained by 
 the ftimulus of the blood 
 driven into irritable ca- 
 vities. 
 
 1 2 1. That nothing elfe is requi- 
 
 red. 
 
 That the reafon cannot be 
 found either in the com- 
 prefiion of the nerves or 
 of the coronary arte- 
 ries. 
 
 122. That the powers of the 
 
 heart are not affifted by 
 the ofcillation of the 
 fmalleft veffels. 
 
 501: 
 
 Nor by the power of exter- 
 nal heat. 
 
 Nor by the contraflile force 
 of the arteries. 
 
 123. The velocity with which 
 
 the blood iffues from the 
 heart. 
 
 The weight of the blood 
 incumbent on the heart. 
 The force of the heart. 
 
 124. That hence many things 
 
 are uncertain. 
 
 That the powers of the 
 heart are notwithftand- 
 ing very ftrong. 
 
 125. That the fame is proved by 
 
 the refiftances which the 
 heart overcomes. 
 
 126. The entrance of the blood 
 
 into the coronary arteries. 
 The two coronary arteries. 
 
 127. Their termination in the 
 
 veins. 
 
 The great coronary vein. 
 
 128. The middle vein. 
 
 The third vein. 
 
 129. The anterior veins. 
 
 130. The middle-fized veins. 
 
 1 3 1 . The leaft veins. 
 
 132. When the coronary arte- 
 
 ries receive the blood. 
 
 133. That the blood returns 
 
 from the coronary arte- 
 ries into the cavities of 
 the heart through the 
 veins. 
 
 134. The lymphatic veffels of 
 
 the heart. 
 
 C H A P. VI. 
 
 The nature of the BLOOD and HUMOURS of the 
 HUMAN BODY. 
 
 13^, The blood in general. 137. That the blood coagulates 
 
 136. The warmth of the blood. when this vapour is fent 
 
 The vapour iffuing from out from it. 
 
 blood when drawn. The cruor is the princi- 
 
 pal 
 
I N D 
 
 E X. 
 
 501 
 
 pal part of the coagu- 
 lum. 
 
 138. The ferum of the blood. 
 
 139. How the blood is changed 
 
 by putrefa6lion. 
 
 140. Befides thefe, that there arc 
 
 in the blood, fea-falt, 
 earth, earth of iron, and 
 air in an inelaftic ftate. 
 
 14 1. What changes are wrought 
 
 upon the blood by the 
 admixture of falts. 
 
 142. The chemical analyfis of 
 
 the blood. 
 
 143. A fummary of thofe things 
 
 that are to be known 
 from thence. 
 
 144. That the red globules are 
 
 diftinguilhed in the blood 
 by the help of the micro- 
 fcope. 
 
 Their figure. 
 
 245. The colour of the globules, 
 their number,magnitude, 
 and figure, variable. 
 Whether or not they break 
 into others fmaller. 
 
 046. That fibres are produced 
 from walhed blood which 
 did not exill in the living 
 animal. 
 
 147. That the crnor is compofed 
 of globules which are in- 
 fiammable. 
 
 148. The chemical analyfis of 
 
 the ferum. 
 
 That the aqueous humours, 
 the faliva and mucus, 
 give over the fame prin- 
 ciples by dillillation. 
 
 149. The quantity of blood in 
 
 the whole body. 
 
 150. That the proportions of the 
 
 elements of the blood are 
 not always the fame. 
 Which of them vary in 
 their proportion. 
 
 15 1. On the different proportion 
 
 of the elements, and the 
 confiderationof the ftruc- 
 ture of the folids, depend 
 the differences of confti- 
 tutions. 
 
 152. The ufe of the red cruor. 
 
 153. The coagulable ferum, 
 
 thinner liquids, faline 
 particles, air, fire; what, 
 and by what means pro- 
 duced. 
 
 154. That the thick blood and 
 
 more thin liquids are 
 equally neceffary for 
 health. 
 
 tyy. The difference between the 
 arterial and venous blood. 
 
 156. That all the reft of the hu- 
 mours are produced from 
 the fame blood. 
 
 CHAP. VII. 
 
 The common OFFICES of the ARTERIES. 
 
 157. The blood propelled from 
 
 the left ventricle into the 
 aorta. 
 
 158. That the arteries are con- 
 
 ftantly full. 
 
 The pulfe of the arteries, 
 and its caufe. 
 
 159. The contradlion of the ar- 
 
 teries. 
 
 160. How it is proved that the 
 
 artery is contrafted, and 
 the blood driven forward 
 by that means. 
 
 1 6 1. That no fuccefSon can be 
 
 perceived in the pulfation 
 of different arteries, al- 
 tho’ we are certain that ft 
 muft aftually take place. 
 
 162. That 
 
 I 
 
E X. 
 
 I N D 
 
 503 
 
 162. That the velocity of the 
 
 blood coining from the 
 heart mull continually 
 be diminilhed as it pro- 
 ceeds farther through the 
 arteries. 
 
 What things feem to be di- 
 miniihed, without aftu- 
 ally being fo. 
 
 163. That the blood does not 
 
 lofe fo much of its velo- 
 city as according to cal- 
 culation it ought to do. 
 The caufe of this. 
 
 164. Why the pulfe vanlfhes in 
 
 the fmalleft arteries. 
 
 165. That the blood prefles a- 
 
 gainft the fides of the 
 veins. 
 
 Why the veins do not beat 
 like the arteries. 
 
 166. That the pulfe is the mea- 
 
 fure of the powers of the 
 heart. 
 
 What is meant by a flow, 
 large, hard, and quick 
 pulfe. 
 
 Where it is beft felt. 
 
 167. That the pulfe is more flow 
 
 in proportion to the bulk 
 of the animal. 
 
 The difference of the pulfe 
 in men, according to the 
 time of the day. 
 
 3 68 . That a frequent pulfe is 
 different from a fwift 
 one. 
 
 Different caufes of a fre- 
 quent pulfe. 
 
 1 69. By what powers the venous 
 
 blood is ipoved. 
 
 1 70. That the fame moves more 
 
 quickly in the trunks 
 than in the branches. 
 
 1 71. By what means a ftagna- 
 
 tion and coagulation of 
 the blood is prevented. 
 
 172. That the venous blood is 
 
 propelled by the afiion 
 of the mufcles. 
 
 173. Other powers compreffing 
 
 the veins. 
 
 174. The power of derivation. 
 What are the ufes of the 
 
 / anaftomofes. 
 
 175. The velocity of the venous 
 
 blood. 
 
 What caufes render its mo- 
 tion more difficult- 
 
 176. The time in which the cir- 
 
 culation is performed. 
 
 177. The effects of the motion 
 
 of the heart and arteries 
 on the blood, by what 
 means they are calcy- 
 lated. 
 
 178. 179. By what means we 
 
 underftand the manner 
 in which thefe things are 
 carried on. 
 
 180. What friftion takes place 
 
 in the arteries. 
 
 Its effefts how calculated. 
 Whence the rednefs of the 
 blood. 
 
 181. Whether heat is produced 
 
 by the motion of the 
 blood. 
 
 182. That the progrellive mo- 
 
 tion of the blood hinders 
 » putrefaflion. 
 
 183. That it is various in diffe- 
 
 rent particles of 3 diffe- 
 rent difpofition. 
 
 184. The effefts of the fyftoles 
 
 of the arteries. 
 
 185. That the fmalleft mouths of 
 
 the arteries are modules 
 in which the fmall maffes 
 of blood are formed. 
 
 1 86. What is the ufe of the re- 
 
 ticular works of the ar- 
 teries. 
 
 187. The effed of a flow motion 
 
 of the blood. 
 
 CHAP, 
 
I N D E X. 
 
 504 
 
 CHAP. VIII. 
 
 Of secretion. 
 
 188. Four clafles of fecreted hu- 
 
 mours. 
 
 That the firft is of the co- 
 agulable ones, which for 
 the moll part exhale. 
 
 189. That the fecond is of fuch 
 
 as are not coagulable, 
 which partly exhale, and 
 partly not. 
 
 190. That the third is of the 
 
 mucous ones. 
 
 191. That the fourth is of the 
 
 inflammable ones. 
 
 192. That the other humours are 
 
 compofed of thefe. 
 
 J 93. That a defcription of the 
 fecretory organs is re- 
 quired, according to 
 what we obferve of the 
 different natures of the 
 humours fecreted by dif- 
 ferent organs. 
 
 194. That the fecretion of co- 
 
 agulable liquors is per- 
 formed without glands. 
 
 195. What glands fccrete the al- 
 
 buminous humour of the 
 joints. 
 
 196. The feat of thefe glands. 
 
 197. That the exhaling liquors 
 
 which are not coagu- 
 lable are fecreted without 
 glands.^ 
 
 198. That fuch liquors as are 
 
 neither coagulable nor 
 exhaling, are fecreted by 
 conglomerate glands. 
 That thefe are made up of 
 kernels. 
 
 199. 200, 201. The ftrufture of 
 
 thefe kernels. 
 
 202. That the liquors of 198 are 
 even fecreted without 
 
 thefe kernelly glands. 
 
 203. That the mucus is every 
 
 where fecreted by glands. 
 The ftrudlurc of a true 
 gland. 
 
 204. How the fecretion Is per- 
 
 formed in thefe glands. 
 
 205. The mouth of the excreto- 
 
 ries. 
 
 The crypto or cells. 
 
 206. The conglutinated glan- 
 
 dules. 
 
 207. The excretory duAs. 
 
 208. The compound glands. 
 
 The agininated or congre- 
 gate glands. 
 
 209. The various fecretion of in- 
 
 flammable liquors. 
 
 That there are many feba- 
 ceous glands without a 
 duA. 
 
 210. That there are other feba- 
 
 ceous ones which have a 
 duA. 
 
 21 1. Compound febaceous ones. 
 2x2. That milk Is fecreted In the 
 
 conglomerate glands. 
 
 2 1 3. The organs being defcrl- 
 
 bed, that we mull return 
 to the queftion 193. 
 
 214. That the blood coming to 
 
 the fecretories is of a par- 
 ticular nature. 
 
 215. That the retardation of the 
 
 blood in the leall veffels 
 feparates the more denfc 
 - humours from the light- 
 er and fuch as are more 
 flow In their motion. 
 
 216. That the mouths of the 
 
 fecretory veffels are of 
 different diameters. 
 
 217. That this inequality may 
 
 alter 
 
I N D E X. 
 
 SOS 
 
 alter the fecreted hu- 
 mours in many different 
 ways. 
 
 218. That moft fecretions hap- 
 
 pen through fmall vef- 
 i'els rifins: from a red 
 
 O 
 
 artery. 
 
 That fome, however, are 
 made by thefe veffels 
 which arife from others 
 of a leffer kind. 
 
 219. That perhaps the angle 
 
 at which the fecretory 
 branch goes off is of 
 fome confequence. 
 
 What things render this 
 probable. 
 
 What things render it 
 doubtful. 
 
 220. That the flexions of veffels 
 
 contribute to fecrction. 
 
 221. That the thicknefs of the 
 
 arteries may do the fame. 
 That their irritability does 
 almoft the fame things. 
 
 222. That various things which 
 
 augment or diminifli the 
 velocity of the blood have 
 great effeft on the fecre- 
 tions. 
 
 223. That the fecreted humours 
 
 vary by a variation of 
 thefe conditions. 
 
 224. That the moft large and 
 
 denfe particles of the 
 blood pafs into the veins. 
 
 225. What becomes of the large, 
 
 flow, and fluggilh par- 
 ticles. 
 
 And of the coagulable ones. 
 
 226. In what veffels the thin and 
 
 aqueous liquors are fe- 
 creted. 
 
 226. * In what veffels arefecreted 
 
 the light aqueous but 
 vifeid and flow humours. 
 
 227. Various hypothefes are 
 
 formed concerning fecre- 
 tion. 
 
 228. It remains to be found out 
 
 how the pure fecretions 
 are made. 
 
 That all humours newly 
 fecreted have an admix- 
 ture of water. 
 
 229. What humours become vi- 
 
 fcld by ftagnating in the 
 veffels. 
 
 230. That liquors may be chang- 
 
 ed in their receptacle by 
 the admixture of a new 
 liquid. 
 
 231. That thereforbed humours 
 
 are alfo of ufe. 
 
 232. The ufe of receptacles. 
 
 2^3. The powers by which the 
 
 retained humours are at 
 laft ejefted. 
 
 CHAP. IX. 
 
 Of respiration. 
 
 234. The figure of the lungs. 
 
 235. The external membrane of 
 
 the lungs. 
 
 236. The ftrufture of the lungs. 
 
 237. The ftrufture of the afpera 
 
 arteria. 
 
 238. The fibres of it are mufeu- 
 
 lar. 
 
 239. Its mucous glandules. 
 
 3 
 
 The conglobate glands in 
 their neighbourhood. 
 
 240. The veffels and nerves of 
 
 the afpera arteria. 
 
 241. Its divlfion into bron- 
 
 chia. 
 
 242. That their ultimate branch- 
 
 es terminate in the cellu- 
 lar texture. 
 
 R 243. The 
 
E X. 
 
 506 I N D 
 
 243. The bronchial arteries and 
 
 veins. 
 
 244. The pulmonary artery. 
 
 245. The pulmonary veins. 
 
 245. * The lymphatic veflels of 
 
 the lungs. 
 
 The nerves of the lungs. 
 
 246. That a very large portion 
 
 of the blood enters the 
 lungs. 
 
 That the utility of this vif- 
 cus depends on the air. 
 
 247. The nature of atmofpheri- 
 
 cal air. 
 
 248. In what manner it is ex- 
 
 cluded from the body. 
 
 It ought to be underftood 
 why it enters the lungs. 
 
 249. It is (hown why it enters 
 
 them. 
 
 250. The general fabric of the 
 
 thorax. 
 
 251. The vertebra of the back. 
 
 252. The articulation of the ribs 
 
 with the vertebra. 
 
 The ligaments of the latter. 
 
 253. How the ribs are joined 
 
 with the fternum. 
 
 254. The length of the ribs. 
 
 255. The direftion of the ribs. 
 Their ftrength various. 
 
 256. The fternum. 
 
 257. That the thorax muft be 
 
 raifed in order to dilate 
 the feat of the lungs. 
 That this is performed by 
 the external intercoftal 
 mufcles. 
 
 258. The internal intercoftals. 
 There are doubts concern- 
 ing the aftion of thefe, 
 but it is certain that they 
 are elevated. 
 
 259. By what means thefe en- 
 
 large the thorax. They 
 are not, however, fuffici- 
 ent to perform this dila- 
 tation. 
 
 260, 261. The diaphragm. 
 
 262. The two holes of the fep- 
 
 turn. 
 
 263. That the contraftion of the 
 
 feptum augments the ca- 
 pacity of the thorax. 
 
 But that this is performed 
 only by means of refpi- 
 ration. 
 
 264. What powers confpire to 
 
 produce the more deep 
 infpirations. 
 
 265. Infplratlon how performed. 
 Its effects on the air and 
 
 blood-veffels. 
 
 266. Whether there is air be- 
 
 tween the lungs and tho- 
 rax. 
 
 267. That the air is vitiated 
 
 by refpiration. 
 
 268. The inconveniencies of too 
 
 long an infpiration. 
 
 269. Tire powers of exfpira- 
 
 tion. 
 
 270. That the abdominal muf- 
 
 cles confpire to produce 
 this efi’edl. 
 
 That the fternocoftals and 
 others alfo affift. 
 
 271. What powers affift the muf- 
 
 cles in the ftronger refpi- 
 rations. 
 
 272. The effects of exfpiration. 
 
 273. That from thence there a- 
 
 rifes a new neceffity for 
 refpiration. 
 
 274. That we can fcarce affign 
 
 any other caufes for al- 
 ternate refpiration. 
 
 275. That refpiration is necefla- 
 
 ry for an adult. 
 
 276. That the ufefulnefs of re- 
 
 fpiration is different from 
 that neceffity. 
 
 277. From whence thefe things 
 
 are difeovered. 
 
 278. "Whether animal-heat is ge- 
 
 nerated in the lungs. 
 
 279. AVhether 
 
INDEX. 
 
 27-9. Whether the blood Is con- 
 denfed in the lungs. 
 
 280. Whether air itfelf is re- 
 
 ceived Into the blood in 
 the lungs. 
 
 What things render this 
 probable. 
 
 281. What things feem to prove 
 
 the contrary. 
 
 282. Whether the blood Is cool- 
 
 ed in the lungs. 
 
 283. Whether the red colour of 
 
 the blood proceeds from 
 the air. , 
 
 285. Whether the ufe of the 
 blood is to abforb nitre 
 
 507 
 
 from the air. 
 
 286. What animals live long 
 
 without air. 
 
 Why every animal dies in 
 air that is not often 
 changed. 
 
 287. What is the agreement be- 
 
 tween the pulfe and re- 
 fpiration. 
 
 288. Cough. 
 
 289. Laughter. 
 
 Weeping. 
 
 Hickup. 
 
 Sneezing. 
 
 290. The accelTory ufes-of refpi- 
 
 ration. 
 
 CHAP. X. [XL] 
 
 The voice and SPEECH. 
 
 291. That the larynx is made of 
 
 cartilages. 
 
 Its veflels and nerves. 
 
 292. The fcutiform cartilage. 
 
 293. The annular cartilage. 
 
 294. The arytenoide cartilages. 
 
 295. The glottis. 
 
 296. The epiglottis. 
 
 297. The ventricles of the la- 
 
 rynx. 
 
 298. The mucous glandules of 
 
 the larynx. 
 
 299. The thyreoide glandule. 
 
 300. The connexion of the la- 
 
 rynx with the os hy- 
 oides. 
 
 The elevation and narrow- 
 ing of the larynx and 
 glottis. 
 
 301. The depreflion and dilata- 
 
 tion of the larynx and 
 glottis. 
 
 302. The cavity of the mouth. 
 The noftrils. 
 
 303. The tongue. 
 
 304. The voice. 
 
 Whifpering. 
 
 305. The ftrength of the voice. 
 How an acute tone Is made. 
 
 306. That a grave tone is pro- 
 
 duced by oppofite caufes. 
 
 307. The caufes of a diverfity of 
 
 tones. 
 
 308. Singing. 
 
 309. Speech. 
 
 310. The pronunciation of let- 
 
 ters. 
 
 CHAP. XI. 
 
 The brain and NERVES. 
 
 31 1. A confideratlon of the or- belong to the brain. 
 
 der. 312. The arch of the aorta, and 
 
 312, — 319. The arteries which the branches produced 
 
 3 R 2 frons 
 
I N D 
 
 E X. 
 
 508 
 
 from it. 
 
 213. The divifion of the carotid. 
 The external carotid. From 
 it proceeds. 
 
 The fuperior thyreoide ar- 
 tery. 
 
 The lingual artery. 
 
 The labial one. 
 
 The afcending pharyngea. 
 
 314. The occipital artery. 
 
 The auricular one. 
 
 315. The temporal artery. 
 
 The internal maxillary one. 
 
 316. The principal branch to the 
 
 dura mater. 
 
 Other branches of the In- 
 ternal maxillary. 
 
 316. * The internal carotid. 
 
 It angles. 
 
 Its paffage through the fo» 
 ramen of the os petro- 
 fum. 
 
 The branches produced 
 from it in the receptacle. 
 
 317. The branches of the inter- 
 
 nal carotid on the bridge 
 and crura of the brain. 
 The branch accompanying 
 the plexus choroidcs and 
 optic nerve. 
 
 The anterior and pofterior 
 branch. 
 
 The ftruftureof thebranch- 
 es of the carotid artery 
 which lie within thefcull. 
 
 318. What may be collefted 
 
 from the hlftory of the 
 arteries of the brain. 
 
 320. 324. The coverings of the 
 brain. 
 
 320. The bony covering of the 
 
 encephalon. 
 
 The hard membranes In ge- 
 neral. 
 
 321. The external and internal 
 
 lamina of the hard mem- 
 brane. 
 
 The falx and tentorla pro- 
 
 ceed from thefe, and w'hat 
 is 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 iupcrior finus of the 
 
 falx. 
 
 The tvanfverfe finufes. 
 
 327. The inferior finus of the 
 
 falx. 
 
 328. The inferior, anterior, and 
 
 pofterior veins of the 
 brain. 
 
 329. The veins of the cerebel- 
 
 lum. 
 
 That the fuperior ones ter- 
 minate In the fourth fi- 
 nus; the Inferior ones in 
 the fuperior and tranf- 
 verfe finus of the os pe- 
 trofum. 
 
 330. A finus like a circle. 
 
 The tranfverfe finufes join- 
 ing the cavernous ones. 
 
 331. The fuperior finus petrofus. 
 The inferior finus petrofus. 
 The pofterior occipital fi- 
 nus. 
 
 332. The anterior occipital fi- 
 
 nus. 
 
 The cavernous finus. 
 
 The conjunction of the fi- 
 nufes and external veins 
 of the cranium with one 
 another, and what hap- 
 pens from thence. 
 
 333. The ufe of the finufes. 
 
 334. Wliat happens to the arte- 
 
 ries with the finufes. 
 
 335. That the blood chiefly 
 
 flows into the jugular 
 veins. 
 
 Their cerebral and facial 
 branches. 
 
 336. The external jugular vein. 
 
 The 
 
INDEX. 
 
 The internal vertebral vein. 
 
 337. The finus of the medulla 
 
 fpinalis. 
 
 338. The ufes of the venal ana- 
 
 ftomofes. 
 
 339. The lymphatic veffels of 
 
 the brain. 
 
 The reforptlon of that 
 which exhales in the 
 brain. 
 
 340. That a great number of 
 
 parts are comprehended 
 under the name of ence- 
 phalon. 
 
 The cerebrum, cerebellum, 
 bridge, and medulla ob- 
 longata, what they are- 
 
 341. The figure of the brain. 
 
 Its gyri or circumvolutions. 
 Its cortex. 
 
 Medulla. 
 
 Lobes. 
 
 342. The more fubtlle ftrufture 
 
 of the brain. 
 
 343 • 53' 'The interior anatomy 
 of the brain. 
 
 343. The oval feftion of the brain. 
 The corpus callofum. 
 
 344. The anterior or three horn- 
 
 ed ventricle. 
 
 345. The corpora ftriata. 
 
 The thalami of the optic 
 nerves. 
 
 The double femicircular 
 centre. 
 
 The anterior commiffure. 
 The mamillary eminences. 
 
 346. The pellucid feptum. 
 
 The fornix. 
 
 The fimbrisE. 
 
 The hippocampi. 
 
 The pfalterium. 
 
 347. The choroid plexus. 
 
 348. The third ventricle. 
 
 349. The pituitary gland. 
 
 350. The pofterior double com- 
 
 miffure. 
 
 351. The reparation of the third 
 
 509 
 
 ventricle from the cala- 
 mus feriptorius. _ 
 
 The anterior commiffure. 
 
 352. The nates. 
 
 The teftes. 
 
 The pineal gland. 
 
 353. The crura of the brain. 
 
 354. The cerebellum. 
 
 355. The bridge. 
 
 The medulla oblongata. 
 The olive-fliaped and p}Ta- 
 mldal bodies. 
 
 The fourth ventricle. 
 
 'The great valve. 
 
 The aqueduft. 
 
 The calamus. 
 
 356. The common origins of 
 
 the nerves of the brain. 
 
 357. The origins of each of the 
 
 fingle nerves of the brain. 
 
 358. The medulla fpinalis. 
 
 The pia mater, arteries, and 
 
 veins of the fame. 
 
 359. The arachnoid membrane 
 
 of the medulla fpinalis. 
 
 360. The hard membrane of the 
 
 medulla fpinalis. 
 
 The toothed ligament. 
 
 361. The common properties of 
 
 the fpinal nerves. 
 
 362. The anterior and pofterior 
 
 trunks of the fpinal 
 nerves. 
 
 The intercoftal nerve. 
 
 The eighth pair. 
 
 The phrenic nerve. 
 
 The acceffory nerve. 
 
 364. The extremity of thenerves. 
 The ftraightnefs of the fi- 
 bres of the nerves. 
 
 That the nerves are fcarce- 
 ly elaftic, and not at all 
 irritable. 
 
 The number of nerves in 
 proportion to the parts 
 to which they are fent. 
 The anaftomoies of the 
 nerves. 
 
 Ganglions. 
 
I N D E 
 
 Ganglions. 
 
 365. How it is proved that fen- 
 
 fation is owing to the 
 nerves. 
 
 That it is the medullary 
 part of the nerve which 
 feels. 
 
 366. That the foul perceives in 
 
 the brain, not imme- 
 diately by the fenforia 
 and branches of the 
 nerves. 
 
 367. How the mufcles are affec- 
 
 ted by comprefling or ir- 
 ritating the nerves. 
 
 368. What impediments of the 
 
 animal motions happen 
 on hurting the brain or 
 fpinal marrow. 
 
 369. From what is laid down In 
 
 367 and 368, the nerves 
 are proved likewife to 
 be the organs of motion. 
 
 370. Whether there is in the 
 
 brain any principal feat 
 in which is the origin of 
 all motions, and the end 
 of all fenfation, where 
 the foul refides. 
 
 That that feat is not in the 
 corpus callofum. 
 
 371. Nor is it the proper pro- 
 
 vince of the cerebellum 
 to carry on the vital mo- 
 tions. 
 
 Nor are we to derive the 
 motions called atiimal 
 and vital from different 
 fources. 
 
 372. That the feat of the foul is 
 
 where the nerves firft be- 
 gin. 
 
 373. That the nerves are the or- 
 
 gans of fenfation and 
 motion, not by their 
 membranes, but their 
 medullary part. 
 
 374. What the medulla Is. 
 
 375. Whether a medullary fibre 
 
 is folid. 
 
 376. That the nerves are entire- 
 
 ly devoid of elafticity. 
 
 377. That motion can only be 
 
 propagated downwards. 
 That from what is already 
 faid, it follows, that the 
 medullary fibre feems to 
 be hollow. 
 
 378. Adifproof of the objeftlons 
 
 ufually brought againfl 
 this. 
 
 379. The nature of the nervous 
 
 fluid. 
 
 How prove 4 not to be e- 
 leArical. 
 
 380. That the nature of that 
 
 fluid Is neither aqueous 
 nor albuminous. 
 
 381. Of what kind the nervous 
 
 fluid ought to be. 
 
 382. How it Is rendered more 
 
 probable that the ner- 
 vous fluid paffes through 
 a hollow tube than thro’ 
 a fpongy folid. 
 
 383. A double motion of the 
 
 nervous juice. 
 
 384. That the fame nerves moft 
 
 evidently ferve both for 
 fenfe and motion. 
 
 385. What becomes of the ner- 
 
 vous fluid. 
 
 Whether it nourifhes the 
 body. 
 
 386. Queftions concerning the 
 
 ufes of the different parts 
 of the brain. 
 
 387. TheofGcesof the ventricles. 
 
 388. What is known concerning 
 
 the ufe of the tubercles. 
 
 389. The offices of the ftriae and 
 
 the internal duds. 
 
 390. The order of thofe things 
 
 which follow confidered. 
 
 CHAP, 
 
INDEX. 
 
 5 " 
 
 CHAP. XII. 
 
 MUSCULAR MOTION. 
 
 391. What is called the dead 
 
 power of the fibre. 
 
 392. The reafon why it is called 
 
 dead. 
 
 Its e£Fe6fs. 
 
 393. The power of the dead fi- 
 
 bre commonly known. 
 The properties of the com- 
 mon red mufcular fibre. 
 304. What the fibres of a muf- 
 cle, and the mufcle itfelf, 
 are. 
 
 395. The fibres treated more 
 
 fully. 
 
 396. The belly, tendon, aponeu- 
 
 rofis, and capfule of a 
 mufcle, what. 
 
 Whether the fibres of the 
 tendons are of a different 
 genus from the mufcular 
 ones. 
 
 The parts in which the muf- 
 cles go off in long ten- 
 dons, and thofe to which 
 they affix themfelves. 
 
 397. The reafons of the tendons 
 
 uniting themfelves with 
 the flefli. 
 
 A pennated mufcle, what. 
 
 398. The arteries, veins, lym- 
 
 phatics, and nerves, of the 
 mufcles. 
 
 399. The ftrudture of the leaft 
 
 fibre which ferves as an 
 element to the mufcle. 
 
 400. That there is a threefold 
 
 force in the mufcle. 
 
 The vis injita of the mufcle. 
 
 401. The meafure of the muf- 
 
 cles fhortening when they 
 contrail. 
 
 402. Other things which relate 
 
 to the vis injita. 
 
 403. The nervous power of the 
 
 mufcle. 
 
 404. In what the nervous power 
 
 and vis infita differ. 
 
 405. The phenomena in the mo- 
 
 tion of the m.ufcles ari- 
 fing from the nervous 
 power and vis infita. 
 
 406. What the arteries contri- 
 
 bute to the motion of the 
 mufcles. 
 
 407. A refutation of the caufea 
 
 by which the nerves are 
 faid to move the muf- 
 cles. 
 
 408. That the nervous fluid 
 
 feems to ferve in the 
 place of a ftimulus ; and 
 that its moving caufe is 
 not the foul, but a la>V 
 derived from God. 
 
 409. What things fhow that in 
 
 the motion arifing from 
 the vis infita, the foul 
 does not interfere. 
 
 410. What things happen to the 
 
 mufcles obeying the will, 
 and to thofe which are 
 governed by a vis infta. 
 
 41 1. The magnitude and lofs of 
 
 the powers which the 
 mufcles exert in their 
 contra dlions. 
 
 412. The proportion of thefe 
 
 Ioffes. 
 
 413. What thofe that are called 
 
 antagonills contribute to 
 the motion of the muf- 
 cles. 
 
 414. Other helps to this motion. 
 
 416. The co-operation of the 
 
 mufcles. 
 
 417. What effedls are produced 
 
 by 
 
E X. 
 
 512 I N D 
 
 by the aftion of the muf- 
 cles. 
 
 418. The relaxation of a ftretch- 
 
 ed mufclc. 
 
 What becomes of the fpin't 
 fent out from the brain. 
 
 CHAP. XIII. 
 
 TOUCH OR FEELING. 
 
 419. What feeling is. 
 
 A confidcration of the or- 
 der. 
 
 420. Touch in general. 
 
 42 1 . Touch in another and more 
 
 proper fenfe. 
 
 422. The true Hein. 
 
 423. The granules and papillae 
 
 of the fltin. 
 
 424. The epidermis. 
 
 425. The rete Malpighianum. 
 
 426. Of what the net-work and 
 
 epidermis are made. 
 
 427. The glands of the Hein. 
 That there is another fpring 
 
 of oily liquor, and what 
 it is. 
 
 428. The hairs. 
 
 429. 1'he nails. 
 
 430. That the fubcutaneous cel- 
 
 lular texture in very 
 few places is free of fat. 
 What purpofe it ferves af- 
 ter it has received the fat. 
 That the ikin and Malpi- 
 ghian mucus, where they 
 feem perforated, are 
 drawn inward and dege- 
 nerate. 
 
 431. The reafon of feeling, and 
 
 the qualities which are 
 known from thence. 
 
 432. The Malpighian mucus. 
 
 hairs and nails, what pur- 
 pofe they ferve. 
 
 433. A vapour perfpires through 
 
 an infinite number of lit- 
 tle arteries of the flein. 
 
 434. The ways of demonftrating 
 
 this exhalation. 
 
 435. Sweat. 
 
 436. The elements of perfpira*. 
 
 tion. 
 
 Water. 
 
 The odours of aliments. 
 The eleftric matter, 
 
 437. Another volatile element of 
 
 perfpiration, fomething 
 of an alkaline nature. 
 
 438. The quantity of perfpiring 
 
 liquid. 
 
 439. Of what ufe the quantity 
 
 of perfpiring liquid is. 
 What things augment or 
 diminifli it, and what 
 follows from thence. 
 
 440. How fweat benefits or 
 
 hurts the body. 
 
 441. The ufe of perfpiration. 
 
 442. Inhalation, by what argu- 
 
 ments it is proved. 
 
 443. How it is proved that both 
 
 the exhaling and inha- 
 ling veffels may be con- 
 tracted and relaxed by 
 the power of the nerves. 
 
 CHAP. XIV. 
 TASTE. 
 
 444 
 
 That tafte Is chiefly ex- 
 ercifedbiy the tongue. 
 
 445, The tongue in general. 
 Firft kind of its papillae. 
 
 446. The 
 
I N 1 ) E X. 
 
 446. The fungiform papillae. 
 The conical ones. 
 
 Others which intervene. 
 
 447. The nerves of the tongue. 
 
 448. The arterious and nervous 
 
 villi which run between 
 them. 
 
 449. The covering of the tongue. 
 
 450. The mufcles of the tongue. 
 
 45 1 . The veflels of the tongue. 
 
 452. The manner of exercifing 
 
 the tafte. 
 
 Flavours, and their caufe. 
 
 453. What things contribute to 
 
 the perception of taftes. 
 
 454. That the fpirits are refumed 
 
 either into the papillae or 
 the abforbing villi of the 
 tongue. 
 
 455. The ufe of the fenfe of 
 
 tafte. 
 
 CHAP. XV. 
 
 Of smell. 
 
 456. The ufe of fmell. 
 
 457. That fmell is exercifed by 
 
 the help of the mem- 
 brane of the noftrils. 
 
 The nerves of that mem- 
 brane. 
 
 458. The arteries, membranes, 
 
 and veins of the noftrils. 
 
 459. What the noftrils are. 
 
 The feptum of the noftrils. 
 
 460. The uppermoft, middle, 
 
 and lowed offa fpongiofa. 
 
 461. The linufes in general, what 
 
 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 
 
 mucus can evacuate it in 
 any fituation of the bo* 
 dy. 
 
 465. The nofe and Its mufcles. 
 
 466. The manner of exercifing 
 
 the fenfe of fmell. 
 
 In what things it agrees or 
 difagrees with the fenfe 
 of tafte. 
 
 467. The ftrength of odours. 
 The parts of the noftrils 
 
 which primarily belong 
 to the fenfe of fmelling. 
 
 CHAP. XVI. 
 
 The hearing, 
 
 468. The reafon of the diffe- 
 
 rence between the organ 
 of hearing and that of 
 the other fenfes. 
 
 469. The lap of the ear and its 
 
 parts. 
 
 470. The glandules and mufcles 
 
 of the lap of the ear. 
 
 471. The meatus auditorius. 
 
 472. The fkin and cuticle of the 
 
 meatus. 
 
 The glandules for feparat* 
 ing its wax, and the was 
 itulf. 
 
 473. 477. Air, according to the 
 
 natural philofophers^ 
 
 474. Tones. 
 
 475. The velocity of founds. 
 
 3 S 476. Sym- 
 
514 index:. 
 
 476. Sympathetic tremors. 
 
 The ftrength of found. 
 Echo. 
 
 477. How found rebounds from 
 
 hard bodies. 
 
 The reafons of the increafe 
 and weaknefs of founds. 
 
 478. The colleftion of founds in 
 
 the meatus auditorius. 
 
 479. The membrane of the tym- 
 
 panum. 
 
 That the founds ftrike up- 
 on it after their ultimate 
 reflexion in the meatus 
 auditorius. 
 
 480. The tympanum. 
 
 481. That the four little bones 
 
 which perform the offlee 
 of hearing are placed in 
 the tympanum. 
 
 The malleus. 
 
 482. The mufcles of the malle- 
 
 us. 
 
 The effefts of a ruptured 
 membrane of the tympa- 
 num. 
 
 483. The incus. 
 
 484. The ftapes and Its mufcle. 
 
 485. The little round bone. 
 
 486. That various canals go out 
 
 of the cavity of the tym- 
 panum. 
 
 A certain appendix to the 
 
 tympanum, of the ligarc 
 of a gnomon. 
 
 Small cells above the ma- 
 millary procefs, and in 
 the procefs itfelf. 
 
 487. The tube. 
 
 488. That two other paflages 
 
 lead from the tympanum 
 into the labyrinth. 
 
 The oval fenellra. 
 
 The veftibulum. 
 
 489. The femicircular canals. 
 
 490. The round fentllra. 
 
 The cochlea. 
 
 491. The veffels of the organ of 
 
 hearing. 
 
 492. The nerves belonging to 
 
 this organ remain to be 
 deferibed. 
 
 The feventh pair of nerves, 
 and its hard portion. 
 The nerves of the lap of the 
 ear. 
 
 493. The foft branch of the fe- 
 
 venth pair of nerves. 
 
 494. 5. Various things con- 
 
 cerning the feat of hear- 
 ing. 
 
 496. What things are more cer- 
 
 tainly underftood con- 
 cerning this matter. 
 
 497. The diftinefion and grate- 
 
 ful nefs of found. 
 
 CHAP. XVII. 
 
 SIGHT. 
 
 498. The difference between 
 
 fight and hearing. 
 
 That the organ of fight 
 Is neceffarlly compound- 
 ed. 
 
 499. The eye-brow. 
 
 500. The palpebra;. 
 
 The conjunctiva. 
 
 The nerves and arteries of 
 the palpebrx. 
 
 501. The tarfus. 
 
 The levator mufcle of the 
 fnperior palpebra. 
 
 The orbicularis palpebra- 
 rum. 
 
 502. The cilia. 
 
 503. The Meibomian febaceous 
 
 glands. 
 
 504. The tears and their foun- 
 
 tains. 
 
 5C5. The 
 
INDEX. 
 
 505<. The duft of the laerymal 
 glands. 
 
 The efFefts of the contrac- 
 tion of the orbicular 
 mufcle. 
 
 506. What becomes of the tears. 
 The caruncula lacrymalis. 
 The third palpebra. 
 
 The punftum lacrymale. 
 
 507. The duftus lacrymalis. 
 
 The lacrymal fac. 
 
 The nafal duft. 
 
 50?. The figure of the eye. 
 
 The orbit. 
 
 The fat poured out around 
 it. 
 
 509. The optic nerve. 
 
 Its progrefs. 
 
 510. What afterwards becomes 
 
 of that which touches the 
 eye. 
 
 511. The fclerotica. 
 
 The cornea. 
 
 512. The choroides. 
 
 The Ruyfchian lamina. 
 
 The ciliary circle. 
 
 The pupil. 
 
 The iris. 
 
 The uvea. 
 
 The membrane covering 
 the pupil In the fetus. 
 
 513. The motion of the iris. 
 
 514. The ciliary ligaments. 
 
 515. The retina. 
 
 516. The humours of the eye. 
 The vitreous humour. 
 
 51 7. The cryftalline lens. 
 
 518. The aqueous humour. 
 
 The arches of the eye. 
 
 519. The llraight mufcles of the 
 
 eye. 
 
 520. The oblique mufcles of the 
 eye. 
 
 52 I, 522. The nerves of the eye. 
 
 521. The ophthalmic branch of 
 
 the fifth pair. 
 
 522. The branches of the third 
 
 pair. 
 
 523.. The motion of the ciliary 
 
 .3 
 
 515 
 
 procelTes. 
 
 524.527. The arteries of the eye. 
 
 528. The veins of the eye. 
 
 529. Light in general. 
 
 530. That light confifts of rays 
 
 fhewing different colours. 
 
 531. The colours proper to every 
 
 body, whence they come. 
 Opake bodies what. 
 
 532. How refraction happens, 
 
 and what it is. 
 
 533. When rays fall on a con- 
 
 vex fpheric body, which 
 of them are refrafted, 
 and which reflected. 
 
 The focus of the refraCled 
 ones. 
 
 534. What rays falling upon the 
 
 cornea are reflefted, or 
 being refracted are fuffo- 
 cated or come to the lens. 
 
 53 5. How the rays are refraCted 
 
 In their paffage through 
 the cornea and aqueous 
 humour. 
 
 536. How they are refraCted by 
 
 the cryftalline humour. 
 
 538. How they are refraCted by 
 
 the vitreous humour, and 
 are at laft collected up- 
 on the retina. 
 
 539. Whether objeCts are rather 
 
 painted on the choroides. 
 
 540. 541. How the eye is 
 
 thought to accommodate 
 itfelf to the various di- 
 ftances of objeCts. 
 
 542. But that nothing of this 
 
 kind happens. 
 
 543. Myopia. 
 
 544. The cure for this diforder. 
 
 545. Prefbyopla. 
 
 546. The remedy for prefbyopia. 
 547* That a medium between 
 
 ftiort and long fighted- 
 nefs is belt. 
 
 548. In what manner we judge 
 of the magnitude of ob- 
 jects. 
 
 S 2 549. The 
 
5i6 1 N D 
 
 549. The force of the light and 
 
 its effefts. 
 
 550. How the place of an objeft 
 
 is eftimated. 
 
 551. Diftance. 
 
 552. How we perceive gibbous 
 
 objefts. 
 
 553. In what manner we judge 
 
 CHAP. 
 
 INT E RNA 
 
 jljS. That fenfation then hap- 
 pens when a new thought 
 arifei in the mind by the 
 pcrcuffion of a nerve. 
 That that thought is not 
 the Image of the obJeA 
 affefting the nerve. 
 
 That thence an arbitrary 
 connexion arifes between 
 the changes produced in 
 the nerves and the 
 thoughts produced in the 
 mind. 
 
 Why, notwithftandlng this, 
 what we perceive of this 
 world Is not falfe. 
 
 S 57 ' What things are joined to- 
 gether while we think. 
 
 558. That the changes produced 
 
 by objefts in the nerves 
 remain a long time in 
 their origin. 
 
 The prefervation and order 
 of thefe traces. 
 
 559. Imagination, what it Is. 
 
 560. Memory. 
 
 561. At what times of life the 
 
 memoryand imagination 
 flouriih, and when they 
 decay. 
 
 562. Thought and attention. 
 Judgment and genius. 
 
 The fprings of error. 
 
 563. Soundnefs ofjudgment, on 
 
 what it depends, and by 
 
 E X. 
 
 of the fituation of the 
 parts of objefts. 
 
 554. That the images of objefts 
 
 remain for a little time, 
 even after the objefts 
 themfelvcs ate removed. 
 
 555. Various queftlons concern- 
 
 ing vifion. 
 
 XVIII. 
 
 L SENSES. 
 
 what It Is weakened. 
 
 564. What ideas raottly affeft 
 
 the will. 
 
 565. The affeftlons of the mind. 
 Effefts of the affeftions of 
 
 the mind. 
 
 566. The caufes of thefe effefts, 
 
 567. Thatthepaflionsofthemind 
 
 are faithfully exprefled 
 in the countenance. 
 Phyfiognomy, whence it 
 arifes. 
 
 568. Confent of parts, whence It 
 
 arifes. 
 
 569. That the nature of the foul 
 
 is different from the body. 
 J70. That the foul, however, is 
 moft clofely conuefted 
 with the body. 
 
 571. That we have no occafion 
 
 to be afhamed of our ig- 
 norance of the reafon of 
 this connexion. 
 
 572. By what arguments chiefly 
 
 thofe are perfuaded who 
 feek for the origin of all 
 the motions and adtions 
 In the body from the foul. 
 
 573. 576. Objeftions agaiuft 
 
 that opinion. 
 
 577. Watching. 
 
 Sleep. 
 
 578. Dreams. 
 
 That with thefe, fome vo- 
 luntary motions are fome- 
 times 
 
I N D 
 
 times conjoined. 
 
 579. What aftions continuetobe 
 
 carried on during fleep. 
 
 580. How the mechanical caufe 
 
 of fleepis to be difeo vered. 
 The phenomena of watch- 
 ing and fleep. 
 
 581.584. What things contri- 
 bute to fleep, and what 
 produce it. 
 
 585. The proximate caufe of 
 fleep. 
 
 E X. 517 
 
 586, 587. That this Is confirmed 
 by the caufes of watch- 
 ing, and what thefe 
 caufes are. 
 
 588. That the feat of fleep Is not 
 
 in the ventricles of the 
 brain. 
 
 Why the vital aftions go o« 
 in the time of fleep. 
 
 589. The effefts of fleep. 
 
 590. Various queftions concern- 
 
 ing the nature of fleep. 
 
 CHAP. XIX. 
 
 MANDUCATION, SALIVA, and DEGLUTITION. 
 
 591. That moft kinds of food 
 
 fland in need of mandu- 
 cation. 
 
 592. That therefore moft ani- 
 
 mals are furniflied with 
 teeth. 
 
 Their ftrufture in general. 
 
 593. That mankind, on account 
 
 of their diverfity of food, 
 have different kinds of 
 teeth. 
 
 The incifors. 
 
 594. The canine teeth. 
 
 595. The grinders. 
 
 596. That the teeth are fixed in 
 
 the jaw-bones. 
 
 The various motions and 
 articulation of the lower 
 jaw. 
 
 597. The levators of the jaw. 
 Thepterygoideus externus. 
 
 598. How the jaw is deprefled. 
 
 599. The powers of the levator 
 
 mufcles. 
 
 The mufcles producing a 
 lateral and circular mo- 
 tion of the jaw. 
 
 600. The cheeks. 
 
 The lips. 
 
 The mouth. 
 
 The fituation and mobility 
 
 of the tongue in the 
 mouth. 
 
 601. The liquor poured upon 
 
 the aliments during ma- 
 ftication. 
 
 Its fountains. 
 
 That the duftus incifivus Is 
 blind. 
 
 602. The faliva. 
 
 603. The parotid gland- 
 
 The gland called the accef- 
 fory one. 
 
 604. The maxillary one. 
 
 The fublingual gland. 
 
 605. That thefe, when compref- 
 
 fed, pour out their liquor 
 during the time of ma- 
 ftication. 
 
 Which compreflion only 
 produces the appetite. 
 
 606. That the aliments are tri- 
 
 turated with faliva and 
 air during the time of 
 feeding. 
 
 That thus they are render- 
 ed fapid. 
 
 That the volatile parts are 
 thus reforbed. 
 
 607. The motion of the tongue 
 
 for revolving the aliment 
 from one part of the ca- 
 vity 
 
I N D E X. 
 
 51B 
 
 vlty of the mouth to an- 
 other. 
 
 608. That the tongue is direfled 
 
 by the os hyoides. 
 
 The mufcles deprefling the 
 os hyoides. 
 
 609. The mufcles railing the os 
 
 hyoides. 
 
 610. The mufcles of the cheeks 
 
 and lips. 
 
 61 1. The aliment being chewed 
 
 is then collefted by the 
 tongue, and protruded 
 towards the fauces. 
 
 612. How the food is carried 
 
 from the mouth into the 
 fauces. 
 
 How the entry into the 
 larynx is clofed. 
 
 613. The pharynx. 
 
 614. The mufcles dilating the 
 
 pharynx. 
 
 6iy. How we take care that no 
 food falls into the larynx. 
 The velum of the palate. 
 The uvula. 
 
 616. How the return of the ali- 
 ment into the mouth is 
 
 prevented. 
 
 How the epiglottis and 
 uvula are eredfed after 
 theyhavebeen deprefled. 
 
 617. The ’powers which prefs the 
 
 aliments downward by 
 the pharynx. 
 
 The aftion of the aryte- 
 noid mufcles. 
 
 618. The mucus of the pharnyx, 
 
 and the various fprings 
 of it. 
 
 619. The tonfils. 
 
 The mucus of them exceed- 
 ingly ropy. 
 
 That the neigh’oouring 
 parts are full of mucous 
 organs, 
 
 O , 
 
 The more fluid mucus of 
 the cefophagus. 
 
 The veffels of the tonlils, 
 pharynx, and cefophagus. 
 
 619. * The cefophagus. 
 
 620. The paflage of the aliment 
 
 through the cefophagus. 
 
 62 1. The contraftion of the up- 
 
 per orifice of the fto- 
 mach. 
 
 CHAP. XX. 
 
 The action of the STOMACH os the ALIMENTS. 
 
 622. The fituation, figure, and 
 
 bignefs of the ftomach. 
 
 623. The vifcera in the neigh- 
 
 bourhood of the ftomach. 
 
 624. The external membrane of 
 
 the ftomach. 
 
 The firft cellular coat. 
 
 625. The mufcular coat of the 
 
 ftomach. 
 
 The ligaments of the pylo- 
 rus. 
 
 626. Another cellular coat. 
 
 The nervous coat of the 
 
 ftomach. 
 
 The third cellular coat. 
 
 The villous coat. 
 
 The valve of the pylorus. 
 The pores of the villous 
 coat, 
 
 627. The arteries of the ftomach. 
 
 628. The diftribution of the ar- 
 
 teries through the coats 
 of the ftomach. 
 
 629. The veins of the ftomach. 
 
 630. The nerves of the ftomach. 
 
 631. The lymphatic veffels of 
 
 the ftomach. 
 
 632. The inorganic pores of it. 
 
 633. A mucus anointing the vil- 
 
 lous membrane. 
 
 The 
 
5^9 
 
 index; 
 
 The limpid humour which 
 the arteries diftll. 
 
 634. The preffure of the dia- 
 
 phragm and mufcles of 
 the abdomen on the fto- 
 mach. 
 
 635. The neceffity of meat and 
 
 drink. 
 
 636. The phenomena of hunger. 
 
 637. New chyle, the ufe of it. 
 
 638. The caufe of hunger. 
 
 639. The feat of thirft. 
 
 How it is excited. 
 
 How quenched. 
 
 640. The pleafure of taking 
 
 food. 
 
 641. That we ought to inquire 
 
 why a diet is required 
 confiding of two kinds 
 of aliments. 
 
 642. Why flelh is required. 
 
 643. Why vegetables. 
 
 644. Drink. 
 
 645. Pickles and fauces 
 
 646. Preparations of aliments. 
 
 647. The meafure of food. 
 
 648. The changes which happen 
 
 to the food in the fto- 
 mach. 
 
 649. What hinders the food from 
 
 degenerating Into a full 
 acidity in the ftomach. 
 That there is no kind of fer- 
 ment here. 
 
 650. The perlftaltic motion of 
 
 the ftomach driving the 
 aliment into the Inte- 
 ftines. 
 
 65 1 . The more powerful force of 
 
 the diaphragm and ab- 
 dominal mufcles. 
 
 In what order and time the 
 aliments go out of the 
 ftomach. 
 
 652. What portion of drink in 
 
 the ftomach Is abforbed 
 into the veins. 
 
 653. Vomiting. 
 
 654. A confideration of the or- 
 
 der. 
 
 CHAP. XXI. 
 
 The OMENTUM. 
 
 655. The peritonaeum and its 
 
 circuit. 
 
 656. That .the cellular texture 
 
 placed round the perito- 
 naeum is continued Into 
 the capfules. 
 
 Its communications with 
 other parts. 
 
 657. The produAIons and liga- 
 
 ments of the perito- 
 naeum. 
 
 By the feparated laminae of 
 the peritonaeum the vif- 
 cera are furrounded, and 
 kept firm ajid defended 
 in motions and concuf- 
 fions of the body. 
 
 658. 659. The mefocolon. 
 
 660. That the mefocolon and 
 
 mefentery are hollow. 
 The flender purfes of the 
 mefocolon. 
 
 661. The mefentery. 
 
 662. What things are found In 
 
 all parts of the mefen- 
 tery and mefocolon, 
 
 663. That many parts come un- 
 
 der the name of omen- 
 tum. 
 
 Their nature In general. 
 
 A membrane coming from 
 the external membrane 
 of the colon, and lofing 
 itfelf in the fiflure of the 
 liver. 
 
 The natural mouth, and 
 common 
 
^20 I N D 
 
 common gate of the o- 
 menta. * 
 
 664. The leffer hepatico-gaftric 
 omentum. 
 
 $65. The anterior lamina of the 
 greater gaftro- colic o- 
 mentum. 
 
 666. Thcpollerior lamina of the 
 
 fame. 
 
 667. The omentum coHcum. 
 
 668- That it is common both to 
 
 the omentum and mefen- 
 tery to prefcrve the fat. 
 How it is proved that this 
 fat is received into the 
 veins. 
 
 E X. 
 
 669. The arteries of the omen* 
 
 ta. 
 
 670. The nerves of the omenta. 
 
 671. The arteries of the mefen- 
 
 tery and mefocolon. 
 
 672. The veins of the omentum 
 
 and mefentery. 
 
 The lymphatic veflelsof the 
 omentum. 
 
 673. Other ufes of the omen* 
 
 turn. 
 
 674. The ufc of the mefentery. 
 673. The water reforbcd by the 
 
 veins of the mefentery, 
 what fort it is, and what 
 it contributes to the bile. 
 
 CHAP. XXII. 
 
 The S ] 
 
 676. The fubftance of the fpleen. 
 Its figure. 
 
 Connexion. 
 
 Its fituation, bulk, and 
 number. 
 
 677. The arteries and veins of 
 
 the fpleen. 
 
 678. The lymphatic veflels of the 
 
 fpleen. 
 
 L E E N. 
 
 679. Its nerves, 
 
 680. Its internal ftrudlure. 
 
 The furrounding mem- 
 brane. 
 
 681. That the fpleen contains a 
 
 great deal of blood. 
 
 Its nature. 
 
 682. 83. The ufe of the fpleen. 
 684. Conjeftures concerning it. 
 
 CHAP. XXIII. 
 The pancreas. 
 
 68y. The pancreatic juice. 
 
 686. The fituation and figure of 
 
 the pancreas. 
 
 Its ftrufture. 
 
 Its veffels. 
 
 Its nerves. 
 
 687. The pancreatic duA. 
 
 688. The quantity of pancreatic 
 
 liquor. 
 
 The powers by which it is 
 expelled. 
 
 The perpetuity of the pan- 
 creas is an argument of 
 its utility. 
 
 Whence the effervefcence 
 with the bile is produced. 
 
 688. * The utility of the pan- 
 creatic juice. 
 
 CHAP. 
 
INDEX. 
 
 521 
 
 CHAP. XXIV. 
 
 The liver, GALL-BLADDER, and BILE. 
 
 689. The bulk of the liver. 
 
 The lituation of the liver 
 
 by reafoa of the dia- 
 phragm. 
 
 The ligaments from it. 
 Other bVaments, 
 
 O 
 
 How it can be moved. 
 
 Its common membrane. 
 
 690. How the liver is fituated 
 
 with refpefl. to the colon, 
 kidneys, duodenum, fto- 
 mach, and pancreas. 
 
 691. The (liape of the liver. 
 
 692. The furrows of the liver. 
 Its lobes. 
 
 693. The arteries of the liver. 
 
 694. The umbilical vein. 
 
 The dudlus venofus. 
 
 695. The large trunks of the ve- 
 
 na portarum. 
 
 696. The capfule of the vena 
 
 portarum. 
 
 The divifions of the branch- 
 es. 
 
 That thefe branches perpe- 
 tually accompany the he- 
 patic artery. 
 
 The proportion of the 
 branches of the vena 
 portarum to its trunk. 
 
 697. The branches of the cava. 
 The proportions of its 
 
 branches to thofe of the 
 vena portarum. 
 
 The trunk of the vena 
 cava. 
 
 The fmaller veins creeping 
 over the furfacc of the li- 
 ver. 
 
 698. The paflage of the blood 
 
 through the vena porta- 
 rum. 
 
 699. The nerves of the liver. 
 
 700. The lymphatic veffels of the 
 
 3 
 
 liver. 
 
 701. 3. The internal ftrufture of 
 the liver. 
 
 704. How it happens that the 
 
 bile is not fecreted from 
 the hepatic artery, but 
 from the vena portarum. 
 
 705. How the fecreted bile is 
 
 driven into the biliary 
 dufls and through them. 
 
 706. The ftrufture of the biliary 
 
 duft. 
 
 Its irritability and fenfa- 
 tion. 
 
 707. The duflus choledochus. 
 
 708. The duftus cyfticus. 
 
 The gall-bladder. 
 
 Its fituation. 
 
 709. The (hape of the gall-blad* 
 
 der. > 
 
 The vyrinkles of the duftus 
 cyfticus. 
 
 710. The coats and muciferous 
 
 pores of the gall-blad- 
 der. 
 
 The exhalation of the arte- 
 ries into the bladder. 
 That the bile exfudes thro’ 
 Inorganic pores. 
 
 711. That in man, no du6ts come 
 
 from the liver into the 
 , gall-bladder. 
 
 71 1. * That the bile flows into 
 the inteftine both from the 
 liver and from the gall- 
 bladder. 
 
 That all the bile is not firft 
 conveyed to the gall- 
 bladder. 
 
 The quantity of bile. 
 
 How often the bile flows 
 into the bladder. 
 
 That the bile is not fecre- 
 ted by its proper veficle. 
 ? 712, The 
 
I N D 
 
 E X. 
 
 532 
 
 712. The return of vitiated bile 
 
 into the blood. 
 
 713. The change which the bile 
 
 undergoes in the cyftis. 
 That it returns to the gall- 
 bladder, when there is no 
 ufe for it in the inte- 
 tlines. 
 
 7 T 4. The powers which exprefs 
 the bile from the gall- 
 
 bladder. 
 
 715. Thequalities, elements, and 
 
 offices of the bile. 
 
 716. Where the bile goes off. 
 That it fometimes comes in- 
 to the ftomach-. 
 
 The coagulation and ufe of 
 the bile in the fetus. 
 
 717. The proper ufe of the liver 
 
 in the fetus. 
 
 CHAP. XXV, 
 
 The small INTESTINES. 
 
 718. The fmall inteftines in ge- 
 
 neral. 
 
 Their divifion. 
 
 719. The duodenum. 
 
 That in it chiefly the bile 
 and pancreatic juice are 
 mixed with the aliments. 
 
 720. The feat of the remaining 
 
 part of the fmall inte- 
 fline in general. 
 
 '721,27. The ftrufture of the 
 fmall inteftines. 
 
 721. The external coat. 
 
 The firft cellular one. 
 
 722. The mufcular coat. 
 
 723. Another cellular coat. 
 
 The nervous coat. 
 
 The third cellular coat. 
 The villous coat. 
 
 Its folds. 
 
 724. The villi of the inteftines. 
 
 725. The veficles of the villi. 
 
 726. The larger pores of the vil- 
 
 lous coat leading to the 
 mucous glands. 
 
 727. The leffer pores likewife de- 
 
 pofiting mucus. 
 
 728. 730. The arteries of the 
 fmall inteftines. 
 
 730. The arteries of the duode- 
 
 num. 
 
 731. The veins of the fmall In- 
 
 teftines. 
 
 How it is proved that thefe 
 abforb a thin humour 
 from the inteftines. 
 
 732. The nerves of the fmall in- 
 
 teftines. 
 
 733. A liquid flowing from the 
 
 arteries into the cavity of 
 the inteftine. 
 
 Its quantity. 
 
 The ufes of the mucus of 
 the fmall inteftines. 
 
 734. 5. The periftaltic motion. 
 
 736. The changes which the 
 
 food undergoes in the 
 fmall inteftines. 
 
 737. The office of the fmall in- 
 
 teftines in general. 
 
 738. The principal caufes which 
 
 change the aliments in 
 the fmall inteftines. 
 
 CHAP. XXVI. 
 
 The large INTESTINES. 
 
 739. The remains of the food af- 740. How the ileon moves itfelf 
 ter the chyle is cxtrafted. towards 
 
INDEX. 
 
 towards the colon. 
 
 The valve of the colon. 
 
 741. The blind extremity of the 
 
 colon. 
 
 The appendix. 
 
 The change of ftrufture 
 which happens tothecas- 
 cum in an adult from 
 what it is in the fetus. 
 That the fetor of the inte- 
 teftines begins chiefly 
 there. 
 
 742. The fituation and connec- 
 
 tions of the inteftinum 
 colon. 
 
 743. The ftrufture of the colon 
 
 in general. 
 
 Its ligaments. 
 
 744. The cells of the colon. 
 
 The wrinkles, follicles, and 
 
 pores of its villous mem- 
 brane. 
 
 745. The veffels of the large in- 
 
 teftine. 
 
 746. The divillon of the veffels to 
 
 the large inteftines. 
 
 The exhalation and reforp- 
 tion from thefe. 
 
 The hemorrhoids. 
 
 747. The lymphatic veffels of 
 
 the large inteftine. 
 
 That chyle is fometimes ob- 
 
 523 
 
 ferved in thefe. 
 
 748. The nerves of the large In- 
 
 teftines. 
 
 749. The feces of the Inteftinum 
 
 colon. 
 
 The periftaltic and anti- 
 periftaltic motion of the 
 colon. 
 
 Flatus. 
 
 750. How the ileon is ftiut up. 
 The paffage of the feces 
 
 through the colon. 
 
 751. The fituation and duft of 
 
 the reft urn. 
 
 752. The external and mufcu- 
 
 lar coat of the reftum. 
 
 753. The internal fpinfter of the 
 
 anus. 
 
 The villous coat of the rec- 
 tum. 
 
 Its folds, and mucous glan- 
 dules. 
 
 The febaceous glandules of 
 the anus. 
 
 754. The external fphinfter of 
 
 the anus, and its aftion. 
 How the anus is naturally 
 cont rafted. 
 
 755. The levator mufcles of the 
 
 anus. 
 
 756. The excretion of the feces. 
 
 757. The feces themfelves. 
 
 C S A P. XXVII. 
 
 The CHYLIFEROUS VESSELS. 
 
 758. The nature of the chyle. 
 
 759. The abforption of the 
 
 chyle, and its paffage 
 through the lafteal vef- 
 ffls. 
 
 In what animals lafteal vef- 
 fels are found. 
 
 How they are difpofed in 
 the different inteftines. 
 
 "60. The valves of the lafteals. 
 The caufes of the chyle’s 
 2 T 
 
 motion through the coats 
 of the Inteftines. 
 
 761. The glands of the mefen- 
 
 tery. 
 
 That the chyle goes from 
 the inteftines to thefe 
 glands. 
 
 762. What happens to the chyle 
 
 in the glands of the me- 
 fentery. 
 
 763. The paffage of the lac* 
 
 3 teals 
 
5H 
 
 INDEX. 
 
 teals from the mefenteric 
 glands to the receptacle 
 of the chyle. 
 
 764. How the paffage into the 
 
 receptacle of the chyle 
 is demonltrated. 
 
 765, 6. The thoracic duft. 
 
 767. That the chyle conaes into 
 
 the blood through the 
 thoracic duft. 
 
 768. The caufe of the motion of 
 
 the chyle in general. 
 
 769. The change of the chyle 
 
 during its circulation 
 with the blood. 
 
 That in the inteftines there 
 are not lafteal and lym- 
 phatic vefTels of different 
 kinds. 
 
 770. That the lymphatic veffels 
 abforb water after the 
 time of digeftion is ex- 
 pired. 
 
 That the thoracic du6t 
 brings back the lymph 
 of the whole body. 
 
 CHAP. XXVIII. 
 
 The kidneys, BLADDER, and URINE. 
 
 771. That a part of the water 
 
 brought into the blood 
 by the chyle is drained 
 through the kidneys. 
 
 772. The fituation and con- 
 
 nexion of the kidneys. 
 Their figure. 
 
 External membrane. 
 
 Their fat. 
 
 Ligaments. 
 
 773. The arteries of the kidneys. 
 
 774. The veins of the kidneys. 
 The quick paffage of the 
 
 blood from the arteries 
 into the veins. 
 
 The veins of the renal fat. 
 
 775. The lymphatic veins of the 
 
 kidneys. 
 
 776. The nerves of the kidneys. 
 
 777. The renal capfule. 
 
 778. 80. The Internal drudfure 
 
 of the kidney. 
 
 778. The drudlure of the corti- 
 
 cal part. 
 
 The uriniferous veffels. 
 
 The glandules. 
 
 779. The papillae of the kidneys. 
 
 780. The infundibula, or funnels. 
 The pelvis. 
 
 781. The fecretion of the urine. 
 The quantity of the urine. 
 
 782. The elements of the urine. 
 
 783. How the ureter moves the 
 
 urine forward. 
 
 The ureter itfelf. 
 
 784. How it is proved that the 
 
 urine is feparated in the 
 kidneys, and defcends by 
 the ureter into the blad- 
 der. 
 
 785. That the urine cannot de- 
 
 fcend by other paffages. 
 
 786. The fituation of the urinary 
 
 bladder. 
 
 787. The figure and magnitude 
 
 of the bladder. 
 
 788. The fird cellular coat of 
 
 the bladder. 
 
 Its longitudinal mufcular 
 fibres. 
 
 789. Its other mufcular fibres. 
 
 790. The contradfile power of 
 
 the bladder. 
 
 791. The fecond cellular coat of 
 
 the bladder. 
 
 The nervous coat. 
 
 The innermod coat of the 
 bladder. 
 
 The mucus of the bladder, 
 and its fprings. 
 
 792. The veffels and nerves of 
 
 the bladder. 
 
 792. The 
 
I N D 
 
 E X. 
 
 525 
 
 The lymphatics, 
 
 793. That the bladder tranfmits 
 
 and abforbs water thro’ 
 its inorganic pores. 
 
 794. That the urine flows thro’ 
 
 the ureter intothebladder. 
 That it remains there. 
 
 The caufes retaining the 
 urine. 
 
 795. How the urine is expelled. 
 
 796. That various noxious mat- 
 
 ters are thrown off by the 
 urine. 
 
 The confequences of a re- 
 tention or fuppreffion of 
 
 CHAP. 
 
 The male ( 
 
 urine, 
 
 797, The urethra in general. 
 
 798. The parts receiving and 
 
 fupporting the urethra. 
 The various capacity and 
 figure of the urethra. 
 
 799 — 802. The mufcles gover- 
 ning the urethra. 
 
 803. That the pyramidal mufcle 
 
 has no effeft in drawing, 
 the bladder downward, 
 
 804. The mucus of the urethra, 
 
 and its various fprings. 
 
 805. The ftone in the urinary- 
 
 bladder. 
 
 XXIX, 
 
 I E N I T A L S. 
 
 806. The reafon of the fituatlon 
 
 of the genital parts. 
 
 807. Aconfideration oftheorder. 
 The various fituation of the 
 
 tefticles. 
 
 808. The fcrotum. 
 
 The dartos. 
 
 809. The cellular texture of the 
 
 fcrotum. 
 
 The cremafter. 
 
 810. The vaginal coat of the 
 
 teflicle. 
 
 The tunica albuginea. 
 
 81 1. The figure and fituation of 
 
 the epidydimis. 
 
 812. The fpermatic artery. 
 
 The abdominal ring. 
 
 The paffage of the fperma- 
 tic cords from thence to 
 the tefticle. 
 
 The fmall arteries to the 
 coats of the tefficle. 
 
 81 3. The diftributlon of the fmall 
 
 arteries thro’ the tefticle. 
 That the arteries have no 
 anaftomofes with the 
 fpermatic vein. 
 
 The motion and quantity 
 of the blood in the tefticle. 
 
 814. The fpermatic vein. 
 
 815. The veffels of the external 
 
 coverings of the tefticle. 
 
 816. The nerves of the tefticle. 
 
 817. The lymphatic veffels of 
 
 the tefticle. 
 
 818. The internal ftruAure of 
 
 the tefticle. 
 
 819. The ftrufture and wander- 
 
 ing veffel of the epidydi- 
 mis. 
 
 820. The motion of the feed. 
 
 821. The vas deferens. 
 
 822. The veficula feminalis. 
 
 823. The femen. 
 
 824. The animalcules of the fe- 
 
 men. 
 
 825. How thefe come to be in 
 
 the femen. 
 
 826. Whence the feed comes. 
 
 Of what humours it is com- 
 
 pofed. 
 
 What is generated in the 
 tefticles is only prolific. 
 How long the femen is pre- 
 ferved in the veffels. 
 
 827. That a part of the femen Is 
 
 abforbed, and its effefts. 
 How the femen is retained 
 in the veffels. 
 
 828. The 
 
E X. 
 
 I N D 
 
 526 
 
 828. The quantity of femen. 
 
 That the femen comes from 
 
 the tefticle Into the femi- 
 nal veffels. 
 
 829. The proftate gland. 
 
 Its liquor. 
 
 829. * The three dilatations of 
 the urethra; its various 
 diredtion; its coats. 
 \Oviitted, by 7 /iiJiake, in its proper 
 place.'] 
 
 “ 829. The urethra, tho’ in ge- 
 “ neralofacylindric figure, is yet 
 “ dilated into three pretty large 
 “ cavities. The firft is in the pro- 
 “ Hate, about the feat of the ca- 
 put gallinaginis; the jther is in 
 “ the bulb; and the third in the 
 “ beginning of the glans. Its 
 “ duft is generally horizontal at 
 “ firft; it then afcends along the 
 “ ofla pubis ; and, laftly, in man 
 “ it is pendulous, except during 
 “ the time of venery. It is con- 
 “ tinned from the nervous coat 
 “ of the bladder, and is covered 
 “ inwardly with a very fmooth 
 “ cuticle, between w'hich and 
 “ the nervous coat is interpofed 
 “ a cellular texture.” 
 
 830. The cavernous bodies of 
 
 the urethra. 
 
 831. How it is proved that the 
 
 blood is poured into this 
 body. 
 
 832. The cavernous bodies of the 
 
 the penis. 
 
 833. The teguments of the penis. 
 The prepuce. 
 
 The odoriferous glands. 
 The fufpenfoiy ligament. 
 
 834. The ufe of the penis. 
 
 835. The eredlion of the penis. 
 Its exciting caufes. 
 
 836. The arteries of the genital 
 
 parts. 
 
 837. The veins of the fame parts. 
 
 838. The lymphatic veffels of 
 
 the penis. 
 
 The nerves of the genital 
 parts. 
 
 839. The immediate caufe of the 
 
 ereftion of the penis. 
 
 840. The expulfion of the femen 
 
 into the urethra. 
 
 841. Its expulfion from the ure- 
 
 thra. 
 
 That this aftion is moft 
 violent, and next to a 
 convulfion. 
 
 CHAP. XXX. 
 
 The V I R G I N W O M B. 
 
 842. The fituation of the uterus 
 
 in the pelvis. 
 
 How the uterus is tied to 
 the peritoneum. 
 
 The broad ligaments. 
 
 843. The body, neck, and inter- 
 
 nal 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 
 
 uterus. 
 
 848. The arteries of the uterus. 
 
 849. Its veins. 
 
 850. The internal veffels of the 
 
 uterus. 
 
 85 1 . The lymphatic veffels cf the 
 
 uterus. 
 
 852. The uterine nerves. 
 
 853. The age at which the men- 
 
 fes begin to flow. 
 
 834. The phenomena of themen- 
 fes. 
 
 The duration of the flux. 
 The periods at which they 
 return. 
 
 855. That the menftrual blood 
 flows from the veffels of 
 the uterus itfelf. 
 
 The 
 
INDEX. 
 
 527 
 
 The nature of the menllrual 
 blood. 
 
 That the uterus being ob- 
 ftrufted, the blood flows 
 out through the vagina, 
 and thro’ other parts. 
 
 556. Whether the moon, fer- 
 
 ments, or the venereal 
 define, are the caufes of 
 the menfes. 
 
 557. The female body in general. 
 The pelvis and its veflcls, 
 
 in as far as they differ 
 from the fabric of the fi- 
 milar parts in a man. 
 How the paflage of the 
 blood through the uterus 
 is thence affedfed. 
 
 559. The inferior limbs, pelvis, 
 
 and uterus, of a female 
 child newly born. 
 
 How the ftrufture of thefe 
 is changed in the adult. 
 The effedfs of thefe changes. 
 
 560. That a plethora is gene- 
 
 rated in both fexes when 
 
 the growth of the body 
 ceafes. 
 
 That this, in males, goes 
 off by the noftrils. 
 
 That in women it finds an 
 eafier paffage by the ute- 
 rine veffels. 
 
 That there are other effedfs 
 of this determination of 
 the blood. 
 
 How the quantity of the 
 menfes is increafed or di- 
 minifhed. 
 
 861. The quantity of the blood 
 
 fent out. 
 
 The reraiffion and return of 
 the period. 
 
 Why the period is com- 
 monly fixed ta a month.. 
 
 Why the menfes ceafe to 
 flow altogether. 
 
 Why brute animals have 
 no menfes. 
 
 Why men want them. 
 
 862. Why the breads fvvell out 
 
 at the fame time. 
 
 CHAP. XXXI. 
 CONCEPTION. 
 
 863. The diiScuIty of treating 
 
 this fubjedt properly. 
 The order of treating it. 
 
 864. The mod Ample animals 
 
 which have no fexes. 
 How they produce their 
 young ones/ 
 
 865. Oviparous animalsof onefex. 
 866, 7. Animals of two fexes 
 joined in one. 
 
 866. "V^Tiat animals impregnate 
 
 themfelves. 
 
 867. Animals of this kind which 
 
 dand in need of one ano- 
 ther’s affidance. 
 
 868. Animals with two fexes di- 
 
 vided. 
 
 869. Confequences which follow 
 
 from what has been faid 
 
 concerning the origin and 
 fexes of animals. 
 
 870. Caufes of the defire of ve- 
 
 nery. 
 
 871. The vagina, andltsfituatlon. 
 The hymen. 
 
 The caruncuhe myrtiformes. 
 
 872. The drudfure of the vagina. 
 
 873. The nymphas. 
 
 The clitoris. 
 
 874. The condridfor mufcle of 
 
 the mouth of the vagina. 
 
 875. Coition. 
 
 What happens to women 
 during the time ofcoition. 
 
 876. The fprings of the mucous 
 
 liquor thrown out in co- 
 ition. 
 
 That 
 
5*8 
 
 INDEX. 
 
 That the tubes in coition 
 are ercded, and moved 
 towards the ovarium. 
 
 877. 8. What changes take place 
 in the ovarium at that 
 time. 
 
 The corpus luteum. 
 
 S78. How it is proved that the 
 tube preffes out the egg, 
 abforbs it, and carries-it 
 towards the uterus. 
 
 679. The feelings of the future 
 ifiother while thefe things 
 are performed. 
 
 How it is proved that con- 
 ception takes place in the 
 ovarium. 
 
 88o.Whythe uterus is thought to 
 be (hut after conception. 
 
 Whence the complaints af- 
 ter conception arife. 
 
 S81-. The original (lamina of the 
 new animal, whether they 
 are from both parents, 
 and the mixture of feeds 
 coming from all parts of 
 the body. 
 
 882. Whether they are only from 
 the male and feminal 
 worms. 
 
 S83. Whether the fetus does not 
 proceed rather from the 
 mother. 
 
 884. Hypothefes concerning the 
 formation of the new a- 
 nimal. 
 
 S85. What can be more certain- 
 ly known concerning this 
 matter. 
 
 886. The (late of the embryo 
 before conception.# 
 
 How it is changed by the 
 male femen. 
 
 8S7. Objedlions from moles, of 
 no weight. 
 
 888. The change of the egg 
 when brought into the 
 uterus. 
 
 Its inofculation with the 
 uterus. 
 
 889. The contents of the egg at 
 
 that time. 
 
 A defeription of the fetus 
 during the firft days of 
 conception. 
 
 890. The incrcafe of the egg 
 
 and the fetus until the 
 placenta is completed. 
 Defeription of the comple- 
 ting of the placenta. 
 
 891. The placenta, and its con- 
 
 neftlon with the ute- 
 rus. 
 
 892. The chorion. 
 
 893. The middle membrane. 
 
 894. The amnion. 
 
 895. The umbilical vein by which 
 
 nourifhment is conveyed 
 to the fetus. 
 
 The cord. 
 
 8q6. The umbilical arteries. 
 That thefe with their veins 
 and cellular texture form 
 the placenta. 
 
 That the blood goes out 
 from the placenta into 
 the veins of the uterus. 
 
 897. Whether the fetus takes In 
 
 the liquor of the amnion 
 by the mouth, and is nou- 
 ri(hed by it. 
 
 What is the fource of this 
 liquor. 
 
 898. The eyrements of the fe- 
 
 tus. 
 
 899. Whether there is no allan- 
 
 tois in the human race. 
 That they certainly have 
 an urachus. 
 
 That the urine is perhaps 
 depofited in the cellular 
 texture of the cord. 
 
 900. That fome compendium of 
 
 the atjthropogenia, or for- 
 mation of the fetus, is to 
 be given. 
 
 901. What 
 
INDEX. 529 
 
 901. What parts are formed at 
 
 the very firft beginnings 
 of the fetus. 
 
 902. The proportion of the fluid 
 
 to the folid parts at that 
 time. 
 
 903. The nutritious juices acce- 
 
 ding to it. 
 
 How the blood and reft of 
 the humours are perfec- 
 ted. 
 
 904. How the folid parts in ge- 
 
 neral are formed. 
 
 905. That the veflels are the old- 
 
 eft parts of the human 
 body. 
 
 How they are produced. 
 
 906. What veflels are at firft 
 
 completed and become 
 confpicuous in the pri- 
 meval fetus. 
 
 What are as yet involved 
 and lie hid. 
 
 907. That the motion of the 
 
 heart accedes to this kind 
 of embryo. 
 
 That the heart is very large 
 at firft in proportion to 
 the reft of the body. 
 
 Its pulfations are moft 
 powerful for diftending 
 and lengthening the vef- 
 fels. 
 
 908. What is oppofed to this 
 
 power of the heart. 
 
 How the arteries are then 
 afFefted. 
 
 909. That the fetus grows moft 
 
 quickly. 
 
 The caufe of this quick in- 
 creafe. 
 
 910. That the embryo is formed 
 
 during its growth. 
 
 910. 14. By what caufes this is 
 chiefly produced. 
 
 910. Expanfion. 
 
 911. Attraffion. 
 
 912. Preflure. 
 
 913. The power of derivation. 
 Of revulfion. 
 
 914. The change of the humour. 
 
 915. How the bone fucceeds the 
 
 cartilage and epiphyfis. 
 
 916. How along bone Is formed. 
 
 917. How the flat bones are 
 
 formed. 
 
 918. How a bone is produced 
 
 from a gluten. 
 
 That this gluten is depofi- 
 ted from the inmoft fub- 
 ftance of the bone, and 
 not from the periofteum. 
 
 919. The periofteum. 
 
 920. The fetus during the firft 
 
 days of pregnancy. 
 
 921. The thymus. 
 
 921, 24. The proper circulation 
 of the blood In the fetus, 
 and the organs by which 
 It is performed. 
 
 925. Whether the fetus breathes 
 
 in the womb. 
 
 Whether it does fo in the 
 ■ vagina. 
 
 926. The changes which hap- 
 
 pen to the uterus during 
 the time of pregnancy. 
 The different fituations of 
 the fetus. 
 
 927. The complaints attending 
 
 pregnancy. 
 
 The time of delivery. 
 
 928. The delivery itfelf. 
 
 929. The number of fetufes. 
 Superfetation. 
 
 930. The loofening of the pla- 
 
 centa. 
 
 Of the navel. 
 
 93 1 . The contraflion of the ute- 
 
 rus after delivery. 
 
 The lochia. 
 
 The fwelling of the breafts, 
 
 944. * The milk. 
 
 Sympathy betwixt the 
 
 breafts and uterus. 
 
 945. The breafts. 
 
 3 U 
 
 Their 
 
530 
 
 INDEX. 
 
 Their veffels. 
 
 And nerves. 
 
 946. The laftiferous dufts in the 
 
 bread. 
 
 The nipple and Its ladllfe- 
 rous dudls. 
 
 The circle furrounding the 
 nipple. 
 
 947. Suftion. 
 
 The colojlra, or firft milk 
 after delivery. 
 
 That milk may be produ- 
 ced without a child. 
 That the breads, after the 
 menfes have ceafed, be- 
 - come effete. 
 
 948. 52. The changes which hap- 
 pen to the child after 
 birth. 
 
 948. Refpiratlon. 
 
 The deflexion of the courfe 
 the blood from the duc- 
 tus arteriofuj. 
 
 949. The (hutting up of the fo- 
 
 ramen ovale. 
 
 950. The (hutting up of the um- 
 
 bilical vein and duChis 
 venofus. 
 
 951. The contraftion of the um- 
 
 bilical veins, and aboli- 
 tion of the ui-achus. 
 
 952. Other changes. 
 
 CHAP. XXXII. 
 
 NUTRITION, GROAVTH, LIFE, and DEATH. 
 
 953. That achild’sgrowth is (low- 
 
 er as it advances in age. 
 Why the growth is conti- 
 nually leffened. 
 
 954. That the heart grows lefs 
 
 than any other part of 
 the body. 
 
 And becomes lefs Irritable. 
 
 955. The end of the increafe of 
 
 the body. 
 
 956. When this date is fald to 
 
 be prefent. 
 
 957. How it Is proved that all 
 
 parts, even the mod folid, 
 are continually confu- 
 ming and changing. 
 
 958. The caufe of the dedruc- 
 
 tlon of the folid parts. 
 
 959. How/this wade of parts is 
 
 repaired. 
 
 960. How the wade of the cel- 
 
 lular fubdance and mod 
 organic parts is repaired. 
 
 961. How the free extremities of 
 
 the parts are repaired. 
 
 F I 1 
 
 962. Fatnefs. 
 
 963. The beginnings of decay. 
 
 964. The progrefs of decay. 
 
 965. The diminution of the vis 
 
 infita and nervous power. 
 
 966. 8. The change of the hu- 
 
 mours. 
 
 966. The decreafe of the hu- 
 
 mours. 
 
 967. The corruption of the hu- 
 
 mours. 
 
 968. The increafe of the quan- 
 
 tity of earth in the hu- 
 mours. 
 
 969. Old age. 
 
 970. Decrepit old age. 
 
 97 t . Longevity. 
 
 972. Natural deathfromold age. 
 
 973. The figns of death. 
 
 974. That the carcafe is deliver- 
 
 ed to corruption. 
 
 That the foul remains after 
 death, and goes to tlwt 
 place where God com-j 
 mands it. 
 
 I S. 
 
 PRINTED MdCFAR^VHAR AND ELLIOT. 
 
BOOKS printed for Charles Elliot, Parliament* 
 fquare, Edinburgh. 
 
 s. A Treatise on the theory and management of ulcers, 
 with a differtation on white fwellings of the joints ;• to 
 which is prefixed, An eflay on the chirurgical treat- 
 ment of inflammation and its confequences, one vol. 8 vo. 
 By Benjamin Bell, member of the College of Surgeons 
 of Edinburgh, and one of the furgeons to the Royal In- 
 firmary. Boards^ ^s. 
 
 2. Van Swieten’s commentaries upon Boerhaave’s apho- 
 rifms, a correct editiony dedicated to Dr Cullen, i8 vols. 
 royal paper, 3 1. 3 s. 
 
 3. Univerfal Short-hand, from which any perfon, in a few 
 weeks, may become perfefUy mailer of the art; — with 
 fpecimens from the ledlures of Drs Cullen and Monro, 
 8 VO. Sewed, 6 s. 
 
 4. Thefaurus Medicus ; five, Difputationum in academia 
 Edinenfi, ad rem medicam pertinentium, a collegio inlli- 
 
 tuto, ad hoc ufque tempus, dele£lus; 2 vols, 8vo 
 
 Vol. I. or II. or any of the fubfequent ones, may be had 
 
 feparately. It is the object of this fele£lion, to exhibit 
 
 a progreflive view of the pra£lice and doflrines that have 
 been taught in this now moll celebrated fchool of medi- 
 cine in Europe. —To accomplilh this purpofe, one dif- 
 
 fertation at leall is given upon every fubjedl that has been 
 
 treated. The whole is executed with the approbation 
 
 of the prefent profeflbrs of the different branches of the 
 healing art. Volume II. now publilhed, brings this col- 
 ledlion down to the 1758; and is enriched with Dr Alex- 
 ander Monro jun‘‘.’s celebrated Thefis de Teftibus et de 
 Semine jn variis animalibus, who obligingly fiirnilhed the 
 publifhcr with the ufe of the accurate orignal engravings 
 for illullrating his fubjcdl. Price 6 s. volume, boards, 
 or 7 s. bound. 
 
 Douglas on the mufcles, a new edition, with an account 
 of the blood-velfels and nerves, 8vo. Sewed, 3 s. 
 
 6. Dr Cullen on the recovery of drowned perfons, i s. 
 
 7. Dr Duncan’s medical cafes, fele£led from the records 
 of the public difpenfatory at Edinburgh; with pra£lical 
 remarks and obfervations, being the fubftance of clinical 
 ledlures delivered during the years 1776 — 7. Boards, 
 
 or 5 s. bound. 
 
 ,8. — Elements of therapeutics, 2 vols. 6s. 
 
 9. Dr 
 
c 2 :i 
 
 9. Dr Duncan’s heads of Ie£fures on the theory and prac- 
 tice of phyfic; to which is prefixed, An addrefs to the 
 ftudents of medicine, delivered in November 1776. One 
 vol. i2mo. 2 s. 6d. boards. 
 
 10. — obfervations on the operation and ufe of 
 
 mercury, 2s. 6d. 
 
 11. addrefs to the ftudents of medicine. Price 
 
 6d. 
 
 12. medical and philofophical commentaries, 
 
 ^ vols 8vo. I 1. 15 s. N. B. Any number may be had fe- 
 parate to complete fets. 
 
 13. A fhort defeription of the human mufcles, chiefly as 
 they appear on dilTetfion; with their feveral ufes, and fy- 
 nonima of the beft authors. By John Innes. The fecond 
 edition, revifed and much improved by Alexander Mon- 
 ro, M. D. profefibr of anatomy in the univerfity of Edin- 
 burgh 
 
 14. Eight anatomical tables of the human body, contain- 
 ing the principal parts of the flceleton and mufcles re- 
 prefented in the large tables of Albinus. To which are 
 added, Concife explanations, by John Innes, late dilfec- 
 tor to Dr Monro. The fecond edition. Price 6s./ewedy 
 and 6 s. 6d. half-bound, in 4to.— About a dozen copies 
 remain of proof-imprefiion, before the figures were af- 
 fixed to the tables, at 4s. each; or bound in with the 
 book, los. 6d. 
 
 15. An anatomical expofition of the ftruifture of the human 
 body, by James Benignus Winflow, profefibr of ana- 
 tomy, phyfic, and furgery, in the univerfity of Paris, 
 member of tbe royal academy of fciences, and of the 
 royal fociety at Berlin, ere. Tranflated from the French, 
 by G. Douglas, M. D. Illuftrated with copperplates. 
 2 vols 8vo. Price 10 s. bound. 
 
 16. Macquer’s elements of the theory and pra£lice of che- 
 miftry, a new edition, complete in one vol. with cuts. 
 Price only 6 s. 
 
 17. Dr Mead’s whole medical works, a new edition, with all 
 the copperplates, 6 s.