COLUMBIA UNIVERSITY 
 DEPARTMENT OF PHYSIOLOGY 
 THE JOHN G. CURTIS LIBRARY 
 
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DISSERTATIONS 
 
 RELATIVE TO THE 
 
 NATURAL HISTORY 
 
 OF 
 
 ANIMALS AND VEGETABLES. 
 
 TRANSLATED FROM THE ITALIANOF TH^ 
 
 ABBE SPALLANZANI, 
 
 Royal Profeflbr of Natural Hiftory in the Univerfity of 
 Pavia, Superintendent of the Public Museum, and 
 Fellow of various learned Societies. 
 
 In TWO VOLUMES. 
 A NEW EDITION CORRECTED AND ENLARGED. 
 
 V Q L I. 
 
 LONDON: 
 
 PRINTED FOR J. MURRAY, NO. 32, FLEET-STREET; 
 M DCC LXXXIX. 
 
S/'^c 
 
 «^// 
 
 
INTRODUCTION. 
 
 IN the courfe of my public demonftrations 
 in the year 1777, I repeated in the pre- 
 fence of my hearers thofe celebrated experi^ 
 ments of the Academy of Cimento, which 
 fhew that the Homachs of fowls and ducks 
 exert fo aflonifhing a force as to reduce hol- 
 low globules of glafs to powder in the fpace 
 of a few hours. Finding them perfedlly exact, 
 I conceived the defign of extending them to 
 fome other individuals of that clafs of birds 
 which have been termed birds with miijcidar 
 Jlomachs or gizzards. Such were the firfl 
 lines of an undertaking, of which till that 
 time I had never entertained the fmallell idea, 
 and which afterwards became more and more 
 extenfive, as my curiofity concerning fo fine 
 and ufeful a fubjed as the important fundtion 
 of Digeftion increafed. Hence from animals 
 with mufcular ilomachs, I was induced to 
 proceed to thofe with intermediate, and from 
 thefe again to animals with membranous fto- 
 VoL. I, B machs. 
 
( " > 
 
 mach^ (a). Thus I enjoyed the pleafure of 
 extending my refearches to the principal 
 claffes of animals, not neglecting Man, the 
 nobleil and moil interefting of all. But thefe 
 phyliological refearches laid me under the 
 neceffity of examining the moil celebrated 
 fyftems concerning Digeilion, and of enquir- 
 ing whether it is effecled by trituration, by a 
 folvent, by fermentation, or by an incipient 
 putrefaction : or whether, according to the 
 opinion of the great Boerhaave, it rather de- 
 pends upon all thefe caufes operating in con- 
 junction. Thus I was obliged to enter anew 
 upon a quefliion of very ancient date, and 
 though difcufTed at great length by many 
 phyfiologifts, yet not in my opinion fuf- 
 ficiently elucidated; lince moil writers have 
 chofen to follow the delufive invitation of 
 theory and hypothecs, rather than the un- 
 erring direction of decilive experiments. The 
 impartial and judicious reader, when he ihall 
 have perufed the prefent eflay, will be able 
 to determine, whether what I aflert, be true 
 or falfe. 
 
 {a) The 1, Lviii, and civ paragraphs will explain what 
 is meant by birds with mufcuiari iuterinediate, and menibra- 
 feus ftomachs, 
 
 DIS- 
 
DISSERTATION I. 
 
 CONCERNING 
 
 DIGESTION* 
 
 On the digestion of Animals wiTit 
 
 MUSCULAR STOMACHS, COMMON FOWLSj* 
 TURKEYS, DUCKS, GEESE, DOVES, PI- 
 GEONS4 
 
 I. 'T^HOUGH there perhaps exifts no 
 A animal, of which the ftomach is not 
 furnifhed with mufcles, yet there is a fingu- 
 lar clafs, juftly denominated by feveral natu- 
 raUlls animah with mufciilar jiomachsy lince 
 that vifcus is provided with remarkably large 
 and powerful mufcles ^ To this clafs belong 
 fowls, ducks, pigeons, g^ti^, partridges, &c. 
 So great is the ftrength of thefe mufcles, that 
 many have imagined that they produce di- 
 geftion by acting violently upon the contents 
 of the ilomach, and breaking down and re- 
 ' B 2 ducing 
 
4 DISSERTATION I. 
 
 ducing them to a pultaceous mafs, in no re- 
 fped diifering from imperfe (51 chyle. This 
 notion was afterwards appUed to other ani- 
 mals, nor was man himfelf exempted ; and it 
 has been pretended, that digeftion is uniyer- 
 fally owing to the alternate adtion of the muf- 
 cles of the ilomach, or, as it has been termed, 
 to trituration. 
 
 II. Now, to confine ourfelves to animals 
 with mufcular itomachs, there was little diffi- 
 culty in deviling the means of determining 
 whether the comminution and folution of 
 food is effed:ed by the galliric mufcles. Such 
 means have been contrived and fuccefsfully 
 put in pracTiice by Reaumur. " Let feveral 
 animals refembling each other in ftrudlure," 
 fays that great naturalift in his two excellent 
 memoirs on this fubjetl, of which, I fhall 
 make frequent ufe in the fequel, " be made 
 to fwallow metallic tubes open at both ends, 
 and filled with fome of their natural food, as 
 grains of the Cere alia when gallinaceous fowls 
 are the fubje(fts of our experiments. Should 
 thefe grains, after they have remained a cer- 
 tain time in the ilomach, be broken down 
 and d.ecompofed, we mufi: afilime a difTolving 
 liquor as the caufe of this phenomenon, fince 
 ^the fides of the metallic tubes muil have been 
 -an insuperable obilacle to the exertions-of the 
 
 gaftric 
 
DISSERTATION I. 5 
 
 gaftric mufcles upon the contents^ but if 
 they Hiould be retrieved in a found and entire 
 i^iitc, it muil be acknowledged, that in thefe 
 animals digeftion does not depend on a fol- 
 vent, but on the adion of mufcles," And 
 iuch was the plan adopted by this fagacious 
 philofopher. He enclofed fome barley in 
 metallic tubes open at each end and forced 
 them down the throats of common fowls, 
 turkeys and ducks. Upon killing the ani- 
 mals fome hours afterwards and taking the 
 tubes out of the flomach, the grains were 
 found quite entire ; whence he inferred, that 
 irubirds of the gallinaceous -clafs the food is 
 not broken down by a folvent, but by flrong 
 mufcularad:ion, 
 
 III. This experiment feems indeed highly 
 favourable to the dodirine of trituration ^ yet 
 I think it would have been rnuch more con- 
 cluiive, if the fame refult had been obtained 
 from other individuals of this clafs, and if be- 
 iides barley, other grains upon which they na- 
 turally feed, fuch a§ wheat, maize, rye, chick- 
 peafe, &c. had been employed, i therefore 
 refolved to put each pf thefe feeds to the tejft 
 of experiment in the following manner. I 
 procured fome tin tubes eight lines in length 
 and four in diameter, and inclofed in each ^, 
 cjuantity of feeds greater or lefs according as 
 B3 they 
 
6 D 1 S S E R T A t I O N I. 
 
 they were themfelyes fmaller or larger, The 
 ends of the tube were left open, but iron wires 
 were made to pafs before them, fo as to -crofs 
 each other, and form a kind of lattice-work. 
 Common fowls were the firft fubjefts qf my 
 experiments : I forced fome of the tubes into 
 the ftomach, condutling them with my fore- 
 finger and thumb through the oefophagus, 
 till I was certain they were in the cavity of 
 that vifcus, When this operation is properly 
 performed, neither fowls nor other animals 
 fuflain any injury. In twenty-four hours the 
 tubes were taken out, and the contents upon 
 examination appeared to be unaltered: even 
 the colour and tafte were unchanged, if we 
 except a flight bitter flavour v^hich they had 
 acquired. They had imbibed fome moifture, 
 and were a little fwoln. The fame feeds in- 
 clofed alfo in tubes, and left in the ilomach 
 two and even three days, under^yent no greater 
 change, 
 
 IV, Several times, immediately after having 
 forced the tubes full of grrains into the do- 
 
 o 
 
 mach, I introduced fome of the fame grains 
 loofe. The latter were broken down in a 
 few hours, but the former remained entire. 
 
 V, The food taken fpontaheoully by thefe 
 birds does not pafs immediately into the fto- 
 mach, but ftops for fome time in the crop, 
 
 where 
 
DISSERTATION 1. 7 
 
 where it is macerated, and becomes fofter* 
 Is fuch a previous maceration necefTary before 
 it can be diflblved within the tubes ? This 
 circumftance feemed to defer ve attention. I 
 therefore repeated the foregoing experiments 
 with feeds taken from the crop of a fowl, 
 after they had undergone a complete macera* 
 tion. Notwithflanding this preparation, they 
 underwent no change within the tubes, 
 
 VI. From thefe refults it was eafy to pre- 
 dict, that no new appearance would occur, if 
 the fkin fhould be taken off, as it really hap- 
 pened. It is proper to add, that other grains 
 treated in the fame manner were no more dif- 
 folved than thofe before-mentioned. 
 
 -VII. The mode which I had hitherto prac- 
 tifed of ufmg tubes open at both ends, at 
 which the gaflric fluid was certainly at liberty 
 to enter, was that of Reaumur. But this 
 fluid having no other accefs, cannot exert its 
 adtion on the inclofed grains fo powerfully as 
 when they are loofe in the ftomach, as Reau- 
 mur ingenuoully confelTes, To obviate this 
 inconvenience in fome meafure, I had the 
 fides of the tubes perforated with a great num- 
 ber of holes. I had moreover recourfe to 
 another expedient. I employed hollow glo- 
 bules of brafs half an inch in diameter, and 
 pierced like a fieve^ which I could open and 
 B 4 (hut 
 
8 DISSERTATION" I. 
 
 fliUt at pleafure by means of a fcrew worked 
 upon the edge of the two hemifpheres, into 
 which each globule was divifible. With 
 thefe new tubes and fpherules I repeated 
 the preceding experiments, not only upon 
 common fowls, but upon ducks, turkeys, 
 geefe, doves, and pigeons: and as a larger 
 quantity of liquor could now find its way to 
 ■ the inclofed fubflances, they were more tho- 
 roughly foaked, and had acquired a bitterer 
 tafte (iii)j but I could never perceive the 
 llighteft token of fol^tion, though they con- 
 tinued along time in the ilomach. 
 
 yiii. Thefe fads afford an irrefragable 
 * proof, that the trituration of feeds in the flo- 
 mach of granivorous birds, is folely owing to 
 ilrong preiTure and repeated and violent per- 
 cufTions: effeds produced by the powerful 
 mufcles with which that organ is furnifhed. 
 
 IX. The contents of the ftomach are fo 
 violently agitated as to be driven in at the 
 open ends and through the holes of the tubes 
 and fpherules, which occafions fome confu- 
 fion. Hence I have frequently found it of 
 fervice to introduce thefe receivers when the 
 itomach was empty, and to keep the animal 
 failing during the whole time of the expe- 
 riment. 
 
 X. The 
 
DISSERTATION 
 
 X. The violent adion of the fides upon the 
 contents of the flomach renders another pre- 
 caution highly neceflary. The thicknefs of 
 the tubes and fpherules Ihould be confider- 
 able, otherwife the obferver, when he takes 
 them out of the flomach, will find them bro- 
 ken, cruflied, or diftorted in a moft lingular 
 manner, if they have been long retained. 
 Reaumur mentions feveral accidents of this 
 fort {a) ; and I have ken inilances without 
 number of fuch contufions, one of which I 
 cannot forbear relating here. Having found 
 that the tin tubes which I ufed for common 
 fowls were incapable of refilling the force of 
 the Homach of turkeys, and not happening 
 at that time to be provided with any tin foil 
 of greater thicknefs, I tried to flrengthen them^ 
 by foldering to the ends two circular plates 
 of the fame metal, perforated only with a few 
 holes for the admiffion of the gaftric fluid. 
 But this contrivance was ineifedual i for after 
 the tubes had been twenty hours in the ilo- 
 mach of a turkey, the circular plates were 
 driven in, and fome of the tubes were broken, 
 fome comprefled, and fome diilorted in the 
 xnofl irregular manner. 
 
 («) In the Memoir quoted above. 
 
 XI. I 
 
lO DISSERTATION I, 
 
 XI. I then tried the following means of 
 preventing this inconvenience. Having per- 
 forated the circular laminas in the center, I 
 pafTed an iron wire through the holes, and 
 bound it tight round the outfide of the tubes 
 and twifled the two ends together. And now 
 though the foldering Ihould be deftroyed, yet 
 this contrivance would prevent the circular 
 laminae from receding from the ends of the 
 tube, unlefs the wire which paffed through 
 them ihould be broken. I prepared four 
 tubes in this manner, and gave them to a tur- 
 key fix months old. After they had remained 
 a whole day in the ftomach, I killed the ani- 
 mal; and was exceedingly furprized to find 
 that the tubes, in fpite of my expedient, were 
 very much damaged. All the iron wires were 
 broken, two where they were twifted, and the 
 two others at tlieir entrance into the tubes : 
 the laminag, fo far from remaining foldered to 
 the tubes, were found amongft the food; they 
 were not flat as at firil, but fome were bent 
 ih as to form an angle, fome curved, and in 
 others, one part was preffed clofe to the other. 
 The tubes had fuftained equal injury; two 
 of them were flattened as if they had been 
 flruck by an hammer, the third v/as moulded 
 into the fhape of a gutter, the foldering of the 
 fourth was deflroyed, and it was made as flat 
 as a wafer. xii. Thefe 
 
DISSERTATION I, IF 
 
 XII. Thefe phsenomena will not (o much 
 furprize thofe who have learned from Redi {a) 
 and Magalotti (^), how ducks, fowls, and 
 pigeons reduce to powder hollow globules of 
 glafs in a very fhort fpace of time, and even 
 folid ones in a few weeks. I have already 
 obferved, that I repeated thefe experiments 
 with the greateft fuccefs {c) . Some fpherules 
 of glafs blown by the lamp, and fo thick that 
 they would feldom break when thrown upon 
 the ground, were commonly reduced to fmall 
 fragments, after remaining three hours in the 
 ftoma-ch of a hen or a capon ; the fragments 
 were not Iharp as when they are broken by 
 the eiForts of the hand, but as obtufe as if 
 their edges and points had been abraded by a 
 grinding-ftone. The longer the fpherules 
 continued in the ftomach, the more minutely 
 were they triturated ; fo that in a few hours 
 they were reduced to a mafs of particles, not 
 larger than grains of fand. Moreover the ra- 
 pidity of this procefs appears in fome meafure 
 proportional to the fize of the animal. A 
 wood- pigeon generally breaks them lefs 
 fpeedily than a chicken, a chicken than a 
 
 (a) Efperienze intorno a cofe natural!. 
 ^i) Saggio di naturali efperienze, 
 (c) In the Introduftion. 
 
 capon-. 
 
■12 DISSERTATION I. 
 
 capon, but a goofe the fooneft of all. The rea* 
 ion is plain, fince the larger fpecies have 
 thicker and more powerful flomachs. 
 
 XIII. From thefe and other fad:s which I 
 ihall adduce hereafter, we may colled: how 
 much the celebrated Pozzi, formerly Pro- 
 felTor at Bologna, was miflaken, when he con- 
 lidered the obfervations {a) of the Florentine 
 Academicians, and of Redi on the power of 
 certain animals to reduce globules of glafs to 
 pieces as falfe, becaufe he faijed in his at- 
 tempts to repeat their experiments on pigeons. 
 Let me here be allowed to remark that it is 
 the cuilom of certain dabblers in philofophy 
 to deny fails, however particularly defcribed, 
 and though related by perfons of the higheft 
 authority, merely becaufe -their own endea- 
 vours fail of fuccefs. But they do not refled:, 
 that this is ading in dired oppofition to the 
 principles of found logic, by which we are 
 taught that a thoufand negative fads cannot 
 deflroy a fingle pofitive fad, lince it is fo very 
 eafy to omit fome one or other of the many, 
 circumftances requifite to the fuccefs of an ex- 
 periment. The Bolognian PhyficianhasfalT- 
 len into this error; inftead of fo ralhly infer- 
 ing from his own obfervation the falfity of the 
 
 {a) In his ihort anatomical cffay ][)rinted at Bologna by 
 
 Laelius a Vulpe. 
 
 contrary 
 
DISSERTATION I. I3 
 
 contrary event, he ought to have muhipHed 
 and varied his experiments ; and if he had 
 done this with proper precautions, he v^ould 
 have confirmed, inllead of contradid:ihg the 
 relation of the Florentine philofophers. We 
 mu-fl fuppofe, that the ftomachs of his pi- 
 geons were too weak and flaccid to abrade 
 and break fubftances of fuch hardnefs as glafs, 
 from their being either in an unhealthy ftate, 
 or too young ; for in thefe cafes they are by 
 no means capable of producing fuch eife(5ls, 
 as I have found from actual experience. 
 
 XIV. My celebrated countryman Vallifneri, 
 in his judicious anatomy of the ojirich^ fuppofes 
 that the hardeil: fubftances, fuch as flones, 
 wood, glafs, and even iron itfelf, are reduced 
 to pieces in the ftomach of this enormous 
 bird by a folvent; he alfo inclines to think, 
 that glafs is attacked and broken by fuch a 
 liquor, which he imagines to exifl: in the flo- 
 machs of fov/ls, without the concurrence- of 
 mufcular adiion. But the hypothelis of Val- 
 lifneri is evidently groundlefs ; for feeds, as 
 we have feen above, remain unaltered when- 
 ever they are defended by tubes. And when 
 pigeons, fowls, or turkeys, are forced to 
 fwallow feveral balls of glafs at once, fome 
 inclofed in tubes, and others loofe, the lat- 
 ter are reduced to fmaii fragments a^s ufual. 
 
14 DISSERTATION U 
 
 while the former remain entire. That the 
 gaftric mufcles are the fole caufe of this ef- 
 fed:, will appear ftill more evidently from 
 fads to be related in the fequel (xv). 
 
 XV. Before I proceed farther in the recital 
 of experiments immediately relating to digef- 
 tion, it may be proper to mention fome other 
 phasnomena analogous to thofe juil defcribed. 
 They may help to convey more diftind; noti- 
 ons concerning this function in animals fur- 
 nifhed with gizzards ; the fmooth and blunt 
 fubftances hitherto employed, could not injure 
 the ftomach. It was therefore an objed: of 
 curiolity to enquire what would happen when 
 fharp bodies were introduced. It is well 
 known how readily broken glafs will lacerate 
 fleih. I therefore gave a cock feveral frag- 
 ments of a broken pane, each about the fize 
 of a pea ; they were wrapped up in paper, to 
 prevent the cefophagus from being torn as they 
 pafTed through it. I was well affured that 
 this cover would be immediately deftroyed on 
 its entrance into the ilomach, and leave the 
 glafs at liberty to acl with its points and 
 edges. The animal Vv^as killed in twenty- 
 four hours, and the glafs was found in the 
 ftomach ; but on this, as well as former oc- 
 cafions, the angles were fo far obliterated, 
 that upon putting fome of the fragments on 
 
 the 
 
DISSERTATION I." 15 
 
 the palm of one hand, and rubbing them for- 
 cibly on the back of the other, I did not re- 
 ceive the leaft hurt. Upon weighing the 
 glafs, it appeared to have loil twenty-four 
 grains; nor was it difficult to difcover what 
 was become of the miffing particles, for the 
 iides of the ftomach, when viewed attentively 
 glittered with innumerable vitreous points^ 
 On the contrary, fome broken bits of glafs, 
 that were inclofed in two tubes, of which 
 one was given to a hen, and the other to a 
 turkey, and left twenty-four hours in the fto- 
 mach, were not at all abraded at their points 
 or edges. 
 
 XVI. Similar pieces of glafs, that remained 
 two day^s in the flomach of a wood- pigeon, 
 gave me an opportunity of obferving other re- 
 markable frad:ures and abraiions. The men- 
 tion of this bird brings to my mind a fa6t re- 
 lating to the prefent fubjed:. I gave a wood- 
 pigeon an unpoliffied twelve-fided garnet, 
 of the iizeof a nut, with the intention of in- 
 fpecfling the ftomach a few hours afterwards ; 
 the bird was confined in a cage, but made its 
 cfcape by fome accident, and mixing among 
 a number of others kept in another place, I 
 was not able to diftinguifli it ; fo that it did 
 not fall into my hands for a month. The 
 garnet, which had remained all this time in 
 
 the 
 
l6 I>ISSERTATIOK I.' 
 
 the ftomach, filled almoft its whole capacity 3 
 a oircumftance which a little furprized me, 
 fince it had taken its food, and been nouriflied 
 very well. But I was ilill more furprized at 
 finding the angles of this hard ftone blunted 
 in fome places. 
 
 XVII. But the reader willfurely be eager to 
 learn what injury the flomach received from 
 the violent agitation thofe fharp bodies mufi: 
 have undergone during the abrafion of their 
 moft pointed parts. To fatisfy my own cu- 
 riofity, as well as that of others, I opened the 
 cock and the two wood-pigeons (xv, xvi), 
 and examined the internal coat of the ftomach 
 with the clofeft attention, after having waihed 
 away the contents. I moreover difiTe^ted it 
 away from the nervous coatj this was eafily 
 eifeded: and I could now examine it to 
 greater advantage, but notwithflanding all 
 my pains, found it perfe(ftly entire. No la- 
 ceration, no divifion, not the fmalleft jagged 
 appearance; it was in every refped; like flo- 
 machs that had not afforded reception to any 
 unufual fubftance. Only the coat of that 
 ftomach which had retained the large garnet 
 for a month, was about three times as thick 
 as it commonly is. 
 
 xviii. Finding that thefe fowls fuftained 
 thefe experiments unhurt, I fubjeded tjiem 
 
 to 
 
DISSERTATION 1.' ly 
 
 to two Others far more dangerous. Twelve 
 ftrong needles were firmly fixed in a ball of 
 lead, in fuch a manner that the points pro- 
 je(5led about a quarter of an inch from the 
 furface. Thus armed, it was covered with 
 a cafe of paper, and forced down the throat 
 of a turkey. The bird retained it for a day 
 and half without fhewing the leafl fymptom 
 of uneafinefs. Why the ftomach fhould 
 have received no injury from fo horrid an in- 
 ftrument, I cannot explain : but the points 
 of the twelve needles were broken off clofe 
 to the furface of the ball, except two or three 
 of which the flumps projected a little higher. 
 The ball had not loft its general fhape, but 
 was marked with feveral indentations, that 
 certainly were not upon it at firft. Tv/o of 
 the points of the needles were found among 
 the food, the other ten I could not difcover 
 either in the ftomach or the long trad: of the 
 inteftines ; and therefore concluded that they 
 had pafled out at the vent. 
 
 XIX. The fecond experiment, ftill more 
 cruel, confifted in fixing twelve fmall lan- 
 cets, with very Iharp points and edges, in a 
 fimilar ball of lead. They were fuch as I 
 ufe for the diffedion of fmall animals. The 
 ball was given to a turkey cock, and left 
 eighteen hours in the ftomach ; at the expi • 
 
 Vol. I. C ration 
 
l8 DiSSERTAtlOfT. I. 
 
 ration of which time it was opened, but nor- 
 thing appeared but the naked ball, the twelve 
 lancets having been broken to pieces ; I dif-» 
 covered three in the large inteftines, pointlefs 
 and mixed with the excrements; the other* 
 nine v/ere miffing^ and had probably been 
 Voided at the vent. The ftomach was as 
 found and entire as that which had received 
 the needles. 
 
 XX; Of two Capons, one fiiflained the ex^ 
 periment with the needles, and the other that 
 with the lancets, eqvially welL My next 
 wifli was to know how much time had elap- 
 fed before thofe fubftances begin to be adled 
 Upon. By repeated experiments on turkeys 
 that were killed after intervals fticceffively 
 fhorter, I found that thefe fharp bodies begiii 
 to be broken and lofe their fhape in about two 
 liours. This at leaft happened in two indi- 
 viduals of that fpecies: in one four of the 
 lancets, and in the other, three of the needles 
 were broken within that fpace ; the reft were 
 blunted, but continued iifm in the balls. 
 
 XXI. Let it not howevet be fuppofed, that 
 the llomach in this clafs of birds is altogether 
 invulnerable^ In pullets it certainly is forne- 
 times very much injured; I obliged two 
 pullets to fwallow fome pins without heads. 
 One was killed in eighty a-nd the other in 
 
 thirty- 
 
DISSERTATION li 19 
 
 thirty- two hours. The former had not at all 
 fuiFered, but two pins were fluck in the fto- 
 ^nach of the latter. Thefe flomachs, as well 
 ias thofe of many other animals, are full of fur- 
 rows, in one of which the two pins were fixed 
 almoft perpendicularly, one to the depth of a 
 line, and the other to that of three lines • they 
 were oppofite to the moil mufcular part of the 
 organ. Some force was required to extra(51: 
 them ; at the pundure appeared a little clotted 
 blood, with an evident livid colour around. 
 
 XXII. But whatever conclufion we are to 
 draw from this laft fa(5lj it is certain, that the 
 ilomach of fuch birds is in general not fubjed; 
 to any injury from the introduction, refidence, 
 and trituration of thefe and the like fubilances, 
 as I have learned from a vaft variety of experi- 
 ments. But how is it polliLle, fome will en- 
 quire, that the gaftric mufcles can contufe, 
 triturate, and even fometimes reduce to im- 
 palpable powder (as when glafs is employed^ 
 XII, XIV, jCVf XVI ) thefe pointed bodies with- 
 out injury to themfelves ? If the mufcles adl 
 with fo much force, mufl not the fubflances 
 necelTarily re-a6l upon the mufcles ? And will 
 not this re-adion caufe the laceration of the 
 internal coat of the ftomach, which, though 
 it is indeed very firm and coriipad:, cannot 
 furely fuflain fuch violent fhocks with im- 
 punity ? Cz XXIII. This 
 
20 DISSERTATION I^ 
 
 XXIII. This obje<5tion was immediately 
 ftarted, upon the difcovery of the wonderful 
 force with which digeflion in poultry is effe9- 
 ted, and an attempt was made to remove it in 
 the following ingenious manner. It had been 
 long known, that fowls, and other birds of 
 the fame clafs, have always a fmaller or larger 
 fupply of little pebbles in their flomachs. It 
 was therefore conceived, that thefe pebbles 
 ferve as a fhield to the mufcles. Hence it 
 follows, that the comminution of bodies 
 forced into the ftomach is the immediate ef- 
 fect of the pebbles, and only the mediate ef- 
 fed: of mufcular action. Accordingly, the 
 Academicians of Cimento have obferved, that 
 thofe ducks and fowls that have moft ftones 
 in their flomachs, fooneft reduce fpherules of 
 glafs to powder. Redi thinks, that the ftones 
 perform the office of teeth {a) ; and Reaumur 
 luppofes them neceflary to digeftion {I?). 
 
 XXIV. In the courfe of my numerous ob- 
 fervations I can fafely alTert, that I never 
 opened the ftomach of a pigeon, turtle-dove, 
 dove, partridge, fowl, turkey, goofe, &c. 
 without finding feme fmall flones in it. I 
 have alfo found what is remarked by Reau- 
 mur, that the fize of the ftones is apparently 
 proportional to the fize of the bird. They 
 are generally of a roundiih iliape, whether 
 
 (a) L. c (i) Mem. cit. 
 
 they 
 
DISSERTATION I. 21 
 
 they acquire it from fridiion within the 
 cavity of the flomach, or have it before they 
 are fwallowed. They are commonly bits of 
 quartz, fometimes mixed with fragments of 
 calcareous ftones. In the ftomach of a turkey 
 hen I have counted above 200, and above 1000 
 in that of a goofe. Their exiftence is there- 
 fore indubitable. But is it equally certain, 
 that they are the immediate instruments of tri- 
 turation? He who is unprejudiced in favour 
 of any theory muft immediately perceive, that 
 this is a mere hypothecs, convenient indeed 
 and plaufible, but requiring to be confirmed 
 by experiment. 
 
 XXV, To this tefl I have endeavoured to 
 bring it, and would willingly hope that I have 
 decided the quefhion. According to the ob- 
 fervation of the Academicians, thofe birds 
 that have moft flones in the ftomach, foonefl 
 triturate hard fubftances. Nothing was more 
 eafy than to repeat the experiment. This I did 
 upon ducks and fowls, the two fpecies men- 
 tioned by thofe learned writers, fometimes 
 obliging them to fwallow globules of glafs, 
 fometimes thin tubes of tin, and at others 
 feeds defended by a ftronger cover, fuch as 
 nuts of a moderate fize. It was neceifary that 
 all circumftances fliould be alike, that the 
 birds fhould be of the fame fpecies and age, 
 
 C 3 and 
 
22' DISSERTATION I, 
 
 and of equal vigour, &c. Not to weary the 
 reader with too minute a detail, I fhall only 
 mention the refults. In a hen and two ducks, 
 not abundantly fupplied with pebbles, the in- 
 jury fuftained by the fubilances was not fo 
 great as in three other like fowls more amply 
 provided with them. But in four hens the 
 eife6t produced was exadly the fame, as far as 
 I could judge, though the itomachs of three 
 were lefs copioufly furnished than that of the 
 fourth. 
 
 XXVI. Having colleded a large quantity of 
 flones from the djlTediion of many gizzards-, 
 I thought they might be ufeful in the prefent 
 inquiry I I therefore gave a certain number 
 to fome fowls and ducks, while others were 
 left with thofe which they had fwallowed 
 fpontaneoully. The former, according to the 
 obfervation of the Florentine Academicians, 
 ought to have broken down hard fubilances 
 fooner than the latter. And fo indeed it fome- 
 times happened, but at others the event was 
 different. Wherefore not being able to afcer- 
 tain the obje6l of my enquiry by thefe expe- 
 riments, I had recourfe to other means of 
 folving the problem, 
 
 XXVII, The moll decifive mode of deter- 
 mining the ufe of flones in digeflion, evi- 
 dently was to take thpm away altogether, 
 
 either 
 
DISSERTATION I. 2^ 
 
 either by expelling thofe already fwallowed, 
 or by preventing the admiffion of any at all. 
 To evacuate thofe ajready accumulated, it 
 was neceflary to confine the birds in cages 
 where they could not |ind frefh ones, and it 
 might be hoped, that the old ones would be 
 gradually voided with the excrements. Ac- 
 cordingly, feveral fowls, turkeys, pigeons^ 
 and ducks 'svere confined feparately, and that 
 gll fufpjcion of their picking up pebbles rnigh^ 
 t)e removed, the cages were raifed to fuch an 
 height that they could not reach the floor 
 with their beaks. The bottoms were madp 
 of ofiers placed at a diflanpe from each other, 
 in order that if the flones fhoujd pafs out with 
 the excrement they might not remain in the 
 cage, and be fwallowed again, but fall to the 
 ground, I fed thepi myfelf the whole time, 
 taking care that the food, confining of corn, 
 vetches, and mai^e^ ihould be free from ali 
 foreign matter^ fo that I was certain not a 
 iingle grain of fand or the fmallefi; flgne was 
 fwallowed by them. 
 
 xxviii. In the cpurfe of a few days I per- 
 ceived ibme iliones among the excrement, 
 and ^hey continued to be voided during the 
 whole time of confinement. Two days be- 
 fore the end of the month, v/hen they were 
 to be killed, I forced fom€ to fwallow tubes 
 C4 _ pf 
 
24 DISSERTATION U 
 
 of tin, others glafs globules, others balls of 
 lead, fome naked and fome armed with nee- 
 dles and lancets (xviii, xix, xx.) I like- 
 wife gave them fome grains of wheat, but 
 did not allow them to undergo the natural 
 procefs of maceration in the crop. On the 
 30th day every Homach was carefully examin- 
 ed, and though I did not completely attain 
 the end in view, yet I gained coniiderable in- 
 formation on the fubject. Not a fingle fto- 
 mach indeed was fi'ee from ftones, but they 
 were few in number, in fome inftances not 
 amounting to above four or five, and thofe 
 very fmall. The contufions, however, on 
 the tin tubes, the indentations on the naked 
 balls, the fradiure of the needles and lancets, 
 the trituration of the grain had alike taken, 
 place in every ftomach; nor did it appear, 
 that the diminution of the quantity of ftones 
 at all contributed to diminilh the alteration 
 of the feveral fubftances, or to occafion any 
 injury to the organ that contained them. And 
 left it ftiould be objected, that thefe hard bo- 
 dies themfelves performed the office of peb- 
 bles by rubbing violently againft each other 
 in confequence of the ad:ion of the gaftric 
 mufcles (a^ objeciionmanifeftly trivial) I had 
 taken care that each bird Ihould not have 
 more than one tin tube, or one glafs globule^ 
 
 6cc. 
 
DISSERTATION I. 25 
 
 &c,. . Thefe folitary fubftances were juft as 
 much bruifed or broken as when many 
 were put into one flomachj and that vifcus 
 remained as free from injury. 
 
 :^xix. Though thefe fads abundantly 
 prove, that trituration does not depend on 
 the flones fwallowed by the birds in queftion, 
 but upon the ftrength and a(^ion of the gaf- 
 tric mufcles, I yet wifhed, by obferving what 
 happens in flomachs that have not received 
 any ftones, for proofs ilill more decifive. The 
 judicious reader will perceive at once, that 
 to accomplilh my purpofe, it was neceffary 
 to procure young neftlings that had never 
 been abroad in queft of food. Accordingly, 
 I procured fome wood- pigeons, yet unfledged, 
 were brought me; but I was difappointed in 
 my exped:ations, for even their tender flo- 
 machs were not free from pebbles, which^ 
 doubtlefs were mixed with the food carried 
 to them by their parents. Three of thefe 
 young birds were facriiiced to my curiolity. 
 The ftomach of the iirft contained eight 
 ftones, of the fecond eleven, of the third 
 fifteen; together they Weighed thirty-two 
 grains, and confifted chiefly of quartz. 
 
 XXX. As thefe experiments did not anfwer 
 my purpofe, it was necefl^ary to take up the 
 enquiry at an earlier period, and make ufe of 
 
 flill 
 
26- DISSERTATION I. 
 
 flill younger neftlingSi nay, for greater cer- 
 tainty fuch as were jufl quitting the eg^y and 
 therefore could not have received foo4 frona 
 their parents, The flomaph, it is obvious, 
 could not contain ilones pf any kind. I wa^ 
 therefore at the pains of keeping feyeral nefl? 
 lings in a warm place, while they remained 
 unfledged, and feeding them till they were 
 able to peck. They were ^he^ confined in a 
 cage, and fi|,pplied at firfl with vetches foaked 
 In warm water, and afterwards in a dry and 
 hard Hate. In a month after they had begun 
 to peck, hard bodies, fucTi as tin tubes, gjafs 
 globules, and fragments of broken glafs were 
 introduced witl^ the food; care was taken that 
 each wood-pigeon fhould fwallow only one 
 of thefe fubiliances. In two days afterwards 
 they were killed, when not one of the ftot 
 machs contained a fmgle pebble, and yet the 
 tubes were bruifed and flattened, and the 
 fpherules and bits of glafs blunted and bro- 
 ken: this happened alike tp each body, nor 
 .did the fmalleft laceration appear on the coats 
 q{ the ftomach. 
 
 XXXI . I did not confine my obfervatiens to 
 a Angle fpecies. With the fame view I fet 
 under a turky-hen feveral eggs, fome her 
 own, and fome from a common hen. When 
 the chickens were hatched I took charge of 
 
 them 
 
DISSERTATION I. 27 
 
 them myfelf, and employed the fame precau- 
 tions as with the wood-pigeons (xxx). They 
 were confined for fifty-five days in feparate 
 cages, and their food confifled of various forts 
 of grain. At lafl I forced them to fwallow 
 the hard indigeflible fubftances fo often men- 
 tioned. Upon examination, the ftomachs 
 appeared to be free from ftones, yet the frag^ 
 ments and fpherules of glafs, and the tin 
 tubes, were not on this account either th? 
 jefs or the more bruifed or broken. Hence 
 then we have at length a decifion of the far 
 mous queflion concerning the ufe of thefe 
 pebble§, fo long agitated by authors. It ap- 
 pears, that they are not at all necefi^ary to the 
 trituration of the firmefl: food, or the hardeil 
 foreign fubllance, which iq contrary to the 
 opinion of fo many anatomifts and phyfiolo:^ 
 gifts, as well ancient as modern ; I will not, 
 however, affert, that when put in motion by 
 the gaflric mufcles, they are incapable of 
 producing q.ny pfifedt pn the contents of the 
 ftomach. 
 
 XXXII. But for what purpofe are they de- 
 figned ? If they are not necefiary to the tritu^ 
 ration of the food, are we to fuppofe that they 
 contribute in any other way to digcftion ? Do 
 they create a keener appetite, or maintain a 
 l^etter ftate of health, as fome conceive ? Are 
 
 they 
 
2,8 DISSERTATION 
 
 I. 
 
 they found in the ftomach hecaufe they are 
 caflially mixed with the food, and as it were 
 concealed by it ; or, becaufe they are fwallowed 
 by choice, and even fought after ? - 
 
 The firft queiHons are already anfwered, 
 or rather precluded, fince we have found, 
 that birds unprovided with pebbles take their 
 food, are nourifhed and grow juft as well, 
 and are as briik and lively as others abound- 
 ing with them ; an obfervation I have made 
 with fatisfacSion upon young pigeons, tur- 
 kies, and chickens reared in the manner de- 
 fcribed above (xxx, xxxi). 
 
 XXXIII. The lafl queftion will be readily 
 folved, if grown up chickens take their food 
 in the fame way as young ones; for thefe 
 fwallow every thing that comes in their way. 
 I have often fcattered amongfl them various 
 fubftances unfit for their nourifliment, fuch 
 as pebbles, bits of brick, chalk, or other 
 rubbifh, which they pecked with eagernefs, 
 whether their ftomach was full or empty. 
 One day I threw among fome chickens a large 
 quantity of the little fifh, termed Lice by 
 Conchologifts, which they devoured till their 
 crop was full, juft as if it had been the moft 
 agreeable food. If they retain the fame dif- 
 pofition when full grown, we may reafonably 
 conclude, that the collecting of pebbles is 
 
 - ' lefs 
 
DISSERTATION I. 29 
 
 lefs the effect of choice than ftupidity ; as the 
 oflrich, according to ValUfneri and BuiFon, 
 devours without diilincflion whatever comes 
 in its way, fticks, and flones, and cords, and 
 glafs, and metals, &c. fuch is its dulnefs, 
 and fo obtufe its organ of tafte (a). But 
 when fowls are grown to their full fize, and 
 when their natural inilind:, which lay dor- 
 mant while they were young, comes to be 
 unfolded, change their manners in this as 
 well as many other refpe6ls. A capon con- 
 fined in a cage by Redi, died of hunger 
 fooner than it would fwallow pebbles offered 
 to it in place of food [b) . With me alfo three 
 hens and a turkey, kept confined, died in the 
 courfe of a few days, when inftead of giving 
 them food, I fcattered before them a quan- 
 tity of fmall flones. After their death, I 
 found that the number of the flones was the 
 fame, though they would appear to be of the 
 mofl proper kind, having been taken from the 
 ftomachs of other individuals belonging to 
 the fame fpecies. When pebbles are mixed 
 with the food, I have obferved, that poultry 
 efpecially when hungry, pick them up and 
 fwallow them* I fhould then incline to be- 
 
 (/z) BufFon Hift. des Oifeaux. T. 2. Ed. In 12. Valliih. 
 Op. in fol. T. I. 
 
 (i) Degli Anim. viventi negli Anim. viventi. 
 
 lieve. 
 
30 iJlSSEkTATiON t. 
 
 lieve, that the flomachs of thefe birds gene- 
 rally contain a quantity of fmall ftones ; not 
 becaufe they are follght for and feled:ed by de- 
 iign, as many fuppofe, but becaufe they fre- 
 quently happen to be mixed with their food. 
 
 XXXIV. Having ihewn that the pebbles 
 are not the caufe of trituration of the food 
 and other fubftancesj we muft conclude, that 
 it is the fole and immediate effed: of the gaf- 
 tric mufcles, which, as it is well known, are 
 very ftrong, and eompofed of firm and corn- 
 pad layers, and muft, therefore, when fct 
 in motion, ad: with great force. To be more 
 fully fatisfied of this, let the ftoinach of a 
 dog, iheep, or a man be compared with the 
 gizzard of a duck, turkey, or goofe^ we 
 
 . fhall then perceive the enormous difference 
 between the thick miifcular coat of the one^ 
 and the thin one of the other 6 
 
 XXXV. The internal coat, or that which 
 immediately lines the cavity of the- ilomach, 
 deferves particular attention; In many ani- 
 mals, and in man himfelf, it is foft and 
 villous j but in gallinaceous birds it is hard 
 and cartilaginous i When feparated from 
 the next, which anatomifls call the ner-* 
 vous coat, it foon becomes dry and very 
 hard. In turkies and geefe, in which it is 
 thicker and ftronger than in common foiwlsi 
 
 I have 
 
Dissertation i. 31 
 
 1 have often difTe^ted it away, and fpreading 
 it upon a table, have draw^n along it lancets, 
 needle§, bits of glafsj and fiich fharp fub- 
 ftances as are triturated in the ftomach vi^ith- 
 out any perceptible injury to it^ If indeed I 
 preiTed v^ith confiderabie force, thofe parts, 
 over v^^hich the keen bodies paffed, v\^ere 
 difunited, whether it was feparated or ad- 
 hered to the other coats. 
 
 XXXVI. But thefe fubftances may ad: in i 
 quite different manner when under the di- 
 redion of the hand, than when fet in mo- 
 tion by the gaflric mufcles, and when the 
 internal coat is not extended but forms a ca*. 
 vity, as it does when the ftomach is entire. 
 I therefore wiflied to know what happens to 
 fubftances inclofed in the ftomach feparated 
 from* the animal, and prefted externally with 
 the palms of both "hands, and agitated in va- 
 rious diredions* The ftomach of a turkey 
 hen was firft cleared of its contents by forcing 
 them out through the pylorus, and then a 
 large quantity of ftiarp pieces of glafs were 
 introduced, which were kept in motion for 
 a quarter of an hour by preffure and^percuf- 
 fion on the outfide of the ftomach. I was 
 in hopes, that I ftiould thus, in fome mea- 
 fure, imitate the* natural motion. Nor was 
 the expedient altogether ineffedluab for the 
 
 internal 
 
32 DISSERTATION I. 
 
 internal coat was only perforated with two 
 little holes, fuch as the point of a needle 
 would have made, and yet part of the glafs 
 was reduced to powder, and part had loft its 
 fharp edges. Different effeds then are pro- 
 duced, when this coat is fubmitted to ex- 
 periment after it has been removed from its 
 natural fituation, and when it adheres to the 
 others. Neverthelefs I am willing to allow, 
 that how it fliould be capable of blunting and 
 breaking the keeneft bodies without fuftain- 
 ing any injury itfelf, ftill continues a matter 
 of great furprize. 
 
 XXXV 1 1 . But if the infide of the gizzard be 
 certainly agitated fo violently during the tri-- 
 turation of the food, will not the motion be 
 perceptible on the outiide ? Reaumur, indu- 
 ced probably by this reflection, laid open the 
 abdomen of fome of the fowls in queftion, 
 and watched the ftomach, but could not per- 
 ceive what he perhaps imagined took place. 
 They always feemed perfectly at reft, except 
 the gizzard of a capon, which contraded and 
 dilated alternately j he moreover faw certain 
 .flefhy cords moving in an undulating direc- 
 tion, but very flowly and gradually {a) . 
 
 s 
 
 {a) Mem, cit. 
 
 XXXVIJI. I 
 
DISSERTATION f, 33 
 
 XXXVIII. I have perceived limilar motions 
 in two turkey cocks. Upon preffing the 
 ilomach forcibly with my hand, I felt a flight 
 pulfation that produced a fenfation of creep- 
 ing, but was foon aware, that this was owing 
 only to the beating of numerous little ar- 
 teries, which run upon the furface of the 
 vifcus. When a perforation is made in the 
 heart of a living animal, and a finger intro- 
 duced through it, it is well known that 
 ftrong preflure is felt at the time of its con- 
 traction . I made this experiment upon the 
 gizzard of a duck, but was not fenfible of 
 the flighted compreffion. 
 
 Conceiving that the ilomach muft exert 
 its principal adion when it is irritated by fub- 
 ftances filling its cavity, I introduced fome 
 nuts into the gizzard of a turkey hen, that 
 had been kept failing for a day. During the 
 whole time I v/atched it attentively, through 
 an opening made in the abdomen; when it 
 had received only a few nuts it fhewed no 
 fign of motion, but when it was nearly full 
 it fwelled violently, and then collapfed again 
 of a fudden. Thefe alternations were fome- 
 times general, and at others confined to a 
 narrow fpace; they did not continue ten 
 minutes, probably becaufe the aperture of 
 the abdomen was bringing on the death of 
 
 Vol. I. iS the 
 
^4 ©ISSERTATION I. 
 
 the animal. The nuts were unbroken, but 
 evident contufions appeared upon their fur- 
 face. This diffcindt view of the motions of 
 the flomach I afcribe to unufual good for- 
 tune, lince, with the exception of only one 
 other turkey, the ilomachs of many birds of 
 the fame clafs remained at perfed: reft, after 
 they had been filled in the fame manner. If 
 however we confider the very morbid ftate 
 of the animal when the abdomen is laid 
 open, we Ihall not be much furprized at this 
 phaenomenon, 
 
 XXXIX. The various fads related in the 
 preceding paragraphs irrefragably prove, that 
 the food of ducks, fowls, gcefe, partridges, 
 6cc. muft undergo the mechanical adion of 
 the gaftric. mufcleSy before it can be broken 
 down, and reduced to an impalpable pulp. 
 But are we to fuppofe, that digeftion depends 
 on this adtion, and that fimple trituration 
 converts the aliment into that pultaceous 
 mafs denominated Chyme ^ Or rather, that 
 this mafs is generated by means of juices 
 either prepared or colleded in the flomach ; 
 and that trituration is a co-operating, but 
 not the immediate caufe of digeflion ? I ima- 
 gined that the tubes and fpherules, which 
 had already afforded me fo much information, 
 would not now be without their ufe* If the 
 
DISSERTAtiON I. 35 
 
 gaftric juices convert into chyme the food 
 which trituration has prepared for digeilion, 
 let fome food fo prepared be inclofed in the 
 tubes and fpherules, and let us fee whether 
 it will be diffolved according to this hypo- 
 thefis j for then it mufl be thoroughly foaked 
 in thofe juices. I accordingly filled a tube 
 and fpherule with crumb of wheaten bread 
 maflicated, and introduced both into the 
 gizzard of a hen. In three and twenty hours 
 they were taken out, when the bread was 
 much diminifhed in quantity, efpecially at 
 the ends of the tube, where it was alfo fofter 
 than at firft, and had acquired a bitter tafi:e« 
 The -fame tube and fpherule were forced into 
 the gizzard of another hen, where they re- 
 mained fourteen hours; after which there 
 was no appearance of bread in either. 
 
 XL. I repeated this experiment upon a 
 third hen, with bread of maize inftead of 
 wheat; the tube and fphere were emptied in 
 a day and half. As there was here no tritu- 
 ration nor any other power, except the adion 
 of the gailric fluid, it feemed reafonable to 
 conclude, that this fluid had dilTolyed and 
 converted the bread into chyme, and fo 
 enabled it to pafs through the holes in the 
 receivers. A doubt however fuggefted itfelf, 
 and kept me in fufpenfe ; without fuppoflng 
 D 2 the 
 
^6 DISSERTATION I. 
 
 the tranfniutation of the bread into chyme, 
 the gaftric fluid by merely dihiting it, hke 
 water, might render it capable of paffing out 
 of the tubes and fpherules. 
 
 XL I. A fubftance not foluble by Umple 
 maceration, and at the fame time fofter than 
 grain, upon which the gaftric juices have no 
 aftion (hi, iv, v, vi, vii.), was wanting 
 to clear up the doubt. Flefli feemed to cor- 
 refpond to this defcription. Flefh is digefted 
 by many birds with gizzards, which for the 
 moft part are both frugivorous and grani- 
 vorous; I therefore filled four tubes with 
 veal {a) bruifed very fmall in order to fupply 
 the want of trituration, and forced them into 
 the ftomach of a hen. They were taken out 
 in twenty-four hours, and the fleih was in the 
 following flate : In the tube that came firfl 
 to my hands- it did not amount to above one- 
 twentieth of its original bulk, in two others 
 it had fuffered nearly the fame diminution ; 
 the only difference appeared in the fourth, 
 which was not open at both extremities like 
 the other three, but clofed at one end v/ith a 
 circular plate of iron. The fleih contiguous 
 to the plate preferved its red colour and na~ 
 
 (i?) Wherever I mention flefh without an epithet. I mean 
 raw iielli. 
 
 tural 
 
DISSERTATION I. 37 
 
 tural confidence, and did not feem at all 
 wafted ;^ but at the open end it was reduced 
 to two thirds of the length of the tube, of 
 which it had at firll occupied the whole ; the 
 part that continued firm and red retained the 
 true flavour of flefli; at the oppofite end it 
 had entirely loft that flavour, and the furface, 
 to the depth of a full line, was befides re- 
 duced to a pulp, and had acquired a cineri- 
 tious colour. The inconfiderable refiduums 
 in the other tubes were altered in the fame 
 manner. 
 
 The immediate confequences of thefe ex- 
 periments are felf-evident. The remarkable 
 diminution of the flefti arofe frpm its having 
 been in great meafure diflblved and digeftedj 
 for all phyfiologifts agree in confidering the 
 change of colour and tafte, and the tranfmu- 
 tation of the food to a pultaceous mafs in the 
 ftomach, as the charadieriftic marks of digef- 
 tion. The three tubes, of which the fides 
 were perforated and the ends open, admitted 
 the gaftric liquor at every part. Hence a 
 confiderable wafte of the flefti in them. The 
 cafe was different in the tube clofed at one 
 extremity, and nothing can be more obvious 
 than the reafon -, for as the liquor couui only 
 enter at one end, it could only there dilfolve 
 the flefti. 
 
 D 3 XLii. This 
 
^8 DISSERTATION I. 
 
 XL II. This experiment decifively proves, 
 that the gaflric liquor was the caufe of di^ 
 geftion in the prefent infl:ance3 and it was 
 eafy to forefee, that others upon the fame clafs 
 of birds wpuld be attended with the fame re- 
 fult. Some tubes filled with fleih were next 
 introduced into the gizzard of a very large 
 turkey cock, but the lattice work at the open 
 ends, though it confifted of iron, could ill 
 withiland the adtion of fuch powerful muf- 
 cles. Upon examination feven hours after- 
 wards, it was found feparated from the tubes, 
 and coiled up in one mafs near the pylorus, 
 in the midfl: of the pebbles and fcorias of the 
 food, fom.e of which were jammed fo tight 
 in the tubes, that there was difficulty in for-^ 
 cing them out with the point of a penknife, 
 I could not perceive the fmalleil fragment of 
 flefh amongil them, and remained in doubt 
 whether it had been digefted, or expelled by 
 thefe extraneous bodies, I refolved to fub- 
 mit this fpecies of bird to further experiments, 
 but was obliged to abandon the tubes, and 
 have recourfe to the hollow fpherules, of 
 which I have fpoken above (vii). They 
 were made thick and ftrong, with many fmall 
 pores over the whole furface, in order to ob- 
 viate two inconveniencies, the one left the re- 
 ceivers fhould be unable to refifl the violent 
 
 impulfes 
 
DISSERTATION I." 39 
 
 iinpulfes of the ftomach, the other to prevent 
 the matters comprelTed and agitated by the 
 adion of the mufcles from entering fo readily 
 into them. Two of thefe fpheres were given 
 to a turkey cock eleven months old, and in 
 twenty-four hours were taken out of the giz- 
 zard. They contained at iirft about twenty- 
 eight grains each of beef and veal bruifed 
 very fmalL Upon opening them after the 
 fame interval as before, and weighing the 
 ilefh, the beef was found to have loft nine, 
 and the veal thirteen grains. I muft not how- 
 ever omit to remark, that they were both 
 fully impregnated with gaftric liquor,, and 
 confequently would have weighed ftill kfs if 
 they had been free from it. The beef and 
 veal, when touched with the point of a knife, 
 feemed tenderer than in their natural ftate, 
 and refembled a foft pafte rather than flefli. 
 They had_the bitter tafte of the gaftric juice 
 with which they were impregnated, and the 
 colour approached more to white than redo 
 They were I'eplaced in the fphere, and kept 
 twelve hours in the gizzard of another tur- 
 key-cock. Upon a frefli examination, the 
 beef weighed only eight, and the veal only 
 five grains. The gaftric fluid had therefore 
 produced a new folution, and this procefs 
 was entirely completed after the fpheres, into 
 D 4 "whicij 
 
40 DISSERTATION I. 
 
 which the iiefh was put for the third time, 
 had continued five hours in the fcomach of a 
 third turkey cock. 
 
 XL II I. Flefh is digefted by the gaflric U- 
 quor of gc&fQ as well as of turkies. Eleven 
 grains of beef, inclofed in a fpherule, were 
 entirely diiTolved in two days in the gizzard 
 of one of thefe large birds. 
 
 I will not defcribe three other refults ob- / 
 tained, one from an hen, and the two others 
 from two capons ; iince, with refped; to the 
 digeflioa of the fleih, they are exactly like 
 thofe jufl mentioned. 
 
 All thefe experiments were made v/ith 
 flefli bruifed veryfmall; this condition is not 
 indeed indifpenfably requiiite, but it very 
 much i^romotes digeflion. The bruifed flefh 
 was always diiTolved in two days, but when 
 entire that procefs was not completed in four, 
 and fometimes not even in five days. The 
 reafon of this difference is obvious. The 
 more flelh is bruifed, the larger furface does 
 it acquire ; and in proportion to the increafe 
 of furface, more points are expofed to the 
 action of the gaftric liquor, which will con- 
 fequently fooner complete the folution. 
 
 XL IV, Before I proceed further and con- 
 clude the prefent differtation, I muft notice 
 an experinaent of Reaumur, which does not 
 
 perfedly 
 
DISSERTATION 1. 4I 
 
 perfcckly agree with thofe jufl related. The 
 ^rreateft part of his memoir is employed in 
 ihewiiig the great force of the gizzard of gaU 
 linaceous fowls in triturating the food; in 
 the remainder he endeavours to prove, that 
 this vifcus contains no menflruum of fuffi- 
 cient efficacy to produce folution. In fup- 
 port of this proportion, be.lides the argument 
 derived from barley continuing unaltered 
 within the tubes, he adduces the following 
 fad:, which requires to be particularly re- 
 lated. It is well known, how greedily ducks 
 devour, and how foon they digeft, flefh. In 
 order therefore to obtain the information he 
 wanted, Reaumur had recourfe to this bird. 
 Having provided fix tubes, four of lead, and 
 two of tin, he inclofed in the former bits of 
 veal of the fize of a grain of barley, and in the 
 latter fome confiderably larger. Thefe fix 
 tubes he gave to a duck at different times ; 
 viz. a leaden one at ten o'clock in the morn- 
 ing, and another at eight in the evening ; 
 next day a third was given at fix in the morn- 
 ing, together with the two tin tubes ; laflly, 
 at nine the fame morning the animal was 
 made to fwallow the lafl: leaden tube, and at 
 ten was killed. Of the four leaden tubes, 
 one was voided the preceding day at nine in 
 the evening; it was that which had been 
 
 taken 
 
42 DISSERTATION I. 
 
 taken at ten in the morning; the other five 
 remained in the gizzard, and the ileih was 
 not only entire, but as firm as at firft. Some 
 of the pieces retained their red colour, three 
 of them however had lofi: it. Of fome of the 
 tubes the whole capacity was no longer filled 
 hy the flefh; not that it had fuiFered any di- 
 minution, but becaufe it was comprelTed by 
 the ftones and food, which had been admit- 
 ted at the open ends of the tube§. From this 
 experiment Reaumur infers, that no men- 
 ilruum had ad:ed on the flefh, -fince it was not 
 either comminuted or difiblved. And though 
 , he does not affirm, that in the gallinaceous 
 clafs digefliion is the efFed: of trituration alone, 
 he yet concludes, that the gizzard contains 
 no folvent capable of decompofing and di- 
 gefling the aliment. 
 
 XLV. What has been above related, Ihews 
 how far Reaumur's conclufion ought to be 
 extended; when we fpeak of aliment of a 
 hard and compad: texture, fuch as feeds, it 
 mufi; be allowed, that the gaftric liquor has 
 no ad:ion upon them (ii, iii, iv, v, vi, 
 VII.) ; but when we are confidering food na- 
 turally tender, as flefh, or fiich as is made fo 
 by art, as grain in the form of maflicated 
 bread, it mufb then be allowed, that a perfed: 
 folution is eifedted by the gafbric juices alone 
 
 (xxxix. 
 
DISSERTATION I. 4^ 
 
 (xxxix, XL, xLi, xLii, xLiii.). In Rcau- 
 mur's experiment the fleih remained fo Ihort 
 a time in the gizzard, that we cannot be fur- 
 prized if it was not fenfibly diilblved. If we 
 attend to the times at which he gave his 
 tubes to the duck, and at which he killed it, 
 we fhall immediately perceive, that the tube 
 which continued longeil in the gizzard, re- 
 mained in it only twenty-four hours ; a fpace 
 infufficient, according to my experiments on 
 fowls, turkies, and geefe (xli, xlii, xliii.), 
 for the gaftric liquor of thefe birds to diifolve 
 any fenfible portion of flefh inclofed in tubes, 
 I ihould however have condemned myfelf 
 for a crime of omiffion, if, to the proof dedu- 
 cible from analogy, I had neglected to add 
 dire6l experiments on ducks. Upon two 
 ducks therefore I repeated the experiment of 
 the French Naturalift, with the following 
 variation ; four tubes, each containing a bit 
 of veal equal in iize to a barley-corn, were 
 given to a duck^ in two of the tubes the flefh 
 was whole, but in the two others it had been 
 previoufly cut into fmall bits : in fourteen 
 hours the gizzard was examined^ the four 
 tubes were found in it ; the two entire pieces 
 of flefh were of their original fize, but in- 
 clining to a white colour; the fmall bits 
 were alfo about the fame fize as at firfl, but 
 
 were 
 
44 P I S S E R T A T I O N. U 
 
 were converted into a gelatinous pafle. The 
 experiment was repeated upon another duck, 
 which was not killed till the end of the fe- 
 cond day; and now the tubes that had con- 
 tained the minute bits of flefh were entirely 
 empty; and in the others, only fome flight 
 traces of a gelatinous concodled matter re- 
 mained. If we combine thefe facts with 
 others before related, it will appear, that in 
 the gallinaceous clafs, trituration and the 
 gailric fluid mutually afTift each other in per- 
 forming the important fundiion of digeflion ; 
 the former by breaking down the aliment, a(fts 
 as the pre-difpofing caufe ; the latter, when 
 it is thus prepared, penetrates into it, de- 
 ilroys the texture, diflblves the particles, and 
 difpofes them to change their nature, and to 
 become animalized. 
 
 XL VI. But what is the origin of this gaf- 
 tric fluid, fo ufeful in digeftion ? How is it 
 mixed with the food? And what fuccelTive 
 changes does the latter undergo from the ac- 
 tion of trituration, joined to that of the gaftric 
 liquor ? Thefe important queflions required 
 a fl:ri6t examination of the oefophagus and 
 gizzard, as alfo of the food during its paflage 
 through thefe parts, and continuance in them. 
 As experiments are more conclufive, the 
 greater the fcale is, on which they are con- 
 
 -.- duded, 
 
DISSERTATION I. 45 
 
 duaed, I conceived that the larger fpecies, 
 as geefty turkies, ducks, and fowls, would 
 be the bell fubjeds for thefe enquiries. To 
 begin then with the cefophagus of a goofe, 
 this canal at the end towards the mouthy has 
 the appearance of an inflated inteftine^ it is 
 above a foot long, and at its origin about an 
 inch in dian^ieter, but widens as it defcends, 
 for the fpace of lix inches and more, when 
 it contracts like a funnel, then enlarges again, 
 and this enlargement continues to the p-iz- 
 zard. The cefophagus is membranous, its 
 fides are ftrong and thick ; they are thickeft 
 at three inches diftance from the ftomach, on 
 account of a fleiliy fafcia, of wliich I fhali 
 fpeak below. If we look very attentively, 
 we can perceive the whole cefophagus covered 
 with points or elongated fpots, which are 
 moil numerous jufh above the funnel. The 
 fafcia appears to coniill of a multitude of cy- 
 lindrical bodies, fomewhat larger than huiked 
 millet-feed. Thefe bodies are feen through 
 a fine membrane, which farrounds the fa- 
 fcia externally. 
 
 XL VI I. If the cefophagus be inverted, and 
 the fpots examined by the help of a glafs, we 
 plainly perceive that they are follicular glands. 
 This likewife is confirmed by the appearance 
 of moiflure on the cefophagus, when they are 
 
 prelTed. 
 
46 DIS'SERTATION l2 
 
 prelTed. But the follicular glands that appear 
 through the fleihy fafcia like cylindrical bo-^ 
 dies, bigger than millet, as we before ob- 
 ferved (xlvi), are far more eafily diflinguiih- 
 able, becaufe far larger. This fafcia, which 
 encircles the cefophagus like a ring, is above 
 an inch in breadth, and about a line in thick- 
 nefs. Great part of it is invefted by a cover- 
 ing of a deep yellow colour, very thin and 
 confequently very hable to be torn. When 
 this is removed, the fafcia externally appears 
 white and rough, on account of the number- 
 lefs prominent papillae, each of which has a 
 palpable pore in the center. When the fafcia 
 is ftretched, and ftill more when it is preffed 
 between, the fingers, a drop of whitifh turbid 
 liquor gufhes out at each pore into the cefo- 
 phagus ; and it may be increafed, by con- 
 tinuing the dilatation or prelTure. The li- 
 quor is denfe, fomewhat vifcid, of a fweetifh, 
 and at the fam.e time faltifli tafte. To com- 
 prehend immediately that the pores are the 
 excretory dudls of the follicular glands lying 
 below, requires very flight anatomical know- 
 ledge : the glands appear very diflindtly, when 
 the membrane in which the pores are in- 
 ferted, is removed. The follicles are of a 
 pale red colour, and full of a turbid liquor, 
 
 which 
 
DISSERTATION I, 47 
 
 which oozes out from the excretory dudts, 
 when the oefophagus is kept under water. 
 
 XL VII I. Below the flefhy fafcia, the oefo- 
 phagus becomes membranous again for nearly 
 the breadth of three quarters of an inch, 
 when it is inferted into the gizzard. This 
 organ is of the fize of the fifb, remarkably 
 hard, and of an irregular elliptical figure^ 
 when opened lengthwife at the thinneft part, 
 it is divided into two large mufcles, each 
 above an inch in thicknefs, and compofed of 
 very compa(5t fibres. It appears plainly, that 
 the whole acflion of thefe great mufcles con- 
 lifts in approximating with violence, and like 
 the fides of a vice, crufhing and breaking to 
 pieces all interpofed fubflances. As the ner- 
 vous coat adheres to thefe ftrong mufcles, 
 and as, however robufi;, it might be injured 
 by fuch impetuous fhocks, nature has faga- 
 cioufly invefted it with a cartilaginous coat, 
 of a ilrudture more capable of refinance, 
 which internally lines the cavity of the giz- 
 zard. 
 
 XL IX. In turkeys the cefophagus and fto- 
 mach very nearly refemble the fame parts in 
 geefe. The former, however, is more mem- 
 branous, and abounds more in follicular 
 glands of a larger fize, and confequently more 
 confpicuous. The excretory duds may be 
 
 eafily 
 
48 DISSERTATION iT 
 
 eaiily feen, and the liquor of the follicles may 
 be readily forced out by preffure. This li- 
 quor is tranfparent, and fomewhat vifcid ; its 
 tafte is rather fweet. But the cefophagus of 
 the turkey has one peculiarity not found in the 
 goofe ; it is provided with a burfa or bladder, 
 well known under the name of the crop or 
 craw. In this fpecies it is very large. The 
 crop at the fides at leaft, if not at every part, 
 is furnifhed with follicular glands, exadly like 
 the others. At the lower part of the cefo- 
 phagus we alfo find the fleihy fafcia, an inch 
 in breadth, and provided with follicles much 
 larger than thofe of the crop or cefophagus, 
 and in great abundance. The liquor feems 
 to have the fame properties as in the goofe. 
 It is vifcid, has a fweetifh and faltifh tafte, 
 a turbid white colour, and conliderable 
 denfity. 
 
 The gizzard, whether its form or the na- 
 ture of its coats be coniidered, is exactly like 
 that of the goofe, only weaker and fmaller 
 in proportion to the inferior iize of the bird. 
 
 L. I have obferved all that has been re- 
 lated with refpedt to the gizzard and folli- 
 cular glands of the goofe and turkey in due 
 proportion in the duck, common fowl, and 
 even in fmaller birds of the fame clafs^ as the 
 pigeon, partridge, wood-pigeon, turtle-dove, 
 
 and 
 
DISSERTATION U 49 
 
 and quail i with this peculiarity only, that in 
 the duck the oefophagus, inftead of forming 
 a crop, has the fame ftrudture as in the goofe 
 (xLvi). I fhall therefore omit a defcription 
 of thefe parts, and proceed to confider the 
 ftomach in a phyfiological light. 
 
 LI. In fpeaking of this organ, I have never 
 mentioned either follicles or glands ; for in 
 the fovv^ls hitherto mentioned, I could never 
 difcover any. The internal coat, from its 
 cartilaginous nature, appears to be unfit for 
 the infertion of glandular bodies ; at leail I 
 was not able to find the fmallefl veftige of 
 them; nor did I fucceed any better in the 
 nervous or mufcular coats, notwithftanding 
 I examined them very narrowly. Reaumur 
 having obferved a vafl number of fhort white 
 filaments between the cartilaginous and ner- 
 vous coats, entertained fome fufpicion of 
 their being tubes or vefTels, placed there in 
 order to difcharge their contents into the flo- 
 mach {a). I have found thefe filaments in 
 all the gallinaceous fowls I have examined ; 
 but cannot agree with him that they remain 
 attached to the nervous, when the cartilagi- 
 nous coat is feparated from it : for after fuch 
 feparation, I have ever feen them adhere to 
 
 [a) Mem. ck. 
 
 Vol. I» E, the 
 
$6 DISSERTATION: !• 
 
 the cartilaginous, never to the nervous coat| 
 but any perfon may readily make the triaL 
 Thefe filaments are very numerous ; they are 
 pointed at the extremity, oppofite to that 
 which is inferted into the cartilaginous coat, 
 and refemble fhort white down, diflindly 
 vifible by the naked eye in the larger birds ) 
 fuch as the goofe and turkey, but requiring 
 the aid of a glafs to be feen in the fmaller " 
 fpecies* I have divided many of various fizes 
 with the points of very fine needles, in order 
 to difcover whether they were hollow or glan- 
 dular, but could never find any appearance of 
 this kind : I have alfo fqueezed them in order 
 to fee if any liquor would ooze out, but to no 
 purpofe: and fo far from fufpefting thefe 
 filaments of Reaumur to be vafcular or glan- 
 dular, I fhould rather fuppofe them to be 
 merely for the purpofe of joining, or at leaft , 
 more clofely conne^5ling the cartilaginous with 
 the nervous coat* 
 
 We fhall fee elfewhere, that ftomachs of 
 the membranous kind, when they are taken 
 out of the animal and rubbed dry, foon be- 
 come moifl again : this moiilure cpmes from 
 invifible vefi"els and glands, difcharging their 
 liquor into the cavity of the ftomach* I have 
 made the j(ame experiment on mufcular ilo- 
 machs, but they always continued dry; the 
 
 fame 
 
t> I S S Z R T A t I O N U 51 
 
 jfame thinp^ alfo took place, when I prefTed 
 them underneath, though this is a very ef- 
 fe<5tual means of arccelerating and increaiing 
 the covering of moiflure. Hence I have good 
 reafon to fappofe, that the juices found in 
 mufcular ilomachs do not properly belong to 
 them, but come chiefly from the oefophagus, 
 and in part from the duodenum, as we fhall 
 fee below. 
 
 Lii. Nature however, has not failed to 
 provide the quantity necelTary for digeflion* 
 We have feen the vaft number of follicular 
 glands with which the oefophagus is provided 
 (xLvi, XLvii, XLviii, XLix*)^ they mufl; 
 needs pour in their liquor in great abundance* 
 And experience confirms what reafon fuggeils. 
 I introduced a fmall piece of dry fpunge, 
 previoufly cleanfed from every impurity, into 
 the craw of a pigeon, in which it was left 
 twelve hours -, at the expiration of which 
 time I opened the craw, and took it out. 
 The fpunge was full of liquor, and on being 
 Squeezed into a glafs, afforded above an ounce. 
 I employed larger pieces of fpunge in fowls 
 and turkeys, and obtained more of this cefo- 
 phageal liquor; the quantity in a turkey 
 amounted to feven ounces in ten hours. A 
 fimilar liquor is procured in equal abundance, 
 from fuch oefophagufes as are dilated, into a 
 E 2 large 
 
52 DISSERTATION I. 
 
 large canal, inftead of a craw, as in ducks 
 and geefe (xlvi, l.). This fluid is un- 
 doubtedly defigned to foften the food which 
 remains a certain time in the craw, or in the 
 large canal; which not only difpofes it to be 
 more readily broken down, but very probably 
 alfo communicates to it fome quality that 
 renders it more eafily digeflible. But it is 
 likewife certain, as I have found from expe- 
 riment, that a confiderable part of this fluid 
 defcends into the fliomach; not to mention 
 that denfer and more vifcid liquor which dif- 
 tils from the fleihy fafcia, lying at the bottom 
 of the oefophagus, (xlvi, xlvii.). 
 
 Liii. Thefe various oefophageal juices ac- 
 quire in the flomach a bitter flavour, refem- 
 bling that of the food in this vifcus: and as 
 this tafte exadly refembles that of the bile, 
 which in thefe animals is difcharged through 
 the cyfl:ic dud: into the duodenum, I am tho- 
 roughly perfuaded that it arifes from this 
 fource, in confequence of the bile regvirgi- 
 tating into the cavity of the fl:omach, and 
 being mixed with the food and oefophageal 
 liquors colled:ed there. I am confirmed in 
 this perfuafion by other fads, for the relation 
 of which I fhall find a more convenient place ; 
 not to mention the well known circumftance 
 
 of 
 
DISSERTATION I. 53 
 
 of the bile being found in the ftomach of va- 
 rious animals [a). 
 
 Liv. This colledion of divers liquors in 
 the gizzard of our fowls, ferves as a men- 
 flruum for the food, and difpofes it to be 
 tranfmuted into chyle. But the firil ftep to- 
 wards this event is taken in the craw. It is 
 there that the aliment is penetrated by the 
 cefophageal liquor, and begins to change its 
 fmell and tafte : that of the hardeil: texture is 
 prepared to be broken down when it difcends 
 into the ftomach, which in thefe birds may 
 be faid to fupply the place of teeth. 
 
 But the way in which the food defcends 
 from the mouth into the flomach, is deferv- 
 ing of attention. When our fowls are abun- 
 dantly fupplied with meat, they foon fill their 
 craw : but it does not immediately pafs hence 
 into the gizzard, nor does not arrive there till 
 after it has been macerated in the craw : it 
 always enters in very fmall quantity, in pro- 
 portion to the progrefs of trituration in the 
 ftomach. Here then, what happens in a 
 mill, may be obferved to take place. A re- 
 ceiver is immoveably fixed above the two 
 large Hones which ferve for grinding the corn 5 
 
 {a) Haller Elem. Phyfiol. T. 6. Vallifn. Op. in Fol. 
 T. I. 
 
 E 7 this 
 
54 DISSERTATION I, 
 
 this receiver lets the corn which it containsj 
 fall continually in fmall quantity into the cen-. 
 tral hole in the upper ftone, through which 
 it paffes, and diffufes itfelf in the void fpace 
 between the two ftones, where jt is broken 
 down, triturated, and pulverized by means 
 of the xlrong friftion of the upper flone that 
 moves round with great velocity upon that 
 below. Meanwhile the flour pafTes from. be-. 
 tween the llones, as fubftances triturated by 
 the gizzard, and diflblved by the gaflric juices, 
 are expelled through the pylorus into the 
 fmall inteflines. 
 
 Lv. All this may be obferved, byinfpect- 
 ing the alimentary canal during the time of 
 digeftion. If the bird has fed upon grains, 
 they are found in the cavity of the gizzard, 
 partly entire, but foftened by a fluid. That 
 part of the oefophagus that lies between the 
 end of the crop and the beginning of the ito^ 
 mach, either contains no grains at all, or 
 only a few quite entire. Trituration takes 
 place in th.Q gizzard only. Thofe which hav€ 
 iirfl; entered this cavity, are found to have 
 loft the farinaceous fubfl:ance, and are re- 
 duced to mere bran; the fucceding ones are 
 more or lefs broken, and the lafl are entire. 
 Amid this mixture of bran, and broken and 
 entire grains, we always find a femi-fluid pul- 
 
 taceous 
 
DISSERTATION 1. ^r^ 
 
 taceous mafs of a wliitifli yellow colour. 
 This is the farinaceous parts of the grains de- 
 ipompofed by the gaftric lic^uor, and conv^rtedi 
 into chyme. Meanwhile frelh grains con- 
 tinue to fall into the gizzard, in order to un- 
 dergo the fame tranfmutation : this admirabj^ 
 procefs continues as long as any grains con- 
 tinue to fall into the ftomach, 
 
 Thefe appearances and changes take place 
 alfo in animal fubftances, whenever birds with 
 mufcular flomachs feed upon them. 
 
 Lvj. At whatever tirne the flomachs of 
 thefe birds happen to be opened, they always 
 contain a certain quantity of gaftric liquor. 
 But it is lefs abundant when they are full of 
 food, (being in this cafe abforbed by the food) 
 than when they contain little or none. If 
 we wifli therefore to be provided with a larg^ 
 quantity of this liquor fgr experiments, it 
 jliould be taken from the empty ftomach. 
 Befides, in this cafe it is purer than when 
 mixed with the food. When examined in a 
 ftate of purity^ its tranfparency, if we except 
 a flight yellow tinge, is little inferior to that 
 of water. It has likewife the fluidity, but 
 not the infipidity of water, being always a 
 Jittle bitter, as well as fait. I have found 
 that the gizzards of turkeys and gecfe abound[ 
 mod in gaftric juices, probably on account of 
 E4 their 
 
$6 DISSERTATION I."" 
 
 their fuperior fize. I was induced by the 
 quantity they afforded to attempt an experi- 
 ment, which if it fucceeded, would ftill fur- 
 ther prove that trituration is only an affifting 
 or predifpoiing, and not the efficient caufe of 
 digeflion. It confifted in trying, whether 
 thefe juices retain their folvent power out of 
 the ftomach. For this purpofe, I took two 
 tubes fealed hermetically at one end, and at 
 the other with wax: into one I put feveral 
 bits of mutton, and into the other feveral 
 bruifed grains of wheat, and then filled them 
 with the gaftric liquor. In order that they 
 might have that condition which in thefe 
 animals precedes digefcion, they had been 
 macerated in the craw of a turkey cock. 
 And as the warmth of the ftomach is proba- 
 bly another condition neceifary to the folution 
 of food, I contrived to fupply it by commu- 
 , nicating to the tubes a degree of heat nearly 
 equal, by fixing them under my axillae. In 
 this fituation I kept them at difi^erent inter- 
 vals for three days, at the expiration of which 
 time I opened them. The tube with the 
 grains of wheat was firft examined; mofh of 
 them now confifted of the bare hufk, the 
 flour having been extra6led, and forming a 
 thick grey fediment at the bottom of the tube. 
 The fleih in the other tube was in great mea- 
 
 fure 
 
DISSERTATION I. 57 
 
 fure dilTolved, (it did not exhale the leaft 
 putrid fmell) and was incorporated with the 
 gaftric juice, which had become more turbid 
 and denfe. What little remained had loft its 
 natural rednefs, and was now exceedingly 
 tender. Upon putting it into another tube, 
 and adding frefh gaftric liquor, and replacing 
 it under the axilla, the remainder was difTolved 
 in the courfe of a day. 
 
 I repeated thefe experiments with other 
 grains of wheat bruifed and macerated in the 
 fame manner, and likewife upon fome flefti 
 of the fame kind, but inftead of gaftric juice 
 I employed common water. After the two 
 tubes had remained three days under my 
 axillae, I found that the grains, where they 
 were broken, were flightly excavated, which 
 was occalioned by an incipient folution of 
 the pulpy fubftance. The flefh had alfo un- 
 dergone a flight fuperficial folution, but in- 
 ternally it appeared fibrous, red, firm, and 
 in ftiort, had all the charaders of flefh. It 
 was alfo putrid -, the wheat too had acquired 
 fome acidity, two circumftances, neither of 
 which took place in the grains and flefti im- 
 merfed in the gaftric liquor. Thefe facfts are 
 then irrefragable proofs that the gaftric juice, 
 even out of its natural fituation, retains the 
 
 power 
 
58 DISSERTATION I, 
 
 power of diffolving animal and vegetable fub- 
 ilances in a degree far fuperior to water. 
 
 Lvii. The gaflric juice which I employed 
 was taken from a turkey. That of a goofe 
 produced iimilar effedis. I have further 
 i9und, that in order to operate the folution of 
 animal and vegetable fubftances, thig juice 
 ihould be frefh. It lofes its eflicacy, when 
 it has been kept fome time i|i veffels, efpeci^ 
 ally if they jQiould happen to be open, Jt alfo 
 becomes inefficacious after it has been ufed 
 for one experiment, Laflly, a confiderable 
 4egree of heat, equal to the temperature of 
 man or birds, muil be applied ; otherwife, the 
 gaftric juices are not more effectual in diflblv- 
 ing fiefli and vegetables than common water. 
 This artificial mode of digeftion is well caU 
 ^ulated to illuilrate the fubjeft I have under-. 
 ta.k.en to treat ; but I fliall have opportunities 
 of fpeaking of it at greater length in the fuba 
 |e<|uent dilTertatipns. 
 
 V I s^ 
 
[ 59 ] 
 
 DISSERTATION II. 
 
 CONCERNING THE DIGESTION OF ANI- 
 MALS WITH AN INTERMEDIATE STO' 
 MACH, CROWS, HERONS. 
 
 LVIII. T3 Y the term intermediate ftomach, 
 I mean fuch a ilomach as,- on 
 the one hand, is not properly mufcular, that 
 is, provided with thick and ftrong lides, as 
 in the galHnaceous family (i.); and on the 
 other, is not merely membranous, that is, 
 very thin, as in birds of prey and man, but 
 has an intermediate degree of thicknefs and 
 flrength. The flomachs of both the raven {a) 
 and grey crow (b) may be conlidered in this 
 light, though in reality they approach nearer 
 to the mufcular than the membranous clafs» 
 
 (a) Thefe two fpecies are called by Linnsus, Corvus cine- 
 Tafcens, capite, jugulo, alis caudaque nigris. 
 
 Corvus ater, dorfo atro-ccerulefcente, cauda fubrotunda. 
 {1} The hooded crow of Pennant, Corvus Comix L. 
 
 The 
 
6o DISSERTATION 
 
 II. 
 
 The intermediate power of thefe flomachs 
 contributes alfo to charadlerize them; it is 
 very far from being equal to the force of muf- 
 cular, but greatly exceeds that of membran- 
 ous ftomachs. Such tubes of tin, as doves 
 and pigeons would flatten and disfigure with 
 the greateft eafe, remain unaltered in the fto- 
 mach of crows. Thus alfo grain is tritu- 
 rated by the former, but continues whole in 
 the latter. Their gaftric mufcles however are 
 not inert. They exert a certain degree of 
 action, but it is far inferior to that of the 
 gizzard in the gallinaceous clafs. Thus, 
 though they cannot comprefs tin tubes, they 
 are capable of producing this eflfedl upon 
 tubes of lead, provided they are very thin : 
 and thofe that continue unaltered at firft, are 
 at length flightly incurvated or diftorted at 
 the edges, and generally filled with frag- 
 ments of the food, evident marks of conli- 
 derable a(flion in the gaftric mufcles ; there 
 are no eifedis which fhew fuch action in ani- 
 mals with membranous ftomachs, as we fhall 
 find in its proper place. I have often fcen 
 thefe phenomena, having kept a great num- 
 ber of grey crows and ravens, which have 
 been very ferviceable in the courfe of my en- 
 quiries, as the reader will learn from a perufal 
 of the prefent diiTertation. 
 
 Lix. Thefe 
 
DISSERTATION II. 6l 
 
 Lix. Thefe birds may, as well as man, be 
 denominated omnivorous. Herbs, grafs, feeds 
 of leguminous plants, fiefh of every kind, 
 alive or dead, ferve equally for their nourifh- 
 ment. As the powers for the concod:ion of 
 various aliments, pofTelTed by thefe fpecies are 
 either entirely the fame as, or ftrongly refem- 
 ble thofe of man, it is obvious, that the 
 knowledge obtained from them will greatly 
 illuftrate the procefs of digeftion in us. They 
 beiides feem formed on purpofe to forward 
 the views of the obferver. When we wifh 
 to know what changes have been produced 
 in fubflances inclofed in fpheres and tubes, 
 and given to gallinaceous birds, it is neceiTary 
 to extrad; the tubes and fpheres from their 
 gizzards ; that is, it is neceiTary to kill them. 
 Hence for every experiment we muft facri- 
 fice an individual, at no fmall expence to our 
 philofophical curiofity. On the contrary, 
 we can perform fuch experiments upon crows 
 as often as we pleafe, without deftrowing a 
 fmgle individual. With refpedl to fubftances 
 they are incapable of digefling, fuch as the 
 .above-mentioned metallic receivers I have 
 difcovered, that they poiTefs the privilege of 
 returning them through the mouth, as birds 
 of prey vomit the feathers and hair of the ani- 
 mal they have devoured, a circumllance well 
 
 known 
 
62 D I S S E ft t A T I O N H.' 
 
 known both to natufalifls, and thofe who 
 train falcons for the field." But whereas this 
 vomiting generally takes place every twenty- 
 four hours in birds of prey, in crows it hap- 
 pens at leafl every nine, and commonly every 
 two or three hours. 
 
 LX. As I obtained the fame refults from 
 both fpecies, I fhall employ in my narration 
 the generic name only [a) . My obfervations 
 were begun in winter, the moll convenient 
 feafon for procuring a large number, owing 
 to the multitudes, efpecially of ravens, with 
 which Auftrian Lombafdy, and indeed almoft 
 all Italy then abounds. All the crows which 
 I could obtain, had when newly taken, a 
 large colledion of pebbles in the ftomach ; the 
 biggeft were of the lize of fmall peafe, the 
 leafb of that of millet: they were of various 
 forts ; I even found rounded pieces of brick. 
 But in lefs than ten days not a flone remained 
 in the body, a circumftance which I learned 
 from the infpe^tion of feveral ilomachs, when 
 I had occaiion to kill fome crows in order to 
 obferve the anatomical ftru6ture of the ali- 
 mentary canal. They were voided partly at 
 the anus, as appeared from the excrements,' 
 
 ^ (fl) Corvus 13 the generic name In Latin, and CornaGhcia 
 in Italian, and Crow may very well ferve for it in Englifti. 
 
 and 
 
D, I S S E R "f A t i O N It.' 6^ 
 
 arid partly by the mouth j in the latter in- 
 ftances they were glued by the gaftric liquor 
 to the outfide of the tubes which I had forced 
 them to fwallow, and which they afterwards 
 threw up. When unprovided with pebbles, 
 they continued to eat and were nouriihed as 
 well as before. Hence it is to be inferred, 
 that they are not more neceffary to digeflion 
 in birds with intermediate, than in thofe with 
 mufcular flomachs, as 'we have feen above 
 (xxxi). And as I inclined to believe, that 
 the laft mentioned clafs do not pick up thefe 
 flones from choice, but by mere accident 
 (xxxiii) ; fo I confider the matter likewife 
 with refped: to crows, having obferved, that 
 though unprovided, they never peck them 
 eagerly, even when hungry, but fwallow 
 them only when they happen to be mixed on 
 purpofe or by chance with their food, and as 
 it were concealed by it. 
 
 Lxi» I began my experiments by putting 
 whole beans or grains of wheat in the tubes [a) , 
 The reader will eafily perceive, that crows 
 are not fo flupid as to take the tubes fpon- 
 taneoufly, but that it is necelTary to force 
 them down the throat, and to pafs the iingei; 
 
 {a) Thefe tubes were the fame I ufed for gallinaceous fowls, 
 and I continued to employ them in the fequcL 
 
 along 
 
64 DISSERTATION. 11^ 
 
 along with them till they are got into the 
 itomach. This I executed in the way I had 
 before done in animals with mufcular fto- 
 iTiachs (ill). The tubes were all thrown up 
 in the fpace of three hours. The beans and 
 wheat appeared as at iiril:, excepting that they 
 were fomewhat foftened and fwelled by the 
 gaflric juice, which had penetrated a little 
 way into them. I replaced the grains in 
 the tubes, and introduced them again into 
 the flomach, where they remained two 
 hours longer, without undergoing any further 
 change. I repeated the fame experiment a 
 great number of times, and upon computing 
 the fpace during which the tubes had con- 
 tinued in the ftomach, I found that it amount- 
 ed to forty-eight hours ; in this interval the 
 feeds had fuffered no other alteration, except 
 in being a little more moiftened. The gaf- 
 tric fluid -is therefore incapable of effecfling 
 the folution of thefe vegetable matters. 
 
 Lxii. But we have before faid, that they 
 were entire ; on which account, it could not 
 ad: upon the farinaceous fubftance of the 
 grain till it had traverfed the hulk; and this 
 might have diminifhed its efficacy. In order 
 to determine how far this fufpicion was well- 
 founded, it became neceffary to repeat the 
 experiment upon the fame feeds bruifed. 
 
 Accord- 
 
DISSERTATION Ii; 6^ 
 
 Accordingly four tubes full of the coarfe flour 
 were given to a crow : they remained eight 
 hours in the ftomach, and proved the juftnefs 
 of my fufpicion j for upon examining the con- 
 tents, I found above a fourth part wanting. 
 This could arife from no other caufe but fo- 
 lution in the gaftric liquor, with which the 
 remainder was fully impregnated. Another 
 obfervation concurred to prove the fame pro- 
 poiition: the largeft bits of wheat and bean. 
 were evidently much diminiilied^ this mufl 
 have been owing to the gaftric liquor having 
 corroded and diffolved good part of them, as 
 the nitrous acid diluted v/ith a large quantity 
 of water, gradually confumes calcareous fub- 
 ftances. I replaced what remained of the 
 feeds in the tubes, and introduced them again 
 into the ftomach, wherein they remainedj at 
 different intervals, twenty-one hours -, when 
 they were entirely diffolved, nothing being 
 left but fome pieces of huili and a few incon- 
 iiderabje fragments of the feed. 
 
 Lxiii. Wheat and beans floating loofe in 
 the cavity of the ftomach, undergo the fame 
 alteration as in the tubes. When I fed my 
 crows with thefe feeds, I obferved, that be- 
 fore they fwallowed them they fet them un- 
 der their feet, and reduced them, to pieces by 
 "repeated ftrokes of their long and heavy beaks. 
 
 Vol, I, F An(} 
 
66 DISSERTATION It. 
 
 And now they digeileci them very well ; nay, 
 this procefs was very rapid in comparifon of 
 that which took place within the tubes. But 
 when the birds either from exceffive hunger 
 or violence fwallowed the feeds entire, the 
 greatefl part of them pafled out entire at the 
 anus, or were returned by the mouth. We 
 cannot therefore be furprized, that the gaftric 
 juice could not diffolve them within the tubes, 
 iince it was incapable of efFed:ing this pro- 
 cefs within the cavity of the ftomach, where 
 its folvent power is far fuperior. 
 
 Lxiv. To avoid prolixity, I fhall not fpeak 
 of other feeds fubmitted to the fame experi- 
 ments i fuch as chicken-peafe, French beans, 
 peafe, and nut-kernels. I will rather men- 
 tion vegetable matters of a fofter and more 
 yielding texture, which did not require to be 
 broken down in order to be diifolved ; fuch 
 as crumb of bread and apples. Thefe fub- 
 ftances were not only diifolved within the 
 tubes, but required a much fhorter time than 
 beans and wheat. Several bits of a ripe ap- 
 ple, weighing together eighty-two grains, 
 and inclofed in tubes, were diifolved in the 
 ipace of twenty-four hours in the ftomach of 
 a crow. Four bits of another apple, weigh- 
 ing an hundred and three grains, were dif- 
 folved in little more than fifteen hours. Of 
 
 an 
 
D f S S E R T A T i d If 11. 6/ 
 
 an hundred and feven grains of crumb of 
 wheaten bread, there only remained eleven 
 in the fpace of thirteen hours, 
 
 Lxv. From vegetable I proceeded to ani* 
 mal fubftances^ The eagernefs which crows 
 fhew for thefe afforded a certain prefage, that 
 they would be dilTolved within the tubes. I 
 filled eight tubes with beef, and gave them 
 to four crows, two to each. The iiefh was 
 not bruifed fmall, as in the cafe of gallinaceous 
 fowls (xLii), but each tube contained a whole 
 piece. An hour had fcarce elapfed when one 
 was thrown up. The flefh^ upon examina-^ 
 tion, did not appear to be fenfibly dimini£hed, 
 but it was thoroughly foaked in the gafliric li- 
 quori The juice was a little bitter, and of a 
 yellowifh green colour ; the flefh had acquired 
 the fame taile and colour in feveral places. 
 In an hour and three quarters two other tubes 
 were vomited up ^ and now the flefh began to 
 fhew marks of folution. The red colour was 
 changed to a dark cineritious hue, and the 
 whole furface was become flabby, and the co- 
 hefion of the parts was dellroyed. In ano- 
 ther tube, difcharged in two hours and an 
 half, the folution had made a greater pro- 
 grefs. A dark covering of jelly furrounded 
 the flefh, which on being touched, adhered 
 to the fingers 5 and v/hen applied to the 
 F z tongue. 
 
6s Dissertation ii. 
 
 tongue, hardly exhibited the flavour of flefh. 
 The folution had proceeded ftill further in four 
 hours, when two other tubes were thrown 
 up ; in which the flefh did not amount to half 
 the original quantity. The remainder was 
 furrounded by the fame gelatinous covering, 
 under which it preferved its natural colour, 
 fibrous ftrudure and favour. There remained 
 only two tubes, which were vomited up fe- 
 ven hours after they had been taken. Both 
 were empty, the flefh therefore had beert 
 completely diffolved, except a few bits of 
 jelly that adhered to the infide. I never could 
 perceive the fmalleft token of putrefadiion 
 either during the progrefs, or at the comple- 
 tion of the folution. And this obfervation, 
 that I may not be under the neceflity of re- 
 peating it continually, is to be extended to all 
 the folutions performed not only by other 
 crows, but by all the animals that I fhall have 
 occafion to mention in this workj for I can 
 afl^ert with the utmofh confidence, that I have 
 never been fenfible of the flightefl flench 
 either in flefli or any other fubflance which I 
 introduced in tubes or any other way. 
 ■ Nothing could be more fatisfadory than 
 the. information obtained from this experi-- 
 ment. It not only rigoroufly demonflrates, 
 that the gailric liquor of crows is the folvent 
 
 of 
 
DISSERTATION U~, 69 
 
 of flefli inclofed In tubes without borrow! no- 
 the leajfb aid from trituration, but it throws 
 iHll ftronger Hght upon the mode of operation 
 of this menftruum in the galHnaceous clafs. 
 It begins by foftening the texture and altering 
 the colour; next fucceeds the de-compolition 
 of the parts ; this tranfmutes the flefh into a 
 kind of jelly of a tafle different from that of 
 flefh: the jelly is then more thoroughly pe- 
 netrated by the juice and extracted out of the 
 tubes, and in the flomach it is changed into 
 chyle. It appears alfo, that this fluid does 
 not penetrate deeply into the flefh, but acts 
 on the furface only, diffolving and removing 
 one layer at a time, if we may fo fpeak, like 
 other corroding menftrua, until it comes to 
 the innermofl part, which it alfo foftens and 
 melts. 
 
 Lxvi. We have feen, that the flefh in the 
 tubes fhewed no lign of folution till an hour 
 and three quarters had elapfed, and that this 
 procefs was completed at the end of feven 
 hours (lxv). But are we to conclude, that 
 this is the meafure of the time required by 
 the gaflric liquor for this operation ? or that 
 it would have been accomplifhed in a fhorter. 
 time, if the liquor had had free accefs to the 
 flefh ? for it is certain, that the tubes are no 
 Imall impediment to the gaflric juice. What 
 F 3 then 
 
yO DISSERTATION II. 
 
 then would happen if the impediment was in 
 part removed ? and what when it is entirely 
 taken away, by putting the flefh loofe into the 
 ftomach ? In oraer to folve the iiril of thefe 
 intereil:ing queftions, I enlarged the perfora- 
 tions in the fides of the tubes as much as 
 poiTible (vii), then filled them with beef, 
 as before (lxv), and introduced them into 
 the fliomachs of feveral crows. I now had 
 the pleafure to perceive the fuperior efficacy 
 of the gaflric liquor. In an hour and an half 
 three of the tubes were thrown up, and above 
 a fourth of the flefh appeared to be wafted. 
 Two other tubes were difcharged in lefs than 
 two hours, and contained little more than 
 half of their original quantity. And before 
 the completion of the fourth hour, the re- 
 maining tubes were entirely empty. 
 
 Lxvii. Before I proceeded to the other 
 queftion, I thought of inverting the fore- 
 going experiment (lxVi), and inftead of al- 
 lowing freer accefs to the gaftric juice, of 
 impeding it more and more, and at laft hin- 
 dering it almioft entirely. I began with em-, 
 ploying the ufual tubes wrapped in cloth; 
 this, although it was thin, was fufficient to ' 
 prevent the folution of the flefli, which now 
 did not begin to take place till three hours 
 ^ftei* the tubes v/ere introduced into the fto- 
 
 mach. 
 
DISSERTATION If, ^l 
 
 mack, and was not completed till ten had 
 elapfed. 
 
 The linen in which the tubes had been 
 wrapped was lingle : I now doubled it in or- 
 der more effectually, to hinder the ingrefs of 
 the liquor, and repeated the experiment in 
 the fame manner. The flefh fhewed no token 
 of folution for four hours, and was not en- 
 tirely diffolved for a whole day. 
 
 Upon wrapping round another fold the fo- 
 lution did not begin for nine hours, and in 
 the fpace of a day the flefl^ was fcarce half 
 confumed. In other refpeds the gaftric juice 
 had ad:ed upon the flelh jufl as it does in open 
 tubes, excepting only the flownefs of its ope- 
 ration. It was become externally gelatinous, 
 and incoherent in its parts , It was tinged 
 yellow in feveral places ; the tafte and fmell 
 at the furface were not different from thofe 
 of the gaftric liquor, 
 
 I concluded thefe experiments, by trying 
 what would be the effed; of putting iieih into 
 tubes with only three or four holes. After 
 they had continued nine hours in the ftomach, 
 the refult was as follows : fmall excavations 
 of greater or lefs depth were made in the 
 parts oppofite to the pores, and from thefe 
 excavations fmall furrows wandered irregularly 
 along the furface of the fiefh. The flefhy 
 F 4 fibres 
 
72 DISSERTATION II. 
 
 iibres both in the cavities and furrows were ' 
 become exceedingly tender, they had befides 
 lofl their red colour, and were turned yellow. 
 The reft of the flelli was unaltered. From 
 what has been faid before, the origin of the 
 cavities and furrows evidently appears to have 
 beei> derived from the gaftric juice, which 
 by inlinuating itfelf through the little perfo- 
 rations, had there diflolved and deftroyed the 
 iiefli; the reft remained entire, becaufe none 
 of the juice could enter, if we except a very 
 flender ftrearn, which had produced the fur- 
 rows. 
 
 Lxviii. Let us now proceed to the fecond 
 queftion and examine how much more readily 
 fleih lying loofe in the ftomach is digefted than 
 when it is enclofed in tubes. Taking fome 
 of the fame kind of fleili that had been ufed 
 before, viz. beef, I parted it into two equal 
 portions, one of which was again divided into 
 fmaller bits before it was put into the tubes, 
 while the other was left entire. Each por- 
 tion weighed eleven pennyweights. I next 
 gave the tubes, which were eight in number, 
 to a crow, and to another bird of the fame 
 fpecies, equally healthy and robuft, I gave at 
 the fame time the whole portion of fleih, to 
 which I had previoufly faftened a thread. 
 This thread, hanging out of the bird's mouth. 
 
DISSERTATION II. 73 
 
 and being wrapped round the neck, I could 
 draw up and examine the flefli at pleafure. 
 And that every circumftance might be ahke, 
 I had taken care that the two crows fhould 
 have their ftomachs empty. In thirty-fix 
 minutes one of the tubes was vomited, and 
 at the fame inftant I drew up the flefh from 
 the ftomach of the other crow. The latter 
 was throughly imbibed with gaftric juice, ef- 
 pecially the part that refted upon the bottom 
 of the ftomach. It had loft its rednefs, and 
 was now of a dirty colour j it weighed forty- 
 two, grains lefs than at iirft; on the contrary, 
 the flefh enclofed in the tube retained its ori- 
 ginal weight. 
 
 The tube and the flefli tied to the ftring, 
 were replaced in their refpeiftive fituationsj 
 and in order that both might remain the fame 
 length of time in the ftomach, I took care to 
 return the tubes as they were thrown up. 
 The flefh was entirely dilfolved in three hours, 
 when I immediately killed the crow that had 
 the tubes. Upon colledting and weighing all 
 the fleih that remained in them, I found it to 
 amount to about feven pennyweights. Hence 
 in three hours and nine minutes it had loft 
 four pennyweights. 
 
 On the other hand, the flefli tied to the 
 ftring was reduced to half a pennyweight, 
 
 which 
 
74 DISSERTATION IT. 
 
 which conlifted of a packet of membranous 
 or cellular fibres, the fiefhy part having been 
 entirely dilTolved. This experiment clearly 
 fhews, that fleih left loofe in the ftomach is 
 more fpeedily digefted than when it is enclo- 
 fed in tubes. And theory perfeftly agrees with 
 fa(5l; for fmce folution is the effed: of the 
 gaftric fluid, it is evident that the food, when 
 loofe in the fliomach, is attacked by a larger 
 quantity than when defended by the tubes. 
 
 Lxix. Young crows, as well as all other 
 young birds, eat more than the adult ^ hence 
 I fufpe^ted their digeflion to be quicker. 
 Having a neft of the grey fpecies brought me 
 in June, I made, among others, the experi- 
 ment related iathe lafl: paragraph. The re- 
 fult was very fatisfadtory. A quarter of an 
 ounce of beef, faflened a§ before, to a thread, 
 had fcarce touched the ftomach, when the 
 folution began, and in forty- three minutes 
 was completed ; but an equal quantity diftri- 
 buted in feveral tubes, required four hours 
 and a half to be diffolved. Upon opening the 
 ilomachs of the two young birds, I immedi- 
 ately perceived the caufe of this rapid folu- 
 tion 3 they contained half a fpoonful of gaf- 
 trie fluid; a quantity feldom met with in the 
 ftomach of adult crows. As the neftlinga 
 require more food. Nature has furnifhed 
 
 thqm 
 
DISSERTATION 11. >j r^ 
 
 them with the mdans of an eaiier and more 
 fpeedy digeflion. 
 
 It is fcarce neceflary to remark, that the 
 experiments related in the Lvth and follow- 
 ing paragraphs, clearly evince this important 
 truth, that the digeflion of food is; propor- 
 tional to the quantity of galliric juice acfting 
 upon it. When this liquor comes in contad; 
 only with a few points, the decompoiition is 
 very flow and inconiiderable (lxvii); when 
 freer accefs is allowed, the folution takes place 
 more fpeedily, and is more coniiderable (lxv, 
 Lxvi); it is very rapid, when every obflacle 
 is removed, and the food is on all fides ex- 
 pofed to the adiion of the folvent liquor, 
 (lxviii, lxix). 
 
 Lxx. It is a queflion of ancient date, and 
 ftiil agitated by modern phyfiologifls, whether 
 certain carnivorous animals are capable of di- 
 gefiing bone.- Among the various points, 
 which I propofed to difcufs in the prefent 
 work, I conceived that this well deferved the 
 refledion and attention of the philofopher ; I 
 fhall therefore both here, and in another part 
 of my work, relate what I have obferved on 
 the fubjed. If we obferve a crow and a bird 
 of prey devouring an animal, we may be dif- 
 pofed to think that the latter has the power 
 pf difToiving bone, but not the former. 
 
 When, 
 
^6 DISSERTATION lU 
 
 When, for inilance, a hawk takes a pigeon, 
 it firil ftrips the back, and devours the muf- 
 cular part of the breaft 5 then proceeds to the 
 entrails; and, laflly, fwallows the ribs, ver- 
 tebrs and head, not even fparing the feet and 
 wings, ifitihould happen to be very hungry. 
 When the fame bird is given to a crow, it 
 fets about ftripping off the flefh; but when 
 it has picked this clean, it leaves the fkele- 
 ton. This rejection of the bones, is how- 
 ever very far from being an indubitable proof, 
 in the eflimation of the philofopher, that 
 they are incapable of digefhing them. At 
 mofl it inclines us to believe it probable; but 
 fuch probability requires to be confirmed by 
 fadls : and being engaged in enquiries of this 
 nature, I could conveniently bring the quef- 
 tion to the teft of experiment. As I hap- 
 pened to be provided with fome phalanges of 
 the human toes, I enclofed two in one of the 
 ufual tubes, which remained thirteen hours 
 in the ftomach. They weighed fifteen pen- 
 nyweights at firfi: ; nor v/as this weight at all 
 diminiilied, or the bones in the leail foftened. 
 Being in doubt whether the two great thick- 
 nefs of thefe bones might not have prevented 
 the gaftric juice from acting upon them, I 
 had recourfe to fmaller ones. Happening 
 one day to find one of mv croVr^s dead in the 
 
 apart- 
 
DISSERTATION II. 77 
 
 apartment where I kept them, and the reft 
 alfembled round the carcafe in crouds, and 
 devouring it eagerly, I took one of the tibias, 
 broke it in two, and enclofed it in a tube. 
 The tube continued a whole day in the fto- 
 mach of another crow, but the bone was 
 neither foftened, nor diminiilied in weight. 
 The fame thing was alfo obfervable, after the 
 bone had been left loofe in the ftomach for 
 fourteen hours longer. 
 
 Lxxi. The greedinefs with which the 
 crows devoured their companion, induces me 
 to digrefs, for the fakfe of noticing a miftake 
 of the celebrated Dr. Cheyne. He pretends, 
 that crows cannot digeft the fieili of their 
 own fpecies ; and that when they happen to 
 fwallow it, they vomit it up again. " Ipfa 
 Cornix (fays Haller, on the authority of 
 Cheyne) cornicis canem ingeftam non poteft 
 coquere & deglutitam vomitu rejicit (^)." 
 But the truth is, that the iiefh which my 
 crows devoured agreed very well with them, 
 nor did they throw any of it up again. Fur- 
 ther, in order to determine certainly whether 
 the above-mentioned writer had fallen into a 
 miftake or not, I killed and plucked another 
 crow, and threw it into the chamber where 
 
 («) PhhloL T. 6, 
 
 its 
 
y^ DISSERTATION II. 
 
 its companions were kept, when they imme- 
 diately leaped upon it, and devoured it with 
 the fame avidity as they had done the other, 
 without afterwards vomiting the leaft parti- 
 cle of it. Upon killing and opening, three 
 hours afterwards, one which appeared to have 
 loaded its ftomach more than any of the reft, 
 I found the flefh partly diffolved, and in the 
 form of a femifluid pulp, and partly in the 
 procefs of folution, the very ftate in which I 
 had feen other fleih. 
 
 Lxxii. But let us return to bones. It ap- 
 pears that, whether large or fmall, they are 
 alike infoluble in the gaftric juices of crows 
 (lxx) . But is this true likewife with refped: 
 to thofe of a foft ftrudture, and which bear 
 fome refemblance to cartilage ? In Order to 
 afcertain this point, I made ufe of another 
 tibia, taken from an unfledged crow, and 
 which therefore had not acquired its natural 
 rigidity, though it was fo hard as to break, 
 when I tried to bend it : and now the gaftric 
 liquor was not inadlive. Of fifteen grains, 
 which it weighed at firft, it had loft five, af- 
 ter continuing fix hours in the ftomach en- 
 clofed in a tube. It was become fo foft, that 
 it was capable of being bent into the ftiape of 
 a bow. It continued to wafte and become 
 fofter; and when it had remained twenty-fe- 
 
 ven 
 
DISSERTATION 11. 79 
 
 veil, hours rn the flomach, it was (o much re- 
 duced as to refemble a thin tube of paper. It 
 was not at all gelatinous -, and when it was 
 preiTed between the fore-iinger and thumb, 
 it fliewed fome elaflicity, by recovering its 
 former fhape when the preiTure was removed. 
 It was not fcabrous either internally or exter- 
 nally, but had rather acquired a greater de- 
 gree of fmoothnefs during its folution. In 
 iive hours more it had loft the fhape of a tube, 
 and was totally reduced to pieces. 
 
 L XXIII. I tried other tender bones belong- 
 ing to larger animals ; and more or lefs of them 
 was diflblved, but with difficulty, and after 
 a very long interval. The folution was more 
 fpeedy in young crows, probably on account 
 of the greater abundance of their gaftric juices 
 (lxix). 
 
 With refpecl then to the queftion concern- 
 ing bones, we muft conclude that they are 
 indigeftible by crows, except only fuch as, 
 on account of their foftnefs, are rather to be 
 confidered as cartilage than bone. 
 
 Lxxiv. In the preceding, as well as the 
 prefent diflertation, I have always fpoken of 
 the ftomach as the place deftined for the con- 
 coction of the food. And in truth, whether 
 we confult antient or modern phyliologifts, or 
 confider my experiments, it v/ill appear fo 
 
 clearly 
 
8o DISSERTATION II. 
 
 clearly proved, that it would be abfurd to en- 
 tertain a doubt of it. But it may be proper 
 to enquire whether this operation belongs ex- 
 cluiively to the ilomach in the birds in quef- 
 tion, or is partly carried on in the cefophagus. 
 This enquiry is fuggefled upon the manifeft 
 decompofition, v/hich has been obferved in 
 part of the food that is found in the cefopha- 
 gus of fome animals, as among others in the 
 fea-crow and the pike [a). In order there- 
 fore to afcertain this point, I was led to make 
 a few experiments, which I fhall relate after 
 I have given a fhort defcription of the cefo- 
 phagus and ftomach in crows, and of the 
 fources of the refpediive liquors in thefe two 
 cavities. 
 
 Lxxv. The cefophagus is membranous, 
 and has no craw. When dilated it is cylin- 
 drical, if we except a flight contraction in the 
 middle. To the naked eye it would feem de- 
 ilitute of follicular glands, v/hich however 
 become confpicuous when it is viewed with a 
 glafs. They are in fuch abundance, that 
 there is not a fmgle point of this canal with- 
 out numbers of them. The excretory ducts 
 are fcarce difcernable, though they emit the 
 liquor of the follicles in great plenty. To fee 
 
 {a) Helvedus Mem. de I'Acad. 1719. Plot Nat. Hift. of 
 Staffordlhire, 
 
 this. 
 
r. ISSERTATION II. 8l 
 
 this, it is fufficient to pafs the finger over 
 them. The Hquor is of a vifcid nature, of 
 a cineritious white colour, and fomewhat 
 fwee tidi to the taile. 
 
 The inferior part of the oefophagus has 
 the fame kind of flefhy fafcia that has been 
 noticed in birds witli mufcular ftomachs» 
 This fafcia in crows is fcarce an inch long; 
 and in them too, as well as in the clafs of 
 birds jufl mentioned, is a tilTue of large folli- 
 cular glands very evident to the naked eye, of 
 a roundifh figure, and full of a fweet fluid, " 
 lefs vifcid than that in the fmall follicles in 
 the membranous part of the oefophagus, but 
 more denfe, and of a lighter cineritious hue. 
 
 Lxxvi. In the gallinaceous tribe we have 
 fpoken of three coats, the cartilaginous, ner- 
 vous, and mufcular (xlviii, xhx), which 
 principally compofe the flomach. Thefe 
 three coats are likewife found in birds with 
 an intermediate ftomach. When the carti- 
 laginous is feparated from the nervous coat, 
 and the latter is viewed with the naked eye, 
 it appears to contain a multitude of whitifh 
 little bodies inchafed in it, which have the, 
 appearance of points ; but when examined by 
 the microfcope, change their appearance to 
 that of follicular glands, much fmaller than 
 thofe in the flefl^y fafcia (lxxv); thefe fol- 
 
 VoL. I. G licles 
 
32 ' DISSERTATION. If* 
 
 licles are full of a vifcid liquor, which they 
 difcharge at the extremity towards the flo- 
 mach, when they are preiTed by the finger, 
 or any other body. The difcovery of thefe 
 glands in the nervous coat having led me to 
 imagine, that they might empty their contents 
 into the ftomach, I examined the cartilagi- 
 nous coat with great attention, in order to 
 try if I could find any minute pores for the 
 tranfiniffion of the liquor into the cavity of 
 that vifcus ; but I acknowledge ingenuoufly, 
 that I could not difcover any. This how- 
 ever by no means proves their non-exiflence ; 
 for they may be fo fmall as to elude the fight, 
 even v/hen aided by the microfcope. And I 
 cannot but believe, that thefe follicles, of 
 which the excretory ducfts are turned towards 
 the ftomach, are deftined by nature for pour- 
 ing their contents into that organ* 
 
 Lxxvii. I now proceed to enquire whe- 
 ther, exclufively of the ilomach, digeftion is 
 at all performed in the cefophagus of crows. 
 In order to determine this, I firmly fixed to 
 an iron wire two equal pieces of veal, one of 
 them to the end of the wire, and the other 
 two inches above. I then forced it down the 
 throat of an hungry unfledged crow; the 
 piece faftened to the end lay in the ftomach, 
 w^hile the other occupied the cefophagus*, 
 
 To 
 
D I S S E k T A t 1 (t N 11.' 83 
 
 To prevent them being thrown up, a firing 
 was failened to the upper end of the wire> 
 brought out at the mouth, and tied roiind the 
 beaks Thus I was enabled to draw up the 
 flefh at pleafure, and examine how much it 
 was diflblved. In an hour the piece that lay 
 in the flomach was quite confumed, except 
 a little cellular fubftance; but the other piece 
 was entire; It was again introduced into the 
 oefophagus, arid re-examined an hour after- 
 wards; but now the oefophageal liquor had 
 begun to ad; upon the iieih: its weight at 
 firft was lix pennyweights, but now only five 
 and a half^ It was kept upon the whole fix 
 hours in the oefophagus, and loft nearly twd 
 pennyweights. Thefe experiments will not 
 permit me to refufe to the oefophagus all 
 power of digeftion, an efFe<ft undoubtedly pro- 
 duced by the fluid of the follicles (lxxv); 
 but it is inconfiderable when compared with 
 that of the ftomach, fince this vifcus diffol- 
 ved fix pennyweights of flefh in an hour, 
 while the oefophagus difTolved but two in fix 
 hours. 
 
 Lxxviii. The experiments I afterwards 
 made on young crows were ftill more deci- 
 five. The fame wire was employed, and two 
 bits of flefh were faftened to it juft in the fame 
 manner, the one lying in the flomach, the 
 G z other 
 
84 DISSERTATION lU 
 
 Other in the oefophagus. The former piece 
 was generally quite difTolved before the folu- 
 tion of the other began, though in time this 
 alfo was very fenfibly wafted. This diminu- 
 tion upon one occalion amounted to five pen- 
 nyweights in the fpace of thirteen hours. 
 
 Lxxix. Laftly, in order to determine whe- 
 ther it was part only of the oefophagus or the 
 whole of that canal in crows which polTelTes 
 the power of folution, I formed a cylinder of 
 flefh half an inch thick, and of the length of 
 the oefophagus and ftomiach taken together. 
 I faftened this cylinder longitudinally to the 
 wire employed before, and forced it down the 
 throat of a crow, fo that one end touched the 
 bottom of the ftomach, and the other reached 
 almoil to the mouth. In a quarter of an 
 hour the whole circumference of the cylinder 
 was imbibed with a fluid, but at the lower 
 end only, which relied upon the bottom of 
 the ftomach had the flelh begun to be dif- 
 folved; here it was become whitifh. In about 
 an hour for near an inch, i. e. for the whole 
 length of the flomach, fcarce any of the cy- 
 linder was left j and what little remained was 
 gelatinous and had loft its cohefion, while 
 the portion that lay in the oefophagus appeared 
 to be unchanged: but it did not continue fo; 
 a fort of erofion began to take place along the 
 
 cylinder. 
 
DISSERTATION ul 8^ 
 
 cylinder, and continued but with extreme 
 ilownefs. And as this eroiion extended along 
 the whole length of the cylinder, I had reafon 
 to believe the whole length of the canal ca- 
 pable of concod:ing the food In a fmall de- 
 gree, whenever it happened to be lodged there 
 for feveral hours. But fuch an event never 
 happens when crows take their food at plea- 
 fure, lince the pieces never exceed the length 
 of the ftomach. In . this refped; they differ 
 from fome other animals, in which the food, 
 after they have fwallowed it, reaches into 
 the oefophagus, 
 
 Lxxx. Upon conlidering the great quan- 
 tity of fluid continually dropping into the 
 craw of gallinaceous fowls (lii), it appeared 
 highly probable, that the concodion of the 
 food is not a little promoted by the ftay it 
 makes there before it falls into the flomach. 
 But thefad is juft thereverfe. The aliment 
 is indeed foftened and macerated (lii), but 
 I could never perceive that It was at all dif- 
 folved: at leaft, I could never fee any trace 
 of folution on feveral vegetable matters, which 
 had been long retained in the craw. In a 
 fpace more or lefs fliort they become foft, and 
 are imbibed with a fluid ; but I have not been 
 able to perceive, that they were in the leall 
 diflblved. We muil therefore conclude, that 
 G 5 the 
 
B6 DISSERTATION 11. 
 
 the oefophageal liquor in gallinaceous~ibwls 
 is different from that of crows. 
 
 Lxxxi, But why is the food fo foon digef- 
 ted in the ftomaph, and fo flowly in the oefo- 
 phagus ? . Is i|: becaufe the gaflric fluid is more 
 efficacious, or in greater quantity, than the 
 cefophageal? What are the properties and 
 charadteriftic marks of thefe two Uquors | 
 May we hope that experiments out of the 
 body will be as inftrut^ive as thofe made in 
 it ? To enable myfelf to procure a large quan- 
 tity of thefe fluids at pleafure, was the firil 
 ilep towards the folution of thefe problems, 
 And as fuch a quantity could not be eaiily got 
 by killing the birds, it became neceffary to 
 invent a contrivance for obtaining it from 
 them alive. To put bits of dry fpnnge into 
 the tubes, and leave them fome time in the 
 oefophagus and ftomach, appeared to be the 
 beft means of attaining this end; for they 
 mufl nepeifarily be fatiirated with the liquor 
 of thefe cavities, and when vomited or drawn 
 up, will fupply the experimenter with a con- 
 iiderable quantity, provided he ufes a number. 
 Three tubes were introduced into the fto- 
 mach of a crow, and four hours afterwards 
 vomited up ; the three little fpunges, when 
 they were taken out and preiTed between the 
 j^ijgcrs, afforded thirty-feven grains of gaftrip 
 
 liquor^ 
 
DISSERTATION II. $7 
 
 liquor, which was frothy, of a turbid yellow 
 colour, had an intermediate tafte between 
 bitter and fait, and being fet to ftand in a 
 watch-glafs, depofited in a few hours a co- 
 pious fediment. As the fediment appeared to 
 arife from the food that was diffolved by the 
 gaflric juice (for the bird had taken food a 
 little before it fwallowed the tubes) I re- 
 peated the experiment upon another crow, of 
 which the ftomach was empty, and continued 
 fo till the tubes were thrown up. This pre^ 
 caution I ever afterwards obferved, at the fame 
 time taking care, that the faft did not lafl top 
 long, left it fhould induce a morbid ilate in the 
 animaL I was likewife careful tp cleanfe the 
 fpunges from every impurity, by repeated 
 wafliings and dryings, before I made ufe of 
 them again, Upop repeating, with thefe pre, 
 cautions, the foregoing experiment with thq 
 three tubes, I obtained thirty-three grains of 
 gaftric juice in a ftate of purity. It differed 
 from the former in being of a tranfparent yel- 
 low colour, ^nd in depofiting very little fedi- 
 meiit^ it had the fame bitter and fait t^fte. 
 It appeared to have very little volatility, as it 
 was kept feyeral days ii> a watch glafs with^ 
 out fufFering almoft any diminution. When 
 thrown upon burning coals, it extinguished 
 |hem inllead of taking fire , and when brought 
 Q 4p pe?,r 
 
8S DISSERTATION 11. 
 
 near a candle, it did not rife in flame. Fur- 
 ther, paper foaked in it and thrown upon the 
 fire, did not burn till the gaftric fluid was 
 evaporated. Nor had it more volatility or in- 
 flammability when jufh taken from the flo- 
 mach and ilill warm. 
 
 Lxxxii. The quantity, which was not in- 
 conflderable, obtained from three fpunges, 
 gave me hopes of collecting enough for che^ 
 mical experiments at large, and for attempt- 
 ing artificial digeftion. Every crow was ca- 
 pable, as I found upon trial, of taking eight 
 inflead of three tubes ; and as they would be 
 thrown up in a few hours, I could repeat the 
 experiment feveral times a day. Therefore to 
 five crows, of which I then happened to be 
 in poireflion, I gave forty tubes furnifhed with 
 littk fpunges, i. e. eight to each. In three 
 hours aiid a half all the tubes were returned 
 by the mouth, and the quantity of gaftric 
 fluid exprefl^ed from them amounted to four 
 hundred and eighty-one grains. In a few 
 days before I had colle<fled thirteen ounces of 
 liquor. I employed it for the purpofes for 
 •which I had defigned it, and which fhall be 
 mentioned in their proper place. 
 
 Lxxxiir. While I was engaged in thefe 
 experiments, I obferved feveral remarkable 
 fadts. The firil was, that the gafcric juice 
 
 flo'^ved 
 
DISSERTAtlON II. ^g 
 
 flowed in great abundance into the cavity of 
 the ftomach; it fometimes happened, that 
 one of the fpunges was brought up in a quar- 
 ter of an hour after it had been fwallowed, and 
 in this fhort fpace it was conliderably loaded, 
 and in an hour as much as it could be. Se- 
 condly, when a confiderable quantity of fluid 
 has been obtained, another, and even a third 
 may be got immediately. Sometimes when 
 a crow has vomited up the eight tubes, I put 
 frefh fpunges into them and returned them 
 without delays and this I repeated a third 
 time and found, that the quantity procured 
 the laft time was as great as the fecond, and 
 even the firft. Thirdly, the fluid had always 
 the qualities above-mentioned (lxxxi), if 
 we except a difference of colour. It is com- 
 monly of a pale orange, but fometimes of a 
 cineritious yellow. 
 
 LXXXI V. I took the fame method to pro- 
 cure the oefophageal liquor, with the varia- 
 tion only of a Angle circumftance. The tubes 
 were now fafl:ened to threads, which were 
 brought out at the mouth, and tied round 
 the beak to prevent its being opened. 
 
 Thus the tubes were fixed in the cefopha- 
 gus, without the leaft danger of their getting 
 into the flomach, or being throv/n up. Be- 
 fides, I could draw them up at pleafure. I 
 
 intro- 
 
90 DISSERTATION II. 
 
 introduced four tubes at once into the cefo^ 
 phagus of a crow, and extradled them again 
 in three hours. I learned from this firft trial, 
 the fcantinefs of the cefophageal compared 
 with the gaftric fluid. The four fpunges fup- 
 plied me with eleven grains only. Doubting 
 whether this might not be accidental, I re- 
 peated the experiment feveral times, and al- 
 lowed the tubes to remain longer in the oefo- 
 phagus, but the fpunges were very far from 
 being fo thoroughly faturated with fluid as in 
 the ilomach : fo that diredt e?:periment proves 
 the great abundance of the gaftric, in qom- 
 parifon with the cefophageal liquor. If the 
 ftomach and cefophagus of a crow be laid 
 open longitudinally, the latter will be found 
 to be moiftened with its proper fluid only, 
 while the former generally affords reception 
 to part of it like wife. Theory too, in the 
 prefent cafe, agrees with fatl. The natural 
 pofl:ure of crows, and indeed of mofl: other 
 birds, is fach, that the liquor which oozes 
 out from the internal furface of the cefopha- 
 gus, muil defcend to the lower parts from the 
 law of gravity, and thence into the Homach^ 
 This organ mufl: therefore be the receptacle 
 of the cefophageal fluid ; but it is more than 
 probable, that it has a peculiar fluid alfo 
 (lxxvi): beiides, we are certain, that the 
 
 bile 
 
DISSERTATION II, 9I, 
 
 |)ile is mixed in confiderable quantity with the 
 gafiric juices. I have very frequently found 
 the bottom of the flomach in crows full of 
 it, and this is the reafon why this juice is al^ 
 v/ays bitter and yellow. Further, upon open- 
 ing the duodenum longitudinally, I have per- 
 ceived the yellowifli green veiliges of the bile, 
 which is difcharged into' that inteftine at the 
 difhance of at leaft three inches from the py- 
 lorus through the cyftic ducfl, which evidently 
 arifes from the gall-bladder, The conjunc- 
 tion of a}l thefe liquors, muft produce a 
 quantity of fluid far larger than that which ' 
 derives its fource from the oefophagus alone. 
 And I doubt not but this is the reafon, why 
 the food is digefted more fpeedily and per- 
 fedly in the ftomach than the oefophagus 
 (lxxvij, lxxviii). Though I ihould alfo 
 fuppofe, that this is in part owing to the 
 greater energy of the gaflric liquor from the 
 admixture of the bile, which never rifes into 
 the cefophagus, as appears from the juice of 
 that canal never being at all yellow or bitter, 
 but nearly infipid and colourlefs. 
 
 Lxxxv. It remains now for me to relate 
 fome attempts to produce artificial digefliion 
 with the gaftric juices, referving for another 
 opportunity the recital of the chemical expe- 
 riments made upon that fluid, obtained both 
 
 from 
 
52 DISSERTATION II, 
 
 from crows and other animals, with the view 
 of acquiring as complete a k novdedge as pof- 
 iibleof its nature and properties. The great 
 abundance I was able to procure from crows, 
 by means of vomiting, gave me the advan- 
 tage of inftituting a greater number of trials, 
 than with that of gallinaceous fowls (lvi, 
 Lvii), from which the gaftric liquor could 
 not eafiiy be procured without killing them. 
 I firil wiflied to examine the effect of the gaf- 
 tric juices of crows upon flefh, in the open 
 air. It was January, and Reaumur's ther- 
 mometer placed near the velTel ufed for the 
 experiment, flood at the fourth and fifth de- 
 gree (a). For greater certainty in thefe ex- 
 periments, I eflablifheda term of comparifon, 
 by employing fimilar vefTels containing the 
 fame fiefh infufed in water. I alfo took care 
 upon the prefent as well as other occafions, 
 that the fiefli ihould be completely immerfed 
 in the refpective liquors, and that the phials 
 fhould be clofed with floppies. For {even 
 days the flefli kept in the gaflric juice, and in 
 water continued the fame. On the eighth I 
 
 (a) Wherever the thermometer is mentioned in this work, 
 the fame, viz. Reaumur's is to be underftood. 
 
 N. B. The fourth and fifth degrees of Reaumur's thermomer 
 ter anfwer to about forty-two and forty-three and one-fourth of 
 
 Fahrenheit's. 
 
 per- 
 
DISSERTATION II. g^ 
 
 perceived a flight folution, for upon agitating; 
 both liquors, feveral particles feparated from 
 the larger mafs, and fell down to the bottom 
 of the phials. No further progrefs was af- 
 terwards made, and the gaftric fluid did not 
 feem at all more efficacious than common wa- 
 ter; only the flefli immerfed in the former 
 was preferved from putrefacftion, but not in 
 the iatter. 
 
 Lxxxvi. In this experiment I had ufed 
 beef; I verified the fame obfervation upon 
 the more tender flelh of calves, chickens, 
 and pigeons, notwithftanding the heat of the 
 atmofphere had now raifed the thermometer 
 to feven degrees [a). While I was making 
 thefe experiments in the natural temperature 
 of the air, I was employed about others of 
 a like nature in a warmer medium, viz. in 
 a flove, in which^ the heat varied between 
 22° {if) and temperate. And now the efFecfls 
 produced by the gaftric fluid, differed from 
 thofe produced by water. In the latter the 
 flefh began to be a little diflblved in two days; 
 this was the effed: of incipient putrefad:ion, 
 as appeared plainly from the foetid fmell which 
 began to be exhaled. The fmell continued 
 
 {a) Forty-eight and three fourths of Fahrenheit's, 
 (6) Seventy-niae and a half of Fahrenheit's. 
 
 to 
 
94 b i S S E R t A T i N It, 
 
 to increafe during the following days, ^rid iii 
 a week became intolerable, when the flefh 
 was reduced to a naufeous pulp. In the; 
 gaftric juice the folution was more rapid^ and 
 exhibited very different phaenomena -, twenty- 
 five hours were fufficient to decompofe the 
 flefli' contained in it, and in a little more than 
 tv/o days there remained only a very fmall 
 morfel entire. Thefe folutions never emitted 
 any bad fmell • whence it is evident, that they 
 did not arife from incipient putrefaction, like 
 thofe in water, but from a more efficacious 
 and a different menflruum, viz, the gaflric 
 liquor. 
 
 Lxxxvii. Being now" engaged by different 
 occupations, I was obliged to interrupt thefe 
 experiments, and could not refume them till 
 the June following; and then taking advan- 
 tage of the feafon, I expofed to the fun twof 
 phials filled to a certain height with gaftric 
 juice from crows, in one of which were im-^ 
 mierfed feveral pieces of beef, and in the other 
 crumb of wheaten bread. Nine hours of fun- 
 fhine much forwarded the artificial digeilon, 
 which was the objed: of enquiry. A good 
 part of the flefh was reduced to a kind of glue, 
 that when it was handled adhered to the fin- 
 gers ; nothing like flefli remained in any of 
 the pieces, but tlie nucleus, which was flill 
 
 con- 
 
DISSERTATION II. 95 
 
 confiftent and fibrous, which tv^'o qualities it 
 loil the next day; after having been expofed 
 fix hours to the fiin the nuclei, like the out- 
 fide, no longer retained a fibrous fi:ru(flure. 
 In the fiin, the heat as well on the firfi: as the 
 lecond day, was between forty and forty- 
 five (a). The gaftric liquor produced upon 
 the bread a change analogous to that which 
 the flefh had undergone. It not only lofi: its 
 \vhite colour and turned grey, but had be- 
 come vifcous, and no longer prefented to the 
 eye the appearance, though it retained fome- 
 what of the tafte of bread. Of bread as well 
 as flefh immerfed in water and expofed to the 
 fun for the fame time, there was a percepti- 
 ble diminution; but it was very fuperficial 
 and inconfiderable when compared with that 
 produced by the gaftric fluid. The bread 
 turned four, and the flefh became putrid, 
 circumftances that did not take place in the 
 leaft, in the other phials. 
 
 ixxxviii. Thus a tolerably complete con- 
 cocftion was obtained in the heat of the fun ; 
 but it was reafonable to fuppofe, that it would 
 be ft ill more perfediin the temperature of th& 
 flomach. In the preceding diflertation 1 have 
 
 {a) An hundred twenty-two, and an hundred thirty-three 
 and one- fourth of Fahrenheit's thermometer. 
 
 oh- 
 
^6 DISSERTATION II. 
 
 obferved, that by v/ay of fubflitute for tbe 
 natural heat of the annual that furnifhed gaf- 
 trie liquor for the experin\ent, I fixed the 
 tubes under my axilla (lvi, lvii)^ fuch an 
 expedient was necellary in that cafe, fince 
 glafs is incapable of re lifting the violent adiion 
 of the gizzard. But there v/as now no lon- 
 ger the fame danger, and the experiment 
 might be made in the following manner. Se- 
 veral glafs tubes fix lines long and three in 
 diameter, were hermetically fealed at one 
 end, and at the other bits of fleili were intro- 
 duced, and then the tube v/as filled with gaf- 
 tric fluid. It was then very carefully flop- 
 ped with fealing-wax, and the tubes were 
 forced into the ilomachs of feveral crows. 
 Should digeftion now take place it might be 
 properly called artificial, fince it muft have 
 been effected in clofe tubes, to which the 
 juices of the fi:omach could h^ve no accefs. 
 But I foon found that the wax became foft in 
 the animal heat, and confequently did not 
 keep the tubes clofejy flopt, as I wiflied. 
 There was however no difficulty in fubfiitu- 
 ting a firmer cement, which w^ould not be 
 either melted or foftened; and with fuch a 
 cement I repeated the experiment juft men- 
 tioned, and others of a like nature, which I 
 Ihall defcribe hereafter. I prepared two 
 
 tubes 
 
DISSERTATION II^ ^7 
 
 tubes ill this manner j they were given to a 
 crow> and returned by vomiting in an hour 
 and an half. I Vv^ill not conceal rav amaze- 
 ment at finding, that the pieces of fleih in- 
 cloled in the tubes were not in the leaffc 
 changed, unlefs it was in having acquired a 
 blueilh red colour* My amazement was ftill 
 more increafed upon obferving, that they had 
 undergone no further alteration after remain- 
 ing four hours longer in the ilomach of the 
 fame crov/, enclofed as before in two fealed 
 tubes. Thefe bits of flefh weis^hed in all 
 twenty-eight grains 5 fo inconfiderable a quan- 
 tity would have been diifolved in a few mi- 
 nutes, if it had been loofe in the ftomach, 
 and in a very few hours, if it had been en- 
 clofed in tubes open at the ends. 
 
 L XXX IX. Did this unexpe(fled failure arife 
 ,from the communication between the ex- 
 ternal air and that within the tubes beins cut 
 oiF, or from a deficiency of gaftric fluid, or 
 elfe for want of the adion of the fiomach 
 upon the fleili? I confidered maturely thefe 
 conjedtural explanations, but they appeared 
 altogether infufficient. With refped: to the 
 lafi, it is repugnant to all thofe fa6ls which 
 prove the folution of aliment within tubes, 
 open indeed at the ends, and perforated along 
 the fides, but which cffecflually prevent the 
 
 Vol. I. H me- 
 
98 DISSERTATION II. 
 
 mechanical adion of the ftomach upon their 
 contents. That the gailiric fluid was in too 
 fmall quantity for the folution of the flefh, is 
 a fufpicion unworthy of attention; for the 
 pieces were always covered by it, fo that the 
 quantity of fluid muft have been greater than 
 that of folid. Laftly, the communication 
 between the external air and that within the 
 tubes being intercepted, cannot in all like- 
 lihood be the reafon why folution did not 
 take place. In order to determine this cer- 
 tainly, I made the following curious experi- 
 ment. Having prepared feveral glafs tubes 
 of the length of fix inches, I fealed them 
 hermetically at one end, by means of a re- 
 verberated flame, and the oppofite extremi- 
 ties were drawn out fo as to form elongated 
 cones. Through the open end of thefe cones 
 I poured a quantity of gaftric fluid, together 
 with a few fmall pieces of flefh, which filled 
 two thirds of the wider part of the cone. 
 I then introduced the cones by their bafls 
 into the flomachs of fome crows, allotting 
 one to each bird -, and when they refled upon 
 the bottom of the flomach, their apexes came 
 out at the mouth. To prevent their being 
 thrown up, I ufed the precautions mentioned 
 in another place (lxxvi). Thefe conical 
 tubes mufl no doubt have been very incom- 
 modious 
 
D I s s E R T A r t n It; 99 
 
 modious to the animals, but they were ex- 
 ceedingly well adapted to the end I had in 
 view, lince a free pallage was allowed for the 
 external air into them* However, notwith- 
 ftanding this, the flefli remained feveral hours 
 immerfed in the gaftric fluid, without fliew* 
 ing any fign of decompoiition* 
 
 xc. It is proper to apprize the reader, that 
 when the fealed tubes, , or the cones, were 
 kept long in th6 flomach, as, for inftance, 
 ten or twelve hours, the flefh was generally 
 reduced to a dark-coloured gelatinous pulp. 
 But this did not remove my furprize at fee** 
 ing fo flow a folution in thofe clofe receivers, 
 in comparifon with the rapidity of the pro- 
 cefs in the flomach. The gaflric juice was 
 quite frefli, it was in fufficient plenty, and 
 the flefh put in the tubes and cones was ex- 
 pofed to the fame degree of heat when it is 
 in immediate conta(fl with the fides of the 
 flomach. 
 
 If crows are killed during the procefs of 
 digeflion, the bottom of the Romach gene- 
 rally abounds in gaflric juice, which when, 
 compared with that expreffed from the fpun- 
 ges, appears to differ a little, being more denfe 
 and bitter, and of a yellow inclining to azure. 
 The juice v/hichis mixed with the food, and 
 occupies the upper parts of the ftomach, ap- 
 H 2 proaches 
 
lOO DISSERTATIOIT II. 
 
 proaches more to the nature of that with 
 which the fpunges are imhibed. Having 
 learned from experiment, that digeftion pro- 
 ceeds mofl rapidly at the bottom of the fto- 
 mach, on account probably of , the gaftric 
 juice being more ad;ive and efficacious there 
 from its immediate mixture with the bile, 
 which gives it the yellowiih azure hue and a 
 bitterer tafte, I preferred this juice to that 
 from the fpunges, and repeated with it the 
 experiments with the fealed and conical tubes 
 mentioned in the Lxxxviiith and Lxxxixth 
 paragraphs. But the event did not anfwer 
 my expectation, no folution of the fleifh ta- 
 king place till feveral hours had elapfed. 
 
 xci. Upon comparing the laboratory dt{~ 
 tined by nature for the procefs of digeilion, 
 and thefe receivers prepared by art to accom- 
 plifli the fame end, I could difcover but two 
 circumftances in which they -differed ; the 
 flefli in the veiTels undergoes the aftion of a 
 fluid which is never renewed 3 while, on the 
 contrary, in the natural laboratory it is con- 
 tinually fubjed:ed to the atlion of freih juices, 
 inceffantly fipplied by an innumerable muU 
 titude of follicular glands. Befides, the gaflric 
 juices being confined within the cavity of the 
 fliomach, there is little or no evaporation ; 
 whereas, when expofed to the air, and con- 
 
 fequently 
 
DISSERTATION II. lOI 
 
 fequently cooled, they cannot but lofe fome of 
 their more volatile and active particles by eva- 
 poration. Does then the flow folution of 
 ilelh in clofe tubes and in cones, depend upon 
 the gaftric juice being deprived by thefe two 
 caufes of part of that energy, on which di- 
 geftion depends ? I found from experiment, 
 that the former caufe, at leaft, the want of 
 renovation had great influence in retarding 
 the folution. If, inftead of perfectly doling 
 the tubes, I left a fmall perforation capable 
 of allowing ingrefs and egrefs to the gaftric 
 juice, the folution of the flefh took place 
 much fooner. The fame thing happened, 
 when, inftead of leaving the fame juice in 
 the cones all the while, I was at the pains 
 of changing it feveral times. But warmth 
 is another condition abfolutely indifpenfable 
 for rendering the gailric fluid of thefe ani- 
 mals fit for digeftion. When this liquor is 
 kept in a temperature not more than four or 
 five degrees above the freezing point, its fol- 
 vent power is fo much impaired, that it does 
 not feem more efficacious than common wa- 
 ter (lxxxv). This is alfo obfervable at 
 feven degrees (^) (lxxxvi). In order to ren- 
 der the effedis of the gaflric juice perfedly 
 
 {a) Forty-feven three 'fourths of Fahrenheit's thermometer, 
 
 H 3 fenfiblcj, 
 
IQ2 DISSERTATION 11. 
 
 fenfible, a ftronger heat is requlfite, as from 
 ten to twenty-two degrees (lxxxvi). Still 
 folution proceeds very llowly ; to remedy this 
 the animal heat is neceffary, viz. about thirty 
 degrees {a) (xc). And fo remarkable is the 
 efFed: of heat in this particular, that the very 
 liquor, which, for want of being renewed, 
 diifolves fleih llowly at thirty degrees (xc), 
 \^ effedls this very fpeedily at forty and forty- 
 iive degrees (b) (lxxxvii), 
 
 xcii. Every time I expreffed the juice 
 from the fponges, I waihed them in pure 
 water, which was tinged yellow by the re- 
 mains. After having made fo many experi- 
 ments on the gaftric fluid in a flate of purity, 
 I conceived it might not be altogether with- 
 out its ufe, to make one with the water in 
 which the fpunges had been waihed; with 
 this water I therefore filled a fmall glafs 
 phial, which was left expofed to the fun, 
 with a piece of lielh in it, for three days in 
 July, The ilelh (which was mutton) lliew- 
 ' ed fome ligns of folution. On the third day, 
 there appeared upon the bottom of the phial 
 a quantity of impalpable matter of a cineri- 
 
 (a) Ninety-five one-half of the fame. 
 
 {h) One hundred and twenty-two, and one hundred and 
 thiny-three onQ-fourth of Fahrenheit's thermometer. 
 
 tious 
 
DISSERTATION II. 1O3 
 
 tlous colour, confifting of particles feparated 
 from the fleih immerfed in the liquor. Not- 
 withftanding the feafon, as it ufually is in 
 July, was very hot, it had acquired little or 
 no foetid fmelli whilft a fimilar piece of 
 flefh, expofed to the fun in the fame manner, 
 but immerfed in water, became intolerably 
 putrid on the fecond day. 
 
 xciii. But it is time to quit the fubje<5t 
 of digeflion in crows, and to proceed to that 
 of herons, the other fpecies of birds which 
 I propofed to examine in this dilTertation. 
 The .-herons upon which my obfervations 
 W)2rre made, and which the nomenclators 
 denovnin2itt i:inerki'ouSy or grey (a), mufl: cer- 
 tainly be clafled among birds with interme- 
 diate ftomachs, fince the fides of this vifcus 
 have an intermediate thicknefs and folidity 
 between membranous and mufcular ftomachs. 
 When this organ is dilated, it appears about 
 two inches wide, and as many long; its form 
 approaches to that of a cylinder. When 
 opened lengthwife, and obferved internally, 
 it prefents the appearance of rugae, of which 
 fome run in a longitudinal, fome in a tranf- 
 verfe, and others in an irregular and oblique 
 dire<ftion. The fides of the ftomach are co- 
 
 (/:) Linn. Syft. Nat.T. 1. Bel. Av. 
 
 H 4 vered 
 
104 Dissertation ir. 
 
 vered with a kind of gelatinous lining, of 
 fome coniiftence, but eafily removed, and of 
 a colour between white and yellow. This 
 lining feems organized j and I fhould be in- 
 clined to fuppofe, that it is the innermofl; coat 
 of the flomach. The nervous coat next pre- 
 fents itfelf; it is of a whitifh colour, and 
 moderate thieknefs, .but its texture is ilrong, 
 and it is not eafily lacerated. When this 
 eoat is. cleaned and dried v/ith a napkin, and 
 then diilended, and compreffed underneath, 
 it is immediately covered with an effufion of 
 very fmall and fcarce viiible drops, v/hich en- 
 larging and approaching towards each other, 
 form at leaft a thin aqueous covering. And 
 if this he wiped away, and the nervous coat 
 be again diflended and fqueezed, another like 
 the firft will a;ppear3 . and in like manner a 
 third, a fourth, &c, with this difference only, 
 that the. quantity of rnoifture is every time di- 
 minifhed,. There can be no doubt of this 
 being a portion of the gaftric fluid, difcharged 
 directly into the cavity of the fcomach. I 
 have employed the utmoft attention in fearch- 
 ing v^hetber this liquor derives its origin from 
 glands, or any analogous bodies, but could 
 never difcover either the one or the other; 
 and therefore we muH fuppofe that it is fe- 
 creted by fmall arteries^ which open into the 
 
 ftomachs 
 
DISSERTATION II. IO5 
 
 flomach, and depofit their contents there. 
 After the nervous, we have the mufcular coat, 
 of a red colour, and fcarce a Hne in thick- 
 nefs. It is compofed of flefliy flris, partly 
 tranfverfe, partly longitudinal. The former 
 appeared to me to occupy the furface only, 
 the latter conftitute the internal ftrata, and 
 are continued to the termination of this coat. 
 There is alfo another coat, confifting of cel- 
 lular fubflance, and this is the laft of all. 
 
 xciv. The flomach always, and efpecially 
 when empty, contains more or lefs gallric 
 fluid, of a bitter tafte, turbid yellov/ colour, 
 and generally of fome denfity. The bitter- 
 nefs is ov/ing to the bile, which has that 
 tafte, but in an intenfer degree ; I have often 
 found it at the bottom of the ftomach, and in 
 the vicinity of the pylorus. The gali-blad- 
 der exceeds an inch in lengthy its greatefl 
 diameter is of five or fix lines ; in fhape it re- 
 fembles a fmall tgg, of which the fharp end 
 is inferted into the liver. Notwithfbanding 
 many careful examinations, I am not certain 
 of having found the cyfli(fb dud: 5 I however 
 fufpe6t that it perforates the duodenum, at 
 the diflance of fix inches from the pylorus; 
 this I collect from a line of an azure-yellow 
 hue, which arifes from the gall-bladder, and 
 is inferted into that part of the intefiine. 
 
 1 xcv. Above 
 
J06 DISSERTATION If. 
 
 xcv. Above the ftomach we meet with 
 the fame kind of flelhy fafcia, which I have 
 noticed in galHnaceous fowls ajid crows, 
 (xxvi, XL VI I, Lxxv). In the grey heron 
 it exceeds an inch in breadth. This fafcia 
 is alfo covered with the fame gelatinous 
 lining that invefls the ftomach (xciii). 
 Next we find a nervous coat of a finer texture 
 than that of the ftomach, of which it appears 
 to be a continuation. This coat, when at- 
 tentively viewed, looks like a fieve, fo much 
 is it perforated at every part. , The perfora- 
 tions are nothing but the apertures or mouths 
 of fubjacent follicular glands, occupying 'al- 
 moft all the infide of the fafcia, and vifible 
 through it. If the nervous coat be any where 
 comprefied, a vifcid, cloudy, and, as far as 
 I could judge, infipid liquor oozes out at thefe 
 pores, and continues 'to ooze out if the pref- 
 fure be continued. The follicles that He 
 beneath, manifeftly fupply this fluid in fuch 
 abundance. It would be fuperflous to de- 
 fcribe thefe glandular bodies ; fince they ex- 
 adlly refemhle thofe of crows and gallinaceous 
 fowls; whether we confider the immenfe 
 number of them, or their pofition, contiguity, 
 fhape, or colour. When we raife this ag- 
 gregation of follicles, we come to the muf- 
 cular coat, which is very thin, and confifts 
 
 of 
 
DISSERTATION II. I07 
 
 of feveral flrata of long and compad; flefhy faf- 
 ciculi ; next to which lies the laft or external 
 coat, the thinneft of all, and confifting of 
 cellular fubftance. 
 
 xcvi. The cefophagus is about twelve 
 inches in length, and in breadth one and a 
 half. Its fhape is nearly cylindrical, but it 
 becomes narrower near the ftomach. Upon 
 examining it externally with a microfcope, I 
 difcovered that it was quite full of minute bo- 
 dies, which are, I fuppofe, glandular. When 
 it has been carefully inverted and inflated, 
 and the humidity, which always covers it, 
 has been wiped away, if now we lay hold of 
 one end, and fqueeze it forcibly, fo that it 
 {hall be enlarged in the adjacent parts, the 
 humidity will appear again; and upon re- 
 peating the compreffion, it will be feen fe- 
 veral fucceffive times, juft as in the ftomach, 
 (xciii); with this difference, however, as I 
 conceive, that the humidity in the ftomach 
 derives its fource from fmall arteries, and in 
 the cefophagus from minute glands, or fome 
 analogous bodies. 
 
 xcvii. It was natural to fuppofe that this 
 apparatus of fluids, which are conftantly 
 trickling into the cavity of the ftomach and 
 cefophagus of herons, is chiefly deligned for 
 digeftion. But the fmall number which I 
 
 polTefted, 
 
Io8 DISSERTATION. II." 
 
 pofTeiTed, and their almoft never vomiting, 
 like crows, indigellible bodies, and confe- 
 quently tubes, did not permit me to make 
 fuch a feries of experiments as I could have 
 wiilied. I have however been able to make 
 the moft eiTential, of which one confifted in 
 enquiring into the manner of digeftion in the 
 flomachs of thefe birds. For this purpofe I 
 had recourfe to the tubes, than which I do 
 not believe there are any means better adapted 
 to fuch enquiries. It is well known that the 
 grey heron feeds on fifhes, frogs, v/ater- 
 fnakes, and feveral forts of aquatic worms and 
 infedls. Thofe in my polTeffion devoured 
 frogs, and efpecially iiihes, with great gree- 
 dinefs ; and I therefore ufed them for my ex- 
 periments. They fwalloW frogs of a mode- 
 rate fize whole. A whole frog, inclofed in a 
 tin tube, was introduced into the ftomach, 
 together with a iifh, of bulk nearly equal, 
 included in another tube. In twenty-four 
 hours the heron was killed, and the ibomach 
 opened; though the tubes were very thin, 
 they had received no damage, if we except 
 two flight contuiions upon one of them; they 
 v/ere fo light, that it was not difficult to guefs 
 that they no longer contained the fame quan- 
 titv of matter that had been put into them. 
 The little fifh v/as all difTolved, except fome 
 
 r 
 OX 
 
DISSERTATION II. IO9 
 
 of the ribs, a few bones of the head, and a 
 bit of the flefh of the back, which had be- 
 come fo tender, that the parts no longer co- 
 hered. The frog's fliape was more eafily dif- 
 tinguiiliable than that of the fifli ^ the pulp 
 of the thighs, and even the bone itfelf, was 
 quite deftroyed ; but the ends of the lower, 
 as well as the upper limbs remained. The 
 integuments of the abdomen and. thorax were 
 no longer to be found; and the fubjacent 
 flefli was become fo foft, that it appeared to 
 have undergone a flight boiling. The bones 
 had acquired the foftnefs of cartilage. Thefe 
 remains of the frog and fifh were impregnated 
 with gaftric fluid, and tafled bitter. The in- 
 telligent reader perceives the immediate con- 
 fequences of this experiment. In the firfl; 
 place the flomach of herons ads with fome 
 force upon the fub fiances it contains, as we 
 may colled: from the flight contufions upon 
 one of the tubes. Secondly, digeftion, whicli 
 was in an advanced .ftate in the frog, and 
 quite complete in the iifh, is not the effedt of 
 trituration, but of the gaflric fluid, which en- 
 tering in at the open extremity of the- tube, 
 or through the holes at the fides, penetrated 
 the two animals, and by virtue of its folvent 
 power, partly confumed them ; but it made 
 greater havock upon the fifh than the fro^, 
 
 on 
 
no DISSERTATION II. 
 
 on account of its being tenderer. Thirdly^ 
 the efficacy of the gaftric fluid of the heron is 
 not limited to the folution of foft parts, fuch 
 as the fkin, flefh, &c. but extends to the 
 hardefl alfo, viz. the bones. 
 
 xcviii. Of the laft circumftance I wifhed 
 to obtain greater certainty, by putting bones 
 alone into the tubes. We have already feen 
 that crow^s are incapable of digefting hard 
 bones, and that they digeft fuch as are ten- 
 der with difficulty (lxx, LXXII, LXXIIl). It 
 was therefore an objetft of great curiofity to 
 difcover what would happen in herons ; and 
 it was eafy to fatisfy this curiofity, by inclo- 
 fing bones of feveral forts in the tubes ; in one 
 I therefore enclofed only the tender bones of 
 frogs or fiihesj in another hard bones, viz. 
 the thigh-bone of a turkey broken in two 
 pieces. The pieces of both the hard and ten- 
 der bones were formed into two bundles, and 
 tied with thread. After an heron had re- 
 tained thefe two tubes in its ftomach twenty- 
 feven hours, it was killed. It was with a 
 mixture of furprize and pleafure that I faw 
 the tube which contained the iifhes and frog's 
 bones empty, while the firing remained en,- 
 tire. The gallric juice had then perfe(5tly 
 difTolved the bones. But this was not the 
 cafe with refped to the contents of the other 
 
 tube.,, 
 
DISSERTATION II. Ill 
 
 tube. I fhould have coniidered them as un- 
 touched, if they had not appeared fmoother, 
 whiter, and perhaps thinner than at firft. 
 They now weighed only eleven pennyweights 
 and fix grains, whereas at firfl they had 
 weighed fourteen pennyweights ; they had 
 therefore lofl of their original weight three 
 pennyweights within fix grains. If this ex- 
 periment be compared with that made upon 
 crows, with the fame intention, ' it will ap- 
 pear evident, that the gaftric juice of the lat- 
 ter is lefs efficacious in dilTolving bones than 
 that of the heron. And in truth, their na- 
 ture requires that they fhould digefl every 
 part of the animals upon which they feed. I 
 gave them fome frogs, and obferved their 
 way of eating them ; when of a moderate lize 
 they fwallow them whole, when very large 
 they feparate them into feveral portions, and 
 fwallow them without parting the flefh from 
 the bones. Since, then, herons do not en- 
 joy the advantage of vomiting up fubflances 
 incapable of being digefled (lxxvii), and 
 the bones of frogs and fuch animals cannot 
 ealily be voided at the anus. Nature has wifely 
 cndov^ed the ftomach with the power of con- 
 C0(fling and afiimilating bone. 
 
 xc I x . It was equally curious and important 
 to enquire, whether the cefophagus of the 
 
 heron 
 
112 DISSERTATION II. 
 
 heron as well as of crows, is capable of per- 
 forming digeftion (lxxvii, lxxviii, lxxix). 
 The great length of the neck, and confe- 
 quently of the cefophagus, is extremely fa- 
 vourable to fuch an enquiry. For this pur- 
 pofe a flead frog was forced half way down 
 this canal with the head downwards, where 
 it was fixed by a firing, of which one end 
 was tied round the hind legs, and the other 
 came out of the mouth, and was wrapped 
 ;round the neck. In this fxtuation it remained 
 two hours, and more was effecfled than I could 
 exped in fo Ihort a fpace. The animal was 
 indeed entire, but was become very tender, 
 though the tendernefs did not penetrate far 
 below the furface. This appearance of in- 
 cipient conco<5tion induced me to puih the 
 experiment further, that I might fee how it 
 would terminate. The frog was therefore 
 replaced in its former iituation, where it con- 
 tinued three hours longer -, I then thought it 
 time to examine the animal, and drev/ up the 
 pack-thread, but nothing came up with it 
 except the hind legs and ribs; the reft re- 
 mained in the throat, and an" inflant after- 
 v/ards I perceived the animal tranfmit it inta 
 the ftomach. I found the legs and thighs 
 half diirolved, and being very defirous of 
 knowing what had happened to the other 
 
 parts 
 
DISSERTATION II. i 17 
 
 parts of the animal, I determined to kill the 
 heron without delay. The frog was in the 
 ftomachj the external mufcular flefh was 
 quite deftroyed, and what remained entire 
 was ealily divifible into feveral portions, ef- 
 pecially at the articulations. The fame ap- 
 pearance of decompofition had taken place, 
 as if it had been macerated in watery but 
 it did not exhibit the fmalleft fign of putre- 
 faction. 
 
 c. Although experiment thus abundantly 
 evinced a feniible concotflion in the cefopha- 
 gus, I had not adverted to one circumftance, 
 which however deferved attention^ viz. to 
 fix the precife lofs which the flefli underwent 
 in that cavity. I therefore repeated the ex- 
 periment with this view, but having no frogs 
 in my pofTeffion, I fubflituted fome fle/li with 
 which I happened to be provided, confifling 
 of cow's lungs, to the amount of half an 
 ounce, forty grains. It was drawn out of the 
 cefophagus by means of the pack-thread, af- 
 ter it had remained there thirteen hours, when 
 it had loft feven pennyweights and two grains. 
 
 As the oefophagus of the heron is mem- 
 branous, it is more than probable, that its 
 mechanical a*£tion did not concur in produ- 
 cing this effect; it however was proper to 
 prove this by dire<ft experiment, v/hich might 
 
 Vol, I. I be 
 
114 B I 5 S B R T A T I O N II; 
 
 be done by means of the tubes. With them 
 therefore I repeated the experiment which I 
 had before made, in order to determine, whe- 
 ther the oefophagus of the heron is capable 
 of digefting food. Solution of the flefh un- 
 doubtedly took place within the tubes, and 
 fo I was convinced, that it did not depend on 
 any motion of the cefophagus, but on the ef- 
 ficacy alone of the fluid which is fecreted by 
 it. 
 
 CI. Another experiment yet remained to 
 be made, whence we might deduce not only 
 the exadt diminution of the flefh, but the 
 proportion between its diminution in the 
 cefophagus and flomach ; two globular pieces, 
 two-thirds of an ounce each, of cow's lights 
 were introduced, one into the cefophagus, and 
 the other the flomach^ each remained {qycii 
 hours in its refpedive fituation, when the 
 heron was killed j the ball from the flomach 
 at firfl of the fize of a walnut, was now no 
 larger than a pea, and weighed only twenty- 
 eight grains. That which had Iain in the oefo- 
 phagus was indeed reduced in bulk, though 
 but very little in comparifon with the other ; 
 it had lofl. three pennyweights eighteen 
 grains. 
 
 ■ Both thefe infl:ances gave me an opportu- 
 nity of remarking, that the juices, whether 
 
 of 
 
DISSERTATION II,' I If; 
 
 of the cefophagus or ftomach, did not feem 
 to ad: by penetrating deeply into the fubftance 
 of the flefli, but by corroding the furface; 
 the external layer was firft dilTolved, and then 
 thofe that lay beneath in their order. And 
 in reality, when I came to wafh the ball ta- 
 ken from the cefophagus, and wipe away the 
 external gelatinous flratum already diflblved 
 by the Gefophageal fluid, the next flratum 
 fhewed the natural fibrous, firm, and red ap- 
 pearance ', and when the ball was cut into two 
 hemifpheres, the infide feemed perfe(5lly 
 found, without the fmalleft lign of having 
 been impregnated or touched by that corro- 
 five liquor. The fame obfervation is appli- 
 cable to the other ball; for notwithftand- 
 ing its great diminution, it was quite found 
 within. 
 
 I had now but two herons left, and thefe 
 I facrificed to the defire of afcertaining ftill 
 further the exceffively rapid concodtion of the 
 flomach, compared with that of the cefopha- 
 gus. And in fad:, I obferved it again on 
 two frogs and as many fifhes, of which the 
 former continued eight hours in the cefopha- 
 gus and flomach, and the latter nine hours. 
 
 Thefe experiments incontrovertibly prove, 
 
 that the cefophagus of the heron as well as 
 
 of the crow, has the privilege of digefling 
 
 I 2 aj>y 
 
liS 1!) f S S E R t A T i O tl It. 
 
 any food that may happen to be lodged in it J 
 this privilege extends like wife to other ani-^ 
 n:i|als, as we fhall fee in fome palTages of the 
 following diflertations. 
 
 cii. The obfervations related in the pre- 
 fent and the preceding dilTertation, prefent us 
 with various inflances of agreement and dif- 
 agreement in the digelf ion of birds with muf-^- 
 cular and of thofe v/ith intermediate flomachs. 
 Let us here, for the convenience of the 
 reader, collect into one point of view thefe 
 fcattered traits ; they may fix more firmly in 
 the mind all that we have obferved, whether 
 curious or interefting, in thefe two clafTes of 
 animals. With refped: to the traits of re* 
 femblance, they may all be reduced to the 
 relation between the gaftric fluids, Firft 
 then it has been proved, that thefe fluids, 
 befides being alike in colour, are always fait 
 and bitter; and that the bitter tafle derives 
 its origin from tlie bile, which regurgitates 
 through the pylorus into the cavity of the 
 ftomach. Secondly, thefe fluids are the im- 
 mediate agents of digeftion, both in mufcu- 
 iar and intermediate ftomachs, independently 
 of trituration. Thirdlyj In thefe two or- 
 ders of birds the fluids ai5t in the fame man- 
 ner in the folution of the food; they fir/t 
 "foften and next convert the furface into jelly, 
 
 then 
 
DISSERTATION II, ny 
 
 then produce the fame effed upon the interior 
 parts, and fo iolinuating themfclves gradually 
 till it is completely diflblved. Fourthly, they 
 do not entirely lofe their folvent efficacy as 
 foon as they are taken out of the flomach, 
 provided they are heated to a proper degree, 
 as artificial digeftion proves. Laflly, The 
 fources from vs^hich thefe fluids fpring, are, 
 in great meafurey the fame in both claiTes, 
 viz. the follicular glands, with which their 
 organs abound, 
 
 cm. The differences are in part reducible 
 to the inferior efficacy of the galiric fluid in 
 mufcular to that of the fame fluid in inter- 
 mediate flomachs. Thus the gallric fluid in 
 the former is incapable of diflolving the fam§ 
 aliment, which in the latter it eaiily diffolves. 
 In like manner the food, which each kind of 
 gallricjui.ce decompofes and digefcs, is fooner 
 fubjedt to this change .from that which be- 
 longs to intermediate ftomachs. And this is 
 alfo the reafon, why artificial digeftion fuc- 
 ceeds much fooner with the firil than the fe- 
 cond. The fame inefficacy that the gaflric 
 juices of birds with mufcular ftomachs fliev7 
 in decompofing certain aliments of a firm 
 texture, extends alfo to their oefophageal 
 juices in decompofing foft fubftances, not- 
 with|landing the latter are tolerably well de~ 
 J 3 compofed 
 
llS D I S S E R t A T I O N II.' 
 
 compofed by the cefophageal juice of birds 
 with intermediate ftomachs. The prodigi- 
 ous eiFed.s of trituration in mufcular fto- 
 machs, qonilitute another very ftriking diffe- 
 rence between thefe two clalTes of birds, the 
 fable force of intermediate ftomachs being 
 fcarpe comparable with the enormous poWer 
 of the other kind. Such a degree of force 
 was abfolutely necefTary in thefe, fince the 
 juices are incapable of decompofmg food of 
 conliderable firmnefs, fuch as feeds, the na-. 
 tural food of birds provided with gizzards; 
 and therefore an agent capable of breaking, 
 triturating,, and thus pre-difpoiing theni for 
 digeftion became neceftary^ and fuch are in 
 teality (he gaftric niufcles in thefe fowls. 
 
 PIS. 
 
t "9 ] 
 
 DISSERTATION III. 
 
 CONCERNING DIGESTION IN ANI- 
 MALS WITH MEMBRANOUS STO- 
 MACHS. FROGS. NEWTS. EARTH 
 AND WATER - SNAKE S. V I P E R Si 
 FISHES. SHEEP. THE OX. THE 
 HORSE. 
 
 TO examine at full length the nature of 
 digeftion is the obje<ft of thefe differ, 
 tations. By extending my enquiries to the 
 three clafles to which all animated beings 
 may be referred, I hope to be enabled to folve 
 the problem in a fatisfadory manner. Of 
 thefe claffes the firfb comprehends animals 
 with mufcular, the fecond with intermediate, 
 and the third with membranous flomachs. 
 The lafl clafs is infinitely more numerous 
 than the two former. If we fufFer our ima- 
 gination to range over the immenfe multi* 
 tudes of quadrupeds, fifh, reptiles, birds of 
 prey, not even excluding man himfelf, we 
 I A ihall 
 
120 DISSEJITATION III. 
 
 ihall find, that they are all, or nearly all, enr 
 dowed with membranous flomachs; not to 
 mention that numberlefs tribe of minute be- 
 ings, the greater part of infeds. My tafk 
 wduld have been endlefs if I had projected 
 enquiries, I will not fay concerning every 
 fpecies of animals included under thefe ge- 
 fiera, a projed: which many academies woul4 
 not be able to execute, much lefs a fingle ob- 
 ferverj but concerning great part of them. 
 J was therefore obliged to confine myfelf to 
 fefearcheg upon a fmall number. Thefe re- 
 fearches combined with others already rela- 
 ted in the two firfi- dilTertations, will be fuf- 
 ficient, if I am not very much miftaken, to 
 fet the theory of digeftion in a clear point .of 
 yie\y, both in animals and man. As the va- 
 rious fpecies, which I take into confideration, 
 pannot be all exhaufted in a fingle difi^ertation, 
 I {ball djfiribute them into feveral, beginning 
 with the animals that are fituated Jo weft in 
 the fcale of fentient beings, and ending with 
 that which occupies the higheft and nobleft 
 place, with man. 
 
 cv. L^t ug begin then with frogs and wa- 
 ter newts, two fpecies of fmall carnivorous 
 animals. As the mouth and cefophagus in 
 the former are large, it was eafy to introduce 
 til bes into their Jong ftomachs. But I wa^ 
 
 fooA 
 
DISSERTATION III. I2]| 
 
 Ibon aware, that It would be neceflaiy tq 
 make experiments upon a great number at 
 once, if I wifhed to know what changes the 
 fleih enclofed within the tubes underwent in 
 the courfe of feveral days ; for the tubes were 
 very often vomited up, and at uncertain in- 
 tervals, fometimes in a few, fometimes in fe- 
 veral hours after they had been fwallowed; 
 at others again, after a whole day, and in 
 fome inftances, after a flill longer interval. 
 As I knew, that this fpecies of animal very 
 greedily devours any fort of flefh that falls in 
 it:s way, I did not think of feleding, but took 
 what happened to come firfl to my hands, and 
 this proved to be a piece of the fmall intef- 
 |:ine of a flieep, which I divided into twelve 
 portions, and enclofed them in as many tubes. 
 Thefe tubes were diflributed among fix of 
 my largefl frogs, two being given to each. 
 They were kept in a very large vefTel of wa- 
 ter v/ith high perpendicular fides, that they 
 might not make their efcape. I neglefted 
 the tubes that wpre thrown up, and examined 
 thofe only which remained in the flomach. 
 In the fpace of a day I obferved the following 
 refults. From the intervals of the grating 
 which lay before the open extremities of the 
 tubes, there oozed out a cinerjitious matter, 
 
 which. 
 
i22 DISSERTATION III, 
 
 which, when touched, adhered to the fin^ 
 gers, and formed long filaments. When the 
 grating was removed, I perceived, that this 
 gluten was nothing but the flefh itfelf, which 
 at that part began to be decompofed and to 
 change its nature, retaining however the cha- 
 rafteriilic marks of flefh in the more internal 
 parts of the tubes. Upon opening the flo- 
 machs I did not find any gaftric fluids they 
 were quite dry. 
 
 cvi. In two tubes that were examined at 
 the expiration of two days, the flefh had un- 
 dergone a further decompofition. It now 
 not only oozed out at the mefhes of the lat- 
 tice-work, but likewife at moft of the per- 
 forations in the fides of the tubes ; and when 
 it was drawn out with the point of a pair of 
 forceps, and then freed by wafhing from the 
 vifcid mucilage, what remained of real flefh 
 or inteiline was fo very little, that I do not 
 believe it exceeded the thirtieth part of its 
 original weight. At the end of the third day 
 there remained but a fingle tube in one frog; 
 in this there was no flefh, but it had been all 
 dilTolved to gluten, had oozed out of the 
 tube, and adhered to the fides of the flo-. 
 mach, excepting a very fmall portion that 
 was flicking to the tube. This vifcid matter 
 
DISSERTATION III. 123 
 
 was inlipid to the tafte, a certain proof that 
 the gaftric fluid had efFed:ed this alteration 
 without the concurrence of any mechanical 
 a(5lion of the flomach. It muft however be 
 allowed, that this fluid is exceedingly flow 
 in producing its effects, flnce it required three 
 days. This flownefs mufl: have arifen either 
 from the fmall quantity or inefiicacy of the 
 fluid, or perhaps from both caufes. In con- 
 fequence of this tardy adlion I found in flmi- 
 lar, experiments upon fix other frogs, that 
 the flefli in fome of the tubes was not entirely 
 confumed at the end of the fifth day. 
 
 cvii, The gafl:ric liquor of frogs is not 
 however on this account incapable of con- 
 codting in time fubfl:ances which we fhould 
 have fuppofed above its power, viz. bones. 
 In a quantity of frogs brought me one day 
 by the fifhermen, there was one fo large, that 
 I was induced by its enormous flze to kill it, 
 in order to fee what it contained; I founds 
 that the enlarged bulk was owing to a moufe 
 in the cavity of the fl:omach. The hair had 
 begun to fall ofl^, and the fkin was become fo 
 very tender, that it had lofl: its cohefion. The 
 fore as well as the hind legs had undergone a 
 greater degree of folution, the bare bones 
 pnly l^eing left, and they were confiderably 
 
 wafled 
 
124 DISSERTATION III, 
 
 wafted and converted into a femi-gektinous 
 fubftance. The moufp upon being opened 
 appeared quite found internally, the deftruc- 
 tion was confined to the furface, an4 there- 
 fore occafioned by the gaftric fluid, which ha4 
 begun to ad: here on the external parts, juft 
 as it does in animals with mufcular and in- 
 termediate ftomach?. The fmallnefs of the 
 extremities permitted the fluid to penetrate 
 them with greater facility, hence it had aU 
 moil confumed them without fparing even the 
 bones. In this jnftance I could net perceive 
 any fign of trituration, for the moufe was 
 neither bruifed jior lacerated ; nor can I con- 
 ceive what Dtlier force can be exerted by fto?- 
 piachs compofed of fuch fine coats, befides 
 that of comprefling the bodies they contain, 
 when they happen to be very large, 
 
 cviii. The mouth and throat of water- 
 newts are both fo narrow, that they would 
 not admit the ufual tubes, they however ad- 
 mitted others made in the fame form, but of 
 a fmaller fize, on purpofe for them. From 
 having kept thefe animals in my houft for fe- 
 yeral years, both when I had occafion to exa- 
 mine the circulation of the blood, and to 
 obferve the admirable reproduction of their 
 lipibs, I had learned, that the food which 
 
 ^hey 
 
DISSERTATION III. I25 
 
 $hey devour with the greateil avidity is Uving 
 earth-worms (a) . Nearly the fame obferva* 
 tion is made by my illuflrious friend, Mr. 
 Bonnet, in his fine memoir concerniizg the re^ 
 produBion of the limbs in water -newts, in 
 which he confirms my difcovery of this won- 
 derful reproduvflion in the clearefi; and moft 
 decifive manner, after it had been queftioned 
 byMefirs. Adanfon and Bomare, for want of 
 addrefs and fkill in making experiments in 
 this branch of zoology [b). I had then re- 
 courfe to earth-worms ; they were cut in 
 pieces, and placed alive in the tubes, which 
 were introduced into the flomachs of feveral 
 falamanders. The gailric fluid of thefe little 
 reptiles adted more fpeedily than that of 
 frogs (cvi). The divided worms began .to 
 change colour in fifteen hours, and to become . 
 foft and flabby. About the thirtieth hour 
 the parts had loft their cohefion, and the 
 
 {a) I treat at full length of thefe aquatic lizards in ray three 
 Works intituled. 
 
 Prodrome di un' opera da imprimerfi fopra le riproduzioni 
 animali, 
 
 Del Azione del Cuore ne' vafi fanguinei, 
 
 De' Fenomeni della Circulazione obfervata nel giro univer^ 
 fale de' vafi. 
 
 {b) The memoir is inferted in Rozier's Journal for No- 
 vember, 1777. 
 
 N. B. It is likewife reprinted in the late colledion of his 
 work?. 
 
 ring 
 
i26 DISSERTATION tlU 
 
 rings were no longer vifible ; and in lefs than 
 two days they were converted into a whitifh 
 pulp, of which the greateft part had run out 
 of the tubes. 
 
 cix. The difledlion and examination of the 
 ftomachs of newts prefented me with a phae- 
 nomenon, which mufl not be concealed from 
 the reader, both on account of its Angularity, 
 and the light it throws on the prefent fubjed:. 
 This phaenomenon is nothing lefs than a great 
 number of fmall white worms in this vifcus, 
 vifible to the naked eye j of the thicknefs of a 
 thread) and the length (at leafl in the largeft) 
 of two-thirds of an inch ; however if we wifh 
 to examine them minutely, we mufl employ 
 the microfcope. They are of two forts; in 
 one both extremities terminate in a point, the 
 other has one end pointed; but the other ob- 
 tufe, and marked with a dark fpot; the latter 
 fpecies is ihorter than the former, and thin- 
 ner in the fame proportion. Each fpecies is 
 furniflied with rings, narrower at the ends of 
 the body, and wider at the middle, as is ge- 
 nerally the cafe in anular worms. Thefe two 
 forts of worms are not flat or comprelTed, but 
 round; it is therefore certain that they do not 
 belong to the genus of tania, or the gourd- 
 worm, but to that of round or columnar worms 
 (teretes). They are not loofe in the cavity of 
 
 the 
 
D I S S E R T A T I O N III. 127 
 
 the floihach, as the worms lodged in the in- 
 teftines of larger animals commonly are, but 
 are always found with one extremity inferted 
 to fome depth in the internal coat of that or- 
 gan; hence it requires fome force to detach 
 them, and frequently they break fooner than 
 feparate. Of thofe that have the dark fpot, 
 the more obtufe end is fixed in the flomach ; 
 it is impofiible to fay whether this is the cafe 
 with refped: to the others, fince both ends 
 are equally pointed. The loofe extremity 
 projedis into the cavity of the ftomach, fome- 
 times coiled up in the form of a circle, and 
 at others twifted in a fpiral. If the flomach 
 be taken out of the animal, and fet to mace^ 
 rate in water, the worms live for many hours 
 without quitting their fituation : if afterwards 
 we feparate them with the hand, without 
 breaking them, and place them upon fome 
 fubilance, in order to obferve their move- 
 ments, they will be feen to writhe in various 
 dirediions; fometimes bringing the mouth 
 towards the tail ; fometimes ftretching them- 
 felves in a right line ; and at others making 
 flrange contortions, as is ufual with reptiles 
 in general. 
 
 ex. Not being able to conjedure for what 
 purpofe the part perpetually inferted in the 
 fubilance of the vifcus, could be deHgned, 
 
 unlefs 
 
128 CISSER^ATIOJT. ifi; 
 
 unlefs it was to fuck the thinnefl and pureft 
 part of the Hquor; and confequently fuppo- 
 fins- it to be the head of the animal, or it 
 leaft fome Analogous part, I tried to difcovef 
 the mouth with the aid of the microfcope ', 
 but my endeavours were vain, I beheve, 
 however, that I found the ahmentary canal ; 
 it is a bright filver-coloured fpecies of intef- 
 tine, running along the worm, in a tortuous 
 manner, from fide to fide> it is always full 
 of a number of particles, which lludluate re- 
 gularly, like a buoyy probably impelled by a 
 fort of periflaltic and antiperiilakic motion. 
 This canal is common to each fpecies ; in that 
 with a dark fpot at one extremity (cix), a 
 fecond canal may be perceived ; it is ftrait, 
 and probably (I fhould rather fay certainly) 
 the receptacle for the eggs 5 for I have al- 
 v/ays obferved it more or lefs full of a great 
 number of corpufcles, of an oval fhape, float- 
 ing in a very tranfparent lymph ; thefe cor- 
 pufcles, when the worm is not in motion, 
 always continue at rell. If we lay hold of 
 the animal by its extremities, and break it in 
 the middle, the little canal v/ill generally be 
 broken, and the ovula will make their efcape 
 in a ilream from the lacerated part. It is not 
 difficult to buril: them between two" pieces c-f 
 talc, when a thin fluid fpri-ts from them; 
 
 after 
 
DISSERTATION III. I29 
 
 after which the eggs become dry and opake, 
 coniiftingnow of nothing but the empty cover, 
 as always happens to the membranaceous 
 eggs of fmall animals. Each worm of this 
 fpecies is furniihed with thofe oval particles 
 enclofed in their canal i if they are real eggs, 
 as there is great reafon to believe, we muil 
 conclude that every individual is an herma-^ 
 phrodite^ it will however remain doubtful 
 whether they are ftricftly fo^ i. e. have no need 
 of copulation, like fweet- water polypes, and 
 many other forts of microfcopical animals, 
 &c. or elfe, in the v/ider acceptation of the 
 term, are like tellaceous and naked fnails and 
 earth-worms; each of which brings forth 
 eggs and living young, but requires the con- 
 currence of another indiviaual. . 
 
 CXI. I might probably be alked whether 
 thefe worms lodge in healthy newts, or ra- 
 ther in fuch only as are difeafed. This doubt 
 fuggefted itfelf to me; and in order to clear 
 it up, I examined not only fuch as I kept at 
 home, and were therefore liable to the fufpi- 
 cion of unhealthinefs, but fuch alfo as were 
 newly caught, and full of health and vigour; 
 but the ftomachs both of the one and the 
 other harboured alike thefe unpleafant guefts. 
 But it muft be obferved that they do not fix 
 their abode in all newts; and that in thofe 
 
 Vol. I. K where 
 
i^6 U t S S E H T A t I O N I!f* 
 
 where they do, they are not equally nume- 
 rous. Of the immenfe number I have opened 
 at different times, and with different views, 
 three-fourths have had a family of worms 
 in their ilomachs ; which is fometimes com- 
 pofed of only five or fix individuals > at others 
 of feveral dozens, and at others again of an 
 hundred or more. 
 
 CXI I . Iri my numerous examinations of the 
 ilomachs of the different animals mentioned 
 in this worky crows alone have exhibited a 
 phaenomenon nearly refembling what is found 
 in newts ; I mean a quantity of worms lodged 
 in the lliomach* But thefe worms are not 
 inferted into the internal coat, as in newts, 
 but are found between tlie internal and the 
 nervous. We are very well acquainted with 
 the little worms that live in trees, and gener- 
 ally fix their abode between the bark and the 
 wood ; and lurking there unfeen, devour the 
 cortical part, which furnifhes them with an 
 agreeable aliment. If the bark ihould be 
 parted from the trunk on purpofe, or by ac- 
 cident, their devaflations are expofed to view, 
 in the form of excavated paths, winding 
 backwards and forwards in a ferpentine di- 
 rediionj nor is it uncommon to furprize the 
 worms adiually employed in forming thefe 
 ^excavations, which ferve them at once for 
 
 food 
 
DiSSERtAtlON in. 131 
 
 food and lodging. The fame thing nearly is 
 t)bfervable with refpe(5l to the worms of erows. 
 If the internal be parted from the nervous 
 coat flowly and carefully, thefe animals are 
 fuddenly expofed to the eye, adhering for the 
 moft part to the back of the internal coat, 
 lurking in certain cavities formed in its fub- 
 ftance, and which in all likelihood, arife from 
 the erolion of thefe very worms. Further, 
 we find fome with both ends expofedj while 
 the middle is deeply buried in the fubilance 
 of the internal coat. Laftly, others have one 
 extremity inferted into this, and the other 
 into the adjacent nervous coat 5 but they ne- 
 ver make their way into the cavity of the fto- 
 mach. Thefe worms do not appear to differ 
 from thofe in newts, in colour, length, thick- 
 nefs, or in the alimentary canal 3 they have 
 however one effential difference, they are 
 without rings, but have a fmooth and flip- 
 pery fkin. In their motions they are dull 
 and languid 3 when taken from their abode, 
 and placed in water, they live many hours. 
 They are found both in grey crows and rooks ; 
 but I have never feen them in any part of the 
 body except the flomach. 
 
 cxiii; But let us return to the worms in 
 
 newts (cix, ex, cxi), and confider them 
 
 in as far as they relate to digeflion. I affert 
 
 K 2, , that 
 
t^l DISSERTATION III. 
 
 that their prefence is an incontrovertible 
 proof, that no fenfible degree offeree is ex- 
 erted by the ftomach -, for how is it poffible 
 to conceive that the fides of the ftomach can 
 rirfb igainft each other, or at kaft impinge 
 againn; -the food, v^ithout doing the fmallefl 
 injury to worms of fo delicate ftru(fture? I 
 have more than once taken the ftomach of a 
 newt between my thumb and finger, and 
 comprelfed it very gently, or rubbed it hghtly, 
 and upon opening it, have always found fome 
 rupture, fome difcontinuation of the parts of 
 thefe worms. We muft therefore conclude, 
 that digeftion in water-newts is folely the ef- 
 fect of the gaftric fluid, of which the efficacy 
 has been already fhewn in the decompofition 
 of earth-worms inclofed in tubes (cviii). I 
 have alfo feen its adlion, in a manner equally 
 ftriking, on worms which newts have taken 
 and fwallowed of their own accord. How 
 tenacious thefe minute reptiles are of life, is 
 abundantly proved by cutting them into fe- 
 veral pieces, in confequence of which they 
 do not die; but on the contrary multiply, as 
 many worms being produced as parts into 
 which they were divided {a). It is true, 
 they do not ceafe to live after having remained 
 
 (e) See Reaumur, Bonnet, and my Profpedus. 
 
 ten 
 
DISSER TATION III. I^^ 
 
 ten or twelve hours in the flcmach of a newt; 
 nay, when they fill it too full, they void fome 
 alive and crawling by the mouth, whether by 
 adlual vomiting, or whether the worms, after 
 various movements in {o difagreeable a place 
 of confinement, at lafl find their w^ay out 
 through the oefophagus. But they certainly 
 die at lafl:, not becaufe they are triturated or 
 crufiied to pieces, for they continue whole 
 for feveral hours ; the gaftric fluid firft foftens 
 and then converts them into a gelatinous fub- 
 ftance, and by a continuance of its action, at 
 length reduces them to an impalpable mafs. 
 
 cxiv. Biit how come the tender worms 
 in the ftomach to efcape folution, when all 
 other infecfts, v/hether aquatic or terreflrial, 
 upon which the newt feeds, die and are di- 
 gefted ? If it fhould be faid, that this hap- 
 pens becaufe they have been habituated to 
 the ftomach by long refidence, the difiiculty 
 would be perhaps removed to a greater dif- 
 tance, but certainly not taken away altoge- 
 ther. As the caufe of this phenomenon, we 
 mufl afiign the inability of the gaftric fluid to 
 decompofe thefe minute beings, however 
 powerful may be its energy upon others of a 
 ilru(5lure lefs delicate 5 juft as a chemical 
 menftruum is capable of diifolving one metal, 
 but not another. Thus aqua regia diffolves 
 K 3 gold, 
 
134 DISSERTATION III. 
 
 gold, but not lilver -, or an acid that com^ 
 bines with the calcareous, has no attrad:ioii 
 for the argillaceous and fiUcepus earths. 
 Nearly the fame difference of digeftion is alfo 
 obferved in that of polypes provided with 
 arms; they fometimes fv/allow their owri 
 arms along with infects; but though the 
 former die and are digefied, the fecond dp 
 not in the leaft fuffer, Thus a polype in- 
 ferted into the flomach of another polype^ 
 (Continues to live as before {a). 
 
 cxv. But let us proceed to ferpents, of 
 which I propofed to treat after frogs an4 
 newts. Thofe which are mofl eafily procu- 
 red in the environs of Pavia are certain ter- 
 reftrial fnakes, called in fome provinces of 
 Italy, Smiroldi {b) ; and water-fnakes, which 
 many naturaliils call fwimming (natrices) [c). 
 The iirfl confiderably exceed the natrices and 
 vipers in lize. The largeil are about an inch 
 and a half in thicknefs towards the middle of 
 the body, and forty-five and fometimes fifty 
 inches long. The lower, part of the body is 
 white mixed with yellow and green ftreaksj 
 
 {a) Trembleyj Mem. fur les polypes. 
 
 {b) Not defcribed by Linnaeus or any other naturallft, as 
 far as I know. 
 
 (c) iVflm^, Linn, Syll. Nat. T. i. Natrix torquata. Ray. 
 
DISSERTATION HI. 135 
 
 rhe upper part is blackifh, but towards the 
 neck and head interfperfed with a milky white. 
 They fly with greater fpeed than the water- 
 fnakes, and far greater than vipers. They 
 are not inferior to the latter in a fpirit of re- 
 venge, and their bite alfo draws blood, as I 
 have myfelf experienced, but is harmlefs. 
 Before I made ufe of the tubes, I wiflied to 
 acquire fome knowledge of the cefophagus 
 and ftomach. Having therefore Ikinned one, 
 and blown up the oefophagus in fuch a man- 
 ner that the air could neither pafs out above 
 nor at the pylorus, it appeared to me to re.- 
 .femble a large inteftine, cylindrical, for about 
 the length of nine inches, and becoming gra- 
 dually narrower below, fo as to form a fun- 
 Bel of the length of four inches and an half. 
 I foon perceived, that this funnel was the true 
 ftomach, and the inteftine the cefophagus. 
 Both the trachea and lungs run along the oefo- 
 phagus, to which they are firmly attached by 
 means of a membrane, as alfo is the hearty 
 which has the fhape of an elongated pyramid, 
 fituated at the origin of the lungs. We find 
 likewife a vifcus ai'ifing from the bafis of the 
 heart, afcending upwards along th^ oefopha- 
 gus, and adhering in great meafure to t^e 
 trachea : it is of the fame length as the lungs, 
 j)]it its fubftance is different, being tender 
 K j. aiid 
 
136 DISSERTATION III. 
 
 and afh-coloured ; I could not then determine 
 what it was. Next below the lungs lies the 
 liver, which, together with the vena port a- 
 rum, refembles a long narrow leaf attached 
 to a very long footflalk , both adhere to the 
 cefophagus. Below the ftomach v/e find the 
 fpleen, nine lines in length and of a very 
 acute oval {hape. The gall-bladder lies in the 
 region of the fmall inteftines, confequently 
 at a great diflance from the liver; when we 
 prefs it the dud: is filled with bile, which 
 it evidently difcharges into the duodenum at 
 about the difiiance of an inch from the pylo- 
 rus. Near the gall-bladder we find another 
 body fmaller than it, attached to the duode- 
 num, and of a fie£hy conlillence. I Hiould 
 fuppofe it to be the pancreas. 
 
 cxvi. If we feparate the cefophagus and 
 ftomach from the lungs and other parts juft 
 defcribed, and open it longitudinally, the 
 cefophagus appears fimply membranous ; the 
 membrane of which it confifls is very thin 
 and of a filver colour. The ftomach is com- 
 pofed of thicker fides, and among the coats 
 which compofe it we have one of flelh, which 
 like the fiefhy coats of other membranous 
 ftom.achs, is very thin. I could not perceive, 
 that the cefophagus is provided with any 
 glands or follicles 3 but I obferved, that the 
 
 ftomach 
 
DISSERTATION III. 137 
 
 llomach was abundantly fupplied v/ith them 
 throughout its whole length ; they difcharge 
 part of their liquor on being preffed, and the 
 internal coat is moiftened with it, 
 
 cxvii. I come now to experiments rela- 
 tive to digellion. I found great facility, not 
 only in pafiing the tubes into the ftomach, 
 but likewife in bringing them up whenever 
 I pleafed. I made an ailiftant lay fafb hold 
 of the fnake fo as to prevent its ftriking or 
 wreathing round the body, while I opened 
 the mouth and forced a tube in lengthv/ife, 
 and then, by means oi a thin rod, thruft it 
 two or three inches dovv^n the throat, i^fter 
 this the reft followed of courfe; for I had 
 only to prefs with my fore-finger and thumb 
 the neck of the animal in the place oppolite 
 to the top of the tube, which was forced to 
 defcend for fome way down the cefophagus, 
 and by a repetition of the fame manceuvre I 
 foon brought the tube to the bottom of the 
 ilomach, which I knew by the refiilance it 
 made when I attempted to pulli it lower; for 
 nov/ the narrow pafTage of the pylorus pre- 
 vented its defcent. By a like preiTure, but 
 made in the oppoiite direction, from below 
 upwards, I could bring up the tube from the 
 ftomach into the cefophagus, and thence out 
 through the mouth. I employed this con- 
 trivance 
 
1^8 DISSERTATION IIF. 
 
 trivance for introducing the tubes into the 
 flomach, and bringing them out at the mouth 
 in water-fnakes likewife, and even vipers, 
 managing the laft however with fome care, 
 which is very requifite, in order to avoid be-, 
 ing bit by thefe ferpents during the operation, 
 when they are highly exafperated, 
 
 cxviii. When I was opening fome of my 
 land-fnakes (fmiroldi) to examine the ahmen- 
 tary canal, I found in the ftomach of one a 
 wall-lizard not in the leafl injured or digefted, 
 I thought of employing it for my experi- 
 ments, as it muft be a kind of food well 
 adapted to thefe reptiles. I therefore enclofed 
 a piece of the tail of this lizard in a tube, 
 which continued for a whole day in the flo- 
 mach without having its contents at all dif- 
 folved. Thirty-iix hours produced fomething 
 more. The tail of the lizard is compofed of 
 a number of little mufcles, enchafed one 
 within the other, and bound round by a thin 
 anular membrane. The piece of tail was 
 placed in the tube in fuch a manner, that the 
 inverting membrane was in contad: with the 
 fides, and the mufcles were bare at the open 
 ends. The membrane had fuflained no in- 
 jury, but the mufcles were eroded on the 
 plane of fediion, and a little excavated. Up- 
 on touching them I found, that they had 
 
 beeii 
 
DISSERTATION III. I39 
 
 been converted into a gluten of ibme vifcidity. 
 The gaftric fluid then (for the mechanical 
 adlion of |:he fcomach could produce no eifed: 
 within the tubes, were any luch adion to be 
 exerted at all) had begun to digeft the fleih, 
 by diflblving what lay at the ends of the tube 
 before it attacked that which was contiguous 
 to the fides ; not only becaufe it v/as not co- 
 vered by the membrane, but alfo becaufe it 
 had freer accefs at the ends : the folution 
 however went on, though very flowly; for 
 after the tube had been five days in the ilo- 
 mach, a little of the mufcular fiefh remained, 
 and the membrane was almoft entire. 
 
 cxix. The fiefh of a lizard's tail is rather 
 tough, and it was probable, that this cir- 
 pumflance had retarded the progrefs of di- 
 geftion; it was therefore proper to employ 
 fome of a lefs firm texture ; accordingly part 
 of the liver of the fame animal was enclofed 
 in the tube, and given to a fnake (Jmiroldo). 
 In this inftance digefl:ion was more fpeedy; 
 for in three days and an half the tube was 
 quite empty. 
 
 But what if inftead of enclofmg the flefh 
 in tubes, we fhould introduce it into the fho- 
 ^nach without any covering ? It v/as obvious 
 to fuppofe, that it would be fooner digefled, 
 fince the gaflric juice would have freer fcope 
 
 for 
 
140 DISSERTATION III. 
 
 for its adlion. And fo in reality it happened, 
 A piece of lizard's tail of the fame fize as in 
 a preceding experiment (cxviii), did not re- 
 quire quite two days for its digeftion ; and a 
 portion of liver, equal to that before-men- 
 tioned (cxviii), underwent the fame pro- 
 cefs in two and thirty hours. Of this I af- 
 fured myfelf by opening the flomachs of the 
 two fnakes, one of which had taken part of 
 the liver, and the other of the tail. 
 
 cxx. We come now to the water-fnakes 
 or the natrices. Nothing can be more ilriking 
 than the refemblance between the ftomach 
 and the cefophagus in this, and the foregoing 
 fpecies. Befides the trachea, lungs, heart, 
 liver, vena portarum, having nearly the fame 
 configuration, and lying on the fame parts 
 of the cefophagus; this cavity is very capa- 
 cious and long, conlifls in like manner of thin 
 membranous coats, and ends in a funnel, 
 which is the true ftomach of the animal. The 
 o-all-bladder too is about an inch diftant from 
 the lungs, and depofits its contents in the 
 duodenum, by means of the cyflic dud:, Thq 
 ftomach - alfo, as we have obferved in the 
 land-fnake (Jmiroldo), is furnifhed with a 
 great number of follicular glands. 
 
 cxxi. It is eafy to learn the nature of the 
 food of \yater-fnakeS;^ and we ought in con- 
 
 fequence 
 
DISSERTATION Itl." I41 
 
 fequence to provide it for our experiments. 
 Among the antients Oliger Jacobeus, where 
 he treats of frogs, and among the moderns 
 VaUfneri will fatisfy us, that thefe reptiles 
 live chiefly upon frogs. Next to man water- 
 fnakes may be denominated their greatefl 
 fcourge. They particularly frequent the wa- 
 ter of ditches, puddles, ponds, lakes, fuch 
 in fhort as is frequented by frogs 3 and here 
 they make an eafy prey of them, notwith- 
 ftanding they mutually give each other no- 
 • tice when they perceive the fnake at a dif- 
 tance, by a kind of whiftle or outcy of dif- 
 trefs, as I have often obferved, at which all 
 fly with the utmoil precipitation : Dante was 
 not acquainted with this circumflance. 
 
 Come le rane innanzi I'lnimica 
 Bifcia per I'acqua fi dileguan tutte, 
 'Finche alia terra ciafcuna s'abbica {a), 
 
 A fifherman having brought me three very 
 large and vigorous water-fnakes, I gave each 
 at the fame time a tube encloiing a different 
 part of a frog ; one mufcle, the other liver, 
 and the third fpleen. The tubes were left 
 three days and an half in the flomach. Upon 
 forcing them out, 1 obferved the fame kind 
 
 {a) Infern. Cant. 9. Fo!. 161, &c. As frogs fcour along 
 the water, at the approach of the water-fnake, without flop- 
 ping, till they have gained the dry ground. 
 
 ♦ of 
 
142 DissfeRTAtioJt/ iit; 
 
 I 
 
 of digeftion that I had before feen in frog^ 
 
 (cv, cvi). The flefh v/as beginning to be 
 
 changed into an adheiive cineritious gluten } 
 
 the interior parts were unaltered. The tubes 
 
 were now introduced a fecond time into the 
 
 ilomachs, and when they ha.d continued there 
 
 two days they were found empty ; fome of the 
 
 adhefive matter ftuck to the outfides of two . 
 
 of them. 
 
 cxxii. It is not unknown to naturaliflsj 
 
 that this fpecies of fnake has no teeth, and is 
 
 confequently obliged to fw'allow its prey. 
 
 whole. In fummer I have often taken them 
 
 with whole frogs in the ftomach. It was 
 
 therefore not unreafonable to fiippofe, that 
 
 /■they are capable of digeiling the bones ; and 
 
 the lefs fo, as it feems difficult for them to 
 
 be voided backwards. On account of the nar- 
 
 rov/nefs of the intefcines. It might indeed 
 
 be fafpedled, that thefe bones are vomited^ 
 
 as I have found to be the cafe with the tubes^ 
 
 both in this and the former fpecies ; but this 
 
 is not a conftant and regular evacuation, as 
 
 in crows (lix) and birds of prey, as we fhall 
 
 fee hereafter; but takes olace at uncertain in- 
 
 tervals, and fometimes does not happen at all 
 
 for feveral days. In or<ier however to afcer- 
 
 tain the fa6t, I broke two tibia? weighing nine 
 
 grains each to pieces, enclofed them in the 
 
 jtubes^ 
 
DISSERTATION III. I43 
 
 tubes, and forced them into the ftomachs of 
 two«water-fnakes. After they had contmued 
 there two days, they were become foft, and 
 had loft three grains. In five days more they 
 were ftill fofter, and now weighed together 
 only five grains. Soon afterwards the two 
 fnakes died, and it was not in my power, 
 though I wifhed it very much, to profecute 
 this curious experiment as far as it would go. 
 From the beginning however of the progrefs 
 we may fuppofe, that the bonesr would have 
 been totally diffolved, and confequently it is 
 highly probable, that water-fnakes digeft 
 the bones of thofe animals upon which they 
 feed. 
 
 c XXIII. By the adivity of the gaftric fluid 
 of the water-fnake in digefting not only fiefli 
 but bonej I was induced to try to procure a 
 quantity that I might examine it more parti- 
 cularly. For this purpofe I employed fpunges 
 as before (lxxxi, lxxxii), and my fuccefs 
 exceeded my expectations. Six little fpunges, 
 that had lain tv/o hours in the ftomachs of 
 three fnakes, enclofed in tubes, afforded me 
 enough to fill a watch- 2"lafs of a moderate 
 fize. It had the following qualities ; the co- 
 lour approached that of foot, it had the 
 •fluidity of water, and evaporated very llowly : 
 it has both a fait and bitter tafte, and is not 
 
 inllam- 
 
144 DISSERTATION Itl, 
 
 inflammable. Hence it appears to bear ^ 
 very ftrong refemblance to the gaftric fluid of 
 the other animals, upon which my experi- 
 ments- were made : this refemblance extends 
 likewife to the odour, which is exactly like 
 that of the fame juices in birds of prey, of 
 which I fhail fpeak particularly in the next 
 Differtation. I refer ve the account of fome 
 chemical experiments made upon this fluid, 
 till I ihall have an ppportunity of fpeaking of 
 the examination of the other gaftric juices 
 which I have already mentioned, or fhall 
 have occafion to mention in the prefent 
 work. 
 
 cxxiv. We have before {ten the flrong 
 analogy between the configuration of the fto- 
 mach and cefophagus in land and v/ater- 
 fnakes. In vipers thefe cavities have the fame, 
 general form ; nor do they differ with refped: 
 to the efficient caufe of digeftion. I repeated 
 upon them moil of the experiments defcribed 
 above: feveral tubes, furniflied with diffe- 
 rent forts of fielh, were left in their ffo- 
 machs for a fpace more or lefs long, and the 
 effed: was jufh the fame as in water and land- 
 Ihakesj it would therefore be fuperfluous to 
 defcribe them particularly. It vv'ill be better 
 to turn the reader's attention to fome experi- 
 ments on thefe three fpecies of reptiles dif- 
 ferently 
 
DISSERTATION III. 14J 
 
 ferehtly modified, but relative to the fame 
 fubjed:. 
 
 cxxv. Having frequently opened thefe 
 animals v^hen newly taken, I have fometimes 
 obferved, that their fbomachs are not large 
 enough to contain the whole prey, and that 
 part lies in the oefophagus. This part never 
 ihewed any mark of concoction, notwith^ 
 ftanding what lay in the cavity of the fto-^ 
 mach was fometimes half digefted. Thus^ 
 for inftance, I have found five or fix large 
 beetles in the body of a land-fnake or viper; 
 thofe that lay in the ftomach were fcarce dif- 
 tinguifhable, while, on the contrary, thofe 
 in the oefophagus were entire, or nearly fo. 
 I once faw a frog with the lower limbs, 
 which projected out of the fi:omach, not at 
 all damaged, while the reil of the body lay 
 'in the ftomach and was half reduced to a 
 pulp. Thefe experiments made by the fer-^ 
 pents themfelves gave me reafon to fuppofe, 
 that what takes place in them is exactly con- 
 trary to what happens in crows and herons, 
 for the reader will remember, that in thefe 
 birds the oefophagus is really capable of di- 
 gefiion (lxxvii, lxxviii, lxxix, xcix, g)^ 
 but in the animals in quefi:ion it feems to be- 
 long exclufively to the ftomach* A very 
 fimple experiment was fufficient to afcertain 
 
 Vol, L L the 
 
146 DISSERTATION HI, 
 
 the point. Into the ftomach of one of thefe 
 ferpents a frog, for inflance, might be fo in- 
 troduced that part fhould He in the cefopha- 
 gus. The frog might be faflened to a cyHn- 
 der of wood, and thus firmly fixed in the 
 fame place. The cylinder fhould touch the 
 bottom of the ftomach with its lower extre- 
 mity, and reach fome way above that organ, 
 I applied this apparatus to a water-fnake, 
 and at the end of the fixth day opened it lon- 
 gitudinally. Upon examination my fufpicion 
 that the oefophagus was without efficacy, was 
 changed into firm perfuafion. The lower 
 limbs, the part of the animal that had lain 
 in the ftomach, had nothing left but the bare 
 bones, whereas the whole body which had 
 extended into the oefophagus had fufFered no 
 injury. , 
 
 cxxvr. The experiments related in the 
 exviith and following paragraphs were made 
 in April, when the animals had lately quitted 
 their fubterraneous lurking places, and ftill 
 retained fomewhat of that torpor which be- 
 numbs them during winter. At this time 
 digellion, as we have feen, is a very flow pro- 
 cefs. Are we to prefume, that when they 
 become more lively, atStive, and vigourous, 
 as the heat of the feafon increafes, they like- 
 wife perform digellion more fpeedily? for the 
 
 efFea 
 
DISSERTATION III^ I47 
 
 efFed of heat in promoting the operation of 
 the gaftric fluid appears from other fads 
 (lxxxvii). This idea was fuggefted by re- 
 perufing the fine memoirs of the illuftrious 
 Trembley on polypes, from which the influ- . 
 ence of the temperature of the atmofphere 
 upon the digeftion of thefe w^onderful ani- 
 mals is evident J infomuch, that the very 
 food which in a hot feafon is completely di- 
 gefted in twelve hours, when it is cold re- 
 quires fometimes two or three days. In or- 
 der to determine whether the fame thing 
 takes place in my reptiles, I chofe July for a 
 term of comparifon, when the difference, if 
 anyexifted, mufl needs be more fhriking, as 
 the thermometer in the ftiade flood at 22° and 
 23** {a) 'y whereas in~April, when the firft ex- 
 periments were made, it did not rife above 
 the twelfth or fourteenth deg. [hi). And now 
 upon repeating the experiments already de- 
 fcribed, I found that heat has fome power 
 in accelerating digeftion, but not fo much as 
 I had fuppofed. Flefh inclofed in tubes did 
 not require above two days to be completely 
 digefled J and when an equal quantity was in- 
 
 [a) Eighty-one and an half, and eighty-three and three- 
 fourths, F. 
 
 (o) Fifty-nine, and fixty -three and an half, F. 
 
 L 2 troduced 
 
148 DISSERTATION IIlT 
 
 troduced into the flomach by itfelf, about 
 half that time was fufficient. 
 
 cxxvii. Naturahfts were already apprized 
 of the tardinefs of digeftion in ferpents. In 
 Bomare we read an account of a ferpent at 
 Martinico, which retained a chicken in its 
 ftomach for three months, and did not com- 
 pletely digeft it, for it fliil preferved fome 
 traces of its fliape, and the feathers ftill ad-^ 
 hered to the fkin [a) . It is a circumflance 
 deferving of particular notice, and which I 
 ihall have occaiion to apply in another place, 
 that flejfh does not become foetid from re- 
 maining long in the ftomachs of thefe cold 
 animals, as I have obferved in the courfe of 
 my experiments, and efpecially in a viper, 
 which having been kept above two months 
 in my houfe, could not. but be unhealthy^ 
 this individual retained in its flomach for fix- 
 teen days a lizard, which had been previoufly 
 macerated in the gaflric fluid ; nor could I ' 
 perceive that it had any odour, except that of 
 this juice. And yet fuch v/as the heat of the 
 feafon, that another lizard, about the fame 
 fize, which I had placed out of curioflty in 
 a clofe velTel, containing a little water, emit- 
 ted an infupportable -flench before the expi- 
 ration of the third day. 
 
 («) Did. d'Hift. Nat. 
 
 CXXVIII. 
 
DISSERTATION HI." I49 
 
 cxxviii. But what can be the caufe of 
 this llownefs of digeftion in ferpents ? As 
 they are cold animals, that is to fay, as their 
 blood very little exceeds the temperature of 
 the air, it may feem probable that this phae- 
 nomenon might be owing to the want of th^t 
 heat, which is peculiar to animals of warm 
 blood. And I ihould not have been unwil- 
 ling to admit this caufe, if other animals, with 
 blood equally cold, had not enjoyed the pri- 
 vilege of digefting their food in a much fliort- 
 er period, as we fhall foon fee (cxxxlv). We 
 cannot affign a deficiency of gafliric fluid as 
 the reafon, for their ftomachs abound with 
 it (cxxiii). I cannot attribute it to any 
 thing but the inefficacy of the fluid itfelf; 
 and this is by no means Angular, for we have 
 already difcovered a circumflance nearly fimi- 
 lar in animals with mufcular fliomachs, in 
 which the gafliric juices do not fo foon digefl; 
 the food, as in animals with intermediate fl:o- 
 machs (cm). 
 
 cxxix. Of flflies I fhall firfl: treat of that 
 fpecies which bears fo fl:rong a refemblance 
 to ferpents, and is even confidered in the 
 chain of animated beings, as the intermediate 
 link between fiflies and ferpents, I mean the 
 eel. The fl:omach in this animal varies from 
 the flrudure generally obferved by nature j it 
 L3 is 
 
150 DISSERTATION III. 
 
 is not a canal immediately continued with 
 the duodenum, but a kind of blind gut, of 
 confiderable length, ending in a point -, after 
 the food has been received into this gut, and 
 been digefted, it muft afcend, and return to 
 the upper part of the ftomach, in order to 
 pafs into the duodenum, which forms an 
 acute angle with that upper part. The na- 
 tural figure of both may be feen in Blafius's 
 Anatomy of Animals (a). 
 
 Into the ftomachs of four eels I introduced 
 feveral tubes, containing pieces of fifh, the 
 food moll agreeable to eels. In order to pre- 
 ferve them alive, I turned them into a fmall 
 ftew, whence I coul : take them at pleafure. 
 They were killed at the end of three days and 
 eighteen hours ; and the tubes were found at 
 the bottom of the ftomach, entirely covered 
 with a dark -coloured mucus, which, on at- 
 tentive examination, appeared to be the re- 
 mains of the fifh, that by this time was di- 
 gefted. Upon wiping the tubes, and examin- 
 ing the infide, five out of eight were empty, 
 and the three others contained a bit of flelh 
 of the fize of a vetch, but it had lofi: its 
 cohefion. 
 
 cxxx. This experiment abundantly proves, 
 that in this fiih digeilion is produced by the 
 
 {a) Plate LI I. Fig. i. 
 
 gaflric 
 
DISSERTATION III. I51 
 
 gaftric fluid j I therefore proceeded to expe- 
 riments upon fuch as are more juftly entitled 
 to the appellation oi Jij%es, I chofe for this 
 purpofe carp, barbels, and pikes, as they were 
 the mofl eafy to be procured. It has been 
 long well known that the alimentary canal in 
 many fcaly fifhes, is provided with one or 
 more blind appendixes, which, becaufe they 
 lie in the vicinity of the pylorus, have been 
 named pyhriciy they are always full of a 
 white, mucilaginous, and faltifh fluid, which 
 is difcharged into the canal, and derives its 
 origin from a number of glands lying in the 
 appendixes. In fome fpecies they are fev/, 
 in others m conflderable numbers, and in 
 others again exceedingly numerous; they 
 amount in the fturgeon to an hundred; in 
 thofe fpecies, in which they are moft nume- 
 rous, the feveral fafciculi meet in a common 
 dud: ; hence, notwithilanding their numbers, 
 they difcharge their contents into the pylo- 
 rus [a) by a few mouths. In the three fpe-» 
 cies I have juft mentioned, this fmgular ap- 
 paratus is not to be found; but the infide of 
 the ftomach and inteftines is furniflied with 
 yellow bodies, that probably contribute in 
 fome way or other to digeftion, though! have 
 
 {a) Haller, El. Phyf. T. 6. 
 
 L4 sot 
 
152 DISSERTATION. III^ 
 
 not been able to afcertain their precife ufe. 
 At firft fight they look like anular worms, 
 adhering, as in newts, to the internal fur- 
 face of the ftomach (cix) ; but if we lay hold 
 of them with the forceps, the anular form 
 vaniihes, and we find that they are real ap- 
 pendiculi to the ftomach and inteilines. 
 When ftretched out, they are three lines 
 long -y each adheres to the villous coat by a 
 footflalk. If Ave ftretch them till they break, 
 a confiderable quantity of yellow liquor if- 
 fues out, and the body becomes more fliri- 
 velledj and if it be nov/ removed from the 
 place of its infertion, we find under it a little 
 tumour, through which a globule is {eeh in- 
 diilindly; and if the tumour be cautiouily 
 raifed, appears diilindly : it is of a yeilowill:^ 
 white colour, from the liquor which it con-, 
 tains. Arethefe globules clufcers of glands, 
 and the vermiform bodies elongated du6ts for 
 conveying the liquor into the cavity of the 
 ftomach ? I would very willingly have adop-. 
 ted this notion, if I had not found that thefe 
 fubftances, when compreffed from the lower 
 end upwards, never difcharge their contents, 
 either from the fummit, or any other part, 
 contrary to wh3.t happens when we fqueeze 
 the follicular glands in birds with mufcular, 
 intermediate, or membranous ftomachs. On 
 
 this 
 
DISSERTATION III. I53 
 
 this account I fufpend my opinion on the fub- 
 ject; although I fhould incHne to fuppofe 
 that they are of fome ufe in digeftion. 
 
 cxxxi. Immediately under the teeth, the 
 very beginning of the osfophagus in the carp 
 is moiflened with a conliderable quantity of a 
 whitifli turbid liquor, of a vifcid confiftence, 
 and infipid tafle, v/hich when wiped oif is 
 inftantly reproduced : and we here find a num- 
 ber of white papillae, broad at their balis, and 
 terminating in a point, which, when prelled, 
 emit the fame kind of fluid. If we make a 
 gentle preffure any where near thefe papillae, 
 a fluid iffues out, but, as I iliould fuppofe, of 
 a different nature, lince it is tranfparent, thin- 
 ner than the former, and not at all vifcid. 
 With the cefophagus, which is very fhort, 
 and of confiderable thicknefs, is continued 
 the flomach, of a mem.branous fl:rud:ure, and 
 very thin. It is eafy to diftinguifh two coats 
 in this organ, the internal and the nervous; 
 in the latter are buried thofe globules, which 
 left m.e in doubt whether I ought to conlider 
 them as clufters of glands (cxxx). In this 
 fhort defcription, we fee fources capable of 
 fupplying the flomach with a large quantity 
 of fluid, notwithftanding it wants the /^/i?r/- 
 cal appendixes, 
 
 CXXXI I, 
 
154 DtSSERtATION III, 
 
 c XXXI I. The conformation of the flomach 
 in the barbel, does not correfpond either with 
 that of the carp, or various other fifhes. The 
 oefophagus, flomach, and inteilines confti^ 
 tute a lingle gut, yearly as in earth-worms, 
 and a variety of infefts ; this gut is only a 
 little dilated at the flomach, and contracted 
 at the commencement of the inteilines. I 
 could not difcover within this canal any vef- 
 tige of glands or analogous. bodies. How- 
 ever, both the oefophagus and ftomach are 
 continually moiftened with a fluid in great 
 abundance ; which when we prefs or dilate 
 either of thefe cavities, is feen to tranfude 
 from the internal furfacCj andfince, accord- 
 ing to every appearance, it does not arife from 
 glands, we mufl fuppofe that it comes from 
 the open extremities of fmall arteries which 
 terminate here. 
 
 cxxxiii. The ftomach of the pike has the 
 fhape of a bag or fack, of much greater length 
 than breadth ; it is full of longitudinal rugjE, 
 of a light fieih colour, and compofed of coats 
 fo thin, as to be femi-tranfparent. The rugte 
 extend upwards into the oefophagus, which 
 is eafily diftinguifhed from the ftomach by its 
 white colour, and greater thicknefs. There 
 is no appearance of glands either in the one 
 
 or 
 
DISSERTATION III. l^t 
 
 or the other, though both, and efpecially the 
 ftomach, abound with Hquor. 
 
 cxxxiv. As fiihes are fubjedt to vomiting, 
 the tubes which I had introduced into the flo- 
 machs of my carps, barbels, and pikes, were 
 frequently returned; and I was often cha- 
 grined at finding them, after a few hours con- 
 tinuance in the body, at the bottom of the 
 vefTel ufed for keeping them alive. Hov/- 
 ever, from frequently repeating my experi- 
 ments, though fo many tubes were ejeded 
 prematurely, a few remained feveral hours 
 in the flomach ; and thefe were fufiicient to 
 fatisfy my wiflies. In the prefent cafe, the 
 fame thing happened which I had fo often 
 obferved in other animals -, the ilefh was di- 
 gellied within the tubes, and that in a much 
 fhorter fpace than in ferpents (cxxvi, cxxvii). 
 This obfervation was verified on the barbels, 
 carp, and pike; the two latter fpecies exhi- 
 bited a phasnomenon, too clofely connected 
 with the prefent fubjed: to be omitted. Hap- 
 pening one day to open a pike, I found with- 
 in it a little fifh, about three inches in length, 
 lying longitudinally along the ftomach, fo 
 that the whole head occupied the oefophagus. 
 I had here a clear view of the origin and pro- 
 grefs of digeftion. The jaws of the fmall 
 iifh retained their natural colour, and appeared 
 
 unal- 
 
156 DISSERTATION III," 
 
 unaltered. The eye was beginning to quit 
 the orbit, and the gills had loft their purple 
 hue, and were become very foft. In the fto- 
 mach the marks of digeftion were more evi- 
 dent. The fleih of the body was more and 
 more tender as I proceeded downwards ; and 
 towards the bottom it had degenerated into a 
 foft and fhapelefs -mafs. The extremity of 
 the tail, which had lain at the bottom of the 
 ftomach, was entirely confumed, and with 
 it the vertebras of the fpine, and the adjacent 
 bones. 
 
 cxxxv. I met with another iimilar circum- 
 ftance in a little carp. It had fwallowed a 
 fmall lamprey, which was ftretched out at 
 full length, and occupied the whole ftomach, 
 and at leaft two thirds of the oefophagus. 
 The part that lay at the bottom of the fto- 
 mach was changed into a kind of mucilage, 
 in which there was no appearance of any thing 
 organized, except fome of the dorfal verte- 
 brae. The parts that lay higher ftill cohe- 
 red, but they came away from the animal on 
 being touched. The others, which occu-' 
 pied the cefophagus, ftiewed like wife marks 
 of an incipient concoction. 
 
 Nothing can be more inftru6tive than thefe 
 two fad:s combined. They iliew, in the iirft 
 place^ that the bottom of the ftomach digefts 
 
 more 
 
DISSERTATION III, 
 
 "^Sl 
 
 more ''quickly than the parts fituated above, 
 as we have feen in other animals (xc): fe- 
 condly, that the cefophagus, as well as the 
 ilomach, is in fome meafure capable of con- 
 coction, a circumflance that has been already 
 noticed with refped: to crows and herons 
 (lxxvii, xcix, c, ci) ; and which phyfiolo- 
 gifts have obferved before me in other fi flies. 
 Laftly, that digeftion in the cefophagus is 
 flower at its beginning, and in its progrefs ; 
 two things that have been remarked in the 
 birds juft mentioned. 
 
 With refped; to the triturating power of 
 the ftomach in thefe three fpecies of fiihes, 
 not to mention that digeftion has been ob- 
 tained in the tubes without its concurrence, 
 I am of opinion that it has no exiflence ; this 
 I infer, from no effed: being produced by it 
 upon the tubes, upon which I have never 
 perceived the fmalleil bruife, contuiion, or 
 injury, in my experiments on fiilies, any more 
 than on frogs, newts, and ferpents, though 
 they were fo thin, that the flightefl force 
 would have been more than fufficient to dif- 
 tort or bruife them. 
 
 cxxxvi. From cold animals let us proceed 
 to fome experiments on the ilomaclis of warm 
 animals, fuch as fheep, oxen and horfes. 
 
 Reau- 
 
158 DISSERTATION III, 
 
 Reaumur, in his fecond and laft Memoir {a) 
 concerning digeftion, after relating at length 
 his obfervations on a kite, flightly touches on 
 fome experiments upon dogs and fheep. I 
 will here quote the refults of his experiments 
 on the latter fpecies, referving thofe on the 
 two others for another place* Delirous of 
 feeing whether digeftion in^lheep is the effedt 
 of the gaftric fluid, he forced down the throat 
 of one of thefe animals four tin tubes, two 
 of which were full of frefh blades of grafs, 
 and the two others of chopped hay. Four- 
 teen hours afterwards the fheep was killed 
 and opened, when the four tubes were found 
 in the firft ftomach, with their contents ; and 
 the grafs and hay were not in the fmalleft de- 
 gree digefted, and but little foftened, 
 
 Sufpedting that they would undergo fur- 
 ther alteration, and be even digefted by a 
 longer continuance in the fliomach, Reaumur 
 caufed eight other tubes to be prepared in the 
 fame manner, i. e. four to be filled with frefh 
 grafs, and the remaining four with hay. The 
 grafs before it was put into two of thefe tubes, 
 and the hay before it was put into two others, 
 were moiftened with human faliva. All the 
 eight were forced down the throat of a iheep, 
 which was killed thirty hours afterwards ^ 
 
 {a) Hia. de I'Acad. Roy. An. 1752. 
 
 during 
 
DISSERTATION III. 159 
 
 during this interval, the animal had been kept 
 ftri(ftly failing; this precaution had alfo been 
 obferved with refpeft to the former fheep, that 
 had not retained the tubes fo long. In the 
 courfe of the thirty hours, the greater part 
 of the tubes were voided at the anus, but a 
 few remained in the iirfl ftomach. 
 
 But neither had the grafs or hay undergone 
 the fmallefl degree of digeftion; they pre- 
 ferved their original form and dimenlions ; and 
 when they were pulled at the two oppolite 
 extremities, refilled efforts to break them 
 with the fame force that limilar pieces of 
 grafs or hay, that- had been a little macerated, 
 would have done. Hence it is inferred by 
 this illuftrious naturalift, that digeflion can- 
 not be effected in the ftomachs of fheep by a 
 folvent, unlefs that folvent be aided by tritu- 
 ration : he was however ingenuous enough to 
 confefs, that thefe two experiments are of 
 themfelves very far from throwing fuch light 
 upon the prefent fubjed: as he could have 
 wifhed. 
 
 cxxxvii. The iirfl thing I undertook 
 with refped: to flieep, was to repeat exadlly 
 Reaumur's experiments. Thinking the tubes 
 I had hitherto employed too fmall, I had fome 
 made eight lines in lengrh, and four in dia- 
 meter. But I could not at firil introduce 
 
 them 
 
l6o DISSERTATION Hi. 
 
 them into the ftomach; After T had put 
 them into the throat with my hand, though 
 I pufhed them as far as my fingers would 
 reach, they were always returned. I was 
 unacquainted with Reaumur's method, for 
 he does not give the leaft information about 
 it. At laft an expedient occurred j it con- 
 fifted in putting the tubes, provided with their 
 contents, into a hollow cane, and intro- 
 ducing this cane into the cefophagus ; I could 
 now pufh them forwards with a rod^ till 
 they dropped out at the lower end of the cane 
 into the cefophagus ; and as the part of the 
 CEfophagus into which the tubes were now 
 introduced, lay at a great diftance from the 
 mouth, the animal, in fpite of all the efforts 
 he made to return them, was obliged to re- 
 ceive them into the ilomach : to the fame con- 
 trivance I had recourfe like wife for oxen and 
 horfes. Six tubes were given to a fheep; in 
 twenty- feven hours it was killed and opened; 
 it had eaten nothing during all the time it 
 retained the tubes; and this precaution was 
 flridtly obferved upon every fheep upon which 
 experiments were made. Notwithflanding 
 fo long a fail, the firfl ftomach contained a 
 large quantity of grais, fomewhat triturated^; 
 and though it had fed upon tl^tis before the 
 experiment, it v/as not yet digefled. In the 
 
 midft 
 
DISSERTATION iri. l6l 
 
 midft of this grafs, that was thoroughly im- 
 bibed with a greenifli fluid, with which great 
 part of the ftomach was filled, lay five of the 
 tubes 3 the fixth had pafTedto the fecond fto- 
 lAach, which may be confidered as an appen- 
 dix to the firfl* The herbs which I enclofed 
 in the tubes, after impregnating with my fa- 
 liva, were beet, trefoil and lettuce 3 for three 
 tubes I had ufed them green, and for the reft 
 dry. Upon opening all the fix, I could not 
 perceive that either the frefh or the dried 
 plants had fuffered any diminution, or under- 
 gone any degree of real concoction ; they had 
 only become a little tenderer, and the frefh 
 herbs had loil their green colour; in fliort, 
 the refult of this experiment was exadily like 
 that of Reaumur's. 
 
 cxxxviii. I Ihould then have fuppofed, 
 that in thefe animals digeftion depends on the 
 triturating power of the ftomach, if it had 
 not occurred, that, as the herbs enclofed in 
 the tubes had not pafiTed further than the firft 
 ftomach, they might not perhaps have felt 
 the influence of that kind of gaftric fluid, 
 which is requifite for the concodiion of the 
 food : for it is ver)^ pofiTible that this fluid may 
 refide in feme of the other ftomachs,' and 
 efpecially in tlie fourth, in which the ali- 
 ments of animals with four ftomachs, fuch 
 
 Vol. I. M as 
 
1^2 DISSERTATION III. 
 
 as fheep, are always found in the ftate of a 
 very foft paile. Reaumur indeed did not 
 perceive any fign of digellion even in the 
 tubes that had been voided at the anus, and 
 confequently muft have paffed through the 
 other ftomachs. But this- obfervation refted 
 upon a fingle experiment ^ and to illuftrate 
 ilill further a matter of fuch importance, it 
 could not but be proper to repeat it. I there- 
 fore treated another fheep in the fame man- 
 ner, and allowed it to live.thirty-feven hours 
 afterwards, that the tubes might have time to 
 pafs beyond the firil llomachs. They did in 
 fadt pais beyond them; and I found all fix 
 in the fourth, which anfwered the end I had 
 in view ; the three fpecies of plants however, 
 mentioned above (cxxxvii), both the green 
 and the dry, were entire, and feemed only a 
 little foftened by maceration. 
 
 cxxxix. I was now about to declare in fa- 
 vour of the neceffity of trituration in this ani- 
 mal, when a doubt occurred. Neither Reau- 
 mur nor myfelf had adverted to a circumfliance, 
 which ever precedes digeftion, both in fheep, 
 and every other quadruped endowed with four 
 ftomachs, as goats, oxen, deer, &c. I mean 
 rumination. We are taught, both by dif- 
 fedion and daily experience, that the food, 
 when it has arrived at the fecond flomach, 
 
 does 
 
BlSSERtATlON til* 163 
 
 does hot immediately proceed to the third,"" 
 and thence to the fourth , but, on the con- 
 trary, returns, and re-afcends up the oefo- 
 phagus; and when it has reached the cavity 
 of the mouth, is mallicated and ground oyer 
 again, and impregnated with a large quantity 
 of faliva^ this procefs is repeated, till it be- 
 comes iit to be digefledi I therefore enter- 
 tained many doubts whether the phenomena 
 obferved by Reaumur and tnyfelf, were not 
 rather owing to the want of rumination than 
 of trituration* Wherefore, in order to de- 
 cide with certainty concerning digeliion in 
 fheep, I perceived it would be neceifary to 
 repeat the experiments with plants previoully 
 triturated* And I did hot conceive that this 
 trituration was any thing fo peculiar in rumi^ 
 hating animals, that it could not be fupplied 
 by man^ provided he mafticated the herbs 
 wellj and impregnated them thoroughly with 
 faiiva. I therefore performed this eafy ope- 
 ration j the ufual tubes were employed; in 
 three of them pieces of the green plants were 
 enclofed, and in three others of the dried; 
 but both had been well mafticated : the lines 
 and nerves that traverfe the leaves, were how- 
 ever eafily diflinguifliable. Left, when thus 
 broken down and divided, they fliould pafs 
 out at the lateral pores, or through the mefhes 
 M 2 ^^ 
 
164 DISSERTATION IJI. 
 
 6f the lattice-work, I thought it would be 
 proper to enclofe each tube in a linen bag; 
 fiippoling that in the prefent cafe that it would 
 not be broken, lince that mufcukr adlion, 
 which is fo coniiderable in gallinaceous fowls, 
 does not exift in the animals in quefVion. I 
 gave the fix tubes to a ram, together with 
 iix others, filled with the fame plants, but 
 not previouily mafticated, that I might be 
 able to form a comparifon. Fourteen hours 
 after the animal had taken them, he vomited 
 three at once ; and in thirty- three hours five 
 more were voided at the anus; at the end of 
 two days he was killed. Of the four remain- 
 ing tubes, two were found in the ftomach, 
 and the other two at the end of the duode- 
 num; the bag in which they w^re enclofed 
 was entire. Thc» tubes that had been vomited 
 had received more or lefs injury ; the contents 
 of two had not been mafticated, nor had 
 thev under2:one the. fmalleft alteration. The 
 contents of the third had been mafticated, 
 and were evidently wafted; for they now oc- 
 cupied little more than half the tube, whereas 
 at firfh they had entirely filled it; they had, 
 acquired a fubacid tafle. Many of the pieces 
 havinsT loft their natural firmnefs, broke when 
 I attempted to ftretch them ; the nerves only 
 madefbiiie refiftance. 
 
 In 
 
DISSERTATION III. 1 65 
 
 111 two of the tubes voided at the anus, the 
 pieces of plant had not been mafticated ; thefe 
 did not feem at all diminiflTied, nor was the 
 cohefion of the parts deftroyed ; on the con- 
 trary, the plants in the other three (which had, ' 
 been mafticated) were reduced almoft to no-* 
 thing; the fmall remains coiififted of bare ■ 
 nerves, with a little of the leaf attached ; and 
 both the one and the other were fo much 
 foftened, that the flighteft force was fafficient 
 to break them. The bag in which they were 
 enclofed was dyed green, particularly in its 
 infide j when twiftedand preffed between the 
 fingers, it yielded a livid yellow juice, of an 
 acid taftct This was far from being the cafe 
 in the bags which contained the two tubes, of 
 which the contents had not been chewed; 
 their infide had fcarce a fliade of green ; and 
 this fhade was ftill lefs perceptible in the juice 
 expreiTed from them. With refpecl to the 
 tubes found in the laft ftomach^ and at the 
 end of the duodenum, the contents of the 
 former had acquired a deep green colour, were 
 a little macerated, but had not loft much of 
 their natural firmnefs, and did not appear tp 
 be diminiftied in bulk. They had not been 
 mafticated, but thofe qf the two others had ; 
 and of them there remained only fpme pf tlw 
 j^rgeft nerves, which were themfelves very 
 M 3 tender. 
 
l66 DISSERTATION HI. 
 
 tender, and half decompofed, I have al« 
 ready obferved, that the tubes voided at the 
 mouth were more or lefs bruifed^ but all the 
 reft v^ere quite free from injury. 
 
 cxL. The reader is already aware of the 
 immediate confequences of thefe experiments. 
 In the firft place it appesirs, that the gaftric 
 fluid of fheep has no effeft in digefting plants^ 
 unlefs they have been previoufly mafticatedi 
 Qtherwife it can only produce a flight mace- 
 ration, nearly as common water would do in 
 a degree of heat fomewhat exceeding the me- 
 dium temperature of the atmofphere, Se-. 
 condly, this fluid is abundantly capable of di- 
 gefting plants, provided they are previoufly 
 reduced to pieces by mafticatjon ; its firfl: ef- 
 fed: is to foften them, and deflroy their na-. 
 tural conflflency ; it then proceeds to difiblve 
 them, not even fparing the toughefl: parts, 
 fuch as the nerves of the leaves; of this foiu- 
 tion we have a clear proof in the green colour 
 that appears on the linen encloflng the tubes, 
 and in the juice exprefl^ed from it {a). Thirdly, 
 the triturating power of the flomach does not 
 
 ^t 
 
 {a) During my agreeable refidence at Geneva in the fummer 
 of 1779, I had what I had long wifhed for, the fatisfaftion of 
 being perfonaliy acquainted with my illuftrious friend Mr, Bon« 
 net^ ftnd of enjoying much of his ccuverfation, I had alfo an 
 
 oppor^ 
 
DISSERTATION III. 167 
 
 at all contribute to digeftion in flieep, but this 
 procefs is entirely effed:ed by the gallric juices. 
 Fourthly, no fuch power exifts in flieep, as 
 we fee from the tubes that were voided at the 
 anus andfound in the ftomach havinp^fuflained 
 
 o 
 
 no injury, notwithflanding prefTure alone be- 
 tween 
 
 opportunity of taking his opinion on fome produdions, which 
 I defigned to publilh, and particularly the prefent work con- 
 cerning digeftion. Three other reputable philofophers and 
 excellent judges of the fubj eel .were prefent at the reading, Mr. 
 Abraham Trembley, Mr. Johannes his worthy nephew, and 
 Mr. Senebier, Librarian of the Republic of Geneva ; and it 
 did not appear tonfie, that my labours were difapproved by this 
 refpedable affembly. Mr. Bonnet gave me a book to perufe 
 on the fame fubje(^, which, as it was new to me, made us ap- 
 prehenlive, left the author fhould have anticipated me ; it was 
 intituled, '* Eflai fur la Digeftion, & furies principales Caufes 
 de la Vigueur & de la Duree de la Vie. Par Mr. Batigne, 
 M. D. Berlin, 1768, izmo." But I was foon aware, that 
 Mr. Batigne and rayfelf had purfued very difFerer^t paths ; in. 
 his book he does not enter into any experimental enquiry cpn- 
 cerning digeftion, but confines himfelf to refleftions, which, 
 although they are very pertinent and fenfible, are calculated 
 rather to excite than fatisfy the reader's curiofity. Hence I 
 fhould not have mentioned it, but for fome objeclions ftarted 
 againft Reaumur's Memoirs on Digeftion. Thefe I {hall touch 
 upon in a few ftiort notes, at fuch places of the text as they 
 feem moft connefted with. And here it is proper to mention' 
 one obje£lion relative to the digeftion of ruminating animals, 
 which, before I was acquainted with Mr. Batigne's book, I 
 had myfelf urged againft Reaumur, and which experiment 
 proves to be perfeftly juft. It confifts in (hewing, that the 
 French naturalift had omitted the maftication of the plants en- 
 clofed in the tubes before he introduced them into the ftomachs 
 «f flieep;^ which was the reafon why they were not digefted. 
 M 4 Nearly 
 
j68 DISSERa*ATiON 
 
 in. 
 
 tween the fingers is fufficient to flatten them. 
 The contulion of the tubes that were vo- 
 inited is no proof of the contrary, fince it is 
 evident, that this contufion was produced by 
 the teeth of the animal during runiination. 
 Laftly, thefe vegetables acquire a flight aci- 
 dity during folution, but of this we fhall have 
 another opportunity of fpeaking hereafter (a). 
 cxL I . This quadruped feeds not only upon 
 grafs, but upon corn alfo whenever it meets 
 with it) it is like wife very fond of bread. 
 In order therefore to confirm ftiil farther 
 what has been advanced, I thought it would 
 be proper to make an experiment upon fome 
 kind of grain. I feledled wheat for this pur- 
 pofe J and as wheat may be procured under the 
 various forms of feed, flour, and bread, I 
 chofe to make trial of all three. Six tubejs 
 were filled, three with thofe fubfl:ances with-. 
 out any other preparation, and three others 
 with the fame after they had been well maA 
 
 Nearly the fame objeftlon is urged by the learned phyfician in 
 theie terms; " The experiments (of Mr. de Reaumur) upon 
 ruminating animals are ftill lefs conciafive; the grals contained 
 in the tubes could be only macerated, lince it was neither 
 chewed nor broken down a fecoad time by rumination." (L. c. 
 Troifieme Reflexion fur les Experiences de Mr. de |leaumur). 
 It was a piece of juftice due to Mr, Batigae not to overlook 
 this pafTage. 
 
 («) In the lalt differtation, 
 
 ticated, 
 
D I S S E R T A T I,.0 N III. 169 
 
 tlcated. The tubes were enclofed in linen 
 bags as before, and given to a lamb fix months 
 old. It^ was killed thirty hours afterwards^ 
 none of the tubes were either vomited or 
 voided at the anus; they were found partly 
 in the third and partly in the fourth flomachs. 
 The refult of this experiment coincided with 
 that related above (cxl). The grain, flour, 
 and bread, that had not been maflicated, were 
 indeed penetrated thoroughly by the gailric 
 fluid, but not at all diffolved. On the con- 
 trary, the corn which I had firft bruifed with 
 a peille and then ground between my teeth 
 and reduced to a coarfe pafte, was in great 
 meafure confumed; nothing remained in the 
 tubes but fragments of the bran, with fome 
 fmall remains of farinaceous matter adhering. 
 The like had happened to the flour and bread, 
 what remained confifled of a mucilaginous 
 mafs, without any appearance of what it had 
 originally been. This matter had a flight 
 degree of acidity, a quality which was far 
 more evident in the bread, flour, and grain 
 that were not diflblved by the gafl:ric fluid for 
 want of previous maceration. 
 
 cxLii. The vafl: quantity of gailric fluid 
 with which ruminating animals are continu- 
 ally fupplied, was already known to phyfio- 
 iogifls, and particularly to the great Haller. 
 
 After 
 
IJ^ DISSERTATION III. 
 
 After a fail: of two whole days, I have found 
 thirty-feven ounces in the two firfl ftomachs 
 of a fheep. It was green, but I know not 
 whether this colour is natural to it, as the 
 yellow hue is to that of crows (lxxxi) ; or 
 rather whether it is adventitious, and de- 
 rives its origin from the plants on which 
 thefe animals feed, of which, notwithftand- 
 ing fo long a fall:, there were Hill fome re- 
 mains in the two flomachs. The great quan- 
 tity of juice I had colled:ed induced me to 
 try whether, like that of feveral other ani- 
 mals, it was capable of digefling food out of 
 the body. I therefore enclofed feveral pieces 
 of leaves of lettuce in two ihort glafs tubes 
 (which I had previoufly filled with the juice), 
 and fealed them with wax at each end. The 
 contents of one tube, as before, were mafti- 
 cated, while thofe of the other were left un- 
 touched. It was proper on the prefent occa- 
 iion to employ a term of comparifon, by re- 
 peating the fame experiment upon two other 
 tubes filled with water. That thefe four tubes 
 might be expofed to a degree of heat nearly 
 equal to the temperature of fheep, I fixed 
 them under my axillae, two under each axillae, 
 where the)^ continued forty-five hours* The 
 leaves immerfed in the gaflric fluid, which 
 had httn previoufly macerated, had under- 
 
 gone 
 
DISSERTATION III. 171 
 
 gone no inconfiderable change. Befides the 
 lofs of their bright green colour, they were 
 converted into a kind of glue, in which it was 
 jufl poflible to find, with the point of a pen- 
 knife, a few nerves, which were the only re- 
 mains of the organization of the plant. This 
 •was far from being the cafe with the leaves 
 that had not been mailicated; for all the 
 pieces were diftinguifhable, and the only dif- 
 ference was, that they did not make fo much 
 reiiilance as at firft. The leaves immerfed in 
 water, both thofe which had been chewed, 
 and thofe which had not, had not loft either 
 their colour or conliftence. From this com- 
 parifon it appears, that the gaftric fluid does 
 not ad: on the plant as a mere aqueous fluid, 
 but as a real folvent, nearly as it acfts in the 
 ftomach itfelf. Nor was the heat to which 
 it was expofed under my axillas a condition 
 without its part in the produdion of this in- 
 cipient digeftionj for in pieces of the fame 
 leaves of lettuce mafticated in the fame man- 
 ner, but kept in my apartment, of which 
 the temperature was about fixteen (a) deg. 
 there appeared only a fuperficial maceration, 
 notwithftanding they remained immerfed in 
 the fame gaftric fluid for the fame fpace of 
 time. 
 
 {a) Sixty-fix, Fahren. 
 
 CXLIII. I 
 
lya DISSERTATION III. 
 
 cxLiii. I clofed my enquiries concerning^ 
 the digeflion of ruminating animals by fome 
 experiments on oxen. In thefe the lame tubes 
 and plants were employed as before, and the 
 refults perfedly coincided with thofe obtained 
 from ilieep ; only in the prefent inflance, Na- 
 ture was more fpeedy in her operation. In- 
 lefs than twenty-four hours the tubes, which 
 had been given to two oxen, were voided along 
 with the excrements not in the leaft contu- 
 fed or injured. When taken out of tb,e linen 
 bags and examined, they were found to con- 
 tain little more than the bare ribs and nerves 
 of the leaves of beet, lettuce, and trefoil 
 (which leaves had been previoufly mafticated). 
 The nerves were alfo in fome degree macera-. 
 ted, and the llightefl: force was fufficient to 
 break them. On the contrary, pieces of the 
 fame plants that had not been fubjeifled to 
 maceration were indeed llightly concocted, and 
 their colour was a little faded, but they were 
 entire. When applied to the tongue, they 
 tafled fubacid, like thofe which had been in 
 the ftomachs of fheep (cxxxix, cxli). 
 ' The horfe does not chew the cud, but he 
 refembles the ox in the membranous ilruc-r' 
 ture of his flomach, and the food upon which 
 he lives. I was therefore deiirous of feeing 
 whal changes mafticated plants v/ould under- 
 go 
 
DISSERTATION III. 1 73 
 
 go by continuing a certain time in the ftomach 
 of this quadruped alfo, enclofed as ufual in 
 tubes. Here too they were digefled, as I 
 learned from fome lettuce and trefoil enclofed 
 in two tubes, which were voided in jfifty-two 
 hours. 
 
 ckLiv. When Ireflecflupon the various ani- 
 mals to which my enquiries concerning digef- 
 tion have been hitherto extended, I perceive, 
 that the ruminating fpecies very nearly refem- 
 ble birds endowed with mufcular flomachs, 
 with refpe6t to the adlion of the gaftric fluid. 
 In both, that fluid requires an agent capable 
 of breaking down and triturating the food, 
 before it can difTolve and digefl: it. From the 
 mouth of granivorous birds, where it under- 
 goes no real alteration, the aliment pafTes im- 
 mediately into the craw, where it is foftened 
 and macerated; from this receptacle it de- 
 fcends into the ftomach : the triturating power 
 of this organ performs the office of teeth, and 
 breaks, grinds, and, if I may fo fpeak, pul- 
 verizes it, and thus renders it fit to be difTolved 
 by the gaftric fluid, and converted into chyme. 
 Nature employs a fimilar contrivance in ru- 
 minating animals. The hay and grafs defcend 
 immediately into the firft and fecond flomachs, 
 in nearly the fame ftate as when they were^ 
 browfed. Here they are foftened by the great 
 
 quantity 
 
174 DISSERTATION III* 
 
 quantity of gaftric juices, as feeds in the craw 
 of birds with gizzards. But as the ftomachs 
 of ruminating quadrupeds have no feniible tri- 
 turating power (cxxxix, cxL, cxLiii),and 
 the food requires trituration, nature has wife* 
 \y provided for this by cauling it to afcend, in 
 confequence of a gentle ftimulus to vomit, 
 into the cavity of the mouth, where, by means 
 of rumination, it receives the neceffary pre- 
 difpofition to be digefled by the gaftric fluid, 
 as happens to the food in the ftomachs of gra- 
 nivorous fowls, after they have been properly^ 
 triturated by thegaflric mufcles. 
 
 DIS^ 
 
r 175 ] 
 
 DISSERTATION IV. 
 
 THE SUBJECT OF DIGESTION IN ANIMALS 
 WITH MEMBRANOUS STOMACHS CON- 
 TINUED. THE LITTLE OWL. THE 
 SCREECH OWL. THE FALCON. THE 
 EAGLE, 
 
 CXLV. "n EAUMUR having treated in 
 **"^ his firft memoir of the mode of 
 digeftion in granivorous and herbivorous fowls 
 which are provided with gizzards, proceeds 
 in his fecond to enquire into the nature of that 
 fundiion in carnivorous birds, of which the 
 flomach is membranous. From the fad:s re- 
 lated in the firft memoir he concludes, that 
 there does not exifl in the gizzard any folvent 
 capable of feparating the particles of the food. 
 This feparation, he thinks, is efFeded by a 
 force refembling that exerted by mill-flones, 
 
 viz. 
 
I'j6 fiiSSERTATIOW IV. 
 
 viz. the adtion of ilomadls of this conilrudiOtt 
 upon their contents. He is moreover of 
 opinion, that the fadts adduced in the fecond 
 memoir prove the exigence of a menftruum in. 
 membranous ftomachs, capable of diffolving 
 and digefting the aliment without borrowing 
 any aid from the adiion of the folid parts. 
 
 As the great object of the firft differtation 
 was to enquire by experiment into the mode 
 of digeflion in fowls with mufcular ftomachs, 
 i had there an opportunity of confidering 
 fully Pvcaumur's experiments on that fubjed:; 
 and we have accordingly feen, that the con- 
 fequences he has deduced from them are by 
 no means to be admitted in their full extent. 
 This is plain from the xxxix, xl, xli, x:lii, 
 XL 1 1 1, XLVth paragraphs, to which, for the 
 fake of avoiding ufelefs repetitions, I refer the 
 reader. The prefent differtation, in which 
 the fubjed; of digeftion in membranous fto- 
 machs is continued, is the proper place for 
 confidering the experiments related in the fe- 
 cond memoir. As of all fowls birds of prey 
 approach nearefl to man in the ftrud:ure of the 
 flomach, he chofe one of thofe large kites that 
 are common in France, for the fubjed: of his 
 enquiries. The periodical vomiting, common 
 to all birds of prey, allowed the French na- 
 turalifl to make a variety of experiments on 
 
 the 
 
DISSERTATION IV» \^J 
 
 the fame individual. He employed tin tubes 
 filled with 'different fubflances, efpecially 
 fleih, which, after having been fome time 
 in the ftomach, were thrown up, and gave 
 him an opportunity of examining the effed:s 
 produced upon the contents* That the flefli 
 was more or lefs digefled according to the 
 length of its continuance in the body of the 
 animal, was the general and invariable refult 
 ' obferved by Reaumur (^). Hence he ju ftly 
 infers, that in this cafe digeftion is produced 
 by the gaftric fluid, without the concurrence 
 of any triturating power. He mentions fome 
 
 («) Mr. Batigne thinks, that flefli ehclofed in tubes was in- 
 fufficient to convey a precife idea of the alteration it undergoes 
 in the ftomach, as it is only macerated in tubes, and not di- 
 gefled. ** On voit de plus que la viande mife dans Ics tubes 
 lie peut donner une idee precife des changements qu'elle fubit 
 dans reftomac de I'animal, puis qu'elle n'y eft que maceree & 
 non point digeree." (L. c. premiere RefieSiion fur les experie?ices 
 de M. de Reaumur.) The author muft allow me to obferve, 
 that in this attack he mifreprefents Reaumur, who, p. 46c, 
 &c. of the Mem. of the Roy. Acad, exprefsly fays, that the flefh 
 given to the kite was not merely macerated or foftened, but 
 completely digefted, and at laft entirely confumed. He might 
 indeed have objected to the fmall number of his experiments, as 
 infufficient to afcertain the efficient caufe of dlgelHon, if that 
 philofopher, whofe ingenuoufnefs was equal to his fkill, had 
 not perceived and publicly owned it himfelf. That tubes, pro- 
 vided the experiments are properly made and varied, are well 
 adapted to fhew the change produced upon food in the ftomach, 
 will be abundantly proved by the fadls adduced in this treatife. 
 
 Vol. I.. N other 
 
178 DISSERTATION IV. 
 
 6ther experiments, which I fhall have occa- 
 fion to confider below, and concludes from 
 analogy, that digeftion in other birds witk 
 membranous ilomachs is produced in the 
 fame manner. He laments, however, that 
 from the death of his kite, and his negled;- 
 ing to fubftitute other animals in its ilead, 
 he could not adduce facfls fufficiently nume- 
 rous to illuftrate the fubjeft fully. He pro- 
 mifes to fupply the deficiency on fome future 
 occalion, but his death, by which a few years 
 afterwards natural philofophy loft one of its 
 great ornaments, prevented him from fulfill- 
 ing his promifes. 
 
 cxLvi. I do not prefume that I ihall be 
 able to accomplifh, what neither this illuftri- 
 bus naturalift, nor any other, as far as I know, 
 has effeded. But fimply with the view of 
 continuing my obfervations and refledlions on 
 digeftion in fowls with membranous ftomachs, 
 I fhall relate fome experiments on different 
 birds of prey, of which fome feek it by night, 
 and others by day. Among the former, I 
 have ufed fuch as I could moft eafily procure, 
 the little owl and the fcreech-owl. The food 
 which I gave the firft-mentioned fpecies (a), 
 
 {a) This fpecies is called by Bnifon petit e ch^uette, HiS:. Nat. 
 des Oifeaux, T. z, Ed. in 8vo. and hy Linnxas ^rijt />ajer:na, 
 i. c, ' 
 
 and 
 
DISSERTATION IV. f^O 
 
 and which it eagerly devoured, has enabled 
 me to folve, among other problems, , one that 
 exercifed the fagacity of M. de Reaumur. 
 Finding that the gaflric fluid of the kite di- 
 gefled flefh, he wifhed to know whether it 
 would alfo digeft vegetables; a circumftance 
 he did not think probable, when he conlidered 
 the repugnance carnivorous birds fhew for 
 them; and fo in fa(ft it happened. When 
 beans, peafe, wheat, inclofed in tubes, had 
 lain fome time in the flomach, they were 
 thrown up juft in the fame fhate as they had 
 been fwallowed : nor did boiling difpofe them 
 to be diffolved any better by the gailric fluid. 
 Some fparrows, which I gave my owls, af- 
 forded me an opportunity of obferving the 
 fame phaenomenon. As they fwallowed them 
 whole, they of courfe would receive into the 
 fhomach feathers and food not yet digefted by 
 the fparrows, and confifting of grain or bread. 
 Now, after the flefh has been digefled, the 
 feathers are vomited generally in the form of 
 ' a hard ball j and along \"\ith the feathers the 
 grain, which, though it is much foftened by 
 maceration, yet continues whole. And if 
 the matted feathers be difentangled, -we may 
 generally perceive evident traces of bread. 
 Hence v/e have a clear proof that the gaftric 
 fluid produces no change on fuch vegetables. 
 
 N 2 CXLVU, 
 
i8o DISSERTATION. IV^ 
 
 CXLVii. This fad, fimple as it is, fhews 
 two things, of fome importance : firft, that 
 the ilomach of this bird is really membranous, 
 and without any power of trituration : this 
 appears from the grains (cxlvi) continuing 
 whole, though they had been foaked till they 
 were become fo tender, as to burft on being 
 gently fqueezed between the fingers. I would 
 not however affirm that the flomach has no 
 a(ftion at all 5 for the globular mats of feathers 
 can only be produced by this vifcus contracting 
 as the flefh is digefled. 
 
 The digeftion of the bones alfo deferves 
 attention. It cannot be faid that they are 
 voided along with the excrem.ents ^ for I mull 
 foon have been aware of this, as I kept my 
 ov/ls in cages ; nor, for the fame reafon, could 
 it have efcaped my notice if they had been vo- 
 mited.. I have indeed fometimes found two 
 or three little bones, as a dorfal vertebra, or 
 a piece of the cranium, among the matted 
 feathers, but never any thing like the whole 
 fkeleton. We mufl therefore conclude that 
 they are digefted. 
 
 CXLVII I. Reaumur's kite was capable of 
 digefling bone, though of the hardefl: tex- 
 ture, and enclofed in tubes [a). Though 
 the experiment juft related is fufficiently de- 
 
 (a) Mem. cit. 
 
 cifive. 
 
DISSERTATION IV. l8l 
 
 cifive, yet, as the bones were loofe in the flo- 
 mach, in order to be abfolutely certain that 
 the efFe(fl was produced by the gaftric fluid 
 alone, it was proper to repeat it with a tube ; 
 with this view a piece of the thigh of a pi- 
 geon was put into one of the fame tubes that 
 I ufed before : thus two experiments, one on 
 the digeflion of flefli, and another on that of 
 bone, were made at once. By long prad:ice 
 upon birds of prey, I learned how to keep 
 the tubes in the flomach as long as I pleafed. 
 When I had given one of my tubes to an 
 owl, after it had been full fed, I found it was 
 not thrown up till all the food was digefted. 
 This obfervation is applicable to all other 
 birds of prey. The fame thing alfo happened 
 when they were fed fparingly. All the dif- 
 ference was, that as the full ftomach requires 
 more time to be emptied, the tubes were re- 
 tai^ed longer, and mce verfa, when they 
 were fafting, the tubes were fure to be re- 
 turned in two or three hours. This obfer^ 
 vation, together with the knowledge I had 
 acquired from experience, of the time thefe 
 birds take to digeft a given quantity of food, 
 enabled me to guefs pretty exadly how long 
 the tubes would continue in the ftomach. 
 
 I return now to the tube in which part of 
 
 a pigeon's thigh had been put. After feven^ 
 
 N 3 teea 
 
1 82 DISSERTATION IV. 
 
 teen hours continuance in the flomach, the 
 bone was no where changed except at the 
 broken ends, which were a little foftened. 
 The flefh, by which it v/as covered, as well 
 as the integuments, had begun to be dif- 
 folved, for the furface was become exceed- 
 ingly tender. In fourteen hours more greater 
 eifedis were produced. The flelli was con- 
 fiderably wafted ; the bone was fhortened at 
 the ends, and was fo foft, as to yield to the 
 preffure of the finger. In twenty-feven hours 
 more, there was no remains of flefh or pe- 
 riofteum, and the bone was a good deal 
 fliorter than at firft, I could not but be de- 
 firous of feeing the end of the experiment, 
 and therefore replaced the bare bone in the 
 tube. When it had remained twenty-one 
 hours in the ftomach, it had loft the marrow, 
 and the internal cavity was enlarged, though 
 the girt was leffened. This arofe from the 
 Corrolion of the internal and external furfaces 
 at the fame time. Both furfaces were covered 
 with a yellow fluid, that had at once a bitter 
 and fait tafte ; and points of gelatinous matter 
 were difperfed over them. The bone, thus 
 half diffolved, was put again into the tube, 
 and left thirty-two hours longer in the fto- 
 mach. If the reader will conceive a cylinder 
 cf thin paper, uneven at the ends, and per- 
 forated 
 
DISSERTATION IV. I S3 
 
 forated with feveral holes, he will have an 
 idea of the flate of the bone when it was ta- 
 ken out of the tube. It was covered with the 
 fame fluid, which mufl have been the gaftric 
 liquor; and the gelatinous points now alfo 
 were difperfed over the furface of the leaf; 
 this jelly was the olTeous matter itfelf, re- 
 duced to this flate by the adiion of the gaftric 
 fluid. Laflly, nine hours longer continuance 
 in the ftomach, left only a few fmall chips. 
 This one experiment convinced me, that the 
 gaftric fluid of the little owl is capable of di- 
 gefliing bone as well as flefh, without the con- 
 currence of any external agent : it alfo fhews 
 the gradual progrefs of digeftion. 
 
 cxLix. Having fo far fatisfied my cu- 
 rioflty, it remained to enquire into the nature 
 of this fluid, and its effeds out of the ani- 
 mal body. With the fmall fpunges, by 
 means of which I obtained fo large a quan^ 
 tity from crows (lxxxi, lxxxii), I pro- 
 cured it in due proportion from the fpecies of 
 owl in quefliion. I fay in due proportion j for 
 it is evident, that as the ftomach of thefe 
 birds will not admit fo many tubes as that of 
 crows, it cannot yield fo much gaftric fluid. 
 Befides, I had only flx I'ttle owls, whereas 
 I could get as many crows as I pleafed. It 
 was wonderful how foon the fpunges were 
 N 4 ^ filled 
 
1 34 DISSERTATION IV. 
 
 filled with liquor. As they were introduced 
 into the empty flomach, they were foon 
 thrown up, agreeably to an obfervation made 
 above (cxlvii) ; and yet they were as full of 
 juice, as if they had been dipped in water; 
 and frefli ones immediately forced down the 
 throat, yielded a nearly equal quantity. I 
 obferved the fame thing in crows (lxxxiii). 
 Whence it appears, with what care Nature 
 provides a large fupply of gaftric liquor 
 in thefe animals, as digeftion is entirely de- 
 pendent upon it. The juice was inftantly 
 fqueezed out of the fpunges into a fmall glafs ; 
 it appeared to have the fluidity of water, but 
 was of a reddilli-yellow colour, like the yolk 
 of an egg. This colour was not inherent 
 in the gaftric liquor itfelf 3 it arofe from an 
 immenfe number of very fmall yellow cor- 
 pufcles, fcarce perceptible by the naked eye, 
 but eaiily feen by help of the microfcope. In 
 a few hours they fubfided to the bottom, in 
 the form of a yellow fediment, and left the 
 fluid above tranfparent, like water, where it 
 has been freed from mud that was difFufed 
 through it and rendered it turbid. The firft 
 time I faw this phaenomenon, I fufpecfted it 
 was owing to fome impurities that remained 
 in the ilomach, and v/ere mixed with the 
 juice. Before the next experiment, in order 
 
 to 
 
DISSERTATION IV. 185 
 
 to be certain that the ftomach was free from 
 heterogeneous fubftances, I kept the animal 
 failing for a longer time than ufual ; but thijj 
 did not prevent the yellow colour from appear- 
 ing. Upon opening the llomach of an owl 
 that had been long kept failing, I could iind 
 no foreign fubftance, but the iiuid was as 
 yellow as that fqueezed out of the fpunges. 
 I was therefore convinced that thefe particles, 
 though I could not difcover their origin, did 
 not come from any remains of the food. 
 The gaflric liquor of the little crow, like 
 other gaflric liquors, is a little fait and bit- 
 ter: it evaporated fooner than water. It 
 leaves a fediment of the yellow particles, 
 which gradually becomes dry, and forms a 
 blueiih yellow crull ; it is not at all inflam- 
 mable. It has one property common to every 
 gaflric fluid I have hitherto examined, or 
 ihall have occafion to mention in the fequel; 
 though it is expofed to the open air for weeks 
 and months, in the hotteil feafon, it never 
 becomes putrid. 
 
 CL. Such are the properties of the gaflric 
 liquor of the fmall owl, when examined 
 alone. Let us proceed to the efted:s it pro- 
 duces on flefh out of the body. In thefe 
 experiments I ufed calves inteflines, a kind 
 of fbod which this bird devours very gree- 
 dily. 
 
1 85 DISSERTATION IV. / 
 
 dily. Forty-fix grains were immerfed in fomc 
 recent gaflric fluids and at the fame time an 
 equal quantity of the fame inteftine was put 
 "into a phial exad:ly like the former, and an 
 equal quantity of water was poured upon it. 
 Whenever 1 have made experiments, with a 
 view to compare the effeds of the gaftric li- 
 quor and water, I have taken care that all 
 circumftances fliould be alike. To prevent 
 evaporation, the mouths of the phials were 
 flopped with papery they were fet near a kit- 
 chen iire, where the ufual heat was between 
 thirty and thirty-five degrees. In eleven -hours 
 fome black fpots began to appear upon the 
 inteftine in the gaftric fluid, which were at 
 iiril: thinly fcattered over it, but became gra- 
 dually more numerous, till in tv/enty-foUr 
 hours they almoil covered it. During the 
 formation of the fpots, 1 examined the intef- 
 tincs with the microfcope, and found that 
 where they appeared, the iiefli was foftened, 
 and had loft its fibrous texture. When. they 
 had fpread over the whole piece, I took it 
 out of the liquor, and waihed it with pure 
 watery and now it recovered its white co- 
 lour, for the black covering confifled of a 
 thin ilratum of fleih, which the gailric fluid 
 had concodted. It was very eafily rubbed off, 
 and fell to the bottom of the water in ex- 
 ceedingly 
 
DISSERTATION IV. 187 
 
 ceedingly fmall particles, where it formed a 
 black lediment, and when viewed by the mi- 
 crofcope, feemed to be a colle6lion of mole- 
 cules of flefli, with no appearance of fibres. 
 When the piece of gut was dried, it weighed 
 only twenty- eight grains, and had therefore 
 loft eighteen; the piece that had ftood in 
 water for the fame length of time, was quite 
 foetid; whereas the other emxitted no difa- 
 greeable fmell : after waihing and drying, it 
 was found to have loft feven grains. Both 
 pieces were again put into the phials, with 
 the fame quantity of water and gaftric fluid, 
 and left in their former fituation for two days. 
 The latter had now loft its fhape and organi- 
 zation, and was converted into a black muci- 
 lage, of which the particles had no longer 
 any cohefion . The gaftric liquor had there- 
 fore diftblved the piece of inteftine complete- 
 ly; an effed;, which neither water nor putre- 
 facftion had produced upon the other; for 
 there was a remainder of nineteen o-rains, that 
 not only retained its fibrous ftrudlure, but 
 made confiderable refiftance when I attempted 
 to tear it. 
 
 CLi. I did not neeleft to examine the 
 ftomach and oefophagus of this fpecies of 
 owl, as I conceived that it would be impro- 
 per to omit a brief defcription of thefe or- 
 gans 
 
10» DISSERTATION IV. 
 
 gans in the animals upon which my experi^ 
 ments were made. If the beginning of the 
 duodenum be tied, fo as to flop the air from. 
 paffing, and the upper end of the oefophagus 
 be inflated, we get a view of the oefophagus 
 and flomach dilated to their utmoll extent; 
 together they refemble a pear, or rather a 
 gourd, of which the belly is formed by the 
 ftomach, and the neck by the oefophagus; 
 when viewed againft the light, the latter ap- 
 pears femi-tranfparent, and the former quite 
 opake. If they are cut longitudinally, and 
 fpread upon a table, we find that the tranfpa- 
 rency of the cefophagus is owing to the thin- 
 nefs of its fides, which thicken as they de- 
 fcend, and render the lower part as opake as 
 the ftomach. It becomes not gradually, but 
 fuddenly thicker, from the multitude of fol- 
 licular glands that form the fame kind of 
 tranfverfe fafcia, that I have defcribed in 
 other birds ; in this fpecies it is about five 
 lines broad. Thefe glands continually fecrete 
 into the cavity of the cefophagus a liquor al- 
 mofl infipid, of a turbid white colour, and 
 of fonje denfity; in a word, refembling the 
 oefophageal juice of other birds. At the be- 
 ginning of the ilomach the follicles difappear, 
 nor could I find the fmalleft vefiige of any 
 thing like them in the coats, though I 
 
 fearched 
 
DISSERTATION IV. 1 89 
 
 fearched with care. Are we then to fuppofe 
 that the fluid, which is always to be found in 
 the flomach, derives its origin from the num- 
 berlefs glands lying at the bottom of the cefo- 
 phagus ? this is probably true of fome part of 
 it; but that no fmall part comes alfo from 
 the arteries of the flomach itfelf, the moif- 
 ture, like what I have defcribed in other ani- 
 mals (xciii, cxxxii), has furnifhedme with 
 an indubitable proof; for it immediately ap- 
 pears again, though it has been wiped off 
 ever fo clean. 
 
 CLii. This defcription will apply to the 
 cefophagus and ftomach of fcreech-owls : I 
 have made experiments on two fpecies of 
 owl ; one variegated with many colours, among 
 which the red and brown, or dull yellow, 
 predominate 3 upon the head are two curious 
 tufts, in the ihape of a crefcent; the other 
 fpecies has not this tuft, but is adorned with 
 a greater variety of elegant colours 3 the iris 
 is dulky, in the former it is yellow (a). My 
 firft experiment was made upon one of the 
 long-eared owls, and the refult greatly fur- 
 prized me. It threw up two tubes in about 
 three hours after it had taken them, nor was 
 
 {a) The former fpecies is called by L'mr.vzm Jinx ofus, and 
 mojen due by BufFon ; the \z.X.1tx firix Jiudida and chat huant. 
 
 the 
 
ipO DISSERTATION IV. 
 
 the flefh at all changed; I could not perceive 
 any alteration, even when it had continued 
 upwards of feven hours in the ftomach. If 
 I had not been very cautious in forming opi- 
 nions, I fhouldhave concluded, that the gaf- 
 tric juices of this fpecies are infufficient of 
 themfelves to produce digeftion; but I re- 
 iledled, that a fingle experiment did not war- 
 rant fuch a concluiion, and that fome adven- 
 titious circumftance might have aiFefted the 
 refult. The bird feemed quite ftupid, and' 
 reduced very much in its flefh ; hence it was 
 probably unhealthy, and confequently inca- 
 pable of digefling its food properly. This 
 fufpicion was confirmed by the account of the 
 peribn from whom I had it, who informed 
 me, that it had refufed food ever fince it was 
 taken, which was now four days. It was an 
 old bird; and, upon turning to BufFon, I 
 found that, in order to rear individuals of 
 this fpecies, it is neceffary to catch them 
 young, for the old ones will not take fufle- 
 nance in confinement {a). In two days and 
 a half longer, that in my pofiefTion died with- 
 out taking any food of itfelf ; it had always 
 returned what I forced down the throat. 
 
 CLiii. This owl fell into my hands in 
 winter; the fpring following I procured two 
 
 (a) A. I.e. 
 
 young 
 
DISSERTATION IV. 19I 
 
 young ones from the neil:, which devoured 
 food with eagernefs whenever they were hun- 
 gry : I now repeated my experiment, and the 
 refult was exad:ly the reverfe of the preceding ^ 
 the flefh in the tubes fliewed iigns of folution 
 in three hours and three quarters, and in fe- 
 ven was entirety dilTolved. This convinced . 
 me, that the failure of the foregoing experi- 
 ment was not owing to the inefficacy of the 
 gaflric fluid, but to the morbid condition of 
 the animal ; which either lelTened its quan- 
 tity, or, what is more probable, impaired its 
 quality. I might, therefore, have omitted 
 mentioning that failure i but it w^as better to 
 relate it, in order to iliew, that when the 
 food inclofed in tubes is not digeiled, we are 
 not immediately to infer, that the gaflric 
 fluid is not capable of producing this efFed:. 
 
 CLiv. But my young owls digeiled not 
 only fleih, but bone ; and that of a hard tex- 
 ture, fuch as the bones of fheep and oxen, 
 not to mention thofe of pigeons and fovvds. 
 The refult was eilentially the fame as in the 
 preceding fpecies (cxlvii, cxlviii); in- 
 llead, therefore, of dwelling upon it, I v/ili 
 relate, at fome length, a fad:, which, in my 
 opinion, deferves to be noticed. I gave one 
 of my owls a frog, and an hour afterwards 
 killed it. The llomach though exceedingly 
 
 dilated. 
 
192 DIlSERtATIQN IV. 
 
 dilated, was incapable of containing the whole 
 frog, of which the head lay in the oefopha- 
 gus, and flretched its fides confiderablyj the 
 hind legs lay at the bottom of the ftomach, 
 and the iiefh was fo much wailed, that the 
 bones were nearly bare : the integuments of 
 the thighs and trunk were almoft corroded, 
 and the flefh was as tender as if it had been 
 boiled. The head, which lay contiguous to 
 the fafcia of follicular glands at the bottom of 
 the oefophagus, had begun to be difjblved. 
 This experiment ihews not only that flefh is 
 digefted with great quicknefs by the gaftric 
 liquor, but like\vife that it is digefted equally 
 foon in the oefophagus and flomach; an ob- 
 fervation I had not yet made upon any other 
 animal. 
 
 CLV. Before I killed both thefe owls, I 
 was defirous of having fome of their gaftric 
 juice, that I might fee whether it retained 
 like others its power of digeftion ; and I found, 
 that it completely diffolves fleih, when it is 
 affifted by a proper degree of heat. 
 
 CLV I. In the other fpecies, the fawny owl, 
 the fame phenomena occurred with refpedt 
 to the folution of flefh and bone in the tubes, 
 whether we confider the digeftion of flefh and 
 bone in tubes, or the fpeedy digeftion in 
 
 the 
 
DISSERTATION IV. 193 
 
 the oefophagus (^), or the remarkable lloXv- 
 nefs of that procefs out of the body. Upon 
 an individual of this fpecies I made an expe- 
 riment, which had been unfuccefsful on the 
 little owl. Obferving, that when they were 
 hungry and open their beak very wide, if I 
 dropped a pea, French-bean, or cherry into 
 it they fwallowed it with as much avidity as 
 if it had been the pleafanteft kind of food, I 
 was delirous of feeing whether the ftomach 
 would digefl vegetable fubflances. * With 
 this view I enclofed fome of the feeds jufl 
 enumerated in tubes, and forced them down 
 the throat, but to no purpofe; for though 
 the liquor fwelled them, and perhaps altered 
 the colour, they underwent no diminution of 
 bulk. They were thrown up undigefted in a 
 day or two, a circumflance which fufficiently 
 fhews, that fuch kind of food, notwithfhand- 
 
 (a) When I was writing this paffage I was ftruck by a re- 
 fleftion; for which this is the proper place. If we compare 
 the prefent with the lxxvii, lxxviii, lxxix, xcix, c, ci, 
 cxxxv, CLivth, it will appear, that the cefophageal before its 
 mixture with the gaftric fluid, in many animals, is endowetj 
 with fome degree of digeftive power. Though it generally 
 exerts this power only when mixed with the gaftric fluid, yet 
 in fome animals, which fwallow their food with great eager- 
 nefs and have not room enough in the ftomach to contain it all, 
 in confequence of which part mull be lodged in the cefophagus, 
 digeftion takes place thei'e. 
 
 Vol. L O ing 
 
194 DISSERTATION I^f. 
 
 ing the birds appear to relifh it, is ill adapted 
 to their gaftric juices. The greedinefs with 
 which they fwallow fuch fubftances can arife 
 only from that blind appetite, in confequence 
 of which young birds take whatever is offered 
 them. 
 
 CLvii. Being fatisfied with thefe experi- 
 ments on nofturnal birds of prey, I turned 
 my attention to fome of the diurnal ones. My 
 iirft fubje(5l was a falcon given me by my il- 
 luflrioits friend the abbe Corti, formerly pro- 
 felTor of natural hiftory at Reggio, and now 
 fuperior of the College of Nobles at Modena, 
 a philofopher well known in the republic of 
 letters by feveral fine publications. It was of 
 the fize of a common hen, and appeared to 
 belong to the fpecies denominated lanarius by 
 Linnaeus. I foon found, that I could not 
 handle this bird fo familiarly as thofe which I 
 have had occafion to mention hitherto. Its 
 llrong beak and long iharp talons would not 
 eafily permit me to open the mouth by force, 
 and thruil the tubes down the throat. I 
 however contrived a method of introducing 
 them into the jftomach unperceived by the 
 bird; it confifted in cutting fome flefh in 
 pieces, making holes in them, and concealing 
 the tubes in thefe holes. When the falcon 
 was hungry he ran eagerly to the pieces of 
 - fleOi 
 
P 1 S S E R T A T I O N IV. ip^. 
 
 fleili, and fwallowed them whole. For the 
 fraud to fucceed, it was neceffary that the 
 tubes fhould be quite covered with fl;^fh; for 
 if any part of them was bare, the falcon would 
 put them under his talons and tear the flefh 
 away with his beak and fwaliow it v/ithout the 
 tubes. 
 
 CLviii. My firft experiment was made 
 with a view to afcertain, whether it v/as ca- 
 pable of digefling bone independently of the 
 adtion of the ilomach, which proved to be the 
 cafe; but I have before faid fo much on the 
 fubjed: of the digeftion of bone, that I fhould 
 forbear to relate the prefent inftance particu- 
 larly but for a new and important pha^nome- 
 non, which renders the detail neceffary. The 
 bone Gonfifted of little fplinters of an ox's 
 thigh bone 3 they were very hard and corn- 
 pad:, and of various fizes, from that of a grain 
 of wheat to that of a bean ; they weighed to- 
 gether iixty-feven grains; I put them into 
 two tubes, in which they were rather clofely 
 crammed. To J>re vent their failing out of 
 the tubes when they began to be diffolved, 
 and confequently to get loofe from each other, 
 I put the tubes in a linen bag, a precaution 
 which I had before employed, an i continued 
 to employ occafionally in 'Uture. ^ la twenty- 
 four hours the bones had ihifted their re- 
 O 2 fpedive 
 
133 D I S 3 Z R T A 7 I K IV. 
 
 frective plsces and rattled in the tube?, a clr- 
 C'jniilir-ce thar ihewed the bulk to be dimi- 
 r.iihed. They ^^•ere moift with gaftric ii- 
 auDr, b-i: hid none of thcic ^e.itinous points 
 which I hid I'ten in an exirrii-nent both on 
 tht little O'.vi icxLviii';, ann the two other 
 '^^cc^. 'T'^e'e '^~''*~r^ vc'e a^ I t en re- 
 marked, the oneou? mairer c:nver:e>a :::mi 
 ielly or chynne by the gaitric hcucr. But 
 what is extraorcinirv wis, that thei^c ibiinters 
 retained tmeir crinnil nardneis ana niiaitv* 
 fz-' rhit at hrfi: iisht one wculd nc: ha'."c lu::- 
 piiea, that tne mud ol me iioniacn nan nad 
 any efted: "ar:n th enn. Hcv.-ever, the con- 
 trary was certain ; for vrhen the gaftric li- 
 quor was wined olt, they weirhed cnly lortv- 
 two Trains. I new renlaced them in the 
 tubes, ana ex:n;:ned them ariin after they 
 had been t'/\. d.ys in the ftirn: :h. The 
 pieces of the fze of grains of wheat were all 
 ceftrcved but tvro, which were now no larser 
 than millet. Three of the fplinters were at 
 £rf: as bir as beans, but nc.y reduced to the 
 n::t c: m:.iz^. Thcie of an intermediate 
 iize were cin^inhhtd m arc rcrtisn, Durins: 
 
 tine tinird examinatisn, aitrr nriv-ieven hours 
 longer continuance m the f::m:.ch, the three 
 Id-fgQ pieces cnly were left, and they were 
 
 now 
 
D I S S Z R T A T I O N* IV. 1 57 
 
 now not lareer than millet: when I ilnick 
 them with an hammer, I found that they re- 
 tained their original haidnefs . 
 
 The gailric Hquor therefore of the falcon 
 does not, like that of owls and many other 
 animals, innnuate itfelf into the iubflance 
 of the bone, but acts on the fjrface onlv. 
 The phasnomenon, I think, m.ay be thus ex- 
 plained: conceive a bone to be compofed„ 
 like wood, or to bring a more familiar in- 
 llance, like an onion, of a great number of 
 ilrata. The lirata of the onion are of conr 
 fiderable thicknefs, but we muil imagine, 
 that in bone they are exceedingly thin. The 
 gallric fluid of owls or eiher animals will 
 firll dilfolve the upper llratum., but while it 
 is doing this it will penetrate and foften the 
 contiguous ftrata, without dilfolvrng them. 
 Hence the tendernefs of bone that has lain 
 in the ilomachs of animals. On the con- 
 trar}', ^ve mull: fuppofe, that the gaftric li- 
 quor of the falcon has no power of pene- 
 trating the internal fbrata, but that its adion 
 is limited to the furface. According to this 
 fuppofition the bone will be digefted without 
 having the internal parts foftened, and thus 
 ftrauim after ilrratum will be taken away, juil 
 as it \Y0uld happen if we had a menflruum 
 capable of dillblving only the fuperncial 
 0{ ' la^-er 
 
I$8 DISSERTATION IV. 
 
 layer of an onion withcut afting upon the 
 others. 
 
 CLix. Before I concluded pofitively that 
 the gaftric juice of this bird does not foften 
 bone at all, I determined to obferve its ef- 
 fedls when it is at liberty to acl without any 
 obdacle; for it is poffible, that its efficacy 
 might be impaired by paffing through the 
 cloth. I therefore took a piece of the fame 
 thigh bone from the thickefl part, and worked 
 it into a fphere by the lathe, to prevent the 
 angles injuring the fine coats of the ftomach j 
 it was then given to the falcon. My pur- 
 pofe was to obferve whether as it was diiiblved 
 it was alfo foftened. 
 
 It continued five days in the flomach with- 
 out becoming in the leafl tenderer. The 
 ihortening of its diameter fhewed that it was 
 lefiened in bulk. Meantime the falcon threw 
 up the fphere once or twice a day, according 
 as he was fupplied with food ; for, as I have 
 obferved with refped; to other birds of the 
 fame clafs (cxlviii), he did not vomit in- 
 digeftible bodies till he had digeiled the other 
 contents of the ftomach. To caufe indigef- 
 tible fabllances to remain in that cavity af- 
 ter other bodies are digefled, I gave him frelh 
 food; for experience having taught me to 
 judge, when that period was approaching^ I 
 
 was 
 
DISSERTATION IV. I95 
 
 was fure to attain my purpofe ^ {ince when the 
 crop is full of food, the contents of the fto» 
 mach cannot be evacuated through the mouth. 
 By this contrivance the falcon v^as made to re- 
 tain the globe twenty-two fucceffive days. It 
 is fearce worth while to obferve, that it was 
 not foftened, fmce the inability of the gailric 
 fluid to produce this eifed; has been fufficiently 
 proved before; but the remarkable diminu- 
 tion it underwent deferves to be noticed. 
 The fphere was at iirft four lines and an half 
 in diameter, and when it had been thirty-five 
 days and feven hours in the ftomach it mea'- 
 fured only a line and about a third; it pre- 
 ferved its form perfectly ; the fame may be 
 faid of its poliili; there was not a furrow, 
 nor an indentation, nor an afperity of any 
 fort upon the furface. This fmoothnefs is, 
 I think, a clear proof, that the ftomach of 
 this fpecies has no triturating power, other- 
 wife the globe would have fuflained fome 
 injury from the friction and impulfes of fo 
 many tin tubes as w^ere introduced into the 
 ftomach during its continuance there. 
 
 CLx. Let it not however be imagined, that 
 bones of a texture lefs compad: require fo much 
 time to be dilTolved; this was very far from 
 being the cafe. My falcon would eat a whole 
 pigeon at once, for birds of this kind when 
 O 4. they. 
 
zoo DISSERTATION IV. 
 
 they take any large prey, always fill themfelves 
 quite full, and then continue feveral days 
 without food. My falcon refufed the en^. 
 trails, the tips of the wings, and the beakj; 
 the reft he devoured with the utmoft greedi- 
 nefs. But no bone or flelh was ever vomited, 
 nor did any thing pafs out at the vent in 
 the form of bone or fleih^ the excrements 
 now, as well as at other times, conlifting of 
 a femifluid matter, partly white and partly 
 black. When dry it might be reduced to an 
 impalpable powder by rubbing between the 
 fingers. This animal therefore digefted not 
 only the flefh, but the bones of a pigeon, and 
 that in the fhort fpace of a day 3 for at the 
 expiration of this time it would eat a fecond 
 pigeon, 
 
 CLXi. While I was examining the man- 
 ner in which the falcon digefts bone, I was 
 flruck with a thought that had never occurred 
 to mq during the whole train of the foregoing 
 experiments ; it was to enquire whether the 
 gailric liquor belides bone is alf • capable of 
 dio-eftino- fome other animal fubftances, fuch 
 
 O CD ' ' 
 
 as the enamel of the teeth, the toughed; ten- 
 dons, and horn. With this view I enclofed 
 two incifors from the lower jaw of a fheep in 
 a tube, which the falcon retained three days 
 and fcvcn hours, Wherever the enamel did 
 
 not 
 
DISSERTATION IV. 201 
 
 not extend they were corroded and wafted, 
 but the other parts were uninjured, and as 
 brilHant as at firft. In four days and an half 
 longer continuance in the ftomach the fang 
 was nearly dillblved, but the enamel was per- 
 fed:ly found. The teeth were kept two days 
 more in the ftomach without the tubes, but 
 no further eifedt was produced ^ whence it 
 was^ neceiTary to infer, that the gaftric juice 
 of the falcon is incapable of diffolving the 
 enamel of the teeth ; a circurnftance which is 
 not very furpriiing, iince it differs from every 
 other ofleous fubftance. 
 
 CLxii. I have elfewhere obferved, that 
 birds of prey, and confequently falcons, vo- 
 mit the feathers of the birds which they 
 eat (lix); it is therefore evident, that the 
 gaftric fluid cannot digeft them. The fmell 
 emitted by burning feathers ftiews, that they 
 refemble horn in their nature ; it was there- 
 fore reafonable to fufpe(ft, that corneous fub- 
 ftances would not be diftblved in the fto- 
 mach, a fufpicion which was verified by the 
 event. Some pieces of ox's and fheep's horo 
 were as ufual concealed in flefh, and given to 
 the falcon. In a few days they were thrown 
 up entire and uninjured. I have remarked, 
 that the internal coat of the ftomach in gal- 
 linaceous fowls is not tender and yielding, 
 
 as 
 
202 b T S S E R T A T I N IV. 
 
 as in many animals, but firm and cartilagi- 
 nous (xxxv, xLvii, xLix, l). Having 
 frequently obferved, that when- burned it ex- 
 hales an odour very much like feathers and 
 horn, I fuppofed that it would in like manner 
 dudethe adiion of the gaftric fluid, which 
 really happened not only in the thick coats of 
 turkeys and geefe, but in the thin ones of 
 pigeons, blackbirds, and quails. When I 
 gave my falcon the whole ftomach of any of 
 thefe fowls, the other coats were foon: digef- 
 ted, but the cartilaginous remained entire. 
 
 In tendons the refult was different j for 
 my experiment I chofe an ox's tendo achillisy 
 one of the tougheft tendons that is to be found 
 in animal bodies. It was hung to dry in 
 fummer for feveral weeks, and thus became 
 fo hard, that a keen knife would hardly cut 
 it. However, the gaftric liquor of the falcon 
 diifolved it both when it was enclofed in 
 tubes, and loofe in the flomach. 
 
 CLxiii. Moft fhoeshave the upper leather 
 of calf-fkin, and the fole of ox's hide. Both 
 thefe fubilances are very readily digeiled by 
 Carnivorous animals when frefh : this at leafl 
 is the cafe with the falcon ,• but the contrary 
 happens when they have been tanned. Ano- 
 ther fact has warned me how cautious we 
 ought to be in forming general rules in phy- 
 
 fics* 
 
DISSERTATION IV. 203 
 
 fics. Who would not have concluded from 
 the lafl experiment, that every other kind of 
 leather is alfo indigeftible? Yet the reverfe 
 happened in {heep-lkin drefled, and dyed 
 yellow. Some lifts of it were enclofed in 
 tubes, and completely digefted in feven hours. 
 CLxiv. As I had found the gailric fluid of 
 other carnivorous animals incapable of digef- 
 ting vegetable matters, it was more than pro- 
 babje, that the fame thing would take place 
 in the falcon. I however thought, that it 
 would be proper to afcertain this point by ex- 
 periment, if for no other reafon, yet on ac- 
 count of the recent inftance of the uncertainty 
 of analogical arguments (cxliii). At the 
 fame time I was defirous of determining whe- 
 ther digeftion is the effect of the gaftric li- 
 quor folely, as it feemed more than probable. 
 The falcon could very well take fix tubes at 
 a time : four were filled with various vegeta- 
 ble fubftances, fuch as crumb of bread, chick- 
 peafe, flices of pears and apples ; in the fifth 
 and fixth were enclofed mutton and beef. 
 Upon thefe fubflancesthe efFeds of the gaf- 
 tric fluid were exadly the reverfe. The fleih 
 was totally diflx)lved in twenty-feven hours, 
 but the vegetables had undergone no altera- 
 tion. Two frefh tubes, containing in the 
 middle a bit of flefli, and at the fides mafli- 
 
 cated 
 
204 DISSERTATION IV. 
 
 cated bread and boiled peafe and chick-peafe, 
 decided the queftion ftill more clearly. The 
 vegetables were undiminifhed, but the flefh, 
 'which was furrounded by them, was entirely 
 deftroyed. Thus the incapability of the gaf- 
 tric juice to diflblve vegetables, and its ef- 
 ficacy on flelh, were fully proved. 
 
 CLXv. By means of little fpunges I pro- 
 cured this fluid fometimes when the ftomach 
 was empty, and at others when it contained 
 fome remains of the food, in which cafe it 
 was always turbid and full of heterogeneous 
 matters, of a cineritious yellow colour, and 
 had not much fluidity. When the ftomach 
 was empty it was fufficiently clear, without 
 any extraneous fubflance, had an interme- 
 diate colour between yellow and white, was 
 very fluid, and had a faltifh and bitter tafl:e. 
 With this I attempted experiments on di- 
 geftion out of the body, like thofe I have al- 
 ready fo often mentioned. The refult was 
 not different. I obtained the folution of va- 
 rious kinds of flefh by renewing the liquor 
 from time to time, and by applying a heat of 
 thirty deg. the common temperature of thefe 
 animals. With thefe precautions I moreover 
 caufed nearly the half of a fplinter of a bone 
 of beef, weighing forty-four grains, to be 
 diiTolved. 
 
 CLXVI* 
 
DISSERTATION IV. 205 
 
 CLxvi. Having made thefe experiments, 
 m my opinion the moffc interefling the fub- 
 je6t admits, my next bufmefs was to examine 
 the ilomach and cefophagus. However, three 
 hours before I killed my falcon, I fed him, 
 in order to fee what efFed: is produced upon 
 the food in the craw. It was in part in this 
 cavity, and part had defcended into the fto- 
 mach, where it had begun to be decompo- 
 fed. It was immerfed in the gaftric fluid, 
 and this incipient digeilion had the fame ap- 
 pearance as it has out of the body. The flefh 
 in the craw, even that which was upon the 
 point of paffing into the ilomach, was only 
 a little difcoloured; this circumflance fhews 
 that digeftion is performed only in the latter 
 cavity, and that in the craw the food is only 
 difpofed to be difiblved more readily. 
 
 CLxvii. When a ligature is made below 
 the pylorus, and air blown in at the top of 
 the cefophagus, this part of the alimentary 
 canal refembles a large intefline about five 
 inches long j a little more than halfway down 
 the cefophagus is dilated and forms die craw, 
 though we fhall find, that it has this name 
 improperly, if we compare it with the craws 
 of gallinaceous fowls, which lie at the fide 
 of the cefophagus, or rather without it; 
 whereas in the falcon the craw is a continua- 
 tion 
 
206 DISSERTATION IV. 
 
 tion of that cavity. If we invert and again 
 iniiate the oefophagus, and then examine it 
 in a flrong hght, or v^ith the microfcope, we 
 can perceive an immenfe number of glands 
 from the beginning to the flefhy fafcia, not 
 excepting the craw. If we blov/ in frefh air, 
 and obferve it again with the gkfs, we ihall 
 fee the glands, which are of an oblong ihape, 
 and project a little above the plane of the 
 cefophagus, each emit a drop of liquid; this 
 liquid is fo vifcid, that one of thefe drops 
 may be drawn out into a filament an inch or 
 more long; it is infipid to the tafle. The 
 greatefl part of the oefophagus, is full of thefe 
 glands, and is entirely membranous ; it only 
 becomes mufcular at the commencement of 
 the fafcia, which in the falcon, as well as 
 other birds, feems to confift only of number- 
 lefs follicular glands, and is above an inch in 
 breadth. Thefe follicles are cylindrical, and 
 are all conned:ed by a fine membrane -, they 
 have one of their extremities implanted in the 
 external, and the other in the nervous coat 
 of the fcomach: through the latter, the ex- 
 cretory dudls open and difcharge the fame 
 kind of whitifh ana vifcid matter that has fe- 
 veral times been ticicribed as belonging to 
 birds th:.thavt .;,>.■; : foll:.cles. Theie glands 
 and ioiiicleti abunaantly fupply the ftomach 
 
 with 
 
DISSERTATION IV. 207 
 
 "with fluid ; and though it is fometimes dtdi^ 
 tute of glandular bodies, yet a liquor con- 
 tinually poured into the cavity by exhalent 
 arteries, forms an addition to that which 
 comes from the cefophagus, as is evident from 
 the moifture which appears upon the fides 
 when they have been wiped dry feveral times. 
 CLxviii. The eagle on which my expe- 
 riments have been made, belongs to the fpe- 
 cies called by Mr. Buffon the common eagle, 
 becaufe it is found upon mofl of the high 
 mountains of Europe ; it was known to Ari- 
 ftotle, by whom it is called meaaina'etos, or 
 the black eagle Hence it has received the 
 denomination of Falco Melmtpetus from Lin- 
 naeus, who refers, with whatever propriety, 
 the eagle and falcon to one family. Though 
 fome naturalifts reckon two fpecies of the 
 common eagle, the brown and the black, I 
 fhould incline with Bufton and Arillotle to 
 fuppofe, that there is only one. The diiTer- 
 ence in colour may depend on the difference 
 of agej for we often fee animals of the 
 fame fpecies, but of different ages, differ in 
 polour. At the time I v/as in poffeffion of 
 my eagle I had ~an opportunity of feeing five 
 others^ four dead and prepared^ and one 
 living, in the poffeffion of the counts Caf- 
 tiglioni of Milan, two noblemen equally re- 
 
 markabje 
 
208 DISSERTATION IV. 
 
 jnarkable for politenefs of manners and fklll 
 in natural philofophy. Thefe animals all 
 differed from each other in colour, fome being 
 of a black more or lefs deep, and others of 
 a darker or lighter brown ; yet they agreed in 
 the effential characflers of the fpecies. They 
 were all nearly of the fame lize, fome what 
 exceeding that of a turkey-cock, their legs 
 and feet were covered with feathers, the nails 
 were black, the feet yellow, the bill blueilh, 
 and the bafe was covered with a bright yel- 
 low cere: fuch are the characters which, ac- 
 cording to the French naturalift, the brown 
 has in common with the black eagle. 
 
 CLxix. The ordinary food of my eagle 
 coniifled of live cats and dogs, when I could 
 procure them. It eaiily killed dogs much 
 larger than itfelf. When I forced one of thefe 
 inimals into the apartment where I kept the 
 eagle, it immediately ruffled the feathers on. 
 the head and neck, caft a dreadful look at the 
 dog, and taking a ihort flight, immediately 
 alighted on his back. It held the neck firm 
 with one foot, by which the dog was pre- 
 vented from turning his head to bite; and 
 with the other grafped one of the flanks, at 
 the fame time driving the talons into the 
 body ; and in this attitude it continued, till 
 the dog expired, in the midil of fruitlefs 
 
 outcries 
 
Dissertation iv* 
 
 209 
 
 outcries and efforts. The beak had been 
 hitherto unemployed, but it was now ufedfor 
 making a fmall hole in the Ikin, which was 
 gradually enlarged ; from this the bird began 
 to tear away and devour the ilefh, and went 
 on till it was fatisiied. I muft not omit ob- 
 ferving, that it never eat any fkin, or intef- 
 tine, or bone, except very fmall ones, fuch 
 as the ribs of cats and fmall dogs. Notwith- 
 ftanding this ferocity, and violent impetu- 
 oiity in attacking animals, it never gave any 
 moleilation to man. I, who was its feeder, 
 could fafely enter the apartment where the 
 bird was kept, without any means of con- 
 fining its movements, and beheld thefe af- 
 faults without dread or apprehenuon : nor 
 was the eao;le at all hindered from attackins: 
 the living prey I offered it, or rendered fliy 
 by my prefence. As it was not always in my 
 power, or at leafl in my will, to give it- liv- 
 ing food (for I had not always dogs and cats 
 at hand ; and gallinaceous fowls, v/hicli were 
 equally acceptable, were too expenfive) I fub- 
 ftituted fiefli which, though it was not fo well 
 relifhed, was not difagreeable. In general, 
 when it had flefh at will, it only made one 
 meal a day. I found, by weighing what it 
 eat, that thirty ounces of fielh ferved it one 
 day with one another. This fpecies of eagle 
 Vol. I. P is 
 
no DISSERTATION. IV,' 
 
 is provided with a very large crav^, which of 
 courfe is the firfi: receptacle of the food j and 
 when it was at liberty to eat its fill, this vif- 
 cus was generally diflended to a larger fize 
 than that of a turkey-cock full of grain. It 
 gradually contracts in proportion as the fleih 
 paffes into the jftomach, jufh as it happens in 
 gallinaceous fowls. 
 
 GLxx. Some of the iirft times I obferved 
 my eagle eat, I was ftruck by a phenome- 
 non, which conftantly recurred whenever it 
 took food. After it had fwallowed a few 
 mouthfuls, a thin ftreani began to flow from 
 each noftril, and to run down the upper fide 
 of the beak; at the end they joined, and 
 formed a large drop, which fometimes fell 
 on the ground, but generally pafTed into the 
 mouth, and was mixed with the food. This 
 drop was continually renev/ed by frefh fup- 
 plies from the noftrils, as long as the animal 
 continued to feed, and after that it ceafed to 
 appear. This liquor was of a fky-blue co- 
 lour, had a fait tafte, and was nearly as fluid 
 as water. But why does it flow only while 
 the eagle is feeding? and what is its ufe? 
 It flows at that particular time only, I fup- 
 pofe, becaufe the receptacle in which it is 
 contained is then only comprefl^ed ; and the 
 preflTure arifes from .the motion of the ^louth^ 
 
 ^ or 
 
DISSERTATION IV. 211 
 
 or the impulfs of the food againft the pa- 
 late, near which this receptacle hes. Of the 
 ufe of this fluid, I candidly own my total 
 ignorance. I fufpect, however, that as it is 
 mixed with the food, it ferves, like the fa- 
 liva, to moill:en it, and facilitate digeftion. 
 
 CLxxi. It is commonly thought, and the 
 opinion has the fand:ion of the heft natura- 
 lifts, that birds of prey, and efpecially eagles, 
 never drink. What 1 have obferved is, that 
 when the fpecies mentioned in the prefent dif- 
 fertation, were left even for feveral months 
 without water, they did not feem to fuffer the 
 fmallefl inconvenience from the want of it; 
 but when they were fupplied with water, 
 they not only get into the veffel, and fprinkle 
 their feathers like other birds, but repeated- 
 ly dip their beak, then raife their head, Jii 
 the manner of common fowls, and fwallow 
 what they have taken up ^ hence it is evident 
 that they drink. For the eagle it was necef- 
 fary to let the water in a large vefTel, other- 
 wife, by its attempts to drink, the veffel was 
 fure to be overturned. 
 
 CLXXI I. To colled into one point of 
 
 view every thing relative to digeftion, let us 
 
 examine another opinion, more immediately 
 
 conneded with our fubjed:. It is faid by * 
 
 P 2 feveral 
 
211 DISSERTATION IV, 
 
 feveral celebrated naturalifts and phyflolo- 
 gifts (a), that the eagle, when unable to pro- 
 cure flefh, will feed upon bread. To afcer- 
 tain this point, I made various experiments. 
 I iirft fet before the bird both ilefh and wheat- 
 en bread ; and finding that it ran towards the 
 ftefh, without even cajfting a look upon the 
 bread, I fet only the latter before it, and this 
 after a day's fali, when it muft have been 
 prefTed by hunger; I did not however attain 
 the end I had in view, and therefore kept it 
 failing for another day, but ftill to no pur- 
 pofe. When the bread was fet near it, it 
 would jufl look at it, and then turn its eyes 
 towards fome other objedt. When I had 
 prolonged the faft to the fourth day, the 
 bird ran towards me, as I opened the door of 
 the apartment, but with no other view than 
 to afk for food; I offered it a piece of bread, 
 but in vain, for, v/ithout even touching it, 
 it returned to the place where 'it ftood before 
 my coming in. 1 might have carried the 
 trial ftill further, but was afraid left the ani- 
 mal fhould fink under it. 
 
 CLXxiii. I therefore abandoned this mode 
 of experiment, and thought it would be bet- 
 ter to make the eagle fwallow fome bread; 
 
 {a) Biifon Hill. Nat. des Oifeaux. T. i. Halhr, T. 6. 
 
 for 
 
DISSERTATION IV. 2 1^ 
 
 for it would either be always thrown up, 
 and then it would be reafonable to infer, 
 that this was an unfuitable kind of food ; or 
 in cafe it fliould neither be vomited, nor 
 voided unaltered along with the excrements, 
 and the animal fhould Ihew no fymptoms of 
 uneafinefs, we muft conclude that it is di- 
 'geiledandaffimilated. I concealed the bread 
 in fome flefh, as I had done in my experi- 
 ments upon the falcon (clvii), and had re- 
 courfe to the fame expedient, whenever I was 
 defirous that my eagle ihould take tubes or 
 other fubftances . For though this ferocious 
 bird was exceedingly gentle towards me, who 
 was his feeder, yet it might have been hazard- 
 ous to irritate it; and that would have been 
 unavoidable, if I had opened the beak, and 
 thru ft bread down the throat by force. The 
 firft portion of bread which the eagle fwal- 
 lowed concealed by flefh, amounted to half 
 an ounce. Indigeftible bodies, fuch as fea- 
 thers, ufed to be thrown up eighteen, twen- 
 ty, or, at mofl, twenty-four hours after they 
 were received into the ftomach. But the 
 bread was not vomited in that period, or a 
 day longer ; nor did the excrements appear to 
 be altered or mixed with bread. I then gave 
 the animal a whole ounce, inftead of half an 
 ounce of bread, none of which was vomited 
 P3 Of 
 
214. DISSERTATION IV. 
 
 or voided unchanged at the vent. The fame 
 thing took place, when the quantity of bread 
 was increafed to fix ounces. My laft expe- 
 riment upon bread, was to fubftitute the crufl 
 inftead of the crumb ; but the refult was juft 
 the fame ; and notwithftanding the eagle had 
 . fhewn fo little appetite for this kind of food, 
 its health did not appear to fuffer. And I 
 was obliged to conclude, that this fpecies of 
 vegetable is digefted, and converted into real 
 nutriment, as well as animal matters. I 
 could not therefore refufe to accede to the 
 opinion of thofe, who aiiirm that eagles, 
 when much prelTed by hunger, will feed upon 
 bread, though mine would not touch it. 
 
 cLxxiv. But in what manner is bread di- 
 gefted in the ftomach of the eagle ? Is it by 
 the gaftric juices alone, or affifted by tritu- 
 ration ? Is any fach action exerted by it? In 
 Ihort, what is the immediate caufe of digef- 
 tion ? Thefe queilions are too clofely con- 
 nedied with the object of my enquiry, to be 
 palled over unnoticed. To begin then with 
 the iiril:. Tubes employed in my ufual man- 
 ner, v/ould determine the mode of digeftion. 
 And in the prefent cafe alfo, I obferved what 
 I had before obferved in fo many other ani- 
 mals, that trituration had no part in this 
 fun^^jon, and that it was the fole effect of 
 
 the 
 
DISSERTATION IV, 21^ 
 
 the gaftric juices. While the eagle retained 
 the tubes, a fpace that never ufed to exceed 
 twenty-four hours (clxxiii), the bread 
 which they contained was completely dif- 
 folved. If they happened not to remain long 
 fo in the flomach, the gaftric fluid had cor- 
 rodfed the bread, and given it a yellowifh co- 
 lour and a bitterifh tafte. Where the adion 
 of that fluid had been chiefly exerted, the 
 bread was changed into a gelatinous pafl:e, 
 which had nothing of its original tafte. 
 
 CLxxv. But the tubes fhewed, that the 
 gafliric liquor of the eagle diflTolves not only 
 bread but Parmefan cheefe. This power, 
 pofl^efl^ed by a bird properly carnivorous, of di- 
 gefliing a fubfl:ance fo different from fiefli, in- 
 duced me to try whether it is capable of pro- 
 ducing the fame effed: on other matters, and 
 particularly vegetables. But with refped: to 
 the latter, T did not find that the efficacy of 
 the gafl:ric fluid extended any further than 
 bread -, for feveral feeds of the cerealia, both 
 raw and boiled, did not appear to undergo any 
 alteration in the tubes, or when loofe in the 
 ilomach. It is fomewhat furp riling, that this ' 
 fhould be the cafe with wheat, when wheaten 
 bread is fo perfedlly digefl:ed. We fee at 
 leaftj that vegetables mufl: be triturated be- 
 P4 . fore 
 
2l6 DISSERTATION IV. 
 
 fore they can be digeiled by the eagle, as well 
 as by gallinaceous fowls (xlv). 
 
 The foregoing experiments, and the con- 
 curring obfervations of others (clxxii), 
 Ihev/, that fome animals, fuppofed to be 
 faiOAy carnivorous becaufe they live always 
 upon flefh, and are 'provided with the moft 
 formidable weapons for feizing and deflroy- 
 ing their prey, may yet, under certain cir- 
 cuniftances, change their difpofition and 
 manners, and become frugivorous. Thus 
 we read of animals naturally herbivorous, as 
 horfes, jfheep, oxen, gradually quitting their 
 ufual aliment, and learning to live upon 
 ileili (a) . I too can produce a recent inftance 
 in a young wood -pigeon, a fpecies of bird 
 which is univerfally known to feed upon any 
 thing rather than ficfh. By dint of hunger 
 I brought it gradually to relifh flelh ih 
 well that it refufed every other kind of fuf- 
 tenance, even grain, of which it is naturally 
 fo fond. Such changes, v/hether effed:ed 
 by defign or accident, will not excite the 
 fmaljefl degree of furprize in thofe who 
 know, that of the various kinds of food 
 ufed by man and animals, the gelatinous part 
 fupplies the nutriment, and that this exifts 
 alike in vegetables and animals (i>). The 
 
 (a) Halier, Phyf. T. ^. (^) lb. T. i. 
 
 example 
 
DISSERTATION IV. 217 
 
 example of the eagle among carnivorous, and 
 of the horfe, ox, pigeon among frugivorous 
 animals, do not hov^ever warrant us to con- 
 clude, that the former can be univerfally 
 converted by art or chance into the latter, 
 and reciprocally i for, on the other hand, 
 Reaumur's kite (cxvi) and my owls and fal- 
 con (cLvi, cLxiv, CLXvi) were incapable 
 of digefling vegetable fubflances {a)-, not 
 that thefe fubflances are unfit for affording 
 them nouriihment, but becaufe the gaftric 
 
 {a) Mr. Batigne, in his critical reflexions on the experi- 
 ments of Reaumur, pretends, that we are not to conclude, be- 
 caufe vegetables undergo no change in the ftomach of the 
 kite, that the gaftric liquor has no aftion upon them. He 
 fuppofes, that its inefficacy arofe from the vegetables not having 
 been prevjoufly mafticated. Premiere Rejlexion fur les Expe- 
 riences de M. de Reaumur. 
 
 But in this Mr. Batigne is miftaken. After I had compleated 
 my dilTertations on digeftion, I procured a kite of the fame 
 fpecles as that of Mr. Reaumur, and had it therefore in my 
 power to repeat and vary his experiments. I conllantly found, 
 that bread, grain, &c. were thrown up unaltered, both when 
 enclofed in tubes and loofe in the llomach, though they had 
 been previoufly well mafticated. This faft agrees with my 
 pbfervation on the falcon, of which the gaftric liquor could 
 not digeft mafticated crumb of bread. I will add, that an 
 owl, fed with chewed bread alone, died upon the fourth day ; 
 and upon diftTeflion, the bread was found in its ftomach undi- 
 gefted. It is therefore evident, that the incapability of the 
 gaftric liquor of fome animals to digeft vegetables does not 
 arife from the want of previous trituration or maftication, and 
 that this fluid is eflTentially unfit for diflbiving fuch fubftances. 
 
 liquor 
 
2lS DISSERTATION IV, 
 
 liquor is incapable of decompofing them, 
 and extradling the nutritious jelly. 
 
 CLXxvi. With refpecl to the fecond quef- 
 tion, whether the ftomach of the eagle tri- 
 turates its contents ? I think I have abundant 
 proof, that it poiTeffes no fuch power. Not 
 to mention the numerous tin tubes that re- 
 mained fo long in it without receiving the 
 llightefl: injury, I can fafely affirm, that I 
 could never perceive the frnaliefl: contuiion 
 upoa the grain (which I gave the bird naked 
 in order to try whether it could digeft it) 
 (cLxxv), whether raw or boiled j in which 
 cafe, the fmalleft compreffion or impulfe 
 would have left evident marks upon the fur-» 
 face. Thefe fafts are confirmed by the foU 
 lowing obfervation : I took fome ftrips, about 
 a line in breadth and three inches in length, 
 of exceedingly thin fheet lead, and rolling 
 them up in the form of a fpiral, introduced 
 them along with fome pieces of flefh into the 
 flomach of the eagle, in which they con- 
 tinued eighteen hours. The leail force would 
 have fufficed to deilroy the fhape of thefe 
 llrips, and being totally inelaftic, they would 
 preferve whatever alteration or diilortion they 
 might receive from prefTure or percuffion. 
 However, when thrown up they retained 
 
 ilieir 
 
DISSERTATION IV, 219 
 
 their fpiral form ; a clear proof that they had 
 not been fubjefted to violence of any kind. 
 
 Let it not however be fuppofed, that I 
 mean to exclude motion entirely from the 
 ftomach of the eagle. Having frequently 
 found foreign fubllances v^ithin the tubes, 
 and fixed in the perforations, I could not but 
 fuppofe, that they had been driven into them 
 by fome force, and this force could be no 
 other than the agitation of the ftorrjach, 
 which was either extriniical, and produced by 
 the adjacent vifcera, or the periflaltic move- 
 ment by which the food is expelled through 
 the pylorus. I only ailert, that the ftomach 
 of the eagle has no acflion capable of breaking 
 and triturating the aliment, as 1 think I have 
 abundantly proved. It is likewife clearly af- 
 certained, that the gaftric fluid is the efficient 
 caufe of digeflion by the expermients made 
 with bread and cheefe enclofed in tubes 
 (cLXxv) ; but this will be more fatisfaftoiily 
 ihewn by the experiments relative to the di- 
 geftion of animal fubilances, which I am now 
 to relate. 
 
 CLXXV II. The firft thing I wiflied to know 
 was what changes fiefh undergoes in the 
 craw, and I had therefore to contrive' a me- 
 thod of getting it back at oleafure. Had this 
 bird been of the fame gentle and peacef d dif- 
 
 pofition 
 
220 DISSERTATION IV, 
 
 pofition as gallinaceous fowls, this would 
 eafily have been eiFeded; for I fhould have 
 had only to prefs the portion of fleih that lay 
 higheil in the craw upwards with my thumb 
 and fore-finger, and by a continuance of this 
 manoeuvre lliould have brought it out at the 
 mouth. By this fimple contrivance I have 
 often examined grain from the craw of fowls, 
 pigeons, and fuch birds; but the ftrength 
 and ferocioufnefs of the eagle altered the cafe 
 totally.- After much refledtion, I thought 
 of an artifice efi^entially the fame as that adop- 
 ted for gallinaceous birds. I gave my eagle 
 only three or four pieces of flefh, of which 
 the lafb was tied in the iliape of a crofs with a 
 fine packthread three or four feet long. The 
 eagle, prefied by hunger, devoured the fle£h 
 greedily without regarding the firing, of 
 which the greater part hung out of the 
 mouth ; nor did the bird make any efforts to 
 fwallow or throw it up. When I thought it 
 time to examine the piece of fleih I pulled the 
 firing forcibly, and the eagle, without grow- 
 ing enraged, opened its beak and allowed me 
 more room for recovering the firing, and by 
 confequence the fiefh that was faflened to it. 
 Sometimes I ufed confiderable force, but did 
 not fucceedj probably on account of the flefh 
 being got too low down in the crawi in this 
 
 cafe. 
 
DISSERTATION IV. 221 
 
 cafe, to free the eagle from the inconvenience, 
 I cut the ftring clofe to the beak^ and gave 
 it fome flefli, which carried dov^n the pack- 
 thread before it into the ilomach, whence it 
 was thrown up in a Ihort timej but I have 
 more frequently fucceeded in drawing up the 
 flefh, and thus obtained an opportunity of 
 examining it at leifure. I never could find, 
 that the craw or its juices were capable of di- 
 geftion. Its weight was nearly the fame af- 
 ter it v/as drawn up as before it was fwallow- 
 ed, nor did it feem as if it was upon the point 
 of being digefled ; the furface was only a 
 little tenderer, and had loft its rednefs; it 
 was penetrated with a fluid that was neither 
 fait nor bitter, but quite inlipid. Flefh 
 therefore is not digefted, it is only macera- 
 ted in the craw of the eagle, as grain and 
 grafs in the craw of gallinaceous fowls. 
 
 CLXxviii. We mufl: therefore conclude, 
 that the whole procefs of digeftion begins 
 and ends in the ftomach. If then it was of 
 xonfequence to know what happens to flefh 
 in the cravv^, it is of much greater impor- 
 tance to obferve how it is altered in the flo- 
 mach. But as the expedient to get the flefh 
 back, mentioned in the lafl paragraph, would 
 not be of any fervice here, I contrived ano- 
 ther, which anfwered wonderfully well. I 
 
 enclofed 
 
222 DISSERTATION IV. 
 
 enclofed the fiefh in little nets with fmall 
 mefhes, which were generally vomited empty; 
 but in fome there were coniiderable remains 
 of flelh. The pieces I ufed for thefe expe- 
 riments were globular, and the remains al- 
 mofc always retained that figure. They were 
 thoroughly impregnated with gaftric liquor, 
 and had both a bitter and fait taile. The 
 furface was gelatinous; when this was re- 
 moved, the fibres were eafily diflinguifhable, 
 but were as tender as if they had been boiled, 
 and the colour was changed to a reddiih blue. 
 When this ftratum of tender fibres was taken 
 off with a fharp knife, that below was firmer 
 and lefs difcoloured, and at the center the 
 flefh did not appear to have undergone an^ 
 change either in its confiflence or colour. It 
 is needlefs to obferve that thefe experiments 
 prove, that the gailric fluid diffolves flefh. 
 The permanency of the globular form clearly 
 fhews, that trituration does not take place, 
 but the whole cfFed:, to repeat it once more, 
 is produced by the gaftric liquor, "which adts 
 upon the furface, and diffolves one ftratum 
 after another till the whole is confumed, as 
 we have {qqh the famx liquor of other animals 
 ad: as well upon flefli as other fubflances 
 (lxv, ci). 
 
 CLXXIX. 
 
DISSERTATION IV. 223 
 
 CLxxix. This lafl experiment rendered it 
 fuperfluous to try, whether the gaftric fluid 
 of the eagle will dilTolve flefh enclofed in 
 tubes* Taking this for granted, I proceed- 
 ed to enquire, whether digeftion would be re- 
 tarded in proportion to the toughnefs of the 
 flefh with which they were filled. With 
 this view fome of the liver, of the mufcular 
 fieih of the thigh and heart, a bit of the 
 brain, and a piece of tendon were enclofed 
 in fo many diftind: tubes. They continued 
 thirteen hours in the ftomach, and the gaf- 
 tric fluid a6led upon them jufi: as I had ima- 
 gined it would. The tube containing the 
 piece of brain was quite empty -, of the liver 
 only a very fmall part remained ; the refiduum 
 of the mufcular fielh of the thigh was more 
 confiderable ; that of the heart was ftill 
 greater; but of the tendon there remained 
 moft of all. Thefe remains of flefli and ten- 
 don had the fame appearances as I had ob- 
 ferved in the balls of flefh that were introdu- 
 ced into the flomach without tubes. The 
 gelatinous matter on the furface, the tender- 
 nefs of the fibres lying immediately below, 
 and the confiflence of thofe at the center 
 clearly fhewed, that the gaflric juices had 
 ad:ed upon the flefh enclofed in tubes jufl: 
 
 as 
 
224 -DISSERTATION IV. 
 
 as upon what was left loofe in the ftomach 
 
 (CLXXVIIl). 
 
 CLxxx. My next wifh was to know whe- 
 ther its adlivity would be impaired or de- 
 flroyed by pafling through linen before it got 
 to the fleih. With this view, two pieces of 
 the fame tendon and heart, equal in lize to 
 thofe employed in the foregoing experiment, 
 were put into two linen bags, and given to 
 the eagle ; in eighteen hours they were thrown 
 up. At firil: the fides of the bags were dif- 
 tended by their contents, but now that which 
 contained the flefh was a good deal collapfed -, 
 for half of it was dilTolved: the other had 
 more of its original dillenlion ; for not above 
 one-third of the tendon was confumed. Upon 
 comparing together the diminution of the 
 fubftances in the bags and in the tubes 
 (cLxxix), I found, that in the former cafe 
 it was lefs, notwithftanding the bags con- 
 tinued eighteen hours, and the tubes only 
 thirteen. It is therefore evident, that the 
 linen is a greater obftacle to the ad:ion of the 
 gailric liquor than the tubes. 
 
 CLxxxi. From my experiments upon 
 crows (lxvii) it was obvious to conjecture, 
 that as more folds of linen were wrapped 
 round the animal fubftances, the action of 
 the gailric liquor would be ftill lefs confi- 
 
 derable. 
 
DISSERTATION IV. 225 
 
 derable. I therefore gave the eagle fix bags, 
 containing each an equal portion of beef^ 
 the iiril was fingle, the fecond double, and 
 fo oil. The bird retained them twenty-three 
 hours, when they were all vomited at once, 
 as ufually happened to tubes and other indi- 
 geftible matters, which when fmall are 
 thrown up all at once, and when large one 
 immediately after another. The two firft 
 bags were empty, and the remainder of flefh 
 in the four others were larger as the folds 
 were more numerous, fo that in the fixth it 
 was the largeil of all . It had however under- 
 gone fome diminution, and the gaftric fluid 
 had therefore begun to diflblve it, notwith- 
 flanding the lix folds, as appeared from its 
 being impregnated with it, and from the ten- 
 dernefs of the fibres, and the change of co- 
 lour on the furface. My next wifh was to 
 try whether the juices of the ftomach were 
 capable of penetrating through a denfer fub- 
 ftancej I therefore fubHituted cloth in the 
 ftead of linen> and having put lixty-eight 
 grains of beef in the bag, tied fome pack- 
 thread very tight round its neck. In four- 
 teen hours it was vomited, and being appa- 
 rently of the fame fize as at firfl, it was re- 
 turned immediately into the ftomach, where 
 it continued twenty-two hours longer. J^ 
 Vol, I, Q^ now 
 
226 DISSERTATIOTI IX* 
 
 now found that the cloth, notwithftanding 
 its clofe texture and great thicknefs which 
 amounted to four-fifths of a line, was tho-^ 
 roughly penetrated by the gaftric liquor. The 
 ilefh was alfo moift with it, and appeared, 
 upon being weighed, to have loft twenty- 
 feven grains. Twenty-feven grains had then 
 been diflblved, and as no veftige of them 
 was to be feen in the infide of the bag, it 
 was evident that they muft have pafTed out 
 through the pores of the cloth, and eonfe- 
 quently that the gaftric fluid is capable of 
 reducing flelh to particles of the utmoft te- 
 nuity. 
 
 CLXXXii. I have before obferved, that 
 the eagle devours the fmaller bones of dogs 
 and cats along with the fiefli (clix). When 
 I gave that in my pofleffion a bird, it would 
 alfo fwallovv all the bones, except thofe of 
 the extremities; and as they were not thrown 
 up, there was good reafon for believing that 
 they vvere digeilied, a circumftance that ex- 
 actly agrees with my obfervations on falcons 
 and various other birds (xcviii, cxLvii, 
 CLiv, CLviii). But greater certainty was. 
 defirfeable, and this I endeavoured to attain in 
 the following 4iianner : two pieces of the rib 
 of a fmall dog, each about two inches long, 
 were tied together, and two thigh bones of 
 
 acock; 
 
DISSERTATION IV. 227 
 
 t cock; this packet was retained twenty- 
 three hours; but the bones were very much 
 altered during that time. The two pieces of 
 rib were reduced to the thinnefs of a mem- 
 brane; the leafl violence was fufficient to 
 break them ; they were totally inelaftic, and 
 had loft all their marrow. The two thieh 
 bones now refembled tubes of parchment; 
 they were ealily compreffible, and when left 
 to themfelves recovered their {hape, and af- 
 ter being bent they would become ftrait 
 again. Upon one of the tibise thus wafted 
 and altered there was a very lingular appear- 
 ance; about one-fifth v/as ftill ofteous, but 
 tender, yielding to the touch, and much at- 
 tenuated. It is therefore apparent, that the 
 juices of the ftomach are capable of dilTolving 
 bone, and that in a fliort fpace. I was un- 
 willing to throw aiide thefe bones thus redu- 
 ced aimoft to nothing, and therefore tyin? 
 them up in a bundle I gave them again to the 
 eagle, in order to fee whether they would be 
 entirely diffolved, or, like a caput mortuum, 
 retain their membranous appearance; but 
 being apprehenfive that this could not be fo 
 well afcertained if they were naked in the 
 ftomach, I enclofed them in a tube. It was 
 retained thirteen hours, and upon examina- 
 tion was entirely empty ; it was therefore 
 Q^ reafonable 
 
228 DISSERTATION IV. 
 
 reafonable to infer, that the gaftric fluid had 
 now completed the folution. 
 
 CLXxxiii. The readinefs with which thefe 
 bones, of a texture by no means tender, were 
 digefted, led me to fuppofe, that the hardeft 
 would not reiift the action pf the gaftric li- 
 quor. To determine this, I began by giving 
 the eagle a fphere worked at the lathe out of 
 an ox's thigh bone, of the fame diameter as 
 that which had been ufed for the falcon, and 
 taken from the fame individual ( c l ix) . Upon 
 that occafion I obferved, that the falcon did 
 not dillblve it during the long fpace of thirty- 
 five days and feven hours. In the prefent 
 cafe it was every day vomited, and immedi- 
 ately returned, and in twenty-five days and 
 nine hours it was completely digeiled. The 
 eagle is then capable not only of digefting the 
 hardeft bones, but of digefting them in a 
 Ihorter fpace than fome other birds of prey. 
 In the account of my experiments on the fal- 
 con I remarked two things, firft, that its di- 
 ameter decreafed without any change of ftiape 5 
 fecondly, that the texture was not foftened 
 during the whole time (clix). The firft 
 phasnomenon occurred on this occafion, the 
 fphere not only maintained its figure, but 
 continued as fmooth as when it came from the 
 lathe. But with refpe(fl to the fecond cir- 
 
 cumftance,, 
 
DISSERTATION IV. 229 
 
 <:umfl:ance, there was a wide difference ; for 
 iiotwithflanding the hardnefs of the bone, the 
 furface was fo foft every time it was thrown 
 up, that it was eafy to pare off with a knife, 
 ilices as flexible as cartilage. The gaftric 
 fluid then of the eagle, befides diffolving the 
 fuperficial ftrata, had penetrated into the lub- 
 ftance of the bone and foftened it; an effedt 
 which that of the falcon is incapable of pro- 
 ducing. Penetrating, however, as it is, it 
 has no a(5lion on the enamel of the teeth, any 
 more than that of the falcon (clxi). 
 
 CL XXXIV. We have feen how much 
 more fpeedily the gaflric fluid of the eagle 
 digeils bone than that of the falcon; the 
 fame obfervation may alfo be extended to 
 flefh. The former bird required thirty ounces 
 a day (clxix), the latter was fatisiied with 
 twelve, and fometimes with ten. The gaf- 
 tric liquor of the one then diffolves, in an 
 equal fpace of time, three times as much as. 
 that of the other, and confequently the ra- 
 pidity of digeflion in one is triple of that in 
 the other. I fliould however, upon mature 
 reflecflion, be inclined to conflder this greater 
 rapidity as apparent, rather than real. The 
 eagle indeed digefls three times as much flefh 
 as the falcon in the fame time, but then the 
 gaflric juice of the former is far more copious 
 0^3 than 
 
a30 DISSERTATION IV. 
 
 than that of the latter ; aud if we fuppofe it 
 to be three times as much, a fuppolition veiy 
 admiffible, as we fhall foon fee, every third 
 part will dilTolve a quantity of flefh equal to 
 that dilTolved by the whole gallric fluid of 
 the falcon. The fame remark is applicable 
 to other animals. With how fmall a quan- 
 tity of flefh is the little owl fatis fied in com- 
 pariibn with the eagle, and confequently 
 how inconflderable is the folution efFed:ed by 
 the gaftric liquor j but then how trifling 
 does the quantity of that liquor appear when 
 we conflder that of the eagle ! The fame re- 
 fle(5lion will recur when we compare a lamb 
 with an ox, or a hare with a horfe. But 
 with refped: to the cafe in quellion, I could 
 not devife any more effecftual means of de- 
 termining whether the greater efte<Sl produced 
 by the juices of the eagle arofe from the greater 
 abundance folely, or in part alfo from its fu- 
 perior eflicacy, than to give each of theie 
 birds a fmall quantity of flefh at the fame 
 time, and obferve what would be the event. 
 It would either be digefted by one as foon as 
 by the other, and then the fame efficacy mufl 
 be afcribed to both ; or elfe the eagle would 
 digeft it more fpeedily than the falcon, in 
 which cafe the fmall quantity of flefh would 
 j^ot allow us to fuppofe, that the fluid of the 
 
 falcon 
 
DISSERTATION 1V« 2^1 
 
 falcon could not fo foon diffolve it on ac- 
 count of" its being in finaller quantity, and 
 we £[:iould therefore be obliged to conclude, 
 that it is lefs capable of digefting flefli than 
 that of the eagle. This experiment I have 
 often repeated, not only upon the falcon and 
 eagle, but upon the two fpecies of owlsalfo, 
 .and crows, and the refult has been, that 
 fometimes one and fometimes another of thefe 
 birds has digefted the fmall portion of flefh 
 fooneft i nor did the eagle at all diftinguiih 
 itfelf above the reft. As the difference of 
 time was very inconfiderable, it may be over- 
 looked, and we may fafely fuppofe, that the 
 digeflive power of the gaflric fluid is nearly 
 equal in thefe feveral fpecies, and confequent- 
 ly that the eagle has no advantage over the 
 refl. It may however be objected, that with 
 refped: to bone, at leafl, the prerogative of 
 digeflion belongs to the eagle in preference 
 to the falcon, which takes above thirty-fiv& 
 days to diflblve the fame fphere which the 
 eagle dilTolves in lefs than twenty-lix (clix, 
 CLxxxiii). I c^n adopt this opinion with- 
 out much relu(5tance, lince there is no in- 
 confiflency in fuppofmg, that two menflrua 
 may agree in the eifedis they produce upon 
 one body, but differ with refpedl to another ^ 
 nay, this idea is confirmed by the facility 
 Q^ 4 with 
 
232 DISSERTATION IV. 
 
 with which the gafliric fluid of the eagle pe- 
 jietrates into and foftens bone, a quaUty which 
 that of the falcon does not pofTefs in the 
 fmalleft degree (cL IX, clxxxiii). 
 
 CLxxxv, Let us now proceed to Ihew 
 the great abundance of gaflric fluid in the 
 eagle in comparifon with fmaller birds, fuch 
 as the falcon, the owl, &c. To procure this 
 fluid I was not obliged, as in other animals 
 (lxxxi), to ufe fmall fpunges. The eagle 
 fupplied me fpontaneoufly. Very foon after 
 it was in my poflTeffion 1 was aware, that along 
 with the tubes a quantity of gafl:ric fluid was 
 thrown up, fo that the floor was often quite 
 wet with it. It was eaiy to devife a method 
 of catching it before it fell on the ground]; 
 for the eagle rarely moved from the place, 
 where it took food, and therefore generally 
 vomited the tubes on the fame fpot. Upon 
 this I fet a large glafs vefl^el, and thus was 
 enabled to collect a large quantity of liquor, 
 which generally exceeded three-fourths of 
 ^n ounce a day on thofe days when the vo- 
 miting took place, a quantity which I could 
 not even hope to procure from all the above^ 
 mentioned birds of prey taken together. 
 What T obtained in this manner was extreme- 
 ly well finite d to my purpofe, not being adul- 
 terated 
 
DISSERTATION IV. 233 
 
 tefated with heterogeneous matters; for it 
 was always thrown up when the ftomach was 
 empty, as I knew by the avidity which the 
 animal fhewed for frefh food at this time. 
 Its fmell, which I cannot defcribe, is not 
 difagreeable, but very much refembles that 
 emitted by the gaflric liquor of other birds 
 of prey. If we except the colour, which in 
 the others is yellow, but in the eagle cineri- 
 tious, it exhibited the fame qualities, whe- 
 ther we confider the bitter and fait tafte, the 
 turbid appearance, which is almoft infepara- 
 t)le from the one as well as the other, its 
 iluidity, which comes near to that of water, 
 its difpolition to evaporate, or the total want 
 of inflammability. 
 
 CLxxxvi. The gaflric juice of the eagle, 
 as well as that of other animals, is capable 
 of digefting animal and vegetable matters 
 out of the body. It has even produced 
 an incipient folution of bone, and an almofl 
 complete one of cartilage ^ but the experi- 
 ments were made in a confiderable heat ; for 
 otherwife little or no folution took place, and 
 the gaflric juices of the eagle now only 
 prevented thefe fubflances from becoming 
 putrid. ^ 
 
 Upon this fluid I made two experiments, 
 to which I had not fubjea;ed that of other 
 
 animals. 
 
DISSERTATION. JV» 
 
 animals. On a very cold day in winter I ex- 
 pofed a fmall quantity in a glafs, on a win-.. 
 dow, along with two other glalTes contain^ 
 ing water, in one of which was difTolved a 
 quantity of common fait fufficient to give it 
 a Wronger tafte than the gailric iluid had^ 
 The thermometer fet befide the glaffes flood 
 at 5 deg. below o {a). Of the three liquors 
 the iirfh that was frozen was the common 
 water, the next was the fait water, and the 
 iaft was the gailric fluid. When I carried 
 them into my apartment, where the tempe- 
 rature was three and an half deg, above o, 
 the firft that thawed was the gaflnc fluid, 
 next the brine, and lailly the water. It muft 
 therefore be fuppofed, that this gallric juice 
 is capable of reiifling cold more than com- 
 mon water. As this cannot be attributed to 
 its faline principle alone (otherwife it would 
 have been fooner frozen than the brine), it 
 is necefTary tb admit fome other principle ca- 
 pable of retarding congelation, whether fpi- 
 rituous or oily, or of whatever other nature '^ 
 and the clofe analogy fubfifting between the 
 gaflric liquor of the eagle and other animals 
 renders it highly probable, that a like princi* 
 pie exifls alfo in them. 
 
 {a) Twenty and three -fourths, Fahren. 
 
 My 
 
DISSERTATIOK IV. 235 
 
 My fecond experiment was the following : 
 having learned from Mr. Levret {a), that 
 the juices of the ftomach have the power 
 of diffolving the inflammatory cruft of the 
 blood, I procured fome of it from a pleuritic 
 patient, and immerfed it in a phial of the 
 gaftric fluid of the eagle. The event com- 
 pletely anfwered my expectation : for in two 
 days and a half, in a temperature of 1 5 deg. 
 the crufl was entirely diflx)lved, and convert- 
 ed into a liquid of a dark hue : this can oc- 
 cafion no furprize; for if the gaftric fluid 
 can diflx>lve animal fubftances of a far harder 
 texture, fuch as mufcle, cartilage, bone, out 
 ©f the body, it will much more ealily pro- 
 duce the fame effedt upon the inflammatory 
 cruft of the blood. 
 
 CLxxxvii. Here the death of the eagle, 
 which happened fomewhat more than five 
 months after it had been in my pofl^eflTion, 
 put a fl:op to my experiments. I however 
 refolved to examine the parts that are fituated 
 internally, the only enquiry relative to di- 
 gefl:ion that could now be made. During 
 the difledion I found, that this individual 
 was a female 5 for there were many eggs, 
 fome fmaller and fome bigger, attached to 
 
 {a) j\xt d'Accoucher. 
 
 the 
 
 « 
 
2^6 DISSERTATION IV. 
 
 the ovarla. It was confequently much larger 
 and llronger than the male of the fame fpe- 
 eies J for it is a conflant obfervationj, that the. 
 male in birds of prey is about a third fmaller 
 and weaker than the female ^ whereas, in 
 other clafTes, the male exceeds the female in 
 both thefe refped:s {a). The intellinal canal 
 was full of the ufual folds and convolutions ; 
 when ftretched out at full length, it was 
 about fifty-nine inches long from the begin- 
 ing of the duodenum to the end of the 
 rettum. There is a double pancreas, and 
 each portion is perfecllv diftin6t and feparate j 
 but the fame obfervation has been made upon 
 other animals. Both thefe glands are of a 
 biueifh flefh-colour, of an oblong fliape, and 
 fmaller toward the end. There is a differ- 
 ence in the lize, one being an inch and an 
 half in length, whereas the other is only 
 an inch and three lines. They lie parallel, 
 ^re fituated about five inches from the pylo- 
 rus, and ilretched along befide the duode- 
 num, one on each fide, and are attached by 
 cellular fubftance. At about fix inches dif- 
 tance from the pylorus an apparent cord, 
 tinged internally with a dark azure-colour, 
 Jies upon the duodenum. If we trace it 
 
 , {a) BuiFon. 1. c. T. ;. 
 
 •* back- 
 
DISSERTATION IV. 237 
 
 backwards, we find it gradually enlarged, 
 and at lafl inferted in the gall-bladder, which, 
 in fhape and fize, refembles a wood-pigeon's 
 egg. From what has been before obferved 
 (lxxxiv, cxv), it is eafy to guefs the ufe 
 of this cord ^ it is the dud: through which 
 the bile paffes from the bladder into the duo- 
 denum. If the gall-bladder be prefTed gently 
 the cord becomes immediately tinged with a 
 deeper azure, and the liquor runs into the 
 duodenum: if we open that gut, the upper 
 part is found tinged with a greenifh azure 
 bile. Upon wiping it away, the entrance of 
 the du6t becomes vifible, and frefh bile runs 
 into the duodenum when the prefTure is re- 
 newed. The gall-bladder lies towards the 
 right lobe of the liver, but is not covered by 
 it. The bile is rather denfe, and has a ftrong 
 bitter tafte. 
 
 CL XXX VII I. When I infpeded the fto- 
 mach I was aftonifhed at its fmall fize, when 
 compared with the crop. The latter cavity 
 is capable of containing thirty-eight ounces 
 of water, whereas the fi:omach can fcarce 
 hold three. V/e muft therefore fuppofe, 
 that the great quantity of flelh devoured by 
 this voracious bird pafTes flowly from the 
 craw to the fi;omach, in propprtion as it is 
 
 digefled 
 
2^$ DISSERTATIOK IV. 
 
 digefted and expelled into the inteflines* 
 Hence it is eafy to compreliend how a fingle 
 meal may ferve feveral days -, for a large prey 
 will be equivalent to feveral fmaller ones. I 
 cannot give a better idea jof the fhape of the 
 ftomach, than by comparing it to a man's leg 
 and foot. At the point of the toes lies the 
 pylorus, the foot refembles the bottom of 
 the ftomach, and the leg the upper part. The 
 flefhy fafcia full of follicular glands, which 
 in other birds, whether granivorous or car- 
 nivorous, is fituatedjuft above the flomach, 
 in the eagle is contained within its cavity, 
 and makes up the fuperior and larger half. 
 The internal coat of this fafcia is fo thin and 
 delicate, that it tears upon being ilightly 
 rubbed with a cloth. We come next to the 
 nervous coat full of an infinite number of 
 pores, out of which, when prelTure is made> 
 iffues a vifcid, cineritious, and infipid liquor. 
 Upon removing this coat thefe pores appear 
 to be the excretory dudts of the follicles, of 
 which one extremity adheres to this, and the 
 ether to the mufcular coatj next the laft 
 mentioned lies the external coat, which ap- 
 pears to be membranous. The glands are 
 cylindrical, a line and one-fourth long j they 
 are tied together by a number of membran- 
 ous 
 
Dissertation iv. 239 
 
 t3us filaments. This Ihort defcription fliews 
 the entire refemblance between the fafcia of 
 the eagle and other birds. The four coats 
 pals on to the inferior part of the ftomach, 
 and extend to the pylorus. The mufcular 
 coat feemed to merit a diilin<ft examination. 
 It confifts of two ftrata. That which lies 
 next the nervous coat is formed by flelhy faf- 
 ciculi, of a lively red colour, running in ^ 
 longitudinal diredion. The other is of a 
 paler red colour, and the fibres interfedl thofe 
 of the other coat at right angles, and of 
 courfe run tranfverfely. Notwithftanding 
 their nearnefs they are perfedly feparatefrom 
 each other, like the rings of certain worms, 
 particularly of the earth-worm, which they 
 moreover refemble in their biueifh fleih-co- 
 lour. Thefe two thin ilrata doubtlefs caufe 
 the various motions of the ftomach, of which 
 the efFed:s have appeared in fome of the ex- 
 periments related above. This coat is one- 
 fourth of a line in thicknefs ; upon the faf- 
 cia it is thinner, and I could only find the 
 tranfverfe ftratum ; v/hence it feems probable, 
 that the motion of the ftomach chiefly takes 
 place in the lower part, which has no, at 
 leail no apparent, glands ; but as a thin tranf- 
 parent Jiquor oozes out on flight prellure, as 
 
 in. 
 
24«5 DISSERTATION IV. 
 
 in the flomach of birds belonging to the fame 
 ckfs (xciii, CLi, CLx-vii), we muft con- 
 clude, that it abounds in fmall arteries, which 
 perform the office of glands ^ 
 
 CLxxxix* The death of my eagle hap- 
 pened a few hours after it had taken food, 
 but I could not difcover the caufe^ Moil of 
 the flefh was in the craw, and a little only had 
 defcended into the ilomach. It lay at the 
 bottom near the pylorus, but fhewed no ap- 
 pearance of being digefled, whether on ac^ 
 count of the morbid condition of the ani- 
 mal, or becaufe it had but juft fallen into 
 the ftomach* It was foftened by the gaftric 
 juices, that tailed very bitter, which, as well 
 as its yellow hue, was owing to the regurgi- 
 tation of the bile into the flomach, and thefe 
 qualities were more apparent in the vicinity 
 of the pylorus. The flefh in the crop was 
 not altered in conliflence or colour, except 
 that which lay in contad: with the fides ; this 
 was a little difcoloured and fomewhat ten- 
 derer than at firfl, circumftances that agree 
 with what was faid at the clofe of the 
 CL XXV nth paragraph. 
 
 Upon emptying, inferting, and then inflat- 
 ing the craw, the furface was covered with a 
 multitude of fmall drops, which, when united 
 
 by 
 
DISSERTATION IV. 24 T 
 
 by fome flat body paiTing over them, formed 
 a fluid as tranfparent and thin as water; it 
 feemed to have a bitterifh favour. Upon in- 
 fpediing the places whence the drops arofe, 
 they feemed fo many points, which the mi- 
 crofcope fliewed to be minute pores. Hence 
 it appeared, that every part of the crop a- 
 bounds with thefe perforations, which I had 
 no helitation in fuppoflng to be the excretory 
 duifts of a multitude of glands lying between 
 the coats, as I had alfo found in the craws 
 of other birds (xlix, l, clxvii). In 
 fearch of them I difl^e(5led away the internal 
 coat, which, in thicknefs and ftrength, re- 
 fembles the nervous coat of the ftomach, of 
 which perhaps it is a continuation. But 
 neither in the fubfl:ance, or between it and 
 the mufcular coat, did I find any appearance 
 like glands. All that I could perceive, when 
 I held the internal coat againfl; the light, was 
 the pores already mentioned, that looked like 
 lucid points. Nor did the mufcular or the 
 external coats, which laft is membranous, 
 contain any glandular body. I was therefore 
 obliged to conclude, that the fluid oozing out 
 in the form of numberlefs drops upon the in- 
 ternal furface of the craw is fecreted^ not 
 by glands, but by arteries too fmall to be 
 Vol. I. R vifible. 
 
54* DISSERTATION tV. 
 
 vifible. The reft of the oefophagus is iTfo 
 full of thefe pores, an4 the fame fluid iflues 
 out from them ; no fmall part of which muil 
 run into the cavity of the ftomach, and con- 
 tribute to the formation of the gaftric men-r 
 ftruum, which is compofed of this and the 
 . proper fluid of the fl:omach^ pf the bile, and 
 the pancreatic juice. 
 
 D I S. 
 
r 243 1 
 
 DISSERTATION V. 
 
 THE SUBJECT OF DIGESTION IN ANIMALS 
 WITH MEMBRANOUS STOMACHS CON- 
 CLUDED. THE CAT, THE DOG. MAN. 
 WHETHER DIGESTION TAKES PLACE 
 AFTER.DEATH, 
 
 CXC. nPHE great difficulty with which 
 cats are made to fwallow tubes, 
 and the faciUty with which they vomit them, 
 hindered me from making experiments upon 
 this irritable animal in the manner I could 
 have wiflied. Among, however, a vaft num- 
 ber of unfuccefsful trials I have ojice or twice 
 fucceeded, and thus have been enabled to il- 
 luftrate one chief obje6l of my enquiries, I 
 mean the efficient caufe of digeftion. I have 
 ufed every effon to oblige this animal to 
 fwallow bread and ilefh, their ordinary food, 
 R z enclofed 
 
244 D I S S E R T A T 1^0 N V. 
 
 enclofed in tubes, and in two individuals, one 
 an adult, and the other a young one, have 
 forced them into the flomach. Both were 
 killed, one after having retained tubes filled 
 with flelh nine, and the other with bread five 
 hours. The former were found near the py- 
 lorus. The outfide was wet with gaftric 
 juice, the grating at the ends was entire, as 
 alfo were the tubes, upon which there did 
 not appear any bruife or other injury. Two 
 of the tubes were empty, the third contained 
 a bit of the fize of a lentil-feed macerated in 
 the gaftric fluid. The center preferved the 
 colour, confifhence, and tafte of flefh ; the 
 furface was changed into a greyifh jelly of a 
 bitterifh tafte. 
 
 The tubes containing bread having re- 
 mained only five hours in the flomach, were 
 not empty. It had been chewed before it 
 was put into the tubes, by which it was 
 moulded into the fhape of cylinders fix lines 
 and three-fourths long. Thefe cylinders 
 were not completely diiTolved, a portion about 
 four lines long remaining tov/ards the middle 
 of the tube, which was externally gelatinous, 
 but internally retained the charafters of bread. 
 This exoeriment then furnifhes an irrefraga- 
 ble proof, that the gafi:ric fluid, as well in 
 the cat as in other animals with membranous 
 
 and 
 
DISSERTATION V. 245 
 
 and intermediate ftomachs, is the efEcient 
 caufe of digeflion independently of any tri- 
 turating power. 
 
 cxci . If the ftomach be inverted and then 
 inflated, it will be covered with humidity, 
 though care fhould have been taken to wipe 
 it dry. This humidity v/ill appear repeatedly 
 after the ftomach has been freed from it, a 
 pha^nomenon common, as we have fccn, to 
 various other animals. It is not poffible to 
 difcover the pores from which this fluid if- 
 fues by the aid of a microfcope, nor can any 
 glandular bodies be perceived in the coats, or 
 the intervals between them; but when the 
 ilomach is held againfl; the light, and exa- 
 mined with a glafs of great magnifying pow- 
 er, a number of bright flat mefhes or eyes 
 appear through the coats. I could not how- 
 ever determine the nature of them, notwith- 
 Handing I confidered the different parts of 
 the fl:omach with fome attention. 
 
 CXCI I. My fuccefs with dogs was m.uch 
 greater than with cats. I could make them 
 take more tubes without being liable to the 
 inconvenience of having them vomited. I 
 .could not however force them down the oefo- 
 phagus, for this operation was attended with 
 the fame danger as in the fiicon and eagle; 
 whenever I attempted it, the animal ufed all 
 R3 its 
 
24^ DISSERTATION V^' 
 
 its efforts to bite me. But as they would 
 fwallow them fpontaneoufly, Hke thofe birds, 
 I had only to conceal them in pieces of flefh, 
 and throw them upon the floor of the place 
 where the victim of my curioiity was kept. 
 As I always took care he fhould be hungry, 
 he generally ran towards the fleih, and fwal- 
 lowed it eagerly without maftication ; where- 
 as, the cat would keep it in the mouth, and 
 after chewing it for fome tim±e, throw out 
 the tubes generally compreiTed by the adtion 
 of the teeth, and fwallow the flefli only. 
 
 I repeated the experiment that fucceeded 
 with the two cats (cxc) upon a dog; the 
 animal took fix tubes, four full of various 
 kinds of animal fublliances, as coagulated 
 blood, lights, mufcle, and cartilage; the 
 two others contained chewed crumb of bread. 
 In fifteen hours the dog was killed, and the 
 flomach examined: it contained onlv four 
 tubes; the other two had not been voided, 
 and I fuppofed they muft have paffed on to 
 the inteftines, where I found them among 
 the excrementitious matter at the beginning 
 of the redum. Before I defcribe the appear- 
 ances in the tubes, I fhall fay a few words of 
 the juices with which the flomach abounded. 
 As it contained nothing but the tubes, we 
 may coniider the gaftric juice as pure. It was 
 
 of 
 
DISSERTATION V. 247 
 
 of a yellow colour, very bitter, almofl with- 
 out fmell, not fo fluid as water, and totally 
 deilitute of inflammability* It evidently 
 conflfts of two fubfl:ances, one very thin, 
 the other vifcid and gelatinous, which was 
 depoflted after flanding a few hours. If the 
 veflel was fet near the fire the clear part eva- 
 porated, and left a crufl which was formed 
 by the gelatinous matter. 
 
 The two tubes that had paffed out of the 
 ftomach were empty, if we except fome ex- 
 crementitious matter that had got in through 
 the mefhes of the grating* Of the other 
 four three were empty, nor could I diflin- 
 guifh which had contained bread and which 
 flefh. The tough and compadt cartilage 
 alone filled part of the tube in which it had 
 been put, but as far as I could judge by my 
 eye, it Was half waflied. It exhibited the 
 fame appearance as on a former occafion ; it 
 was imbibed with gaftric fluid, and had ac- 
 quired the fame tafte, at leaft on the furface. 
 It was fo foft, that it feemed to approach 
 more to the nature of membrane than car-^ 
 tilage. 
 
 cxciii. The refult of this experiment 
 
 does not coincide with an obfervation in the 
 
 PrakBiones Academkce of the illuftrious 
 
 Boerhaave, publifhed with a commentary by 
 
 R 4 Halkir, 
 
248 Di^SSERTATION V. 
 
 Haller. The pafTage is fo important, that I 
 muH: quote it as it ftands in the original. 
 " Receptum eft in hominum opinione quod 
 ofla animaUbus fubigantur; cum Helmon- 
 tianis oHm fenlit Boerhaavius ^ ut vero certior 
 elTet, curam adhibuit, ut obfervaret, quid 
 cibis fieret in ventricuhs animaUum valde 
 cibos coquentium, & experimento cognovit 
 non fubigi. Dedit cani devoranda intellina 
 animahum, famehcus erat, affatim deglutiit, 
 fubegit minime & per extremum inteflinum 
 pendula mifere port fe traxit. Dedit famehco 
 cani olTa butyro inund:a, reddidit furfura, ne- 
 que quidquam diffolvit nifi quod in aqua dif- 
 folvi poteft. Dedit carnes, reddidit fibras 
 carnis exfuccas. Dedit hgamenta, ea pofl 
 tridium nihil mutata egeffit {a)." 
 
 I referve till hereafter what I have to fay 
 'on the famous problem concerning the di- 
 
 ((«) It is a general opinion that animals digeft bone, and 
 Eoerhaave once entertained it in common with the followers of 
 V. Helmont. But in order to be certain, he made the experi- 
 ment upon a fpecies of animal endowed with ilrong digeftive 
 powers. He gave an hungry dog fome intelline, but found 
 that inftead of digefting it, that it tormented him by hanging 
 cut of his anus. Bones dipped in butter were alio given to an 
 hungry dog, but he returned the fragments without diflblving 
 any thing more than water is capable of diffolving. When he 
 tried fl:!h che fibres were voided with their juices expreffed, and 
 ligament was voided in three days unchanged. 
 
 geftion 
 
DISSERTATION V. 249 
 
 geflion of bone by dogs, and now confine 
 myfelf to that part of the experiment that 
 relates to the inteftine, flefh, and hgament. 
 I mafl; candidly own, that the different re- 
 fults obtained by Boerhaave and myfelf fur- 
 prized me. My furprize increafed when I 
 coniidered, that the fubflances were loofe in 
 the ftomach of his dog, and of courfe more 
 liable to be attacked and diffolved by the 
 gaftric liquor; whereas my tubes mufl more 
 or lefs impede its accefs. Upon further re- 
 flection it occurred to me, that perhaps the 
 dog was affeded by fome internal malady, 
 which might alter the properties of the gaf- 
 tric fluid, as in the owl mentioned in the 
 fourth diilertation, of which the gaflric fluid 
 was rendered unfit for digeflion by too long 
 failing ( c L 1 1 ) . This reflediion however was 
 not quite fatisfactory, and therefore to clear 
 up the matter, I thought it v/ould be better 
 to repeat Boerhaave' s experiment, and give 
 a dog fome inteftine, in order to fee what 
 changes it would undergo in the alimentary 
 canal. A middle-fized dog accordingly eat 
 four pieces of the colon and ileum of a flieep, 
 and at the fame time took two tubes, con- 
 taining each a portion of the fame inteflines. 
 The tubes were voided before the time I had 
 fixed for killing the animal, for both were 
 
 found 
 
250 DlSSEfttAflOW V. 
 
 found among the excrements within about 
 eleven hours after they were fwallowed. When 
 the tubes were wafhed clean, I found that 
 the pieces of intefline were about half di- 
 eefted. The folvent havinp- afted upon both 
 furfaces had reduced their thicknefs conli- 
 derably, but what was left flill retained its 
 Original ifrudlure. I then wafhed the ex- 
 crements, and difcovered feveral pieces of in- 
 teftine, wafted indeed, as well as thofe con- 
 tained in the tubes, yet eafily diftinguifhable* 
 
 cxciv. This experiment does not exactly 
 coincide with that - of Boerhaave j it is not 
 however totally repugnant to it, fmce the 
 pieces of inteftine were not completely dif- 
 folved. My long acquaintance with the cir- 
 cumftances attending digeftion gave rife to a 
 conje(5ture, which I refolved to fubmit ta 
 the teft of experiment. The digeftion of 
 thefe pieces of inteftine, faid I to myfelf, was 
 not complete in the ftiort fpace of eleven 
 hours (cxciii) j but may it not be fo in a 
 longer time ? Is not the quantity of foiution 
 in fome meafure proportional to the quantity 
 of time? Does not this appear from unde- 
 niable fadts related in the foregoing differ- 
 tations ? 
 
 In order to verify my conjecture, I had only 
 to contrive a method to prevent the inteftine 
 
 from 
 
DISSERTATION V. 25 1 
 
 » from paffing fo foon through the pylorus ; and 
 this, I conceived, might be done by enlarg- 
 ing the tubes beyond their ufual lize. I got 
 the laft-mentioned dog to take three fuch 
 tubes filled with as many pieces of the large 
 inteiline of a Iheep, as amounted to half an 
 ounce and four penny-weights. The tubes 
 were concealed in pieces of the fame in tef- 
 tine. The dog, which as ufual, was hungry 
 at the timiC of the experiment and was ftill 
 kept fafting, voided fome excrement in twen- 
 ty-one hours, and upon minutely examining 
 it, I thought I had fome foundation for be- 
 lieving, that my conjecture was not fallaci- 
 ous; for though fome membranous and fi- 
 brous fragments appeared among it, which 
 could be nothing but pieces of the inteftine 
 in which the tubes were concealed, yet they 
 were much more wafted, and much lefs eafily 
 diftinguifhable than in the former experi- 
 ment (cxciii), on account of their longer 
 continuance in the body. As the procefs of 
 digeflion is lefs rapid in the tubes than in the 
 open ftomach, I let the dog live twenty hours 
 longer, when the three tubes had remained 
 forty-one hours in the llomach. They all 
 three lay clofe together at the inferior orifice 
 of the ftomach, wrapped up in fome bits of 
 rag, which in all likelihood the animal had 
 
 fwallowed 
 
±^Z DISSERTATION. V, 
 
 fwallowed before the experiment, and both 
 the tubes and rags were immerfed in gaflric 
 fluid. I make no mention of this juice, 
 having found it to poiTefs the properties de- 
 fcribed in the cxciid paragraph. The rea- 
 der is more interefled in knowing what hap- 
 pened to the inteftines contained in the tubes. 
 Nothing could have fucceeded better than this 
 experiment: two of the tubes were empty, 
 and what remained in the third did not amount 
 to eleven grains -, and thus I had the fatis- 
 fa(5lion of finding, as I had conjectured, that 
 the incomplete digeftion of pieces of inteftine 
 fometimes obferved in dogs, is no proof of 
 the inability of the gaftric fluid to diflblve 
 them; it only fhews, that they have not been 
 long enough fubjed:ed to its adiion. Hence 
 the reafon of Boerhaave's mifliake appears 
 evident. Perceiving fome intefline which he 
 had given to a dog hanging out behind, he 
 concluded that the animal could not digefl: 
 fuch fubflances (cxciii) ^ whereas from the 
 fad:s juft adduced it is obvious, that they had 
 only not continued in the fl:omach a fuflicient 
 length of time. 
 
 cxcv. Thefe fa(5ls alfo fhew, that flefli 
 lofes its fibrous fliruclure in the fl:omach of 
 the dog, and it retains only when it happens 
 to be voided foon after it has been fwallowed. 
 
 But 
 
PISSERTATION V. 253 
 
 But it might be objecfled by a rigid partizan 
 of Boerhaave, that I have not flrid:ly proved, 
 that the folution extends to the fibres^ for 
 they may have been gradually feparated from 
 the common mafs, and paffing out at the 
 pores, and efpecially through the meflies of 
 the lattice-work, have left the cavity of the 
 tube empty. I therefore thought it would 
 be proper to throw further light upon the 
 fubjecft by a decilive experiment. If pieces 
 of flefh were inclofed in purfes of very thick 
 linen, they would either be diifolved and leave 
 no veilige behind them, as by other animals in 
 like circumftances (lxvii, clxxx, clxxxi)^ 
 and in this cafe v^e muft infer, that dogs are 
 capable of diilblving flefh completely, or eife 
 the fibres would remain in the purfes, and 
 thecL we fliould be obliged to agree with Boer- 
 haave, that the digeflion of flefh by dogs 
 conlifl: in expreffmg the juices and converting 
 them into chyme, while the folid parts re- 
 mained unaltered. But along with the flefh 
 I fubje(fbed harder and more tenacious animal 
 fubflances, fuch as tendon and ligament, to 
 the teft of experiment. Six bags of very 
 thick linen were given to two dogs ; four con- 
 taining four different forts of flefh, viz. beef, 
 veal, horfeflefh, and mutton; and the two 
 Others tendon and ligament of an ox. Each 
 
 bag 
 
254 DISSERTATION V. 
 
 bag contained a quarter of an ounce; and it 
 is to be obferved, that the contents were not 
 cut into fmall pieces. Being apprehenfive 
 left thefe bags, though of fome bulk, would 
 pafs through the pylorus before the time for 
 examining them, I tied to each a bit of dry 
 fpunge. They continued four days in the 
 ilomachs of the two dogs ; but fearing left 
 fo Ion? a faft mi^ht be hurtful to the animals, 
 and of courfe difturb the procefs of digeftion, 
 I fed them feveral times, though rather fpa^ 
 ringly. At the expiration of the time juft 
 mentioned, I killed, and immediately opened 
 them. The experiment fucceeded juft as I 
 could have wiflied ; for all the bags were in 
 the cavity of the ftomach. Sufpeding that 
 they might have been torn by the teeth of the 
 dogs, I took particular care to examine them, 
 but they were whole, and the four firft upon 
 being cut open v/ere as empty as if they had 
 never contained any ilefh, but of the tendon 
 and ligament there remained about the fize of 
 a hazle-nut j there was no hole in either of 
 the bags. The tendon appeared, upon being 
 weighed, to have loft three-fourths, and the 
 ligament above one half. I examined with 
 particular attention, whether this diminution 
 of bulk and v/eight arofe from the exprefTion 
 of the juices, but the contrary was evident; 
 
 for 
 
DISSERTATION V. 255 
 
 for they were as pulpy and moift as at firjd. 
 Hence I had every reafon for concluding, that 
 the gaftric fluid had really attacked and dif- 
 folved the folid parts, (o as to enable them to 
 pafs through the pores of the linen. The 
 fame thing had happened to the flefh. The 
 folution was flill further confirmed, by the 
 condition of the external Urata of the tendon 
 and ligament, which were become fo tender 
 as to be torn by the flighted violence. I was 
 thus fully convinced of the efficacy of the gaf- 
 tric fluid of the dog in diffolving the fibres 
 both of flejfh, tendon, and ligament, though 
 the procefs is lefs rapid in the latter on ac- 
 count of their greater tenacity and harihnefs. 
 That Boerhaave's dog fhould void the liga- 
 ments unchanged on the third day (eapojl 
 triduum nihil miitata egejjit^ cxciii), if by 
 this expreffion he means that they retained 
 the nature of ligament, and it feems incapa- 
 ble of any other interpretation, I have not 
 the fmalleft fcruple in believing, having {^tw 
 the fame thing in a ligament that had been 
 four days in the ftomach of a dog. It had 
 indeed undergone a confiderable diminution, 
 a circumflance which the celebrated Dutch 
 phyfician would alfo have obferved if, inflead 
 of judging by his eye, he had taken the pre- 
 caution 
 
256 DISSERTATION V. 
 
 caution of weighing it before it was fwal- 
 lowed, and after it had been voided. 
 
 cxcvi. We now come to coniider whe- 
 ther dogs are capable of digefting bone; a 
 problem which, if we may rely upon the ob- 
 fervations of feveral celebrated phyfiologifts 
 and phyficians, would appear to be decided 
 in the negative. We have already feen that 
 Boerhaave's dog, after having eaten bones 
 dipped in butter, produced no other change 
 upon them than fimple water would have 
 done (cxciii). This he alfo endeavours to 
 confirm by the following remark : ** Deinde 
 in ftercore canino, quod Albwn Gn^cum vo- 
 cant, fragmenta offium pene non mutata re- 
 periuntur, & fit mera ofiium rafura, quiE 
 dentibus canis adrofit, exfuccorum & in unam 
 mafiam redu(5lorum." It appears from fome 
 notes on this paflage and from his great 
 work [a), that his illuflrious difciple, Albert 
 Halier, adopted the fame opinion. Dr. Pozzi 
 alfoafi^erts in his work quoted above (xiii), 
 that dogs do not digeil bone. Of the two 
 experiments which he relates, the following 
 appears the moll: conclufive. Fie gave a dog 
 that had been kept failing for five days three 
 bones which, though dry, the animal fwal- 
 lowed for the fake of the butter with which 
 
 (^) El. Phyf, T. 6. '" ^ 
 
 they 
 
DiSSERTAtlON V. 257 
 
 they were anointed. One of the bones weighed 
 three ounces, another two, and the third 
 one. In three days they were voided, and 
 had only loft fix grains. 
 
 Such are the ftrongefl: arguments adduced 
 by phyfiologifts againft the vulgar opinion. 
 This opinion however found in Reaumur an 
 able advocate, one who eminently poiTeiled 
 the difficult art of making experiments with 
 fuccefs. Of the feveral produdions by which 
 he has fignalized himfelf, none have contri- 
 buted more to his reputation, than the two 
 beautiful memoirs on digeftion, which I have 
 fo often quoted with applaufe. To illuilrate 
 the prefent curious and interefting fubjedt he 
 made the following experiment (a). Two 
 compad; cylindrical bones, each feven lines 
 long and two in diameter, were given to a 
 fmall bitch, which was killed in twenty-fix 
 hours. The bones that were ftill in the flo- 
 mach were diminiflied in bulk, and it ap- 
 peared to him that feveral lamina? were re- 
 moved. They had moreover acquired the 
 flexibility of horn, though they were at iirfl 
 rigid and inelaflic. Hence he infers, that 
 they had been in part dilTolved by the gaflric 
 fluid. 
 
 Vol. L S ' cxcvii. 
 
258 DISSERTATION Vj 
 
 cxcvii. Having noticed the experiments 
 of others, let me relate my own. In the fto- 
 mach and inteflines of the dog, mentioned 
 in the cxciid paragraph, I found feveral 
 pieces of bone. They feemed to belong to 
 fome quadruped, probably a iheep, and muffc 
 have been eaten before the dog came into my 
 polTeffion. I did not v\^eigh them, but as far 
 as I could judge by infpedion, they amounted 
 to above iix ounces. Upon wailiing and 
 then examining them attentively, I perceived 
 feveral fears and longitudinal furrows, of 
 which I doubted whether they were produced 
 by the gaftric liquor or the teeth of the dog ; 
 belides, many of the angles and edges were 
 evidently blunted, at the light of which the 
 idea of what happens to the hardeft bodies in 
 a mufcular ftomach recurred. I moreover 
 obferved, that thefe places were not fo hard 
 as the thicker parts of the bone. But thefe ■ 
 phaenomena only fuggefted doubts, which I . : 
 refolvedto diffipate by the light of experiment. '. 
 I therefore filled fome tubes with pieces of 
 bone, and gave them to a dog. The bones ♦ 
 were of various kinds and degrees of hardnefs : 
 the tubes, v/hich were two in number, were 
 put into a bag of linen, in order to prevent 
 the bits of bone from getting out. To al- 
 low the gaftric juices a proper time for pro- 
 ducing 
 
i)ISSERTAtiON V. 259I 
 
 ducing their eiFecfls, the dog v/as fufFered to 
 live for feven days, and during th'S time was 
 fed moderately. One of the tubes, though 
 they were rather large, had palTed into the 
 ccecum, and was furrounded by feculent 
 matter; the other remained in the fto- 
 mach. They were neither of them empty^ 
 but their contents, which at firft weighed 
 three-fourths of an ounce and eighteen grains, 
 now amounted only to four peony-Aveights 
 and {tvQYi grains. All the angles and edges 
 were deftroyed. The foftefl bones had fuf- 
 fered moft. They could now be eafily cut in 
 the thin places with a knife. The thinnefl 
 parts of the bone were dilTolved and had paf- 
 fed through the bag, not a v^ftige of them 
 remaining. This experiment proves two 
 proportions, viz. that the digeflive powers 
 of the dog ad; upon bone as well as fiefh ; 
 . though the latter, on account of its foftnefs,' 
 is more fpeedily dilTolved, and that the gallric 
 juices are the fole efficient caufe of digeilion. 
 
 cxcviii. This experiment was repeated 
 three times, and the refult was elTentiaiiy the 
 fame; but there occurred two circum fiances 
 that deferve to be noticed. One oi the dogs 
 produced only a fmall diminution of the bonea 
 in eight days, though it was fed plentifully^ 
 and feemed to be in perfed health the v, hole 
 S Z time* 
 
l6o i)ISSERTATION V. 
 
 time. This fhews, that little or no efftO: 
 being produced upon the bone, which fome- 
 times happens, as in the cafes alledged by 
 Boerhaave and Pozzi (cxcvi), is no proof of 
 the inefficacy of the gaftric fluid of this ani- 
 mal; it only fhews, that the digeftive powers 
 are unequal; nor ought this to excite our 
 furprize, as the fame thing is obfervable in 
 our own fpecies. 
 
 The other remarkable circumftance, to 
 which I alluded, is the reverfe of the prece- 
 ding. Among the bones given to one of the 
 dogs, were two dentes incifores from the 
 upper jaw of a fheep. It has been already 
 obferved, that the enamel of the teeth re- 
 ceives no injury from the gaftric fluids that 
 are capable of diflblving the hardeft bones, 
 fuch as thofe of the eagle and falcon (clxi, 
 cxxxiii); yet the gaflric fluid of the dog in 
 queflion, damaged this compact fubflance. 
 I have now before me the two teeth, which 
 I keep as a curiolity. The enamel of one is 
 corroded in two, and of the other in three 
 places ; the five cavities are above a line long, 
 and penetrate to the nucleus of the bone. 
 The roots of the teeth were almoffc entirely 
 deftroyed. The powerful menftruum of the 
 ftomach, had made greater havock among 
 the other bones that were enclofed along with 
 
 the 
 
t>lSSERTATION V. 261 
 
 the teeth; the excavations as they were 
 wrought in a tenderer fubftance were more 
 conliderable. Upon comparing this pha^no- 
 menon with the furrows mentioned in the 
 cxcviith paragraph, I have no doubt but 
 they were occalioned by the gailric fcjvent. 
 It deferves to be remarked, that in the cafe 
 where the enamel of the teeth was deftroyed, 
 the hnen bag had not fuftained the fmalleft 
 injury, though the folvent neceffarily palled 
 tHrough it: nor is this to be wondered at; 
 for we have inftances of many gaflric fluids 
 that are capable of decompofmg the moil 
 compadl animal fubftances, though they do not 
 produce any effedion the fofteft vegetable mat- 
 ters (cxLvi, CLvi). This is alfo true of che- 
 mical menflruums; the nitrous acid difTolves 
 the hardeft calcareous flones, but leaves the 
 moil friable gypfum and clay untouched. 
 
 cxcix. Though my experiments on dogs 
 deciiively prove, that digeflion is the effed: 
 of the gaflric fluid alone; yet it was proper 
 to enquire, whether the fides of the ftomach 
 have any motion during digeftion, and what 
 that motion is ? There were two ways of 
 making this enquiry; mediately, that is, by 
 the effects ; and immediately, that is, by 
 opening the abdomen and infpeding the 
 ftomach. 
 
 S3 With 
 
262 DISSERTATION V. 
 
 With refped: to the firil mode, though I 
 was certain that the ftomach of the dog had 
 no coniiderable motion, becaufe neither the 
 tubes nor the bags had fuftained any injury ^ 
 yet in order to fee whether it has any motion 
 at all, I gave a dog fome thin tubes open at 
 the ends, which were therefore liable to be 
 compreiTcd by the fmalleft violence. But I 
 could not find the leall contufion upon them, 
 ^fter they had been three days in the ftomach. 
 The infpeftion of the tubes, however, prcr 
 fented a phenomenon which ihewed, that 
 the fides of the ftomach had not been inac- 
 tive all the time. Upon opening this vifcus 
 I found a mafs of hairs, which were of a 
 different colour from tholfe of the dog, and 
 could not therefore have been fwallowed 
 while the animal was licking itfelf. They 
 mufl: have belonged to fome other animal 
 that had been devoured by the dog, before it 
 fell into my hands. Many of thefe hairs had 
 likewife got into the tubes ; which mufl have 
 been effected by the action pf the ftomach. 
 
 cc. I opened five living dogs, taking care 
 not to wound the flomach. This operation 
 was performed foon after they had taken 
 food I for I prefumed that the mufcular fi- 
 bres, 'irritated by the diftenfion, would con- 
 trajft more evidently at this time. The 
 
 flomach 
 
DISSERTATION V.' 26^ 
 
 floniach of the firfl was perfetftly quiefcent 
 when it was left to itfelf. But when the 
 point of a knife was drawn over it, the parts 
 that were touched and thofe that were adja- 
 cent immediately contracted, and then re- 
 turned to their former fituation. Upon 
 throwing round a ligature above the cardia 
 and below the pylorus, and taking the ll:o- 
 mach oiit of the body, I thought I perceived 
 a flight periftaltic motion, but it was of fhort 
 duration. The contrad:ion and dilatation 
 continued to fucceed each other in the places 
 that were touched with the knife, or any ir- 
 ritating body, for half an hour. The llio- 
 mach of the fecond was not only deftitute of 
 fpontaneous motion, but was infenfible to 
 every ftimulus. In the third ilomach the 
 periitaltic motion was very confpicuous; the 
 contradion began jufl below the fuperior 
 orifice, and proceeded with a gentle undula- 
 tion to the pylorus, and the dilatation regu- 
 larly followed. This fpedacle lafled for feven 
 minutes. And I could refufcitate the mo- 
 tion by irritating the upper part of the ilo- 
 mach, but it continued only a little while. 
 The periflaltic movement did not appear on 
 the ftomach of the fourth dog, but irritation 
 would excite it. And it was in this cafe con- 
 lined to the ring or circular band correfpond- 
 S 4 ing 
 
264 DISSERTATION V. 
 
 ing to the place where the ftiniulus was ap-. 
 plied. This band contradied gently, and the 
 diameter of the flomach was fenlibly dimi- 
 nifhed; in a few minutes it dilated jufl as 
 flowly. In the fifth ilomach the periftaltic 
 motion was as apparent as in the third; it 
 lafted fome minutes longer, and when it had 
 ceafed in all the other parts of the vifcus, a 
 band juft above the pylorus continued thefe 
 alternations. The contraction was fo confi-. 
 derable, that the oppofite lides of the flo- 
 mach almofl touched each other j but all 
 thefe motions were exceedingly flow, nor did 
 the fides of the flomach ever dilate or con^ 
 trad fuddenly or forcibly. 
 
 c c I . At the fame time I examined the fto^ 
 mach of fome cats in the fame manner. The 
 refult was exactly alike. A gradual move- 
 iTient of contraftion and dilatation, beginning 
 at the upper end and extending to the lower, 
 was generally perceptible. 
 
 All thefe experiments, and the reader will 
 find fimilar ones in Haller, though made 
 with a different view {a), clearly fhew, that 
 the motion of the flomach of the dog and 
 cat are not capable of triturating the food, 
 but calculated to carry it flowly from the fu- 
 
 (a) Mem. fyirles part. init. & fenfib, T. i. 
 
 perior 
 
DISSERTATION V. 265 
 
 perior to the inferior orifice, and thence ex- 
 pel it into the duodenum. 
 
 From the great number of dogs that were 
 fubjed:ed to thefe experiments I collected a 
 large quantity of gaflric fluid, and found it 
 as capable of producing an incipient digef- 
 tion out of the body, as that of the other 
 animals mentioned above, both of boiled and 
 raw meat, and like wife of feveral vegetables. 
 It was however neceffary to apply a pretty 
 ftrong heat, and to change the liquor feveral 
 times, as in other inflances. 
 
 ecu. Blafius, in his laborious and accu^ 
 rate anatomy of the dog, fays, that the in- 
 ternal coat of the fcomach is compofed of a 
 congeries of glands (^). My opportunities 
 of afcertaining this have been frequent. I 
 have examined it with my naked eye and with 
 the microfcope, but could never perceive any 
 glandular appearance. Upon wiping it dry 
 and pi effing it, it was covered with an aque- 
 ous exfudation, but I could not diflinguifli 
 the pores from which this exfudation iffues. 
 I have examined feveral pieces with the folar 
 and the fimple microfcope, and in fome per- 
 ceived a vafc number of lucid points, while 
 in others there appeared nothing of this kind. 
 I then examined the back part, which is con- 
 
 (a) Anat. Anim. 
 
 tiguous 
 
265 DISSERTATION V. 
 
 tiguous to the nervous coat, and immediately 
 faw, that it is compofed of a congeries of 
 oblong particles, of a pale flefh-colour, clofe- 
 ly compacted together. Thefe are probably 
 the glands of Blafius ; but I cannot affirm 
 that they are really glands, not having been 
 able to diftinguifh the charadleriftic marks of 
 glandular bodies in them. But however this 
 may be, it is certain they are deftined to 
 tranfmit a fluid into the fliomach ; for when- 
 ever they are prefTed, the above-mentioned 
 exfudation appears upon the internal furface. 
 And this fluid may be exprefl^ed feveral days 
 after the ilomach has been taken out of the 
 body. 
 
 I have before faid, that the pores from 
 which the gafliric liquor iflues are invifible; 
 but the parts contiguous to the pylorus mufl 
 be excepted, in which they are very conspi- 
 cuous. Upon comparing the fluid that thus 
 oozes out with that which is collecfted in the 
 flomach when it is opened, we ihall find a 
 very ftriking difl^erence. The latter, as we 
 have feen above, is yellow, bitter, and fome- 
 what gelatinous (cxcii). But the former 
 has not one of thefe properties, being co- 
 lourlefs, infipid, and very fluid. Hence it 
 is evident, that the gaftric liquor of the dog, 
 that liquor which is the efficient caufe of di- 
 
 geflion. 
 
DISSERTATION V* 267 
 
 g'efllon, confifts, as in other animals, of fe- 
 veral different principles, viz. of faliva, of 
 the oefophageal juice, of that which is pe- 
 culiar to the flomach, of the pancreatic juice, 
 and of bile. 
 
 cciii. To complete my refearches on ani- 
 mals with membranous flomachs, it remain- 
 ed to examine that of Man . One may indeed 
 draw very plaufible inferences concerning 
 human digefhion, from obfervations on the 
 other fpecies of this numerous clafs ; efpecially 
 from birds of prey, the cat and dog, v/hich 
 refemble us fo much in the jflrudure of the 
 llomach. But analogical arguments are pro- 
 bable indeed, but not concluiive. And it is 
 an objedt of much higher importance to at- 
 tain certainty in Man than in animals. In 
 the writings of antient and modern phyficians 
 no topic is more frequently difculTed, yet 
 there is little elfe befide fuppofition: dired: 
 experiments upon Man are entirely wanting, 
 and their refearches are illuminated only by 
 the twilight of conjecture, and fupported by 
 precarious hypotheiis. If therefore it was 
 necelTary on other occafions to have recourfe 
 to experiment, on the prefent it was abfo- 
 lutely indifpenfible. Upon reflexion it ap- 
 peared, that the principal experiments were 
 reducible to two heads, viz. to procure hu- 
 man 
 
268 DISSERTATION V. 
 
 man gaftric fluid, in order to examine it in 
 the manner that of animals has been already 
 examined; and to fwallow tubes full of va- 
 rious vegetable and animal fubftances, in 
 order to fee v^hat changes they undergo in 
 the ftomach. I v^all candidly ov\^n, that the 
 latter kind gave me fome apprehenfion. The 
 hiftories of indigeftible fubftances occalioning 
 troublefome fymptoms, and being vomited 
 after a conliderable time (a), occurred to my 
 mind. I alfo recolledted inftances w^here 
 fuch bodies had flopped in the alimentary 
 canal. Other fad;s however v^here the re- 
 fult v^^as contrary, and of more frequent oc- 
 currence, gave me confidence. Thus we 
 every day fee the flones of cherries, medlars, 
 plums, &c. fwallowed and voided with im- 
 punity. This coniideration at laft deter- 
 mined me to make a trial v/ith as great cau-- 
 tion as poflible. 
 
 cciv. I fwallowed in the morning fafhing 
 a linen bag, containing fifty-two grains of 
 maflicated bread. All the following expe- 
 riments were made under the like circum- 
 ilances. I retained the purfe twenty- three 
 hours without experiencing the fmalleft in- 
 convenience, and then voided it quite empty. 
 
 {a) Haller, Phyf. T. 6, 
 
 The 
 
DISSERTATION V. 269 
 
 The firing ufed for fewing and tying it was 
 entire, nor was there any rent in the bag it- 
 felf. Hence it is plain, that it had not re- 
 ceived any damage either in my flomach or 
 inteftines. The fortunate refult of this ex- 
 periment gave me great encouragement to 
 undertake others. I immediately repeated 
 it with two of the fame bags, with this va- 
 riation, that one was double, and the other 
 had three folds. My motive obvioufly was 
 to fee, whether thefe additional folds would 
 impede digeftion. The bags were voided in 
 twenty-feven hours, and the double one was 
 empty i but the other ftill contained a fmall 
 quantity that had yet the charadlers of bread, 
 ccv. From vegetable I proceeded to ani- 
 mal fubflances. In a fingle Hnen bag fixty 
 grains of boiled pigeon were enclofed, and 
 in another the fame quantity of boiled veal ; 
 both previoully mailiicated. The purfes were 
 voided in eighteen hours and three-quarters, 
 and the fleih was entirely confumed. Inftead 
 of fixty I next took eighty grains, of which 
 the bulk was not fo great as to m^ake me ap- 
 prehend any danger from its flopping in th« 
 oefophagus, and flill lefs from its not getting 
 out through the pylorus, as at that time it 
 muft of necefBty be very much diminilhed in 
 bulk. The flefli had been p.^xvioufly boiled 
 
 and 
 
Z'JQ DISSERTATION V. 
 
 and mafllcated. I retained it twenty-nine 
 hours, at the expiration of which time there 
 remained eleven grains undilTolved. This 
 flefh differed in appearance from that which 
 is taken undigefled out of the ftomachs of 
 animals. The furface of the latter is gela- 
 tinous, but the former was as void of fuccu- 
 ^lencyas if it had been fet' under a prefs. > 
 This appearance, which is analogous to that 
 of the bread in the preceding experiment 
 (cciv), made me fufpe(ft, that perhaps the 
 human flomach might poffefs a power of 
 compreffing its contents, though others of 
 the fame ftrudture are deflitute of fuch. a 
 power. I therefore determined to bring this 
 fufpicion to the tefl: of experiment. 
 
 ccvi. Finding that I could digeil; dreifed 
 meat that had been mailicated, I wi/hed to 
 knov/ v/hether I was capable of digefting it 
 without maftication. I fwaliowed eighty 
 grains of the breafl: of a capon, enclofed in a 
 bag. The bag was retained thirty-feven 
 hours. So long a fpace had produced con- 
 fiderable eifed:s, for it had loft fifty-fix 
 grains. The furface of the remainder was 
 dry, but the internal fibres appeared to be . 
 more fucculent. Digefcion feemed to have 
 gone on uniformly, fbr the piece retained its 
 original fliape, 
 
 ccVii. I 
 
DISSERTATION V.' 27 1 
 
 ccvii. I next wiHied to know whether 
 this drynefs of the furface would be obferved 
 in raw as well as dreffed fiefh. I did not 
 doubt but I fhould digefh it in this ftate more 
 or lefs fpeedily; for the human ftomach is 
 adapted to the digeftion of the one as well as 
 the other, whole nations living upon raw 
 flefh, and raw ii£h being eaten in fome ma- 
 ritime countries ; not to mention that oyflers, 
 cockles, &c. in the ftate they are taken, are 
 among the delicacies of the elegant and luxu- 
 rious, though a food of difficult digeftion. 
 I took failing fifty-fix grains of raw veal and 
 as much beef, enclofed in two bags, which 
 were returned about the middle of the next 
 day. Of the veal, as it was the tenderer, 
 there remained fourteen grains, and of the 
 beef twenty-three. In both there was the 
 fame drynefs on the furface as if the bags 
 had been v^rung, or prefled by fome external 
 violence. 
 
 CCVII I. As then this phenomenon is con- 
 ftant, are we to fuppofe, that the digeftion of 
 flefti and bread, which is produced by the 
 gaftric fluid within the bags, is aided by the 
 triturating power of the ftomach ? Does any 
 fuch power exift at all ? I could devife no 
 better means of folvinTj thefe doubts, than by 
 obferving what happens to animal and vege- 
 table 
 
272 DISSERTAtlON V. 
 
 table fubftances enclofed in tubes. Should 
 they either not be at all or imperfedlly digef- 
 ted, we muft infer, that there was wanting 
 fome circumftance either neceffary, or at leaft 
 expedient^ and we might prefume, that it is 
 trituration. I was then under the neceffity 
 of fwallowing tubes. Having fuffered no- 
 thing from the former experiments, I en- 
 tered upon thefe without much apprehenlion. 
 Inftead of tin I had my tubes made of wood, 
 fearing left the refidence of the metal in the 
 ^ftomach and bowels ihould be producflive of 
 bad confequences, although I never perceived 
 any in other animals. The gaftric fluid had 
 never corroded it, the furface was only turned 
 bla<^k. My wooden tubes were five lines in 
 length and three in diameter. The fides were, 
 as ufual, perforated with a great number of 
 holes, in order to allow free ingrefs to the 
 juices of the ftomach, along the whole length 
 of the tubes, as well as at the ends. To 
 prevent the entrance of the foeculent matter 
 during their palTage through the long track, 
 of the inteftines, they were enclofed in linen 
 bags, a precaution not always employed upon 
 other occafions of th€ like nature. At firft 
 I took a fingle tube, containing thirty-fix 
 grains of boiled veal previoufly mafticated. 
 The tubes was voided empty in twenty- two 
 
 hours, ' 
 
PISSERTATION V." 27 
 
 hours. The cover of Hnen was entire, and 
 had prevented any extraneous matter from 
 getting in. 
 
 ccix. This experiment, which is by no 
 means favourable to the dodrine of tritura- 
 tion, induced me to attempt others before I 
 drew any concluiion. As the tube was ca- 
 pable of containing above thirty-fix grains, I 
 put in forty-five. I retained it feventeen 
 hours. There was a reliduum of twenty-one 
 grains 5 and now appearances were changed; 
 the veal not only had its natural fucculence, 
 but the furface was foft and gelatinous, the 
 center alone remaining fibrous. The jelly 
 was fweet, its fmell was not at all putrid, 
 any more than that of the refiduums in the 
 purfes. Thefe appearances were obferved in 
 three other experiments with boiled, and one 
 with raw fiefh of feveral different kinds. I 
 hefitated not to conclude, that in Man, as 
 well as numberlefs other animals, the gaftric 
 fluid dio;efls the food without the concurrence 
 of trituration. It is indeed not poffible that 
 it fliould concur ; for I have dired: proofs, that 
 no mufcular adiion capable of producing fuch 
 effe(5ls is ever exerted by the human flomach. 
 Among the wooden tubes employed in thefe 
 experiments, I procured fome to be made fo 
 thin that the llighteft preffure would crufh 
 
 Vol. I. T them 
 
274 DISSERTATION T. 
 
 them to pieces ; and though I frequently ufed 
 them, not one was ever broken. If I took 
 off the hnen cover, which was always entire, 
 and examined them with ever fo much at- 
 tention, I could never perceive the fmalleft 
 iilTure. 
 
 ccx. Thefe perfedly coincide with the 
 following facets. Cherries and grapes are faid 
 to be voided entire [a). I refolved to afcer- 
 tain by my own experience the truth of thefe 
 obfervations. I firft fwallowed four unripe 
 grapes, becaufe in that flate they have greater 
 firmnefs. In a day they were all voided with 
 the ikin whole ; the colour was changed from 
 a greyifh w^hite to yellow. I next made trial 
 of ripe grapes, which, as every one knows, 
 burft on the flightefl: prellure. Of twenty- 
 five which I fwallov/ed eighteen were voided 
 entire, of the other feven the ikins only ap- 
 peared. I made the fame experiments with 
 many cherries, as well ripe as unripe, and by 
 far the greater number were voided entire. 
 Thefe experiments, together with thofe made 
 on the thin tubes, afford the mofc conclu- 
 live evidence, that no triturating force is ex- 
 erted by the human ffomach. 
 
 I ihall be perhaps afked, w^hat is the caufe 
 of the drynefs of the fibres, fo often obferved 
 (a) Haller, Phyf. T. 6. 
 
 in 
 
DISSERTATION V. 275 
 
 in flefh enclofed in the linen bagSy which 
 would appear to have been forcibly preiled 
 (cciv, ccv, ccvi, ccvii) ?• Upon confi- 
 dering the matter I was led to fuppofe, that 
 the inteflines are more concerned in this phse- 
 nomenon than the flomach. While the bags 
 remain in the flomach, the flefh is converted 
 into a gelatinous matter; for there is no rea- 
 fon to believe that this happens in the tubes 
 only, and not in the bags. But when they 
 are protruded into the inteflines, they mull 
 be furrounded and prelTed by the foeculent 
 matter. Hence the jelly is fqueezed out, 
 and the fibres lofe their fucculence. And 
 this, not the adion of the flomach, I take to 
 be the reafon why cherries and grapes are 
 now and then burft. 
 
 ccxi. Having thus efiabliflied this fun- ' 
 damental proportion, viz. that the digeflion 
 of flefh and bread is produced in my flomach 
 by the gaflric fluid independently of tritura- 
 tion (cciv, ccv, ccvi, CCVII, ccviir, 
 ccix, ccx), I had before me a fine field for 
 experiments that could not fail to fuggefl 
 fome important truth. The neceflity of maf- 
 tication is fufBciently knov/n. There is, per- 
 haps, no perfon vv'ho has not fome time or 
 other been fubjecl to indigeflion for want of 
 having chewed his food properly. In the 
 
 T 2 courfe 
 
2.76 DISSERTATION. V. 
 
 courfe of my experiments I had fwallowed 
 fome maflicated flelh, and fome without maf- 
 tication ; but having never taken care that it 
 ihould be of equal fize, I had no term of 
 comparifon, and hence was not certain which 
 was mofi: fpeedily digefted. I therefore fup- 
 pHed this omiilion in the following manner. 
 I took two pieces from a pigeon's heart, each 
 weighing forty-five grains, and having chew- 
 ed one as much as I ufed to chew my food, 
 enclofed them in two tubes, and fwallowed 
 them at the fame time, but without attain- 
 ing the -end I had in view^ for the tube con- 
 taining the chewed flefh was voided in twen- 
 ty-five hours, and the other in thirty-feven, 
 both empty. Another experiment made un- 
 der the fame circumflances fucceeded better, ' 
 both the tubes were voided in nineteen hours, 
 and I then faw how much digeflion is pro- 
 moted by maflication. Of the maflicated 
 flefh there remained only four grains, where- 
 as of the other there were eighteen left. This 
 was confirmed by two other experiments, 
 one made with mutton, the other with veal. 
 The reafon is obvious. Not to mention the 
 faliva which moiflens the food and predifpofes 
 it to be dilTolved, it cannot be doubted, that 
 when it is i-educed to pieces by the adion of 
 the teeth, the gaflric fluid penetrates more 
 
 readily. 
 
DISSERTATION V. 277 
 
 readily, and by attacking it at more points^ 
 diffolves it more fpeedily than when it is 
 whole. This is true of menflrua in general, 
 which always difTolve bodies fooner when 
 they have been previouily broken in pieces. 
 This is alfo the reafon why in other experi- 
 ments, marticated bread and drelTed flefh were 
 more readily diflblved than unchewed bread 
 and raw flefh. The boiling had made it ten- 
 derer, and confequently difpofed it to allow 
 ingrefs to the gaftric fluid. 
 
 ccxii. It is an opinion common among 
 modern phyiiologifts, that flefhy fibres, ten- 
 don, cartilage, and bone lofe their juices in 
 the human ftomach, but that the folid parts 
 are not diflblved or digefled. With refpecft 
 to flefliy fibres, I mufl differ from them, 
 having clearly proved the contrary by expe- 
 riment (ccv, ccviii, ccxi). As I could 
 bring the other fubflances to the fame tefl, 
 I would not neglect an enquiry of fo much 
 importance. I at firfl took membrane er^- 
 clofed in a tube without maflication or divi- 
 fion, weighing about fixty-five grains. The 
 tube was voided in thirty- two hours, and 
 prefented the following appearances : The 
 inembrane was entire, but feemed thinner 
 and fhorter. It weighed only twenty-eight 
 grains. This diminution, however, was not 
 T 3 a fuf- 
 
278 DISSERTATION V. 
 
 a fufHcient proof of the folution of the folid 
 parts j it might depend upon the privation of 
 -• the fluids. It was therefore proper to return 
 it into the fliomach, and wait the refult. The 
 membrane was voided in fifteen hours 5 it 
 was ilili in one piece, but exceedingly redu- 
 ced, weighing now only five grains. This 
 petty remainder I fw alio wed a third time; the 
 tube was voided in twenty-two hours, and 
 was now completely empty. I afterwards 
 obferved the fame phenomena in membranes 
 of greater thicknefs and tenacity ; and I once 
 digefted the aorta of a calf after it had been 
 boiled. The only difference I could perceive 
 was, that the compader membranes requir€d 
 more time to be diffolved. 
 
 ccxiii. I made experiments upon carti-r 
 lage and tendon at the fame time. To avoid 
 difgufling the reader by too particular a re- 
 cital, I will only mention the bare refults. 
 The cartilage was mbre fpeedily diffolved than 
 the tendon, the former being totally con- 
 fumed in eighty-five and the latter in ninety- 
 feven hours. Both were taken from an ox, 
 and had been previoufly boiled for half ar^ 
 hour, 
 
 ccxiv. Bones flill remained, and I fub- 
 mitted fome both of a hard and foft texture 
 fp experiment. The latter were completely 
 
 diflblyed. 
 
DISSERTATION V. 279 
 
 dilTolved, and required about the fame time 
 as cartilage. But the former underwent no 
 perceptible diminution, though it continued ^ 
 upwards of eighty hours in my flomach. I ' 
 likewife fvv^allowed a naked ball of hard beef 
 bone three lines in diameter, and in thirty- 
 ihree hours voided it undiminiflied. 
 
 It is therefore certain, that the ilomach is 
 capable of digeiling not only mufcular fibres, 
 but membrane, tendon, cartilage, and even 
 bone itfelf, provided it is not too hard 5 
 though moil phyfiologifts and phyficians 
 have been led to adopt a contrary opinion by 
 obferving, that thefe fubftances are evacuated 
 unaltered. But this is no proof that they are 
 indigeflible (for if they had made the expe- 
 riment on themfelves, and weighed the fub- 
 ftances, they would have obferved a wafle), 
 it only ihews, that they are not fo foon di~ 
 geiled as other kinds of food, which are dif- 
 folved in a few hours j whereas, membrane, 
 tendon, cartilage, 6cc. require feveral days, 
 on account of their tenacity and hardnefs. 
 
 Let no one fuppofe, that my llomach, be- 
 ing ftronger than common, is capable of di- 
 geiling what that of others cannot digeft. I 
 own, with concern, that it is weak, as is 
 iifual in thofe whofe purfuits condemn thenl 
 to a fedentary and unwbolcfome way of life. 
 T4- My 
 
 •'N. 
 
2S0 DISSERTATION V. 
 
 My ftomach digefts food fo flowly, that I 
 cannot ftudy for five or fix hours after a 
 fparing dinner, and am liable to indigeflion 
 whenever I feed more plentifully than com- 
 mon. 
 
 Before I quit this fubjedt let me obferve, 
 that though I have mentioned the gaflric 
 juices as the efficient caufe of digeftion in 
 the experiments on myfelf, yet I mean not 
 to exclude thofe of the inteftines from their 
 fhare. We know, that the fmall inteflines 
 complete the procefs of chylificaiio?i., v/hich 
 is but begun in the fhomach. I muft there- 
 fore allow, that the digeflion of animal and 
 vegetable fubflances in the bags and tubes 
 is perfected in the inteflines. But this is 
 not in the leaft repugnant to the refult of 
 thofe experiments that fhew the human flo- 
 mach to be deflitute of any triturating force, 
 and digeflion to be the effeft of the gaflric 
 fluid alone, though the fluid which is fecre- 
 ted by the fides of the fmall inteflines may 
 complete the procefs. 
 
 ccxv. In the cciiid paragraph I re- 
 marked, that the chief experiments on man 
 were reducible to two heads, thofe which 
 relate to the natural procefs, as it may be ob- 
 ferved by means of tubes and fuch contri- 
 vances, and thofe v/hich relate to artificial 
 
 digeitionj 
 
DISSERTATION V. 28 1 
 
 digeftion, provided the gaftric juices can be 
 procured. Having treated the former of thefe 
 divilions as well as circumftances would per- 
 mit, it remained for me to make fome enqui- 
 ries relative to the fecond. It was firft ne- 
 celTary to devife a method of procuring the 
 gaflric fluid. The firft idea that ftruck me 
 was to fearch for it in dead bodies, but after 
 examining feveral flomachs I was obliged to 
 abandon this fearch; for they v/ere either 
 without any fluid, or elfe what they contain- 
 ed was fo turbid and fo much adulterated 
 with heterogeneous matters, that it would 
 by no means fuit my purpofe. Nor were the 
 little fpunges, which had ferved fo well in 
 animals, better adapted to the prefent occa- 
 fion. Two fpunges would not fupply me 
 with a fuflicient quantity, and I could ven- 
 ture only to fwallow two tubes at once, for 
 fear of forming an obflruction in my fl:omach. 
 Beiides, the juice thus procured would have 
 been very impure, on account of the hete- 
 rogeneous matters that the tubes mufl: ne- 
 cefTarily have imbibed during their paflage 
 through the inteflines. 
 
 There remained only to obtain it by ex- 
 citing vomiting while the ftomach was empty. 
 To effed this, I chofe rather to tickle the 
 fliuces than drink warm water, as in this cafe 
 
 the 
 
282 DISSERTATION V. 
 
 the gaftric fluid muft have been diluted. 
 In this manner therefore, before I took meat 
 or drink, I procured in two mornings a quan- - 
 tity fufficient for a few experiments, of which 
 the refult fhall be related below, I could 
 have vvdfhed to have made a greater number, 
 but the difagreeable feelings occafioned by the 
 a^^ of vom.iting, the convullions of my whole 
 frame, and more efpecially of my ftomach, 
 that continued for feveral hours after it, left 
 upon my mind fuch a repugnance for the 
 operation, that I was abfolutely incapable of 
 repeating it, notwithflandiirg my earneft de- 
 iire of procuring more gaftric liquor. 
 
 ccxvi. I was therefore obliged to con- 
 tent myfelf with what thefe two vomits af- 
 forded me. The firfc time it amounted to an 
 ounce and thirty- two grains. It was frothy 
 at its being thrown up, and fomewhat glu- 
 tinous. After it had been at reft a few hours 
 and depoiited a fmall fediment, it was as lim- 
 ped as water. It v/as a little fait to the tafte, 
 but not at all bitter. It did not, either when 
 thrown on the fire or brought near a candle, 
 fhev/ any token of inflammability {a). It 
 
 evaporated 
 
 (a) From this and the Lxxxift, cxxiiid, cxLixth, and 
 CLXxxvth paragraphs we may colle£t, that the gaftric juices 
 both of man and animals are deilitute of inflammability. I 
 
 jnadfi 
 
DISSERTATION V. 28^ 
 
 evaporated in the open air, and when I put 
 j&fty-two grains into a vefTel and fet it on hot 
 coals, it emitted a thick fmoke. Another 
 fmall portion, weighing eighty-three grains, 
 was put in a phial, which was clofed with 
 a ilopple to prevent it from evaporating. It 
 did not change colour or tafle, nor did it ac- 
 quire any bad fmell, no twith flan ding it was 
 jkept above a month in the hottefl feafon of 
 the year. I thus employed about one half, 
 the remainder was ufed for an attempt to ob- 
 tain artificial digeftion. It was put into a 
 glafs tube two inches long, fealed hermeti- 
 cally at one end, and very narrow at the other; 
 I then introduced a fmall quantity of mafli- 
 
 made thefe experiments, becaufe Reaumur thought that that 
 of his kite was inflammable, which quality Dr. Badgne im- 
 putes to the bile, a fluid confifling principally of oil (premiere 
 Reflexion fur les Exper. de Reaumur). But were this true, the 
 gallricjuices of moft of my birds ought to have taken fire. As 
 all mine are contrary to Reaumur's fingle experiment, I fhould 
 fufpeft, that what he obferved was owing to accident. His 
 experiment was the following : To take away the fmell of 'pu- 
 trid flefh, which one of his tubes had acquired, he fet it upon 
 fome burning coals, when immediately there iflued a flame 
 from the infide that Jailed above a minute (Seconde Mem.). 
 But it is eafy to perceive, that this might have been owing to 
 fome fat of the enclofed flefli adhering to the tube. I am more 
 confirmed in this fufpicion from having obferved, that the gaf- 
 tric fluid of a kite, fuch as Reaumur's, mentioned in a note to 
 paragraph clxxv, was not -more difpofed to take fire than the 
 pilfer gailric juices which I examined, 
 
 cated 
 
2B4 DISSERTATION V. 
 
 cated boiled beef, and itopping the tube with 
 cotton, fet it in a ftove clofe to a kitchen 
 fire, where there was a confiderable heat, 
 though not perhaps exacflly equal to the tem- 
 perature of my ftomach. By the fide of this 
 tube I placed another, containing the fame 
 quantity of iieih immerfed in water. The 
 appearances in both were the following : In 
 twelve hours the flefh in the former began 
 to lofe its fibrous flrudture, and in thirty- 
 five it had fo far loft its confiftence, that 
 when I attempted to lay hold of it, it flipped 
 from betv/een my fingers. But though to the 
 .naked eye it appeared to be reduced to a pul- 
 taceous mafs and to have lofl its fibrous tex- 
 ture, yet the microfcope rendered the fibres 
 vifible ; they were however reduced to a great 
 degree of minutenefs. After this femifluid 
 Jiiapelefs mafs had continued two days longer 
 in the gaflric fluid, the folution did not feem 
 to have ma<^e any further progrefs, and the 
 reduced fibres were flilljuft as apparent. The 
 R^ra did not emit the leaft bad fmell, while 
 that immerfed in water became putrid in fix- 
 teen hours, and grew worfe and worfe the 
 two followinp- days. It lofl in fome meafure 
 its fibrous flrudiure, as always happens du- 
 . ring putrefaction : but this appearance did not 
 
 proceed 
 
DISSERTATION V. 285 
 
 proceed fo far as in the other portion, for 
 the fibres were entire on the third day. 
 
 ccxvii. I vomited the fecond time more 
 gaftric fluid, and was now, enabled to examine 
 it again as I had done before ; and it appeared 
 to polfefs exactly the fame properties. In or- 
 der to determine the influence of heat two 
 tubes were filled with it, and fome fleih was 
 immerfed as before (ccxvi). One of the 
 tubes was placed in the ftove, and the other 
 left in the open air. In the former the flefli 
 was juftas much diiTolved as in the preceding 
 experiment; but in the latter the folution pro- 
 ceeded no farther than when water was em- 
 ployed ( c ex V I ) . There was however no pu- 
 trid fmell, though the flefh was left immerfed 
 in the gaftric fluid feven days. 
 
 Before I conclude this account, I muft 
 mention a circumftance that happened the 
 fecond time I procured gailric liquor by vo- 
 miting. Four hours before I fubmitted to 
 this difagreeable operation, I had fwallowed 
 two tubes filled with beef, one of which was 
 thrown up- the flxfh was thoroughly foaked 
 in the fluid of the fcomach, and the furface 
 was foft and gelatinous; it had moreover 
 wafted from fifty- three to thirty-eight grains. 
 This experiment proves, that there takes 
 place a confiderable degree of digeflion in the 
 
 ilomachj 
 
286 DISSERTATION V. 
 
 ilomach, before the food pafies into the in-^ 
 teilines. 
 
 ccxviii. We may now fafely lay down 
 fome general confequerrces concerning di- 
 geftion in Man and animals. In the experi- 
 ments on birds with mufcular ftomachs, we 
 have feen how trituration difpofes the food 
 to be digefted. Hence Nature has furnilhed 
 that clafs with gaflric mufcles of fufficient 
 power to effed: this necelTary preparation. 
 But we have likewife feen how digeftion, 
 which confifts in the tranfmutation of the 
 aliment into chyme, is the effect of the jui- 
 ces alone with which the llomach abounds 
 (Diif. i). 
 
 We next proceeded to birds with interme- 
 diate ftomachs, fuch as crows and herons, 
 and found, that in them digeftion was owing 
 to the gaftric fluid alone (DilT. ii). 
 
 We next confidered animals with mem- 
 branous ftomachs, a clafs fo numerous and 
 various, that it comprehends almoft every fa- 
 mily of living creatures ; it includes the in- 
 habitants of fait and frefh water; amphibi- 
 ous animals, as the frog, the newt, and wa- 
 tcr-fnake; reptiles, as the viper, the land- 
 fnake, and many others ; quadrupeds, as ths 
 cat, the dog, the horfe, the ox^ birds, as 
 
 birds 
 
DISSERTATION V, 2S7 
 
 birds of prey : to this catalogue Man himfelf 
 is alfo to be added. 
 
 In feyeral of thefe animals we have feen 
 the neceffity of previous trituration, as in the 
 ruminating order and in Man ; in them it is 
 produced by the teeth, as in gallinaceous fov^ls 
 by the mufcles of the ftomach. But in others^ 
 as in the frog, the nevv^t, ferpents, and birds 
 of prey, it has no ihare in the procefs of di- 
 gellion. But in the latter, as well as the for- 
 mer cafes, we have ken how the food is dif- 
 folved and digefled by the gaftric fluid (Diff, 
 Ui, iv). 
 
 In every order of animals, Nature, always 
 uniform in her operations, employs one prin- 
 ciple for the performance of this vital func- 
 tion. Hence fhe has fo copioully furnifhed 
 the oefophagus and ftomach with glands, fol- 
 licles, and other contrivances that anfwer 
 the fame end, whence continually flow the 
 juices fo neccfliiry to the life of Man and ani- 
 mals. Thefe juices agree in many properties, 
 but the difference of efFedl fhews, that they 
 differ in others. In the frog, the newt, 
 fcaly iifhes, and other cold animals, the 
 gaflric fluid produces digeftion in a tempera- 
 . ture nearly equal to that of the atmofphere. 
 But the gaftric fluid of hot animals is inca- 
 pable of diffolving the aliment in a degree of 
 
 heat 
 
288 DISSERTATION V. 
 
 heat lower than that of the animals them- 
 felves. There is alfo a difference in celerity 
 of action, and in efficacy. In celerity, be- 
 caufe the food in hot animals is digefted in a 
 few hours ; whereas, in the oppoUte kind it 
 requires feveral days and even weeks, parti- 
 cularly in ferpents. In efficacy, becaufe the 
 gaftric juices of fome animals, as the gallina- 
 ceous clafs, can only difTolve bodies of a foft 
 and yielding texture, and fuch as have been 
 previoully triturated; while thofe of others, 
 as ferpents, the heron, birds of prey, the 
 dog, decompofe fubilances of great tenacity, 
 as ligament and tendon, and of conliderable 
 hardnefs, as the hardeft bone. Man belongs 
 to this divilion ; but his gaffric fluid feems to 
 have no action on the hardeff kind of bones. 
 Further, fome fpecies, as birds of prey, are 
 incapable of digefting vegetables. But Man, 
 the dog, the cat, crows, &c. diffolve the 
 individuals of both kingdoms alike. In ge- 
 neral thefe juices produce their effecfls out of 
 the body, as the numerous inftances of in- 
 cipient digeftion under this circumftance, 
 both with the gallric fluid of animals and 
 Man abundantly ihew. 
 
 ccxix. Having thus brought into one 
 point of view the principal circumflances re- 
 lative to the efficient caufe of digeflion, let 
 
 ♦ U9 
 
DISSERTATION V. 289 
 
 US compare them with what has been moft 
 plaufibly written upon this topic fo intereft- 
 • ing to the phyfician. The opinion that pre- 
 vails chiefly in the fchools of Europe is that 
 advanced by Boerhaave, who has in truth 
 done nothing but reconcile the opinions that 
 had been propofed at different times before 
 him. He obferves, in the firft place, that 
 the various' folid and fluid fubflances which 
 ■ferve for food, being received into a clofe, • 
 moift, and warm velTel, mufl, according to 
 the nature of each, fooner or later begin to 
 ferment or putrefy. There are alfo various 
 fluids continually running into the cavity of 
 the flomach, viz. the faliva, the cefophageal 
 liquor, that thin tranfparent fluid which is 
 fecreted by the gaflric arteries, and a vifcid 
 humour fecreted by glands in the flomach^ 
 If we confider the properties of thefe ingre- 
 dients, and moreover take into the account 
 the remains of the food which ferve as a 
 ferment, the air which produces an inteftine 
 movement of the integrant parts, the heat 
 which excites this heterogeneous mafs, we 
 fliall find, that the aliment will be macerated, 
 diluted, attenuated, diflolved, determined to 
 an incipient fermentation, and in fhort, im- 
 prefied with the primary principle of vitality. 
 Thus it is that Boerhaave explains the di- 
 VoL. I, U geflion 
 
i^O DISSERTATION V. 
 
 geftion of foft food. With refped to that 
 t)f a firmer texture, imagining, that the caufes 
 above recited are infufficient to explain the 
 digeftion of them, he has reeourfe to the tri- 
 turating power of the ftomach, produced hy 
 the adtion of the mufcular coat, and the pul- 
 fation of the aorta and the other adjacent ar- 
 teries j the nervous fluid, which perhaps flows 
 into the flomach more copioufly than elfe- 
 where; and laffcly, the continual and flrong 
 compreffion of the diaphragm and abdominal 
 mufcles. In confequence of thefe additional 
 caufes, the food in the firft place, will be 
 broken down into a pulp, and acquire a ci- 
 neritious hue; fecondly, the fibres, tendons, 
 cartilages, &c. will be deprived of their 
 juices while they retain their cohefion > thirdly, 
 from vegetable and animal fubflances thus 
 diilblved, will be produced a fluid refembling 
 thofe of the human body. 
 
 ccxx. Thus has this celebrated phyfi- 
 cian explained his ideas concerning digeflion 
 in his Inflitutions. He fuppofes, that there 
 are two principal agents in this vital function, 
 viz. the difterent fluids that are colledied in 
 the flomach, and the mechanical ailion of 
 that organ ^ the fecondary agents are heat, 
 iir, the nerVous fiuid, the remains of the 
 lood, and an incipient fermentation. 
 
 With 
 
DISSERTATION V. 29I 
 
 With refpedl to the gaflric fluid, his ideas 
 were indeterminate and unfettled. On CDni- 
 paring this paflage with his Pr'cele<5tions it 
 will appear, that he conceived that it adted- 
 in the folution of the food like a limple di-= 
 luent, as water heated to the fame degree. 
 But fad:s without number related above (hew,, 
 that it does not a(ft in this manner, but as a 
 real folvent. That the folution is more 
 fpeedy and effecSual than, that obtained by 
 mere water, appears from experiments equally 
 numerous. Moreover, this fluid does not 
 dilTolve foft and yielding fubflances only, but 
 the hardeft and moil tenacious, contrary to 
 Boerhaave's opinion. 
 
 With refpeft to trituration, the attentive 
 reader will ealily anticipate my anfwer. How- 
 ever remarkable the efFedls produced by the 
 mechanical adion of mufcular flomachs may 
 be, intermediate and membranous ftomachs 
 have no fuch power. I have made particular 
 obfervations on the flomach of the dog, which 
 fo nearly refembles that of Man, and it ne- 
 ver appeared to have any motion fufficient to 
 break down the food. This was not only 
 proved by thin tubes receiving no injury, but 
 by infpedion of the flomach during the time 
 ofdigeftion (cxcix, cc). The reader will 
 find fimilar proofs taken from the effedis pro- 
 U 2 duced 
 
292 DISSERTATION V. 
 
 duced by my own ftomach, in the ccixtli 
 and ccxth paragraphs. Thefe direift argu- 
 ments ihew the infufHciency of the Boerhaa- 
 vian hypothefis. It is befides eafy to lliew its 
 falfity, by examining the foundation on which 
 it reils. He deduces the triturating power 
 from the adlion of the mufcular coat and the 
 contiguous parts ; but this coat is fo thin in 
 membranous ftomachs, that its effects mull 
 needs be inconliderable. Nor is the pref- 
 fure of the adjacent parts of much importance, 
 at leaft in the cat and dog; for upon opening 
 the abdomen and feehng the ftomach, I per- 
 ceived nothing but the pulfation of the arte- 
 ries, as I had before done in fome birds with 
 mufcular ilomachs ( xxx v 1 1 1 ) . But this pul - 
 fation does not comprefs the ftomach. I 
 likewife perceived by my touch, that this 
 vifcus is affed:ed by the vibrations of the 
 neighbouring arteries ; but the eifecfls of thefe 
 vibrations are not more confiderable than the 
 pulfation of its own arteries. The whole 
 ftomach was lifted up, and depreffed by the 
 motion attending refpiration. The periftal- 
 tic movement was alfo general in fome cafes ; 
 but the former did not produce contradion, 
 and the contraction produced by the latter 
 was gentle, and incapable of triturating the 
 
 aliment* 
 
DISSERTATION V. 293 
 
 aliment. It could only agitate, and fo dif- 
 pofe it to be more readily diffolved. 
 
 ccxxi. Heat, I readily agree with Boer- 
 haave, in coniidering as a co-operating caufe. 
 My experiments prove its great importance. 
 Though the gaftric fluid is not inflammable 
 (lxxxi, cxxiii, cxlix, clxxxv, ccxvi), 
 yet it is difpofed by warmth to infinuate itfelf 
 into digeftible fubftances, and reduce them 
 to that gelatinous matter which ferves imme- 
 diately for nutriment. The fame obfervation 
 is applicable to menftrua in general. 
 
 I willingly admit, that particles of air, 
 while they are extricated from the food among 
 which they are entangled by means of the fa- 
 liva, contribute to its more fpeedy folution. 
 
 But I cannot fo readily allow, that digef- 
 tion is promoted by the nervous fluid flowing 
 copioufly into the ftomach ; for its very ex- 
 ifl:ence is uncertain, and the hypothefls is al- 
 together without foundation. 
 
 Much lefs can I grant, that the remains 
 of the aliment ferve any fuch purpofe as he 
 afcribes to them. The great Haller juftly 
 obferves, that our appetite and digefl:ion are 
 good only when the fl;omach is empty [a) . I 
 have had feveral opportunities of feeing this 
 
 {a) Phyf. T, 6. 
 U 3 confirmed. 
 
294 DISSERTATION V. 
 
 confirmed. When I fed a crow, a heron, or 
 a falcon fparingly, the ftomach would be 
 empty in fix or feven hours ; when they would 
 take food again very greedily and digefl it 
 completely, as I found upon opening the flo- 
 mach. 
 
 Whether an incipient fernientation contri- 
 butes to digeftion, according to the opinion 
 of this writer, is a queftion which fhall be 
 examined at fome length in the fullov/ing dif- 
 fertation, as it has been the fubjed; gf many 
 modern experiments. 
 
 Laftly, I mull again differ from hjm with 
 refped: to fibres of flefh, membrane, tendon, 
 cartilage, bone, which, in his opinion, are 
 not digefted in the human flomach, but only 
 have their juices expreffed; for the experi-. 
 ments I made on myfelf prove, that the folid 
 parts are really diffolved, if we except only 
 the hardefl bones (ccv, ccviii, ccxii, 
 ccxiii, ccxiv). As Boerhaave endeavoured 
 to reconcile the various opinions of phyficians 
 concerning digeftion, he feems inclined to 
 adopt in fome meafure the notion of thofe 
 who fuppofe, that the oiiice of tlie flomach 
 confifts in extrading the juice of animal and 
 vegetable matters, among whom Mr. Hec- 
 quet has particularly diftinguiflied him.felf. 
 And a note to the pafTage, in which he ob- 
 
 ferves^ 
 
DISSERTATION V. 295 
 
 ferves, that the flalks of hay are flill vifible 
 in the dung of the horfe and the ox, notwith- 
 ilanding it is chewed fo often by the latter, 
 ftill more clearly explains his idea, I con- 
 lidered it as of great importance to enquire, 
 v/hether the fame thing happens in animal$ 
 belonging to other claiies, which was really 
 the cafe in fome. We have feen, that the 
 two fpecies of crow above-mentioned are both 
 granivorous and carnivorous. I fometimes 
 fed them with wheat a little bruifed, and 
 notwithftanding they feemed to eat it greedily, 
 their- excrements confifted of dry fragments 
 of this grain. This iikewife happened when 
 they had eaten tough flefh, If I put the 
 excrement in water and fliook it brifkly, the 
 greater part would be fufpended, but a little 
 would fall to the bottom r, this, upon exami-- 
 nation, proyed to be the cellular fubftance 
 with a fewmufcular fibres, of which the par- 
 ticles cohered pretty firmly^ the longefb 
 pieces meafured about an inch. What re- 
 mained fufpended in the water was more thaiTt 
 twice as much as that which fell to the bot- 
 tom, and ftill retained the charadiers of flefh; 
 Young crows, which digeil more fpecdily 
 than the adult (lxix), do not completely di- 
 gefl: tough meat. 1 could eafrly find cellular 
 lubflance am.ong their excrement; but when 
 U 4 infte^id 
 
296 DISSERTATION V. 
 
 inftead of hard they were fed with tender 
 flefh, and with fome foft vegetable inftead of 
 wheat, the excrement did not ihew the leaft 
 appearance of this fort. 
 
 ccxxii. I made the fame obfervation 
 upon frogs. As thefe animals generally feed 
 upon irifecfts, I often found among the excre- 
 ment, when treated in the way jull defcribed, 
 legs, thighs, and wings of locuils, and the 
 cruftaceous parts of other infed:s. 
 ) Leuwenhoeck, upon examining the excre- 
 ment of the m.elvel, found, that it confiiled 
 of filaments refembling the hairs of the beard 
 cut off by the razors thefe filaments he fup- 
 ,pofed to be the undigefled remains of the 
 filhes which the melvel had eaten {a), I can 
 eafily believe this to have been the cafe, ef- 
 pecially as it coincides with an obfervation 
 of my own upon the excrement of the tench, 
 in which, though I could not perceive any 
 flefhy fibres, yet the fragments of bone were 
 diflindlly vifible. I mufl however add, that 
 though I have examined the foeculent mat- 
 ter of many other fifhes with glaffes of vari- 
 ous magnifying powers, I could never dif- 
 tinguifli the leafl atom that had the charac- 
 ters of animal or vegetable matter. I have 
 
 (a) Philof. Tranfaft. n, 152, 1683. 
 
 obferved 
 
DISSERTATION V. 297 
 
 ©bferved the fame thing in that of no6lurnal 
 and diurnal birds of prey. The tough flefh, of 
 which a fmall part was voided along with the 
 excrement of crows (ccxxi), is entirely di- 
 gerted by the eagle, falcon, and owl. This 
 obfervation may be extended to a multitude 
 of birds of various kinds, of which, though 
 I have preferved the names in my journal, to 
 avoid prolixity I forbear to enumerate them. 
 Serpents, though fo flow of digeftion, dif- 
 folve their food fo completely, that not a vef- 
 tige of any organized matter appears in their 
 excrements. This at leaft I have feen in vi- 
 pers, water and land-fnakes. 
 
 Upon comparing my obfervations upon ex- 
 crement with thofe related by Boerhaave and 
 others, 1 think it muft be concluded, that 
 conlidering animals in general, fome fub- 
 flances of both kingdoms are voided un- 
 changed along with their excrements, be- 
 caufe the gaftric fluid is incapable of dif- 
 folving them; but others are voided un- 
 changed, only becaufe they do not continue 
 long enough in the flomach to be digefted. 
 This is fully proved by my experiments on 
 flelli, membrane, tendon, and bone, the very 
 fubftances of which Boerhaave fuppofed, 
 that the folid parts were indigeftible. Flefh 
 taken fporitaneoufly by crows, part of which 
 
 is 
 
ZpS DISSERT A- TION V. 
 
 is voided undigefted, but when kept many 
 hours in the ftomach is completely dilTolved, 
 furnifhes another decifive proof of the fanie 
 propolition. 
 
 It is furely not neceflary to add, that I do 
 not wiili by thefe ftridtures to leiien the high 
 reputation of the Dutch Hippocrates. Un- 
 provided w^ith experiments pf his own, he 
 colledied the opinions of others, and framed 
 a iyitem concerning digeilion fo ingenious 
 and piaufible, that J willingly own that I 
 former^ adopted jt, and would not now re-. 
 jecl it, if I was not comoelled by conclufive 
 experiments. 
 
 ccxxiii. I will conclude this diflertation, 
 with fome remarks on a problem cloiely con- 
 nected with refearches concerning the effici- 
 ent caufe of digellion. Mr. Hunter, one of 
 the beft Engliih anatomiils of the prefent 
 age, frequently found in the dead bodies which 
 he opened that the great curvature of the ilo- 
 mach was confiderably eroded, and fometimes 
 entirely diifolved. In the former cafe, the 
 edges o£ the wound were as foft as half-di^ 
 gefted food, and the contents of the ftomach 
 had got into the cavity of the abdomen. He 
 obferves, that fuch a wound could not have 
 exifled in life, as it had no connecflion v/ith 
 the difeafe, and more frequently appeared in 
 
 perfons 
 
DISSERTATION V. 299 
 
 t 
 
 pcrfons who died violent deaths. In order 
 to difcover the caufe of this pha3nomenon, he 
 examined the ilomachs of various animals,^ 
 both immediately and fome time after death. 
 In feveral he obferved the fame appearance. 
 Hence he thought he was enabled to affign 
 the caufe. He fuppcfes the folution to be 
 owing to a continuance of digeilion after death, 
 and that the gaftric fluid is capable of dif- 
 folving the ilomach when it has loft its vital 
 principle. From this difcovery he infers, 
 that digeflion neither depends on the action of 
 the Ilomach nor on heat, but on the gaflric 
 juices, which he confiders as the true men- 
 flruum of the food {a) . 
 
 ccxxiv. When Mr. Hunter's fhort but 
 fenfible paper came to my hands, I was en- 
 gaged in experiments on digeftion. I had 
 difcovered the primary importance of the gaf- 
 trie fluid in this procefs, and that it adis out 
 of the body ; that is to fay, in the dead body. 
 I knew alfo, that after death this fluid ifl^ues 
 from the coats of the ftomach. From thefe 
 data I had little difficulty in believing the facl 
 related by the Englifli anatomifl:, and adopt- 
 ing his explanation of it : neverthelefs it was 
 proper to repeat the experiment. Being un- 
 
 if) Ph. TranC 
 
 pr 
 
 rovided 
 
300 DISSERTATION V. 
 
 provided with human fubjedls, I had re- 
 courfe to animals. Some were opened fooner, 
 and others later after death; but among the 
 numbers I infpeeled, not one had its great 
 curvature diffolved, or much eroded. . I fay, 
 much eroded, becaufe I have often feen a 
 Yitt]t erolion, efpecially in diiFerent iifhes, in 
 which, when I had cleared the flomach of 
 its contents, the internal coat was wanting. 
 The injury was always confined to the infe- 
 rior part of the fhomach. If thefe fads are 
 favourable to Mr. Hunter, a great number 
 are againll him. They do not however de- 
 flroy his obfervations ; mine are only nega- 
 tive, his are politive; and we know that a 
 thoufand of the former do not deftroy a fingle 
 one of the latter, provided it is well afcer- 
 tained. I have no reafon to diftruft Mr. 
 Hunter, for his paper has the air of inge- 
 nuoufnefs and candour which ufually accom- 
 panies truth. 
 
 ccxxv. The ill fuccefs of my experi- 
 ments did not induce m.e to abandon the idea 
 of digeftion after death, it only led me to 
 confider it in another point of view. If it 
 be true, faid I to myfelf, that the gailric fluid 
 , exerts its a(fi;ion after death, it mufl produce 
 fome folution of the food. Let then an ani- 
 mal be fed and immediately killed, after fome 
 
 time 
 
DISSERTATION V. 3OI 
 
 time let it be opened, and let us fee whether 
 the food has been at all digefted. I deter- 
 mined to bring this obvious inference to the 
 teft of experiment ; I therefore kept a raven 
 fafling' feven hours in order to empty its flo- 
 mach, and then fet before it an hundred and 
 fourteen grains of beef, which were imme- 
 diately eaten, and muft have paffed into the 
 ftomach, as this bird has no crop. I then 
 killed it, and as it was v/inter, put it into a 
 ftove, where it w^as left fix hours. Sup- 
 poUng this to be a fufficient time for the gaf- 
 tric fluid to exert its adion, I opened the fto- 
 mach, and found the flefh in the following 
 ftate. It was impregnated with gaflric 
 fluid, and was become tender; the colour 
 was changed to a pale red, and the furface 
 had a bitter tafte, w^hile the internal parts re- 
 tained the tafte of iiefli. After the gaftric 
 fluid was wiped away, it weighed only fifty- 
 two grains j it had therefore loft above half 
 its weight in fix hours, or, what amounts to 
 the fame thing, was above half digefted. 
 The pylorus, and the duodenum for about 
 an inch, were occupied by an afti-coloured 
 mucus, which muft have been the diflblved 
 part of the flelli. 
 
 At the fame time I gave another raven, that 
 had in like manner been keot faftins; {even 
 
 hou 
 
 rs. 
 
^02 DISSERTATION. V. 
 
 hourSj an equal quantity of flelh, and killed 
 it in two hours and a quarter. My view was 
 to obferve the difference between what had 
 lain lix hours in the dead, and two and a quar- 
 ter in the living flomach, and it was very 
 great -, for in this latter cafe the flefh was to- 
 tally diffolved, except a little cellular fub- 
 ftance, which I have found to be always 
 longer in being digefted than the mufcular 
 fibres; the mucus was the fame as beforcy 
 only in larger quantity, and occupied more 
 of the duodenum. Thefe two experiments 
 compared together prove two things, firft, 
 that digeftion continues after death -, and fe- 
 condly, that it is then far lefs^ confiderable 
 than in the living animal, though in the pre- 
 fent inftance the heat of the ftoVe, which was 
 about 1 00" {a)y mull: have promoted it not a 
 little. The heat of the living raven did not 
 exceed 30° (^). 
 
 ccxxvi. Another dead raven was kept 
 five hours in the fame ftove, after I had forced 
 two dead lampreys, weighing together^ an 
 hundred and twelve grains, down its throat. 
 One lay in the oefophagus, the other had 
 reached the flomach and was completely de- 
 
 {a) Two hundred fifty-feven deg. Fahr, Thef. 
 (i) One hundred nine and an half ditto.. 
 
 . compofed. 
 
Dissertation v. 303 
 
 compofed, while the former was indeed en- 
 tire, but foft and flaccid* This accid^^nt 
 proves, that the gaftric fluid is capable of pro- 
 ducing a fenlible degree of digeftion at a time 
 when the oefophageal juices are inert. 
 
 ccxxvii, Thefe experiments were made 
 in winter. I determined to repeat them the 
 next fummer, becaufe then I could expofe 
 the dead animals to a greater heat. Accord- 
 ingly in that feafon fome bruifed veal was 
 given to two ravens, which v/ere immedi- 
 ately killed, and left fQvcn hours in a window 
 expofed to the fim. We have already feen 
 in feveral pafl^ages, the influence of heat 
 in promoting artificial digefliion (cxlii, 
 CLxxxvi, cci, ccxvii). Nor did it now 
 appear lefs confiderable. Each raven had 
 eaten fixty-eight grains of fiefh, of which 
 there was not an atom left entire; it was all 
 difibived into the ufual gelatinous pulp, and 
 the greater part had paflTed through the py- 
 lorus. 
 
 Thefe fads, I think, decifively prove, 
 that animals, at leaft the fpecies jufl: men- 
 tioned, continue to digeffc after death. If 
 we confider the matter rigofoufly, it will be 
 proper to obviate a difficulty that may be 
 Aarted. Hov/ever careful we are to kill 
 
 the 
 
304. DISSERTATION V. 
 
 the animal immediately after it has fwallow* 
 cd food, it is certain, that there will be a 
 fliort interval between the time the food gets 
 into the ftomach and the death of the animal, 
 and that the gaftric fluids ad: upon it du- 
 ring this interval. Moreover, after death 
 they will a6t for fome time juffc as in life, 
 fince the vital heat is not inflantly exftin- 
 guifhed. The digeflion therefore obferved 
 in dead animals may, if not entirely, at 
 leail in part, be produced by the gailric 
 fluid adiing during life, and a fliort time 
 after death. 
 
 Nothing could be more eafy than to afcer- 
 tain the juflnefs of this fufpicion, fince we 
 have only to thruft a little food into the flo- 
 niach of a dead and cold animal, and obferve 
 the confequence. I made the experiment 
 upon a raven that had been dead an hour, and 
 had now only the temperature of the atmo- 
 sphere. Forty- two grains of beef cut into 
 pieces were forced into the ftomach, which 
 was opened after the bird had lain feven hours 
 expofed to the fun . And here inflead of pieces 
 of folid flefh, I found only the ufual pulpy 
 mafs, partly in the llomach and partly in the 
 duodenum. The folution was therefore ef- 
 feded by the gaftric fluid, independently of 
 the powers of life. 
 
 CCXXVIIIo 
 
DISSERTATION V. ^o^ 
 
 fccxxviii. The experiment was repeated 
 Upon an owl and a blackbird, which were 
 killed immediately after meat had been given 
 them, and left fsven hours in a warm tem- 
 perature. The fiefh given to the black- bird 
 had been cut into three pieces, which to- 
 gether, amounted to eighty-two grains 5 the 
 owl had fvvallowed half an ounce and iix 
 .grains in one piece. Upon opening the 
 ftomachsi I found the four pieces 5 but the 
 furface was covered with a ilratum of mu- 
 cus, which fliewed, that the fleih had been 
 dilTolved. 
 
 I thought, that perhaps if the flefh had re- 
 mained a longer time in the ftomach it v/ould 
 be more digefted; but this did not happen^ 
 at leall when I repeated the two preceding 
 experiments under the fame circumftances> 
 except that the birds were expofed to the fun 
 for twenty-two hours* I could not perceive, 
 that the folution of the flefh was carried any 
 further. The entrails emitted a putrid fmell, 
 but this was not the cafe either with the fto*. 
 mach or its contents. 
 
 ccxxix. That I mi^ht be warranted in 
 deducing general confequences, I refolved to 
 repeat this fmgular experiment upon various 
 piaffes of animals, and therefore had recourfe 
 to iiihes and quadrupeds. Of the former^ 
 
 Vol. L X the 
 
306 DISSERTATION V.' 
 
 the iifh-market at Pavia only affords the pike, 
 carp, barbel, tench, eel, and the like -, but I 
 took care to procure fuch as were veryfrefh. 
 I introduced into the flomach various animal 
 fubftances, as little fiihes, bits of veal and 
 beef, frogs, grubs, 6cc. and opened them af- 
 ter an interval, fometimes fhorter and fome- 
 times longer. I will give in a few words 
 what is fet down at great length in my Jour- 
 nals. The part of thefe fubftances that lay 
 in the oefophagus, a polition which they of- 
 ten had, was unaltered; this was fome- 
 times the cafe with that which had got into 
 the ftomach, but it was generally more or 
 lefs eroded. A circumftance refpecling frogs 
 deferves to be mentioned. The tough {kin 
 of thefe- animals was often deftroyed, efpe- 
 cially at the bottom of the ftomach ; and 
 where it ftill remained it was fo much foft-^ 
 ened, that the flighteft force was fufficient 
 to- lacerate it. > Hence it appears, that the 
 gaftric fluid of fifhes retains its property of 
 diffolving flefh, but in an inferior degree 
 to that of birds, fince it did not diffolve fo 
 much. 
 
 CO XXX. The quadrupeds upon which I 
 made thefe experiments, were dogs and cats. 
 After keeping them falling many hours, I 
 gave them a certain quantity of fleih, and 
 
 then 
 
DISSERTATION V. ^07 
 
 then flrangled them without delay. Of three 
 dogs and three cats, two of the former and 
 as many of the latter were expofed to the fun 
 for nine hours ; the others were left in the 
 fhade. In the firfl the furface of the flefli 
 was gelatinous as ufual, but in the laft this 
 appearance was fcarce perceptible. Thefe 
 experiments confirm the utility, I fhould ra- 
 ther fay, the neceflity of heat to digeftion in 
 many animals. 
 
 ccxxxi. To conclude this curious en- 
 quiry, I refolved to fee what change would 
 take place upon fleih when the ftomach was 
 taken out of the body, I made this experi- 
 ment upon a cat, a raven, and an owl. Hav- 
 ing fed them fparingly, I cut out the fto- 
 mach, and threw ligatures round the cardia 
 and pylorus to prevent the contents from get- 
 ting out. They were expofed to the fun in 
 a velTel of water, left the heat ftiould dry 
 them. In five hours and an half they were 
 opened : the water had tranfuded through the 
 coats j the -furface of the flefti was a little 
 gelatinous, efpecially in the ftomach of the 
 raven and owl; but the folution was trifling, 
 in comparifon with that which took place 
 when the ftomach w^as left in the body. This 
 was what might be expected, when the cefo- 
 X 2 . phagus 
 
3o8 DISSERTATION V. 
 
 phagus no longer poured its liquor into the 
 flomach. 
 
 In thefe experiments I did not perceive any 
 erolion of the ftomach, any more than in 
 thofe made with the view of verifying Mr. 
 Hunter's (ccxxiv). I only faw what I had 
 feen before (ibid), a flight excoriation of 
 the inferior part. We mufl therefore infer, 
 that the coats of the ftomach fuffer lefs after 
 death than flefh introduced into it. I gave 
 an hungry dog fome pieces cut out of the 
 ftomach of another dog ; he eat and it killed 
 him immediately. Aft^r the body had lain 
 in a warm lituation nine hours, the ftomach 
 was opened. The pieces were fenlibly dif- 
 folved, but no change was produced upon 
 the ftomach of the animal, if we except the 
 large curvature, which was fo much mace- 
 rated, that the villous coat might eafily be 
 rubbed off. It is, I think, not difficult ^o 
 affign the reafon, why the ftomachs of dead 
 animals are not liable, like their contents, to 
 be dillolved. Thefe bodies are inverted on 
 all lides by the gaflric fluid, whereas it ads 
 only on the internal furface of the ftomach. 
 
 Upon reviev/ing the experiments related in 
 the ccxxvth and fbllowing paragraphs it 
 cannot, I think, be doubted, that digeftion 
 
 goes 
 
DISSERTATION V. 3(59 
 
 goes on for fome time after death. I there- 
 fore entirely agree fo far with the celebrated 
 Englifh anatomifl, but I cannot with him 
 fuppofe, that this funcflion is independent of 
 heat (ccxxiii); numberlefs fa(fls related in 
 this work fully prove the contrary. 
 
 X 3 D I S- 
 
t 310 3 
 
 DISSERTATION VI. 
 
 WHETHER THE FOOD FERMENTS IN THE 
 STOMACH, 
 
 CCXXXIL T WILL now, agreeably to my 
 promife in the foregoing dif- 
 fertation (ccxxi), enquire whether the food 
 ferments in the ftomach. This opinion was 
 almoft univerfally adopted by phyficians about 
 the middle of the laft century, an aera at 
 which the explanation of the various func- 
 tions of the human body was fought in fer- 
 mentations of various kinds, as it had be-, 
 fore been in a fubtile matter, as it has fince 
 been in elediricity, and is at prefent in divers 
 forts of elaftic fluids. This notion was af-^ 
 terwards combated among others by Boer-» 
 haave, who found, by diredl obfervations, 
 that this multiplicity of fermentations did 
 
 nut 
 
DISSERTATION VI, 311 
 
 not exifl in nature, but was merely the fug- 
 geftion of fancy. Of the numberlefs modi- 
 fications of this procefs, which phyfiologifls 
 had imagined, he admitted only that very li- 
 mited and imperfedt one, which, according 
 to him, takes place in the ftomach. The 
 food in the flomach of animals, and parti- 
 cularly of Man, is, in his opinion, in cir- 
 cumftances highly favourable to fermenta- 
 tion. The faliva and the gaftric fluid ferve 
 inflead of water; the free accefs of air, the 
 clofenefs and heat of the flomach, the nature, 
 of the food itfelf neceffarily produce fermen- 
 tation, as is farther evident from the eruc- 
 tations confequent upon taking food, and 
 the rumbling noife frequently heard in the 
 belly. But the fhort continuance of the food 
 in that vifcus, and other caufes, prevent the 
 procefs from being ever carried to its utmofl 
 pitch. 
 
 ccxxxiii. Thus far only, according ^to 
 Boerhaave and his followers, does the fer- 
 mentation of the food proceed in the flo- 
 mach. This limitation has been thought 
 too great by Dr. Pringle and Dr. Macbride, 
 two celebrated modern phyficians. They 
 find no difficulty in fuppofing, that a com- 
 plete fermentation takes place in digeflion, 
 and that it is the chief agent in this impor- 
 X4 tant 
 
312 DISSERTATION VI. 
 
 tant fun(flion. In their refearches on this 
 fubjed:. they have endeavoured to imitate the 
 pperations of nature out of the body. They 
 took various aninial and vegetable fubftances, 
 fuch as are ufed every day for food; they 
 placed them both by themfelves, and mixed 
 with feveral other fubflances in a vs^arm tem- 
 perature, adding a quantity of v^ater or fali-r 
 ya. Under thefe circumftances they found, 
 that they fooner or later began to ferment -, 
 that this procefs afterv^ards ran very high, 
 then abated, and at laft ended in the decom^- 
 pofition of the feveral fubftances, which ac- 
 quired alfo a fweet tafk. Thefe different 
 gradations of fermentation were evident from 
 the fwelling, rarefad:ion, and intelline move- 
 n^ent of the mafs, from the generation of a 
 multitude of air-bubbles, and from the fub- 
 jflances which at iirft funk to the bottom, at 
 length floating on the furface of the fluid. 
 Thefe experiments firft made by Pringle, and 
 afterv/ards repeate4 and varied by Macbride, 
 determined them both to confider digeflion as 
 a procefs merely fermentative. Their theory 
 is as follov/s. The food divided bymaflica- 
 ■4ion and penetrated by the faliva, begins as 
 foon as it gets into the flomach to be agitated 
 J3y that intefline movement which always 
 accompanies fermentation ^ this movement 
 
DISSERTATION VI. 313 
 
 is excited by the warmth of the place, by 
 the remains of food taken before, by the gaf-r 
 trie fluid, and above all by the faliva, which 
 is particularly adapted to produce and pro- 
 mote this procefs. The firft etfed: of the in- 
 teftine commotion will be to raife the folid 
 parts of the aliment to the furface of the gaf- 
 tric liquor J here they will be fuftained for 
 fome time by the air-bubbles ; but on their 
 izeffation they will fall down again and be tho- 
 roughly incorporated with the fluids of the 
 ilornach? The perilialtic motion, the alter- 
 nate prelTure of the diaphragm and abdomi- 
 pal mufcles, and the continual pulfation of 
 the adjacent large veflfels will render this mix- 
 ture fl:ill more complete. In fuch a fl:ate the 
 food pafl^es into the fmall intefl:ines, where 
 the fermentative motion produces fl:ill greater 
 changes in confequence of the mixture of the 
 bile and pancreatic juice. And now the va- 
 rious kinds of food are changed into a fweet, 
 mild, nutritious matter, which ferments 
 briflfly, and is denominated chyle. In con- 
 formity with this theory, thefe phyficians 
 efl:abliih a new fyfl:em of great importance, 
 according to them, in the practice of medi- 
 cine. It is ingenioufly explained by Pringle, 
 in his Appendix containing Experiments on 
 fceptjc and antifeptic Subfl:ances, and by 
 
 Macbride 
 
314 DISSERTATION Vf," 
 
 Macbride in his experimental EiTays on the 
 Fermentation of alimentary Mixtures. 
 
 ccxxxiv. The opinion of thefe two mo- 
 dern writers have been adopted by many phy- 
 fiologifts, while others have ftill adhered to 
 the doctrine of Boerhaave, concerning an in- 
 cipient and incomplete fermentation only 
 taking place in the ftomach 5 fo that on this 
 fubjed: the phylicians of Europe feem to be 
 divided into two fecfts. When I read Pringle 
 and Macbride, I had only made a few expe- 
 riments on the digeftion of fome animal and 
 vegetable fubftances enclofed in tubes by gal- 
 linaceous birds (xxxix, xl, xli, xlii, 
 XLiii); and I began to perceive, that the 
 gaftric juice aded as a menilruum upon the 
 food. But I could not learn from thefe ex- 
 periments, whether fermentation takes place 
 at the time they are diffolved. As indeed the 
 gaftric fluid is a folvent, it may ad: indepen- 
 dently of fermentation; chemiftry affords 
 numerous inilances, in which there is no to- 
 ken of fermentation during the diffolution of 
 the folvend. But there is no abfurdity in 
 fuppofing, that an intefline fermentative mo- 
 tion is generated in the mixture, at the time 
 the gaflric fluid diflblves the aliment. And 
 in this cafe, fermentation would accompany 
 digefl;ion, though it would not according 
 
 to 
 
DISSERTATION VI. 315 
 
 to the dodrine of Pringle and Macbride 
 (ccxxxiii), be the efficient caufe. In order 
 to obtain information concerning this phse- 
 nomenon which I had not noticed, I had re- 
 courfe to further experiments. As the theory 
 in queftion is entirely founded on the fermen- 
 tation of animal and vegetable matters in vef- 
 fels, I fet in glafs phials breads flefh, and 
 faliva; bread, flefh, andv^ater; flour, faliva, 
 and flefh; for in thefe mixtures the writers 
 above-mentioned obferved the moil; rapid 
 fermentation. The phials were flopped, and 
 fet in a place where the heat amounted to 
 20° — 24° {a). The mixtures began, fome 
 fooner and others later, to emit air-bubbles, 
 which foon encreafed in frequency and fize ; 
 the furface of the liquor was covered with 
 froth, which continued as long as any air was 
 generated. During this time the mafs fwelled 
 greatly, the inteftine commotion was mani- 
 fefl, and the fubll;ances immerfed being made 
 fpecifically lighter by the air-bubbles that 
 adhered to them and the increafe of bulk, 
 rofe to the furface of the fluid. Here then 
 the tokens of fermentation were apparent, 
 and fo far I entirely agree with Pringle and 
 Macbride. 
 
 {a) Seventy.feven and eighty-fixdeg. of Fahr. Ther. 
 
 ccxxxv. But 
 / 
 
^l6 DISSERTATION VI. 
 
 cexxx,v, But found logic forbaiie rtie to 
 allow fo readily, that the fame procefs takes 
 place in the ftomach. I had indeed many 
 reafons for with-holding my affent. Not to 
 mention the fhort continuance of the food in 
 that vifcus, a circumftance which did not 
 efcape Boerhaave (ccxxxii). I confidered, 
 that although the faliva produces and pro- 
 motes fermentation, the gaftric fluid may not 
 have this property. Though the gaftric fluid 
 confifhs in part of faliva, yet as there are fe- 
 veral other ingredients, a compound mufl be 
 formed with properties different from thofe 
 of its confliituent parts. I have adduced many 
 inftances to prove, that the gaftric fluid re^ 
 tains in fome meafure its folvent power out 
 of the body; but the faliva never exhibited 
 any fuch property. I have already ihewn, 
 and iGhiall ftill more clearly fhew in the fequel, 
 that fleih immerfed in the gaftric fluid is not 
 liable to putrefaction; but when put into far 
 liva, it putrefies fooner than in water. This 
 was one of my motives for not immediately 
 adopting the ideas of Pringle and Macbride. 
 It were to be wifhed, that thefe phyfician.s 
 had made trial of the gaftric liquor alfo, be- 
 fore they concluded, that what they obferv- 
 ed in vefl^els takes place likewife in the fto- 
 m^-ch,* nor can I well conceive, how they 
 
 both 
 
D I S S E R T A T I b N VI. 3!^ 
 
 both came to overlook a circumftance of fo 
 great importance. Moreover we know, that 
 refl is necefTary to fermentation ; but the flo'^ 
 mach, belides the motion of the w^hole body, 
 has a movement peculiar to itfelf. Lailly, 
 iliould fermentation once begin, it muft in 
 all likelihood be foon flopped by the frefh fa- 
 liva and gaftric liquor that are running per- 
 petually, and in no fmall quantity, into the 
 flomach. Thefe two lafl objed:ions have 
 been already ftarted, though nobody, as far 
 as I know, has taken the pains of verifying 
 them by experiment. But as the queftioii 
 could be decided in this way only, I deter- 
 mined to undertake to fupply the omiffion. 
 
 ccxxxvi. I have already fpoken of ar- 
 tificial digeflion in feveral pafTages. Experi- 
 ments of this kind afforded me an excellent 
 opportunity of obferving, whether the folu- 
 tion of flefh out of the body was accompa- 
 nied by fermentation, and I never failed in a 
 fmgle inflance to attend to this circumflance. 
 I found, that when the veflels remained at 
 refl, a few fmall air-bubbles began to arifc 
 in the fpace of a few hours ; they afterwards 
 became larger and more frequent, and adhe- 
 ring to the immerfed fubflances, caufed them 
 to rife to the furface of the liquor. This air 
 .was either entangled in the mixture, cr, ac- 
 cording 
 
3l8 DISSERTATION. Vt. 
 
 cording to Pringle and Macbride, formed 
 part of it, was extricated, and rendered elaf- 
 tic by the heat, or what feems more probable^, 
 came from both thefe fources. The mix- 
 tures either funk again or continued to float, 
 while they were difToh^ed by the gajftric men- 
 fl:ruum; not the llighteft inteftine motion 
 was ever perceptible, juft contrary to what 
 happens when faliva is employed. If I now 
 and then fhook the vefTel a few hours after 
 making the infufion, very few air-bubbles 
 were generated, and the mixture hardly ever 
 rofe to the furface, though it was juft as 
 well dilfolved as when the velTel remained at 
 perfect reft. I find in my Journals, that I 
 agitated the vefTels upon fourteen different oc- 
 cafions without obferving the fmallell diffe- 
 rence in the refult of the experiment. I 
 could not therefore allow, that fermentation 
 was the efficient caufe of thefe artificial di- 
 geflions, nor even that it was a concomitant 
 circumllance, or an effe6l; andfrefh experi- 
 ments inclined me more and more to rej^d: 
 this opinion. I have already mentioned the 
 great abundance of gaflric fluid in crows, and 
 the facility with which they digefl their 
 food, more efpecially neftlings (lxix, 
 Lxxxiii). Among the various trials I 
 made with this fluid out of the body, I en- 
 deavoured 
 
DISSERTATION VI. 319 
 
 deavoured to renew it, as it is renewed in the 
 itomach. Several glafs tubes were filled with 
 it to a certain height, and fufpended in a ver- 
 tical polition; into the upper extremity a 
 fmall funnel was put; fome gaftric fluid was 
 poured into it from time to time, the nar- 
 rownefs of the orifice of the funnel allowed 
 it to fall only drop by drop into the tubes. 
 The lower extremity of the tubes was not 
 clofely ftopped, that nearly as much might 
 run out below as fell in from above. Mat- 
 ters being thus arranged, I immerfed in the 
 tube flelli and bread, both by themfelves 
 and mixed together. The folution was ex- 
 ceedingly fpeedy, on account both of the 
 warmth of the atmofphere, and the conflant 
 renewal of the gaftric fluid. Notwith- 
 flianding the tubes remained at perfed: reft, 
 .only a few air-bubbles were difchargedj not 
 the leafl: intefliine motion could be perceived; 
 the flefh and bread fell immediately to the 
 bottom, and remained there till they were 
 gradually incorporated with the gailric fluid : 
 in fhort, they were digefted without a Angle 
 circumftance occurring that ufually attends 
 fermentation. 
 
 ccxxxvii. If this procefs does not take 
 place out of the body, it feems highly impro- 
 bable that it fhould within ; however, to be 
 
 certain 
 
325 DISSERTATION fl. 
 
 Certain of this, it was proper to confult th6 
 fenfes. Is digeftion, according to Pringld 
 and Macbride, a fermentative procefs ? Let 
 us then obferve it while it is going on, fur- 
 prize Nature in her operation, and fee in what 
 it eonlifts. With this view, I gave four- 
 hens that had been kept failing twelve hoursj 
 fome wheat j and in five hours opened the 
 gizzard without killing them. This method 
 I pradtifed in the following experiments^ be-^ 
 ing apprehenfive left opening the animal after 
 death might not anfwer the end I had in view; 
 Both gizzards were full of grains of wheat 
 moflly broken, and mixed with a femifluid 
 farinaceous parte. The orifice of the pylorus 
 and great part of the duodenum was full of the 
 iame pafte, which had not in this cafe much 
 fluidity. Upon examining this pafle^ both 
 with my naked eye and the microfcope, I 
 could not perceive any fign of fermentation ', 
 the parts were at perfecft reft, and entirely 
 free from air-bubbles. I waited three hours 
 longer before I opened the gizzards of the 
 other two ducks, in order to fee v/hether what 
 had not taken place at the beginning of the 
 procefs, might not have happened when it 
 was further advanced. In this cafe, the pafte 
 was more diluted with gaftrie liquor*, and of 
 the grains of wheat little was left but the 
 
 bran I 
 
DISSERTATION VI^ 32I 
 
 bian; I obferved no more intefline motion 
 or air-bubbles than before. 
 
 c cxxx V III. My next experiment Was made 
 "upon three ravens that had not yet quitted 
 the neft. Two hours after I had fed them 
 with beef, I opened the ftomach of one of 
 them. The flefh was half diffolved, but I 
 could not perceive any lign of fermentation. 
 I made the fame obfervation upon the two 
 others, which were opened an hour and three 
 quarters afterwards, notwithftanding digef- 
 tion was finiflied; for nothing remained in 
 the ftomach but a denfe grey fluid, confift- 
 ing of flelli dilTolved in the gaftric fluid. 
 
 Of animals with membranous ftomachs I 
 examined an owl, feveral dogs, cats, and 
 land and water-fnakes, endeavouring always 
 to make my obfervations at three diftind: 
 times, at the beginning, towards the mid- 
 dle, and at the end of digeftion. But at no 
 time did I perceive any tendency to fermen- 
 tation. In one dog and one cat only did I ob- 
 ferye a few air-bubbles among the food after 
 it v^as completely digefted ; but there was not 
 the leaft inteftine motion perceptible. Ser- 
 pents, which are animals fo fl^ow of digeftion, 
 were well adapted to fhew the progrefs of 
 this fundiion^ but neither did they form an 
 exception to the general obfervation. Thefe 
 
 Vol. I, Y fads 
 
322 BlSSEfi^TATION Vl. 
 
 Jadls obliged me to reje(ft the opinion of the 
 Britifh phyficians and their followers; nor 
 do I know whethef that of Boerhaave is 
 ^^dmiflible, who, while he excludes a com- 
 plete, infers an incipient fermentation from 
 the eradiations that arife after taking food 
 (cCxxxii); but this maybe occafioned by 
 the rarefadtion of the air entangled among 
 the aliment, by the mere heat of the fto- 
 mach. 
 
 ccxxxix. Modern chemiUs have diilin- 
 g'uiihed three fpecies or degrees of fermenta- 
 tion, the vinous or the fweet, the acetous, 
 and the putrid. As they effentially confift in 
 an inteftine motion excited by heat and a pro- 
 per degree of moifture [a], and as no fuch 
 motion can be feen in the food in the fto- 
 mach, it follows, that not even the vinous, 
 much lefs the acetous or putrid takes place ia 
 digeftion. It remains to be enquired, whe- 
 ther this fiin<ftion is connected with a prin- 
 ciple of acidity, as fome fuppofe, or of pu- 
 trefaftion, according to others. I Ihall ftate 
 the fads- which appear to favour each of thefe 
 opinions. In behalf of the iirft, its advo- 
 cates adduce acid eru<flations and vomitings 
 from the haman ftomach, that difagreeable 
 
 («) Macquer Dift. Artt Fermentation* 
 
 acid 
 
DISSERTATION VI. 32g 
 
 acid fmell which is exhaled from the flomachs 
 of granivorous birds and ruminating animals, 
 the acetous tafle of the internal coat 3 the 
 diminution of the bulk of the contents of the 
 ftomach of man and animals, not to mention 
 other arguments that may be feen in modern . 
 phyiiologifts, and efpecially in Haller. 
 
 ccxL . The prodigious number of ftomachs 
 I have opened, have afforded me opportuni- 
 ties of acquiring full information on this 
 point. In animals flrictly carnivorous, fuch - 
 as birds of prey and ferpents, the food never 
 has an acetous tafte, either to the tafte or 
 fmell during the time of digeftion* Th.6 
 fame obfervation will apply to frogs and fifhes ; 
 and it maybe extended to omnivorous animals, 
 fuch as crows, when they feed upon fleih ; 
 but the pultaceous mafs refulting frdm vege^ 
 tables, and in particular from bread, now 
 and theil acquire a flight acidity. I have 
 obferved the fame tafte in two dogs, and more 
 frequently in herbivorous animals, fuch as 
 fheep and oxen; and alfo in thofe which are 
 at once herbivorous and granivorous, viz. in 
 the gallinaceous kind; and in the laft-men- 
 tioned clafs, not only the food in the fto- 
 mach had an acetous tafte, but that in the 
 craw likewife. In the third differtation will 
 be found fpme inftances of thi§ (cxxxix, 
 
 Y 2 • CXL, 
 
^44 DISSERTATION Vt. 
 
 cxLy CXLI, cxLiii). With refpedl to Mafl^ 
 I will relate what has happened to myfelf^ 
 During the whole month of May and great 
 part of June^ I eat flrawberrieS with fugar 
 and white wine at dinner and fupper. Frorii 
 this agreeable mixture I never experience any 
 inconvenience in the day-time ) but by what 
 I eat in the evening my fleep is frequently 
 difturbed; the coiltents of my flomach rife 
 dlmoft into rriy mouth, and then fall back 
 again, leaving a moft difagreeable four tafte 
 behind. This unpleafant circumftance does 
 not, however, prevent me frorri recovering 
 my reft, and digefting my food perfetflly. I 
 have befides many times been fubjedt to a 
 like difagreeable fenfation, after eating tOQ 
 much fruit in fummer and autumn. Every 
 inan muft fome time or other have been fen- 
 fible of his meat and drink having turned 
 fbur. 
 
 ccxLi. I was further defirous of know- 
 ing, whether the acid principle fometimes 
 found in the ftomach, is capable of diflblving 
 calcareous earth, and fuch other bodies as 
 acids ad: upon. I accordingly gave fome car*, 
 nivorous birds pieces of coral and fea-fhells, 
 and they were thrown up without any change 
 6t colour, or diminution of weight* This 
 was what might be expeded. I next made 
 
 the 
 
BISSERTATION VI. 325 
 
 the fame experiment on a hen and a turkey, 
 which were killed in two days, The coraj 
 aud ^ells were very much corroded, and the 
 former was reduced to pieces; but a mo- 
 ment's refled;ion fhewed me, that the corro- 
 fion might be owing to the ad:ion of the flo- 
 mach, and not to an acid. The doubt, how- 
 ever, might eafily be removeci, by enclofjng 
 the fame fuhftances in (trong metallic tubes „ 
 The refult of feveral experimqnts made ja 
 this nianner vv^as, firfl, that the pieces of cot 
 ral and fhejl were almofl always dimini(he4; 
 but the diminution fcarce ever exceeded three 
 pr four grains: fecondly, that the furface 
 was foftened j; and thirdly, that it was turned 
 black, efpecially in the coral. I immerfed 
 at the fame time the fame fubftances in, di- 
 luted vinegar, and as fimilar effed;s were pro- 
 duced, and particularly the black colour, I 
 inferred, that the pha^nomena rpfe from a 
 like caufe ^ laftly, I repeated the experiment 
 on myfelf^ The tubes vvere covered as her 
 fore (ccviii), to prevent any feculent matter 
 from getting into them. They were all voide^i 
 without inconyenience. When I eat flefh, 
 with the ad4ition only of a little bread, the 
 fubflances were neither diminifhed no^ altered 
 in their colour. But upon eating a large 
 quantitj^ of different vegetables, the coral 
 
 T3 ^"4 
 
326 DISSERTATION VI. 
 
 and fhells were generally diminifhed and dark^ 
 ened. Thefe facts prove the prefence of an 
 acid principle in the flomachs of fome ani- 
 mals, and Man himfelf. It is, however, not 
 perpetual, hut depends on the quality of the 
 food. 
 
 ccxLii. This acid foon difappears. I 
 gave feveral gallinaceous fowls fome bread at 
 the fame time. The ftomachs were examin- 
 ed at different intervals, viz. two, three, three 
 and an half, four, and five hours afterwards. 
 As long as the bread preferved its cpnfiftence, 
 it was frequently acid ; but as foon as it was. 
 reduced to chyme this tafte was totally loil. 
 Nor could I perceive the leaft fign of it in 
 that which had paffed into the duodenum. 
 I made upon myfelf the following obferva- 
 tion. 
 
 When the unpleafant acid tafte mentioned, 
 above (ccxl) came into my mouth in con- 
 fequence of eating ftrawberries, I kept my- 
 felf awake twice during the remainder of the 
 night. Acid erudiations continued to arife 
 for fome time ; they at laft ceafed y yet from 
 a fenfe of weight I knew, that the contents, 
 of the ftomach were not entirely digefled ; 
 but the flatulence that came from them had 
 no longer the flighteft acidity. 
 
 qcxLiu. But 
 
DISSERTATION VI. 327 
 
 ccxLiii. But what produces this acidity 
 in the ftorqach ? Does it come from the gaf -^ 
 trie fluid, or from the food ? There are gooci 
 grounds for rejediing the former, and admits 
 ting the latter of thefe fources. In the firft 
 place, this acidity does not appear on all oc- 
 calions ; I never could obferve it arifing from 
 flelh. Now if it came from the gaftric fluid, 
 why fliould it not be communicated to every 
 kind of food, fmce every kind is alike impreg- 
 nated with it ? Secondly, when I eat vegeta- 
 bles, the eiFet^ts of an acid in my ftomach were 
 apparent, but not when I eat fleih (ccxli)-. 
 Thirdly, when vegetable food is completely 
 diflToIved by the gaflric fluid, it then lofes all 
 acidity (ccxlii), Lafl:ly, if acid bread be 
 enclofed in tubes and given to a crow, when 
 it is thrown up four or five hours afterwards^ 
 the little that remains inftead of being four, 
 is now turned fweet. 
 
 CO XL IV. Notwithflianding thefe proofs^ 
 that this acidity is not owing to the gaftric 
 fluid, but to the tendency the food itfelf has 
 to turn four whenever it is in a warm tempe- 
 rature, is it not fuppofed, that this fluid both 
 in Man and animals is of an acid nature ? 
 Have not molf of the antient and many mo> 
 dern phyficians fubfcribed to this opinion ? I 
 iliould therefore have incurred the reproach 
 Y 4 of 
 
32S DISSERTATION VI.' 
 
 of negligence, if I had not undertaken a 
 chemical analyfis of it. The gaftric fluid of 
 every animal mentioned in thefe dilTertations, 
 not excepting my own, was fubmitted tq 
 the following experiments. Having taken 
 the precautions above defcribed (lxxxi, 
 ccxv), to procure it in a ftate of purity, I 
 dropped it upon fait of tartar per deliquiunty 
 and into the nitrous and marine acids, without 
 ever perceiving any change of colour, any mo- 
 tion or effervefcence ; whence I was obliged 
 to infer, that the gaftric fluid is neither acid 
 nor alkaline, but neutral. I thought it 
 would alfo be proper to fubjed; thofe kinds 
 which could be procured in larg^ quantity, 
 as that of the crow, to the adion of fire; I 
 therefore entreated my illuftrious colleague 
 and frierid, Counfellor Scopoli, to undertake 
 the analyfis, as he was not only provided with 
 the proper apparatus, but eminent for his 
 &ill in chemiftry, of which fcience he is de- 
 fervedly public profefibr. He complied with 
 my requeft, and in a few days favoured tjie 
 with the following account, 
 
 Chemical 
 
DISSERTATION VI. 329 
 
 Chejnical Analyjts of the Gafiric Fluid of tlpe 
 
 Crow, 
 
 ** The liquor is turbid, and of a darkifh 
 colour. When fhaken it emits a fmell rather 
 difagreeable. 
 
 When triturated with quickrlirne or fait of 
 tartar, a fetid urinous odour is exhaled. 
 
 It does not effervefce with either of th^ 
 .mineral acids. It gives rather ^ green hue tp 
 fyrup of viplets. 
 
 Two drachms expofed to a gentle heat left 
 a dark - coloured fediment weighing two 
 grains, which attracfted the humidity of the 
 air. This reliduum had a naufeous fmelL 
 It did not effervefce with acids. 
 
 I next filtered and diflilled it. A darkiih 
 matter was left upon the filter, which, when 
 it was dried, appeared in the form pf a nut- 
 brown powder, of a fait and bitter tafte. 
 
 The liquor which pafled into the receiver 
 w^s diyided into five portiojis. The firfl had 
 a flight tafle, and an empyreumatic fmell. 
 The fecond had a flronger tafle and fmell. 
 The third, fourth, and fifth refembled the 
 fecond, but the lafl had the flrongefl empy- 
 ^■euma. 
 
 The 
 
330 DISSERTATION VI. 
 
 The belly of the retort was almoft en- 
 tirely covered with a white faline fubftance, 
 which upon being tritura^ted with quick-lime 
 emitted a fetid urinous fmell. In the bottorn 
 there remained a tough dark-coloured fub^ 
 ftance, refembling an extract. It did not ef- 
 fervefce vv^ith acids ; its fmell was ernpyreu^ 
 matic, and its tafte fait, bitter j and naufeous. 
 This fait is neither acid nor alkaline, for it 
 does not efFervefce either with acid or aU 
 kalies ; but when a little oil of tartar per de^ 
 liquium is mixed with it, it emits a pene-*» 
 trating urinous odour, exa<5lly like that of 
 fal ammoniac » , 
 
 From thefe experiments we may conclude^ 
 that the gaftric fluid contains, lirft, pure 
 watery fecondly, a faponaceous and gelatinous- 
 animal fubllance; thirdly, faf ammoniac 5 
 fourthly, an earthy matter like that which 
 exifts in all -animal fluids. 
 
 The faponaceous fubfl:ance altered by fire 
 emits that unpleafant empyreumatic fmell. 
 
 The fal ammoniac being enveloped by the 
 foapy matter does not fublime, as it does 
 when not entangled by other fubilances. 
 
 The gailric fluid of the crow precipitates 
 filver from nitrous acid> and forms lun^ cor-^ 
 nea. This phiEnomenon might induce us to 
 fuppofej that common fait exifl:s ii> the gaf- 
 
 tric^ 
 
DISSERTATION VI. 33I 
 
 trie fluid; but as the fait contained in this 
 fluid is not common fait but fal ammoniac, 
 we mufl fuppofe, that the filver is feparated 
 from the nitrous, on account of its ilronger 
 attraction for the marine acid, which alfo far 
 exceeds the attradion of the volatile alkali 
 for the latter acid, 
 
 I v/i(h you would repeat thefe obferva-? 
 tions on the craftric fluid of animals feeding 
 only on vegetables, If in this alfo fal ammo- 
 niac fhould be found, we rnufl: conclude, that 
 the marine acid is generated by the animal 
 powers ; and we might fufped:, that the ma- 
 rine acid of fea fait is produced by the ani- 
 mals that inhabit the ocean. This is how- 
 ever a mere conjecture. 
 
 I am. Sec, 
 
 SCOPOLI." 
 
 A little after I had received this account 
 from my celebrated colleague, I quitted Pa- 
 via, to fpend the fummer vacation in my own 
 country, where I had no opportunity of 
 making experiments on the gaftric fluid of any 
 animal ftridly herbivorous, though I earnefl:ly 
 Wiiiied for it. I obtained, l:^owever, fatis- 
 
 factory 
 
33? DISSERTATION Vf. 
 
 fa(flory proofs from the raven, that the ammo* 
 niacal fait does not depe-nd on anirpal fpod, 
 but on the powers of life. I fed five ravens 
 for fifteen days on vegetables ajpne, ^nd then 
 by m?ans of fpunges procured a quantity of 
 gaflric fluid, w^hich I fuppofed v^ould have 
 no properties that could be afcribed to ani-r 
 mal food. When I made v^ith it the expe- 
 riments defcribed above, it did not appear 
 to be acid of alkaline ; it had a fait tafie, and 
 upon ppuring a few drop^ into a folution of 
 filver in the nitroi4S acid, luna cornea was 
 precipitated. There is therefore every rea-r 
 Ion to fuppofe, that if this fluid was diflilkd, 
 fa] ammoniac woyld be obtained ; and there- 
 fore, that the marine acid is the produ(5t of 
 tlie animal powers. But whatever we are 
 to think either pf this or the other ingenious 
 conjedture of my colleague, which have in- 
 deed little connecflion with our prefent en-e 
 qoiry^ it is certain, both from his experi- 
 ments and my own, that the gaflric fluid is, 
 not either acid or alkaline, but neutral, 
 
 ccxLv. But I muft not conceal thofe ar- 
 guments which are adduced to prove, that 
 there is a latent acid in this fluid, though i;t 
 cannot be detedted by any of the ordinary 
 chemical means, It is well known, that a 
 frnall quantity of aci4 will cur41e: milkj an 
 
 eifed; 
 
UlSSERfAtlbtf Vi. r:|33 
 
 elFe^l produced in the ftomach of animals, 
 and of fucking calves in particular, in which 
 cafe we cannot fufped any vegetable acid to 
 be prefentj the phasnomenon muft, there- 
 fore, be attributed to the latent acidity of th^ 
 gaftric fluid. And as it is continually fe- 
 creted by the internal coat of the Itomach, 
 we -cannot be furprized> that this coat in fome 
 animals fliould retain the property of curdling 
 milk. This is well known to cooks, who, 
 when they have no rennet, take the innermofl 
 coat of the ftomach of a fowl and fteep it iii 
 water *, which water, when thus impregnated 
 with the juice of the llomach, will ferve for 
 turning milk as well as rennet itfelf. 
 
 Hence fome have fuppofed, that the ilo- 
 machs contains a latent acid. My firfi; ftep 
 was to afcertain the fadt. I therefore tritu- 
 rated the internal coat of a hen with water, 
 which was thus rendered turbid, and in an 
 hour and a half curdled a quantity of milk. 
 The fame eifed; was produced by the internal 
 coat of other gallinaceous birds, viz. the ca- 
 pon, turkey, duck, goofe, pigeon, partridge^ 
 quail, treated in the fame manner. I further 
 difcovered, that this property belongs alfa to 
 intermediate and membranous ilomachs, by 
 experiments on that of the crow, heron, birds 
 of prey, the rabbit, the dog, cat, various 
 
 reptiles^ 
 
3J4 DISSERTATION. Vl. 
 
 reptiles, and feveral fcaly fifhes. In thefe 
 trials the ilomachs were frefli. I next tried 
 dried ones, chiefly taken from the galUna- 
 ceous clafs, which being almoffc of the con- 
 iiilence of hornj become dry in a very fhort 
 fpace, and at the fame time exceedingly 
 brittle. The refults were the fame as before. 
 Nor did it make any difference> though they 
 had been kept ever fo long* I have had for 
 three years the internal coats of the ftomach 
 of jfeveral fowls, and upon triturating them 
 with water, while I am writing, they curdle 
 milk as well as at iirfti If they are pounded 
 ^nd mixed with milk, they anfwer the pur- 
 pofe equally Well* 
 
 ccxLvi* But is this property confined to 
 the internal coat? It was eafy to determine 
 this by treating the others in the fame man- 
 lier* The nervous coat has this property iii 
 fome degree, but falls fart fliort of the inter- 
 nal. Whether cut into fmall pieces and ma-* 
 cerated in water, or mixed immediately with 
 milk, the eife6l is not fo fpeedily produced^ 
 nor fo coniiderable, nor are the curds fo hard. 
 The mufcular and cellular coats have not this 
 property in the fmxalleft degree, at leall in 
 gallinaceous birds, upon which thefe expe* 
 riments were made. Hence it would feem, 
 that it relides in the internal coat folely -, fot 
 
 the 
 
DISSERTATION VI. 335 
 
 the effe(5ts produced by the nervous coat, may 
 be owing to its lying in contav5l with the 
 former, 
 
 ccxLvii* But is this property inherent in 
 the internal coat, or adventitious, and owing 
 to the gaftric fluid with which it is impreg- 
 nated? I incline to the latter opinion, iince 
 the gaftric fluid fo readily curdles milk. I 
 fhould weary my reader, was I to recount all 
 my experim.ents. I will therefore only fay, 
 that the gaftric fluid, from whatever animal 
 it was obtained, poflfeffes this property, whe- 
 ther procured by fpunges, by opening the fto- 
 mach and exprefting it out of the glands, and 
 the mouths of the little arteries, with which, 
 this vifcus in general abounds. I have fur- 
 ther found, that the gaftric fluid need not be 
 frefh. 'That of crows, at leaft, preferves its^ 
 virtue for three months. 
 
 ccxLviii, But is itaneceflaryconfequence 
 of thefe experiments, that the gaftric fluid 
 contains an acid ? As no chemical teft lliews 
 this quality, there can be no juft motive to ad- 
 mit it, unlefs it can be proved to be a necef- 
 fary confequence of the curdling of milk. 
 This is maintained by the illuftrious Mac- 
 quer among others, who is of opinion, that 
 whatever bodies of the anin^iai and vegetable 
 
 kingdom 
 
g^6 DISSERTATION vL 
 
 kingdom coagulate milk, have either a ma- 
 nifell or occult acidity [d). 
 
 The foundation of this opinion is the com^ 
 liion obfervation, that acids are the fole caufe 
 of the curdling of milk. To this reafoning, 
 i fhall only oppofe a iingle fad: : I have dif- 
 covered, that though feveral animal fubftances 
 are incapable of producing this effed:, yet 
 others have this property^ Thus for inftance, 
 if the blood or bile of a turkey be mixed 
 with milk, it will retain its fluidity; but 
 pieces of the heart, liver^ or lungs of that 
 birdj v^ill curdle it readily; This obfervation 
 is not merely owing to accident ; I have made 
 the experiment repeatedly with different tur-i 
 keys, and always with the fame fuccefs. If 
 therefore the coagulation of milk be always 
 owing to an acid, we muft fuppofe an acid in 
 the heart, liver, and lungs of the turkey; I 
 am aware, that many chemifts, in op^ofi- 
 tion to the Boerhavian fchool, think a real 
 acid exifts in the different parts of animals^ 
 and particularly in the blood ; but according 
 to this hypothecs, I cannot comprehend^ 
 why the blood of the turkey and other ani- 
 mals does not coagulate milk. With refped; 
 to the latent acid of the gaftric fluid, 1 ihall 
 
 («) Art. Milk. 
 
 Very 
 
DISSERTATION Vf, ^SJ 
 
 very willingly leave my readers to adopt what 
 opinion they fhall think moft probable. The 
 milk I employed for my experiments^ was 
 ibmetimes that of the flieep, but generally 
 of the cow. It curdles fpontaneoufly, aS 
 every one knows, fooner or later, according 
 to the temperature of the atmofphere. When 
 1 mixed it with gaftric juice, or any other 
 fluid, I always left another portion by itfelf; 
 In the former cafe, the coagulation foon took 
 place without any fign of acidity, whereas 
 milk alone required feveral hours, and fome- 
 times a day or two, and the coagulum had 
 always an acid tafle. 
 
 ccxLix. But it is time to eonfider the rea- 
 fons adduced by others, to prove that digeftion 
 is attended with an incipient putrefacftion. 
 Thefe reafons are founded upon fad:s related 
 by different authors, 'and detailed in their 
 order by Haller, in his great work {a). No- 
 thing, according to them, can be more evi- 
 dent, than the lign? of putrefadiion during 
 digeftion. The ftomach of a hyena and of 
 a ferpent, have been obferved to emit an in- 
 tolerable ftench. The breath of the lion and 
 eagle is very foetid, as alfo that of the dog, 
 when digeftion has been prevented by the? 
 
 {a) T. 6. 
 Vol. L % exhi- 
 
3^38 DISSERTATION VI,' 
 
 exhibition of opium. A dog without taking 
 opium, was obferved to emit an excremen- 
 titious odour from his ftomachj the food in 
 the ilomach of birds has nearly that fmell. 
 The fame obfervation has been apphed to 
 £lhes; and the inftance of a dog~fifh has 
 been adduced, of which the ftomach was full 
 of a foetid jelly, that contained the food dif- 
 folved. The contents of the human ftomach 
 fometimes become foetid. Vegetable fub- 
 ftances alfo degenerate into a putrid mafs, 
 when they continue long in the ftomach, as 
 appears from the putrid fmell they exhale, 
 the green colour they impart to tindiure of 
 mallows, and the alcaline principle they af- 
 ford on diftillation. 
 
 After having related thefe fadls, the Swifs 
 phyliologiil proceeds to give his own opinion. 
 He thinks, that in digeftion there is only 
 an incipient, not a complete putrefad:ion ; 
 which only takes place when the food remains 
 a long time in the ftomach, as is evident from 
 the facfts juft mentioned. He alfo fuppofes, 
 that the change produced by the digefhive 
 powers, efpecially in the human ftomach, ap- 
 proaches nearer to putrefaction than acef- 
 ■ cency ; this he infers, from the putrid fmell 
 that exhales from flefh found in the fliomach 
 of fome animals, notwithftanding there has 
 
 been 
 
DISSERTATION VI. 339 
 
 been no impediment to digellion [a). This 
 opinion^ adopted before Haller by Boer- 
 haave {d)^ has moreover beeh received by two 
 celebrated writers^ Gardane [c), and Mac- 
 quer [d). 
 
 ccL. Notwithflanding the refped:able au- 
 thority of thefe authors, I do not think the 
 fa6ls adduced, fufficient to perfuade an im- 
 partial philofopher; they are not only too 
 few, but were obferved by mere accident ^ nor 
 had the obfervers the fmalleft intention of en- 
 tering into a full difcuffion of this point. 
 
 Though the time requifite for digeflion in 
 different animals is different, yet in many it 
 does not exceed five or fix hours, and in fome 
 is flill fhorter. Now it feemed proper to exa- 
 mine what change flefh fet to putrify, would 
 undergo in that fpace of time 3 I therefore 
 took fome frefh veal cut into fmall pieces, 
 and put it in a phial of water, which was 
 ftopped with papers The phial was put into 
 a ftove, Vv'here the mercury rofe to between 
 30 and 35'', 
 
 About the beo-inning; of the fourth hour, 
 the fleih had loil its red colour, and was 
 
 (a) L. C. 
 
 {i). Chem. T. i. 
 
 {c) EfTai pour fervir a THtiibire de la pittrefa^ion, 
 
 («■") AiL. eommon Salt;. 
 
 Z z turning 
 
340 DISSERTATION VI, 
 
 turning blue. It v/as alfo become flabby, but 
 for nine hours it had no putrid fmell. Mut- 
 ton and beef, in feveral trials, did not anfwer 
 to this time exadlly, but no bad fmell was 
 ever perceptible for eight hours. Thefe ex- 
 periments ihew, that flefh eaten by many ani- 
 mals, among v^hich Man may be enumerated, 
 has not time to run into the putrefactive fer- 
 mentation, efpecially as the temperature of 
 animals is lower than that to which thefe fe- 
 veral forts of meat were expofed. However, 
 for greater certainty, I made the following 
 trials. I have before mentioned introducing 
 into the flomachs of crows, pyriform glafs 
 veifels, of which the fmall end was open, 
 and came out at the mouth (lxxxix). 
 
 I now took two of them, and putting fomc 
 beef, with a little water, into one, and fome 
 veal into the other, forced them down the 
 throat of fome crows. In order to examine 
 the ftate of the flefh, I now and then drew 
 them up,, and im^mediately returned them. 
 Between the ninth and tenth hours, the beef 
 emitted an odour, which though it could not 
 be called putrid, was difagreeable. At the 
 expiration of the tenth hour, there was a 
 diftincft putrid fmell that became gradually 
 ftronger and flronger. In a day the fiefli 
 turned livid, acquired a naufeous tafte, , and 
 
 the 
 
DISSERTATION VI. 34I 
 
 the particles began to feparate. The fame 
 appearances took place rather fooner in the 
 veal. It therefore appears, that fleih in the 
 heat of this fpecies of bird requires a longer 
 time to putrify, than to be digefled. After 
 the glafs velfels were taken out of the fto- 
 mach, I gave one of them the fame quantity 
 ©f beef and veal ; and upon opening the fto- 
 mach in three hours, found that it was en- 
 tirely confumed. 
 
 ccLi. Thefe experiments prove, that no 
 putrid tendency is ever acquired by meat du- 
 ring digeftion. Nor did I ever perceive any 
 fuch tendency in food lying in the ftomach 
 (lxv, ccix); yet as I had never made ex-^ 
 periments for this exprefs purpofe, and as 
 fome phyfiologillis adduce fad;s to prove the 
 contrary (ccxlix), I was under the neceffity 
 of examining the ftomach of various animals, 
 with this fole view. 
 
 Four hens were fed with kid, and in two 
 hours one was killed : the ftomach was full ; 
 the flefh flill retained its natural fweet favour, 
 whiehat the furface was mixed with a bitterifli 
 tafte, occafioned by its being impregnated with 
 the gaftric fluid. Jt had no fmell, except that 
 of this fluid. An hour afterwards the fto- 
 mach of another hen was examined ; and here 
 the flefli was beginning to be converted into 
 
 >Z 3 ^ §^- 
 
342 DISSERTATION VI. 
 
 a gelatinous pafle, its fmell was rather dif- 
 agreeable^ I know not how to defcribe it, 
 but it was not at all penetrating, or putrid ^ 
 the colour was ftill reddifh, it had not the 
 leaft naufeous tafte, nor did it efFervefce with 
 acids, or change the colour of fyrup of vio- 
 lets. Thus we fee, it ihewed no fign either 
 of incipient, or advanced putrefadiion. Iri 
 another hour the third hen was killed : the 
 Homach contained a pultaceous mafs, more 
 iluid than, in the former cafej but there was 
 not the fiPAalleft token of putrefaction, any 
 more than in the fourth hen, which was 
 opened three hours afterwards, when the 
 praw was empty, and the contents of the 
 gizzard were noW dilTolved. 
 
 GCLii. Some frogs juft killed were fet be- 
 fore two herons ; the birds being hungry, de- 
 voured them greedily. In fix hours one of 
 theni was opened j but whether the toughr 
 nefs of the fkin retarded digeflion, or whether 
 . that procefs is flow in herons, the frogs had 
 not loft their fliape; though the heads and 
 limbs were either feparated, or on the point 
 of being feparated from the trunk, and the 
 flefh was become very foft. The tafte, exr 
 cept the ufual bitternefs, had nothing nau- 
 feou§, and the fmell was by no means putrid. 
 I waited five hours longer before I killed the 
 
 fecond ; 
 
DISSERTATION VI. 343 
 
 fecond ; when I found but little flefli In the 
 ilomach, and that little was entirely decom- 
 pofed, but did not emit the leaf!: putrid 
 fmell. 
 
 If fowls and herons afforded no token of 
 putrefa(ftion, much lefs could I exped: it from 
 the birds upon which my next trials were 
 madej I mean, young owls, which digefl 
 flefli in three, or at moft four hours. A young 
 dog and cat were next fed, at the fame time, 
 with boiled beef. The former was opened in 
 four hours and an half. The fliomach was 
 full of a mafs of foftened fleili, which emitted 
 a very flight fmell, exadly refembling the 
 fmell of the gaftric fluid. The fliomach of 
 the cat was opened in five hours and an half, 
 and was found to contain fome remains of 
 fiefli, or rather a pulpy matter, which as in 
 the former cafe, had the fmell of gafl:ric fluid. 
 The flefli, when nearly digefl:ed, did not 
 change the colour of fyrup of violets, or ef- 
 fery efce with acids. 
 
 ccLiii. There are animals which retain 
 the food in the fliomach for a much longer 
 time, ,as the fafcon. Of that upon which I 
 made fo many experiments, I have already ob- 
 ferved, that it would devour a whole pigeon 
 at once, and continue without food the whole 
 day afterwards (clx). Whence, as alio from 
 Z 4 its 
 
344 DISSERTATION VI* 
 
 its great bulk, we may infer, that thp flelh re- 
 mains a long time in the body before it is en- 
 tirely digefted. Sqme months after this was 
 killed, another of a different fpecies fell into 
 my hands j it was of a larger iize, and had 
 110 craw, fo that the food paffed immediately 
 into the ftomach. Notwithilanding it was 
 pretty tame, and therefore valuable, yet I 
 facrificed it for the fake of thefe experiments, 
 eighteen hours after it had devoured a chicken. 
 What remained in the ftom^ach weighed two 
 ounces j it confiiled of a pulp, in which the 
 fibres could yet, be difcernedj but neither 
 when fubjeded to the before-mentioned che- 
 mical trials, or when fmelled and tailed, did 
 it iliew any lign of putrefacflion. But among 
 the animals that retain their food for a long 
 time in the ftomach, thofe vv^ith cold blood, 
 and efpecially vipers, are, as we have feen, 
 the mofl remarkable. A piece of lizard's tail 
 prefsrved fomev/hat of its mufcular flrudure, 
 after having remained five days in the ftomach 
 pf a land-fnake (cxviii). Three water 
 fnakes had not cpnfumed all their food at the 
 end of three days (cxxi). Another not even 
 in fix days (cxxv). A lizard remained fix- 
 teen days in the flomach of a viper, without 
 lofing its natural form (cxxvii). Other 
 eold animals, fuch as eels, newts, and fro^s, 
 
 mufi; 
 
DISSERTATION VI. 345 
 
 muft not be forgotten. Four eels that had 
 eaten iifh, retained a little after the expira- 
 tion of three days, eighteen hours (cxxix). 
 On the fifth day, fome frogs had not quite 
 digefted pieces of inteftine (cvi) ; which ■alfo 
 happened to newts, two days after they had 
 been fed with earth- v/orms (cvin). But 
 notwithilanding the food continued fo long 
 in the ftomach of thefe feveral animals, I 
 have exprefsly noticed, that it had not begun 
 to putrify (cxxvii). 
 
 ccLiv. I have met only with two in- 
 llances which though they do not coincide 
 with this invariable conilancy of nature, by 
 no means detradt from the certainty of the 
 conffequences that are to be deduced from it. 
 Among the crows that were oblio-edto fwallow 
 tubes for a confiderable length of time, fome 
 fuffered in their healths, and became lean, 
 though they were copioufly fupplied with food. 
 But as they did not take it voluntarily, and as 
 it was my wifh to keep them alive for the fike 
 of experiments, I forced fome fleili down the 
 throats of two, but to no purpofe ; for they 
 both died, one thirteen, the other fifteen 
 hours afterjkvards. My curiofity led me to 
 open them, and I found that the fleih con- 
 tinued whole and undigefled, and moreover 
 that it was become putrid. But this evidently 
 
 arofe 
 
54^ DISSERTATION VI, 
 
 arofe from the morbid condition of the ani- 
 mal, by which the gaftric fluid was altered, 
 and rendered inefficacious. For this fpecies 
 of birds, as I have feen in a hundred inftances, 
 dig&fts fiefh very fpeedily, and without any 
 token of putrefaction appearing. It is alfo 
 probable, that the putrid ftate of the food in 
 the animals mentioned in the ccxLixth pa- 
 ragraph, arofe from their morbid condition; 
 efpecially as it remained fo long in the fto- 
 mach of fome of them. It may alfo happen, 
 that when an animal in health is killed and 
 kept unopened a conliderable time, as often 
 happens, the food in the ftomach may be found 
 in a putrid ilate. 
 
 In the fame paragraph, the breath of the 
 lion and eagle are faid to be foetid. That of 
 the lion I never had an opportunity of examin- 
 ing, but with the eagle it is far otherwife; 
 for when I ftroaked the head gently, it would 
 fome times open its mouth, and raife a gentle 
 cry; on thefe occaiions it necelTarily made a 
 long expiration, and in winter the breath ap- 
 peared in the form of a little cloud. This 
 cloud I have often fmelled, and caufed others 
 tp fmell, both when the bird was fafting, 
 when the fliomach was full, and when the 
 food was recently digefled ^ but it was never 
 
 foetid. 
 
DISSERTATION VI, g 47 
 
 foetid, and indeed did not feem to have any 
 kind of odour, 
 
 CCLV. The experiments defcribed in the 
 ccL, ccLi, ccLii, and ccLiiid paragraphs, 
 not only fliew that digeflion is unaccompanied 
 by putrefaction, but might induce us to fup- 
 pofe, that the ftomach is provided with aa 
 antifeptic principle. Flefli inclofed in the 
 pyriform glaffes that were introduced into the 
 ilomach of crows, fliewed evident iigns of 
 putrefadiion in ten hours ; whereas in eighteen 
 they fhew no appearance of the kind, when 
 it is in immediate contad: with the ftomach 
 (ccLiii). And although ferpents, and the 
 other amphibious animals above-mentioned 
 (ccLiii) are of a cold temperature j yet in 
 their temperature, which is nearly equal to 
 that of the atmofphere, flefh becomes putrid in 
 two days, fometimes in one, and fometimes 
 even in a fhorter time, while in their ftoniachs 
 it remains untainted frequently for a much lon- 
 ger fpace. I could not therefore but conclude, 
 that there is prefent in thefe cafes, fomecaufe 
 that prevents the corruption which fapervencs 
 out of the body. What can this caufe be ? -It 
 was not difficult to deted: it. I called to mind 
 thofe unfiniflied digeflions, which take place 
 when fleiliis immerfedin gaflric fluid contained 
 in phials 3 where it is diflolved without ever 
 
 turning 
 
34^ DISSERTATION VI. 
 
 turning putrid, notwithftanding it is kept long 
 enough, and expofed to a fufficient heat. I 
 could not then doubt, that the gaftric juices 
 are at once the folvent, and the prefervative 
 from putrefaction. Further refledlion fur- 
 niilied me with proofs ftill more decifive. It 
 appears from various pafTages in the prece- 
 ding diifertations, that in attempts to produce 
 artificial digeilion, little or no folution takes 
 place, unlefs the fluid extracted from the flo- 
 mach is expofed to a confiderable heat (cxlii, 
 CLxxxvi, ccj, ccxvii). But without this 
 condition, it retains its antifeptic powers 
 (cLxxxvi, ccxvii). Two phials, one con- 
 taining fome gaftric fluid from a crow, and 
 the other from a dog, together with fome veal 
 and mutton, were kept thirty-feven days in 
 winter, in an apartment without fire : the 
 flefli was not either confumed or turned pu- 
 trid ; while fome that was immerfed in water, 
 began to emit a foetid fmell on the feventh, 
 and about the thirtieth day was changed into 
 a very ofFenfive liquamen. It is proper to 
 add, that the gaflric fluid at.lail lofe-s, though 
 kept in phials ever fo clofely flopped, its an- 
 tifeptic quality, but it never becomes putrid, 
 itfelf. This at leaft I found to be the cafe 
 with fome taken from a crow, and kept tv/o 
 months. 
 
 ccLvi. The 
 
DISSERTATION VI. 349 
 
 ccLvi. The difcovery of this antlfeptic 
 property led me to enquire what would be 
 the effed: of immerfing flefh, more or lefs pu- 
 trid, in gaftric fluid. Four portions that had 
 an infupportable fmell, were fet in four bot- 
 tles, which I filled with four different kinds 
 of gaftric fluid, viz. of a dog, a crow, an 
 owl, and an eagle. This vras done in March, 
 and the bottles were kept twenty-five days in 
 an apartment, where the heat was never lefs 
 than 8, and never exceeded 12°. I could 
 ~not perceive that it was at all more diflx>lved 
 than if it had been immerfed in water. With 
 refpedt to the foetid fmell in the phials con- 
 taining lamb and veal, it continued unchang- 
 ed ^ but in the two others, which contained 
 fowl and pigeon, it feemed rather diminifhed. 
 This refult fiiggefled to me, that the gailric 
 fluid might not only impede putrefacftion, but 
 refl:ore putrified fubflances. I therefore re- 
 peated the experiment in June, and found 
 that my fufpicion was Vv^ell founded. Some 
 fowl and pigeon, in which putrefad:ion was 
 pretty far advanced, were immerfed in the 
 gaflric fluid of a dog and falcon, and re- 
 mained in it thirty-feven hours, in which 
 time they were reduced to a jelly, but had 
 nearly loft their offenfive fmell. On com- 
 paring this v/ith the preceding experiment, 
 
 I con- 
 
^50 DISSERTATION VI. 
 
 I conjecflured, that the fuperior efficacy of the 
 gaftric fluid in the latter cafe, proceeded from 
 the warmth of the feafon : and this induced 
 me to expofe the fame flefh under the fame 
 circumftances, to the fun about the middle 
 of June, And now ten hours completely 
 took away the foetid fmell . I did not negle(ft 
 making the fame experiment with the gaftric 
 fluid of other animals 5 the flefh generally 
 lofl its difagreeable odour, but fometimes for 
 a reafon, which I cannot aflign, retained it in 
 part. It is proper to add, that the recent 
 fluid was always more efficacious thaa the 
 old. 
 
 ccLvii. If we conlider the cclv and 
 ccLvith paragraphs, wemuil conclude, that 
 putrid flefii lofes this quality in the llomach 
 of anmials. Before I attempted to afcertain 
 this point by experiment, nature herfelf gave 
 me a decilive proof of it. At the time I kept 
 a great number of fowls for my enquiries, I 
 -perceived that when they are allowed to eat 
 at will, they cram their craw fo full, that it 
 is fixteen or twenty hours before it is com- 
 pletely evacuated. Curiolity led me to kill a 
 cockrel that had about an ounce of meat> 
 which happened- to be bruifed flefh, remain- 
 ing in its craw : and I was flruck with fur- 
 prize, when I perceived that it had a ilrong 
 
 putrid 
 
DISSERTATION VI.' 351 
 
 putrid fmell ; it was become foft, had a dull 
 red colour, and a naufeous tafte: I imme- 
 diately proceeded to examine the contents of 
 the ftomach; but here I found the flefh quite 
 decompofed with a bitter fweet tafle, and a 
 fmell not in the leafl foetid. The liquor 
 therefore of the flomach, had corrected the 
 putrid quality which the flefh had acquired in 
 the craw. The fame thing took place in fome 
 hens. The flelh in the craw became putrid 
 in iixteen hours, while that in the ftomach 
 had no difagreeable odour. It fhould, how- 
 ever, be remarked, that the putrefactive fer- 
 mentation never tuns fo high within the craw, 
 as it does out of the body, even when the heat 
 is lefs flrong. Whence I fufpedied, that the 
 fluid of the craw might alfo polTefs an anti- 
 feptic power, though in a degree very far in- 
 ferior to that of the ftomach. 
 
 ccLviii. I took a putrid piece of beef's 
 lights, and dividing it into five portions, faf- 
 tened a ftring to each, and then thrull them 
 into the ftomachs of live ravens. The end of 
 the ftring was brought out at the beak, as on 
 former occafions (lxviii), that I might be 
 able to examine the flefti at pleafure. In three 
 quarters of an hour, two of the pieces were 
 drawn up: they were wafted, and at firft 
 feemed to have loft their putrid fmell, but 
 
 upon 
 
35^ D I S S E B. T A T I ^^ VI. 
 
 upon wiping oit the gall:ric fluid., it became 
 again feniible, but it was much diminilhed. 
 Half an hour afterwards another piece, upon 
 examination, was found to be flill more 
 wafted, and to have loll: almoll all its bad 
 odour, even when the gallric fluid was care- 
 fully wiped away. In an hour afterwards the 
 two remaining pieces were drawn up. They 
 were reduced to the fize of a pea^ and it would 
 have been impollible to tell that they had been 
 ever putrid, fo perfectly were they recovered ^ 
 even the tafle had nothing difagreeable, ex- 
 cept the bitternefs which is always prefent on 
 fuch occalions. 
 
 The great length of the neck prevented 
 ra.e from. re';)eating this experiment upon the 
 heron. I forced a femi-putrid frog, from 
 which the ikin had been taken, into the fto- 
 raach, but I could not draw it ud ajain; it 
 was therefore neceHary to cut the fcring at 
 the beak, when the bird immediately fwal- 
 lowed it. It was my intention to kill the 
 heron in about an hour, that I might ex- 
 amine what change the frog had undergone. 
 But it was vomited before that time, pro- 
 bably on account of its being a difgufting 
 foodf for however greedily the heron devours 
 living fiflies and frogs, it abilains from them 
 when thev are turning putrid. The gailric 
 
 fluid 
 
15 I S s E R T A T I \ rr. qr* 
 
 j: 
 
 fluid had, notwithllanding, exerted both its 
 antifeptic aiid iblvent powers, during the 
 fort\'- three minutes the frog had been in the 
 ilomach. Some tin tube? were then filled 
 with putrid filh, and given to the animal; 
 they were not, as before, thrown up, perhaos, 
 becauie the putrid matter was not in contao: 
 with the iLomach. The bird was killed three 
 hours' afterwards ; what remained in the tubes 
 weighed one-feventh of an ounce; it re- 
 fembled a thick 2:elatinous Dafle, in which a 
 few fieihy fibres might yet be diilinguiihed, 
 and which retained no veftige oi its former 
 putrid liate. 
 
 c c L IX. I treated federal {mall birds of prev, 
 fuch as the two fpecies of owl above de- 
 fcribed, and a young hawk, as I had done 
 crows ( c L VI 1 1 u They were fed with intef- 
 tine, liver, and lungs of iheeOj more or iei'^ 
 putrid. Solution took place, and the putre^ 
 faction was corrected according to the time of 
 the continuance of the neih in the ilomach. 
 The hawk twice threw up what it had fwal- 
 lowed, probably, becaufe its putrid ilate made 
 it difagree with the ilomach, for this never 
 haDoened when it was fed with Ixeili meat. 
 The galVric iuices of the eagle produced the 
 fame tticct upon deih inclcfed in tubes, and 
 introduced into its ilomach. Animals of cold 
 Vol. L a a blood 
 
354 DISSERTATION VI. 
 
 blood having very flow digeftive powers^ were 
 long in correcting the putrefad:ion of flefh. 
 This eiFe6t^ however, was at laft produced. 
 The only precaution neceffary,. was to return 
 the fubftances into the flomach when they 
 were vomited, which often happened. 
 
 The lafl: experiments I made with this view, 
 were upon a cat,, a dog, and myfelf. I was 
 obliged to force the putrid flefh down the 
 throat of thefe animals, for not withflan ding 
 they were exceedingly hungry, they obfli- 
 nately refufed it. The dog retained what was 
 forced upon him, but the cat vomited it along 
 with a quantity of foam, and a liquor that 
 appeared to be gaflric fluid. The flefh., which 
 when it was given was exceedingly foetid, 
 had now loft its fmell entirely ; of this, ano- 
 ther cat, by eating it without afterwards 
 throwing it up, gave me a clear proof. Upon 
 opening the ftomach, I found the flefh half 
 digefted, and with no other fmell than that 
 •which frefli meat ufually emits in like cir- 
 cumftances . In two hours and a half the dog 
 was opened. The flefh lay in a little lake of 
 gaflric fluid, nearly decompofed, nor did it 
 either in tafte or fmell refemble tainted meat* 
 The experiment I made on myfelf, conflfl:ed 
 in fwallowing, at five different times, five 
 tubes covered with linen, like thofe men- 
 
 tioaed 
 
DISiSERTATION VI. 355 
 
 tloned in the ccviiith paragraph: theywere 
 full of different forts of putrid flefh. I voided 
 them feparately, and in each there was fome 
 of the contents remaining, but not one ex- 
 hibited the fmalleft token of putrefaction. 
 Hence then it appears, that the various clafTes 
 of animals, and Man among the reft, in an 
 healthy ftate, are endowed with the power, 
 not only of checking the putrefadion of fub- 
 ftances lodged in the ftomach, but alfo of 
 correcting them when already putrid. 
 
 ccLx. By this difcovery I was led to reflect, 
 that many animals living upon flefli, and mat- 
 ters that have a tendency to run into the pu- 
 trefactive fermentation, never feed but upon 
 fuch as are frefh and fweet; and that, if by 
 any accident putrid food fhould get into the 
 ftomach, they are fubjed: to vomiting and va- 
 rious bad fymptoms, and even death itfelf : 
 fome inftances of vomiting excited by this, 
 caufe, maybe feen above (cclviii, cclix); 
 while on the other hand, many animals de- 
 light in corrupted fubftances, as for inftance, 
 the multitude of loathfome infeCts and worms 
 that refide in fewers and fepulchres, and feed 
 upon decaying carcafes. Among birds and 
 quadrupeds, there are alfo fome that feek 
 tainted flefh ^ fuch as the crow, the kite, the 
 vulture, among the former ^ and among the 
 A a 2 lat- 
 
35" Dissertation vi.' 
 
 latter, the chacal and the hyena. While other 
 animals fly the miafmata that arife from bodies 
 in fuch a ftate, thefe feek and are guided by 
 them to their abominable repafts. But now 
 we are acquainted with the antifeptic virtue 
 of the gallric fluid, the difgufling manners of 
 thefe animals ought no longer to furprize us, 
 for the food, however putrid, muft be totally 
 changed before it is converted into nutriment 
 and animalized. And although the putrid 
 quality is corre6led by other animals, yet food 
 in that flate is noxious to them, on account 
 of the difagreeable impreffion it makes on the 
 organs of fmell and tafte, as alfo upon the 
 ftomach, by which, and particularly by their 
 noifome miafmata, the nervous fyflem is pro- 
 bably irritated. It befides feems likely, that 
 the antifeptic power of the gaftric fluid of the 
 former, is greater and more efiicacious, and 
 confequently that it more readily and more 
 completely corredts putrefaction. Habit, 
 which is jufhly reputed a fecond nature, may 
 bring animals, that naturally abominate pu- 
 trid food, to live very well upon it. We 
 have already feen the converfion of a pigeon 
 from a granivorous into a carnivorous animal 
 (cLxxv); and I brought it to eat not only 
 frefh flelh, but fuch as was fcEtid, and even 
 completely putrified. The bird at firfl; ab- 
 
 fblutelj 
 
DISSE R TATION VI,' 357 
 
 folutely refafed it, and I was obliged to force 
 it into the ilomach ; for fome days it faffered 
 from this treatment, and became evidently 
 leaner. But by degrees nature became inured 
 to the food, and the pigeon, ftimulated by 
 hunger, tojok it fpontaneoufly, till at laft it 
 recovered its plumpnefs ; and now its appe- 
 tite for tainted, was as keen as it had been 
 before for fweet meat. We may learn fron;i 
 this inftance, that cuftom is capable of chang- 
 ing difagreeable, and even noxious food, into 
 good nourishment. 
 
 CCLXI. But what fhall we fuppofe enabjes 
 the gaftric fluid to check and corredt putre-^ 
 fa6tion? As it contains a fait, and that of the 
 ammonical kind (ccxlvi), and as befides the 
 experiments of Pringle Ihew, that all falts, 
 whether acid, alkaline, or neutral, whether 
 volatile or fixed, are antifeptic (<7), it is ob-r 
 vious to conjecfbure, that thefe two qualities 
 arife from the fame fource, I conceived, 
 however, before I determined abfolutely, that 
 it would be proper to attempt a few experi- 
 ments. It is obferved by Pringle, that we 
 mull employ common fait, which fo nearly, 
 refembles fal ammoniac, in confiderable quan- 
 tity, if vv e wi(h it to ad as an antifeptic ; other- 
 
 (a) Appendix, containing experiments ^n' feptic and anti- 
 i'pptic fab Ranees. 
 
 A a 3 wife, 
 
55^ DISSERTATION VI. 
 
 wife, it is fo far from checkings that it pro^ 
 motes pi^trefadtion, Thus a drachm of fait, 
 dilTolved in two ounces of water, keeps meat 
 i^A^eet but a little while, and twenty -^iave grains 
 a ftill lefs time; while ten, fifteen, and even 
 twenty grains haften its corruption. This 
 paradox has been confirmed in France by the 
 learned Mr, Gardane, Notwithftanding thefe 
 authorities, I determined to bring the matter 
 to the teft of experiment. I therefore took 
 four phials, and putting into each three penny^ 
 weights, fix grains of freih beef, pounded 
 very fmall, I poured upon it an ounce and half 
 of water. In the firil: phial were dilTolved ten 
 grains of common fait, in the fecond fifteen, 
 in the third twenty, and the fourth was left 
 without fait, as a term of comparifon . The 
 temperature of the place where they were 
 kept, was about fifteen degrees. The firft 
 phial Hegan firft to emit a fcetid fmell, the 
 fourth next, then the fecond, and laftly the 
 third. The other tokens of putrefadiion ap- 
 peared in the fame order. When fal ammo- 
 niac was fubilituted in the place of common 
 fait, the only difference in the refult, con- 
 fifled in the phial which contained no fait, 
 and that which contained ten grains, begins- 
 ning to exhale a putrid fmell at the fame 
 time. It appears, therefore, that Pringle's ex-s 
 
 . periment 
 
DISSERTATION. VI. 2 S9 
 
 periment was accurate, and that the fame thing 
 nearly is true of fal ammoniac. In order to 
 determine whether the antifeptic property of 
 the gaftric fluid arifes from the fal ammoniac 
 it contains, I dilTolved a quantity of that fait 
 by degrees in water, till it had nearly ac- 
 quired the fame faltnefs as the gaflric fluid; 
 fome bruifed flelh was then immerfed in it. 
 That the water and the liquor of the ftomach 
 had nearly the fame faltnefs, I afliired myfelf, 
 both by tailing it, and by dropping a few 
 drops of each into a folution of filver in the 
 nitrous acid, when each afforded the fame 
 white precipitate. But it is this caufe that 
 prevents putrefaction; for the flefh immerfed 
 in the fait water, emitted a foetid odour fooner 
 than other flefh of the fame kind, infufed in 
 common water: and although when more 
 fal ammoniac was employed, putrefad:ion was 
 retarded, it was not prevented ; to attain this 
 end, eighteen or twenty times as much fait 
 as is contained in the gaftric fluid was requi- 
 fite. Thefe fad:s feem clearly to fhew, that 
 the antifeptic quality of the gaftric fluid does 
 not depend on the fmall quantity of fal am- 
 moniac it contains. 
 
 ccLxii, From the fceptic power of com- 
 mon fait in fmall quantity, Mr. Gardane de- 
 duces a confequence, which it may be pro- 
 A a 4 per 
 
S^P PISSERTATION YI. 
 
 per to notice in paffing. He thinks the com- 
 mon fait we take with our food, being always 
 in little dofes, forwards digeflion, by pro- 
 moting putrefad'ion ; upon which, accord- 
 ing to him, as we have feen above (ccxlix), 
 that function; depends. Though my nume- 
 rous experiments completely dellroy this fup- 
 pofition, yet it feemed worth wliile to try 
 what would happen to flefh feafoned with 
 fuch a proportion of common fait as haftens 
 putrefa(3:ion, and given to different animals. 
 Some tubes, filled with iieih thus prepared, 
 and others, with fome of the fame kind, 
 wdthout fait, were given to a dog and -a cat. 
 The animals were opened in five hours, and 
 upon examining the tubes, I could not per- 
 ceive that the fait had occaiioned any differ- 
 ence. What remained undifTolved, had flill 
 a flight fait tafle, but not the leafl: difagree- 
 able fmell; and it was juft as m^ich wafted as 
 the other. It therefore appears, that this fmall 
 dofe of fait had neither promoted digeftion, 
 nor produced any tendency to putrefadion, 
 being overpowered by the antifeptic quality 
 of the gaftric fluid. 
 
 ccLxiii. But to return from this digref- 
 iion. If the fait contained in the gaftric fluid 
 is not the caufe of its antifeptic power, tq 
 what other principle can it be owing ? Mac^. 
 
 bride's 
 
D I S S E R 1- A T I O N \1, ^D i 
 
 bride's theory concerning the origin of this 
 property in fo many bodies, has great inge- 
 nuity. ' The cohelion and foHdity of fiD- 
 fcances, is in his opinign owing to the fixed 
 air they contain. Now when by any means 
 this is taken away, the mutual adhefion of 
 the feveral parts will be deftroyed, and the 
 body will either run into the putrefacStive fer- 
 mentation, or crumble into dud, according 
 to the nature of its conftituent parts. Hence 
 it necelTarily follows, that whatever fubftance 
 has the power of impeding the feparation of 
 fixed air, or reitoring it when feparated, will 
 alfo prevent o^ corredt putrefa<5tion. But an- 
 tifeptic matters have, according to this phy- 
 fician, fuch a power. A piece of flefli, for 
 infiiance, furrounded by a fubftance of this 
 kind, is kept fweet, becaufe the fixed air can- 
 not make its efcape; and that, probably, on 
 account of its pores being blocked up by the 
 finer particles of the antifeptic matter. Hence 
 the flefh will long preferve its natural tafte 
 and confiftence. If it has already become 
 putrid, it will receive fixed air from the anti- 
 feptic body, and hence ceafe by degrees to 
 ^^haje a foetid fmell, lofe its fluidity and flab- 
 binefs,,and at laft recover its fweetnefs and 
 firmnefs [a). 
 
 («) Macbride, I. c. 
 
 WiU 
 
J 
 
 62 DISSERTATION VI. 
 
 Will not this theory account for the anti- 
 feptic power of the gaftric fluid ? Without 
 going out of my way to examine the founda- 
 tion on which it rells, I will obferve, that it 
 feems by no means to afford the information - 
 wanted, iince the gaflric fluid is an antifeptic 
 of a Angular fort. Other fubfl:ances poflTef- 
 fing this property, while they keep away pu- 
 trefad:ion, preferve or refl:ore the coheflon of 
 the parts ; whereas the gafliric fluid being at 
 once an antifeptic and folvent, while it pre- 
 vents or correds putrefaction, reduces bodies 
 into very fmall particles. We muil therefore 
 conclude, that the property of this animal 
 fluid arifes from fome other principle, though 
 I cannot determine what that principle is, 
 both for want of experimental data, and on 
 account of the imperfed: fliate in which phy- 
 licians have left the theory of putrefadion, 
 I^ therefore chofe to acknowledge my igno- 
 rance, rather than invent fome gratuitous hy- 
 pothefis ; fuch a mode of proceeding would 
 ill agree with the difpofltion of one, who has 
 no other objedt in view than the difcovery of 
 truth. . 
 
 ccLxiv. For the fake of my readers, it 
 may be proper to recapitulate what has been 
 proved in this difl^ertation. Firfl:, of the three 
 fpecies of fermentation eflablifhed by modern 
 
 chemiils 
 
DISSERTATION VI. 363 
 
 ehemifts and naturalifls, viz. the fweet, the 
 acetous, and the putrid, neither takes place in 
 digeftion. Secondly, Though an acid fome- 
 times appears during this procefs, yet it dif- 
 appears entirely towards the conclulion of it. 
 Thirdly, Putrefad;ion never in health attends 
 digeftion. Fourthly, The gaftric fluid is a 
 real antifeptic. I fuppofe my proofs, 'how- 
 ever conclufive, will not avail with thofe who 
 eflablifli it as an axiom, that wherever there 
 is heat and moifture, there mufl: be fermen- 
 tation; and think that it muil therefore ne- 
 celTarily take place in the food, and not only 
 in the llomach and inteflines, but in the chy- 
 liferous and fanguiferous velTels : they indeed 
 limit their do(5trine fo far as to fay, that where- 
 as out of the body it goes on rapidly, and 
 with an.intelline commotion, in the body of 
 it is flow, weak, and generally impercepti- 
 ble. Let me intreat thefe learned and zea- 
 lous advocates for fermentation to refle6t, 
 that my experiments are not direftly repug- 
 nant to theirs. I only pretend to fliew, that 
 not the fmalleft fenfible fermentation takes 
 place in the ftomach of animals or Man. 
 -With refpe6t to fenfible fermentation, as it 
 is amongft uncertain things, found logic for- 
 bids me alike either to admit or reje6t it. 
 
 x'^PPEN- 
 
[ 365 ] 
 
 APPENDIX. 
 
 ON THE 
 
 DIGESTION 
 
 OF THE 
 
 STOMACH AFTER DEATH. 
 
 By John Hunter, F. R. S. and Surgeon 
 to St. George's Hofpital*. 
 
 A N accurate knowledge of the appear- 
 : ances in animal bodies that die of a vio- 
 
 lent death, that is, in perfect health, or in a 
 found ilate, ought to be confidered as a ne- 
 celTary foundation for judging of the ilate of 
 the body in thofe that are difeafed. 
 
 But as an animal body undergoes changes 
 after death, or when dead, it has never been 
 fufficiently coniidered what thofe changes 
 are J and till this be done, it is impoflible we 
 
 f See Philofophical Tranfaftionij Vol. lxix. p. 447. 
 
 iliould 
 
366 APPENDIX. 
 
 fhould judge accurately of the appearances in 
 dead bodies. The difeafes which the hving' 
 body undergoes (mortification excepted) are 
 always connected with the living principle, 
 and are not in the leaft fimilar to what may 
 be called difeafes or changes in the dead body : 
 without this knov/ledge, our judgment of the 
 appearances in dead bodies muft often be very 
 imperfect, or very erroneous ; we may fee ap- 
 pearances which are natural, and may fup- 
 pofe them to have arifen from difeafe; we 
 may fee difeafed parts, and fuppofe them in a 
 natural ftate; and we may fuppofe a circum- 
 - fiance to have exifted before death, which 
 was really a confequence of it; or we may 
 imagine it to be a natural change after death, 
 when it was truly a difeafe of the living body. 
 It is eafy to fee therefore, how a man in this 
 ftate of ignorance muft blunder, when he 
 comes to conned: the appearances in a dead 
 body with the fymptoms that were obferved 
 in life ; and indeed, all the ufefulnefs of open- 
 ing dead bodies depends upon the judgment 
 and fagacity with which this fort of compa- 
 rifon is made. 
 
 There is a cafe of a mixed nature, which 
 cannot be reckoned a procefs of the living 
 body, nor of the dead> it participates of 
 
 both, 
 
APPENDIX.' 357 
 
 both, inafmuch as its caufe arifes from the 
 Jiving, yet cannot take efFe6t till after death. 
 
 This fhall be the objecft of the prefent pa- 
 per; and, to render the fubjed: more intelli- 
 gible, it will be necelTary to give fome gene- 
 ral ideas concerning the caufe and eifefts. 
 
 An animal fubftance when joined with 
 the living principle, cannot undergo any 
 change in its properties but as an animal; 
 this principle always acting and preferving 
 the fubftance, which it inhabits, from diffo- 
 lution, and from being changed according to 
 the natural changes, which other fubftances, 
 applied to it, undergo. 
 
 There are a great many powers in nature, 
 which the living principle does not enable 
 the animal matter, with which is is com- 
 bined, to reiill:, viz. the mechanical and moil: 
 of the ftronger chemical folvents. It renders 
 it however capable of relifling the powers of 
 fermentation, digeflion, and perhaps feveral 
 others, which are well known to ad: on this 
 fame matter, when deprived of the living 
 principle, and entirely to decompofe it. The 
 number of powers, which thus adl differently 
 on the living and dead animal fubflance, is 
 not afcertained : we fhall take notice of tv/o, 
 which can only affed; this fubflance when 
 deprived of the living principle; which are, 
 
 putre- 
 
^€S A p p E 1^ r^ I :jr*.' 
 
 putrefadidn and digeftion. Putrefaction is 
 an effe&i which arifes fpontaneoufly ^ digeA 
 tion is an eiFed; of another principle ad:ing 
 upon it, and fhall here be confidered a littl6 
 more particularly^ 
 
 Animals, or parts of animals, pofTeffed of 
 the living priticiple, when taken into the fto- 
 machi are not the leafl affected by the powers 
 of that vifcug, fo long as the animal princi- 
 ple remains; hence it is that we find animals 
 of various kinds living in the fliomach, or 
 even hatched and bred there : but the mo- 
 ment that any of thofe lofe the living prin- 
 ciple, they become fubjeCt to the digeftive 
 powers of the ftomach. If it were poffible 
 for a man's hand, for example, to be intro- 
 duced into^ the flomach of a living animal, 
 and kept there for fome conliderable time, 
 it would be found, that the diiTolvent powers 
 of the ftoniach could have no effed: upon it ; 
 but if the fame hand were feparated from the 
 body, and introduced into the fame flomach^ 
 we fhould then find that the ftomach would 
 immediately ad upon it. 
 
 Indeedj if this were not the cafe, we 
 fliould find that the ftomach itfelf . ought 
 to have been made of indigeftible materials ; 
 for, if the living principle was not capable of 
 preferving animal fubilances from undergo- 
 
 ing 
 
APPENDIX^ '369 
 
 ing that procefs, the ftomach itfelf would be 
 digefted. 
 
 But we find on the contrary, that the fto- 
 mach, which at one inftant, that is, while 
 pofTefFed of the living: principle, was capable 
 of reiifling the digeftive powers which it con- 
 tained, the next moment, viz. when deprived 
 of the living principle, is itfelf capable of 
 being digefled, either by the digeftive powers 
 of other ftomachs, or by the remains of that 
 power which it had of digefting other things. 
 
 From thefe obfervations, we are led to ac- 
 count for an appearance which we often find 
 in the ftomachs of dead bodies ; and at the 
 fame time they throw a conftderable light 
 upon the nature of digeftion. The appear- 
 ance which has been hinted at, is a difTolu- 
 tion of the ftomach at its greateft extremity; 
 in confequence of which, there is frequently 
 a conftderable aperture made in that vifcus. 
 The edges of this opening appear to be half 
 diftblved, very much like that kind of diftb- 
 lution which fleiliy parts undergo when half 
 digefted in a living ftomach, or when dif- 
 folved by a cauftic alkali, viz. pulpy, tender, 
 and ragged. 
 
 In thefe cafes, the contents of the ftomach 
 are generally found loofe in the cavity of the 
 abdomen, about the fpleen and diaphragm. 
 
 Vol. I, Bb In 
 
2 JO APPENDIX. 
 
 In many fubjefts this digeflive power extends 
 much further than through the ftomach* 
 I have often found, that after it had difTolved 
 the ftomach at the ufual place, the contents 
 of the ftomach had come into contaft with 
 the fpleen and diaphragm, had partly dilTolved 
 the adjacent fide of the fpleen, and had diffolved 
 the diaphragm quite through ; fo that the con- 
 tents of the ftomach were found in the cavity 
 of the thorax, and had even affecfled the lungs 
 in a fmall degree. 
 
 There are very few dead bodies, in which 
 the ftomach is not, at its great end, in fome 
 degree digefted; and one who is acquainted 
 with difteclions, can eafily trace the gradations 
 from the fmalleft to the greateft. 
 
 To be fenlible of this effeft, nothing more 
 is neceftary, than to compare the inner furface 
 of the great end of the ftomach, with any 
 other part of the inner furface; what is found, 
 will appear foft, fpongy, and granulated^ 
 and without diftin(£l blood-veftels, opake and 
 thick; while the other will appear fmooth, 
 thin, and more tranfparent ; and the veftels 
 will be feen ramifying in its fubftance, and 
 upon fqueezing the blood which they con- 
 tain from the larger branches to the fmaller, 
 it will he found to pafs out at the digefted 
 
 end& 
 
APPENDIX. 371 
 
 ends of the veffels, and appear like drops on 
 the inner furface. 
 
 Thefe appearances I had often feen, and I 
 do fuppofe that they had been feen by others ; 
 but I was at a lofs to account for them; at 
 lirft, I fuppofed them to have been produced 
 during life, and was therefore difpofed to 
 look upon them as the caufe of death ; but I 
 never found that they had any connexion 
 with the fymptoms : and I was ftill more at 
 a lofs to account for thefe appearances, w^hen 
 I found that they were moft frequent in thofe 
 who died of violent deaths, which made me 
 fufped that the true caufe was not even 
 imagined (^). 
 
 At this time I was making many experi- 
 ments upon digeflion, on different ""animals, 
 all of which were killed, at different times, 
 after being fed with different kinds of food; 
 B b 2 fome 
 
 {a) The firil time that I had oecafion to obferve this ap- 
 pearance in fuch 23 died of violence and fuddenly, and in 
 whom therefore I could not eafily fuppofe it to be the effeO. of 
 difeafe in the living body, was in a man who had his ikull 
 fraftured, and was killed outright by one blow of a poker. 
 Juft before this accident, he had been in perfeft health, and 
 had taken a hearty fupper of cold meat, cheefe, bread, and 
 ale. Upon opening the abdomen, I found that the ftomach, 
 though it ftill contained a good deal, wr.s dilTolved at its great 
 end, and a confiderable part of thefe its contents lay loofe ia 
 the general cavity of the belly. This appearance puzzled me 
 
 very 
 
^72 APPENDIX^ 
 
 fome of them were not opened immediately- 
 after death, and in fome of them I found the 
 appearances above defcribed in the ftomach. 
 For, purfuing the enquiry about digeftion, 
 1 got the flomachs of a vaft variety of iiih, 
 which all die of violent deaths, and all may 
 be faid to die in perfed: health, and with their 
 flomach commonly full ; in thefe animals we 
 fee the progrefs of digeftion moil diftincSly; 
 for as they fwallowed their food whole, that 
 is, without maftication, and fwallow fiih that 
 are much larger than the digefting part of the 
 ftomach can contain (the ihape of the iifh 
 fwallowed being very favourable for this en- 
 quiry), we find in many inftances that the part 
 of the fwallowed filh which is lodged in the 
 digefting part of the ftomach is more or lefs 
 diffolved, while that part which remains in 
 the oefophagus is perfedly found. 
 
 And in many of thefe I found, that this 
 digefting part of the ftomach was itfelf re- 
 very much. The fecond time was at St. George^s Hofpital, , 
 In a man who died a few hours after receiving a blow on his 
 head, which fractured his IkuU likewife. From thofe two cafes, 
 among other conjeftures about fo ftrange an appearance, I be- 
 gan to fufpeft that it might be peculiar to cafes of fraftured 
 ikulls ; and therefore, whenever I had an opportunity, 1 ex- 
 amined the ftomach of every perfon who died of that accident: 
 but I found many of them which had not this appearance. 
 Afterwards I met wiUi it in a foldier who had been hanged. 
 
 duced 
 
APPENDIX.' ' '^y§ 
 
 duced to the fame difTolved ftate as the dlgef- 
 ted part of the food. 
 
 Being employed upon this fubje(5t, and 
 therefore enabled to account more readily for 
 appearances which had any connection with 
 it, and obferving that the half- difTolved parts 
 of the ftomach, &c. were fimilar to the half- 
 digefled food, it immediately flruck me, that 
 it was from the procefs of digeflion going on 
 after death, that the ftomach, being dead, 
 was no longer capable of refifling the powers 
 of that menftruum, which itfelf had formed 
 for the digeftion of its contents^ with this 
 idea, I fet about making experiments to pro- 
 duce thefe appearances at pleafure, which 
 would have taught us how long the animal 
 ought to live after feeding, and how long it 
 fhould remain after death before it is opened ; 
 ^nd above all, to find out the method of pro- 
 ducing the greateft digeftive power in the liv- 
 ing ftomach : but this purfuit led me into ari 
 unbounded field. 
 
 Thefe appearances throw confiderable 
 light on the principles of digeftion; they 
 ftiew that it is not mechanical power, nor 
 contractions of the ftomach, nor heat, but 
 fomething fecreted in the coats of the fto- 
 jnach, which is thrown into its cavity^ and 
 B b 3 there 
 
374 APPENDIX. 
 
 there animalifes the food {a), or affimilates it 
 to the nature of the blood. The power of 
 this juice is confined or Umited to certain 
 fubftances, efpecialJy of the vegetable and 
 animal kingdoms ^ and although this men- 
 flruum is capable of ad:ing independently of 
 the ftomach, yet it is obliged to that vifcus 
 for its continuance. 
 
 (a) In all the animals, whether carnivorous or not, upon 
 which I made obfervations or experiments to difcover whether 
 or not there was an acid in the ftomach, (and I tried this in a 
 great variety), I conilantly found that there was an acid, but 
 not a ftrong one, in the juices contained in that vifcus in a na- 
 tural flate. 
 
 EXPE- 
 
[ 375 ] 
 EXPERIMENTS 
 
 CONCERNING 
 
 DIGESTION. 
 
 TRANSLATED FROM THE 
 
 INAUGURAL DISSERTATION 
 
 O F 
 
 Dr. STEVENS. 
 
 Publifhed at Edinburgh in 1777. 
 
 nPHE following experiments were made 
 -■• at Edinburgh upon an Huffar, a man of 
 weak underftanding, who gained a miferable 
 livelihood, by fwaliowing ftones for the a- 
 mufement of the common people, at the im-=- 
 minent hazard of his life. He began this 
 praftice at the age of feven, and has now fol- 
 lowed it twenty years. His ftomach is fo 
 much diftended, that he can fwallow feveral 
 Hones at a time ; and thefe may not only be 
 plainly felt, but may be heard, whenever the 
 Jiypogaftric region is flruck. 
 
 B b 4 EXPERI« 
 
2'/6 APPENDIX. 
 
 EXPERIMENT I. 
 
 At eight o'clock in the evening, I gave the 
 fubjed; of my experiments a hollow filver. 
 fphere, divided into two cavities by a parti- 
 tion, and perforated on the furface with a 
 great number of holes, capable of admitting 
 a needle: into one of thefe cavities was put 
 four fcruples and a half of raw beef, and intQ 
 the other five fcruples of raw bleak. The 
 fphere v/as voided in twenty-one hours, when 
 the beef was found to have loft one fcruple 
 and a half, and the fifh two fcruples.' The 
 reft was much foftened, but had no difagree- 
 able fmell. 
 
 II. A few days afterwards he took the fanie 
 fphere, containing in on,e cavity a fcruple 
 and four grains of raw beef, and in the other 
 four fcruples and eight grains of the fame 
 boiled. In forty-three hours the fphere was 
 returned, and the raw fleih had loft one fcru- 
 ple and two grains, and the boiled one fcru- 
 ple and lixteen grains. 
 
 III. Sufpeding that if thefe fubftances 
 were divided, fo that the folvent could have 
 freer accefs to them, more of them would be 
 diftblved. I procured another fphere with 
 holes, fo large as to receive a crow's quill, 
 and enclofed fome beef a little mafticated in 
 
 it. 
 
APPENDIX, 377 
 
 it. It was voided quite empty, thirty-eight 
 hours after it was fwallowed. 
 
 IV. Seeing how readily the chewed meat 
 was dilTolved, I thought of trying whether it 
 would be as foon diffolved in a fphere with 
 large holes, but without being chewed. I 
 therefore put a fcruple and eight grains of 
 pork into one cavity, and into the other the 
 lame quantity of cheefe. The fphere was 
 retaineci forty -three hours, at the end of 
 which not the fmalleft remains of either pork 
 or cheefe could be found. 
 
 V. He afterwards fwallowed the fame 
 fphere, containing in one partition fome 
 roailed turkey, and in the other fome boiled 
 fait herring. In forty-fix hours it was void- 
 ed, and nothing of the turkey or herring now 
 appeared, both having been completely dif- 
 folved. 
 
 VI. Having found that anim.al fbb fiances, 
 though inclofed in tubes, are eafily concoded, 
 I next determined to try whether vegetables, 
 which are more difficulty digelled, would 
 be fo too. I therefore encloied an equal 
 quantity of raw parfnep and potatoe in a 
 fphere. It was voided after having continued 
 forty-eight hours in the alimentary canal, 
 when both fpecies of vegetable were found 
 to be difTolved, 
 
 VII. Pieces 
 
37^ APPENDIX. 
 
 VII. Pieces of apple and turnep, both 
 raw and boiled, were diflblved in thirty-fix 
 hours. 
 
 VIII. He next fwallowed fome grains of 
 wheat, rye, barley, oats, and peafe, contained 
 in a fphere, which remained feveral hours in 
 the alimentary canal, but no alteration was 
 produced on any of its contents, except upon 
 the peafe, Vv^hich v/ere fwoln, and burft by 
 the humidity they had imbibed. 
 
 IX. The readinefs with which the gaflric 
 fluid had acfted upon roafted animal fubftances, 
 induced me to try what change would be pro- 
 duced by it upon hard ones, fuch as bone. 
 I therefore inclofed in one partition of a 
 fphere, fome of the bone from a leg of mut- 
 ton, and in the other part of a turkey's wing. 
 The fphere was retained forty-eight hours. 
 The bone was weighed, and found to have 
 loll nothing of its weight, while the fleih, 
 {Iduj and ligaments were quite difTolved, fo 
 that the bones of the wing were now quite 
 feparate; but they had undergone no per- 
 ceptible alteration. 
 
 X. Inanimate matters being fo readily fo- 
 luble, I refolved to enquire how far living 
 animals are capable of refifting the adion of 
 this powerful menftruum. With this view, 
 an animal fuppofed to be deftitute of pores> 
 
 and. 
 
■"■ APPENDIX. Q,y^ 
 
 and, according to my experiments, capable 
 of faftaining a degree of heat equal to the 
 human temperature, was cnclofed in a fphere 
 perforated with fmall holes, to prevent the 
 leech from wounding the ftomach. The 
 HuiTar took it, and voided it about the ufual 
 time, Vv'hen nothing was found except a black 
 vifcid miafma, the remains of the digefted 
 leech. This experiment was repeated with 
 earth-worms, and they were dillblved with 
 equal facility. But as they cannot fo well 
 fupport the human temperature, it is pro- 
 bable they died before they began to be dif- 
 folved*. 
 
 It was my intention to make more experi- 
 ments of this kind, but as the HulTar left 
 Edinburgh foon afterwards, I was obliged to 
 have recourfe to dogs and ruminating ani- 
 mals. 
 
 XI. A whelp, three months old, having 
 been kept fourteen hours without food, was 
 forced to fwallow four oval ivory globes, of 
 different lizes, and perforated with many 
 fmall holes. One contained beef, another 
 haddock, a third potatoe, and a fourth cab- 
 bage, all raw, and weighing each iixteen 
 grains. In four hours the animal was killed 
 and opened. The globes were found in the 
 
 * Perhaps this is alfo the cafe with leeches. 
 
 flomach. 
 
3S0 APPENDIX. 
 
 ftomach, and their refpedive contents were 
 diminifhed in the following proportions : The 
 fifli had loft nine grains, the beef five, the 
 potatoe three, and the cabbage one. The 
 globes themfelves appeared to be thinner, but 
 as I had no fufpicion that the ivory would be 
 affedted by the gaftric fluid, I did not weigh 
 them before the experiment. I could not 
 therefore exad:ly afcertain their diminution. 
 
 XII. Having procured a whelp five months 
 old, it was kept fafting fixteen hours, and 
 then four of the globes ufed in the foregpipg 
 experiment,* each containing a certain quan- 
 tity of mutton, turbot, parfnep, and pota-i 
 toe were forced upon it. Thefe fubftances 
 had been previoully expofed to the adlion of 
 fire, and each weighed fixteen grains. Seven 
 hours afterwards the animal was killed, and 
 the globes were taken out of the ftomach; 
 when the fifh was found to have loft ten 
 grains and a half, the mutton fix, the po^ 
 tatoe five, and the parfnep nothing. The 
 fpheres were become ftill thinner, but I had 
 as before, neglefted to weigh them. 
 
 XIII. A dog fix months old was kept faft- 
 ing the ufual time, and the fame four fpheres 
 were given him. The firft contained fixteen 
 grains of boiled mutton, the fecond as much 
 boiled fiih, the third the fame quantity of 
 
 boiled 
 
APPENDIX. 381 
 
 boiled potatoe, and the fourth of boiled parf- 
 nep. In eight hours it was killed and opened. 
 .The globes were found greatly altered. The 
 extreme parts, not the middle, were totally 
 difTolved, fo that the contents lay loofe in 
 the ftomach. The fpheres, before the ex- 
 periment, weighed together three fern pies 
 iixteen grains ; the fragments weighed only 
 one fcruple and twenty grains. The mutton 
 and iifh were entirely concodted, the potatoe 
 had loft twenty-one grains -, but the parfnep 
 was unchanged. 
 
 XIV. Being furprized at the fpeedy folu- 
 tion of ivory by the gaftric fluid, I deter- 
 mined to fubjedt other hard bodies to its 
 action. I therefore carefully weighed three 
 pieces of a fheep's thigh bone, and gave 
 them to a dog that had. been long kept fail- 
 ing. Seven hours afterwards the animal was 
 killed, and the bones were taken out of the 
 ftomach. The fiirft had loft feven, the fe- 
 cond nine, and the third twelve grains. The 
 folution began at the internal furface, and 
 advanced towards the center, fo that the ca- 
 vity was conliderably augmented [a). 
 
 I more- 
 
 {a) In order to aflure myfelf that this folution was not owing 
 to fermentarion, or an acid, I imnierfed a bone of the fame 
 kind, in an alimentary mixture, confiding of roafted beef, 
 
 ivheaten 
 
382 APPENDIX. 
 
 I moreover obliged my dog to fwallcvr 
 pieces of cartilage, but I found that the gaf-* 
 trie fluid produced no effedl upon them. 
 
 XV. As the ivory fpheres and bones were 
 fo readily dilTolved in the foregoing experi- 
 ments, I was induced to make trial of fome 
 bodies ftill harder. With this view I pro- 
 cured fome cylindrical tin tubes, perforated 
 with a great number of holes 3 of which 
 four were given to a dog that had been kept 
 failing twelve hours. The firil contained 
 iixteen grains of roafted beef, the fecond the 
 fame quantity of veal, the third of fat, and 
 the fourth of wheaten bread. In ten hours 
 the animal was killed and opened, and the 
 tubes were taken out of its ftomach. The 
 beef and bread were quite dilTolved -, the veal 
 had loil only ten grains, and the fat eight and 
 a half. The tubes had not undergone the 
 fmalleft alteration. 
 
 XVI. As in the laft experiment the veal. 
 was not fo foon diifolved as the beef, I began 
 to fufpedt that the iiefh of young animals in 
 general is lefs eafy to digeil than that of old 
 
 wheaten bread and water, beaten into a pulp. When it had 
 remained forty-eight hours in a temperature, equal to 102 deg, 
 of Fahr. Therm, it was examined: the fermentation had run 
 very high, and the acidity was ftrong, but the bone had under- 
 gone no diminution. ItVas, however, much foftened. 
 
 ones. 
 
APPENDIX. 383 
 
 ones, i therefore took care to repeat the ex- 
 periment with lamb and mutton, which were 
 put in equal quantities into two tubes. The 
 refult was as before. In feven hours the 
 mutton was quite diilblved, whereas the lamb 
 had loft only ten grains. The remains of 
 veal and lamb in thefe experiments were fur- 
 rOunded with a vifcid gelatinous matter. 
 
 XVII* Sixteen grains of raw beef, and the 
 fame quantity of roafted were inclofed in two 
 tubes, and given to a dog, Vv^hich w^as killed 
 feven hours afterwards, when the former was 
 found to have loft fifteen grains, while the 
 latter was completely dilTolved. 
 
 XVIII. The fame experiment was repeated 
 with fifh inflead of fiefh. Sixteen grains of 
 raw and as much boiled haddock, were en- 
 clofed in two tubes, and given to a dog. 
 When he was killed, no remains of the boiled 
 could be founds the raw portion had loll: 
 fourteen grains. 
 
 XIX. I next enquired whether quadrupeds 
 or birds arc moft ealily digefted. For this 
 purpofe, equal quantities of beef, mutton, 
 and fowl were inclofed in three tubes, and 
 given to a dog^ they were each roafled, and 
 weighed fixteen grains. Upon killing the 
 dog, and examinin^g the tubes, I found that 
 
 the 
 
384 AppENbri. 
 
 the mutton and beef had been dliTdlved, 
 while the fowl had only loft eleven grains. 
 
 Moft of the experiments related above^ 
 were repeated oftner than once, and afforded 
 the fame refult. We cannot therefore enter- 
 tain any doubt concerning the mode of di- 
 geftion in this clafs of animals. Whether 
 the concodtion of ruminating animals is ef- 
 fedled in the fame md.nner, I endeavoured to 
 afcertain by the following experiments^ 
 
 XX. I gave a iheep four cylindrical tin 
 tubes, each containing fixteen grains of raw 
 beef, falmon, turnep, or potatoes fix hours 
 afterwards the animal was killed 3 the tubes 
 were found in the firft ftomach. The filh 
 and flefh were unaltered, whereas the turnep 
 and potatoe were quite diffolved. 
 
 XXI. The fame experiment being repeated 
 with the fame fubftances boiled, afforded the 
 Tame refult. The vegetables were digefted, 
 and the beef and falmon unchanged. 
 
 XXII. Having found that the fheep di- 
 gefts vegetables very readily, but is incapable 
 of diffolving animal fubftances, I had next 
 recourfe to the ox. Four tubes, one con- 
 taining raw beef, another fifh, a third chop- 
 ped hay, and the fourth leaves of pot-herbs, 
 were given to an animal of this fpecies, and 
 it was killed ten hours afterwards . The tubes 
 
 lay 
 
APPENDIX. 38^ 
 
 lay in the firll: Homach; the fifh and flefh 
 were not altered; but I could find no remains 
 of the hay or herbs. 
 
 Many experiments of the fame kind were 
 made upon this animal, and they led me to 
 the fame conclufion, viz. that the eaftric 
 fluid of the ox kind, eafily and fpeedily dif- 
 folves vegetables, but is incapable of pro- 
 ducing this effed: upon animal fubftances. 
 
 In all thefe experiments, I attribute the 
 fulution of the food to a powerful menflruum 
 fecreted by the coats of the fliomach. It 
 may be objected, that my experiments do 
 not clearly iliew whether the food is con- 
 coded by the gaftric fluid, or by fermenta- 
 tion, for both caufes may a(ft equally upon 
 aliment inclofed in the fpheres. But befldes 
 the arguments already adduced to fhew (a)y 
 that fermentation does not produce this ef- 
 fed, many circumftances attending thefe ex- 
 periments clearly fliew the eflicacy of the 
 gafl:ric liquor. For in the experiments in 
 which the food was not quite diflblved, the 
 folution always began at the furface, and 
 proceeded towards the center, and what re- 
 mained, ihewed no tokens of fermentation. 
 
 («) In the part that has been omitted. 
 
 Vol. I» C c In 
 
386 APPENDIX. 
 
 In the XI nth experiment ivory was dif- 
 folved, while parfnep, a vegetable of foft 
 texture, and liable to fermentation > was not 
 at all altered. 
 
 To remove every doubt, the following ex- 
 periment was feveral times repeated, and al* 
 ways afforded the fame refult* 
 
 xxiii. Having kept a dog falling eigh^ 
 teen hours, that his flomach might be free 
 from the remains of food, I killed it, and 
 Golledled about half an ounce of pure gaftric 
 iiuid, which was put into a phial with twelve 
 grains of roafl: beef* The fame quantity of 
 the fame beef was put into another phial, 
 containing water, in order to ferve for a term 
 of comparifon. Both phials were placed in 
 a furnace, of which the temperature was 
 equal to 102—104° of Fahrenheit's thermo- 
 meter. In eight hours the beef in the gaftric 
 fluid was quite diffolved, whereas that in the 
 water had undergone no perceptible altera- 
 tion. In twenty-four hours both phials 
 were taken out of the furnace and carefully 
 examined.. The food diffolved in the gaflric 
 fluid emitted a rancid and pungent, but by 
 no means a putrid odour; it refembled very 
 much the fmell of burnt feathers. The meat 
 in the other phial was quite putrid, and in- 
 tolerably 
 
APPENDIX. 3S7 
 
 tolerably fetid; but its bulk was not dimi^ 
 pifhed. 
 
 I carefully obferved the phial containing 
 the gaftric fluid during the folution, but 
 could perceive no air-bubbles ariling, or any 
 other token of fermentation. I repeated this 
 experiment with maflicated meat, when the 
 folution was much more fpeedily com- 
 pleted. 
 
 I afterwards made trial of mutton, veal, 
 lamb, and other animal, together with a great 
 variety of vegetable fubftances ; all were ealily 
 difTolved; but the time requifite for the com- 
 pletion of this procefs was different, and 
 anfwered exad:ly to the refults of the prece- 
 ding experiments. 
 
 As in this experiment there was no fign of 
 fermentation or putrefaction, I fufpefted that 
 the gaftric fluid, as well as the faliva [a)^ 
 retards both the one and the other. In order 
 to determine this, I made the following ex- 
 periment. 
 
 XXIV. I took two alimentary mixtures, 
 each confifting of mutton and bread in equal 
 quantities. Upon one, half an ounce of the 
 recent gaftric juice of a dog was poured, and 
 
 (a) Where did the author learn that the faliva checks fer- 
 mentation ? It appears from all the experiments that have been 
 made to forward it. T. 
 
 C c 2 upon 
 
3S8 APPENDIX. 
 
 iapon the other the fame quantity of pure 
 water. Both mixtures were beaten to a pulp, 
 and inclofed in phials accurately flopped; 
 they were then fet in a furnace, heated to 
 the load deg. of Fahrenheit's thermometer* 
 Fermentation took place in a few hours in- 
 the phials that contained the water, the folid 
 contents rofe to the furface, and air was ex- 
 tricated with a conliderable inteftine motion. 
 The mixture immerfed in the gaftric fluid, 
 remained fourteen hours with fcarce any to- 
 kens of fermentation ; but a fhort time af- 
 terwards, this procefs evidently took place. 
 The bread and flelh arofe to the furface of the 
 mixture, a fediment began to be depofited^ 
 and air-bubbles were continually extricated. 
 But thefe pha^nomena continued much lon- 
 ger than in the other phial; the commotion 
 was lefs violentj and the air was not fo ra- 
 pidly extricated. When the fermentation 
 had entirely ceafed, the tafle of the mixture in 
 this phial was indeed acid, but not fo ilrong 
 as in the other, and it was converted into a 
 fluid by the folvent power of the gafl:ric 
 liquor^ 
 
 XXV. I divided a piece of putrid mutton 
 into two parts, each of which was put into 
 a feparate phial, and to one, half an ounce of 
 the recent gafl:ric fluid of a dog was added, 
 
 and 
 
APPENDIX. 389 
 
 and to the other, which was defigned as a,, 
 term of comparifon, as much water. They 
 were fet in a cool place, and two days after- 
 wards I examined them, when the latter e- 
 mitted an intolerably putrid fmell, and the 
 other, though it had yet a bad odour, did 
 not fmell fo difagreeably as the preceding, 
 nor even fo difagreeably as at firft. Upon 
 fliaking the phial, the meat fell to pieces, 
 but it was not quite dilfolve^. This, per- 
 haps, happened, .becaufe it was not expofed 
 to a fufficient heat. 
 
 Thefe experiments throw great light on 
 digeilion. They fliew, that it is not the ef^ 
 fed; of heat, trituration, putrefa6lion, or 
 fermentation alone, but of a powerful fol- 
 vent, fecreted by the coats of the ftomach, 
 which converts the aliment into a fluid, re- 
 fembling the blood. If it fhould be afked, 
 what defends the organ itfelf, I would an-, 
 fwer, that it is the vital principle, as Mr. 
 Hunter's [a) obfervations fhew; after death 
 it is diflblved as readily as any other inanimate 
 (uhftance. It is probable, that every fpecies 
 " ' .- ' '^C3 • pf 
 
 {a) Philofopl). Tranf. for 1772. The ingenious obferver 
 feems, however, to attribute too much to this principle. He, 
 fuppofes, that whatever poffeffes it, is capable of refilling the, 
 adUon of the galtric liquor j his arguments by no means prove 
 
 ' ' ■ " ' '- t\n3. 
 
£90 A P P E N D I X.^ 
 
 of animal has its peculiar gaftric liquor, ca- 
 pable of diffolving certain fubflances only. 
 Some living folely upon vegetables, others, 
 upon animals, and thefe cannot be obliged 
 to feed upon plants, by a fail of whatever 
 continuance. All, by an infallible inftind:, 
 choofe what is befl adapted to their gafcric 
 fluid. The food, when diffolved, is expel- 
 led from the ftomach, and being mixed with 
 the bile and pancreatic juice in the duode- 
 num, is chans^ed into a mild blood and in- 
 
 this. Worms, indeed, live in the human fiomach, but it does 
 not follow, that other animals alfo can, for nature may have 
 given thera a particular ftrufture of body. The following con- 
 iiderations will render the general propofition very doubtful. 
 Fifties fwallow and digeft living crabs, lobilers, &c. The 
 leech is concodled by the human ftomach, though it has no 
 pores, and can fuftain a temperature equal to that of man. 
 Cornelius found a fnalce half digcfied in a bird's ftomach, but 
 ftill alive. Plot favv one eye confumed, while the lifti was alive. 
 It feems therefore probable, that the gaftric liquor afts alfo upon 
 living things. Perhaps, likewife, it is fometimes fo changed, 
 as to a6l on the ftomach itfelf. The following cafes commu- 
 nicated by Dr. Monro render this probable. A lady, that 
 ufed, to complain of pain in the ftomach, died fuddenly. Upon 
 opening the body, a hole was found in the left fide, and the 
 coats were relaxed as if they were half putrified. There were 
 1^0 appearances of gangrene. A boy died after having long 
 ftruggled with fimilar pains. The ftomach exhibited the very 
 fame appearance, if we except the hole. From the preceding 
 fymptoms, one may venture to fuppofe, that fome alteration 
 was produced before death. Bot this is only conjedure, and 
 future experiments muft determine the queftion. 
 
 odorous 
 
APPENDIX. 391 
 
 odorous liquid, which is denominated chyle. 
 The chyle is abforbed by numberlefs vefTels, 
 and is carried by the thoracic du(fl into the 
 fubclavian vein, in order to repair the con- 
 ftant wafte of the body. 
 
 Cc4 AN 
 
AN 
 
 ANALYTICAL INDEX 
 
 OF THE 
 
 O N T E NTS 
 
 ■OF THE SIX PRECEDING 
 
 DISSERTATIONS. 
 
 INTRODUCTION. 
 
 Ty EASONS of the author for treating concerning DI- 
 •f geftion. Syftems relative to this fundion Page! 
 
 DISSERTATION I. 
 
 OM THE DIGESTION OF ANIMALS WITH MUSCULAR STO- 
 MACHS, COMMON FOWLS, TURKEYS, DUCKS, GEESE, 
 DOVES, PlGEpKS. 
 
 2. Owing to mere trituration, according to feveral authors. 
 This opinion extended by them to all other animals 3 
 
 If. Reaumur's experiments on one kind of grain, whence 
 
 , he infers, that the redudion of the food to pieces is the 
 
 effect of trituration alone in birds with mufcular'fto- 
 
 machs or gizzards ■ 4 
 
 III. Reaumur's exp€riments extended by the author to 
 other grain — — 5 
 
 IV. Variation of thefe experiments — 6 
 
 V. Other variations of them by previoufly macerating the 
 grain in the craw of gallinaceous fowls ib. 
 
 VI. By taking off the fkin 7 
 
 VII. The fame fubjeded to frefh trials in ducks, turkies, 
 geefe, doves, and pigeons -= ib. 
 
 viii^ Conclufion >■ ■ 8 
 
INDEX. 
 
 IX. A necefTary precaution ' ■ ,.« p, 8 
 
 X. Tin tubes broken and diftorted in the gixzards of 
 turkies - . a 
 
 XI. '■r — -liable to the fame accidents, though ftrengthened 
 with iron wire, injuries ftill more furprizing lo 
 
 XII. A full confirmation of the Florentine experiments, 
 concerning the trituration of empty glafs globules in 
 the ftomach of gallinaceous fowls, the longer they re- 
 main in tlie ftomach, the more finely are they pulveri- 
 zed. 1 he facility with which they are broken, in pro- 
 
 ' portion to the fize of the animal - i j 
 
 XIII. Profeffor Pozzi denies the trituration of thefe 
 balls - - - 12 
 
 XIV. Vallifneri miftakcn, iq fuppofing that thefe efFe£l:§ 
 are produced by the gaftric fluid - 13 
 
 XV. Pieces of glafs !ofe their edges and points by con- 
 tinuing in the gizzard of a cock - 14 
 
 XVI. Angles of a large garnet abraded in the gizzard gf- 
 a pigeon - - - 15 
 
 XVII. Coats of the gizzard not hurt by thefe fubftan-' 
 ces - - - 16 
 
 xviii. Large needles fixed in a leaden ball, broken by 
 the allien of the gizzard of a turkey, without injury 
 to that organ. Injury done to the ball - ' ib. 
 
 XIX. Lancets broken in the fame manner - 17- 
 
 XX. Time requifite for thefe effects to be produced 18 
 
 XXI. The gizzard of young fowls fometimes a little hurt 
 by the metallic points - - ib. 
 
 xxn. Why does not the gizzard fufFer from thofe fub- 
 ftances " " ~ '9 
 
 xxiu. Whether, as fom..e fuppofe, becaufe the pebbles 
 that are always found in it reduce thefe hard fubftances 
 to pieces - - - 20 
 
 XXIV. This is a mere hypothelis, and fliould be verified 
 by experiment - - ib. 
 
 XXV, XXVI. No foundation for the opinion of the Flo- 
 rentine academicians, that hard bodies are more eafily 
 broken, the more pebbles the bird has in its giz- 
 zard - - - - 21, 22 
 
 XXVII. Means contrived for afcertaining the ufe of thefe 
 pebbles - - - 22 
 
 XXVIIl. 
 
INDEX, 
 
 xxyiii. When mofi of them are come away, the effecis 
 
 of trituration not at all diminifhed. The gizzard not 
 
 hurt by ftarp bodies when it contains no (tones 2'^ 
 
 xxrx. Pebbles in the gizzard of neitiings - 25 
 
 jfxx. When it is proper to examine thele biids, in order 
 
 to find their gizzards without ftones. Thofe without 
 
 them break, down haid and ihort bodies without fuf- 
 
 taining any injury ~ - ib. 
 
 -XXXI. The queftion decided, whether digeftion depends 
 
 on thefe fiones - - 26 
 
 xxxii. Decifion of other curious queftions 27 
 
 xxxiii. Fowls of this clafs do not feem to feek them 
 
 from defign, but only to fwallow them becaufe they 
 
 are mixed among their food - 2^ 
 
 XXXIV. Trituration is the immediate effed: of the gaf- 
 trie mufcles - - 30 
 
 XXXV. ISJature of the internal coat of the gizzard. It is 
 • divided by drawing {harp fubftances over it ib. 
 
 xxxvr. Not fo when they are inclofed and agitated by 
 the hand _ - _ ^i 
 
 XXXVII. Reaumur's obfervations on the living gizzard. 
 Slight motion of it - - 32 
 
 xxxvili. Similar motion obferved by the author 33 
 
 XXXIX. Whether the gaftric mufcles alfo change the 
 food into that pultaceous mafs called chyme. Fadis af- 
 fording room to fui'pedt, that the gaftric fluid produces 
 this efl-eft - - 34. 
 
 XL. Other fatSis that add ftrength to thefe fu fpicions 35 
 XLi. Decifive experiments in favour of this opinion 36 
 XLi r, XL! 1 1. Others equally decifive— Precaution 38—40 
 xLiv, xLV. How an experiment of Reaumur ought to 
 be underftood - - 4.0-- 42 
 
 XLvi. Tounderftand digeftion thoroughly, it is necefl'ary 
 to examine the cefophagus and gizzard likewife. De- 
 fcription of the oefophagus of a goofe - 44 
 
 XLyii. Numerous follicles of different lizes in it. Ex- 
 cretory du6ts, and the fluid that oozes out - 45 
 xLviii. Defcription of the ftomach. Largenefs of the 
 mufcles. Their action,' Cartilaginous coat 47 
 
 ixLix. QEfophagus and gizzard of the fowl and turkey. 
 'Follicles. !Huid. Craw, and its glands ib. 
 
 L. ^JO' 
 
INDEX. 
 
 L. CEfophagus and gizzard ^f other gallinaceous 
 fowls . _ ^g 
 
 LI, No appearance of glands in the gizzard. Whether 
 any fluid can come into it by any other meang. Suf- 
 picion of Reaun^ur on this fubjefl. Experiments 49 
 
 Lii, Liquor falls in plenty out of the oe.fophagus into the 
 Iftomach - - - '51 
 
 tin. Bitternefs of the gaftric fluid occafioned by the 
 bile - - "52 
 
 Liv. Maceration in the gizzard, the firfl: ftep towards 
 digeftion. The manner in which it paffes from the 
 craw to the gizzard. " " 53 
 
 LV= No trituration in the craw. Changes the food un- 
 dergoes in the gizzard - 54 
 
 IVJ. Artificial digeftion. The gaftric fluid more effica- 
 cious than water - "55 
 
 LYii. The farne.- Necefl^ary- precaution - 5S 
 
 DISSERTATION II. 
 
 ON THE DIGESTION OF ANIMALS WITH INTERMEDIATE 
 STOMACHS, CROWS, HERONS. 
 
 Lviii. In what fenfe crows can be called animal? with 
 intermediate ftomachs - 5^ 
 
 Lix. Ufe of experiments on crovys, bscaufe they, like 
 man, are omi.ivorous. Very convenient ori account 
 of their throwing up indigeftible bodies - 6i 
 
 LX. The ftones in the ftomach more eafily evacuated 
 from crows than gallinaceous birds. Not requifite for 
 digeftion. Swallowed only becaufe they happen to be 
 mixed among the food. - 6z 
 
 Lxi. Gaftric fluid incapable of diflblvln.g enti,re grains 6^ 
 
 i,xH. But it difi'olves bruifed ones. The mechanical 
 action of the ftomach does not contribute to this 64 
 
 Lxni. Variation of thefe experiments - 65 
 
 LXiT. Tender vegetables eafily and foon diflToIved by 
 crows - - 66 
 
 X.XV. Flefti diflblved without the concurrence of mufcu^ 
 Jar action, Manner ot aftion of fhe gaftric fluid 67 
 
 iXv'I, 
 
I N D E X« 
 
 Lxvr, LXVii, Lxviii. Experiments {hewing, that the di- 
 geftion of the flefti is nearly proportional to the quan- 
 tity of gaftric fluid by which it is invefted 69, 70-72 
 LXix. Gaftric fluid of neftlings more efficacious than that 
 of adult ones - -74 
 
 Lxx, Lxxi, Lxxii, LXXiii. An error of Cheyne. Gaf- 
 tric fluid of crows incapable of diffolving hard bones-- 
 DilTolves tender ones » - 75' "79 
 
 txxiv. Whether the oefophagus of this bird will dif- 
 folve flefli like that of fome fifhes ~ 79 
 
 LXxv. CEfophagusof the crowdefcribed. The follicles 
 and the fluid - - 80 
 
 Lxxvi. The ftomach defcribed— its glands and their 
 liquor - - ^i 
 
 LXX VII. Qi^fophageal juice produces fome concoc- 
 tion - - 82 
 Lxxviii. The oefophagus of neftlings more efficacious ia 
 this refpe£l - * ^3 
 Lxxix. The whole length capable of digeftion 84, 
 LXXX. The craw of gallinaceous birds does not digelt 
 food - - g^ 
 j,xxxi, Lxxxii, LxxxiTi. Convenient mode of procu- 
 ring gaftric fluid from crows without killing them. 
 Its abundance. Its qualities, is continually fecre- 
 ted into the ftomach - 86-88 
 Lxxxiv. The oefophageal fluid procured in the fame way. 
 Its fmall quantity. Bile gets into the ftomach. The 
 reafon why the ftomach digefts fafter than the cefo- 
 phagus - _ gg 
 Lxxxv. Gaftric fluid out of the body and in the cold, 
 not more efficacious than water - gi 
 Lxxxvi.- But when heat is appHed, it then produces 
 folution — Difference betweeji its effects and thofe of 
 water - " 92 
 Lxxxvii. Speedy concoilion of animal and vegetable 
 matters by the gaftiic fluid in the fun - 94 
 Lxxxviii, Lxxxix, xc, xci. Flefti immerfed in gaftiic 
 fluid, not difliblved in the fpace of a few hours, within 
 tubes perfedly clofe and introduced into the ftomach. 
 Some infufficient conjectural explanations of this phe- 
 nomenon. The true realbn. Refledtion on the im- 
 portance of heat in thefc experiments - 97—100 
 
INDEX. 
 
 xcli. Gaftric fluid diluted with a great deal of water,- 
 produces folution in a brifk heat - 102 
 
 XClir. Herons have an intermediate ftomach. Defciip- 
 tion of it. Liquor fecreted from the nervous coat into 
 the cavity of the ftomach, not by glands, but pro- 
 bably by arteries - - J03 
 
 xciv. Stomach of herons always contains gaftric fluid. 
 Its qualities. Gall bladder. The cyftic du£t pro- 
 bably inferted into the duodenum - 105 
 
 xcv, xcvi. Defcription of the oefophagus. Its folli- 
 cles and liquor - - 106—107 
 
 xcvii. Stomach of herons comprefies its contents. Di- 
 geftion, however, does not depend on this a£tion, but 
 on the gaftric fluid alone' - 1 07 
 
 xcviii. That of the heron more elEcacious in diiTolving 
 bone than that of the crow - - ^lo 
 
 xcix, c. The (sfophagus of herons Capable of produ- 
 cing a fenfible degree of digeftion " III — 113 
 
 CI. Proportion between the conco^ion of the oefophagus 
 and ftomach - - - 1 14 
 
 cii, cm. Comparifon between birds with mufcular and 
 thofe with intermediate ftomachs, with refpedl to di- 
 geftion - - 116—117 
 
 DISSERTATION III. 
 
 OF THE DIGESTION OF ANIMALS WITH MEMBRANOUS 
 STOMACHS. THE FROG. NEWT. LAND AND WA- 
 
 TER-SNAKE. VIPER. FISHES, SHEEP. OX. HORSE, 
 
 Reafons for treating this fubjeft in feveral difterta- 
 tions - - iig 
 
 cv. Singular way in which the gaftric fluid of the frog 
 in a day's time begins to difTolve flefh - 120 
 
 cvi. In a longer time it difiblves it completely without 
 the adion of the gaftric mufcles. Slownefs of this 
 procefs - - - 121 
 
 cvii. In time it difTolves bone - 122 
 
 CVI II. The gaftric fluid of water-newts more fpeedy in 
 producing its efFech than that of frogs - 324 
 
 CIX 
 
I N D E Xi 
 
 Clx* DlfcoVery of two fpecles of worms in the ftomach 
 of this animal ~ - 126 
 
 ex. Defcription. Reafon for fuppofing that one fpecies 
 is hermaphrodite and oviparous - 127 
 
 CXI. Stomach of this animal the refidence of thefe 
 worms - - - 129 
 
 CXI I. Similar worms between the internal and nervous 
 coat in crows - - 130 
 
 exiii. This is a certain proofs that the ftontach of the 
 water- newt has no fenfibie adtion - 135: 
 
 cxiv. The reafon why infe£ts that ferve the newt for 
 food are digefted, and yet this never happens to the 
 worms - " - 13-5 
 
 cxv, Gxvi. Defcription of the ftomach and oefophaous 
 in fome land-fnakes - 134--136 
 
 cxvii. Means contrived by the author, for obferving 
 the various changes the food undergoes in the ftomacii 
 of ferpents without killing them - 137 
 
 Cxviii. Gaftric fluid of itfelf capable of digefting fieili 
 in certain land-fnakes. Slownefs of this procefs 138 
 
 cxix. The fame lefs flow, as the meat is lefs tough, and 
 thegaftric fluid has freer accefs - 139 
 
 cxx. CEfophagus and ftomach of water-fnakes (deno- 
 minated natrices) very like thofe of land-fnakes 140 
 
 cxx I. In them digeftion is the efFe61: of the gaftric fluid 
 alone - - ib. 
 
 cxxii. Probable arguments that this fluid diflblves bone 
 alfo - - 142 
 
 CXXII I. Analogy between the gaftric fluid of this and 
 other animals - - 143 
 
 cxx I v. Vipers refemble fnakes in the form of the oeio- 
 phagus and ftomach, and in the mode of digeftion 544. 
 
 cxxv. No digeftion in the cefophagus of ihtie. ani- 
 mals - - 145 
 
 cxxvi. Digeftion quicker in the warmer feafons 146 
 
 cxxvii, cxxvui. inftances of flcfti lying a longtime 
 in the ftomach of thefe animals without putrify- 
 ing - .. - 148—149 
 
 cxxix. Of digeftion in the eel - 149 
 
 cxxx, cxxxi. Defcription of the ftomach and celo- 
 phagus of the carp. The fource of the gaftric fluid 
 
 ISO- 153 
 
 -CXXX'il, 
 
INDEX. 
 
 cxxxit, cxxxiir. Defcription of thefe parts in the bar- 
 bel and pike - - 154, 
 
 cxxxr V. Digeftion in fifhes the efFe(3: of the gaftric fluid. 
 Origin and progrefs in a piice - 155 
 
 cxxxv. The fame in a carp. The inferior part of the 
 ftomach digefts more rapidly than the fuperior. Some 
 degree of di^eftion in the oefophagus. Proof that in 
 fifhes, ferpents, the newt, and the frog, digeftion is 
 independent of trituration - 156 
 
 cxxxvi. Two experiments of Reaumur on {heep 157 
 
 cxxxvii. Reaumur's experiments repeated fuccefs- 
 fuUy - « _ 159 
 
 cxxxviii. Doubts whether they are deciflve in favour' 
 of trituration - - 161 
 
 cxxxix. Important circumftance overlooked by the 
 French naturalift, which proves digeftion in fheep to 
 be folely owing to the gaftric fluid - 162 
 
 CXL. Confequences of thefe experiments - 166 
 
 cxLi. The gaftnc fluid of ftieep diflblves other fub- 
 ftances befides herbs - 168 
 
 cxLii. An incipient digeftion obtained out of the body. 
 Heat neceflary for this - 169 
 
 CXLI 1 1. The gaftric fluid is the caufe of digeftion in the 
 ox and horfe - - 172 
 
 CXL IV. Ruminating animals very much refemble birds 
 with gizzards, with refpe6l to the action of the gaftric 
 fluid - - 173 
 
 DISSERTATION IV. 
 
 THE SUBJECT OF DIGESTION IN ANIMALS WITH MEMBRA- 
 NOUS STOMACHS CONTINUED, THE LITTLE OWL. THE 
 SCREECH-OWL. THB FALCON. THE EAGLE. 
 
 CXLV. Recapitulation of Reaumur's experiments on the 
 digeftion of animals with membranous ftomachs 175 
 
 cxLVi. Birdsofprey. The gaftric fluid of the little owl 
 incapable of digefting fome vegetable fubftances 178 
 
 CXLVii. Though capable of produciiig this effect on 
 bone. The ftomach has no triturating power 1 80 
 
 CXLVI n. 
 
! N D E Xi 
 
 txLvni. Contrivance of the author for bringing up 
 tubes out of the ftomdch of birds of piey at pleafure. 
 Gradual folution of bone and flefli in tubes by this 
 owl - - 180 
 
 CxLix. Tnexhauftible fource of the gaftric fluid— Pro- 
 perties - - 183 
 
 CL. It diflblves flelh oatof thebody - 185 
 
 CLi. Defcription ot the cefophagus and ftomacH. Source 
 of the gaftric fluid - 187 
 
 CLii. JVlorbid condition of a fcreech-owl, that rendered 
 the gaftric fluid incapable of digefting flefh 189 
 
 CLiii. Which is very efficacious in health ~ igo 
 
 CLiv. Then even bone is readily dilTolved. The dsfo- 
 phagus, in one fpecies of fcreech-owl, diflblves flefh 
 nearly as well us the ftomach - igi 
 
 CLV. Artificial digeftion with the gaftric fluid of this 
 fpecies - ~ - 192 
 
 CLVi. Another fpecies of fcreech-owl, ekaflly like the 
 preceding - - ib* 
 
 CLVii. Way to give tube's to a large falcon without- ir- 
 ritating it - - 194 
 
 CLviii. Singular digeftion of bone in tubes 195 
 
 CLix. Of the fame loofe in the ftomach. Hard bones 
 long in being diftblved - 198 
 
 CLx. Soft ones the contrary -* 19^ 
 
 CLXi. Enamel of the teeth not diftblved - 200 
 
 CLXii. The fame thing with refpeft to horn, and the 
 cartilaginous coat of the gizzard. Tfendoh digefted 20 r 
 
 CLxiii. Leather not digefted. Another kind digefted 202 
 
 CLxiV. Gaftric fluid of the falcon does not digeft vege- 
 tables - - 2D3 
 
 CLxv. Flefli and bone digefted out of the body in a fuf- 
 ficient heat - - 204. 
 
 CLxvi. Mode of digeftion within and without the body- 
 alike. The crapy does not diftblve flefh 205 
 
 CLXVII. CEfophagus and craw full of glands. Part of 
 the gaftric fluid comes from the ftomach ib. 
 
 CLxyiii. Eagle - - 207 
 
 ^Lxix. Its food. Courage in attacking and deftroying 
 animals larger than itfelf • 208 
 
 «Lxx. Liquor running from the noftrils into ths mouth 
 while it takes, food, Conjedlure on its ufe 210 
 
 Vol, L D d clxxi. 
 
1 BJ tJ E S. 
 
 tLXXi. Falfehood of the opinion, that birds of prcy^ awl 
 efpecially eagles, never drink - 211 
 
 tLxxii. Whether the eagle can live on bread. Its aver- 
 fion for this food - - ib. 
 
 CLXxiii. When introduced into the ftamach it is cafily 
 digefted - - 212 
 
 CLXxiv. This is the mere eiFe<Sl of the gaftric fturd alone, f 
 Manner of its ad ion - 214 
 
 CLxxv. Gaftric fluid of the eagle readily digefts other 
 fubftances befides animal ones. Some carnivorous 
 birds turn frugivorous, and reciprocally 215 
 
 CLXXYI. Stomach of the eagle has fome motion, but is 
 incapable of triturating - 218 
 
 CLxxvii. Craw has no part in producing digeftion 219 
 
 CLXxviii. The manner in vi^hich fiefh is decompofed in 
 the flbmach of the eagle - 221 
 
 CLXxix. It adls in the fame manner on flefh inclofed in 
 tubes - - 223 
 
 CLXxx. Flefli digefted in proportion as the accefs of the 
 gaftric fluid is more or lefs free - 224 
 
 CLxxxi. Rcadinefs with which the gaftric fluid tnfmuates 
 itfelf into compadl bodies - ib» 
 
 CLXXxii. This fluid foon diffolves hard bones. Singu- 
 lar phaenomena attending thefe folutions 226 
 
 CLxxxixi. Gaftric fluid of the eagle fooner diflTolves bone 
 than that of other birds— -does not a6i on the enantel 
 of the teeth - - 228 
 
 CLxxxiv. Whether it diflx>lves fiefh alfo fooner. Rlif- 
 take that may arifein this enquiry - 229. 
 
 CLxxxV. A quantity of gaftric fluid vomited fpontane- 
 oufly every day by the eagle. Its qualities 232 
 
 exxxxvx. Artificial digeftion. The gaftric liquor does 
 
 . not eafily freeze - - 233 
 
 €Lxxxvii. Inteftines, pancreas, and gall-bladder de- 
 fcribed - - 235 
 
 cjLxxxviii. Small fize of the ftomaeh compeared with 
 the craw. Coats of the ftomachs. Glands 237 
 
 CLXxxix. Gaftric juices made bitter by the bile. Li- 
 quor that oozes out from the infide of the craw. CE- 
 jbphagus and craw without glands. DiiFerent.iiquors 
 compofing the gaftric fluid - 24a 
 
 PISSER. 
 
N D E St. 
 
 DISSERTATION V. 
 
 THE SUBJECT OV DIGESTION IN ANIMALS WITH MEMBRAp 
 NOUS STOMACHS CONCLUDED. THE CAT. DOG. MAN. 
 WHETHER DIGESTION CONTINUES AFTER DEATH. 
 
 pxc. The gaftric fluid of the cat the efficacious caufe of 
 digeftion - - 243 
 
 cxci. Enquiry concerning the origin of this fluid 245 
 cxcir. Slight analyfis of the gaftric fluid of the dog. It 
 diffoives flefli, bread, and cartilage, inclofed in tubes ib» 
 cxciii, cxciy, cxcv. Boerhaave thinks that dogs can- 
 not digeft inteftine fleih and ligament. Is miftaken. 
 Caufe of his error - 247--252 
 
 cxcvi. Undetermined queftion, whether dogs can dif- 
 folve bone - - 256 
 
 ^xcVii, cxcviii. Experimental enquiry. Determination 
 in the aflHrmative. Gaftric fluid of fome dogs corrodes 
 the enamel of thp teeth. At the timeitdiftblves bone, 
 leaves linen untouched - 258, 259 
 
 cxcix. Slight motion in the ftomach during digeftion 261 
 CC. Vifible, however, on opening the abdomen 262 
 
 cci. The fame in the cat. incipient digeftion produce4 
 by the gaftric fluid out of the body - 264 
 
 ecu. Enquiry concerning the origin of this fluid 265 
 cciii. The chief of thefe experiments repeated upon 
 iVlano Neceflity for this - 267 
 
 cciv. Mafticated bread inclofed in bags, perfedlly digef- 
 ted in the author's ftomach. Not completely, vy^hen 
 the folds of linen are very numerous - 268 
 
 iijcv. The fame with refpe£t to different kinds of flefh 
 boiled and chewed, and inclofed in (ingle bags 26g 
 ccvi. The fame in boiled flcfli not chewed 270 
 
 ccvii. As alfo in raw flefh - ■ 271 
 
 ccviii, ccix. Flefh inclofed in tubes, digefted in the 
 author's ftomach. This is the tffcS: of the gaftric 
 fluid alone. Proofs that the human ftomach does not 
 triturate food - - 271 — 273 
 
 ccx. Confirmation of thefe proofs. Explanation of h 
 fmgular phsnomenon - 274 
 
 ccxi. Chev/ed fiefh and bread fooner digeftex^han that 
 which is not chewed, Rcafoa of this diff'^ience 275 
 D d 3 ccxiii 
 
INDEX. 
 
 CCxiT, ccxiii. Flefh, membrane, tendon, cartilage^ 
 perfectly dfgefted in the human ftomach ' 277, 278, 
 
 ccxiv. Alfo tender bones, but not hard ones. -The intef- 
 tinal fluid has fpme part in producing thefeeffeils 278 
 
 ccxy. The author's method to procure the gaftric fluid 
 in a ftate of purity - 280 
 
 cpxvi. its qualities. Incipient digeft|on out of thq 
 body - - 282 
 
 ccxvir. Confirmation of this experiment. Proof of th^ 
 neceffity of a pertain degree of heat, j^xperiment pro- 
 
 ■ ving, that a great degree of digeftion is produced be- 
 fore the food pafles to the inteftiijes -" 285 
 
 ccxviii. Recapitulation <- 286 
 
 ccxix. Boerhaave's opinion concerning digeftion 288 
 
 ccxx, ccxxi, ccxxii. Fadts that oblige the author to 
 relinquifli this opinion. Refutation of an opinion, 
 which confines the acSlion of the ftomach to the extrac- 
 tion of the juices of animal and vegetable fubftan- 
 ces ' - 2.90—296 
 
 ccxxiii. Whether, according to Hunter, the great 
 curvature of the ftornach is diflblved after death; 
 whence he infeis, that digeftion continues after deatl? 
 
 - 29S 
 
 ,ccxxjv. The author's obfervatipns do not exactly coin- 
 cide with Hunter's - 299 
 
 ccxxv. Means to determine, whether digeftion does 
 really take place after death. Employed in a crow, 
 and feem to prove the affirmative. Comparifon be- 
 tween digeftion in a dead and living animal 300 
 
 jccxxvi. No digeftion in the oefophagus after death 302 
 
 ccxxvii. The influence of heat in thefc experiments* 
 Digeftion goe§ on equally well after death, whether the 
 animal is killed immediately after having fwallowe4 
 food, or food is introduced after the animal is killed 303 
 
 CCXXVII I. Further experiments. When birds havp 
 digefted the food to a certain degree, that procefs ad- 
 vances ap farther, though if fhould continue longer in 
 the ftomach - - 305 
 
 CCXX IX, ccxxx. Digeftion after death in fifties an4 
 quadrupeds. Proofs of the neceffity of heat to digef- 
 tion in many anirtials - ib. 30I& 
 
 ccxxx J. Digeftion a,fter death does not go on fo well 
 
 when 
 
INDEX. 
 
 Vviheil the tlomach is taken out of the body. Reafont 
 why the ftomach fs not loon iubjedl to be diflblved as 
 the food - - ^07 
 
 DISSERTATIQN VI. 
 
 );VHETHER THE FOOD FEE.MENTS IN THE STOMACH, 
 
 ccxxxii. Boerhaave thinks, that an incipient fermen* 
 tation only can take place in the ftomach 310 
 
 ccxxxiii. Difterent opinions of Pringle and IVIacbride. 
 Thejr proofs, that digeftion is a fermentative procefs 
 deduced from food fee in vefTels. Application to the 
 human body - - 311 
 
 ccxxxiv. This procefs takes p-lace in veflels, whether 
 water or faliva is employed - 314. 
 
 ccxxxv. Doubts whether this would happen with the 
 gaftric fliuid - - -^16 
 
 ccxxxvi. Experiments that prove the negative 317 
 
 ccxxxvii, ccxxxyiii. Examination of the food during 
 the time of digeillon in fevefal animals. No fermen- 
 tation obferved. Reafons for doubting, whether even 
 an incipient fermentation takes p^ace 3I9--32I 
 
 Ccxxxix. Whether any acid principle accompanies di- 
 geftion. Proofs adduced by fome in favuur of this 
 opinion - - 322 
 
 CCXL, ccxLi, ccxLii. This principle is very far from 
 being obferved jn all food, and all animals. When it 
 is obferved, it difappears at the completion of digef- 
 tion - - 323-326 
 
 CcxLi 1 1. This acid does not come from the gaftric fluid, 
 but the food - - ~ 327 
 
 ccxLiv. Chemical analyfis, which fhews, that the gaf- 
 tric fluid is neither acid nor alkaline, but neutral ib. 
 
 ccxLv. Arguqient of fome phylicians, in f^vourof a la- 
 tent acid in the gaftric fluid, deduced from the coagu- 
 lation of milk in the ftomach. Experiments with the 
 internal coat of the ftomach - 332 
 
 ccxLvi. Th-Q other coats do not curdle milk 334 
 
 ' ' CCXLVIV 
 
INDEX. 
 
 ecKLVii. It is probable that this property is communi-- 
 cated to the internal coat by the gaftric fluid. This 
 fluid curdles milk as well as rennet - 335 
 
 CcXLViii. It is very doubtful, whether this property is 
 a proof of latent acidity - ib. 
 
 ccxLjx. Fa6i:s adduced to pioye, that digeftion is ac- 
 companied with putrefaction - 337 
 ccL.. Digeftion is over in fome animals, before putre- 
 fadion can begin - - 33(1 
 ccLijCCi^ii, ccLiii. Examination of feveral animals 
 during the time of digeftion. No token of putrefac- 
 tion - - 34 1 --343 
 ccLTV. Except in fick animals. The fafls mentioned iri 
 ccxLix. examined and explained - 345 
 ccLV. The gaftric fluid is not only a menftruum, but 
 antifeptic - - 347 
 CELVI. It corrects putrefacSlion in phials 349 
 ccLvii. Putrefaciion begins in the craw of gallinaceous 
 birds, but is checked v/hen the food paflTes into the 
 gizzard - - 350 
 ccLvrii, ccLix. The ftomach has the power of cor- 
 recting putrefied food - 35 ^'"353 
 ccix. Refle6lion on the anim.als that feed on putrid flefh. 
 Some animals that naturally abhor it, may be brought 
 to feed on it - - 355 
 ccLXi. The antifeptic power of the gaftric fluid not ow- 
 ing to the fait it contains - 357 
 ccLXii. Error of a learned French writer, who fuppofes 
 that a little common fait promotes digeftion 359 
 CCLxiii. The antifeptic property of the gaftric fluid 
 cannot be explained by the fpecious theory of Mac- 
 bride. The caufe unknown to the author 360 
 ccLxiv. Recapitulation - 362 
 Mr. Hunter's Paper - - 365 
 Dr. Stevens's Experim.ents - 375 
 
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