EXPERIMENTS AND OBSERVATIONS 
ON 
DIGESTION: 
AN INAUGURAL ESSAY, 
$ 
FOR THE DEGREE OF 
DOCTOR OF MEDICINE. 
SUBMITTED TO THE EXAMINATION OF THE REV. JOHN AN- 
DREWS, D. D. PROVOST (PRO TEMPORE) THE TRUSTEES 
AND MEDICAL PROFESSORS OF THE UNIVERSITY OF PENN- 
SYLVANIA, ON THE EIGHTH DAY OF JUNE, 1803. 
BY OLIVER II. SPENCER, 
OF NEW-ORLEANS, HONORARY MEMBER OF THE PHILA- 
DELPHIA MEDICAL AND CHYMICAL SOCIETIES. 
PHILADELPHIA: 
PRINTED AT THE OFFICE OF THE GAZETTE OF THE 
UNITED STATES. 
1803. TO DR. RICHARD ALLISON, 
OF THE STATE OF OHIO, 
THIS ESSAY, 
AS A 
TESTIMONY OF THE MOST LIVELY FRIENDSHIP, 
IS INSCRIBED, 
BY 
AN AFFECTIONATE AND GRATEFUL PUPIL, 
THE AUTHOR. TO BENJAMIN SMITH BARTON, M.D. 
PROFESSOR OF MATERIA MEDIC A, NATURAL 
HISTORY AND BOTANY, 
IN THE UNIVERSITY OF PENNSYLVANIA, 
THIS ESSAY 
IS ALSO RESPECTFULLY INSCRIBED, 
AS 
A TRIBUTE OF RESPECT, 
AND 
THE MOST LIVELY ESTEEM, 
BY FIIS FRIEND AND HUMBLE SERVANT, 
THE AUTHOR. EXPERIMENTS AND OBSERVATIONS 
ON 
DIGESTION. 
PREVIOUS to commencing the fubjeCt of our 
cffay, it will be proper to take afhort anatomical view of 
the ftomach. The other vifcera concerned in chyli- 
fication, by means of the different fluids which they 
fecrete, we think it unneceffary to notice; becaufe in 
no part of the work fliall we examine the changes which 
the chyle undergoes, after leaving the ftomach and 
mixing with the fluids fecreted by thefe vifcera. 
The human ftomach is oblong, large, and mem- 
branous; of different dimenfions in different perfons, 
and capable of conliderable contraction as well as de- 
tention, without much inconvenience: the former 
ftate is obferved in the favage of our country, who is 
obliged,frequently, to fubfift for months on a fpare diet, 
during which time the ftomach is contracted by its 
mufcular fibres, and he returns from his excurfions 
with a conliderable depreffion in the epigaftrium, as 8 
well as the whole abdomen: civil fociety prefents us 
with daily proofs of the latter date, from indulging in 
the pleafures of the table. 
It is fituated partly in the epigaflrium, and partly 
in the left h.ypochondrium, immediately under the 
diaphragm, and contiguous to the heart, liver, fpleen, 
and pancreas; and when diftended with food, lies in 
an oblique direction, inclining anteriorly downwards 
and forwards. 
The ftomach is formed of four tunicas, or coats, 
connected ftrongly to each other, by condenfed cellu- 
lar membrane. The firft, or outer coat, is fimply mem- 
branous, and is common to the inteftines as well as to 
the ftomach ; being a continuation of the peritoneum, 
which, after lining the whole cavity of the abdomen, 
is reflected and forms a covering to all its vifcera; in 
fome inflances, indeed, but partial, as is the cafe with 
the kidneys, which lie without the peritoneum. Im- 
mediately under the firft lies the fecond, or mufcular 
coat, compofed of fibres in a circular and longitudinal 
direction, upon the contraction and relaxation of which 
depends the periflaltic motion of the ftomach. 
The third may properly be called cellular, being 
made up, almoft entirely, of condenfed cellular mem- 
brane, and capillary veffels, fupported by fine ligamen- 
tary filaments. Laftly, the inner coat, termed by the 
ancients fungofa, is exceedingly delicate, and forms 
with the cellular coat, to which it adheres, a number 9 
of rugae upon the inner furface of the ftomach, particu- 
larly about the pylorus, which ferve to counteract its 
periftaltic motion, by preventing the food from being- 
thrown too haftily into the duodenum. 
The nerves of the ftomach arife, chiefly, from the 
parvagum, or eighth pair; and from the intercoftalis, 
or great fympathetic nerve, by means of the (tomachic 
nerve, the ganglions of the plexus hepaticus, and plex- 
us fplenicus. 
Its arteries arederived, principally,from thecceliac; 
and as no glands are to be met with in the fubflance 
of the ftomach, agreeable to Morgagni, Haller, and 
Sabbatier, it is probable that the gaflric juice is 
poured out by the minute branches of thefe arteries, 
which are interfperfed throughout the coats of this 
organ. 
The ftomach is a vifcus of primary importance in 
the animal economy. To a proper ftate of its fecretion 
(depending, we fuppofe, upon a certain tone, and 
healthy a&ion of itsveflels) are we indebted for health, 
mental enjoyment, and long life. Few men, obferves 
profeflor Rufli in his manufcript lectures, attain to 
old age, who have been fubjeCt, in their youth, to dyf- 
p'eptic complaints. We cannot,therefore,be furprifed, 
when we find it fo abundantly fupplied with blood- 
veflels and nerves. 
Preparatory to the food being received into the 
ftomach, it is neceflary, in molt perfons, that it fhould 10 
be minutely divided by maftication, and formed, by 
mixture with the faliva, into a foft mafs; not only to 
render it eafy of deglutition, but to favour, likewife, 
its more fpeedy folution in the ftomach. To the la- 
bouring part of mankind, particularly thofe who exer- 
cife much in the. open air, we find that the minute 
divifion of the food is by no means foneceflary as for 
fedentary people. The former, we obferve, often 
fwallow food of the mod difficult folution, almoft en- 
tire, without experiencing, afterwards, any inconveni- 
ence. Exercife gives tone to the fyftem, and by in- 
creafing the circulation, a large quantity of gaftric 
fluid is fecreted; and food, being well mafticated, 
would, in fuch a ftomach, be diffolved and formed 
into chyle in greater abundance than is required for 
the nutrition of the fyftem, if the appetite of hunger 
was fatisfied as often as the ftomach became empty. 
Happily and wifely for mankind, the gratification 
of the appetite of hunger and thirft is attended with 
pleafure, fulficient, in moft inftances, independent of 
the love of life, to compenfate for the trouble of ob- 
taining the means. The ftimulus of the gaftric juice 
upon the fenfible coats of the ftomach, and the weight 
of the liver, unfuftained and pulling downwards the 
diaphragm, to which it is attached by means of the 
middle ligament, caufes that uneafv fenfation we call 
hunger, the principal feat of which is generally fup- 
pofed to be at the cardia. But for this, mankind would 
not have, perhaps, a fulficient incitement to roufe them 
from their natural indolence. 11 
By the term Digeftion we mean the procefs which 
the aliment undergoes in the ftomach. It Ihould ex- 
tend farther, and embrace in its iignification, not only 
this change, but the alteration which farther takes 
place before the chyle is finally emptied into the fub- 
clavian veflels. Want of time, however, will prevent 
us from going thus far. 
Much controverfy has prevailed in every age, re- 
fpetting the manner in which digeftion is begun and 
carried on in the ftomach; and, until the talents and 
attention of Reaumur, M‘Bride, Stephens, Spallanzani, 
and Hunter had been exerted, the fubjett was involv- 
ed in obfcurity; and for want of a juft phyfiology, the 
difeafes of this organ were frequently very improperly 
treated. The limits of my eflay will not permit me to 
examine the variety and contradi&ory opinions which 
prevailed among the ancients upon this fubjecft. Some 
of them, for their fingularity, are worthy the attention 
of the curious, but, as relating either to medicine or 
natural hiftory, are of but little importance in their 
application. 
Trituration, one of the caufes, according to an- 
cient opinion, and perhaps the molt probable of them, 
was revived as late as the beginning of the laft cen- 
tury; and from the general reception which it met 
with at that time, it has been common for the phyfio- 
logifts of the prefent day, when writing upon the fub- 
je<ft, to notice the do&rine. 12 
In accounting for this procefs, fermentation and 
putrefa&ion have likewife had their advocates; but 
the latter having lefs plaufibility, and being difagree- 
able in its contemplation, has been lefs generally em- 
braced than the former particularly fince the writings 
of the celebrated Dr. Cullen have been publifhed. 
We lhall proceed to examine thefe feveral do&rines 
in rotation; and after introducing fome experiments 
performed, not with a view to eltablilh any favourite 
theory (for I had none when I began them) and quo- 
ting a variety of others, ingenioully made by celebrated 
men in the literary world, endeavour to draw fair con- 
clufions from eftablilhed fa£ts, unbialfed by prejudice. 
The fupportersof the do&rine of mechanical force, 
or trituration, infill on it, as a proof of their theory, 
that birds digelt their food by this means. We cannot 
conceive how this can be alleged in favour of the 
opinion; for there is certainly but little analogy be- 
tween the Ilomach of man, and the mufcular llrong 
ilomach of thefe animals. No doubt the minute divi- 
iion of their food, which is performed in the Ilomach, 
affills its folution, in the fame way that any fubltance 
is rendered more readily foluble in a menllruum by 
divilion, inafmuch as a greater furface is expofed to be 
a&ed upon by the fluid. 
Reaumur took a buzzard, becaufe that bird has a 
membranous Ilomach, incapable of any great degree of 
triturative power. To preclude, however, the pofli- 
bility of any, he employed perforated tin tubes, that 13 
would admit the gaflric fluid to come in contaft with 
the beef which he employed in the experiment. This 
was forcibly thrufl into the bird’s flomach, and re- 
mained there twenty-four hours. Upon examination, 
the beef was found reduced to three-fourths of its 
original quantity: what remained had the appearance 
of threads, extremely fine, but was neither putrid, 
acid, nor volatile, but quite infipid. Spallanzani, the 
illuftrious profeflbr of natural history, in the univerfity 
at Pavia, made a number of experiments upon this 
point, which are decifive in eflablilhing the power of 
the gaflric juice, while they lhow the falfity of the 
other theories. He enclofed, after the example of 
Reaumur, entire barley, in perforated metal tubes. 
Thefe were given to common fowls, turkeys, &c. and 
after remaining, in fome inftances. forty-eight hours, 
were taken out of their flomachs undigefted, and 
without beingfenfibly altered; but upon bruifing the 
fame food, and again introducing it by means of the 
tubes, when voided they were frequently found, in the 
courfe of the experiments, to be empty. The fame 
able experimenter filled tubes with raw veal, finely 
divided, which were forcibly given to a hen. They 
remained in the flomach twenty-four hours, and when 
taken out the flefli was found to be confiderably dimi- 
niflied ; the parts which continued firm were red, and 
retained the true flavour of flefli. 
If we deemed it neceflary, a variety of other facts 
might be advanced, which prove that trituration 
aflifls, but is not requifite for digeftion. In 14 
fowls, poflefled of mufcular ftomachs, it anfwers the 
purpofe of maflication. In fa<ft, it is to them what 
maflication is to man and to the phytivorous animals: 
they fvvallow their food whole, and the ftrong coats 
of the ftomach break it down, and prepare it for folu- 
tion in the gaftric fluid. To eftimate this force, we 
have only to confult the repeated experiments of 
Reaumur and Spallanzani. Tin tubes of confiderable 
ftrength were found, after remaining fome time in the 
ftomach of turkeys, to be bent and diftorted in a An- 
gular manner. ‘Having found,’ fays Spallanzani, ‘that 
‘ the tin tubes, which I ufed for common fowls, were 
‘ incapable of refilling the ftomach of turkeys, and 
6 not happening, at that time, to be provided with any 
‘ tin plates of greater thicknefs, I tried to ftrengthen 
‘ them, by foldering to the ends two circular plates of 
* the fame metal, perforated only with a few holes for 
‘ the admiflion of the gaftric fluid. But this contri- 
‘ vance was ineffectual; for, after the tubes had been 
‘ twenty-four hours in the ftomach of a turkey, the 
‘ circular plates were driven in, and fome of the tubes 
‘ were broken, fome comprefled, and fome diftorted 
‘ in the molt irregular manner.’* 
The fame author employed, afterwards, a variety 
of fliarp bodies, as angular pieces of glafs, ftrong tin 
needles, and even lancets, fixed in balls of lead; and 
found them all to be equally incapable of withftanding 
the comminuting force of their ftomach. ‘ The ball, 
* Spallanzani’s Dissertations, vol. i. p. 12. 15 
* armed with the lancets, was given to a turkey cock, 
6 and left eight hours in the flomach ; at the expira- 
• tion of which time, that organ was opened ; but 
c nothing appeared except the naked ball, the lancets 
4 having been broken to pieces/* We obferve, that 
children frequently fwallow currants, cherries, Szc. 
in an entire hate, and void them as unbroken as when 
they were firft taken into the flomach. Thefe fruits, 
when ripe, are foft, eafily broken, and incapable, 
we muft fuppofe, of refilling the flighted; degree of 
preflure. 
Next in order, we proceed to examine the difler- 
ent kinds of fermentation, as promoting or impeding 
folution in the human flomach. The experiments al- 
readyquoted from Reaumur and Spallanzani, although 
pofitive in proving that trituration is not neceflary for 
digeflion, do not fhew but that fermentation is a part 
of the procefs. After Boerhaave, chymifls have divi- 
ded fermentation into three kinds: the fpirituous, 
which furnifhes ardent fpirits; the acetous, which 
yields the acid of vinegar; and the putrefa&ive, which 
produces volatile alkaline gas, &c. For the firft, or 
fpirituous fermentation, faccharine bodies are abfo- 
lutely, and when aflifled by heat to a certain degree, 
with air and humidity, only neceflary. The fecond, 
or acetous fermentation, depends on mucilage. The 
putrefactive, upon the prefence of a gluten. 
* Spallanzani’s Dissertations, vol. i, p. 13. 16 
Dr. Cullen, in his Le&ures on the Materia Medica, 
delivered in the univerfity of Edinburgh, in the year 
1769, fuppofes, that the acetous fermentation always 
takes place during digeftion, in the ftomach of healthy 
perfons; ‘And I am certain, from experiment,* fays 
he, ‘ that the vegetable aliment firft turns acid in the 
‘ftomach; for every ftomach, human or brute, is 
‘ always, on examination, found to have an acid pre- 
‘ fent in it. Hence that acefcency is not a difeafe, but a 
‘ ftep towards aflimilation. Whenever the aliment 
‘ enters into a high vinous fermentation, with copious 
‘ generation of fixed air, commonly called gas filveftre, 
‘ as of the fame nature with that produced in the ordi- 
* nary vinous procefc, it becomes a difeafe, and has the 
‘ power of deftroying the mobility and contra&ility 
‘ of the moving fibres, and even the tone of the fto- 
‘ mach itfelf.* 
In order to produce fermentation, a confiderable 
mafs of matter favourable to it muft be prefent; but 
this is by no means the cafe in the ftomach of infers, 
birds, and other fmall animals, fome of which we know 
have, in a furprifing degree, the power of diffolving 
hard and even folid bodies. Secondly, if the ftomach 
was a vifeus intended merely as a velfel to contain the 
aliment for fermentation, as this doftrine, if eftablifli- 
ed, would go to prove, why, I would ask, are tonics 
given, with fuch evident advantage, in debility of that 
organ? If this was the principal procefs, it would only 
be neceffary to regulate it by mixing with our food a 
proportion of vegetables difpofed for fermentation, 17 
and every purpofe would he anfwered,when indigeftioii 
occurred. The power of bitters, fays the fame writer, 
in correcting acidity and flatulence in the flomach, 
may be afcribed to their power of checking acef- 
cent fermentation. He fuppofes, that digeflion com- 
mences with a fermentation of the acefcent kind. If 
bitters check this, it muft, agreeable to his own doc- 
trine, impede, inftead of aflifling the procefs ; for we 
cannot conceive that a fubflance, aCting thus chymi- 
cally, can produce two fuch oppofite effects. A variety 
of tonics, among which are the different preparations 
of iron, have as falutary an effeCt in preventing aci- 
dity, by giving tone, we prefume, to the ftomach, as 
do the clafs of bitters. 
DoCtor Fordyce attentively examined the chyle, in 
the beginning of the duodenum of the fheep and the 
cow, with a view to afcertain whether, fermentation 
generally took place in the healthy, living fubjeCt. We 
might fuppofe that it would appear, if any where, in 
thefe animals, which live on acefcent, faccharine foodj 
fince every thing really neceffary is prefent, and a mafs 
confiderably large and finely broken down. Fie did not 
however, difcover, by the ufual tefts employed for de- 
tecting the prefence of an acid, that any did really ex id- 
The fnpporters of the theory of fermentation, as 
being a neceffary part of digeflion, allege, againft the 
experiments of Dr. Fordyce, and others who have ex- 
perimented upon the chyle in the duodenum, that the 
bile is a real animal foap, compofed of an alkali in fuf- 18 
iicient abundance to neutralize the acid produced by 
digeftion, and prevent its being detected, after mixing 
with that fluid. A variety of correCt and judicious 
experiments by Dr. Roebuck, of the Ifland of St. 
Croix, made with a view to analyze the bile, contradict 
and fully explode the theory of its faponaceous nature 
and Dr. Boerhaave’s fpeculations, fo ably fupported 
by Cadet. Thefe experiments fhow, that different 
neutral falts are generally prefent in the bile ; as the 
muriate and phofphate of lime and foda; and that 
the bile of different animals, although fomewhat va- 
rious, does not contain a particle of an alkali in an 
uncombined hate : therefore to neutralize the acid by 
an alkali or earth, it muff decompofe the muriate or 
phofphate of lime or foda (which is impoflible from 
the natural order of affinity) contained in the bile and 
unite with their radicals producing an acetite of lime, 
or foda. But even if this chymical decompofition 
could take place, what would become of the acids 
originally combined in forming the neutral falts ? 
In order to determine whether an acid is always, 
or even frequently, prefent in the ftomach, upon the 
eflablifhing or contradiction of which the whole 
doCtrine which we are examining depends, I had 
recourfe to the following experiments. 
EXPERIMENT /. 
I gave to a middle aged man, of a delicate form, 
but enjoying a perfeCt flate of health, a fmall quantity 
of emetic tartar in a glafs of wine. He had break- 
fafted five hours before on tea, bread and butter and 19 
iaufage. In half an hour he was feized with naufea 
and vomiting. The firft retchings threw up part of 
the food which had been eaten in the morning ; and 
after drinking plentifully of warm water, which I 
prevailed upon him to do, he vomited repeatedly, 
which emptied his ftomach, perhaps entirely. Neither 
the firft nor the laft dil'charges altered the colour of 
litmus paper, nor the blue colour of the fyrup of 
violets. 
EXPERIMENT II. 
For a conliderable compenfation I prevailed upon 
a healthy negro man, aged twenty-five years, to take 
a folution of emetic tartar at ten o’clock, A. M. 
He had breakfafted two hours before on coffee, and 
bread and butter. In a few minutes it produced a 
very confiderable, long, and obffinate vomiting ; dur- 
ing which he threw up the whole of his breakfaft, 
which was but little altered from its natural ftate, 
retaining its original fmell and appearance. I could 
not, by the teffs employed, difcover the prefence of 
acidity. This man was of a temperament oppofite to 
that of the former; being of a full habit, with a broad 
cheff, and mufcular form. 
The extreme difficulty I found in procuring human 
fubje&s for experiments, prevented me from making 
fo many of them as I could have wifhed, and at firff 
intended; and obliged me to have recourfe fo expe- 
riment made upon our domeffic animals, whofe fimila- 
rity of ffru&ure and food will permit a fair analogy 
to be drawn. 20 
EXPERIMENT III. 
I fed a dog, for feveral days, on frefh boiled and 
baked meat, bread, cabbage and parfnips. During 
the time, he drank water when he chofe, and occafion- 
ally had milk. In four hours after eating moderately, 
1 had him killed, and after fecuring, by ligature, the 
upper and lower part of the duodenum, 1 opened the 
domach and examined its contents. The beef, which 
had been eaten four hours before was difiolved in a 
confiderable degree, the bread and cabbage a little, 
but not much altered. The whole mafs was mild, of 
its natural odour, and without an appearance of putre- 
faction. After repeated immerfions of the litmus 
paper in this, and in the chyle which I found in confid- 
erable quantity in the duodenum (owing probably to 
the animal’s having been plentifully fed, while pre- 
paring for the experiment) I could not difcover any 
change produced in its colour. 
EXPERIMENT 17. 
A cat having been fed moderately, for three days, 
on bread, fifh, and roafted veal, during which time (he 
drank nothing but milk, or a mixture of milk and 
water, was killed on the evening of the third day, 
after having faded five hours. I found the contents of 
the ftomach were perfectly digefted, with the excep- 
tion of a fmall piece of bread, which had been lad 
eaten. I could not difcover any acidity, or fcetor indi- 
cative of putrefadion. 21 
EXPERIMENT V. 
I fed a healthy male cat plentifully, for feveral days, 
on a diet of boiled beef, fifh, bread, and potatoes; allow- 
ing him as much water as he pleafed to drink, fie was 
killed four hours after eating. On opening the flomach, 
I found the beef and fifh foft, and confiderably diffolved, 
retaining much of their natural flavour, fweet, and 
without rancidity or pungency. In this infiance, the 
bread and potatoes had advanced much flower towards 
a fiate of chylification, than the other kinds of food 
which had been given a fliort time after, viz. the flefh 
and fifh. Syrup of violets, and litmus paper, both of 
which tefts I made ufe of, did not fhow the prefence 
of any acidity. 
EXPERIMENT VI. 
While making the lafi experiment I procured a 
large dog of the mafiiff breed, apparently healthy, but 
weak and much emaciated. He ate ravenoufly, every 
thing that was offered him, from whence I concluded 
that his leannefs was owing to want of f od alone. He 
was fed fix days plentifully, on bread, beef, foup, and 
potatoes, at the end of which period eight hours after 
having eaten, he was killed ; and, after having fecured 
the lower part of the flomach, l opened its coats, and 
brought the digefiing mafs into view. I was furprized 
to obferve a large number of the lumbrici, or round 
worms, fome of which meafured a foot, and many of 
them ten inches, in length. In other rdpefls the di- 
gefting aliment looked natural, but had rather an un- 22 
pleafant flavour, though not putrid. The general tex- 
ture of the food, which had been eaten during the day, 
was deftroycd, and much of it, in the lower part of the 
ftomach, formed into chyle, and ready to pafs into the 
duodenum. After repeated trials, my tefls could not 
difcover an appearance of acidity, either in the ftomach 
or in the duodenum, which I alfo examined with at- 
tention. 
From the refult of thefe experiments, conduced 
with much care and attention, we infer, that when the 
ftomach is in a ftate of health, the appetite good, and 
proper food only employed, digeftion goes on ra- 
pidly, without the aliment undergoing any fermenta- 
tion by which an acid is produced, either in the courfe 
of the ftomach or duodenum: and farther, that when 
acidity does take place, it is a proof of the unhealthy 
condiiion of the ftomach. The ftomach may, no doubt, 
have its functions impeded, like every other part of 
the fyftem, by too much or too little excitement. In 
the dileafed ftate of the ftomach, called dyfpepfia, we 
fuppofe, that the aftion of the veflels pouring out the 
gaftric liquor for the purpofe of digeftion, is fometimes 
exceftive. From this view of the fubjeft, and from the 
fmall, frequently chorded pulfe, fo often obferved in 
dyfpeptic habits, might we not reafonably expeft 
greater fuccefs from depletion than from ftimulants 
and tonics,—the remedies heretofore moft generally 
employed, owing to the idea, that dyfpepfia depends 
on imbecility, and want of tone in the mufcular fibres 
of the ftomach ? 23 
In preparing my animals, I was attentive to give 
them fucli food only, as they would eat with avidity; 
principally flelh, but with a fufficient proportion of 
vegetables to undergo the vinous, or acetous fermen- 
tations if either was neceflary for the complete chy- 
lification of our food. 
On a review of the above experiments, we find, 
that animal food was more readily foluble in the fto- 
mach of dogs and cats, than bread, potatoes, or 
parfnips. I was more particular in obferving this faCf, 
becaufe the experiments of Walceus, made upon dogs, 
had led me to believe, that even fome carnivorus ani- 
mals digefted herbs, and bread fooner than butcher’s 
meat.* The conftant ftate of reft in which the animals 
were kept for feveral days, previous to being killed, 
was favourable to the formation of an acid, by alfilting 
fermentation. 
The arguments in favour of the theory of animal pu- 
trefaction, which we are next to confider, as occuring 
during, andconfiitutingapartof theprocefsof digeftion, 
requires I conceive, but little labour to refute. During 
animal putrefaction, the fubjeCt matter, after lofing its 
natural fmell, gives out a putrid, naufeous odour, with 
one of a more penetrating kind, arifing from the dis- 
engagement of ammoniacal gas, the fmalleft quantity 
of which from its extreme volatility, would be made, 
in the mod difagreeable manner, fenfible to our feelings 
during digellion. 
* Vid. Epist. de mot. chyl. et sang, ad Thom. Bartholin. 24 
Dr. Stevens, in an inaugural thefis publifhed at 
Edinburgh, in the year 1777,tells us that he collected, 
from a dog, a quantity of frefh gaftric juice, half an 
ounce of which he added to twelve grains of beef, 
which had been previoufly put into a vial. He put 
the fame quantity of beef into another vial, and poured 
upon it half an ounce of water. Having placed both 
in a furnace heated to 102 or 103 degrees of Faren- 
heit’s thermometer, and fuffering it to remain in that 
temperature for eight hours, he examined the vials, 
and found that the beef which was immerfed in 
the gaftric fluid was entirely diflolved, while the 
other had undergone no fenfible alteration. Twenty- 
four hours afterwards the tw'o vials were removed 
from the furnace, and attentively examined The one 
which contained the gaftric juice and beef, emitted a 
rancid, and pungent fmell; while the other, with the 
water and beef, had become putrid, and emitted an 
intolerable flench. During the folution of the beef 
in the gaftric juice, there were no figns of fermen- 
tation in the vial, fuch as an appearance of air, &c.* 
A repetition of the experiment produced a fimilar 
refult. Spallanzani’s experiments, made on the gaftric 
fluid of various animals, had the fame efleft w?ith thofe 
made by Dr. Stevens. Some of them, indeed, go 
farther and {hew that animal food may even be 
recovered from a flight degree of putrefcency, by being 
placed for a fliort time in gaftric juice.f 
* Stevens’s Dissertation, Exp. 23. 
t Spallanzani’s Dissertations, vol. i. p. 349, 353, 355. 25 
Dr. Cullen, whofe ingenuity and abilities we mud 
ever venerate, although we cannot always admit his 
fpeculations, pofuively fays, that no man can fubfid, 
even for a few days, on animal food alone, without 
its becoming highly putrefcent in the domach and 
producing naufea and third; and, when carried into 
the bowels, violent purging, cholera, and dyfentery, 
from putrid exhalations. This difpofition of the animal 
food to undergo putridity, he fuppofes, is corrected 
by the quantity of vegetable matter, which we are in 
the habit of mixing with it at our meals. 
We are informed by the mod refpe&able autho- 
rities, that whole nations fubfid on animal food alone, 
without experiencing the difeafes which the profeffor 
tells us would be produced in a few days by fuch a 
diet. Dr. Fordyce, in his treatise upon digedion, 
obferves, that the Laplander, inhabiting a country 
extremely cold and incapable of affording vegetables 
for the fubfidence of its inhabitants, lives for the 
greater part of the year upon the defh of the rein 
deer, without mixing with it any vegetable food ; and 
no appearance is indicated of a putrefcent matter 
being formed in the domach, or organs of digedion. 
The inhabitants of the banks of the Orange river, in 
Africa, fays the fame author, live on limpets, dead and 
putrid feals, and whales, without tading a particle 
of vegetable food of any kind whatever, except 
aromatics. 26 
if a high degree, or indeed, any putrefa&ion took 
place during digeflion, the whole of the circulating 
fluids mult, in a fliort fpace of time, become affefled 
through the medium of the abforbent fyftem; the 
breath, and the fecretions neceflary to life, would be- 
come acrimonious, and the evil, conftantly increafing 
by the taking in of frefh food, would end only with 
the extermination of the people ufing it, unlefs a dif- 
ferent diet was reforted to. 
It is a fa& well known to thofe who are acquainted 
with the aborigines of our country, that the tribes, 
particularly thofe which inhabit the northern parts of 
the United States, frequently fubfift, for whole weeks, 
on animal food alone, when hunting at a diftancefrom 
their towns, or at war. In the latter cafe, they eat 
what the people of the back country call jirk, which is 
the mufcular part of the game which they kill, pre- 
ferred by drying and fmoaking over a very gentle fire, 
fo as to deprive it entirely of its juices. When thus 
prepared, it will keep for a long time during the heat 
of fummer, and is very nutritious for its weight and 
bulk;' a circumftance of great importance to Indians 
on long excurfions. 1 he lavage will live, expofed to 
the greatefl fatigue, on a few ounces of this fubftance, 
which nothing but the power of habit could enable 
him to do. 
Not only man, wrho by nature is reflri&ed to no 
particular kinds of aliment, can fubfifi on one entirely 
of flefli, but even phytivorous animals, intended cer- 27 
tainly to live upon herbage, grain, &c. In proof of 
whichDr. Barton informed me of the following intereft- 
ing faft: During a voyage of two and thirty days acrofs 
the Atlantic, faid the profeffor, a pair of (sciurus volu- 
cella, or) flying fquirrels, were fed on dry falted beef, 
which they continued to eat until the veffel arrived in 
Europe: in this time they became fond of their animal 
diet,andrefufed, afterwards, their accuflomed vegetable 
one. A flmilar one, I think, is mentioned by Reaumur, 
but not having, at this time, an opportunity of confult- 
ing his works, I will not infill that the fa61 is recorded by 
him. Aflieep was fed, for a confiderable length of time, 
on flefli, varying in kind, and differently prepared. He 
became, at length, fond of it, and when the two were 
offered, ate it in preference to the vegetable. 
In the courfe of the experiments on ruminating 
animals, as the fheep and the ox, inftituted by Dr. 
Stevens, he difcovered that the gaftric juice readily 
diffolved vegetables, and made but little impreflion 
upon beef, mutton, and veal. My experiments upon 
dogs and cats, carnivorous animals, fliow that they 
digeft animal food much fooner than vegetable, but 
ftill, that they are capable of completely digefling the 
latter. rl hough they are altogether carnivorous, ne- 
ceflity, by obliging them to eat frequently of vegeta- 
bles, makes it, at length, a cuftomary part of their 
food. Had the animals employed by Dr. Stevens 
been gradually deprived of the ufe of vegetables, and 
fed upon flefli, they would in a fliort time, no doubt, 
have digefled the latter with perfefl facility. 28 
From thefe feve-ral experiments, we conclude that 
nature has given to the different claffes of animals 
folvents of different qualities and powers, calculated 
for the folution of the peculiar food, which Ihe inten- 
ded them to ufe; but at the fame time, capable of 
being changed, if requifite for the life of the indivi- 
dual, and accommodated for the folution of food of a 
different nature. 
Independent of the arguments which we have 
advanced the variety of faCls mentioned, particularly 
applicable to the point in queflion, can admit of no 
refutation : they are, we conceive, fufficient to efla- 
blifh the pofition, that putrefa&ion is a procefs never, 
perhaps, prefent during the folution of our food in 
the Aomach, as fermentation frequently is, owing to an 
unhealthy fecretion of the gaflric liquor, when that 
fluid from infufficiency in point of quantity, or quality, 
is incapable of refilling the difpofition of the vegetable 
part of our food to run into fermentation. To admit 
either of the do&rines which we have been endeavour- 
ing to refute, would be conndering nature as deviating 
from that general order of fimplicity which marks her 
productions, throughout the whole of the animated 
world ; for neither of the three kinds of fermentation 
alone can account for the various phenomena produced 
in digeltion. If the acetous fermentation takes place 
as a neceffary part of it, we muff believe that the putrid 
does likewife ; or how lhall we account for the folution 
of animal fubftances ? For in no circumflances do they 
undergo the acetous fermentation. The experiments 29 
of Stevens, with the vials, enclofing beef in the gaflric 
juice, and my own with the dogs and cats, difprove 
the theory of putridity. Laflly, the acetous fermenta- 
tion cannot in any degree take place without evolving 
an acid, which our experiments could not, in a fingle 
inftance, difcover. 
Dr. Stevens performed a number of experiments 
upon a poor German who for many years had gained 
a miferable fubfiflance by fwallowing hones for the 
amufement of fpe&ators ; he gave him to fwallow 
filver fpheres, perforated, fo as to admit the gaflric 
fluid freely to pafs: at different times were enclofed 
filh, raw and boiled beef, pork, and cheefe ; the 
fphere was, for the mod part, retained from thirty to 
forty hours, and when voided, generally found to have 
loft the moft, and frequently the whole of its contents. 
Having obferved that animal fubftances were readily 
diflolved by the gaflric juice, theDo&or tried whether 
the fame effe£l would be produced on vegetables.— 
He enclofed in his fphere raw parfnip and potatoe, 
which were fwallowed as before by the German, and 
retained for forty-eight hours ; and when voided, not 
a veftige of either remained. Apples and turnips, 
both raw and boiled, were digefted in thirty-fix hours. 
The fame experimenter enclofed live leeches and 
earth worms in different fpheres, which the German, 
as ufual, fwallowed. He retained them for fome time, 
and when difcharged in the natural way, the animals 
were deprived of life, and completely diflolved. It is a 30 
pleafing reileftion, that no reptile, if taken into the 
ftomach accidentally, or otherwife, can refift the ope- 
ration of this powerful fecreted menftruum, the gaftric 
liquor. Worms, hatched in the inteftines, are alone an 
exception. 
In accounting for the procefs of digeflion by folu- 
tion alone, a very natural queftion has frequently been 
alked by its oppofers: 6 If the gaftric liquor afts as a 
4 folvent, why is not the ftomach afted upon, feeing it 
4 is compofed of the fame materials we make ufe of in 
diet?* The ftomach, as long as it retains the principle 
of life, is not aifefted by the gaftric liquor; but the 
moment that this principle is deftroyed, and death takes 
place, it is equally liable to be corroded as other fub- 
ftances. The fame thing happens to live animals gene- 
rated in the alimentary canal. As long as they have 
the vital principle, it relifts the power of digeftion. 
4 Hence it is,’ Mr. Hunter remarks, 4 that we find 
4 animals of various kinds living in the ftomach, or even 
4 hatched and bred there; but the moment that any 
4 of thefe lofe the living principle, they become fubjeft 
4 to the digeftive powers of the ftomach. If it were 
4 pofiible, for example, for a man’s hand to be intro- 
4 duced into the ftomach of a living animal, and kept 
4 there for fome conliderable time, it would be found 
4 that the dilfolvent powers of the ftomach could have 
4 no effeft upon it. But, if the fame hand were fepara- 
4 ted from the body, and introduced into the fame fto- 
4 mach, wre fliould then fee, that the ftomach would 
4 immediately aft upon it. Indeed, if this were not the * cafe, we fhould find that the ftomach itfelf ought to 
6 have been made of indigeftible materials; for, if the 
4 living principle was not capable of preferving animal 
4 fubftances from undergoing that procefs, the ftomach 
4 itfelf would be digefled. But we find, on the con- 
4 trary, that the ftomach, which at one inftant, that is, 
4 while poflefled of the living principle, was capable of 
4 refilling the digeftive powers which it contained; the 
4 next moment, viz. when deprived of the living prin- 
( ciple, is itfelf capable of being digefted; either by the 
4 digeftive power of other ftomachs, or by the remains 
4 of that power which it had of digefting other things.’ 
Mr. Hunter mentions three cafes of perfons who 
had died of violent deaths, without previous indifpo- 
fition, where he obferved the ftomach had been cor- 
roded by the gaftric fluid. 4 In thefe cafes,’ fays he, 
4 the contents of the ftomach are generally found loofe 
4 in the cavity of the abdomen, about the fpleen and 
4 diaphragm. In many fubjedts this digeftive power 
4 extends much farther than through the ftomach.— 
4 I have often found, that, after it had diflolved the 
4 ftomach at the ufual place, the contents of the fto- 
4 mach had come into contact with the fpleen and 
4 diaphragm, had partly diflolved the adjacent fide of 
4 the fpleen, and had diflolved the ftomach quite 
4 through; fo that the contents of the stomach were 
4 found in the cavity of the thorax, and had even aftedft 
4 ed the lungs in a fraall degree.’ 
31 32 
It is only by the aid of fa&s and experiments that 
we can arrive at truth, particularly in refearches con- 
nected with natural philofophy and medicine. The 
phyfiologift who would inftruCt himfelf, or teach 
others, by conje&ure alone, had better do nothing, 
but leave the fubjeft for others, pofleffed of more in- 
duftry or more leifure than himfelf. 
FINIS.