ANATOM 
thefe fubftanees were divided, the folvent would have a 
freer accefs to them, and more of them would be diffolved, 
Dr. StevenS procured another fphere, with holes large 
enough to receive a crow’s quill. He inclofed fome beef 
in it a little mailicated. In thirty-eight hours after it was 
fwallowed, it was voided quite empty. Perceiving how 
readily the chewed meat was diffolved, lie tried whether 
it would diffolve equally Coon without being chewed. With 
this view, he put a fcruple and eight grains of pork into 
one cavity, and the fame quantity of cheefe into the other. 
The fphere was retained in the German’s ftomach and in¬ 
teftines forty-three hours ; at the end of which time, not 
the fmalleft quantity of pork or cheefe was to be found in 
the fphere. He next fwallowed the fame fphere, which 
contained, in one partition, fome roafied turkey, and fome 
boiled fait herring in the other. The fphere was voided 
in forty-fix hours; but no part of the turkey or herring- 
appeared, for both had been completely diffolved. Hav¬ 
ing difeovered that animal fubftanees, though inclofed in 
tubes, were eafily diffolved by the gaftrie juice, the doCtor 
tried whether it would produce the fame effect upon ve¬ 
getables. He therefore inclofed an equal quantity of raw 
parfnep and potatoe in a fphere. After continuing forty- 
eight hours in the alimentary canal, not a veftige of either 
remained. Pieces of apple and turnip, both raw and boiled, 
were diffolved in thirty-fix hours. 
It is a comfortable circumftance, that no animal, per¬ 
haps, except thofe worms which are hatched in the human 
inteftines, can refill the diffolving power of the gaftrie juice. 
Dr. Stevens inclofed live leeches, and earth-worms, in dif¬ 
ferent fpheres, and made the German fvvallow them. When 
the fpheres tvere' difcha.rged, the animals w ere not only de¬ 
prived of life, but completely diffolved by the operation 
of this powerful menftruum. Hence, if any live reptile 
Ihould chance to be fwallowed, we, have no reafon to ap¬ 
prehend any danger from fitch an accident. And as the 
gaftrie juice of the human ftomach is capable of diffolv¬ 
ing, nearly with equal eafe, both animal and vegetable 
food, this circumftance affords a ftrong and almoft an ir- 
refiftible proof, that nature originally intended man to feed 
promifcuoufly on both. 
Live animals, as - long as the vital principle remains in 
them, are not affected by the folvent powers of the fto- 
niach. “ Hence it is,” Mr. Hunter remarks, “ that we 
find animals of various kinds living in the ftomach, or 
even hatched and bred there ; but the moment that any 
of thefe lofe the living principle, they become fubjeCt to 
tlie digeftive powers of the ftomach. If it were poffible, 
for example, for a man’s hand to be introduced into the 
ftomach of a living animal, and kept there for fome con- 
ftderable time, it would be found that .the dilfolvent powers 
of the ftomach couid have no effect upon it: but,- if the 
fame hand were feparated from the body, and introduced 
into the fame ftomach, we fhould then find, that the fto¬ 
mach w'ould immediately aft upon it. Indeed, if this w'ere 
not the cafe, we fhould find that the ftomach itfelf ought 
to have been made of indigeftible materials; for, if the 
living principle was not capable of preferving animal fub- 
ftances from undergoing that prccefs, the ftomach itfelf 
would be digefted. But we find, on the contrary, that the 
ftomach, which at one inftant, that is, while poffelfed of 
the living principle, was. capable of refilling the digeftive 
powers which it contained, the next moment, viz. when 
deprived of the living principle, is itfelf capable of being 
digefted, either by the digeftive powers of other ftomachs, 
er by the remains of that power which it had of digeft- 
ing other things.” 
The ftefhy fibres of the ftomach being irritated by the 
flatus, the weight, and the acrimony, of the food, begin to 
contraft themfelves more powerfully than when the fto¬ 
mach is empty, and with a greater force in proportion as 
it is more full. And, firft, the mufcirlar ftratum, which 
paffes along the leifer curvature, draws the pylorus to the 
cefophagus ; and, being inferted only into the left face of 
the former, draws it to the right. The principal ftratum 
of the circular fibres contracts the rapacity of the fto¬ 
mach according to>its length; grinds or intermixes its 
contents with the liquors; and determines them both, like 
the preifure of two hands placed oppofite, to flow towards 
the pylorus: but this flux through the pylorus is not con¬ 
tinual, on account of the valvula pylori, and likewife be- 
caufe this motion begins from fome part that is more irri¬ 
tated, and, as we fee by numerous experiments, part of it 
is very foon received into the blood. Thefe alternate con- 
traftions at laft terminate in a full evacuation. In this 
aftion of the ftomach, there is nothing which refembles 
the triture made by the ftrong gizzards of granivorous- 
fowls, which fome anatomifts have falfely aferibed to the 
human ftomach. The ftomach, however, has a confidera- 
ble degree of ftrength, fince the contraction of its fibres 
is often more than a third part of their length ; for we fre¬ 
quently fee the ftomach reduced to lefs than a third part 
of its diameter. The ftomach is alfo frequently obferved 
to be diminifhed to much lefs than its third part, even to- 
the breadth of an inch, fo that it can expel the fmalleft 
fubftanees, and entirely evacuate itfelf. 
The ftomach being irritated by too great a quantity or 
acrimony of the food, by iicknefs, by a repulfion of the 
bile, or other caufes, does, by an antiperiftaltic or reverted 
motion of its fibres, drive its contents upwards through 
the open and relaxed cefophagus. Any part of the w hole 
inteftinal canal, from the pharynx to the reftum, may be 
conftrifted, either fuddenly or (lowly, by an antiperiftaltic 
motion. If it happens fuddenly to the upper parts of the 
ftomach, the diaphragm, and likewife the abdominal muf¬ 
fles, being convulfed at the fame time, it is called viunit¬ 
ing-, if it is flowly performed, it may be called ruminatio ; 
if the fmall, and particularly the great, inteftines, return 
their contents upwards, the difeafe is called ileus. The 
effect of vomiting is partly from the preifure of the abdo¬ 
minal mufcles depreffing the falfe ribs, and urging the 
contents of the abdomen againft the diaphragm, which, at 
the fame time, contracting itfelf to a plane downwards., 
forces the ftomach, as between the iides of a prefs, to 
throw' up its contents. 
The periftaltic motion, which is more particularly ftrong' 
and evident in the fmall inteftines, is the chief power by. 
which the digefted aliments are propelled along the intef¬ 
tinal tube. Any part of the inteftine, irritated by flatus or 
any (harp or rough body, contracts itfelf, even after death, 
moft violently in that part where the ftimulus is applied, 
in order to free itfelf from the offending or diftending 
body, which it expels into the next open part of the lax 
inteftine; where, being received, it is again propelled for¬ 
ward, by exciting a like ftimulus and contraction as be¬ 
fore. This contracting motion of the inteftines is made in 
various parts of the gut, either fucceilively or at the fains- 
time, wherever the flatus or aliment excites a ftimulus, 
without obferving any certain order. So well fitted, how¬ 
ever, are’the inteftines for this motion, that they even ex¬ 
ceed the irritability of the heart. When they are not irri¬ 
tated, they remain at reft ; and we may fuppofe this to be 
the caufe why the fat is depefited in the abdomen. The 
principal ftimulus is the air ; next to that is the aliment; 
and laftly, the bile. This motion is performed by a fort 
of alternate creeping and revolution of the inteftines, which 
difleftion eafily demonftrates in brute animals, and cafes of 
wounds in the abdomen and ruptures have maniftfted it 
in the human fpecies. Among fo many inflexions, the 
weight of the aliment is but of little confequence, for it 
eafily afeends or defeends through the irritated inteftine, 
which thus empties itfelf. This periftaltic motion of the 
inteftines is performed by the conftriftion of their circular 
fibres, which empty the tube exactly, without injuring it 
againft pins, needles, or any other fharp bodies accidentally 
introduced into it. 
OF THE LIVER, 
The liver is a large and folid mafS, of a dark red colour, 
a little inclined to yellow, fituated immediately-under the 
arch 
