STOMACH 
DIGESTION. 
by 
DR. FRANK H. MURDOCH, 
Pittsburgh, Pa. 
Read before the Allegheny County Medical 
Society, August 18th, 1896. Stomach Digestion. 
BY DR, FRANK H. MURDOCH. 
PITTSBURGH, PA. 
Physiologists divide digestion into seven 
stages: Prehension, mastication, insaliva- 
tion, stomach and intestinal digestion, and 
defecation. This evening we have to do 
with digestion as it occurs in the stomach, 
which, as we know, is one of the most impor- 
tant, and, at the same time, one of the most 
abused organs in the human body. This 
habit of abusing the stomach seems to have 
been practiced at a very early age in the 
world's history, for the ancient Egyptians 
taught that "The greater part of the aliment 
taken is superfluous, which superfluity is the 
cause of all our distempers;" and Hippocrates 
taught that "Excess in drinking is not quite 
as bad as excess in eating." 
The capacity of the human stomach is 
from eight to fifty-six ounces. When it holds 2 
more than fifty-seven ounces, Ewald con- 
siders it to be in a condition of dilatation. 
During rest, the stomach should be empty 
or contain at most only a small quantity of 
clear mucus. 
During digestion it becomes a closed sac. 
Its contents are subjected to a sort of churn- 
ing motion from the contraction of its walls, 
and, at the same time, a free secretion of 
gastric juice takes place from the gastric 
glands. 
As soon as any portion of the contents 
becomes properly prepared, the pyloric ori- 
fice opens to allow of its passage into the 
intestine. This is repeated at intervals un- 
til, in the course of a few hours, the stom- 
ach becomes empty, and then the peristaltic 
action ceases, as does also the secretion of 
gastric juice, until food is again taken into it. 
Gastric juice is a clear, colorless fluid, of 
a specific gravity of from 1002 to 1003, and, 
besides hydrochloric acid, contains two fer- 
ments, rennet and pepsin. The amount se- 
creted in twenty-four hours is about seven 
liters, or nearly one-tenth of the body 
weight. 
The glands which secrete the gastric juice 3 
open upon the mucous membrane of the 
stomach and are of two classes, the cardiac 
and the pyloric. 
The cardiac glands are tubular and sev- 
eral open upon the surface by one duct. They 
are lined by two kinds of cells, one, form- 
ing the greater number, are the chief, cen- 
tral or adelomorphous cells for the secre- 
tion of pepsin and rennet. The other larger, 
but also granular and nucleated, are the 
parietal, dilomorphous, or oxyntic cells for 
the secretion of hydrochloric acid. The 
pyloric glands are without the parietal cells, 
and consequently do not secrete hydro- 
chloric acid, but pepsin and rennet only. 
The epithelial lining of the mucous coat 
of the stomach is formed partly by colum- 
nar cells, and partly by goblet cells for the 
secretion of mucus. 
Pepsin and rennet are not secreted by the 
gastric glands as such, but exist in a pre- 
liminary stage, the one as a proenzyme or 
rennet zymogen; the other as pepsinogen, 
both requiring the presence of an acid, es- 
pecially hydrochloric acid, to convert , them 
into active ferments. Rennet precipitates the 
casein of the milk, and with it the fat, leav- 4 
ing a liquid part which contains the salts 
and lactose. As the gastric filtrate, although 
neutral in reaction, may contain both rennet 
zymogen and pepsinogen, it should be acid- 
ulated with hydrochloric acid before mak- 
ing the test for either rennet or pepsin. 
Rennet, like pepsin, is a constant constit- 
uent of the gastric juice, and its absence 
indicates atrophy of the gastric mucosa, al- 
though Einhorn has reported two cases 
where, for a long time, there was entire ab- 
sence of gastric juice, but where eventually 
it reappeared in almost normal quantity. 
Pepsin, in the presence of an acid, has 
the power of transforming albumin, wheth- 
er serum, plant albumin, or casein, 
into a soluble and easily diffusible form, 
peptone. Propeptone is a transformation 
product of albumin, absent in the digestion 
of meat, but present in the digestion of plant 
albuminates and pure egg albumen, hence 
always found in an ordinary mixed diet. 
Its presence in abundance at the end of an 
hour after the test breakfast, indicates an 
abnormally slow digestion of the nitrogen- 
ous part of the food, for it should have been 
converted into peptone, or, at least, be found 
onlv in traces. 5 
Ewald has shown that peptone may be 
formed in the presence of other acids than 
hydrochloric acid, especially lactic acid; 
and, artificially, at least a certain amount 
of digestion takes place at the end of an 
hour and forty minutes in a test tube con- 
taining a solution of coagulated albumin, 
water, pepsin, and acetic acid; but when a 
similar mixture is acidulated with butyric 
acid, and treated in the same manner, no di- 
gestion whatever takes place (Martin). 
As early as ten or fifteen minutes after 
taking food, the stomach contents obtained, 
are acid, the acidity depending for the first 
half hour upon the presence of lactic acid. 
For the next half hour, hydrochloric acid ex- 
ists with the lactic acid; but after the first 
hour hydrochloric acid alone should be 
found. Lactic, acetic and butyric acids are 
not secreted by the gastric glands, but are 
either swallowed with the food, or formed in 
the stomach from the non-nitrogenous part 
of the food by bacterial fermentation. 
The normal acidity of the gastric juice is 
from forty to sixty, but in patients com- 
plaining of stomach trouble, this condition 
is very rarely found. Ina series of five hun- 
dred and sixty-four cases examined by Ein- 6 
horn, the acidity was normal only ninety- 
one times. In one hundred and eighty- 
seven cases there was too little acid, and in 
two hundred and eighty-six cases, too much. 
In one hundred and twenty cases hydro- 
chloric acid was entirely absent. In twenty- 
six cases in which I have recently examined 
the gastric juice, the acidity was not nor- 
mal in a single instance. In five of the 
cases it was too low; and, in all these cases 
hydrochloric acid was absent, while in the 
remaining twenty-one cases the degree of 
acidity was too high. 
Hydrochloric acid acts in several ways in 
the stomach. It stimulates the peristaltic 
action, it develops active ferments out of 
inactive pro-enzymes, and, with the aid of 
pepsin, converts albumin into peptone. It 
has nothing to do with the digestion of the 
carbohydrates of the food. 
The digestion of starch begins in the 
mouth, the ptyalin of the saliva converting 
a certain portion of it into sugar. But the 
action of the ptyalin dees not stop in the 
mouth, for the saliva which is swallowed 
with the food continues its action on the 
amylaceous substances, even in the stom- 
ach, until its action is arrested by the acid 7 
of the gastric juice. No further change 
takes place until the stomach empties itself 
into the duodenum, where the acid chyme, 
coming in contact with the pancreatic juice, 
is rendered alkaline, and the digestion of 
the starch is completed. 
As albumins are changed into propep- 
tone before being converted into peptone, 
so starch is changed into erythrodextrin, 
and then into achroodextrin, before being 
finally converted into sugar, so that at the 
end of an hour after the test breakfast if 
erythrodextrin be found, we know that the 
digestion of starch is abnormally slow. 
The conditions interfering with stomach 
digestion are, improper quality or quantity 
of food, bad teeth, insufficient mastication, 
absence of hydrochloric acid, too low or too 
high a degree of acidity, whether due to 
hydrochloric acid, or to the presence of on 
ganic acids, diminished absorption, and di- 
latation or loss of motor power due to atony 
of the muscular coats. 
515 Penn Avenue. REPRINTED FROM THE 
PITTSBURGH MEDICAL REVIEW, 
SEPTEMBER, 1896. 
PRESS OF 
MURDOCH, KERR &. CO , INC- 
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