VARIATIONS IN GASTRIC JUICE DURING DIGESTION. 545 
5-7 
1-6 
"S-4 
|-3 
cs 
1-2 
Btriking feature Ie the absence of coincidence between the pepsin con- 
tents of the pyloric and the fundus region of the stomar-h. 
In general, it may be pointed out that the maximal yield of pepsin 
from the pyloric region is at the same interval after ingestion of food as 
marks the minimal yield of pepsin from the fundus. 
A great number of observations have been directed to estimating the 
acidity of the contents of the stomach at different intervals after a meal 
has been taken. Gastric juice commences to he secreted almost as soon 
as suitable food enters the stomach. For a time the acid juice merely 
neutralises the alkalinity of the food and saliva, and the hydrochloric 
acid combines with various food substances, so that free hydrochloric 
acid does not occur till after an appreciable interval. Yon den Yelden l 
states that free hydrochloric acid 
cannot be detected until three- 
quarters of an hour after a meal 
is taken. Eichet 2 states that in 
the human stomach the acidity 
gradually increases during diges- 
tion, and that it is apparently 
independent of the quantity of 
fluid taken. Towards the end 
of digestion he finds that the 
total acidity of the stomach con- 
tents may be further increased, 
but this is to Lie referred to the 
production of organic acids by 
the decomposition of the food. 
He also points out that the feebler 
the activity of the juice, the 
greater the amount of organic 
acid liberated. Chischin's 3 observations give precise details of the course 
of digestion with different foods. The annexed diagram (Fig. 45) shows 
the course of the production of hydrochloric acid in an isolated portion 
of the fundus, when the animal was fed with mixed food, comprising 
milk, meat, and bread. The animal did not undergo the "psychical" 
stimulation of the food, or the maximal percentage of hydrochloric acid 
would probably have been in the first hour, instead of in the second or 
third. If meat alone be given to such an animal under similar conditions, 
the maximal acidity occurs in the first hour. With mixed food the digest- 
ive power averages 3'5 mm. (Mette's method of estimation by columns 
of coagulated egg-white) : 4 with simply meat food, about 4 mm. With 
bread alone as food, the duration of secretion was found to be more 
protracted, but the digestive strength was much greater, varying between 
5 "22 mm. and 7 '5 6 mm. The digestive power was very marked in the 
first hour, increased further in the second hour, and remained high both 
in the third and fourth hours. With milk, the course of secretion is 
much more irregular. The digestive power is moderately high at first, 
but sinks, after the first hour, about one-half. It remains at this 
strength for the third and fourth hours, but in the fifth hour increases 
again to the original strength, and may, in the sixth hour, even go 
1 "Zur Lehre toii der Wirkung des Mundspeichels im Magen," Ztschr. f. pkysiol. 
Chciii.. Strassburg, 1879, vol. iii. 
2 Op. cit. 3 Op. cit. * For Mette's method, see p. 325. 
VOL. I. T,Z 
1 2 3 4 5 6 7 
Time in hours after food is taken 
Fig. 45. — Chart showing acidity of gastric 
juice after feeding with mixed food (300 
c.c. milk, 50 grins, meat, and 50 gnus. 
white bread). The animal was not sub- 
jected to the "psychical stimulation 1 ' of 
the food. 
