VARIATIONS IN GASTRIC JUICE DURING DIGESTION. 545 



striking feature is the absence of coincidence between the pepsin con- 

 tents of the pyloric and the fundus region of the stomach. 



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 be 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. Von den Velden l 

 states that free hydrochloric acid 

 cannot be detected until three- 

 quarters of an hour after a meal 

 is taken. Kichet 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- I ' 1 

 tents may be further increased, 

 but this is to be 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 -2 2 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 



" Zur Lelire von der Wirkung des Mundspeiohels im Magen," Ztschr. f. physiol. 

 Chem., Strassburg, 1879, vol. iii. 



2 Op. Git. 3 Op. cit. 4 For Mette's method, see p. 325. 



VOL. i. 35 



1 2345 



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 grins, 

 white bread). The animal was not sub- 

 jected to the "psychical stimulation" of 

 the food. 



