440 



DIGESTION 



appetite juice. 10 By such a mechanism gastric juice would continue to be 

 secreted so long as any half-digested food remains in the stomach. 



The action of gastrin is the first instance of a hormone control of the 

 digestive glands. In the earlier stages of digestion, the secretion of saliva 

 and appetite juice is mediated through the nervous system, because these 

 juices must be produced promptly. In the later stages of gastric diges- 

 tion, such promptitude in response on the part of the gland is no longer 

 necessary, so that the slower, more continuous process of hormone con- 

 trol is sufficient. 



Quantity of Gastric Juice Secreted 



According to Carlson, the total amount of gastric juice secreted in 

 man on an average meal composed of meat, bread, vegetables, coffee or 



Hours 

 12 

 10 



8 



6 



4 



2 







345678123456789 10 12 3 456 



c 

 a 



Flesh. 200 gm. 



Bread, 200 gm. 



Milk, 600 c.c. 



Fig. 150. — Cubic centimeters of gastric juice secreted after diets of meat, bread, and milk. (From 



Pavlov.) 



milk, and dessert, amounts to about 700 c.c, being divided into 200 c.c. 

 in the first hour, 150 in the second, and 350 c.c. during the third, fourth 

 and fifth hours. These figures were estimated partly on the basis of 

 observations made on the man with the gastric fistula, and partly from 

 the data supplied by Pavlov's observations on dogs. Carlson believes 

 that Pavlov overestimated the relative importance of the appetite juice 

 in gastric digestion. He found, for example, that after division of both 

 vagus nerves in dogs normal gastric digestion might be regained a few 

 days after the operation, although, of course, under such circumstances no 

 appetite juice could have been secreted. Moreover, he observed that cats 

 when forcibly fed with unpalatable food may digest that food as rapidly 

 as when they eat voluntarily. In support of his contention, Carlson 

 states that he has frequently removed all of the appetite juice from his 

 patient's stomach before the masticated meal was put into it without 

 any evident interference with the digestive process. 



Fat has a distinct inhibiting influence on the direct secretion of gas- 



