i88 



A MANUAL OF VETERINARY PHYSIOLOGY 



are two, perhaps three, enzymes present in the juice — viz., 

 pepsin, rennin, and possibly lipase : the former is unable to act, 

 excepting in an acid medium, and furnishes the only example 

 in the body of this necessary combination. Exclusive of the 

 ferments, protein is present. How far the gastric juice of other 

 animals resembles in its composition that of the dog we have 

 no means of knowing, inasmuch as a pure secretion has not been 

 obtained ; but in all cases an acid and an enzyme are present. 

 The enzyme is invariably pepsin, but the acid is not always 

 hydrochloric. The amount of juice secreted is uncertain; in 



Serosa 



Musculans 



Fig. 69. — Pawlow's Stomach Pouch. 

 S, The completed pouch ; V, cavity of the stomach ; A, A, the abdominal wall. 



the dog some 700 c.c. (24J ounces) have been collected in a few 

 hours, from which we may perhaps imagine that a considerable 

 amount is formed in the stomach of the larger animals. 



Pawlow's experiments on the dog show that the amount of 

 juice secreted is directly proportional to the amount of food 

 eaten : for example, 100 grammes of meat required 26 c.c. of 

 juice, and 400 grammes needed 106 c.c. The same fact was 

 observed on a mixed diet of meat, bread, and milk ; if these were 

 increased by half or doubled the juice was increased in the same 

 ratios. 



