356 VETERINAKY PHYSIOLOGY 



It is found that, soon after food is taken, a constriction forms 

 about the middle of the stomach and slowly passes on towards 

 the pylorus. Another constriction forms and follows the first, 

 and thus the pyloric part of the stomach is set into active 

 peristalsis. The cardiac fundus acts as a reservoir, and, by a 

 steady contraction, presses the gastric contents into the more 

 active pylorus, so that, at the end of gastric digestion, it is 

 completely emptied. 



The pylorus is closed by the strong sphincter muscle, which, 

 however, relaxes from time to time during gastric digestion to 

 allow the escape of the more fluid contents of the stomach 

 into the intestine. These openings are at first slight and 



FIG. 157. Tracings of the shadows of the contents of the stomach and intestine 

 of a cat two hours after feeding (A) with boiled lean beef, and (B) with 

 boiled rice to show the more rapid emptying of the stomach after the 

 carbohydrate food. The small divisions of the food in some of the 

 intestinal loops represent the process of rhythmic segmentation (see 

 p. 375). (CANNON.) 



transitory, but as time goes on they become more marked and 

 more frequent, and when gastric digestion is complete usually 

 at the end of five or six hours the sphincter is completely 

 relaxed and allows the stomach to be emptied. The openings 

 are regulated by a local nervous mechanism which is brought 

 into play by the escape of the acid gastric contents into the 

 duodenum. This leads to an immediate closure of the pylorus, 

 which does not again open till the contents of the duodenum 

 have been neutralised by the alkaline secretions which are 

 poured into it. The rate of passage from the stomach of 

 various kinds of food has been studied by feeding cats with 

 equal amounts of each kind of food mixed with bismuth, and 



