THE FOOD AND DIGESTION 339 



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 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 



FIG. 149. 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. 

 The small divisions of the food in some of the intestinal loops represent the 

 process of rhythmic segmentation (see p. 354). (CANNON.) 



sphincter is completely relaxed and allows the stomach 

 to be emptied. The rate of passage from the stomach of 

 various kinds of food proteid, carbohydrate, and fat has 

 been studied by feeding cats with equal amounts of each 

 special food mixed with bismuth, and then, by X rays, 

 getting the outline of the contents of the small intestine 

 at different periods. Carbohydrates were found toipass on 

 most rapidly and fats most slowly. 



Nervous Mechanism of the Movements. Even after the 

 section of all the gastric nerves, movements of the stomach 

 may be observed, but the mechanism of these has not been 

 fully studied. The action of the vagus and sympathetic 

 fibres is complicated, and their influence on the wall of the 

 stomach and the sphincters requires further investigation. 



