316 VETERINARY PHYSIOLOGY 



middle of the stomach, due to the contraction of the 

 prepyloric spliincter which separates the cardiac from 

 the pyloric end. This contraction passes on towards the 

 pylorus. Another contraction forms and follows the first, 

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

 movement. 



The fundus acts as a reservoir, and, by a steady con- 

 traction, presses the gastric contents into the more active 

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

 pletely emptied. 



While the food is well mixed in the p3doric canal, no 



A r-^ B 



Fig. 152. — 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 waves of contraction in 

 the pyloric part of the stomach are shown. The small divisions of 

 the food in some of the intestinal loops represent the process of 

 rhythmic segmentation. (Cannon.) 



great mixing takes place in the fundus of the stomach, 

 and, by feeding with different coloured foods, its distribution 

 may clearl}^ be seen (fig. 1 5 3). 



The pylorus is closed by the strong sphincter pylori 

 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, Avhen gastric 

 digestion is complete — after an ordinary meal at the end of 

 four or five hours, the sphincter is completely relaxed and 

 allows the stomach to be emptied. The openings are regu- 



