SUMMABY OP DIGESTION 117 



gators showed that while this mixing does take place the 

 method is somewhat different from what was formerly 

 supposed. According to these investigators, the stomach 

 cavity may be divided into two parts, in only one of which 

 does the actual mixing take place. The cardiac end of 

 the stomach or fundus shows almost no movement and 

 acts simply as a storehouse. The contractions start in the 

 middle of the stomach and run toward the pylorus end, 

 and only the portion in this end is actually in process of 

 mixing. These contraction waves are repeated at inter- 

 vals of two minutes or less, and finally reduce the food 

 in this end to a thin liquid. At intervals depending upon 

 the character of the food, the sphincter pylorus relaxes and 

 portions of the liquid mass are spirted into the intestine 

 while new material flows forward from the storage end to 

 take its place. When the food is liquid these relaxations 

 of the sphincter are very frequent, while for solid food 

 they occur at longer intervals. The time required for the 

 stomach to empty itself in this way is from two to five 

 hours after a meal. The exact time, of course, depends 

 upon the amount of food taken into the stomach, and ease 

 with which it may be broken up. After the stomach has 

 been empty for a certain length of time we feel a sense 

 of hunger, and this is the signal for a renewal of the food 

 supply. Meanwhile, the chyme which has entered the 

 intestine is undergoing further digestive changes. 



Summary of Digestion in the Stomach. 



1. The food enters the stomach by the cardiac orifice, and by 

 the peristaltic action of the muscular walls is mixed with the gastric 

 juice. 



2. The hydrochloric acid stops the action of the ptyalin and the 

 digestion of starch, and makes possible the action of the pepsin. 



