THE PERISTALSIS OF THE STOMACH 



355 



mixed with the gastric juice, forming the chyme. Figure 261 gives an idea of 

 the movement of the food in the antrum. The peristaltic contractions carry 

 it forward, but if the valve does not open to permit passage to the duodenum, 

 then the pressure will force the chyme back through the center toward the 

 fundus. After several minutes, i.e., when the secretion of alkaline bile and 

 pancreatic juice into the duodenum is well established, the pyloric sphincter 



11A.M. 



12M. 



2RM. 



5RM. 



FIG. 262. Outlines of the Roentgen-ray Shadows of the Stomach Content as Digestion 



Progresses. (Cannon.) 



\rill relax more often to allow fluid food to pass to the duodenum, but when 

 the more solid particles come up against the valve the sphincter promptly 

 contracts and remains so for some time. Toward the completion of digestion 

 even solid undigested particles are carried on into the intestine. 



The movements of the stomach are under extraneous nervous regulation. 

 Cannon found that the peristalses were promptly inhibited in cats by ex- 

 citement. Stimulation of the vagi leads to contractions of the stomach 



