DIGESTION. 73 



once in about every two or three minutes; the time and regularity 

 are,, however, much influenced by the quantity and quality of the 

 food ingested. As a result of these combined movements, not only 

 is the chymified food propelled into the duodenum, but there are 

 set up regular currents among the contents. 



Dr. Cannon has studied the movements of the stomach in cats 

 by means of the Eoentgen rays. He states that the stomach con- 



WAVES 



CONSTOI CTlON 1 



PYLORUS^ 



Fig. 15a. Functional Divisions of the Stomach. 



The fundus serves as a reservoir in which the food is gradually mixetl with 

 the gastric juice. The fundus squeezes the food into the tube between the 

 fundus and antrum, called the pre-antral or middle portion. This pre-antral 

 tube has muscular constrictions about every fifteen seconds. In the pyloric end 

 the forcible and active movements mix the food with the gastric juice, 

 rubbing it down to a fluid, which is gradually forced out into the duodenum. 



(HUTCHISON.) 



sists of two physiologically distinct parts: the pyloric part and the 

 fundus. Over the pyloric part while food is present constriction 

 waves are seen continually coursing toward the pylorus. The fundus 

 is an active reservoir for the food, and squeezes out its contents 

 gradually into the pyloric part. The stomach is emptied by the 

 formation between the fundus and the antrum of a tube along which 

 the constrictions pass. The contents of the fundus are pressed into 

 the tube and the tube and antrum slowly cleared of food by the 

 waves of constriction. The constriction waves have three func- 



