FOOD AND DIGESTION 355 



is also influenced by the action of a chemical substance 

 produced in the mucous membrane of the pyloric end of the 

 stomach. It has been found that the injection into the 

 blood stream of an extract of this membrane made by boiling 

 with acid or peptone causes a production of gastric juice. In 

 all probability the initial secretion of gastric juice is dependent 

 on the nervous mechanism, and the secondary secretion, when 



HOSE 

 EYE 



,'/ STOMACH 



POUCH 



FIG. 156. To show the nervous mechanism of gastric secretion and how it 

 is reflexly induced through various ingoing channels. 



food is in the stomach, on the action of this substance. In 

 the case of the pancreas such a chemical stimulant plays a 

 very important part (p. 420). Such substances have been 

 named Hormones. 



3. Movements of the Stomach. These have been studied 

 by feeding an animal with food containing bismuth, and then 

 applying X-rays, which are intercepted by the coating of 

 bismuth, so that a shadow picture of the shape of the stomach 

 is given (fig. 157). 



