1 68 



Physiology. 



Mouth of Giand 



Epithelium 



The Gastric Juice. The liquid secreted by these glands 

 is called the gastric juice. The gastric juice is chiefly 

 water, containing a substance called pepsin, and a small 

 amount of acid. The amount of gastric juice secreted 

 daily has been estimated at four or five quarts. Of course, 

 we must bear in mind that nearly all of this is again 

 absorbed from the digestive tube, and is not a loss to the 

 body. 



Blood Supply of the Stomach. The mucous membrane 

 is well supplied with blood-tubes, but while it is resting the 



blood flow is dimin- 

 ished, and it is pale. 

 But as soon as food 

 is introduced into the 

 stomach the blood flow 

 is greatly increased, 

 principal and the mucous mem- 

 brane becomes red. 

 This blood supply gives 

 the glands the materi- 

 als with which they 

 manufacture the gastric 

 juice. At the same 

 time the cells of the 



glands are stimulated to action, and the secretion is poured 

 out rapidly. The saliva also aids in stimulating the secre- 

 tion of the gastric juice. 



The Work of the Gastric Juice. The special work of the 

 gastric juice is accomplished by the pepsin, aided by the 

 acid ; these change proteids into a soluble substance, called 

 peptone, which can be absorbed through the walls of the 

 digestive tube into the blood. 



Celts 



Connective Tissue 

 Fig. 73. Three Glands of the Stomach. 



