THE DIGESTIVE SYSTEM. 1 73 



The Gastric Glands. In the inner surface of the 

 mucous membrane are many holes. These are the mouths 

 of the ducts of the gastric glands. If a duct is traced 

 inward, it is found to divide into several branches, usually 

 two or three. These gastric glands vary somewhat in their 

 structure in different parts of the stomach. 



The Gastric Juice. The liquid secreted by the differ- 

 ent glands also varies considerably, but the liquid as a 

 whole is called the gastric juice. The gastric juice is 



Fig. 60. Longitudinal Section of Stomach, showing Gastric Glands in Position. 

 (Dorsal View. Mucous Coat Unduly Thickened.) 



chiefly water, containing a ferment, or enzyme, called 

 pepsin, and a small amount of acid. The amount of 

 gastric juice secreted daily has been estimated at from 

 five to ten quarts. Of course, we must bear in mind that 

 nearly all of this is again absorbed from the digestive tube, 

 and is not a permanent loss to the body. 



Blood Supply of the Stomach. The mucous mem- 

 brane is abundantly supplied with blood tubes, but 

 during the time of its rest the blood flow here is 



