THE STOMACH. 213 



The muscular coat of the stomach consists of three layers, 

 distinguished by the arrangement of the fibers, a circular 

 layer, a longitudinal layer, and an oblique layer. 



The mucous lining is somewhat loosely attached to the 

 muscular coat, and when the stomach collapses the mucous 

 coat is thrown into folds, usually running lengthwise. 



SMALL 



TINE 



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

 (Dorsal View. Mucous Coat Unduly Thickened.) 



If the inner surface of the mucous membrane is examined 

 with a lens many small holes may be seen. These are the 

 mouths of the ducts of the Gastric Glands. If the duct is 

 traced inward, it is found to divide into several branches, usu- 

 ally two or three. These gastric glands vary somewhat in 

 their structure in different parts of the stomach. The liquid 

 secreted by the different glands also varies considerably, but 

 the liquid as a whole is called the Gastric Juice. The gastric 

 juice is 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 



