Digestion in the Stomach. 167 



is an oval sac lying just beneath the diaphragm, with the 

 large end to the left and the small end to the right. The 

 smaller end, by narrowing, becomes the small intestine. 

 When the stomach is empty it collapses, as its walls are 

 soft and flexible. When distended it may hold three pints, 

 or, when greatly distended, even more. 



The Coats of the Stomach. The stomach and intestines have four 

 coats, in the following order, beginning at the outside : the peritoneum, 

 the muscular, the submucous, and the mucous coats. The muscular 

 coat of the stomach consists of three layers, distinguished by the arrange- 



GULLET 



Fig. 72. Longitudinal Section of Stomach, showing Gastric Glands in Position. 

 (Back View. Mucous Coat unduly Thickened.) 



ment of the fibers, a circular layer, a longitudinal layer, and an oblique 

 layer. The mucous lining is somewhat loosely attached to the muscular 

 coat by the submucous coat between them, and when the stomach col- 

 lapses, the mucous coat is thrown into folds, usually running lengthwise. 



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 be either a simple tube (see Fig. 73) or to divide 

 into branches, usually two or three. 



