140 



PHYSIOLOGY TOR BEGINNERS 



disposed so as to form -a band, or sphincter, which by its 

 contraction closes or nearly closes the passage. Outside the 

 muscular coat the stomach is covered with the thin transparent 

 peritoneum, by means of which it is connected with the dia- 

 phragm above, and to the abdominal organs near it. This layer 

 of peritoneum on the stomach is sometimes called the third or 

 serous coat. When the stomach is cut open and emptied, its 

 internal surface is found to be thrown into folds, forming pro- 

 minent ridges, called rugae. The external surface is not thrown 

 in this way into folds. The muscular coat is elastic, and when 



FIG. 62. The stomach laid open. 



a, (Esophagus; /', cardiac dilatation on left side of stomach; c, the upper wall ; </, 

 the pylorus ; e, bile duct ; f, gall bladder ; g, pancreatic duct, o|>eiiing with bile 

 duct into A, i, the duodenum. 



the stomach is full and distended, is put on the stretch, 

 shrinking again when the stomach is empty. The mucous 

 coat, on the other hand, does not shrink in the same way, and 

 being only loosely attached to the muscular coat, is thrown 

 into folds when the stomach empties itself and diminishes in 

 size. When the stomach is empty the mucous coat is, as it 

 were, too large for the muscular coat. The mucous membrane 

 of the stomach differs from that of the (esophagus and mouth. 

 Its epithelium, the epithelium at the internal surface of the 



