DIGESTION AND ABSORPTION IN THE STOMACH 83 



dextra and the gastro-epiploica-sinistra arteries running 

 along it between the two folds of the omentum. Where the 

 anterior and posterior walls meet superiorly, the stomach is 

 joined by the lesser omentum, the two layers of which are 

 continued in front and behind as the serous covering of the 

 stomach. This is the lesser curvature, and has the gastric 

 and pyloric branch of the hepatic arteries running along be- 

 tween the two layers of the lesser omentum. The large left 

 hand portion of the stomach cavity 'is called the fundus or 

 greater pouch. The opposite portion of the cavity is called 

 the lesser pouch or antrum pylori. At one end is the 

 cardiac or esophageal opening, at the other the pyloric. 



Histology. The coats of the stomach walls are four. 

 From without inward these are the (i) peritoneal, or serous, 

 (2) muscular, (3) submucous, and (4) mucous. 



1. The peritoneal coat covers the whole of the organ ex- 

 cepting an inconsiderable linear area, where the two layers 

 of the lesser (gastro-hepatic) omentum join it along the 

 lesser curvature, and a similar area along the greater curva- 

 ture, where the serous coats of the anterior and posterior 

 walls leave the organ to form the great omentum. This coat 

 is simply a fold given off from the peritoneum to envelop the 

 stomach in practically the same manner as the other abdomi- 

 nal viscera. Its structure is that of serous membranes in 

 general. 



2. The muscular coat, varying in thickness from %o in. 

 over the fundus to M.2 in. at the pylorus, is disposed in three 

 layers, (a) the external longitudinal, (b) middle circular, 

 and (c) internal oblique. The longitudinal fibers are con- 

 tinued from the corresponding fibers of the esophagus. They 

 are marked along the lesser curvature, but not very distinct 

 over other parts. The circular fibers are not abundant to the 

 left of the esophageal opening. They progressively increase 

 toward the right, and at the pyloric opening constitute a dis- 

 tinct and powerful muscular ring, the pyloric sphincter, 

 which, projecting into the lumen presents a more or less 



