Chap. XV.] 



ALIMENTATION. 



181 



leading into the small intestine, the pyloric. The pyloric aper- 

 ture is guarded by a kind of valve composed of circular mus- 

 cular fibres, which form a constricted ring projecting into the 

 pyloric opening. By this arrangement, the food is kept in the 

 stomach until it is ready for intestinal digestion, when the cir- 

 cular fibres relax and allow it to pass. 



When moderately distended, the stomach measures about 

 four inches (102 mm.) vertically and twelve inches (305 mm.) 

 from side to side. It has four coats. The outer serous coat is 

 formed by a fold of the peritoneum. The fold is slung over 

 the stomach, in much the same way as we sling a towel over a 



Fig. 114. — Vertical and Longitudinal Section of Stomach, Gall-bladder, 

 AND Duodenum. 1, oesophagus; 2, cardiac orifice of stomach; 5, lesser curvature; 

 6, greater curvature; 8, rugre in interior of stomach; 9, pyloric orifice; 10, 11, 

 13, interior of duodenum, showing valvulffi conniventes; 12, duct conveying bile, and 

 P, duct conveying pancreatic juice, into the duodenum; 14, gall-bladder; 15, com- 

 mencement of jejunum. 



clothes-line, and covers it before and behind. The anterior and 

 posterior folds unite at the lower border of the stomach and 

 form an apron-like appendage, the omentum, which covers the 

 whole of the intestines. The omentum often contains a large 

 amount of fat. 



The muscular coat of the stomach consists of three layers of 

 unstriped muscular tissue : an outer, formed of longitudinal 

 fibres ; a middle, of circular ; and an inner, of less well-devel- 



