THE DIGESTION 



211 



mucous lining then lies in deep wrinkles or folds. The 

 opening where the gullet ends and through which the food 

 enters, is called the cardiac orifice because it is near the 

 heart. The opening where the intestines begin and 

 through which the food leaves, is called the pyloric orifice ; 

 both openings can be 

 closed by circular mus- 

 cles in their walls. 



375. Peritoneum. 

 The abdominal cavity, 

 or the portion of the 

 large cavity of the trunk 

 below the diaphragm, 

 has, like the thoracic 

 cavity, a lining to pre- 

 vent friction. This 

 membranous lining is 

 called the peritonfaim, 

 and like the pleura, it is 

 double. It comes 

 the wall of the 

 all around, lining it like 

 a thin sheet, until it 



reaches the place under the diaphragm where the gullet 

 and larger blood vessels (aorta and vena cava) enter, where 

 it is reflected and courses downward, enveloping the 

 stomach and other digestive organs. It penetrates be- 

 tween them by means of foldings and turnings, thus 

 assisting to hold them in place. The largest fold of all 

 is called the great omentum and surrounds the small 

 intestine. It is fan-shaped and its contracted part is 

 attached to the spinal column for a firm support. The 

 alimentary canal, beginning with the stomach, may be 

 said, therefore, to have a fourth layer, or covering, the 

 peritoneum. 



FIG. 167. The Stomach laid open. 



Up a, esophagus; b, cardiac dilatation on left side of 

 stomach; c, the upper wall; d, the pylorus; e, bile 

 duct . ^ gall bladder; g, pancreatic duct, opening 

 with bile duct into h, :', duodenum (see Plate V). 



