108 



DIGESTION 



Rejection of food. In case the food taken is irritat- 

 ing to the stomach because of its poisonous nature, or 

 is so excessive in amount as unduly to stretch its walls, 

 the stomach empties itself by sending the food back 



the way it came. This swal- 

 lowing up, as it may be called, 

 is accomplished on the part of 

 both stomach and esophagus by 

 a reverse process of muscular 

 contraction. The esophagus re- 

 laxes to permit the food's exit, 

 instead of the pylorus. 



'Small intestine. After its 

 exit from the stomach through 

 the pylorus, the chyme passes 

 into the upper end of the small 

 intestine. This is a tube about 

 twenty feet in length, with mus- 

 cular walls lined with a mucous 

 membrane of closely packed cells. 

 Lying in and beneath this mem- 

 brane are many small glands, 

 which discharge into the intestine a secretion, the in- 

 testinal juice. The intestinal juice contains a number of 

 ferments that have the power of digesting starch and 

 proteid, and of changing cane sugar into grape sugar, in 

 which form only it can be utilized by the body. 



Li ver . Opening into the small intestine near the 

 stomach are two small tubes or ducts. One of these 

 comes from the liver and its reservoir, the gall-bladder. 

 The liver is the largest gland in the body and weighs 

 from three to four pounds. It is reddish-brown in color, 

 firm in consistency but easily torn, and lies across the 

 body at the level of the lower ribs. It has several im- 



FIG. 72. Diagram illustrating 

 the muscular contractions of 

 a cat's stomach after eating a 

 meal just before 11 A.M. By 

 these contractions, the con- 

 tents are squeezed toward the 

 pylorus. (Cannon.) 



