156 HOW FOOD IS PREPARED FOR BODY USES 



released into the blood at the time food passes from the stomach 

 through the pylorus. This food is acid, and the acid, on striking 

 the lining of the small intestine, causes the formation of secretin 

 in its walls. This secretin passes into the blood and stimulates the 

 pancreas and liver to release their fluids. 



Liver. — The liver is the largest gland in the body. In man, it 

 hangs just below the diaphragm, a little to the right side of the 

 body. During life, its color is deep red. It is divided into three 

 lobes, between two of which is the gall bladder, sl thin-walled sac 

 which holds the hile, a secretion of the liver. Bile is a strongly alka- 

 line fluid of golden brown color. It reaches the intestine through 

 the same opening as the pancreatic fluid. Almost one quart of 

 bile and about a pint of pancreatic fluid are passed daily into the 

 digestive canal. The color of bile is due to certain waste sub- 

 stances which come from the destruction of worn-out red cor- 

 puscles of the blood. This destruction takes place in the liver 

 (and also in the spleen, a large ductless glandlike organ near the 

 stomach.) 



Functions of Bile. — The liver is not primarily a digestive gland. 

 Bile contains no enzym.es, although it may have the power of ren- 

 dering more active the enzyme in the pancreatic fluid that acts 

 upon fats. Certain substances in the bile aid especially in the 

 absorption of fats Bile seems to be mostly a waste product from 

 the blood. It stimulates the peristaltic movements of the intes- 

 tine, thus preventing extreme constipation. It also has a slight 

 antiseptic effect in the intestine. 



The Liver a Storehouse. — Perhaps the most important func- 

 tion of the liver is the formation and storing of a material called 

 gly'cogen, or animal starch. The liver is supplied with blood from 

 two sources. Some comes from the heart, but a greater amount 

 comes directly from the walls of the stomach and intestine. The 

 liver normally contains about one fifth of all the blood in the 

 body. This blood is very rich in food materials, and from it the 

 cells of the liver take out sugars to form glycogen.^ Glycogen is 

 stored in the liver until such a time as a food is needed that can be 

 quickly oxidized; then it is changed to sugar and carried off by 



1 It is known that glycogen may be formed in the body from protein, and possibly 

 from fatty foods. 



