DIGESTION AND ABSORPTION 



307 



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

 bile is passed daily into the digestive canal. The color of bile is 

 due to certain waste substances which come from the destruction 

 of worn-out red corpuscles of the blood. This destruction takes 

 place in the liver. 



Functions of Bile. — The action of bile is not very well known. 

 It has the very important faculty of aiding the pancreatic fluid in 

 digestion, though alone it 

 has sligh{ if any digestive 

 power. Certain substances 

 in the bile aid especially in 

 the absorption of fats. 

 Bile seems to be mostly a 

 waste product from the 

 blood and as such inci- 

 dentally serves to keep the 

 contents of the intestine in 

 a more or less soft condi- 

 tion, thus preventing ex- 

 treme constipation. 



The Liver a Storehouse. 

 — Perhaps the most impor- 

 tant function of the Hver is 

 the formation within it of a 

 material called glycogen, or Diagram of a bit of the wall of the small in- 

 animal starch. The liver ^^^^^^^ greatly magnifiod. a, mouths of 



intestinal glands; o, villus cut lengthwise 

 IS supplied by blood from to show blood vessels and lacteal (in center) ; 



two sources. The greater ': ^.^f^^! sending branches to other villi; 



® , I, intestinal glands; tn, artery; v, vein; 



amount of blood received l, t, muscular coats of intestine wall. 



by the liver comes directly 



from the walls of the stomach and intestine to this organ. It 

 normafly 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 



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

 from fatty foods. 



