CHAPTER IV 



THE FUNCTIONS OF THE LIVER 



That the liver plays an important part in the nutri- 

 tion of the body might be inferred both from the size 

 of the organ and the enormous stream of blood poured 

 into it by the portal vein; for in addition to the hepatic 

 artery, which carries blood to nourish the tissue of the 

 organ, the portal vein, which receives blood from the 

 entire digestive and absorptive tract, ' pours this great 

 stream of blood into the doorway of the liver, plainly 

 not for the benefit of that organ, but that it may effect 

 necessary changes in tiie material of which this blood 

 alone is the bearer. Three such changes appear; i.e., 

 the secretion of bile and the formation of glycogen and 

 urea. 



Bile is partly an excretion of substances to be re- 

 moved and partly a secretion of a product useful but 

 not essential to digestion. Ii is secreted at all times but, 

 in man, is stored in the gall bladder and ejected into 

 the duodenum only when needed. The quantity formed 

 in a day is from 500 to 800 c.c. The color, in man, is a 

 greenish yellow. It contains about 97 l /2 per cent water 

 and about 21/2 per cent solids of which the chief are 

 bile pigment, derived from broken-down red blood cor- 

 puscles, bile acids, taurocholate, and glycocholate of 

 soda,- fats, soaps, lecithin, a substance which occurs in 

 greatest quantity in the white matter of the nervous 

 system, and cholestcrin. 



Bile pigment is called ~bilirubin when red, and bili- 

 verdin when green. The pigments appear to be re- 



73 



