82 ELEMENTARY PHYSIOLOGY. 



They are very numerous, covering the intestinal 

 membrane as with a coat of hair. The word signi- 

 fies hair-like bodies. These villi, which dip into the 

 liquid contents of the alimentary canal, are not 

 themselves the absorbents; but they contain small 

 rootlets which take up the food and start it on the 

 way toward the heart. 



In each villus (singular of villi) there 

 TWO classes are two kinds of little workers gather- 



of Absorbents . _... . . , f . -, ,., 



in the villi. ing up different kinds of food particles 

 from the liquid mass in the intestines. 

 These are known as blood-vessels and lacteals, and 

 are the starting points of two different routes by 

 which the food is carried to the heart and into the 

 circulation. 



The blood-vessels or veins are arranged 

 veins in the aroun( j the center of the villus, form- 

 ing a sort of net- work. They all unite 

 and form one large vein, plainly shown here on the 

 Aid (20). This vein is called the portal vein. 



portal The route by which the blood and food 



circulation, carried by the veins reach the heart 

 constitutes the portal circulation, which we will 

 now consider a little more fully. The portal vein 

 (20) empties its contents into the liver (33) from 

 below, and divides and subdivides, finally forming 

 the capillaries of the liver. The structure of the 

 liver is shown by the Aid at (18) (under microscopic 

 structure of the textures). In the liver an important 



