174 



LIFE PROCESSES OF MAN 



The digested proteins and sugars pass directly into blood 

 vessels which lead to the liver. In the liver, these blood 

 vessels unite to form the portal (por'tal) vein, which is 

 divided into minute branches that distribute the blood to 

 the cells of the liver. As the blood thus passes among the 

 liver cells, the larger part of the sugar is changed into 

 glycogen (gli'ko-jen), an animal starch, and stored tempo- 

 rarily in the liver cells. This stored-up starch is given 



out gradually and changed 



urn 



/esse! 



lph or 



vessels 



Wall 

 \of 



Irtres+ine 



back into sugar, which re- 

 sults in keeping a uniform 

 amount of sugar in the 

 blood. 



The fats pass into certain 

 distinct vessels, lacteah (lak'- 

 te-als), which in turn open 

 into larger ones. Eventu- 

 ally these vessels unite to 

 form a large duct — the 

 thoracic — which empties into 

 one of the veins near the 

 heart. The food is now in 

 the blood stream and is 

 carried to the individual 

 cells of the body. Each 

 cell takes the kind of food which it needs and bv a series 

 of changes, as yet only partly known, makes the food 

 into living protoplasm. 



The indigestible part of the food is not absorbed, but 

 continues to move through the small intestine into the 

 large intestine, and on through the rectum. During this 

 progress much moisture is absorbed, especially in the large 

 intestine, which leaves the " undissolved food " harder 

 and harder. The regular removal of the unused part of 



Figure 189. — Diagram of Villus. 



