lS2 THE VITAL PROCESSES 



regulating the amount that shall be present in the blood, ot 

 of supplying- it to the cells as their needs require. They 

 must take it in excess of their needs, regardless of the 

 effect, at least until the organs of excretion can throw off 

 the surplus as waste. Compared with proteid, carbo- 

 hydrates, or fats, alcohol is an unmanageable substance in 

 the body. Attempting to use it as a food is as foolish as 

 trying to burn gasolene or kerosene in an ordinary wood 

 stove. It may be done to a limited extent, but is an ex- 

 ceedingly hazardous experiment. Not being adapted to 

 the body method of using materials, alcohol cannot be 

 classed as a food. 



Assimilation. Digestion, absorption, circulation, and 

 storage of foods are the processes that finally make them 

 available to the cells in the different parts of the "body. 

 There still remains another process for these materials to 

 undergo before they serve their final purposes. This last 

 process, known as assimilation, is the appropriation of 

 the food material by the cell protoplasm. In a sense the 

 storage of fat by connective tissue cells and of glycogen by 

 the liver cells is assimilation. The term is limited, how- 

 ever, to the disposition of material with reference to its 

 final use. Whether all the materials used by the cells 

 actually become a part of the protoplasm is not known. 

 It is known, however, that the cells are the places where 

 most of the oxidations of the body occur and that materials 

 taking part in these oxidations must, at least, come in 

 close contact with the protoplasm. Assimilation, then, is 

 the last event in a series of processes by which oxygen, 

 food materials, and cell protoplasm are brought into close 

 and active relations. The steps leading up to assimilation 

 are shown in Table II. 



