CHAPTER VIII. 

 FOODS. 



The functional activity of every organ and tissue of the body is 

 accompanied by a more or less active disintegration of the living 

 material, the bioplasm, of which it is composed. The complex and 

 highly unstable molecules of this living material are continually 

 undergoing disruption and falling into less complex and more stable 

 compounds; these, through oxidative processes, are eventually re- 

 duced through a series of descending chemic stages to a small number 

 of simpler compounds which, being of no further value to the organ- 

 ism, are eliminated by the various eliminating or excretory organs, 

 the lungs, skin, kidney, liver. ^Among these excreted compounds the 

 more important are urea, uric acid, and carbon dioxioV^ Many other 

 compounds, organic as well as inorganic, are also eliminated from, 

 the body in the various excretions, though they are present in but 

 small amounts. Coincident with this disintegration of living material 

 there is a transformation of its potential into kinetic energy, which 

 manifests itself for the most part as heat and mechanic motion. 



In order that the organs and tissues may continue in the per- 

 formance of their functions, it is essential that they be supplied with 

 nutritive materials similar to those which enter into their own com- 

 position: viz., proteids, fat, carbohydrates, water, and inorganic 

 salts. These compounds, though originally derived from the food, 

 are immediately derived from the blood as it flows through the capil- 

 lary blood-vessels. The blood is therefore to be regarded as a_resr- 

 voir of nutritive material in a condition to be absorbed and trans- 

 formed into utilizable and living material. Inasmuch as the mate- 

 rials lost to the body daily, through disintegration and oxidation, 

 though considerable, are supplied by the blood, it is evident that this 

 fluid would diminish rapidly in volume, with a corresponding decline 

 in functional activity, were it not restored by the introduction into 

 the body of new material in the food. With the diminution of the 

 volume of the blood and an insufficient supply to the tissues, there 

 arise the sensations of hunger and thirst, which lead to the consump- 

 tion of food and the subsequent restoration of the physiologic condi- 

 tion of the tissues. /These two sensations are also partially dependent 

 on the empty condition of the stomach and the dryness of the mucous 

 membrane of the mouth and throat, jj 



