FOODS. 



137 



Disposition of Food. The proteid principles of the food, after 

 undergoing digestion and conversion into peptones, are absorbed 

 into the blood. During the act of absorption they are transformed 

 into the form of proteids characteristic of blood. After being dis- 

 tributed by the blood-stream to the tissues, they are brought into 

 relation with the living cells. The disposition made of the proteid 

 material by the bioplasm of the cell has not been definitely deter- 

 mined. According to Voit, of the proteid thus brought into contact 

 with the living tissues, only a small percentage is utilized and assimi- 

 lated for tissue repair. This he terms tissue or organ_projid. The 

 remaining large percentage circulating in the interstices of the tissues, 

 though not forming an integral part of them, is acted on directly by 

 them, merely in virtue of contact split up, oxidized, and reduced to 

 simpler compounds. This he terms circulating proteid. 



According to Pfliiger and others, this view is not tenable. Pfliiger 

 asserts that, as material changes or metabolism can only take place 

 within living cells, all the proteid must first be assimilated and organ- 

 ized by the cells before it can undergo metabolic changes. Metab- 

 olism by contact action is denied, and the division of proteids into 

 organ and circulating proteid is not justifiable. 



In the process of metabolism the proteid suffers disintegration, giv- 

 ing rise through oxidation to some carbon-holding compound, possibly 

 fat, and to some nitrogen-holding compounds, which eventually give 

 rise to urea. The intermediate stages, though not definitely known, are 

 possibly represented by glycin, creatin, ammonium carbamate, etc. 

 The disintegration of the proteids is attended by the disengagement of 

 heat, thus contributing to the general store of the energy of the body. 



The fat principles, after digestion, are absorbed by the lymphatic 

 vessels ancTdischarged by the thoracic ducj'/nto the blood, from which 

 they rapidly disappear./ Though it is possible that a portion of the 

 fat enters directly into the formation of the living material, it is gener- 

 ally believed that it is at once oxidized and reduced to carbon dioxid 

 and water with the liberation of energy .// The natural supposition 

 that a portion of the ingested fat was directly stored up in the cells of 

 the areolar connective tissue, thus giving rise to adipose tissue, has 

 been a subject of much controversy, though modern experimentation 

 renders this very probable./^ The body-fat, under physiologic con- 

 ditions, is also a product of the metabolic activity of connective-tissue 

 cells and is a derivative of both proteids and carbohydrates./^ 



Tho^carJj^lLydrate principles, after digestion, are^aBsbrbed into 

 the blood as dextrose^ This compound is tfren stojed up in thejjyer 

 and muscles as gly^ggn. // The intermediate stages which glycogen 

 passes through before it is reduced to carbon dioxid and water are 

 only imperfectly known. Though a large part of the carbohydrate 

 material is at once oxidized, it is now well established that another 



