NUTRITION AND THE CHANGES IN THE TISSUES. 375 

 THE INTER- RELATION OF THE FATS AND CARBOHYDRATES. 



It was of course long known that a proteid diet might 

 result in the fattening of an animal; also that proteids 

 might give rise to sugar. It has been an important but 

 difficult question whether the carbohydrates ever give rise 

 to fats; whether a sugary diet leads directly to the produc- 

 tion of fatty tissues. Until very recently it was almost uni- 

 versally held that the carbohydrates could not form fats in 

 the body, and that the fattening resulting from adding a 

 carbohydrate food was due merely to the saving of fats, 

 these being substituted for them. Just as on the dinner 

 table it might be possible to produce an accumulation of 

 bread by having plenty of pie. Of late, however, investi- 

 gations have been made which seem to show that carbohy- 

 drates in the body may be changed into fats and so stored. 

 Attention is here called to this claim since it is possible 

 that future observations may establish its correctness; but 

 the point remains that in spite of these claims there is much 

 evidence that fats are never the direct result of the sugars 

 or the sugars of the fats, and that there is in, no way a 

 direct causal relation between them. 



No attention has been given to the nutritive importance 

 of the water and the salts. It has not been deemed neces- 

 sary to go into detail here. Water is the general solvent of 

 the body and the medium in which the cells live, and as 

 such is absolutely indispensable. The salts, -too, are neces- 

 sary parts, frequently being directly used in the formation 

 of tissues, as in the case of bones and red corpuscles, or 

 directly serving an intermediate function in the process of 

 osmosis or solution. 



The attempt has been made in the chapter to try to pic- 

 ture the phenomena which take place in the individual liv- 

 ing cells while these cells are in growth or action. We 

 have now to determine somewhat more quantitatively the re- 

 sults of the energy so derived, the purposes of this energy, 

 especially that of the temperature of the body, and finally 

 the manner in which this temperature is maintained at a 

 steady and fixed level under normal conditions. 



