224 THE HUMAN MECHANISM 



litter of eight were killed and the total amount of fat in 

 their bodies determined. The other four pigs were fattened 

 for a time, then killed, and the fat in their bodies eventually 

 determined. Assuming that the second set of four pigs 

 originally had the same quantity of fat as the first four, the 

 difference between the two quantities of fat found would 

 give the quantity of fat the last four had stored up. Mean- 

 time, strict account had been kept of the fat supplied in the 

 food of the last four, and it was shown that for every 100 

 parts of fat fed to them these pigs had laid up 472 parts of 

 fat. They had evidently manufactured fat from some substance 

 other than the fat in their food. 



9. Fats can be stored from fats and carbohydrates in food. 

 There is no doubt that fat may be both stored away and 

 manufactured from the fats in the food. There is also no 

 doubt that large quantities of fat may be and often are 

 manufactured and stored from the carbohydrates (sugars, 

 starches, etc.) of the food; so that, while there is some 

 truth in the idea that one may get fat by eating fat, it is 

 equally true that we can get fat by eating other foods. 



10. Are proteins a source of fat? Whether fats are nor- 

 mally made in the body from proteins is a more difficult 

 question. There is no undisputed case on record of such 

 manufacture and storage ; and while the facts do not yet 

 justify us in denying the possibility, it is very doubtful 

 whether such transformation takes place to any great ex- 

 tent, and it is possible that in the mammalian body it does 

 not normally occur at all. 



Fats, then, are manufactured readily from fats and car- 

 bohydrates and sparingly, if at all, from proteins. Their 

 disappearance during starvation, when they are drawn upon 

 to supply power and heat for the body, shows that they 

 serve as a true reserve food material. They are a kind 

 of food capital or hoard, saved and laid up by the body 

 against a rainy day. 



