FUNCTIONS OF THE NUTRIENTS 161 



carbohydrates furnish much the larger part of that which 

 is needed for this purpose. 



234. Fats from carbohydrates. — Contrary to views 

 that held for a time* it is now well established that the 

 animal fats may have their source in the carbohydrates; 

 in other words, starch and sugar and related bodies may 

 serve the main purpose in feeding animals for fattening. 

 In many experiments, notably those with swine, the pro- 

 tein and fat of the food have fallen far short of account- 

 ing for the fat in the body increase, sometimes much the 

 greater part of the latter having no possible source other 

 than the carbohydrates. A practical expression of this 

 general conclusion concerning the fat-forming function 

 of carbohydrates is seen in the well-recognized value of 

 corn meal as a fattening food, a feeding-stuff nearly seven- 

 tenths of which consists of starch and its allies. Experi- 

 ments with milch cows leave no doubt that milk-fat may 

 also be derived from carbohydrates. These more recent 

 views tend to magnify the importance of the carbo- 

 hydrates as nutrients. 



FUNCTIONS OF THE FATS AND OILS 



235. Fats and carbohydrates similar in function. — 



So far as is at present known, the possible uses of the 

 food fats and oils and of the carbohydrates are similar. 

 In other words, both may serve as fuel and both may be 

 a source of animal fat. The differences are that the supply 

 of carbohydrates is much the larger, and the fuel value 

 of a unit weight of fats is over twice as great as that 

 of starch and sugar. Moreover, it seems possible for a 

 food fat to become deposited as such in the animal or 

 in milk without essentia} change, whereas fat formation 



