Carhohijdraifs and Protein 119 



which may be dissolved from a feeding stuff by 

 ether. It includes, besides the true fats, wax 

 and coloring matter. Fat in the food may be 

 either stored in the body as fat, or burned to pro- 

 duce heat and energy. 



d. Carbohydrates. — This term includes two 

 groups: (1) nitrogen-free extract, such as starch, 

 sugar, gum, etc., and (2) fiber, or the woody part 

 of plants. The former are rather freely digested, 

 the latter much less so, though fulfilling the same 

 function to the extent to which they are digested. 

 The carbohydrates constitute the largest part of 

 vegetable foods. They are not stored in the ani- 

 mal body as such, but are converted into fat or 

 used (burned) to produce heat and energy. 



Since the carbohydrates and fat serve nearly 

 the same purpose in the animal economy, they 

 may, for convenience, be grouped together. Ex- 

 periments, however, have shown that fat is about 

 2% times as effective as a food as are the carbo- 

 hydrates. Hence it is customary to multiply the 

 amount of fat by 2X to reduce it to a "starch 

 equivalent" before adding it to the amount of 

 the carbohydrates. 



e. Protein. — The protein of foods, like that of 

 the animal body, is characterized by containing 

 nitrogen. It, therefore, is frequently termed 

 "nitrogenous matter." The term " albumenoids " 

 is sometimes used to designate this group, though 



