1890.] PUBLIC DOCUMENT — No. 4. 225 



So far as the proportion of proteine, fat and carbohydrates 

 is concerned, it would seem quite well suited to such animals ; 

 but feeding it would not give good results, because to get 

 enough of these ingredients the animal must consume too 

 much water. 



The substances (other than ash), then, in foods which are 

 of value for animal nutrition, may be reduced to classes 

 similar to those found in the body; viz., proteine and fat, 

 and one other already mentioned, — carbohydrates. To these 

 three the name nutrients has been sjiven. In tables giving 

 the composition of foods you will usually find at least four 

 columns, headed, respectively, ])roteine, fat, nitrogen-free 

 extract and crude fibre. The first two yon can understand ; 

 the last two both belong to the same class, — viz., carbo- 

 hijdrates. 



Now, each of these three nutrients has distinct functions 

 in the body, just as nitrogen, potash and phosphoric acid 

 each has its distinct functions in the plant ; and, just as the 

 latter must be supplied to the plant in certain suitable pro- 

 portions and quantities for the best results, so these nutrients 

 must be given to the animal in certain proportions and 

 amounts ; and, further, just as the requirements of two 

 plants dififer, so the requirements of animals difler ; and, 

 more, the requirements of the same animal are difierent at 

 difierent ages. 



Just what the functions of the difierent nutrients in the 

 body may be is not in all cases known, and it is not im- 

 portant for our present purpose ; but much is known, 

 and the leading points believed to be made out — mostly 

 as the result of German work — I will briefiy state. The 

 proteine of the food may produce fiesh (lean meat), fat, 

 heat or force. The fat may be stored up in the body as 

 such ; it may produce heat, or possibly force. The carbo- 

 hydrates may produce heat or fat, and, it is believed by 

 some, force also. 



Without dwelling longer upon this matter, I want to 

 repeat that, for the most profitable feeding, it is essential to 

 give each animal daily a certain amount of each of these 

 nutrients. Between the difierent ones there must exist a 

 certain proportion. If we give an excess of one, that excess 



