FOOD. 429 



that the respiratory food enters also, in a changed form, 

 into the composition of the blood, the former term 

 can scarcely be regarded- as distinctive. The latter, 

 which designates the office of the protein bodies in 

 furnishing material to build up the organs of the body, 

 is much to be preferred. 



1065. PROPORTIONS OF FOOD. For the 



What is said . ,,.,..,, 



of the import- economical sustenance of animals, it is of 

 Proportion of i m Pr tance tnat a proper relation of quanti- 

 thetwo kinds ty should be maintained between these two 

 varieties of food. Respiratory food alone, 

 provides no material for supplying the waste of the or- 

 ganized tissues. Plastic food, on the other hand, is es- 

 pecially adapted to this end, but is poor fuel for sus- 

 taining the heat of the body. Yet in lack of other 

 material, it is diverted from its natural use, and thus 

 appropriated at great economical disadvantage. 



1066. Nature teaches us something on 



What does na- 

 ture teach on this subject, in the composition of milk 

 this subject? am j tnose g ra i ns which constitute the 



principal food of man. It will be found by reference 

 to the table in the Appendix, that the quantity of 

 respiratory matter in these substances, is from three to 

 six times greater than that of the plastic material. 

 When the object is to fatten an animal, the proportion 

 of respiratory matter may be considerably increased 

 by the use of potatoes, rice, and other farinaceous food. 

 Being furnished in excess, it accumulates in the body 

 in the form of fat. Working animals, on the other 

 hand, must be supplied with nitrogenous or plastic 



