PROPORTION OF CARBON IN ARTICLES OF FOOD. 



507 



temperature is derived either solely from the heat-givers or 

 jointly from the heat-givers and the flesh -formers, but the car- 

 bon applied to the production of other kinds of work, vital, 

 mental, and mechanical, we regard as obtained from the flesh- 

 formers alone ; because, by an axiom in physiology, no vital 

 act can take place without a decomposition of tissue having 

 the same chemical composition as the flesh-forming nutrient 

 proximate principles. 



In applying this view to the choice of food for the horse, it 

 will be enough to recall the following particulars as to the 

 proportion of carbon in a few of the principal articles of 

 his food : 



Professor Play fair's plan, which deserves to be first con- 

 sidered, consists in making choice of an undoubted diet for the 

 horse one while at rest, another while under exertion and 

 then comparing these by means of the standard supplied in the 

 doctrine of the " conservation of energy " with each other, and 

 the amount of labour that the horse is known to accomplish. 



On the authority of the late Professor Dick, Professor Play- 

 fair makes the following statement: "A horse may be kept 





