MANUAL OF OATTLE-FEEDIKG. 210 



muscular exertion does not necessarily imply an increased 

 decomposition of the source of the power and because 

 secondary effects may come in to vitiate our conclusions. 

 "We must, then, seek for further evidence. 



Force Value of Nutrients.— Much vahiable evidence 

 concerning the question under discussion may be gained 

 by a consideration of the force vahie of food, and the ad- 

 vocates of the non-nitrogenous matter as the source of 

 muscularpower rely largely, in support of their views, upon 

 calculations of this sort, L e., calculations of the amount of 

 force that can be liberated by the conversion of a certain 

 amount of albuminoids, fat or carbhydrates into the final 

 products of their oxidation in the body, viz., carbonic acid, 

 water and urea. 



The basis of this calculation is the amount of heat which 

 the several nutrients evolve when burned. For example : 

 one gramme of albumin, when completely burned, evolves 

 a certain definite amount of heat; the lU'ea from one 

 gramme of albumin likewise evolves a definite, though 

 smaller, amount when bmiied. Sul)tracting the lattcir 

 from the former, we have left the amount of heat whicli 

 would be produced by the conversion of one gramme oi 

 albumin into carbonic acid, watei*, and xu'oa, and tliis 

 amount, by a well-known law of physics, is equivalent to a 

 certain fixed amount of mechanical motion — that is, 

 work. 



Having once obtained, then, accurate data as to the heat 

 of combustion of each substance involved, and knowing 

 the amount of work performed, M^e are able to ehtimatc 

 whether, in a given case, the amount of any hubbtanc»e or 

 class of substances dentroyed during the experiment m 

 sufficient to set free the amount of force a<itually exerted 

 The earliest and best known experiment of this sort m 



