short time before the temperature of the air and the tempera- 

 ture of the ox would be alike. But as a matter of fact the tem- 

 perature of the blood never varies much from loi" in health, 

 and it makes no difference whether the air is at 30° below zero 

 or at 90° above. The temperature of the body is kept up by 

 the yJ?^^/ consumed just as that of the locomotive is by the wood 

 burned. Again the fuel consumed by a locomotive while stand- 

 ing idle is only, an amount suffcient to supply the loss of heat. 

 This is a comparitively small amount, when the same locomotive 

 is coupled to a train of loaded cars, and is started on an up 

 grade, it will be found necessary to open the drafts and in- 

 crease the consumption of fuel, in drawing this load, energy is 

 required and this is obtained from the extra fuel consumed. An 

 ox or a horse, when drawing heavy loads, must also expend more 

 energy than when standing in the stall, and to develope this 

 energy requires more food : food is to the ox \\\\-A\.fiiel is to the 

 locomotive. 



There is one other object for which we feed, namely, the 

 production of growth, under this head comes increase of live 

 weight whether in growing animals or fattening one, growth of 

 wool, or the production of milk. If an animal weighs one hun- 

 dred pounds at birth and fifteen hundred pounds when three 

 years old this gain of fourteen hundred pounds mus' come from 

 the food and water used, if a cow yields annually, six thousand 

 pounds of milk, this also must come from the food and water 

 consumed. 



The uses of food, then, are : to produce heat ; to produce 

 force, (muscular energy) ; to produce new tissue, (including in- 

 crease of live weight, growth of wool or yield of milk). 



Having noted the use to which food is put we may inquire 

 whether one part of the food is better adapted to one require- 

 ment, and another part to another requirement, or whether all 

 the digestible parts are equally effective. 



I St, what part of the food produces heat. The best author- 

 ities answer this by saying that the changes which take place 

 in all parts of the body produce heat. The contraction of a 

 muscle, the activity of the liver, etc., all liberate heat an.l hence 

 it cannot be said that one constituent of the food more than an- 

 other is the source, but that both the nitrogenous and non-nitro- 

 genous contribute toward keeping up the temperature. 



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