RELATIONS OF COLD, HEAT, ETC., TO FOOD 6i 



have been unable to notice any marked good arising from 

 a change of food, unless when the new article of diet 

 contained elements of nutrition deficient in the other. 



Salt is the only necessary food that is not supplied in 

 sufficient quantity by the grain and grass consumed by 

 the animal. A moderate excess of it can, in nowise, prove 

 injurious ; for it will be speedily eliminated by the 

 kidneys, after the system has taken up sufficient for its 

 own requirements. It furnishes the elements for the 

 supply of the hydrochloric acid which is a constituent of 

 the gastric juice. It also plays a most important part in 

 the whole nutrition of the body. " It was demonstrated 

 by Boussingault, that when, of two sets of oxen, one was 

 allowed the unrestricted use of salt, whilst the other was 

 as far as possible deprived of its use, a marked contrast 

 was observable in the course of a few weeks between them, 

 and manifestly to the advantage of the former. The 

 desire for common salt on the part of animals and man is 

 extremely powerful, leading the former, especially if they 

 be vegetable feeders, to traverse great distances to reach 

 saline deposits." {Carpenter.) 



Relations of Cold, Heat, and Clothing to Food.— 

 When the temperature of the surrounding air falls much 

 below its normal degree, a proportionate increase of starch 

 and fat, to keep up the natural temperature of the body, 

 should be made to the food of the animal, if it be unsupplied 

 with w\arm clothing, which, by preventing radiation, 

 supplements the action of the fatty layer which lies 

 immediately underneath the skin. Hence a judicious 

 addition of clothing may be practically regarded as an 

 addition to the food; so that, when it cannot be made, 



