AMERICAN INSTITUTE. 479 



are oxidized for the production of animal heat, passing out of the 

 lungs in the form of carbonic acid. He has inferred, and that 

 inference is now adopted generally by physiologists, that all the 

 diiferent organs are supported by different properties of the food, 

 and that the appetite for diiferent and various kinds of food in 

 men and animals, is the instinctive expression of the various 

 wants of the organs of the system in some such way as the sen- 

 sation of thirst is occasioned by a deficiency of water in the blood. 



When the different component parts of the food are made to 

 correspond most perfectly to the wants of the diiferent organs for 

 the production of animal heat, of motion, of nervous influence, 

 etc., both in absolute and in relative quantity — the highest con- 

 dition of individual health results. Practically, however, this is 

 never fully attained-, a certain amount of surplusage being taken 

 into the system to furnish sufficient nutriment for some particular 

 organ, this surplus material being thrown out as waste, when in 

 excess produces obstruction of the natural drains, and thus origi- 

 nates disease. Thus horses fed on hay, or other food poor in 

 nitrogen, sweat with exercise, for they must dispose of much car- 

 bonaceous matter to obtain the necessary nitrogenous matter. Or 

 when stabled in cold weather, and prevented from exercise, if 

 highly fed on oats the nitrogenous matter must be disposed of as 

 waste through the kidneys, in order to obtain the carbonaceous 

 matter necessary for the support of animal heat, and thus urinary 

 obstructions arise. For the same reason horses thus fed feel an 

 instinctive desire for motion, or are antic, have*'great power to 

 endure exercise, and perspire very sparingly. 



As the duties of a muscle are made greater it increases in ca- 

 pacity to perform them only to a certain limit, beyond this limit 

 it succumbs, and organic disease results. The stage men increase 

 the labor of the horses as long as they eat more, and decrease it, 

 when practicable, as soon as they begin to eat less. The excre- 

 tory organs have been proved, like the muscles, to perform their 

 duties and form their secretions by a like species of cell growth, 

 and consequently are subject to tlie same law. Their organic 

 diseases probably arise also in the same way. When science has 

 fully succeeded in adapting the food of men and animals to the 



