ON WHAT THE FITNESS OF FOOD DEPENDS. 483 



such and such animal bodies and the constituent elements of 

 the kinds of food on which they thrive. But if any one thinks 

 it certain that he has found out a new kind of food for the 

 perfect nourishment of a horse, an ox, or a sheep, merely 

 because he has become acquainted with an article which con- 

 tains all the elements known to exist in the chemical constitu- 

 tion of any one of these animals, he has failed to catch up the 

 true spirit of physiology, and runs to a far too hasty conclu- 

 sion. He has reached a strong probability, but nothing 

 more. He must be content to try his conclusion by successive 

 cautious experiments on sufficient numbers of the animals to 

 which it is applicable. It may be that the article in question, 

 besides the requisite elements, contains some element that 

 proves injurious, or in some way or other interferes with the 

 due nutrition of the animal. The necessary elements, again, 

 may be mingled with nothing hurtful, but maybe put together 

 in too coarse a manner to permit the organs of assimilation to 

 appropriate them for the required reparation of the exhausted 

 tissues. It is, in short, to be remembered that the nutrition 

 of an animal is not a simple chemical operation, but one of 

 particular complexity; and that, in proportion to the com- 

 plexity of any such operation, the sources of failure are more 

 and more increased in number, so as to afford, in the like de- 

 gree, a widened scope for the exercise of sagacity in the several 

 steps required to be taken. 



Besides knowing what kinds of food suffice to nourish the 

 horse, the ox, the sheep, the consideration is required of the 

 particular circumstances under which the animal to be nour- 

 ished is placed at the time. The race-horse, the hunter, the 

 roadster, the coach-horse, the dray-horse, the farm -horse, 

 demand each a special mode of feeding and management ; and 

 to carry such management to its utmost degree of perfection, 

 the knowledge becomes necessary, not only of the kind of 



