OEDINARY CONDITIONS OF HEALTH 67 



Closely connected with food and water, both being free from im- 

 purities as far as possible, is the air which the animal breathes. Even 

 for the life of the most simple organisms air is necessary, and in the 

 case of the higher organisms its withdrawal would be immediately fatal. 

 And even when supplied in sufficient quantity it is capable of carrying 

 with it deleterious constituents, some of them quite inappreciable by the 

 senses under ordinary circumstances, but deadly in their influences to 

 the animal's vital functions. The supply of a sufficient quantity of pure 

 air at a proper temperature, and at the same time the elimination of 

 stagnant air, is absolutely essential to the maintenance of health. Be- 

 cause, just as the process of nutrition implies the deposit of new material 

 in place of the worn-out structures, which, if they had been allowed to 

 accumulate in the system, would have poisoned the animal; so, on the 

 other hand, the function of respiration is associated with the introduc- 

 tion into the system of fresh vitalizing air, and excretion of effete materials 

 in a gaseous form, which, mixed with the air in the lungs, are exhaled 

 at every expiration and discharged into the external atmosphere. These 

 products of the respiratory process are poisonous, and if, owing to the 

 absence of any means of escape from the building in which an animal 

 is kept, they were permitted to accumulate, they would soon render the 

 air contained therein effete and incapable of maintaining life and health. 

 So it appears that food, water, and air, in proper quantity, and, so far 

 as possible, in a state of purity, are the three primary conditions for the 

 healthy environment. 



It must be evident that the conditions above referred to are essentially 

 concerned with the functions of organic life, and for the purpose of keep- 

 ing a horse in the state of usefulness it may be further necessary that 

 certain special organs should receive particular attention. The animal 

 is required for purposes of locomotion. It is, therefore, indispensable 

 that the feet should be kept in perfect condition; in other words, they 

 cannot be left, as other parts of the organism may, to be maintained in 

 a normal state under the influence of the ordinary reparative processes, 

 because in domestication they are subjected to an excessive degree of 

 wear and tear, from which in a state of nature they would be exempt. 



The feet are protected by a covering of dense, but elastic, horny 

 substance, which grows in proportion to the amount of wear which takes 

 place under natural conditions, when the animal's movements are under 

 its own control. In domestication, however, the experiment, which has 

 been repeatedly tried, of working horses without some additional protec- 

 tion to the hoof has invariably failed, and the early practice of protect- 

 ing the soles of the feet, or some portion of them, with iron plates or 



