182 THE HORSE. 



a portion of the air, impregnated with the carbon, and rendered poisonous 

 in its turn, is squeezed out. Presently the chest expands ai^ain, and the 

 lung-s expand with it, and fresh pure air is admitted, which is shortly 

 pressed out again, empoisoned by the carbon of the blood ; and these 

 alternate expansions and contractions constitute the act of breathing. 



When the animal powerfully exerts himself, a more ample supply of 

 pure blood is required to sustain the energies of life, and the action of the 

 muscles forces the blood more rapidly through the veins ; hence the quick 

 and deep breathing of a horse at speed ; hence the necessity of a capa- 

 cious chest, in order to yield an adequate supply, and the connexion of this 

 capacity of the chest with the speed and the endurance of the horse ; hence 

 the wonderful relief which the mere loosening of the girths affords to a horse 

 blown and distressed, enabling the chest to expand and to contract to a 

 greater extent, in order to yield more purified blood ; and hence the relief af- 

 forded by even a short period of rest, during which this expenditure is not 

 required, and the almost exhausted energies of these organs have time to 

 recover. ' Hence, likewise, appears the necessity of an ample chest for the 

 accumulation of much flesh and fat; for, if a considerable portion of the 

 blood be employed in the growth of the animal, and it be thus rapidly 

 changed, there must be provision for its rapid purification, and that can 

 only be effected by the increased bulk of the lungs, and the corresponding 

 largeness of the chest to contain them. 



Tne diseases of these organs are among the most serious to which the 

 horse is exposed, and interfere most with his usefulness. A glandered 

 horse may be, and often is too long employed in our service ; a blind 

 horse, under the guidance of the driver, may employ both his strength and 

 his speed for our benefit; but a horse with diseased lungs is worth nothing 

 at all, and hence some of the difficulties with which the veterinary practi- 

 tioner has to struggle. A surgeon who practises on the human body will 

 obtain the gratitude of his patient, if he so far removes a severe affection as 

 to enable him to live on with a certain degree of comfort, although his 

 activity and his power of exertion may be considerably impaired ; but 

 the veterinary surgeon is thought to have done nothing, unless he renders 

 the animal perfectly sound — unless, in fact, he does that which it is abso- 

 lutely impossible to accomplish. 



INFLAMMATION OF THE LUNGS. 



There is no animal among all those w^hom we have subdued that, previous 

 to his breaking in, is so free from disease as the horse; there is no 

 animal which, after he has been enlisted in our service, is so liable to disease, 

 and especially of the lungs. How do we account for this ? Few things 

 can be more injurious to the delicate membrane that lines the cells of the 

 lungs, than the sudden change from heat to cold, to which, under the 

 usual stable management, the horse is subject. In the spring and autumn,^ 

 the temperature or heat of most stables is several degrees higher than that of 

 the open air ; in winter it is frequently more than thirty degrees. Tlie ne- 

 cessary effect of this must be to weaken and exhaust the energies of the 

 parts most exposed to the influence of these changes, and they are the 

 lungs. It is, however, not only heated but empoisoned air that the 

 horse respires; — composed of his own contaminated breath, and of 

 vapours from his dung, and particularly from his urine, strongly impreg- 

 nated witfi hartshorn, painful to the eyes and irritating to the chest. 



There is likewise an intim.ile connexion between the lungs and the func- 

 tions of the skin. When the insensible perspiration is suddenly stopped, 



