CAUSES OF DISEASE. 2l 



bad, disease is apt to assume a pyaemic character, and an 

 ordinary inflammation may lead to the formation of multiple 

 abscesses, purulent infiltrations, or even gangrene. 



Wo7^k — over-exertion — by its debilitating effects, tends to in- 

 duce disease : for example, we have congestion and apoplexy 

 of the lungs, as well as laminitis, myositis, and spasm of the 

 diaphragm, from severe exertion, especially when a horse is 

 not in condition ; and from the more continued over-work, as 

 seen in cart-horses, stiffness of the joints and back, unthriftiness, 

 a tendency to and actual development of diabetes, and its 

 sequelce, farcy and glanders. 



Exercise is beneficial to all animals, but when in degree or 

 continuance it exceeds what the strength can bear or rest 

 can recruit, the animal functions are exhausted and lose their 

 balance, muscular tone is impaired, nervous excitability takes 

 the place of strength, the circulation fails, congestions ensue, 

 the blood is not properly purified, and the various organs are 

 on the brink of disease. Hence it is that animals which do 

 not actually become diseased from over-exertion are more 

 j)rone to succumb to the influence of any epizootic that might 

 prevail at the time. 



Want of exercise is a frequent cause of disease ; the muscular 

 system, and with it the circulation of the blood, is the first to 

 suffer, the movements become sluggish, sweats break out upon 

 the least exertion, there is want of condition, in horse phrase, 

 swelled legs, grease ; the respiration being but little exercised, 

 the task of decarbonizing the blood falls upon the liver, hence 

 the accumulation of fat and the occurrence of derangements of 

 that organ. 



Heat and cold are very prevalent causes, and act as follows : — 

 Heat relaxes the whole system ; under its influence the muscles, 

 and with them the heart and arteries, lose power and tone, 

 perspiration becomes profuse, the internal organs especially are 

 too much stimulated by blood which has lost more than usual 

 of its water, and less of its hydrocarbon. You will often find 

 that upon the sudden accession of hot weather horses suffer 

 greatly from congestive diseases. In ]\Iay and June 1867 this 

 was the case in Bradford. The weather had been cold, but very 

 suddenly it became hot, and immediately numerous cases of 

 congestive hepatitis occurred ; in other seasons we had to contend 



