572 JNEEVOUS DISEASEh^. 



the animal is unconscious of external impressions, which fact will 

 serve to distinguish this disease from hgemoglobinuria (p. 520). 

 The temperatm'e is high. The eyes are staring, but they evidently 

 do not see, because their surface can be touched by the finger with 

 little or no wincing, on the part of the patient, from the contact. 

 Apparently, head symptoms predominate. The breathing is shallow 

 and greatly quickened, and in bad cases the pulse is so frequent 

 and weak that it is all but imperceptible. The skin may be dry, 

 or partially covered with perspiration. In severe cases, the 

 muscles over the whole sm"fac© of the body will often be in a 

 state of continued tremor. If the disease is going to run a fatal 

 course, it will usually do so within about six hours. Some horses 

 apparently get all right after an attack of sunstroke, but begin to 

 " blow " again in a few hours, in which case they generally die from 

 congestion of the lungs. When a horse which has fallen down from 

 sunstroke gets up, we may regard him as convalescent. Horses 

 that drop from smistroke do so, as a rule, after 2 or 3 o'clock in 

 the afternoon. 



CAUSES. — Although I have seen heat apoplexy during very hot 

 weather, affect horses travelling by rail in open trucks, and others 

 which were kept in ill-ventilated stalls; such cases were so few in 

 number compared to those struck down during work, that I must 

 regard fatigue as a marked accessory cause. I have never known 

 a horse get sunstroke, in the first instance, from standing in the 

 open, no matter how hot the weather may have been, provided 

 that he had the advantage of shade which, like that of a tree 

 with good foliage overhead, did not interfere with the circulation 

 of air. The Tramway Company of Calcutta (in which city cases 

 of equine sunstroke are very common in the summer), by reducing 

 during the hot months the length of their stages to distances of 

 IJ or 1^ mile, almost entirely stopped among their horses the 

 occurrence of sunstroke, which, with longer stages, had previously 

 been frequent; although they did not alter the length of the 

 daily average journey of 12 J miles. The danger of sunstroke from 

 work, either in saddle or harness, during hot weather, is greatly 

 increased by keeping the animal exposed to the direct rays of 

 the sun some time before starting. The history of many cases 

 of sunstroke which I have seen, suggests the conclusion that the 

 effect which the direct rays of the sun, when very hot, have on 

 the skin, is, at first, that of checking, instead of stimulating, 

 the excretion of perspiration, so that the animal in place of being 

 cooled down by copious evaporation from the skin, feels as does 

 a man who is in the hot stage of an attack of intermittent fever. 

 But, as I have often found when riding and driving long distances 



