620 Sunstroke and Heatstroke. 



of chronic dropsy of the ventricles or encephalitis may be easily 

 mistaken for hyperemia of the brain. 



Treatment. In slight cases it is sufficient to bring the ani- 

 mal into a large airy box where it can be quiet, and supply it 

 with easily digested food and fresh water. 



In severe cases of active hj^oeremia, prompt venesection in 

 the early stages may give very good results, cold compresses 

 applied to the head, and irrigations with cold water may bring 

 about the disappearance of the hyperemia. For internal treat- 

 ment purgatives are indicated, but overdosing with drastic 

 drugs may do harm. 



Efforts must be made to get rid of the cause of the hyper- 

 emia if possible, and animals that are liable to be affected for 

 any reason must be guarded against excitement. 



Literature. Dexler, Nervenkrankheiten cl. Pferdes, 1899, 188. 



4. Sunstroke and Heatstroke. 



Etiology. Severe nervous disturbances not rarely occur 

 in animals that are exposed to the direct rays of the sun during 

 hot weather while at work, or driven in large herds, or trans- 

 ported in open cars. But similar cases also occur without the 

 animals being exposed to the sun, the symptoms being due sim- 

 ply to the heat. Cases come under observation especially in the 

 army during drill, maneuvers, or war, in droves of pigs, sheep 

 and cattle, and during transport by rail. The occurrence of such 

 cases is comparatively rare in the temperate zones. 



The disease named by Bongartz '' Summer heaves" (Sommer- 

 dampfigkeit) belongs to this class of disease. This atfects horses sud- 

 denly that are working in the open. A proportion of the disease termed 

 "fatigue diseases" (Ermiidnngskrankheiten) also comes under this 

 heading (Bartke, Schiraraelpfennig) . 



Pathogenesis. The direct rays of the sun falling on the 

 cranium may possibly cause dilatation of the intracranial ves- 

 sels and thus cause hyperemia, but the severe disturbances 

 which are sometimes fatal within a short time can hardly he 

 caused solely in this way. The possibility must be considered 

 wdiether the sun's rays, the chemical and not the heat rays, 

 cannot be the cause of the inflammatory processes. Such a pos- 

 sibility is difficult to conceive in spite of the fact that Amato 

 believes that the nerve cells may be injured by ultra-violet rays. 

 A more probable view is that the direct rays beating upon the 

 cranium cause excessive heating of the central nervous system, 

 thus setting up paralysis of the vaso-motor and respiratory cen- 

 ters. As a result of this, there is a drop in the arterial blood 



