40 Veterinary MediciJie. 



violent exertion in a hot atmosphere. There is more or less im- 

 pairment of the vaso-motor nerve centre in the niednlla, relaxa- 

 tion of the capillary system, and flagging of the heart's action, 

 which loses its customary stimulus, by reason of the defective 

 supply of blood returned by the veins. This may become so ex- 

 treme that the patient dies by syncope. In other cases the 

 paresis is mainly shown in the vaso-motor system, and its centres 

 in the medulla, the blood is delayed in the distended capillaries 

 and veins, it becomes overcharged with carbon dioxide, the 

 heart's action is accelerated and feeble, the pulse rapid, weak 

 and fluttering, perspiration breaks out on the skin, and the tem- 

 perature is normal or subnormal. The muscular weakness, the 

 flaccid condition of the facial muscles, and general depression 

 suggest a state of collapse. This condition is not necessarily due 

 to exposure to the intensity of the sun's rays, but may come on 

 in animals subjected for a length of time to artificial heat, and 

 especially if the air is impure, and if the subject has to undergo 

 severe physical exertion. 



Treatment. In slight cases of this kind a stimulant is usually 

 desirable and ammonium carbonate in bolus or solution will 

 usually serve a good purpose. In its absence alcohol or spirits 

 of nitrous ether may be given. Digitalis is of great value in 

 sustaining the flagging action of the heart and has the advantage 

 that as digitalin it can be given hypodermically when it is im- 

 possible to give ammonia, alcohol or ether by the mouth. For 

 the same reason nitro-glycerine may be resorted to, or even 

 atropia as a vaso-motor stimulant. Active friction of the body 

 and limbs will aid circulation and indirectly stimulate the heart, 

 and in case of subnormal temperature it may be supplemented by 

 a warm bath in the smaller animals, kept up until the normal 

 temperature in the rectum has been restored. 



Thermic Fever. Sun-stroke. 



This is readily distinguished from heat exhatistio?i by the pre- 

 dominance of the hyperthermia. While in heat exhaustion 

 the temperature is usually subnormal, in sun-stroke it is exces- 

 sive, (io8°-ii3° F.). 



Causes. The inmiediate cause of sun-stroke is exposure to 

 undue heat, but this need not be the heat of the sun's rays direct. 



