8 August, 1907.] J'Ucmcnts of Animal P/iysiology. 467 



The Variations of Heat. — The capability of regulating the tempera- 

 ture within narrow limits varies with different species. In the non-sweating 

 animals and paiticularly with those that have a thick woolly covering 

 (sheep) or a thick layer of skin-fat (pig), exertion in warm weather may 

 readily bring about an accumulation of heat in the body which is often 

 dangerous. Man and the horse owing to their rich supply of sweat glands 

 are far better off in this respect than cattle. The wonderful endurance of 

 the horse is in large measure due to this provision; it can keep on trotting 

 without any marked rise of temperature whereas a bull after a few rushes 

 mounts up to fever-heat and shows distressed respiration. This same 

 provision is also responsible for the fact that man and the horse can stand 

 temperatures much higher than that of the body, provided the air be dry 

 and in motion. Under these conditions a man can readily stand a tempera- 

 ture above the boiling point of water. If however the air be warm, moist 

 and calm, thus giving little play to conduction and evaporation, violent 

 exertion in all animals wil] bring about a rise in temperature which is 

 often serious and occasionally fatal. 



When an animal is exposed to cold so extreme that it cannot be com- 

 bated by increased heat formation and decreased heat loss, the temperature 

 of the bodv sinks, the animal falls into a deep sleep, and eventuallv dies. 

 Recovery can occur bv artificial warming if the temperature has not fallen 

 below 50 degrees F. If a part of the body be frozen, gangrene generally 

 results and the frozen part is lost. As tO' the highest internal temperature 

 which the animal body can stand the limit usually given is; 113 degrees 

 F. The highest authentic case in man followed by recovery was in degrees 

 F., which occurred in rheumatic fever. 



The temperature of an animal varies slightlv with age being higher 

 in extreme youth and also, according to some observers., in extreme old age. 

 Starvation tends to lower temperature, and the taking of food tends to 

 elevate it. In all diseased conditions where there is true inflammation a 

 rise of temperature is observed. 



In conclusion a few points mav be noticed some of which have a prac- 

 tical interest. 



Cold is not well borne l)y animals that are thin or by animals that 

 are small in size. In this latter case the surface of the body is much 

 greater compared with the weight than it is in larger animals. 



Clipping or shearing throws a great strain on the heat regulating 

 mechanism particularly in moist, cold weather. Animals may actually 

 show a higher temperature after clipping than befoTe — this means a' very 

 great increase in the heat production. 



Animals exposed to cold eat more food than if not so exposed, as part 

 of the food is used in the body for heat formation. 



Animals that sweat feebly, and particularly those with heavy coats or 

 with much skin fat, are very liable to develop a high temperature; they 

 invariably do so if over exerted. 



Moisture in cold air aids conduction, moisture in warm air hinders 

 evaporation. 



Air that is moist and warm is specially harmful if impure through 

 defective ventilation. 



