2L INFLUENCE OF COLD 



IN WARM-BLOODED animals, when the body temperature 

 rises or falls a few degrees above or below the normal, 

 death occurs. When the body temperature of man rises to 

 io8.5F., he is in the inaugural state of heatstroke. When 

 the body temperature of man falls a limited number of 

 degrees below the normal, death from cold occurs. 



From the equator to the arctic region, every degree of 

 habitat temperature exists. Countless animals and men 

 live between equator and the arctic region. The wide swings 

 of the cold of winter and of the torrid heat of summer 

 profoundly affect man and the wild and domestic animals. 

 In the cold north, animals live as if within a Thermos bottle, 

 fur, fat, blubber, and oil serving as nonconductors of heat 

 from within and of the icy cold from without. 



In winter, in the temperate zones, many animals put on 

 a thicker fur arid may gain some fat. In the tropics all 

 animals are lean. No seal or mink or otter skins are found 

 in the tropics. On the contrary, in the hot climate there is 

 protection against external heat by hair, not fur. All 

 carnivores pant in the hot noon of the tropics; sweating 

 over all the body is seen only in man and the horse. 



In the heat of the day, in the tropics, a universal truce is 

 observed by lions, leopards, foxes, the antelopes, and man. 

 The external conflict occurs only in the cool of night and 

 in the early morning. Such great animals as the elephant, 

 with its critically low facility for cooling, are adapted to the 

 water and the swamps. 



Let us now turn from considering these external negative 

 adaptations to extremes of heat and cold to internal 

 adaptations, such as the size of the energy-controlling 

 organs, the blood volume, fat, and blubber. 



Theoretically, we should expect to find that the principal 

 adaptation against cold alone in the arctic would be a 



170 



