ANIMAL HEAT 161 



ing facts are suggestive: A rabbit paralyzed by large doses 

 of curare is no longer able to maintain its temperature. It 

 behaves like a cold-blooded animal. The same result is obtained 

 by section of all the motor nerves or, what is the equivalent, 

 section of the cord in the cervical region. In a normal fasting 

 guinea-pig the body temperature remained constant while 

 raising the outside temperature from to 35 C., but the 

 oxidations as determined by the calorimeter were twice as 

 great at the lower temperature. The regulation of heat pro- 

 duction by the outside cold is a chemical regulation. By 

 voluntary muscular contractions man possesses a certain mean 

 of counteracting the effect of outside cold. Another method 

 of increasing heat production lies in an increase in the food 

 ingested, since most of the material of the daily diet is promptly 

 burned by the body. Thermogenesis in this case is not strictly 

 voluntary. The appetite stimulated either by exercise or by 

 outside cold leads to an increase in the food eaten. 



Thermolysis is brought about by the following agencies: 



1. Through the various excreta, urine, feces, etc., which 

 are at the temperature of the body when voided. This loss 

 equals 1.8 per cent, of the total. 



2. Through expired air in the warming of the air and in 

 the vaporization of water from the lungs. This loss equals 

 10.7 per cent, of the total. 



3. By evaporation from the skin, equal to about 14.5 per 

 cent, of the total. 



4. By radiation and conduction from the skin. By this 

 means 73 per cent, of the total heat of the body is lost. Loss 

 of heat in man is controlled chiefly by varying the amount 

 of clothing which determines the amount of evaporation and 

 radiation from the skin. A more important means of control- 

 ling heat loss exists in the reflex control through sweat nerves 

 and vasomotor nerves. This method is a physical regulation. 

 Warm weather induces the secretion of sweat through a reflex 

 stimulation of the nerves supplying sweat glands. The greater 

 quantity of water for evaporation from the skin the greater 

 will be the heat loss. A similar reflex mechanism brings about 

 a vasodilatation of the skin vessels. Cold, on the other hand, 

 causes a vasoconstriction. Finally, the acceleration of respira- 

 tion which occurs in some animals, especially in dogs, with 



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