xn, B, 1 Shaklee: Experimental Acclimatization 17 



monkey resting on the roof in a hot sun, the sweating decreased 

 and the body temperature began to rise almost immediately 

 and soon reached such a dangerous height that it was deemed 

 necessary to remove the animal to the shade to prevent prostra- 

 tion and death from heat stroke. A like dose of atropin pro- 

 duced no change in the body temperature of monkeys in the 

 shade. In fact, after such doses given to monkeys in the shade, 

 I saw no marked symptoms of any sort. These experiments 

 with atropin strongly support the inference already drawn that 

 the difference in the amount of perspiring in acclimatized and 

 unacclimatized monkeys is enough to account for the fact that 

 unacclimatized monkeys die of heat stroke under conditions 

 that do not raise the temperatures of acclimatized monkeys above 

 the normal. 



Thirdly, it was observe that when the relative humidity of 

 the atmosphere was much higher the tendency to rise of the 

 body temperature of an acclimatized monkey in the sun on the 

 roof was markedly greater. Since an increase in relative hu- 

 midity has a tendency to raise the body temperature by diminish- 

 ing the rate of evaporation of water from the surfaces of the 

 body, this supports the inference that it was the sweating of 

 the acclimatized monkey which caused its temperature to re- 

 main normal under circumstances that killed the unacclimatized 

 monkey with heat stroke. 



Fourthly, attempts to acclimatize rabbits failed signally. The 

 methods that had proved successful in acclimatization of monkeys 

 were tried with rabbits. Rabbits were carefully exposed to the 

 sun day after day, being removed to the shade as soon as they 

 seemed approaching danger of heat prostration. The rabbits 

 remained in good condition, but no increase in resistance to 

 the action of the heat could be detected. On succeeding days 

 the period of exposure could not be appreciably lengthened with 

 safety to the animal. Rabbits that had been submitted to this 

 process of acclimatization for many days in succession were 

 exposed alongside of rabbits that had not been previously ex- 

 posed. I was not able to detect any difference in the powers 

 of resistance between the rabbits that had been submitted to 

 the acclimatizing process and those that had not been previously 

 exposed. The rabbits that had been submitted became prostrated 

 as soon after insolation as the unexposed and died as soon. 

 Rabbits are not known to perspire. Here there was no per- 

 spiring to be increased, and no acclimatization resulted. This 

 fact, therefore, also gives indirectly some support to the infer- 



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