101 



In order to determine the effect of the sun's heat rays in 

 Alanila, Aron made a number of experiments, some of vvhicn are 

 quoted below. 



One thermometer was placed in the rectum of a dead dog, 

 and another under its skin, and the body suspended in the sun. 

 Ihe thermometer placed under the skin very soon registered a 

 temperature of 46" C, while the one in the rectum showed a 

 gradual rise due to absorption of heat. A living body absorbs 

 lieat in the same way, but a rise in the body temperature is pre- 

 vented by the physiological mechanism for increasing the loss of 

 heat. 



A dog kept exposed to tropical sunshine soon suffers from 

 acute discomlort, and its rectal temperature is found to rise from 

 38° C to 39''C. ; a thermometer placed under its skin, however, 

 shows a rise to 40''C. or higher. Rabbits placed under similar 

 conditions show a greater rise of temperature, the thermometer 

 placed under the skin recording as much as 46° C, but when these 

 temperatures are reached the animals soon die. 



Ihe most instructive experiments were those conducted on 

 monkeys {Macaciis philip., Geoff. J. When a strong and healthy 

 monkey is placed, so that it is continuously exposed to the sun- 

 shine, its temperature rapidly rises, and seventy to eighty min- 

 utes' exposure, even between 8 and 9 a. m. in iJecember or Jan- 

 uary, is sufficient to kill it. If protected from the direct rays of 

 the sun, it can be kept in the same place for any length of time 

 without suffering any injury. 



Normally the rectal temperature of the monkey is 0.5° to PC. 

 higher than its subcutaneous temperature. When exposed to the 

 sun's rays the body temperature rapidly rises, but the subcutan- 

 eous temperature is always 1° to 2^C. above that of the rectum. 

 The immediate effect of shaving a monkey is to reduce its tem- 

 perature generally, but the effect is more marked on the subcu- 

 taneous temperature. When shaved monkeys were exposed to 

 direct rays of the sun, the rise in temperature and subsequent 

 death took place more rapidly than in similar animals whose hair 

 had not been removed. 



That the animals exposed to the sun's rays died as a direct 

 result of hyperpyrexia is shown by the following experiments, 

 ^lonkeys were exposed to the sun's rays as in the previous ex- 

 periments, but by means of fans a strong current of air was di- 

 rected on to the animal's body. In spite of several hours' ex- 

 posure under these conditions the rise in body temperature was 

 only slight, and the animals remained healthy. A control animal 

 exposed within a few yards of the first one, but not artificially 

 cooled, died of hyperpyrexia in fifty-eight minutes. 



In another experiment the body of a monkey was placed in a 

 wooden box with perforated walls, which was again placed in- 

 side a larger one, leaving an air space between the two, so that 



