20 FREER. 



then, it will also radiate more readily, so that heat rapidly taken 

 up on the sunny side will also rapidly be lost on the shaded one 

 and it is the balance between the two which determines the 

 ultimate degree of rise in temperature. This balance evidently 

 results against the Negro. On the other hand, with the white 

 skin we have the phenomenon of sunburn, with its resultant 

 irritation of the nerve-endings and hypersemia of the peripheral 

 tissues, and this would cause a rise which, apparently, just about 

 offsets the rise in the brown skin due to the pigmentation. 



The decidedly higher skin temperature of the Negro made it 

 of importance to investigate the behavior of animals of such 

 decided differences in color that the contrasts would show with 

 greater certainty. For this purpose 6 rabbits: 2 pure white, 

 2 gray, and 2 black, were used. These were placed in the sun, 

 side by side, with only a few centimeters between, the subcuta- 

 neous temperature being taken through a small slit in the lower 

 dorsal region. The first 3 animals remained in the sun for 

 thirty-six minutes, from 9.10 to 9.46 in the morning, at which 

 time they were returned to the shade. The white and gray 

 rabbits soon recovered from the exposure, but the black one 

 died at 12.30 in the afternoon. 



The subcutaneous temperatures rose from 38°. 6 for the white 

 and gray and 41°. 8 for the black to a final height of 41°.0, 

 42°. 8, and 44°.2 for white, gray, and black in the order named. 



In the second series the black and gray animals were strong 

 and healthy specimens, whereas the white was much weaker. 



The subcutaneous temperatures at the beginning were 38°. 0, 

 37°. 85, and 37°. 7; the exposures were for one hour and thirty 

 minutes, from 9.02 to 10.32 in the morning. The black rabbit 

 reached a maximum of 47°. 8 in thirty-one minutes and then 

 died; the gray rabbit, a final temperature of 44°. 9 in one hour 

 and twenty-six minutes, when it died; the white rabbit a final 

 temperature of 45°. 7, and when put in the shade, it recovered 

 although much exhausted.^*' 



These experiments appear conclusive. None of the animals 

 suffer from sunburn as does the white man, and it is evident 

 that the darker the coat, the greater the heat absorption and the 

 more apparent do the effects of insolation become. It appears 



" Monkeys exposed to the sun at Bagnio developed higher subcutaneous 

 temperatures than in Manila; a maximum of 54° being reached in one case 

 before death, and in another 48°. 3 before death. Rectal temperatures were 

 not taken. 



