528 THE POPULAR SCIENCE MONTHLY 



the Kegro than for the white man. "With the white skin we have the 

 phenomenon of sunburn^ with its resultant irritation of the nerve-end- 

 ings and hyperemia of the peripheral tissues, and this will cause a rise 

 which, apparently, just about offsets the rise in the pigmented brown 

 skin due to the sunlight. To determine definitely the decided difference 

 brought about by the color of the subjects, it was decided to use experi- 

 mental animals which would show great contrasts; and white, gray 

 and black rabbits gave the data sought. I will select one experiment. 

 When exposed side by side to the sun, the black rabbit reached a maxi- 

 mum subcutaneous temperature 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 and then died; the white rabbit a final tempera- 

 ture of 45°. 7 and when put in the shade it recovered, although much 

 exhausted. ISTone 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. 



These experiments bring us to the conclusion that, all other things 

 being equal, the Negro will suffer more from the heat effects of the sun 

 than the lighter-skinned races, and all of the work tends to show that 

 the rays of greater refrangibility in the violet and ultraviolet portions 

 of the spectrum are not the important factors, except in so far as they 

 cause sunburn and subsequent excessive pigmentation. However, pro- 

 tection from these rays is easily accomplished and has been accom- 

 plished so long as man has worn clothes. These experiments also show 

 that the whiter the clothing the better it is adapted for protection 

 against sunlight and that even in the tropics, if care is taken to seek 

 the shade, no untoward effects can be observed. Indeed, Major W. P. 

 Chamberlain, United States Army Medical Corps, who investigated the 

 systolic blood pressure of a large number of residents in the Philippines, 

 concluded that there is no progressive tendency for the pressure to in- 

 crease or to decrease with a continued tropical residence covering 

 periods of over three years, beyond which length of time his observa- 

 tions do not extend. 



Prom all of our present studies it would seem legitimate to draw 

 the conclusion that a climate such as we have in the Philippines, where 

 we are surrounded by the sea which modifies the extreme of tempera- 

 tures and where we have such a large proportion of cloud, is not by any 

 means deleterious to the white man if he takes ordinary precautions 

 which are not as elaborate as those he would take in a northern climate 

 to keep out the cold. In the Philippines the nights are rarely too hot 

 for comfort ; they may even be quite cool. 



The actual number of hours of insolation per year on the earth's 

 surface, were the sky always clear, is greatest at the equator and dimin- 

 ishes toward the poles, the ratio between 0° and 45° being 1.83 to 1.34, 



