126 



ARON. 



must be for this reason that the brown skin, while absorbing more heat, 

 is found to have lower temperatures than the white skin under similar 

 conditions. The regulatory apparatus of the brown is more sensitive 

 and Avorks more promptly and successfully. This statement deserves at- 

 tention, because the experiments on dead skin only served to convey a 

 wrong impression of the behavior of colored and white skin when exposed 

 to the sun's rays. 



Table IX. — Comparative increase in temperature of white skin and broum skin 

 when exposed to sun, as obtained in the three foregoing experiments. 



Time in minutes. 



Temperature of cheek. 



In sun. 



In 

 shade. 



I. 



n. 



1 

 III. 



White. 



Brown. 



White. 



Brown. 



White. 



Brown. 





 10 

 20 

 80 

 40 

 50 

 60 







10 

 20 

 30 

 50 

 60 







°C. 

 32.4 



°C. 

 32.6 



°C. 

 33.1 

 35.2 



°C. 

 32.9 

 34.1 



°C. 



33.3 



36.6 



37.4 



36.3 



°C. 

 34.0 

 36.6 

 36.4 

 35.4 





36.5 



36.3 





35.6 



34.4 





•33.0 



>32.6 



















35.2 



34.8 



















Temperature of forehead. 



33.4 



33.8 



33.3 

 36.2 



33.5 



35.6 



33.9 



36.4 

 35.9 

 35.6 



34.4 

 35.9 

 35.4 

 35.2 





36.3 



36.1 





35.4 



34.8 





_ __ - 

 •32.4 



■33.6 





35.4 



34.8 

















* Muscular work. 



It is a matter of general observation that, at a time when the white 

 man is perspiring over his entire body and the sweat is dropping from 

 his face and forehead, the brown man shows only a fine, velvet like layer 

 on his skin. It is not the sweat which we see, but that which we do 

 not see which exerts the cooling effect; in other words, the water 

 evaporated, not the water secreted is of value. Sweat which drops is 

 water lost from the body without the corresponding cooling effect. 

 There is economy in sweating, and the most economical way is to 

 secrete no more water than can and will be evaporated. Hypersecretion 

 is useless, and it deprives the body of water. It seems to me that the 

 brovioi man is superior to the white in this economy of sweating, and 

 we find an expression of that superiority in the lower skin temperature 

 of the brown man in the sun. It is as yet undecided whether the result 

 is due to the color, or if the nervous regulation of the sweat glands, or 



