STUDY OF THE EFFECT OF TROPICAL SUNLIGHT. 



99 



visible perspiration. One week after the thirty minutes' expo- 

 sure to the sun the entire epidermis of his back peeled off. 



Wind screens were used to protect the subjects from the coolinp: eflfects 

 of the breezes. A li^ht wind was blowinji; during the above observations 

 and occasionally eddies reached the men. In the column under remarks, 

 breeze and lip:ht wind refer only to the gentlest of zephyrs, for the men 

 were so protected that only eddies reached them. 



In this table it is of interest to observe that in spite of the fact that 

 the American's temperature in the shade was, on the average, 2^.9 lower 

 in the beginning:, than the Igorot's (Igorot A. 32°. 4, M. 32°. 52, American 

 30°. 06), on moving into the sun the three subjects reached, on the average, 

 about an equal temperature, near the maximum, in thirteen minutes for 

 the American and about thirty minutes for the Igorots. The white skin 

 warmed much faster than the darker-colored skins. While this fact 

 is contrary to what would be expected from a consideration of the 

 rates at which different colored objects absorb heat, it may be accounted 

 for by the irritation which is undoubtedly produced by the rays. This 

 irritation of either the sensory nerve-endings, nerve-endings in the vessel 

 walls, or of the vessel walls produces a flushing of the skin due to a 

 greater quantity of blood and a more rapid flow. The pigmentation of 

 the darker skins is undoubtedly a protection against this irritation of 

 the sun's rays. 



Table IV. — Comparison of skin temperatures of a Canadian, a Filipino, 

 and a Negro in sun and in shade, May 20, 1911. 



Subject. 



Time. 



Temperatui 



e— 



Remarks. 



Over 

 third 



Over 



fifth 



Over 



upper 







dorsal 

 verte- 



dorsal 

 verte- 



rif?ht 

 angrle 

 of scap- 

 ula. 









bra. 



bra. 







a. m. 













'9.20 



33.20 



33.80 



33.95 



Temperature in shade. 





9.23 



34.20 



35.85 



36.80 



In sun. 





9.28 



38.75 



38.20 



39.20 



1 



Ray. Tagulog. 















9.36 



38.30 



37.60 



38.30 



Visible perspiration at 9.35. | 





9.42 



38.75 



38.80 



38.78 



Axillary temperature at end of experi- 













ment, 85°. 48. 





' 9.22 



33.65 



34.35 



33.90 



Temperature in shade. 





9.25 



36.30 



36.90 



36.95 



In sun. 



1 



9.29 



37.95 



37.55 



38.25 





1 



9.34 



36.53 



37.00 



37.55 



Very sligrht breeze; slight perspiration 



R. Canadian. | 











visible. 





9.38 



37.90 



37.30 



38.10 



1 





9.40 



38.30 



37,55 



38.10 







9.44 



38.55 



37.40 



38.85 



Axillary temperature at end of experi- 





^ 









ment, 35^.78. 





' 9.24 



34.80 



34.80 



34.96 



' Temperature in shade. 





9.26 



37.26 



37.35 



39.42 



In Bun. 



C. Negro. 



9.30 



38.70 



38.75 



39.46 



1 Perspiration vi.^ible at 9..35. 



' 9.37 



38.90 



38.75 



.38.90 







9.43 



39.32 



88.85 



39. 15 



Axillary temperature at end of cxperi- 





. 







! 



1 ment. 33°.38. 



inocs — s 



