INFLUENCE OF PHILIPPINE CLIMATE ON WHITE MEN. 459 



that pigmented skin will absorb these haraiful waves. (2) (7) The pig- 

 mentation following sunburn is considered a conservative effort oh the 

 part of the organism. The supporters of the actinic theory advocate the 

 use of protective clothing, a red, orange-red, or black layer being, recom- 

 mended. Some advise a tinfoil lining for the headgear. Now it is a 

 matter of general observation that the covered portions of the body do 

 not become tanned or sunburned when ordinary clothing is worn. ^ If 

 sunburn an.d tanning are due to actinic rays, and if the usual clothing 

 is able to protect the skin from their effects, it seems to us reasonable 

 to assume that the same clothing will protect the body as a whole from 

 the effects of these rays. This argument of course does not take into 

 consideration that quantity of rays which may enter through the face 

 and hands, but no one, as far as we are aware, has recommended covering 

 these parts. Therefore, it seems probable on theoretical grounds that 

 ordinary clothing gives sufficient protection, and the result of an ex- 

 tensive practical experiment by the Board (10) supported this view by 

 showing that no benefit resulted from the use of orange-red hat linings 

 and underwear. 



Eecently Aron(4) has shown that monkeys, when exposed to the direct 

 rays of the sun in Manila, quickly develop a high temperature and die 

 in one or two hours. Monkeys exposed under similar conditions, while 

 at the same time a strong current of air from an electric fan blew 

 over their bodies, did not suffer any discomfort. Of course the amount 

 of chemical rays falling on the animals was identical in the two cases. 

 The inability of monlceys to stand sun exposure is considered by Aron 

 to be due to the fact that these animals possess no sweat glands, and 

 consequently have only a limited power of thermic regulation. There- 

 fore, hyperpyrexia occurs as a result of the absorption of solar heat 

 rays. jSTo rise of temperature and no ill results occurred when monkeys' 

 heads were exposed for several days while their bodies were protected 

 from the sun. Aron concludes that "hyperthermia alone must be re- 

 garded as the true cause of the death and of the injurious effects 

 brought about by the radiation of the sun." While Aron was working 

 at the Bureau of Science in Manila on the thermic factor in the tropical 

 sunlight, Freer (1) and others have been engaged in the investigation of 

 the chemical side of the problem without producing any results which 

 would show that the actinic rays of the spectrum were distinctly detri- 

 mental to man. 



The researches of Freer and Aron, the results of the orange-red clothing 



,test by Phalen(lO) of this Board, the observations of Wickline(9) ' on 



blonds and brunettes and our own work on the same subject render it 



106711 3 



