458 CHAMBERLAIN. 



SXJilMAEY OF PART VII. 



Unfortunatel)^ we have no exact statistics to show what may have 

 been the proportions of the two complexion types in the cities under 

 consideration. Woodruff states that the blonds are less numerous in 

 the cities than in the countiy. Our Army is recruited from both urban 

 and rural sources and it is doubtful if the figures for complexion type 

 in the cities differ very much from those found in the military service. 

 If this be true^ then it is obvious from a study of Group III that the 

 blonds in the United States were not quite as subject to insolation as 

 were the brunettes. If any deductions are to be drawn from Groups I 

 and II, they would be that the harmful effects of the sun are very much 

 less manifest among the fair skinned individuals. 



PART VIII. DISCUSSION OF CLIMATIC INFLUENCES AND PIGMENTATION: 

 GENERAL SUMMARY: CONCLUSIONS. 



It seems to us by no means proved that the pigmentation of tropical 

 races and the tanning of Caucasians is a protective effort on the part 

 of nature against the chemical activity of sunlight. Several other ex- 

 planations suggest themselves, but will not be discussed here. The 

 integument of the negro is able to radiate heat more readily than that 

 of a white man, but this advantage is least manifest when most needed, 

 namely in direct sunlight, where the superior radiating power of the 

 black skin is more than counterbalanced by the facility with which the 

 dark colors absorb thermic rays. However, it does seem proven that on 

 the living subject the brown or black skin, when exposed to the sun, is 

 always slightly cooler than the skin of a white man. (4) This apparent 

 anomaly is explained on the ground that the cooling effects produced })y 

 evaporation are more marked in the case of the dark races, because of 

 anatomical differences in the skin. Daubler states that the negro has 

 sweat glands which are larger and better developed than those of the 

 Caucasian. Some claim that the number of glands in a given area is 

 greater. Aron considers that the brown skin is cooled more efficiently 

 because the perspiration is secreted more evenly, the evaporation is com- 

 plete, and the waste, due to the sweat dropping off, is avoided. The 

 above conditions, taken together with the fact that the working native 

 wears very little clothing, place the pigmented native in a better position 

 than the Caucasian as regards the heat regulation of his Iwdy in the 

 Tropics. 



The advocates of the theory that certain deleterious effects noted in 

 the Tropics are due to the chemical rays of the sunlight, point to sxm- 

 burn as an evidence of injury produced b}'' actinic rays and maintain 



