180 



Oh ilic Skin in tJie Dark Races of ManJiind. 



[July 



appear satisfied with his explanation of the extraordinary fact he relates, 

 for he gives another furnished by Davy, who, indeed, is made to ascribe 

 the alleged difference in v- sicating power between black and white sur- 

 faces, to the former rendering the heat sensible. Were I not quoting frorri 

 the Philosophical Transactions, a misprint might be suspected. I con- 

 clude that a black skin will absorb more heat than a white skin, and 

 w^ere it not for other accompanying circumstances, would produce incon- 

 venience precisely in the rvtio of the amount of heat absorbed. It must 

 not be overlooked, however, that in the Negro the pigment is not 

 superficial, but covered by a layer of translucent cuticle. The experi- 

 ments of Dr. Stark prove that colours absorb heat in proportion to 

 their depth of shade through transparent media. It only rem lins to 

 show the cuticle to be a medium in the condition of those. For this 

 purpose, I covered the balls of a differential thermometer, one with 

 cuticle, the other with cuticle of the same thickcess, having ivory black 

 rubbed on its inner surface ; on bringing the thermometer into the sun's 

 rays, the column of liquid descended rapidly in the stem, the ball of 

 which was covered with the blackened cuticle. 



It is evident, from the resu't of experiments which I have related, 

 that a much less degree of heat can be borne when the heat is applied 

 locally, or so that the perspiratory process is not excited over the whole 

 system, than Sir Joseph Banks and others were able to bear in heated 

 apartments where perspiration was fully excited. 



This circumstance leads me to offer an explanation of the functions, 

 or, not to speak mincingly, of the uses served by the peculiar colouring 

 matter in the dark races. Blumenbach and Dr. Winterbottom concur in 

 stating the Negro to perspire more readily than the European or White, 

 and Dr John Davy, in the 3d vol. of the Medico- Chirurgical Transac- 

 tions, gives its due influence to this property. After noticing that the 

 excessive perspiration in dark people must keep down the temperature, 

 he proceeds, " In the inhabitants of the tropics, the exhalant arteries of 

 the skin seem unusually expanded, and the whole apparatus peculiar to 

 this secretion unusually developed ; and I believe that the blood itself is 

 less viscid, more fluid, and flows more readily through the vessels, so as 

 to promote perspiration, and by that means contributing to the cooling 

 of the surface, and being cooled itself, it contributes again when it flows 

 back upon the heart, to the reduction of the temperature of the internal 

 parts." 



Were the inhabitant of the tropic not possessed of this organization, 

 his system could not respond to the stimulus of heat, by a determina- 

 tion of fluid to the surface of the body. And the heat absorbed by the 



