356 Wm. Lowe: 



Some evidence may now be adduced in support of the above 

 statements. Tlie truth will be obvious to those who are familiar 

 with the laws which regulate radiant energies and the wet bulb 

 thermometer as recorded in Balfour Stewart or Deschanel's 

 Elementary Physics, combined with a knowledge of the histology 

 of the skin as in Schafer, and of the functioning of the sweat 

 glands, to be found in any up-to-date work on physiology. 



Physical science clearly demonstrates the fact that the pig- 

 ment embedded in the rete malpighian layer of the skin of man 

 and animals, will, in proportion to the density of the deposit, 

 arrest the radiant energies of the sun, transforming and absorb- 

 ing them as heat. This, in a measure, is advanced by Woodruff, 

 but his difficulty was the disposal of the heat, for he only re- 

 garded pigment as a protection against the evils of. light, but 

 which would otherwise render the coloured man more vulnerable 

 to heat. To get over his dilemma he describes the black man 

 as a nocturnal animal. He failed to see that pigment is in a 

 position to control the functioning of the sweat glands, and 

 that instead of the heat being absorbed and dispersed by radia- 

 tion, it could be dissipated in the evaporation of sweat. Wood- 

 ruff, on page 86, states = — 



" Undoubtedly the negro, when in the shade, is able to radiate 

 heat better than whites, and this enables him to keep cool in 

 the Tropics, but put him at a disadvantage in the North, where 

 a white man can keep warmer with less clothing and less fire in 

 the house. But it is a secondary cause enhancing the first, 

 because, when it comes to a question of light and cold, Nature 

 makes no mistake, but selects a colour able to exclude the light." 



In the disposal of his body heat the pigment of a black man 

 may give him some advantage, as an absorber and radiator, over 

 the white man, but a black man is something more than a pig- 

 mented lump of clay, and even in the matter of loss of heat by 

 evaporation of sweat, something more than a porous water 

 bottle. He certainly responds to the laws that regulate the 

 heating and cooling of inanimate things, but it is all important 

 that we should recognise the physiological significance of the 

 histological elements that lie buried in his skin, constructed to 

 meet the exigencies of light and heat. 



