358 Win. Loive: 



an electric lamp placed in the mouth will readily demonstrate 

 this fact by comparing the fair with the dark skins, or by artifi- 

 cially darkening the skin with melanin pigment, burnt cork, sol. 

 nitrate of silver, etc.. or, perhaps what may be more simple, 

 compare the transparency of variously pigmented skins by hold- 

 ing their hands before a beam of sunlight. 



Our next object in the course of experimental evidence is to 

 show what proof there is of heated pigment re-acting on the 

 circulation, and increasing the activity of the sweat glands. 

 From personal experience I know that heat reddens the skin and 

 promotes sweating, and from personal observatio^n I also know 

 that the black man, of all men, is a profuse sweater. 



We can, so far, sum up this discussion by confidently affirm- 

 ing : — 



(1) That pigment, in proportion to the density of the 

 deposit, renders the skin opaque to the sun's rays. 



(2) That pigment transforms these energies into heat. 



(3) That the temperature of the pigment reacts on 

 the blood-vessels of the skin. 



Thus, heated pigment induces sweating, whereby heat is dissi- 

 pated. 



Heatstroke. 



From Avhat has already been stated, it can be conchided that 

 in the shade, all other things being equal, the power to resist 

 high temperatures, dry or moist, is in favour of the pigmented 

 skins, but the individual will succumb when it has reached the 

 limits of his phj^siological activity. In exposure to the sun, 

 there is an obvious advantage that pigmentation bestows on 

 diurnal animals. It permits the loss of the body hair so that 

 it shall not be an impediment to dispersion of heat by the 

 evaporation of sweat, as with the buffaloes of Southern Asia. 

 To man it gives the same security, his pigmented skin enables 

 him to do without clothes, and nature, as is well known, reduces 

 the hair of the scalp in many negroes tO' small, woolly tufts 

 whereby danger from heat is reduced to its minimum. 



It is a curious deduction of Dr. Woodruff to conclude that a 

 negro's kinky hair is designed by nature to protect him from 

 light, especially in face of the evidence he might have obtained 



