The Tropics and Pigment. 357 



The pigmented epithelial cells which form the rete malpighii 

 lie in contact with the corium. Tlirough the meshes of the rete, 

 filaments of the nerves pierce and interlace over its surface, so 

 that the particles of pigment are in the closest contact with the 

 surrounding nerve structure. Thus the variations of internal 

 and external temperature which affect the pigment granules, 

 would be directly imparted to the nerve terminals, and thence a 

 communication to the central nervous system, with a correspond- 

 ing reaction on the superficial blood-vessels. If the pigment is 

 heated, a dilatation of the blood-vessels follows, with a flushing 

 of the sweat glands. If the pigment is chilled, then a contrac- 

 tion of the blood-vessels takes place, which tends to prevent the 

 loss of heat. It is natural, then, to conclude that pigment 

 renders a man more sensitive tO' the cold, but this offers no 

 impediment to a coloured man's progress, or even a black man's, 

 for we find them both wandering from the equator to the poles, 

 The Laplander and Eskimo are coloured men, and it was re- 

 ported in the daily press that an American negro accompanied 

 Captain Peary in his final rush for the Pole. Captain Peary's 

 reason for this was that he considered that the black man, on 

 account of his pigment, was better able to meet the emergencies 

 that might arise from exposure. 



Experimental evidence of the physical properties of pigment 

 can be easily demonstrated by a piece of smoked window glass. 

 We are all familiar with the protection that the deposit of 

 smoke affords to the eyesight, but to appreciate the fact that it 

 will also protect us from the sun's heat, alternately interpose 

 between the exposed skin and the sun's rays a piece, of glass 

 smoked, and another not smoked. The effect can be heightened 

 by concentrating the sun's rays with a biconvex glass condenser. 

 The carbon will transform and absorb the rays in proportion to 

 the density of the deposit. The heat will be radiated, but it may 

 be dissipated by the evaporntion of fluid if some spirituous 

 liquid is poured over the glass. A similar result was obtained by 

 the use of melanin pigment. Tlie pigment for this experiment 

 was procured by Dr. Stapley, of the Melbourne Veterinary 

 School. 



To show that pigment interferes with the passage of the sun's 

 ravs throuo'h animal tissues, the radiance of translumination of 



