xiv] COLOUR OF SKIN IN MAN 



a certain amount of plasmative force when, wandering northwards 

 towards colder regions, he learnt to seek refuge in caves. The 

 diminution of light may have caused a diminution in the cutaneous 

 pigments ; and the lower temperature causing the blood to accu- 

 mulate towards the periphery to compensate for the loss of heat on 

 the surface of the body may have communicated the rosy tint to 

 the skin. This colour is very rare in mammals, and combined with 

 the scarcity of hair is only found, as far as I am aware, in a small 

 and most remarkable hypogeal rodent of the deserts of Somaliland, 

 Heterocephalus glaber of Riippell, and accidentally in the " white " 

 elephants and in certain races of swine in which the black colour of 

 the skin has disappeared, it seems, through breeding in covered 

 styes in a cold climate, and thus under circumstances analogous 

 to those in which the white skin may be conjectured to have appeared 

 in Man. 



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