GENERATION OF ANIMALS, V. v. 



tion, and the protection keeps off the wind. Also, it 

 is an assistance if the hair is anointed with a mixture 

 of oil and water. This is because, although the 

 water cools it, the oil which is mixed with it prevents 

 the hair from drying off quickly, water being easily 

 dried off. (h) The following proves that greyness is 

 not a form of withering, and that when hair goes 

 white it is not due to withering, as it is in the case of 

 grass. Some hairs are grey from the very beginning 

 of their growth, and nothing begins its growth in a 

 withered condition. In many instances, too, hairs 

 go white at the tip ; this is because very little heat 

 gets into parts which are at the extreme end and 

 very thin. 



In certain of the other animals white hairs make 

 their appearance ; but this is natural and not due to 

 any affection. The reason of the colours in these 

 other animals is the skin : thus, if they are white, 

 the skin is white ; if black, the skin is black ; if 

 piebald, made up of a mixture of colour, the skin is, 

 we find, white in some places and black in others. 

 In the case of human beings, however, the skin has 

 nothing whatever to do with it, for even people with 

 white skin have intensely black hair. The reason for 

 this is that, for his size, man has the thinnest skin of 

 all animals, and on that account it has no power at 

 all to effect any change in the hair ; instead of that, 

 the skin, by reason of its own weakness, changes its 

 colour itself, and also is darkened by the action of 

 the sun and the wind, while the hair undergoes no 

 simultaneous change at all. With the other animals, 

 the skin, on account of its thickness, possesses the 

 character of the region in which the animal hves ; 

 and that is why the hair changes in accordance with 



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