GENERATION OF ANIMALS, V. vi. 



creature suffers some distortion during the process of 

 its formation, for, since the beginning of things that 

 pass through such a process is on a small scale, they 

 are small at that time, and what is small can easily 

 be given a different turn and spoilt." 



The ones that change most are those which, though 

 whole-coloured by nature, belong to a class which is 

 many-coloured. This is due to the varieties of water 

 involved. Hot water makes the hair white, cold 

 water makes it dark, which is exactly what happens 

 in the case of plants. The reason is that the hot ones 

 contain more pneuma than they do water, and it is the 

 air shining through that causes the whiteness, just as 

 it makes froth white.'' Therefore, just as there is a 

 difference between skins that are white by nature 

 and those that are white o\\'ing to some affection, so 

 there is a difference between the whiteness of hair 

 which is due to nature and that which is due to disease 

 or age — and the difference lies in the fact that the 

 cause is different. In the former case, the whiteness 

 is caused by the natural heat, in the latter, by ex- 

 traneous heat."^ It is the vaporous air shut up inside 

 them which produces whiteness in all things ; and 

 that, too, is why those animals which are not single- 

 coloured are all whiter under the bellv than else- 

 where. Thus too practically all white animals are 

 hotter and tastier for the same cause : their good 

 flavour is produced by concoction, and concoction is 

 produced by heat. And the same cause holds also 

 in the -case of those animals which, being single- 

 coloured, are either dark or white ; since it is heat 

 and cold which are the cause of the nature of the 

 skin and of the hair, each of the parts of the body 

 having its own proper heat.^ 



539 



