GENERATION OF ANIMALS, V. iii. 



more is the depth at which they are found). Their 

 spines are long because the growth of the body is 

 diverted to them, since, as the creatures possess but 

 Httle heat, they cannot concoct the nourishment, and 

 so contain a great deal of residue ; and it is out 

 of residue that spines and hair and the like are 

 formed. Their spines are hard and petrified on 

 account of the cold and its congealing effect. And in 

 the same way plants, too, are harder, and earthier, 

 and more petrified if they grow where the aspect is 

 northerly, or in a windy situation, than if they grow 

 where the aspect is southerly, or in a sheltered spot. 

 It is because they all get more chilled, and their fluid 

 evaporates. Hardening, then, is brought about by 

 both cold and heat : the effect of both is to cause the 

 fluid to evaporate : it is evaporated by heat per se, 

 but by cold per accidens — in the latter case the fluid 

 accompanies the heat when it makes its exit, as there 

 is no fluid ^^ithout its heat." There is this difference, 

 however : cold causes compression as well as harden- 

 ing, whereas heat lightens a thing's consistency.'' 



For the same cause hair, feathers and scales in the 

 various animals respectively become harder as they 

 get on in years : it is because their skins grow harder 

 and thicker then, and that is due to their drying up, 

 and old age or to " get on in years " is something 

 earthy (as the similarity of the word with y earth, the 

 old form of " earth," shows),'' and this is due to the 

 fact that the heat is faiUng and with it the fluid. 



generation. See also P.A. 653 b 8 ff. and App. B § 11 and 

 § 17 and note. 



* This hardly agrees with Aristotle's statements elsewhere 

 {e.g., 765 biff.) about the thickening effects of concoction. 



' This is a piece of " etj'mology " comparable with that 

 of the original Greek : geras (old age), geeron (earthy). 



521 



