PARTS OF ANIMALS, II. ii. 



heat is their own ; in others it has been derived from 

 without. And there is a very great difference be- 

 tween these two ways of being hot, because one of 

 them conies near to being hot " by accident " and 

 not hot " of itself" ; as is obvious, supposing anyone 

 Avere to assert, if a fever-patient were " by accident " 

 a man of culture, that the man of culture is hotter 

 than a man whose heat is due to his perfect health. 

 Thus some things are hot " of themselves " and 

 some hot " by accident," and though the former cool 

 more slowly, the latter are in many cases hotter in 

 their effect upon the senses. Again, the former have 

 a greater power of burning : e.g. a flame burns you 

 more than boiling water, yet the boiling water, 

 which is hot only " by accident," causes a stronger 

 sensation of heat if you touch it. From this it is 

 plain that it is no simple matter to decide which of 

 two things is the hotter. The first will be hotter in 

 one way, and the second in another. In some cases 

 of this sort it is actually impossible to say simply that 

 a thing is hot or is not hot. I mean cases in Λvhich 

 the substratum in its permanent nature is not hot, 

 but when coupled <Mith heat) is hot ; as if we were 

 to give a special name to hot water or hot iron : that 

 is the mode in which blood is hot." These cases, in 

 which the substratum is hot merely through some 

 external influence, make it clear that cold is not just a 

 privation but a real thing in itself. Perhaps even fire 

 may be an instance of this kind. It may be that its 

 substratum is smoke or charcoal : and, though smoke 

 is ahvays hot because it is an exhalation, charcoal 

 when it goes out is cold. In the same way oil 

 and firwood ^ become cold. Further, practically all 



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