PARTS OF ANIMALS, I. i. 



the early days ° spent their time in trying to discover 

 what the material principle or the material Cause ^ 

 was, and what it was like ; they tried to find out 

 how the Universe is formed out of it ; what set 

 the process going (Strife, it might be, or Friendship, 

 Mind, or Spontaneity) ; assuming throughout that 

 the underlying material had, by necessity, some 

 definite nature : e.g. that the nature of Fire was hot, 

 and light ; of Earth, cold, and heavy. At any rate, 

 that is how they actually explain the formation of 

 the world-order. In a like manner they describe the 

 formation of animals and plants, saying (e.g.) that the 

 stomach and every kind of receptacle for food and for 

 residue "^ is formed by the water flowing in the body, 

 and the nostril openings are forcibly made by the 

 passage of the breath.'* Air and water, of course, 

 according to them, are the material of which the body 

 is made : they all say that Nature is composed of 

 substances of this sort. Yet if man and the animals 

 and their parts ^ are products of Nature, then account 

 must be taken of flesh, bone, blood, in fact of all the 

 " uniform parts," ^ and indeed of the " non-uniform 

 parts " too, viz. face, hand, foot ; and it must be 

 explained how it comes to pass that each of these is 

 characterized as it is, and by what force this is effected. 

 It is not enough to state simply the substances out of 

 which they are made, as " Out of fire," or " Out of 

 earth." If we were describing a bed or any other 

 like article, we should endeavour to describe the form 

 of it rather than the matter (bronze, or wood) — or, at 



' " Uniform " and " non-uniform " : see Introduction, pp. 

 28 ff. The distinction between " uniform " and " non-uniform " 

 parts is, historically, the predecessor of the distinction be- 

 tween " tissues " and " organs." 



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