PROGRESSION OF ANIMALS, iii.-iv. 



having to carry the weight, and the part which is 

 raised is extended by that wliich carries the weight. 

 And so nothing that is without parts can move in 

 this manner ; for it does not contain in itself the 

 distinction between what is to be passive and what 

 is to be active. 



IV. Now the dimensions by which animals are 

 naturally bounded are six in number, namely, 

 superior and inferior, front and back, and also right 

 and left." Now all living things have a superior and 

 an inferior part ; for the superior and the inferior is 

 found not only in the animals but also in plants.^ 

 The distinction is one of function and not merely of 

 position in relation to the earth and heavens. For 

 the part from which is derived the distribution of 

 nutriment and the growth in any particular thing is 

 the superior ; the part to which the growth extends 

 and in which it finally ends is the inferior. The one 

 is a kind of origin, the other a termination ; and it is 

 the superior which is an origin. It might, however, 

 seem that in plants the inferior is the more essential ® 

 part ; for the superior and the inferior are not in the 

 same position in them as in the animals. Though in 

 relation to the universe they have not the same posi- 

 tion, they are similarly situated as regards function. 

 For in plants the roots are the superior part ^ ; for it 

 is from them that the nutriment is distributed to the 

 parts that grow, and it is from their roots that plants 

 receive it, as do animals from their mouths. 



Things which not only live but are also animals have 

 both a front and a back. For all animals have sense- 

 perception, and it is on account of sense-perception 

 that the front and the back are distinguished ; for 

 the parts in which the sense-perception is implanted 



491 



