PARTS OF ANIMALS, II. i. 



each of the sense-orgsms with one of the elementary 

 substances, and they assert that this sense-organ is 

 air, this one fire. 



Sensation thus takes place in the simple parts of 

 the body. The organ in which touch takes place is, 

 however, as we should expect, the least simple of all 

 the sense-organs, though of course like the others it 

 is uniform. This is evidently because the sense of 

 touch deals with more kinds of sense-objects than 

 one : and these objects may have several sorts of 

 oppositions in them, e.g. hot and cold, solid and fluid, 

 and the like. So the sense-organ which deals with 

 these — viz. the flesh, or its counterpart — is the most 

 corporeal of all the sense-organs. Another reason 

 we might adduce why animals must of necessity 

 possess some uniform parts at any rate, is that there 

 cannot be such a thing as an animal with no power 

 of sensation, and the seat of sensation is the uniform 

 parts. (The non-uniform parts supply the means for 

 the various activities, not for sensation.) 



Further, since the faculties of sensation and of 

 motion and of nutrition are situated in one and the 

 same part of the body, as I stated in an earlier work,° 

 that part, Mhich is the primary seat of these principles, 

 must of necessity be included not only among the 

 simple parts but also among the non-uniform parts — 

 the former in virtue of receiving all that is perceived 

 through the senses, the latter because it has to do 

 with motion and action. In blooded animals this 

 part is the heart, in bloodless animals the counterpart 

 of the heart, for the heart, like every one of the other 

 viscera, can be divided up into uniform pieces ; but 

 on the other hand it is non-uniform owing to its 

 shape and formation. Every one of the other so- 



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