22 11. I. — 11. 2 



the most corporeal,'* being either the flesh, or the substance which 

 in some animals takes the place of flesh. 



Now as there cannot possibly be an animal without sensation, 

 it follows as a necessary consequence that every animal must have 

 some homogeneous parts ; for these alone are capable of sensation, 

 the heterogeneous parts serving for the active functions. Again 

 as the sensory faculty, the motor faculty, and the nutritive faculty, 

 are all lodged in one and the same part of the body, as was stated 

 in a former treatise,'-'' it is necessary that the part which is the 

 primary seat of these principles shall on the one hand, in its 

 character of general sensory recipient, be one of the simple parts ; 

 and on the other hand shall, in its motor and active character, be 

 one of the heterogeneous parts. For this reason it is the heart 

 which in sanguineous animals constitutes this central part, and in 

 bloodless animals it is that which takes the place of a heart. For 

 the heart, like the other viscera, is one of the homogeneous parts ; 

 for, if cut up, its pieces are homogeneous in substance with each 

 other. But it is at the same time heterogeneous in virtue of its 

 definite configuration.'^ And the same is true of the other so- 

 called viscera, which are indeed formed from the same material 

 as the heart. For all these viscera have a sanguineous character 

 owing to their being situated upon vascular ducts and branches. 

 For just as a stream of water deposits mud, so the various 

 viscera, the heart excepted,'"' are, as it were, deposits from the 

 stream of blood in the vessels. And as to the heart, the very 

 starting-point of the vessels, and the actual seat of the force by 

 which the blood is first fabricated, it is but what one would 

 naturally expect, that out of the selfsame nutriment of which it 

 is the recipient its own proper substance shall be formed.'^ Such 

 then are the reasons why the viscera are of sanguineous aspect ; 

 and why in one point of view they are homogeneous, in another 

 heterogeneous. 



(Ch. 2.) Of the homogeneous parts of animals, some are soft 

 and fluid, others hard and solid ; and of the former some are fluid 

 permanently, others only so long as they are in the living body. 



Among the fluids ' are blood, serum, lard, suet, marrow, semen, 

 bile, milk when present, flesh, and their various analogues. For 

 the parts enumerated are not to be found in all animals, some 

 animals only having parts analogous to them. Of the hard and 

 solid homogeneous parts bone, fish-spine,^ sinew, blood-vessel, are 

 647 b. 



