PARTS OF ANIMALS, II. ii. 



Now first of all there are many sorts of Cause °' to 

 which the existence of these uniform parts, both the 

 fluid and the solid ones, is to be ascribed. Some of 

 them act as the material for the non-uniform parts 

 {e.g. each of the instrumental parts is composed of 

 these uniform parts — bones, sinews, fleshes, and the 

 like, which contribute either to its essence, or else 

 towards the discharge of its proper function). An- 

 other group of the uniform parts — fluid ones — act as 

 nutriment for the ones just mentioned, since every- 

 thing that grows gets the material for its growth 

 from what is fluid ; and yet a third group are residues ^ 

 produced from the second group : examples, the 

 excrement deposited from the solid nutriment and 

 (in those animals which have a bladder) from the fluid 

 nutriment. 



Further, variations are found among different 

 specimens of these uniform parts, and this is to sub- 

 serve a good purpose. Blood is an excellent illustra- 

 tion. Blood can be thin or thick, clear or muddy, 

 cold or warm ; and it can be different in different 

 parts of the same animal : instances are known of 

 animals in M'hich the blood in the upper parts differs 

 from that in the lower parts in respect of the char- 

 acteristics just enumerated. And of course the 

 blood of one animal differs from that of another. 

 And there is the general division between the 

 animals that have blood and those which instead of it 

 have a parf^ which is similar to it though not actually 

 blood. 



The thicker and warmer the blood is, the more it 

 makes for strength ; if it tends to be thin and cold, 

 it is conducive to sensation and intelligence.'^ The 

 same difference holds good with the counterpart of 



119 



