iii. 10 — iii. I2. 85 



The purposes then for which the viscera severally exist have 

 now been stated. It is of necessity upon the inner terminations 

 of the vessels that they are developed ; for moisture, and that 

 of a bloody character, cannot but exude at these points, and it 

 is of this, solidified and coagulated, that the substance of the 

 viscera is formed.^^ Thus they are of a bloody character, and 

 in substance resemble each other while they differ from other parts. 



(Ch. \\.) The viscera are enclosed each in a membrane. For 

 they require some covering to. protect them from injury, and 

 require moreover that this covering shall be light. To such 

 requirements membrane is well adapted ; for it is close in texture 

 so as to form a good protection, destitute of flesh so as neither 

 to attract nor hold moisture, and thin so as to be light and not 

 add to the weight of the body. Of the membranes those are 

 the stoutest and strongest, which invest the heart and the brain ; ^ 

 as is but consistent with reason. For these are the parts which 

 require most protection, seeing that they are the main governing 

 powers of life,^ and that it is to governing powers that guard is due. 



(Ch. \2.) Some animals have all the viscera that have been 

 enumerated ; others have only some of them. In what kind 'of 

 animals this latter is the case, and what is the explanation, has 

 already been stated. Moreover the self-same viscera present 

 differences in different possessors. For the heart is not precisely 

 alike in all animals that have one ; nor in fact is any yiscus what- 

 soever. Thus the liver is in some animals split into several parts, 

 while in others it is comparatively undivided.^ Such differences 

 in its form present themselves even among the viviparous quad- 

 rupeds, but are more marked in fishes and in the oviparous 

 quadrupeds, and this whether we compare them with each other 

 or with the vivip'ara. As for birds, their liver very nearly resembles 

 that of the vivipara ; for in them, as in these, it is of a pure and 

 blood-like colour. The reason of this is that the body in both 

 these classes of animals admits of the freest exhalation, so that 

 the amount of foul residual matter within is but small. Hence 

 it is that some of the vivipara are without any gall-bladder ^ at 

 all. For the liver takes a large share in maintaining the purity 

 of composition and the healthiness of the body. For these are 

 conditions that depend finally and in the main upon the blood, 

 and there is more blood in the liver than in any of the other 

 viscera, the heart only excepted.' On the other hand the liver 

 673b. 



