PARTS OF ANIMALS, IV. ii.-iii. 



animals, and so it is quite reasonable to hold that the 

 condition of it controls the length of its owner's life. 

 And it is equally reasonable to hold that the liver 

 produces a residue such as the bile although none of 

 the other viscera does so. Take the heart : no such 

 humour as bile could possibly come near the heart, 

 because the heart cannot withstand any violent 

 affection. Of the other viscera none is indispensable 

 to an animal, except the liver only, and that is why 

 this phenomenon occurs in connexion Avith the liver 

 exclusively. And it would be absurd to say that 

 phlegm and the sediment produced by the stomach 

 are residues when found in some places but not in 

 others ; and clearly the same applies to bile : its 

 locality makes no difference. 



We have now spoken of the gall-bladder, and we 

 have shoΛvn why some animals have it and why some 

 have not. III. It remains to speak of the Mesentery 

 and of the Omentum. These are in the same region 

 and close to the parts we have just described. 



The Omentum is a membrane, formed of suet Omentum, 

 or lard according to the animal in Avhich it is. (We 

 have already stated Λvhich animals contain suet and 

 which lard.) " Whether the animal has one stomach 

 or many, the Omentum is always fastened to the 

 middle of the stomach, on the line marked on it like a 

 seam ; and it covers the rest of the stomach and most 

 of the intestines. This is so in all blooded creatures, 

 land- and water-animals alike. 



As for the necessary * formation of this part, it 



occurs as follows. When a mixture containing solid 



substance and fluid is warmed up, the surface of 



it always becomes skin-hke and membranous ; and 



• At 651 a 26 ff. * See Introd. p. 22. 



311 



