PARTS OF ANIMALS, IV. iii.-iv. 



the place \vhere the Omentum is is full of nutriment 

 of this very sort. Furthermore, owing to the thick- 

 ness of the membrane, that portion of the blood-like 

 nutriment which percolates through it must of neces- 

 sity be fatty, because that is the finest in texture ; 

 and then owing to the heat in that part it will be 

 concocted and so become suet or lard instead of some 

 fleshy or blood-like substance. This, then, is the way 

 in which the formation of the Omentum occurs. 

 Nature, however, turns the Omentum to advantage in 

 the concoction of the food, so as to enable the animal 

 to concoct its food more easily and more quickly ; 

 for the Omentum is fat ; fat things are hot, and hot 

 things aid concoction. For this reason, too, the 

 Omentum is fastened to the middle of the stomach ; 

 since as regards that part of the stomach which is 

 beyond, the liver which is close by it assists it in 

 concoction. So much for the Omentum. 



IV. What is called the Mesentery is also a mem- Mesentery. 

 brane ; and it extends continuously from the line of 

 extension of the intestines as far as the Great Blood- 

 vessel and the Aorta. It is full of blood-vessels, 

 which are many in number and closely packed 

 together ; and they extend from the intestines as 

 far as the Great Blood-vessel and the Aorta. We 

 shall find, as with the other parts, that the develop- 

 ment and formation of the Mesentery is the result 

 o^ necessity . As for its purpose in the blooded animals, 

 that is clear enough to those who consider. Animals 

 must of necessity take in nutriment from without ; 

 and, again, out of this the " ultimate nutriment " 

 has to be made ; and from this store the supply is 

 distributed directly to the parts of the body. (In 

 blooded animals this is called blood ; there is no 



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