PARTS OF ANIMALS, II. iii. 



which effect the concoction of the food by its aid. 

 And, just as the mouth (and in some animals the 

 so-called oesophagus too which is continuous with 

 it) is the passage for the as yet untreated food, and 

 conveys it to the stomach ; so there must be other 

 passages through which as from a manger the body 

 as a whole may receive its food from the stomach and 

 from the system of the intestines." Plants get their 

 food from the earth by their roots ; and since it 

 is already treated and prepared no residue is pro- 

 duced by plants — they use the earth and the heat 

 in it instead of a stomach, whereas practically all 

 animals, and unmistakably those that move about 

 from place to place, have a stomach, or bag, — as it 

 were an earth inside them — and in order to get the 

 food out of this, so that finally after the successive 

 stages of concoction it may reach its completion, they 

 must have some instrument corresponding to the 

 roots of a plant. The mouth, then, having done its 

 duty by the food, passes it on to the stomach, and 

 there must of necessity be another part to receive it 

 in its turn from the stomach. This duty is under- 

 taken by the blood-vessels, which begin at the bottom 

 of the mesentery,^ and extend throughout the length 

 of it right up to the stomach. These matters should 

 be studied in the Dissections ^ and my treatise on 

 Natural History.^ 



We see then that there is a receptacle for the food 

 at each of its stages, and also for the residues that 

 are produced ; and as the blood-vessels are a sort of 

 container for the blood, it is plain that the blood (or 

 its counterpart) is the final form of that food in Uving 



^ The Natural History, otherwise History of Animals or 

 Researches upon Animals. See 495 b 19 IT., 514 b 10 ff. 



135 



