PARTS OF ANIMALS, III. xiv. 



as regards position and appearance, the Researches 

 upon Animals'^ and the treatises on Anatomy should be 

 consulted. 



The same reason as has just been described accounts 

 for the difference which presents itself in birds in the 

 part which receives the food. Birds, like the other 

 animals, do not get the full service from the mouth in 

 dealing with the food — since they have no teeth at 

 all, and they have nothing with which to bite up or 

 grind down the food ; and so some of them have, 

 before the stomach, what is called the crop, to per- 

 form the work instead of the mouth. Others have 

 a broad oesophagus ; or their oesophagus has a 

 bulge in it, just before it reaches the stomach, in 

 which they keep a preliminary store of untreated 

 food ; or some part of the stomach itself sticks out. 

 Others have a strong and fleshy stomach ^ which 

 is thus able to store the food up for a long period 

 and to concoct it although it has not been ground 

 down ; thus Nature makes up for the deficiency of 

 the mouth by means not only of the heat of the 

 stomach but also by its special character. Other 

 birds have none of these devices, but a long crop,^ 

 because their food is moist : these are the long-legged 

 marsh birds. The reason for this is that the food 

 which all of these take is easily ground down, and 

 the result is that the stomachs of birds of this sort 

 are moist [o"\\ing to the unconcocted and moist state 

 of the food]. 



The tribe of fishes have teeth : practically all have 

 saw-teeth. There is one small group to which this 

 does not apply, e.g. the Scarus,^ as it is called, and 

 it seems reasonable to suppose that this is why 



^ The parrot-fish ; see above, 6Q2 a 7. 



293 



