«8 ill. 14. • 



of the food ; and the reason for these variations is the same as 

 in the animals just mentioned. For here again it is because the 

 mouth fails to perform its office and fails ev«n more completely; — 

 for birds have no teeth at all, nor any instrument whatsoever with 

 which to comminute or grind down their food^it is, I say, because 

 of this, that in some of them ^ what is called the crop precedes 

 the stomach and does the work of the mouth ; while in others 

 the oesophagus either is dilated throughout,^ or expands just 

 before it enters the stomach, so as to form a preparatory store- 

 house for the unreduced food ; ^^ or the stomach itself has a 

 protuberance in some part,^^ or is strong and fleshy ,^2 so as to be 

 able to store up the food for a considerable period and to concoct 

 it, in spite of its not having been ground into a pulp. For nature 

 retrieves the inefficiency of the mouth by increasing the efficiency 

 and heat of the stomach. Other birds there are, such, namely, 

 as have long legs and live in marshes, that have none of these 

 provisions, but merely an elongated cesophagus.^^ The explanation 

 of this is to be found in the moist character of their food. For 

 all these birds feed on substances easy of reduction, and their 

 food being moist and not requiring much concoction, their digestive 

 cavities are of a corresponding character.^* 



Fish are provided with tepth, which are almost invariably of the 

 serrated kind. For there is but one small section in which it is 

 otherwise. Of these the fish called Scarus is an example. And 

 this is^^ probably the reason why this fish apparently ruminates, 

 though no other fishes do so. For those horned animals that 

 have no front teeth in the upper jaw also ruminate. 



In all fishes the teeth are sharp ; ^^ so that these animals can 

 divide their food, though imperfectly. For it is impossible for 

 a fish to linger or spend time in the act of mastication, ^' and 

 therefore they have no teeth that are flat or suitable for grinding; 

 for such teeth would be to no purpose. The oesophagus again 

 in some fishes is entirely wanting, and in the rest is but short.^^ 

 In order however to facilitate the concoction of the food, some 

 of them, as the Cestreus, have a fleshy stomach resembling 

 that of a bird ; *^ while most of them have numerous processes 

 close against, the stomach, to serve as a sort of antechamber in 

 which the food may be stored up and undergo putrefaction 2° 

 and concoction. There is a contrast between fishes and birds 

 in the position of these processes. For in fishes they are placed 

 675a. 



