BOOK IV 



What has been said already on the subject of the 

 viscera, the stomach, and each of the other parts 

 mentioned, appUes to the footless creatures (such as 

 the Serpents) as well as to the oviparous quadrupeds. 

 Indeed, the Serpents are akin to these : for a serpent 

 is like a long and footless lizard. A third class in 

 which all these parts are similar is the Fishes : the 

 only difference is that the first two classes are land- 

 creatures and therefore have a lung, whereas fishes 

 have no lung but gills instead. Fishes have no 

 bladder, nor has any of these creatures (except the 

 tortoise) ; the reason is that they drink little (because 

 their lung is bloodless), and the moisture in them 

 is diverted to the horny scales, just as in birds it is 

 diverted to the feathers. And in all these creatures, 

 as in birds, the residue ^ is white on the surface, 

 since in those animals that have a bladder, when the 

 residue has been voided an earthy salt deposit 

 settles in the vessels, the sweet and non-briny por- 

 tion, o^^^ng to its lightness, being used up upon the 

 flesh. 



The Vipers have the same peculiarity among the 

 Serpents as the Selachia have among the Fishes. 

 Both of them are externally viviparous, though 

 they first produce their ova internally. All these 



" See Introduction, pp. 32 ff. 



^03 



