72 



fishes are formed rather in the soft parts of the 

 mouth, than in the jaws ; but those of the rays 

 and sharks agree with those of higher classes of 

 animals in being formed in the jaws alone, 

 which are furnished with several rows of them. 

 They are in these animals of a triangular shape ; 

 but in the majority of fishes, more or less hook- 

 ed ; and in all they are calculated rather for 

 lacerating and holding, than for chewing their 

 food a structure well adapted to the kind of 

 food on which they subsist, and to the nature of 

 their digestive process. 



The lips of reptiles have nothing remarkable 

 in their structure ; and the frogs and turtles, for 

 the same reason as fishes, are destitute of sali- 

 vary glands. Many serpents, however, as the 

 rattle-snake, and the cobra-da-capello, arid some 

 kinds of boa, have glands somewhat analogous to 

 them, for the secretion of their venom, situated 

 behind and below the orbits of their eyes, and 

 compressed by proper muscles, so as to squeeze 

 the venom through the hollow tusks which are 

 placed in front of the upper jaw, and serve as 

 ducts for the glands in question. A similar struc- 

 ture, as we have seen, is met with in some venom- 

 ous insects, as the spider. With respect to the 

 tongue of reptiles, it is short, and fixed to the floor 

 of the mouth in frogs, salamanders and tortoises ; 

 while in serpents, on the contrary, it is exceed- 

 ingly long and moveable, being enclosed, when 

 retracted, in a proper sheath formed by the re- 

 flected membrane of the mouth ; in most reptiles 



