REPTILIA. 561 



animal it endeavours to drown ; it might therefore become a 

 question which of the two would survive immersion longest. The 

 mechanism employed under these circumstances to give the Cro- 

 codile the advantage over its prey is very complete : A broad 

 cartilaginous plate (fig. 25, f) stands vertically from the os 

 hyoides, and projects upwards into the back part of the mouth ; 

 a similar valve (g) hangs down from the back of the palate, so 

 that the two together form a kind of flood-gate, which, when the 

 mouth is widely opened, effect a complete partition between the 

 cavity of the mouth and the fauces, where the aperture of the 

 larynx (h) is situated. The nostrils, moreover, are placed quite 

 at the extremity of the snout, and the nasal passages leading from 

 them are prolonged through the whole length of the upper jaw 

 until they communicate with the fauces behind the velum of the 

 palate (g). Such being the arrangement, it is immediately ob- 

 vious, that, when the communication between the mouth and the 

 fauces is cut off by means of the two valves (gjO, the Crocodile, 

 by merely keeping the tip of its snout above the water, breathes 

 with the utmost facility, and it is thus enabled to keep its prey 

 submerged for any length of time that may be requisite to extin- 

 guish life. 



(618.) The teeth of the Crocodile, and of the higher Saurians 

 are not merely consolidated with the bones of the skull to which 

 they are appended, but are implanted in sockets formed in the 

 bones composing the upper and lower jaws. Each tooth is a 

 simple hollow cone, and encloses a vascular pulp, from the surface 

 of which the bony matter of the tooth was formed. When a tooth 

 becomes old and worn, a second is secreted by the same pulp 

 within, the cavity of the first, and the original one is shed, so 

 that a succession of teeth thus make their appearance. 



(619.) The alimentary canal of Reptiles offers little that requires 

 special description. The oesophagus (Jig. 257,jf, f) is generally 

 extremely capacious, and the stomach of very variable shape and 

 capacity. The latter viscus is for the most part pyriform, tapering 

 gradually towards the pylorus ; such is the case in the CHELONIA 

 and in the BATRACOJD AMPHIBIA : in SERPENTS it resembles 

 a long bowel, and is capable of extraordinary dilatation ; and in the 

 PERENNIBRANCHIATE AMPHIBIA, as in the Proteus /?g.254,z) 

 and the Menopoma (Jig. 257, g), it looks like a mere dilatation of 

 the intestine. 



The stomach of the Crocodile is remarkable as affording ano- 



