162 REP TIL I A. 



of the poison-gland, and opens anteriorly at some little distance from 

 the apex of the tooth, as is the case in Vipera, Crotalus, Trigono- 

 cephalus, and others. During the commencement of development of 

 the teeth, this canal is an open channel, or groove in the tooth, which 

 becomes either a closed canal at a later period of existence, or re- 

 mains always open in particular genera, as already mentioned. 



The Cavity of the Mouth is occasionally bounded from that of the 

 pharynx by membranous folds ; in the Crocodile these form a true 

 velum pelati, and opposite to this, inferiorly behind the tongue, a 

 second fold projects ; hard papillae frequently occur upon the 

 palate. 



As regards the structure of the organs of digestion, and of the 

 alimentary canal, the differences that occur are by no means so 

 great as might be anticipated upon viewing the varieties of outward 

 form, and of the rest of the organization in the several orders of Rep- 

 tilia. The peritoneum, frequently colored, as in Fishes, by black 

 pigment, forms mesenteric folds, but never true omenta. It however 

 invests, more or less completely, all the viscera contained within the 

 abdominal cavity. 



The CSsophagus is generally wide, or at least very extensible, as 

 in the Ophidia, where it is thin and membranous ; it is much more 

 muscular in the Batrachia. In the Marine Tortoises, numerous 

 soft, cylindrical, and pointed papillae, arranged in an imbricated 

 manner, are developed upon the epithelium, and have received the 

 name of oesophageal teeth ; similar papillae occur also in the Fresh- 

 water Tortoises, but are much smaller in size, and more sparingly 

 distributed. 



The Intestinal Canal always presents a gastric dilatation, although 

 that is frequently but slight, as in the Proteus, where the canal 

 passes as a tube, nearly as broad as it is straight from the mouth to 

 the anus. The stomach is generally very elongated, and has a 

 more or less perpendicular direction ; frequently, however, as in the 

 Chameleon, it is placed horizontally, and presents a somewhat 

 curved figure. It is here also most muscular, and provided inter- 

 nally with strong longitudinal folds, while, on the other hand, it is 

 most membranous in the Serpents. The Crocodiles are distinguished 

 by a very rounded form of stomach, divided into two cavities. The 

 first, which closely resembles the gizzard of a rapacious Bird, is of 

 very considerable size, lined with a hard epithelium, and exhibits ex- 

 ternally a feebly developed tendinous disc, while, by means of a narrow 

 opening, it leads upward and backward into the second lesser and 



