540 MANUAL OF ZOOLOGY. 



the mouth in the Snakes is capable of opening to an enormous 

 width, and the most astonishing feats in the way of swallowing 

 can be performed. Secondly, this structure of the jaws accords 

 exactly with the structure of the teeth, both concurring to 

 render the Snakes wholly incapable of anything like mastica- 

 tion, and at the same time capable of swallowing immense 

 morsels entire. The teeth, namely, are simply fitted for 

 seizing and holding the prey, but not in any way for dividing 

 or chewing it. In the non-venomous and most typical Snakes, 

 the jaws and palatine bones carry continuous rows of solid 

 conical teeth, so that there are four rows above and two below ; 

 and the superior maxillae are very long and are not movable. 

 Thirdly, in the Viperine Snakes, and the Crotalida, the ordi- 

 nary teeth are wanting upon the superior maxillae, whilst these 

 bones are themselves very much shortened, and are capable 

 of being raised and depressed at will. In place of the ordi- 

 nary teeth, each maxilla carries a " poison-fang," in the form 

 of a long, conical, curved fang, which is concealed in a fold 

 of the mucous membrane when not in use, and has numerous 

 germs or reserve-fangs behind it (figs. 296, 13, and 297). Each 



Fig. 297 - Skull of the Rattlesnake (after Dumeril and Bibron). / Left ramus of the 

 lower jaw, united to the skull by the quadrate bone (q) ; m Upper jaw carrying the 

 poison-fang ; p Series of teeth upon the palate. 



tooth is perforated by a tube, opening by a distinct aperture 

 at the apex of the tooth, and conveying the duct of the so- 

 called poison-gland. (In reality the poison-duct of the fang is 

 formed by an inflection of the tooth upon itself, and not by its 

 actual perforation.) This is a gland (fig. 298), probably pro- 

 duced by a modification of one of the buccal salivary glands, 

 situated behind and under the eye on each side, and secreting 

 the fluid which renders the bite of these snakes dangerous or 

 fatal. When the animal strikes its prey, the poison-fangs are 

 erected by the elevation of the movable maxillae (to which 



