MANUAL OF ZOOLOGY. 



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 the ordinary 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 ordinary 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 

 (fig. 196, B). Each 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, 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 

 they are anchylosed), and the poison is forced through the tube 

 which perforates each, partly by the contractions of the 

 muscular walls of the gland, and partly by the muscles of the 

 jaws. In most poisonous snakes the superior maxillae carry no 

 other teeth except the poison-fangs and their rudimentary suc- 

 cessors, but in some cases there are a few teeth behind the 

 fangs ; whilst the palatine teeth are always present, as in the 

 harmless species. In some other venomous Snakes, again 

 (e.g., Naja and the Hydrcphidcz), the jaws and teeth agree in 

 most characters with those of the non-venomous Snakes, but 

 the first maxillary teeth are larger than the others, and form 

 canaliculated fangs. Lastly, in a few forms the terminal 

 maxillary teeth are deeply canaliculated, but are not connected 

 with the duct of any poison-gland. 



Fourthly, in all the Serpents the teeth are anchylosed 

 with the jaw, and are never sunk into distinct sockets or 

 alveoli. 



A good classification of the Ophidia is still a desideratum, 

 and probably, in the meanwhile, the one proposed by Dr Gray 



