14 



moved forwards in order to erect the maxillary and fang are 

 the same as those which move the ectopterygoid and maxil- 

 lary bones in harmless snakes while swallowing their prey. 

 The action is principally effected by the postfrontopterj-goid 

 and presphenopterygoid muscles (h and i in the plates) and 

 these are antagonized by the ectopterygoid, entopterygoid 

 and presphenopalatine muscles, /, g and j. 



In the vipers the fang is much longer than in the cobra 

 and other Elapidce, but its length has been greatly exagge- 

 rated, as it rarely exceeds half an inch in the largest species. 

 It is however so long that it cannot, as in the Elapidce, be 

 received semi-erect into a pit in the lower lip ; hence the 

 necessity for its complete depression when the mouth is 

 shut. This is effected bj' the aid of a slip of the ecto- 

 pterygoid muscle passing to the mucous envelope. The 

 tube of the fang is also of larger calibre and the poison duct 

 is plainly seen to open into the mouth just in front 

 of the basal orifice ; the duct winds round a groove in the 

 surface of the maxillary, (Plate IV) and a bristle passed along 

 its canal, from behind forwards, will be seen to pass out by 

 the orifice at the base of the mucous envelope of the fane. 



The mechanism of the bite of a poisonous snake may 

 differ somewhat in the viperine families from that usual 

 with the ElapidcB. The cobra bites just as a doo' does, the 

 re-curved position of the fangs rendering a slip impos- 

 sible ; whilst the vipers, though biting also, are able to strike 

 sideways with their long erected fangs. In either case the 

 effect is the same, though a bite will be much more effectual 

 than a mere prick without any counterpressure from the 

 lower jaw. The mucous envelope of the fang is mechani- 

 cally puckered up, and by its contraction forces the poison- 

 ous saliva, as it issues from the duct, to flow into the canal 

 of the fang by its basal orifice. Muscular pressure and 

 spasmodic • action of the gland cause an ejection of poison 



