558 REPTILIA. 



(615.) In the venomous serpents those teeth, which are fixed to 

 the margin of the superior maxillary bone of the innoxious genera, 

 are generally deficient ; and instead of them there is found an appa- 

 ratus of poison-fangs, constituting perhaps the most terrible weapons 

 of attack met with in the animal creation. The poison-teeth (fig. 

 251, a) are two in number, one fixed to each superior maxillary bone : 

 when not in use, they are laid flat upon the roof of the mouth, and 



Fig. 251. 



covered by a kind of sheath formed by the mucous membrane of 

 the palate ; but when the animal is irritated, or about to strike its 

 prey, they are plucked up from their concealment by muscles in- 

 serted into the upper maxillary bone, and stand out like two long 

 lancets attached to the upper jaw. Each fang is traversed by a canal ; 

 not, as it is generally described, excavated in the substance of the 

 tooth, but formed by bending as it were the tooth upon itself, so 

 as to enclose a narrow channel through which the poison flows. 

 The canal so formed opens towards the base of the tooth by a 

 large triangular orifice, but at the opposite extremity it terminates 

 near the point of the fang by a narrow longitudinal fissure. The 

 gland wherein the poison is elaborated occupies the greater part 

 of the temporal fossa, and is enclosed in a white and tendinous 

 capsule (Jig. 251, ); the substance of the organ is spongy, and 

 composed of cells communicating with its excretory duct (c), by 

 which the venom is conveyed to the opening at the base of the 

 fang.* The poison-gland is covered by a strong process of the tem- 



quence of the mechanism referred to, to disgorge it, was found dead, and the skin and 

 muscles of its neck absolutely rent from excessive stretching. 



* M6moire sur les caracteres tir6s de 1'Anatomie pour distinguer les Serpens venimeux 

 des Serpens non-venimeux ; par M. Duvernoy, D. M. Annales des Sc. Nat. torn. xxvi. 



