226 POISONOUS SERPENTS. 



its cervical integument can be expanded into a hood, constitutes an 

 immediate link between the Bungarus and Naja.{\) 



The superior maxillary bone diminishes in length with the 

 decreasing number of teeth which it supports : the transverse or 

 external pterygoid bone elongates in the same ratio, so as to retain its 

 position as an abutment against the shortened maxillary, and the 

 muscles implanted into this external pterygoid style communicate, 

 through it, to the maxillary bone the hinge-like movements backwards 

 and forwards upon the ginglymoid articulations connecting that 

 bone with the anterior frontal and palatine bones. As the fully 

 developed poison-fangs are attached by the same firm basal 

 anchylosis to shallow maxillary sockets, which forms the characteristic 

 mode of attachment of the simple or solid teeth, they necessarily 

 follow all the movements of the superior maxillary bone ; when the 

 external pterygoid is retracted the superior maxillary rotates back- 

 w^ards, and the poison-fang is concealed in the lax mucous gum, with 

 its point turned backwards : when the muscles draw forward the 

 external pterygoid, the superior maxillary bone is pushed forwards 

 and the recumbent fang withdrawn from its concealment and 

 erected. 



In this power of changing the direction of a large tooth, so that it 

 may not impede the passage of food through the mouth, we may perceive 

 an analogy between the viper and the lophius ; but in the fish the move- 

 ment is confined to the tooth alone, and is dependent on the mere 

 physical property of the elastic medium of attachment : in the 

 Serpent the tooth has no independent motion, but rotates with 

 the jaw, whose movements are governed by muscular actions. In the 

 fish the great teeth are erect, except when pressed down by some 

 extraneous force : in the Serpent the habitual position of the fang is the 

 recumbent one, and its erection takes' place only when the envenomed 

 blow is to be struck. 



The peculiar structure of the poison-fang was first described 

 byFontana as it exists in the viper (2), and subsequently received addi- 



(1) Dr. Canter, Proceedings of the Zoological Society, 1838, p. 73. 



(2) Fontana's description is as follows : " The tooth of the viper has a double pipe or tubule 

 almost for its whole length, a circumstance hitherto entirely unknown to observers. These two 



