MECHANICS OF SNAKES — LEUTSCHER 



311 



attempt was made to strike. It once took and swallowed a lizard alive, 

 in which act the fangs remained in the resting position. 



The groove along the front edge of the fang, as seen in cobras, is' 

 completed into an internal canal in the Viperidae. In such a canalized 

 tooth there is an inner opening which appears as a slit at the base of 

 the fang on the posterior side. This communicates with a duct lead- 

 ing to the poison sac, which in the viper is a modified salivary gland 

 lying in the roof of the mouth just below the eye. The outer opening 



SQUAMOSAL 



QUADRATE 



MAXILLA 



FANG 



ATTACHED TO MAXILLA 



Figure 4. — Erection of fang caused [hy rotation of the maxilla and the chain of bones 



connected to it. 



of the fang is set just behind the tip, whose needle sharpness is thereby 

 not impaired. Venom is stored in the spaces within the sac, upon 

 which pressure is brought to bear by the flexion of the facial muscles. 

 These are in close relation with the venom sac, which is squeezed by 

 the muscles in a kind of wringing action. Venom passes via the duct 

 that lies over the maxillary bone, into the hollow fang which is pro- 

 tected by a thick, mucous sheath, and so into the wound. Not a single 

 drop need be wasted (fig. 3). 



In some cases poison is actually thrown from the fang some distance 

 from its target. In some of the "spitting cobras'' the poison may be 



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