250 A MANUAL OF DENTAL ANATOMY. 



to look backwards. Hence these fangs lie along the roof of 

 the mouth, concealed between folds of the mucous mem- 

 brane. But when the animal opens its mouth for the 

 purpose of striking its prey, the digastric muscles, pulling 

 up the angle of the mandible, at the same time thrust the 

 distal end of the quadrate bone forwards. This necessitates 

 the pushing forward of the pterygoid, the result of which 

 is twofold : firstly, the bending of the pterygo-palatine joint; 

 secondly, the partial rotation of the maxillary upon its 

 lachrymal joint, the hidden edge of the maxillary being 

 thrust downwards and forwards. 



"In virtue of this rotation of the maxillary through about 

 a quarter of a circle, the dentigerous face of the maxilla 

 looks downwards and the fangs are erected into a vertical 

 position. The snake ' strikes ' by the simultaneous contrac- 

 tion of the crotaphite muscle, part of which extends over 

 the poison gland, the poison is injected into the wound 

 through the canal of the fang, and this being withdrawn, 

 the mouth is shut, all the previous movements reversed, 

 and the parts return to their first position." 



The poison fang is a long, pointed, slightly recurved tooth, 

 traversed by a canal which commences on its front surface, 

 near to the bone, and terminates also on its front surface, a 

 little distance short of its point ; in the figure a bristle has 

 been passed through it, and shows the points where it com- 

 mences and terminates. This tube conveys the poison into 

 the puncture, its upper orifice being in close relation with 

 the end of the duct of the poison gland. 



It has been mentioned that some snakes which have not 

 definite poison fangs have a few of the large posterior teeth 

 grooved upon their front surfaces, the object of this grooving 

 being, as a matter of conjecture, to convey a more or less 

 poisonous saliva into the wounds inflicted by them. 



By imagining such an anterior groove to be deepened, 

 and finally converted into a canal by its edges growing up 



