POISONOUS SNAKES OF NORTH AMERICA. 



377 



power applied through the maxillary bone. These movements elevate a little the 

 muzzle of the snake, so as to give to the face a very siugular expression during the 

 act of striking. Their more obvious and important result is the elevation of the 

 fang, which, rising, thrusts off from its convexity the cloak-like vagina-deutis so 

 that it gathers in loose folds at its base (fig. 22.) 



As the unsheathed tooth penetrates the flesh of the victim a series of movements 

 occur, which must be contemporaneous, or nearly so. The body of the snake, still 

 resting in coil, makes, as it were, an anchor, while the muscles of the neck contract- 

 ing draw upon the head so violently that when a small animal is the prey it is 

 often dragged back bv the effort here described. If now the head and fang remained 



Fig. 22. 



PALATE OF THE RATTLESNAKE. 



«' Fang; f sheath (vagina dentis) covering the fang; /sheath thrown back so as to show the fang; 

 g palatine teeth. (Alter nuvernoy. ) 



passive the pull upon the head would withdraw the fang too soon ; but at this 

 moment the head is probably stayed in its position by the muscles below, or in front 

 of the spine; while the pterygoideus externus and spheuo-palatine acting upon the 

 fang through their respective insertions, into the posterior apophysis of the sub- 

 maxillary bone, and the inside of the palate bone, draw its point violently back- 

 ward, so as to drive it more deeply into the flesh. The muscles alluded to, there- 

 fore, antagonize the spheno-pterygoid. At this instant occurs a third series of 

 motions, which result in the further deepening of wound and in the injection of -the 

 poison. The lower jaw is closed upon the bitten part or member. Where the surface 

 struck is flat and large this action will have but slight influence. 



Where the jaw shuts on a small limb or memljer, the consequent eflects will be far 

 more likely to prove serious, since the power thus to shut the mouth materially aids 



