Poison Fangs of the Viper. 47 



26. Poisonous Snakes. The most remarkable, 

 though not the most numerous group of serpents, 

 are those provided with poison-fangs, the vipers and 

 rattlesnakes. Of these the best known is the rattle- 

 snake, in which animal the epidermal clothing of the 

 last few tail-joints is loose, and consists of hard, horny 

 rings loosely embracing each other ; these cause the 

 rattling noise, when the animal's tail is shaken, which 

 nas given rise to the name of this dreaded American 

 snake. Like most other poisonous snakes, it has 



FIG. 20. 



Poison apparatus of rattlesnake. 

 #, poison bag and duct ; e, i, g, t, u y muscles of jaw. 



a flat triangular head, and in its mouth there can be 

 seen the two long grooved maxillary teeth in which 

 are the channels for the poison. These are the only 

 large teeth in the mouth, all the others being small 

 and obscure. They are placed far forwards in the 

 upper jaw, and are movable along with the movable 

 maxilla, being bent upwards towards the palate in the 



