THE PBINCIPAL SPECIES OF POISONOUS SNAKES 



71 



body becomes twice the oudiuary size. It then doubles back its 

 head and neck in the shape of an S, and emits a loud and 

 prolonged hiss. Before biting, it first strikes a blow with its head 



Fig. 37. — Bitis arietans (the Puff Adder). (After^^Dumeril and Bibron. 



as with a battering-ram, thus justifying its French name, vipere 

 heurtante (Striking Viper). 



The natives of South Africa assert that this Viper is able to 



