240 THE TOWER MENAGERIE. 
erected when he is irritated, and affords at the same time 
the means of inflicting the wound and of insinuating 
into it the deadly fluid with which it is charged. In the 
Rattlesnakes these two fangs are the only visible teeth 
implanted in the upper jaw; but behind each of them are 
several rudiments of others by which they are from time 
to time replaced. Their other distinguishing characters 
consist in the whole of the transverse plates which cover 
the under surface of the body and of the tail being 
simple, and in the singular apparatus by which the 
latter is terminated, and which is formed of a series, 
more or less numerous according to the age of the indi- 
vidual, of flattened rings loosely attached one within the 
other in such a manner as to produce a peculiar rattling 
sound when thé tail is moved with any degree of quick- 
ness. The number of rings commonly varies from five 
to twelve; but in very old specimens it is said to have 
been found to exceed forty. 
All the known species are natives of America, in the 
vast forests of which they may be said literally to swarm; 
but happily, like most of the other venomous snakes, 
they never exert their terrible qualities upon man except 
in self-defence, and the warning rattle is always heard 
to give notice of their approach. Their bite is almost 
uniformly fatal even to the largest animals, and the latter 
frequently evince such an instinctive dread of them, that, 
according to M. Bosc, it is almost impossible to compel 
a horse or a dog to advance towards them. Their food 
consists principally of the smaller quadrupeds, such as 
squirrels and rabbits, of other reptiles, and of birds, 
although they rarely climb trees in pursuit of their prey. 
It was long believed, and the notion is still popularly 
