THE REPTILES 1 77 



oped a remarkable degree of strength, quickness and effect- 

 iveness which has enabled them to become one of the 

 dominant groups of reptiles. By the winding movements 

 of the body, snakes can progress with considerable rapidity, 

 and they are especially adapted to making headway 

 through masses of vegetation which would greatly impede 

 the movements of other animals. The large overlapping 

 scales of the ventral side of the body with their free 

 posterior edges serve to facilitate forward movement by 

 catching in the irregularities of the surface over which 

 the animal glides. 



Snakes are carnivorous and feed upon living animals. 

 The teeth of snakes are conical and adapted for seizing 

 and retaining prey which is 

 always swallowed entire. The 

 jaws are especially adapted to 

 swallowing large animals in 

 being separable from the skull 

 at the base, thus permitting 

 a great enlargement of the FIG. 141. Jaws of rattlesnake 



thrnst 'srmlrpc f r P> mi P rvH Ar showing fang, F, and poison sac, 



equently p (After We i r Mitchell.) 

 swallow animals whose bodies 



are much thicker than their own, and when distended with 

 food they may remain for several days in a dormant con- 

 dition while their meal is undergoing digestion. 



Periodically snakes shed their outer skin which usually 

 comes off in a single piece. Even the covering of the 

 eyes is shed along with the rest, these organs being pro- 

 tected by a transparent part of the general skin instead 

 of eyelids. While most snakes lay eggs, others, such as our 

 common garter-snakes, bring forth their young alive. 

 Despite stories of snakes taking their young into 

 the mouth to protect them from danger there is almost no 

 care for the young on the part of the parents; the young 



12 



