324 



PRACTICAL ZOOLOGY 



but they are fused over the eyeball. In the center is a trans- 

 parent part through which the reptile receives light waves. 

 Ear openings are lacking and the sense of hearing is consequently 

 very feeble. The long forked tongue, however, which is often 

 erroneously considered injurious, is very sensitive to vibrations 

 and probably serves as an auditory organ. 



As in the amphibians and lizards, the teeth are sharp, conical 

 structures fitted for holding struggling animals. They are 

 curved inward and help the snake force the food down the throat. 

 A snake can swallow objects much thicker than its own body; 

 this is due to the elasticity of the body and to the fact that the 

 jaws are loosely fastened together. 



Most of the snakes lay eggs, but in a few cases, for instance the 

 common garter snake, the eggs hatch within the body of the 

 mother and the young are then born. There is no reason for be- 

 lieving the popular story that snakes swallow their young to 

 protect them and then disgorge them again when the danger is 

 past. 



FIG. 202. Garter snake. (Photo, of living animal. From Davenport.) 



Harmless Snakes. Only a few of the snakes inhabiting 

 North America are poisonous; most of them are either of no 

 special importance or else beneficial. The commonest snakes 



