CLASS REPTILIA 



395 



crawls out of its old skin, which becomes turned inside out in the process. 

 When snakes are about to shed, the old skin becomes dull and opaque. 

 The eyehds are fused over the eyes, which are covered with transparent 

 scales, and since at this time these scales also become opaque, the snake 

 is partially bhnd. After shedding, the new covering is bright and the 

 eyes are once more perfectly clear. 



Snakes possess very good vision. As they have no tympanic mem- 

 brane, their sense of hearing is not highly developed. Their sense of 



Fig. 284. — Timber rattlesnake, Crotalus horridus Linnaeus, of the eastern United 

 States. Range from Vermont to Florida and west to the Missouri river. Referred to by 

 Ditmars as "one of the most beautiful of the North American rattlesnakes." A very 

 poisonous snake. {Photographed and contributed by George E. Hudson.) 



smell is good, but that of taste poor. The tongue is slender, deeply 

 forked, and lodged in a sac in the floor of the mouth. When the jaws 

 themselves are closed, the tongue may be protruded through an opening 

 formed by notches in the two jaws (Fig. 276). The tongue is used as an 

 organ of touch and with it the snake tests objects. Contrary to popular 

 opinion it can inflict no wound. 



The majority of snakes lay eggs but a few are vi\aparous. The 

 idea is prevalent that snakes can swallow their young when danger 

 threatens but this is not supported by scientific observation. 



