CLASS REPTILIA 385 



used on a smooth surface where the scutes do not gain a hold. When the 

 snake is alarmed, it attempts to make more rapid headway by alternately 

 throwing the body into coils and then straightening it again. Swimming 

 is also accomplished by lateral convolutions of the body. 



The whole epidermal covering is shed at one time and several times 

 during a year. After a new horny covering is formed under the old one, 

 the latter is freed along the margins of the jaws and the animal literally 

 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 eyelids 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 blind. 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 

 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. 261). 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 viviparous. The 

 idea is prevalent that snakes can swallow their young when danger 

 threatens but this is not supported by scientific observation. 



Snakes are more abundant in the tropics than elsewhere and are 

 frequently absent from islands, though found on the adjacent continents. 

 Some snakes live mostly in and about fresh water; some live in salt 

 water; others are subterranean, burrowing in the ground; while still others 

 are expert tree climbers. The largest of snakes are a python found in 

 Burma, which reaches a length of over 30 feet, and an anaconda of the 

 region of the Amazon in South America, which may approach 40 feet 

 in length. 



417. Venomous Snakes. — The sea snakes are very poisonous. They 

 are tropical forms found in the Indian Ocean, the adjacent parts of 

 the Pacific, and along the western coast of South America. They 

 belong to the same general group as the coral snakes and the cobras, all 

 having tubular fangs in the anterior part of the upper jaw, in connection 

 with which are poison glands which secrete a very effective venom. The 

 cobras are found in India, China, the Malay Archipelago, and Africa. 

 These snakes are capable of expanding the anterior part of the body 

 and of raising the head and that part of the body well off the ground. 

 In this attitude they strike. India is outstanding for the number of 

 species of venomous snake living in its area and many people die there 

 from snake bites each year. 



