28 



r 



The Living Things of the Earth unit i 



Fig. 36 (above) Aj7 adult copperhead 

 may be two or two and one half feet 

 long. As in rattlers and water vioc- 

 casins, the head is triangiilar. (u. s. bu- 

 reau OF BIOLOGICAL SURVEY) 



Fig. 37 (right) This x-ray photograph 

 of a snake shows the long backbone 

 and the 7?iany ribs which help in 

 locomotion, (general electric x-ray 



CORP.) 



uncommon in the south. The water moc- 

 casin, which lives in swamps, is some- 

 times called "cottonmouth" because the 

 inside of its mouth is white. The coral 

 snake is smaller than the water moccasin 

 and has short fangs but when it bites, 

 it hangs on, and sometimes its bite is 

 serious. It often burrows in damp 

 ground. Do Exercises 7 and 8. 



Peculiarities of snakes. Snakes have 

 an enormously long backbone, consist- 

 ing of many vertebrae each of which, 

 except at the tail end, has a pair of ribs. 

 Muscles connect the ribs with the scales 

 on the lower part of the snake. By mov- 

 ing the ribs, the scales are hooked onto 

 the uneven surface of the ground, one 

 after the other. Thus the snake really 

 wriggles on its scales, but this happens 



so fast and evenly that it looks like a 

 smooth gliding motion. No snakes have 

 legs, although the pythons (pie'thons) 

 of Asia have tiny stumps of hind legs 

 which are not used. 



Because of its peculiar formation, a 

 snake's mouth can be opened so wide 

 that it will admit an animal broader 

 than the head of the snake. The animal 

 must be swallowed whole since the 

 teeth are not used for biting off or chew- 

 ing food. At irregular intervals as snakes 

 gro\\' they develop a nt\x skin under- 

 neatii the old one. The old skin is then 

 shed as in the photograph. Figure 39. 



Snakes of other countries. While snakes 

 in our part of the world arc not a real 

 danger, in India, Central and South 

 America, and other tropical regions 



