Snakes and Frogs and Their Relatives [ 197 



drop in temperature is enough to cause sluggishness; and a slug- 

 gish snake does not have the energy to procure food. The solution 

 in cold climates is to hibernate in a well-sheltered rocky crevice 

 or in the ground below the frost line. In this way the snake is 

 protected from a fall in body temperature that would be low 

 enough to cause death. The animal can survive hibernation 

 without eating, provided it is in a healthy and well-fattened 

 condition at the beginning of its long rest. 



THE SNAKE'S BODY MORE THAN A TAIL 



Many children, and countless adults as well, think of a 

 snake as a long tail attached to a head. This is far from a true 

 picture there is a very efficient body between head and tail! 



This body contains a stomach capable of amazing distension 

 and digestive powers, a liver, kidneys, and other organs too. The 

 snake's heart differs from a mammal's in having only three 

 chambers. (A mammal's heart has four.) The right lung is quite 

 elongated, much more developed than the left. 



THE SNAKE'S TAIL 



The length of the tail differs according to the species. 

 However, if you scrutinize a snake's underside, you will see that 

 the tail has a definite starting point. There a distinctly enlarged 

 scale sometimes divided into two overlapping parts covers the 

 orifice through which wastes pass. This marks the beginning of 

 the tail. 



Another way of distinguishing the tail from the rest of the 

 body in most snakes is that the underside scales are large and 

 each of them extends across the whole undersurface of the body 

 whereas the scales on the underside of the tail are almost always 

 arranged in two columns. A zoologist dissecting a snake observes a 

 still more obvious division of tail and body, for the long series 

 of ribs ends where the ribless tail begins. 



THE SNAKE'S HEAD 



There are two reasons for the snake's fixed gaze: It has 

 no movable eyelids, and its eyeballs are capable of only slight 



