THE ANIMAL CLIMAX-THE CHORDATES 



329 



without lids. Their sound-recording -organs 

 are superior to those of amphibians. The 

 snake possesses a long forked tongue which 

 jDasses in and out through a notch in the 

 upper lip, a conspicuous habit when it is 

 investigating new territoiy. The tongue has 

 sensory functions in tracking down prey 

 (Fig. 13-48). 



The snake's mouth is equipped with 

 sharp teeth that curve inward and are well 

 adapted for holding its victim ( Fig. 13-49 ) ; 

 any struggling movement of the prey tends 

 to force the creature further down the 

 throat of the snake. Since all of the snake's 

 diet consists of whole animals, another con- 

 venient adaptation associated with food 

 taking is the enormous potential size of the 

 mouth, which can be stretched to accom- 



modate an animal several times its own 

 diameter (Fig. 13-50). A python has been 

 known to swallow a full-grown hog. The 

 reason for this great distention lies in the 



coostnctor. 

 muscle 



poison 

 gland 



nostril 



poison duct 

 opening oP 



fang 



.tongue 



Fig. 13-48. Head of rattlesnake with the right cheek dis- 

 sected away in order to show the poison sac and 

 other parts. 



Fig. 13-49. The skull of a rattlesnake. Note how loosely the jaw bones are attached to the skull. This, together with 

 the lack of fusion of the jaw bones in front, makes it possible for the snake to swallow an animal several times 

 its own diameter. One of the fangs has been enlarged in the lower picture to show its hollow construction. It 

 resembles an inoculating needle. 



