354 



GENERAL ZOOLOGY 



13 



externally by the absence of eyelids and limbs, although 

 rudimentary hind legs are to be found in a few forms, such 

 as the pythons of Asia, Africa, and Australia. Teeth are 



present in all ophidians, 



...^^y;^ ^ *- 



and are of two types, 

 the ordinary teeth, used 

 for seizing food, and the 

 poison-fangs, which are 

 perforated, forming a 

 passage for the poison 

 secreted in a gland at 

 their base. Both kinds 

 of teeth are shown in the 

 illustration of the skull 

 of the rattlesnake (Fig. 

 180), which shows also the 

 gland where the poison is 

 secreted (Fig. 180, 9), and 

 the reserve fangs (Fig. 

 180, 11) which replace the 

 first pair when the former 

 are broken or shed. In the 

 non-poisonous species the 

 number of teeth is much 

 greater than in the rattle- 

 snake. 



The tongue of a snake 

 is a long, slender, forked 

 structure, used principally 

 as an organ of touch. The 

 lower jaw is joined to the upper jaw in such a way (see Fig. 

 180) as to admit of so much freedom of movement that the 

 snake's mouth can be opened wide enough to swallow animals 

 greater in diameter than itself. The passage of food into the 



Fir.. 180. Skull of Rattlesnake, showing 

 Poison-Fangs 



1, 2, bones of cranium; 3, prefrontal bone; 

 4, quadrate bone; 5, maxillary bone; 

 6, fang ; 7, bones of lower jaw ; 8, tip of 

 snout ; 9, poison-gland ; 10, poison-duct ; 

 11, reserve fangs ; 12, tip of fang ; 13, tem- 

 poral muscle 



(From Baskett's Story of the Amphibians 

 and Reptiles) 



