94 



STORY OF THE REPTILES 



of the forward active one, should it be broken ; so 

 that jerking the poison-fangs out of a rattlesnake 

 makes it harmless for a short time only. The new 

 ones do not have to grow much, but merely 7'ise into 

 place (Fig. 51). 



Cranium 

 Nasal bone 



Upper jaw 

 Poison-fansjs 



Lower jaw^ 



•Mastoid bone' 

 which, to- 

 gether with 

 the tympanic 

 bone, sus- 

 pends the 

 lower to the 

 upper jaw. 



'"Tympanic 

 bone. 



Nostrils •• 



Poison-gland connect- 

 ed by a passage with 

 the movable hollow 

 tube as here shown. 



Two large movable 

 teeth or fangs through 

 which the poison 

 reaches a wound 

 made by them. 



Salivary glands--'"' 

 Poison-gland • 



Passage from the poi- • 

 son-gland to ihe fang. 



Hollow fang ••- 

 Reserve fangs ■• 



Muscles which 

 elevate the 

 lowerjawand 

 also serve to 

 compress the 

 poison-gland, 

 thus forcing 

 the venom 

 into the 

 fangs. 



...-Small aperture in end of 

 fang through which 

 the poison escapes into 

 a wound. 



Fig. 51. — 1, skull of rattlesnake, showing the manner in which the 

 upper jaw is connected with the lower one ; 2, head of rattlesnake 

 di.ssected to show poison-glands, etc. ; 3, poison-gland of rattle- 

 snake. 



Tongues 



The tongues of reptiles are various in shapes. 

 So far as known none are tied down in front only, or 

 are largely free behind, as in the amphibians. The 



