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 rise into 

 place (Fig. 51). 



Cranium — 

 Nasal bone 



Upper jaw 

 Poison-fangs -^ 



Lower jaw 



Nostrils 

 Poison-gland connect- 

 ed by a passage with 

 the movable hollow 

 tube as here shown. 

 Two large movable 

 teeth orfangs through 

 which the poison 

 reaches a wound 

 made by them. 



Salivary glands 

 Poison-gland 

 Passage from the poi- 

 son-gland to I he fang. 



Hollow fang 

 Eeserve fangs 



• Mastoid bone- 

 w h i c h , to- 

 gether with 

 the tympanic 

 bone, sus- 

 pends the 

 lower to the 

 upper jaw. 



''Tympanic 

 bone. 



• Muscles which 

 elevate the 

 lower jaw and 

 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 

 dissected 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 



