THE REPTILES 



187 



not concerned with the protection of the brain. In the 

 reptiles the lower jaw does not unite directly with the 

 skull, as in the higher animals, but to an intermediate 

 bone, the quadrate, which is attached to the skull. In the 

 snakes these unions are made by means of elastic liga- 

 ments. The two halves of the lower jaw are also held 



FIG. 112. Blacksnake (Bascanion constrictor). Photograph by W. H. FISHER. 



together by a similar band, so that the entire palate and 

 lower jaw are loosely hung together. This enables the 

 snake to distend its mouth and throat to an extraordinary 

 degree, and to swallow frogs and toads but slightly smaller 

 than itself. Where the prey is of relatively small size, the 

 halves of the lower jaw alternate with each other in pulling 

 backward, thus drawing the food down the throat. The 

 food is never masticated. The teeth are usually small and 

 recurved, and serve only to hold the food until it may be 

 swallowed. The latter process is facilitated by the copious 

 secretion of the salivary glands, which become very active 

 at this time. 



A further character of the snakes is the absence exter- 



