33 8 COMPARATIVE ANATOMY AND PHYSIOLOGY. 



united by a symphysial suture, but are only con- 

 nected by an elastic ligament. Thanks to this dis- 

 position of the separate parts in front and behind, 

 the cavity of the mouth is capable of very considerable 

 enlargement. 



In the venomous snakes the arrangements are 





M/t 



Fig. 142. Skull of Crotalus. 



Pmp, Premaxilla; Ma;, maxilla; La, lachrymal; vl, palatine; Ft, pterygoid ; 

 QU, quadrate; MM, lower jaw. (After Huxley.) 



even more elaborate ; the maxilla, instead of being 

 elongated backwards, is shortened antero-posteriorly, 

 so that its longer axis is directed downwards ; it 

 carries one long tooth, the "poison fang," and is 

 excavated on its upper outer surface, where there lies 

 the duct of the poison gland ; the maxilla moves freely 

 on the lachrymal, which again can move en the 

 frontal. The palato-pterygoid bar (Fig. 142 ; P, pt) is 

 jointed, and the pterygoid is further connected with 



