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 



Fig. 142. Skull of Crotalus. 



pmp, Premaxilla; TAX, maxilla; La, lachrymal; p/, palatine; pj, pterygoid ; 

 QM, quadrate; M, 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 

 oil the lachrymal, which again can move cii the 

 frontal. The palato-pterygoid bar (Fig. 142 ; pi, Pt) is 

 jointed, and the pterygoid is further connected with 



