2-14 



COMPARATIVE ANATOMY 



is perforated by a poison-canal, which is incompletely surrounded 

 by the pulp-cavity, the latter having the form of a half-ring in 



Fig. 194. — A, Diaobams of Tkansvekse Section through the Jaws of 

 Reptiles, showing Pleurodont (a), Aceodont (b), and Thecodont (c) 

 Dentitions. B, a, Lower Jaw of Zootoca vivipara ; b, of Anguis fragilis.. 

 (After Leydig. ) 



transverse section (Fig. 195, B, C,) : the duct of the poison-gland 

 passes into an aperture at the base of the tooth which leads into. 



T^ 



C 



Tig. 195. — Figures of the Poison-Fangs op a Viperine Snake. 



A, skull of Rattlesnake ; B, transverse section through about the middle of the- 

 poison-fang of Vipera ammodytea ; C, transverse section through the poison- 

 fang of Vipera ammodytes near its distal end. (B and C after Leydig.) 



Gz, poison-fang; Rz, reserve fangs ; OC, poison-canal ; PH, pulp-cavity. 



the poison-canal, and the latter opens at a short distance from the- 

 apex of the tooth (see the course of the arrow in Fig. 195, A). 



