244 



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, DIAGRAMS OF TRANSVERSE SECTION THROUGH THE JAWS OF 

 REPTILES, SHOWING PLEURODONT (a), ACRODONT (6), 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 



FIG. 195. FIGURES OF THE POISON-FANGS OF A VIPERINE SNAKE. 



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

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

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



Gz, poison-fang ; /?z, reserve fangs ; GO, 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). 



