70 OUR REPTILES. 



shown in at once biting out the piece of flesh. The poison, 

 however, had swelled up his arm through his veins as high 

 as his shoulder ; but by the next day this black streak of 

 poison apparent in the veins of his arm had completely dis- 

 appeared, and in the course of a few weeks the boy was 

 perfectly restored to health.* 



The poison apparatus of the viper (see wood- 

 cut at the head of this chapter) consists of the 

 gland in which it is secreted, the duct or canal 

 along which it travels, and the fang by means 

 of which it is injected. The gland is placed at 

 the side of the head (a], and consists of an 

 assemblage of lobes. The substance is soft and 

 yellow, with a spongy appearance. The duct or 

 canal through which the poison is conveyed to the 

 fang is a narrow cylindrical tube (b) swelling in 

 the centre of its course into a kind of reservoir, 

 and terminating at the base of the fang (c) . This 

 latter is a tooth in the form of a tube, much 

 longer than the other teeth, and curved (d). It is 

 placed in the upper jaw, one on each side of 

 the mouth. Behind these are the similarly 

 shaped, but smaller, fangs of replacement. 

 On the outer surface of the fang, near the 

 apex, is an elongated opening or slit (e} } from 

 which a canal passes through the hollow in the 

 interior of the tooth and is united to the duct 

 which communicates with the poison-gland. 



* Hardwicke's Science Gossip, vol. i. p. 131. 



