SNAKES. 



125 



poisonous weapons of these creatures are to be 

 found in a pair of specially modified teeth in the 

 upper jaw, and a corresponding pair of poison 

 bags or glands. These teeth in some forms are 

 marked by a deep furrow in front ; in others, 

 the edges of the furrow meet to form a channel 

 open only at the point of the tooth. At the 

 base of each tooth is the bag of poison, so placed 

 that the opening of the mouth causes the poison 

 fang which has been lying folded back towards 



FIG. 10. Head of a poisonous snake dissected to show the poison gland 

 and fang through which the venom is conducted. After GADOW. 



the throat to press upon the bag and force out 

 of it into the groove, or tube of the tooth, a 

 small but deadly quantity of venom, which is 

 introduced into the body of the snake's victim 

 as the fang buries itself in the flesh thereof. 



The poison bag is formed by a modification of 

 either of certain salivary glands known as the 

 upper labial gland, or of the gland answering 

 to the parotid gland. The fact that two different 

 glands have been utilised for the same purpose, 

 coupled with the fact that the bones bearing the 

 fangs differ remarkably in size, is strong evidence 



