30 



REPTILES AND BATRACHIANS. 



But the chief characteristic of the viper is its poison tooth. 

 "The perfection of mechanism culminates in the viperine fang," 

 writes Dr. Edward Nicholson, a distinguished ophiologist. And 

 by mechanism he refers to its mobility, the action of it. Among 

 the various wonders which we discover in the structure of a snake 

 and its control over parts of its frame that are stationary in other 

 creatures, the power in the viper to raise and fold back its fangs is 

 perhaps the greatest. Vipers, it will be remembered, have only one 

 tooth, the fang, in each upper jaw, and this when at rest lies back 

 along the gum (as in a, fig. 12), and when in use is " erected," that 

 is, brought down ready to inflict the bite (as in b), 

 and the action is instantaneous, rapid as is that of 

 the viper in striking its victim. The fang is curved, 

 pointed as a fine needle, and " hollow," commonly 

 so called. Strictly speaking, a snake's fang is a 

 long finely pointed tooth, flattened out and rolled 

 over to form a groove, as seen in the magnified examples (fig. r3). 

 In the viper the " join " — as we will call it — is so complete as to be 

 scarcely percepti- ble, in other snakes the fold is more or 



ing a channel down which the venom 

 ger example, a, the groove is more 

 At the base the venom enters from a 

 Close to the point in a viper's fang 

 and through this slit the venom is 

 forced out again into the wound by 

 the action of " striking," as the rapid 

 bite is called. All is swift as a flash ; 

 but the noxious power of the venom 

 is so great that in that moment of 

 time enough has passed through the 

 tiny slit into the flesh of the bitten 

 creature to cause its death. The 

 viper then draws back its head, and 

 waits till the victim ceases to struggle, 

 when it again approaches stealthily, 

 cautiously surveys the prey, and if 

 quite dead grasps it conveniently, and 

 proceeds to swallow it. I have seen 

 some vipers never letting go their 

 hold after striking, but swallowing the 

 prey at once. Usually they are 

 extremely cautious, and this from fear, 

 being absurdly cowardly. 



It used to be supposed that the 



Fig. 



less evident, form 

 flows. In the lar- 

 open than in b. 

 gland at its root. 

 is a very tiny slit, 



Fig. 13. — Two fangs magnified, 

 showing the slit or join more or 

 less complete. f is a section. 

 From Fayrer's Thanatophidia. 



