346 THE SNAKES OF SOUTH AFRICA. 
thus forcing the maximum amount of venom into the punctures. 
Many snakes, such as the Puff Adder and Boomslang, hang on 
and worry the flesh if allowed. 
Inserted into the tough fibrous capsule of the poison glands 
are some of the fibres of the Masseter muscles. The instant the 
snake bites, these muscle fibres contract powerfully, and the 
gland is wrung after the manner of twisting and wringing a wet 
rag to remove its moisture. A comparatively large lymph-like 
space surrounds the gland, and so permits of this wringing. The 
Fic. 136.—The sheathed fangs of a Puff Adder. When lying back in this position they are 
enveloped by a protecting membrane or sheath known as the Vagina dentis. 
venom which is stored up in the numerous little cavities within 
the glands is thus driven with considerable power into the 
channels or conducting tubes which communicate with the 
bases of the hollow or grooved fangs. It rushes down the grooved 
or hollow fangs and issues out in two fine streams. 
The bringing together of the end of the poison duct with the 
hole at the base of the fang is completed with marvellous exact- 
ness. By a wonderful arrangement of muscle-fibres, the harder 
the snake presses his jaws when biting, the tighter does the 
papilla at the end of the duct plug the hole in the fang. In fact, 
