176 THE SNAKES OF SOUTH AFRICA. 
African snakes which expand a “hood.” If a snake is seen 
rearing the fore part of its body perpendicularly above the 
ground, and expanding the skin of its neck in the well-known 
manner of Cobras, you may be perfectly sure it is one of the 
Cobras, and that it is a very highly venomous serpent. 
THE PoIson APPARATUS. 
The Cobra has strong poison fangs in the upper jaw—two on 
each side. These fangs are deeply grooved down their front 
Fic. 75.—This picture shows the elongated ribs of the neck of a Cobra with 
the muscle attachments. By means of these long ribs and muscles the 
hood is spread. The head is on the right. 
surface. In most individuals the sides of the channels meet and 
form hollow fangs. The grooves or channels are for the con- 
veyance of the venom from the poison glands into the wounds 
made by the fangs. The bite and the compression and contraction 
of the poison glands is simultaneous. 
The fangs of Cobras are set in front of the upper jaw, in a bone 
called the anterior maxillary. This bone is not very movable. 
On the contrary, with the Viper family of snakesit is mobile, and 
hinge-like in its movements. 
