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Biting mechanism of snake:-, The skull and jaw bones of poisonous snakes are very flexible. They are loosely articulated thus allowing a considerable degree of adjustment during the act of swallowing or striking. In cobras, the fangs are permanently erect. But in vipers the large fangs lie against the roof of mouth when closed. Thus the mechanism of biting serves two main purposes-, a. Erection of fangs andb. Injection of poison into victim’s body, During a strike a series of movements occur in chain. Contraction of diagastric muscles lowers the mandibles so that mouth opens and lower end of quadrate thrusts forward. This in turn pushes the pterygoid forward. The forward pull of pterygoid in turn pushes the ectopterygoid upwards. This causes the maxilla bearing fangs to rotate through 90degree. As a result fangs become vertically erect and in the most effective position to strike. A simultaneous stretching of constrictor muscles around the poison gland forces its poison through poison duct into the canal of fang to be injected into the victim. When mouth is closed by the contraction of temporal muscles, the above movements are reversed. The fangs embed in the prey which is drawn in the mouth. At the same time the vertical fangs rotate to become horizontal.