Showing fangs of rhinoceros viper (Bitis nasicornis). The vipers have the most highly developed venom delivery system of all snakes. The venom glands are located below and behind the eyes and the venom is carried by a duct on each side to the base of the fangs. The hollow fang resembles a hypodermic needle. The fangs are attached to a system of hinged bones which allow the fangs to become erect and deliver the venom with great efficiency when the snake strikes and bites. 1965.