All snakes have a large amount of saliva that helps them swallow and digest prey. In the venomous snakes one of the salivary glands produces a substance that is poisonous to the snakes prey. This substance is the snakes venom or poison.
Some snakes have venom that is strong enough to kill an elephant. Others have mild venom which can kill only small lizard. About two hundred species of venomous snakes can be considered dangerous to man.
Among the venomous species of snakes known, the cobras and the related snakes make up one family, the vipers, the second. There are some venomous snakes among a kind known as the colubrids, the largest family of snakes.
There is spitting cobra that can spray venom from its fangs. The cobra aims at the eyes of a threatening animal. The spray reaches about eight feet and causes almost instant blindness.
In general cobra venom affects the nervous system of the victim and makes him unable to move. When the venom reaches the nerve centres that control breathing or heartbeat the victim dies.
Vipers have very long fangs. Their venom affects mainly the blood cells and blood vessels of the victims.
