snakebite wound inflicted by the teeth of a snake. The bite of a nonvenomous snake is rarely serious. Venomous snakes have fangs, hollow teeth through which poison is injected into a victim. All types of snake venom contain a toxin that affects the nerves and tends to paralyze the victim. In addition, the venom of the coral snake, the cobra, and the South American rattlesnake contains constituents that damage blood cells and dissolve the linings of the blood vessels and the lymphatic vessels, causing severe or fatal internal hemorrhage and collapse. First aid for venomous snakebites consists of retarding the spread of the poison through the circulatory system by applying a constricting band or an ice pack, or by spraying ethyl chloride on the wound. It is essential that the patient avoid exertion and the taking of stimulants, as both increase the pulse rate. The constricting band should be applied above the swelling caused by the wound; it should be tight, but not tight enough to stop the pulsing of the blood. If only a few minutes have passed since the infliction of the bite, it is possible to remove much of the poison by suction (see first aid ). Antivenins, which counteract the toxins, are available for most types of snake venom. The two main groups of poisonous snakes in the United States are the coral snakes, which rarely attack humans unless provoked, and the pit vipers (copperhead, cottonmouth moccasin, the various rattlers), which require no provocation.