Numerous experiments have been conducted to determine the susceptibility of various snakes to venom. The majority of these experiments were performed to learn whether or not venomous snakes were immune to their own poison. Conant (1934:382) reported on a 30-inch cottonmouth that killed two Pacific rattlesnakes and another cottonmouth. One rattlesnake was bitten on the tail and the other on or near the head and partially swallowed. Gloyd (1933:13-14) recorded fatal effects to a rattlesnake from the bite of a cottonmouth. He also reported on the observations of three other crotalids bitten by themselves or other snakes, from which no harmful effects were observed. Allen (1937) injected several snakes with dried cottonmouth venom which was diluted with distilled water just before each injection. Four cottonmouths receiving 9, 18, 19, and 20 milligrams of venom per ounce of body weight survived, while another receiving 18.7 milligrams per ounce died after three hours. A specimen of _S. miliarius_ receiving 8.3 milligrams per ounce died in about ten hours, while a _C. durissus_ receiving 12.5 milligrams per ounce succumbed in 45 minutes. An alligator receiving 6 milligrams per ounce died in 14 hours. Even the snakes that survived showed some degree of swelling. The studies of Keegan and Andrews (1942:252) show that king-snakes are sometimes killed by poisonous snakes. A _Lampropeltis calligaster_ injected with _A. contortrix_ venom (0.767 milligrams per gram) died five days following the injection. This amount was more than twice the amount of _A. piscivorus_ venom injected into a _L. getulus_ by Allen (1937) in which the snake showed no ill effects. Keegan and Andrews (_loc. cit._) stated that success in overpowering and eating poisonous snakes by _Lampropeltis_ and _Drymarchon_ may be due to the ability to avoid bites rather than to immunity to the venom. However, Rosenfeld and Glass (1940) demonstrated that the plasma of _L. g. getulus_ had an inhibiting effect on the hemorrhagic action on mice of the venoms of several vipers. One of the more extensive studies on effects of venoms on snakes is that by Swanson (1946:242-249). In his studies freshly extracted liquid venom was used. His studies indicated that snakes are not immune to venom of their own kind or to closely related species. Copperhead venom killed copperheads faster than did other venoms but took more time to kill massasaugas, cottonmouths, and timber rattlers. However, most of the snakes were able to survive normal or average doses of venom although they are not necessarily immune to it.