The venom of several species of poisonous snakes acts to spread India ink through the skin as do the spreading factors procurable from certain tissues and elaborated by invasive bacteria. The factor is most abundant in the venom of the Viperidae (rattlesnake) family and relatively scant in the venom of Colubridae proteroglypha (cobra) family, and it is absent from toad venom. Extracts of the supralabial glands of harmless snakes contain only negligible amounts of the factor.
Rattlesnake venom heated at 65° to 100° loses a large proportion of its toxicity but retains the ability to spread ink.
Rattlesnake venom that has lost its toxicity on standing or on heating markedly enhances the infection produced by bacterial or virus suspension in the rabbit skin.
Antivenine serum inactivates both the toxic and spreading factors of venom.