One of the poisonous principles found in the venom of Brazilian rattlesnakes, Crotalus terrificus crotaminicus Goncalves, Crotalidae. A polypeptide having mol wt 10,000-15,000 and isoelectric point at pH 10.3. Purification and properties: Goncalves in Venoms, E. E. Buckley, N. Porges, Eds. (Publ. no. 44 of the Am. Assoc. Adv. Science, Washington, D.C., 1956) pp 261-274. Pharmacology: Moussatché et al., ibid. pp 275-279.