The thromboplastic activity of Russell's viper venom and its relationship to factor VII.

as a powerful local haemostatic agent in the treatment of haemophilia. Fullerton (1940) substituted Russell's viper venom for rabbit-brain thromboplastin in his modification of Quick's one-stage prothrombin time, since viper venom could be obtained in a more convenient and more stable form than brain extract It soon became apparent, however, that the two methods gave widely different results. Wilson (1947) and many other workers found that in cases treated with dicoumarol much higher plasma prothrombin values were obtained with venom than with brain thromboplastin, and, in fact, Fullerton's modification could be dangerous, since it gave inadequate warning of prothrombin values low enough to cause haemorrhage. It has been shown by Macfarlane, Trevan, and Attwood (1941) that a lipoid substance in the plasma is necessary for the action of viper venom, and an excess of lipoid, such as occurs after a fatty meal, shortens the prothrornbin time with venom but not with brain thromboplastin (Fullerton and Anastasopoulos, 1949). A further source of the difference in action of the two thromboplastins became apparent when it