The clotting action of Russell viper venom.

By SAMUEL I. RAPAPORT, KNIJT AAS ANI) PAUL A. OWREN T HE DE1\IONSTRATION of the thromboplastin-hike activity of Russell viper venom by Macfarlane and Barnett’ was followed by its use in some laboratories as a substitute for brain thromboplastin in “prothrombin time” determinations. However, it gradually became apparemit that there were importamit differences between the ‘thromboplastic” activity of Russell viper venom amid that of brain thromboplastins. These include: (1) the failure of venom to accelerate the (‘lotting of plasma from which all platelet and lipoid material has 1)eemi removed,2 amid the variation in the venom clotting time which may be produced l)y alteration of the platelet and/or lipoid content of plasma,3 ‘ . ‘ 6