Abstract
Summary
1. A factor (plasma thromboplastin) can be absorbed from citrated human plasma which shortens the clotting time of normal oxalated recalcified human plasma and increases the prothrombin utilization of platelet-poor hemophilic and thrombocytopenic plasma. This factor has been eluted and purified. An assay for its activity has been developed. A unit of activity, physicochemical properties and biologic activity have been defined. 2. Plasma thromboplastin can be clearly differentiated from other known coagulation factors on the basis of its properties; its evolution requires one or more platelet and plasma factors and contact with a foreign surface. It probably represents the final product of the first phase of blood coagulation (activation of thromboplastin). Its administration has been proven to correct in vivo the defective prothrombin utilization of thromboplastin-deficiency states.
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