Serum and Plasma Antithrombin. ∗

Abstract

Summary

A method of estimating the rate of natural antithrombic activity is suggested. When this method was used, dog plasma, regardless of the prothrombin level after dicumarolization, seemed to exert about the same antithrombic activity. On the other hand, dog serum antithrombin tended to vary inversely with the prothrombin content of its original plasma, and serum obtained from blood containing little prothrombin was antithrombic to about the same extent as plasma. These observations suggest that antithrombic activity be determined on plasma unless due consideration is given to the antithrombic activity already performed by serum.