Studies of hemophilia; the assay of the antihemophilic clot-promoting principle in normal human plasma with some observations on the relative potency of certain plasma fractions.

Ever since Sahli ( 1 ) demonstrated that the coagulation of hemophilic blood is accelerated by the addition of normal blood 2 many workers (2 to 9) have focused attention on its clot-promoting property. Since cell-free plasma seemed as effective as platelet-rich plasma this action could not be directly attributed to any of the cellular components of blood (2). Hemophilic plasma ws found to be inert. The antihemophilic factors in normal plasma seem to be associated with the globulins and fibrinogen (3 to 7), and appear preponderantly in Fraction I obtained by Cohn and his collaborators (7, 10 to 12). The present communication deals with the quantitative relationship between the amount of normal plasma added to hemophilic blood and the coagulation time of such mixtures. We believe that the observations provide a basis for estimating antihemophilic activity of plasma, and we present them in the hope that they will be extended by others in studies of the coagulation defect of hemophilic blood. Also included are some observations on the potency of certain plasma fractions, which demonstrate the applicability of the relationship to work aimed at the separation of the clot-promoting principle from plasma.