Prior to 1934, any male with a congenitally acquired bleeding disorder was promptly classified as a hemophiliac. Women were not allowed this distinction, but were merely called "bleeders." However, in 1934 there began a series of important observations which clarified the role of the prothrombin complex in the clotting mechanism and the importance of vitamin K and bishydroxycoumarin (Dicumarol). Quick and his co-workers opened up a new era in the study of coagulation by describing a simple quantitative test for the estimation of prothrombin.1 Thus, for the first time, it became possible to classify patients with the common cause of bleeding into two groups; (1) those involving defects in thromboplastin formation, and (2) those with defects in the prothrombin complex.
Tn 1941 Rhoads and Fitzhugh2 ushered in this new era when they reported a patient who had been called a hemophiliac for nine years, but the development of