Lack of Christmas Factor in Horse Plasma

Bell, Archer and Tomlin 1 , using the thromboplastin generation test, recently found the prolonged clotting time of horse blood to be due to a deficiency of anti-hæmophilic factor. However, Soulier and Larrieu 2 have used horse plasma as a source of this factor. The thrombin generation test 3,4 is useful in differentiating between classical hæmophilia and Christmas disease 5 . Applied to citrated horse plasma (containing 130,000 platelets per c.mm.) the following results were obtained (Fig. 1).