ACKNOWLEDGEMENTS This study was aided by a grant from the Blood Transfusion Association of Greater New York. The synkayvite was supplied by Dr. Leo A. Pirk of the Hoffmann-LaRoche Company, Nutley, New Jersey. The hykinone was supplied by Dr. Richard K. Richards of Abbott Laboratories, North Chicago, Illinois. The thromoplastin was supplied by Dr. Ralph Overman of the Maltine Company, Brooklyn, New York. Herbert Fensterheim of Washington Square College, New York University, assisted in making the statistical analyses.