The intravenous use of a vitamin K active substance in prothrombin deficient patients was first reported by Smith, Ziffren, Owen and Hoffman1 in 1939. Phthiocol (2-methyl-3-hydroxy-1, 4-naphthoquinone), synthesized by Anderson and Newman2 sixteen years earlier, was used. Forty-five cc. of a 0.2 per cent solution given in divided doses was sufficient to raise the prothrombin level in 1 case from 39 to 75 per cent in twenty-four hours. In other cases it was found effective in doses of 40 to 100 mg.3 No toxic effects were observed.
Subsequently Butt, Snell and Osterberg4 reported the effective administration of the same material in 9 cases of hypoprothrombinemia. They found that a dose of 25 mg. was not adequate but that 50 mg. brought the prothrombin to a safe level. Later, Butt, Snell, Osterberg and Bollman5 found that 1,4-dehydroxy-2-methyl-3-naphthaldehyde was effective in 8 cases in which the material