TY - JOUR T1 - SUpplementary report on vitamin k AU - SNELL AM, BUTT HR Y1 - 1939/12/02 N1 - 10.1001/jama.1939.72800480004011 JO - Journal of the American Medical Association SP - 2056 EP - 2059 VL - 113 IS - 23 N2 - In April 1939 a report on the sources, nature and clinical use of vitamin K was prepared by one of us (Snell1) at the request of the Council on Pharmacy and Chemistry. Since the publication of this report, attention has been called to inaccuracies in the matter of defining a unit of the vitamin. Certain investigators have also questioned some of the statements made with regard to the fundamental causes of deficiency in prothrombin, the methods of recognizing them and the means of dealing with them. This supplementary report has been prepared in an effort both to clarify these matters and to bring up to date the present knowledge of the chemical nature of the vitamin.DEFINITION OF A UNIT  The Dam unit of activity as defined in some detail in an article by Dam and Glavind2 refers to a special preparation of dried spinach, to which a SN - 0002-9955 M3 - doi: 10.1001/jama.1939.72800480004011 UR - http://dx.doi.org/10.1001/jama.1939.72800480004011 ER -