RT Journal
A1 SNELL AM, BUTT HR
T1 SUpplementary report on vitamin k
JF Journal of the American Medical Association
JO Journal of the American Medical Association
YR 1939
FD December 2
VO 113
IS 23
SP 2056
OP 2059
DO 10.1001/jama.1939.72800480004011
UL http://dx.doi.org/10.1001/jama.1939.72800480004011
AB 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