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July 3, 1937


Author Affiliations

Milwaukee. Associate Professor of Pharmacology, Marquette University School of Medicine.

JAMA. 1937;109(1):66. doi:10.1001/jama.1937.02780270068023

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To the Editor:—  It seems unfortunate that the recent editorial on the antihemorrhagic factor in foods (The Journal, May 15, p. 1717) failed to consider certain researches bearing directly on the subject of vitamin K, for obviously at this stage in the study of this new vitamin all results obtained by carefully executed research are apt to be helpful in determining its function and possible therapeutic usefulness.Vitamin K appears definitely to be a food accessory factor required for the synthesis of prothrombin. By means of a new quantitative method for prothrombin (J. Biol. Chem.109:1xxiii [May] 1935) I was able to follow the changes in this important clotting factor in chicks deprived of vitamin K (Am. J. Physiol.118:260 [Feb.] 1937). In some of the chicks, a drop of 50 per cent in the prothrombin concentration was observed as early as the fourth day. When the prothrombin

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