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During the revision of the U. S. P. X it became apparent that the newly discovered fat-soluble vitamin A should be recognized as an important factor in the potency of cod liver oil. It was also being demonstrated that "the antirachitic factor" should be given consideration, but at that time it had not been sufficiently studied so that there was knowledge of how to evaluate it. A group of those active in developing vitamin knowledge, including Drs. Sherman, McCollum, Anderson, Holmes and the late Alfred F. Hess, were invited by the Pharmacopeia Committee to suggest the basis for the new U. S. P. text; they developed the first standard vitamin A assay method (1924) (U. S. P. X, p. 263) and this is still essentially correct. In setting a vitamin A standard for cod liver oil, these early workers realized that no one then knew what was the potency of
Miscellany. JAMA. 1934;102(22):1877–1878. doi:10.1001/jama.1934.02750220055035