All students of vitamins have long recognized that real progress in our understanding of the physiologic functions and the biologic origins of these indispensable food components depends in no small measure on the possibility of securing the potent substances in chemically pure forms. This applies similarly to the hormones that are so effective in influencing bodily processes and reactions. The crystallization of epinephrine and thyroxine, for example, led to the establishment of their chemical constitution; and this was followed with almost unexpected rapidity by the artificial synthesis of the active compounds.1 The laboratory has thus triumphed once again over nature by making it possible to replace naturally occurring potent substances by the identical products of human ingenuity.
Commendable progress has lately been made in the domain of vitamin research. Notable is the demonstration that the yellow pigment carotene, now readily obtainable in crystalline form and chemical purity, is transformed
CRYSTALLINE VITAMIN D. JAMA. 1931;97(22):1628. doi:10.1001/jama.1931.02730220050015
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