1. Evidence is presented to confirm the existence of a qualitative chemical change in a substance extractable with alcohol and ether from epidermis undergoing carcinogenesis. Alteration in the structure of the compound is manifested by a difference in the type of polarographic waves and in their half-wave potentials and also by a difference in absorption in the ultraviolet. There is also a dissimilarity between muscle and muscle tumor in that the purified substance from the latter absorbs at 260 mμ while that of the former does not. On the other hand, the substance from normal liver and hepatoma appears quite similar with respect to the half-wave potentials and absorption in the ultraviolet.

  2. A method for the preparation of these reducible substances from various tissues is described, and some of the properties of the highly purified substances are given. Present data indicate that these substances belong to one class of compounds.

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This investigation was aided by grants from the Charles F. Kettering Foundation, the American Cancer Society, and the National Cancer Institute.

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