A note on the identity of the indophenol-reducing substances in brain tissue.

HARRIS [1933] concluded from the results of biological tests that only about one-third of the material in Jensen rat sarcoma which reduces 2:6-dichlorophenolindophenol is ascorbic acid. Later Young & Mitolo [1934] and Mitolo [1934] brought forward evidence which they believed to indicate that brain tissue also contains an indophenol-reducing factor (I.F.) which is not ascorbic acid. Recent investigations have cast doubt on the conclusion that tumour tissue contains an I.F. other than ascorbic acid [Woodward et al. 1936; Watson, 1936; Kellie & Zilva, 1936]. The experiments described in this paper suggest further that the evidence previously believed to demonstrate the existence of a non-ascorbic acid I.F. in brain tissue is inconclusive. The evidence previously presented that brain tissue contains such a substance [Young &; Mitolo, 1934; Mitolo, 1934] was as follows: