ABSTRACT
A New approach to the problems of cellular metabolism was opened by J. and D. Needham (8) who used the micro-injection of reversible indicators to determine the oxidation-reduction intensity of living protoplasm. Prerequisites for this work were the elaboration of a series, as yet incomplete, of such indicators, and the electrometric standardisation of the position of each dye on the scale of reduction (or oxidation) electrode potential by Clark, Cohen and their co-workers (1, 4, 5, 7). Discussions of the various theoretical phases of oxidation-reduction and their possible applications to the study of life processes are found in the papers of Clark and Cohen (5).
Brilliant cresyl blue and phenosafranin were purified commercial preparations.
The dyes are listed here under the same designations as in the first paper of this series (6). Since not all the dyes were used here the lettering is incomplete.
