W. MANSFIELD CLARK 197 



would leave one discrete molecule of oxygen in a cube the order of magnitude of which 

 would be about a million meters to the edge. Therefore, if an approach to an equi- 

 librium condition can be shown to be reasonably attained, Pasteur's intuition is 

 established as correct and anaerobiosis is an indisputable fact. 



Since many dye systems give very satisfactory electrode potentials, it is an easy 

 matter to study with this method the kinetics of dye reduction. It has also been possi- 

 ble to determine by the method outlined the dissociation constants of acidic or basic 

 groups in dyes of importance to the art of staining. But even in the absence of the 

 dye, Gillespie (1920) found definite drifts of potential in bacterial cultures. Further 

 work on this was reported by Clark (1920), and was taken up again by Cannan, 

 Cohen, and Clark (1926). 



More detail concerning the theory, the measurement of dye systems, and applica- 

 tions to various subjects of interest to bacteriology will be found in the following 

 papers by Clark and his co-workers:' 



STUDIES ON OXIDATION REDUCTION 

 I. Introduction, Pub. Health Rep., 38, 443. 1923. (Reprint No. 823.) 

 II. "An Analysis of the Theoretical Relations between Reduction Potentials and pH," 

 ibid., p. 666. 1923. (Reprint No. 826.) 



III. "Electrode Potentials of Mixtures of i-Naphthol-2-Sulphonic Acid Indophenol and 

 the Reduction Product," ibid., p. 933. 1923. (Reprint No. 834.) 



IV. "Electrode Potentials of Indigo Sulphonates, Each in Equilibrium with Its Reduction 

 Product," ibid., p. 1669. 1923. (Reprint No. 848.) 



V. "Electrode Potentials of Simple Indophenols, Each in Equilibrium with Its Reduction 



Product," ibid., 39, 381. 1924. (Reprint No. 904.) 

 VI. "A Preliminary Study of Indophenols: (A) Dibromo Substitution Products of Phenol 

 Indophenol; (B) Substituted Indophenols of the Ortho Type; (C) Miscellaneous," 

 ibid., p. 804. 1924. (Reprint No. 915.) 

 VII. "A Study of Dichloro Substitution Products of Phenol Indophenols," ibid., 40, 649. 



1925. (Reprint No. looi.) 

 VIII. "Methylene Blue," ibid., p. 1131. 1925. (Reprint No. 1017.) 

 IX. "A Potentiometric and Spectrophotometric Study of Meriquinones of the p-Phenylene 



Diamine and Benzidine Series," Supplement No. 54 to ibid. 1926. 

 X. "Reduction Potentials in Cell Suspensions," Supplement No. 55 to ibid. 1926. 

 XI. "Potentiometric and Spectrophotometric Studies of Bindschedler's Green and 

 Toluylene Blue," Supplement No. 61 to ibid. 1927. 



Other papers on the subject are referred to in reviews by Clark^ and by Conant.' 

 A review of particular biochemical interest is that of Joseph and Dorothy Needham.'' 



' Clark, W. M., Cohen, B., Gibbs, H. D., Sullivan, M. X., Cannan, R. K., and Phillips, M. 



* Clark, W. M.: C/rew. i?CT., 2, 127. 1925. 



J Conant, J. B: ibid., 3, i. 1926. 



^Needham, J. and D.: Protoplasm, i, 255. 1926. 



