CELLS 



75 



Attempts to override some of these difficulties have been made by using a series 

 of different dyes, both in the oxidised and reduced form, and by observation of the 

 cells for considerable periods. Nevertheless considerable discrepancies still remain 

 to be explained. 



There is a considerable body of opinion that the electrode potential of the cell 

 interior has little significance. It is certainly difficult to consider the conditions of 

 the cell interior without taking account of the medium surrounding the cell. 



Many of the results obtained with cells have been quoted in terms of rH, which, 

 as shown in a previous chapter, involves imjustifiable assumptions concerning the 

 effect of pH on the electrode potential. 



The Needhams (1925, 1926) and Rapkine and Wurmser (1926, 1927) working 

 with various cells, including eggs of Parencentrotus lividus, Asterias glacialis, Ascidia 

 mentala, and Sabellaria alveolata ; and Amceba proteus, Nyctotherus conliformis, and 

 salivary gland cells of larvae, observed, under aerobic conditions, rH of 19-22 at pH 

 6-6 to 7-6. Cohen, Chambers and Reznikoff (1928), Chambers, Pollack and Cohen 

 (1929) and Chambers, Cohen and Pollack (1931) observed in cells under aerobic 

 conditions an rH as low as 12 ( —0-06 v.). The Needhams state that aerobic Amcebae 

 have well poised potentials not lowered under anaerobic conditions. This is disputed 

 by Chambers, Pollack and Cohen who find that the rH is lowered under anaerobic 

 conditions. Rapkine and Wurmser (1926) claim that the nucleus has the same rH 

 as protoplasm, but Chambers, Pollack and Cohen (1929), using the immature starfish 

 egg, comment on the difficulties of this work. They found that many dyes stained 

 the nucleus and all proved toxic, and they could draw no conclusions from the results.. 

 Chambers, Cohen and Pollack (1931) note the toxicity of dyes to echinoderm ova. 



Dixon (1926) emphasises the difficulties in the use of dyes and points out that 

 non-sulphonated dyes may be reduced by cells but not the sulphonic dyestufis so 

 that the chemical constitution of the indicator dye affects the results. He further 

 underlines the time factor in the use of dyes so that unless the time of observation is. 

 very long, equilibrium will not have been reached by the end of the experiment, since 

 the dye will still remain partially in its original oxidised condition. 



Turning to green cells. Brooks (1926) with the marine Alga valonia found the- 

 cell juice to have rH 16 to 18, whilst that of the protoplasm was rather undefined. 

 Rapkine and Wurmser (1926) found that spirogyra cells were of rH 14 to 16 at pH 6. 



Cohen and Chen (1933) injected oxidised and reduced dyes into Amceba dubia, 

 kept under anaerobic conditions, with the following results : — 



TABLE 16 



^ ^-it-^i^i-i, 



The E^ of the cell interior under anaerobic conditions would thus appear to bo 

 about —0-25 to —0-3 v. It has been found by Beck (1933) that acids and bases 



