354 PROTOPLASM 



further fact that different regions in a cell are more or less 

 independently engaged in physiological activities suggests that 

 their ionic activities differ, which is but to say that their electric 

 activities differ and that there are therefore potential differences 

 between them. Proof of differences in acidity is sufficient 

 evidence that differences in electric pressure exist. That this 

 is true is evident from the fact that one of the ways of measuring 

 the hydrogen-ion concentration of a system is to measure the 

 potential set up by the ions. The same is true of other activities 

 in the cell; thus, if the rate of oxidation differs in various parts 

 of the cell, a potential is set up. Indeed, any type of chemical 

 activity involving the hberation or interchange of ions will 

 produce a potential. We need only, therefore, establish evi- 

 dence that differences in such activities exist within the cell 

 in order to have proof that the cell is a source of electric 

 forces. 



Basic dyes, which ionize as R+ and Cl~, stain the nucleus more 

 readily than they do the cytoplasm. The nucleus is, therefore, 

 electronegative, because it adsorbs the positive or color ion 

 R+ of the dye. Cytoplasm, on the other hand, stains better 

 with acid dyes which ionize as H+ and R". It is, therefore, 

 less negative than the nucleus, i.e., electropositive in reference 

 to the nucleus. Similar evidence leads to the conclusion that 

 the nucleolus is less negative than the nucleus. The cell is thus 

 a system with a more positive nucleolus, a negative nucleus, 

 and a more positive cytoplasm. The outer solution which 

 bathes the cell probably differs electrically from the cell proto- 

 plasm (as already pointed out from pH values, page 330). 

 This means that differences in electric potential exist between 

 nucleolus, nucleus, cytoplasm, and external medium. The living 

 cell is thus the seat of electric forces. Keller terms it an accumu- 

 lator, that is to say, an electric storage cell in which the nucleus 

 is the cathode, or negative pole. 



The staining of cytoplasm with acid dyes suggests that it is 

 electropositive, as does also the idea that the nucleus is the 

 cathode; yet both statements need indicate only that the cyto- 

 plasm is less negative than the nucleus. Other (cataphoretic) 

 experimental findings show the cell to be negative as a whole. 

 Evidence purporting to indicate that certain living cells may 

 be positive has been advanced, but opinion and experimental 



