igii] E. Newton Harvey 229 



Mathews, on the other band, demonstrated that the acid dyes form 

 combinations with proteins in acid Solution, tbe basic dyes in alka- 

 line Solution ; a Statement true also for the stainability o£ the lecith- 

 albumin yolk platelets of the frog tgg, as I have determined. It 

 is therefore conceivable that a dye must combine with the surface 

 layer of a cell in order to enter, a theory which Mathews has recently 

 upheld. 



Three complications arise from the use of an indicator to detect 

 the entrance of alkali. First, the neutral red is not in watery Solu- 

 tion but, as already mentioned, in combined form within the 

 cell and the combination must be decomposed by the alkali. 

 Second, neutral red, as I have determined by experiment, even in 

 Solution, cannot detect, in the presence of proteins like tgg albu- 

 men, a certain amount of added alkali which combines with the 

 albumen. Third, an acid may be secreted by the cell which neu- 

 tralizes entering alkali. Such a secretion is actually formed by 

 red stained Elodea cells when treated with Chloroform water, if a 

 deepening in color of the red dye is to be interpreted as the result 

 of acid formation. 



The above three objections may be met by comparing the rate 

 of entrance of the alkali into similar living and dead cells, the latter 

 serving as controls to determine the resistance, for there Is always a 

 resistance — although slight for some alkalies — offered by the nor- 

 mal cells. Thus the concentration of alkali which brings about 

 instantaneous decomposition of the indicator in chloroform-killed 

 cells can be determined. It can likewise be shown that the great 

 impermeability of living plant and animal cells for the inorganic 

 alkalies is an actual impermeability, dependent on the composi- 

 tion and properties of the cell surface and not an apparent one 

 due to the time consumed by alkali in its decomposition of indicator 

 Compound, or in its combination with cell protein or in its neutraliza- 

 tion of acid secretion. Chloroform saturated water has no effect on 

 the combining power of egg albumen with either sodium hydroxid 

 or ammonium hydroxid. 



As regards penetrating power two classes of alkalies may be 

 recognized, the strong [including Na, K, Ca, Sr, Ba and N(C2H5)4 

 hydroxids] and the weak (including NH4OH, methyl, dimethyl, 



