230 Permeability of Cells for Dyes and Alkalies [Dec. 



trimethyl, ethyl, propyl and isopropyl amines). All the cells 

 thus far tested are very little more permeable to the latter group 

 when dead than when living. Practically no resistance is encoun- 

 tered at the cell surface. With red stained Elodea leaves, for 

 instance, the color change takes place in 1-2 minutes in M/40 concen- 

 tration. With the strong inorganic alkalies on the other hand, 

 from about fifteen minutes for the penetration of w/40 Ba(OH)2 

 to twenty-five minutes for n/4.0 NaOH is required. All the strong 

 alkalies penetrate similar leaves of Elodea in less than one minute 

 when killed In various ways ; by heat, by Chloroform, by HCl or by 

 HgCla- Such a post-mortem increase in permeability has been de- 

 scribed by many investigators for other classes of substances and 

 hardly requires special emphasis for the inorganic hydroxides ex- 

 cept as showing the degree of impermeability of the normal surface. 



Elodea leaves which have been " decolorized " by Na, K, Ca, Sr 

 or N(C2H5)40H and then immediately placed in fresh water, never 

 recover and the neutral red never becomes red again. If decolor- 

 ized with ammonia and the amines, the cells not only become red 

 in pure water but no irreversible effects are produced by the action 

 of NH4OH or trimethyl amine at all, although methyl, dimethyl, 

 ethyl, propyl and isopropyl amines generally kill the cells. Deatli 

 of the cell is thus not necessarily connected with the intracellular 

 presence of a certain concentration of OH ions, and the Saturation 

 of cell proteins with NH4OH appears to be possible without detri- 

 ment to the cell. The opposite is the case with NaOH. 



Making use of the facts described in the last paragraph we can 

 readily conduct a striking demonstration of the characteristic permea- 

 bility relations of Elodea for NaOH (representing the strong alka- 

 lies) and NH4OH (representing the weak), an excellent example 

 of selective permeability. A leaf is " decolorized " in M/50 

 NH4OH and then placed in M/50 NaOH. Although the indicator 

 is already in the alkaline condition, and the cell proteins are satu- 

 rated with NH4OH, and the leaf cells are surrounded with M/50 

 NaOH, not enough NaOH enters the leaf to maintain the yellow 

 color of the dye, but the whole leaf becomes red again in NaOH, 

 from the diffusing away of the NH4OH. Only after the usual 25- 

 35 minutes does the NaOH break through the resistance offered by 

 the surface and decolorize the leaf. 



