532 EDMUND NEWTON HARVEY 



saturated water and then placed in /o NaOH the red precipitate 

 becomes yellow immediately. On adding dilute HCl the thread 

 again becomes red and the precipitate begins to dissolve. 



As shown above, chloroform has no effect on the alkali com- 

 bining power of egg albumen and presumably none on cell pro- 

 teids. It must be that the inability of the alkali to enter is due 

 rather to the inability to pass the surface layer of the Spirogyra cell 

 than to a neutralization by proteid or acid after passing this layer. 



The color change in the tannin precipitate takes place practi- 

 cally instantaneously in efo NaOH (or KOH, Ca(0H)2, Ba- 

 (0H)2 or Sr(0H)2), if we cut the cell transversely so as to allow 

 ready mixture of solution and precipitate. In weaker concen- 

 trations the color change also occurs but it takes a much longer 

 time. Thus, dead Spirogyra filamants (red stained) become 

 decolorized in less than 15 hours in 5x^0 NaOH, while the control 

 in water remained red. 



Every cell which I have tested (Cabomba rosafolia, containing 

 a natural red pigment, Elodea Canadensis, Spirogyra, Para- 

 moecium, Vorticella and various marine eggs) has proved to be 

 resistant to the entrance of the inorganic hydroxides, a condition 

 which is lost on death (by chloroform, HCl, heat coagulation, 

 drying, etc.) This post-mortem increase of permeability has 

 been so often emphasized by many writers for very diverse sub- 

 stances that it hardly requires special confirmation for the alkalies, 

 except as showing the degree of impermeability which the normal 

 living cell possesses. 



b. Weakly dissociated alkalies: — Exactly opposite results are 

 obtained when ammonia and its primary, secondary and tertiary 

 alkyl substitution products^ are studied, instead of the inorganic 

 hydroxides. All these substances pass into the cell with very 

 little if any resistance. Elodea is more suited to experimentation 

 than Spirogyra^ because the color change is more marked 

 (tables 4 and 5). 



^ If a red stained filament of Spirogyra is placed -^g NH4OH it becomes dark 

 gieen in one minute. On washing in water the red color soon returns. In weaker 

 solutions of ammonia the formation of the NH4 — tannate compound prevents a 

 sharp color change in the neutral red-tannate compound. 



