526 EDMUND NEWTON HARVEY 



comment. Evidence will be given in the body of this paper to 

 show that the generally accepted view is only in part the truth, 

 so far at least as the penetration of alkalies is concerned. 



Animal cells suitable for experimental studies contain no pig- 

 ment exhibiting a marked color change in alkalies. We may 

 overcome the diffiulty by introducing a dye which does so change. 

 Neutral red is excellent for the purpose. In solution, it turns 

 from red to yellow in an H ion concentration of 1.10~ to 1.10~ , 

 and is perfectly harmless for the cells providing they are not allowed 

 to take up over a certain maximal amount. For the sake of com- 

 parison neutral red was employed in plant cells as well. 



I have endeavored to answer for the alkalies the following 

 general questions, many of which have already been settled for 

 other classes of substances by previous workers in the field of cell 

 permeability. 



1. Do plant and animal cells exhibit essentially similar per- 

 meability relations for alkalies? 



2. Do living and dead cells exhibit similar permeabihty rela- 

 tions for alkalies? 



3. Are there distinct classes of alkalies in regard to permea- 

 bility? 



4. Are the effects of different alkahes reversible or irreversible 

 after an equal amount (OH ion concentration) has entered the 

 cell? 



5. May the composition of the medium affect permeability 

 without irreversibly injuring the cells themselves? 



6. Are there any relations between functional changes and 

 permeability for alkalies? 



7. May alkalies produce marked functional changes without 

 entering the cell? 



Many of these questions can be decided only with an especially 

 favorable type of cell and the evidence one way or the other has 

 therefore been given in describing the permeability phenomena 

 of that particular cell. The connection between the penetrating 

 power and the physical properties of the various alkalies are taken 

 up in the discussion. I have taken the greatest precaution to 



