THE PERMEABILITY OF CELLS FOR DYES 



AND ALKALIES^ 



E. NEWTON HARVEY 

 (Zoölogical Laboratory, Columbia University) 



Of the many methods employed by various investigators in 

 the study of cell permeability, by far the most reliable are those 

 which make use of some microchemical test to determine the pene- 

 tration of the substance in question. The chemical reagent may 

 normally occur within the cell, or, if harmless, may be introduced 

 from without to serve as an indicator. Pfeffer made use of the 

 tannin Compounds occurring in the sap vacuoles of such algse as 

 Spiro gyra to study the absorption of aniline dyes, while O verton 

 also employed Spirogyra in studying the penetration of the alka- 

 loids and organic alkalies. The tannin is precipitated, forming a 

 tannate. Plant cells often contain natural pigments, anthocyan 

 Compounds, which may serve, by their color changes, as indicators 

 of the penetration of all the alkalies. Both Pfeffer and de Vries 

 have studied the permeability of such pigmented cells for ammo- 

 nium hydroxid, potassium hydroxid, sodium hydroxid and also for 

 acids. 



I have investigated the permeability relations of four types of 

 cells (those of Elodea leaves, Spirogyra filaments, Paramoecium and 

 the eggs of various Echinoderms) for organic and inorganic alka- 

 lies. The dye, neutral red, was introduced to serve as an indicator 

 for alkali. The color change in water from red (in neutral and 

 acid Solution) to yellow (in alkaline Solutions) occurs in an H ion 

 concentration of i.io"'^ to i.io"^. Within the cell the dye unites 

 with certain constituents, forming red Compounds, precipitates or 

 non-diosmotic substances. Hence a continuous accumulation takes 

 place and the dye Compound becomes clearly visible even in a space 

 of one cell diameter. 



^The original paper of which the foUowing is an abstract, appeared in the 

 Journal of Experimental Zoölogy, 191 1, x, p. 507. 



227 



