THE PERMEABILITY OF CELLS 517 



3. The relations of basic dyes are exactly comparable to those 

 found by Overton ('97) for certain alkaloids which are weak 

 bases, and do not enter cells in acid solution. In the acid an 

 alkaloid salt is of course formed. 



I have observed that caffein, on the contrary, enters equally 

 well in acid, neutral, and alkaline solution. It was compared 

 with strychnin in similar percentage concentrations: 



Spirogyra cells were placed in the following solutions: 



A. 0.01 per cent strychnin sulphate in ^?^ NaOH tap water. 



B. 0.01 per cent strychnin sulphate in y^j HCl tap water. 



C. 0.01 per cent strychnin sulphate in tap water. 



D. 0.0125 per cent caffein in ^fg NaOH tap water. 



E. 0.0125 per cent caffein in y^^ HCl tap water. 



F. 0.0125 per cent caffein in tap water. 



G. y^^ NaOH tap water. 

 H. ySg. HCl tap water. 



In A the strychnin passes into the cells and forms a granular 

 reticulum and within twenty minutes the cells have lost their 

 turgor and secrete a sticky substance. In C strychnin also enters 

 but less rapidly and death results after about one hour. In B 

 no strychnin precipitate is formed and the cells are normal after 

 one hour. 



In D, E, and F, an equal amount of caffein precipitate is formed 

 after 45 minutes in each case. 



The cells in G and H are quite unaffected by the acid or alkali 

 after one hour. 



e. Spirogyra: Exactly the same permeability relations hold for 

 Spirogyra, sea urchin and starfish eggs, and Paramoecium. The 

 mechanism of accumulation is different in each case. In the 

 study of dyes we have always to consider two points — in what 

 condition the dye enters and by what means it is made visible 

 within. There must always be an accumulation of some kind for 

 otherwise the color would not be apparent in so small a layer. 



I have also studied the entrance of several others dyes in the 

 acid and alkaline condition into Spirogyra and the same general 

 law appears to hold. The results are best given in the form of a 

 table which does not pretend to be exhaustive, but simply to 



