376 



FLOYD JOHN BRINLEY. 



curve represents the average of three to five tests. It may be seen 

 from this figure that, with the exception of the two low concen- 

 trations (M/225 and -M/3I3), the total amount of cyanide within 

 the cell at equilibrium was the same for all the concentrations. 

 The rate of entrance of cyanide increased with an increase in 



70 



60 



ZSO 



LJ 

 O 



LJ 

 Q_ 



30 



20 



I 



------ M\160 



----- M\225 

 - M\3I3 



1,5 



30 

 MINUTES 



60 



FIG. 8. Curve showing the effect of concentration of HCN upon the 

 permeability of frog skin to cyanide. Concentrations of HCN used were 

 M/iog, M/I24, M/i6o, M/i$6, M/22$, and M/3\3. Abscissae represents the 

 time in minutes ; ordinates per cent, cyanide. 



concentration. At a concentration of M/iog, equilibrium was 

 reached within 30 minutes, while at lower concentrations equi- 

 librium was not reached for a period of 45 minutes. The fact 

 that the skin is not killed can be proved by substituting for the 

 cyanide solution a mineral acid, which is known not to pass 

 through living membranes, and testing the pH of the internal solu- 

 tion. As there is no change in the intracellular acidity, it is evi- 

 dent that no acid has passed through the skin. 



Although, it is known that the frog skin is not killed by the 

 above treatment with HCN, it is desirable to ascertain what effect 

 the cyanide does have upon it. A series of experiments was con- 

 ducted to determine the effect of hydrogen cyanide on the po- 



