FLOYD JOHN BRINLEY. 



form of undissociated molecules ; thus it was deemed advisable to 

 study the effect of dissociated and undissociated molecules of 

 HCN on the potential difference of frog skin. Control experi- 

 ments were conducted using borax-boric buffer free from cyanide 

 at a pH of 6.8 and 8.5 to determine whether or not the hydrogen 

 ion has any effect on the frog skin. Fig. 12 shows the results 







20 30 

 MINUTES 



50 60 



FIG. 12. Curve showing the effect of pH of the borax buffer on the 

 potential difference of frog skin. pH valves 6.8 and 8.5. Abscissae repre- 

 sents the exposure in minutes ; ordinates, the P.D. in volts. 



obtained. It is obvious that the two curves coincide very closely 

 and that the hydrogen ion had no effect on the skin. It may be 

 noted that the curves are strikingly similar to the control curves 

 plotted in Fig. 9. The initial rise followed by a gradual decline 

 was again manifested. Fig. 13 shows the results obtained by 

 placing the frog skin " cells " in a solution of HCN in borax 

 buffer at pH values of 6.8 and 8.5. The concentration of cyanide 

 used was M/I54. The temperature was constant at 22 C. 0.5. 

 The " cells " were placed for ten minutes in a borax buffer solu- 

 tion at pH values of 6.8 and 8.5 respectively; at the end of that 

 time they were removed and put in a borax buffer containing 



