38o 



FLOYD JOHN BRINLEY. 



recovered when removed from the cyanide. It is obvious from 

 Fig. 10, that a weak solution of cyanide acted at first as a stimu- 

 lant and this was followed by a delayed toxicity. As the concen- 



q MIN 



10 20 



MINUTES 



FIG. u. Curve showing the effect of short exposures of cyanide to the 

 P.D. of frog skin. The time between arrows represents the period of ex- 

 posure to HCN, at other times the skin was exposed to borax buffer alone. 

 Solid line represents a three minute exposure to cyanide ; dotted line, 6. min. 

 exposure and broken line 9 min. exposure. Abscissae represents the exposure 

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



tration of cyanide was increased, the stimulation decreased and the 

 toxic effect increased until a point was reached where stimulation 

 no longer occurred and at this point the toxic action was pro- 

 nounced. This initial stimulation of frog skin by cyanide was 

 apparently overlooked by Lund (70) who took readings every fif- 

 teen minutes. He did notice, however, a rapid rise followed by 

 a rapid fall in the electrical resistance in Obelia during a period 



