464 



ANNALS NEW YORK ACADEMY OF SCIENCES 



200 



> 

 u 



Z 



u 



D 

 Of 



u 

 q: 

 ii. 



O 10 20 



MINUTES 



Figure 6. Time-course of discharge (impulses per second in a single fiber), after topical appli- 

 cation of isotonic solution containing sodium citrate (35 mM) and sodium chloride. 



Open circles : gradual increase of frequency during first period of chemical excitation. 



Squares: response to second application of same solution, after intervening 2 hours in reference 

 fluid. ^ . , 



Filled circles: response to a third application, after another hour in Ringer s fluid. 



200 







20 



40 60 



MINUTES 



80 



100 



FiatiBE 7. The discharge of impulses continuing at high frequency for many minutes during 

 topical application of isotonic sodium citrate. Approximately 540,000 impulses were produced by 

 the single fiber, during the activity plotted in this figure. 



