484 ANNALS NEW YORK ACADEMY OF SCIENCES 



A similar analysis of frequency relations, during the time of in- 

 creased response caused by the cathodal polarization, was then made. 

 The distribution of intervals between impulses is plotted in the upper 

 part of FIGURE 23. The total number of impulses there considered is 

 the same as in the lower plot. During this time, the most probable 

 period for the excitatory process was only slightly changed, but the 

 probability that impulses would recur at the longer intervals was then 

 practically zero. The action of the polarizing current caused more im- 

 pulses to be discharged at the basic interval, and this increased the aver- 

 age frequency to 305 per second. In general, changes in this average 

 frequency of impulses, caused by superimposed chemical or physical 

 agents, occur with only slight modification of the most probable least 

 interval. It should be pointed out, however, that, under certain con- 

 ditions of intense stimulation, this interval can be decreased. 



Since the temporal distribution of impulses initiated by chemically 

 excited nerve appears to be regulated by a local rhythmic process, which 

 is determined by the intrinsic characteristics of the nerve, the possibil- 

 ity arises that the same mechanism may govern the discharge of im- 

 pulses from naturally excited sense organs and motor nerve cells. 

 Whether the mechanisms described above do have such a general sig- 

 nificance, must wait upon further investigations. 



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