EFFECT OF IRRITATION OF A POLARIZED NERVE. 



401 



Tbe next series of experiments was made with the assistance of the 

 apparatns before described, with the addition of a Marey myograph to 

 Avrite the strength of the contractions. The results obtained were simi- 

 hir to those obtained when the irritations were made by means of the 

 induced current. The supposition that the effect of a constant current 

 on the excitability of the nerves can be modifled by changing- the strength 

 of the irritation employed being settled in the affirmative, it seemed 

 very probable that a change in the strength of the polarizing current 

 could produce a similar effect. This was also found to be so in a long 

 series of experiments. It was also determined that the effect of a polar- 

 izing current may change after a varying period of time, so that it will 

 take a stronger current (the irritation remaining the same) to cause the 

 same relation to be produced between the contx.iotions from the irrita- 

 tion of the non-polarized and ijolarized nerves as was produced in an 

 earlier stage of the experiment. 



A few of these experiments are here given as ilbistrations. They, I 

 think, will set this vexed question in nervous physiology at rest. For, 

 as results from these experiments, the excitability of a polarized nerve 

 can be increased or decreased at will, not only by changing the direction 

 of the current, but also by changing the intensities of the currents, these 

 two facts nnist in conjunction ibrm a law. 



The excitaMUty of a polarized nerve is determined by the proportion exist- 

 ing heticeen the strengths of the piolarizind and irritating eurrents. With 

 certain proportions of the strengths of these currents the excitahility of the 

 anelectrotonic portion of the nerve is reversely influenced from that of the 

 hatelectrotonic por tion. 



EXPERIMENT 186. 



Irritation alone. 



Strength of the irritation. 



1 small Daniel 



loeU 



S. Mis. 59- 



3^ 



Irritation plus polarization. 



strength of the constant 

 current. 



cent. 

 1 Diiniel : 



RlK'Ocbord 38 



do 38 



do 38 



do 38 



do 38 



do 33 



do 33 



do 33 



do 48 



do 48 



do 48 



do 53 



do 53 



do 53 



do 33 



do 33 



do 33 



do 33 



do 50 



, do 56 



do 06 



do 56 



] cell 



do 



do 



do 



Height of 

 the con- 

 tractions. 



Remarks. 



An asce'iding polarizing 

 curient applied G""" 

 abovf a descending ir- 

 ritating current. 



