THE CONDUCTIVITY BALANCE 



491 



depression than corresponding sodium salts. But neutral 

 salts, generally speaking, affect conductivity to a much 

 slighter extent than responsivity. There is, however, a very 

 curious exception to this rule in the case of animal nerve, 

 where 6'i per cent, of Nal is found to affect the conductivity 

 to a much greater extent than the responsive excitability. 

 I find a remarkable parallelism to these effects in the case of 

 vegetable nerve, which 

 is capable of striking 

 demonstration by the 

 comparative method of 

 simultaneous variations 

 of conductivity and 

 excitability already de- 

 scribed. In order to 

 demonstrate these con- 

 trasted effects of KI 

 and Nal on conductivity 

 and excitability, I shall 

 here give an account 

 of two different experi- 

 ments. In the first, 

 after obtaining the pre- 

 liminary balance, KI 

 was applied at c, on 

 the right arm, the same 

 reagent being also ap- 

 plied at the end E' of 

 the left arm, this pro- 

 cess being represented 

 by the formula E' KI C KI . The record seen in fig.]299 shows, 

 by its resultant up-responses, that a greater depression of 

 responsivity at E' than of conductivity at C has been induced- 

 In the next experiment (fig. 300) Nal was applied instead of 

 KI, on C to the right, and E' to the left, the formula thus 

 being E' NaI C NaI The resultant responses were now down- 

 wards, showing that there was a relatively greater depression 



FIG. 299. RESPONSIVITY versus 

 CONDUCTIVITY under KI 



This photographic record shows the effect of 

 KI on responsivity and conductivity when 

 reagent applied at E' and C simultaneously. 

 The formula is E'KiCKi- Record shows 

 greater depression of responsivity than of 

 conductivity. 



