112 ANIMAL ELECTRICITY. LECTURE V. 



In this connection the next effects to be analysed 

 will be those first discovered by Bernstein and by 

 Hermann, viz., the electrotonic decrement and the 

 polarisation increment. 



But before doing this I should like to take up two 

 or three further points relating- to the electrotonic 

 currents themselves. 



I shall recapitulate these points by means of a few 

 simple experiments, showing how the magnitude of 

 the extrapolar current varies (i°) with the magnitude 

 of the polarising current and (2°) with the distance 

 between leading-In and leading-out electrodes. 



(1°) The nerve is resting upon two pairs of elec- 

 trodes p p' and e e' as shown in fig. 44. A polar- 

 ising current of 0*1 volt grives rise to an electrotonic 

 deflection of 1*5; with the polarising current at 0*2 

 and 0*3 volt, the deflection is 3 and 4*5. From which 

 (and perhaps still better from the record reproduced 

 in fig. 48), we learn that the magnitude of the extra- 

 polar current led off at e e' varies directly as the 

 magnitude of the polarising current led in at p p'. 

 This is quite in harmony with the view that the 

 extrapolar current Is an electrolytic effect, and with 

 the fact that electrolysis varies directly with current 

 density. 



Now for the effect of distance between leading-in 

 and leadlng-out electrodes. 



(2°) A nerve is resting upon six electrodes ; i and 

 2 are to remain throughout electrodes of the polar- 



