ANIMAL ELECTRICITY. LECTURE IV. 89 



In the galvanometer by opening" K3 ; the galvano- 

 meter indicates current against the direction of the 

 arrows, arising from the now polarised electrodes. 

 The key K^ with which these are connected has 

 remained open throughout the experiment. The 

 electrodes have been so to say charged at K^ from the 

 battery, and discharged at K. through the galvano- 

 meter, and, as you may have noticed, the magnitude 

 of the deflection has increased with the duration of 

 polarisation, and has diminished with the interval 

 between closure of K^ and opening of K^—i.e., with 

 the time during which depolarisation has proceeded. 



We seem to be a long way off from the case of a 

 living nerve, yet the distance between this case and 

 that of the polarisation cell is not so great as it seems. 

 Two more experiments will, I think, suffice to bridge 

 the gap — or at least to serve as stepping-stones 

 between the two orders of phenomena — from the 

 electrolysis that is purely physical to the electrolysis 

 that is at the same time physiological — from the dis- 

 ruption of inert matter to the disruption of living 

 matter : — 



Of these two experiments one is intended to illus- 

 trate the fact — first established by du Bois-Reymond — 

 that the interface between different moist electrolytes 

 may be the seat of electrolytic polarisation ; the other 

 to illustrate the physical mechanism of the electrotonic 

 or extrapolar currents to which such polarisation gives 

 rise. 



