88 ON THE INTERNAL POLARISATION OF NERVES. 



From all these experiments it appears : that if the polarising 

 current acts on the nerve for unequal and increasing lengths of time, 

 other conditions being the same, the polarisation of the nerve increases, 

 more rapidly at first, afterwards more and more slowly, finally ap- 

 proaching its maximum with extreme slowness. 



3. The duration and course of polarisation. 



After the polarising current is opened, the polarisation remains 

 at its height for only a short time, and then very rapidly declines. 

 It lasts, however, as Hermann found, for a long time afterwards, 

 though with very much diminished strength, so that it is always 

 necessary to compensate the residual polarisation between every 

 two experiments, as it would otherwise be impossible to bring an 

 experiment to a conclusion. 



To obtain a closer acquaintance with the duration and course 

 of polarisation I proceeded as follows. I passed a current of 

 definite strength through the nerve for a given time. Then I 

 opened the polarising current at K (see diagram) and closed the 

 galvanometer-circuit after intervals which differed in different 

 observations. In this way I made myself acquainted with the 

 residual polarisation. I performed the experiments in such a 

 way, as, first of all, to close the galvanometer-circuit instantly 

 after the polarising current was opened, just as in the experi- 

 ments previously described. Then I closed the galvanometer- 

 circuit i, 2, 3, 4, 5, 6, 7, 8, 9, 10 seconds and so on after the 

 polarising-current was opened. In these experiments, then, the 

 current passed along the nerve always for the same length of time, 

 but the galvanometer-circuit was closed at different intervals after 

 the current was broken. 



These experiments are more difficult to carry out than the pre- 

 ceding ones with the simple appliances at my disposal, because 

 the strength of polarisation falls off very rapidly, especially in the 

 first seconds after interruption of the current, while, at the same 

 time, the galvanometer-circuit has to be completed at the right 

 moment with perfect accuracy. Still, the experiments recorded in 

 Table III give an amply sufficient idea of the particular way in 

 which polarisation falls off in nerves. 



