PRODUCED BY A CONSTANT CURRENT. 13 



firming his results, and he conjectured therefore that they were 

 due to defective insulation, inasmuch as strong- currents might easily 

 enough have in part found their way to the nearest electrode 

 of the test-current by conduction in the moist chamber, in which 

 case its direction would of necessity be reversed. For further 

 information as to the controversy the reader is referred to the 

 originals 1 . 



All the investigations which I have so far referred to were in 

 the main conducted by the same experimental methods. About 

 the same time Wundt and Griinhagen sought to throw light on 

 the question from a new point of view. 



These enquirers had independently proposed to themselves to 

 test the excitability of the nerve during the first moments after 

 opening and closing the polarising current. With this object 

 Wundt 2 availed himself of the pendulum myograph, and applied 

 the test-stimulus at a short and accurately measured time after 

 opening or closing of the polarising current. The essential part 

 of his results is as follows 'Directly after the closing of the 

 polarising current the excitability begins to rise through the whole 

 length of the nerve. This increase of excitability continues, in the 

 neighbourhood of the kathode, into the persistent katelectrotonic 

 increase. In the neighbourhood of the anode the excitability 

 mounts to a maximum and then again sinks gradually to make way 

 for the anelectrotonic diminution. During a certain period, there- 

 fore, after closure of the constant current excitability is increased 

 along the whole course of the nerve. This stage of increased 

 excitability in both phases of electrotonus exceeds notably in dura- 

 tion the course of a muscular contraction with its associated stage 

 of latent stimulation. At the moment the circuit is broken, with 

 strengths of current which are not such as to introduce differences 

 of conduction due to inhibitory processes, there occurs an excitation 

 of which the intensity is the same whether on the kathodic or 

 anodic side, and whether inside or outside of the poles. Along with 

 this excitation, however, an inhibition sets in, which in part is 

 occasioned by the remanent inhibition at the anode at closure of 

 the current, and in part comes into existence at opening, in con- 

 sequence of the occurrence of changes at the kathode which are 



1 Bernstein, Archiv fur die ges. Physiologic, viii, pp. 498-505. Hermann, ib. ix, 

 1874, pp. 28-34. 



a Wundt, Archiv fur die ges. Physiologic, iii, 1870, pp. 437-440 ; Untersuchungen 

 zur Mechanik der Nerven und Nervencentren, i. Erlangen, 1871. 



