174 



ELECTRO-PHYSIOLOGY 



CHAR. 



current of low intensity (the ascending direction is, on the whole, 

 to be recommended, because the anodic effect is there developed 

 without interference) there will soon be seen along with the 

 retarded opening twitch, which is alone visible at first, a second, 

 which commences at the moment of breaking the circuit, filling 

 up the interval before the delayed muscle twitch begins, and thus 

 being in some sort introductory to it (Figs. 190, 191,1). Whether 

 this effect appears as a perfectly distinct twitch, the muscle relaxing 

 again completely before the retarded twitch (opening twitch II) 

 begins, or whether it fuses with the latter partially or completely, 

 depends of course upon the time that elapses between the moment 

 of opening and the commencement of break twitch II, and thus 

 upon the duration of the current also. 



The excitability of the nerve sinks gradually as the alcohol 



A. 



Ji 



FIG. 193. Bud of series, Fig. 191. Decrease of break twitch II to zero, with persistence (and sub- 

 sequent increase) of break twitch I. 



treatment takes effect, the height of the closure twitch, as well as 

 of the opening twitch II, being proportionately diminished, and 

 it is remarkable that the first opening twitch (break twitch I) 

 reaches its greatest height when the excitability is already much 

 diminished. The second opening twitch fails altogether at a 

 somewhat later period, and does not reappear even with pro- 

 longed passage of current ; break twitch I, however, persists 

 along with the reduced closure twitch, with which it is for the 

 most part equal, if it does not exceed it (Fig. 193). If the whole 

 preparation is freely moistened at this time with a 0*6 / Q solution 

 of NaGl, it is easy to restore the normal relations of excitability 

 in the nerve, so that a closure twitch is the only effect of excita- 

 tion at any point, with moderately strong ascending or descending 

 currents. Upon renewed application of dilute alcohol the former 

 series of effects may be repeated a second and sometimes even a 

 third time. 



The treatment of a nerve with alcoholic saline has the ad van- 



