ix ELECTRICAL EXCITATION OF NERVE 125 



wards broader, while the abruptly rising currents give the reverse, 

 the decomposition being marked at first and subsequently 

 diminishing (Fig. 177). While investigating this electroly to- 

 graphic method Griitzner also found that the steeply rising break 

 induction current of an ordinary du Bois' sliding apparatus had 

 a far more marked electrolytic action than the gradually rising- 

 make induction current. 



In the frog's nerve-muscle preparation, with low intensity of 

 current, abruptly rising currents are always the most effective 

 (now one and now the other, according as the electrodes are 

 situated on the nerve). On increasing the current, a second 

 smaller twitch appears, corresponding with the other steeply rising 



FIG. 177. 



(and opposite) current. Further increase of current intensity 

 complicates the excitatory effects still further, since with an 

 ascending direction of current the anodic inhibition becomes 

 apparent. In rare cases, all four induction currents may excite, 

 and there are then at each revolution two strong and two weak 

 twitches, alternating as one strong and one weak twitch. The 

 most significant result of Griitzner's investigation is the pre- 

 dominant action of the abruptly rising currents, where the direction 

 is again of importance, inasmuch as (according to the observations 

 of Hermann and Fleischl, supra] the upper portion of the nerve 

 is first excited by descending, the lower portion by ascending 

 currents, while they both take effect at the " equator " only. It 

 is with much higher intensities of current that the gradually 

 rising currents also become effective. 



The beneficial influence of great abruptness of oscillation is 

 shown inter alia by the fact that even very strong currents may 

 be shunted into the nerve without perceptible signs of excitation, 



