iv ELECTROMOTIVE ACTION IN MUSCLE 327 



different concentrations of NaCl solution, Kiihne found that 

 solutions of fixed alkalies and mineral acids up to 0*1 / Q 

 were very effective, as well as solutions of different salts, but he 

 failed to detect a twitch when the section was brought into con- 

 tact with distilled water, alcohol, creosote, concentrated glycerin, 

 and syrupy lactic acid; Wundt and Schelske further noted thaf 

 concentrated solutions of sublimate produce no twitch from the 

 transverse section. Kiihne held that (supra) all cases in which 

 he observed twitches, on touching a fresh section with fluid, 

 were due to chemical excitation of the exposed fibres. But this 

 is a doubtful hypothesis in view of the fact that with 0'5-0'6 / 

 NaCl solution, which is well known to be comparatively harm- 

 less, the effects in question appear peculiarly well marked and per- 

 sistent. It is, moreover, remarkable that salt solution when applied 

 to the muscle section that has been moistened, does not produce 

 any permanent excitation, as would be the case if the fluid acted 

 as a chemical stimulus. And it may be shown that the excitatory 

 effect fails if the solution is applied to the transverse section only, 

 and hardly, if at all, to the longitudinal surface of the muscle. 

 Hering (4) produced this, inter alia, by placing a small strip 

 of greased paper round the cross-section of the muscle, so that its 

 lower margin coincided with the margin of the section. A muscle 

 prepared in this way does not twitch on bringing the transverse 

 section into contact with the salt solution, as must inevitably 

 occur if it was a chemical excitation. " If, on the other hand, the 

 muscle is dipped into the fluid above the strip, the twitch 

 reappears again." Accordingly if the experiment is to succeed 

 " it is essential that there should be on the one hand a connection 

 between the transverse section and the lowest part of the longi- 

 tudinal surface, while on the other this conductor must not have 

 too great a resistance, i.e. the quantity of NaCl. solution which 

 produces it must not be insufficient." If then as can hardly be 

 doubted from the above this is an electrical excitation of the 

 muscle, by sudden short-circuiting of its own current within the 

 wall of fluid that rises at the moment of contact, from transverse 

 to longitudinal section, it is easy to understand that all non- 

 conducting, or ill-conducting fluids, as we learn from experiment, 

 are ineffective, even if they have a demonstrable chemical action 

 on the substance of muscle (sublimate, alcohol, water). Indeed, 

 as Hering pointed out, the mere reaction of the muscle on 



