272 ELECTRO-PHYSIOLOGY CHAP. 



longer excited to greater activity at the negative, but only at 

 the positive, pole. Engelmann, also, came to the conclusion later 

 that such a complete reversal of phenomena (i.e. of the law 

 of polar excitation) might take place. But until it has been 

 determined by unexceptional experiments, there must be great 

 scepticism in regard to such statements. 



Aeby also set up experiments in which a single muscle 

 (sartorius, adductor magnus) was fixed at the middle with a 

 clamp, so that both halves moved freely. By reversing the 

 direction of current the twitch of one (the lower) half only was 

 graphically recorded. " At the closing twitch more energy was 

 invariably developed at the negative than at the positive pole, in 

 a fresh muscle " ; with very weak currents the kathodic half only 

 contracted. The break twitch usually behaves conversely to the 

 make twitch. Engelmann is inclined to refer this effect to the 

 disturbance of conductivity at the clamped part, whence it 

 would follow that, e.g. at closure, the excitation starting from 

 the kathode cannot propagate itself without diminution to 

 the anodic side. Here, again, however, Aeby's conclusion 

 " that the negative twitch suffers much more from fatigue 

 than the positive," and that with much fatigue the reaction 

 of the fresh muscle may be inverted, appears to be of value. 

 The preceding observations on the clamped sartorius might easily 

 be recorded as a further confirmation of Aeby's conclusions (cf. 

 Fig. 94), but the phenomena in question only appear character- 

 istically with such strong currents that the effectuation of 

 secondary kathodic, or anodic, points is not thereby excluded, 

 and may, even in Aeby's experiments, have played a considerable 

 part. 



In conclusion, we must not omit the much talked -of 

 alterations hitherto investigated by the pathologist only 

 which appear after the peripheral paralysis of striated (warm- 

 blooded) muscles, in regard to electrical reaction. These, as pre- 

 viously stated, express themselves partly in quantitative changes 

 of excitability towards induced and constant currents, partly, as 

 will be shown, by a qualitative alteration of the polar effects of 

 excitation, and that in the direction stated above for Aeby's 

 fatigued muscle. While, under normal conditions, the kathodic 

 effect of excitation (so-called "kathodic closure twitch") pre- 

 ponderates considerably in direct unipolar excitation of a 



