43 



THE PROPERTIES OF STRIPED MUSCLE. 



current. 



polarising one. For, in the experiment just referred to, the current of each 

 circuit must, if both are closed at the same time, flow into the other, in 

 proportion dependent on its resistance. The same thing would happen if 

 the testing electrodes were separated from the others, to whatever part of the 



muscle they were applied. Conse- 

 quently, the existence of these 

 derivation currents would modify 

 the excitability of the parts ex- 

 plored, and thus vitiate the results 

 of the comparisons. Biedermann l 

 seeks to avoid this difficulty by 

 introducing into the exciting circuit 

 a resistance so great, that the 

 derivation currents in question are 

 too inconsiderable to have any effect. 

 By this method he has arrived at 

 the conclusion, that in the curarised 

 sartorius, so long as the testing elec- 



Fio. 243. /and// the primaryand secondary trodes are applied outside of the 

 coils of "the Inductorium K rheochord lar reg ions, no alteration of ex- 

 through which the current of B flows in r ., ,.,., e ' , -. , , , , . 

 the direction of the arrow. A current citability can be detected during 

 derived therefrom flows from a to b the flow of the polarising current, 

 through the muscle M and the secondary 

 coil. The current through the primary 

 coil can be closed by the key k' . At the In experiments of this kind, 



moment that this takes place a closing the current should be so weak 



that its closure scarcely evokes 

 an excitation. So long as this is 

 the case, the effect continues 



without alteration. By increasing its intensity the effect is at 

 first increased, but beyond a certain degree of intensity, which is soon 

 reached, it begins to diminish. 2 The effect is strongest during 

 the fifteen or twenty seconds immediately following closure, and 

 disappears if the circuit remains closed. A few seconds later the 

 response to the induction shock may be so weakened as to suggest 

 that the increased excitability which at first presents itself has produced 

 a sort of fatigue. The previous state of increased response, Biedermann 

 speaks of as a " latent state of excitation." 3 The changes of excitability 

 at the anode during the passage of a voltaic current have also been 

 investigated by him, and have yielded results which appear to be in 

 harmony with those above stated. 



We have seen that in curarised muscles the cathodic increase 

 of excitability which shows itself immediately after the closure of a 

 voltaic current, diminishes in a few seconds, and is eventually replaced 

 by an opposite state. If a current of sufficient strength to evoke a 

 strong response at closure is broken, and after a very short interval of 

 time again closed, the second closure is often without effect. But on 

 closing the current in the opposite direction the response is as strong 

 as before. This phenomenon is analogous to that which in nerve 

 has been long known as that of " voltaic alternatives." The failure of 

 the second closure is evidently another manifestation of the state 

 resembling fatigue already referred to. It can, however, be shown 

 that a muscle of which the excitability has been diminished by real 



; Elektrophysiologie," 1895, S. 238 ; Translation, 

 ,oc. cit., S. 242 ; Translation, vol. i. pp. 284-286. 



, vol. i. p. 281. 



3 Loc. cit., S. 244. 





