350 Dr. K. Sassa. Effects of Constant Galvanic Currents upon 



(3) On Continuous Excitation in the Nerve during the Passage of the Current. 



During the flow of weak constant galvanic currents in eitlier direction, no 

 continuous reflex effect occurs. With stronger stimulation, the reflex 

 phenomena obtainable during the passage of current through the nerve are 

 different according to its direction, as was seen by Sherrington and Sowton (12). 

 With the ascending current, the excitatory effect at its make increases 

 progressively with the strength of excitation and then often passes over into 

 a rebound contraction following an inhibitory relaxation of short duration. 

 The rebound contraction is, in its turn, followed by a shortening reaction or 

 relaxes gradually. A passive plastic reaction is easily obtained during the 

 passage of strong ascending currents, except immediately after its closure 

 when the rebound phenomenon is still in progress. This is a convincing proof 

 that no excitation is occurring during the passage of even a strong ascending 

 current. This rebound phenomenon is, however, often so prolonged that one 

 may think that excitation is still in progress. In such a case, the lengthening 

 reaction is more limited than before the application of the current. This 

 excitatory process is neither more nor less than a prolonged rebound pheno- 

 menon. If the preparation is of poor rigidity, where any reflex effect is only 

 inhibitory relaxation of the tone of the muscle, the effect at make of a 

 constant ascending current of sufficient strength is inhibition followed by a 

 lengthening reaction without any rebound contraction. This is another sign 

 that there is no continuous reflex effect during the passage of the current, 

 since the plastic reaction is unchanged by its application. 



At make of a stronger descending current the tonic contraction of the 

 muscle relaxes. This relaxation is somewhat prolonged, and is followed by a 

 rebound contraction weaker than that produced by a like stimulus of ascend- 

 ing direction. This seems to correspond with the result seen in the nerve- 

 muscle preparation, that the contraction at make of currents of moderate 

 strength is prolonged in its phase of relaxation. The poor rebound phenomenon 

 may result from depression by a prolongation of the inhibitory effect at make, 

 so that the resulting level of the myogram line is determined by the algebraic 

 sum of excitatory and inhibitory processes. By further increase in the intensity 

 of stimulation, the inhibitory relaxation becomes more complete and the suc- 

 ceeding rebound contraction is less marked, until the former attains its full 

 extent and the latter no longer takes place. The phenomenon is not merely a 

 lengthening reaction following inhibition, since the muscle is felt to be more 

 flaccid than before the application of the current, and the passive shortening 

 reaction is no longer easily obtainable. If the lower limb is then passively 

 extended, so that the myogram line is at a high level, this falls slowly and 



