274 ELECTRO-PHYSIOLOGY CHAP. 



of the wave varies considerably, but is always insignificant. 

 Hermann (I.e.) estimates it in fresh, freely-undulating prepara- 

 tions at 4 to 5 mm. per sec. We have already shown that toler- 

 ably strong currents are necessary in order to produce a clear 

 effect. It is fundamental to the conception of the wave as an 

 excitation phenomenon that it is exclusively characteristic of 

 striated living muscle, and is non-existent in other moist tissues ; 1 

 further, as Hermann showed (I.e.), an effect of fatigue and re- 

 covery of the muscle may be demonstrated, since the energy and 

 rapidity of the wave diminish gradually, to increase again after a 

 prolonged period of quiescence. Above all, however, it must be 

 noted that, as in muscular excitation in general, the temperature 

 of the moment affects the galvanic wave in a m,ost striking manner. 

 On sending current through fresh muscles (sartorius) in a warm 

 oil bath, Hermann (I.e.) found that the effect appeared in 

 extreme perfection, no idea of which could be formed from 

 ordinary experiments. The diffusion, as well as the height and 

 velocity of the wave, are enormously increased by higher tem- 

 perature ; on the other hand, the effect disappears entirely 

 with even moderate cooling. The effect of muscular tension is 

 further very conspicuous. The wave is always most marked 

 with the ordinary medium degree of tension, and ceases to be 

 visible with either very high, or completely absent, tension. 

 When the significance of the degree of tension at any given 

 moment to muscular excitation (as also to metabolism) in the 

 entire muscle is remembered, this reaction can hardly be sur- 

 prising. 



It has already been shown that the direction of the wave is 

 always from anode to kathode, but the anode itself is not the 

 starting-point of the waves of contraction. If excitation is effected 

 with a current of such intensity that the wave is just perceptible, 

 it appears, as a rule, to be most marked in that tract of the 

 muscle which, during closure, is thrown into persistent contraction. 

 It frequently happens that the extreme ends of the fibres on the 

 anodic side, as also the entire kathodic half of the muscle, show 

 no trace of the wave, while the greater part of the anodic side is 



1 On applying strong currents Neumann (12) frequently observed a phenomenon 

 in cardiac muscle (of frog) which appears to be analogous with the galvanic wave, in- 

 asmuch as peristaltic waves spread during closure in the direction of the current in 

 such regular succession "that the heart seems to give faint, delicate pulsations." 



