iv ELECTROMOTIVE ACTION IN MUSCLE 387 



tachygraphic " method, as described above) published a graphic 

 record of the gastrocnernius action current, which, on leading off 

 from the tendo achilles and from a point proximal to the nervous 

 equator, gives double-topped curves, in which the first descending 

 phase is succeeded by a second, weaker, ascending variation, after 

 which the magnet returns to its zero with some insignificant- 

 deflections (Fig. 122). 



This dissimilarity is apparently due to a partial superposition 

 of the two phases ; the excitation has not entirely passed the 

 upper lead-off before it reaches the lower. The gastrocnemius 

 curve of electrical variation is even more complicated on lead- 

 ing off from the centre and tendo achilles, as in the observa- 

 tions of Lee which we have frequently referred to, in which the 

 more sluggish galvanometer is replaced by the sensitive capillary 

 electrometer. The rheotome method can also be applied here. 

 The curve (Fig. 123, a) corre- 

 sponds with a triphasic varia- 

 tion, its two negative sections 

 being separated by a double- 

 topped, positive, and very steep 

 segment. The duration of the 

 entire process amounts to 0'26 

 sec., a value which we have 

 seen to be approximately equi- 

 valent to the duration of a 



twitch in the muscle. The wave of variation in the sartorius, on 

 the other hand (when led off from the middle and end of the muscle), 

 was found by Lee to be diphasic, no conspicuous decrement being 

 visible in the fresh, uninjured muscle. Both sections exhibited a 

 tolerably symmetrical figure (Fig. 123, b). . If, however, the tendon 

 end of the muscle is injured ever so slightly, the first (" negative ") 

 phase prevails, and the second may disappear entirely, as shown 

 by the lower curve of the same figure. In this case the variation, 

 which is now monophasic, does not appear perceptibly shorter 

 than the sum of the two earlier phases, which again implies 

 superposition of the two components. The triphasic wave of the 

 gastrocnemius again (in progressive fatigue, or injury, of the lower 

 end of the muscle) undergoes alteration in the sense that the middle 

 positive section disappears, or is merely indicated. For the rest, 

 the fatigue changes in the curve of electrical variation in striated 



