iv ELECTROMOTIVE ACTION IN MUSCLE 379 



sections of the primary muscle, or was merely in contact with 

 the latter. It is obvious that we cannot here speak a priori 

 of a negative variation, since the current which should vary is 

 absent, at least as regards any branch that can be led off to the 

 galvanometer. It is therefore imperative to investigate the _ 

 galvanic effects of excitation in the uninjured, currentless 

 muscle. But before we enter upon the complicated relations 

 of indirect excitation of the gastrocnemius it is advisable to 

 examine the simplest case of direct excitation of the currentless 

 sartorius. 



If one end of the muscle is tetanised while leading off at 

 the other end from the natural cross-section and a point on the 

 longitudinal surface at about the middle of the muscle, a current 

 appears, as du Bois-Reymond found, during excitation, in the 

 direction of a negative variation, even where no trace of a 

 regular muscle current had previously been present, inasmuch 

 as the tendon end is positive towards every point of the longi- 

 tudinal surface. We must adopt Hermann's designation of this V 

 as the " action current " because, independent of the presence 

 or absence of a current of rest, it characterises the active state 

 of the muscle. As a corollary to Hermann's view, the negative ^ 

 variation of the demarcation current was explained above as 

 signifying that the contractile substance under the electrode 

 in contact with the longitudinal surface becomes more or less 

 negative at the instant when a wave of excitation, or " ex- 

 citatory wave," passes under it, when the original difference of 

 potential between longitudinal and artificial transverse section is 

 of course diminished in proportion. But it is evident that the 

 same canon of interpretation cannot be prima facie applied to 

 the present case of uninjured, and therefore currentless, muscle. 

 For if we are to assume that the normal ends of fibres, like all 

 other parts of the muscle, take part in the excitation (and there 

 is no evidence to the contrary), they must, when the excitatory 

 wave reaches them, become as negative as every preceding 

 segment. Then, however, under the given conditions, a 

 descending current directed in the muscle from longitudinal 

 section to tendon could not appear during tetanisation, much 

 rather would the absence of current, obtaining before the 

 excitation, continue also during stimulation. Later on, Her- 

 mann's theory will be found to give a simple solution of this 



