iv ELECTROMOTIVE ACTION IN MUSCLE 373 



twitch, but the time which such a deflection occupies corre- 

 sponds much less closely with the time of the variation of 

 current, than the movement of the capillary electrometer 

 (which for the rest is far too insensitive for the object before 

 us). Nevertheless, the construction of the curve of varia- 

 tion by a direct record is eminently desirable. Since it does 

 not appear possible to overcome the sluggishness of the magnet, 

 and to raise its mobility so far as to enable it to follow 

 the quicker variations of the current faithfully, Hermann has 

 recently tried the reverse method, by attempting to retard the 

 galvanic process under observation as much as possible (21). 

 He accomplished this by the simple and ingenious method of 

 turning the two copper knobs, which effect contact with the 

 galvanometer, and are attached to an ebonite disc, in the same 

 direction as the wheel of the Bernstein rheotome during 

 its revolution, only much more slowly. It is obvious that the 

 interval between stimulus and galvanometer closure would thus 

 be constantly altered, so that the whole process of the negative 

 variation may be read off at a given reduction of time upon 

 the galvanometer. The magnet would then follow the time- 

 relations of the electrical change with complete fidelity, and 

 it would only be necessary to transfer its movements by means of 

 a ray of light reflected from the mirror on to a moving sensitive 

 surface, in order to obtain a true photographic record of the curve 

 of variation. It is superfluous to say that the results obtained 

 by this method (" rheotachygraphy ") coincide with the conclusions 

 of the ordinary rheotome experiments. 



The ' variation curve : ' therefore corresponds with the 

 development and time-relations of the negative variation in a 

 definite part of the muscle, i.e. the point of the longitudinal 

 section from which it is led oft'. But since the changes funda- 

 mental to it, which are unequivocally in direct ratio with the 

 excitatory process, proceed pari passu with the rapidity at which 

 excitation is propagated from section to section, it is legitimate to 

 inquire in what length of muscle the single points are found after 

 excitation to be simultaneously at different phases of negative 

 variation. And thus we come to Bernstein's original proposition 

 of the " excitatory wave " in muscle. " A muscle fibre (M, M) (Fig. 

 118) is led off from its artificial cross-section (q~) and from the 

 surface of the elements (d, 1/" T ), which is hypothetically marked 



