iv ELECTROMOTIVE ACTION IN MUSCLE 391 



such a case that superficial corrosion of the natural cross-section 

 proximal to the tendon might not immediately develop a normal 

 current, if the negativity of the leading-off contact of the longi- 

 tudinal section is equal to, or greater than, that of the artificial 

 cross-section at the end of the muscle. Such a wave of contrac- 

 tion is easily produced at any given point of a muscle with 

 parallel fibres by the local application of veratrin solution, which, 

 of course, retards the decline of the excitation very considerably. 

 Hermann obtained the same result by energetic cooling of the 

 muscle. And lastly, if it counts as the touchstone of a theory 

 that new facts can be predicted upon its basis, the " secondary 

 electromotive manifestations " must be cited, to which we shall 

 return later. 



After it had been ascertained from experiments on isolated 

 muscles that the state of activity is accompanied by electro- 

 motive alterations demonstrable on the galvanometer, it became a 

 desideratum to establish the same for uninjured muscle in situ, 

 in man and other warm-blooded animals. Du Bois-Reymond 

 accordingly, with admirable perseverance, carried out a research 

 which is a pattern of sustained and deliberate investigation. If 

 his attempts to discover differences of potential in the sense of a 

 " resting muscle current " through the skin of the intact frog were 

 frustrated by the strong electromotivity of the skin itself, the 

 experiment was no less difficult on the human subject. But we 

 need not dwell on the point, since there now appeal's as little 

 reason for ascribing demonstrable electromotive activity to human 

 muscles during rest, as to those of the frog or any other animal. 

 On the other hand, clu Bois-Eeymond's attempts to demonstrate 

 currents that could be led off externally during voluntary con- 

 traction, or, in the language of his theory, the negative variation 

 of the pre-existent muscle current, were crowned with success. 



His classical experiment, which, when first published, created 

 an enormous interest, is arranged as follows : One or more fingers 

 (preferably the forefingers) of each hand dip into the vessels of 

 conducting fluid, which again are conveniently connected with the 

 terminals of the galvanometer or multiplier circuit (Fig. 124). 

 When the magnet has come to rest under the influence of the 

 natural (and usually insignificant) current which results from in- 

 equalities in the two points of the skin from which the current is 

 led off, a sharp contraction of the muscles of one arm generally 



