236 RESEARCHES ON SECONDARY ELECTROMOTIVE 



were at such a distance from the exciting ones as to be beyond 

 the limits of the corresponding- anodic and kathodic tracts, and 

 the exciting currents were weak or of very short duration, the 

 polarisation-currents produced at the intersection would be, in 

 fact, the only ones which manifested themselves galvanometrically. 

 But even when the exciting currents were stronger or more pro- 

 tracted, and persistent break-excitations were induced, a new factor 

 must have come into play. 



Every stimulation with persistent and stronger currents neces- 

 sarily induces persistent break-excitation in two tracts of the 

 muscle ; in the first place, an excitation which, commencing in the 

 region of the stimulating anode spreads more or less towards the 

 centre of the muscle, and a second which starting from the tendinous 

 intersection spreads more or less towards the stimulating kathode. 

 These two concomitant persistent excitations must, as a rule, be of 

 different strengths and extent, for the conditions under which the 

 current enters the individual fibres of the muscle from the stimu- 

 lating electrode applied laterally, are quite different from those 

 under which it enters the natural cross sections of the fibres of 

 the second half of the muscle from the tendinous intersection. 

 It is at all events plain, that the relations of current density in 

 the anodic spots of the individual fibres must be quite different in 

 the one case from what they are in the other, and on these current 

 densities depends essentially the break-excitation of each fibre. 



Another equally complicating element I have hitherto only in- 

 cidentally mentioned. Every polarisation-current is to be regarded 

 as the algebraic sum of the individual amounts contributed by the 

 muscle-fibres. Supposing, for example, the current entered the 

 thin end of a muscle and passed thence to its thicker centre. The 

 current would in this case decrease in density so long as there was 

 an increase in the transverse section of the muscle. In such a tract 

 the current enters the natural ends of all the added fibres of the 

 muscle, and the density with which it enters is much less to- 

 wards the equator of the muscle than it is towards the end. In 

 this last position the density of the current would perhaps be suffi- 

 cient to produce positive anodic polarisation, whereas in the former 

 position it only shows negative polarisation. The anodic tract will 

 therefore show, after breaking the stimulating current, polarisation 

 in two opposite directions. As the semimembranosus has fresh 

 accessions of fibres far up, the circumstances above mentioned 

 demand consideration. 



