in ELECTRICAL EXCITATION OF MUSCLE 205 



kathode at closure and the anode at opening, it may further be 

 asked how far the different direction of current accounts for 

 this disparity. This question, however, is answered by v. 

 Bezold's hypothesis, according to which the direct conclusion 

 from the above experiment is as follows : " That on the closure of 

 a constant current, (striated) muscle is at first excited in the region 

 of the negative electrode and not in the region of the positive 

 electrode, while on opening the current flowing through the muscle, 

 the immediate excitation would l>e at the positive and not at the 

 negative pole." 



These data of v. Bezold, and the conclusions drawn from 

 them, are borne out by the well-known fact that, on exciting 

 with the constant current under certain conditions (i.e. diminished 

 conductivity), the manifestations of contraction are confined to 

 the region of the point at which the current leaves the muscle 

 (kathode), and that this occurs invariably in the persistent 

 closure contraction when currents that are not unduly strong are 

 sent into the muscle. With reference to the first point, v. 

 Bezold refers back to an older observation of Schiff (21), who 

 found that when a moribund muscle had already ceased to yield 

 a closure twitch there was still at the negative pole of a constant 

 current a weak, localised idio-muscular contraction, far less dis- 

 tinctly expressed than the effect of mechanical excitation, which 

 persists uniformly so long as the current continues, and then dies 

 away again. It is not difficult to show that this " idio- 

 nmscular " kathodic persistent contraction is completely identical 

 with the persistent closure contraction described above, provided 

 the currents used for excitation are not excessively strong. 

 Engelmann (5) obtained direct experimental proof that in 

 perfectly fresh muscle also the sustained contraction following 

 on the closure twitch is confined to the region of the kathode. 

 The method of his experiment is evident from the accompanying- 

 diagram (Fig. 85). Engelmann passed a current through the 

 entire sartorius, and fixed the upper section with a clamp which 

 was 7 mm. or more below the upper electrode, while the lower 

 electrode was formed by a wire hook introduced into the muscle. 

 The section of muscle below the clamp was therefore the only 

 movable part, and recorded its contractions upon a slowly 

 travelling surface. When the current in the muscle was 

 descending, the lever remained above the abscissa after the make 



