498 ELECTRO-PHYSIOLOGY 



this connection. It is easily explained by the fact that the opening of a 

 constant current leads, under certain conditions, to the protracted excitation 

 (persistent opening contraction) of the muscle. This gradually declines, 

 becoming more and more restricted to the anodic points of the muscle. Even, 

 however, in cases where (as with weaker currents, or brief closure of strong- 

 currents) there is no visible persistent break contraction, nor even a break 

 twitch, we are free to regard the positive polarisation current as the ex- 

 pression of a break excitation lasting for a considerable period inasmuch as 

 a low degree of contraction is difficult or impossible to demonstrate, especially 

 when it is confined to the immediate vicinity of the anodic or kathodic points 

 of the muscle, while negativity may be present as the expression of excitation, 

 without the slightest manifestation of contraction. 



Hermann's view of the positive anodic after-current only differs from 

 that of Hering in that (starting with the assumption of an intrapolar 

 electrotonus) he locates the break action current in the entire anelectrotonic 

 tract of the muscle. But it has already been shown (supra) that, provided 

 we avoid an undue strength of polarising current, the alterations that are 

 termed collectively " electrotonus " are all strictly confined to the physio- 

 logical electrode points. 



With respect to kathodic polarisation, we find that it is almost exclusively 

 negative in striated muscle. On leading off from a sartorius (through 

 which current is passing) by the kathodic end, and centre, of the muscle, 

 polarisation first appears, with very weak currents, after a closure of several 

 seconds, and is steadily augmented with increased strength of current and 

 longer closure. On comparing it with the positive anodic after- currents 

 observed at the same end of the muscle, at the same strength of current 

 and duration of closure, the latter soon exceed it very considerably. With 

 very strong currents and prolonged closure, negative kathodic polarisation 

 may become as strong as the equally abterminal muscle current seen on 

 killing the same end of the muscle, without shifting the galvanometer 

 electrodes. Induction currents also give negative kathodic polarisation, but 

 it is essentially weaker than the positive anodic polarisation produced by the 

 same strength of induction current in the same (sartorius) muscle. The 

 conclusion is therefore that, icith ///c/v^x///// stn'i/i/th .ml ilnrntinn nf c^ritii,,/ 

 i-i'rrcnt, the ItatlioiHr region i if the muscle (physiological kathode) IHWIH,* moreand 

 more negative in comparison n'itli tin' rr////v of the m-nscle. If this effect were 

 the equivalent of internal physical polarisation, the negative polarisation 

 current would, as has been shown, appear at approximately constant strength 

 on leading off from any point within the intrapolar tract ; and Hering has 

 shown that this never is the case. On the contrary, when the leading-off 

 electrodes are placed at the boundary between the upper and middle thirds 

 of the sartorius, while the polarising current is led in as before through the 

 bones, there is either no polarisation current, or it is so insignificant in com- 

 parison with the anodic and kathodic polarisation that it is practically 

 negligible. The relatively weak effects which may be observed in the 

 intrapolar tract with very strong polarising currents, and prolonged closure, 

 are to be explained by the fact that the polar points of the muscle are never 

 confined exclusively to its ends, e.rj. in the sartorius there are not infre- 

 quently short fibres which terminate, or begin, somewhere in the length of 

 the muM.-le. Again, the appearance of the make and break persistent con- 



