in ELECTRICAL EXCITATION OF MUSCLE 317 



most, protozoans, where the excitation is indeed conspicuously polar, 

 but appears at closure to be localised at the anode, on opening 

 the current at the kathode ; and Eoux's observations upon the 

 morphological " polarisation " of ova also fall under this category. 

 Further, in many cases an equally marked inhibitory action of the 

 current is exhibited in corresponding changes of form, which- 

 appear simultaneously with the manifestations of excitation, but 

 are localised at the opposite pole. Kathodic closure excitation there- 

 fore implies a simultaneous anodic closure inhibition, anodic break 

 excitation, kathodic "break inhibition. Thus both the simultaneous 

 polar effects, or after-effects, of current, and the subsequent effects 

 at the same pole, as a rule, exhibit an antagonism (as is more 

 particularly expressed in the opposite reactions of " electrotonic " 

 changes of excitability at the physiological poles) by which it is 

 possible to demonstrate the inhibitory effects even in such cases 

 where, failing a tonic state of excitation, no visible alteration of 

 form appears. So far as may be concluded from experiments on 

 muscle, the current, provided its strength does not exceed certain 

 limits, appears to traverse the intrapolar area without producing 

 any perceptible alterations within it. Under some conditions 

 excitation phenomena appear in the vicinity of the physiological 

 pole during closure of the anode and after opening the kathode ; 

 but these seem to be due to diffusion of current and formation 

 of secondary electrode points, and are accompanied by simul- 

 taneous, antagonistic changes (inhibition) in the region of the 

 other pole. 



The persistence of the excitatory or inhibitory effect of current 

 during closure, as well as the localisation and antagonism at the 

 poles, prove incontestably that the consequences of electrical excita- 

 tion are only a special manifestation of commencing electrolysis in 

 the living substance. On this assumption it becomes intelligible 

 that the anodic and kathodic alterations should neutralise each 

 other when produced by a transverse current at the opposite 

 longitudinal margins of a muscle-fibril, or any minute tract of 

 contractile substance (e.g. a pseudopodium). This view is not 

 contradicted by the fact that in certain kinds of protoplasm the 

 changes which underlie the excitation appear to be localised not 

 at the kathode, but conversely at the anode ; for this is ob- 

 viously dependent on the quality of the excitable substance, which 

 is not necessarily the same in all cases. These brief observations 



