452 ELECTRO-PHYSIOLOGY CHAP. 



discharges perceptible mechanical excitation effects, although it 

 still works changes in the muscle-substance which are expressed 

 in other ways, more especially by an alteration of excitability 

 at the points of entrance and exit. Further, it is known (as 

 Hering pointed out) that the break excitation may be identified 

 on the galvanometer as a positive anodic after-current, " even 

 where this is not visible to the eye, nor even perhaps micro- 

 scopically." At all events there are excitations which must be 

 termed subliminal as regards change of form in the muscle, 

 while in a narcotised muscle the strongest excitation fails to 

 develop any directly visible reaction. These facts make it clear 

 that the relation between contraction and excitation is by no 

 means so immediate as might a priori be supposed, but that the 

 indirectly demonstrable changes in the muscle -substance may 

 occur in consequence of previous excitation, without perceptible 

 changes of form. And it is very remarkable in the etherised 

 muscle that the polarisation effects described show no perceptible 

 weakening throughout the entire period of narcosis. This tells 

 in favour of the fundamental independence of excitability in the 

 muscle from its contractility and conductivity. 



Under these circumstances it is the more interesting that the 

 possibility of excitation seems to exist in another and different 

 alteration of the muscle -substance, in which contractility is 

 equally more or less affected. In this case it is not merely 

 the polarisation phenomena under discussion that continue, 

 but (where the changes that occur are local, and con- 

 fined to the seat of direct excitation) there are also changes 

 of form in the normal section of the muscle. We have 

 already seen that striated muscle is capable of taking up a 

 considerable bulk of water without losing its capacity for elec- 

 tromotive response, when irritated, as under normal conditions. 

 If the water treatment is confined to one or the other end of a 

 sartorius, this end may in consequence of imbibition undergo 

 great alteration in its physical properties, without, as we have 

 seen above, becoming negative to the uninjured part of the pre- 

 paration. This agrees with the fact that excitability towards 

 the electrical current is not perceptibly affected, if it is sent 

 through the muscle in such a way that the point of direct ex- 

 citation is situated at the altered end of the muscle. This is found 

 on the one hand from comparing the height of twitch, on the 



