KATHODIC POLARISATION OF MUSCLE. 339 



The phenomena which I hoped, vainly however, to show on 

 electrical excitation of tonically contracted muscle of Anodonta, 

 appear under these circumstances with convincing clearness in a 

 frog's sartorius poisoned with veratrine. 



If the muscle is fastened with proper precaution in a completely 

 relaxed condition in the double myograph, and the middle is fixed 

 with great care between oil clay, and if a single induction- shock 

 of corresponding strength is sent either through the whole length 

 of the muscle or through only a part of it, then, as a rule, both 

 halves are nearly equally shortened, and the attached levers (one 

 upwards and the other downwards) draw curves, which, except 

 as to differences in size, are in every respect similar to those of 

 freely twitching muscle described above. If, whilst the muscle 

 continues at its maximum contraction, a battery current of sufficient 

 strength is closed in the ascending direction, the anodic half is 

 seen to lengthen considerably at once, the curve corresponding- 

 to it rapidly sinking, whilst as a rule, the kathodic half of the 

 muscle shortens a little more, or undergoes no perceptible change 

 in length. If now after the closing has lasted a short time, the 

 current is again opened, in a successful experiment, exactly the 

 opposite changes of form present themselves. The anodic half 

 now shortens to an often not inconsiderable extent, this con- 

 traction being obviously the expression of the opening excitation, 

 whilst at the same time the half corresponding to the kathode 

 is distinctly more relaxed than would have been presumably 

 the case had it not been stimulated. If the excitations are 

 rapidly repeated with the same direction of current, the same 

 phenomena, though diminishing in amount, appear as at the 

 beginning of the experiment, provided that the muscle is still 

 shortened to a considerable extent. A fact mentioned above repeats 

 itself here, viz. that the readiness of the kathodic half of the muscle 

 to respond to the excitation of closing, does not always increase 

 in proportion to the progress of relaxation ; it often indeed seems 

 actually diminished, when the muscle has already regained its 

 original length. After a longer pause however, the original 

 excitability is recovered again without exception, and thus one is 

 in a position to repeat the experiment several times in succession 

 on the same preparation with like results. 



It is hardly necessary to remark, that nothing essential is changed 

 in the preceding experiment, if from the beginning, one excites with 

 a descending instead of an ascending current, except that in the 



z 2 



