KATHODIC POLARISATION OF MUSCLE. 347 



end and the middle of a muscle, none at all events which the 

 galvanometer is capable of showing. If the exciting electrodes 

 are now applied to the bones at both ends, and the current of two 

 Daniells is closed for a very short time in a descending direction, 

 so that it traverses the whole length of the muscle, then if the 

 galvanometer circuit is closed directly afterwards by turning the 

 switch, there results a very strong deflection in the direction of 

 a current opposed to the polarising one. The intensity of this 

 current is always incomparably greater than that of a negative 

 kathodic polarisation current which appears in normal muscle 

 preparations under similar conditions but after a much longer 

 period of closure. It even exceeds that of the demarcation current. 



It can hardly be doubted that this difference of tension is caused 

 by the strong and protracted excitation of the tract of muscle 

 which has been treated with veratrine, and the current produced 

 by it must accordingly be considered as an ' action current.' 



The development of this current, as regards time", very frequently 

 results in such a manner (and these are exactly the most favourable 

 cases for the following experiments) that immediately after opening 

 the exciting circuit and closing that of the galvanometer, the 

 deflection attains a certain amount very quickly, remains constant 

 at this amount for a short time, and then increases gradually 

 during several seconds, until finally it passes away slowly. If 

 now, after compensating as quickly as possible, the excitation is 

 repeated with a descending current in the same way as before, 

 whilst the position of the magnet remains unchanged or is still 

 in the act of increasing, then, without exception, there follows a more 

 or less considerable backward swing, indicating a polarisation current 

 which has the same direction as that of the stimulating current, and 

 is therefore positive. The image of the scale then either returns to 

 its former position more slowly, sometimes passing beyond it, or it 

 takes up a new position, which indicates a persistent diminution 

 of negativity of the fibres at the kathodic spots. 



Whether the one or the other happens, depends essentially upon 

 the stage of the development of the action current when the ex- 

 citation takes place. If the polarising current is closed immediately 

 after it begins or only a little later, then after an excitation of 

 short duration, the diminution of the negative after-current caused 

 by it, is seen almost uniformly to be succeeded by a corresponding 

 increase ; and the same experiment can be repeated several times 

 in succession with the same result. If however the excitation 



