348 INHIBITION BY EXCITATION AND 



takes place at a time when the spontaneous decrease of the after- 

 current is imminent, or has already begun, then as a rule only 

 a more or less considerable and sudden acceleration of the return 

 is effected; if the excitation takes place later still, negative 

 polarisation is again produced, although it is much feebler than at 

 the commencement of the series of experiments. Sometimes in this 

 case also, the opposite positive action becomes still perceptible by 

 a transient delay of the negative deflection. 



It is noteworthy that if directly after the passing away of the 

 action current, which always takes a rather long time, the same 

 descending current, which at first produced such powerful effects, 

 is closed, only comparatively trifling deflections in the direction 

 of a negative polarisation current are obtained. If however, the 

 muscle has a longer period of repose, being left in a physiological 

 solution of common salt in the interval, then on the same excitation 

 exactly the same phenomena described above are repeated. This 

 is very much in favour of the assumption of a local fatigue, caused 

 by the strong and prolonged state of excitation of the poisoned 

 part of the muscle ; and another fact is in accordance with it, viz. 

 that the mechanical results of excitation under the same circum- 

 stances often seem to be seriously impaired. 



The following tabulated results of experiments will serve to 

 explain the foregoing more clearly. 



The horizontally stretched muscle is to be supposed throughout as 

 having its lower end turned towards the left ; two out of the three 

 galvanometer electrodes were in direct contact with the tendinous 

 ends, and the third was in contact with a corresponding point of 

 the middle of the muscle. The exciting electrodes were applied to 

 the two stumps of bone. The leading off was as a rule only from 

 the left kathodic half. The direction of the polarising current is 

 indicated in the tables by arrows. 



i. Rana temporaria, curarised, the lower end of the sartorius 

 dipped in o-oi/ solution of veratrine for 5 min., afterwards treated 

 with 0-6% Na Cl. solution for 15 min. Cl. T = closing time. 

 M. St. = momentary stimulation effected by a rapid closing and 

 opening of the exciting circuit by means of the double switch. 

 Before the first stimulation, the muscle is found to be without 

 current on leading off from the kathodic half. The strong negative 

 action current after the first, fifth, and ninth excitations is rapidly 

 compensated every time. 



