in ELECTRICAL EXCITATION OF MUSCLE 265 



electrical current, of which the direct and normal effect is 

 contraction of the relaxed and " resting " muscle, is able no 

 less legitimately to inhibit a pre-existing excitation, and to pro- 

 duce an active relaxation of the contracted muscle. It may 

 further be demonstrated that these "inhibitory effects" of the 

 current cause true " polar effects " just as much as the excitatory 

 process, and as in this last two "excitations," distinct with 

 regard to time and place, if otherwise equivalent, may be dis- 

 tinguished as the closing and opening excitation, so here it seems 

 justifiable in the cases cited to speak of two equally distinct 

 " inhibitions," a closing and an opening inhibition, or, more 

 properly, anodic and kathodic inhibition, inasmuch as the one 

 appears at the point of entrance, the other at the point of 

 exit of the current. It was to be expected a priori from the 

 complete coincidence in physiological properties between cardiac 

 and skeletal muscle-fibres, that under favourable conditions there 

 should be polar effects of inhibition at the latter also. 



It is evident that, in order to decide this question, a 

 suitable muscle must be thrown into a state of persistent excita- 

 tion, comparable with that of cardiac muscle during systolic con- 

 traction, or during the characteristic " tonus " of the snail's heart. 

 This is best effected by the use of veratrin, which, as has been said, 

 so changes the muscle-substance that after a short impact of stimu- 

 lation there is not, as under normal conditions, a rapid twitch, but a 

 prolonged tonic contraction, often persisting unchanged for several 

 seconds, during which period the effects of the electrical current 

 can be conveniently studied (36). We have found it advisable 

 to introduce 6 to 7 drops of acetate of veratrin (1 % solution) into 

 the posterior lymph -sac of a frog, which was killed about ten 

 minutes later. The typical curve of contraction of a muscle thus 

 poisoned (sartorius) has already been described. It is only 

 necessary to recall the effect observed when a muscle, fixed in 

 the middle, and extended in Hering's double myograph, and 

 excited by a single induction shock, is traversed, after the maxi- 

 mum of contraction has been reached, by a battery current, pre- 

 ferably ascending. The anodic half of the muscle will then, at 

 the moment of closure, lengthen considerably, and the correspond- 

 ing curve makes a sudden drop, while the kathodic half, as a 

 rule, becomes more contracted at the same moment, or at any 

 rate shows no longitudinal changes. If the current is then 



