

PRODUCED BY A CONSTANT CURRENT. 23 



Experiment 3. 



+ P = 10 ; P = 19 ; E 25 ; 2 Meidinger, Eh. = 450 ; y = 20. 



a. The mechanical stimulus produced no muscular contractions ; 

 the constant current produced a make- but no break-contraction. 

 Under the influence of the current there occurred remarkably large 

 contractions of uniform strength, which instantaneously disappeared 

 when the current was opened, to return when it was again closed. 



b. When the nerve was subjected to the same intensity of me- 

 chanical stimulation somewhat higher up (E = 26), the contractions 

 that took place during the passage of the current were not nearly 

 so strong as in a ; and on the other hand they underwent a slow 

 decrease during each period that the current was closed. 



c. When the polarising current was strengthened (2 Meidinger, 

 Eh. = 1,450), so that contraction took place when it was opened 

 the contractions were notably stronger on stimulation of the spots 

 above mentioned than they previously were, or even than in a. The 

 slow decline of the contractions with continuance of the current can 

 here be clearly recognised. In each experiment of these series, (a, 6, c,) 

 however, the contractions elicited during the action of the constant 

 current are always of nearly the same height. Thus in c one can 

 make out no diminution of the contractions at the end as compared 

 with those at the beginning, but on the contrary the latter are a little 

 less than the former ; and yet the nerve had been subjected during 

 nearly 160 seconds to at least 240 stimulations. 



2. The extrapolar changes of irritability at the positive pole 

 of an ascending current. 



The excitability of the nerve is considerably diminished. An 

 intensity of the stimulus, which a short time previously elicited very 

 large contractions, now causes quite small ones or none. This 

 diminished excitability lasts all the time the current is closed. In 

 the circumstances under which my experiments were conducted the 

 diminution set in directly the current was closed. At the same time 

 the first contraction was sometimes greater than those following it. 

 Occasionally, on the other hand, while the current continued to flow 

 through the nerve, the muscular contractions increased from their 

 first minimum, only however to a trifling extent and often scarcely 

 perceptibly, in some cases not at all. When the current is opened 

 the muscular contractions return to their original strength, without 

 at the same time any recognisable inhibition exhibiting itself in 

 the first moments. On the contrary, there appears in the nerve a 



