54 CONTRIBUTION TO THE 



impossible to conceive that the displacing 1 power of a very weak 

 current, such as is just able to produce a muscular contraction, 

 would be sufficiently great and could occur with sufficient sudden- 

 ness to exert such an action. Moreover, the facts made out by 

 Munk in this connection relative to the changes of excitability pro- 

 duced by a constant current, which were to have supported his 

 conception, do not agree with the results of foregoing- and succeeding 

 investigations. Besides, he has never published the complete account 

 of his theory. We need therefore give it no further consideration. 



II. 



Certain phenomena, which I observed in the course of my inves- 

 tigations upon the changes of excitability produced in nerves 

 by the constant current, led me to enquire whether the internal 

 polarisation of nerves might not be the true cause of the break- 

 contraction. Accordingly, I devoted myself in the first place 

 to a thorough investigation of the internal polarisation of nerves, 

 and soon found that it afforded in a remarkable degree the con- 

 ditions required for the production of a break-contraction. 



The chief laws of the internal polarisation of nerves are these : 



1. With a current whose strength is not greater than that pro- 

 duced by three Meidinger's elements polarisation is, as near as may 

 be, directly proportional to the strength of the current. 



2. If the polarising current acts on the nerve for unequal and 

 increasing lengths of time, other conditions being the same, polari- 

 sation increases ; it rises more rapidly at first, and afterwards more 

 slowly, finally approaching its maximum with extreme slowness. 



3. When the polarising current is opened, polarisation instantly 

 attains its highest value, and after this declines continuously. This 

 decline proceeds at first very rapidly, afterwards however more 

 and more slowly, so that polarisation is still present for a long time 

 after the opening of the polarising current, and approaches the zero 

 point only asymptotically. 



The two chief conditions on which the strength of polarisa- 

 tion depends are identical with those which determine the break- 

 contraction, as to which it has long been known that it is in 

 the main a function of the strength and duration of the po- 

 larising current. But the third law of polarisation also tells in 

 the occurrence of the break-contraction in a very remarkable way. 

 Since polarisation lasts for an appreciable time after interruption of 

 the polarising current, the break-contraction, if it has once occurred 



