104 THE NATURE OF THE 



current ; that (2) the polarisation-current increases with the 

 duration of the polarising- current. My observations were however 

 only continued over shorter periods than those of Tigerstedt. 

 Nevertheless in them too the law became evident that the greatest 

 effect is produced in the first seconds during which the polarising 

 current remains closed and that a more prolonged closure of the 

 primary current only increases the secondary current to a slight 

 extent. (3) I investigated in exactly the same way as Tigerstedt 

 the rate at which the polarisation-current disappears from the 

 .nerve, and found, although more time elapsed in my experiments 

 than in those of Tigerstedt between the moment of opening the 

 primary current and closing the galvanometer-circuit, that the 

 secondary polarisation-current is stongest during the first moments 

 after closure, and then gradually becomes weaker, first quickly, 

 and afterwards slowly, but that it can still be observed for a very 

 long time in the case of muscle after the lapse of minutes. 



Quite recently there was published a thorough investigation of 

 this subject by du Bois-Beymond, in which a very important 

 and altogether new fact was brought to light, namely that of 

 positive polarisation. Du Bois-Beymond found that if a current is 

 passed through a muscle or nerve, and its electrical condition 

 immediately after opening tested by means of a second pair of 

 electrodes placed between those of the polarising current and 

 connected with a galvanometer, under certain conditions positive 

 polarisation appears at first, that is to say there is a current with the 

 direction of the primary current, while negative polarisation does 

 not appear until later. Like Tigerstedt 1 , I have not observed this 

 positive polarisation in my experiments, doubtless for the simple 

 reason that I used primary currents of insufficient strength, and 

 further that my periods of break the periods of time, that is to say, 

 elapsing between the breaking of the primary current and making 

 of the galvanometer-circuit and of make were too long. For du 

 Bois-Beymond observed strongest positive polarisation in muscle 

 with a make of "075 seconds' duration and a current of twenty 

 Groves. If the duration of make in the case of nerve was 

 longer than a second, polarisation was always negative; and the 

 weaker the primary current, the earlier did negative polarisation 

 appear. Now even if the polarisation indicated by the galvano- 

 meter is to be regarded as the algebraical sum of the two kinds of 



1 Sitzungsberichte der Akademie der Wissenschaften zu Berlin, Sitzung 5 April, 

 1 883, p. 343. 



