ACTION OF VOLTAIC CURRENT ON MUSCLE. 



427 



used. This consists of a revolving bar, which carries platinum contacts so 

 arranged that the battery circuit is closed at each revolution, and immediately 

 afterwards the galvanometer circuit is closed. The duration of the closure 

 can be varied at will. 



The opposed secondary current resembles so closely the so-called 

 negative polarisation current of electrolytes, investigated many years ago 

 by Peltier, that there need be no hesitation in regarding it as a physical 

 phenomenon, and applying to it the term polarisation, in the sense 

 in which it is used by physicists. 

 The effect in question shows itself 

 immediately after the polarising cir- 

 cuit is opened, and is very transitory. 

 The most important facts relating to 

 it are — (1) That it is not confined to 

 the anode or cathode, but can be 

 shown to exist throughout the region 

 through which the polarising current 

 has flowed ; (2) that it subsides very 

 rapidly; and (3) that its amount is 

 in obvious relation to the strength 

 and duration of the polarising current. 

 In all these respects the results ob- 

 tained in experiments on muscle {e.g. 

 on the sartorius) correspond with 

 those observed when a conductor of 

 similar form, consisting of porous 

 material soaked with liquid contain- 

 ing electrolytes, is investigated in a 

 similar way (Peltier's polarisation). 

 Another point of importance, as 

 showing that it is dependent on the 

 structural and chemical properties 

 of muscle, not on its functional 

 activity, is that although absent in 

 muscles of which the structure has 



been altered by subjecting them to high temperature, or other- 

 wise, the negative after-effects can be nearly as well observed in an 

 exhausted muscle which fails to respond to stimulation, as in a fresh 

 muscle. 



The secondary current, of which the direction is the same as that 

 of the polarising current, is of a different nature. Its characteristics 

 are — (1) That it chiefly manifests itself in the neighbourhood of the 

 anode, i.e., that the effect is best observed when the galvanometer 

 contacts are placed, one at the anode, the other at a short distance from 

 it ; (2) that in this case the effect is increased by shortening the 

 duration and increasing the intensity of the polarising current l ; (3) that 

 it fails to appear unless the muscle experimented on is fresh and 

 vigorous. The phenomenon appears to be dependent on the functional 

 disturbance which the muscular structure undergoes in consequence of 

 the passage of the current. By du Bois-Reymond it was called polarisa- 



1 Four to six Daniells, for from a half to a quarter of a second, may be used for the 

 sartorius. 



Fig. 242. — p is a paraffin block with mer- 

 cury pools at qqqq; t is also a 

 paraffin block, and tilts on its bearings 

 at a a. When r r on the battery side 

 dip into qq, the muscle is in circuit 

 with the battery. In the diagram it 

 is represented in circuit with the 

 galvanometer. 



