ELECTROLYTES IN LIVING MATTER 99 



loidal solutions which contain also salts. It is obvious that such a 

 system can act only as a Uquid conductor in which the current is carried 

 by the dissociated ions or such colloidal particles as possess an electric 

 charge. The concentration of the colloidal particles is very small 

 compared with that of the electrolytes in solution, so that for the con- 

 duction the latter are mainly or practically exclusively responsible. 



When a constant current is sent through a nerve-muscle prepara- 

 tion or through a muscle, two kinds of effects are to be considered: 

 the one effect shows itself only at a rapid change in the intensity of the 

 current, and consists in a twitching of the muscle. The second effect 

 shows itself throughout the whole duration of the current, and consists 

 in an increase of irritabihty at the cathode and a decrease at the anode. 

 It can be shown that the twitching originates on the making of the cur- 

 rent at the cathode and on the breaking at the anode. The two effects 

 of a current are therefore different at the two poles. 



When a current goes through a liquid conductor its work consists, 

 first, in the pulling of the ions through the liquid to the electrodes, and 

 second, in the withdrawal of the charges from the ions and the trans- 

 formation of the latter into uncharged atoms at the electrodes. The 

 question arises as to which of the two effects of the current the physio- 

 logical actions are due: to the increase of the concentrations of ions 

 at the electrodes, or to the withdrawal of their charges. I believe 

 that this question can be decided for the twitchings in favor of the idea 

 that the twitchings are due solely to the increase in the concentration 

 of the ions at one pole, and not to the loss of the charge of the ions. 



It had been known for a long time that the galvanic current can 

 only cause a twitching in the muscle, when it goes lengthwise through 

 its nerve; while its effect diminishes or becomes zero when it travels 

 crosswise through the nerve. I ah 



have shown that the same is O O 



true when the nerves are stimu- 

 lated by induction.* Let a 

 and h (Fig. 16) be the elec- 

 trodes of a Toepler-Holtz ma- 

 chine, and cd the nerve of a 

 nerve-muscle preparation of a frog; the preparation is placed on an 

 insulated glass plate. If cd is parallel to the spark discharge and at 

 not too great a distance from it, the muscle twitches every time a spark 

 passes between a and h. If, however, this nerve is put at right angles 

 to the spark discharge and symmetrical to the two electrodes,- but 

 equally near or even a little nearer to it than before (Fig. 17), no twitch- 

 * Loeb, Pfliiger's Archiv, Vol. 67, p. 483, 1897 ; ^^^ Vol. 69, p. 99, 1897. 



