308 



ELECTRO-PHYSIOLOGY 



CHAP. 



paramrecia soon begin to swim about in all directions, and in a 

 short time are once more uniformly distributed throughout the 

 drop. This manoeuvre is repeated as often as the current is 

 closed, with the same precision. 



It is easy to prove that the living state is an essential condi- 

 tion of these phenomena by repeating the experiment after killing 

 the animals with ether or chloroform. 



If unpolarisable electrodes are used with points of baked clay 

 dipping into the infusion, instead of the excitation chamber 



FIG. 99. Galvanotropism of 1'ummcucium aiifdin. (Verworn.) 



described above, the effects are very curious. At closure of the 

 current all the paramsecia arrange themselves longitudinally, in 

 accordance with the current curves, and swim along these lines 

 towards the kathode, so that those which happen to be at the 

 outer part of the drop follow an almost semicircular course. 

 If the current is frequently reversed, the paranuecia may be 

 driven now in one direction, now in the other. As may readily 

 be understood, very rapid alternations of current do not cause 

 them to travel in a definite direction, nor give rise to any polar 

 accumulation. A priori there can be no doubt that in this case, 

 as in that of Amceba, we have to do with a " galvanotropic 



