362 



LOCOMOTORY AND PROTOPLASMIC MOVEMENTS 



tested. The current should be led in by non-polarizable electrodes *, the brushes 

 soaked in normal saline solution touching the porous sides of the cell. By reversing 

 the commutator and changing the direction of the current, the reacting organisms will 

 be caused to collect at the opposite electrode, and this may be repeated many times. 

 The striking reaction shown by Paramaecium may be made visible to a large audience 

 by means of a projection lantern 2 . If a current of from five to twenty volts is used, 

 the best current strength is readily reached by adjusting the resistance. According 

 to Ludloff, this lies between oi to 0-6 of a milliampere in the case of Paramaecium^ 

 whereas with 0-06 of a milliampere the reaction is barely perceptible 8 . 



Little doubt can exist that we are here dealing with a physiological 

 movement due to stimulation, and that the movement is not the direct 



result of the kata- 

 phoric action of the 

 electrical current. 

 That strong cur- 

 rents may exercise 

 such an action is 

 certain, but never- 

 theless, it is not 

 possible to agree 

 with BirukofY and 

 Pearl in ascribing 

 the movements to 

 the direct action of 

 the current 4 . For 

 instance, using a 

 mixture of species, 

 the positively gal- 

 vanotactic forms 

 will move towards 



the anode, the negatively galvanotactic forms towards the kathode, while 

 dead individuals do not move at all. 



Infusoria and Flagellatae show a typical tactic reaction, that is, they 

 orient themselves in regard to the direction of the current by presenting the 

 front end towards either the kathode or anode, and always swimming with 

 the same end first. At the same time, the movement may either be 



FIG. 64. Apparatus to show galvanotaxis. The non-polarizable electrodes c are 

 applied to the bars of porous porcelain (' biscuit '). These are joined at b b by bars 

 of wax-colophonium mixture. The water in the cell contains the negatively 

 galvanotactic Paramaecium aurelia which moves towards the kathode. 



1 On non-polarizable electrodes cf. Biedermann, 1. c., p. 150; Hermann, 1. c., p. 29; Cyon, 

 Methoden d. physiolog. Experimente, 1876, p. 386. 



2 Pfeffer, Jahrb. f. wiss. Bot., 1900, Bd. xxxv, p. 719. 



3 [The current density within the cell, which in the case of a uniform conductor depends upon the 

 area of cross-section and upon the current strength, requires consideration.] 



4 Birukoff, Pfliiger's Archiv f. Physiologic, 1899, Bd. LXXVII, p. 555 ; Pearl, American Journal 

 of Physiology, 1900, Vol. IV, p. 96. See also Putter, Archiv f. Anatomic u. Physiologic, 1900^ 

 Supplementband, p. 299. 



