90 FACTORS AFFECTING CILIARY ACTIVITY 



cathode. With a still stronger current, the rate of movement 

 tov^ards the cathode is first slowed, and then reversed so that the 

 animals swim backwards towards the anode. Ultimately, the 

 paramecia shorten and burst in a very strong current. Induction 

 shocks have a similar effect. 



An effect of electric current on the protoplasm of Paramecium 

 was reported by Kinosita (1936). Paramecia which were stained 

 with neutral red or nile blue sulphate and subjected to an electric 

 current, showed a different colour at the two ends, giving an acid 

 reaction at the cathodal end and an alkaline reaction at the anodal 

 end. With increased current, the alkaline region spreads forward 

 to cover the whole body. 



It appears that the immediate cause of the changes in swimming 

 direction has been found by Ludloff (1895), who noted that the 

 direction of beat of the cilia on the surface of the animal nearest 

 to the cathode was reversed when a current was passed between 

 the electrodes. If the strength of current was increased, cilia over 

 a larger area of the body showed a reversed beat. This effect 

 could account not only for the reversal of movement in a strong 

 current, but also for the orientation of the animal towards the 

 cathode. Jahn (1960, 1961) has suggested that Ludloff 's results 

 are best explained by assuming that Paramecium is a " core 

 conductor." He claims that by application of the laws of polarizing 

 current he can explain the reversal of the ciliary beat and the 

 activation of cilia of immobilized animals by the effects of the 

 current on the membrane potential of the animal. 



In relation to this last suggestion, several reports of work on 

 Opalina by Japanese workers are very interesting. Okajima 



(1953) found that the direction of beat of the ciha in the area 

 around the eletrode was changed by stimulation with a micro - 

 electrode placed on the body surface. The area of response 

 depends on the strength of the current and on the position on the 

 body. Currents of the order of 10~' A were used here. Kinosita 



(1954) found that when he induced a temporary reversal of the 

 ciliary beat with isotonic KCl, the cell membrane potential 

 (measured with internal and external microelectrodes) suddenly 

 fell to zero, with perhaps a transient overshoot. In fact, the 

 membrane potential and direction of beat changed in close 

 association. A reduction in membrane potential has also been 



