§2] 



EFFECT ON STRUCTURE AND FUNCTIONS 



131 



on muscle, that it is the " making " only of a single induction 

 shock which produces the response ; but Vbewoen ('89°, pp. 

 19-22) has found that in the rhizopod Pelomyxa it is, on the 

 contrary, the breaking excitation which causes the response. 

 The subject deserves further study. 



Finally, the effect of an alternating current must be con- 

 sidered. This current is characterized by the fact that it is 

 composed of a series of rapidly repeated instantaneous shocks 



■■-.•.:->-fc>'?'« 



?V-T.^ . "'■.■■■■■"■ 



Fig. 29. — Feianema. a, quietly swimming; b, irritated by an induction stroke. 



(From Verwobn, '95.) 

 FiQ. 30. — Actinosphserium eiehhornii, Stein. Showing effect of the alternating 



current. At both poles the i^seudopodia are undergoing a disintegration, which 



proceeds equally at the two poles. (From Verwobn, '89.) 



which alternately reverse their direction. Thus, each pole of 

 the organism subjected to such a current receives alternately 

 the making (or breaking) effects at anode and kathode. The 

 maximum action is thus obtained. When an Aetinospheerium 

 is stimulated by such a current, the pseudopodia at both poles 

 contract and become varicose ; and, finally, the protoplasmic 

 substance begins to disintegrate and to flow out from the cell 

 towards the two electrodes, until the body acquires a biconcave 

 form. (Verwobn, '89% p. 11.) In this case the disintegra- 



