§ 2] EFFECT ON STRUCTURE AND FUNCTIONS 139 



So far then we liave distinguislied two chief effects of the 

 current on protoplasm — a dissociation effect and a chemical 

 effect. It may now be worth while to mention that there is 

 good reason for believing that in the more highly differentiated 

 animals, like Vertebrates, not all protoplasm is affected to the 

 same degree nor in the same way. Thus a nervous and a 

 muscular effect can be clearly distinguished in frogs, for ex- 

 ample. The principal effect is exerted upon the central nervous 

 system, for Hermann ('86, p. 415) found that the tail of 

 tadpoles is responsive only so long as it contains a piece of 

 spinal nerve ; and upon frogs subjected to curare, which inhib- 

 its the action of the nerve alone, the current produces a much- 

 diminished effect, giving rise merely to muscular twitchings. 

 (Blasitjs and Schweizbe, '93, p. 528.) Very little progress 

 has been made, however, upon the determination of the action 

 of different intensities upon the different tissues of which the 

 Vertebrate body is composed. 



We have seen that the electric current provokes a response, 

 and we have seen also that organisms vary in their responsive- 

 ness so that a current strong enough to call forth a response in 

 one species is not sufficient to excite another species. We may 

 say that the one species is attuned to a different strength of 

 current from the other. This difference in responsiveness indi- 

 cates, of course, a corresponding difference in composition of 

 the protoplasm. Such a difference may, moreover, be produced 

 in a single individual by artificial means. These means are 

 the subjection for a considerable period to the electric current. 

 Suppose we subject an organism to a current of a strength only 

 slightly greater than that just necessary to provoke a response. 

 After the current has acted for some time we find that it no 

 longer excites. This phenomenon of acclimatization to the 

 galvanic current was first observed among the Protista, so far 

 as I know, by KiJHNB ('64, pp. 76, 78), who. found that in 

 iMyxomycetes, after a few induction shocks had been sent 

 through the plasmodium, additional shocks of the same intensity 

 were without effect, and stronger shocks had to be sent through 

 to cause contraction. Similar results were obtained by Vee- 

 WOEN ('89% p. 10 ; '89', p. 272) in subjecting Actinosphaerium 



