130 



ELECTRICITY AND PROTOPLASM [Ch. VI 



Fig. 28. — Actinosphserium eichhornii in four successive stages of polar excitation 

 by means of the constant electric current. Disintegration begins at the anode 

 (+) pole. (From Vekwokn, '95.) 



Allied, apparently, to the foregoing phenomena are the pro- 

 toplasmic changes which follow the sudden hreahing of the 

 current. Unless the current has been very feeble, the pseudo- 

 podia of Actinosphserium begin, at the moment of breaking, to 

 contract and become varicose upon the kathode side, while the 

 formerly irritated anode side is quiet. Thus, the breaking of 

 the current also acts as a stimulus, but this is, in general, 

 weaker than that caused by making. 



If, now, a current which endures for only an instant — if a 

 single induction shock — is sent through, the making and break- 

 ing stimuli are practically coincident, and a violent response 

 may be called forth. Thus, Engelmann ('69, p. 317) found 

 that Amoeba, subjected to a strong shock, retracted its pseudo- 

 podia, and assumed a spherical form within two seconds ; and 

 GoLUBBW ('68, p. 567) has described a similar response in 

 leucocytes. Under similar circumstances, the flagellum of the 

 flagellate Peranema (Fig. 29) made an energetic stroke. (Vek- 

 wokn, '95, p. 414.) I have spoken above as though there were 

 both a making and a breaking stimulus ; but this is not known 

 to be the case. It is generally recognized from experiments 



