PEARL ON ELECTROTACTIC REACTION. 73 



SOME ASPPJCTS OF THE ELECTKOTA(JTIC REACTION OP 



LOWER ORGANISMS. 



BY RAYMOND I'KAHL. 



(Abstract.) 



1. It has been showu^ that in the case of the infusoria the electric- 

 current causes the cilia of the body to take certain definite positions. 

 The cilia on the kathode half of the body are reversed and i)oint towards 

 the anterior end. This effect is different from that produced by any 

 other stimulus so far as is known, and is distinctly localized with refer- 

 ence to the poles of the electric field. In addition to this effect the cur- 

 rent stimulates the organism as a whole to react by its usual "motor 

 reflex." We are able then in the case of the infusoria to distinguisli 

 two factors in the reaction to the current; one, a special response marked 

 by the reversal of the cilia on tlie kathode side, and the other a general 

 reaction ("motor reflex factor''). The question arises: How general 

 is the occurren(;e of two factors in the reaction to the current? Do 

 they appear in any other group than the Protozoa? From a study of 

 the electrotactic reaction of Hydra- it appears that in this form there 

 are two distinct phases in the reaction to the current. On the one 

 hand the current causes a localized contraction on the anode side of 

 the extended body, while on the other hand, it brings about, under cer- 

 tain conditions, a general, violent contraction of the animal as a whole 

 such as is caused by any other strong stimulus. The localized anode 

 contraction of the body seems to correspond to the special localized 

 reaction in the case of the infusoria (the reversal of the cilia on the 

 kathode side). Similarly two factors have been observcnl in the re- 

 action of the rhabdocoele Stcnof<tonia hiicops O. Schm. 



2. It seems probable that the organism as a whole is not stimulated 

 by the current when the reaction is of the special localized form (reversal 

 of cilia or anode bending of body). On the contrai-y in this cnse a part 

 of the motor mechanism is set into a certain definite sort of activity-- 

 more or less violent — without affecting the whole organism. 



3. The contraction of Hi/dni on Ihe anode side of the body when 

 under the action of the current results in its orientation with the orai 

 end towards the anode provided the foot is attached. Experiments with 

 the body extended in line with the current show that the animal is much 

 more strongly stimulated when it is in this i)Ositi(»n with the oral end 

 towards the anode, than when it is in the opjxjsite position with this 

 end towards the kathode. This indicates that the essential thing in the 



1 Pearl, R. : Studies on Eleetrotaxis. I. — On the Reactions of Certain Infusoria to the 

 Electric Current. Amer. Jour. Pliysiol. 4 : 06-123. 1900. 



"Pearl. R. : Studies on tlie Effects of Electricity on Orjianisnis. II. — The Reactions of Hydra 

 to the Constant Current. Amer. Jour. Physiol. ."> : ;!01-ai'0. I'JOl. 



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