138 ELECTRICITY AND PROTOPLASM [Cn. VI 



and weak muscle fibres ; the second or katex type found espe- 

 cially among some Flagellata, Arthropoda, and Vertebrata. A 

 third possible type (katanex type) is certainly of very limited 

 distribution. Between the two types we notice this connecting 

 link, that in some Vertebrates a weak current produces one 

 type of response ; a strong current the other. The reason for 

 the existence of these two distinct types one of which char- 

 acterizes animals with less differentiated, the other those with 

 more differentiated, muscular and nervous systems is still 

 greatly in need of investigation. 



The nature of the protoplasmic change wrought by the 

 current is an important matter. We have already accounted 

 for the effect that we see in the Protista, on the ground of re- 

 duced cohesion. It is probable also that the current gives rise 

 in the cytoplasm to chemical changes which are different at the 

 two poles. It is well known that when a current is passed 

 through a neutral solution of a salt there is produced an acid 

 at the anode, and an alkali at the kathode. Since in the higher 

 animals, at least, the body contains such solutions, it seems 

 probable that acid and alkaline substances are here likewise 

 produced by the passing current. This probability is supported 

 by an observation of KUHNE ('64, p. 100), who found that the 

 violet coloring matter of the stamen hairs of Tradescantia 

 become changed by the action of a very strong induction shock. 

 He says that a change in the violet fluid, like that which occurs 

 at the anode, can be brought about by dilute hydrochloric acid ; 

 while a change like that appearing at the kathode can be pro- 

 duced by potassic hydrate. An observation of NAGEL ('92 a , p. 

 346) suggests also that the current acts by producing a chemi- 

 cal change. He finds that that part of the body of the snail 

 and the leech which shows most markedly the anode-making 

 excitation is coincident with that which is most sensitive to 

 chemical substances. So that the reaction to a galvanic, still 

 more to a faradic, stimulation resembles that to a strong, dis- 

 agreeable taste (quinine). In this case the response may 

 result either from the chemical substance acting directly on 

 the muscles or attacking first the sense organs. In the latter 

 case the response would occur through the mediation of the 

 nervous system. 



