CHAPTER IV 



GALVANOTROPISM 



When we send a galvanic current lengthwise through 

 a nerve, at the region near the anode the irritability of 

 tiie nerve is diminished, while it is increased near the 

 cathode. The condition of decreased irritability near 

 the anode is called anelectrotonus and the increased irrita- 

 bility near the cathode is called catelectrotonus. When 

 a current is sent through an animal, those nerve elements 

 which lie in the direction of the current will have an ane- 

 lectrotonic and a catelectrotonic region; while the nerves 

 through which the current goes at or nearly at right angles 

 are not affected. Ganglia or nerve tracts in the anelectro- 

 tonic condition will, therefore, act as if they were tem- 

 porarily injured, and hence we need not be surprised to 

 find that the galvanic current causes forced movements 

 which last as long as the current lasts, and which cease 

 with the current. 



Hermann reported in 1885 204 that when a current 

 is sent through a trough containing tadpoles of a frog, 

 the tadpoles orient themselves in the direction of the 

 current curves putting their heads to the anode. a Blasius 

 and Schweizer 523 found soon afterwards that a large 

 number of animals when put into a trough with water 

 through which a galvanic current passes have a tendency 

 to go to the anode. The explanation given by Hermann 

 and by Blasius and Schweizer is not correct. Thoy 



a The writer has never been able to repeat this observation. 

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