EXCITATORY POLAR EFFECTS OF CURRENTS 



197 



kathode at make, and from anode at break. The following 



tabular statement exhibits these various effects in a concise 



form. 



Table showing Effects of Moderate E.M.F. 



Experiments with highly excitable tissues.— In ex- 

 perimenting on the polar excitation of animal tissues, using 

 a nerve-and-muscle preparation, it is found that when the 

 proximal end of the nerve is made kathode, that is to say, 

 when the current is ascend- 

 ing, the indicating muscle WkM 

 shows response. This is 

 due to the make action of 

 the kathode. At break 

 also response occurs ; but 

 this is due to the trans- 

 mitted action of the break 

 excitation of the distant 

 anode. When the current 

 is reversed, that is to say, 

 made to descend, there is 

 also response, due to the 

 make excitation of the 

 distant kathode. When the current is broken, response 

 takes place again, in consequence of the break of the 

 proximal anode. All these cases are rendered possible by 

 the high conducting power of the intervening tissue, the 

 nerve. 



I have been able to obtain precisely similar results, by 

 selecting very highly excitable specimens of Mimosa. One 

 electrode was placed at the junction of stem and petiole, the 



fTSVCC 



Fig. 94. Effects of Ascending and De- 

 scending Currents, on Highly Excitable 

 Specimen of Mimosa 



In the figure to the left, the anode is below 

 and kathode above, and current ascend- 

 ing. In the figure to the right, the 

 kathode below, anode above, and cur- 

 rent descending. 



