St 



EFFECTS OF ANODE AND KATHODE 239 



to the left represent the effect of descending, those to the 

 right the effect of ascending, current. In the case of the 

 descending current the terminal indicator is to the left of k, 

 and the conducting tissue between k and A. In the case 

 of the ascending current the terminal indicator is to the 

 left of a. Transmitted excitation can be detected by the 



Descending Ascending 



Ki \A Ax i* 



Feeble \ '• 



ong \ \ 1 



break , - x A « 'v 



*-!->■ .' 



Fig. i2i. — Effects of Descending and Ascending currents at make and 

 break on nerve-muscle and petiole-pulvinus. Excited leaflets shaded 

 dark. Vertical series to left represent effects of descending currents ; 

 series to right effects of ascending currents. With feeble current, 

 terminal leaflets excited by both descending and ascending currents 

 at make and not at break. With strong currents, excitation of 

 terminal leaflets takes place only at make of descending and break 

 of ascending currents. Two upper pairs of leaves exhibit effects of 

 feeble current at make and break. The two lower pairs of leaves 

 show effects of strong current. 



contraction of muscle or leaflet, to the left of k in the case of 

 descending, and to the left of A in the case of ascending 

 current. But the characteristic effect at the electrodal 

 points, k and a themselves, or the overflow of the effect 

 between the two points, cannot be detected in the case of 

 frog's nerve. It can, however, be detected in the case of 



