THE LEAF CONSIDERED AS AN ELECTRIC ORGAN 253 



ever, we obtain true excitatory effects, unmodified by any 

 such elements of uncertainty. In order to show how perfect 

 the results obtained by this method become, I give here 

 (fig. 1 60) the records of two successive excitatory responses 

 obtained from a leaf of Bryop/tyllum calycinum^ the responsive 

 current being from the lower or anterior surface to the upper 

 or posterior. In this mode 

 of stimulation, by equal 

 and opposite shocks, as 

 already said, no advantage 

 is given to either surface 

 over the other. Neverthe- 

 less, I thought it well to 

 take two successive records 

 under shocks, in which the 

 alternating currents in the 

 primary circuit were first 

 right-left-right, and then left- 

 right-left. 



In the electrical organ 

 of Torpedo Gotch found 

 the maximum electromotive 

 change to be attained in 

 about - oi second after the 

 application of the excitatory 

 shock. In leaves, again, I 

 find the rapidity with which 

 the maximum effect is at- 

 tained to depend on the 

 nature of the tissue, and 

 also on the intensity of the 

 exciting shock. In sluggish specimens this may be as long 

 as '2 second. It should be remembered that in the case 

 of mechanical stimulation of moderate intensity also, this 

 period was, similarly, about '2 second (p. 51). With very 

 vigorous leaves of Nymph&a alba, however, and employing 

 a stronger electrical stimulus, the maximum effect was 



FIG. 1 60. Records of Two Successive 

 Responses in Leaf of Bryophyllum 

 calycinum under Equi-alternating 

 Electrical Shocks 



