THE THEORY OF ELECTRIC ORGANS 269 



The most difficult problem with regard to these electrical 

 organs having thus been solved, it remains to say a few 

 words concerning two other points : namely, the natural 

 current of rest and the repeating character of the excitatory 

 discharge. 



As regards the first of these, Du Bois-Reymond found 

 the current of rest which he designated as the organ-current 

 to be in the direction of the electrical discharge. We have 

 found, however, that, as a general rule, in the primary 

 condition, the true natural current flows in the opposite 

 direction to that of excitation, that is to say, from the less 

 to the more excitable. In agreement with this, I find, in 

 the leaf of Pterospernmm, the electrical reaction of which 

 is similar to that of the plate of Torpedo, that while its 

 excitatory current is from the more excitable ventral to 

 the less excitable dorsal, its resting-current is opposite to 

 this that is to say, from dorsal to ventral. With regard 

 to the electrical organ, then, there can be little doubt that 

 here also the true resting-current would have been found 

 to be opposite in direction to the excitatory, if it could 

 have been observed and recorded under an absolute con- 

 dition of physiological rest. In a highly excitable struc- 

 ture, however, the shock of preparation, as we have seen 

 and shall further see, leaves an after-effect which reverses 

 the natural current of rest. For this reason, the current 

 of rest observed in preparations of the electrical organ 

 has not, in all probability, represented the true current, but 

 rather the excitatory reversal of it. This view is supported 

 by the fact that while in the organ -preparation of 

 Torpedo, this reversed, or ingoing-current of rest is con- 

 siderable, in the intact fish it is negligible. It must be borne 

 in mind that the fish is spontaneously excitable, and also 

 that there must remain a certain residual effect from the 

 organ-discharges. Nevertheless Zantedeschi found a resting- 

 current to occur in the intact fish in the reverse direction to 

 that of the excitatory discharge. This was evidently the 

 true resting-current. This view of the organ-current, of 



