ELECTRICAL FISHES 



461 



the induction-current equally well in both directions, as appears 

 from the following table: 



There is as little reason for assuming irreciprocal conduction 

 in the less differentiated electrical organ of Raja. With direct 

 excitation of an excised strip of organ, by single induction-shocks, 

 there will be a single discharge after an interval of about 

 Q'005 sec., the direction of the exciting current being quite 

 immaterial. It is only when the closure of the galvanometer 

 circuit occurs at a time when the discharge of the organ has 

 already taken place that the apparent irreciprocity is again 

 visible in consequence of the algebraic summation between the 

 discharge and the exciting current. When the direction of the 

 induction-current coincides with that of the discharge, the deflec- 

 tion increases with the duration of closure, while in other cases 

 it declines, and is eventually reversed (Gotch, 13 c). This is not 

 the place to enter more in detail into du Bois-Keymond's treat- 

 ment of the teleological significance of " irreciprocal conduc- 

 tion " of the electrical organ. 



VIII. THEOKY OF DISCHARGE FKOM ELECTEICAL FISHES 



Without entering further into the older and in part very 

 naive views that were briefly alluded to at the beginning of this 

 chapter, and which do not at the present level of knowledge call 

 for serious discussion, we will only consider certain newer theories, 

 in re the discharge of electrical fishes, which have indeed been 

 contradicted, but which still claim our interest, because they 

 show how the theories predominating in nerve- and muscle- 

 physiology were adapted to the electrical organ also. 



