THE ACTIVITY OF EIECTRICAL ORGANS. 59 i 



excited nerves lie outside or inside the organ columns. In one organ, that of 

 Malapterurus, the expanded disc has no nerves in its substance, these all ending 

 in the slender stalk which projects from the disc ; and the disc expansion itself 

 affords no structural differences to account for corresponding electromotive 

 differences between its surfaces. 



(2) The only excitable structures in the organ are thus the nerves and their 

 fine terminations, and since these are known to be the seat of electrical changes 

 during activity, it seems more reasonable to presume that the organ change is 

 in reality closely related to the production of molecular disturbances in its 

 contained nerves. Apart from the consideration that the nerves are the only 

 structures present which we know to be capable of developing such electrical 

 changes, there are other circumstances which favour this view. The time 

 relations of the organ shock and those of nerve closely correspond ; it is true 

 that the organ shows a period of delay, but this can be accounted for by 

 transmission time either along nerve trunks or fine nerve-endings. There are 

 in fact only two discrepancies of moment ; the organ can be fatigued by activity, 

 and the electromotive force of the change in each organ element is greater 

 than that present during nerve activity. With regard to organ fatigue, it may 

 be pointed out that this occurs even in nerve as far as the finer terminations 

 are concerned, and as regards the electromotive force discrepancy it has been 

 recently shown that the sciatic nerve of the frog can develop a change of more 

 than *03 volt in response to a single stimulus. 1 The electromotive force of 

 each organ element varies between *03 and *05 volt ; the discrepancy is thus 

 not so great as to offer any insuperable objection to the view that the organ 

 effect is essentially that of active nerve. It is not fanciful to imagine that the 

 disc itself may play somewhat the same secondary part in regard to the primary 

 and essential nervous disturbance, as a resonator can play in the case of sound, 

 or an electrophorus in the case of the electrified body which charges it. 2 



But whether the protoplasmic expansion of the disc plays such a reinforcing 

 role or not, the clear fact remains that the essential primary disturbance which 

 constitutes the organ shock is a nervous one ; without nerves, the discs, having 

 nothing to reinforce, would be impotent and absolutely inexcitable. The 

 primary cause of the organ shock is thus in all probability a change identical 

 in nature with that producing the electromotive phenomena of nerve, and if 

 so, then it will be interesting to see how far the various theoretical explana- 

 tions of these phenomena can be extended so as to comprise those of the 

 electrical organ. One such hypothesis can undoubtedly be so extended — the 

 alteration theory, as given either by Hermann or by Hering. It is far more 

 difficult to extend any molecular theory in this direction, or indeed any view 

 which involves the pre-existence of electromotive elements. Electrical organs 

 show no resting electrical effects ; all the effects are connected with excitation 

 and its concomitant alteration. This may be produced by the sudden stimulus 

 of electrical currents or the prolonged one of a persistent localised injury of 

 nerve trunks. In all cases the alteration in the nerve is accompanied by 

 the rapid development of electrical changes, whilst the structural disposition 

 of the organ is such that the changes present in each group of nerve 

 terminations can, by summing with those in the neighbouring groups, become 

 conspicuous. 



1 Gotch and Burch, Proc. Roy. Soc. London, 1898, vol. lxiii. p. 300. 



2 Compare Kiihne's views on the causative value of electrical changes in motor nerve- 

 endings for the production of indirect muscular contraction. The above interpretation of the 

 phenomena of the electrical organ undoubtedly supports Kiihne's suggestion that "a nerve 

 throws a muscle into contraction by means of its currents of action." Kiihne, Croonian 

 Lecture, "Ueber die Entstehung der vitalen Bewegung," Proc. Bo>/. Soc. London, 1888, 

 vol. xliv. pp. 429-446. 



