ON LIVING MALAPTERURUS. 411 



be concluded from this experiment that the threshold of excitation 

 for electrical nerves is abnormally high. There was no twitching of 

 the muscles of the trunk, even when the coil was pushed quite up 

 and with two Groves in the primary circuit of the induction 

 apparatus ; on the other hand, the muscles of the head and intestine 

 contracted. But, as regards the former, it must be added that 

 they did not respond to the irritation of a saturated solution of 

 common salt either. 



After circulation had ceased for af hours, the organ, when 

 irritated through its nerve, acted upon the multiplier ; but when 

 irritated directly, either mechanically or with caustic potash, it 

 acted neither upon the multiplier nor upon the nerve-muscle pre- 

 paration. 



The electrical nerve, with its longitudinal and cross section 

 properly laid upon the pads of the nerve-multiplier, failed to 

 exhibit any nerve-current, or on being tetanised, any negative 

 variation. This appears natural when we consider that the nerve 

 consists of a single nerve-tube, which is no doubt unusually thick, 

 but is also surrounded by a disproportionately strong 1 sheath, the 

 effect of which is to efface the electromotive action of the nerve- 

 tube by derivation. It is however conceivable, that a more 

 efficient electrical nerve of the Malapterurus might show traces on 

 the galvanometer of the nerve-current and of its negative 

 variation. 



Electrotonic currents were clearly perceived with two Groves ; 

 after cutting through the nerve between the stimulated and led- 

 off tract and joining the cut ends, feeble actions in the wrong 

 direction, depending upon escape of current, afforded evidence of 

 the genuineness of the previously observed deflections. 



Here, the experiments on the electromotive activity of the 

 organ at rest, and on its secondary electromotive actions come to a 

 close. A more detailed report of both is given in 6 of the 

 1 Experimental criticism of the discharge hypothesis.' 



1 Bilharz, loc. cit. p. 21, states the thickness of the sheath containing the vessel as 

 nine times that of the empty sheath. The diameter of the fibres themselves is to 

 that of the empty sheath in the proportion of 2-6 : 24-6 according to his drawings, 

 loc. cit. Tab. iii. Fig. 9. Hence the ratio of the cross section of the fibres to that of 

 the whole nerve is shown to be I : 8950. Max Schultze gives the ratio of the fibres 

 to the empty sheath still more unfavourably in his illustration in Fig. 7, Tab. i. of 

 his paper (3-25 : 33-10.) 



