ELECTRICAL FISHES 



429 



Raymond's zinc trough, as in Fig. 271. It is evident that there 

 must under these conditions be cur- 

 rent escape into the galvanometer 

 circuit, which must be investigated, 

 and allowed for at the end of the 

 experiment. There is in the first 

 place the not very striking fact that 

 make shocks do not excite the organ- 

 preparation, while break induction 

 currents elicit effective discharges. 

 The electrical organ therefore reacts 

 like most excitable substances. It is 

 further remarkable that (according to 

 Sachs' experiments) break shocks 

 heterodromous to the discharge from 

 the organ excite more strongly than 

 homodromous currents. Schonlein 

 was unable to confirm this for Tor- 

 pedo. Induction shocks passed trans- 

 versely to the organ appear to have 

 the least effect. A rapid series of 

 induced (alternating) currents (tetanus) 

 gives large deflections in the direction 

 of the discharge, with a distance of 

 coil at which single break shocks, 

 under the most favourable conditions, 

 give little or no effect. This is again 

 the same reaction as on stimulating 

 ganglion- and gland-cells, as well as 

 all sluggishly reacting contractile 

 substances. 



The simple method of curarising, 

 by which it is so easy to exclude the 

 nerves in the muscles of most ver- 

 tebrates, breaks down almost entirely 

 for the electrical organs, since electrical 

 fishes, and more especially Torpedo, 

 are, like all other fish, comparatively 

 immune to curare. This is evident 

 in the nerves to the muscles, but still more in the electrical organs 



FIG. 271. 



