428 ELECTKO-PHYSIOLOGY CHAP. 



Seeing the extraordinary wealth of nerves in the electrical 

 organ, and the comparative inefficacy of curare (infra), direct 

 excitation, more particularly electrical, does not give safe evidence 

 for the independent excitability of the substance of the electrical 

 plates. At the same time certain results undoubtedly point to 

 such a reaction. Matteucci made some successful experiments 

 with direct mechanical stimulation (pricking, cutting, etc.) upon 

 the excised prisms of Torpedo. He then observed twitches in 

 the rheoscopic frog's leg, when its nerve was applied to the 

 preparation. Du Bois-Eeymond, it is true, points out that 

 Matteucci seems " always to have hit upon a visible branch of 

 the nerve." 



Babuchin (1) elicited "fairly strong shocks" from Mcdapterurus, 

 on cutting the organ, even at parts where the unaided eye failed 

 to discover any fibres of nerve upon the inner surface, and Sachs 

 also succeeded, by striking an organ-preparation placed between 

 unpolarisable electrodes in the galvanometer circuit lightly with 

 the flat part of a ruler, in obtaining frequent deflections, the size 

 of which depended unmistakably upon the strength of the 

 mechanical stimulation. The same occurred on touching the 

 preparation with a hot soldering-iron. The action of chemical 

 stimulants is especially interesting, since it is here that we should 

 expect excitation of the plates, independent of the ingoing nerves 

 that ramify in them. Sachs found on placing a strip of filter- 

 paper upon the skinned lateral surface of the long section of a 

 strip of organ 3-4 cm. in length (of which all the sections were 

 artificial, the lead-off being from the two cross-sections), that the 

 galvanometer magnet was at once deflected in the direction of 

 the discharge when ammonia was dropped on the paper with a 

 pipette. Ammonia is, of course, a strong stimulus to muscle, 

 while it does not appreciably excite the nerve. Moistening of 

 the cross-section, on the other hand, gives no perceptible effect 

 on the same preparation (4 c, p. 178), which may be due to the 

 fact that the ammonia here can only penetrate slowly through 

 the transverse partitions, while it easily gets " into the upper and 

 lower spaces opened by longitudinal section in all the compart- 

 ments that are beneath the wetted part of the filter-paper." 



In order to test the action of .direct electrical excitation, 

 Sachs led single induction shocks, through unpolarisable electrodes, 

 into a prismatic organ-preparation lying on the pads of du Bois- 



