XI 



ELECTRICAL FISHES 



361 



ficial aspect. The latter is easily obtained by a method first 

 employed by Savi ; this consists in cutting off the convex trans- 

 verse section of a column with scissors, and then separating out 

 the single thin plates of which it consists, in some indifferent 

 fluid. It is these fine discs, lying one upon the other like 

 the coins in a rouleau, or the plates in a voltaic pile (Fig. 230), 

 which (as du Bois-Reymond was 

 the first to point out) become 

 electromotive under the influence 

 of the nervous system. " The 

 electromotive components of the 

 primitive batteries of the fish's 

 columns must not be sought in 

 optically separable structures, in 

 heterogeneous, contiguous tissues, 

 or in animal fluids. The seat 

 of E.M.F. lies rather in the centre 

 of a morphologically homogeneous 

 tissue, the so - called ' electrical 

 plate ' " (du Bois-Reymond 4 d, II.). 

 In their normal position in 

 situ the plates are approximately 

 horizontal, curving only in the 

 middle towards the back of the 

 animal. On treating them with 

 reagents, however, various strata 

 appear in the longitudinal sections. 

 Each plate seems to be bent 

 backwards at the margin, where 

 it is attached to the connective- 

 tissue septa, the ventral half being more particularly involved 

 (Fig. 231). The single plates are somewhat further apart 

 in the larger than in the smaller columns. From the ventral 

 aspect, each plate exhibits a rich plexus of nerve-fibres, with a 

 sprinkling of capillaries, embedded in a gelatinous tissue studded 

 with star-cells, which fills the intermediate spaces of the plates, 

 and gives the appearance of a quivering jelly to the fresh sub- 

 stance of the prisms. When we remember the number of nerve- 

 fibres in each single plate, the wealth of nerves in the entire 

 organ is surprising, and witnesses to its intimate relations with 



FIG. 230. Schema of a single prism in 

 Torpedo with ingoing nerve (Wagner's 

 end-brush). (Fritsch.) 



