XIII 



ELECTRIC ORGANS 



365 



ae. 



associate particular sounds with the possession of dangerous 

 spines, .and warned by the sounds, they refrain from attacking 

 the owner of the spines, to the mutual advantage of both. 



Electric Organs. 

 Electric organs 

 capable of generat- 

 ing more or less 

 powerful electric 

 discharges are pre- 

 sent in certain 

 Fishes, both marine 

 and freshwater. 

 They occur in a 

 few Elasmobranchs 

 (species of Raia, 

 Torpedo, and 

 Hypnos), in such 

 Teleosts as the 

 African Silurid 

 Malopterurus, the 

 "Electric Eel" 

 (Gymnotus), and in 

 species of Mormy- 

 ridae (e.g. Mor- 

 myrus). With one 

 exception electric 

 organs are com- 

 posed of metamor- 

 phosed niUS- FIG. 209. An Electric Kay (Torpedo) dissected to^ show its 



cular fibres, and 

 their nerve-endings 

 or motor end- 

 plates. The species 

 of Eaia have two 

 small electric 

 organs, one on each 

 side of the terminal portion of the tail. 1 In Gymnotus" the 



electric organs. On the left the nerves supplying the 

 organ are dissected out. The prismatic areas on the 

 surface of the organ indicate the vertical columns of 

 electric plates, of which there may be 500,000 in each 

 organ. The dorsal surface of the brain is exposed, br, 

 Gills ; f, spiracle ; o, eye ; o.e, electric organs ; t, mucus 

 canals ; tr, tri-geminal nerve ; tr', its electric branch ; 

 v, vagus ; 7, fore-brain ; //, mid-brain ; ///, cerebellum ; 

 IV, electric lobe of the medulla oblongata. (From Parker 

 and Haswell, after Gegenbaur.) 



1 Ewart, Phil. Trans. 179 (B), 1888, pp. 399, 410, and 539 ; 183 (B), 1893, p. 389. 



2 Ballowitz, Arch. Mikr. Anat. 1. 1897, p. 686 ; Carl Sachs, Untersuchungen am 

 Zitteraal, Leipzig, 1881. 



