ELECTRIC ORGANS 



147 



Jl- 



TM- 



Monnyridse, for example, there is on each side an vipper and lower 

 row of electric organs. 



The electric apparatus in all the above-named Fishes is to be 

 regarded from the same point of view both as concerns its mode 

 of development and its 

 anatomical relations : 

 all electric organs are 

 to be looked upon as 

 consisting of metamor- 

 phosed muscular fibres 

 and the nerve-endings 

 belonging to them as 

 homologues of theraotor 

 end-plates which are 

 ordinarily found on 

 muscles. 



As regards the 

 structure of the elec- 

 tric organs, tlie same 

 essential arrange- 

 ments are met with 

 in all : the details of 

 their histology ami 

 physiology cannot be 

 entered into here. The 

 framework is formed 

 of fibrous tissue en- 

 closing numerous cells, 

 which, running partly 

 longitudinally, partly 

 transversely through 

 the organ, gives rise 

 to numerous poly- 

 gonal or more or less 

 rounded chambers or 

 compartments. These 

 latter are arranged in 

 rows, either along the 

 longitudinal axis of 

 the body (Gymnotus, 

 Malopterurus) or in a 

 dorso-ventral direction 

 (Torpedo), forming definite prismatic columns (Fig. 120). 



Numerous vessels and nerves ramify in the connective-tissue 

 lying between these compartments, the nerves being enclosed in 

 thick sheaths, and having a different origin in the different 

 forms. In Torpedo, in which the electric organs probably arise 



muscle of the mandible 



Fig. 119, A and B. — The Electric Organ of 

 Gymnotus electricus. (B, from a preparation by 

 A. Ecker.) 



H, skin ; Fl, fin ; DM, D3P, dorsal portions of the 

 great lateral muscles, seen partly in transverse, 

 partly in longitudinal, section ; VM, VAP, 

 ventral portions of ditto ; 111, the electric organ, 

 seen in transverse section at E (B), and from 

 the side at S^ ; WS, vertebral column from 

 the side, and the spinal nerves, and WS', 

 in transverse section ; LEC, posterior end of 

 body cavity ; Sep, median longitudinal fibrous 

 septum between the left and right electric 

 organ and lateral trunk-muscles ; A, anus. 



in connection with the great adductor 



L 2 



