Elements of the comparative anatomy Elements of the comparative anatomy of vertebrates elementsofcompar00wied Year: 1886 126 COMPARATIVE ANATOMY. of the cud of the tail, and have a metameric arrangement like that of the caudal muscles; in the Mormyridae, for example, there is on each side an upper and an under 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 anatomical relations: all electric organs are to be looked upon as metamorphosed muscular tracts, .and the nerve-ending
Elements of the comparative anatomy Elements of the comparative anatomy of vertebrates elementsofcompar00wied Year: 1886 126 COMPARATIVE ANATOMY. of the cud of the tail, and have a metameric arrangement like that of the caudal muscles; in the Mormyridae, for example, there is on each side an upper and an under 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 anatomical relations: all electric organs are to be looked upon as metamorphosed muscular tracts, .and the nerve-endings belonging to them as homologues o o o o of the motor end-plates which are ordinarily found on m uscles. As regards the minute structure of the electric organs, the same essential arrangements are met with in all. The framework is fornii'd of fibrous tissue, which, running partly longitudinally, partly transversely through the organ, gives rise to numerous polygonal or more or less rounded chambers or compartments. These latter are arranged in rows, either along the longitudinal axis of the body (Gymnotus, Malapterurus) or in a dorso-ventral direction (Torpedo), forming definite prismatic columns (Fig. 102). FIG. 102. — KLEeTiiic I'IMSMS UK '/''/•/' ''' in'trnui,-itt/i. (Semidiagrammatic.) Numerous vessels and nerves ramify in the connective-tissue lying between these compartments, the nerves being enclosed in very thick sheaths, and having a great variety of origin accord- ing to the species of Fish under consideration. In Torpedo, they arise from the ' electric lobe' of the medulla oblongata, a single branch coming also from the trigeminal; in all pseudo- electric Fishes, as well as in Gyinnotus, in which over two hundred nerves pass to the electric organ, they arise from the spinal cord, and most probably are in the closest relation with the ventral cornua of the latter, which are particularly well developed in the last-named Fish. It is very remarkable that the elec
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