File:Image from page 400 of "On the anatomy of vertebrates (electronic resource)" (1866) (14753222454).jpg

Identifier: b20416039_001 Title: On the anatomy of vertebrates [electronic resource] Year: 1866 (1860s) Authors: Owen, Richard, 1804-1892 Subjects: Anatomy, Comparative Vertebrates Fishes Reptiles Mammals Birds Publisher: London : Longmans, Green Contributing Library: Wellcome Library Digitizing Sponsor: Wellcome Library

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Text Appearing Before Image: is also formed uponthe nerve beyond its origin, from which the trunk is continuedalong the side of the body, like a i nervus lateralis, and distributesbranches to the diffused organ. The structure of the organ is suchthat the electric currents run in all directions, anda discharge would take place from any point ofits surface, whence, perhaps, the necessity for alayer of nonconducting substance, E, betweenthe proper body of the fish and the organ. Theshock delivered, wanting the concentration re-sulting from the structure in the Torpedo, iscomparatively feeble, but suffices for defence;the fish being protected by its electrifying coat,as is the hedgehog by its spines. In the Mormyrus longipinnis the electric organconsists of four series of membranous septaplaced longitudinally on the tail, two on eachside. Each series consists of about 150 septawith intervals of ^yth of a line, filled by albu-minous fluid. The septa are stronger thanthose in the hexagonal columns of the Torpedo.2 235

Text Appearing After Image: E D C Section of electric organ,Malapterurus, ccxvin.a, skin ; b, electric cells ;c, fascia ; d, cellular tis-sue, with a, artery, v,vein, n, nerve; e, adi-pose tissue. xcn. and ccxix. A A 2 356 ANATOMY OF VERTEBRATES. An animal must be in communication with the Torpedo bytwo distinct points, in order to receive the shock.1 If an insulatedfrogs leg, fig. 207, C, touches the Torpedo by the end of the nerveonly, no muscular contractions ensue on the discharge of the bat-tery; but a second contact by a portion of muscle, or any otherpart of the leg, immediately produces them.2 The dorsal surface of the electric organ is positive, the ven-tral surface negative. The Torpedo has no power of otherwisedirecting the electric currents ; but Matteucci found that wound-ing the electric lobes of the brain sometimes reversed the direc-tion.3 These currents, besides their effects on the living body,exercise all the other known powers of electricity ; they renderthe needle magnetic,4 decompose chemic

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