ELECTRIC ORGANS OF EISHES. 



35.5 



234 



Sectiun of Maldplerurus d'iciricns. ccxrx. 



to the fore j^art of tlie enormous batteries ; for the digestive and 

 generative viscera, with the respiratory and circulating organs, 

 the hrain and organs of sense, — 

 all, in fact, that constitute the 

 proper animal, — are confined to 

 that small segment of the entire 

 Ijody which is anterior to the elec- 

 trical apparatus, fig. 232, b. The 

 vent even opens beneath the head, 

 in advance of the pectoral fins. 



The electric organs of the Ma- 

 lapterurus electricus ' form a layer 

 fig. 234, A, immediately beneath 

 the skin, enveloping the whole 

 body except the head and fins, and sei)arated from the muscles, 

 ib. G, by a fiiscia with vessels and nerves, ib. B, and by a layer 

 of adipose tissue, ib. E. The electric organ is divided by fine 

 decussating membranes into minute lozenge-shaped cells, about a 

 third of a line in diameter, fig. 235, u. It is snpp)lied b)^ a large 

 nerve issuing from the beginning of the myelon and arising from 

 a mass, in its substance, of ganglion-cells, like those in the electric 

 lobes of the Torpedo. A considerable ganglion is also formed npion 

 the nerve beyond its origin, from which the trunk is continued 

 ahnig the side of the body, like a ' nervus lateralis,' and distriljutes 

 l^ranches to the diffused organ. The structure of the organ is such 

 that the electric currents run in all directions, and 

 a discharge would take jilace from any point of 235 



its surface, whence, jjerhaps, the necessity fV>r a 

 layer of nonconducting substance, E, between 

 the proper body of the fish and the organ. The 

 shock delivered, wanting the concentration re- 

 sulting from the structure in the Torpedo, is 

 comparatively feel^le, but suffices for defence ; 

 the fish being protected by its electrifying coat, 

 as is the hedgehog by its spines. 



In the Mormyrus longijnnnis the electric organ 

 consists of four series of membranous septa 

 placed longitudinally on the tail, two on each 

 side. Each series consists of about 150 septa 

 with intervals of -i^th. of a line, filled by albu- 

 minous fiuid. The septa are stronger than 

 those in tlie hexagonal columns of the Torpedo." 



Seotionof tloctric organ, 

 MalapUrurus, ccxvilj. 

 A, skill ; B, electric ceils 

 c, fascia : ij, cellular tis- 

 sue, with a, artery, v, 

 vein, n, nerve : e, adi- 

 pose tissue. 



' xcii. and coxix. 



A A 2 



