ELECTRIC ORGANS OF FISHES. 213 



conspicuous in Preparations 2176 and 2177. Hunter, who counted 

 470 columns in each organ, describes the partitions as being very- 

 vascular : — "The arteries," he says, " are branches from the vessels 

 of the gills, which convey the blood that has received the influence 

 of respiration." But the most characteristic feature of the organi- 

 sation of the electric battery is, as Hunter also demonstrates, its 

 enormous supply of nervous matter. Each organ derives this supply 

 from one branch of the trigeminal (Jig. 45, 5), and from four branches 

 of the vagal nerves (ibid. 8, 8), and the four anterior nerves are each 

 as thick as the spinal chord : the last nerve is a feeble branch of the 

 vagus. The trigeminal and vagal enlargements of the olivary and 

 restiform tracts coalesce on each side, forming the so-called ' electric 

 lobes' of the medulla oblongata. The electric branch of the fifth 

 nerve may be defined, even at its origin, from the true ganglionic 

 part of that nerve ; and Professor Savi* affirms that both this and 

 the vagal branches consist entirely of the primitive nerve-fibres of 

 animal life, or "a double contour;" and that they are distributed by 

 successive resolution into smaller and smaller fasciculi, until they 

 finally penetrate the septa of the columns, and terminate thei'eon by 

 meshes formed by loops, or by the return and anastomosis of the 

 terminal elementary nerve-fibres, f 



In the eel-like Gymnotus the electric organs are four in number, 

 and are situated two on each side the body, extending from behind 

 the pectoral fins to near the end of the tail (see Preps. 2186, 2187). 

 They occupy and almost constitute the whole lower half of the trunk ; 

 the upper organ is mucli larger than the lower one, from which it is 

 separated by a thin muscular and aponeurotic stratum. The organs 

 of one side are separated from those of the other, above by the verte- 

 bral column and its muscles, then by the air-bladder, and below this 

 by an aponeurotic septum. From this septum, and from that covering 

 the air-bladder, there extend outwards, to be attached to the skin, a 

 series of horizontal, or nearly horizontal, membranes, arranged in the 

 longitudinal axis of the body nearly parallel to one another ; tliey are 

 of great but varying length, some being co-extensive with the whole 

 organ ; their breadth is almost that of the semidiameter of the 

 plane of the body in which they are situated. These membranes are 

 about half a line apart at their outer borders ; but, as they pass from 

 the skin towards their inner attachments, they approach one another. 

 They are intersected transversely by more delicate vertical plates, 

 extending from the skin to the median aponeurosis, and co-extensive 

 in length with the breadth of the septa between which they are 



* Lxxvi. p. 318. 



f Savi. " Actes du Congros Scientifique, a Florence," 1840. 

 p 3 



