292 ELECTRICAL ORGANS IN FISHES. 



mately connected to one another by a thin aponeurosis only. 

 These small batteries are, therefore, peculiar, not only in their 

 close approximation, but also in being enveloped in mus- 

 cular substance. 



The batteries in Gymnotus consist of a number of piles 

 placed horizontally in a direction from head to tail. From 

 this circumstance, as well as from their peculiar structure, they 

 are aptly compared by Eudolphi to galvanic troughs. These 

 troughs are in the form of flattened masses, separated from, 

 but connected to one another by aponeurotic septa, which, 

 diverging, extend outwards from the inner to the outer aspect 

 of each battery. It is not easy to determine the exact number 

 of the piles or troughs in a battery, as they vary in number 

 in different parts of it, and are lost as they pass backwards 

 and downwards. From the statements of Mr. Hunter (An 

 Account of the Gymnotus Mectricus ; Phil. Trans. 1775), 

 and Valentin (loc. cit.\ and my own observations, the number 

 of troughs in the great battery ranges from thirty to sixty ; 

 in the lesser from eight to fourteen. Hunter (loc. cit!), Eu- 

 dolphi (uber die Mectrischen Fiscke in Alhand. der Akad. 

 zu Berlin, 1822), Knox (Edin. Jour, of Science, 1824), Valentin 

 (loc. cit), and all observers previous to Pacini, state what may 

 be easily verified, that the troughs in Gymnotus consist of 

 numerous perpendicular laminae, which extend transversely 

 between the aponeurotic septa, with fluid interposed, as in the 

 piles of Torpedo. Pacini's account (loc. cit.) of the structure 

 and relations of the electrical laminse or diaphragms of 

 Gymnotus is much more precise ; and elucidates in a remark- 

 able manner a structure hitherto sufficiently obscure. The 

 more important features of Pacini's account, as verified by 

 myself, may be thus described. Each of the electric dia- 

 phragms in Gymnotus, instead of being, as in Torpedo, a 

 single lamina with the nerves distributed on one of its surfaces, 

 consists of two lamina^ with a thin layer of fluid interposed. 



