212 LECTURE VIII. 



proportions of the labyrinth and eyeball to the conditions under 

 which the fish receives its impressions of the sonorous and luminous 

 undulations. 



Electric Organs. 



Extraordinary as are the modifications and appendages of the peri- 

 pheral extremities of the nerves of smell, sight, and hearing, other 

 nerves in fishes are subject to still stranger combinations, and con- 

 stitute organs quite unknown in any other class of Vertebrate Ani- 

 mals ; those, viz., which endow a fish with the wonderful property of 

 accumulating, concentrating, and applying in its own behoof an impon- 

 derable agent of a purely physical nature, which gives it the power to 

 communicate electric shocks, — to wield at will the artillery of the skies. 



But few fishes are known to possess this faculty, and I shall limit 

 the demonstration of the electric organs to the two genera, which 

 possess them in the highest state of development, and which are most 

 dreaded for the force of the shocks they impart ; these are the Tor- 

 pedo and the Gymnotus. 



In the Torpedo Galvani* the organs are two in number, are 

 large, flattened, reniform bodies, lodged on each side the head and 

 gills, and encompassed by these and by the anterior borders of the 

 pectoral fins {Jig. 45. e), and they consist of a mass of vei'tical, for 

 the most part hexagonal, prisms, the ends of which are covered by 

 the dorsal and ventral integuments. When you reflect these, you 

 find the organs immediately coated by a thin glistening aponeurosis, 

 which sends down partitions forming the chambers of the prismatic 

 columns. Each column, when insulated in the recent fish, seems 

 like a mass of clear trembling jelly ; but consists of a series of de- 

 licate membranous plates inclosed by, or adherent by their margins 

 to a proper capsule, and separated from each other by a small quan- 

 tity of a limpid albuminous fluid. Each flattened cell thus formed, is 

 lined by an epithelium of nucleated corpuscles : the fibrous tissue of 

 the plates and common capsule presents the microscopic characters of 

 elastic tissue ; between it and the epithelium is a clear unorganised 

 layer, the seat of the ultimate ramifications of the vessels and nerves. 

 The proper capsule adheres to the aponeurotic partition-walls which 

 support the columns and the larger branches of the nerves and vessels 

 of the organ. f The transverse plates of the vertical columns are 



* The electric organs in the Torp. Narce and Torp. NobUiana do not materially 

 differ from those above described and illustrated by the dissections of Hunter. — 

 See Nos. 2167 — 2179., and lxxx. 



■f- Some of the vertical columns do not extend through the entire thickness of 

 the organ. I have found them interrupted where the deep-seated nerves traverse 

 the substance of the battery, but have not, in any instance, succeeded in finding a 

 natural division of the organ into two strata of dorsal and ventral columns. — See 

 xci. p. 60. 



