RELATION OF ANIMAL BODIES TO HEAT, &C. 107 



that the nervous system is capable of developing electricity, 

 under the influence of vitality. 



9. Certain fishes, such as the torpedo, the electrical eel, 

 and live or six other species, are provided with special organs 

 for the production of electricity^ Tin the torpedo they consist 

 of a large number of prisms, of from three to six sides, stand- 

 ing close together, near the gills of the fish, and perpendicu- 

 lar to the surface. They are composed of membranous 

 tubes, divided into numerous transverse cells, abundantly 

 supplied with blood vessels and nerves. These vessels arc 

 filled with a fluid of an albuminous nature. These organs 

 are connected with the brain by three large nerves on each 

 side,) 



10. In the gymnotus the electrical apparatus may be com- 

 pared to a battery of galvanic troughs. Two of these are 

 found on each side of the spine, separated from each other by 

 a long ligament, and extending the whole length of the fish. 

 They arc composed of horizontal membranous plates, sepa- 

 rated from one another by a small interval, and crossed in a 

 perpendicular direction by membranous partitions, so as to 

 form a great number of cells, which arc filled with a gelati- 

 nous fluid. These organs receive numerous branches and 

 nerves from the spinal marrow. 



11. The resemblance of these organs to the galvanic pile 

 is very striking. The latter consists of alternate plates of 

 copper and zinc with a fluid between them. Thus we have 

 in these fishes alternate layers of membranous partitions and 

 albuminous fluid. But is is worthy of particular notice that 

 these organs lose their electric powers if tho nerves which 

 supply them arc divided. There can bo no doubt then, that 

 the electric shock which they give is a vital act, depending 

 on a nervous influence, and under the control of the animal's 

 will. 



VJ. Tho sensation produced by the shock of an electrical 

 fish, is also similar to that of common electricity. It is pow- 

 erful enough to kill small fishes, and is the animal's weapon 



