

ANIMAL ELECTRICITY. ELECTRIC FISHES. 431 



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actually in progress, analogous to that which, when it occurs after 

 death, imparts luminosity to the decaying body. One instance is 

 recorded, in which a large cancerous sore of the breast emitted light 

 enough to enable the hands on a watch-dial to be distinctly seen when 

 it was held within a few inches of the ulcer ; here, too, decomposition 

 was obviously going on, and the phosphorescent matter produced by it 

 as exposed to the oxygenating action of the atmosphere. 



771. Slight manifestations of free Electricity, or, in other words, 

 sturbances of Electric equilibrium, are very frequent in living ani- 

 mals ; and they are readily accounted for, when we bear in mirid that 

 nearly all chemical changes are attended with some alteration in the 

 electric state of the bodies concerned ; and when we consider the num- 

 ber and variety of such changes in the living animal body. When slight, 

 however, they can only be detected by refined means of observation ; 

 and it is only when they are considerable, that they attract notice. 

 The most remarkable examples of the evolution of free Electricity in 

 Animals, are to be found in certain species of the class of Fishes; the 

 best known of which are the Torpedo or Electric Ray, and the Grym- 

 notus or Electric Eel. These possess organs, in which Electricity may 

 be generated and accumulated in large quantities, and from which it 

 may be discharged at will. The shock of a large and vigorous Gym- 

 notus is sufficiently powerful to kill small animals, and to paralyse large 

 ones, such as men and horses ; that of the Torpedo is less severe, but 

 it is sufficient to benumb the hand that touches it. 



772. The electric organs of the Torpedo (which, from being found 

 on European shores, has been the most studied) are of flattened shape, 

 and occupy the front and sides of the body ; forming two large masses, 

 which extend backwards and outwards from each side of the head. 

 They are composed of two layers of membrane separated by a consi- 

 derable space; and this space 'is divided by vertical partitions into 

 hexagonal cells like those of a honeycomb, the ends of which are 

 directed towards the two surfaces of the body. These cells, which are 

 filled with a whitish soft pulp, somewhat resembling the substance of 

 the brain, but containing more water, are again subdivided horizon- 

 tally by membranous partitions ; and all these partitions are profusely 

 supplied with blood-vessels and nerves. The electrical organs of the 

 Gymnotus are essentially the same in structure ; but they differ in 

 shape, in accordance with the conformation of th'e animal. In these, 

 and the other Electrical fishes, the electric organs are supplied with 

 nerves of very great size, larger than any others in the same animals, 

 and larger than any nerves in other animals of similar bulk. These 

 nerves arise from a peculiar ganglionic enlargement of the Medulla 

 Oblongata, termed the electric lobe, and seem chiefly analogous to the 

 pneumogastrics of other animals. 



773. The following conditions appear to be essential to the manifes- 

 tation of the Electric powers of these animals. Two parts of the body 

 must be touched at the same time ; and these two must be in different 

 electrical states. The most energetic discharge is procured from the 

 Torpedo, by touching its back and belly simultaneously ; the electricity 

 of the back being positive, and that of the belly negative. When two 





