304 ELECTRICAL ORGANS IN FISHES. 



the water suiTOUiidiiig the fish. The entire current force of 

 the batteries must, in fact, be subdivided into numerous sub- 

 ordinate axes of force arranged in lines which come round the 

 margins of Torpedo from back to belly, and along the sides of 

 Gymnotus from head to tail. It is evident, therefore, that 

 another fish placed so that its antero-posterior axis is in the 

 line of inductive action in the water, will be affected less 

 powerfully by the circulating electric power than if it were 

 placed across these lines. Mr. Faraday {Phil. Trans. 1839) 

 found that although the Gymnotus can stun and kill fishes 

 which are in various positions in relation to its own body, it 

 can, moreover, by throwing itself so as to form a coil enclosing 

 the fish, the latter representing a diameter across it, so concen- 

 trate its currents of one side as to strike it motionless as if by 

 lightning. The Torpedo would also appear, from the observa- 

 tions of Dr. Davy, instinctively to elevate or arrange its 

 margin so as to adjust the direction of its currents to the 

 position of the object through which it wishes to pass them. 

 " Thus," as Mr. Faraday observes, " the very conducting power 

 which the water has ; that which it gives to the moistened 

 skin of the fish or animal to be struck ; the extent of surface 

 by which the fish and water conducting the charge to it are 

 in contact ; all conduce to favour and increase the shock upon 

 the doomed animal" [Phil. Trans. 1839). Here, it is to be 

 noted that one of the chief difficulties in explaining the 

 operation of the electrical apparatus in the fish has been the 

 necessity of admitting a certain amount of insulating property 

 in certain of the textures composing and surrounding it ; and 

 in conceiving the apparatus acting at all in a medium which 

 conducts so freely as water. The apparatus in fact owes its 

 efficiency in such a medium to its peculiar combination of 

 quantity and intensity. The battery of the fish, in relation to 

 its final purpose, is a perfect instrument ; yet, from another 

 point of view, and in one sense, when compared with an arti- 



