244: INNERVATION. [c HAP. IX. 



force is developed in muscle under similar influence. Both tissues 

 are characterized by their tendency to assume a polar state, dif- 

 ferent in each, although analogous, in obedience to certain exci- 

 tants. That this polarity bears a remarkable analogy to that 

 which may be produced in inorganic matter is evident. Further 

 observation and research conducted with a full knowledge of the 

 details of anatomy, as well as of the laws of the polar forces as 

 displayed in inorganic substances, will doubtless throw great light 

 on this intricate subject ; for, as Faraday remarks, if there be 

 reasons for supposing that magnetism is a higher relation of force 

 than electricity, so it may well be imagined that the nervous 

 power may be of a still more exalted character, and yet within the 

 reach of experiment.* 



Of the Electrical Fishes. The fact that some fishes possess a 

 peculiar electrical apparatus, which they are enabled to discharge 

 under voluntary influence, is supposed by the adherents of the 

 electrical theory to favour their views. The torpedo, the gymnotus 

 electricus, or electrical eel, and the silurus electricus, are the best 

 known of the electrical fishes. From the two former, the most 

 unequivocal evidence has been obtained by Walshe, Davy, Linari, 

 Matteucci, and recently by Faraday, that electricity is discharged. 

 Conductors or non-conductors are affected by the electrical apparatus 

 of these fishes just as by ordinary electricity : a chain of several per- 

 sons, of whom those at the extremities touch the fish, feel the shock 

 as they would that of a Leyden jar. The sensation produced by the 

 shock from the fish is exactly that which is caused by accumulated 

 electricity as developed by the ordinary machine. A spark has been 

 obtained during the discharge : chemical decomposition or electro- 

 lysis has been effected by it. The galvanometer is also readily dis- 

 turbed, and indicates that the current passes from the anterior to the 

 posterior part of the animal. And a needle has been made a magnet 

 when placed in a helix through which the current passes. These 

 effects have been obtained from the torpedo and the gymnotus. 



It is further shewn, that the electricity cannot be developed in 

 these animals if the organ be removed, or if its communication 

 with the brain be cut off. If the nerves of the organ of one side be 

 cut, it will cease to develop electricity ; but the opposite organ 

 will continue to act perfectly. When the organ is partially cut 

 away, the remaining portion continues to discharge; or, if some of 

 its nerves be cut, that portion of which the nerves are entire will 

 continue to develop electricity. The nerves excite some change in 



* Phil. Trans. 1839. 



