ELECTRIC FISH. 129 



is a very powerful instrument ; and, in the larger 

 kinds of fish, can inflict severe, and even fatal 

 blows. 



Another very curious organ with which many 

 fish are furnished, is the air-bladder : this is 

 double, and being placed within their bodies, gives 

 them the power of ascending or descending in the 

 water without any apparent effort. It renders 

 the body, too, exceedingly buoyant, and about 

 the same weight as the water in which they dwell. 

 Such fish as are unprovided with this organ are 

 generally found at the bottom of ponds, lakes, and 

 seas, as the different kinds of flat fish. It is sup- 

 posed that the fish has the power of secreting or 

 forming air to fill this bladder, and we know of 

 no other animal which possesses any thing of the 

 kind. 



Several fish are provided, as a means of defence, 

 with a species of electric or galvanic battery, 

 which acts just like a shock from an electrical ma- 

 chine. This is a very extraordinary provision, 

 and is possessed in great perfection by the torpedo 

 and the gymnote, or electrical eel. This last crea- 

 ture abounds in the rivers and ponds of some parts 

 of South America, and grows to a large size. So 

 powerful is the shock they are capable of giving, 

 as to prove almost fatal both to man and animals : 

 mules and oxen, when about to cross a stream in- 

 fested by these creatures, take the greatest precau- 

 tion to avoid being entangled in their folds, and 

 exhibit every mark of terror when attacked by 



