9S NATURAL HISTORY READER. 



are so powerful that even the shark, the terror of al] the tin- 

 ny tribe, after one encounter never seeks another, but gives 

 them a wide berth. As all varieties of the electric fishes 

 live quietly, and usually in the mud in shallow waters, they 

 would bo peculiarly exposed to the attacks of the larger fish, 

 but their power of self-defense renders them invulnerable. 

 For purposes other than defense it is not certainly known 

 how this peculiar apparatus serves the fish, but the most 

 reasonable hypothesis appears to be that the shock both 

 stuns the prey so that it is easily caught, and effects a 

 change by which digestion is facilitated. In support of 

 this latter point, we have the fact that the alimentary canal 

 in the electric fishes, where digestion takes place, is much 

 shorter than in any other of the vertebrated animals. 



2. The electric discharge from the fish is precisely the 

 same as that from a battery, as is shown by rendering the 

 needle magnetic, by its effect upon chemical compounds, 

 a.:d by the heat evolved and the electric spark obtained. 

 Upon an examination of the fishes, the electric apparatus 

 is found to consist of cells arranged and connected as in 

 a galvanic battery, the electric conditions probably being 

 maintained through the nervous structure of the animal. 



3. The most widely scattered of the electric fishes is 

 the torpedo, which belongs to the rays or skates. The 

 body is smooth and rounded, the tail short and thick, 

 cylindrical at the end and keeled on the sides. The tor- 

 pedo, take it all in all, is an innocent-looking fish, and the 

 quizzical expression of its face adds to the harmlessness of 

 its aspect. But woe lie unto man or animal which ventures 

 to trench on its dignity ! 



4. The electrical apparatus is arranged in two masses, 

 one on each side of the skull. It is composed of a multi- 

 tude of perpendicular columns, in the shape of eight-sided 

 prisms, separated by walls of membrane containing a fluid 

 freely sunnlied with blood, and laced with an immense 



