ELECTRICAL GYMNOTE. 53 



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it incloses more of the lateral parts of the body, 

 becomes narrower towards the end of the tail, oc- 

 cupying less and less of the sides of the animal, till 

 at last it ends almost in a point. These two organs 

 are separated from one another at the upper part 

 by the muscles of the back, which keep their pos- 

 terior or upper edges at a considerable distance from 

 one another : below that, and towards the middle, 

 they are separated by the air-bag; and at their lower 

 parts they are separated by the middle partition. 

 They begin forwards, by a pretty regular edge, 

 almost at right angles with the longitudinal axis of 

 the body, situated on the lower and lateral parts of 

 the abdomen. Their upper edge is a pretty strait 

 Jine, with small indentations made by the nerves 

 and blood-vessels which pass round it to the skin. 

 At the anterior end they go as far towards the 

 back as the middle line of the animal ; but in their 

 approach towards the tail, they gradually leave that 

 line, coming nearer to the lower surface of the ani- 

 mal. The general shape of the organ, on an ex- 

 terior or side view, is broad at the end next to the 

 head of the animal, becoming gradually narrower 

 towards the tail, and ending there almost in a point. 

 The other surfaces, of the organ are fitted to the 

 shape of the parts with which they come in con- 

 tact : therefore on the upper and inner surface it is 

 hollowed, to receive the muscles of the back. There 

 is also a longitudinal depression on its lower edge, 

 where a substance lies which divides it from the 

 small organ, and which gives a kind of fixed point 

 for the lateral muscles of the fin. Its most internal 



