370 PHILOSOPHY OF ZOOLOGY. 
The nerves of the organs arise from the medulla oblonga- 
ta. Each organ is liberally supplied by three large trunks, 
which, after communicating a few filaments to the gills, ra- 
mify in every direction between the columns, and send in 
small branches upon each partition. 
The electrical organs of the Gymnotus electricus, as ex- 
amined by Hunrer*, differ considerably from those of the 
Torpedo. The largést, or superior organs, consist each of 
a series‘of thin tender membranes, parallel to one another, 
extending longitudinally the whole length of the organ ; 
and, in breadth, reaching from their central to the dermal 
surface. ‘The uppermost membranes are concave dorsad, 
the middle ones are nearly horizontal ; and the inferior ones: 
are concave sternad. Their dermal edges are united with 
the skin and its muscles, their central edges with the mid- 
dle partition, the air-bag, and the dorsal muscles. They 
are farthest distant from each other at their dermal edges,. 
and gradually approach as they proceed to their central at- 
tachment. Where the organ becomes narrower towards 
the tail, two of the membranes sometimes unite, and form 
into one. In a fish, 2 feet 4 inches in length, they are 
77th of an inch distant from one another ; and the whole 
organ, where broadest, is an inch and a quarter in breadth, 
and contains thirty-four membranes. In the inferior or 
smaller organ, the membranes are nearer each other, bemg: 
only about j7,th of an inch asunder. The superior ones 
are the broadest, and they decrease in breadth the nearer 
they are situated to the ventral line of the animal. In both 
organs there are numerous partitions, dividmg the spaces 
included between the different layers, into narrow vertical 
transverse cells. Each cell is m the form of a compressed qua- 

* Phil. Trans. 1775, p, 339. 
