Electric Organs. 529 



below the air bladder, backbone, and muscle layers, one part extending 

 to the skin on either side and separating these parts from the electrical 

 apparatus below. The horizontal aponeurotic layers, before mentioned, 

 extend from this vertical septum outward on each side to the skin. 



FIG 263. Vertical cross section of Gymnotus ( Electrical Eel ). Natural size. (Dr. Knox.) 

 a. Skin. h. Vertical electrical plates in upper organs. 



6. Fin. m Horizontal laminae separating the electrical 



c. Muscles. plates. 



d Air bladder. i Lower electrical organs. 



e. Backbone. k. Aponeurotic partition or septum. 



They are as long as the organ, but as that runs to a point at the rear 

 some of the layers are much longer than others. The vertical plates 

 extend from the middle partition to the skin, and are therefore as long 

 as the horizontal layers are wide. They are about half a line high at 

 their outward ends next the skin, but somewhat less at their inner ends, 

 as the horizontal membranes approach each other as they go inward. 

 There are about 240 of these vertical plates to the inch, measured 

 lengthwise of the fish. The spaces between these vertical plates is occu- 

 pied by cells and a fluid ; but their arrangement differs from that of the 

 cells and fluid in the organs of the Torpedo, for in the Gymnotus the 

 cells are in a double layer, which occupies the middle of the space be- 

 tween the vertical plates, the fluid being separated into two parts, one 



