368 



ELECTRO-PHYSIOLOGY 



CHAi'. 



To summarise the main points relating to structure, and more 

 particularly to innervation, of the organ of Torpedo, this much is 

 certain. Each ganglion-cell of the electric lobe in the brain gives 

 off an axis-cylinder process (analogous to Deiter's process in the 

 ganglion -cells of the spinal cord), which continues as an un- 

 branched constituent of the electric nerve, down to one of the 

 columns that compose the organ. Here the medullated fibre 

 suddenly breaks up into a number (12 20) of small ramifications 

 (Wagner's brush), which are arranged regularly, one over the 

 other, and each partially supply a plate. On entering the mucous 

 tissue that fills up the space between every pair of plates, each 



FJG. 237. Gymnotus electrieus. 



terminal fibre divides many times dichotomously, and finally ends, 

 after losing its medullated sheath, at the ventral surface of the 

 plate, in a manner analogous with the terminal ramification of 

 the axis-cylinder in the motor end-plates of striated muscle-fibres. 

 The nature of the true ending and whether it is free, or, as 

 Fritsch says, lies within the palisade layer, is still undecided, and 

 awaits further investigation. 



The uniformity of structure and internal relations in the 

 electrical organ is of great moment to the theory of the discharge 

 of these fishes. In G-ymnotus, as in Torpedo, the organs exhibit 

 a bilateral symmetry, and are so powerfully developed that the 

 fish might be said to consist principally of electric organs. Fig. 

 237 is a good representation of the form of the fish. Notwith- 



