ON LIVING MALAPTERURUS. 371 



and by the side of each other, the substance of which, according to 

 Bilharz, does not distinctly differ from the substance of ganglion 

 cells. These are connected with the electrical nerves, and are the 

 seat of the development of electricity ; i. e. at the command of the 

 electrical nerves the surfaces of all the little plates which look in 

 one direction become positively electrical, and the opposite surfaces 

 become negatively so. On this account the little plates are called 

 electrical plates. The direction of the shock is always vertical to 

 the plane of the plates. In the Torpedo, as the plates lie hori- 

 zontally in the natural position of the fish, the direction of the 

 shock is vertical in the organ from the belly to the back. In 

 the Gymnotus, where the plates lie vertically, the direction of the 

 shock is horizontal in the organ from the tail to the head. In the 

 Malapterurus, according to Bilharz, the plates also lie in vertical 

 planes. Thus we might infer that in this fish, as in the Gymnotus, 

 the electricity will flow horizontally. But what will be the direc- 

 tion of the shock ? Will positive electricity flow from the tail 

 towards the head, in other words, will the front surface of the plates 

 be the positive, and the back be the negative, as in the Gymnotus, 

 or conversely ? 



On this point also Bilharz' investigations already permitted 

 a conjecture. The connexion of the electrical plates with the 

 nervous system is as follows. The electrical nerves, by continuous 

 division, resolve themselves into numberless terminal branches, 

 which finally sink into one of the surfaces of each electrical plate 

 and are merged into its substance. As Signer Pacini has already 

 observed 1 t this embedding of the ends of the nerves in the case of 

 the Torpedo and of the Gymnotus, is exclusively into that surface of 

 the electrical plates which becomes negative in the discharge. 

 Thus in the Torpedo this is the lower, and in the Gymnotus 

 the posterior surface of the plate. Now in the Malapterurus, the 

 nerves also seem to enter the posterior surface of the plates. 

 Hence Bilharz inferred that in this fish, as in the Gymnotus at the 

 moment of discharge, the posterior surface becomes negative, the 

 anterior positive, that is, that the discharge in the organ would 

 pass from back to front 2 . He was obliged to let the matter rest 

 there, without being able to put this conclusion to the test of 

 experiment. According to his account and that of Herr Mar- 



1 Sulla Struttura dell' Organo elettrico del Gimnoto e di altri pesci elettrici. 

 Florence, 1852, p. 25. 



2 Loc. cit. p. 44. 



B b 1 



