ELECTRICAL ORGANS IN FISHES. 299 



the one on each side, by a longitudinal nen'e, accompanied hy 

 an artery and vein, which pass along on their mesial aspects. 

 This neiTe was lurnierly considered to be a branch of the 

 eighth pair ; but Pacini {sopra ronjano elcttrico del Siluro 

 elettrico del Nilo, 1846) describes it as derived from the first 

 spinal nerve. Ecker has more recently stated (Siebold and 

 Kolliker's Ziiisrhri/t, Jubj 1854), that, according to Billiarz, 

 " the electrical nerve on each side appears to be a new ele- 

 ment intercalated between the third and fourth spinal nerves." 

 From the same communication it appears that Bilharz has 

 found the trunk of the electrical nerve of the Nilotic Malap- 

 terunis to consist not of a bundle of idtimate filaments, but 

 of one such filament only, one-fourth of a line in diameter, 

 surrounded by three fibrous sheaths, so as to present an entire 

 thickness of one line. From this remarkaljle structure, Ecker 

 has suggested to Bilharz further observations to determine 

 whether the nervous centre of the electrical apparatus in this 

 fish may not be a colossal unipolar nerve cell. From the 

 peculiar structure of the trunk of the nerve, it is also evident 

 that its branches and twigs of distribution must be subdivi- 

 sions of the original single filament ; in this respect resembling 

 the subdivisions of the ultimate filaments in Torpedo, as 

 observed by Wagner. 



The presumed electrical organs in the tail of the skate are 

 supplied by numerous nervous twigs, derived from the ventral 

 or motor roots of the spinal nerves of the corresponding portion 

 of the tail. These are distributed, as already stated, on the 

 anterior faces of the discs, and do not exhibit at their spinal 

 extremities any appreciable centr.d development. 



Physiologists admit, as a general fact, the disturbance of 

 the electric equilibrium in the processes of the living organised 

 body. In vegetables this development of electricity is re- 

 markalile. In animals the discovery of Galvani, and the 

 researches of Matteucci, and more particulaily of Du Boi.>* 



