To-peJo, Gymnotus ehnrlcus and Silurus elsar'icus. 133 



of the eighth pair in the fikirus eleftricus have a diredlion and 

 vokime which are peciihar to that fpecies : they defcend, ap- 

 proachino; each other on their iiruing from the cranium to- 

 wards the bodv of the firft vertebra, which they traverfe. 

 They firft introduce therufelves through an orifice pecuhar 

 to each of them, and then ifllie on the oppofite fide by one 

 aperture : after reafcending they fuddenly feparate, and pro- 

 ceed under each of the lateral lines. They are tlien found 

 lodged between the abdominal mufcles and the general apo- 

 neurofis which extends over the cleftric reticulation. In 

 the laft place, thev penetrate beneath the fkin by means of 

 larce branches, which proceed to the right and left of the 

 principal nerve. Thefe branches are in number 12 or 15 on 

 each fide ; they pierce the aponeurofis which lines the inte- 

 rior furface of the reticular tifilie, penetrate to the centre of 

 the reticulation, and at laft expand in it. 



The examination of the three clcftric organs^ which I have 

 compared with each other, neceftarilv condufts us to fonie 

 interefting refults refpe(5ling the kind of modification which 

 orcjans common to all fifties ought to undergo to develop in 

 fome fpecies ele£lric properties. We find, lit, That the part 

 where the electric batteries are lodged is a matter of indifle- 

 rence, as they are dilfufed all-around the filurus eleftricus, 

 collected in the tail of the gymnotus, and united on the fides 

 of the head in the torpedo. 2d, That no branch of the ner- 

 vous fyftem is particularly fet apart for thefe organs, fince the 

 nerves diftributed thither are all different. 3d, That the form 

 of the cells is nlfo of little importance, as this form varies in 

 each fpecies ; but in other rcfpcfts it is found alfo that the 

 eleftric batteries, which on the firft view we might be tempted 

 to believe to be fo difierent, have however a great many re- 

 lations with each other, and may be reduced to tlie fame 

 fvftcm of organization. This will appear evident, when it is 

 confidered that the elcftric fifties are the only ones in which 

 we find aponeurofes fo extenfive and fo multiplied in their 

 furfaces, with fo confiderable an accumulation of gelatine and 

 albumen in the cells formed by ihefc aponeurofes, and ner- 

 vous rami fo large and of fuch a length. It is by the union, 

 indeed, of thefe fimple inftruments that the cledlric organ is 

 conftituted; and in this ftate_, according to the judicious re- 

 mark of my colleague Lacepede '■', it may be compared to 

 the Leyden flaft^, or'an eleftric pidurc, fii>ce it is alternately 

 compofed of bodies which conduA the elcAric ftuid (the 

 iiervcs, and the albumino-gelatinous pulp to which the action 



• llijhhf HiUunlk dn P'tjpjm, vol. ii. Defcriptiou of the Gjmnoiin 

 'i-ib'icus, p. 166. 



K3 Of 



