ELECTRIC ORGANS. 219 



with layers of epithelium. In the intervals between the septa is 

 found some fluid. Upon the septa themselves may be recognised 

 the terminal plexuses of vessels and nerves, those of the latter organs 

 resembling the terminal plexuses within the substance of voluntary 

 or transversely striated muscles. The electric organs, taken as a 

 whole, are very rich in vessels and nerves. Upon either side they 

 are supplied by four large nervous trunks, one of which, a branch of 

 the trigeminal nerve (n. electr. trigemini), is distributed specially 

 upon the most anterior part of the electric organ, while the three 

 other trunks are given oft* by the vagus ; the most anterior of these 

 is the largest, and much more developed than the branch of the 

 fifth ; the posterior is the smallest. The origin and mode of distri- 

 bution of these branches offer to our notice several remarkable pe- 

 culiarities. Thus the n. electricus trigemini arises, along with the 

 inferior maxillary branch, deeper than the remaining roots of the 

 fifth pair from the medulla oblongata, and appears to correspond to 

 the lesser or motor root of that pair of nerves. The branches 

 proceeding from the tenth pair or n. vagus, pass to the electric 

 organs between the branchiae, and give off alternate twigs to them. 

 The branchial branches are furnished with ganglionic enlargements 

 containing ganglionic corpuscules, but these are absent upon the 

 far thicker fasciculi of the electric nerves. It appears that these 

 motor fibres, which here reach their maximum development, corre- 

 spond to the accessory nerve of the higher Vertebrata. 



The structure of the electric organ is in Narcine very similar, but 

 here its shape is the reverse of that in Torpedo, being narrower an- 

 teriorly ; the nervous branch corresponding to the r. electricus nervi 

 trigemini is much more feebly developed. 



In the Electrical Eel the organ in question is situated in the tail, 

 which, from the very anterior position of the anus, is so large in this 

 animal as to exceed more than a quarter the length of the whole 

 body, and is in great part filled up by the very largely developed 

 electric apparatus. This is divided into two detached parts and a 

 single one consisting of two that have coalesced : the first are situ- 

 ated laterally and more toward the upper surface, the last inferiorly, 

 and the extent of all three organs closely accord with that of the 

 caudal fin. Each of the two lateral organs is invested by a ten- 

 dinous membrane, and glimmers through the external integument ; 

 superiorly they abut against the muscles of the back, inferiorly 

 against the muscular system of the caudal fin ; posteriorly they run 

 to a point. The inferior electric organ is situated above and between 



