1890.] 



Hie Cranial Nerves of the Torpedo. 



291 



The glossopharyngeus, a slender nerve in the skate, is represented 

 in the torpedo by a thick cord which escapes by a large foramen 

 in the outer wall of the auditory capsule. This large nerve consists 

 of two portions, one of which is small and completely covered by the 

 large superficial division. The small deep division, which in its 

 course and distribution closely resembles the glossopharyugeal in the 

 skate, presents on leaving the auditory capsule a distinct ganglionic 

 swelling, beyond which it breaks up into the branchial and other 

 branches. The large superficial division emanates from the electric 

 lobe behind the origin of the first electric nerve, and at once runs 

 outwards to reach and supply the majority of the columns of the 

 anterior half of the electric organ. 



The vagus complex consists of the nervus lateralis, the rervus in- 

 testinalis, and of five branchial nerves, of which the two anterior are 

 accompanied by the third and fourth electric nerves. The nervus 

 lateralis, lying superficial to all the other nerves, arises on a level 

 with the root of the glossopharyngeus, and then curves backwards 

 dorsal to the posterior electric nerve to reach the canal of the lateral 

 line. Shortly after leaving the cranium it presents a distinct gan- 

 glionic swelling, which is crowded with large cells. The four bran- 

 chial nerves for the four functional branchiae, the slender filament 

 Avhich represents a sixth branchial nerve, and the intestinal nerve lie 

 at first in contact with each other under cover of the third and fourth 

 electric nerves. When the branchial and intestinal nerves are care- 

 fully examined, they are found to present four, sometimes five, 

 ganglionic enlargements, and in addition ganglionic cells can some- 

 times be detected at the proximal end of the slender sixth branchial 

 nerve. The third and fourth electric nerves lie over and are especially 

 related to the second and third branchial nerves. These large electric 

 nerves spring from the posterior half of the electric lobe, and find 

 their way outwards partly behind, and partly under the auditory 

 capsule, to terminate in the posterior half of the electric organ. 



It thus appears that all the electric nerves spring from the electric 

 lobe, that the first accompanies the hyomandibular division of the 

 facial complex, the second the glossopharyngeus, and the third and 

 fourth the first two branchial nerves of the vagus complex. It re- 

 mains to be seen whether the electric nerves have been derived from 

 motor branches of the nerves with which they are respectively asso- 

 ciated by an enormous increase in the number of their fibres, as 

 the muscular fibres were gradually transformed into electric plates. 



VOL. XLV1T. 



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