THE CEANIAL KERA-JuS AND LATEEAL SENSE OEGANS OE EISHES. 143 



to it variously as the prtE-branchial, prse-trematic, palatine, or fasniculus communis 

 ganglion (in part). Some of the older anatomists regarded it as belonging to the 

 trigemino-facial complex, and others described more than one ganglion in this 

 region in Teleosts. 

 (4) We have seen that tlie facial ganglion is a ganglion placed on fibres that un- 

 doubtedly belong to the seventh or facial cranial nerve. It seems therefore to 

 belong to the trigemino-facial complex, and cannot, in face of this fact, be 

 considered a purely sympathetic ganglion. But we have further seen that it has 

 many sympathetic characters, for in the first place it is connected with the fibres 

 of the fasciculus communis system which we know to be essentially sympathetic 

 in character ; in the second, its cells are small, and correspond to the cells found in 

 the ciliary and true sympathetic gnnglia; and in the third, it gives origin to the 

 cephalic sympathetic trunk. It cannot, by the very nature of its structure and 

 connections, correspond to a prc-vertebral ganglion, as Shore has suggested (and, 

 indeed, Shore himself advances a very good reason against this), nor can it 

 represent a typical vagrant ganglion, since these are connected with, visceral 

 motor fibres. The only alternative left is that it represents the visceral portion of 

 a dorsal root ganglion, since the latter is partly in connection with visceral sensory 

 fibres. And this I believe to be the case. How, then, is its isolated position to be 

 explained? We know from Gaskell's classic researches on the sympathetic 

 nervous system, for which every vertebrate morphologist is grateful to him, that 

 the splanchnic ganglia on the main trunk of the sympathetic system, or " vagrant " 

 ganglia as he calls them, are in reality ganglia belonging to the roots of the meta- 

 meric nerves which have wandered from their original position. May not the facial 

 ganglion of the Cod be in an intermediate condition ? Here we have a ganglion 

 of which the structural relations are such that it defies classification — it can 

 neither be classified as a cranial nerve ganglion nor as a typical sympathetic 

 ganglion, unless indeed we disassociate the fasciculus communis system from the 

 cranial nerves altogether and add it to the sympathetic. In the Elasmobranch 

 fishes, which we know from pakeontology represent a more primitive condition 

 than the Teleosts, the pre-spiracular ganglion (=facial of Cod) is still in very close 

 association with the main facial ganglion. In the specialised Teleosts, on the 

 other hand, the ganglion is found to be completely separate from the trigemino- 

 facial complex. We are therefore forced to the conclusion that the facial ganglion 

 of Teleosts is in the act of doing what ^\■e know the visceral motor ganglion to 

 have done, i. e. is migrating from its original position, and will perhaps become 

 in the course of time a typical sympathetic ganglion. In short the facial ganglion 

 of the Cod is an exemplification of the principle of evolution, and shows us a 

 stationary ganglion l;ecoming converted into a vagrant or true sympathetic 

 ganglion. 



