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ganglion and the same side of the whole subventral chain. Now 

 there is this point of difference between the two kinds of centres 

 compared together, that while the last-mentioned set of fibres on 

 the one side is continuous with that on the other, as a transverse 

 band through the cephalic ganglion, the subventral cords, although 

 continuous with these on their respective sides, form no such con- 

 nexion with each other across the lateral halves of their own ganglia, 

 but run parallel and directly backwards through them. Such a 

 communication, however, is established for the latter, individually, 

 by the transverse fibres of their own nerves ; and just as these fibres 

 unite the lateral halves of each separate ganglion, independently of 

 the cephalic, so do the last-mentioned set of fibres of the crura con- 

 nect together the two lateral halves of the entire chain in and through 

 the cephalic ganglion, which is their dominant and controlling 

 centre. 



Two parts of the human brain may be compared to this transverse 

 cephalic band. One is the arched and commissural band of fibres 

 prolonged through the corpora quadrigemina, from the upper and 

 inner part of the fillet on each side. But the outer part of the fillet 

 turns forwards and upwards beneath the corpus geniculatum internum 

 and optic tract, to enter the optic thalamus. It is not improbable, 

 therefore, that some of the fibres of the tract may descend along 

 this portion of the fillet, to form loops with the roots of the fifth 

 nerve, over which it passes, since in Lumbricus it has been seen that 

 many of the roots of the cephalic nerves run down the pharyngeal 

 crus to form loops with others to which it gives origin. In a former 

 memoir by the author, it was shown that some of the roots of the 

 spinal accessory nerve reach the anterior grey cornu and mingle, 

 perhaps pass out with, the spinal roots ; and he has since observed 

 the equally interesting fact, that the same nerve forms a similar 

 connexion with the vesicular nucleus of the hypoglossal, which may 

 be considered a representative of the anterior spinal. The spinal- 

 accessory, therefore, takes it origin from at least three different 

 sources, from its own nucleus, and from the nuclei of the hypo- 

 glossal and anterior spinal nerves. The peripheral communications 

 of both the former with the latter nerves in the cervical plexus is 

 well known. The author believes he has also made out an intimate 

 connexion by loops between at least the portio intermedia of the 



