64 NERVE COMPONENTS OF BONY FISHES. 



If Van Gehuchten's results stand, it would require modification of 

 the homologies proposed above to this extent: The chief, or dorsal, 

 vagal nucleus of mammals would be a viscero-motor centre and the 

 homologue of the sensory portion of the lobus vagi would have to be 

 sought in the "spinal nucleus of the vagus" of mammals only. 



Attention may also be called to the fact that the series of transec- 

 tions of the medulla of the rabbit given by Van Gehuchteu (pp. 294- 

 295) shows that the dorsal vagus nucleus and the fasciculus solitarius 

 run down into the intermediate zone rather than into the dorsal horn 

 region, thus agreeing with our findings in the fishes. 



If we regard the fasciculus communis as the intra- 

 cranial continuation of the visceral system of the ' ' inter- 

 mediate zone" of the spinal cord, as suggested above, we 

 should expect to find in it or intimatety associated with it 

 many kinds of fibres, both afferent and efferent, for the 

 various visceral functions. Such indeed is clearly the 

 case, though we cannot as yet effect their analysis cen- 

 trally. These being the primitive elements of the com- 

 munis system, it follows that the fibres from the taste 

 buds and terminal buds of the skin are phylogenetically 

 later acquisitions, developed as a direct result of advanc- 

 ing cephalization. It is a significant fact that fibres from 

 terminal buds are never found in the spinal nerves. Even 

 in an extreme case, like the free tactile rays of the pec- 

 toral fins of the Triglidae, which receive a surprisingly 

 rich innervation from enormously hypertrophied spinal 

 nerves and which by analogy with the barbels of other 

 fishes we should expect to find covered with terminal 

 buds, the most patient and skilful application of modern 

 nerve methods (Morrill, '95) failed to reveal any terminal 

 buds or other similar specialized organs in the areas sup- 

 plied by these spinal nerves. On the other hand, when- 

 ever terminal buds occur on the bodies of fishes, as they 

 often do over the entire surface, they are always inner- 

 vated by recurrent nerves from the head. The terminal 



