14(1 



THE NERVOUS SYSTEM. 



trigeminal nucleus. According- to Reissner the latter fibres are 

 motor, the former sensory. Probably other nerves are connected 

 with the hinder part of this group. 



4. The abducens nucleus (Fig. 100 o). From its superficial 

 origin, the fibres of the abducens nerve may be traced vertically 

 upwards to a small, rounded, grey mass ; at this point the mass 

 is somewhat isolated, but further forwards it may be traced 

 as belonging to the central grey matter ; it contains small spindle 

 cells. 



Fig. 101. 



Transverse section of the Medulla oblongata, at the point of origin of the auditory nerve, from 

 Stieda. (Magnified 30x80.) 



h Fourth ventricle. 



n Auditory nucleus. 



o Abducens nucleus. 



p Auditory nerve. 



p' Ganglion of auditory nerve. 



<j Hinder portion of trigeminal nerve. 



r Bundle of fibres arising from trigeminal nucleus and joining the auditory nerve. 



5. The pneumogastric nucleus. The pneumogastric, with its 

 numerous irregular roots, arises from the side of the medulla ol- 

 longata. The hindermost fibres can be traced as a small bundle, 

 passing almost transversely through the white matter to the outer 

 margin of the grey matter. The larger portion of the fibres is 

 placed in front of these ; part of this seems to be directly con- 

 tinuous with the longitudinal fibres of the white matter; a 

 second part, however, can be traced from the surface transversely 



