OF THE NER\ 7 US OCTAVUS. 55 



proximally (see fig. 2 on Plate II) , there appear normal fibres 

 resting upon the lateral border of the oval area, which only may 

 be brought to degeneration after the section of the eight nerve 

 (see -fig. 4 on Plate IV). On this traject the dorsal rootfibres enter 

 into the ventral nucleus and the tuberculum acusticum in a way 

 to be described further on and the remaining fibres reach also the 

 portio interim of the corpus restiforine in its latero-dorsal part. 



These remaining fibres are the root-fibres of the lateral root, 

 which participate in the formation of the ,,systema dorsale nervi 

 octavi". 



Each of the three portions of these lateral root-fibres has its own 

 adventures, and shall be separately described, as soon as the initial 

 distribution of the ventral root-fibres is known. In the description 

 of the initial ways of the lateral root-fibres here given I differ 

 essentially from the opinion of VAN GEHUCIITEN, and approach to 

 that of TIUCOMI-ALLEGRA , not only because the Marchi-degeneration 

 demonstrates it, but also because it is concordant with the results 

 of other methods of investigation. 



b. The fresh degeneration in the root- fibres taking place after 



the section of tlie VIII th nerve and tie initial traject 



of the ventral (medial] root in the central system. 



The ventral root may be brought to degeneration, together with 

 the dorsal root by sectioning the VIII' h nerve in the ineatus audi- 

 torius intern us. 



The comparison of the degenerated fibres found after the removal 

 of the cochlea, with those found after the section of the VIII th may 

 be used to study the course of the vestibular fibres and those of 

 the ventral root. 



This study teaches us , that the ventral root-fibres divide in three 

 portions, exactly in the same manner as is done by the dorsal 

 root-fibres. 



l e . Some fibres, mostly thick fibres, leave the ventral root 

 rectangularly , bending in lateral direction in the corpus trapezoides 

 (see Plate VIII fig. 15 N. 9, 10 and 11). 



Those fibres increase the number of degenerated fibres entering 

 there from the dorsal root, for after the section of the auditory 

 nerve the degeneration in the corpus trapezoides is nearly doubled 

 in intensity , as compared with that after removal of the cochlea. 



Those fibres are the ventral root-fibres participating in the for- 

 mation of the ,,systema ventrale nervi octavi". 



