50 C. WINKLER. THE CENTRAL COURSE 



This peculiarity influences the results of MARcm-degeneration and 

 offers an advantage as well as a danger. 



Besides the somewhat' different behaviour of the two nerves 

 towards their periferical ganglia , they also show a certain difference 

 in structure, the vestibular being composed mostly of thick fibres, 

 the cochlear mostly of small ones. This difference is not caused by 

 the circumstance that the cochlear-nerve contains root-fibres and the 

 vestibular partly periferical and partly root-fibres , for then the same 

 difference should be found in the roots. The dorsal root should be 

 composed of small, the ventral of large fibres. 



In this way the difference in the structure of the terminal organs 

 (cochlea and vestibulum) should be reproduced in the structure 

 of their centripetal nerves, as if a complete independency of the 

 two organs and their nerves existed. 



Yet this difference must not be thought too important. Firstly 

 in rabbits the two nerves exchange many fibres. Consequently large 

 fibres are found in the cochlear and in the dorsal root, small 

 fibres in the vestibular and in the ventral root. In animals - - for 

 instance horse and sheep where the nerves do not exchange 



fibres and where they run strictly separated, it is not otherwise, 

 Sections perpendicular to the longitudinal axis of the root demon- 

 strate with certainty, that there exists a certain prevailing of thick 

 fibres in the ventral root above those in the dorsal root, but this 

 difference in structure is only a relative difference. 



Far more interesting than the supposed difference in structure 

 of the two component branches of the nervus octavus is the nearly 

 generally admitted opinion , that the cochlear and the vestibular 

 nerve , after entering the medulla oblongata , pursue a completely 

 different course in the central nervous system. 



The cochlear nerve is continuated in the dorsal root and enters 

 in the latero-dorsal layer of the corpus restiforme. It turns in this 

 layer round the oval area of the restiform body, sending fibres during 

 this traject in the ventral nucleus, in the tuberculum acusticum , 

 perhaps also in the lateral part of the dorsal nucleus of the N. VIII. 



The vestibular nerve however, continuated in the ventral root, 

 finds its way between the restiform body and the spinal root of 

 the V th nerve, goes straight to the internal part of the corpus resti- 

 forme and dividing itself into a descending and an ascending branch 

 ends in the nucleus dorsalis N. VIII, in the nucleus griseus rami 

 descender! tis radicis ventralis and in the so-called nucleus of BECHTI-.REW. 



In this way the cochlear and the vestibular nerves, being pur- 

 sued to different nuclei, originating out of different periferical 



