OF THE NERVUS OCTAVUS. 51 



endings, presenting each a special arrangement of their periferical 

 ganglia and showing a somewhat different structure in regard to 

 the thickness of their fibres , should betray themselves , anatomically 

 spoken , as complete independent nerves , though they compose 

 together the VIII th nerve. 



But the distribution of the root-fibres in the central system is 

 not exactly so, as the generally admitted opinions, described above, 

 hold it to be. The greater part of my anatomical investigations will 

 be consecrated to demonstrating that the root-fibres of both nerves , 

 may be pursued in all the primary nuclei and in all the secundary 

 systems of the nervus octavus. The difference in the central distri- 

 bution of the cochlear and the vestibular nerve is a difference 

 concerning the quantity of fibres thrown into the nuclei. 



Therefore the complete independency of the two nerves , may be 

 not so surely proved by their anatomy, as many investigators 

 believe. 



But not only strictly anatomical data are brought forward to 

 prove that independency. The comparative anatomy also may fur- 

 nish some arguments to defend this opinion. 



Indeed , the comparative anatomy allows the assertion that the 

 static organ is of a very old age in the phylogenetic history, for 

 it is nearly everywhere present in lower animals as an organ 

 bearing the otoliths. 



Much later and gradually the cochlea has been differentiated 

 from this static organ. In fishes scarcely existing, in birds repre- 

 sentated by the lagaena with half a spiral convolution , it reaches 

 in the mammalia its total development with its three characteristic 

 convolutions. In the same series of ideas the embryonic argument 

 may be ranged , that in the ontogenetic development the fibres of 

 the phylogenetic much older nerve - - the vestibular - - begin their 

 myelinisation at an earlier period of foetal life, than the fibres of 

 the cochlear nerve. 



This argument offers a support to the opinion that a certain 

 independence of the two organs of the labyrinth and of their nerves 

 exists, but nothing more. 



My experiences are not at all in favour of the opinion , that the 

 cochlear and vestibular nerves are myelinisated as if they were inde- 

 pendent nerves. 



Certainly the myelinisation begins at the radix medialis (ventralis) 

 at an earlier period than in the dorsal root , still hardly the myelini- 

 sation of the former has become evident but there also appear 

 medullated fibres in the cochlear. 



4* 



