OF THE NEKVUS OCTAVUS. 53 



may prove that the course of the root-fibres of the dorsal and the 

 ventral root, is the same. Only the quantity of fibres, which are to 

 be traced from the root in a distinct central part, does vary. Both 

 roots innervate in larger or smaller quantity all the so-called primary 

 nuclei, both are searching in larger or smaller quantity the same 

 so-called secundary paths. 



An endeavour to demonstrate this, I intend to make in the 

 next paragraphs 



3. TUP: PRIMARY SYSTEMS OR THE ROOT-FIBRES 

 OF THE NERVUS OCTAVUS 



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



the isolated removal of the cochlea and the initial coarse 



of the dorsal (lateral) root in the central system. 



We have seen that it is possible in rabbits to remove the cochlea 

 without damaging the vestibulnm. We have seen that this operation 

 is equal to a section of the cochlear nerve between the spiral 

 ganglion and the medulla oblongata. A succesfnlly executed opera- 

 tion of this kind is always followed by a degeneration in the 

 cochlear-nerve , within a week. 



MARCHI'S method then gives in those cases an evident result. 



The lateral (dorsal) root of the VIII th nerve is covered with 

 black grains, whereas Jhe portion of the medial (ventral] root , that is 

 found between f/anylion vestibulare and 'medulla oblonf/ata is totally 

 exempt of them. (See fig. \a on Plate I and fig. 2 on Plate II). 



This fact does not prove that the degeneration in the lateral root 

 is a complete one. There are reasons, as we will find, to admit 

 that this is not the case. 



But in this fact we have an expedient to study the fibres, 

 taking their origin in the ganglion spirale, and to isolate them 

 from the rest. Unfortunately it is not possible to remove the con- 

 tents of the vestibulum without lesion of the cochlear nerve. 



A comparison of the degeneration in the lateral root after remo- 

 ve I of the cochlea may therefore only be made with the degeneration 

 following the total section of the VIII th nerve. 



The degenerated fibres of the ganglion spirale (tjie cochlear 

 root-fibres) throw themselves through the lateral root in the latero- 

 dorsal layer of fibres, that turns round the oval area of the restiform 

 body to reach the internal part of it. But after total section of the 

 VIII th nerve the number of degenerated fibres in the latero-dorsal 



