OF THE NEiiVUS OCTAVUS. I 19 



In this way there may exist two systems, differentiated in the 

 central secundary octavus-systems, the one to be used for the 

 higher psychical function of hearing, the other for the automatic 

 and reflex-functions, defining the influence upon movements, which 

 the N. octavus has. 



b. T/ie longitudinal secondary systems participating in the 

 systema dorsale nervi octavi. 



As may be seen best in an horizontal section of an elder foetus 

 of a rabbit (Plate VI fig. 19 C) the dorsal systema is forming 

 a powerful mass of medullated fibres , spread over an extensive area, 



A medullated bundle runs from it proximally (Plate VI fig. 19 C. 

 syst. dors. N. VIII). 



After rootsection (Plate XIV fig. 14 B, Plate XI fig. 16 K) in 

 this tract, some degenerate rootfibres are found, which could be 

 traced towards the nucleus of the IV th nerve. 



After section of the dorsal system, this tract degenerates nearly 

 totally. 



Very instructive in this respect are here the results of the double- 

 sided ablation of the tub. acusticum (Plate XIX, XX fig. 25 X A). 



There on the right side, the incision falls not so far proximal- 

 ward as on the left side. The nucleus of DEITERS, on the left, has 

 been totally destroyed. On the right its destruction is only complete 

 at its distal end and at its proximal end some very well developed, 

 normal cells are seen in it (Plate XIX, XX fig. 25 E, F at the 

 right side): 



Now from the proximal end of the damaged nucleus DEITERS 

 on the left, there appears a large radiation of degenerated fibres 

 (Plate XIX fig. 25 E). They radiate in medial direction, at first 

 dorsally from the spinal fibres of the V lhe root, which is just 

 preparing its issue from the central system. At its issue they pursue 

 their medial course, now situated dorsally from the sensible and 

 motor V th nucleus. (Plate XIX fig. 25 D). They now bend in 

 longitudinal direction , lying among the longitudinal fibres in the 

 dorsal part of the formatio reticularis half way between the fasc. 

 long. post, and the bracchium conjunctivum cerebelli (Plate XIX 

 fig. 25 G). Slightly approaching the fasc. long, post., they touch 

 its lateral border, and as ari united bundle the (degenerated) fasc. 

 long. post, and that here described (Plate XIX fig. 25 B) pursue 

 their common proximal course. Those degenerated fibres at first 

 remain lateral from the fascic. long. post. , but as the nucleus of 



