OF THE NERVTJS OCTAVUS. 101 



q. The descending root and the transverse dorsal -fibres. 

 The farther course of the sy sterna dorsalis nervi octavi. 



Its ascending tracts and its descending tracts. 

 Its relations with the nuclei of the VI lh , IV th , III d nerve. 



The degenerated descending root may now be traced in its distal 

 course as well in frontal as in horizontal sections. In frontal sections 

 this root is composed by a great many bundles of fibres, separated 

 by grey matter (Plate IV fig. 4). Near its origin it is resting 

 dorsally upon the spinal V th root (Plate VIII fig, 15 N. 7 and 

 N. 8), and in its bundles the degenerated fibres are found. More 

 distally, as the spinal root of the V th nerve takes a more lateral 

 position, the descending radix, recognisable at its degenerate sepa- 

 rated bundles, has not followed the nervus trigeminus. It is now 

 resting upon the dorsal surface of the transparent nucleus nervi 

 vagi (Plate VIII fig. 15 N. 5). But here some degenerated fibres 

 leave the radix descendens, to pursue their way in the fasciculus 

 solitarius N. X, and may be traced far distally (Plate VIII fig. 15. 

 N. 5 N. 1). In horizontal sections (Plate XIV fig. 14 A, 

 Plate X fig. 16 H) in the same way the continuation of degene- 

 rated fibres from the radix descendens after rootsection, into the 

 fasc. solitarius N. vagi may be seen. 



In the transparent nucleus of the N. X, the fibres of the solitary 

 tract are sending scarcely degenerated collaterals, parting from them 

 in a perpendicular direction, in quite the same way as the descending 

 root is giving collaterals to the dorsal nucleus of the VIII th nerve. 



Not long ago VAN GEHUCHTEN has emitted the view, that fibres 

 going from the descending root in the fasc. solitarius N. X, may 

 be fibres from the nervus intermedius WRISBERGII. VAN GEHUCHTEN 

 has torn out the facial nerve with its ganglion geniculi and has 

 concluded that the degenerations found after this lesion were caused 

 by the lesion of the nervus WRISBERGII. 



I can only state that without the least lesion of the facial nerve, 

 the removal of the contents of the labyrinth and if necessary , root- 

 section is performed, and that, in cases of important degeneration 

 of the descending root, always fibres in the solitary tract of the 

 X th nerve are found degenerated also. But the greater part of the 

 fibres of the descending root may be traced distally otherwise. 



As it is seen, on Plate XIV fig. 14 A, the degenerated root-fibres, 

 sending collaterals into the dorsal VIII th nucleus and even directly 

 to the nucleus of the VI th nerve , appear as if ending all in the 



