146 C. WINKLER. THE CENTRAL COURSE 



fibres, most of them from the ventral, a few from the dorsal root. 



In NISSI/S or in carmin-preparations of this region, or in other 

 preparations with succesful staining of the nerve-cells, it may be 

 demonstrated, that in this area nerve-cells are very numerous. 

 Cells of middling size are found along the fibres perforating the 

 inferior cerebellar peduncle. Cells of small, of middling and even 

 of large size are also found between the longitudinal fibres of 

 this area. 



Now Marchi-preparations after removal of the labyrinth show, 

 that many of those descending fibres degenerate. In great number 

 they are found there, where the ventral root enters (fig. 26 D). 

 In more distal sections they seem to be gathered in two distinct 

 area's, the one is found more laterally, the other more medially 

 (fig. 26 C and B). The lateral field of degenerated descending 

 fibres, if traced distally, disappears at the beginning of the nucleus 

 N. X. A great many descending fibres apparently remain in the 

 area itself, and after a descendent course of relative short duration 

 end between the cells found there (fig. 26 C). 



The more medial field of degenerated descending fibres may be 

 traced far more distally. From those fibres also several remain in 

 the area, but during their descendent course, they pass along the 

 nucleus of the VI th nerve, sending fibres into it, and when the 

 nucleus of the X th nerve appears, these fibres, situated dorso-laterally 

 from it (fig. 26 A) are giving fibres to this nucleus too. They have 

 disappeared, when the latter is no longer seen. 



These all are descending root-fibres. 



But in tracing the ventral bundle of degenerate root-fibres in 

 proximal regions, we find, that a part of them do not follow the 

 straight medial path, but slightly bend proximally to form ascending 

 degenerated fibres (fig. 26 D and E). 



The ventral bundle , by which the portio interna was divided 

 in two area's, the dorsal one being by far the smallest, and chiefly 

 occupated by the magno-cellular nucleus, now divides. In its dorsal 

 part, ventro-late rally of the nucleus magno-cellularis, a great many 

 ascending degenerated fibres are found in proximal regions, but 

 fibres going medially to the nucleus parvo-cellularis also exist here. 



In this way the ventral bundle divides itself in three distinct 

 portions of rootfibres. 



There are l ly descending rootfibres. Most of these remain in the 

 here described area among the cells found there. Other fibres go 

 medialward to aid in the formation of transverse dorsal fibres , and 

 provide the nucleus N. VI and that of the X (fig. 26 A C). 



