144 C. WINKLER. THE CENTRAL COURSE 



aquaeductus, immediately below their ependyma. This nucleus, con- 

 taining cells of middling and small size, may be called, conform 

 to the nomenclature adopted by WALLENBERG, the nucleus parvo- 

 cellularis of the nervus octavus. 



It has the shape of a half moon or of a bean. 



Its convex face, looking dorsally and laterally in distal levels is 

 surrounded by a layer of medullated fibres. From its hilus a new 

 fasciculus issues. 



In distal regions this fasciculus, taking a ventro-medial direction 

 towards the raphe, is small (fig. 26 A, B, C). 



In proximal levels it is an important bundle. 



But there the hilus also changes its position. Opening to the 

 medio-ventral side in distal regions, it soon turns medially, and 

 in the proximal end of the nucleus, the hilus is even found ope- 

 ning dorsally (fig. 26 D and E). 



This new fasciculus forms a part of the systema dorsale nervi 

 octavi, which soon will be discussed. 



Now, as the drawings in fig. 26 demonstrate in a very evident 

 manner, the two degenerated bundles of rootfibres may both be 

 continued in the medullary surroundings of this nucleus. Those 

 surroundings now are completely degenerated at the lateral side of 

 the nucleus and among its cells every- where small black globules 

 are found. In the fasciculus, issued from te hilus and forming 

 a part of the systema dorsale n. octavi, there also are found several 

 degenerate fibres but their discussion will take place in the follo- 

 wing paragraph. At all events there may be spoken of a great contrast. 

 The lateral surroundings of the hilus are intensely degenerated, the 

 hilus itself is so in a far lesser degree. 



Now , the ventral-root-fibres , in order to reach the parvocellular 

 nucleus, must necessarily cross the area, which is found between 

 this nucleus and the place , where they leave the fibres of the infe- 

 rior cerebellar peduncle , perforated by them. 



This area may be called the portio interna of the inferior cere- 

 bellar peduncle and the ventral bundle , crossing it far dorsally 

 from the V lh spinal root, divides it into two unequal parts, a 

 ventral one much more extensive than the dorsal one. (fig. 26 C). 



This area moreover is sharply defined. It is bordered ventrally, 

 by the spinal root of the V th nerve and by a great many trans- 

 verse dorsal fibres, to be discussed afterwards; laterally, by the 

 fibres of the inferior cerebellar peduncle (here perforated by the 

 entering root-fibres of the ventral root) and by the nucleus angu- 

 laris; medially, by the fibres issuing from the nucleus parvocellu- 



