98 C. WINKLER. THE CENTRAL COURSE 



are compared with frontal (Plate I fig. la Plate II fig. 2) sections 

 after cochlea-removal or after root-section (Plate IV fig. 4) or with 

 horizontal sections after rootsection (Plate V fig. 9) treated with 

 MARCH: , the similitude is striking. 



Degenerated fibres are found situated at the place, where medul- 

 lated fibres are seen, normal fibres there, where no myelinisation is 

 found. In this way the dorsal and ventral systems present the same 

 points of similitude. 



Secundary octavus-fibres are not all medullated at birth. Some fibres 

 are not. in the dorsal system these are the middle layer (Plate XII 

 fig. 17 A in /3 , Plate I fig. 5 in /3) and the latero-dorsal part of 

 the portio interna. In the ventral system these are the stratum c 

 in the corpus trapezoides. 



If it were an established fact, that all medullated fibres in the elder 

 foetus were only root-fibres, they should be present in the dorsal 

 as well as in the ventral system in a rather abundant number. In 

 regard to this question I at present only state, that MARCHi-method 

 indeed shows degenerate fibres after rootsection at the same places, 

 where medullated fibres are found, without more. 



Now in the sections through the foetal medulla in this region 

 there still are seen medullated fibres in two not yet described 

 tracts, that may possibly contain rootfibres of the eighth nerve. 



The first is the fasciculus longitudinalis posterior. 



The second medullated bundle passes through or originates in 

 the nucleus of DEITERS, and is known as the vestibulo-spinal tract, 

 or better called - - with LEWANDOSKI - - the tractus DEITERS des- 

 cendens. In frontal sections of rabbit (Plate XII fig. 17 A and B 

 f. DEIT. desc.) and of cat (Plate I fig. 5 in f. DEFT, desc.) it leaves 

 the nucleus of DEITERS, crosses the rootfibres of the nucleus of the 

 VII th nerve, which are forming the genu; afterwards, dorsally from 

 the nucleus of the VII th nerve, it bends into the longitudinal axis of 

 the medulla, deviating slightly medialwards, but always situated 

 laterally from the root-bundles of the XII th nerve, this tractus may 

 be traced into the spinal cord at the ventral border of the anterior 

 and lateral collumns. 



In sagittal sections the tractus DEITERS descendens (Plate XIII 

 fig. 18 E in f. DEIT. desc.), its bending distally into the longitudinal 

 axis of the oblongata, as is passes through the facial root-fibres is 

 demonstrated very clearly. 



Whether rootfibres also may be found in those two tacts will be 

 discussed in the following paragraph. Here they are easily demon- 

 strated as medullated tracts. 



