OP THE NERVliS OCTAVUS. 65 



usually taught by the authors , controversing the existence of root- 

 fibres in the corporis trapezoides. 



Ordinarily the opinion is defended , that the systema ventrale is 

 composed only by fibres of the secundary system originating in the 

 ventral auditory nucleus and in the nucleus olivaris superior. 



However, the results of the myelinisation are in perfect concor- 

 dance with those taught by the Marchi-degeneration, demonstrating 

 different root-fibres in the systema ventrale. 



Frontal sections through the oblongata of the rabbit , shortly 

 before it is born , and even still the first days after birth may 

 easily demonstrate this concordance. (Plate XII fig. 17 A, B and C). 



And as the structure of the corpus trapezoides in the cat seems 

 the same as in rabbits, frontal sections through the medulla oblon- 

 gata of young born cat may be used likewise (Plate I fig. 5). 

 Sagittal sections may also serve to this demonstration (Plate XIII). 



In new-born animals the two auditory roots are both provided 

 with medullated fibres, though the ventral root more than the dorsal. 

 The systema ventrale is partly myelinisated, partly not. Intermittent 

 strata of medullated and non medullated transversal fibres are found 

 in it. In frontal sections one may distinguish in ventro-dorsal direc- 

 tion four layers. 



Most ventrallv a mighty layer of thick medullated fibres appears 

 (Plate XII tig. 17 B, Plate I fig. 5, Plate XIII fig. 18 F the 

 str. ventr. a.), limited dorsally by a second layer of much smaller, 

 but also medullated and transversal fibres (the stratum b in the 

 figures), among which many non-medullated fibres are found. More 

 dorsally between the nuclei supra-olivares then comes a layer of 

 non-medullated fibres (the stratum c in the figures) and still more 

 dorsally at the boundary a fourth band of medullated small fibres 

 is seen (the stratum d or the fibres of HELD in the figures). The 

 latter fibres seem to unite the dorsal borders of the two nuclei 

 supra-olivares. 



In sagittal sections (Plate XIII fig 18 F) again these four 

 I;i\ers may be seen, but here as strata of queer-sectioned fibres, 

 and in such a way, that between the two ranks of superficial 

 medullated queer-sections and those of HELD , the stratum of non 

 medullated fibres is present. 



There exists a striking resemblance between the frontal section 

 through the oblongata of the new-born rabbit (Plate XII fig. 17 B) 

 and that through the oblongata of the rabbit, treated with Marchi- 

 inethod (Plate IX fig. 15 N. 12 and N. 13) within a fortnight 

 after the rootsection. The medullated fibres in the systema ventrale 



Verhand. Kon. Akad. v. Wetensch. (Tweede Sectie Dl. XIV). 5 



