36 .4 Reconstruction of the Nuclear Masses in 



lateral border of the median nucleus curves directly laterally for some 

 distance, then abruptly cei)halad. This curving forms a lateral shoulder to 

 the nucleus which approaches the dorsal cochlear cell-mass. Ascending, the 

 lateral border again leaves the mid-line in a beak-like projection into the 

 most lateral portion of the main cell-mass, the nucleus nervi vestibuli lateralis. 

 Higher uj) the lateral margin continues straight cephalad, with a slight mesial 

 slope, into the lateral border of the superior nucleus. Just mesial and 

 somewhat cephalic to the projection constituting the lateral nucleus, the 

 dorsal projection of the nucleus appears. This shows a prominent caudal 

 margin which overhangs the main dorsal surface and curves into a sharp 

 mesial border, receding above (figures 2 and 3). The dorsal projection is 

 marked laterally by a slight ridge which terminates below in a marked dorsal 

 spur. Between these borders is an irregular concavity (corresponding to 

 the outline of the brachium conjunctivum) marked by two fenestrations 

 (figure 3) in the nuclear material, through which large fiber bundles course. 

 Just inferior to the caudal margin of the dorsal elevation is a marked space 

 or hole separating the lateral nucleus from the mesial a space resulting 

 from failure to model the fiber bundles. Mesial to the depressed opening 

 for this fiber bundle is a slight ridge on the mesial cell-mass. 



The mesial surface of the nucleus nervi vestibuli medialis is well-defined 

 and of a marked mesial convexity in the caudal half. In its wider cephalic 

 portion the nuclear surface is poorly defined and is apparently a direct dorso- 

 ventral surface, sharply limited from its dorsal and ventral aspect. The 

 surface is widened considerably at a point on a level with the nucleus nervi 

 vestibuli lateralis, but this widening is gradual and not abrupt. 



The ventral surface is somewhat poorly marked in the caudal portion 

 as the mesial curve is continued upon it. In the cephalic half it is fairly 

 regular except for the elevation corresponding to the widening mentioned 

 as occurring in the mesial surface. The ventral surface looks also mcsially 

 and in its sujierior portion passes directly into the lateral surface, being 

 marked by de])ressions and irregularities along the line of its relationship 

 to the substantia gelatinosa. In the caudal half the ventral surface termi- 

 nates with its junction with the nucleus nervi vestil:)uli spinalis. 



From lateral view (figure 2) the prominent features of (he median 

 vestibular nucleus are the dorsal projections of the cephalic part of the 

 nucleus and the marked overhang (dorso-lateral projection) of the nucleus 

 as it underlies the floor of the entrance to the lateral recess of the foin-th 

 ventricle. The gradual and complete fusion of the four nuclei in the complex 

 is well shown in this view. 



NUCLEUS NERVI VESTIBULI SPINALIS. 



The radix descendens, with its accompaniment of iniclear material, has 

 been modeled throughout its extent, even tliough in the more caudal portions 

 the greater part of the tract was composed of fibers and not of gray matter, 



