418 JOHN H. STOKES 



Finally, in studying the figures of the models, the following 

 points should be remembered: (1) certain connections of a minor 

 nature or requiring special consideration are dealt with in discus- 

 sing the typical sections shown ; (2) all of the vestibular above the 

 level of Deiter's may be regarded as in the cerebellum, not the 

 medulla; (3) the view of the apparatus from above (fig. 4) repre- 

 sents it with a piece cut from the nucleo-cerebellar tract in order 

 to give a better conception of the position and relation of Deiter's 

 nucleus, and the connection between its two apparently separate 

 parts. 



Passing now to the detailed description of the vestibular system 

 as reconstructed for the opossum, the N. vestibularis appears as a 

 fiber bundle of somewhat smaller size than the N. cochlearis, 

 the root being composed of a number of separate fasciculi, 

 easily demonstrated in careful examination of the gross specimen, 

 in contrast to the single sohd bundle of fibers presented by the 

 cochlear root before it reaches the lateral surface of the medulla. 

 The vestibular root enters just anterior to the cochlear, at a 

 slightly sharper angle, some of its strands underlying those of the 

 latter nerve. The restiform body passes up into the cerebellum 

 so far posterior as to lie entirely above the level of entrance of 

 the vestibular nerve, and so forms no part of the picture in this 

 inmiediate area. As soon as the root has pierced the corpus 

 trapezoideum, bifurcation into ascending and descending roots 

 occurs. This bifurcation takes place in a region rather closely 

 confined by surrounding structures. Laterally the larger part of 

 the root and its divisions is overlaid by the anterior part of the 

 ventral cochlear nucleus. The root of the seventh nerve is closely 

 applied to the anterior and lower border of the vestibular, the 

 ascending root of the latter passing into the superior nucleus and 

 the cerebellum above the anterior limb of the genu. Just medial 

 to the point of bifurcation the olivo-cochlear tract passes down- 

 ward through the medial vestibular nucleus to the superior olive. 

 In the same way the cerebellar part of the ascending tract is sur- 

 rounded medially, posteriorly and postero-laterally by the cochlear 

 nuclei and on its antero-lateral aspect bears a shallow depression 

 in which lies the corpus restiforme. Just as the dorsal cochlear 



