38 A Reconstruction of the Nuclear Masses in 



the main nuclear form the nucleus of Deiters shows a sharp caudo-lateral 

 angle (figure 3) and a definite border ascending from this. Ventrally a 

 sharp curve takes the cell-collection toward the mid-line. The lateral 

 aspect (figure 2), shows this lateral wall curving sharply mesially and some- 

 what ventrally, to lose its character as the cells pass mesially through the 

 lateral portion of the spinal nucleus. It is not a well-defined area at all and 

 would not be differentiated on morphological grounds. It is merely a 

 curving cap of cells over the lateral aspect of the medial vestibular nucleus. 

 Tracing the cell-mass toward the mid-line, we find only scattered cells for a 

 slight distance mesially, but these larger cells again become somewhat 

 clumped as one approaches nearer the raphe. This increase in size of the 

 cell-mass is represented in the form of the mesial vestibular nucleus by the 

 eminence or smooth elevation on its ventral surface. As they approach the 

 mesial surface of the medial nucleus, these motor cells become somewhat more 

 scattered and the cell-mass curves dorsally to end in the medial nucleus. 

 With such a morphology the nucleus lateralis of the vestibular nerve can 

 not be regarded as more than a group of large cells Ij^ing upon the lateral 

 and ventral surfaces of the medial vestibular nucleus and modifying in 

 slight degree the external morjihology of this chief nucleus. Miss Sabin 

 in the new-born was able to make out a lateral and mesial cell-mass as con- 

 stituting this nucleus of Deiters, but here in the adult the ventro-lateral 

 portion is more developed with the mesial enlargement merely a scattering 

 of the cells in the medial vestibular nucleus. 



NUCLEUS NERVI VESTIBULI SUPERIOR. 



Miss Sabin was unable to model completely the superior nucleus of the 

 vestibular nerve, as some of it was destroyed when the cerebellum was cut 

 from the brain-stem. In general she pictures the nucleus as being a tapering 

 superior extremity of the median vestibular complex, with its medial surface 

 parallel to the raphe. With this morphology this reconstruction of the 

 adult nucleus coincides in the main. The nucleus represents the sujierior 

 j)ortion of the medial and also the spinal nucleus, with the dorsal projections 

 more prominent than the mesial portion beneath the ventricular floor. 

 Cephalad the nucleus ends at the caudal extremity of the main nucleus of 

 the fifth nerve, as shown in figures 2, 3, and 4. Tlic nucleus can best be 

 described by consideration of the various surfaces of the other nuclei which 

 pass into the superior nucleus. 



When viewed dorsally (figure 3), the greater part of the superior nucleus 

 appearing is that which lies just ventral to the brachium conjunctivum. 

 The dorsal surface of this nucleus, underlying the floor, is quickly rendered 

 very narrow by the two lateral deflections of the mesial border of the whole 

 cell-mass the inferior at the caudal limit of the nucleus nervi abducentis 

 and the superior at the corresponding point of the nucleus incertus. This 

 superior angle makes room for the outward coursing fibers of the seventh 



