The Lower Partidii of the Iluinan Brain-tStciii. 33 



a ventral portion of the nucleus from the dorsal may be made, although it 

 must be realized that the dorsal and ventral nuclei are undoulitedly the 

 same continuous cochlear complex. 



On dorsal view (figure 3) the nucleus shows the cur\ing about the corpus 

 restiforme and the very considerable transverse diameter of the nucleus. 

 The groove suggesting the separation into ventral and dorsal nuclei is here 

 readily seen. The ventral portion of the nucleus on this view shows as a 

 triangular mass on cross-section, with the apex dorsal. This line of the 

 apices lies in about the middle of the ventral mass and continues caudally 

 below the point of origin of the fissure between the two parts of the nucleus. 

 Over the lateral surface of the dorsal nucleus is a rather long and thin strip 

 of nuclear matter similar to that of the nucleus. 



On cephalic view, the most striking feature of the nucleus not shown 

 on the other views is a marked hollowing of the superior surface of the 

 ventral portion. The cephalic line, which shows on lateral view in this 

 ventral j^ortion of the nucleus, abruptly plunges medially into the smooth 

 slope which forms the lateral nuclear wall of this fiber hollowing. The 

 cephalic notch observed on the ventral surface is connected with this hollow- 

 ing and the mesial wall is formed from the medial angle of the notch pro- 

 jecting dorsally and somewhat cephalad. On cephalic inspection also the 

 transverse thickness of the nucleus can be made out. In the dorsal portion, 

 the transverse diameter is about the same as the cephalo-caudal, but in the 

 so-called ventral nucleus this transverse diameter is but two-thirds the 

 cephalo-caudal diameter. The cephalo-caudal diameter of the ventral 

 enlargement of the nucleus is thrice that of the dorsal projection. 



Mesially the nucleus shows a fairly smooth curving outline, conforming 

 to the lateral curve of the corpus restiforme. 



NUCLEUS NERVI VESTIBULI. 



In figure 3 is given the best idea of the general form of the nuclei of the 

 vestibular nerve. The whole nuclear complex is shown more or less as a 

 unit mass, extending from the cephalic limit of the nucleus fasciculi gracilis 

 to the nucleus of the fifth nerve. In this ceplialo-caudal diameter the nucleus 

 of the vestibular nerve measures 14.7 millimeters. Its greatest transverse 

 diameter, occurring on a level with the so-called ventral cochlear nucleus, 

 measures 6.0 millimeters. 



Study of the nuclei of the vestibular nerve has led to the conclusion 

 that the individual cell-collections should really be considered only as parts 

 of the main vestibular complex. ISIiss Sabin, in her reconstruction of the 

 nuclei from the brain-stem of the new-born babe, divided the nuclear matter 

 into two main masses the cell-mass median to the vestibular tract (includ- 

 ing the descending and ascending roots) and the cell-masses lateral and mesial 

 to the tract and main cell-mass (the two composing the nucleus ner\i vesti- 

 buli lateralis). The main cell-mass Miss Sabin then described under the 



