852 MAN 



this nucleus. It is more or less pyramidal in shape, its base being supported 

 by the gray matter forming the floor of the fourtli ventricle while its apex is 

 directed outward ventrolaterallx' and is inserted between the substantia 

 gclatinosa trigemini and the corpus restiforme. 



Tlie nucleus of Deiters definitely appears in the vestiljular area at the 

 lower portion of the fourth ventricle and continues to increase in size until it 

 reaches the mid-ventricular level of the stem. From this point it diminishes 

 and rapidly comes to a termination below the level at which the substantia 

 gclatinosa trigemini disappears within the reticular formation. Prior to its 

 disappearance the nucleus of von Bechterew appears as a dorsal extension of 

 the \estibular area in the lateral wall of the fourth ventricle. 



The nucleus of Schwalbc or the triangular nucleus of the vestibular 

 complex appears as a triangular field lying directly subjacent to the gray 

 matter forming the floor of the fourth \entricle and mesial to the nucleus of 

 Deiters.lt rapidly increases in size, being quite extensive transversely, and 

 bulges forward to come into contact with the dorsal surface of the reticular 

 formation ventrallw Its greatest size corresponds with the maximum devel- 

 opment of the nucleus of Deiters. It then rapidly diminishes in size and 

 entirely disap])ears at the level of the nucleus of von Bechterew. At its acme 

 it occupies the lateral three-fifths of the sube|3endymal portion of the gray 

 matter ol the lloor of the fourth \i'ntricle in the mid-\entncular portion, 

 forming a considerable eminence on the \cntricular floor, the acoustic emi- 

 nence, but its ce|)halo-caudal extent is relati\ely insignificant. Its lowest 

 extremity corresponds with the ui)per \v\v\ of the cochlear nucleus and its 

 upper limit with tlu' nucleus of von Bechterew, thus occupx ing the middle 

 portion of the fourth \entriclc. 



The Cochlear Neceei 

 These nuclei make their appearance at a le\cl slightly below the mid- 

 point of the incdullai\ portion of the fourth \entricle as a collection of 



