400 THE INTERMEDIATE PRIMATES 



The micleus of Deiters' area rapidly increases in size and maintains 

 its position of contact with the subependymal gray matter of the iloor of the 

 fourth ventricle. As the upper hmit of the nucleus of the cohimn of Burdacli 

 is approached, the nucleus of Deiters extends ventrally and laterally, assum- 

 ing the position previously occupied by the nucleus of the cokmm of Burdach 

 and presenting two prolongations — one mesial, closely applied to the lateral 

 surface of the reticular formation, the other lateral and in close proximity to 

 the entering root of the cochlear nerve. In this recess formed by the mesial 

 and lateral prolongations is located the ascending nuclear mass of the sub- 

 stantia gelatinosa trigemini (Rolando). Somewhat above the mid-ventricu- 

 lar level of the stem it rapidly diminishes in size and is superseded by the 

 triangular nucleus, the uLicleus of Schwalbe, belonging to the vestibular 

 complex which has fn"st appeared just below the lateral recess of the fourth 

 ventricle. The triangular nucleus rapidly becomes a comparatively bulky 

 nucleus extending mesially to the base of the lateral wall of the ventricle, 

 and laterally to the dorsolateral angle of the reticular formation. It extends 

 upward almost to the upper limit of the metencephalon and then disappears 

 gradually. The ascending nucleus of the vestibular complex, the nucleus of 

 Bechterew, is contained in the lateral wall of the fourth ventricle and is 

 not of sufiicient bulk to be represented satisfactorily in the reconstruction. 



The Cochlear Complex 



The cochlear complex of nuclei makes its appearance at the upper 

 level of the inferior olivary nucleus as two masses of gray matter form- 

 ing the ventral and dorsal cochlear nuclei. The large ventral cochlear 

 nucleus is located at the extreme ventrolateral angle of the brain stem at 

 the point of entrance of the cochlear nerve into the brain stem. It forms a 

 fairly well-developed trough in which the cochlear nerve lies, covering this 

 nerve on its cephalic, lateral and caudal surfaces. 



