8o THE LOWER PRIMATES 



The Vestibular Nuclei 



In reconstruction this mass of gray matter first makes its appearance as 

 the large nucleus of Deiters at a point a little above the mid-decussational 

 pyramidal level. It appears as a small, wedge-shaped mass of gray matter 

 located between the upper extremity of the nucleus of Burdach, the nucleus 

 of Goll and the central gray matter. It also j^articipates in the general 

 lateral swing occasioned by the opening of the fourth ventricle and rapidly 

 increases in size. It occupies a position beneath the central gray matter and 

 in relation with the ccphahc extremity of the nucleus of Burdach. In the 

 mid-ventricular region the triangular nucleus of Schwalbe makes its appear- 

 ance mesial to the nucleus of Deiters and in relation with the central gray 

 matter. The nucleus of Deiters gradually dwindles as it extends cepha- 

 lad, wliilc the triangular nucleus is continued upward as a large, irregular 

 mass in the lateral reticular formation dorsal to the substantia gelatinosa 

 trigemini. Dorsally and cephalically the nucleus of von Bechterew appears as 

 a small, indefinite mass of gray matter in the lateral wall of the fourth ven- 

 tricle close to the thin subependymal layer of central graj^ matter. 



The Cochlear Nuclei 



The reconstruction of this nuclear mass shows a large ventral cochlear 

 nucleus which extends for a considerable distance into the lower pontile 

 regions of the brain stem. It is separated from the ventrolateral angle of the 

 tegmentum of the stem by the collected mass of the middle and inferior 

 cerebellar peduncles and the descending trigeminal tract. It is connected with 

 the stem only by the fibers of the cochlear nerve. 



The large dorsal cochlear nucleus is situated at the extreme dorsolateral 

 angle of the tegmentum in the extremity of the lateral angle of the fourth 

 ventricle. It begins below the recess and extends about an ccjual distance 

 above the recess. It is limited in extent by the pontile peduncular fibers but 



