MEDULLA OBLONGATA AND TEGMENTUM OF THE PONS. 391 



roots entering the posterior columns, before splitting up in the gray matter, 

 emit fibers posteriorly, the descending root of the acusticus (Roller). A part 

 of the fibers of the nervus vestibularis does not end in the dorsal nucleus, 

 but is distributed to nuclei, as yet insufficiently known, lying between the 

 vermis cerebelli and the medulla oblongata. 



The nucleus dorsalis, nucleus nervi vestibularis, is an elongated body, 

 prismatic on cross-section, which appears in sections lower down, where the 

 anterior vagus root is given oflE (vide Fig. 244). 



Of the other end-stations, at present the most certain is Bfechterew's 

 nucleus, which lies in the lateral wall of the ventricle median to the fibers of 

 the corpus restiforme rising to the cerebellum, and which extends in scat- 

 tered gray clumps upward to near the cerebellum. 



The vestibular nerve has, too, a large number of anatomical relations 

 with other regions of the brain. The nucleus dorsalis is connected with the 

 superior olive by one tract, and with the cerebellum by another issuing 

 laterally. About the cerebellar relations of the vestibular fibers, which 

 extend farther upward above this nucleus, we know, as yet, nothing certain. 



The origins of the acusticus^ which remained long obscure, have been studied 

 in late years by different investigators, who did not all arrive at the same con- 

 clusions as those given here, the results of personal examinations. Freud and the 

 author, working on human embryos, came to practically the same conclusions; 

 Bechterew and Flechsig contend that the anterior root does not come from the dorsal 

 nucleus, but rather from cells in the neighborhood of Deiter's nucleus. The origin 

 of the posterior root in the ventral nucleus is admitted by all. This nucleus becomes 

 atrophic after pulling away the auditory nerve (Forel, Onufrowics, Baginsky). We 

 are indebted to Kolliker for a very exact examination of the entire apparatus. 



Eetzius and Gehuchten have studied the end-branches in the ear, so important 

 to our understanding of the acusticus, and the relations of the ganglion-cells there 

 found. For the finer details as to the arborization in the single nuclei, the directions 

 of Held have been followed; his examination, made priniepally by the use of Golgi's 

 method, based on earlier studies, has recently been corroborated by Bumm in ex- 

 perimental work. 



Lateral from the nucleus acustici dorsalis lies the field of the direct 

 cerebellar sensory tract. From it probably pass fibers to the acusticus. It 

 passes to the cerebellum, occupying at this level the inner division of the 

 restiform lody. In its substance at this point lies a nucleus, of as yet un- 

 known significance, formerly termed the external auditory nucleus. It 

 atrophies when the corresponding half of the cervical cord is cut through 

 (Monakow). Its connection with the auditory nerve is not yet established. 

 For the present it is, perhaps, better to call it Deiter's nucleus, after its dis- 

 coverer, who has rendered such distinguished service in bulbar anatomy. 



In those sections which contain the ventral acusticus center the nucleus 

 of the facial nerve is visible (Fig. 348). It consists of a long row of cells 



