308 THE RHOMBENCEPHALON. 



ize and terminate about its cells. Lateral to the principal nucleus 

 are the nucleus of Deilers and the nucleus of the descending root. 

 Deiters's nucleus is spread along the medial surface of the resti- 

 form body, chiefly in the pons. It becomes a distinct nucleus 

 as the lower border of the pons is approached and grows larger 

 for some distance above that point. In the pons it is bent back- 

 ward with the restiform body toward the cerebellum. Its upper 

 end is thus placed in the lateral wall of the fourth ventricle between 

 the restiform body and the brachium conjunctivum. This por- 

 tion is called the superior nucleus (of Bechterew or Flechsig). 

 Deiters's nucleus is made up of cell-bodies which are large in 

 comparison with those of the principal nucleus. It receives the 

 descending fibers of the acustico-cerebellar tract from cerebellar 

 ganglia and cortex and originates axones that proceed down the 

 cord in the anterior descending cerebello-spinal tract, thus form- 

 ing a relay in the cerebello-spinal path; and this is its chief func- 

 tion. It is only a subordinate terminal nucleus of the vestibular 

 nerve. The nucleus of the descending root is, in all probability, 

 a relay station in the conduction path from the vestibular nerve, 

 but not a terminal nucleus of that nerve. It is composed of 

 cell-bodies scattered through a strand of fibers, called the descend- 

 ing root, which extends from the level of the principal nucleus 

 down to the nucleus funiculi cuneati (Bruce). It is placed some- 

 what under cover of the medial border of the restiform body and, 

 with the enveloping descending root, separates this body from 

 the principal nucleus. Certain fibers of the descending root 

 terminate in the nucleus of the same name. 



Cortical Connections. Axones of the terminal nuclei of the 

 vestibular nerve enter the opposite medial fillet and, by way of the 

 descending root, also the nucleus funiculi cuneati. The medial 

 fillet continues the direct path to the thalamus and the cortical 

 fillet completes it up to the temporal cortex. The descending 

 root and the arcuate fibers from the nucleus funiculi cuneati 

 constitute the connecting link between the vestibular nuclei and 

 the cortex of the cerebellum. The reflex connections of the 

 vestibular nerve are established, first, with cerebral nerves, by 

 fibers which join the medial longitudinal bundle and terminate 



