414 .JOHN H. STOKES 



presented will be taken up after consideration of the vestibular 

 reconstruction. 



VESTIBULAR APPARATUS 



A reasonably correct understanding of the structure of the 

 central apparatus for the vestibular nerve is a matter of compara- 

 tively recent development, and its conduction relations are only 

 beginning to be elaborated with any very great degree of detail. 

 Especially is this true of the cerebellar relations of the vestibular 

 complex, knowledge of which is still in a rather unsatisfactory 

 state. Enough is definitely known, however, about the apparatus 

 as a whole to serve as guide to its reconstruction. This has 

 been done by Sabin ('01) for the human brain in her general recon- 

 struction of the medulla and mesencephalon of the new-born 

 child. As a guide to the present work the following brief resum^ 

 condensed from Barker's summary of the conclusions of von 

 Bechterew, Flechsig, Baginski, von Monakow, Sala, Held, Cajal 

 and others, and Sabin's description of her model, may be of service. 



With the central vestibular apparatus there are now known 

 to be associated at least four definite nuclei, (1) the medial 

 (Schwalbe's), (2) the lateral (Deiter's), (3) the superior (Bech- 

 terew's) and (4) the nucleus of the spinal root. In relation with 

 these are three large groups of fibers, the ascending and descend- 

 ing roots, and the nucleo-cerebellar tract, the latter containing 

 fibers from various parts of the system, passing to the basal nuclei 

 of the cerebellum. The entering fibers of the vestibular nerve 

 bifurcate at once on gaining the interior of the medulla, the de- 

 scending branches passing downward in the descending limb or 

 spinal root, many of them (according to Cajal, most of them) 

 terminating in this immediate region. All their terminations are 

 not fully known, however. The ascending limb fibers pass up- 

 ward in the medulla in the ascending root, some of them to ter- 

 minate in the superior and lateral vestibular nuclei, others to 

 ascend into the cerebellum to terminate in connection with the 

 nuclei of the roof. Of the nuclei, the medial and lateral and the 

 nucleus of the spinal root are quite well defined and easily recog- 

 nized. The exact limits of the superior nucleus are more doubt- 



