HYLOBATES HOOLOCK. THE GIBBON 431 



LE\EL OF THE VESTIBULAR NUCLEI (FIG. 203) 



At this level the eonliguration of the cross section is altered by the 

 further marked enlarfj;enient of the fourth ventricle. Intricate changes depend 



FIG. 203. GIBBON. LEVEL OF THE VESTIBULAR NUCLEI. 



CTT, Central Tegmental Tract; cow, Ventral Spinocerebellar Tract; hel, Spino-olivary Tract of Helweg; 

 ICP, Inferior Cerebellar Peduncle; 10, Inferior Olive; mf, Mesial Fillet; nd, Deiters' Nucleus; nr, Nucleus of 

 Rolando; NSC, Nucleus of Schwalbe; n8, Auditory Nerve; pd, Predorsal Bundle; pl. Posterior Longitudinal 

 Fasciculus; py, Pyramid; ref. Reticular Formation; rst, Rubrospinal Tract; spt. Spinothalamic Tract; 

 TRD, Descending Trigeminal Tract; tub, Tuberculum Acusticum. [Accession No. 141. Section 141. Actual 

 Size 14 X 7 mm.] 



upon the replacement of the dorsal columns of Goll and Burdacli by the 

 large elements of the vestibular area. The existence of a long proprioceptive 

 column in the alar plate of the oblongata has already been noted. In its 

 more caudal portion this column makes provision for the transmission of 

 proprioceptive stimuli arising in the muscles and joints of the extremities 

 and trunk. The cephalic division of this column serves in a similar capacity 

 for the proprioceptors in the vestibular portion of the internal ear. This 



