PITHECUS RHESUS, MACACUS RHESUS 3-3 



fourth ventricle and the appearance of the hiteral recesses. Among the 

 intrinsic modifications of the axis at this level is a group of nuclei connected 

 with the internal ear, serving as relays for impulses concerned with the special 



FIG. 175. MACACUS. Il\ll i)i THE \EST1BULAR NUCLEI. 

 DT, Deiterso-spinal Tract; GOw, Ventral Spinucerebellar Tract; icp, Inferior Cerebellar Peduncle; lo, 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; pv. Pyramid; ref. Reticular 

 Formation; rst, Rubrospinal Tract; spt. Spinothalamic Tract; trd. Descending Trigeminal Tract; TLB, 

 Tuberculum Acusticum. (Accession No. 149. Section 185. Actual Size 17X7 mm.| 



sense of hearing as well as with the balancing mechanism. Situated immedi- 

 ately beneath the floor of the fourth ventricle, underlying the ependymal 

 gray matter, is a large triangular nucleus of small cells, the nucleus of 

 Schwalbe (NSc), and lateral to this a nucleus containing many large 

 cells, the nucleus magnocellularis of Deiters (ND). Dispersed among 

 the cells of the latter nucleus are many small bundles of heavily mye- 

 linated axons. These two nuclei constitute the vestibular complex. They 

 have assumed, in a general way, the positions occupied in the lower levels 

 by the nuclei of Goll and Burdach. In the topographical relation of these 



