PITHECUS RHESUS, MACACUS RHESUS 



387 



tion rcMiiiniscL'nt ofits rornicr high speciaHzatiun when, as in the reptiles and 

 birds, it presented fourteen distinet layers of alternating nerve cells and 

 fibers. 



FIG. 182. MACACUS. LEVEL OF THE OPTIC CHLA.S.\L 

 CIN, Internal Capsule; fdp, Descending Pillar of the Fornix; for. Fornix; glp, Globus Pallidus; nli, Nucleus 

 Lateralis Internis Thalami; nlt, Nucleus Lateralis Thalami; nmt, Nucleus Mesialis Thalami; OPX, Optic 

 Decussation; put, Putamen; \y. Fasciculus of Vicq d'Azyr. (Accession No. 149. Section 505. Actual Size 

 30 X 16 mm.] 



The central gray matter (Cen) surrounds the Sylvian aqueduct as 

 it is approaching its cephalic orifice to communicate with the thud ventricle. 

 Its ventral portion is much prolonged by the appearance in it ot an extremely 

 important nuclear body, the nucleus oculomotorious (Noc) of the third 

 cranial nerve from which emerge libers destined for the oculomotor groove. 

 Here they leave the stem en route to supply all of the muscles of the eyeball, 

 both extrinsic and intrinsic, with the exception of the external rectus and 

 the superior oblique. In the midline and connected with this nucleus are a 

 number of fibers crossing from one side to the other. These are the commissu- 

 ral and decussating fibers associating the oculomotor nuclei. Their nnpor- 



