332 THE INTERMEDIATE PRIMATES 



which has been attributed the regulation, in part at least, of certain auto- 

 matic associated movements. Immediately dorsal to the substantia nigra 

 is the mesial iillet (Mf). In a position in front of the oculomotor nucleus 



FIG. 155. BABOON. LEVEL OF THE OPTIC CHIASM. 



ciN, Internal Capsule; cph, Corpus Hypothalamicum; fdp. Descending Pillar of Fornix; for, Fornix; len, 

 Lenticular Nucleus; nl, Lateral Nucleus of the Thalamus; nli. Nucleus Thalami Lateralis Internus; nm. 

 Nucleus Medialis Thalami; opx, Optic Chiasm; opt, Optic Tract; vo. Fasciculus of Vicq D'Azyr; V3, Third 

 Ventricle. [Accession No. 150. Section 525. Actual Size 33 X 21 mm.) 



are two systems of decussating fibers, one, the dorsal decussation of Mey- 

 nert through which the emergent fibers of the third nerve make their way 

 toward the surface, and ventral to this is the \entral decussation of Forel. 

 These decussations represent respectively the crossing fibers arising in the 



