444 THE INTERMEDIATE PRIMATES 



cephalon from the tegmentum. The specific functions of the substantia 

 nigra arc yet surrounded by doubt, although many writers attribute to it 

 some regulating control of the automatic associated movements of the body. 



FIG. 211. GIBBON. LEVEL OF THE OPTIC CHIASM. 

 CIN, Internal Capsule; cph, Corpus Hypotlialamiciim; fdp, Descending Pillars of the Fornix; for, Fornix; 

 GLP, Globus Pallidus; nl, Lateral Nucleus of the Thalamus; nli, Internal Lateral Nucleus of the Thalamus; 

 opx. Optic Chiasm; put, Putamen. (Accession No. 141. Section 440. Actual Size 34 X 19 mm.] 



This opinion is in part conjectural, although the structure as a whole has the 

 appearance of a very important element in the brain stem. 



LEVEL OF THE OPTIC CHIASM (fIG. 21 I ) 



At this level the configuration of the section again shows those marked 

 alterations due to the fact that the brain stem is about to reach its cephalic 

 termination. Some of the massive lateral additions of the endbrain are ah-eady 



