HYLOBATES HOOLOCK, THE GIBBON 



445 



apparent. The most ventral structure in the cross section is the optic chiasm 

 (Opx) which talces the form observed in all primates, of a lateral elonga- 

 tion, together with the obtuse angulation in relation to the optic nerves and 



FIG. 212. GIBBON. LEVEL OF THE ANTERIOR COMMISSURE. 



AC, Anterior Commissure; ciN, Internal Capsule; fdp, Descending Pillars of the Fornix; for, Fornix; glp. 

 Globus Pallidus; nca. Nucleus Caudatus; nl. Lateral Nucleus of the Thalamus; nm. Nucleus Medialis 

 Thaianii; put, Putamen. [Accession No. 141. Section 486. Actual Size 34 X 10 mm.] 



optic tracts. The supra-optic portion of the third ventricle appears immedi- 

 ately dorsal to the optic chiasm. Flanking either side of the ventricle 

 are the dense masses of the optic thalami, which in turn are separated 

 by the internal capsule (Gin) from the lenticular portion of the stratum. 

 This nucleus presents its two characteristic portions, the mesial and darker 

 area constituting the globus pallidus (Glp) and the outer and lighter 

 portion, the putamen (Put). The evolutional significance of such com- 

 plex elements as the thalamus and the lenticular nucleus could scarcely 

 be approached within the limits of this work. 



