334 THE INTERMEDIATE PRIMATES 



LEVEL OF THE OPTIC CHL\SM (fIG. 1 55) 



Here the crossing libers of the optic pathway are the identifying 

 feature (Opx). The optic thalamus appears as another element, which 

 represents the last relay station for all the pathways of sensibihty with 

 the exception of the olfactory sense. In it ends the mesial fillet, and from 

 it start those axons serving to carry the last relay of the somesthetic 

 pathw-ay from the thalamus to the parietal lobes of the cerebral cortex. 

 Dorsal to the optic chiasm are crossing fibers which constitute the supra- 

 optic commissure of Meynert. In a position dorsal to the optic tract 

 (Opt) is a dense mass forming the internal capsule (Cin). Bordering 

 upon these fibers of the capsule is a collection of striated gray and white 

 matter, the lenticular nucleus (Len). This, being one of the most important 

 portions of the endbrain, does not properly belong to the description of the 

 brain stem. The remaining structures of interest in this section are indicated 

 in the legend beneath the figure. 



LEVEL OF THE ANTERIOR COMMISSURE (fIG. 1 56) 



At this level the section illustrates the cephalic limit of the brain stem, 

 the last remaining structure of the anterior portion of the optic thalamus. 

 The structures of topographical interest in this section are indicated by 

 corresponding letters in the legend beneath the figure. 



