LEMUR MONGOZ 71 



pallidus (GIp). This is one of the most important portions of the end- 

 brain. Being especially concerned with the regulation of automatic associated 

 movements, it constitutes an outstanding division of the basal telencephahc 

 ganglia. Resting upon and dorsal to the globus pallidus is a fairly large mass 

 of myehnatcd nerve fibers representing axons which arise in the motor cortex 

 and descend as the pyramidal system. Associated with these arc the 

 many fibers which form the main part of the pallio-pontile system. The 

 mass of fibers situated between the thalamus and the globus pallidus con- 

 stitutes a portion of the internal capsule (Cin). In contact with the 

 dorsal aspect of the internal capsule is a mass of gray matter surrounded by a 

 considerable capsule of myehnized fibers. This is the corpus hypothalamicum 

 (Cph) which contains the hypothalamic nucleus of Luys and the adja- 

 cent medullary substance comprising the tivo fields of Forel known as Hi and 

 H2. Mesial to the corpus hypothalamicum is the fasciculus of Vicq d' Azyr 

 and ventral to this a bundle of small, weakly staining fibers, the descend- 

 ing pillar of the fornix ( Fdp). 



LEVEL OF THE ANTERIOR COMMISSURE (fIG. 35) 



At the level of the anterior commissure (AC) the section illustrates 

 the cephalic limit of the brain stem, the last remaining structure of which 

 is the anterior portion of the optic thalamus. Other structures of topo- 

 graphical interest at this level are indicated in the caption. 



