RECONSTRUCTION OF TARSIUS SPECTRUM 143 



liculi, and a small vcntronicsial insinuation which appears between the 

 mesial extremity of the substantia nigra and the interpeduncular gray 

 matter. 



FIG. 66. LATERAL SURFACE OF THE GRAY ALATTER OF THE BRAIN STEM, 

 TARSIUS SPECTRUM. 

 Kev to Diagram, coch. complex, Cochlear Complex; inf. coll.. Inferior Colliculus; interped. gray 

 MATTER, Interpenduncular Gray Matter; mes. gen.. Mesial Geniculate Body; nuc. cun., Nucleus Cuneatus; 

 pontile nuc. Pontile Nuclei; ret. form.. Reticular Formation; sub. gel. trigem.. Substantia Gelatinosa 

 Trigcmini; subst. nig., Substantia Nigra; ven. gray col.. Ventral Gray Column; vestib. comp.. Vestibular 

 Complex. 



On the dorsal aspect of the reconstruction, the reticular formation only 

 appears in the region immediately caudal to the isthmus, at which point its 

 dorsolateral angle is seen between the central gray matter mesially, and the 

 substantia gelatinosa of Rolando laterally. In this region, the reticular for- 

 mation sends dorsally and mesially a thin prolongation which extends around 

 and finally completely surrounds a tunnel which is occupied by the superior 

 cerebellar peduncle. This peduncle in the tarsius is very small, insignificant 

 and occupies a flattened, oval tunnel, directed upward, inward and forward. 

 The superior cerebellar peduncle continues this course through the reticular 

 formation of the mesencephalon, decussating across the midline to end in the 



