326 



THE INTERMEDIATE PRIMATES 



marked at this level, as is also the stratum complexum containing many 

 transverse pontile fibers scattered among which are the bundles of the pyram- 

 idal system ( Py ) and the hirge masses of the pontile nuclei ( PN ). 



FIG. 152. BABOON. LEVEL OF THE INFERIOR COLLICULUS SHOWING ALSO 

 THE EMERGENCE OF THE FOURTH NERVE. 

 CEN, Central Gray Matter; ctt, Central Tegmental Tract; ic, Inferior Colliculus; lf. Lateral Fillet; mf. 

 Mesial Fillet; N4, Trochlear Nerve; pd, Predorsal Bundle; pl. Posterior Longitudinal Fasciculus; pn. Pontile 

 Nuclei; pns. Pons Varolii; py, Pyramid; ref, Reticular Formation; rst, Rubrospinal Tract; scp, Superior 

 Cerebellar Peduncle; spt, Spinothalamic Tract. [Accession No. 150. Section 345. Actual Size 19 X 15 mm.] 



The mesial fillet (Mf) forms the boundary hne between the basal and 

 tegmental portions of the axis. 



