438 



THE INTERMEDIATE PRIMATES 



ticular. The boundary between the tegmentum and basis pontis is provided 

 by the mesial iillct (Mf), while the reticular formation ( Ref) shows no 

 specialization of nuclear collections at this level. 



FIG. 207. GIBBON. LEVEL OF THE EMERGENCE OF THE TROCHLEAR NERVE. 



CEN, Central Gray Matter; ctt. Central Tegmental Tract; lf, Lateral Fillet; mf. Mesial Fillet; mcp, Middle 

 Cerebellar Peduncle; N4, Trochlear Nerve; pd, Predorsal Bundle; PL, Posterior Longitudinal Fasciculus; 

 PN, Pontile Nuclei; pv. Pyramid; ref, Reticular Formation; rst. Rubrospinal Tract; scp, Superior Cerebellar 

 Peduncle; spt. Spinothalamic Tract. [Accession No. 141. Section 250. Actual Size 16X12 mm.] 



level of the emergence of the trochlear or fourth cranial nerve 



(fig. 207) 



Here the appearance of the section has undergone considerable modifi- 

 cation due to the fact that the axis is approaching its mesencephalic portion 



