PAPIO CVNOCEPHALUS 



327 



The major changes appear in the tectal portions of tliis section as 

 the inferior collieiili ( IC). These structures are significant because of the 

 relation thej- bear to the sense of hearing. They are primitive receiving 



FIG. 153. BABOON. LEVEL OF THE INFERIOR COLLICULUS. 



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 

 Nucleus; pns. Pons Varolii; py. Pyramid; ref, Reticular Formation; rst. Rubrospinal Tract; spt. Spino- 

 thalamic Tract; SPX, Crossing of Superio- Cerebellar Peduncle. [Accession No. 150. Section 351. Actual Size 

 19 X 15 mm.) 



