428 THE INTERMEDIATE PRIMATES 



substantia gelatinosa trigemini (NR), while lateral to it and contiguous 

 with its external surface is the descending trigeminal tract ( Trd ). Occupy- 

 ing the most dorsal position in the lateral field is the cephalic extremity of 



FIG. 201. GIBBON. LEVEL THROUGH THE MIDDLE OF THE INFERIOR OLIVE. 



DO, Dorsal Accessory Olive; dt, Deiterso-spinal Tract; fle, Dorsal Spinocerebellar Tract; cow, Ventral 

 Spinocerebellar Tract; lO, Inferior Olive; iv, Fourth Ventricle; mf. Mesial Fillet; nb, Nucleus of Burdach; 

 NFS, Nucleus Fasciculus Solitarius; nhv. Hypoglossal Nucleus; nr. Nucleus of Rolando; nvd. Dorsal Vagal 

 Nucleus; N12, Twelfth or Hypoglossal Nerve; pd, Predorsal Bundle; PL, Posterior Longitudinal Fasciculus; 

 pv, Pyramid; ref. Reticular Formation; rst. Rubrospinal Tract; spt. Spinothalamic Tract; trd, Descending 

 Trigeminal Tract; vo. Ventral Accessory Olive. (Accession No. 141. Section loi. Actual Size 14 X 10 mm.] 



the nucleus of Blumenau (NBl), fn^n which numerous internal arcuate 

 fibers make their way forward and inward through the reticular formation 

 toward the median raphe, where they undergo decussation and enter the 

 mesial iillet ( Mi ) on their way to higher levels m the brain. 



