3o6 



THE INTERMEDIATE PRIMATES 



fasciculus of GoII. The functional significance of this disparity in the size of 

 the two columns becomes apparent when the relation of Burdach's tract with 

 the upper extremity, and especially its manual portion, is recalled. 



FIG. 144. BABOON. LEVEL OF THE PYRAMIDAL DECUSSATION. 

 CB, Column of Burdacli; cen. Central Gray Matter; CG, Column of Goll; dt, Deiterso-spinal Tract; fle. 

 Dorsal Spinocerebellar Tract; cow, Ventral Spinocerebellar Tract; hel, Spino-olivary Tract of Helweg; 

 NB, Nucleus of Burdach; ng. Nucleus of Goll; nr. Nucleus of Rolando; py, Pyramid; pyx, Pyramidal 

 Decussation; rst. Rubrospinal Tract; spt, Spinothalamic Tract; trd, Descending Trigeminal Tract; 

 VEN, Ventral Gray Column; xpy. Crossed Pyramidal Tract. [Accession No. 150. Section 5. Actual Size 

 10 X 6 mm.] 



A collection of gray matter forming one of the most conspicuous ele- 

 ments in the dorsal fields at this level is the extensive substantia gelatinosa 

 trigemini (NR) which acts as a relay station for all fibers bearing im- 

 pressions from the trigeminal areas of the face and head. This area of 

 innervation corresponds to the region anterior to the interparietal hne. 



