422 



THE INTERMEDIATE PRIMATES 



what may be called the modern agents of volitional behavior. According as 

 their volume is large or small, they indicate the directing capacity of the 

 cerebral cortex and as such transmit the orders of the supreme motor author- 



FIG. 199. GIBBON. LEVEL OF THE PYRAMIDAL DECUSSATION. 

 CEN, Central Gray Matter; cb, Column of Burdach; CG, Column of Goll; dt, Deiterso-spinal Tract; FLE, 

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

 MR, Nucleus of Rolando; pyx, Pyramidal Decussation; rst, Rubrospinal Tract; spt, Spinothalamic Tract; 

 TRD, Descending Trigeminal Tract; ven. Ventral Gray Matter; xpv. Crossed Pyramidal Tract. [Accession 

 No. 141. Section 5. Actual size 8X7 mm.] 



