1 66 



THE LOWER PRIMATES 



functionally more prominent than the hind extremity with its poorly dif- 

 ferentiated foot. This disproportion is less striking than in lemur, for 

 although marmoset makes but limited use of its hand, its tail and hind leg 



FIG. 80. MARMOSET. LEVEL OF THE DORSAL SENSORY NUCLEI. 

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

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

 NB, Nucleus of Burdach; ng, Nucleus of Goll; nr, Nucleus of Rolando; pv, Pyramid, pyx. Pyramidal Decus- 

 sation; REF, Reticular Formation; rst, Rubrospinal Tract; spt. Spinothalamic Tract; trd. Descending 

 Trigeminal Tract; yen, Ventral Gray Matter. [Accession No. 146. Section 8. Actual Size 6X4 mm.] 



manifest as much adaptive significance as in the case of lemur. That the 

 discriminative type of sensibility has a low representation in marmoset, thus 

 providing a meager substratum for the development of its skilled acts, is 

 further substantiated by the fact that the pyramidal tract (Py) is a 



