RECONSTRUCTION OF PAPIO CVNOCEPHALUS 



341 



In the lower mescneephalic areas this process has continued so far that 

 the central mass of the reticular formation gradually disappears and its mass 

 assumes a much greater expansion. In this region of the mesencephalon the 



FIG. I5Q. VENTRAL SURFACE OF THE GRAY MATTER OF THE BRAIN STEM, 

 PAPIO CVNOCEPHALUS. 



Key to Diagram, inf. olive, Inferior Olive; lat. gen. body. Lateral Geniculate Body; meso-gen. body. 

 Mesial Geniculate Body; nucl. of burd., Nucleus of Burdach; pontile. Pontile Nuclei; ret. form.. Reticu- 

 lar Formation; subst. gel. rol. and subst. gel. rolando, Substantia Gelatinosa of Rolando; subst. 

 nigra. Substantia Nigra; vent, cochlear. Ventral Cochlear Nucleus; vent, gray col., Ventral Gray 

 Column, 



reticular formation now gives place to a specialization forming the large 

 nucleus ruber which is surrounded by a capsule derived from the superior 

 cerebellar peduncle and descending striato-rubral fibers. The lateral mass of 

 the reticular formation follows closely the course of the superior cerebellar 

 peduncle as this structure approaches the nucleus ruber. Above the level of 

 the red nucleus the reticular formation again reaches the midline and its most 

 central portion assumes its original position and importance. It is separated 

 from the central gray matter by the longitudinally coursing median bundles 



