THE CENTRAL NERVOUS SYSTEM. 399 



On reaching the inferior olivary bodies, new groups of ele- 

 ments are introduced ; of these the most important is the nucleus 

 of the olive, or corpus dentatum. This consists of a wavy sheet 

 of gray matter so disposed that it forms collectively a compressed 

 ovoid capsule or shell, closed externally, but open towards the 

 median side, through which hilurn the nerve-fibres gain access to 



FIG. 334. 



Section of medulla of child through olivary bodies : a, anterior median groove ; b, raphe ; c, 

 formatio reticularis ; d, gray matter of nucleus dentatus of olive ; e, dorsal accessory olivary body ; 

 f, root-fibres of hypoglossal nerve ; g, nucleus arciformis ; h, external arcuate fibres ; i, anterior 

 pyramidal tract ; k, remains of nucleus lateralis ; /, substantia gelatinosa of Rolando and fibres of 

 ascending trifacial root ; m, n, gray matter of posterior funiculus ; o, funiculus solitarius ; p, nucleus 

 ambiguus ; q, root-fibres of pneumogastric nerve ; r, s, hypoglossal and vagus nuclei ; /, nerve-cells 

 of posterior funiculus ; , posterior medullary velum closing in fourth ventricle, IV. 



the interior. The considerable tract of nerve-fibres entering the 

 hilum constitute the olivary peduncle, having crossed the raphe 

 from the tracts of the opposite side. After gaining the interior of 

 the olivary body, they diverge towards the lamina of gray matter, 

 which they traverse in their course to the restiform body and thence 

 to the cerebellum. These olivary bundles form part of the lateral 

 arcuate fibres, but consist, for the most part, of nerve-fibres of 

 smaller diameter than those composing the internal arcuate fibres. 

 Two additional small areas of gray substance are seen in 



