THE CENTRAL NERVOUS SYSTEM. 



299 



their loops the anterior pyramids and the olivary bodies. The 

 nerve-cells are not uniformly distributed within the gray matter 

 of the reticulum, since in the ventral portion of the medulla 

 the cells are very sparingly distributed, or even wanting, while 

 in the lateral area, where the remains of the anterior cornu are 

 found, the nerve-cells are numerous and of large size. 



On reaching the level of the 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 band 

 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 hilus the nerve-fibres gain access to 



FIG. 334. 



Section of medulla of child through olivary bodies : a, anterior median groove ; b, raph ; 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; /, 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 ; t, nerve-cells 

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



the interior of the nucleus. The wavy zone of gray matter is 

 composed of neuroglia, in which lie numerous small multipolar 

 ganglion-cells. 



Two additional small areas of gray substance are seen in 



