THE MEDULLA OBLONGATA. 



231 



in its deeper part of a similar reticular formation (figs. 259, 260, f.r.), 

 but with more grey matter and nerve-cells (reticularis grisea, fig. 261, 

 r.g.). Superficially there is developed within it a peculiar wavy lamina 

 of grey matter containing a large number of small nerve- cells ; this is 

 the dentate nucleus of the olivary body (figs. 259, 260, n.d.o.). The lamina 

 is incomplete at its mesial aspect (hilum olivaB, fig. 260, h.o.) } and here 

 a large number of fibres issue, and passing through the raphe course as 

 inner arcuate fibres to the opposite restiform body, and thus to the 



r -ff- XII r.a 



FIG. 261. PART OF THE RETICULAR FORMATION OF THE MEDULLA OBLONGATA 



(Henle.) 



r.a., reticularis alba, without nerve-cells ; r.g., reticularis grisea, with large nerve cells ; 

 between them a root-bundle of the hypoglossus (XII.). The longitudinal fibres of the 

 reticular formation are cut across ; the transversely coursing fibres are internal arcuate 

 fibres, passing on the right of the figure towards the raphe. 



cerebellum. Some, however, turn sharply round and course below the 

 dentate nucleus, forming an investment and capsule to it (siliqua oliw, 

 fig. 260, s.o.), and pass towards the restiform body of the same side. 

 Just dorsal, or dorso-lateral to the olive is the continuation upwards 

 of the antero-lateral ascending tract of the spinal cord ; the continuation 

 of the direct cerebellar tract is now passing into the restiform body. 



