THE CENTRAL NERVOUS SYSTEM 



771 



neurons whose axons run in the dorsal cerebellar tract are there- 

 fore the second link in an afferent path. The direct cerebellar 

 tract runs right up to the cerebellum through the restiform body, 

 without crossing and without being further interrupted by nerve- 

 cells. The restiform body ends partly in the dentate nucleus of 



Tl.C 



n.XZT. 



a.m.f. 



FIG. 321. TRANSVERSE SECTION OF ME- 

 DULLA OBLONGATA AT THE LEVEL OF 

 THE DECUSSATION OF THE FILLET (HAL- 

 LIBURTON, AFTER SCHWALBE). 



a.m.f, anterior, and p.m.f, posterior 

 median fissure ; f.a and f.a 2 , external arcu- 

 ate fibres ; f.a', internal arcuate fibres be- 

 coming external ; n.a.r, nuclei of arcuate 

 fibres ; py, pyramid ; o, o' , lower end of 

 nucleus of olive ; f.r, formatio reticularis ; 

 n.l, lateral nucleus ; n.g, nucleus gracilis ; 

 f.g, funiculus gracilis ; n.c, nucleus cuneatus ; 

 n.c', external cuneate nucleus ; f.c, funiculus 

 cuneatus ; g, substance of Rolando ; c.c, 

 central canal surrounded by grey matter ; 

 n.XI, nucleus of spinal accessory ; n.XII, 

 of hypoglossal ; a.V, ascending root of fifth 

 nerve ; s.d, the decussation of the fillet, or 

 superior decussation. 



f.r- 



xir 



FIG. 322. TRANSVERSE SECTION OF ME- 

 DULLA OBLONGATA AT ABOUT THE 

 MIDDLE OF THE OLIVE (HALLIBURTON, 

 AFTER SCHWALBE). 



f.l.a, anterior median fissure ; n.a.r, 

 arcuate nucleus ; p., pyramid ; n.XII, hypo- 

 glossal nucleus ; XII, root bundle of hypo- 

 glossal nerve coming off from the surface ; 

 at b it runs between the pyramid and the 

 dentate nucleus of the olive, o ; f.a.e, ex- 

 ternal arcuate fibres ; n.l, lateral nucleus ; 

 a, arcuate fibres going to restiform body 

 c.r, partly through the substantia gelatinosa 

 g, partly superficial to the ascending root 

 of the fifth nerve a.V ; X, root-bundle of 

 vagus ; n.X, n.X', two portions of vagus 

 nucleus ; f.r, formatio reticularis ; n.g, 

 nucleus gracilis ; n.c, nucleus cuneatus ; 

 n.t, nucleus of the funiculus teres ; n.am, 

 nucleus ambiguus ; r, raphe ; o', o", acces- 

 sory olivary nucleus ; p.o.l, peduncle of the 

 olive. 



the cerebellum, partly in the vermis, and among the fibres which 

 end in the vermis are those of the direct cerebellar tract. In the 

 dorsal cerebellar tract there is a definite stratification of the 

 fibres : the fibres from the lowest segments of the cord lie outer- 



492 



