INTERNAL STRUCTURE OF THE PONS VAROLII. 



59 



The inner or deep arched fibres emerge from the raphe, and traverse the thickness 

 of the bulb, tending towards the olives, the restiform body, and the nuclei of the 

 cuneate and slender f uniculi. Those which pass through and in front of the olives 

 are in continuity with the superficial arched fibres. 



Traced backwards into the raphe, the deep arched fibres cross obliquely to the 

 other side of the medulla, where some become longitudinal, joining the fibres of the 

 fillet. Others are the fine fibres before alluded to as connecting the cerebellar 

 hemisphere with the opposite olive. 



Fig. 49. TRANSVERSE SECTION OP PONS VAROLII THROUGH THE ORIGIN OF THE AUDITORY NEKVE. 

 (E.A.S.) (From a photograph. ) Magnified about 4 diameters. / 



v.IV. , 4th ventricle ; c., white matter of cerebellar hemisphere ; c.d., corpus dentatum cerebelli ; 

 /. , flocculus ; c. r. , corpus restiforme ; E, Holler's ascending auditory bundle ; I), Deiter's nucleus ; 

 VIII, issuing root of auditory nerve ; VIII. d., dorsal nucleus ; VIII.v., ventral (accessory) nucleus 

 of auditory; n.tr., small-celled nucleus traversed by fibres of the trapezium; tr., trapezium;/., 

 fillet ; p.l.b., posterior longitudinal bundle ; f.r., formatio reticulario ; n, n', n", nuclei in formatio 

 reticularis ; V.a., ascending root of 5th; s.ff., substantia gelatinosa ; s.o., upper olive; VII, issuing 

 root of facial ; n. VII., nucleus of facial ; VI, root bundles of abducens ; py., pyramid bundles ; n.p. , 

 nuclei pontis. 



Nuclei of the superficial arched fibres. Amongst the superficial arched 

 fibres, or between them and the subjacent columns of the bulb, small collections 

 of grey matter with nerve-cells are here and there met with, which are distinguished 

 by the above name. The principal group of cells lies superficial to the pyramid on 

 either side (figs. 44, 46, n.ar.). This group becomes very largely developed at the 

 junction of the medulla oblongata with the pons Varolii. 



The raphe or septum (fig. 44, r) is composed of fibres which run in part dorso- 

 ventrally (fibras rectse), in part longitudinally, and in part across the septum more 

 or less obliquely. Intermixed with the nerve-fibres are a number of nerve-cells in 

 grey matter. The fibrse rectae are continuous ventrally with the superficial arched 

 fibres, which emerge at the anterior median fissure ; dorsally in the upper part of the 

 bulb with fibres from the medullary strise (cf. p. 50). The longitudinal are chiefly 



