CH. XLIV.] 



INTERIOR OF THE BULB. 



635 



nerve (a V) ; the lateral nucleus (n I) (remains of the anterior 

 cornu of the cord) ; the lower part of the grey matter of the 

 olivary body (o, o 1 ), and most anteriorly the pyramid (py). 



Third section. This (fig. 468) is taken at about the middle 

 of the olivary body, and passes also through the lower part of the 

 floor of the fourth ventricle. The central canal has now opened out 

 into the fourth ventricle, and the grey matter on its floor contains 

 the nuclei of the twelfth and tenth nerves ; bundles of the fibres 

 of these nerves course through the substance of the bulb, leaving 

 it at the places indicated in the diagram. 



Fig. 469. Section'acron the pong, about the middle of the fourth ventricle, py., pyramidal 

 bundles ; pn., transverse fibre* passing po t , behind, and po,, in front of py ; r., raphe ; 

 <>.., superior olive; a. I'., bundles of ascending root of V. nerve enclosed in a pro- 

 longation of the substance of Rolando ; (. trapezium ; VI., the sixth nerve, n. VI., its 

 nucleus ; VII., facial nerve; Vll.a., intermediate portion, n.VII., its nucleus; VIII., 

 auditory nerve, n. VIII., lateral nucleus of the auditory. (After Quain.) 



The nucleus gracilis, nucleus cuneatus, and tubercle of Rolando 

 are pushed into a more lateral position ; the restiform body (C.r.) 

 now forms a well-marked prominence, and the olivary body is 

 well seen with its dentate nucleus ; from the open mouth of this 

 corrugated layer of grey matter a large number of fibres issue, 

 and passing through the raphe, course as internal arcuate fibres 

 to the opposite restiform body, and thus to the cerebellum ; some 

 pass to the restiform body of the same side; the continuation of the 

 direct cerebellar tract of the cord also passes into the restiform 

 body. Its fibres terminate by arborisations round Purkinje's cells in 

 the vermis of the cerebellum. The funiculus solitarius and nucleus 



