THE CEREBELLUM. 



it is only separated from its fellow by a narrow septum of white matter, is a rather 

 larger portion of grey substance, which lies in the anterior part of the white centre 

 of the worm, and close to the upper wall of the tent-like projection in the roof of 

 the fourth ventricle. It is termed the nucleus of the roof or nucleus fastigii. 



Fig. 61. HORIZONTAL SECTION THROUGH 



THE WHITE CENTRE OF THE CEREBELLUM, 

 SHOWIKG THE NUCLEI OF GREY MATTER. 



(From Henle, after Stilling. ) f 



The section is taken just over the roof of 

 the fourth ventricle. The nuclei are repre- 

 sented lighter than the white matter in which 

 they are embedded. 



C d, corpus dentatum ; x, nucleus emboli- 

 formis ; y, y, nucleus globosus ; z, nucleus 

 fastigii. Above the two coalesced roof-nuclei 

 are seen some of the fibres of the superior 

 (anterior) decussation, and above these again 

 the laminae and furrows of the lingula (Lg) ; 

 whilst below the roof-nuclei one or two 

 laminae and furrows of the inferior vermiform 

 process are included in the section. Ccq, 

 superior cerebellar peduncle. 



These several portions of grey matter 

 are not entirely isolated, but are 

 connected here and there both with 

 one another and with the dentate 

 nucleus. 



The structure of the corpus den- 

 tatum resembles that of the olivary body. Stellate cells -oVo fc h t -oW-h i ncn 

 (6/ot to 10/t) in size, lie in grey matter which is traversed by bundles of nerve-fibres, 

 passing in various directions but chiefly from without inwards. 



The nucleus emboliformis agrees closely in structure with the nucleus dentatus, to 

 which it seems to bear the same relation as do the accessory olivary nuclei to the 

 chief olivary nucleus. The nucleus fastigii and nucleus globosus differ somewhat in 

 structure from the dentate nucleus, and chiefly in the much larger size of their cells, 

 which, according to Meynert, are very similar to those of the nucleus of Deiters in 

 the medulla oblongata (see p. 56). 



Commissural fibres in the white matter of the cerebellum. Two chief 

 sets of decussating commissural fibres were described by Stilling in the middle line of 

 the cerebellum ; one at the superior part of the worm at the base of the central 

 lobule the superior commissure (fig. 60, com') ; the other at the inferior part 

 (inferior commissure (com") ). Commissural fibres also pierce the nuclei of the 

 roof. In addition to these crossing fibres, which connect the two halves of the 

 white centre, other association fibres connect one lamina with another, passing 

 in the white substance of the laminae across their general direction, and arching 

 round the fissures between the laminas. 



Peduncles of the cerebellum. The cerebellar peduncles are constituted by 

 white fibres which pass out from or into the 'white medullary substance of the 

 hemispheres. 



The superior peduncles (crura ad cerebrum) emerge from the upper and mesial 

 part of the medullary substance of the hemispheres, and run upwards and forwards 

 towards the corpora quadrigemina, under which they eventually pass and thus dis- 

 appear from the surface. They are situated at first at the side, but subsequently in 

 the roof, of the upper part of the fourth ventricle. These peduncles are concealed 

 by the upper part of the cerebellum, so that to see them properly this must be 



