VIII 



THE HTND-BEAIN 



421 



of Vieussens, which extends to the corpora quadrigemina and the 

 roof of the aqueduct of Sylvius (Fig. 200). 



Most anatomists distinguish a, verm is or median lobe and two 

 hemispheres, or lateral lobes, in the cerebellum. Bolk (1902), 

 however, on the basis of accurate investigation and patient phylo- 

 genetic comparison of many mammalian cerebella, demonstrated 

 that this organ is divided not in the sagittal but in the transverse 



V.IV. 





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FIG. 220. - Transverse section of pons Varolii through origin of auditory nerve. (Schafer.) From a 

 photograph. Magnified about -1 diameters. J". 1 V., fourth ventricle ; c, white matter of cerebelhir 

 hemisphere ; r.il., corpus dentatvim cerebelli ; //., flocculus ; c.r., corpus restiforme ; R., Roller's 

 ascending auditory bundle; D, Deiters' nucleus ; VIII, issuing root of auditory nerve ; VIII. d., 

 dorsal nucleus; VIII. v., ventral (accessory) nucleus of auditory ; it.ti:, small-celled nucleus 

 traversed by fibres of trapezium ; tr., trapezium ; /., fillet ; ii.l.li., posterior longitudinal bundle ; 

 ./'.;., formatio n-ticularis ; ('.a., ascending root of .5th; s.g., substantia gelatinosa ; s.o., upper 

 olive; VII., issuing root of facial; H.V1I., nucleus of facial; VI., root bundles of abducens ; 

 py., pyramid bundles; n.p., nuclei pontis. 



direction. According to the Dutch anatomist, the cerebellum of 

 mammalia presents one uniform type ; despite any variations from 

 this, there is always a deep primary sulcus which usually extends 

 to the white matter, and divides the cerebellum into an anterior 

 and a posterior part (Fig. 222). 



In man the anterior lobe of Bolk includes the so-called vermis 

 superior (lobulis centralis and lingula), the monticulus and the 

 lobus quadratus anterior. This anterior lobe forms a single un- 

 paired median organ. 



