VIII 



THE HIND-BEAIN 



421 



of Vieussens, which extends to the corpora quadrigemina and the 

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



Most anatomists distinguish a vermis 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 



tft. 



Fio. 220. - Transverse section of pens Varolii through origin of auditory nerve. (Schiifer.) From a 

 photograph. Magnified about 4 diameters. V. I V. , fourth ventricle ; c, white matter of cerebellar 

 hemisphere ; c.rf., corpus dentatum cerebelli ; fl., 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 ; n.tr., small-celled nucleus 

 traversed by fibres of trapezium ; tr., trapezium ; /., fillet ; p.l.b., posterior longitudinal bundle ; 

 /.?-., formatio reticularis ; V.a., ascending root of 5th; s.g., substantia gelatinosa ; s.o., upper- 

 olive; VII., issuing root of facial; n.VIL, 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. 



