THE CEREBELLUM 



887 



lodges the cerebellar falx. separates the hemispheres as these project beyond 

 the inferior vermis. 



The cerebellum is arbitrarily subdivided into a medial segment, the vermis or 

 worm, from its annulated appearance, and two lateral portions, commonly called 

 the cerebellar "hemispheres." The vermis may, according to the aspect in which 

 it is viewed, be divided into the superior vermis or prevermis on the upper or cephalic 

 .surface, and the inferior vermis or postvermis on the inferior or caudal aspect. 

 The superior vermis is hardly distinguished from the adjacent sloping surfaces 

 of the hemispheres; occasionally a slight furrow exists on either side. Ordinarily 

 the term is to be restricted to the high median elevation usually called the mon- 

 ticulus cerebelli. The inferior vermis is more distinctly bounded by a deep fissure, 

 the sulcus valleculae, on each side, separating it from the corresponding lateral 

 hemisphere. 



Among the many fissures which traverse the surface of the cerebellum, one is 

 particularly conspicuous as a deep cleft which may be traced along the dorso- 

 lateral margin from the dorsal notch to the point of entrance of the cerebellar 



Post-nodular fissure. 



Flocculus. 



Pre- 



pyramidal 

 fissure. 



Great 



horizontal 



fissure. 



Post- 

 pyramidal 

 fissure. 



Tuber vtdndt 

 FIG. 652. Under surface of the cerebellur 



(Schiifer.) 





peduncles. This is the peduncular sulcus or great horizontal sulcus (sulcus horizon- 

 talis cerebelli}, and it divides the cerebellum into a cephalic or upper and caudal 

 or lower part. The sulcus is usually quite deep in the hemispheral portion, but 

 it frequently fails to traverse the vermis. Other deep fissures demarcate the lobes 

 or major subdivisions of the intricately convoluted surface of the cerebellum. 

 Conventionally the lobes and fissures or sulci are described upon the " upper" and 

 "lower" surfaces respectively, and this mode of description is partially adhered to 

 here. A better idea of the topographical relations of the lobes and sulci in the 

 vermis and the hemispheres may be gained from a study of the divisions of the 

 cerebellum as if extended in one plane as well as on sagittal sections through 

 the mesal and lateral planes. 



Lobes and Fissures of the Cerebellum. The surface of the cerebellum is traversed 

 by eight more or less curved and deep fissures demarcating nine lobar subdivisions. 

 Distinctive names are given to the portions of each lobe in the hemispheres as 

 contrasted with that in the vermis, although often without warrant, as the two are 

 quite continuous and merit no such distinction. This burdensome nomenclature 

 seems so firmly rooted in descriptive anatomy that the various terms must be 



