THE CEREBELLUM. 1085 



the monticulus, is called the culmen i oilmen monticuli). It is formed by a half dozen or more 

 longer and shorter folia that laterally are continuous with a lunate area of the hemisphere known 

 as the anterior crescentic lobule (pars anterior lobuli quadrangularis). The latter is the most 

 anterior division of the upper surface of the hemisphere and is a broad crescentic tract limited 

 behind by the preclival fissure(sulcus superior anterior). The two anterior crescentic lobules and 

 the culmen constitute the lobus culminis. 



Lobus Clivi. The fourth segment of the superior worm slopes rapidly downward from the 

 culmen and receives the name clivus (declive monticuli). It is separated from the preceding part 

 of the worm by a deep cleft, the central part of the preclival sulcus, which on account of its mor- 

 phological importance has been called the fissura prima (Elliot Smith). Laterally the clivus is 

 connected on each side with the posterior crescentic lobule (pars posterior lobuli quadrangularis) 

 which resembles the lobule in front and is separated from the one behind by the postclival 

 fissure (sulcus superior posterior). The clivus and the two posterior crescentic lobules constitute 

 the lobus clivi. 



The two crescentic lobules, the anterior and posterior, are regarded by German anatomists 

 as constituting one tract, the lobulus quadrangularis, of which the crescentic lobes then become 

 the pars anterior and pars posterior respectively. 



Lobus Cacuminis. The fifth and last segment of the superior worm, the folium cacuminis 

 (folium vermis), varies greatly in its details. It consists of a narrow plate that lies between 

 the clivus above and the tuber below and includes usually only one or two, exceptionally 

 as many as five or six, small folia. Sometimes it reaches the level of the adjoining parts of 

 the worm, of which it forms the posterior end ; at other times it is so sunken and buried that 

 its presence can be demonstrated only after separating the clivus and tuber, with either of 

 which it is occasionally joined. At best it is insignificant in comparison with the large 

 crescentic tracts, the postero-superior lobules, that it connects. The postero-superior lobule 

 (lobulus semilunaris posterior) includes the remainder of the upper cerebellar hemisphere of 

 which it forms the most expanded and lateral tract. In front it is separated from the posterior 

 crescentic lobule by the postclival fissure and behind is limited by the great horizontal 

 sulcus, which it overhangs at the side. The folium cacuminis and the two postero-superior 

 lobules constitute the lobus cacuminis. 



LOBES AND FISSURES OF THE LOWER SURFACE. The inferior surface of 

 the cerebellum is modified by a wide depression, the vallecula, in the broader 

 upper half of which the posterior surface of the tapering medulla oblongata is 

 received. The bottom of the valley is occupied by the irregular projection of 

 the inferior worm, which, when the brain-stem is in place, is covered and not 

 seen, except at its posterior third (Fig. 940). After removal of the pons and 

 medulla by cutting through the cerebellar peduncles and the medullary vela, not 

 only the entire inferior worm is exposed, but also the lobulus centralis and its 

 alae are seen to good advantage. The inferior worm is separated on each side 

 from the adjacent surfaces of the cerebellar hemispheres by a groove, the sulcus 

 valleculae, that is deepened in its anterior third by the close apposition of its lateral 

 boundary (the tonsil) with the worm. 



The connections between the divisions of the inferior worm from before back- 

 ward (i) the nodule, (2) the uvula, (3) the pyramid and (4) the tuber and the 

 related parts of the hemisphere are less evident and direct than on the upper surface 

 of the cerebellum. The inferior surface includes four lobules which, from before 

 backward, are: (i) the flocculus, (2) the tonsil, (3) the biventral lobule and (4) the 

 postero-inferior lobule. 



Lobus Noduli. The nodule (nodulus^, the most anterior segment of the inferior worm, 

 varies much in size and form, but frequently appears as a rounded triangular prominence, made 

 up of about a dozen folia, that are limited at the sides by the sulcus valleculse and behind by the 

 postnodular fissure. The relation of the nodule to the inferior medullary velum is somewhat 

 analogous, but less intimate, to that of the lingula to the superior velum. The two structures are 

 more or less extensively united, and the nodule thus excluded from the fourth ventricle by the 

 inferior velum that passes beneath the inferior worm to the apex of the posterior recess of 

 the ventricle (Fig. 938). 



The division of the hemisphere associated with the nodule, the flocculus, lies at some 

 distance from the worm and appears, on either side of the cerebellum, as a wedge-shaped 

 group of short irregular folia that project between the middle cerebellar peduncle and the 

 anterior border of the hemisphere. When well developed it may touch the adjacent margin 

 of the anterior crescentic lobule of the upper surface. In addition to the chief floccules, 



