Central Lobule and Aix, .Lobus Centralis (Figs. 102 and 104).—The lobulus centralis is situated between the precentral and post-central sulci, in the anterior cerebellar notch. It covers the lingula and in turn is overhung by the culmen. Four or five small transverse gyri make it up. On sagittal section, it is seen to form a single branch of the corpus medullare (arbor vita). The gyri of the central lobule, continuing along the anterior cerebellar notch into either hemisphere, form a triangu lar or wing-like lobule, the ala (ala lobuli centralis).
Culmen and Anterior Part of Quadrangular Lobules, Lobus Culminis (Figs. r or and o4).—In the culmen monticuli the surface of the cerebellum reaches its highest elevation. It is a large lobule and occupies half of the tentorial surface of the worm. It is made up of three or four prominent gyri, which extend laterally into the hemispheres; and, in each, forms the anterior part of the quadrangular lobule. The pars anterior lobuli quadrangularis occupies about one-third of the tentorial surface of the hemisphere. The predeclivil sulcus separates the culmen and the pars anterior of either side (the lobe of the culmen) from the declivil lobe.
Declive and Posterior Parts of Quadrangular Lobules, Lobus Declivis (Figs. 'or and r04).—The declive monticuli forms the posterior slope, as the culmen forms the summit, of the mon ticulus cerebelli. The declive has about half the extent of the culmen. Its gyri are continued into either hemisphere, where
they form a large crescentic lobule, the pars posterior lobuli quadrangularis. The increased size of the lobe in the hemisphere is due to the expansion of the secondary gyri found in the worm The anterior and posterior parts of the quadrangular lobule constitute the lobulus quadrangularis which forms the anterior two-thirds of the tentorial surface of the hemisphere. The declive and its hemispheral extensions are inclosed between the predeclivil and post-declivil sulci.
The folium vermis and superior semilunar lobules, lobus folii vermis (Figs. ioi and 1o4), lies behind the post-declivil and above the horizontal sulcus. The folium vermis is the terminal lobule in the superior worm, and occupies the posterior cere bellar notch. It appears near birth in the bottom of a trans verse groove common to the post-declivil and horizontal sulci (Cunningham). Rarely it is absent. It contains a single medullary lamina beset with rudimentary gyri, which are largely developed in the hemispheres. The superior semilunar lobule is, therefore, very large in comparison with the folium vermis. It expands lateralward to the postero-lateral border of the hemisphere, which it forms. It comprises the posterior third of the hemisphere's tentorial surface, and forms one of the remarkable features of the human cerebellum.