SUPERIOR SURFACE OF THE CEREBELLUM The superior surface of the cerebellum (facies cerebelli su perior) is bounded by the horizontal sulcus and the superior lamina of the medullary body (Figs. lox and 104). The posterior and larger part of this surface is covered by the tentorium cerebelli, the tentorial area; the small incisural area bounds the anterior cerebellar notch. The superior surface is divided into five continuous lobes by four crescentic sulci called inter lobular sulci.
Sulci of Upper interlobular sulci (sulci inter lobulares) divide the worm and both hemispheres into lobules; and each lobe is composed of a central and two lateral lobules. These sulci are best seen in a median section of the vermis and are named in accordance with their relations to the lobules in the worm, viz.: i. The precentral sulcus (s..precentralis), which is located in the anterior cerebellar notch just above the superior velum (Fig. 104). It is between the lingula and lobulus centralis, in the worm; between the vinculum and ala, in the hemisphere. It terminates in the horizontal sulcus. When the vinculum is • wanting the precentral sulcus is present only in the vermis.
2. The sulcus (s. post-centralis), in the worm separates the lobulus centralis from the culmen; and in the hemisphere the ala from the anterior part of the quadrangular lobule (Figs. 102 and 104). The sulcus is situated at the upper border of the anterior cerebellar notch and runs just under the anterior border of the tentorial surface of the cerebellar hemi sphere. Both central sulci terminate on the dorsum of the supe rior medullary lamina in the horizontal sulcus.
3. Predeclivil Sulcus (S. prcedeclivis, s. primarius) (Figs. To' and 1o4).—Behind the culmen and anterior part of the quad rangular lobule, 13 mm. from the anterior border of the ten torial surface, there is the predeclivil sulcus. It bounds the declive and posterior part of the quadrangular lobule in front. It ends at the junction of the anterior and middle thirds of the antero-lateral border of the hemisphere in the horizontal sulcus.
Embryologically it is second to appear; it is the deepest sulcus of the cerebellum, hence the name, sulcus primaries, given it by Kuithan. Its development begins near the end of the third
month in utero (Cunningham).
4. The post-declivil sulcus (s. post-declivis) (Figs. 'or and IN.) is located in the posterior cerebellar notch, from which it curves outward and forward in the superior surface of the hemi spheres. It separates the declivil lobe from the folium vermis, in the worm and from the superior semilunar lobules in the hemispheres. It ends in the horizontal sulcus at the junction of the posterior and middle thirds of the antero-lateral border. Being behind the crescentic gyri of the quadrangular lobule, this sulcus may be called the sulcus post-lunatus. It appears a month later than the predeclivil sulcus.
Sulci and lobules of the upper surface of the cerebellum from before backward: Hemisphere Worm Hemisphere Vinculum Lingula Vinculum Precentral sulcus Ala Lobulus centralis Ala Post-central sulcus Lobulus quadrangularis, Culmen monticuli Lobulus quadrangularis, pars pars anterior anterior Predeclivil sulcus Lobulus quadrangularis, Declive monticuli Lobulus quadrangularis, pars pars posterior posterior Post-declivil sulcus Semilunaris superior Folium verniis Semilunaris superior Horizontal sulcus Lobes of Superior Surface (Figs. and 104) .—The lobes of the superior surface of the cerebellum should be studied first in a median section, where the branches of the medullary body (lamince medullares) will guide the student and where the sulci are most easily identified. These lobes include the divisions of the worm and of the hemispheres, and are five in number.
Lingula and Vincula, Lobus Lingula'.—The lingula is a very small lobule of the vermis entirely concealed in the anterior cerebellar notch by the overhanging central lobule. It is a tongue-shaped group of four or five rudimentary transverse gyri. It rests upon the superior medullary velum, with which its white center is continuous. Laterally, the lingula tapers off and is sometimes represented in the hemisphere by a very thin gyrus called the vinculum lingula. The vinculum is bounded by the brachium conjunctivum cerebelli in front, and by the precentral sulcus behind. The precentral sulcus separates the lobe of the lingula from the central lobe.