THE CEREBELLUM 



199 



2. The biventral lobule, occupying the ventrolateral part of the inferior surface. 



3. The tonsil, a small rounded lobule near the inferior vermis. 



4. The flocculus is the smallest of the lobules; and from it there runs toward 

 the median plane a thin white band, the posterior medullary velum, and the 

 peduncle of the flocculus. 



Structure of the Cerebellum. The cerebellum is composed of a thin super- 

 ficial lamina of gray matter, spread over an irregular white center that con- 

 tains several compact nuclear masses. This white medullary body forms a 

 compact mass in the interior and is continuous from hemisphere to hemisphere 

 through the vermis, within which, however, it is smaller than in the hemi- 

 spheres (Figs. 140, 141). As is most readily seen in sagittal sections through the 

 cerebellum, the medullary body gives off numerous thick laminae, which pro- 



Dentate nucleus 



Central lobule 

 Lingula 



Fissura prima 



Declive 



Folium 



Nodule Uvula 



Fig. 140. Fig. 141. 



Figs. 140 and 141. Sagittal sections of the human cerebellum: Fig. 140 passes through the 

 hemisphere and dentate nucleus; Fig. 141, through the vermis in the median plane. 



ject into the lobules of the cerebellum; and from these there are given off sec- 

 ondary and tertiary laminse at various angles. Thus a very irregular white 

 mass is formed, over the surface of which the much folded cortex is spread in 

 a thin but even layer. Supported by the white laminae, the cortex forms long 

 narrow folds, known as folia, which are separated by sulci and which are aggre- 

 gated into lobules that, in turn, are separated by more or less deep fissures. 

 Sections through the cerebellum at right angles to the long axis of the folia thus 

 present an arborescent appearance to which the name arbor vita has been ap- 

 plied. This is particularly evident in sections through the vermis (Fig. 141). 



MORPHOLOGY OF THE CEREBELLUM 



According to Elliott Smith (1903) and Bolk (1906), who have carried out extensive 

 investigations on the morphology of the mammalian cerebellum, the fissura prima is an 



