790 



THE NERVOUS SYSTEM 



The biventral lobe is smaller and more curved than the inferior semilunar lobe 

 from the anterior margin of which it is separated by the curved parapyramidal 

 fissure. Its inner extremity is pointed and does not extend to the vermis; its outer 

 extremity is broader and curves anteriorly to the inner and ventral extremity ot the 

 horizontal fissure the line of outer termination of the inferior semilunar lobe 



The tonsil (amygdala) is a rounded, triangular mass, placed mesmlly within 

 the inner curvature of the biventral lobe, and separated from it by the retrotonsillar 

 fissure. Its mesial border slightly overlaps the vermis. 



The smallest of the lobes is the flocculus. It lies adjacent to the inferior and 

 lateral surface of the mass of white substance produced by the confluence of the cere- 

 bellar peduncles, and extends into the inner extremity of the horizontal 1 

 is so flattened that its short folia give it the appearance suggesting its name, 

 casionally there is added a second, less perfectly formed portion, the secondary 

 flocculus From each floccular lobe there passes towards the mid-line a thin band I oi 

 white substance, the peduncle of the flocculus; these extend to meet each other 

 at the most anterior portion of the inferior vermis, and thus form the narrow pos- 

 terior medullary velum. 



FIG. 586. DIAGRAM OF THE DORSAL SURFACE OF THE CEREBELLUM. 



TEGMENTUM 

 FRENULUM VELI 



ALA Of CENTRAL 

 LOBULE 



ANTERIOR SEMI- 

 LUNAR LOXE 



POSTERIOR 



XEM1LINAR 



LOBE 



SUPERIOR 



SEMILUNAR 



LOBE 



HORIZONTAL 

 FISSURE 



INFERIOR 



SEMILUNAR 



LOBE 



CEREBRAL PEDUNCLE 

 SUBSTANTIA N1GRA 



INFERIOR QUADRIGEMIN- 

 A TE MOD Y 



CENTRAL 

 LOBULE 



POSTERIOR CEREBELLAR NOTCH 



CLIVUS OF MONTICULUS 

 \ 



FOLIUM OF VERMIS 



The inferior vermis is more definitely demarcated than the superior. Lying in 

 the floor of the inferior notch, it is separated on each side from the adjacent lobes of 

 the hemispheres by a well-marked sulcus, the vallecula cerebelli. By contour and 

 by deeper transverse fissures (sulci) occurring at intervals across it, four divisions or 

 lobules of the inferior vermis are recognised. These lobules, like those of the su- 

 perior vermis, are each in intimate relation with the pair of lobes of the hemispheres 

 adjacent to it on either side. 



1. The tuber vermis is adjacent to the folium vermis of the dorsal aspect, and 

 thus is the most inferior lobule of the inferior vermis. It is a short, somewhat 

 pyramidal-shaped division, whose four or five transversely arranged folia are con- 

 tinuous with the folia of the inferior crescentic lobes on either side. 



2. The pyramid is separated from the tuber vermis by the post-pyramidal fis- 

 sure. Its several folia cross the vallecula cerebelli and curve to connect with the 

 biventral lobes on either side. 



3. The uvula is separated from the pyramid by the prepyramidal fissure. It 

 is triangular in shape. Its base or broader inferior portion appears as two laterally 

 projecting ridges of grey substance, the furrowed bands, which extend across the 

 floor of the vallecula and under the mesial margins of the tonsils on either side. In 



