808 THE NERVOUS SYSTEM 



to meet each other at the most anterior portion of the inferior vermis, and thus 

 form the narrow posterior medullary velum. 



The inferior vermis (figs. 634, 636) is more definitely demarcated than the 

 superior. Lying in the fioor of the vallecula cerebelli, it is separated on each side 

 from the adjacent lobes of the hemispheres by a well-marked sulcus about it, 

 the nidus avis. 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 superior 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 superior 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 semilunar lobes on either side. 



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

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

 the biventral lobes on either side. 



3. The uvulva is separated from the pyramid by the prepyramidal sulcus. 

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

 laterally projecting ridges of grey substance, the furrowed bands or aloe uvulce, 

 which extend across the floor of the nidus avis and under the mesial margins of the 

 tonsils on either side. In these bands its folia curve and become continuous with 

 the tonsils. The uvula and the two tonsils are sometimes referred to collectively 

 as the uvular lobe. 



4. The nodule is the smallest and most anterior division of the inferior vermis. 

 It is separated from the uvula by the post-nodular sulcus, and is closely associated 

 anteriorly with the posterior medullary velum, the transverse continuation of the 

 peduncles of the floccular lobes. 



Summary of External Features of Cerebellum 

 Superior Surface. 



Hemisphere Vermis 



Anterior border — Anterior medullary velum — Anterior border 

 Vinculum of Lingula Lingula 



Precentral sulcus 

 Ala of central lobule Central lobule 



Post-central sulcus 



Anterior semilunar lobule Culmen 1 



Quadran- I Anterior semilunar fissure I Monticulus 



gular lobe ] Posterior semilunar lobule Declive | 



[ Posterior semilunar fissure J 



Superior semilunar lobe Folium. 



Horizontal Fissure 



Inferior Surface 



Horizontal Fissure 



Inferior ( Posterior slender lobule 1 



semilunar ■{ Posterior-inferior sulcus [ Tuber 



lobe [ Anterior slender lobule j 



Anterior-inferior sulcus Post-pyramidal sulcus 



Biventral lobe Pyramid 



Retro-tonsillar fissure Prepyramidal sulcus 



Tonsil Uvula 



Horizontal Fissure Post-nodular sulcus 



Flocculus Nodule 



Posterior medullary velum 



Internal structure of the cerebellum (fig. 637). — The white substance of the 

 cerebellum is continuous with its peduncles and forms a compact central mass. 

 Over the surface of this the grey substance or cortex is spread in a thin but uniform 

 and much folded layer. Upon section of the cerebellum certain of the sulci as 

 well as the fissures are shown to be much deeper than is apparent from the surface. 

 The deeper sulci separate the lobes into divisions, the medullary laminae, each of 

 which is composed of a number of folia and each of which has its own core of white 

 substance. The folia of tlie lamina' line the sulci (and fissures), and also comprise 

 their surface aspect, and are separated by the shallow, secondary sulci. The larger 



