732 



THE NERVOUS SYSTEM. 



line, with the apex at the " connecting ridge " just mentioned. Its laminae or subdi- 

 visions, due to its intralobular fissures, are curved, concavity forward and inward, 

 but short, and tend more antero-posteriorly ; hence the lobule is embraced pos- 

 teriorly by the anterior slender lobe and post-pyramidal fissure, both of which are 

 decidedly concave, while the laminae of the former are much longer than those 

 of the digastric lobule. The base is anterior, and is on a line with the ante- 

 rior extremity of the amygdala, and is separated from the flocculus, just in 

 front, by the prolongation of the post-nodular fissure. Mesially the digastric 

 lobule is separated from the amygdala by the prepyramidal fissure, which on 

 the hemisphere runs almost antero-posteriorly, while on the inferior worm it is 

 transverse. 



Uvula and Amygdalae (Fig. 434 and those preceding). The uvula is longer 

 than the pyramid. It is more prominent posteriorly than anteriorly. It has 



Sup. med. vel. 

 Lob. centr. 



cerebel. ped. 



Nodulus Uvula Horizontal fissure 



FIG. 434. The cerebellum from in front and somewhat from below, X . (Gegeiibaur.) 



three or four well-marked transversely running intralobular fissures, clearly seen 

 on antero-posterior section. It is connected Avith the amygdala on each side by 

 means of a corrugated ridge of gray matter, the furrowed band, which lies in the 

 sulcus valleculse. The amygdala or tonsil is a rounded mass smaller than the 

 digastric lobule. It has a large number of intralobular fissures and laminae. 

 These last are short and directed sagittally. Externally is the prepyramidal fis- 

 sure, between it and the digastric. On removal of the amygdala a marked hol- 

 low (Fig. 433) is seen on the mesial side of the digastric. This hollow is the 

 nidus avis (bird's nest). Internally, the amygdala is connected to the uvula by 

 the furrowed band, and besides has a free surface bounded by the sulcus valleculse. 

 In the natural position this surface is applied closely to the side of the uvula, 

 which, together with that of the opposite tonsil, it conceals from view. Ante- 

 riorly is the post-nodular fissure. 



Nodulus and Flocculi (Figs. 426-434). The nodule is the most anterior as 

 well as the smallest lobule of the lower worm. Its cut surface shows a single 

 folium indented by a few intralobular fissures. It is larger than the lingula. 

 Its white matter is usually a single stem, which branches peripherally. This 

 stem, furthermore, like the small projections of white matter in the lingula (see 

 page 729), which are derived from the valve of Vieussens, is seen in its turn to 

 come from a similar, but more curved, lamina of white matter which lies at first 

 ventral and anterior to the nodulus, and then dorsally or over it. This lamina is 

 the inferior medullary velum (see below). The sulcus valleculae on each side of 

 the nodulus is deep and wider than it is posteriorly. 



The post-nodular fissure, transverse between nodule and uvula, becomes irreg- 

 ularly curved on the hemisphere. On leaving the worm it is at first concave for- 

 ward in the sulcus valleculse, then bends, convexity forward, around the front of 

 the amygdala and runs laterally, between the base of the digastric lobe behind 

 and the flocculus in front, to terminate in the great horizontal fissure. In its 

 course it receives the anterior end of the prepyramidal fissure, and at its termi- 

 nation in the horizontal fissure is joined by the anterior end of the post-pyram- 



