76 THE CEREBELLUM. 



arbor vitas (fig. 59 A). It can only be seen after the cerebellum is separated from 

 the medulla oblongata and pons, or in a median section, being almost entirely con- 

 cealed by the uvula when the organ is viewed from below. The lateral part of 

 the inferior medullary velum is continued on either side of the nodule as a thin 

 white semilunar band with a thickened concave free lower border (fig. 58 B, v.m.i).- 

 Traced laterally towards the hemisphere, the white lamella becomes thickened and 

 covered with grey matter (pedunculus flocculi), and at length expands into a small 

 irregular lobule lying in the groove between the biventral lobe and the middle 

 peduncle of the cerebellum, and composed of a few short irregular laminas, which 

 tend to diverge from the attachment of the stalk. The nodule, with the inferior 

 medullary velum, the stalk of the flocculus, and the flocculus itself constitute 

 collectively a small but distinct subdivision of the cerebellum (lolus noduli). 



Other small portions of laminated grey matter sometimes 6ccur attached to the flocculus, 

 usually lying between it and the middle peduncle. These have been termed accessomj 

 ftocculi. 



The uvula and tonsils : lobus uvulae. The uvula forms a considerable 

 portion of the lower worm, being elongated from before back ; three considerable 

 secondary laminas, beset with eight or more tertiary folia, appear at the surface. 

 It is least prominent close to the nodule, and from this part it enlarges rapidly 

 downwards and backwards to attain its greatest prominence next to the pyramid. 

 Like the nodule and the pyramid it is purely a median prominence, being separated 

 from the hemispheres by the deep groove (sulcus valleculse) which prolongs the 

 vallecula on either side of this part of the worm. At the bottom of this groove 

 on either side of the uvula is a low corrugated greyish ridge which connects the 

 narrow stalk of the uvula with the stalk of the tonsil : this concealed connecting 

 ridge is known as the furrowed band. From its outer extremity the rounded 

 amygdala projects downwards and backwards into the vallecular groove, concealing 

 the sides of the uvula mesially, and the narrow connection between the pyramid 

 and biventral lobe posteriorly. The uvula, furrowed band and tonsil constitute col- 

 lectively another distinct subdivision of the hemisphere (amygdalo-uvular lobe, lobus 

 uvulcc). The amygdala or tonsil forms a rounded projection of about 10 or 12 

 folia, which run nearly in a sagittal direction, so that in a sagittal section of the 

 cerebellum passing through the tonsil, its branch of the arbor vitas appears expanded 

 and not obviously dendritic (fig. 59 C). Above and in front it has a few transverse 

 laminae which are only seen in sections, being concealed, in the natural position of 

 the parts, by the rest of the projection. Opposite the inferior medullary velum 

 its white matter comes for a certain distance to the surface, covered, of course, by 

 pia mater. The amygdala is lodged in a depression (nidus avis) at the front of the 

 vallecula, which is bounded by the uvula mesially and the biventral lobe laterally ; 

 the surface which rests against the uvula is nearly smooth, as is the corresponding 

 concave surface of the uvula ; a continuation of the postnodular sulcus separates 

 it from the inferior medullary velum. 



The pyramid and biventral lobes : lobus pyramidis. The pyramid forms 

 the most marked prominence of the lower worm, but as seen from the surface, it 

 shows only three or four transverse laminae. It is in reality a long clavate projection 

 attached to the stem of the arbor vitas by a narrow stalk, and it is not only separated 

 from the uvula and tuber valvulas by deep fissures, but also from the hemispheres 

 by the sulcus valleculae on either side of it. Its connection with the biventral lobe 

 of the hemisphere is here maintained by a low narrow ridge, which joins the stalk 

 of the pyramid with the mesial pointed extremity of the biventral lobe. This 

 connecting ridge is evidently analogous with the furrowed band of the preceding 

 lobe, but it is an even less distinct structure. To see it the amygdala must be 



