INFERIOR SURFACE OF THE CEREBELLUM. 



253 



cave in the hemispheres. It curves outward and forward around 

 the tonsil, separating it from the biventral lobule. It terminates 

 behind the flocculus in the postnodular sulcus. 



(3) The postpyramidal sulcus (s. postpyramidalis] (Figs 

 79 and 80), between the pyramid and tuber vermis, is near the 

 posterior end of the worm. It forms an oblique groove in either 

 sulcus valleculae, from which three concentric sulci extend into 

 the hemisphere. The anterior of the three (the pregracile), 

 usually considered the postpyramidal sulcus in the hemisphere, 

 separates the biventral lobule from the slender lobule (1. gracilis); 

 the remaining two (midgracile and postgracile) subdivide the 

 slender lobule into anterior and posterior slender, and separate 

 the lobulus gracilis from the inferior semilunar lobule. The 

 last is bounded behind by the horizontal sulcus. 



Sulci and lobules of the lower surface of the cerebellum, from 

 before backward: 



Hemisphere. 

 Flocculus. 



Tonsil. 

 Biventral lobule. 



Slender lobule and infe- 

 rior semilunar lobule. 



Worm. 



Nodule. 



Postnodular sulcus. 

 Uvula. 



Prepyramidal sulcus. 

 Pyramid. 



Postpyramidal sulcus. 

 Tuber vermis. 

 Horizontal sulcus. 



Hemisphere. 



Flocculus. 



Tonsil. 

 Biventral lobule. 



Slender lobule and infe- 

 rior semilunar lobule. 



Lobes of Lower Surface. They are not continuous from the 

 worm to the hemisphere as on the upper surface (Figs. 76 and 80). 

 Excepting in the posterior lobe, only a small ridge beneath the sul- 

 cus valleculae joins the central and lateral lobules together. The 

 inferior lobes are four in number. Each is composed of a central 

 and two lateral lobules as on the upper surface. The lobule in 

 the worm gives its name to the lobe. 



Nodules and Flocculi, LobusNoduli (Figs. 79 and 80). The 

 nodule (nodulus vermis) is a small lobule at the anterior end of 

 the inferior worm. It is composed of three or four gyri, which 

 project from the middle of the dorsal surface of the inferior med- 

 ullary velum. It comprises a single branch of the arbor vitae. 



