THE CEREBELLUM. 



69 



THE CEREBELLUM. 



The cerebellum (figs. 55, 56, and 58) consists of two lateral hemispheres joined 

 together by a median portion called, from the peculiar appearance caused by the 

 transverse furrows or ridges upon it, the worm or vermiform process. This is seen 



Fig. 55. INFERIOR SURFACE OF 

 THE CEREBELLUM WITH THE 

 PONS VAROLII AND MEDULLA 

 OBLONGATA. (From Sappey after 

 Hirschfeld and Leveille.) | 



1,1, inferior vermiform pro- 

 cess ; 2, 2, median depression or 

 vallecula ; 3, 3, postero-inferior 

 lobe of the hemisphere ; 4, amyg- 

 dala ; 5, flocculus ; 6, biventral 

 lobe ; 7, pons Varolii ; 8, middle 

 peduncle of the cerebellum ; 9, 

 medulla oblongata ; 10, 11, ante- 

 rior part of the great horizontal 

 fissure; 12, 13, smaller and larger 

 roots of the fifth pair of nerves ; 

 14, sixth pair ; 15, facial nerve ; 

 16, pars intermedia ; 17, auditory 

 nerve ; 18, glosso-pharyngeal ; 

 19, pneumo-gastric ; 20. spinal 

 accessory ; 21, hypoglossal nerve. 



on the under surface in the fossa between the hemispheres as a well-marked pro- 

 jection named the inferior warm, but above forms only a slight elevation, the 

 superior worm. In birds, and in animals lower in the scale, this middle part of the 

 cerebellum alone exists, and in mammals it is the first part to be developed and to be 

 marked off into subdivisions ; moreover, in most mammals it forms a large median 

 lobe very distinct from the hemispheres. 



The cerebellum occupies the posterior fossa of the cranium. Its median portion 

 lies behind the 4th ventricle and behind and below the corpora quadrigemina, to 



Fig. 56. LOWER SURFACE OF THE 



CEREBELLUM WITH THE INFE- 

 RIOR (POSTERIOR) MEDULLARY 

 VELUH. (Allen Thomson after 

 Reil and Reichert, and from 

 nature. ) | 



The medulla oblongata is cut 

 across near the pons Vavolii ; and 

 the latter has been separated 

 somewhat from the cerebellum in 

 order to bring into view the pos- 

 terior medullary velum. To dis- 

 play this better the amygdalae 

 have been removed. 



/ h, horizontal fissure ; p s, 

 postero-superior lobe ; p i and ff, 

 postero-inferior lobe ; g, slender 

 lobe ; b i, biventral lobe ; /, flocculus ; c to n, inferior vermiform process, on which are, c, tuber 

 valvulae, p, pyramid, u, uvula, n, nodule ; p v, on each side, placed on the cut surface where the 

 amygdalae have been removed, points by a line to the lateral part of the inferior (posterior) medullary 

 velum ; its median part is lost under the nodule ; v, v, cavity of the fourth ventricle ; the cavity 

 extends on each side into the lateral recess ; m, cut surface of medulla oblongata ; V, VI, roots of the 

 fifth and sixth cranial nerves. 



which it appears suspended by its superior peduncles. Below and at the sides it 

 receives the inferior peduncles (restiform bodies) from the medulla oblongata, and 



