THE HIND-BRAIN. 



685 



The sides of the notches are formed by the margins of the hemispheres, while the 

 bottom of the notches is formed by the anterior and posterior extremities of the 

 worm respectively. The cerebellum is characterized by its laminated or foliated 

 appearance; it is everywhere marked by deep, transverse, somewhat curved fis- 

 sures, which lie close together, and extend for a considerable depth into the sub- 

 stance of the cerebellum, dividing it into a series of layers or leaves. Upon making 

 sections across the laminae it will be seen that the folia, though differing in appear- 

 ance from the convolutions of the cerebrum, are homologous Avith them, inasmuch 

 as they consist of a central white substance, with a covering or cortex of gray 

 matter. 



The largest and deepest fissure is the great horizontal fissure. It commences 

 in front at the pons, and passes horizontally round the free margin of the hemi- 

 sphere to the middle line behind, and divides the cerebellum into an upper and 



Ala lobuli cent rolls. Post-central Pre-dival fissure. 

 Lobulus centralis. \ \ fissure. 



Great 



horizontal 



fissure. 



Post-cllval fissure. 



FIG. 363. Upper surface of the cerebellum. (Schafer.) 



lower portion. Several secondary but deep fissures separate the cerebellum into 

 lobes, and these are further subdivided by shallower sulci, which separate the indi- 

 vidual folia or laminse from each other. 



The cerebellum is connected to the cerebrum, pons, and medulla by three pairs 

 of peduncles ; which will be described in the sequel ; a superior pair, connect it 

 with the cerebrum ; a middle pair, with the pons ; and an inferior pair, with the 

 medulla. 



Upper Surface of Cerebellum (Fig. 363). The superior surface of the cerebel- 

 lum is somewhat elevated in the middle line and sloped toward its circumference, 

 its hemispheres being connected together by an elevated median portion or lobe, 

 the superior worm or superior vermiform process. The surface is traversed by four 

 curved fissures, which are named from their situation, in front or behind two promi- 

 nent lobes of the worm, the central lobe and the clivus, (1) the pre-central fissure, 



(2) the post-central fissure, (3) the pre-clival fissure, and (4) the post-clival fissure. 

 These four fissures divide the entire upper surface of the cerebellum into five lobes, 

 but the portion of the lobe in the worm has received a different name from that in 

 the hemisphere, though the two are continuous with each other. The five lobes in 

 the worm are named from before backward : (1) the lingula, (.2) the lobulus eentralu, 



(3) the culmen monticuli, (4) the clivus monticuli, and (5) the folium cacuminis. 

 The five lobes in the hemispheres are named from before backward : (1) the/nr?m- 

 lum, (2) the ala lobuli centralis, (3) anterior crescentic, (4) posterior crescentic, and 

 (5) posterior superior. The arrangement of these fissures and lobules will be under- 

 stood by reference to the accompanying schematic arrangement, in which the lob- 

 ules are named in order from before backward with the fissures which separate 

 them : 



