578 



THE NERVOUS SYSTEM 



IV. THE CEREBELLUM. 



The cerebellum is a large division of the brain, located just beneath the 

 cerebrum and behind the medulla and pons. It is connected with the rest 

 of the brain by three peduncles on each side: the superior, the middle, and the 

 inferior peduncle, figure 384. 



The cerebellum is composed of white and gray matter, the latter being 

 external as in the cerebrum, and, like it, infolded so that a larger area may be 

 contained in a given space. The convolutions of the gray matter, however, 



FIG. 384. Cerebellum in Section and Fourth Ventricle, with the Neighboring Parts. 

 I, Median groove of fourth ventricle, ending below in the calamus scriptorius, with the 

 longitudinal eminences formed by the fasciculi teretes, one on each side; 2, the same groove, 

 at the place where the white streaks of the auditory nerve emerge from it to cross the floor 

 of the ventricle; 3, inferior crus or peduncle of the cerebellum, formed by the restiform 

 body; 4, posterior pyramid; above this is the calamus scriptorius; 5, superior crus of 

 cerebellum, or processus e cerebello ad cerebrum (or ad testes); 6, 6, fillet to the side of the 

 crura cerebri; 7, 7, lateral grooves of the crura cerebri; 8, corpora quadrigemina. (From 

 Sappey, after Hirschfeld and Leveille.) 



are arranged after a different pattern, as shown in figure 385. Besides the 

 gray substance on the surface, there is, near the center of the white substance 

 of each hemisphere, a small capsule of gray matter called the corpus dentatum, 

 figure 385, resembling very closely the corpus dentatum of the olivary body of 

 the medulla oblongata. 



If a section be taken through the gray matter of the cerebellum, it will be 

 found to be composed of two layers, an outer, or molecular, and an inner, or 

 granular, layer. Each of these layers contains a large number of peculiar- 

 shaped nerve cells and very rich plexuses of nerve fibers. Recent studies 

 of the cortex of the cerebellum by modern methods have revealed a most 

 complex and beautiful arrangement of the parts. 



