562 THE NERVOUS SYSTEM 



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 393, 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 of the cerebellum. 



The General Structure of the Cerebellum. The molecular layer 

 of the cerebellum contains several peculiar types of nerve cells, of which may be 



FIG. 393. Outline Sketch of a Section of the Cerebellum, Showing the Corpus Dentatum. The 

 section has been carried through the left lateral part of the pons, so as to divide the superior pe- 

 duncle and pass nearly through the middle of the left cerebellar hemisphere. The olivary body 

 has also been divided longitudinally so as to expose in section its corpus dentatum. cr, Crus cerebri ; 

 f, fillet; q, corpora quadrigemina; sp, superior peduncle of the cerebellum, divided; mp, middle 

 peduncle or lateral part of the pons Varolii, with fibers passing from it into the white stem; av, 

 continuation of the white stem radiating toward the arbor vitae of the folia; o, olivary body with 

 its corpus dentatum; p, anterior pyramid. (Allen Thomson.) 



specially mentioned Purkinje's cells and the basket cells. The cells of Pur- 

 kinje lie along the internal margin of the layer, being, in fact, practically 

 at the boundary of the molecular and granular layers. They measure 40 to 60 // 

 in diameter, and have large, round nuclei. Each cell gives off an enormous 

 number of branching dendrites, which run up toward the surface of the cere- 

 bellum in the shape of a bush. 



The cells of Purkinje give off at their deeper surface an axone which 

 runs down into the white matter of the cerebellum. 



Lying in the molecular layer, somewhat external to the Purkinje cells, 

 are the cells of the type known as basket cells. These cells have a number of 

 dendrites, also send out an axone which runs parallel to the surf ace of the cortex, 

 which gives off numerous collaterals in its course that form baskets around 

 the cell bodies of the Purkinje cells, figure 394, ZK. 



