644 HANDBOOK OF PHYSIOLOGY. 



poos Varolii), while the superior crura with the valve of Vieussens con- 

 nect it with the cerebrum (5, fig. 387), and the inferior crura (formed 

 by the prolonged restiform bodies) connect it with the medulla oblongata 

 (3, fig. 387). 



Structure. The cerebellum is composed of white and gray matter, 

 the latter being external, like that of the cerebrum, and like it infolded, 

 so that a larger area may be contained in a given space. The convolu- 

 tions of the gray matter, "however, are arranged after a different pattern, 

 as shown in fig. 387. Besides the gray substance on the surface, there 

 is, near the centre of the white substance of each hemisphere, a small 

 capsule of gray matter called the corpus dentatum (fig. 388, a/), resem- 

 bling very closely the corpus dentatum of the olivary body of the medulla 

 oblongata (figs. 362, 388, o). 



Fig. 388. 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. c r, crus 

 cerebri; /, fillet; g, corpora quadrigemina ; s p, superior peduncle of the cerebellum divided; 

 m p, middle peduncle or lateral part of the pons Varolii, with fibres passing from it into the 

 white stem; a i-, continuation of the white stem radiating toward the arbor vitae of the folia; 

 c d, corpus dentatum; o, olivary body with its corpus dentatum; p, anterior pyramid. (Allen 

 Thomson. ) %. 



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 num- 

 ber of peculiar shaped nerve-cells, and very rich plexuses of nerve-fibres. 

 .Recent studies of the cortex of the cerebellum by modern methods have 

 revealed a most complex and beautiful arrangement of the parts, which 

 we shall describe briefly here. 



The molecular layer contains two kinds of cells, one large and known 

 as PurMnje's cell, the other smaller and known as stellate cells. The 

 cells of Purkinje lie along the internal margin of the layer, being, ir 

 fact, practically at the boundary of the molecular and granular layers. 

 They measure 40x30 /*, and have large, round nuclei. Each cell gives 

 off an enormous number of branching dendrites, which run up toward 

 the surface of the cerebellum in the shape of a bush. Each little branch 

 sends off from the side small buds, which are called the gemmules or 

 thorns. These branching dendrites do not pass up altogether like the 

 branches of a round bush, but are flattened like a bush that has been 



