298 NORMAL HISTOLOGY. 



The climbing-fibres ascend through the granule to the molecular layer, 

 where their tendril-like ramifications entwine and cling to the principal den- 

 drites of the Purkinje cells. Additional fibres within the granule layer are, 

 evidently, the axones of the granule cells and the collaterals of the cells of 

 Purkinje, whilst a large proportion of the fibres within the molecular layer 

 are the ramifications of the axones of the granule, the basket and the smaller 

 cortical cells. 



The neuroglia forms a supporting framework of considerable density 

 within both the cortex and the medulla. In preparations colored with 

 nuclear stains, the neuroglia cells are conspicuous within the granule layer, 

 to whose numerous small nuclei they materially contribute. A number of 

 relatively large neuroglia cells lie within the outer part of the molecular 

 layer, near the Purkinje cells; in addition to short and irregular centrally 

 directed processes, these elements give off brush-like groups of fibres which 

 penetrate the molecular layer, seldom branching, as far as the surface of the 

 folium, where they end in minute triangular expansions. By the apposition 

 of the latter a delicate subpial condensation, a sort of limiting membrane, is 

 produced. The radial disposition of the neuroglia fibres, as well as of the 

 Purkinje dendrites, climbing fibres and larger blood-vessels, confer upon 

 the molecular layer a vertical striation. Other neuroglia cells, stellate with 

 spider-like radiating fibres, occupy all levels of the molecular layer; similar 

 cells, with more extended processes, occur between the nerve-fibres of the 

 medullary substance. 



The Internal Nuclei. In addition to and unconnected with the 

 cerebellar cortex, four paired masses of gray matter, the internal nuclei 

 one of considerable size and the others small lie embedded within the 

 white matter. 



The nucleus dentatus, or corpus dentatum, the largest and most 

 important of the internal nuclei (Fig. 346), consists of a plicated sac of gray 

 matter, enclosing nerve-fibres, and resembles in many respects the inferior 

 olivary nucleus. It lies within the anterior part of the median half of the 

 hemisphere and measures from 1520 mm. in its longest dimension. 



Of the other paired internal collections of gray matter the nucleus 

 fastigii, the nucleus emboliformis and the nucleus globosus the nucleus 

 fastigii, or the roof-nucleus, is the best defined. It is an egg-shaped mass, 

 about 10 mm. long, and lies within the core of the worm (the tract connecting 

 the hemispheres) close to the mid-line and to its fellow of the opposite side. 



The nucleus emboliformis and the nucleus globosus are irregular 

 masses of gray matter lying between the dentate and roof-nuclei, with which 

 they are respectively united, as well as with each other. 



In structure the internal nuclei differ markedly from the cerebellar 

 cortex, since in the main they are composed of irregularly disposed nerve- 

 cells of one kind, interspersed with nerve-fibres. The dentate nucleus con- 

 tains cells (20-30 /;.), angular or stellate in outline and pigmented. Their 

 processes are usually so disposed that the axones pass into the medullary 

 substance enclosed by the plicated lamina and the dendrites into the sur- 

 rounding white matter of the hemisphere. Numerous fibres enter the 

 dentate body from without, many being the axones of Purkinje cells, and 

 ramify within the folded sheet of gray substance. Since the nuclei emboli- 

 formis and globosus are only incompletely separated parts of the dentate 

 nucleus, their structure corresponds closely with that of the chief mass. 

 The roof-nuclei, on the contrary, possess cells of much larger size (40-80 /-t), 

 more rounded form and greater uniformity in tint, although they are distinctly 



