NORMAL HISTOLOGY. 



processes ramify within the outer part of the molecular layer, the 

 axis-cylinder process, after a short course, passes horizontally 

 near the margin of the large-celled layer, and, at various intervals, 

 sends off lateral branches which subdivide to form net-works of 

 fibrils, the fibre-baskets, or basket-works, around the bodies 

 of Purkinje's cells. In addition to the nervous elements, cells 

 belonging to the neuroglia are scattered throughout the zone. As 

 already stated, certain of the nerve-fibres entering the granule zone 

 continue into the outer layer ; these fibres, after penetrating for a 

 short distance, divide into terminal branches, many of which 

 extend horizontally, parallel to the boundaries of the zone, to end 

 free, in close relation but without direct continuity with the 

 nerve-cells. 



In addition to the peripheral cortical layer, the cerebellum possesses 

 other masses of gray matter, the central nuclei, embedded within 

 the medullary substance of the vermiform process and of the adjacent 

 parts of the hemispheres. The central nuclei are two : the nucleus 

 dentatus, situated within the hemisphere of each side, and the 

 nuclei of the roof, within the worm ; the nucleus emboliformis 

 and nucleus globosus, sometimes described as separate centres, are 

 really parts of the complicated dentate nucleus. 



The dentate nucleus consists of a greatly plicated pouch-like 

 sheet of gray substance, .3-. 5 mm. in thickness, situated within the 

 fibre-tract of the superior peduncle of the cerebellum. The nerve- 

 cells contained within the band are of moderate size (25-35 /0 an d 

 pigmented to a variable degree ; the loosely-packed cells possess 

 branched processes extending outward, and an axis-cylinder 

 process directed towards the medulla. Numerous nerve-fibres 

 pass between the cells and connect the white core within the nucleus 

 with the surrounding medullary substance. 



The nuclei of the roof consist of irregularly ovoid areas of gray 

 substance (6-8 mm. in length) situated within the vermiform process, 

 almost in contact along the mesial line. The masses contain large 

 pigmented multipolar ganglion-cells (45-80 mm.) and numerous 

 nerve-fibres, some of which are exceptionally large. 



The medullary or white substance of the cerebellum em- 

 braces the numerous bundles of nerve-fibres which maintain the 

 intricate and far-reaching communications of this division of the 

 brain. The cerebellar fibres are arranged in three principal 

 tracts, the cerebellar peduncles ; the lower of these corre- 

 sponds to the corpus restiforme, the middle to the pedunculi 

 pontis, and the upper to the processus cerebelli ad corpora 

 quadrigemina. 



The fibres of the white matter are disposed in thin flat bundles, 



