1376 A MANUAL OF ANATOMY 



layer; (5) the fibres of Bergmann, which represent the processes of 

 glia-cells in the granular layer ; (6) the dendrons of the cells of Golgi ; 

 and (7) some fibres from the white medullary substance of the lamina. 



The granular layer consists of (i) nerve- and glia-cells, and 

 (2) fibres. 



The nerve-cells are of two kinds — ^namely, granule-cells and cells 

 of Golgi. 



The granule-cells are small and very numerous. They are 

 closely packed together and impart to this layer a granular appear- 

 ance. Each has several dendrons and one axon. The dendrons 

 soon ramify and the dendritic processes terminate in minute 

 clusters within the granular layer, which are closely related to the 

 granule-cells. The axon of each granule-cell passes into the mole- 

 cular layer, where it ramifies, its branches diverging and being 

 closely related to the dendritic processes of the cells of Purkinje. 



The cells of Golgi lie near the cells of Purkinje, and are larger 

 than the granule-cells. They are stellate, and each has several 

 dendrons and an axon. The dendrons enter the molecular layer, 

 in which they ramify. The axon ramifies very freely in the granular 

 layer. The cells of Golgi may be regarded as association-cells. 



The glia-cells are situated close to the cells of Purkinje, and lie 

 between the outer granule-cells. Their superficial processes enter 

 the molecular layer and constitute the fibres of Bergmann, which 

 pass as far as the pia-matral covering of the lamina. Their deep 

 processes pass between the granule-cells of the granular layer, and 

 some of them enter the white medullary substance. 



The fibres of the granular layer are derived from the following 

 sources: (i) The axons of the cells of Purkinje; (2) the moss-fibres 

 of Cajal; (3) the dendritic processes of the granule-cells; (4) the 

 ramifications of the axons of the cells of Golgi ; (5) some of the deep 

 processes of the glia-cells; and (6) some fibres from the white 

 medullary substance. 



White Matter. — ^The white matter of a cerebellar lamina is an 

 offshoot of the principal white medullary substance, and composed 

 of nerve-fibres, (i) Some of these are the axons of the cells of 

 Purkinje, and these enter the white matter. (2) Others pass 

 through the granular layer into the molecular layer, where they 

 divide into branches which are closely related to the more deeply 

 placed dendritic processes of the cells of Purkinje. (3) A third set 

 terminate in the granular layer, where they divide into branches 

 which present moss-like swellings, furnished with short delicate 

 filaments. These fibres are known as the moss-fibres of Cajal. 



Development ol the Cerebellum. — The cerebellum is developed from the 

 roof-plate of the mctcncephalon, which is the cephalic division of the rhom- 

 bencepalon. 



4. The Fourth Ventricle, 



The fourth ventricle {ventriculus quartus B.) is situated behind 

 (i) the upper or open half of the medulla oblongata or bulb and 

 (2) the pons Varolii. It has two walls — ventral and dorsal. 



