92 THE CEREBELLUM. 



molecular layer. The cell-origin of the fibres which pass from the white centre 

 into the grey cortex is entirely unknown, but in many cases it is probably situated 

 in the spinal cord (see diagram, fig. 20, p. 23). 



Neuroglia-cells. Lying amongst the nerve-cells of the granule-layer which are 

 nearest the cells of Purkinje, are a number of relatively large cells (fig. 68) giving 

 off dendritic processes which are directed towards the periphery, and which course 

 through the molecular layer as the fibres of Bergmann before mentioned. From the 

 other side of these cells other processes pass off and become lost, partly amongst the 

 granules, partly amongst the fibres of the white centre. These centrally-directed 

 fibres somewhat resemble the axis-cylinder processes of nerve-cells, but the cells in 

 question are usually regarded as glia-cells, belonging, therefore, to the supporting 



Fig. 70. TRANSVERSE SECTION OF THE CEREBELLUM OF A 16-DAY OLD PUPPY, GOLGI'S METHOD. 



(Ram6n y Cajal.) 



A, epithelium-like layer of superficial zone ; B, layer of horizontal bipolar cells ; C, molecular 

 layer ; D, granule-layer. 



a, epithelium-like cell ; b, bipolar horizontal cell ; c, cell sending a process downwards into the 

 molecular layer ; e, f, g, bipolar vertical cells ; h, cell of Purkinje ; i, its nerve-fibre process giving off 

 a collateral towards the molecular layer ; j, n, o, s, fibres from the white substance passing to form 

 plexuses (I, m) which envelop the upper part of the bodies and the proximal part of the dendrites of 

 cells of Purkinje ; r, "moss" fibre. 



tissue of the nerve-centre. The peripherally-directed fibres expand at the surface of 

 the organ immediately underneath the pia mater into small conical enlargements, 

 with their bases directed superficially ; here they form a sort of limiting membrane 

 similar to the internal limiting membrane of the retina, which is formed by the 

 fibres of Miiller. Although many of the neuroglia- cells have this arrangement, 

 others, which are stellate in form, lie more deeply amongst the granules, or amongst 

 the nerve-fibres of the medullary centre. 



In the embryonic cerebellum and in most animals for a few days after birth, there is a 

 layer of granule-like cells, several deep, superficial to the molecular layer. This has been 

 termed by B,am6n y Cajal, the zone of superficial granules, and he has shown that it is formed 

 at a certain stage of development of two distinct strata, one the more superficial composed 

 of epithelium-like elements set perpendicularly to the surface, and the other next to the 

 molecular layer composed of bipolar cells placed parallel to the surface, and to the direction 



