Section 5. 

 The Cerebellum. 



The cerebellum is broadly divided into a central body, known 

 as the vermis, or worm, on either side of which are the hemi- 

 spheres. It is situated above and in front of the medulla, and is 

 remarkable for the curious foldings of its grey and white matter, 

 which give it a characteristic appearance on section. The grey 

 matter is placed externally, a reversal of the order found in the 

 cord. The grey matter of the cere- 

 bellum is found to consist micro- 

 scopically of two layers, an outer and 

 inner. In the outer or molecular layer 

 two types of cells are found : one is 

 known as a ' basket cell/ from the 

 peculiar manner in which its axon 

 dips down and encloses the large 

 characteristic cells of Purkinje, which 

 are placed between the outer and 

 inner layer of the cortex (Fig. 142). 

 In the second type of cell found in 

 the outer layer of the cortex the 

 axons run longitudinally to the 

 surface of the cerebellum, giving off 

 collaterals which dip down and ar- 

 borise around the dendrites of the 

 cells of Purkinje. In the inner or 

 granular layer of the cortex the 

 cells are small, their axons travel 

 towards the surface of the cere- 

 bellum, where a T-piece is formed, 

 which, running parallel to the surface, 

 makes connections with the dendrites 

 of the Purkinje and other cells, such 



as those of Golgi's second type, which are also present. Purkinje's 

 cells, as above mentioned, are placed between the two layers 

 of the cortex. They are distinguished by their considerable 

 size and by possessing a single dendrite, which breaks up into a 

 remarkable branching tuft and runs towards the surface of the 

 organ, while the axon passes into the white matter, giving off 

 collaterals (Figs. 143 and 144). 



The white substance of the cerebellum consists of both afferent 



479 



Fig. 142. — Pericellular 

 Baskets (Schafer, after 

 Ramon y Cajal). 



Two cells of Purkinje from the 

 cerebellum are seen sur- 

 rounded by end ramifica- 

 tions forming a basket-work : 

 b, derived from the branch- 

 ing of axons ; a, of small 

 nerve-cells in the molecular 

 layer. 



