PHYSIOLOGICAL ANATOMY OF THE CEREBELLUM 



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hemispheres are subdivided into smaller lobes, which it is unnecessary 

 to describe. Beneath the cerebellum, bounded in front and below by 

 the bulb and pons Varolii, laterally, by the superior peduncles, and 

 above, by the cerebellum itself, is a lozenge-shaped cavity, called the 

 fourth ventricle. 



The gray substance of the cerebellum is divided quite distinctly 

 into two layers. The external layer is called the molecular layer, and 

 the internal, the granular layer. 



The molecular layer contains the large cells of Purkinje. These 

 send off arborescent dendrites that extend toward the. surface, giving 

 off small telodendrites in their course. The neurites pass downward 



Fig. 149. Section of a cerebellar lamina parallel to its axis (R. y Cajal). 



A, molecular layer; B, granular layer ; C, white substance; a, small stellate cell of the granular 

 layer, with its bifurcating neurite ; b, bifurcation ; e, bulbous end of a neurite ; /, neurite of a cell of 

 Purkinje. 



into the white substance. In passing through the white matter, they 

 give off collaterals, which reascend to the molecular layer. The mo- 

 lecular layer also contains small stellate cells, which give off neurites 

 that send collaterals to form a basket-like arrangement around the cells. 



The granular layer presents small stellate cells which have a few 

 short dendrites and long bifurcating neurites, the latter extending into 

 the molecular layer. This layer also has large stellate cells that send 

 their dendrites into the molecular layer and distribute their neurites 

 in the granular layer. 



The histology of the structures found in the cerebellum is complex ; 

 and its physiological significance is as yet so obscure that it does not 

 seem necessary here to describe it more in detail. 



