CEREBELLUM 



429 



Nuclei of small cells of 

 the granular stratum. 



Some of the fibers form bundles parallel with the surface, running be- 

 tween the granular and ganglionic strata in the sagittal direction; they 

 send branches into the gray layer. A small portion of the granular stra- 

 tum is formed by the medullated neuraxons of the cells in the ganglion 

 layer. 



The middle ganglionic stratum consists entirely of a single layer of 

 very large multipolar ganglion cells, called Purkinje's cells. Their oval 

 or pear-shaped bodies send two large dendrites into the gray stratum, 

 where they form an extraordinary arborization (Fig. 442) Their many 

 branches do not extend in all directions but are confined to the sagittal 

 plane, that is, to a plane at right angles with the long axes of the convolu- 

 tions. When the convolutions are cut lengthwise, Purkinje's cells appear 

 as in Fig. 440. The neuraxons arise 

 from the deep surface of the cell bodies, 

 and as medullated fibers they pass 

 through the granular stratum to the 

 white substance. Within the granular 

 layer they produce collateral fibers 

 which branch and in part run back into 

 the ganglionic layer, ending near the 

 bodies of other Purkinje's cells (Fig. 

 442). 



The outer gray stratum, of gray 

 color, contains two sorts of nerve cells, 

 the large and the small cortical cells. 

 The large cortical or basket cells are 

 multipolar ganglion cells, the dendrites of which pass chiefly toward the 

 surface. Their long neuraxons, thin at first but later becoming thicker, 

 run parallel with the surface in the sagittal plane. They send occasional 

 collaterals toward the surface, and at intervals produce fine branches which 

 descend and terminate in baskets around the bodies of Purkinje's cells 

 (Fig. 442), often surrounding also the beginning of their neuraxons. 



The small cortical cells, distinguishable from the basket cells since 

 their neuraxons are not in relation with Purkinje's cells, may be divided 

 into two types, connected by intermediate forms. The cell bodies of the 

 first type are nearly or quite as large as those of the basket cells. Their 

 two to five dendrites lie in the sagittal plane like those of Purkinje's cells; 

 the slender neuraxons, i mm. long or more, sometimes form loops and 

 are characterized by abundant branches in their proximal parts. The 

 terminal branches are few. Cells of the second type are in general some- 

 what smaller; their shorter neuraxons branch in the immediate vicinity 

 of the cell bodies. The elements of the first type form the bulk of the 

 relatively numerous small cortical cells, and are found throughout the 



FIG. 441. FROM A THIN SECTION OF THE 

 CEREBELLUM OF AN ADULT. X 400. 



