THE CEREBELLUM. 



297 



what blends. The granule layer contains two varieties of nerve-cells the 

 granule cells and the large stellate cells. 



The granule cells are very small (7-10 /*) and numerous and so closely 

 packed that they confer a distinct density on the stratum, of which they are 

 the chief components. They are provided with from three to six short 

 radiating dendrites that end in peculiar claw-like arborizations (Fig. 344) in 

 relation with other granule cells. Their axones, directed towards the surface, 

 enter the molecular layer, within which they undergo T-division at various 

 levels, corresponding to the depth at which the cells lie. The two resulting 

 branches run horizontally and lengthwise in the folium, that is, parallel to 

 the surface and at right angles to the plane of expansion of the Purkinje 

 dendrites, through whose arborizations they find their way and with which 

 they probably come into close relation. The axones apparently end free 

 and without arborizations. 



The large stellate cells are present in varying number, but are never 

 many. They lie close to the outer limit of the granule layer and possess a 

 cell-body of uncertain and irregular form, from 30-40 fj. in diameter, from 

 which usually several richly branched dendrites pass in different directions, 

 but largely into the molecular layer. The axone is most distinctive, since 

 very soon after leaving the cell-body it splits up into an arborization of 

 unusual extent and complexity, which, however, is confined to the granule 

 layer. These cells, therefore, belong to type II (page 66). Since their 

 processes are brought into intimate relation with a number of other neurones, 

 these elements are probably 

 association cells. Additional 

 nervous elements within the 

 granule layer, few in number 

 and fusiform an outline, are 

 described as the solitary cells, 

 concerning which little is 

 known. 



The cortical nerve- 

 fibres include three chief 

 varieties, (i) The axones of 

 Purkinje cells contribute an 

 inconsiderable portion of the 

 fibres passing between the cer- 

 ebellar cortex and medullary 

 substance. They end, for the 

 most part, in the dentate 

 nucleus within the white core 

 near the root of the superior cerebellar peduncles, some probably terminating 

 in the smaller internal nuclei and, perhaps, in relation with the cells of the 

 vestibular and inferior olivary nuclei. (2) The so-called moss-fibres ^ which 

 ascend from the medullary into the granule layer, within the latter repeatedly 

 branch and bear moss-like tufts that end in large part in irregular small masses 

 of stainable substance, known as the eosin-bodies, that lie between the granule 

 cells (Fig. 345). According to Cajal, these bodies are formed by the intri- 

 cate interlacement of the terminal ramifications of the afferent axones and the 

 dendrites of the granule and, perhaps, also of the axones of the Golgi cells. 

 In view of their convoluted complexity they have been called the glomeruli 

 of the cerebellum: Other filaments of the moss-fibres are continued into 

 the molecular layer, bending horizontally and repeatedly branching. (3) 



Eosin-body 



FIG. 345. Portion of granule layer of young cerebellum, 

 showing eosin-bodies and nerve-fibres. X 220. 



