228 NERVOUS SYSTEM. [sect. 114. 



by a practised eye; 2, in the nucleus dentatus, whose greyish-red 

 lamella contains a considerable number of yellowish pigmentatec 

 nerve-cells of medium size (o'oo8'" to <roi6'"), furnished witl 

 from two to five processes, which are not directly connected witl 

 the numerous nerve-fibres passing between them from the white 

 centre of the nucleus dentatus into the white substance of the 

 hemispheres. 



The relations of the grey substance upon the surface of the 

 convolutions of the cerebellum are more complicated (see my 

 Microsc. Anat., tab. iv. fig- 4). That substance, as is well known, 

 consists everywhere of an inner rust-coloured and an outer grey 

 layer, which, except in the furrows, in which the inner layer is 

 generally thicker, are nearly of equal thickness the one with the 

 other, although their absolute thickness is not everywhere the 

 same. 



The inner rust-coloured layer contains nerve-fibres and large 

 collections of free nuclei. The former come from the white sub- 

 stance, and pass directly from within into the rust-coloured layer, 

 generally parallel to each other, although in all the convolutions 

 on a transverse section the fibres spread out in a slight degree like 

 a brush. In this layer, they likevyise run from within outwards, 

 as far as the grey layer, but break up into many, mostly fine 

 bundles, which are variously interwoven with each other. In the 

 meshes of these nerve-fibres are situated immense numbers 

 of dark, round corpuscles, of croc^"^ to o - oo4"', on an average 

 0"003'", in size, which appear to be free cell-nuclei, and very fre- 

 quently present a distinct nucleolus. The nerve-fibres, diminished 

 to o - ooi2'" in diameter, pass out of the rust-coloured layer into 

 the outer grey layer. The latter, although in outward appear- 

 ance everywhere quite uniform, consists of two, but not sharply 

 defined layers, of which the inner contains nerve-fibres and very 

 beautiful large nerve-cells, the outer, on the other hand, presents 

 only a finely -granular, pale, slightly yellowish substance, which, in 

 general, is distributed throughout the whole grey layer, and small 

 nerve-cells with delicate processes. Altogether different from 

 these smaller elements, and, at the same time, very peculiar, are 

 the large cells of the grey layer (fig. 96), discovered by Purkinje. 

 These cells, of o - oi6" to o - o3'" in size, and of a round, pyriform, 

 or ovoid shape, with finely granular, colourless contents, are found 

 only in the innermost parts of the grey layer at the limit of the 

 rust-coloured substance, in a single or double layer, and possess ! 

 usually from 2 to 3 long, variously branched processes, of which 



