SECT. 115.] 



NERVOUS SYSTEM. 



229 



one more delicate is directed inwards, the thicker outwards. The 

 outer processes have at the root a thickness of crooj"' or o'oo8"', 



Fi-r. 9C. 



Large cells of the grey layer of the cortical substance of the human cerebellum. 



Magnified 350 times. 



and are there very finely granular in substance, or very delicately 

 streaked; but, in their further course, they become more homo- 

 geneous, and, at the same time, ramify in the most varied and 

 beautiful manner, so that at last each process ends in a large tuft 

 of very fine fibrils, the finest of which are scarcely o'ooo2'" in 

 diameter. A part of them penetrate more horizontally into the 

 grey layer; most of them, however, proceed directly outwards, 

 and extend into two-thirds or three-fourths of its thickness. 



In the innermost part of the grey layer, between the large cells, 

 there are also nerve-fibres which become progressively finer, and 

 exchanging their dark contours for paler, diminish in thickness to 

 o - ooo6'" and o'0004'"; finally, running in a more straight direction 

 and isolated, and becoming almost as pale as processes of nerve- 

 cells, thev are lost at the limit between the inner and middle third 

 of the grey layer. All the crura cerebelli consist of parallel 

 nerve-tubes. 



§ 115. Ganglia of the Cerebrum. — All the three pairs of ganglia 

 of the brain, corpora quadrigemina, optic thalami, and corpora 

 striata, consist of large collections of grey substance and of nerve- 

 fibres, of which the former are in part perfectly isolated (corpus 

 striatum), in part connected with each other and with grey parts 

 situate deeper (thalami optici, corpora quadrigemina) ; whilst the 



