STRUCTURE OF THE CEREBELLUM. 



463 



fibres (softness, proneness to become varicose, easy isolation of the 

 axis-fibre, &c.); and do not require a special description. They 

 average g ^Vo f an inch; the extreme being TI y^ and goVtr f an 

 inch. 



The gray substance of the convolutions of the cerebellum alone 

 requires a special description. It everywhere consists of a layer 

 externally gray, and internally of a rusty color (ferruginous layer). 

 The latter contains nerve-fibres and large masses of free nuclei. 

 The fibres are continuations of those of the white substance; and 

 extending through the ferruginous layer to the gray layer, they 

 break up into numerous fine fasciculi, so interlaced that the whole 

 ferruginous layer is penetrated by a close but delicate network of 

 fine fibres somewhat resembling the terminal plexus of the acoustic 

 nerve. The free nuclei lie in the meshes formed by the nerve- 



fibres; being from g^^ to 

 quently exhibiting a dis- 

 tinct nucleolus and some- 

 times other granules. 

 The nerve-fibres, however, 

 do not terminate in the 

 ferruginous layer. Be- 

 coming attenuated mostly 

 to a diameter of TIT^U of 

 an inch, they enter the ex- 

 ternal gray layer to termi- 

 nate in its inner stratum, 

 which contains nerve-fi- 

 bres and well-marked 

 large nerve-cells ; while 

 the outer portion contains 

 no nerve-cells, but merely 

 a finely granular, pale, 

 light-yellowish substance, 

 agreeing in all respects 

 with the already described 

 contents of the nerve-cells. 

 The cells 



f an i ncn i n diameter, and fre- 



Fig. 308. 



n 



Ganglion-cells, with their processes, nuclei, and nucleoli. 

 a, a. From the deeper part of the gray matter of the con- 

 volutions of the cerebellum. The larger processes are di- 

 rected towards the surface. &. Another form from the cere- 

 bellum. c, d. Others from the posterior horn of gray matter 

 the gray matter resemble of the dorsal region of the cord. These contain pigment 



those of the cord, already ^ ichsarroiindsthenncl e si n()- m an these specimens 



' J the processes are more or less broken. (Magnified 200 dia- 



described. Entirely dif- meters.) 



