152 ELEMENTS OF HISTOLOGY. [Chap. xvm. 



brain are situated in pericellular lymph-spaces (Ober- 

 steiner). 



199. We now follow the above description of 

 the structure of the medulla with that of the cere- 

 bellum and pons Yarolii. 



I. The cerebellum is composed of laminae, 

 folds, or convolutions, composed of secondary folds, 

 each of which consists of a central tract of white 

 matter covered with grey ma.tter. The tracts of white 

 matter of neighbouring convolutions of one lobe or 

 division join, and thus form the principal tracts of 

 white matter. 



The white matter of the cerebellar hemisphere is 

 connected (a) with the medulla oblongata by the 

 corpus restiforme, this forming the inferior peduncle 

 of the cerebellum ; (6) with the cerebrum by the 

 processus cerebelli ad cerebrum, this forming the 

 superior pedunculus ; and (c) with the other cerebellar 

 hemisphere by the commissure passing through the 

 pons Yarolii ; this is the pedunculus cerebelli ad 

 pontem, or the middle pedunculus. 



200. On a vertical section, through a lamina of the 

 cerebellum (Fig. 90), the following layers are seen : (a) 

 the pia mater covering the general surface, and pene- 

 trating with the larger blood-vessels into the superficial 

 substance of the lamina ; (b) a thick layer of cortical 

 grey matter ; (c) the layer of Purkinje'a ganglion 

 cells ; (d) the nuclear layer, and (e) the central white 

 matter. 



201. The layer of ganglion cells of Purkinje is the 

 most interesting layer ; it consists of a single row of 

 large multipolar ganglion cells, each with a large 

 vesicular nucleus. Each possesses also a thin axis 

 cylinder process, directed towards the depth, the 

 cell sending out in the opposite direction i.e., towards 

 the surface a thick process which soon branches 

 like the antlers of a deer, the processes being all very 



