638 STRUCTURE OF THE CEREBELLUM. [CH. XLV. 



The further relationships of these parts of the brain we shall 

 study in connection with vision. 



Seventh section. This is through the crus. It is made up 

 of crusta (which contains the motor fibres), 

 S.N. tegmentum (which contains the sensory fibres, 

 especially the bundle called the mesial fillet), 

 and the substantia nigra, the grey matter 

 which separates them. 



The destination of one of the spinal cord 

 t tracts we have not yet mentioned : this is 



Fig. 471. Section through mu- - j 



cms of cerebrum. Cr, the tract of Gowers. This is continued up 



nig^-' T, N tegmentum a through the ventral part of the pons lateral 



to the pyramidal bundles ; when it reaches 



the superior cerebellar peduncles the main part of the tract 



takes a sharp backward turn and enters the middle lobe or 



vermis of the cerebellum by the superior peduncle and superior 



medullary velum. Some of the fibres of the tract are continued, 



however, into the corpora quadrigemina. 



CHAPTER XLV. 



STRUCTURE OF THE CEREBEL'LUM. 



THE Cerebellum is composed of an elongated central portion or 

 lobe, called the vermis or vermiform process, and two hemispheres. 

 Each hemisphere is connected with its fellow, not only by means 

 of the vermiform process, but also by a bundle of fibres called 

 the middle peduncle (the latter forming the greater part of the 

 transverse fibres of the pons Varolii), while the superior peduncles, 

 which decussate in the mid-brain, connect it with the cerebrum 

 (5, fig. 472), and the inferior peduncles (restiform bodies) connect 

 it with the medulla oblongata (3, fig. 472). 



The cerebellum is composed of white and grey matter, the 

 latter being external, like that of the cerebrum, and like it, 

 infolded, so that a larger area may be contained in a given space. 

 The convolutions of the grey matter, however, are arranged 

 after a different pattern, as shown in fig. 472. The tree-like 

 arrangement of the white matter has given rise to the name 

 arbor vitce. Besides the grey substance on the surface, there are, 

 in the centre of the white substance of each hemisphere, small 



