THE BRAIN AND ITS MEMBRANES. 



735 



Fibres of the Peduncles (Fig. 435). The fibres of the superior peduncles on 

 entering the hemisphere pass to a great extent into the interior of the corpus 

 dentatum (see below), though some wind round it and reach the gray cortical 

 matter, especially on its inferior surface, while others pass into the white matter 



Cut surface 

 of pong\* 



Sup. 



,Xid. ped. (cut) 

 . ped. (cut) 



Dentate nucleus. 



Fie*. 435. A section of the cerebellum to show dentate nucleus. (Henle.) 



of the worm. Into the white matter of the worm pass the fibres of the superior 

 velum, of which certain longitudinal ones are quite distinct. These last are the 

 antero-lateral ascending cerebellar tracts of cord and medulla (see page 717). 



The fibres of the middle peduncles on entering the hemisphere have a gen- 

 erally dorsal tendency, after which they go in various directions : the upper fibres 

 of the tuber annulare pass to the lower part of the hemisphere ; the lower fibres 

 of the tuber pass into the upper part of the hemisphere ; while the remaining 

 fibres (middle of tuber and dorsal transverse ; see Pons) pass for the most part 

 into the middle region of the hemisphere. 



The fibres of the inferior peduncles on entering the cerebellum are placed 

 between the middle peduncle externally and superior internally. They then pass 

 upward, and radiate into the upper part of the hemisphere, curving over the 

 corpus dentatum ; some are extended into the white matter of the worm. These 

 last are the continuations of the direct cerebellar tract. 



The Hbres already described, which make up the inferior peduncle or restiform 

 body, may be summarized as follows : 1. Direct cerebellar tract ; 2. External 

 arciform fibres ; 3. Internal arciform fibres (from opposite olivary nucleus) ; 4. 

 Fibres from accessory cuneate nucleus ; 5. Fibres from antero-lateral descending 

 cerebellar tract of cord ; 6. Fibres of Solly. These last are occasionally found, 

 and are seen on the surface of the medulla running upward and backward from 

 the direct pyramidal tract of the cord just before it enters the pyramid. 



The fibrae propriae of the cerebellum are of two kinds : (1) commissural fibres, 

 which cross the middle line to connect the opposite halves of the hemispheres, 

 some at the anterior part, and others at the posterior part, of the vermiform pro- 

 cess ; (2) arcuate or association fibres, which connect one lamina with another, 

 arching across the fissures between the laminae. 



The GRAY MATTER OF THE CEREBELLUM is found in two situations : (1) on the 

 surface, forming the cortex ; (2) as independent masses in the interior. 



(1) The gray matter of the cortex presents a characteristic foliated appearance, 

 due to the series of laminae which are given off from the central white matter : 

 these laminae give off secondary laminae which are covered with gray matter. 

 This arrangement gives to the cut surface of the organ the foliated appearance 

 already described. Externally the cortex is covered by pia mater, and internally 

 is the medullary centre, consisting mainly of nerve-fibres. 



