780 



INTERNAL STRUCTURES. 



White 

 centre 



consists of 

 radiating, 



commis- 

 sural, 



and 



collateral 

 fibres. 



Dentate 



body: 



situation, 



and 

 structure. 



Other grey 

 masses. 



Superior 

 peduncle : 



origin, 



and 

 destination. 



the upper surface on the left side. This dissection may bt 

 accomplished by placing the scalpel in the horizontal fissun 

 at the circumference, and carrying it inwards as far as th 

 upper vermiform process, so as to detach the anterior and pos- 

 terior lobes of the upper aspect. If the corpus dentatum doe* 

 not at first appear, thin slices may be made anteriorly till it it 

 reached. 



The medullary centre of the cerebellum forms a large oval mass 

 in each hemisphere, but is flattened and narrow in the middle 

 between the vermiform processes. The lateral part contains tin- 

 grey corpus dentatum, and is continued in front into a large 

 stalk-like process, which becomes divided into the three peduncles 

 From its surface, as already stated, offsets are furnished to the 

 different lobes and laminae. The white centre is composed mainly 

 of the fibres of the peduncles radiating to the cortical gre\ 

 matter ; but there are in addition, as in the cerebrum, commissure 

 fibres between the two hemispheres, which are most developed at 

 the fore part of the superior vermiform process, and at the back 

 close to the median notch, as well as a system of association-fibres 

 uniting the laminae beneath the sulci. 



The corpus dentatum is situate in the inner part of the whiu 

 mass of the hemisphere, and resembles the nucleus in the olivar\ 

 body of the medulla oblongata. It measures about three-quarters 

 of an inch from before back, and consists of a plicated capsule, 

 which when cut across by a sagittal section about a third of 

 the way across the cerebellum from the middle line outwards, 

 appears as a thin, wavy, greyish-yellow line : it is open at the 

 fore and inner part, and encloses a core of white substance. 

 Through its aperture issue a band of fibres to join the superior 

 peduncle. 



Between the two dentate bodies, embedded in the central white 

 matter, are some smaller portions of grey substance, the chief of 

 which is an oval mass on each side, nearly half an inch long, lying 

 close to the middle line in the fore part of the superior vermiform 

 process, and known as the roof -nucleus from its relation to the fourth 

 ventricle (fig. 274). 



PEDUNCLES OF THE CEREBELLUM (fig. 282, p. 773). These are 

 three in number on each side, an upper ( x ) passing to the cere- 

 brum, a middle ( 2 ) to the pons, and an inferior ( 3 ) to the medulla 

 oblongata. 



The superior peduncle (processus ad cerebrum; fig. 277 I, p. 765) 

 is directed forwards, and disappears beneath the corpora quadri- 

 gemina. It is rather flattened in shape, and forms part of the 

 roof of the fourth ventricle. The processes of the two sides are 

 united by the superior medullary velum, or the valve of Vieus- 

 sens (&). Its fibres are derived mainly from the interior of the 

 dentate body, but a few are added from the white centre of the 

 hemisphere and the worm. Beneath the corpora quadrigeniina 

 the superior peduncle enters the tegmentum of the crus cerebri, 

 and crosses the middle line decussating with the one of the 



