THE CEREBELLAR PEDUNCLES. 471 
the general direction of its fissures and folia, a highly arborescent appearance is 
thus presented by the cut surface. To this the term arbor vite cerebelli is applied. 
Corpus Dentatum and other Gray Nuclei in the White Matter of the 
Cerebellum.— Embedded in the midst of the mass of white matter which forms the 
central core of each lateral hemisphere there is an isolated nucleus of gray matter, 
which presents a 
strong resem- 
blance to the in- 
ferior olivary 
nucleus of the - 
Culmen monticuli 
: Mesen- ~ Y ae 
medulla. It is — cephalon | NS 
called the corpus F ‘= 
dentatum (nucleus = D corpus 
dentatus), and it se dentatum 
iddle 
consists of a peduncle of = 
AVA? 2 , cerebellum > 4) 
cor ugated o1 ee 
plicated lamina <LE f 
of oray matter Inferior olivary nucleus 
“ED > 
which is folded 
on itself so as to 
enclose, in a flask- 
like manner, a Fic. 350.—SacitraL SECTION THROUGH THE LErr LATERAL HEMISPHERE OF 
perion ol the Showing the “ Aen 7 ad te oes dentatum, 
central white 
matter. This gray capsule is not completely closed. It presents an open mouth, 
termed the hilum, which is directed inwards and upwards, and out of this stream 
the great majority of the fibres of the superior cerebellar peduncle. 
Three small additional masses of gray matter are also present on either side of the mesial 
plane in the central white matter of the cerebellum. These are termed the nucleus emboli- 
formis, the nucleus globosus, and the nucleus fastigii. The nucleus emboliformis or embolus is a 
small lamina of gray matter which lies immediately internal to the hilum of the corpus dentatum, 
being thus related to it somewhat in the same manner that the mesial accessory olivary nucleus 
is related to the main inferior olivary nucleus. The nucleus globosus lies internal to the embolus 
and on a somewhat deeper horizontal plane. The nucleus fastigii or roof nucleus is placed in 
the white substance of the worm (corpus trapezoides) close to the mesial plane and its fellow of 
the opposite side. It is, therefore, situated on the mesial aspect of the nucleus globosus. 
Although isolated from the gray matter of the surface, these small nuclei and the corpus 
dentatum are connected at certain points with each other. The corpus dentatum and the 
embolus present a structure very similar to that of the inferior olivary nucleus. In the nucleus 
globosus and the nucleus fastigii the cells are somewhat larger in size. 
Cerebellar Peduncles.—These are three in number on each side, viz. the 
middle, the inferior, and the superior. The fibres of which they are composed all 
enter or emerge from the white medullary centre of the cerebellum. 
The middle peduncle is much the largest of the three, and has already been 
described on pp. 450 and 462. It is formed by the transverse fibres of the pons, 
and it enters the cerebellar hemisphere on the outer aspect of the other two 
peduncles. The lips of the anterior part of the great horizontal fissure are 
separated widely from each other to give it admission. Within the cerebellar 
hemisphere its fibres are distributed in two great bundles. Of these, one, com- 
posed of the upper transverse fibres of the pons, radiates out in the lower part of 
the hemisphere; whilst the other, consisting of the lower transverse fibres of the 
pons, spreads out in the upper part of the hemisphere. 
The inferior peduncle is simply the restiform body of the medulla. After 
leaving the medulla it ascends for a short distance on the dorsal surface of the 
pons and then turns sharply backwards, to enter the cerebellum between the other 
two peduncles. 
The superior peduncle, as it issues from the cerebellum, lies close to the inner 
side of the middle peduncle (Fig. 549). Its further course upwards on the dorsum 
of the pons to the inferior quadrigeminal body has been previously described (p. 451). 
Connexions established by the Peduncular Fibres.—The fibres of the middle 
30 a 
