THE STRUCTURE OF THE CEREBELLUM. 245 



and surface, by crescentic furrows, or sulci, into numerous parallel, 

 thin lamince, some of which may be traced continuously over the ver- 

 miform processes, from one hemisphere to another. 



The superficial part of the cerebellum, even of its minutest laminae, 

 many of which are hidden at the bottom of the principal sulci, consists 

 of gray or cineritious matter, named, as in the cerebrum, the cortical 

 substance. It is composed of large multipolar nerve cells mixed with 

 white fibres, and arranged in thin strata. The interior of the cere- 

 bellum consists of white or medullary substance, which projects into 

 the various lobes, and thence again, in the form of thin plates, into 

 the multitudinous laminae; hence a vertical section through the cere- 

 bellum, made across its laminae, presents a beautiful arborescent inter- 

 nal white substance, surrounded by foliated bendings of the gray 

 matter, an appearance which has been named the arbor vitce, or tree 

 of life, Fig. 59, d. Embedded in the white substance of each hemi- 

 sphere, is a plicated or folded sac of gray matter, open in the direction 

 of the peduncles of the cerebellum, and having white substance in its 

 interior. Owing to the indented gray line which they present when cut 

 through, these masses of gray matter are named the corpora dentata 

 of the cerebellum. The peduncles of the cerebellum, composed of 

 white fibres, form three sets, as follows: First, a superior pair of 

 peduncles, which pass upwards, at the back of the cerebral peduncles, 

 to the corpora quadrigemina and adjacent parts; the white fibres of 

 these peduncles, chiefly issue from the interior of the corpora dentata. 

 Secondly, a middle pair, which cross below, and embrace, the pedun- 

 cles of the cerebellum, and so form the pons Varolii. Lastly, an 

 inferior pair, which pass down to the sides and back of the medulla 

 oblongata, of which they form the so-called restiform bodies, and, by 

 them, are connected with the posterior and lateral columns of the 

 spinal cord. The superior peduncles of the cerebellum, may be said 

 to be composed of longitudinal commissural fibres, uniting it to a part 

 of the cerebrum; the middle peduncles form transverse commissural 

 fibres, which connect the two cerebellar hemispheres together, and 

 bring them into relation with the gray matter diffused in the substance 

 of the pons Varolii, forming in fact its transverse fibres. Finally, the 

 inferior peduncles are longitudinal commissural fibres, connecting the 

 cerebellum with the medulla oblongata and spinal cord. It has been 

 recently stated that all the fibres of the three peduncles of the cere- 

 bellum, proceed from, or end in, the interior of the folded sacs of gray 

 matter known as the corpora dentata ; and that it is from the outer 

 surface of these sacs, that all the fibres reaching to the laminated gray 

 matter on the surface of the organ, in reality proceed; the fibres of 

 the superior and inferior peduncles are said to decussate within the 

 cerebellum; those of the former, end in a mass of gray matter, in the 

 back part of the cerebral peduncles: those of the latter, in the gray 

 nucleus of the olivary body of the medulla oblongata. (Luys.) These 

 statements require confirmation. 



Beneath the superior peduncles, and bounded below by the back of 

 the medulla oblongata, is a space, communicating, by a narrow canal, 



