522 THE CEREBELLUM. 



prolonged throughout the whole height of the pons in its back part, but 

 becomes indistinct in approaching the front or basilar surface, except towards 

 its upper and lower edge, where the superficial fibres of the pons are mani- 

 festly continuous in the median line with these septal fibres. Bundles of 

 white fibres, belonging to the same system, encircle the crura cerebri at 

 their emergence from the upper border of the pons. 



According to Foville, a few fibres from each of the three principal longitudinal 

 elements of the medulla turn forwards and become continuous with the transverse 

 fibres of the pons ; and, in like manner, one or more small bundles from each of the 

 crura cerebri take a similar transverse course. (Foville, op. cit., pi. II., figs. 2 and 3 ; 

 pi. III., figs. 5 and 6.) 



THE CEREBELLUM, hinder brain, consists of a body and of three pairs of 

 crura or peduncles, by which it is connected with the rest of the eucephalon. 

 These crura are named superior, middle, and inferior. 



Fig. 354. Fig. 354. OUTLINE OP THE UPPER 



SURFACE OF THE CEREBELLUM. 



At the upper part of the figure, the 

 crura cerebri and parts behind them 

 have been cut through and left in con- 

 nection with the cerebellum. 



Ill, the third pair of nerves lying 

 upon the crura cerebri ; c r, white 

 matter or crust of the crura cerebri ; 

 In, locus niger ; t, tegmentum contain- 

 ing grey matter in the upper part of 

 the crura ; a s, aqueduct of Sylvius ; 

 q, corpora quadrigemina, the upper 

 elevations divided ; s v, superior ver- 

 miform process or central folia of the 

 middle lobe of the cerebellum ; I q, 

 lobulus quadratus ; p s, posterior supe- 

 rior lobe; fh, horizontal fissure ; pi, 

 posterior inferior lobe; n, the notch 

 between the hemispheres. 



The superior peduncles, crura ad cerebrum or processus ad testes, together 

 with the valve of Vieusseus, a lamina stretched between them, connect the 

 cerebellum with the cerebrum. 



The inferior peduncles, crura ad medullam, are the upper extremities of 

 the restiform bodies. 



The middle peduncles, or crura ad pontem, much the largest, are the 

 lateral extremities of the transverse fibres of the pons Varolii. They 

 connect together the two halves of the cerebellum inferiorly. 



All these peduncles consist of white fibres only ; and they pass into the 

 interior of the cerebellum at its fore part. 



The cerebellum is covered with grey cortical substance, rather darker 

 than that of the cerebrum. Its greatest diameter is transverse, and 

 extends to about three and a half or four inches : its width from before 

 backwards is about two or two and a half inches ; and its greatest depth 

 is about two inches, but it is much thinner round its outer border. 



It consists of two lateral hemispheres joined together by a median portion 

 called the vermiform process, which in the human subject is distinguishable 

 only as a small though well-marked part below, named the inferior vermiform 

 process, and a mere elevation above, called the superior vermiform process. 

 In birds, and in animals lower in the scale, this middle part of the cerebellum 



