714 THE yERVOUS SYSTEM 



level of the hemisi)lieres as seen from above, ^vhel•e it constitutes the superior 

 vermiform process (fig. 427); but, as seen from below (inferior vermiform 

 process), it forms the roof of a deep recess between the hemisi)lR-res, the vallecula, 

 which is occupied for the most part by the mi-dulla. Tht- vallecula terminates in 

 front at the cavity of the fourth ventricle. Behind, it passes into a deep notch, the 

 incisura marsupialis, which is occupied by the falx cerebelli and the cisterna 

 nuunia of the sul)araelnioid space. The surface of the cerebellum is covered by a 

 number of folia, which are curved, Avith a general direction convex backwards and 

 outwards. The folia are much narrower than the cerebral convolutions, and are of 

 a darker grey color than the latter. They are separated ])y fissures, some of which 

 appear on the surface separating individual folia; others dip in for some distance 

 below the surface, and within these secondary fissures are developed. In this way 

 the great horizontal fissure and the interlobar fissures are formed. The separation 

 hito lobes is somewhat arbitrary, as fissures reseml)ling the interlobar fissures in 

 character traverse the substance of the lobes. 



The cerebellum is connected to the adjacent parts of the cerebro-spinal axis by 

 three pairs of peduncles : a superior pair to the cerebrum; a middle pair to the 

 pons; and an inferior pair to the medulla. 



The great horizontal fissure is deei>er than the interlobar fissures. It com- 

 mences at the point where the middle peduncle of the cerebellum enters the hemi- 

 sphere and pursues a curved course around the margin of the hemisphere, inclining 

 first downwards, and then curving slightly upwards, and crossing the middle line 

 immediately above the incisura marsupialis, to pursue a similar course on the 

 opposite side. On opening up the fissure, numerous folia are seen to run oljliquely 

 within it, some of which cross the floor of the fissure so as to connect the upper 

 and lower surfaces which bound the fissure. The great horizontal fissure separates 

 the superior and inferior surfaces of the cerebellum. 



The superior surface of the cerebellum has a general inclination backwards 

 and outwards. This surface is approximately flat, but shows a slight concavity 

 corresponding to the superjacent occipital lol^e of the cerebrum. Mesially the slope 

 of the surface becomes more abrupt, and forms the superior vermiform process. 

 Of the fissures which traverse this surface the most important is the sulcus cere- 

 belli superior, which branches off from the great horizontal fissure at its com- 

 mencement and curves over the posterior part of the upper surface to approach the 

 great horizontal fissure again at the superior vermiform process, where the two 

 fissures are separated only by a narrow bandj the folium cacuminis (fig. 427). The 

 sulcus cerebelli superior divides the superior surface into a larger anterior part, the 

 quadrate lobe, and a smaller semilunar posterior portion, the posterior superior 

 lobe. Another fissure divides the quadrate lobe into an anterior crescentic and 

 a posterior crescentic portion. The anterior crescentic portion is usually sub- 

 divided into two })()vtions by another sulcus parallel to the fissure last mentioned. 



The superior vermiform process is divided by fissures, continuous with the 

 sulci above described, into parts which are placed in the following order from l)efore 

 l»ack wards: lol^ulus centralis, monticulus cerebelli, and folium cacuminis. The 

 lobulus centralis is a small squarish mass which is placed below and behind the 

 testes, separated from the latter by a fold of pia mater. It rests below on the 

 lingula, which separates it from the valve of Vieussens (fig. 426). It ex])ands 

 laterally into a pair of somewhat triangular folds, tlie alae (fig. 426), which are 

 entirely overlapped and hidden l)y the quadrate lobes when tlie cereV)ellum is viewed 

 from above in its undisturbed position. The lingula is a small tongue-shaped 

 portion of the cerebellum which lies on, and is adherent to, the valve of Vieussens. 

 Its basal part is continuous with the lobulus centralis, and it consists of from four 

 to five transverse folia. The monticulus cerebelli is divided into an anterior 

 elevated portion, the culmen, and a posterior sloping part, the declive. The culmen 

 connects the anterior crescentic portions of the quadrate lobes of opposite sides, and 

 is traversed by the fissures which intersect these portions. The declive connects 

 the posterior crescentic portions, and consists of about six or seven transverse folia. 

 The folium cacuminis is a narrow band whicli connects the posterior superior 

 lobes of opposite sides. It is not a simple folium, but is marked on its superior 

 and inferior surfaces by transverse furrows. 



