CLIVUS AND POSTERIOR CRESCENTIC LOBES. 73 



Lobes of the upper surface. We may now describe in detail the subdivisions 

 of the upper surface, taking (since they are directly continuous with one another) 

 those of the worm and hemispheres together. 



The lingula. This is usually confined to the worm, and from the surface it is 

 entirely concealed by the next lobe : it is best seen in a median section of the organ 

 (figs. 57 and 59). It consists of a small tongue-shaped group of four or five trans- 

 verse laininse, which may be said to lie upon the middle of the superior medullary 

 velum (fig. 58, I). Its medullary centre is in continuity with the velum, and 

 forms part of the roof or dorsal boundary of the fourth ventricle which here has a 

 tent-shaped projection into the middle of the cerebellum (fig. 57, 4). 



The lingula gradually shades off at the sides and is usually unrepresented in the 

 hemispheres, but its laminae are sometimes prolonged laterally for a little distance 

 over the superior cerebellar peduncle (frcenulum linyulcc}. 



The central lobe and its alae. The central lobe is largely concealed by the 

 culmen when the cerebellum is in its natural position, but when the organ is cut 

 away from the adjacent structures this lobe is seen in the anterior notch, where 

 its laminae appear at the surface. They are prolonged beyond the limit of the worm, 

 for some distance along the upper and anterior part of the hemispheres, where 

 they form wing-like continuations of the central lobe which are known as the 

 alee lobuli centralis (fig. 58). The central lobe receives a primary branch of the 

 arbor vitas which passes upwards and forwards into it from the enlargement of 

 the white centre which is known as the trapezoidal body, but the fissures (pre- 

 central and postcentral) which separate it from the lingula and culminate lobe 

 respectively, are not better marked at the surface than those which intervene 

 between the laminae of the culminate lobe, and, as a glance at the sections (fig. 59) 

 shows, its laminae all belong to the same (ascending) group of folia as those which 

 constitute the culminate lobe. 



The culmen and anterior crescentic lobes : lobus culminis. The culmen 

 occupies rather more than half of the upper surface of the worm, and, as its name 

 implies, constitutes the most prominent part of the upper worm. Its surface shows 

 three or four well-marked lamellae, beset by a number of secondary and tertiary folia. 

 'It is separated from the next part of the worm by a deep groove which descends to 

 the middle of the organ ; this sulcus is prolonged, as we have already seen, on to 

 either hemisphere, having there been termed the antero-superior sulcus, and passing 

 in a curved manner parallel with the general disposition of the laminae on this sur- 

 face to the antero-lateral margin, where it runs into the anterior part of the great 

 horizontal fissure. The antero-superior sulci together may conveniently be termed 

 the preclival. The subdivision of the hemisphere which is cut off between this 

 preclival fissure behind and the postcentral sulcus in front has been known as the 

 anterior crescentic lobe (lobus lunatus anterior, Ko'lliker). The two anterior crescentic 

 lobes, together with the culmen with which they are in complete lateral continuity, 

 form a main subdivision of the upper surface of the cerebellum, which may appro- 

 priately be termed the lobe of the culmen. The lateral parts of the lobe each receive 

 three well-marked branches of the medullary centre of the hemispheres ; in the 

 central part they come off by a common stem from the corpus trapezoides of the 

 worm (fig. 59). 



The clivus and posterior crescentic lobes : lobus clivi. Behind the 

 antero-superior or preclival fissure, and extending as far as the folium cacuminis 

 (from which it is separated by the postero-superior or postcUval fissure), is another 

 considerable group of laminae which receive their branches from the upper aspect of 

 the horizontal stem of the arbor vitae. In a median section of the worm these 

 laminae appear to form one group with the folium cacuminis and the laminae of the 

 tuber valvulse (fig. 59 A), and this group has been described by Schwalbe as con- 



