74 THE CEREBELLUM. 



stituting a posterior lobe. In fact, however, the great horizontal fissure below the 

 folium cacuminis and the postclival fissure above this folium separate the group 

 into three well-marked divisions, of very unequal size it is true in the worm, owing 

 to the rudimentary character of the central or cacuminate division, but far more 

 distinct and equal in the hemispheres ; they may therefore be conveniently thus 

 subdivided in the worm also, and of them, two (the clivus and folium cacuminis) 

 belong to the upper worm, the third, tuber valvulse, to the lower. 



Two or three secondary laminae. of the clivus reach the surface of the worm, but 

 they are beset with many tertiary folia, and other important folia belonging to the 

 same group lie concealed in the preclival fissure. 



The lateral extension of the clivus on to each hemisphere is known as the 

 posterior crescentic lobe (I. lunatus posterior, Kolliker), and the two posterior 

 crescentic lobes with the clivus between them, bounded in front by the preclival, 

 behind by the postclival fissure, may collectively be termed the lobe of the clivus. 

 The lateral parts of this lobe each receive two or three primary branches of the 

 medullary centre of the hemisphere (fig. 59). 



The combined anterior and posterior crescentic lobes of each, hemisphere were formerly 

 termed the quadrilateral lobe. 



The folium cacuminis and postero-superior lobes : lobus cacuminis. 



The folium cacuminis is formed by the extremity or apex of the main horizontal 

 stem of the arbor vitse vermis (figs. 57, 59). As the vertical section shows, it is 

 composed of but a single primary folium, which may be either plain or beset 

 with rudimentary folia. But at the side of the worm it rapidly expands, with 

 divergence of its bounding fissures and a great increase of size of its main branch of 

 the arbor vitae and the formation of numerous secondary and tertiary folia, a large 

 lobe being thereby produced at the posterior and upper part of each hemisphere 

 which has been termed the postero-superior lobe. The expansion occurs mostly 

 above the horizontal plane, and its branch of the arbor vitas has a direction no longer 

 directly backwards, but rather upwards and backwards ; this upward shifting 

 appears to be due to the great development of the lobes of the lower surface of the 

 hemisphere. The postero-superior lobes are bounded, like the folium cacuminis itself, 

 in front and above by the postclival fissure, below by the great horizontal fissure ; 

 joined as they are in the middle line by the folium cacuminis, they form a great 

 winged mass which occupies the posterior third of the upper surface of the cerebellar 

 hemispheres, and forms the rounded postero-lateral border ; to this conjoined mass 

 the term lobus cacuminis may be applied. 



UNDER SURFACE. Turning now our attention to the under surface of the 

 organ, we here meet with considerably greater complexity, and the correspondence 

 between the parts of the worm and those of the hemisphere is less clearly apparent. 

 The lower worm extends from the inferior medullary velum to the folium cacuminis 

 (great horizontal fissure), and the parts or lobules which are enumerated in 

 it are four in number, viz. : from before back (1) the nodule, (2) the uvula, 

 (3) the pyramid, and (4) the tuber valvulce, seu posticum. On the hemisphere a 

 greater number of lobes are distinguished, viz. : (1) the flocculus, corresponding 

 with the nodule ; (2) the tonsil (amygdala), corresponding with the uvula ; 

 (3) the bi-ventral lobe, corresponding with the pyramid ; (4) the slender lobe, formed 

 of an anterior and a posterior part well marked off from one another ; and (5) the 

 inferior semiltmar lobe, which also shows a tendency to subdivision. This 

 last lobe corresponds with and is directly in lateral continuity with the tuber 

 posticum of the worm. The slender lobes are interpolated in the hemisphere, and 

 have not any obvious prominence of the worm corresponding with them, but they 

 appear to represent a development of certain rudimentary folia which are seen in 



