(88) 



region cUid do not penetrate into the hemispheres; this broad middle- 

 piece is the Pyramis. The parts of the hemispheres corresponding 

 to the Pyramis are sepai'ated relatively late from the rest of the 

 cerebellum. This separating is connected with other phenomena 

 which are of importance for the topographical relation of the cerebellar 

 lobules. The fissura secunda namely, which limites the regions of the 

 Uvula and the Tonsilla on the upper side, extends originally from one 

 lateral border of the cerebellum to the other (Fig. 11 — 14). The 

 area however, situated above the transversal zone formed by Uvula 

 and Tonsilla, increases more rapidly in trans\'ersal direction than 

 the Tonsilla does and in this way the latter is enclosed. By this 

 process the tissura secunda ends no longer at the lateral borders of 

 the cerebellum, but, if observed from behind, at the myelencephalic 

 border (Fig. J 5). Now it is mainly that part of the hemispheres 

 which gets situated at the side of the Tonsillae, which by a narrow 

 lamella remains connected with the Pyramis and develops to the 

 lobulus biventer. 



The region of the lobulus biventer and Pyramis shows in its lamel- 

 lisation a characteristic that indicates that the surface-expansions of 

 the middle- and side-pieces are more or less independent of each 

 other. Already I drew attention to the fact that in an early period 

 of development one or two grooxes appear in the Pyramis which 

 do not extend into the hemispheres; figures 11 — 19 show these 

 grooves at a number of two or three. Now we see, that the furrows 

 of the lobulus biventer take their origin quite independently of those 

 of the Pyramis. For according to my preparations the lobulus 

 biventer is lamellised in two ways. From the underlip of the sulcus 

 praepyramidalis arises a groove on some distance from the middleline. 

 This groove lengthening itself in a lateral direction reaches the 

 margin of the cerebellum and divides the lobulus into an upper 

 and under part. In Figures 17, 18 and 19 this groove is indicated 

 by a h and is identical with the sulcus bipartiens of Ziehen. The 

 lamel lisation of both parts of the lobulus biventer takes place in a 

 different manner. The upper part of this lobule, which is cuneiform 

 in shape develops new grooves, taking their origin from the underlip 

 of the sulcus praepyramidalis or from the upperlip of the sulcus 

 bipartiens, which grooves lengthen laterally; the grooves of the under 

 part, which is a narrow lobule connected with the Pyramis arise 

 from the margin of the cerebellum and grow out mesially. Especially 

 figure 18 shows very clearly this difference in the folding of the 

 cortex of both parts of the lobulus biventer, which difference gets 

 more important when it is compared with the mode of folding in 



