( 87 ) 



logical one. The obvious difference in llie extension of (lie cortex of 

 the different lobules ou^ht to have a physiological base. 



In the stage of development in which the sulcus horizontalis forms 

 a short straight groove in the forelip of the sulcus praepyramidalis, 

 the Tuber vermis does not jet reach the surface, whereas the folium 

 vermis, which in a later period is concealed, still appears broadly 

 on the surface. This relation is modified b}- a lamella which mounts 

 to the surface from the bottom of the sulcus praepyramidaHs, and 

 which pushing forwards the sulcus horizontalis, separates the latter 

 from the sulcus praepyramidalis (Fig. 12 and 13. h, 4). This lamella, 

 arising from the fore wall of the sulcus praepyramidalis is the first 

 "Anlage" of the Tuber vermis. 



At the same time the sulcus horizontalis has lengthened and pene- 

 trates into the hemispheres, soon being equal in length to the sulcus 

 superior posterior (Fig. 15c). These sulci include a cuneiform lobule 

 with its top directed raesially, on the surface of which arise secon- 

 dary furrows, even before the sulcus horizontalis has reached the 

 lateral border of the cerebellum (Fig. 15a b and c). This w^edge- 

 shaped lobule is the lobulus semilunaris superior. 



The sulcus prae})yramidalis has also extended into the hemispheres 

 (cf. Fig. 11 till 15. 4) and with that keeps its typical form for a 

 long time: namely a median horizontal portion of which the lateral 

 parts bend sharply down and back. This typical form enables us to 

 recognize easily this groove. By this course of the sulcus a second 

 cuneiform lobule is formed with its top directed mesially, bordered 

 above by the sulcus horizontalis {It) below by the sulcus praepyramidalis 

 (4). This region becomes the lobulus semilunaris inferior. It is remarkable 

 that the first groove wdiicli subdivides this lobule also rises from the 

 upperlip of the sulcus praepyramidalis from which again appears 

 that here exists a focus of very intense surface-expansion. This groove 

 penetrating into the lobulus semilunaris inferior can be seen in 

 Fig. 13, 14 and 15 in different phases of development, whereas in 

 Fig. 16r/, a second groove emerges from the underlip of the sulcus 

 horizontalis, quite near the middleline, which grows out into the 

 lobulus semilunaris inferior. By these two intralobular grooves is 

 initiated the subdivision of the lobulus semilunaris inferior into three 

 sublobuli, a fact, to which Ziehen has fixed attention. 



The region between the sulcus praepyramidalis (4) ajid the fissura 

 secunda (2) undergoes but fewer changes and takes part in a slighter 

 degree in the surface-expansion. For a long while this area is broadest 

 in its median zone (Fig. 11, 12, 13 and 14) and shows there one 

 or two short grooves which are however limited to the middle 



