78 



THE CEREBELLUM. 



DIAGRAMMATIC TABLE to show the corresponding parts of the worm and hemispheres and 

 the fissures which separate them into lobes. The positions of the principal intra-lobar 

 fissures of the hemisphere are marked by thin lines. 



WORM AND 

 HEMISPHERE. 



Sulcus precentralis. . 



Sulcus postcentralis 



Sulcus preclivalis 



Sulcus postclivalis 



Sulcus horizontalis ) 

 magnus ) 



Sulcus postgracilis 



Sulcus intragracilis ... 



Sulcus pregracilis ) 

 s. postpyramidalis j 



Sulcus prepyramidalis . . 

 Sulcus postnodularis . . 



Lobus lingrulse 



Lobus centralis 



Lobus culminis 



Lobus clivi 



Lobus cacuminis 



Lobus tuberis 



Lobus pyramidis 



Lobus uvulae 



Lobus noduli 



Description of the arbor vitae cerebelli. When a section is made through 

 the worm or through either hemisphere across the direction of the folia, the organ is 

 seen, as already mentioned, to be composed of a white or medullary centre and of a 

 uniform cortex of grey matter, and the section presents a dendritic appearance 

 (arbor vitae cerebelli) in consequence of the fact that the larger laminae are them- 

 selves formed of secondary, and these again are beset with tertiary folia. It is 

 only in such sections that the relative depth and importance of the fissures can be 

 estimated, and a description of the sections is therefore fully as important as that 

 of the surface-markings, and is in fact necessary for the elucidation of the latter. 



The mode of transition of the parts of the worm into those of the hemispheres 

 can also best be made out by the inspection of successive sagittal sections ; 

 beginning with a median section through the worm, and passing gradually to the 

 side, the successive sections being made in planes parallel with the median plane, or 

 only so far inclined to it, and to one another, as to cut the majority of the lamellae 

 at right angles. 



1. Section of the cerebellum in the median plane of the woi'tn (fig. 59 A, and 

 fig. 57). In front we notice the tent of the fourth ventricle projecting with a 

 sharp angle into the enlargement of the white substance known as the corpus 

 trapezoides (c.tr). The apex of the angle is directed backwards with a slight down- 

 ward tilt, so as to leave only a thin layer of white matter the middle part of the 

 inferior medullary velum between it and the nodule. The corresponding layer of 



