132 LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



them in a section through the upper part of the pons. The 

 main points of difference are the changed position of the cere- 

 bellar peduncles and the altered shape of the gray matter under 

 the broadening aqueduct, where new nerve-nuclei now appear. 



In sections lower down, however, the whole appearance of 

 things is changed. This comes from the fact that the roof of 

 the ventricle, caudad of the velum medullare anticum, is devel- 

 oped into the cerebellum, and that fibres from both the tegmentnm 

 and the crusta enter into intimate association with the latter. 



The anterior peduncles and the fibres of the pons disappear 

 into the cerebellum. From the medulla oblongata and the 

 spinal cord below come fibres which are first interwoven with 

 the tegmentum and then pass to the cerebellum. 



It is, therefore, better for us to abandon temporarily the 

 study of the tegmental fibres at this point, just behind the 

 corpora quadrigemina, and to turn our attention to other parts 

 of the central nervous system, whose processes and prolonga- 

 tions all meet just here. You will, unquestionably, be better 

 prepared to understand a section through the tegmentum after 

 you have learned the arrangement of fibres in the cerebellum, 

 and have obtained an insight into the structure of the medulla 

 oblongata and the spinal cord. 



The cerebellum consists of a median portion, or " worm ' 

 (vermis), and the two hemispheres. It is connected with the 

 inter-brain by its anterior peduncles from the red nuclei, with 

 the fore-brain through the brachia pontis, median peduncles. 

 Through the former it receives fibres from the thalamus and the 

 region of the tegmental radiation, through the latter fibres from 

 the cortex of the frontal, parietal, and temporal lobes. A third 

 connection is effected through the posterior peduncles (corpora 

 restiformia, which we shall consider later), with the mednlla 

 oblongata and the spinal cord. In the accompanying figure, 

 which shows the cerebellum as seen from above, we observe 



1. The situation with respect' to the corpora quadrigemina, 

 from beneath which the anterior peduncles pass to the cere- 

 bellum. 



