520 THE BEAIN OF MAMMALS, BY TH. MEYNERT. 



corresponding side, but in part, at least, following the sinuosr- 

 ties of its upper borders, into that of the opposite side. They 

 thus pass through a slender medullary median layer, a kind of 

 raphe, which extends between the roof-nuclei, and which being 

 traversed by antero-posterior medullary fibres (median fasciculi 

 of Stilling) appears very opaque. In this raphe' they decussate, 

 and near the lower border enter into the opposite roof-nucleus. 

 In their further course they must reach the medulla of the 

 inferior vermiform process, by the commissural fibres of which 

 they must be brought into connection with all the lobes of the 

 inferior cortical region of the hemispheres. The most anterior 

 of these commissures is the posterior medullary velum, which 

 joins the cortex of the flocculus by means of a fasciculus of 

 the peduncle of the latter. 



The second fasciculus of the peduncle of the flocculus passes, 

 as is well known, over the auditory nerve, to run up to the 

 lateral wall of the fourth ventricle, and still higher up to 

 return again into the cerebellum with the crus cerebelli 

 (fig. 255, F). 



The external fasciculi of the internal column of the crus 

 cerebelli (fig. 255, H*), after they have passed through the 

 superior peduncle, enter without decussating into the medulla 

 of the cerebellum, leaving the roof-nuclei on their inner side. 



The fasciculi of the internal column at all events diverge in 

 so many directions from each other in the cerebellum, that 

 we may reasonably admit their connection with all parts of 

 the cortex of the cerebellum (as is also true of the processus 

 ad pontem and of the restiform body). 



The course which the tract representing the auditory nerve 

 pursues in the cerebellum is still imperfectly ascertained in 

 regard to its decussation. The non- decussating fasciculi of 

 the anterior auditory root (fig. 255, 8 4 , and the corresponding 

 fasciculus on the left), escape the decussation in the roof-nuclei 

 by passing directly through the superior peduncle and nucleus 

 dentatus. But whether also the portions of the anterior and of 

 the posterior auditory roots, that have already undergone decus- 

 sation in the posterior division of the pons, remain in that half 

 of the cerebellum they have once reached, 'where they are no 

 longer distinguishable from the fasciculi proceeding from the 



