THE CEREBELLUM. 519 



described, are external to the cerebellum. They remain in the 

 substance of the cerebellum itself up to the point where they 

 penetrate into the cortex, on the same side as that on which 

 they enter, though, no doubt, so far as they also penetrate into 

 the most central portions they are directed inwards, and are 

 consequently so disposed as readily to give rise to an erroneous 

 impression of running towards a point of decussation. 



The relations of the prolongations of the brachia of the cere- 

 bellum to one another is determined by the disposition of the 

 grey substance with which they unite in the cerebellum. The 

 processus ad pontem and the corpora restiformia are only 

 connected with the cortex ; the superior peduncle, however, is 

 previously connected with the nucleus dentatus, and the 

 inner division of the cerebellar peduncle with the roof nuclei 

 of the cerebellum. Now, since the cortex is the most ex- 

 ternally situated mass of grey substance, whilst the dentated 

 nucleus lies in the middle of the medullary layer between it 

 and the internally situated roof nuclei, these arms are so dis- 

 posed in the medulla of the cerebellum, that the processus ad 

 pontem and corpus restiforme form the most external, the 

 superior peduncle the middle, and the so-called internal division 

 the innermost mass of its layers (fig. 255, Br, St, B, If). 



The nucleus dentatus, moreover, is immediately covered by 

 a smooth separable layer of the restiform body, which fills up 

 the furrows of its surface, and the fibres of which perhaps 

 also enter into connection with its nerve corpuscles. 



The superior peduncle, which has already decussated in the 

 substance of the tegmentum, like the external arms, runs 

 straight in the cerebellum, and reaches the hilus of the nucleus 

 dentatus (Gratiolet), within which it diverges to meet the 

 nerve corpuscles radiating towards them. As far as to the hilus, 

 however, it does not present a pure and unmixed sectional 

 area, but just as in its free course it is already traversed by 

 fasciculi of the fifth, and further downwards by those of the 

 auditory nerves, so it is here freely traversed by other fasciculi 

 of the medulla of the cerebellum, especially by the inner division 

 of the cerebellar peduncle. This internal column of the crus 

 cerebelli appears to pursue a double course. Its internal 

 fasciculi in part enter straightway into the roof-nucleus of the 



