464 THE INTERNAL STRUCTURE 



throw themselves into, and ascend as part of, the Lower 

 Peduncle. Thus, the fibres of each ' posterior column ' 

 sink beneath the surface of the Spinal Cord, and after 

 passing through the corresponding ' olivary body ' and 

 thence crossing the middle line of the Medulla and pass- 

 ing round the opposite ' olivary body,' they emerge as 

 parts of the ' restiform body ' or Lower Peduncle of the 

 Cerebellum. This arrangement is not to be regarded as 

 established beyond the reach of doubt : it is in fact denied 

 by Luys. 



The Middle Peduncles together form the 'pons Varolii.' 

 The fibres of each (fig. 166) emerge from different parts of 

 the cortical substance of the corresponding ' lateral lobe ' of 

 the Cerebellum ; and whilst a few of its fibres are believed 

 to be ' commissural ' in nature, and merely to pass across 

 from one to the other of these lateral lobes, the majority 

 of the fibres of one side decussate, at the middle line, 

 with those of the opposite Middle Peduncle. By their 

 intervention each half of the Cerebellum is brought into 

 relation either with the motor fibres descending from the 

 opposite Corpus Striatum (in the corresponding Cerebral 

 Peduncle) ; or else with some of the cells of the Corpus 

 Striatum itself, owing to some of the Cerebellar pedun- 

 cular fibres bending upwards from the ' pons ' to end in 

 these ganglia just as others, taking a similar course, are 

 thought to pass through them on their way to the Cere- 

 bral Convolutions. 



All that is positively known is, that each ' lateral lobe ' 

 of the Cerebellum is principally in relation, through its 

 Middle Peduncle, with the * motor tract ' from the 

 opposite Cerebral Hemisphere. And this fact itself is one 

 of some importance, since, amidst all the other doubts 

 concerning the Cerebellum it would seem positively to 

 imply that the bulk of the fibres of these particular 



