508 THE FUNCTIONAL RELATIONS OF THE 



As these ' efferent ' fibres of the Cerebellum proceed to the 

 opposite motor tracts of the Cerebrum above their seat of ' decus- 

 sation' in the Medulla the half of the Cerebellum whence they 

 issue would (by reason of this lower ' decussation ' of the Anterior 

 Pyramids) be brought into relation with the limbs of the corres- 

 ponding side of the body. This direct, rather than cross, relation 

 is also indicated by experimental observations with lower animals, 

 and by the phenomena of disease observable in Man. 



Putting all these facts together, it seems that the Cere- 

 bell am may be regarded as an enormously developed 

 supreme 'motor centre,' the Lateral Lobes of which co- 

 operate in cross- relation with those of the Cerebrum in 

 the actual execution of Voluntary Movements ; though it 

 is also an organ accustomed to act perhaps to a far 

 greater extent and more continuously in the execution 

 of complicated Automatic Movements, in response to 

 ' unfelt ' impressions coming to it (mainly through inter- 

 nuncial fibres) from ' sensory nuclei ' of all kinds. 



Though the Upper and Lower Peduncles would seem 

 to be the principal channels through which these latter 

 afferent impressions reach the Cerebellum, only a part 

 of their related outgoing stimuli may go along the Lower 

 Peduncles ; others of them may, in higher animals, 

 traverse the Middle Peduncles. However this may be, it 

 would appear that all afferent Cerebellar impressions that 

 are destined to excite Automatic Movements, and which 

 happen to emanate from one half of the body, proceed to 

 the corresponding half of the Cerebellum whether they 

 go direct (as seems to be the case with fibres from the 

 Fifth, the Auditory and other cranial nerves), or only after 

 two decussations (as seems to be the case with fibres from 



fibres as well as descending (' efferent') fibres, if Meynert's con- 

 clusions are correct ; though the writer's notion is that some at. 

 least of the Cerebral * afferent ' fibres reach the Cerebellum by the 

 ' upper peduncles.' 



