( .)<S TIIK NKuvors sisTKM AND ITS r< >\si.i;\ \TION 



The work of more recent students lias shown that the 

 control formerly credited to the cerebellum was too 

 absolute and exclusive. < >ur belief is still that this 

 part of the brain is much concerned with subconscious 

 muscular adjustments requiring extensive coordination, 

 but we no longer regard it as the sole seat of such regula- 

 tion. It has been found that animals recover in great 

 part from the profound effects of the removal of the 

 cerebellum, and it is natural to conclude that the imme- 

 diate results which are so striking are due largely to irrita- 

 tion at the place operated upon and not so definitely to 

 the loss of its functioning. The recovery is never com- 

 plete. A dog without a cerebellum may walk and swim 

 again, but not with the full vigor and steadiness of the 

 normal animal. Some clement of reinforcement or com- 

 pensation is permanently lacking. 



As regards the human nervous system, it is usually held 

 that the cerebellum is developed by practice and that it 

 comes to contain much of the synaptic machinery for 

 maintaining the balance at rest and in motion. It has 

 often been supposed to assume command of complex 

 movements which were at first guided at all stages by 

 the cerebrum. Thus, it has been imagined that a child 

 learning to walk, whose attention is plainly concentrated 

 upon the taking of each step, is dictating its uncertain 

 movements from the cerebral cortex, but that the higher 

 mechanism is in time relieved of the detail and set free 

 for new activities, the cerebellum taking its place, at least 

 to a considerable extent . 



If this is a correct conception, it may be inferred that 

 later acquirement- .if the individual, such as swimming 

 <>r -kating, may likewise call for cerebral direction until 

 they become easy and unconscious, when their govern- 

 ment may be cerebellar. According to this view, the 

 cerebellum is intimately related to all accomplishments 

 which we can -peak of a- "second nature." Hut this is 

 more certainly true of those which involve a large share 

 of the muscles than of localized actions. The use of a 



