THE SPINAL CORD AND CEREBELLUM 145 



pigment, it may be asked, or to a more plentiful 

 supply of blood than goes to other parts of the 

 organ? One is also naturally led to connect this 

 matter with the colouration of the red nucleus, 

 which is in very close anatomical relationship to 

 the cerebellum. 



Perrier asserts that the mechanism of cerebellar 

 co-ordination is essentially independent of conscious- 

 ness and volition, a statement which, seeing that 

 voluntary muscular action is almost invariably one of 

 the chief factors in it, sounds at first rather like a 

 contradiction in terms. He contends that in many 

 animals you may abolish both consciousness and 

 volition by removing the cerebral hemispheres, and 

 still leave the mechanism of equilibration intact. But 

 it is evident that if the sensory element is to be found 

 in the cerebral cortex, removal of the latter or of the 

 greater part of the hemispheres would leave a most 

 essential part of the mechanism of volition un- 

 touched. 



That one-half of the cerebellum should correspond The rela- 

 tionship 

 to one-half of the body — nay, more, that individual between 



parts of each half should bear a functional relationship cerebellum 



to certain groups or sets of muscles, or even to certain of muscjS! 



movements — is perfectly natural and in accordance 



with the ' increase of impulse ' theory of cerebellar 



functions. It also agrees with the fact that when 



lesions as nearly as possible symmetrical are produced 



on both sides of the cerebellum, the amount of 



disturbance of the equilibrium is very slight. This, 



10 



