Chap. XXIV.J PRINCIPAL PARTS OF THE BRAIN« 509 



the Optic Nerves, and with the ordinary Sensory Nerves of 

 the body). 



In the relations, therefore, of the Cerebrum with the 

 Cerebellum for the execution of Voluntary Movements, cross 

 connections exist analogous to those between the Cerebral 

 Hemispheres and the opposite halves of the Spinal Cord. 

 Whilst in the part which it plays as a supreme motor • 

 centre in connection with the higher kinds of Automatic 

 Movements, the Cerebellum is again called into activity 

 precisely as if it were a very specialized segment of the 

 Spinal Cord itself.* 



If we are to attempt shortly to sum up its functions, it 

 may be said that the Cerebellum is a supreme Motor 

 Centre for reinforcing and for helping to regulate the 

 qualitative and quantitative distrihiition of outgoing cur- 

 rents, in Voluntanj and Automatic Actions respectively : 

 or, more briefly still, that it is a supreme organ for 

 the reinforcement and regulative distribution of out- 

 going currents. 



After what has been already set forth, and in face of all 

 the difficulties previously enumerated, it is easy to imagine 

 that the Cerebellum might appear to some to be an 

 organ largely concerned with the ' co-ordination of move- 

 ments '; that it might be regarded by others as the seat of 

 a ' muscular sense ' ; and that it should seem to others 

 still, to have to do with the ' supply or liberation of motor 

 force for movements generally.' On the other hand, that 

 it should appear to have nothing to do with Instinct, 



* See p. 502. Many of these ' sensori-motor ' or Automatic Move- 

 ments would, however, be of a bilateral type; and such Movements 

 would probably be excitable through either half of the Cerebellum 

 (as it is with the Cerebrum). Hence we have another reason why 

 unilateral diseases of the Cerebellum should often be associated with 

 obscure and ill-defined motor defects. 



