CHAPTER XIII. 



LOCALISATION OF FUNCTION. 



Connections of the central system Segmental arrangement- 

 Localisation Multiple innervation Crossed connections 

 Relative importance of cerebral centres Difficulty in the 

 way of a general interpretation Pathway of fibres Cortical 

 areas Motor areas Arrangement in man Character of 

 movements Nature of cortical control Latent areas 

 Modification of cortical discharge Refinement of control 

 Afferent impulses affecting development Pyramidal tracts 

 Sensory areas Multiple representation Crossed control 

 Secondary pathways Problem of the " unused" hemisphere. 



IF we picture the entire nervous system of man com- 

 posed of a central axis from which nerves pass to all 

 the portions of the body, we shall have the basis from 

 which to start the present inquiry (see Fig. 50). 



The roots here represented as arising from the central 

 axis caudad to the pons, contain fibres which transmit 

 not only afferent, but efferent impulses. The fibres 

 which give sensibility to any part, enter the central 

 system near the point from which emerge those that 

 control its movements. As might be expected, there- 

 fore, the parts to be controlled are most directly under 

 the influence of the afferent stimuli which arise in their 

 immediate neighbourhood. This arrangement recalls 

 the segmental structure of the central system, whereby 

 both the sensory and motor nerves belonging to a given 

 segment of the body are localised in a corresponding 



