OH. XLVin.] 



MOTOR AREAS. 



671 



consequence that area of the brain loses its blue tint. If the animal is so 

 deeply narcotised that the brain does not discharge an impulse, the part 

 stimulated remains blue. 



By such means the cortex has been mapped out into what we 

 may provisionally term motor areas, and sensory areas. 



Motor areas. These areas are also termed sensori-motor or 

 kincesthetic, for reasons which will be explained more fully later. 

 The name Rolandic area which they have also received is derived 

 from their anatomical position. 



Stimulation of them produces movement of some part of the 



CORD 



Fig. 495. Degeneration after destruction of the Rolandic area of the right hemisphere. 



(After Gowers.) 



opposite side of the body ; excitation of the same spot is always 

 followed by the same movement in the same animal. In different 

 animals excitation of anatomically corresponding spots produces 

 similar or corresponding results. It is this which has enabled one 

 to apply the results of stimulating areas of the monkey's brain 

 to the elucidation of the function of the similar brain of man. 



Extirpation, or removal, of these areas produces paralysis of the 

 same muscles which are thrown into action by stimulation. 



The degeneration tracts after destruction of the Rolandic area 

 are shown in fig. 495. 



The shaded area in each case represents the injured or de- 

 generated material ; A in the cortex, B in the anterior part of the 

 posterior limb of the internal capsule, c in the middle of the 

 crusta of crus and mid-brain, D in the pyramidal bundles of 



