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FUNCTIONS OF THE CEREBRUM 



[CH. L. 



brain to the elucidation of the function of the similar brain of 

 man. 



If the stimulation used is too powerful the movement spreads to 

 other parts, and a considerable portion of the body may be thrown 

 into convulsive movements similar to those seen in epilepsy. 



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

 same groups of muscles which are thrown into action by stimulation. 



The degeneration tracts after destruction of the motor area are 

 shown in fig. 447. The shaded area in each case represents the 

 injured or degenerated material ; A in the cortex, B in the anterior 

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



CORD 



MID. BRAIN 



FIG. 447. Degeneration after destruction of the Rolandic area of the right hemisphere. 

 (After Gowers.) 



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

 of the pons, E in the pyramid of the bulb, and F in the crossed 

 and direct pyramidal tracts of the cord. 



Sensory areas. Stimulation of these produces no direct move- 

 ments, but doubtless sets up a sensation called a subjective sensation ; 

 that is, one produced in the animal's own brain, and this indirectly 

 leads to movements which are reflex; thus on stimulating the 

 auditory area there is a pricking up of the ears ; on stimulating the 

 visual area there is a turning of the head and eyes in the direction 

 of the supposed visual impulse. That such movements are reflex 

 and not direct, is shown by the long period of delay intervening 

 between the stimulation and the movement. 



Extirpation of a sensory area leads to loss of the sense in question. 



