244 HUMAN PHYSIOLOGY 



Partial extirpation often results in the temporary dis- 

 appearance of functions, but after some time these functions 

 reappear. 



The results of experiments in stimulation and extirpation 

 have been variously interpreted. The adherents to the 

 localization theory hold that the effect of stimulation is pro- 

 duced by the stimulation of the motor centres which arc 

 employed in executing voluntary movements ; the opponents 

 of this theory hold that by this stimulation we do not really 

 stimulate the centres, but the motor fibres which pass through 

 the stimulated spot. The disappearance of a function by 

 extirpation and the subsequent reappearance of that function 

 depend, according to the adherents of the localization 

 theory, upon the fact that the centre in which the function 

 is located has been removed, but that subsequently other 

 centres have gradually taken up this function. In the re- 

 appearance of the function after partial extirpation the 

 opponents of the localization theory find support for their 

 position that the psychical functions are not definitely 

 localized. The first disappearance of the function they re- 

 gard as due to the inhibitory influences caused by the injury 

 [Hemmungserscheinungen] . 



Although at present the views concerning the localization 

 of functions in the cerebral cortex of animals are at variance, 

 yet there are many observations which render it almost 

 certain that in man there is, to a certain extent, a localiza- 

 tion of the psychical functions in the cerebral hemispheres. 



The theory of the psychological topography of the human 

 cerebral cortex is based upon: 



(1) Anatomical and embryological investigations on the 

 course of fibres, by which parts of the cerebral cortex are 

 connected with each other as well as with other parts of the 

 central nervous system. 



(2) Upon clinical observations in connection with the 

 results of pathological anatomical investigations. 



Topography of the cerebral cortex of man. The cere- 

 bral cortex of man may be divided into : 



