Scr 



COR 



ff. 



FUNCTIONS OF THE CEREBRAL HEMISPHERES 435 



was a matter of indifference whether the brain substance was taken from the 

 anterior or from the posterior portions of the hemispheres. Flourens there- 

 fore concluded that the cerebral hemispheres acted as a whole as the seat of 

 the will and intelligence. There is no doubt that Flourens was so far per- 

 fectly correct, since all parts of the brain must co-operate in determining 

 the psychical condition of any individual in any given moment. He was 

 however, as later researches showed, in error in thinking that no difference 

 could be distinguished between the parts contributed by the various con- 

 volutions of the brain to the organic whole which is called consciousness. 



As we have seen, histological 

 evidence, which in the case of 

 the cerebellum displays a 

 marked uniformity throughout 

 the whole cortex, in the case 

 of the cerebrum reveals strik- 

 ing differences between its 

 various areas. The demarca- 

 tion of the cerebral cortex into 

 areas according to the histo- 

 logical structure of their grey 

 matter agrees with, and in 

 many cases supplements, the 

 results procured by an experi- 

 mental inquiry into the func- 

 tions of the different parts. 



That there is a localisation 



of function in the COrteX SO FIG. 225. Upper surface of dog's brain, showing 



far as concerns the movements results of excitation. (FRITSCH and HITZIG.) 



e , i -i f . ! i -i A, neck muscles : +, movements of fore limb ; 



Ot the two Sides Ot the body ^ movements of hind limb; O, movements of 



was known to Galen, who men- f ace ; ASG > anterior sigmoid gyrus ; PSG, posterior 



,. , sigmoid gyrus ; COR, coronary fissures ; Scr, crucial 



tions the occurrence 01 paralysis su icus. 

 on one side of the body as a re- 

 sult of lesions in the brain of the opposite side. In 1861 a French physician, 

 Broca, confirming older statements by Dax and Bouillaud, maintained that 

 aphasia, i.e. loss of power of speech, when it occurred in right-handed people 

 was always associated with a lesion of the third frontal convolution of the 

 left hemisphere, which has ever since that time been known as Broca's 

 convolution. Hughlings Jackson in 1864 drew attention to the connection of 

 localised spasms (Jacksonian epilepsy) with lesions of certain parts of the 

 central convolutions. On anatomical grounds Meynert considered that the 

 posterior portions of the hemispheres were probably mare nearly connected 

 with sensation, and the anterior with the power of movement ; but direct 

 evidence of motor localisation was first brought by Fritsch and Hitzig in 

 1870JI These observers pointed out, in contradiction of the then received 

 idea/'that the grey matter of the cortex was excitable, and that it was 

 possible to evoke co-ordinated movements of the limbs on stimulating the 



