30 PSYCIIOLOGT. 



substrata of consciousness), are made up of notliing else 

 than nervous arrangements, rejiresenting impressions and 

 movements. ... I do not see of what other materials 

 the brain can be made." Meynert represents the matter 

 similarly when he calls the cortex of the hemispheres the 

 surface of projection for every muscle and every sensitive 

 point of the body. The muscles and the sensitive points 

 are represented each by a cortical point, and the brain is 

 nothing but the sum of all these cortical points, to which, 

 on the mental side, as many ideas correspond. Ideas of 

 sensation, ideas of motion are, on the other hand, the ele- 

 mentary factors out of ivhich the mind is built up by the 

 associationists in psychology. There is a complete parallel- 

 ism between the two analyses, the same diagram of little 

 dots, circles, or triangles joined by lines symbolizes equally 

 well the cerebral and mental processes : the dots stand for 

 cells or ideas, the lines for fibres or associations. We shall 

 have later to criticise this analysis so far as it relates to 

 the mind ; but there is no doubt that it is a most convenient, 

 and has been a most useful, hyjDothesis, formulating the 

 facts in an extremely natural way. 



If, then, we grant that motor and sensory ideas variously 

 associated are the materials of the mind, all we need do to get 

 a complete diagram of the mind's and the brain's relations 

 should be to ascertain which sensory idea corresponds to 

 which sensational surface of projection, and which motor 

 idea to which muscular surface of projection. The associa- 

 tions would then correspond to the fibrous connections be- 

 tween the various surfaces. This distinct cerebral localization 

 of the various elementary sorts of idea has been treated as 

 a ' postulate ' by many physiologists (e.g. Munk) ; and the 

 most stirring controversy in nerve-physiology which the 

 present generation has seen has been the localization- 

 question. 



THE LOCALIZATION OF FUNCTIONS IN THE 

 HEMISPHERES. 



Up to 1870, the opinion which prevailed was that which 

 the experiments of Floureus on pigeons' brains had made 

 plausible, namely, that the different functions of the he mi- 



