CHAPTER XXIX. 



THE CEREBRAL RELATIONS OF SPEECH AND THOUGHT. 



Our powers of Perception or Apprehension, of Thinking 

 or Reasoning, of Speaking, Naming, Writing — even of 

 expressing Thoughts by Gestures or the simplest Signs- 

 are all dependent upon cerebral processes very complexly 

 interrelated, as may have been gathered from what has 

 already been said. Much attention has of late years been 

 given by physicians and pathologists to the investigation 

 of disturbances of the normal relations existing between 

 these several processes, brought about by limited lesions 

 or injuries of different portions of the Brain. An analysis 

 of some of the typical conditions thus revealed will throw 

 more light than could otherwise be done upon the manner 

 in which Cerebro-mental processes are correlated with one 

 another. It will serve to convey some faint outline of the 

 mode in w^hich the higher processes of Sensory Apprehen- 

 sion, Thought, and Intellectual Expression (and conse- 

 quently of ' Volition ') are dependent upon one another, 

 and also of the mode in which these processes are related 

 to the activity of some imperfectly defined areas in the 

 cortex of the Cerebral Hemispheres. 



What is now to be set forth by means of illustrations 

 selected from some of the abnormal mental conditions 

 produced by Cerebral Disease, whilst it will suffice to test 

 and illustrate the accuracy of the views expounded in the 

 last chapter, may also be regarded as the continuation 

 of what has been said in Chapters xxiv. and xxv. We 

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