CHAP. XXIV.] PRINCIPAL PARTS OF THE BRAIN. 487 



in course of the day, after the sleep had lasted many hours ; the 

 awakening being due, it might be, to intrinsic stimuli started in 

 the brain, or it might be to slight external unavoidable stimuli act- 

 ing through his still functional sense organs, and making them- 

 selves felt in consequence of the sensitiveness of the brain being 

 increased during the repose of sleep." 







Nothing could show more distinctly than such a case as 

 this the importance of the activity of the Sensorial Regions 

 of the Hemispheres for the production of what we know 

 as Consciousness. It seems clear, indeed, that if Con- 

 sciousness is not in some way an immediate appanage of 

 the activity of these very regions of the Hemispheres, 

 their activity is, at all events, an essential forerunner 

 of that of some other regions between whose activity 

 and Consciousness there is such an immediate associa- 

 tion. 



On the other hand, it is equally clear that the stimulat- 

 ing sensorial impressions are double, coming to each 

 Hemisphere of the Brain from opposite halves of the body, 

 and that their subjective accompaniments are merged 

 into a single Consciousness of this or that kind. The final 

 proof of this position is afforded by the effects of injury 

 to certain portions of the Brain on one side only in some of 

 the lower animals, and by the effects of unilateral disease 

 of corresponding regions of the Brain in Man. Thus, where 

 we have to do with injury or with disease of the posterior 

 third of what is known as the ' internal capsule ' that is, 

 of that portion of the expansion of the Cerebral Peduncle 

 which lies between the posterior part of the Corpus Stria- 

 turn and the Thalamus there is found to be complete 

 loss of sensibility on the opposite half of the body (Hemi- 

 anaesthesia). No touch can be felt, and all the other 

 avenues of sense on this side are similarly closed the 

 tongue and side of the mouth are dead to flavours, the 



