CHAP. XXVII.] CEREBRAL MENTAL SUBSTRATA. 593 



Centre may, at times, and according to the nature of the 

 stimulus, form the starting point both in 'sensori-motor' 

 and in l ideo-motor' Acts, whence outgoing stimuli issue 

 to rouse the Motor Centres. But whether these im- 

 pulses pass off from such ' special' or 'visceral' Centres 

 directly, or whether (without our consciousness) they pass 

 from them to, and then oif from, some parts of the Kin- 

 aesthetic Centres must be considered to remain, for the 

 present, very uncertain. 



On other occasions, either of the ' special ' Perceptive 

 Centres may receive impressions which form the initial 

 starting points of currents ending in Voluntary Acts ; 

 though the immediate execution of the Movement thus 

 prompted may, in the case of the majority of limb-move- 

 ments, be dependent upon the secondarily excited guidance 

 of co-active Visual and Kinaesthetic Centres just as in 

 the case of the complex movements concerned in Articu- 

 late Speech, the immediate execution of such movements 

 is dependent upon the regulative activity of the combined 

 Auditory and Kinaesthetic Centres.* 



Owing to the great preponderance of movements of the 

 right arm and hand, as compared with those on the left side, 

 the Kinaesthetic Centre of the left Cerebral Hemisphere 

 would be much better developed, in the great majority of 

 persons, than that of the right Hemisphere. The impres- 

 sions of the Kinaesthetic Sense are, in this respect, pre- 

 cisely like those of Touch and these two kinds of sensory 

 endowments, as we have seen, merge into one another 

 so imperceptibly as to make it, in part, impossible to 

 separate their Cerebral Centres from one another. 



This preponderating activity of the left Cerebral Hemi- 

 sphere in regard to Tactile and Kinaesthetic Impressions 

 (about which there is no room for doubt) raay have some- 

 * See p. 555, and Chap. xxix. 



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