CHAPTER XXIV 

 MOTOR IMPRESSIONS 



THE very fact that the sense of touch becomes lodged, 

 to so large an extent, in the emancipated hand of the 

 arboreal animal becomes a guarantee that this hand will 

 be called upon to discharge its tactile function in a variety 

 of ways. All sorts of uses, previously quite foreign to it, 

 will be demanded of it in virtue of its possibilities as a 

 tactile organ. The combination of the increasing tactile 

 perceptions, and the freedom of movement, creates a 

 condition which ultimately leads to the most important 

 developments. 



The sensory stimuli streaming from the hand towards 

 the central nervous system must become associated in the 

 most intimate way with the motor impulses streaming 

 to the mobile fingers. There is, in the end result, no 

 gross alteration of the mechanism of the hand, but there 

 is an enormous alteration in the nervous control over 

 the hand, and the purposive skill with which it can be 

 used. The hand, as a strangely primitive anatomical 

 structure, becomes applied to all the finer and more 

 skilful movements which the life necessities of the animal 

 can demand of it. Every increase in cerebral develop- 

 ment will make new demands upon it, and these demands 

 are met by an increase of range of controlled, co-ordinated, 

 fine movements. To those who, in the literature of a 

 bygone age, were termed the " curious " it will appeal 

 as an interesting theme that this hand, anatomically one 

 of the most primitive parts of Man's body, one to be so 

 nearly matched among the " hands " of the lowest 

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