SENSATION 



no longer of all the small, subtle shades of sensation and 

 acts of will which were necessary in learning. The mere 

 impulse of the will to paint the picture once more or 

 play the piece again suffices to release the whole chain 

 of complicated movements and accompanying sensations 

 which had originally to be learned slowly, laboriously, 

 and with full consciousness. An experienced pianist 

 plays the most difficult piece — if he has learned it and 

 repeated it thousands of times — "half in a dream." 

 But it needs only a slight accident, such as a mistake or 

 a sudden interruption, to bring back the wandering 

 attention to the work. The piece is now played with 

 clear consciousness. The same may be said of thousands 

 of sensations and movements which we learned at first 

 consciously in childhood, and then repeat daily after- 

 wards without noticing — such as in walking, eating, 

 speaking, and so on. These familiar facts prove of them- 

 selves that consciousness is a complicated function of the 

 brain, by no means necessarily connected with sensation 

 or will. To bind up the ideas of consciousness and sensa- 

 tion inseparably is the more absurd, as the mechanism or 

 the real nature of consciousness seems very obscure to 

 us, while the idea of it is perfectly clear: we know that 

 we know, feel, and will. 



The word "irritability" is generally taken by modem 

 physiology to mean that the living matter has the 

 property of reacting on stimuli — that is to say, of 

 responding by changes in itself to changes in its en- 

 vironment. The stimulus, or action of a foreign energy, 

 must, however, be felt by the plasm before the cor- 

 responding stimulated movement (in the form of va- 

 rious manifestations of energy) will be produced. Hence 

 the question whether this sensation is (in certain 

 cases) associated with consciousness or (generally) 

 remains unconscious is of a subordinate interest. The 

 plant that is caused to open its floral calyx by the 



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