THE NERVOUS SYSTEM 357 



to attention is made by the impulses which pass through it. It 

 is as if currents which have to overcome resistance in a narrow 

 path acquire a higher potential than those which find an open 

 road. And since the making of the road depends upon atten- 

 tion, the limit of broadening is reached when a volitional act 

 becomes a habit. The first time that a piece of music is played 

 consciousness is alert. Marks on the page and movements of 

 the fingers are felt intensely. With each repetition the need for 

 attention subsides. 



A skilled movement is impossible in the absence of guiding 

 sensations. I decide to button my coat. Sensation-paths 

 from the muscles of the forearm are opened into motor paths 

 extending from the large pyramids in the arm-centres of the 

 kinaesthetic cortex. But it is not sufficient that the action be 

 started : it must be guided by the sensations which move- 

 ment produces. If my fingers are numb with cold, I cannot 

 button the coat. The muscles which move the fingers are 

 warm enough beneath the sleeve, but my attempts to will them 

 to move are as futile as they would be if the muscles belonged 

 to some other person. The will has no power over the muscles. 

 It is essential that the sensations which accompany the act of 

 buttoning the coat flow through the same paths as hitherto 

 in the cortex of the brain. Flowing through the same paths, 

 they produce the same effect in consciousness, the same per- 

 ceptions. In ordinary parlance, one cannot perform any act 

 unless one can remember what it felt like to perform it on a 

 previous occasion. It is almost as sound physiology to describe 

 the voluntary action of fastening a button as commencing in 

 the skin of the fingers as to describe is as commencing in the 

 brain. The act is due to the direction of attention to impulses 

 which flow from muscle to muscle, and from skin to muscle. 



All skill in the use of muscles is acquired by the method of 

 trial and error. Familiar movements are tried, combined, 

 modified with a view to the production of a new result. A 

 man accustomed to striking with the right hand forwards 

 endeavours to swing a golf-club with the left hand backwards. 

 For a long time the result is anything but a success. At 

 length the head of the club takes the right curve. It not only 

 hits the ball with its centre, but it carries it through in the right 

 line. The ball travels 120 yards or so towards the green. 



