76 PHYSIOLOGY AND HEALTH. 



the air, not many hundred, but even many thousand, times 

 a second. 



636. These muscles work in concert, and produce, by 

 their cooperation, just the motions that are required. It is 

 interesting to see how exact is this harmony, and with what 

 precision is the power measured from, and exertion made 

 by, each one in creating any motion. We lift the hand to 

 the chin, then to the mouth, then to the nose, to the eye, 

 and to the forehead. In each of these motions, there is a 

 combination of several or many muscular actions ; each 

 muscle and each fibre pulls just so much as, and no more 

 than, is necessary to carry the hand exactly to the place 

 appointed. A very sjight change of force of one of the 

 muscles in the shoulder carries the hand from the mouth 

 to the nose, and from the nose to the eye, or lets it fall upon 

 the breast. 



637. Performers on the piano strike the varied notes 

 with equal precision: first a, then b, then c sharp, then 

 an octave, or a fifth, or a third. In all these changes, the 

 hand moves half an inch r quarter of an inch, four inches 

 and one half, six inches and a quarter, whatever distance 

 is required, it moves just so much and no more, and hits 

 the exact note. This is done by the muscles of the shoul- 

 der, elbow, and the wrist, all in harmonious cooper- 

 ation. However small an extent of contraction of the 

 muscle at the shoulder, at the short end of the lever, 

 is needed to carry the hand a quarter of an inch to the 

 right or to the left, just that extent, that hair-breadth of 

 contraction, is made, no more, no less, and the unerr- 

 ing finger hits the note. 



638. The complete government of the muscular action 

 is still more remarkably manifested in the skilful violinist. 

 He determines his notes by touching the tip of his finger 

 on the strings. If he touch them a little higher or a little 

 lowor, he varies the note. The most accomplished players 

 acqaire such exact control and discipline of the muscles 

 of their fingers, that they can produce at will the minutest 



