The hand allows man to use tools. If you have watched the cleverest trained ape use the simplest tool, a spoon for instance, you realize that he really has a modified paw. He has nothing like the range of motions of a human hand. No wonder that we speak of a good workman as being handy with his tools.
Small as the hand is in comparison to the rest of the body, it has twenty-seven bones, counting those in the wrist; and there are nearly half a hundred joints. There are so many ligaments supporting these joints that I doubt if they all have names.
Right here you should be reminded that in speaking of the front, back, inner, and outer sides of the hand, we consider the man as standing upright with his little fingers to the seams of his trousers and his thumbs out. Hence the palm is the front, even though when you are standing at ease or walking about you habitually hold your hands in the opposite position. There is rather a small amount of motion in any of the joints and the direction of the movement is usually very limited. Compare them with the shoulder joint which with the aid of some motion in the shoulder blade allows the arm to move across the front of the body for 360°, a full circle, and about three-quarters of a circle in a plane at right angles to this, not to mention much motion in the third plane.
The one finger that really has a fair amount of varied motion is the thumb. What a foolish metaphor we use when, in speaking of a man who is clumsy with his hands, we say that he is all thumbs. Lose your thumb and your hand is not much better than an elaborate hook. Your forefinger is easily the best of your four fingers, but, if you lose it, you soon learn to substitute your middle or even your ring finger. You cannot substitute a finger for your thumb.
This is because the thumb is set off to one side with an arrangement of joints and muscles very different from that of the fingers. This allows the front or working part of the thumb to be opposed directly to the front of the fingers. The most delicately sensitive skin of the body is found on these soft front pads. So highly may the feeling and finely adjusted motions here be developed that we often speak of the "educated finger" of the surgeon.
The motions of the digits require many muscles, some of which start as high as the elbow and have long tendons running through tunnels. Who of you ever heard of the seven interossei and four lumbrical muscles of the hand? Yet these eleven little slips allowed Benvenuto Cellini to fashion his magnificent jewels and Fritz Kreisler to charm us with his violin. Either man could have lost many pounds of thigh or calf muscles, of which you are so well aware, yet the world would have lost little.