In order that the complex mechanism of the hand may work so wondrously, it is abundantly supplied with blood and nerves. All of you have had your pulse taken at the wrist. Your nurse or doctor counts beats here because there are few places in the body where so much blood surges through an artery near the surface. Yet I can assure you that if that radial artery is cut, plenty of blood will get to the hand by other routes. Nature intends to look out for that important hand.
Nature has also provided plenty of nerves to move all these important muscles and give plenty of feeling. The ulnar nerve is over on the little finger side, the median in the middle, and the musculo-spiral on the thumb side. A warning may be issued right here. If these names are really important to you, look them up. I may be using old-fashioned names. In my student days we called the first bone in the wrist the scaphoid, which is Greek for "like a boat." A young physician just graduated would not now understand me, for he says "navicular," which is Latin for "like a boat." In my childhood, the oldsters were buried by undertakers. Later when I began to sign death certificates they were collected by morticians. Now I find from the yellow pages of the telephone book that funeral directors have taken over. Fashion rules in anatomy or death.
Many of the nerves of the body have a specialized function. They are either motor for moving muscles, or sensory for feeling. The nerves of the hand are mixed. Thus the ulnar moves some muscles, especially the smallest giving the most accurate movements. But it also gives feeling in the skin. If the ulnar nerve has been cut, a pin prick will not be felt on the little finger or on the adjacent half of the ring finger. The feeling of the other side of the ring finger is supplied by the median nerve as are the other fingers. The musculo-spiral supplies little feeling in the skin. I do not expect you to remember all this but you can see that a surgeon who does can tell pretty well what nerves have been injured. The palm of the hand may in the manual laborer become very tough and calloused and yet retain much sensitivity and pliability. Its toughness and strength are due to the fact that beneath the skin and firmly attached to it is a sheath of so-called fascia which is very dense, strong tissue. The anatomists describe three main furrows or creases which allow the necessary pliability. There are always numerous minor creases on which palmists base their interpretations of character. It is safe to say that palmistry's occult claims are analogous to those of phrenology in the last century. Bumps on the outside of the skull were then supposed to reveal the inner secrets of men's personalities. They were more likely to be due to accidents.
But no part of the body is entirely sufficient to itself. Some of the motions of the hand, for instance, start at the elbow. Possibly a professional pianist could earn a living if his hands were always held palms down, but I cannot think of any other workman who could do his job without some roll of the hand which has to start at the elbow.