🖐️ Our Wonderful Skin — And What It Does For Us
Making certain outgrowths of skin which we all know very well.
Our skin does not produce so many of these as does the skin of many animals, but at any rate it produces two kinds of outgrowth: hair and nails. Our nails are very interesting, for they correspond to the claws of a cat or a tiger, and also to the hoofs of a horse.
A horse's hoof is really the nail of the middle finger or the middle toe; it has lost the other fingers and toes, or rather its ancestors lost them for it. For many creatures, these outgrowths of the skin at the ends of their fingers and toes are extremely important.
Perhaps they catch their prey by them, or else they walk upon them, or else they can climb by them. But in us these things have lost their importance, just as so many other parts of our bodies have lost their importance, because we have intelligence, by means of which we are able to do things for which animals require to use claws and teeth, and so on.
Still, our nails remain, though they are too weak and thin to be of much use, but at least they have a very interesting history. They grow from below, and can be completely removed without destroying the cells which make them.
If you play base-ball, or even if you do not, you may have had a nail banged. If it is [black and] blue, there has been some bleeding under the nail. In course of time the nail gets loose and comes off, and then a new nail gradually forms underneath it. But if damage had been done to the special cells which have the power of making the nail, then no new nail could ever form again.
Perhaps you have noticed that sometimes the nails show white lines across them, or perhaps even little grooves.
After an illness, these marks may appear on all our nails, and at just about the same height in each case. They mean that during the illness the blood was not quite well, and so the cells that make the nails did not do their work quite properly, and therefore these little flaws appear.
Gradually they pass up to the tip of the nail, as it is pushed onwards, until at last they disappear. Anyone who notices this could guess that you had had an illness. I think this is one of the ways in which clever people sometimes pretend that they can tell you all about yourself by looking at your hands.
Hair is the other thing which our skin produces. The part of the hair that shows above the skin is really made of very much the same kind of material as the epidermis, or outer ski.
The law of life.
There is a fine saying of one of the greatest men who ever lived, the Italian artist Leonardo da Vinci: "Thou, O God, has given all good things to man at the price of labor." This applies to everything, even to the people who cannot stand sun or cold or fresh air because they coddle themselves up too much. They have taught their skin not to labor for itself, and have made it weak and helpless.
THE WONDERFUL LITTLE STRUCTURES THAT GIVE US THE SENSE OF TOUCH
But there still remain some most important facts about the skin of which we have said nothing. It is one of the great organs of sense or feeling. We are rather apt to confuse the various kinds of sensation that our skin gives us, as if they were all varieties of the same thing, but they are not. There is, first of all, the pressure sense, or sense of touch. This is quite different from the sense of pain, or of temperature.
If we examine the true skin, and especially if we examine it in the tips of the fingers and toes, we find special little structures in it which are there for the purpose of touch. Nerves run to them, and the ends of the nerves spread out within them. Wherever these little touch-bodies, as they are called, are most numerous, there our sense of touch is most delicate, and that is why so many of them are found in the tips of the fingers, where it is necessary that we should feel very delicately.
Many of them are also found in the skin of the lips, and they also occur in the tip of the tongue. Two points can be felt as two by the skin of a forefinger, when they are very close together, but if the distance between them is increased by twenty times, we can only feel them as one when they are applied to the skin of the back. The skin of the forehead and of the palm of the hand will feel the lightest weight, while the skin of the chin requires the weight to be twenty times as heavy before it can be felt.
THE NERVES THAT GIVE US THE FEELING OF HEAT AND COLD
The sense of heat and cold is quite distinct from the sense of touch, and has a quite special set of nerves for itself. If you take a cold thing, like the tip of a lead pencil, and pass it over your cheek, you will find that it feels colder at some spots than at others, and the same is true of anything hot. The skin seems to be made up of a host of little spots: pressure spots that are sensitive to pressure or touch, cold spots that are sensitive to cold, and do not feel heat at all, and hot spots that are sensitive to heat, and do not feel cold at all.
Finally, there is the pain sense. Different parts of the body are very differently sensitive to pain, and the skin is far more sensitive in general than the inside of the body. The pain sense has a special set of nerves of its own, and in some people, who have something the matter with these nerves so that the nerves cannot act, the skin of the hand will appreciate heat and cold and touch, but pins can be run into it, or it can be pinched, without any feeling of pain at all.
HOW THE SKIN PROBABLY HELPS US TO KNOW THE POSITION OF OUR BODY
So we must think of the skin as the organ for three senses (pressure, temperature, and pain) and not as the organ merely of one sense. People often say that we have five senses, but, as a matter of fact, the number of senses we possess is far more, and three of them must be put down to the credit of the skin alone. It is also probable that we are helped to know the position of our body (where our hands and feet are, and so on) by the amount of stretching of the skin in one part, or loosening of it in another part, which helps the brain to know where the different parts of the body are. So, in addition to everything else that it does, the skin contributes to our sense of position, one of the senses without which it would be exceedingly difficult to live, but about which great numbers of people have never heard anything.
📌 Source:
Excerpt from: The Book of Our Own Life — from The Book of Knowledge
Status: ✅ Public domain — shared here for educational purposes