CHAPTER XXIX

PROTECTED BY THE SKIN

There is no doubt about the value of the work which certain scientists did in 1775. These men were anxious to know how much heat the body of man can endure and still keep at its work. For the sake of making no great blunder, they began their tests by passing from one heated room to another until they found themselves living and breathing in a room in which the thermometer showed a heat of 210° F. This is but two degrees cooler than the temperature which water needs for boiling.

As may be imagined, the air of the room felt very hot. One man, however, stayed in it for ten minutes. During this time the heat was so great that it twisted and broke the ivory frames of all the thermometers but one. More than this, the air which the man inhaled was so much hotter than that which he exhaled, that, with each breath which he drew, he felt as if he were scorching his nostrils. But with each exhalation his nostrils were cooled again. He took the thermometer in his hand and blew on it. At once the mercury sank in the

1 Fahrenheit.

tube, showing that his breath was cooler than the room. He blew on his fingers and they were cooled too.

In another experiment afterwards, the same men went into a small room which was even hotter than any they had been in before. Here the thermometer showed 260° F. This, then, was forty-eight degrees hotter than water needs for boiling. As they entered, the air felt hot but they could bear it. And while they stayed there they did various things to show what the heat of the room was able to accomplish. They took a piece of raw beefsteak, left it uncovered, took a pair of bellows, blew the heated air across the steak for thirteen minutes, and found that it was rather overcooked. An egg was roasted hard in twenty minutes; water soon boiled and bubbled; watch chains became too hot to be touched; and rings had to be left off, lest the heated metal should burn a deep circle about the tender flesh of the finger. Leather shoes could not be worn, for the leather itself curled up and was ruined.

All this happened to their possessions, but the men themselves, although surrounded by the same heated air, were neither boiled nor roasted. They lived and breathed in the place, escaped alive, and their escape was no miracle. It was explained by the power of the sweat glands. If these small laboratories had stayed inactive, the scientists might have suffered from the heat even as did the steak. But their glands were able to save them.

As soon as the men entered the heated room the sweat glands began their work; perspiration was manufactured in quantities; it poured from the open flues of countless small laboratories and emptied itself upon the skin, whence it was evaporated. Thus perspiration kept

A SWEAT GLAND

ON THE SKIN

the skin moist, and the evaporation of the moisture kept the surface of the body cool enough to save it from being cooked. Certainly the men were uncomfortable from first to last, but they did not suffer. The record of these experiments is given in the Philosophical Transactions of the Royal Society of London for the year 1775.

If you ever have the chance, watch the streaming, steaming backs of such men as pitch coal into the huge furnace of an ocean liner. There you will see the same work of protection carried on by AND ITS OUTLET these tireless glands. Their exact number is unknown, but by counting a few, in a small area of the skin, and by multiplying this number by the extent of the surface of the body, men estimate that each of us is supplied with about two million sweatgland laboratories. All are slightly busy most of the time, but only extraordinarily busy when emergencies overtake the body.

Just here review your knowledge of the skin and of perspiration as learned in Good Health:

1. The outside layer of the skin is called epidermis. It can be cut or pricked without giving pain. It protects all that lies underneath it, in the second layer of the skin.

2. The second layer- the dermis-holds capillaries, nerve fibers, hair cells with their muscles and oil glands, sweat glands, and pigment cells. These last contain coloring matter pigment which gives one boy freckles and another boy tan; which makes one man brown and another man yellow. Both nails and hair are constantly being formed in the dermis and pushed upward.1

3. Perspiration is a mixture of water and waste. It is poured out by the sweat glands when the body is heated or exercised. The water soon evaporates and cools the skin. The waste stays on the skin and must be washed or rubbed off; otherwise it mixes with oil from the oil glands, with bits of epidermis, with dust from the clothes and from the air, and stays like a snug, thin, perfectly fitting coat on the outside of the body from head to heel. A thick wrap of this sort interferes with the healthy action of the skin, and gives off an unpleasant smell. It may be removed by a hard, dry rub, and it is

1 Full directions about the care of both are given in Good Health.

CUT THROUGH THE LAYERS OF THE SKIN

A, horny layer of epider

mis; B, deeper layer of

epidermis; C, duct of sweat gland; D, dermis;

E, connective tissue in

which the black lines rep

resent blood vessels

important to take the rub when

ever a bath is out of the question. Since the skin is so well provided with blood vessels, it is natural that small wounds should heal quickly. Even when a patch of skin is entirely destroyed by being scalded or burned, there is such power of life left along the edges, that new skin grows out from it day by day until the chasm is entirely covered.

But there is a limit to what can be done in this direction, and at such times doctors step in with their wonderful help from grafted skin.

For each of us, however, there is something far more important than hot ovens, burned flesh, and the grafting of the skin. It is not probable that we ourselves shall meet these terrible experiences. But a very practical, everyday danger is always at hand. We may take cold through our ignorance of the laws of skin health and vigor. Let us therefore remember.

that the skin is constantly covered with a slight moisture called insensible perspiration, and that when there is