The Blood Vessels under the Skin. Not merely the nails and the lips, but the whole surface of the skin is underlaid with a thick mat, or network, of blood vessels. These vessels are all quite small, so that a cut has to go down completely through the skin, and generally well down into the muscles, before it will reach any blood vessel which will bleed at a dangerous rate. But there are so many of them, and they cover such a wide surface throughout the body, that they are actually capable of holding, at one time, nearly one-tenth of all the blood in the body.
This "water-jacket" coat of tiny blood vessels all over our body has some very important uses: It allows the heart to pump large amounts of blood out to the surface to be purified by the sweat glands, and to breathe out a little of its carbon dioxid and other gas-poisons.
The Skin as a Heat Regulator. Heat, as well as waste, is given off by the blood when it is poured out to the surface; so another most important use of the skin is as a heat regulator. As we have already seen, every movement which we make with our muscles, whether of arms and limbs, heart, or food tube, causes heat to be given off. We very well know, when we work hard at anything, we are likely to "get warmed up." Although a certain amount of this heat is necessary to our bodily health, too much of it is very dangerous.
Just as it is best for the temperature, or heat, of a room to be at about a certain level, somewhere from 60° to 70° F., so it is best for the interior of our bodies to be kept at about a certain heat. This, as we can show by putting a little glass thermometer under the tongue, or in the armpit, and holding it there for a few minutes, is a little over 98° F. (98.4° to be exact); and this we call "body heat," or "blood heat," or "normal temperature." Our body cells are, in one way, a very delicate and sensitive sort of hot-house plants, though tough enough in other respects.
Whenever our body heat goes down more than five or six degrees, or up more than two or three degrees, then trouble at once begins. If our temperature goes down, as from cold or starvation, we begin to be drowsy and weak, and finally die. If, on the other hand, our temperature climbs up two, three, or four degrees, then we begin to be dizzy and suffer from headache and say we have "a fever."
A fever, or rise of temperature, that can be noted with a thermometer, is usually due to disease germs of some sort in the body; and most of the discomfort that we suffer is really due more to the poisons (toxins) of the germs than to the mere increase of heat, though this alone will finally work serious damage.
However, as we well know from repeated experience, we need only to run or work hard in the sun for a comparatively short time to make ourselves quite hot enough to be very uncomfortable; and if we had no way to relieve ourselves by getting rid of some of this heat, we should either have to stop work at once, or become seriously ill. This relief, however, is just what nature has provided for in this thick coat of blood vessels in our skin; it enables us to throw great quantities of blood out to the surface where it can get rid of, or, as the scientists say, "radiate," its heat. This cooling process is hastened by the evaporation of the perspiration poured out at the same time, as we have seen.
One of the chief things in training for athletics is teaching our skin and heart together to get rid of the heat made by our muscles, as fast, or nearly as fast, as we make it, thus enabling us to keep on running, or working, without discomfort. As soon as we stop running, or working, the heart begins to slow down, the blood vessels in the skin contract and diminish in size, the flush fades, and we begin to cool off. We are not making either as much heat or as much waste as we were, and hence do not need to get rid of so much through our skins.
When we feel cold, just the opposite kinds of change occur in the skin. The blood vessels in the skin contract so as to keep as much of our warm blood as possible in the deeper parts of our body, and prevent its losing heat. As blood showing through the pavement-layer of the skin is what gives us our color, or complexion, our skin becomes pale and pasty-looking; and if all the blood is driven in from the surface, our lips and finger nails will become blue with cold. Here again, by changes in the skin, nature is simply trying to protect herself from the loss of too much heat.
If we exercise briskly, or eat a good warm meal, and thus make more heat inside of our body, then there is no longer any need to save its surface loss in this way; and the blood vessels in our skin fill up, the heart pumps harder, and the warm, rich color comes back to our faces and lips and finger nails.
So perfectly and wonderfully does this skin mesh of ours work, by increasing or preventing the loss of heat, that it is almost impossible to put a healthy man under conditions that will raise or lower his temperature more than about a degree, that is to say, about one per cent above, or below, its healthful level. Men studying this power of the skin have shut themselves into chambers, or little rooms, built like ovens, with a fire in the wall or under the floor, and found that if they had plenty of water to drink and perspired freely, they could stand a temperature of over 150° F. without great discomfort and without raising the temperature of their own bodies more than about one degree. If, however, the air in the chamber was moistened with the vapor of water, or steam, so that the perspiration could no longer evaporate freely from the surface of their bodies, then they could not stand a temperature much above 108° or 110° without discomfort.
Other men, who were trained athletes, have been put to work in a closed chamber, at very vigorous muscular exercise, so as to make them perspire freely. But while a thermometer placed in that chamber showed that the men were giving off enormous amounts of heat to the air around them, another thermometer placed under their tongues showed that they were raising the temperature of their own bodies only about half a degree. One man, however, happened to try this test one morning when he was not feeling very well, and didn't perspire properly, and the thermometer under his tongue went up nearly four degrees.
This "water-jacket" coat of tiny blood vessels all over our body has some very important uses: It allows the heart to pump large amounts of blood out to the surface to be purified by the sweat glands, and to breathe out a little of its carbon dioxid and other gas-poisons.
The Skin as a Heat Regulator. Heat, as well as waste, is given off by the blood when it is poured out to the surface; so another most important use of the skin is as a heat regulator. As we have already seen, every movement which we make with our muscles, whether of arms and limbs, heart, or food tube, causes heat to be given off. We very well know, when we work hard at anything, we are likely to "get warmed up." Although a certain amount of this heat is necessary to our bodily health, too much of it is very dangerous.
Just as it is best for the temperature, or heat, of a room to be at about a certain level, somewhere from 60° to 70° F., so it is best for the interior of our bodies to be kept at about a certain heat. This, as we can show by putting a little glass thermometer under the tongue, or in the armpit, and holding it there for a few minutes, is a little over 98° F. (98.4° to be exact); and this we call "body heat," or "blood heat," or "normal temperature." Our body cells are, in one way, a very delicate and sensitive sort of hot-house plants, though tough enough in other respects.
Whenever our body heat goes down more than five or six degrees, or up more than two or three degrees, then trouble at once begins. If our temperature goes down, as from cold or starvation, we begin to be drowsy and weak, and finally die. If, on the other hand, our temperature climbs up two, three, or four degrees, then we begin to be dizzy and suffer from headache and say we have "a fever."
A fever, or rise of temperature, that can be noted with a thermometer, is usually due to disease germs of some sort in the body; and most of the discomfort that we suffer is really due more to the poisons (toxins) of the germs than to the mere increase of heat, though this alone will finally work serious damage.
However, as we well know from repeated experience, we need only to run or work hard in the sun for a comparatively short time to make ourselves quite hot enough to be very uncomfortable; and if we had no way to relieve ourselves by getting rid of some of this heat, we should either have to stop work at once, or become seriously ill. This relief, however, is just what nature has provided for in this thick coat of blood vessels in our skin; it enables us to throw great quantities of blood out to the surface where it can get rid of, or, as the scientists say, "radiate," its heat. This cooling process is hastened by the evaporation of the perspiration poured out at the same time, as we have seen.
One of the chief things in training for athletics is teaching our skin and heart together to get rid of the heat made by our muscles, as fast, or nearly as fast, as we make it, thus enabling us to keep on running, or working, without discomfort. As soon as we stop running, or working, the heart begins to slow down, the blood vessels in the skin contract and diminish in size, the flush fades, and we begin to cool off. We are not making either as much heat or as much waste as we were, and hence do not need to get rid of so much through our skins.
When we feel cold, just the opposite kinds of change occur in the skin. The blood vessels in the skin contract so as to keep as much of our warm blood as possible in the deeper parts of our body, and prevent its losing heat. As blood showing through the pavement-layer of the skin is what gives us our color, or complexion, our skin becomes pale and pasty-looking; and if all the blood is driven in from the surface, our lips and finger nails will become blue with cold. Here again, by changes in the skin, nature is simply trying to protect herself from the loss of too much heat.
If we exercise briskly, or eat a good warm meal, and thus make more heat inside of our body, then there is no longer any need to save its surface loss in this way; and the blood vessels in our skin fill up, the heart pumps harder, and the warm, rich color comes back to our faces and lips and finger nails.
So perfectly and wonderfully does this skin mesh of ours work, by increasing or preventing the loss of heat, that it is almost impossible to put a healthy man under conditions that will raise or lower his temperature more than about a degree, that is to say, about one per cent above, or below, its healthful level. Men studying this power of the skin have shut themselves into chambers, or little rooms, built like ovens, with a fire in the wall or under the floor, and found that if they had plenty of water to drink and perspired freely, they could stand a temperature of over 150° F. without great discomfort and without raising the temperature of their own bodies more than about one degree. If, however, the air in the chamber was moistened with the vapor of water, or steam, so that the perspiration could no longer evaporate freely from the surface of their bodies, then they could not stand a temperature much above 108° or 110° without discomfort.
Other men, who were trained athletes, have been put to work in a closed chamber, at very vigorous muscular exercise, so as to make them perspire freely. But while a thermometer placed in that chamber showed that the men were giving off enormous amounts of heat to the air around them, another thermometer placed under their tongues showed that they were raising the temperature of their own bodies only about half a degree. One man, however, happened to try this test one morning when he was not feeling very well, and didn't perspire properly, and the thermometer under his tongue went up nearly four degrees.
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