A Handbook of Health by Woods Hutchinson (learn to read books .txt) 📖

The Wastes of the Body. Almost everything that the body does in the process of living means the breaking down, or burning, of food; and produces, like every other kind of burning, two kinds of waste—"smoke" and "ashes."

The carbon dioxid "smoke," as we have already learned, is carried in the blood to the lungs, where it passes off in the breath. The solid part of our body waste, or the "ashes," is of two kinds—that which can be melted in water, or is, as we say, soluble; and that which cannot be melted in water, or is insoluble. The insoluble part of our solid body waste goes into the feces and is thus disposed of.

The soluble part of the body waste goes by a somewhat more roundabout route. With the carbon dioxid it is poured by the body cells into the veins, carried to the heart, and pumped through the lungs, where the carbon dioxid is thrown off. Going back to the heart it is pumped all over the body, part of it going through a very large artery to the liver, part through two large arteries to the kidneys, part to the skin, and the rest all over the remainder of the body.

The blood goes completely round the body-circuit from the heart to the fingers and toes, and back again to the heart, in less than forty-five seconds. Practically every drop of blood in the body will be pumped through the liver, the kidneys, and the skin, about once every half minute, so that they get plenty of chance to purify it thoroughly when they are working properly.

This sounds rather complicated; but is interesting, because it shows how much of a "mind of their own" the different organs and stuffs in our bodies have, or what, in scientific language, we call "power of selection." The skin glands pick out of the blood those waste substances which they are able to get rid of. The kidneys pick out another class of waste substances, which they are best able to deal with; while the liver which is the most important of all, attacks almost every kind of waste brought to it by the blood, and prepares it for disposal by the intestines, skin, and kidneys.

The Liver. The liver has a size to match its importance. It is the largest and heaviest gland, or organ, in the body, and weighs about three pounds, a little more than the brain. It buds off from the food tube just below the stomach, so that its waste tube, the bile duct—about the size of a goose quill—opens into the upper part of the intestine.

The main work of the liver is to receive the blood from all over the body and to act upon its waste substances, burning them up so that they can be taken up, and got rid of, by the glands of the skin and the kidneys. In the process it very frequently changes these waste substances from poisonous into harmless forms; and even when disease germs get into the body and infect it, the poisons, or toxins, which they pour into the blood are carried to the liver and there usually burned up, or turned into harmless substances.

The liver is, therefore, to be regarded as a great poison filter for the entire body. So long as it can deal with the poisons as fast as they are formed, either by the body itself, or in the food, or by disease germs, the body is safe and will remain healthy. But if the poisons come faster than the liver can deal with them, as, for instance, when we have eaten tainted meat or spoiled fruit, or have drunk alcohol, they begin to poison our nerves and muscles, and we become, as we say, "bilious." Our head aches, our tongue becomes coated, we have a bad taste in the mouth, we lose our appetite and feel stupid, dull, and feverish.

Such waste materials as the liver cannot burn down so that the kidneys and skin can handle them, it pours out through its duct into the intestine as the bile. The bile is a yellowish-brown fluid, which assists the pancreatic juice in the digestion of the food, and helps to dissolve the fats eaten, but is chiefly a waste product. It turns green when it has been acted upon by acids, or exposed to the air. So that the bile which you throw up when you are very sick at your stomach, is green because it has been acted upon by your gastric juice.

As you will remember, the blood which comes from the stomach and bowels is carried by the portal vein to the liver first and, through that, to the heart, instead of going directly to the heart, as all the other impure blood in the body does. This is owing, in part, to the fact that this blood, being full of substances freshly taken or made from the food, is very likely to contain poisons; indeed, as a matter of fact, blood taken from these veins on its way to the liver, and injected directly into the blood vessels of an animal, acts like a mild poison.

In part, however, this blood goes first to the liver, because the liver, besides being a great blood purifier, is a "blood-maker" in the sense that it changes raw food-stuffs in the blood from the intestines into forms which are more suitable for use by the brain, the muscles, and the other tissues of the body. Some of the sugars, for instance, the liver turns into a kind of animal starch (glycogen), which it stores away in its own cells. It also turns both sugars and proteins in the portal blood into fat, part of which it pours into the blood, and part of which it stores away also in its own cells. Thus the liver owes its great size partly to the large amount of blood-purifying, filtering, and poison-destroying work which it has to do, and partly to its acting as a storehouse of starch and fat, which the body can readily draw upon as it needs them.