The blood-corpuscles are like millions or tens of millions of little workmen in the body, each with a particular work to do; each on duty and quickly responsive to call every moment. When we recognize the fact that the body is constantly being broken down and rebuilt; that every atom of broken-down material must be floated away in the blood, and new atoms built in to keep the structure from deterioration; that all the broken-down material is poisonous, and must be eliminated from the body without delay, we realize that the internal activities are almost bewildering. When we consider that all the blood in the body passes through the heart every two or three minutes, carrying food to every cell, and at the same time carrying away the poisonous products of physical and mental activities, disposing of them by various processes; when we remember that the supply to every cell is delicately adjusted to constantly varying requirements; that all this goes on so quietly and so smoothly that we are unconscious of it - when we remember all this, we begin to have some appreciation of the Psalmist's exclamation, "I am fearfully and wonderfully made." How faithful these little workmen are! Not for an instant do they leave their tasks. Verily, they are the sentinels forever at the portals. In our work, in our pleasures, they are ever active; in our sleep, they sleep not. Not for an instant do they cease watch. Is there a wound - be it a great rent or a tiny pinprick, they are there in force to repair it, to wall up the breach and to make it whole - swarming to the rent as the Lowlanders to a break in the dike. Has a foreign substance penetrated the structure? - instantly they set about to expel it; but if this be impossible, they seal it in a capsule of impervious integument that it may do no harm, or, the least possible injury.

A seeming consciousness in the automatic action of the blood.

The human body a power-plant.

If these little workmen are not conscious as we know consciousness, at least their work shows purposeful action, and when we see an obvious purpose definitely carried out by every available agency, we may be sure there is a consciousness back of it, whether it be like ours or not.

But while these workmen are faithful - -while they will stand to their tasks to the end, they are limited in their power, and will break ranks under long-continued hindrances.

The human body is a power-plant, a combined engine and boiler, and there is a close analogy between this conscious, self-acting power-plant and the one that furnishes the power to generate electricity, or to turn the wheels of a factory.

Symptoms compared with electric lights.

The stomach and the lungs of this leviathan.

When your electric lights grow dim, and the defect is not cured by renewing the lamps, then you are convinced that the trouble is elsewhere. If the lights in every part of the house are dim, you will know (if you are a skilful electrician - a good diagnostician) that the trouble is not in the electric nervous system of the house. It may be between your house and the electric station, but before taking the trouble to examine the line, ask those of your neighbors who are on a different line, whether their lights are dim. If they are, you may go to the electric station with reasonable certainty of finding the cause.

Suppose we have come to the station and are commissioned to locate the difficulty. We go into the engine room and find everything in good order. The engine is a fine piece of mechanism; it has no loose joints, no leaky valves, yet it seems to lack power; is overloaded. Inquiry shows there are no more lights than formerly, while the service was satisfactory. You go at once to the boiler room. It may also be in good order so far as appearances go, but you look at the steam gage and find the pressure is low. "Yes," says the fireman, "I simply can't keep the pressure up. I shovel in coal and keep the drafts on so that I have a roaring fire, but, in spite of all, my steam pressure runs down." Look into the furnace (the stomach) of this leviathan! If the grate-bars are clean; if there is no accumulation of ashes, cinders, or clinkers to interfere with the combustion (digestion) of the black provender fed to it, you may close the furnace door and open another. Look into the fire tubes (the lungs) of the laboring monster that has shown signs of weakness! If the fire tubes are clean, free from soot and dust, the trouble is not there.

"Scale," like an irritated mucous lining.

"Scale," the cause of dim light.

We have now gone almost the full course; there is but one place left to explore, and that is closed. The trouble is inside the boiler. It is lined with scale deposited from the water evaporated in producing steam. This scale, which may be likened unto an irritated mucous lining of the stomach, or the intestines, forms a coating upon the lower inside of the boiler, and the upper side of the fire tubes, just as it is deposited on the bottom of a teakettle, and it shuts out the heat from the water. The heat being the source of energy, and the steam only the means of applying it, the power-plant is crippled. Seldom does it happen that so great a thickness of scale is to be found in a boiler as may be seen in almost every household teakettle, yet the effects (symptoms) are found in the dimmed lights miles away, and if the difficulty is not dealt with, it will rapidly increase until the service becomes intolerably inefficient.

Difficulty in dealing with the "scale".

Treating the "dim light" disease.

Had we found the grate-bars choked with ashes, cinders, and clinkers, and the fire tubes (lungs) smothered with soot and dust, we should have instructed the fireman to keep them clean and free. This is not a difficult thing to do, requiring only-careful daily attention, but the scale inside the boiler is not so easily dealt with. It is completely enclosed, and there is no possibility of getting at it except by extinguishing the fire and letting the boiler cool - by making the boiler "dead,'* or "killing" it, as firemen term it.

Having diagnosed this case of the lighting system, starting with the symptoms of a dim light in a residence some miles away, and having located the difficulty inside of the boiler of the power-plant, we desire to treat it. The boiler can be "killed," and the scales removed by going into the boiler. It can then be revived by refilling it with water and rekindling the fire.

Removing the cause of the scaly deposit.

Then, too, let us assume that there are two boilers, and that we can keep the plant alive with one; a low ebb of life, to be sure, but not dead. We will then cool one boiler at a time, go into it, and remove the scale, thus restoring the plant to full efficiency.

This method can be used where the boiler may be cooled, but as this cannot be done with the human power-plant, for the sake of our analogy, let us suppose that the steam boiler, like the human body, must always be kept under pressure that it cannot be "killed" and revived. What, then, shall be done?

It is evident that the first thing to do is to cease the use of water containing the solution of mineral, which causes the scaly deposit. This will prevent the condition from growing gradually worse, and may be accomplished by distilling the water before introducing it into the boiler, or, by using rain-water. As to the scale already in the boiler, it must be dissolved, and gradually eliminated, or remain there. There are many so-called "boiler compounds" for the purpose, and every well-informed man in charge of such a "plant" knows how important it is to avoid using a compound that may cause damage to the boiler itself. A "compound" that would attack the steel, as well as the scale, would be a desperate remedy indeed.