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 pin-prick, 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
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 a power-plant
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 light
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.