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potato-should be capable of being put to so many different uses! that out of it the brittle bones are made, the soft and pulpy brain, the hard and horny nails, the silky hair, the flesh, the fat, the skin, the bitter bile, the salt perspiration, every thing, in fact, from the sweat on the brow of labor to the dew on the lip of beauty! And yet such is the case. A mysterious power, engaged in building up and nourishing our bodies, is constantly working within us-a power which we can not fathom, which we can not comprehend. He only, who created it, knows the hidden causes of its action.
9. At the ends of the myriads of minute channels in which the arteries terminate, are the beginnings of other minute channels which receive the blood, and use it in repairing the body. All these minute hair-like blood-vessels, which connect the arteries and the veins, are called capillaries.5 Into the returning veins such particles of the body as are worn out and useless are carried by the capillaries, and thus the blood again begins to be filled with impurities; and by the time it gets back to the right auricle of the heart it is a dark and filthy stream, and must be again sent to the lungs to have its color and its purity restored.
10. Such is the circuit which the blood is constantly making, in carrying on the repairs of the system, and removing its waste particles. And all the blood in the body, which is estimated at nearly ten quarts in a person of full size, is supposed to pass through the heart as often as once in six or eight minutes. The heart is the great engine which keeps it in motion. And so long as life lasts, it keeps beating away, stroke after stroke-sometimes seventy or eighty, and sometimes more than a hundred and fifty times in a minute-forcing the blood onward through the arteries, dispersing it through the capillaries, receiving it back through the veins, never stopping a moment, and never wearying of the labor which God has assigned to it.
11. And all this it does without any thought of ours, and without any direction from us. Its action is involuntary— that is, it is not, like the movements of our hands and feet, dependent on our will. Our will can not even stop its action; for it works by a will greater than ours, by the will of
Him who made it, whose servant it is, and whose servants Yet its labors gradually wear upon it; it can not keep going forever. It seems strange to us that it should keep going so long. But though it may exert itself millions of times in our service, each pulsation brings it nearer and nearer to the end.
3. My heaving lungs, while they have power
Shall sing thy praises, O my God!
Thy wond'rous skill proclaim.
1 Pronounced BAD.
AIR AND EXERCISE.
LONDON QUARTERLY REVIEW.
SPECIAL attention should be given, both by parents and teachers, to the physical development of the child. Pure air and free exercise are indispensable, and wherever either of
these is withheld, the consequences will be certain to extend themselves over the whole future life. The seeds of protract ed and hopeless suffering have, in innumerable instances, been sown in the constitution of the child simply through ignorance of this great fundamental physical law; and the time has come when the united voices of these innocent victims should ascend, "trumpet-tongued," to the ears of every parent and every teacher in the land. "Give us free air and wholesome exercise; give us leave to develop our expanding energies in accordance with the laws of our being; give us full scope for the elastic and bounding impulses of our youthful blood!"
ABUSES OF THE LUNGS.
1. As the chief office of the lungs is to purify the blood, through the medium of the air which is taken into them in breathing, it will readily be seen that if impure air be inhaled,' the blood will not be purified. Pure air is composed chiefly of two invisible gases, which are always mixed in exactly the same proportions—that is, a hundred pounds of pure air consist of twenty-one pounds of oxygen and seventy-nine of nitrogen. The proportions are the same whether the air be collected on the top of high mountains, over marshes, or over deserts.
2. When this air is taken into the lungs, the blood sent there from the heart is purified in the following manner. The oxygen of the air, having a strong affinity for the blood —that is, having a strong tendency to unite with it—leaves the nitrogen, and, passing into the blood-vessels, mixes there with the blood and the chyle, and completes the process of changing the latter into pure blood. This is the first step in the process. The second is the following:
3. The waste particles of the body consist chiefly of a substance called carbon, which has a strong affinity for oxygen —that is, it unites readily with it. The union of carbon and oxygen forms what is called carbonic acid gas, which is a
poison to the body, and needs to be removed from it. This union of the waste particles of the body with oxygen is effected in the capillary blood-vessels which we have before described; and the impurities of the blood in the veins are thus changed into carbonic acid gas, for the purpose of being easily removed. When the blood reaches the lungs, the carbonic acid gas, which mixes readily with the air, is thrown off through the mouth and nostrils in the process of breathing. Thus the process of purifying the blood is completed.
4. It is the chemical2 union of carbon and oxygen in the capillary vessels that gives warmth to the body. When a piece of wood is burned in the open air, the same kind of union between the carbon of the wood and the oxygen of the air takes place, and carbonic acid gas is produced by the fire, the same as by the union of carbon and oxygen in our bodies. Thus there is a slow fire constantly burning within us. The stomach provides the fuel, the lungs supply the oxygen to consume it, the arteries carry the fuel and fire to the capillaries, where the combustion3 takes place, and the smoke passes off through the mouth and nostrils. If we should allow that fire to go out by not providing a supply of carbon in our food, and of oxygen in the air we breathe, the result would be death.
5. The poisonous carbonic acid gas, whether thrown off from the lungs or produced by combustion, can not be inhaled without danger, as it not only furnishes no oxygen for purifying the blood, but it adds additional poison to it. The quantity of this gas thrown off from the lungs of a man is not less than twenty-four cubic inches each minute, or more than six gallons during an hour; and, at the same time, an equal quantity of oxygen is withdrawn from the air around him, so that a very large quantity of air is thus rendered impure, and unfit to be taken into the lungs. N
6. We see at once, therefore, the danger of breathing over again our own breath, or the breath of others. When a person sleeps with his head covered by the bedclothes, he is breathing poisoned air; and, if he sleeps in a small and close room, he is in danger from the same cause.
A close room,
crowded with persons, soon becomes so filled with the poisonous gas as to produce a kind of stupor1 and violent headache in those who breathe it. Crowded school-rooms, churches, and all public assembly rooms, therefore require to be ventilated by the constant or frequent admission of fresh air, in order to remove the poison and furnish a new supply of oxygen.
7. Many sad results have occurred from an ignorance or disregard of this principle, but we have room to cite only one. In the year 1756 one hundred and forty-six Englishmen were shut up in Calcutta, in a room called the Black Hole, which was a confined space, partly underground, and only eighteen feet square. There were only two very small windows by which air could be admitted, and, as both of these were on the same side, a free ventilation was utterly impossible.
8. Scarcely was the door closed upon the prisoners when their sufferings commenced, and in a short time a delirious and mortal struggle ensued to get near the windows. Within four hours those who survived lay in the silence of apoplectic stupor; and, at the end of six hours, ninety-six had been relieved by death. In the morning, when the door was opened, only twenty-three were found alive; and many of these were subsequently carried off by putrid fevers, caused by the poisonous air which they had breathed.
9. As combustion can not be produced in common air without consuming oxygen, and giving out in its place carbonic acid gas, an open fire in a close room must render the air impure. If a lighted taper be placed in a closed jar containing common air, the oxygen will soon be burned up, its place will be supplied with carbonic acid gas and vapor, and the light of the taper will be extinguished. If a living animal, a mouse, for example, be now placed in the jar, and especially at the lower part of it, the animal will almost immediately go into convulsions, and die in two or three minutes.
10. As pure charcoal consists wholly of carbon, the burning of charcoal produces a large quantity of carbonic acid gas; and every year cases occur of individuals having lost their lives by entering close rooms in which charcoal was