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that its character may be readily seen. The wind-pipe branches out into several millions of fine twig-like tubes, and then each tube ends in a blind extremity, or chamber exactly like this.

Do you observe that the air-chamber in the picture is covered by a sort of net-work, stretched tightly over it? That net-work is formed of blood-vessels, through which the blood is constantly streaming, driven on by the action of the heart. This blood sucks air from the air-chambers into itself, and carries that air onwards to all parts of the living frame. But the blood-streams in the net-work of vessels also steam out into the airchambers poison-vapours, which are then driven out through the windpipe and the mouth. Thus the breath which goes into the mouth is fresh air; but the breath which comes out of the mouth is foul air. Air is spoiled, and, as it were, converted to poison, by being breathed; but the body is purified by the breathing, because it is its poison-vapours that are carried away, mingled with the spoiled air.

This, then, is why men breathe. Breathing is the blowing of a fresh wind through the living body for the cleansing away of its impurities. The purifying part of the air which is breathed actually circulates with the blood through all parts of the frame.

Exercise quickens and exalts the cleansing powers of the breathing and this is why it is of such great importance to the health. When you go and take a brisk walk in the open air, you increase the force of the internal breeze. The exertion makes your chest expand to a larger size, so that it can admit more fresh air, and it also causes your blood-streams to course along more rapidly, so that a greater abundance of the air is carried on through your frame.

A very large quantity of fresh air is spoiled and rendered foul by the act of breathing. You, yourself, spoil not less than a gallon every minute. In eight hours' breathing a full-grown man spoils as much fresh

air as seventeen three-bushel sacks could hold! If you were shut up in a room seven feet broad, seven feet long, and seven feet high, the door and windows fitting so tightly that no air could pass through, you would die, poisoned by your own breath in a very few hours; in twenty-four hours you would have spoiled all the air contained in the room, and have converted it into poison, provided you could have lived therein so long.

I will explain how all the mischief, which results from breathing foul air, may be prevented. Come down with me into the garden, and creatures that you believe to be of far inferior powers to yourself shall give you a lesson.

You keep bees. Here is a hive, I see, crowded with the busy insects. By the numbers that I observe clustering about the low arched door, and bustling out and in so incessantly, I learn that the industrious little fellows must be very closely packed together in their straw house. There must be many thousands of them dwelling together in a space that cannot, at the most, equal more than a couple of square feet; and there is not a single window in the straw wall; no opening of any kind but the low, and half-choked entrance. Really if those bees need to breathe, you who have furnished them with their dwelling must be nearly as bad as the cruel Nabob, who shut up his prisoners in the Indian Black Hole!

Those bees certainly do need to breathe every bit as much as men and women; and what is more, they manage to breathe ten times better than you do at night. Notwithstanding all the crowding there is within their close dwelling, the air never gets there into the poisonous state in which the air of your sleeping room is by the morning. The bees take care that it shall not do so. Just bend down your ear and listen near the hive for a minute. Do you hear that incessant low humming? That is the bees hard at work, making an artificial wind. It is the sound of a couple of score

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of broad, stiff fans, flapping to and fro with great rapidity. Look, I drop this piece of light thistle-down near the door of the hive, and you see it is at once blown away from it by a steady draught. If you could see through the straw walls, you would discern twenty little sturdy fellows holding on to the floor of the hive with their feet, just within the door, and flapping their wings backwards and forwards without a moment's pause. Now and then one or two tired insects drop out from the line of the fanners, but their places are immediately filled by fresh recruits, who lay hold of the floor and fall vigorously to work with their wings. This is the appointed band of air-purifiers, plying their business for the good of the entire community, and wafting a fresh breeze continuously through the hive. The bees take it by turns to carry on this necessary labour, and some of them are always at it. The humming caused by the rapid vibrations of their fans, scarcely ever ceases. It has been ascertained that air taken from the inside of a crowded hive, is quite as pure as the fresh air that floats in the open space around; so perfectly do these little earnest workmen accomplish their purifying task.

The industrious bees, then, are an example to mankind. If people dwell in close rooms, they must cause an artificial breeze of fresh air to blow through them. Having shut out the great wind, that it may not chill too much by its uncontrollable currents, they must introduce such a little wind as they can keep thoroughly under control, but which nevertheless is sufficient to perform the office of purification as far as it is required. This process of causing an artificial wind to blow through the inside of a dwelling is called ventilation, from a Latin word which signifies "to blow" or fan with the wind.

In very hot climates where dwellings need to be ventilated for the sake of coolness, as well as for purification, men follow precisely the example set by the

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bees. They hang up broad and stiff canvass fans, which they call punkas, near the ceiling, and cause these to flap backwards and forwards constantly, by pulling them to and fro with ropes. In more temperate climates, it is rarely found necessary to take all this trouble, for the air readily makes currents of its own accord inside of rooms, if only allowed to do so. All that is necessary is the furnishing a free passage into the room, and a free passage out, and it will then make a clear march through. One opening will not do, when fans are not kept going, because then the entering and departing air would meet face to face and obstruct each other. There must be "in" and "out" doors, just as one sees in much frequented offices and banks, in great towns.From "The Worth of Fresh Air," one of the Household Tracts for the People.

LESSON 43.-PURE WATER AND GOOD

HEALTH.-Part 1.

In a large parish in the open country, there are not more than a thousand people, living in a space some two miles square. The land itself is a high flat heath, over which the wind sweeps with the greatest freedom. But there are now upon it rich fields, full of grass, and corn, and sweet clover, and green turnips. A pleasant stream of pure water runs through the parish one way, and a broad turnpike-road crosses it the other. Near to a handsome church, standing upon the top of a gentle hill, there is a house surrounded by a lawn, over which two fine old chesnut trees extend their seared branches through masses of young foliage; and in this house there lives a clergyman, who thinks of the bodies of his flock as well as their souls, and does all he can to show his parishioners how to value rightly the substantial blessings God has given them. Nature, indeed, seems to have furnished to this place every advantage that is needed for the preservation of health.

But, unfortunately, the cottagers in this parish have taken a perverse fancy into their heads, to make pits close to their doors and windows, into which they throw all the waste and refuse substances of their houses, leaving them to decay and putrefy there as manure. They have, generally, small gardens round their dwellings, but they dig the manure-pits close to their doors, so that they may not have to walk a few yards further when they have anything to throw in. Very often, too, there are pigsties, and even stables for donkeys and ponies, by the sides of the manure-pits. The immediate consequence of all this is, that when anyone walks in among these cottages, he finds his nose offended, directly, by all kinds of foul smells. The people, themselves, get so used to these smells, that they do not appear to mind them. Sometimes, indeed, they seem to have been trained by custom, rather to like them than otherwise.

But there is also another consequence which follows in the company of these smells: the parish is, commonly, not free from infectious fever, for months at a time. I have seen this horrible disease again and again, stalk slowly through the parish, occupying months, and even years, by its progress; passing by clean and well-kept cottages, but stopping at every one, where there were manure-pits and pigsties, and seizing from them victims, sometimes two and three, and sometimes more. I have known the fever to cling, for months, to the same dwelling, until manure-pits close by, were removed, either from their owners being at length convinced of their hurtfulness, or because the clergyman, or the parish and medical officers interfered; and I have then been an eye-witness to the fact, that the sick people almost directly got out of their beds, and in a few days, became quite well. I have known as many as twenty people die in the course of two months, in one small spot, in the parish where the holders of the houses were obstinate, and refused to part with their manure-pits. I remember a cottage, in particular, in which a labourer

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