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QUESTIONS FOR THE FORMULA.

1.  What are the lungs?

2.  Describe the lungs.

3.  How do you breathe?

4.  Why can you not live without breathing?

5.  What is necessary if you would have healthy lungs?

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THE AIR AND THE LUNGS.

The air which enters through the nose and mouth passes into a tube of muscles and ring-like pieces of cartilage.  The upper part of this tube is the voice-box or larynx, covered by a spoon-shaped lid which closes when we swallow; the lower part is the trachea, and the two parts are the windpipe.  The trachea divides into two branches, the bronchial tubes, one for each lung.  These tubes divide again and again like the branches of a tree, and end in exceedingly small sacs or bags.  The air in these sacs, or air-cells, gives oxygen to the blood in the tiny blood-vessels of the lungs and takes from them the poison, carbonic-acid gas, water, and impurities, which it carries back through the windpipe into the outside air.

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QUESTIONS ON THE LUNGS AND RESPIRATION.

Of what are the lungs composed?—­“Of a soft, fleshy substance, full of small air-cells and tubes.”

Of what use are the lungs?—­“They are the breathing machines of the body.”

How do the lungs appear when healthy?—­“Porous and spongy.”

How does the air get into the lungs?—­“The air flows through the nose and mouth, into the windpipe and along the air-tubes, into the air-cells of the lungs.”

What does the air do in the lungs?—­“It swells the lungs and causes the chest to expand.”

What do you mean by expand?—­“To increase in size.”

How is the air expelled from the lungs?—­“The chest contracts and sends the impure air through the tubes and windpipe, the nose and mouth, into the atmosphere.”

What do you mean by contracts?—­“Becomes smaller.”

What do you mean by atmosphere?—­“The air.”

Of what use is the air when it is in the lungs?—­“It makes the blood pure.”

Why can you not live without breathing?—­“Because, if I do not breathe, pure air cannot get into the lungs to make the bad blood pure, and I cannot live if the dark, impure blood is sent back again through my body.”

Why must you live in the sunlight?—­“Because the sunlight helps to purify the blood and strengthen the body.”

Why must you wear loose clothing?—­“Because tight clothing stops the circulation of the blood.”

Why must you avoid tight-lacing?—­“Because tight-lacing crowds the ribs against the lungs, so that the lungs cannot move freely.”

Why should you wear clean clothing?—­“That nothing impure may pass into the body through the pores of the skin.”

Why should you keep the body clean?—­“That the pores of the skin may not be closed, but remain open to let the perspiration pass through.”