CHAPTER IV.

THE HEART AND LUNGS.

1. I WILL now tell you, children, about this curious heart of ours. You will recollect that you learned in my first lesson, that our food made blood. Suppose, then, we had bones, muscles, ligaments, skin, and stomach, but no vessel or receptacle to receive the blood when it was made.

2. Life, under such circumstances, could no more be sustained, than a steamboat could sail through the water of a thousand little streams, if it were not collected together in a river or bed of water. The heart is a double organ, and lies in the middle of the chest, with the point inclining to the left side, which gave rise to the idea that it was situated there.

The letter a is the left ventricle; b, is the right ventricle; c, e, f, is the great artery that proceeds from the left ventricle; g, h, i, are arteries that proceed from the great artery; k, is the artery that goes from the right ventricle to the lungs; 7, 7, are branches of the artery going to the two sides of the lungs, which carry the blood there; m, m, the veins which bring the blood back from the lungs to the left side of the heart; n, is the right auricle; o and p, are the ascending and descend

What is the subject of chapter fourth? 1. What do we need beside skin, bones, muscles, and blood? 2. What would be the result if there was no receptacle for the blood? Describe the heart and its situation. Explain the cut.

ing veins, which meet and form the right auricle; p represents the veins from the liver, spleen, and bowels; s, is the left artery, one which nourishes the heart.

3. The heart has four divisions: two to receive the blood after it is made from the food, called auricles; and two others, called ventricles, to send it to the several stations where it is most needed.

4. After the blood comes to the heart from the veins, it is necessary to send it to the lungs before it is fit for For this purpose there are muscles in the heart which contract and force it out to the lungs.

use.

3. How many divisions has the heart? What are they called? What is the office of the auricles? What is the office of the ventricles? 4. Where is the blood, that comes to the heart from the veins, sent? How is this accomplished?

5

5. Motion is of two kinds: voluntary and involuntary. That is voluntary, which is performed by means of the bones, muscles, and tendons, and is influenced by the will or mind.

Involuntary motion is that produced by organs not connected with the bones, but which possess muscular fibres; as, for instance, the stomach, which is a hollow muscle, and digests its food without the knowledge of the mind.

6. The heart is also a hollow muscle, which contracts and expands, to receive and send out the blood when necessary. It is protected by a bag called the pericardium, which is made of strong and rough materials. This case holds a very little water; just enough to permit the heart to move freely and easily, and is placed between the lungs.

water.

7. The lungs fill all that cavity in the chest, not occupied by the heart, and are composed of blood and airvessels. They are so light that they would float in the They are sometimes called bellows, because they contain so much air. They appear like the branches of a tree, and extend each side of the heart. When we take in a breath of air, we inhale it; when we throw out a breath we exhale it.

8. We inhale it, to change the color of; and to purify

5. What are the two kinds of motion? What is voluntary motion? What is involuntary motion? What is an example of involuntary motion? 6. How is the heart enabled to receive and send out the blood? By what is the heart protected? What does this case contain, and for what purpose? Where is the heart situated? Of what are the lungs composed? Where are the lungs situated? What is said of their weight? What are they sometimes called? What do they resemble in appearance ? What is meant by inhalation? What is meant by exhalation? 8. What is the use of inhalation? What is the use of exhalation?

the blood. We exhale all that does us no good, but which would, if retained in the body, be an injury to us. You know, children, that air is all around us; we could not move or live without it; and though we can neither see nor handle it, yet it has been divided into several gases, called oxygen, carbon, and nitrogen.

9. When the air is thus divided, one part of it will sustain life, and the others are very injurious. The oxygen of the air unites with the dark blood in the lungs, and turns it to a red color, which then rushes back into the heart. The muscles of the heart contract, and send it out through the vessels, called arteries, to make skin, bone, flesh, hair, nails, and every other part of the body. It finally terminates in the small capillaries and veins, when it is changed into a dark red color.

10. It is then unfit again for nourishment, as some of the good qualities have been taken out in its circulation. This dark red blood then unites with the chyle, is sent into the heart, thence to the lungs, and is purified by the air, then sent back with its color changed, and proceeds as I have previously stated.

11. You may ask why the blood does not rush back again to the heart after it has entered the artery. It is because there are little valves or trap-doors that shut over the arteries when the blood has entered them.

8. Is air confined to any particular space? Into which has it been divided? What are these gases called? 9. Are these different gases equally healthy? What effect has the oxygen on the dark blood, and what becomes of the blood? By what means is the blood sent from the heart? For what purpose is it sent through the arteries? What becomes of this blood? 10. Why is this blood then unfit for nourishment? Describe the farther course of the blood. 11. What query might here suggest itself? What prevents the flow of the blood back again into the heart through the artery?

VEINS AND ARTERIES.

67

These move as easily as a door closes on its hinges, and prevent the return of the blood.

12. The arteries are larger than the veins, and lie deeper in the system, or more removed from the surface. They serve to carry the blood out of the heart, and to distribute the proper nourishment where it is required. The veins are more numerous, and smaller in size than the arteries, and bring the blood to the heart.

13. There was great wisdom manifested by our Maker in locating these different vessels; for if we accidentally cut a vein, there is not much danger; but if an artery be severed, and the ends are not immediately tied, death will be the result.

66

14. You will hear physicians frequently speak of feeling the pulse ;" and, for that purpose, take hold of the wrist. All they mean, is, that they wish to know how rapidly the blood passes or circulates, and as the artery at the wrist is nearer the surface than any other, it can be relied on with more certainty, although the blood does not flow through this one, more rapidly than through the others.

15. By palpitation of the heart, we mean that there is some obstruction in the way, which makes the circulation irregular. Our lives and existence depend on the regular circulation of the blood; hence, this palpitation is considered very dangerous. We ought not to

12. Describe the arteries, and their use. Describe the veins, and their specific purpose. 13. How was the wisdom of our Maker displayed? Do the veins or arteries require the most care, and why? 14. What is meant by "feeling the pulse ?" Why do physicians always judge of the condition of the body by the artery at the wrist? 15. What is meant by the palpitation of the heart? Why is palpitation considered dangerous?