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Mamma. Yes, two; one on the right, and one on the left of the chest, and they contain both air and blood vessels. That on the right side is divided into three parts or lobes; that on the left side is divided into two lobes, between which is a space where the point of the heart lies.
Emity. How are they separated from each other?
Mamma. Each lung is contained in a strong membraneous bag, called the pleura, and the air-vessels which are connected with the wind-pipe, through which you know we breathe, run along between the blood vessels in the lungs, and so give to them that quantity of air which is required to change the colour of the blood, as I have already told you, and to render it fit for circulation.
Frank. I want to know how it is, that when the blood is sent from the auricle into the ventricle, it does not run back again?
Mamma. There is a curious provision to prevent this, which is, that the one is separated from the other by valves.
Jane. What are those, mamma?
Mamma. The simplest idea I can give you of them is, that they are like little doors, which, if shut up by a force on one side, continue closed, and cannot be opened by any pressure on the opposite side.
Jane. But are they made of wood ?
Mamma. No, nor of one membrane, but of several. The valve remains open whilst the blood is passing through the right way, but if any were to flow back, it would lift the door from the side on which it was hanging, and shut up the passage entirely.
Frank. What a wise plan! How exactly it must answer the purpose !
Mamma. It does so completely, and gives us one of the many proofs we everywhere meet with, of the wonderful care of God in our formation.
Emily. Are the lungs then very liable to be hurt?
Mamma. They are; and it is for this reason they are so well protected. Can you conceive of any situation in the body where they could have been so safe, as in the hollow strong box, made by the spine, the breast-bone, and the ribs ?
Emily. They are well taken care of, indeed.
Frank. I think every body who studies these things much, must love God exceedingly, and be very pious—are they not, mamma? They must see more of his wonders than any one else.
Mamma. It should be so, my dear, but I fear it is not always the case, for we know that no outward thing will change the heart: this must be the work of God's Holy Spirit,
Frank. I want to ask you one thing more, and that is, how the discovery was made of the circulation of the blood, and who made it?
Mamma. A very wise author seems to have known it, one whose works you have read.
Frank. I, mamma ?
Mamma. Yes, a very wise man, who when he was asked whether he would be rich, or powerful,,or wise, chose the latter, before all the others.
Emily. O, mamma means Solomon; but is there anything in the Bible about the circulation of the blood ? I do not remember it.
Mamma. There is a passage in the Ecclesiastes, which is generally understood to refer to this subject.
Frank. Do not tell us which it is, mamma, do let us try and find out.
Emily looked some time, and then said-Well I do not see anything like that; do you, Frank?
Frank. No, not yet, but perhaps I may presently. I have got to the tenth chapter, but it may be after that—is it, mamma?
Frank. Oh, I think I have it in the twelfth ; is it not in that account that you told us meant death ?
Mamma. Yes, it is; which verse appears like a description of the circulation of the blood ?
Frank. It must be the 6th to the end of the 7th : “ Or ever the cord be loosed, or the golden bowl be broken, or the pitcher be broken at the fountain, or the wheel broken at the cistern. Then shall the dust return to the earth as it was, and the spirit shall return to God who gave it.”
Mamma. Yes, that is a beautiful and poetical description of the way in which the blood is thrown out by the heart, which is compared to a cistern, at which a wheel is continually turning, and throwing forth its contents. God, who gave Solomon the spirit of wisdom above all the men who dwelt on the earth, most probably taught him this wonderful thing, amongst the many others in which he instructed him.
Frank. Was it known, then, from Solomon's time to the present ?
Mamma. That is a much disputed poivt. Some suppose that the Greeks and Romans were acquainted with it; but, at all events, the full discovery was made by a countryman of our own, William Harvey, who was born at Folkestone, in Kent, on
April 1st, 1578, and who died in his eightieth year. He lived in the reigns of James I. and Charles I. when learning was much more rare than it is at present.
Frank. Did he find it out all at once ?
Mamma. No, but by slow degrees, and after he was sure that he was correct, it was a long time before he published to the world what he had found out; and not till after many and repeated experiments, he had ascertained the fact beyond a doubt.
Jane. Did not every body wonder at his cleverness, and praise him much for it.
Mamma. No, just the contrary; like most other wise men, who know more than the generality, he was very much persecuted by some, and ridiculed by others.
Emily. How old was he, when he found out about the circulation of the blood ?
Mamma. He was born in 1578, and it is thought that it was about 1616 that he published what he had discovered, now tell me bow old he was ?
Emily. Just 38, mamma.
Mamma. No, when he began to be known, King James I. paid him great respect, and showed him much favour, and so did his successor, Charles I., who used to go sometimes with his courtiers, to hear him lecture, and see him prove by experiment what he taught.
Frank. I am glad every body did not neglect him.
Mamma. In the end he became generally esteemed and beloved, and his name is come down to us, as one of the greatest of men, and it will be remembered while time endures.-I must not talk to you any more now; but I have told you enough to make you wonder, when you think of your own bodies, and of the ceaseless work which is carried on within them, of which we know so little.