This is very curious, and I dare say you have never thought about it before.

Do you know the story of a certain lady called Penelope, who was the wife of Ulysses, a very celebrated king of whom the world has talked for the last 3000 years--thanks to a poet called Homer, who did him the honor of making him his hero! The husband of Penelope had left her for a long time to go to the wars, and as he did not return, people tried to persuade her to marry again. For peace and quiet's sake, she promised to do so when she should have finished a piece of cloth she was weaving, at which she worked all day long. They thought to get hold of her very soon, but her importunate lovers were disappointed; for the faithful wife, determined to await the return of her husband, unwove every night the portion she had woven during the day; and I leave you to judge what progress the web made in the course of a year!

Now, every part of our bodies is a kind of Penelope's web, with this difference--that here the web unravels at one end as fast as the work progresses at the other. As the little masons put new bricks to the house on one side, the old ones crumble away on another--in this manner the work might go on forever without the house becoming bigger; while, on the other hand, the house is always being rebuilt. People who are fond of building, as some are, would quite enjoy having such a mansion as this on hand!

At your early age, my love, fewer bricks drop out than are added, and this is why you grow from year to year. At your papa's age, just the same number perish and are replaced; and therefore he continues the same size, although in the course of the year he swallows three times his own weight of food. But when I say this, do not suppose it is an offensive remark, or that I think him either too little a man, or too great an eater; seeing that there are 365 days in the year, and that a quart of water weighs two pounds: I need not say more!

But the next question is, what becomes of all the refuse which this perpetual destruction produces?

What becomes of it? Have you forgotten our steward who looks after everything? He is a more active fellow than I have represented him!

To the office of purveyor-general he adds that of universal scavenger.

But in the latter department he obtains help. Wherever he pa.s.ses along, troops of little scavengers press forward, like himself always busy; and while he holds out a new brick to the mason as he hurries by, the little scavenger slips out the old one and conveys it away. The history of these scavengers is a very curious one, and we shall have to speak about it a little further on. They are minute pipes, _i.e. ducts_, spread all over the body, which they envelope as if with fine net work.

They all communicate together, and end by emptying the whole of their contents into one large ca.n.a.l, which, in its turn, empties itself into the great stream of the blood. Imagine all the drains of a great town flowing into one large one, which should empty itself into the river on which the town was built, and you will have a fair idea of the whole transaction. What the river would in such a case be to the town, the blood is to the body--the universal scavenger, as I said before. But you will ask further, What does the blood do with all this?--a question which brings us back once more to the liver.

You must have seen, just now, that the pockets of our dear steward would be rapidly overloaded, were he to keep constantly filling them with the old worn-out materials which the builders rejected, unless he had some means of emptying them as he went along. Accordingly, a wise Providence has furnished the body, on all sides, with cl.u.s.ters of small chambers or cells, in which the blood deposits, as he goes by, all the refuse he has picked up, and which makes its exit from the body sometimes in one way, sometimes in another. Now, the cells of the liver are among these refuse-chambers. One may even consider them as some of the most important ones. When the blood has run its course through the lower compartment, I mean the _abdomen_, it collects from all directions and rushes into a large ca.n.a.l called the _portal vein_, which conveys it to the liver. As soon as this ca.n.a.l has entered the liver, it divides and subdivides itself in every direction, like the limbs and branches of a tree diverging from the trunk; and very soon the blood finds itself disseminating through an infinity of small ca.n.a.ls or pipes, whose ultimate extremities, a thousand times finer than the finest hairs of your head, communicate with the tiny cells of the liver. There, each of the imperceptible little drops, thus carried into these imperceptibly minute cell-chambers, rids itself--but no one knows how--of a part of the sweepings it has carried along with it. Which done, the little drops thread their way back through other ca.n.a.ls as fine as the first, and which go on uniting more and more to each other, like the branches of a tree on their way to the trunk--forming at last one large ca.n.a.l, through which the blood escapes from the liver, once more relieved from its weight of rubbish, and ready to recommence its work.

You are going to ask me, "What is all this to me--this history of the blood and its sweepings? It was the bile you undertook to tell me about, that liquid you spoke of as so necessary for the transformation of the food: we were to get out of the intestinal tubes by the help of the bile, you promised me."

Well, my little impatient minx, it is the history of the bile that I have been relating to you, and what is most remarkable about it is this. You have perhaps heard of those wholesale ragpickers, who makelarge fortunes by collecting out of the mud and dirt of the streets, the many valuable things which have been dropped there? Well, the liver is the master-ragpicker of the body. He fabricates, out of the refuse of the blood, that bile which is so valuable in the economy of the human frame. This bile is neither more nor less than the deposit left by the little drops of blood in the innumerable minute liver-cells.

See what an ingenious arrangement, and in what a simple way two objects are effected by one operation!

Now you have learnt the genealogy of the bile, and the double office of the liver, which benefits the blood by what it takes from it, benefits the _chyme_ by what it gives it, and is an economist at the same time--since it only gives back what it has received. This was what I particularly wished to explain to you: the rest you will easily learn.

The bile does not make a long stay in the little cells, it also escapes, by ca.n.a.ls similar to those which carry off the blood, after itspurification; and which in a similar way unite by degrees together, until at length they terminate in a single ca.n.a.l, communicating with a little bag placed close against the liver, where the bile acc.u.mulates between the periods of digestion--so forming a stock on hand, ready to pour at once into the _duodenum_ when the latter calls for its a.s.sistance. The next time the cook cleans out a fowl, ask her to show you the little greenish bladder which she calls the gall and which she takes such care not to burst, because it contains a bitter liquid which, if spilt upon it, would quite ruin the flavor of the fowl. Such, precisely, is the bag which holds the bile. Moreover, it is close by the liver of the fowl that you will find it placed: and you can convince yourself in a moment by it, that the little provision I tell you of is always stored away therein.

We have also within us a mult.i.tude of minute electric telegraphs, which transmit intelligence of all that occurs from one part of the body to another, in a more wonderful manner even than the telegraphs of man's making; later we shall see how they work. By their means the little bag by the liver is made aware in the twinkling of an eye of the entrance of the _chyme_ into the _duodenum,_ and forthwith the bile returns for some distance by the ca.n.a.l which brought it, and then branches off into a larger one which opens into the _duodenum._

The liver, on getting this intelligence, sets to work more diligently than ever, and the bile flows in streams into the _duodenum,_ where it mixes as it arrives with the current which comes from the _pancreas._ Thus combined, the two liquids flow over the _chyme,_ which they saturate on all sides; and here, as I have said, the work of the intestinal ca.n.a.l ends. What is serviceable for the blood is separated from the useless refuse, and nothing remains but to get it out of the intestines. It is true that in their character of tubes these are closed on all sides. But do not trouble yourself: a means of escape is prepared.

Before we part, however, I must apologize for something. I have not described to you what the bile consists of, or what kind of refuse the blood leaves in the liver; nevertheless, as you take an interest in this much-neglected book of nature, you ought to know these things.

It is, however, very difficult to lead you by the hand through so many wonder*, where the secrets of nature are all in operation at once, and to explain each as soon as we meet with it. They combine, and progress together like the waves of the sea, where one breath suffices to agitate the whole ma.s.s.

When we have talked about the lungs, we will have another word to say about the liver.

LETTER XII. THE CHYLE.

To-day we have to begin by making acquaintance with a new term. I would willingly have spared you this, if I could, for the word is neither a pretty, nor a well-chosen one, but we cannot get on without it.

You are aware now that the learned, unknown sponsors, who gave names to the different parts of the body, bestowed the odd-enough one of _chyme_ on that pasty substance which pa.s.ses out of the stomach when the cooking is over. We have said quite enough about it, and you know enough of it I am sure. Well! the people seem to have had quite a fancy for the word _chyme_, for they adopted it again, with only a very slight alteration, when they wanted to specify separately the quintessence of the _chyme_ (the useful part that is), which has to unite with the blood, and which we have been speaking of as the _gold_ of the aliments--this then they called _chyle_. I give you the name as I received it, but have no responsibility in the matter.

In concluding the last chapter I said we were sure to find there was a plan for extracting the best part of the _chyme_, viz. the _chyle_, from the intestinal ca.n.a.l; and a very simple one it is. A complete regiment of those little scavengers lately described, are drawn up in battle-array along the whole length of the small intestine, but especially round about the _duodenum._ There, a thousand minute pipes pierce in all directions through the coat of the intestine, and suck, like so many constantly open mouths, the drops of _chyle_ as fast as they are formed. They are called _chyliferous vessels_ or chyle-bearers, just as we might call hot-air stoves _caloriferous_ or heat-bearers--from the Latin word _fero,_ which means to carry or bear. I mentioned before that there were, within the intestine, certain elastic valves which obstruct the progress of the _chyme,_ and oblige it to be constantly stopping. There are in fact so many of these, and the skin which lines the intestinal ca.n.a.l is so folded and plaited, that if it were stretched out at full length on a big table, it would cover at least as large a surface as that other skin, with which you are so well acquainted, which entirely clothes the body outside.

Now, the _chyliferous vessels_ we have been speaking of insinuate themselves into all the plaits and folds alluded to, and thus they reach at last the very centre of the _chymous_ paste, and not a single drop of _chyle_ can escape them. They do their work so well, that the separation is effected long before the paste reaches the large intestine; and when that has forced its way through the door which guards the entrance, and which prevents its ever returning again, the _chyle_ is already far off on its mission. It has threaded its way along the little pipes, and, always creeping nearer and nearer, is on the high-road to the heart, where it is anxiously expected.

And what becomes of the rest? There is nothing further to be said about it, but that it shares the fate of everything else which, having answered its purpose in its place, is no longer wanted and must be got rid of. Thus in works where iron-stone smelting is carried on, the refuse that remains after the ore is extracted, though available for road-making or other purposes, is thrown out of the manufactory as a useless inc.u.mbrance there.

Our history requires us to follow the fate of that golden aliment the _chyle,_ which is now in a condition to support the life of the body, and every drop of which will turn into blood--the blood which beats at our hearts, nourishes our limbs, and sets at work the fibres of our brain.

I ought to tell you first that the _chyle,_ when it leaves the intestine, is very like milk. It is a white, rather fatty juice, having the appearance, when you look closely at it, of a kind of _whey,_ in which a crowd of globules, or little b.a.l.l.s if you prefer it, infinitesimally small, are swimming about. Some people, whose curiosity nothing can check, have put the tips of their tongue to it; so I am able to tell you, if you care for the information, that it has rather a saltish taste.

At this point it is what may be called new-born blood, and to carry on the metaphor, blood whose education has yet to be completed. All the elements of blood are there already, but in confusion and intermingled, so that they cannot yet be recognised. A wonderful fact, and one of which I have no explanation to offer you, because among the many mysteries which are silently going on within us is this, that the education of the new-born blood begins entirely of itself in the vessels which are carrying it along. During their very journey, the confused elements are setting themselves in order and forming into groups. In short the _chyle,_ when it comes out of the chyliferous vessels, is already much more like blood than when it entered them, and yet one cannot account for the change. It is changed, however; its whiteness has already a.s.sumed a rosy tinge, and if it is exposed to the air it may be seen turning slightly red, as if to give notice to the observer of what it is about to become.

You know that all our scavengers uniting together deposit their sweepings in one large ca.n.a.l, which is called the _thoracic duct._ The _chyle_ scavengers arrive there just like the rest, and there our poor friend finds himself confounded for a moment with all the dross of the body, as sometimes happens to men who devote themselves to the public good. But the crisis pa.s.ses in an instant. A little further off, the _thoracic duct_ pours its whole contents together into a large vein situated close to the heart, and the blood has no difficulty in recognising and appropriating what belongs to him.

Here, my dear little scholar, we conclude the first part of our story.

To eat is to nourish oneself; that is, to furnish all parts of the body with the substances necessary to them for the proper performance of their functions. The mouth receives these substances in their crude condition, the intestinal ca.n.a.l prepares them for use, and the blood distributes them.

After the history of the _preparation,_ comes naturally that of the _distribution._

The first is called the DIGESTION. It is the history of the _chyle,_ which begins between the thumb and forefinger while as yet invisible, hid in the thousand prisons of our different sorts of food, and ends in the _thoracic duct_, when, disengaged from all previous bonds, purified and refined by the ordeals of its intestinal life, it leaps into the blood, carrying with it a renewal of life and power.

The second history is that of the CIRCULATION. It is the history of the _Blood,_ that indefatigable traveler, who is constantly _circulating_ or describing a circle (the Latins called it _circulus_) through the body; by which I mean that it is continually retracing its steps, coming out of the heart to return to it, re-entering it only to leave it again, and so on without intermission, until the hour of death.

The history of the _Digestion_, which we have just gone through, goes on quietly from one end to the other without any complication.

That of the _Circulation_, which we are about to begin, is mixed up with another history, from which it cannot be kept separate while the description is going on, although the two histories are in reality quite distinct from each other. The blood describes two circles, to speak correctly: 1st. A wide one, which extends from the extremities of the body to the heart, and back again from the heart to the extremities. 2d. A more contracted one, which goes from the heart to the lungs, and back from the lungs to the heart. Whilst circulating in the lungs, it encounters the air we breathe; and here takes place, between it and the air, one of the most curious transactions imaginable, without which the blood would not be able to nourish the body even for five minutes. This is called RESPIRATION, or the act of breathing.

Digestion, circulation, respiration, the three histories together form but one--that of NUTRITION, or the act of nourishing; in other words, of supporting life. This is what I called _eating_ at first, that I might not mystify you at the beginning with hard words. But now that we are growing learned ourselves, we must accustom ourselves to the terms in use among learned people, especially when they are not more formidable than those I have just taught you.

Our next subject for consideration, then, Will be the circulation; and we will begin with the heart, since that is to the circulation what the stomach is to the digestion--viz., master of the establishment.

He is a very important person, this heart, as I hardly need tell you.

Even ignorant people speak respectfully of him, and I am sure beforehand that his history will interest you very much.

Do you feel as I do, my dear child? I am quite happy at having brought you thus far on our journey, and at being able to take a rest with you at the gateway of the new country into which we are about to enter, like travelers sitting down upon a boundary frontier. What a distance we have come, since the day when I took you by the hand to conduct you inside this little body, of which you were making use without knowing anything about it! How many things we have learned already, and how many more remain to be learned, of which you have at present no idea!

I a.s.sure you I should be almost afraid myself of what is before us yet, if I did not rely upon my own strong desire to instruct you, and the tender affection I bear to you. Believe me, the greatest of constraining powers is love; and when I get bewildered in the midst of some difficult explanation which will not come out clearly, I have only to place before me those laughing eyes of yours, where sleeps a soul that must soon awaken to consciousness, in order to make the daylight come into my own!

Must I add, too, that I am not working for you only? We are all placed in this world to help each other, and in striving to bring down light into your intellect, and good sentiments into your heart, I am thinking also of those to whom you, in your turn, may render the same good service hereafter, provided I have the happiness of succeeding now with you. This ought to be so, ought it not? You should resolve to be numbered one day among those who have not lived altogether for themselves, but who have given the world something worth having as they pa.s.sed through it. To-day's labor will have been well employed if, later on, it turns out that this history of the _chyle_ has not been told you in vain!

LETTER XIII.

THE HEART.

There was once upon a time a banker, a millionaire, who could reckon his wealth not by millions only, but by hundreds of millions and more; who was, in fact, so tremendously rich that he did not know what to do with his money--a difficulty in which n.o.body had ever been before.

This man took it into his head to build a palace infinitely superior to anything that had hitherto been seen. Marbles, carpets, gildings, silk hangings, pictures, and statues--in fact, the whole ma.s.s of common-place luxuries as one sees them even in the grandest royal abodes, fell short of his magnificent pretensions. He was an intelligent man, and thoroughly understood the respect due to his riches; and the common fate of kings seemed to him far too shabby for the entertainment of his dynasty, which he looked upon as very superior to all the families of crowned heads in the world. In consequence he sent to the four quarters of the globe for the most ill.u.s.trious professors, the most skilful engineers, the cleverest and most ingenious workmen in every department; and giving them unlimited permission as to expenditure? ordered them to adorn his palace with all the wonders of science and human industry.

Science, and human industry, and unlimited means--what will they not accomplish? No wonder that nothing was talked of for a hundred miles around but the magic building--of which, by the way, I do not venture to give you a description, because it would carry me too far away. Let it suffice to say, that never Emperor of China, Caliph of Bagdad, or Great Mogul had such a habitation as our banker, and for a very good reason--he was twenty times as rich as any such gentry as I have named ever were in their lives.

When all was finished one trifling flaw was discovered: the place was not supplied with water. A spring-seeker, who was summoned to the premises, could only discover a small subterranean watercourse, a sort of zigzag pipe, formed by nature, between two beds of clay, in which the rain of the neighborhood collected as in a sort of reservoir. The water was neither very clear nor very plentiful, as you may imagine; and the professor appointed to examine it, having begun by tasting it, made a horrible face, and declared there was no use in proceeding any further; for it had a stagnant flavor which would not be agreeable to my lord.

To the amazement of every body, my lord jumped for joy when he heard this unpleasant news. It was proposed to him to fetch water from a river which flowed a few miles' distance off; but he would hear of nothing of the sort. What he wanted was something new, unexpected, impossible--that was his object throughout. He took a pen and drew up at a sitting the following programme, which caused our poor professors to open their eyes in dismay:--

1st. We will use the water on the premises.