The wonderful thing is, that when an Englishman goes to India, he takes his roast beef and his spirits with him, and in a temperature of more than thirty degrees of heat, quietly heaps up fuel in his stove, just as if he was in England, or nearly so. You think he will set fire to the house, perhaps. But no. Send the thermometer to his mouth for information, and it will only mark down thirty-seven degrees; neither more nor less than in the mouth of a rice-eater! The stove has more sense than its owner. It only burns just what hydrogen and carbon it wants, and takes no more trouble about the remainder than if it had not been eaten.

How about the remainder, then? you ask; if it is not consumed for use, what becomes of it? Do you remember, my dear child, that long ago, after explaining the office of the bile and the liver, I put off telling you what the bile _consisted of_, until we had talked about the lungs and respiration? Well, the time has come now; so listen.

The hydrogen and carbon which is not consumed by the oxygen in the blood, is seized upon by the liver, who employs it in the manufacture of bile. Therefore the greater the amount of unemployed hydrogen and carbon there is in the blood, the greater is the quant.i.ty of bile manufactured by the liver--that is all. When once the body has attained to its proper degree of heat, it is in vain you load it with combustibles; it will not get any warmer, do what you will. Only you will have cut out so much extra work for the liver, and the poor wretch will have to get through it as he can. Accordingly, what happens in the long run to our great eaters and drinkers, whether in India or elsewhere? The bile-manufacturer, overwhelmed with work, gets worn out at last, and kicks; and people come home with that miserable disease, which is called the "liver-complaint."

This is one explanation of that wonderful uniformity of temperature which, happily, human imprudence cannot disturb. But the blood has a second resource for getting rid of its superfluity of hydrogen and carbon, and herein especially is displayed the beautiful foresight with which everything about us has been prearranged. We are told that wolves, when they get hold of a larger piece of meat than they care to eat at the moment, carry off what they do not want to some corner and bury it in the ground, whence they get it again when their hunger returns. Dogs sometimes do the same; and the blood has a similar instinct. Listen attentively, for this is very interesting.

I light a candle and you see a bright flame, which will last as long as there is any tallow below the wick. Can you tell me what it proceeds from?

Nay, do not laugh at the question; it is quite to the purpose, I a.s.sure you.

We know, do we not, that the substances which burn best are those which are full of hydrogen and carbon? Tallow, then, is one of those substances. But tell me further, if you please, what is tallow?

Tallow is _mutton fat_, allow me to say, if you never heard it before.

Now comes the question, who provided the sheep's fat with such a quant.i.ty of hydrogen and carbon as to qualify it for making candles?

The sheep's blood undoubtedly, since blood is the purveyor-general of living bodies--of the sheep's body as well as of our own.

But how came it that the sheep's blood had so large a stock of these materials?

Undoubtedly, again, because there was more of them in the food the sheep had eaten than the oxygen was able to consume or the liver to employ. In short, the sheep has lungs and a bile-manufactory, as we have; oxygen performs the same office for it as for us. What takes place in its body in the matter of respiration is an exact counterpart of what happens in ours, and the history of its fat is simply the history of our own.

Now do you think it is for our sakes that the sheep's blood deposits its fat in little pellet-like morsels throughout the body; do you suppose the poor creature works in this manner merely to have the honor of providing us with candles? It is not likely. I was talking about the wolf just now; but there is no need to look beyond ourselves. In many poor people's cottages there is somewhere an old earthen pot in which the savings of each day are carefully put by, penny by penny, as a last resource in time of need. Should a wicked thief succeed in murdering the owner and laying hold of the treasure, he will squander in a few hours of brilliant revelry the precious h.o.a.rd so slowly got together as a provision for possible needs. And this is what man does, when he kills the sheep and takes its fat to make candles of! The poor animal's blood knew well that bad times might come, that gra.s.s might fail, and the combustible matter conveyed into the body become insufficient to maintain its thirty-nine or forty degrees of heat (which is the sheep's measure, who is rather hotter than we are). So it quietly laid up its surplus stock of combustible so conveniently brought to hand, and destined to be burnt little by little in the depths of the organs, should times of scarcity arise. But here steps in man, the universal thief of Nature, and turns it into a beautiful flame, regardless of cost, and burns in one evening what his victim had been economizing for so long. To burn for burning's sake, however, has always been the fate of tallow, the only difference being in the way it is done. Like the poor man's clumsy pence, which were put by to be spent some day or other, only in another manner. It is worth noting here, that some of the Russian soldiers who were in France in 1815 had a very good idea of restoring candles to their original destiny. As children of the north, driven to get fire wherever they could, they ate all the candle-ends they could lay hold of, preferring to burn the tallow, sheep's fashion, inside rather than out!

Fat is, then, the savings' bank of the blood; there it deposits its savings, and there it can always find them again in time of need.

Witness the fat pig described by Liebig, the great German chemist, which having been swallowed up by a landslip, was found alive at the end of 160 days. Fat was out of the question there, of course; the animal weighed ten stone less than before. We will take the ill.u.s.trious professor's word on trust, but were a few days subtracted from the account the case would still be a splendid example of the resource which blood finds in fat when other nourishment fails; for the pig had certainly been breathing during the whole 160 days, and as, in all probability, he moved about much slower than usual, his hydrogen and carbon fire was never extinguished for a single instant; of that I am perfectly certain, and you shall soon know why. It was well for the poor fellow himself that he had put by his provisions in time of plenty.

And who suffered? Why, the pig's master, who had looked forward with pleasure to the rashers of bacon he should cut by and by from the stores of combustibles in his larder. For once Master Piggy ate his own bacon himself!

You understand now, I hope, by what ingenious management that marvellous stove, called an animal, never burns too much fuel, whatever be the quant.i.ty it is supplied with, and how, on the other hand, it has always as much as it wants.

I have now to explain how important it is that it _should_ always have enough, and that this is not merely a question of heat and cold, as with dining-room stoves, but one of life and death! Cheer up! I have only one more word to say about Respiration, and when you have heard it you will appreciate still better the lesson of economy which you have learnt from Nature to-day.

LETTER XXIII.

ACTION OF THE BLOOD UPON THE ORGANS.

The first time we talked about the Blood, my dear little pupil, I introduced him to you as the steward of your body, and what a steward to be sure! Always awake, as you may remember, always in motion; his pockets ever full of the materials unceasingly required by the indefatigable builders of that human edifice in which it has pleased G.o.d to house your dear little self. If you wish really to understand what follows now, we must carry on the simile a little further.

A steward not only provides the workmen with materials, but gives them orders as well, and this is part of the blood's business also. He is not only commissary-general, but _whipper-in_ of the whole household, and besides the care of giving out all the stores, has the charge to see that everything is properly done. The unhappy men who purchase prosperity at the dreadful cost of maintaining slavery, pretend that their slaves would do no work worth looking at, were there not always some one behind them with a whip in his hand. Well, our organs are slaves, and slaves of the worst sort. They would never do anything at all, if the blood were not everlastingly whipping them up in his ceaseless rounds. Let him come to a stand-still for one minute, for a second even, and everything stops short; then we are at once in the castle of the Sleeping Beauty in the wood. But perhaps I cannot do better than to compare our bodily machine to a violin--to hit upon something less dismal than slaves--a violin with blood for its bow.

As long as the bow runs over the strings the violin makes music and lives; when the bow stops, it is silent and dies.

You have never yet had a fainting fit, my dear child; it rarely happens at your age. But you may possibly have seen somebody faint; or, at any rate, you have heard it talked about. Do you know what takes place in such cases? Now and then, in consequence of some violent emotion, but how or why I cannot tell you, all the blood rushes suddenly back towards the heart, as during an earthquake a river will sometimes flow back towards its source, leaving its bed dry. Thereupon the face turns white, as if to give notice that there is no longer anything red below the skin. The organs, no longer stimulated by the blood, leave off work altogether. The brain goes to sleep, the muscles relax, consciousness ceases, and you behold the poor body, from which the soul seems to have departed, give way on all sides, and fall to the ground like a corpse. This is not exactly death, but it is yet an interruption of life. It would be death if nature did not get the upper hand again, and send back the deserter to his post.

I may remark here that it was partly on this account that some of the ancients thought the soul was seated in the blood; not a bad idea for people who were determined to p.r.o.nounce where the soul was, when it is so easy to say one knows nothing about it. But those who placed it in the breath, and who have bequeathed to us those beautiful expressions--_yielding up the last breath--giving up the ghost_--were not wrong neither.

In point of fact the blood is not the soul of the body; in other words, does not keep the body alive, otherwise than by keeping up unceasingly and everywhere that magic fire of which we were talking last time.

The French people, in their picturesque language, have found an expression, full of energy, to express the action exercised by the master workman, who knows how to make his people work: "_Il vous met le feu sous le ventre._" [Footnote: Literally, _he puts fire under their bellies;_ but here signifying that he makes it so hot that the organs are compelled to continue in motion.] This is, to the letter, the process employed by the blood to make the organs work. It makes a fire under the belly. Unhappily their work only lasts as long as the fire which causes the heat, and which is so necessary to life that it is almost confounded with it. It is the sacred fire of the Roman Vestals, which must be fed night and day under pain of death should it go out. Now, if to feed the sacred fire of life, it be necessary that the blood should everywhere find hydrogen and carbon _unattached_, that is to say, free and ready to unite themselves to oxygen, it is no less necessary that he should bring oxygen with him everywhere. Else there would be no marriage, and therefore no fire.

Oxygen is, then, the talisman which brings the organs to obedience.

Without oxygen he would be a slave-driver without his whip; his orders would be despised. If the organs were to be deluged with _venous_ blood--with that black blood which has lost its oxygen, they would not stir any more than if they had received so much water. They acknowledge nothing but _arterial_ blood--red blood--blood rich in oxygen.

That is what they respect, and which has authority over them; the other is a bankrupt who has lost his credit with his cash; those whom he fed but lately now laugh in his face. And as our good steward spends all his oxygen every time he goes his rounds, it would soon be over with him, and, consequently, with us, too, if he had not some method of replenishing his purse after each journey. Happily the lungs are the inexhaustible chest to which he always returns to renew his right of authority; that is, his power of preserving life. When it comes to the _last sigh_, the last effort of the diaphragm by which the chest is closed forever, we must bid adieu to life. In yielding up that, we have in very truth yielded up the ghost.

This is no joke, as you see, and it would not do to be caught unprepared, with an inexorable necessity hanging over one, which never allows a moment's respite. The blood acts like a reasonable being, therefore, in laying up his stores of combustible in reserve. Moreover, whether he has done so or not, the fire must go on all the same; that is absolutely necessary; and if he has no spare fat to feed it with, when, from any cause, the stomach leaves off working, he makes use of anything he can lay his hands upon.

I know a story on this subject which will amuse you.

There lived, in the reign of Francis I. of France, an honest countryman, of Perigord, named Bernard Palissy. At that time everybody could not afford to have earthenware plates, as they have now. It was a manufacture of which only the Italians had the secret, and Bernard, who knew something of the matter, from being a gla.s.s-worker, took it into his head to try and find it out entirely by himself. So, without asking anybody's advice, he turned potter, built ovens, picked up wood as he could, manufactured his first pots, whether well or ill, made a beginning, and waited. He had fifteen or sixteen years of it before he succeeded; fifteen or sixteen years of ruinous experiments, which would have discouraged a less st.u.r.dy heart than his. But he, after he had succeeded in picking up some money by his church windows, returned to his work with unconquerable perseverance, insensible to poverty, deaf to the ridicule of neighbors, and unmoved by the abuse of his wife, who was furious, as you may suppose, at being forced to play the heroine without having the least turn for it. And one fine day there was a grand uproar in La Chapelle-Biron (that was the name of his village). "Bernard Palissy has gone mad," said everybody; "he is burning up his house to bake his pots." And upon my word it was true! Wood happened to be wanting while a batch was in the oven, and Bernard having begun by using up the garden palisades, took next the large tables, and at last the floor of the house! What his wife had to say, I leave you to judge; as for him he listened to nothing; but, fixing his eyes on the insatiable furnace, threw in one thing after another, caring only for the risk to his handiwork. The ceiling would have followed the floor had not his pots been sufficiently baked without.

And thus, and thus, does the blood, when combustible matter fails him!

He demolishes the house, and throws it, bit by bit, into the fire. The fat goes into it naturally enough, as I have already explained to you.

It is the fuel-store of the house. It was put by on purpose, and may be used up without injury. Then comes the turn of the muscles; more useful without being indispensable. Those are Bernard Palissy's palisades one may contrive to do without them. They melt away, so to speak, after a few days' fast, and you find yourself what people call "nothing but skin and bone." But then, if this condition is prolonged, and the exhausted flesh cannot supply the demand, the blood does not hesitate a moment. He boldly falls upon the most important organs, without stopping to consider; he, too, is devoted solely to his work, and that, like the baking of pots, never comes to an end by being completed; if external help does not arrive in time, the house soon becomes uninhabitable, and life slips away. The man dies of hunger.

But in the same way that poor Bernard Palissy was in reality working, all the time, for his wife and children, whose future well-being he strove for as the final end of all his efforts, though at the risk of letting them sleep under the bare heavens; so the blood was laboring up to the last moment for that very life which he at last turned out of doors; and the work of destruction which caused its final departure has had in reality the effect of prolonging its stay. Without it, all would have been over long before.

LETTER XXIV.

THE WORK OP THE ORGANS.

Thus much is settled, then. It is the blood which sets everything in motion throughout the body. The organs are idlers who would do nothing but for him; they only work when goaded on, if I may use the expression, by that fire--always on the point of going out--which he is perpetually coming back to rekindle, thanks to the oxygen he carries with him from the lungs.

This will enable me to explain many things, which, although not new to you, you have probably never tried to account for before.

To begin with: do you remember what happened to you the other day, when you tried to overtake your mischievous brother in running, and he, taking advantage of his school-boy legs, led you mercilessly through all the garden walks, without having the grace even to let you catch him at the end? You were quite out of breath; your heart beat so rapidly it almost hurt you; and you were so hot that the perspiration poured in great drops down your face, so that your mamma, quite frightened, took you up in her arms and carried you to the fire; for the coolness of evening was coming on, and a little girl drenched with perspiration is soon chilled.

Tell me now, what connection was there between your overrunning yourself in a race and the extraordinary degree of heat which came over you so soon? Your cheeks were cool and fresh when you began to run; what made them so red all at once, and especially at a moment when the air was cool and fresh in the garden?

You open your eyes in surprise; you had never thought of this. No!

that is just the way with little girls. They run; they get hot; it seems as natural as warming oneself in the sun, and they never ask why it is so.

Yet you could almost tell me the "why" yourself, if you stopped to think about it, now that you are what your school-boy brother would say "_up to a thing or two;_" but to save time, I will help you.

You run as a bird flies, without thinking about it. Nevertheless, if you could see with a magic gla.s.s all that takes place in your body while those active little feet are carrying it like a feather across the garden, you would be perfectly amazed. One of these days, when we have finished our present history, I will tell you that other one, which is equally worth the trouble. It is enough for the present to know, that a very complicated piece of work is being carried on there, in which almost all the muscles of the body take part at the same time, contracting and relaxing in turn, like so many springs, of which each either drives forward or holds back a part of the machine. In fact, while your eyes and thoughts are fixed on the b.u.t.terfly which is flitting away from you through the air, there is going on within you such an unheard-of outlay of efforts as could never be got out of our idlers if the terrible steward did not lash them severely.

Now, his lash, as we have said often enough, is that eternal fire, the materials of which he conveys to all parts of the body. On those special occasions, therefore, he is obliged to make his fire burn much more briskly than usual--exactly like railway engine-drivers, who increase the heat of their fire to get up steam in proportion to the speed they wish to go.

From this you will understand that it is no great wonder that your small frame should get heated from such work as racing and chasing; and that if you pursue it too long, the perspiration which comes out all over you is sufficiently explained.

This is not all, however. The fire, whose strength has to be increased, naturally requires a larger amount of combustible matter than before, and forasmuch as there is only a certain fixed quant.i.ty in each drop of blood, whenever the muscles want more than usual, the blood itself must flow to them in greater abundance. Now if it were a question of supplying only one part of the body (as it is, you may remember, of supplying the stomach during the progress of digestion), he might contrive to accomplish his task there by neglecting it elsewhere, and overflow one organ at his ease, at the expense of all the rest. But in this case he is wanted everywhere in the same abundance. It is not a question of taking one muscle's share for the benefit of another.

From one end of the body to the other, all want to be deluged at once.

And remember that these exigencies do not bring a drop more blood into the body. How is he to get out of his difficulty then, this overwhelmed steward of ours? Well! just as your mamma manages, my dear, when there is more to do than usual in the house;--by running quicker than ever from the cellar to the garret, and from your room to your papa's! That is called doubling oneself; and this gallant blood doubles itself to some purpose. He runs and runs and runs, arrives in hurried streams, and returns full gallop, pa.s.sing and repa.s.sing through the heart, which empties and fills itself in sudden jerks. Unluckily, the poor heart is a delicate sort of person, who does not like having his habits disarranged, and this forced work soon makes him desperate. The other day, in his despair, he knocked with all his strength against the walls of his little chamber, to warn his young mistress that he could bear no more, and that they were both of them in danger. In fact, you ought to know that if one was infatuated enough to go on running too long, one might die of it. When you learn ancient history, you will probably be told of what happened to the soldier of Marathon, who flew like an arrow from the field of battle to the gates of Athens, that he might tell his fellow-citizens a quarter of an hour earlier, that his country was saved; and he fell dead on his arrival.

But it is not the heart only which suffers by this mad career of the blood. During each journey it performs it pa.s.ses through the lungs, which in their turn are forced to play with hasty jerks. And this is well for our good steward; for the lungs, filling with air at each descent of the diaphragm (if you remember what we have said before), more air, and consequently more oxygen, comes in, and the blood has by this means a larger stock on hand, ready to help him out in the unusual waste which is just then going on in the muscles. I spoke just now of railway steam-engines. See how self-supporting ours is! The greater the amount of fire wanted, the faster the blood flows; and the faster the blood flows, the oftener does the coffer re-fill itself, whence comes the supply of oxygen requisite for keeping up the fire.

All this goes on at once, by one impulse, and the balance between the receipts and expenditure settles itself of its own accord. How thankful many families would be if their money-chest would but fill itself in the same way--in exact proportion as they spend the cash! There is only one slight drawback, which is, that the diaphragm gets tired with the unaccustomed gallop it is thus forced into. It falls into convulsions, therefore, like its neighbor the heart, and the breathing is stopped, from having been driven too rapidly. An excellent example for people who want to spend too much at once; showing that Nature herself cries out against it, even when the only thing wanted is atmospheric air.