The History of a Mouthful of Bread Part 25

LETTER x.x.xIX.

VERMES--ZOOPHYTA. (_Worms and Zoophytes_).

_Worms._

The worm of worms, the one you know best, is the earthworm: so he shall have the honor of representing his group.

He will not take much time to describe. He is, in brief, a tube, open at both ends, so as to allow food to come in and go out. That is all.

I talked to you before about the ruminants, those food-manufacturers who are employed in cooking victuals for the stomach, and in disengaging alb.u.men from the coa.r.s.e materials among which it is apparently lost, so as to give it out again in a more acceptable form. The ruminant has other workmen under him, whom I keep in store for you as the last of the eaters, and who prepare the raw material for him*. These are the vegetables, who seek out the elements of alb.u.men in earth, water, and air, those final sources of all alimentation. The earthworm also is a _preparer_, but in a peculiar way. Look along the garden-walks in summer-time, after rainy weather: you will see here and there, little heaps of earth moulded into small sticks, like dough which has been pa.s.sed through a tube. [Footnote: M. Mace's account of the earthworm's life seems founded on the a.s.sumption that it extracts its nourishment from the earth itself, i.e., from inorganic matter, as _vegetables_ do, to use his own words. But this notion is so entirely at variance with present received opinions, and also with the fact that the animal possesses a gizzard for digesting, as well as an intestinal ca.n.a.l, that it has been necessary to make considerable alterations in the description. To dismiss his theory of the primitive animal, etc., altogether, was, however, impossible, without omitting the whole chapter; but as young heads are not likely to trouble themselves about it, and it is very innocent in itself, it will do no harm; subject to this warning, that M. Mace has taken the earthworm for a more simply organised creature than it really is.--TR.] This is the damp soil which the worm has pa.s.sed through his tube, after extracting from it, during its pa.s.sage, the various elements of fertility he requires for the support of his life. This is what makes him so particularly fond of garden soil, because it is richer in animal and vegetable matter than common earth, and proves therefore more nourishing food. The worm, then, feeds on the fat of the earth, which he converts into azotic aliment for the use of moles, hens and Chinese.

It only figures, it is true, for want of something better, in Chinese cookery, so profusely hospitable for all that; but the hen doats upon it, and you do not despise it yourself when it comes back to you in the form of a chicken's wing, that second transformation of the matter of which the soil of your garden is composed. It is told of certain savage tribes, the victims of constant scarcity, that they swallow little b.a.l.l.s of clay in order to keep down their hunger; and during the great famines in India the distracted inhabitants may, we are told, be seen digging up the banks of the rivers to feed on the fertile clay in which the splendid vegetation of their country is developed. This is a desperate trial of that primeval system of alimentation which answers perfectly with the worm, but becomes a cruel mockery in the case of an organisation as exacting as that of man. Let us examine a little more closely, then, this wonderful tube.

At first sight one notices, to begin with, that it is composed of perfectly distinct rings, all quite alike. Inside as well as out each of these rings is an exact repet.i.tion of the other. They are all formed of circular muscles, enclosed between two coats, which extend from one to the other. A series of ganglions, arranged in the form of a necklace along the whole length of the body, set in motion the muscular system of the rings, each of which possesses its local centre of impulsion.

Each feeds itself in its place from the nourishing juices with which it is in contact, the interior coat enjoying the double property of distilling digestive juices and absorbing digested ones. These juices pa.s.s through the muscular part.i.tion, and proceed to bathe the outer coat, which plays, at the same time, the part of coat and lung, and affords a pa.s.sage to the air through its soft, damp surface, like that of gills. From all this results a fine red blood, such as we have not met with since we left the reptiles, and which is manufactured in all parts of the body at once.

Each of these rings, then, the worm's only organs, is a little eating machine to and for itself, and at the same time a little movement machine also; in fact, a complete animal. Each one could, if necessary, nourish itself and live apart; and this is what he really does. Learn hence, to despise nothing in nature. One tramples an earthworm under foot, and there below one's heel lies a little revealer of secrets, whose organisation throws the most unexpected light upon one of the greatest mysteries in our own life.

I said to you before, and I felt at the time that it was rather beyond you, that "each one of our organs is a distinct being, which has its particular nature and special office, its separate life consequently; and our individual life is the sum total of all these lesser lives, independent one of the other, but which nevertheless blend together, by a mysterious combination, into one common life, which is diffused everywhere, but can be apprehended nowhere in particular."

The study of the worm admirably explains this out-of-the-way sentence.

And here observe my adjective--my out-of-the-way--for it is a case in point. We may call it a literary worm; a worm of four rings, each perfect in itself, but yet compounded together into a whole with its own idea.

That which makes this idea of life most difficult to comprehend is, that one cannot prove it by a direct experiment, since there is not one of our organs which could exist separately from the others. Although independent in their special action, yet these multiplied lives are nevertheless in a state of absolute and mutual dependence, from the imperative need they have of each other to make them act, each having for its share only one particular function, the effect of which extends to all the others. This is called the division of labor; and if you still do not understand me clearly, I will explain it in another way.

The heart sends to all the organs--does it not?--the blood, without which they could not live: separated from the heart, the lungs would die immediately. It is to the lungs the blood goes to find the air, without which it could not maintain life. Separated from the lungs, the heart would die immediately. There is nothing belonging to us which can avoid the inexorable requirements of blood and air; consequently, there is nothing which can live an isolated life.

I will borrow a simile from human society which you will understand at once. In civilised countries, where division of labor is established, the tailor makes clothes, the mason makes houses, and the baker makes bread. If you could throw them each alone by himself into a wood, the mason would not be able to dress himself, the baker would sleep in the open air, and the tailor would not know how to make bread. Or rather, as not one of them can carry on his trade without the co-operation of a mult.i.tude of hands, they could none of them do anything at all. Each completely independent in his work, yet each dependent upon the others, both for living, and even for being able to work, our workmen can only act when they remain bound in close union with the vast society of which they form a part; and our organs--those other laborers whom you have seen working for so long--our organs are just in the same predicament. But in the primitive societies, among savage tribes, where each man can make his clothes, his house, his bread (when he has any), and everything else for himself, you might take such an individual if you liked, and separate him from the rest of the tribe, and he would go on living as before. And so with the rings of the worm, that primitive society of organs. Each of them is a universal workman, who knows how to make everything. Separate him from his fellows, it will not disturb him at all, and he will go on living as if nothing was thematter.

I still remember some profound reflections I indulged in one day some years ago whilst leaning on my spade and looking at a worm that I had just cut in two, and whose two halves were walking off one on each side.

"There was only one creature here just now," I said to myself, "and now there are two! Have I had power, then, to create one with a stroke of the spade?"

I had not then got hold of the key which I now give you, and to which no possible objection can be raised. If there are two beings after the stroke of the spade it is because there were two before. Nay, there were even many more, if we may trust to the "Manual of Zoology" by Milne Edwards, a very good book, excellent for an old scholar like myself, and which I have found very useful in my country-home, as it has enabled me to relate to you one after another the mysterious wonders of life.

He says that, "if one cuts an earthworm across into two, three, ten, or even twenty morsels, each of these morsels will go on living in the same way as the whole, and will form a new individual."

Twenty! that seems to me a great many, because, as far as I can trust to my brief observations as a gardener, it is necessary that some of the rings should remain united together and afford each other mutual support, in order to succeed in repairing the bleeding breaches; but I would much rather believe it than try the operation. My mind is easy when I am defending the plants that I have sown in my garden from the gluttonous worm who would rob them of their food; but it would not be so if I were cutting them up on my table to learn something about them.

Besides, there is no need of an operation to convince oneself of the particular life of each ring. There is one worm, well known by name at least, though happily not to be met with every day, and that is the tape-worm, who establishes himself in the intestine of man, and lives on the chyme, as the other worm does on garden-mould. They call him the _Solitary_ worm in France; and if ever one might suppose a creature appropriately named, it would surely be him; for certainly there is not much society to be looked for in the dwelling he chooses for himself! But it happens that this pretended _solitary_ worm, with his unlimited chain of rings, is only a long row of perfectly distinct beings, so distinct indeed that, from time to time, some of the rings let themselves go, fall off like ripe fruit, and go away to live elsewhere, ready to become the nucleus of a new set, if a happy accident carries them into another intestine, the only place favorable to their development.

At last, then, here is a corner of the curtain raised; here we see the a.s.sociated organs which const.i.tute an animal, living for once a life positively and in all respects their own. We are now satisfied about this; and when at another time we find them bound together in the chains of a union too ingenious to be severed with impunity--which we shall discover by seeing their action stop at the moment of separation--we shall know the cause.

Do not think, my dear child, that a wretched earthworm can prove nothing as regards other creatures. The worm is the starting-point of all the organisations which come after him. Of what is he composed? Of a tubewhich is itself composed of rings. Well, it is upon this very tube that the whole animal machine has been founded: and these rings, as they expand and modify themselves in a thousand different ways, give birth to all those varieties of being which drive cla.s.sifiers to despair, because they will not understand that there ought only to be one animal, since there is only one Creator of animals. Now, this animal is a digestive tube served by organs; it is a worm, _i.e.,_ which goes on constantly embellishing itself. I said to you long ago, and at a time when you scarcely knew anything, "Have you ever observed a worm or a leech in motion? You see a successive swelling up of the whole surface of its body as the creature gradually pushes forward, as if there was something in its inside rolling along from the tail to the head. Such is precisely the appearance which the oesophagus would present to you as the food pa.s.ses down it, if you had the opportunity of seeing it in action; and this has been called the _vermicular_ movement, in consequence of its resemblance to the movement of a worm."

And afterwards, in speaking of the intestine:

"If your body were made of gla.s.s, so that you could look through it to watch the intestine at work, it would appear to you like an enormous worm, coiled up into a bundle, heaving and moving with all its rings at once."

You have now got hold of the secret, namely, that from the beginning to the end of the digestive tube, its movements are those of a worm.

What a wonder! and that the worm is a digestive tube which can walk.

This worm, or this tube, whichever you please to call it, has never ceased crawling under our eyes since we began this study. Lost sight of in man in the midst of the riches he has picked up on his road, invisible and coiled backward and forward in his palace like an Eastern despot who leaves everything to be done by his slaves; behold him here in his first stage naked, shivering in the air, forced to go off himself and alone to his pasture--ground! But in the coa.r.s.e earth with which he fills himself I can already see the delicate chyme which his numerous servants will prepare for him later on, and into which the heart-tree will one day send down its roots--the chyliferous vessels.

A short time ago I called the oyster the primitive animal, but I was in too great a hurry. The worm is the real primitive animal. He is to be found in the oyster, as the oyster is to be found in us; and that poor little beast is, by comparison, an animal of high pretension, who would be shocked, I am sure, if he could understand what we are saying, and heard us a.s.sert that he is nothing but an embellished worm.

_Zoophytes._

Two centuries ago it was believed that below the worm, animal life, properly so called, ceased, and the creatures whom I am about to introduce you to were supposed to be animated plants rather than living organisms. Hence their name was especially chosen to express that double nature by which they were thought to have a share in two kingdoms at one time--viz., the animal and vegetable--_zoon_ in Greek meaning animal, and _phuton_ a plant. Zoophytes were set down as animal plants.

And although later discoveries have long ago established the fact of the complete animality of zoophytes, the old name is still in general use. But you must not let it deceive you. Zoophytes are animals every inch of them, however low in the organic scale, and although many of the compound ones imitate the growth of plants and shrubs so exactly in their mode of spreading that it is only by the closest observation we can persuade ourselves they do not belong to the vegetable kingdom.

Of these there are the delicate buff-colored, prettily-branched, h.o.r.n.y specimens found on the sh.o.r.e, which make so beautiful a variety in seaweed pictures among the red and green colors of the real seaweed; but of these also are those wonderful stony shrubs which grow on the submerged rocks of islands in warm seas, and the material which you know so well by the name of coral--the very coral of which the necklaces and bracelets in the jeweller's window are composed.

In all cases of compound zoophytes, however, there is one great point which they have in common with the worm, viz., that there is an a.s.sociation of distinct lives acting unanimously; or, rather, to the same end. Plainly as this is seen in the worm, it is still more obvious in the zoophyte. There is no need here either of cutting them up yourself or of taking other people's dissecting operations upon trust.

It is enough to use your eyes, with the help, it is true, now and then, of the microscope's clearer sight.

You know the old oak-tree which stands on the outskirts of the wood, and is called among the country folk _the patriarch_? Now, this is clearly not an individual, but a nation. It is not a tree; it is a forest. Nay, may I not call it a green field? For this trunk, so truly venerable from ages of growth that one feels inclined to bow to it as one goes by, is, in fact, a collection of structures, acc.u.mulated by countless generations of fleeting herbs, _i.e.,_ leaves, not one of which has lived for the s.p.a.ce of a whole year round. Every spring some thousands and thousands of buds open to the sun; each one, therefore, affording a pa.s.sage to a little green point; and this point is an oak, who comes into the world, like the first oak, the grandfather who formerly came forth from an acorn, under the form of an herb or tender leaf, which a sheep might have browsed upon. Yet it is so thoroughly an oak, that you have only to take out the bud carefully before it has expanded and fasten it into another one's place upon a tree of the same family, though of a different species, and it will produce an oak of the same sort as its old companions, and which will, as it progresses, look quite a stranger among the indigenous branches.

This is the secret of what the gardeners call _grafting_, and I advise you to try the operation upon rose-trees, for nothing is more amusing. When the autumnal frosts set in, all these troops of new little oaks die, and deliver up their leaves to the wind; but they leave behind, as their summer's work, a tiny morsel of new wood, upon which, if you look carefully, you will see a fresh bud dawning--the hope of the coming season. And thus the great life of the tree is perpetuated from century to century by an uninterrupted succession of transient lives, reminding one in all respects of the life of a nation; and the similitude is complete in the evergreen trees, where the new leaf makes its appearance before the old one has quitted the stem.

And such is the life of the great stone trees and shrubs of various kinds which grow under tropical seas, and whose makers and inhabitants are the coral polyps, the undoubted heads of the Zoophyte race.

But before considering the _polypidom,_ or external dwelling (otherwise called the _coeneciun,_ or "common house"), you must learn something of its originator, the little _polyp,_ who lives inside, and belongs to a family so widely spread over the face of the earth, that there are scarcely any waters, whether salt or fresh, without them.

In your own neighborhood, if you know how to look for them, are to be found on the banks of ponds, or along the borders of streams which lie sleeping in roadside ditches, extraordinary beings which, a hundred years and more ago, completely bewildered the good Dutch naturalist Trembley, who had taken it into his head to study them. Picture to yourself some very tiny bags made of a kind of jelly; gray, brown, or, most commonly of all, green in color, always transparent, and fastened by their base to the stalks of _carex,_ water-lentils, or the confervas, which grow in still water. A hunter on the watch, this bag shoots out on all sides a number of slender threads, like so many whip-lashes, arranged within a circle round the edge of its opening or mouth; and with these whip-lashes all the animalcules which come within reach are entwined, stifled, and carried away to the ever-yawning little gulf, where they are digested in less than no time. Whatever will not digest comes out afterwards by the way it went in. Of what becomes of the results of this digestion it is impossible to form an idea. Were you to cut up the bag and put little morsels of it under the best microscope possible, you would see positively nothing but solid jelly, without the least sign of any organisation whatever. But this is not all. Replace these morsels in the water, and come back tolook at them at the end of five, twenty, or thirty hours. Each one of them will have become a perfect bag, ready to multiply itself afresh if you submit it to the same operation. Sometimes, on some part of the original bag, there suddenly appears a little raised spot, like that which came on your baby brother's arm the other day after he had been vaccinated. What would you have said, if this ugly spot had grown larger and larger without stopping; if it had a.s.sumed legs, arms, and a head, and so become another baby, growing from the arm of the first one? Yet this is just what the spots do which come on the bag I have been telling you of; and people have come across bags of a larger species still--between one and two inches in size, in fact--which in this way carried twelve young ones on their backs, if one is allowed to talk of stomachs having _backs_. You perceive at once that this commencement of animal life is not even a digestive tube, and that nothing in it can be found but a stomach, opening straight to the air above and closed up below.

It was Reaumur, the originator of the famous thermometer, who gave a name to the wonderful bags discovered by Trembley. Aristotle had previously bestowed the t.i.tle of _polypus_ (many feet) upon a mollusk outwardly formed upon a similar model [Footnote: This is the cuttle-fish, called _polypus_ by old naturalists. We shall speak of it fully hereafter in the history of the movement machine.] with large whips disposed regularly in a circle round the mouth, and intended for a similar use, only that they have another function besides; that of carrying the body along in the capacity of feet by clinging on to the rocks with their suckers as they go. Reaumur transferred this name to the newcomers, and called them fresh-water polyps, to the infinite amus.e.m.e.nt of Voltaire, who had declared that they were only blades of gra.s.s; a new proof, among many others, that in natural history all the intellect in the world is not worth a pair of good eyes.

But it was soon found out that, in collecting these bits of living jelly near the Hague, Trembley had laid his hands on little beings of immense importance on the surface of the globe, and that he had discovered under his microscope the explanation of a mystery which had spread itself, setting human science at defiance, over some thousands of square miles.

I talked to you just now of the jeweller's coral, of which ornaments so becoming to dark-haired people are made. That is one of the stony polypidoms I spoke of as stone trees found at the bottom of the sea, where it grows attached to the rocks in the form of a charming little shrub, stretching its red branches in all directions. The Greeks, who were never at a loss, relate that Perseus one day laid down upon the sea-sh.o.r.e the famous head of Medusa, the sight of which had the property of turning everything to stone, and that the nymphs, in sport, showed it to the coral shrubs; a fact which explained everything quite naturally. Without exactly holding this mythological explanation, modern philosophers had not got much farther, and coral was still a puzzle to them, which they were not fond of troubling themselves about; till, roused by Trembley's revelations, they examined it more carefully, and discovered in its soft extremities (hitherto unnoticed) those same living jelly-bags or sacs, with their circlets of legs, or rather arms, charged with supplying them with food. These were marine polyps, which grow, like those in fresh water, one upon another, but each in its own crusty cell; and like the buds of the oak, these buds of the stony tree form each its special deposit, which it bequeaths in dying to the general ma.s.s. In short, as the tender shoot of the oak is filled by degrees with the wood which forms within it, and hardens into a branch, that goes on increasing by perpetually new growths, so the jelly polyp of the polypidom hardens below into stone and dies incessantly at the base, while it lives on indefinitely above in its constantly-renewed summit.

Do not get tired of all this phantasmagoria, my dear pupil: it is a matter of the highest interest. Here is the point of junction--the bond, as it were, between the three kingdoms: an animal growing vegetable-wise produces a mineral ma.s.s, extracted from the waters of the sea by an infinity of little living crucibles, who carry on under our eyes the work begun in the first ages of the globe, and quietly manufacture continents for the use of future generations. This ought to console you, my dear child, for being little. It is by little things that G.o.d loves to effect what is truly great. He did not seek out the elephant or the whale to form these worlds; He chose workmen no bigger than a pin's head. I have spoken to you about jeweller's coral, which is made into toys or presents for ladies to adorn themselves with; but its brethren, the madrepores of the Pacific Ocean play a very different part. They have formed in front of the sh.o.r.es of New Holland a barrier of reefs three hundred leagues in extent and twenty wide. What are all our buildings after this?--those pyramids and cathedrals which seem so gigantic to us? This ever-increasing wave of coral polypidoms will one day shut against navigators the entrance to one part of the sea's tropical region; and lands not to be found on the map to-day will then lie stretched out under the sun, covered with plants and animals; and this in places where ships now plough the ocean. Know, also, that a great portion of the soil which we tread under foot has no other origin.

It was manufactured formerly in the sea by infinite myriads of beings, often infinitely small. Each one, whether polype or sh.e.l.l, produced its grain of stone, and from all these grains G.o.d, who directed their work, has made our country.

But it is time to bring this chattering to a close, for it will never end if I do not force myself to stop. I leave it with regret; but all these paths through which I have threaded my way one after another without counting them, have already made a volume which may possibly be considered too large for you. There are many other zoophytes besides the coral polypes, and all of them beautiful and curious. They all inhabit the fertile depths of the waters where G.o.d has deposited the first germs of life. I cannot describe them to you now. But to make amends, I will give you a piece of advice which will perhaps make some people stare. Ask your papa to lend you Michelet's book, _The Sea_, and look there for what is said about the mysterious animals which lie hid beneath the waves. His book was not written for you as this one is: and if, in spite of all my good intentions, I have not always succeeded in being as comprehensible as I meant to be, Michelet, who never thought about little people when he took up his pen, will certainly startle you now and then. But do not be disheartened by a word. You will find there, that which will be forever plain to you, the poesy of nature, and children comprehend that better than learned men.

LETTER XL.

THE NOURISHMENT OF PLANTS.

One more word before we part about the last of the eaters, about Vegetables. They will furnish you with a new and very clearly marked proof of the uniformity of the fundamental conditions to which the Author of life has subjected all organised beings.

Let us look once more at this oak, of whose manner of growth I was obliged to give you a sketch beforehand, in order to show you the ties which unite it with its immediate neighbors in the animal kingdom. How does it feed? I need not tell you this. It feeds by its roots, which suck up in the bosom of the earth the water charged with the juices which form its nourishment. Are you aware that every large branch had its subterranean fellow or representative, and that the annual shoot at the top of the tree is reproduced at the base by fresh fibres, which extend themselves in the soil of the earth, in proportion as their sisters above make their way in the air? And thus, by means of organs ever young, the life and progress of the great a.s.sociation is kept up, while those members whose day of work is over still remain there as the supports of the edifice. It is the same with human societies. They are sustained by what is old, but they live and progress only by what is young. The sap, then, which is the name given to the moisture or water sucked in by the young roots, having once got into the cells of which the tissue of the fibres is composed, pa.s.ses from one to another, and travels thus to the top of the tree, where it is wanted by the leaves.

There is no obvious machinery here, however, to impel it forward. It journeys on of itself, as it were, under the action of laws which have never been satisfactorily explained, but all of which are dependent on the vital force or life-power of the tree, inasmuch as without it there is no circulation. One agent, but by no means the princ.i.p.al, or it would act as well in a dead tree as a living one, is _capillary attraction_; and, if you wish to know what that is, you have only to think of what happens to a towel, if you hang it upon a peg, and leave the end of it soaking in water. Does not the "wet" seem to climb up it thread by thread, till it is damp from one end to the other? A little in this way--but these similes are very imperfect, and will not bear close application--the sap rises in a tree, stealing up branch by branch; and it is then called _ascending sap_. [Footnote: M. Mace speaks of this sap as the _blood of the tree_, and of the leaves only as _lungs_. These statements have been modified so as to meet the fact that _ascending sap_ consists of, and conveys the raw elements of _food_ to, the leaves; that in the leaves this food is _digested_, as well as brought in contact with the air, and that it is thus converted into that nourishing fluid, the _descending sap_, which certainly plays the part of steward to the tree as our blood does to us, and therefore may now be called the blood of the tree. It must be remembered, however, that each tree has its own sort of steward, as the case of the _Euphorbia_ (quoted afterwards) plainly shows. The a.n.a.logy with the more general substance of blood is therefore not very complete.-TR.]

It arrives at last at the leaves, which it enters as our food enters our stomachs, and for the same purpose; for in them takes place, as in all true stomachs, that process of digestion by which the elements of the crude sap-food are decomposed from their first condition, and converted into a nourishing chyle; in each tree of a sort "after its kind."

But more than this. Like the outer coat of the earthworm, the coat of the leaf affords a pa.s.sage to air and moisture through its surface; and here, therefore, takes place that mysterious exchange which is everywhere the essential condition of life. Here is the charcoal-market as before, only the bargainers have changed parts. The air, which in the other case received the _carbon,_ delivers it up, now, and receives oxygen in exchange; exactly the reverse of its traffic with animals. In other words, the tree inhales through its leaves the carbonic acid gas thrown into the atmosphere by our lungs. On its own responsibility it breaks through the alliance between the carbon and oxygen contracted in our organs; keeps the carbon for its own use, to restore it to us another day under the form of wood, or, by the aid of the charcoal-burner, in the pure and simple state of charcoal; and sets at liberty the oxygen, which once more goes off in search of new lungs and a fresh alliance. Thus a constant equilibrium is maintained in the atmosphere; and thus, by a system of perpetual rotation or everlasting merry-go-round, the same substances serve, indefinitely, to support life of every opposite description.