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The History of a Mouthful of Bread - And its effect on the organization of men and animals
by Jean Mace
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The Armadillo, for instance, which comes next to the ant-eater, looks far more like the tortoise or lizard than its noble mammalian brethren. It is covered with scales; and, to look at it, you would say it was a reptile, in spite of its higher internal organization. As for teeth, it has certainly enough of them to give the lie to its name of edentata; but they are not very serviceable ones. They are called molars, however, because they are situated in that part of the mouth which is always assigned to molars; but they are miserable grindstones, very unlike any of which we have hitherto treated. They are all of them flattened cylinders, with no enamel bars to strengthen them; are small and poor, and are placed at rather wide intervals from one another. The poor armadillo munches with these, as best he can, slugs, tender roots, and other prey of the same sort, with which he is obliged to content himself, and which do not require very formidable tools.

The most questionable member of this class is the Unau, or Two-toed Sloth. It only wants incisors to be as toothless as ourselves! and the first time I saw it I took it for a little bear. It is true I was then younger than you are now; for the bear, who is one of our nearest neighbors, ought not to have been confounded with the unhappy being before us, one of the drudges of the animal creation; though M. de Blainville (who had not my excuse) proposed placing it still nearer to us, namely, amongst the Quadrumana. Observe that instead of hands it has at the end of its fore-limbs only two enormously curved claws, which have somewhat the appearance of a gigantic fork accidentally twisted. Accordingly its illustrious sponsor offered it to the world as an irregular quadrumane. I believe so, indeed! This quadrumane without hands—this edentate whose molars are preceded by magnificent canines—this enigma of nature, created for the confusion and despair of all classification—does, I must in all humility confess, completely upset the rule I laid down so stringently when speaking of the horse, as to the objects for which canine teeth were framed. The canine teeth of the sloth are more developed than its molars, and yet I cannot tell you what they are there for at all. It feeds upon the leaves of trees; and old travellers in South America, where it inhabits, have told us that, when it has once hoisted itself up a tree, it will strip it to its last leaf, and afterwards drop to the ground to avoid the trouble of crawling down. This was what first obtained for it the villanous name of sloth, a title which is certainly justified by its gait when on the ground; for it is so ill-made that it cannot stand upright on its legs, but moves clumsily forward by dragging itself on its elbows. It seems, however, that when once in a tree it is a different creature altogether, and can scramble lightly from branch to branch. Moreover, if its claws cannot reasonably be reckoned as hands, they are at all events excellent hooks; and when it is springing about thus in the forest, suspended to the branches by its long arms, one might be tempted, while watching it from below, to decide in favor of M. de Blainville's opinion. I saw it originally myself in a cage.

As to the sloth's relationship to the armadillo, this rests upon a detail which bears directly upon our subject. The molars in both animals are cylindrical and smooth, this is a trifle, but what would you have? The animal had to be classed somehow; since naturalists have not had the wit to make detached companies, as they do in regiments of soldiers. ORDER 11. Amphibia (two-lived).

We are going farther and farther away. Here are animals who are nearly half fishes (amphis, double, and bios,life). The Amphibia have two lives: one in the water, which is their true life, and where they are in their element; the other upon land, where they can only crawl; for their paws, which are but half developed, are destined to perform the office of fins, and the hinder ones are extended flatly behind them, and act like a fish's tail. They are divided into two families, the seal and the walrus. The first feed on fish, and have the same internal organization as the Carnivora, as well as the same dental conformation. Some species have even exactly thirty-two teeth, as we have. The jaw of the walrus is the least regular, and the incisors are generally wanting, especially in the full-grown animal; for it appears they lose them very young, as you lost your milk teeth, only, unluckily for the walrus, his never grow again. On the other hand, he has two canines in his upper jaw, which, next to the elephant's tusks, are the largest we have yet met with. They are sometimes as much as two feet long, and incline downwards with a curve, like the two bars of a pick- axe. They would play the walrus the same trick that the incisors of rodents are apt to do when they have not work enough to wear them down; that is, stop up the entrance of its mouth, were it not that the lower jaw is contracted in front, in order to fit into the space between the two canines, which thus form a sort of passage in which it manoeuvres freely. As you may suppose, the walrus cannot insert prey of any great size into this contracted passage; but that is no matter, as he lives partly on seaweeds, and partly—indeed principally—on shell-fish; his molars being specially adapted for breaking shells. They are short massive cylinders—the upper ones fitting into the lower as a pestle into a mortar.

After the walrus comes a strange animal which has been ranked among Cetaceans (we shall see why presently), but which it would be better not to separate from the Amphibians, since an Amphibian order has been made, for it crawls from time to time upon land: this is the Manatee, or Sea-cow. It comes still nearer a fish than the others. Its forelimbs are absolute fins, with mere vestiges of nails at their edges; it has no hind ones, and its body, which is quite cylindrical, ends in a fin tail in the shape of a shovel. The sea-cow feeds on plants and herbage, and lives at the mouths of great rivers, going up them occasionally to great distances, their banks serving it for pasture ground. In some respects it is half brother to the hippopotamus and the great grass eating Pachydermata, to whom it comes so near in internal organization, and above all in the structure of its molars, that M. de Blainville seriously proposed ranking it among the elephants, though as an irregular elephant, as you may suppose. But then Cuvier had even placed the seal among the Carnivora, by the side of the cat, whose whiskers it possessed, and of the dog, whom it resembled in the formation of its head. A naturalist's office is sometimes very perplexing, I assure you; and as we are touching on this subject, I cannot resist telling you that the sea-cow laid claim to, on so many sides, had by right a free admission to the celebrated order of Primates, although it looks exactly like a large barrel elongated at the two ends. It suckles its young at the breast like man and the monkey; and if Linnaeus flinched from this rather too absurd parentage, old navigators were less scrupulous. Observing this creature in the distance, sporting on the waves, the upper part of its body quite out of the sea, the sailors, whose eye is not of the most refined, and who have no objections generally to the marvellous, imagined they saw a new species of human beings; and hence arose those stories of mermaids and sirens which have been told from the days of Homer downwards, and the traditions of which have not yet quite died out in seaport towns. To have been passed from man to the whale, touching the elephant on the road, is a long way to travel, especially when, after all, one is only a huge barrel of amphibious fat; and you may judge from this that it is not always an easy thing to classify animals.

ORDER 12. Cetacea (whale-kind).

Cetaceans are whales; and if I had been consulted on the matter, I should have joined this order and the last together, under whatever name was thought most appropriate. The passage from the seal to the whale through the walrus and the sea-cow is an easy and natural one, the two latter being obviously the connecting links; and in spite of certain diversities of food, they form in reality one family-party, as do the marsupials.

But it is too late in the day to talk of this, my dear child, and you and I cannot pretend to alter what is taught in the schools.

But you are astonished, are you not? to hear that the whale is not a fish: and no wonder. It is with it, however, as with the armadillo; it is a fish with a higher organisation inside. The interior of this enormous mass is a faithful reproduction, as a whole, of that of the shrew-mouse; and when we come to talk of fishes you will have some faint idea of the prodigious distance which this places between the whale and his countrymen of the ocean.

As far as we are concerned, the chief difference is in their way of breathing. The cetaceans breathe like ourselves, and are obliged to come to the surface of the water to take air; while fishes have a special apparatus, which I will explain to you presently, which enables them to breathe in the water. This is a disadvantage to the cetacean in his fish life; nevertheless, of all the mammals (as may easily be imagined) he is the one who can remain longest under the water. With us, for instance, the best divers one ever heard of, those who go to the bottom of the sea after the pearl-oyster, can scarcely stay below longer than two minutes; and even during that short time the veins of the head become so overcharged with the blood, which cannot return to the lungs owing to its forced inactivity, that when the diver comes back to the surface it is by no means unusual to see him streaming with blood from both nose and ears. The cetaceans remain under water for half an hour at a time without seeming to suffer in the least; and Breschet, a clever French naturalist, has given a very satisfactory explanation of this wonderful faculty. In dissecting a cetacean, he discovered all along the vertebral column an extensive network of large veins, which are not found in other mammals, and which seemed designed to serve as a refuge place for the blood during the time the animal remains submerged. According to him, this network would act as a reservoir, to which any overplus in the head or important organs would flow through vessels communicating therewith, and which might swell out as it pleased, without any risk to the inert bed of fat against which it lies. From thence the blood rushes to the lungs, as soon as the animal's return to the air enables them to play as usual. It must be admitted, at the same time, that all this involves the necessity of a much less active life than that of land mammals, that is to say, a consumption of oxygen much smaller in proportion than theirs; for were you to be furnished down your back with the finest network reservoir in the world for venous blood, it would still not enable you to remain half an hour without breathing.

There is nothing remarkable in the digestive apparatus of the cetaceans except about the mouth, which is, as you know, the essentially variable point among animals. To begin with, the cetacean tongue has the most original appearance possible. Indeed, it is not a tongue, but a large carpet, spread over the floor of the animal's mouth, and bears not the faintest trace of resemblance to that nimble delicate porter, who does you such good service. Imagine a thick soft lump absolutely crammed with fat, and completely immovable, because it is glued down along its whole length to the bottom of the mouth, and you will have a good idea of this strange tongue, which in the whale, the largest of the cetaceans, attains to the length of twenty-five feet and the width of twelve, and of itself alone furnishes the whale-fishers with from five to six tons of oil. This is a great deal farther from us than even the long string which serves as a tongue to the ant-eater; and you feel at once that we are getting among strangers.

With respect to teeth, I have now a melancholy piece of news to tell you. We have done with them; we have seen the last of incisors, canines, and molars, henceforth you will hear no more about those valuable instruments. The teeth of the cetaceans, with whom this painful falling-off begins, are no more teeth than his tongue is a tongue. They are like so many nails set in a row in the jaw, and can only be of use in retaining prey, not in grinding it; so that of the many processes your bit of bread has to go through before it becomes a part of yourself, there is one which is dispensed with here altogether, namely, mastication. Cetaceans swallow their food without chewing it.

Besides, they have not got a whole set even of these unmasticating teeth. Dolphins and porpoises, those faithful companions of the sailor, around whose vessel they come playing and tumbling in the seas of all countries, are the only ones who have them in both jaws. And these are the small fry of the order; they do not usually exceed six or ten feet in length.

The Cachalot, or Spermaceti Whale, an enormous cetacean, which rivals the true whale in size, and whose head alone forms nearly the half of its body, has teeth in the lower jaw only. This lower jaw, whose two sides are joined together for half their length (a new deviation, very unlike anything we have found before), is so little proportioned to the gigantic head which contains it, that it is almost lost to sight, and seems like a small plank slipped under a great square block.

Such as it is, however, it possesses many very respectable teeth, of which some weigh as much as two pounds; and with these the cachalot, whose ferocity is tremendous, tears in pieces everything that comes near it, sometimes even the boats of the fishermen who risk their lives in the dangerous pursuit of capturing them. By a singular arrangement, of which this is the only known instance, there is, opposite each of the cachalot's teeth, a corresponding cavity in the upper jaw, into which they fit closely, turning the monster's muzzle into the most formidable pair of pincers to be found in the animal kingdom. Another curiosity in the order is the tooth of the Narwhal, a modest cetacean, who is not much more than twenty feet long!

I speak of the tooth, because the creature has commonly but one; a cylindrical-pointed tooth, spirally furrowed, whose length varies from six to ten feet, and which comes straight out from the extreme front of the upper jaw, like a soldier's pike. There are two sockets at this extremity of the jaw, each furnished with a tooth-germ; but as a general rule the germ on the left side is the only one which develops, the other lying asleep in its socket, where it is choked up and never appears. Behind this long pike, which, like the tusk of the elephant, attracts to itself all the ivory in the body, lies a completely unfurnished mouth; so that the owner of this magnificent weapon, invaluable as a war-tool, but quite inapplicable to the purpose of supporting life, is obliged to feed on small fishes and mollusks. We have not yet spoken about these latter, but if you have ever seen slugs and snails you will know what a mollusk is.

The same wretched food falls to the lot of the whale also, that giant of the ocean, whose open mouth forms an aperture twenty feet in extent. Geoffroy St. Hilaire, in his indefatigable endeavors to trace out points of resemblance connecting together animals the most unlike in outward appearance, discovered, along the lower jaw of a young whale, certain traces of teeth, indicating a last effort on the part of nature to carry out her usual plan in furnishing the jaws of mammals; but, like the right-hand tooth of the narwhal, these vain attempts soon disappear, overgrown and lost in the tissue of the bone, so that the whale offers us a true type of an edentate, classable with the ant-eater, if one dared, and some people have dared, which by this time will not surprise you. A classifying professor is utterly merciless, whether he gets hold of the poor beasts by the mouth or by the paw: they may protest with all the rest of their body against the peg on which they are hung; so much the worse for them! If one were to listen to what they have all got to say, it would be impossible to classify even one.

To return to the whale. As a compensation for the teeth which she found herself unable to give him, nature has manufactured on the two sides of his upper jaw the most extraordinary apparatus without exception to be found in the mammal mouth. You know what is called the whalebone used in stay-making, &c. The name is quite correct; for those little flexible black strips, which support the figure so nicely, began life in wandering over the polar or Australasian seas, fastened to the palate of some monstrous whale.

On the two sides of the upper jaw the membrane which covers the palate sends out rows of broad, thin, horny plates, which are from eight to ten feet long (they have sometimes been seen twenty-five feet) in the centre of each side, but which decrease gradually towards the extremities. These are plates of whalebone (sometimes called whale's whiskers), and the industry of man has turned them to a thousand different uses; and you will open your eyes in astonishment when I tell you that 800 or 900 of them have been sometimes counted on each side of one mouth. Think of the number of stays that could be furnished from the whalebone plates of one whale! It is true, they were not exactly designed for this purpose originally. At the tips and on the edges of these plates, the elastic fibres of which they are composed unravel and peel off, and hang down from the lip like tufts of horsehair. The Arctic seas, which the whale inhabits, are, like other seas, full of innumerable troops of various little sea-animals, and it is these which are destined to the honor of nourishing this gigantic mass of flesh. When the colossus wishes to take a meal, he stretches his mouth to its utmost width, and the salt water rushing in as into a gulf, carries with it the imprudent little fry, who disappear then and there for ever, being retained by the fringe-like sieve of the whalebone. But as, in this way of eating, the stomach of the whale, however large, would be terribly overgorged with water, he is furnished with another apparatus for preventing the inconvenience. All the superfluous water is rejected by the pharynx, and springs up in spouts of fifteen or twenty feet high, through the nostrils, i.e. the nasal openings, sometimes called "vents," sometimes "blow-holes," which are pierced exactly at the top of the head. This is a peculiarity common to all cetaceans, who have thence received the name of "blowers," alluding to the powerful blast which is necessary to send those majestic columns of water into the air; but it takes a much milder form with the lesser cetaceans, such as dolphins and porpoises. There is but a slight jet with them: the water escapes comparatively quite quietly from the nostril-vents, trickling away down the animal's sides.

I hope you consider that I have told you something new this time, my dear child, and that our machine is beginning to change its appearance very materially. I told you before that we had reached the outskirts of the mammal kingdom. When we got to the armadillo we were within a stone's throw of the reptiles, and here, one step more would take us to the fishes. But we must first consider the birds, who are a very superior set of animals to either of the latter; and we have accordingly an order of mammals (Monotremes) which, as you will now find, opens the road on that side also.

There are but two sorts, and both of them are natives of Australia, which is, as you may have heard, the land of the wonderful in natural history, and their existence was unknown to the learned men of Europe till within the last sixty years. The most extraordinary of the two is the Ornithorhynchus, or, to translate the hard Greek word into English, the Duck-bill. Its mouth is a true duck's bill, a downright horny beak, and its short paws sprawling sideways with a membrane joining the toes together below, and coming a good deal beyond them in front, seem intermediate between the flippers of the seal and the webbed feet of a water-bird. The first naturalist who had anything to do with the ornithorhynchus, Blumenbach the German, who gave it its pretty name, did not think it was able to suckle its young, so much did it differ from mammals in some respects, though looking so like them on the whole. And presently a report arose in the learned world that the new animal which had been classed at all risks among mammals (it having the close fur and almost the body of the otter), a report arose, I say, that this ornithorhynchus of Blumenbach laid eggs like a real duck. The uproar in the Academies was tremendous. As early as 1829, indeed, a learned Englishman, Sir Everard Home had sent over to France an authenticated drawing, as he said, of an ornithorhynchian egg, to the delight of the hunters after analogies among animal races; while Cuvier looked sadly askance at the intruder, whose arrival threw his animal outlines into confusion, there being no place in them for such a beast. Happily for the poor animal, he has ended by almost settling the matter for himself. The ornithorhynchian egg has never turned up. But in the animal's nest have been found baby ornithorhynchuses, newly born, under two inches long (the full-grown animal being more than a foot and a half), and not a trace of eggshells near. Further investigations showed that the mother ornithorhynchus nursed her young with milk, for curdled milk was found in their stomachs; so the Australian phenomenon has been restored triumphantly to the Mammalian order, whence Geoffroy St. Hilaire had excluded both it and its companion, the echidna, a sort of hedgehog, provided like the ornithorhynchus with a bird-like bill, only more of the canary-bird sort; and like it, also, approximating to the bird tribe by other details which do not belong to our subject. And so the matter stands at present; and all we venture to say is that classification had a very lucky escape.

And now, my dear child, that I have made you acquainted in detail with your nearest neighbors, the last of whom, nevertheless, are strangely unlike you outside, however they may resemble you within, I shall take the liberty of going more quickly over the ground, and shall point out in the mass only the more important changes which lead from one class of animals to another. I should be found fault with if I tried to make you too learned, and you yourself might be tempted to tell me, to my sorrow, that you had heard about enough.



LETTER XXXIV.

AVES. (Birds.)

Tell me, my dear child, when you have seen birds taking their flight into the air, and going boldly to their object, without a thought of all the barriers, ditches, rivers, and mountains, which hinder man at every step in his travels, did it never strike you to wish for their wings, and imagine how you would fly off if you had them? If you ever dreamt this dream, do not apologise for it; it is one as old as the world. 'Oh that I had wings like a dove!' cried the Prophet, nearly 3,000 years ago; and the dialogue of the swallow and the prisoner, so often sung by poets, has been repeated in prose behind all the prison-bars on the globe since prisons were first invented.

Now you will not think it kind on my part, but I must undeceive you about this fancy, as you will be undeceived some day about many others. The wings of a dove or swallow would be of no use to you if you had them, any more than the formidable swords of the middle ages would be to our modern gentlemen, were any one to put such into their hands. We are not adapted for them, nor they for us.

You saw, some time ago, what an amount of muscular exertion was required for running—what a violent flow of blood, what hurried play of the lungs. Now in flying it is still worse; for the earth, at any rate, holds us up quite naturally, whereas the air will not hold up the bird unless it is beaten vigorously and unremittingly by an untiring wing. If we men, constructed as we are, had to do such work, we should be out of breath at once; the heart would cry out immediately for quarter, and the diaphragm turn red with anger. And only just imagine in what a critical position a poor wretch launched into the air on the wings of a swallow would find himself when, at the end of five minutes, his servants should refuse point-blank to go on working at a height of 500 feet above the ground!

But a bird has not these internal rebellions to fear. In the first place, it has no diaphragm; so here is another friend to whom we must say good-bye. We shall not meet with him again anywhere. The journey we are taking together, my dear, is somewhat like the journey of life. One sets off, surrounded by friends and acquaintances, but whoever travels on to the end is apt to find himself alone at last; this is what is happening to the digestive tube, which we shall see losing all its accessories, one by one, as we gradually advance in our study. Even now here is one essential fundamental difference in the internal machinery. The body has only one compartment instead of two; and the lungs, masters of the whole space, extend freely to its utmost depths. When a fowl is cut up at table, look along the body, and you will find lodged in the cavity of the ribs, a long, blackish, and spongy mass: this is the lungs. There is not, therefore, the same danger of a bird's getting out of breath as with us; that delicate board which is found in our bellows is wanting in his. His is set in action solely by the to-and-fro movement of the ribs, which is produced by muscular exertions, which are greatly increased during the action of the wings. From which it follows, that the rapidity of flight itself regulates the arrival of air, and consequently the expenditure of strength, or, if you like better, the activity of the fire, since the energy of the muscles depends, as we have seen, upon the quantity of oxygen that feeds the internal stove.

This is not all. These elongated lungs are still not sufficient to furnish the blood with all the oxygen demanded by this excessive labor of flight. They are pierced with holes, through which issue pipes which carry the air all over the body. You know what is said of spendthrifts?-that they burn the candle at both ends. It is so with the blood of birds. That fillip which in our case it receives in the lungs, and which sends it back full of vigor into the arteries, is repeated in the bird at the other end of the arteries as well. The capillaries, those delicate vessels at the end of the arteries, plunge from all sides into little reservoirs of air-lungs, therefore-where the blood renews its provision of oxygen, and relights its half-extinguished fire, so that it sends the combustion afresh into the muscles on its return back to the heart, and sets them going a second time.

The natural consequence of this prodigality of combustion is, that there must be, in proportion, much more oxygen in birds than in us; and that of all animals a bird is the one most quickly poisoned by his own carbonic acid when the air is not renewed around him. Therefore, let me beg you never to think of putting a poor little bird under a wine-glass, as a child of my acquaintance once did, that she might examine her little friend more closely. In the twinkling of an eye he would consume all the oxygen inside his prison, and you would soon see him fall upon his side and die.

On the other hand, the temperature of these flying machines, which consume so much oxygen, is very much higher than ours. It rises to 41 deg., 42 deg. (centigrade), and sometimes to 44 deg., 7 deg. higher than with us. If ever you have taken hold of a little bird, you will have remarked how warm it makes your hand: this is quite natural, since there is always a double fire going on within him, to meet the extraordinary expenditure of strength that is required of him whenever he takes wing. Besides, do but look at the poor little creature when you have imprisoned it in a cage! How it goes up! How it comes down! How it hops from one perch to another, with a quick sudden movement, like that of a spring when it unbends. There is no apparent cause for this state of continual agitation; and yet there is a cause, and only too serious a one. Its fire is not slackened because you have put it into a cage, and its muscles, lashed furiously on by the double-oxygenized blood, drive it hap-hazard into a thousand movements, in which it expends, as best it can, a superabundance of power, which no longer finds natural employment. Little children, who are the real singing-birds of our homes, and whose blood also drives much more energetically along than ours—little children I say—often fare no better than caged birds in those larger cages we call schools; and schoolmasters and governesses would scold rather less if they thought rather more about this. It is right, I do not deny it, that the rebellious young rogues should be taught in good time not to abandon themselves, like wild birds, to the mere animal impulses of the blood: but, in dealing with them, one must also make allowances, as they say, for the fire within, and know how to open the cage now and then. It is not for you, however, that I say this, young lady: you are no longer a little child; but it may happen that you may have some to take care of some day. Believe me, then, you must not expect too much wisdom from them, and you must allow them to change their perch every now and then. It is a law of our Almighty Father that little children, and little birds, should not stay too long in one place.

The mechanism of the circulation is here the same as with us, and does not offer any important peculiarity. Only the left ventricle of the heart has walls of extreme thickness, which enable it to launch the blood into the members with greater vigor and rapidity; and the blood itself, although it is composed of precisely the same materials as that of the mammals, differs from it nevertheless as regards the globules. In the first place, they are more numerous; secondly, they are larger; and finally, instead of being round like a plate, they are drawn out ovally, and are almost shaped like those long dishes on which fish is usually served. I shall not attempt to give you the reason of their size and form. This is hidden from us in the same mystery which envelopes all the microscopic population of the blood; but is it not a curious thing, this strange persistency of form in the globules ofall animals of one class? In all birds they are oval; in all mammals they are round. In all? Nay, I am wrong. As if the better to hide from us the key to this riddle, nature has amused herself by making an exception. Camels and llamas, I forgot to tell you, have also globules in the form of long dishes, like the hen and the chaffinch. Find out why, if you can. As to the reason of the number, it is a very simple one. Since the energy of the blood resides in the globules, it follows that the most energetic blood will contain the largest amount of globules. Looking at you, for instance, little monkey, running and jumping about the garden, I would lay a wager, without counting first, that there are, in one drop of your blood, some millions more globules than in one of mine.

Let us now go on to the digestion, with which, properly, we ought to have begun; but I preferred pointing out to you, first, the particular character which is the chief mark of distinction in the organization of the bird.

'When hens grow teeth,' says a shrewd proverb, meaning of course, never. Birds have no teeth, and in this respect there is no variety among them. All, from the first to the last, have uniformly the same tool to eat with—the bill, that is—which is, in all cases, composed of the same elements, two jawbones elongated to a point, and clothed in a horny armour, which makes their edges sharp and cutting. At the same time were we to review the birds in detail, as we have done the mammals, you would see that there are almost more modifications to be observed in this one single instrument than in our thirty-two teeth. All birds have a beak, but each has his own, organized expressly with reference to the kind of food needed by its owner. The eagle's beak, which mangles living prey, is pointed, bent, and hard as steel; the bill of the duck, which laps up water from ponds and puddles, in order to get worms and half-decomposed refuse out of it, is soft, and flattened like a shovel. The woodpecker's, which has to pierce the trunks of trees, is like a pickaxe; that of the humming-bird, which has to suck up the juice of flowers from the bottom of their corollas, is slender as a needle. The swallow feeds on flies, which it snaps up on the wing, and has a soft bill, which opens like a little oven. The stork picks up reptiles in the mud of the marshes; its beak is straight-pointed, cutting as a knife, and resembles a long pair of pincers. The sparrow feeds especially on hard grains, difficult to break; accordingly its beak is stumpy, short, and thick, and is arched on the upper side for still further solidity. But I should never end if I began to enumerate all the thousand varieties in the bills of birds. Each variety, too, corresponds with some peculiar sort of life, and consequently with a general conformation (easily ascertained) of the animal in which it appears. Give a naturalist the bill of a bird —only its bill remember—and he will tell you half its history without fear of being mistaken.

On the other hand, we must not deceive ourselves as to the real value of this complaisant bill. Let it transform itself as it pleases into all manner of forms for the better fulfilment of its task, it makes, at the best, but a very poor instrument for mastication; nay, to say the truth, it breaks, cuts, and tears, but it never masticates at all. Thus the bird's mouthful is far from undergoing as perfect a preparation as ours does. It is no sooner taken in than it is swallowed, and the salivary glands, which are still to be found under the tongue, seem only to be there as a matter of form; what little saliva they produce is thick and sticky, and has none of the qualities necessary for making that liquid paste which our tongue sweeps up from every corner of the mouth. Besides, it must be owned that a bird's tongue would be a very awkward implement in such a task. Open a hen's bill and you will see therein a very inferior sort of porter. It is merely a dry hard lance, as it were, armed with prickles at the point, as ill-qualified for tasting as for sweeping. So the hen does not waste her time in finding out the flavor of what is thrown to her. She picks up and swallows over and over again, without appearing to experience any other pleasure than that of satisfying her appetite. Birds of prey, it is true, have rather more convenient tongues, capable, moreover, of tasting up to a certain point; and the parrot, who is a complete epicure, and chews his food philosophically, has a charming-little black one, thick, fleshy, and susceptible—a true porter, in fact-who enables Polly thoroughly to enjoy her breakfast. But certain birds who live on insects surpass even the hen in the dryness and hardness of their tongues. That of the woodpecker, especially, is a model of the kind, and deserves a few words more than the others. Picture to yourselves a long pin, terminated by an iron point with barbs like those of fish-hooks. An ingenious mechanism enables the bird to dart it out with the rapidity of lightning, far beyond his bill, upon the insects to which he gives chase. The point pierces them, and the hooks retain them, without any need of assistance from the bill. I have just told you that this bill pierces the bark of trees; but it only plays the part of gamekeepers on grand sporting occasions, who beat the bushes to make the game rise. The woodpecker's bill routs up the insects by destroying their shelter; but the real sportsman is the tongue. Good-bye to any notion of a cosy little chat in such a porter's lodge as that! What could a harpoon have to say for itself?

Do not, however, let this miserable entrance-hall alarm you, at the same time, for the fate of the mouthful thus presented half-dressed to the oesophagus. You will find it only so much the better treated within. In the first place, the oesophagus, when half-way down to the stomach, swells out suddenly and forms a pocket, which is generally particularly well developed in birds who feed on grain; this is called the crop in English, in French jabot; whence comes the application of that word to those full shirt-frills which have sometimes been the fashion. It is the pigeon's crop that gives him the rounded chest over which he bridles so prettily. The crop is a receptacle where the food makes a halt: it is something between the pouch of the monkey and the paunch of the ox; a preparatory stomach, which does not, it is true, send back the grain to the bill, for the bill could do it no good, but in which that grain lies until there is room for it further on.

Prom thence it resumes its journey; but, before reaching the true stomach, it passes through a second enlargement of the oesophagus, whose walls are pitted with numberless little cavities, from which pour over it the juices destined to supply the place of the saliva that was wanting above.

It reaches its destination at last, but still hard, and generally whole. No matter, however. The stomach which receives it, and which is called the gizzard, is quite a different sort of thing from a useless membrane, thin and delicate like ours. It is a thick muscle of enormous power, lined inside with a kind of horny skin, so tough that nothing can break through it. You may form some idea of the prodigious strength of this organ, when I tell you that turkey-fowls have been made to swallow hollow balls of glass, so thick as not to break when dropped to the ground, and that at the end of a few days they have been found reduced almost to powder in the uninjured stomach. No fear of indigestion with such an apparatus as that. Though the grain may not have been masticated in the bill, what does it signify? There is a power here, as you see, quite equal to carrying the whole work through. Thanks, indeed, to the invaluable horn which lines it, fowls which have no teeth of their own can safely present themselves with as many and as hard ones as they please. They swallow small pebbles, which rub against the grain, during the contractions of the gizzard, and act just as effectually as if they were fixed in the jawbone. Well, this terrible gizzard performs its crushing work with such energy, that not only the grain but the pebbles themselves are ground down there, and end by being pounded into fine sand. When you rear fowls, do not forget, if you keep them shut up, to put within their reach a store of small pebbles, so that they may have teeth to run to in time of need.

You remember the pylorus—the porter down below, who keeps the door of egress from our stomach? He is as badly provided for here as his fellow-workmen up above; worse in fact. It is a gaping hole, and we cannot expect a very strict supervision from it. Birds who feed on fruits profit by this fact to carry vegetables from one country to another. With such an easy opening, seeds have a good many chances of passing from the stomach unaltered; and then they drop from the clouds, as is supposed, hap-hazard, and germinate afterwards, when circumstances prove favorable, to grow up before the astonished eyes of the natives into plants of which they have never even heard. The French Acclimatization Society, which I spoke of lately, and which, though so modern, has correspondents all over the globe, is at this moment laboring to effect an exchange between all countries of the natural productions of their soil. But here you see that nature had thought of this before, and established her acclimatization society long ago.

To complete the internal work of digestion, so feebly begun in the bill, an extremely large liver pours torrents of bile into the duodenum, and the manufacture of chyle proceeds with that wild rapidity which characterizes all the living actions of birds. But speaking of this liver, I think I ought to give you an account of a celebrated dish, considered a great dainty by epicures, called pates de foies grasfat liver patties, to translate it into its meaning. Very likely you will not care to eat them after hearing my story; but that will be no great loss to you, for it is a very indigestible sort of food, and not at all good for children.

You remember my telling you about Englishmen going to India and coming back with a liver-complaint, from having eaten and drunk more than the climate allowed? By an imitation of this process, human ingenuity—occasionally so cruel—has created the pates de foies gras, the glory of Strasburg. I have been in the country, and can tell you how it is managed. They shut a goose up in a square box, where there is just room for his body. They open his bill at feeding-time, and cram down with the finger as much food as can be got in. This is throttling rather than feeding it. The poor beast, who can use no resistance, since it cannot move, and who is kept in the dark to prevent excitement; the poor beast is quite unable to burn all the mass of combustibles with which the blood soon finds itself loaded. This carries them to the liver to be turned into bile; but the liver is not equal to the work, becomes loaded in its turn by unemployed materials, and grows and grows, till at last, having filled up all the space around it, it stops the play of the heart and lungs. When the animal is nearly suffocated they kill it; and this is how we come to have pates de foies gras to eat! If they give us a fit of indigestion afterwards, it is a vengeance we richly deserve. At Toulouse, where the same trade is carried on on a large scale, they used formerly to go even beyond this. They fastened the goose by the feet before the fire-place, after having put out its eyes. The imitation of the Englishman's proceeding was still more perfect here, for the fire acted the part of the Indian sun to perfection. I do not know that part of the country well enough to tell you whether they have quite given up this piece of wicked ingenuity; all I can say is, I devoutly hope so.

The intestine of birds is much shorter than that of mammals. Here everything is done at full gallop, and the chyle has not to go far before it is absorbed. I have before me a book, in which I am told that the wagtails eaten in France can be fattened in twenty-four hours, if you only know how to set about it, and these birds are not rare; they belong to the same family as the red-breasts, the tomtits, and the nightingale. Thrushes and wheatears (ortolans) require, for the same purpose, four or five days in the same country, left to themselves to roam about, when the vine keeps open table for them.

This incredible quickness, not only in digesting, but, what is much more, in transforming food into fresh living material (assimilating it, as it is called), has often a fatal result for the bird. He is prohibited from fasting; his life is a fire of straw, which must be replenished unceasingly, or it will die out in the twinkling of an eye. Our own little birds—children—eat oftener than grown-up people, and if by any accident they are kept waiting awhile, they soon cry out with hunger. You know this, do you not? Well, then, if any one should give you a bird to keep in a cage, remember that you have undertaken a great responsibility, and that it will not do to be careless with him. To neglect feeding him for one day is to run the risk of finding him starved to death next morning. With this warning, I will conclude my chapter on birds. I hope I have not spoken in vain in behalf of those poor little captive songsters, whose fragile lives are at the mercy of their young masters and mistresses.



LETTER XXXV.

REPTILIA. (Reptiles.)

Passing from birds to reptiles is like falling from a torrent into still water. Life drags on as sluggishly with the second as it dashes furiously forward with the first.

I spoke to you just now about a fire of straw: now we have a fire such as Frenchwomen make in their chaufferettes, or foot-stoves. A handful of charcoal-dust, and a few live embers between two layers of ashes, is enough for the whole day; which is economical, is it not? but then it throws out only just warmth enough to keep one's feet comfortable. And so it is with reptiles. They live at very small expense. If you feed them once a month they will not complain, for so slow a fire does not often need replenishing with combustibles. It is even said that the experiment has been carried so far with tortoises that they have been made to fast for more than a year, and still the charcoal fire kept up its languid pace. Of course, on the other hand, there is not nearly so much oxygen consumed at once upon such a diet as this. Where a bird would perish twenty times over in five minutes for want of oxygen, a lizard can remain whole hours with impunity. Moreover, the animal heat of reptiles is in proportion to their expenditure of it. Graceful as is the snake (that living jewel so often copied by bracelet-makers), you feel on touching it an instinctive horror, caused by the thrill of cold it produces. All the animals we have considered hitherto have warm blood, and bear within themselves the source of their heat, which is pretty nearly always the same. But reptiles are cold-blooded, and heat comes to them chiefly from without.

If, at the end of a cold winter, we go to some favorable corner to catch the first rays of spring sunshine, we feel ourselves almost re-born, as it were, as if a new life had come into us with the sunbeams. Look at the little lizard you see frisking on the white stones of the wall; upon him decidedly the sun is darting actual life from its rays. While the cold lasted he staid squatting in his hiding-place—not asleep, but annihilated—congealed, so to speak, like water caught by the frost; no longer digesting, and hardly breathing, he had ceased to live in reality: and it is no imaginary regeneration which the return of warmth brings to him. Like those helpless people who have not the power to carve out their own destinies, reptiles have within them only an insufficient source of animation; their life is at the mercy of the sun, and is high or low, according as that rises or sets in the heavens. At Martinique, where at noonday it darts its devouring rays perpendicularly upon the cane-fields, and every one flies into the shade to escape its scorching heat, the rattlesnake traverses the country, monarch of all he surveys; he strikes rapidly with a vigorous tail upon the calcined ground; and woe then to any one who receives his bite! All the fire of the atmosphere has passed into his frame. Now go to the Zoological Gardens, and see him there: he crawls languidly under the coverings that shelter him; if by chance he bites any one, it is with an idle tooth that no longer knows how to kill; his life was left behind with the sun of the tropics, and it is little more than a corpse that you are looking at.

And so among ourselves, my dear child: we meet with people whose whole power comes from without, who are brilliant and haughty in the sunshine of good fortune, but crest-fallen, cowardly, and cringing in the cold days of adversity. Nevertheless, they are constituted originally like other people: they are neither greater fools as a general rule, nor less gifted than their neighbors; where they fail is in the heart, but that is enough to spoil everything. And so with reptiles: the heart is their weak point also. Like us, they have lungs into which the air pours without any difficulty, and a heart to send the blood to them; so it seems at first sight as if there could be nothing to prevent their resisting the changes of external temperature just as well as ourselves. There is only one small trifle wanting, and that is a partition in the middle of the heart; but this one defect is enough to disorder the whole machinery.

You know that, with us, the heart is divided into two compartments: the right ventricle, which receives the venous blood from the organs and sends it to the lungs; the left ventricle, which receives it (now become arterial) from the lungs and returns it to the organs. Hence the double system of veins and arteries, the one going from the heart to the lungs, the other from the heart to the organs. All this is found the same in reptiles: except that the partition, which separates our two ventricles from each other, does not exist in them; and the heart has only one common room, in which, therefore, arterial and venous blood become mixed together. It follows from this that, at each contraction of the heart, it is a mixture of arterial and venous blood which is sent in the two opposite directions at the same time, and that the organs receive some which has been used before, while the lungs have some returned to them which has been regenerated already. Now, on the one hand, this mixed blood can only keep up an imperfect combustion in the body (like the live embers between two layers of ashes that we spoke of lately), and, on the other hand, the air in the lungs can only act upon a part of the blood it meets with there, the rest having already undergone the regenerating process. And this accounts for both the feeble animal heat and the small consumption of oxygen in reptiles.

Added to which the lungs of a reptile are coarsely constructed, and composed of cells enormous in comparison with ours, so that the blood does not find nearly as many little chambers to rush into for a taste of air as with us. Moreover, you must understand that there is no such thing as a diaphragm here: the lungs float loosely in the form of elongated bags in the one only cavity of the body, and the slight movement of the ribs does not allow them to dilate sufficiently to take in much air at a time.

All these things, taken together, make the reptile a very poor stove, and render him incapable of any prolonged exertion. The serpent darts like an arrow upon his prey; but he could not pursue it for half a mile without stopping, not even over the burning soil of the equator. The lizard is very nimble, is it not? and the quickness of its movements rather reminds one of the agility of a bird. But watch it, and you will see it only moves in jerks, and keeps stopping every minute; it cannot escape you if there is no hole near into which it can disappear. In France there is a large green lizard that runs among the vine trees. If you pursue him he is off like lightning for a second; then he stops suddenly short. You return to the charge, and he starts afresh, but only to stop again. At the fourth or fifth attack he is quite out of breath; you poke him with the stick with which you have been hunting him, but in vain; there he lies motionless, in spite of his alarm. A few steps have brought him to the end of his powers, like a man whose heart is diseased and who cannot go far. This, however, is a peculiarity common to all reptiles. Each of the three orders of which this third class of Vertebrata is composed has its own particular history besides. You must excuse my mentioning the barbarous names that have been given them, and allow me to call them tortoises, lizards, and serpents, like other people. The hard names mean no more than these; but they are Greek, which is always more imposing.

The slowness of the tortoise has passed into a proverb, which is not to be wondered at; for they cannot inhale the air, because their ribs (which are a reptile's only resource for breathing) are condemned to absolute immobility. The carapace, or shell, which the tortoise carries on his back, and under which it retreats upon the least alarm, as under a shield, is really formed of its ribs, each of which has widened itself so as to join on to its neighbor, like the boards of an inlaid floor, which run one into another. Of course there is no question of moving up and down with such ribs, and the poor bellows cannot work at all. How does the tortoise get out of this difficulty then, you will ask? I answer, it swallows air, as we should swallow a glass of water. You see its mouth open and then shut again, thereby taking in an actual mouthful of air, which the sides of the mouth, by contracting themselves, send straight to the lungs. These, which are very large, get filled in this way by degrees, and, when they are quite inflated, they expel the overplus by collapsing, like an over-stretched spring. You may imagine that this does not produce a very active respiration, and that a tortoise would be puzzled to run at even a moderate trot. To be sure, when he has once filled his great lungs with air, he has enough for a long time. Most tortoises are aquatic, and, as divers, leave the cetaceans far behind. Mery, an obscure French naturalist of the days of the Empire, pretended that he had kept in his house, for a month, some tortoises, whose breathing he had completely stopped. Only imagine from this how far their life must be below ours, although it is the result of similar actions, performed by organs which after all are copies (imperfect ones, it is true) of our own.

Some tortoises feed on vegetable substances, and some upon fish or small soft-bodied animals. Like birds, they mash their food with difficulty, by means of a real bill. Their jawbones are generally arched forward toward the front, and are furnished with sharp horny plates, in which a fairly-marked denticulation or notching may sometimes be traced, as in the bills of birds of prey. Indeed there is one, the caretta, whose hooked and notched beak so completely recalls the warlike bill of a hawk, that it is usually known by the name of the "Hawk's-bill Turtle." You ought to know about this tortoise, for it is the one which furnishes tortoise-shell, that nice material which is so smooth to the touch, so pretty to look at, and so very fragile, that it seems only fit for the use of ladies' hands. I could hardly speak of tortoises without saying something of this one, out of whose back was carved the handle of your own pretty little penknife.

Behind this bill of the hawk's-bill there is a tongue, but of the character of a whale's tongue, and it is fastened underneath to the bottom of the mouth. At the base of it there is a sort of fleshy pad or cushion, which serves instead of a soft palate, that being another detail which is about to disappear from our history. We are now really entering upon the simplification of the digestive tube, which will, I forewarn you, end by being nothing more than a perfectly straight pipe, without any appendages whatever. In tortoises the intestine is still tolerably long, and is doubled up backwards and forwards many times in the abdomen; but it is already beginning to lose that variety of form which its different parts assumed in the higher animals. The large intestine can no longer be clearly distinguished from the smaller one, nor this from the stomach, which itself seems to be a continuation of the oesophagus, without any very distinct boundary line between them. The porter, who with us keeps the door of the stomach, does his duty here so badly, that there are certain kinds of tortoises whose oesophagus is covered with spines, the points inclined backward, to prevent the food from rising up into the mouth whilst the oesophagus is driving it down by its contractions.

In the gray lizards of our walls we find teeth again, but very different from any that we have hitherto seen. In the first place, they are not content with their usual place on the edge of the jaws, but encroach upon the surface of the palate, where they stretch out in close lines. Besides, they are even still less like teeth than the great nails in the jaws of the cetaceans. They are little ivory prongs, with the points turned inwards, analogous to the thorns of the oesophagus in the tortoise, and serve the lizard solely to retain and bruise his prey. He lives on insects, especially flies, which he seizes on the wing with the greatest skill, hastily catching and engulphing them in his open jaw; they pierce themselves on the little prongs, and are swallowed promiscuously. The tongue of the lizard has also a curious peculiarity, which is shared by that of the serpent: it is divided at the end into two threads, which dart in and out of its mouth, and by means of which it laps, like a dog, the few drops of water it requires to satisfy its thirst. I have seen lizards which had been tamed by children greedily sucking up the saliva from their lips by drawing across them those little forked tongues of theirs, which, after all, are very soft, and perfectly inoffensive.

The tongue of the chameleon, another species of lizard, is still more curious. You must know that the chameleon is a lumbering lazy animal, who feeds on flies and other swift insects, and who would, therefore, be constantly liable to go without his dinner but that his tongue serves him for a hunting weapon, like those of the wood-pecker and the ant-eater. When at rest, it is an oval spongy mass, lying comfortably in the mouth, with nothing formidable in its appearance; but let the prey come frisking round the chameleon, as if despising so helpless an enemy, and this great soft tongue is transformed into an active dart. It shoots forth like an arrow, and will sometimes seize the rash intruder at half a foot's distance, transferring it with equal rapidity to the motionless mouth. The blow is so soon struck, that it is very difficult to see how it all happens. Some say that the chameleon curves the tip of his tongue by a sudden effort, and then catches his flies with it, just as you would catch them with your hand. Others maintain (and this is the general opinion) that the tongue of the chameleon is terminated by a sort of sticky cushion, on which the flies are caught, like birds with birdlime. This singular dart is always out-jerked with such force that, if it strikes against a glass (the experiment has been tried with chameleons in captivity), it makes a sound as loud as that of a pea from a pea-shooter; so you may judge if it is not strong enough to stun a fly. Besides this, too, the chameleon (who is by-the-by, a hideous little beast) has given endless trouble to naturalists on another and very different point. It is he who is so celebrated for his faculty of changing color when any emotion agitates him; and ever since the days of Aristotle, who lived more than two thousand years ago, people have been trying to explain this, without any one being able to flatter himself that he has found out the exact answer to the riddle.

But there is a lizard more interesting still, and that is the crocodile. He stands alone among reptiles. His heart has two ventricles, and you would think that he ought to be included in the class of warm-blooded animals. But, no. The separation of the two kinds of blood takes place in the heart, it is true, and it is really true arterial blood which the aorta carries away from the left ventricle. But the right ventricle has two doors of exit. One communicates with the lungs, the other with the aorta; and the latter has hardly performed its distribution in the upper part of the body when it meets, as it descends, with a treacherous tube bringing to it a current of venous blood. In this way only half the blood that comes from the veins passes on to be regenerated by contact with the air, and all the hinder part of the body receives nothing but the mixed blood common to reptiles, while the head and fore members enjoy the privilege of the superior orders. After this go and lay down your laws of classification! Nature, while maintaining amongst all animals the same principle of life—the regeneration of the blood by oxygen—has in their construction followed many systems leading to the same result by different combinations, and which seem to permit the establishment of essential distinctions among them. Here is an animal who, if I may so express myself, is climbing up from one system to the other, and you would have to cut him in two before you could classify him properly, since his fore-quarters have risen to the warm-blooded animals, while his hind ones are left behind among the cold-blooded reptiles!

But there is something which even outdoes this.

On dry land the crocodile is timid, faltering, a bad walker, incapable of regular combat, and a man can manage him with a stick. One feels that he is betrayed by the hinder half of his body, through which circulates the only half-oxygenized blood. But when once he has plunged into the water his whole behavior suddenly alters; he is a ferocious being, high-mettled, indomitable, a savage enemy, redoubling his exertions, as if the entire mass of his blood had suddenly become arterial. Geoffroy St. Hilaire, who followed Bonaparte as a scientific explorer when he set out for the conquest of Egypt, the country of crocodiles, was deeply struck by studying on the spot this double life, which seems in a way to maintain two beings in the same body. He afterwards gave an extremely curious explanation of it in his work on the crocodiles of Egypt. Here it is; but I forewarn you that you will not understand it:

"The crocodile, when it is under water, receives by two canals into the cavity of the abdomen, a considerable quantity of water, which the animal can renew at will."

You are not much the wiser, are you? But wait a moment. We are soon coming to the fishes, and you will then see what an unlimited scope nature has allowed herself here. Not satisfied with two systems in one animal, she appears to have got hold of three.

If we continue the examination of this privileged reptile, we shall find many other infractions of the usual rules of his class. His tongue, certainly, is fastened to his mouth like that of the tortoise, so much so that the ancient Egyptians told the Greeks he had not got one; but his set of teeth clearly approach those of the lower mammals. You have probably heard a great deal of the strength of the crocodile's formidable teeth. Travellers have given them this reputation; but we have nothing to do with that now. They stand in battle array, in a single line, along the whole length of the jaws, into which they are sunk with genuine fangs, whilst the prongs of our little lizard are merely fastened to the surface of the bones which support them. Indeed, in one way, the crocodile is even better provided than the mammals. He possesses under each tooth one or two germs, the life of which lasts as long as that of the animal, and which are always there ready toreplace the previous one should it chance to fall out. There are many ladies, and (not to be rude) gentlemen as well, who would, I am sure, give a great deal to have as many teeth at their service. Indeed, they may possibly think Dame Nature very unjust to have selected this great villanous beast rather than us as the object of a gift which they would have been so well able to appreciate. But we must not blame nature too quickly: she had her reasons. We, during our infancy, have teeth in reserve. Now, a reptile may be considered as an imperfect rough draft of a mammal; and the crocodile gives one thoroughly the idea of a mammal half-finished and fixed for life in a state of childhood. I am sorry that I cannot enter into full details, that you might see how far the idea is a just one. Moreover, in his character of a perpetual child, he is always growing bigger all his life long, and never seems able to die but by accident, hardly ever, I may really say, from old age. By specimens kept in captivity, it has been ascertained that their growth is very slow. Well, imagine their being only from seven to eight inches long when they come out of the shell, and that full-grown crocodiles have been found thirty feet in length, and calculate accordingly. You will not account for it under a century; and I should like to know what would become of this venerable child of more than a hundred years old if kind Mother Nature had not left him our system of milk-teeth to the end?

A curious peculiarity of these persistent teeth is, that they are hollow inside, so much so, that the bowls of tobacco-pipes are said to be made from them in Europe. I mention the fact, although of no great interest to you, for the benefit of any pipe-merchants who have not yet thought of sending for such things to Cairo.

But let us return to the efforts perceptible in the organization of the crocodile to raise itself to a higher level. The soft palate, as we called it (Letter VII.), is wanting in other reptiles; but here there is one which completely closes the entrance of the windpipe (the larynx). I announced, too, the disappearance of the diaphragm; and we bewailed together the loss of that servant of the good old times, whose touching history you must, I am sure, remember. But I reckoned without this wretched crocodile, who seems determined to give the lie to all we have been saying. He has a diaphragm, and one which acts well enough in the main, although it is pierced right through the middle, as if it were rather ashamed of being there, and wished to make up for dividing the body into two compartments, against all proper reptile regulations, by opening a door of communication between them. What shall I tell you besides? The lungs, not to be behind the rest of this aristocratic reptile's organization, are hollowed into cells much more complicated than those of his fellows. You find here no end of nooks and corners, which multiply opportunities of contact between the air and the blood, and so give the crocodile almost the respiration of the mammals, as he has already got pretty nearly their system of circulation.

With serpents, again, we fall very low. When we were speaking of the tortoises I told you that, in proportion as we come down in the scale, the digestive tube has a tendency to get rid of its accessories, and to assume the appearance of a perfectly straight tube. If any one were to cut open a serpent before you, you would see this final condition almost reached already. In the first place, the soft palate is entirely suppressed, and the mouth extends straight into the oesophagus, whose tube seems to run through the whole length of the body without interruption, with just four or five doublings towards the base, in that part which represents the intestines. An imperceptible swelling indicates the place where the real stomach lies within; but in another sense one may call the oesophagus, and I might almost add the mouth itself, its stomach. You shall see how.

The jaws of serpents are even in a more unfinished state than those of other reptiles. Nature has not taken the time to weld the different parts of them together; but these begin by not being very firmly joined, remember, in young mammals. The bones of the head, which support the jaws, are themselves movable, and can be detached from the skull if necessary, so as to allow the throat to open extraordinarily wide; thus it is not uncommon to see a serpent swallow animals much larger than itself. You will be horrified when I tell you that the anaconda, one of the giants of the family, swallows large quadrupeds at a single mouthful. What are our mouthfuls in comparison with his? however, it must be confessed, that his often take several days to go down. When the animal has rolled up his prey in his terrible folds, he pounds and kneads it till it is reduced to a kind of long roll, which he moistens with a copious slaver to make it slip down more easily. Then, attacking it at one end, he fastens this very expansive jaw upon it, and the gigantic mouthful slowly begins its journey; what was left outside the mouth, advancing little by little, in proportion as the digestion reduces what has entered to pulp, and sends it farther down. This is on great occasions; but in the case of more modest prey—a rabbit, for instance—the mouthful goes in whole at one gulp and remains stationary, partly in the oesophagus, partly in the stomach, while the powerful juices distilled by the walls of the latter are dissolving it.

You can see that a soft palate would have been quite useless here, and that the serpent has not much need of teeth to chew his food. Accordingly, his are nothing but simple prongs, like those of the lizard, and, like his, they extend over the palate, the more effectually to cut off the return of the swallowed masses of food. About a hundred and twenty have been counted in the throat of the boa-constrictor; but their number varies considerably in the different species. They are not organs of the highest order, and nature is not very particular about the quantity.

There is only one tooth among serpents of which she takes any particular care, and that is the venomous tooth which she has bestowed on certain species, and which serves them for striking down, as it were, the animals on which they feed. Let us study it in the rattlesnake, the most celebrated of this odious race. On each side of the upper jaw you may see, isolated from the others, and exceeding them all in length, a very sharp fang pierced through by a tiny canal, which opens into a gland placed at the root of the tooth. The bone which supports this little apparatus is very flexible, and when at rest, the fang, falling back, hides itself in a fold of the gum. When the animal wishes to bite, it springs up again, and the gland, compressed by the action of biting, sends into the little canal a jet of poison, which runs through it into the wound. As far as can be ascertained, this poison paralyses the victim and disorders the blood, which at once loses its power, and no longer acts upon the organs as before; still it is only injurious when it has been carried by the current of circulation into the mass of the blood; if swallowed, it has no effect whatever on the stomach. Now do not look at me with such incredulous eyes, as if it were quite impossible any one should think of swallowing such a thing. You have no idea what a scientific man is capable of when he comes to close quarters with nature, for the purpose of extracting one of her secrets. He has his own fields of battle, where very often as much courage is displayed as on any other.

These two fangs, in which lie all the power of the animal, are of the greatest importance to him, and their want of solidity makes them liable to remain in the wounds which they have made. In consequence of this, they enjoy the same privilege as the teeth of the crocodile, and in a still greater degree even. Behind each poison fang lie in wait, not one nor two, but several sentinel germs, ready at the first alarm of a loss to set to work and re-supply the disarmed serpent with his venomous needle. So the serpent also lives in a state of perpetual childhood: he is always growing; and I could not tell you the exact natural limits of his life any more than of that of the crocodile. They are gentlemen who do not allow themselves to be very closely studied in a state of freedom. But these also grow very slowly, and some have been met with whose size had extended quite enormously from their first start. I ought to tell you, once for all, that this indefinite growth, joined to extreme longevity, is found in many of the inferior species whom we have yet to consider. It seems the portion of these unfinished creatures, in which nature has only as it were sketched in her work, and who seem vowed to endless youth, in testimony of the state of childhood they represent, a state transitory among the superior animals, but permanent with them. It belonged of right, therefore, to the serpent, which is the most unfinished animal we have yet met with, and who, at the first glance, seems almost reduced to a mere digestive tube, lodged between a vertebral column and a series of small ribs, whose number sometimes reaches three hundred. The liver, which, with us, presents such a distinct and bulky mass, is here elongated into a thin cord, which runs the whole length of the oesophagus and intestine, to the walls of which it is, to some extent, attached.

It is the same with the lungs. There is rarely room for the full development of two in this narrow conduit, where everything has to follow the shape of the master of the house: one, therefore, is often merely indicated by a very slight protuberance; the other, presenting the appearance of a long tube, which extends nearly half-way down the body, and whose feeble action halts periodically at each of those monstrous repasts, after which the torpid animal becomes nothing but a huge digesting machine. We have now reached the extreme limits of that organization, the most perfect model of which we find in man, and which is no longer to be recognized in fishes.



LETTER XXXVI.

PISCES. (Fishes.)

We are becoming terribly learned, my poor child, and I am half afraid you will be getting tired of me. When I was little myself, I had rather a fancy for breaking open those barking pasteboard dogs you know so well; to see what was inside them. Why should you not, then, feel a certain amount of interest in looking with me into the insides of real animals? Still I cannot conceal from myself that the subject grows very serious at last, and that while I am busied in struggling to make myself intelligible through the endless crowd of facts which surround me, I am apt to neglect chatting with you as we go along. Happily, however, here is an opportunity for so doing.

Up to the present time we have lived, as it were, upon the explanations I gave you whilst studying the action of life in yourself, and all the organs we have met with since, have been only, properly speaking, reproductions, more or less exact, of those which you yourself possess. But, in passing over into the kingdom of fishes, we find ourselves in the presence of something altogether new, and I must go back to our old familiar style of talking to open the subject.

Take a water-bottle half-filled with water, and shake it well, and you will see a quantity of white froth come to the surface of the liquid. This is the air which having been drawn in by the water, as it went up and down in the bottle, is now struggling to fly off again in bubbles as fast as it can. But the whole of it does not get away; a small portion remains behind, and melts, as it were, into the water, as a morsel of sugar would do, taking up its abode therein. This seems odd to you, but I will tell you how you may convince yourself of the fact. Get a small white glass bottle, slightly rounded, and thin at the bottom, if possible; fill it with water, and hold it for a short time over a lighted taper. If you do this carefully there is no danger. You will soon see tiny little balls, looking like drops of silver, rise from the bottom of the bottle, come up to the surface, and burst. This is the air which was installed in the water, as I described above, and which is now running away from the heat of the candle, as the inhabitants run away from a house on fire. After a time the whole will have passed off, and the little balls will cease to rise.

But what has all this to do with fishes? you ask.

A very great deal, I assure you, dear child. If there had been a little fish in your bottle, before it was exposed to the flame, it would have found means to make use of that air, whose original presence in the water you cannot refuse to believe after having seen it come out. It is with this air that fishes breathe in the water. They do so rather feebly, I admit; but, as if to make up to them for the small amount of the air placed at their disposal, it contains more oxygen than that we breathe ourselves, because oxygen, dissolving more readily in water than nitrogen, is there in greater proportion. Of course, you do not suppose that fishes have lungs like ours? I dare say you know the two large openings on each side of their head, called gills, by which the fishermen string them together to carry them away more easily? It is there you will find their lungs, to which the name of branchiae, or gills, has been given, because they are so different from other organs of respiration that it was impossible to use one word for the two. The arrangement of the gills varies considerably in the different species, but their general form is the same everywhere. They are composed of a number of plates, consisting of an infinitude of leaflets, arranged like a fringe, and suspended by bony arches, into which plates and leaflets the blood pours from a thousand invisible canals.

First of all, then, we must see how blood circulates in fishes.

Like reptiles, their heart has only one ventricle, and yet the arterial and venous blood go each its separate way without the slightest risk of being mixed; but this is because fishes have not that double system of veins and arteries which hitherto we have always met with. The venous blood goes to the heart, which drives it into the gills, from whence it passes forward of its own accord, as arterial blood into the organs, under the remote influence of the original impetus from the heart, the newly-arrived blood incessantly driving the other before it into the vessels of circulation. It does not flow very quickly, as you may suppose; and as the heart is close to the head, its action is but very feebly felt at the extremity of the body, when this happens to be very long. Nature has, in consequence, taken pity on the eel, whose tail is so far from its heart, and provided accordingly. Dr. Marshall Hall has discovered near the tip a second, reinforcing heart, so to speak, which has its own pulsations, independent of the pulsations of the one above, and gives a fresh impetus to the sluggish blood, [Footnote: Many observers refer this to the lymphatic system.—TR.] which otherwise, as it would seem, would scarcely be able to accomplish the long return journey. Finally, even with an additional heart in thetail, the circulation among fishes is quite on a par with their respiration. They have a melancholy steward, whose legs are very heavy, and his pockets very light, and their life comes down a peg lower in consequence. It is always the same life nevertheless—you must never lose sight of that fact: it gets low in consequence of the imperfection of the machine, but without changing its nature, any more than the light in our different sorts of lighting apparatus. You remember that comparison of the lamp with which I began my story, and which you could not at the time see the full value of? From a dungeon lamp up to a candle, you have always grease burning in the air at the end of the threads of a wick. It does not burn equally well everywhere, and does not always give the same amount of light; but that is all the difference. From the mammal to the fish, it is always hydrogen and carbon (as we have said of the grease) which oxygen sets on fire in the human body at the fine-drawn extremities of the blood-vessels; only the fire is lower in some than others, and the life with it. Let us now look at the circulation of water in the fish's body.

The gills communicate with the mouth by a sort of grating, formed by the bony arches to which the gill-plates are suspended. The fish begins by swallowing water, which then passes through the grating and circulates round the innumerable leaflets of which each plate is composed, and among which creep the blood-vessels. It is through the thin coats of these leaflets that the mysterious exchange is made of the unemployed oxygen in the water and the carbonic acid in the blood. When this is over, the cover which closes the gills opens to let out the water, and a fresh gulp takes its place; and so on continually. When the fish is out of the water its gills fall together and dry up; the course of the blood, already so weak, is interrupted by the breaking down and shrinking of the vessels, and the animal can no longer breathe; so that we have here the curious instance of a creature breathing oxygen like ourselves, who is drowned, if we may use the expression, in the air in which we find life, and lives in the water in which we are drowned. While he is in the water matters take another course, and his gills, moistened and supported, accommodate themselves perfectly to the contact of the air, which desires nothing better than to give up its oxygen to the blood, through the coats of the capillaries. Accordingly you will often see fishes—carps, for example—come to the surface of the water to inhale the air like a mammal or a reptile. This is a valuable resource, which supplements the parsimonious allowance of air given out to them by the water. There are even certain fishes whose gills, more firmly closed than those of others, have, in addition, a number of cells, which retain for a considerable time a sufficient quantity of water to preserve the gills in their natural state. These fishes can easily take an airing on land, where they breathe the air as you or I do, and are downright amphibians.

The most celebrated of these is the Anabas, or "climbing-fish." an Indian fish, which not only can remain many days out of the water, but also amuses itself by climbing up the palm trees—it is hard to say how—and establishing itself in the little pools of water left by the rain at the roots of the leaves. But we need not go to India to find those wandering fishes. There is one of them living among ourselves who can walk about in the grass, and I was talking to you about him only just now—that is the eel. If you ever put eels in a fish-pond you must, I assure you, try to make it agreeable to them, otherwise they will have no scruple in setting politeness at defiance and moving off to seek their fortune elsewhere. In a country walk, when the dew is on the ground, you yourself may chance to come across one or two of these gentlemen, who have had their reasons for changing their residence, and whom you will see gliding so briskly along that they will deceive you into taking them for snakes if you have not a very experienced eye; so much so, that in certain parts of France where the peasants ate snakes formerly, they reconciled themselves to the sickly idea by christening them hedgerow-eels.

On the other hand, fishes may be drowned in water just as easily as ourselves if it does not contain air. The little fish who could have lived very well in the bottle we were just now talking about before you exposed it to the flame of the taper, would have died in it after all the air-bubbles had gone off; and I hope I need not tell you why. In the same way, if you leave fishes too long in a small quantity of water without renewing it, they suffer exactly as we do if the air which we breathe is not changed often enough. As soon as they have consumed what oxygen is in the water, it can no longer keep them alive. It is then, especially, you will see them come gasping to the surface to call upon the air for help. Those who keep gold fish in a glass bowl ought to know this, and to change their water oftener than is generally done. When we take poor little creatures from their natural way of life, and set a human providence over them in the place of the Divine one which has hitherto been their safeguard, the least we can do is to acquaint ourselves with the laws of their existence, so that we may not expose them to the risk of suffering by our ignorance. Finally, there are fishes whose gills, still more greedy of oxygen, will not act well except in thoroughly aerated water, and who would soon die in our tanks. This is the case with the trout, who is only happy in the waters of hilly countries; rich with all the air they have carried along with them as they fell from rock to rock. Now that people are beginning to do with fishes what has long since been done with sheep and oxen—keep them in flocks to have them always ready for use—you may perhaps hear a good deal said about vessels made expressly for the carriage of trout, with a thousand inventions besides for sending air into the water, and you will not have to ask the meaning of this now.

I promised last time that I would revert in the chapter of fishes to that marvellous transformation of the crocodile which has been explained by the torrent of water he draws into his stomach. You could understand nothing about it the other day; but after what we have just seen the explanation suggests itself. Just as the extraordinary activity of life in birds is explained by that double oxygenization of blood, of which part takes place in the lungs and part in the reservoirs of air placed everywhere in the way of the capillaries, so this sudden increase of energy in the crocodile the moment it plunges into water may be explained by a second respiration suddenly established in the vast cavity of the abdomen, by the contact of the capillaries with the water which penetrates there. Hence the crocodile would then have, like the bird, a double respiration: only with him the one would be permanent and from the lungs, the other temporary and from the stomach. By this, on the one hand, he would rise up to the birds, since the blood encounters air twice over in its course, while, at the same time, he would plunge into the world of fishes, since the blood has to seek air in the water. The above, be it remembered, is only a supposition, and I ought to add that in this case there would be a good deal of danger in observing nature at work, for in front of the laboratory, where she is toiling in secret, stands on guard a row of teeth, by no means encouraging to indiscreet intruders. At the same time, if there ever were a legitimate conjecture, this is it. Everything seems to confirm it; and if it be true, we should have in the crocodile a specimen of each of the four systems adopted by nature for the mammal, the bird, the reptile and the fish. At first I spoke of two, then of three; so that even in my addition I was modestly below the mark, and had really some grounds for recommending our friends the classifiers to beware what they asserted in this case.

Talking of puzzling classifications, this is just the place for mentioning the batrachians, who have been made into a class by themselves, but who most distinctly belong to two classes at the same time; not like the crocodile by details borrowed from each, but by a fundamental change which takes place at a certain period in their organization. The batrachians are in reality reptiles, but they are reptiles which begin by being fishes, and real fishes too.

If you have ever strolled about in the country, you must have often come across those great pools of water which collect at rainy seasons in the ruts of deep lanes. Amuse yourself by looking into them in early summer, and unless the land is too parched and dry, the chances are that you will see quantities of little black fishes, almost entirely composed of a long tail joined to a large head, playing jovially in the muddy waters, and looking as if they had dropped there from the skies. These are young frogs—tadpoles, as we call them—and they are beginning their apprenticeship of life. Enclosed in each side of those great heads, they have gills, and they breathe in the same manner as fishes. Presently the two hind feet begin to bud out and grow, little by little; then the fore feet; finally, the tail wastes away till it disappears; and thus insensibly the tadpole is transformed into a frog. Observe here that the tadpole's gills share the same fate as his fish-tail; they wither and disappear by slow degrees, and gradually as they do so, his lungs are developed. The animal changes his class very quietly, and without ceasing to be genuinely the same, although it would be impossible at last to recognize the old individual in the new if you had not heard its history beforehand. This is one of the most striking exemplifications I know of the mysterious process by which nature has insensibly raised animals from one class to another, always improving upon her original plan without ever abandoning it.

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