for it cannot be seen any more than the air which fills an empty glass. But I can tell you where there is some, and you even probably know it by its effects, although you have never heard its name.
Do you remember, on your aunt’s wedding-day, that there was a sparkling wine called champagne, at the grand breakfast? You smile, so I conclude somebody gave you a little to taste; and if so, you will remember how sharp it felt to your tongue. Do you remember, too, how the cork flew out when they were opening the bottle, and how the noise of the “pop!” startled more little girls than one? It was _carbonic acid_ which sent the cork flying in that wild way; the carbonic acid which was imprisoned in the bottle, in desperately close quarters with the wine, and which accordingly flew out, like a regular goblin, the moment the iron wire which held down the cork was removed. What sparkled in the glass, making that pretty white froth which phizzed so gently, as if inviting you to drink, was the carbonic acid in the wine, making its escape in thousands of tiny bubbles. What felt so sharp to your tongue was the same carbonic acid, in its quality of acidity, for thence it has its name; the word _acid_ being borrowed from a Latin word signifying the sharp pungent taste, almost _fine-pointed_ as it were, peculiar to all substances which we call _acids_.
It is carbonic acid also which causes the froth in beer and in new wine when bottled. It is he who makes soda-water sparkle and sting the tongue, and ginger-beer the same, if you happen to like it; and so far you have no particular reason for thinking ill of him. But beware. It is with him as with a good many others who have sparkling spirits, who make conversation effervesce with gayety, and who are very seductive in society when you have nothing else to do but to laugh over your glass, but whose society is fatal to the soul which delivers itself up to them. This charming carbonic acid is a mortal poison to any one who allows it to get into his lungs.
You remember what a violent headache your servant suffered from the other day after ironing all those clothes you had in the wash? She owed that headache entirely to this work which she did for you. She had remained too long standing over the coals over which her flat-irons were being heated. You know already that when charcoal burns, it is from the carbon uniting with the oxygen of the air; from this union proceeds that mischievous child, carbonic acid gas, in torrents, and the poor girl was ill, because she had breathed more of this than was good for her health. Observe well, that the room-door was open to let in the fresh air, and that there was a chimney, to allow the carbonic acid to escape. It was on this account that she got off with only a headache. Unhappily, there have sometimes been miserable people who, weary of life, and knowing this, but not knowing or thinking about the God who overrules every sorrow for good, have shut themselves up in a room with a brazier of burning charcoal, after taking the fatal precaution of stopping up every opening by which air could possibly get in; and when at last, in such a case, uneasy friends have forced open the well-closed door, they have found nothing within but a corpse. Then, too, there are those frightful accidents of which we hear so often, of workmen groping their way down into long disused wells, who have died as they reached the bottom; or of sudden deaths in coal-pits. In general these have been owing to the poor victims encountering the long pent-up carbonic acid gas, whose poisonous breath blasted and destroyed them at once.
You may well ask why I am telling you such horrible stories, and what I am coming to with my carbonic acid? But you have more to do with it than you think, dear child. You, and I, and everybody we meet, nay, and the very animals themselves, since their machines are of the same sort as ours, are all little manufactories of carbonic acid. The thing is quite clear. Since there is a charcoal fire lit in every part of our body, there always arises from the union of the oxygen brought by the blood with the carbon it meets in our organs, that mischievous child we have been talking about; and our throat is the chimney by which he gets away. He would kill us outright were he to stop in the house.
This is how it comes about: In proportion as the blood loses its oxygen, it picks up in exchange the carbonic acid produced by combustion, so that it is quite loaded with it by the time it returns to the lungs. There it takes in a fresh supply of oxygen, and discharges at the same time its overplus of carbonic acid, which is driven out of the body by the contractions of the chest, pell-mell with the air which has just been made use of in breathing. You are aware that this air is not the same at its exit as at its entrance to the body, and that if you try and breathe it over again it will no longer be of the same use to you. That is because it has lost part of its oxygen and brings back to you the carbonic acid which it had just carried off. If you take it in a third time, it will be still worse for you; and in case you should continue to persist–the oxygen always diminishing, and the carbonic acid always increasing in quantity–the air which was at first the means of your life will at last become the cause of your death. Try, as an experiment, to shut yourself up in a small trunk, where no fresh air can get in; or even in a narrow closely-shut closet, and you will soon tell me strange news. There will be no occasion to light a charcoal fire for you in there. Enough is kept burning in your own little stove, and you will poison yourself.
You see now that the dreadful stories I was telling a short time ago have something to do with you, and that it is a good thing to be warned beforehand. And now tell me, when a hundred people–or I ought to say, a hundred manufactories of carbonic acid–are crowded together for a whole evening, sometimes for a whole night, in a space just big enough to allow them to go in and come out; tell me, I say, if that is a sort of thing which can be beneficial to the health of little girls whose blood flows so fast, and who require so much oxygen; and whether, on the contrary, it is not one’s duty to keep them away from such scenes?
There may be amusement there, I know; but the best pleasures are those for which one does not pay too dearly. I have seen the very wax lights faint and turn pale all at once, in the very midst of those murderous assemblies, as if to warn the imprudent guests that there was only just time to open the windows.
And this reminds me of a point I had nearly forgotten. Wax-candles arc like ourselves. In order to burn, they must have oxygen, and, like us, they are extinguished by carbonic acid. But like us also–and indeed to a greater extent, because they consume much more charcoal at once–they manufacture carbonic acid. Hence that very illumination which affords the company so much pleasure and pride is plainly an additional cause of danger. Each of those wax-lights which is spread around with such a prodigal hand, the only fear being that there may not be enough of them, is a hungry intruder employed in devouring with all his might the scanty amount of oxygen provided for the consumption of the guests.
From each of those cheerful flames–the suns, as it were, of the festive assembly–shoots out a strong jet of carbonic acid, contributing by so much to swell out the already formidable streams of poisoned gas, exhaled to the utmost extent by the dancers. And wait–there is still something else I was forgetting. You dance. And I told you last time at what cost you have to dance. You have to make the fire burn much quicker than usual, that is, to consume a great deal more oxygen at once, and so you double and treble the activity of the carbonic acid manufacture: and this just at the moment when it would be so convenient that it should go on as slowly as possible! After this, you need not be surprised that people should look fagged and exhausted next morning. What astonishes me is that they are not obliged to lie in bed altogether, after treating their poor lungs to such an entertainment. And even if you have spared your legs, you are not much better off, as you are sure to find out in time, especially if the thing is repeated too often.
When I told you just now that the dance of labor was worth as much as the dance of the ball-room, was I right or wrong? What do you say yourself?
I could repeat the same of theatres–places of entertainment specially adapted for impoverishing the blood, and ruining the health of the happy mortals who go there, evening after evening, to purchase at the door the right of filling their lungs with carbonic acid, not to speak of other poisons. You must see clearly that such places as those are not fit for little lungs as dainty as yours; and this may help you to submit with a good grace when you see people going there without you. Grown-up people escape moreover, because the human machine possesses a strange elasticity, which enables it to accommodate itself–one scarcely knows how–to the sometimes very critical positions in which its lords and masters place it without a thought. But to do this, it is well that it should be thoroughly formed and established; for you run a risk of injuring it for ever, if you misuse it too early in life. Tell this to your dear schoolboy brother, when he wants to smoke his cigar like a man. If his lungs could speak, they would call out to him that it was very hard upon them, at their age, to be so treated, and that he ought at any rate to wait till they had passed their examinations!
But I must not get into a dispute with so important an individual, by throwing stones into a garden which is not under my care. For you, my dear child, the moral of this day’s lesson–which to my mind is much more alarming than a hobgoblin tale, since it concerns the realities of every-day life–is clear; and it is this:
Seek your amusements as far as possible in the fresh air. In the summer, when the lamp is lit, bid your mamma a sweet good-night, and go to bed. In the winter do not wait till there is a great quantity of carbonic acid in the room where the grown-up people are sitting, before you retire to your own like a reasonable girl, anxious not to do mischief to that valuable and indefatigable servant, the poor blood! Not to mention that if she were to injure him too much, she would have to bear his grumbling for the rest of her life. We cannot change him as we change other servants.
LETTER XXVI.
ALIMENTS OF COMBUSTION.
We have spent a very long time, my dear child, over the little fire, which goes on burning secretly in every one of us, quietly devouring what little girls eat with such a good appetite, quite unsuspicious of what they are doing it for. However, if I mean to finish the history of our mouthful of bread, I must push on to its last chapter.
The _whole_ of what we eat is not burnt, as you may easily suppose; for, if it were, what would the blood have left to feed the body with, and to repair in due proportion the continual destruction or waste which goes on in our organs? Our food, or “_aliments_” as the general collection of different sorts of food is called, are divided into two very distinct sets: some, which are destined to be burnt, and which are called _aliments of combustion_; others, which are destined to nourish the body, and which are called _aliments of nutrition_. I have to tell you now about these last, and you will find their history by no means uninteresting.
Learned men having detected, beyond the possibility of a doubt, the existence of these two sorts of aliments, one is tempted to think they ought to have made it known to the cooks, and that ever since so important a discovery, the dishes on all well-regulated tables should have been arranged accordingly; aliments of combustion on one side, aliments of nutrition on the other. It cannot be enough merely to give your guests a treat; you ought to provide them with everything necessary for the proper fulfilment of the claims within; and if you give some nothing but combustibles, leaving the others no share of fuel, how will they be able to manage? Nobody thinks about this, however; not even cooks, to begin with, who, as far as fire is concerned, find they have had quite enough to do with it in their cooking; and as for the guests, when they have had their dinner they go away satisfied, as a matter of course, quite as well provided for as if the mistress of the house had made her calculations, pen in hand, while writing out the bill of fare, with a view to combustion and nutrition. Now, how is that?
It is because the two sorts of aliments are, for the most part, met with together in everything we eat, so that we swallow them at once in one mouthful; and have therefore no need to trouble ourselves further on the subject. There is our bit of bread, for instance. What is bread made of? Of flour. Bread, then, must contain all that was previously in the flour. Very good. Now I will teach you how to discover in flour the aliment of combustion on the one hand, and the aliment of nutrition on the other.
Take a handful of flour, and hold it under a small stream of water; knead it lightly between your fingers. The water will be quite white as it leaves it, carrying away with it a fine powder, which you could easily collect if you were to let the water run into a vase, where the powder would soon settle to the bottom. That powder is starch–the same starch as washerwomen use for starching linen, and which our grandfathers employed in powdering their wigs. You had some put on your own hair one day when you were dressed up as a court-lady of olden time. Now, starch is an excellent combustible. People have succeeded, by means which I will not offer to detail here, in ascertaining almost exactly what it is made of, and they have found in it three of our old acquaintances, oxygen, hydrogen, and carbon, combined together in such proportions that 100 ounces of starch contain as follows:
Ounces.
Carbon 45
Hydrogen 6
Oxygen 49
—
100
I give you the calculation in round numbers, so as not to burden your memory with fractions; and I will do the same with the other sums I shall have to go through to-day, this being, let me tell you, an arithmetical day. Besides, I could scarcely take upon myself to warrant the absolute correctness of those very precise fractions people sometimes go into. Even our learned friends squabble now and then as to which is right or wrong over the 100th part of a grain, more or less, in making out their balance, and you and I will not offer to decide between them. I always think we have accomplished wonders in getting even _near_ the mark, and with their permission we will stop there.
Starch, then, of whose weight carbon constitutes nearly one-half, is of course a first-rate combustible. Indeed, one may almost consider it the parent, as it were, of at least half our aliments of combustion, for if (in consequence of a certain operation, which nature has the power of performing for herself, in certain circumstances) it loses a portion of its carbon, so that there remain but 36 ounces of it in the 100 of starch, our starch is turned into something else; now can you guess what that something is? Neither more nor less than _sugar_! Witness the grand manufactories at Colmar, in France, where bags of starch are converted into casks of syrup by a process of nature alone; so that the inhabitants of the neighborhood sweeten their coffee at breakfast with what might have been made into rolls, had it been left alone. And this is not all. Give back this starch-sugar into the hands of Nature once more by putting it into certain other conditions, and a new process begins in it. About a third of its carbon will unite itself, of its own accord, with the two-thirds of its oxygen, so as to make carbonic acid, (you are acquainted with that gentleman now) which shall fly off and away, and there will remain–what do you think?–_Alcohol_, that other combustible we talked about, and which burns even better than sugar and starch, since in a hundred ounces it contains as follows:–
Ounces.
Carbon 53
Hydrogen 13
Oxygen 34
—
100
All this astonishes you. What would you say then if I were to tell you that your pocket-handkerchief is composed of entirely the same materials as starch, and in the same proportions too, and that if a chemist were to take a fancy, by way of a joke, to make you a tumbler of sugar and water, or a small glass of brandy out of it, he could do so if he chose. Wonders are found, you see, in other places besides fairy tales; and since I have begun this subject I will go on to the end. Know then that from the log on the fire, to the back of your chair, everything made of wood, is in pretty nearly the same predicament as your pocket-handkerchief; and if people are not in the habit of making casks of syrup and kegs of brandy out of the trees they cut down in the woods, it is only, I assure you, because such sugar and brandy would cost more to make than other sorts, and would not be so good in the end. Should some one ever invent and bring to perfection an economical process for doing it thoroughly well, sugar-makers and spirit-distillers will have to be on their guard!
But we are wandering from our subject. If I have allowed myself to make this digression, however, it is because I am not sorry to accustom your mind early to the idea of those wonderful transformations which nature accomplishes, and of which I could give you many other instances.
To return to our flour. As soon as all the starch is gone out of it, there remains in your hand a whitish, elastic substance, which is also sticky or _glutinous_, so that it makes a very good glue if you choose; and hence its name of _gluten_, which is the Latin word for glue.
When dried, this _gluten_ becomes brittle and semi-transparent. It keeps for an unlimited time in _alcohol_, putrefies very soon in water exposed to the air, and is easily dissolved in a wash of soda or potash. Finally 100 ounces of it contain as follows:–
Ounces.
Carbon 63
Hydrogen 7
Oxygen 13
Nitrogen 17
—
100
Observe the last material named. It is a new arrival, of which I shall soon have something to say.
But where am I leading you? you will ask, with all these uninteresting details about glue.
Wait a little and you shall hear.
You have probably never seen any one bled, which is a pity, as it happens; for if you had, you might have noticed (provided you had had the courage to look into the basin), that after a few seconds, the blood which had been taken away separated itself of its own accord into two portions; the one a yellowish transparent liquid, the other an opaque red mass floating on the top, and which is called the _coagulum_ of the blood or _clot_. This _coagulum_ owes its color to an infinity of minute red bodies of which we will speak more fully by and by, and which are retained as if in a net, in the meshes of a peculiar substance to which I am now going to call your attention.
That substance is whitish, elastic and sticky; and when dried becomes brittle and semi-transparent. It keeps for an unlimited time in alcohol, putrefies very soon in water exposed to the air, and is easily dissolved in a wash of soda or potash. Finally 100 ounces of it contain as follows:–
Ounces.
Carbon 63
Hydrogen 7
Oxygen 13
Nitrogen 17
—
100
This substance is called _fibrine_. It goes to form the fibres of those muscles which are contained in a half formed state in the blood.
You are laughing by this time I know, and I also know the reason why. I have told you the same story twice over. You have not forgotten my wearisome description of _gluten_, and here I am, saying exactly the same thing of _fibrine_! You conclude I am dreaming, and have made a mistake!
But no, I am wide awake, I assure you, and mean what I say. And if these details are the same in the two cases, it is for the simple reason that the two bodies are one and the same thing; _gluten_ and _fibrine_ being in reality but one substance, so that were the most skilful professor to see the two together dried, he would be puzzled to say which came from the flour, and which from the blood. I mentioned that our muscles existed in a half-formed state in the blood. Here is something further. The _fibres_ of muscles exist previously in full perfection, in the bread we eat; and when you make little round pills of the crumbs at your side, it is composed of fibres stolen from your muscles which enable the particles to stick together; and I say _stolen from your muscles_, because they are the _gluten_ which you ought to have eaten. I hope the thought of this may cure you of a foolish habit, which is sometimes far from agreeable to those who sit by you.
This, then, is the first great _aliment of nutrition_, and you may make yourself perfectly easy about the fate of those who eat bread. If little girls should now and then have to lunch on dry bread, I do not see that they are much to be pitied. There is the starch to keep up their fire, and the gluten for their nourishment, and that is all they require. The porter above is the only one who finds fault. And in these days porters have become more difficult to please than the masters themselves.
Then as to babies who drink nothing but milk, you perhaps wish to know where they get their share of fibrine.
And I am obliged to own there is none in the milk itself; but, I daresay, you know curdled milk or _rennet_? The same separation into two portions has taken place there which occurs in the blood when drawn from the arm; underneath is a yellowish transparent liquid,–that is the _whey_; above a white curd of which cheese is made, and which contains a great part of what would have made butter. By carefully clearing the curd from all its buttery particles you obtain a kind of white powder which is the essential principle of cheese, and to which the pretty name of _casein_ is given because _caseus_ is the Latin for cheese. I shall not trouble you now with details about _casein_; but there is one thing you ought to know. A hundred ounces of _casein_ contain as follows:–
Ounces.
Carbon 63
Hydrogen 7
Oxygen 13
Nitrogen 17
—
100
Exactly like gluten and fibrine!
Now, then, you can understand that no particular credit is due to the blood for manufacturing muscles out of the cheese of the milk which a little baby sucks. He has much less trouble than the manufacturers at Colmar have in turning their starch into sugar; because in his case the new substance is not only composed of the same materials as the old one, but contains them in exactly the same proportion also.
We have a second aliment of nutrition, you see, and I must warn you that it is not found in milk only. It exists in large quantities in peas, beans, lentils, and kidney-beans, which are actually full of cheese, however strange this may seem to you. It would not surprise you so much, however, if you had been in China and had tasted those delicious little cheeses which are sold in the streets of Canton. They cannot be distinguished from our own. Only the Chinese (from whom we shall learn a great many things when we have beaten them so that they will conclude to be friends with us)–the Chinese, I say, do without milk altogether. They stew down peas into a thin pulp. They curdle this pulp just as we do milk, and in the same way they squeeze the curd well, salt it, and put it into moulds–just as we do–and out comes a cheese at last–a real cheese, composed of real _casein_! Put it into the hands of a chemist, and ask him the component parts of a hundred grains of it, and he will tell you as follows:–
Ounces.
Carbon 63
Hydrogen 7, etc.
I stop there; for you surely know the list by this time!
Only the third aliment of nutrition remains to be considered, for there are but three; and I will tell you in confidence, what is stranger still, viz., that there is in reality but one! But we have had enough food for one day, and I do not wish to spoil your appetite. We will reserve the rest for another meal.
LETTER XXVII.
ALIMENTS OF NUTRITION (_continued_).
NITROGEN OR AZOTE.
There is a favorite conjuring trick, which always amuses people, though it deceives no one. The conjuror shows you an egg, holds it up to the light that you may see it is quite fresh, then breaks it; and–crack–out comes a poor little wet bird, who flies away as well as he can.
This trick is repeated in earnest by nature every day, under our very eyes, without our paying any attention to it. She brings a chicken out of the egg, which we place under the hen for twenty-two days, instead of eating it in the shell as we might have done, and we view it as a matter of course. Yet we do not say here that the bird may not have come down the conjuror’s sleeve, or the hen may not have brought it from under her wing. It was really in the egg, and its own beak tapped against the shell from within and cracked it.
How has this come about? No one can have put that beak, those feathers, those feet, the whole little body, in short, into the egg while the hen was sitting upon it, that is certain. It is equally certain, then, that the liquid inside the egg must have contained materials for all those things beforehand; and if Nature could manufacture the bones, muscles, eyes, etc., of the chicken, out of that liquid while in the egg, she would probably have found no more difficulty in manufacturing your bones, muscles, eyes, etc., from it had you swallowed the egg yourself.
Here, then, is an undeniable _aliment of nutrition_.
It is called _albumen_, which is the Latin word for _white of egg_. It is easily recognized by a very obvious characteristic. When exposed to a temperature varying from sixty to seventy-five degrees of heat, according to the quantity of water with which it is mixed, _albumen_ hardens, and changes from a colorless transparent liquid, into that opaque white substance, which everybody who has eaten “hard-boiled eggs” is perfectly well acquainted with.
I will only add one trifling detail. 100 ounces of albumen contain as follows:
Ounces.
Carbon 63
Hydrogen —
You can fill up this number yourself, can you not? And knowing the 7 of hydrogen, you may guess what follows! After what we have talked of last time, here is already an explanation of the chicken’s growth. But let us go on.
You recollect that yellowish liquid I spoke about, which lies underneath the _clot_, or _coagulum_ of the blood? I will tell you its name, that we may get on more easily afterward. It is called the _serum_, a Latin word, which, for once, people have not taken the trouble of translating, and which also means _whey_. Put this _serum_ on the fire, and in scarcely longer time than it takes to boil an egg hard, it will be full of an opaque white substance, which is the very _albumen_ we are speaking of. Our blood, then, contains _white of egg_; it contains in fact–if you care to know it–sixty-five times more white of egg than fibrine, for in 1,000 ounces of blood, you will find 195 of _albumen_, and only three of _fibrine_; of _casein_, none.
Nevertheless we eat cheese from time to time. And we generally eat more meat than eggs, and meat is principally composed of fibrine! I should be a good deal puzzled to make you understand this, if we had not our grand list to refer to.
Ounces.
Carbon 63
Hydrogen 7, etc.
_Fibrine_, casein_, _albumen_, they are all the same thing in the main. It is one substance assuming different appearances, according to the occasion; like actors who play several parts in a piece, and go behind the scenes from time to time to change their dresses. The usual appearance of the aliment of nutrition in the blood is _albumen_; and in the stomach, which is the dressing-room of our actors, _fibrine_ and _casein_ disguise themselves ingeniously as _albumen_; trusting to _albumen_ to come forward afterwards as _fibrine_ or _casein_, when there is either a muscle to be formed, or milk to be produced.
Know, moreover, that _albumen_ very often comes to us ready dressed, and it is not only from eggs we get it. As we have already found the _fibrine_ of the muscle and the _casein_ of milk in vegetables, so we shall also find there, and that without looking far, the albumen of the egg. It exists in grass, in salad, and in all the soft parts of vegetables. The juice of root-vegetables in particular contains remarkable quantities of it. Boil, for instance, the juice of a turnip, after straining it quite clear, and you will see a white, opaque substance produced, exactly like that which you would observe under similar circumstances in the _serum_ of the blood; real _white of egg_, that is to say–to call it by the name you are most familiar with–with all its due proportions of carbon, hydrogen, oxygen, and nitrogen.
I wonder whether you feel as I do, dear child; for I own that I turn giddy almost when I look too long into these depths of the mysteries of nature. Here, for instance, is the substance which is found everywhere, and everywhere the same–in the grass as in the egg, in your blood as in turnip-juice! And with this one sole substance which it has pleased the great Creator to throw broadcast into everything you eat, He has fashioned all the thousand portions of your frame, diverse and delicate as they are; never once undoing it, so to speak, to re-arrange differently the elements of which it is composed. From time to time it receives some slight impulse which alters its appearance but not its nature, and that is all. As the chemist found it in the bit of salad, so he will find it again in the tip of your nose, if you will trust him with that for examination. We are proud of our personal appearance sometimes, and smile at ourselves in the looking-glass; we think the body a very precious thing; but yet when we look deeply into it we find it merely so much charcoal, water and air.
This reminds me that we have not yet made acquaintance with the new personage who was lately introduced upon the scene. _Nitrogen_ or _azote_, I mean. He plays too important a part to be allowed to remain in obscurity.
You have already learnt that oxygen united with hydrogen produces water. Combined with nitrogen it produces air; but in that case there is no union of the two. They are merely neighbors, occupying between them the whole space extending from the earth’s surface to forty or fifty miles above our heads; together everywhere, but everywhere as entire strangers to each other as two Englishmen who have never been introduced! I should be a good deal puzzled to say what nitrogen does in the air: he is there as an inert body, and leaves all the business to the oxygen. When we breathe, for instance, the nitrogen enters our lungs together with its inseparable companion, but it goes out as it went in, without leaving a trace of its passage. Nevertheless, as sometimes happens among men, the one who does nothing takes up the most room. Nitrogen alone occupies four-fifths of the atmosphere, where it is of no other use than to moderate the ardent activity of king oxygen, who would consume everything were he alone. I can compare it to nothing better than to the water you mix with wine, which would be too fiery for your inside if you drank it by itself. This is what nitrogen does. It puts the drag on the car of combustion; as in society, the large proportion of quiet people put the drag on the car of progress (let us for once indulge ourselves in talking like the newspapers!); and such people are of definite use, however irritating their interference may appear in some cases. The world would go on too rapidly if there were nothing but oxygen among men. We have quite enough in having a fifth of it!
But what in the world am I talking about? Let us get back to nitrogen as fast as we can!
We must not imagine there is no energy in this quiet moderator of oxygen. Like those calm people who become terrible when once roused, our nitrogen becomes extremely violent in his actions when he is excited by another substance, and is bent on forming alliances. Sometimes the usually cold neighbor unites itself to oxygen in the closest bonds; in which case the two together form that powerful liquid, _aqua-fortis_, of which you may have heard, and which corrodes copper, burns the skin, and devours indiscriminately almost everything it comes in contact with. Combined with hydrogen, nitrogen forms _ammonia_, which is still often called by its old name _volatile alkali_; one of the most powerful bodies in existence, and one for which you would very soon learn to entertain a proper respect, if somebody were to uncork a bottle of it under your nose. Finally, nitrogen and carbon combined, produce a quite foreign substance (_cyanogen_), resembling neither father nor mother in its actions and powers, to the confusion of all preconceived ideas, when Gay-Lussac, a Frenchman, introduced it to the world, where it fell like a bombshell upon the theory of chemical combinations. This impertinent fellow, combining with hydrogen in his turn, produces _prussic acid_, the most frightful of poisons; one drop of which placed on the tongue of a horse strikes it dead as if by lightning.
You perceive that you must not trust our worthy friend too far. You have learnt, however, elsewhere, that it is not equally formidable in all its combinations. Those very substances which, when paired off into small separate groups, destroy all before them, constitute, all four together, that precious aliment of nutrition of which we are formed. Moreover, its real name is “_azotized aliment_” because it is the presence of nitrogen or azote in it, which, above all, determines its quality, so that people are in the habit of estimating the nourishing power of our food by the amount of nitrogen it contains. In fact, nitrogen seems to be a substance especially inclined towards everything that has life. His three comrades wander in mighty streams, so to speak, through every part of creation; but he, except in the vast domain of the atmosphere, where he reigns in such majestic repose, is rarely met with, except in animals, or in such portions of plants as are destined for the support of animal life.
On this point I will tell you the history of his original name, _azote_, which you will find curious enough. A short time before the French Revolution, in 1789, the principal properties of this gas were made known to the world by a learned Frenchman, who may be almost considered the father of modern chemistry, and whose name I must beg you to recollect. [Footnote: Dr. Daniel Rutherford (Edinburgh) discovered the existence of _Nitrogen_, A. D. 1772; but he never investigated its character.] He was called _Lavoisier_. While endeavoring to account satisfactorily for _combustion_, which before his time people explained any way they could, Lavoisier succeeded in separating our two friends, the neighbors in the atmosphere, one from the other, and was the first man in the world who managed to secure in two bottles–on the one hand, the bubbling oxygen freed from his tiresome mentor; on the other, the sober *azote, snatched away from his giddy pupil. What he did with the bottle of oxygen matters but little to us; but in the bottle of _azote_ he plunged, by way of experiment, an unfortunate mouse, and subsequently a little bird, both of whom, finding no oxygen to breathe, died one after the other. Nothing could live in it, as you may suppose; and Lavoisier thought it must be right to give so destructive a gas the name of _azote_, which in Greek means “_opposed to life_.” Meantime, science went on progressing by the gleam of the lamp he had lit, and then followed the discoveries of his successors, who forced their way into the obscure laboratory where the elements of living bodies are prepared. And at last it was ascertained that this _azote_, opposed to life as it was thought to be, was actually an essential property of life; that it accompanied it everywhere, and that without it the whole framework of the animal machine would fall to pieces. It is still known by its old name, which custom had sanctioned; but I imagine no learned man can ever utter it now without a feeling of humility, and without the thought that the future has possibly many contradictions in store for him also. Besides, nitrogen has to pass through many fine-drawing processes before it attains that post of honor which has been assigned to it in the animal kingdom. The animal himself can do nothing with it, unless it has been previously absorbed and digested by the vegetable, and the vegetable in its turn could get no good from it, were it to remain isolated and indifferent in the bosom of the atmosphere. It is only when it has formed one of those combinations I have been telling you about, and more particularly the second, which produces _ammonia_, that it fairly enters upon the round of life. And then, in the mysterious depths of vegetable existence is organized that wonderful _quadrille_ of the _aliments of nutrition_, the history of which has now been sufficiently explained to you.
The vegetable kingdom, therefore, is simply the great kitchen in which the dinner of the animal kingdom is being constantly made ready; and when we eat beef, it is, in fact, the grass which the ox has eaten, which nourishes us. The animal is only a medium which transmits intact to us the _albumen_ extracted in his own stomach from the juices furnished to him in the fields. He is the waiter of the eating-house; the dishes which he brings us have been given him already cooked in the kitchen. But to appreciate properly the service he renders us we must remember that the dishes to be obtained from grass are very, very small, and that it would be a great fatigue to the stomach if it could only get at such tiny scraps at a time; as, alas! has sometimes happened to the famine-stricken poor, who have tried in vain to support life from the grass in the field. But these minute dishes are brought to us in the mass whenever we eat beef, and our stomachs benefit accordingly. Do not forget this, my child; and when mamma asks you to eat meat, obey her with a good grace; if, that is to say, you wish to grow up to be a woman.
LETTER XXVIII.
COMPOSITION OF THE BLOOD.
One word more before we finish. We must not leave off without bidding a last farewell to the good servant of whom we have spoken so much; the model steward so exact in giving back everything he receives–the factotum of the house in short. We have watched him at work long enough, but I have not yet described him personally to you, nor told you exactly what he is composed of.
And here I shall be obliged to begin again with figures and calculations, although I am told young people are not very fond of them. Nevertheless, none of us can manage our affairs properly without them. Hereafter, when you are at the head of a family, you will be obliged to practise arithmetic, if you want to know what is going on in your house. Never allow yourself to look upon what is necessary as wearisome; the true secret of being punctual in our duties is to throw our heart and interest into them.
I choose, therefore, to suppose that you will be interested to know that 1000 ounces of blood generally contain, (for there are shades of difference between one sort of blood and another) 870 ounces of the _serum_ I have been talking about, and 130 ounces of _clot_. At first sight one would take the quantity of _clot_ to be much greater than it really is; but in the state you see it, in the basin, it contains a considerable amount of water, which belongs by right to its companion _serum_, and which has to be drained away from it before it can be weighed.
Now, in our 870 ounces of serum, we shall find, to begin with, 790 of water; do not be astonished at the quantity. Most of the weight of all animals is produced by water; they weigh comparatively nothing after being thoroughly dried in a stove–when they are dead of course–for neither animal nor plant can live unless saturated with water. This, by the way, may serve to explain the ease with which we can keep ourselves floating in water; we are not much more than water ourselves! Were it not for those abominable bones which are a little bit heavier than the rest, we should never sink unless a stone were hung round our necks.
I repeat then; 790 ounces of water in 870 of _serum_, which leaves 80. Of this, _albumen_ furnishes seventy, and the ten others, with the exception of a small portion of fat which floats here and there ready-made, are _salts_. It would take too long to explain what _salts_ are here, but there is one sort of salt you know perfectly well; viz., that which is put on the dinner-table in a salt-cellar. And it is the most important of all. More than half the ten ounces of salts consist of it alone, which will make you understand better than before, what I explained with reference to the stomach; that is, why we put salt in our food. The porter above is quite up to his business when he asks everyone who enters to produce his little bit of salt. It is an attention which the blood appreciates very highly, although table-salt is of no great use to him in his building operations; but it evidently keeps him in good humor, and he would work badly without it. It is the same with all the animals man makes use of, and even the plants he cultivates, find that salt gives them an appetite. And it would almost seem as if nature had purposely dealt with us in this matter on a magnificent scale. She has made salt-magazines of the sea and the bosom of the earth, where it exists in prodigious masses which cost nothing but the labor of stooping to pick up, except in countries where a gentleman called a tax-gatherer, stands by to count the lumps and allow them to pass on by paying a duty. For my part, if I were the government–this is a secret between you and me, mind–I would look out for something else to stand in the place of the salt-tax. It is not well to interpose between man and the gratuities of Dame Nature, and to make him pay more heavily for the blood’s chosen friend than she meant him to be charged.
But to proceed, the kitchen-salt being deducted from the ten ounces of salts-in-general, there remain altogether from four to five ounces, which contain—-. But here I stop, for it puzzles me very much how to go on! Enough, that to enable you to follow me, you would require at least as much knowledge of chemistry as will be expected of a young man who has to pass an examination in medicine. Fancy the contents of a whole druggist’s shop! I will tell you a few names, that you may have a specimen of the style in use, but I forewarn you that they are not inviting: _hydrochlorate of ammonia; hydrochlorate of potash; carbonate of lime; sulphate of potash; phosphate of lime; phosphate of magnesia; lactate of soda._ I spare you the others, for many others there are, without counting those which have not yet been discovered I All these things are to be found, I must tell you, in fibrine and albumen, but in such minute quantities that it is scarcely possible to recognize them.
In the serum, for instance, the gentlemen are so very small, and so completely entangled one with the other, that it is startling to think of the skill and patience requisite for making them all out, to say nothing of affixing the right name–uncouth as it may seem–to each grain of this almost imperceptible dust! He who first called man an epitome of creation, scarcely knew how truly he was speaking, for man bears about in his veins, ascertained samples of at least half the primitive substances from which all others are made, and if the whole of them should some day be found to be there, I for one should not be surprised.
This is well worth knowing, is it not? and I have not come to the end of my story yet.
We have still the 130 ounces of _clot_ to speak about. But their contents are easily reckoned. Three ounces of fibrine and 127 of _globules_.
Here, however, we enter upon such a world of wonders, that I am quite delighted to be able to finish with it. It will be the masterpiece of our exhibition!
You feel quite sure blood is red, do you not? Well! it is no more red than the water of a stream would be, if you were to fill it with little red fishes. Suppose the fishes to be very very small, as small as a grain of sand; and closely crowded together through the whole depth of the stream: the water would look quite red, would it not? And this is the way in which blood looks red: only observe one thing; a grain of sand is a mountain in comparison with the little red fishes in the blood. If I were to tell you they measured about the 3,200th part of an inch in diameter, you would not be much the wiser, so I prefer saying (by way of giving you a more striking idea of their minuteness) that there would be about a million in such a drop of blood as would hang on the point of a needle. I say so on the authority of a scientific Frenchman–M. Bouillet. Not that he ever counted them, as you may suppose, any more than I have done; but this is as near an approach as can be made by calculation to the size of those fabulous blood-fishes, which are the 3,200th part of an inch in diameter.
These littlest fishes are called _globules_; but they are not exactly shaped like _little globes_, as the word would lead you to suppose. They are more like little plates slightly hollowed out on both sides. The central nucleus is surrounded by a flattened margin rather bladdery in appearance, of a beautiful red color, formed of a sort of very soft and very elastic jelly. I scarcely need tell you that all this was discovered through the microscope, and moreover, by examining the blood of frogs, in which the globules are much larger than in ours. [Footnote: Authentic portraits of these globules drawn–so to speak–by Nature herself, are to be seen on the admirable Photographs obtained by Bertsch, with the aid of the solar microscope, invented by himself and Arnaud. There you see them magnified 250,000 times, and may study them at your ease, and verify my description for yourself without any fear of being deceived. You must persuade your father to procure one. This result of photography is among the wonders of modern science.]
It was in 1661–rather more than two hundred years ago–that an Italian and a Dutchman discovered, each by himself in his own country, the microscopic population of the blood. The name of the Italian is not very difficult–_Malpighi_. As to the Dutchman’s, you must pronounce it in the best way you can–he was called _Leeuwenhock_. You smile, but he was nevertheless one of the first men who really comprehended what a wonderful auxiliary human science had just got hold of in the microscope, and he has helped to open the eyes of the world to the marvels of miniature creation. So content yourself, young lady, with mis-pronouncing his name, and beware of laughing at it! Names are something like faces, one may live to be ashamed of ridiculing the wrong one.
This discovery of the globules of the blood, was destined to throw great light upon the way in which the _nutrition of the organs_ was carried on. Modern chemists, who are always fond of investigation, have examined what they are made of, and can find little else in them but _albumen_. Out of our 127 ounces of globules, 125 are albumen; and these, with the 70 ounces which we found before in the serum, make up the 195 ounces (of albumen) which I told you were contained in the 1,000 ounces of blood. Forgive me all these ounces and figures. Exact accounts give exact information.
These globules, then, are composed almost entirely of albumen. Nearly two-thirds of all the albumen in the blood is concentrated in them; and you know now the use of albumen, viz., that it is the foundation of all the buildings of which the blood is the architect. Everything leads us to believe that the formation of globules in the blood is the last touch given by nature to that magical provision begun in thevegetable, continued in the stomach, and finished in the veins, to which, in combination with carbon, hydrogen, oxygen, and nitrogen, we are indebted for the subsistence of every portion of our body. Thus the blood-globules may be considered as albumen which has finished its education, and is ready to go into the world; while the albumen of the serum is, like our young friends, the generations in reserve, who are still at school awaiting their turn.
This is more than a mere supposition. Scientific men have taken to themselves, on their own authority, all sorts of rights over animals, and we profit basely enough by their crimes–I will not withdraw the word–in order to increase our knowledge. Accordingly, they conceived the idea of opening the veins of animals, and allowing the blood to flow until the victim was prostrate and motionless as a corpse. This done, they proceeded to fill the exhausted veins with blood, similar to that which had been withdrawn, and with the blood, life was seen gradually to return, till the animal rose from the ground, walked, and resumed its disturbed existence, as if nothing had happened. The interesting part of the experiment to us is, that if serum only, without globules, be restored to the unfortunate animal, it is of no use whatever, and the corpse does not revive.
It is evident, then, that all the power and virtue of the blood lies in the globules; and according as their number is great or small it is “rich” or “poor,” as it is called; and where their number is not up to the mark, the blood acts more feebly on the organs, life is calmer, and people are no longer troubled with emotions–in other words, with violent heats of the blood. Hence the impassible character of _lymphatic_ people, who often get on in the struggle of life better than others, because they are never in a hurry, and know how to wait for opportunities. You will occasionally hear the word _lymphatic_, for it has become the fashion, and it is time for me to explain it; but unluckily the explanation is not in its favor.
You remember those little scavengers we spoke about formerly, who came from the depths of all the organs, carrying away with them the worn-out building materials, and covering the surface of the body with an inextricable net work of tiny canals. These canals are called _lymphatic vessels_, in consequence of being filled with a liquid which is called _lymph_ (_water_, in Latin), but why I cannot tell you, for it is, in fact, simple _serum_. There was a very simple way of ascertaining this by making out an inventory of the contents of the _lymph_ liquid, and when this was done, they were found to consist of water, albumen, and the salts of serum; there was even a little fibrine; the only thing wanting was _globules_.
How the truant serum finds its way into the lymphatic vessels is probably as follows:–I have already mentioned the inconceivable delicacy of the capillary vessels, those last ramifications of our arteries and veins. It needs all the impulsive power of the heart to enable the blood to force its way through these narrow passages; and minute as are the globules, it would seem that they have but just room to pass, for in examining under the microscope a corner of the tongue of a live frog, the globules have been seen doubling themselves up to pass through the capillaries, resuming their natural form afterwards.
It was this, indeed, which made me tell you just now that their margins were elastic. During this momentary crush, part of the serum being forced on too fast, oozes through the wall of the over-filled capillaries, as water oozes through the leathern pipes of a fire-engine, and hence probably the appearance of serum or _lymph_ in the organs, where it is immediately sucked up (i. e., _absorbed_) by the lymphatic vessels. Now, you will easily understand that the larger the proportion of serum in the blood, the greater will be the quantity to be expelled in passing through the capillaries, and the more will the lymphatic vessels swell. In such cases the temperament or constitution is said to be _lymphatic_. If, on the contrary, the globules are in excess, the lymphatic vessels receive less serum, and diminish in size. The temperament is then called _sanguine_, as if there were no serum in the blood. You shall be judge yourself, knowing what you now do, whether it would not be more reasonable to call such temperaments _serous_ and _globulous_. At any rate those names would give people an idea of the real state of things, and teach them that there were such things as globules in the blood.
[Footnote: Here is a summary of the contents of 1000 oz. of blood:–
Ounces.
Water………………. 790
Serum. Albumen……………….70 870 Salts……………….. 10
Fibrine………………. 3
Clot. Globules Albumen.. 125 130 Coloring matter…… 2 127
—-
1000
—-]
To conclude, I must give you an account of the two ounces which still remain of the 127 of globules, albumen taking up only 125, as you know. Those two poor little ounces–the remainder of the thousand with which we started–would you believe it?–they alone have the honor of conferring upon the blood its beautiful red color. They constitute the coloring matter of the globules, and you will never guess its chief element. It is iron; ay, actually iron, young lady–the iron of swords and bayonets. We often accuse it of tingeing the earth with blood; and you may now know further, that it reddens blood itself by way of compensation. Do not trouble yourself as to where it comes from. Our fields are full of it, our very plants have stores of it. It sometimes happens that our digestive apparatus, put out of order by other occupations, fails to make use of the amount of iron offered to it; in which case the blood is discolored, and the face turns pallid as wax: this is an illness requiring great care. If it should ever befall you, you will not be surprised, after to-day’s lesson, to hear the doctor say that you must have some iron. But be easy–you will not have to swallow it whole! If you will take my advice, you will obey the doctor’s orders as soon as you can.
Not that looking pale signifies any thing: indeed, some young ladies think it an advantage. But it is no advantage to any body when the blood-globules are distressed for want of their proper supply of iron, and do their work grudgingly, like ill-fed laborers. Nothing can go on without them, you know, and they are people whom it is not well to leave too long out of sorts. Else languor comes on; languor which is the beginning of death: and pray remember that iron, which so often causes death, is equally useful for keeping it at bay. By sending it to the discolored globules, you give them back their energy and brilliancy together.
I have come here to the end of all that is known with any certainty about these wonderful globules which are to us the medium of life. Shall I go further, is the question, and take you with me into the fields of supposition, so full of noxious weeds? And yet why not? Science owes its present position to the praiseworthy rule of never adopting any theory which is not supported by well-established facts; and I would be the last to advise a change. Were I to tell you, what I am now going to say to you, at a meeting of the British Association of Science, they would turn me out of the room, and with very good reason. Nothing ought to be taught there but what can be proved. But this is of no consequence to you and me, and we have a right to amuse ourselves a little, after having worked so hard.
Well, there is an idea which nothing shall ever drive out of my head, however imperfectly it may be proved as yet; namely, that each of our globules is an animated being; and that our life is the mysterious result of these millions of lesser lives, each of them insignificant in itself; in the same way that the mighty existence of a nation, is a compound of crowds of existences, each, for the most part, without individual importance. Take our own or any other country as an instance; where millions of brains, many of them by no means first-rate in power, go to form a national character, the highest (as each _nation_ is apt to think of itself) in the world. According to this idea, you must be a sort of nation yourself, my dear child, which is gratifying to think of on the whole.
This is much more extraordinary than what I told you some time ago, of the individual life of the organs, each of which on this new system would be a province in itself! Do not exclaim too hastily. Whether the globules are animated or not, it is very certain, let me tell you, that your life depends entirely upon them; that it is weakened if they are weakened; that it revives with them; and that whether you attribute individual life to them or not, makes no alteration in the fact: their action upon you remains the same. And he must be a very clever man who can show me the exact difference between action and life. Hereafter, when we have descended the scale of the animal world together, and are arrived at the study of what are called microscopic animals, you will better understand the words which appear so strange to you now. What little our feeble instruments have revealed to us so far, of the history of those globules, places them almost on a level with those strange creatures, inexplicable to us, which are found in innumerable multitudes, in a variety of liquids. We trace in them the beginning of organization; their form and size are alike in all individuals of the same species; and species vary enough to induce one to believe, that there is a necessary relation between an animal’s way of life and that of its globules. If the microscope has not yet caught them in any overt living act, who can be surprised? it is only dead blood which has been submitted to the test. They ought to be observed in the exercise of their functions, in the living animal itself, as has been done to some extent in the frog; and if our foolish chat could influence scientific observers, I would say to them what M. Leverrier said years ago to the astonished astronomers: “Look yonder; you ought to see a light there with which you are not yet acquainted!”
I am carrying you a long way on the wings of my fancy, my dear child; but have no fears; I will not let you fall. This life of our globules, which would, after all, be only one mystery the more among many, opens before our eyes a magnificent vista of the uniformity in the scheme of creation; which goes on repeating itself, while enlarging its circles to infinity. We may, all of us, be only so many globules of the great invisible fabric of humanity, in which we go up and down one after another; and those vast globes which our telescopes follow through celestial space, may be but globules of one, as yet unknown, to which the Almighty alone can give a name.
Take this page to your father, my dear child, if you do not understand it rightly; and now, shake hands, my history is ended!
PART SECOND–ANIMALS.
LETTER XXIX.
CLASSIFICATION OF ANIMALS.
‘It is dangerous to show man how much he resembles the beasts, without at the same time pointing out to him his own greatness. It is also dangerous to show him his greatness, without pointing out his baseness. It is more dangerous still to leave him in ignorance of both. But it is greatly for his advantage to have both set before him.’–_Pensées de Pascal_.
The man who wrote that, my dear child, did not trouble himself much about children. He was one of the gravest specimens of literary genius–a man who can scarcely be said to have ever been a child himself; for as the story goes, he was found one day, when only twelve years old, inventing geometry, and his father only saved him from trouble, by putting the great book of Euclid into his hands; and, at sixteen, he wrote a treatise on _Conic Sections_, which was the wonder of all the learned men of the day. I have not a very clear idea of what Conic Sections are myself; but I tell you this to show that Pascal was a very profound and learned man, under whose authority, therefore, I am very glad to take shelter, now that I am going to set before you the very startling points of resemblance which exist between you and the beasts.
As to your greatness, it delights me to explain it to you. It is not due to the handsome clothes you wear when you are going out, nor to the luxurious furniture of mamma’s drawing-room, but to the possession of that young soul which is beginning to dawn within you, as the sun rises in the morning sky, and pierces through the early mists; in that growing intelligence which has enabled you to understand so far all the pretty stories I have told you; in that fresh unsullied conscience, which congratulates you when you have been good, and reproves you when you have done wrong: all of them gifts which are not bestowed on the lower animals, or certainly not to the same extent as upon you–gifts by which you rise more and more above them, the more they are developed in yourself. Your baseness–but, begging Pascal’s pardon, I cannot call it baseness–your connecting link with the brute creation lies in those other gifts of God which you and they share in common–in those wonders of your organization, which we shall now meet with in them again, in full perfection at first, and that in every respect; by which fact you may learn, if you never thought of it before, that the lower animals come from the same creating hand as yourself, and ought to be looked upon to some extent as younger brothers, however distasteful such a notion may seem at first. Societies have been established of late, both in France and England, for the protection of animals; and a noble and honorable task they have undertaken, in spite of the jokes that have been made at their expense. It is a mischievous cavil to tell people who are doing good in one direction, that more might have been done somewhere else. Everything hangs together in the progress of public morality, and you cannot strike a blow at cruelty to animals without at the same time making a hit at cruelty to man. And the best argument in favor of the rights of beasts to protection, will be found in the tour you and I are now going to make together through the different classes of the animal creation.
Let us begin with the horse–one of the beasts which oftenest needs our protection. Give him the mouthful of bread whose history we have just finished. He accepts it as a treat, and needs no pressing to eat it. And if it could tell you all its adventures afterwards, you would find that you were listening to precisely the same story as your own over again; that nothing was different, nothing wanting. First of all–teeth to grind it, and a tongue to swallow it with, as a matter of course. Next a _larynx_, which hides itself to avoid it, and an oesophagus,* which receives it, just as in your case; a stomach with its _gastric juices_, the same as yours, in bagpipe form, and its _pylorus_, like your own; a _lesser intestine_, into which bile pours from a liver like yours; _chyliferous vessels_ which suck up a milky chyle, as with you; farther on a _large intestine_; and so on to the end. Nor is this all:–the horse has also a heart, with its two _ventricles_, and its double play of valves; a heart which the little girl in our tale might confidently have exhibited to the engineers as her own, but that it would have been somewhat too big, of course; into which heart, as into ours, comes _venous_ blood, to be changed afterwards to _arterial_; in lungs to which the air keeps rushing, forced thither by the see-saw action of a _diaphragm_, as faithful a servant to him as to you. And those lungs like our own, are a charcoal market: the same exchange takes place there, of carbonic acid for oxygen, as in ours, an unanswerable proof that the stove inside the horse burns fuel in the same way as our own: and if you were to place the thermometer inside his mouth (for we are polite enough to call it his mouth), it would mark 37 1-2 degrees of heat (centigrade)–a difference from ourselves not worth mentioning. Finally, if you examine his blood, you will meet with the same _serum_ and _clot_, the whole company of _hydroclorates, phosphates, carbonates, &c._, from which we shrank before, and globules made like your own; having the same construction, and the same life, or action, if you like it better. I need scarcely add that 100 oz. of its _fibrine_ and _albumen_ contain:
Of carbon……… 63 oz.
Of hydrogen…….. 7
This is understood all along as being the case everywhere, from man down to the turnip; so that, like you, this noble animal, as the horse is called, is in point of fact only so much carbon, so much water, and so much air, joined to a handful of salt, which represents the earth’s share in the bodies of animals.
You must confess that, if we cannot quite call the horse a fellow-creature, he is nevertheless very like us. And it is the same with all those animals which man makes use of as his servants, and which have really a sort of right to the protection of society, since they form, to a certain extent, a portion of the human family. I do not speak here of the dog, who pays his taxes, poor fellow, in his quality of friend to man.
When I think of the almost identical organization of man and his next-door neighbors, I am astonished how it could possibly have come into the head of a certain learned individual (I will not mention his name), when drawing up a plan of natural history, to give to man a separate kingdom, as a sequel to the three kingdoms already established–the mineral, vegetable, and animal. One might have forgiven Pascal if such an idea had got into his head after writing his treatise on Conic Sections; there being nothing in them to throw light on such a subject. But in a naturalist, an observer who had spent his life in the study of living creatures, the thing seems almost incredible. Possibly he had reasons for what he did, but he certainly did not find them in the subjects of his studies.
Forgive me, my dear child, for forgetting you in this fit of indignation upon a point you cannot care much about. It leads me naturally enough to my present business, which is none of the easiest, but you must help me by paying attention. I am going to describe the _classification of the animal kingdom_.
There are a terrible number of animals, as you know; and if we wish to study them to any real purpose, we must begin by introducing some sort of order into the innumerable crowds which throng, pell-mell, around us for observation. We should otherwise never know where to begin, or when we had come to an end.
There are many ways of setting a crowd in order, but they all go upon the same plan. The individuals composing the crowd are parcelled off into companies, each company having a distinguishing mark peculiar to those who compose it. Thus the first division is into a few large companies, which are afterwards subdivided into smaller ones, and those into others still less, until the divisions have gone far enough. And this is what is called a _classification_.
Let us imagine, as an example, a large crowd in a public garden; I will soon classify it for you. I shall put the men on one side and the women on the other. Then–to begin with the women–I shall subdivide them into married and single. Then among married women I shall make a company of mammas, and another of those who have no children. Among the unmarried I shall have a group of those who have never been married–girls, that is–and another of widows–those who were once married, but are so no longer. Then, following the girls, I shall separate them into tall and short. And among the short ones I shall divide the brunettes from the blondes, and so I shall get at last to a little blonde girl, whose classification (were she a soldier) in military rank would be as follows:–_squadron_ of blondes; _company_ of shorts; _battalion_ of girls; _regiment_ of unmarried women; _division_ of women. The division of men could be carried out in the same manner; and thus we should classify our mob into complete military order. This is easy enough, however; but the classifying of animals is a very different affair, and I will tell you why. We ourselves require a classification to study them by, though none was needed for their creation. The Almighty has formed them all on one uniform plan, around which He has, if I may so express it, lavished an infinity of modifications separating species from species, yet without placing between the different species those fixed barriers which we should require now to enable us to classify them strictly. You who are learning the pianoforte have perhaps been told the meaning of a _theme_ of music–the first idea of the composer who follows it throughout the piece from one end to the other, embroidering on it, as on a bit of canvas, a thousand variations melting one into another. Such is pretty nearly, if we may venture the comparison, the way in which we can picture to ourselves the Almighty moving through the work of animal creation. Step in afterwards and divide away into regiments and battalions, if you please. Nature permits it, but she will never, to accommodate your classifications, separate what in her is really united.
There is still a way, however, and that is to do as I did just now in the case of the crowd. To take, viz., only one _character_ (as we call a distinguishing mark in natural history), and to throw together all the individuals which possess it, the blondes, the shorts, the girls, &c. In this way it may soon be done; but what is the result? You are in one class, your eldest sister is in another, your mamma in a third, and your brother in a different division altogether, a long way from you all. Such a classification is called _artificial_, and you can see at once that it is worthless.
The most natural plan is to put together those that are of the same family; and the classifications made on this principle are called _natural_ classifications.
It is a classification of this sort which has been adopted for the animal kingdom. People have taken all the animals which possess in common not one character only, but a collection of characters of the most important kind, _dominant characters_, as they are called; and of these animals they have formed, to begin with, large primary groups; subdividing these afterwards according to the secondary differences, which distinguish different species in the same group from each other.
In this manner all the different sorts of animals are included in different systematic divisions of one vast whole, through which it is easy to find one’s way, because there is a beginning and an end; and in which animals of the same family are always grouped side by side. Were I to mention all the divisions of this immense classification at once, you would find the account a little long, and not very amusing. We will go through them by degrees therefore, and, to simplify matters, will, throughout the whole, only consider those particular characters which are connected with our special study, the nourishment of life, that is to say: so that you will always find yourself on well-known ground.
I must tell you once for all, however, that it is with this as it is with grammar. Here and there are–and it cannot be avoided–certain exceptional cases which keep protesting timidly against the arbitrariness of rules; but no matter; we must be contented with what we can get, and be grateful into the bargain to those who have given us this skillful classification, at once so ingenious and useful, in spite of its inevitable imperfections. What is impossible is expected of nobody. You could not understand, even if I wished to explain it to you, the amount of science, labor and genius requisite for making out that long list, which, tiresome as it may seem to children, is absolutely beautiful in the eyes of learned men; too beautiful, perhaps, and I will tell you why when we have finished. Meantime, as the best reward we can give to those who have done us some great service is to teach their names to children, I will tell you, before bidding you good-bye, to whom we owe this classification, the details of which I do not enter upon to-day.
In the first place, we owe the method employed in its establishment, the method of _natural classification, i.e._, to a learned man of the last century–a learned Frenchman, Bernard de Jussieu–who tried it upon plants; another large flock by no means very easy to put in order, as you may convince yourself any day by studying botany. The man who applied this system to animals was also a learned Frenchman, the clearness of the French mind adapting them peculiarly for that sort of work. And he, too, is one of the glories of that nation. His labors and discoveries gave a perfectly new impulse to the study of nature. It was George Cuvier, whose statue you may see at Montbéliard, if you should ever go there. Not that Cuvier carried through this gigantic work alone, though the credit of it is justly his due, he having directed and inspired it. He was assisted by many. But among his assistants there was one, Laurillard, the most modest, yet the most active of all, whose name I will mention also, because, like the others, more or less celebrated, he has never had his reward. [Footnote: In the earlier editions of this work, there was, in this place, a severe reproach upon Cuvier for not having given proper credit to Laurillard. This reproach I have since learned was unjust. M. Valenciennes himself, one of the most illustrious of the collaborators of the great Cuvier, has written me a letter in which he defends the reputation of his friend with a warm indignation which does honor to both of them; and cites passages in which Cuvier has spoken of Laurillard, and among others, in the third volume of the _Ossements Fossiles_, p. 32, ed. of 1822.]
It only remains for me, therefore, to let the lash, which I was laying upon the shoulders of another, fall now upon my own, and to deplore the too great facility with which I had credited, without sufficient proofs, an assertion which I had otherwise good reason to believe to be exact–coming to me, as it did, from Montbéliard himself, on the testimony, it is said, of the family of Laurillard. From this avowal, a little painful, I confess, my young readers may learn the inconvenience of rashly condemning others! As I said in the concluding passage, which truth, only too late, now compels me to suppress–“The truth is sure to come out at last.”
LETTER XXX.
MAMMALIA. (_Mammals_.)
Do you remember of my talking of the _vertebral column_ when I was describing that great artery, the _aorta_, to which it forms a rampart of defence? I should not have named it without explanation, but that you had only to pass your hand down your back to find out what it was. Now the _vertebral column_, or backbone, is one of those _dominant characters_ which always carries along with it a train of other points of resemblance in the animals where it is found. It has been chosen, therefore, as the rallying-point of the first great group. I must tell you beforehand that there are four of these groups, four large companies, _i.e._, which naturalists have called by various names; as Groups, Sections, Primary Divisions and even Branches; in this case comparing them to four great branches of a tree, going off in different directions from the same trunk.
And, first of all, we have to begin with the group of the _Vertebrata_–vertebrata animals–vertebrata being a word which explains itself.
Of course we ourselves belong to this group. In fact, we are at the head of it; but it descends far below us. It goes on to the frog and the fish, and includes the monkey, the ox, the fowl and the lizard; for all these creatures possess the vertebral column. The frog does not appear to be very much like us at first sight; and yet, by virtue of its vertebra, it has its points of resemblance to us, which are worth the trouble of considering. Vertebrated animals are all furnished with a head, containing a brain, which gives its orders to the whole body; they have all an internal skeleton, that is to say, a system of bones linked together, forming a solid base by which all the organs are supported. I was going to add that they have all four limbs; but here the serpent glides in to call me to order, and to hiss at our childish craving for fine-drawn divisions, in perfect order, where there is an exactly proper place for everything. However, each has, without exception, a heart, with its network of blood-vessels; red blood, under its two conditions of arterial and venous; and also a digestive tube, acting, on the whole, pretty much like our own. I do not insist, mind, upon this last point, viz., that of the digestive tube; for we shall see, by-and-by, that it is a character beyond the pale of the primary groups. It is the fundamental character of the trunk itself, which necessarily exists, therefore, in all the groups; and, as I told you in my first letter, you will find it everywhere.
This is–to let you into the secret at once–the theme on which the Great Composer has based all His infinite varieties of animal life; and herein lies the uniformity of the animal creation, that startling uniformity which has given so much offence to many learned men, and which is so obvious that it will strike you of itself, I feel sure. But I reserve this subject to the end of my letters, when you will have heard all, and be able to judge for yourself.
It would be plunging back into confusion to attempt to examine all the vertebrated classes at once. After making a division you must go on. The groups have, therefore, been subdivided into _five classes_, which we will study in succession, only naming each now: viz. _mammals_, _birds_, _reptiles_, _fish_, and _batrachians_. Do not alarm yourself at this last name: it is a Greek word, meaning simply frogs.
The mammals are our immediate neighbors. Mammalia are the animals which produce milk. They bring forth their young alive, and give suck to them as soon as they are born. This was your first nourishment, my dear child, so you yourself are a little mammal.
What I said to you in the last letter about the horse, applies pretty nearly as well to all mammals. We shall not, therefore, have any great variations to notice here. Nevertheless, as these are the animals which interest us most nearly, as they are in fact our nearest of kin, so to speak, and those with whom we have the most to do, we will now pass in review the different orders of which their class is composed. I must explain to you that the _classes_ are subdivided into _orders_, the orders into _families_, the families into _genera_, the genera into _species_; as in armies divisions subdivide into regiments, regiments into battalions, &c. It became necessary, moreover, to make use of special names, in order to make these subdivisions comprehensible, and the following are those which have been adopted.
ORDER 1. _Bimana (two-handed)_.
Here we may pass on at once, for we have discussed this order enough already. We are _bimane_ ourselves, since we have the distinction of possessing two hands. Yes; that is the pretty title which the professors have been so polite as to give us, instead of leaving us simply our proper name of man. Yet it would have been very easy to do this, seeing that we are the only family, the only genus, and the only species of the order. In railway travelling, people of distinction have a reserved carriage to themselves: so we decidedly deserve an order to ourselves; but that is not quite the same as a separate kingdom. In short, you are a _bimane_; so make the best you can of it.
ORDER 2. _Quadrumana (four-handed)_.
These, as their name indicates, have four hands: two at the end of the arms, and two at the end of the legs; such are the monkeys. There is nothing to remark; they are all alike. Stay; I am wrong, though: there is something, insignificant it is true, but still pointing to deviation. In some the canine teeth are set forward, _i.e._ project, and are longer than the rest, and some species, as the ape, for instance, have just under their cheeks convenient little pockets, which open into the mouth, and in which they can deposit a reserve of nuts to be devoured at leisure; these are called _pouches_.
It is a trifle in itself, but we have here a first example of the eccentricities of nature in the construction of animals. At one time she adds a detail; at another she suppresses one. Sometimes she is pleased to enlarge an organ, as in the canine teeth of the monkey; sometimes she reduces it; or perhaps here she makes its construction more simple; there again more complicated: but still it is always the same organ. So the dressmaker shapes the sleeves of a dress, sometimes open, sometimes closed, flat or puffed, plain or ornamented, pagoda-shaped or gigot-formed: but still they are all of them sleeves.
ORDER 3. _Cheiroptera (wing-handed)_.
I am quite ashamed of offering you such a word as this, my dear child. It was a Greek fancy of the learned men, who would not condescend to use the vulgar name Bats. In the Greek, _cheir_ means hand, and _pteron_ wing. The Cheiroptera are animals with winged hands; in fact, the fingers which terminate the fore-limbs of the bat lengthen as they spread out to an extravagant extent; and are connected together by a membrane springing from the body, with which they beat the air as with a wing, and which enables them to fly with such ease that theyare often taken for birds.
But, so far from really being a bird, this curious little creature has the same internal organization as ours, and indeed comes so near us, though without looking as if it did, that a scientific man, and a very distinguished one too, placed the bat in the first family of the animal kingdom, with the monkey, and, you will hardly believe it, with man. It is found that the bat, like man and the monkey, suckles its young at the breast; and it was this very character which Linnæus, the leader of artificial classification, thought of selecting as the distinguishing mark of his first family in the animal kingdom. It is true that in honor of the human race he had given that first family a much more sonorous name than our usual one of _man_–viz. _primates_, the first in rank–that is, the princes. But, alas! we were to be princes on an equality with bats; and, for my own part, I prefer being a _bimane_, and alone. I really believe that it was to put this saucy little creature back into its proper place that, at the time of the great revolution in favor of natural classification, the conclave of professors assembled at the Botanical Gardens in Paris inflicted this horrid name of Cheiroptera on the bat, ejecting it contemptuously from the overthrown dynasty of the _primates_.
I have not been sorry to make you acquainted as we went along, with this little trait in the history of classification; but beyond it there is really nothing particular to say about the apparatus for the nourishment of the deposed bat-princes, which is a plain proof how nearly it must be like our own. By-the-by, there is one trifling remark to be made with regard to her teeth. The bats we have in our country (France), for there are many varieties of species in the world, live on insects, which they catch in their flight by night. These insects are often enveloped in a very hard outer case, which molars like ours would have some difficulty in chewing properly; consequently the molars of our little friend are fringed with conical points, and with these she grinds down her prey without difficulty.
In America there is a large bat, the vampire, which lives on the blood of animals, and nature has armed it accordingly. It has at the extremityof its muzzle two sharp beak-like incisors, like the lancets of a surgeon. The vampire bat, which roams by night like other bats, goes straight at the large animals it sees asleep, delicately opens a vein in the throat without waking them, and sucks their blood in long draughts, taking care, by fanning them with its wings, to lull them into a cool and balmy slumber. It does not, as you see, make a savage attack on its victim: it merely inflicts a bite like that of the leech, but the result may be death. This is the best emblem I know of the sycophant, who undermines your soul while he fans your vanity; and observe, while we are on the subject, that this species has always had the art of insinuating itself among princes.
ORDER 4. _Carnivora (flesh-eaters)_.
When translated into English, this word needs no explanation. And here we have the tribe of bears, wolves, foxes, weasels, dogs, cats, tigers, lions, of all the fighting animals, _i.e._, those which steep their muzzles in blood, and live by devouring others. These have a similar apparatus for nutrition to our own; especially the bear, who, with the monkey, is the animal most nearly resembling man, seeing that he has feet like ours, with scarcely any tail, while the monkey has our hands, without specifying any other points of resemblance. Like ourselves, too, the bear is omnivorous; that is to say, it eats everything, vegetables and fruit as well as meat; and nature, which has given it our diet, has furnished it with molars almost exactly like our own. Its canine teeth alone differ from ours: they are more prominent even than those of the _quadrumana_; and this is the case with all the members of the order, in whom we find them sometimes developed into actual daggers. But those of them which are purely carnivorous have molars peculiar to themselves. The lion, for example, who does not share the bear’s taste for carrots, and who would die of hunger surrounded by the honey and grapes of which the bear is so fond–the lion, who never takes anything but raw meat between his teeth, has molars furnished with sharp cutting edges, intended to slice the meat like the chopping knives used by cooks for making a hash.
The lion offers another peculiarity, which is common to him with all the _Carnivora_. Place your finger close to the lower end of your ear, and work your jaw; you will feel something hard moving backward and forward against your finger. This is where the lower jaw is set into a bone of the skull, called the _temporal_, if you care to know its name; in other words, the bone of the temple. The extremity of the jaw bends, and forms a kind of little knob, called _condyle_, which fits into a cavity of the temporal bone. With us the cavity is not very deep, nor the knob very large, so that it can play very freely; and it is this which allows us that second movement from side to side, of which I spoke to you formerly, and thanks to which, our little mills reduce a mouthful of bread into paste. But this freedom of action has also its inconveniences. You must never attempt to force too large an article into your mouth at once–an apple, for instance–the efforts you would then be obliged to make might easily cause the _condyle_ to slip out of its little cavity, where its hold is but slight, and to get under the _temporal bone_; and there you would be with your mouth wide open until the doctor arrived. The lion, whose voracious jaw opens like the door of an oven, so that the tamers of wild beasts have no scruple in thrusting in their whole heads, a mouthful a good deal larger than an apple; the lion, who has no doctors, would often be liable to this accident–an irremediable one in his case–if nature had not made a special provision for him. In order to secure greater firmness and strength, the second movement is in his case sacrificed by embedding the _condyles_ deeply in their cavities, where they are fastened in such a fashion that they can only move up and down, like the handles of a pair of pincers. This is a restraint which enables the jaw to be safely thrown open as wide as the fiery impulse of its terrible proprietor impels it. Less freedom, in exchange for more power, is a bargain which any one would gladly accept who plays the part of a lion!
I have here a remark to make. We have now passed in review three orders besides our own, and have only had to point out a change in the fastenings of the jaws and in the teeth; and you will find that the same sort of modifications take place in the whole class of mammals. This is in fact the essentially movable and variable point in their apparatus for nutrition. The jaw and its weapons vary their character from one species to another, according to the nature of their food; but the modifications generally terminate there, _i.e._ on the threshold, as it were. The interior arrangements of the house remain otherwise much the same in all.
Here, however, in the lion, there is an interior change to be described; but not in the arrangement of the parts, only in their size; the stomach in this species being even smaller and weaker in proportion than ours, and the digestive tube more than twice as short. The digestive tube of an ordinary sized man is about seven times the length of his body, whilst that of the lion only measures three times the length of the animal. This is a natural consequence of the kind of nourishment he takes. Flesh and blood, on which he lives entirely, is concentrated _albumen_, prepared beforehand in the bodies of his victims; so that no great preparation is needed here to convert it into lion’s blood. A professor of chemistry, who has a good assistant, does not need a very large laboratory. This is the case with the lion; and nature, which makes nothing in vain, has here economised space. Tame the monarch of the forest into a domestic animal, and change his food, and I will wager anything you please that, in the course of a few generations, his digestive tube will lengthen itself. Examine the inside of the cat, his little cousin, formed originally on the same pattern as himself, and, without having ascertained the fact myself, I am sure that, by dint of feeding it daily on sops and milk from generation to generation, its digestive tube has become more than three times the length of its body.
Here you ought to be told at once a very important fact relative to the organization of the lower animals, one which places them all very far below the order of _Bimana_, since there is such an order. In bestowing intelligence and freedom of action on man, the Almighty has given him the unspeakable privilege of working in His footsteps–if I may presume to use the expression–of following up His work of creation as it came from His hand. Now especially that man begins to see a little more clearly into the laws of life, he has entered more directly into the possession of this almost divine privilege, which the Almighty has graciously vouchsafed him. You can even now have an ox or a sheep made to order in England, giving your dimensions, as if you were ordering a cabinet; and in a few years, if you have not asked actual impossibilities, your commission will be executed to within an inch. This is not said in reference to the _Carnivora_. But in bidding you good-bye, my dear little mammal, I could not bear to leave you under the weight of that debasing title: I wanted also to show you your greatness.
LETTER XXXI.
MAMMALIA. _(Mammals)–continued_.
Let us continue to pass in review the different orders of the class Mammalia. We may meet elsewhere with facts more important to science, but nowhere with any so personally interesting to ourselves.
ORDER 5. _Insectivora (insect-eaters)_.
This order devours insects, as their name tells you plainly enough. They feed in the same manner as the bats; consequently they have molars like theirs, as was necessary. It is an unimportant little family, and we will not waste much time upon it. The chief of the order is the hedgehog, a native of our country–not very large, about nine inches long–which lives in the woods, and which when rolled up into a ball, with all its quills standing out, looks very much like an enormous horse-chestnut in its shell. Its canines have not much work to do, consequently they are very small; but, on the other hand, its two front incisors are prolonged beyond the others, the better to seize its prey, which creeps upon the ground. Internally there is nothing to remark upon.
Next to the hedgehog I will mention as a curiosity the shrew or sand-mouse, which, in spite of its name, is no mouse at all, but has the honor, if honor it be, of being the smallest animal known of the class Mammalia.
It is about two inches in length altogether; and if you carefully examine its little body, you will find that it contains all the organs you possess yourself–oesophagus, stomach, liver, intestines, veins, arteries, heart, lungs–nothing is wanting: the machinery is absolutely the same.
ORDER 6. _Rodentia (rodents)_.
Were we to translate this word into its meaning, namely, the _Gnawers_, there would be some comfort in it, for we would at once know what it means: but no matter. Rodents, or Gnawers, are rats, hares, rabbits, beavers, marmosets, squirrels, in fact all the creatures which _nibble_. To _nibble_, if you do not exactly understand the word, means to chew with the points of the teeth. The rodents have no other way of eating but by filing, if one may so say, their food with the points of two incisors with which both the jaws are provided; these incisors are very long, much longer even than those of the hedgehog. The next time you see a rabbit at table, ask to see the head; and you will find that it has four pretty little teeth, very sharp, shaped like a joiner’s chisel; that is to say, with a “bevelled edge,” to use the received expression; in other words, with one edge thinner than the other.
Here, then, we begin to diverge from the old model. First, there is a different fastening, or _articulation_, as it is called, of the jaw. Its _condyles_, which we saw just now in the _Carnivora_ enlarged transversely and deeply embedded in the _fossae_ or cavity of the temporal bone, extend here longitudinally; an arrangement which enables the jaw to move backward and forward at pleasure, like the arm of the locksmith when using the file. Furthermore, those little teeth, which are constantly rubbing against each other, would be very soon worn out, if, like our own, they were made once for all; accordingly their germ, or _pulp_, to use the proper term, instead of perishing, as with us, when the tooth has once come, retains its life, and works on throughout the life of the animal. They sometimes say of a man who has not eaten for a long while, that his teeth have grown long. This is a joke with us; but in the case of a _rodent_ would be too serious a matter to be a joke; for, as their incisors are always growing, like our nails, they would soon become too long if the animal ceased for any length of time to wear them down by eating. It is for this reason that rats and mice have such incessant appetites, and that with them “all is fish that comes to the net;” old books, rags, and even planks of wood, which they will gnaw for want of something better. Come what may, they must keep up at an equal rate the wear and tear of the incisors, and the internal growth of the pulp beneath, which is always pushing the tooth forward. This dull continuous work might otherwise have a terrible result, which you would never suspect. It is very disastrous for a young lady to lose a front tooth, as it is called, for it sadly spoils a pretty face; but for a _rodent_ such a loss is much worse; in fact, it is a death- warrant. The corresponding tooth, having no longer anything to rub against, ceases to wear out; and as it does not stop growing on this account, it lengthens indefinitely, until at last it pushes out beyond the mouth, and places itself like a bar between the two Remaining teeth and the food of the animal, who, poor beast, being unable to eat, ceases to live.
The canines, whose duty it is to pierce the food, have, of course, no use in a jaw that grinds, nor are they to be found there. Between the incisors and the molars there is a large vacant space, which you will easily detect if you examine a rabbit’s head.
Finally, animals which can fall back in time of need on a plank for their dinner, require a very different-sized cooking apparatus to that of the _Carnivora_. Thus the rat, the most perfect sample of the rodent order, possesses a digestive tube of a prodigious length, through which the scrapings of wood have plenty of time for travelling, while the minute nutritive particles they contain are being thoroughly disengaged; and as every part of the animal organization tends towards keeping our insatiable rodents in the constant state of voracity required by its inexorable pulps, nature has given it an enormous heart whose size exceeds even that of its stomach.
Perhaps you do not catch at once the connection which exists between the size of the heart and of the appetite; yet it is very simple. Large barrels are requisite for those who brew a great deal of beer, and large hearts for those who make a great deal of blood. Now, it is the blood, as you know, which carries heat; in other words, life, throughout the body; when it pours in in torrents, the fire goes twice as fast, and, consequently, the feeding must be kept up. A medical friend of mine told me that he once had some rats sent to him–a boxful in fact–for one of those scientific experiments which one would venture to condemn more earnestly if their results were not sometimes beneficial. Next morning there were only two or three animals to be found, and these had eaten up the others. See the consequence of having too much heart!
ORDER 7. _Pachydermata (thick-skinned)_.
In Greek _pachus_ means thick, and _derma_ skin. _Pachyderms_, therefore, are thick-skinned animals. It is rather a vague denomination, as you perceive, and does not tell us much about them; but it appears that it was not very easy to find a better term. For my own part I should be very much puzzled to find a name really suitable for such an irregular company as this, in which all the huge beasts of the earth–the elephant, the rhinoceros, the hippopotamus–are heaped one upon the other, side by side with the horse, the ass, and the hog; begging your pardon for an ugly word.
All these creatures live on vegetables, with the exception of the hog, to whom nothing comes amiss; or who, in other words, is _omnivorous_, like the bear, and also another member of the class _Mammalia_, which I do not name for fear of making you blush at your companionship. This assures you that, in the order of the _Pachydermata_, the digestive apparatus is very fully developed. The horse, for instance, has a very voluminous stomach, which extends much farther back than the point at which the oesophagus empties itself; and in which, on close examination, a sort of contraction is observed which appears to divide it in half, producing the false effect of there being two stomachs. But, after all, we do not find, even in this case, any essential difference to remark upon in the internal arrangements; it is always the teeth we must look at if we want to have something to say. There, indeed, we have only to choose; nature has indulged herself in all manner of fantastic freaks.
To begin with the elephant, the grand master of the order, he presents us with one of the most oddly-furnished jaws in existence. Every one knows those two enormous tusks which protrude from his mouth, and which furnish human industry with nearly the whole store of ivory it has need of. Those two teeth are the largest, beyond comparison, of any in the animal kingdom; yet they are two merely ornamental teeth, perfectly useless in the operation of eating, and very ruinous into the bargain to the proprietor. All those stores of the blood which furnish the materials for ivory pass into these tusks, and, as often happens to people who give way to a taste for luxuries, there is nothing left wherewith to provide the animal with serviceable teeth. Those tusks of the elephant are nothing but his upper incisors, the only ones, observe, which curve in coming out of his jaw. In the lower jaw he has no incisors at all; canine teeth are entirely wanting; and by way of dental apparatus, this meagerly-furnished mouth possesses on each side of either jaw one or two molars, enormous in size, but not of ivory. They are composed of a number of enamelled upright layers of tooth-substance (_dentine_), soldered together with a bony cement; and these are our giant’s only resource for chewing the grass, young shoots, and leaves of trees, which are his natural food. [Footnote: These teeth are nevertheless very efficient grindstones.] As a consolation, he has the glory of knowing that he possesses the very finest teeth in the world, the terror of all who approach him; and I can compare him to nothing so well as to a vain woman, who is contented to live on potatoes that she may wear fine clothes and excite the envy of her neighbors.
The hippopotamus also has incisors in the upper jaw, which curve as they come out of the mouth; but these never attain anything like the size of the elephant’s tusks, neither do they hinder the development of the other teeth, of which this animal has a very respectable collection. The upper incisors bend downward; those in the lower jaw stand out horizontally, and terminate in sharp points like plough-shares; and indeed the hippopotamus uses them for tearing up the ground in order to get at the roots which form its nutriment. These are, besides, formidable weapons, with which when enraged the animal can tear even boats in pieces; for, as you are aware, the hippopotamus is almost amphibious, and browses on water-plants, and lives in the great rivers of Africa, its native country. Its name alone would have told you this had you understood Greek; [Footnote: _Ippos_, a horse, and _potamos_, a river. The Greeks, who had seen the hippopotamus in the Nile, in Egypt, named it the river-horse; as afterwards the Romans called the elephant the ox of Lucania, because they first saw it in Lucania during the war with Pyrrhus.] but I have no complaint to make this time, for it was the Greeks themselves who gave it. You would find it very awkward, would you not? if you had to breakfast at the bottom of the Thames, and could not swallow a morsel without having your nose filled with water? But the hippopotamus labors under no such inconvenience. Its nostrils are provided with two little doors, which it closes at will, and behind this screen the lungs keep quite quiet while the animal goes backwards and forwards in the water. There is generally a hippopotamus in every large menagerie. The next time you visit one look at him. You will see him with a large stomach almost trailing on the ground: and no wonder; he needs plenty of room in which to stow away all the canes, reeds, and water-plants from the bottoms of rivers, which are not very nutritious food. Accordingly the stomach of the river-horse presents the appearance not only of two compartments, like that of the true horse, but looks as if it were divided into three or four.
To conclude my account of this animal, I must add that the ivory of its teeth is even more beautiful than that of the elephant’s tusks, and that dentists carve it into very magnificent teeth for their patients. This is not a matter to interest you much at present, but we never know what may happen. I advise you, however, never to make use of hippopotamus’s teeth; they turn yellow very quickly, and, when people are driven to buy teeth, the least they can try for, is to get good-looking ones for their money.
I should like to say something about the rhinoceros while we are on the colossal tribes, but it is a very unsatisfactory subject. The animal has no canines, sometimes no incisors even; sometimes it has as many as thirty-six teeth, according to the species, as naturalists aver; and this is all I have to say about this great lump of flesh, so misshapen outside, yet so regularly formed within. He it is who especially deserves the title _pachydermata_, his skin being so hard and thick that bullets glance off its surface. But this has nothing to do with our present subject, any more than the horn upon his nose, whose turn for description may come if I ever give you the history of the skin and all connected with it.
The hog also has canines, and very strong ones; but it is in the wild state, when it is called a boar, that these appear in their real form. There we find them projecting out of the mouth with a curve, as is so commonly seen among the _pachydermata_, forming those terrible, sharp, and pointed tusks which have been so often fatal to the hunter. The wild boar of the forest is supposed to be the original ancestor of the domestic pig; and if, as is probable, this is really the case, we have here a remarkable instance of the effect of man’s treatment upon the organisation of the animals he collects around him. The wild boar lives only on fruits and roots, which, like the hippopotamus, he tears up with his tusks, those safeguards of his, amid the many perils of his life in the woods. In the service of man, on the contrary, he becomes lazy, cowardly, and greedy; unlearns his energy and combativeness, eats all that is offered to him in the trough, even meat, when it happens to be thrown in; and, in order to do this moreeasily, has recalled toward his mouth those formidable war-tusks of his, so tremendous as weapons, so useless as teeth; has, in fact, turned his sword into a fork. It is the case of a Tartar degenerated into a Chinaman. [Footnote: China, about which we have heard a great deal of late years, has been several times invaded by the warrior hordes of Tartary. But at each time, unto the second and third generations, the vanquishers have taken the effeminate manners, the costume and the usages of the vanquished, and so many conquests have only resulted in converting millions of Tartars into Chinese.]
This suggests to me an idea relative to the horse, the last important member of the _pachydermata_ which remains to be spoken of. It also has its canines, but very small ones; they disappear, so to speak, in a large vacancy between the incisors and the molars, where man inserts the bit, by means of which the animal has been subdued. Small as these are, however, these canines indicate that the horse might eat flesh, canine teeth being the distinctive attribute of the carnivorous mammals. I have read somewhere, but I do not remember where, that an unusual development of strength could be produced in the horse by feeding it on flesh; and the old Greek poets write of a king [Footnote: Diomed, King of Thrace] in the barbarous ages who gave his horses, men for food. If I knew some rich professor who was inclined to spend money in the investigation of a curious fact, I would advise him to set apart a sum for putting horses on a meat diet, from sire to son, gradually increasing the quantity; and I would boldly warrant that in the course of successive generations the canines would become so large as to impede the entrance of the bit into the mouth, and, moreover, would make it rather a ticklish office for the groom to place it there. But let us set aside the teeth the horse might possibly have, in order to examine those it has already. There are six incisors in each jaw; these are long and rather projecting teeth, by examining which, the age of the horse can be detected from certain marks which appear in them from year to year. The molars are flat, square, furrowed with bars of enamel, marking out more or less distinct crescents; perfectly constructed, in short, for chewing hay and oats. Nevertheless, I should never be surprised to see the enamel crescents become sharp-cutting in our rich professor’s stable; so skillful is the unseen Architect who created animals, in altering the house when the tenant changes his habits.
ORDER 8. _Ruminantia (ruminants)._
I shall retain through life a pleasant recollection of the _ruminants_. Through them I obtained the first prize for natural history which was ever given in France to the pupils of the learned university. It is thirty years ago since this happened, and I own, without any false modesty, that even now the word _ruminant_ rings very agreeably in my ear. It reminds me of one of the proudest moments of my life, of the honor done to me by the illustrious Geoffroy St. Hilaire, when he called me, a little college urchin, up to him, that he might have a nearer view, as he said, of the baby-professor who had spoken so well on ruminants. Yes, it is more than thirty years ago, for alas! it was in 1831. There needed no less an event, as I have told you before, than the revolution of 1830 in France to induce the big-wigs of education to sacrifice two hours per week in one class to the study of natural history. Yes, my dear child, it is only that short time ago since natural history became one of the subjects of study in French colleges; and the gray-haired men of the present day finished their education, as it is called, without having learnt a single word of what I am now taking the trouble to teach you, a mere child. You see you have come into the world just at the right time, and will be able to instruct others in your turn. But before giving lessons to other people you must first finish learning your own. Forgive me this involuntary reference to a happy time when I was not much more rational than you are. And now, let us return to our ruminants–those dear, good beasts, the nourishing fathers of the human race.
LETTER XXXII.
MAMMALIA–_continued_.
ORDER 8. _Ruminants–continued_.
Every created thing has an appointed part to perform; but there are some mysterious parts of which we cannot understand the drift. That of the ruminants, however, is so clearly marked out, that we detect it at a glance.
To qualify myself for supplying your young mind with the food I am going to offer it to-day, I have been obliged, my dear child, to browse in a good many books of which you could have understood but little yourself; and I have been forced to ruminate a long time upon what I have read, and to digest it slowly in my head, which I may say, without vanity, is of larger capacity than yours; no great wonder at my age. Now, if I have succeeded in my undertaking, you will benefit by all the work which has been going on in my mind for the purpose of feeding yours without over-fatigue to it; and I shall almost have the right to say that its nourishment has been derived from me. My lamp could tell you what it has sometimes cost me to supply a single page which might instruct, without repelling you.
Now, this is precisely what the _ruminant_ does. The part he has to perform is to collect in the meadows a sort of food, which would disgust less well-organized stomachs than his own, to work it well up within him, and to give it back in a more palatable and less indigestible form. The little flesh-eaters (_carnivora_) come afterwards to the feast, and the feast is himself!
The whole history, then, of the ruminant is to be read in his stomach. His real office is to digest, and in fact he devotes the best hours of his days to the perfecting of that beneficent labor, on which the life of so many weak stomachs depends. Have you ever amused yourself by watching a large ox lying down in a meadow? Long after he has finished grazing, his jaw continues to work, turning round and round like the grindstone of a painter when he is rubbing down his colors. Look, and you will see that he will remain there for hours together, motionless and contemplative, absorbed in this incomprehensible mastication, rolling about in his throat from time to time some invisible food. Do not laugh at him, however. As you sec him there he is performing his part in life, he is _ruminating_.
To ruminate is to chew over again what has been already swallowed; and, however droll this may seem to you, it is the business which all ruminants are born to. You remember the monkey’s pouch, which serves him as a larder, whence he takes out his provisions as he wants to eat. The ruminant has an immense pouch of the same kind, into which, while he is grazing, he hastily conveys large masses of half-bitten grass. You probably think he is eating when he has his head down in the grass; but you are mistaken. This is only a preparatory work; he is hastily heaping up in his larder the food he intends to eat by-and-by; only his larder, instead of being, like the monkey’s, in his cheeks, where, indeed, there would not have been half room enough for those great bundles he tucks in, is in the middle of his body, close to the extremity of the oesophagus, whose lower wall, being slit at that part, becomes an imperfectly secure tube, ready to burst open under pressure, and allow the food to escape between the edges of the slit; these, otherwise, remaining naturally closed. As soon as the large bundles of grass come to this part, they press against the walls of the tube, which they by this means separate, and fall into the provision-pouch, which bears the name of paunch, or grass-pocket, in fact. As soon as the paunch is well filled, and the animal sure of his dinner, he lies down in some quiet corner, where he proceeds gravely with the important act, which is the real object of his existence. A little below the entrance to the paunch, and communicating both with it and the canal of the oesophagus, is a second receptacle, which old French naturalists, not being much acquainted with Greek, named the _cap_, on account of its fancied resemblance to the caps worn on the head, and which we call ‘king’s hood’ or ‘honey-comb bag.’ This second stomach now contracts (at least so it is supposed), and thus retains, as if with a closed fist, a portion of the grass accumulated in the paunch: of this it forms a pellet, which it sends back into the oesophagus, and the oesophagus, by continued contractions from below upwards, returns it to the mouth, where at last the grassy lump is chewed in good earnest, and to some purpose. There is no necessity for hurry; the ruminant has no other business on the face of the earth but this, and thus hour after hour passes away, the food pellets rising one after another to the onslaught of the teeth. Nor do they go back again until they have been reduced by long mastication into an almost liquid paste, which glides through the oesophagus without forcing open the slit, and falls straight into a third pouch, called by old Frenchmen the _leaf_, on account of certain large folds, some what like the leaves of a book, which line the interior; and known to us as the _manyplies_. From this stomach, No. 3, this grass-pap passes into a fourth and last bag, which is the real stomach, and where the final work of digestion is accomplished. This fourth pouch also has a pretty little name of the