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 bombsh.e.l.l 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, const.i.tute, 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 princ.i.p.al 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, s.n.a.t.c.hed 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 pa.s.s through many fine-drawing processes before it attains that post of honor which has been a.s.signed 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 gra.s.s which the ox has eaten, which nourishes us. The animal is only a medium which transmits intact to us the _alb.u.men_ 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 gra.s.s are very, very small, and that it would be a great fatigue to the stomach if it could only get at such tiny sc.r.a.ps at a time; as, alas! has sometimes happened to the famine-stricken poor, who have tried in vain to support life from the gra.s.s in the field. But these minute dishes are brought to us in the ma.s.s 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 quant.i.ty 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 quant.i.ty. 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, _alb.u.men_ 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 appet.i.te. 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 ma.s.ses 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 pa.s.s 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 pa.s.s 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 alb.u.men, but in such minute quant.i.ties 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 p.r.o.nounce 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-p.r.o.nouncing 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 _alb.u.men_. Out of our 127 ounces of globules, 125 are alb.u.men; and these, with the 70 ounces which we found before in the serum, make up the 195 ounces (of alb.u.men) 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 alb.u.men. Nearly two-thirds of all the alb.u.men in the blood is concentrated in them; and you know now the use of alb.u.men, 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 alb.u.men which has finished its education, and is ready to go into the world; while the alb.u.men 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 impa.s.sible 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 ca.n.a.ls. These ca.n.a.ls 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, alb.u.men, 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 pa.s.sages; and minute as are the globules, it would seem that they have but just room to pa.s.s, for in examining under the microscope a corner of the tongue of a live frog, the globules have been seen doubling themselves up to pa.s.s 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 quant.i.ty to be expelled in pa.s.sing through the capillaries, and the more will the lymphatic vessels swell. In such cases the temperament or const.i.tution 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. Alb.u.men...................70 870 Salts.................... 10

Fibrine................... 3 Clot. Globules Alb.u.men.. 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, alb.u.men 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 const.i.tute 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 a.s.sociation 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 mult.i.tudes, 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 s.p.a.ce, 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.

CLa.s.sIFICATION 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.'--_Pensees 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 G.o.d 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 n.o.ble 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 cla.s.ses of the animal creation.