Chapter XII: The Naturalist's View of Life 254 (6)

Inheritance and adaptation, says Haeckel, are sufficient to account for all the variety of animal and vegetable forms on the earth. But is there not a previous question? Do we not want inheritance and adaptation accounted for? What mysteries they hold! Does the river-bed account for the river? How can a body adapt itself to its environment unless it possess an inherent, plastic, changing, and adaptive principle? A stone does not adapt itself to its surroundings; its change is external and not internal. There is mechanical adjustment between inert bodies, but there is no adaptation without the push of life. A response to new conditions by change of form implies something actively responsive--something that profits by the change.

VII

If we could tell what determines the division of labor in the hive of bees or a colony of ants, we could tell what determines the division of labor among the cells in the body. A hive of bees and a colony of ants is a unit--a single organism. The spirit of the body, that which regulates all its economies, which directs all its functions, which coördinates its powers, which brings about all its adaptations, which adjusts it to its environment, which sees to its repairs, heals its wounds, meets its demands, provides more force when more is needed, which makes one organ help do the work of another, which wages war on disease germs by specific ferments, which renders us immune to this or that disease; in fact, which carries on all the processes of our physical life without asking leave or seeking counsel of us,--all this is on another plane from the mechanical or chemical--super-mechanical.

The human spirit, the brute spirit, the vegetable spirit--all are mere names to fill a void. The spirit of the oak, the beech, the pine, the palm--how different! how different the plan or idea or interior economies of each, though the chemical and mechanical processes are the same, the same mineral and gaseous elements build them up, the same sun is their architect! But what physical principle can account for the difference between a pine and an oak, or, for that matter, between a man and his dog, or a bird and a fish, or a crow and a lark? What play and action or interaction and reaction of purely chemical and mechanical forces can throw any light on the course evolution has taken in the animal life of the globe--why the camel is the camel, and the horse the horse? or in the development of the nervous system, or the circulatory system, or the digestive system, or of the eye, or of the ear?

A living body is never in a state of chemical repose, but inorganic bodies usually are. Take away the organism and the environment remains essentially the same; take away the environment and the organism changes rapidly and perishes--it goes back to the inorganic. Now, what keeps up the constant interchange--this seesaw? The environment is permanent; the organism is transient. The spray of the falls is permanent; the bow comes and goes. Life struggles to appropriate the environment; a rock, for example, does not, in the same sense, struggle with its surroundings, it weathers passively, but a tree struggles with the winds, and to appropriate minerals and water from the soil, and the leaves struggle to store up the sun's energy. The body struggles to eliminate poisons or to neutralize them; it becomes immune to certain diseases, learns to resist them; the thing is _alive_. Organisms struggle with one another; inert bodies clash and pulverize one another, but do not devour one another.

Life is a struggle between two forces, a force within and a force without, but the force within does all the struggling. The air does not struggle to get into the lungs, nor the lime and iron to get into our blood. The body struggles to digest and assimilate the food; the chlorophyll in the leaf struggles to store up the solar energy. The environment is unaware of the organism; the light is indifferent to the sensitized plate of the photographer. Something in the seed we plant avails itself of the heat and the moisture. The relation is not that of a thermometer or hygrometer to the warmth and moisture of the air; it is a vital relation.

Life may be called an aquatic phenomenon, because there can be no life without water. It may be called a thermal phenomenon, because there can be no life below or above a certain degree of temperature. It may be called a chemical phenomenon, because there can be no life without chemical reactions. Yet none of these things define life. We may discuss biological facts in terms of chemistry without throwing any light on the nature of life itself. If we say the particular essence of life is chemical, do we mean any more than that life is inseparable from chemical reactions?

After we have mastered the chemistry of life, laid bare all its processes, named all its transformations and transmutations, analyzed the living cell, seen the inorganic pass into the organic, and beheld chemical reaction, the chief priestess of this hidden rite, we shall have to ask ourselves, Is chemistry the creator of life, or does life create or use chemistry? These "chemical reaction complexes" in living cells, as the biochemists call them, are they the cause of life, or only the effect of life? We shall decide according to our temperaments or our habits of thought.

IX

THE JOURNEYING ATOMS

I

Emerson confessed in his "Journal" that he could not read the physicists; their works did not appeal to him. He was probably repelled by their formulas and their mathematics. But add a touch of chemistry, and he was interested. Chemistry leads up to life. He said he did not think he would feel threatened or insulted if a chemist should take his protoplasm, or mix his hydrogen, oxygen, and carbon, and make an animalcule incontestably swimming and jumping before his eyes. It would be only evidence of a new degree of power over matter which man had attained to. It would all finally redound to the glory of matter itself, which, it appears, "is impregnated with thought and heaven, and is really of God, and not of the Devil, as we had too hastily believed." This conception of matter underlies the new materialism of such men as Huxley and Tyndall. But there is much in the new physics apart from its chemical aspects that ought to appeal to the Emersonian type of mind. Did not Emerson in his first poem, "The Sphinx," sing of

Journeying atoms,
Primordial wholes?

In those ever-moving and indivisible atoms he touches the very corner-stone of the modern scientific conception of matter. It is hardly an exaggeration to say that in this conception we are brought into contact with a kind of transcendental physics. A new world for the imagination is open--a world where the laws and necessities of ponderable bodies do not apply. The world of gross matter disappears, and in its place we see matter dematerialized, and escaping from the bondage of the world of tangible bodies; we see a world where friction is abolished, where perpetual motion is no longer impossible; where two bodies may occupy the same space at the same time; where collisions and disruptions take place without loss of energy; where subtraction often means more--as when the poison of a substance is rendered more virulent by the removal of one or more atoms of one of the elements; and where addition often means less--as when three parts of the gases of oxygen and hydrogen unite and form only two parts of watery vapor; where mass and form, centre and circumference, size and structure, exist without any of the qualities ordinarily associated with these things through our experience in a three-dimension world. We see, or contemplate, bodies which are indivisible; if we divide them, their nature changes; if we divide a molecule of water, we get atoms of hydrogen and oxygen gas; if we divide a molecule of salt, we get atoms of chlorine gas and atoms of the metal sodium, which means that we have reached a point where matter is no longer divisible in a mechanical sense, but only in a chemical sense; which again means that great and small, place and time, inside and outside, dimensions and spatial relations, have lost their ordinary meanings. Two bodies get inside of each other. To the physicist, heat and motion are one; light is only a mechanical vibration in the ether; sound is only a vibration in the air, which the ear interprets as sound. The world is as still as death till the living ear comes to receive the vibrations in the air; motion, or the energy which it implies, is the life of the universe.

Physics proves to us the impossibility of perpetual motion among visible, tangible bodies, at the same time that it reveals to us a world where perpetual motion is the rule--the world of molecules and atoms. In the world of gross matter, or of ponderable bodies, perpetual motion is impossible because here it takes energy, or its equivalent, to beget energy. Friction very soon turns the kinetic energy of motion into the potential energy of heat, which quickly disappears in that great sea of energy, the low uniform temperature of the earth. But when we reach the interior world of matter, the world of molecules, atoms, and electrons, we have reached a world where perpetual motion _is_ the rule; we have reached the fountain-head of energy, and the motion of one body is not at the expense of the motion of some other body, but is a part of the spontaneous struggling and jostling and vibration that go on forever in all the matter of the universe. What is called the Brunonian movement (first discovered by the botanist Robert Brown in 1827) is within reach of the eye armed with a high-power microscope. Look into any liquid that holds in suspension very small particles of solid matter, such as dust particles in the air, or the granules of ordinary water-color paints dissolved in water: not a single one of the particles is at rest; they are all mysteriously agitated; they jump hither and thither; it is a wild chaotic whirl and dance of minute particles. Brown at first thought they were alive, but they were only non-living particles dancing to the same tune which probably sets suns and systems whirling in the heavens. Ramsay says that tobacco smoke confined in the small flat chamber formed in the slide of a microscope, shows this movement, in appearance like the flight of minute butterflies. The Brunonian movement is now believed to be due to the bombardment of the particles by the molecules of the liquid or gas in which they are suspended. The smaller the particles, the livelier they are. These particles themselves are made up of a vast number of molecules, among which the same movement or agitation, much more intense, is supposed to be taking place; the atoms which compose the molecules are dancing and frisking about like gnats in the air, and the electrons inside the atoms are still more rapidly changing places.

We meet with the same staggering figures in the science of the infinitely little that we do in the science of the infinitely vast. Thus the physicist deals with a quantity of matter a million million times smaller than can be detected in the most delicate chemical balance. Molecules inconceivably small rush about in molecular space inconceivably small. Ramsay calculates how many collisions the molecules of gas make with other molecules every second, which is four and one half quintillions. This staggers the mind like the tremendous revelations of astronomy. Mathematics has no trouble to compute the figures, but our slow, clumsy minds feel helpless before them. In every drop of water we drink, and in every mouthful of air we breathe, there is a movement and collision of particles so rapid in every second of time that it can only be expressed by four with eighteen naughts. If the movement of these particles were attended by friction, or if the energy of their impact were translated into heat, what hot mouthfuls we should have! But the heat, as well as the particles, is infinitesimal, and is not perceptible.

II

The molecules and atoms and electrons into which science resolves matter are hypothetical bodies which no human eye has ever seen, or ever can see, but they build up the solid frame of the universe. The air and the rocks are not so far apart in their constituents as they might seem to our senses. The invisible and indivisible molecules of oxygen which we breathe, and which keep our life-currents going, form about half the crust of the earth. The soft breeze that fans and refreshes us, and the rocks that crush us, are at least half-brothers. And herein we get a glimpse of the magic of chemical combinations. That mysterious property in matter which we call chemical affinity, a property beside which human affinities and passions are tame and inconstant affairs, is the architect of the universe. Certain elements attract certain other elements with a fierce and unalterable attraction, and when they unite, the resultant compound is a body totally unlike either of the constituents. Both substances have disappeared, and a new one has taken their place. This is the magic of chemical change. A physical change, as of water into ice, or into steam, is a simple matter; it is merely a matter of more or less heat; but the change of oxygen and hydrogen into water, or of chlorine gas and the mineral sodium into common salt, is a chemical change. In nature, chlorine and sodium are not found in a free or separate state; they hunted each other up long ago, and united to produce the enormous quantities of rock salt that the earth holds. One can give his imagination free range in trying to picture what takes place when two or more elements unite chemically, but probably there is no physical image that can afford even a hint of it. A snake trying to swallow himself, or two fishes swallowing each other, or two bullets meeting in the air and each going through the centre of the other, or the fourth dimension, or almost any other impossible thing, from the point of view of tangible bodies, will serve as well as anything. The atoms seem to get inside of one another, to jump down one another's throats, and to suffer a complete transformation. Yet we know that they do not; oxygen is still oxygen, and carbon still carbon, amid all the strange partnerships entered into, and all the disguises assumed. We can easily evoke hydrogen and oxygen from water, but just how their molecules unite, how they interpenetrate and are lost in one another, it is impossible for us to conceive.

We cannot visualize a chemical combination because we have no experience upon which to found it. It is so fundamentally unlike a mechanical mixture that even our imagination can give us no clew to it. It is thinkable that the particles of two or more substances however fine, mechanically mixed, could be seen and recognized if sufficiently magnified; but in a chemical combination, say like iron sulphide, no amount of magnification could reveal the two elements of iron and sulphur. They no longer exist. A third substance unlike either has taken their place.

We extract aluminum from clay, but no conceivable power of vision could reveal to us that metal in the clay. It is there only potentially. In a chemical combination the different substances interpenetrate and are lost in one another: they are not mechanically separable nor individually distinguishable. The iron in the red corpuscles of the blood is not the metal we know, but one of its many chemical disguises. Indeed it seems as if what we call the ultimate particles of matter did not belong to the visible order and hence were incapable of magnification.

That mysterious force, chemical affinity, is the true and original magic. That two substances should cleave to each other and absorb each other and produce a third totally unlike either is one of the profound mysteries of science. Of the nature of the change that takes place, I say, we can form no image. Chemical force is selective; it is not promiscuous and indiscriminate like gravity, but specific and individual. Nearly all the elements have their preferences and they will choose no other. Oxygen comes the nearest to being a free lover among the elements, but its power of choice is limited.

Science conceives of all matter as grained or discrete, like a bag of shot, or a pile of sand. Matter does not occupy space continuously, not even in the hardest substances, such as the diamond; there is space, molecular space, between the particles. A rifle bullet whizzing past is no more a continuous body than is a flock of birds wheeling and swooping in the air. Air spaces separate the birds, and molecular spaces separate the molecules of the bullet. Of course it is unthinkable that indivisible particles of matter can occupy space and have dimensions. But science goes upon this hypothesis, and the hypothesis proves itself.

After we have reached the point of the utmost divisibility of matter in the atom, we are called upon to go still further and divide the indivisible. The electrons, of which the atom is composed, are one hundred thousand times smaller, and two thousand times lighter than the smallest particle hitherto recognized, namely, the hydrogen atom. A French physicist conceives of the electrons as rushing about in the interior of the atom like swarms of gnats whirling about in the dome of a cathedral. The smallest particle of dust that we can recognize in the air is millions of times larger than the atom, and millions of millions of times larger than the electron. Yet science avers that the manifestations of energy which we call light, radiant heat, magnetism, and electricity, all come from the activities of the electrons. Sir J. J. Thomson conceives of a free electron as dashing about from one atom to another at a speed so great as to change its location forty million times a second. In the electron we have matter dematerialized; the electron is not a material particle. Hence the step to the electric constitution of matter is an easy one. In the last analysis we have pure disembodied energy. "With many of the feelings of an air-man," says Soddy, "who has left behind for the first time the solid ground beneath him," we make this plunge into the demonstrable verities of the newest physics; matter in the old sense--gross matter--fades away. To the three states in which we have always known it, the solid, the liquid, and the gaseous, we must add a fourth, the ethereal--the state of matter which Sir Oliver Lodge thinks borders on, or is identical with, what we call the spiritual, and which affords the key to all the occult phenomena of life and mind.

As we have said, no human eye has ever seen, or will see, an atom; only the mind's eye, or the imagination, sees atoms and molecules, yet the atomic theory of matter rests upon the sure foundation of experimental science. Both the chemist and the physicist are as convinced of the existence of these atoms as they are of the objects we see and touch. The theory "is a necessity to explain the experimental facts of chemical composition." "Through metaphysics first," says Soddy, "then through alchemy and chemistry, through physical and astronomical spectroscopy, lastly through radio-activity, science has slowly groped its way to the atom." The physicists make definite statements about these hypothetical bodies all based upon definite chemical phenomena. Thus Clerk Maxwell assumes that they are spherical, that the spheres are hard and elastic like billiard-balls, that they collide and glance off from one another in the same way, that is, that they collide at their surfaces and not at their centres.

Only two of our senses make us acquainted with matter in a state which may be said to approach the atomic--smell and taste. Odors are material emanations, and represent a division of matter into inconceivably small particles. What are the perfumes we smell but emanations, flying atoms or electrons, radiating in all directions, and continuing for a shorter or longer time without any appreciable diminution in bulk or weight of the substances that give them off? How many millions or trillions of times does the rose divide its heart in the perfume it sheds so freely upon the air? The odor of the musk of certain animals lingers under certain conditions for years. The imagination is baffled in trying to conceive of the number and minuteness of the particles which the fox leaves of itself in the snow where its foot was imprinted--so palpable that the scent of a hound can seize upon them hours after the fox has passed! The all but infinite divisibility of matter is proved by every odor that the breeze brings us from field and wood, and by the delicate flavors that the tongue detects in the food we eat and drink. But these emanations and solutions that affect our senses probably do not represent a chemical division of matter; when we smell an apple or a flower, we probably get a real fragment of the apple, or of the flower, and not one or more of its chemical constituents represented by atoms or electrons. A chemical analysis of odors, if it were possible, would probably show the elements in the same state of combination as the substances from which the odors emanated.

The physicists herd these ultimate particles of matter about; they have a regular circus with them; they make them go through films and screens; they guide them through openings; they count them as their tiny flash is seen on a sensitized plate; they weigh them; they reckon their velocity. The alpha-rays from radio-active substances are swarms of tiny meteors flying at the incredible speed of twelve thousand miles a second, while the meteors of the midnight sky fly at the speed of only forty miles a second. Those alpha particles are helium atoms. They are much larger than beta particles, and have less penetrative power. Sir J. J. Thomson has devised a method by which he has been able to photograph the atoms. The photographic plate upon which their flight is recorded suggests a shower of shooting stars. Oxygen is found to be made up of atoms of several different forms.

III

The "free path" of molecules, both in liquids and in gases, is so minute as to be beyond the reach of the most powerful microscope. This free path in liquids is a zigzag course, owing to the perpetual collisions with other molecules. The molecular behavior of liquids differs from that of gases only in what is called surface tension. Liquids have a skin, a peculiar stress of the surface molecules; gases do not, but tend to dissipate and fill all space. A drop of water remains intact till vaporization sets in; then it too becomes more and more diffused.

When two substances combine chemically, more or less heat is evolved. When the combination is effected slowly, as in an animal's body, heat is slowly evolved. When the combustion is rapid, as in actual fire, heat is rapidly evolved. The same phenomenon may reach the eye as light, and the hand as heat, though different senses get two different impressions of the same thing. So a mechanical disturbance may reach the ear as sound, and be so interpreted, and reach the hand as motion in matter. In combustion, the oxygen combines rapidly with the carbon, giving out heat and light and carbon dioxide, but why it does so admits of no explanation. Herein again is where life differs from fire; we can describe combustion in terms of chemistry, but after we have described life in the same terms something--and this something is the main thing--remains untouched.

The facts of radio-activity alone demonstrate the truth of the atomic theory. The beta rays, or emanations from radium, penetrating one foot of solid iron are very convincing. And this may go on for hundreds of years without any appreciable diminution of size or weight of the radio-active substance. "A gram of such substance," says Sir Oliver Lodge, "might lose a few thousand of atoms a second, and yet we could not detect the loss if we continued to weigh it for a century." The volatile essences of organic bodies which we detect in odors and flavors, are not potent like the radium emanations. We can confine them and control them, but we cannot control the rays of radio-active matter any more than we can confine a spirit. We can separate the three different kinds of rays--the alpha, the beta, and the gamma--by magnetic devices, but we cannot cork them up and isolate them, as we can musk and the attar of roses.

And these emanations are taking place more or less continuously all about us and we know it not. In fact, we are at all times subjected to a molecular bombardment of which we never dream; minute projectiles, indivisible points of matter, are shot out at us in the form of electrons from glowing metals, from lighted candles, and from other noiseless and unsuspected batteries at a speed of tens of thousands of miles a second, and we are none the wiser for it. Indeed, if we could see or feel or be made aware of it, in what a different world we should find ourselves! How many million-or billion-fold our sense of sight and touch would have to be increased to bring this about! We live in a world of collisions, disruptions, and hurtling missiles of which our senses give us not the slightest evidence, and it is well that they do not. There is a tremendous activity in the air we breathe, in the water we drink, in the food we eat, and in the soil we walk upon, which, if magnified till our senses could take it in, would probably drive us mad. It is in this interior world of molecular activity, this world of electric vibrations and oscillations, that the many transformations of energy take place. This is the hiding-place of the lightning, of the electrons which moulded together make the thunderbolt. What an underworld of mystery and power it is! In it slumbers all the might and menace of the storm, the power that rends the earth and shakes the heavens. With the mind's eye one can see the indivisible atoms giving up their electrons, see the invisible hosts, in numbers beyond the power of mathematics to compute, being summoned and marshalled by some mysterious commander and hurled in terrible fiery phalanxes across the battlefield of the storm.

The physicist describes the atom and talks about it as if it were "a tangible body which one could hold in his hand like a baseball." "An atom," Sir Oliver Lodge says, "consists of a globular mass of positive electricity with minute negative electrons embedded in it." He speaks of the spherical form of the atom, and of its outer surface, of its centre, and of its passing through other atoms, and of the electrons that revolve around its centre as planets around a sun. The electron, one hundred thousand times smaller than an atom, yet has surface, and that surface is a dimpled and corrugated sheet--like the cover of a mattress. What a flight of the scientific imagination is that!

The disproportion between the size of an atom and the size of an electron is vastly greater than that between the sun and the earth. Represent an atom, says Sir Oliver Lodge, by a church one hundred and sixty feet long, eighty feet broad, and forty feet high; the electrons are like gnats inside it. Yet on the electric theory of matter, electrons are all of the atom there is; there is no church, but only the gnats rushing about. We know of nothing so empty and hollow, so near a vacuum, as matter in this conception of it. Indeed, in the new physics, matter is only a hole in the ether. Hence the newspaper joke about the bank sliding down and leaving the woodchuck-hole sticking out, looks like pretty good physics. The electrons give matter its inertia, and give it the force we call cohesion, give it its toughness, its strength, and all its other properties. They make water wet, and the diamond hard. They are the fountain-head of the immense stores of the inter-atomic energy, which, if it could be tapped and controlled, would so easily do all the work of the world. But this we cannot do. "We are no more competent," says Professor Soddy, "to make use of these supplies of atomic energy than a savage, ignorant of how to kindle a fire, could make use of a steam-engine." The natural rate of flow of this energy from its atomic sources we get as heat, and it suffices to keep life going upon this planet. It is the source of all the activity we see upon the globe. Its results, in the geologic ages, are stored up for us in coal and oil and natural gas, and, in our day, are available in the winds, the tides, and the waterfalls, and in electricity.

IV

The electric constitution of matter is quite beyond anything we can imagine. The atoms are little worlds by themselves, and the whole mystery of life and death is in their keeping. The whole difference in the types of mind and character among men is supposed to be in their keeping. The different qualities and properties of bodies are in their keeping. Whether an object is hot or cold to our senses, depends upon the character of their vibrations; whether it be sweet or sour, poisonous or innocuous to us, depends upon how the atoms select their partners in the whirl and dance of their activities. The hardness and brilliancy of the diamond is supposed to depend upon how the atoms of carbon unite and join hands.

I have heard the view expressed that all matter, as such, is dead matter, that the molecules of hydrogen, oxygen, carbon, nitrogen, iron, phosphorus, calcium, and so on, in a living body, are themselves no more alive than the same molecules in inorganic matter. Nearly nine tenths of a living body is water; is not this water the same as the water we get at the spring or the brook? is it any more alive? does water undergo any chemical change in the body? is it anything more than a solvent, than a current that carries the other elements to all parts of the body? There are any number of chemical changes or reactions in a living body, but are the atoms and molecules that are involved in such changes radically changed? Can oxygen be anything but oxygen, or carbon anything but carbon? Is what we call life the result of their various new combinations? Many modern biologists hold to this view. In this conception merely a change in the order of arrangement of the molecules of a substance--which follows which or which is joined to which--is fraught with consequences as great as the order in which the letters of the alphabet are arranged in words, or the words themselves are arranged in sentences. The change of one letter in a word often utterly changes the meaning of that word, and the changing of a word in the sentence may give expression to an entirely different idea. Reverse the letters in the word "God," and you get the name of our faithful friend the dog. Huxley and Tyndall both taught that it was the way that the ultimate particles of matter are compounded that makes the whole difference between a cabbage and an oak, or between a frog and a man. It is a hard proposition. We know with scientific certainty that the difference between a diamond and a piece of charcoal, or between a pearl and an oyster-shell, is the way that the particles of carbon in the one case, and of calcium carbide in the other, are arranged. We know with equal certainty that the difference between certain chemical bodies, like alcohol and ether, is the arrangement of their ultimate particles, since both have the same chemical formula. We do not spell acetic acid, alcohol, sugar, starch, animal fat, vegetable oils, glycerine, and the like, with the same letters; yet nature compounds them all of the same atoms of carbon, hydrogen, and oxygen, but in different proportions and in different orders.

Chemistry is all-potent. A mechanical mixture of two or more elements is a simple affair, but a chemical mixture introduces an element of magic. No conjurer's trick can approach such a transformation as that of oxygen and hydrogen gases into water. The miracle of turning water into wine is tame by comparison. Dip plain cotton into a mixture of nitric and sulphuric acids and let it dry, and we have that terrible explosive, guncotton. Or, take the cellulose of which cotton is composed, and add two atoms of hydrogen and one of oxygen, and we have sugar. But we are to remember that the difference here indicated is not a quantitative, but a qualitative one, not one affecting bulk, but affecting structure. Truly chemistry works wonders. Take ethyl alcohol, or ordinary spirits of wine, and add four more atoms of carbon to the carbon molecule, and we have the poison carbolic acid. Pure alcohol can be turned into a deadly poison, not by adding to, but simply by taking from it; take out one atom of carbon and two of hydrogen from the alcohol molecule, and we have the poison methyl alcohol. But we are to remember that the difference here indicated is not a quantitative, but a qualitative one, not one affecting bulk, but affecting structure.

In our atmosphere we have a mechanical mixture of nitrogen and oxygen, four parts of nitrogen to one of oxygen. By uniting the nitrogen and oxygen chemically (N_{2}O) we have nitrous oxide, laughing-gas. Ordinary starch is made up of three different elements--six parts of carbon, ten parts of hydrogen, and five parts of oxygen (C_{6}H_{10}O_{5}). Now if we add water to this compound, we have a simple mixture of starch and water, but if we bring about a chemical union with the elements of water (hydrogen and oxygen), we have grape sugar. This sugar is formed in green leaves by the agency of sunlight, and is the basis of all plant and animal food, and hence one of the most important things in nature.

Carbon is a solid, and is seen in its pure state in the diamond, the hardest body in nature and the most valued of all precious stones, but it enters largely into all living bodies and is an important constituent of all the food we eat. As a gas, united with the oxygen of the air, forming carbon dioxide, it was present at the beginning of life, and probably helped kindle the first vital spark. In the shape of wood and coal, it now warms us and makes the wheels of our material civilization go round. Diamond stuff, through the magic of chemistry, plays one of the principle rôles in our physical life; we eat it, and are warmed and propelled by it, and cheered by it. Taken as carbonic acid gas into our lungs, it poisons us; taken into our stomachs, it stimulates us; dissolved in water, it disintegrates the rocks, eating out the carbonate of lime which they contain. It is one of the principal actors in the drama of organized matter.

V

We have a good illustration of the power of chemistry, and how closely it is dogging the footsteps of life, in the many organic compounds it has built up out of the elements, such as sugar, starch, indigo, camphor, rubber, and so forth, all of which used to be looked upon as impossible aside from life-processes. It is such progress as this that leads some men of science to believe that the creation of life itself is within the reach of chemistry. I do not believe that any occult or transcendental principle bars the way, but that some unknown and perhaps unknowable condition does, as mysterious and unrepeatable as that which separates our mental life from our physical. The transmutation of the physical into the psychical takes place, but the secret of it we do not know. It does not seem to fall within the law of the correlation and the conservation of energy.

Free or single atoms are very rare; they all quickly find their mates or partners. This eagerness of the elements to combine is one of the mysteries. If the world of visible matter were at one stroke resolved into its constituent atoms, it would practically disappear; we might smell it, or taste it, if we were left, but we could not see it, or feel it; the water would vanish, the solid ground would vanish--more than half of it into oxygen atoms, and the rest mainly into silicon atoms.

The atoms of different bodies are all alike, and presumably each holds the same amount of electric energy. One wonders, then, how the order in which they are arranged can affect them so widely as to produce bodies so unlike as, say, alcohol and ether. This brings before us again the mystery of chemical arrangement or combination, so different from anything we know among tangible bodies. It seems to imply that each atom has its own individuality. Mix up a lot of pebbles together, and the result would be hardly affected by the order of the arrangement, but mix up a lot of people, and the result would be greatly affected by the fact of who is elbowing who. It seems the same among the mysterious atoms, as if some complemented or stimulated those next them, or had an opposite effect. But can we think of the atoms in a chemical compound as being next one another, or merely in juxtaposition? Do we not rather have to think of them as identified with one another to an extent that has no parallel in the world of ponderable bodies? A kind of sympathy or affinity makes them one in a sense that we only see realized among living beings.

Chemical activity is the first step from physical activity to vital activity, but the last step is taken rarely--the other two are universal. Chemical changes involve the atom. What do vital changes involve? We do not know. We can easily bring about the chemical changes, but not so the vital changes. A chemical change destroys one or more substances and produces others totally unlike them; a vital change breaks up substances and builds up other bodies out of them; it results in new compounds that finally cover the earth with myriads of new and strange forms.

X

THE VITAL ORDER

I

The mechanistic theory of life--the theory that all living things can be explained and fully accounted for on purely physico-chemical principles--has many defenders in our day. The main aim of the foregoing chapters is to point out the inadequacy of this view. At the risk of wearying my reader I am going to collect under the above heading a few more considerations bearing on this point.

A thing that grows, that develops, cannot, except by very free use of language, be called a machine. We speak of the body as a machine, but we have to qualify it by prefixing the adjective living--the living machine, which takes it out of the mechanical order of things fabricated, contrived, built up from without, and puts it in the order we call vital, the order of things self-developed from within, the order of things autonomous, as contrasted with things automatic. All the mechanical principles are operative in the life processes, but they have been vitalized, not changed in any way but in the service of a new order of reality. The heart with its chambers and valves is a pump that forces the blood through the system, but a pump that works itself and does not depend upon pneumatic pressure--a pump in which vital energy takes the place of gravitational energy. The peristaltic movement in the intestines involves a mechanical principle, but it is set up by an inward stimulus, and not by outward force. It is these inward stimuli, which of course involve chemical reactions, that afford the motive power for all living bodies and that put the living in another order from the mechanical. The eye is an optical instrument,--a rather crude one, it is said,--but it cannot be separated from its function, as can a mere instrument--the eye sees as literally as the brain thinks. In breathing we unconsciously apply the principle of the bellows; it is a bellows again which works itself, but the function of which, in a very limited sense, we can inhibit and control. An artificial, or man-made, machine always implies an artificer, but the living machine is not made in any such sense; it grows, it arises out of the organizing principle that becomes active in matter under conditions that we only dimly understand, and that we cannot reproduce.

The vital and the mechanical coöperate in all our bodily functions. Swallowing our food is a mechanical process, the digestion of it is a chemical process and the assimilation and elimination of it a vital process. Inhaling and exhaling the air is a mechanical process, the oxidation of the blood is a chemical process, and the renewal of the corpuscles is a vital process. Growth, assimilation, elimination, reproduction, metabolism, and secretion, are all vital processes which cannot be described in terms of physics and chemistry. All our bodily movements--lifting, striking, walking, running--are mechanical, but seeing, hearing, and tasting, are of another order. And that which controls, directs, coördinates, and inhibits our activities belongs to a still higher order, the psychic. The world of thoughts and emotions within us, while dependent upon and interacting with the physical world without us, cannot be accounted for in terms of the physical world. A living thing is more than a machine, more than a chemical laboratory.

We can analyze the processes of a tree into their mechanical and chemical elements, but there is besides a kind of force there which we must call vital. The whole growth and development of the tree, its manner of branching and gripping the soil, its fixity of species, its individuality--all imply something that does not belong to the order of the inorganic, automatic forces. In the living animal how the psychic stands related to the physical or physiological and arises out of it, science cannot tell us, but the relation must be real; only philosophy can grapple with that question. To resolve the psychic and the vital into the mechanical and chemical and refuse to see any other factors at work is the essence of materialism.

II

Any contrivance which shows an interdependence of parts, that results in unity of action, is super-mechanical. The solar system may be regarded as a unit, but it has not the purposive unity of a living body. It is one only in the sense that its separate bodies are all made of one stuff, and obey the same laws and move together in the same direction, but a living body is a unit because all its parts are in the service of one purposive end. An army is a unit, a flock of gregarious birds, a colony of ants or bees, is a unit because the spirit and purpose of one is the spirit and purpose of all; the unity is psychological.

Only living bodies are adaptive. Adaptation, of course, has its physics or its chemistry, because it is a physical phenomenon; but there is no adaptation of a rock or a clay-bank to its environment; there is only mechanical and chemical adjustment. The influence of the environment may bring about chemical and physical changes in a non-living body, but they are not purposive as in a living body. The fat in the seeds of plants in northern countries is liquid and solid at a lower temperature than in tropical climates. Living organisms alone react in a formative or deformative way to external stimuli. In warm climates the fur of animals and the wool of sheep become thin and light. The colder the climate, the thicker these coverings. Such facts only show that in the matter of adaptation among living organisms, there is a factor at work other than chemistry and physics--not independent of them, but making a purposive use of them. Cut off the central shoot that leads the young spruce tree upwards, and one of the shoots from the whirl of lateral branches below it slowly rises up and takes the place of the lost leader. Here is an action not prompted by the environment, but by the morphological needs of the tree, and it illustrates how different is its unity from the unity of a mere machine. I am only aiming to point out that in all living things the material forces behave in a purposive way to a degree that cannot be affirmed of them in non-living, and that, therefore, they imply intelligence.

Evidently the cells in the body do not all have the same degree of life,--that is, the same degree of irritability. The bone cells and the hair cells, for instance, can hardly be so much alive--or so irritable--as the muscle cells; nor these as intensely alive as the nerve and brain cells. Does not a bird possess a higher degree of life than a mollusk, or a turtle? Is not a brook trout more alive than a mud-sucker? You can freeze the latter as stiff as an icicle and resuscitate it, but not the former. There is a scale of degrees in life as clearly as there is a scale of degrees in temperature. There is an endless gradation of sensibilities of the living cells, dependent probably upon the degree of differentiation of function. Anæsthetics dull or suspend this irritability. The more highly developed and complex the nervous system, the higher the degree of life, till we pass from mere physical life to psychic life. Science might trace this difference to cell structure, but what brings about the change in the character of the cell, or starts the cells to building a complex nervous system, is a question unanswerable to science. The biologist imagines this and that about the invisible or hypothetical molecular structure; he assigns different functions to the atoms; some are for endosmosis, others for contraction, others for conduction of stimuli. Intramolecular oxygen plays a part. Other names are given to the mystery--the micellar strings of Naegeli, the biophores of Weismann, the plastidules of Haeckel; they all presuppose millions of molecules peculiarly arranged in the protoplasm.

On purely mechanical and chemical principles Tyndall accounts for the growth from the germ of a tree. The germ would be quiet, but the solar light and heat disturb its dreams, break up its atomic equilibrium. The germ makes an "effort" to restore it (why does it make an effort?), which effort is necessarily defeated and incessantly renewed, and in the turmoil or "scrapping" between the germ and the solar forces, matter is gathered from the soil and from the air and built into the special form of a tree. Why not in the form of a cabbage, or a donkey, or a clam? If the forces are purely automatic, why not? Why should matter be gathered in at all in a mechanical struggle between inorganic elements? But these are not all inorganic; the seed is organic. Ah! that makes the difference! That accounts for the "effort." So we have to have the organic to start with, then the rest is easy. No doubt the molecules of the seed would remain in a quiescent state, if they were not disturbed by external influences, chemical and mechanical. But there is something latent or potential in that seed that is the opposite of the mechanical, namely, the vital, and in what that consists, and where it came from, is the mystery.

III

I fancy that the difficulty which an increasing number of persons find in accepting the mechanistic view of life, or evolution,--the view which Herbert Spencer built into such a ponderous system of philosophy, and which such men as Huxley, Tyndall, Gifford, Haeckel, Verworn, and others, have upheld and illustrated,--is temperamental rather than logical. The view is distasteful to a certain type of mind--the flexible, imaginative, artistic, and literary type--the type that loves to see itself reflected in nature or that reads its own thoughts and emotions into nature. In a few eminent examples the two types of mind to which I refer seem more or less blended. Sir Oliver Lodge is a case in point. Sir Oliver is an eminent physicist who in his conception of the totality of things is yet a thoroughgoing idealist and mystic. His solution of the problem of living things is extra-scientific. He sees in life a distinct transcendental principle, not involved in the constitution of matter, but independent of it, entering into it and using it for its own purposes.

Tyndall was another great scientist with an inborn idealistic strain in him. His famous, and to many minds disquieting, declaration, made in his Belfast address over thirty years ago, that in matter itself he saw the promise and the potency of all terrestrial life, stamps him as a scientific materialist. But his conception of matter, as "at bottom essentially mystical and transcendental," stamps him as also an idealist. The idealist in him speaks very eloquently in the passage which, in the same address, he puts into the mouth of Bishop Butler, in the latter's imaginary debate with Lucretius: "Your atoms," says the Bishop, "are individually without sensation, much more are they without intelligence. May I ask you, then, to try your hand upon this problem. Take your dead hydrogen atoms, your dead oxygen atoms, your dead carbon atoms, your dead nitrogen atoms, your dead phosphorus atoms, and all the other atoms, dead as grains of shot, of which the brain is formed. Imagine them separate and sensationless, observe them running together and forming all imaginable combinations. This, as a purely mechanical process, is _seeable_ by the mind. But can you see or dream, or in any way imagine, how out of that mechanical art, and from these individually dead atoms, sensation, thought, and emotion are to arise? Are you likely to extract Homer out of the rattling of dice, or the Differential Calculus out of the clash of billiard balls?" Could any vitalist, or Bergsonian idealist have stated his case better?

Now the Bishop Butler type of mind--the visualizing, idealizing, analogy-loving, literary, and philosophical mind--is shared by a good many people; it is shared by or is characteristic of all the great poets, artists, seers, idealists of the world; it is the humanistic type that sees man everywhere reflected in nature; and is radically different from the strictly scientific type which dehumanizes nature and reduces it to impersonal laws and forces, which distrusts analogy and sentiment and poetry, and clings to a rigid logical method.

This type of mind is bound to have trouble in accepting the physico-chemical theory of the nature and origin of life. It visualizes life, sees it as a distinct force or principle working in and through matter but not of it, super-physical in its origin and psychological in its nature. This is the view Henri Bergson exploits in his "Creative Evolution." This is the view Kant took when he said, "It is quite certain that we cannot even satisfactorily understand, much less explain, the nature of an organism and its internal forces on purely mechanical principles." It is the view Goethe took when he said, "Matter can never exist without spirit, nor spirit without matter."

Tyndall says Goethe was helped by his poetic training in the field of natural history, but hindered as regards the physical and mechanical sciences. "He could not formulate distinct mechanical conceptions; he could not see the force of mechanical reasoning." His literary culture helped him to a literary interpretation of living nature, but not to a scientific explanation of it; it helped put him in sympathy with living things, and just to that extent barred him from the mechanistic conception of those of pure science. Goethe, like every great poet, saw the universe through the colored medium of his imagination, his emotional and æsthetic nature; in short, through his humanism, and not in the white light of the scientific reason. His contributions to literature were of the first order, but his contributions to science have not taken high rank. He was a "prophet of the soul," and not a disciple of the scientific understanding.