One of the fundamental characteristics of life is power of adaptation; it will adapt itself to almost any condition; it is willing and accommodating. It is like a stream that can be turned into various channels; the gall insects turn it into channels to suit their ends when they sting the leaf of a tree or the stalk of a plant, and deposit an egg in the wound. "Build me a home and a nursery for my young," says the insect. "With all my heart," says the leaf, and forthwith forgets its function as a leaf, and proceeds to build up a structure, often of great delicacy and complexity, to house and cradle its enemy. The current of life flows on blindly and takes any form imposed upon it. But in the case of the vegetable galls it takes life to control life. Man cannot produce these galls by artificial means. But we can take various mechanical and chemical liberties with embryonic animal life in its lower sea-forms. Professor Loeb has fertilized the eggs of sea-urchins by artificial means. The eggs of certain forms may be made to produce twins by altering the const.i.tution of the sea-water, and the twins can be made to grow together so as to produce monstrosities by another chemical change in the sea-water. The eyes of certain fish embryos may be fused into a single cyclopean eye by adding magnesium chloride to the water in which they live. Loeb says, "It is _a priori_ obvious that an unlimited number of pathological variations might be produced by a variation in the concentration and const.i.tution of the sea water, and experience confirms this statement." It has been found that when frog's eggs are turned upside down and compressed between two gla.s.s plates for a number of hours, some of the eggs give rise to twins. Professor Morgan found that if he destroyed half of a frog's egg after the first segmentation, the remaining half gave rise to half an embryo, but that if he put the half-egg upside down, and compressed it between two gla.s.s plates, he got a perfect embryo frog of half the normal size. Such things show how plastic and adaptive life is. Dr. Carrel's experiments with living animal tissue immersed in a proper mother-liquid ill.u.s.trate how the vital process--cell-multiplication--may be induced to go on and on, blindly, aimlessly, for an almost indefinite time. The cells multiply, but they do not organize themselves into a constructive community and build an organ or any purposeful part. They may be likened to a lot of blind masons piling up brick and mortar without any architect to direct their work or furnish them a plan. A living body of the higher type is not merely an a.s.sociation of cells; it is an a.s.sociation and cooperation of communities of cells, each community working to a definite end and building an harmonious whole. The biochemist who would produce life in the laboratory has before him the problem of compounding matter charged with this organizing tendency or power, and doubtless if he ever should evoke this mysterious process through his chemical reactions, it would possess this power, as this is what distinguishes the organic from the inorganic.

I do not see mind or intelligence in the inorganic world in the sense in which I see it in the organic. In the heavens one sees power, vastness, sublimity, unspeakable, but one sees only the physical laws working on a grander scale than on the earth. Celestial mechanics do not differ from terrestrial mechanics, however tremendous and imposing the result of their activities. But in the humblest living thing--in a spear of gra.s.s by the roadside, in a gnat, in a flea--there lurks a greater mystery. In an animate body, however small, there abides something of which we get no trace in the vast reaches of astronomy, a kind of activity that is incalculable, indeterminate, and super-mechanical, not lawless, but making its own laws, and escaping from the iron necessity that rules in the inorganic world.

Our mathematics and our science can break into the circle of the celestial and the terrestrial forces, and weigh and measure and separate them, and in a degree understand them; but the forces of life defy our a.n.a.lysis as well as our synthesis.

Knowing as we do all the elements that make up the body and brain of a man, all the physiological processes, and all the relations and interdependence of his various organs, if, in addition, we knew all his inheritances, his whole ancestry back to the primordial cells from which he sprang, and if we also knew that of every person with whom he comes in contact and who influences his life, could we forecast his future, predict the orbit in which his life would revolve, indicate its eclipses, its perturbations, and the like, as we do that of an astronomic body? or could we foresee his affinities and combinations as we do that of a chemical body? Had we known any of the animal forms in his line of ascent, could we have foretold man as we know him to-day?

Could we have foretold the future of any form of life from its remote beginnings? Would our mathematics and our chemistry have been of any avail in our dealing with such a problem? Biology is not in the same category with geology and astronomy. In the inorganic world, chemical affinity builds up and pulls down. It integrates the rocks and, under changed conditions, it disintegrates them. In the organic world chemical affinity is equally active, but it plays a subordinate part. It neither builds up nor pulls down. Vital activities, if we must shun the term "vital force," do both. Barring accidents, the life of all organisms is terminated by other organisms. In the order of nature, life destroys life, and compounds destroy compounds. When the air and soil and water hold no invisible living germs, organic bodies never decay. It is not the heat that begets putrefaction, but germs in the air. Sufficient heat kills the germs, but what disintegrates the germs and reduces them to dust? Other still smaller organisms? and so on _ad infinitum_? Does the sequence of life have no end? The destruction of one chemical compound means the formation of other chemical compounds; chemical affinity cannot be annulled, but the activity we call vital is easily arrested. A living body can be killed, but a chemical body can only be changed into another chemical body.

The least of living things, I repeat, holds a more profound mystery than all our astronomy and our geology hold. It introduces us to activities which our mathematics do not help us to deal with. Our science can describe the processes of a living body, and name all the material elements that enter into it, but it cannot tell us in what the peculiar activity consists, or just what it is that differentiates living matter from non-living. Its a.n.a.lysis reveals no difference. But this difference consists in something beyond the reach of chemistry and of physics; it is active intelligence, the power of self-direction, of self-adjustment, of self-maintenance, of adapting means to an end. It is notorious that the hand cannot always cover the flea; this atom has will, and knows the road to safety. Behold what our bodies know over and above what we know! Professor Czapek reveals to us a chemist at work in the body who proceeds precisely like the chemist in his laboratory; they might both have graduated at the same school. Thus the chemist in the laboratory is accustomed to dissolve the substance which is to be used in an experiment to react on other substances. The chemical course in living cells is the same. All substances destined for reactions are first dissolved. No compound is taken up in living cells before it is dissolved. Digestion is essentially identical with dissolving or bringing into a liquid state. On the other hand, when the chemist wishes to preserve a living substance from chemical change, he transfers it from a state of solution into a solid state. The chemist in the living body does the same thing. Substances which are to be stored up, such as starch, fat, or protein bodies, are deposited in insoluble form, ready to be dissolved and used whenever wanted for the life processes.

Poisonous substances are eliminated from living bodies by the same process of precipitation. Oxalic acid is a product of oxidation in living cells, and has strong poisonous properties. To get rid of it, the chemist inside the body, by the aid of calcium salts, forms insoluble compounds of it, and thus casts it out. To separate substances from each other by filtration, or by shaking with suitable liquids, is one of the daily tasks of the chemist. a.n.a.logous processes occur regularly in living cells. Again, when the chemist wishes to finish his filtration quickly, he uses filters which have a large surface. "In living protoplasms, this condition is very well fulfilled by the foam-like structure which affords an immense surface in a very small s.p.a.ce." In the laboratory the chemist mixes his substances by stirring. The body chemist achieves the same result by the streaming of protoplasm. The cells know what they want, and how to attain it, as clearly as the chemist does. The intelligence of the living body, or what we must call such for want of a better term, is shown in scores of ways--by the means it takes to protect itself against microbes, by the ant.i.toxins that it forms. Indeed, if we knew all that our bodies know, what mysteries would be revealed to us!

IV

Life goes up-stream--goes against the tendency to a static equilibrium in matter; decay and death go down. What is it in the body that struggles against poisons and seeks to neutralize their effects? What is it that protects the body against a second attack of certain diseases, making it immune? Chemical changes, undoubtedly, but what brings about the chemical changes? The body is a _colony_ of living units called cells, that behaves much like a colony of insects when it takes measures to protect itself against its enemies. The body forms anti-toxins when it has to. It knows how to do it as well as bees know how to ventilate the hive, or how to seal up or entomb the grub of an invading moth.

Indeed, how much the act of the body, in encysting a bullet in its tissues, is like the act of the bees in encasing with wax a worm in the combs!

What is that in the body which at great alt.i.tudes increases the number of red corpuscles in the blood, those oxygen-bearers, so as to make up for the lessened amount of oxygen breathed by reason of the rarity of the air? Under such conditions, the amount of haemoglobin is almost doubled. I do not call this thing a force; I call it an intelligence--the intelligence that pervades the body and all animate nature, and does the right thing at the right time. We, no doubt, speak too loosely of it when we say that it prompts or causes the body to do this, or to do that; it _is_ the body; the relation of the two has no human a.n.a.logy; the two are one.

Man breaks into the circuit of the natural inorganic forces and arrests them and controls them, and makes them do his work--turn his wheels, drive his engines, run his errands, etc.; but he cannot do this in the same sense with the organic forces; he cannot put a spell upon the pine tree and cause it to build him a house or a nursery. Only the insects can do a thing like that; only certain insects can break into the circuit of vegetable life and divert its forces to serve their special ends. One kind of an insect stings a bud or a leaf of the oak, and the tree forthwith grows a solid nutlike protuberance the size of a chestnut, in which the larvae of the insect live and feed and mature.

Another insect stings the same leaf and produces the common oak-apple--a smooth, round, green, sh.e.l.l-like body filled with a network of radiating filaments, with the egg and then the grub of the insect at the centre.

Still another kind of insect stings the oak bud and deposits its eggs there, and the oak proceeds to grow a large white ball made up of a kind of succulent vegetable wool with red spots evenly distributed over its surface, as if it were some kind of spotted fruit or flower. In June, it is about the size of a small apple. Cut it in half and you find scores of small sh.e.l.l-like growths radiating from the bud-stem, like the seeds of the dandelion, each with a kind of vegetable pappus rising from it, and together making up the ball as the pappus of the dandelion seeds makes up the seed-globe of this plant. It is one of the most singular vegetable products, or vegetable perversions, that I know of. A sham fruit filled with sham seeds; each seed-like growth contains a grub, which later in the season pupates and eats its way out, a winged insect.

How foreign to anything we know as mechanical or chemical it all is!--the surprising and incalculable tricks of life!

Another kind of insect stings the oak leaf and there develops a pale, smooth, solid, semi-transparent sphere, the size of a robin's egg, dense and succulent like the flesh of an apple, with the larvae of the insect subsisting in its interior. Each of these widely different forms is evoked from the oak leaf by the magic of an insect's ovipositor.

Chemically, the const.i.tuents of all of them are undoubtedly the same.

It is one of the most curious and suggestive things in living nature. It shows how plastic and versatile life is, and how utterly unmechanical.

Life plays so many and such various tunes upon the same instruments; or rather, the living organism is like many instruments in one; the tones of all instruments slumber in it to be awakened when the right performer appears. At least four different insects get four different tunes, so to speak, out of the oak leaf.

Certain insects avail themselves of the animal organism also and go through their cycle of development and metamorphosis within its tissues or organs in a similar manner.

V

On the threshold of the world of living organisms stands that wonderful minute body, the cell, the unit of life--a piece of self-regulating and self-renewing mechanism that holds the key to all the myriads of living forms that fill the world, from the amoeba up to man. For chemistry to produce the cell is apparently as impossible as for it to produce a bird's egg, or a living flower, or the heart and brain of man. The body is a communal state made up of myriads of cells that all work together to build up and keep going the human personality. There is the same cooperation and division of labor that takes place in the civic state, and in certain insect communities. As in the social and political organism, thousands of the citizen cells die every day and new cells of the same kind take their place. Or, it is like an army in battle being constantly recruited--as fast as a soldier falls another takes his place, till the whole army is changed, and yet remains the same. The waste is greatest at the surface of the body through the skin, and through the stomach and lungs. The worker cells, namely, the tissue cells, like the worker bees in the hive, pa.s.s away the most rapidly; then, according to Haeckel, there are certain constants, certain cells that remain throughout life. "There is always a solid groundwork of conservative cells, the descendants of which secure the further regeneration." The traditions of the state are kept up by the citizen-cells that remain, so that, though all is changed in time, the genius of the state remains; the individuality of the man is not lost.

"The sense of personal ident.i.ty is maintained across the flight of molecules," just as it is maintained in the state or nation, by the units that remain, and by the established order. There is an unwritten const.i.tution, a spirit that governs, like Maeterlinck's "spirit of the hive." The traditions of the body are handed down from mother cell to daughter cell, though just what that means in terms of physiology or metabolism I do not know. But this we know--that you are you and I am I, and that human life and personality can never be fully explained or accounted for in terms of the material forces.

VIII

LIFE AND SCIENCE

I

The limited and peculiar activity which arises in matter and which we call vital; which comes and goes; which will not stay to be a.n.a.lyzed; which we in vain try to reproduce in our laboratories; which is inseparable from chemistry and physics, but which is not summed up by them; which seems to use them and direct them to new ends,--an ent.i.ty which seems to have invaded the kingdom of inert matter at some definite time in the earth's history, and to have set up an insurgent movement there; cutting across the circuits of the mechanical and chemical forces; turning them about, pitting one against the other; availing itself of gravity, of chemical affinity, of fluids and gases, of osmosis and exosmosis, of colloids, of oxidation and hydration, and yet explicable by none of these things; clothing itself with garments of warmth and color and perfume woven from the cold, insensate elements; setting up new activities in matter; building up myriads of new unstable compounds; struggling against the tendency of the physical forces to a dead equilibrium; indeterminate, intermittent, fugitive; limited in time, limited in s.p.a.ce; present in some worlds, absent from others; breaking up the old routine of the material forces, and inst.i.tuting new currents, new tendencies; departing from the linear activities of the inorganic, and setting up the circular activities of living currents; replacing change by metamorphosis, revolution by evolution, accretion by secretion, crystallization by cell-formation, aggregation by growth; and, finally, introducing a new power into the world--the mind and soul of man--this wonderful, and apparently transcendental something which we call life--how baffling and yet how fascinating is the inquiry into its nature and origin! Are we to regard it as Tyndall did, and as others before and since his time did and do, as potential in the const.i.tution of matter, and self-evolved, like the chemical compounds that are involved in its processes?

As mechanical energy is latent in coal, and in all combustible bodies, is vital energy latent in carbon, hydrogen, oxygen, and so forth, needing only the right conditions to bring it out? Mechanical energy is convertible into electrical energy, and _vice versa_. Indeed, the circle of the physical forces is easily traced, easily broken into, but when or how these forces merge into the vital and psychic forces, or support them, or become them--there is the puzzle. If we limit the natural to the inorganic order, then are living bodies supernatural?

Super-mechanical and super-chemical certainly, and chemics and mechanics and electro-statics include all the material forces. Is life outside this circle? It is certain that this circle does not always include life, but can life exist outside this circle? When it appears it is always inside it.

Science can only deal with life as a physical phenomenon; as a psychic phenomenon it is beyond its scope, except so far as the psychic is manifested through the physical. Not till it has produced living matter from dead can it speak with authority upon the question of the origin of life. Its province is limited to the description and a.n.a.lysis of life processes, but when it essays to name what inst.i.tutes the processes, or to disclose the secret of organization, it becomes philosophy or theology. When Haeckel says that life originated spontaneously, he does not speak with the authority of science, because he cannot prove his a.s.sertion; it is his opinion, and that is all. When Helmholtz says that life had no beginning, he is in the same case. When our later biophysicists say that life is of physico-chemical origin, they are in the same case; when Tyndall says that there is no energy in the universe but solar energy, he is in the same case; when Sir Oliver Lodge says that life is an ent.i.ty outside of and independent of matter, he is in the same case. Philosophy and theology can take leaps in the dark, but science must have solid ground to go upon. When it speculates or theorizes, it must make its speculations good. Scientific prophecy is amenable to the same tests as other prophecy. In the absence of proof by experiment--scientific proof--to get the living out of the non-living we have either got to conceive of matter itself as fundamentally creative, as the new materialism a.s.sumes, or else we have got to have an external Creator, as the old theology a.s.sumes. And the difference is more apparent than real. Tyndall is "baffled and bewildered" by the fact that out of its molecular vibrations and activities "things so utterly incongruous with them as sensation, thought, and emotion can be derived." His science is baffled and bewildered because it cannot, bound as it is by the iron law of the conservation and correlation of energy, trace the connection between them. But his philosophy or his theology would experience little difficulty. Henri Bergson shows no hesitation in declaring that the fate of consciousness is not involved in the fate of the brain through which it is manifested, but it is his philosophy and not his science that inspires this faith. Tyndall deifies matter to get life out of it--makes the creative energy potential in it. Bergson deifies or spiritualizes life as a psychic, creative principle, and makes matter its instrument or vehicle.

Science is supreme in its own sphere, the sphere, or hemisphere, of the objective world, but it does not embrace the whole of human life, because human life is made up of two spheres, or hemispheres, one of which is the subjective world. There is a world within us also, the world of our memories, thoughts, emotions, aspirations, imaginings, which overarches the world of our practical lives and material experience, as the sky overarches the earth. It is in the spirit of science that we conquer and use the material world in which we live; it is in the spirit of art and literature, philosophy and religion, that we explore and draw upon the immaterial world of our own hearts and souls.

Of course the man of science is also a philosopher--may I not even say he is also a prophet and poet? Not otherwise could he organize his scientific facts and see their due relations, see their drift and the sequence of forces that bind the universe into a whole. As a man of science he traces out the causes of the tides and the seasons, the nature and origin of disease, and a thousand and one other things; but only as a philosopher can he see the body as a whole and speculate about the mystery of its organization; only as a philosopher can he frame theories and compare values and interpret the phenomena he sees about him.

II

We can only know, in the scientific sense, the physical and chemical phenomena of life; its essence, its origin, we can only know as philosophy and idealism know them. We have to turn philosophers when we ask any ultimate question. The feeling we have that the scientific conception of life is inadequate springs from the philosophical habit of mind. Yet this habit is quite as legitimate as the scientific habit, and is bound to supplement the latter all through life.

The great men of science, like Darwin and Huxley, are philosophers in their theories and conclusions, and men of science in their observations and experiments. The limitations of science in dealing with such a problem are seen in the fact that science can take no step till it has life to begin with. When it has got the living body, it can a.n.a.lyze its phenomena and reduce them to their chemical and physical equivalents, and thus persuade itself that the secret of life may yet be hit upon in the laboratory. Professor Czapek, of the University of Prague, in his work on "The Chemical Phenomena of Life" speaks for science when he says, "What we call life is nothing else but a complex of innumerable chemical reactions in the living substance which we call protoplasm."

The "living substance" is a.s.sumed to begin with, and then we are told that the secret of its living lies in its chemical and physical processes. This is in one sense true. No doubt at all that if these processes were arrested, life would speedily end, but do they alone account for its origin? Is it not like accounting for a baby in terms of its breathing and eating? It was a baby before it did either, and it would seem as if life must in some way ante-date the physical and chemical processes that attend it, or at least be bound up in them in a way that no scientific a.n.a.lysis can reveal.

If life is merely a mode of motion in matter, it is fundamentally unlike any and all other modes of motion, because, while we can inst.i.tute all the others at will, we are powerless to inst.i.tute this. The mode of motion we call heat is going on in varying degrees of velocity all about us at all times and seasons, but the vital motion of matter is limited to a comparatively narrow circle. We can end it, but we cannot start it.

The rigidly scientific type of mind sees no greater mystery in the difference in contour of different animal bodies than a mere difference in the density of the germ cells: "one density results in a sequence of cell-densities to form a horse; another a dog; another a cat"; and avers that if we "repeat the same complex conditions, the same results are as inevitable as the sequences of forces that result in the formation of hydrogen monoxide from hydrogen and oxygen."

Different degrees of density may throw light on the different behavior of gases and fluids and solids, but can it throw any light on the question of why a horse is a horse, and a dog a dog? or why one is an herbivorous feeder, and the other a carnivorous?

The scientific explanation of life phenomena is a.n.a.logous to reducing a living body to its ashes and pointing to them--the lime, the iron, the phosphorus, the hydrogen, the oxygen, the carbon, the nitrogen--as the whole secret.

Professor Czapek is not entirely consistent. He says that it is his conviction that there is something in physiology that transcends the chemistry and the physics of inorganic nature. At the same time he affirms, "It becomes more and more improbable that Life develops forces which are unknown in inanimate Nature." But psychic forces are a product of life, and they certainly are not found in inanimate nature. But without laying stress upon this fact, may we not say that if no new force is developed by, or is characteristic of, life, certainly new effects, new processes, new compounds of matter are produced by life?

Matter undergoes some change that chemical a.n.a.lysis does not reveal. The mystery of isomeric substances appears, a vast number of new compounds of carbon appear, the face of the earth changes. The appearance of life in inert matter is a change a.n.a.logous to the appearance of the mind of man in animate nature. The old elements and forces are turned to new and higher uses. Man does not add to the list of forces or elements in the earth, but he develops them, and turns them to new purposes; they now obey and serve him, just as the old chemistry and physics obey and serve life. Czapek tells us of the vast number of what are called enzymes, or ferments, that appear in living bodies--"never found in inorganic Nature and not to be gained by chemical synthesis." Orders and suborders of enzymes, they play a part in respiration, in digestion, in a.s.similation. Some act on the fats, some on the carbohydrates, some produce inversion, others dissolution and precipitation. These enzymes are at once the products and the agents of life. They must exert force, chemical force, or, shall we say, they transform chemical force into life force, or, to use Professor Moore's term, into "biotic energy"?

III

The inorganic seems dreaming of the organic. Behold its dreams in the fern and tree forms upon the window pane and upon the stone flagging of a winter morning! In the Brunonian movement of matter in solution, in crystallization, in chemical affinity, in polarity, in osmosis, in the growth of flint or chert nodules, in limestone formations--like seeking like--in these and in other activities, inert matter seems dreaming of life.

The chemists have played upon this tendency in the inorganic to parody or simulate some of the forms of living matter. A noted European chemist, Dr. Leduc, has produced what he calls "osmotic growths," from purely unorganized mineral matter--growths in form like seaweed and polyps and corals and trees. His seeds are fragments of calcium chloride, and his soil is a solution of the alkaline carbonates, phosphates, or silicates. When his seeds are sown in these solutions, we see inert matter germinating, "putting forth bud and stem and root and branch and leaf and fruit," precisely as in the living vegetable kingdom. It is not a growth by accretion, as in crystallization, but by intussusception, as in life. These ghostly things exhibit the phenomena of circulation and respiration and nutrition, and a crude sort of reproduction by budding; they repair their injuries, and are able to perform periodic movements, just as does an animal or a plant; they have a period of vigorous youthful growth, of old age, of decay, and of death. In form, in color, in texture, and in cell structure, they imitate so closely the cell structures of organic growth as to suggest something uncanny or diabolical. And yet the author of them does not claim that they are alive. They are not edible, they contain no protoplasm--no starch or sugar or peptone or fats or carbohydrates.

These chemical creations by Dr. Leduc are still dead matter--dead colloids--only one remove from crystallization; on the road to life, fore-runners of life, but not life. If he could set up the chlorophyllian process in his chemical reactions among inorganic compounds, the secret of life would be in his hands. But only the green leaf can produce chlorophyll; and yet, which was first, the leaf or the chlorophyll?

Professor Czapek is convinced that "some substances must exist in protoplasm which are directly responsible for the life processes," and yet the chemists cannot isolate and identify those substances.

How utterly unmechanical a living body is, at least how far it transcends mere mechanics is shown by what the chemists call "autolysis." Pulverize your watch, and you have completely destroyed everything that made it a watch except the dead matter; but pulverize or reduce to a pulp a living plant, and though you have destroyed all cell structure, you have not yet destroyed the living substance; you have annihilated the mechanism, but you have not killed the something that keeps up the life process. Protoplasm takes time to die, but your machine stops instantly, and its elements are no more potent in a new machine than they were at first. "In the pulp prepared by grinding down living organisms in a mortar, some vital phenomena continue for a long time." The life processes cease, and the substances or elements of the dead body remain as before. Their chemical reactions are the same. There is no new chemistry, no new mechanics, no new substance in a live body, but there is a new tendency or force or impulse acting in matter, inspiring it, so to speak, to new ends. It is here that idealism parts company with exact science. It is here that the philosophers go one way, and the rigid scientists the other. It is from this point of view that the philosophy of Henri Bergson, based so largely as it is upon scientific material, has been so bitterly a.s.sailed from the scientific camp.

The living cell is a wonderful machine, but if we ask which is first, life or the cell, where are we? There is the synthetical reaction in the cell, and the a.n.a.lytical or splitting reaction--the organizing, and the disorganizing processes--what keeps up this seesaw and preserves the equilibrium? A life force, said the older scientists; only chemical laws, say the new. A prodigious change in the behavior of matter is wrought by life, and whether we say it is by chemical laws, or by a life force, the mystery remains.

The whole secret of life centres in the cell, in the plant cell; and this cell does not exceed .005 millimetres in diameter. An enormous number of chemical reactions take place in this minute s.p.a.ce. It is a world in little. Here are bodies of different shapes whose service is to absorb carbon dioxide, and form sugar and carbohydrates. Must we go outside of matter itself, and of chemical reactions, to account for it?

Call this unknown factor "vital force," as has so long been done, or name it "biotic energy," as Professor Moore has lately done, and the mystery remains the same. It is a new behavior in matter, call it by what name we will.

Inanimate nature seems governed by definite laws; that is, given the same conditions, the same results always follow. The reactions between two chemical elements under the same conditions are always the same. The physical forces go their unchanging ways, and are variable only as the conditions vary. In dealing with them we know exactly what to expect. We know at what degree of temperature, under the same conditions, water will boil, and at what degree of temperature it will freeze. Chance and probability play no part in such matters. But when we reach the world of animate nature, what a contrast we behold! Here, within certain limits, all is in perpetual flux and change. Living bodies are never two moments the same. Variability is the rule. We never know just how a living body will behave, under given conditions, till we try it. A late spring frost may kill nearly every bean stalk or potato plant or hill of corn in your garden, or nearly every shoot upon your grapevine. The survivors have greater powers of resistance--a larger measure of that mysterious something we call vitality. One horse will endure hardships and exposures that will kill scores of others. What will agitate one community will not in the same measure agitate another. What will break or discourage one human heart will sit much more lightly upon another.

Life introduces an element of uncertainty or indeterminateness that we do not find in the inorganic world. Bodies still have their laws or conditions of activity, but they are elastic and variable. Among living things we have in a measure escaped from the iron necessity that holds the world of dead matter in its grip. Dead matter ever tends to a static equilibrium; living matter to a dynamic poise, or a balance between the intake and the output of energy. Life is a peculiar activity in matter.

If the bicyclist stops, his wheel falls down; no mechanical contrivance could be devised that could take his place on the wheel, and no combination of purely chemical and physical forces can alone do with matter what life does with it. The a.n.a.logy here hinted at is only tentative. I would not imply that the relation of life to matter is merely mechanical and external, like that of the rider to his wheel. In life, the rider and his wheel are one, but when life vanishes, the wheel falls down. The chemical and physical activity of matter is perpetual; with a high-power microscope we may see the Brunonian movement in liquids and gases any time and at all times, but the movement we call vitality dominates these and turns them to new ends. I suppose the nature of the activity of the bombarding molecules of gases and liquids is the same in our bodies as out; that turmoil of the particles goes on forever; it is, in itself, blind, fateful, purposeless; but life furnishes, or _is_, an organizing principle that brings order and purpose out of this chaos. It does not annul any of the mechanical or chemical principles, but under its tutelage or inspiration they produce a host of new substances, and a world of new and beautiful and wonderful forms.