III
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 constitution 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 constitution 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 glass 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 glass 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 illustrate 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 association of cells; it is an association and coöperation 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 grass 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 analysis 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 analysis 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. Analogous 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 space." 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 antitoxins that it forms. Indeed, if we knew all that our bodies know, what mysteries would be revealed to us!