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 altitudes 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 hæmoglobin 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 analogy; 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 larvæ of the insect live and feed and mature. Another insect stings the same leaf and produces the common oak-apple—a smooth, round, green, shell-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 shell-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 larvæ 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 constituents 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 amœba 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 coöperation 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, pass 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 identity 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 constitution, 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.