by Guy Murchie
Plankton living near the bottom who haven't learned how to make houses or traps by exuding them whole from their bodies often do about as well by secreting a sticky mortar with which they pick up sand grains, sponge spicules, mica flakes or other available hard materials, gradually compounding them into shells around themselves. The many spiny or shelled plankton have indeed thus evolved hundreds of slightly different techniques for construction of the thousand varieties of their skeletons, shells and shelters, most of them automatic methods, such as the absorption of mineral elements into their bodies along with food to be later excreted ready-mixed for unconscious building. And a typically ingenious method of preying is that of Foraminifera or "sea spiders," so called because they sprout hollow bristles fine and numerous enough to crisscross into webs which enmesh microscopic prey that the bristles digest on the spot by exuding gastric juices, then sucking the nutrients into their central calcareous shells that are often attached to seaweed. The while myriad crumbs and skeletons of dying older generations of sea spiders hail slowly but inexorably downward to the ocean bottom to cumulate in 100 million years such massive deposits of chalk as the white cliffs of Dover. The procedure is different of course with coral polyps, but the excreted cumulation just as sure and the building material much the same.
Virtually all planktonic sea creatures range thus through the earth's watery expanses and in various mediums react upon each other in ways that demonstrate them to be essentially parts of one organism. Indeed as the atmosphere circulates water, dust, spores, pollen, seeds, lichen, microbes, insects, spiders, birds, bats, man and other odd beings and baggage, acting somewhat as the planet's breath, which is occasionally infectious as well as refreshing, so is the sea a kind of blood to the Earth's living body that continuously conveys not only all the obvious creatures but, along with the already mentioned invisible ones, immeasurable quantities of germ cells, eggs, hormones, enzymes, vitamins, chemicals and other mysterious, subtle secretions that influence and coordinate the whole in space and time.
DIRT
Most concentrated of all the earth's mediums of life, though less vast and volatile than air or ocean, is the solid land - particularly the soil, which normally contains more living protoplasm and is of a higher level of organization than all that is in the roots embedded in it. I am speaking of the microcosmic earth we are made of and which obversely, to some degree, is made of us.
As you probably suspected, it is a dirty story - in the most literal sense. Of course you know I'm not talking about filthy dirt but rather the earthy kind. Even filthy dirt, however, is primarily a mental abstraction, since a bread crumb becomes "dirt" only when it falls away from its loaf, say, onto an otherwise clean floor. "Dirt," in other words, is something that is out of place. But the only dirt in the fundamental sense is soil or earth and the microscopic airborne and seaborne dusts that are largely composed of it. Ultimately, of course, all these kinds of dirt derive from space dust, which is thought to have aggregated the whole earth over billions of years and whose most significant ingredient turns out to be graphite, stuff sticky enough to collect such wandering interstellar atoms as hydrogen and oxygen and combine them into all the familiar chemical compounds of our world.
One of dirt's most vital characteristics, moreover, is that it is highly absorptive, for nothing is too dirty to be absorbed by dirt. Indeed its metabolism is quite indispensable in pollution control, while it supports not only the visible, macrocosmic plants like trees and flowers but also the microcosmic ones like mold and bacteria that rot and disintegrate them, making it the natural and ultimate refuge of refuse, of dead bodies, sewage and waste. If dirt, in this sense, is an agent of death, it is even more (and paradoxically) the stuff of life. For God was not speaking figuratively when He told Adam, "Dust thou art, and unto dust shalt thou return." In fact dirt is literally what you and I are made of, what we sprang from, what we walk on, what our food was raised in, what we will soon be buried in and must ultimately diffuse into. And we are the heirs of uncountable generations that passed the same stuff down from one to the next: "earth to earth, ashes to ashes, dust to dust ..."
The human "clay" that forms our bones and tissues is thus actually molded into man (as we will see in Chapter 6) by a temporary (genetic) rearrangement of the same elements to be found in any common clay or soil: ordinary atoms of carbon, oxygen, hydrogen, nitrogen, silicon, sodium, chlorine, phosphorus, sulfur, aluminum, manganese, calcium, potassium, iron, copper, magnesium, zinc, cobalt, etc., which are arranged in both organic and inorganic molecules in the living body and, to a surprising degree, similarly in the living ground. This means that dirt is something basically congenial to us - which is to say: friendly stuff. In fact, next to flesh, dirt turns out to be about the friendliest stuff imaginable. And as a vital ingredient of the sky and the nuclei of rain, its airborne form (dust) is part of our very breath and blood. It is likewise a prime factor in the ocean that evolved our ancestors and, according to modern genetics, has so many ancestors in common with ours that it is more than our kith, being to a measurable degree our actual kin.
But what exactly are dust and soil? Do they in any sense have a definable structure? One might not think so to hear farmers bemoaning the fact that no two fields are the same or even recognizably similar, yet soil scientists agree that the most varied earths have a lot in common. For all soil is more or less porous, being composed about half of air, which may be largely replaced with water after a rain, and half of rock particles that serve as a bony skeleton to which clings organic matter teeming with microbes and almost as active chemically as living flesh. The rock portion is primarily made of tiny grains of quartz, the hardest part of most rock, which survives the slow erosion of its softer components of feldspar, mica, etc., under the impact of sunlight, wind, rain, ice, flowing streams, chemical digestion, groping lichen, moss, the roots of plants and the hoofs of animals.
During the first few million years of this grinding and wearing process the skeletal grains are sand. At least geologists define them as sand down to a diameter of about one thousandth of an inch, then as silt from one thousandth to one ten-thousandth of an inch and, below that, clay. While not usually considered alive, they effectively serve as the bones of dirt and, in their way, are about as complex and active as the bones of an animal. This is particularly evident in the molecular
structure of clay, which comprises at least 30 elements whose crystals tend to align themselves in alternating sheets of silica and hydrated alumina like club sandwiches, the layers of which can be only one thirty-five-millionth of an inch apart, and electrically charged so that rather intense chemical interactions take place between them. In one typical form of mica clay the alumina sheets have hexagonal holes that line up opposite similar holes in the silica, and the sheets get riveted together with potassium ions that exactly fit the holes. But the greatest potential in clay probably results from the very smallness of its particles, on the geometric principle that cutting any solid into pieces increases its total surface area proportionately to the smallness of the pieces (page 15), the effect becoming dramatic when these get down to the caliber of fine powder. Thus the finest clays have surfaces as vast as ten acres per ounce, which makes them strongly colloidal, notoriously sticky when wet and chemically potent enough to be molded and baked into bricks, tiles and pottery.
Another vital part of soil is called humus, which comes from rotting vegetable and animal matter and is the mucky protein that helps hold the skeletal grains of quartz together, along with many other compounds of carbon, oxygen, nitrogen, phosphorus, etc., that add up to the basic living substance of Earth. And all these parts of soil, both organic and inorganic, are mixed together none too evenly while, except in sandy places, they tend to form crumbs up to about one eighth of an inch in diameter, which are each a tiny sample of the local earth. These crumbs are familiar to anyone who gardens or handles dirt, and seem to be tranquil little clods of inert, mellow tilth. But their apparent quiescence is almo
st completely illusory, for they are not only teeming with individual vegetable and animal life but are in a real sense alive themselves. They actually inhale oxygen and exhale carbon dioxide, and tests show that normally the air in soil down to about 5 inches deep is completely renewed every hour. And for many feet below that the soil breathes, though progressively more slowly as the moisture and carbon dioxide content of the air increase with depth. If it seems incredible that hard clay could be breathing, just remember that crevices only one thousandth of an inch wide, much too small to see without a microscope, are as much bigger than an Oxygen molecule as a valley 120 miles wide is bigger than a man.
SOIL CREATURES
Of course the breathing of soil is to a ponderable extent the collective respiration of the myriad individual lives within it, which are rather staggering in their interrelated profusion and, as we shall see, may quite logically be considered cells so inherent in their corporate organism that, without them, it becomes not only infertile but hardly deserving of the name of soil. In order to find out just what or who populates the soil various teams of scientists have marked out random sections of wild forest land in New York State, grassy meadows in England, farms in Sweden, etc., and sliced off the top layers of earth for detailed examination. Not counting the larger animals like foxes, rabbits, mice, moles, shrews, snakes, turtles, toads, ground birds, that here and there had burrowed into it, the scientific census of all visible smaller inhabitants washed and sieved out of the dirt showed an average of about 40,000 living visible animals per top cubic foot, including some 25,000 barely visible mites and 10,000 tiny springtails, with the remaining 5000 divided between about 100 kinds of bugs, beetles, bristletails, lice, spiders, ants, wasps, worms, millipedes, centipedes, crickets, flies, moths, slugs and other forms. And when it came to microscopic life, the numbers were literally billions of times greater, since a single ounce of average fertile soil has been found to contain not only well over a mile of fungus mycelium and comparable lengths of other roots, but about 20 times as many bacteria as all the men, women and children on Earth, with progressively greater and lesser numbers of viruses and other microbes in roughly inverse proportion to their sizes.
If you visualize this immense population in three dimensions, densest at the surface just under the soil's roof of grasses or leafy litter, its continuous bustle increasing as the temperature rises in spring, decreasing as it falls in autumn, you will begin to grasp the real nature of earth - its vast hordes of eight-legged mites crawling in the dark between the black crumbs of loam each of which is itself a seething ferment of microbes around a charged crystal, often meeting nervous little springtails, slithering nematode worms, tardigrades, odd lice, baby spiders and occasionally a huge milling millipede or a giant earthworm hunching its way through the tangle of thirsty root hairs and creeping fingers of fungus. It is a world full of ambush, stealth, surprise, instant reaction and fierce fighting for survival, yet there is harmony and contentment too, even love of a sort, where fungus and probing root embrace each other and mating worms intertwine.
But the predominant interrelation seems to be predatory, which, as elsewhere, assumes the form of chains: with burrowing owls hunting shrews, shrews digging worms, worms eating fungi and amebas, both of whom eat worms in turn. The worms eaten in turn, moreover, are not earthworms but tiny threadworms or nematodes, most species of whom are thousands of times smaller than earthworms and glide snakelike between the microscopic crumbs of soil, now sipping juice from root hairs with their dainty stylets, now swallowing bacteria or worms smaller than themselves. A census of the soil around grass roots has counted nematodes in numbers exceeding 10,000 per cubic inch, and they are well known to form the principal diet of certain ingeniously predacious fungi which may constitute more than half the total weight of living tissue in the same soil; when these fungi "smell" nematodes nearby, they are known to grow sticky knob "worm traps" upon their mycelium threads as well as loop snares, through some of which, sooner or later, worms will try to pass. One of the simpler of these amazingly varied types of snares contains about three sensitively triggered cells arranged in a single loop which, within one tenth of a second of when they feel pressure inside the circle, swell enough to close it or constrict anything inside it in a resilient but relentless stranglehold, which almost always subdues a caught nematode, despite its frantic writhings for freedom. Thereupon the snare starts sprouting shoots of mycelium into the victim which in a few hours grow the full length of his juicy body and rapidly digest it from within. Even if the lashing of a snared worm breaks the noose from its parent mycelium and he crawls away with a fungus collar, shoots of mycelium will still grow into him from the collar and he will usually be dead in an hour. The sticky knob traps work differently, being evidently as attractively flavored as are lollipops to a child, but when a nematode puts his mouth around one he discovers too late that it not only sticks like glue, anchoring him to the spot, but soon shoots mycelium down his throat to digest him from inside, just like the loop snares.
It seems fantastic to realize that such desperate warfare is being fought perpetually between armies of animals and vegetables inside almost every flower pot or swatch of mud that sticks to your shoe or shovel. But more than murder is going on all through the dirt, and the friendly bargaining and bartering there may be even more prevalent than the killing. At least a great many mycorrhizal threads of fungus (as we mentioned in Chapter 2) are now known to grow toward neighboring tree roots and when the fungus meets the root hairs it seems to be welcomed into the tree's body where it has been actually seen (under the microscope) to invade the root, cell by cell, until parts of it are completely consumed or digested. At the same time some of the bast gruel from the outer tree is drawn down into the fungus that enfolds the root hairs where its sun-derived energy is obviously welcomed in return. But all the underground dealings and conversations between plants are not expressed through such close embraces, because some roots are known to exude hormones capable of diffusing outward for several feet to where they find and activate the spores of other plants, causing them to release spermlike flagellates with whiptails that swim confidently straight back through the soil to the plant roots like homing pigeons. It is thus that the vegetable kingdom nourishes and fertilizes its members. And thus, among other ways, do vital traces of minerals get around: magnesium atoms slipping stealthily into chlorophyll, iron into blood and wandering atoms of copper, zinc, cobalt, molybdenum, iodine and cadmium into almost any organisms that will have them - these and all such exchanges exemplifying the great principle of universal interrelatedness that we will be coming back to in Chapter 13.
GERMS
Meantime, to return now briefly to Antony van Leeuwenhoek, I must point out that he was so busy and excited for almost two decades in discovering and reporting the endless wonders of his little animals who "hopped liked magpies" and "swam with their hair" that he could hardly find a moment to reflect on their significance for humanity and the world. Indeed it was only in 1692 that he got around to attributing his good health to his drinking every morning the new Ethiopian beverage called coffee so steaming hot that it "scalded the animalcules" in his mouth and, he was confident, finished off at least most of those on his front teeth.
This is about as close as he got to proposing a germ theory of disease, for he was probably too much of a realist to want to add to the numerous vague and ill-founded speculations about invisible "fever carriers." These had been recorded through history, certainly as far back as Aristotle, who theorized on the subject in the fourth century B.C. In most of the ancient world, moreover, despite Lucretius and Varro (page 83), illness and affliction had generally been considered divine punishment for sin and their treatment was primarily religious, a frank appeasement of angry gods. Only very occasionally did more advanced theories arise, like the Hindu concept of the "five winds" that activate the body or the Greeks' Hippocratic thesis that life is a precarious balance of the "four humors," of white phlegm, red blood, an
d black bile and yellow bile.
So far as anyone now knows, ancient diseases were generally similar to present ones, and I have found evidence of at least forty familiar ailments that were rife in ancient Egypt and almost as many in each of Babylon, India, China, Greece, Mexico and Peru. These include scores of afflictions like ulcers (treated with mercury in ancient China), mumps (salved with music in Greece), the common cold (soothed with sage in Egypt) and constipation (helped by sarsaparilla in Aztec Mexico, by corn silk in Inca Peru, rhubarb in China, oxgall enemas funneled through a bull's horn in Egypt or through a medicinal flute in Babylon).
The really serious diseases, however, those that obviously affected mankind the most, were the plaguey sort such as smallpox, which may have originated in China - where it was described in 1700 B.C. - and spread westward to India, the Near East and Egypt, where King Ramses V is known to have suffered from it half a millennium later. The great plague of Athens described by Thucydides in 430 B.C. is now believed to have been smallpox, the virus of which may well have decided the outcome of the Peloponnesian War, as the germ of a similar epidemic, reported by Diodorus Siculus to have ravaged the Carthaginian army besieging Syracuse in 396 B.C., set the Mediterranean stage in favor of Rome before the Punic Wars.
Bubonic plague is another such scourge of mankind whose origins are dim in ancient history, but it may have been crucial in stopping the Persians after Thermopylae in 479 B.C. and is thought to be the organism behind the so-called great plague of Justinian that hit Egypt in A.D. 540, spread swiftly to Palestine and shattered Byzantium to the tune of 10,000 deaths a day, undeniably delivering the coup de grace to Roman civilization. Bubonic plague evidently also erupted in the hot summer of 1204 in Asia Minor to such lethal effect that the Fourth Crusade was stopped in its tracks and forced to abandon all hope of reaching Jerusalem. But it was in the fourteenth century that this frightful disease, then called "the Black Death," attained its zenith, appearing suddenly out of the east in 1348 to wipe out more than half of Europe's population of over 100 million. It struck again in 1361, not quite as deadly but killing nearly half of the survivors and their children; again it showed up in 1371, this time afflicting only about a tenth of the remaining people, many of whom recovered; and afterward yet a dozen times, gradually diminishing in force until 1820, when it seems finally to have faded out as a serious danger to the Western World.