Popular Science Monthly/Volume 20/March 1882/To Eat and to Be Eaten
NATURE has many of what we are accustomed to call the small economies of life. She does nothing without a purpose, and she has a horror of waste. In the world of living beings, particularly, is she careful of her materials. It is no easy lift to bring matter up to the organic level. She has to call in the sun to her assistance, and get their united shoulders under the load, ere it can be raised to the required height; and she can not afford to let it down again while there is any pith left in it.
It is interesting to follow her through this portion of her housekeeping, and watch the care with which she gets all the life-force possible out of her organic stock in trade, letting not a crumb go to waste. She invites a guest with a special appetite for every morsel— guests furnished with teeth to rend, nip, and gnaw, claws to tear, augers and chisels to bore and gouge, saws, drills, punches, and suction tubes—that no fragment of the feast shall be left on the unswept tables.
There are guests of every shape, size, and description, alike only in the one particular of being normally hungry. Like the sitters-down at a public dinner, they all seem to have been saving up appetite for the occasion. Some there are, indeed, of such omnivorous tastes that we would be quite willing to have them left out from the general invitation. But that is not Dame Nature's way. Every crumb must be eaten; and we know little of her facility of invention if we imagine that she can not find a tooth for every hard morsel. She is ready for any such emergency, and you will be bound to find some queer creature gnawing away at the indigestible fragment with as much zest as if it were a dish fit for a king.
Let us take a sly glance in at Nature's kitchen and watch her guests at their meal. We shall not call it breakfast, dinner, supper, or lunch, for there is no such formal division. It is a whole-day feast, and a whole-night feast, too, for that matter. The tables are always spread, the guests always hungry; they crowd in from high-ways and by-ways; always one ready to take up every vacant knife, fork, and spoon; or to plunge in with fingers, teeth, and claws, in the true primitive fashion.
Nature does her cooking by sunlight. The great, glaring sun is her cook-stove, and by its aid she concocts, from such materials as water, carbonic acid, and ammonia, various palatable dishes, such as sugar, bread, fruits, greens, and a host of similar delicacies.
"There is your dinner," she says, "make yourselves at home." And so they do, without waiting to hear the dinner-bell; rich and poor, high and low; the dainty epicureans confining themselves to the fruits and seeds; others feasting on the green leaves and the lush grasses. But these are only the nobility, those who sit above the salt. The commonalty are more greedy and less particular. They bore in and saw in and dig in. Leaf and flower and fruit, branch and stem and root, each has its epicures. Some take a mean advantage by laying their eggs in the heart of rosy apple or luscious pear, so that their babes may revel in a perfect mountain of provender. There they lie, odd little white worms, like the chap who wished that Lake Superior was all ice-cream, and he plunged into its midst and condemned to eat his way out.
It has been no trifling task to lift that lofty tree or that broad field of waving grain up out of the lifeless world, and Nature is bound to make it pay its full duty to the world of life before it drops back again. It is her business to set going all the variety and abundance of life possible, and tree, grass, and grain must furnish food for those high-strung creatures who can not, like these plants, live on rock, dust, water, and air, but must have their victuals ready cooked and served.
Look at the throng of vegetarians! Here is man, daintily plucking the luscious fruits and juicy berries, the rich seeds and fat roots, and extracting sugars and wines, vinegars and spices, to make his meal palatable. Yonder are the hosts of the cloven-footed, perfectly content to grow fat upon leaves and grasses. And here are armies of humbler guests—cherry-pecking birds, honey-sucking bees, leaf-eating grubs, that convert the waving banner of a leafing tree into one great spider-web, and then perchance go to sleep in hammocks of silk; carpenters and miners who bore into the hard wood itself, and leave behind them long, winding galleries that look like the lanes and alleys of an Old World city; locusts, army-worms, and potato-bugs that ruin man's harvests; and millions of centipeds and millepeds, ticks, mites, and gnats, that suck the living juices and fatten on the palatable meat of the tree.
But all this is only the beginning of the feast. What we call death is only, in another sense, the spring-tide of life. The leaves fall and rot, the grass decays, but not to return to the inorganic world. They are dished up as food for new waving fields and flaunting leaves. In the chemical balance of Nature part of this nutriment bears down its side of the scale into the lifeless world, yielding force to lift the nutriment in the other scale back again into the circle of life.
And when the great tree dies, what then? Its dead body is but a vast nursery of life. The long, lithe, twisting and clinging parasites, that have drunk its blood while alive, are replaced by flat lichens, umbrella-like fungi, and luxuriant mosses, which feast on its decaying trunk; while borers, chiselers, and miners do their part in transforming the great dead mass. again into living forms.
And when it drops into a heap of decaying vegetable flesh, what new hosts of life batten upon it! And when the earth takes back the ruins of the dead giant beneath her generous breast, it is not to keep them there. They have too much vitality left for that. They climb to the air and the sunlight again in grasses and ferns and airy little plants. They blossom into flowers, eye-gladdening, honey-yielding, color-mad clumps of bloom, from which not alone the bee drinks sweets.
Thus is the fallen tree transformed into multitudinous life, bursting above the soil in new generations of beauty, until scarce a shred remains that does not live again. And creeping rootlets of trees hunt these last fragments underground, and crawling, flexible worms eagerly swallow the earth itself, and digest from it the stray crumbs of the old tree that are mixed throughout the soil.
Nor have we yet got to the bottom of this cycle of vegetable life. There are worlds, solar systems of life beneath all this, dwelling far below the reach of the eyesight of man. Let some of the decaying stuff fall into standing water, and there, under the hot summer sun, slowly dissolve. Put, then, a single drop of this water under the microscope, and let us try to rediscover the fibers and flesh of our tree. Lo! instead of this dead matter we behold a swarming, writhing, twisting, shooting, creeping sea of life, thousands, millions of living forms into which Nature has transformed her seeming organic waste: the rod-like bacteria, the boat-like diatom, the globe-like volvox, the line-like algæ among vegetables; and among animals the arm-making amoeba, the whip-lash monad, the shelled and twisted foraminifera, the strangely-varied infusorian; there, where to the unaided eye all seemed death and stagnation, lies a bewildering phantasmagoria of created things, life crowding in indescribable multitudes and numberless variety out of the heart of death, the eaters and the eaten in innumerable profusion. Such is the full cycle of the life of our tree; such the boundless variety produced by Nature's economical administration of her materials.
But let us not imagine that we have yet exhausted the subject. Nature is in no readier mood to waste animal than vegetable food. It also must do its duty in widening out the circle of life. Animals prey on animals. Alive and dead they are eaten and re-eaten. Animal, like vegetable life, is turned again and again into new life, until every atom of it has had all its vitality squeezed out, and has fallen, bit by bit, back into the inorganic world.
The carnivora equal, if they do not exceed, the herbivora in number. The flesh which the latter has formed out of plant material the former rends and consumes, turning it into new animal forms. And so the endless metempsychosis of life goes on, the great preying upon the small, the greater upon the great, and man indiscriminately upon all, little that is eatable escaping his omnivorous appetite.
It is all one to Nature. She is determined that there shall be no waste, that none of her laborious efforts to build the organic out of the inorganic world shall be for naught, and that the utmost abundance and most endless variety of life shall flow into being out of the bosom of the inanimate.
It is not alone the battle of the great upon the small, the strong upon the weak. The small as well make their harvest upon the bodies of the great. As minute plants feed upon great trees, so do the midges upon the giants of the animal world.
Insects are not content with preying upon one another—spiders dragging their nets through the air for unwary flies, ant-lions digging sand-craters for curious ants, ichneumon-flies nestling their young in the bodies of fat caterpillars—but they prey as persistently upon the world of giant animals.
Look at these minute pests of man, for instance. How little Nature seems inclined to exempt her best and highest from the inexorable law of to eat and to be eaten! The name of the creatures, who fondly imagine that this fair human form was spread as a banquet for them, is legion. Gnats, ticks, lice, mites, flies, fleas, mosquitoes, form a few of our temperate host, while in torrid regions they swarm in tenfold profusion and variety, causing the happy dwellers in the land of eternal summer to spend a considerable portion of their lazy days and nights in the monotonous labor of scratching, slapping, squirming, and perhaps occasionally swearing their jaw-breaking oaths at the torments which surround them.
And inside as well as outside man is a harvest-field for the midges. Worms of unpleasing variety infest him in every organ, troubling not alone the digestive region, but lying. hid in the firm flesh, the brain, even the eye. And that minute but multitudinous creature with which a pork diet furnishes him—the trichina—makes the whole body its home, and literally eats him up alive.
Nor has our economical mother Nature more mercy on her other gigantic creatures than upon man. They are all the prey of some special insects or other parasites. And not alone the great, but the small, for we perceive creatures visible only under the microscope that form the homes of still smaller parasites. It becomes, indeed, an unpleasant wonder what marvelous adaptations of animal life have been formed apparently for no other purpose than to batten and fatten upon and make miserable all larger creatures, for whose greater size they make up by vaster multitudes.
It is economy all. There must be no waste of organic material. If some suffer thereby, it is their misfortune. The law can not be set aside for special purposes. There are no good ends ever gained without certain unpleasant drawbacks. The end here to be gained is life—abounding, immeasurable life. To reach this result, no organic force can be spared, and if some have to scratch and squirm, still it will be found here, as in all Nature's economies, that the evil is small, the good attained great. She works by law alone, and a law of Nature is never laid aside because it happens to tread on some crippled creature's corns. Law is immutable, and will inevitably crush every laggard who is not strong enough or quick enough to get out of its path.
And when the animal dies, it dies not to drop at once into the dust whence it sprang. Its dead flesh is too valuable life-building material to be allowed to escape Nature's uses in any such hasty fashion. Complete death can only be reached by the road of life. The mineral world is too far off to be arrived at by a single downward step. Successive steps are necessary, and every step is a living form. What we call fermentation in plants is but a growth of new plants out of the stuff of old ones. And putrefaction in animals is but another form of the same process.
As we have seen a host of plants growing out of the ruins of the dead tree, so we now perceive a host of animals growing out of the ruin of their dead predecessor. What is not otherwise devoured serves as a receptacle for the eggs of insects, and it soon swarms with grubs and maggots, destined eventually to sail in winged lightness in the air, without a hint in their aërial grace that their floating life had this unpleasant source.
And they shall be eaten—and their eaters eaten; and thus the organic world, which grew up by this devouring process from the smallest plant to man, slowly drops back by form after form through the lower world of animals and plants, until every grain of vitality is sucked out of it, and it falls at last, utterly juiceless and lifeless, into the mineral world from which it came.
Such is Nature's most striking economy. Such the work she gets from the subscriptions from the lower world, ere they are paid back into the treasury whence they were drawn. They form the coin of life, passing from hand to hand, and abraded by every touch, until utterly worn away, and needs to be replaced by new coins from the organic mint.
And there is yet another feature in this round of economies with which we may safely close our review. Nature not only provides us with new food, but makes our old nutriment do duty again and again, ere every possibility of use is squeezed out of it. Thus the nitrogenous material of the body, which is thrown into the circulation by waste of the muscles, does not appear to be at once carried out of the body as useless refuse. It is too precious to be so lightly thrown away. On the contrary, it is probably worked over again in the blood, a portion of it becoming mineral matter, and yielding force to lift another portion into the condition of nutriment. A similar process of reemployment of nitrogenous material takes place in vegetables. Thus, a part of the coin is worn off, and the remainder paid back into the bank of life for its existing value. And so it may be paid back again and again, until it is all lost in this successive wear and tear, and the mineral world gets its own again.
This is Nature's thrifty housekeeping. Not an ounce of force is wasted. All the possible life in organic material is worked out of it ere it can escape. And even those vegetable forms that have avoided this process by being turned into stone have but temporarily locked up their forces, which flow out eventually in the form of light and heat, to invigorate, vivify, and gladden the world of living beings.