Popular Science Monthly/Volume 11/July 1877/The Material Resources of Life
| THE MATERIAL RESOURCES OF LIFE.[1] |
By ALBERT B. PRESCOTT.
TO be able to live, in any way known to us, it is indispensable to have a body. And, as living bodies come by growth and continue by nourishment, it is first necessary to have materials whereof bodies can be made—and renewed and kept in warmth and strength. Just these materials, with permission of the reader, we will try to take account of, as resources of life. Life is not maintained "by bread alone;" other needful resources being known to physical science, and still other resources greater than all being recognized by their results in life; but we have the bread alone, as enough, certainly, to be considered in the present article.
Living things are in very deed made of "the dust of the earth;" but it is by no means all of the dust of the earth that serves this purpose. We have to distinguish between substances out of which organized instruments of life can be made, and a much larger number of substances never used in the making of these instruments.
We have it in mind that matter is made up of sixty-three simples. At all events, the earth's crust and air are constituted, substantially, of these sixty-three sorts of atoms, and, as a good many of the same are already revealed in the sun and stars by the spectroscope, it is likely that they are the chief elements in the universe of matter. Of the sixty-three, certain elements, found only in very small quantities, appear to be of subordinate importance in that part of the universe under our immediate observation, Whatever purposes they may fulfill in other earths or in the centre of our own, or at other epochs. Others of the elements bear an important part in the structure of the globe or in the uses of mankind, but are not organizable materials, and they are not in our present consideration. Of the sixty-three, only fourteen or fifteen simples, about one-fourth of those known to us, are used in the construction of plants and animals. These, then, are before us, as the elemental resources of life.
It will be understood that the tissues are not built directly of these fourteen elements, but of their chemical compounds. Each one of these compounds is a definite substance in external character distinct from its constituents, as, in a familiar example, water is distinct from the hydrogen and oxygen of which it is composed. The number of these chemical compounds built into living tissues is very great, a number uncounted. It is of these compound substances—of their molecules—that the cells are builded; builded by an action very unlike chemical action and into shapes very unlike chemical results. Also, it is by the consumption of these compounds of the fourteen elements that animal warmth and activity are sustained. But, not turning aside here to question the chemistry (the making of molecules) going on in cells, or the vital organization (the building together of molecules) going on in cells, not once lifting our eyes toward any of the dynamical sources of life, we bend our attention to find out, if we can, the raw material for cells, the inorganic resources of the organic world.
It is the organic world together, to be sure, that is able to subsist on the fourteen elements as these are given by the earth, the animal kingdom obtaining most of its material at second hand, as elaborated by the vegetable. The two kingdoms are, in the end, mutually dependent on each other in gaining sustenance from the earth's supplies.
The fourteen indispensable simples may be classified, in different ways for different ends. There is a privilege of provisional classification, for the sake of comparison and of acquaintance; and, with the promise not to impose our arrangement upon any other occasion, we would like, for the purposes of our present quest, to divide the elemental resources of life into two categories, as follows: 1. Those supplied so abundantly on the earth that all individuals share them alike, without favor of fortune or forethought of mind. We may name them redundant resources. 2. Those provided so sparingly that individuals do not share them alike, but secure them by effort and by opportunity. They may be termed adequate resources.
From the provision of the first class of materials, it results that, in certain great essentials of organization, all individuals are placed on a footing of equality with their fellows. It results from the provision of the second class of materials, that unequal qualities and quantities of organization are derived by different individuals of the same species. Through our redundant resources we are taught the common brotherhood of the created. Through our adequate resources come the assurances of our responsibility—our commissions as stewards of the earth. Materials given in a superabundance that cannot be wasted constitute a dispensation of mercy; its benefits falling alike on the just and on the unjust, the lazy and the diligent, the foolish and the prudent. Materials given in a competence that must be guarded constitute a dispensation of compensation; inciting to exertion, rewarding for attainment, and training the powers of volition. By the first, the democracy of equal privileges and inalienable possessions is maintained; by the second, the aristocracy of merit is preserved.
The redundant resources so abound that they can have no value, in the sense of exchangeable value, in society; even though needed as they are in more constant supply than those of the other class. The resources which are barely adequate are those which come to be objects of personal possession; they are the things of which mine and thine are declared, and it is because of them that title-deeds are drawn and prices-current established. The substrata of poverty and of riches rest in the chemical elements.
With the definition of each class in mind, let us now consider the supply of some of the more important of the elemental resources. From the fourteen, let us take at least three elements of each class, as representatives. For the redundant resources, we will take carbon, oxygen, and hydrogen. Then, for the adequate resources, we will examine nitrogen, phosphorus, and potassium.
Carbon is the one element never left out of an organic compound. Its atoms are not only constituents, they are corner-stones of all the organic molecules. In the human body, thirteen parts in a hundred, or forty per cent, of the solids, are carbon. Looking for its supply, we see that it is obtained for the organic world by the plants, and from the carbonic-acid gas of the air. It is taken from the air chiefly by the leaf of the plant. How much carbon is taken from the organic mould of the soil and from acid carbonates, through the roots, is perhaps not fully settled; but we are well assured that the main and sure resource of the plant for this element is the air. The supply, then, is as abundant and impartial as the open air itself. The carbon-material forms but a small part of the air, it is true, only about five parts in 10,000; nevertheless, it is enough, at least for the average rate of vegetable nutrition. Carried around the globe in the viewless air to every plant alike, the carbon-atoms are supplied for the framework of every cell in plant and animal. A dwarfed shrub or rootless lichen, clinging to the crevices of a naked rock on a frigid shore, has at hand a good supply of the same resource that is furnished to a luxuriant palm spreading from a tropic soil.
And the carbon-supply in the air is not a reservoir diminishing, however slowly, from age to age; but, to be sure, it is a returning fountain, replenished from the exhalations of animals and the decomposing remains of all organized bodies. In Nature's economy, the same carbon-atoms are used over and over again as material for organization. This perpetual replenishment, a thrifty provision against future exhaustion, is one not peculiar to carbon, but it is a provision made in good degree for every one of the elemental resources of life, whether redundant or only adequate in its immediate supply.
That plants feed upon the carbonic acid of the air is known to the school-children, and has been known to men for a hundred and one years at least. Priestley, whose discoveries were celebrated in the chemical centennial at Northumberland, Pennsylvania, two years ago, placed it on record very clearly that "air vitiated by animal respiration is a pabulum to vegetable life." This was but the next year after Priestley's discovery of oxygen itself; yet to this day there lingers in our common thought an undefined impression that the carbonic acid of the air is just an impurity, tolerated because there is only a little of it, but an impurity that it were as well to be rid of altogether. Now, if the redundant resources of life were at our human disposal, we might be in danger, some day, in the sheer forgetfulness of self-regard, of throwing away as an impurity the very foundations of sustenance. Some one, perhaps, would set forth that this gas when not diluted is immediately fatal to human life; another would declare, "Once a poison, always a poison;" and another would ask why we should imperil our own health for the sake of the plants.
Oxygen was named next, among the primary resources, redundant in supply. It is a prominent constituent of all living tissues, forming seventy-two parts in a hundred of the human body with its fluids. It is taken in two conditions: first, in combination, chiefly by the plants; second, in the elemental state, by animals. In combination, it is taken by the plants from carbonic-acid gas, just noticed as a source of carbon; from water, to be considered as a source of hydrogen; and, in smaller quantities, from a considerable number of other substances. The greater part of the oxygen in animal tissues is obtained in the products elaborated by the plants.
But for all animal life the most imperative demand is for oxygen in the elemental state.
The other elemental resources are available only in their compounds; oxygen does its best service when alone. The others serve life as materials for its bodily tissues; oxygen has an additional duty, the maintenance of operations giving warmth and strength. The activities of life consume various materials, but most constantly of all they demand a raw material of inorganic nature, a simple material in its primitive condition. This supply of elemental oxygen, a necessity for all animal life, is a necessity that is imminent in direct proportion to vital activity, and for man is absolutely imperative. When supplied with oxygen, we can subsist days without other food; when deprived of oxygen, life fails in a few minutes. It is scarcely a figure of speech to say that the breath is the life. The energy of oxygenation is told in every stroke of the heart. The food that is eaten does not raise an iota of bodily strength without the help of the pound and a quarter of pure oxygen that is daily inhaled. To breathe poorly is to faint; to eat richly and breathe poorly is to suffocate and perish.
The supply of elemental oxygen is certainly impartial and bountiful without reservation. It is more than given—it is pressed upon us; to escape from it is a work of toil and difficulty. No one is poor from want of it, or rich from gain of it. Were it furnished for pay, all that a man hath would he give for an hour's supply of it. The poor, taken together, fare best in its use; while the wealthy, in their rate contrivances to exclude the cold and wet and wind and glare of the weather, can make but slight impediments to its distribution.
One other element we were to inquire of, among the redundant materials: the unit of chemical measures, hydrogen. As light as it is, it makes over nine weights in a hundred of the body of man. It is obtained chiefly by the plants; mostly from water, but to some extent from ammonia, the latter being more notable as a source of another element.
Water is not quite always as free as air—failing the needs of the stationary bodies of plants more often than it does the wants of animals, and in the quantities taken as food by man hardly liable to a notable value in exchange. As a substance not wholly gaseous, it is not easy to conceive how water could be more abundantly supplied than it is, without being a burden and a hinderance to life. It is doubtful whether mankind would vote for any uniform increase in the quantity of water on the planet. If water was supplied in vapor more abundantly than it is, by having a lower vaporizing-point, the conditions of all life would be changed—the atmosphere would be put out of its adjustment with the organic creations.
Some of the simpler forms of life subsist almost wholly upon the three elemental materials we have had in consideration, with a few others of the plentiful resources; and living beings taken together use much larger quantities of these than of the substances more sparingly supplied. But, as to the relative importance of the two classes of resources, it can only be said that the higher forms of life can no more exist without the one than without the other.
Of the adequate resources, nitrogen is needed by the largest number of living bodies and used in the largest quantities. It enters into most animal tissues and the more complex of the vegetable products; being two and a half parts in a hundred of the body of man, or eight per cent, of its solids. It is obtained for the organic world solely by the plants, and obtained only from combinations of nitrogen, the ammonia and nitrates of the air and the soil.
The supply of this combined or available nitrogen in the air is limited—enough for a measure of vegetation, but not near enough for the greatest growth of food-plants and grains. The quantity of combined nitrogen carried by the rain from the air to the plant-roots was found to be, in the rainfall of a year in Great Britain, equal to seven pounds of ammonia on an acre; another year it equaled nine and a half pounds per acre. The constituents of wheat are such that twenty-four bushels require the nitrogen of forty-five pounds of ammonia; that is, for the crop on a given surface, about five times as much as the rain furnishes. Plants doubtless gather directly from the nitrogen compounds of the air without help of the rain, and obtain a larger supply from the organic mould of good soils; but that all these sources together provide hardly enough is pretty clearly proved by feeding the roots of the plant with additional nitrogen compounds. On all but the richest soils, the suitable application of ammonia or nitrates causes a notable increase in the quantity of food-plants, and also causes an increased proportion of the nitrogenous constituents of plants. If nitrogen compounds could be laid down cheaply enough, it would augment the supplies of food and raiment, and the comfort of man, in no small degree.
Right here it comes to mind that uncombined nitrogen forms over three-fourths of the weight of the air—a provision of about eleven pounds on every horizontal square inch—and a question rises, "Why cannot the vital forces take hold on the pure element and use freely from its most lavish supply?" Well, because the universe exists. The stomach does not digest the carbon of charcoal; nor do the lungs take oxygen from water. To propose any alteration in the character of one of the sixty-three elements is to undertake the reconstruction of the universe. It is the character of nitrogen to refuse chemical combinations. Uncombined nitrogen is nowhere available for vital uses, to any appreciable extent. Filling perfectly its humble service in Nature as a diluent in the air, its qualification is to be inert and to remain changeless. Among the resources of life and in the marts of subsistence where its compounds rank high in value, nitrogen as a simple has no place at all.
This barrier between nitrogen and its compounds seems to hold firm from age to age. Out of the ocean of atmospheric nitrogen the plant selects the scattering molecules of nitrogen compounds and elaborates therefrom many nitrogenous substances. The animal elaborates some of these into other compounds. But in the final decay of products and tissues, and food not assimilated, the nitrogen of all returns again to ammonia—again in the aerial ocean, and again the resource of plants. If ammonia is oxidized in the air to nitric acid, the latter is deoxidized in the soil to nitrous acid and then to ammonia. All these compounds are very frail, and change most constantly, but together they hold the little stock of united nitrogen, losing little of it and gaining little for it, from epoch to epoch.
There are leakages, to and fro through this remarkable barrier, it is true, but they are so small that little is known of them, except that they show the strength of the barrier that limits them. On the one side, there is a little loss, by the liberation of traces of nitrogen in certain organic decompositions. Also, the explosive agents used by man in warfare and the arts result in the liberation of nitrogen—an expenditure of life-resources. On the other side, by the electrical disturbances of the atmosphere, traces of nitrogen are brought into union. The roll of thunder indicates the restoration of a modicum of that good material which was wasted for the roll of artillery. Again, it is believed that in organic decay under restricted conditions some measure of nitrogen is brought into union with nascent hydrogen. Chemical art has not done anything toward the appropriation of this obstinate element. Nothing nitrogenous can be made of nitrogen. The manufacturers depend on gatherings from the sparingly distributed nitrates of the earth. As machinists have dreamed of perpetual motion, sleeping chemists may dream of an invention to bring atmospheric nitrogen into use, that all the barren places may be made fertile, and the whole earth flourish as a garden of fatness. But for this dream to realize the proportions of a fair probability it is quite essential that chemistry should be well asleep.
The chief commodities bearing nitrogen are nitre or saltpetre (potassium or sodium nitrate), and ammonia. In Hindostan, the rich soil-mould, warm and alkaline, becomes thinly crusted with nitrate, which is gathered and brought to market as East India nitre. Gunpowder, gun-cotton, and nitro-glycerine, as well as chemical products, are made with it. In the War of 1812, America was thrown upon her own sources for gunpowder-material, and enough nitre was found in the cave-deposits of the Southwestern States. Then France was hemmed in by hostile armies, and had neither nitre nor cave-deposits, but it was after the work of "Lavoisier of immortal memory," and the government put trust in chemistry. Berthollet and the rest soon justified the trust in the perfection of the "nitre-plantations"—beds of farm-refuse with wood-ashes exposed to the air.
These products, soil-nitre and compost-nitre, and the ammonia obtained as a by-product in the manufacture of illuminating gas, serve their several purposes in the arts and applications of man, but their limited quantities do not warrant their addition to the soil for the increased growth of food. Now, unlike these common supplies, the earth possesses a special resource for nitrogen in combination, anomalous in being fully mineralized and remarkable in being both concentrated and extensive, a chain of mines full of nitre. On the Pacific coast of South America, extending from the fourth to the fortieth degree of south latitude, about 2,400 miles along the slope of the Andes to the sea, in Bolivia, Peru, and part of Chili, there has been found a line of deposits of sodium nitrate, the "Peruvian nitre." The beds are of variable thickness, covered by one to ten yards' depth of earth and half-formed sandstone. The dry soil of the most of this rainless country is pervaded, in some degree, with this deposit. The mummied remains of the old Peruvian people are embalmed with it by the earth in which they were buried; and its crystals glisten on those ghastly relicts which were presented in the Peruvian department of the Centennial Exhibition, and those brought to this country by Dr. Steere. It has been estimated that in the province of Tarapaca, within fifty square leagues, the quantity of the nitre is not less than 63,000,000 tons. The appropriation of this vast resource has been taken up rather slowly, but has much increased for ten or twelve years past. Vessels laden with it go to the coasts of manufacturing countries. At Glasgow the works devoted to the production of ordinary saltpetre from the nitre of Peru extend over acres of ground. In 1868, 100,000,000 pounds were used in Great Britain. As yet, it has been applied to the nourishment of crops only to a limited extent. But this seems to be its chief destination, and for this use it lies in the earth, a vast mine of wealth, for the disposal of coming generations. When multiplied population puts the sustaining power of the earth really to the test, this fund of sustenance on the Peruvian coast must come to outweigh in value the gold and silver mines of the Californian coast.
Of the several nitrogen compounds which nourish plants, ammonia yields the most immediately satisfactory results. And, of this fertilizing material, some well nigh mineralized deposits must be counted in with the earth's possessions. To take note of these ammoniacal materials, we have again to begin at Peru. Standing on the shores which front the nitre-beds, and looking westward upon the Pacific, there are seen, as we are told, the low patches of the Cincha Islands—islands which shine with the whiteness of a powdery covering, a loose deposit of considerable depth. A cargo of this substance was first taken to London in 1840, stored and advertised for sale, and after a while thrown into the Thames. A second cargo was tried as a fertilizer by an English farmer, and found to give such marvelous results that the shipping company made good haste to contract with the Peruvian Government for the entire deposit. This article, well known as guano, has held a settled value ever since its introduction, and, had it come into the hands of the alchemists, it would, very likely, have been presented as an elixir of vegetable life. Now, its worth is graded by analysis, and is indicated chiefly by the proportion of ammonia it contains.
The absence of rain will account, perhaps correctly, for the unusual retention of the soluble material characteristic of the guano of Peru; but the formation of the nitre-beds of that region is a problem in geological chemistry more difficult to determine. There are evidences of volcanic overflow and of marine deposition, and the alkali in the compound may have originated in either of these or other sources, but neither the volcano nor the sea could furnish the nitrogen of the compound. If not from organic accumulations, we seem to be referred to the air as the source of nitrogen, and left to conjecture the conditions and forces which could bring elemental nitrogen into union in so great a quantity. Without pursuing these inquiries, it may be permitted to cite a fact which seems entitled to consideration in the case, namely, the conditions for an unusual overflow of atmospheric ammonia in this region. It is fed by perpetual trade-winds—winds coming from the southeast across a wide continent of soil that is rich to rankness, and warmed under a vertical sun. Coming from the Atlantic and saturated with water, these winds gather the exhalations of a continent, and then, shedding their water on the Andes, leave their ammonia (it may be supposed) to find its way by some means to the valleys of the western slope.
Again, these same mountain-valleys of Peru may claim to have given the world still another token of unexampled sources of nourishment, in the growth of the cinchona-tree, bearing the richest stock of nitrogenous bases in the vegetable world. It seems, indeed, more than a coincidence that this narrow, rainless, wind-nurtured slope of land should send to all the earth three such eminent resources as Peruvian nitre, Peruvian guano, and Peruvian bark.
Another of the materials adequate for no more than the needs of life is phosphorus. This element so far differs from nitrogen that it is not found uncombined in Nature, and if separated by art it immediately enters into combination on exposure to the air. It occurs chiefly as phosphate of lime, taken from the mineral kingdom by plants and also by animals. The hard part of bone is about nine-tenths phosphate, and phosphorus is an element of molecules organized into muscle and nerve.
The proportion of phosphates in the crust of the earth below organic remains is very slight, insufficient for the support of the higher forms of vegetable or animal life. It has been concentrated and gathered into the soil by the selective agency of the organic world, as it continues to be concentrated from the soil by each individual plant, and from vegetable products by each individual animal. Nearly all the phosphorus accessible on the planet has been a constituent of living bodies. Its proportion in the soil is a main factor in the growth of cereal grains. Already, and with the stretch of land to the westward, bone-earth and phosphatic guanos are well known in American markets. When phosphates fail at the root of the plant, grain fails at the mill; and when, from waste at the mill, phosphates fail in the bread, the bones and the teeth fail in growing bodies. The improvidence that leaves excretory phosphates to be washed away to the salt sea, farther from the reach of life than they were in the primitive rocks, is an improvidence that prepares an inheritance of poverty for after-generations. And the ruthlessness that permits the purveyors of food to sift phosphates from the food of men does its part to enfeeble the present generation.
There remains to notice another representative of the adequate resources, potassium. The statements made as to the supply of phosphorus, with some reservation, become true for potassium. Certain of the rocks contain a proportion of it, but from insolubility this is slowly available, and is insufficient for the needs of higher organic life. The soils contain more, because the organic world has gleaned for the soil. Potassa and soda are two alkalies which replace each other in the laboratory at the convenience of the chemist, but, in the choosing of the living cell, one of these is always taken and the other left. We get potassa free from soda in the ash of a tree which grew in a soil having more soda than potassa. From sea-water, containing near 200 parts of soda to one of potassa, the sea-weeds furnish an ash having two to twenty times more potassa than soda. From the blood of man, having ten to fifteen times more soda than potassa, the muscles obtain a composition of six or seven times more potassa than soda.
This gleaning is good proof of the value of more, and the evidence is confirmed by the application of potassa as a fertilizer. The stock of potassa—which is used somewhat in the arts—is derived mainly from the gatherings of the organic world. The ash-wagon takes up the savings of the hearth. In France the washings of sheep's-wool are saved, and 160 pounds of good potassium carbonate are obtained from a ton of the wool. In the pioneer life of this country, the housewives have burned corn-cobs and taken the ash for baking-powder, eighty per cent, potassium carbonate, and preferable to the "dietetic saleratus" now used. Should the ash of the entire corn-crops of the United States be taken without loss, it is estimated that over 100,000,000 pounds of potassium carbonate would be obtained. In the salt-beds of Stassfurt, Germany, there is a good proportion of potassa, and the use of this supply has been steadily increasing, both as material in manufactures and as a fertilizer.
At the present time, the market value of the resources of life engages little general attention. There is a narrow branch of commerce, wherein the prices-current of the three elemental materials which we have taken as "adequate resources" are the values constantly under calculation in daily business. In this guild, one sells nitrogen at thirty cents, another offers phosphoric acid at five cents; and all parties have a tacit understanding that the values of nitrogen, phosphoric acid, and potassa, are to each other about as six, one and a half, and one, and that these are the only values to be considered. The technical terms of any profession or pursuit are jargon to the general ear. But hearing a man say that he "sold a hundred tons of rectified Peruvian at thirty-one cents for nitrogen, this morning," it is not so much as understood in what sort of business such jargon belongs.
Thinking of the multiplication of life and the waste of its resources, it seems that, in the time coming, the phrases that tell the rise and fall of value in commercial fertilizers may find some general recognition—may even have as much meaning for everybody as the terms of the gold-market and the silver-stocks.
It is only about a hundred years since man began to attain such definite knowledge of the components of matter as enables him to trace (we by no means say to understand) the transmutations of earth and air into tissues fit for life. Thirty-six years ago, Liebig commenced giving the people the first really systematic lessons upon the material resources of life. Seeing the value of a knowledge that goes below the surface of things, in 1852 he wrote his conviction that, "ere long, a knowledge of the principal truth of chemistry will be expected in the political economist and statesman, as it already is held indispensable to the manufacturer and physician." And, seeing the meanings and the mysteries that cluster around the primary forms of matter, he wrote at another time: "It is not the mere practical utility of these truths which is of importance. Their influence upon mental culture is most beneficial; and the views acquired by knowledge of them enable the mind to trace, in the phenomena of Nature, proofs of an infinite wisdom—for the unfathomable depths of which language has no expression."
- ↑ An address given before the Detroit Scientific Association, December 13, 1876.