by Will Durant
Philip Miller, in 1721, gave the first known account of plant fertilization by bees. He removed the “apices” of certain flowers before they could “cast their dust”; yet the seed of these apparently emasculated flowers ripened normally. Friends questioned his report; he repeated the same experiment more carefully, with the same result.
About two days after, as I was sitting in my garden, I perceived in a bed of tulips near me some bees very busy in the middle of the flowers; on viewing them I saw them come out with their legs and bellies loaded with dust, and one of them flew into a tulip that I had castrated; upon which I took my microscope, and examined the tulip he flew into, and found he had left dust enough to impregnate the tulip; which, when I told my friends, … reconciled them again.… Unless there be provision to keep out insects, plants may be impregnated by insects much smaller than bees.90
Josef Kölreuter, professor of natural history at Karlsruhe, made a special study (1760 f.) of cross-fertilization and the physiochemistry of pollination. His sixty-five experiments had immense influence on agriculture in several continents. He concluded that crossing is fruitful only in closely related plants; but when it is successful the hybrids grow more rapidly, flower sooner, last longer, and produce young shoots more abundantly than the original varieties, and are not weakened by developing seed. Konrad Sprengel showed (1793) that cross-fertilization—usually by insects, less often by wind—is common within a species; and he argued, with warm teleological conviction, that the form and arrangement of parts in many flowers is designed to prevent self-fertilization. Johann Hedwig opened up a new field of research by studying the reproductive process in cryptogams (1782). Between 1788 and 1791 Joseph Gärtner of Württemberg issued, in two installments, his encyclopedic survey of the fruit and seeds of plants; this became the groundwork of nineteenth-century botany.
In 1759 Caspar Friedrich Wolff, in his Theoria Generationis, enunciated a theory of plant development usually ascribed to Goethe:
In the entire plant, whose parts we wonder at as being at first glance so extraordinarily diverse, I finally perceive and recognize nothing beyond leaves and stem, for the root may be regarded as a stem.… All parts of the plant, except the stem, are modified leaves.91
Meanwhile a major figure in eighteenth-century science, Stephen Hales, explored the mystery of plant nutrition. He was another of those many Anglican clergymen who found no hindrance in their flexible theology to the pursuit of science or scholarship. Though accepting divine design, he made no use of this in his scientific inquiries. In 1727 he published his results in one of the classics of botany, Vegetable Staticks, … an Essay towards a Natural History of Vegetation. His preface explained:
About twenty years since, I made several haemostatical experiments on dogs, and six years afterwards repeated the same on horses and other animals, in order to find out the force of the blood in the arteries [our “systolic blood pressure”].… At which time I wished I could have made the like experiments to discover the force of the sap in vegetables; but despaired of ever effecting it till, about seven years since, I hit upon it while I was endeavoring by several ways to stop the bleeding of an old stem of a vine.92
Harvey’s discovery of the circulation of the blood in animals had led botanists to assume a similar circulatory movement of liquids in plants. Hales disproved this supposition by experiments that showed a tree absorbing water at its branches’ ends as well as by its roots; water moved inward from branches to trunk as well as from trunk to branches; and he was able to measure the absorption. Sap, however, moved up from roots to leaves through the pressure of sap expanding in the roots. The leaves absorbed nourishment from the air.
At this point the ingenious Priestley illuminated the problem by one of the most brilliant discoveries of the century—the nutritive absorption, by the chlorophyll of plants in sunlight, of carbon dioxide exhaled by animals. He described this part of his work in the first volume (1774) of his Experiments and Observations:
I took a quantity of air, made thoroughly noxious by mice breathing and dying in it, and divided it into two parts; one of which I put into a phial immersed in water; and in the other [which was] contained in a glass jar standing in water, I put a sprig of mint. This was about the beginning of August, 1771, and after eight or nine days I found that a mouse lived perfectly well in that part of the air in which the sprig of mint had grown, but died the moment it was put into the other part of the same original quantity of air, and which I had kept in the very same exposure, but without any plant growing in it.
After several similar experiments Priestley concluded that
the injury which is continually done to the atmosphere by the respiration of such a number of animals, and the putrefaction of such masses of both vegetable and animal matter, is in part at least repaired by the vegetable creation. And notwithstanding the prodigious mass of air that is corrupted daily by the abovementioned causes, yet, if we consider the immense profusion of vegetables upon the face of the earth, … it can hardly be thought but that it may be a sufficient counterbalance to it, and that the remedy is adequate to the evil.93
In 1764 the Dutch biologist Jan Ingenhousz, domiciled in London, became acquainted with Priestley. He was impressed by the theory that plants purified the air by absorbing, and thriving on, the carbon dioxide exhaled by animals. But Ingenhousz found that plants do not perform this function in the dark. In Experiments on Vegetables (1779) he showed that plants as well as animals exhale carbon dioxide, and that their green leaves and shoots absorb this, and exhale oxygen, only in clear daylight. So we remove flowers from hospital rooms at night.
The light of the sun, and not the warmth, is the chief reason, if not the only one, which makes the plants yield their dephlogisticated air [i.e., oxygen].… A plant … not capable … of going in search of its food must find, within … the space it occupies, everything which is wanted for itself.… The tree spreads through the air those numberless fans, disposing them … to incumber each other as little as possible in pumping from the surrounding air all that they can absorb from it, and to present … this substance … to the direct rays of the sun, on purpose to receive the benefit which that great luminary can give it.94
This, of course, was only a partial picture of plant nutrition. Jean Senebier, a Geneva pastor, showed (1800) that only the green parts of plants are able to decompose the carbon dioxide of the air into carbon and oxygen. In 1804 Nicolas Théodore de Saussure, son of the Alpine explorer, studied the contribution of the soil, in water and salts, to the nourishment of plants. All these studies had vital results in the epochal development of soil fertility and agricultural production in the nineteenth and twentieth centuries. Here the vision and patience of scientists enriched the table of almost every family in Christendom.
VIII. ZOOLOGY
1. Buffon
The greatest naturalist of the eighteenth century was born at Mont-bard in Burgundy (1707) to a councilor of the Dijon Parlement. Dijon was then an independent center of French culture; it was a competition proposed by the Dijon Academy that gave an opening to Rousseau’s revolt against civilization and Voltaire. Georges Louis Leclerc de Buffon studied at the Jesuit college in Dijon. There he became attached to a young Englishman, Lord Kingston, with whom, after graduation, he traveled in Italy and England. In 1732 he fell heir to a considerable property, bringing him some 300,000 livres a year; now he was free to abandon the law, for which his father had intended him, and to indulge his interest in science. On a hill at the end of his garden at Montbard, two hundred yards from his house, he built a study in an old tower called the Tour de St.-Louis. Here he secluded himself from six o’clock every morning, and here he wrote most of his books. Excited by the story of how Archimedes burned a hostile fleet in the harbor of Syracuse by a series of burning mirrors, he made eight experiments, combining at last 154 mirrors, and thereby setting fire to planks of wood 150 feet away.95 For a time he hesitated between “natural history” and astronomy; in 1735 he translate
d Hales’s Vegetable Staticks, and grounded himself in botany; but in 1740 he translated Newton’s Fluxions, and felt the seduction of mathematics; Euclid joined Archimedes in his pantheon.
In 1739 he was appointed director (intendant) of the Jardin du Roi, and he moved to Paris. Only then did he make biology his main enterprise. Under his supervision the royal botanical garden was enriched with hundreds of new plants from every quarter of the earth. Buffon admitted to the Jardin all interested students, and made it a school of botany. Later, leaving it in good hands, he returned to Montbard and his Tour de St.-Louis, and began to organize his observations into the most famous scientific book of the century.
The first three volumes of the Histoire naturelle, générale et particulière, were published in 1749. Paris was in a mood to learn science, and now that it found geology and biology dressed in stately, lucid prose, and illustrated with alluring plates, it made these volumes almost as popular as Montesquieu’s L’Esprit des lois, which had appeared only a year before. Aided in botany by the brothers Antoine and Bernard de Jussieu, and in zoology by Louis Daubenton, Guéneau de Montbéliard, and others, Buffon proceeded to add volume upon volume to his opus; twelve more were sent forth by 1767; nine more, on birds, in 1770–83; five on minerals in 1783–88; seven on other topics in 1774–89. After his death (1788) his unpublished manuscripts were edited and issued in eight volumes (1788–1804) by Étienne de Lacépède. All in all, the Histoire naturelle finally comprised forty-four volumes, which had consumed more than one life in their preparation, and over half a century in their publication. Day after day Buffon rose early, walked to his tower, and advanced step by step to his goal. Having survived some sexual escapades in his youth, he seems to have put women out of his life until 1752, when, aged forty-five, he married Marie de Saint-Belon. Though he made no pretense to marital fidelity,96 he learned to love his wife, as many Frenchmen do after adultery, and her death in 1769 darkened his remaining years.
The Histoire naturelle undertook to describe the heavens, the earth, and the whole known world of plants and animals, including man. Buffon sought to reduce all this wilderness of facts to an order and law through the conceptions of universal continuity and necessity. We have noted his theory of the planets as fragments broken from the sun by collision with a comet, and his “epochs of nature” as stages in the evolution of the globe. In the world of plants he rejected Linnaeus’ classification by sexual organs as too arbitrary, inadequate, and rigid. He accepted the Linnaean nomenclature reluctantly, and on condition that the names be placed on the underside of the labels attached to the plants in the Jardin.97 His own classification of animals was absurd, but confessedly provisional; he arranged them by their utility to man, and so began with the horse; later, prodded by Daubenton, he adopted a classification by distinctive characteristics. His professional critics laughed at his classifications, and questioned his generalizations, but his readers rejoiced in his vivid descriptions and the lordly breadth of his views.
He helped to establish anthropology by studying the variations of the human species under the influence of climate, soil, institutions, and beliefs; such forces, he thought, have varied the color and features of races, and have generated diversity of manners, tastes, and ideas. One of his boldest hypotheses was that there are no fixed and unchangeable species in nature, that one species melts into the next, and that science, if matured, could ascend step by step from supposedly lifeless minerals to man himself. He saw only a difference of degree between the inorganic and the organic.
He noted that new varieties of animals have been formed by artificial selection, and argued that similar results could be produced in nature by geographical migration and segregation. He anticipated Malthus by observing that the limitless fertility of plant and animal species repeatedly places an intolerable burden upon the fertility of the soil, leading to the elimination of many individuals and species in the struggle for existence.
Species less perfect, more delicate, heavier, less active, less well armed, have already disappeared, or will disappear.98 … Many species have been perfected, or made degenerate, by great changes in land or sea, by the favors or disfavors of Nature, by food, by the prolonged influences of climate, contrary or favorable … [and] are no longer what they formerly were.99
Though he conceded a soul to man, he recognized in the human body the same sensory organs, nerves, muscles, and bones as in the higher beasts. Consequently he reduced “romantic love” to the same physiological basis as in the sexual magnetism of animals; indeed, he reserved the poetry of love to his eloquent descriptions of matings and parentage in birds. “Why,” he asked, “does love make all other beings happy, but bring so much un-happiness to man? It is because only the physical part of this passion is good; the moral elements in it are worth nothing.”100 (Mme. de Pompadour reproved him for this passage, but quite amiably.)101 Man, Buffon concluded, “is an animal in every material point.”102 And
if we once admit that there are families of plants and animals, so that the ass may be of the family of the horse, and that one might differ from another only by degeneration from a common ancestor, … we might be driven to admit that the ape is of the family of man, that he is but a degenerate man, and that he and man have had a common ancestor.… If the point were once gained that among animals and vegetables there had been … even a single species which had been produced in the course of direct descent from another species, … then there is no further limit to be set to the power of Nature, and we should not be wrong in supposing that with sufficient time she could have evolved all other organic forms from one primordial type.
Then, suddenly remembering Genesis and the Sorbonne, Buffon added: “But no! It is certain from divine revelation that all animals have alike been favored with the grace of an act of direct creation, and that the first pair of every species issued full-formed from the hands of the Creator.”103
Nevertheless the Syndic of the Sorbonne, or Faculty of Theology at the University of Paris, notified Buffon (June 15, 1751) that some parts of his Histoire naturelle contradicted the teachings of religion, and must be withdrawn—especially his ideas on the great age of the earth, the derivation of the planets from the sun, and the assertion that truth is derived only from science. The author smilingly apologized:
I declare that I had no intention of contradicting the text of Scripture; that I believe most firmly all that is therein related about creation, both as to the order of time and as to matter of fact. I abandon everything in my book respecting the formation of the earth, and generally all that may be contrary to the narrative of Moses.104
Probably Buffon, aristocrat, felt that it would be bad manners to quarrel publicly with the faith of the people, and that an unmollified Sorbonne might interfere with his great plan; in any case his work, if completed, would be an illuminating commentary on his apology. The educated classes saw the smile in his retraction, and noted that his later volumes continued his heresies. But Buffon would not join Voltaire and Diderot in their attack upon Christianity. He rejected the claim of La Mettrie and other materialists to have reduced life and thought to matter in mechanical motion. “Organization, life, soul, are our real and proper existence; matter is only a foreign envelope whose connection with the soul is unknown, and whose presence is an obstacle.”105
The philosophes, however, welcomed him as a powerful ally. They noted that his enthusiasm and apostrophes were directed to an impersonal Nature, creative and fecund, rather than to a personal deity. God, in Buffon as in Voltaire, sowed the seeds of life, and then allowed natural causes to do all the rest. Buffon rejected design in nature, and inclined to a Spinozistic pantheism. Like Turgenev he saw reality as a vast cosmic laboratory in which nature, through spacious eons, experimented with one form, organ, or species after another. In this vision he came to a conclusion apparently contradicting his criticism of Linnaeus; now it was the individual that seemed unreal, and the species was the relatively lasting reality. But the contradiction coul
d be resolved: species, genus, family, and class are still only ideas, constructed by the mind to give some manageable order to our experience of the confusing profusion of organisms; individuals remain the sole living realities; but their existence is so brief that to the philosopher they appear as merely flickering impressions of some larger and more lasting form. In this sense Plato was right: man is real, men are fleeting moments in the phantasmagoria of life.
Buffon’s readers enjoyed these dizzy visions, but his critics complained that he lost himself too recklessly in generalizations, sometimes sacrificing accuracy in details. Voltaire laughed at his acceptance of spontaneous generation; Linnaeus scorned his work on plants; Réaumur had no respect for Buffon on bees; and zoologists were amused by his classification of animals according to their usefulness for man. But everyone applauded his style.
For Buffon belongs to literature as well as to science, and only integrated history can do him justice. Rarely had a scientist expressed himself with such stately eloquence. Rousseau, himself a master of style, said of Buffon: “As a writer I know none his equal. His is the first pen of his century.”106 Here the judicious Grimm, though Rousseau’s foe, agreed with him: “One is justly surprised to read discourses of a hundred pages written, from the first line to the last, always with the same nobility of style and the same fire, adorned with the most brilliant and the most natural coloring.”107 Buffon wrote as a man freed from want and dowered with time; there was nothing hurried in his work, as often in Voltaire; he labored as carefully with his words as with his specimens. As he saw a Leibnizian law of continuity in things, so he established one in style, smoothing every transition, and ordering all ideas in a sequence that made his language flow like a broad, deep stream. Whereas the secret of Voltaire’s style was the quick and lucid expression of incisive thought, Buffon’s method was a leisurely ordering of spacious ideas vitalized with feeling. He felt the majesty of nature, and made his science a song of praise.
