A Garden of Marvels Read online

  The Bologna obscurantists do not deny the truth of their colleague’s findings, but dismiss them nonetheless. It is not possible, they say, that structures so tiny they can only be seen through a microscope could have anything to do with how a body operates. No more would detailing the delicate embroidery on a handkerchief tell you anything essential about how a handkerchief functions. Professor Sbaraglia points out that although Galen promoted the investigation of the shapes, positions, and connections of major organs, he believed that examining the smaller parts was useless. Galenic cures have nothing to do with remedying the malfunction of organs, which is why Professor Mini declares “anatomy does not contribute to medicine.” Besides, Galen, the world’s greatest physician, did not use microscopes, ergo, microscopial information is irrelevant to medicine. In the years ahead, Mini will urge students to stop dissecting since it is “performed only by persons of little talent and little brain.”

  Malpighi participated in the disputatio when he was younger, but now he often attends without wearing his medical robes and simply listens. (Because his family had not lived in Bologna for the requisite number of generations, he was technically ineligible to lecture in the rotuli, although if his colleagues hadn’t detested him, no doubt an exception would have been made.) Today, he hears Paltroni discuss the papillae, which are the tiny, sensory bumps on the cutis, an inner layer of skin that Malpighi had discovered. Paltroni immediately falls into trouble. One professor argues that “there is no cutis in the glans penis and [yet] it is sensitive; ergo, the cutis is not the external organ of touch.” Sbaraglia declares that “the brain is the organ that gives indications of tangible qualities; ergo, the cutis is not the organ of touch.” As Paltroni explains the function of other organs that Malpighi has written about, the professors challenge him scornfully. How ludicrous to think that kidneys filter blood or that muscles move by contraction rather than by “inclination.”

  There has long been an additional component, a personal one, to Sbaraglia’s animus for Malpighi. In 1659, Malpighi’s brother, Bartolommeo, stabbed Sbaraglia’s older brother to death during an argument on the dark streets of Bologna. Salt in the stiletto wound: Although Bartolommeo was at first condemned to death and all his property was to be confiscated, eighteen months later the court pardoned him and required a payment of only ninety-nine ducats. At the time of Paltroni’s lecture, Sbaraglia and company’s antagonism has been spurred by their colleague’s burgeoning international fame. Henry Oldenburg, secretary of the Royal Society, having read Malpighi’s work on the anatomy of lungs, had written to ask if the author had any works on any other subject—animal, mineral, or vegetable—he could send. The silkworm, he mentioned, was of particular interest to the Society. Malpighi, flattered and delighted to have contact with sympathetic intellects, immediately took up the subject, and spent the next year anatomizing all stages of the bombyce, from larva to moth. His sixty-thousand-word, illustrated opus, the first-ever exploration of a dissected invertebrate, dazzled the Society members. They had been amazed by Robert Hooke’s close-up portrait of a flea, but this work was vastly more informative. Aristotle had written—and no one had looked for any evidence to the contrary—that insects have no internal organs, except perhaps a stomach and a gut, and that they didn’t breathe. Malpighi demonstrated that the interiors of insects are filled with organs, including tracheae that have openings in their abdomens and conduct air throughout their bodies, as well as tubes that conduct fluids and emit urine. His work shattered the ancient model. The Society immediately voted to publish his Dissertatio Epistolica de Bombyce and make its author a Fellow.

  Still, of all the possible subjects that Oldenburg offered, why had Malpighi chosen an insect? No doubt he had been eager to make sure his correspondent would be pleased with his work, but the dissection of a silkworm also happened to fit his own research agenda. For all the information he had gathered in recent years on the anatomy of human and animal organs, he felt he had made little progress in understanding how they worked. Examining the intricacies of their insides did not mean understanding their “connection, movement, and use.” He was disappointed that his investigations had added nothing to the practice of healing, a fact that seemed to give substance to his colleagues’ charges. He chose to analyze the silkworm because, in part, he hoped it would prove to be a simpler, more comprehensible model of an animal.

  To his disappointment, his investigation of silkworm anatomy shed no light on human anatomy or illness. The connections among organs were still obscure, and before he finished de Bombyce, he decided he needed to try even simpler beings. He had been pondering plants as analogues for animals for a number of years. The hollow tubes in a broken stem of a chestnut tree reminded him of the tracheae of animals, and he thought the tough fibers of the stems might reveal the secrets of bones and growth. In 1668, he began spending most of his time at his country property outside Bologna, where he had an endless supply of plants. Despite having spent that spring sick in bed—he suffered from kidney stones and recurrent fevers, probably caused by the malaria endemic in the region—on November 1, 1671, Malpighi sent a preliminary study to Oldenburg on the anatomy of plants. “If you tell me that my work is superfluous,” he wrote in his cover letter, “I shall permit my body, perpetually exhausted with sickness, to rest. But if you consider it not entirely useless, I shall spend the rest of my life perfecting it.”

  Oldenburg responded immediately, thanking him for what he titled Anatome plantarum idea. The Society has “embraced [the work] with greatest pleasure,” he reported, and urged him to continue his research “without hesitation” and to send an enlarged and illustrated manuscript. Malpighi received this letter three months later, at the end of January 1672, just at the time he was sitting in the anatomy theater enduring the attacks on Paltroni. “To the kindness of the Royal Society and your own good offices,” he replied, “I acknowledge an obligation so great that I can find no words to express it.” Harassed by his colleagues and ill, he abandoned Bologna for the country, and promised to devote himself to finishing the manuscript, confident that he would make a unique contribution to science and medicine.

  five

  Inside a Plant

  What Oldenburg did not tell Malpighi in that letter was that the Royal Society had already received another excellent preliminary work on the anatomy of plants, submitted by one Nehemiah Grew, a twenty-nine-year-old English country medical practitioner. Perhaps Oldenburg, a diplomat by training, chose to give his suffering Italian correspondent time to enjoy unalloyed good news. Maybe he thought that if Malpighi started the project, he would be less likely to abandon it, to the detriment of science and the Society. In any case, after dispatching the letter, Oldenburg and other Fellows then had to tend to Grew, who, on learning of the Italian’s work, promptly offered to withdraw from the field. Grew was overawed. He didn’t even own a microscope, and Malpighi’s anatomical studies were renowned.

  Nehemiah Grew had grown up in the town of Coventry, about a hundred miles northwest of London. His father, Obadiah, had attended Oxford and was then ordained in the Church of England and granted a living in Coventry. When the Civil War broke out in 1642, Obadiah sided with the parliamentary party, which had a stronghold in the town, and became a leader in the opposition. After the restoration of the monarchy and the authority of the Anglican Church in 1661, his conscience would not allow him to swear the religious oaths required under the Act of Uniformity, and he had to resign his living. (Four years later, such “ejected” ministers were required to live at least five miles from their former parishes, and he had to leave the town altogether.) His son was lucky to have finished his undergraduate degree at Cambridge just before Nonconformists were barred from the national universities.

  Nehemiah returned to Coventry to live with his father, but found himself in a difficult spot. His Cambridge education had prepared him for a Nonconformist ministry, but now a clerical career promised only persecution. Other university-educated Nonconformists, in
cluding his older half brother, Henry Sampson, were heading for medicine, having discovered that people tend to overlook the fine points of a doctor’s beliefs if they like the medical care. Qualifying to practice medicine, though, was another matter. A physician might earn a fine living in London, but the city required a university medical degree to practice. A man didn’t need a degree to practice in the countryside, but he would need the approval of the relevant Anglican bishop, so that avenue was closed, too. Then there was the Leiden route. The University of Leiden in the Netherlands was nonsectarian and drew men—including Henry Sampson—from across Europe whose minority religious views, whether Catholic, Protestant, or Jewish, denied them access to their national institutions. (Women were unwanted everywhere.) If Grew had already been competent, he could simply have paid a fee, taken an exam, submitted a paper, and returned with a degree in a few weeks. But he was an utter novice.

  Finally, it was possible to practice without a degree or a license. Unlicensed practitioners provided much of the medical care in rural England, and in reality there was little difference between the treatments of the officially sanctioned physicians and unauthorized healers. Both ordered the phlebotomies, “vomits,” and purges advised by Galen (whose work had been translated into English); both prescribed the folk remedies made from local herbs. Neither knew how to cure infectious or most other serious diseases. Neither the Galenist’s enema nor the healer’s salve of chamomile, marigold, and earthworms could cure malaria or rickets.

  Nehemiah chose this last option. It must have been a painful choice for a Cambridge-educated man, but these were harsh times. He seems to have informally apprenticed himself and studied on his own, and put out his shingle in Coventry. He accumulated patients, thanks to his kindly, down-to-earth personality and a humble piety that considered nature, including its human inhabitants, as a reflection of God’s wisdom. The divinely created human body, he wrote, was able not only “to prevent, but also to cure or mitigate diseases,” and so he treated his patients cautiously, giving the body time to work its own solution.* “In most wounds,” he wrote, “if kept clean . . . the flesh will glew together with its own native balm.” He was dubious about the value of the medications of his time, commenting wryly that “if you turn over an herbal [a book of plant-based remedies], you shall find almost every herb to be good for every disease.” In any case, he had found that apothecaries’ ingredients were often counterfeit. Expensive “red oyl of scorpions” in apothecaries’ shops, he wrote, was nothing more than tinted vegetable oil.

  In 1664, having started a small garden by his house, no doubt so he could have a supply of genuine ingredients for medications, he decided to study plants to see if he might add to the storehouse of knowledge “which the best botanicks had left bare and empty.” He cut open stems, flowers, and roots, looked carefully—at this period, with only an unaided eye or perhaps a hand lens—and drew what he saw. He was in no hurry and had no thought of publication; he was simply hoping to reveal more of God’s magnificent natural world, revering Him by appreciating His works. In 1668, his half brother, by then a well-connected London physician, encouraged him to write up his findings, and two years later, Sampson passed on the work to Oldenburg, who shared it with Wilkins and others. On May 11, 1671, the Royal Society licensed for publication Anatomy of Plants Begun, which summarized his preliminary discoveries and included a proposal for a program of research. In November, Dr. Grew (at Sampson’s insistence, he had recently gone to Leiden to get his medical degree) traveled from Coventry to London and was admitted as a Fellow of the Royal Society.

  News of Malpighi’s similar proposal reached Grew shortly after he returned home, and greatly disconcerted him. Wilkins urged him to consider that there was room for more than one investigator into such a novel subject. (Grew was probably echoing Wilkins when he later wrote to Malpighi that “although [one man] may have no mind to deceive, yet it is more likely for one, than for two, to be deceived.”) Wilkins also began to solicit funds so that Grew, who depended on the income of his practice, could pursue his research. With the promise of £50 per year, Grew moved to London. The Royal Society’s financial support over the next five years would prove inconsistent and often in arrears, but he worked on. Fortunately, he had a nearly Panglossian optimism and an unshakable commitment to completing his work.

  Between 1671 and 1679, the Society published Grew’s beautifully illustrated essays on roots, trunks, flowers, fruits, and seed development. It also published the two volumes of Malpighi’s Anatome Plantarum, the fulfillment of Anatome Plantarum Idea. Malpighi had Grew’s work translated into Latin, and the two men corresponded amiably if sporadically. (A regular correspondence was difficult; it could take several months for a letter to travel from London to Bologna.) In 1682, the Society issued Grew’s masterwork, which incorporated all his essays plus insights he gathered from—and credited to—Malpighi. We can consider Grew’s Anatomy of Plants to be a compendium of the work of the two men, a sort of textbook or encyclopedia of the subject.

  The Anatomy was illustrated with dozens of morphological and microscopic drawings. Grew uncovered and drew fine details in flowers, down to the ovules inside ovaries; leaves, down to the tiny holes on their undersides, called stomata; roots, down to the microscopic root cap; and details of the internal structures of trunks and stems. He dissected his specimens in a distinctly modern fashion, cutting them longitudinally, obliquely, and transversely to display an astonishing architecture never seen before, and to demonstrate that from species to species and specimen to specimen, that architecture is consistent.

  In modern terms, the two men discovered that there are two basic kinds of tissue in plants. One is parenchyma (pa-REN-kuh-ma), the spongy, living tissue in leaves, flowers, fruit, and the bulk of a stem. (In a stem, the parenchyma is called the pith.) Parenchyma is made of masses of living cells and looks under the microscope, as Grew wrote, like “the froth on beer.” The second kind of tissue looks threadlike and is composed of two types: fibers and vessels (meaning tubes or ducts). The fibers include collenchyma and sclerenchyma whose cells have thickened walls that provide structural support for a plant, like the studs in a wood-frame house. Collenchyma is made of living cells that form, for example, the strings in celery. Sclerenchyma is made of dead cells, and forms the fibers we prize in flax for making linen and in hemp for making rope.

  Vessels are strings of cells that have an opening at top and bottom and fit together like sections of pipe, so that they conduct fluids. Grew saw that vessels run vertically through the parenchyma of trunks, stalks, and stems. In trees, they encircle the perimeter of the branch or trunk, just under the bark. In many other nonwoody plants, like maize and wheat, they are randomly distributed throughout the parenchyma. Neither Grew nor Malpighi could see that what they perceived as a single vessel is actually a bundle of vessels, or vascular bundles. Each bundle contains two different kinds of conduits, the water-carrying xylem and the sugar-carrying phloem (which we’ll get to momentarily). Looking at the boundary between bark and wood, Grew saw that in woody species, every spring a new layer of sap-carrying vessels, which he called “lympheducts,” develops. By the end of the year, the new layer “losing its original softness by degrees . . . turned into a dry and hard ring of perfect wood.” Wood, he realized, is “nothing but a mass of antiquated” lympheducts. Each year a new layer grew and lignified, adding a ring to the wood and increasing the tree’s girth. What he could not see was that the new growth comes from the cambium, the layer that citrus grafters have to match between the rootstock and bud.

  Nehemiah Grew’s illustration of the stalk of a thistle reveals the basic anatomy of woody plants. In this re-labeled version of the drawing, (A) is the protective phloem fiber cap, (B) is the phloem, and (C) is the xylem. In non-woody (i.e., herbaceous) plants, vascular bundles of xylem and phloem are distributed throughout the parenchyma.

  Both men also noted the narrow rows of cells we call medullary rays, which run at right angles thro
ugh the rings of wood from the cambium to the pith. (They couldn’t understand their function, but we know the rays transport toxic tannins and other waste products of the living cells at the trunk’s periphery into its dead interior where they are safely sequestered. Admire the rich colors of the heartwood of mahogany and walnut? You’re looking at the contents of the trees’ waste disposal system.) As for the development of new branches, Sir Kenelm Digby, a founding member of the Royal Society, had written authoritatively that juices sent up from the earth accumulate at the top of a tree, where increasing pressure creates a breach in the bark, and “so a new piece . . . is thrust out and begins on the sides, which we call a Branch.” Grew disproved this theory. When he dissected axillary leaf buds, he revealed a small miracle. Beneath the outer scales, he found the coming spring’s leaves, tiny and intricately folded, waiting for the stem growth that would slide them toward the sun.

  Brussels sprouts are axillary leaf buds, meaning they develop in the angle between the leaf stem and the plant stalk. If not picked, a Brussels sprout will grow into a branch and develop leaves and flowers. (When you eat a Brussels sprout, you are eating, botanically speaking, an embryonic branch.)

  Grew and Malpighi also realized that trunks grow taller and stems grow longer only at their tips, meaning that plant growth is fundamentally different than animal growth. If children grew like plants, every year their fingers would send out new joints from each fingertip. In fact, initials carved by teenage lovers into a sapling’s bark will still be at eye level when the tree is sixty feet tall and the lovers are on their second marriages. And it means that if you plant a sapling whose lowest branches emerge only a few feet off the ground, and you want to stroll under the tree one day, you had better cut off the branches because the trunk will never carry them higher.