Even so, the acceptance of cell theory was decades in coming. In hindsight, Virchow’s declaration that Omnis cellula e cellula (“all cells come from cells”) rings with the authority of E pluribus unum. At the time, it was one controversial view among many. But at the least, it would not be ignored. Rudolf Virchow would see to that.
Virchow, who became the most prominent of the cell theory pioneers, was brilliant, opinionated, often wrong-headed, and always in the middle of a dozen far-flung activities at once. He fought in the streets of Berlin in the Revolution of 1848; he was the first person to realize that cancer arose when a healthy cell turned rogue; he explored the ruins of Troy with Heinrich Schliemann; he vigorously opposed the theory of evolution (while claiming, in a half-hearted stab at good manners, that he did not mean to imply that Darwin and his followers were “stark fools and idiots”); he debunked the thrilling discovery of a Neanderthal skull and insisted that in fact it belonged to a modern man whose head someone had bashed in.
Controversy was meat and drink to Virchow. (Even his medical views reflected his combative nature; cancer was, for instance, “civil war between cells.”) A crusader and a political liberal, he led campaigns for clean water and safe food. For thirteen years he served in the German Reichstag. At one point Virchow so enraged Otto von Bismarck (by insisting that the military budget was too high) that the Iron Chancellor challenged him to a duel. Virchow, because he was the man challenged, had the right to pick the weapons. He chose sausages, one raw and infested with the organisms that cause trichinosis, for Bismarck to eat, and one safe and cooked, for himself. Bismarck withdrew his challenge.
The fight over cell theory was so prolonged partly because it made bold, sweeping claims and partly because it shone a spotlight on all the still unsettled questions about the existence of a “life force.” Theodor Schwann lined up proudly in the pro-mechanist, anti-vital force camp. Life was chemistry, he proclaimed, not auras and pixie dust. Living organisms followed “blind laws… like those of inorganic nature, which are established by the very existence of matter.” The way forward was clear. Don’t bother with “forces.” Find out how cells operate.
Find out, in particular, how sperm and egg cells operate. That goal, so elusive for so long, now seemed tantalizingly within reach. The first to grab the prize, in 1875, was a vain and grumpy German scientist working at a laboratory in Naples, Italy. Oscar Hertwig would not have figured on anyone’s list of likely sexual pioneers. Hertwig was frosty and forbidding, a small man with a neat beard, a bald head, a brilliant mind, and a vast disdain for virtually everyone except his brother, Richard, his coauthor on a host of scientific papers.
Many of those papers had to do with sea urchins, which themselves hardly leap to mind as creatures whose sex lives would repay close attention. But the pairing of the short-tempered scientist and the spiny sea creatures that thrived in the Bay of Naples would make biological history.
Hertwig had come to Naples to work at a newly established marine research station. Early on, the scientists there had not yet decided which creatures would make the best research subjects. Sea urchins rose to fame by accident, the marine counterparts of those aspiring actors who one day happened to serve drinks to a Hollywood mogul.
Local fishermen, who liked to gulp down sea urchin eggs, had provided the clue. The eggs were delicious (as admirers of uni can attest), and they were abundant (even from a single urchin). More important, they were see-through. You could put them under a microscope and see inside, almost as if you had found a peephole onto a construction site. Easy-to-harvest, transparent eggs were a scientific godsend, all the more so since you could dine on any extra experimental subjects you might have gathered.
On a spring day in 1875, Hertwig stared into his microscope at a sea urchin egg. For sea urchins, as for frogs, fertilization is external. Within the clear egg, the nucleus was distinct and unmistakable. Hertwig poked a drop of sea urchin semen near the egg. A tiny sperm cell pushed against the egg’s outer surface. Moments later the nucleus of the sperm cell came into view, inside the egg, like a message thrust inside a bottle. Somehow the nucleus of the sperm cell traveled through the giant egg, making its way toward the nucleus of the egg.
Suddenly the two nuclei were in contact, and then—before Hertwig’s eyes—the two nuclei fused into one. No one in history had ever seen the process of fertilization play out. Until Hertwig. The emergence of a single nucleus where there had been two, he wrote, in perhaps the only lapse into poetry in his long career, “arises to completion like a sun within the egg.”
HERTWIG NOTED, TOO, THAT A SINGLE SPERM FERTILIZES A single egg. The next order of business was sorting out what goes on when a fertilized egg divides. Here, again, Hertwig helped lead the way. He and his fellow embryologists spent hour upon hour watching, fascinated, as one cell became two, those two became four, and so on. All this was terribly complicated, even in principle, since each tiny cell included a vast array of motors and assembly lines working at top speed, a fully automated Boeing airplane factory churning away in a space the size of the dot over the letter i in the word impossible.
How could it be that each cell contained its own complicated factory? A fertilized egg started as a single cell. When that cell divided in two, did each of the two “daughter” cells receive half the original machinery? Or did all the machines and tools somehow replicate themselves and then move to their new homes?
Both alternatives seemed inconceivable. Machines that made copies of themselves? Machines that could be split in two but that kept working nonetheless? Worse yet, this was not a one-time miracle but an endless series of miracles. That first fertilized cell gave rise to billions upon billions of new cells, each of them unimaginably intricate and complex. And the cell choreography proceeded on two levels simultaneously. Cells interacted with one another in intricate ways, and at the same time, countless components inside each cell carried on a high-speed dance.
A zoologist named Hans Driesch, at Naples, devised an ingenious experiment to probe these changes. Driesch was snobbish and made a hobby of cultivating enemies, but no one disputed his scientific talent. His idea was to wait for a sea urchin embryo to divide into two cells and then tease those two cells apart, ever so gently. What would happen? Driesch kept watch. He might have guessed that both cells would die. Both lived. He might have guessed that they would live, and one cell would develop into half of an adult sea urchin and the other cell into the other half. They didn’t.
Instead, both cells grew into complete, intact, sea urchin adults, sound in mind and body. Driesch tried a variation, this time letting the embryo reach the four-cell stage and then tweaking it apart into four. Again, each of the four cells grew into a complete, functioning adult.
Observing was one thing, understanding another. Driesch’s findings set off a battle among biologists. (Driesch, always happy to outrage his peers, insisted that he had demonstrated the existence of the much-reviled “life force.” Life, he declared, contained mysteries that mere chemistry would never explain.) The story grew ever more complex. After several more cell divisions, individual cells lost the ability to give rise to entire organisms. Instead, cells specialized. In mammals, for instance, they took on the roles of bone and brain and heart and hair.
Unraveling the mysteries of cell growth and cell division would take decades; the saga played out over the first half of the twentieth century. The path of discovery would wend through genes and chromosomes and DNA, the landmarks in the history of modern biology. How those chromosomes governed identity and how they divvied themselves up, inside sperm and egg, and then how they spliced themselves together inside an embryo—all those discoveries lay ahead. The resolution of the mystery was a revelation: it wasn’t just the machinery in the cell that was passed along when a cell divided but instructions for constructing a whole array of new machines.
No one had dreamed of such a thing in 1677, when Antony van Leeuwenhoek leapt from his marriage bed, or in 1827 when Karl von Bae
r stared dumbfounded at an egg from a dog’s ovary, or in 1875 when Oscar Hertwig saw sperm and egg fuse into one. Those pioneering scientist-detectives had not solved the mystery themselves, but they had, at least, found the crucial clues that would enable their successors to close the case.
WE WILL NEVER KNOW WHAT ANCIENT ANCESTOR OF OURS FIRST asked where babies come from. Was it a new mother who had sweated and screamed as she pushed a baby into this harsh world? Or perhaps a sage elder staring into a fire and pondering unknowable riddles? Or an alert six-year-old watching her helpless, brand-new sister?
All of them, and countless of our forebears, would have looked around them at babies crying and nursing and gurgling and howling, and birds flying, and bugs scurrying, and wondered how those marvelous, maddening creatures came to be. Then a spark from the fire or a clap of thunder would have distracted them, and they would have stopped wondering and gone on with their lives.
So do we all. Familiarity drains the surprise from events that should make our jaws drop in disbelief. We think there is something magical about getting a rabbit out of a hat, the writer John Stewart Collis once observed. Not so. The real magic is getting a rabbit out of a rabbit.
ACKNOWLEDGMENTS
WE STROLL ALONG A PATH HACKED OUT WITH ENORMOUS LABOR BY OUR intellectual ancestors, but it is easy to neglect their achievements. The distinguishing feature of science, the anthropologist Max Gluckman remarked, is that “the fool of this generation can go beyond the point reached by the genius of the last generation.” It is vital to remember that they were geniuses, despite their eccentric decision to have lived so long before our own enlightened age. We are all prone to a kind of present-day provincialism; I have tried hard to guard against it. To venture into the past with these bewildered, determined explorers is to marvel at the expanse of the deep forest and to gain respect for those who managed, eventually, to find paths through it. I hope I have conveyed both their genius and their befuddlement.
I relied for guidance on the scientific explorers themselves and on accounts by a host of present-day scientists and historians. I’m especially grateful to the research staffs at the New York Public Library and the American Museum of Natural History. I owe special thanks, also, to Douglas Anderson, a historian I have never met. Anderson has put together a marvelous website called Lens on Leeuwenhoek. For anyone with an interest in the history of science, the site is indispensable.
I’m relieved, too, no longer to have to face the sneers of the postman, as he delivers yet another manual on seventeenth-century sexual practices.
Alison MacKeen, Ben Platt, and Leah Stecher provided wise advice on topics both tiny and sweeping. Beth Wright copyedited with a deft hand and a sharp eye. Flip Brophy, my agent and my friend, has more verve and pizzazz than a dozen lesser souls; she embraced and guided this project from Day 1. Over countless cups of coffee throughout the course of a twenty-year breakfast seminar, my friend Al Singer provided a model of the scientific mind at work. For his challenges, insights, and, above all, encouragement, I owe him an enormous debt.
My two sons, one a novelist and the other an editor, weighed in on countless decisions. No writer could have better allies.
Lynn deserves more thanks than I can put in words.
LYNN GOLDEN
EDWARD DOLNICK is the former chief science writer for the Boston Globe and the author of The Clockwork Universe, The Forger’s Spell, Down the Great Unknown, The Rush, Madness on the Couch, and the Edgar Award–winning The Rescue Artist. He splits his time between Virginia and New York City.
ILLUSTRATION CREDITS
Figure 3.1: Copyright © The Trustees of the British Museum 27
Figure 3.2: Copyright © The Trustees of the British Museum 31
Figure 4.1: British Library 39
Figure 4.2: Royal Collection Trust / Copyright © Her Majesty Queen Elizabeth II 2016 44
Figure 4.3: Copyright © Bayonne, France, Musée Bonnat-Helleu / A. Vaquero 46
Figure 4.4: Royal Collection Trust / Copyright © Her Majesty Queen Elizabeth II 2016 49
Figure 5.1: Collection Amsterdam Museum 53
Figure 5.2: Andreas Vesalius, De humani corporis fabrica, 1543 55
Figure 5.3: Paul Bock / Alamy 61
Figure 6.1: Left, Anthony van Dyck, Bridgeman Images; right, Mary Evans Picture Library / Alamy 66
Figure 8.1: Regnier de Graaf, Philosophical Transactions of the Royal Society, 1669 91
Figure 8.2: Nicolaus Steno, Elementorum Myologiae Specimen, 1667 94
Figure 10.1: Robert Hooke, Micrographia, 1665 108
Figure 11.1: Cambridge University Press 116
Figure 13.1: National Gallery of Art, Gift of Mrs. Lessing J. Rosenwald 140
Figure 13.2: Jan Swammerdam, De respiratione, 1667 142
Figure 14.1: Copyright © 2009–2016 by Douglas Anderson 150
Figure 14.2: Nicolaas Hartsoeker, Essai de dioptrique, 1694 154
Figure 14.3: R. & L. Perry & Co., The Silent Friend, 1847 158
Figure 15.1: Wellcome Library 164
Figure 15.2: Ambroise Paré, On Monsters and Marvels, 1573 167
Figure 16.1: Digital image courtesy of the Getty’s Open Content Program 174
Figure 19.1: Creative Commons 218
Figure 22.1: New York Public Library 242
Figure 22.2: New York Public Library 244
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