Life's Ratchet: How Molecular Machines Extract Order from Chaos (7 page)

Epigenesis, by contrast, claimed that unformed matter was shaped into a complex living being during embryonic development. This also posed problems. What directed this development? How could a lump of undifferentiated matter turn into a chicken or a frog? Mechanism could not explain how such spontaneous self-organization would work, even in principle. Epigenesis was the favorite of the vitalists. The formation of biological complexity from unformed matter was a task equal only to their beloved vital force—indeed, it was proof that such a force had to exist.

The dissatisfaction with mechanism led to a more romantic philosophy of life. Proponents of
Naturphilosophie
(“nature philosophy”) saw a vital force acting throughout nature, striving to bring about higher and higher forms of being—a notion that sounded very much like animism. However, many German biologists were averse to explanations that seemed to invoke supernatural forces. While they allowed that a vital force was necessary, this vital force needed to be a part of nature and subject to scientific inquiry.

Trying to steer a path between mechanism and vitalism, the German philosopher Immanuel Kant (1724–1804) and his friend, biologist Johann Friedrich Blumenbach (1752–1840), created a new approach to the study of life: teleomechanism.
^*
In 1790, Kant wrote to Blumenbach: “Your recent unification of the two principles, namely the physico-mechanical and
the teleological, which everyone had otherwise thought to be incompatible, has a very close relation to the ideas that currently occupy me.” In the Aristotelian tradition, Kant and Blumenbach thought that life was directed by purpose (Greek
teleo
). In particular, Blumenbach espoused the existence of a formational drive (
Bildungstrieb
in German), which would provide the “means [by] which [the organisms] receive a determinate shape originally, then maintain it, and when it is destroyed repair it where possible.” Blumenbach, and the biologists who came after him, did not see this vital force as a separate entity from the organism. Rather, it was a force contained within an organism, a result of its special organization and structure.

This view of self-contained special forces in organically organized bodies helped shape biology into an autonomous science. With the renewed recognition that life was special, life scientists could develop their own methods, ideas, and approaches. The role of the biologist was to find the rules by which special vital forces acted on organic matter. The German biologist Carl Friedrich Kielmeyer (1765–1844) went as far as to create a set of Newtonian laws that the vital forces would obey. First, he identified the forces acting in living beings: sensibility, irritability, reproduction, secretion, and propulsion. Then, he came up with various laws for these forces (most of which were subsequently proven wrong) and called them “the physics of the animal realm.”

The biological tradition founded by Kant and Blumenbach led to several important discoveries in embryology and physiology. One of the most profound discoveries was the cell theory—the recognition that all living beings were made of smallest units, called cells. This insight was long overdue—after all, Hooke had coined the term
cells
, for the little compartments he saw in cork, as early as the late 1600s. The cell theory is usually credited to Matthias Jakob Schleiden (1804–1881), a German botanist; Theodor Schwann (1810–1882), a German zoologist; and Rudolf Virchow (1821–1902), a German physician, although numerous other scientists, from several countries, contributed to the final theory.

The cell theory corresponded to a kind of biological atomism, with cells as the “atoms” of life. But cells were not indivisible like atoms. Microscopists discovered even smaller structures inside cells, starting with the cell nucleus, which was named by Robert Brown in 1833.

The age of the German vitalist biologists opened up new vistas for inquiry. The teleomechanists were superb experimentalists and founded new schools of embryology, developmental biology, botany, and physiology. If these scientists were misguided in their theoretical ideas about vital forces, we may forgive them: Their experimental results have generally withstood the test of time.

With an anxiety that almost amounted to agony, I collected the instruments of life around me, that I might infuse a spark of being into the lifeless thing that lay at my feet. It was already one in the morning; the rain pattered dismally against the panes, and my candle was nearly burnt out, when, by the glimmer of the half-extinguished light, I saw the dull yellow eye of the creature open; it breathed hard, and a convulsive motion agitated its limbs.

—M
ARY
S
HELLEY
,
F
RANKENSTEIN

Irritability, one of Kielmeyer’s five vital forces, spurred the imagination of scientists, philosophers, and writers. One of them was La Mettrie, who was most impressed by the motions of muscles separated from their animal hosts. La Mettrie made irritability the center of his argument that life is pure mechanism, a complicated clockwork. But irritability also supported vitalist ideas: If muscles could move on their own, did this not prove the presence of a vital force? And could such a vital force, if distilled to its essence, not be used to bring life to dead tissue? At the height of the Romantic period, in the early 1800s, such speculation inspired a young woman with literary aspirations, vacationing with her lover in a villa on Lake Geneva, to write a novel.

Mary Wollstonecraft Shelley (1797–1851) conceived the idea for her novel
Frankenstein; or, The Modern Prometheus
, when she and her husband Percy Bysshe Shelley were holed up in the Villa Diodati with several friends, including the poet Lord Byron. It was 1816, the dreary “year without a summer,” when a giant eruption of the Indonesian volcano Tambora darkened the European skies. During late-night chats, she and her friends talked about the increasingly gruesome experiments of scientists who
were applying high voltages to dead animals and humans to demonstrate irritability. When her friends challenged each other to write a story or poem to entertain themselves, Shelley conceived of a gothic horror story about a scientist creating life from dead flesh.

The study of irritability, which La Mettrie had used as evidence for the mechanical nature of life, reached fever pitch when scientists of the day discovered that the newly founded science of electricity could be used to study living organisms. The iconic experiment of this era was conducted by Luigi Galvani (1737–1798), who attached a charged Leyden jar (a capacitor to store large amounts of electrical charge) to severed frog legs and observed that they kicked and twitched when electricity passed through them. Such experiments suggested that electricity could be the mysterious vital force philosophers had sought for centuries. In 1803, Galvani’s nephew, Giovanni Aldini, went as far as to experiment with human corpses, making their faces twitch, their eyes open, and their extremities lift up. Such horrible experiments were supposed to show that “animal electricity” was a vital force responsible for the motion of muscles as it traveled along the nervous system. Unfortunately, what these experiments really inspired (much helped by Shelley’s novel) was the idea of the overreaching, mad scientist—a figure that has since dominated much of the public’s imagination.

I had not read Shelley’s book until I started writing this book (although I was familiar with several movie versions, including the classic with Boris Karloff as the monster) and was surprised to find that Shelley never mentioned exactly how Dr. Frankenstein vitalized his creation. Shelley’s hero deliberately keeps the reader in the dark, supposedly to prevent a repeat of the tragedy about to unfold: “I see by your eagerness and the wonder and hope which your eyes express, my friend, that you expect to be informed of the secret with which I am acquainted,” explains Frankenstein in the novel, “that cannot be; listen patiently until the end of my story, and you will easily perceive why I am reserved on that subject.” The giant switches and the lightning storm seen in various movie versions are all inventions of Hollywood, but it is clear that the studies of irritability, which were in the news in the early 1800s, provided the inspiration for Shelley’s iconic novel.

Ever since its discovery by the Greeks (
electron
means “amber” in Greek, and amber generates static electricity when rubbed), electricity
was considered a mysterious force and a subtle fluid. Such a mysterious force had to have some connection to the great mystery of life. Even Newton had suggested that electricity was responsible for animal motion. In the second edition of
Philosophiae Naturalis Principia Mathematica
, he speculated that the “subtle spirit” of electricity, transmitted through the nerves, “stimulated sensations” and “moved limbs.”

Who was the inspiration for Shelley’s Dr. Frankenstein? With animal electricity as the scientific object du jour, there were many candidates for this rather ignoble honor. Aldini, who passed large currents through the limbs of recently hanged criminals in front of large London crowds—to horrific effect—was certainly one of them. Another was Johann Wilhelm Ritter (1776–1810), a German scientist who preferred to apply the large currents to himself instead. Applied to his eyes, they made him see red and blue flashes, depending on which electric pole he had connected to his eyeball. Ritter died at a young age of unknown causes—but repeatedly electrocuting oneself cannot be too healthy.

Although the late eighteenth to the mid-nineteenth century had become the age of teleomechanists and vitalists, by the mid-nineteenth century, mechanism had again gained the upper hand. This return to mechanistic explanations was mainly the work of two men: the English naturalist Charles Darwin (1809–1882), who destroyed teleology, and the German physiologist and physicist Hermann von Helmholtz (1821–1894), who vanquished the vital force.

Helmholtz was one of the last truly universal scientists. He made significant contributions to medicine, biology, and physics, in areas as diverse as heat in animals, irritability, the vital force, thermodynamics, electro dynamics, the conservation of energy, turbulence in liquids, and the physiology of the senses. His insights were groundbreaking, and most have withstood the test of time. He also invented several new experimental apparatuses, including the ophthalmoscope, the special microscope eye doctors point at your eyes to check the retina. His broad knowledge allowed him to make novel connections between different sciences. He could look at a system as complex
as living tissue and determine the one parameter that linked it to the inanimate, mechanical world. He decided that this parameter was energy.

Physicists of the more arrogant sort often think that the interactions between physics and biology are purely one-way: Physics may explain biology, but biology has no bearing on physics. To cure such a misguided view of science, one should consider how Helmholtz came to argue for the law of energy conservation (or the conservation of force, as he called it). Helmholtz, trained as a physician, started his scientific career working on physiological experiments. It was these biological experiments that convinced him of the law of energy conservation.

Energy conservation had been in the air for a while. Descartes, Newton, and Leibniz had all argued for some quantity to be conserved in interactions between material corpuscles, although they could not agree on the type of conserved quantity (Newton argued for momentum or quantity of motion, while Leibniz argued for kinetic energy or
vis viva
[“the living force”]). Others had shown that work and kinetic energy could be converted into one another, for example, during free fall. Heat had been shown to be a type of motion, and it was already known that kinetic energy could be converted to heat through friction. In 1845, James Joule (1818–1889) showed that a fixed amount of work would result in a fixed amount of heat (what he called the mechanical equivalent of heat): “When equal quantities of mechanical effect are produced by any means whatever from purely thermal sources, or lost in purely thermal effects, then equal quantities of heat are put out of existence or are generated.”

Drawing on his own biological observations and diligent studies of mathematical physics, Helmholtz extended energy conservation to all types of energy, thus declaring energy conservation a fundamental law of the universe. He showed how the conservation of energy can be mathematically derived from simple assumptions. While the mathematical treatment was Helmholtz’s achievement alone, the idea of a universal law of energy conservation had been formulated some years earlier by another German scientist, Julius Robert von Mayer (1814–1878). Just like Helmholtz, Mayer was a physician venturing into physics and was also inspired by biology to proclaim the universal law of energy conservation. Helmholtz was unaware of Mayer’s 1841 paper when he published his own ideas six years later. In his paper, Mayer repudiated vital forces, as
Helmholtz would do a short time later, and stated that “the cause of the chemical tension produced in the plant . . . is physical force.” This physical force, or energy, as we would say today, was the same as the energy that would be obtained if we were burning the plant. Furthermore, this energy had to come from somewhere. If we postulated a mysterious vital force— a force that would require no source—we would be “carried . . . into unbridled fantasy,” and all further investigation would “be cut off.” No, said Mayer, the real explanation had to be that energy and matter were only converted from one form to another, and “that creation of either one or the other never takes place.” In other words, even in something as complicated as a plant or an animal, energy was only transformed, but never created or destroyed. This is the universal statement of energy conservation.