Author Essays, Interviews, and Excerpts, History and Philosophy of Science

August excerpt: The Restless Clock


“William Harvey’s Restless Clock”*

Against this passivity, however, there were those who struggled to hold matter, feeling, and will together: to keep the machinery not just alive but active, life-like. These holdouts accordingly had something very different in mind when they talked about the “animal-machine.” William Harvey, whom we have already seen comparing the heart to a pump or other kind of hydraulic machinery, also invoked automata to describe the process of animal generation. Observing the development of a chick embryo, Harvey noted that a great many things happened in a certain order “in the same way as we see one wheel moving another in automata,and other pieces of mechanism.” But, Harvey wrote, adopting Aristotle’s view, the parts of the mechanism were not moving in the sense of “changing their places,” pushing on another like the gears of a clock set in motion by the clockmaker winding the spring. Rather, the parts were remaining in place, but transforming in qualities, “in hardness, softness, colour, &ce.” It was a mechanism made of changing parts.

This was an idea to which Harvey returned regularly. Animals, he surmised, were like automata whose parts were perpetually transforming: expanding and contracting in response to heat and cold, imagination and sensation and ideas. These changes took place as a succession of connected developments that were also, somehow, all occurring at once. Similarly, Harvey wrote with regard to the heart that its consecutive action of auricles and ventricles was like “in a piece of machinery, in which, though one wheel gives motion to another, yet all the wheels seem to move simultaneously.” Geared mechanisms represented constellations of motions that seemed at once sequential and simultaneous, a congress of mutual causes and effects.

The first appearance of life, as Harvey described it, seemed to happen both all at once and as a sequence of events. Harvey wrote of seeing the chick first as a “little cloud,” and then, “in the midst of the cloudlet in question,” the heart appeared as a tiny bloody point, like the point of a pin, so small that it disappeared altogether during contraction, then reappeared again “so that betwixt the visible and the invisible, betwixt being and not being, as it were, it gave by its pulses a kind of representation of the commencement of life.” A gathering cloud and, in the midst, a barely perceptible movement between being and not being: the origin of life. Harvey invoked clockwork and firearm mechanisms to model a defining feature of this cloudy pulse that was the beginning of life: causes and effects happening all at once, together.


In addition to geared mechanisms and firearms, Harvey invoked another analogy that would become commonplace by the end of the century—we have seen Descartes and his followers invoke it—the analogy between an animal body and a church organ. Muscles, Harvey suggested, worked like “play on the organ, virginals.” Under James I, English churches had resumed the use of organs in services, so they were once again a feature of the landscape and available as a source of models for living systems. The organ signified to Harvey something more like what it meant in the ancient and medieval tradition of animal machinery, rather than the intricate sequence of contrived movements of parts that it later came to signify. Harvey wrote that the muscles performed their actions by “harmony and rhythm,” a kind of “silent music.” Mind, he said, was the “master of the choir”: “mind sets the mass in motion.”

The particular ways in which Harvey invoked artificial mechanisms make it difficult to classify him, as historians have been inclined to do, either as a “mechanist” or otherwise, the problem being that the meaning of “mechanism” and related terms was very much in flux. Lecturing at the College of Physicians in London in April 1616, Harvey told his anatomy and surgery students that anatomy was “philosophical, medical and mechanical.”But what did he mean, and what did his students understand, by “mechanical”?

In part, he likely meant that there was no need to invoke ethereal or celestial substances in explaining physiological phenomena, because the mundane elements seemed to transcend their own limits when they acted. The “air and water, the winds and the ocean” could “waft navies to either India and round this globe.” The terrestrial elements could also “grind, bake, dig, pump, saw timber, sustain fire, support some things, overwhelm others.” Fire could cook, heat, soften, harden, melt, sublime, transform, set in motion, and produce iron itself. The compass pointing north, the clock indicating the hours, all were accomplished simply by means of the ordinary elements, each of which “exceeded its own proper powers in action.” This was a form of mechanism that was not reductive, but really the reverse: a rising of mechanical parts to new powers, which could conceivably include the power to produce life.

Similarly, Harvey elsewhere defined “mechanics” as “that which overcame things by which Nature is overcome.” His examples were things having “little power of movement” in themselves that were nonetheless able to move great weights, such as a pulley. Mechanics, understood in this way, could include natural phenomena that overcame the usual course of nature, not just artificial ones. Harvey again mentioned the muscles. When he said that the muscles worked mechanically in this instance he meant that the muscles, like artificial devices such as a pulley, overcame the usual course of nature and moved great weights without themselves being weighty.

Motion, relatedly, was a term with various meanings, as Harvey himself emphasized. He noted many different kinds of local movement: the movement of a nigh-blooming tree and that of a heliotrope; the movements caused by a magnet and those caused by a rubbed piece of jet. In what were likely some notes for a treatise on the physiology of movement, he jotted down any form of local movement that came to mind, such as the presumably peristaltic and undeniably graphic “shit by degrees not by squirts.” He identified too, as a distinct form of movement, a kind of controlled escalation, as “in going forward, mounting up, with the consent of the intellect in a state of emotion.”

Harvey drew upon another form of casual motion to resolve another critical mystery in the generation of life: how did the sperm act upon the egg once it was no longer in contact with the egg? Like the apparently simultaneous occurrence of causally connected events, this quandary seemed to pose a problem for a properly “mechanical”anatomy. Invoking Aristotle, Harvey proposed that embryos arose form a kind of contagion, “a vital virus,” with which the sperm infected the egg. But after the initial moment of contact, once the contaminating element had disappeared and become “a nonentity,” Harvey wondered, how did the process continue? “How, I ask, does a nonentity act?” How could something no longer extant continue to act on a material entity? The process seemed to involve too a kind of action at a distance: “How does a thing which is not in contact fashion another thing like itself?”

Aristotle had invoked “automatic puppets” to explain precisely this seeming mystery. He had surmised that the initial contact at conception set off a succession of linked motions that constituted the development of the embryo. According to this model, as Harvey explained, the seed formed the fetus “by motion” transmitted through a kind of automatic mechanism. Harvey rejected this explanation along with a whole host of other traditional explanations by analogy: to clocks, to kingdoms governed by the mandates of their sovereigns, and to instruments used to produce works of art. All, he thought, were insufficient.

In their place, Harvey proposed a different analogy: one between the uterus and the brain. The two, he observed, were strikingly similar in structure and a mechanical anatomy should correlate structures with physiological functions: “Where the same structure exists,” Harvey reasoned,there must be “the same function implanted.” The uterus, when ready to conceive, strongly resembled the “ventricles” of the brain and the functions of each were called “conceptions.” Perhaps, then, these were essentially the same sort of process.

Harvey taught his anatomy and surgery students that the brain was a kind of workshop, a “manufactory.” Brains produced works of art by bringing an immaterial idea or form to matter. Perhaps a uterus produced an embryo in the same way, by means of a “plastic art” capable of bringing an idea or form to flesh. The form of an embryo existed in the uterus of the mother just as the form of a house existed in the brain of the builder. This would solve the apparent problems of action at a distance and nonentities acting upon material entities. The moment of insemination endowed the uterus with an ability to conceive embryos in the same way that education endowed the brain with the ability to conceive ideas. Once the seed disappeared, it no longer needed to act: the uterus itself took over the task of fashioning the embryo.

The idea that the uterus functioned like a brain, actively fashioning an embryo the way a brain fleshes out an idea, was for Harvey not only within the bounds of the “mechanical,” but a model that could actually rescue mechanism by eliminating the need for action at a distance.

*This excerpt has been adapted (without endnotes) from The Restless Clock: A History of the Centuries-Long Argument over What Makes Living Things Tick        by Jessica Riskin (2016).


To read more about The Restless Clock, click here.