Mechanics of the Human Walking Apparatus, 1836

By Allison Muri ~

Originally published in Hidden Treasure: The National Library of Medicine, 2011.

Few movements in a living human depend so much on external forces, occur so evenly and are so little altered by the Will” as walking. So wrote Wilhelm Weber (1804–91) and Eduard Weber (1795–1881) in their treatise on the mechanics of human motion, a work that continued a line of inquiry that began in the seventeenth century. Rene Descartes’s conception of the human as a machine animated by a soul and Giovanni Borelli’s application of mechanics to anatomy in On the Motions of Animals (1680–81) had helped to initiate the long debate over mechanism versus the immaterial soul and materialism versus vitalism. The suggestion that mechanics—matter and motion defined by mathematically expressed laws—could explain perception, thought, will, and action was politically dangerous and morally suspect. To consider the human a mere “engine” bordered on atheism. Borelli prudently avowed that the principal cause of movement is the soul and the active instrument is the will.

At the beginning of the nineteenth century the Weber brothers also avowed that walking and running “depend on free will,” but then methodically demonstrated that “such mechanical movements can be predicted by calculation,” so that “a voluntary act of will is not needed to move the active instruments successively in the necessary order.” That the legs can oscillate like a pendulum, for instance, is a property that makes possible the regularity of successive steps. “It appears,” they determined, “that the constant period of the oscillations results from the force of gravity without requiring an act of will.”

The Webers were the first investigators to systematically study the mechanics of human motion. To do that they needed to devise a way of capturing reliable data. Artists, they argued, had misrepresented the curvature of the spine and angle of the pelvis. The investigator seeking an accurate visualization of body mechanisms must instead use mechanical and mathematical approaches. The Webers employed the crosshairs of a telescope to measure pelvic tilt at different phases of movement, and then analyzed the phases using differential equations. To illustrate “the bases of the human walking machine” they encased bones in plaster blocks and sawed them into segments to make imprints on paper. This method, they claimed, “is so true that it replaces the actual specimen.” A draftsman using their equations to determine the body’s position at different phases of motion could illustrate running and springing figures as they might appear on a stroboscopic disk. Because the legs articulate “like hinges” set in a frame or the cogwheels of a watch, they obey strict rules. Such mathematically reconstructed figures can create an impression of movement “corresponding exactly to nature.”

By using mechanical principles so rigorously, the Webers contributed to the ascendancy of a new materialist science of life. Increasingly, inventions such as pumps, telegraphs, combustion engines, and assembly lines would be made to serve as models of organisms and body parts—and would even eventually replace or augment them. Humans and machines seemed now disconcertingly equivalent: the mechanics of living bodies subverted the idea not only of spirit enlivening the human frame but also of free will and even God.

Allison Muri,PhD, is Professor at the University of Saskatchewan. Her research interests include digital media studies and the history of cyberculture in early modern science, medicine, and technologies of communication. In The Enlightenment Cyborg: A History of Communications and Control in the Human Machine, 1660–1830 she examines the history of mechanically steered, or “cyber,” humans in the works of seventeenth- and eighteenth-century thinkers.