Carl Nägeli’s 1858 schematic diagrams of “micellar” structure of plant starch granules: surface (above) and radial cross section (below). Nägeli neither saw nor made such a cross section of starch granules. Carl Nägeli, Die Stärkekörner: Morphologische, physiologische, chemisch-physicalische und systematisch-botanische Monographie (Friedrich Schulthess, 1858), p. 362.

Project (2017)

Crystals, Colloids, and Fibers: The Organization of (Living) Matter and the Limits of Microscopic Vision, 1882–1938

What does it mean for living matter to be “organized”? For much of the nineteenth century it was assumed that the complexity of vital phenomena corresponded to an anatomical and structural division of labor—an assumption which, paired with the microscope, had driven refinements and revolutions in anatomy, histology, and physiology. But by 1890, increasing concerns about the prevalence of fixation and staining artifacts, along with Ernst Abbe’s discovery of the microscope’s diffraction limit, ended hopes for any discovery of the organization of living matter and the so-called “structure of protoplasm” through an easy reductionism-by-magnification. To overcome this purely visual and physical epistemological limit, the plant physiologists such as Carl Nägeli, Wilhelm Pfeffer, and Hermann Ambronn theorized that starch granules, plant fibers, and even chromosomes were composed of micelles—crystalline, submicroscopic (and therefore invisible) particles, which might be indirectly revealed through the ingenious use of polarized light.

Few accepted or even understood what seemed like an extravagant, pseudo-molecular theory, and others still doubted imaginary units were useful for describing vital phenomena. Today the micelle as a unit of organized matter exists only within the narrow confines of soap and lipid chemistry, while past historical scholarship has suggested the micelle was a misguided theory of macromolecular structure. This project will show how the hypothetical micelle drove biologists to push the limits of microscopic vision into the molecular realm: rather than thinking of micelles as sites of biochemical activity, they were the scale which biologists expanded their ability to visualize structure. My project shows how Ambronn and a team of physical chemists at Carl Zeiss worked to overcome the physical limits microscopy through a combination of inferential and low-magnification optical tools, as well as extensive use of simple diagrams and visually-oriented language. The micelle was also the locus around which x-ray crystallographers, polymer chemists, and biologists alike could collaborate, and Daniel Liu endeavors to show how this collaboration led to a broad convergence towards molecular theories of biological structure.