“THAT ROSE FROM THE SEA TO ASTOUND US”: AQUATIC BIOLOGY, NEURONS, AND THE TRANSFORMATION OF NEUROBIOLOGY, 1891-1952

Abstract

From 1891 through 1952, comparative studies of aquatic organisms—what I call a natural history of aquatic life—transformed neurobiology. More particularly, studies of the enormous nerve fibers, or axons, of aquatic invertebrates provided new materials, methods, and mechanisms for examining and interpreting neurons, or nerve cells, creating an aquatic style of cellular neurobiology. This spilled into subsequent work, including the “neurosciences” of the 1960s. The present dissertation documents and defines this style, explains why and how it appeared, and examines some effects.The aquatic style emerged from three changes inflecting neurobiology, I argue. In the late 19th century, experimental convenience and comparative interests prompted life scientists to study aquatic organisms. Such work generated new patterns of comparative analyses, which then drove shifts in neurons as epistemic things. Fueled by comparative analyses especially of squid axons, which were exceptionally suited to biophysical and biochemical methods, by 1952 biologists had revised several assumptions about neurons, which when implemented in practice coalesced into an aquatic style. Single fibers could arise from cellular fusions, for example, diversifying the materials deemed acceptable for neuronal study. Axonal functions were also analogized to circuit behaviors, transforming experiments, and enabling generalization of interpretations via physics. Finally, aquatic biologists introduced intraneuronal measurements and manipulations of voltages across axon membranes, rendering neurons more controllable and, via the mathematical modeling and explanation of functions through ion currents, more predictable. From 1952 through 2000, in turn, the materials, methods, and mechanisms of the aquatic style spread. This took place most directly via intracellular studies of ion currents in squid axons, but also through other aquatic axons and nerve cell parts. In conjunction with other enduring comparative work on aquatic neurons, biologists within the aquatic style promoted a broader trend towards comparative studies of nerve cells in biophysical and biochemical perspective, including for terrestrial organisms. Consequently, some investigators even concluded that the aggregate capacities of neurons could give rise to the properties of brains. Finally, this history provides insights into how neurobiologists might continue to learn from aquatic life, including at the cellular but also at other levels.