The conservation of nervous energy: Neurophysiology and energy conservation in the work of Sigmund Exner and Josef Breuer

This article explores the assimilation of the law of energy conservation in the psychological sciences of the late nineteenth century by comparing two similar neurophysiological projects conceived in largely the same social milieu and at the same time – namely, Sigmund Exner's Project for a physiological explanation of psychic phenomena (1894) and Josef Breuer's “Theoretical” chapter for Studies on Hysteria (1895). As shall be demonstrated, even within the narrow context of fin-de siècle Viennese neurophysiology, energetic concepts were used in apparently similar models, but defending widely distinct perspectives on life and the mind. While Exner formulated his project with a view of reducing mental processes to the exchange of neuronal energy, thus eliminating remnants of vital force in psychology, and generally following the methodological precepts of organic physics and of the thermodynamic method, Breuer in turn formulated a model whereby the electricity of neuronal exchanges was considered equivalent to a modified version of vital forces. Although the difference in their approach cannot be reduced to a single factor, the article suggests that the role played by medical practice in theory-construction provides one key condition for the variation in their otherwise analogous projects. While Exner conducted his work exclusively within the physiological laboratory, and still shared the “therapeutic nihilism” characteristic of the Second Vienna Medical School, for Breuer instead theory was both intimately allied with, and secondary to, his medical practice.