This article examines the science of electrophysiology developed by Emil du Bois-Reymond in Berlin in the 1840s. In it I recount his major findings, the most significant being his proof of the electrical nature of nerve signals. Du Bois-Reymond also went on to detect this same ‘negative variation’, or action current, in live human subjects. In 1850 he travelled to Paris to defend this startling claim. The essay concludes with a discussion of why his demonstration failed to convince his hosts (...) at the French Academy of Sciences. (shrink)

ArgumentAfter having measured the velocity of the nervous impulse in the 1850s, Helmholtz began doing research on the temporal dimensions of visual perception. Experiments dealing with the velocity of propagation in nerves were carried out occasionally for some fifteen years until their final publication in 1871. Although the temporal dimension of perception seems to have interested Helmholtz less than problems of geometry and space, his experiments on the time of perception were technically rather subtle and seminal, especially compared with experiments (...) performed by his contemporaries, such as Sigmund Exner, William James, Rudolf Hermann Lotze, Ernst Mach, Wilhelm Volkmann, and Wilhelm Wundt. Helmholtz’s conception of the temporal aspects of perception reflects the continuity that holds between psychophysiological research and the Kantian philosophical background. (shrink)

The Belgian polymath Lambert Adolphe Jacques Quetelet pioneered social statistics. Applying his training in mathematics to the physical and psychological dimensions of individuals, he identified the 'average man' as characterised by the mean values of measured variables that follow a normal distribution. He believed that comparing the features of individuals against this average would allow scientists to better explore the processes that determine normal and abnormal qualities. Quetelet's methods influenced many, among them Florence Nightingale, and his simple measure for classifying (...) a person's weight, dividing it by the square of their height, is widely known as the body mass index. First published in French in 1835 and reissued here in the 1842 English translation, this is his most influential work and includes a new preface that succinctly states his aim to be 'the analysis of normal man through his actions and of intellectual man through his productions'. (shrink)