Inspiring imagination – embarrassing analogies: coping with the causes of cytoplasmic streaming.

In the late eighteenth and early nineteenth centuries, the observation of a phenomenon that we call today cyclosis or cytoplasmic streaming provoked great astonishment, and also raised great expectations of being able to penetrate into the secrets of living matter. From the outset, the steady circling flow of liquids and granules inside the cells of algae posed an explanatory challenge, because it seemed to contradict the laws of physics. With scarce epistemic support at hand, researchers adopted a series of analogies to give plausibility to their conclusions. None of these enjoyed lasting success. On the contrary, over the years, we can observe an ongoing proliferation of explanations, and a diversification of alleged mechanisms and agents. Moreover, all the adduced analogies were severely criticized by scientific contemporaries; several were even subjected to derision. Nevertheless, it seemed that nobody could do without them. This paper will focus on the period 1774–1840, and will analyze the contributions and analogical arguments of some prominent microscopists of the time, among them Bonaventura Corti, Charles Bonnet, Ludolph Christian Treviranus, Carl Heinrich Schultz-Schultzenstein, Giovanni Battista Amici, Henri Dutrochet, and Franz Meyen. [ABSTRACT FROM AUTHOR]