The ArgumentMicroscopical consideration played a crucial role in German physiology in the period of, grosso modo, 1780–1830. Specifically, a conception of material change was established, according to which all life is grounded in the process of the generation of microscopical forms out of an amorphous, primitive generative substance. Embryological development, tissue growth, and the generation of microorganisms were all considered to be the manifestation of this fundamental developmental process. In contrast to the common historiography, I try to understand Theodor Schwann's (...) 1838 discovery of the cell theory in terms of the epistemological categories he applied to the prevailing conceptions of life and living matter. I argue that Schwann was able to discern cells not because of any superior microscopical methods, but rather as part of his wider investigative endeavor to explicate life processes according to specific causal agents. I argue that Schwann was able to demonstrate the existence of cells only when he considered animal tissues in terms of a causal relation between specific material agents and their effect, that is, the developmental history of tissue. (shrink)

The paper analyses the impact of the discovery of the division of infusoria on eighteenth century microscopical iconography. In Autumn 1765, when reproducing the antispontaneist experiments of Lazzaro Spallanzani, Horace-Bénédict de Saussure (1740-1799) discovered a new method of generation of the animalcules of the infusions, namely their division. Drawing a dividing animalcule raised particular problems, notably the question of how to depict the time sequence of a microscopical creature. Although Saussure's journal of microscopical experiments remained unpublished, the discovery was soon (...) diffused and acknowledged by the European naturalists who began to repeat the observations and quickly faced iconographic problems similar to those experienced by Saussure. Indeed, linearity, used to picture time, is a construction, and, notably for public images, scholars had to contend with the conventions of drawers and engravers. The analysis of microscopical iconographic material of the period 1740-1786 shows that during this period, certain naturalists invented new solutions for depicting time, but diffusion of their innovations was not immediate. Nevertheless, in regards to the illustration of microscopical creatures, it is between 1765 and 1776 that the use of linearity was established as a solution enabling an audience to read an iconographic time process as a text. (shrink)

The controversy of neuroanatomy on the principal structure of the nervous systems, which took place at the end of the nineteenth century, is described. Two groups of scientists are identified: one that favoured the idea of a discrete cellular organization of the nervous tissue, and one that favoured a syncytial organization. These two interpretations arose from different histological techniques that produced conflicting pictures of the organization of the nervous tissue. In an experimental reexamination of the techniques used at the end (...) of the nineteenth century, the present study concerns the impact of these different histological procedures on the controversy about the principle nature of the nervous tissue. This controversy could not be resolved by neuroanatomy itself until the 1950s when electron microscopy was introduced into neurobiology. Thus, in a critical period of the conceptual development of neurosciences, neuroanatomy failed to establish a proper base for an interpretation of the functional morphology of nervous tissues. (shrink)