Sigmund Freud's contribution to the history of the neuronal cytoskeleton.
In the summers of 1879 and 1881, while Freud was a research student in Ernst von Brücke's laboratory at the Institute of Physiology at the University of Vienna, he carried out an important though seldom remembered investigation on the internal structure of nerve fibers and cells. His contribution to this field is here examined in the context of the 19th-century debate regarding the existence of neurofibrils and of present views on the cytoskeleton. Freud was able to discern separate fine fibrils following straight courses within the nerve fibers, as well as concentric loops of striae surrounding the nuclei and converging towards the processes of the cell bodies in crayfish nervous tissue. He thus confirmed and extended observations made by Robert Remak almost 40 years earlier, which had remained controversial. Electron microscopy of the crustacean nervous system confirmed Freud's main points, which in turn vindicated those of Remak. Both researchers were looking at small bundles of microtubules, and thus they were among the first to picture the lacy intracellular framework that future cell biologists would call the cytoskeleton.