Sigmund Freud's place in the history of the neuronal cytoskeleton
E. FRIXIONE <email@example.com>
Freud's seldom remembered and unfairly overlooked important investigation on the internal structure of nerve fibers and cells, carried out in the summers of 1879-1881 while he was a students at Ernst Brücke's laboratory in the Vienna Institute of Physiology, is examined in the context of the contemporary debate regarding the existence of neurofibrils, and of present views on the cytoskeleton.
The controversy as to whether the protoplasm of nerve fibers and cells should be considered either structureless and homogenous throughout, or rather containing a finely fibrous texture, was then a hot though hardly new issue. It originated nearly 40 years earlier, since Robert Remak's 1843-1844 pioneer descriptions of bundless of labile fibrils within the microscopic "tubes" and "globes" found constituting the nerve cord of the crayfish. Further work by other microscopists --including such acknowledged masters as Max Schultze and Albert von Kölliker --on nervous tissues of both vertebrate and invertebrate species had either supported, questioned or ignored Remak's claim. But even many of those who succeeded in finding internal fibrils attributed them to artifacts. As recently as 1880 the influential Thomas H. Huxley, in an exhaustive treatise on the crayfish as an example of a thorough zoological study, stated that the contents of the tubes seen in fresh nerves are "perfectly pellucid, and without the least indication of structure". Thus Huxley implicitly denied the existence of fibrils in nerve elements of the same animal in which Remak sustained to have discovered them. It was at a bout this time when Freud decided to analyze such a contentious matter by himself, selecting also the crayfish for his observations.
Taking special care to work almost exclusively with fresh specimens, Freud inspected the inner structure of nerve fibers and nerve cells independently, as well as processes extending from the latter. He was able to resolve separate fine fibrils following straight courses within the fibers, and concentric loops of striae or thick threads surrounding the nucleus and converging towards the outgrowths of the cell bodies, where they seemed to become continuous with the fine fibrils. Furthermore, he followed the progressive breakdown of these delicate structures as minutes elapsed after dissection. The conclusions in his 1882 extensive paper on the subject were unambiguous: "The nerve cells in the brain and in the ventral ganglionic chain consist of two substances, one of which arranged as a network in the fibrils of the nerve fibers, and the other is homogeneously continuous in between." He then discusses cautiously but favorably the probable general validity of those conclusions for the nervous tissues of other animals. Some of his comments may perhaps be taken as harbingers of the soon to rise neuron theory.
Current knowledge of the fine structure of the crustacean nervous system has confirmed Freud's main points, which in turn vindicated and expanded those of Remak. Both researchers were looking at small bundles of axonal and somal microtubules, and thus they were among the first to picture the lacy intracellular framework that later on would be called the cytoskeleton. Not long after Freud's paper appeared the neurofibrils became widely accepted as true cellular components, the dispute shifting then to their physiological significance, as in the writings by Stephan von Apáthy, Albrecht Bethe and Santiago Ramón y Cajal, among other. Nevertheless, in contrast to the often cited Remak's work, Freud's contribution to cell biology went largely unnoticed. Except for an occasional mention in biographical accounts, it still remains neglected by the specialized scientific literature.
Session IV -- Mid to Late 19th century
Providence, Rhode Island, USA