The history of tabes dorsalis and the impact of observational studies in neurology.

It is common for a particular aspect of scientific knowledge to undergo a great advance in a brief period of time after the discovery of new investigational procedures that broaden research horizons. Knowledge of neurosyphilis increased markedly during the second half of the 19th century. As revealed by the example of tabes dorsalis, this progress was not related to new research methods but instead to the impetus of careful clinical observations.