The rotameter and the waterwheel.

The publication imparts information about the personal life and professional sphere of activity of J.A. Segner, Karl Küppers, Maximilian Neu, Hans Bunte, and Felix Meyer, as far as they were involved with the invention of devices for measuring gas flow, especially their involvement in testing the introduction of Rotameters into the medical field. The knowledge that the threat of deportation in October 1940, due to his Jewish background and in view of the politics of the National Socialists at the time, led to Maximilian Neu's committing suicide, is of added historical interest. Together with biographical details, the role played by the Institute of Research in Karlsruhe and the establishment of the Rotameter site in Aachen is presented. The historical outline finishes with a short report of the author's first experience with Rotameters at the Nuffeld Department of Anaesthetics, Oxford University during the Second World War and with his subsequent efforts to introduce Rotameters into anesthesia equipment design in the United States.