John Snow's Ether Inhaler
Date of manufacture:
Within one month of the arrival of the news of anaesthesia arriving in London, John Snow had investigated the properties of ether, established the concentrations required and designed, tested and published the results of using a vaporising device. Manufactured from sheet copper, it consisted of a black japanned box containing a flattened circular vaporising chamber. Contact between inhaled air and liquid ether was achieved by a spiral copper guide. The peripheral air inlet was protected by a chimney that prevented the heavy ether vapour from escaping. The patient outlet was central to the vaporiser. There was a wide bore breathing tube and a valved mask prevented rebreathing. In addition, the exhalation valve of the mask could be deflected by the anaesthetist to control a variable amount of air dilution. When the case was filled with water, to enhance thermal stability, the vaporiser delivered outstanding performance.
Barbara Duncum, 'Development of Inhalation Anaesthesia', Wellcome, 1947.