Anaesthetic inhaler used by A D Waller, 1907-08.
© Science Museum / Science & Society Picture Library
Prototype Alcock copper chloroform inhaler, manufactured by C F Palmer, London. This example is incomplete, with no provision for a thermometer. By the late 19th century, chloroform was used routinely to render patients unconscious during surgery. However, doctors became increasingly aware that it was important to be able to regulate the amount of chloroform that was administered over time. Waller was the first to devise an apparatus which gave a continuous reading of the concentration of anaesthetic chloroform vapour to a patient. This was his chloroform balance, which he first described to the Physiological Society in 1908.