The evolution of anaesthesia. 4. Pneumatic medicine.

ALTHOUGH none of the work done by the eighteenth-century scientists forms a direct link with anaesthesia, yet knowledge of any kind is bound to influence the future. The discovery of gases in the second half of the century was not only of profound consequence to chemistry, but also to medicine and the world. In order to understand how the discovery of anaesthesia is placed in history, it is necessary to know something of the medical and scientific background from which it evolved. In this connection the work of Priestley, Beddoes and Davy is of paramount importance. Pneumatic medicine—the treatment of disease by the inhalation of gases—arose out of gas (or "pneumatic") chemistry and foremost in this study was the dissenting minister, Joseph Priestley (1733-1804). Like so many intellectual men of his time, his interests were wide. He concerned himself not only with theology and philosophy, but also with chemistry and physics, and he had his own laboratory. It was through his work on gases that many advances in chemistry were made possible, but he himself was hampered by being a staunch believer in the Phlogiston Theory.* He discovered both nitrous oxide and oxygen: the first though it supported the flame of a candle yet destroyed animal life; but the second not only rekindled a glowing taper, but caused it to burn with a flame of extraordinary brilliance. Finding that mice lived a long time in it, Priestley (Vol. 2, p. 102) then had the temerity to breathe this gas himself. He fancied that his breast felt "peculiarly light and easy for some time afterwards", and this experience convinced him of the