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Ralph M. Waters, M.D.
JAMA. 1933;100(16):1275-1276. doi:10.1001/jama.1933.02740160059028.
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To the Editor:  —I am wondering whether your reply to a question as to the toxicity of carbon dioxide in Queries and Minor Notes (The Journal, February 18, p. 519) is entirely safe. In 1829, Hickman reported experiments in which he had put animals into a state of unconsciousness during which they were insensitive to surgical trauma, by exposure to the gas evolved when sulphuric acid was added to carbonate of lime. Paul Bert (La pression barométrique, Paris, 1878) wrote: "Small animals exposed to varying percentages of carbon dioxide in the presence of 'ample oxygen' do not die until concentrations of 30 per cent are reached." Haldane and Smith (The Physiological Effects of Air Vitiated by Respiration, J. Path. & Bact.1: 168, 1892) reported that human subjects exposed to 10 per cent carbon dioxide in the presence of ample oxygen "became stupefied." In his book on Respiration (1921), Haldane


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