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Early use of manual ventilation during the polio epidemic in Denmark. The medical student provides the power for ventilation using a non–self-inflating bag. An early electric humidifier is also shown. From Lassen HCA, Management of life-threatening poliomyelitis. Copenhagen 1952–1956, with a survey of autopsy findings in 115 cases. Edinburgh: ES Livingstone;1956:65, with permission.
