Invented by engineer Philip Drinker, an iron lung is a device that can produce artificial respiration for extended periods of time. It consists of an airtight metal tank that encloses nearly the entire body and forces the lungs to inhale and exhale by regulating changes in air pressure. Developed for the treatment of coal gas poisoning and first used to save an unconscious child in respiratory failure, the device was eventually most widely used for the treatment of what disease? Discuss