Perhaps Bell's most famous post-telephone invention was what he called a vacuum jacket. This so-called vacuum jacket would become widely known as the iron lung, a device that prolonged the lives of victims of polio during the polio epidemic which raged in the late 1940s. Aleck began working on this machine in the aftermath of his son Edward's death; the boy died in infancy due to respiratory problems. The iron lung was an airtight iron cylinder which fitted closely around the torso. Once a patient was strapped into the cylinder, a suction pump forced air in and out of the "iron lung," stimulating the patient's own lungs into action.