One afternoon in November 1944, the chief of surgery at Johns Hopkins Hospital in Baltimore, Alfred Blalock, sat in his office deep in thought. As usual, he had a cigarette on the go: Even after losing two years of his early career to tuberculosis, he had never quite managed to give up his 40-a-day habit. With his neatly combed hair, immaculate chalk-stripe suit, and donnish glasses, he might easily have been mistaken for a prosperous lawyer, but at the age of 45, he was already known as one of America's foremost clinical researchers. A few years earlier he had revolutionized the treatment of circulatory shock, a life-threatening condition in which blood loss makes it difficult for the heart to pump enough fluid to the body. Shock was one of the biggest killers in wartime, frequently the consequence of injury by shrapnel or explosives. Blalock's experiments led to the routine use of blood-plasma transfusions to treat those with severe wounds, a measure which saved the lives of thousands of servicemen in the Second World War.

This achievement alone was enough to ensure Blalock's place in the medical pantheon, but this afternoon he felt only frustration. When his senior resident surgeon, William Longmire, walked into the room he found his boss sitting disconsolately behind a pile of books. In recent weeks Blalock had attempted a series of ambitious and difficult procedures on patients seriously ill with abdominal disorders: None had been successful, and most of the patients had died.

"Bill, I am discouraged," he said to Longmire. "Nothing I do works."

Blalock was desperate to make an original contribution to surgical history and to silence colleagues who complained that he was a competent researcher but a mediocre clinician. Recently he had been concentrating his efforts on developing new methods to treat problems with the pancreas and intestines. But only a few days later he would perform a novel and entirely different kind of operation, one that would catapult him to fame and make Johns Hopkins a place of pilgrimage for patients and surgeons from all over the world.

Shortly after their conversation, Longmire was summoned to the third floor of the clinic, where Blalock took him to a cot containing one of the hospital's youngest patients. Her name was Eileen Saxon, and she had been born at Johns Hopkins the previous year. Now 15 months old, she was desperately ill and being kept alive in an oxygen tent. Longmire was shocked by her condition. She was unusually small for her age, but the first thing he noticed was her color. Her skin had a deathly pallor, and her lips and fingernails were a dark, inky blue. Eileen was suffering from a congenital condition called tetralogy of Fallot; children unlucky enough to be born with it were known as "blue babies," and there was little that could be done for them. The blue tinge to Eileen's skin was cyanosis, the result of blood bypassing the lungs and circulating through the body unoxygenated. Half of all children in her position would die before the age of 3, and fewer than a quarter would make it to the age of 10. Those who survived for any length of time endured a miserable existence. Many physicians believed that the smallest degree of excitement would be fatal, and everyday pursuits — school, outdoor play, the cinema, even travel by motor vehicle — were often prohibited. Eileen's future looked bleak.

When Blalock told his junior that he intended to try a new type of operation on her, Longmire was horrified: Given her state, he could not believe that she would survive an anesthetic, let alone a procedure that had never before been attempted. The chief anesthetist, Austin Lamont, concurred. When he heard of Blalock's plans he flatly refused to take part in proceedings, and the operation was canceled. But one of Lamont's colleagues, Merel Harmel, was prepared to take the risk, and it was rescheduled for the following day.

Early on the morning of Wednesday, November 29, little Eileen was taken into room 706, an operating theater on the seventh floor of the building that in later years would be known simply as "the heart room." Two large windows provided most of the light; in the summer these were usually thrown open in a futile attempt to gain some respite from the fierce Maryland heat. There was a small observation gallery overlooking the operating table, and several hospital staff were leaning over its rail, having heard rumors that something unusual was about to take place. As Blalock scanned the faces of the spectators he caught sight of his laboratory assistant and called out to him: "Vivien, you'd better come down here."

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