Medicine: Blue Babies

With some misgivings, Johns Hopkins' Surgeon Alfred Blalock made a long incision and exposed the child's beating heart. Then, for three hours he worked at an operation no one had ever done before. The 15-month-old child on the operating table was a "blue baby" and was expected to die. Dr. Blalock believed that he and Dr. Helen Taussig, of the children's hospital at the Hopkins, had figured out how to save blue babies.

A blue baby is so-called because its lips and fingertips are constantly blue; its blood does not contain enough oxygen. A common...