Christiaan Barnard was a 45-year-old South African surgeon who had spent two years practicing on dogs. By late 1967, he had perfected a technique to remove a heart from a recently dead donor and stitch it into a recipient's chest. He had no clinical proof it would work in a human. He just had a willing patient.

The patient was Louis Washkansky, 53, dying of heart failure. The donor was Denise Darvall, 25, hit by a car earlier that day. At Groote Schuur Hospital in Cape Town, just after midnight on December 3, 1967, Barnard's team disconnected Washkansky from his own heart and stitched in Darvall's. Barnard later said the moment was electric — the new heart, in a stranger's body, started beating.

Washkansky woke up. He talked. He recognized his wife. The world's press swarmed Cape Town. Within days he was the most famous patient in history.

He died 18 days later of pneumonia. The transplant itself was working. The drugs needed to suppress his immune system — to keep his body from rejecting the foreign heart — had also suppressed his ability to fight off infection. He drowned in his own lungs.

Barnard's second patient survived 19 months. His sixth lived 23 years.

The breakthrough wasn't the surgery — that was already understood. It was the discovery in the 1970s of cyclosporine, an immunosuppressant that kept rejection at bay without destroying the immune system. Today, around 5,500 heart transplants are performed each year. Median survival is over 12 years.

The future of organ transplantation was won in an 18-day window of impossibility.