Forty years ago a team of physicians led by Edward F. Scanlon reported, in the journal Cancer, that they had “decided to transplant small pieces of tumor from a cancer patient into a healthy donor, on a well informed volunteer basis, in the hope of gaining a little better understanding of cancer immunity,” which they thought might help in treating the patient. The patient was a fifty-year-old woman with advanced melanoma; the “donor” was her healthy eighty-year-old mother, who had agreed to receive a bit of the tumor by surgical transplant. One day after the transplant procedure, the daughter died suddenly from a perforated bowel. Scanlon’s report neglects to explain why the experiment wasn’t promptly terminated—why they didn’t dive back in surgically to undo what had been done to the mother. Instead, three weeks were allowed to pass, at which point the mother had developed a tumor indistinguishable from her daughter’s. Now it was too late for surgery. This cancer moved fast. It metastasized, and the mother died about fifteen months later, with tumors in her lungs, ribs, lymph nodes, and diaphragm.