I moved the slide slowly across the microscope stage (sticky in the tropical heat), paused near the edge of the smear of blood, and focused. Even with the instrument at the lowest magnification, I saw that this boy's blood had far, far too many white cells. So many, in fact, that the blood had become almost a ghostly white. I changed the objective to a higher power and peered into the nucleus, the very center of the cell. If cells have souls they must lie there, locked within the regulators of the genes. These nuclei were, in the pathologist's parlance, primitive, and the regulators that control them were running wild. If my suspicions were correct, the marrow of the bones was already filled with these primeval white cells and they were spilling out into the blood—leukemia.
This past February I went to Grenada, the isle of spice, as it is known, on a working vacation to practice tropical medicine. I found the island to be a place of extinct volcanoes, rain forests, blue seas, spices, gentle people, and poverty. The hospital, a converted 19th-century army barracks, sat on a hill overlooking a blue harbor. The interior, at first glance,