The Immortal Life of Henrietta Lacks. By Rebecca Skloot. Crown; 384 pages; $26. Macmillan; £18.99. Buy from,

THIS moving book, which was published in America in February and is now coming out in Britain, intertwines two stories, one of a personal tragedy, the other of an epoch in modern medicine. Both start in 1951, with the death from cervical cancer of 31-year-old Henrietta Lacks, a poor black tobacco farmer living in rural Maryland. She was treated at Johns Hopkins Hospital in Baltimore, pretty well by the standards of the day. But by the end her sufferings were horrible, her abdomen badly burnt by the radiation treatment, the pain from her multiplying tumours far beyond the reach of morphine.

Four of Lacks's children stayed with their father after her death, to suffer neglect and worse. The fifth, damaged in utero by syphilis, died just four years after her mother in a “Hospital for the Negro Insane”. One son grew up to serve 15 years for murder; one daughter, Deborah, who became close to the author, died as the book was being finished. None of Lacks's children travelled far, or succeeded in rising out of poverty.

And then there is the story of the other fruit of her womb. Though neither she nor her family knew it, when Lacks arrived at Johns Hopkins complaining of a knot in her insides, the doctors who treated her had been trying to grow cancer cells in vitro for some time. They wanted to watch as the cells divided and multiplied, to understand how they differed from ordinary cells and how the disease got its start. Sometimes cells would survive for a few days, but they always petered out eventually—until the arrival of Lacks. The cells from her tumour, in the words of the laboratory assistant who prepared them for culture, grew “like crabgrass”. Their descendants are growing still.

Scarcely a development in modern medicine does not owe something to HeLa, as the cell line has been labelled. The Salk polio vaccine was tested on the cells shortly after Lacks died. Since then researchers have infected them with herpes, measles, salmonella, tuberculosis and many other diseases too. They were sent up with early space flights to see how human cells coped with zero gravity and exposed to radiation to test the effects of nuclear weapons. According to one estimate, if all the HeLa cells ever cultured were laid end to end they would encircle the globe three times.

This book also takes in some of the darker episodes of 20th-century medicine. The first place to produce HeLa samples on an industrial scale was the Tuskegee Institute—where, at the same time, syphilitic black men were left untreated so doctors could observe the progress of the disease. Later, at Ohio State Penitentiary, doctors injected HeLa cells into prisoners without telling them what they were doing: some developed tumours as a result.

Lacks had been dead a quarter-century before her children found out that descendants of their mother's cells still lived. They gave blood samples to researchers—but a cavalier approach to explaining things left them with the impression that they were being treated for hereditary cancer, rather than simply helping scientists to gain a better understanding of the world's most important cell line.

Their mother's identity was made public with no thought for her descendants' privacy; now much of their DNA profile is a matter of public record. Poor in a country without comprehensive health-care insurance, they struggle to pay for medicines her cells helped to develop. Difficult medical matters—such as the asymmetry in power and knowledge between doctor and patient, and issues of privacy, consent and access to treatment—take on a particularly bitter flavour in this tale. A poor woman who died as a charity case in a “coloured” ward—but whose legacy transformed medicine for us all.