Howell and Ford are excellent storytellers, and here they've recounted one dozen medical investigations in clear and gripping fashion. The cases range from pinning down information about important diseases (such as identifying the mode of transmission of yellow fever) to instances where the mechanism was understood but diagnosis in an individual case was tricky (such as with an incident of cantharidin poisoning). The authors always detail the steps that ingenious and patient investigators went through, giving an idea of the various ways that medical mysteries may be solved, and due credit to innovators, but they pay equal attention to the circumstances under which the investigations took place, how social circumstances could help or hinder, and how the findings fed back into policy and public thought. (In the case of the poisoning of an American ambassador to Italy, the political implications of the investigation are really the entire story, since the diagnosis was easily made.) Some of the chapters provide interesting contrast with each other; for example, the 19th century's very long struggle to get obstetricians to admit that puerperal fever was caused by infectious material transmitted by the doctors themselves is very different from what happened in the mid-20th c. when the introduction of routine supplemental oxygen use with premature infants caused a spike in cases of retinopathy; then, the problem was identified within a decade and hospitals immediately changed their practices, and it's clear that there had been a profound change in the culture of medicine. Not all of these stories were new to me, but even those I'd read about repeatedly, like John Snow's investigation of the Broad Street cholera epidemic, were told in a fresh manner. All in all, quite a fine book.