How the Cows Turned Mad describes the centuries-long search for the cause of obscure and always fatal diseases that first apparently afflicted sheep and later were found to attack people as well. This search led to the discovery of prions, the paradoxical proteins that scientists now believe are the cause of mad cow disease, Creutzfeldt Jakob disease (CJD), kuru, and scrapie. Along the way, researchers earned two Nobel Prizes. Author Maxime Schwartz is a molecular biologist, former head of the Institut Pasteur, and director of laboratories for the French agency for food safety, among his other scientific achievements. He is also an exceptionally clear writer.