A popular interest book about how a 300 million year old organism became essential to the modern pharmaceutical industry. Sargent traces the discovery of horseshoe crab blood as the perfect in-vitro test for gram-negative bacteria through the development of a multi-million dollar business. He recounts the battles between multinational pharmaceutical companies to “bleed” enough crabs for Limulus lysate and the demand for crabs by the bait fishery. Regulation of the fishery by individual states complicates the issue of preserving this natural resource.