In the past, Native Americans ate the flesh of horseshoe crabs, and used the tail spines as spear tips and the shells to bail water out of their canoes. More recent attempts to use horseshoe crabs as food for livestock were abandoned when it was found that this gave the meat a bad taste. Horseshoe crab blood contains a clotting agent, "limulus amebocyte lysate", which is used to test antibiotics and kidney machines to ensure that they are free of dangerous bacteria, and to detect spinal meningitis and some cancers.