Leeches

Almost everyone has heard of a leech .But not every one knows that not all leeches are parasitic. One thing they all are related to earthworms and  both are annelids. Annelids are worms that have segments. I bet you did not know this. Leeches are good swimmers. They swim in an S shape.Most leech species do not feed on human blood, but instead prey on small invertebrates, which they eat whole. The ones that are parasitic do eat blood though. If one does bite you, you wont notice it .This is because they have anesthetic in their saliva or spit. A long time ago people thought sickness was caused by bad blood . So they put leeches on  the sick .  Did you think that worked ? It  never did. Then they put leeches in hospitals again. They let the leeches feed on a spot near an operation. Their anticoagulant makes the blood keep flowing to the spot so it can heal faster.
 My dad told me if you put rock salt on a leach that is biting you , it will stop. Leeches are pretty
misunderstood.