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A bloodsucking water worm, belonging to the phylum Annelida, class Hirudinea, parasitic on humans and other animals. Leeches are a source of hirudin, an anticoagulant secreted by their buccal glands. In addition to hirudin, leech saliva contains several active substances including inhibitors of platelet aggregation, that have been synthesized for use as anticoagulants in clotting disorders.
SEE: Annelida; SEE: hirudin; SEE: Hirudinea
Leeches were used as a means of bloodletting, common until the mid-19th century but now almost completely abandoned.

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