It had taken surgeon, Joseph Upton ten hours to sew the 5-year -old's ear back on, after a dog had bitten it off. At first the operation appeared to be a success, but after four days, trouble began. Blood flow in the ear was blocked. Close examination showed that the arteries that the surgeon had repaired were fine, but the smaller veins were becoming congested. So Dr. Upton tried an experimental technique--he applied twenty-four leeches to the wound area.

The leeches latched on for up to an hour each, drinking the boy's blood. Leech saliva contains several biochemicals, one of which is potent anticoagulant called hirudin in honor of its source, the medicinal leech Hirudo medicinalis. Unlike conventional anticlotting agents such as heparin, which are short-acting, hirudin works for up to 24 hours after the leech has drunk its fill and dropped off. Hirudin blocks thrombin specifically in veins. The long acting leech biochemical gave the boy's ear time to heal. Leeches have long been part of medical practice, with references hailing back to the ancient Egyptians 2000 years ago. The leech's popularity peaked in Europe in the nineteenth century, when French physicians alone used more than a billion a year, to drain "bad humours" from the body to cure nearly every ill. Use of leeches fell in the latter half of the nineteenth century. They were rediscovered by Yugoslav plastic surgeons in 1960 and by French microsurgeons in the early 1980s. In 1985 Dr. Upton made headlines and brought leeches into the limelight by saving the boy's ear at Children's Hospital in Boston.

A leech's bite does not hurt, patients say. But for those unwilling to have one or more 3-inch long, slimy green-gray invertebrates picnicking on a wound, hirudin is being developed as a drug produced by recombinant DNA technology. It will be called hirulog.

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