BLOODSUCKERS.(use of leeches in modern medicine)

On a recent morning in Hendy, a tiny, rain-drenched town in southern Wales, a young man named Ioan Cunningham appeared at Biopharm, a commercial leech farm housed in a long, low brick building that sits on thirty-five acres of marshland near the center of town. Cunningham plays rugby for the local team, the Llanelli Scarlets, and during a match two days earlier he had slammed into another player and suffered a cauliflower ear. When the ear did not improve--it remained purplish-black and had swollen nearly inside out--the team's doctor sent him to Biopharm. There he was greeted by Carl Peters, the farm's thirty-year-old assistant manager, who pronounced the injury "one of the worst cauliflower ears I've seen." He invited Cunningham to take a seat in the small front office, and went down the hall to fetch some leeches.

Peters entered a large windowless room maintained at eighty-two degrees Fahrenheit. Dimly lit and quiet, the room contained sixty-seven aquariums stacked on steel racks that stretched from the floor to a height of six feet. From a shelf in an adjoining room, Peters removed a plastic jar filled with purified water and about ten dark, ribbonlike creatures. He lifted the lid and peered inside. Five hundred years ago, Leonardo da Vinci, in a sketch, attempted to capture the mesmerizing rippling motion with which leeches propel themselves through water. Peters was merely trying to identify the fastest swimmers--"Since those are hungriest," he said.

He darted his bare hand into the jar and, as though he were plucking a cigarette from an ashtray, seized a leech between his index and middle fingers and flicked it into a small plastic container. He repeated this feat, then clipped on the lid and carried the wriggling leeches back to the office where his patient sat, stoically waiting. Peters placed some cotton wool in Cunningham's ear canal--leeches can move with startling speed and are apt to crawl into any available orifice--and, with a pair of plastic forceps, brought one of the animals to the injured ear. The leech recoiled, curling back against the forceps' tongs. The second leech reacted similarly. "It's your hair products," Peters told Cunningham. With a wet cloth, he cleaned the hair around the ear and tried again. This time, the leech brushed its head against the bruised flesh and latched on.

The leeches used for medicinal purposes are parasites, typically between two and four inches long, with disklike suction cups at either end of their bodies. They subsist on the blood of mammals, and have evolved over millions of years to take their meals with efficiency and stealth. At the center of a leech's head sucker are three jaws, arranged in a Y-shaped pattern and each containing about a hundred teeth, which penetrate the skin in a sawing motion. An anesthetic in the leech's saliva is pumped into the bite from minute ducts between its teeth. This is what had started to happen to Cunningham. "I felt a slight prick, then nothing," he said. As the leech began to suck, it released several other substances into his ear: a powerful anti-coagulant, which prevented his blood from clotting; a vasodilator, which opened his vessels, helping to increase blood flow; and a spreading factor, which moved these chemicals quickly into tissue farthest from the bite, liquefying any hardening blood. The leech grew bloated as it dangled from the ear, expanding to roughly seven times its normal size until it resembled a plump, glistening cigar. After twenty minutes, the animal released its jaws, dropped into the container Cunningham held open beneath it, and lay sated and immobile.

Cunningham was feeling better, too. His ear was noticeably pinker and smaller, but the full effect of the leeching would become apparent only over time, as his wound, infused with the animal's anti-clotting enzymes, continued to bleed heavily for the next few hours. "Come back in two days for one more leech and you'll be right as rain," Peters told him. Then he doused the leech in a weak solution of alcohol to knock it out--"More humane," he said--followed by a strong solution of alcohol, which killed it. He placed the dead leech in its container in the trash can beside his desk. "Think about it," he said. "It's like a dirty needle--that can walk."

Biopharm is one of the world's largest commercial leech farms. (There are three others, in France, Germany, and Russia.) Last year, Biopharm sold approximately fifty thousand leeches, most of them to hospitals in Britain and the United States. Once symbols of medical ignorance and barbarity, leeches are now on hand at many major American hospitals, where they owe their unlikely rehabilitation to a high-tech branch of medicine that emerged in the nineteen-eighties: microsurgery, in which doctors repair tiny blood vessels while peering through a microscope.

Bruce Minkin, a surgeon in Asheville, North Carolina, who performs microsurgery to reattach severed fingers, keeps leeches in a jar of distilled water in his office. "When you're sewing on a finger, it's relatively easy to join up the arteries that pump blood into the digit, because they're big and they've got thick walls," he says. "But it's tougher to connect the tiny veins that drain the blood away from the finger and back to the heart." When veins fail to connect properly, venous congestion--what Minkin calls the "sludging up" of excess blood--can occur. A congested finger will turn blue and cold and, unless circulation is quickly restored, will die.