Crewman Fredrick Persson was on deck, helping to bring the Swedish cargo ship 'Carman' into Bristol docks, when a rope coiled round his right hand suddenly jerked tight, all but severing his four fingers. He was rushed to the special reconstructive-surgery unit at a local hospital, where doctors decided two of his fingers were too badly mangled to be saved. In a delicate eight-hour operation using the most sophisticated microsurgery techniques, plastic surgeon Donald Sammut succeeded in re-attaching the others. 'I am happy to have even two fingers left,' the young Swede said gratefully as he came out of the surgery.His relief was short-lived. Within 48 hours, the fingers started to go black. A blockage of blood was building up,' explains Sammut. Modern surgery could not do more, so Sammut resorted to one of the medicine's oldest aids: the leech. Over the next two days, he fastened a succession of the black slippery creatures to Persson's fingers. They sucked out surplus blood, freeing veins to reconnect naturally so that circulation was restored. A fortnight later, in November 1993, Persson flew home. Leeches come in around 650 species, from 1.5 centimetre long slivers to specimens that reach a jumbo 45 centimetres when fully extended, and are found in many parts of the world. These annelids - not all bloodsucking - breathe through the skin, have two hearts and go for months between meals. Some have suckers at each end of the body. They are making an astonishing comeback in medicine. In recent years Hirudo medicinalis, the leech used for medical purposes, has performed its quiet miracles for thousands of surgical patients and accident victims around the world. When the leech bites into the flesh with its 300 sharp teeth, leaving an inverted Y-shaped mark, it injects a powerful anaesthetic; the patient feels no pain. As it starts sucking, the leech secretes a cocktail of substances that act as an anti-coagulant, to ensure the blood's purity and keeps it flowing. Even though the leech may suck for only 30 minutes, bleeding' may continue for several hours or so, clearing the most challenging blockage. Ear reconnections are notoriously difficult because the ear's blood vessels are so small, measuring no more than half a millimetre in diameter. When five-year-old Guy Condelli had his right ear bitten off by a dog, surgeons reattached it in a 12-hour operation. But three days later it turned blue, then purple.​