Leeches were one of the most commonly prescribed medical treatments until the late nineteenth century. They were a convenient way of taking blood from a patient in days when this was believed a beneficial procedure, and 20 or 30 were often applied at a time: in one case a woman with bowel problems had no fewer than 400 attached to her abdomen. In the 1890s bitter feuds were still being fought in the pages of The Lancet between older physicians who had grown up in an age when leech therapy was the orthodoxy, and their junior colleagues, who thought the practice of bleeding was antiquated and ineffective.
Until I read the following passage from John Millingen’s Curiosities of Medical Experience (1839) it had never occurred to me to wonder where all these leeches came from. He tells us that leech-farming is big business in France:
If ever you pass through La Brenne, you will see a man, pale and straight-haired with a woollen cap on his head, and his legs and arms naked; he walks along the borders of a marsh, among the spots left dry by the surrounding waters. This man is a leech-fisher. To see him from a distance — his woebegone aspect, his hollow eyes, his livid lips, his singular gestures — you would take him for a maniac. If you observe him every now and then raising his legs and examining them one after another, you might suppose him a fool; but he is an intelligent leech-fisher. The leeches attach themselves to his legs and feet as he moves among their haunts; he feels their bite, and gathers them as they cluster about the roots of the bulrushes and aquatic weeds, or beneath the stones covered with a green and slimy moss. He may thus collect, ten or twelve dozen in three or four hours.
What a way to earn a living!
One of these traders was known to collect, with the aid of his children, seventeen thousand five hundred leeches in the course of a few months; these he had deposited in a reservoir, where, in one night, they were all frozen en masse. But congelation [freezing] does not kill them, and they can easily be thawed into life, by melting the ice that surrounds them.
There follows a useful tip which I would be tempted to test for myself, if I had some leeches to hand:
Leeches kept in a glass bottle may serve as a barometer, as they invariably ascend or descend in the water as the weather changes from dry to wet, and they generally come to the surface prior to a thunder-storm.
Millingen was an army surgeon who served under Wellington; the story he cites from his experiences in Portugal hardly bears thinking about:
Many serious accidents have arisen from leeches being swallowed in the water of swamps and marshes, too frequently drunk with avidity by the thirsty and exhausted soldier. Larrey mentions several cases of the kind during the French campaign in Egypt, and two fatal instances fell under my observation during the Peninsular War; draughts of salt-water, vinegar, and various stimulating injections could not loosen their hold, and they were too deeply attached in the throat to be seized with a forceps.
Patriots will be glad to learn that we did not rely on French imports for our own leech consumption: good old British leeches were also available.
Norfolk supplies the greater part of the leeches brought to London, but they are also found in Kent, Suffolk, Essex, and Wales. The best are the green, with yellow stripes along the body. The horse-leech, which is used in the north of Europe, but also common in England is entirely brown, or only marked with a marginal yellow line. A popular belief prevails, that the application of this variety is most dangerous, as they are said to suck out all the blood in the body.
This may be a myth, but I might steer clear of horse-leeches, just to be on the safe side.