Collecting leeches is a remarkably straightforward process. Find a swamp, put some bait into it, wait for the leeches to attach, harvest them, and sell them for profit. According to Ripley’s, the job was generally done by poorer people, particularly women. One method involved using the legs of an older and useless horse as bait. Another method eliminated the middle man, so to speak, and involved the collectors using their own legs as bait. The collector, once bitten, would have to wait about 20 minutes to remove the worm, as it’s generally easier to get rid of a leech once it’s gorged on blood. Workers who subjected themselves to these conditions often caught diseases, or at the very least, were weakened by blood loss at the end of a day’s work. Fortunately, medicine eventually moved on from using leeches in favor of other therapies, and the practice of leech collecting died out.

As it turns out, however, leeches are still used in medicine today, according to Healthline, albeit for very specific purposes. The worms produce peptides and proteins that help to prevent blood clots, and as such, they’re sometimes used in plastic surgery or microsurgery. However, the medical community gets its leeches these days not from freelance collectors risking their own health, but from farms.