Leech Jar
Glencoe Folk Museum

Leeches were stored in this jar in a pharmacy before being sold to physicians. These parasitic worms were used for bloodletting, once a popular therapy believed to cure a range of conditions.   

The practice of bloodletting relied on Galen’s humoral theory, which proposed that human health relied on a balance of the four humours: blood, phlegm, black bile and yellow bile. If blood was seen to be in excess, doctors prescribed leeches to restore the balance.   

It may come as a surprise to hear that leeches still play a part in modern medical practice, although not quite in the same way. They are now often used as treatment for skin grafts and reconstructive surgeries, in which tissue is at risk of dying due to insufficient blood supply. Placing leeches in the affected area encourages blood flow to the tissue, and keeps the skin graft alive.