We have a replica leeches jar in our History of Medicine Collection.
Leeches have been used in medicine since ancient times. During the 19th century, when bloodletting was very popular, leeches were used by physicians on a massive scale. It was believed that weakening the body through the reduction of blood flow treated a variety of disorders, especially fevers and inflammatory diseases. Medicinal leeches were used along with such surgical instruments as lancets and fleams to drain blood.
Jars like these were used by pharmacists to show their supply of medicinal leeches. Holes were cut into the lid to allow for air, and the pharmacist stocked the jar with leeches intended for sale that day. The elaborate decoration of the jars demonstrated the high value leeches held. They were sold in great numbers to members of the medical profession and the public.
Leeches are still occasionally used in modern medicine in reattachment surgery and skin grafts.