A poultice, also known as cataplasm, was a soft moist mass which was spread on a cloth, to treat a part of the body that was injured.
In 2378, Commander Chakotay's leg was injured after he and Seven of Nine beamed off their class 2 shuttle just before it was destroyed by an energy barrier on Ledos. After being taken in by the Ventu, a group of primitives, Chakotay's leg was healed by them when they attached the poultice to his leg. After Chakotay returned to the USS Voyager, The Doctor examined his leg in sickbay and was impressed with the medical expertise of the Ventu. (VOY: "Natural Law")