An extractable device is used to insert a medicinal filling into an animal tissue. The device comprises a filling member and a pasty medicine. The filling member is made of a flexible and hermetic wall and is provided with a holding portion and an injection port via which the pasty medicine is injected into the holding portion after the filling member is inserted into the animal tissue. The holding portion is provided with an opening which is releasably lashed by one end of one or more threads so as to make the opening leakproof. Upon completion of solidification of the pasty medicine in the holding portion of the filling member, other end of the thread is pulled to unlash the opening of the holding portion, thereby enabling the filling member to be extracted from the animal tissue so as to leave only the medicine in the animal tissue.