This was probably a used to introduce chemicals per urethra for the treatment of syphilis and other venereal diseases which were rife at the turn of the 19th century.
It can be dissembled into its constituent parts. The body is made from a single hollow tube of bone onto which flat disks of bone are screwed at either end. The plunger fits through one of these and waxed chord wound around the distal end would have made a watertight connection with the body. The other end accommodates a nozzle which is also secured with a screw. The style of the instrument and the finial of the plunger date the piece to the late 18th or early 19th century.