The<unk>  is a medical device previously used to determine the location and aid the removal of bullets and shrapnel in a patient's body. The device would be used by a surgeon who would, with the help of x-ray photographs, precisely remove the foreign object. The device would usually give a location within 1 or 2 millimeters of the foreign object. At its peak, the average rate of projectile removal when the device was used by local surgeons reached approximately 90%. The device was extensively used during World War I.
Hirtz compass
Ocular tilt reaction
Haller index
Cup-to-disc ratio
Krogh length
Stenger test
Mentzer index
Acoustic reflex