Heaf gun syringe, 20th century. This was used to perform a Heaf, or Sterneedle, test to test for exposure to tuberculosis. This model consists of a spring-loaded plunger and multiple short sharp needles behind a plate with holes for the needles to pass through. The depth of needle penetration can be adjusted to either 1 or 2 mm. It was used to inject multiple samples of tuberculin purified protein derivative (PPD) testing serum under the skin at once. If there was a skin reaction to the PPD, the patient had been exposed to tuberculosis.