A high-quality medical instrument designed to test reflexes and sensory function in the body, the Dejerine percussion hammer is commonly used in neurologic examinations. This medical device has a small, flat head on one end and a rubber-tipped end on the other. The flat end is used for percussion, or tapping, on the body to test reflexes, while the rubber-tipped end is used for testing sensory functions, such as touch and vibration sensation.