Abstract: An improved reflex gun (21) is adapted to measure certain parameters of a stimulus supplied to a tendon, and the patient's response thereto. The gun has a trigger (29) which, when squeezed, supplies a signal to a computer (24). The computer then causes a waveform generator (32) to provide current pulses of desired magnitude, shape and duration to a solenoid (50) in the gun. Such energization of the solenoid coil, causes a plunger (52) to impact against one end of a force sensor (22). The other end of the force sensor is held against the patient's skin with a preload force sufficient to measure the patient's response to a force stimulus. The force sensor has a transducer (132) for measuring the certain parameters of the impact force and the patient's response. The improved device may be used to determine quantitatively certain parameters of the stimulus and response, and provides a diagnostic tool for a physician.