1. An electrodynamograph comprising: a hand-driven device repeatedly squeezable and provided with a transducer; a recorder operatively connected to said transducer for producing a trace of the output thereof as a function of time; an audio-frequency generator producing an acoustic signal; a multivibrator control switch connected to said audio-frequency generator for interrupting the signal produced thereby; a loudspeaker connected to said multivibrator control switch for rendering the audio-frequency output audible to the test subject at a predetermined cadence, said cadence and the amplitude of the audio output of said multivibrator control switch being adjustable, said transducer comprising a primary coil and a secondary coil inductively coupled to said primary coil, and a metallic screen displaceable between said coils by said device, said audio-frequency generator applying said audio frequency signal to said primary coil to generate an audio-frequency current in said secondary coil; a multivibrator switch of adjustable frequency connected between said transducer and said recorder for periodically interrupting the signal applied to said recorder to provide time markings on said trace; and a first counter registering stroke-start operations of said device and a second counter registering stroke end operations of said device, said counters being controlled by two pairs of electrical contacts associated with said transducer whereby a first of said contacts is closed at the beginning of said stroke and the second of said contacts at the end of said stroke.