A Study of the Action Currents of Nerve with the Cathode Ray Oscillograph

The instruments which have been used heretofore for the observation of nerve action currents have been galvanometers of the moving coil or magnet type with or without the aid of a rheotome, the capillary electrometer and the string galvanometer. Each of these instruments possesses considerable inertia. The slower galvanometers are unaffected by single action currents and give a sustained deflection when the action currents are monophasic and rapidly repeated. The size of the deflection is the mean value of the individual waves which in turn depends upon their shape and the rate at which they are repeated. As the former is not known the deflections are mainly of qualitative significance. All of these instruments are governed by the laws of forced vibration with damping. The differential equation expressing this law is