Graphic records of the movements of the eyes in nystagmus can be obtained by means of the electrocardiograph. The records, like the electrocardiogram, are based on the fact that a muscle under the influence of a stimulus, including a nerve impulse, is traversed by a wave of negativity, the so-called action current, immediately preceding its contraction. The current, if led off through a string galvanometer, produces a deflection of the suspended thread between its magnetic poles, the direction of the deflection varying with the direction of the current. A photograph of the deflection when obtained on a moving film thus furnishes a record not only of activity in the muscle but of the origin and course along which the current is propagated. The current flows from the point of higher to that of lower potential and, accordingly, the point at which it enters the galvanometric arc of the circuit is
MEYERS IL. ELECTRONYSTAGMOGRAPHY: A GRAPHIC STUDY OF THE ACTION CURRENTS IN NYSTAGMUS. Arch NeurPsych. 1929;21(4):901–918. doi:10.1001/archneurpsyc.1929.02210220172009
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