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The cathode ray is practically free from inertia and therefore an ideal instrumentality for studying variations in electrical potential. A cathode ray oscilloscope with an amplifier system of high frequency response and an expanded time scale, 330 mm. per second, were employed to record electrocardiograms. Such tracings revealed considerable notching, slurring, and other peculiarities not seen in the conventional electrocardiographic records on the same individuals. An instrument should have a frequency response curve flat to well over 330 cycles per second to record faithfully the human electrocardiogram. This is much higher than the frequency response of instruments usually used for electrocardiography.
Paul H. Langner (Fri,) studied this question.