Comparative recording of the heart beat by ultralow frequency and direct body methods with evidence of their basic clinical identity.

An attempt has been made to validate the d-v-a modification of the direct body electromagnetic shin bar in the ballistocardiographic evaluation of cardiac function. Its essential mirror reflections of body movements recorded with Ulf have been amply illustrated. A plea is made for a resumption of interest in its wider clinical application within a rigid correlative framework.