Abstract
The low-frequency precordial vibrations originating at the point of the apex beat, and especially those in the subaudible range, seem to offer considerable clinical usefulness. In this paper I have briefly outlined some of the physiologic, pathologic, and pharmacologic evidence to support this impression. The instrumentation we have used is crude and undoubtedly we have been misled on occasion by artifacts. However, there is sufficient validity in the technic, reproducibility of result, and correlation with intracardiac events to warrant intensive study.