Abstract
Summary and Conclusions
1. The motion of the mediastinum, relative to thoracic skeleton, was studied in cadavers, using photoelectric recording of oscillations after tapping the heart of cadavers with the thoracic cage intact except for removal of 2 costal cartilages. 2. In very cold bodies frequencies of the mediastinum were as low as 2/sec. and damping nearly 100%. In 10 fresh, warm cadavers the average frequency of oscillation was 8/sec. and damping varied from 40 to 86% of critical with an average of about 65%. In a given subject, there was variation in frequency and damping in the 3 planes, so that forces may not be equally transmitted in these planes. 3. Distortion of ballistocardiographic forces in transmission from mediastinum to skeleton should be less than taht in transmission from throacic skeleton to a high frequency table, or to the head or tibiae in direct recording of head-foot waves, because the natural frequency is not as close to that of the ballistocardiographic waves.
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