Many years ago Bardeen introduced in this country a technic for measuring the size of the heart by means of long-distance roentgenograms. Four points are involved:
A knowledge of the approximate amount of triangular distortion remaining even for distances of 2 meters or greater. This is usually less than 5 per cent.
A method of drawing in, more or less arbitrarily, the upper and lower borders, thus completing the outline of an area bounded on either side by the edges of the heart silhouetted against air-containing lung.
Adaptation of a simple engineering instrument for the measurement of the area thus outlined.
The establishment of tables showing the normal range of the relationship between this area and certain body measurements in normal subjects.
Nine years ago one of us, working with Eyster at the University of Wisconsin, amplified Bardeen's tables of the normal size of the heart of adults by developing