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Is the epigastric region. Also, and more properly, the region of the heart. A line drawn from the inferior margins of the third ribs across the sternum, passes over the valves of the pulmonary artery a little to the left of the mesial line, and those of the aorta are behind them, but about half an inch lower down. A vertical line, coinciding with the left margin of the sternum, has about one-third of the heart, comprising the upper portion of the right ventricle, on the right, - and two-thirds, comprising the lower portion of the right ventricle and the whole of the left, on the left. This is the precordial region.