This section is from the "Impaired Health: Its Cause And Cure" (Volume 1) book, by John H. Tilden. Also available from Amazon: Impaired health its cause and cure: A repudiation of the conventional treatment of disease
In examining the heart, there are two zones--namely, a superficial, which corresponds to a lung-dull sound, and means that portion of the heart covered by the lung; and a heart-dull sound, which is triangular- shaped and flat. The lung-dullness is bounded by a line extending along the left border of the sternum, at the lower border of the second rib, and extending by an imaginary curved line reaching the apex of the heart. Then draw a second line from the border of the second rib to meet the end of the imaginary line at the apex, curving it to the left somewhat. The two lines leading downward from the second rib may be called the right and left arms of an irregular triangle; the point where they meet at the top may be called the apex of the triangle; and the line connecting the right and left arms at the apex of the heart may be called the base of the triangle. The flat or heart-dull sound begins at the level of the fourth rib and terminates at the apex of the heart.
The flatness (heart-dullness) of the base of the triangle may be confounded with liver-dullness; but the physician will follow the outline of the liver and make his deductions as to liver and heart sounds.
It is to be understood that the area of dullness and flatness may vary in health, and the variation must be greater in disease.
The principal modifications are:
First, in hypertrophy of the left ventricle, the apex is pushed downward and outward. The flatness is slightly above the nipple.
Second, in hypertrophy of the right ventricle, the apex is pushed outward, and the flatness is slightly above the nipple and to the right of the sternum.
If the accumulation is slight, the flatness extends below the apex beat. When the effusion is great, the flatness extends over much more of the chest wall.
The most important mode of exploration of the chest is by auscultation. It requires a good ear to be educated into reading symptoms by sound.
The aortic orifice is in the right second intercostal space. The pulmonary orifice is in the left third intercostal space. The mitral orifice is at the apex beat. The tricuspid orifice is at the xiphoid appendix.