|Henry Gray (18251861). Anatomy of the Human Body. 1918.|
| In the position of expiration the lower border of the lung may be marked by a slightly curved line with its convexity downward, from the sixth sternocostal junction to the tenth thoracic spinous process. This line crosses the mid-clavicular line at the sixth, and the midaxillary line at the eighth rib.|
| The posterior borders of the lungs are indicated by lines drawn from the level of the spinous process of the seventh cervical vertebra, down either side of the vertebral column, across the costovertebral joints, as low as the spinous process of the tenth thoracic vertebra.|
| The position of the oblique fissure in either lung can be shown by a line drawn from the spinous process of the second thoracic vertebra around the side of the thorax to the sixth rib in the mid-clavicular line; this line corresponds roughly to the line of the vertebral border of the scapula when the hand is placed on the top of the head. The horizontal fissure in the right lung is indicated by a line drawn from the midpoint of the preceding, or from the point where it cuts the midaxillary line, to the midsternal line at the level of the fourth costal cartilage.|
Trachea.This may be marked out on the back by a line from the spinous process of the sixth cervical to that of the fourth thoracic vertebra where it bifurcates; from its bifurcation the two bronchi are directed downward and lateralward. In front, the point of bifurcation corresponds to the sternal angle.
Esophagus.The extent of the esophagus may be indicated on the back by a line from the sixth cervical to the level of the ninth thoracic spinous process, 2.5 cm. to the left of the middle line.
Heart.The outline of the heart in relation to the front of the thorax (Figs 1216, 1218) can be represented by a quadrangular figure. The apex of the heart is first determined, either by its pulsation or as a point in the fifth interspace, 9 cm. to the left of the midsternal line. The other three points are: (a) the seventh right sternocostal articulation; (b) a point on the upper border of the third right costal cartilage 1 cm. from the right lateral sternal line; (c) a point on the lower border of the second left costal cartilage 2.5 cm. from the left lateral sternal line. A line joining the apex to point (a) and traversing the junction of the body of the sternum with the xiphoid process represents the lowest limit of the heartits acute margin. The right and left borders are represented respectively by lines joining (a) to (b) and the apex to (c); both lines are convex lateralward, but the convexity is more marked on the right where its summit is 4 cm. distant from the midsternal line opposite the fourth costal cartilage.
| A portion of the area of the heart thus mapped out is uncovered by lung, and therefore gives a dull note on percussion; the remainder being overlapped by lung gives a more or less resonant note. The former is known as the area of superficial cardiac dulness, the latter as the area of deep cardiac dulness. The area of superficial cardiac dulness is somewhat triangular; from the apex of the heart two lines are drawn to the midsternal line, one to the level of the fourth costal cartilage, the other to the junction between the body and xiphoid process; the portion of the midsternal line between these points is the base of the triangle. Latham lays down the following rule as a sufficient practical guide for the definition of the area of superficial dulness. Make a circle of two inches in diameter around a point midway between the nipple and the end of the sternum.|
| The coronary sulcus can be indicated by a line from the third left, to the sixth right, sternocostal joint. The anterior longitudinal sulcus is a fingers breadth to the right of the left margin of the heart.|
| The position of the various orifices is as follows: The pulmonary orifice is situated in the upper angle of the third left sternocostal articulation; the aortic orifice is a little below and medial to this, close to the articulation. The left atrioventricular opening is opposite the fourth costal cartilage, and rather to the left of the midsternal line; the right atrioventricular opening is a little lower, opposite