Henry Gray (18251861). Anatomy of the Human Body. 1918.
On the left side, beginning at the sternoclavicular articulation, it reaches the midpoint of the junction between the manubrium and body of the sternum and extends down the midsternal line in contact with that of the opposite side to the level of the fourth costal cartilage. It then diverges lateralward and is continued downward slightly lateral to the sternal border, as far as the sixth costal cartilage. Running downward and lateralward from this point it crosses the seventh costal cartilage, and from this onward it is similar to the line on the right side, but at a slightly lower level.
Lungs (Figs. 1216,1217).The apex of the lung is situated in the neck above the medial third of the clavicle. The height to which it rises above the clavicle varies very considerably, but is generally about 2.5 cm. It may, however, extend as high as 4 or 5 cm., or, on the other hand, may scarcely project above the level of this bone.
FIG. 1217 Side of thorax, showing surface markings for bones, lungs (purple), pleura (blue), and spleen (green). (See enlarged image)
In order to mark out the anterior borders of the lungs a line is drawn from each apex point2.5 cm. above the clavicle and rather nearer the anterior than the posterior border of Sternocleidomastoideusdownward and medialward across the sternoclavicular articulation and manubrium sterni until it meets, or almost meets, its fellow of the other side at the midpoint of the junction between the manubrium and body of the sternum. From this point the two lines run downward, practically along the midsternal line, as far as the level of the fourth costal cartilages. The continuation of the anterior border of the right lung is marked by a prolongation of its line vertically downward to the level of the sixth costal cartilage, and then it turns lateralward and downward. The line on the left side curves lateralward and downward across the fourth sternocostal articulation to reach the parasternal line at the fifth costal cartilage, and then turns medialward and downward to the sixth sternocostal articulation.