The<unk>  is divided into two lobes, an upper and a lower, by the oblique fissure, which extends from the costal to the mediastinal surface of the<unk>  both above and below the hilus.
As seen on the surface, this fissure begins on the mediastinal surface of the<unk>  at the upper and posterior part of the hilus, and runs backward and upward to the posterior border, which it crosses at a point about 6 cm. below the apex.
It then extends downward and forward over the costal surface, and reaches the lower border a little behind its anterior extremity, and its further course can be followed upward and backward across the mediastinal surface as far as the lower part of the hilus.
Left lung
Right lung
Hilum of lung
Inferior border of lung
Mediastinum
Horizontal fissure of right lung
Thoracic cavity
Mediastinal surface of lung