THE LUNGS. 



Fig. 432. The Posterior Mediastinum. 



183 



The external or thoracic surface is smooth, convex, of considerable extent, and 

 corresponds to the form of the cavity of the chest, being deeper behind than 

 in front. 



The inner surface is concave. It presents, in front, a depression correspond- 

 ing to the convex surface of the pericardium, and behind, a deep fissure (the 

 hilum pulmonis) which gives attachment to the root of the lung. 



The posterior border is rounded and broad, and is received in the deep con- 



