3 o THORAX 



part of the root, below and slightly posterior to the main 

 bronchus. If the specimen is well injected, branches of the 

 right bronchial artery may be distinguished on the posterior 

 faces of the air tubes ; and anterior to and between the great 

 blood-vessels, and between them and the bronchi, are a 

 number of bronchial glands, which are easily distinguished 

 by the black pigment deposited within them. 



On the left side, in the posterior part of the root of the lung, 

 the dissectors will see the cut section of the left bronchus, 

 and, in many cases, a section of its first ventral branch also. 

 The left pulmonary artery is above the bronchus, and its 

 anterior wall is on a slightly anterior plane. The upper left 

 pulmonary vein is anterior to the bronchus, and the lower 

 left pulmonary vein is below the bronchus. In a well in- 

 jected specimen the two left bronchial arteries may be seen 

 on the posterior wall of the bronchus, and a number of 

 bronchial glands will be found between and around the large 

 blood-vessels and the bronchus. 



Turning next to the mediastinal pleura on the right side, 

 the dissectors will note, anterior to and below the root of the 

 lung, a large bulging, due to the heart and pericardium, which 

 lie in the middle mediastinal area. Continuous with the 

 upper and lower ends of the posterior part of this bulging 

 they will see two longitudinal elevations. The upper, from 

 the level of the third costal cartilage to the lower margin 

 of the first rib, is due to the superior vena cava, and above 

 that level, to the right innominate vein. The lower elevation 

 is very short, and is caused by the upper part of the inferior 

 vena cava. A secondary ridge, formed by the phrenic nerve 

 and the accompanying blood-vessels, descends along the 

 elevation caused by the innominate vein and the superior 

 vena cava, crosses anterior to the root of the lung, runs down 

 along the posterior part of the bulging due to the heart, and 

 the anterior border of the inferior caval elevation. Arching 

 over the root of the lung is a curved ridge, due to the upper 

 part of the vena azygos, as it passes forwards to join the 

 superior cava. Above the vena azygos and posterior to the 

 superior cava, the right surface of the trachea, or main air 

 tube, may be seen or felt in the superior mediastinal region, 

 and, descending obliquely across it, from above downwards 

 and backwards, the right vagus nerve can be palpated or 

 seen. Behind to the root of the lung and to the bulging 



