22 THORAX 



with the limits of the pleural sacs, he should examine the cut 

 section of the root of the lung, and should endeavour to 

 recognise, through the mediastinal part of the parietal pleura, 

 the positions of the main constituent parts of the mediastinum. 

 As these vary on the opposite sides, each side must be con- 

 sidered separately, and each dissector must make himself well 

 acquainted with the conditions on both sides. 



On the right side, in the posterior part of the face of the section 

 of the lung root, at least two parts of the bronchial tube will 

 be seen ; an upper, which is the so-called eparterial bronchus, 

 and a lower, the main stem of the right bronchus. Anterior 

 to and between the two bronchi is the pulmonary artery, and 

 more anteriorly, and at a slightly lower level, the upper pul- 

 monary vein. The lower pulmonary vein lies in the lowest 

 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. 



In the posterior part of the root of the lung, on the left side, 

 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 



