PLATE LVI. 

 THE POSTERIOR VIEW OF THORAX. 



In this dissection the whole of the vertebrae were removed, also the ribs as far as 

 their angles. The body had not been dissected from the front of the thorax, so that 

 everything is nearly in its normal position ; save that, owing to the removal of the con- 

 necting vertebras, the space has been elongated by the weight of the abdomen and head 

 and neck dragging in opposite directions over the blocks on which the trunk was 

 supported. The obliquity of the higher aortic intercostals is also well shown ; these in 

 the early foetus come off at right angles to the aorta, and it is only after the first year of 

 birth that the obliquity makes its appearance. 



The posterior mediastinum includes that portion of the interpleural space behind 

 the pericardium and below the level of the fourth dorsal vertebra. It is bounded 

 In front, by the pericardium ; 

 Behind, by the bodies of the vertebrae ; and 



Above, by a plane passing through the joint of the manubrium and gladiolus sterni 



and the lower part of fourth dorsal vertebra. 

 Beloit', by the diaphragm. 



Contents. Descending part of aortic arch and thoracic aorta ; origin of the aortic 



intercostals ; azygos major, minor, and left upper azygos veins. 

 (Esophagus and thoracic duct. 

 Posterior mediastinal glands. 

 Vagi and plexus guhe. 



Professor Macalister limits the term ' aortic arch ' to the transverse portion of the 

 aorta as the ascending portion belongs to the ventral, and the descending portion to the 

 dorsal or thoracic aorta. 



