274 CLINICAL APPLIED ANATOMY. 



of the root of the left lung and the back of the sinus obliquus 

 of the pericardium. Paroxysmal cough, spasmodic dyspnoea, 

 bronchitis, and deficient air entry in the left lung are very 

 characteristic of aneurysm in the region of the lung root which 

 presses on the back of the left bronchus, into which it may and 

 often does open. More rarely the aneurysm opens into the 

 trachea near its bifurcation. When the aneurysm lies lower 

 down it is behind the heart and pericardium. It is rather excep- 

 tional for the pericardium to be perforated in this position, but 

 both heart and pericardium may be forcibly pressed forwards 

 against the anterior chest wall, giving rise to an extensive area 

 of visible cardiac pulsation. 



The oesophagus is at first to the right of the descending 

 thoracic aorta, but later comes to lie in front of the vessel, and 

 may even pass a little to its left side, just above the oesophageal 

 opening in the diaphragm. In consequence of its intimate 

 relation to the artery, dysphagia may be produced, and the 

 aneurysm may burst into the food passage. Before passing a 

 bougie in the investigation of dysphagia the possibility of the 

 presence of an aneurysm of this part of the aorta should be 

 carefully considered. 



By backward expansion the aneurysm may erode the vertebral 

 bodies. The yielding intervertebral discs persist in a charac- 

 teristic way, while the resistant vertebral bodies are extensively 

 destroyed. Deep-seated gnawing pain may be the result of the 

 bone erosion, and the corresponding intercostal nerves may be 

 involved, with resulting intercostal neuralgia and segmental 

 hyperaesthesia or anaesthesia. Pressure may be exerted on the 

 spinal cord, either gradually by the advancing aneurysm or 

 suddenly as the result of fracture of the weakened spinal column. 

 In the upper part of the posterior mediastinum the descending 

 aorta is placed on the left sides of the bodies of the vertebrae, 

 and when aneurysm is present an area of dulness, and even 

 of pulsation with projection, may be recognised between the 

 spinal column and the scapula on the left side. The gangliated 

 chain of the sympathetic lies over the costo-central articulations 



