512 THE THORAX AND VERTEBRAL COLUMN 



pharynx, and it is caused by the bougie impinging against the 

 upper border of the posterior part of the cricoid cartilage. If 

 the patient swallows, the instrument readily slips past the 

 obstruction. At a distance of rather more than sixteen inches 

 from the incisor teeth, the bougie enters the cardiac orifice of 

 the stomach. 



Opposite the fourth thoracic vertebra, the oesophagus is 

 crossed anteriorly by the aortic arch and, in cases of cesophageal 

 obstruction, the possibility that the condition may be caused 



Mediastinal pleura ... 



- ~^^' Mediastmal pleura 



" 8a ^|P;> 

 Aortic arch 



Left bronchus , 



^ ^ '/,' Vena azygos 



Left recurrent nerve | 



Descending thoracic aorta i^^^^^^jThoracic duct 



Fourth thoracic vertebra 



FIG. 152. Transverse Section through the Thorax at the Level of the 

 Fourth Thoracic Vertebra. 



by aneurismal pressure must be excluded before a bougie is 

 passed. 



Malignant disease of the oesophagus commonly occurs at 

 the three places where the tube is normally constricted, and, 

 when it is situated in the upper thoracic region, the growth may 

 compress the left recurrent nerve, which ascends in the groove 

 between the left side of the trachea and the oesophagus (Fig. 152). 

 In this situation, too, it may perforate the left bronchus and give 

 rise to septic pneumonia. 



When the lower end of the thoracic part of the oesophagus 

 is the site of new growth, the disease may invade the right 

 pleural sac and cause an empysema. 



