1402 



SUKFACE AND SUEGICAL ANATOMY 



On the right side the posterior mediastinal pleura, as it passes from the posterior 

 aspect of the pericardium, backwards, to the front of the vertebral column, sweeps over the 

 right side of the oesophagus ; hence malignant ulcers of the oesophagus are more likely 

 to invade the right pleura than the left. On the left side the posterior mediastinal pleura 

 passes from the lateral aspect of the bodies of the vertebrae on to the left side of the 

 aorta. Hence, to evacuate pus from the posterior mediastinum, there is less risk of 

 opening the pleura if the space is entered from the left side of the vertebral column. 



The seat of 

 election for tapping 

 the pleura (para- 

 centesis pleurae) is 

 the sixth or seventh 

 costal interspace, a 

 little in front of the 

 posterior axillary 

 fold. To allow of 

 the introduction of 

 a tube to drain 

 away the pus from 

 the pleural cavity 

 in empyema, a por- 

 tion of one of the 

 ribs (sixth to ninth) 

 is resected. The 

 intercostal vessels 

 and nerves, which 

 lie in the groove at 

 the inferior border 

 of the rib, are 

 avoided by remov- 

 ing the portion of 

 bone subperioste- 

 ally. If the chest 

 is opened in the 

 scapular line, care 

 must be taken not 

 to resect either the 

 seventh or the 

 eighth ribs, which 

 are exposed when 

 the arm is elevated, 

 but are overlapped 

 by the inferior 

 angle of the scapula 

 when the arm is 

 lowered. 



Anteriorly, 

 the bifurcation of 

 the trachea lies 

 opposite, or a little 

 below, the angulus 



FIG. 1094. DISSECTION OF THE PLEURAL SACS FROM BEHIND. steTni, while pOS- 



The blue lines indicate the outlines and the fissures of the lungs. (From Cunningham.) teriorly it lies a 



little below the 



level of the root of the spine of the scapula, opposite the fourth thoracic spine. 

 The bifurcation takes place one vertebra higher in the infant than in the adult 

 (Symington). 



The septum between the right and the left bronchus lies a little to the left of the 

 middle of the trachea, and the right bronchus is wider and more nearly in a line 

 with the trachea than the left bronchus ; hence the greater tendency of foreign 

 bodies to enter the right bronchus. 



