DISSECTION OF THE THORAX 405 



gated by the method devised by Sir William Turner. (See Fig. 

 201.) 



Saw through the sternum as follows : 



(1) Transversely through manubrium sterni on a line connecting the 



lower margins of the incisurae costales I., i.e., parallel to the 

 lower margins of the first pair of costal cartilages. 



(2) Transversely through the lower part of the corpus sterni, midway 



between incisura costalis V. and incisura costalis VI. 



(3) Obliquely, almost vertically,, from the inferior transverse cut near 



the left margin of the sternum, upward to the middle of the supe- 

 rior transverse cut. 



The saw should not be permitted to pass through the perios- 

 teum on the back of the sternum ; this is to be cautiously divided 

 with a scalpel. 



Gently separate the two lateral portions of the central piece 

 of the sternum ; observe the parietal pleura on each side passing 

 backward towards the pericardium. Insert the finger between 

 the right and the left pleura, and pass it upward and downward 

 through the loose areolar tissue of the anterior mediastinal cav- 

 ity (cavum mediastinale anterius) (O. T. anterior mediastinum), 

 between them, until the pericardium is exposed. 



Next separate the pleura costalis from the ribs, as far for- 

 ward as the cartilages, by carefully passing the index-finger 

 between the pleura and each rib and running it backward and 

 forward ; be sure not to detach the pleura from the costal carti- 

 lages. Excise, with bone-forceps, the second, third, fourth, fifth, 

 and sixth ribs, cutting through them in front at their junctions 

 with the costal cartilages, and behind as far back as is possible. 

 Leave the sternum and costal cartilages, with adherent pleura, 

 for the present, in position. 



Cut vertically through the pleura costalis, midway between 

 spine and sternum, from level of costa II. to level of costa VII. 

 Make two transverse incisions medialward for a distance of five 

 or seven centimetres, one from each end of this vertical incision, 

 and reflect the large flap of costal pleura medialward. The 

 cavity of the pleura (cavum pleurae) has now been opened. 



Exploration of Pleural Cavity. 



Pass the hand into the cavum pleurae and trace the membrane 

 (1) in a transversal direction, (2) in the vertical direction. Con- 

 trol your exploration by a study of the figures in atlases and by 

 a description in a good systematic text-book. Trace the parietal 



