t 

 THE MEDIASTINUM, OR INTERPLEURAL SPACE 1187 



as far as the Diaphragm (but is not attached thereto) between the pericardium 

 and the lower part of the inner surface of the lung, having a free falciform border 

 below, between the lung and the Diaphragm. It serves to retain the lower part 

 of the lung in position. 



Structure of the Pleura. The pleura is composed of fibroelastic connective tissue, its free 

 surface being covered with a single layer of flat endothelial cells. It is fastened to adjacent 

 structures by subserous areolar tissue. The subserbus tissue of the visceral pleura is continuous 

 with the areolar tissue of the lung. 



Vessels and Nerves. The arteries of the pleura are derived from the intercostal, the internal 

 mammary, the musculophrenic, thymic, pericardiac, and bronchial arteries. The veins cor- 

 respond to the arteries. The lymphatics are very numerous in the pleura and subserous tissue. 

 The lymphatics of the visceral layer empty into the superficial pulmonary trunks; the lym- 

 phatics of the costal pleura empty into the intercostal trunks ; of the diaphragmatic pleura, into 

 the diaphragmatic trunks ; of the mediastinal pleura, into the posterior mediastinal nodes. The 

 nerves are derived from the phrenic and sympathetic (Luschka). 



Applied Anatomy. In operations upon the kidney it must be borne in mind that the pleura 

 may sometimes extend below the level of the last rib, and may therefore be opened in these 

 operations, especially when the last rib is removed, in order to give more room. It is best to 

 keep the incision at least one inch below the last rib, enlarging the wound afterward, when the 

 finger can be introduced as a guide. 



In wounds of the Diaphragm the pleura may be injured. In operations about the root of the 

 neck, especially in the removal of lymph nodes and the ligation of the first part of the subclavian 

 artery, the pleura may be injured. 



Punctured wounds of the root of the neck are apt to reach the pleura. 



Empyema is a surgical disease. In acute empyema the treatment is drainage. A portion of 

 the fifth or sixth rib in the axillary line is removed by subperiosteal resection, the pleura is opened, 

 and a tube is introduced. In chronic empyema the lung is contracted and adherent and cannot 

 expand; hence drainage will not cure it. It is necessary to perform multiple rib resection in 

 order to permit the thoracic wall to sink in and obliterate the cavity, which, as the lung is unable 

 to expand, it cannot do. The necessary operation may be the one of either Estlander, Schede, 

 or Fowler (p. 168). 



If a large wound admits suddenly a quantity of air into the pleura, dangerous or fatal pneumo- 

 thorax arises, and the lung collapses. This is usually met during operations by using the Fell- 

 O'Dwyer apparatus for artificial respiration, as advised by Matas. 1 This apparatus keeps the 

 lung expanded, in spite of the entrance of air into the pleural sac. A surgeon can open the pleura 

 widely without any fear of the lung collapsing if he operates in a Sauerbruch chamber. The 

 pressure within this chamber is negative. The patient's head is outside of the chamber, his body 

 is within it. The bronchioles are distended by the patient inhaling air at the ordinary pressure, 

 but the exposed lung is subjected to negative pressure, hence the lung does not collapse in 'spite of 

 a large wound in the pleura. In surgical pneumothorax the lung may be sutured to the thoracic 

 wall, so as to block the opening. Sometimes, in order to arrest dangerous pulmonary bleeding, a 

 surgeon deliberately induces pneumothorax, in the hope that the collapse of the lung will arrest 

 bleeding. 



When an abscess of the liver is posterior and on the dorsum, transpleural hepatotomy is per- 

 formed. A portion of the tenth and eleventh ribs below the angle of the scapula is removed. 

 As a rule, the pleura is found obliterated at this point. If it is opened, it is at once sutured or 

 closed with gauze packing. The exposed Diaphragm is incised, and, as it is usually adherent to 

 the liver, the abscess cavity is entered. If it is not adherent, the liver is exposed and the abscess 

 sought for with an aspirating needle. 



Grocco's sign is the presence of a triangular area of paravertebral dulness above the level of 

 the twelfth rib on the side opposite to a pleural effusion. The dulness is believed to be due to a 

 displacement of the contents of the posterior mediastinum by the fluid. . 



THE MEDIASTINUM, OR INTERPLEURAL SPACE. 



The mediastinum is the space left in the median portion of the thorax by the non- 

 apposition of the two pleurae. It extends from the sternum in front to the vertebral 

 column behind, and contains all the thoracic viscera excepting the lungs. The 

 mediastinum may be divided for purposes of description into two parts an 



1 Annals of Surgery, April, 1899. 



