THE THORAX. 207 



base of the lung rests on the pulmonary surface of the diaphragm. The lung has 

 a pleuritic attachment to the vertebral column, called the ligauicntum latmn 

 pulmonis. 



Anatomical Root of the Lung. Like the root of the liver, the root of the 

 lung transmits structures whereby the lung carries on (i) the functional activity ; 

 (2) the nutritive activity of the lung. By the latter the lung as an organ lives ; 

 by the former the lung as an organ aerates the blood. Pull the lung carefully 

 over the cut margin of the ribs (Fig. 145) and you will see the root structures. 



Inflate the lungs and study the lobes and fissures. Introduce a one-half inch 

 rubber tube into the trachea and inflate the lungs. You will then see a space, 

 corresponding to one-third the anterior surface of the heart, that is not covered 

 by the lungs when they are inflated. If you could mark on the chest-wall the size 

 of this space, that would give you the area of precordial dullness on percussion. 

 As you inflate the lungs you notice the right lung has three, the left two, lobes. 



The root structures of the lungs are : 



1. The bronchial tubes, air-conveying conduits. 



2. The bronchial arteries, nutritive conduits to the lungs. 



3. The pulmonary artery, bearing blood laden with CO 2 . 



PLEURA PULMONIS 



PLEURAL CAVITY 



PLEURA COSTAUS 



FIG. 146. INVAGINATION OF PLEURA. 



The three structures produced by invagination of pleura may be schematically represented as the above 

 figure shows. I. The visceral layer, or pars pleurae invaginata. 2. The parietal layer, or pars pleurse 

 costalis. 3. The pleural cavity. The same schemejgives like results in accounting for the cavity and 

 layers in connection with peritoneum and pericardium. 



4. The pulmonary veins, bearing blood -j-O, and CO 2 . 



5. The pulmonary sympathetic nerves, from the pulmonary part of the cardiac 

 plexus. 



You are to learn that the thoracic, abdominal, and pelvic viscera are inner- 

 vated' by the sympathetic nerve. ' The cardiac gangliated plexus supplies the 

 thoracic organs ; the solar, the abdominal organs ; the Jiypogastric, the pelvic 

 organs. Each plexus, however, has a primary element, sympathetic, and a 

 secondary piieumogastric element ; hence we say, in general, the nerve-supply is 

 from the sympathetic. Analytically, we speak of the nerve-supply as sympa- 

 thetic and pneumogastric. 



The Pulmonary Trio. The sympathetic nerve always accompanies the 

 artery to an organ. The artery that nourishes the lungs is the bronchial ; but 

 this artery accompanies the bronchial tube. The pulmonary trio, then, consists 

 of the bronchus, the bronchial artery, and the sympathetic nerve-supply. 



Relation of bronchus, artery, and veins on the two sides are as follows : (i) 

 On the right side, from above down bronchus, artery, and vein. From before 

 back vein, artery, bronchus. 



O the left side, from above down artery, bronchus, vein. From before 

 back vein, artery, bronchus. 



