THE CONTENTS OF THE THORAX. 99 



panying the splanchnic nerves through the lumbar origin (crura) of the muscle; the thoracic 

 duct, through the aortic opening; and the superior epigastric veins through the fissure of Larrey. 



The arteries supplying the upper surface of the diaphragm are the comes nervi phrenici 

 (pericardiaco-phrenic artery, see Plate 8, a) and the musculophrenic, one of the two terminal 

 branches of the internal mammary. The blood-supply of the lower surface of the diaphragm 

 is furnished by the phrenic arteries, which arise from the aorta in the aortic opening or from the 

 celiac axis. 



The phrenic nerves from the cervical plexus may be easily found in the neck upon the anterior 

 surface of the scalenus anticus muscle. In the chest they run upon the pericardium and are 

 covered by the pleura mediastinalis (Plate 8). The diaphragm also receives branches from the 

 seventh to the twelfth intercostal nerves. 



The central portion of the upper surface of the diaphragm is adherent to the pericardium ; 

 the lateral portions are attached to the pleural sacs (diaphragmatic pleura). The pericardial 

 sac is in relation with the central tendon, but also extends to the left over the muscular portion 

 of the diaphragm (Fig. 44). Since the left lung is not so voluminous as the right, the left dia- 

 phragmatic pleura is not so extensive as the corresponding layer upon the right side. 



Diaphragmatic hernias are produced when abdominal viscera pass into the thorax through 

 the diaphragm. They may be congenital or acquired. The favorite site for such hernias is 

 in the vicinity of the esophageal foramen, in which the esophagus, in contrast to the aorta and 

 vena cava, is fixed by only a loose connective tissue. Such hernias are usually left-sided, since 

 the liver is situated immediately below the right dome of the diaphragm. They may contain 

 the stomach, the omentum, the large intestine, the small intestine, the spleen and other viscera. 

 The peritoneum, which lines the under surface of the diaphragm, is protruded into the thorax 

 and, together with the pleura, forms the sac of the hernia. Such a hernial sac is wanting when 

 one of the abdominal viscera enters the thoracic cavity through a complete tear in the diaphragm ; 

 this is the condition of affairs in the majority of cases of diaphragmatic hernia. There have 

 been individuals in whom the stomach has been situated above the diaphragm for many years. 



As the inferior vena cava is firmly fixed in the foramen quadratum, a marked left-sided 

 pleural exudate may, by pushing the heart over to the right, bend the vena cava to almost a 

 right angle. This may produce symptoms of cerebral anemia, unconsciousness, or even death. 

 At the same time, symptoms of venous stasis will appear in the lower extremities. It should 

 also be remembered that the diaphragm reaches much lower at the vertebral column than ante- 

 riorly at the sternum, so that horizontal penetrating wounds may open the abdominal cavity 

 in front and a pleural cavity behind (see Plate 13). 



THE CONTENTS OF THE THORAX. 



The greater portion of the inner surface of the thoracic wall is lined by the pleura. This 

 forms two sacs or cavities, the right and the left pleural cavities, which are completely separated 

 from each other and almost entirely filled by the right and left lungs. The lungs are so closely 

 applied against the pleural surface that injuries of the pleura without concomitant injury of the 

 lung are comparatively rare. The pleura lining the inner surfaces of the ribs and the inter- 



