158 The Thorax 



As it traverses the thorax it receives the lymphatics from the oeso- 

 phagus, trachea, left heart and lung, and from the left thoracic wall. 



The right lymphatic duct, one inch long, brings the lymph from the 

 right side of the head, neck, thorax and heart, and from the right upper 

 extremity and lung ; it enters the confluence of the right internal 

 jugular and subclavian veins. 



THE PERICARDIUM 



The serous layer of the pericardium covers the heart and the first 

 i in. of the large vessels, and is thence reflected on to the interior of 

 the fibrous sac. It sends seven more or less complete tubular sheaths 

 round the vessels a common one for the aorta and the pulmonary 

 artery, four for the pulmonary veins, one for the superior cava, and a 

 scanty one for the inferior cava, which last vessel enters the auricle 

 directly after coming through the diaphragm. 



Laterally the pericardium is covered by the pleurae and lungs, the 

 phrenic nerves intervening between them. The anterior borders of 

 the lungs and the pleurae are also in front above, but, below, the peri- 

 cardium approaches the thoracic wall in an important triangular area 

 (p. 165) without the intervention of lung. 



The close proximity of the pericardium and pleura explains the 

 frequency with which inflammation of one membrane follows that of 

 the other. 



The external layer of the pericardium is of strong interlacing fibres, 

 and is firmly connected with the central tendon of the diaphragm. 

 Above, the fibrous sheath passes off in tubular prolongations which 

 blend with the outer coats of the transverse aorta and of the right and 

 left pulmonary arteries and veins, and of the superior cava. The lining 

 is of pavement endothelium. 



The close association between heart, lungs, and diaphragm not 

 only causes a descent of the thoracic viscera during inspiration, but 

 even of the trachea, as may be easily recognised by laying the 

 finger on the larynx whilst a deep breath is taken. 



When the pericardium is opened from the front the following struc- 

 tures are seen : the front of the right ventricle and the apex of the left ; 

 the right auricle and its appendix, and the appendix of left auricle ; 

 the root of the pulmonary artery, and a little of the aorta and of the 

 cavae. 



Supply. Pericardial twigs are derived from the aorta and from 

 the internal mammary, bronchial, oesophageal, and phrenic arteries. 

 Nerve-filaments come from the phrenic, the sympathetic, and the right 

 vagus. 



At the beginning of an attack of pericarditis the lining membrane 

 is dry, and roughened from fibrinous deposit, and the heart no longer 

 moves noiselessly against the parietal layer, but rubs against it, pro- 



