CHAPTER XII. 



DISEASES OF THE VASCULAR SYSTEM. 



HEART AND PERICARDIUM. 



PERICARDITIS. 



INFECTION carried by the blood stream or by lymphatics, is 

 probably the commonest cause of pericarditis. This is the ex- 

 planation of rheumatic, tuberculous, septic and some pneumonic 

 varieties. The vessels and lymphatics of the serous pericardium 

 are intimately connected with those of the myocardium so both 

 the heart and its investing sac may be involved simultaneously. 



Extension from neighbouring structures occasionally gives 

 rise to pericardial inflammation. The close way in which the 

 pericardium is enveloped by the lungs and pleural sacs explains 

 the occasional spread of inflammation to it from pneumonic, 

 tuberculous or gangrenous lung. Empyemata may in similar 

 manner give rise to purulent pericarditis. The connective tissue 

 basis of the pericardium is continuous with that of the lung, 

 pleura and mediastinum, and inflammation may simultaneously 

 involve all these structures or extend from one to the other. 

 Adjacent lymphatic glands may invade or infect the pericardium. 

 Four groups of these lie in immediate contact with the sac. The 

 glands which lie along the internal mammary arteries are in 

 front, the cardiac group of glands above, the glands around the 

 tracheal bifurcation, and those about the lower end of the 

 oesophagus, behind. Most of these glands are in direct lymphatic 

 connexion with the sac, and may themselves become enlarged 

 as the result of pericarditis. 



Occasionally aortic aneurysms burst into the pericardial cavity. 

 The first part of the aorta is actually within the sac, and the 

 descending thoracic aorta passes down close behind it. Aneurysms 



