422 THE CIRCULATORY SYSTEM. 



may result from the organization of a blood clot following haemorrhage 

 into the sac. It may occur as the result of the latter process early in life. 



SUPRA- ARTERIAL EPICARDIAL FIBROID NODULES. Small fibrous 

 nodules are occasionally formed along the branches of the coronary arte- 

 ries, especially on the surface of the ventricles. According to the studies 

 of Knox 1 they are frequently associated with lesions of the arteries, lead- 

 ing to the weakening of their walls at these situations. 



Tuberculous Pericarditis. This lesion may occur by itself, but is apt 

 to be associated with other tuberculous inflammation in the vicinity of 

 the heart. There may be miliary tubercles scattered diffusely, or limited 

 to certain regions in the pericardium, which is otherwise little changed. 

 Not infrequently, however, there is a considerable thickening of the peri- 

 cardium, either visceral or parietal, or both. 



In such cases the new -formed tissue consists of fibrous tissue and of 

 tubercle tissue which has undergone extensive cheesy degeneration (Fig. 

 220). The thickened visceral and parietal layers of the pericardium are 

 often more or less grown together, so that the pericardial sac may be 

 partially or almost completely obliterated. An inflammatory exudate 

 often accompanies the tuberculous process. 



f ._-._ - . r-r-^-frc-r-^-:-^ ' 





FIG. 220. TUBERCULOUS PERICARDITIS. 



The greatly thickened pericardium shows diffuse tubercle tissue with giant cells and irregular areas of 

 cheesy degeneration. The free upper surface is covered with a layer of fresh fibrin. 



TUMORS. 



Fibromata are sometimes developed in the pericardium. They are 

 often of polypoid form, and from atrophy of the pedicle may become 

 free in the pericardial sac. Endotheliomata are of occasional occurrence 

 as primary tumors. 



Sarcomata and carcinomata occur as secondary growths either from 

 continuous infiltration or as metastatic tumors. Primary sarcoma of the 

 pericardium has been described. 4 



1 Knox, Journal of Experimental Medicine, vol. iv. ( p. 245, 1899. 

 8 Williams, New York Med. Jour., April 14th, 1900, bibl. 



