444 THE CIRCULATORY SYSTEM. 



It has furthermore been found that a lesion or injury of the endo- 

 cardium, either on the heart valves or elsewhere, predisposes to the lodg- 

 ment and growth upon it of pathogenic bacteria when once they have 

 gained access to the circulating blood. 



Mycotic endocarditis is frequently a secondary complicating lesion, 

 but may occur as a primary disease. It is most apt to be associated 

 with the acute infectious diseases, and may be one of the local manifes- 

 tations of pyaemia. 



FIG. 241. CHRONIC ENDOCARDITIS WITH CALCIFICATION OF THE THICKENED VALVES. 



In some cases there is a formation of new tissue in the form of organ- 

 ized vegetations on the valves or general endocardium ; in other cases 

 necrosis either of the new-formed or the old tissue is the most marked 

 feature. Thrombi are apt to form on the affected surfaces and often 

 largely make up the so-called vegetations. The mitral and aortic valves 

 are frequently the seat of the lesion, but it may occur elsewhere. 



1 For a study of local predisposing factors in malignant endocarditis see Prudden, 

 Am. Jour. Med. Sciences, vol. xciii., p. 55, 1887. 



