442 



THE CIRCULATORY SYSTEM. 



The endocardium which forms the valves is that which is most fre- 

 quently involved, but the other portions of it are by no means exempt. 



In fostal life it is the endocardium of the right heart, in extra-uterine 

 life that of the left heart, which is usually affected. 



1. Simple Acute Endocarditis. This is frequent with rheumatism, but 

 may occur under other conditions. It may occur in a heart previously 

 healthy, or in one already the seat of chronic endocarditis. 



In some cases the only lesion is a simple swelling of the valves. These 

 are thick and succulent, but their surfaces remain smooth. The base- 

 ment substance is swollen, and there is a 

 moderate production of new connective-tissue 

 cells. In other cases the growth of connective- 

 tissue cells is more marked, the basement sub- 

 stance is split up, and little cellular fungous 

 masses of connective tissue, called "vegeta- 

 tions," project from the free surface of the 

 endocardium. On these roughened surfaces 

 the fibrin of the blood is 

 deposited, and thus vegeta- 

 tions of considerable size 

 may be formed (see Fig. 

 237). In still other cases 

 the cell growth, while in 

 some places forming vege- 

 tations, in other places de- 

 generates, and thus por- 

 tions of the valves are 

 destroyed. This is simple 

 acute ulcerative endocarditis. 

 In some cases of this disease the patients 

 recover and the valves seem to return to a 

 normal condition; in other cases the valves 

 are left permanently damaged; and in still 

 others chronic endocarditis follows the acute 

 form. 



2. Mycotic or Malignant Endocarditis (Ma- 

 lignant Ulcerative Endocarditis). 



The direct excitants of simple acute endocarditis of the forms described 

 above are unknown, but in a considerable number of cases of acute 

 endocarditis bacteria have been found in and about the vegetations, and 

 proved, by careful experiments, to stand in a causative relation to the 

 lesion. 



Those cases of acute endocarditis in which the lesions are induced by 

 the direct action of bacteria are called mycotic or malignant endocarditis ; 

 or, since the new-formed as well as the old tissue about the bacteria is 

 apt to become necrotic and thus lead to larger or smaller losses of sub- 

 stance, the lesion is often called malignant ulcerative endocarditis. 



FIG. 239. CHRONIC ENDOCARDITIS. 



Section showing thickening of the 

 cusp of the aortic valve. 



