ENDOCARDITIS 223 



Endocarditis. There is now strong presumptive evidence 

 that all cases of endocarditis are due to bacterial infection. In 

 the simple or vegetative form, so often the result of acute 

 rheumatism, the micrococcus rheumaticus (p. 228) has been 

 cultivated from the valves in a certain number of cases, and is 

 probably the causal agent in most instances. 



Endocarditis of the ulcerative type may be produced by 

 various organisms, chiefly pyogenic. Of these the streptococci 

 and staphylococci are most frequently found ; the former pro- 

 ducing less destructive changes, the formation of abundant 

 vegetations being not uncommon. In some cases of ulcerative 

 endocarditis following pneumonia the pneumococcus (Fraenkel's) 

 is present; in these the vegetations often reach a large size 

 and have not so much tendency to break down as in the 

 case of staphylococcus infections. Other organisms have been 

 cultivated from different cases of the disease, and some of 

 these have received special names; for example, the diplo- 

 coccus endocarditidis encapsulatus, bacillus endocarditidis griseus 

 (Weichselbaum), and others. In some cases the bacillus coli 

 communis has been found, and occasionally in endocarditis 

 following typhoid the typhoid bacillus has been described as the 

 organism present, but further observations on this point are 

 desirable. The gonococcus also has been shown to affect the 

 heart valves (p. 266), though this is a very rare occurrence. 

 Tubercle nodules on the heart valves have been found in a few 

 cases of acute tuberculosis, though no vegetative or ulcerative 

 condition is usually produced. 



In some cases, though we believe not often, the pyogenic 

 organisms may attack healthy valves, producing a primary 

 ulcerative endocarditis, but more frequently the valves have been 

 the seat of previous endocarditis, secondary ulcerative endocarditis 

 being thus produced. In some cases, especially when the valves 

 have been previously diseased, the source of the infection is 

 quite obscure. It is evident that as the vegetations are composed 

 for the most part of unorganised material, they do not offer the 

 same resistance to the growth of bacteria, when a few reach them, 

 as a healthy cellular tissue does. On microscopic examination 

 of the diseased valves the organisms are usually to be found 

 in enormous numbers (Fig. 58). By their action breaking 

 down of the vegetations occurs, and the emboli thus produced 

 act as the carriers of infection to other organs, and give rise to 

 secondary suppurations. 



Experimental. Occasionally ulcerative endocarditis is produced by the 

 simple intravenous injection of staphylococci and streptococci into the 



