ULCERATIVE ENDOCARDITIS. 



165 



pneumonia. 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. 



FIG. 47. Section of a vegetation in ulcerative endocarditis, showing 

 numerous staphylococci lying in the spaces. The lower portion is a 

 fragment in process of separation. 



Stained by Gram's method and Bismarck-brown. x 600. 



On microscopic examination of the diseased valves the 

 organisms are usually to be found in enormous numbers, 

 sometimes forming an almost continuous layer on the 

 surface, or occurring in large masses or clusters in spaces in 

 the vegetation (Fig. 47). By their action a certain amount 

 of softening or breaking down of the vegetations occurs, 



