SPECIFIC INFECTIOUS DISEASES PRODUCED BY COCCI 217 



of the fibrin and other exudates supervenes, and the material 

 passes off through the air-passages or is resorbed. 



Metastatic infections with the pneumococcus are common 

 in man. Inflammations of the endocardium, the pericardium, 

 the pleura, and the meninges have been found to be due to 

 this organism in a small percentage of cases. Otitis media 

 is sometimes the initial infection, and may be followed by 

 meningitis. 



Immunity. No toxin has been demonstrated in this organism. 

 Endotoxins may be demonstrated, but whether they account for 



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Fig. 92. Streptococcus pneumonia. Stained preparations showing capsules 

 (Buerger, in "Journal of Infectious Diseases"). 



its pathogenicity is uncertain. Agglutination of the pneumo- 

 coccus occurs with the blood-serum of an infected individual, 

 but not usually in greater dilutions than 1 : 50. Opsonins, both 

 normal and immune, have been demonstrated, and likewise there 

 has been isolated from virulent Streptococci a substance that 

 inhibits phagocytosis. 



Immunity to pneumonia is transient; relapses frequently 

 occur, possibly due to decrease in immunity during convalescence. 

 Recovery in some cases seems to be followed by increased sus- 

 ceptibility. The immunity developed is evidently opsonic in 



