THE PNEUMOCOCCUS 291 



cance unless the type of the organism is determined. Dochez and 

 Avery 1 have found that the common mouth pneumococcus is usually 

 the avirulent type (Type IV); convalescents from pneumonia usually 

 exhibit the virulent types, I to III, as a rule. These types can be 

 identified by agglutination reactions with the specific sera prepared by 

 Cole. 



Pneumococci isolated from pleural and pericardial exudates, middle- 

 ear infection, empyema and pneumococcic cerebrospinal meningitis 

 can be identified morphologically by their lanceolate shape and Gram- 

 positiveness ; the type of organism, however, must be determined by 

 serological reactions. 



They are best obtained in pure culture, if they are mixed with other 

 bacteria, upon blood agar plates. A green halo surrounds the typical 

 pneumococcus colony. 



The prophylaxis is the same as for any acute respiratory disease. 



1 Quoted by Cole, loc. cit. 



