CHAPTER IX 
THE PNEUMOCOCCUS GROUP (DIPLOCOCCUS 
PNEUMONIAE, DIPLOCOCCUS, LANCEO- 
LATUS—‘ ‘ L ANCE-SH APED ’ ’) 
I. Historical 
Pasteur isolated the organism from the saliva in 1881; 
at the same time, quite independently, it was discovered 
by the American bacteriologist, Sternberg (late Surgeon- 
General, United States Army). Fraenkel and Weichsel- 
baum in 1886 definitely described it as the cause of 
pneumonia, in 90 per cent of cases. 
II. Distribution 
It is widely distributed, in close association with man. 
III. Morphology 
Through the brilliant work of Cole, Dochez, Avery and 
other workers at the Rockefeller Institute for Medical 
Research in New York, we now know that there are at 
least four different strains of pneumococci, which may 
be recognized by serologic methods (agglutination and 
precipitin reaction), but morphologically can not. 
Pneumococcus is a lance-shaped, oval organism gen¬ 
erally occurring in pairs (in very young cultures not 
uncommonly it is seen in chains) of varying sizes; it 
is invariably encapsulated when freshly isolated from 
animal tissues, but readily loses the capsule on pro- 
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