Knowledge of pneumococcus infection and immunity, and the evolution of "antipneumococcus serum" have been of slow progress and along paths beset with many difficulties.
In 1880 Sternberg1 discovered in saliva a diplococcus which, when inoculated into rabbits, produced fatal septicemia. To this micro-organism he subsequently— 1885—gave the name "micrococcus Pasteuri."
Pasteur2 subsequently rediscovered the same microorganism, but neither he nor Sternberg seem to have recognized its importance in connection with croupous pneumonia. A. Fraenkel3 observed the almost constant occurrence of the diplococci in large numbers in the rusty sputum of pneumonia, and cultivated it from several cases of pneumonia empyema, and one of meningitis. These and later observations4 led Fraenkel to declare the diplococcus to be the pneumococcus, the cause of croupous pneumonia. Weichselbaum and Netter fully established his claims, and ever since the microorganism has been called the "pneumococcus of Fraenkel and Weichselbaum."