It is a matter of history that the diplococcus discovered in human saliva by Sternberg in 1880 and shown to produce in rabbits fatal septicemia, was found by Fraenkel a few years later to be almost constant in the rusty sputum of patients suffering from croupous pneumonia and in certain associated lesions. The confirmation of these observations by Weichselbaum led to the designation of this micro-organism as the pneumococcus of Fraenkel and Weichselbaum. The rapidly following studies of Zaufal, Netter, Weichselbaum and others established the fact that the organism in question is present in the lesion of croupous pneumonia, the accompanying pleurisy, and in such intercurrent conditions as endocarditis, arthritis, middle-ear inflammations, parotitis, meningitis, pericarditis and others and in some cases of bronchopneumonia, orchitis, conjunctivitis and other inflammatory affections not necessarily associated with croupous pneumonia. It is, however, most commonly and closely identified with the last named disease. The inoculation