COCCCAE.E AND THEIR PARASITIC RELATIONSHIPS 257 



ascitic-fluid agar should be made. The recognition of a Gram- 

 negative intracellular diplococcus in the fluid is sufficient for a 

 tentative diagnosis, and the appearance of characteristic colonies 

 on the plates may be considered conclusive. 



Diplococcus (Micrococcus) Catarrhalis. This organism is 

 commonly present on the mucous membrane of the upper air 

 passages, especially in catarrhal inflammations. It is usually 

 seen as a Gram-negative intracellular diplococcus not to be 

 distinguished microscopically from the meningococcus or gono- 

 coccus. In examining material from the air passages this organ- 

 ism has to be considered. It is readily distinguished by cultural 

 methods. On ascitic-fluid agar the colony is dry and brittle, 

 quite different from the meningococcus or gonococcus. Further- 

 more, it grows readily at once on ordinary agar. 



Diplococcus Pneumoniae. Sternberg in 1880 injected the 

 saliva of healthy persons into rabbits and produced a rapidly 

 fatal bacteremia with abundant lance-shaped diplococci in the 

 blood and internal organs of the animal. Pasteur, independently 

 and at about the same time, injected the saliva of a boy suffering 

 from rabies into rabbits with a similar result. The organism 

 was spoken of as the diplococcus of sputum septicemia or the 

 septicemic microbe of saliva. Koch in 1881 demonstrated the 

 organism microscopically in sections of lung. Friedlaender 

 (1882-1884) found the organism microscopically in a large 

 number of cases of pneumonia and accurately described its form, 

 the capsules and staining properties. His cultures, however, 

 which were made on gelatin at room temperature, brought to 

 development not the pneumococcus but a wholly different organ- 

 ism which he believed to be identical with it, Friedlaender's 

 pneumobacillus. A. Fraenkel obtained the first undoubted pure 

 cultures on solidified blood serum, proved the identity of the organ- 

 ism in pneumonia with that of normal saliva seen by Sternberg 

 and Pasteur, and distinguished it absolutely from the pneumo- 

 bacillus of Friedlaender. He also succeeded in producing typical 

 pneumonia by injecting cultures of moderate virulence intrave- 

 17 



