THE GENUS DIPLOCOCCUS 127 



Occurs in cerebrospinal exudate in epidemic meningitis. 

 Exhibits group serum reactions with D. gonorrhcece. 



D. Weichselbaumii has been found in the nose and 

 throat of infected persons and, sometimes, of normal ones. 

 It is not known to occur in animals, but Bertarelli (1906) 

 isolated a form closely resembling it from nodules in the 

 liver and ganglia of the iguana. 



The organism described by Class (1899) as the cause of 

 scarlet fever probably belonged in the genus Diplococ- 

 cus, since it occurred in pairs of " coffee-bean" shaped 

 cells, formed glutinous colonies, and grew badly on ordi- 

 nary media. It was not, however, distinguished from 

 D. Weichselbaumii by sufficiently definite characters to 

 deserve specific rank. 



An organism more or less closely related to D. Weich- 

 selbaumii, but exhibiting much higher viability on media 

 than either of the two preceding pathogenic species, occurs 

 not infrequently in normal throats. This is D. catarrhalis, 

 first described and named in print by Frosch and Kolle 

 (1896), by whom credit for verbal description is given to 

 Pfeiffer. It might be considered only a partially sapro- 

 phytic meningococcus; but the frequency with which it 

 has been isolated, and the fact that it shows distinct serum 

 reactions (Jaeger, 1903; Wollstein, 1907), seem to warrant 

 its recognition as a distinct type center. 



The first careful study of this organism was made by 

 Ghon, Pfeiffer, and Sederl (1902), and these investigators 

 noted the following characteristics. D. catarrhalis is a 



