THE GENUS DIPLOCOCCUS 129 



On the whole it seems justifiable to recognize a type 

 center of semi-parasitic forms, resembling D. Weichsel- 

 baumii in most of its characters, but distinguished and 

 defined as follows: 



4. D. CATARRHALIS (Frosch and Kolle). A coccus 

 occurring commonly in pairs of flattened coffee-bean shaped 

 cells. Decolorizes by Gram. Grows fairly well on artificial 

 media, forming grayish-white colonies with a denser center. 

 Growth on streak, dry and friable. Virulence slight. 

 Occurs in normal throat. 



M. albicans-tardissimus, Flugge, M. magnus, Rosen- 

 thai, M. subtilis, Migula, and other imperfectly described 

 diplococci may perhaps belong to this species. 



There is still another type of organism which should 

 probably be referred to the genus Diplococcus, and 

 which apparently links such specialized forms as 

 D. pneumonia with the other less strictly parasitic 

 genera of the Coccaceae. This is the type previously 

 referred to as Str. mucosus, a form found not uncommonly 

 in the nose and throat, which resembles Streptococcus in 

 the fact that it forms chains and grows easily on artificial 

 media; but agrees with the diplococci in fermentative 

 powers and in the possession of a well-marked capsule. 



This capsulated streptococcus was observed by Ortmann 

 (1888) and Besser (1889) and named Str. involutus by 

 Kurth (1893) and Str. capsulatus by Binaghi (1897). 

 Kurth erroneously believed this organism to be the specific 

 cause of foot-and-mouth disease; but his general descrip- 



