THE GENUS DIPLOCOCCUS 131 



the frequent occurrence in the chains of oval forms like 

 D. pneumonia. Gram reactions were variable. Milk 

 was coagulated after several days. Schumacher (1906) 

 apparently worked with a somewhat different form, since 

 his cultures failed to ferment lactose; but they were 

 identical with those described by Schottmuller (1903) 

 as Str. capsulatus in respect to their failure to exert hemo- 

 lytic action. If a capsule-forming streptococcus really 

 exists which shows the fermentation reactions of the 

 genus Streptococcus, it should retain the name of Str. cap- 

 sulatus of Binaghi. All the observers in this country 

 have, however, worked with D. involutus. Thus Park 

 and Williams (1905), like Buerger, found that the culture 

 which they studied produced a green coloration in blood- 

 agar plates and coagulated inulin-serum media. It was 

 distinguished from typical D. pneumonia by the fact that 

 it appeared always to ferment mannite and was never 

 affected by specific opsonins. Collins (1905) in a study 

 of agglutinative reactions found the same general rela- 

 tions to hold. Str. mucosus showed distinct group reac- 

 tions; but exhaustion experiments indicated that its agglu- 

 tinins were more nearly related to those of D. pneumoniae 

 than to those of Str . pyogenes. 



In view of all these facts this type may be recognized 

 as a valid one, and identified as follows : 



5. D. involutus (Kurth), Winslow. A coccus occur- 

 ring commonly in chains, the elements of which are grouped 

 in pairs. In the body, and on media, the chains are 



