CHAPTER V. 

 THE GENUS DIPLOCOCCUS. 



The genus Diplococcus of Weichselbaum has been 

 defined above as follows: 



Strict parasites, not growing, or growing very poorly, 

 on artificial media. Cells normally in pairs, surrounded 

 by a capsule. Fermentative powers high, most strains 

 forming acid in dextrose, lactose, saccharose, and inulin. 

 Hemolytic power generally lacking. Characteristic group 

 serum reactions. 



The type organism of this genus is D. pneumonia 

 (Weichselbaum) ; this species and its allies, the gonococcus 

 and the meningococcus, all occur in capsulated pairs, as 

 the causative agents in the specific diseases with which 

 they are associated. None of the three are known to 

 occur outside the animal body. 



These diplococci have been grouped by most sys- 

 tematic bacteriologists (Migula, 1900; Chester, 1901) 

 with the streptococci. It seemed to us, in our first 

 revision of the Coccaceae (Winslow and Rogers, 1905), 

 that the typical growth form and strict parasitic habit 

 warranted the retention of the distinct genus Diplococcus 

 for the three types mentioned. Since that time evidence 



has accumulated, from the study of biochemical properties 



no 



