128 RELATIONSHIPS OF THE COCCACE^ 



coccus, occurring generally in pairs of "coffee-bean" 

 shaped cells, closely resembling in appearance D. gonor- 

 rhoea. It occurs at times in tetrads and is always Gram- 

 negative. It is frequently found in small numbers in 

 normal throats, and may be associated with acute inflam- 

 matory conditions of the respiratory tract. On agar it 

 forms grayish-white shining colonies with a denser center. 

 It produces scum and sediment in broth and fails to 

 coagulate milk. Its virulence is slight. 



Celler (1902), after a careful study, points out the 

 following distinctive marks of D. catarrhalis. It grows 

 more profusely on agar than D. W eichselbaumii and its 

 colonies have distinct darker centers with whitish shining 

 outer zones. On slants the growth of D. W eichselbaumii 

 is gray, shining, and moist, while that of D. catarrhalis is 

 white, dry, and crumbly. D. catarrhalis produces acid 

 in glucose and saccharose, and is more distinctly patho- 

 genic than D. W eichselbaumii. Dunham (1906) observed 

 that organisms of the D. catarrhalis type, isolated from 

 the nose and throat, formed sediment when suspended in 

 .75 per cent salt solution and were easily filtered out or 

 removed by a centrifuge; the meningococci, on the other 

 hand, formed a fine suspension impossible to separate 

 by the centrifuge and clogged filters very rapidly. The 

 meningococcus always produced acid in ascites-agar but 

 without coagulation. Some of the forms from the nose 

 and throat coagulated milk, and some failed to produce 

 acid at all. 



