50 STUDY AND IDENTIFICATION OF BACTERIA. 



latter, in fresh material, show a striking uniformity morphologically. 

 The meningococcus is at times not abundant early in the case, how- 

 ever, the picture may be similar to that of gonorrhoea. 



On blood- serum the colonies appear after 24 to 48 hours as discrete, 

 very slightly hazy colonies, about one-eighth of an inch in diameter. 

 On serum agar, as ascites or hydrocele agar, they grow best. Unless 

 considerable cerebrospinal fluid is transferred with the inoculating 

 loop, they do not grow on plain agar. They will grow at times on 

 glycerin agar. It ferments dextrose and only grows at blood temper- 



FIG. 15. Diplococcus intracellularis meningitidis and pus-cells 

 (X 1000.) (Williams.} 



ature, thus distinguishing it from the M. catarrhalis. It is scarcely 

 pathogenic for laboratory animals when injected subcutaneously. 

 Intradural injections give results. The cultures die out very rapidly, 

 so that it is necessary to make transfers every one or two days. The 

 meningococcus has been isolated from the nasal secretions of patients. 

 The possibility of these organisms being the M. catarrhalis must be 

 considered. 



The meningococcus has very slight resistance to sun or drying so 

 that its aerial transmission seems doubtful. It is supposed to effect 

 an entrance by the nares, thence reaching the cerebral meninges. 

 Infection is probably by direct contagion. Several cases have been 



