242 A MANUAL OF BACTERIOLOGY 



he named the Diplococcus intracellularis meningitidis, and 

 further research has confirmed the accuracy of Weichsel- 

 baum's discovery and the etiological relationship of the 

 organism to the disease. 



Morphology, etc. The meningococcus, as it may be 

 termed, occurs as single cocci and diplococci in groups 

 within the leucocytes (Plate III. a) ; in grouping and 

 general appearance, in fact, it closely resembles the gono- 

 coccus, and, like the last-named, is Gram- negative, though 

 staining well with the ordinary anilin dyes and with the 

 Leishman stain. In cultures it occurs as cocci, diplococci, 

 and occasionally as tetrads. 



Cultural characters. The meningococcus is an obligatory 

 aerobe, and does not grow at a temperature below 25 C. 

 It will occasionally grow in primary culture on glycerin 

 agar, but frequently not, though when acclimatised it 

 grows fairly well on agar and in broth. The organism 

 develops best on agar smeared with blood, on ascitic-fluid 

 agar or broth, or on the nutrose ascitic agar of Wassermann 

 (termed by Gordon " nasgar ") : 



Ascitic fluid . . . . .16 c.c. 

 Distilled water . . . . .35 c.c. 

 Nutrose ...... 1 grm. 



The mixture is placed in a flask, brought to the boil with constant 

 shaking, and filtered. It is then mixed with double the volume of 

 ordinary nutrient agar, steamed for thirty minutes, filtered, and 

 filled into tubes. 



The colonies of the meningococcus on this medium after 

 twenty-four hours' incubation at 37 C. appear as moist, 

 grey, translucent, circular or oval discs with regular 

 outline ; after a further twenty hours' growth they may 

 attain a diameter of 3 to 4 mm. The colonies never 

 exhibit any yellowish coloration as do those of some other 

 Gram-negative cocci. Ascitic fluid broth (ascitic fluid 

 1 part, broth 9 parts) is also a good culture medium, and 



