646 THE MENINGOCOCCUS 



infrequently two diplococci are seen arranged as tetrads. Isolated individuals 

 are round and of variable size : chains are never seen. Most of the organisms 

 are contained within the leucocytes, some of the latter being crowded with 

 cocci. 



FIG. 304. Meningococcal exudate. Jenner's stain. (Oc. 2, obj. ^th. Zeiss. 



In the cerebro-spinal fluid and in meningeal exudates the Meningococcus 

 is rarely encapsulated, but exceptionally individuals show a very distinct 

 membrane. In cultures on rabbit serum the capsules are very apparent. 



In cultures, as in pathological exudates, the cocci may occur singly, or in 

 pairs, or as very distinct tetrads : they are frequently found in small agglu- 

 tinated clumps : chains have never been observed. 1 



Staining reactions. The Meningococcus is readily stained by the basic 

 aniline dyes ; carbol-blue and carbol-thionin are especially useful. 



The organism is gram-negative. 



f t 







f^'4-f 



C * f.*J! 



'' ^' ** 



J> S ft O 



fi 



FIG. 305. Meningococcai exudate. Gram's stain and eosin. (Oc. 2, obj. T ^th. Zeiss.) 



Schottmiiller examined 43 strains and found that they were all decolourized by 

 Gram's method even after being sub-cultivated many times. But according to 



1 The Jaeger- Heubner diplococcus, on the other hand, forms long chains in liquid media. 



