374 PATHOGENIC MICROORGANISMS 



is no question now, however, that the cocci decolorize by Gram's method 

 when this is carefully carried out. 



In spinal fluid very beautiful preparations may be obtained 

 by staining in Jenner's blood stain. Councilman, Mallory, and 

 Wright * were the first to notice that, when stained with Loeffler's 

 methylene-blue, meningococcus stains irregularly, showing metachro- 

 matic granules in the center of the cell bodies. These granules can be 

 demonstrated more clearly with the Neisser stain employed for similar 

 demonstration in the case of B. diphtherise (see p. 107) and have some 

 value in differentiating meningococcus from gonococcus. 



Cultivation. Micrococcus intracellularis meningitidis grows readily 

 upon all the meat-infusion culture media. It may even be culti- 

 vated upon meat-extract media, but growth upon these is not profuse. 

 Upon agar, colonies appear within eighteen to twenty-four hours as 

 grayish, glistening spots with smooth edges and raised granular centers. 

 These show a tendency to enlargement and eventual confluence. 



Growth is more luxuriant and rapid upon media to which animal 

 proteid in the form of blood serum or ascitic fluid has been added. Co- 

 agulated serum is not liquefied. For cultivation of the meningococcus 

 directly from the human body it is wise to use the richer serum or blood 

 media, ability to grow easily upon simple agar being occasionally acquired 

 only after previous cultivation upon richer media. Agar to which whole 

 rabbit's blood has been added forms an excellent medium, both for cul- 

 tivation and for keeping the organism alive. Loeffler's blood serum 

 is also very favorable. It is advisable, too, when cultivating directly 

 from spinal fluid, to plant rather large quantities (1 to 2 c.c.), since 

 many of the cocci in the exudate will fail to develop colonies, possibly 

 because of their prolonged exposure either to the body fluids or to their 

 own products in a closed space. 



Upon broth, growth is slow and takes place chiefly upon the surface, 

 the sediment consisting mainly of dead bacteria. Glucose added to agar 

 or to broth renders the medium more favorable for rapid growth, but, 

 owing to acid formation, tends to cause a more rapid death of the culture. 

 In flasks of broth containing glucose one per cent, and CaCO 3 one per- 

 cent, however, cultures have been kept alive for as long as fourteen 

 months (Hiss). On milk, growth takes place without coagulation 

 of the casein. Potatoes are not a favorable medium, though growth 

 occasionally takes place. 



1 Councilman, Mallory, and Wright, Rep. Mass. State Bd. of Health, 1898. 



