328 AGKICULTUEAL AND INDUSTEIAL BACTERIOLOGY 



retaining the organisms for months or for years. Appar- 

 ently in some eases the organisms lie dormant or latent and 

 produce symptoms not sufficiently acute to be noticed for 

 long periods of time. Under certain conditions the disease 

 may flare up again. 



No antisera have been prepared which give relief or 

 effect a cure in this disease. It has been claimed that vac- 

 cines have been used with some success in immunizing those 

 who have the disease in chronic form. 



Neisseria meningitidis 



Synonyms. — Diplococcus meningitidis, Diplococcus intror- 

 cellularis, Micrococcus meningitidis. The organism is fre- 

 quently known by its casual name, meningococcus. 



The disease produced, acute contagious cerebrospinal 

 meningitis, is characteristic of man, although it may be 

 transmitted by experimental inoculations to some animals, 

 particularly to the monkey. 



Morphology. — The meningococcus in the body exudates 

 usually appears as a diplococcus, or occasionally in groups 

 of four. In culture media, the organism is usually about 1m 

 in diameter and commonly occurs in pairs, rarely in short 

 chains. Capsules are not produced. The organisms stain 

 readily with the usual aniline dyes and are Gram-negative. 

 Inasmuch as there are other organisms, such as streptococci 

 and the pneumococcus which occasionally cause meningitis, 

 the latter fact is important in differential diagnosis. 



The organism may frequently be secured in pure culture 

 by making a lumbar puncture with a sterile hypodermic 

 needle and transferring directly to a suitable medium. The 

 medium must be carefully prepared, have the correct acid- 

 ity and usually it is necessary, upon first culture at least, to 

 add blood serum. Upon this medium white discrete colonies 

 develop. The organism undergoes autolysis or self-digestion 

 so readily that frequent transfers must be made to keep it 



