MENINGOCOCCUS 169 



flammation of the middle ear or frontal sinuses may by extension 

 produce meningitis. In such cases the infecting organisms are 

 usually staphylococci or streptococci. Sometimes meningitis is 

 part of a septicemic or pyemic condition ; occasionally it is due 

 to a mixed infection, and not infrequently the pneumococcus has 

 been found associated with the tubercle bacillus and also with 

 meningococcus. 



It has been estimated that about 70 per cent of all acute cases 

 of meningitis appear in the form designated epidemic cerebrospinal 

 meningitis, due to the organism usually termed the meningococcus. 

 In 1884 Weichselbaum found the organism in six cases of menin- 

 gitis, two of which were not complicated with pneumonia. He 

 studied it in pure culture and showed that it possessed character- 

 istics which clearly distinguished it from the pneumococcus. 

 Because of its frequent presence in the interior of pus cells he 

 gave to it its name of diplococcus intracellularis meningitidis. 



Morphology and Staining. The organisms appear as small 

 cocci usually arranged in pairs, the adjacent sides being somewhat 

 flattened against each other. Occasionally they are seen in groups 

 of four or in small masses. They are non-motile, non-spore- 

 bearing, and form no visible capsule. They stain with all the 

 ordinary dyes and are Gram negative. 



Cultivation. The optimum temperature for the meningococcus 

 is about 37.5 C. ; growth will occur between 25 C. and 40 C. 

 They can rarely be isolated on plain nutrient agar ; the addition 

 of a body fluid is usually necessary. On glucose ascitic agar the 

 colonies appear as small, grayish white, finely granular disks. In 

 broth development is slow and takes place near the surface. 

 Different strains vary in their power to ferment carbohydrates 

 and in their ability to grow on artificial culture media. Cultures 

 may remain alive for several weeks. Certain strains, however, 

 tend to die within three or four days and consequently require 

 transplanting to a fresh medium at very short intervals. 



Resistance. The organism is readily destroyed by sunlight 

 or drying or by exposure to a moderate degree of heat or cold. 

 It is killed in from one to five minutes by 1 to 1000 solution of 



