CHAPTER XX 



THE MENINGOCOCCUS 



THE meningococcus, also called the Diplococcus intra- 

 cellularis meningitidis, was discovered by Weichsel- 

 baum in 1887. It is a somewhat flattened organism, 

 occurring mostly in twos (diplococcus), and occasionally 

 in small chains of fours. When stained according to 

 Gram's method it decolorizes; that is, it is Gram-nega- 

 tive. It does not grow well except on media to which 

 blood-serum or ascitic fluid has been added. The 

 organism is not very resistant, and dies readily on dry- 

 ing or on exposure to direct sunlight. 



The meningococcus is the cause of epidemic cerebro- 

 spinal meningitis. Other forms of meningitis are caused 

 by the tubercle bacillus, by the pneumococcus and 

 streptococcus, and occasionally also by other bacteria. 

 In epidemic cerebrospinal meningitis the meningococcus 

 is found in the purulent exudate covering the meninges 

 and in the cerebrospinal fluid drawn by means of lumbar 

 puncture. In fact, it is only by means of lumbar punc- 

 ture that the variety of meningitis present can be deter- 

 mined. 



It has also been found that the meningococcus is 

 present in the nasal secretions of patients suffering from 

 epidemic cerebrospinal meningitis, and in the nasal 

 secretions of about 10 per cent, of the persons in inti- 

 mate contact with such patients. The exact mode of 

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