258 EPIDEMIC CEREBRO-SPINAL MENINGITIS 



Methods of Examination. During life these involve the 

 microscopic investigation of the centrifuged lumbar puncture 

 fluid and making cultures therefrom. For the former Gram- 

 stained smears make the recognition of the meningococcus re- 

 latively easy, and the presence of Gram-negative cocci, especially 

 within cells, is practically diagnostic of a case of cerebro-spinal 

 fever. Tubes of serum-agar, nasgar (pp. 42, 43), or agar 

 containing 25 per cent, of ascitic or ovarian fluid, may then be 

 inoculated. The difficult cases are those where no bacteria can 

 be found microscopically in the lumbar fluid. Here the character 

 of the exudate may give help. A predominance of polymorpho- 

 nuclear cells is usually manifest in meningococcic, pneumo- 

 coccic, and influenzal cases, whereas in tubercular meningitis the 

 exudate is, as a rule, chiefly lymphocytic. In such circumstances, 

 besides other media, a tube of blood-smeared agar should be 

 inoculated in case the pneumococcus or the influenza bacillus 

 is the causal organism. To speak generally, if with a polymorpho- 

 nuclear exudate no growth occurs in the media mentioned 

 the case is most likely to be due to the meningococcus. In 

 tubercular cases it is sometimes impossible to demonstrate the 

 bacilli microscopically in the exudate, though on careful search 

 they may often be found. 



