254 EPIDEMIC CEREBROSPINAL MENINGITIS 



presence of Gram-negative cocci, especially within cells, is 

 practically diagnostic of a case of cerebro-spinal fever. Tubes 

 of trypagar, serum agar (pp. 43, 45), 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, though poly- 

 morphs, often degenerated, also occur. 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. The 

 isolation of the organism from the naso-pharynx (p. 72) will 

 give confirmatory, though of course not conclusive, evidence. 

 It must be kept in view, however, that in meningitis high 

 up, produced by any of the organisms mentioned, polymorph 

 leucocytes may be present in the fluid obtained by lumbar 

 puncture before the organisms themselves appear. In tubercular 

 cases it is sometimes impossible to demonstrate the bacilli 

 microscopically in the exudate, though on careful search they 

 may usually be found. 



For method of examination of the naso-pharynx vide p. 72. 



