SUPPURATION AND SEPTIC DISEASES 141 



meningococcus are present in the healthy mouth, contami- 

 nation of the swab with saliva must, as far as possible, be 

 avoided. West's swab is recommended. The swab from 

 the naso-pharynx is lightly brought in contact with one 

 portion only of ready set nasgar in a Petri. The material 

 from the infected area is spread over the medium by means 

 of a sterile glass spreader, and, without reinfection, this 

 spreader is rubbed over the surface of a second plate. 

 The plates are then incubated at blood-heat. It is 

 imperative that the culture should be made immediately 

 after the swabbing of the naso-pharynx or else the in- 

 fected swab should be kept warm until it can be used. 

 When the colonies are up, a film is stained by Gram's 

 method, meningococci being Gram-negative. Sub- 

 cultures are made and incubated at 37 C. and 23 C. 

 respectively. The vast majority of the Gram-negative 

 cocci of the normal mouth grow readily at 23 C., while 

 the meningococcus does not. 



Gaskell (Jour. R.A.M.C., September, 1915) says that 

 when the puncture fluid is allowed to stand for twelve to 

 eighteen hours in the blood-heat incubator and the 

 sedimented pus sown on blood- agar slopes, success is 

 more frequent than with generous sowings of fresh fluid. 



Organisms that may possibly be mistaken for the 

 meningococcus are 



(1) Gonococcus. For practical purposes this may be 

 excluded. 



(2) Micrococcus catarrhalis. Distinguished by fermen- 

 tation tests (vide supra) and by its growth at 23 C. 



(3) Diplococcus pharyngis siccus. Grows at 23 C. 

 Colonies are very tough, those of the meningococcus 

 being easily removed and readily emulsified with water. 



(4) Diplococcus mucosus. Gives slimy colonies. Grows 

 at 23 C. 



(5) Diplococcus crassus. Gram-positive. 



(6) Chromogenic cocci are not likely to lead astray, 

 unless the colour does not develop. Under this circum- 

 stance Micrococcus flavus gives colonies that closely 

 resemble those of the meningococcus. 



(7) Pneuinococcus. Gram-positive. 



(8) Pseudo-meningococcus. 



(9) Streptococcus mucosus. Gram-positive; on serum - 

 agar gives a colony as clear as water. 



