138 AIDS TO BACTERIOLOGY 



Eyre and Stewart state that the B. xerosis, which is 

 frequently present in the healthy and seldom absent from 

 the diseased, genital tract, forms colonies on blood- agar 

 which are indistinguishable from those of the gonococcus 

 to the naked eye. 



Seeligman considers pruritus vulvse to be due to a diplo- 

 coccus, which resembles the gonococcus in appearance, 

 but is Gram-positive. 



The Meningococcus. 



Morphology. In epidemic cerebro- spinal meningitis 

 (' spotted fever ') the causative organism is the Diplococcus 

 intracellularis meningitidis of Weichselbaum (meningo- 

 coccus). 



While found in the polymorphonuclear leucocytes of 

 or lying free in the cerebro-spinal fluid as a diplococcus, 

 on culture it is a markedly pleomorphic organism, and 

 involution forms appear on media early. Lundie, Thomas, 

 and Fleming (Lancet, September 25, 1915) state that 

 associated with the meningococcus in the naso-pharynx 

 and brain, there is nearly always a Gram-positive ' strepto- 

 coccus,' tending on culture to become Gram-negative 

 and producing involution forms in the blood they are 

 often Gram-negative. Donaldson (Lancet, June 26, 1915) 

 suggests the true cause of cerebro-spinal fever to be a 

 diphtheroid bacillus of which the meningococcus is only 

 a phase. Lundie, Thomas, and Fleming have also de- 

 scribed pseuclo-diphtheroids and they state the clots 

 do not stain by Neisser like the Klebs-Loffler bacillus. 

 These authors (loc. cit.) describe the ' caterpillar,' 

 ' Zeppelin,' and ' bomb ' forms also met with. 



Like the gonococcus, which it resembles in appearance 

 and arrangement, the meningococcus is Gram-negative. 

 It is very susceptible to cold, and infected swabs or other 

 material intended for culture experiments must be kept 

 as near body-heat as possible, if an interval between 

 sampling and plating-out is unavoidable. Halliday 

 Sutherland (Lancet, October 16, 1915) says the meningo- 

 coccus soon dies at 72 F. and is killed in thirty minutes 

 at 62. 



Culture. For primary cultures from suspected material, 

 blood-smeared agar may be used, but Wassermann's 

 nutro.se ascitic agar ('Nasgar') is the popular medium. 



