THE MENINGOCOCCUS 291 



mannitol, dulcitol and a number of glucosides. It was 

 formerly stated to ferment galactose, but this seems to 

 be an error due to the galactose used undergoing partial 

 decomposition during sterilisation of the medium. Man- 

 nose is acidified in three to four days, but in six to seven 

 days the medium returns to its original slight alkalinity 

 and colour. Dextrin is stated by Symmers and Wilson 1 

 to be acidified. The fermentation reactions are liable to 

 some variation ; thus Gordon met with three strains 

 which failed to ferment glucose. If an atypical result is 

 obtained, if, for instance, what appears to be a typic'al 

 meningococcus fails to ferment glucose, the culture should 

 be examined by subculture to ascertain that the organism 

 is alive, or if a sugar is fermented which should not be, 

 the culture should be examined for the presence of other 

 cocci or streptococci. 



Agglutination and Races. An agglutination reaction 

 is given in some cases with the patient's serum, but is 

 neither constant nor marked enough to form a sure 

 means of diagnosis. The macroscopic method is to be 

 preferred, and the mixtures of serum and culture should 

 be kept at 55 C. for twenty-four hours and the readings 

 then taken. 



Symmers and Wilson 2 found that the blood of cerebro- 

 spinal fever cases may occasionally agglutinate the B. 

 typhosus and B. coli in comparatively high dilutions. 



Agglutination is a valuable means for the recognition 

 of the meningococcus. The immune serum is best pre- 

 pared, according to Hine, by giving a j/oung rabbit in- 

 travenously a dose of 1,000 million killed cocci, followed 

 one hour later by a dose of 500 million, and on the sixth 

 day by a dose of 3,000 million. The serum is tested on the 

 eighth day, and if satisfactory the animal is bled to death 



1 Journ. of Hygiene, vol. ix, 1909, p. 



2 Ibid., vol. viii, 1908, p. 314. 



192 



