252 EPIDEMIC CEKEBRO-SPINAL MENINGITIS 



occurs ; sub-cultures especially often fail to give any growth on 

 this medium. In serum bouillon the organism produces a 

 general turbidity with formation of some deposit after a day or 

 two. It ferments maltose and dextrose with acid production, 

 a property which distinguishes it from the micrococcus catarr- 

 halis (vide infra). Fermentation tests are most satisfactorily 

 carried out by means of solid serum media containing 1 per 

 cent, of the sugar to be tested (p. 82). In all cases growth 

 occurs best when the medium has a neutral or very slightly 

 alkaline reaction. In cultures the organism presents the same 

 appearance as in the body, and often shows tetrad formation. 

 There is also a great tendency to the production of involution 



FIG. 71. Two-day colonies of the meningococcus en Martin's 

 medium (p. 43), x 9 ; b. the same, in which illumination has 

 been arranged to" show finely granular centre and transparent 

 margin, x 12. Compare with Pig. 74. 



From photographs by Dr. W. B. M. Martin. 



forms (Fig. 72), many of the cocci becoming much swollen, 

 staining badly, and afterwards undergoing disintegration. This 

 change, according to Flexner's observations, would appear to be 

 due to the production of an autolytic enzyme, and he has also 

 found that this substance has the property of producing 

 dissolution of the bodies of other bacteria. The life of 

 the organism in cultures is a comparatively short one ; after a 

 few days cultures will often be found to be dead, but, by making 

 sub-cultures every three or four days, stains can be maintained 

 alive for considerable periods. The organism is readily killed by 

 heat at 60 C., and it is also very sensitive to weak antiseptics 

 drying for a period of a day has been found to be fatal to it. 

 The facts established accordingly show it to be a somewhat 

 delicate parasite. 



