CULTURAL CHARACTERS OF THE MENINGOCOCCUS 537 



either glucose or maltose. We ourselves have isolated organisms from the naso- 

 pharynx which fermented maltose, but not glucose. Other workers have observed 

 similar irregularities in the behaviour of this group. 



We append a detailed description of N . meningitidis and A'^. gonorrhoscB, together 

 with some further notes on their differentiation ; descriptions of those Gram- 

 negative cocci which have received specific names ; and a table giving particulars 

 of the main differential criteria that have been relied upon by different workers 

 in subdividing this group. We would add our personal opinion that there is, at 

 present, little justification for the recognition of separate species among the 

 Gram-negative cocci of the normal nasopharynx, with the possible exception 

 of N. catarrhalis. We should, ourselves, combine the remaining types into a 

 single species, with some appropriate name such as N. pharyngis, which we might 

 define as follows : 



Neisseria pharyngis. — Non-motile, Gram-negative diplococcus, arranged sometimes in 

 tetrads and often in dense clumps. Grows on agar, giving rise to either rough or smooth 

 colonies, which are generally coherent, tenacious, membranous, and friable, are difficult 

 to emulsify, and are auto-agglutinable when suspended in saline. Grows in serum broth 

 with the production of little or no turbidity, as a rule, and a coarsely granular sediment 

 not disintegrating completely on shaking ; a surface ring growth is not infrequently 

 formed, particularly by the rough variants. A yellow,'' golden-yellow, or greenish-yellow 

 pigment may be produced, but is variable in its appearance. The sugar reactions are 

 subject to variation ; glucose, maltose, or sucrose may be fermented with the production 

 of acid. Aerobic ; will not grow under strictly anaerobic conditions. Growth is best 

 at 37° C, but will generally occur at 23° C. Non-pathogenic on subcutaneous injection 

 into mice ; large doses intraperitoneally may cause death from toxaemia. The species 

 is subject to great variation in colonial appearance, and, apart from the smooth and rough 

 types, a smooth variant may occur that is of butyrous consistency and easy to emulsify, 

 and also a mucoid variant containing capsulated diplococci (Wilson, G. S. and Smith 

 1928). 



The Meningococcus 



Cultural Characters The meningococcus generally gives rise to a smooth 

 typically lenticular colony. Atkin (1923), however, and more recently Kake (1933), 

 have demonstrated the existence of colonial variants. The appearance of the 

 colony depends on the nature of the medium, the age of the strain, and the anti- 

 genic type of the organisms. Freshly isolated strains of Group I generally form 

 smooth colonies, which may be mucoid if the organisms are capsulated ; on incu- 

 bation for some days their edge may become crenated or dentate and secondary 

 papUlse may appear on the surface. Organisms of Group II tend to form rather 

 smaller colonies, and may assume a deep-yellowish tint on suitable media. Rough 

 colonies, which are generally smaller than those of the smooth form, often appear 

 in strains subjected to laboratory cultivation. 



On primary isolation the meningococcus must be provided with such accessory 

 growth factors as are present in blood, serum, milk, and other animal fluids, and 

 in certain vegetable extracts (Lloyd 1916-17). After a few generations on such 

 an enriched medium, it may sometimes be brought to grow on what are described 

 as ordinary culture media, but its vitality under these conditions is uncertain 

 (Murray 1929). Growth is usually favoured by the presence of 5 to 10 per cent. 

 COj. For preservation the meningococcus should be frozen and dried. If this 

 is impossible, it should be maintained in ascitic fluid agar stabs or on Dorset egg 

 slopes ; the tubes should be corked to prevent evaporation and kept in the incu- 



