CULTURAL CHARACTERS OF THE MENINGOCOCCUS 543 



Morphology. — Oval or spherical cocci, 0-8 X 0-6 ^, often arranged in pairs, with adjacent 

 sides flattened ; long axis of oval lies at right angles to axis joining the two cocci. 

 In cultures great variation in size and in depth of staining occurs, due to 

 autolysis ; in the body the cocci are more regular a«id are generally intracellular. 

 Non-motile ; non-capsulated ; Gram-negative. 



Serum Agar Plate. — 24 hours, 37° C. Round, convex, bluish-grey, translucent, amor- 

 phous colonies, 1 mm. in diameter, with smooth, moist, glistening surface and 

 entire edge ; consistency butyrous ; easily emulsifiable. Colony is typically 

 lenticular. Later, colonies increase in size, become more yellow and opaque, and 

 may show a granular centre, and a radiate periphery. 



Serum Agar Slope. — 24 hours, 37° C. Moderate, partly confluent, raised, greyish-yellow 

 growth with smooth or irregular surface due to imperfect fusion of colonies ; edge 

 is undulate or made up of single colonies. 



Gelatin Stab. — No growth. 



Serum Broth. — 24 hours, 37° C. Poor to moderate turbidity with slight granular or 

 viscous deposit. No surface growth. 



Resistance. — Highly susceptible to inimical agencies. When dried, and kept at room 

 temperature, cocci die in under 3 hours. Killed by moist heat at 55° C. in less 

 than 5 minutes. Killed by 1 per cent, phenol in 1 minute, and by 0-1 per cent. 

 HgCla almost instantaneously. Sealed cultures kept at 37° C. often live for 4 or 

 5 weeks, and occasionally for 2 or 3 months, but when kept at room temperature 

 they generally die in a few days. 



Metabolism. — Optimum H-ion concentration is pH 7-4-7-6. Optimum temperatiu-e for 

 growth is 37° C. ; little or no growth below 30° C. Fails to grow on plain nutrient 

 agar, but grows on trypagar, glucose agar, and agar to which blood, serum, or 

 ascitic fluid has been added. Some strains show a slight formation of yellow 

 pigment. Aerobe ; no growth under strictly anaerobic conditions ; growth favoured 

 by 5 to 10 per cent. CO2. Produces a weak hsemolysin. 



Biochemical — Produces acid, no gas, in glucose and maltose. No change in litmus milk. 

 Catalase-|- ; methylene blue reduction -(- . M.R. — or weak -|- ; V.P. — ; indole 

 — ; HjS — . 



Antigenic Structure. — Divided by agglutination and absorption of agglutinins into two 

 main groups, Groups I and II. Some workers divide Group I into Types I and 

 III and Group II into Types II and IV. Group II tends to be more heterogeneous 

 than Group I. 



Pathogenicity. — Responsible for sporadic and epidemic cerebrospinal meningitis in man. 

 Experimentally, it is pathogenic to mice, guinea-pigs, and rabbits, if injected 

 intraperitoneaUy in fairly large doses ; causes death by toxsemia in 1 to 4 days ; 

 there is little or no multiplication of the organisms in the body. 



The Gonococcus 



Cultural Characters. — In culture the isolated cocci are round. According to 

 Neisser (1882), as the spherical coccus grows, it becomes oval; division occurs, 

 and two cocci are formed, which cling closely together. These then separate a 

 little, and each one grows and divides again, but in a plane at right angles to that 

 of the first division, so that tetrads result. Each member of the tetrad divides 

 in the same plane as that of the first division. The result is that four pairs of 

 cocci are formed. 



The gonococcus is the most difficult member of the group to cultivate. It was 

 first grown by Leistikow and Loefiler (Leistikow 1882) on blood serum gelatin at 

 37° C, and by Bumm (1885a) first on coagulated bovine or sheep serum at 30°-34° C, 

 and later (Bumm 1885&) with more success on coagulated human serum. Since then 



