644 NEISSERIA 



a host of other media have been introduced ; reference may be made to a few 

 (Wertheim 1891, Kiefer 1895, Wassermann 1897, Thahnann 1900, Lipschutz 1904, 

 Martin 1911, Vedder 1915, Hall 1916, Cole and Lloyd 1917, Thomson 1917, Clark 

 1920, Swartz and Davis 1920, Buschke and Langer 1921, Cook and Stafford 1921, 

 Jenkins 1921, 1922, Costa and Boyer 1922, Erickson and Albert 1922, Kandiba 



1922, Lorentz 1922, Torrey and Buckell 1922a, Torrey et al. 1922, Macnaughton 



1923, Leboeuf 1924, Gordon, J., 1926). 



According to Sordelli, Miravent and Negroni (1926), an excellent medium results from 

 adding to nutrient agar 17 per cent, of liver extract. This extract is prepared by macerating 

 ox Uver in 5 per cent. NaCl solution for 2-4 hours at 45° C, raising the temperature gently 

 to 60° C, keeping it at 60° C. for 10 minutes, and filtering first through paper, then through 

 a Berkefeld candle. The liver extract, if kept in the ice-chest, remains potent for months. 



As the result of long experience in routine cultivation, McLeod and his col- 

 leagues (1934) recommend the use of 10 per cent, heated blood agar of pH 7-4, 

 prepared from broth in which the extraction of the meat has been carried out by 

 Wright's (1933) method. The minimum amount of agar consistent with stability 



Fig. 111. — Neisseria gonorrhozce. Fig. 112. — Neisseria gonorrhoece. 



Surface colonies on serum agar, 24 hours, Surface colony on serum agar, 7 davs, 



37° C. (X 8). 37° C. (X 8). 



is used. The cultures are incubated in air containing 8 per cent. CO,. For ordinary 

 purposes a satisfactory medium is provided by nutrient agar containing 

 10 per cent, ascitic or hydrocele fluid, and having a pH of 7-6 ; the slopes or 

 plates should be moist, and the air in the incubator should be saturated with 

 water vapour. Stock cultures are best kept in a similar medium containing 

 0-75 per cent, agar, and put up in the form of stabs ; these tubes should be corked 

 and kept in the incubator. Media with a high amino-acid concentration are not 

 usually satisfactory (Torrey and Buckell 1922a, Gordon, J. and M'Leod 1926), 

 but the addition of — SH groups is beneficial (Boor 1942). Glucose does not im- 

 prove growth. 



Numerous workers (de Christmas 1897, Wassermann 1898, Lipschutz 1904, 

 Gurd 1908, Martin 1911, Cohn 1923) have noticed that the cultural characters 

 of the gonococcus are subject to variation. More recently Atkin (1925) has studied 

 this phenomenon and found that, as with the meningococcus, there is a definite 

 correlation between the serological type of the organism and its colonial appear- 

 ance. By growing gonococci on thick trypagar plates of pH 7-8 he observed 

 two different types of colony : Type I gave a large, irregularly round, flattened, 

 translucent colony with an undulate edge, and a surface that in 5 days or so 



