PATHOGENIC BACTERIA. 257 



desired, the diagnosis may become very difficult and is frequently 

 impossible, except by culture-methods, owing to secondary 

 infection with the ordinary pus-forming or other bacteria, 

 which may be present in larger numbers than the gonococci 

 themselves. 



The gonococcus grows only in the. incubator, and cannot 

 therefore be cultivated upon gelatin. Its cultivation is, in 

 fact, a matter of some difficulty. The medium usually selected 

 is a mixture of agar with human blood-serum. The blood- 

 serum from the placental blood or pleuritic or peritoneal 

 transudates, or hydrocele fluid, has been employed. Human 

 urine, steriUzed by filtration through porcelain, added to the 

 mixture of blood-serum and agar, improves its character, 

 according to some writers. A convenient medium is one con- 

 sisting of one part of human serum derived from a pleuritic effu- 

 sion, added to two parts of a 2 per cent, nutrient agar previously 

 sterilized. The two are mixed in tubes while fluid and cooled 

 while in an incHned position, and sterilized between 65° and 

 70° C. by the fractional method on six consecutive days. They 

 are afterward tested in the incubator for two days. 



The colonies of the gonococcus are very small, grayish- white, 

 circular, translucent; appearing after from twenty-four to 

 forty-eight hours. They may attain a diameter of i to 2 mm. 

 The gonococcus will occasionally develop on ordinary glycerinv 

 agar or Loffler's blood-serum medium, but the growth is likely 

 to be feeble and cannot be relied on. The cultures live for a 

 considerable time if kept from drying. The gonococcus is 

 not known to produce urethritis or conjunctivitis in any of the 

 lower animals. In the peritoneum it may cause suppurative 

 inflammation in mice and guinea-pigs. Reproduction of the 

 disease in man has been effected by experimental inoculation 

 with pure cultures. Besides being the cause of gonorrheal 

 urethritis and infection of the cervix uteri, the gonococcus has 

 been isolated from cases of vaginitis in little girls and from 



