PATHOGENIC BACTERIA. 



259 



addition of human urine, -sterilized by filtration through 

 porcelain, to the mixture of blood-serum and agar im- 

 proves its character according to some writers. A con- 

 venient medium is one consisting of one part of human 

 serum derived from a pleuritic effusion, added to two parts 

 of a 2 per cent, nutrient agar. The agar has previously 



FIG. 64. 



Gonococci and pus-cells. (X 1000.) 



been sterilized; the two are mixed in tubes while fluid; 

 they are cooled while in an inclined position, and are 

 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 glycerin-agar or Loffler's blood-serum medium, 

 but the growth is likely to be feeble and cannot be relied 



