292 BACTERIOLOGY. 



solidify with a slanting surface. When the medium 

 in the tubes has solidified the tubes are placed in the 

 incubator for about twenty-four hours to test for con- 

 taminations, after which they are ready for use." 



The successive dilutions are now to be made upon 

 the slanting surface of this mixture, as the mass in the 

 tubes cannot be redissolved without exposure to a de- 

 gree of heat that apparently interferes with the nutri- 

 tive value of the serum contained in the medium. 



When inoculated with gonorrhoeal pus, by smearing 

 a loopful over the surface, the tubes are to be kept at 

 from 37 to 38 C. The organism does not develop 

 properly at a temperature below this point. 



After twenty-four hours the colonies of the gono- 

 coccus appear on the surface of the medium, accord- 

 ing to Wright, as very tiny, grayish, semi-translucent 

 points. After forty-eight hours they may be about 

 1 millimetre or so in diameter, slightly elevated, with 

 a rounded outline, grayish in color, and semi-translu- 

 cent by transmitted light. By reflected light their sur- 

 face has the appearance of frosted glass. Later, if few 

 in number, so that their growth is unimpeded, the colo- 

 nies may attain a diameter of 2 millimetres or more, be- 

 come thicker and denser, with a faintly brownish tinge 

 about their centres, and a slightly irregular outline. 



Under a low power of the microscope a fully de- 

 veloped colony is seen to consist of a general circular 

 expansion, with thin, translucent, smooth, sharply de- 

 fined margin, but becoming brownish, granular, and 

 thicker toward the central portion, which is made up 

 of coarse, granular, brown-colored clumps closely packed 

 together. 



