COCCACE^E AND THEIR PARASITIC RELATIONSHIPS 



251 



made by mixing human blood serum at 40 C., one part, with 

 ordinary nutrient agar melted and cooled to 40 C., two parts. 

 The medium may be inclined in tubes or may be employed for 

 plating. Human ascitic fluid or hydrocele fluid is just as good 

 as blood serum. A large drop of pus from an acute urethritis 

 should be mixed with 2 to 3 c.c. of serum or ascitic fluid in a 

 test-tube and from this, dilutions made to a second and a third 

 tube. The contents of a tube of agar (5 to 6 c.c.), previously 

 melted and cooled to about 40 C., is then added to each tube of 



FIG. 103. Gonococci and pus-cells. Xiooo. 



serum, mixed thoroughly and poured into Petri dishes to solidify. 

 At 37 C., colonies appear within 24 hours and at the end of this 

 time measure about i mm. in diameter. The colony is circular, 

 grayish-blue and transparent and of a mucoid consistency. 

 The individual cocci disintegrate rapidly, even within the first 

 24 hours at the center of the colony, and for microscopic study, 

 simple staining and staining by Gram's method, cultures 5 to 10 

 hours old are recommended. Even under favorable conditions 

 the gonococcus ordinarily dies out in the culture tube in about a 

 week, although exceptionally it may survive for three weeks. 



