MICROBIAL DISEASES OF MAN AND ANIMALS. 



537 



the aniline dyes and is Gram-negative. The temperature range is 30 to 38.5 with 

 an optimum of 37.5. Aerobic conditions are preferred though a slight growth may 

 be obtained anaerobically. The most favorable reaction of artificial media is said to 

 be about 0.6 per cent acid to phenolphthalein. On serum agar or similar suitable 

 media, colonies appear in twenty-four hours as fine slightly elevated, translucent 

 or opalescent spots frequently referred to as "dew-drop" colonies. They possess 

 a faint bluish or grayish white color with a slightly marked concentric or radial 

 striation with a scalloped margin and finely granular center. In serum broth there 

 may occasionally be a uniform clouding though, as a rule, there is a finely granular 

 sediment somewhat slimy with clear fluid above. Only in exceptional cases has growth 



FIG. 100.- Gonococci and pus cells. X 1000. (After Williams.} 



been observed in gelatin because of the unfavorable temperature. On inspissated 

 blood serum growth may sometimes be observed as discrete pale yellowish or brown- 

 ish colonies. Dextrose is changed with the development of acid but no gas. Alkali 

 is not formed in any medium by typical strains. No gas, indol or pigment are formed. 

 The toxins are intracellular and quite thermostable. Resistance is very slight 

 towards external influences. Cultures undergo rapid autolytic changes and die out 

 at room temperature, often within forty-eight hours. A temperature of 41 to 45 

 will kill in a few hours. To light and drying they are also very sensitive, and are 

 rapidly killed by the ordinary disinfectants. 



Animals inoculated subcutaneously or intraperitoneally show symp- 

 toms of poisoning with suppuration and necrosis locally and may 

 succumb. 



The virulence of the organism is variable. They may apparently lie 



