280 MICROBIOLOGY 



reflected light as bluish-gray nebulous spots ; by transmitted 

 light they appear more distinctly as very delicate, bluish 

 translucent areas. The colonies in general are round, but they 

 have no sharp outline, gradually fading into the surrounding 

 clear gelatin. After six days the colonies attain a diameter of 

 4-7 mm. with round, slightly more opaque centers, a few of 

 which appear to be quite solid. Several days later the colonies 

 .are very indistinct and cloudlike. There is a small amount of 

 liquefaction of the gelatin which does not seem, however, to be 

 associated with the colonies. "When crowded they present the 

 appearance of two kinds of colonies, (1) those which have a 

 simple nebulous appearance and (2) those which have a minute 

 solid nucleus. The latter are much smaller than the former. 

 The largest are about 2 mm. in diameter. They are separated 

 by a distance of 0.25 to 0.5 cm. At the end of ten days about' 

 one half of the colonies show the solid nucleus. The colonies 

 are about 0.5 to 1 mm. in diameter and consist of a central 

 portion surrounded by a translucent band which is bounded 

 externally by an opaque ring. 



Potato. No growth. 



Serum. On blood serum no growth. 



Bouillon. The day following its inoculation the liquid is 

 faintly but uniformly cloudy. When the tube is shaken this 

 cloudiness has the appearance of clouds of dust. A few days 

 later it is less marked, with a very slight deposit in the bottom 

 of the tube. In bouillon containing 2% glucose in fermenta- 

 tion tubes at 36 C., after twenty-four hours the liquid is 

 usually uniformly clouded throughout. Occasionally, how- 

 ever, the liquid in the closed bulb remains clear for forty- 

 eight hours. Gas is not produced. 



Milk. At 36 C. no appreciable change is produced in its 

 appearance. Milk in which these organisms have multiplied 

 may or may not coagulate on boiling. A microscopical exami- 

 nation shows a vigorous multiplication of the bacteria in this 

 medium. 



Life conditions and properties. It is an aerobe and fac- 

 ultative anaerobe. It grows best at a temperature of 36 to 



