GENUS BACTERIUM 307 



water becomes cloudy, viscid, and after considerable evapora- 

 tion has occurred, brownish in color. 



Gelatin. Surface colonies appear first as minute grayish 

 points on the surface of the medium. Older colonies are 

 nearly circular with a sharply defined border, and distinct cir- 

 cular markings. The colonies, at first whitish in color and 

 opalescent, later become distinctly yellow. The growth is 

 viscid like that on agar. The gelatin is not liquefied even after 

 long standing. 



Potato. A thin growth appears after 24 hours. It can 

 be distinguished with difficulty, being of the same color as the 

 potato. Later, the growth becomes more abundant and viscid, 

 assuming a drab color. 



Bouillon. In 24 hours, the bouillon becomes slightly 

 clouded and somewhat viscid. A thin grayish growth adheres 

 to the sides of the tube at the surface of the liquid. If the 

 culture is undisturbed, a thick viscid pellicle forms after about 

 a week. When the culture is agitated daily, the pellicle does 

 not form and the liquid becomes uniformly viscid throughout. 

 A quantity of white, tenacious sediment is deposited. The 

 reaction is alkaline. 



Milk. The cream on the milk becomes viscid in 12 hours 

 after inoculation. The milk below, while ropy in young cul- 

 tures, does not exhibit the maximum viscosity until several 

 weeks have elapsed. In old cultures, the milk will spin out in 

 opalescent, gossamer-like threads frequently a yard long. 

 Only after considerable evaporation has occurred do milk cul- 

 tures assume a semi-fluid consistency. The reaction, at first 

 alkaline to litmus, becomes feebly acid after about two months. 



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

 quires a low temperature for its best development. It does 

 not grow in the incubator at all regularly. The indol reaction 

 is not clear. Its peculiar property of producing ropy milk is 

 supposed to be due to the gelatinous capsule which surrounds 

 it. It is not pathogenic for animals. 



Resistance. It is destroyed by a temperature of 58 C. 

 for 10 minutes. Milk utensils that become infected can be 

 properly cleansed if washed with boiling water. 



