Bacillus Coli Communis 519 



The colonies rapidly increase in size and become more and 

 more opaque. The gelatin is not liquefied. 



Gelatin Punctures. In gelatin punctures development 

 upon the surface, and also in the needle's track, causes the 

 formation of a nail-like growth. The head of the nail may 

 reach the walls of the test-tube. Gas may be formed in ordi- 

 nary gelatin, and when i per cent, of dextrose is dissolved in 

 the medium, the gas-production is often so copious and rapid 

 as to form large bubbles, which subsequently break it up 

 irregularly. The gelatin may become slightly clouded as the 

 bacilli grow, but is not liquefied. 



Agar-agar. Upon agar-agar along the line of inocula- 

 tion a grayish-white, translucent, smeary growth devoid of 

 any characteristics takes place. The entire surface of the 

 culture medium is never covered, the growth remaining con- 

 fined to the inoculation line, except where the moisture of 

 the condensation fluid allows it to spread out at the bottom. 

 Kruse says that crystals may form in old cultures. 



Bouillon. Bouillon is densely clouded by the growth of 

 the bacteria, a delicate pellicle at times forming upon the sur- 

 face. There is usually considerable sediment in the culture. 



Potato. Upon potato the growth is luxuriant. The 

 bacillus forms a yellowish-brown, glistening layer spreading 

 from the line of inoculation over about one-half to two- 

 thirds of the potato. The color varies considerably, some- 

 times being pale, sometimes quite brown, sometimes green- 

 ish. It cannot, therefore, be taken as a characteristic of 

 much importance. The growth on potato may be almost 

 invisible. 



Milk. In milk rapid coagulation and acidulation occur, 

 with the evolution of gas. The culture gives off a fecal odor. 

 Litmus added to the culture media is first reddened, then 

 decolorized by the bacilli. 



Vital Resistance. It is quite resistant to antiseptics 

 and germicides, and grows in culture media containing 

 from 0.1-0.2 per cent, of carbolic acid. It is, however, 

 easily killed by heat, and is destroyed by exposure to 60 

 C. for ten minutes. 



Metabolic Products. Wiirtz found that Bacillus coli 

 produced ammonia in culture media free from sugar, and 

 thus caused an intense alkaline reaction in the culture 

 media. The cultures usually give off an odor that varies 

 somewhat, but is, as a rule, unpleasant. 



