Bacilli Resembling the Typhoid Bacillus 659 



brown, and homogeneous. As they increase in size they become 

 opaque. The superficial colonies are larger and spread out upon the 

 surface. The edges are dentate and slightly resemble grape-vine 

 leaves, often showing radiating ridges suggestive of the veins of a 

 leaf. They may have a slightly concentric appearance. The col- 

 onies rapidly increase in size and become more and more opaque. 

 The gelatin is not liquefied. 



Gelatin Punctures. — Development in gelatin punctures occurs 

 upon the surface, and also in the needle's track, causing the forma- 

 tion of a nail-like growth. The head of the nail may reach the walls 

 of the test-tube. No gas is formed in ordinary gelatin, but should 

 any dextrose be present, suflacient gas-production may occur to 

 break up the medium. The gelatin may become slightly clouded 

 but is not liquefied. 



Agar-agar. — Upon agar-agar, along the line of inoculation, a gray- 

 ish-white, translucent, smeary growth, devoid of any characteristics, 

 takes place. The entire surface of the culture-medium is never cov- 

 ered, the growth remaining confined to the inoculation line, except 

 where the moisture of condensation 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 bac- 

 teria, a delicate pelhcle at times forming upon the surface. 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 in- 

 oculation over about one-half to two-thirds of the potato. The 

 color varies considerably, sometimes being pale, sometimes quite 

 brown, sometimes greenish. It cannot, therefore, be taken as a 

 characteristic of much importance. The growth on potato may be 

 almost invisible. 



Milk. — In milk coagulation and acidulation occur, with varying 

 rapidity. 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 germi- 

 cides, and grows in qulture-media containing from 0.1-0.2 per cent, 

 of carbolic acid. It is, however, easily killed by heat, and is de- 

 stroyed by exposiure to 6o°C. for 120 minutes (Frankel) or 7S°C. 

 for fifteen minutes (Kendall). 



Metabolic Products. — Wiirtz found that BaciUus coU produced 

 ammonia in culture-media free from sugar, and thus caused an in- 

 tense alkaline reaction in the culture-media. The cultures usually 

 give off an unpleasant odor. 



Nitrates are reduced to nitrites by the growth of the bacillus. 



In bouiUon containing i per cent, of dextrose, lactose, levulose, 

 galactose, and mannite, the colon bacillus spUts up the sugar, lib- 



H 2 



eratmg CO2 and H, the gas formula being t^ = y This gas for- 



