MICROCOCCUS AGILIS OF A LI-COHEN. 



145 



brownish. A similar organism is found in water, but it does 

 not liquefy gelatin. 



Bacillus acidi lactici : Found in sour milk. It is a short, 

 thick rod, usually occurring in pairs ; non-motile, with large 

 shining spores. It has no flagella. It is a facultative 

 anaerobe, and grows on all the usual media without liquefy- 

 ing the gelatin. When grown in milk, it breaks up the milk- 

 sugar and forms lactic acid and gases, with precipitation of 

 the casein. It stains readily with the anilin dyes. Its tem- 

 perature optimum is about 20 C. On gelatin it forms a 

 thick, dry, whitish crust. It differs from the Bacterium acidi 



FIG. 55. 



FIG. 56. 



Bacterium acidi lactici. 



lactici (Figs. 55 and 56) in that it does not produce alcohol 

 in milk. 



Bacillus butyricus : This organism is found also in milk, 

 and is the cause of butyric acid fermentation. It is a very 

 slender rod, of varying length, with rounded ends and a large 

 central spore. It is flagellated and very motile. It is 

 strongly aerobic, and grows best at the temperature of the 

 body. Gelatin is rapidly liquefied. The casein of milk is 

 coagulated and decomposed, with butyric acid fermentation. 

 On gelatin it forms a very delicate, yellowish surface covering 

 which is quite characteristic. It is stained easily with the 

 usual dyes. 



Micrococcus agilis of Ali-Cohen : This organism can be culti- 

 vated from drinking-water, and is the only flagellated, motile 



10 Bact, 



