BACTERIA AND FERMENTATION 131 



acid ; there is the same method of starting the process by 

 inoculation of sour milk or cheese or any substance contain- 

 ing the specific bacillus. It is probable that such inoculated 

 matter will contain a mixture of micro-organisms, but if the 

 lactic bacillus is present, it will grow so vigorously and 

 abundantly that the fermentation will be readily set up. 



TJie Bacillus Acidi Lactici. Rods about 2 //, long and 4 /A 

 wide, occurring singly or in chains and threads. It is non- 







CO 



B. ACIDI LACTICI 



motile. Spore formation is present, the spores appearing 

 irregularly or at one end of the rod. 



On the surface of gelatine a delicate growth appears along 

 the track of the needle, with round colonies appearing at the 

 edges of the growth. It does not liquefy gelatine. It 

 grows best at blood-heat ; but much above that it fails to 

 produce its fermentation, and it ceases to grow under 10 C. 

 It inverts milk-sugar and changes it to dextrose, from which 

 it then produces lactic acid. Sugars do, however, differ 

 considerably in the degrees to which they respond to the 

 influence of the lactic ferment, and some which are readily 

 changed by the alcoholic ferment are untouched by the 

 Bacillus acidi lactici. It will be necessary to refer again to 

 this micro-organism when we come to speak of milk and 

 other dairy products. 



Van Laer has described a saccharobacillus which produces 

 lactic acid amongst other products, and brings about a 

 characteristic disease in beer, named tourne. The liquid 



