CHARACTERS OF LACTIC BACTERIA 277 



bitterness in cheese, Micrococcus casei amari, Freudrch., 

 . and Conn's Micrococcus of bitter milk, belong to this 

 group also. 



Ex. 135. Inoculate tubes of sterile milk with pure cultures 

 of: 



(a) Str. lacticus, Kr. 



(b) Bs. acidi lactici, Hueppe. 



(c) Bact. lactis aerogenes, Esch. 



(d) Bact. coli, Esch. 



(e) Bs. bulgaricus, Hpl. 



Note the kind of curd thrown down by each, and the presence 

 or absence of gas bubbles in it. 



Ex. 136. Make cover-films from pure cultures of the organ- 

 isms mentioned in the previous experiment, and stain them 

 with : 



(a) weak gentian violet, 



(b) Loeffler's methylene blue, 



(c) carbol fuchsin, 



(d) Gram's stain. 



Examine with the highest power available and make drawings 

 of the organisms. 



Ex. 137. Mix a few drops of sour milk in a test-tube with 

 sterile water. 



Inoculate tubes of melted litmus gelatine and litmus agar 

 with a loopful of the diluted milk, and pour into separate Petri 

 dishes. 



(a) Incubate the gelatine plates at 20 C., the agar plates at 

 35 C., and note the number, form, and acidity of the colonies 

 obtained. 



Do any of them liquefy the gelatine ? 



(b) Inoculate tubes of litmus milk with small portions of the 

 different colonies observed. 



Incubate at 20 C. and make notes on the following points 

 during seven to fourteen days : 



i . The presence or absence of curd. 



