297 



The elective culture of Lactococcus takes place by allowing milk to sour in 

 a stoppered bottle at 20 to 25 C. and transfer it repeatedly to boiled milk at 

 that temperature. The thereby obtained stocks of Lactococcus lactis are mostly 

 anaerobic but specifically not to be distinguished from the more aerobic forms 

 which may be produced by the same experiment. The acid mostly remains at 

 about 8 c.c. of normal acid per 100 c.c. of milk, but may become 10 to 12 c.c. 



The elective culture of Laetobadllus succeeds best by cultivating buttermilk 

 in absence of air at 37 to 40 C. and inoculating it into boiled milk, at 30 C. 

 and higher, the acidity can rise from 18 to 25 c.c. of normal acid per 100 c.c. 

 of milk. 



The active lactic acid ferments are very variable; as factors of hereditary 

 constant variation are recognised cultivation at too high or too low oxygen 

 pressure, and cultivation at a temperature above the optimum of growth. 



Lactic acid ferments do not lack in the intestinal flora, but play there an 

 inferior part. 



A considerable difference between Eastern and Western lactic acid ferments 

 does not exist. 



Yoghurt and other such like sour milk preparations deserve the attention of 

 hygienists. 



