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into well boiled milk, which is done by transferring a trace of the 

 first culture to the second bottle, quite tilled with boiled, air-free 

 milk, and so on, the lactococci free themselves completely from all 

 foreign microbes and a material is obtained, which displays a high 

 degree of purity and of practical usefulness. If the acidifying power 

 of the microbes obtained by the experiment is lower than wished 

 for, for example 5, whilst 8 to 1<> c.c. of normal acid on 100 c.c. 

 milk is desire'd, this must be attributed to the accidentally present 

 stock. It is necessary then to begin a new experiment, following the 

 same way as described, or it can be advisable to perform the first 

 inoculation with some good butter-milk. 



As buttermilk, however, very often contains lactose yeast, in the 

 latter case a vigorous alcohol fermentation may at first be expected 

 in the bottles. Hut it soon disappears by inoculation into milk rendered 

 free from oxygen by boiling. 



If in this way, thus in absence of air, the culture has been 

 prolonged, a fairly constant acid amount is obtained at each renewed 

 inoculation, which does not, however, rise above 10 — 12 c.c. normal 

 in 100 c.c. of milk. On whey agar or whey gelatin plates the growth 

 at the air of the thus obtained lactococci is different, as sometimes 

 a great many aerobic colonies arise, which cause the same acidi- 

 fication as the cultures in the bottles, while in other cases nothing 

 is seen to grow. 



The first group corresponds with the usual commercial forms 

 destined for the souring of cream, which commonly consist of 

 cultures of the microbes dried on milk sugar or starch; moreover 

 there are commercial aerobic pure cultures in milk or whey, which 

 are sold in bottles. 



The second group, that is the cultures non-growing at die air, 

 may still better be used for the cream souring than the aerobic 

 stocks, as the anaerobic forms of Lactococcus show more aptness to 

 secrete the flavour desired in butter, than the more aërophilous 

 bacteria. ') 



As well for this reason as for the great purity of the cultures made 

 after this "bottle method", there is reason to prefer them in dairy 

 work to the commercial so-called pure cultures, which for the greater 

 part are by no means pure, but mostly contain, besides lactococci, 

 numerous contamination germs of the milk. In consecpience of 

 frequent investigations I can therefore advise interested persons to 

 use the here described method. Best would be if these cultures were 



!) Of fate I have also met with such like anaerobic lactic acid bacteria in com- 

 mercial preparations. 



