( 20 ) 



prepared in the creameries themselves, but also the sellers of pure 

 cultures, by following the above prescriptions, will obtain a better 

 product than by the more usual way of selection of aerobic colonies. 

 Besides, the management is simpler and more scientific. 



To my opinion there is no satisfying ground to class the aerobic 

 and anaerobic forms of Lactococcus, which can be produced after 

 the said method, in separate species. They are but variants of one 

 and the same species, whose oxygen requirements are different, which 

 also appears from the fact that in the course of time one and the 

 same stock shows considerable differences with regard to the said 

 relation. Moreover, by several isolations all transitions between the 

 more or less aerobic stocks may be obtained. 



Finally it should be borne in mind, that by applying the "bottle 

 method" at low temperature, in rare cases instead of a culture of 

 real Lactococcus a Lactobacillus is obtained, which may likewise be 

 had by colony selection from cheese. Using this Lactobacillus I did 

 not observe at all the pleasant flavour of' the anaerobic lactococci, 

 so that 1 do not recommend these bacilli for cream souring. 



5. Elective culture of the lactic acid bacilli. 



If milk, soured spontaneously by Lactococcus lactis, or still better, 

 buttermilk, is placed at exclusion of air in a thermostat of ca. 

 40^ C, the original acid amount of 8 to 12 c.c. will in most cases 

 rise after some days to about 18 or 20 c.c. per J00 c.c. of milk. 

 For this experiment it is best to use a stoppered bottle of 250 to 

 300 c.c. capacity quite tilled with milk. If for the first experiment 

 a smaller quantity is used the result becomes uncertain, either by 

 the disturbing influence of the air, or by the scarcity of the inferred 

 bacteria. 



The first change commonly observed in the sour milk is a mode- 

 rately vigorous alcoholic fermentation, caused by the hardly ever 

 lacking lactose yeast, and at the same time a complete separation 

 of the caseine, which is driven to the surface of the liquid by the 

 carbonic acid. 



Microscopically we find that the lactococci present at first, are 

 succeeded by more lengthened forms, truncated at the ends and 

 united in chains, whereby the acid titer may considerably diminish, 

 for instance in 12 hours from 8 c.c. to G c.c, which should be 

 ascribed to the lactose yeast, for which the free lactic acid can 

 serve as carbon food. By transference, at exlusion of air, the lactose 

 yeast, as in the elective culture of lactococci, is rapidly dispelled 

 by the then stronger lactic acid ferments. 



