zgi 



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 moderately vigo- 

 rous 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 

 6 c.c., which should be ascribed to the lactose yeast, for which the free lactic 

 acid can serve as carbon food. By transference, at exclusion of air, the lactose 

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

 stronger lactic acid ferments. 



Real lactobacilli mostly appear after 2 or 3 days and then the acid rises rapidly 

 parallel to their multiplication to 20, even to 25 c.c. normal per 100 c.c. of milk. 

 When this degree of souring is reached, there is usually no further increase ob- 

 served, not even after several days, and whenever this does take place, there should 

 be thought of aeration, by which the growth of vinegar bacteria and acetic acid 

 formation from alcohol, have become possible. 



The pure culture of lactobacilli is sometimes easy, in other cases, with more 

 anaerobic stocks, it is more difficult. Always, however, it is troublesome with 

 these pure cultures to obtain a considerable souring in milk and there is most 

 chance of success (but even then the succes is not quite certain) by souring 

 lactobacilli together with Lactococeus which serves for the first souring to 8 c.c. 

 If this amount of acid is reached, and the pressure of the oxygen sufficiently 

 diminished, which in a stoppered bottle is likewise brought about by the presence 

 of the lactococci, the lactobacilli can develop and cause further souring. 



From the observation that by the described experiment more or less perfectly 

 anaerobic lactobacilli are obtained, follows that here as in the case of Lactococeus 

 different varieties may be expected. At a continued research the differences prove 

 to extend over other characteristics also and may become so great, as well from 

 a morphologic as from a physiologic point of view, that it seems necessary to 

 create new species. 



Especially the dimensions of the rods, the more or less branched state of 

 the colonies on agar plates, the slime formation, the either or not originating of 

 carbonic acid as fermentation gas beside the lactic acid, and the action or non 

 action on different sugars give rise to this consideration. The deeper however 

 we enter into these distinctions, the more troublesome it becomes to devise such 

 descriptions as are wanted to present to other investigators an image of the re- 

 sults of our own researches; so numerous become the forms which nature, or 

 better perhaps, which culture produces, and so slight are the differences by which 

 these forms are distinguished, if we do not confine ourselves to the extremes of 

 the groups 1 ). 



') For further information see W. Henneberg, Zur Kenntnis der Milchsaure- 

 bakterien. Sonderabdruck aus Zeitschrift fiir Spiritusindustrie. No. 2231, 1903. Pa- 

 rey, Berlin. 



19* 



