100 



22 



IL will be seen from Table VI, that we have found in the case of the betabacteria a 

 division exactly answering to the equation 



6 arabinose = 8 lactic acid + 3 acetic acid. 



The bacteria thus appear as true lactic acid bacteria, inasmuch as they form the 

 greatest possible quantity of lactic acid from the source of energy giva'n^). This is, how- 

 ever, on the supposition that chalk is added to the cultures; without chalk, we obtain 

 here, as in other cases, proportionately more acetic acid. 



Table VI. 



Betabacterium breve No. 10 



Arabinose 

 fer- 

 mented 



"loo 



Lactic 

 acid 

 formed 



"loo 



Acetic 

 acid 

 formed 



"loo 



Lactic 

 acid 

 formed 



.. n 

 cm- 4 



Acetic 

 acid 

 formed 

 cmä^ 



Ratio 

 equiva- 

 lent: 



Lactic acid 

 Acetic acid 



Arabinose casein pepton broth with chalk. 



35,2 



28,0 



7,2 



125 



48 



8:3 



» » » » without » 



17,8 



13,1 



4,7 



58 



31 



2:1 



Up to now. We have reckoned the entire quantity of volatile acids as acetic acid and 

 this we may safely do, as there is at the outside ^ 'k,, more often only propionic acid, 

 and a trace of formic acid mixed therewith. 



In the case of certain betabacteria, we have already mentioned that more gas is formed 

 with cultures in a freshly isolated state, and as regards the betacocci, the develo])ment of 

 gas is undoubtedly in proportion to their well-being. Much would seem to suggest that the 

 transformation of sugar in all cases takes place by way of lactic acid, and that it can only 

 be further divided — i. e. made to yield more energy — by strains of particularh'^ marked 

 vitality. The majority of the true lactic acid bacteria, which do not develop any measurable 

 quantity of gas, can, however, — likewise when in a state of particular vitality — produce 

 in milk so much carbonic acid that fine stripes appear in the curd. The lactic acid 

 bacteria, then, as mentioned, form most acetic acid under unfavourable 

 conditions, whereas exactly the reverse is the case with the carbonic acid, 

 of which most is formed under favourable conditions. 



Experiences from our previous works warrant the supposition that the rotary ])()wer of 

 the lactic acid formed constitutes an important specific character for the true lactic acid bac- 

 teria, and we have therefore determined, in the case of all strains examined, what sort of lactic 

 acid they formed, not only in milk, but also in broth with dilTerent carbon and nitrogen 

 sources. These investigations we have repeated from year to year. The new investigations 

 have on the Whole confirmed the correctness of our sui)])osition. As a rule, neither the carbon 

 sources nor the nitrogen sources affect the modification of the lactic acid. Those strains 

 which in milk form |)ure d ex tro- or I ævo- lactic acid will also in a nu- 



M Tilis is the more surprising, as tlie ancestors of the strains used {Bucilhis y. in my tlusis above 

 quoted), formed much succinic acid, with abundant gas development. 



