212 
Journal of Agricultural Research 
Vol. II, No. 3 
The next organisms investigated with respect to forms of lactic acid 
produced were those which belong to the Bacterium casei group and 
which produce a much higher acidity than B. lactis acidi , although they 
grow more slowly than the latter. Several solutions of sterile milk and 
calcium carbonate inoculated with a culture of B. casei gave, on incuba¬ 
tion, levo-lactic acid, although Heinemann (1909), experimenting in the 
same direction with members of this group, obtained racemic acid. 
Another culture which was isolated from milk gave dextro acid instead 
of the levo form. These were evidently two different varieties of B. 
casei. They will be designated “ Bacterium casei 1” and u Bacterium 
casei 2 
Bacterium casei 2 was inoculated into 250 c. c, of sterile milk. Calcium 
carbonate was added, and the medium was allowed to stand for 
months. The liquid of the medium had almost evaporated at the end 
of that time, and crystals had deposited on the bottom of the flask. 
These crystals were purified by repeated crystallization and then dried 
in the desiccator. In the resulting product was found 18.07 P er cent 
of calcium, the theoretical percentage of calcium being 18.34 f° r anhy¬ 
drous calcium lactate. Rough isolation of lactic acid gave about 0.900 
gram of zinc-lactate crystals. Fractional crystallation proved that it 
was active, the salt being levo-rotatory—that is, the free acid was dextro¬ 
rotatory. 
Pure cultures of Bacterium lactis acidi and B . casei and mixtures of 
these two cultures with and without calcium carbonate were examined, 
to determine the types of lactic acid present. 
Tactic acid was isolated. Its zinc salt was fractionally crystallized, 
and the water of crystallization was estimated in each fraction of crystals. 
See Table XXII. 
Table; XXII .—Analysis of 300 c. c. of sterilized milk , showing production of lactic add 
by Bacterium lactis acidi and Bacterium casei 1 
Fraction No. 
1. 
Bacterium lactis 
acidi. 
II. 
Bacterium lactis 
acidi and B. casei i. 
III. 
Bacterium lactis 
acidi and B. casei i 
with calcium car¬ 
bonate. 
1 IV. 
Bacterium casei i. 
Zinc 
lactate. 
Water of 
crystal¬ 
lization. 
Zinc 
lactate. 
Water of 
crystal¬ 
lization. 
Zinc 
lactate. 
Water of 
crystal¬ 
lization. 
Zinc 
lactate. 
Water of 
crystal¬ 
lization. 
I. 
Grants. 
I. 66 
• 73 
Per cent. 
Grams. 
i -47 
.92 
. 06 
Per cent. 
18. 06 
I 7-25 
17-95 
Grams. \ 
4. 40 
3 - 3 ° 
3.00 
3.00 
•34 
. - 6 S, 
Per cent. 
18. 36 
12. 75 
13. 24 
12. 90 
12. 26 
11. 98 
Grams. 
2. 54 
. 16 
. 16 
Per cent. 
12. 87 
12. 88 
12. 89 
2. 
r 3 - 36 
2. 
O 
4. 
5. 
6. 
1 
Tevo- 
salt. 
Dextro- 
salt. 
Dextro- 
salt. 
