INVESTIGATIONS OF ACID ORGANISMS OF MILK. Sele ie 
might be avoided. In all there were 205 such tubes obtained 
from the 70 cows. ‘The first set of tubes were kept at about 
18° C.; the second and third sets were kept in an incubator at 
35%4° C. for 72 hours. Of the first set of 70 tubes only 5 had 
curdled in the course of 6 days. Plate cultures made from 
these 5 tubes showed the presence of 2. acidi lactic® in 2 of 
them, while in the other 3 there were BZ. lactis aerogenes and 
several miscellaneous bacteria. Of the second set a large num- 
ber curdled, 31 in all. These were all examined by means of 
plate cultures. Of the 31 tubes, 6 showed the presence of B. 
actdt lactici?, and all contained the two other lactic bacteria. In 
the third set, 12 tubes curdled, all of which were examined by 
plate cultures, but in none of them was #&. acidz lactict dis- 
covered. In comparing the three sets together it was found 
that in no case did the milk from the same cow curdle in all 
three tests. In 12 cases only did the milk from the same cow 
curdle in two of the tests, and in all of these cases careful 
plate cultures failed to reveal the presence of 2B. acidi lactictz. 
In these tests 8, as indicated, showed the presence of B. acidz 
lactict in the milk. To determine whether this organism was 
actually present in the fresh milk of the cows furnishing these 
samples, the 8 cows were again tested in the same way as 
before, this time 5 samples being taken from each cow. In 
the milking in this case the plugging of the tubes with cotton 
was slightly delayed, so that the chances for air contamination 
were a little greater than in the previous test. Of these 4o 
tubes, all of which were placed at 35%° C. for 48 hours, a 
single one alone showed the presence of B. acidt lactict. ‘The 
cow furnishing this milk was again tested by having samples 
taken in sterile tubes during the milking. In this case the 
milking was more rapid and the possibility of secondary con- 
tamination lessened. ‘These tubes were placed at 35%° C. for 
36 hours, but in no case was &. acidz lactict present. 
These experiments plainly indicated that the freshly drawn 
milk from this herd does not contain &. acidt lactict. Asa 
confirmatory test, in order to demonstrate that the milk from 
this barn is not different from the milk of ordinary dairies in 
respect to the presence of this organism, the following simple 
experiment was made: Milk was taken from the milk cans 
containing the mixed milk of the whole herd. The samples of 
