BACTERIA IN FRESHLY DRAWN MILK. Q7. 
2. Freshly drawn milk contains a small number of lactic 
bacteria, the number varying from 10 to 60 or occasionally 70 
per cent., usually below 30 per cent. In these cases, however, 
the lactic organisms present are rarely the typical dairy bac- 
teria, B. lactis acidi I, and //.; these species being either absent 
or present in very small quantity in fresh milk. 2B. aerogenes 
is occasionally present, and also &. colz; other lactic bacteria 
which are of less significance in dairy problems constitute the 
lactic organisms of fresh milk. 
3. At ordinary temperatures the few individuals of B. lactis 
acidt begin to grow rapidly as soon as the milk is drawn from 
the cow, and become more and more numerous each hour. At 
the end of 36 to 48 hours this species usually comprises 95 to 
I0o per cent. of the bacteria present in milk preserved at 
ordinary temperatures. 
4. Market milk, as distributed in a small community where 
the milk producers are near the consumers, can be qualitatively 
analyzed by methods herein reported, and the analysis enables 
us to determine not only the number of bacteria, but also 
whether the milk containing large numbers is old milk with 
harmless species or fresh milk badly contaminated with sus- 
picious forms. 
5. The temperature at which milk is preserved is a factor of 
more importance as affecting the keeping property of the milk 
than is the original cleanliness in the dairy. When milk is 
drawn under ordinary conditions and has 3,000 or more bac- 
teria per cubic centimeter, the number of bacteria found, unless 
there be more than 50,000, has very little to do with the keep- 
ing property of the milk; for no parallel can be drawn between 
the number of bacteria at the outset and the number found 
after one, two, or three days, nor between the number in fresh 
nilk and the time of souring and curdling. 
6. When, however, special aseptic precautions are taken to 
reduce the contamination of milk by external bacteria, a very 
great effect is produced upon the keeping property of the milk; 
