
BACTERIA IN THE DAIRY. 21 
since it was frequently found that a sample of cream taken at 
one date would disclose a large number of bacteria which 
liquefied gelatine, while another taken a few days later would 
show no liquefying bacteria. The presence of the liquefying 
organisms is most easily determined; in fact one can never fail 
to detect them. ‘Their presence in quantity in some cases, and 
their absence in others is, therefore, significant. 
Variation with the Cow.—One series of experiments con- 
sisted in the testing of the milk from eight cows in the same 
barn. ‘These cows were kept in adjoining stalls and fed in the 
same manner, and their milk was drawn into sterilized bottles 
and then tested separately. After a few weeks the same eight © 
cows were again tested in the same way, and the same test was 
repeated at short intervals for several months. It was found 
in these tests that there was the most striking difference 
between the bacteria in the milk of the separate cows. The 
number varied surprisingly. "The milk from two of the cows 
contained not more than 250 bacteria per loop full (a loop fullisa 
drop about the size of the head of a large pin), while the milk 
from a third, contained 20,000, and a fourth, 60,000, in the 
same quantity of milk. The variety of bacteria was no less 
interesting. In the first place, it was found that no two of 
these eight samples of milk, when left to themselves and care- 
fully guarded from outside contamination, underwent the same 
kind of fermentation. Some of them curdled and soured, some 
of them curdled without souring, some developed a cheesy odor, 
others a putrefactive odor, and, among the lot, there was one 
cow that gave milk that became slimy. When the same cows 
were tested a second time, a few weeks later, the effects were 
different. ‘he cow that previously gave slimy milk, no longer 
produced milk with this defect, and all of the samples but one 
soured, although not in the same way in any two.cases. In 
the third test still other variations occurred. When the bac- 
teria from the eight samples were studied, it was found, as was 
to be expected, that there was a good deal of variation. There 
were one or two species that were common to nearly all of the 
‘cows, while others were found in one lot of milk, and others, 
again, in one or two lots. It must be always kept in mind 
that these bacteria of which we are now speaking do not come 
5) 
