T/te Fermentations of Milk. 
799 
it in that state on board ship, and under other conditions where 
fresh milk is not easily obtainable. 
It is nevertheless true that to sterilise milk that has been once 
exposed to the air, by the most ordinary method in use among 
scientists — namely, heating or boiling, — is by no means easy. In 
order to succeed, it is necessary to heat the milk not once, as with 
many other liquids, but several times, and that on successive days. 
The fact is that the spores of some of the organisms which gain 
access to milk are not killed by being heated in that liquid even to 
the boiling temperature. In the intervals of discontinuous heating, 
however, the spores have time to germinate, and, once germinated, 
they are easily killed by heat. 
A most important corollary from this teaching is that all 
abnormal conditions of milk may be prevented by care and clean- 
liness. Instead of imagining something to be wrong with the cow, 
or with the feeding, when once it is realised that milk goes wrong 
on account of something which gets into it from outside, the cure 
will be sought in keeping the surroundings of the cows free from 
filth, in enforcing absolute cleanliness in the milk pails and dairy 
vessels, and in refrigerating the milk immediately after it is drawn. 
These truths are so well known to our large dairy companies, 
and are so thoroughly acted on by them, as to make any advice of 
the sort appear trite and commonplace ; but when we think of the 
multitude of those who ai’e quite in the dark as to the way in 
which any changes are set up in milk, it cannot be out of place to 
take any suitable opportunity of putting the gist of the matter 
plainly before them. We feel justified, therefore, in quoting in 
extenso a few sentences from Dr. Conn in reference to the use of a 
low temperature in preserving milk from change : — 
“ To be of most use it should be applied immediately after the 
milk is drawn. When drawn from the cow, milk is at a high tem- 
perature, and, indeed, at ^ust the temperature at ivhicli numbers of 
bacteria grow most rapidly. Under the influence of the atmospheric 
temperature, especially in the summer, the milk becomes cool very 
slowly, but never becomes cooler than the air. The bacteria which 
have got into the milk will therefore have the very best oppor- 
tunity for rapid multiplication, and the milk will sour very rapidly. 
If, however, the milk is cooled to a low temperature immediately 
after it is drawn, the bacterial growth is checked at once, and will 
not begin again with much rapidity until the milk has become 
warmed once more. The warming will take place slowly, and there- 
fore the cooled milk will remain sweet many hours longer than that 
which is not cooled. It frequently happens from this cause that a 
milkman finds his morning’s milk will sour earlier than the milk 
of the night before. The milk drawn in the evening is put in a 
cool place at once, and becomes quite cool during the night, whilst 
the morning’s milk is at once put in cans and taken for delivery. 
It will thus happen that the older milk will actually keep longer 
than the newer milk, simply because it has been cooled, and must 
be warmed again before bacteria can begin to grow very rapidly.” 
