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14
all the cattle which are affected by tuberculosis. They also
suggest that in the cultivation of a high standard of
personal vitality lies our present chief defence against
infection by tubercular and other germs.
The establishment of large dairies using only cows
which have been tested and proved free from tubercular
disease will doubtless be a powerful factor in the future
improvement of our supplies of milk and meat. It is
obvious that such dairies, so soon as they are in vogue, will
command the public custom for milk, and will supersede
small dairies which are not scientifically supervised, and
from which questionable cows are not sacrificed. Meanwhile
there is the very practical device of sterilizing the
milk. Several useful and effective forms of patent saucepan
sterilizers* have been introduced, and are in large and
increasing demand. But the principle by which sterilization
of milk is effected is very simple and intelligible.
Sterilization can be done perfectly by the use of a bottle
to contain the milk, and an ordinary saucepan to contain
water in which the bottle of milk can be immersed up to a
level with the top of the milk. All that is then needed is to
heat the water in the saucepan slowly until it boils, and
to boil it for five minutes. It can then be set aside to
cool down slowly, while the bottle of milk remains in
the water. It is only necessary to raise the milk nearly
to the temperature of boiling water, and to keep it at
that temperature for 10 minutes. This makes the milk
safe by killing any tubercular or other germs which may
be present—as a similar exposure to the boiling water
would kill an egg. An ordinary glass-stoppered bottle
(perfectly clean) to receive the milk, may safely be
exposed to this method of heating in any ordinary iron
saucepan ; but in order to protect the bottom of the bottle
from the direct heat of the fire and to prevent the milk
from being burnt, a disc of thick wire netting should be
placed upon the bottom of the saucepan, and on this the
* Aymard's Patent Milk Sterilizer is simple and effective.