s, from clean cows, by clean persons; and the other that the
milk shall be cooled to a temperature of fifty degrees or less as soon
as received from the cow. Neither of these requirements is difficult to
attain, but they constitute the sole reason why some milk contains a
million or more bacteria and other milk less than a thousand; and it is
quite possible by enforcing these two requirements to change the number
of bacteria in milk from the large figure to the small one.

Probably it is in the stable where the cows are milked that the most
important factor in producing large numbers of bacteria is to be found.
Not long ago the writer saw a number of stables, the ceilings of which
were poles on which the winter supply of hay was stored and the
atmosphere was noticeably dust-laden. A good milk could not be
furnished from such a stable, and therefore it may be set down as the
first requirement that the ceiling of the stable should be entirely
dust-tight. Some of the best stables in the country for this reason have
no loft of any sort above the cattle, but if the ceiling is tight,--that
is, made with tongue-and-groove boards and then painted,--there can be
no objection to the storage of hay in the loft. Hay should not be taken
from the loft or fed to the cows just before milking, because the very
moving of a forkful of hay through the air of the stable stirs up so
large a number of bacteria in the air that quantities of them will later
fall into the milk-pail.

_Light and air_ in a stable are both important, not so much for the
quality of the milk as for the health of the cows that furnish the milk.
Ventilation and sunlight are both excellent antiseptics. The ordinary
rule for the amount of window area per cow as given by the United States
Department of Agriculture is four square feet of window surface. But it
is not easy to definitely state any fixed amount of window area, since
the value of the window is in its disinfecting power on the bacterial
life of the stable, and this is greater or less as the windows receive
the direct sunlight or are hidden under eaves where no sunlight reaches
them.

The next factor in the production of good milk is the condition of the
_walls of the stable_. Like the ceiling, they should be absolutely free
from dust, and should be smooth, so that they may be brushed or even
washed clean. For this reason, walls with ledges are objectionable, and
all horizontal surfaces in a stable are undesir