on must always be given to the resistance of the organism
it is desired to destroy. Those that form spores are very resistant
toward all chemical agents, while those that do not produce these
resistant bodies are easily killed. In the dairy and factory, it is
often necessary to destroy the organisms that develop in decomposing
organic matter. Here, as in all disinfection, a thorough cleaning
should precede the application of any disinfectant. Some chemicals
act as deodorants, _i.e._, destroy the offensive odor, without
removing the cause. It is impossible effectually to destroy bacteria
embedded in a mass of organic matter, and through the removal of the
material itself, the larger part of the bacteria will be removed.
The disinfectant then comes in direct contact with the surface to be
disinfected, consequently destroys the bacteria not removed in the
cleaning.

All places in which dairy work of any kind is done should be
provided with an abundance of light and air. The direct rays of
the sun have a powerful disinfecting action, and light makes evident
accumulations of dirt that in a darker room would be unnoticed.
Ventilation keeps the rooms dry and thus prevents the growth of mold
and the development of a musty odor.

Disinfectants are divided into two classes: (1) solid materials used
in suspension, or in watery solutions; (2) gaseous substances. The
latter are preferable for room disinfection when their use is
permissible, for the gas penetrates to every part of the space, even
into the cracks. Gaseous disinfectants can only be used when the
space is tightly closed, for the gas must be confined for several
hours in the room, in order to make the process effective. Such
disinfectants can often be used to advantage in the treatment of
refrigerators and cheese rooms to destroy mold spores. In less
tightly closed spaces, reliance must be placed on the use of the
solid or liquid disinfectants.

=Lime.= Quick lime or stone lime has a considerable disinfecting
action. On exposure to the air, quick lime becomes air slaked, and
then has no disinfecting action whatever. Water-slaked lime used in
the form of white wash, lime water, or the powder is effective.
Air-slaked and water-slaked lime are similar in appearance, but a
difference can be noted by placing a particle of each on the tongue;
the air-slaked tastes like chalk while the water-slaked material
causes the tongue to burn.

White wash is one of the most effecti