milk.

This same method is sometimes applied in dealing with certain abnormal
fermentations that are apt to occur on the farm. It is particularly
useful with those tainted milks known as "sweet curdling." The ferment
organisms concerned in this change are unable to develop in the
presence of lactic acid bacteria, so the addition of a clean sour milk
as a starter restores the normal conditions by giving the ordinary milk
bacteria the ascendency.

~Chemical disinfection.~ In exceptional instances it may be necessary to
employ chemical disinfectants to restore the normal conditions. Of
course with such diseases as tuberculosis, very stringent measures are
required, as they are such a direct menace to human life, but with these
abnormal or taint-producing fermentations, care and cleanliness, well
directed, will usually overcome the trouble.

If it becomes necessary to employ chemical substances as disinfecting
agents, their use should always be preceded by a thorough cleansing with
hot water so that the germicide may come in direct contact with the
surface to be disinfected.

It must be borne in mind that many chemicals act as deodorants, _i.e._,
destroy the offensive odor, without destroying the cause of the trouble.

_Sulfur_ is often recommended as a disinfecting agent, but its use
should be carefully controlled, otherwise the vapors have but little
germicidal power. The common practice of burning a small quantity in a
room or any closed space for a few moments has little or no effect upon
germ life. The effect of sulfur vapor (SO_{2}) alone upon germ life is
relatively slight, but if this gas is produced in the presence of
moisture, sulfurous acid (H_{2}SO_{3}) is formed, which is much more
efficient. To use this agent effectively, it must be burned in large
quantities in a moist atmosphere (three lbs. to every 1,000 cubic feet
of space), for at least twelve hours. After this operation, the space
should be thoroughly aired.

_Formalin_, a watery solution of a gas known as formaldehyde, is a new
disinfectant that recent experience has demonstrated to be very useful.
It may be used as a gas where rooms are to be disinfected, or applied as
a liquid where desired. It is much more powerful in its action than
sulfur, and it has a great advantage over mercury and other strong
disinfectants, as it is not so poisonous to man as it is to the lower
forms of life.

_Bleaching powder or chloride of lime_ is often recommende