the cooking of foods destroys many organisms, it
often fails to render innocuous the poisons which they produce, and
furthermore the unsound foods when cooked are not entirely wholesome,
and they have poor keeping qualities.

Often meats, vegetables, and other foods eaten uncooked, as well as the
numerous cooked foods, are exposed in dirty market places, and
accumulate large amounts of filth, and are inoculated with disease germs
by flies. Protection of food from flies is a matter of vital importance,
as they are carriers of many diseases. In the case of typhoid fever,
next to impure drinking water flies are credited with being the greatest
distributors of the disease germs.[96]

[Illustration: FIG. 66.--DIPHTHERIA BACILLI. (After CONN.)

Often present in dust particles and in food unprotected from dust.]

282. Infection from Impure Air.--The dust particles of the air contain
decayed animal and vegetable matter in which bacteria are present; these
find their way into the food when it is not carefully protected, into
the water supply, and also into the lungs and other organs of the body.
When foods are protected from the mechanical impurities which gain
access through the air, and fermentation is delayed by storage at a low
temperature, digestion disorders are greatly lessened. From a sanitary
point of view, the air of food storerooms and of living rooms should be
of equally high purity. When foods are kept in unventilated living
rooms, they become contaminated with the impurities thrown off from the
lungs in respiration, which include not only carbon dioxid, but the more
objectionable toxic organic materials.

Vegetable foods need to be stored in well-ventilated places, as the
plant cells are still alive and carrying on life functions, as the
giving off of carbon dioxid, which is akin to animal respiration; in
fact, it is plant-cell respiration. Provision should be made for the
removal of the carbon dioxid and other products, as they contaminate the
air. When vegetable tissue ceases to produce carbon dioxid, death and
decay set in, accompanied by fermentation changes.

283. Storage of Food in Cellars.--Cellars are often in a very
unsanitary condition, damp, poorly lighted, unventilated, and the air
filled with floating particles from decaying vegetables. The walls and
shelves absorb the dust and germs from the foul air and are bacterially
contaminated, and whenever a sound food is stored in such a cellar, it
readi