nothing can move.

PRINCIPLES OF CANNING AND PRESERVING.

In the preservation of foods by canning, preserving, etc., the most
essential things in the processes are the sterilization of the food and
all the utensils and the sealing of the sterilized food to exclude all
germs.

BACTERIA, YEASTS, AND FERMENTATION.

Over one hundred years ago Francois Appert was the first to make
practical application of the method of preserving food by putting it in
cans or bottles, which he hermetically sealed. He then put the full
bottles or cans in water and boiled them for more or less time,
depending upon the kinds of food.

In Appert's time and, indeed, until recent years it was generally
thought that the oxygen of the air caused the decomposition of food.
Appert's theory was that the things essential to the preservation of
food in this manner were the exclusion of air and the application of
gentle heat, as in the water bath, which caused a fusion of the
principal constituents and ferments in such a manner that the power of
the ferments was destroyed.

The investigations of scientists, particularly of Pasteur, have shown
that it is not the oxygen of the air which causes fermentation and
putrefaction, but bacteria and other microscopic organisms.

Appert's theory as to the cause of the spoiling of food was incorrect,
but his method of preserving it by sealing and cooking was correct, and
the world owes him a debt of gratitude.

In their investigations scientists have found that if food is perfectly
sterilized and the opening of the jar or bottle plugged with sterilized
cotton, food will not ferment, for the bacteria and yeasts to which such
changes are due can not pass through the cotton. This method can not be
conveniently followed with large jars.

Bacteria and yeasts exist in the air, in the soil, and on all vegetable
and animal substances, and even in the living body, but although of such
universal occurrence, the true knowledge of their nature and economic
importance has only been gained during the last forty years.

There are a great many kinds of these micro-organisms. Some do great
harm, but it is thought that the greater part of them are beneficial
rather than injurious.

Bacteria are one-celled and so small they can only be seen by aid of a
microscope. The process of reproduction is simple and rapid. The
bacterium becomes constricted, divides, and finally there are two cells
instead of one. Under fav