e word POISON plainly written in
large letters across the label. Fasten the cork of a bottle containing
poison to the bottle itself with copper or iron wire twisted into a knot
at the top. This is an effective means of preventing any mistakes,
especially in the night.

This subject of poisons assumes nowadays great importance, as it is a
common custom to keep about stables, workshops, bathrooms, and living
rooms generally a more or less formidable array of germicides,
disinfectants, horse-liniments, insect-poisons, and other preparations of
a similar character. For the most part they contain poisonous
ingredients.

Bacteria.

394. Nature Of Bacteria. The word bacteria is the name applied to
very low forms of plant life of microscopic size. Thus, if hay be soaked
in water for some time, and a few drops of the liquid are examined under a
high power of the microscope, the water is found to be swarming with
various forms of living vegetable organisms, or bacteria. These
microscopic plants belong to the great fungus division, and consist of
many varieties, which may be roughly divided into groups, according as
they are spherical, rod-like, spiral, or otherwise in shape.

Each plant consists of a mass of protoplasm surrounded by an
ill-defined cell wall. The bacteria vary cably in size. Some of the
rod-shaped varieties are from 1/12,000 to 1/8,000 of an inch in length, and
average about 1/50,000 of an inch in diameter. It has been calculated that
a space of one cubic millimeter would contain 250,000,000 of these minute
organisms, and that they would not weigh more than a milligram.

[Illustration: Fig. 168.--Examples of Micro-Organisms called Bacteria.
(Drawn from photographs.)

A, spheroidal bacteria (called _cocci_) in pairs;
B, same kind of bacteria in chains;
C, bacteria found in pus (grouped in masses like a bunch of grapes).
[Bacteria in A, B, and C magnified about 1000 diameters].
D, bacteria found in pus (tendency to grow in the form of chains).
[Magnified about 500 diameters.]
]

Bacteria are propagated in a very simple manner. The parent cell divides
into two; these two into two others, and so on. The rapidity with which
these organisms multiply under favorable conditions, makes them, in some
cases, most dangerous enemies. It has been calculated that if all of the
organisms survived, one bacterium would lead to the production of several
billions of others in twenty-four hours.