CHAPTER II.
BIOLOGY OF BACTERIA.

THE distribution of bacteria is wellnigh universal.
They and their spores float in the atmosphere we breathe,
swim in the water we drink, grow upon the food we eat,
and luxuriate in the soil beneath our feet. Nor is this
all, for, entering the palpebral fissures, they develop upon
the conjunctiva ; entering the nares, they establish them-
selves in the nose ; the mouth is always replete with
them ; and, as many are swallowed, the digestive appa-
ratus always contains them. The surface of the body
never escapes their establishment, and so deeply are
some individuals situated beneath the epithelial cells
that the most careful washing and scrubbing and the use
of the most powerful germicides are required to rid the
surgeon's hands of what may prove to be dangerous
hindrances to the healing of wounds. The ear is not
without its microscopic flora ; special varieties live be-
neath the finger-nails, and especially the toe-nails, in
the vagina, and beneath the prepuce.

While so general, however, they are not ubiquitous.
Tyndall succeeded in proving that the atmosphere of
high Alpine altitudes was free from them, and likewise
that the glacier ice contained none. Wherever man, ani-
mals, or even plants, live, die, and decompose, bacteria
are sure to be present.

Notwithstanding their extreme familiarity with the
animal body, there are certain parts of it into which
bacteria do not enter, or, entering, remain vital for a
very short time, for the body-juices and tissues of normal
animals are free from them, and their occurrence there
may 'almost always be accepted as a sign of disease.

The presence of bacteria in the air is generally de-

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