of decaying matter wherever it may be. Manure heaps, dead bodies
of animals, decaying trees, filth and slime and muck everywhere
are filled with them, for it is in such places that they find
their best nourishment. The bodies of animals contain them in the
mouth, stomach, and intestine in great numbers, and this is, of
course, equally true of man. On the surface of the body they cling
in great quantity; attached to the clothes, under the finger
nails, among the hairs, in every possible crevice or hiding place
in the skin, and in all secretions. They do not, however, occur in
the tissues of a healthy individual, either in the blood, muscle,
gland, or any other organ. Secretions, such as milk, urine, etc.,
always contain them, however, since the bacteria do exist in the
ducts of the glands which conduct the secretions to the exterior,
and thus, while the bacteria are never in the healthy gland
itself, they always succeed in contaminating the secretion as it
passes to the exterior. Not only higher animals, but the lower
animals also have their bodies more or less covered with bacteria.
Flies have them on their feet, bees among their hairs, etc.

In short, wherever on the face of Nature there is a lodging place
for dust there will be found bacteria. In most of these localities
they are dormant, or at least growing only a little. The bacteria
clinging to the dry hair can grow but little, if at all, and those
in pure water multiply very little. When dried as dust they are
entirely dormant. But each individual bacterium or spore has the
potential power of multiplication already noticed, and as soon as
it by accident falls upon a place where there is food and moisture
it will begin to multiply. Everywhere in Nature, then, exists this
group of organisms with its almost inconceivable power of
multiplication, but a power held in check by lack of food. Furnish