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DENTAL MEDICINE.
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the newly-formed and the old capillaries, and is the same force
that carries the nutritive material to the tissues. Healthy pus is
of a yellowish-white color, sometimes assuming a pale greenish
tint, of cream-like consistence ; a slightly saltish taste, but some-
what sweet ; a faint animal odor, with an alkaline reaction. The
presence of bile may give to pus a deep orange color, while all of
the other shades are due to the coloring matter of the blood,
known as haematoidin. As long as the air has access to it, there
is little tendency to putrefaction ; and even when it is removed
from the body and exposed to ordinary temperature, change in it
occurs very slowly. Pus consists of two portions—a solid portion,
know as pus corpuscles^ and which consists almost entirely of
young pus cells or leucocytes, and a liquid portion known as
liquor puris^ which is a serous fluid, and constitutes about three-
fourths of its bulk.
When pus is subjected to pressure, as sometimes occurs in ab-
scess of the antrum, and about bones, it may become a yellowish,
cheesy mass, owing to the compression of the pus cells. The
solid portion of pus consists of more than nine-tenths of leucocytes
or young pus cells, which, in freshly formed pus, presents under
the microscope a granular appearance, and also the peculiar
movements of active, young and healthy leucocytes ; but pus
which has collected in an abscess for several days shows no such
movements, thereby indicating that the leucocytes have died.
Living and dead pus cells may be found in ordinary pus, mingled
together. The most common forms of micro-organisms which
produce suppuration are the staphylococci and the streptococci.
Varieties of Pus.—The constitution of pus, which is subject to
constant change, depends upon the form of the disease, the lo-
cality and the condition of the patient. When pus is of a yel-
lowish-white color, of the consistence of cream, and composed of
a great number of pus globules, it is called " healthy," " pure,"
or " laudable." When pus is thin, reddish and mixed with blood,
it is termed "sanious" pus, and is common to diseases of the
bones, irritable ulcers, etc., and Is also frequently mixed with
particles of fibrin, and dead tissue. In chronic and cold abscesses
the pus-corpuscles become pale and watery, showing that they are