e excised and the raw
surfaces approximated with stitches.

The _tuberculous sinus_ is described under Tuberculosis.

A #fistula# is an abnormal canal passing from a mucous surface to the
skin or to another mucous surface. Fistulae resulting from suppuration
usually occur near the natural openings of mucous canals--for example,
on the cheek, as a salivary fistula; beside the inner angle of the eye,
as a lacrymal fistula; near the ear, as a mastoid fistula; or close to
the anus, as a fistula-in-ano. Intestinal fistulae are sometimes met with
in the abdominal wall after strangulated hernia, operations for
appendicitis, tuberculous peritonitis, and other conditions. In the
perineum, fistulae frequently complicate stricture of the urethra.

Fistulae also occur between the bladder and vagina (_vesico-vaginal
fistula_), or between the bladder and the rectum (_recto-vesical
fistula_).

The _treatment_ of these various forms of fistula will be described in
the sections dealing with the regions in which they occur.

_Congenital fistulae_, such as occur in the neck from imperfect closure
of branchial clefts, or in the abdomen from unobliterated foetal ducts
such as the urachus or Meckel's diverticulum, will be described in their
proper places.

CONSTITUTIONAL MANIFESTATIONS OF PYOGENIC INFECTION

We have here to consider under the terms Sapraemia, Septicaemia, and
Pyaemia certain general effects of pyogenic infection, which, although
their clinical manifestations may vary, are all associated with the
action of the same forms of bacteria. They may occur separately or in
combination, or one may follow on and merge into another.

#Sapraemia#, or septic intoxication, is the name applied to a form of
poisoning resulting from the absorption into the blood of the toxic
products of pyogenic bacteria. These products, which are of the nature
of alkaloids, act immediately on their entrance into the circulation,
and produce effects in direct proportion to the amount absorbed. As the
toxins are gradually eliminated from the body the symptoms abate, and if
no more are introduced they disappear. Sapraemia in these respects,
therefore, is comparable to poisoning by any other form of alkaloid,
such as strychnin or morphin.

_Clinical Features._--The symptoms of sapraemia seldom manifest
themselves within twenty-four hours of an operation or injury, because
it takes some time for the bacteria to produce a sufficient dose of
their pois