of bones, or solid paraffin employed to
correct deformities. Other substances, such as gauze, drainage tubes,
or metal instruments, may be unintentionally left in a wound.

Foreign bodies may also lodge in accidentally inflicted wounds, for
example, bullets, needles, splinters of wood, or fragments of clothing.
The needles of hypodermic syringes sometimes break and a portion remains
embedded in the tissues. As a result of explosions, particles of carbon,
in the form of coal-dust or gunpowder, or portions of shale, may lodge
in a wound.

The embedded foreign body at first acts as an irritant, and induces a
reaction in the tissues in which it lodges, in the form of hyperaemia,
local leucocytosis, proliferation of fibroblasts, and the formation of
granulation tissue. The subsequent changes depend upon whether or not
the wound is infected with pyogenic bacteria. If it is so infected,
suppuration ensues, a sinus forms, and persists until the foreign body
is either cast out or removed.

If the wound is aseptic, the fate of the foreign body varies with its
character. A substance that is absorbable, such as catgut or fine silk,
is surrounded and permeated by the phagocytes, which soften and
disintegrate it, the debris being gradually absorbed in much the same
manner as a fibrinous exudate. Minute bodies that are not capable of
being absorbed, such as particles of carbon, or of pigment used in
tattooing, are taken up by the phagocytes, and in course of time
removed. Larger bodies, such as needles or bullets, which are not
capable of being destroyed by the phagocytes, become encapsulated. In
the granulation tissue by which they are surrounded large multinuclear
giant-cells appear ("_foreign-body giant-cells_") and attach themselves
to the foreign body, the fibroblasts proliferate and a capsule of scar
tissue is eventually formed around the body. The tissues of the capsule
may show evidence of iron pigmentation. Sometimes fluid accumulates
around a foreign body within its capsule, constituting a cyst.

Substances like paraffin, strands of silk used to bridge a gap in a
tendon, or portions of calcined bone, instead of being encapsulated, are
gradually permeated and eventually replaced by new connective tissue.

Embedded bodies may remain in the tissues for an indefinite period
without giving rise to inconvenience. At any time, however, they may
cause trouble, either as a result of infective complications, or by
inducing the fo