the foreskin becomes
stuck in the retracted position, causing
painful swelling of the glans that needs
The inability to remem-
A colourless, pungent,
irritant gas. In medicine, a solution of
formaldehyde and a small amount of
alcohol in water, a preparation known
as formalin, is used to preserve tissue
specimens or to harden them before
they are stained and examined. Forma-
lin is also used as a
An unpleasant sensation,
as if ants were crawling over the skin.
This may occur following abuse of cer-
tain drugs, such as alcohol or morphine.
A way of expressing
the constituents of a chemical in sym-
bols and numbers. Water, for example,
has the formula H
O, indicating that
each molecule is composed of
of hydrogen (H
of oxygen (O).
A book of formulae. The term
formulary is commonly used to refer to
a publication that lists drug prepara-
tions and their components and effects.
The contents of a formulary can be
decided by a group of medical profes-
sionals working together to ensure
similar patterns of drug usage.
An area of the
in the eye
that has the highest concentration of
light-sensitive cells. It is responsible for
detailed vision. (See also
A break in a bone, usually across
its width. There are 2 main types: closed
(simple) or open (compound) fractures.
In a closed fracture, the broken bone
ends remain beneath the skin and little
surrounding tissue is damaged; in an
or both bone ends pro-
ject through the skin. If the bone ends
are not aligned, the fracture is termed
“displaced”. Fractures can be further
divided according to the pattern of the
break, for example, transverse or spiral
fractures of long bones. In a greenstick
fracture, the break is not through the
full width of the bone. This type of frac-
ture occurs only in children because
their bones are more pliable. In an avul-
sion fracture, a small piece of bone is
pulled off by a tendon.
Most fractures are the result of a fall,
the bone is weak-
ened, and fractures such as compression
fractures of the vertebrae are common.
Common sites of fracture include the
hand, wrist (see
C oles' fracture), ankle
, and the neck of the femur
femur, fracture of
). There is usually
swelling and tenderness at the fracture
site. The pain is often severe and is usu-
ally made worse by movement.
X-rays can confirm a fracture. Because
bone begins to heal soon after it has
broken, the first aim of treatment is to
ensure that the bone ends are aligned.
Displaced bone ends are manoeuvred
through the skin or through an incision.
The bone is then immobilized. In some
cases the ends of the bone may be fixed
with metal pins or plates.
Most fractures heal without any prob-
lems. Healing is sometimes delayed
because the blood supply to the affec-
ted bone is inadequate (as a result of
damaged blood vessels) or because the
bone ends are not close enough together.
If the fracture fails to unite, internal fix-
ation or a
may be needed.
is a possible complication
of open fractures. (See also