round-structured virus (SRSV), w hich
affects shellfish. This form of poison-
ing can occur when raw or partly
cooked foods have been in contact
with water that has been contaminated
by human excrement.
OTHER INFECTIVE CAUSES
The protozoan parasite C
r y p t o s p o r i d i u m
w hich p rinci-
passed on to humans through drinking
water supplies, swim m ing pools, or by
direct contact w ith infected animals.
People w ith
particularly susceptible to contracting
this type of food poisoning.
There are a number of noninfective
of food poisoning including
poisonous mushrooms and toadstools
and vegetables contaminated w ith high
doses of insecticide, and chemical poi-
soning from some foods, such as fruit
made partly from zinc.
Certain foods, such as puffer fish,
considered a delicacy in Japan, or cas-
sava, a staple food in many tropical
countries, can also cause moderate to
lethal poisoning if im properly cooked
The onset of symptoms depends on the
cause of poisoning. Symptoms usually
develop w ithin 30 minutes in cases of
chemical poisoning, between one and
hours in cases of bacterial toxins,
12 and 48 hours with
most bacterial and viral infections.
Symptoms of food poisoning usually
include diarrhoea, nausea and vom it-
ing, stomach pain, and, in severe cases,
and collapse. Botulism affects the
nervous system, causing visual distur-
bances, difficulty with speech, para-
lysis, and vomiting.
The diagnosis of bacterial food poison-
can usually be
of a sample
Chemical poisoning can often be diag-
nosed from a description of what the
person has eaten, and from analysis of a
sample of the suspect food.
M ild cases can be treated at home by
replacement of lost fluids (see
In severe cases, or when
the very young or elderly are affected,
hospital treatment may be necessary. If
poisoning by a chemical or bacterial
toxin is suspected, the stomach may be
washed out (see
Except for botulism and some cases
of mushroom poisoning, most food
poisoning is not serious; recovery usu-
ally occurs w ithin about three days.
Some strains of E.
c o i i
damage red blood cells, causing
cholera; dysentery; seafood poi-
soning; typhoid fever.)
eliminate the risk of food poisoning.
Hands should always be washed before
food is handled, and fresh fruit and
vegetables should be rinsed in clean
water. Cutting boards and implements
should be washed w ith hot water be-
fore being used for other foods. Meat,
poultry, and eggs must be cooked thor-
oughly. Raw and cooked foods should
be stored well apart in the refrigerator,
and raw meat should be kept in the
coldest part. Advice should be sought
when preparing unfamiliar foods.
The foot has two vital functions. The
first of these functions is to support
the weight of the body in standing or
ANATOMY OF THE FOOT
An adult has
bones (about one
eighth of the total number in the
entire skeleton) in each foot. The
calcaneus is attached to the talus
above. In front are the navicular,
cuboid, and cuneiform bones, which
are attached to the metatarsals. The
phalanges form the toes.
walking; the second function of the
foot is to act as a lever that propels the
The largest bone of the foot, the heel-
is jointed with
the ankle bone (the talus). The tarsal
bones are located in front of the talus
and calcaneus and they are jointed to
The bones of
the toes are called the
big toe has two phalanges and all the
remaining toes have three.
Tendons passing around the ankle
connect the muscles that act on the
various bones of the foot and toe. The
main blood vessels and nerves pass in
front of and behind the inside of the
ankle to supply the foot. The under-
natural arch that is supported by liga-
tissue) and fat form the sole of the
foot, w hich is covered by a layer of
Injuries to the foot often result in
of the foot bones (the metatarsals
fracture following a fall from a height
on to a hard surface.
fairly common and include club-foot
is a common deformity of the
foot in w hich a thickened
filled pad) lies over the joint at the base
of the big toe.
are small areas of thickened
skin that are usually caused by tightly
) develop on the soles of the feet.
is a fungal infection that
causing it to become very itchy, sore,
is a relatively common type of
arthritis that often affects the joint at
the base of the big toe or one of the
joints in the foot. An ingrowing toenail
) commonly oc-
curs on the big toe and may lead to
surrounding tissues (see
is the inability to raise the
foot properly causing it to drag along
the ground when the person is walk-
condition may occur as a
result of damage to the muscles in the
leg that are responsible for performing
this movement or, alternatively, to the
nerves that supply these muscles.