temperature of the
sions give an almost instant reading.
There are also disposable skin ther-
mometers that employ heat-sensitive
specific temperatures. These are not as
however. Clinical thermom-
eters may be calibrated in degrees
Celsius (centigrade), degrees Fahren-
heit, or sometimes both.
vitamin B complex.
thiazides A type of
widely used as a general anaesthetic
). Thiopental is
given by intravenous injection.
It is now used only
under specialist supervision because of
potentially serious side effects.
thirst The desire to drink. Thirst is one
means by which the amount of water in
the body is controlled (the other is the
volume of urine excreted).
Thirst is stimulated by an increased
concentration of salt, sugar, or certain
other substances in the blood. As the
blood passes through the
in the brain, special nerve receptors are
stimulated, inducing the sensation of
thirst. Thirst is also stimulated if blood
volume decreases as a result of sweating,
vomiting, diarrhoea, severe bleeding, or
extensive burns. Thirst may also be
caused by a dry mouth.
thirst, excessive A strong and persis-
tent need to drink, most commonly due
. Other causes include
, kidney failure, treatment with
phenothiazine drugs, and severe blood
loss. Abnormal thirst may also be due
to a psychological condition known as
thoracic outlet syndrome A condition
in which pressure on the
causes pain in the arms and shoulders,
pins-and-needles sensation in the fin-
gers, and weakness of grip and other
hand movements. Severe symptoms are
usually caused by a
outlet syndrome may also be caused by
drooping of the shoulders, an enlarged
scalenus muscle in the neck, or a tumour.
The condition is made worse by lifting
and carrying heavy loads or by increases
in body weight.
Treatment of thoracic outlet syndrome
usually consists of exercises to improve
posture, sometimes together with
steroidal anti-inflammatory drugs
may be treated by surgical removal of
thoracic surgery A surgical speciality
concerned with operations on organs
within the chest cavity. Sometimes, tho-
racic surgery is combined with heart
surgery, in which case it is known as
thoracotomy An operation in which
the chest is opened to provide access to
organs in the chest cavity.
There are 2 types of thoracotomy:
lateral and anterior. In a lateral thora-
cotomy the chest is opened between
ribs to provide access to the
major blood vessels, and the
. In an anterior thoracotomy, an
incision down the sternum (breast-
bone) provides access to the
thorax The medical name for the chest.
The thorax extends from the base of the
neck to the
thought The mental activity that enables
humans to reason, form judgments, and
solve problems. The essential features
of thought include the substitution of
symbols (in the form of words, numbers,
or images) for objects, the formation of
symbols into ideas, and the arrangement
of ideas into a certain order in the mind.
thought disorders Abnormalities in
the structure or content of
reflected in a person's speech, writing,
or behaviour. S
eral thought disorders, including loss of
logical connections between associa-
tions, the invention of new words (see
), thought blocking (sudden
interruption in the train of thought), the
feeling that thoughts are being inserted
into or withdrawn from the mind, and
Incoherent thoughts occur in all types
delirium. Rapidly jumping from one idea